diff options
| author | Roger Frank <rfrank@pglaf.org> | 2025-10-15 05:17:59 -0700 |
|---|---|---|
| committer | Roger Frank <rfrank@pglaf.org> | 2025-10-15 05:17:59 -0700 |
| commit | 97f7e955b25db39603ed6131740b39fae6b2fa4d (patch) | |
| tree | e02d333dfa9c31abe04c7fdad8973aefcd42df79 | |
| -rw-r--r-- | .gitattributes | 3 | ||||
| -rw-r--r-- | 1909-h.zip | bin | 0 -> 624570 bytes | |||
| -rw-r--r-- | 1909-h/1909-h.htm | 30870 | ||||
| -rw-r--r-- | 1909.txt | 28456 | ||||
| -rw-r--r-- | 1909.zip | bin | 0 -> 607677 bytes | |||
| -rw-r--r-- | LICENSE.txt | 11 | ||||
| -rw-r--r-- | README.md | 2 | ||||
| -rw-r--r-- | old/drwnm10.txt | 27636 | ||||
| -rw-r--r-- | old/drwnm10.zip | bin | 0 -> 606640 bytes |
9 files changed, 86978 insertions, 0 deletions
diff --git a/.gitattributes b/.gitattributes new file mode 100644 index 0000000..6833f05 --- /dev/null +++ b/.gitattributes @@ -0,0 +1,3 @@ +* text=auto +*.txt text +*.md text diff --git a/1909-h.zip b/1909-h.zip Binary files differnew file mode 100644 index 0000000..2812566 --- /dev/null +++ b/1909-h.zip diff --git a/1909-h/1909-h.htm b/1909-h/1909-h.htm new file mode 100644 index 0000000..2fb670d --- /dev/null +++ b/1909-h/1909-h.htm @@ -0,0 +1,30870 @@ +<?xml version="1.0" encoding="us-ascii"?> + +<!DOCTYPE html + PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" + "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd" > + +<html xmlns="http://www.w3.org/1999/xhtml" lang="en"> + <head> + <title> + Darwin and Modern Science, by A.C. Seward and Others + </title> + <style type="text/css" xml:space="preserve"> + + body { margin:5%; background:#faebd0; text-align:justify} + P { text-indent: 1em; margin-top: .25em; margin-bottom: .25em; } + H1,H2,H3,H4,H5,H6 { text-align: center; margin-left: 15%; margin-right: 15%; } + hr { width: 50%; text-align: center;} + .foot { margin-left: 20%; margin-right: 20%; text-align: justify; text-indent: -3em; font-size: 90%; } + blockquote {font-size: 97%; font-style: italic; margin-left: 10%; margin-right: 10%;} + .mynote {background-color: #DDE; color: #000; padding: .5em; margin-left: 10%; margin-right: 10%; font-family: sans-serif; font-size: 95%;} + .toc { margin-left: 10%; margin-bottom: .75em;} + .toc2 { margin-left: 20%;} + div.fig { display:block; margin:0 auto; text-align:center; } + div.middle { margin-left: 20%; margin-right: 20%; text-align: justify; } + .figleft {float: left; margin-left: 0%; margin-right: 1%;} + .figright {float: right; margin-right: 0%; margin-left: 1%;} + .pagenum {display:inline; font-size: 70%; font-style:normal; + margin: 0; padding: 0; position: absolute; right: 1%; + text-align: right;} + pre { font-style: italic; font-size: 90%; margin-left: 10%;} + +</style> + </head> + <body> +<pre xml:space="preserve"> + +Project Gutenberg's Darwin and Modern Science, by A.C. Seward and Others + +This eBook is for the use of anyone anywhere at no cost and with +almost no restrictions whatsoever. You may copy it, give it away or +re-use it under the terms of the Project Gutenberg License included +with this eBook or online at www.gutenberg.org + + +Title: Darwin and Modern Science + +Author: A.C. Seward and Others + +Release Date: November 20, 2009 [EBook #1909] +Last Updated: January 22, 2013 + +Language: English + +Character set encoding: ASCII + +*** START OF THIS PROJECT GUTENBERG EBOOK DARWIN AND MODERN SCIENCE *** + + + + +Produced by Sue Asscher, and David Widger + + + + + + +</pre> + <p> + <br /><br /> + </p> + <h1> + DARWIN AND MODERN SCIENCE + </h1> + <h2> + ESSAYS IN COMMEMORATION OF THE CENTENARY OF THE BIRTH OF CHARLES DARWIN + AND OF THE FIFTIETH ANNIVERSARY OF THE PUBLICATION OF "THE ORIGIN OF + SPECIES" + </h2> + <p> + <br /> + </p> + <h2> + By A.C. Seward and Others + </h2> + <p> + <br /> <br /> + </p> + <hr /> + <p> + <br /> <br /> + </p> + <p> + <i> "My success as a man of science, whatever this may have amounted to, + has been determined, as far as I can judge, by complex and diversified + mental qualities and conditions. Of these, the most important have been—the + love of science—unbounded patience in long reflecting over any + subject—industry in observing and collecting facts—and a fair + share of invention as well as of common sense. With such moderate + abilities as I possess, it is truly surprising that I should have + influenced to a considerable extent the belief of scientific men on some + important points." </i> + </p> + <p> + <i>Autobiography (1881); "The Life and Letters of Charles Darwin", Vol. 1. + page 107.</i> + </p> + <p> + <br /> <br /> + </p> + <hr /> + <p> + <br /> <br /> <a name="link2H_PREF" id="link2H_PREF"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + PREFACE + </h2> + <p> + At the suggestion of the Cambridge Philosophical Society, the Syndics of + the University Press decided in March, 1908, to arrange for the + publication of a series of Essays in commemoration of the Centenary of the + birth of Charles Darwin and of the Fiftieth anniversary of the publication + of "The Origin of Species". The preliminary arrangements were made by a + committee consisting of the following representatives of the Council of + the Philosophical Society and of the Press Syndicate: Dr H.K. Anderson, + Prof. Bateson, Mr Francis Darwin, Dr Hobson, Dr Marr, Prof. Sedgwick, Mr + David Sharp, Mr Shipley, Prof. Sorley, Prof. Seward. In the course of the + preparation of the volume, the original scheme and list of authors have + been modified: a few of those invited to contribute essays were, for + various reasons, unable to do so, and some alterations have been made in + the titles of articles. For the selection of authors and for the choice of + subjects, the committee are mainly responsible, but for such share of the + work in the preparation of the volume as usually falls to the lot of an + editor I accept full responsibility. + </p> + <p> + Authors were asked to address themselves primarily to the educated layman + rather than to the expert. It was hoped that the publication of the essays + would serve the double purpose of illustrating the far-reaching influence + of Darwin's work on the progress of knowledge and the present attitude of + original investigators and thinkers towards the views embodied in Darwin's + works. + </p> + <p> + In regard to the interpretation of a passage in "The Origin of Species" + quoted by Hugo de Vries, it seemed advisable to add an editorial footnote; + but, with this exception, I have not felt it necessary to record any + opinion on views stated in the essays. + </p> + <p> + In reading the essays in proof I have availed myself freely of the willing + assistance of several Cambridge friends, among whom I wish more especially + to thank Mr Francis Darwin for the active interest he has taken in the + preparation of the volume. Mrs J.A. Thomson kindly undertook the + translation of the essays by Prof. Weismann and Prof. Schwalbe; Mrs James + Ward was good enough to assist me by translating Prof. Bougle's article on + Sociology, and to Mr McCabe I am indebted for the translation of the essay + by Prof. Haeckel. For the translation of the botanical articles by Prof. + Goebel, Prof. Klebs and Prof. Strasburger, I am responsible; in the + revision of the translation of Prof. Strasburger's essay Madame Errera of + Brussels rendered valuable help. Mr Wright, the Secretary of the Press + Syndicate, and Mr Waller, the Assistant Secretary, have cordially + cooperated with me in my editorial work; nor can I omit to thank the + readers of the University Press for keeping watchful eyes on my + shortcomings in the correction of proofs. + </p> + <p> + The two portraits of Darwin are reproduced by permission of Messrs Maull + and Fox and Messrs Elliott and Fry. The photogravure of the study at Down + is reproduced from an etching by Mr Axel Haig, lent by Mr Francis Darwin; + the coloured plate illustrating Prof. Weismann's essay was originally + published by him in his "Vortrage uber Descendenztheorie" which afterwards + appeared (1904) in English under the title "The Evolution Theory". Copies + of this plate were supplied by Messrs Fischer of Jena. + </p> + <p> + The Syndics of the University Press have agreed, in the event of this + volume being a financial success, to hand over the profits to a University + fund for the endowment of biological research. + </p> + <p> + It is clearly impossible to express adequately in a single volume of + Essays the influence of Darwin's contributions to knowledge on the + subsequent progress of scientific inquiry. As Huxley said in 1885: + "Whatever be the ultimate verdict of posterity upon this or that opinion + which Mr Darwin has propounded; whatever adumbrations or anticipations of + his doctrines may be found in the writings of his predecessors; the broad + fact remains that, since the publication and by reason of the publication + of "The Origin of Species" the fundamental conceptions and the aims of the + students of living Nature have been completely changed... But the impulse + thus given to scientific thought rapidly spread beyond the ordinarily + recognised limits of Biology. Psychology, Ethics, Cosmology were stirred + to their foundations, and 'The Origin of Species' proved itself to be the + fixed point which the general doctrine needed in order to move the world." + </p> + <p> + In the contributions to this Memorial Volume, some of the authors have + more especially concerned themselves with the results achieved by Darwin's + own work, while others pass in review the progress of research on lines + which, though unknown or but little followed in his day, are the direct + outcome of his work. + </p> + <p> + The divergence of views among biologists in regard to the origin of + species and as to the most promising directions in which to seek for truth + is illustrated by the different opinions of contributors. Whether Darwin's + views on the modus operandi of evolutionary forces receive further + confirmation in the future, or whether they are materially modified, in no + way affects the truth of the statement that, by employing his life "in + adding a little to Natural Science," he revolutionised the world of + thought. Darwin wrote in 1872 to Alfred Russel Wallace: "How grand is the + onward rush of science: it is enough to console us for the many errors + which we have committed, and for our efforts being overlaid and forgotten + in the mass of new facts and new views which are daily turning up." In the + onward rush, it is easy for students convinced of the correctness of their + own views and equally convinced of the falsity of those of their + fellow-workers to forget the lessons of Darwin's life. In his + autobiographical sketch, he tells us, "I have steadily endeavoured to keep + my mind free so as to give up any hypothesis, however much beloved...as + soon as facts are shown to be opposed to it." Writing to Mr J. Scott, he + says, "It is a golden rule, which I try to follow, to put every fact which + is opposed to one's preconceived opinion in the strongest light. Absolute + accuracy is the hardest merit to attain, and the highest merit. Any + deviation is ruin." + </p> + <p> + He acted strictly in accordance with his determination expressed in a + letter to Lyell in 1844, "I shall keep out of controversy, and just give + my own facts." As was said of another son of Cambridge, Sir George Stokes, + "He would no more have thought of disputing about priority, or the + authorship of an idea, than of writing a report for a company promoter." + Darwin's life affords a striking confirmation of the truth of Hazlitt's + aphorism, "Where the pursuit of truth has been the habitual study of any + man's life, the love of truth will be his ruling passion." Great as was + the intellect of Darwin, his character, as Huxley wrote, was even nobler + than his intellect. + </p> + <p> + A.C. SEWARD. + </p> + <p> + Botany School, Cambridge, March 20, 1909. + </p> + <p> + <br /> <br /> + </p> + <hr /> + <p> + <br /> <br /> + </p> + <blockquote> + <p class="toc"> + <big><b>CONTENTS</b></big> + </p> + <p> + <br /> + </p> + <p class="toc"> + <a href="#link2H_PREF"> PREFACE </a> + </p> + <p class="toc"> + <a href="#link2H_4_0002"> DATES OF THE PUBLICATION Of CHARLES DARWIN'S + BOOKS AND OF THE PRINCIPAL EVENTS IN HIS LIFE </a> + </p> + <p class="toc"> + <a href="#link2H_4_0003"> I. INTRODUCTORY LETTER From Sir Joseph Dalton + Hooker, O.M., G.C.S.I., C.B., M.D., D.C.L., LL.D., F.R.S., ETC. </a> + </p> + <p class="toc"> + <a href="#link2H_4_0004"> II. DARWIN'S PREDECESSORS. By J. Arthur + Thomson. </a> + </p> + <p class="toc"> + <a href="#link2H_4_0005"> III. THE SELECTION THEORY, By August Weismann. + </a> + </p> + <p class="toc"> + <a href="#link2H_4_0006"> IV. VARIATION. By HUGO DE VRIES. </a> + </p> + <p class="toc"> + <a href="#link2H_4_0007"> V. HEREDITY AND VARIATION IN MODERN LIGHTS. By + W. Bateson, M.A., F.R.S. </a> + </p> + <p class="toc"> + <a href="#link2H_4_0008"> VI. THE MINUTE STRUCTURE OF CELLS IN RELATION + TO HEREDITY. By Eduard Strasburger. </a> + </p> + <p class="toc"> + <a href="#link2H_4_0009"> VII. "THE DESCENT OF MAN". By G. Schwalbe. + </a> + </p> + <p class="toc"> + <a href="#link2H_4_0010"> VIII. CHARLES DARWIN AS AN ANTHROPOLOGIST. By + Ernst Haeckel. </a> + </p> + <p class="toc"> + <a href="#link2H_4_0011"> X. THE INFLUENCE OF DARWIN ON THE STUDY OF + ANIMAL EMBRYOLOGY. By A. Sedgwick, M.A., F.R.S. </a> + </p> + <p class="toc"> + <a href="#link2H_4_0012"> XI. THE PALAEONTOLOGICAL RECORD. By W.B. + Scott. </a> + </p> + <p class="toc"> + <a href="#link2H_4_0013"> XII. THE PALAEONTOLOGICAL RECORD. By D.H. + Scott, F.R.S. </a> + </p> + <p class="toc"> + <a href="#link2H_4_0014"> XIII. THE INFLUENCE OF ENVIRONMENT ON THE + FORMS OF PLANTS. By Georg Klebs, PH.D. </a> + </p> + <p class="toc"> + <a href="#link2H_4_0015"> XIV. EXPERIMENTAL STUDY OF THE INFLUENCE OF + ENVIRONMENT ON ANIMALS. By Jacques Loeb, M.D. Professor of Physiology in + the University of California. </a> + </p> + <p class="toc"> + <a href="#link2H_4_0016"> XV. THE VALUE OF COLOUR IN THE STRUGGLE FOR + LIFE. By E.B. Poulton. </a> + </p> + <p class="toc"> + <a href="#link2H_4_0018"> XVI. GEOGRAPHICAL DISTRIBUTION OF PLANTS. By + Sir William Thiselton-Dyer, K.C.M.G., C.I.E. Sc.D., F.R.S. </a> + </p> + <p class="toc"> + <a href="#link2H_4_0019"> XVII. GEOGRAPHICAL DISTRIBUTION OF ANIMALS. By + Hans Gadow, M.A., Ph.D., F.R.S. </a> + </p> + <p class="toc"> + <a href="#link2H_4_0020"> XVIII. DARWIN AND GEOLOGY. By J.W. Judd, C.B., + LL.D., F.R.S. </a> + </p> + <p class="toc"> + <a href="#link2H_4_0021"> XIX. DARWIN'S WORK ON THE MOVEMENTS OF PLANTS. + By Francis Darwin, </a> + </p> + <p class="toc"> + <a href="#link2H_4_0022"> XX. THE BIOLOGY OF FLOWERS. By K. Goebel, + Ph.D. </a> + </p> + <p class="toc"> + <a href="#link2H_4_0023"> XXI. MENTAL FACTORS IN EVOLUTION. By C. Lloyd + Morgan, LL.D., F.R.S. </a> + </p> + <p class="toc"> + <a href="#link2H_4_0024"> XXII. THE INFLUENCE OF THE CONCEPTION OF + EVOLUTION ON MODERN PHILOSOPHY. By H. Hoffding. </a> + </p> + <p class="toc"> + <a href="#link2H_4_0025"> XXIII. DARWINISM AND SOCIOLOGY. By C. Bougle. + </a> + </p> + <p class="toc"> + <a href="#link2H_4_0026"> XXIV. THE INFLUENCE OF DARWIN UPON RELIGIOUS + THOUGHT. By P.N. Waggett, M.A., S.S.J.E. </a> + </p> + <p class="toc"> + <a href="#link2H_4_0027"> XXV. THE INFLUENCE OF DARWINISM ON THE STUDY + OF RELIGIONS. By Jane Ellen Harrison. </a> + </p> + <p class="toc"> + <a href="#link2H_4_0028"> XXVI. EVOLUTION AND THE SCIENCE OF LANGUAGE. + By P. Giles, M.A., LL.D. (Aberdeen), </a> + </p> + <p class="toc"> + <a href="#link2H_4_0029"> XXVII. DARWINISM AND HISTORY. By J.B. Bury, + Litt.D., LL.D. </a> + </p> + <p class="toc"> + <a href="#link2H_4_0030"> XXVIII. THE GENESIS OF DOUBLE STARS. By Sir + George Darwin, K.C.B., F.R.S. </a> + </p> + <p class="toc"> + <a href="#link2H_4_0031"> XXIX. THE EVOLUTION OF MATTER. By W.C.D. + Whetham, M.A., F.R.S. </a> + </p> + <p class="toc"> + <a href="#link2H_4_0032"> INDEX. </a> + </p> + </blockquote> + <p> + <br /> <br /> + </p> + <hr /> + <p> + <br /> <br /> <a name="link2H_4_0002" id="link2H_4_0002"> + <!-- H2 anchor --> </a> + </p> + <h2> + DATES OF THE PUBLICATION Of CHARLES DARWIN'S BOOKS AND OF THE PRINCIPAL + EVENTS IN HIS LIFE + </h2> + <h3> + 1809: + </h3> + <p> + Charles Darwin born at Shrewsbury, February 12. + </p> + <p> + 1817: + </p> + <p> + "At 8 1/2 years old I went to Mr Case's school." (A day-school at + Shrewsbury kept by the Rev G. Case, Minister of the Unitarian Chapel.) + </p> + <p> + 1818: + </p> + <p> + "I was at school at Shrewsbury under a great scholar, Dr Butler; I learnt + absolutely nothing, except by amusing myself by reading and experimenting + in Chemistry." + </p> + <p> + 1825: + </p> + <p> + "As I was doing no good at school, my father wisely took me away at a + rather earlier age than usual, and sent me (Oct. 1825) to Edinburgh + University with my brother, where I stayed for two years." + </p> + <p> + 1828: + </p> + <p> + Began residence at Christ's College, Cambridge. + </p> + <p> + "I went to Cambridge early in the year 1828, and soon became acquainted + with Professor Henslow...Nothing could be more simple, cordial and + unpretending than the encouragement which he afforded to all young + naturalists." + </p> + <p> + "During the three years which I spent at Cambridge my time was wasted, as + far as the academical studies were concerned, as completely as at + Edinburgh and at school." + </p> + <p> + "In order to pass the B.A. Examination, it was...necessary to get up + Paley's 'Evidences of Christianity,' and his 'Moral Philosophy'... The + careful study of these works, without attempting to learn any part by + rote, was the only part of the academical course which...was of the least + use to me in the education of my mind." + </p> + <p> + 1831: + </p> + <p> + Passed the examination for the B.A. degree in January and kept the + following terms. + </p> + <p> + "I gained a good place among the oi polloi or crowd of men who do not go + in for honours." + </p> + <p> + "I am very busy,...and see a great deal of Henslow, whom I do not know + whether I love or respect most." + </p> + <p> + Dec. 27. "Sailed from England on our circumnavigation," in H.M.S. + "Beagle", a barque of 235 tons carrying 6 guns, under Capt. FitzRoy. + </p> + <p> + "There is indeed a tide in the affairs of men." + </p> + <p> + 1836: + </p> + <p> + Oct. 4. "Reached Shrewsbury after absence of 5 years and 2 days." + </p> + <p> + "You cannot imagine how gloriously delightful my first visit was at home; + it was worth the banishment." + </p> + <p> + Dec. 13. Went to live at Cambridge (Fitzwilliam Street). + </p> + <p> + "The only evil I found in Cambridge was its being too pleasant." + </p> + <p> + 1837: + </p> + <p> + "On my return home (in the 'Beagle') in the autumn of 1836 I immediately + began to prepare my journal for publication, and then saw how many facts + indicated the common descent of species... In July (1837) I opened my + first note-book for facts in relation to the Origin of Species, about + which I had long reflected, and never ceased working for the next twenty + years... Had been greatly struck from about the month of previous March on + character of South American fossils, and species on Galapagos Archipelago. + These facts (especially latter), origin of all my views." + </p> + <p> + "On March 7, 1837 I took lodgings in (36) Great Marlborough Street in + London, and remained there for nearly two years, until I was married." + </p> + <p> + 1838: + </p> + <p> + "In October, that is fifteen months after I had begun my systematic + enquiry, I happened to read for amusement 'Malthus on Population,' and + being well prepared to appreciate the struggle for existence which + everywhere goes on from long-continued observation of the habits of + animals and plants, it at once struck me that under these circumstances + favourable variations would tend to be preserved, and unfavourable ones to + be destroyed. The result of this would be the formation of new species. + Here then I had at last got a theory by which to work; but I was so + anxious to avoid prejudice, that I determined not for some time to write + even the briefest sketch of it." + </p> + <p> + 1839: + </p> + <p> + Married at Maer (Staffordshire) to his first cousin Emma Wedgwood, + daughter of Josiah Wedgwood. + </p> + <p> + "I marvel at my good fortune that she, so infinitely my superior in every + single moral quality, consented to be my wife. She has been my wise + adviser and cheerful comforter throughout life, which without her would + have been during a very long period a miserable one from ill-health. She + has earned the love of every soul near her" (Autobiography). + </p> + <p> + Dec. 31. "Entered 12 Upper Gower street" (now 110 Gower street, London). + "There never was so good a house for me, and I devoutly trust you (his + future wife) will approve of it equally. The little garden is worth its + weight in gold." + </p> + <p> + Published "Journal and Researches", being Vol. III. of the "Narrative of + the Surveying Voyage of H.M.S. 'Adventure' and 'Beagle'"... + </p> + <p> + Publication of the "Zoology of the Voyage of H.M.S. 'Beagle'", Part II., + "Mammalia", by G.R. Waterhouse, with a "Notice of their habits and + ranges", by Charles Darwin. + </p> + <p> + 1840: + </p> + <p> + Contributed Geological Introduction to Part I. ("Fossil Mammalia") of the + "Zoology of the Voyage of H.M.S. 'Beagle'" by Richard Owen. + </p> + <p> + 1842: + </p> + <p> + "In June 1842 I first allowed myself the satisfaction of writing a very + brief abstract of my (species) theory in pencil in 35 pages; and this was + enlarged during the summer of 1844 into one of 230 pages, which I had + fairly copied out and still (1876) possess." (The first draft of "The + Origin of Species", edited by Mr Francis Darwin, will be published this + year (1909) by the Syndics of the Cambridge University Press.) + </p> + <p> + Sept. 14. Settled at the village of Down in Kent. + </p> + <p> + "I think I was never in a more perfectly quiet country." + </p> + <p> + Publication of "The Structure and Distribution of Coral Reefs"; being Part + I. of the "Geology of the Voyage of the Beagle". + </p> + <p> + 1844: + </p> + <p> + Publication of "Geological Observations on the Volcanic Islands visited + during the Voyage of H.M.S. 'Beagle'"; being Part II. of the "Geology of + the Voyage of the 'Beagle'". + </p> + <p> + "I think much more highly of my book on Volcanic Islands since Mr Judd, by + far the best judge on the subject in England, has, as I hear, learnt much + from it." (Autobiography, 1876.) + </p> + <p> + 1845: + </p> + <p> + Publication of the "Journal of Researches" as a separate book. + </p> + <p> + 1846: + </p> + <p> + Publication of "Geological Observations on South America"; being Part III. + of the "Geology of the Voyage of the 'Beagle'". + </p> + <p> + 1851: + </p> + <p> + Publication of a "Monograph of the Fossil Lepadidae" and of a "Monograph + of the sub-class Cirripedia". + </p> + <p> + "I fear the study of the Cirripedia will ever remain 'wholly unapplied,' + and yet I feel that such study is better than castle-building." + </p> + <p> + 1854: + </p> + <p> + Publication of Monographs of the Balanidae and Verrucidae. + </p> + <p> + "I worked steadily on this subject for...eight years, and ultimately + published two thick volumes, describing all the known living species, and + two thin quartos on the extinct species... My work was of considerable use + to me, when I had to discuss in the "Origin of Species" the principles of + a natural classification. Nevertheless, I doubt whether the work was worth + the consumption of so much time." + </p> + <p> + "From September 1854 I devoted my whole time to arranging my huge pile of + notes, to observing, and to experimenting in relation to the transmutation + of species." + </p> + <p> + 1856: + </p> + <p> + "Early in 1856 Lyell advised me to write out my views pretty fully, and I + began at once to do so on a scale three or four times as extensive as that + which was afterwards followed in my 'Origin of Species'." + </p> + <p> + 1858: + </p> + <p> + Joint paper by Charles Darwin and Alfred Russel Wallace "On the Tendency + of Species to form Varieties; and on the perpetuation of Varieties and + Species by Natural Means of Selection," communicated to the Linnean + Society by Sir Charles Lyell and Sir Joseph Hooker. + </p> + <p> + "I was at first very unwilling to consent (to the communication of his MS. + to the Society) as I thought Mr Wallace might consider my doing so + unjustifiable, for I did not then know how generous and noble was his + disposition." + </p> + <p> + "July 20 to Aug. 12 at Sandown (Isle of Wight) began abstract of Species + book." + </p> + <p> + 1859: + </p> + <p> + Nov. 24. Publication of "The Origin of Species" (1250 copies). + </p> + <p> + "Oh, good heavens, the relief to my head and body to banish the whole + subject from my mind!... But, alas, how frequent, how almost universal it + is in an author to persuade himself of the truth of his own dogmas. My + only hope is that I certainly see many difficulties of gigantic stature." + </p> + <p> + 1860: + </p> + <p> + Publication of the second edition of the "Origin" (3000 copies). + </p> + <p> + Publication of a "Naturalist's Voyage". + </p> + <p> + 1861: + </p> + <p> + Publication of the third edition of the "Origin" (2000 copies). + </p> + <p> + "I am going to write a little book... on Orchids, and to-day I hate them + worse than everything." + </p> + <p> + 1862: + </p> + <p> + Publication of the book "On the various contrivances by which Orchids are + fertilised by Insects". + </p> + <p> + 1865: + </p> + <p> + Read paper before the Linnean Society "On the Movements and Habits of + Climbing plants". (Published as a book in 1875.) + </p> + <p> + 1866: + </p> + <p> + Publication of the fourth edition of the "Origin" (1250 copies). + </p> + <p> + 1868: + </p> + <p> + "I have sent the MS. of my big book, and horridly, disgustingly big it + will be, to the printers." + </p> + <p> + Publication of the "Variation of Animals and Plants under Domestication". + </p> + <p> + "About my book, I will give you (Sir Joseph Hooker) a bit of advice. Skip + the whole of Vol. I, except the last chapter, (and that need only be + skimmed), and skip largely in the 2nd volume; and then you will say it is + a very good book." + </p> + <p> + "Towards the end of the work I give my well-abused hypothesis of + Pangenesis. An unverified hypothesis is of little or no value; but if + anyone should hereafter be led to make observations by which some such + hypothesis could be established, I shall have done good service, as an + astonishing number of isolated facts can be thus connected together and + rendered intelligible." + </p> + <p> + 1869: + </p> + <p> + Publication of the fifth edition of the "Origin". + </p> + <p> + 1871: + </p> + <p> + Publication of "The Descent of Man". + </p> + <p> + "Although in the 'Origin of Species' the derivation of any particular + species is never discussed, yet I thought it best, in order that no + honourable man should accuse me of concealing my views, to add that by the + work 'light would be thrown on the origin of man and his history'." + </p> + <p> + 1872: + </p> + <p> + Publication of the sixth edition of the "Origin". + </p> + <p> + Publication of "The Expression of the Emotions in Man and Animals". + </p> + <p> + 1874: + </p> + <p> + Publication of the second edition of "The Descent of Man". + </p> + <p> + "The new edition of the "Descent" has turned out an awful job. It took me + ten days merely to glance over letters and reviews with criticisms and new + facts. It is a devil of a job." + </p> + <p> + Publication of the second edition of "The Structure and Distribution of + Coral Reefs". + </p> + <p> + 1875: + </p> + <p> + Publication of "Insectivorous Plants". + </p> + <p> + "I begin to think that every one who publishes a book is a fool." + </p> + <p> + Publication of the second edition of "Variation in Animals and Plants". + </p> + <p> + Publication of "The Movements and Habits of Climbing Plants" as a separate + book. + </p> + <p> + 1876: + </p> + <p> + Wrote Autobiographical Sketch ("Life and Letters", Vol. I., Chap II.). + </p> + <p> + Publication of "The Effects of Cross and Self fertilisation". + </p> + <p> + "I now (1881) believe, however,...that I ought to have insisted more + strongly than I did on the many adaptations for self-fertilisation." + </p> + <p> + Publication of the second edition of "Observations on Volcanic Islands". + </p> + <p> + 1877: + </p> + <p> + Publication of "The Different Forms of Flowers on Plants of the same + species". + </p> + <p> + "I do not suppose that I shall publish any more books... I cannot endure + being idle, but heaven knows whether I am capable of any more good work." + </p> + <p> + Publication of the second edition of the Orchid book. + </p> + <p> + 1878: + </p> + <p> + Publication of the second edition of "The Effects of Cross and Self + fertilisation". + </p> + <p> + 1879: + </p> + <p> + Publication of an English translation of Ernst Krause's "Erasmus Darwin", + with a notice by Charles Darwin. "I am EXTREMELY glad that you approve of + the little 'Life' of our Grandfather, for I have been repenting that I + ever undertook it, as the work was quite beyond my tether." (To Mr Francis + Galton, Nov. 14, 1879.) + </p> + <p> + 1880: + </p> + <p> + Publication of "The Power of Movement in Plants". + </p> + <p> + "It has always pleased me to exalt plants in the scale of organised + beings." + </p> + <p> + Publication of the second edition of "The Different Forms of Flowers". + </p> + <p> + 1881: + </p> + <p> + Wrote a continuation of the Autobiography. + </p> + <p> + Publication of "The Formation of Vegetable Mould, through the Action of + Worms". + </p> + <p> + "It is the completion of a short paper read before the Geological Society + more than forty years ago, and has revived old geological thoughts... As + far as I can judge it will be a curious little book." + </p> + <p> + 1882: + </p> + <p> + Charles Darwin died at Down, April 19, and was buried in Westminster + Abbey, April 26, in the north aisle of the Nave a few feet from the grave + of Sir Isaac Newton. + </p> + <p> + "As for myself, I believe that I have acted rightly in steadily following + and devoting my life to Science. I feel no remorse from having committed + any great sin, but have often and often regretted that I have not done + more direct good to my fellow creatures." + </p> + <p> + The quotations in the above Epitome are taken from the Autobiography and + published Letters:— + </p> + <p> + "The Life and Letters of Charles Darwin", including an Autobiographical + Chapter. Edited by his son, Francis Darwin, 3 Vols., London, 1887. + </p> + <p> + "Charles Darwin": His life told in an Autobiographical Chapter, and in a + selected series of his published Letters. Edited by his son, Francis + Darwin, London, 1902. + </p> + <p> + "More Letters of Charles Darwin". A record of his work in a series of + hitherto unpublished Letters. Edited by Francis Darwin and A.C. Seward, 2 + Vols., London, 1903. + </p> + <p> + <a name="link2H_4_0003" id="link2H_4_0003"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + I. INTRODUCTORY LETTER From Sir Joseph Dalton Hooker, O.M., G.C.S.I., + C.B., M.D., D.C.L., LL.D., F.R.S., ETC. + </h2> + <p> + The Camp, + </p> + <p> + near Sunningdale, + </p> + <p> + January 15, 1909. + </p> + <p> + Dear Professor Seward, + </p> + <p> + The publication of a Series of Essays in Commemoration of the century of + the birth of Charles Darwin and of the fiftieth anniversary of the + publication of "The Origin of Species" is assuredly welcome and is a + subject of congratulation to all students of Science. + </p> + <p> + These Essays on the progress of Science and Philosophy as affected by + Darwin's labours have been written by men known for their ability to + discuss the problems which he so successfully worked to solve. They cannot + but prove to be of enduring value, whether for the information of the + general reader or as guides to investigators occupied with problems + similar to those which engaged the attention of Darwin. + </p> + <p> + The essayists have been fortunate in having for reference the five + published volumes of Charles Darwin's Life and Correspondence. For there + is set forth in his own words the inception in his mind of the problems, + geological, zoological and botanical, hypothetical and theoretical, which + he set himself to solve and the steps by which he proceeded to investigate + them with the view of correlating the phenomena of life with the evolution + of living things. In his letters he expressed himself in language so lucid + and so little burthened with technical terms that they may be regarded as + models for those who were asked to address themselves primarily to the + educated reader rather than to the expert. + </p> + <p> + I may add that by no one can the perusal of the Essays be more vividly + appreciated than by the writer of these lines. It was my privilege for + forty years to possess the intimate friendship of Charles Darwin and to be + his companion during many of his working hours in Study, Laboratory, and + Garden. I was the recipient of letters from him, relating mainly to the + progress of his researches, the copies of which (the originals are now in + the possession of his family) cover upwards of a thousand pages of + foolscap, each page containing, on an average, three hundred words. + </p> + <p> + That the editorship of these Essays has been entrusted to a Cambridge + Professor of Botany must be gratifying to all concerned in their + production and in their perusal, recalling as it does the fact that + Charles Darwin's instructor in scientific methods was his lifelong friend + the late Rev. J.S. Henslow at that time Professor of Botany in the + University. It was owing to his recommendation that his pupil was + appointed Naturalist to H.M.S. "Beagle", a service which Darwin himself + regarded as marking the dawn of his scientific career. + </p> + <p> + Very sincerely yours, + </p> + <p> + J.D. HOOKER. <a name="link2H_4_0004" id="link2H_4_0004"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + II. DARWIN'S PREDECESSORS. By J. Arthur Thomson. + </h2> + <h3> + Professor of Natural History in the University of Aberdeen. + </h3> + <p> + In seeking to discover Darwin's relation to his predecessors it is useful + to distinguish the various services which he rendered to the theory of + organic evolution. + </p> + <p> + (I) As everyone knows, the general idea of the Doctrine of Descent is that + the plants and animals of the present-day are the lineal descendants of + ancestors on the whole somewhat simpler, that these again are descended + from yet simpler forms, and so on backwards towards the literal "Protozoa" + and "Protophyta" about which we unfortunately know nothing. Now no one + supposes that Darwin originated this idea, which in rudiment at least is + as old as Aristotle. What Darwin did was to make it current intellectual + coin. He gave it a form that commended itself to the scientific and public + intelligence of the day, and he won wide-spread conviction by showing with + consummate skill that it was an effective formula to work with, a key + which no lock refused. In a scholarly, critical, and pre-eminently + fair-minded way, admitting difficulties and removing them, foreseeing + objections and forestalling them, he showed that the doctrine of descent + supplied a modal interpretation of how our present-day fauna and flora + have come to be. + </p> + <p> + (II) In the second place, Darwin applied the evolution-idea to particular + problems, such as the descent of man, and showed what a powerful organon + it is, introducing order into masses of uncorrelated facts, interpreting + enigmas both of structure and function, both bodily and mental, and, best + of all, stimulating and guiding further investigation. But here again it + cannot be claimed that Darwin was original. The problem of the descent or + ascent of man, and other particular cases of evolution, had attracted not + a few naturalists before Darwin's day, though no one (except Herbert + Spencer in the psychological domain (1855)) had come near him in precision + and thoroughness of inquiry. + </p> + <p> + (III) In the third place, Darwin contributed largely to a knowledge of the + factors in the evolution-process, especially by his analysis of what + occurs in the case of domestic animals and cultivated plants, and by his + elaboration of the theory of Natural Selection, which Alfred Russel + Wallace independently stated at the same time, and of which there had been + a few previous suggestions of a more or less vague description. It was + here that Darwin's originality was greatest, for he revealed to + naturalists the many different forms—often very subtle—which + natural selection takes, and with the insight of a disciplined scientific + imagination he realised what a mighty engine of progress it has been and + is. + </p> + <p> + (IV) As an epoch-marking contribution, not only to Aetiology but to + Natural History in the widest sense, we rank the picture which Darwin gave + to the world of the web of life, that is to say, of the inter-relations + and linkages in Nature. For the Biology of the individual—if that be + not a contradiction in terms—no idea is more fundamental than that + of the correlation of organs, but Darwin's most characteristic + contribution was not less fundamental,—it was the idea of the + correlation of organisms. This, again, was not novel; we find it in the + works of naturalist like Christian Conrad Sprengel, Gilbert White, and + Alexander von Humboldt, but the realisation of its full import was + distinctively Darwinian. + </p> + <p> + AS REGARDS THE GENERAL IDEA OF ORGANIC EVOLUTION. + </p> + <p> + While it is true, as Prof. H.F. Osborn puts it, that "'Before and after + Darwin' will always be the ante et post urbem conditam of biological + history," it is also true that the general idea of organic evolution is + very ancient. In his admirable sketch "From the Greeks to Darwin" + ("Columbia University Biological Series", Vol. I. New York and London, + 1894. We must acknowledge our great indebtness to this fine piece of + work.), Prof. Osborn has shown that several of the ancient philosophers + looked upon Nature as a gradual development and as still in process of + change. In the suggestions of Empedocles, to take the best instance, there + were "four sparks of truth,—first, that the development of life was + a gradual process; second, that plants were evolved before animals; third, + that imperfect forms were gradually replaced (not succeeded) by perfect + forms; fourth, that the natural cause of the production of perfect forms + was the extinction of the imperfect." (Op. cit. page 41.) But the + fundamental idea of one stage giving origin to another was absent. As the + blue Aegean teemed with treasures of beauty and threw many upon its + shores, so did Nature produce like a fertile artist what had to be + rejected as well as what was able to survive, but the idea of one species + emerging out of another was not yet conceived. + </p> + <p> + Aristotle's views of Nature (See G.J. Romanes, "Aristotle as a + Naturalist", "Contemporary Review", Vol. LIX. page 275, 1891; G. Pouchet + "La Biologie Aristotelique", Paris, 1885; E. Zeller, "A History of Greek + Philosophy", London, 1881, and "Ueber die griechischen Vorganger + Darwin's", "Abhandl. Berlin Akad." 1878, pages 111-124.) seem to have been + more definitely evolutionist than those of his predecessors, in this + sense, at least, that he recognised not only an ascending scale, but a + genetic series from polyp to man and an age-long movement towards + perfection. "It is due to the resistance of matter to form that Nature can + only rise by degrees from lower to higher types." "Nature produces those + things which, being continually moved by a certain principle contained in + themselves, arrive at a certain end." + </p> + <p> + To discern the outcrop of evolution-doctrine in the long interval between + Aristotle and Bacon seems to be very difficult, and some of the instances + that have been cited strike one as forced. Epicurus and Lucretius, often + called poets of evolution, both pictured animals as arising directly out + of the earth, very much as Milton's lion long afterwards pawed its way + out. Even when we come to Bruno who wrote that "to the sound of the harp + of the Universal Apollo (the World Spirit), the lower organisms are called + by stages to higher, and the lower stages are connected by intermediate + forms with the higher," there is great room, as Prof. Osborn points out + (op. cit. page 81.), for difference of opinion as to how far he was an + evolutionist in our sense of the term. + </p> + <p> + The awakening of natural science in the sixteenth century brought the + possibility of a concrete evolution theory nearer, and in the early + seventeenth century we find evidences of a new spirit—in the + embryology of Harvey and the classifications of Ray. Besides sober + naturalists there were speculative dreamers in the sixteenth and + seventeenth centuries who had at least got beyond static formulae, but, as + Professor Osborn points out (op. cit. page 87.), "it is a very striking + fact, that the basis of our modern methods of studying the Evolution + problem was established not by the early naturalists nor by the + speculative writers, but by the Philosophers." He refers to Bacon, + Descartes, Leibnitz, Hume, Kant, Lessing, Herder, and Schelling. "They + alone were upon the main track of modern thought. It is evident that they + were groping in the dark for a working theory of the Evolution of life, + and it is remarkable that they clearly perceived from the outset that the + point to which observation should be directed was not the past but the + present mutability of species, and further, that this mutability was + simply the variation of individuals on an extended scale." + </p> + <p> + Bacon seems to have been one of the first to think definitely about the + mutability of species, and he was far ahead of his age in his suggestion + of what we now call a Station of Experimental Evolution. Leibnitz + discusses in so many words how the species of animals may be changed and + how intermediate species may once have linked those that now seem + discontinuous. "All natural orders of beings present but a single + chain"... "All advances by degrees in Nature, and nothing by leaps." + Similar evolutionist statements are to be found in the works of the other + "philosophers," to whom Prof. Osborn refers, who were, indeed, more + scientific than the naturalists of their day. It must be borne in mind + that the general idea of organic evolution—that the present is the + child of the past—is in great part just the idea of human history + projected upon the natural world, differentiated by the qualification that + the continuous "Becoming" has been wrought out by forces inherent in the + organisms themselves and in their environment. + </p> + <p> + A reference to Kant (See Brock, "Die Stellung Kant's zur + Deszendenztheorie," "Biol. Centralbl." VIII. 1889, pages 641-648. Fritz + Schultze, "Kant und Darwin", Jena, 1875.) should come in historical order + after Buffon, with whose writings he was acquainted, but he seems, along + with Herder and Schelling, to be best regarded as the culmination of the + evolutionist philosophers—of those at least who interested + themselves in scientific problems. In a famous passage he speaks of "the + agreement of so many kinds of animals in a certain common plan of + structure"... an "analogy of forms" which "strengthens the supposition + that they have an actual blood-relationship, due to derivation from a + common parent." He speaks of "the great Family of creatures, for as a + Family we must conceive it, if the above-mentioned continuous and + connected relationship has a real foundation." Prof. Osborn alludes to the + scientific caution which led Kant, biology being what it was, to refuse to + entertain the hope "that a Newton may one day arise even to make the + production of a blade of grass comprehensible, according to natural laws + ordained by no intention." As Prof. Haeckel finely observes, Darwin rose + up as Kant's Newton. (Mr Alfred Russel Wallace writes: "We claim for + Darwin that he is the Newton of natural history, and that, just so surely + as that the discovery and demonstration by Newton of the law of + gravitation established order in place of chaos and laid a sure foundation + for all future study of the starry heavens, so surely has Darwin, by his + discovery of the law of natural selection and his demonstration of the + great principle of the preservation of useful variations in the struggle + for life, not only thrown a flood of light on the process of development + of the whole organic world, but also established a firm foundation for all + future study of nature." ("Darwinism", London, 1889, page 9). See also + Prof. Karl Pearson's "Grammar of Science" (2nd edition), London, 1900, + page 32. See Osborn, op. cit. Page 100.)) + </p> + <p> + The scientific renaissance brought a wealth of fresh impressions and some + freedom from the tyranny of tradition, and the twofold stimulus stirred + the speculative activity of a great variety of men from old Claude Duret + of Moulins, of whose weird transformism (1609) Dr Henry de Varigny + ("Experimental Evolution". London, 1892. Chap. 1. page 14.) gives us a + glimpse, to Lorenz Oken (1799-1851) whose writings are such mixtures of + sense and nonsense that some regard him as a far-seeing prophet and others + as a fatuous follower of intellectual will-o'-the-wisps. Similarly, for De + Maillet, Maupertuis, Diderot, Bonnet, and others, we must agree with + Professor Osborn that they were not actually in the main Evolution + movement. Some have been included in the roll of honour on very slender + evidence, Robinet for instance, whose evolutionism seems to us extremely + dubious. (See J. Arthur Thomson, "The Science of Life". London, 1899. + Chap. XVI. "Evolution of Evolution Theory".) + </p> + <p> + The first naturalist to give a broad and concrete expression to the + evolutionist doctrine of descent was Buffon (1707-1788), but it is + interesting to recall the fact that his contemporary Linnaeus (1707-1778), + protagonist of the counter-doctrine of the fixity of species (See Carus + Sterne (Ernest Krause), "Die allgemeine Weltanschauung in ihrer + historischen Entwickelung". Stuttgart, 1889. Chapter entitled + "Bestandigkeit oder Veranderlichkeit der Naturwesen".), went the length of + admitting (in 1762) that new species might arise by intercrossing. + Buffon's position among the pioneers of the evolution-doctrine is weakened + by his habit of vacillating between his own conclusions and the orthodoxy + of the Sorbonne, but there is no doubt that he had a firm grasp of the + general idea of "l'enchainement des etres." + </p> + <p> + Erasmus Darwin (1731-1802), probably influenced by Buffon, was another + firm evolutionist, and the outline of his argument in the "Zoonomia" + ("Zoonomia, or the Laws of Organic Life", 2 vols. London, 1794; Osborn op. + cit. page 145.) might serve in part at least to-day. "When we revolve in + our minds the metamorphoses of animals, as from the tadpole to the frog; + secondly, the changes produced by artificial cultivation, as in the breeds + of horses, dogs, and sheep; thirdly, the changes produced by conditions of + climate and of season, as in the sheep of warm climates being covered with + hair instead of wool, and the hares and partridges of northern climates + becoming white in winter: when, further, we observe the changes of + structure produced by habit, as seen especially in men of different + occupations; or the changes produced by artificial mutilation and prenatal + influences, as in the crossing of species and production of monsters; + fourth, when we observe the essential unity of plan in all warm-blooded + animals,—we are led to conclude that they have been alike produced + from a similar living filament"... "From thus meditating upon the minute + portion of time in which many of the above changes have been produced, + would it be too bold to imagine, in the great length of time since the + earth began to exist, perhaps millions of years before the commencement of + the history of mankind, that all warm-blooded animals have arisen from one + living filament?"... "This idea of the gradual generation of all things + seems to have been as familiar to the ancient philosophers as to the + modern ones, and to have given rise to the beautiful hieroglyphic figure + of the proton oon, or first great egg, produced by night, that is, whose + origin is involved in obscurity, and animated by Eros, that is, by Divine + Love; from whence proceeded all things which exist." + </p> + <p> + Lamarck (1744-1829) seems to have become an evolutionist independently of + Erasmus Darwin's influence, though the parallelism between them is + striking. He probably owed something to Buffon, but he developed his + theory along a different line. Whatever view be held in regard to that + theory there is no doubt that Lamarck was a thorough-going evolutionist. + Professor Haeckel speaks of the "Philosophie Zoologique" as "the first + connected and thoroughly logical exposition of the theory of descent." + (See Alpheus S. Packard, "Lamarck, the Founder of Evolution, His Life and + Work, with Translations of his writings on Organic Evolution". London, + 1901.) + </p> + <p> + Besides the three old masters, as we may call them, Buffon, Erasmus + Darwin, and Lamarck, there were other quite convinced pre-Darwinian + evolutionists. The historian of the theory of descent must take account of + Treviranus whose "Biology or Philosophy of Animate Nature" is full of + evolutionary suggestions; of Etienne Geoffroy St Hilaire, who in 1830, + before the French Academy of Sciences, fought with Cuvier, the + fellow-worker of his youth, an intellectual duel on the question of + descent; of Goethe, one of the founders of morphology and the greatest + poet of Evolution—who, in his eighty-first year, heard the tidings + of Geoffroy St Hilaire's defeat with an interest which transcended the + political anxieties of the time; and of many others who had gained with + more or less confidence and clearness a new outlook on Nature. It will be + remembered that Darwin refers to thirty-four more or less evolutionist + authors in his Historical Sketch, and the list might be added to. + Especially when we come near to 1858 do the numbers increase, and one of + the most remarkable, as also most independent champions of the + evolution-idea before that date was Herbert Spencer, who not only + marshalled the arguments in a very forcible way in 1852, but applied the + formula in detail in his "Principles of Psychology" in 1855. (See Edward + Clodd, "Pioneers of Evolution", London, page 161, 1897.) + </p> + <p> + It is right and proper that we should shake ourselves free from all + creationist appreciations of Darwin, and that we should recognise the + services of pre-Darwinian evolutionists who helped to make the time ripe, + yet one cannot help feeling that the citation of them is apt to suggest + two fallacies. It may suggest that Darwin simply entered into the labours + of his predecessors, whereas, as a matter of fact, he knew very little + about them till after he had been for years at work. To write, as Samuel + Butler did, "Buffon planted, Erasmus Darwin and Lamarck watered, but it + was Mr Darwin who said 'That fruit is ripe,' and shook it into his lap"... + seems to us a quite misleading version of the facts of the case. The + second fallacy which the historical citation is a little apt to suggest is + that the filiation of ideas is a simple problem. On the contrary, the + history of an idea, like the pedigree of an organism, is often very + intricate, and the evolution of the evolution-idea is bound up with the + whole progress of the world. Thus in order to interpret Darwin's clear + formulation of the idea of organic evolution and his convincing + presentation of it, we have to do more than go back to his immediate + predecessors, such as Buffon, Erasmus Darwin, and Lamarck; we have to + inquire into the acceptance of evolutionary conceptions in regard to other + orders of facts, such as the earth and the solar system (See Chapter IX. + "The Genetic View of Nature" in J.T. Merz's "History of European Thought + in the Nineteenth Century", Vol. 2, Edinburgh and London, 1903.); we have + to realise how the growing success of scientific interpretation along + other lines gave confidence to those who refused to admit that there was + any domain from which science could be excluded as a trespasser; we have + to take account of the development of philosophical thought, and even of + theological and religious movements; we should also, if we are wise + enough, consider social changes. In short, we must abandon the idea that + we can understand the history of any science as such, without reference to + contemporary evolution in other departments of activity. + </p> + <p> + While there were many evolutionists before Darwin, few of them were expert + naturalists and few were known outside a small circle; what was of much + more importance was that the genetic view of nature was insinuating itself + in regard to other than biological orders of facts, here a little and + there a little, and that the scientific spirit had ripened since the days + when Cuvier laughed Lamarck out of court. How was it that Darwin succeeded + where others had failed? Because, in the first place, he had clear visions—"pensees + de la jeunesse, executees par l'age mur"—which a University + curriculum had not made impossible, which the "Beagle" voyage made vivid, + which an unrivalled British doggedness made real—visions of the web + of life, of the fountain of change within the organism, of the struggle + for existence and its winnowing, and of the spreading genealogical tree. + Because, in the second place, he put so much grit into the verification of + his visions, putting them to the proof in an argument which is of its kind—direct + demonstration being out of the question—quite unequalled. Because, + in the third place, he broke down the opposition which the most scientific + had felt to the seductive modal formula of evolution by bringing forward a + more plausible theory of the process than had been previously suggested. + Nor can one forget, since questions of this magnitude are human and not + merely academic, that he wrote so that all men could understand. + </p> + <p> + AS REGARDS THE FACTORS OF EVOLUTION. + </p> + <p> + It is admitted by all who are acquainted with the history of biology that + the general idea of organic evolution as expressed in the Doctrine of + Descent was quite familiar to Darwin's grandfather, and to others before + and after him, as we have briefly indicated. It must also be admitted that + some of these pioneers of evolutionism did more than apply the + evolution-idea as a modal formula of becoming, they began to inquire into + the factors in the process. Thus there were pre-Darwinian theories of + evolution, and to these we must now briefly refer. (See Prof. W.A. Locy's + "Biology and its Makers". New York, 1908. Part II. "The Doctrine of + Organic Evolution".) + </p> + <p> + In all biological thinking we have to work with the categories Organism—Function—Environment, + and theories of evolution may be classified in relation to these. To some + it has always seemed that the fundamental fact is the living organism,—a + creative agent, a striving will, a changeful Proteus, selecting its + environment, adjusting itself to it, self-differentiating and + self-adaptive. The necessity of recognising the importance of the organism + is admitted by all Darwinians who start with inborn variations, but it is + open to question whether the whole truth of what we might call the + Goethian position is exhausted in the postulate of inherent variability. + </p> + <p> + To others it has always seemed that the emphasis should be laid on + Function,—on use and disuse, on doing and not doing. Practice makes + perfect; c'est a force de forger qu'on devient forgeron. This is one of + the fundamental ideas of Lamarckism; to some extent it met with Darwin's + approval; and it finds many supporters to-day. One of the ablest of these—Mr + Francis Darwin—has recently given strong reasons for combining a + modernised Lamarckism with what we usually regard as sound Darwinism. + (Presidential Address to the British Association meeting at Dublin in + 1908.) + </p> + <p> + To others it has always seemed that the emphasis should be laid on the + Environment, which wakes the organism to action, prompts it to change, + makes dints upon it, moulds it, prunes it, and finally, perhaps, kills it. + It is again impossible to doubt that there is truth in this view, for even + if environmentally induced "modifications" be not transmissible, + environmentally induced "variations" are; and even if the direct influence + of the environment be less important than many enthusiastic supporters of + this view—may we call them Buffonians—think, there remains the + indirect influence which Darwinians in part rely on,—the eliminative + process. Even if the extreme view be held that the only form of + discriminate elimination that counts is inter-organismal competition, this + might be included under the rubric of the animate environment. + </p> + <p> + In many passages Buffon (See in particular Samuel Butler, "Evolution Old + and New", London, 1879; J.L. de Lanessan, "Buffon et Darwin", "Revue + Scientifique", XLIII. pages 385-391, 425-432, 1889.) definitely suggested + that environmental influences—especially of climate and food—were + directly productive of changes in organisms, but he did not discuss the + question of the transmissibility of the modifications so induced, and it + is difficult to gather from his inconsistent writings what extent of + transformation he really believed in. Prof. Osborn says of Buffon: "The + struggle for existence, the elimination of the least-perfected species, + the contest between the fecundity of certain species and their constant + destruction, are all clearly expressed in various passages." He quotes two + of these (op. cit. page 136.): + </p> + <p> + "Le cours ordinaire de la nature vivante, est en general toujours + constant, toujours le meme; son mouvement, toujours regulier, roule sur + deux points inebranlables: l'un, la fecondite sans bornes donnee a toutes + les especes; l'autre, les obstacles sans nombre qui reduisent cette + fecondite a une mesure determinee et ne laissent en tout temps qu'a peu + pres la meme quantite d'individus de chaque espece"... "Les especes les + moins parfaites, les plus delicates, les plus pesantes, les moins + agissantes, les moins armees, etc., ont deja disparu ou disparaitront." + </p> + <p> + Erasmus Darwin (See Ernst Krause and Charles Darwin, "Erasmus Darwin", + London, 1879.) had a firm grip of the "idea of the gradual formation and + improvement of the Animal world," and he had his theory of the process. No + sentence is more characteristic than this: "All animals undergo + transformations which are in part produced by their own exertions, in + response to pleasures and pains, and many of these acquired forms or + propensities are transmitted to their posterity." This is Lamarckism + before Lamarck, as his grandson pointed out. His central idea is that + wants stimulate efforts and that these result in improvements, which + subsequent generations make better still. He realised something of the + struggle for existence and even pointed out that this advantageously + checks the rapid multiplication. "As Dr Krause points out, Darwin just + misses the connection between this struggle and the Survival of the + Fittest." (Osborn op. cit. page 142.) + </p> + <p> + Lamarck (1744-1829) (See E. Perrier "La Philosophie Zoologique avant + Darwin", Paris, 1884; A. de Quatrefages, "Darwin et ses Precurseurs + Francais", Paris, 1870; Packard op. cit.; also Claus, "Lamarck als + Begrunder der Descendenzlehre", Wien, 1888; Haeckel, "Natural History of + Creation", English translation London, 1879; Lang "Zur Charakteristik der + Forschungswege von Lamarck und Darwin", Jena, 1889.) seems to have thought + out his theory of evolution without any knowledge of Erasmus Darwin's + which it closely resembled. The central idea of his theory was the + cumulative inheritance of functional modifications. "Changes in + environment bring about changes in the habits of animals. Changes in their + wants necessarily bring about parallel changes in their habits. If new + wants become constant or very lasting, they form new habits, the new + habits involve the use of new parts, or a different use of old parts, + which results finally in the production of new organs and the modification + of old ones." He differed from Buffon in not attaching importance, as far + as animals are concerned, to the direct influence of the environment, "for + environment can effect no direct change whatever upon the organisation of + animals," but in regard to plants he agreed with Buffon that external + conditions directly moulded them. + </p> + <p> + Treviranus (1776-1837) (See Huxley's article "Evolution in Biology", + "Encyclopaedia Britannica" (9th edit.), 1878, pages 744-751, and Sully's + article, "Evolution in Philosophy", ibid. pages 751-772.), whom Huxley + ranked beside Lamarck, was on the whole Buffonian, attaching chief + importance to the influence of a changeful environment both in modifying + and in eliminating, but he was also Goethian, for instance in his idea + that species like individuals pass through periods of growth, full bloom, + and decline. "Thus, it is not only the great catastrophes of Nature which + have caused extinction, but the completion of cycles of existence, out of + which new cycles have begun." A characteristic sentence is quoted by Prof. + Osborn: "In every living being there exists a capability of an endless + variety of form-assumption; each possesses the power to adapt its + organisation to the changes of the outer world, and it is this power, put + into action by the change of the universe, that has raised the simple + zoophytes of the primitive world to continually higher stages of + organisation, and has introduced a countless variety of species into + animate Nature." + </p> + <p> + Goethe (1749-1832) (See Haeckel, "Die Naturanschauung von Darwin, Goethe + und Lamarck", Jena, 1882.), who knew Buffon's work but not Lamarck's, is + peculiarly interesting as one of the first to use the evolution-idea as a + guiding hypothesis, e.g. in the interpretation of vestigial structures in + man, and to realise that organisms express an attempt to make a compromise + between specific inertia and individual change. He gave the finest + expression that science has yet known—if it has known it—of + the kernel-idea of what is called "bathmism," the idea of an "inherent + growth-force"—and at the same time he held that "the way of life + powerfully reacts upon all form" and that the orderly growth of form + "yields to change from externally acting causes." + </p> + <p> + Besides Buffon, Erasmus Darwin, Lamarck, Treviranus, and Goethe, there + were other "pioneers of evolution," whose views have been often discussed + and appraised. Etienne Geoffroy Saint-Hilaire (1772-1844), whose work + Goethe so much admired, was on the whole Buffonian, emphasising the direct + action of the changeful milieu. "Species vary with their environment, and + existing species have descended by modification from earlier and somewhat + simpler species." He had a glimpse of the selection idea, and believed in + mutations or sudden leaps—induced in the embryonic condition by + external influences. The complete history of evolution-theories will + include many instances of guesses at truth which were afterwards + substantiated, thus the geographer von Buch (1773-1853) detected the + importance of the Isolation factor on which Wagner, Romanes, Gulick and + others have laid great stress, but we must content ourselves with + recalling one other pioneer, the author of the "Vestiges of Creation" + (1844), a work which passed through ten editions in nine years and + certainly helped to harrow the soil for Darwin's sowing. As Darwin said, + "it did excellent service in this country in calling attention to the + subject, in removing prejudice, and in thus preparing the ground for the + reception of analogous views." ("Origin of Species" (6th edition), page + xvii.) Its author, Robert Chambers (1802-1871) was in part a Buffonian—maintaining + that environment moulded organisms adaptively, and in part a Goethian—believing + in an inherent progressive impulse which lifted organisms from one grade + of organisation to another. + </p> + <p> + AS REGARDS NATURAL SELECTION. + </p> + <p> + The only thinker to whom Darwin was directly indebted, so far as the + theory of Natural Selection is concerned, was Malthus, and we may once + more quote the well-known passage in the Autobiography: "In October, 1838, + that is, fifteen months after I had begun my systematic enquiry, I + happened to read for amusement 'Malthus on Population', and being well + prepared to appreciate the struggle for existence which everywhere goes on + from long-continued observation of the habits of animals and plants, it at + once struck me that under these circumstances favourable variations would + tend to be preserved, and unfavourable ones to be destroyed. The result of + this would be the formation of new species." ("The Life and Letters of + Charles Darwin", Vol. 1. page 83. London, 1887.) + </p> + <p> + Although Malthus gives no adumbration of the idea of Natural Selection in + his exposition of the eliminative processes which go on in mankind, the + suggestive value of his essay is undeniable, as is strikingly borne out by + the fact that it gave to Alfred Russel Wallace also "the long-sought clue + to the effective agent in the evolution of organic species." (A.R. + Wallace, "My Life, A Record of Events and Opinions", London, 1905, Vol. 1. + page 232.) One day in Ternate when he was resting between fits of fever, + something brought to his recollection the work of Malthus which he had + read twelve years before. "I thought of his clear exposition of 'the + positive checks to increase'—disease, accidents, war, and famine—which + keep down the population of savage races to so much lower an average than + that of more civilized peoples. It then occurred to me that these causes + or their equivalents are continually acting in the case of animals also; + and as animals usually breed much more rapidly than does mankind, the + destruction every year from these causes must be enormous in order to keep + down the numbers of each species, since they evidently do not increase + regularly from year to year, as otherwise the world would long ago have + been densely crowded with those that breed most quickly. Vaguely thinking + over the enormous and constant destruction which this implied, it occurred + to me to ask the question, Why do some die and some live? And the answer + was clearly, that on the whole the best fitted live. From the effects of + disease the most healthy escaped; from enemies the strongest, the + swiftest, or the most cunning; from famine the best hunters or those with + the best digestion; and so on. Then it suddenly flashed upon me that this + self-acting process would necessarily IMPROVE THE RACE, because in every + generation the inferior would inevitably be killed off and the superior + would remain—that is, THE FITTEST WOULD SURVIVE." (Ibid. Vol. 1. + page 361.) We need not apologise for this long quotation, it is a tribute + to Darwin's magnanimous colleague, the Nestor of the evolutionist camp,—and + it probably indicates the line of thought which Darwin himself followed. + It is interesting also to recall the fact that in 1852, when Herbert + Spencer wrote his famous "Leader" article on "The Development Hypothesis" + in which he argued powerfully for the thesis that the whole animate world + is the result of an age-long process of natural transformation, he wrote + for "The Westminster Review" another important essay, "A Theory of + Population deduced from the General Law of Animal Fertility", towards the + close of which he came within an ace of recognising that the struggle for + existence was a factor in organic evolution. At a time when pressure of + population was practically interesting men's minds, Darwin, Wallace, and + Spencer were being independently led from a social problem to a biological + theory. There could be no better illustration, as Prof. Patrick Geddes has + pointed out, of the Comtian thesis that science is a "social phenomenon." + </p> + <p> + Therefore, as far more important than any further ferreting out of vague + hints of Natural Selection in books which Darwin never read, we would + indicate by a quotation the view that the central idea in Darwinism is + correlated with contemporary social evolution. "The substitution of Darwin + for Paley as the chief interpreter of the order of nature is currently + regarded as the displacement of an anthropomorphic view by a purely + scientific one: a little reflection, however, will show that what has + actually happened has been merely the replacement of the anthropomorphism + of the eighteenth century by that of the nineteenth. For the place vacated + by Paley's theological and metaphysical explanation has simply been + occupied by that suggested to Darwin and Wallace by Malthus in terms of + the prevalent severity of industrial competition, and those phenomena of + the struggle for existence which the light of contemporary economic theory + has enabled us to discern, have thus come to be temporarily exalted into a + complete explanation of organic progress." (P. Geddes, article "Biology", + "Chambers's Encyclopaedia".) It goes without saying that the idea + suggested by Malthus was developed by Darwin into a biological theory + which was then painstakingly verified by being used as an interpretative + formula, and that the validity of a theory so established is not affected + by what suggested it, but the practical question which this line of + thought raises in the mind is this: if Biology did thus borrow with such + splendid results from social theory, why should we not more deliberately + repeat the experiment? + </p> + <p> + Darwin was characteristically frank and generous in admitting that the + principle of Natural Selection had been independently recognised by Dr + W.C. Wells in 1813 and by Mr Patrick Matthew in 1831, but he had no + knowledge of these anticipations when he published the first edition of + "The Origin of Species". Wells, whose "Essay on Dew" is still remembered, + read in 1813 before the Royal Society a short paper entitled "An account + of a White Female, part of whose skin resembles that of a Negro" + (published in 1818). In this communication, as Darwin said, "he observes, + firstly, that all animals tend to vary in some degree, and, secondly, that + agriculturists improve their domesticated animals by selection; and then, + he adds, but what is done in this latter case 'by art, seems to be done + with equal efficacy, though more slowly, by nature, in the formation of + varieties of mankind, fitted for the country which they inhabit.'" + ("Origin of Species" (6th edition) page xv.) Thus Wells had the clear idea + of survival dependent upon a favourable variation, but he makes no more + use of the idea and applies it only to man. There is not in the paper the + least hint that the author ever thought of generalising the remarkable + sentence quoted above. + </p> + <p> + Of Mr Patrick Matthew, who buried his treasure in an appendix to a work on + "Naval Timber and Arboriculture", Darwin said that "he clearly saw the + full force of the principle of natural selection." In 1860 Darwin wrote—very + characteristically—about this to Lyell: "Mr Patrick Matthew + publishes a long extract from his work on "Naval Timber and + Arboriculture", published in 1831, in which he briefly but completely + anticipates the theory of Natural Selection. I have ordered the book, as + some passages are rather obscure, but it is certainly, I think, a complete + but not developed anticipation. Erasmus always said that surely this would + be shown to be the case some day. Anyhow, one may be excused in not having + discovered the fact in a work on Naval Timber." ("Life and Letters" II. + page 301.) + </p> + <p> + De Quatrefages and De Varigny have maintained that the botanist Naudin + stated the theory of evolution by natural selection in 1852. He explains + very clearly the process of artificial selection, and says that in the + garden we are following Nature's method. "We do not think that Nature has + made her species in a different fashion from that in which we proceed + ourselves in order to make our variations." But, as Darwin said, "he does + not show how selection acts under nature." Similarly it must be noted in + regard to several pre-Darwinian pictures of the struggle for existence + (such as Herder's, who wrote in 1790 "All is in struggle... each one for + himself" and so on), that a recognition of this is only the first step in + Darwinism. + </p> + <p> + Profs. E. Perrier and H.F. Osborn have called attention to a remarkable + anticipation of the selection-idea which is to be found in the + speculations of Etienne Geoffroy St Hilaire (1825-1828) on the evolution + of modern Crocodilians from the ancient Teleosaurs. Changing environment + induced changes in the respiratory system and far-reaching consequences + followed. The atmosphere, acting upon the pulmonary cells, brings about + "modifications which are favourable or destructive ('funestes'); these are + inherited, and they influence all the rest of the organisation of the + animal because if these modifications lead to injurious effects, the + animals which exhibit them perish and are replaced by others of a somewhat + different form, a form changed so as to be adapted to (a la convenance) + the new environment." + </p> + <p> + Prof. E.B. Poulton ("Science Progress", New Series, Vol. I. 1897. "A + Remarkable Anticipation of Modern Views on Evolution". See also Chap. VI. + in "Essays on Evolution", Oxford, 1908.) has shown that the anthropologist + James Cowles Prichard (1786-1848) must be included, even in spite of + himself, among the precursors of Darwin. In some passages of the second + edition of his "Researches into the Physical History of Mankind" (1826), + he certainly talks evolution and anticipates Prof. Weismann in denying the + transmission of acquired characters. He is, however, sadly + self-contradictory and his evolutionism weakens in subsequent editions—the + only ones that Darwin saw. Prof. Poulton finds in Prichard's work a + recognition of the operation of Natural Selection. "After enquiring how it + is that 'these varieties are developed and preserved in connection with + particular climates and differences of local situation,' he gives the + following very significant answer: 'One cause which tends to maintain this + relation is obvious. Individuals and families, and even whole colonies, + perish and disappear in climates for which they are, by peculiarity of + constitution, not adapted. Of this fact proofs have been already + mentioned.'" Mr Francis Darwin and Prof. A.C. Seward discuss Prichard's + "anticipations" in "More Letters of Charles Darwin", Vol. I. page 43, and + come to the conclusion that the evolutionary passages are entirely + neutralised by others of an opposite trend. There is the same difficulty + with Buffon. + </p> + <p> + Hints of the idea of Natural Selection have been detected elsewhere. James + Watt (See Prof. Patrick Geddes's article "Variation and Selection", + "Encyclopaedia Britannica (9th edition) 1888.), for instance, has been + reported as one of the anticipators (1851). But we need not prolong the + inquiry further, since Darwin did not know of any anticipations until + after he had published the immortal work of 1859, and since none of those + who got hold of the idea made any use of it. What Darwin did was to follow + the clue which Malthus gave him, to realise, first by genius and + afterwards by patience, how the complex and subtle struggle for existence + works out a natural selection of those organisms which vary in the + direction of fitter adaptation to the conditions of their life. So much + success attended his application of the Selection-formula that for a time + he regarded Natural Selection as almost the sole factor in evolution, + variations being pre-supposed; gradually, however, he came to recognise + that there was some validity in the factors which had been emphasized by + Lamarck and by Buffon, and in his well-known summing up in the sixth + edition of the "Origin" he says of the transformation of species: "This + has been effected chiefly through the natural selection of numerous + successive, slight, favourable variations; aided in an important manner by + the inherited effects of the use and disuse of parts; and in an + unimportant manner, that is, in relation to adaptive structures, whether + past or present, by the direct action of external conditions, and by + variations which seem to us in our ignorance to arise spontaneously." + </p> + <p> + To sum up: the idea of organic evolution, older than Aristotle, slowly + developed from the stage of suggestion to the stage of verification, and + the first convincing verification was Darwin's; from being an a priori + anticipation it has become an interpretation of nature, and Darwin is + still the chief interpreter; from being a modal interpretation it has + advanced to the rank of a causal theory, the most convincing part of which + men will never cease to call Darwinism. + </p> + <p> + <a name="link2H_4_0005" id="link2H_4_0005"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + III. THE SELECTION THEORY, By August Weismann. + </h2> + <h3> + Professor of Zoology in the University of Freiburg (Baden). + </h3> + <p> + I. THE IDEA OF SELECTION. + </p> + <p> + Many and diverse were the discoveries made by Charles Darwin in the course + of a long and strenuous life, but none of them has had so far-reaching an + influence on the science and thought of his time as the theory of + selection. I do not believe that the theory of evolution would have made + its way so easily and so quickly after Darwin took up the cudgels in + favour of it, if he had not been able to support it by a principle which + was capable of solving, in a simple manner, the greatest riddle that + living nature presents to us,—I mean the purposiveness of every + living form relative to the conditions of its life and its marvellously + exact adaptation to these. + </p> + <p> + Everyone knows that Darwin was not alone in discovering the principle of + selection, and that the same idea occurred simultaneously and + independently to Alfred Russel Wallace. At the memorable meeting of the + Linnean Society on 1st July, 1858, two papers were read (communicated by + Lyell and Hooker) both setting forth the same idea of selection. One was + written by Charles Darwin in Kent, the other by Alfred Wallace in Ternate, + in the Malay Archipelago. It was a splendid proof of the magnanimity of + these two investigators, that they thus, in all friendliness and without + envy, united in laying their ideas before a scientific tribunal: their + names will always shine side by side as two of the brightest stars in the + scientific sky. + </p> + <p> + But it is with Charles Darwin that I am here chiefly concerned, since this + paper is intended to aid in the commemoration of the hundredth anniversary + of his birth. + </p> + <p> + The idea of selection set forth by the two naturalists was at the time + absolutely new, but it was also so simple that Huxley could say of it + later, "How extremely stupid not to have thought of that." As Darwin was + led to the general doctrine of descent, not through the labours of his + predecessors in the early years of the century, but by his own + observations, so it was in regard to the principle of selection. He was + struck by the innumerable cases of adaptation, as, for instance, that of + the woodpeckers and tree-frogs to climbing, or the hooks and feather-like + appendages of seeds, which aid in the distribution of plants, and he said + to himself that an explanation of adaptations was the first thing to be + sought for in attempting to formulate a theory of evolution. + </p> + <p> + But since adaptations point to CHANGES which have been undergone by the + ancestral forms of existing species, it is necessary, first of all, to + inquire how far species in general are VARIABLE. Thus Darwin's attention + was directed in the first place to the phenomenon of variability, and the + use man has made of this, from very early times, in the breeding of his + domesticated animals and cultivated plants. He inquired carefully how + breeders set to work, when they wished to modify the structure and + appearance of a species to their own ends, and it was soon clear to him + that SELECTION FOR BREEDING PURPOSES played the chief part. + </p> + <p> + But how was it possible that such processes should occur in free nature? + Who is here the breeder, making the selection, choosing out one individual + to bring forth offspring and rejecting others? That was the problem that + for a long time remained a riddle to him. + </p> + <p> + Darwin himself relates how illumination suddenly came to him. He had been + reading, for his own pleasure, Malthus' book on Population, and, as he had + long known from numerous observations, that every species gives rise to + many more descendants than ever attain to maturity, and that, therefore, + the greater number of the descendants of a species perish without + reproducing, the idea came to him that the decision as to which member of + a species was to perish, and which was to attain to maturity and + reproduction might not be a matter of chance, but might be determined by + the constitution of the individuals themselves, according as they were + more or less fitted for survival. With this idea the foundation of the + theory of selection was laid. + </p> + <p> + In ARTIFICIAL SELECTION the breeder chooses out for pairing only such + individuals as possess the character desired by him in a somewhat higher + degree than the rest of the race. Some of the descendants inherit this + character, often in a still higher degree, and if this method be pursued + throughout several generations, the race is transformed in respect of that + particular character. + </p> + <p> + NATURAL SELECTION depends on the same three factors as ARTIFICIAL + SELECTION: on VARIABILITY, INHERITANCE, and SELECTION FOR BREEDING, but + this last is here carried out not by a breeder but by what Darwin called + the "struggle for existence." This last factor is one of the special + features of the Darwinian conception of nature. That there are carnivorous + animals which take heavy toll in every generation of the progeny of the + animals on which they prey, and that there are herbivores which decimate + the plants in every generation had long been known, but it is only since + Darwin's time that sufficient attention has been paid to the facts that, + in addition to this regular destruction, there exists between the members + of a species a keen competition for space and food, which limits + multiplication, and that numerous individuals of each species perish + because of unfavourable climatic conditions. The "struggle for existence," + which Darwin regarded as taking the place of the human breeder in free + nature, is not a direct struggle between carnivores and their prey, but is + the assumed competition for survival between individuals OF THE SAME + species, of which, on an average, only those survive to reproduce which + have the greatest power of resistance, while the others, less favourably + constituted, perish early. This struggle is so keen, that, within a + limited area, where the conditions of life have long remained unchanged, + of every species, whatever be the degree of fertility, only two, ON AN + AVERAGE, of the descendants of each pair survive; the others succumb + either to enemies, or to disadvantages of climate, or to accident. A high + degree of fertility is thus not an indication of the special success of a + species, but of the numerous dangers that have attended its evolution. Of + the six young brought forth by a pair of elephants in the course of their + lives only two survive in a given area; similarly, of the millions of eggs + which two thread-worms leave behind them only two survive. It is thus + possible to estimate the dangers which threaten a species by its ratio of + elimination, or, since this cannot be done directly, by its fertility. + </p> + <p> + Although a great number of the descendants of each generation fall victims + to accident, among those that remain it is still the greater or lesser + fitness of the organism that determines the "selection for breeding + purposes," and it would be incomprehensible if, in this competition, it + were not ultimately, that is, on an average, the best equipped which + survive, in the sense of living long enough to reproduce. + </p> + <p> + Thus the principle of natural selection is THE SELECTION OF THE BEST FOR + REPRODUCTION, whether the "best" refers to the whole constitution, to one + or more parts of the organism, or to one or more stages of development. + Every organ, every part, every character of an animal, fertility and + intelligence included, must be improved in this manner, and be gradually + brought up in the course of generations to its highest attainable state of + perfection. And not only may improvement of parts be brought about in this + way, but new parts and organs may arise, since, through the slow and + minute steps of individual or "fluctuating" variations, a part may be + added here or dropped out there, and thus something new is produced. + </p> + <p> + The principle of selection solved the riddle as to how what was purposive + could conceivably be brought about without the intervention of a directing + power, the riddle which animate nature presents to our intelligence at + every turn, and in face of which the mind of a Kant could find no way out, + for he regarded a solution of it as not to be hoped for. For, even if we + were to assume an evolutionary force that is continually transforming the + most primitive and the simplest forms of life into ever higher forms, and + the homogeneity of primitive times into the infinite variety of the + present, we should still be unable to infer from this alone how each of + the numberless forms adapted to particular conditions of life should have + appeared PRECISELY AT THE RIGHT MOMENT IN THE HISTORY OF THE EARTH to + which their adaptations were appropriate, and precisely at the proper + place in which all the conditions of life to which they were adapted + occurred: the humming-birds at the same time as the flowers; the trichina + at the same time as the pig; the bark-coloured moth at the same time as + the oak, and the wasp-like moth at the same time as the wasp which + protects it. Without processes of selection we should be obliged to assume + a "pre-established harmony" after the famous Leibnitzian model, by means + of which the clock of the evolution of organisms is so regulated as to + strike in exact synchronism with that of the history of the earth! All + forms of life are strictly adapted to the conditions of their life, and + can persist under these conditions alone. + </p> + <p> + There must therefore be an intrinsic connection between the conditions and + the structural adaptations of the organism, and, SINCE THE CONDITIONS OF + LIFE CANNOT BE DETERMINED BY THE ANIMAL ITSELF, THE ADAPTATIONS MUST BE + CALLED FORTH BY THE CONDITIONS. + </p> + <p> + The selection theory teaches us how this is conceivable, since it enables + us to understand that there is a continual production of what is + non-purposive as well as of what is purposive, but the purposive alone + survives, while the non-purposive perishes in the very act of arising. + This is the old wisdom taught long ago by Empedocles. + </p> + <p> + II. THE LAMARCKIAN PRINCIPLE. + </p> + <p> + Lamarck, as is well known, formulated a definite theory of evolution at + the beginning of the nineteenth century, exactly fifty years before the + Darwin-Wallace principle of selection was given to the world. This + brilliant investigator also endeavoured to support his theory by + demonstrating forces which might have brought about the transformations of + the organic world in the course of the ages. In addition to other factors, + he laid special emphasis on the increased or diminished use of the parts + of the body, assuming that the strengthening or weakening which takes + place from this cause during the individual life, could be handed on to + the offspring, and thus intensified and raised to the rank of a specific + character. Darwin also regarded this LAMARCKIAN PRINCIPLE, as it is now + generally called, as a factor in evolution, but he was not fully convinced + of the transmissibility of acquired characters. + </p> + <p> + As I have here to deal only with the theory of selection, I need not + discuss the Lamarckian hypothesis, but I must express my opinion that + there is room for much doubt as to the cooperation of this principle in + evolution. Not only is it difficult to imagine how the transmission of + functional modifications could take place, but, up to the present time, + notwithstanding the endeavours of many excellent investigators, not a + single actual proof of such inheritance has been brought forward. Semon's + experiments on plants are, according to the botanist Pfeffer, not to be + relied on, and even the recent, beautiful experiments made by Dr Kammerer + on salamanders, cannot, as I hope to show elsewhere, be regarded as proof, + if only because they do not deal at all with functional modifications, + that is, with modifications brought about by use, and it is to these ALONE + that the Lamarckian principle refers. + </p> + <p> + III. OBJECTIONS TO THE THEORY OF SELECTION. + </p> + <p> + (a) Saltatory evolution. + </p> + <p> + The Darwinian doctrine of evolution depends essentially on THE CUMULATIVE + AUGMENTATION of minute variations in the direction of utility. But can + such minute variations, which are undoubtedly continually appearing among + the individuals of the same species, possess any selection-value; can they + determine which individuals are to survive, and which are to succumb; can + they be increased by natural selection till they attain to the highest + development of a purposive variation? + </p> + <p> + To many this seems so improbable that they have urged a theory of + evolution by leaps from species to species. Kolliker, in 1872, compared + the evolution of species with the processes which we can observe in the + individual life in cases of alternation of generations. But a polyp only + gives rise to a medusa because it has itself arisen from one, and there + can be no question of a medusa ever having arisen suddenly and de novo + from a polyp-bud, if only because both forms are adapted in their + structure as a whole, and in every detail to the conditions of their life. + A sudden origin, in a natural way, of numerous adaptations is + inconceivable. Even the degeneration of a medusoid from a free-swimming + animal to a mere brood-sac (gonophore) is not sudden and saltatory, but + occurs by imperceptible modifications throughout hundreds of years, as we + can learn from the numerous stages of the process of degeneration + persisting at the same time in different species. + </p> + <p> + If, then, the degeneration to a simple brood-sac takes place only by very + slow transitions, each stage of which may last for centuries, how could + the much more complex ASCENDING evolution possibly have taken place by + sudden leaps? I regard this argument as capable of further extension, for + wherever in nature we come upon degeneration, it is taking place by minute + steps and with a slowness that makes it not directly perceptible, and I + believe that this in itself justifies us in concluding that THE SAME MUST + BE TRUE OF ASCENDING evolution. But in the latter case the goal can seldom + be distinctly recognised while in cases of degeneration the starting-point + of the process can often be inferred, because several nearly related + species may represent different stages. + </p> + <p> + In recent years Bateson in particular has championed the idea of + saltatory, or so-called discontinuous evolution, and has collected a + number of cases in which more or less marked variations have suddenly + appeared. These are taken for the most part from among domesticated + animals which have been bred and crossed for a long time, and it is hardly + to be wondered at that their much mixed and much influenced germ-plasm + should, under certain conditions, give rise to remarkable phenomena, often + indeed producing forms which are strongly suggestive of monstrosities, and + which would undoubtedly not survive in free nature, unprotected by man. I + should regard such cases as due to an intensified germinal selection—though + this is to anticipate a little—and from this point of view it cannot + be denied that they have a special interest. But they seem to me to have + no significance as far as the transformation of species is concerned, if + only because of the extreme rarity of their occurrence. + </p> + <p> + There are, however, many variations which have appeared in a sudden and + saltatory manner, and some of these Darwin pointed out and discussed in + detail: the copper beech, the weeping trees, the oak with "fern-like + leaves," certain garden-flowers, etc. But none of them have persisted in + free nature, or evolved into permanent types. + </p> + <p> + On the other hand, wherever enduring types have arisen, we find traces of + a gradual origin by successive stages, even if, at first sight, their + origin may appear to have been sudden. This is the case with SEASONAL + DIMORPHISM, the first known cases of which exhibited marked differences + between the two generations, the winter and the summer brood. Take for + instance the much discussed and studied form Vanessa (Araschnia) + levana-prorsa. Here the differences between the two forms are so great and + so apparently disconnected, that one might almost believe it to be a + sudden mutation, were it not that old transition-stages can be called + forth by particular temperatures, and we know other butterflies, as for + instance our Garden Whites, in which the differences between the two + generations are not nearly so marked; indeed, they are so little apparent + that they are scarcely likely to be noticed except by experts. Thus here + again there are small initial steps, some of which, indeed, must be + regarded as adaptations, such as the green-sprinkled or lightly tinted + under-surface which gives them a deceptive resemblance to parsley or to + Cardamine leaves. + </p> + <p> + Even if saltatory variations do occur, we cannot assume that these HAVE + EVER LED TO FORMS WHICH ARE CAPABLE OF SURVIVAL UNDER THE CONDITIONS OF + WILD LIFE. Experience has shown that in plants which have suddenly varied + the power of persistence is diminished. Korschinksky attributes to them + weaknesses of organisation in general; "they bloom late, ripen few of + their seeds, and show great sensitiveness to cold." These are not the + characters which make for success in the struggle for existence. + </p> + <p> + We must briefly refer here to the views—much discussed in the last + decade—of H. de Vries, who believes that the roots of transformation + must be sought for in SALTATORY VARIATIONS ARISING FROM INTERNAL CAUSES, + and distinguishes such MUTATIONS, as he has called them, from ordinary + individual variations, in that they breed true, that is, with strict + inbreeding they are handed on pure to the next generation. I have + elsewhere endeavoured to point out the weaknesses of this theory + ("Vortrage uber Descendenztheorie", Jena, 1904, II. 269. English + Translation London, 1904, II. page 317.), and I am the less inclined to + return to it here that it now appears (See Poulton, "Essays on Evolution", + Oxford, 1908, pages xix-xxii.) that the far-reaching conclusions drawn by + de Vries from his observations on the Evening Primrose, Oenothera + lamarckiana, rest upon a very insecure foundation. The plant from which de + Vries saw numerous "species"—his "mutations"—arise was not, as + he assumed, a WILD SPECIES that had been introduced to Europe from + America, but was probably a hybrid form which was first discovered in the + Jardin des Plantes in Paris, and which does not appear to exist anywhere + in America as a wild species. + </p> + <p> + This gives a severe shock to the "Mutation theory," for the other ACTUALLY + WILD species with which de Vries experimented showed no "mutations" but + yielded only negative results. + </p> + <p> + Thus we come to the conclusion that Darwin ("Origin of Species" (6th + edition), pages 176 et seq.) was right in regarding transformations as + taking place by minute steps, which, if useful, are augmented in the + course of innumerable generations, because their possessors more + frequently survive in the struggle for existence. + </p> + <p> + (b) SELECTION-VALUE OF THE INITIAL STEPS. + </p> + <p> + Is it possible that the significant deviations which we know as + "individual variations" can form the beginning of a process of selection? + Can they decide which is to perish and which to survive? To use a phrase + of Romanes, can they have SELECTION-VALUE? + </p> + <p> + Darwin himself answered this question, and brought together many excellent + examples to show that differences, apparently insignificant because very + small, might be of decisive importance for the life of the possessor. But + it is by no means enough to bring forward cases of this kind, for the + question is not merely whether finished adaptations have selection-value, + but whether the first beginnings of these, and whether the small, I might + almost say minimal increments, which have led up from these beginnings to + the perfect adaptation, have also had selection-value. To this question + even one who, like myself, has been for many years a convinced adherent of + the theory of selection, can only reply: WE MUST ASSUME SO, BUT WE CANNOT + PROVE IT IN ANY CASE. It is not upon demonstrative evidence that we rely + when we champion the doctrine of selection as a scientific truth; we base + our argument on quite other grounds. Undoubtedly there are many apparently + insignificant features, which can nevertheless be shown to be adaptations—for + instance, the thickness of the basin-shaped shell of the limpets that live + among the breakers on the shore. There can be no doubt that the thickness + of these shells, combined with their flat form, protects the animals from + the force of the waves breaking upon them,—but how have they become + so thick? What proportion of thickness was sufficient to decide that of + two variants of a limpet one should survive, the other be eliminated? We + can say nothing more than that we infer from the present state of the + shell, that it must have varied in regard to differences in + shell-thickness, and that these differences must have had selection-value,—no + proof therefore, but an assumption which we must show to be convincing. + </p> + <p> + For a long time the marvellously complex RADIATE and LATTICE-WORK + skeletons of Radiolarians were regarded as a mere outflow of "Nature's + infinite wealth of form," as an instance of a purely morphological + character with no biological significance. But recent investigations have + shown that these, too, have an adaptive significance (Hacker). The same + thing has been shown by Schutt in regard to the lowly unicellular plants, + the Peridineae, which abound alike on the surface of the ocean and in its + depths. It has been shown that the long skeletal processes which grow out + from these organisms have significance not merely as a supporting + skeleton, but also as an extension of the superficial area, which + increases the contact with the water-particles, and prevents the floating + organisms from sinking. It has been established that the processes are + considerably shorter in the colder layers of the ocean, and that they may + be twelve times as long (Chun, "Reise der Valdivia", Leipzig, 1904.) in + the warmer layers, thus corresponding to the greater or smaller amount of + friction which takes place in the denser and less dense layers of the + water. + </p> + <p> + The Peridineae of the warmer ocean layers have thus become long-rayed, + those of the colder layers short-rayed, not through the direct effect of + friction on the protoplasm, but through processes of selection, which + favoured the longer rays in warm water, since they kept the organism + afloat, while those with short rays sank and were eliminated. If we put + the question as to selection-value in this case, and ask how great the + variations in the length of processes must be in order to possess + selection-value; what can we answer except that these variations must have + been minimal, and yet sufficient to prevent too rapid sinking and + consequent elimination? Yet this very case would give the ideal + opportunity for a mathematical calculation of the minimal selection-value, + although of course it is not feasible from lack of data to carry out the + actual calculation. + </p> + <p> + But even in organisms of more than microscopic size there must frequently + be minute, even microscopic differences which set going the process of + selection, and regulate its progress to the highest possible perfection. + </p> + <p> + Many tropical trees possess thick, leathery leaves, as a protection + against the force of the tropical rain drops. The DIRECT influence of the + rain cannot be the cause of this power of resistance, for the leaves, + while they were still thin, would simply have been torn to pieces. Their + toughness must therefore be referred to selection, which would favour the + trees with slightly thicker leaves, though we cannot calculate with any + exactness how great the first stages of increase in thickness must have + been. Our hypothesis receives further support from the fact that, in many + such trees, the leaves are drawn out into a beak-like prolongation (Stahl + and Haberlandt) which facilitates the rapid falling off of the rain water, + and also from the fact that the leaves, while they are still young, hang + limply down in bunches which offer the least possible resistance to the + rain. Thus there are here three adaptations which can only be interpreted + as due to selection. The initial stages of these adaptations must + undoubtedly have had selection-value. + </p> + <p> + But even in regard to this case we are reasoning in a circle, not giving + "proofs," and no one who does not wish to believe in the selection-value + of the initial stages can be forced to do so. Among the many pieces of + presumptive evidence a particularly weighty one seems to me to be THE + SMALLNESS OF THE STEPS OF PROGRESS which we can observe in certain cases, + as for instance in leaf-imitation among butterflies, and in mimicry + generally. The resemblance to a leaf, for instance of a particular + Kallima, seems to us so close as to be deceptive, and yet we find in + another individual, or it may be in many others, a spot added which + increases the resemblance, and which could not have become fixed unless + the increased deceptiveness so produced had frequently led to the + overlooking of its much persecuted possessor. But if we take the + selection-value of the initial stages for granted, we are confronted with + the further question which I myself formulated many years ago: How does it + happen THAT THE NECESSARY BEGINNINGS OF A USEFUL VARIATION ARE ALWAYS + PRESENT? How could insects which live upon or among green leaves become + all green, while those that live on bark become brown? How have the desert + animals become yellow and the Arctic animals white? Why were the necessary + variations always present? How could the green locust lay brown eggs, or + the privet caterpillar develop white and lilac-coloured lines on its green + skin? + </p> + <p> + It is of no use answering to this that the question is wrongly formulated + (Plate, "Selektionsprinzip u. Probleme der Artbildung" (3rd edition), + Leipzig, 1908.) and that it is the converse that is true; that the process + of selection takes place in accordance with the variations that present + themselves. This proposition is undeniably true, but so also is another, + which apparently negatives it: the variation required has in the majority + of cases actually presented itself. Selection cannot solve this + contradiction; it does not call forth the useful variation, but simply + works upon it. The ultimate reason why one and the same insect should + occur in green and in brown, as often happens in caterpillars and locusts, + lies in the fact that variations towards brown presented themselves, and + so also did variations towards green: THE KERNEL OF THE RIDDLE LIES IN THE + VARYING, and for the present we can only say, that small variations in + different directions present themselves in every species. Otherwise so + many different kinds of variations could not have arisen. I have + endeavoured to explain this remarkable fact by means of the intimate + processes that must take place within the germ-plasm, and I shall return + to the problem when dealing with "germinal selection." + </p> + <p> + We have, however, to make still greater demands on variation, for it is + not enough that the necessary variation should occur in isolated + individuals, because in that case there would be small prospect of its + being preserved, notwithstanding its utility. Darwin at first believed, + that even single variations might lead to transformation of the species, + but later he became convinced that this was impossible, at least without + the cooperation of other factors, such as isolation and sexual selection. + </p> + <p> + In the case of the GREEN CATERPILLARS WITH BRIGHT LONGITUDINAL STRIPES, + numerous individuals exhibiting this useful variation must have been + produced to start with. In all higher, that is, multicellular organisms, + the germ-substance is the source of all transmissible variations, and this + germ-plasm is not a simple substance but is made up of many primary + constituents. The question can therefore be more precisely stated thus: + How does it come about that in so many cases the useful variations present + themselves in numbers just where they are required, the white oblique + lines in the leaf-caterpillar on the under surface of the body, the + accompanying coloured stripes just above them? And, further, how has it + come about that in grass caterpillars, not oblique but longitudinal + stripes, which are more effective for concealment among grass and plants, + have been evolved? And finally, how is it that the same Hawk-moth + caterpillars, which to-day show oblique stripes, possessed longitudinal + stripes in Tertiary times? We can read this fact from the history of their + development, and I have before attempted to show the biological + significance of this change of colour. ("Studien zur Descendenz-Theorie" + II., "Die Enstehung der Zeichnung bei den Schmetterlings-raupen," Leipzig, + 1876.) + </p> + <p> + For the present I need only draw the conclusion that one and the same + caterpillar may exhibit the initial stages of both, and that it depends on + the manner in which these marking elements are INTENSIFIED and COMBINED by + natural selection whether whitish longitudinal or oblique stripes should + result. In this case then the "useful variations" were actually "always + there," and we see that in the same group of Lepidoptera, e.g. species of + Sphingidae, evolution has occurred in both directions according to whether + the form lived among grass or on broad leaves with oblique lateral veins, + and we can observe even now that the species with oblique stripes have + longitudinal stripes when young, that is to say, while the stripes have no + biological significance. The white places in the skin which gave rise, + probably first as small spots, to this protective marking could be + combined in one way or another according to the requirements of the + species. They must therefore either have possessed selection-value from + the first, or, if this was not the case at their earliest occurrence, + there must have been SOME OTHER FACTORS which raised them to the point of + selection-value. I shall return to this in discussing germinal selection. + But the case may be followed still farther, and leads us to the same + alternative on a still more secure basis. + </p> + <p> + Many years ago I observed in caterpillars of Smerinthus populi (the poplar + hawk-moth), which also possess white oblique stripes, that certain + individuals showed RED SPOTS above these stripes; these spots occurred + only on certain segments, and never flowed together to form continuous + stripes. In another species (Smerinthus tiliae) similar blood-red spots + unite to form a line-like coloured seam in the last stage of larval life, + while in S. ocellata rust-red spots appear in individual caterpillars, but + more rarely than in S. Populi, and they show no tendency to flow together. + </p> + <p> + Thus we have here the origin of a new character, arising from small + beginnings, at least in S. tiliae, in which species the coloured stripes + are a normal specific character. In the other species, S. populi and S. + ocellata, we find the beginnings of the same variation, in one more rarely + than in the other, and we can imagine that, in the course of time, in + these two species, coloured lines over the oblique stripes will arise. In + any case these spots are the elements of variation, out of which coloured + lines MAY be evolved, if they are combined in this direction through the + agency of natural selection. In S. populi the spots are often small, but + sometimes it seems as though several had united to form large spots. + Whether a process of selection in this direction will arise in S. populi + and S. ocellata, or whether it is now going on cannot be determined, since + we cannot tell in advance what biological value the marking might have for + these two species. It is conceivable that the spots may have no + selection-value as far as these species are concerned, and may therefore + disappear again in the course of phylogeny, or, on the other hand, that + they may be changed in another direction, for instance towards imitation + of the rust-red fungoid patches on poplar and willow leaves. In any case + we may regard the smallest spots as the initial stages of variation, the + larger as a cumulative summation of these. Therefore either these initial + stages must already possess selection-value, or, as I said before: THERE + MUST BE SOME OTHER REASON FOR THEIR CUMULATIVE SUMMATION. I should like to + give one more example, in which we can infer, though we cannot directly + observe, the initial stages. + </p> + <p> + All the Holothurians or sea-cucumbers have in the skin calcareous bodies + of different forms, usually thick and irregular, which make the skin tough + and resistant. In a small group of them—the species of Synapta—the + calcareous bodies occur in the form of delicate anchors of microscopic + size. Up till 1897 these anchors, like many other delicate microscopic + structures, were regarded as curiosities, as natural marvels. But a + Swedish observer, Oestergren, has recently shown that they have a + biological significance: they serve the footless Synapta as auxiliary + organs of locomotion, since, when the body swells up in the act of + creeping, they press firmly with their tips, which are embedded in the + skin, against the substratum on which the animal creeps, and thus prevent + slipping backwards. In other Holothurians this slipping is made impossible + by the fixing of the tube-feet. The anchors act automatically, sinking + their tips towards the ground when the corresponding part of the body + thickens, and returning to the original position at an angle of 45 degrees + to the upper surface when the part becomes thin again. The arms of the + anchor do not lie in the same plane as the shaft, and thus the curve of + the arms forms the outermost part of the anchor, and offers no further + resistance to the gliding of the animal. Every detail of the anchor, the + curved portion, the little teeth at the head, the arms, etc., can be + interpreted in the most beautiful way, above all the form of the anchor + itself, for the two arms prevent it from swaying round to the side. The + position of the anchors, too, is definite and significant; they lie + obliquely to the longitudinal axis of the animal, and therefore they act + alike whether the animal is creeping backwards or forwards. Moreover, the + tips would pierce through the skin if the anchors lay in the longitudinal + direction. Synapta burrows in the sand; it first pushes in the thin + anterior end, and thickens this again, thus enlarging the hole, then the + anterior tentacles displace more sand, the body is worked in a little + farther, and the process begins anew. In the first act the anchors are + passive, but they begin to take an active share in the forward movement + when the body is contracted again. Frequently the animal retains only the + posterior end buried in the sand, and then the anchors keep it in + position, and make rapid withdrawal possible. + </p> + <p> + Thus we have in these apparently random forms of the calcareous bodies, + complex adaptations in which every little detail as to direction, curve, + and pointing is exactly determined. That they have selection-value in + their present perfected form is beyond all doubt, since the animals are + enabled by means of them to bore rapidly into the ground and so to escape + from enemies. We do not know what the initial stages were, but we cannot + doubt that the little improvements, which occurred as variations of the + originally simple slimy bodies of the Holothurians, were preserved because + they already possessed selection-value for the Synaptidae. For such minute + microscopic structures whose form is so delicately adapted to the role + they have to play in the life of the animal, cannot have arisen suddenly + and as a whole, and every new variation of the anchor, that is, in the + direction of the development of the two arms, and every curving of the + shaft which prevented the tips from projecting at the wrong time, in + short, every little adaptation in the modelling of the anchor must have + possessed selection-value. And that such minute changes of form fall + within the sphere of fluctuating variations, that is to say, THAT THEY + OCCUR is beyond all doubt. + </p> + <p> + In many of the Synaptidae the anchors are replaced by calcareous rods bent + in the form of an S, which are said to act in the same way. Others, such + as those of the genus Ankyroderma, have anchors which project considerably + beyond the skin, and, according to Oestergren, serve "to catch + plant-particles and other substances" and so mask the animal. Thus we see + that in the Synaptidae the thick and irregular calcareous bodies of the + Holothurians have been modified and transformed in various ways in + adaptation to the footlessness of these animals, and to the peculiar + conditions of their life, and we must conclude that the earlier stages of + these changes presented themselves to the processes of selection in the + form of microscopic variations. For it is as impossible to think of any + origin other than through selection in this case as in the case of the + toughness, and the "drip-tips" of tropical leaves. And as these last could + not have been produced directly by the beating of the heavy rain-drops + upon them, so the calcareous anchors of Synapta cannot have been produced + directly by the friction of the sand and mud at the bottom of the sea, + and, since they are parts whose function is PASSIVE the Lamarckian factor + of use and disuse does not come into question. The conclusion is + unavoidable, that the microscopically small variations of the calcareous + bodies in the ancestral forms have been intensified and accumulated in a + particular direction, till they have led to the formation of the anchor. + Whether this has taken place by the action of natural selection alone, or + whether the laws of variation and the intimate processes within the + germ-plasm have cooperated will become clear in the discussion of germinal + selection. This whole process of adaptation has obviously taken place + within the time that has elapsed since this group of sea-cucumbers lost + their tube-feet, those characteristic organs of locomotion which occur in + no group except the Echinoderms, and yet have totally disappeared in the + Synaptidae. And after all what would animals that live in sand and mud do + with tube-feet? + </p> + <p> + (c) COADAPTATION. + </p> + <p> + Darwin pointed out that one of the essential differences between + artificial and natural selection lies in the fact that the former can + modify only a few characters, usually only one at a time, while Nature + preserves in the struggle for existence all the variations of a species, + at the same time and in a purely mechanical way, if they possess + selection-value. + </p> + <p> + Herbert Spencer, though himself an adherent of the theory of selection, + declared in the beginning of the nineties that in his opinion the range of + this principle was greatly over-estimated, if the great changes which have + taken place in so many organisms in the course of ages are to be + interpreted as due to this process of selection alone, since no + transformation of any importance can be evolved by itself; it is always + accompanied by a host of secondary changes. He gives the familiar example + of the Giant Stag of the Irish peat, the enormous antlers of which + required not only a much stronger skull cap, but also greater strength of + the sinews, muscles, nerves and bones of the whole anterior half of the + animal, if their mass was not to weigh down the animal altogether. It is + inconceivable, he says, that so many processes of selection should take + place SIMULTANEOUSLY, and we are therefore forced to fall back on the + Lamarckian factor of the use and disuse of functional parts. And how, he + asks, could natural selection follow two opposite directions of evolution + in different parts of the body at the same time, as for instance in the + case of the kangaroo, in which the forelegs must have become shorter, + while the hind legs and the tail were becoming longer and stronger? + </p> + <p> + Spencer's main object was to substantiate the validity of the Lamarckian + principle, the cooperation of which with selection had been doubted by + many. And it does seem as though this principle, if it operates in nature + at all, offers a ready and simple explanation of all such secondary + variations. Not only muscles, but nerves, bones, sinews, in short all + tissues which function actively, increase in strength in proportion as + they are used, and conversely they decrease when the claims on them + diminish. All the parts, therefore, which depend on the part that varied + first, as for instance the enlarged antlers of the Irish Elk, must have + been increased or decreased in strength, in exact proportion to the claims + made upon them,—just as is actually the case. + </p> + <p> + But beautiful as this explanation would be, I regard it as untenable, + because it assumes the TRANSMISSIBILITY OF FUNCTIONAL MODIFICATIONS + (so-called "acquired" characters), and this is not only undemonstrable, + but is scarcely theoretically conceivable, for the secondary variations + which accompany or follow the first as correlative variations, occur also + in cases in which the animals concerned are sterile and THEREFORE CANNOT + TRANSMIT ANYTHING TO THEIR DESCENDANTS. This is true of WORKER BEES, and + particularly of ANTS, and I shall here give a brief survey of the present + state of the problem as it appears to me. + </p> + <p> + Much has been written on both sides of this question since the published + controversy on the subject in the nineties between Herbert Spencer and + myself. I should like to return to the matter in detail, if the space at + my disposal permitted, because it seems to me that the arguments I + advanced at that time are equally cogent to-day, notwithstanding all the + objections that have since been urged against them. Moreover, the matter + is by no means one of subordinate interest; it is the very kernel of the + whole question of the reality and value of the principle of selection. For + if selection alone does not suffice to explain "HARMONIOUS ADAPTATION" as + I have called Spencer's COADAPTATION, and if we require to call in the aid + of the Lamarckian factor it would be questionable whether selection could + explain any adaptations whatever. In this particular case—of worker + bees—the Lamarckian factor may be excluded altogether, for it can be + demonstrated that here at any rate the effects of use and disuse cannot be + transmitted. + </p> + <p> + But if it be asked why we are unwilling to admit the cooperation of the + Darwinian factor of selection and the Lamarckian factor, since this would + afford us an easy and satisfactory explanation of the phenomena, I answer: + BECAUSE THE LAMARCKIAN PRINCIPLE IS FALLACIOUS, AND BECAUSE BY ACCEPTING + IT WE CLOSE THE WAY TOWARDS DEEPER INSIGHT. It is not a spirit of + combativeness or a desire for self-vindication that induces me to take the + field once more against the Lamarckian principle, it is the conviction + that the progress of our knowledge is being obstructed by the acceptance + of this fallacious principle, since the facile explanation it apparently + affords prevents our seeking after a truer explanation and a deeper + analysis. + </p> + <p> + The workers in the various species of ants are sterile, that is to say, + they take no regular part in the reproduction of the species, although + individuals among them may occasionally lay eggs. In addition to this they + have lost the wings, and the receptaculum seminis, and their compound eyes + have degenerated to a few facets. How could this last change have come + about through disuse, since the eyes of workers are exposed to light in + the same way as are those of the sexual insects and thus in this + particular case are not liable to "disuse" at all? The same is true of the + receptaculum seminis, which can only have been disused as far as its + glandular portion and its stalk are concerned, and also of the wings, the + nerves tracheae and epidermal cells of which could not cease to function + until the whole wing had degenerated, for the chitinous skeleton of the + wing does not function at all in the active sense. + </p> + <p> + But, on the other hand, the workers in all species have undergone + modifications in a positive direction, as, for instance, the greater + development of brain. In many species large workers have evolved,—the + so-called SOLDIERS, with enormous jaws and teeth, which defend the colony,—and + in others there are SMALL workers which have taken over other special + functions, such as the rearing of the young Aphides. This kind of division + of the workers into two castes occurs among several tropical species of + ants, but it is also present in the Italian species, Colobopsis truncata. + Beautifully as the size of the jaws could be explained as due to the + increased use made of them by the "soldiers," or the enlarged brain as due + to the mental activities of the workers, the fact of the infertility of + these forms is an insurmountable obstacle to accepting such an + explanation. Neither jaws nor brain can have been evolved on the + Lamarckian principle. + </p> + <p> + The problem of coadaptation is no easier in the case of the ant than in + the case of the Giant Stag. Darwin himself gave a pretty illustration to + show how imposing the difference between the two kinds of workers in one + species would seem if we translated it into human terms. In regard to the + Driver ants (Anomma) we must picture to ourselves a piece of work, "for + instance the building of a house, being carried on by two kinds of + workers, of which one group was five feet four inches high, the other + sixteen feet high." ("Origin of Species" (6th edition), page 232.) + </p> + <p> + Although the ant is a small animal as compared with man or with the Irish + Elk, the "soldier" with its relatively enormous jaws is hardly less + heavily burdened than the Elk with its antlers, and in the ant's case, + too, a strengthening of the skeleton, of the muscles, the nerves of the + head, and of the legs must have taken place parallel with the enlargement + of the jaws. HARMONIOUS ADAPTATION (coadaptation) has here been active in + a high degree, and yet these "soldiers" are sterile! There thus remains + nothing for it but to refer all their adaptations, positive and negative + alike, to processes of selection which have taken place in the rudiments + of the workers within the egg and sperm-cells of their parents. There is + no way out of the difficulty except the one Darwin pointed out. He himself + did not find the solution of the riddle at once. At first he believed that + the case of the workers among social insects presented "the most serious + special difficulty" in the way of his theory of natural selection; and it + was only after it had become clear to him, that it was not the sterile + insects themselves but their parents that were selected, according as they + produced more or less well adapted workers, that he was able to refer to + this very case of the conditions among ants "IN ORDER TO SHOW THE POWER OF + NATURAL SELECTION" ("Origin of Species", page 233; see also edition 1, + page 242.). He explains his view by a simple but interesting illustration. + Gardeners have produced, by means of long continued artificial selection, + a variety of Stock, which bears entirely double, and therefore infertile + flowers (Ibid. page 230.). Nevertheless the variety continues to be + reproduced from seed, because in addition to the double and infertile + flowers, the seeds always produce a certain number of single, fertile + blossoms, and these are used to reproduce the double variety. These single + and fertile plants correspond "to the males and females of an ant-colony, + the infertile plants, which are regularly produced in large numbers, to + the neuter workers of the colony." + </p> + <p> + This illustration is entirely apt, the only difference between the two + cases consisting in the fact that the variation in the flower is not a + useful, but a disadvantageous one, which can only be preserved by + artificial selection on the part of the gardener, while the + transformations that have taken place parallel with the sterility of the + ants are useful, since they procure for the colony an advantage in the + struggle for existence, and they are therefore preserved by natural + selection. Even the sterility itself in this case is not disadvantageous, + since the fertility of the true females has at the same time considerably + increased. We may therefore regard the sterile forms of ants, which have + gradually been adapted in several directions to varying functions, AS A + CERTAIN PROOF that selection really takes place in the germ-cells of the + fathers and mothers of the workers, and that SPECIAL COMPLEXES OF + PRIMORDIA (IDS) are present in the workers and in the males and females, + and these complexes contain the primordia of the individual parts + (DETERMINANTS). But since all living entities vary, the determinants must + also vary, now in a favourable, now in an unfavourable direction. If a + female produces eggs, which contain favourably varying determinants in the + worker-ids, then these eggs will give rise to workers modified in the + favourable direction, and if this happens with many females, the colony + concerned will contain a better kind of worker than other colonies. + </p> + <p> + I digress here in order to give an account of the intimate processes, + which, according to my view, take place within the germ-plasm, and which I + have called "GERMINAL SELECTION." These processes are of importance since + they form the roots of variation, which in its turn is the root of natural + selection. I cannot here do more than give a brief outline of the theory + in order to show how the Darwin-Wallace theory of selection has gained + support from it. + </p> + <p> + With others, I regard the minimal amount of substance which is contained + within the nucleus of the germ-cells, in the form of rods, bands, or + granules, as the GERM-SUBSTANCE or GERM-PLASM, and I call the individual + granules IDS. There is always a multiplicity of such ids present in the + nucleus, either occurring individually, or united in the form of rods or + bands (chromosomes). Each id contains the primary constituents of a WHOLE + individual, so that several ids are concerned in the development of a new + individual. + </p> + <p> + In every being of complex structure thousands of primary constituents must + go to make up a single id; these I call DETERMINANTS, and I mean by this + name very small individual particles, far below the limits of microscopic + visibility, vital units which feed, grow, and multiply by division. These + determinants control the parts of the developing embryo,—in what + manner need not here concern us. The determinants differ among themselves, + those of a muscle are differently constituted from those of a nerve-cell + or a glandular cell, etc., and every determinant is in its turn made up of + minute vital units, which I call BIOPHORS, or the bearers of life. + According to my view, these determinants not only assimilate, like every + other living unit, but they VARY in the course of their growth, as every + living unit does; they may vary qualitatively if the elements of which + they are composed vary, they may grow and divide more or less rapidly, and + their variations give rise to CORRESPONDING variations of the organ, cell, + or cell-group which they determine. That they are undergoing ceaseless + fluctuations in regard to size and quality seems to me the inevitable + consequence of their unequal nutrition; for although the germ-cell as a + whole usually receives sufficient nutriment, minute fluctuations in the + amount carried to different parts within the germ-plasm cannot fail to + occur. + </p> + <p> + Now, if a determinant, for instance of a sensory cell, receives for a + considerable time more abundant nutriment than before, it will grow more + rapidly—become bigger, and divide more quickly, and, later, when the + id concerned develops into an embryo, this sensory cell will become + stronger than in the parents, possibly even twice as strong. This is an + instance of a HEREDITARY INDIVIDUAL VARIATION, arising from the germ. + </p> + <p> + The nutritive stream which, according to our hypothesis, favours the + determinant N by chance, that is, for reasons unknown to us, may remain + strong for a considerable time, or may decrease again; but even in the + latter case it is conceivable that the ascending movement of the + determinant may continue, because the strengthened determinant now + ACTIVELY nourishes itself more abundantly,—that is to say, it + attracts the nutriment to itself, and to a certain extent withdraws it + from its fellow-determinants. In this way, it may—as it seems to me—get + into PERMANENT UPWARD MOVEMENT, AND ATTAIN A DEGREE OF STRENGTH FROM WHICH + THERE IS NO FALLING BACK. Then positive or negative selection sets in, + favouring the variations which are advantageous, setting aside those which + are disadvantageous. + </p> + <p> + In a similar manner a DOWNWARD variation of the determinants may take + place, if its progress be started by a diminished flow of nutriment. The + determinants which are weakened by this diminished flow will have less + affinity for attracting nutriment because of their diminished strength, + and they will assimilate more feebly and grow more slowly, unless chance + streams of nutriment help them to recover themselves. But, as will + presently be shown, a change of direction cannot take place at EVERY stage + of the degenerative process. If a certain critical stage of downward + progress be passed, even favourable conditions of food-supply will no + longer suffice permanently to change the direction of the variation. Only + two cases are conceivable; if the determinant corresponds to a USEFUL + organ, only its removal can bring back the germ-plasm to its former level; + therefore personal selection removes the id in question, with its + determinants, from the germ-plasm, by causing the elimination of the + individual in the struggle for existence. But there is another conceivable + case; the determinants concerned may be those of an organ which has become + USELESS, and they will then continue unobstructed, but with exceeding + slowness, along the downward path, until the organ becomes vestigial, and + finally disappears altogether. + </p> + <p> + The fluctuations of the determinants hither and thither may thus be + transformed into a lasting ascending or descending movement; and THIS IS + THE CRUCIAL POINT OF THESE GERMINAL PROCESSES. + </p> + <p> + This is not a fantastic assumption; we can read it in the fact of the + degeneration of disused parts. USELESS ORGANS ARE THE ONLY ONES WHICH ARE + NOT HELPED TO ASCEND AGAIN BY PERSONAL SELECTION, AND THEREFORE IN THEIR + CASE ALONE CAN WE FORM ANY IDEA OF HOW THE PRIMARY CONSTITUENTS BEHAVE, + WHEN THEY ARE SUBJECT SOLELY TO INTRA-GERMINAL FORCES. + </p> + <p> + The whole determinant system of an id, as I conceive it, is in a state of + continual fluctuation upwards and downwards. In most cases the + fluctuations will counteract one another, because the passive streams of + nutriment soon change, but in many cases the limit from which a return is + possible will be passed, and then the determinants concerned will continue + to vary in the same direction, till they attain positive or negative + selection-value. At this stage personal selection intervenes and sets + aside the variation if it is disadvantageous, or favours—that is to + say, preserves—it if it is advantageous. Only THE DETERMINANT OF A + USELESS ORGAN IS UNINFLUENCED BY PERSONAL SELECTION, and, as experience + shows, it sinks downwards; that is, the organ that corresponds to it + degenerates very slowly but uninterruptedly till, after what must + obviously be an immense stretch of time, it disappears from the germ-plasm + altogether. + </p> + <p> + Thus we find in the fact of the degeneration of disused parts the proof + that not all the fluctuations of a determinant return to equilibrium + again, but that, when the movement has attained to a certain strength, it + continues IN THE SAME DIRECTION. We have entire certainty in regard to + this as far as the downward progress is concerned, and we must assume it + also in regard to ascending variations, as the phenomena of artificial + selection certainly justify us in doing. If the Japanese breeders were + able to lengthen the tail feathers of the cock to six feet, it can only + have been because the determinants of the tail-feathers in the germ-plasm + had already struck out a path of ascending variation, and this movement + was taken advantage of by the breeder, who continually selected for + reproduction the individuals in which the ascending variation was most + marked. For all breeding depends upon the unconscious selection of + germinal variations. + </p> + <p> + Of course these germinal processes cannot be proved mathematically, since + we cannot actually see the play of forces of the passive fluctuations and + their causes. We cannot say how great these fluctuations are, and how + quickly or slowly, how regularly or irregularly they change. Nor do we + know how far a determinant must be strengthened by the passive flow of the + nutritive stream if it is to be beyond the danger of unfavourable + variations, or how far it must be weakened passively before it loses the + power of recovering itself by its own strength. It is no more possible to + bring forward actual proofs in this case than it was in regard to the + selection-value of the initial stages of an adaptation. But if we consider + that all heritable variations must have their roots in the germ-plasm, and + further, that when personal selection does not intervene, that is to say, + in the case of parts which have become useless, a degeneration of the + part, and therefore also of its determinant must inevitably take place; + then we must conclude that processes such as I have assumed are running + their course within the germ-plasm, and we can do this with as much + certainty as we were able to infer, from the phenomena of adaptation, the + selection-value of their initial stages. The fact of the degeneration of + disused parts seems to me to afford irrefutable proof that the + fluctuations within the germ-plasm ARE THE REAL ROOT OF ALL HEREDITARY + VARIATION, and the preliminary condition for the occurrence of the + Darwin-Wallace factor of selection. Germinal selection supplies the stones + out of which personal selection builds her temples and palaces: + ADAPTATIONS. The importance for the theory of the process of degeneration + of disused parts cannot be over-estimated, especially when it occurs in + sterile animal forms, where we are free from the doubt as to the alleged + LAMARCKIAN FACTOR which is apt to confuse our ideas in regard to other + cases. + </p> + <p> + If we regard the variation of the many determinants concerned in the + transformation of the female into the sterile worker as having come about + through the gradual transformation of the ids into worker-ids, we shall + see that the germ-plasm of the sexual ants must contain three kinds of + ids, male, female, and worker ids, or if the workers have diverged into + soldiers and nest-builders, then four kinds. We understand that the + worker-ids arose because their determinants struck out a useful path of + variation, whether upward or downward, and that they continued in this + path until the highest attainable degree of utility of the parts + determined was reached. But in addition to the organs of positive or + negative selection-value, there were some which were indifferent as far as + the success and especially the functional capacity of the workers was + concerned: wings, ovarian tubes, receptaculum seminis, a number of the + facets of the eye, perhaps even the whole eye. As to the ovarian tubes it + is possible that their degeneration was an advantage for the workers, in + saving energy, and if so selection would favour the degeneration; but how + could the presence of eyes diminish the usefulness of the workers to the + colony? or the minute receptaculum seminis, or even the wings? These parts + have therefore degenerated BECAUSE THEY WERE OF NO FURTHER VALUE TO THE + INSECT. But if selection did not influence the setting aside of these + parts because they were neither of advantage nor of disadvantage to the + species, then the Darwinian factor of selection is here confronted with a + puzzle which it cannot solve alone, but which at once becomes clear when + germinal selection is added. For the determinants of organs that have no + further value for the organism, must, as we have already explained, embark + on a gradual course of retrograde development. + </p> + <p> + In ants the degeneration has gone so far that there are no wing-rudiments + present in ANY species, as is the case with so many butterflies, flies, + and locusts, but in the larvae the imaginal discs of the wings are still + laid down. With regard to the ovaries, degeneration has reached different + levels in different species of ants, as has been shown by the researches + of my former pupil, Elizabeth Bickford. In many species there are twelve + ovarian tubes, and they decrease from that number to one; indeed, in one + species no ovarian tube at all is present. So much at least is certain + from what has been said, that in this case EVERYTHING depends on the + fluctuations of the elements of the germ-plasm. Germinal selection, here + as elsewhere, presents the variations of the determinants, and personal + selection favours or rejects these, or,—if it be a question of + organs which have become useless,—it does not come into play at all, + and allows the descending variation free course. + </p> + <p> + It is obvious that even the problem of COADAPTATION IN STERILE ANIMALS can + thus be satisfactorily explained. If the determinants are oscillating + upwards and downwards in continual fluctuation, and varying more + pronouncedly now in one direction now in the other, useful variations of + every determinant will continually present themselves anew, and may, in + the course of generations, be combined with one another in various ways. + But there is one character of the determinants that greatly facilitates + this complex process of selection, that, after a certain limit has been + reached, they go on varying in the same direction. From this it follows + that development along a path once struck out may proceed without the + continual intervention of personal selection. This factor only operates, + so to speak, at the beginning, when it selects the determinants which are + varying in the right direction, and again at the end, when it is necessary + to put a check upon further variation. In addition to this, enormously + long periods have been available for all these adaptations, as the very + gradual transition stages between females and workers in many species + plainly show, and thus this process of transformation loses the marvellous + and mysterious character that seemed at the first glance to invest it, and + takes rank, without any straining, among the other processes of selection. + It seems to me that, from the facts that sterile animal forms can adapt + themselves to new vital functions, their superfluous parts degenerate, and + the parts more used adapt themselves in an ascending direction, those less + used in a descending direction, we must draw the conclusion that + harmonious adaptation here comes about WITHOUT THE COOPERATION OF THE + LAMARCKIAN PRINCIPLE. This conclusion once established, however, we have + no reason to refer the thousands of cases of harmonious adaptation, which + occur in exactly the same way among other animals or plants, to a + principle, the ACTIVE INTERVENTION OF WHICH IN THE TRANSFORMATION OF + SPECIES IS NOWHERE PROVED. WE DO NOT REQUIRE IT TO EXPLAIN THE FACTS, AND + THEREFORE WE MUST NOT ASSUME IT. + </p> + <p> + The fact of coadaptation, which was supposed to furnish the strongest + argument against the principle of selection, in reality yields the + clearest evidence in favour of it. We MUST assume it, BECAUSE NO OTHER + POSSIBILITY OF EXPLANATION IS OPEN TO US, AND BECAUSE THESE ADAPTATIONS + ACTUALLY EXIST, THAT IS TO SAY, HAVE REALLY TAKEN PLACE. With this + conviction I attempted, as far back as 1894, when the idea of germinal + selection had not yet occurred to me, to make "harmonious adaptation" + (coadaptation) more easily intelligible in some way or other, and so I was + led to the idea, which was subsequently expounded in detail by Baldwin, + and Lloyd Morgan, and also by Osborn, and Gulick as ORGANIC SELECTION. It + seemed to me that it was not necessary that all the germinal variations + required for secondary variations should have occurred SIMULTANEOUSLY, + since, for instance, in the case of the stag, the bones, muscles, sinews, + and nerves would be incited by the increasing heaviness of the antlers to + greater activity in THE INDIVIDUAL LIFE, and so would be strengthened. The + antlers can only have increased in size by very slow degrees, so that the + muscles and bones may have been able to keep pace with their growth in the + individual life, until the requisite germinal variations presented + themselves. In this way a disharmony between the increasing weight of the + antlers and the parts which support and move them would be avoided, since + time would be given for the appropriate germinal variations to occur, and + so to set agoing the HEREDITARY variation of the muscles, sinews, and + bones. ("The Effect of External Influences upon Development", Romanes + Lecture, Oxford, 1894.) + </p> + <p> + I still regard this idea as correct, but I attribute less importance to + "organic selection" than I did at that time, in so far that I do not + believe that it ALONE could effect complex harmonious adaptations. + Germinal selection now seems to me to play the chief part in bringing + about such adaptations. Something the same is true of the principle I have + called "Panmixia". As I became more and more convinced, in the course of + years, that the LAMARCKIAN PRINCIPLE ought not to be called in to explain + the dwindling of disused parts, I believed that this process might be + simply explained as due to the cessation of the conservative effect of + natural selection. I said to myself that, from the moment in which a part + ceases to be of use, natural selection withdraws its hand from it, and + then it must inevitably fall from the height of its adaptiveness, because + inferior variants would have as good a chance of persisting as better + ones, since all grades of fitness of the part in question would be mingled + with one another indiscriminately. This is undoubtedly true, as Romanes + pointed out ten years before I did, and this mingling of the bad with the + good probably does bring about a deterioration of the part concerned. But + it cannot account for the steady diminution, which always occurs when a + part is in process of becoming rudimentary, and which goes on until it + ultimately disappears altogether. The process of dwindling cannot + therefore be explained as due to panmixia alone; we can only find a + sufficient explanation in germinal selection. + </p> + <p> + IV. DERIVATIVES OF THE THEORY OF SELECTION. + </p> + <p> + The impetus in all directions given by Darwin through his theory of + selection has been an immeasurable one, and its influence is still felt. + It falls within the province of the historian of science to enumerate all + the ideas which, in the last quarter of the nineteenth century, grew out + of Darwin's theories, in the endeavour to penetrate more deeply into the + problem of the evolution of the organic world. Within the narrow limits to + which this paper is restricted, I cannot attempt to discuss any of these. + </p> + <p> + V. ARGUMENTS FOR THE REALITY OF THE PROCESSES OF SELECTION. + </p> + <p> + (a) SEXUAL SELECTION. + </p> + <p> + Sexual selection goes hand in hand with natural selection. From the very + first I have regarded sexual selection as affording an extremely important + and interesting corroboration of natural selection, but, singularly + enough, it is precisely against this theory that an adverse judgment has + been pronounced in so many quarters, and it is only quite recently, and + probably in proportion as the wealth of facts in proof of it penetrates + into a wider circle, that we seem to be approaching a more general + recognition of this side of the problem of adaptation. Thus Darwin's words + in his preface to the second edition (1874) of his book, "The Descent of + Man and Sexual Selection", are being justified: "My conviction as to the + operation of natural selection remains unshaken," and further, "If + naturalists were to become more familiar with the idea of sexual + selection, it would, I think, be accepted to a much greater extent, and + already it is fully and favourably accepted by many competent judges." + Darwin was able to speak thus because he was already acquainted with an + immense mass of facts, which, taken together, yield overwhelming evidence + of the validity of the principle of sexual selection. + </p> + <p> + NATURAL SELECTION chooses out for reproduction the individuals that are + best equipped for the struggle for existence, and it does so at every + stage of development; it thus improves the species in all its stages and + forms. SEXUAL SELECTION operates only on individuals that are already + capable of reproduction, and does so only in relation to the attainment of + reproduction. It arises from the rivalry of one sex, usually the male, for + the possession of the other, usually the female. Its influence can + therefore only DIRECTLY affect one sex, in that it equips it better for + attaining possession of the other. But the effect may extend indirectly to + the female sex, and thus the whole species may be modified, without, + however, becoming any more capable of resistance in the struggle for + existence, for sexual selection only gives rise to adaptations which are + likely to give their possessor the victory over rivals in the struggle for + possession of the female, and which are therefore peculiar to the wooing + sex: the manifold "secondary sexual characters." The diversity of these + characters is so great that I cannot here attempt to give anything + approaching a complete treatment of them, but I should like to give a + sufficient number of examples to make the principle itself, in its various + modes of expression, quite clear. + </p> + <p> + One of the chief preliminary postulates of sexual selection is the unequal + number of individuals in the two sexes, for if every male immediately + finds his mate there can be no competition for the possession of the + female. Darwin has shown that, for the most part, the inequality between + the sexes is due simply to the fact that there are more males than + females, and therefore the males must take some pains to secure a mate. + But the inequality does not always depend on the numerical preponderance + of the males, it is often due to polygamy; for, if one male claims several + females, the number of females in proportion to the rest of the males will + be reduced. Since it is almost always the males that are the wooers, we + must expect to find the occurrence of secondary sexual characters chiefly + among them, and to find it especially frequent in polygamous species. And + this is actually the case. + </p> + <p> + If we were to try to guess—without knowing the facts—what + means the male animals make use of to overcome their rivals in the + struggle for the possession of the female, we might name many kinds of + means, but it would be difficult to suggest any which is not actually + employed in some animal group or other. I begin with the mere difference + in strength, through which the male of many animals is so sharply + distinguished from the female, as, for instance, the lion, walrus, + "sea-elephant," and others. Among these the males fight violently for the + possession of the female, who falls to the victor in the combat. In this + simple case no one can doubt the operation of selection, and there is just + as little room for doubt as to the selection-value of the initial stages + of the variation. Differences in bodily strength are apparent even among + human beings, although in their case the struggle for the possession of + the female is no longer decided by bodily strength alone. + </p> + <p> + Combats between male animals are often violent and obstinate, and the + employment of the natural weapons of the species in this way has led to + perfecting of these, e.g. the tusks of the boar, the antlers of the stag, + and the enormous, antler-like jaws of the stag-beetle. Here again it is + impossible to doubt that variations in these organs presented themselves, + and that these were considerable enough to be decisive in combat, and so + to lead to the improvement of the weapon. + </p> + <p> + Among many animals, however, the females at first withdraw from the males; + they are coy, and have to be sought out, and sometimes held by force. This + tracking and grasping of the females by the males has given rise to many + different characters in the latter, as, for instance, the larger eyes of + the male bee, and especially of the males of the Ephemerids (May-flies), + some species of which show, in addition to the usual compound eyes, large, + so-called turban-eyes, so that the whole head is covered with seeing + surfaces. In these species the females are very greatly in the minority + (1-100), and it is easy to understand that a keen competition for them + must take place, and that, when the insects of both sexes are floating + freely in the air, an unusually wide range of vision will carry with it a + decided advantage. Here again the actual adaptations are in accordance + with the preliminary postulates of the theory. We do not know the stages + through which the eye has passed to its present perfected state, but, + since the number of simple eyes (facets) has become very much greater in + the male than in the female, we may assume that their increase is due to a + gradual duplication of the determinants of the ommatidium in the + germ-plasm, as I have already indicated in regard to sense-organs in + general. In this case, again, the selection-value of the initial stages + hardly admits of doubt; better vision DIRECTLY secures reproduction. + </p> + <p> + In many cases THE ORGAN OF SMELL shows a similar improvement. Many lower + Crustaceans (Daphnidae) have better developed organs of smell in the male + sex. The difference is often slight and amounts only to one or two + olfactory filaments, but certain species show a difference of nearly a + hundred of these filaments (Leptodora). The same thing occurs among + insects. + </p> + <p> + We must briefly consider the clasping or grasping organs which have + developed in the males among many lower Crustaceans, but here natural + selection plays its part along with sexual selection, for the union of the + sexes is an indispensable condition for the maintenance of the species, + and as Darwin himself pointed out, in many cases the two forms of + selection merge into each other. This fact has always seemed to me to be a + proof of natural selection, for, in regard to sexual selection, it is + quite obvious that the victory of the best-equipped could have brought + about the improvement only of the organs concerned, the factors in the + struggle, such as the eye and the olfactory organ. + </p> + <p> + We come now to the EXCITANTS; that is, to the group of sexual characters + whose origin through processes of selection has been most frequently + called in question. We may cite the LOVE-CALLS produced by many male + insects, such as crickets and cicadas. These could only have arisen in + animal groups in which the female did not rapidly flee from the male, but + was inclined to accept his wooing from the first. Thus, notes like the + chirping of the male cricket serve to entice the females. At first they + were merely the signal which showed the presence of a male in the + neighbourhood, and the female was gradually enticed nearer and nearer by + the continued chirping. The male that could make himself heard to the + greatest distance would obtain the largest following, and would transmit + the beginnings, and, later, the improvement of his voice to the greatest + number of descendants. But sexual excitement in the female became + associated with the hearing of the love-call, and then the sound-producing + organ of the male began to improve, until it attained to the emission of + the long-drawn-out soft notes of the mole-cricket or the maenad-like cry + of the cicadas. I cannot here follow the process of development in detail, + but will call attention to the fact that the original purpose of the + voice, the announcing of the male's presence, became subsidiary, and the + exciting of the female became the chief goal to be aimed at. The loudest + singers awakened the strongest excitement, and the improvement resulted as + a matter of course. I conceive of the origin of bird-song in a somewhat + similar manner, first as a means of enticing, then of exciting the female. + </p> + <p> + One more kind of secondary sexual character must here be mentioned: the + odour which emanates from so many animals at the breeding season. It is + possible that this odour also served at first merely to give notice of the + presence of individuals of the other sex, but it soon became an excitant, + and as the individuals which caused the greatest degree of excitement were + preferred, it reached as high a pitch of perfection as was possible to it. + I shall confine myself here to the comparatively recently discovered + fragrance of butterflies. Since Fritz Muller found out that certain + Brazilian butterflies gave off fragrance "like a flower," we have become + acquainted with many such cases, and we now know that in all lands, not + only many diurnal Lepidoptera but nocturnal ones also give off a delicate + odour, which is agreeable even to man. The ethereal oil to which this + fragrance is due is secreted by the skin-cells, usually of the wing, as I + showed soon after the discovery of the SCENT-SCALES. This is the case in + the males; the females have no SPECIAL scent-scales recognisable as such + by their form, but they must, nevertheless, give off an extremely delicate + fragrance, although our imperfect organ of smell cannot perceive it, for + the males become aware of the presence of a female, even at night, from a + long distance off, and gather round her. We may therefore conclude, that + both sexes have long given forth a very delicate perfume, which announced + their presence to others of the same species, and that in many species + (NOT IN ALL) these small beginnings became, in the males, particularly + strong scent-scales of characteristic form (lute, brush, or lyre-shaped). + At first these scales were scattered over the surface of the wing, but + gradually they concentrated themselves, and formed broad, velvety bands, + or strong, prominent brushes, and they attained their highest pitch of + evolution when they became enclosed within pits or folds of the skin, + which could be opened to let the delicious fragrance stream forth suddenly + towards the female. Thus in this case also we see that characters, the + original use of which was to bring the sexes together, and so to maintain + the species, have been evolved in the males into means for exciting the + female. And we can hardly doubt, that the females are most readily enticed + to yield to the butterfly that sends out the strongest fragrance,—that + is to say, that excites them to the highest degree. It is a pity that our + organs of smell are not fine enough to examine the fragrance of male + Lepidoptera in general, and to compare it with other perfumes which + attract these insects. (See Poulton, "Essays on Evolution", 1908, pages + 316, 317.) As far as we can perceive them they resemble the fragrance of + flowers, but there are Lepidoptera whose scent suggests musk. A smell of + musk is also given off by several plants: it is a sexual excitant in the + musk-deer, the musk-sheep, and the crocodile. + </p> + <p> + As far as we know, then, it is perfumes similar to those of flowers that + the male Lepidoptera give off in order to entice their mates, and this is + a further indication that animals, like plants, can to a large extent meet + the claims made upon them by life, and produce the adaptations which are + most purposive,—a further proof, too, of my proposition that the + useful variations, so to speak, are ALWAYS THERE. The flowers developed + the perfumes which entice their visitors, and the male Lepidoptera + developed the perfumes which entice and excite their mates. + </p> + <p> + There are many pretty little problems to be solved in this connection, for + there are insects, such as some flies, that are attracted by smells which + are unpleasant to us, like those from decaying flesh and carrion. But + there are also certain flowers, some orchids for instance, which give + forth no very agreeable odour, but one which is to us repulsive and + disgusting; and we should therefore expect that the males of such insects + would give off a smell unpleasant to us, but there is no case known to me + in which this has been demonstrated. + </p> + <p> + In cases such as we have discussed, it is obvious that there is no + possible explanation except through selection. This brings us to the last + kind of secondary sexual characters, and the one in regard to which doubt + has been most frequently expressed,—decorative colours and + decorative forms, the brilliant plumage of the male pheasant, the + humming-birds, and the bird of Paradise, as well as the bright colours of + many species of butterfly, from the beautiful blue of our little + Lycaenidae to the magnificent azure of the large Morphinae of Brazil. In a + great many cases, though not by any means in all, the male butterflies are + "more beautiful" than the females, and in the Tropics in particular they + shine and glow in the most superb colours. I really see no reason why we + should doubt the power of sexual selection, and I myself stand wholly on + Darwin's side. Even though we certainly cannot assume that the females + exercise a conscious choice of the "handsomest" mate, and deliberate like + the judges in a court of justice over the perfections of their wooers, we + have no reason to doubt that distinctive forms (decorative feathers) and + colours have a particularly exciting effect upon the female, just as + certain odours have among animals of so many different groups, including + the butterflies. The doubts which existed for a considerable time, as a + result of fallacious experiments, as to whether the colours of flowers + really had any influence in attracting butterflies have now been set at + rest through a series of more careful investigations; we now know that the + colours of flowers are there on account of the butterflies, as Sprengel + first showed, and that the blossoms of Phanerogams are selected in + relation to them, as Darwin pointed out. + </p> + <p> + Certainly it is not possible to bring forward any convincing proof of the + origin of decorative colours through sexual selection, but there are many + weighty arguments in favour of it, and these form a body of presumptive + evidence so strong that it almost amounts to certainty. + </p> + <p> + In the first place, there is the analogy with other secondary sexual + characters. If the song of birds and the chirping of the cricket have been + evolved through sexual selection, if the penetrating odours of male + animals,—the crocodile, the musk-deer, the beaver, the carnivores, + and, finally, the flower-like fragrances of the butterflies have been + evolved to their present pitch in this way, why should decorative colours + have arisen in some other way? Why should the eye be less sensitive to + SPECIFICALLY MALE colours and other VISIBLE signs ENTICING TO THE FEMALE, + than the olfactory sense to specifically male odours, or the sense of + hearing to specifically male sounds? Moreover, the decorative feathers of + birds are almost always spread out and displayed before the female during + courtship. I have elsewhere ("The Evolution Theory", London, 1904, I. page + 219.) pointed out that decorative colouring and sweet-scentedness may + replace one another in Lepidoptera as well as in flowers, for just as some + modestly coloured flowers (mignonette and violet) have often a strong + perfume, while strikingly coloured ones are sometimes quite devoid of + fragrance, so we find that the most beautiful and gaily-coloured of our + native Lepidoptera, the species of Vanessa, have no scent-scales, while + these are often markedly developed in grey nocturnal Lepidoptera. Both + attractions may, however, be combined in butterflies, just as in flowers. + Of course, we cannot explain why both means of attraction should exist in + one genus, and only one of them in another, since we do not know the + minutest details of the conditions of life of the genera concerned. But + from the sporadic distribution of scent-scales in Lepidoptera, and from + their occurrence or absence in nearly related species, we may conclude + that fragrance is a relatively MODERN acquirement, more recent than + brilliant colouring. + </p> + <p> + One thing in particular that stamps decorative colouring as a product of + selection is ITS GRADUAL INTENSIFICATION by the addition of new spots, + which we can quite well observe, because in many cases the colours have + been first acquired by the males, and later transmitted to the females by + inheritance. The scent-scales are never thus transmitted, probably for the + same reason that the decorative colours of many birds are often not + transmitted to the females: because with these they would be exposed to + too great elimination by enemies. Wallace was the first to point out that + in species with concealed nests the beautiful feathers of the male + occurred in the female also, as in the parrots, for instance, but this is + not the case in species which brood on an exposed nest. In the parrots one + can often observe that the general brilliant colouring of the male is + found in the female, but that certain spots of colour are absent, and + these have probably been acquired comparatively recently by the male and + have not yet been transmitted to the female. + </p> + <p> + Isolation of the group of individuals which is in process of varying is + undoubtedly of great value in sexual selection, for even a solitary + conspicuous variation will become dominant much sooner in a small isolated + colony, than among a large number of members of a species. + </p> + <p> + Anyone who agrees with me in deriving variations from germinal selection + will regard that process as an essential aid towards explaining the + selection of distinctive courtship-characters, such as coloured spots, + decorative feathers, horny outgrowths in birds and reptiles, combs, + feather-tufts, and the like, since the beginnings of these would be + presented with relative frequency in the struggle between the determinants + within the germ-plasm. The process of transmission of decorative feathers + to the female results, as Darwin pointed out and illustrated by + interesting examples, in the COLOUR-TRANSFORMATION OF A WHOLE SPECIES, and + this process, as the phyletically older colouring of young birds shows, + must, in the course of thousands of years, have repeated itself several + times in a line of descent. + </p> + <p> + If we survey the wealth of phenomena presented to us by secondary sexual + characters, we can hardly fail to be convinced of the truth of the + principle of sexual selection. And certainly no one who has accepted + natural selection should reject sexual selection, for, not only do the two + processes rest upon the same basis, but they merge into one another, so + that it is often impossible to say how much of a particular character + depends on one and how much on the other form of selection. + </p> + <p> + (b) NATURAL SELECTION. + </p> + <p> + An actual proof of the theory of sexual selection is out of the question, + if only because we cannot tell when a variation attains to + selection-value. It is certain that a delicate sense of smell is of value + to the male moth in his search for the female, but whether the possession + of one additional olfactory hair, or of ten, or of twenty additional hairs + leads to the success of its possessor we are unable to tell. And we are + groping even more in the dark when we discuss the excitement caused in the + female by agreeable perfumes, or by striking and beautiful colours. That + these do make an impression is beyond doubt; but we can only assume that + slight intensifications of them give any advantage, and we MUST assume + this SINCE OTHERWISE SECONDARY SEXUAL CHARACTERS REMAIN INEXPLICABLE. + </p> + <p> + The same thing is true in regard to natural selection. It is not possible + to bring forward any actual proof of the selection-value of the initial + stages, and the stages in the increase of variations, as has been already + shown. But the selection-value of a finished adaptation can in many cases + be statistically determined. Cesnola and Poulton have made valuable + experiments in this direction. The former attached forty-five individuals + of the green, and sixty-five of the brown variety of the praying mantis + (Mantis religiosa), by a silk thread to plants, and watched them for + seventeen days. The insects which were on a surface of a colour similar to + their own remained uneaten, while twenty-five green insects on brown parts + of plants had all disappeared in eleven days. + </p> + <p> + The experiments of Poulton and Sanders ("Report of the British + Association" (Bristol, 1898), London, 1899, pages 906-909.) were made with + 600 pupae of Vanessa urticae, the "tortoise-shell butterfly." The pupae + were artificially attached to nettles, tree-trunks, fences, walls, and to + the ground, some at Oxford, some at St Helens in the Isle of Wight. In the + course of a month 93 per cent of the pupae at Oxford were killed, chiefly + by small birds, while at St Helens 68 per cent perished. The experiments + showed very clearly that the colour and character of the surface on which + the pupa rests—and thus its own conspicuousness—are of the + greatest importance. At Oxford only the four pupae which were fastened to + nettles emerged; all the rest—on bark, stones and the like—perished. + At St Helens the elimination was as follows: on fences where the pupae + were conspicuous, 92 per cent; on bark, 66 per cent; on walls, 54 per + cent; and among nettles, 57 per cent. These interesting experiments + confirm our views as to protective coloration, and show further, THAT THE + RATIO OF ELIMINATION IN THE SPECIES IS A VERY HIGH ONE, AND THAT THEREFORE + SELECTION MUST BE VERY KEEN. + </p> + <p> + We may say that the process of selection follows as a logical necessity + from the fulfilment of the three preliminary postulates of the theory: + variability, heredity, and the struggle for existence, with its enormous + ratio of elimination in all species. To this we must add a fourth factor, + the INTENSIFICATION of variations which Darwin established as a fact, and + which we are now able to account for theoretically on the basis of + germinal selection. It may be objected that there is considerable + uncertainty about this LOGICAL proof, because of our inability to + demonstrate the selection-value of the initial stages and the individual + stages of increase. We have therefore to fall back on PRESUMPTIVE + EVIDENCE. This is to be found in THE INTERPRETATIVE VALUE OF THE THEORY. + Let us consider this point in greater detail. + </p> + <p> + In the first place, it is necessary to emphasise what is often overlooked, + namely, that the theory not only explains the TRANSFORMATIONS of species, + it also explains THEIR REMAINING THE SAME; in addition to the principle of + varying, it contains within itself that of PERSISTING. It is part of the + essence of selection, that it not only causes a part to VARY till it has + reached its highest pitch of adaptation, but that it MAINTAINS IT AT THIS + PITCH. THIS CONSERVING INFLUENCE OF NATURAL SELECTION is of great + importance, and was early recognised by Darwin; it follows naturally from + the principle of the survival of the fittest. + </p> + <p> + We understand from this how it is that a species which has become fully + adapted to certain conditions of life ceases to vary, but remains + "constant," as long as the conditions of life FOR IT remain unchanged, + whether this be for thousands of years, or for whole geological epochs. + But the most convincing proof of the power of the principle of selection + lies in the innumerable multitude of phenomena which cannot be explained + in any other way. To this category belong all structures which are only + PASSIVELY of advantage to the organism, because none of these can have + arisen by the alleged LAMARCKIAN PRINCIPLE. These have been so often + discussed that we need do no more than indicate them here. Until quite + recently the sympathetic coloration of animals—for instance, the + whiteness of Arctic animals—was referred, at least in part, to the + DIRECT influence of external factors, but the facts can best be explained + by referring them to the processes of selection, for then it is + unnecessary to make the gratuitous assumption that many species are + sensitive to the stimulus of cold and that others are not. The great + majority of Arctic land-animals, mammals and birds, are white, and this + proves that they were all able to present the variation which was most + useful for them. The sable is brown, but it lives in trees, where the + brown colouring protects and conceals it more effectively. The musk-sheep + (Ovibos moschatus) is also brown, and contrasts sharply with the ice and + snow, but it is protected from beasts of prey by its gregarious habit, and + therefore it is of advantage to be visible from as great a distance as + possible. That so many species have been able to give rise to white + varieties does not depend on a special sensitiveness of the skin to the + influence of cold, but to the fact that Mammals and Birds have a general + tendency to vary towards white. Even with us, many birds—starlings, + blackbirds, swallows, etc.—occasionally produce white individuals, + but the white variety does not persist, because it readily falls a victim + to the carnivores. This is true of white fawns, foxes, deer, etc. The + whiteness, therefore, arises from internal causes, and only persists when + it is useful. A great many animals living in a GREEN ENVIRONMENT have + become clothed in green, especially insects, caterpillars, and Mantidae, + both persecuted and persecutors. + </p> + <p> + That it is not the direct effect of the environment which calls forth the + green colour is shown by the many kinds of caterpillar which rest on + leaves and feed on them, but are nevertheless brown. These feed by night + and betake themselves through the day to the trunk of the tree, and hide + in the furrows of the bark. We cannot, however, conclude from this that + they were UNABLE to vary towards green, for there are Arctic animals which + are white only in winter and brown in summer (Alpine hare, and the + ptarmigan of the Alps), and there are also green leaf-insects which remain + green only while they are young and difficult to see on the leaf, but + which become brown again in the last stage of larval life, when they have + outgrown the leaf. They then conceal themselves by day, sometimes only + among withered leaves on the ground, sometimes in the earth itself. It is + interesting that in one genus, Chaerocampa, one species is brown in the + last stage of larval life, another becomes brown earlier, and in many + species the last stage is not wholly brown, a part remaining green. + Whether this is a case of a double adaptation, or whether the green is + being gradually crowded out by the brown, the fact remains that the same + species, even the same individual, can exhibit both variations. The case + is the same with many of the leaf-like Orthoptera, as, for instance, the + praying mantis (Mantis religiosa) which we have already mentioned. + </p> + <p> + But the best proofs are furnished by those often-cited cases in which the + insect bears a deceptive resemblance to another object. We now know many + such cases, such as the numerous imitations of green or withered leaves, + which are brought about in the most diverse ways, sometimes by mere + variations in the form of the insect and in its colour, sometimes by an + elaborate marking, like that which occurs in the Indian leaf-butterflies, + Kallima inachis. In the single butterfly-genus Anaea, in the woods of + South America, there are about a hundred species which are all gaily + coloured on the upper surface, and on the reverse side exhibit the most + delicate imitation of the colouring and pattern of a leaf, generally + without any indication of the leaf-ribs, but extremely deceptive + nevertheless. Anyone who has seen only one such butterfly may doubt + whether many of the insignificant details of the marking can really be of + advantage to the insect. Such details are for instance the apparent holes + and splits in the apparently dry or half-rotten leaf, which are usually + due to the fact that the scales are absent on a circular or oval patch so + that the colourless wing-membrane lies bare, and one can look through the + spot as through a window. Whether the bird which is seeking or pursuing + the butterflies takes these holes for dewdrops, or for the work of a + devouring insect, does not affect the question; the mirror-like spot + undoubtedly increases the general deceptiveness, for the same thing occurs + in many leaf-butterflies, though not in all, and in some cases it is + replaced in quite a peculiar manner. In one species of Anaea (A. divina), + the resting butterfly looks exactly like a leaf out of the outer edge of + which a large semicircular piece has been eaten, possibly by a + caterpillar; but if we look more closely it is obvious that there is no + part of the wing absent, and that the semicircular piece is of a clear, + pale yellow colour, while the rest of the wing is of a strongly contrasted + dark brown. + </p> + <p> + But the deceptive resemblance may be caused in quite a different manner. I + have often speculated as to what advantage the brilliant white C could + give to the otherwise dusky-coloured "Comma butterfly" (Grapta C. album). + Poulton's recent observations ("Proc. Ent. Soc"., London, May 6, 1903.) + have shown that this represents the imitation of a crack such as is often + seen in dry leaves, and is very conspicuous because the light shines + through it. + </p> + <p> + The utility obviously lies in presenting to the bird the very familiar + picture of a broken leaf with a clear shining slit, and we may conclude, + from the imitation of such small details, that the birds are very sharp + observers and that the smallest deviation from the usual arrests their + attention and incites them to closer investigation. It is obvious that + such detailed—we might almost say such subtle—deceptive + resemblances could only have come about in the course of long ages through + the acquirement from time to time of something new which heightened the + already existing resemblance. + </p> + <p> + In face of facts like these there can be no question of chance, and no one + has succeeded so far in finding any other explanation to replace that by + selection. For the rest, the apparent leaves are by no means perfect + copies of a leaf; many of them only represent the torn or broken piece, or + the half or two-thirds of a leaf, but then the leaves themselves + frequently do not present themselves to the eye as a whole, but partially + concealed among other leaves. Even those butterflies which, like the + species of Kallima and Anaea, represent the whole of a leaf with stalk, + ribs, apex, and the whole breadth, are not actual copies which would + satisfy a botanist; there is often much wanting. In Kallima the lateral + ribs of the leaf are never all included in the markings; there are only + two or three on the left side and at most four or five on the right, and + in many individuals these are rather obscure, while in others they are + comparatively distinct. This furnishes us with fresh evidence in favour of + their origin through processes of selection, for a botanically perfect + picture could not arise in this way; there could only be a fixing of such + details as heightened the deceptive resemblance. + </p> + <p> + Our postulate of origin through selection also enables us to understand + why the leaf-imitation is on the lower surface of the wing in the diurnal + Lepidoptera, and on the upper surface in the nocturnal forms, + corresponding to the attitude of the wings in the resting position of the + two groups. + </p> + <p> + The strongest of all proofs of the theory, however, is afforded by cases + of true "mimicry," those adaptations discovered by Bates in 1861, + consisting in the imitation of one species by another, which becomes more + and more like its model. The model is always a species that enjoys some + special protection from enemies, whether because it is unpleasant to + taste, or because it is in some way dangerous. + </p> + <p> + It is chiefly among insects and especially among butterflies that we find + the greatest number of such cases. Several of these have been minutely + studied, and every detail has been investigated, so that it is difficult + to understand how there can still be disbelief in regard to them. If the + many and exact observations which have been carefully collected and + critically discussed, for instance by Poulton ("Essays on Evolution", + 1889-1907, Oxford, 1908, passim, e.g. page 269.) were thoroughly studied, + the arguments which are still frequently urged against mimicry would be + found untenable; we can hardly hope to find more convincing proof of the + actuality of the processes of selection than these cases put into our + hands. The preliminary postulates of the theory of mimicry have been + disputed, for instance, that diurnal butterflies are persecuted and eaten + by birds, but observations specially directed towards this point in India, + Africa, America and Europe have placed it beyond all doubt. If it were + necessary I could myself furnish an account of my own observations on this + point. + </p> + <p> + In the same way it has been established by experiment and observation in + the field that in all the great regions of distribution there are + butterflies which are rejected by birds and lizards, their chief enemies, + on account of their unpleasant smell or taste. These butterflies are + usually gaily and conspicuously coloured and thus—as Wallace first + interpreted it—are furnished with an easily recognisable sign: a + sign of unpalatableness or WARNING COLOURS. If they were not thus + recognisable easily and from a distance, they would frequently be pecked + at by birds, and then rejected because of their unpleasant taste; but as + it is, the insect-eaters recognise them at once as unpalatable booty and + ignore them. Such IMMUNE (The expression does not refer to all the enemies + of this butterfly; against ichneumon-flies, for instance, their unpleasant + smell usually gives no protection.) species, wherever they occur, are + imitated by other palatable species, which thus acquire a certain degree + of protection. + </p> + <p> + It is true that this explanation of the bright, conspicuous colours is + only a hypothesis, but its foundations,—unpalatableness, and the + liability of other butterflies to be eaten,—are certain, and its + consequences—the existence of mimetic palatable forms—confirm + it in the most convincing manner. Of the many cases now known I select + one, which is especially remarkable, and which has been thoroughly + investigated, Papilio dardanus (merope), a large, beautiful, diurnal + butterfly which ranges from Abyssinia throughout the whole of Africa to + the south coast of Cape Colony. + </p> + <p> + The males of this form are everywhere ALMOST the same in colour and in + form of wings, save for a few variations in the sparse black markings on + the pale yellow ground. But the females occur in several quite different + forms and colourings, and one of these only, the Abyssinian form, is like + the male, while the other three or four are MIMETIC, that is to say, they + copy a butterfly of quite a different family the Danaids, which are among + the IMMUNE forms. In each region the females have thus copied two or three + different immune species. There is much that is interesting to be said in + regard to these species, but it would be out of keeping with the general + tenor of this paper to give details of this very complicated case of + polymorphism in P. dardanus. Anyone who is interested in the matter will + find a full and exact statement of the case in as far as we know it, in + Poulton's "Essays on Evolution" (pages 373-375). (Professor Poulton has + corrected some wrong descriptions which I had unfortunately overlooked in + the Plates of my book "Vortrage uber Descendenztheorie", and which refer + to Papilio dardanus (merope). These mistakes are of no importance as far + as and understanding of the mimicry-theory is concerned, but I hope + shortly to be able to correct them in a later edition.) I need only add + that three different mimetic female forms have been reared from the eggs + of a single female in South Africa. The resemblance of these forms to + their immune models goes so far that even the details of the LOCAL forms + of the models are copied by the mimetic species. + </p> + <p> + It remains to be said that in Madagascar a butterfly, Papilio meriones, + occurs, of which both sexes are very similar in form and markings to the + non-mimetic male of P. dardanus, so that it probably represents the + ancestor of this latter species. + </p> + <p> + In face of such facts as these every attempt at another explanation must + fail. Similarly all the other details of the case fulfil the preliminary + postulates of selection, and leave no room for any other interpretation. + That the males do not take on the protective colouring is easily + explained, because they are in general more numerous, and the females are + more important for the preservation of the species, and must also live + longer in order to deposit their eggs. We find the same state of things in + many other species, and in one case (Elymnias undularis) in which the male + is also mimetically coloured, it copies quite a differently coloured + immune species from the model followed by the female. This is quite + intelligible when we consider that if there were TOO MANY false immune + types, the birds would soon discover that there were palatable individuals + among those with unpalatable warning colours. Hence the imitation of + different immune species by Papilio dardanus! + </p> + <p> + I regret that lack of space prevents my bringing forward more examples of + mimicry and discussing them fully. But from the case of Papilio dardanus + alone there is much to be learnt which is of the highest importance for + our understanding of transformations. It shows us chiefly what I once + called, somewhat strongly perhaps, THE OMNIPOTENCE OF NATURAL SELECTION in + answer to an opponent who had spoken of its "inadequacy." We here see that + one and the same species is capable of producing four or five different + patterns of colouring and marking; thus the colouring and marking are not, + as has often been supposed, a necessary outcome of the specific nature of + the species, but a true adaptation, which cannot arise as a direct effect + of climatic conditions, but solely through what I may call the sorting out + of the variations produced by the species, according to their utility. + That caterpillars may be either green or brown is already something more + than could have been expected according to the old conception of species, + but that one and the same butterfly should be now pale yellow, with black; + now red with black and pure white; now deep black with large, pure white + spots; and again black with a large ochreous-yellow spot, and many small + white and yellow spots; that in one sub-species it may be tailed like the + ancestral form, and in another tailless like its Danaid model,—all + this shows a far-reaching capacity for variation and adaptation that wide + never have expected if we did not see the facts before us. How it is + possible that the primary colour-variations should thus be intensified and + combined remains a puzzle even now; we are reminded of the modern + three-colour printing,—perhaps similar combinations of the primary + colours take place in this case; in any case the direction of these + primary variations is determined by the artist whom we know as natural + selection, for there is no other conceivable way in which the model could + affect the butterfly that is becoming more and more like it. The same + climate surrounds all four forms of female; they are subject to the same + conditions of nutrition. Moreover, Papilio dardanus is by no means the + only species of butterfly which exhibits different kinds of colour-pattern + on its wings. Many species of the Asiatic genus Elymnias have on the upper + surface a very good imitation of an immune Euploeine (Danainae), often + with a steel-blue ground-colour, while the under surface is well concealed + when the butterfly is at rest,—thus there are two kinds of + protective coloration each with a different meaning! The same thing may be + observed in many non-mimetic butterflies, for instance in all our species + of Vanessa, in which the under side shows a grey-brown or brownish-black + protective coloration, but we do not yet know with certainty what may be + the biological significance of the gaily coloured upper surface. + </p> + <p> + In general it may be said that mimetic butterflies are comparatively rare + species, but there are exceptions, for instance Limenitis archippus in + North America, of which the immune model (Danaida plexippus) also occurs + in enormous numbers. + </p> + <p> + In another mimicry-category the imitators are often more numerous than the + models, namely in the case of the imitation of DANGEROUS INSECTS by + harmless species. Bees and wasps are dreaded for their sting, and they are + copied by harmless flies of the genera Eristalis and Syrphus, and these + mimics often occur in swarms about flowering plants without damage to + themselves or to their models; they are feared and are therefore left + unmolested. + </p> + <p> + In regard also to the FAITHFULNESS OF THE COPY the facts are quite in + harmony with the theory, according to which the resemblance must have + arisen and increased BY DEGREES. We can recognise this in many cases, for + even now the mimetic species show very VARYING DEGREES OF RESEMBLANCE to + their immune model. If we compare, for instance, the many different + imitators of Danaida chrysippus we find that, with their brownish-yellow + ground-colour, and the position and size, and more or less sharp + limitation of their clear marginal spots, they have reached very different + degrees of nearness to their model. Or compare the female of Elymnias + undularis with its model Danaida genutia; there is a general resemblance, + but the marking of the Danaida is very roughly imitated in Elymnias. + </p> + <p> + Another fact that bears out the theory of mimicry is, that even when the + resemblance in colour-pattern is very great, the WING-VENATION, which is + so constant, and so important in determining the systematic position of + butterflies, is never affected by the variation. The pursuers of the + butterfly have no time to trouble about entomological intricacies. + </p> + <p> + I must not pass over a discovery of Poulton's which is of great + theoretical importance—that mimetic butterflies may reach the same + effect by very different means. ("Journ. Linn. Soc. London (Zool.)", Vol. + XXVI. 1898, pages 598-602.) Thus the glass-like transparency of the wing + of a certain Ithomiine (Methona) and its Pierine mimic (Dismorphia orise) + depends on a diminution in the size of the scales; in the Danaine genus + Ituna it is due to the fewness of the scales, and in a third imitator, a + moth (Castnia linus var. heliconoides) the glass-like appearance of the + wing is due neither to diminution nor to absence of scales, but to their + absolute colourlessness and transparency, and to the fact that they stand + upright. In another moth mimic (Anthomyza) the arrangement of the + transparent scales is normal. Thus it is not some unknown external + influence that has brought about the transparency of the wing in these + five forms, as has sometimes been supposed. Nor is it a hypothetical + INTERNAL evolutionary tendency, for all three vary in a different manner. + The cause of this agreement can only lie in selection, which preserves and + intensifies in each species the favourable variations that present + themselves. The great faithfulness of the copy is astonishing in these + cases, for it is not THE WHOLE wing which is transparent; certain markings + are black in colour, and these contrast sharply with the glass-like + ground. It is obvious that the pursuers of these butterflies must be very + sharp-sighted, for otherwise the agreement between the species could never + have been pushed so far. The less the enemies see and observe, the more + defective must the imitation be, and if they had been blind, no visible + resemblance between the species which required protection could ever have + arisen. + </p> + <p> + A seemingly irreconcilable contradiction to the mimicry theory is + presented in the following cases, which were known to Bates, who, however, + never succeeded in bringing them into line with the principle of mimicry. + </p> + <p> + In South America there are, as we have already said, many mimics of the + immune Ithomiinae (or as Bates called them Heliconidae). Among these there + occur not merely species which are edible, and thus require the protection + of a disguise, but others which are rejected on account of their + unpalatableness. How could the Ithomiine dress have developed in their + case, and of what use is it, since the species would in any case be + immune? In Eastern Brazil, for instance, there are four butterflies, which + bear a most confusing resemblance to one another in colour, marking, and + form of wing, and all four are unpalatable to birds. They belong to four + different genera and three sub-families, and we have to inquire: Whence + came this resemblance and what end does it serve? For a long time no + satisfactory answer could be found, but Fritz Muller (In "Kosmos", 1879, + page 100.), seventeen years after Bates, offered a solution to the riddle, + when he pointed out that young birds could not have an instinctive + knowledge of the unpalatableness of the Ithomiines, but must learn by + experience which species were edible and which inedible. Thus each young + bird must have tasted at least one individual of each inedible species and + discovered its unpalatability, before it learnt to avoid, and thus to + spare the species. But if the four species resemble each other very + closely the bird will regard them all as of the same kind, and avoid them + all. Thus there developed a process of selection which resulted in the + survival of the Ithomiine-like individuals, and in so great an increase of + resemblance between the four species, that they are difficult to + distinguish one from another even in a collection. The advantage for the + four species, living side by side as they do e.g. in Bahia, lies in the + fact that only one individual from the MIMICRY-RING ("inedible + association") need be tasted by a young bird, instead of at least four + individuals, as would otherwise be the case. As the number of young birds + is great, this makes a considerable difference in the ratio of + elimination. + </p> + <p> + These interesting mimicry-rings (trusts), which have much significance for + the theory, have been the subject of numerous and careful investigations, + and at least their essential features are now fully established. Muller + took for granted, without making any investigations, that young birds only + learn by experience to distinguish between different kinds of victims. But + Lloyd Morgan's ("Habit and Instinct", London, 1896.) experiments with + young birds proved that this is really the case, and at the same time + furnished an additional argument against the LAMARCKIAN PRINCIPLE. + </p> + <p> + In addition to the mimicry-rings first observed in South America, others + have been described from Tropical India by Moore, and by Poulton and Dixey + from Africa, and we may expect to learn many more interesting facts in + this connection. Here again the preliminary postulates of the theory are + satisfied. And how much more that would lead to the same conclusion might + be added! + </p> + <p> + As in the case of mimicry many species have come to resemble one another + through processes of selection, so we know whole classes of phenomena in + which plants and animals have become adapted to one another, and have thus + been modified to a considerable degree. I refer particularly to the + relation between flowers and insects; but as there is an article on "The + Biology of Flowers" in this volume, I need not discuss the subject, but + will confine myself to pointing out the significance of these remarkable + cases for the theory of selection. Darwin has shown that the originally + inconspicuous blossoms of the phanerogams were transformed into flowers + through the visits of insects, and that, conversely, several large orders + of insects have been gradually modified by their association with flowers, + especially as regards the parts of their body actively concerned. Bees and + butterflies in particular have become what they are through their relation + to flowers. In this case again all that is apparently contradictory to the + theory can, on closer investigation, be beautifully interpreted in + corroboration of it. Selection can give rise only to what is of use to the + organism actually concerned, never to what is of use to some other + organism, and we must therefore expect to find that in flowers only + characters of use to THEMSELVES have arisen, never characters which are of + use to insects only, and conversely that in the insects characters useful + to them and not merely to the plants would have originated. For a long + time it seemed as if an exception to this rule existed in the case of the + fertilisation of the yucca blossoms by a little moth, Pronuba yuccasella. + This little moth has a sickle-shaped appendage to its mouth-parts which + occurs in no other Lepidopteron, and which is used for pushing the yellow + pollen into the opening of the pistil, thus fertilising the flower. Thus + it appears as if a new structure, which is useful only to the plant, has + arisen in the insect. But the difficulty is solved as soon as we learn + that the moth lays its eggs in the fruit-buds of the Yucca, and that the + larvae, when they emerge, feed on the developing seeds. In effecting the + fertilisation of the flower the moth is at the same time making provision + for its own offspring, since it is only after fertilisation that the seeds + begin to develop. There is thus nothing to prevent our referring this + structural adaptation in Pronuba yuccasella to processes of selection, + which have gradually transformed the maxillary palps of the female into + the sickle-shaped instrument for collecting the pollen, and which have at + the same time developed in the insect the instinct to press the pollen + into the pistil. + </p> + <p> + In this domain, then, the theory of selection finds nothing but + corroboration, and it would be impossible to substitute for it any other + explanation, which, now that the facts are so well known, could be + regarded as a serious rival to it. That selection is a factor, and a very + powerful factor in the evolution of organisms, can no longer be doubted. + Even although we cannot bring forward formal proofs of it IN DETAIL, + cannot calculate definitely the size of the variations which present + themselves, and their selection-value, cannot, in short, reduce the whole + process to a mathematical formula, yet we must assume selection, because + it is the only possible explanation applicable to whole classes of + phenomena, and because, on the other hand, it is made up of factors which + we know can be proved actually to exist, and which, IF they exist, must of + logical necessity cooperate in the manner required by the theory. WE MUST + ACCEPT IT BECAUSE THE PHENOMENA OF EVOLUTION AND ADAPTATION MUST HAVE A + NATURAL BASIS, AND BECAUSE IT IS THE ONLY POSSIBLE EXPLANATION OF THEM. + (This has been discussed in many of my earlier works. See for instance + "The All-Sufficiency of Natural Selection, a reply to Herbert Spencer", + London, 1893.) + </p> + <p> + Many people are willing to admit that selection explains adaptations, but + they maintain that only a part of the phenomena are thus explained, + because everything does not depend upon adaptation. They regard adaptation + as, so to speak, a special effort on the part of Nature, which she keeps + in readiness to meet particularly difficult claims of the external world + on organisms. But if we look at the matter more carefully we shall find + that adaptations are by no means exceptional, but that they are present + everywhere in such enormous numbers, that it would be difficult in regard + to any structure whatever, to prove that adaptation had NOT played a part + in its evolution. + </p> + <p> + How often has the senseless objection been urged against selection that it + can create nothing, it can only reject. It is true that it cannot create + either the living substance or the variations of it; both must be given. + But in rejecting one thing it preserves another, intensifies it, combines + it, and in this way CREATES what is new. EVERYTHING in organisms depends + on adaptation; that is to say, everything must be admitted through the + narrow door of selection, otherwise it can take no part in the building up + of the whole. But, it is asked, what of the direct effect of external + conditions, temperature, nutrition, climate and the like? Undoubtedly + these can give rise to variations, but they too must pass through the door + of selection, and if they cannot do this they are rejected, eliminated + from the constitution of the species. + </p> + <p> + It may, perhaps, be objected that such external influences are often of a + compelling power, and that every animal MUST submit to them, and that thus + selection has no choice and can neither select nor reject. There may be + such cases; let us assume for instance that the effect of the cold of the + Arctic regions was to make all the mammals become black; the result would + be that they would all be eliminated by selection, and that no mammals + would be able to live there at all. But in most cases a certain percentage + of animals resists these strong influences, and thus selection secures a + foothold on which to work, eliminating the unfavourable variation, and + establishing a useful colouring, consistent with what is required for the + maintenance of the species. + </p> + <p> + Everything depends upon adaptation! We have spoken much of adaptation in + colouring, in connection with the examples brought into prominence by + Darwin, because these are conspicuous, easily verified, and at the same + time convincing for the theory of selection. But is it only desert and + polar animals whose colouring is determined through adaptation? Or the + leaf-butterflies, and the mimetic species, or the terrifying markings, and + "warning-colours" and a thousand other kinds of sympathetic colouring? It + is, indeed, never the colouring alone which makes up the adaptation; the + structure of the animal plays a part, often a very essential part, in the + protective disguise, and thus MANY variations may cooperate towards ONE + common end. And it is to be noted that it is by no means only external + parts that are changed; internal parts are ALWAYS modified at the same + time—for instance, the delicate elements of the nervous system on + which depend the INSTINCT of the insect to hold its wings, when at rest, + in a perfectly definite position, which, in the leaf-butterfly, has the + effect of bringing the two pieces on which the marking occurs on the + anterior and posterior wing into the same direction, and thus displaying + as a whole the fine curve of the midrib on the seeming leaf. But the + wing-holding instinct is not regulated in the same way in all + leaf-butterflies; even our indigenous species of Vanessa, with their + protective ground-colouring, have quite a distinctive way of holding their + wings so that the greater part of the anterior wing is covered by the + posterior when the butterfly is at rest. But the protective colouring + appears on the posterior wing and on the tip of the anterior, TO PRECISELY + THE DISTANCE TO WHICH IT IS LEFT UNCOVERED. This occurs, as Standfuss has + shown, in different degree in our two most nearly allied species, the + uncovered portion being smaller in V. urticae than in V. polychloros. In + this case, as in most leaf-butterflies, the holding of the wing was + probably the primary character; only after that was thoroughly established + did the protective marking develop. In any case, the instinctive manner of + holding the wings is associated with the protective colouring, and must + remain as it is if the latter is to be effective. How greatly instincts + may change, that is to say, may be adapted, is shown by the case of the + Noctuid "shark" moth, Xylina vetusta. This form bears a most deceptive + resemblance to a piece of rotten wood, and the appearance is greatly + increased by the modification of the innate impulse to flight common to so + many animals, which has here been transformed into an almost contrary + instinct. This moth does not fly away from danger, but "feigns death," + that is, it draws antennae, legs and wings close to the body, and remains + perfectly motionless. It may be touched, picked up, and thrown down again, + and still it does not move. This remarkable instinct must surely have + developed simultaneously with the wood-colouring; at all events, both + cooperating variations are now present, and prove that both the external + and the most minute internal structure have undergone a process of + adaptation. + </p> + <p> + The case is the same with all structural variations of animal parts, which + are not absolutely insignificant. When the insects acquired wings they + must also have acquired the mechanism with which to move them—the + musculature, and the nervous apparatus necessary for its automatic + regulation. All instincts depend upon compound reflex mechanisms and are + just as indispensable as the parts they have to set in motion, and all may + have arisen through processes of selection if the reasons which I have + elsewhere given for this view are correct. ("The Evolution Theory", + London, 1904, page 144.) + </p> + <p> + Thus there is no lack of adaptations within the organism, and particularly + in its most important and complicated parts, so that we may say that there + is no actively functional organ that has not undergone a process of + adaptation relative to its function and the requirements of the organism. + Not only is every gland structurally adapted, down to the very minutest + histological details, to its function, but the function is equally + minutely adapted to the needs of the body. Every cell in the mucous lining + of the intestine is exactly regulated in its relation to the different + nutritive substances, and behaves in quite a different way towards the + fats, and towards nitrogenous substances, or peptones. + </p> + <p> + I have elsewhere called attention to the many adaptations of the whale to + the surrounding medium, and have pointed out—what has long been + known, but is not universally admitted, even now—that in it a great + number of important organs have been transformed in adaptation to the + peculiar conditions of aquatic life, although the ancestors of the whale + must have lived, like other hair-covered mammals, on land. I cited a + number of these transformations—the fish-like form of the body, the + hairlessness of the skin, the transformation of the fore-limbs to fins, + the disappearance of the hind-limbs and the development of a tail fin, the + layer of blubber under the skin, which affords the protection from cold + necessary to a warm-blooded animal, the disappearance of the ear-muscles + and the auditory passages, the displacement of the external nares to the + forehead for the greater security of the breathing-hole during the brief + appearance at the surface, and certain remarkable changes in the + respiratory and circulatory organs which enable the animal to remain for a + long time under water. I might have added many more, for the list of + adaptations in the whale to aquatic life is by no means exhausted; they + are found in the histological structure and in the minutest combinations + in the nervous system. For it is obvious that a tail-fin must be used in + quite a different way from a tail, which serves as a fly-brush in hoofed + animals, or as an aid to springing in the kangaroo or as a climbing organ; + it will require quite different reflex-mechanisms and nerve-combinations + in the motor centres. + </p> + <p> + I used this example in order to show how unnecessary it is to assume a + special internal evolutionary power for the phylogenesis of species, for + this whole order of whales is, so to speak, MADE UP OF ADAPTATIONS; it + deviates in many essential respects from the usual mammalian type, and all + the deviations are adaptations to aquatic life. But if precisely the most + essential features of the organisation thus depend upon adaptation, what + is left for a phyletic force to do, since it is these essential features + of the structure it would have to determine? There are few people now who + believe in a phyletic evolutionary power, which is not made up of the + forces known to us—adaptation and heredity—but the conviction + that EVERY part of an organism depends upon adaptation has not yet gained + a firm footing. Nevertheless, I must continue to regard this conception as + the correct one, as I have long done. + </p> + <p> + I may be permitted one more example. The feather of a bird is a marvellous + structure, and no one will deny that as a whole it depends upon + adaptation. But what part of it DOES NOT depend upon adaptation? The + hollow quill, the shaft with its hard, thin, light cortex, and the spongy + substance within it, its square section compared with the round section of + the quill, the flat barbs, their short, hooked barbules which, in the + flight-feathers, hook into one another with just sufficient firmness to + resist the pressure of the air at each wing-beat, the lightness and + firmness of the whole apparatus, the elasticity of the vane, and so on. + And yet all this belongs to an organ which is only passively functional, + and therefore can have nothing to do with the LAMARCKIAN PRINCIPLE. Nor + can the feather have arisen through some magical effect of temperature, + moisture, electricity, or specific nutrition, and thus selection is again + our only anchor of safety. + </p> + <p> + But—it will be objected—the substance of which the feather + consists, this peculiar kind of horny substance, did not first arise + through selection in the course of the evolution of the birds, for it + formed the covering of the scales of their reptilian ancestors. It is + quite true that a similar substance covered the scales of the Reptiles, + but why should it not have arisen among them through selection? Or in what + other way could it have arisen, since scales are also passively useful + parts? It is true that if we are only to call adaptation what has been + acquired by the species we happen to be considering, there would remain a + great deal that could not be referred to selection; but we are postulating + an evolution which has stretched back through aeons, and in the course of + which innumerable adaptations took place, which had not merely ephemeral + persistence in a genus, a family or a class, but which was continued into + whole Phyla of animals, with continual fresh adaptations to the special + conditions of each species, family, or class, yet with persistence of the + fundamental elements. Thus the feather, once acquired, persisted in all + birds, and the vertebral column, once gained by adaptation in the lowest + forms, has persisted in all the Vertebrates, from Amphioxus upwards, + although with constant readaptation to the conditions of each particular + group. Thus everything we can see in animals is adaptation, whether of + to-day, or of yesterday, or of ages long gone by; every kind of cell, + whether glandular, muscular, nervous, epidermic, or skeletal, is adapted + to absolutely definite and specific functions, and every organ which is + composed of these different kinds of cells contains them in the proper + proportions, and in the particular arrangement which best serves the + function of the organ; it is thus adapted to its function. + </p> + <p> + All parts of the organism are tuned to one another, that is, THEY ARE + ADAPTED TO ONE ANOTHER, and in the same way THE ORGANISM AS A WHOLE IS + ADAPTED TO THE CONDITIONS OF ITS LIFE, AND IT IS SO AT EVERY STAGE OF ITS + EVOLUTION. + </p> + <p> + But all adaptations CAN be referred to selection; the only point that + remains doubtful is whether they all MUST be referred to it. + </p> + <p> + However that may be, whether the LAMARCKIAN PRINCIPLE is a factor that has + cooperated with selection in evolution, or whether it is altogether + fallacious, the fact remains, that selection is the cause of a great part + of the phyletic evolution of organisms on our earth. Those who agree with + me in rejecting the LAMARCKIAN PRINCIPLE will regard selection as the only + GUIDING factor in evolution, which creates what is new out of the + transmissible variations, by ordering and arranging these, selecting them + in relation to their number and size, as the architect does his + building-stones so that a particular style must result. ("Variation under + Domestication", 1875 II. pages 426, 427.) But the building-stones + themselves, the variations, have their basis in the influences which cause + variation in those vital units which are handed on from one generation to + another, whether, taken together they form the WHOLE organism, as in + Bacteria and other low forms of life, or only a germ-substance, as in + unicellular and multicellular organisms. (The Author and Editor are + indebted to Professor Poulton for kindly assisting in the revision of the + proof of this Essay.) + </p> + <p> + <a name="link2H_4_0006" id="link2H_4_0006"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + IV. VARIATION. By HUGO DE VRIES. + </h2> + <h3> + Professor of Botany in the University of Amsterdam. + </h3> + <p> + I. DIFFERENT KINDS OF VARIABILITY. + </p> + <p> + Before Darwin, little was known concerning the phenomena of variability. + The fact, that hardly two leaves on a tree were exactly the same, could + not escape observation: small deviations of the same kind were met with + everywhere, among individuals as well as among the organs of the same + plant. Larger aberrations, spoken of as monstrosities, were for a long + time regarded as lying outside the range of ordinary phenomena. A special + branch of inquiry, that of Teratology, was devoted to them, but it + constituted a science by itself, sometimes connected with morphology, but + having scarcely any bearing on the processes of evolution and heredity. + </p> + <p> + Darwin was the first to take a broad survey of the whole range of + variations in the animal and vegetable kingdoms. His theory of Natural + Selection is based on the fact of variability. In order that this + foundation should be as strong as possible he collected all the facts, + scattered in the literature of his time, and tried to arrange them in a + scientific way. He succeeded in showing that variations may be grouped + along a line of almost continuous gradations, beginning with simple + differences in size and ending with monstrosities. He was struck by the + fact that, as a rule, the smaller the deviations, the more frequently they + appear, very abrupt breaks in characters being of rare occurrence. + </p> + <p> + Among these numerous degrees of variability Darwin was always on the look + out for those which might, with the greatest probability, be considered as + affording material for natural selection to act upon in the development of + new species. Neither of the extremes complied with his conceptions. He + often pointed out, that there are a good many small fluctuations, which in + this respect must be absolutely useless. On the other hand, he strongly + combated the belief, that great changes would be necessary to explain the + origin of species. Some authors had propounded the idea that highly + adapted organs, e.g. the wings of a bird, could not have been developed in + any other way than by a comparatively sudden modification of a well + defined and important kind. Such a conception would allow of great breaks + or discontinuity in the evolution of highly differentiated animals and + plants, shortening the time for the evolution of the whole organic kingdom + and getting over numerous difficulties inherent in the theory of slow and + gradual progress. It would, moreover, account for the genetic relation of + the larger groups of both animals and plants. It would, in a word, + undoubtedly afford an easy means of simplifying the problem of descent + with modification. + </p> + <p> + Darwin, however, considered such hypotheses as hardly belonging to the + domain of science; they belong, he said, to the realm of miracles. That + species have a capacity for change is admitted by all evolutionists; but + there is no need to invoke modifications other than those represented by + ordinary variability. It is well known that in artificial selection this + tendency to vary has given rise to numerous distinct races, and there is + no reason for denying that it can do the same in nature, by the aid of + natural selection. On both lines an advance may be expected with equal + probability. + </p> + <p> + His main argument, however, is that the most striking and most highly + adapted modifications may be acquired by successive variations. Each of + these may be slight, and they may affect different organs, gradually + adapting them to the same purpose. The direction of the adaptations will + be determined by the needs in the struggle for life, and natural selection + will simply exclude all such changes as occur on opposite or deviating + lines. In this way, it is not variability itself which is called upon to + explain beautiful adaptations, but it is quite sufficient to suppose that + natural selection has operated during long periods in the same way. + Eventually, all the acquired characters, being transmitted together, would + appear to us, as if they had all been simultaneously developed. + </p> + <p> + Correlations must play a large part in such special evolutions: when one + part is modified, so will be other parts. The distribution of nourishment + will come in as one of the causes, the reactions of different organs to + the same external influences as another. But no doubt the more effective + cause is that of the internal correlations, which, however, are still but + dimly understood. Darwin repeatedly laid great stress on this view, + although a definite proof of its correctness could not be given in his + time. Such proof requires the direct observation of a mutation, and it + should be stated here that even the first observations made in this + direction have clearly confirmed Darwin's ideas. The new evening primroses + which have sprung in my garden from the old form of Oenothera Lamarckiana, + and which have evidently been derived from it, in each case, by a single + mutation, do not differ from their parent species in one character only, + but in almost all their organs and qualities. Oenothera gigas, for + example, has stouter stems and denser foliage; the leaves are larger and + broader; its thick flower-buds produce gigantic flowers, but only small + fruits with large seeds. Correlative changes of this kind are seen in all + my new forms, and they lend support to the view that in the gradual + development of highly adapted structures, analogous correlations may have + played a large part. They easily explain large deviations from an original + type, without requiring the assumption of too many steps. + </p> + <p> + Monstrosities, as their name implies, are widely different in character + from natural species; they cannot, therefore, be adduced as evidence in + the investigation of the origin of species. There is no doubt that they + may have much in common as regards their manner of origin, and that the + origin of species, once understood, may lead to a better understanding of + the monstrosities. But the reverse is not true, at least not as regards + the main lines of development. Here, it is clear, monstrosities cannot + have played a part of any significance. + </p> + <p> + Reversions, or atavistic changes, would seem to give a better support to + the theory of descent through modifications. These have been of paramount + importance on many lines of evolution of the animal as well as of the + vegetable kingdom. It is often assumed that monocotyledons are descended + from some lower group of dicotyledons, probably allied to that which + includes the buttercup family. On this view the monocotyledons must be + assumed to have lost the cambium and all its influence on secondary + growth, the differentiation of the flower into calyx and corolla, the + second cotyledon or seed-leaf and several other characters. Losses of + characters such as these may have been the result of abrupt changes, but + this does not prove that the characters themselves have been produced with + equal suddenness. On the contrary, Darwin shows very convincingly that a + modification may well be developed by a series of steps, and afterwards + suddenly disappear. Many monstrosities, such as those represented by + twisted stems, furnish direct proofs in support of this view, since they + are produced by the loss of one character and this loss implies secondary + changes in a large number of other organs and qualities. + </p> + <p> + Darwin criticises in detail the hypothesis of great and abrupt changes and + comes to the conclusion that it does not give even a shadow of an + explanation of the origin of species. It is as improbable as it is + unnecessary. + </p> + <p> + Sports and spontaneous variations must now be considered. It is well known + that they have produced a large number of fine horticultural varieties. + The cut-leaved maple and many other trees and shrubs with split leaves are + known to have been produced at a single step; this is true in the case of + the single-leaf strawberry plant and of the laciniate variety of the + greater celandine: many white flowers, white or yellow berries and + numerous other forms had a similar origin. But changes such as these do + not come under the head of adaptations, as they consist for the most part + in the loss of some quality or organ belonging to the species from which + they were derived. Darwin thinks it impossible to attribute to this cause + the innumerable structures, which are so well adapted to the habits of + life of each species. At the present time we should say that such + adaptations require progressive modifications, which are additions to the + stock of qualities already possessed by the ancestors, and cannot, + therefore, be explained on the ground of a supposed analogy with sports, + which are for the most part of a retrogressive nature. + </p> + <p> + Excluding all these more or less sudden changes, there remains a long + series of gradations of variability, but all of these are not assumed by + Darwin to be equally fit for the production of new species. In the first + place, he disregards all mere temporary variations, such as size, + albinism, etc.; further, he points out that very many species have almost + certainly been produced by steps, not greater, and probably not very much + smaller, than those separating closely related varieties. For varieties + are only small species. Next comes the question of polymorphic species: + their occurrence seems to have been a source of much doubt and difficulty + in Darwin's mind, although at present it forms one of the main supports of + the prevailing explanation of the origin of new species. Darwin simply + states that this kind of variability seems to be of a peculiar nature; + since polymorphic species are now in a stable condition their occurrence + gives no clue as to the mode of origin of new species. Polymorphic species + are the expression of the result of previous variability acting on a large + scale; but they now simply consist of more or less numerous elementary + species, which, as far as we know, do not at present exhibit a larger + degree of variability than any other more uniform species. The vernal + whitlow-grass (Draba verna) and the wild pansy are the best known + examples; both have spread over almost the whole of Europe and are split + up into hundreds of elementary forms. These sub-species show no signs of + any extraordinary degree of variability, when cultivated under conditions + necessary for the exclusion of inter-crossing. Hooker has shown, in the + case of some ferns distributed over still wider areas, that the extinction + of some of the intermediate forms in such groups would suffice to justify + the elevation of the remaining types to the rank of distinct species. + Polymorphic species may now be regarded as the link which unites ordinary + variability with the historical production of species. But it does not + appear that they had this significance for Darwin; and, in fact, they + exhibit no phenomena which could explain the processes by which one + species has been derived from another. By thus narrowing the limits of the + species-producing variability Darwin was led to regard small deviations as + the source from which natural selection derives material upon which to + act. But even these are not all of the same type, and Darwin was well + aware of the fact. + </p> + <p> + It should here be pointed out that in order to be selected, a change must + first have been produced. This proposition, which now seems self-evident, + has, however, been a source of much difference of opinion among Darwin's + followers. The opinion that natural selection produces changes in useful + directions has prevailed for a long time. In other words, it was assumed + that natural selection, by the simple means of singling out, could induce + small and useful changes to increase and to reach any desired degree of + deviation from the original type. In my opinion this view was never + actually held by Darwin. It is in contradiction with the acknowledged aim + of all his work,—the explanation of the origin of species by means + of natural forces and phenomena only. Natural selection acts as a sieve; + it does not single out the best variations, but it simply destroys the + larger number of those which are, from some cause or another, unfit for + their present environment. In this way it keeps the strains up to the + required standard, and, in special circumstances, may even improve them. + </p> + <p> + Returning to the variations which afford the material for the + sieving-action of natural selection, we may distinguish two main kinds. It + is true that the distinction between these was not clear at the time of + Darwin, and that he was unable to draw a sharp line between them. + Nevertheless, in many cases, he was able to separate them, and he often + discussed the question which of the two would be the real source of the + differentiation of species. Certain variations constantly occur, + especially such as are connected with size, weight, colour, etc. They are + usually too small for natural selection to act upon, having hardly any + influence in the struggle for life: others are more rare, occurring only + from time to time, perhaps once or twice in a century, perhaps even only + once in a thousand years. Moreover, these are of another type, not simply + affecting size, number or weight, but bringing about something new, which + may be useful or not. Whenever the variation is useful natural selection + will take hold of it and preserve it; in other cases the variation may + either persist or disappear. + </p> + <p> + In his criticism of miscellaneous objections brought forward against the + theory of natural selection after the publication of the first edition of + "The Origin of Species", Darwin stated his view on this point very + clearly:—"The doctrine of natural selection or the survival of the + fittest, which implies that when variations or individual differences of a + beneficial nature happen to arise, these will be preserved." ("Origin of + Species" (6th edition), page 169, 1882.) In this sentence the words + "HAPPEN TO ARISE" appear to me of prominent significance. They are + evidently due to the same general conception which prevailed in Darwin's + Pangenesis hypothesis. (Cf. de Vries, "Intracellulare Pangenesis", page + 73, Jena, 1889, and "Die Mutationstheorie", I. page 63. Leipzig, 1901.) + </p> + <p> + A distinction is indicated between ordinary fluctuations which are always + present, and such variations as "happen to arise" from time to time. ((I + think it right to point out that the interpretation of this passage from + the "Origin" by Professor de Vries is not accepted as correct either by Mr + Francis Darwin or by myself. We do not believe that Darwin intended to + draw any distinction between TWO TYPES of variation; the words "when + variations or individual differences of a beneficial nature happen to + arise" are not in our opinion meant to imply a distinction between + ordinary fluctuations and variations which "happen to arise," but we + believe that "or" is here used in the sense of ALIAS. With the permission + of Professor de Vries, the following extract is quoted from a letter in + which he replied to the objection raised to his reading of the passage in + question: + </p> + <p> + "As to your remarks on the passage on page 6, I agree that it is now + impossible to see clearly how far Darwin went in his distinction of the + different kinds of variability. Distinctions were only dimly guessed at by + him. But in our endeavour to arrive at a true conception of his view I + think that the chapter on Pangenesis should be our leading guide, and that + we should try to interpret the more difficult passages by that chapter. A + careful and often repeated study of the Pangenesis hypothesis has + convinced me that Darwin, when he wrote that chapter, was well aware that + ordinary variability has nothing to do with evolution, but that other + kinds of variation were necessary. In some chapters he comes nearer to a + clear distinction than in others. To my mind the expression 'happen to + arise' is the sharpest indication of his inclining in this direction. I am + quite convinced that numerous expressions in his book become much clearer + when looked at in this way." + </p> + <p> + The statement in this passage that "Darwin was well aware that ordinary + variability has nothing to do with evolution, but that other kinds of + variation were necessary" is contradicted by many passages in the + "Origin". A.C.S.)) The latter afford the material for natural selection to + act upon on the broad lines of organic development, but the first do not. + Fortuitous variations are the species-producing kind, which the theory + requires; continuous fluctuations constitute, in this respect, a useless + type. + </p> + <p> + Of late, the study of variability has returned to the recognition of this + distinction. Darwin's variations, which from time to time happen to arise, + are MUTATIONS, the opposite type being commonly designed fluctuations. A + large mass of facts, collected during the last few decades, has confirmed + this view, which in Darwin's time could only be expressed with much + reserve, and everyone knows that Darwin was always very careful in + statements of this kind. + </p> + <p> + From the same chapter I may here cite the following paragraph: "Thus as I + am inclined to believe, morphological differences,... such as the + arrangement of the leaves, the divisions of the flower or of the ovarium, + the position of the ovules, etc.—first appeared in many cases as + fluctuating variations, which sooner or later became constant through the + nature of the organism and of the surrounding conditions... but NOT + THROUGH NATURAL SELECTION (The italics are mine (H. de V.).); for as these + morphological characters do not affect the welfare of the species, any + slight deviation in them could not have been governed or accumulated + through this latter agency." ("Origin of Species" (6th edition), page + 176.) We thus see that in Darwin's opinion, all small variations had not + the same importance. In favourable circumstances some could become + constant, but others could not. + </p> + <p> + Since the appearance of the first edition of "The Origin of Species" + fluctuating variability has been thoroughly studied by Quetelet. He + discovered the law, which governs all phenomena of organic life falling + under this head. It is a very simple law, and states that individual + variations follow the laws of probability. He proved it, in the first + place, for the size of the human body, using the measurements published + for Belgian recruits; he then extended it to various other measurements of + parts of the body, and finally concluded that it must be of universal + validity for all organic beings. It must hold true for all characters in + man, physical as well as intellectual and moral qualities; it must hold + true for the plant kingdom as well as for the animal kingdom; in short, it + must include the whole living world. + </p> + <p> + Quetelet's law may be most easily studied in those cases where the + variability relates to measure, number and weight, and a vast number of + facts have since confirmed its exactness and its validity for all kinds of + organisms, organs and qualities. But if we examine it more closely, we + find that it includes just those minute variations, which, as Darwin + repeatedly pointed out, have often no significance for the origin of + species. In the phenomena, described by Quetelet's law nothing "happens to + arise"; all is governed by the common law, which states that small + deviations from the mean type are frequent, but that larger aberrations + are rare, the rarer as they are larger. Any degree of variation will be + found to occur, if only the number of individuals studied is large enough: + it is even possible to calculate before hand, how many specimens must be + compared in order to find a previously fixed degree of deviation. + </p> + <p> + The variations, which from time to time happen to appear, are evidently + not governed by this law. They cannot, as yet, be produced at will: no + sowings of thousands or even of millions of plants will induce them, + although by such means the chance of their occurring will obviously be + increased. But they are known to occur, and to occur suddenly and + abruptly. They have been observed especially in horticulture, where they + are ranged in the large and ill-defined group called sports. Korschinsky + has collected all the evidence which horticultural literature affords on + this point. (S. Korschinsky, "Heterogenesis und Evolution", "Flora", Vol. + LXXXIX. pages 240-363, 1901.) Several cases of the first appearance of a + horticultural novelty have been recorded: this has always happened in the + same way; it appeared suddenly and unexpectedly without any definite + relation to previously existing variability. Dwarf types are one of the + commonest and most favourite varieties of flowering plants; they are not + originated by a repeated selection of the smallest specimens, but appear + at once, without intermediates and without any previous indication. In + many instances they are only about half the height of the original type, + thus constituting obvious novelties. So it is in other cases described by + Korschinsky: these sports or mutations are now recognised to be the main + source of varieties of horticultural plants. + </p> + <p> + As already stated, I do not pretend that the production of horticultural + novelties is the prototype of the origin of new species in nature. I + assume that they are, as a rule, derived from the parent species by the + loss of some organ or quality, whereas the main lines of the evolution of + the animal and vegetable kingdom are of course determined by progressive + changes. Darwin himself has often pointed out this difference. But the + saltatory origin of horticultural novelties is as yet the simplest + parallel for natural mutations, since it relates to forms and phenomena, + best known to the general student of evolution. + </p> + <p> + The point which I wish to insist upon is this. The difference between + small and ever present fluctuations and rare and more sudden variations + was clear to Darwin, although the facts known at his time were too meagre + to enable a sharp line to be drawn between these two great classes of + variability. Since Darwin's time evidence, which proves the correctness of + his view, has accumulated with increasing rapidity. Fluctuations + constitute one type; they are never absent and follow the law of chance, + but they do not afford the material from which to build new species. + Mutations, on the other hand, only happen to occur from time to time. They + do not necessarily produce greater changes than fluctuations, but such as + may become, or rather are from their very nature, constant. It is this + constancy which is the mark of specific characters, and on this basis + every new specific character may be assumed to have arisen by mutation. + </p> + <p> + Some authors have tried to show that the theory of mutation is opposed to + Darwin's views. But this is erroneous. On the contrary, it is in fullest + harmony with the great principle laid down by Darwin. In order to be acted + upon by that complex of environmental forces, which Darwin has called + natural selection, the changes must obviously first be there. The manner + in which they are produced is of secondary importance and has hardly any + bearing on the theory of descent with modification. ("Life and Letters" + II. 125.) + </p> + <p> + A critical survey of all the facts of variability of plants in nature as + well as under cultivation has led me to the conviction, that Darwin was + right in stating that those rare beneficial variations, which from time to + time happen to arise,—the now so-called mutations—are the real + source of progress in the whole realm of the organic world. + </p> + <p> + II. EXTERNAL AND INTERNAL CAUSES OF VARIABILITY. + </p> + <p> + All phenomena of animal and plant life are governed by two sets of causes; + one of these is external, the other internal. As a rule the internal + causes determine the nature of a phenomenon—what an organism can do + and what it cannot do. The external causes, on the other hand, decide when + a certain variation will occur, and to what extent its features may be + developed. + </p> + <p> + As a very clear and wholly typical instance I cite the cocks-combs + (Celosia). This race is distinguished from allied forms by its faculty of + producing the well-known broad and much twisted combs. Every single + individual possesses this power, but all individuals do not exhibit it in + its most complete form. In some cases this faculty may not be exhibited at + the top of the main stem, although developed in lateral branches: in + others it begins too late for full development. Much depends upon + nourishment and cultivation, but almost always the horticulturist has to + single out the best individuals and to reject those which do not come up + to the standard. + </p> + <p> + The internal causes are of a historical nature. The external ones may be + defined as nourishment and environment. In some cases nutrition is the + main factor, as, for instance, in fluctuating variability, but in natural + selection environment usually plays the larger part. + </p> + <p> + The internal or historical causes are constant during the life-time of a + species, using the term species in its most limited sense, as designating + the so-called elementary species or the units out of which the ordinary + species are built up. These historical causes are simply the specific + characters, since in the origin of a species one or more of these must + have been changed, thus producing the characters of the new type. These + changes must, of course, also be due partly to internal and partly to + external causes. + </p> + <p> + In contrast to these changes of the internal causes, the ordinary + variability which is exhibited during the life-time of a species is called + fluctuating variability. The name mutations or mutating variability is + then given to the changes in the specific characters. It is desirable to + consider these two main divisions of variability separately. + </p> + <p> + In the case of fluctuations the internal causes, as well as the external + ones, are often apparent. The specific characters may be designated as the + mean about which the observed forms vary. Almost every character may be + developed to a greater or a less degree, but the variations of the single + characters producing a small deviation from the mean are usually the + commonest. The limits of these fluctuations may be called wide or narrow, + according to the way we look at them, but in numerous cases the extreme on + the favoured side hardly surpasses double the value of that on the other + side. The degree of this development, for every individual and for every + organ, is dependent mainly on nutrition. Better nourishment or an + increased supply of food produces a higher development; only it is not + always easy to determine which direction is the fuller and which is the + poorer one. The differences among individuals grown from different seeds + are described as examples of individual variability, but those which may + be observed on the same plant, or on cuttings, bulbs or roots derived from + one individual are referred to as cases of partial variability. Partial + variability, therefore, determines the differences among the flowers, + fruits, leaves or branches of one individual: in the main, it follows the + same laws as individual variability, but the position of a branch on a + plant also determines its strength, and the part it may take in the + nourishment of the whole. Composite flowers and umbels therefore have, as + a rule, fewer rays on weak branches than on the strong main ones. The + number of carpels in the fruits of poppies becomes very small on the weak + lateral branches, which are produced towards the autumn, as well as on + crowded, and therefore on weakened individuals. Double flowers follow the + same rule, and numerous other instances could easily be adduced. + </p> + <p> + Mutating variability occurs along three main lines. Either a character may + disappear, or, as we now say, become latent; or a latent character may + reappear, reproducing thereby a character which was once prominent in more + or less remote ancestors. The third and most interesting case is that of + the production of quite new characters which never existed in the + ancestors. Upon this progressive mutability the main development of the + animal and vegetable kingdom evidently depends. In contrast to this, the + two other cases are called retrogressive and degressive mutability. In + nature retrogressive mutability plays a large part; in agriculture and in + horticulture it gives rise to numerous varieties, which have in the past + been preserved, either on account of their usefulness or beauty, or simply + as fancy-types. In fact the possession of numbers of varieties may be + considered as the main character of domesticated animals and cultivated + plants. + </p> + <p> + In the case of retrogressive and degressive mutability the internal cause + is at once apparent, for it is this which causes the disappearance or + reappearance of some character. With progressive mutations the case is not + so simple, since the new character must first be produced and then + displayed. These two processes are theoretically different, but they may + occur together or after long intervals. The production of the new + character I call premutation, and the displaying mutation. Both of course + must have their external as well as their internal causes, as I have + repeatedly pointed out in my work on the Mutation Theory. ("Die + Mutationstheorie", 2 vols., Leipzig, 1901.) + </p> + <p> + It is probable that nutrition plays as important a part among the external + causes of mutability as it does among those of fluctuating variability. + Observations in support of this view, however, are too scanty to allow of + a definite judgment. Darwin assumed an accumulative influence of external + causes in the case of the production of new varieties or species. The + accumulation might be limited to the life-time of a single individual, or + embrace that of two or more generations. In the end a degree of + instability in the equilibrium of one or more characters might be + attained, great enough for a character to give way under a small shock + produced by changed conditions of life. The character would then be thrown + over from the old state of equilibrium into a new one. + </p> + <p> + Characters which happen to be in this state of unstable equilibrium are + called mutable. They may be either latent or active, being in the former + case derived from old active ones or produced as new ones (by the process, + designated premutation). They may be inherited in this mutable condition + during a long series of generations. I have shown that in the case of the + evening primrose of Lamarck this state of mutability must have existed for + at least half a century, for this species was introduced from Texas into + England about the year 1860, and since then all the strains derived from + its first distribution over the several countries of Europe show the same + phenomena in producing new forms. The production of the dwarf evening + primrose, or Oenothera nanella, is assumed to be due to one of the + factors, which determines the tall stature of the parent form, becoming + latent; this would, therefore, afford an example of retrogressive + mutation. Most of the other types of my new mutants, on the other hand, + seem to be due to progressive mutability. + </p> + <p> + The external causes of this curious period of mutability are as yet wholly + unknown and can hardly be guessed at, since the origin of the Oenothera + Lamarckiana is veiled in mystery. The seeds, introduced into England about + 1860, were said to have come from Texas, but whether from wild or from + cultivated plants we do not know. Nor has the species been recorded as + having been observed in the wild condition. This, however, is nothing + peculiar. The European types of Oenothera biennis and O. muricata are in + the same condition. The first is said to have been introduced from + Virginia, and the second from Canada, but both probably from plants + cultivated in the gardens of these countries. Whether the same elementary + species are still growing on those spots is unknown, mainly because the + different sub-species of the species mentioned have not been + systematically studied and distinguished. + </p> + <p> + The origin of new species, which is in part the effect of mutability, is, + however, due mainly to natural selection. Mutability provides the new + characters and new elementary species. Natural selection, on the other + hand, decides what is to live and what to die. Mutability seems to be + free, and not restricted to previously determined lines. Selection, + however, may take place along the same main lines in the course of long + geological epochs, thus directing the development of large branches of the + animal and vegetable kingdom. In natural selection it is evident that + nutrition and environment are the main factors. But it is probable that, + while nutrition may be one of the main causes of mutability, environment + may play the chief part in the decisions ascribed to natural selection. + Relations to neighbouring plants and to injurious or useful animals, have + been considered the most important determining factors ever since the time + when Darwin pointed out their prevailing influence. + </p> + <p> + From this discussion of the main causes of variability we may derive the + proposition that the study of every phenomenon in the field of heredity, + of variability, and of the origin of new species will have to be + considered from two standpoints; on one hand we have the internal causes, + on the other the external ones. Sometimes the first are more easily + detected, in other cases the latter are more accessible to investigation. + But the complete elucidation of any phenomenon of life must always combine + the study of the influence of internal with that of external causes. + </p> + <p> + III. POLYMORPHIC VARIABILITY IN CEREALS. + </p> + <p> + One of the propositions of Darwin's theory of the struggle for life + maintains that the largest amount of life can be supported on any area, by + great diversification or divergence in the structure and constitution of + its inhabitants. Every meadow and every forest affords a proof of this + thesis. The numerical proportion of the different species of the flora is + always changing according to external influences. Thus, in a given meadow, + some species will flower abundantly in one year and then almost disappear, + until, after a series of years, circumstances allow them again to multiply + rapidly. Other species, which have taken their places, will then become + rare. It follows from this principle, that notwithstanding the constantly + changing conditions, a suitable selection from the constituents of a + meadow will ensure a continued high production. But, although the + principle is quite clear, artificial selection has, as yet, done very + little towards reaching a really high standard. + </p> + <p> + The same holds good for cereals. In ordinary circumstances a field will + give a greater yield, if the crop grown consists of a number of + sufficiently differing types. Hence it happens that almost all older + varieties of wheat are mixtures of more or less diverging forms. In the + same variety the numerical composition will vary from year to year, and in + oats this may, in bad years, go so far as to destroy more than half of the + harvest, the wind-oats (Avena fatua), which scatter their grain to the + winds as soon as it ripens, increasing so rapidly that they assume the + dominant place. A severe winter, a cold spring and other extreme + conditions of life will destroy one form more completely than another, and + it is evident that great changes in the numerical composition of the + mixture may thus be brought about. + </p> + <p> + This mixed condition of the common varieties of cereals was well known to + Darwin. For him it constituted one of the many types of variability. It is + of that peculiar nature to which, in describing other groups, he applies + the term polymorphy. It does not imply that the single constituents of the + varieties are at present really changing their characters. On the other + hand, it does not exclude the possibility of such changes. It simply + states that observation shows the existence of different forms; how these + have originated is a question which it does not deal with. In his + well-known discussion of the variability of cereals, Darwin is mainly + concerned with the question, whether under cultivation they have undergone + great changes or only small ones. The decision ultimately depends on the + question, how many forms have originally been taken into cultivation. + Assuming five or six initial species, the variability must be assumed to + have been very large, but on the assumption that there were between ten + and fifteen types, the necessary range of variability is obviously much + smaller. But in regard to this point, we are of course entirely without + historical data. + </p> + <p> + Few of the varieties of wheat show conspicuous differences, although their + number is great. If we compare the differentiating characters of the + smaller types of cereals with those of ordinary wild species, even within + the same genus or family, they are obviously much less marked. All these + small characters, however, are strictly inherited, and this fact makes it + very probable that the less obvious constituents of the mixtures in + ordinary fields must be constant and pure as long as they do not + intercross. Natural crossing is in most cereals a phenomenon of rare + occurrence, common enough to admit of the production of all possible + hybrid combinations, but requiring the lapse of a long series of years to + reach its full effect. + </p> + <p> + Darwin laid great stress on this high amount of variability in the plants + of the same variety, and illustrated it by the experience of Colonel Le + Couteur ("On the Varieties, Properties, and Classification of Wheat", + Jersey, 1837.) on his farm on the isle of Jersey, who cultivated upwards + of 150 varieties of wheat, which he claimed were as pure as those of any + other agriculturalist. But Professor La Gasca of Madrid, who visited him, + drew attention to aberrant ears, and pointed out, that some of them might + be better yielders than the majority of plants in the crop, whilst others + might be poor types. Thence he concluded that the isolation of the better + ones might be a means of increasing his crops. Le Couteur seems to have + considered the constancy of such smaller types after isolation as + absolutely probable, since he did not even discuss the possibility of + their being variable or of their yielding a changeable or mixed progeny. + This curious fact proves that he considered the types, discovered in his + fields by La Gasca to be of the same kind as his other varieties, which + until that time he had relied upon as being pure and uniform. Thus we see, + that for him, the variability of cereals was what we now call polymorphy. + He looked through his fields for useful aberrations, and collected + twenty-three new types of wheat. He was, moreover, clear about one point, + which, on being rediscovered after half a century, has become the + starting-point for the new Swedish principle of selecting agricultural + plants. It was the principle of single-ear sowing, instead of mixing the + grains of all the selected ears together. By sowing each ear on a separate + plot he intended not only to multiply them, but also to compare their + value. This comparison ultimately led him to the choice of some few + valuable sorts, one of which, the "Bellevue de Talavera," still holds its + place among the prominent sorts of wheat cultivated in France. This + variety seems to be really a uniform type, a quality very useful under + favourable conditions of cultivation, but which seems to have destroyed + its capacity for further improvement by selection. + </p> + <p> + The principle of single-ear sowing, with a view to obtain pure and uniform + strains without further selection, has, until a few years ago, been almost + entirely lost sight of. Only a very few agriculturists have applied it: + among these are Patrick Shirreff ("Die Verbesserung der Getreide-Arten", + translated by R. Hesse, Halle, 1880.) in Scotland and Willet M. Hays + ("Wheat, varieties, breeding, cultivation", Univ. Minnesota, Agricultural + Experimental Station, Bull. no. 62, 1899.) in Minnesota. Patrick Shirreff + observed the fact, that in large fields of cereals, single plants may from + time to time be found with larger ears, which justify the expectation of a + far greater yield. In the course of about twenty-five years he isolated in + this way two varieties of wheat and two of oats. He simply multiplied them + as fast as possible, without any selection, and put them on the market. + </p> + <p> + Hays was struck by the fact that the yield of wheat in Minnesota was far + beneath that in the neighbouring States. The local varieties were Fife and + Blue Stem. They gave him, on inspection, some better specimens, + "phenomenal yielders" as he called them. These were simply isolated and + propagated, and, after comparison with the parent-variety and with some + other selected strains of less value, were judged to be of sufficient + importance to be tested by cultivation all over the State of Minnesota. + They have since almost supplanted the original types, at least in most + parts of the State, with the result that the total yield of wheat in + Minnesota is said to have been increased by about a million dollars + yearly. + </p> + <p> + Definite progress in the method of single-ear sowing has, however, been + made only recently. It had been foreshadowed by Patrick Shirreff, who + after the production of the four varieties already mentioned, tried to + carry out his work on a larger scale, by including numerous minor + deviations from the main type. He found by doing so that the chances of + obtaining a better form were sufficiently increased to justify the trial. + But it was Nilsson who discovered the almost inexhaustible polymorphy of + cereals and other agricultural crops and made it the starting-point for a + new and entirely trustworthy method of the highest utility. By this means + he has produced during the last fifteen years a number of new and valuable + races, which have already supplanted the old types on numerous farms in + Sweden and which are now being introduced on a large scale into Germany + and other European countries. + </p> + <p> + It is now twenty years since the station at Svalof was founded. During the + first period of its work, embracing about five years, selection was + practised on the principle which was then generally used in Germany. In + order to improve a race a sample of the best ears was carefully selected + from the best fields of the variety. These ears were considered as + representatives of the type under cultivation, and it was assumed that by + sowing their grains on a small plot a family could be obtained, which + could afterwards be improved by a continuous selection. Differences + between the collected ears were either not observed or disregarded. At + Svalof this method of selection was practised on a far larger scale than + on any German farm, and the result was, broadly speaking, the same. This + may be stated in the following words: improvement in a few cases, failure + in all the others. Some few varieties could be improved and yielded + excellent new types, some of which have since been introduced into Swedish + agriculture and are now prominent races in the southern and middle parts + of the country. But the station had definite aims, and among them was the + improvement of the Chevalier barley. This, in Middle Sweden, is a fine + brewer's barley, but liable to failure during unfavourable summers on + account of its slender stems. It was selected with a view of giving it + stiffer stems, but in spite of all the care and work bestowed upon it no + satisfactory result was obtained. + </p> + <p> + This experience, combined with a number of analogous failures, could not + fail to throw doubt upon the whole method. It was evident that good + results were only exceptions, and that in most cases the principle was not + one that could be relied upon. The exceptions might be due to unknown + causes, and not to the validity of the method; it became therefore of much + more interest to search for the causes than to continue the work along + these lines. + </p> + <p> + In the year 1892 a number of different varieties of cereals were + cultivated on a large scale and a selection was again made from them. + About two hundred samples of ears were chosen, each apparently + constituting a different type. Their seeds were sown on separate plots and + manured and treated as much as possible in the same manner. The plots were + small and arranged in rows so as to facilitate the comparison of allied + types. During the whole period of growth and during the ripening of the + ears the plots were carefully studied and compared: they were harvested + separately; ears and kernels were counted and weighed, and notes were made + concerning layering, rust and other cereal pests. + </p> + <p> + The result of this experiment was, in the main, no distinct improvement. + Nilsson was especially struck by the fact that the plots, which should + represent distinct types, were far from uniform. Many of them were as + multiform as the fields from which the parent-ears were taken. Others + showed variability in a less degree, but in almost all of them it was + clear that a pure race had not been obtained. The experiment was a fair + one, inasmuch as it demonstrated the polymorphic variability of cereals + beyond all doubt and in a degree hitherto unsuspected; but from the + standpoint of the selectionist it was a failure. Fortunately there were, + however, one or two exceptions. A few lots showed a perfect uniformity in + regard to all the stalks and ears: these were small families. This fact + suggested the idea that each might have been derived from a single ear. + During the selection in the previous summer, Nilsson had tried to find as + many ears as possible of each new type which he recognised in his fields. + But the variability of his crops was so great, that he was rarely able to + include more than two or three ears in the same group, and, in a few + cases, he found only one representative of the supposed type. It might, + therefore, be possible that those small uniform plots were the direct + progeny of ears, the grains of which had not been mixed with those from + other ears before sowing. Exact records had, of course, been kept of the + chosen samples, and the number of ears had been noted in each case. It + was, therefore, possible to answer the question and it was found that + those plots alone were uniform on which the kernels of one single ear only + had been sown. Nilsson concluded that the mixture of two or more ears in a + single sowing might be the cause of the lack of uniformity in the progeny. + Apparently similar ears might be different in their progeny. + </p> + <p> + Once discovered, this fact was elevated to the rank of a leading principle + and tested on as large a scale as possible. The fields were again + carefully investigated and every single ear, which showed a distinct + divergence from the main type in one character or another, was selected. A + thousand samples were chosen, but this time each sample consisted of one + ear only. Next year, the result corresponded to the expectation. + Uniformity prevailed almost everywhere; only a few lots showed a + discrepancy, which might be ascribed to the accidental selection of hybrid + ears. It was now clear that the progeny of single ears was, as a rule, + pure, whereas that of mixed ears was impure. The single-ear selection or + single-ear sowing, which had fallen into discredit in Germany and + elsewhere in Europe, was rediscovered. It proved to be the only + trustworthy principle of selection. Once isolated, such single-parent + races are constant from seed and remain true to their type. No further + selection is needed; they have simply to be multiplied and their real + value tested. + </p> + <p> + Patrick Shirreff, in his early experiments, Le Couteur, Hays and others + had observed the rare occurrence of exceptionally good yielders and the + value of their isolation to the agriculturist. The possibility of error in + the choice of such striking specimens and the necessity of judging their + value by their progeny were also known to these investigators, but they + had not the slightest idea of all the possibilities suggested by their + principle. Nilsson, who is a botanist as well as an agriculturist, + discovered that, besides these exceptionably good yielders, every variety + of a cereal consists of hundreds of different types, which find the best + conditions for success when grown together, but which, after isolation, + prove to be constant. Their preference for mixed growth is so definite, + that once isolated, their claims on manure and treatment are found to be + much higher than those of the original mixed variety. Moreover, the + greatest care is necessary to enable them to retain their purity, and as + soon as they are left to themselves they begin to deteriorate through + accidental crosses and admixtures and rapidly return to the mixed + condition. + </p> + <p> + Reverting now to Darwin's discussion of the variability of cereals, we may + conclude that subsequent investigation has proved it to be exactly of the + kind which he describes. The only difference is that in reality it reaches + a degree, quite unexpected by Darwin and his contemporaries. But it is + polymorphic variability in the strictest sense of the word. How the single + constituents of a variety originate we do not see. We may assume, and + there can hardly be a doubt about the truth of the assumption, that a new + character, once produced, will slowly but surely be combined through + accidental crosses with a large number of previously existing types, and + so will tend to double the number of the constituents of the variety. But + whether it first appears suddenly or whether it is only slowly evolved we + cannot determine. It would, of course, be impossible to observe either + process in such a mixture. Only cultures of pure races, of single-parent + races as we have called them, can afford an opportunity for this kind of + observation. In the fields of Svalof new and unexpected qualities have + recently been seen, from time to time, to appear suddenly. These + characters are as distinct as the older ones and appear to be constant + from the moment of their origin. + </p> + <p> + Darwin has repeatedly insisted that man does not cause variability. He + simply selects the variations given to him by the hand of nature. He may + repeat this process in order to accumulate different new characters in the + same family, thus producing varieties of a higher order. This process of + accumulation would, if continued for a longer time, lead to the + augmentation of the slight differences characteristic of varieties into + the greater differences characteristic of species and genera. It is in + this way that horticultural and agricultural experience contribute to the + problem of the conversion of varieties into species, and to the + explanation of the admirable adaptations of each organism to its complex + conditions of life. In the long run new forms, distinguished from their + allies by quite a number of new characters, would, by the extermination of + the older intermediates, become distinct species. + </p> + <p> + Thus we see that the theory of the origin of species by means of natural + selection is quite independent of the question, how the variations to be + selected arise. They may arise slowly, from simple fluctuations, or + suddenly, by mutations; in both cases natural selection will take hold of + them, will multiply them if they are beneficial, and in the course of time + accumulate them, so as to produce that great diversity of organic life, + which we so highly admire. + </p> + <p> + Darwin has left the decision of this difficult and obviously subordinate + point to his followers. But in his Pangenesis hypothesis he has given us + the clue for a close study and ultimate elucidation of the subject under + discussion. + </p> + <p> + <a name="link2H_4_0007" id="link2H_4_0007"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + V. HEREDITY AND VARIATION IN MODERN LIGHTS. By W. Bateson, M.A., F.R.S. + </h2> + <h3> + Professor of Biology in the University of Cambridge. + </h3> + <p> + Darwin's work has the property of greatness in that it may be admired from + more aspects than one. For some the perception of the principle of Natural + Selection stands out as his most wonderful achievement to which all the + rest is subordinate. Others, among whom I would range myself, look up to + him rather as the first who plainly distinguished, collected, and + comprehensively studied that new class of evidence from which hereafter a + true understanding of the process of Evolution may be developed. We each + prefer our own standpoint of admiration; but I think that it will be in + their wider aspect that his labours will most command the veneration of + posterity. + </p> + <p> + A treatise written to advance knowledge may be read in two moods. The + reader may keep his mind passive, willing merely to receive the impress of + the writer's thought; or he may read with his attention strained and + alert, asking at every instant how the new knowledge can be used in a + further advance, watching continually for fresh footholds by which to + climb higher still. Of Shelley it has been said that he was a poet for + poets: so Darwin was a naturalist for naturalists. It is when his writings + are used in the critical and more exacting spirit with which we test the + outfit for our own enterprise that we learn their full value and strength. + Whether we glance back and compare his performance with the efforts of his + predecessors, or look forward along the course which modern research is + disclosing, we shall honour most in him not the rounded merit of finite + accomplishment, but the creative power by which he inaugurated a line of + discovery endless in variety and extension. Let us attempt thus to see his + work in true perspective between the past from which it grew, and the + present which is its consequence. Darwin attacked the problem of Evolution + by reference to facts of three classes: Variation; Heredity; Natural + Selection. His work was not as the laity suppose, a sudden and unheralded + revelation, but the first fruit of a long and hitherto barren controversy. + The occurrence of variation from type, and the hereditary transmission of + such variation had of course been long familiar to practical men, and + inferences as to the possible bearing of those phenomena on the nature of + specific difference had been from time to time drawn by naturalists. + Maupertuis, for example, wrote "Ce qui nous reste a examiner, c'est + comment d'un seul individu, il a pu naitre tant d'especes si differentes." + And again "La Nature contient le fonds de toutes ces varietes: mais le + hasard ou l'art les mettent en oeuvre. C'est ainsi que ceux dont + l'industrie s'applique a satisfaire le gout des curieux, sont, pour ainsi + dire, creatures d'especes nouvelles." ("Venus Physique, contenant deux + Dissertations, l'une sur l'origine des Hommes et des Animaux: Et l'autre + sur l'origine des Noirs" La Haye, 1746, pages 124 and 129. For an + introduction to the writings of Maupertuis I am indebted to an article by + Professor Lovejoy in "Popular Sci. Monthly", 1902.) + </p> + <p> + Such passages, of which many (though few so emphatic) can be found in + eighteenth century writers, indicate a true perception of the mode of + Evolution. The speculations hinted at by Buffon (For the fullest account + of the views of these pioneers of Evolution, see the works of Samuel + Butler, especially "Evolution, Old and New" (2nd edition) 1882. Butler's + claims on behalf of Buffon have met with some acceptance; but after + reading what Butler has said, and a considerable part of Buffon's own + works, the word "hinted" seems to me a sufficiently correct description of + the part he played. It is interesting to note that in the chapter on the + Ass, which contains some of his evolutionary passages, there is a + reference to "plusieurs idees tres-elevees sur la generation" contained in + the Letters of Maupertuis.), developed by Erasmus Darwin, and + independently proclaimed above all by Lamarck, gave to the doctrine of + descent a wide renown. The uniformitarian teaching which Lyell deduced + from geological observation had gained acceptance. The facts of + geographical distribution (See especially W. Lawrence, "Lectures on + Physiology", London, 1823, pages 213 f.) had been shown to be obviously + inconsistent with the Mosaic legend. Prichard, and Lawrence, following the + example of Blumenbach, had successfully demonstrated that the races of Man + could be regarded as different forms of one species, contrary to the + opinion up till then received. These treatises all begin, it is true, with + a profound obeisance to the sons of Noah, but that performed, they + continue on strictly modern lines. The question of the mutability of + species was thus prominently raised. + </p> + <p> + Those who rate Lamarck no higher than did Huxley in his contemptuous + phrase "buccinator tantum," will scarcely deny that the sound of the + trumpet had carried far, or that its note was clear. If then there were + few who had already turned to evolution with positive conviction, all + scientific men must at least have known that such views had been + promulgated; and many must, as Huxley says, have taken up his own position + of "critical expectancy." (See the chapter contributed to the "Life and + Letters of Charles Darwin" II. page 195. I do not clearly understand the + sense in which Darwin wrote (Autobiography, ibid. I. page 87): "It has + sometimes been said that the success of the "Origin" proved 'that the + subject was in the air,' or 'that men's minds were prepared for it.' I do + not think that this is strictly true, for I occasionally sounded not a few + naturalists, and never happened to come across a single one who seemed to + doubt about the permanence of species." This experience may perhaps have + been an accident due to Darwin's isolation. The literature of the period + abounds with indications of "critical expectancy." A most interesting + expression of that feeling is given in the charming account of the "Early + Days of Darwinism" by Alfred Newton, "Macmillan's Magazine", LVII. 1888, + page 241. He tells how in 1858 when spending a dreary summer in Iceland, + he and his friend, the ornithologist John Wolley, in default of active + occupation, spent their days in discussion. "Both of us taking a keen + interest in Natural History, it was but reasonable that a question, which + in those days was always coming up wherever two or more naturalists were + gathered together, should be continually recurring. That question was, + 'What is a species?' and connected therewith was the other question, 'How + did a species begin?'... Now we were of course fairly well acquainted with + what had been published on these subjects." He then enumerates some of + these publications, mentioning among others T. Vernon Wollaston's + "Variation of Species"—a work which has in my opinion never been + adequately appreciated. He proceeds: "Of course we never arrived at + anything like a solution of these problems, general or special, but we + felt very strongly that a solution ought to be found, and that quickly, if + the study of Botany and Zoology was to make any great advance." He then + describes how on his return home he received the famous number of the + "Linnean Journal" on a certain evening. "I sat up late that night to read + it; and never shall I forget the impression it made upon me. Herein was + contained a perfectly simple solution of all the difficulties which had + been troubling me for months past... I went to bed satisfied that a + solution had been found.") + </p> + <p> + Why, then, was it, that Darwin succeeded where the rest had failed? The + cause of that success was two-fold. First, and obviously, in the principle + of Natural Selection he had a suggestion which would work. It might not go + the whole way, but it was true as far as it went. Evolution could thus in + great measure be fairly represented as a consequence of demonstrable + processes. Darwin seldom endangers the mechanism he devised by putting on + it strains much greater than it can bear. He at least was under no + illusion as to the omnipotence of Selection; and he introduces none of the + forced pleading which in recent years has threatened to discredit that + principle. + </p> + <p> + For example, in the latest text of the "Origin" ("Origin", (6th edition + (1882), page 421.)) we find him saying: + </p> + <p> + "But as my conclusions have lately been much misrepresented, and it has + been stated that I attribute the modification of species exclusively to + natural selection, I may be permitted to remark that in the first edition + of this work, and subsequently, I placed in a most conspicuous position—namely, + at the close of the Introduction—the following words: 'I am + convinced that natural selection has been the main but not the exclusive + means of modification.'" + </p> + <p> + But apart from the invention of this reasonable hypothesis, which may + well, as Huxley estimated, "be the guide of biological and psychological + speculation for the next three or four generations," Darwin made a more + significant and imperishable contribution. Not for a few generations, but + through all ages he should be remembered as the first who showed clearly + that the problems of Heredity and Variation are soluble by observation, + and laid down the course by which we must proceed to their solution. + (Whatever be our estimate of the importance of Natural Selection, in this + we all agree. Samuel Butler, the most brilliant, and by far the most + interesting of Darwin's opponents—whose works are at length emerging + from oblivion—in his Preface (1882) to the 2nd edition of + "Evolution, Old and New", repeats his earlier expression of homage to one + whom he had come to regard as an enemy: "To the end of time, if the + question be asked, 'Who taught people to believe in Evolution?' the answer + must be that it was Mr. Darwin. This is true, and it is hard to see what + palm of higher praise can be awarded to any philosopher.") The moment of + inspiration did not come with the reading of Malthus, but with the opening + of the "first note-book on Transmutation of Species." ("Life and Letters", + I. pages 276 and 83.) Evolution is a process of Variation and Heredity. + The older writers, though they had some vague idea that it must be so, did + not study Variation and Heredity. Darwin did, and so begat not a theory, + but a science. + </p> + <p> + The extent to which this is true, the scientific world is only beginning + to realise. So little was the fact appreciated in Darwin's own time that + the success of his writings was followed by an almost total cessation of + work in that special field. Of the causes which led to this remarkable + consequence I have spoken elsewhere. They proceeded from circumstances + peculiar to the time; but whatever the causes there is no doubt that this + statement of the result is historically exact, and those who make it their + business to collect facts elucidating the physiology of Heredity and + Variation are well aware that they will find little to reward their quest + in the leading scientific Journals of the Darwinian epoch. + </p> + <p> + In those thirty years the original stock of evidence current and in + circulation even underwent a process of attrition. As in the story of the + Eastern sage who first wrote the collected learning of the universe for + his sons in a thousand volumes, and by successive compression and burning + reduced them to one, and from this by further burning distilled the single + ejaculation of the Faith, "There is no god but God and Mohamed is the + Prophet of God," which was all his maturer wisdom deemed essential:—so + in the books of that period do we find the corpus of genetic knowledge + dwindle to a few prerogative instances, and these at last to the brief + formula of an unquestioned creed. + </p> + <p> + And yet in all else that concerns biological science this period was, in + very truth, our Golden Age, when the natural history of the earth was + explored as never before; morphology and embryology were exhaustively + ransacked; the physiology of plants and animals began to rival chemistry + and physics in precision of method and in the rapidity of its advances; + and the foundations of pathology were laid. + </p> + <p> + In contrast with this immense activity elsewhere the neglect which befel + the special physiology of Descent, or Genetics as we now call it, is + astonishing. This may of course be interpreted as meaning that the + favoured studies seemed to promise a quicker return for effort, but it + would be more true to say that those who chose these other pursuits did so + without making any such comparison; for the idea that the physiology of + Heredity and Variation was a coherent science, offering possibilities of + extraordinary discovery, was not present to their minds at all. In a word, + the existence of such a science was well nigh forgotten. It is true that + in ancillary periodicals, as for example those that treat of entomology or + horticulture, or in the writings of the already isolated systematists + (This isolation of the systematists is the one most melancholy sequela of + Darwinism. It seems an irony that we should read in the peroration to the + "Origin" that when the Darwinian view is accepted "Systematists will be + able to pursue their labours as at present; but they will not be + incessantly haunted by the shadowy doubt whether this or that form be a + true species. This, I feel sure, and I speak after experience, will be no + slight relief. The endless disputes whether or not some fifty species of + British brambles are good species will cease." "Origin", 6th edition + (1882), page 425. True they have ceased to attract the attention of those + who lead opinion, but anyone who will turn to the literature of + systematics will find that they have not ceased in any other sense. Should + there not be something disquieting in the fact that among the workers who + come most into contact with specific differences, are to be found the only + men who have failed to be persuaded of the unreality of those + differences?), observations with this special bearing were from time to + time related, but the class of fact on which Darwin built his conceptions + of Heredity and Variation was not seen in the highways of biology. It + formed no part of the official curriculum of biological students, and + found no place among the subjects which their teachers were investigating. + </p> + <p> + During this period nevertheless one distinct advance was made, that with + which Weismann's name is prominently connected. In Darwin's genetic scheme + the hereditary transmission of parental experience and its consequences + played a considerable role. Exactly how great that role was supposed to + be, he with his habitual caution refrained from specifying, for the + sufficient reason that he did not know. Nevertheless much of the process + of Evolution, especially that by which organs have become degenerate and + rudimentary, was certainly attributed by Darwin to such inheritance, + though since belief in the inheritance of acquired characters fell into + disrepute, the fact has been a good deal overlooked. The "Origin" without + "use and disuse" would be a materially different book. A certain + vacillation is discernible in Darwin's utterances on this question, and + the fact gave to the astute Butler an opportunity for his most telling + attack. The discussion which best illustrates the genetic views of the + period arose in regard to the production of the rudimentary condition of + the wings of many beetles in the Madeira group of islands, and by + comparing passages from the "Origin" (6th edition pages 109 and 401. See + Butler, "Essays on Life, Art, and Science", page 265, reprinted 1908, and + "Evolution, Old and New", chapter XXII. (2nd edition), 1882.) Butler + convicts Darwin of saying first that this condition was in the main the + result of Selection, with disuse aiding, and in another place that the + main cause of degeneration was disuse, but that Selection had aided. To + Darwin however I think the point would have seemed one of dialectics + merely. To him the one paramount purpose was to show that somehow an + Evolution by means of Variation and Heredity might have brought about the + facts observed, and whether they had come to pass in the one way or the + other was a matter of subordinate concern. + </p> + <p> + To us moderns the question at issue has a diminished significance. For + over all such debates a change has been brought by Weismann's challenge + for evidence that use and disuse have any transmitted effects at all. + Hitherto the transmission of many acquired characteristics had seemed to + most naturalists so obvious as not to call for demonstration. (W. Lawrence + was one of the few who consistently maintained the contrary opinion. + Prichard, who previously had expressed himself in the same sense, does + not, I believe repeat these views in his later writings, and there are + signs that he came to believe in the transmission of acquired habits. See + Lawrence, "Lect. Physiol." 1823, pages 436-437, 447 Prichard, Edin. Inaug. + Disp. 1808 (not seen by me), quoted ibid. and "Nat. Hist. Man", 1843, + pages 34 f.) Weismann's demand for facts in support of the main + proposition revealed at once that none having real cogency could be + produced. The time-honoured examples were easily shown to be capable of + different explanations. A few certainly remain which cannot be so + summarily dismissed, but—though it is manifestly impossible here to + do justice to such a subject—I think no one will dispute that these + residual and doubtful phenomena, whatever be their true nature, are not of + a kind to help us much in the interpretation of any of those complex cases + of adaptation which on the hypothesis of unguided Natural Selection are + especially difficult to understand. Use and disuse were invoked expressly + to help us over these hard places; but whatever changes can be induced in + offspring by direct treatment of the parents, they are not of a kind to + encourage hope of real assistance from that quarter. It is not to be + denied that through the collapse of this second line of argument the + Selection hypothesis has had to take an increased and perilous burden. + Various ways of meeting the difficulty have been proposed, but these + mostly resolve themselves into improbable attempts to expand or magnify + the powers of Natural Selection. + </p> + <p> + Weismann's interpellation, though negative in purpose, has had a lasting + and beneficial effect, for through his thorough demolition of the old + loose and distracting notions of inherited experience, the ground has been + cleared for the construction of a true knowledge of heredity based on + experimental fact. + </p> + <p> + In another way he made a contribution of a more positive character, for + his elaborate speculations as to the genetic meaning of cytological + appearances have led to a minute investigation of the visible phenomena + occurring in those divisions by which germ-cells arise. Though the + particular views he advocated have very largely proved incompatible with + the observed facts of heredity, yet we must acknowledge that it was + chiefly through the stimulus of Weismann's ideas that those advances in + cytology were made; and though the doctrine of the continuity of + germ-plasm cannot be maintained in the form originally propounded, it is + in the main true and illuminating. (It is interesting to see how nearly + Butler was led by natural penetration, and from absolutely opposite + conclusions, back to this underlying truth: "So that each ovum when + impregnate should be considered not as descended from its ancestors, but + as being a continuation of the personality of every ovum in the chain of + its ancestry, which every ovum IT ACTUALLY IS quite as truly as the + octogenarian IS the same identity with the ovum from which he has been + developed. This process cannot stop short of the primordial cell, which + again will probably turn out to be but a brief resting-place. We therefore + prove each one of us to BE ACTUALLY the primordial cell which never died + nor dies, but has differentiated itself into the life of the world, all + living beings whatever, being one with it and members one of another," + "Life and Habit", 1878, page 86.) Nevertheless in the present state of + knowledge we are still as a rule quite unable to connect cytological + appearances with any genetic consequence and save in one respect + (obviously of extreme importance—to be spoken of later) the two sets + of phenomena might, for all we can see, be entirely distinct. + </p> + <p> + I cannot avoid attaching importance to this want of connection between the + nuclear phenomena and the features of bodily organisation. All attempts to + investigate Heredity by cytological means lie under the disadvantage that + it is the nuclear changes which can alone be effectively observed. + Important as they must surely be, I have never been persuaded that the + rest of the cell counts for nothing. What we know of the behaviour and + variability of chromosomes seems in my opinion quite incompatible with the + belief that they alone govern form, and are the sole agents responsible in + heredity. (This view is no doubt contrary to the received opinion. I am + however interested to see it lately maintained by Driesch ("Science and + Philosophy of the Organism", London, 1907, page 233), and from the recent + observations of Godlewski it has received distinct experimental support.) + </p> + <p> + If, then, progress was to be made in Genetics, work of a different kind + was required. To learn the laws of Heredity and Variation there is no + other way than that which Darwin himself followed, the direct examination + of the phenomena. A beginning could be made by collecting fortuitous + observations of this class, which have often thrown a suggestive light, + but such evidence can be at best but superficial and some more penetrating + instrument of research is required. This can only be provided by actual + experiments in breeding. + </p> + <p> + The truth of these general considerations was becoming gradually clear to + many of us when in 1900 Mendel's work was rediscovered. Segregation, a + phenomenon of the utmost novelty, was thus revealed. From that moment not + only in the problem of the origin of species, but in all the great + problems of biology a new era began. So unexpected was the discovery that + many naturalists were convinced it was untrue, and at once proclaimed + Mendel's conclusions as either altogether mistaken, or if true, of very + limited application. Many fantastic notions about the workings of Heredity + had been asserted as general principles before: this was probably only + another fancy of the same class. + </p> + <p> + Nevertheless those who had a preliminary acquaintance with the facts of + Variation were not wholly unprepared for some such revelation. The + essential deduction from the discovery of segregation was that the + characters of living things are dependent on the presence of definite + elements or factors, which are treated as units in the processes of + Heredity. These factors can thus be recombined in various ways. They act + sometimes separately, and sometimes they interact in conjunction with each + other, producing their various effects. All this indicates a definiteness + and specific order in heredity, and therefore in variation. This order + cannot by the nature of the case be dependent on Natural Selection for its + existence, but must be a consequence of the fundamental chemical and + physical nature of living things. The study of Variation had from the + first shown that an orderliness of this kind was present. The bodies and + the properties of living things are cosmic, not chaotic. No matter how low + in the scale we go, never do we find the slightest hint of a diminution in + that all-pervading orderliness, nor can we conceive an organism existing + for a moment in any other state. Moreover not only does this order prevail + in normal forms, but again and again it is to be seen in newly-sprung + varieties, which by general consent cannot have been subjected to a + prolonged Selection. The discovery of Mendelian elements admirably + coincided with and at once gave a rationale of these facts. Genetic + Variation is then primarily the consequence of additions to, or omissions + from, the stock of elements which the species contains. The further + investigation of the species-problem must thus proceed by the analytical + method which breeding experiments provide. + </p> + <p> + In the nine years which have elapsed since Mendel's clue became generally + known, progress has been rapid. We now understand the process by which a + polymorphic race maintains its polymorphism. When a family consists of + dissimilar members, given the numerical proportions in which these members + are occurring, we can represent their composition symbolically and state + what types can be transmitted by the various members. The difficulty of + the "swamping effects of intercrossing" is practically at an end. Even the + famous puzzle of sex-limited inheritance is solved, at all events in its + more regular manifestations, and we know now how it is brought about that + the normal sisters of a colour-blind man can transmit the colour-blindness + while his normal brothers cannot transmit it. + </p> + <p> + We are still only on the fringe of the inquiry. It can be seen extending + and ramifying in many directions. To enumerate these here would be + impossible. A whole new range of possibilities is being brought into view + by study of the interrelations between the simple factors. By following up + the evidence as to segregation, indications have been obtained which can + only be interpreted as meaning that when many factors are being + simultaneously redistributed among the germ-cells, certain of them exert + what must be described as a repulsion upon other factors. We cannot + surmise whither this discovery may lead. + </p> + <p> + In the new light all the old problems wear a fresh aspect. Upon the + question of the nature of Sex, for example, the bearing of Mendelian + evidence is close. Elsewhere I have shown that from several sets of + parallel experiments the conclusion is almost forced upon us that, in the + types investigated, of the two sexes the female is to be regarded as + heterozygous in sex, containing one unpaired dominant element, while the + male is similarly homozygous in the absence of that element. (In other + words, the ova are each EITHER female, OR male (i.e. non-female), but the + sperms are all non-female.) It is not a little remarkable that on this + point—which is the only one where observations of the nuclear + processes of gameto-genesis have yet been brought into relation with the + visible characteristics of the organisms themselves—there should be + diametrical opposition between the results of breeding experiments and + those derived from cytology. + </p> + <p> + Those who have followed the researches of the American school will be + aware that, after it had been found in certain insects that the + spermatozoa were of two kinds according as they contained or did not + contain the accessory chromosome, E.B. Wilson succeeded in proving that + the sperms possessing this accessory body were destined to form FEMALES on + fertilisation, while sperms without it form males, the eggs being + apparently indifferent. Perhaps the most striking of all this series of + observations is that lately made by T.H. Morgan (Morgan, "Proc. Soc. Exp. + Biol. Med." V. 1908, and von Baehr, "Zool. Anz." XXXII. page 507, 1908.), + since confirmed by von Baehr, that in a Phylloxeran two kinds of + spermatids are formed, respectively with and without an accessory (in this + case, DOUBLE) chromosome. Of these, only those possessing the accessory + body become functional spermatozoa, the others degenerating. We have thus + an elucidation of the puzzling fact that in these forms fertilisation + results in the formation of FEMALES only. How the males are formed—for + of course males are eventually produced by the parthenogenetic females—we + do not know. + </p> + <p> + If the accessory body is really to be regarded as bearing the factor for + femaleness, then in Mendelian terms female is DD and male is DR. The eggs + are indifferent and the spermatozoa are each male, OR female. But + according to the evidence derived from a study of the sex-limited descent + of certain features in other animals the conclusion seems equally clear + that in them female must be regarded as DR and male as RR. The eggs are + thus each either male or female and the spermatozoa are indifferent. How + this contradictory evidence is to be reconciled we do not yet know. The + breeding work concerns fowls, canaries, and the Currant moth (Abraxas + grossulariata). The accessory chromosome has been now observed in most of + the great divisions of insects (As Wilson has proved, the unpaired body is + not a universal feature even in those orders in which it has been + observed. Nearly allied types may differ. In some it is altogether + unpaired. In others it is paired with a body of much smaller size, and by + selection of various types all gradations can be demonstrated ranging to + the condition in which the members of the pair are indistinguishable from + each other.), except, as it happens, Lepidoptera. At first sight it seems + difficult to suppose that a feature apparently so fundamental as sex + should be differently constituted in different animals, but that seems at + present the least improbable inference. I mention these two groups of + facts as illustrating the nature and methods of modern genetic work. We + must proceed by minute and specific analytical investigation. Wherever we + look we find traces of the operation of precise and specific rules. + </p> + <p> + In the light of present knowledge it is evident that before we can attack + the Species-problem with any hope of success there are vast arrears to be + made up. He would be a bold man who would now assert that there was no + sense in which the term Species might not have a strict and concrete + meaning in contradistinction to the term Variety. We have been taught to + regard the difference between species and variety as one of degree. I + think it unlikely that this conclusion will bear the test of further + research. To Darwin the question, What is a variation? presented no + difficulties. Any difference between parent and offspring was a variation. + Now we have to be more precise. First we must, as de Vries has shown, + distinguish real, genetic, variation from FLUCTUATIONAL variations, due to + environmental and other accidents, which cannot be transmitted. Having + excluded these sources of error the variations observed must be expressed + in terms of the factors to which they are due before their significance + can be understood. For example, numbers of the variations seen under + domestication, and not a few witnessed in nature, are simply the + consequence of some ingredient being in an unknown way omitted from the + composition of the varying individual. The variation may on the contrary + be due to the addition of some new element, but to prove that it is so is + by no means an easy matter. Casual observation is useless, for though + these latter variations will always be dominants, yet many dominant + characteristics may arise from another cause, namely the meeting of + complementary factors, and special study of each case in two generations + at least is needed before these two phenomena can be distinguished. + </p> + <p> + When such considerations are fully appreciated it will be realised that + medleys of most dissimilar occurrences are all confused together under the + term Variation. One of the first objects of genetic analysis is to + disentangle this mass of confusion. + </p> + <p> + To those who have made no study of heredity it sometimes appears that the + question of the effect of conditions in causing variation is one which we + should immediately investigate, but a little thought will show that before + any critical inquiry into such possibilities can be attempted, a knowledge + of the working of heredity under conditions as far as possible uniform + must be obtained. At the time when Darwin was writing, if a plant brought + into cultivation gave off an albino variety, such an event was without + hesitation ascribed to the change of life. Now we see that albino GAMETES, + germs, that is to say, which are destitute of the pigment-forming factor, + may have been originally produced by individuals standing an indefinite + number of generations back in the ancestry of the actual albino, and it is + indeed almost certain that the variation to which the appearance of the + albino is due cannot have taken place in a generation later than that of + the grandparents. It is true that when a new DOMINANT appears we should + feel greater confidence that we were witnessing the original variation, + but such events are of extreme rarity, and no such case has come under the + notice of an experimenter in modern times, as far as I am aware. That they + must have appeared is clear enough. Nothing corresponding to the + Brown-breasted Game fowl is known wild, yet that colour is a most definite + dominant, and at some moment since Gallus bankiva was domesticated, the + element on which that special colour depends must have at least once been + formed in the germ-cell of a fowl; but we need harder evidence than any + which has yet been produced before we can declare that this novelty came + through over-feeding, or change of climate, or any other disturbance + consequent on domestication. When we reflect on the intricacies of genetic + problems as we must now conceive them there come moments when we feel + almost thankful that the Mendelian principles were unknown to Darwin. The + time called for a bold pronouncement, and he made it, to our lasting + profit and delight. With fuller knowledge we pass once more into a period + of cautious expectation and reserve. + </p> + <p> + In every arduous enterprise it is pleasanter to look back at difficulties + overcome than forward to those which still seem insurmountable, but in the + next stage there is nothing to be gained by disguising the fact that the + attributes of living things are not what we used to suppose. If they are + more complex in the sense that the properties they display are throughout + so regular (I have in view, for example, the marvellous and specific + phenomena of regeneration, and those discovered by the students of + "Entwicklungsmechanik". The circumstances of its occurrence here preclude + any suggestion that this regularity has been brought about by the workings + of Selection. The attempts thus to represent the phenomena have resulted + in mere parodies of scientific reasoning.) that the Selection of minute + random variations is an unacceptable account of the origin of their + diversity, yet by virtue of that very regularity the problem is limited in + scope and thus simplified. + </p> + <p> + To begin with, we must relegate Selection to its proper place. Selection + permits the viable to continue and decides that the non-viable shall + perish; just as the temperature of our atmosphere decides that no liquid + carbon shall be found on the face of the earth: but we do not suppose that + the form of the diamond has been gradually achieved by a process of + Selection. So again, as the course of descent branches in the successive + generations, Selection determines along which branch Evolution shall + proceed, but it does not decide what novelties that branch shall bring + forth. "La Nature contient le fonds de toutes ces varietes, mais le hazard + ou l'art les mettent en oeuvre," as Maupertuis most truly said. + </p> + <p> + Not till knowledge of the genetic properties of organisms has attained to + far greater completeness can evolutionary speculations have more than a + suggestive value. By genetic experiment, cytology and physiological + chemistry aiding, we may hope to acquire such knowledge. In 1872 Nathusius + wrote ("Vortrage uber Viehzucht und Rassenerkenntniss", page 120, Berlin, + 1872.): "Das Gesetz der Vererbung ist noch nicht erkannt; der Apfel ist + noch nicht vom Baum der Erkenntniss gefallen, welcher, der Sage nach, + Newton auf den rechten Weg zur Ergrundung der Gravitationsgesetze fuhrte." + We cannot pretend that the words are not still true, but in Mendelian + analysis the seeds of that apple-tree at last are sown. + </p> + <p> + If we were asked what discovery would do most to forward our inquiry, what + one bit of knowledge would more than any other illuminate the problem, I + think we may give the answer without hesitation. The greatest advance that + we can foresee will be made when it is found possible to connect the + geometrical phenomena of development with the chemical. The geometrical + symmetry of living things is the key to a knowledge of their regularity, + and the forces which cause it. In the symmetry of the dividing cell the + basis of that resemblance we call Heredity is contained. To imitate the + morphological phenomena of life we have to devise a system which can + divide. It must be able to divide, and to segment as—grossly—a + vibrating plate or rod does, or as an icicle can do as it becomes ribbed + in a continuous stream of water; but with this distinction, that the + distribution of chemical differences and properties must simultaneously be + decided and disposed in orderly relation to the pattern of the + segmentation. Even if a model which would do this could be constructed it + might prove to be a useful beginning. + </p> + <p> + This may be looking too far ahead. If we had to choose some one piece of + more proximate knowledge which we would more especially like to acquire, I + suppose we should ask for the secret of interracial sterility. Nothing has + yet been discovered to remove the grave difficulty, by which Huxley in + particular was so much oppressed, that among the many varieties produced + under domestication—which we all regard as analogous to the species + seen in nature—no clear case of interracial sterility has been + demonstrated. The phenomenon is probably the only one to which the + domesticated products seem to afford no parallel. No solution of the + difficulty can be offered which has positive value, but it is perhaps + worth considering the facts in the light of modern ideas. It should be + observed that we are not discussing incompatibility of two species to + produce offspring (a totally distinct phenomenon), but the sterility of + the offspring which many of them do produce. + </p> + <p> + When two species, both perfectly fertile severally, produce on crossing a + sterile progeny, there is a presumption that the sterility is due to the + development in the hybrid of some substance which can only be formed by + the meeting of two complementary factors. That some such account is + correct in essence may be inferred from the well-known observation that if + the hybrid is not totally sterile but only partially so, and thus is able + to form some good germ-cells which develop into new individuals, the + sterility of these daughter-individuals is sensibly reduced or may be + entirely absent. The fertility once re-established, the sterility does not + return in the later progeny, a fact strongly suggestive of segregation. + Now if the sterility of the cross-bred be really the consequence of the + meeting of two complementary factors, we see that the phenomenon could + only be produced among the divergent offspring of one species by the + acquisition of at least TWO new factors; for if the acquisition of a + single factor caused sterility the line would then end. Moreover each + factor must be separately acquired by distinct individuals, for if both + were present together, the possessors would by hypothesis be sterile. And + in order to imitate the case of species each of these factors must be + acquired by distinct breeds. The factors need not, and probably would not, + produce any other perceptible effects; they might, like the colour-factors + present in white flowers, make no difference in the form or other + characters. Not till the cross was actually made between the two + complementary individuals would either factor come into play, and the + effects even then might be unobserved until an attempt was made to breed + from the cross-bred. + </p> + <p> + Next, if the factors responsible for sterility were acquired, they would + in all probability be peculiar to certain individuals and would not + readily be distributed to the whole breed. Any member of the breed also + into which BOTH the factors were introduced would drop out of the pedigree + by virtue of its sterility. Hence the evidence that the various + domesticated breeds say of dogs or fowls can when mated together produce + fertile offspring, is beside the mark. The real question is, Do they ever + produce sterile offspring? I think the evidence is clearly that sometimes + they do, oftener perhaps than is commonly supposed. These suggestions are + quite amenable to experimental tests. The most obvious way to begin is to + get a pair of parents which are known to have had any sterile offspring, + and to find the proportions in which these steriles were produced. If, as + I anticipate, these proportions are found to be definite, the rest is + simple. + </p> + <p> + In passing, certain other considerations may be referred to. First, that + there are observations favouring the view that the production of totally + sterile cross-breds is seldom a universal property of two species, and + that it may be a matter of individuals, which is just what on the view + here proposed would be expected. Moreover, as we all know now, though + incompatibility may be dependent to some extent on the degree to which the + species are dissimilar, no such principle can be demonstrated to determine + sterility or fertility in general. For example, though all our Finches can + breed together, the hybrids are all sterile. Of Ducks some species can + breed together without producing the slightest sterility; others have + totally sterile offspring, and so on. The hybrids between several genera + of Orchids are perfectly fertile on the female side, and some on the male + side also, but the hybrids produced between the Turnip (Brassica napus) + and the Swede (Brassica campestris), which, according to our estimates of + affinity should be nearly allied forms, are totally sterile. (See Sutton, + A.W., "Journ. Linn. Soc." XXXVIII. page 341, 1908.) Lastly, it may be + recalled that in sterility we are almost certainly considering a meristic + phenomenon. FAILURE TO DIVIDE is, we may feel fairly sure, the immediate + "cause" of the sterility. Now, though we know very little about the + heredity of meristic differences, all that we do know points to the + conclusion that the less-divided is dominant to the more-divided, and we + are thus justified in supposing that there are factors which can arrest or + prevent cell-division. My conjecture therefore is that in the case of + sterility of cross-breds we see the effect produced by a complementary + pair of such factors. This and many similar problems are now open to our + analysis. + </p> + <p> + The question is sometimes asked, Do the new lights on Variation and + Heredity make the process of Evolution easier to understand? On the whole + the answer may be given that they do. There is some appearance of loss of + simplicity, but the gain is real. As was said above, the time is not ripe + for the discussion of the origin of species. With faith in Evolution + unshaken—if indeed the word faith can be used in application to that + which is certain—we look on the manner and causation of adapted + differentiation as still wholly mysterious. As Samuel Butler so truly + said: "To me it seems that the 'Origin of Variation,' whatever it is, is + the only true 'Origin of Species'" ("Life and Habit", London, page 263, + 1878.), and of that Origin not one of us knows anything. But given + Variation—and it is given: assuming further that the variations are + not guided into paths of adaptation—and both to the Darwinian and to + the modern school this hypothesis appears to be sound if unproven—an + evolution of species proceeding by definite steps is more, rather than + less, easy to imagine than an evolution proceeding by the accumulation of + indefinite and insensible steps. Those who have lost themselves in + contemplating the miracles of Adaptation (whether real or spurious) have + not unnaturally fixed their hopes rather on the indefinite than on the + definite changes. The reasons are obvious. By suggesting that the steps + through which an adaptative mechanism arose were indefinite and + insensible, all further trouble is spared. While it could be said that + species arise by an insensible and imperceptible process of variation, + there was clearly no use in tiring ourselves by trying to perceive that + process. This labour-saving counsel found great favour. All that had to be + done to develop evolution-theory was to discover the good in everything, a + task which, in the complete absence of any control or test whereby to + check the truth of the discovery, is not very onerous. The doctrine "que + tout est au mieux" was therefore preached with fresh vigour, and examples + of that illuminating principle were discovered with a facility that + Pangloss himself might have envied, till at last even the spectators + wearied of such dazzling performances. + </p> + <p> + But in all seriousness, why should indefinite and unlimited variation have + been regarded as a more probable account of the origin of Adaptation? + Only, I think, because the obstacle was shifted one plane back, and so + looked rather less prominent. The abundance of Adaptation, we all grant, + is an immense, almost an unsurpassable difficulty in all non-Lamarckian + views of Evolution; but if the steps by which that adaptation arose were + fortuitous, to imagine them insensible is assuredly no help. In one most + important respect indeed, as has often been observed, it is a + multiplication of troubles. For the smaller the steps, the less could + Natural Selection act upon them. Definite variations—and of the + occurrence of definite variations in abundance we have now the most + convincing proof—have at least the obvious merit that they can make + and often do make a real difference in the chances of life. + </p> + <p> + There is another aspect of the Adaptation problem to which I can only + allude very briefly. May not our present ideas of the universality and + precision of Adaptation be greatly exaggerated? The fit of organism to its + environment is not after all so very close—a proposition unwelcome + perhaps, but one which could be illustrated by very copious evidence. + Natural Selection is stern, but she has her tolerant moods. + </p> + <p> + We have now most certain and irrefragable proof that much definiteness + exists in living things apart from Selection, and also much that may very + well have been preserved and so in a sense constituted by Selection. Here + the matter is likely to rest. There is a passage in the sixth edition of + the "Origin" which has I think been overlooked. On page 70 Darwin says + "The tuft of hair on the breast of the wild turkey-cock cannot be of any + use, and it is doubtful whether it can be ornamental in the eyes of the + female bird." This tuft of hair is a most definite and unusual structure, + and I am afraid that the remark that it "cannot be of any use" may have + been made inadvertently; but it may have been intended, for in the first + edition the usual qualification was given and must therefore have been + deliberately excised. Anyhow I should like to think that Darwin did throw + over that tuft of hair, and that he felt relief when he had done so. + Whether however we have his great authority for such a course or not, I + feel quite sure that we shall be rightly interpreting the facts of nature + if we cease to expect to find purposefulness wherever we meet with + definite structures or patterns. Such things are, as often as not, I + suspect rather of the nature of tool-marks, mere incidents of manufacture, + benefiting their possessor not more than the wire-marks in a sheet of + paper, or the ribbing on the bottom of an oriental plate renders those + objects more attractive in our eyes. + </p> + <p> + If Variation may be in any way definite, the question once more arises, + may it not be definite in direction? The belief that it is has had many + supporters, from Lamarck onwards, who held that it was guided by need, and + others who, like Nageli, while laying no emphasis on need, yet were + convinced that there was guidance of some kind. The latter view under the + name of "Orthogenesis," devised I believe by Eimer, at the present day + commends itself to some naturalists. The objection to such a suggestion is + of course that no fragment of real evidence can be produced in its + support. On the other hand, with the experimental proof that variation + consists largely in the unpacking and repacking of an original complexity, + it is not so certain as we might like to think that the order of these + events is not pre-determined. For instance the original "pack" may have + been made in such a way that at the nth division of the germ-cells of a + Sweet Pea a colour-factor might be dropped, and that at the n plus n prime + division the hooded variety be given off, and so on. I see no ground + whatever for holding such a view, but in fairness the possibility should + not be forgotten, and in the light of modern research it scarcely looks so + absurdly improbable as before. + </p> + <p> + No one can survey the work of recent years without perceiving that + evolutionary orthodoxy developed too fast, and that a great deal has got + to come down; but this satisfaction at least remains, that in the + experimental methods which Mendel inaugurated, we have means of reaching + certainty in regard to the physiology of Heredity and Variation upon which + a more lasting structure may be built. + </p> + <p> + <a name="link2H_4_0008" id="link2H_4_0008"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + VI. THE MINUTE STRUCTURE OF CELLS IN RELATION TO HEREDITY. By Eduard + Strasburger. + </h2> + <h3> + Professor of Botany in the University of Bonn. + </h3> + <p> + Since 1875 an unexpected insight has been gained into the internal + structure of cells. Those who are familiar with the results of + investigations in this branch of Science are convinced that any modern + theory of heredity must rest on a basis of cytology and cannot be at + variance with cytological facts. Many histological discoveries, both such + as have been proved correct and others which may be accepted as probably + well founded, have acquired a fundamental importance from the point of + view of the problems of heredity. + </p> + <p> + My aim is to describe the present position of our knowledge of Cytology. + The account must be confined to essentials and cannot deal with + far-reaching and controversial questions. In cases where difference of + opinion exists, I adopt my own view for which I hold myself responsible. I + hope to succeed in making myself intelligible even without the aid of + illustrations: in order to convey to the uninitiated an adequate idea of + the phenomena connected with the life of a cell, a greater number of + figures would be required than could be included within the scope of this + article. + </p> + <p> + So long as the most eminent investigators (As for example the illustrious + Wilhelm Hofmeister in his "Lehre von der Pflanzenzelle" (1867).) believed + that the nucleus of a cell was destroyed in the course of each division + and that the nuclei of the daughter-cells were produced de novo, theories + of heredity were able to dispense with the nucleus. If they sought, as did + Charles Darwin, who showed a correct grasp of the problem in the + enunciation of his Pangenesis hypothesis, for histological connecting + links, their hypotheses, or at least the best of them, had reference to + the cell as a whole. It was known to Darwin that the cell multiplied by + division and was derived from a similar pre-existing cell. Towards 1870 it + was first demonstrated that cell-nuclei do not arise de novo, but are + invariably the result of division of pre-existing nuclei. Better methods + of investigation rendered possible a deeper insight into the phenomena + accompanying cell and nuclear divisions and at the same time disclosed the + existence of remarkable structures. The work of O. Butschli, O. Hertwig, + W. Flemming H. Fol and of the author of this article (For further + reference to literature, see my article on "Die Ontogenie der Zelle seit + 1875", in the "Progressus Rei Botanicae", Vol. I. page 1, Jena, 1907.), + have furnished conclusive evidence in favour of these facts. It was found + that when the reticular framework of a nucleus prepares to divide, it + separates into single segments. These then become thicker and denser, + taking up with avidity certain stains, which are used as aids to + investigation, and finally form longer or shorter, variously bent, rodlets + of uniform thickness. In these organs which, on account of their special + property of absorbing certain stains, were styled Chromosomes (By W. + Waldeyer in 1888.), there may usually be recognised a separation into + thicker and thinner discs; the former are often termed Chromomeres. + (Discovered by W. Pfitzner in 1880.) In the course of division of the + nucleus, the single rows of chromomeres in the chromosomes are doubled and + this produces a band-like flattening and leads to the longitudinal + splitting by which each chromosome is divided into two exactly equal + halves. The nuclear membrane then disappears and fibrillar cell-plasma or + cytoplasm invades the nuclear area. In animal cells these fibrillae in the + cytoplasm centre on definite bodies (Their existence and their + multiplication by fission were demonstrated by E. van Beneden and Th. + Boveri in 1887.), which it is customary to speak of as Centrosomes. + Radiating lines in the adjacent cell-plasma suggest that these bodies + constitute centres of force. The cells of the higher plants do not possess + such individualised centres; they have probably disappeared in the course + of phylogenetic development: in spite of this, however, in the nuclear + division-figures the fibrillae of the cell-plasma are seen to radiate from + two opposite poles. In both animal and plant cells a fibrillar bipolar + spindle is formed, the fibrillae of which grasp the longitudinally divided + chromosomes from two opposite sides and arrange them on the equatorial + plane of the spindle as the so-called nuclear or equatorial plate. Each + half-chromosome is connected with one of the spindle poles only and is + then drawn towards that pole. (These important facts, suspected by W. + Flemming in 1882, were demonstrated by E. Heuser, L. Guignard, E. van + Beneden, M. Nussbaum, and C. Rabl.) + </p> + <p> + The formation of the daughter-nuclei is then effected. The changes which + the daughter-chromosomes undergo in the process of producing the + daughter-nuclei repeat in the reverse order the changes which they went + through in the course of their progressive differentiation from the + mother-nucleus. The division of the cell-body is completed midway between + the two daughter-nuclei. In animal cells, which possess no chemically + differentiated membrane, separation is effected by simple constriction, + while in the case of plant cells provided with a definite wall, the + process begins with the formation of a cytoplasmic separating layer. + </p> + <p> + The phenomena observed in the course of the division of the nucleus show + beyond doubt that an exact halving of its substance is of the greatest + importance. (First shown by W. Roux in 1883.) Compared with the method of + division of the nucleus, that of the cytoplasm appears to be very simple. + This led to the conception that the cell-nucleus must be the chief if not + the sole carrier of hereditary characters in the organism. It is for this + reason that the detailed investigation of fertilisation phenomena + immediately followed researches into the nucleus. The fundamental + discovery of the union of two nuclei in the sexual act was then made (By + O. Hertwig in 1875.) and this afforded a new support for the correct + conception of the nuclear functions. The minute study of the behaviour of + the other constituents of sexual cells during fertilisation led to the + result, that the nucleus alone is concerned with handing on hereditary + characters (This was done by O. Hertwig and the author of this essay + simultaneously in 1884.) from one generation to another. Especially + important, from the point of view of this conclusion, is the study of + fertilisation in Angiosperms (Flowering plants); in these plants the male + sexual cells lose their cell-body in the pollen-tube and the nucleus only—the + sperm-nucleus—reaches the egg. The cytoplasm of the male sexual cell + is therefore not necessary to ensure a transference of hereditary + characters from parents to offspring. I lay stress on the case of the + Angiosperms because researches recently repeated with the help of the + latest methods failed to obtain different results. As regards the + descendants of angiospermous plants, the same laws of heredity hold good + as for other sexually differentiated organisms; we may, therefore, extend + to the latter what the Angiosperms so clearly teach us. + </p> + <p> + The next advance in the hitherto rapid progress in our knowledge of + nuclear division was delayed, because it was not at once recognised that + there are two absolutely different methods of nuclear division. All such + nuclear divisions were united under the head of indirect or mitotic + divisions; these were also spoken of as karyo-kineses, and were + distinguished from the direct or amitotic divisions which are + characterised by a simple constriction of the nuclear body. So long as the + two kinds of indirect nuclear division were not clearly distinguished, + their correct interpretation was impossible. This was accomplished after + long and laborious research, which has recently been carried out and with + results which should, perhaps, be regarded as provisional. + </p> + <p> + Soon after the new study of the nucleus began, investigators were struck + by the fact that the course of nuclear division in the mother-cells, or + more correctly in the grandmother-cells, of spores, pollen-grains, and + embryo-sacs of the more highly organised plants and in the spermatozoids + and eggs of the higher animals, exhibits similar phenomena, distinct from + those which occur in the somatic cells. + </p> + <p> + In the nuclei of all those cells which we may group together as + gonotokonts (At the suggestion of J.P. Lotsy in 1904.) (i.e. cells + concerned in reproduction) there are fewer chromosomes than in the + adjacent body-cells (somatic cells). It was noticed also that there is a + peculiarity characteristic of the gonotokonts, namely the occurrence of + two nuclear divisions rapidly succeeding one another. It was afterwards + recognised that in the first stage of nuclear division in the gonotokonts + the chromosomes unite in pairs: it is these chromosome-pairs, and not the + two longitudinal halves of single chromosomes, which form the nuclear + plate in the equatorial plane of the nuclear spindle. It has been proposed + to call these pairs gemini. (J.E.S. Moore and A.L. Embleton, "Proc. Roy. + Soc." London, Vol. LXXVII. page 555, 1906; V. Gregoire, 1907.) In the + course of this division the spindle-fibrillae attach themselves to the + gemini, i.e. to entire chromosomes and direct them to the points where the + new daughter-nuclei are formed, that is to those positions towards which + the longitudinal halves of the chromosomes travel in ordinary nuclear + divisions. It is clear that in this way the number of chromosomes which + the daughter-nuclei contain, as the result of the first stage in division + in the gonotokonts, will be reduced by one half, while in ordinary + divisions the number of chromosomes always remains the same. The first + stage in the division of the nucleus in the gonotokonts has therefore been + termed the reduction division. (In 1887 W. Flemming termed this the + heterotypic form of nuclear division.) This stage in division determines + the conditions for the second division which rapidly ensues. Each of the + paired chromosomes of the mother-nucleus has already, as in an ordinary + nuclear division, completed the longitudinal fission, but in this case it + is not succeeded by the immediate separation of the longitudinal halves + and their allotment to different nuclei. Each chromosome, therefore, takes + its two longitudinal halves into the same daughter-nucleus. Thus, in each + daughter-nucleus the longitudinal halves of the chromosomes are present + ready for the next stage in the division; they only require to be arranged + in the nuclear plate and then distributed among the granddaughter-nuclei. + This method of division, which takes place with chromosomes already split, + and which have only to provide for the distribution of their longitudinal + halves to the next nuclear generation, has been called homotypic nuclear + division. (The name was proposed by W. Flemming in 1887; the nature of + this type of division was, however, not explained until later.) + </p> + <p> + Reduction division and homotypic nuclear division are included together + under the term allotypic nuclear division and are distinguished from the + ordinary or typical nuclear division. The name Meiosis (By J. Bretland + Farmer and J.E.S. Moore in 1905.) has also been proposed for these two + allotypic nuclear divisions. The typical divisions are often spoken of as + somatic. + </p> + <p> + Observers who were actively engaged in this branch of recent histological + research soon noticed that the chromosomes of a given organism are + differentiated in definite numbers from the nuclear network in the course + of division. This is especially striking in the gonotokonts, but it + applies also to the somatic tissues. In the latter, one usually finds + twice as many chromosomes as in the gonotokonts. Thus the conclusion was + gradually reached that the doubling of chromosomes, which necessarily + accompanies fertilisation, is maintained in the product of fertilisation, + to be again reduced to one half in the gonotokonts at the stage of + reduction-division. This enabled us to form a conception as to the essence + of true alternation of generations, in which generations containing single + and double chromosomes alternate with one another. + </p> + <p> + The single-chromosome generation, which I will call the HAPLOID, must have + been the primitive generation in all organisms; it might also persist as + the only generation. Every sexual differentiation in organisms, which + occurred in the course of phylogenetic development, was followed by + fertilisation and therefore by the creation of a diploid or + double-chromosome product. So long as the germination of the product of + fertilisation, the zygote, began with a reducing process, a special + DIPLOID generation was not represented. This, however, appeared later as a + product of the further evolution of the zygote, and the reduction division + was correspondingly postponed. In animals, as in plants, the diploid + generation attained the higher development and gradually assumed the + dominant position. The haploid generation suffered a proportional + reduction, until it finally ceased to have an independent existence and + became restricted to the role of producing the sexual products within the + body of the diploid generation. Those who do not possess the necessary + special knowledge are unable to realise what remains of the first haploid + generation in a phanerogamic plant or in a vertebrate animal. In + Angiosperms this is actually represented only by the short developmental + stages which extend from the pollen mother-cells to the sperm-nucleus of + the pollen-tube, and from the embryo-sac mother-cell to the egg and the + endosperm tissue. The embryo-sac remains enclosed in the diploid ovule, + and within this from the fertilised egg is formed the embryo which + introduces the new diploid generation. On the full development of the + diploid embryo of the next generation, the diploid ovule of the preceding + diploid generation is separated from the latter as a ripe seed. The + uninitiated sees in the more highly organised plants only a succession of + diploid generations. Similarly all the higher animals appear to us as + independent organisms with diploid nuclei only. The haploid generation is + confined in them to the cells produced as the result of the reduction + division of the gonotokonts; the development of these is completed with + the homotypic stage of division which succeeds the reduction division and + produces the sexual products. + </p> + <p> + The constancy of the numbers in which the chromosomes separate themselves + from the nuclear network during division gave rise to the conception that, + in a certain degree, chromosomes possess individuality. Indeed the most + careful investigations (Particularly those of V. Gregoire and his pupils.) + have shown that the segments of the nuclear network, which separate from + one another and condense so as to produce chromosomes for a new division, + correspond to the segments produced from the chromosomes of the preceding + division. The behaviour of such nuclei as possess chromosomes of unequal + size affords confirmatory evidence of the permanence of individual + chromosomes in corresponding sections of an apparently uniform nuclear + network. Moreover at each stage in division chromosomes with the same + differences in size reappear. Other cases are known in which thicker + portions occur in the substance of the resting nucleus, and these agree in + number with the chromosomes. In this network, therefore, the individual + chromosomes must have retained their original position. But the + chromosomes cannot be regarded as the ultimate hereditary units in the + nuclei, as their number is too small. Moreover, related species not + infrequently show a difference in the number of their chromosomes, whereas + the number of hereditary units must approximately agree. We thus picture + to ourselves the carriers of hereditary characters as enclosed in the + chromosomes; the transmitted fixed number of chromosomes is for us only + the visible expression of the conception that the number of hereditary + units which the chromosomes carry must be also constant. The ultimate + hereditary units may, like the chromosomes themselves, retain a definite + position in the resting nucleus. Further, it may be assumed that during + the separation of the chromosomes from one another and during their + assumption of the rod-like form, the hereditary units become aggregated in + the chromomeres and that these are characterised by a constant order of + succession. The hereditary units then grow, divide into two and are + uniformly distributed by the fission of the chromosomes between their + longitudinal halves. + </p> + <p> + As the contraction and rod-like separation of the chromosomes serve to + isnure the transmission of all hereditary units in the products of + division of a nucleus, so, on the other hand, the reticular distension of + each chromosome in the so-called resting nucleus may effect a separation + of the carriers of hereditary units from each other and facilitate the + specific activity of each of them. + </p> + <p> + In the stages preliminary to their division, the chromosomes become denser + and take up a substance which increases their staining capacity; this is + called chromatin. This substance collects in the chromomeres and may form + the nutritive material for the carriers of hereditary units which we now + believe to be enclosed in them. The chromatin cannot itself be the + hereditary substance, as it afterwards leaves the chromosomes, and the + amount of it is subject to considerable variation in the nucleus, + according to its stage of development. Conjointly with the materials which + take part in the formation of the nuclear spindle and other processes in + the cell, the chromatin accumulates in the resting nucleus to form the + nucleoli. + </p> + <p> + Naturally connected with the conclusion that the nuclei are the carriers + of hereditary characters in the organism, is the question whether + enucleate organisms can also exist. Phylogenetic considerations give an + affirmative answer to this question. The differentiation into nucleus and + cytoplasm represents a division of labour in the protoplast. A study of + organisms which belong to the lowest class of the organic world teaches us + how this was accomplished. Instead of well-defined nuclei, scattered + granules have been described in the protoplasm of several of these + organisms (Bacteria, Cyanophyceae, Protozoa.), characterised by the same + reactions as nuclear material, provided also with a nuclear network, but + without a limiting membrane. (This is the result of the work of R. Hertwig + and of the most recently published investigations.) Thus the carriers of + hereditary characters may originally have been distributed in the common + protoplasm, afterwards coming together and eventually assuming a definite + form as special organs of the cell. It may be also assumed that in the + protoplasm and in the primitive types of nucleus, the carriers of the same + hereditary unit were represented in considerable quantity; they became + gradually differentiated to an extent commensurate with newly acquired + characters. It was also necessary that, in proportion as this happened, + the mechanism of nuclear division must be refined. At first processes + resembling a simple constriction would suffice to provide for the + distribution of all hereditary units to each of the products of division, + but eventually in both organic kingdoms nuclear division, which alone + insured the qualitative identity of the products of division, became a + more marked feature in the course of cell-multiplication. + </p> + <p> + Where direct nuclear division occurs by constriction in the higher + organisms, it does not result in the halving of hereditary units. So far + as my observations go, direct nuclear division occurs in the more highly + organised plants only in cells which have lost their specific functions. + Such cells are no longer capable of specific reproduction. An interesting + case in this connection is afforded by the internodal cells of the + Characeae, which possess only vegetative functions. These cells grow + vigorously and their cytoplasm increases, their growth being accompanied + by a correspondingly direct multiplication of the nuclei. They serve + chiefly to nourish the plant, but, unlike the other cells, they are + incapable of producing any offspring. This is a very instructive case, + because it clearly shows that the nuclei are not only carriers of + hereditary characters, but that they also play a definite part in the + metabolism of the protoplasts. + </p> + <p> + Attention was drawn to the fact that during the reducing division of + nuclei which contain chromosomes of unequal size, gemini are constantly + produced by the pairing of chromosomes of the same size. This led to the + conclusion that the pairing chromosomes are homologous, and that one comes + from the father, the other from the mother. (First stated by T.H. + Montgomery in 1901 and by W.S. Sutton in 1902.) This evidently applies + also to the pairing of chromosomes in those reduction-divisions in which + differences in size do not enable us to distinguish the individual + chromosomes. In this case also each pair would be formed by two homologous + chromosomes, the one of paternal, the other of maternal origin. When the + separation of these chromosomes and their distribution to both + daughter-nuclei occur a chromosome of each kind is provided for each of + these nuclei. It would seem that the components of each pair might pass to + either pole of the nuclear spindle, so that the paternal and maternal + chromosomes would be distributed in varying proportion between the + daughter-nuclei; and it is not impossible that one daughter-nucleus might + occasionally contain paternal chromosomes only and its sister-nucleus + exclusively maternal chromosomes. + </p> + <p> + The fact that in nuclei containing chromosomes of various sizes, the + chromosomes which pair together in reduction-division are always of equal + size, constitutes a further and more important proof of their qualitative + difference. This is supported also by ingenious experiments which led to + an unequal distribution of chromosomes in the products of division of a + sea-urchin's egg, with the result that a difference was induced in their + further development. (Demonstrated by Th. Boveri in 1902.) + </p> + <p> + The recently discovered fact that in diploid nuclei the chromosomes are + arranged in pairs affords additional evidence in favour of the unequal + value of the chromosomes. This is still more striking in the case of + chromosomes of different sizes. It has been shown that in the first + division-figure in the nucleus of the fertilised egg the chromosomes of + corresponding size form pairs. They appear with this arrangement in all + subsequent nuclear divisions in the diploid generation. The longitudinal + fissions of the chromosomes provide for the unaltered preservation of this + condition. In the reduction nucleus of the gonotokonts the homologous + chromosomes being near together need not seek out one another; they are + ready to form gemini. The next stage is their separation to the haploid + daughter-nuclei, which have resulted from the reduction process. + </p> + <p> + Peculiar phenomena in the reduction nucleus accompany the formation of + gemini in both organic kingdoms. (This has been shown more particularly by + the work of L. Guignard, M. Mottier, J.B. Farmer, C.B. Wilson, V. Hacker + and more recently by V. Gregoire and his pupil C.A. Allen, by the + researches conducted in the Bonn Botanical Institute, and by A. and K.E. + Schreiner.) Probably for the purpose of entering into most intimate + relation, the pairs are stretched to long threads in which the chromomeres + come to lie opposite one another. (C.A. Allen, A. and K.E. Schreiner, and + Strasburger.) It seems probable that these are homologous chromomeres, and + that the pairs afterwards unite for a short time, so that an exchange of + hereditary units is rendered possible. (H. de Vries and Strasburger.) This + cannot be actually seen, but certain facts of heredity point to the + conclusion that this occurs. It follows from these phenomena that any + exchange which may be effected must be one of homologous carriers of + hereditary units only. These units continue to form exchangeable segments + after they have undergone unequal changes; they then constitute + allelotropic pairs. We may thus calculate what sum of possible + combinations the exchange of homologous hereditary units between the + pairing chromosomes provides for before the reduction division and the + subsequent distribution of paternal and maternal chromosomes in the + haploid daughter-nuclei. These nuclei then transmit their characters to + the sexual cells, the conjugation of which in fertilization again produces + the most varied combinations. (A. Weismann gave the impulse to these ideas + in his theory on "Amphimixis".) In this way all the cooperations which the + carriers of hereditary characters are capable of in a species are + produced; this must give it an appreciable advantage in the struggle for + life. + </p> + <p> + The admirers of Charles Darwin must deeply regret that he did not live to + see the results achieved by the new Cytology. What service would they have + been to him in the presentation of his hypothesis of Pangenesis; what an + outlook into the future would they have given to his active mind! + </p> + <p> + The Darwinian hypothesis of Pangenesis rests on the conception that all + inheritable properties are represented in the cells by small invisible + particles or gemmules and that these gemmules increase by division. + Cytology began to develop on new lines some years after the publication in + 1868 of Charles Darwin's "Provisional hypothesis of Pangenesis" ("Animals + and Plants under Domestication", London, 1868, Chapter XXVII.), and when + he died in 1882 it was still in its infancy. Darwin would have soon + suggested the substitution of the nuclei for his gemmules. At least the + great majority of present-day investigators in the domain of cytology have + been led to the conclusion that the nucleus is the carrier of hereditary + characters, and they also believe that hereditary characters are + represented in the nucleus as distinct units. Such would be Darwin's + gemmules, which in conformity with the name of his hypothesis may be + called pangens (So called by H. de Vries in 1889.): these pangens multiply + by division. All recently adopted views may be thus linked on to this part + of Darwin's hypothesis. It is otherwise with Darwin's conception to which + Pangenesis owes its name, namely the view that all cells continually give + off gemmules, which migrate to other places in the organism, where they + unite to form reproductive cells. When Darwin foresaw this possibility, + the continuity of the germinal substance was still unknown (Demonstrated + by Nussbaum in 1880, by Sachs in 1882, and by Weismann in 1885.), a fact + which excludes a transference of gemmules. + </p> + <p> + But even Charles Darwin's genius was confined within finite boundaries by + the state of science in his day. + </p> + <p> + It is not my province to deal with other theories of development which + followed from Darwin's Pangenesis, or to discuss their histological + probabilities. We can, however, affirm that Charles Darwin's idea that + invisible gemmules are the carriers of hereditary characters and that they + multiply by division has been removed from the position of a provisional + hypothesis to that of a well-founded theory. It is supported by histology, + and the results of experimental work in heredity, which are now assuming + extraordinary prominence, are in close agreement with it. + </p> + <p> + <a name="link2H_4_0009" id="link2H_4_0009"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + VII. "THE DESCENT OF MAN". By G. Schwalbe. + </h2> + <h3> + Professor of Anatomy in the University of Strassburg. + </h3> + <p> + The problem of the origin of the human race, of the descent of man, is + ranked by Huxley in his epoch-making book "Man's Place in Nature", as the + deepest with which biology has to concern itself, "the question of + questions,"—the problem which underlies all others. In the same + brilliant and lucid exposition, which appeared in 1863, soon after the + publication of Darwin's "Origin of Species", Huxley stated his own views + in regard to this great problem. He tells us how the idea of a natural + descent of man gradually grew up in his mind, it was especially the + assertions of Owen in regard to the total difference between the human and + the simian brain that called forth strong dissent from the great anatomist + Huxley, and he easily succeeded in showing that Owen's supposed + differences had no real existence; he even established, on the basis of + his own anatomical investigations, the proposition that the anatomical + differences between the Marmoset and the Chimpanzee are much greater than + those between the Chimpanzee and Man. + </p> + <p> + But why do we thus introduce the study of Darwin's "Descent of Man", which + is to occupy us here, by insisting on the fact that Huxley had taken the + field in defence of the descent of man in 1863, while Darwin's book on the + subject did not appear till 1871? It is in order that we may clearly + understand how it happened that from this time onwards Darwin and Huxley + followed the same great aim in the most intimate association. + </p> + <p> + Huxley and Darwin working at the same Problema maximum! Huxley fiery, + impetuous, eager for battle, contemptuous of the resistance of a dull + world, or energetically triumphing over it. Darwin calm, weighing every + problem slowly, letting it mature thoroughly,—not a fighter, yet + having the greater and more lasting influence by virtue of his immense + mass of critically sifted proofs. Darwin's friend, Huxley, was the first + to do him justice, to understand his nature, and to find in it the reason + why the detailed and carefully considered book on the descent of man made + its appearance so late. Huxley, always generous, never thought of claiming + priority for himself. In enthusiastic language he tells how Darwin's + immortal work, "The Origin of Species", first shed light for him on the + problem of the descent of man; the recognition of a vera causa in the + transformation of species illuminated his thoughts as with a flash. He was + now content to leave what perplexed him, what he could not yet solve, as + he says himself, "in the mighty hands of Darwin." Happy in the bustle of + strife against old and deep-rooted prejudices, against intolerance and + superstition, he wielded his sharp weapons on Darwin's behalf; wearing + Darwin's armour he joyously overthrew adversary after adversary. Darwin + spoke of Huxley as his "general agent." ("Life and Letters of Thomas Henry + Huxley", Vol. I. page 171, London, 1900.) Huxley says of himself "I am + Darwin's bulldog." (Ibid. page 363.) + </p> + <p> + Thus Huxley openly acknowledged that it was Darwin's "Origin of Species" + that first set the problem of the descent of man in its true light, that + made the question of the origin of the human race a pressing one. That + this was the logical consequence of his book Darwin himself had long felt. + He had been reproached with intentionally shirking the application of his + theory to Man. Let us hear what he says on this point in his + autobiography: "As soon as I had become, in the year 1837 or 1838, + convinced that species were mutable productions, I could not avoid the + belief that man must come under the same law. Accordingly I collected + notes on the subject for my own satisfaction, and not for a long time with + any intention of publishing. Although in the 'Origin of Species' the + derivation of any particular species is never discussed, yet I thought it + best, in order THAT NO HONOURABLE MAN SHOULD ACCUSE ME OF CONCEALING MY + VIEWS (No italics in original.), to add that by the work 'light would be + thrown on the origin of man and his history.' It would have been useless + and injurious to the success of the book to have paraded, without giving + any evidence, my conviction with respect to his origin." ("Life and + Letters of Charles Darwin", Vol. 1. page 93.) + </p> + <p> + In a letter written in January, 1860, to the Rev. L. Blomefield, Darwin + expresses himself in similar terms. "With respect to man, I am very far + from wishing to obtrude my belief; but I thought it dishonest to quite + conceal my opinion." (Ibid. Vol. II. page 263.) + </p> + <p> + The brief allusion in the "Origin of Species" is so far from prominent and + so incidental that it was excusable to assume that Darwin had not touched + upon the descent of man in this work. It was solely the desire to have his + mass of evidence sufficiently complete, solely Darwin's great + characteristic of never publishing till he had carefully weighed all + aspects of his subject for years, solely, in short, his most fastidious + scientific conscience that restrained him from challenging the world in + 1859 with a book in which the theory of the descent of man was fully set + forth. Three years, frequently interrupted by ill-health, were needed for + the actual writing of the book ("Life and Letters", Vol. I. page 94.): the + first edition, which appeared in 1871, was followed in 1874 by a much + improved second edition, the preparation of which he very reluctantly + undertook. (Ibid. Vol. III. page 175.) + </p> + <p> + This, briefly, is the history of the work, which, with the "Origin of + Species", marks an epoch in the history of biological sciences—the + work with which the cautious, peace-loving investigator ventured forth + from his contemplative life into the arena of strife and unrest, and laid + himself open to all the annoyances that deep-rooted belief and prejudice, + and the prevailing tendency of scientific thought at the time could + devise. + </p> + <p> + Darwin did not take this step lightly. Of great interest in this + connection is a letter written to Wallace on Dec. 22, 1857 (Ibid. Vol. II. + page 109.), in which he says "You ask whether I shall discuss 'man.' I + think I shall avoid the whole subject, as so surrounded with prejudices; + though I fully admit that it is the highest and most interesting problem + for the naturalist." But his conscientiousness compelled him to state + briefly his opinion on the subject in the "Origin of Species" in 1859. + Nevertheless he did not escape reproaches for having been so reticent. + This is unmistakably apparent from a letter to Fritz Muller dated February + 22 (1869?), in which he says: "I am thinking of writing a little essay on + the Origin of Mankind, as I have been taunted with concealing my + opinions." (Ibid. Vol. III. page 112.) + </p> + <p> + It might be thought that Darwin behaved thus hesitatingly, and was so slow + in deciding on the full publication of his collected material in regard to + the descent of man, because he had religious difficulties to overcome. + </p> + <p> + But this was not the case, as we can see from his admirable confession of + faith, the publication of which we owe to his son Francis. (Ibid. Vol. I. + pages 304-317.) Whoever wishes really to understand the lofty character of + this great man should read these immortal lines in which he unfolds to us + in simple and straightforward words the development of his conception of + the universe. He describes how, though he was still quite orthodox during + his voyage round the world on board the "Beagle", he came gradually to + see, shortly afterwards (1836-1839) that the Old Testament was no more to + be trusted than the Sacred Books of the Hindoos; the miracles by which + Christianity is supported, the discrepancies between the accounts in the + different Gospels, gradually led him to disbelieve in Christianity as a + divine revelation. "Thus," he writes ("Life and Letters", Vol. 1. page + 309.), "disbelief crept over me at a very slow rate, but was at last + complete. The rate was so slow that I felt no distress." But Darwin was + too modest to presume to go beyond the limits laid down by science. He + wanted nothing more than to be able to go, freely and unhampered by belief + in authority or in the Bible, as far as human knowledge could lead him. We + learn this from the concluding words of his chapter on religion: "The + mystery of the beginning of all things is insoluble by us; and I for one + must be content to remain an Agnostic." (Loc. cit. page 313.) + </p> + <p> + Darwin was always very unwilling to give publicity to his views in regard + to religion. In a letter to Asa Gray on May 22, 1860 (Ibid. Vol. II. page + 310.), he declares that it is always painful to him to have to enter into + discussion of religious problems. He had, he said, no intention of writing + atheistically. + </p> + <p> + Finally, let us cite one characteristic sentence from a letter from Darwin + to C. Ridley (Ibid. Vol. III. page. 236. ("C. Ridley," Mr Francis Darwin + points out to me, should be H.N. Ridley. A.C.S.)) (Nov. 28, 1878.) A + clergyman, Dr Pusey, had asserted that Darwin had written the "Origin of + Species" with some relation to theology. Darwin writes emphatically, "Many + years ago, when I was collecting facts for the 'Origin', my belief in what + is called a personal God was as firm as that of Dr Pusey himself, and as + to the eternity of matter I never troubled myself about such insoluble + questions." The expression "many years ago" refers to the time of his + voyage round the world, as has already been pointed out. Darwin means by + this utterance that the views which had gradually developed in his mind in + regard to the origin of species were quite compatible with the faith of + the Church. + </p> + <p> + If we consider all these utterances of Darwin in regard to religion and to + his outlook on life (Weltanschauung), we shall see at least so much, that + religious reflection could in no way have influenced him in regard to the + writing and publishing of his book on "The Descent of Man". Darwin had + early won for himself freedom of thought, and to this freedom he remained + true to the end of his life, uninfluenced by the customs and opinions of + the world around him. + </p> + <p> + Darwin was thus inwardly fortified and armed against the host of + calumnies, accusations, and attacks called forth by the publication of the + "Origin of Species", and to an even greater extent by the appearance of + the "Descent of Man". But in his defence he could rely on the aid of a + band of distinguished auxiliaries of the rarest ability. His faithful + confederate, Huxley, was joined by the botanist Hooker, and, after longer + resistance, by the famous geologist Lyell, whose "conversion" afforded + Darwin peculiar satisfaction. All three took the field with enthusiasm in + defence of the natural descent of man. From Wallace, on the other hand, + though he shared with him the idea of natural selection, Darwin got no + support in this matter. Wallace expressed himself in a strange manner. He + admitted everything in regard to the morphological descent of man, but + maintained, in a mystic way, that something else, something of a spiritual + nature must have been added to what man inherited from his animal + ancestors. Darwin, whose esteem for Wallace was extraordinarily high, + could not understand how he could give utterance to such a mystical view + in regard to man; the idea seemed to him so "incredibly strange" that he + thought some one else must have added these sentences to Wallace's paper. + </p> + <p> + Even now there are thinkers who, like Wallace, shrink from applying to man + the ultimate consequences of the theory of descent. The idea that man is + derived from ape-like forms is to them unpleasant and humiliating. + </p> + <p> + So far I have been depicting the development of Darwin's work on the + descent of man. In what follows I shall endeavour to give a condensed + survey of the contents of the book. + </p> + <p> + It must at once be said that the contents of Darwin's work fall into two + parts, dealing with entirely different subjects. "The Descent of Man" + includes a very detailed investigation in regard to secondary sexual + characters in the animal series, and on this investigation Darwin founded + a new theory, that of sexual selection. With astonishing patience he + gathered together an immense mass of material, and showed, in regard to + Arthropods and Vertebrates, the wide distribution of secondary characters, + which develop almost exclusively in the male, and which enable him, on the + one hand, to get the better of his rivals in the struggle for the female + by the greater perfection of his weapons, and on the other hand, to offer + greater allurements to the female through the higher development of + decorative characters, of song, or of scent-producing glands. The best + equipped males will thus crowd out the less well-equipped in the matter of + reproduction, and thus the relevant characters will be increased and + perfected through sexual selection. It is, of course, a necessary + assumption that these secondary sexual characters may be transmitted to + the female, although perhaps in rudimentary form. + </p> + <p> + As we have said, this theory of sexual selection takes up a great deal of + space in Darwin's book, and it need only be considered here in so far as + Darwin applied it to the descent of man. To this latter problem the whole + of Part I is devoted, while Part III contains a discussion of sexual + selection in relation to man, and a general summary. Part II treats of + sexual selection in general, and may be disregarded in our present study. + Moreover, many interesting details must necessarily be passed over in what + follows, for want of space. + </p> + <p> + The first part of the "Descent of Man" begins with an enumeration of the + proofs of the animal descent of man taken from the structure of the human + body. Darwin chiefly emphasises the fact that the human body consists of + the same organs and of the same tissues as those of the other mammals; he + shows also that man is subject to the same diseases and tormented by the + same parasites as the apes. He further dwells on the general agreement + exhibited by young, embryonic forms, and he illustrates this by two + figures placed one above the other, one representing a human embryo, after + Eaker, the other a dog embryo, after Bischoff. ("Descent of Man" (Popular + Edition, 1901), fig. 1, page 14.) + </p> + <p> + Darwin finds further proofs of the animal origin of man in the reduced + structures, in themselves extremely variable, which are either absolutely + useless to their possessors, or of so little use that they could never + have developed under existing conditions. Of such vestiges he enumerates: + the defective development of the panniculus carnosus (muscle of the skin) + so widely distributed among mammals, the ear-muscles, the occasional + persistence of the animal ear-point in man, the rudimentary nictitating + membrane (plica semilunaris) in the human eye, the slight development of + the organ of smell, the general hairiness of the human body, the + frequently defective development or entire absence of the third molar (the + wisdom tooth), the vermiform appendix, the occasional reappearance of a + bony canal (foramen supracondyloideum) at the lower end of the humerus, + the rudimentary tail of man (the so-called taillessness), and so on. Of + these rudimentary structures the occasional occurrence of the animal + ear-point in man is most fully discussed. Darwin's attention was called to + this interesting structure by the sculptor Woolner. He figures such a case + observed in man, and also the head of an alleged orang-foetus, the + photograph of which he received from Nitsche. + </p> + <p> + Darwin's interpretation of Woolner's case as having arisen through a + folding over of the free edge of a pointed ear has been fully borne out by + my investigations on the external ear. (G. Schwalbe, "Das Darwin'sche + Spitzohr beim menschlichen Embryo", "Anatom. Anzeiger", 1889, pages + 176-189, and other papers.) In particular, it was established by these + investigations that the human foetus, about the middle of its embryonic + life, possesses a pointed ear somewhat similar to that of the monkey genus + Macacus. One of Darwin's statements in regard to the head of the + orang-foetus must be corrected. A LARGE ear with a point is shown in the + photograph ("Descent of Man", fig.3, page 24.), but it can easily be + demonstrated—and Deniker has already pointed this out—that the + figure is not that of an orang-foetus at all, for that form has much + smaller ears with no point; nor can it be a gibbon-foetus, as Deniker + supposes, for the gibbon ear is also without a point. I myself regard it + as that of a Macacus-embryo. But this mistake, which is due to Nitsche, in + no way affects the fact recognised by Darwin, that ear-forms showing the + point characteristic of the animal ear occur in man with extraordinary + frequency. + </p> + <p> + Finally, there is a discussion of those rudimentary structures which occur + only in ONE sex, such as the rudimentary mammary glands in the male, the + vesicula prostatica, which corresponds to the uterus of the female, and + others. All these facts tell in favour of the common descent of man and + all other vertebrates. The conclusion of this section is characteristic: + "IT IS ONLY OUR NATURAL PREJUDICE, AND THAT ARROGANCE WHICH MADE OUR + FOREFATHERS DECLARE THAT THEY WERE DESCENDED FROM DEMI-GODS, WHICH LEADS + US TO DEMUR TO THIS CONCLUSION. BUT THE TIME WILL BEFORE LONG COME, WHEN + IT WILL BE THOUGHT WONDERFUL THAT NATURALISTS, WHO WERE WELL ACQUAINTED + WITH THE COMPARATIVE STRUCTURE AND DEVELOPMENT OF MAN, AND OTHER MAMMALS, + SHOULD HAVE BELIEVED THAT EACH WAS THE WORK OF A SEPARATE ACT OF + CREATION." (Ibid. page 36.) + </p> + <p> + In the second chapter there is a more detailed discussion, again based + upon an extraordinary wealth of facts, of the problem as to the manner in + which, and the causes through which, man evolved from a lower form. + Precisely the same causes are here suggested for the origin of man, as for + the origin of species in general. Variability, which is a necessary + assumption in regard to all transformations, occurs in man to a high + degree. Moreover, the rapid multiplication of the human race creates + conditions which necessitate an energetic struggle for existence, and thus + afford scope for the intervention of natural selection. Of the exercise of + ARTIFICIAL selection in the human race, there is nothing to be said, + unless we cite such cases as the grenadiers of Frederick William I, or the + population of ancient Sparta. In the passages already referred to and in + those which follow, the transmission of acquired characters, upon which + Darwin does not dwell, is taken for granted. In man, direct effects of + changed conditions can be demonstrated (for instance in regard to bodily + size), and there are also proofs of the influence exerted on his physical + constitution by increased use or disuse. Reference is here made to the + fact, established by Forbes, that the Quechua-Indians of the high plateaus + of Peru show a striking development of lungs and thorax, as a result of + living constantly at high altitudes. + </p> + <p> + Such special forms of variation as arrests of development (microcephalism) + and reversion to lower forms are next discussed. Darwin himself felt + ("Descent of Man", page 54.) that these subjects are so nearly related to + the cases mentioned in the first chapter, that many of them might as well + have been dealt with there. It seems to me that it would have been better + so, for the citation of additional instances of reversion at this place + rather disturbs the logical sequence of his ideas as to the conditions + which have brought about the evolution of man from lower forms. The + instances of reversion here discussed are microcephalism, which Darwin + wrongly interpreted as atavistic, supernumerary mammae, supernumerary + digits, bicornuate uterus, the development of abnormal muscles, and so on. + Brief mention is also made of correlative variations observed in man. + </p> + <p> + Darwin next discusses the question as to the manner in which man attained + to the erect position from the state of a climbing quadruped. Here again + he puts the influence of Natural Selection in the first rank. The + immediate progenitors of man had to maintain a struggle for existence in + which success was to the more intelligent, and to those with social + instincts. The hand of these climbing ancestors, which had little skill + and served mainly for locomotion, could only undergo further development + when some early member of the Primate series came to live more on the + ground and less among trees. + </p> + <p> + A bipedal existence thus became possible, and with it the liberation of + the hand from locomotion, and the one-sided development of the human foot. + The upright position brought about correlated variations in the bodily + structure; with the free use of the hand it became possible to manufacture + weapons and to use them; and this again resulted in a degeneration of the + powerful canine teeth and the jaws, which were then no longer necessary + for defence. Above all, however, the intelligence immediately increased, + and with it skull and brain. The nakedness of man, and the absence of a + tail (rudimentariness of the tail vertebrae) are next discussed. Darwin is + inclined to attribute the nakedness of man, not to the action of natural + selection on ancestors who originally inhabited a tropical land, but to + sexual selection, which, for aesthetic reasons, brought about the loss of + the hairy covering in man, or primarily in woman. An interesting + discussion of the loss of the tail, which, however, man shares with the + anthropoid apes, some other monkeys and lemurs, forms the conclusion of + the almost superabundant material which Darwin worked up in the second + chapter. His object was to show that some of the most distinctive human + characters are in all probability directly or indirectly due to natural + selection. With characteristic modesty he adds ("Descent of Man", page + 92.): "Hence, if I have erred in giving to natural selection great power, + which I am very far from admitting, or in having exaggerated its power, + which is in itself probable, I have at least, as I hope, done good service + in aiding to overthrow the dogma of separate creations." At the end of the + chapter he touches upon the objection as to man's helpless and defenceless + condition. Against this he urges his intelligence and social instincts. + </p> + <p> + The two following chapters contain a detailed discussion of the objections + drawn from the supposed great differences between the mental powers of men + and animals. Darwin at once admits that the differences are enormous, but + not that any fundamental difference between the two can be found. Very + characteristic of him is the following passage: "In what manner the mental + powers were first developed in the lowest organisms, is as hopeless an + enquiry as how life itself first originated. These are problems for the + distant future, if they are ever to be solved by man." (Ibid. page 100.) + </p> + <p> + After some brief observations on instinct and intelligence, Darwin brings + forward evidence to show that the greater number of the emotional states, + such as pleasure and pain, happiness and misery, love and hate are common + to man and the higher animals. He goes on to give various examples showing + that wonder and curiosity, imitation, attention, memory and imagination + (dreams of animals), can also be observed in the higher mammals, + especially in apes. In regard even to reason there are no sharply defined + limits. A certain faculty of deliberation is characteristic of some + animals, and the more thoroughly we know an animal the more intelligence + we are inclined to credit it with. Examples are brought forward of the + intelligent and deliberate actions of apes, dogs and elephants. But + although no sharply defined differences exist between man and animals, + there is, nevertheless, a series of other mental powers which are + characteristics usually regarded as absolutely peculiar to man. Some of + these characteristics are examined in detail, and it is shown that the + arguments drawn from them are not conclusive. Man alone is said to be + capable of progressive improvement; but against this must be placed as + something analogous in animals, the fact that they learn cunning and + caution through long continued persecution. Even the use of tools is not + in itself peculiar to man (monkeys use sticks, stones and twigs), but man + alone fashions and uses implements DESIGNED FOR A SPECIAL PURPOSE. In this + connection the remarks taken from Lubbock in regard to the origin and + gradual development of the earliest flint implements will be read with + interest; these are similar to the observations on modern eoliths, and + their bearing on the development of the stone-industry. It is interesting + to learn from a letter to Hooker ("Life and Letters", Vol. II. page 161, + June 22, 1859.), that Darwin himself at first doubted whether the stone + implements discovered by Boucher de Perthes were really of the nature of + tools. With the relentless candour as to himself which characterised him, + he writes four years later in a letter to Lyell in regard to this view of + Boucher de Perthes' discoveries: "I know something about his errors, and + looked at his book many years ago, and am ashamed to think that I + concluded the whole was rubbish! Yet he has done for man something like + what Agassiz did for glaciers." (Ibid. Vol. III. page 15, March 17, 1863.) + </p> + <p> + To return to Darwin's further comparisons between the higher mental powers + of man and animals. He takes much of the force from the argument that man + alone is capable of abstraction and self-consciousness by his own + observations on dogs. One of the main differences between man and animals, + speech, receives detailed treatment. He points out that various animals + (birds, monkeys, dogs) have a large number of different sounds for + different emotions, that, further, man produces in common with animals a + whole series of inarticulate cries combined with gestures, and that dogs + learn to understand whole sentences of human speech. In regard to human + language, Darwin expresses a view contrary to that held by Max Muller + ("Descent of Man", page 132.): "I cannot doubt that language owes its + origin to the imitation and modification of various natural sounds, the + voices of other animals, and man's own instinctive cries, aided by signs + and gestures." The development of actual language presupposes a higher + degree of intelligence than is found in any kind of ape. Darwin remarks on + this point (Ibid. pages 136, 137.): "The fact of the higher apes not using + their vocal organs for speech no doubt depends on their intelligence not + having been sufficiently advanced." + </p> + <p> + The sense of beauty, too, has been alleged to be peculiar to man. In + refutation of this assertion Darwin points to the decorative colours of + birds, which are used for display. And to the last objection, that man + alone has religion, that he alone has a belief in God, it is answered + "that numerous races have existed, and still exist, who have no idea of + one or more gods, and who have no words in their languages to express such + an idea." (Ibid. page 143.) + </p> + <p> + The result of the investigations recorded in this chapter is to show that, + great as the difference in mental powers between man and the higher + animals may be, it is undoubtedly only a difference "of degree and not of + kind." ("Descent of Man", page 193.) + </p> + <p> + In the fourth chapter Darwin deals with the MORAL SENSE or CONSCIENCE, + which is the most important of all differences between man and animals. It + is a result of social instincts, which lead to sympathy for other members + of the same society, to non-egoistic actions for the good of others. + Darwin shows that social tendencies are found among many animals, and that + among these love and kin-sympathy exist, and he gives examples of animals + (especially dogs) which may exhibit characters that we should call moral + in man (e.g. disinterested self-sacrifice for the sake of others). The + early ape-like progenitors of the human race were undoubtedly social. With + the increase of intelligence the moral sense develops farther; with the + acquisition of speech public opinion arises, and finally, moral sense + becomes habit. The rest of Darwin's detailed discussions on moral + philosophy may be passed over. + </p> + <p> + The fifth chapter may be very briefly summarised. In it Darwin shows that + the intellectual and moral faculties are perfected through natural + selection. He inquires how it can come about that a tribe at a low level + of evolution attains to a higher, although the best and bravest among them + often pay for their fidelity and courage with their lives without leaving + any descendants. In this case it is the sentiment of glory, praise and + blame, the admiration of others, which bring about the increase of the + better members of the tribe. Property, fixed dwellings, and the + association of families into a community are also indispensable + requirements for civilisation. In the longer second section of the fifth + chapter Darwin acts mainly as recorder. On the basis of numerous + investigations, especially those of Greg, Wallace, and Galton, he inquires + how far the influence of natural selection can be demonstrated in regard + to civilised nations. In the final section, which deals with the proofs + that all civilised nations were once barbarians, Darwin again uses the + results gained by other investigators, such as Lubbock and Tylor. There + are two sets of facts which prove the proposition in question. In the + first place, we find traces of a former lower state in the customs and + beliefs of all civilised nations, and in the second place, there are + proofs to show that savage races are independently able to raise + themselves a few steps in the scale of civilisation, and that they have + thus raised themselves. + </p> + <p> + In the sixth chapter of the work, Morphology comes into the foreground + once more. Darwin first goes back, however, to the argument based on the + great difference between the mental powers of the highest animals and + those of man. That this is only quantitative, not qualitative, he has + already shown. Very instructive in this connection is the reference to the + enormous difference in mental powers in another class. No one would draw + from the fact that the cochineal insect (Coccus) and the ant exhibit + enormous differences in their mental powers, the conclusion that the ant + should therefore be regarded as something quite distinct, and withdrawn + from the class of insects altogether. + </p> + <p> + Darwin next attempts to establish the SPECIFIC genealogical tree of man, + and carefully weighs the differences and resemblances between the + different families of the Primates. The erect position of man is an + adaptive character, just as are the various characters referable to + aquatic life in the seals, which, notwithstanding these, are ranked as a + mere family of the Carnivores. The following utterance is very + characteristic of Darwin ("Descent of Man", page 231.): "If man had not + been his own classifier, he would never have thought of founding a + separate order for his own reception." In numerous characters not + mentioned in systematic works, in the features of the face, in the form of + the nose, in the structure of the external ear, man resembles the apes. + The arrangement of the hair in man has also much in common with the apes; + as also the occurrence of hair on the forehead of the human embryo, the + beard, the convergence of the hair of the upper and under arm towards the + elbow, which occurs not only in the anthropoid apes, but also in some + American monkeys. Darwin here adopts Wallace's explanation of the origin + of the ascending direction of the hair in the forearm of the orang,—that + it has arisen through the habit of holding the hands over the head in + rain. But this explanation cannot be maintained when we consider that this + disposition of the hair is widely distributed among the most different + mammals, being found in the dog, in the sloth, and in many of the lower + monkeys. + </p> + <p> + After further careful analysis of the anatomical characters Darwin reaches + the conclusion that the New World monkeys (Platyrrhine) may be excluded + from the genealogical tree altogether, but that man is an offshoot from + the Old World monkeys (Catarrhine) whose progenitors existed as far back + as the Miocene period. Among these Old World monkeys the forms to which + man shows the greatest resemblance are the anthropoid apes, which, like + him, possess neither tail nor ischial callosities. The platyrrhine and + catarrhine monkeys have their primitive ancestor among extinct forms of + the Lemuridae. Darwin also touches on the question of the original home of + the human race and supposes that it may have been in Africa, because it is + there that man's nearest relatives, the gorilla and the chimpanzee, are + found. But he regards speculation on this point as useless. It is + remarkable that, in this connection, Darwin regards the loss of the + hair-covering in man as having some relation to a warm climate, while + elsewhere he is inclined to make sexual selection responsible for it. + Darwin recognises the great gap between man and his nearest relatives, but + similar gaps exist at other parts of the mammalian genealogical tree: the + allied forms have become extinct. After the extermination of the lower + races of mankind, on the one hand, and of the anthropoid apes on the + other, which will undoubtedly take place, the gulf will be greater than + ever, since the baboons will then bound it on the one side, and the white + races on the other. Little weight need be attached to the lack of fossil + remains to fill up this gap, since the discovery of these depends upon + chance. The last part of the chapter is devoted to a discussion of the + earlier stages in the genealogy of man. Here Darwin accepts in the main + the genealogical tree, which had meantime been published by Haeckel, who + traces the pedigree back through Monotremes, Reptiles, Amphibians, and + Fishes, to Amphioxus. + </p> + <p> + Then follows an attempt to reconstruct, from the atavistic characters, a + picture of our primitive ancestor who was undoubtedly an arboreal animal. + The occurrence of rudiments of parts in one sex which only come to full + development in the other is next discussed. This state of things Darwin + regards as derived from an original hermaphroditism. In regard to the + mammary glands of the male he does not accept the theory that they are + vestigial, but considers them rather as not fully developed. + </p> + <p> + The last chapter of Part I deals with the question whether the different + races of man are to be regarded as different species, or as sub-species of + a race of monophyletic origin. The striking differences between the races + are first emphasised, and the question of the fertility or infertility of + hybrids is discussed. That fertility is the more usual is shown by the + excessive fertility of the hybrid population of Brazil. This, and the + great variability of the distinguishing characters of the different races, + as well as the fact that all grades of transition stages are found between + these, while considerable general agreement exists, tell in favour of the + unity of the races and lead to the conclusion that they all had a common + primitive ancestor. + </p> + <p> + Darwin therefore classifies all the different races as sub-species of ONE + AND THE SAME SPECIES. Then follows an interesting inquiry into the reasons + for the extinction of human races. He recognises as the ultimate reason + the injurious effects of a change of the conditions of life, which may + bring about an increase in infantile mortality, and a diminished + fertility. It is precisely the reproductive system, among animals also, + which is most susceptible to changes in the environment. + </p> + <p> + The final section of this chapter deals with the formation of the races of + mankind. Darwin discusses the question how far the direct effect of + different conditions of life, or the inherited effects of increased use or + disuse may have brought about the characteristic differences between the + different races. Even in regard to the origin of the colour of the skin he + rejects the transmitted effects of an original difference of climate as an + explanation. In so doing he is following his tendency to exclude + Lamarckian explanations as far as possible. But here he makes gratuitous + difficulties from which, since natural selection fails, there is no escape + except by bringing in the principle of sexual selection, to which, he + regarded it as possible, skin-colouring, arrangement of hair, and form of + features might be traced. But with his characteristic conscientiousness he + guards himself thus: "I do not intend to assert that sexual selection will + account for all the differences between the races." ("Descent of Man", + page 308.) + </p> + <p> + I may be permitted a remark as to Darwin's attitude towards Lamarck. + While, at an earlier stage, when he was engaged in the preliminary labours + for his immortal work, "The Origin of Species", Darwin expresses himself + very forcibly against the views of Lamarck, speaking of Lamarckian + "nonsense," ("Life and Letters", Vol. II. page 23.), and of Lamarck's + "absurd, though clever work" (Loc. cit. page 39.) and expressly declaring, + "I attribute very little to the direct action of climate, etc." (Loc. cit. + (1856), page 82.) yet in later life he became more and more convinced of + the influence of external conditions. In 1876, that is, two years after + the appearance of the second edition of "The Descent of Man", he writes + with his usual candid honesty: "In my opinion the greatest error which I + have committed, has been not allowing sufficient weight to the direct + action of the environment, i.e. food, climate, etc. independently of + natural selection." (Ibid. Vol. III. page 159.) It is certain from this + change of opinion that, if he had been able to make up his mind to issue a + third edition of "The Descent of Man", he would have ascribed a much + greater influence to the effect of external conditions in explaining the + different characters of the races of man than he did in the second + edition. He would also undoubtedly have attributed less influence to + sexual selection as a factor in the origin of the different bodily + characteristics, if indeed he would not have excluded it altogether. + </p> + <p> + In Part III of the "Descent" two additional chapters are devoted to the + discussion of sexual selection in relation to man. These may be very + briefly referred to. Darwin here seeks to show that sexual selection has + been operative on man and his primitive progenitor. Space fails me to + follow out his interesting arguments. I can only mention that he is + inclined to trace back hairlessness, the development of the beard in man, + and the characteristic colour of the different human races to sexual + selection. Since bareness of the skin could be no advantage, but rather a + disadvantage, this character cannot have been brought about by natural + selection. Darwin also rejected a direct influence of climate as a cause + of the origin of the skin-colour. I have already expressed the opinion, + based on the development of his views as shown in his letters, that in a + third edition Darwin would probably have laid more stress on the influence + of external environment. He himself feels that there are gaps in his + proofs here, and says in self-criticism: "The views here advanced, on the + part which sexual selection has played in the history of man, want + scientific precision." ("Descent of Man", page 924.) I need here only + point out that it is impossible to explain the graduated stages of + skin-colour by sexual selection, since it would have produced races + sharply defined by their colour and not united to other races by + transition stages, and this, it is well known, is not the case. Moreover, + the fact established by me ("Die Hautfarbe des Menschen", "Mitteilungen + der Anthropologischen Gesellschaft in Wien", Vol. XXXIV. pages 331-352.), + that in all races the ventral side of the trunk is paler than the dorsal + side, and the inner surface of the extremities paler than the outer side, + cannot be explained by sexual selection in the Darwinian sense. + </p> + <p> + With this I conclude my brief survey of the rich contents of Darwin's + book. I may be permitted to conclude by quoting the magnificent final + words of "The Descent of Man": "We must, however, acknowledge, as it seems + to me, that man, with all his noble qualities, with sympathy which feels + for the most debased, with benevolence which extends not only to other men + but to the humblest living creature, with his god-like intellect which has + penetrated into the movements and constitution of the solar system—with + all these exalted powers—Man still bears in his bodily frame the + indelible stamp of his lowly origin." (Ibid. page 947.) + </p> + <p> + What has been the fate of Darwin's doctrines since his great achievement? + How have they been received and followed up by the scientific and lay + world? And what do the successors of the mighty hero and genius think now + in regard to the origin of the human race? + </p> + <p> + At the present time we are incomparably more favourably placed than Darwin + was for answering this question of all questions. We have at our command + an incomparably greater wealth of material than he had at his disposal. + And we are more fortunate than he in this respect, that we now know + transition-forms which help to fill up the gap, still great, between the + lowest human races and the highest apes. Let us consider for a little the + more essential additions to our knowledge since the publication of "The + Descent of Man". + </p> + <p> + Since that time our knowledge of animal embryos has increased enormously. + While Darwin was obliged to content himself with comparing a human embryo + with that of a dog, there are now available the youngest embryos of + monkeys of all possible groups (Orang, Gibbon, Semnopithecus, Macacus), + thanks to Selenka's most successful tour in the East Indies in search of + such material. We can now compare corresponding stages of the lower + monkeys and of the Anthropoid apes with human embryos, and convince + ourselves of their great resemblance to one another, thus strengthening + enormously the armour prepared by Darwin in defence of his view on man's + nearest relatives. It may be said that Selenka's material fils up the + blanks in Darwin's array of proofs in the most satisfactory manner. + </p> + <p> + The deepening of our knowledge of comparative anatomy also gives us much + surer foundations than those on which Darwin was obliged to build. Just of + late there have been many workers in the domain of the anatomy of apes and + lemurs, and their investigations extend to the most different organs. Our + knowledge of fossil apes and lemurs has also become much wider and more + exact since Darwin's time: the fossil lemurs have been especially worked + up by Cope, Forsyth Major, Ameghino, and others. Darwin knew very little + about fossil monkeys. He mentions two or three anthropoid apes as + occurring in the Miocene of Europe ("Descent of Man", page 240.), but only + names Dryopithecus, the largest form from the Miocene of France. It was + erroneously supposed that this form was related to Hylobates. We now know + not only a form that actually stands near to the gibbon (Pliopithecus), + and remains of other anthropoids (Pliohylobates and the fossil chimpanzee, + Palaeopithecus), but also several lower catarrhine monkeys, of which + Mesopithecus, a form nearly related to the modern Sacred Monkeys (a + species of Semnopithecus) and found in strata of the Miocene period in + Greece, is the most important. Quite recently, too, Ameghino's + investigations have made us acquainted with fossil monkeys from South + America (Anthropops, Homunculus), which, according to their discoverer, + are to be regarded as in the line of human descent. + </p> + <p> + What Darwin missed most of all—intermediate forms between apes and + man—has been recently furnished. (E. Dubois, as is well known, + discovered in 1893, near Trinil in Java, in the alluvial deposits of the + river Bengawan, an important form represented by a skull-cap, some molars, + and a femur. His opinion—much disputed as it has been—that in + this form, which he named Pithecanthropus, he has found a long-desired + transition-form is shared by the present writer. And although the + geological age of these fossils, which, according to Dubois, belong to the + uppermost Tertiary series, the Pliocene, has recently been fixed at a + later date (the older Diluvium)), the MORPHOLOGICAL VALUE of these + interesting remains, that is, the intermediate position of + Pithecanthropus, still holds good. Volz says with justice ("Das + geologische Alter der Pithecanthropus-Schichten bei Trinil, Ost-Java". + "Neues Jahrb. f.Mineralogie". Festband, 1907.), that even if + Pithecanthropus is not THE missing link, it is undoubtedly <i>A</i> + missing link. + </p> + <p> + As on the one hand there has been found in Pithecanthropus a form which, + though intermediate between apes and man, is nevertheless more closely + allied to the apes, so on the other hand, much progress has been made + since Darwin's day in the discovery and description of the older human + remains. Since the famous roof of a skull and the bones of the extremities + belonging to it were found in 1856 in the Neandertal near Dusseldorf, the + most varied judgments have been expressed in regard to the significance of + the remains and of the skull in particular. In Darwin's "Descent of Man" + there is only a passing allusion to them ("Descent of Man", page 82.) in + connection with the discussion of the skull-capacity, although the + investigations of Schaaffhausen, King, and Huxley were then known. I + believe I have shown, in a series of papers, that the skull in question + belongs to a form different from any of the races of man now living, and, + with King and Cope, I regard it as at least a different species from + living man, and have therefore designated it Homo primigenius. The form + unquestionably belongs to the older Diluvium, and in the later Diluvium + human forms already appear, which agree in all essential points with + existing human races. + </p> + <p> + As far back as 1886 the value of the Neandertal skull was greatly enhanced + by Fraipont's discovery of two skulls and skeletons from Spy in Belgium. + These are excellently described by their discoverer ("La race humaine de + Neanderthal ou de Canstatt en Belgique". "Arch. de Biologie", VII. 1887.), + and are regarded as belonging to the same group of forms as the Neandertal + remains. In 1899 and the following years came the discovery by + Gorjanovic-Kramberger of different skeletal parts of at least ten + individuals in a cave near Krapina in Croatia. (Gorjanovic-Kramberger "Der + diluviale Mensch von Krapina in Kroatien", 1906.) It is in particular the + form of the lower jaw which is different from that of all recent races of + man, and which clearly indicates the lowly position of Homo primigenius, + while, on the other hand, the long-known skull from Gibraltar, which I + ("Studien zur Vorgeschichte des Menschen", 1906, pages 154 ff.) have + referred to Homo primigenius, and which has lately been examined in detail + by Sollas ("On the cranial and facial characters of the Neandertal Race". + "Trans. R. Soc." London, vol. 199, 1908, page 281.), has made us + acquainted with the surprising shape of the eye-orbit, of the nose, and of + the whole upper part of the face. Isolated lower jaws found at La Naulette + in Belgium, and at Malarnaud in France, increase our material which is now + as abundant as could be desired. The most recent discovery of all is that + of a skull dug up in August of this year (1908) by Klaatsch and Hauser in + the lower grotto of the Le Moustier in Southern France, but this skull has + not yet been fully described. Thus Homo primigenius must also be regarded + as occupying a position in the gap existing between the highest apes and + the lowest human races, Pithecanthropus, standing in the lower part of it, + and Homo primigenius in the higher, near man. In order to prevent + misunderstanding, I should like here to emphasise that in arranging this + structural series—anthropoid apes, Pithecanthropus, Homo + primigenius, Homo sapiens—I have no intention of establishing it as + a direct genealogical series. I shall have something to say in regard to + the genetic relations of these forms, one to another, when discussing the + different theories of descent current at the present day. ((Since this + essay was written Schoetensack has discovered near Heidelberg and briefly + described an exceedingly interesting lower jaw from rocks between the + Pliocene and Diluvial beds. This exhibits interesting differences from the + forms of lower jaw of Homo primigenius. (Schoetensack "Der Unterkiefer des + Homo heidelbergensis". Leipzig, 1908.) G.S.)) + </p> + <p> + In quite a different domain from that of morphological relationship, + namely in the physiological study of the blood, results have recently been + gained which are of the highest importance to the doctrine of descent. + Uhlenhuth, Nuttall, and others have established the fact that the + blood-serum of a rabbit which has previously had human blood injected into + it, forms a precipitate with human blood. This biological reaction was + tried with a great variety of mammalian species, and it was found that + those far removed from man gave no precipitate under these conditions. But + as in other cases among mammals all nearly related forms yield an almost + equally marked precipitate, so the serum of a rabbit treated with human + blood and then added to the blood of an anthropoid ape gives ALMOST as + marked a precipitate as in human blood; the reaction to the blood of the + lower Eastern monkeys is weaker, that to the Western monkeys weaker still; + indeed in this last case there is only a slight clouding after a + considerable time and no actual precipitate. The blood of the Lemuridae + (Nuttall) gives no reaction or an extremely weak one, that of the other + mammals none whatever. We have in this not only a proof of the literal + blood-relationship between man and apes, but the degree of relationship + with the different main groups of apes can be determined beyond + possibility of mistake. + </p> + <p> + Finally, it must be briefly mentioned that in regard to remains of human + handicraft also, the material at our disposal has greatly increased of + late years, that, as a result of this, the opinions of archaeologists have + undergone many changes, and that, in particular, their views in regard to + the age of the human race have been greatly influenced. There is a + tendency at the present time to refer the origin of man back to Tertiary + times. It is true that no remains of Tertiary man have been found, but + flints have been discovered which, according to the opinion of most + investigators, bear traces either of use, or of very primitive + workmanship. Since Rutot's time, following Mortillet's example, + investigators have called these "eoliths," and they have been traced back + by Verworn to the Miocene of the Auvergne, and by Rutot even to the upper + Oligocene. Although these eoliths are even nowadays the subject of many + different views, the preoccupation with them has kept the problem of the + age of the human race continually before us. + </p> + <p> + Geology, too, has made great progress since the days of Darwin and Lyell, + and has endeavoured with satisfactory results to arrange the human remains + of the Diluvial period in chronological order (Penck). I do not intend to + enter upon the question of the primitive home of the human race; since the + space at my disposal will not allow of my touching even very briefly upon + all the departments of science which are concerned in the problem of the + descent of man. How Darwin would have rejoiced over each of the + discoveries here briefly outlined! What use he would have made of the new + and precious material, which would have prevented the discouragement from + which he suffered when preparing the second edition of "The Descent of + Man"! But it was not granted to him to see this progress towards filling + up the gaps in his edifice of which he was so painfully conscious. + </p> + <p> + He did, however, have the satisfaction of seeing his ideas steadily + gaining ground, notwithstanding much hostility and deep-rooted prejudice. + Even in the years between the appearance of "The Origin of Species" and of + the first edition of the "Descent", the idea of a natural descent of man, + which was only briefly indicated in the work of 1859, had been eagerly + welcomed in some quarters. It has been already pointed out how brilliantly + Huxley contributed to the defence and diffusion of Darwin's doctrines, and + how in "Man's Place in Nature" he has given us a classic work as a + foundation for the doctrine of the descent of man. As Huxley was Darwin's + champion in England, so in Germany Carl Vogt, in particular, made himself + master of the Darwinian ideas. But above all it was Haeckel who, in + energy, eagerness for battle, and knowledge may be placed side by side + with Huxley, who took over the leadership in the controversy over the new + conception of the universe. As far back as 1866, in his "Generelle + Morphologie", he had inquired minutely into the question of the descent of + man, and not content with urging merely the general theory of descent from + lower animal forms, he drew up for the first time genealogical trees + showing the close relationships of the different animal groups; the last + of these illustrated the relationships of Mammals, and among them of all + groups of the Primates, including man. It was Haeckel's genealogical trees + that formed the basis of the special discussion of the relationships of + man, in the sixth chapter of Darwin's "Descent of Man". + </p> + <p> + In the last section of this essay I shall return to Haeckel's conception + of the special descent of man, the main features of which he still + upholds, and rightly so. Haeckel has contributed more than any one else to + the spread of the Darwinian doctrine. + </p> + <p> + I can only allow myself a few words as to the spread of the theory of the + natural descent of man in other countries. The Parisian anthropological + school, founded and guided by the genius of Broca, took up the idea of the + descent of man, and made many notable contributions to it (Broca, + Manouvrier, Mahoudeau, Deniker and others). In England itself Darwin's + work did not die. Huxley took care of that, for he, with his lofty and + unprejudiced mind, dominated and inspired English biology until his death + on June 29, 1895. He had the satisfaction shortly before his death of + learning of Dubois' discovery, which he illustrated by a humorous sketch. + ("Life and Letters of Thomas Henry Huxley", Vol. II. page 394.) But there + are still many followers in Darwin's footsteps in England. Keane has + worked at the special genealogical tree of the Primates; Keith has + inquired which of the anthropoid apes has the greatest number of + characters in common with man; Morris concerns himself with the evolution + of man in general, especially with his acquisition of the erect position. + The recent discoveries of Pithecanthropus and Homo primigenius are being + vigorously discussed; but the present writer is not in a position to form + an opinion of the extent to which the idea of descent has penetrated + throughout England generally. + </p> + <p> + In Italy independent work in the domain of the descent of man is being + produced, especially by Morselli; with him are associated, in the + investigation of related problems, Sergi and Giuffrida-Ruggeri. From the + ranks of American investigators we may single out in particular the + eminent geologist Cope, who championed with much decision the idea of the + specific difference of Homo neandertalensis (primigenius) and maintained a + more direct descent of man from the fossil Lemuridae. In South America + too, in Argentina, new life is stirring in this department of science. + Ameghino in Buenos Ayres has awakened the fossil primates of the Pampas + formation to new life; he even believes that in Tetraprothomo, represented + by a femur, he has discovered a direct ancestor of man. Lehmann-Nitsche is + working at the other side of the gulf between apes and men, and he + describes a remarkable first cervical vertebra (atlas) from Monte Hermoso + as belonging to a form which may bear the same relation to Homo sapiens in + South America as Homo primigenius does in the Old World. After a minute + investigation he establishes a human species Homo neogaeus, while Ameghino + ascribes this atlas vertebra to his Tetraprothomo. + </p> + <p> + Thus throughout the whole scientific world there is arising a new life, an + eager endeavour to get nearer to Huxley's problema maximum, to penetrate + more deeply into the origin of the human race. There are to-day very few + experts in anatomy and zoology who deny the animal descent of man in + general. Religious considerations, old prejudices, the reluctance to + accept man, who so far surpasses mentally all other creatures, as + descended from "soulless" animals, prevent a few investigators from giving + full adherence to the doctrine. But there are very few of these who still + postulate a special act of creation for man. Although the majority of + experts in anatomy and zoology accept unconditionally the descent of man + from lower forms, there is much diversity of opinion among them in regard + to the special line of descent. + </p> + <p> + In trying to establish any special hypothesis of descent, whether by the + graphic method of drawing up genealogical trees or otherwise, let us + always bear in mind Darwin's words ("Descent of Man", page 229.) and use + them as a critical guiding line: "As we have no record of the lines of + descent, the pedigree can be discovered only by observing the degrees of + resemblance between the beings which are to be classed." Darwin carries + this further by stating "that resemblances in several unimportant + structures, in useless and rudimentary organs, or not now functionally + active, or in an embryological condition, are by far the most serviceable + for classification." (Loc. cit.) It has also to be remembered that + NUMEROUS separate points of agreement are of much greater importance than + the amount of similarity or dissimilarity in a few points. + </p> + <p> + The hypotheses as to descent current at the present day may be divided + into two main groups. The first group seeks for the roots of the human + race not among any of the families of the apes—the anatomically + nearest forms—nor among their very similar but less specialised + ancestral forms, the fossil representatives of which we can know only in + part, but, setting the monkeys on one side, it seeks for them lower down + among the fossil Eocene Pseudo-lemuridae or Lemuridae (Cope), or even + among the primitive pentadactylous Eocene forms, which may either have led + directly to the evolution of man (Adloff), or have given rise to an + ancestral form common to apes and men (Klaatsch (Klaatsch in his last + publications speaks in the main only of an ancestral form common to men + and anthropoid apes.), Giuffrida-Ruggeri). The common ancestral form, from + which man and apes are thus supposed to have arisen independently, may + explain the numerous resemblances which actually exist between them. That + is to say, all the characters upon which the great structural resemblance + between apes and man depends must have been present in their common + ancestor. Let us take an example of such a common character. The bony + external ear-passage is in general as highly developed in the lower + Eastern monkeys and the anthropoid apes as in man. This character must, + therefore, have already been present in the common primitive form. In that + case it is not easy to understand why the Western monkeys have not also + inherited the character, instead of possessing only a tympanic ring. But + it becomes more intelligible if we assume that forms with a primitive + tympanic ring were the original type, and that from these were evolved, on + the one hand, the existing New World monkeys with persistent tympanic + ring, and on the other an ancestral form common to the lower Old World + monkeys, the anthropoid apes and man. For man shares with these the + character in question, and it is also one of the "unimportant" characters + required by Darwin. Thus we have two divergent lines arising from the + ancestral form, the Western monkeys (Platyrrhine) on the one hand, and an + ancestral form common to the lower Eastern monkeys, the anthropoid apes, + and man, on the other. But considerations similar to those which showed it + to be impossible that man should have developed from an ancestor common to + him and the monkeys, yet outside of and parallel with these, may be urged + also against the likelihood of a parallel evolution of the lower Eastern + monkeys, the anthropoid apes, and man. The anthropoid apes have in common + with man many characters which are not present in the lower Old World + monkeys. These characters must therefore have been present in the + ancestral form common to the three groups. But here, again, it is + difficult to understand why the lower Eastern monkeys should not also have + inherited these characters. As this is not the case, there remains no + alternative but to assume divergent evolution from an indifferent form. + The lower Eastern monkeys are carrying on the evolution in one direction—I + might almost say towards a blind alley—while anthropoids and men + have struck out a progressive path, at first in common, which explains the + many points of resemblance between them, without regarding man as derived + directly from the anthropoids. Their many striking points of agreement + indicate a common descent, and cannot be explained as phenomena of + convergence. + </p> + <p> + I believe I have shown in the above sketch that a theory which derives man + directly from lower forms without regarding apes as transition-types leads + ad absurdum. The close structural relationship between man and monkeys can + only be understood if both are brought into the same line of evolution. To + trace man's line of descent directly back to the old Eocene mammals, + alongside of, but with no relation to these very similar forms, is to + abandon the method of exact comparison, which, as Darwin rightly + recognised, alone justifies us in drawing up genealogical trees on the + basis of resemblances and differences. The farther down we go the more + does the ground slip from beneath our feet. Even the Lemuridae show very + numerous divergent conditions, much more so the Eocene mammals (Creodonta, + Condylarthra), the chief resemblance of which to man consists in the + possession of pentadactylous hands and feet! Thus the farther course of + the line of descent disappears in the darkness of the ancestry of the + mammals. With just as much reason we might pass by the Vertebrates + altogether, and go back to the lower Invertebrates, but in that case it + would be much easier to say that man has arisen independently, and has + evolved, without relation to any animals, from the lowest primitive form + to his present isolated and dominant position. But this would be to deny + all value to classification, which must after all be the ultimate basis of + a genealogical tree. We can, as Darwin rightly observed, only infer the + line of descent from the degree of resemblance between single forms. If we + regard man as directly derived from primitive forms very far back, we have + no way of explaining the many points of agreement between him and the + monkeys in general, and the anthropoid apes in particular. These must + remain an inexplicable marvel. + </p> + <p> + I have thus, I trust, shown that the first class of special theories of + descent, which assumes that man has developed, parallel with the monkeys, + but without relation to them, from very low primitive forms cannot be + upheld, because it fails to take into account the close structural + affinity of man and monkeys. I cannot but regard this hypothesis as + lamentably retrograde, for it makes impossible any application of the + facts that have been discovered in the course of the anatomical and + embryological study of man and monkeys, and indeed prejudges + investigations of that class as pointless. The whole method is perverted; + an unjustifiable theory of descent is first formulated with the aid of the + imagination, and then we are asked to declare that all structural + relations between man and monkeys, and between the different groups of the + latter, are valueless,—the fact being that they are the only true + basis on which a genealogical tree can be constructed. + </p> + <p> + So much for this most modern method of classification, which has probably + found adherents because it would deliver us from the relationship to apes + which many people so much dislike. In contrast to it we have the second + class of special hypotheses of descent, which keeps strictly to the + nearest structural relationships. This is the only basis that justifies + the drawing up of a special hypothesis of descent. If this fundamental + proposition be recognised, it will be admitted that the doctrine of + special descent upheld by Haeckel, and set forth in Darwin's "Descent of + Man", is still valid to-day. In the genealogical tree, man's place is + quite close to the anthropoid apes; these again have as their nearest + relatives the lower Old World monkeys, and their progenitors must be + sought among the less differentiated Platyrrhine monkeys, whose most + important characters have been handed on to the present day New World + monkeys. How the different genera are to be arranged within the general + scheme indicated depends in the main on the classificatory value + attributed to individual characters. This is particularly true in regard + to Pithecanthropus, which I consider as the root of a branch which has + sprung from the anthropoid ape root and has led up to man; the latter I + have designated the family of the Hominidae. + </p> + <p> + For the rest, there are, as we have said, various possible ways of + constructing the narrower genealogy within the limits of this branch + including men and apes, and these methods will probably continue to change + with the accumulation of new facts. Haeckel himself has modified his + genealogical tree of the Primates in certain details since the publication + of his "Generelle Morphologie" in 1866, but its general basis remains the + same. (Haeckel's latest genealogical tree is to be found in his most + recent work, "Unsere Ahnenreihe". Jena, 1908.) All the special + genealogical trees drawn up on the lines laid down by Haeckel and Darwin—and + that of Dubois may be specially mentioned—are based, in general, on + the close relationship of monkeys and men, although they may vary in + detail. Various hypotheses have been formulated on these lines, with + special reference to the evolution of man. "Pithecanthropus" is regarded + by some authorities as the direct ancestor of man, by others as a + side-track failure in the attempt at the evolution of man. The problem of + the monophyletic or polyphyletic origin of the human race has also been + much discussed. Sergi (Sergi G. "Europa", 1908.) inclines towards the + assumption of a polyphyletic origin of the three main races of man, the + African primitive form of which has given rise also to the gorilla and + chimpanzee, the Asiatic to the Orang, the Gibbon, and Pithecanthropus. + Kollmann regards existing human races as derived from small primitive + races (pigmies), and considers that Homo primigenius must have arisen in a + secondary and degenerative manner. + </p> + <p> + But this is not the place, nor have I the space to criticise the various + special theories of descent. One, however, must receive particular notice. + According to Ameghino, the South American monkeys (Pitheculites) from the + oldest Tertiary of the Pampas are the forms from which have arisen the + existing American monkeys on the one hand, and on the other, the extinct + South American Homunculidae, which are also small forms. From these last, + anthropoid apes and man have, he believes, been evolved. Among the + progenitors of man, Ameghino reckons the form discovered by him + (Tetraprothomo), from which a South American primitive man, Homo pampaeus, + might be directly evolved, while on the other hand all the lower Old World + monkeys may have arisen from older fossil South American forms + (Clenialitidae), the distribution of which may be explained by the bridge + formerly existing between South America and Africa, as may be the + derivation of all existing human races from Homo pampaeus. (See Ameghino's + latest paper, "Notas preliminares sobre el Tetraprothomo argentinus", etc. + "Anales del Museo nacional de Buenos Aires", XVI. pages 107-242, 1907.) + The fossil forms discovered by Ameghino deserve the most minute + investigation, as does also the fossil man from South America of which + Lehmann-Nitsche ("Nouvelles recherches sur la formation pampeenne et + l'homme fossile de la Republique Argentine". "Rivista del Museo de la + Plata", T. XIV. pages 193-488.) has made a thorough study. + </p> + <p> + It is obvious that, notwithstanding the necessity for fitting man's line + of descent into the genealogical tree of the Primates, especially the + apes, opinions in regard to it differ greatly in detail. This could not be + otherwise, since the different Primate forms, especially the fossil forms, + are still far from being exhaustively known. But one thing remains + certain,—the idea of the close relationship between man and monkeys + set forth in Darwin's "Descent of Man". Only those who deny the many + points of agreement, the sole basis of classification, and thus of a + natural genealogical tree, can look upon the position of Darwin and + Haeckel as antiquated, or as standing on an insufficient foundation. For + such a genealogical tree is nothing more than a summarised representation + of what is known in regard to the degree of resemblance between the + different forms. + </p> + <p> + Darwin's work in regard to the descent of man has not been surpassed; the + more we immerse ourselves in the study of the structural relationships + between apes and man, the more is our path illumined by the clear light + radiating from him, and through his calm and deliberate investigation, + based on a mass of material in the accumulation of which he has never had + an equal. Darwin's fame will be bound up for all time with the + unprejudiced investigation of the question of all questions, the descent + of the human race. + </p> + <p> + <a name="link2H_4_0010" id="link2H_4_0010"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + VIII. CHARLES DARWIN AS AN ANTHROPOLOGIST. By Ernst Haeckel. + </h2> + <h3> + Professor of Zoology in the University of Jena. + </h3> + <p> + The great advance that anthropology has made in the second half of the + nineteenth century is due in the first place, to Darwin's discovery of the + origin of man. No other problem in the whole field of research is so + momentous as that of "Man's place in nature," which was justly described + by Huxley (1863) as the most fundamental of all questions. Yet the + scientific solution of this problem was impossible until the theory of + descent had been established. + </p> + <p> + It is now a hundred years since the great French biologist Jean Lamarck + published his "Philosophie Zoologique". By a remarkable coincidence the + year in which that work was issued, 1809, was the year of the birth of his + most distinguished successor, Charles Darwin. Lamarck had already + recognised that the descent of man from a series of other Vertebrates—that + is, from a series of Ape-like Primates—was essentially involved in + the general theory of transformation which he had erected on a broad + inductive basis; and he had sufficient penetration to detect the agencies + that had been at work in the evolution of the erect bimanous man from the + arboreal and quadrumanous ape. He had, however, few empirical arguments to + advance in support of his hypothesis, and it could not be established + until the further development of the biological sciences—the + founding of comparative embryology by Baer (1828) and of the cell-theory + by Schleiden and Schwann (1838), the advance of physiology under Johannes + Muller (1833), and the enormous progress of palaeontology and comparative + anatomy between 1820 and 1860—provided this necessary foundation. + Darwin was the first to coordinate the ample results of these lines of + research. With no less comprehensiveness than discrimination he + consolidated them as a basis of a modified theory of descent, and + associated with them his own theory of natural selection, which we take to + be distinctive of "Darwinism" in the stricter sense. The illuminating + truth of these cumulative arguments was so great in every branch of + biology that, in spite of the most vehement opposition, the battle was won + within a single decade, and Darwin secured the general admiration and + recognition that had been denied to his forerunner, Lamarck, up to the + hour of his death (1829). + </p> + <p> + Before, however, we consider the momentous influence that Darwinism has + had in anthropology, we shall find it useful to glance at its history in + the course of the last half century, and notice the various theories that + have contributed to its advance. The first attempt to give extensive + expression to the reform of biology by Darwin's work will be found in my + "Generelle Morphologie" (1866) ("Generelle Morphologie der Organismen", 2 + vols., Berlin, 1866.) which was followed by a more popular treatment of + the subject in my "Naturliche Schopfungsgeschichte" (1868) (English + translation; "The History of Creation", London, 1876.), a compilation from + the earlier work. In the first volume of the "Generelle Morphologie" I + endeavoured to show the great importance of evolution in settling the + fundamental questions of biological philosophy, especially in regard to + comparative anatomy. In the second volume I dealt broadly with the + principle of evolution, distinguishing ontogeny and phylogeny as its two + coordinate main branches, and associating the two in the Biogenetic Law. + The Law may be formulated thus: "Ontogeny (embryology or the development + of the individual) is a concise and compressed recapitulation of phylogeny + (the palaeontological or genealogical series) conditioned by laws of + heredity and adaptation." The "Systematic introduction to general + evolution," with which the second volume of the "Generelle Morphologie" + opens, was the first attempt to draw up a natural system of organisms (in + harmony with the principles of Lamarck and Darwin) in the form of a + hypothetical pedigree, and was provisionally set forth in eight + genealogical tables. + </p> + <p> + In the nineteenth chapter of the "Generelle Morphologie"—a part of + which has been republished, without any alteration, after a lapse of forty + years—I made a critical study of Lamarck's theory of descent and of + Darwin's theory of selection, and endeavoured to bring the complex + phenomena of heredity and adaptation under definite laws for the first + time. Heredity I divided into conservative and progressive: adaptation + into indirect (or potential) and direct (or actual). I then found it + possible to give some explanation of the correlation of the two + physiological functions in the struggle for life (selection), and to + indicate the important laws of divergence (or differentiation) and + complexity (or division of labour), which are the direct and inevitable + outcome of selection. Finally, I marked off dysteleology as the science of + the aimless (vestigial, abortive, atrophied, and useless) organs and parts + of the body. In all this I worked from a strictly monistic standpoint, and + sought to explain all biological phenomena on the mechanical and + naturalistic lines that had long been recognised in the study of inorganic + nature. Then (1866), as now, being convinced of the unity of nature, the + fundamental identity of the agencies at work in the inorganic and the + organic worlds, I discarded vitalism, teleology, and all hypotheses of a + mystic character. + </p> + <p> + It was clear from the first that it was essential, in the monistic + conception of evolution, to distinguish between the laws of conservative + and progressive heredity. Conservative heredity maintains from generation + to generation the enduring characters of the species. Each organism + transmits to its descendants a part of the morphological and physiological + qualities that it has received from its parents and ancestors. On the + other hand, progressive heredity brings new characters to the species—characters + that were not found in preceding generations. Each organism may transmit + to its offspring a part of the morphological and physiological features + that it has itself acquired, by adaptation, in the course of its + individual career, through the use or disuse of particular organs, the + influence of environment, climate, nutrition, etc. At that time I gave the + name of "progressive heredity" to this inheritance of acquired characters, + as a short and convenient expression, but have since changed the term to + "transformative heredity" (as distinguished from conservative). This term + is preferable, as inherited regressive modifications (degeneration, + retrograde metamorphisis, etc.) come under the same head. + </p> + <p> + Transformative heredity—or the transmission of acquired characters—is + one of the most important principles in evolutionary science. Unless we + admit it most of the facts of comparative anatomy and physiology are + inexplicable. That was the conviction of Darwin no less than of Lamarck, + of Spencer as well as Virchow, of Huxley as well as Gegenbaur, indeed of + the great majority of speculative biologists. This fundamental principle + was for the first time called in question and assailed in 1885 by August + Weismann of Freiburg, the eminent zoologist to whom the theory of + evolution owes a great deal of valuable support, and who has attained + distinction by his extension of the theory of selection. In explanation of + the phenomena of heredity he introduced a new theory, the "theory of the + continuity of the germ-plasm." According to him the living substance in + all organisms consists of two quite distinct kinds of plasm, somatic and + germinal. The permanent germ-plasm, or the active substance of the two + germ-cells (egg-cell and sperm-cell), passes unchanged through a series of + generations, and is not affected by environmental influences. The + environment modifies only the soma-plasm, the organs and tissues of the + body. The modifications that these parts undergo through the influence of + the environment or their own activity (use and habit), do not affect the + germ-plasm, and cannot therefore be transmitted. + </p> + <p> + This theory of the continuity of the germ-plasm has been expounded by + Weismann during the last twenty-four years in a number of able volumes, + and is regarded by many biologists, such as Mr Francis Galton, Sir E. Ray + Lankester, and Professor J. Arthur Thomson (who has recently made a + thoroughgoing defence of it in his important work "Heredity" (London, + 1908.)), as the most striking advance in evolutionary science. On the + other hand, the theory has been rejected by Herbert Spencer, Sir W. + Turner, Gegenbaur, Kolliker, Hertwig, and many others. For my part I have, + with all respect for the distinguished Darwinian, contested the theory + from the first, because its whole foundation seems to me erroneous, and + its deductions do not seem to be in accord with the main facts of + comparative morphology and physiology. Weismann's theory in its entirety + is a finely conceived molecular hypothesis, but it is devoid of empirical + basis. The notion of the absolute and permanent independence of the + germ-plasm, as distinguished from the soma-plasm, is purely speculative; + as is also the theory of germinal selection. The determinants, ids, and + idants, are purely hypothetical elements. The experiments that have been + devised to demonstrate their existence really prove nothing. + </p> + <p> + It seems to me quite improper to describe this hypothetical structure as + "Neodarwinism." Darwin was just as convinced as Lamarck of the + transmission of acquired characters and its great importance in the scheme + of evolution. I had the good fortune to visit Darwin at Down three times + and discuss with him the main principles of his system, and on each + occasion we were fully agreed as to the incalculable importance of what I + call transformative inheritance. It is only proper to point out that + Weismann's theory of the germ-plasm is in express contradiction to the + fundamental principles of Darwin and Lamarck. Nor is it more acceptable in + what one may call its "ultradarwinism"—the idea that the theory of + selection explains everything in the evolution of the organic world. This + belief in the "omnipotence of natural selection" was not shared by Darwin + himself. Assuredly, I regard it as of the utmost value, as the process of + natural selection through the struggle for life affords an explanation of + the mechanical origin of the adapted organisation. It solves the great + problem: how could the finely adapted structure of the animal or plant + body be formed unless it was built on a preconceived plan? It thus enables + us to dispense with the teleology of the metaphysician and the dualist, + and to set aside the old mythological and poetic legends of creation. The + idea had occurred in vague form to the great Empedocles 2000 years before + the time of Darwin, but it was reserved for modern research to give it + ample expression. Nevertheless, natural selection does not of itself give + the solution of all our evolutionary problems. It has to be taken in + conjunction with the transformism of Lamarck, with which it is in complete + harmony. + </p> + <p> + The monumental greatness of Charles Darwin, who surpasses every other + student of science in the nineteenth century by the loftiness of his + monistic conception of nature and the progressive influence of his ideas, + is perhaps best seen in the fact that not one of his many successors has + succeeded in modifying his theory of descent in any essential point or in + discovering an entirely new standpoint in the interpretation of the + organic world. Neither Nageli nor Weismann, neither De Vries nor Roux, has + done this. Nageli, in his "Mechanisch-Physiologische Theorie der + Abstammungslehre" (Munich, 1884.), which is to a great extent in agreement + with Weismann, constructed a theory of the idioplasm, that represents it + (like the germ-plasm) as developing continuously in a definite direction + from internal causes. But his internal "principle of progress" is at the + bottom just as teleological as the vital force of the Vitalists, and the + micellar structure of the idioplasm is just as hypothetical as the + "dominant" structure of the germ-plasm. In 1889 Moritz Wagner sought to + explain the origin of species by migration and isolation, and on that + basis constructed a special "migration-theory." This, however, is not out + of harmony with the theory of selection. It merely elevates one single + factor in the theory to a predominant position. Isolation is only a + special case of selection, as I had pointed out in the fifteenth chapter + of my "Natural history of creation". The "mutation-theory" of De Vries + ("Die Mutationstheorie", Leipzig, 1903.), that would explain the origin of + species by sudden and saltatory variations rather than by gradual + modification, is regarded by many botanists as a great step in advance, + but it is generally rejected by zoologists. It affords no explanation of + the facts of adaptation, and has no causal value. + </p> + <p> + Much more important than these theories is that of Wilhelm Roux ("Der + Kampf der Theile im Organismus", Leipzig, 1881.) of "the struggle of parts + within the organism, a supplementation of the theory of mechanical + adaptation." He explains the functional autoformation of the purposive + structure by a combination of Darwin's principle of selection with + Lamarck's idea of transformative heredity, and applies the two in + conjunction to the facts of histology. He lays stress on the significance + of functional adaptation, which I had described in 1866, under the head of + cumulative adaptation, as the most important factor in evolution. Pointing + out its influence in the cell-life of the tissues, he puts "cellular + selection" above "personal selection," and shows how the finest + conceivable adaptations in the structure of the tissue may be brought + about quite mechanically, without preconceived plan. This "mechanical + teleology" is a valuable extension of Darwin's monistic principle of + selection to the whole field of cellular physiology and histology, and is + wholly destructive of dualistic vitalism. + </p> + <p> + The most important advance that evolution has made since Darwin and the + most valuable amplification of his theory of selection is, in my opinion, + the work of Richard Semon: "Die Mneme als erhaltendes Prinzip im Wechsel + des organischen Geschehens" (Leipzig, 1904.). He offers a psychological + explanation of the facts of heredity by reducing them to a process of + (unconscious) memory. The physiologist Ewald Hering had shown in 1870 that + memory must be regarded as a general function of organic matter, and that + we are quite unable to explain the chief vital phenomena, especially those + of reproduction and inheritance, unless we admit this unconscious memory. + In my essay "Die Perigenesis der Plastidule" (Berlin, 1876.) I elaborated + this far-reaching idea, and applied the physical principle of transmitted + motion to the plastidules, or active molecules of plasm. I concluded that + "heredity is the memory of the plastidules, and variability their power of + comprehension." This "provisional attempt to give a mechanical explanation + of the elementary processes of evolution" I afterwards extended by showing + that sensitiveness is (as Carl Nageli, Ernst Mach, and Albrecht Rau + express it) a general quality of matter. This form of panpsychism finds + its simplest expression in the "trinity of substance." + </p> + <p> + To the two fundamental attributes that Spinoza ascribed to substance—Extension + (matter as occupying space) and Cogitation (energy, force)—we now + add the third fundamental quality of Psychoma (sensitiveness, soul). I + further elaborated this trinitarian conception of substance in the + nineteenth chapter of my "Die Lebenswunder" (1904) ("Wonders of Life", + London, 1904.), and it seems to me well calculated to afford a monistic + solution of many of the antitheses of philosophy. + </p> + <p> + This important Mneme-theory of Semon and the luminous physiological + experiments and observations associated with it not only throw + considerable light on transformative inheritance, but provide a sound + physiological foundation for the biogenetic law. I had endeavoured to show + in 1874, in the first chapter of my "Anthropogenie" (English translation; + "The Evolution of Man", 2 volumes, London, 1879 and 1905.), that this + fundamental law of organic evolution holds good generally, and that there + is everywhere a direct causal connection between ontogeny and phylogeny. + "Phylogenesis is the mechanical cause of ontogenesis"; in other words, + "The evolution of the stem or race is—in accordance with the laws of + heredity and adaptation—the real cause of all the changes that + appear, in a condensed form, in the development of the individual organism + from the ovum, in either the embryo or the larva." + </p> + <p> + It is now fifty years since Charles Darwin pointed out, in the thirteenth + chapter of his epoch-making "Origin of Species", the fundamental + importance of embryology in connection with his theory of descent: + </p> + <p> + "The leading facts in embryology, which are second to none in importance, + are explained on the principle of variations in the many descendants from + some one ancient progenitor, having appeared at a not very early period of + life, and having been inherited at a corresponding period." ("Origin of + Species" (6th edition), page 396.) + </p> + <p> + He then shows that the striking resemblance of the embryos and larvae of + closely related animals, which in the mature stage belong to widely + different species and genera, can only be explained by their descent from + a common progenitor. Fritz Muller made a closer study of these important + phenomena in the instructive instance of the Crustacean larva, as given in + his able work "Fur Darwin" (1864). (English translation; "Facts and + Arguments for Darwin", London, 1869.) I then, in 1872, extended the range + so as to include all animals (with the exception of the unicellular + Protozoa) and showed, by means of the theory of the Gastraea, that all + multicellular, tissue-forming animals—all the Metazoa—develop + in essentially the same way from the primary germ-layers. I conceived the + embryonic form, in which the whole structure consists of only two layers + of cells, and is known as the gastrula, to be the ontogenetic + recapitulation, maintained by tenacious heredity, of a primitive common + progenitor of all the Metazoa, the Gastraea. At a later date (1895) + Monticelli discovered that this conjectural ancestral form is still + preserved in certain primitive Coelenterata—Pemmatodiscus, + Kunstleria, and the nearly-related Orthonectida. + </p> + <p> + The general application of the biogenetic law to all classes of animals + and plants has been proved in my "Systematische Phylogenie". (3 volumes, + Berlin, 1894-96.) It has, however, been frequently challenged, both by + botanists and zoologists, chiefly owing to the fact that many have failed + to distinguish its two essential elements, palingenesis and cenogenesis. + As early as 1874 I had emphasised, in the first chapter of my "Evolution + of Man", the importance of discriminating carefully between these two sets + of phenomena: + </p> + <p> + "In the evolutionary appreciation of the facts of embryology we must take + particular care to distinguish sharply and clearly between the primary, + palingenetic evolutionary processes and the secondary, cenogenetic + processes. The palingenetic phenomena, or embryonic RECAPITULATIONS, are + due to heredity, to the transmission of characters from one generation to + another. They enable us to draw direct inferences in regard to + corresponding structures in the development of the species (e.g. the + chorda or the branchial arches in all vertebrate embryos). The cenogenetic + phenomena, on the other hand, or the embryonic VARIATIONS, cannot be + traced to inheritance from a mature ancestor, but are due to the + adaptation of the embryo or the larva to certain conditions of its + individual development (e.g. the amnion, the allantois, and the vitelline + arteries in the embryos of the higher vertebrates). These cenogenetic + phenomena are later additions; we must not infer from them that there were + corresponding processes in the ancestral history, and hence they are apt + to mislead." + </p> + <p> + The fundamental importance of these facts of comparative anatomy, atavism, + and the rudimentary organs, was pointed out by Darwin in the first part of + his classic work, "The Descent of Man and Selection in Relation to Sex" + (1871). ("Descent of Man" (Popular Edition), page 927.) In the "General + summary and conclusion" (chapter XXI.) he was able to say, with perfect + justice: "He who is not content to look, like a savage, at the phenomena + of nature as disconnected, cannot any longer believe that man is the work + of a separate act of creation. He will be forced to admit that the close + resemblance of the embryo of man to that, for instance, of a dog—the + construction of his skull, limbs, and whole frame on the same plan with + that of other mammals, independently of the uses to which the parts may be + put—the occasional reappearance of various structures, for instance + of several muscles, which man does not normally possess, but which are + common to the Quadrumana—and a crowd of analogous facts—all + point in the plainest manner to the conclusion that man is the + co-descendant with other mammals of a common progenitor." + </p> + <p> + These few lines of Darwin's have a greater scientific value than hundreds + of those so-called "anthropological treatises," which give detailed + descriptions of single organs, or mathematical tables with series of + numbers and what are claimed to be "exact analyses," but are devoid of + synoptic conclusions and a philosophical spirit. + </p> + <p> + Charles Darwin is not generally recognised as a great anthropologist, nor + does the school of modern anthropologists regard him as a leading + authority. In Germany, especially, the great majority of the members of + the anthropological societies took up an attitude of hostility to him from + the very beginning of the controversy in 1860. "The Descent of Man" was + not merely rejected, but even the discussion of it was forbidden on the + ground that it was "unscientific." + </p> + <p> + The centre of this inveterate hostility for thirty years—especially + after 1877—was Rudolph Virchow of Berlin, the leading investigator + in pathological anatomy, who did so much for the reform of medicine by his + establishment of cellular pathology in 1858. As a prominent representative + of "exact" or "descriptive" anthropology, and lacking a broad equipment in + comparative anatomy and ontogeny, he was unable to accept the theory of + descent. In earlier years, and especially during his splendid period of + activity at Wurzburg (1848-1856), he had been a consistent free-thinker, + and had in a number of able articles (collected in his "Gesammelte + Abhandlungen") ("Gesammelte Abhandlungen zur wissenschaftlichen Medizin", + Berlin, 1856.) upheld the unity of human nature, the inseparability of + body and spirit. In later years at Berlin, where he was more occupied with + political work and sociology (especially after 1866), he abandoned the + positive monistic position for one of agnosticism and scepticism, and made + concessions to the dualistic dogma of a spiritual world apart from the + material frame. + </p> + <p> + In the course of a Scientific Congress at Munich in 1877 the conflict of + these antithetic views of nature came into sharp relief. At this memorable + Congress I had undertaken to deliver the first address (September 18th) on + the subject of "Modern evolution in relation to the whole of science." I + maintained that Darwin's theory not only solved the great problem of the + origin of species, but that its implications, especially in regard to the + nature of man, threw considerable light on the whole of science, and on + anthropology in particular. The discovery of the real origin of man by + evolution from a long series of mammal ancestors threw light on his place + in nature in every aspect, as Huxley had already shown in his excellent + lectures of 1863. Just as all the organs and tissues of the human body had + originated from those of the nearest related mammals, certain ape-like + forms, so we were bound to conclude that his mental qualities also had + been derived from those of his extinct primate ancestor. + </p> + <p> + This monistic view of the origin and nature of man, which is now admitted + by nearly all who have the requisite acquaintance with biology, and + approach the subject without prejudice, encountered a sharp opposition at + that time. The opposition found its strongest expression in an address + that Virchow delivered at Munich four days afterwards (September 22nd), on + "The freedom of science in the modern State." He spoke of the theory of + evolution as an unproved hypothesis, and declared that it ought not to be + taught in the schools, because it was dangerous to the State. "We must + not," he said, "teach that man has descended from the ape or any other + animal." When Darwin, usually so lenient in his judgment, read the English + translation of Virchow's speech, he expressed his disapproval in strong + terms. But the great authority that Virchow had—an authority well + founded in pathology and sociology—and his prestige as President of + the German Anthropological Society, had the effect of preventing any + member of the Society from raising serious opposition to him for thirty + years. Numbers of journals and treatises repeated his dogmatic statement: + "It is quite certain that man has descended neither from the ape nor from + any other animal." In this he persisted till his death in 1902. Since that + time the whole position of German anthropology has changed. The question + is no longer whether man was created by a distinct supernatural act or + evolved from other mammals, but to which line of the animal hierarchy we + must look for the actual series of ancestors. The interested reader will + find an account of this "battle of Munich" (1877) in my three Berlin + lectures (April, 1905) ("Der Kampf um die Entwickelungs-Gedanken". + (English translation; "Last Words on Evolution", London, 1906.)) + </p> + <p> + The main points in our genealogical tree were clearly recognised by Darwin + in the sixth chapter of the "Descent of Man". Lowly organised fishes, like + the lancelet (Amphioxus), are descended from lower invertebrates + resembling the larvae of an existing Tunicate (Appendicularia). From these + primitive fishes were evolved higher fishes of the ganoid type and others + of the type of Lepidosiren (Dipneusta). It is a very small step from these + to the Amphibia: + </p> + <p> + "In the class of mammals the steps are not difficult to conceive which led + from the ancient Monotremata to the ancient Marsupials; and from these to + the early progenitors of the placental mammals. We may thus ascend to the + Lemuridae; and the interval is not very wide from these to the Simiadae. + The Simiadae then branched off into two great stems, the New World and Old + World monkeys; and from the latter, at a remote period, Man, the wonder + and glory of the Universe, proceeded." ("Descent of Man" (Popular + Edition), page 255.) + </p> + <p> + In these few lines Darwin clearly indicated the way in which we were to + conceive our ancestral series within the vertebrates. It is fully + confirmed by all the arguments of comparative anatomy and embryology, of + palaeontology and physiology; and all the research of the subsequent forty + years has gone to establish it. The deep interest in geology which Darwin + maintained throughout his life and his complete knowledge of palaeontology + enabled him to grasp the fundamental importance of the palaeontological + record more clearly than anthropologists and zoologists usually do. + </p> + <p> + There has been much debate in subsequent decades whether Darwin himself + maintained that man was descended from the ape, and many writers have + sought to deny it. But the lines I have quoted verbatim from the + conclusion of the sixth chapter of the "Descent of Man" (1871) leave no + doubt that he was as firmly convinced of it as was his great precursor + Jean Lamarck in 1809. Moreover, Darwin adds, with particular explicitness, + in the "general summary and conclusion" (chapter XXI.) of that standard + work ("Descent of Man", page 930.): + </p> + <p> + "By considering the embryological structure of man—the homologies + which he presents with the lower animals,—the rudiments which he + retains,—and the reversions to which he is liable, we can partly + recall in imagination the former condition of our early progenitors; and + can approximately place them in their proper place in the zoological + series. We thus learn that man is descended from a hairy, tailed + quadruped, probably arboreal in its habits, and an inhabitant of the Old + World. This creature, if its whole structure had been examined by a + naturalist, would have been classed amongst the Quadrumana, as surely as + the still more ancient progenitor of the Old and New World monkeys." + </p> + <p> + These clear and definite lines leave no doubt that Darwin—so + critical and cautious in regard to important conclusions—was quite + as firmly convinced of the descent of man from the apes (the Catarrhinae, + in particular) as Lamarck was in 1809 and Huxley in 1863. + </p> + <p> + It is to be noted particularly that, in these and other observations on + the subject, Darwin decidedly assumes the monophyletic origin of the + mammals, including man. It is my own conviction that this is of the + greatest importance. A number of difficult questions in regard to the + development of man, in respect of anatomy, physiology, psychology, and + embryology, are easily settled if we do not merely extend our progonotaxis + to our nearest relatives, the anthropoid apes and the tailed monkeys from + which these have descended, but go further back and find an ancestor in + the group of the Lemuridae, and still further back to the Marsupials and + Monotremata. The essential identity of all the Mammals in point of + anatomical structure and embryonic development—in spite of their + astonishing differences in external appearance and habits of life—is + so palpably significant that modern zoologists are agreed in the + hypothesis that they have all sprung from a common root, and that this + root may be sought in the earlier Palaeozoic Amphibia. + </p> + <p> + The fundamental importance of this comparative morphology of the Mammals, + as a sound basis of scientific anthropology, was recognised just before + the beginning of the nineteenth century, when Lamarck first emphasised + (1794) the division of the animal kingdom into Vertebrates and + Invertebrates. Even thirteen years earlier (1781), when Goethe made a + close study of the mammal skeleton in the Anatomical Institute at Jena, he + was intensely interested to find that the composition of the skull was the + same in man as in the other mammals. His discovery of the os + intermaxillare in man (1784), which was contradicted by most of the + anatomists of the time, and his ingenious "vertebral theory of the skull," + were the splendid fruit of his morphological studies. They remind us how + Germany's greatest philosopher and poet was for many years ardently + absorbed in the comparative anatomy of man and the mammals, and how he + divined that their wonderful identity in structure was no mere superficial + resemblance, but pointed to a deep internal connection. In my "Generelle + Morphologie" (1866), in which I published the first attempts to construct + phylogenetic trees, I have given a number of remarkable theses of Goethe, + which may be called "phyletic prophecies." They justify us in regarding + him as a precursor of Darwin. + </p> + <p> + In the ensuing forty years I have made many conscientious efforts to + penetrate further along that line of anthropological research that was + opened up by Goethe, Lamarck, and Darwin. I have brought together the many + valuable results that have constantly been reached in comparative anatomy, + physiology, ontogeny, and palaeontology, and maintained the effort to + reform the classification of animals and plants in an evolutionary sense. + The first rough drafts of pedigrees that were published in the "Generelle + Morphologie" have been improved time after time in the ten editions of my + "Naturaliche Schopfungsgeschichte" (1868-1902). (English translation; "The + History of Creation", London, 1876.) A sounder basis for my phyletic + hypotheses, derived from a discriminating combination of the three great + records—morphology, ontogeny, and palaeontology—was provided + in the three volumes of my "Systematische Phylogenie" (Berlin, 1894-96.) + (1894 Protists and Plants, 1895 Vertebrates, 1896 Invertebrates). In my + "Anthropogenie" (Leipzig, 1874, 5th edition 1905. English translation; + "The Evolution of Man", London, 1905.) I endeavoured to employ all the + known facts of comparative ontogeny (embryology) for the purpose of + completing my scheme of human phylogeny (evolution). I attempted to sketch + the historical development of each organ of the body, beginning with the + most elementary structures in the germ-layers of the Gastraea. At the same + time I drew up a corrected statement of the most important steps in the + line of our ancestral series. + </p> + <p> + At the fourth International Congress of Zoology at Cambridge (August 26th, + 1898) I delivered an address on "Our present knowledge of the Descent of + Man." It was translated into English, enriched with many valuable notes + and additions, by my friend and pupil in earlier days Dr Hans Gadow + (Cambridge), and published under the title: "The Last Link; our present + knowledge of the Descent of Man". (London, 1898.) The determination of the + chief animal forms that occur in the line of our ancestry is there + restricted to thirty types, and these are distributed in six main groups. + </p> + <p> + The first half of this "Progonotaxis hominis," which has no support from + fossil evidence, comprises three groups: (i) Protista (unicellular + organisms, 1-5: (ii) Invertebrate Metazoa (Coelenteria 6-8, Vermalia + 9-11): (iii) Monorrhine Vertebrates (Acrania 12-13, Cyclostoma 14-15). The + second half, which is based on fossil records, also comprises three + groups: (iv) Palaeozoic cold-blooded Craniota (Fishes 16-18, Amphibia 19, + Reptiles 20: (v) Mesozoic Mammals (Monotrema 21, Marsupialia 22, + Mallotheria 23): (vi) Cenozoic Primates (Lemuridae 24-25, Tailed Apes + 26-27, Anthropomorpha 28-30). An improved and enlarged edition of this + hypothetic "Progonotaxis hominis" was published in 1908, in my essay + "Unsere Ahnenreihe". ("Festschrift zur 350-jahrigen Jubelfeier der + Thuringer Universitat Jena". Jena, 1908.) + </p> + <p> + If I have succeeded in furthering, in some degree, by these + anthropological works, the solution of the great problem of Man's place in + nature, and particularly in helping to trace the definite stages in our + ancestral series, I owe the success, not merely to the vast progress that + biology has made in the last half century, but largely to the luminous + example of the great investigators who have applied themselves to the + problem, with so much assiduity and genius, for a century and a quarter—I + mean Goethe and Lamarck, Gegenbaur and Huxley, but, above all, Charles + Darwin. It was the great genius of Darwin that first brought together the + scattered material of biology and shaped it into that symmetrical temple + of scientific knowledge, the theory of descent. It was Darwin who put the + crown on the edifice by his theory of natural selection. Not until this + broad inductive law was firmly established was it possible to vindicate + the special conclusion, the descent of man from a series of other + Vertebrates. By his illuminating discovery Darwin did more for + anthropology than thousands of those writers, who are more specifically + titled anthropologists, have done by their technical treatises. We may, + indeed, say that it is not merely as an exact observer and ingenious + experimenter, but as a distinguished anthropologist and far-seeing + thinker, that Darwin takes his place among the greatest men of science of + the nineteenth century. + </p> + <p> + To appreciate fully the immortal merit of Darwin in connection with + anthropology, we must remember that not only did his chief work, "The + Origin of Species", which opened up a new era in natural history in 1859, + sustain the most virulent and widespread opposition for a lengthy period, + but even thirty years later, when its principles were generally recognised + and adopted, the application of them to man was energetically contested by + many high scientific authorities. Even Alfred Russel Wallace, who + discovered the principle of natural selection independently in 1858, did + not concede that it was applicable to the higher mental and moral + qualities of man. Dr Wallace still holds a spiritualist and dualist view + of the nature of man, contending that he is composed of a material frame + (descended from the apes) and an immortal immaterial soul (infused by a + higher power). This dual conception, moreover, is still predominant in the + wide circles of modern theology and metaphysics, and has the general and + influential adherence of the more conservative classes of society. + </p> + <p> + In strict contradiction to this mystical dualism, which is generally + connected with teleology and vitalism, Darwin always maintained the + complete unity of human nature, and showed convincingly that the + psychological side of man was developed, in the same way as the body, from + the less advanced soul of the anthropoid ape, and, at a still more remote + period, from the cerebral functions of the older vertebrates. The eighth + chapter of the "Origin of Species", which is devoted to instinct, contains + weighty evidence that the instincts of animals are subject, like all other + vital processes, to the general laws of historic development. The special + instincts of particular species were formed by adaptation, and the + modifications thus acquired were handed on to posterity by heredity; in + their formation and preservation natural selection plays the same part as + in the transformation of every other physiological function. The higher + moral qualities of civilised man have been derived from the lower mental + functions of the uncultivated barbarians and savages, and these in turn + from the social instincts of the mammals. This natural and monistic + psychology of Darwin's was afterwards more fully developed by his friend + George Romanes in his excellent works "Mental Evolution in Animals" and + "Mental Evolution in Man". (London, 1885; 1888.) + </p> + <p> + Many valuable and most interesting contributions to this monistic + psychology of man were made by Darwin in his fine work on "The Descent of + Man and Selection in Relation to Sex", and again in his supplementary + work, "The Expression of the Emotions in Man and Animals". To understand + the historical development of Darwin's anthropology one must read his life + and the introduction to "The Descent of Man". From the moment that he was + convinced of the truth of the principle of descent—that is to say, + from his thirtieth year, in 1838—he recognised clearly that man + could not be excluded from its range. He recognised as a logical necessity + the important conclusion that "man is the co-descendant with other species + of some ancient, lower, and extinct form." For many years he gathered + notes and arguments in support of this thesis, and for the purpose of + showing the probable line of man's ancestry. But in the first edition of + "The Origin of Species" (1859) he restricted himself to the single line, + that by this work "light would be thrown on the origin of man and his + history." In the fifty years that have elapsed since that time the science + of the origin and nature of man has made astonishing progress, and we are + now fairly agreed in a monistic conception of nature that regards the + whole universe, including man, as a wonderful unity, governed by + unalterable and eternal laws. In my philosophical book "Die Weltratsel" + (1899) ("The Riddle of the Universe", London, 1900.) and in the + supplementary volume "Die Lebenswunder" (1904) "The Wonders of Life", + London, (1904.), I have endeavoured to show that this pure monism is + securely established, and that the admission of the all-powerful rule of + the same principle of evolution throughout the universe compels us to + formulate a single supreme law—the all-embracing "Law of Substance," + or the united laws of the constancy of matter and the conservation of + energy. We should never have reached this supreme general conception if + Charles Darwin—a "monistic philosopher" in the true sense of the + word—had not prepared the way by his theory of descent by natural + selection, and crowned the great work of his life by the association of + this theory with a naturalistic anthropology. + </p> + <p> + IX. SOME PRIMITIVE THEORIES OF THE ORIGIN OF MAN. + </p> + <p> + By J.G. FRAZER. Fellow of Trinity College, Cambridge. + </p> + <p> + On a bright day in late autumn a good many years ago I had ascended the + hill of Panopeus in Phocis to examine the ancient Greek fortifications + which crest its brow. It was the first of November, but the weather was + very hot; and when my work among the ruins was done, I was glad to rest + under the shade of a clump of fine holly-oaks, to inhale the sweet + refreshing perfume of the wild thyme which scented all the air, and to + enjoy the distant prospects, rich in natural beauty, rich too in memories + of the legendary and historic past. To the south the finely-cut peak of + Helicon peered over the low intervening hills. In the west loomed the + mighty mass of Parnassus, its middle slopes darkened by pine-woods like + shadows of clouds brooding on the mountain-side; while at its skirts + nestled the ivy-mantled walls of Daulis overhanging the deep glen, whose + romantic beauty accords so well with the loves and sorrows of Procne and + Philomela, which Greek tradition associated with the spot. Northwards, + across the broad plain to which the hill of Panopeus descends, steep and + bare, the eye rested on the gap in the hills through which the Cephissus + winds his tortuous way to flow under grey willows, at the foot of barren + stony hills, till his turbid waters lose themselves, no longer in the vast + reedy swamps of the now vanished Copaic Lake, but in the darkness of a + cavern in the limestone rock. Eastward, clinging to the slopes of the + bleak range of which the hill of Panopeus forms part, were the ruins of + Chaeronea, the birthplace of Plutarch; and out there in the plain was + fought the disastrous battle which laid Greece at the feet of Macedonia. + There, too, in a later age East and West met in deadly conflict, when the + Roman armies under Sulla defeated the Asiatic hosts of Mithridates. Such + was the landscape spread out before me on one of those farewell autumn + days of almost pathetic splendour, when the departing summer seems to + linger fondly, as if loth to resign to winter the enchanted mountains of + Greece. Next day the scene had changed: summer was gone. A grey November + mist hung low on the hills which only yesterday had shone resplendent in + the sun, and under its melancholy curtain the dead flat of the Chaeronean + plain, a wide treeless expanse shut in by desolate slopes, wore an aspect + of chilly sadness befitting the battlefield where a nation's freedom was + lost. + </p> + <p> + But crowded as the prospect from Panopeus is with memories of the past, + the place itself, now so still and deserted, was once the scene of an + event even more ancient and memorable, if Greek story-tellers can be + trusted. For here, they say, the sage Prometheus created our first parents + by fashioning them, like a potter, out of clay. (Pausanias X. 4.4. Compare + Apollodorus, "Bibliotheca", I. 7. 1; Ovid, "Metamorph." I. 82 sq.; + Juvenal, "Sat". XIV. 35. According to another version of the tale, this + creation of mankind took place not at Panopeus, but at Iconium in + Lycaonia. After the original race of mankind had been destroyed in the + great flood of Deucalion, the Greek Noah, Zeus commanded Prometheus and + Athena to create men afresh by moulding images out of clay, breathing the + winds into them, and making them live. See "Etymologicum Magnum", s.v. + "'Ikonion", pages 470 sq. It is said that Prometheus fashioned the animals + as well as men, giving to each kind of beast its proper nature. See + Philemon, quoted by Stobaeus, "Florilegium" II. 27. The creation of man by + Prometheus is figured on ancient works of art. See J. Toutain, "Etudes de + Mythologie et d'Histoire des Religions Antiques" (Paris, 1909), page 190. + According to Hesiod ("Works and Days", 60 sqq.) it was Hephaestus who at + the bidding of Zeus moulded the first woman out of moist earth.) The very + spot where he did so can still be seen. It is a forlorn little glen or + rather hollow behind the hill of Panopeus, below the ruined but still + stately walls and towers which crown the grey rocks of the summit. The + glen, when I visited it that hot day after the long drought of summer, was + quite dry; no water trickled down its bushy sides, but in the bottom I + found a reddish crumbling earth, a relic perhaps of the clay out of which + the potter Prometheus moulded the Greek Adam and Eve. In a volume + dedicated to the honour of one who has done more than any other in modern + times to shape the ideas of mankind as to their origin it may not be out + of place to recall this crude Greek notion of the creation of the human + race, and to compare or contrast it with other rudimentary speculations of + primitive peoples on the same subject, if only for the sake of marking the + interval which divides the childhood from the maturity of science. + </p> + <p> + The simple notion that the first man and woman were modelled out of clay + by a god or other superhuman being is found in the traditions of many + peoples. This is the Hebrew belief recorded in Genesis: "The Lord God + formed man of the dust of the ground, and breathed into his nostrils the + breath of life; and man became a living soul." (Genesis ii.7.) To the + Hebrews this derivation of our species suggested itself all the more + naturally because in their language the word for "ground" (adamah) is in + form the feminine of the word for man (adam). (S.R. Driver and + W.H.Bennett, in their commentaries on Genesis ii. 7.) From various + allusions in Babylonian literature it would seem that the Babylonians also + conceived man to have been moulded out of clay. (H. Zimmern, in E. + Schrader's "Die Keilinschriften und das Alte Testament" 3 (Berlin, 1902), + page 506.) According to Berosus, the Babylonian priest whose account of + creation has been preserved in a Greek version, the god Bel cut off his + own head, and the other gods caught the flowing blood, mixed it with + earth, and fashioned men out of the bloody paste; and that, they said, is + why men are so wise, because their mortal clay is tempered with divine + blood. (Eusebius, "Chronicon", ed. A. Schoene, Vol. I. (Berlin, 1875), + col. 16.) In Egyptian mythology Khnoumou, the Father of the gods, is said + to have moulded men out of clay. (G. Maspero, "Histoire Ancienne des + Peuples de l'Orient Classique", I. (Paris, 1895), page 128.) We cannot + doubt that such crude conceptions of the origin of our race were handed + down to the civilised peoples of antiquity by their savage or barbarous + forefathers. Certainly stories of the same sort are known to be current + among savages and barbarians. + </p> + <p> + Thus the Australian blacks in the neighbourhood of Melbourne said that + Pund-jel, the creator, cut three large sheets of bark with his big knife. + On one of these he placed some clay and worked it up with his knife into a + proper consistence. He then laid a portion of the clay on one of the other + pieces of bark and shaped it into a human form; first he made the feet, + then the legs, then the trunk, the arms, and the head. Thus he made a clay + man on each of the two pieces of bark; and being well pleased with them he + danced round them for joy. Next he took stringy bark from the Eucalyptus + tree, made hair of it, and stuck it on the heads of his clay men. Then he + looked at them again, was pleased with his work, and again danced round + them for joy. He then lay down on them, blew his breath hard into their + mouths, their noses, and their navels; and presently they stirred, spoke, + and rose up as full-grown men. (R. Brough Smyth, "The Aborigines of + Victoria" (Melbourne, 1878), I. 424. This and many of the following + legends of creation have been already cited by me in a note on Pausanias + X. 4. 4 ("Pausanias's Description of Greece, translated with a Commentary" + (London, 1898), Vol V. pages 220 sq.).) The Maoris of New Zealand say that + Tiki made man after his own image. He took red clay, kneaded it, like the + Babylonian Bel, with his own blood, fashioned it in human form, and gave + the image breath. As he had made man in his own likeness he called him + Tiki-ahua or Tiki's likeness. (R. Taylor "Te Ika A Maui, or New Zealand + and its Inhabitants", Second Edition (London, 1870), page 117. Compare E. + Shortland, "Maori Religion and Mythology" (London, 1882), pages 21 sq.) A + very generally received tradition in Tahiti was that the first human pair + was made by Taaroa, the chief god. They say that after he had formed the + world he created man out of red earth, which was also the food of mankind + until bread-fruit was produced. Further, some say that one day Taaroa + called for the man by name, and when he came he made him fall asleep. As + he slept, the creator took out one of his bones (ivi) and made a woman of + it, whom he gave to the man to be his wife, and the pair became the + progenitors of mankind. This narrative was taken down from the lips of the + natives in the early years of the mission to Tahiti. The missionary who + records it observes: "This always appeared to me a mere recital of the + Mosaic account of creation, which they had heard from some European, and I + never placed any reliance on it, although they have repeatedly told me it + was a tradition among them before any foreigner arrived. Some have also + stated that the woman's name was Ivi, which would be by them pronounced as + if written "Eve". "Ivi" is an aboriginal word, and not only signifies a + bone, but also a widow, and a victim slain in war. Notwithstanding the + assertion of the natives, I am disposed to think that "Ivi", or Eve, is + the only aboriginal part of the story, as far as it respects the mother of + the human race. (W. Ellis, "Polynesian Researches", Second Edition + (London, 1832), I. 110 sq. "Ivi" or "iwi" is the regular word for "bone" + in the various Polynesian languages. See E. Tregear, "The Maori-Polynesian + Comparative Dictionary" (Wellington, New Zealand, 1891), page 109.) + However, the same tradition has been recorded in other parts of Polynesia + besides Tahiti. Thus the natives of Fakaofo or Bowditch Island say that + the first man was produced out of a stone. After a time he bethought him + of making a woman. So he gathered earth and moulded the figure of a woman + out of it, and having done so he took a rib out of his left side and + thrust it into the earthen figure, which thereupon started up a live + woman. He called her Ivi (Eevee) or "rib" and took her to wife, and the + whole human race sprang from this pair. (G. Turner, "Samoa" (London, + 1884), pages 267 sq.) The Maoris also are reported to believe that the + first woman was made out of the first man's ribs. (J.L. Nicholas, + "Narrative of a Voyage to New Zealand" (London, 1817), I. 59, who writes + "and to add still more to this strange coincidence, the general term for + bone is 'Hevee'.") This wide diffusion of the story in Polynesia raises a + doubt whether it is merely, as Ellis thought, a repetition of the Biblical + narrative learned from Europeans. In Nui, or Netherland Island, it was the + god Aulialia who made earthen models of a man and woman, raised them up, + and made them live. He called the man Tepapa and the woman Tetata. (G. + Turner, "Samoa", pages 300 sq.) + </p> + <p> + In the Pelew Islands they say that a brother and sister made men out of + clay kneaded with the blood of various animals, and that the characters of + these first men and of their descendants were determined by the characters + of the animals whose blood had been kneaded with the primordial clay; for + instance, men who have rat's blood in them are thieves, men who have + serpent's blood in them are sneaks, and men who have cock's blood in them + are brave. (J. Kubary, "Die Religion der Pelauer", in A. Bastian's + "Allerlei aus Volks- und Menschenkunde" (Berlin, 1888), I. 3, 56.) + According to a Melanesian legend, told in Mota, one of the Banks Islands, + the hero Qat moulded men of clay, the red clay from the marshy river-side + at Vanua Lava. At first he made men and pigs just alike, but his brothers + remonstrated with him, so he beat down the pigs to go on all fours and + made men walk upright. Qat fashioned the first woman out of supple twigs, + and when she smiled he knew she was a living woman. (R.H. Codrington, "The + Melanesians" (Oxford, 1891), page 158.) A somewhat different version of + the Melanesian story is told at Lakona, in Santa Maria. There they say + that Qat and another spirit ("vui") called Marawa both made men. Qat made + them out of the wood of dracaena-trees. Six days he worked at them, + carving their limbs and fitting them together. Then he allowed them six + days to come to life. Three days he hid them away, and three days more he + worked to make them live. He set them up and danced to them and beat his + drum, and little by little they stirred, till at last they could stand all + by themselves. Then Qat divided them into pairs and called each pair + husband and wife. Marawa also made men out of a tree, but it was a + different tree, the tavisoviso. He likewise worked at them six days, beat + his drum, and made them live, just as Qat did. But when he saw them move, + he dug a pit and buried them in it for six days, and then, when he scraped + away the earth to see what they were doing, he found them all rotten and + stinking. That was the origin of death. (R.H. Codrington op. cit., pages + 157 sq.) + </p> + <p> + The inhabitants of Noo-Hoo-roa, in the Kei Islands say that their + ancestors were fashioned out of clay by the supreme god, Dooadlera, who + breathed life into the clay figures. (C.M. Pleyte, "Ethnographische + Beschrijving der Kei-Eilanden", "Tijdschrift van het Nederlandsch + Aardrijkskundig Genootschap", Tweede Serie X. (1893), page 564.) The + aborigines of Minahassa, in the north of Celebes, say that two beings + called Wailan Wangko and Wangi were alone on an island, on which grew a + cocoa-nut tree. Said Wailan Wangko to Wangi, "Remain on earth while I + climb up the tree." Said Wangi to Wailan Wangko, "Good." But then a + thought occurred to Wangi and he climbed up the tree to ask Wailan Wangko + why he, Wangi, should remain down there all alone. Said Wailan Wangko to + Wangi, "Return and take earth and make two images, a man and a woman." + Wangi did so, and both images were men who could move but could not speak. + So Wangi climbed up the tree to ask Wailan Wangko, "How now? The two + images are made, but they cannot speak." Said Wailan Wangko to Wangi, + "Take this ginger and go and blow it on the skulls and the ears of these + two images, that they may be able to speak; call the man Adam and the + woman Ewa." (N. Graafland "De Minahassa" (Rotterdam, 1869), I. pages 96 + sq.) In this narrative the names of the man and woman betray European + influence, but the rest of the story may be aboriginal. The Dyaks of + Sakarran in British Borneo say that the first man was made by two large + birds. At first they tried to make men out of trees, but in vain. Then + they hewed them out of rocks, but the figures could not speak. Then they + moulded a man out of damp earth and infused into his veins the red gum of + the kumpang-tree. After that they called to him and he answered; they cut + him and blood flowed from his wounds. (Horsburgh, quoted by H. Ling Roth, + "The Natives of Sarawak and of British North Borneo" (London, 1896), I. + pages 299 sq. Compare The Lord Bishop of Labuan, "On the Wild Tribes of + the North-West Coast of Borneo," "Transactions of the Ethnological Society + of London", New Series, II. (1863), page 27.) + </p> + <p> + The Kumis of South-Eastern India related to Captain Lewin, the Deputy + Commissioner of Hill Tracts, the following tradition of the creation of + man. "God made the world and the trees and the creeping things first, and + after that he set to work to make one man and one woman, forming their + bodies of clay; but each night, on the completion of his work, there came + a great snake, which, while God was sleeping, devoured the two images. + This happened twice or thrice, and God was at his wit's end, for he had to + work all day, and could not finish the pair in less than twelve hours; + besides, if he did not sleep, he would be no good," said Captain Lewin's + informant. "If he were not obliged to sleep, there would be no death, nor + would mankind be afflicted with illness. It is when he rests that the + snake carries us off to this day. Well, he was at his wit's end, so at + last he got up early one morning and first made a dog and put life into + it, and that night, when he had finished the images, he set the dog to + watch them, and when the snake came, the dog barked and frightened it + away. This is the reason at this day that when a man is dying the dogs + begin to howl; but I suppose God sleeps heavily now-a-days, or the snake + is bolder, for men die all the same." (Capt. T.H. Lewin, "Wild Races of + South-Eastern India" (London, 1870), pages 224-26.) The Khasis of Assam + tell a similar tale. (A. Bastian, "Volkerstamme am Brahmaputra und + verwandtschaftliche Nachbarn" (Berlin, 1883), page 8; Major P.R.T. Gurdon, + "The Khasis" (London, 1907), page 106.) + </p> + <p> + The Ewe-speaking tribes of Togo-land, in West Africa, think that God still + makes men out of clay. When a little of the water with which he moistens + the clay remains over, he pours it on the ground and out of that he makes + the bad and disobedient people. When he wishes to make a good man he makes + him out of good clay; but when he wishes to make a bad man, he employs + only bad clay for the purpose. In the beginning God fashioned a man and + set him on the earth; after that he fashioned a woman. The two looked at + each other and began to laugh, whereupon God sent them into the world. (J. + Spieth, "Die Ewe-Stamme, Material zur Kunde des Ewe-Volkes in + Deutsch-Togo" (Berlin, 1906), pages 828, 840.) The Innuit or Esquimaux of + Point Barrow, in Alaska, tell of a time when there was no man in the land, + till a spirit named "a se lu", who resided at Point Barrow, made a clay + man, set him up on the shore to dry, breathed into him and gave him life. + ("Report of the International Expedition to Point Barrow" (Washington, + 1885), page 47.) Other Esquimaux of Alaska relate how the Raven made the + first woman out of clay to be a companion to the first man; he fastened + water-grass to the back of the head to be hair, flapped his wings over the + clay figure, and it arose, a beautiful young woman. (E.W. Nelson, "The + Eskimo about Bering Strait", "Eighteenth Annual Report of the Bureau of + American Ethnology", Part I. (Washington, 1899), page 454.) The Acagchemem + Indians of California said that a powerful being called Chinigchinich + created man out of clay which he found on the banks of a lake; male and + female created he them, and the Indians of the present day are their + descendants. (Friar Geronimo Boscana, "Chinigchinich", appended to (A. + Robinson's) "Life in California" (New York, 1846), page 247.) A priest of + the Natchez Indians in Louisiana told Du Pratz "that God had kneaded some + clay, such as that which potters use and had made it into a little man; + and that after examining it, and finding it well formed, he blew up his + work, and forthwith that little man had life, grew, acted, walked, and + found himself a man perfectly well shaped." As to the mode in which the + first woman was created, the priest had no information, but thought she + was probably made in the same way as the first man; so Du Pratz corrected + his imperfect notions by reference to Scripture. (M. Le Page Du Pratz, + "The History of Louisiana" (London, 1774), page 330.) The Michoacans of + Mexico said that the great god Tucapacha first made man and woman out of + clay, but that when the couple went to bathe in a river they absorbed so + much water that the clay of which they were composed all fell to pieces. + Then the creator went to work again and moulded them afresh out of ashes, + and after that he essayed a third time and made them of metal. This last + attempt succeeded. The metal man and woman bathed in the river without + falling to pieces, and by their union they became the progenitors of + mankind. (A. de Herrera, "General History of the vast Continent and + Islands of America", translated into English by Capt. J. Stevens (London, + 1725, 1726), III. 254; Brasseur de Bourbourg, "Histoire des Nations + Civilisees du Mexique et de l'Amerique-Centrale" (Paris, 1857—1859), + III. 80 sq; compare id. I. 54 sq.) + </p> + <p> + According to a legend of the Peruvian Indians, which was told to a Spanish + priest in Cuzco about half a century after the conquest, it was in + Tiahuanaco that man was first created, or at least was created afresh + after the deluge. "There (in Tiahuanaco)," so runs the legend, "the + Creator began to raise up the people and nations that are in that region, + making one of each nation of clay, and painting the dresses that each one + was to wear; those that were to wear their hair, with hair, and those that + were to be shorn, with hair cut. And to each nation was given the + language, that was to be spoken, and the songs to be sung, and the seeds + and food that they were to sow. When the Creator had finished painting and + making the said nations and figures of clay, he gave life and soul to each + one, as well men as women, and ordered that they should pass under the + earth. Thence each nation came up in the places to which he ordered them + to go." (E.J. Payne, "History of the New World called America", I. + (Oxford, 1892), page 462.) + </p> + <p> + These examples suffice to prove that the theory of the creation of man out + of dust or clay has been current among savages in many parts of the world. + But it is by no means the only explanation which the savage philosopher + has given of the beginnings of human life on earth. Struck by the + resemblances which may be traced between himself and the beasts, he has + often supposed, like Darwin himself, that mankind has been developed out + of lower forms of animal life. For the simple savage has none of that high + notion of the transcendant dignity of man which makes so many superior + persons shrink with horror from the suggestion that they are distant + cousins of the brutes. He on the contrary is not too proud to own his + humble relations; indeed his difficulty often is to perceive the + distinction between him and them. Questioned by a missionary, a Bushman of + more than average intelligence "could not state any difference between a + man and a brute—he did not know but a buffalo might shoot with bows + and arrows as well as man, if it had them." (Reverend John Campbell, + "Travels in South Africa" (London, 1822, II. page 34.) When the Russians + first landed on one of the Alaskan islands, the natives took them for + cuttle-fish "on account of the buttons on their clothes." (I. Petroff, + "Report on the Population, Industries, and Resources of Alaska", page + 145.) The Giliaks of the Amoor think that the outward form and size of an + animal are only apparent; in substance every beast is a real man, just + like a Giliak himself, only endowed with an intelligence and strength, + which often surpass those of mere ordinary human beings. (L. Sternberg, + "Die Religion der Giljaken", "Archiv fur Religionswissenschaft", VIII. + (1905), page 248.) The Borororos, an Indian tribe of Brazil, will have it + that they are parrots of a gorgeous red plumage which live in their native + forests. Accordingly they treat the birds as their fellow-tribesmen, + keeping them in captivity, refusing to eat their flesh, and mourning for + them when they die. (K. von den Steinen, "Unter den Naturvolkern + Zentral-Brasiliens" (Berlin, 1894), pages 352 sq., 512.)) + </p> + <p> + This sense of the close relationship of man to the lower creation is the + essence of totemism, that curious system of superstition which unites by a + mystic bond a group of human kinsfolk to a species of animals or plants. + Where that system exists in full force, the members of a totem clan + identify themselves with their totem animals in a way and to an extent + which we find it hard even to imagine. For example, men of the Cassowary + clan in Mabuiag think that cassowaries are men or nearly so. "Cassowary, + he all same as relation, he belong same family," is the account they give + of their relationship with the long-legged bird. Conversely they hold that + they themselves are cassowaries for all practical purposes. They pride + themselves on having long thin legs like a cassowary. This reflection + affords them peculiar satisfaction when they go out to fight, or to run + away, as the case may be; for at such times a Cassowary man will say to + himself, "My leg is long and thin, I can run and not feel tired; my legs + will go quickly and the grass will not entangle them." Members of the + Cassowary clan are reputed to be pugnacious, because the cassowary is a + bird of very uncertain temper and can kick with extreme violence. (A.C. + Haddon, "The Ethnography of the Western Tribe of Torres Straits", "Journal + of the Anthropological Institute", XIX. (1890), page 393; "Reports of the + Cambridge Anthropological Expedition to Torres Straits", V. (Cambridge, + 1904), pages 166, 184.) So among the Ojibways men of the Bear clan are + reputed to be surly and pugnacious like bears, and men of the Crane clan + to have clear ringing voices like cranes. (W.W. Warren, "History of the + Ojibways", "Collections of the Minnesota Historical Society", V. (Saint + Paul, Minn. 1885), pages 47, 49.) Hence the savage will often speak of his + totem animal as his father or his brother, and will neither kill it + himself nor allow others to do so, if he can help it. For example, if + somebody were to kill a bird in the presence of a native Australian who + had the bird for his totem, the black might say, "What for you kill that + fellow? that my father!" or "That brother belonging to me you have killed; + why did you do it?" (E. Palmer, "Notes on some Australian Tribes", + "Journal of the Anthropological Institute", XIII. (1884), page 300.) + Bechuanas of the Porcupine clan are greatly afflicted if anybody hurts or + kills a porcupine in their presence. They say, "They have killed our + brother, our master, one of ourselves, him whom we sing of"; and so saying + they piously gather the quills of their murdered brother, spit on them, + and rub their eyebrows with them. They think they would die if they + touched its flesh. In like manner Bechuanas of the Crocodile clan call the + crocodile one of themselves, their master, their brother; and they mark + the ears of their cattle with a long slit like a crocodile's mouth by way + of a family crest. Similarly Bechuanas of the Lion clan would not, like + the members of other clans, partake of lion's flesh; for how, say they, + could they eat their grandfather? If they are forced in self-defence to + kill a lion, they do so with great regret and rub their eyes carefully + with its skin, fearing to lose their sight if they neglected this + precaution. (T. Arbousset et F. Daumas, "Relation d'un Voyage + d'Exploration au Nord-Est de la Colonie du Cap de Bonne-Esperance" (Paris, + 1842), pages 349 sq., 422-24.) A Mandingo porter has been known to offer + the whole of his month's pay to save the life of a python, because the + python was his totem and he therefore regarded the reptile as his + relation; he thought that if he allowed the creature to be killed, the + whole of his own family would perish, probably through the vengeance to be + taken by the reptile kinsfolk of the murdered serpent. (M. le Docteur + Tautain, "Notes sur les Croyances et Pratiques Religieuses des Banmanas", + "Revue d'Ethnographie", III. (1885), pages 396 sq.; A. Rancon, "Dans la + Haute-Gambie, Voyage d'Exploration Scientifique" (Paris, 1894), page 445.) + </p> + <p> + Sometimes, indeed, the savage goes further and identifies the revered + animal not merely with a kinsman but with himself; he imagines that one of + his own more or less numerous souls, or at all events that a vital part of + himself, is in the beast, so that if it is killed he must die. Thus, the + Balong tribe of the Cameroons, in West Africa, think that every man has + several souls, of which one is lodged in an elephant, a wild boar, a + leopard, or what not. When any one comes home, feels ill, and says, "I + shall soon die," and is as good as his word, his friends are of opinion + that one of his souls has been shot by a hunter in a wild boar or a + leopard, for example, and that that is the real cause of his death. (J. + Keller, "Ueber das Land und Volk der Balong", "Deutsches Kolonialblatt", 1 + October, 1895, page 484.) A Catholic missionary, sleeping in the hut of a + chief of the Fan negroes, awoke in the middle of the night to see a huge + black serpent of the most dangerous sort in the act of darting at him. He + was about to shoot it when the chief stopped him, saying, "In killing that + serpent, it is me that you would have killed. Fear nothing, the serpent is + my elangela." (Father Trilles, "Chez les Fang, leurs Moeurs, leur Langue, + leur Religion", "Les Missions Catholiques", XXX. (1898), page 322.) At + Calabar there used to be some years ago a huge old crocodile which was + well known to contain the spirit of a chief who resided in the flesh at + Duke Town. Sporting Vice-Consuls, with a reckless disregard of human life, + from time to time made determined attempts to injure the animal, and once + a peculiarly active officer succeeded in hitting it. The chief was + immediately laid up with a wound in his leg. He SAID that a dog had bitten + him, but few people perhaps were deceived by so flimsy a pretext. (Miss + Mary H. Kingsley, "Travels in West Africa" (London, 1897), pages 538 sq. + As to the external or bush souls of human beings, which in this part of + Africa are supposed to be lodged in the bodies of animals, see Miss Mary + H. Kingsley op. cit. pages 459-461; R. Henshaw, "Notes on the Efik belief + in 'bush soul'", "Man", VI.(1906), pages 121 sq.; J. Parkinson, "Notes on + the Asaba people (Ibos) of the Niger", "Journal of the Anthropological + Institute", XXXVI. (1906), pages 314 sq.) Once when Mr Partridge's + canoe-men were about to catch fish near an Assiga town in Southern + Nigeria, the natives of the town objected, saying, "Our souls live in + those fish, and if you kill them we shall die." (Charles Partridge, "Cross + River Natives" (London, 1905), pages 225 sq.) On another occasion, in the + same region, an Englishman shot a hippopotamus near a native village. The + same night a woman died in the village, and her friends demanded and + obtained from the marksman five pounds as compensation for the murder of + the woman, whose soul or second self had been in that hippopotamus. (C.H. + Robinson, "Hausaland" (London, 1896), pages 36 sq.) Similarly at Ndolo, in + the Congo region, we hear of a chief whose life was bound up with a + hippopotamus, but he prudently suffered no one to fire at the animal. + ("Notes Analytiques sur les Collections Ethnographiques du Musee du + Congo", I. (Brussels, 1902-06), page 150.) + </p> + <p> + Amongst people who thus fail to perceive any sharp line of distinction + between beasts and men it is not surprising to meet with the belief that + human beings are directly descended from animals. Such a belief is often + found among totemic tribes who imagine that their ancestors sprang from + their totemic animals or plants; but it is by no means confined to them. + Thus, to take instances, some of the Californian Indians, in whose + mythology the coyote or prairie-wolf is a leading personage, think that + they are descended from coyotes. At first they walked on all fours; then + they began to have some members of the human body, one finger, one toe, + one eye, one ear, and so on; then they got two fingers, two toes, two + eyes, two ears, and so forth; till at last, progressing from period to + period, they became perfect human beings. The loss of their tails, which + they still deplore, was produced by the habit of sitting upright. (H.R. + Schoolcraft, "Indian Tribes of the United States", IV. (Philadelphia, + 1856), pages 224 sq.; compare id. V. page 217. The descent of some, not + all, Indians from coyotes is mentioned also by Friar Boscana, in (A. + Robinson's) "Life in California" (New York, 1846), page 299.) Similarly + Darwin thought that "the tail has disappeared in man and the + anthropomorphous apes, owing to the terminal portion having been injured + by friction during a long lapse of time; the basal and embedded portion + having been reduced and modified, so as to become suitable to the erect or + semi-erect position." (Charles Darwin, "The Descent of Man", Second + Edition (London, 1879), page 60.) The Turtle clam of the Iroquois think + that they are descended from real mud turtles which used to live in a + pool. One hot summer the pool dried up, and the mud turtles set out to + find another. A very fat turtle, waddling after the rest in the heat, was + much incommoded by the weight of his shell, till by a great effort he + heaved it off altogether. After that he gradually developed into a man and + became the progenitor of the Turtle clan. (E.A. Smith, "Myths of the + Iroquois", "Second Annual Report of the Bureau of Ethnology" (Washington, + 1883), page 77.) The Crawfish band of the Choctaws are in like manner + descended from real crawfish, which used to live under ground, only coming + up occasionally through the mud to the surface. Once a party of Choctaws + smoked them out, taught them the Choctaw language, taught them to walk on + two legs, made them cut off their toe nails and pluck the hair from their + bodies, after which they adopted them into the tribe. But the rest of + their kindred, the crawfish, are crawfish under ground to this day. (Geo. + Catlin, "North American Indians" 4 (London, 1844), II. page 128.) The + Osage Indians universally believed that they were descended from a male + snail and a female beaver. A flood swept the snail down to the Missouri + and left him high and dry on the bank, where the sun ripened him into a + man. He met and married a beaver maid, and from the pair the tribe of the + Osages is descended. For a long time these Indians retained a pious + reverence for their animal ancestors and refrained from hunting beavers, + because in killing a beaver they killed a brother of the Osages. But when + white men came among them and offered high prices for beaver skins, the + Osages yielded to the temptation and took the lives of their furry + brethren. (Lewis and Clarke, "Travels to the Source of the Missouri River" + (London, 1815), I. 12 (Vol. I. pages 44 sq. of the London reprint, 1905).) + The Carp clan of the Ootawak Indians are descended from the eggs of a carp + which had been deposited by the fish on the banks of a stream and warmed + by the sun. ("Lettres Edifiantes et Curieuses", Nouvelle Edition, VI. + (Paris, 1781), page 171.) The Crane clan of the Ojibways are sprung + originally from a pair of cranes, which after long wanderings settled on + the rapids at the outlet of Lake Superior, where they were changed by the + Great Spirit into a man and woman. (L.H. Morgan, "Ancient Society" + (London, 1877), page 180.) The members of two Omaha clans were originally + buffaloes and lived, oddly enough, under water, which they splashed about, + making it muddy. And at death all the members of these clans went back to + their ancestors the buffaloes. So when one of them lay adying, his friends + used to wrap him up in a buffalo skin with the hair outside and say to + him, "You came hither from the animals and you are going back thither. Do + not face this way again. When you go, continue walking. (J. Owen Dorsey, + "Omaha Sociology", "Third Annual Report of the Bureau of Ethnology" + (Washington, 1884), pages 229, 233.) The Haida Indians of Queen Charlotte + Islands believe that long ago the raven, who is the chief figure in the + mythology of North-West America, took a cockle from the beach and married + it; the cockle gave birth to a female child, whom the raven took to wife, + and from their union the Indians were produced. (G.M. Dawson, "Report on + the Queen Charlotte Islands" (Montreal, 1880), pages 149B sq. ("Geological + Survey of Canada"); F. Poole, "Queen Charlotte Islands", page 136.) The + Delaware Indians called the rattle-snake their grandfather and would on no + account destroy one of these reptiles, believing that were they to do so + the whole race of rattle-snakes would rise up and bite them. Under the + influence of the white man, however, their respect for their grandfather + the rattle-snake gradually died away, till at last they killed him without + compunction or ceremony whenever they met him. The writer who records the + old custom observes that he had often reflected on the curious connection + which appears to subsist in the mind of an Indian between man and the + brute creation; "all animated nature," says he, "in whatever degree, is in + their eyes a great whole, from which they have not yet ventured to + separate themselves." (Rev. John Heckewelder, "An Account of the History, + Manners, and Customs, of the Indian Nations, who once inhabited + Pennsylvania and the Neighbouring States", "Transactions of the Historical + and Literary Committee of the American Philosophical Society", I. + (Philadelphia, 1819), pages 245, 247, 248.) + </p> + <p> + Some of the Indians of Peru boasted of being descended from the puma or + American lion; hence they adored the lion as a god and appeared at + festivals like Hercules dressed in the skins of lions with the heads of + the beasts fixed over their own. Others claimed to be sprung from condors + and attired themselves in great black and white wings, like that enormous + bird. (Garcilasso de la Vega, "First Part of the Royal Commentaries of the + Yncas", Vol. I. page 323, Vol. II. page 156 (Markham's translation).) The + Wanika of East Africa look upon the hyaena as one of their ancestors or as + associated in some way with their origin and destiny. The death of a + hyaena is mourned by the whole people, and the greatest funeral ceremonies + which they perform are performed for this brute. The wake held over a + chief is as nothing compared to the wake held over a hyaena; one tribe + only mourns the death of its chief, but all the tribes unite to celebrate + the obsequies of a hyaena. (Charles New, "Life, Wanderings, and Labours in + Eastern Africa" (London, 1873) page 122.) Some Malagasy families claim to + be descended from the babacoote (Lichanotus brevicaudatus), a large lemur + of grave appearance and staid demeanour, which lives in the depth of the + forest. When they find one of these creatures dead, his human descendants + bury it solemnly, digging a grave for it, wrapping it in a shroud, and + weeping and lamenting over its carcase. A doctor who had shot a babacoote + was accused by the inhabitants of a Betsimisaraka village of having killed + "one of their grandfathers in the forest," and to appease their + indignation he had to promise not to skin the animal in the village but in + a solitary place where nobody could see him. (Father Abinal, "Croyances + fabuleuses des Malgaches", "Les Missions Catholiques", XII. (1880), page + 526; G.H. Smith, "Some Betsimisaraka superstitions", "The Antananarivo + Annual and Madagascar Magazine", No. 10 (Antananarivo, 1886), page 239; + H.W. Little, "Madagascar, its History and People" (London, 1884), pages + 321 sq; A. van Gennep, "Tabou et Totemisme a Madagascar" (Paris, 1904), + pages 214 sqq.) Many of the Betsimisaraka believe that the curious + nocturnal animal called the aye-aye (Cheiromys madagascariensis) "is the + embodiment of their forefathers, and hence will not touch it, much less do + it an injury. It is said that when one is discovered dead in the forest, + these people make a tomb for it and bury it with all the forms of a + funeral. They think that if they attempt to entrap it, they will surely + die in consequence." (G.A. Shaw, "The Aye-aye", "Antananarivo Annual and + Madagascar Magazine", Vol. II. (Antananarivo, 1896), pages 201, 203 + (Reprint of the Second four Numbers). Compare A. van Gennep, "Tabou et + Totemisme a Madagascar", pages 223 sq.) Some Malagasy tribes believe + themselves descended from crocodiles and accordingly they deem the + formidable reptiles their brothers. If one of these scaly brothers so far + forgets the ties of kinship as to devour a man, the chief of the tribe, or + in his absence an old man familiar with the tribal customs, repairs at the + head of the people to the edge of the water, and summons the family of the + culprit to deliver him up to the arm of justice. A hook is then baited and + cast into the river or lake. Next day the guilty brother or one of his + family is dragged ashore, formally tried, sentenced to death, and + executed. The claims of justice being thus satisfied, the dead animal is + lamented and buried like a kinsman; a mound is raised over his grave and a + stone marks the place of his head. (Father Abinal, "Croyances fabuleuses + des Malgaches", "Les Missions Catholiques", XII. (1880), page 527; A. van + Gennep, "Tabou et Totemisme a Madagascar", pages 281 sq.) + </p> + <p> + Amongst the Tshi-speaking tribes of the Gold Coast in West Africa the + Horse-mackerel family traces its descent from a real horse-mackerel whom + an ancestor of theirs once took to wife. She lived with him happily in + human shape on shore till one day a second wife, whom the man had married, + cruelly taunted her with being nothing but a fish. That hurt her so much + that bidding her husband farewell she returned to her old home in the sea, + with her youngest child in her arms, and never came back again. But ever + since the Horse-mackerel people have refrained from eating + horse-mackerels, because the lost wife and mother was a fish of that sort. + (A.B. Ellis, "The Tshi-speaking Peoples of the Gold Coast of West Africa" + (London, 1887), pages 208-11. A similar tale is told by another fish + family who abstain from eating the fish (appei) from which they take their + name (A.B. Ellis op. cit. pages 211 sq.).) Some of the Land Dyaks of + Borneo tell a similar tale to explain a similar custom. "There is a fish + which is taken in their rivers called a puttin, which they would on no + account touch, under the idea that if they did they would be eating their + relations. The tradition respecting it is, that a solitary old man went + out fishing and caught a puttin, which he dragged out of the water and + laid down in his boat. On turning round, he found it had changed into a + very pretty little girl. Conceiving the idea she would make, what he had + long wished for, a charming wife for his son, he took her home and + educated her until she was fit to be married. She consented to be the + son's wife cautioning her husband to use her well. Some time after their + marriage, however, being out of temper, he struck her, when she screamed, + and rushed away into the water; but not without leaving behind her a + beautiful daughter, who became afterwards the mother of the race." (The + Lord Bishop of Labuan, "On the Wild Tribes of the North-West Coast of + Borneo", "Transactions of the Ethnological Society of London", New Series + II. (London, 1863), pages 26 sq. Such stories conform to a well-known type + which may be called the Swan-Maiden type of story, or Beauty and the + Beast, or Cupid and Psyche. The occurrence of stories of this type among + totemic peoples, such as the Tshi-speaking negroes of the Gold Coast, who + tell them to explain their totemic taboos, suggests that all such tales + may have originated in totemism. I shall deal with this question + elsewhere.) + </p> + <p> + Members of a clan in Mandailing, on the west coast of Sumatra, assert that + they are descended from a tiger, and at the present day, when a tiger is + shot, the women of the clan are bound to offer betel to the dead beast. + When members of this clan come upon the tracks of a tiger, they must, as a + mark of homage, enclose them with three little sticks. Further, it is + believed that the tiger will not attack or lacerate his kinsmen, the + members of the clan. (H. Ris, "De Onderafdeeling Klein Mandailing Oeloe en + Pahantan en hare Bevolking met uitzondering van de Oeloes", "Bijdragen tot + de Tall- Land- en Volkenkunde van Nederlansch-Indie, XLVI." (1896), page + 473.) The Battas of Central Sumatra are divided into a number of clans + which have for their totems white buffaloes, goats, wild turtle-doves, + dogs, cats, apes, tigers, and so forth; and one of the explanations which + they give of their totems is that these creatures were their ancestors, + and that their own souls after death can transmigrate into the animals. + (J.B. Neumann, "Het Pane en Bila-stroomgebied op het eiland Sumatra", + "Tijdschrift van het Nederlandsch Aardrijkskundig Genootschap", Tweede + Serie, III. Afdeeling, Meer uitgebreide Artikelen, No. 2 (Amsterdam, + 1886), pages 311 sq.; id. ib. Tweede Serie, IV. Afdeeling, Meer + uitgebreide Artikelen, No. 1 (Amsterdam, 1887), pages 8 sq.) In Amboyna + and the neighbouring islands the inhabitants of some villages aver that + they are descended from trees, such as the Capellenia moluccana, which had + been fertilised by the Pandion Haliaetus. Others claim to be sprung from + pigs, octopuses, crocodiles, sharks, and eels. People will not burn the + wood of the trees from which they trace their descent, nor eat the flesh + of the animals which they regard as their ancestors. Sicknesses of all + sorts are believed to result from disregarding these taboos. (J.G.F. + Riedel, "De sluik- en kroesharige rassen tusschen Selebes en Papua" (The + Hague, 1886), pages 32, 61; G.W.W.C. Baron van Hoevell, "Ambon en meer + bepaaldelijk de Oeliasers" (Dordrecht, 1875), page 152.) Similarly in + Ceram persons who think they are descended from crocodiles, serpents, + iguanas, and sharks will not eat the flesh of these animals. (J.G.F. + Riedel op. cit. page 122.) Many other peoples of the Molucca Islands + entertain similar beliefs and observe similar taboos. (J.G.F. Riedel "De + sluik- en kroesharige rassen tusschen Selebes en Papua" (The Hague, 1886), + pages 253, 334, 341, 348, 412, 414, 432.) Again, in Ponape, one of the + Caroline Islands, "The different families suppose themselves to stand in a + certain relation to animals, and especially to fishes, and believe in + their descent from them. They actually name these animals 'mothers'; the + creatures are sacred to the family and may not be injured. Great dances, + accompanied with the offering of prayers, are performed in their honour. + Any person who killed such an animal would expose himself to contempt and + punishment, certainly also to the vengeance of the insulted deity." + Blindness is commonly supposed to be the consequence of such a sacrilege. + (Dr Hahl, "Mittheilungen uber Sitten und rechtliche Verhaltnisse auf + Ponape", "Ethnologisches Notizblatt", Vol. II. Heft 2 (Berlin, 1901), page + 10.) + </p> + <p> + Some of the aborigines of Western Australia believe that their ancestors + were swans, ducks, or various other species of water-fowl before they were + transformed into men. (Captain G. Grey, "A Vocabulary of the Dialects of + South Western Australia", Second Edition (London, 1840), pages 29, 37, 61, + 63, 66, 71.) The Dieri tribe of Central Australia, who are divided into + totemic clans, explain their origin by the following legend. They say that + in the beginning the earth opened in the midst of Perigundi Lake, and the + totems (murdus or madas) came trooping out one after the other. Out came + the crow, and the shell parakeet, and the emu, and all the rest. Being as + yet imperfectly formed and without members or organs of sense, they laid + themselves down on the sandhills which surrounded the lake then just as + they do now. It was a bright day and the totems lay basking in the + sunshine, till at last, refreshed and invigorated by it, they stood up as + human beings and dispersed in all directions. That is why people of the + same totem are now scattered all over the country. You may still see the + island in the lake out of which the totems came trooping long ago. (A.W. + Howitt, "Native Tribes of South-East Australia" (London, 1904), pages 476, + 779 sq.) Another Dieri legend relates how Paralina, one of the Mura-Muras + or mythical predecessors of the Dieri, perfected mankind. He was out + hunting kangaroos, when he saw four incomplete beings cowering together. + So he went up to them, smoothed their bodies, stretched out their limbs, + slit up their fingers and toes, formed their mouths, noses, and eyes, + stuck ears on them, and blew into their ears in order that they might + hear. Having perfected their organs and so produced mankind out of these + rudimentary beings, he went about making men everywhere. (A.W. Howitt op. + cit., pages 476, 780 sq.) Yet another Dieri tradition sets forth how the + Mura-Mura produced the race of man out of a species of small black + lizards, which may still be met with under dry bark. To do this he divided + the feet of the lizards into fingers and toes, and, applying his + forefinger to the middle of their faces, created a nose; likewise he gave + them human eyes, mouths and ears. He next set one of them upright, but it + fell down again because of its tail; so he cut off its tail and the lizard + then walked on its hind legs. That is the origin of mankind. (S. Gason, + "The Manners and Customs of the Dieyerie tribe of Australian Aborigines", + "Native Tribes of South Australia" (Adelaide, 1879), page 260. This writer + fell into the mistake of regarding the Mura-Mura (Mooramoora) as a + Good-Spirit instead of as one of the mythical but more or less human + predecessors of the Dieri in the country. See A.W. Howitt, "Native Tribes + of South-East Australia", pages 475 sqq.) + </p> + <p> + The Arunta tribe of Central Australia similarly tell how in the beginning + mankind was developed out of various rudimentary forms of animal life. + They say that in those days two beings called Ungambikula, that is, "out + of nothing," or "self-existing," dwelt in the western sky. From their + lofty abode they could see, far away to the east, a number of inapertwa + creatures, that is, rudimentary human beings or incomplete men, whom it + was their mission to make into real men and women. For at that time there + were no real men and women; the rudimentary creatures (inapertwa) were of + various shapes and dwelt in groups along the shore of the salt water which + covered the country. These embryos, as we may call them, had no distinct + limbs or organs of sight, hearing, and smell; they did not eat food, and + they presented the appearance of human beings all doubled up into a + rounded mass, in which only the outline of the different parts of the body + could be vaguely perceived. Coming down from their home in the western + sky, armed with great stone knives, the Ungambikula took hold of the + embryos, one after the other. First of all they released the arms from the + bodies, then making four clefts at the end of each arm they fashioned + hands and fingers; afterwards legs, feet, and toes were added in the same + way. The figure could now stand; a nose was then moulded and the nostrils + bored with the fingers. A cut with the knife made the mouth, which was + pulled open several times to render it flexible. A slit on each side of + the face separated the upper and lower eye-lids, disclosing the eyes, + which already existed behind them; and a few strokes more completed the + body. Thus out of the rudimentary creatures were formed men and women. + These rudimentary creatures or embryos, we are told, "were in reality + stages in the transformation of various animals and plants into human + beings, and thus they were naturally, when made into human beings, + intimately associated with the particular animal or plant, as the case may + be, of which they were the transformations—in other words, each + individual of necessity belonged to a totem, the name of which was of + course that of the animal or plant of which he or she was a + transformation." However, it is not said that all the totemic clans of the + Arunta were thus developed; no such tradition, for example, is told to + explain the origin of the important Witchetty Grub clan. The clans which + are positively known, or at least said, to have originated out of embryos + in the way described are the Plum Tree, the Grass Seed, the Large Lizard, + the Small Lizard, the Alexandra Parakeet, and the Small Rat clans. When + the Ungambikula had thus fashioned people of these totems, they + circumcised them all, except the Plum Tree men, by means of a fire-stick. + After that, having done the work of creation or evolution, the Ungambikula + turned themselves into little lizards which bear a name meaning + "snappers-up of flies." (Baldwin Spencer and F.J. Gillen, "Native Tribes + of Central Australia" (London, 1899), pages 388 sq.; compare id., + "Northern Tribes of Central Australia" (London, 1904), page 150.) + </p> + <p> + This Arunta tradition of the origin of man, as Messrs Spencer and Gillen, + who have recorded it, justly observe, "is of considerable interest; it is + in the first place evidently a crude attempt to describe the origin of + human beings out of non-human creatures who were of various forms; some of + them were representatives of animals, others of plants, but in all cases + they are to be regarded as intermediate stages in the transition of an + animal or plant ancestor into a human individual who bore its name as that + of his or her totem." (Baldwin Spencer and F.J. Gillen, "Native Tribes of + Central Australia", pages 391 sq.) In a sense these speculations of the + Arunta on their own origin may be said to combine the theory of creation + with the theory of evolution; for while they represent men as developed + out of much simpler forms of life, they at the same time assume that this + development was effected by the agency of two powerful beings, whom so far + we may call creators. It is well known that at a far higher stage of + culture a crude form of the evolutionary hypothesis was propounded by the + Greek philosopher Empedocles. He imagined that shapeless lumps of earth + and water, thrown up by the subterranean fires, developed into monstrous + animals, bulls with the heads of men, men with the heads of bulls, and so + forth; till at last, these hybrid forms being gradually eliminated, the + various existing species of animals and men were evolved. (E. Zeller, "Die + Philosophie der Griechen", I.4 (Leipsic, 1876), pages 718 sq.; H. Ritter + et L. Preller, "Historia Philosophiae Graecae et Romanae ex fontium locis + contexta" 5, pages 102 sq. H. Diels, "Die Fragmente der Vorsokratiker" 2, + I. (Berlin, 1906), pages 190 sqq. Compare Lucretius "De rerum natura", V. + 837 sqq.) The theory of the civilised Greek of Sicily may be set beside + the similar theory of the savage Arunta of Central Australia. Both + represent gropings of the human mind in the dark abyss of the past; both + were in a measure grotesque anticipations of the modern theory of + evolution. + </p> + <p> + In this essay I have made no attempt to illustrate all the many various + and divergent views which primitive man has taken of his own origin. I + have confined myself to collecting examples of two radically different + views, which may be distinguished as the theory of creation and the theory + of evolution. According to the one, man was fashioned in his existing + shape by a god or other powerful being; according to the other he was + evolved by a natural process out of lower forms of animal life. Roughly + speaking, these two theories still divide the civilised world between + them. The partisans of each can appeal in support of their view to a large + consensus of opinion; and if truth were to be decided by weighing the one + consensus against the other, with "Genesis" in the one scale and "The + Origin of Species" in the other, it might perhaps be found, when the + scales were finally trimmed, that the balance hung very even between + creation and evolution. + </p> + <p> + <a name="link2H_4_0011" id="link2H_4_0011"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + X. THE INFLUENCE OF DARWIN ON THE STUDY OF ANIMAL EMBRYOLOGY. By A. + Sedgwick, M.A., F.R.S. + </h2> + <h3> + Professor of Zoology and Comparative Anatomy in the University of + Cambridge. + </h3> + <p> + The publication of "The Origin of Species" ushered in a new era in the + study of Embryology. Whereas, before the year 1859 the facts of anatomy + and development were loosely held together by the theory of types, which + owed its origin to the great anatomists of the preceding generation, to + Cuvier, L. Agassiz, J. Muller, and R. Owen, they were now combined + together into one organic whole by the theory of descent and by the + hypothesis of recapitulation which was deduced from that theory. The view + (First clearly enunciated by Fritz Muller in his well-known work, "Fur + Darwin", Leipzig, 1864; (English Edition, "Facts for Darwin", 1869).) that + a knowledge of embryonic and larval histories would lay bare the secrets + of race-history and enable the course of evolution to be traced, and so + lead to the discovery of the natural system of classification, gave a + powerful stimulus to morphological study in general and to embryological + investigation in particular. In Darwin's words: "Embryology rises greatly + in interest, when we look at the embryo as a picture, more or less + obscured, of the progenitor, either in its adult or larval state, of all + the members of the same great class." ("Origin" (6th edition), page 396.) + In the period under consideration the output of embryological work has + been enormous. No group of the animal kingdom has escaped exhaustive + examination and no effort has been spared to obtain the embryos of + isolated and out of the way forms, the development of which might have an + important bearing upon questions of phylogeny and classification. Marine + zoological stations have been established, expeditions have been sent to + distant countries, and the methods of investigation have been greatly + improved. The result of this activity has been that the main features of + the developmental history of all the most important animals are now known + and the curiosity as to developmental processes, so greatly excited by the + promulgation of the Darwinian theory, has to a considerable extent been + satisfied. + </p> + <p> + To what extent have the results of this vast activity fulfilled the + expectations of the workers who have achieved them? The Darwin centenary + is a fitting moment at which to take stock of our position. In this + inquiry we shall leave out of consideration the immense and intensely + interesting additions to our knowledge of Natural History. These may be + said to constitute a capital fund upon which philosophers, poets and men + of science will draw for many generations. The interest of Natural History + existed long before Darwinian evolution was thought of and will endure + without any reference to philosophic speculations. She is a mistress in + whose face are beauties and in whose arms are delights elsewhere + unattainable. She is and always has been pursued for her own sake without + any reference to philosophy, science, or utility. + </p> + <p> + Darwin's own views of the bearing of the facts of embryology upon + questions of wide scientific interest are perfectly clear. He writes + ("Origin" (6th edition), page 395.): + </p> + <p> + "On the other hand it is highly probable that with many animals the + embryonic or larval stages show us, more or less completely, the condition + of the progenitor of the whole group in its adult state. In the great + class of the Crustacea, forms wonderfully distinct from each other, + namely, suctorial parasites, cirripedes, entomostraca, and even the + malacostraca, appear at first as larvae under the nauplius-form; and as + these larvae live and feed in the open sea, and are not adapted for any + peculiar habits of life, and from other reasons assigned by Fritz Muller, + it is probable that at some very remote period an independent adult + animal, resembling the Nauplius, existed, and subsequently produced, along + several divergent lines of descent, the above-named great Crustacean + groups. So again it is probable, from what we know of the embryos of + mammals, birds, fishes, and reptiles, that these animals are the modified + descendants of some ancient progenitor, which was furnished in its adult + state with branchiae, a swim-bladder, four fin-like limbs, and a long + tail, all fitted for an aquatic life. + </p> + <p> + "As all the organic beings, extinct and recent, which have ever lived, can + be arranged within a few great classes; and as all within each class have, + according to our theory, been connected together by fine gradations, the + best, and, if our collections were nearly perfect, the only possible + arrangement, would be genealogical; descent being the hidden bond of + connexion which naturalists have been seeking under the term of the + Natural System. On this view we can understand how it is that, in the eyes + of most naturalists, the structure of the embryo is even more important + for classification than that of the adult. In two or more groups of + animals, however much they may differ from each other in structure and + habits in their adult condition, if they pass through closely similar + embryonic stages, we may feel assured that they all are descended from one + parent-form, and are therefore closely related. Thus, community in + embryonic structure reveals community of descent; but dissimilarity in + embryonic development does not prove discommunity of descent, for in one + of two groups the developmental stages may have been suppressed, or may + have been so greatly modified through adaptation to new habits of life, as + to be no longer recognisable. Even in groups, in which the adults have + been modified to an extreme degree, community of origin is often revealed + by the structure of the larvae; we have seen, for instance, that + cirripedes, though externally so like shell-fish, are at once known by + their larvae to belong to the great class of crustaceans. As the embryo + often shows us more or less plainly the structure of the less modified and + ancient progenitor of the group, we can see why ancient and extinct forms + so often resemble in their adult state the embryos of existing species of + the same class. Agassiz believes this to be a universal law of nature; and + we may hope hereafter to see the law proved true. It can, however, be + proved true only in those cases in which the ancient state of the + progenitor of the group has not been wholly obliterated, either by + successive variations having supervened at a very early period of growth, + or by such variations having been inherited at an earlier stage than that + at which they first appeared. It should also be borne in mind, that the + law may be true, but yet, owing to the geological record not extending far + enough back in time, may remain for a long period, or for ever, incapable + of demonstration. The law will not strictly hold good in those cases in + which an ancient form became adapted in its larval state to some special + line of life, and transmitted the same larval state to a whole group of + descendants; for such larvae will not resemble any still more ancient form + in its adult state." + </p> + <p> + As this passage shows, Darwin held that embryology was of interest because + of the light it seems to throw upon ancestral history (phylogeny) and + because of the help it would give in enabling us to arrive at a natural + system of classification. With regard to the latter point, he quotes with + approval the opinion that "the structure of the embryo is even more + important for classification than that of the adult." What justification + is there for this view? The phase of life chosen for the ordinary + anatomical and physiological studies, namely, the adult phase, is merely + one of the large number of stages of structure through which the organism + passes. By far the greater number of these are included in what is + specially called the developmental or (if we include larvae with embryos) + embryonic period, for the developmental changes are more numerous and take + place with greater rapidity at the beginning of life than in its later + periods. As each of these stages is equal in value, for our present + purpose, to the adult phase, it clearly follows that if there is anything + in the view that the anatomical study of organisms is of importance in + determining their mutual relations, the study of the organism in its + various embryonic (and larval) stages must have a greater importance than + the study of the single and arbitrarily selected stage of life called the + adult. + </p> + <p> + But a deeper reason than this has been assigned for the importance of + embryology in classification. It has been asserted, and is implied by + Darwin in the passage quoted, that the ancestral history is repeated in a + condensed form in the embryonic, and that a study of the latter enables us + to form a picture of the stages of structure through which the organism + has passed in its evolution. It enables us on this view to reconstruct the + pedigrees of animals and so to form a genealogical tree which shall be the + true expression of their natural relations. + </p> + <p> + The real question which we have to consider is to what extent the + embryological studies of the last 50 years have confirmed or rendered + probable this "theory of recapitulation." In the first place it must be + noted that the recapitulation theory is itself a deduction from the theory + of evolution. The facts of embryology, particularly of vertebrate + embryology, and of larval history receive, it is argued, an explanation on + the view that the successive stages of development are, on the whole, + records of adult stages of structure which the species has passed through + in its evolution. Whether this statement will bear a critical verbal + examination I will not now pause to inquire, for it is more important to + determine whether any independent facts can be alleged in favour of the + theory. If it could be shown, as was stated to be the case by L. Agassiz, + that ancient and extinct forms of life present features of structure now + only found in embryos, we should have a body of facts of the greatest + importance in the present discussion. But as Huxley (See Huxley's + "Scientific Memoirs", London, 1898, Vol. I. page 303: "There is no real + parallel between the successive forms assumed in the development of the + life of the individual at present, and those which have appeared at + different epochs in the past." See also his Address to the Geological + Society of London (1862) 'On the Palaeontological Evidence of Evolution', + ibid. Vol. II. page 512.) has shown and as the whole course of + palaeontological and embryological investigation has demonstrated, no such + statement can be made. The extinct forms of life are very similar to those + now existing and there is nothing specially embryonic about them. So that + the facts, as we know them, lend no support to theory. + </p> + <p> + But there is another class of facts which have been alleged in favour of + the theory, viz. the facts which have been included in the generalisation + known as the Law of v. Baer. The law asserts that embryos of different + species of animals of the same group are more alike than the adults and + that, the younger the embryo, the greater are the resemblances. If this + law could be established it would undoubtedly be a strong argument in + favour of the "recapitulation" explanation of the facts of embryology. But + its truth has been seriously disputed. If it were true we should expect to + find that the embryos of closely similar species would be + indistinguishable from one another, but this is notoriously not the case. + It is more difficult to meet the assertion when it is made in the form + given above, for here we are dealing with matters of opinion. For + instance, no one would deny that the embryo of a dogfish is different from + the embryo of a rabbit, but there is room for difference of opinion when + it is asserted that the difference is less than the difference between an + adult dogfish and an adult rabbit. It would be perfectly true to say that + the differences between the embryos concern other organs more than do the + differences between the adults, but who is prepared to affirm that the + presence of a cephalic coelom and of cranial segments, of external gills, + of six gill slits, of the kidney tubes opening into the muscle-plate + coelom, of an enormous yolk-sac, of a neurenteric canal, and the absence + of any trace of an amnion, of an allantois and of a primitive streak are + not morphological facts of as high an import as those implied by the + differences between the adults? The generalisation undoubtedly had its + origin in the fact that there is what may be called a family resemblance + between embryos and larvae, but this resemblance, which is by no means + exact, is largely superficial and does not extend to anatomical detail. + </p> + <p> + It is useless to say, as Weismann has stated ("The Evolution Theory", by + A. Weismann, English Translation, Vol. II. page 176, London, 1904.), that + "it cannot be disputed that the rudiments [vestiges his translator means] + of gill-arches and gill-clefts, which are peculiar to one stage of human + ontogeny, give us every ground for concluding that we possessed fish-like + ancestors." The question at issue is: did the pharyngeal arches and clefts + of mammalian embryos ever discharge a branchial function in an adult + ancestor of the mammalia? We cannot therefore, without begging the + question at issue in the grossest manner, apply to them the terms + "gill-arches" and "gill-clefts". That they are homologous with the + "gill-arches" and "gill-clefts" of fishes is true; but there is no + evidence to show that they ever discharged a branchial function. Until + such evidence is forthcoming, it is beside the point to say that it + "cannot be disputed" that they are evidence of a piscine ancestry. + </p> + <p> + It must, therefore, be admitted that one outcome of the progress of + embryological and palaeontological research for the last 50 years is + negative. The recapitulation theory originated as a deduction from the + evolution theory and as a deduction it still remains. + </p> + <p> + Let us before leaving the subject apply another test. If the evolution + theory and the recapitulation theory are both true, how is it that living + birds are not only without teeth but have no rudiments of teeth at any + stage of their existence? How is it that the missing digits in birds and + mammals, the missing or reduced limb of snakes and whales, the reduced + mandibulo-hyoid cleft of elasmobranch fishes are not present or relatively + more highly developed in the embryo than in the adult? How is it that when + a marked variation, such as an extra digit, or a reduced limb, or an extra + segment, makes its appearance, it is not confined to the adult but can be + seen all through the development? All the clear evidence we can get tends + to show that marked variations, whether of reduction or increase, of + organs are manifest during the whole of the development of the organ and + do not merely affect the adult. And on reflection we see that it could + hardly be otherwise. All such evidence is distinctly at variance with the + theory of recapitulation, at least as applied to embryos. In the case of + larvae of course the case will be different, for in them the organs are + functional, and reduction in the adult will not be accompanied by + reduction in the larva unless a change in the conditions of life of the + larva enables it to occur. + </p> + <p> + If after 50 years of research and close examination of the facts of + embryology the recapitulation theory is still without satisfactory proof, + it seems desirable to take a wider sweep and to inquire whether the facts + of embryology cannot be included in a larger category. + </p> + <p> + As has been pointed out by Huxley, development and life are co-extensive, + and it is impossible to point to any period in the life of an organism + when the developmental changes cease. It is true that these changes take + place more rapidly at the commencement of life, but they are never wholly + absent, and those which occur in the later or so-called adult stages of + life do not differ in their essence, however much they may differ in their + degree, from those which occur during the embryonic and larval periods. + This consideration at once brings the changes of the embryonic period into + the same category as those of the adult and suggests that an explanation + which will account for the one will account for the other. What then is + the problem we are dealing with? Surely it is this: Why does an organism + as soon as it is established at the fertilisation of the ovum enter upon a + cycle of transformations which never cease until death puts an end to + them? In other words what is the meaning of that cycle of changes which + all organisms present in a greater or less degree and which constitute the + very essence of life? It is impossible to give an answer to this question + so long as we remain within the precincts of Biology—and it is not + my present purpose to penetrate beyond those precincts into the realms of + philosophy. We have to do with an ultimate biological fact, with a + fundamental property of living matter, which governs and includes all its + other properties. How may this property be stated? Thus: it is a property + of living matter to react in a remarkable way to external forces without + undergoing destruction. The life-cycle, of which the embryonic and larval + periods are a part, consists of the orderly interaction between the + organism and its environment. The action of the environment produces + certain morphological changes in the organism. These changes enable the + organism to come into relation with new external forces, to move into what + is practically a new environment, which in its turn produces further + structural changes in the organism. These in their turn enable, indeed + necessitate, the organism to move again into a new environment, and so the + process continues until the structural changes are of such a nature that + the organism is unable to adapt itself to the environment in which it + finds itself. The essential condition of success in this process is that + the organism should always shift into the environment to which its new + structure is suited—any failure in this leading to the impairment of + the organism. In most cases the shifting of the environment is a very + gradual process (whether consisting in the very slight and gradual + alteration in the relation of the embryo as a whole to the egg-shell or + uterine wall, or in the relations of its parts to each other, or in the + successive phases of adult life), and the morphological changes in + connection with each step of it are but slight. But in some cases jumps + are made such as we find in the phenomena known as hatching, birth, and + metamorphosis. + </p> + <p> + This property of reacting to the environment without undergoing + destruction is, as has been stated, a fundamental property of organisms. + It is impossible to conceive of any matter, to which the term living could + be applied, being without it. And with this property of reacting to the + environment goes the further property of undergoing a change which alters + the relation of the organism to the old environment and places it in a new + environment. If this reasoning is correct, it necessarily follows that + this property must have been possessed by living matter at its first + appearance on the earth. In other words living matter must always have + presented a life-cycle, and the question arises what kind of modification + has that cycle undergone? Has it increased or diminished in duration and + complexity since organisms first appeared on the earth? The current view + is that the cycle was at first very short and that it has increased in + length by the evolutionary creation of new adult phases, that these new + phases are in addition to those already existing and that each of them as + it appears takes over from the preceding adult phase the functional + condition of the reproductive organs. According to the same view the old + adult phases are not obliterated but persist in a more or less modified + form as larval stages. It is further supposed that as the life-history + lengthens at one end by the addition of new adult phases, it is shortened + at the other by the abbreviation of embryonic development and by the + absorption of some of the early larval stages into the embryonic period; + but on the whole the lengthening process has exceeded that of shortening, + so that the whole life-history has, with the progress of evolution, become + longer and more complicated. + </p> + <p> + Now there can be no doubt that the life-history of organisms has been + shortened in the way above suggested, for cases are known in which this + can practically be seen to occur at the present day. But the process of + lengthening by the creation of new stages at the other end of the + life-cycle is more difficult to conceive and moreover there is no evidence + for its having occurred. This, indeed, may have occurred, as is suggested + below, but the evidence we have seems to indicate that evolutionary + modification has proceeded by ALTERING and not by SUPERSEDING: that is to + say that each stage in the life-history, as we see it to-day, has + proceeded from a corresponding stage in a former era by the modification + of that stage and not by the creation of a new one. Let me, at the risk of + repetition, explain my meaning more fully by taking a concrete + illustration. The mandibulo-hyoid cleft (spiracle) of the elasmobranch + fishes, the lateral digits of the pig's foot, the hind-limbs of whales, + the enlarged digit of the ostrich's foot are supposed to be organs which + have been recently modified. This modification is not confined to the + final adult stage of the life-history but characterises them throughout + the whole of their development. A stage with a reduced spiracle does not + proceed in development from a preceding stage in which the spiracle shows + no reduction: it is reduced at its first appearance. The same statement + may be made of organs which have entirely disappeared in the adult, such + as bird's teeth and snake's fore-limbs: the adult stage in which they have + disappeared is not preceded by embryonic stages in which the teeth and + limbs or rudiments of them are present. In fact the evidence indicates + that adult variations of any part are accompanied by precedent variations + in the same direction in the embryo. The evidence seems to show, not that + a stage is added on at the end of the life-history, but only that some of + the stages in the life-history are modified. Indeed, on the wider view of + development taken in this essay, a view which makes it coincident with + life, one would not expect often to find, even if new stages are added in + the course of evolution, that they are added at the end of the series when + the organism has passed through its reproductive period. It is possible of + course that new stages have been intercalated in the course of the + life-history, though it is difficult to see how this has occurred. It is + much more likely, if we may judge from available evidence, that every + stage has had its counterpart in the ancestral form from which it has been + derived by descent with modification. Just as the adult phase of the + living form differs, owing to evolutionary modification, from the adult + phase of the ancestor from which it has proceeded, so each larval phase + will differ for the same reason from the corresponding larval phase in the + life-history of the ancestor. Inasmuch as the organism is variable at + every stage of its independent existence and is exposed to the action of + natural selection there is no reason why it should escape modification at + any stage. + </p> + <p> + If there is any truth in these considerations it would seem to follow that + at the dawn of life the life-cycle must have been, either in posse or in + esse, at least as long as it is at the present time, and that the + peculiarity of passing through a series of stages in which new characters + are successively evolved is a primordial quality of living matter. + </p> + <p> + Before leaving this part of the subject, it is necessary to touch upon + another aspect of it. What are these variations in structure which succeed + one another in the life-history of an organism? I am conscious that I am + here on the threshold of a chamber which contains the clue to some of our + difficulties, and that I cannot enter it. Looked at from one point of view + they belong to the class of genetic variations, which depend upon the + structure or constitution of the protoplasm; but instead of appearing in + different zygotes (A zygote is a fertilised ovum, i.e. a new organism + resulting from the fusion of an ovum and a spermatozoon.), they are + present in the same zygote though at different times in its life-history. + They are of the same order as the mutational variations of the modern + biologist upon which the appearance of a new character depends. What is a + genetic or mutational variation? It is a genetic character which was not + present in either of the parents. But these "growth variations" were + present in the parents, and in this they differ from mutational + variations. But what are genetic characters? They are characters which + must appear if any development occurs. They are usually contrasted with + "acquired characters," using the expression "acquired character" in the + Lamarckian sense. But strictly speaking they ARE acquired characters, for + the zygote at first has none of the characters which it subsequently + acquires, but only the power of acquiring them in response to the action + of the environment. But the characters so acquired are not what we + technically understand and what Lamarck meant by "acquired characters." + They are genetic characters, as defined above. What then are Lamarck's + "acquired characters"? They are variations in genetic characters caused in + a particular way. There are, in fact, two kinds of variation in genetic + characters depending on the mode of causation. Firstly, there are those + variations consequent upon a variation in the constitution of the + protoplasm of a particular zygote, and independent of the environment in + which the organism develops, save in so far as this simply calls them + forth: these are the so-called genetic or mutational variations. Secondly, + there are those variations which occur in zygotes of similar germinal + constitution and which are caused solely by differences in the environment + to which the individuals are respectively exposed: these are the "acquired + characters" of Lamarck and of authors generally. In consequence of this + double sense in which the term "acquired characters" may be used, great + confusion may and does occur. If the protoplasm be compared to a machine, + and the external conditions to the hand that works the machine, then it + may be said that, as the machine can only work in one way, it can only + produce one kind of result (genetic character), but the particular form or + quality (Lamarckian "acquired character") of the result will depend upon + the hand that works the machine (environment), just as the quality of the + sound produced by a fiddle depends entirely upon the hand which plays upon + it. It would be improper to apply the term "mutation" to those genetic + characters which are not new characters or new variants of old characters, + but such genetic characters are of the same nature as those characters to + which the term mutation has been applied. It may be noticed in passing + that it is very questionable if the modern biologist has acted in the real + interests of science in applying the term mutation in the sense in which + he has applied it. The genetic characters of organisms come from one of + two sources: either they are old characters and are due to the action of + what we call inheritance or they are new and are due to what we call + variation. If the term mutation is applied to the actual alteration of the + machinery of the protoplasm, no objection can be felt to its use; but if + it be applied, as it is, to the product of the action of the altered + machine, viz. to the new genetic character, it leads to confusion. + Inheritance is the persistence of the structure of the machine; characters + are the products of the working of the machine; variation in genetic + characters is due to the alteration (mutation) in the arrangement of the + machinery, while variation in acquired characters (Lamarckian) is due to + differences in the mode of working the machinery. The machinery when it + starts (in the new zygote) has the power of grinding out certain results, + which we call the characters of the organism. These appear at successive + intervals of time, and the orderly manifestation of them is what we call + the life-history of the organism. This brings us back to the question with + which we started this discussion, viz. what is the relation of these + variations in structure, which successively appear in an organism and + constitute its life-history, to the mutational variations which appear in + different organisms of the same brood or species. The question is brought + home to us when we ask what is a bud-sport, such as a nectarine appearing + on a peach-tree? From one point of view, it is simply a mutation appearing + in asexual reproduction; from another it is one of these successional + characters ("growth variations") which constitute the life-history of the + zygote, for it appears in the same zygote which first produces a peach. + Here our analogy of a machine which only works in one way seems to fail + us, for these bud-sports do not appear in all parts of the organism, only + in certain buds or parts of it, so that one part of the zygotic machine + would appear to work differently to another. To discuss this question + further would take us too far from our subject. Suffice it to say that we + cannot answer it, any more than we can this further question of burning + interest at the present day, viz. to what extent and in what manner is the + machine itself altered by the particular way in which it is worked. In + connection with this question we can only submit one consideration: the + zygotic machine can, by its nature, only work once, so that any alteration + in it can only be ascertained by studying the replicas of it which are + produced in the reproductive organs. + </p> + <p> + It is a peculiarity that the result which we call the ripening of the + generative organs nearly always appears among the final products of the + action of the zygotic machine. It is remarkable that this should be the + case. What is the reason of it? The late appearance of functional + reproductive organs is almost a universal law, and the explanation of it + is suggested by expressing the law in another way, viz. that the machine + is almost always so constituted that it ceases to work efficiently soon + after the reproductive organs have sufficiently discharged their function. + Why this should occur we cannot explain: it is an ultimate fact of nature, + and cannot be included in any wider category. The period during which the + reproductive organs can act may be short as in ephemerids or long as in + man and trees, and there is no reason to suppose that their action damages + the vital machinery, though sometimes, as in the case of annual plants + (Metschnikoff), it may incidentally do so; but, long or short, the + cessation of their actions is always a prelude to the end. When they and + their action are impaired, the organism ceases to react with precision to + the environment, and the organism as a whole undergoes retrogressive + changes. + </p> + <p> + It has been pointed out above that there is reason to believe that at the + dawn of life the life-cycle was, EITHER IN ESSE OR IN POSSE, at least as + long as it is at the present time. The qualification implied by the words + in italics is necessary, for it is clearly possible that the external + conditions then existing were not suitable for the production of all the + stages of the potential life-history, and that what we call organic + evolution has consisted in a gradual evolution of new environments to + which the organism's innate capacity of change has enabled it to adapt + itself. We have warrant for this possibility in the case of the Axolotl + and in other similar cases of neoteny. And these cases further bring home + to us the fact, to which I have already referred, that the full + development of the functional reproductive organs is nearly always + associated with the final stages of the life-history. + </p> + <p> + On this view of the succession of characters in the life-history of + organisms, how shall we explain the undoubted fact that the development of + buds hardly ever presents any phenomena corresponding to the embryonic and + larval changes? The reason is clearly this, that budding usually occurs + after the embryonic stage is past; when the characters of embryonic life + have been worked out by the machine. When it takes place at an early stage + in embryonic life, as it does in cases of so-called embryonic fission, the + product shows, either partly or entirely, phenomena similar to those of + embryonic development. The only case known to me in which budding by the + adult is accompanied by morphological features similar to those displayed + by embryos is furnished by the budding of the medusiform spore-sacs of + hydrozoon polyps. But this case is exceptional, for here we have to do + with an attempt, which fails, to form a free-swimming organism, the + medusa; and the vestiges which appear in the buds are the umbrella-cavity, + marginal tentacles, circular canal, etc., of the medusa arrested in + development. + </p> + <p> + But the question still remains, are there no cases in which, as implied by + the recapitulation theory, variations in any organ are confined to the + period in which the organ is functional and do not affect it in the + embryonic stages? The teeth of the whalebone whales may be cited as a case + in which this is said to occur; but here the teeth are only imperfectly + developed in the embryo and are soon absorbed. They have been affected by + the change which has produced their disappearance in the adult, but not to + complete extinction. Nor are they now likely to be extinguished, for + having become exclusively embryonic they are largely protected from the + action of natural selection. This consideration brings up a most important + aspect of the question, so far as disappearing organs are concerned. Every + organ is laid down at a certain period in the embryo and undergoes a + certain course of growth until it obtains full functional development. + When for any cause reduction begins, it is affected at all stages of its + growth, unless it has functional importance in the larva, and in some + cases its life is shortened at one or both ends. In cases, as in that of + the whale's teeth, in which it entirely disappears in the adult, the + latter part of its life is cut off; in others, the beginning of its life + may be deferred. This happens, for instance, with the spiracle of many + Elasmobranchs, which makes its appearance after the hyobranchial cleft, + not before it as it should do, being anterior to it in position, and as it + does in the Amniota in which it shows no reduction in size as compared + with the other pharyngeal clefts. In those Elasmobranchs in which it is + absent in the adult but present in the embryo (e.g. Carcharias) its life + is shortened at both ends. Many more instances of organs, of which the + beginning and end have been cut off, might be mentioned; e.g. the + muscle-plate coelom of Aves, the primitive streak and the neurenteric + canal of amniote blastoderms. In yet other cases in which the reduced + organ is almost on the verge of disappearance, it may appear for a moment + and disappear more than once in the course of development. As an instance + of this striking phenomenon I may mention the neurenteric canal of avine + embryos, and the anterior neuropore of Ascidians. Lastly the reduced organ + may disappear in the developing stages before it does so in the adult. As + an instance of this may be mentioned the mandibular palp of those + Crustacea with zoaea larvae. This structure disappears in the larva only + to reappear in a reduced form in later stages. In all these cases we are + dealing with an organ which, we imagine, attained a fuller functional + development at some previous stage in race-history, but in most of them we + have no proof that it did so. It may be, and the possibility must not be + lost sight of, that these organs never were anything else than + functionless and that though they have been got rid of in the adult by + elimination in the course of time, they have been able to persist in + embryonic stages which are protected from the full action of natural + selection. There is no reason to suppose that living matter at its first + appearance differed from non-living matter in possessing only properties + conducive to its well-being and prolonged existence. No one thinks that + the properties of the various forms of inorganic matter are all strictly + related to external conditions. Of what use to the diamond is its high + specific gravity and high refrangibility, and to gold of its yellow colour + and great weight? These substances continue to exist in virtue of other + properties than these. It is impossible to suppose that the properties of + living matter at its first appearance were all useful to it, for even now + after aeons of elimination we find that it possesses many useless organs + and that many of its relations to the external world are capable of + considerable improvement. + </p> + <p> + In writing this essay I have purposely refrained from taking a definite + position with regard to the problems touched. My desire has been to write + a chapter showing the influence of Darwin's work so far as Embryology is + concerned, and the various points which come up for consideration in + discussing his views. Darwin was the last man who would have claimed + finality for any of his doctrines, but he might fairly have claimed to + have set going a process of intellectual fermentation which is still very + far from completion. + </p> + <p> + <a name="link2H_4_0012" id="link2H_4_0012"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + XI. THE PALAEONTOLOGICAL RECORD. By W.B. Scott. + </h2> + <h3> + Professor of Geology in the University of Princeton, U.S.A. + </h3> + <p> + I. ANIMALS. + </p> + <p> + To no branch of science did the publication of "The Origin of Species" + prove to be a more vivifying and transforming influence than to + Palaeontology. This science had suffered, and to some extent, still + suffers from its rather anomalous position between geology and biology, + each of which makes claim to its territory, and it was held in strict + bondage to the Linnean and Cuvierian dogma that species were immutable + entities. There is, however, reason to maintain that this strict bondage + to a dogma now abandoned, was not without its good side, and served the + purpose of keeping the infant science in leading-strings until it was able + to walk alone, and preventing a flood of premature generalisations and + speculations. + </p> + <p> + As Zittel has said: "Two directions were from the first apparent in + palaeontological research—a stratigraphical and a biological. + Stratigraphers wished from palaeontology mainly confirmation regarding the + true order or relative age of zones of rock-deposits in the field. + Biologists had, theoretically at least, the more genuine interest in + fossil organisms as individual forms of life." (Zittel, "History of + Geology and Palaeontology", page 363, London, 1901.) The geological or + stratigraphical direction of the science was given by the work of William + Smith, "the father of historical geology," in the closing decade of the + eighteenth century. Smith was the first to make a systematic use of + fossils in determining the order of succession of the rocks which make up + the accessible crust of the earth, and this use has continued, without + essential change, to the present day. It is true that the theory of + evolution has greatly modified our conceptions concerning the introduction + of new species and the manner in which palaeontological data are to be + interpreted in terms of stratigraphy, but, broadly speaking, the method + remains fundamentally the same as that introduced by Smith. + </p> + <p> + The biological direction of palaeontology was due to Cuvier and his + associates, who first showed that fossils were not merely varieties of + existing organisms, but belonged to extinct species and genera, an + altogether revolutionary conception, which startled the scientific world. + Cuvier made careful studies, especially of fossil vertebrates, from the + standpoint of zoology and was thus the founder of palaeontology as a + biological science. His great work on "Ossements Fossiles" (Paris, 1821) + has never been surpassed as a masterpiece of the comparative method of + anatomical investigation, and has furnished to the palaeontologist the + indispensable implements of research. + </p> + <p> + On the other hand, Cuvier's theoretical views regarding the history of the + earth and its successive faunas and floras are such as no one believes + to-day. He held that the earth had been repeatedly devastated by great + cataclysms, which destroyed every living thing, necessitating an entirely + new creation, thus regarding the geological periods as sharply demarcated + and strictly contemporaneous for the whole earth, and each species of + animal and plant as confined to a single period. Cuvier's immense + authority and his commanding personality dominated scientific thought for + more than a generation and marked out the line which the development of + palaeontology was to follow. The work was enthusiastically taken up by + many very able men in the various European countries and in the United + States, but, controlled as it was by the belief in the fixity of species, + it remained almost entirely descriptive and consisted in the description + and classification of the different groups of fossil organisms. As already + intimated, this narrowness of view had its compensations, for it deferred + generalisations until some adequate foundations for these had been laid. + </p> + <p> + Dominant as it was, Cuvier's authority was slowly undermined by the + progress of knowledge and the way was prepared for the introduction of + more rational conceptions. The theory of "Catastrophism" was attacked by + several geologists, most effectively by Sir Charles Lyell, who greatly + amplified the principles enunciated by Hutton and Playfair in the + preceding century, and inaugurated a new era in geology. Lyell's + uniformitarian views of the earth's history and of the agencies which had + wrought its changes, had undoubted effect in educating men's minds for the + acceptance of essentially similar views regarding the organic world. In + palaeontology too the doctrine of the immutability of species, though + vehemently maintained and reasserted, was gradually weakening. In + reviewing long series of fossils, relations were observed which pointed to + genetic connections and yet were interpreted as purely ideal. Agassiz, for + example, who never accepted the evolutionary theory, drew attention to + facts which could be satisfactorily interpreted only in terms of that + theory. Among the fossils he indicated "progressive," "synthetic," + "prophetic," and "embryonic" types, and pointed out the parallelism which + obtains between the geological succession of ancient animals and the + ontogenetic development of recent forms. In Darwin's words: "This view + accords admirably well with our theory." ("Origin of Species" (6th + edition), page 310.) Of similar import were Owen's views on "generalised + types" and "archetypes." + </p> + <p> + The appearance of "The Origin of Species" in 1859 revolutionised all the + biological sciences. From the very nature of the case, Darwin was + compelled to give careful consideration to the palaeontological evidence; + indeed, it was the palaeontology and modern distribution of animals in + South America which first led him to reflect upon the great problem. In + his own words: "I had been deeply impressed by discovering in the Pampean + formation great fossil animals covered with armour like that on the + existing armadillos; secondly, by the manner in which closely allied + animals replace one another in proceeding southward over the Continent; + and thirdly, by the South American character of most of the productions of + the Galapagos archipelago, and more especially by the manner in which they + differ slightly on each island of the group." ("Life and Letters of + Charles Darwin", I. page 82.) In the famous tenth and eleventh chapters of + the "Origin", the palaeontological evidence is examined at length and the + imperfection of the geological record is strongly emphasised. The + conclusion is reached, that, in view of this extreme imperfection, + palaeontology could not reasonably be expected to yield complete and + convincing proof of the evolutionary theory. "I look at the geological + record as a history of the world imperfectly kept, and written in a + changing dialect; of this history we possess the last volume alone, + relating only to two or three countries. Of this volume, only here and + there a short chapter has been preserved; and of each page, only here and + there a few lines." ("Origin of Species", page 289.) Yet, aside from these + inevitable difficulties, he concludes, that "the other great leading facts + in palaeontology agree admirably with the theory of descent with + modification through variation and natural selection." (Ibid. page 313.) + </p> + <p> + Darwin's theory gave an entirely new significance and importance to + palaeontology. Cuvier's conception of the science had been a limited, + though a lofty one. "How glorious it would be if we could arrange the + organised products of the universe in their chronological order!... The + chronological succession of organised forms, the exact determination of + those types which appeared first, the simultaneous origin of certain + species and their gradual decay, would perhaps teach us as much about the + mysteries of organisation as we can possibly learn through experiments + with living organisms." (Zittel op. cit. page 140.) This, however, was + rather the expression of a hope for the distant future than an account of + what was attainable, and in practice the science remained almost purely + descriptive, until Darwin gave it a new standpoint, new problems and an + altogether fresh interest and charm. The revolution thus accomplished is + comparable only to that produced by the Copernican astronomy. + </p> + <p> + From the first it was obvious that one of the most searching tests of the + evolutionary theory would be given by the advance of palaeontological + discovery. However imperfect the geological record might be, its + ascertained facts would necessarily be consistent, under any reasonable + interpretation, with the demands of a true theory; otherwise the theory + would eventually be overwhelmed by the mass of irreconcilable data. A very + great stimulus was thus given to geological investigation and to the + exploration of new lands. In the last forty years, the examination of + North and South America, of Africa and Asia has brought to light many + chapters in the history of life, which are astonishingly full and + complete. The flood of new material continues to accumulate at such a rate + that it is impossible to keep abreast of it, and the very wealth of the + collections is a source of difficulty and embarrassment. In modern + palaeontology phylogenetic questions and problems occupy a foremost place + and, as a result of the labours of many eminent investigators in many + lands, it may be said that this science has proved to be one of the most + solid supports of Darwin's theory. True, there are very many unsolved + problems, and the discouraged worker is often tempted to believe that the + fossils raise more questions than they answer. Yet, on the other hand, the + whole trend of the evidence is so strongly in favour of the evolutionary + doctrine, that no other interpretation seems at all rational. + </p> + <p> + To present any adequate account of the palaeontological record from the + evolutionary standpoint, would require a large volume and a singularly + unequal, broken and disjointed history it would be. Here the record is + scanty, interrupted, even unintelligible, while there it is crowded with + embarrassing wealth of material, but too often these full chapters are + separated by such stretches of unrecorded time, that it is difficult to + connect them. It will be more profitable to present a few illustrative + examples than to attempt an outline of the whole history. + </p> + <p> + At the outset, the reader should be cautioned not to expect too much, for + the task of determining phylogenies fairly bristles with difficulties and + encounters many unanswered questions. Even when the evidence seems to be + as copious and as complete as could be wished, different observers will + put different interpretations upon it, as in the notorious case of the + Steinheim shells. (In the Miocene beds of Steinheim, Wurtemberg, occur + countless fresh-water shells, which show numerous lines of modification, + but these have been very differently interpreted by different writers.) + The ludicrous discrepances which often appear between the phylogenetic + "trees" of various writers have cast an undue discredit upon the science + and have led many zoologists to ignore palaeontology altogether as + unworthy of serious attention. One principal cause of these discrepant and + often contradictory results is our ignorance concerning the exact modes of + developmental change. What one writer postulates as almost axiomatic, + another will reject as impossible and absurd. Few will be found to agree + as to how far a given resemblance is offset by a given unlikeness, and so + long as the question is one of weighing evidence and balancing + probabilities, complete harmony is not to be looked for. These formidable + difficulties confront us even in attempting to work out from abundant + material a brief chapter in the phylogenetic history of some small and + clearly limited group, and they become disproportionately greater, when we + extend our view over vast periods of time and undertake to determine the + mutual relationships of classes and types. If the evidence were complete + and available, we should hardly be able to unravel its infinite + complexity, or to find a clue through the mazes of the labyrinth. "Our + ideas of the course of descent must of necessity be diagrammatic." (D.H. + Scott, "Studies in Fossil Botany", page 524. London, 1900.) + </p> + <p> + Some of the most complete and convincing examples of descent with + modification are to be found among the mammals, and nowhere more + abundantly than in North America, where the series of continental + formations, running through the whole Tertiary period, is remarkably full. + Most of these formations contain a marvellous wealth of mammalian remains + and in an unusual state of preservation. The oldest Eocene (Paleocene) has + yielded a mammalian fauna which is still of prevailingly Mesozoic + character, and contains but few forms which can be regarded as ancestral + to those of later times. The succeeding fauna of the lower Eocene proper + (Wasatch stage) is radically different and, while a few forms continue + over from the Paleocene, the majority are evidently recent immigrants from + some region not yet identified. From the Wasatch onward, the development + of many phyla may be traced in almost unbroken continuity, though from + time to time the record is somewhat obscured by migrations from the Old + World and South America. As a rule, however, it is easy to distinguish + between the immigrant and the indigenous elements of the fauna. + </p> + <p> + From their gregarious habits and individual abundance, the history of many + hoofed animals is preserved with especial clearness. So well known as to + have become a commonplace, is the phylogeny of the horses, which, contrary + to all that would have been expected, ran the greater part of its course + in North America. So far as it has yet been traced, the line begins in the + lower Eocene with the genus Eohippus, a little creature not much larger + than a cat, which has a short neck, relatively short limbs, and in + particular, short feet, with four functional digits and a splint-like + rudiment in the fore-foot, three functional digits and a rudiment in the + hind-foot. The forearm bones (ulna and radius) are complete and separate, + as are also the bones of the lower leg (fibula and tibia). The skull has a + short face, with the orbit, or eye-socket, incompletely enclosed with + bone, and the brain-case is slender and of small capacity. The teeth are + short-crowned, the incisors without "mark," or enamel pit, on the cutting + edge; the premolars are all smaller and simpler than the molars. The + pattern of the upper molars is so entirely different from that seen in the + modern horses that, without the intermediate connecting steps, no one + would have ventured to derive the later from the earlier plan. This + pattern is quadritubercular, with four principal, conical cusps arranged + in two transverse pairs, forming a square, and two minute cuspules between + each transverse pair, a tooth which is much more pig-like than horse-like. + In the lower molars the cusps have already united to form two crescents, + one behind the other, forming a pattern which is extremely common in the + early representatives of many different families, both of the + Perissodactyla and the Artiodactyla. In spite of the manifold differences + in all parts of the skeleton between Eohippus and the recent horses, the + former has stamped upon it an equine character which is unmistakable, + though it can hardly be expressed in words. + </p> + <p> + Each one of the different Eocene and Oligocene horizons has its + characteristic genus of horses, showing a slow, steady progress in a + definite direction, all parts of the structure participating in the + advance. It is not necessary to follow each of these successive steps of + change, but it should be emphasised that the changes are gradual and + uninterrupted. The genus Mesohippus, of the middle Oligocene, may be + selected as a kind of half-way stage in the long progression. Comparing + Mesohippus with Eohippus, we observe that the former is much larger, some + species attaining the size of a sheep, and has a relatively longer neck, + longer limbs and much more elongate feet, which are tridactyl, and the + middle toe is so enlarged that it bears most of the weight, while the + lateral digits are very much more slender. The fore-arm bones have begun + to co-ossify and the ulna is greatly reduced, while the fibula, though + still complete, is hardly more than a thread of bone. The skull has a + longer face and a nearly enclosed orbit, and the brain-case is fuller and + more capacious, the internal cast of which shows that the brain was richly + convoluted. The teeth are still very short-crowned, but the upper incisors + plainly show the beginning of the "mark"; the premolars have assumed the + molar form, and the upper molars, though plainly derived from those of + Eohippus, have made a long stride toward the horse pattern, in that the + separate cusps have united to form a continuous outer wall and two + transverse crests. + </p> + <p> + In the lower Miocene the interesting genus Desmatippus shows a further + advance in the development of the teeth, which are beginning to assume the + long-crowned shape, delaying the formation of roots; a thin layer of + cement covers the crowns, and the transverse crests of the upper grinding + teeth display an incipient degree of their modern complexity. This + tooth-pattern is strictly intermediate between the recent type and the + ancient type seen in Mesohippus and its predecessors. The upper Miocene + genera, Protohippus and Hipparion are, to all intents and purposes, modern + in character, but their smaller size, tridactyl feet and somewhat + shorter-crowned teeth are reminiscences of their ancestry. + </p> + <p> + From time to time, when a land-connection between North America and + Eurasia was established, some of the successive equine genera migrated to + the Old World, but they do not seem to have gained a permanent footing + there until the end of the Miocene or beginning of the Pliocene, + eventually diversifying into the horses, asses, and zebras of Africa, Asia + and Europe. At about the same period, the family extended its range to + South America and there gave rise to a number of species and genera, some + of them extremely peculiar. For some unknown reason, all the horse tribe + had become extinct in the western hemisphere before the European + discovery, but not until after the native race of man had peopled the + continents. + </p> + <p> + In addition to the main stem of equine descent, briefly considered in the + foregoing paragraphs, several side-branches were given off at successive + levels of the stem. Most of these branches were short-lived, but some of + them flourished for a considerable period and ramified into many species. + </p> + <p> + Apparently related to the horses and derived from the same root-stock is + the family of the Palaeotheres, confined to the Eocene and Oligocene of + Europe, dying out without descendants. In the earlier attempts to work out + the history of the horses, as in the famous essay of Kowalevsky ("Sur + l'Anchitherium aurelianense Cuv. et sur l'histoire paleontologique des + Chevaux", "Mem. de l'Acad. Imp. des Sc. de St Petersbourg", XX. no. 5, + 1873.), the Palaeotheres were placed in the direct line, because the + number of adequately known Eocene mammals was then so small, that Cuvier's + types were forced into various incongruous positions, to serve as + ancestors for unrelated series. + </p> + <p> + The American family of the Titanotheres may also be distantly related to + the horses, but passed through an entirely different course of + development. From the lower Eocene to the lower sub-stage of the middle + Oligocene the series is complete, beginning with small and rather lightly + built animals. Gradually the stature and massiveness increase, a + transverse pair of nasal horns make their appearance and, as these + increase in size, the canine tusks and incisors diminish correspondingly. + Already in the oldest known genus the number of digits had been reduced to + four in the fore-foot and three in the hind, but there the reduction + stops, for the increasing body-weight made necessary the development of + broad and heavy feet. The final members of the series comprise only large, + almost elephantine animals, with immensely developed and very various + nasal horns, huge and massive heads, and altogether a grotesque + appearance. The growth of the brain did not at all keep pace with the + increase of the head and body, and the ludicrously small brain may will + have been one of the factors which determined the startlingly sudden + disappearance and extinction of the group. + </p> + <p> + Less completely known, but of unusual interest, is the genealogy of the + rhinoceros family, which probably, though not certainly, was likewise of + American origin. The group in North America at least, comprised three + divisions, or sub-families, of very different proportions, appearance and + habits, representing three divergent lines from the same stem. Though the + relationship between the three lines seems hardly open to question, yet + the form ancestral to all of them has not yet been identified. This is + because of our still very incomplete knowledge of several perissodactyl + genera of the Eocene, any one of which may eventually prove to be the + ancestor sought for. + </p> + <p> + The first sub-family is the entirely extinct group of Hyracodonts, which + may be traced in successive modifications through the upper Eocene, lower + and middle Oligocene, then disappearing altogether. As yet, the + hyracodonts have been found only in North America, and the last genus of + the series, Hyracodon, was a cursorial animal. Very briefly stated, the + modifications consist in a gradual increase in size, with greater + slenderness of proportions, accompanied by elongation of the neck, limbs, + and feet, which become tridactyl and very narrow. The grinding teeth have + assumed the rhinoceros-like pattern and the premolars resemble the molars + in form; on the other hand, the front teeth, incisors and canines, have + become very small and are useless as weapons. As the animal had no horns, + it was quite defenceless and must have found its safety in its swift + running, for Hyracodon displays many superficial resemblances to the + contemporary Oligocene horses, and was evidently adapted for speed. It may + well have been the competition of the horses which led to the extinction + of these cursorial rhinoceroses. + </p> + <p> + The second sub-family, that of the Amynodonts, followed a totally + different course of development, becoming short-legged and short-footed, + massive animals, the proportions of which suggest aquatic habits; they + retained four digits in the front foot. The animal was well provided with + weapons in the large canine tusks, but was without horns. Some members of + this group extended their range to the Old World, but they all died out in + the middle Oligocene, leaving no successors. + </p> + <p> + The sub-family of the true rhinoceroses cannot yet be certainly traced + farther back than to the base of the middle Oligocene, though some + fragmentary remains found in the lower Oligocene are probably also + referable to it. The most ancient and most primitive member of this series + yet discovered, the genus Trigonias, is unmistakably a rhinoceros, yet + much less massive, having more the proportions of a tapir; it had four + toes in the front foot, three in the hind, and had a full complement of + teeth, except for the lower canines, though the upper canines are about to + disappear, and the peculiar modification of the incisors, characteristic + of the true rhinoceroses, is already apparent; the skull is hornless. + Representatives of this sub-family continue through the Oligocene and + Miocene of North America, becoming rare and localised in the Pliocene and + then disappearing altogether. In the Old World, on the other hand, where + the line appeared almost as early as it did in America, this group + underwent a great expansion and ramification, giving rise not only to the + Asiatic and African forms, but also to several extinct series. + </p> + <p> + Turning now to the Artiodactyla, we find still another group of mammals, + that of the camels and llamas, which has long vanished from North America, + yet took its rise and ran the greater part of its course in that + continent. From the lower Eocene onward the history of this series is + substantially complete, though much remains to be learned concerning the + earlier members of the family. The story is very like that of the horses, + to which in many respects it runs curiously parallel. Beginning with very + small, five-toed animals, we observe in the successive genera a gradual + transformation in all parts of the skeleton, an elongation of the neck, + limbs and feet, a reduction of the digits from five to two, and eventually + the coalescence of the remaining two digits into a "cannon-bone." The + grinding teeth, by equally gradual steps, take on the ruminant pattern. In + the upper Miocene the line divides into the two branches of the camels and + llamas, the former migrating to Eurasia and the latter to South America, + though representatives of both lines persisted in North America until a + very late period. Interesting side-branches of this line have also been + found, one of which ended in the upper Miocene in animals which had almost + the proportions of the giraffes and must have resembled them in + appearance. + </p> + <p> + The American Tertiary has yielded several other groups of ruminant-like + animals, some of which form beautifully complete evolutionary series, but + space forbids more than this passing mention of them. + </p> + <p> + It was in Europe that the Artiodactyla had their principal development, + and the upper Eocene, Oligocene and Miocene are crowded with such an + overwhelming number and variety of forms that it is hardly possible to + marshal them in orderly array and determine their mutual relationships. + Yet in this chaotic exuberance of life, certain important facts stand out + clearly, among these none is of greater interest and importance than the + genealogy of the true Ruminants, or Pecora, which may be traced from the + upper Eocene onward. The steps of modification and change are very similar + to those through which the camel phylum passed in North America, but it is + instructive to note that, despite their many resemblances, the two series + can be connected only in their far distant beginnings. The pecoran stock + became vastly more expanded and diversified than did the camel line and + was evidently more plastic and adaptable, spreading eventually over all + the continents except Australia, and forming to-day one of the dominant + types of mammals, while the camels are on the decline and not far from + extinction. The Pecora successively ramified into the deer, antelopes, + sheep, goats and oxen, and did not reach North America till the Miocene, + when they were already far advanced in specialisation. To this invasion of + the Pecora, or true ruminants, it seems probable that the decline and + eventual disappearance of the camels is to be ascribed. + </p> + <p> + Recent discoveries in Egypt have thrown much light upon a problem which + long baffled the palaeontologist, namely, the origin of the elephants. + (C.W. Andrews, "On the Evolution of the Proboscidea", "Phil. Trans. Roy. + Soc." London, Vol. 196, 1904, page 99.) Early representatives of this + order, Mastodons, had appeared almost simultaneously (in the geological + sense of that word) in the upper Miocene of Europe and North America, but + in neither continent was any more ancient type known which could plausibly + be regarded as ancestral to them. Evidently, these problematical animals + had reached the northern continents by migrating from some other region, + but no one could say where that region lay. The Eocene and Oligocene beds + of the Fayoum show us that the region sought for is Africa, and that the + elephants form just such a series of gradual modifications as we have + found among other hoofed animals. The later steps of the transformation, + by which the mastodons lost their lower tusks, and their relatively small + and simple grinding teeth acquired the great size and highly complex + structure of the true elephants, may be followed in the uppermost Miocene + and Pliocene fossils of India and southern Europe. + </p> + <p> + Egypt has also of late furnished some very welcome material which + contributes to the solution of another unsolved problem which had quite + eluded research, the origin of the whales. The toothed-whales may be + traced back in several more or less parallel lines as far as the lower + Miocene, but their predecessors in the Oligocene are still so incompletely + known that safe conclusions can hardly be drawn from them. In the middle + Eocene of Egypt, however, has been found a small, whale-like animal + (Protocetus), which shows what the ancestral toothed-whale was like, and + at the same time seems to connect these thoroughly marine mammals with + land-animals. Though already entirely adapted to an aquatic mode of life, + the teeth, skull and backbone of Protocetus display so many differences + from those of the later whales and so many approximations to those of + primitive, carnivorous land-mammals, as, in a large degree, to bridge over + the gap between the two groups. Thus one of the most puzzling of + palaeontological questions is in a fair way to receive a satisfactory + answer. The origin of the whalebone-whales and their relations to the + toothed-whales cannot yet be determined, since the necessary fossils have + not been discovered. + </p> + <p> + Among the carnivorous mammals, phylogenetic series are not so clear and + distinct as among the hoofed animals, chiefly because the carnivores are + individually much less abundant, and well-preserved skeletons are among + the prizes of the collector. Nevertheless, much has already been learned + concerning the mutual relations of the carnivorous families, and several + phylogenetic series, notably that of the dogs, are quite complete. It has + been made extremely probable that the primitive dogs of the Eocene + represent the central stock, from which nearly or quite all the other + families branched off, though the origin and descent of the cats have not + yet been determined. + </p> + <p> + It should be clearly understood that the foregoing account of mammalian + descent is merely a selection of a few representative cases and might be + almost indefinitely extended. Nothing has been said, for example, of the + wonderful museum of ancient mammalian life which is entombed in the rocks + of South America, especially of Patagonia, and which opens a world so + entirely different from that of the northern continents, yet exemplifying + the same laws of "descent with modification." Very beautiful phylogenetic + series have already been established among these most interesting and + marvellously preserved fossils, but lack of space forbids a consideration + of them. + </p> + <p> + The origin of the mammalia, as a class, offers a problem of which + palaeontology can as yet present no definitive solution. Many + morphologists regard the early amphibia as the ancestral group from which + the mammals were derived, while most palaeontologists believe that the + mammals are descended from the reptiles. The most ancient known mammals, + those from the upper Triassic of Europe and North America, are so + extremely rare and so very imperfectly known, that they give little help + in determining the descent of the class, but, on the other hand, certain + reptilian orders of the Permian period, especially well represented in + South Africa, display so many and such close approximations to mammalian + structure, as strongly to suggest a genetic relationship. It is difficult + to believe that all those likenesses should have been independently + acquired and are without phylogenetic significance. + </p> + <p> + Birds are comparatively rare as fossils and we should therefore look in + vain among them for any such long and closely knit series as the mammals + display in abundance. Nevertheless, a few extremely fortunate discoveries + have made it practically certain that birds are descended from reptiles, + of which they represent a highly specialised branch. The most ancient + representative of this class is the extraordinary genus Archaeopteryx from + the upper Jurassic of Bavaria, which, though an unmistakable bird, retains + so many reptilian structures and characteristics as to make its derivation + plain. Not to linger over anatomical minutiae, it may suffice to mention + the absence of a horny beak, which is replaced by numerous true teeth, and + the long lizard-like tail, which is made up of numerous distinct + vertebrae, each with a pair of quill-like feathers attached to it. Birds + with teeth are also found in the Cretaceous, though in most other respects + the birds of that period had attained a substantially modern structure. + Concerning the interrelations of the various orders and families of birds, + palaeontology has as yet little to tell us. + </p> + <p> + The life of the Mesozoic era was characterised by an astonishing number + and variety of reptiles, which were adapted to every mode of life, and + dominated the air, the sea and the land, and many of which were of + colossal proportions. Owing to the conditions of preservation which + obtained during the Mesozoic period, the history of the reptiles is a + broken and interrupted one, so that we can make out many short series, + rather than any one of considerable length. While the relations of several + reptilian orders can be satisfactorily determined, others still baffle us + entirely, making their first known appearance in a fully differentiated + state. We can trace the descent of the sea-dragons, the Ichthyosaurs and + Plesiosaurs, from terrestrial ancestors, but the most ancient turtles yet + discovered show us no closer approximation to any other order than do the + recent turtles; and the oldest known Pterosaurs, the flying dragons of the + Jurassic, are already fully differentiated. There is, however, no ground + for discouragement in this, for the progress of discovery has been so + rapid of late years, and our knowledge of Mesozoic life has increased with + such leaps and bounds, that there is every reason to expect a solution of + many of the outstanding problems in the near future. + </p> + <p> + Passing over the lower vertebrates, for lack of space to give them any + adequate consideration, we may briefly take up the record of invertebrate + life. From the overwhelming mass of material it is difficult to make a + representative selection and even more difficult to state the facts + intelligibly without the use of unduly technical language and without the + aid of illustrations. + </p> + <p> + Several groups of the Mollusca, or shell-fish, yield very full and + convincing evidence of their descent from earlier and simpler forms, and + of these none is of greater interest than the Ammonites, an extinct order + of the cephalopoda. The nearest living ally of the ammonites is the pearly + nautilus, the other existing cephalopods, such as the squids, cuttle-fish, + octopus, etc., are much more distantly related. Like the nautilus, the + ammonites all possess a coiled and chambered shell, but their especial + characteristic is the complexity of the "sutures." By sutures is meant the + edges of the transverse partitions, or septa, where these join the + shell-wall, and their complexity in the fully developed genera is + extraordinary, forming patterns like the most elaborate oak-leaf + embroidery, while in the nautiloids the sutures form simple curves. In the + rocks of the Mesozoic era, wherever conditions of preservation are + favourable, these beautiful shells are stored in countless multitudes, of + an incredible variety of form, size and ornamentation, as is shown by the + fact that nearly 5000 species have already been described. The ammonites + are particularly well adapted for phylogenetic studies, because, by + removing the successive whorls of the coiled shell, the individual + development may be followed back in inverse order, to the microscopic + "protoconch," or embryonic shell, which lies concealed in the middle of + the coil. Thus the valuable aid of embryology is obtained in determining + relationships. + </p> + <p> + The descent of the ammonites, taken as a group, is simple and clear; they + arose as a branch of the nautiloids in the lower Devonian, the shells + known as goniatites having zigzag, angulated sutures. Late in the + succeeding Carboniferous period appear shells with a truly ammonoid + complexity of sutures, and in the Permian their number and variety cause + them to form a striking element of the marine faunas. It is in the + Mesozoic era, however, that these shells attain their full development; + increasing enormously in the Triassic, they culminate in the Jurassic in + the number of families, genera and species, in the complexity of the + sutures, and in the variety of shell-ornamentation. A slow decline begins + in the Cretaceous, ending in the complete extinction of the whole group at + the end of that period. As a final phase in the history of the ammonites, + there appear many so-called "abnormal" genera, in which the shell is + irregularly coiled, or more or less uncoiled, in some forms becoming + actually straight. It is interesting to observe that some of these genera + are not natural groups, but are "polyphyletic," i.e. are each derived from + several distinct ancestral genera, which have undergone a similar kind of + degeneration. + </p> + <p> + In the huge assembly of ammonites it is not yet possible to arrange all + the forms in a truly natural classification, which shall express the + various interrelations of the genera, yet several beautiful series have + already been determined. In these series the individual development of the + later general shows transitory stages which are permanent in antecedent + genera. To give a mere catalogue of names without figures would not make + these series more intelligible. + </p> + <p> + The Brachiopoda, or "lamp-shells," are a phylum of which comparatively few + survive to the present day; their shells have a superficial likeness to + those of the bivalved Mollusca, but are not homologous with the latter, + and the phylum is really very distinct from the molluscs. While greatly + reduced now, these animals were incredibly abundant throughout the + Palaeozoic era, great masses of limestone being often composed almost + exclusively of their shells, and their variety is in keeping with their + individual abundance. As in the case of the ammonites, the problem is to + arrange this great multitude of forms in an orderly array that shall + express the ramifications of the group according to a genetic system. For + many brachiopods, both recent and fossil, the individual development, or + ontogeny, has been worked out and has proved to be of great assistance in + the problems of classification and phylogeny. Already very encouraging + progress has been made in the solution of these problems. All brachiopods + form first a tiny, embryonic shell, called the protegulum, which is + believed to represent the ancestral form of the whole group, and in the + more advanced genera the developmental stages clearly indicate the + ancestral genera of the series, the succession of adult forms in time + corresponding to the order of the ontogenetic stages. The transformation + of the delicate calcareous supports of the arms, often exquisitely + preserved, are extremely interesting. Many of the Palaeozoic genera had + these supports coiled like a pair of spiral springs, and it has been shown + that these genera were derived from types in which the supports were + simply shelly loops. + </p> + <p> + The long extinct class of crustacea known as the Trilobites are likewise + very favourable subjects for phylogenetic studies. So far as the known + record can inform us, the trilobites are exclusively Palaeozoic in + distribution, but their course must have begun long before that era, as is + shown by the number of distinct types among the genera of the lower + Cambrian. The group reached the acme of abundance and relative importance + in the Cambrian and Ordovician; then followed a long, slow decline, ending + in complete and final disappearance before the end of the Permian. The + newly-hatched and tiny trilobite larva, known as the protaspis, is very + near to the primitive larval form of all the crustacea. By the aid of the + correlated ontogenetic stages and the succession of the adult forms in the + rocks, many phylogenetic series have been established and a basis for the + natural arrangement of the whole class has been laid. + </p> + <p> + Very instructive series may also be observed among the Echinoderms and, + what is very rare, we are able in this sub-kingdom to demonstrate the + derivation of one class from another. Indeed, there is much reason to + believe that the extinct class Cystidea of the Cambrian is the ancestral + group, from which all the other Echinoderms, star-fishes, brittle-stars, + sea-urchins, feather-stars, etc., are descended. + </p> + <p> + The foregoing sketch of the palaeontological record is, of necessity, + extremely meagre, and does not represent even an outline of the evidence, + but merely a few illustrative examples, selected almost at random from an + immense body of material. However, it will perhaps suffice to show that + the geological record is not so hopelessly incomplete as Darwin believed + it to be. Since "The Origin of Species" was written, our knowledge of that + record has been enormously extended and we now possess, no complete + volumes, it is true, but some remarkably full and illuminating chapters. + The main significance of the whole lies in the fact, that JUST IN + PROPORTION TO THE COMPLETENESS OF THE RECORD IS THE UNEQUIVOCAL CHARACTER + OF ITS TESTIMONY TO THE TRUTH OF THE EVOLUTIONARY THEORY. + </p> + <p> + The test of a true, as distinguished from a false, theory is the manner in + which newly discovered and unanticipated facts arrange themselves under + it. No more striking illustration of this can be found than in the + contrasted fates of Cuvier's theory and of that of Darwin. Even before + Cuvier's death his views had been undermined and the progress of discovery + soon laid them in irreparable ruin, while the activity of half-a-century + in many different lines of inquiry has established the theory of evolution + upon a foundation of ever growing solidity. It is Darwin's imperishable + glory that he prescribed the lines along which all the biological sciences + were to advance to conquests not dreamed of when he wrote. + </p> + <p> + <a name="link2H_4_0013" id="link2H_4_0013"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + XII. THE PALAEONTOLOGICAL RECORD. By D.H. Scott, F.R.S. + </h2> + <h3> + President of the Linnean Society. + </h3> + <p> + II. PLANTS. + </p> + <p> + There are several points of view from which the subject of the present + essay may be regarded. We may consider the fossil record of plants in its + bearing: I. on the truth of the doctrine of Evolution; II. on Phylogeny, + or the course of Evolution; III. on the theory of Natural Selection. The + remarks which follow, illustrating certain aspects only of an extensive + subject, may conveniently be grouped under these three headings. + </p> + <p> + I. THE TRUTH OF EVOLUTION. + </p> + <p> + When "The Origin of Species" was written, it was necessary to show that + the Geological Record was favourable to, or at least consistent with, the + Theory of Descent. The point is argued, closely and fully, in Chapter X. + "On the Imperfection of the Geological Record," and Chapter XI. "On the + Geological Succession of Organic Beings"; there is, however, little about + plants in these chapters. At the present time the truth of Evolution is no + longer seriously disputed, though there are writers, like Reinke, who + insist, and rightly so, that the doctrine is still only a belief, rather + than an established fact of science. (J. Reinke, "Kritische + Abstammungslehre", "Wiesner-Festschrift", page 11, Vienna, 1908.) + Evidently, then, however little the Theory of Descent may be questioned in + our own day, it is desirable to assure ourselves how the case stands, and + in particular how far the evidence from fossil plants has grown stronger + with time. + </p> + <p> + As regards direct evidence for the derivation of one species from another, + there has probably been little advance since Darwin wrote, at least so we + must infer from the emphasis laid on the discontinuity of successive + fossil species by great systematic authorities like Grand'Eury and Zeiller + in their most recent writings. We must either adopt the mutationist views + of those authors (referred to in the last section of this essay) or must + still rely on Darwin's explanation of the absence of numerous intermediate + varieties. The attempts which have been made to trace, in the Tertiary + rocks, the evolution of recent species, cannot, owing to the imperfect + character of the evidence, be regarded as wholly satisfactory. + </p> + <p> + When we come to groups of a somewhat higher order we have an interesting + history of the evolution of a recent family in the work, not yet + completed, of Kidston and Gwynne-Vaughan on the fossil Osmundaceae. + ("Trans. Royal Soc. Edinburgh", Vol. 45, Part III. 1907, Vol. 46, Part II. + 1908, Vol. 46, Part III. 1909.) The authors are able, mainly on anatomical + evidence, to trace back this now limited group of Ferns, through the + Tertiary and Mesozoic to the Permian, and to show, with great probability, + how their structure has been derived from that of early Palaeozoic types. + </p> + <p> + The history of the Ginkgoaceae, now represented only by the isolated + maidenhair tree, scarcely known in a wild state, offers another striking + example of a family which can be traced with certainty to the older + Mesozoic and perhaps further back still. (See Seward and Gowan, "The + Maidenhair Tree (Gingko biloba)", "Annals of Botany", Vol. XIV. 1900, page + 109; also A. Sprecher "Le Ginkgo biloba", L., Geneva, 1907.) + </p> + <p> + On the wider question of the derivation of the great groups of plants, a + very considerable advance has been made, and, so far as the higher plants + are concerned, we are now able to form a far better conception than before + of the probable course of evolution. This is a matter of phylogeny, and + the facts will be considered under that head; our immediate point is that + the new knowledge of the relations between the classes of plants in + question materially strengthens the case for the theory of descent. The + discoveries of the last few years throw light especially on the relation + of the Angiosperms to the Gymnosperms, on that of the Seed-plants + generally to the Ferns, and on the interrelations between the various + classes of the higher Cryptogams. + </p> + <p> + That the fossil record has not done still more for Evolution is due to the + fact that it begins too late—a point on which Darwin laid stress + ("Origin of Species" (6th edition), page 286.) and which has more recently + been elaborated by Poulton. ("Essays on Evolution", pages 46 et seq., + Oxford, 1908.) An immense proportion of the whole evolutionary history + lies behind the lowest fossiliferous rocks, and the case is worse for + plants than for animals, as the record for the former begins, for all + practical purposes, much higher up in the rocks. + </p> + <p> + It may be well here to call attention to a question, often overlooked, + which has lately been revived by Reinke. (Reinke, loc. cit. page 13.) As + all admit, we know nothing of the origin of life; consequently, for all we + can tell, it is as probable that life began, on this planet, with many + living things, as with one. If the first organic beings were many, they + may have been heterogeneous, or at least exposed to different conditions, + from their origin; in either case there would have been a number of + distinct series from the beginning, and if so we should not be justified + in assuming that all organisms are related to one another. There may + conceivably be several of the original lines of descent still surviving, + or represented among extinct forms—to reverse the remark of a + distinguished botanist, there may be several Vegetable Kingdoms! However + improbable this may sound, the possibility is one to be borne in mind. + </p> + <p> + That all VASCULAR plants really belong to one stock seems certain, and + here the palaeontological record has materially strengthened the case for + a monophyletic history. The Bryophyta are not likely to be absolutely + distinct, for their sexual organs, and the stomata of the Mosses strongly + suggest community of descent with the higher plants; if this be so it no + doubt establishes a certain presumption in favour of a common origin for + plants generally, for the gap between "Mosses and Ferns" has been regarded + as the widest in the Vegetable Kingdom. The direct evidence of + consanguinity is however much weaker when we come to the Algae, and it is + conceivable (even if improbable) that the higher plants may have had a + distinct ancestry (now wholly lost) from the beginning. The question had + been raised in Darwin's time, and he referred to it in these words: "No + doubt it is possible, as Mr G.H. Lewes has urged, that at the first + commencement of life many different forms were evolved; but if so, we may + conclude that only a very few have left modified descendants." ("Origin of + Species", page 425.) This question, though it deserves attention, does not + immediately affect the subject of the palaeontological record of plants, + for there can be no reasonable doubt as to the interrelationship of those + groups on which the record at present throws light. + </p> + <p> + The past history of plants by no means shows a regular progression from + the simple to the complex, but often the contrary. This apparent anomaly + is due to two causes. + </p> + <p> + 1. The palaeobotanical record is essentially the story of the successive + ascendancy of a series of dominant families, each of which attained its + maximum, in organisation as well as in extent, and then sank into + comparative obscurity, giving place to other families, which under new + conditions were better able to take a leading place. As each family ran + its downward course, either its members underwent an actual reduction in + structure as they became relegated to herbaceous or perhaps aquatic life + (this may have happened with the Horsetails and with Isoetes if derived + from Lepidodendreae), or the higher branches of the family were crowded + out altogether and only the "poor relations" were able to maintain their + position by evading the competition of the ascendant races; this is also + illustrated by the history of the Lycopod phylum. In either case there + would result a lowering of the type of organisation within the group. + </p> + <p> + 2. The course of real progress is often from the complex to the simple. + If, as we shall find some grounds for believing, the Angiosperms came from + a type with a flower resembling in its complexity that of Mesozoic + "Cycads," almost the whole evolution of the flower in the highest plants + has been a process of reduction. The stamen, in particular, has + undoubtedly become extremely simplified during evolution; in the most + primitive known seed-plants it was a highly compound leaf or pinna; its + reduction has gone on in the Conifers and modern Cycads, as well as in the + Angiosperms, though in different ways and to a varying extent. + </p> + <p> + The seed offers another striking example; the Palaeozoic seeds (if we + leave the seed-like organs of certain Lycopods out of consideration) were + always, so far as we know, highly complex structures, with an elaborate + vascular system, a pollen-chamber, and often a much-differentiated testa. + In the present day such seeds exist only in a few Gymnosperms which retain + their ancient characters—in all the higher Spermophytes the + structure is very much simplified, and this holds good even in the + Coniferae, where there is no countervailing complication of ovary and + stigma. + </p> + <p> + Reduction, in fact, is not always, or even generally, the same thing as + degeneration. Simplification of parts is one of the most usual means of + advance for the organism as a whole. A large proportion of the higher + plants are microphyllous in comparison with the highly megaphyllous + fern-like forms from which they appear to have been derived. + </p> + <p> + Darwin treated the general question of advance in organisation with much + caution, saying: "The geological record... does not extend far enough + back, to show with unmistakeable clearness that within the known history + of the world organisation has largely advanced." ("Origin of Species", + page 308.) Further on (Ibid. page 309.) he gives two standards by which + advance may be measured: "We ought not solely to compare the highest + members of a class at any two periods... but we ought to compare all the + members, high and low, at the two periods." Judged by either standard the + Horsetails and Club Mosses of the Carboniferous were higher than those of + our own day, and the same is true of the Mesozoic Cycads. There is a + general advance in the succession of classes, but not within each class. + </p> + <p> + Darwin's argument that "the inhabitants of the world at each successive + period in its history have beaten their predecessors in the race for life, + and are, in so far, higher in the scale" ("Origin of Species", page 315.) + is unanswerable, but we must remember that "higher in the scale" only + means "better adapted to the existing conditions." Darwin points out + (Ibid. page 279.) that species have remained unchanged for long periods, + probably longer than the periods of modification, and only underwent + change when the conditions of their life were altered. Higher + organisation, judged by the test of success, is thus purely relative to + the changing conditions, a fact of which we have a striking illustration + in the sudden incoming of the Angiosperms with all their wonderful floral + adaptations to fertilisation by the higher families of Insects. + </p> + <p> + II. PHYLOGENY. + </p> + <p> + The question of phylogeny is really inseparable from that of the truth of + the doctrine of evolution, for we cannot have historical evidence that + evolution has actually taken place without at the same time having + evidence of the course it has followed. + </p> + <p> + As already pointed out, the progress hitherto made has been rather in the + way of joining up the great classes of plants than in tracing the descent + of particular species or genera of the recent flora. There appears to be a + difference in this respect from the Animal record, which tells us so much + about the descent of living species, such as the elephant or the horse. + The reason for this difference is no doubt to be found in the fact that + the later part of the palaeontological record is the most satisfactory in + the case of animals and the least so in the case of plants. The Tertiary + plant-remains, in the great majority of instances, are impressions of + leaves, the conclusions to be drawn from which are highly precarious; + until the whole subject of Angiospermous palaeobotany has been + reinvestigated, it would be rash to venture on any statements as to the + descent of the families of Dicotyledons or Monocotyledons. + </p> + <p> + Our attention will be concentrated on the following questions, all + relating to the phylogeny of main groups of plants: i. The Origin of the + Angiosperms. ii. The Origin of the Seed-plants. iii. The Origin of the + different classes of the Higher Cryptogamia. + </p> + <p> + i. THE ORIGIN OF THE ANGIOSPERMS. + </p> + <p> + The first of these questions has long been the great crux of botanical + phylogeny, and until quite recently no light had been thrown upon the + difficulty. The Angiosperms are the Flowering Plants, par excellence, and + form, beyond comparison, the dominant sub-kingdom in the flora of our own + age, including, apart from a few Conifers and Ferns, all the most familiar + plants of our fields and gardens, and practically all plants of service to + man. All recent work has tended to separate the Angiosperms more widely + from the other seed-plants now living, the Gymnosperms. Vast as is the + range of organisation presented by the great modern sub-kingdom, embracing + forms adapted to every environment, there is yet a marked uniformity in + certain points of structure, as in the development of the embryo-sac and + its contents, the pollination through the intervention of a stigma, the + strange phenomenon of double fertilisation (One sperm fertilising the egg, + while the other unites with the embryo-sac nucleus, itself the product of + a nuclear fusion, to give rise to a nutritive tissue, the endosperm.), the + structure of the stamens, and the arrangement of the parts of the flower. + All these points are common to Monocotyledons and Dicotyledons, and + separate the Angiosperms collectively from all other plants. + </p> + <p> + In geological history the Angiosperms first appear in the Lower + Cretaceous, and by Upper Cretaceous times had already swamped all other + vegetation and seized the dominant position which they still hold. Thus + they are isolated structurally from the rest of the Vegetable Kingdom, + while historically they suddenly appear, almost in full force, and + apparently without intermediaries with other groups. To quote Darwin's + vigorous words: "The rapid development, as far as we can judge, of all the + higher plants within recent geological times is an abominable mystery." + ("More Letters of Charles Darwin", Vol. II. page 20, letter to J.D. + Hooker, 1879.) A couple of years later he made a bold suggestion (which he + only called an "idle thought") to meet this difficulty. He says: "I have + been so astonished at the apparently sudden coming in of the higher + phanerogams, that I have sometimes fancied that development might have + slowly gone on for an immense period in some isolated continent or large + island, perhaps near the South Pole." (Ibid, page 26, letter to Hooker, + 1881.) This idea of an Angiospermous invasion from some lost southern land + has sometimes been revived since, but has not, so far as the writer is + aware, been supported by evidence. Light on the problem has come from a + different direction. + </p> + <p> + The immense development of plants with the habit of Cycads, during the + Mesozoic Period up to the Lower Cretaceous, has long been known. The + existing Order Cycadaceae is a small family, with 9 genera and perhaps 100 + species, occurring in the tropical and sub-tropical zones of both the Old + and New World, but nowhere forming a dominant feature in the vegetation. + Some few attain the stature of small trees, while in the majority the stem + is short, though often living to a great age. The large pinnate or rarely + bipinnate leaves give the Cycads a superficial resemblance in habit to + Palms. Recent Cycads are dioecious; throughout the family the male + fructification is in the form of a cone, each scale of the cone + representing a stamen, and bearing on its lower surface numerous + pollen-sacs, grouped in sori like the sporangia of Ferns. In all the + genera, except Cycas itself, the female fructifications are likewise + cones, each carpel bearing two ovules on its margin. In Cycas, however, no + female cone is produced, but the leaf-like carpels, bearing from two to + six ovules each, are borne directly on the main stem of the plant in + rosettes alternating with those of the ordinary leaves—the most + primitive arrangement known in any living seed-plant. The whole Order is + relatively primitive, as shown most strikingly in its cryptogamic mode of + fertilisation, by means of spermatozoids, which it shares with the + maidenhair tree alone, among recent seed-plants. + </p> + <p> + In all the older Mesozoic rocks, from the Trias to the Lower Cretaceous, + plants of the Cycad class (Cycadophyta, to use Nathorst's comprehensive + name) are extraordinarily abundant in all parts of the world; in fact they + were almost as prominent in the flora of those ages as the Dicotyledons + are in that of our own day. In habit and to a great extent in anatomy, the + Mesozoic Cycadophyta for the most part much resemble the recent + Cycadaceae. But, strange to say, it is only in the rarest cases that the + fructification has proved to be of the simple type characteristic of the + recent family; the vast majority of the abundant fertile specimens yielded + by the Mesozoic rocks possess a type of reproductive apparatus far more + elaborate than anything known in Cycadaceae or other Gymnosperms. The + predominant Mesozoic family, characterised by this advanced reproductive + organisation, is known as the Bennettiteae; in habit these plants + resembled the more stunted Cycads of the recent flora, but differed from + them in the presence of numerous lateral fructifications, like large buds, + borne on the stem among the crowded bases of the leaves. The organisation + of these fructifications was first worked out on European specimens by + Carruthers, Solms-Laubach, Lignier and others, but these observers had + only more or less ripe fruits to deal with; the complete structure of the + flower has only been elucidated within the last few years by the + researches of Wieland on the magnificent American material, derived from + the Upper Jurassic and Lower Cretaceous beds of Maryland, Dakota and + Wyoming. (G.R. Wieland, "American Fossil Cycads", Carnegie Institution, + Washington, 1906.) The word "flower" is used deliberately, for reasons + which will be apparent from the following brief description, based on + Wieland's observations. + </p> + <p> + The fructification is attached to the stem by a thick stalk, which, in its + upper part, bears a large number of spirally arranged bracts, forming + collectively a kind of perianth and completely enclosing the essential + organs of reproduction. The latter consist of a whorl of stamens, of + extremely elaborate structure, surrounding a central cone or receptacle + bearing numerous ovules. The stamens resemble the fertile fronds of a + fern; they are of a compound, pinnate form, and bear very large numbers of + pollen-sacs, each of which is itself a compound structure consisting of a + number of compartments in which the pollen was formed. In their lower part + the stamens are fused together by their stalks, like the "monadelphous" + stamens of a mallow. The numerous ovules borne on the central receptacle + are stalked, and are intermixed with sterile scales; the latter are + expanded at their outer ends, which are united to form a kind of pericarp + or ovary-wall, only interrupted by the protruding micropyles of the + ovules. There is thus an approach to the closed pistil of an Angiosperm, + but it is evident that the ovules received the pollen directly. The whole + fructification is of large size; in the case of Cycadeoidea dacotensis, + one of the species investigated by Wieland, the total length, in the bud + condition, is about 12 cm., half of which belongs to the peduncle. + </p> + <p> + The general arrangement of the organs is manifestly the same as in a + typical Angiospermous flower, with a central pistil, a surrounding whorl + of stamens and an enveloping perianth; there is, as we have seen, some + approach to the closed ovary of an Angiosperm; another point, first + discovered nearly 20 years ago by Solms-Laubach in his investigation of a + British species, is that the seed was practically "exalbuminous," its + cavity being filled by the large, dicotyledonous embryo, whereas in all + known Gymnosperms a large part of the sac is occupied by a nutritive + tissue, the prothallus or endosperm; here also we have a condition only + met with elsewhere among the higher Flowering Plants. + </p> + <p> + Taking all the characters into account, the indications of affinity + between the Mesozoic Cycadophyta and the Angiosperms appear extremely + significant, as was recognised by Wieland when he first discovered the + hermaphrodite nature of the Bennettitean flower. The Angiosperm with which + he specially compared the fossil type was the Tulip tree (Liriodendron) + and certainly there is a remarkable analogy with the Magnoliaceous + flowers, and with those of related orders such as Ranunculaceae and the + Water-lilies. It cannot, of course, be maintained that the Bennettiteae, + or any other Mesozoic Cycadophyta at present known, were on the direct + line of descent of the Angiosperms, for there are some important points of + difference, as, for example, in the great complexity of the stamens, and + in the fact that the ovary-wall or pericarp was not formed by the carpels + themselves, but by the accompanying sterile scale-leaves. Botanists, since + the discovery of the bisexual flowers of the Bennettiteae, have expressed + different views as to the nearness of their relation to the higher + Flowering Plants, but the points of agreement are so many that it is + difficult to resist the conviction that a real relation exists, and that + the ancestry of the Angiosperms, so long shrouded in complete obscurity, + is to be sought among the great plexus of Cycad-like plants which + dominated the flora of the world in Mesozoic times. (On this subject see, + in addition to Wieland's great work above cited, F.W. Oliver, + "Pteridosperms and Angiosperms", "New Phytologist", Vol. V. 1906; D.H. + Scott, "The Flowering Plants of the Mesozoic Age in the Light of Recent + Discoveries", "Journal R. Microscop. Soc." 1907, and especially E.A.N. + Arber and J. Parkin, "On the Origin of Angiosperms", "Journal Linn. Soc." + (Bot.) Vol. XXXVIII. page 29, 1907.) + </p> + <p> + The great complexity of the Bennettitean flower, the earliest known + fructification to which the word "flower" can be applied without forcing + the sense, renders it probable, as Wieland and others have pointed out, + that the evolution of the flower in Angiosperms has consisted essentially + in a process of reduction, and that the simplest forms of flower are not + to be regarded as the most primitive. The older morphologists generally + took the view that such simple flowers were to be explained as reductions + from a more perfect type, and this opinion, though abandoned by many later + writers, appears likely to be true when we consider the elaboration of + floral structure attained among the Mesozoic Cycadophyta, which preceded + the Angiosperms in evolution. + </p> + <p> + If, as now seems probable, the Angiosperms were derived from ancestors + allied to the Cycads, it would naturally follow that the Dicotyledons were + first evolved, for their structure has most in common with that of the + Cycadophyta. We should then have to regard the Monocotyledons as a + side-line, diverging probably at a very early stage from the main + dicotyledonous stock, a view which many botanists have maintained, of + late, on other grounds. (See especially Ethel Sargant, "The Reconstruction + of a Race of Primitive Angiosperms", "Annals of Botany", Vol. XXII. page + 121, 1908.) So far, however, as the palaeontological record shows, the + Monocotyledons were little if at all later in their appearance than the + Dicotyledons, though always subordinate in numbers. The typical and + beautifully preserved Palm-wood from Cretaceous rocks is striking evidence + of the early evolution of a characteristic monocotyledonous family. It + must be admitted that the whole question of the evolution of + Monocotyledons remains to be solved. + </p> + <p> + Accepting, provisionally, the theory of the cycadophytic origin of + Angiosperms, it is interesting to see to what further conclusions we are + led. The Bennettiteae, at any rate, were still at the gymnospermous level + as regards their pollination, for the exposed micropyles of the ovules + were in a position to receive the pollen directly, without the + intervention of a stigma. It is thus indicated that the Angiosperms sprang + from a gymnospermous source, and that the two great phyla of Seed-plants + have not been distinct from the first, though no doubt the great majority + of known Gymnosperms, especially the Coniferae, represent branch-lines of + their own. + </p> + <p> + The stamens of the Bennettiteae are arranged precisely as in an + angiospermous flower, but in form and structure they are like the fertile + fronds of a Fern, in fact the compound pollen-sacs, or synangia as they + are technically called, almost exactly agree with the spore-sacs of a + particular family of Ferns—the Marattiaceae, a limited group, now + mainly tropical, which was probably more prominent in the later Palaeozoic + times than at present. The scaly hairs, or ramenta, which clothe every + part of the plant, are also like those of Ferns. + </p> + <p> + It is not likely that the characters in which the Bennettiteae resemble + the Ferns came to them directly from ancestors belonging to that class; an + extensive group of Seed-plants, the Pteridospermeae, existed in Palaeozoic + times and bear evident marks of affinity with the Fern phylum. The + fern-like characters so remarkably persistent in the highly organised + Cycadophyta of the Mesozoic were in all likelihood derived through the + Pteridosperms, plants which show an unmistakable approach to the + cycadophytic type. + </p> + <p> + The family Bennettiteae thus presents an extraordinary association of + characters, exhibiting, side by side, features which belong to the + Angiosperms, the Gymnosperms and the Ferns. + </p> + <p> + ii. ORIGIN OF SEED-PLANTS. + </p> + <p> + The general relation of the gymnospermous Seed-plants to the Higher + Cryptogamia was cleared up, independently of fossil evidence, by the + brilliant researches of Hofmeister, dating from the middle of the past + century. (W. Hofmeister, "On the Germination, Development and + Fructification of the Higher Cryptogamia", Ray Society, London, 1862. The + original German treatise appeared in 1851.) He showed that "the embryo-sac + of the Coniferae may be looked upon as a spore remaining enclosed in its + sporangium; the prothallium which it forms does not come to the light." + (Ibid. page 438.) He thus determined the homologies on the female side. + Recognising, as some previous observers had already done, that the + microspores of those Cryptogams in which two kinds of spore are developed, + are equivalent to the pollen-grains of the higher plants, he further + pointed out that fertilisation "in the Rhizocarpeae and Selaginellae takes + place by free spermatozoa, and in the Coniferae by a pollen-tube, in the + interior of which spermatozoa are probably formed"—a remarkable + instance of prescience, for though spermatozoids have not been found in + the Conifers proper, they were demonstrated in the allied groups + Cycadaceae and Ginkgo, in 1896, by the Japanese botanists Ikeno and + Hirase. A new link was thus established between the Gymnosperms and the + Cryptogams. + </p> + <p> + It remained uncertain, however, from which line of Cryptogams the + gymnospermous Seed-plants had sprung. The great point of morphological + comparison was the presence of two kinds of spore, and this was known to + occur in the recent Lycopods and Water-ferns (Rhizocarpeae) and was also + found in fossil representatives of the third phylum, that of the + Horsetails. As a matter of fact all the three great Cryptogamic classes + have found champions to maintain their claim to the ancestry of the + Seed-plants, and in every case fossil evidence was called in. For a long + time the Lycopods were the favourites, while the Ferns found the least + support. The writer remembers, however, in the year 1881, hearing the late + Prof. Sachs maintain, in a lecture to his class, that the descent of the + Cycads could be traced, not merely from Ferns, but from a definite family + of Ferns, the Marattiaceae, a view which, though in a somewhat crude form, + anticipated more modern ideas. + </p> + <p> + Williamson appears to have been the first to recognise the presence, in + the Carboniferous flora, of plants combining the characters of Ferns and + Cycads. (See especially his "Organisation of the Fossil Plants of the + Coal-Measures", Part XIII. "Phil. Trans. Royal Soc." 1887 B. page 299.) + This conclusion was first reached in the case of the genera Heterangium + and Lyginodendron, plants, which with a wholly fern-like habit, were found + to unite an anatomical structure holding the balance between that of Ferns + and Cycads, Heterangium inclining more to the former and Lyginodendron to + the latter. Later researches placed Williamson's original suggestion on a + firmer basis, and clearly proved the intermediate nature of these genera, + and of a number of others, so far as their vegetative organs were + concerned. This stage in our knowledge was marked by the institution of + the class Cycadofilices by Potonie in 1897. + </p> + <p> + Nothing, however, was known of the organs of reproduction of the + Cycadofilices, until F.W. Oliver, in 1903, identified a fossil seed, + Lagenostoma Lomaxi, as belonging to Lyginodendron, the identification + depending, in the first instance, on the recognition of an identical form + of gland, of very characteristic structure, on the vegetative organs of + Lyginodendron and on the cupule enveloping the seed. This evidence was + supported by the discovery of a close anatomical agreement in other + respects, as well as by constant association between the seed and the + plant. (F.W. Oliver and D.H. Scott, "On the Structure of the Palaeozoic + Seed, Lagenostoma Lomaxi, etc." "Phil. Trans. Royal Soc." Vol. 197 B. + 1904.) The structure of the seed of Lyginodendron, proved to be of the + same general type as that of the Cycads, as shown especially by the + presence of a pollen-chamber or special cavity for the reception of the + pollen-grains, an organ only known in the Cycads and Ginkgo among recent + plants. + </p> + <p> + Within a few months after the discovery of the seed of Lyginodendron, + Kidston found the large, nut-like seed of a Neuropteris, another fern-like + Carboniferous plant, in actual connection with the pinnules of the frond, + and since then seeds have been observed on the frond in species of + Aneimites and Pecopteris, and a vast body of evidence, direct or indirect, + has accumulated, showing that a large proportion of the Palaeozoic plants + formerly classed as Ferns were in reality reproduced by seeds of the same + type as those of recent Cycadaceae. (A summary of the evidence will be + found in the writer's article "On the present position of Palaeozoic + Botany", "Progressus Rei Botanicae", 1907, page 139, and "Studies in + Fossil Botany", Vol. II. (2nd edition) London, 1909.) At the same time, + the anatomical structure, where it is open to investigation, confirms the + suggestion given by the habit, and shows that these early seed-bearing + plants had a real affinity with Ferns. This conclusion received strong + corroboration when Kidston, in 1905, discovered the male organs of + Lyginodendron, and showed that they were identical with a fructification + of the genus Crossotheca, hitherto regarded as belonging to Marattiaceous + Ferns. (Kidston, "On the Microsporangia of the Pteridospermeae, etc." + "Phil. Trans. Royal Soc." Vol. 198, B. 1906.) + </p> + <p> + The general conclusion which follows from the various observations alluded + to, is that in Palaeozoic times there was a great body of plants + (including, as it appears, a large majority of the fossils previously + regarded as Ferns) which had attained the rank of Spermophyta, bearing + seeds of a Cycadean type on fronds scarcely differing from the vegetative + foliage, and in other respects, namely anatomy, habit and the structure of + the pollen-bearing organs, retaining many of the characters of Ferns. From + this extensive class of plants, to which the name Pteridospermeae has been + given, it can scarcely be doubted that the abundant Cycadophyta, of the + succeeding Mesozoic period, were derived. This conclusion is of + far-reaching significance, for we have already found reason to think that + the Angiosperms themselves sprang, in later times, from the Cycadophytic + stock; it thus appears that the Fern-phylum, taken in a broad sense, + ultimately represents the source from which the main line of descent of + the Phanerogams took its rise. + </p> + <p> + It must further be borne in mind that in the Palaeozoic period there + existed another group of seed-bearing plants, the Cordaiteae, far more + advanced than the Pteridospermeae, and in many respects approaching the + Coniferae, which themselves begin to appear in the latest Palaeozoic + rocks. The Cordaiteae, while wholly different in habit from the + contemporary fern-like Seed-plants, show unmistakable signs of a common + origin with them. Not only is there a whole series of forms connecting the + anatomical structure of the Cordaiteae with that of the Lyginodendreae + among Pteridosperms, but a still more important point is that the seeds of + the Cordaiteae, which have long been known, are of the same Cycadean type + as those of the Pteridosperms, so that it is not always possible, as yet, + to discriminate between the seeds of the two groups. These facts indicate + that the same fern-like stock which gave rise to the Cycadophyta and + through them, as appears probable, to the Angiosperms, was also the source + of the Cordaiteae, which in their turn show manifest affinity with some at + least of the Coniferae. Unless the latter are an artificial group, a view + which does not commend itself to the writer, it would appear probable that + the Gymnosperms generally, as well as the Angiosperms, were derived from + an ancient race of Cryptogams, most nearly related to the Ferns. (Some + botanists, however, believe that the Coniferae, or some of them, are + probably more nearly related to the Lycopods. See Seward and Ford, "The + Araucarieae, Recent and Extinct", "Phil. Trans. Royal Soc." Vol. 198 B. + 1906.) + </p> + <p> + It may be mentioned here that the small gymnospermous group Gnetales + (including the extraordinary West African plant Welwitschia) which were + formerly regarded by some authorities as akin to the Equisetales, have + recently been referred, on better grounds, to a common origin with the + Angiosperms, from the Mesozoic Cycadophyta. + </p> + <p> + The tendency, therefore, of modern work on the palaeontological record of + the Seed-plants has been to exalt the importance of the Fern-phylum, + which, on present evidence, appears to be that from which the great + majority, possibly the whole, of the Spermophyta have been derived. + </p> + <p> + One word of caution, however, is necessary. The Seed-plants are of + enormous antiquity; both the Pteridosperms and the more highly organised + family Cordaiteae, go back as far in geological history (namely to the + Devonian) as the Ferns themselves or any other Vascular Cryptogams. It + must therefore be understood that in speaking of the derivation of the + Spermophyta from the Fern-phylum, we refer to that phylum at a very early + stage, probably earlier than the most ancient period to which our record + of land-plants extends. The affinity between the oldest Seed-plants and + the Ferns, in the widest sense, seems established, but the common stock + from which they actually arose is still unknown; though no doubt nearer to + the Ferns than to any other group, it must have differed widely from the + Ferns as we now know them, or perhaps even from any which the fossil + record has yet revealed to us. + </p> + <p> + iii. THE ORIGIN OF THE HIGHER CRYPTOGAMIA. + </p> + <p> + The Sub-kingdom of the higher Spore-plants, the Cryptogamia possessing a + vascular system, was more prominent in early geological periods than at + present. It is true that the dominance of the Pteridophyta in Palaeozoic + times has been much exaggerated owing to the assumption that everything + which looked like a Fern really was a Fern. But, allowing for the fact, + now established, that most of the Palaeozoic fern-like plants were already + Spermophyta, there remains a vast mass of Cryptogamic forms of that + period, and the familiar statement that they formed the main constituent + of the Coal-forests still holds good. The three classes, Ferns + (Filicales), Horsetails (Equisetales) and Club-mosses (Lycopodiales), + under which we now group the Vascular Cryptogams, all extend back in + geological history as far as we have any record of the flora of the land; + in the Palaeozoic, however, a fourth class, the Sphenophyllales, was + present. + </p> + <p> + As regards the early history of the Ferns, which are of special interest + from their relation to the Seed-plants, it is impossible to speak quite + positively, owing to the difficulty of discriminating between true fossil + Ferns and the Pteridosperms which so closely simulated them. The + difficulty especially affects the question of the position of + Marattiaceous Ferns in the Palaeozoic Floras. This family, now so + restricted, was until recently believed to have been one of the most + important groups of Palaeozoic plants, especially during later + Carboniferous and Permian times. Evidence both from anatomy and from + sporangial characters appeared to establish this conclusion. Of late, + however, doubts have arisen, owing to the discovery that some supposed + members of the Marattiaceae bore seeds, and that a form of fructification + previously referred to that family (Crossotheca) was really the + pollen-bearing apparatus of a Pteridosperm (Lyginodendron). The question + presents much difficulty; though it seems certain that our ideas of the + extent of the family in Palaeozoic times will have to be restricted, there + is still a decided balance of evidence in favour of the view that a + considerable body of Marattiaceous Ferns actually existed. The plants in + question were of large size (often arborescent) and highly organised—they + represent, in fact, one of the highest developments of the Fern-stock, + rather than a primitive type of the class. + </p> + <p> + There was, however, in the Palaeozoic period, a considerable group of + comparatively simple Ferns (for which Arber has proposed the collective + name Primofilices); the best known of these are referred to the family + Botryopterideae, consisting of plants of small or moderate dimensions, + with, on the whole, a simple anatomical structure, in certain cases + actually simpler than that of any recent Ferns. On the other hand the + sporangia of these plants were usually borne on special fertile fronds, a + mark of rather high differentiation. This group goes back to the Devonian + and includes some of the earliest types of Fern with which we are + acquainted. It is probable that the Primofilices (though not the + particular family Botryopterideae) represent the stock from which the + various families of modern Ferns, already developed in the Mesozoic + period, may have sprung. + </p> + <p> + None of the early Ferns show any clear approach to other classes of + Vascular Cryptogams; so far as the fossil record affords any evidence, + Ferns have always been plants with relatively large and usually compound + leaves. There is no indication of their derivation from a microphyllous + ancestry, though, as we shall see, there is some slight evidence for the + converse hypothesis. Whatever the origin of the Ferns may have been it is + hidden in the older rocks. + </p> + <p> + It has, however, been held that certain other Cryptogamic phyla had a + common origin with the Ferns. The Equisetales are at present a + well-defined group; even in the rich Palaeozoic floras the habit, anatomy + and reproductive characters usually render the members of this class + unmistakable, in spite of the great development and stature which they + then attained. It is interesting, however, to find that in the oldest + known representatives of the Equisetales the leaves were highly developed + and dichotomously divided, thus differing greatly from the mere + scale-leaves of the recent Horsetails, or even from the simple linear + leaves of the later Calamites. The early members of the class, in their + forked leaves, and in anatomical characters, show an approximation to the + Sphenophyllales, which are chiefly represented by the large genus + Sphenophyllum, ranging through the Palaeozoic from the Middle Devonian + onwards. These were plants with rather slender, ribbed stems, bearing + whorls of wedge-shaped or deeply forked leaves, six being the typical + number in each whorl. From their weak habit it has been conjectured, with + much probability, that they may have been climbing plants, like the + scrambling Bedstraws of our hedgerows. The anatomy of the stem is simple + and root-like; the cones are remarkable for the fact that each scale or + sporophyll is a double structure, consisting of a lower, usually sterile + lobe and one or more upper lobes bearing the sporangia; in one species + both parts of the sporophyll were fertile. Sphenophyllum was evidently + much specialised; the only other known genus is based on an isolated cone, + Cheirostrobus, of Lower Carboniferous age, with an extraordinarily complex + structure. In this genus especially, but also in the entire group, there + is an evident relation to the Equisetales; hence it is of great interest + that Nathorst has described, from the Devonian of Bear Island in the + Arctic regions, a new genus Pseudobornia, consisting of large plants, + remarkable for their highly compound leaves which, when found detached, + were taken for the fronds of a Fern. The whorled arrangement of the + leaves, and the habit of the plant, suggest affinities either with the + Equisetales or the Sphenophyllales; Nathorst makes the genus the type of a + new class, the Pseudoborniales. (A.G. Nathorst, "Zur Oberdevonischen Flora + der Baren-Insel", "Kongl. Svenska Vetenskaps-Akademiens Handlingar" Bd. + 36, No. 3, Stockholm, 1902.) + </p> + <p> + The available data, though still very fragmentary, certainly suggest that + both Equisetales and Sphenophyllales may have sprung from a common stock + having certain fern-like characters. On the other hand the Sphenophylls, + and especially the peculiar genus Cheirostrobus, have in their anatomy a + good deal in common with the Lycopods, and of late years they have been + regarded as the derivatives of a stock common to that class and the + Equisetales. At any rate the characters of the Sphenophyllales and of the + new group Pseudoborniales suggest the existence, at a very early period, + of a synthetic race of plants, combining the characters of various phyla + of the Vascular Cryptogams. It may further be mentioned that the + Psilotaceae, an isolated epiphytic family hitherto referred to the + Lycopods, have been regarded by several recent authors as the last + survivors of the Sphenophyllales, which they resemble both in their + anatomy and in the position of their sporangia. + </p> + <p> + The Lycopods, so far as their early history is known, are remarkable + rather for their high development in Palaeozoic times than for any + indications of a more primitive ancestry. In the recent Flora, two of the + four living genera (Excluding Psilotaceae.) (Selaginella and Isoetes) have + spores of two kinds, while the other two (Lycopodium and Phylloglossum) + are homosporous. Curiously enough, no certain instance of a homosporous + Palaeozoic Lycopod has yet been discovered, though well-preserved + fructifications are numerous. Wherever the facts have been definitely + ascertained, we find two kinds of spore, differentiated quite as sharply + as in any living members of the group. Some of the Palaeozoic Lycopods, in + fact, went further, and produced bodies of the nature of seeds, some of + which were actually regarded, for many years, as the seeds of Gymnosperms. + This specially advanced form of fructification goes back at least as far + as the Lower Carboniferous, while the oldest known genus of Lycopods, + Bothrodendron, which is found in the Devonian, though not seed-bearing, + was typically heterosporous, if we may judge from the Coal-measure + species. No doubt homosporous Lycopods existed, but the great prevalence + of the higher mode of reproduction in days which to us appear ancient, + shows how long a course of evolution must have already been passed through + before the oldest known members of the group came into being. The other + characters of the Palaeozoic Lycopods tell the same tale; most of them + attained the stature of trees, with a corresponding elaboration of + anatomical structure, and even the herbaceous forms show no special + simplicity. It appears from recent work that herbaceous Lycopods, + indistinguishable from our recent Selaginellas, already existed in the + time of the Coal-measures, while one herbaceous form (Miadesmia) is known + to have borne seeds. + </p> + <p> + The utmost that can be said for primitiveness of character in Palaeozoic + Lycopods is that the anatomy of the stem, in its primary ground-plan, as + distinguished from its secondary growth, was simpler than that of most + Lycopodiums and Selaginellas at the present day. There are also some + peculiarities in the underground organs (Stigmaria) which suggest the + possibility of a somewhat imperfect differentiation between root and stem, + but precisely parallel difficulties are met with in the case of the living + Selaginellas, and in some degree in species of Lycopodium. + </p> + <p> + In spite of their high development in past ages the Lycopods, recent and + fossil, constitute, on the whole, a homogeneous group, and there is little + at present to connect them with other phyla. Anatomically some relation to + the Sphenophylls is indicated, and perhaps the recent Psilotaceae give + some support to this connection, for while their nearest alliance appears + to be with the Sphenophylls, they approach the Lycopods in anatomy, habit, + and mode of branching. + </p> + <p> + The typically microphyllous character of the Lycopods, and the simple + relation between sporangium and sporophyll which obtains throughout the + class, have led various botanists to regard them as the most primitive + phylum of the Vascular Cryptogams. There is nothing in the fossil record + to disprove this view, but neither is there anything to support it, for + this class so far as we know is no more ancient than the megaphyllous + Cryptogams, and its earliest representatives show no special simplicity. + If the indications of affinity with Sphenophylls are of any value the + Lycopods are open to suspicion of reduction from a megaphyllous ancestry, + but there is no direct palaeontological evidence for such a history. + </p> + <p> + The general conclusions to which we are led by a consideration of the + fossil record of the Vascular Cryptogams are still very hypothetical, but + may be provisionally stated as follows: + </p> + <p> + The Ferns go back to the earliest known period. In Mesozoic times + practically all the existing families had appeared; in the Palaeozoic the + class was less extensive than formerly believed, a majority of the + supposed Ferns of that age having proved to be seed-bearing plants. The + oldest authentic representatives of the Ferns were megaphyllous plants, + broadly speaking, of the same type as those of later epochs, though + differing much in detail. As far back as the record extends they show no + sign of becoming merged with other phyla in any synthetic group. + </p> + <p> + The Equisetales likewise have a long history, and manifestly attained + their greatest development in Palaeozoic times. Their oldest forms show an + approach to the extinct class Sphenophyllales, which connects them to some + extent, by anatomical characters, with the Lycopods. At the same time the + oldest Equisetales show a somewhat megaphyllous character, which was more + marked in the Devonian Pseudoborniales. Some remote affinity with the + Ferns (which has also been upheld on other grounds) may thus be indicated. + It is possible that in the Sphenophyllales we may have the much-modified + representatives of a very ancient synthetic group. + </p> + <p> + The Lycopods likewise attained their maximum in the Palaeozoic, and show, + on the whole, a greater elaboration of structure in their early forms than + at any later period, while at the same time maintaining a considerable + degree of uniformity in morphological characters throughout their history. + The Sphenophyllales are the only other class with which they show any + relation; if such a connection existed, the common point of origin must + lie exceedingly far back. + </p> + <p> + The fossil record, as at present known, cannot, in the nature of things, + throw any direct light on what is perhaps the most disputed question in + the morphology of plants—the origin of the alternating generations + of the higher Cryptogams and the Spermophyta. At the earliest period to + which terrestrial plants have been traced back all the groups of Vascular + Cryptogams were in a highly advanced stage of evolution, while innumerable + Seed-plants—presumably the descendants of Cryptogamic ancestors—were + already flourishing. On the other hand we know practically nothing of + Palaeozoic Bryophyta, and the evidence even for their existence at that + period cannot be termed conclusive. While there are thus no + palaeontological grounds for the hypothesis that the Vascular plants came + of a Bryophytic stock, the question of their actual origin remains + unsolved. + </p> + <p> + III. NATURAL SELECTION. + </p> + <p> + Hitherto we have considered the palaeontological record of plants in + relation to Evolution. The question remains, whether the record throws any + light on the theory of which Darwin and Wallace were the authors—that + of Natural Selection. The subject is clearly one which must be + investigated by other methods than those of the palaeontologist; still + there are certain important points involved, on which the palaeontological + record appears to bear. + </p> + <p> + One of these points is the supposed distinction between morphological and + adaptive characters, on which Nageli, in particular, laid so much stress. + The question is a difficult one; it was discussed by Darwin ("Origin of + Species" (6th edition), pages 170-176.), who, while showing that the + apparent distinction is in part to be explained by our imperfect knowledge + of function, recognised the existence of important morphological + characters which are not adaptations. The following passage expresses his + conclusion. "Thus, as I am inclined to believe, morphological differences, + which we consider as important—such as the arrangement of the + leaves, the divisions of the flower or of the ovarium, the position of the + ovules, etc.—first appeared in many cases as fluctuating variations, + which sooner or later became constant through the nature of the organism + and of the surrounding conditions, as well as through the inter-crossing + of distinct individuals, but not through natural selection; for as these + morphological characters do not affect the welfare of the species, any + slight deviations in them could not have been governed or accumulated + through this latter agency." (Ibid. page 176.) + </p> + <p> + This is a sufficiently liberal concession; Nageli, however, went much + further when he said: "I do not know among plants a morphological + modification which can be explained on utilitarian principles." (See "More + Letters", Vol. II. page 375 (footnote).) If this were true the field of + Natural Selection would be so seriously restricted, as to leave the theory + only a very limited importance. + </p> + <p> + It can be shown, as the writer believes, that many typical "morphological + characters," on which the distinction between great classes of plants is + based, were adaptive in origin, and even that their constancy is due to + their functional importance. Only one or two cases will be mentioned, + where the fossil evidence affects the question. + </p> + <p> + The pollen-tube is one of the most important morphological characters of + the Spermophyta as now existing—in fact the name Siphonogama is used + by Engler in his classification, as expressing a peculiarly constant + character of the Seed-plants. Yet the pollen-tube is a manifest + adaptation, following on the adoption of the seed-habit, and serving first + to bring the spermatozoids with greater precision to their goal, and + ultimately to relieve them of the necessity for independent movement. The + pollen-tube is constant because it has proved to be indispensable. + </p> + <p> + In the Palaeozoic Seed-plants there are a number of instances in which the + pollen-grains, contained in the pollen-chamber of a seed, are so + beautifully preserved that the presence of a group of cells within the + grain can be demonstrated; sometimes we can even see how the cell-walls + broke down to emit the sperms, and quite lately it is said that the sperms + themselves have been recognised. (F.W. Oliver, "On Physostoma elegans, an + archaic type of seed from the Palaeozoic Rocks", "Annals of Botany", + January, 1909. See also the earlier papers there cited.) In no case, + however, is there as yet any satisfactory evidence for the formation of a + pollen-tube; it is probable that in these early Seed-plants the + pollen-grains remained at about the evolutionary level of the microspores + in Pilularia or Selaginella, and discharged their spermatozoids directly, + leaving them to find their own way to the female cells. It thus appears + that there were once Spermophyta without pollen-tubes. The pollen-tube + method ultimately prevailed, becoming a constant "morphological + character," for no other reason than because, under the new conditions, it + provided a more perfect mechanism for the accomplishment of the act of + fertilisation. We have still, in the Cycads and Ginkgo, the transitional + case, where the tube remains short, serves mainly as an anchor and + water-reservoir, but yet is able, by its slight growth, to give the + spermatozoids a "lift" in the right direction. In other Seed-plants the + sperms are mere passengers, carried all the way by the pollen-tube; this + fact has alone rendered the Angiospermous method of fertilisation through + a stigma possible. + </p> + <p> + We may next take the seed itself—the very type of a morphological + character. Our fossil record does not go far enough back to tell us the + origin of the seed in the Cycadophyta and Pteridosperms (the main line of + its development) but some interesting sidelights may be obtained from the + Lycopod phylum. In two Palaeozoic genera, as we have seen, seed-like + organs are known to have been developed, resembling true seeds in the + presence of an integument and of a single functional embryo-sac, as well + as in some other points. We will call these organs "seeds" for the sake of + shortness. In one genus (Lepidocarpon) the seeds were borne on a cone + indistinguishable from that of the ordinary cryptogamic Lepidodendreae, + the typical Lycopods of the period, while the seed itself retained much of + the detailed structure of the sporangium of that family. In the second + genus, Miadesmia, the seed-bearing plant was herbaceous, and much like a + recent Selaginella. (See Margaret Benson, "Miadesmia membranacea, a new + Palaeozoic Lycopod with a seed-like structure", "Phil. Trans. Royal Soc. + Vol." 199, B. 1908.) The seeds of the two genera are differently + constructed, and evidently had an independent origin. Here, then, we have + seeds arising casually, as it were, at different points among plants which + otherwise retain all the characters of their cryptogamic fellows; the seed + is not yet a morphological character of importance. To suppose that in + these isolated cases the seed sprang into being in obedience to a Law of + Advance ("Vervollkommungsprincip"), from which other contemporary Lycopods + were exempt, involves us in unnecessary mysticism. On the other hand it is + not difficult to see how these seeds may have arisen, as adaptive + structures, under the influence of Natural Selection. The seed-like + structure afforded protection to the prothallus, and may have enabled the + embryo to be launched on the world in greater security. There was further, + as we may suppose, a gain in certainty of fertilisation. As the writer has + pointed out elsewhere, the chances against the necessary association of + the small male with the large female spores must have been enormously + great when the cones were borne high up on tall trees. The same difficulty + may have existed in the case of the herbaceous Miadesmia, if, as Miss + Benson conjectures, it was an epiphyte. One way of solving the problem was + for pollination to take place while the megaspore was still on the parent + plant, and this is just what the formation of an ovule or seed was likely + to secure. + </p> + <p> + The seeds of the Pteridosperms, unlike those of the Lycopod stock, have + not yet been found in statu nascendi—in all known cases they were + already highly developed organs and far removed from the cryptogamic + sporangium. But in two respects we find that these seeds, or some of them, + had not yet realised their possibilities. In the seed of Lyginodendron and + other cases the micropyle, or orifice of the integument, was not the + passage through which the pollen entered; the open neck of the + pollen-chamber protruded through the micropyle and itself received the + pollen. We have met with an analogous case, at a more advanced stage of + evolution, in the Bennettiteae, where the wall of the gynaecium, though + otherwise closed, did not provide a stigma to catch the pollen, but + allowed the micropyles of the ovules to protrude and receive the pollen in + the old gymnospermous fashion. The integument in the one case and the + pistil in the other had not yet assumed all the functions to which the + organ ultimately became adapted. Again, no Palaeozoic seed has yet been + found to contain an embryo, though the preservation is often good enough + for it to have been recognised if present. It is probable that the nursing + of the embryo had not yet come to be one of the functions of the seed, and + that the whole embryonic development was relegated to the germination + stage. + </p> + <p> + In these two points, the reception of the pollen by the micropyle and the + nursing of the embryo, it appears that many Palaeozoic seeds were + imperfect, as compared with the typical seeds of later times. As evolution + went on, one function was superadded on another, and it appears impossible + to resist the conclusion that the whole differentiation of the seed was a + process of adaptation, and consequently governed by Natural Selection, + just as much as the specialisation of the rostellum in an Orchid, or of + the pappus in a Composite. + </p> + <p> + Did space allow, other examples might be added. We may venture to maintain + that the glimpses which the fossil record allows us into early stages in + the evolution of organs now of high systematic importance, by no means + justify the belief in any essential distinction between morphological and + adaptive characters. + </p> + <p> + Another point, closely connected with Darwin's theory, on which the fossil + history of plants has been supposed to have some bearing, is the question + of Mutation, as opposed to indefinite variation. Arber and Parkin, in + their interesting memoir on the Origin of Angiosperms, have suggested + calling in Mutation to explain the apparently sudden transition from the + cycadean to the angiospermous type of foliage, in late Mesozoic times, + though they express themselves with much caution, and point out "a + distinct danger that Mutation may become the last resort of the + phylogenetically destitute"! + </p> + <p> + The distinguished French palaeobotanists, Grand'Eury (C. Grand'Eury, "Sur + les mutations de quelques Plantes fossiles du Terrain houiller". "Comptes + Rendus", CXLII. page 25, 1906.) and Zeiller (R. Zeiller "Les Vegetaux + fossiles et leurs Enchainements", "Revue du Mois", III. February, 1907.), + are of opinion, to quote the words of the latter writer, that the facts of + fossil Botany are in agreement with the sudden appearance of new forms, + differing by marked characters from those that have given them birth; he + adds that these results give more amplitude to this idea of Mutation, + extending it to groups of a higher order, and even revealing the existence + of discontinuous series between the successive terms of which we yet + recognise bonds of filiation. (Loc. cit. page 23.) + </p> + <p> + If Zeiller's opinion should be confirmed, it would no doubt be a serious + blow to the Darwinian theory. As Darwin said: "Under a scientific point of + view, and as leading to further investigation, but little advantage is + gained by believing that new forms are suddenly developed in an + inexplicable manner from old and widely different forms, over the old + belief in the creation of species from the dust of the earth." ("Origin of + Species", page 424.) + </p> + <p> + It most however be pointed out, that such mutations as Zeiller, and to + some extent Arber and Parkin, appear to have in view, bridging the gulf + between different Orders and Classes, bear no relation to any mutations + which have been actually observed, such as the comparatively small + changes, of sub-specific value, described by De Vries in the type-case of + Oenothera Lamarckiana. The results of palaeobotanical research have + undoubtedly tended to fill up gaps in the Natural System of plants—that + many such gaps still persist is not surprising; their presence may well + serve as an incentive to further research but does not, as it seems to the + writer, justify the assumption of changes in the past, wholly without + analogy among living organisms. + </p> + <p> + As regards the succession of species, there are no greater authorities + than Grand'Eury and Zeiller, and great weight must be attached to their + opinion that the evidence from continuous deposits favours a somewhat + sudden change from one specific form to another. At the same time it will + be well to bear in mind that the subject of the "absence of numerous + intermediate varieties in any single formation" was fully discussed by + Darwin. ("Origin of Species", pages 275-282, and page 312.); the + explanation which he gave may go a long way to account for the facts which + recent writers have regarded as favouring the theory of saltatory + mutation. + </p> + <p> + The rapid sketch given in the present essay can do no more than call + attention to a few salient points, in which the palaeontological records + of plants has an evident bearing on the Darwinian theory. At the present + day the whole subject of palaeobotany is a study in evolution, and derives + its chief inspiration from the ideas of Darwin and Wallace. In return it + contributes something to the verification of their teaching; the recent + progress of the subject, in spite of the immense difficulties which still + remain, has added fresh force to Darwin's statement that "the great + leading facts in palaeontology agree admirably with the theory of descent + with modification through variation and natural selection." (Ibid. page + 313.) + </p> + <p> + <a name="link2H_4_0014" id="link2H_4_0014"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + XIII. THE INFLUENCE OF ENVIRONMENT ON THE FORMS OF PLANTS. By Georg Klebs, + PH.D. + </h2> + <h3> + Professor of Botany in the University of Heidelberg. + </h3> + <p> + The dependence of plants on their environment became the object of + scientific research when the phenomena of life were first investigated and + physiology took its place as a special branch of science. This occurred in + the course of the eighteenth century as the result of the pioneer work of + Hales, Duhamel, Ingenhousz, Senebier and others. In the nineteenth + century, particularly in the second half, physiology experienced an + unprecedented development in that it began to concern itself with the + experimental study of nutrition and growth, and with the phenomena + associated with stimulus and movement; on the other hand, physiology + neglected phenomena connected with the production of form, a department of + knowledge which was the province of morphology, a purely descriptive + science. It was in the middle of the last century that the growth of + comparative morphology and the study of phases of development reached + their highest point. + </p> + <p> + The forms of plants appeared to be the expression of their inscrutable + inner nature; the stages passed through in the development of the + individual were regarded as the outcome of purely internal and hidden + laws. The feasibility of experimental inquiry seemed therefore remote. + Meanwhile, the recognition of the great importance of such a causal + morphology emerged from the researches of the physiologists of that time, + more especially from those of Hofmeister (Hofmeister, "Allgemeine + Morphologie", Leipzig, 1868, page 579.), and afterwards from the work of + Sachs. (Sachs, "Stoff und Form der Pflanzenorgane", Vol. I. 1880; Vol. II. + 1882. "Gesammelte Abhandlungen uber Pflanzen-Physiologie", II. Leipzig, + 1893.) Hofmeister, in speaking of this line of inquiry, described it as + "the most pressing and immediate aim of the investigator to discover to + what extent external forces acting on the organism are of importance in + determining its form." This advance was the outcome of the influence of + that potent force in biology which was created by Darwin's "Origin of + Species" (1859). + </p> + <p> + The significance of the splendid conception of the transformation of + species was first recognised and discussed by Lamarck (1809); as an + explanation of transformation he at once seized upon the idea—an + intelligible view—that the external world is the determining factor. + Lamarck (Lamarck, "Philosophie zoologique", pages 223-227. Paris, 1809.) + endeavoured, more especially, to demonstrate from the behaviour of plants + that changes in environment induce change in form which eventually leads + to the production of new species. In the case of animals, Lamarck adopted + the teleological view that alterations in the environment first lead to + alterations in the needs of the organisms, which, as the result of a kind + of conscious effort of will, induce useful modifications and even the + development of new organs. His work has not exercised any influence on the + progress of science: Darwin himself confessed in regard to Lamarck's work—"I + got not a fact or idea from it." ("Life and Letters", Vol. II. page 215.) + </p> + <p> + On a mass of incomparably richer and more essential data Darwin based his + view of the descent of organisms and gained for it general acceptance; as + an explanation of modification he elaborated the ingeniously conceived + selection theory. The question of special interest in this connection, + namely what is the importance of the influence of the environment, Darwin + always answered with some hesitation and caution, indeed with a certain + amount of indecision. + </p> + <p> + The fundamental principle underlying his theory is that of general + variability as a whole, the nature and extent of which, especially in + cultivated organisms, are fully dealt with in his well-known book. + (Darwin, "The variation of Animals and Plants under domestication", 2 + vols., edition 1, 1868; edition 2, 1875; popular edition 1905.) In regard + to the question as to the cause of variability Darwin adopts a + consistently mechanical view. He says: "These several considerations alone + render it probable that variability of every kind is directly or + indirectly caused by changed conditions of life. Or, to put the case under + another point of view, if it were possible to expose all the individuals + of a species during many generations to absolutely uniform conditions of + life, there would be no variability." ("The variation of Animals and + Plants" (2nd edition), Vol. II. page 242.) Darwin did not draw further + conclusions from this general principle. + </p> + <p> + Variations produced in organisms by the environment are distinguished by + Darwin as "the definite" and "the indefinite." (Ibid. II. page 260. See + also "Origin of Species" (6th edition), page 6.) The first occur "when all + or nearly all the offspring of an individual exposed to certain conditions + during several generations are modified in the same manner." Indefinite + variation is much more general and a more important factor in the + production of new species; as a result of this, single individuals are + distinguished from one another by "slight" differences, first in one then + in another character. There may also occur, though this is very rare, more + marked modifications, "variations which seem to us in our ignorance to + arise spontaneously." ("Origin of Species" (6th edition), page 421.) The + selection theory demands the further postulate that such changes, "whether + extremely slight or strongly marked," are inherited. Darwin was no nearer + to an experimental proof of this assumption than to the discovery of the + actual cause of variability. It was not until the later years of his life + that Darwin was occupied with the "perplexing problem... what causes + almost every cultivated plant to vary" ("Life and Letters", Vol. III. page + 342.): he began to make experiments on the influence of the soil, but + these were soon given up. + </p> + <p> + In the course of the violent controversy which was the outcome of Darwin's + work the fundamental principles of his teaching were not advanced by any + decisive observations. Among the supporters and opponents, Nageli (Nageli, + "Theorie der Abstammungslehre", Munich, 1884; cf. Chapter III.) was one of + the few who sought to obtain proofs by experimental methods. His extensive + cultural experiments with alpine Hieracia led him to form the opinion that + the changes which are induced by an alteration in the food-supply, in + climate or in habitat, are not inherited and are therefore of no + importance from the point of view of the production of species. And yet + Nageli did attribute an important influence to the external world; he + believed that adaptations of plants arise as reactions to continuous + stimuli, which supply a need and are therefore useful. These opinions, + which recall the teleological aspect of Lamarckism, are entirely + unsupported by proof. While other far-reaching attempts at an explanation + of the theory of descent were formulated both in Nageli's time and + afterwards, some in support of, others in opposition to Darwin, the + necessity of investigating, from different standpoints, the underlying + causes, variability and heredity, was more and more realised. To this + category belong the statistical investigations undertaken by Quetelet and + Galton, the researches into hybridisation, to which an impetus was given + by the re-discovery of the Mendelian law of segregation, as also by the + culture experiments on mutating species following the work of de Vries, + and lastly the consideration of the question how far variation and + heredity are governed by external influences. These latter problems, which + are concerned in general with the causes of form-production and + form-modification, may be treated in a short summary which falls under two + heads, one having reference to the conditions of form-production in single + species, the other being concerned with the conditions governing the + transformation of species. + </p> + <p> + I. THE INFLUENCE OF EXTERNAL CONDITIONS ON FORM-PRODUCTION IN SINGLE + SPECIES. + </p> + <p> + The members of plants, which we express by the terms stem, leaf, flower, + etc. are capable of modification within certain limits; since Lamarck's + time this power of modification has been brought more or less into + relation with the environment. We are concerned not only with the question + of experimental demonstration of this relationship, but, more generally, + with an examination of the origin of forms, the sequences of stages in + development that are governed by recognisable causes. We have to consider + the general problem; to study the conditions of all typical as well as of + atypic forms, in other words, to found a physiology of form. + </p> + <p> + If we survey the endless variety of plant-forms and consider the highly + complex and still little known processes in the interior of cells, and if + we remember that the whole of this branch of investigation came into + existence only a few decades ago, we are able to grasp the fact that a + satisfactory explanation of the factors determining form cannot be + discovered all at once. The goal is still far away. We are not concerned + now with the controversial question, whether, on the whole, the + fundamental processes in the development of form can be recognised by + physiological means. A belief in the possibility of this can in any case + do no harm. What we may and must attempt is this—to discover points + of attack on one side or another, which may enable us by means of + experimental methods to come into closer touch with these elusive and + difficult problems. While we are forced to admit that there is at present + much that is insoluble there remains an inexhaustible supply of problems + capable of solution. + </p> + <p> + The object of our investigations is the species; but as regards the + question, what is a species, science of to-day takes up a position + different from that of Darwin. For him it was the Linnean species which + illustrates variation: we now know, thanks to the work of Jordan, de Bary, + and particularly to that of de Vries (de Vries, "Die Mutationstheorie", + Leipzig, 1901, Vol. I. page 33.), that the Linnean species consists of a + large or small number of entities, elementary species. In experimental + investigation it is essential that observations be made on a pure species, + or, as Johannsen (Johannsen, "Ueber Erblichkeit in Populationen und reinen + Linien", Jena, 1903.) says, on a pure "line." What has long been + recognised as necessary in the investigation of fungi, bacteria and algae + must also be insisted on in the case of flowering plants; we must start + with a single individual which is reproduced vegetatively or by strict + self-fertilisation. In dioecious plants we must aim at the reproduction of + brothers and sisters. + </p> + <p> + We may at the outset take it for granted that a pure species remains the + same under similar external conditions; it varies as these vary. IT IS + CHARACTERISTIC OF A SPECIES THAT IT ALWAYS EXHIBITS A CONSTANT RELATION TO + A PARTICULAR ENVIRONMENT. In the case of two different species, e.g. the + hay and anthrax bacilli or two varieties of Campanula with blue and white + flowers respectively, a similar environment produces a constant + difference. The cause of this is a mystery. + </p> + <p> + According to the modern standpoint, the living cell is a complex + chemico-physical system which is regarded as a dynamical system of + equilibrium, a conception suggested by Herbert Spencer and which has + acquired a constantly increasing importance in the light of modern + developments in physical chemistry. The various chemical compounds, + proteids, carbohydrates, fats, the whole series of different ferments, + etc. occur in the cell in a definite physical arrangement. The two systems + of two species must as a matter of fact possess a constant difference, + which it is necessary to define by a special term. We say, therefore, that + the SPECIFIC STRUCTURE is different. + </p> + <p> + By way of illustrating this provisionally, we may assume that the proteids + of the two species possess a constant chemical difference. This conception + of specific structure is specially important in its bearing on a further + treatment of the subject. In the original cell, eventually also in every + cell of a plant, the characters which afterwards become apparent must + exist somewhere; they are integral parts of the capabilities or + potentialities of specific structure. Thus not only the characters which + are exhibited under ordinary conditions in nature, but also many others + which become apparent only under special conditions (In this connection I + leave out of account, as before, the idea of material carriers of heredity + which since the publication of Darwin's Pangenesis hypothesis has been + frequently suggested. See my remarks in "Variationen der Bluten", + "Pringsheim's Jahrb. Wiss. Bot." 1905, page 298; also Detto, "Biol. + Centralbl." 1907, page 81, "Die Erklarbarkeit der Ontogenese durch + materielle Anlagen".), are to be included as such potentialities in cells; + the conception of specific structure includes the WHOLE OF THE + POTENTIALITIES OF A SPECIES; specific structure comprises that which we + must always assume without being able to explain it. + </p> + <p> + A relatively simple substance, such as oxalate of lime, is known under a + great number of different crystalline forms belonging to different systems + (Compare Kohl's work on "Anatomisch-phys. Untersuchungen uber Kalksalze", + etc. Marburg, 1889.); these may occur as single crystals, concretions or + as concentric sphaerites. The power to assume this variety of form is in + some way inherent in the molecular structure, though we cannot, even in + this case, explain the necessary connection between structure and + crystalline form. These potentialities can only become operative under the + influence of external conditions; their stimulation into activity depends + on the degree of concentration of the various solutions, on the nature of + the particular calcium salt, on the acid or alkaline reactions. Broadly + speaking, the plant cell behaves in a similar way. The manifestation of + each form, which is inherent as a potentiality in the specific structure, + is ultimately to be referred to external conditions. + </p> + <p> + An insight into this connection is, however, rendered exceedingly + difficult, often quite impossible, because the environment never directly + calls into action the potentialities. Its influence is exerted on what we + may call the inner world of the organism, the importance of which + increases with the degree of differentiation. The production of form in + every plant depends upon processes in the interior of the cells, and the + nature of these determines which among the possible characters is to be + brought to light. In no single case are we acquainted with the internal + process responsible for the production of a particular form. All possible + factors may play a part, such as osmotic pressure, permeability of the + protoplasm, the degree of concentration of the various chemical + substances, etc.; all these factors should be included in the category of + INTERNAL CONDITIONS. This inner world appears the more hidden from our ken + because it is always represented by a certain definite state, whether we + are dealing with a single cell or with a small group of cells. These have + been produced from pre-existing cells and they in turn from others; the + problem is constantly pushed back through a succession of generations + until it becomes identified with that of the origin of species. + </p> + <p> + A way, however, is opened for investigation; experience teaches us that + this inner world is not a constant factor: on the contrary, it appears to + be very variable. The dependence of VARIABLE INTERNAL on VARIABLE EXTERNAL + conditions gives us the key with which research may open the door. In the + lower plants this dependence is at once apparent, each cell is directly + subject to external influences. In the higher plants with their different + organs, these influences were transmitted to cells in course of + development along exceedingly complex lines. In the case of the + growing-point of a bud, which is capable of producing a complete plant, + direct influences play a much less important part than those exerted + through other organs, particularly through the roots and leaves, which are + essential in nutrition. These correlations, as we may call them, are of + the greatest importance as aids to an understanding of form-production. + When a bud is produced on a particular part of a plant, it undergoes + definite internal modifications induced by the influence of other organs, + the activity of which is governed by the environment, and as the result of + this it develops along a certain direction; it may, for example, become a + flower. The particular direction of development is determined before the + rudiment is differentiated and is exerted so strongly that further + development ensues without interruption, even though the external + conditions vary considerably and exert a positively inimical influence: + this produces the impression that development proceeds entirely + independently of the outer world. The widespread belief that such + independence exists is very premature and at all events unproven. + </p> + <p> + The state of the young rudiment is the outcome of previous influences of + the external world communicated through other organs. Experiments show + that in certain cases, if the efficiency of roots and leaves as organs + concerned with nutrition is interfered with, the production of flowers is + affected, and their characters, which are normally very constant, undergo + far-reaching modifications. To find the right moment at which to make the + necessary alteration in the environment is indeed difficult and in many + cases not yet possible. This is especially the case with fertilised eggs, + which in a higher degree than buds have acquired, through parental + influences, an apparently fixed internal organisation, and this seems to + have pre-determined their development. It is, however, highly probable + that it will be possible, by influencing the parents, to alter the + internal organisation and to switch off development on to other lines. + </p> + <p> + Having made these general observations I will now cite a few of the many + facts at our disposal, in order to illustrate the methods and aim of the + experimental methods of research. As a matter of convenience I will deal + separately with modification of development and with modification of + single organs. + </p> + <p> + I. EFFECT OF ENVIRONMENT UPON THE COURSE OF DEVELOPMENT. + </p> + <p> + Every plant, whether an alga or a flowering plant passes, under natural + conditions, through a series of developmental stages characteristic of + each species, and these consist in a regular sequence of definite forms. + It is impossible to form an opinion from mere observation and description + as to what inner changes are essential for the production of the several + forms. We must endeavour to influence the inner factors by known external + conditions in such a way that the individual stages in development are + separately controlled and the order of their sequence determined at will + by experimental treatment. Such control over the course of development may + be gained with special certainty in the case of the lower organisms. + </p> + <p> + With these it is practicable to control the principal conditions of + cultivation and to vary them in various ways. By this means it has been + demonstrated that each developmental stage depends upon special external + conditions, and in cases where our knowledge is sufficient, a particular + stage may be obtained at will. In the Green Algae (See Klebs, "Die + Bedingung der Fortpflanzung... ", Jena, 1896; also "Jahrb. fur Wiss. Bot." + 1898 and 1900; "Probleme der Entwickelung, III." "Biol. Centralbl." 1904, + page 452.), as in the case of Fungi, we may classify the stages of + development into purely vegetative growth (growth, cell-division, + branching), asexual reproduction (formation of zoospores, conidia) and + sexual processes (formation of male and female sexual organs). By + modifying the external conditions it is possible to induce algae or fungi + (Vaucheria, Saprolegnia) to grow continuously for several years or, in the + course of a few days, to die after an enormous production of asexual or + sexual cells. In some instances even an almost complete stoppage of growth + may be caused, reproductive cells being scarcely formed before the + organism is again compelled to resort to reproduction. Thus the sequence + of the different stages in development can be modified as we may desire. + </p> + <p> + The result of a more thorough investigation of the determining conditions + appears to produce at first sight a confused impression of all sorts of + possibilities. Even closely allied species exhibit differences in regard + to the connection between their development and external conditions. It is + especially noteworthy that the same form in development may be produced as + the result of very different alterations in the environment. At the same + time we can undoubtedly detect a certain unity in the multiplicity of the + individual phenomena. + </p> + <p> + If we compare the factors essential for the different stages in + development, we see that the question always resolves itself into one of + modification of similar conditions common to all life-processes. We should + rather have inferred that there exist specific external stimuli for each + developmental stage, for instance, certain chemical agencies. Experiments + hitherto made support the conclusion that QUANTITATIVE alterations in the + general conditions of life produce different types of development. An alga + or a fungus grows so long as all the conditions of nutrition remain at a + certain optimum for growth. In order to bring about asexual reproduction, + e.g. the formation of zoospores, it is sometimes necessary to increase the + degree of intensity of external factors; sometimes, on the other hand, + these must be reduced in intensity. In the case of many algae a decrease + in light-intensity or in the amount of salts in the culture solution, or + in the temperature, induces asexual reproduction, while in others, on the + contrary, an increase in regard to each of these factors is required to + produce the same result. This holds good for the quantitative variations + which induce sexual reproduction in algae. The controlling factor is found + to be a reduction in the supply of nutritive salts and the exposure of the + plants to prolonged illumination or, better still, an increase in the + intensity of the light, the efficiency of illumination depending on the + consequent formation of organic substances such as carbohydrates. + </p> + <p> + The quantitative alterations of external conditions may be spoken of as + releasing stimuli. They produce, in the complex equilibrium of the cell, + quantitative modifications in the arrangement and distribution of mass, by + means of which other chemical processes are at once set in motion, and + finally a new condition of equilibrium is attained. But the commonly + expressed view that the environment can as a rule act only as a releasing + agent is incorrect, because it overlooks an essential point. The power of + a cell to receive stimuli is only acquired as the result of previous + nutrition, which has produced a definite condition of concentration of + different substances. Quantities are in this case the determining factors. + The distribution of quantities is especially important in the sexual + reproduction of algae, for which a vigorous production of the materials + formed during carbon-assimilation appears to be essential. + </p> + <p> + In the Flowering plants, on the other hand, for reasons already mentioned, + the whole problem is more complicated. Investigations on changes in the + course of development of fertilised eggs have hitherto been unsuccessful; + the difficulty of influencing egg-cells deeply immersed in tissue + constitutes a serious obstacle. Other parts of plants are, however, + convenient objects of experiment; e.g. the growing apices of buds which + serve as cuttings for reproductive purposes, or buds on tubers, runners, + rhizomes, etc. A growing apex consists of cells capable of division in + which, as in egg-cells, a complete series of latent possibilities of + development is embodied. Which of these possibilities becomes effective + depends upon the action of the outer world transmitted by organs concerned + with nutrition. + </p> + <p> + Of the different stages which a flowering plant passes through in the + course of its development we will deal only with one in order to show + that, in spite of its great complexity, the problem is, in essentials, + equally open to attack in the higher plants and in the simplest organisms. + The most important stage in the life of a flowering plant is the + transition from purely vegetative growth to sexual reproduction—that + is, the production of flowers. In certain cases it can be demonstrated + that there is no internal cause, dependent simply on the specific + structure, which compels a plant to produce its flowers after a definite + period of vegetative growth. (Klebs, "Willkurliche + Entwickelungsanderungen", Jena 1903; see also "Probleme der Entwickelung", + I. II. "Centralbl." 1904.) + </p> + <p> + One extreme case, that of exceptionally early flowering, has been observed + in nature and more often in cultivation. A number of plants under certain + conditions are able to flower soon after germination. (Cf. numerous + records of this kind by Diels, "Jugendformen und Bluten", Berlin, 1906.) + This shortening of the period of development is exhibited in the most + striking form in trees, as in the oak (Mobius, "Beitrage zur Lehre von der + Fortpflanzung", Jena, 1897, page 89.), flowering seedlings of which have + been observed from one to three years old, whereas normally the tree does + not flower until it is sixty or eighty years old. + </p> + <p> + Another extreme case is represented by prolonged vegetative growth leading + to the complete suppression of flower-production. This result may be + obtained with several plants, such as Glechoma, the sugar beet, Digitalis, + and others, if they are kept during the winter in a warm, damp atmosphere, + and in rich soil; in the following spring or summer they fail to flower. + (Klebs, "Willkurliche Aenderungen", etc. Jena, 1903, page 130.) + Theoretically, however, experiments are of greater importance in which the + production of flowers is inhibited by very favourable conditions of + nutrition (Klebs, "Ueber kunstliche Metamorphosen", Stuttgart, 1906, page + 115) ("Abh. Naturf. Ges. Halle", XXV.) occurring at the normal flowering + period. Even in the case of plants of Sempervivum several years old, + which, as is shown by control experiments on precisely similar plants, are + on the point of flowering, flowering is rendered impossible if they are + forced to very vigorous growth by an abundant supply of water and salts in + the spring. Flowering, however, occurs, if such plants are cultivated in + relatively dry sandy soil and in the presence of strong light. Careful + researches into the conditions of growth have led, in the cases + Sempervivum, to the following results: (1) With a strong light and + vigorous carbon-assimilation a considerably increased supply of water and + nutritive salts produces active vegetative growth. (2) With a vigorous + carbon-assimilation in strong light, and a decrease in the supply of water + and salts active flower-production is induced. (3) If an average supply of + water and salts is given both processes are possible; the intensity of + carbon-assimilation determines which of the two is manifested. A + diminution in the production of organic substances, particularly of + carbohydrates, induces vegetative growth. This can be effected by culture + in feeble light or in light deprived of the yellow-red rays: on the other + hand, flower-production follows an increase in light-intensity. These + results are essentially in agreement with well-known observations on + cultivated plants, according to which, the application of much moisture, + after a plentiful supply of manure composed of inorganic salts, hinders + the flower-production of many vegetables, while a decrease in the supply + of water and salts favours flowering. + </p> + <p> + ii. INFLUENCE OF THE ENVIRONMENT ON THE FORM OF SINGLE ORGANS. (A + considerable number of observations bearing on this question are given by + Goebel in his "Experimentelle Morphologie der Pflanzen", Leipzig, 1908. It + is not possible to deal here with the alteration in anatomical structure; + cf. Kuster, "Pathologische Pflanzenanatomie", Jena, 1903.) + </p> + <p> + If we look closely into the development of a flowering plant, we notice + that in a given species differently formed organs occur in definite + positions. In a potato plant colourless runners are formed from the base + of the main stem which grow underground and produce tubers at their tips: + from a higher level foliage shoots arise nearer the apex. External + appearances suggest that both the place of origin and the form of these + organs were predetermined in the egg-cell or in the tuber. But it was + shown experimentally by the well-known investigator Knight (Knight, + "Selection from the Physiological and Horticultural Papers", London, + 1841.) that tubers may be developed on the aerial stem in place of foliage + shoots. These observations were considerably extended by Vochting. + (Vochting, "Ueber die Bildung der Knollen", Cassel, 1887; see also "Bot. + Zeit." 1902, 87.) In one kind of potato, germinating tubers were induced + to form foliage shoots under the influence of a higher temperature; at a + lower temperature they formed tuber-bearing shoots. Many other examples of + the conversion of foliage-shoots into runners and rhizomes, or vice versa, + have been described by Goebel and others. As in the asexual reproduction + of algae quantitative alteration in the amount of moisture, light, + temperature, etc. determines whether this or that form of shoot is + produced. If the primordia of these organs are exposed to altered + conditions of nutrition at a sufficiently early stage a complete + substitution of one organ for another is effected. If the rudiment has + reached a certain stage in development before it is exposed to these + influences, extraordinary intermediate forms are obtained, bearing the + characters of both organs. + </p> + <p> + The study of regeneration following injury is of greater importance as + regards the problem of the development and place of origin of organs. + (Reference may be made to the full summary of results given by Goebel in + his "Experimentelle Morphologie", Leipzig and Berlin, 1908, Section IV.) + Only in relatively very rare cases is there a complete re-formation of the + injured organ itself, as e.g. in the growing-apex. Much more commonly + injury leads to the development of complementary formations, it may be the + rejuvenescence of a hitherto dormant rudiment, or it may be the formation + of such ab initio. In all organs, stems, roots, leaves, as well as + inflorescences, this kind of regeneration, which occurs in a great variety + of ways according to the species, may be observed on detached pieces of + the plant. Cases are also known, such, for example, as the leaves of many + plants which readily form roots but not shoots, where a complete + regeneration does not occur. + </p> + <p> + The widely spread power of reacting to wounding affords a very valuable + means of inducing a fresh development of buds and roots on places where + they do not occur in normal circumstances. Injury creates special + conditions, but little is known as yet in regard to alterations directly + produced in this way. Where the injury consists in the separation of an + organ from its normal connections, the factors concerned are more + comprehensible. A detached leaf, e.g., is at once cut off from a supply of + water and salts, and is deprived of the means of getting rid of organic + substances which it produces; the result is a considerable alteration in + the degree of concentration. No experimental investigation on these lines + has yet been made. Our ignorance has often led to the view that we are + dealing with a force whose specific quality is the restitution of the + parts lost by operation; the proof, therefore, that in certain cases a + similar production of new roots or buds may be induced without previous + injury and simply by a change in external conditions assumes an + importance. (Klebs, "Willkurliche Entwickelung", page 100; also, "Probleme + der Entwickelung", "Biol. Centralbl." 1904, page 610.) + </p> + <p> + A specially striking phenomenon of regeneration, exhibited also by + uninjured plants, is afforded by polarity, which was discovered by + Vochting. (See the classic work of Vochting, "Ueber Organbildung im + Pflanzenreich", I. Bonn, 1888; also "Bot. Zeit." 1906, page 101; cf. + Goebel, "Experimentelle Morphologie", Leipzig and Berlin, 1908, Section V, + Polaritat.) It is found, for example, that roots are formed from the base + of a detached piece of stem and shoots from the apex. Within the limits of + this essay it is impossible to go into this difficult question; it is, + however, important from the point of view of our general survey to + emphasise the fact that the physiological distinctions between base and + apex of pieces of stem are only of a quantitative kind, that is, they + consist in the inhibition of certain phenomena or in favouring them. As a + matter of fact roots may be produced from the apices of willows and + cuttings of other plants; the distinction is thus obliterated under the + influence of environment. The fixed polarity of cuttings from full grown + stems cannot be destroyed; it is the expression of previous development. + Vochting speaks of polarity as a fixed inherited character. This is an + unconvincing conclusion, as nothing can be deduced from our present + knowledge as to the causes which led up to polarity. We know that the + fertilised egg, like the embryo, is fixed at one end by which it hangs + freely in the embryo-sac and afterwards in the endosperm. From the first, + therefore, the two ends have different natures, and these are revealed in + the differentiation into root-apex and stem-apex. A definite direction in + the flow of food-substances is correlated with this arrangement, and this + eventually leads to a polarity in the tissues. This view requires + experimental proof, which in the case of the egg-cells of flowering plants + hardly appears possible; but it derives considerable support from the fact + that in herbaceous plants, e.g. Sempervivum (Klebs, "Variationen der + Bluten", "Jahrb. Wiss. Bot." 1905, page 260.), rosettes or flower-shoots + are formed in response to external conditions at the base, in the middle, + or at the apex of the stem, so that polarity as it occurs under normal + conditions cannot be the result of unalterable hereditary factors. On the + other hand, the lower plants should furnish decisive evidence on this + question, and the experiments of Stahl, Winkler, Kniep, and others + indicate the right method of attacking the problem. + </p> + <p> + The relation of leaf-form to environment has often been investigated and + is well known. The leaves of bog and water plants (Cf.Goebel, loc. cit. + chapter II.; also Gluck, "Untersuchungen uber Wasser- und Sumpfgewachse", + Jena, Vols. I.-II. 1905-06.) afford the most striking examples of + modifications: according as they are grown in water, moist or dry air, the + form of the species characteristic of the particular habitat is produced, + since the stems are also modified. To the same group of phenomena belongs + the modification of the forms of leaves and stems in plants on + transplantation from the plains to the mountains (Bonnier, "Recherches sur + l'Anatomie experimentale des Vegetaux", Corbeil, 1895.) or vice versa. + Such variations are by no means isolated examples. All plants exhibit a + definite alteration in form as the result of prolonged cultivation in + moist or dry air, in strong or feeble light, or in darkness, or in salt + solutions of different composition and strength. + </p> + <p> + Every individual which is exposed to definite combinations of external + factors exhibits eventually the same type of modification. This is the + type of variation which Darwin termed "definite." It is easy to realise + that indefinite or fluctuating variations belong essentially to the same + class of phenomena; both are reactions to changes in environment. In the + production of individual variations two different influences undoubtedly + cooperate. One set of variations is caused by different external + conditions, during the production, either of sexual cells or of vegetative + primordia; another set is the result of varying external conditions during + the development of the embryo into an adult plant. The two sets of + influences cannot as yet be sharply differentiated. If, for purposes of + vegetative reproduction, we select pieces of the same parent-plant of a + pure species, the second type of variation predominates. Individual + fluctuations depend essentially in such cases on small variations in + environment during development. + </p> + <p> + These relations must be borne in mind if we wish to understand the results + of statistical methods. Since the work of Quetelet, Galton, and others the + statistical examination of individual differences in animals and plants + has become a special science, which is primarily based on the + consideration that the application of the theory of probability renders + possible mathematical statement and control of the results. The facts show + that any character, size of leaf, length of stem, the number of members in + a flower, etc. do not vary haphazard but in a very regular manner. In most + cases it is found that there is a value which occurs most commonly, the + average or medium value, from which the larger and smaller deviations, the + so-called plus and minus variations fall away in a continuous series and + end in a limiting value. In the simpler cases a falling off occurs equally + on both sides of the curve; the curve constructed from such data agrees + very closely with the Gaussian curve of error. In more complicated cases + irregular curves of different kinds are obtained which may be calculated + on certain suppositions. + </p> + <p> + The regular fluctuations about a mean according to the rule of probability + is often attributed to some law underlying variability. (de Vries, + "Mutationstheorie", Vol. I. page 35, Leipzig, 1901.) But there is no such + law which compels a plant to vary in a particular manner. Every + experimental investigation shows, as we have already remarked, that the + fluctuation of characters depends on fluctuation in the external factors. + The applicability of the method of probability follows from the fact that + the numerous individuals of a species are influenced by a limited number + of variable conditions. (Klebs, "Willkurl. Ent." Jena, 1903, page 141.) As + each of these conditions includes within certain limits all possible + values and exhibits all possible combinations, it follows that, according + to the rules of probability, there must be a mean value, about which the + larger and smaller deviations are distributed. Any character will be found + to have the mean value which corresponds with that combination of + determining factors which occurs most frequently. Deviations towards plus + and minus values will be correspondingly produced by rarer conditions. + </p> + <p> + A conclusion of fundamental importance may be drawn from this conception, + which is, to a certain extent, supported by experimental investigation. + (Klebs, "Studien uber Variation", "Arch. fur Entw." 1907.) There is no + normal curve for a particular CHARACTER, there is only a curve for the + varying combinations of conditions occurring in nature or under + cultivation. Under other conditions entirely different curves may be + obtained with other variants as a mean value. If, for example, under + ordinary conditions the number 10 is the most frequent variant for the + stamens of Sedum spectabile, in special circumstances (red light) this is + replaced by the number 5. The more accurately we know the conditions for a + particular form or number, and are able to reproduce it by experiment, the + nearer we are to achieving our aim of rendering a particular variation + impossible or of making it dominant. + </p> + <p> + In addition to the individual variations of a species, more pronounced + fluctuations occur relatively rarely and sporadically which are spoken of + as "single variations," or if specially striking as abnormalities or + monstrosities. These forms have long attracted the attention of + morphologists; a large number of observations of this kind are given in + the handbooks of Masters (Masters, "Vegetable Teratology", London, 1869.) + and Penzig (Penzig, "Pflanzen-Teratologie", Vols I. and II. Genua, + 1890-94.) These variations, which used to be regarded as curiosities, have + now assumed considerable importance in connection with the causes of + form-development. They also possess special interest in relation to the + question of heredity, a subject which does not at present concern us, as + such deviations from normal development undoubtedly arise as individual + variations induced by the influence of environment. + </p> + <p> + Abnormal developments of all kinds in stems, leaves, and flowers, may be + produced by parasites, insects, or fungi. They may also be induced by + injury, as Blaringhem (Blaringhem, "Mutation et traumatismes", Paris, + 1907.) has more particularly demonstrated, which, by cutting away the + leading shoots of branches in an early stage of development, caused + fasciation, torsion, anomalous flowers, etc. The experiments of Blaringhem + point to the probability that disturbances in the conditions of + food-supply consequent on injury are the cause of the production of + monstrosities. This is certainly the case in my experiments with species + of Sempervivum (Klebs, "Kunstliche Metamorphosen", Stuttgart, 1906.); + individuals, which at first formed normal flowers, produced a great + variety of abnormalities as the result of changes in nutrition, we may + call to mind the fact that the formation of inflorescences occurs normally + when a vigorous production of organic compounds, such as starch, sugar, + etc. follows a diminution in the supply of mineral salts. On the other + hand, the development of inflorescences is entirely suppressed if, at a + suitable moment before the actual foundations have been laid, water and + mineral salts are supplied to the roots. If, during the week when the + inflorescence has just been laid down and is growing very slowly, the + supply of water and salts is increased, the internal conditions of the + cells are essentially changed. At a later stage, after the elongation of + the inflorescence, rosettes of leaves are produced instead of flowers, and + structures intermediate between the two kinds of organs; a number of + peculiar plant-forms are thus obtained (Cf. Lotsy, "Vorlesungen uber + Deszendenztheorien", Vol. II. pl. 3, Jena, 1908.) Abnormalities in the + greatest variety are produced in flowers by varying the time at which the + stimulus is applied, and by the cooperation of other factors such as + temperature, darkness, etc. In number and arrangement the several floral + members vary within wide limits; sepals, petals, stamens, and carpels are + altered in form and colour, a transformation of stamens to carpels and + from carpels to stamens occurs in varying degrees. The majority of the + deviations observed had not previously been seen either under natural + conditions or in cultivation; they were first brought to light through the + influence of external factors. + </p> + <p> + Such transformations of flowers become apparent at a time, which is + separated by about two months from the period at which the particular + cause began to act. There is, therefore, no close connection between the + appearance of the modifications and the external conditions which prevail + at the moment. When we are ignorant of the causes which are operative so + long before the results are seen, we gain the impression that such + variations as occur are spontaneous or autonomous expressions of the inner + nature of the plant. It is much more likely that, as in Sempervivum, they + were originally produced by an external stimulus which had previously + reached the sexual cells or the young embryo. In any case abnormalities of + this kind appear to be of a special type as compared with ordinary + fluctuating variations. Darwin pointed out this difference; Bateson + (Bateson, "Materials for the study of Variation", London, 1894, page 5.) + has attempted to make the distinction sharper, at the same time + emphasising its importance in heredity. + </p> + <p> + Bateson applies the term CONTINUOUS to small variations connected with one + another by transitional stages, while those which are more striking and + characterised from the first by a certain completeness, he names + DISCONTINUOUS. He drew attention to a great difficulty which stands in the + way of Lamarck's hypothesis, as also of Darwin's view. "According to both + theories, specific diversity of form is consequent upon diversity of + environment, and diversity of environment is thus the ultimate measure of + diversity of specific form. Here then we meet the difficulty that diverse + environments often shade into each other insensibly and form a continuous + series, whereas the Specific Forms of life which are subject to them on + the whole form a Discontinuous Series." This difficulty is, however, not + of fundamental importance as well authenticated facts have been adduced + showing that by alteration of the environment discontinuous variations, + such as alterations in the number and form of members of a flower, may be + produced. We can as yet no more explain how this happens than we can + explain the existence of continuous variations. We can only assert that + both kinds of variation arise in response to quantitative alterations in + external conditions. The question as to which kind of variation is + produced depends on the greater or less degree of alteration; it is + correlated with the state of the particular cells at the moment. + </p> + <p> + In this short sketch it is only possible to deal superficially with a + small part of the subject. It has been clearly shown that in view of the + general dependence of development on the factors of the environment a + number of problems are ready for experimental treatment. One must, + however, not forget that the science of the physiology of form has not + progressed beyond its initial stages. Just now our first duty is to + demonstrate the dependence on external factors in as many forms of plants + as possible, in order to obtain a more thorough control of all the + different plant-forms. The problem is not only to produce at will (and + independently of their normal mode of life) forms which occur in nature, + but also to stimulate into operation potentialities which necessarily lie + dormant under the conditions which prevail in nature. The constitution of + a species is much richer in possibilities of development than would appear + to be the case under normal conditions. It remains for man to stimulate + into activity all the potentialities. + </p> + <p> + But the control of plant-form is only a preliminary step—the + foundation stones on which to erect a coherent scientific structure. We + must discover what are the internal processes in the cell produced by + external factors, which as a necessary consequence result in the + appearance of a definite form. We are here brought into contact with the + most obscure problem of life. Progress can only be made pari passu with + progress in physics and chemistry, and with the growth of our knowledge of + nutrition, growth, etc. + </p> + <p> + Let us take one of the simplest cases—an alteration in form. A + cylindrical cell of the alga Stigeoclonium assumes, as Livingstone + (Livingstone, "On the nature of the stimulus which causes the change of + form, etc." "Botanical Gazette", XXX. 1900; also XXXII. 1901.) has shown, + a spherical form when the osmotic pressure of the culture fluid is + increased; or a spore of Mucor, which, in a sugar solution grows into a + branched filament, in the presence of a small quantity of acid (hydrogen + ions) becomes a comparatively large sphere. (Ritter, "Ueber Kugelhefe, + etc." "Ber. bot. Gesell." Berlin, XXV. page 255, 1907.) In both cases + there has undoubtedly been an alteration in the osmotic pressure of the + cell-sap, but this does not suffice to explain the alteration in form, + since the unknown alterations, which are induced in the protoplasm, must + in their turn influence the cell-membrane. In the case of the very much + more complex alterations in form, such as we encounter in the course of + development of plants, there do not appear to be any clues which lead us + to a deeper insight into the phenomena. Nevertheless we continue the + attempt, seeking with the help of any available hypothesis for points of + attack, which may enable us to acquire a more complete mastery of + physiological methods. To quote a single example; I may put the question, + what internal changes produce a transition from vegetative growth to + sexual reproduction? + </p> + <p> + The facts, which are as clearly established from the lower as for the + higher plants, teach us that quantitative alteration in the environment + produces such a transition. This suggests the conclusion that quantitative + internal changes in the cells, and with them disturbances in the degree of + concentration, are induced, through which the chemical reactions are led + in the direction of sexual reproduction. An increase in the production of + organic substances in the presence of light, chiefly of the carbohydrates, + with a simultaneous decrease in the amount of inorganic salts and water, + are the cause of the disturbance and at the same time of the alteration in + the direction of development. Possibly indeed mineral salts as such are + not in question, but only in the form of other organic combinations, + particularly proteid material, so that we are concerned with an alteration + in the relation of the carbohydrates and proteids. The difficulties of + such researches are very great because the methods are not yet + sufficiently exact to demonstrate the frequently small quantitative + differences in chemical composition. Questions relating to the enzymes, + which are of the greatest importance in all these life-processes, are + especially complicated. In any case it is the necessary result of such an + hypothesis that we must employ chemical methods of investigation in + dealing with problems connected with the physiology of form. + </p> + <p> + II. INFLUENCE OF ENVIRONMENT ON THE TRANSFORMATION OF SPECIES. + </p> + <p> + The study of the physiology of form-development in a pure species has + already yielded results and makes slow but sure progress. The physiology + of the possibility of the transformation of one species into another is + based, as yet, rather on pious hope than on accomplished fact. From the + first it appeared to be hopeless to investigate physiologically the origin + of Linnean species and at the same time that of the natural system, an aim + which Darwin had before him in his enduring work. The historical sequence + of events, of which an organism is the expression, can only be treated + hypothetically with the help of facts supplied by comparative morphology, + the history of development, geographical distribution, and palaeontology. + (See Lotsy, "Vorlesungen" (Jena, I. 1906, II. 1908), for summary of the + facts.) A glance at the controversy which is going on today in regard to + different hypotheses shows that the same material may lead different + investigators to form entirely different opinions. Our ultimate aim is to + find a solution of the problem as to the cause of the origin of species. + Indeed such attempts are now being made: they are justified by the fact + that under cultivation new and permanent strains are produced; the + fundamental importance of this was first grasped by Darwin. New points of + view in regard to these lines of inquiry have been adopted by H. de Vries + who has succeeded in obtaining from Oenothera Lamarckiana a number of + constant "elementary" species. Even if it is demonstrated that he was + simply dealing with the complex splitting up of a hybrid (Bateson, + "Reports to the Evolution Committee of the Royal Society", London, 1902; + cf. also Lotsy, "Vorlesungen", Vol. I. page 234.), the facts adduced in no + sense lose their very great value. + </p> + <p> + We must look at the problem in its simplest form; we find it in every case + where a new race differs essentially from the original type in a single + character only; for example, in the colour of the flowers or in the + petalody of the stamens (doubling of flowers). In this connection we must + keep in view the fact that every visible character in a plant is the + resultant of the cooperation of specific structure, with its various + potentialities, and the influence of the environment. We know, that in a + pure species all characters vary, that a blue-flowering Campanula or a red + Sempervivum can be converted by experiment into white-flowering forms, + that a transformation of stamens into petals may be caused by fungi or by + the influence of changed conditions of nutrition, or that plants in dry + and poor soil become dwarfed. But so far as the experiments justify a + conclusion, it would appear that such alterations are not inherited by the + offspring. Like all other variations they appear only so long as special + conditions prevail in the surroundings. + </p> + <p> + It has been shown that the case is quite different as regards the + white-flowering, double or dwarf races, because these retain their + characters when cultivated under practically identical conditions, and + side by side with the blue, single-flowering or tall races. The problem + may therefore be stated thus: how can a character, which appears in the + one case only under the strictly limited conditions of the experiment, in + other cases become apparent under the very much wider conditions of + ordinary cultivation? If a character appears, in these circumstances, in + the case of all individuals, we then speak of constant races. In such + simple cases the essential point is not the creation of a new character + but rather an ALTERATION OF THIS CHARACTER IN ACCORDANCE WITH THE + ENVIRONMENT. In the examples mentioned the modified character in the + simple varieties (or a number of characters in elementary species) appears + more or less suddenly and is constant in the above sense. The result is + what de Vries has termed a Mutation. In this connection we must bear in + mind the fact that no difference, recognisable externally, need exist + between individual variation and mutation. Even the most minute + quantitative difference between two plants may be of specific value if it + is preserved under similar external conditions during many successive + generations. We do not know how this happens. We may state the problem in + other terms; by saying that the specific structure must be altered. It is + possible, to some extent, to explain this sudden alteration, if we regard + it as a chemical alteration of structure either in the specific qualities + of the proteids or of the unknown carriers of life. In the case of many + organic compounds their morphological characters (the physical condition, + crystalline form, etc.) are at once changed by alteration of atomic + relations or by incorporation of new radicals. (For instance ethylchloride + (C2H5Cl) is a gas at 21 deg C., ethylenechloride (C2H4Cl2) a fluid boiling + at 84 deg C., beta trichlorethane (C2H3Cl3) a fluid boiling at 113 deg C., + perchlorethane (C2Cl6) a crystalline substance. Klebs, ("Willkurliche + Entwickelungsanderungen" page 158.) Much more important, however, would be + an answer to the question, whether an individual variation can be + converted experimentally into an inherited character—a mutation in + de Vries's sense. + </p> + <p> + In all circumstances we may recognise as a guiding principle the + assumption adopted by Lamarck, Darwin, and many others, that the + inheritance of any one character, or in more general terms, the + transformation of one species into another, is, in the last instance, to + be referred to a change in the environment. From a causal-mechanical point + of view it is not a priori conceivable that one species can ever become + changed into another so long as external conditions remain constant. The + inner structure of a species must be essentially altered by external + influences. Two methods of experimental research may be adopted, the + effect of crossing distinct species and, secondly, the effect of definite + factors of the environment. + </p> + <p> + The subject of hybridisation is dealt with in another part of this essay. + It is enough to refer here to the most important fact, that as the result + of combinations of characters of different species new and constant forms + are produced. Further, Tschermack, Bateson and others have demonstrated + the possibility that hitherto unknown inheritable characters may be + produced by hybridisation. + </p> + <p> + The other method of producing constant races by the influence of special + external conditions has often been employed. The sporeless races of + Bacteria and Yeasts (Cf. Detto, "Die Theorie der direkten Anpassung... ", + pages 98 et seq., Jena, 1904; see also Lotsy, "Vorlesungen", II. pages 636 + et seq., where other similar cases are described.) are well known, in + which an internal alteration of the cells is induced by the influence of + poison or higher temperature, so that the power of producing spores even + under normal conditions appears to be lost. A similar state of things is + found in some races which under certain definite conditions lose their + colour or their virulence. Among the phanerogams the investigations of + Schubler on cereals afford parallel cases, in which the influence of a + northern climate produces individuals which ripen their seeds early; these + seeds produce plants which seed early in southern countries. Analogous + results were obtained by Cieslar in his experiments; seeds of conifers + from the Alps when planted in the plains produced plants of slow growth + and small diameter. + </p> + <p> + All these observations are of considerable interest theoretically; they + show that the action of environment certainly induces such internal + changes, and that these are transmitted to the next generation. But as + regards the main question, whether constant races may be obtained by this + means, the experiments cannot as yet supply a definite answer. In + phanerogams, the influence very soon dies out in succeeding generations; + in the case of bacteria, in which it is only a question of the loss of a + character it is relatively easy for this to reappear. It is not + impossible, that in all such cases there is a material hanging-on of + certain internal conditions, in consequence of which the modification of + the character persists for a time in the descendants, although the + original external conditions are no longer present. + </p> + <p> + Thus a slow dying-out of the effect of a stimulus was seen in my + experiments on Veronica chamaedrys. (Klebs, "Kunstliche Metamorphosen", + Stuttgart, 1906, page 132.) During the cultivation of an artificially + modified inflorescence I obtained a race showing modifications in + different directions, among which twisting was especially conspicuous. + This plant, however, does not behave as the twisted race of Dipsacus + isolated by de Vries (de Vries, "Mutationstheorie", Vol. II. Leipzig, + 1903, page 573.), which produced each year a definite percentage of + twisted individuals. In the vegetative reproduction of this Veronica the + torsion appeared in the first, also in the second and third year, but with + diminishing intensity. In spite of good cultivation this character has + apparently now disappeared; it disappeared still more quickly in + seedlings. In another character of the same Veronica chamaedrys the + influence of the environment was stronger. The transformation of the + inflorescences to foliage-shoots formed the starting-point; it occurred + only under narrowly defined conditions, namely on cultivation as a cutting + in moist air and on removal of all other leaf-buds. In the majority (7/10) + of the plants obtained from the transformed shoots, the modification + appeared in the following year without any interference. Of the three + plants which were under observation several years the first lost the + character in a short time, while the two others still retain it, after + vegetative propagation, in varying degrees. The same character occurs also + in some of the seedlings; but anything approaching a constant race has not + been produced. + </p> + <p> + Another means of producing new races has been attempted by Blaringhem. + (Blaringhem, "Mutation et Traumatisme", Paris, 1907.) On removing at an + early stage the main shoots of different plants he observed various + abnormalities in the newly formed basal shoots. From the seeds of such + plants he obtained races, a large percentage of which exhibited these + abnormalities. Starting from a male Maize plant with a fasciated + inflorescence, on which a proportion of the flowers had become male, a new + race was bred in which hermaphrodite flowers were frequently produced. In + the same way Blaringhem obtained, among other similar results, a race of + barley with branched ears. These races, however, behaved in essentials + like those which have been demonstrated by de Vries to be inconstant, e.g. + Trifolium pratense quinquefolium and others. The abnormality appears in a + proportion of the individuals and only under very special conditions. It + must be remembered too that Blaringhem worked with old cultivated plants, + which from the first had been disposed to split into a great variety of + races. It is possible, but difficult to prove, that injury contributed to + this result. + </p> + <p> + A third method has been adopted by MacDougal (MacDougal, "Heredity and + Origin of species", "Monist", 1906; "Report of department of botanical + research", "Fifth Year-book of the Carnegie Institution of Washington", + page 119, 1907.) who injected strong (10 percent) sugar solution or weak + solutions of calcium nitrate and zinc sulphate into young carpels of + different plants. From the seeds of a plant of Raimannia odorata the + carpels of which had been thus treated he obtained several plants + distinguished from the parent-forms by the absence of hairs and by + distinct forms of leaves. Further examination showed that he had here to + do with a new elementary species. MacDougal also obtained a more or less + distinct mutant of Oenothera biennis. We cannot as yet form an opinion as + to how far the effect is due to the wound or to the injection of fluid as + such, or to its chemical properties. This, however, is not so essential as + to decide whether the mutant stands in any relation to the influence of + external factors. It is at any rate very important that this kind of + investigation should be carried further. + </p> + <p> + If it could be shown that new and inherited races were obtained by + MacDougal's method, it would be safe to conclude that the same end might + be gained by altering the conditions of the food-stuff conducted to the + sexual cells. New races or elementary species, however, arise without + wounding or injection. This at once raises the much discussed question, + how far garden-cultivation has led to the creation of new races? Contrary + to the opinion expressed by Darwin and others, de Vries + ("Mutationstheorie", Vol. I. pages 412 et seq.) tried to show that + garden-races have been produced only from spontaneous types which occur in + a wild state or from sub-races, which the breeder has accidentally + discovered but not originated. In a small number of cases only has de + Vries adduced definite proof. On the other side we have the work of + Korschinsky (Korschinsky, "Heterogenesis und Evolution", "Flora", 1901.) + which shows that whole series of garden-races have made their appearance + only after years of cultivation. In the majority of races we are entirely + ignorant of their origin. + </p> + <p> + It is, however, a fact that if a plant is removed from natural conditions + into cultivation, a well-marked variation occurs. The well-known + plant-breeder L. de Vilmorin (L. de Vilmorin, "Notices sur l'amelioration + des plantes", Paris, 1886, page 36.), speaking from his own experience, + states that a plant is induced to "affoler," that is to exhibit all + possible variations from which the breeder may make a further selection + only after cultivation for several generations. The effect of cultivation + was particularly striking in Veronica chamaedrys (Klebs, "Kunstliche + Metamorphosen", Stuttgart, 1906, page 152.) which, in spite of its wide + distribution in nature, varies very little. After a few years of + cultivation this "good" and constant species becomes highly variable. The + specimens on which the experiments were made were three modified + inflorescence cuttings, the parent-plants of which certainly exhibited no + striking abnormalities. In a short time many hitherto latent + potentialities became apparent, so that characters, never previously + observed, or at least very rarely, were exhibited, such as scattered + leaf-arrangement, torsion, terminal or branched inflorescences, the + conversion of the inflorescence into foliage-shoots, every conceivable + alteration in the colour of flowers, the assumption of a green colour by + parts of the flowers, the proliferation of flowers. + </p> + <p> + All this points to some disturbance in the species resulting from methods + of cultivation. It has, however, not yet been possible to produce constant + races with any one of these modified characters. But variations appeared + among the seedlings, some of which, e.g. yellow variegation, were not + inheritable, while others have proved constant. This holds good, so far as + we know at present, for a small rose-coloured form which is to be reckoned + as a mutation. Thus the prospect of producing new races by cultivation + appears to be full of promise. + </p> + <p> + So long as the view is held that good nourishment, i.e. a plentiful supply + of water and salts, constitutes the essential characteristic of + garden-cultivation, we can hardly conceive that new mutations can be thus + produced. But perhaps the view here put forward in regard to the + production of form throws new light on this puzzling problem. + </p> + <p> + Good manuring is in the highest degree favourable to vegetative growth, + but is in no way equally favourable to the formation of flowers. The + constantly repeated expression, good or favourable nourishment, is not + only vague but misleading, because circumstances favourable to growth + differ from those which promote reproduction; for the production of every + form there are certain favourable conditions of nourishment, which may be + defined for each species. Experience shows that, within definite and often + very wide limits, it does not depend upon the ABSOLUTE AMOUNT of the + various food substances, but upon their respective degrees of + concentration. As we have already stated, the production of flowers + follows a relative increase in the amount of carbohydrates formed in the + presence of light, as compared with the inorganic salts on which the + formation of albuminous substances depends. (Klebs, "Kunstliche + Metamorphosen", page 117.) The various modifications of flowers are due to + the fact that a relatively too strong solution of salts is supplied to the + rudiments of these organs. As a general rule every plant form depends upon + a certain relation between the different chemical substances in the cells + and is modified by an alteration of that relation. + </p> + <p> + During long cultivation under conditions which vary in very different + degrees, such as moisture, the amount of salts, light intensity, + temperature, oxygen, it is possible that sudden and special disturbances + in the relations of the cell substances have a directive influence on the + inner organisation of the sexual cells, so that not only inconstant but + also constant varieties will be formed. + </p> + <p> + Definite proof in support of this view has not yet been furnished, and we + must admit that the question as to the cause of heredity remains, + fundamentally, as far from solution as it was in Darwin's time. As the + result of the work of many investigators, particularly de Vries, the + problem is constantly becoming clearer and more definite. The penetration + into this most difficult and therefore most interesting problem of life + and the creation by experiment of new races or elementary species are no + longer beyond the region of possibility. + </p> + <p> + <a name="link2H_4_0015" id="link2H_4_0015"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + XIV. EXPERIMENTAL STUDY OF THE INFLUENCE OF ENVIRONMENT ON ANIMALS. By + Jacques Loeb, M.D. Professor of Physiology in the University of + California. + </h2> + <p> + I. INTRODUCTORY REMARKS. + </p> + <p> + What the biologist calls the natural environment of an animal is from a + physical point of view a rather rigid combination of definite forces. It + is obvious that by a purposeful and systematic variation of these and by + the application of other forces in the laboratory, results must be + obtainable which do not appear in the natural environment. This is the + reasoning underlying the modern development of the study of the effects of + environment upon animal life. It was perhaps not the least important of + Darwin's services to science that the boldness of his conceptions gave to + the experimental biologist courage to enter upon the attempt of + controlling at will the life-phenomena of animals, and of bringing about + effects which cannot be expected in Nature. + </p> + <p> + The systematic physico-chemical analysis of the effect of outside forces + upon the form and reactions of animals is also our only means of + unravelling the mechanism of heredity beyond the scope of the Mendelian + law. The manner in which a germ-cell can force upon the adult certain + characters will not be understood until we succeed in varying and + controlling hereditary characteristics; and this can only be accomplished + on the basis of a systematic study of the effects of chemical and physical + forces upon living matter. + </p> + <p> + Owing to limitation of space this sketch is necessarily very incomplete, + and it must not be inferred that studies which are not mentioned here were + considered to be of minor importance. All the writer could hope to do was + to bring together a few instances of the experimental analysis of the + effect of environment, which indicate the nature and extent of our control + over life-phenomena and which also have some relation to the work of + Darwin. In the selection of these instances preference is given to those + problems which are not too technical for the general reader. + </p> + <p> + The forces, the influence of which we shall discuss, are in succession + chemical agencies, temperature, light, and gravitation. We shall also + treat separately the effect of these forces upon form and instinctive + reactions. + </p> + <p> + II. THE EFFECTS OF CHEMICAL AGENCIES. + </p> + <p> + (a) HETEROGENEOUS HYBRIDISATION. + </p> + <p> + It was held until recently that hybridisation is not possible except + between closely related species and that even among these a successful + hybridisation cannot always be counted upon. This view was well supported + by experience. It is, for instance, well known that the majority of marine + animals lay their unfertilised eggs in the ocean and that the males shed + their sperm also into the sea-water. The numerical excess of the + spermatozoa over the ova in the sea-water is the only guarantee that the + eggs are fertilised, for the spermatozoa are carried to the eggs by chance + and are not attracted by the latter. This statement is the result of + numerous experiments by various authors, and is contrary to common belief. + As a rule all or the majority of individuals of a species in a given + region spawn on the same day, and when this occurs the sea-water + constitutes a veritable suspension of sperm. It has been shown by + experiment that in fresh sea-water the sperm may live and retain its + fertilising power for several days. It is thus unavoidable that at certain + periods more than one kind of spermatozoon is suspended in the sea-water + and it is a matter of surprise that the most heterogeneous hybridisations + do not constantly occur. The reason for this becomes obvious if we bring + together mature eggs and equally mature and active sperm of a different + family. When this is done no egg is, as a rule, fertilised. The eggs of a + sea-urchin can be fertilised by sperm of their own species, or, though in + smaller numbers, by the sperm of other species of sea-urchins, but not by + the sperm of other groups of echinoderms, e.g. starfish, brittle-stars, + holothurians or crinoids, and still less by the sperm of more distant + groups of animals. The consensus of opinion seemed to be that the + spermatozoon must enter the egg through a narrow opening or canal, the + so-called micropyle, and that the micropyle allowed only the spermatozoa + of the same or of a closely related species to enter the egg. + </p> + <p> + It seemed to the writer that the cause of this limitation of hybridisation + might be of another kind and that by a change in the constitution of the + sea-water it might be possible to bring about heterogenous hybridisations, + which in normal sea-water are impossible. This assumption proved correct. + Sea-water has a faintly alkaline reaction (in terms of the physical + chemist its concentration of hydroxyl ions is about (10 to the power minus + six)N at Pacific Grove, California, and about (10 to the power minus 5)N + at Woods Hole, Massachusetts). If we slightly raise the alkalinity of the + sea-water by adding to it a small but definite quantity of sodium + hydroxide or some other alkali, the eggs of the sea-urchin can be + fertilised with the sperm of widely different groups of animals, possibly + with the sperm of any marine animal which sheds it into the ocean. In 1903 + it was shown that if we add from about 0.5 to 0.8 cubic centimetre N/10 + sodium hydroxide to 50 cubic centimetres of sea-water, the eggs of + Strongylocentrotus purpuratus (a sea-urchin which is found on the coast of + California) can be fertilised in large quantities by the sperm of various + kinds of starfish, brittle-stars and holothurians; while in normal + sea-water or with less sodium hydroxide not a single egg of the same + female could be fertilised with the starfish sperm which proved effective + in the hyper-alkaline sea-water. The sperm of the various forms of + starfish was not equally effective for these hybridisations; the sperm of + Asterias ochracea and A. capitata gave the best results, since it was + possible to fertilise 50 per cent or more of the sea-urchin eggs, while + the sperm of Pycnopodia and Asterina fertilised only 2 per cent of the + same eggs. + </p> + <p> + Godlewski used the same method for the hybridisation of the sea-urchin + eggs with the sperm of a crinoid (Antedon rosacea). Kupelwieser afterwards + obtained results which seemed to indicate the possibility of fertilising + the eggs of Strongylocentrotus with the sperm of a mollusc (Mytilus.) + Recently, the writer succeeded in fertilising the eggs of + Strongylocentrotus franciscanus with the sperm of a mollusc—Chlorostoma. + This result could only be obtained in sea-water the alkalinity of which + had been increased (through the addition of 0.8 cubic centimetre N/10 + sodium hydroxide to 50 cubic centimetres of sea-water). We thus see that + by increasing the alkalinity of the sea-water it is possible to effect + heterogeneous hybridisations which are at present impossible in the + natural environment of these animals. + </p> + <p> + It is, however, conceivable that in former periods of the earth's history + such heterogeneous hybridisations were possible. It is known that in + solutions like sea-water the degree of alkalinity must increase when the + amount of carbon-dioxide in the atmosphere is diminished. If it be true, + as Arrhenius assumes, that the Ice age was caused or preceded by a + diminution in the amount of carbon-dioxide in the air, such a diminution + must also have resulted in an increase of the alkalinity of the sea-water, + and one result of such an increase must have been to render possible + heterogeneous hybridisations in the ocean which in the present state of + alkalinity are practically excluded. + </p> + <p> + But granted that such hybridisations were possible, would they have + influenced the character of the fauna? In other words, are the hybrids + between sea-urchin and starfish, or better still, between sea-urchin and + mollusc, capable of development, and if so, what is their character? The + first experiment made it appear doubtful whether these heterogeneous + hybrids could live. The sea-urchin eggs which were fertilised in the + laboratory by the spermatozoa of the starfish, as a rule, died earlier + than those of the pure breeds. But more recent results indicate that this + was due merely to deficiencies in the technique of the earlier + experiments. The writer has recently obtained hybrid larvae between the + sea-urchin egg and the sperm of a mollusc (Chlorostoma) which, in the + laboratory, developed as well and lived as long as the pure breeds of the + sea-urchin, and there was nothing to indicate any difference in the + vitality of the two breeds. + </p> + <p> + So far as the question of heredity is concerned, all the experiments on + heterogeneous hybridisation of the egg of the sea-urchin with the sperm of + starfish, brittle-stars, crinoids and molluscs, have led to the same + result, namely, that the larvae have purely maternal characteristics and + differ in no way from the pure breed of the form from which the egg is + taken. By way of illustration it may be said that the larvae of the + sea-urchin reach on the third day or earlier (according to species and + temperature) the so-called pluteus stage, in which they possess a typical + skeleton; while neither the larvae of the starfish nor those of the + mollusc form a skeleton at the corresponding stage. It was, therefore, a + matter of some interest to find out whether or not the larvae produced by + the fertilisation of the sea-urchin egg with the sperm of starfish or + mollusc would form the normal and typical pluteus skeleton. This was + invariably the case in the experiments of Godlewski, Kupelwieser, + Hagedoorn, and the writer. These hybrid larvae were exclusively maternal + in character. + </p> + <p> + It might be argued that in the case of heterogeneous hybridisation the + sperm-nucleus does not fuse with the egg-nucleus, and that, therefore, the + spermatozoon cannot transmit its hereditary substances to the larvae. But + these objections are refuted by Godlewski's experiments, in which he + showed definitely that if the egg of the sea-urchin is fertilised with the + sperm of a crinoid the fusion of the egg-nucleus and sperm-nucleus takes + place in the normal way. It remains for further experiments to decide what + the character of the adult hybrids would be. + </p> + <p> + (b). ARTIFICIAL PARTHENOGENESIS. + </p> + <p> + Possibly in no other field of Biology has our ability to control + life-phenomena by outside conditions been proved to such an extent as in + the domain of fertilisation. The reader knows that the eggs of the + overwhelming majority of animals cannot develop unless a spermatozoon + enters them. In this case a living agency is the cause of development and + the problem arises whether it is possible to accomplish the same result + through the application of well-known physico-chemical agencies. This is, + indeed, true, and during the last ten years living larvae have been + produced by chemical agencies from the unfertilised eggs of sea-urchins, + starfish, holothurians and a number of annelids and molluscs; in fact this + holds true in regard to the eggs of practically all forms of animals with + which such experiments have been tried long enough. In each form the + method of procedure is somewhat different and a long series of experiments + is often required before the successful method is found. + </p> + <p> + The facts of Artificial Parthenogenesis, as the chemical fertilisation of + the egg is called, have, perhaps, some bearing on the problem of + evolution. If we wish to form a mental image of the process of evolution + we have to reckon with the possibility that parthenogenetic propagation + may have preceded sexual reproduction. This suggests also the possibility + that at that period outside forces may have supplied the conditions for + the development of the egg which at present the spermatozoon has to + supply. For this, if for no other reason, a brief consideration of the + means of artificial parthenogenesis may be of interest to the student of + evolution. + </p> + <p> + It seemed necessary in these experiments to imitate as completely as + possible by chemical agencies the effects of the spermatozoon upon the + egg. When a spermatozoon enters the egg of a sea-urchin or certain + starfish or annelids, the immediate effect is a characteristic change of + the surface of the egg, namely the formation of the so-called membrane of + fertilisation. The writer found that we can produce this membrane in the + unfertilised egg by certain acids, especially the monobasic acids of the + fatty series, e.g. formic, acetic, propionic, butyric, etc. Carbon-dioxide + is also very efficient in this direction. It was also found that the + higher acids are more efficient than the lower ones, and it is possible + that the spermatozoon induces membrane-formation by carrying into the egg + a higher fatty acid, namely oleic acid or one of its salts or esters. + </p> + <p> + The physico-chemical process which underlies the formation of the membrane + seems to be the cause of the development of the egg. In all cases in which + the unfertilised egg has been treated in such a way as to cause it to form + a membrane it begins to develop. For the eggs of certain animals + membrane-formation is all that is required to induce a complete + development of the unfertilised egg, e.g. in the starfish and certain + annelids. For the eggs of other animals a second treatment is necessary, + presumably to overcome some of the injurious effects of acid treatment. + Thus the unfertilised eggs of the sea-urchin Strongylocentrotus purpuratus + of the Californian coast begin to develop when membrane-formation has been + induced by treatment with a fatty acid, e.g. butyric acid; but the + development soon ceases and the eggs perish in the early stages of + segmentation, or after the first nuclear division. But if we treat the + same eggs, after membrane-formation, for from 35 to 55 minutes (at 15 deg + C.) with sea-water the concentration (osmotic pressure) of which has been + raised through the addition of a definite amount of some salt or sugar, + the eggs will segment and develop normally, when transferred back to + normal sea-water. If care is taken, practically all the eggs can be caused + to develop into plutei, the majority of which may be perfectly normal and + may live as long as larvae produced from eggs fertilised with sperm. + </p> + <p> + It is obvious that the sea-urchin egg is injured in the process of + membrane-formation and that the subsequent treatment with a hypertonic + solution only acts as a remedy. The nature of this injury became clear + when it was discovered that all the agencies which cause haemolysis, i.e. + the destruction of the red blood corpuscles, also cause membrane-formation + in unfertilised eggs, e.g. fatty acids or ether, alcohols or chloroform, + etc., or saponin, solanin, digitalin, bile salts and alkali. It thus + happens that the phenomena of artificial parthenogenesis are linked + together with the phenomena of haemolysis which at present play so + important a role in the study of immunity. The difference between + cytolysis (or haemolysis) and fertilisation seems to be this, that the + latter is caused by a superficial or slight cytolysis of the egg, while if + the cytolytic agencies have time to act on the whole egg the latter is + completely destroyed. If we put unfertilised eggs of a sea-urchin into + sea-water which contains a trace of saponin we notice that, after a few + minutes, all the eggs form the typical membrane of fertilisation. If the + eggs are then taken out of the saponin solution, freed from all traces of + saponin by repeated washing in normal sea-water, and transferred to the + hypertonic sea-water for from 35 to 55 minutes, they develop into larvae. + If, however, they are left in the sea-water containing the saponin they + undergo, a few minutes after membrane-formation, the disintegration known + in pathology as CYTOLYSIS. Membrane-formation is, therefore, caused by a + superficial or incomplete cytolysis. The writer believes that the + subsequent treatment of the egg with hypertonic sea-water is needed only + to overcome the destructive effects of this partial cytolysis. The full + reasons for this belief cannot be given in a short essay. + </p> + <p> + Many pathologists assume that haemolysis or cytolysis is due to a + liquefaction of certain fatty or fat-like compounds, the so-called + lipoids, in the cell. If this view is correct, it would be necessary to + ascribe the fertilisation of the egg to the same process. + </p> + <p> + The analogy between haemolysis and fertilisation throws, possibly, some + light on a curious observation. It is well known that the blood + corpuscles, as a rule, undergo cytolysis if injected into the blood of an + animal which belongs to a different family. The writer found last year + that the blood of mammals, e.g. the rabbit, pig, and cattle, causes the + egg of Strongylocentrotus to form a typical fertilisation-membrane. If + such eggs are afterwards treated for a short period with hypertonic + sea-water they develop into normal larvae (plutei). Some substance + contained in the blood causes, presumably, a superficial cytolysis of the + egg and thus starts its development. + </p> + <p> + We can also cause the development of the sea-urchin egg without + membrane-formation. The early experiments of the writer were done in this + way and many experimenters still use such methods. It is probable that in + this case the mechanism of fertilisation is essentially the same as in the + case where the membrane-formation is brought about, with this difference + only, that the cytolytic effect is less when no fertilisation-membrane is + formed. This inference is corroborated by observations on the + fertilisation of the sea-urchin egg with ox blood. It very frequently + happens that not all of the eggs form membranes in this process. Those + eggs which form membranes begin to develop, but perish if they are not + treated with hypertonic sea-water. Some of the other eggs, however, which + do not form membranes, develop directly into normal larvae without any + treatment with hypertonic sea-water, provided they are exposed to the + blood for only a few minutes. Presumably some blood enters the eggs and + causes the cytolytic effects in a less degree than is necessary for + membrane-formation, but in a sufficient degree to cause their development. + The slightness of the cytolytic effect allows the egg to develop without + treatment with hypertonic sea-water. + </p> + <p> + Since the entrance of the spermatozoon causes that degree of cytolysis + which leads to membrane-formation, it is probable that, in addition to the + cytolytic or membrane-forming substance (presumably a higher fatty acid), + it carries another substance into the egg which counteracts the + deleterious cytolytic effects underlying membrane-formation. + </p> + <p> + The question may be raised whether the larvae produced by artificial + parthenogenesis can reach the mature stage. This question may be answered + in the affirmative, since Delage has succeeded in raising several + parthenogenetic sea-urchin larvae beyond the metamorphosis into the adult + stage and since in all the experiments made by the writer the + parthenogenetic plutei lived as long as the plutei produced from + fertilised eggs. + </p> + <p> + (c). ON THE PRODUCTION OF TWINS FROM ONE EGG THROUGH A CHANGE IN THE + CHEMICAL CONSTITUTION OF THE SEA-WATER. + </p> + <p> + The reader is probably familiar with the fact that there exist two + different types of human twins. In the one type the twins differ as much + as two children of the same parents born at different periods; they may or + may not have the same sex. In the second type the twins have invariably + the same sex and resemble each other most closely. Twins of the latter + type are produced from the same egg, while twins of the former type are + produced from two different eggs. + </p> + <p> + The experiments of Driesch and others have taught us that twins originate + from one egg in this manner, namely, that the first two cells into which + the egg divides after fertilisation become separated from each other. This + separation can be brought about by a change in the chemical constitution + of the sea-water. Herbst observed that if the fertilised eggs of the + sea-urchin are put into sea-water which is freed from calcium, the cells + into which the egg divides have a tendency to fall apart. Driesch + afterwards noticed that eggs of the sea-urchin treated with sea-water + which is free from lime have a tendency to give rise to twins. The writer + has recently found that twins can be produced not only by the absence of + lime, but also through the absence of sodium or of potassium; in other + words, through the absence of one or two of the three important metals in + the sea-water. There is, however, a second condition, namely, that the + solution used for the production of twins must have a neutral or at least + not an alkaline reaction. + </p> + <p> + The procedure for the production of twins in the sea-urchin egg consists + simply in this:—the eggs are fertilised as usual in normal sea-water + and then, after repeated washing in a neutral solution of sodium chloride + (of the concentration of the sea-water), are placed in a neutral mixture + of potassium chloride and calcium chloride, or of sodium chloride and + potassium chloride, or of sodium chloride and calcium chloride, or of + sodium chloride and magnesium chloride. The eggs must remain in this + solution until half an hour or an hour after they have reached the + two-cell stage. They are then transferred into normal sea-water and + allowed to develop. From 50 to 90 per cent of the eggs of + Strongylocentrotus purpuratus treated in this manner may develop into + twins. These twins may remain separate or grow partially together and form + double monsters, or heal together so completely that only slight or even + no imperfections indicate that the individual started its career as a pair + of twins. It is also possible to control the tendency of such twins to + grow together by a change in the constitution of the sea-water. If we use + as a twin-producing solution a mixture of sodium, magnesium and potassium + chlorides (in the proportion in which these salts exist in the sea-water) + the tendency of the twins to grow together is much more pronounced than if + we use simply a mixture of sodium chloride and magnesium chloride. + </p> + <p> + The mechanism of the origin of twins, as the result of altering the + composition of the sea-water, is revealed by observation of the first + segmentation of the egg in these solutions. This cell-division is modified + in a way which leads to a separation of the first two cells. If the egg is + afterwards transferred back into normal sea-water, each of these two cells + develops into an independent embryo. Since normal sea-water contains all + three metals, sodium, calcium, and potassium, and since it has besides an + alkaline reaction, we perceive the reason why twins are not normally + produced from one egg. These experiments suggest the possibility of a + chemical cause for the origin of twins from one egg or of double + monstrosities in mammals. If, for some reason, the liquids which surround + the human egg a short time before and after the first cell-division are + slightly acid, and at the same time lacking in one of the three important + metals, the conditions for the separation of the first two cells and the + formation of identical twins are provided. + </p> + <p> + In conclusion it may be pointed out that the reverse result, namely, the + fusion of normally double organs, can also be brought about experimentally + through a change in the chemical constitution of the sea-water. Stockard + succeeded in causing the eyes of fish embryos (Fundulus heteroclitus) to + fuse into a single cyclopean eye through the addition of magnesium + chloride to the sea-water. When he added about 6 grams of magnesium + chloride to 100 cubic centimetres of sea-water and placed the fertilised + eggs in the mixture, about 50 per cent of the eggs gave rise to one-eyed + embryos. "When the embryos were studied the one-eyed condition was found + to result from the union or fusion of the 'anlagen' of the two eyes. Cases + were observed which showed various degrees in this fusion; it appeared as + though the optic vessels were formed too far forward and ventral, so that + their antero-ventro-median surfaces fused. This produces one large optic + cup, which in all cases gives more or less evidence of its double nature." + (Stockard, "Archiv f. Entwickelungsmechanik", Vol. 23, page 249, 1907.) + </p> + <p> + We have confined ourselves to a discussion of rather simple effects of the + change in the constitution of the sea-water upon development. It is a + priori obvious, however, that an unlimited number of pathological + variations might be produced by a variation in the concentration and + constitution of the sea-water, and experience confirms this statement. As + an example we may mention the abnormalities observed by Herbst in the + development of sea-urchins through the addition of lithium to sea-water. + It is, however, as yet impossible to connect in a rational way the effects + produced in this and similar cases with the cause which produced them; and + it is also impossible to define in a simple way the character of the + change produced. + </p> + <p> + III. THE INFLUENCE OF TEMPERATURE. + </p> + <p> + (a) THE INFLUENCE OF TEMPERATURE UPON THE DENSITY OF PELAGIC ORGANISMS AND + THE DURATION OF LIFE. + </p> + <p> + It has often been noticed by explorers who have had a chance to compare + the faunas in different climates that in polar seas such species as thrive + at all in those regions occur, as a rule, in much greater density than + they do in the moderate or warmer regions of the ocean. This refers to + those members of the fauna which live at or near the surface, since they + alone lend themselves to a statistical comparison. In his account of the + Valdivia expedition, Chun (Chun, "Aus den Tiefen des Weltmeeres", page + 225, Jena, 1903.) calls especial attention to this quantitative difference + in the surface fauna and flora of different regions. "In the icy water of + the Antarctic, the temperature of which is below 0 deg C., we find an + astonishingly rich animal and plant life. The same condition with which we + are familiar in the Arctic seas is repeated here, namely, that the + quantity of plankton material exceeds that of the temperate and warm + seas." And again, in regard to the pelagic fauna in the region of the + Kerguelen Islands, he states: "The ocean is alive with transparent jelly + fish, Ctenophores (Bolina and Callianira) and of Siphonophore colonies of + the genus Agalma." + </p> + <p> + The paradoxical character of this general observation lies in the fact + that a low temperature retards development, and hence should be expected + to have the opposite effect from that mentioned by Chun. Recent + investigations have led to the result that life-phenomena are affected by + temperature in the same sense as the velocity of chemical reactions. In + the case of the latter van't Hoff had shown that a decrease in temperature + by 10 degrees reduces their velocity to one half or less, and the same has + been found for the influence of temperature on the velocity of + physiological processes. Thus Snyder and T.B. Robertson found that the + rate of heartbeat in the tortoise and in Daphnia is reduced to about + one-half if the temperature is lowered 10 deg C., and Maxwell, Keith + Lucas, and Snyder found the same influence of temperature for the rate + with which an impulse travels in the nerve. Peter observed that the rate + of development in a sea-urchin's egg is reduced to less than one-half if + the temperature (within certain limits) is reduced by 10 degrees. The same + effect of temperature upon the rate of development holds for the egg of + the frog, as Cohen and Peter calculated from the experiments of O. + Hertwig. The writer found the same temperature-coefficient for the rate of + maturation of the egg of a mollusc (Lottia). + </p> + <p> + All these facts prove that the velocity of development of animal life in + Arctic regions, where the temperature is near the freezing point of water, + must be from two to three times smaller than in regions where the + temperature of the ocean is about 10 deg C. and from four to nine times + smaller than in seas the temperature of which is about 20 deg C. It is, + therefore, exactly the reverse of what we should expect when authors state + that the density of organisms at or near the surface of the ocean in polar + regions is greater than in more temperate regions. + </p> + <p> + The writer believes that this paradox finds its explanation in experiments + which he has recently made on the influence of temperature on the duration + of life of cold-blooded marine animals. The experiments were made on the + fertilised and unfertilised eggs of the sea-urchin, and yielded the result + that for the lowering of temperature by 1 deg C. the duration of life was + about doubled. Lowering the temperature by 10 degrees therefore prolongs + the life of the organism 2 to the power 10, i.e. over a thousand times, + and a lowering by 20 degrees prolongs it about one million times. Since + this prolongation of life is far in excess of the retardation of + development through a lowering of temperature, it is obvious that, in + spite of the retardation of development in Arctic seas, animal life must + be denser there than in temperate or tropical seas. The excessive increase + of the duration of life at the poles will necessitate the simultaneous + existence of more successive generations of the same species in these + regions than in the temperate or tropical regions. + </p> + <p> + The writer is inclined to believe that these results have some bearing + upon a problem which plays an important role in theories of evolution, + namely, the cause of natural death. It has been stated that the processes + of differentiation and development lead also to the natural death of the + individual. If we express this in chemical terms it means that the + chemical processes which underlie development also determine natural + death. Physical chemistry has taught us to identify two chemical processes + even if only certain of their features are known. One of these means of + identification is the temperature coefficient. When two chemical processes + are identical, their velocity must be reduced by the same amount if the + temperature is lowered to the same extent. The temperature coefficient for + the duration of life of cold-blooded organisms seems, however, to differ + enormously from the temperature coefficient for their rate of development. + For a difference in temperature of 10 deg C. the duration of life is + altered five hundred times as much as the rate of development; and, for a + change of 20 deg C., it is altered more than a hundred thousand times as + much. From this we may conclude that, at least for the sea-urchin eggs and + embryo, the chemical processes which determine natural death are certainly + not identical with the processes which underlie their development. T.B. + Robertson has also arrived at the conclusion, for quite different reasons, + that the process of senile decay is essentially different from that of + growth and development. + </p> + <p> + (b) CHANGES IN THE COLOUR OF BUTTERFLIES PRODUCED THROUGH THE INFLUENCE OF + TEMPERATURE. + </p> + <p> + The experiments of Dorfmeister, Weismann, Merrifield, Standfuss, and + Fischer, on seasonal dimorphism and the aberration of colour in + butterflies have so often been discussed in biological literature that a + short reference to them will suffice. By seasonal dimorphism is meant the + fact that species may appear at different seasons of the year in a + somewhat different form or colour. Vanessa prorsa is the summer form, + Vanessa levana the winter form of the same species. By keeping the pupae + of Vanessa prorsa several weeks at a temperature of from 0 deg to 1 deg + Weismann succeeded in obtaining from the summer chrysalids specimens which + resembled the winter variety, Vanessa levana. + </p> + <p> + If we wish to get a clear understanding of the causes of variation in the + colour and pattern of butterflies, we must direct our attention to the + experiments of Fischer, who worked with more extreme temperatures than his + predecessors, and found that almost identical aberrations of colour could + be produced by both extremely high and extremely low temperatures. This + can be clearly seen from the following tabulated results of his + observations. At the head of each column the reader finds the temperature + to which Fischer submitted the pupae, and in the vertical column below are + found the varieties that were produced. In the vertical column A are given + the normal forms: + </p> + <p> + (Temperatures in deg C.) + </p> +<pre xml:space="preserve"> + 0 to -20 0 to +10 A. +35 to +37 +36 to +41 +42 to +46 + (Normal forms) + + ichnusoides polaris urticae ichnusa polaris ichnusoides + (nigrita) (nigrita) + + antigone fischeri io - fischeri antigone + (iokaste) (iokaste) + + testudo dixeyi polychloros erythromelas dixeyi testudo + + hygiaea artemis antiopa epione artemis hygiaea + + elymi wiskotti cardui - wiskotti elymi + + klymene merrifieldi atalanta - merrifieldi klymene + + weismanni porima prorsa - porima weismanni +</pre> + <p> + The reader will notice that the aberrations produced at a very low + temperature (from 0 to -20 deg C.) are absolutely identical with the + aberrations produced by exposing the pupae to extremely high temperatures + (42 to 46 deg C.). Moreover the aberrations produced by a moderately low + temperature (from 0 to 10 deg C.) are identical with the aberrations + produced by a moderately high temperature (36 to 41 deg C.) + </p> + <p> + From these observations Fischer concludes that it is erroneous to speak of + a specific effect of high and of low temperatures, but that there must be + a common cause for the aberration found at the high as well as at the low + temperature limits. This cause he seems to find in the inhibiting effects + of extreme temperatures upon development. + </p> + <p> + If we try to analyse such results as Fischer's from a physico-chemical + point of view, we must realise that what we call life consists of a series + of chemical reactions, which are connected in a catenary way; inasmuch as + one reaction or group of reactions (a) (e.g. hydrolyses) causes or + furnishes the material for a second reaction or group of reactions (b) + (e.g. oxydations). We know that the temperature coefficient for + physiological processes varies slightly at various parts of the scale; as + a rule it is higher near 0 and lower near 30 deg. But we know also that + the temperature coefficients do not vary equally from the various + physiological processes. It is, therefore, to be expected that the + temperature coefficients for the group of reactions of the type (a) will + not be identical through the whole scale with the temperature coefficients + for the reactions of the type (b). If therefore a certain substance is + formed at the normal temperature of the animal in such quantities as are + needed for the catenary reaction (b), it is not to be expected that this + same perfect balance will be maintained for extremely high or extremely + low temperatures; it is more probable that one group of reactions will + exceed the other and thus produce aberrant chemical effects, which may + underlie the colour aberrations observed by Fischer and other + experimenters. + </p> + <p> + It is important to notice that Fischer was also able to produce + aberrations through the application of narcotics. Wolfgang Ostwald has + produced experimentally, through variation of temperature, dimorphism of + form in Daphnia. Lack of space precludes an account of these important + experiments, as of so many others. + </p> + <p> + IV. THE EFFECTS OF LIGHT. + </p> + <p> + At the present day nobody seriously questions the statement that the + action of light upon organisms is primarily one of a chemical character. + While this chemical action is of the utmost importance for organisms, the + nutrition of which depends upon the action of chlorophyll, it becomes of + less importance for organisms devoid of chlorophyll. Nevertheless, we find + animals in which the formation of organs by regeneration is not possible + unless they are exposed to light. An observation made by the writer on the + regeneration of polyps in a hydroid, Eudendrium racemosum, at Woods Hole, + may be mentioned as an instance of this. If the stem of this hydroid, + which is usually covered with polyps, is put into an aquarium the polyps + soon fall off. If the stems are kept in an aquarium where light strikes + them during the day, a regeneration of numerous polyps takes place in a + few days. If, however, the stems of Eudendrium are kept permanently in the + dark, no polyps are formed even after an interval of some weeks; but they + are formed in a few days after the same stems have been transferred from + the dark to the light. Diffused daylight suffices for this effect. + Goldfarb, who repeated these experiments, states that an exposure of + comparatively short duration is sufficient for this effect, it is possible + that the light favours the formation of substances which are a + prerequisite for the origin of polyps and their growth. + </p> + <p> + Of much greater significance than this observation are the facts which + show that a large number of animals assume, to some extent, the colour of + the ground on which they are placed. Pouchet found through experiments + upon crustaceans and fish that this influence of the ground on the colour + of animals is produced through the medium of the eyes. If the eyes are + removed or the animals made blind in another way these phenomena cease. + The second general fact found by Pouchet was that the variation in the + colour of the animal is brought about through an action of the nerves on + the pigment-cells of the skin; the nerve-action being induced through the + agency of the eye. + </p> + <p> + The mechanism and the conditions for the change in colouration were made + clear through the beautiful investigations of Keeble and Gamble, on the + colour-change in crustaceans. According to these authors the pigment-cells + can, as a rule, be considered as consisting of a central body from which a + system of more or less complicated ramifications or processes spreads out + in all directions. As a rule, the centre of the cell contains one or more + different pigments which under the influence of nerves can spread out + separately or together into the ramifications. These phenomena of + spreading and retraction of the pigments into or from the ramifications of + the pigment-cells form on the whole the basis for the colour changes under + the influence of environment. Thus Keeble and Gamble observed that + Macromysis flexuosa appears transparent and colourless or grey on sandy + ground. On a dark ground their colour becomes darker. These animals have + two pigments in their chromatophores, a brown pigment and a whitish or + yellow pigment; the former is much more plentiful than the latter. When + the animal appears transparent all the pigment is contained in the centre + of the cells, while the ramifications are free from pigment. When the + animal appears brown both pigments are spread out into the ramifications. + In the condition of maximal spreading the animals appear black. + </p> + <p> + This is a comparatively simple case. Much more complicated conditions were + found by Keeble and Gamble in other crustaceans, e.g. in Hippolyte + cranchii, but the influence of the surroundings upon the colouration of + this form was also satisfactorily analysed by these authors. + </p> + <p> + While many animals show transitory changes in colour under the influence + of their surroundings, in a few cases permanent changes can be produced. + The best examples of this are those which were observed by Poulton in the + chrysalids of various butterflies, especially the small tortoise-shell. + These experiments are so well known that a short reference to them will + suffice. Poulton (Poulton, E.B., "Colours of Animals" (The International + Scientific Series), London, 1890, page 121.) found that in gilt or white + surroundings the pupae became light coloured and there was often an + immense development of the golden spots, "so that in many cases the whole + surface of the pupae glittered with an apparent metallic lustre. So + remarkable was the appearance that a physicist to whom I showed the + chrysalids, suggested that I had played a trick and had covered them with + goldleaf." When black surroundings were used "the pupae were as a rule + extremely dark, with only the smallest trace, and often no trace at all, + of the golden spots which are so conspicuous in the lighter form." The + susceptibility of the animal to this influence of its surroundings was + found to be greatest during a definite period when the caterpillar + undergoes the metamorphosis into the chrysalis stage. As far as the writer + is aware, no physico-chemical explanation, except possibly Wiener's + suggestion of colour-photography by mechanical colour adaptation, has ever + been offered for the results of the type of those observed by Poulton. + </p> + <p> + V. EFFECTS OF GRAVITATION. + </p> + <p> + (a) EXPERIMENTS ON THE EGG OF THE FROG. + </p> + <p> + Gravitation can only indirectly affect life-phenomena; namely, when we + have in a cell two different non-miscible liquids (or a liquid and a + solid) of different specific gravity, so that a change in the position of + the cell or the organ may give results which can be traced to a change in + the position of the two substances. This is very nicely illustrated by the + frog's egg, which has two layers of very viscous protoplasm one of which + is black and one white. The dark one occupies normally the upper position + in the egg and may therefore be assumed to possess a smaller specific + gravity than the white substance. When the egg is turned with the white + pole upwards a tendency of the white protoplasm to flow down again + manifests itself. It is, however, possible to prevent or retard this + rotation of the highly viscous protoplasm, by compressing the eggs between + horizontal glass plates. Such compression experiments may lead to rather + interesting results, as O. Schultze first pointed out. Pflueger had + already shown that the first plane of division in a fertilised frog's egg + is vertical and Roux established the fact that the first plane of division + is identical with the plane of symmetry of the later embryo. Schultze + found that if the frog's egg is turned upside down at the time of its + first division and kept in this abnormal position, through compression + between two glass plates for about 20 hours, a small number of eggs may + give rise to twins. It is possible, in this case, that the tendency of the + black part of the egg to rotate upwards along the surface of the egg leads + to a separation of its first cells, such a separation leading to the + formation of twins. + </p> + <p> + T.H. Morgan made an interesting additional observation. He destroyed one + half of the egg after the first segmentation and found that the half which + remained alive gave rise to only one half of an embryo, thus confirming an + older observation of Roux. When, however, Morgan put the egg upside down + after the destruction of one of the first two cells, and compressed the + eggs between two glass plates, the surviving half of the egg gave rise to + a perfect embryo of half size (and not to a half embryo of normal size as + before.) Obviously in this case the tendency of the protoplasm to flow + back to its normal position was partially successful and led to a partial + or complete separation of the living from the dead half; whereby the + former was enabled to form a whole embryo, which, of course, possessed + only half the size of an embryo originating from a whole egg. + </p> + <p> + (b) EXPERIMENTS ON HYDROIDS. + </p> + <p> + A striking influence of gravitation can be observed in a hydroid, + Antennularia antennina, from the bay of Naples. This hydroid consists of a + long straight main stem which grows vertically upwards and which has at + regular intervals very fine and short bristle-like lateral branches, on + the upper side of which the polyps grow. The main stem is negatively + geotropic, i.e. its apex continues to grow vertically upwards when we put + it obliquely into the aquarium, while the roots grow vertically downwards. + The writer observed that when the stem is put horizontally into the water + the short lateral branches on the lower side give rise to an altogether + different kind of organ, namely, to roots, and these roots grow + indefinitely in length and attach themselves to solid bodies; while if the + stem had remained in its normal position no further growth would have + occurred in the lateral branches. From the upper side of the horizontal + stem new stems grow out, mostly directly from the original stem, + occasionally also from the short lateral branches. It is thus possible to + force upon this hydroid an arrangement of organs which is altogether + different from the hereditary arrangement. The writer had called the + change in the hereditary arrangement of organs or the transformation of + organs by external forces HETEROMORPHOSIS. We cannot now go any further + into this subject, which should, however, prove of interest in relation to + the problem of heredity. + </p> + <p> + If it is correct to apply inferences drawn from the observation on the + frog's egg to the behaviour of Antennularia, one might conclude that the + cells of Antennularia also contain non-miscible substances of different + specific gravity, and that wherever the specifically lighter substance + comes in contact with the sea-water (or gets near the surface of the cell) + the growth of a stem is favoured; while contact with the sea-water of the + specifically heavier of the substances, will favour the formation of + roots. + </p> + <p> + VI. THE EXPERIMENTAL CONTROL OF ANIMAL INSTINCTS. + </p> + <p> + (a) EXPERIMENTS ON THE MECHANISM OF HELIOTROPIC REACTIONS IN ANIMALS. + </p> + <p> + Since the instinctive reactions of animals are as hereditary as their + morphological character, a discussion of experiments on the + physico-chemical character of the instinctive reactions of animals should + not be entirely omitted from this sketch. It is obvious that such + experiments must begin with the simplest type of instincts, if they are + expected to lead to any results; and it is also obvious that only such + animals must be selected for this purpose, the reactions of which are not + complicated by associative memory, or, as it may preferably be termed, + associative hysteresis. + </p> + <p> + The simplest type of instincts is represented by the purposeful motions of + animals to or from a source of energy, e.g. light; and it is with some of + these that we intend to deal here. When we expose winged aphides (after + they have flown away from the plant), or young caterpillars of Porthesia + chrysorrhoea (when they are aroused from their winter sleep) or marine or + freshwater copepods and many other animals, to diffused daylight falling + in from a window, we notice a tendency among these animals to move towards + the source of light. If the animals are naturally sensitive, or if they + are rendered sensitive through the agencies which we shall mention later, + and if the light is strong enough, they move towards the source of light + in as straight a line as the imperfections and peculiarities of their + locomotor apparatus will permit. It is also obvious that we are here + dealing with a forced reaction in which the animals have no more choice in + the direction of their motion than have the iron filings in their + arrangement in a magnetic field. This can be proved very nicely in the + case of starving caterpillars of Porthesia. The writer put such + caterpillars into a glass tube the axis of which was at right angles to + the plane of the window: the caterpillars went to the window side of the + tube and remained there, even if leaves of their food-plant were put into + the tube directly behind them. Under such conditions the animals actually + died from starvation, the light preventing them from turning to the food, + which they eagerly ate when the light allowed them to do so. One cannot + say that these animals, which we call positively helioptropic, are + attracted by the light, since it can be shown that they go towards the + source of the light even if in so doing they move from places of a higher + to places of a lower degree of illumination. + </p> + <p> + The writer has advanced the following theory of these instinctive + reactions. Animals of the type of those mentioned are automatically + orientated by the light in such a way that symmetrical elements of their + retina (or skin) are struck by the rays of light at the same angle. In + this case the intensity of light is the same for both retinae or + symmetrical parts of the skin. + </p> + <p> + This automatic orientation is determined by two factors, first a peculiar + photo-sensitiveness of the retina (or skin), and second a peculiar nervous + connection between the retina and the muscular apparatus. In symmetrically + built heliotropic animals in which the symmetrical muscles participate + equally in locomotion, the symmetrical muscles work with equal energy as + long as the photo-chemical processes in both eyes are identical. If, + however, one eye is struck by stronger light than the other, the + symmetrical muscles will work unequally and in positively heliotropic + animals those muscles will work with greater energy which bring the plane + of symmetry back into the direction of the rays of light and the head + towards the source of light. As soon as both eyes are struck by the rays + of light at the same angle, there is no more reason for the animal to + deviate from this direction and it will move in a straight line. All this + holds good on the supposition that the animals are exposed to only one + source of light and are very sensitive to light. + </p> + <p> + Additional proof for the correctness of this theory was furnished through + the experiments of G.H. Parker and S.J. Holmes. The former worked on a + butterfly, Vanessa antiope, the latter on other arthropods. All the + animals were in a marked degree positively heliotropic. These authors + found that if one cornea is blackened in such an animal, it moves + continually in a circle when it is exposed to a source of light, and in + these motions the eye which is not covered with paint is directed towards + the centre of the circle. The animal behaves, therefore, as if the + darkened eye were in the shade. + </p> + <p> + (b) THE PRODUCTION OF POSITIVE HELIOTROPISM BY ACIDS AND OTHER MEANS AND + THE PERIODIC DEPTH-MIGRATIONS OF PELAGIC ANIMALS. + </p> + <p> + When we observe a dense mass of copepods collected from a freshwater pond, + we notice that some have a tendency to go to the light while others go in + the opposite direction and many, if not the majority, are indifferent to + light. It is an easy matter to make the negatively heliotropic or the + indifferent copepods almost instantly positively heliotropic by adding a + small but definite amount of carbon-dioxide in the form of carbonated + water to the water in which the animals are contained. If the animals are + contained in 50 cubic centimetres of water it suffices to add from three + to six cubic centimetres of carbonated water to make all the copepods + energetically positively heliotropic. This heliotropism lasts about half + an hour (probably until all the carbon-dioxide has again diffused into the + air.) Similar results may be obtained with any other acid. + </p> + <p> + The same experiments may be made with another freshwater crustacean, + namely Daphnia, with this difference, however, that it is as a rule + necessary to lower the temperature of the water also. If the water + containing the Daphniae is cooled and at the same time carbon-dioxide + added, the animals which were before indifferent to light now become most + strikingly positively heliotropic. Marine copepods can be made positively + heliotropic by the lowering of the temperature alone, or by a sudden + increase in the concentration of the sea-water. + </p> + <p> + These data have a bearing upon the depth-migrations of pelagic animals, as + was pointed out years ago by Theo. T. Groom and the writer. It is well + known that many animals living near the surface of the ocean or freshwater + lakes, have a tendency to migrate upwards towards evening and downwards in + the morning and during the day. These periodic motions are determined to a + large extent, if not exclusively, by the heliotropism of these animals. + Since the consumption of carbon-dioxide by the green plants ceases towards + evening, the tension of this gas in the water must rise and this must have + the effect of inducing positive heliotropism or increasing its intensity. + At the same time the temperature of the water near the surface is lowered + and this also increases the positive heliotropism in the organisms. + </p> + <p> + The faint light from the sky is sufficient to cause animals which are in a + high degree positively heliotropic to move vertically upwards towards the + light, as experiments with such pelagic animals, e.g. copepods, have + shown. When, in the morning, the absorption of carbon-dioxide by the green + algae begins again and the temperature of the water rises, the animals + lose their positive heliotropism, and slowly sink down or become + negatively heliotropic and migrate actively downwards. + </p> + <p> + These experiments have also a bearing upon the problem of the inheritance + of instincts. The character which is transmitted in this case is not the + tendency to migrate periodically upwards and downwards, but the positive + heliotropism. The tendency to migrate is the outcome of the fact that + periodically varying external conditions induce a periodic change in the + sense and intensity of the heliotropism of these animals. It is of course + immaterial for the result, whether the carbon-dioxide or any other acid + diffuse into the animal from the outside or whether they are produced + inside in the tissue cells of the animals. Davenport and Cannon found that + Daphniae, which at the beginning of the experiment, react sluggishly to + light react much more quickly after they have been made to go to the light + a few times. The writer is inclined to attribute this result to the effect + of acids, e.g. carbon-dioxide, produced in the animals themselves in + consequence of their motion. A similar effect of the acids was shown by + A.D. Waller in the case of the response of nerve to stimuli. + </p> + <p> + The writer observed many years ago that winged male and female ants are + positively helioptropic and that their heliotropic sensitiveness increases + and reaches its maximum towards the period of nuptial flight. Since the + workers show no heliotropism it looks as if an internal secretion from the + sexual glands were the cause of their heliotropic sensitiveness. V. + Kellogg has observed that bees also become intensely positively + heliotropic at the period of their wedding flight, in fact so much so that + by letting light fall into the observation hive from above, the bees are + prevented from leaving the hive through the exit at the lower end. + </p> + <p> + We notice also the reverse phenomenon, namely, that chemical changes + produced in the animal destroy its heliotropism. The caterpillars of + Porthesia chrysorrhoea are very strongly positively heliotropic when they + are first aroused from their winter sleep. This heliotropic sensitiveness + lasts only as long as they are not fed. If they are kept permanently + without food they remain permanently positively heliotropic until they die + from starvation. It is to be inferred that as soon as these animals take + up food, a substance or substances are formed in their bodies which + diminish or annihilate their heliotropic sensitiveness. + </p> + <p> + The heliotropism of animals is identical with the heliotropism of plants. + The writer has shown that the experiments on the effect of acids on the + heliotropism of copepods can be repeated with the same result in Volvox. + It is therefore erroneous to try to explain these heliotropic reactions of + animals on the basis of peculiarities (e.g. vision) which are not found in + plants. + </p> + <p> + We may briefly discuss the question of the transmission through the sex + cells of such instincts as are based upon heliotropism. This problem + reduces itself simply to that of the method whereby the gametes transmit + heliotropism to the larvae or to the adult. The writer has expressed the + idea that all that is necessary for this transmission is the presence in + the eyes (or in the skin) of the animal of a photo-sensitive substance. + For the transmission of this the gametes need not contain anything more + than a catalyser or ferment for the synthesis of the photo-sensitive + substance in the body of the animal. What has been said in regard to + animal heliotropism might, if space permitted, be extended, mutatis + mutandis, to geotropism and stereotropism. + </p> + <p> + (c) THE TROPIC REACTIONS OF CERTAIN TISSUE-CELLS AND THE MORPHOGENETIC + EFFECTS OF THESE REACTIONS. + </p> + <p> + Since plant-cells show heliotropic reactions identical with those of + animals, it is not surprising that certain tissue-cells also show + reactions which belong to the class of tropisms. These reactions of + tissue-cells are of special interest by reason of their bearing upon the + inheritance of morphological characters. An example of this is found in + the tiger-like marking of the yolk-sac of the embryo of Fundulus and in + the marking of the young fish itself. The writer found that the former is + entirely, and the latter at least in part, due to the creeping of the + chromatophores upon the blood-vessels. The chromatophores are at first + scattered irregularly over the yolk-sac and show their characteristic + ramifications. There is at that time no definite relation between + blood-vessels and chromatophores. As soon as a ramification of a + chromatophore comes in contact with a blood-vessel the whole mass of the + chromatophore creeps gradually on the blood-vessel and forms a complete + sheath around the vessel, until finally all the chromatophores form a + sheath around the vessels and no more pigment cells are found in the + meshes between the vessels. Nobody who has not actually watched the + process of the creeping of the chromatophores upon the blood-vessels would + anticipate that the tiger-like colouration of the yolk-sac in the later + stages of the development was brought about in this way. Similar facts can + be observed in regard to the first marking of the embryo itself. The + writer is inclined to believe that we are here dealing with a case of + chemotropism, and that the oxygen of the blood may be the cause of the + spreading of the chromatophores around the blood-vessels. Certain + observations seem to indicate the possibility that in the adult the + chromatophores have, in some forms at least, a more rigid structure and + are prevented from acting in the way indicated. It seems to the writer + that such observations as those made on Fundulus might simplify the + problem of the hereditary transmission of certain markings. + </p> + <p> + Driesch has found that a tropism underlies the arrangement of the skeleton + in the pluteus larvae of the sea-urchin. The position of this skeleton is + predetermined by the arrangement of the mesenchyme cells, and Driesch has + shown that these cells migrate actively to the place of their destination, + possibly led there under the influence of certain chemical substances. + When Driesch scattered these cells mechanically before their migration, + they nevertheless reached their destination. + </p> + <p> + In the developing eggs of insects the nuclei, together with some + cytoplasm, migrate to the periphery of the egg. Herbst pointed out that + this might be a case of chemotropism, caused by the oxygen surrounding the + egg. The writer has expressed the opinion that the formation of the + blastula may be caused generally by a tropic reaction of the blastomeres, + the latter being forced by an outside influence to creep to the surface of + the egg. + </p> + <p> + These examples may suffice to indicate that the arrangement of definite + groups of cells and the morphological effects resulting therefrom may be + determined by forces lying outside the cells. Since these forces are + ubiquitous and constant it appears as if we were dealing exclusively with + the influence of a gamete; while in reality all that it is necessary for + the gamete to transmit is a certain form of irritability. + </p> + <p> + (d) FACTORS WHICH DETERMINE PLACE AND TIME FOR THE DEPOSITION OF EGGS. + </p> + <p> + For the preservation of species the instinct of animals to lay their eggs + in places in which the young larvae find their food and can develop is of + paramount importance. A simple example of this instinct is the fact that + the common fly lays its eggs on putrid material which serves as food for + the young larvae. When a piece of meat and of fat of the same animal are + placed side by side, the fly will deposit its eggs upon the meat on which + the larvae can grow, and not upon the fat, on which they would starve. + Here we are dealing with the effect of a volatile nitrogenous substance + which reflexly causes the peristaltic motions for the laying of the egg in + the female fly. + </p> + <p> + Kammerer has investigated the conditions for the laying of eggs in two + forms of salamanders, e.g. Salamandra atra and S. maculosa. In both forms + the eggs are fertilised in the body and begin to develop in the uterus. + Since there is room only for a few larvae in the uterus, a large number of + eggs perish and this number is the greater the longer the period of + gestation. It thus happens that when the animals retain their eggs a long + time, very few young ones are born; and these are in a rather advanced + stage of development, owing to the long time which elapsed since they were + fertilised. When the animal lays its eggs comparatively soon after + copulation, many eggs (from 12 to 72) are produced and the larvae are of + course in an early stage of development. In the early stage the larvae + possess gills and can therefore live in water, while in later stages they + have no gills and breathe through their lungs. Kammerer showed that both + forms of Salamandra can be induced to lay their eggs early or late, + according to the physical conditions surrounding them. If they are kept in + water or in proximity to water and in a moist atmosphere they have a + tendency to lay their eggs earlier and a comparatively high temperature + enhances the tendency to shorten the period of gestation. If the + salamanders are kept in comparative dryness they show a tendency to lay + their eggs rather late and a low temperature enhances this tendency. + </p> + <p> + Since Salamandra atra is found in rather dry alpine regions with a + relatively low temperature and Salamandra maculosa in lower regions with + plenty of water and a higher temperature, the fact that S. atra bears + young which are already developed and beyond the stage of aquatic life, + while S. maculosa bears young ones in an earlier stage, has been termed + adaptation. Kammerer's experiments, however, show that we are dealing with + the direct effects of definite outside forces. While we may speak of + adaptation when all or some of the variables which determine a reaction + are unknown, it is obviously in the interest of further scientific + progress to connect cause and effect directly whenever our knowledge + allows us to do so. + </p> + <p> + VII. CONCLUDING REMARKS. + </p> + <p> + The discovery of De Vries, that new species may arise by mutation and the + wide if not universal applicability of Mendel's Law to phenomena of + heredity, as shown especially by Bateson and his pupils, must, for the + time being, if not permanently, serve as a basis for theories of + evolution. These discoveries place before the experimental biologist the + definite task of producing mutations by physico-chemical means. It is true + that certain authors claim to have succeeded in this, but the writer + wishes to apologise to these authors for his inability to convince himself + of the validity of their claims at the present moment. He thinks that only + continued breeding of these apparent mutants through several generations + can afford convincing evidence that we are here dealing with mutants + rather than with merely pathological variations. + </p> + <p> + What was said in regard to the production of new species by + physico-chemical means may be repeated with still more justification in + regard to the second problem of transformation, namely the making of + living from inanimate matter. The purely morphological imitations of + bacteria or cells which physicists have now and then proclaimed as + artificially produced living beings; or the plays on words by which, e.g. + the regeneration of broken crystals and the regeneration of lost limbs by + a crustacean were declared identical, will not appeal to the biologist. We + know that growth and development in animals and plants are determined by + definite although complicated series of catenary chemical reactions, which + result in the synthesis of a DEFINITE compound or group of compounds, + namely, NUCLEINS. + </p> + <p> + The nucleins have the peculiarity of acting as ferments or enzymes for + their own synthesis. Thus a given type of nucleus will continue to + synthesise other nuclein of its own kind. This determines the continuity + of a species; since each species has, probably, its own specific nuclein + or nuclear material. But it also shows us that whoever claims to have + succeeded in making living matter from inanimate will have to prove that + he has succeeded in producing nuclein material which acts as a ferment for + its own synthesis and thus reproduces itself. Nobody has thus far + succeeded in this, although nothing warrants us in taking it for granted + that this task is beyond the power of science. + </p> + <p> + <a name="link2H_4_0016" id="link2H_4_0016"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + XV. THE VALUE OF COLOUR IN THE STRUGGLE FOR LIFE. By E.B. Poulton. + </h2> + <h3> + Hope Professor of Zoology in the University of Oxford. + </h3> + <p> + INTRODUCTION. + </p> + <p> + The following pages have been written almost entirely from the historical + stand-point. Their principal object has been to give some account of the + impressions produced on the mind of Darwin and his great compeer Wallace + by various difficult problems suggested by the colours of living nature. + In order to render the brief summary of Darwin's thoughts and opinions on + the subject in any way complete, it was found necessary to say again much + that has often been said before. No attempt has been made to display as a + whole the vast contribution of Wallace; but certain of its features are + incidentally revealed in passages quoted from Darwin's letters. It is + assumed that the reader is familiar with the well-known theories of + Protective Resemblance, Warning Colours, and Mimicry both Batesian and + Mullerian. It would have been superfluous to explain these on the present + occasion; for a far more detailed account than could have been attempted + in these pages has recently appeared. (Poulton, "Essays on Evolution" + Oxford, 1908, pages 293-382.) Among the older records I have made a point + of bringing together the principal observations scattered through the + note-books and collections of W.J. Burchell. These have never hitherto + found a place in any memoir dealing with the significance of the colours + of animals. + </p> + <p> + INCIDENTAL COLOURS. + </p> + <p> + Darwin fully recognised that the colours of living beings are not + necessarily of value as colours, but that they may be an incidental result + of chemical or physical structure. Thus he wrote to T. Meehan, Oct. 9, + 1874: "I am glad that you are attending to the colours of dioecious + flowers; but it is well to remember that their colours may be as + unimportant to them as those of a gall, or, indeed, as the colour of an + amethyst or ruby is to these gems." ("More Letters of Charles Darwin", + Vol. I. pages 354, 355. See also the admirable account of incidental + colours in "Descent of Man" (2nd edition), 1874, pages 261, 262.) + </p> + <p> + Incidental colours remain as available assets of the organism ready to be + turned to account by natural selection. It is a probable speculation that + all pigmentary colours were originally incidental; but now and for immense + periods of time the visible tints of animals have been modified and + arranged so as to assist in the struggle with other organisms or in + courtship. The dominant colouring of plants, on the other hand, is an + essential element in the paramount physiological activity of chlorophyll. + In exceptional instances, however, the shapes and visible colours of + plants may be modified in order to promote concealment. + </p> + <p> + TELEOLOGY AND ADAPTATION. + </p> + <p> + In the department of Biology which forms the subject of this essay, the + adaptation of means to an end is probably more evident than in any other; + and it is therefore of interest to compare, in a brief introductory + section, the older with the newer teleological views. + </p> + <p> + The distinctive feature of Natural Selection as contrasted with other + attempts to explain the process of Evolution is the part played by the + struggle for existence. All naturalists in all ages must have known + something of the operations of "Nature red in tooth and claw"; but it was + left for this great theory to suggest that vast extermination is a + necessary condition of progress, and even of maintaining the ground + already gained. + </p> + <p> + Realising that fitness is the outcome of this fierce struggle, thus turned + to account for the first time, we are sometimes led to associate the + recognition of adaptation itself too exclusively with Natural Selection. + Adaptation had been studied with the warmest enthusiasm nearly forty years + before this great theory was given to the scientific world, and it is + difficult now to realise the impetus which the works of Paley gave to the + study of Natural History. That they did inspire the naturalists of the + early part of the last century is clearly shown in the following passages. + </p> + <p> + In the year 1824 the Ashmolean Museum at Oxford was intrusted to the care + of J.S. Duncan of New College. He was succeeded in this office by his + brother, P.B. Duncan, of the same College, author of a History of the + Museum, which shows very clearly the influence of Paley upon the study of + nature, and the dominant position given to his teachings: "Happily at this + time (1824) a taste for the study of natural history had been excited in + the University by Dr Paley's very interesting work on Natural Theology, + and the very popular lectures of Dr Kidd on Comparative Anatomy, and Dr + Buckland on Geology." In the arrangement of the contents of the Museum the + illustration of Paley's work was given the foremost place by J.S. Duncan: + "The first division proposes to familiarize the eye to those relations of + all natural objects which form the basis of argument in Dr Paley's Natural + Theology; to induce a mental habit of associating the view of natural + phenomena with the conviction that they are the media of Divine + manifestation; and by such association to give proper dignity to every + branch of natural science." (From "History and Arrangement of the + Ashmolean Museum" by P.B. Duncan: see pages vi, vii of "A Catalogue of the + Ashmolean Museum", Oxford, 1836.) + </p> + <p> + The great naturalist, W.J. Burchell, in his classical work shows the same + recognition of adaptation in nature at a still earlier date. Upon the + subject of collections he wrote ("Travels in the Interior of Southern + Africa", London, Vol. I. 1822, page 505. The references to Burchell's + observations in the present essay are adapted from the author's article in + "Report of the British and South African Associations", 1905, Vol. III. + pages 57-110.): "It must not be supposed that these charms (the pleasures + of Nature) are produced by the mere discovery of new objects: it is the + harmony with which they have been adapted by the Creator to each other, + and to the situations in which they are found, which delights the observer + in countries where Art has not yet introduced her discords." The remainder + of the passage is so admirable that I venture to quote it: "To him who is + satisfied with amassing collections of curious objects, simply for the + pleasure of possessing them, such objects can afford, at best, but a + childish gratification, faint and fleeting; while he who extends his view + beyond the narrow field of nomenclature, beholds a boundless expanse, the + exploring of which is worthy of the philosopher, and of the best talents + of a reasonable being." + </p> + <p> + On September 14, 1811, Burchell was at Zand Valley (Vlei), or Sand Pool, a + few miles south-west of the site of Prieska, on the Orange River. Here he + found a Mesembryanthemum (M. turbiniforme, now M. truncatum) and also a + "Gryllus" (Acridian), closely resembling the pebbles with which their + locality was strewn. He says of both of these, "The intention of Nature, + in these instances, seems to have been the same as when she gave to the + Chameleon the power of accommodating its color, in a certain degree, to + that of the object nearest to it, in order to compensate for the + deficiency of its locomotive powers. By their form and colour, this insect + may pass unobserved by those birds, which otherwise would soon extirpate a + species so little able to elude its pursuers, and this juicy little + Mesembryanthemum may generally escape the notice of cattle and wild + animals." (Loc. cit. pages 310, 311. See Sir William Thiselton-Dyer + "Morphological Notes", XI.; "Protective Adaptations", I.; "Annals of + Botany", Vol. XX. page 124. In plates VII., VIII. and IX. accompanying + this article the author represents the species observed by Burchell, + together with others in which analogous adaptations exist. He writes: + "Burchell was clearly on the track on which Darwin reached the goal. But + the time had not come for emancipation from the old teleology. This, + however, in no respect detracts from the merit or value of his work. For, + as Huxley has pointed out ("Life and Letters of Thomas Henry Huxley", + London, 1900, I. page 457), the facts of the old teleology are immediately + transferable to Darwinism, which simply supplies them with a natural in + place of a supernatural explanation.") Burchell here seems to miss, at + least in part, the meaning of the relationship between the quiescence of + the Acridian and its cryptic colouring. Quiescence is an essential element + in the protective resemblance to a stone—probably even more + indispensable than the details of the form and colouring. Although + Burchell appears to overlook this point he fully recognised the community + between protection by concealment and more aggressive modes of defence; + for, in the passage of which a part is quoted above, he specially refers + to some earlier remarks on page 226 of his Vol. I. We here find that even + when the oxen were resting by the Juk rivier (Yoke river), on July 19, + 1811, Burchell observed "Geranium spinosum, with a fleshy stem and large + white flowers...; and a succulent species of Pelargonium... so defended by + the old panicles, grown to hard woody thorns, that no cattle could browze + upon it." He goes on to say, "In this arid country, where every juicy + vegetable would soon be eaten up by the wild animals, the Great Creating + Power, with all-provident wisdom, has given to such plants either an acrid + or poisonous juice, or sharp thorns, to preserve the species from + annihilation... " All these modes of defence, especially adapted to a + desert environment, have since been generally recognised, and it is very + interesting to place beside Burchell's statement the following passage + from a letter written by Darwin, Aug. 7, 1868, to G.H. Lewes; "That + Natural Selection would tend to produce the most formidable thorns will be + admitted by every one who has observed the distribution in South America + and Africa (vide Livingstone) of thorn-bearing plants, for they always + appear where the bushes grow isolated and are exposed to the attacks of + mammals. Even in England it has been noticed that all spine-bearing and + sting-bearing plants are palatable to quadrupeds, when the thorns are + crushed." ("More Letters", I. page 308.) + </p> + <p> + ADAPTATION AND NATURAL SELECTION. + </p> + <p> + I have preferred to show the influence of the older teleology upon Natural + History by quotations from a single great and insufficiently appreciated + naturalist. It might have been seen equally well in the pages of Kirby and + Spence and those of many other writers. If the older naturalists who + thought and spoke with Burchell of "the intention of Nature" and the + adaptation of beings "to each other, and to the situations in which they + are found," could have conceived the possibility of evolution, they must + have been led, as Darwin was, by the same considerations to Natural + Selection. This was impossible for them, because the philosophy which they + followed contemplated the phenomena of adaptation as part of a static + immutable system. Darwin, convinced that the system is dynamic and + mutable, was prevented by these very phenomena from accepting anything + short of the crowning interpretation offered by Natural Selection. ("I had + always been much struck by such adaptations (e.g. woodpecker and tree-frog + for climbing, seeds for dispersal), and until these could be explained it + seemed to me almost useless to endeavour to prove by indirect evidence + that species have been modified." "Autobiography" in "Life and Letters of + Charles Darwin", Vol. I. page 82. The same thought is repeated again and + again in Darwin's letters to his friends. It is forcibly urged in the + Introduction to the "Origin" (1859), page 3.) And the birth of Darwin's + unalterable conviction that adaptation is of dominant importance in the + organic world,—a conviction confirmed and ever again confirmed by + his experience as a naturalist—may probably be traced to the + influence of the great theologian. Thus Darwin, speaking of his + Undergraduate days, tells us in his "Autobiography" that the logic of + Paley's "Evidences of Christianity" and "Moral Philosophy" gave him as + much delight as did Euclid. + </p> + <p> + "The careful study of these works, without attempting to learn any part by + rote, was the only part of the academical course which, as I then felt and + as I still believe, was of the least use to me in the education of my + mind. I did not at that time trouble myself about Paley's premises; and + taking these on trust, I was charmed and convinced by the long line of + argumentation." ("Life and Letters", I. page 47.) + </p> + <p> + When Darwin came to write the "Origin" he quoted in relation to Natural + Selection one of Paley's conclusions. "No organ will be formed, as Paley + has remarked, for the purpose of causing pain or for doing an injury to + its possessor." ("Origin of Species" (1st edition) 1859, page 201.) + </p> + <p> + The study of adaptation always had for Darwin, as it has for many, a + peculiar charm. His words, written Nov. 28, 1880, to Sir W. + Thiselton-Dyer, are by no means inapplicable to-day: "Many of the Germans + are very contemptuous about making out use of organs; but they may sneer + the souls out of their bodies, and I for one shall think it the most + interesting part of natural history." ("More Letters" II. page 428.) + </p> + <p> + PROTECTIVE AND AGGRESSIVE RESEMBLANCE: PROCRYPTIC AND ANTICRYPTIC + COLOURING. + </p> + <p> + Colouring for the purpose of concealment is sometimes included under the + head Mimicry, a classification adopted by H.W. Bates in his classical + paper. Such an arrangement is inconvenient, and I have followed Wallace in + keeping the two categories distinct. + </p> + <p> + The visible colours of animals are far more commonly adapted for + Protective Resemblance than for any other purpose. The concealment of + animals by their colours, shapes and attitudes, must have been well known + from the period at which human beings first began to take an intelligent + interest in Nature. An interesting early record is that of Samuel Felton, + who (Dec. 2, 1763) figured and gave some account of an Acridian + (Phyllotettix) from Jamaica. Of this insect he says "THE THORAX is like a + leaf that is raised perpendicularly from the body." ("Phil. Trans. Roy. + Soc." Vol. LIV. Tab. VI. page 55.) + </p> + <p> + Both Protective and Aggressive Resemblances were appreciated and clearly + explained by Erasmus Darwin in 1794: "The colours of many animals seem + adapted to their purposes of concealing themselves either to avoid danger, + or to spring upon their prey." ("Zoonomia", Vol. I. page 509, London, + 1794.) + </p> + <p> + Protective Resemblance of a very marked and beautiful kind is found in + certain plants, inhabitants of desert areas. Examples observed by Burchell + almost exactly a hundred years ago have already been mentioned. In + addition to the resemblance to stones Burchell observed, although he did + not publish the fact, a South African plant concealed by its likeness to + the dung of birds. (Sir William Thiselton-Dyer has suggested the same + method of concealment ("Annals of Botany", Vol. XX. page 123). Referring + to Anacampseros papyracea, figured on plate IX., the author says of its + adaptive resemblance: "At the risk of suggesting one perhaps somewhat + far-fetched, I must confess that the aspect of the plant always calls to + my mind the dejecta of some bird, and the more so owing to the whitening + of the branches towards the tips" (loc. cit. page 126). The student of + insects, who is so familiar with this very form of protective resemblance + in larvae, and even perfect insects, will not be inclined to consider the + suggestion far-fetched.) The observation is recorded in one of the + manuscript journals kept by the great explorer during his journey. I owe + the opportunity of studying it to the kindness of Mr Francis A. Burchell + of the Rhodes University College, Grahamstown. The following account is + given under the date July 5, 1812, when Burchell was at the Makkwarin + River, about half-way between the Kuruman River and Litakun the old + capital of the Bachapins (Bechuanas): "I found a curious little Crassula + (not in flower) so snow white, that I should never has (have) + distinguished it from the white limestones... It was an inch high and a + little branchy,... and was at first mistaken for the dung of birds of the + passerine order. I have often had occasion to remark that in stony + place(s) there grow many small succulent plants and abound insects + (chiefly Grylli) which have exactly the same colour as the ground and must + for ever escape observation unless a person sit on the ground and observe + very attentively." + </p> + <p> + The cryptic resemblances of animals impressed Darwin and Wallace in very + different degrees, probably in part due to the fact that Wallace's + tropical experiences were so largely derived from the insect world, in + part to the importance assigned by Darwin to Sexual Selection "a subject + which had always greatly interested me," as he says in his + "Autobiography", ("Life and Letters", Vol. I. page 94.) There is no + reference to Cryptic Resemblance in Darwin's section of the Joint Essay, + although he gives an excellent short account of Sexual Selection (see page + 295). Wallace's section on the other hand contains the following + statement: "Even the peculiar colours of many animals, especially insects, + so closely resembling the soil or the leaves or the trunks on which they + habitually reside, are explained on the same principle; for though in the + course of ages varieties of many tints may have occurred, YET THOSE RACES + HAVING COLOURS BEST ADAPTED TO CONCEALMENT FROM THEIR ENEMIES WOULD + INEVITABLY SURVIVE THE LONGEST." ("Journ. Proc. Linn. Soc." Vol. III. + 1859, page 61. The italics are Wallace's.) + </p> + <p> + It would occupy too much space to attempt any discussion of the difference + between the views of these two naturalists, but it is clear that Darwin, + although fully believing in the efficiency of protective resemblance and + replying to St George Mivart's contention that Natural Selection was + incompetent to produce it ("Origin" (6th edition) London, 1872, pages 181, + 182; see also page 66.), never entirely agreed with Wallace's estimate of + its importance. Thus the following extract from a letter to Sir Joseph + Hooker, May 21, 1868, refers to Wallace: "I find I must (and I always + distrust myself when I differ from him) separate rather widely from him + all about birds' nests and protection; he is riding that hobby to death." + ("More Letters", I. page 304.) It is clear from the account given in "The + Descent of Man", (London, 1874, pages 452-458. See also "Life and + Letters", III. pages 123-125, and "More Letters", II. pages 59-63, 72-74, + 76-78, 84-90, 92, 93.), that the divergence was due to the fact that + Darwin ascribed more importance to Sexual Selection than did Wallace, and + Wallace more importance to Protective Resemblance than Darwin. Thus Darwin + wrote to Wallace, Oct. 12 and 13, 1867: "By the way, I cannot but think + that you push protection too far in some cases, as with the stripes on the + tiger." ("More Letters", I. page 283.) Here too Darwin was preferring the + explanation offered by Sexual Selection ("Descent of Man" (2nd edition) + 1874, pages 545, 546.), a preference which, considering the relation of + the colouring of the lion and tiger to their respective environments, few + naturalists will be found to share. It is also shown that Darwin + contemplated the possibility of cryptic colours such as those of + Patagonian animals being due to sexual selection influenced by the aspect + of surrounding nature. + </p> + <p> + Nearly a year later Darwin in his letter of May 5, 1868?, expressed his + agreement with Wallace's views: "Expect that I should put sexual selection + as an equal, or perhaps as even a more important agent in giving colour + than Natural Selection for protection." ("More Letters", II. pages 77, + 78.) The conclusion expressed in the above quoted passage is opposed by + the extraordinary development of Protective Resemblance in the immature + stages of animals, especially insects. + </p> + <p> + It must not be supposed, however, that Darwin ascribed an unimportant role + to Cryptic Resemblances, and as observations accumulated he came to + recognise their efficiency in fresh groups of the animal kingdom. Thus he + wrote to Wallace, May 5, 1867: "Haeckel has recently well shown that the + transparency and absence of colour in the lower oceanic animals, belonging + to the most different classes, may be well accounted for on the principle + of protection." ("More Letters", II. page 62. See also "Descent of Man", + page 261.) Darwin also admitted the justice of Professor E.S. Morse's + contention that the shells of molluscs are often adaptively coloured. + ("More Letters", II. page 95.) But he looked upon cryptic colouring and + also mimicry as more especially Wallace's departments, and sent to him and + to Professor Meldola observations and notes bearing upon these subjects. + Thus the following letter given to me by Dr A.R. Wallace and now, by kind + permission, published for the first time, accompanied a photograph of the + chrysalis of Papilio sarpedon choredon, Feld., suspended from a leaf of + its food-plant: + </p> + <p> + July 9th, Down, Beckenham, Kent. + </p> + <p> + My Dear Wallace, + </p> + <p> + Dr G. Krefft has sent me the enclosed from Sydney. A nurseryman saw a + caterpillar feeding on a plant and covered the whole up, but when he + searched for the cocoon (pupa), was long before he could find it, so good + was its imitation in colour and form to the leaf to which it was attached. + I hope that the world goes well with you. Do not trouble yourself by + acknowledging this. + </p> + <p> + Ever yours + </p> + <p> + Ch. Darwin. + </p> + <p> + Another deeply interesting letter of Darwin's bearing upon protective + resemblance, has only recently been shown to me by my friend Professor + E.B. Wilson, the great American Cytologist. With his kind consent and that + of Mr Francis Darwin, this letter, written four months before Darwin's + death on April 19, 1882, is reproduced here (The letter is addressed: + "Edmund B. Wilson, Esq., Assistant in Biology, John Hopkins University, + Baltimore Md, U. States."): + </p> + <p> + December 21, 1881. + </p> + <p> + Dear Sir, + </p> + <p> + I thank you much for having taken so much trouble in describing fully your + interesting and curious case of mimickry. + </p> + <p> + I am in the habit of looking through many scientific Journals, and though + my memory is now not nearly so good as it was, I feel pretty sure that no + such case as yours has been described (amongst the nudibranch) molluscs. + You perhaps know the case of a fish allied to Hippocampus, (described some + years ago by Dr Gunther in "Proc. Zoolog. Socy.") which clings by its tail + to sea-weeds, and is covered with waving filaments so as itself to look + like a piece of the same sea-weed. The parallelism between your and Dr + Gunther's case makes both of them the more interesting; considering how + far a fish and a mollusc stand apart. It would be difficult for anyone to + explain such cases by the direct action of the environment.—I am + glad that you intend to make further observations on this mollusc, and I + hope that you will give a figure and if possible a coloured figure. + </p> + <p> + With all good wishes from an old brother naturalist, + </p> + <p> + I remain, Dear Sir, + </p> + <p> + Yours faithfully, + </p> + <p> + Charles Darwin. + </p> + <p> + Professor E.B. Wilson has kindly given the following account of the + circumstances under which he had written to Darwin: "The case to which + Darwin's letter refers is that of the nudibranch mollusc Scyllaea, which + lives on the floating Sargassum and shows a really astonishing resemblance + to the plant, having leaf-shaped processes very closely similar to the + fronds of the sea-weed both in shape and in colour. The concealment of the + animal may be judged from the fact that we found the animal quite by + accident on a piece of Sargassum that had been in a glass jar in the + laboratory for some time and had been closely examined in the search for + hydroids and the like without disclosing the presence upon it of two large + specimens of the Scyllaea (the animal, as I recall it, is about two inches + long). It was first detected by its movements alone, by someone (I think a + casual visitor to the laboratory) who was looking closely at the Sargassum + and exclaimed 'Why, the sea-weed is moving its leaves'! We found the + example in the summer of 1880 or 1881 at Beaufort, N.C., where the Johns + Hopkins laboratory was located for the time being. It must have been seen + by many others, before or since. + </p> + <p> + "I wrote and sent to Darwin a short description of the case at the + suggestion of Brooks, with whom I was at the time a student. I was, of + course, entirely unknown to Darwin (or to anyone else) and to me the + principal interest of Darwin's letter is the evidence that it gives of his + extraordinary kindness and friendliness towards an obscure youngster who + had of course absolutely no claim upon his time or attention. The little + incident made an indelible impression upon my memory and taught me a + lesson that was worth learning." + </p> + <p> + VARIABLE PROTECTIVE RESEMBLANCE. + </p> + <p> + The wonderful power of rapid colour adjustment possessed by the + cuttle-fish was observed by Darwin in 1832 at St Jago, Cape de Verd + Islands, the first place visited during the voyage of the "Beagle". From + Rio he wrote to Henslow, giving the following account of his observations, + May 18, 1832: "I took several specimens of an Octopus which possessed a + most marvellous power of changing its colours, equalling any chameleon, + and evidently accommodating the changes to the colour of the ground which + it passed over. Yellowish green, dark brown, and red, were the prevailing + colours; this fact appears to be new, as far as I can find out." ("Life + and Letters", I. pages 235, 236. See also Darwin's "Journal of + Researches", 1876, pages 6-8, where a far more detailed account is given + together with a reference to "Encycl. of Anat. and Physiol.") + </p> + <p> + Darwin was well aware of the power of individual colour adjustment, now + known to be possessed by large numbers of lepidopterous pupae and larvae. + An excellent example was brought to his notice by C.V. Riley ("More + Letters" II, pages 385, 386.), while the most striking of the early + results obtained with the pupae of butterflies—those of Mrs M.E. + Barber upon Papilio nireus—was communicated by him to the + Entomological Society of London. ("Trans. Ent. Soc. Lond." 1874, page 519. + See also "More Letters", II. page 403.) + </p> + <p> + It is also necessary to direct attention to C.W. Beebe's ("Zoologica: N.Y. + Zool. Soc." Vol. I. No. 1, Sept. 25, 1907: "Geographic variation in birds + with especial reference to the effects of humidity".) recent discovery + that the pigmentation of the plumage of certain birds is increased by + confinement in a superhumid atmosphere. In Scardafella inca, on which the + most complete series of experiments was made, the changes took place only + at the moults, whether normal and annual or artificially induced at + shorter periods. There was a corresponding increase in the choroidal + pigment of the eye. At a certain advanced stage of feather pigmentation a + brilliant iridescent bronze or green tint made its appearance on those + areas where iridescence most often occurs in allied genera. Thus in birds + no less than in insects, characters previously regarded as of taxonomic + value, can be evoked or withheld by the forces of the environment. + </p> + <p> + WARNING OR APOSEMATIC COLOURS. + </p> + <p> + From Darwin's description of the colours and habits it is evident that he + observed, in 1833, an excellent example of warning colouring in a little + South American toad (Phryniscus nigricans). He described it in a letter to + Henslow, written from Monte Video, Nov. 24, 1832: "As for one little toad, + I hope it may be new, that it may be christened 'diabolicus.' Milton must + allude to this very individual when he talks of 'squat like a toad'; its + colours are by Werner ("Nomenclature of Colours", 1821) ink black, + vermilion red and buff orange." ("More Letters", I. page 12.) In the + "Journal of Researches" (1876, page 97.) its colours are described as + follows: "If we imagine, first, that it had been steeped in the blackest + ink, and then, when dry, allowed to crawl over a board, freshly painted + with the brightest vermilion, so as to colour the soles of its feet and + parts of its stomach, a good idea of its appearance will be gained." + "Instead of being nocturnal in its habits, as other toads are, and living + in damp obscure recesses, it crawls during the heat of the day about the + dry sand-hillocks and arid plains,... " The appearance and habits recall + T. Belt's well-known description of the conspicuous little Nicaraguan frog + which he found to be distasteful to a duck. ("The Naturalist in Nicaragua" + (2nd edition) London, 1888, page 321.) + </p> + <p> + The recognition of the Warning Colours of caterpillars is due in the first + instance to Darwin, who, reflecting on Sexual Selection, was puzzled by + the splendid colours of sexually immature organisms. He applied to Wallace + "who has an innate genius for solving difficulties." ("Descent of Man", + page 325. On this and the following page an excellent account of the + discovery will be found, as well as in Wallace's "Natural Selection", + London, 1875, pages 117-122.) Darwin's original letter exists ("Life and + Letters", III. pages 93, 94.), and in it we are told that he had taken the + advice given by Bates: "You had better ask Wallace." After some + consideration Wallace replied that he believed the colours of conspicuous + caterpillars and perfect insects were a warning of distastefulness and + that such forms would be refused by birds. Darwin's reply ("Life and + Letters", III. pages 94, 95.) is extremely interesting both for its + enthusiasm at the brilliancy of the hypothesis and its caution in + acceptance without full confirmation: + </p> + <p> + "Bates was quite right; you are the man to apply to in a difficulty. I + never heard anything more ingenious than your suggestion, and I hope you + may be able to prove it true. That is a splendid fact about the white + moths (A single white moth which was rejected by young turkeys, while + other moths were greedily devoured: "Natural Selection", 1875, page 78.); + it warms one's very blood to see a theory thus almost proved to be true." + </p> + <p> + Two years later the hypothesis was proved to hold for caterpillars of many + kinds by J. Jenner Weir and A.G. Butler, whose observations have since + been abundantly confirmed by many naturalists. Darwin wrote to Weir, May + 13, 1869: "Your verification of Wallace's suggestion seems to me to amount + to quite a discovery." ("More Letters", II. page 71 (footnote).) + </p> + <p> + RECOGNITION OR EPISEMATIC CHARACTERS. + </p> + <p> + This principle does not appear to have been in any way foreseen by Darwin, + although he draws special attention to several elements of pattern which + would now be interpreted by many naturalists as epismes. He believed that + the markings in question interfered with the cryptic effect, and came to + the conclusion that, even when common to both sexes, they "are the result + of sexual selection primarily applied to the male." ("Descent of Man", + page 544.) The most familiar of all recognition characters was carefully + explained by him, although here too explained as an ornamental feature now + equally transmitted to both sexes: "The hare on her form is a familiar + instance of concealment through colour; yet this principle partly fails in + a closely-allied species, the rabbit, for when running to its burrow, it + is made conspicuous to the sportsman, and no doubt to all beasts of prey, + by its upturned white tail." ("Descent of Man", page 542.) + </p> + <p> + The analogous episematic use of the bright colours of flowers to attract + insects for effecting cross-fertilisation and of fruits to attract + vertebrates for effecting dispersal is very clearly explained in the + "Origin". (Edition 1872, page 161. For a good example of Darwin's caution + in dealing with exceptions see the allusion to brightly coloured fruit in + "More Letters", II. page 348.) + </p> + <p> + It is not, at this point, necessary to treat sematic characters at any + greater length. They will form the subject of a large part of the + following section, where the models of Batesian (Pseudaposematic) mimicry + are considered as well as the Mullerian (Synaposematic) combinations of + Warning Colours. + </p> + <p> + MIMICRY,—BATESIAN OR PSEUDAPOSEMATIC, MULLERIAN OR SYNAPOSEMATIC. + </p> + <p> + The existence of superficial resemblances between animals of various + degrees of affinity must have been observed for hundreds of years. Among + the early examples, the best known to me have been found in the manuscript + note-books and collections of W.J. Burchell, the great traveller in Africa + (1810-15) and Brazil (1825-30). The most interesting of his records on + this subject are brought together in the following paragraphs. + </p> + <p> + Conspicuous among well-defended insects are the dark steely or iridescent + greenish blue fossorial wasps or sand-wasps, Sphex and the allied genera. + Many Longicorn beetles mimic these in colour, slender shape of body and + limbs, rapid movements, and the readiness with which they take to flight. + On Dec. 21, 1812, Burchell captured one such beetle (Promeces viridis) at + Kosi Fountain on the journey from the source of the Kuruman River to + Klaarwater. It is correctly placed among the Longicorns in his catalogue, + but opposite to its number is the comment "Sphex! totus purpureus." + </p> + <p> + In our own country the black-and-yellow colouring of many stinging + insects, especially the ordinary wasps, affords perhaps the commonest + model for mimicry. It is reproduced with more or less accuracy on moths, + flies and beetles. Among the latter it is again a Longicorn which offers + one of the best-known, although by no means one of the most perfect, + examples. The appearance of the well-known "wasp-beetle" (Clytus arietis) + in the living state is sufficiently suggestive to prevent the great + majority of people from touching it. In Burchell's Brazilian collection + there is a nearly allied species (Neoclytus curvatus) which appears to be + somewhat less wasp-like than the British beetle. The specimen bears the + number "1188," and the date March 27, 1827, when Burchell was collecting + in the neighbourhood of San Paulo. Turning to the corresponding number in + the Brazilian note-book we find this record: "It runs rapidly like an + ichneumon or wasp, of which it has the appearance." + </p> + <p> + The formidable, well-defended ants are as freely mimicked by other insects + as the sand-wasps, ordinary wasps and bees. Thus on February 17, 1901, Guy + A.K. Marshall captured, near Salisbury, Mashonaland, three similar species + of ants (Hymenoptera) with a bug (Hemiptera) and a Locustid (Orthoptera), + the two latter mimicking the former. All the insects, seven in number, + were caught on a single plant, a small bushy vetch. ("Trans. Ent. Soc. + Lond." 1902, page 535, plate XIX. figs. 53-59.) + </p> + <p> + This is an interesting recent example from South Africa, and large numbers + of others might be added—the observations of many naturalists in + many lands; but nearly all of them known since that general awakening of + interest in the subject which was inspired by the great hypotheses of H.W. + Bates and Fritz Muller. We find, however, that Burchell had more than once + recorded the mimetic resemblance to ants. An extremely ant-like bug (the + larva of a species of Alydus) in his Brazilian collection is labelled + "1141," with the date December 8, 1826, when Burchell was at the Rio das + Pedras, Cubatao, near Santos. In the note-book the record is as follows: + "1141 Cimex. I collected this for a Formica." + </p> + <p> + Some of the chief mimics of ants are the active little hunting spiders + belonging to the family Attidae. Examples have been brought forward during + many recent years, especially by my friends Dr and Mrs Peckham, of + Milwaukee, the great authorities on this group of Araneae. Here too we + find an observation of the mimetic resemblance recorded by Burchell, and + one which adds in the most interesting manner to our knowledge of the + subject. A fragment, all that is now left, of an Attid spider, captured on + June 30, 1828, at Goyaz, Brazil, bears the following note, in this case on + the specimen and not in the note-book: "Black... runs and seems like an + ant with large extended jaws." My friend Mr R.I. Pocock, to whom I have + submitted the specimen, tells me that it is not one of the group of + species hitherto regarded as ant-like, and he adds, "It is most + interesting that Burchell should have noticed the resemblance to an ant in + its movements. This suggests that the perfect imitation in shape, as well + as in movement, seen in many species was started in forms of an + appropriate size and colour by the mimicry of movement alone." Up to the + present time Burchell is the only naturalist who has observed an example + which still exhibits this ancestral stage in the evolution of mimetic + likeness. + </p> + <p> + Following the teachings of his day, Burchell was driven to believe that it + was part of the fixed and inexorable scheme of things that these strange + superficial resemblances existed. Thus, when he found other examples of + Hemipterous mimics, including one (Luteva macrophthalma) with "exactly the + manners of a Mantis," he added the sentence, "In the genus Cimex (Linn.) + are to be found the outward resemblances of insects of many other genera + and orders" (February 15, 1829). Of another Brazilian bug, which is not to + be found in his collection, and cannot therefore be precisely identified, + he wrote: "Cimex... Nature seems to have intended it to imitate a Sphex, + both in colour and the rapid palpitating and movement of the antennae" + (November 15, 1826). At the same time it is impossible not to feel the + conviction that Burchell felt the advantage of a likeness to stinging + insects and to aggressive ants, just as he recognised the benefits + conferred on desert plants by spines and by concealment. Such an + interpretation of mimicry was perfectly consistent with the theological + doctrines of his day. (See Kirby and Spence, "An Introduction to + Entomology" (1st edition), London, Vol. II. 1817, page 223.) + </p> + <p> + The last note I have selected from Burchell's manuscript refers to one of + the chief mimics of the highly protected Lycid beetles. The whole + assemblage of African insects with a Lycoid colouring forms a most + important combination and one which has an interesting bearing upon the + theories of Bates and Fritz Muller. This most wonderful set of mimetic + forms, described in 1902 by Guy A.K. Marshall, is composed of + flower-haunting beetles belonging to the family Lycidae, and the + heterogeneous group of varied insects which mimic their conspicuous and + simple scheme of colouring. The Lycid beetles, forming the centre or + "models" of the whole company, are orange-brown in front for about + two-thirds of the exposed surface, black behind for the remaining third. + They are undoubtedly protected by qualities which make them excessively + unpalatable to the bulk of insect-eating animals. Some experimental proof + of this has been obtained by Mr Guy Marshall. What are the forms which + surround them? According to the hypothesis of Bates they would be, at any + rate mainly, palatable hard-pressed insects which only hold their own in + the struggle for life by a fraudulent imitation of the trade-mark of the + successful and powerful Lycidae. According to Fritz Muller's hypothesis we + should expect that the mimickers would be highly protected, successful and + abundant species, which (metaphorically speaking) have found it to their + advantage to possess an advertisement, a danger-signal, in common with + each other, and in common with the beetles in the centre of the group. + </p> + <p> + How far does the constitution of this wonderful combination—the + largest and most complicated as yet known in all the world—convey to + us the idea of mimicry working along the lines supposed by Bates or those + suggested by Muller? Figures 1 to 52 of Mr Marshall's coloured plate + ("Trans. Ent. Soc. Lond." 1902, plate XVIII. See also page 517, where the + group is analysed.) represent a set of forty-two or forty-three species or + forms of insects captured in Mashonaland, and all except two in the + neighbourhood of Salisbury. The combination includes six species of + Lycidae; nine beetles of five groups all specially protected by nauseous + qualities, Telephoridae, Melyridae, Phytophaga, Lagriidae, Cantharidae; + six Longicorn beetles; one Coprid beetle; eight stinging Hymenoptera; + three or four parasitic Hymenoptera (Braconidae, a group much mimicked and + shown by some experiments to be distasteful); five bugs (Hemiptera, a + largely unpalatable group); three moths (Arctiidae and Zygaenidae, + distasteful families); one fly. In fact the whole combination, except + perhaps one Phytophagous, one Coprid and the Longicorn beetles, and the + fly, fall under the hypothesis of Muller and not under that of Bates. And + it is very doubtful whether these exceptions will be sustained: indeed the + suspicion of unpalatability already besets the Longicorns and is always on + the heels,—I should say the hind tarsi—of a Phytophagous + beetle. + </p> + <p> + This most remarkable group which illustrates so well the problem of + mimicry and the alternative hypotheses proposed for its solution, was, as + I have said, first described in 1902. Among the most perfect of the + mimetic resemblances in it is that between the Longicorn beetle, + Amphidesmus analis, and the Lycidae. It was with the utmost astonishment + and pleasure that I found this very resemblance had almost certainly been + observed by Burchell. A specimen of the Amphidesmus exists in his + collection and it bears "651." Turning to the same number in the African + Catalogue we find that the beetle is correctly placed among the + Longicorns, that it was captured at Uitenhage on Nov. 18, 1813, and that + it was found associated with Lycid beetles in flowers ("consocians cum + Lycis 78-87 in floribus"). Looking up Nos. 78-87 in the collection and + catalogue, three species of Lycidae are found, all captured on Nov. 18, + 1813, at Uitenhage. Burchell recognised the wide difference in affinity, + shown by the distance between the respective numbers; for his catalogue is + arranged to represent relationships. He observed, what students of mimicry + are only just beginning to note and record, the coincidence between model + and mimic in time and space and in habits. We are justified in concluding + that he observed the close superficial likeness although he does not in + this case expressly allude to it. + </p> + <p> + One of the most interesting among the early observations of superficial + resemblance between forms remote in the scale of classification was made + by Darwin himself, as described in the following passage from his letter + to Henslow, written from Monte Video, Aug. 15, 1832: "Amongst the lower + animals nothing has so much interested me as finding two species of + elegantly coloured true Planaria inhabiting the dewy forest! The false + relation they bear to snails is the most extraordinary thing of the kind I + have ever seen." ("More Letters", I. page 9.) + </p> + <p> + Many years later, in 1867, he wrote to Fritz Muller suggesting that the + resemblance of a soberly coloured British Planarian to a slug might be due + to mimicry. ("Life and Letters", III. page 71.) + </p> + <p> + The most interesting copy of Bates's classical memoir on Mimicry + ("Contributions to an Insect Fauna of the Amazon Valley". "Trans. Linn. + Soc." Vol. XXIII. 1862, page 495.), read before the Linnean Society in + 1861, is that given by him to the man who has done most to support and + extend the theory. My kind friend has given that copy to me; it bears the + inscription: + </p> + <p> + "Mr A.R. Wallace from his old travelling companion the Author." + </p> + <p> + Only a year and a half after the publication of the "Origin", we find that + Darwin wrote to Bates on the subject which was to provide such striking + evidence of the truth of Natural Selection: "I am glad to hear that you + have specially attended to 'mimetic' analogies—a most curious + subject; I hope you publish on it. I have for a long time wished to know + whether what Dr Collingwood asserts is true—that the most striking + cases generally occur between insects inhabiting the same country." (The + letter is dated April 4, 1861. "More Letters", I. page 183.) + </p> + <p> + The next letter, written about six months later, reveals the remarkable + fact that the illustrious naturalist who had anticipated Edward Forbes in + the explanation of arctic forms on alpine heights ("I was forestalled in + only one important point, which my vanity has always made me regret, + namely, the explanation by means of the Glacial period of the presence of + the same species of plants and of some few animals on distant mountain + summits and in the arctic regions. This view pleased me so much that I + wrote it out in extenso, and I believe that it was read by Hooker some + years before E. Forbes published his celebrated memoir on the subject. In + the very few points in which we differed, I still think that I was in the + right. I have never, of course, alluded in print to my having + independently worked out this view." "Autobiography, Life and Letters", I. + page 88.), had also anticipated H.W. Bates in the theory of Mimicry: "What + a capital paper yours will be on mimetic resemblances! You will make quite + a new subject of it. I had thought of such cases as a difficulty; and + once, when corresponding with Dr Collingwood, I thought of your + explanation; but I drove it from my mind, for I felt that I had not + knowledge to judge one way or the other." (The letter is dated Sept. 25, + 1861: "More Letters", I. page 197.) + </p> + <p> + Bates read his paper before the Linnean Society, Nov. 21, 1861, and + Darwin's impressions on hearing it were conveyed in a letter to the author + dated Dec. 3: "Under a general point of view, I am quite convinced (Hooker + and Huxley took the same view some months ago) that a philosophic view of + nature can solely be driven into naturalists by treating special subjects + as you have done. Under a special point of view, I think you have solved + one of the most perplexing problems which could be given to solve." ("Life + and Letters", II. page 378.) The memoir appeared in the following year, + and after reading it Darwin wrote as follows, Nov. 20, 1862: "... In my + opinion it is one of the most remarkable and admirable papers I ever read + in my life... I am rejoiced that I passed over the whole subject in the + "Origin", for I should have made a precious mess of it. You have most + clearly stated and solved a wonderful problem... Your paper is too good to + be largely appreciated by the mob of naturalists without souls; but, rely + on it, that it will have LASTING value, and I cordially congratulate you + on your first great work. You will find, I should think, that Wallace will + fully appreciate it." ("Life and Letters", II. pages 391-393.) Four days + later, Nov. 24, Darwin wrote to Hooker on the same subject: "I have now + finished his paper...' it seems to me admirable. To my mind the act of + segregation of varieties into species was never so plainly brought + forward, and there are heaps of capital miscellaneous observations." + ("More Letters", I. page 214.) + </p> + <p> + Darwin was here referring to the tendency of similar varieties of the same + species to pair together, and on Nov. 25 he wrote to Bates asking for + fuller information on this subject. ("More Letters", I. page 215. See also + parts of Darwin's letter to Bates in "Life and Letters", II. page 392.) If + Bates's opinion were well founded, sexual selection would bear a most + important part in the establishment of such species. (See Poulton, "Essays + on Evolution", 1908, pages 65, 85-88.) It must be admitted, however, that + the evidence is as yet quite insufficient to establish this conclusion. It + is interesting to observe how Darwin at once fixed on the part of Bates's + memoir which seemed to bear upon sexual selection. A review of Bates's + theory of Mimicry was contributed by Darwin to the "Natural History + Review" (New Ser. Vol. III. 1863, page 219.) and an account of it is to be + found in the "Origin" (Edition 1872, pages 375-378.) and in "The Descent + of Man". (Edition 1874, pages 323-325.) + </p> + <p> + Darwin continually writes of the value of hypothesis as the inspiration of + inquiry. We find an example in his letter to Bates, Nov. 22, 1860: "I have + an old belief that a good observer really means a good theorist, and I + fully expect to find your observations most valuable." ("More Letters", I. + page 176.) Darwin's letter refers to many problems upon which Bates had + theorised and observed, but as regards Mimicry itself the hypothesis was + thought out after the return of the letter from the Amazons, when he no + longer had the opportunity of testing it by the observation of living + Nature. It is by no means improbable that, had he been able to apply this + test, Bates would have recognised that his division of butterfly + resemblances into two classes,—one due to the theory of mimicry, the + other to the influence of local conditions,—could not be sustained. + </p> + <p> + Fritz Muller's contributions to the problem of Mimicry were all made in + S.E. Brazil, and numbers of them were communicated, with other + observations on natural history, to Darwin, and by him sent to Professor + R. Meldola who published many of the facts. Darwin's letters to Meldola + (Poulton, "Charles Darwin and the theory of Natural Selection", London, + 1896, pages 199-218.) contain abundant proofs of his interest in Muller's + work upon Mimicry. One deeply interesting letter (Loc. cit. pages 201, + 202.) dated Jan. 23, 1872, proves that Fritz Muller before he originated + the theory of Common Warning Colours (Synaposematic Resemblance or + Mullerian Mimicry), which will ever be associated with his name, had + conceived the idea of the production of mimetic likeness by sexual + selection. + </p> + <p> + Darwin's letter to Meldola shows that he was by no means inclined to + dismiss the suggestion as worthless, although he considered it daring. + "You will also see in this letter a strange speculation, which I should + not dare to publish, about the appreciation of certain colours being + developed in those species which frequently behold other forms similarly + ornamented. I do not feel at all sure that this view is as incredible as + it may at first appear. Similar ideas have passed through my mind when + considering the dull colours of all the organisms which inhabit + dull-coloured regions, such as Patagonia and the Galapagos Is." A little + later, on April 5, he wrote to Professor August Weismann on the same + subject: "It may be suspected that even the habit of viewing differently + coloured surrounding objects would influence their taste, and Fritz Muller + even goes so far as to believe that the sight of gaudy butterflies might + influence the taste of distinct species." ("Life and Letters", III. page + 157.) + </p> + <p> + This remarkable suggestion affords interesting evidence that F. Muller was + not satisfied with the sufficiency of Bates's theory. Nor is this + surprising when we think of the numbers of abundant conspicuous + butterflies which he saw exhibiting mimetic likenesses. The common + instances in his locality, and indeed everywhere in tropical America, were + anything but the hard-pressed struggling forms assumed by the theory of + Bates. They belonged to the groups which were themselves mimicked by other + butterflies. Fritz Muller's suggestion also shows that he did not accept + Bates's alternative explanation of a superficial likeness between models + themselves, based on some unknown influence of local physico-chemical + forces. At the same time Muller's own suggestion was subject to this + apparently fatal objection, that the sexual selection he invoked would + tend to produce resemblances in the males rather than the females, while + it is well known that when the sexes differ the females are almost + invariably more perfectly mimetic than the males and in a high proportion + of cases are mimetic while the males are non-mimetic. + </p> + <p> + The difficulty was met several years later by Fritz Muller's well-known + theory, published in 1879 ("Kosmos", May 1879, page 100.), and immediately + translated by Meldola and brought before the Entomological Society. + ("Proc. Ent. Soc. Lond." 1879, page xx.) Darwin's letter to Meldola dated + June 6, 1879, shows "that the first introduction of this new and most + suggestive hypothesis into this country was due to the direct influence of + Darwin himself, who brought it before the notice of the one man who was + likely to appreciate it at its true value and to find the means for its + presentation to English naturalists." ("Charles Darwin and the Theory of + Natural Selection", page 214.) Of the hypothesis itself Darwin wrote "F. + Muller's view of the mutual protection was quite new to me." (Ibid. page + 213.) The hypothesis of Mullerian mimicry was at first strongly opposed. + Bates himself could never make up his mind to accept it. As the Fellows + were walking out of the meeting at which Professor Meldola explained the + hypothesis, an eminent entomologist, now deceased, was heard to say to + Bates: "It's a case of save me from my friends!" The new ideas encountered + and still encounter to a great extent the difficulty that the theory of + Bates had so completely penetrated the literature of natural history. The + present writer has observed that naturalists who have not thoroughly + absorbed the older hypothesis are usually far more impressed by the newer + one than are those whose allegiance has already been rendered. The + acceptance of Natural Selection itself was at first hindered by similar + causes, as Darwin clearly recognised: "If you argue about the + non-acceptance of Natural Selection, it seems to me a very striking fact + that the Newtonian theory of gravitation, which seems to every one now so + certain and plain, was rejected by a man so extraordinarily able as + Leibnitz. The truth will not penetrate a preoccupied mind." (To Sir J. + Hooker, July 28, 1868, "More Letters", I. page 305. See also the letter to + A.R. Wallace, April 30, 1868, in "More Letters" II. page 77, lines 6-8 + from top.) + </p> + <p> + There are many naturalists, especially students of insects, who appear to + entertain an inveterate hostility to any theory of mimicry. Some of them + are eager investigators in the fascinating field of geographical + distribution, so essential for the study of Mimicry itself. The changes of + pattern undergone by a species of Erebia as we follow it over different + parts of the mountain ranges of Europe is indeed a most interesting + inquiry, but not more so than the differences between e.g. the Acraea + johnstoni of S.E. Rhodesia and of Kilimanjaro. A naturalist who is + interested by the Erebia should be equally interested by the Acraea; and + so he would be if the student of mimicry did not also record that the + characteristics which distinguish the northern from the southern + individuals of the African species correspond with the presence, in the + north but not in the south, of certain entirely different butterflies. + That this additional information should so greatly weaken, in certain + minds, the appeal of a favourite study, is a psychological problem of no + little interest. This curious antagonism is I believe confined to a few + students of insects. Those naturalists who, standing rather farther off, + are able to see the bearings of the subject more clearly, will usually + admit the general support yielded by an ever-growing mass of observations + to the theories of Mimicry propounded by H.W. Bates and Fritz Muller. In + like manner natural selection itself was in the early days often best + understood and most readily accepted by those who were not naturalists. + Thus Darwin wrote to D.T. Ansted, Oct. 27, 1860: "I am often in despair in + making the generality of NATURALISTS even comprehend me. Intelligent men + who are not naturalists and have not a bigoted idea of the term species, + show more clearness of mind." ("More Letters", I. page 175.) + </p> + <p> + Even before the "Origin" appeared Darwin anticipated the first results + upon the mind of naturalists. He wrote to Asa Gray, Dec. 21, 1859: "I have + made up my mind to be well abused; but I think it of importance that my + notions should be read by intelligent men, accustomed to scientific + argument, though NOT naturalists. It may seem absurd, but I think such men + will drag after them those naturalists who have too firmly fixed in their + heads that a species is an entity." ("Life and Letters" II. page 245.) + </p> + <p> + Mimicry was not only one of the first great departments of zoological + knowledge to be studied under the inspiration of natural Selection, it is + still and will always remain one of the most interesting and important of + subjects in relation to this theory as well as to evolution. In mimicry we + investigate the effect of environment in its simplest form: we trace the + effects of the pattern of a single species upon that of another far + removed from it in the scale of classification. When there is reason to + believe that the model is an invader from another region and has only + recently become an element in the environment of the species native to its + second home, the problem gains a special interest and fascination. + Although we are chiefly dealing with the fleeting and changeable element + of colour we expect to find and we do find evidence of a comparatively + rapid evolution. The invasion of a fresh model is for certain species an + unusually sudden change in the forces of the environment and in some + instances we have grounds for the belief that the mimetic response has not + been long delayed. + </p> + <p> + MIMICRY AND SEX. + </p> + <p> + Ever since Wallace's classical memoir on mimicry in the Malayan + Swallowtail butterflies, those naturalists who have written on the subject + have followed his interpretation of the marked prevalence of mimetic + resemblance in the female sex as compared with the male. They have + believed with Wallace that the greater dangers of the female, with slower + flight and often alighting for oviposition, have been in part met by the + high development of this special mode of protection. The fact cannot be + doubted. It is extremely common for a non-mimetic male to be accompanied + by a beautifully mimetic female and often by two or three different forms + of female, each mimicking a different model. The male of a polymorphic + mimetic female is, in fact, usually non-mimetic (e.g. Papilio dardanus = + merope), or if a mimic (e.g. the Nymphaline genus Euripus), resembles a + very different model. On the other hand a non-mimetic female accompanied + by a mimetic male is excessively rare. An example is afforded by the + Oriental Nymphaline, Cethosia, in which the males of some species are + rough mimics of the brown Danaines. In some of the orb-weaving spiders the + males mimic ants, while the much larger females are non-mimetic. When both + sexes mimic, it is very common in butterflies and is also known in moths, + for the females to be better and often far better mimics than the males. + </p> + <p> + Although still believing that Wallace's hypothesis in large part accounts + for the facts briefly summarised above, the present writer has recently + been led to doubt whether it offers a complete explanation. Mimicry in the + male, even though less beneficial to the species than mimicry in the + female, would still surely be advantageous. Why then is it so often + entirely restricted to the female? While the attempt to find an answer to + this question was haunting me, I re-read a letter written by Darwin to + Wallace, April 15, 1868, containing the following sentences: "When female + butterflies are more brilliant than their males you believe that they have + in most cases, or in all cases, been rendered brilliant so as to mimic + some other species, and thus escape danger. But can you account for the + males not having been rendered equally brilliant and equally protected? + Although it may be most for the welfare of the species that the female + should be protected, yet it would be some advantage, certainly no + disadvantage, for the unfortunate male to enjoy an equal immunity from + danger. For my part, I should say that the female alone had happened to + vary in the right manner, and that the beneficial variations had been + transmitted to the same sex alone. Believing in this, I can see no + improbability (but from analogy of domestic animals a strong probability) + that variations leading to beauty must often have occurred in the males + alone, and been transmitted to that sex alone. Thus I should account in + many cases for the greater beauty of the male over the female, without the + need of the protective principle." ("More Letters", II. pages 73, 74. On + the same subject—"the gay-coloured females of Pieris" (Perrhybris + (Mylothris) pyrrha of Brazil), Darwin wrote to Wallace, May 5, 1868, as + follows: "I believe I quite follow you in believing that the colours are + wholly due to mimicry; and I further believe that the male is not + brilliant from not having received through inheritance colour from the + female, and from not himself having varied; in short, that he has not been + influenced by selection." It should be noted that the male of this species + does exhibit a mimetic pattern on the under surface. "More Letters" II. + page 78.) + </p> + <p> + The consideration of the facts of mimicry thus led Darwin to the + conclusion that the female happens to vary in the right manner more + commonly than the male, while the secondary sexual characters of males + supported the conviction "that from some unknown cause such characters + (viz. new characters arising in one sex and transmitted to it alone) + apparently appear oftener in the male than in the female." (Letter from + Darwin to Wallace, May 5, 1867, "More Letters", II. Page 61.) + </p> + <p> + Comparing these conflicting arguments we are led to believe that the first + is the stronger. Mimicry in the male would be no disadvantage but an + advantage, and when it appears would be and is taken advantage of by + selection. The secondary sexual characters of males would be no advantage + but a disadvantage to females, and, as Wallace thinks, are withheld from + this sex by selection. It is indeed possible that mimicry has been + hindered and often prevented from passing to the males by sexual + selection. We know that Darwin was much impressed ("Descent of Man", page + 325.) by Thomas Belt's daring and brilliant suggestion that the white + patches which exist, although ordinarily concealed, on the wings of + mimetic males of certain Pierinae (Dismorphia), have been preserved by + preferential mating. He supposed this result to have been brought about by + the females exhibiting a deep-seated preference for males that displayed + the chief ancestral colour, inherited from periods before any mimetic + pattern had been evolved in the species. But it has always appeared to me + that Belt's deeply interesting suggestion requires much solid evidence and + repeated confirmation before it can be accepted as a valid interpretation + of the facts. In the present state of our knowledge, at any rate of + insects and especially of Lepidoptera, it is probable that the female is + more apt to vary than the male and that an important element in the + interpretation of prevalent female mimicry is provided by this fact. + </p> + <p> + In order adequately to discuss the question of mimicry and sex it would be + necessary to analyse the whole of the facts, so far as they are known in + butterflies. On the present occasion it is only possible to state the + inferences which have been drawn from general impressions,—inferences + which it is believed will be sustained by future inquiry. + </p> + <p> + (1) Mimicry may occasionally arise in one sex because the differences + which distinguish it from the other sex happen to be such as to afford a + starting-point for the resemblance. Here the male is at no disadvantage as + compared with the female, and the rarity of mimicry in the male alone + (e.g. Cethosia) is evidence that the great predominance of female mimicry + is not to be thus explained. + </p> + <p> + (2) The tendency of the female to dimorphism and polymorphism has been of + great importance in determining this predominance. Thus if the female + appear in two different forms and the male in only one it will be twice as + probable that she will happen to possess a sufficient foundation for the + evolution of mimicry. + </p> + <p> + (3) The appearance of melanic or partially melanic forms in the female has + been of very great service, providing as it does a change of + ground-colour. Thus the mimicry of the black generally red-marked American + "Aristolochia swallowtails" (Pharmacophagus) by the females of Papilio + swallowtails was probably begun in this way. + </p> + <p> + (4) It is probably incorrect to assume with Haase that mimicry always + arose in the female and was later acquired by the male. Both sexes of the + third section of swallowtails (Cosmodesmus) mimic Pharmacophagus in + America, far more perfectly than do the females of Papilio. But this is + not due to Cosmodesmus presenting us with a later stage of history begun + in Papilio; for in Africa Cosmodesmus is still mimetic (of Danainae) in + both sexes although the resemblances attained are imperfect, while many + African species of Papilio have non-mimetic males with beautifully mimetic + females. The explanation is probably to be sought in the fact that the + females of Papilio are more variable and more often tend to become + dimorphic than those of Cosmodesmus, while the latter group has more often + happened to possess a sufficient foundation for the origin of the + resemblance in patterns which, from the start, were common to male and + female. + </p> + <p> + (5) In very variable species with sexes alike, mimicry can be rapidly + evolved in both sexes out of very small beginnings. Thus the reddish marks + which are common in many individuals of Limenitis arthemis were almost + certainly the starting-point for the evolution of the beautifully mimetic + L. archippus. Nevertheless in such cases, although there is no reason to + suspect any greater variability, the female is commonly a somewhat better + mimic than the male and often a very much better mimic. Wallace's + principle seems here to supply the obvious interpretation. + </p> + <p> + (6) When the difference between the patterns of the model and presumed + ancestor of the mimic is very great, the female is often alone mimetic; + when the difference is comparatively small, both sexes are commonly + mimetic. The Nymphaline genus Hypolimnas is a good example. In Hypolimnas + itself the females mimic Danainae with patterns very different from those + preserved by the non-mimetic males: in the sub-genus Euralia, both sexes + resemble the black and white Ethiopian Danaines with patterns not very + dissimilar from that which we infer to have existed in the non-mimetic + ancestor. + </p> + <p> + (7) Although a melanic form or other large variation may be of the utmost + importance in facilitating the start of a mimetic likeness, it is + impossible to explain the evolution of any detailed resemblance in this + manner. And even the large colour variation itself may well be the + expression of a minute and "continuous" change in the chemical and + physical constitution of pigments. + </p> + <p> + SEXUAL SELECTION (EPIGAMIC CHARACTERS). + </p> + <p> + We do not know the date at which the idea of Sexual Selection arose in + Darwin's mind, but it was probably not many years after the sudden flash + of insight which, in October 1838, gave to him the theory of Natural + Selection. An excellent account of Sexual Selection occupies the + concluding paragraph of Part I. of Darwin's Section of the Joint Essay on + Natural Selection, read July 1st, 1858, before the Linnean Society. + ("Journ. Proc. Linn. Soc." Vol. III. 1859, page 50.) The principles are so + clearly and sufficiently stated in these brief sentences that it is + appropriate to quote the whole: "Besides this natural means of selection, + by which those individuals are preserved, whether in their egg, or larval, + or mature state, which are best adapted to the place they fill in nature, + there is a second agency at work in most unisexual animals, tending to + produce the same effect, namely, the struggle of the males for the + females. These struggles are generally decided by the law of battle, but + in the case of birds, apparently, by the charms of their song, by their + beauty or their power of courtship, as in the dancing rock-thrush of + Guiana. The most vigorous and healthy males, implying perfect adaptation, + must generally gain the victory in their contests. This kind of selection, + however, is less rigorous than the other; it does not require the death of + the less successful, but gives to them fewer descendants. The struggle + falls, moreover, at a time of year when food is generally abundant, and + perhaps the effect chiefly produced would be the modification of the + secondary sexual characters, which are not related to the power of + obtaining food, or to defence from enemies, but to fighting with or + rivalling other males. The result of this struggle amongst the males may + be compared in some respects to that produced by those agriculturists who + pay less attention to the careful selection of all their young animals, + and more to the occasional use of a choice mate." + </p> + <p> + A full exposition of Sexual Selection appeared in the "The Descent of Man" + in 1871, and in the greatly augmented second edition, in 1874. It has been + remarked that the two subjects, "The Descent of Man and Selection in + Relation to Sex", seem to fuse somewhat imperfectly into the single work + of which they form the title. The reason for their association is clearly + shown in a letter to Wallace, dated May 28, 1864: "... I suspect that a + sort of sexual selection has been the most powerful means of changing the + races of man." ("More Letters", II. page 33.) + </p> + <p> + Darwin, as we know from his Autobiography ("Life and Letters", I. page + 94.), was always greatly interested in this hypothesis, and it has been + shown in the preceding pages that he was inclined to look favourably upon + it as an interpretation of many appearances usually explained by Natural + Selection. Hence Sexual Selection, incidentally discussed in other + sections of the present essay, need not be considered at any length, in + the section specially allotted to it. + </p> + <p> + Although so interested in the subject and notwithstanding his conviction + that the hypothesis was sound, Darwin was quite aware that it was probably + the most vulnerable part of the "Origin". Thus he wrote to H.W. Bates, + April 4, 1861: "If I had to cut up myself in a review I would have + (worried?) and quizzed sexual selection; therefore, though I am fully + convinced that it is largely true, you may imagine how pleased I am at + what you say on your belief." ("More Letters", I. page 183.) + </p> + <p> + The existence of sound-producing organs in the males of insects was, + Darwin considered, the strongest evidence in favour of the operation of + sexual selection in this group. ("Life and Letters", III. pages 94, 138.) + Such a conclusion has received strong support in recent years by the + numerous careful observations of Dr F.A. Dixey ("Proc. Ent. Soc. Lond." + 1904, page lvi; 1905, pages xxxvii, liv; 1906, page ii.) and Dr G.B. + Longstaff ("Proc. Ent. Soc. Lond." 1905, page xxxv; "Trans. Ent. Soc. + Lond." 1905, page 136; 1908, page 607.) on the scents of male butterflies. + The experience of these naturalists abundantly confirms and extends the + account given by Fritz Muller ("Jen. Zeit." Vol. XI. 1877, page 99; + "Trans. Ent. Soc. Lond." 1878, page 211.) of the scents of certain + Brazilian butterflies. It is a remarkable fact that the apparently + epigamic scents of male butterflies should be pleasing to man while the + apparently aposematic scents in both sexes of species with warning colours + should be displeasing to him. But the former is far more surprising than + the latter. It is not perhaps astonishing that a scent which is ex + hypothesi unpleasant to an insect-eating Vertebrate should be displeasing + to the human sense; but it is certainly wonderful that an odour which is + ex hypothesi agreeable to a female butterfly should also be agreeable to + man. + </p> + <p> + Entirely new light upon the seasonal appearance of epigamic characters is + shed by the recent researches of C.W. Beebe ("The American Naturalist", + Vol. XLII. No. 493, Jan. 1908, page 34.), who caused the scarlet tanager + (Piranga erythromelas) and the bobolink (Dolichonyx oryzivorus) to retain + their breeding plumage through the whole year by means of fattening food, + dim illumination, and reduced activity. Gradual restoration to the light + and the addition of meal-worms to the diet invariably brought back the + spring song, even in the middle of winter. A sudden alteration of + temperature, either higher or lower, caused the birds nearly to stop + feeding, and one tanager lost weight rapidly and in two weeks moulted into + the olive-green winter plumage. After a year, and at the beginning of the + normal breeding season, "individual tanagers and bobolinks were gradually + brought under normal conditions and activities," and in every case moulted + from nuptial plumage to nuptial plumage. "The dull colours of the winter + season had been skipped." The author justly claims to have established + "that the sequence of plumage in these birds is not in any way predestined + through inheritance..., but that it may be interrupted by certain factors + in the environmental complex." + </p> + <p> + <a name="link2H_4_0018" id="link2H_4_0018"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + XVI. GEOGRAPHICAL DISTRIBUTION OF PLANTS. By Sir William Thiselton-Dyer, + K.C.M.G., C.I.E. Sc.D., F.R.S. + </h2> + <p> + The publication of "The Origin of Species" placed the study of Botanical + Geography on an entirely new basis. It is only necessary to study the + monumental "Geographie Botanique raisonnee" of Alphonse De Candolle, + published four years earlier (1855), to realise how profound and + far-reaching was the change. After a masterly and exhaustive discussion of + all available data De Candolle in his final conclusions could only arrive + at a deadlock. It is sufficient to quote a few sentences:— + </p> + <p> + "L'opinion de Lamarck est aujourd'hui abandonee par tous les naturalistes + qui ont etudie sagement les modifications possibles des etres organises... + </p> + <p> + "Et si l'on s'ecarte des exagerations de Lamarck, si l'on suppose un + premier type de chaque genre, de chaque famille tout au moins, on se + trouve encore a l'egard de l'origine de ces types en presence de la grande + question de la creation. + </p> + <p> + "Le seul parti a prendre est donc d'envisager les etres organises comme + existant depuis certaines epoques, avec leurs qualites particulieres." + (Vol. II. page 1107.) + </p> + <p> + Reviewing the position fourteen years afterwards, Bentham remarked:—"These + views, generally received by the great majority of naturalists at the time + De Candolle wrote, and still maintained by a few, must, if adhered to, + check all further enquiry into any connection of facts with causes," and + he added, "there is little doubt but that if De Candolle were to revise + his work, he would follow the example of so many other eminent + naturalists, and... insist that the present geographical distribution of + plants was in most instances a derivative one, altered from a very + different former distribution." ("Pres. Addr." (1869) "Proc. Linn. Soc." + 1868-69, page lxviii.) + </p> + <p> + Writing to Asa Gray in 1856, Darwin gave a brief preliminary account of + his ideas as to the origin of species, and said that geographical + distribution must be one of the tests of their validity. ("Life and + Letters", II. page 78.) What is of supreme interest is that it was also + their starting-point. He tells us:—"When I visited, during the + voyage of H.M.S. "Beagle", the Galapagos Archipelago,... I fancied myself + brought near to the very act of creation. I often asked myself how these + many peculiar animals and plants had been produced: the simplest answer + seemed to be that the inhabitants of the several islands had descended + from each other, undergoing modification in the course of their descent." + ("The Variation of Animals and Plants" (2nd edition), 1890, I. pages 9, + 10.) We need not be surprised then, that in writing in 1845 to Sir Joseph + Hooker, he speaks of "that grand subject, that almost keystone of the laws + of creation, Geographical Distribution." ("Life and Letters", I. page + 336.) + </p> + <p> + Yet De Candolle was, as Bentham saw, unconsciously feeling his way, like + Lyell, towards evolution, without being able to grasp it. They both strove + to explain phenomena by means of agencies which they saw actually at work. + If De Candolle gave up the ultimate problem as insoluble:—"La + creation ou premiere formation des etres organises echappe, par sa nature + et par son anciennete, a nos moyens d'observation" (Loc. cit. page 1106.), + he steadily endeavoured to minimise its scope. At least half of his great + work is devoted to the researches by which he extricated himself from a + belief in species having had a multiple origin, the view which had been + held by successive naturalists from Gmelin to Agassiz. To account for the + obvious fact that species constantly occupy dissevered areas, De Candolle + made a minute study of their means of transport. This was found to dispose + of the vast majority of cases, and the remainder he accounted for by + geographical change. (Loc. cit. page 1116.) + </p> + <p> + But Darwin strenuously objected to invoking geographical change as a + solution of every difficulty. He had apparently long satisfied himself as + to the "permanence of continents and great oceans." Dana, he tells us + "was, I believe, the first man who maintained" this ("Life and Letters", + III. page 247. Dana says:—"The continents and oceans had their + general outline or form defined in earliest time," "Manual of Geology", + revised edition. Philadelphia, 1869, page 732. I have no access to an + earlier edition.), but he had himself probably arrived at it + independently. Modern physical research tends to confirm it. The earth's + centre of gravity, as pointed out by Pratt from the existence of the + Pacific Ocean, does not coincide with its centre of figure, and it has + been conjectured that the Pacific Ocean dates its origin from the + separation of the moon from the earth. + </p> + <p> + The conjecture appears to be unnecessary. Love shows that "the force that + keeps the Pacific Ocean on one side of the earth is gravity, directed more + towards the centre of gravity than the centre of the figure." ("Report of + the 77th Meeting of the British Association" (Leicester, 1907), London, + 1908, page 431.) I can only summarise the conclusions of a technical but + masterly discussion. "The broad general features of the distribution of + continent and ocean can be regarded as the consequences of simple causes + of a dynamical character," and finally, "As regards the contour of the + great ocean basins, we seem to be justified in saying that the earth is + approximately an oblate spheroid, but more nearly an ellipsoid with three + unequal axes, having its surface furrowed according to the formula for a + certain spherical harmonic of the third degree" (Ibid. page 436.), and he + shows that this furrowed surface must be produced "if the density is + greater in one hemispheroid than in the other, so that the position of the + centre of gravity is eccentric." (Ibid. page 431.) Such a modelling of the + earth's surface can only be referred to a primitive period of plasticity. + If the furrows account for the great ocean basins, the disposition of the + continents seems equally to follow. Sir George Darwin has pointed out that + they necessarily "arise from a supposed primitive viscosity or plasticity + of the earth's mass. For during this course of evolution the earth's mass + must have suffered a screwing motion, so that the polar regions have + travelled a little from west to east relatively to the equator. This + affords a possible explanation of the north and south trend of our great + continents." ("Encycl. Brit." (9th edition), Vol. XXIII. "Tides", page + 379.) + </p> + <p> + It would be trespassing on the province of the geologist to pursue the + subject at any length. But as Wallace ("Island Life" (2nd edition), 1895, + page 103.), who has admirably vindicated Darwin's position, points out, + the "question of the permanence of our continents... lies at the root of + all our inquiries into the great changes of the earth and its + inhabitants." But he proceeds: "The very same evidence which has been + adduced to prove the GENERAL stability and permanence of our continental + areas also goes to prove that they have been subjected to wonderful and + repeated changes in DETAIL." (Loc. cit. page 101.) Darwin of course would + have admitted this, for with a happy expression he insisted to Lyell + (1856) that "the skeletons, at least, of our continents are ancient." + ("More Letters", II. page 135.) It is impossible not to admire the courage + and tenacity with which he carried on the conflict single-handed. But he + failed to convince Lyell. For we still find him maintaining in the last + edition of the "Principles": "Continents therefore, although permanent for + whole geological epochs, shift their positions entirely in the course of + ages." (Lyell's "Principles of Geology" (11th edition), London, 1872, I. + page 258.) + </p> + <p> + Evidence, however, steadily accumulates in Darwin's support. His position + still remains inexpugnable that it is not permissible to invoke + geographical change to explain difficulties in distribution without valid + geological and physical support. Writing to Mellard Reade, who in 1878 had + said, "While believing that the ocean-depths are of enormous age, it is + impossible to reject other evidences that they have once been land," he + pointed out "the statement from the 'Challenger' that all sediment is + deposited within one or two hundred miles from the shores." ("More + Letters", II. page 146.) The following year Sir Archibald Geikie + ("Geographical Evolution", "Proc. R. Geogr. Soc." 1879, page 427.) + informed the Royal Geographical Society that "No part of the results + obtained by the 'Challenger' expedition has a profounder interest for + geologists and geographers than the proof which they furnish that the + floor of the ocean basins has no real analogy among the sedimentary + formations which form most of the framework of the land." + </p> + <p> + Nor has Darwin's earlier argument ever been upset. "The fact which I + pointed out many years ago, that all oceanic islands are volcanic (except + St Paul's, and now that is viewed by some as the nucleus of an ancient + volcano), seem to me a strong argument that no continent ever occupied the + great oceans." ("More Letters", II. page 146.) + </p> + <p> + Dr Guppy, who devoted several years to geological and botanical + investigations in the Pacific, found himself forced to similar + conclusions. "It may be at once observed," he says, "that my belief in the + general principle that islands have always been islands has not been + shaken," and he entirely rejects "the hypothesis of a Pacific continent." + He comes back, in full view of the problems on the spot, to the position + from which, as has been seen, Darwin started: "If the distribution of a + particular group of plants or animals does not seem to accord with the + present arrangement of the land, it is by far the safest plan, even after + exhausting all likely modes of explanation, not to invoke the intervention + of geographical changes; and I scarcely think that our knowledge of any + one group of organisms is ever sufficiently precise to justify a recourse + to hypothetical alterations in the present relations of land and sea." + ("Observations of a Naturalist in the Pacific between 1896 and 1899", + London, 1903, I. page 380.) Wallace clinches the matter when he finds + "almost the whole of the vast areas of the Atlantic, Pacific, Indian, and + Southern Oceans, without a solitary relic of the great islands or + continents supposed to have sunk beneath their waves." ("Island Life", + page 105.) + </p> + <p> + Writing to Wallace (1876), Darwin warmly approves the former's "protest + against sinking imaginary continents in a quite reckless manner, as was + stated by Forbes, followed, alas, by Hooker, and caricatured by Wollaston + and (Andrew) Murray." ("Life and Letters", III. page 230.) The transport + question thus became of enormously enhanced importance. We need not be + surprised then at his writing to Lyell in 1856:—"I cannot avoid + thinking that Forbes's 'Atlantis' was an ill-service to science, as + checking a close study of means of dissemination" (Ibid. II. page 78.), + and Darwin spared no pains to extend our knowledge of them. He implores + Hooker, ten years later, to "admit how little is known on the subject," + and summarises with some satisfaction what he had himself achieved:—"Remember + how recently you and others thought that salt water would soon kill + seeds... Remember that no one knew that seeds would remain for many hours + in the crops of birds and retain their vitality; that fish eat seeds, and + that when the fish are devoured by birds the seeds can germinate, etc. + Remember that every year many birds are blown to Madeira and to the + Bermudas. Remember that dust is blown 1000 miles across the Atlantic." + ("More Letters", I. page 483.) + </p> + <p> + It has always been the fashion to minimise Darwin's conclusions, and these + have not escaped objection. The advocatus diaboli has a useful function in + science. But in attacking Darwin his brief is generally found to be + founded on a slender basis of facts. Thus Winge and Knud Andersen have + examined many thousands of migratory birds and found "that their crops and + stomachs were always empty. They never observed any seeds adhering to the + feathers, beaks or feet of the birds." (R.F. Scharff, "European Animals", + page 64, London, 1907.) The most considerable investigation of the problem + of Plant Dispersal since Darwin is that of Guppy. He gives a striking + illustration of how easily an observer may be led into error by relying on + negative evidence. + </p> + <p> + "When Ekstam published, in 1895, the results of his observations on the + plants of Nova Zembla, he observed that he possessed no data to show + whether swimming and wading birds fed on berries; and he attached all + importance to dispersal by winds. On subsequently visiting Spitzbergen he + must have been at first inclined, therefore, to the opinion of Nathorst, + who, having found only a solitary species of bird (a snow-sparrow) in that + region, naturally concluded that birds had been of no importance as agents + in the plant-stocking. However, Ekstam's opportunities were greater, and + he tells us that in the craws of six specimens of Lagopus hyperboreus shot + in Spitzbergen in August he found represented almost 25 per cent. of the + usual phanerogamic flora of that region in the form of fruits, seeds, + bulbils, flower-buds, leaf-buds, etc... " + </p> + <p> + "The result of Ekstam's observations in Spitzbergen was to lead him to + attach a very considerable importance in plant dispersal to the agency of + birds; and when in explanation of the Scandinavian elements in the + Spitzbergen flora he had to choose between a former land connection and + the agency of birds, he preferred the bird." (Guppy, op. cit. II. pages + 511, 512.) + </p> + <p> + Darwin objected to "continental extensions" on geological grounds, but he + also objected to Lyell that they do not "account for all the phenomena of + distribution on islands" ("Life and Letters", II. page 77.), such for + example as the absence of Acacias and Banksias in New Zealand. He agreed + with De Candolle that "it is poor work putting together the merely + POSSIBLE means of distribution." But he also agreed with him that they + were the only practicable door of escape from multiple origins. If they + would not work then "every one who believes in single centres will have to + admit continental extensions" (Ibid. II. page 82.), and that he regarded + as a mere counsel of despair:—"to make continents, as easily as a + cook does pancakes." (Ibid. II. page 74.) + </p> + <p> + The question of multiple origins however presented itself in another shape + where the solution was much more difficult. The problem, as stated by + Darwin, is this:—"The identity of many plants and animals, on + mountain-summits, separated from each other by hundreds of miles of + lowlands... without the apparent possibility of their having migrated from + one point to the other." He continues, "even as long ago as 1747, such + facts led Gmelin to conclude that the same species must have been + independently created at several distinct points; and we might have + remained in this same belief, had not Agassiz and others called vivid + attention to the Glacial period, which affords... a simple explanation of + the facts." ("Origin of Species" (6th edition) page 330.) + </p> + <p> + The "simple explanation" was substantially given by E. Forbes in 1846. It + is scarcely too much to say that it belongs to the same class of fertile + and far-reaching ideas as "natural selection" itself. It is an + extraordinary instance, if one were wanted at all, of Darwin's magnanimity + and intense modesty that though he had arrived at the theory himself, he + acquiesced in Forbes receiving the well-merited credit. "I have never," he + says, "of course alluded in print to my having independently worked out + this view." But he would have been more than human if he had not added:—"I + was forestalled in... one important point, which my vanity has always made + me regret." ("Life and Letters", I. page 88.) + </p> + <p> + Darwin, however, by applying the theory to trans-tropical migration, went + far beyond Forbes. The first enunciation to this is apparently contained + in a letter to Asa Gray in 1858. The whole is too long to quote, but the + pith is contained in one paragraph. "There is a considerable body of + geological evidence that during the Glacial epoch the whole world was + colder; I inferred that,... from erratic boulder phenomena carefully + observed by me on both the east and west coast of South America. Now I am + so bold as to believe that at the height of the Glacial epoch, AND WHEN + ALL TROPICAL PRODUCTIONS MUST HAVE BEEN CONSIDERABLY DISTRESSED, several + temperate forms slowly travelled into the heart of the Tropics, and even + reached the southern hemisphere; and some few southern forms penetrated in + a reverse direction northward." ("Life and Letters", II. page 136.) Here + again it is clear that though he credits Agassiz with having called vivid + attention to the Glacial period, he had himself much earlier grasped the + idea of periods of refrigeration. + </p> + <p> + Putting aside the fact, which has only been made known to us since + Darwin's death, that he had anticipated Forbes, it is clear that he gave + the theory a generality of which the latter had no conception. This is + pointed out by Hooker in his classical paper "On the Distribution of + Arctic Plants" (1860). "The theory of a southern migration of northern + types being due to the cold epochs preceding and during the glacial, + originated, I believe, with the late Edward Forbes; the extended one, of + the trans-tropical migration, is Mr Darwin's." ("Linn. Trans." XXIII. page + 253. The attempt appears to have been made to claim for Heer priority in + what I may term for short the arctic-alpine theory (Scharff, "European + Animals", page 128). I find no suggestion of his having hit upon it in his + correspondence with Darwin or Hooker. Nor am I aware of any reference to + his having done so in his later publications. I am indebted to his + biographer, Professor Schroter, of Zurich, for an examination of his + earlier papers with an equally negative result.) Assuming that local races + have derived from a common ancestor, Hooker's great paper placed the fact + of the migration on an impregnable basis. And, as he pointed out, Darwin + has shown that "such an explanation meets the difficulty of accounting for + the restriction of so many American and Asiatic arctic types to their own + peculiar longitudinal zones, and for what is a far greater difficulty, the + representation of the same arctic genera by most closely allied species in + different longitudes." + </p> + <p> + The facts of botanical geography were vital to Darwin's argument. He had + to show that they admitted of explanation without assuming multiple + origins for species, which would be fatal to the theory of Descent. He had + therefore to strengthen and extend De Candolle's work as to means of + transport. He refused to supplement them by hypothetical geographical + changes for which there was no independent evidence: this was simply to + attempt to explain ignotum per ignotius. He found a real and, as it has + turned out, a far-reaching solution in climatic change due to cosmical + causes which compelled the migration of species as a condition of their + existence. The logical force of the argument consists in dispensing with + any violent assumption, and in showing that the principle of descent is + adequate to explain the ascertained facts. + </p> + <p> + It does not, I think, detract from the merit of Darwin's conclusions that + the tendency of modern research has been to show that the effects of the + Glacial period were less simple, more localised and less general than he + perhaps supposed. He admitted that "equatorial refrigeration... must have + been small." ("More Letters", I. page 177.) It may prove possible to + dispense with it altogether. One cannot but regret that as he wrote to + Bates:—"the sketch in the 'Origin' gives a very meagre account of my + fuller MS. essay on this subject." (Loc. cit.) Wallace fully accepted "the + effect of the Glacial epoch in bringing about the present distribution of + Alpine and Arctic plants in the NORTHERN HEMISPHERE," but rejected "the + lowering of the temperature of the tropical regions during the Glacial + period" in order to account for their presence in the SOUTHERN hemisphere. + ("More Letters", II. page 25 (footnote 1).) The divergence however does + not lie very deep. Wallace attaches more importance to ordinary means of + transport. "If plants can pass in considerable numbers and variety over + wide seas and oceans, it must be yet more easy for them to traverse + continuous areas of land, wherever mountain-chains offer suitable + stations." ("Island Life" (2nd edition), London, 1895, page 512.) And he + argues that such periodical changes of climate, of which the Glacial + period may be taken as a type, would facilitate if not stimulate the + process. (Loc. cit. page 518.) + </p> + <p> + It is interesting to remark that Darwin drew from the facts of plant + distribution one of his most ingenious arguments in support of this + theory. (See "More Letters", I. page 424.) He tells us, "I was led to + anticipate that the species of the larger genera in each country would + oftener present varieties, than the species of the smaller genera." + ("Origin", page 44.) He argues "where, if we may use the expression, the + manufactory of species has been active, we ought generally to find the + manufactory still in action." (Ibid. page 45.) This proved to be the case. + But the labour imposed upon him in the study was immense. He tabulated + local floras "belting the whole northern hemisphere" ("More Letters", I. + page 107.), besides voluminous works such as De Candolle's "Prodromus". + The results scarcely fill a couple of pages. This is a good illustration + of the enormous pains which he took to base any statement on a secure + foundation of evidence, and for this the world, till the publication of + his letters, could not do him justice. He was a great admirer of Herbert + Spencer, whose "prodigality of original thought" astonished him. "But," he + says, "the reflection constantly recurred to me that each suggestion, to + be of real value to service, would require years of work." (Ibid. II. page + 235.) + </p> + <p> + At last the ground was cleared and we are led to the final conclusion. "If + the difficulties be not insuperable in admitting that in the long course + of time all the individuals of the same species belonging to the same + genus, have proceeded from some one source; then all the grand leading + facts of geographical distribution are explicable on the theory of + migration, together with subsequent modification and the multiplication of + new forms." ("Origin", page 360.) In this single sentence Darwin has + stated a theory which, as his son F. Darwin has said with justice, has + "revolutionized botanical geography." ("The Botanical Work of Darwin", + "Ann. Bot." 1899, page xi.) It explains how physical barriers separate and + form botanical regions; how allied species become concentrated in the same + areas; how, under similar physical conditions, plants may be essentially + dissimilar, showing that descent and not the surroundings is the + controlling factor; how insular floras have acquired their peculiarities; + in short how the most various and apparently uncorrelated problems fall + easily and inevitably into line. + </p> + <p> + The argument from plant distribution was in fact irresistible. A proof, if + one were wanted, was the immediate conversion of what Hooker called "the + stern keen intellect" ("More Letters", I. page 134.) of Bentham, by + general consent the leading botanical systematist at the time. It is a + striking historical fact that a paper of his own had been set down for + reading at the Linnean Society on the same day as Darwin's, but had to + give way. In this he advocated the fixity of species. He withdrew it after + hearing Darwin's. We can hardly realise now the momentous effect on the + scientific thought of the day of the announcement of the new theory. Years + afterwards (1882) Bentham, notwithstanding his habitual restraint, could + not write of it without emotion. "I was forced, however reluctantly, to + give up my long-cherished convictions, the results of much labour and + study." The revelation came without preparation. Darwin, he wrote, "never + made any communications to me in relation to his views and labours." But, + he adds, "I... fully adopted his theories and conclusions, notwithstanding + the severe pain and disappointment they at first occasioned me." ("Life + and Letters", II. page 294.) Scientific history can have few incidents + more worthy. I do not know what is most striking in the story, the pathos + or the moral dignity of Bentham's attitude. + </p> + <p> + Darwin necessarily restricted himself in the "Origin" to establishing the + general principles which would account for the facts of distribution, as a + part of his larger argument, without attempting to illustrate them in + particular cases. This he appears to have contemplated doing in a separate + work. But writing to Hooker in 1868 he said:—"I shall to the day of + my death keep up my full interest in Geographical Distribution, but I + doubt whether I shall ever have strength to come in any fuller detail than + in the "Origin" to this grand subject." ("More Letters", II. page 7.) This + must be always a matter for regret. But we may gather some indication of + his later speculations from the letters, the careful publication of which + by F. Darwin has rendered a service to science, the value of which it is + difficult to exaggerate. They admit us to the workshop, where we see a + great theory, as it were, in the making. The later ideas that they contain + were not it is true public property at the time. But they were + communicated to the leading biologists of the day and indirectly have had + a large influence. + </p> + <p> + If Darwin laid the foundation, the present fabric of Botanical Geography + must be credited to Hooker. It was a happy partnership. The far-seeing, + generalising power of the one was supplied with data and checked in + conclusions by the vast detailed knowledge of the other. It may be + permitted to quote Darwin's generous acknowledgment when writing the + "Origin":—"I never did pick any one's pocket, but whilst writing my + present chapter I keep on feeling (even when differing most from you) just + as if I were stealing from you, so much do I owe to your writings and + conversation, so much more than mere acknowledgements show." ("Life and + Letters", II. page 148 (footnote).) Fourteen years before he had written + to Hooker: "I know I shall live to see you the first authority in Europe + on... Geographical Distribution." (Ibid. I. page 336.) We owe it to Hooker + that no one now undertakes the flora of a country without indicating the + range of the species it contains. Bentham tells us: "After De Candolle, + independently of the great works of Darwin... the first important addition + to the science of geographical botany was that made by Hooker in his + "Introductory Essay to the Flora of Tasmania", which, though + contemporaneous only with the "Origin of Species", was drawn up with a + general knowledge of his friend's observations and views." (Pres. Addr. + (1869), "Proc. Linn. Soc." 1868-69, page lxxiv.) It cannot be doubted that + this and the great memoir on the "Distribution of Arctic Plants" were only + less epoch-making than the "Origin" itself, and must have supplied a + powerful support to the general theory of organic evolution. + </p> + <p> + Darwin always asserted his "entire ignorance of Botany." ("More Letters", + I. page 400.) But this was only part of his constant half-humorous + self-depreciation. He had been a pupil of Henslow, and it is evident that + he had a good working knowledge of systematic botany. He could find his + way about in the literature and always cites the names of plants with + scrupulous accuracy. It was because he felt the want of such a work for + his own researches that he urged the preparation of the "Index Kewensis", + and undertook to defray the expense. It has been thought singular that he + should have been elected a "correspondant" of the Academie des Sciences in + the section of Botany, but it is not surprising that his work in + Geographical Botany made the botanists anxious to claim him. His heart + went with them. "It has always pleased me," he tells us, "to exalt plants + in the scale of organised beings." ("Life and Letters", I. page 98.) And + he declares that he finds "any proposition more easily tested in botanical + works (Ibid. II. page 99.) than in zoological." + </p> + <p> + In the "Introductory Essay" Hooker dwelt on the "continuous current of + vegetation from Scandinavia to Tasmania" ("Introductory Essay to the Flora + of Tasmania", London, 1859. Reprinted from the "Botany of the Antarctic + Expedition", Part III., "Flora of Tasmania", Vol I. page ciii.), but finds + little evidence of one in the reverse direction. "In the New World, + Arctic, Scandinavian, and North American genera and species are + continuously extended from the north to the south temperate and even + Antarctic zones; but scarcely one Antarctic species, or even genus + advances north beyond the Gulf of Mexico" (page civ.). Hooker considered + that this negatived "the idea that the Southern and Northern Floras have + had common origin within comparatively modern geological epochs." (Loc. + cit.) This is no doubt a correct conclusion. But it is difficult to + explain on Darwin's view alone, of alternating cold in the two + hemispheres, the preponderant migration from the north to the south. He + suggests, therefore, that it "is due to the greater extent of land in the + north and to the northern forms... having... been advanced through natural + selection and competition to a higher stage of perfection or dominating + power." ("Origin of Species" (6th edition), page 340; cf. also "Life and + Letters", II. page 142.) The present state of the Flora of New Zealand + affords a striking illustration of the correctness of this view. It is + poor in species, numbering only some 1400, of which three-fourths are + endemic. They seem however quite unable to resist the invasion of new + comers and already 600 species of foreign origin have succeeded in + establishing themselves. + </p> + <p> + If we accept the general configuration of the earth's surface as permanent + a continuous and progressive dispersal of species from the centre to the + circumference, i.e. southwards, seems inevitable. If an observer were + placed above a point in St George's Channel from which one half of the + globe was visible he would see the greatest possible quantity of land + spread out in a sort of stellate figure. The maritime supremacy of the + English race has perhaps flowed from the central position of its home. + That such a disposition would facilitate a centrifugal migration of land + organisms is at any rate obvious, and fluctuating conditions of climate + operating from the pole would supply an effective means of propulsion. As + these became more rigorous animals at any rate would move southwards to + escape them. It would be equally the case with plants if no insuperable + obstacle interposed. This implies a mobility in plants, notwithstanding + what we know of means of transport which is at first sight paradoxical. + Bentham has stated this in a striking way: "Fixed and immovable as is the + individual plant, there is no class in which the race is endowed with + greater facilities for the widest dispersion... Plants cast away their + offspring in a dormant state, ready to be carried to any distance by those + external agencies which we may deem fortuitous, but without which many a + race might perish from the exhaustion of the limited spot of soil in which + it is rooted." (Pres. Addr.(1869), "Proc. Linn. Soc." 1868-69, pages lxvi, + lxvii.) + </p> + <p> + I have quoted this passage from Bentham because it emphasises a point + which Darwin for his purpose did not find it necessary to dwell upon, + though he no doubt assumed it. Dispersal to a distance is, so to speak, an + accidental incident in the life of a species. Lepidium Draba, a native of + South-eastern Europe, owes its prevalence in the Isle of Thanet to the + disastrous Walcheren expedition; the straw-stuffing of the mattresses of + the fever-stricken soldiers who were landed there was used by a farmer for + manure. Sir Joseph Hooker ("Royal Institution Lecture", April 12, 1878.) + tells us that landing on Lord Auckland's Island, which was uninhabited, + "the first evidence I met with of its having been previously visited by + man was the English chickweed; and this I traced to a mound that marked + the grave of a British sailor, and that was covered with the plant, + doubtless the offspring of seed that had adhered to the spade or mattock + with which the grave had been dug." + </p> + <p> + Some migration from the spot where the individuals of a species have + germinated is an essential provision against extinction. Their descendants + otherwise would be liable to suppression by more vigorous competitors. But + they would eventually be extinguished inevitably, as pointed out by + Bentham, by the exhaustion of at any rate some one necessary constituent + of the soil. Gilbert showed by actual analysis that the production of a + "fairy ring" is simply due to the using up by the fungi of the available + nitrogen in the enclosed area which continually enlarges as they seek a + fresh supply on the outside margin. Anyone who cultivates a garden can + easily verify the fact that every plant has some adaptation for varying + degrees of seed-dispersal. It cannot be doubted that slow but persistent + terrestrial migration has played an enormous part in bringing about + existing plant-distribution, or that climatic changes would intensify the + effect because they would force the abandonment of a former area and the + occupation of a new one. We are compelled to admit that as an incident of + the Glacial period a whole flora may have moved down and up a mountain + side, while only some of its constituent species would be able to take + advantage of means of long-distance transport. + </p> + <p> + I have dwelt on the importance of what I may call short-distance dispersal + as a necessary condition of plant life, because I think it suggests the + solution of a difficulty which leads Guppy to a conclusion with which I am + unable to agree. But the work which he has done taken as a whole appears + to me so admirable that I do so with the utmost respect. He points out, as + Bentham had already done, that long-distance dispersal is fortuitous. And + being so it cannot have been provided for by previous adaptation. He says + (Guppy, op. cit. II. page 99.): "It is not conceivable that an organism + can be adapted to conditions outside its environment." To this we must + agree; but, it may be asked, do the general means of plant dispersal + violate so obvious a principle? He proceeds: "The great variety of the + modes of dispersal of seeds is in itself an indication that the dispersing + agencies avail themselves in a hap-hazard fashion of characters and + capacities that have been developed in other connections." (Loc. cit. page + 102.) "Their utility in these respects is an accident in the plant's + life." (Loc. cit. page 100.) He attributes this utility to a "determining + agency," an influence which constantly reappears in various shapes in the + literature of Evolution and is ultra-scientific in the sense that it bars + the way to the search for material causes. He goes so far as to doubt + whether fleshy fruits are an adaptation for the dispersal of their + contained seeds. (Loc. cit. page 102.) Writing as I am from a hillside + which is covered by hawthorn bushes sown by birds, I confess I can feel + little doubt on the subject myself. The essential fact which Guppy brings + out is that long-distance unlike short-distance dispersal is not universal + and purposeful, but selective and in that sense accidental. But it is not + difficult to see how under favouring conditions one must merge into the + other. + </p> + <p> + Guppy has raised one novel point which can only be briefly referred to but + which is of extreme interest. There are grounds for thinking that flowers + and insects have mutually reacted upon one another in their evolution. + Guppy suggests that something of the same kind may be true of birds. I + must content myself with the quotation of a single sentence. "With the + secular drying of the globe and the consequent differentiation of climate + is to be connected the suspension to a great extent of the agency of birds + as plant dispersers in later ages, not only in the Pacific Islands but all + over the tropics. The changes of climate, birds and plants have gone on + together, the range of the bird being controlled by the climate, and the + distribution of the plant being largely dependent on the bird." (Loc.cit. + II. page 221.) + </p> + <p> + Darwin was clearly prepared to go further than Hooker in accounting for + the southern flora by dispersion from the north. Thus he says: "We must, I + suppose, admit that every yard of land has been successively covered with + a beech-forest between the Caucasus and Japan." ("More Letters", II. page + 9.) Hooker accounted for the dissevered condition of the southern flora by + geographical change, but this Darwin could not admit. He suggested to + Hooker that the Australian and Cape floras might have had a point of + connection through Abyssinia (Ibid. I. page 447.), an idea which was + promptly snuffed out. Similarly he remarked to Bentham (1869): "I suppose + you think that the Restiaceae, Proteaceae, etc., etc. once extended over + the whole world, leaving fragments in the south." (Ibid. I. page 380.) + Eventually he conjectured "that there must have been a Tertiary Antarctic + continent, from which various forms radiated to the southern extremities + of our present continents." ("Life and Letters", III. page 231.) But + characteristically he could not admit any land connections and trusted to + "floating ice for transporting seed." ("More Letters", I. page 116.) I am + far from saying that this theory is not deserving of serious attention, + though there seems to be no positive evidence to support it, and it + immediately raises the difficulty how did such a continent come to be + stocked? + </p> + <p> + We must, however, agree with Hooker that the common origin of the northern + and southern floras must be referred to a remote past. That Darwin had + this in his mind at the time of the publication of the "Origin" is clear + from a letter to Hooker. "The view which I should have looked at as + perhaps most probable (though it hardly differs from yours) is that the + whole world during the Secondary ages was inhabited by marsupials, + araucarias (Mem.—Fossil wood of this nature in South America), + Banksia, etc.; and that these were supplanted and exterminated in the + greater area of the north, but were left alive in the south." (Ibid. I. + page 453.) Remembering that Araucaria, unlike Banksia, belongs to the + earlier Jurassic not to the angiospermous flora, this view is a germinal + idea of the widest generality. + </p> + <p> + The extraordinary congestion in species of the peninsulas of the Old World + points to the long-continued action of a migration southwards. Each is in + fact a cul-de-sac into which they have poured and from which there is no + escape. On the other hand the high degree of specialisation in the + southern floras and the little power the species possess of holding their + own in competition or in adaptation to new conditions point to + long-continued isolation. "An island... will prevent free immigration and + competition, hence a greater number of ancient forms will survive." (Ibid. + I. page 481.) But variability is itself subject to variation. The nemesis + of a high degree of protected specialisation is the loss of adaptability. + (See Lyell, "The Geological Evidences of the Antiquity of Man", London, + 1863, page 446.) It is probable that many elements of the southern flora + are doomed: there is, for example, reason to think that the singular + Stapelieae of S. Africa are a disappearing group. The tree Lobelias which + linger in the mountains of Central Africa, in Tropical America and in the + Sandwich Islands have the aspect of extreme antiquity. I may add a further + striking illustration from Professor Seward: "The tall, graceful fronds of + Matonia pectinata, forming miniature forests on the slopes of Mount Ophir + and other districts in the Malay Peninsula in association with Dipteris + conjugata and Dipteris lobbiana, represent a phase of Mesozoic life which + survives 'Like a dim picture of the drowned past.'" ("Report of the 73rd + Meeting of the British Assoc." (Southport, 1903), London, 1904, page 844.) + </p> + <p> + The Matonineae are ferns with an unusually complex vascular system and + were abundant "in the northern hemisphere during the earlier part of the + Mesozoic era." + </p> + <p> + It was fortunate for science that Wallace took up the task which his + colleague had abandoned. Writing to him on the publication of his + "Geographical Distribution of Animals" Darwin said: "I feel sure that you + have laid a broad and safe foundation for all future work on Distribution. + How interesting it will be to see hereafter plants treated in strict + relation to your views." ("More Letters", II. page 12.) This hope was + fulfilled in "Island Life". I may quote a passage from it which admirably + summarises the contrast between the northern and the southern floras. + </p> + <p> + "Instead of the enormous northern area, in which highly organised and + dominant groups of plants have been developed gifted with great colonising + and aggressive powers, we have in the south three comparatively small and + detached areas, in which rich floras have been developed with SPECIAL + adaptations to soil, climate, and organic environment, but comparatively + impotent and inferior beyond their own domain." (Wallace, "Island Life", + pages 527, 528.) + </p> + <p> + It will be noticed that in the summary I have attempted to give of the + history of the subject, efforts have been concentrated on bringing into + relation the temperate floras of the northern and southern hemispheres, + but no account has been taken of the rich tropical vegetation which belts + the world and little to account for the original starting-point of + existing vegetation generally. It must be remembered on the one hand that + our detailed knowledge of the floras of the tropics is still very + incomplete and far inferior to that of temperate regions; on the other + hand palaeontological discoveries have put the problem in an entirely new + light. Well might Darwin, writing to Heer in 1875, say: "Many as have been + the wonderful discoveries in Geology during the last half-century, I think + none have exceeded in interest your results with respect to the plants + which formerly existed in the arctic regions." ("More Letters", II. page + 240.) + </p> + <p> + As early as 1848 Debey had described from the Upper Cretaceous rocks of + Aix-la-Chapelle Flowering plants of as high a degree of development as + those now existing. The fact was commented upon by Hooker ("Introd. Essay + to the Flora of Tasmania", page xx.), but its full significance seems to + have been scarcely appreciated. For it implied not merely that their + evolution must have taken place but the foundations of existing + distribution must have been laid in a preceding age. We now know from the + discoveries of the last fifty years that the remains of the Neocomian + flora occur over an area extending through 30 deg of latitude. The + conclusion is irresistible that within this was its centre of distribution + and probably of origin. + </p> + <p> + Darwin was immensely impressed with the outburst on the world of a fully + fledged angiospermous vegetation. He warmly approved the brilliant theory + of Saporta that this happened "as soon (as) flower-frequenting insects + were developed and favoured intercrossing." ("More Letters", II. page 21.) + Writing to him in 1877 he says: "Your idea that dicotyledonous plants were + not developed in force until sucking insects had been evolved seems to me + a splendid one. I am surprised that the idea never occurred to me, but + this is always the case when one first hears a new and simple explanation + of some mysterious phenomenon." ("Life and Letters", III. page 285. + Substantially the same idea had occurred earlier to F.W.A. Miquel. + Remarking that "sucking insects (Haustellata)... perform in nature the + important duty of maintaining the existence of the vegetable kingdom, at + least as far as the higher orders are concerned," he points our that "the + appearance in great numbers of haustellate insects occurs at and after the + Cretaceous epoch, when the plants with pollen and closed carpels + (Angiosperms) are found, and acquire little by little the preponderance in + the vegetable kingdom." "Archives Neerlandaises", III. (1868). English + translation in "Journ. of Bot." 1869, page 101.) + </p> + <p> + Even with this help the abruptness still remains an almost insoluble + problem, though a forecast of floral structure is now recognised in some + Jurassic and Lower Cretaceous plants. But the gap between this and the + structural complexity and diversity of angiosperms is enormous. Darwin + thought that the evolution might have been accomplished during a period of + prolonged isolation. Writing to Hooker (1881) he says: "Nothing is more + extraordinary in the history of the Vegetable Kingdom, as it seems to me, + than the APPARENTLY very sudden or abrupt development of the higher + plants. I have sometimes speculated whether there did not exist somewhere + during long ages an extremely isolated continent, perhaps near the South + Pole." ("Life and Letters", III. page 248.) + </p> + <p> + The present trend of evidence is, however, all in favour of a northern + origin for flowering plants, and we can only appeal to the imperfection of + the geological record as a last resource to extricate us from the + difficulty of tracing the process. But Darwin's instinct that at some time + or other the southern hemisphere had played an important part in the + evolution of the vegetable kingdom did not mislead him. Nothing probably + would have given him greater satisfaction than the masterly summary in + which Seward has brought together the evidence for the origin of the + Glossopteris flora in Gondwana land. + </p> + <p> + "A vast continental area, of which remnants are preserved in Australia, + South Africa and South America... A tract of enormous extent occupying an + area, part of which has since given place to a southern ocean, while + detached masses persist as portions of more modern continents, which have + enabled us to read in their fossil plants and ice-scratched boulders the + records of a lost continent, in which the Mesozoic vegetation of the + northern continent had its birth." ("Encycl. Brit." (10th edition 1902), + Vol. XXXI. ("Palaeobotany; Mesozoic"), page 422.) Darwin would probably + have demurred on physical grounds to the extent of the continent, and + preferred to account for the transoceanic distribution of its flora by the + same means which must have accomplished it on land. + </p> + <p> + It must in fairness be added that Guppy's later views give some support to + the conjectural existence of the "lost continent." "The distribution of + the genus Dammara" (Agathis) led him to modify his earlier conclusions. He + tells us:—"In my volume on the geology of Vanua Levu it was shown + that the Tertiary period was an age of submergence in the Western Pacific, + and a disbelief in any previous continental condition was expressed. My + later view is more in accordance with that of Wichmann, who, on geological + grounds, contended that the islands of the Western Pacific were in a + continental condition during the Palaeozoic and Mesozoic periods, and that + their submergence and subsequent emergence took place in Tertiary times." + (Guppy, op. cit. II. page 304.) + </p> + <p> + The weight of the geological evidence I am unable to scrutinise. But + though I must admit the possibility of some unconscious bias in my own + mind on the subject, I am impressed with the fact that the known + distribution of the Glossopteris flora in the southern hemisphere is + precisely paralleled by that of Proteaceae and Restiaceae in it at the + present time. It is not unreasonable to suppose that both phenomena, so + similar, may admit of the same explanation. I confess it would not + surprise me if fresh discoveries in the distribution of the Glossopteris + flora were to point to the possibility of its also having migrated + southwards from a centre of origin in the northern hemisphere. + </p> + <p> + Darwin, however, remained sceptical "about the travelling of plants from + the north EXCEPT DURING THE TERTIARY PERIOD." But he added, "such + speculations seem to me hardly scientific, seeing how little we know of + the old floras." ("Life and Letters", III. page 247.) That in later + geological times the south has been the grave of the weakened offspring of + the aggressive north can hardly be doubted. But if we look to the + Glossopteris flora for the ancestry of Angiosperms during the Secondary + period, Darwin's prevision might be justified, though he has given us no + clue as to how he arrived at it. + </p> + <p> + It may be true that technically Darwin was not a botanist. But in two + pages of the "Origin" he has given us a masterly explanation of "the + relationship, with very little identity, between the productions of North + America and Europe." (Pages 333, 334.) He showed that this could be + accounted for by their migration southwards from a common area, and he + told Wallace that he "doubted much whether the now called Palaearctic and + Neartic regions ought to be separated." ("Life and Letters", III. page + 230.) Catkin-bearing deciduous trees had long been seen to justify + Darwin's doubt: oaks, chestnuts, beeches, hazels, hornbeams, birches, + alders, willows and poplars are common both to the Old and New World. + Newton found that the separate regions could not be sustained for birds, + and he is now usually followed in uniting them as the Holartic. One feels + inclined to say in reading the two pages, as Lord Kelvin did to a + correspondent who asked for some further development of one of his papers, + It is all there. We have only to apply the principle to previous + geological ages to understand why the flora of the Southern United States + preserves a Cretaceous facies. Applying it still further we can understand + why, when the northern hemisphere gradually cooled through the Tertiary + period, the plants of the Eocene "suggest a comparison of the climate and + forests with those of the Malay Archipelago and Tropical America." + (Clement Reid, "Encycl. Brit." (10th edition), Vol. XXXI. ("Palaeobotany; + Tertiary"), page 435.) Writing to Asa Gray in 1856 with respect to the + United States flora, Darwin said that "nothing has surprised me more than + the greater generic and specific affinity with East Asia than with West + America." ("More Letters", I. page 434.) The recent discoveries of a Tulip + tree and a Sassafras in China afford fresh illustrations. A few years + later Asa Gray found the explanation in both areas being centres of + preservation of the Cretaceous flora from a common origin. It is + interesting to note that the paper in which this was enunciated at once + established his reputation. + </p> + <p> + In Europe the latitudinal range of the great mountain chains gave the + Miocene flora no chance of escape during the Glacial period, and the + Mediterranean appears to have equally intercepted the flow of alpine + plants to the Atlas. (John Ball in Appendix G, page 438, in "Journal of a + Tour in Morocco and the Great Atlas", J.D. Hooker and J. Ball, London, + 1878.) In Southern Europe the myrtle, the laurel, the fig and the + dwarf-palm are the sole representatives of as many great tropical + families. Another great tropical family, the Gesneraceae has left single + representatives from the Pyrenees to the Balkans; and in the former a + diminutive yam still lingers. These are only illustrations of the evidence + which constantly accumulates and which finds no rational explanation + except that which Darwin has given to it. + </p> + <p> + The theory of southward migration is the key to the interpretation of the + geographical distribution of plants. It derived enormous support from the + researches of Heer and has now become an accepted commonplace. Saporta in + 1888 described the vegetable kingdom as "emigrant pour suivre une + direction determinee et marcher du nord au sud, a la recherche de regions + et de stations plus favorables, mieux appropriees aux adaptations + acquises, a meme que la temperature terrestre perd ses conditions + premieres." ("Origine Paleontologique des arbres", Paris, 1888, page 28.) + If, as is so often the case, the theory now seems to be a priori + inevitable, the historian of science will not omit to record that the + first germ sprang from the brain of Darwin. + </p> + <p> + In attempting this sketch of Darwin's influence on Geographical + Distribution, I have found it impossible to treat it from an external + point of view. His interest in it was unflagging; all I could say became + necessarily a record of that interest and could not be detached from it. + He was in more or less intimate touch with everyone who was working at it. + In reading the letters we move amongst great names. With an extraordinary + charm of persuasive correspondence he was constantly suggesting, + criticising and stimulating. It is hardly an exaggeration to say that from + the quiet of his study at Down he was founding and directing a wide-world + school. + </p> + <p> + POSTSCRIPTUM. + </p> + <p> + Since this essay was put in type Dr Ernst's striking account of the "New + Flora of the Volcanic Island of Krakatau" (Cambridge, 1909.) has reached + me. All botanists must feel a debt of gratitude to Prof. Seward for his + admirable translation of a memoir which in its original form is + practically unprocurable and to the liberality of the Cambridge University + Press for its publication. In the preceding pages I have traced the + laborious research by which the methods of Plant Dispersal were + established by Darwin. In the island of Krakatau nature has supplied a + crucial experiment which, if it had occurred earlier, would have at once + secured conviction of their efficiency. A quarter of a century ago every + trace of organic life in the island was "destroyed and buried under a + thick covering of glowing stones." Now, it is "again covered with a mantle + of green, the growth being in places so luxuriant that it is necessary to + cut one's way laboriously through the vegetation." (Op. cit. page 4.) + Ernst traces minutely how this has been brought about by the combined + action of wind, birds and sea currents, as means of transport. The process + will continue, and he concludes:—"At last after a long interval the + vegetation on the desolated island will again acquire that wealth of + variety and luxuriance which we see in the fullest development which + Nature has reached in the primaeval forest in the tropics." (Op. cit. page + 72.) The possibility of such a result revealed itself to the insight of + Darwin with little encouragement or support from contemporary opinion. + </p> + <p> + One of the most remarkable facts established by Ernst is that this has not + been accomplished by the transport of seeds alone. "Tree stems and + branches played an important part in the colonisation of Krakatau by + plants and animals. Large piles of floating trees, stems, branches and + bamboos are met with everywhere on the beach above high-water mark and + often carried a considerable distance inland. Some of the animals on the + island, such as the fat Iguana (Varanus salvator) which suns itself in the + beds of streams, may have travelled on floating wood, possibly also the + ancestors of the numerous ants, but certainly plants." (Op. cit. page 56.) + Darwin actually had a prevision of this. Writing to Hooker he says:—"Would + it not be a prodigy if an unstocked island did not in the course of ages + receive colonists from coasts whence the currents flow, trees are drifted + and birds are driven by gales?" ("More Letters", I. page 483.) And ten + years earlier:—"I must believe in the... whole plant or branch being + washed into the sea; with floods and slips and earthquakes; this must + continually be happening." ("Life and Letters", II. pages 56, 57.) If we + give to "continually" a cosmic measure, can the fact be doubted? All this, + in the light of our present knowledge, is too obvious to us to admit of + discussion. But it seems to me nothing less than pathetic to see how in + the teeth of the obsession as to continental extension, Darwin fought + single-handed for what we now know to be the truth. + </p> + <p> + Guppy's heart failed him when he had to deal with the isolated case of + Agathis which alone seemed inexplicable by known means of transport. But + when we remember that it is a relic of the pre-Angiospermous flora, and is + of Araucarian ancestry, it cannot be said that the impossibility, in so + prolonged a history, of the bodily transference of cone-bearing branches + or even of trees, compels us as a last resort to fall back on continental + extension to account for its existing distribution. + </p> + <p> + When Darwin was in the Galapagos Archipelago, he tells us that he fancied + himself "brought near to the very act of creation." He saw how new species + might arise from a common stock. Krakatau shows us an earlier stage and + how by simple agencies, continually at work, that stock might be supplied. + It also shows us how the mixed and casual elements of a new colony enter + into competition for the ground and become mutually adjusted. The study of + Plant Distribution from a Darwinian standpoint has opened up a new field + of research in Ecology. The means of transport supply the materials for a + flora, but their ultimate fate depends on their equipment for the + "struggle for existence." The whole subject can no longer be regarded as a + mere statistical inquiry which has seemed doubtless to many of somewhat + arid interest. The fate of every element of the earth's vegetation has + sooner or later depended on its ability to travel and to hold its own + under new conditions. And the means by which it has secured success is an + each case a biological problem which demands and will reward the most + attentive study. This is the lesson which Darwin has bequeathed to us. It + is summed up in the concluding paragraph of the "Origin" ("Origin of + Species" (6th edition), page 429.):—"It is interesting to + contemplate a tangled bank, clothed with many plants of many kinds, with + birds singing on the bushes, with various insects flitting about, and with + worms crawling through the damp earth, and to reflect that these + elaborately constructed forms, so different from each other, and dependent + upon each other in so complex a manner, have all been produced by laws + acting around us." + </p> + <p> + <a name="link2H_4_0019" id="link2H_4_0019"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + XVII. GEOGRAPHICAL DISTRIBUTION OF ANIMALS. By Hans Gadow, M.A., Ph.D., + F.R.S. + </h2> + <h3> + Strickland Curator and Lecturer on Zoology in the University of Cambridge. + </h3> + <p> + The first general ideas about geographical distribution may be found in + some of the brilliant speculations contained in Buffon's "Histoire + Naturelle". The first special treatise on the subject was however written + in 1777 by E.A.W. Zimmermann, Professor of Natural Science at Brunswick, + whose large volume, "Specimen Zoologiae Geographicae Quadrupedum"..., + deals in a statistical way with the mammals; important features of the + large accompanying map of the world are the ranges of mountains and the + names of hundreds of genera indicating their geographical range. In a + second work he laid special stress on domesticated animals with reference + to the spreading of the various races of Mankind. + </p> + <p> + In the following year appeared the "Philosophia Entomologica" by J.C. + Fabricius, who was the first to divide the world into eight regions. In + 1803 G.R. Treviranus ("Biologie oder Philosophie der lebenden Natur", Vol. + II. Gottingen, 1803.) devoted a long chapter of his great work on + "Biologie" to a philosophical and coherent treatment of the distribution + of the whole animal kingdom. Remarkable progress was made in 1810 by F. + Tiedemann ("Anatomie und Naturgeschichte der Vogel". Heidelberg, 1810.) of + Heidelberg. Few, if any, of the many subsequent Ornithologists seem to + have appreciated, or known of, the ingenious way in which Tiedemann + marshalled his statistics in order to arrive at general conclusions. There + are, for instance, long lists of birds arranged in accordance with their + occurrence in one or more continents: by correlating the distribution of + the birds with their food he concludes "that the countries of the East + Indian flora have no vegetable feeders in common with America," and "that + it is probably due to the great peculiarity of the African flora that + Africa has few phytophagous kinds in common with other countries, whilst + zoophagous birds have a far more independent, often cosmopolitan, + distribution." There are also remarkable chapters on the influence of + environment, distribution, and migration, upon the structure of the Birds! + In short, this anatomist dealt with some of the fundamental causes of + distribution. + </p> + <p> + Whilst Tiedemann restricted himself to Birds, A. Desmoulins in 1822 wrote + a short but most suggestive paper on the Vertebrata, omitting the birds; + he combated the view recently proposed by the entomologist Latreille that + temperature was the main factor in distribution. Some of his ten main + conclusions show a peculiar mixture of evolutionary ideas coupled with the + conception of the stability of species: whilst each species must have + started from but one creative centre, there may be several "analogous + centres of creation" so far as genera and families are concerned. + Countries with different faunas, but lying within the same climatic zones, + are proof of the effective and permanent existence of barriers preventing + an exchange between the original creative centres. + </p> + <p> + The first book dealing with the "geography and classification" of the + whole animal kingdom was written by W. Swainson ("A Treatise on the + Geography and Classification of Animals", Lardner's "Cabinet Cyclopaedia" + London, 1835.) in 1835. He saw in the five races of Man the clue to the + mapping of the world into as many "true zoological divisions," and he + reconciled the five continents with his mystical quinary circles. + </p> + <p> + Lyell's "Principles of Geology" should have marked a new epoch, since in + his "Elements" he treats of the past history of the globe and the + distribution of animals in time, and in his "Principles" of their + distribution in space in connection with the actual changes undergone by + the surface of the world. But as the sub-title of his great work "Modern + changes of the Earth and its inhabitants" indicates, he restricted himself + to comparatively minor changes, and, emphatically believing in the + permanency of the great oceans, his numerous and careful interpretations + of the effect of the geological changes upon the dispersal of animals did + after all advance the problem but little. + </p> + <p> + Hitherto the marine faunas had been neglected. This was remedied by E. + Forbes, who established nine homozoic zones, based mainly on the study of + the mollusca, the determining factors being to a great extent the + isotherms of the sea, whilst the 25 provinces were given by the + configuration of the land. He was followed by J.D. Dana, who, taking + principally the Crustacea as a basis, and as leading factors the mean + temperatures of the coldest and of the warmest months, established five + latitudinal zones. By using these as divisors into an American, + Afro-European, Oriental, Arctic and Antarctic realm, most of which were + limited by an eastern and western land-boundary, he arrived at about + threescore provinces. + </p> + <p> + In 1853 appeared L.K. Schmarda's ("Die geographische Verbreitung der + Thiere", Wien, 1853.) two volumes, embracing the whole subject. Various + centres of creation being, according to him, still traceable, he formed + the hypothesis that these centres were originally islands, which later + became enlarged and joined together to form the great continents, so that + the original faunas could overlap and mix whilst still remaining pure at + their respective centres. After devoting many chapters to the possible + physical causes and modes of dispersal, he divided the land into 21 realms + which he shortly characterises, e.g. Australia as the only country + inhabited by marsupials, monotremes and meliphagous birds. Ten main marine + divisions were diagnosed in a similar way. Although some of these realms + were not badly selected from the point of view of being applicable to more + than one class of animals, they were obviously too numerous for general + purposes, and this drawback was overcome, in 1857, by P.L. Sclater. ("On + the general Geographical Distribution of the members of the class Aves", + "Proc. Linn. Soc." (Zoology II. 1858, pages 130-145.)) Starting with the + idea, that "each species must have been created within and over the + geographical area, which it now occupies," he concluded "that the most + natural primary ontological divisions of the Earth's surface" were those + six regions, which since their adoption by Wallace in his epoch-making + work, have become classical. Broadly speaking, these six regions are + equivalent to the great masses of land; they are convenient terms for + geographical facts, especially since the Palaearctic region expresses the + unity of Europe with the bulk of Asia. Sclater further brigaded the + regions of the Old World as Palaeogaea and the two Americas as Neogaea, a + fundamental mistake, justifiable to a certain extent only since he based + his regions mainly upon the present distribution of the Passerine birds. + </p> + <p> + Unfortunately these six regions are not of equal value. The Indian + countries and the Ethiopian region (Africa south of the Sahara) are + obviously nothing but the tropical, southern continuations or appendages + of one greater complex. Further, the great eastern mass of land is so + intimately connected with North America that this continent has much more + in common with Europe and Asia than with South America. Therefore, instead + of dividing the world longitudinally as Sclater had done, Huxley, in 1868 + ("On the classification and distribution of the Alectoromorphae and + Heteromorphae", "Proc. Zool. Soc." 1868, page 294.), gave weighty reasons + for dividing it transversely. Accordingly he established two primary + divisions, Arctogaea or the North world in a wider sense, comprising + Sclater's Indian, African, Palaearctic and Neartic regions; and Notogaea, + the Southern world, which he divided into (1) Austro-Columbia (an + unfortunate substitute for the neotropical region), (2) Australasia, and + (3) New Zealand, the number of big regions thus being reduced to three but + for the separation of New Zealand upon rather negative characters. Sclater + was the first to accept these four great regions and showed, in 1874 ("The + geographical distribution of Mammals", "Manchester Science Lectures", + 1874.), that they were well borne out by the present distribution of the + Mammals. + </p> + <p> + Although applicable to various other groups of animals, for instance to + the tailless Amphibia and to Birds (Huxley himself had been led to found + his two fundamental divisions on the distribution of the Gallinaceous + birds), the combination of South America with Australia was gradually + found to be too sweeping a measure. The obvious and satisfactory solution + was provided by W.T. Blanford (Anniversary address (Geological Society, + 1889), "Proc. Geol. Soc." 1889-90, page 67; "Quart. Journ." XLVI 1890.), + who in 1890 recognised three main divisions, namely Australian, South + American, and the rest, for which the already existing terms (although + used partly in a new sense, as proposed by an anonymous writer in "Natural + Science", III. page 289) "Notogaea," "Neogaea" and "Arctogaea" have been + gladly accepted by a number of English writers. + </p> + <p> + After this historical survey of the search for larger and largest or + fundamental centres of animal creation, which resulted in the mapping of + the world into zoological regions and realms of after all doubtful value, + we have to return to the year 1858. The eleventh and twelfth chapters of + "The Origin of Species" (1859), dealing with "Geographical Distribution," + are based upon a great amount of observation, experiment and reading. As + Darwin's main problem was the origin of species, nature's way of making + species by gradual changes from others previously existing, he had to + dispose of the view, held universally, of the independent creation of each + species and at the same time to insist upon a single centre of creation + for each species; and in order to emphasise his main point, the theory of + descent, he had to disallow convergent, or as they were then called, + analogous forms. To appreciate the difficulty of his position we have to + take the standpoint of fifty years ago, when the immutability of the + species was an axiom and each was supposed to have been created within or + over the geographical area which it now occupies. If he once admitted that + a species could arise from many individuals instead of from one pair, + there was no way of shutting the door against the possibility that these + individuals may have been so numerous that they occupied a very large + district, even so large that it had become as discontinuous as the + distribution of many a species actually is. Such a concession would at + once be taken as an admission of multiple, independent, origin instead of + descent in Darwin's sense. + </p> + <p> + For the so-called multiple, independently repeated creation of species as + an explanation of their very wide and often quite discontinuous + distribution, he substituted colonisation from the nearest and readiest + source together with subsequent modification and better adaptation to + their new home. + </p> + <p> + He was the first seriously to call attention to the many accidental means, + "which more properly should be called occasional means of distribution," + especially to oceanic islands. His specific, even individual, centres of + creation made migrations all the more necessary, but their extent was + sadly baulked by the prevailing dogma of the permanency of the oceans. Any + number of small changes ("many islands having existed as halting places, + of which not a wreck now remains" ("The Origin of Species" (1st edition), + page 396.).) were conceded freely, but few, if any, great enough to permit + migration of truly terrestrial creatures. The only means of getting across + the gaps was by the principle of the "flotsam and jetsam," a theory which + Darwin took over from Lyell and further elaborated so as to make it + applicable to many kinds of plants and animals, but sadly deficient, often + grotesque, in the case of most terrestrial creatures. + </p> + <p> + Another very fertile source was Darwin's strong insistence upon the great + influence which the last glacial epoch must have had upon the distribution + of animals and plants. Why was the migration of northern creatures + southwards of far-reaching and most significant importance? More + northerners have established themselves in southern lands than vice versa, + because there is such a great mass of land in the north and greater + continents imply greater intensity of selection. "The productions of real + islands have everywhere largely yielded to continental forms." (Ibid. page + 380.)... "The Alpine forms have almost everywhere largely yielded to the + more dominant forms generated in the larger areas and more efficient + workshops of the North." + </p> + <p> + Let us now pass in rapid survey the influence of the publication of "The + Origin of Species" upon the study of Geographical Distribution in its + wider sense. + </p> + <p> + Hitherto the following thought ran through the minds of most writers: + Wherever we examine two or more widely separated countries their + respective faunas are very different, but where two faunas can come into + contact with each other, they intermingle. Consequently these faunas + represent centres of creation, whence the component creatures have spread + peripherally so far as existing boundaries allowed them to do so. This is + of course the fundamental idea of "regions." There is not one of the + numerous writers who considered the possibility that these intermediate + belts might represent not a mixture of species but transitional forms, the + result of changes undergone by the most peripheral migrants in adaptation + to their new surroundings. The usual standpoint was also that of Pucheran + ("Note sur l'equateur zoologique", "Rev. et Mag. de Zoologie", 1855; also + several other papers, ibid. 1865, 1866, and 1867.) in 1855. But what a + change within the next ten years! Pucheran explains the agreement in + coloration between the desert and its fauna as "une harmonie + post-etablie"; the Sahara, formerly a marine basin, was peopled by + immigrants from the neighbouring countries, and these new animals adapted + themselves to the new environment. He also discusses, among other similar + questions, the Isthmus of Panama with regard to its having once been a + strait. From the same author may be quoted the following passage as a + strong proof of the new influence: "By the radiation of the + contemporaneous faunas, each from one centre, whence as the various parts + of the world successively were formed and became habitable, they spread + and became modified according to the local physical conditions." + </p> + <p> + The "multiple" origin of each species as advocated by Sclater and Murray, + although giving the species a broader basis, suffered from the same + difficulties. There was only one alternative to the old orthodox view of + independent creation, namely the bold acceptance of land-connections to an + extent for which geological and palaeontological science was not yet ripe. + Those who shrank from either view, gave up the problem as mysterious and + beyond the human intellect. This was the expressed opinion of men like + Swainson, Lyell and Humboldt. Only Darwin had the courage to say that the + problem was not insoluble. If we admit "that in the long course of time + the individuals of the same species, and likewise of allied species, have + proceeded from some one source; then I think all the grand leading facts + of geographical distribution are explicable on the theory of migration... + together with subsequent modification and the multiplication of new + forms." We can thus understand how it is that in some countries the + inhabitants "are linked to the extinct beings which formerly inhabited the + same continent." We can see why two areas, having nearly the same physical + conditions, should often be inhabited by very different forms of life,... + and "we can see why in two areas, however distant from each other, there + should be a correlation, in the presence of identical species... and of + distinct but representative species." ("The Origin of Species" (1st + edition), pages 408, 409.) + </p> + <p> + Darwin's reluctance to assume great geological changes, such as a + land-connection of Europe with North America, is easily explained by the + fact that he restricted himself to the distribution of the present and + comparatively recent species. "I do not believe that it will ever be + proved that within the recent period continents which are now quite + separate, have been continuously, or almost continuously, united with each + other, and with the many existing oceanic islands." (Ibid. page 357.) + Again, "believing... that our continents have long remained in nearly the + same relative position, though subjected to large, but partial + oscillations of level," that means to say within the period of existing + species, or "within the recent period." (Ibid. page. 370.) The difficulty + was to a great extent one of his own making. Whilst almost everybody else + believed in the immutability of the species, which implies an enormous + age, logically since the dawn of creation, to him the actually existing + species as the latest results of evolution, were necessarily something + very new, so young that only the very latest of the geological epochs + could have affected them. It has since come to our knowledge that a great + number of terrestrial "recent" species, even those of the higher classes + of Vertebrates, date much farther back than had been thought possible. + Many of them reach well into the Miocene, a time since which the world + seems to have assumed the main outlines of the present continents. + </p> + <p> + In the year 1866 appeared A. Murray's work on the "Geographical + Distribution of Mammals", a book which has perhaps received less + recognition than it deserves. His treatment of the general introductory + questions marks a considerable advance of our problem, although, and + partly because, he did not entirely agree with Darwin's views as laid down + in the first edition of "The Origin of Species", which after all was the + great impulse given to Murray's work. Like Forbes he did not shrink from + assuming enormous changes in the configuration of the continents and + oceans because the theory of descent, with its necessary postulate of + great migrations, required them. He stated, for instance, "that a Miocene + Atlantis sufficiently explains the common distribution of animals and + plants in Europe and America up to the glacial epoch." And next he + considers how, and by what changes, the rehabilitation and distribution of + these lands themselves were effected subsequent to that period. Further, + he deserves credit for having cleared up a misunderstanding of the idea of + specific centres of creation. Whilst for instance Schmarda assumed without + hesitation that the same species, if occurring at places separated by + great distances, or apparently insurmountable barriers, had been there + created independently (multiple centres), Lyell and Darwin held that each + species had only one single centre, and with this view most of us agree, + but their starting point was to them represented by one individual, or + rather one single pair. According to Murray, on the other hand, this + centre of a species is formed by all the individuals of a species, all of + which equally undergo those changes which new conditions may impose upon + them. In this respect a new species has a multiple origin, but this in a + sense very different from that which was upheld by L. Agassiz. As Murray + himself puts it: "To my multiple origin, communication and direct + derivation is essential. The species is compounded of many influences + brought together through many individuals, and distilled by Nature into + one species; and, being once established it may roam and spread wherever + it finds the conditions of life not materially different from those of its + original centre." (Murray, "The Geographical Distribution of Mammals", + page 14. London, 1866.) This declaration fairly agrees with more modern + views, and it must be borne in mind that the application of the + single-centre principle to the genera, families and larger groups in the + search for descent inevitably leads to one creative centre for the whole + animal kingdom, a condition as unwarrantable as the myth of Adam and Eve + being the first representatives of Mankind. + </p> + <p> + It looks as if it had required almost ten years for "The Origin of + Species" to show its full effect, since the year 1868 marks the + publication of Haeckel's "Naturliche Schoepfungsgeschichte" in addition to + other great works. The terms "Oecology" (the relation of organisms to + their environment) and "Chorology" (their distribution in space) had been + given us in his "Generelle Morphologie" in 1866. The fourteenth chapter of + the "History of Creation" is devoted to the distribution of organisms, + their chorology, with the emphatic assertion that "not until Darwin can + chorology be spoken of as a separate science, since he supplied the acting + causes for the elucidation of the hitherto accumulated mass of facts." A + map (a "hypothetical sketch") shows the monophyletic origin and the routes + of distribution of Man. + </p> + <p> + Natural Selection may be all-mighty, all-sufficient, but it requires time, + so much that the countless aeons required for the evolution of the present + fauna were soon felt to be one of the most serious drawbacks of the + theory. Therefore every help to ease and shorten this process should have + been welcomed. In 1868 M. Wagner (The first to formulate clearly the + fundamental idea of a theory of migration and its importance in the origin + of new species was L. von Buch, who in his "Physikalische Beschreibung der + Canarischen Inseln", written in 1825, wrote as follows: "Upon the + continents the individuals of the genera by spreading far, form, through + differences of the locality, food and soil, varieties which finally become + constant as new species, since owing to the distances they could never be + crossed with other varieties and thus be brought back to the main type. + Next they may again, perhaps upon different roads, return to the old home + where they find the old type likewise changed, both having become so + different that they can interbreed no longer. Not so upon islands, where + the individuals shut up in narrow valleys or within narrow districts, can + always meet one another and thereby destroy every new attempt towards the + fixing of a new variety." Clearly von Buch explains here why island types + remain fixed, and why these types themselves have become so different from + their continental congeners.—Actually von Buch is aware of a most + important point, the difference in the process of development which exists + between a new species b, which is the result of an ancestral species a + having itself changed into b and thereby vanished itself, and a new + species c which arose through separation out of the same ancestral a, + which itself persists as such unaltered. Von Buch's prophetic view seems + to have escaped Lyell's and even Wagner's notice.) came to the rescue with + his "Darwin'sche Theorie und das Migrations-Gesetz der Organismen". + (Leipzig, 1868.) He shows that migration, i.e. change of locality, implies + new environmental conditions (never mind whether these be new stimuli to + variation, or only acting as their selectors or censors), and moreover + secures separation from the original stock and thus eliminates or lessens + the reactionary dangers of panmixia. Darwin accepted Wagner's theory as + "advantageous." Through the heated polemics of the more ardent + selectionists Wagner's theory came to grow into an alternative instead of + a help to the theory of selectional evolution. Separation is now rightly + considered a most important factor by modern students of geographical + distribution. + </p> + <p> + For the same year, 1868, we have to mention Huxley, whose Arctogaea and + Notogaea are nothing less than the reconstructed main masses of land of + the Mesozoic period. Beyond doubt the configuration of land at that remote + period has left recognisable traces in the present continents, but whether + they can account for the distribution of such a much later group as the + Gallinaceous birds is more than questionable. In any case he took for his + text a large natural group of birds, cosmopolitan as a whole, but with a + striking distribution. The Peristeropodes, or pigeon-footed division, are + restricted to the Australian and Neotropical regions, in distinction to + the Alectoropodes (with the hallux inserted at a level above the front + toes) which inhabit the whole of the Arctogaea, only a few members having + spread into the South World. Further, as Asia alone has its Pheasants and + allies, so is Africa characterised by its Guinea-fowls and relations, + America has the Turkey as an endemic genus, and the Grouse tribe in a + wider sense has its centre in the holarctic region: a splendid object + lesson of descent, world-wide spreading and subsequent differentiation. + Huxley, by the way, was the first—at least in private talk—to + state that it will be for the morphologist, the well-trained anatomist, to + give the casting vote in questions of geographical distribution, since he + alone can determine whether we have to deal with homologous, or analogous, + convergent, representative forms. + </p> + <p> + It seems late to introduce Wallace's name in 1876, the year of the + publication of his standard work. ("The Geographical Distribution of + Animals", 2 vols. London, 1876.) We cannot do better than quote the + author's own words, expressing the hope that his "book should bear a + similar relation to the eleventh and twelfth chapters of the "Origin of + Species" as Darwin's "Animals and Plants under Domestication" does to the + first chapter of that work," and to add that he has amply succeeded. + Pleading for a few primary centres he accepts Sclater's six regions and + does not follow Huxley's courageous changes which Sclater himself had + accepted in 1874. Holding the view of the permanence of the oceans he + accounts for the colonisation of outlying islands by further elaborating + the views of Lyell and Darwin, especially in his fascinating "Island + Life", with remarkable chapters on the Ice Age, Climate and Time and other + fundamental factors. His method of arriving at the degree of relationship + of the faunas of the various regions is eminently statistical. Long lists + of genera determine by their numbers the affinity and hence the source of + colonisation. In order to make sure of his material he performed the + laborious task of evolving a new classification of the host of Passerine + birds. This statistical method has been followed by many authors, who, + relying more upon quantity than quality, have obscured the fact that the + key to the present distribution lies in the past changes of the earth's + surface. However, with Wallace begins the modern study of the geographical + distribution of animals and the sudden interest taken in this subject by + an ever widening circle of enthusiasts far beyond the professional + brotherhood. + </p> + <p> + A considerable literature has since grown up, almost bewildering in its + range, diversity of aims and style of procedure. It is a chaos, with many + paths leading into the maze, but as yet very few take us to a position + commanding a view of the whole intricate terrain with its impenetrable + tangle and pitfalls. + </p> + <p> + One line of research, not initiated but greatly influenced by Wallace's + works, became so prominent as to almost constitute a period which may be + characterised as that of the search by specialists for either the + justification or the amending of his regions. As class after class of + animals was brought up to reveal the secret of the true regions, some + authors saw in their different results nothing but the faultiness of + previously established regions; others looked upon eventual agreements as + their final corroboration, especially when for instance such diverse + groups as mammals and scorpions could, with some ingenuity, be made to + harmonise. But the obvious result of all these efforts was the growing + knowledge that almost every class seemed to follow principles of its own. + The regions tallied neither in extent nor in numbers, although most of + them gravitated more and more towards three centres, namely Australia, + South America and the rest of the world. Still zoologists persisted in the + search, and the various modes and capabilities of dispersal of the + respective groups were thought sufficient explanation of the divergent + results in trying to bring the mapping of the world under one scheme. + </p> + <p> + Contemporary literature is full of devices for the mechanical dispersal of + animals. Marine currents, warm and cold, were favoured all the more since + they showed the probable original homes of the creatures in question. If + these could not stand sea-water, they floated upon logs or icebergs, or + they were blown across by storms; fishes were lifted over barriers by + waterspouts, and there is on record even an hypothetical land tortoise, + full of eggs, which colonised an oceanic island after a perilous sea + voyage upon a tree trunk. Accidents will happen, and beyond doubt many + freaks of discontinuous distribution have to be accounted for by some such + means. But whilst sufficient for the scanty settlers of true oceanic + islands, they cannot be held seriously to account for the rich fauna of a + large continent, over which palaeontology shows us that the immigrants + have passed like waves. It should also be borne in mind that there is a + great difference between flotsam and jetsam. A current is an extension of + the same medium and the animals in it may suffer no change during even a + long voyage, since they may be brought from one litoral to another where + they will still be in the same or but slightly altered environment. But + the jetsam is in the position of a passenger who has been carried off by + the wrong train. Almost every year some American land birds arrive at our + western coasts and none of them have gained a permanent footing although + such visits must have taken place since prehistoric times. It was + therefore argued that only those groups of animals should be used for + locating and defining regions which were absolutely bound to the soil. + This method likewise gave results not reconcilable with each other, even + when the distribution of fossils was taken into account, but it pointed to + the absolute necessity of searching for former land-connections regardless + of their extent and the present depths to which they may have sunk. + </p> + <p> + That the key to the present distribution lies in the past had been felt + long ago, but at last it was appreciated that the various classes of + animals and plants have appeared in successive geological epochs and also + at many places remote from each other. The key to the distribution of any + group lies in the configuration of land and water of that epoch in which + it made its first appearance. Although this sounds like a platitude, it + has frequently been ignored. If, for argument's sake, Amphibia were + evolved somewhere upon the great southern land-mass of Carboniferous times + (supposed by some to have stretched from South America across Africa to + Australia), the distribution of this developing class must have proceeded + upon lines altogether different from that of the mammals which dated + perhaps from lower Triassic times, when the old south continental belt was + already broken up. The broad lines of this distribution could never + coincide with that of the other, older class, no matter whether the + original mammalian centre was in the Afro-Indian, Australian, or Brazilian + portion. If all the various groups of animals had come into existence at + the same time and at the same place, then it would be possible, with + sufficient geological data, to construct a map showing the generalised + results applicable to the whole animal kingdom. But the premises are + wrong. Whatever regions we may seek to establish applicable to all + classes, we are necessarily mixing up several principles, namely + geological, historical, i.e. evolutionary, with present day statistical + facts. We might as well attempt one compound picture representing a + chick's growth into an adult bird and a child's growth into manhood. + </p> + <p> + In short there are no general regions, not even for each class separately, + unless this class be one which is confined to a comparatively short + geological period. Most of the great classes have far too long a history + and have evolved many successive main groups. Let us take the mammals. + Marsupials live now in Australia and in both Americas, because they + already existed in Mesozoic times; Ungulata existed at one time or other + all over the world except in Australia, because they are post-Cretaceous; + Insectivores, although as old as any Placentalia, are cosmopolitan + excepting South America and Australia; Stags and Bears, as examples of + comparatively recent Arctogaeans, are found everywhere with the exception + of Ethiopia and Australia. Each of these groups teaches a valuable + historical lesson, but when these are combined into the establishment of a + few mammalian "realms," they mean nothing but statistical majorities. If + there is one at all, Australia is such a realm backed against the rest of + the world, but as certainly it is not a mammalian creative centre! + </p> + <p> + Well then, if the idea of generally applicable regions is a mare's nest, + as was the search for the Holy Grail, what is the object of the study of + geographical distribution? It is nothing less than the history of the + evolution of life in space and time in the widest sense. The attempt to + account for the present distribution of any group of organisms involves + the aid of every branch of science. It bids fair to become a history of + the world. It started in a mild, statistical way, restricting itself to + the present fauna and flora and to the present configuration of land and + water. Next came Oceanography concerned with the depths of the seas, their + currents and temperatures; then enquiries into climatic changes, + culminating in irreconcilable astronomical hypotheses as to glacial + epochs; theories about changes of the level of the seas, mainly from the + point of view of the physicist and astronomer. Then came more and more to + the front the importance of the geological record, hand in hand with the + palaeontological data and the search for the natural affinities, the + genetic system of the organisms. Now and then it almost seems as if the + biologists had done their share by supplying the problems and that the + physicists and geologists would settle them, but in reality it is not so. + The biologists not only set the problems, they alone can check the offered + solutions. The mere fact of palms having flourished in Miocene Spitzbergen + led to an hypothetical shifting of the axis of the world rather than to + the assumption, by way of explanation, that the palms themselves might + have changed their nature. One of the most valuable aids in geological + research, often the only means for reconstructing the face of the earth in + by-gone periods, is afforded by fossils, but only the morphologist can + pronounce as to their trustworthiness as witnesses, because of the danger + of mistaking analogous for homologous forms. This difficulty applies + equally to living groups, and it is so important that a few instances may + not be amiss. + </p> + <p> + There is undeniable similarity between the faunas of Madagascar and South + America. This was supported by the Centetidae and Dendrobatidae, two + entire "families," as also by other facts. The value of the Insectivores, + Solenodon in Cuba, Centetes in Madagascar, has been much lessened by their + recognition as an extremely ancient group and as a case of convergence, + but if they are no longer put into the same family, this amendment is + really to a great extent due to their widely discontinuous distribution. + The only systematic difference of the Dendrobatidae from the Ranidae is + the absence of teeth, morphologically a very unimportant character, and it + is now agreed, on the strength of their distribution, that these little + arboreal, conspicuously coloured frogs, Dendrobates in South America, + Mantella in Madagascar, do not form a natural group, although a third + genus, Cardioglossa in West Africa, seems also to belong to them. If these + creatures lived all on the same continent, we should unhesitatingly look + upon them as forming a well-defined, natural little group. On the other + hand the Aglossa, with their three very divergent genera, namely Pipa in + South America, Xenopus and Hymenochirus in Africa, are so well + characterised as one ancient group that we use their distribution + unhesitatingly as a hint of a former connection between the two + continents. We are indeed arguing in vicious circles. The Ratitae as such + are absolutely worthless since they are a most heterogeneous assembly, and + there are untold groups, of the artificiality of which many a + zoo-geographer had not the slightest suspicion when he took his + statistical material, the genera and families, from some systematic + catalogues or similar lists. A lamentable instance is that of certain + flightless Rails, recently extinct or sub-fossil, on the isalnds of + Mauritius, Rodriguez and Chatham. Being flightless they have been used in + support of a former huge Antarctic continent, instead of ruling them out + of court as Rails which, each in its island, have lost the power of + flight, a process which must have taken place so recently that it is + difficult, upon morphological grounds, to justify their separation into + Aphanapteryx in Mauritius, Erythromachus in Rodriguez and Diaphorapteryx + on Chatham Island. Morphologically they may well form but one genus, since + they have sprung from the same stock and have developed upon the same + lines; they are therefore monogenetic: but since we know that they have + become what they are independently of each other (now unlike any other + Rails), they are polygenetic and therefore could not form one genus in the + old Darwinian sense. Further, they are not a case of convergence, since + their ancestry is not divergent but leads into the same stratum. + </p> + <p> + THE RECONSTRUCTION OF THE GEOGRAPHY OF SUCCESSIVE EPOCHS. + </p> + <p> + A promising method is the study by the specialist of a large, widely + distributed group of animals from an evolutionary point of view. Good + examples of this method are afforded by A.E. Ortmann's ("The geographical + distribution of Freshwater Decapods and its bearing upon ancient + geography", "Proc. Amer. Phil. Soc." Vol. 41, 1902.) exhaustive paper and + by A.W. Grabau's "Phylogeny of Fusus and its Allies" ("Smithsonian Misc. + Coll." 44, 1904.) After many important groups of animals have been treated + in this way—as yet sparingly attempted—the results as to + hypothetical land-connections etc. are sure to be corrective and + supplementary, and their problems will be solved, since they are not + imaginary. + </p> + <p> + The same problems are attacked, in the reverse way, by starting with the + whole fauna of a country and thence, so to speak, letting the research + radiate. Some groups will be considered as autochthonous, others as + immigrants, and the directions followed by them will be inquired into; the + search may lead far and in various directions, and by comparison of + results, by making compound maps, certain routes will assume definite + shape, and if they lead across straits and seas they are warrants to + search for land-connections in the past. (A fair sample of this method is + C.H. Eigenmann's "The Freshwater Fishes of South and Middle America", + "Popular Science Monthly", Vol. 68, 1906.) There are now not a few maps + purporting to show the outlines of land and water at various epochs. Many + of these attempts do not tally with each other, owing to the lamentable + deficiencies of geological and fossil data, but the bolder the + hypothetical outlines are drawn, the better, and this is preferable to the + insertion of bays and similar detail which give such maps a fallacious + look of certainty where none exists. Moreover it must be borne in mind + that, when we draw a broad continental belt across an ocean, this belt + need never have existed in its entirety at any one time. The features of + dispersal, intended to be explained by it, would be accomplished just as + well by an unknown number of islands which have joined into larger + complexes while elsewhere they subsided again: like pontoon-bridges which + may be opened anywhere, or like a series of superimposed dissolving views + of land and sea-scapes. Hence the reconstructed maps of Europe, the only + continent tolerably known, show a considerable number of islands in + puzzling changes, while elsewhere, e.g. in Asia, we have to be satisfied + with sweeping generalisations. + </p> + <p> + At present about half-a-dozen big connections are engaging our attention, + leaving as comparatively settled the extent and the duration of such minor + "bridges" as that between Africa and Madagascar, Tasmania and Australia, + the Antilles and Central America, Europe and North Africa. (Not a few of + those who are fascinated by, and satisfied with, the statistical aspect of + distribution still have a strong dislike to the use of "bridges" if these + lead over deep seas, and they get over present discontinuous occurrences + by a former "universal or sub-universal distribution" of their groups.) + This is indeed an easy method of cutting the knot, but in reality they + shunt the question only a stage or two back, never troubling to explain + how their groups managed to attain to that sub-universal range; or do they + still suppose that the whole world was originally one paradise where + everything lived side by side, until sin and strife and glacial epochs + left nothing but scattered survivors? + </p> + <p> + The permanence of the great ocean-basins had become a dogma since it was + found that a universal elevation of the land to the extent of 100 fathoms + would produce but little changes, and when it was shown that even the 1000 + fathom-line followed the great masses of land rather closely, and still + leaving the great basins (although transgression of the sea to the same + extent would change the map of the world beyond recognition), by general + consent one mile was allowed as the utmost speculative limit of + subsidence. Naturally two or three miles, the average depth of the oceans, + seems enormous, and yet such a difference in level is as nothing in + comparison with the size of the Earth. On a clay model globe ten feet in + diameter an ocean bed three miles deep would scarcely be detected, and the + highest mountains would be smaller than the unavoidable grains in the + glazed surface of our model. There are but few countries which have not be + submerged at some time or other. + </p> + <p> + CONNECTION OF SOUTH EASTERN ASIA WITH AUSTRALIA. Neumayr's Sino-Australian + continent during mid-Mesozoic times was probably a much changing + Archipelago, with final separations subsequent to the Cretaceous period. + Henceforth Australasia was left to its own fate, but for a possible + connection with the antarctic continent. + </p> + <p> + AFRICA, MADAGASCAR, INDIA. The "Lemuria" of Sclater and Haeckel cannot + have been more than a broad bridge in Jurassic times; whether it was ever + available for the Lemurs themselves must depend upon the time of its + duration, the more recent the better, but it is difficult to show that it + lasted into the Miocene. + </p> + <p> + AFRICA AND SOUTH AMERICA. Since the opposite coasts show an entire absence + of marine fossils and deposits during the Mesozoic period, whilst further + north and south such are known to exist and are mostly identical on either + side, Neumayr suggested the existence of a great Afro-Son American mass of + land during the Jurassic epoch. Such land is almost a necessity and is + supported by many facts; it would easily explain the distribution of + numerous groups of terrestrial creatures. Moreover to the north of this + hypothetical land, somewhere across from the Antilles and Guiana to North + Africa and South Western Europe, existed an almost identical fauna of + Corals and Molluscs, indicating either a coast-line or a series of islands + interrupted by shallow seas, just as one would expect if, and when, a + Brazil-Ethiopian mass of land were breaking up. Lastly from Central + America to the Mediterranean stretches one of the Tertiary tectonic lines + of the geologists. Here also the great question is how long this continent + lasted. Apparently the South Atlantic began to encroach from the south so + that by the later Cretaceous epoch the land was reduced to a comparatively + narrow Brazil-West Africa, remnants of which persisted certainly into the + early Tertiary, until the South Atlantic joined across the equator with + the Atlantic portion of the "Thetys," leaving what remained of South + America isolated from the rest of the world. + </p> + <p> + ANTARCTIC CONNECTIONS. Patagonia and Argentina seem to have joined + Antartica during the Cretaceous epoch, and this South Georgian bridge had + broken down again by mid-Tertiary times when South America became + consolidated. The Antarctic continent, presuming that it existed, seems + also to have been joined, by way of Tasmania, with Australia, also during + the Cretaceous epoch, and it is assumed that the great + Australia-Antarctic-Patagonian land was severed first to the south of + Tasmania and then at the South Georgian bridge. No connection, and this is + important, is indicated between Antarctica and either Africa or + Madagascar. + </p> + <p> + So far we have followed what may be called the vicissitudes of the great + Permo-Carboniferous Gondwana land in its fullest imaginary extent, an + enormous equatorial and south temperate belt from South America to Africa, + South India and Australia, which seems to have provided the foundation of + the present Southern continents, two of which temporarily joined + Antarctica, of which however we know nothing except that it exists now. + </p> + <p> + Let us next consider the Arctic and periarctic lands. Unfortunately very + little is known about the region within the arctic circle. If it was all + land, or more likely great changing archipelagoes, faunistic exchange + between North America, Europe and Siberia would present no difficulties, + but there is one connection which engages much attention, namely a land + where now lies the North temperate and Northern part of the Atlantic + ocean. How far south did it ever extend and what is the latest date of a + direct practicable communication, say from North Western Europe to + Greenland? Connections, perhaps often interrupted, e.g. between Greenland + and Labrador, at another time between Greenland and Scandinavia, seem to + have existed at least since the Permo-Carboniferous epoch. If they existed + also in late Cretaceous and in Tertiary times, they would of course easily + explain exchanges which we know to have repeatedly taken place between + America and Europe, but they are not proved thereby, since most of these + exchanges can almost as easily have occurred across the polar regions, and + others still more easily by repeated junction of Siberia with Alaska. + </p> + <p> + Let us now describe a hypothetical case based on the supposition of + connecting bridges. Not to work in a circle, we select an important group + which has not served as a basis for the reconstruction of bridges; and it + must be a group which we feel justified in assuming to be old enough to + have availed itself of ancient land-connections. + </p> + <p> + The occurrence of one species of Peripatus in the whole of Australia, + Tasmania and New Zealand (the latter being joined to Australia by way of + New Britain in Cretaceous times but not later) puts the genus back into + this epoch, no unsatisfactory assumption to the morphologist. The apparent + absence of Peripatus in Madagascar indicates that it did not come from the + east into Africa, that it was neither Afro-Indian, nor Afro-Australian; + nor can it have started in South America. We therefore assume as its + creative centre Australia or Malaya in the Cretaceous epoch, whence its + occurrence in Sumatra, Malay Peninsula, New Britain, New Zealand and + Australia is easily explained. Then extension across Antarctica to + Patagonia and Chile, whence it could spread into the rest of South America + as this became consolidated in early Tertiary times. For getting to the + Antilles and into Mexico it would have to wait until the Miocene, but long + before that time it could arrive in Africa, there surviving as a Congolese + and a Cape species. This story is unsupported by a single fossil. + Peripatus may have been "sub-universal" all over greater Gondwana land in + Carboniferous times, and then its absence from Madagascar would be + difficult to explain, but the migrations suggested above amount to little + considering that the distance from Tasmania to South America could be + covered in far less time than that represented by the whole of the Eocene + epoch alone. + </p> + <p> + There is yet another field, essentially the domain of geographical + distribution, the cultivation of which promises fair to throw much light + upon Nature's way of making species. This is the study of the organisms + with regard to their environment. Instead of revealing pedigrees or of + showing how and when the creatures got to a certain locality, it + investigates how they behaved to meet the ever changing conditions of + their habitats. There is a facies, characteristic of, and often peculiar + to, the fauna of tropical moist forests, another of deserts, of high + mountains, of underground life and so forth; these same facies are stamped + upon whole associations of animals and plants, although these may be—and + in widely separated countries generally are—drawn from totally + different families of their respective orders. It does not go to the root + of the matter to say that these facies have been brought about by the + extermination of all the others which did not happen to fit into their + particular environment. One might almost say that tropical moist forests + must have arboreal frogs and that these are made out of whatever suitable + material happened to be available; in Australia and South America Hylidae, + in Africa Ranidae, since there Hylas are absent. The deserts must have + lizards capable of standing the glare, the great changes of temperature, + of running over or burrowing into the loose sand. When as in America + Iguanids are available, some of these are thus modified, while in Africa + and Asia the Agamids are drawn upon. Both in the Damara and in the + Transcaspian deserts, a Gecko has been turned into a runner upon sand! + </p> + <p> + We cannot assume that at various epochs deserts, and at others moist + forests were continuous all over the world. The different facies and + associations were developed at various times and places. Are we to suppose + that, wherever tropical forests came into existence, amongst the stock of + humivagous lizards were always some which presented those nascent + variations which made them keep step with the similarly nascent forests, + the overwhelming rest being eliminated? This principle would imply that + the same stratum of lizards always had variations ready to fit any changed + environment, forests and deserts, rocks and swamps. The study of Ecology + indicates a different procedure, a great, almost boundless plasticity of + the organism, not in the sense of an exuberant moulding force, but of a + readiness to be moulded, and of this the "variations" are the visible + outcome. In most cases identical facies are produced by heterogeneous + convergences and these may seem to be but superficial, affecting only what + some authors are pleased to call the physiological characters; but + environment presumably affects first those parts by which the organism + comes into contact with it most directly, and if the internal structures + remain unchanged, it is not because these are less easily modified but + because they are not directly affected. When they are affected, they too + change deeply enough. + </p> + <p> + That the plasticity should react so quickly—indeed this very + quickness seems to have initiated our mistaking the variations called + forth for something performed—and to the point, is itself the + outcome of the long training which protoplasm has undergone since its + creation. + </p> + <p> + In Nature's workshop he does not succeed who has ready an arsenal of tools + for every conceivable emergency, but he who can make a tool at the spur of + the moment. The ordeal of the practical test is Charles Darwin's glorious + conception of Natural Selection. + </p> + <p> + <a name="link2H_4_0020" id="link2H_4_0020"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + XVIII. DARWIN AND GEOLOGY. By J.W. Judd, C.B., LL.D., F.R.S. + </h2> + <p> + (Mr Francis Darwin has related how his father occasionally came up from + Down to spend a few days with his brother Erasmus in London, and, after + his brother's death, with his daughter, Mrs Litchfield. On these + occasions, it was his habit to arrange meetings with Huxley, to talk over + zoological questions, with Hooker, to discuss botanical problems, and with + Lyell to hold conversations on geology. After the death of Lyell, Darwin, + knowing my close intimacy with his friend during his later years, used to + ask me to meet him when he came to town, and "talk geology." The "talks" + took place sometimes at Jermyn Street Museum, at other times in the Royal + College of Science, South Kensington; but more frequently, after having + lunch with him, at his brother's or his daughter's house. On several + occasions, however, I had the pleasure of visiting him at Down. In the + postscript of a letter (of April 15, 1880) arranging one of these visits, + he writes: "Since poor, dear Lyell's death, I rarely have the pleasure of + geological talk with anyone.") + </p> + <p> + In one of the very interesting conversations which I had with Charles + Darwin during the last seven years of his life, he asked me in a very + pointed manner if I were able to recall the circumstances, accidental or + otherwise, which had led me to devote myself to geological studies. He + informed me that he was making similar inquiries of other friends, and I + gathered from what he said that he contemplated at that time a study of + the causes producing SCIENTIFIC BIAS in individual minds. I have no means + of knowing how far this project ever assumed anything like concrete form, + but certain it is that Darwin himself often indulged in the processes of + mental introspection and analysis; and he has thus fortunately left us—in + his fragments of autobiography and in his correspondence—the + materials from which may be reconstructed a fairly complete history of his + own mental development. + </p> + <p> + There are two perfectly distinct inquiries which we have to undertake in + connection with the development of Darwin's ideas on the subject of + evolution: + </p> + <p> + FIRST. How, when, and under what conditions was Darwin led to a conviction + that species were not immutable, but were derived from pre-existing forms? + </p> + <p> + SECONDLY. By what lines of reasoning and research was he brought to regard + "natural selection" as a vera causa in the process of evolution? + </p> + <p> + It is the first of these inquiries which specially interests the + geologist; though geology undoubtedly played a part—and by no means + an insignificant part—in respect to the second inquiry. + </p> + <p> + When, indeed, the history comes to be written of that great revolution of + thought in the nineteenth century, by which the doctrine of evolution, + from being the dream of poets and visionaries, gradually grew to be the + accepted creed of naturalists, the paramount influence exerted by the + infant science of geology—and especially that resulting from the + publication of Lyell's epoch-making work, the "Principles of Geology"—cannot + fail to be regarded as one of the leading factors. Herbert Spencer in his + "Autobiography" bears testimony to the effect produced on his mind by the + recently published "Principles", when, at the age of twenty, he had + already begun to speculate on the subject of evolution (Herbert Spencer's + "Autobiography", London, 1904, Vol. I. pages 175-177.); and Alfred Russel + Wallace is scarcely less emphatic concerning the part played by Lyell's + teaching in his scientific education. (See "My Life; a record of Events + and Opinions", London, 1905, Vol. I. page 355, etc. Also his review of + Lyell's "Principles" in "Quarterly Review" (Vol. 126), 1869, pages + 359-394. See also "The Darwin-Wallace Celebration by the Linnean Society" + (1909), page 118.) Huxley wrote in 1887 "I owe more than I can tell to the + careful study of the "Principles of Geology" in my young days." ("Science + and Pseudo Science"; "Collected Essays", London, 1902, Vol. V. page 101.) + As for Charles Darwin, he never tired—either in his published + writings, his private correspondence or his most intimate conversations—of + ascribing the awakening of his enthusiasm and the direction of his + energies towards the elucidation of the problem of development to the + "Principles of Geology" and the personal influence of its author. Huxley + has well expressed what the author of the "Origin of Species" so + constantly insisted upon, in the statements "Darwin's greatest work is the + outcome of the unflinching application to Biology of the leading idea and + the method applied in the "Principles" to Geology ("Proc. Roy. Soc." Vol. + XLIV. (1888), page viii.; "Collected Essays" II. page 268, 1902.), and + "Lyell, for others, as for myself, was the chief agent in smoothing the + road for Darwin." ("Life and Letters of Charles Darwin" II. page 190.) + </p> + <p> + We propose therefore to consider, first, what Darwin owed to geology and + its cultivators, and in the second place how he was able in the end so + fully to pay a great debt which he never failed to acknowledge. Thanks to + the invaluable materials contained in the "Life and Letters of Charles + Darwin" (3 vols.) published by Mr Francis Darwin in 1887; and to "More + Letters of Charles Darwin" (2 vols.) issued by the same author, in + conjunction with Professor A.C. Seward, in 1903, we are permitted to + follow the various movements in Darwin's mind, and are able to record the + story almost entirely in his own words. (The first of these works is + indicated in the following pages by the letters "L.L."; the second by + "M.L.") + </p> + <p> + From the point of view of the geologist, Darwin's life naturally divides + itself into four periods. In the first, covering twenty-two years, various + influences were at work militating, now for and now against, his adoption + of a geological career; in the second period—the five memorable + years of the voyage of the "Beagle"—the ardent sportsman with some + natural-history tastes, gradually became the most enthusiastic and + enlightened of geologists; in the third period, lasting ten years, the + valuable geological recruit devoted nearly all his energies and time to + geological study and discussion and to preparing for publication the + numerous observations made by him during the voyage; the fourth period, + which covers the latter half of his life, found Darwin gradually drawn + more and more from geological to biological studies, though always + retaining the deepest interest in the progress and fortunes of his "old + love." But geologists gladly recognise the fact that Darwin immeasurably + better served their science by this biological work, than he could + possibly have done by confining himself to purely geological questions. + </p> + <p> + From his earliest childhood, Darwin was a collector, though up to the time + when, at eight years of age, he went to a preparatory school, seals, + franks and similar trifles appear to have been the only objects of his + quest. But a stone, which one of his schoolfellows at that time gave to + him, seems to have attracted his attention and set him seeking for pebbles + and minerals; as the result of this newly acquired taste, he says (writing + in 1838) "I distinctly recollect the desire I had of being able to know + something about every pebble in front of the hall door—it was my + earliest and only geological aspiration at that time." ("M.L." I. page 3.) + He further suspects that while at Mr Case's school "I do not remember any + mental pursuits except those of collecting stones," etc... "I was born a + naturalist." ("M.L." I. page 4.) + </p> + <p> + The court-yard in front of the hall door at the Mount House, Darwin's + birthplace and the home of his childhood, is surrounded by beds or + rockeries on which lie a number of pebbles. Some of these pebbles (in + quite recent times as I am informed) have been collected to form a + "cobbled" space in front of the gate in the outer wall, which fronts the + hall door; and a similar "cobbled area," there is reason to believe, may + have existed in Darwin's childhood before the door itself. The pebbles, + which were obtained from a neighbouring gravel-pit, being derived from the + glacial drift, exhibit very striking differences in colour and form. It + was probably this circumstance which awakened in the child his love of + observation and speculation. It is certainly remarkable that "aspirations" + of the kind should have arisen in the mind of a child of 9 or 10! + </p> + <p> + When he went to Shrewsbury School, he relates "I continued collecting + minerals with much zeal, but quite unscientifically,—all that I + cared about was a new-NAMED mineral, and I hardly attempted to classify + them." ("L.L." I. page 34.) + </p> + <p> + There has stood from very early times in Darwin's native town of + Shrewsbury, a very notable boulder which has probably marked a boundary + and is known as the "Bell-stone"—giving its name to a house and + street. Darwin tells us in his "Autobiography" that while he was at + Shrewsbury School at the age of 13 or 14 "an old Mr Cotton in Shropshire, + who knew a good deal about rocks" pointed out to me "... the 'bell-stone'; + he told me that there was no rock of the same kind nearer than Cumberland + or Scotland, and he solemnly assured me that the world would come to an + end before anyone would be able to explain how this stone came where it + now lay"! Darwin adds "This produced a deep impression on me, and I + meditated over this wonderful stone." ("L.L." I. page 41.) + </p> + <p> + The "bell-stone" has now, owing to the necessities of building, been + removed a short distance from its original site, and is carefully + preserved within the walls of a bank. It is a block of irregular shape 3 + feet long and 2 feet wide, and about 1 foot thick, weighing probably not + less than one-third of a ton. By the courtesy of the directors of the + National Provincial Bank of England, I have been able to make a minute + examination of it, and Professors Bonney and Watts, with Mr Harker and Mr + Fearnsides have given me their valuable assistance. The rock is a much + altered andesite and was probably derived from the Arenig district in + North Wales, or possibly from a point nearer the Welsh Border. (I am + greatly indebted to the Managers of the Bank at Shrewsbury for kind + assistance in the examination of this interesting memorial: and Mr H.T. + Beddoes, the Curator of the Shrewsbury Museum, has given me some + archaeological information concerning the stone. Mr Richard Cotton was a + good local naturalist, a Fellow both of the Geological and Linnean + Societies; and to the officers of these societies I am indebted for + information concerning him. He died in 1839, and although he does not + appear to have published any scientific papers, he did far more for + science by influencing the career of the school boy!) It was of course + brought to where Shrewsbury now stands by the agency of a glacier—as + Darwin afterwards learnt. + </p> + <p> + We can well believe from the perusal of these reminiscences that, at this + time, Darwin's mind was, as he himself says, "prepared for a philosophical + treatment of the subject" of Geology. ("L.L." I. page 41.) When at the age + of 16, however, he was entered as a medical student at Edinburgh + University, he not only did not get any encouragement of his scientific + tastes, but was positively repelled by the ordinary instruction given + there. Dr Hope's lectures on Chemistry, it is true, interested the boy, + who with his brother Erasmus had made a laboratory in the toolhouse, and + was nicknamed "Gas" by his schoolfellows, while undergoing solemn and + public reprimand from Dr Butler at Shrewsbury School for thus wasting his + time. ("L.L." I. page 35.) But most of the other Edinburgh lectures were + "intolerably dull," "as dull as the professors" themselves, "something + fearful to remember." In after life the memory of these lectures was like + a nightmare to him. He speaks in 1840 of Jameson's lectures as something + "I... for my sins experienced!" ("L.L." I. page 340.) Darwin especially + signalises these lectures on Geology and Zoology, which he attended in his + second year, as being worst of all "incredibly dull. The sole effect they + produced on me was the determination never so long as I lived to read a + book on Geology, or in any way to study the science!" ("L.L." I. page 41.) + </p> + <p> + The misfortune was that Edinburgh at that time had become the cockpit in + which the barren conflict between "Neptunism" and "Plutonism" was being + waged with blind fury and theological bitterness. Jameson and his pupils, + on the one hand, and the friends and disciples of Hutton, on the other, + went to the wildest extremes in opposing each other's peculiar tenets. + Darwin tells us that he actually heard Jameson "in a field lecture at + Salisbury Craigs, discoursing on a trap-dyke, with amygdaloidal margins + and the strata indurated on each side, with volcanic rocks all around us, + say that it was a fissure filled with sediment from above, adding with a + sneer that there were men who maintained that it had been injected from + beneath in a molten condition." ("L.L." I. pages 41-42.) "When I think of + this lecture," added Darwin, "I do not wonder that I determined never to + attend to Geology." (This was written in 1876 and Darwin had in the summer + of 1839 revisited and carefully studied the locality ("L.L." I. page 290.) + It is probable that most of Jameson's teaching was of the same + controversial and unilluminating character as this field-lecture at + Salisbury Craigs. + </p> + <p> + There can be no doubt that, while at Edinburgh, Darwin must have become + acquainted with the doctrines of the Huttonian School. Though so young, he + mixed freely with the scientific society of the city, Macgillivray, Grant, + Leonard Horner, Coldstream, Ainsworth and others being among his + acquaintances, while he attended and even read papers at the local + scientific societies. It is to be feared, however, that what Darwin would + hear most of, as characteristic of the Huttonian teaching, would be + assertions that chalk-flints were intrusions of molten silica, that fossil + wood and other petrifactions had been impregnated with fused materials, + that heat—but never water—was always the agent by which the + induration and crystallisation of rock-materials (even siliceous + conglomerate, limestone and rock-salt) had been effected! These + extravagant "anti-Wernerian" views the young student might well regard as + not one whit less absurd and repellant than the doctrine of the "aqueous + precipitation" of basalt. There is no evidence that Darwin, even if he + ever heard of them, was in any way impressed, in his early career, by the + suggestive passages in Hutton and Playfair, to which Lyell afterwards + called attention, and which foreshadowed the main principles of + Uniformitarianism. + </p> + <p> + As a matter of fact, I believe that the influence of Hutton and Playfair + in the development of a philosophical theory of geology has been very + greatly exaggerated by later writers on the subject. Just as Wells and + Matthew anticipated the views of Darwin on Natural Selection, but without + producing any real influence on the course of biological thought, so + Hutton and Playfair adumbrated doctrines which only became the basis of + vivifying theory in the hands of Lyell. Alfred Russel Wallace has very + justly remarked that when Lyell wrote the "Principles of Geology", "the + doctrines of Hutton and Playfair, so much in advance of their age, seemed + to be utterly forgotten." ("Quarterly Review", Vol. CXXVI. (1869), page + 363.) In proof of this it is only necessary to point to the works of the + great masters of English geology, who preceded Lyell, in which the works + of Hutton and his followers are scarcely ever mentioned. This is true even + of the "Researches in Theoretical Geology" and the other works of the + sagacious De la Beche. (Of the strength and persistence of the prejudice + felt against Lyell's views by his contemporaries, I had a striking + illustration some little time after Lyell's death. One of the old + geologists who in the early years of the century had done really good work + in connection with the Geological Society expressed a hope that I was not + "one of those who had been carried away by poor Lyell's fads." My surprise + was indeed great when further conversation showed me that the whole of the + "Principles" were included in the "fads"!) Darwin himself possessed a copy + of Playfair's "Illustrations of the Huttonian Theory", and occasionally + quotes it; but I have met with only one reference to Hutton, and that a + somewhat enigmatical one, in all Darwin's writings. In a letter to Lyell + in 1841, when his mind was much exercised concerning glacial questions, he + says "What a grand new feature all this ice work is in Geology! How old + Hutton would have stared!" ("M.L." II. page 149.) + </p> + <p> + As a consequence of the influences brought to bear on his mind during his + two years' residence in Edinburgh, Darwin, who had entered that University + with strong geological aspirations, left it and proceeded to Cambridge + with a pronounced distaste for the whole subject. The result of this was + that, during his career as an under-graduate, he neglected all the + opportunities for geological study. During that important period of life, + when he was between eighteen and twenty years of age, Darwin spent his + time in riding, shooting and beetle-hunting, pursuits which were + undoubtedly an admirable preparation for his future work as an explorer; + but in none of his letters of this period does he even mention geology. He + says, however, "I was so sickened with lectures at Edinburgh that I did + not even attend Sedgwick's eloquent and interesting lectures." ("L.L." I. + page 48.) + </p> + <p> + It was only after passing his examination, and when he went up to spend + two extra terms at Cambridge, that geology again began to attract his + attention. The reading of Sir John Herschel's "Introduction to the Study + of Natural Philosophy", and of Humboldt's "Personal Narrative", a copy of + which last had been given to him by his good friend and mentor Henslow, + roused his dormant enthusiasm for science, and awakened in his mind a + passionate desire for travel. And it was from Henslow, whom he had + accompanied in his excursions, but without imbibing any marked taste, at + that time, for botany, that the advice came to think of and to "begin the + study of geology." ("L.L." I. page 56.) This was in 1831, and in the + summer vacation of that year we find him back again at Shrewsbury "working + like a tiger" at geology and endeavouring to make a map and section of + Shropshire—work which he says was not "as easy as I expected." + ("L.L." I. page 189.) No better field for geological studies could + possibly be found than Darwin's native county. + </p> + <p> + Writing to Henslow at this time, and referring to a form of the instrument + devised by his friend, Darwin says: "I am very glad to say I think the + clinometer will answer admirably. I put all the tables in my bedroom at + every conceivable angle and direction. I will venture to say that I have + measured them as accurately as any geologist going could do." But he adds: + "I have been working at so many things that I have not got on much with + geology. I suspect the first expedition I take, clinometer and hammer in + hand, will send me back very little wiser and a good deal more puzzled + than when I started." ("L.L." I. page 189.) Valuable aid was, however, at + hand, for at this time Sedgwick, to whom Darwin had been introduced by the + ever-helpful Henslow, was making one of his expeditions into Wales, and + consented to accept the young student as his companion during the + geological tour. ("L.L." I. page 56.) We find Darwin looking forward to + this privilege with the keenest interest. ("L.L." I. page 189.) + </p> + <p> + When at the beginning of August (1831), Sedgwick arrived at his father's + house in Shrewsbury, where he spent a night, Darwin began to receive his + first and only instruction as a field-geologist. The journey they took + together led them through Llangollen, Conway, Bangor, and Capel Curig, at + which latter place they parted after spending many hours in examining the + rocks at Cwm Idwal with extreme care, seeking for fossils but without + success. Sedgwick's mode of instruction was admirable—he from time + to time sent the pupil off on a line parallel to his own, "telling me to + bring back specimens of the rocks and to mark the stratification on a + map." ("L.L." I. page 57.) On his return to Shrewsbury, Darwin wrote to + Henslow, "My trip with Sedgwick answered most perfectly," ("L.L." I. page + 195.), and in the following year he wrote again from South America to the + same friend, "Tell Professor Sedgwick he does not know how much I am + indebted to him for the Welsh expedition; it has given me an interest in + Geology which I would not give up for any consideration. I do not think I + ever spent a more delightful three weeks than pounding the north-west + mountains." ("L.L." I. pages 237-8.) + </p> + <p> + It would be a mistake, however, to suppose that at this time Darwin had + acquired anything like the affection for geological study, which he + afterwards developed. After parting with Sedgwick, he walked in a straight + line by compass and map across the mountains to Barmouth to visit a + reading party there, but taking care to return to Shropshire before + September 1st, in order to be ready for the shooting. For as he candidly + tells us, "I should have thought myself mad to give up the first days of + partridge-shooting for geology or any other science!" ("L.L." I. page 58.) + </p> + <p> + Any regret we may be disposed to feel that Darwin did not use his + opportunities at Edinburgh and Cambridge to obtain systematic and + practical instruction in mineralogy and geology, will be mitigated, + however, when we reflect on the danger which he would run of being + indoctrinated with the crude "catastrophic" views of geology, which were + at that time prevalent in all the centres of learning. + </p> + <p> + Writing to Henslow in the summer of 1831, Darwin says "As yet I have only + indulged in hypotheses, but they are such powerful ones that I suppose, if + they were put into action but for one day, the world would come to an + end." ("L.L." I. page 189.) + </p> + <p> + May we not read in this passage an indication that the self-taught + geologist had, even at this early stage, begun to feel a distrust for the + prevalent catastrophism, and that his mind was becoming a field in which + the seeds which Lyell was afterwards to sow would "fall on good ground"? + </p> + <p> + The second period of Darwin's geological career—the five years spent + by him on board the "Beagle"—was the one in which by far the most + important stage in his mental development was accomplished. He left + England a healthy, vigorous and enthusiastic collector; he returned five + years later with unique experiences, the germs of great ideas, and a + knowledge which placed him at once in the foremost ranks of the geologists + of that day. Huxley has well said that "Darwin found on board the "Beagle" + that which neither the pedagogues of Shrewsbury, nor the professoriate of + Edinburgh, nor the tutors of Cambridge had managed to give him." ("Proc. + Roy. Soc." Vol. XLIV. (1888), page IX.) Darwin himself wrote, referring to + the date at which the voyage was expected to begin: "My second life will + then commence, and it shall be as a birthday for the rest of my life." + ("L.L." I. page 214.); and looking back on the voyage after forty years, + he wrote; "The voyage of the 'Beagle' has been by far the most important + event in my life, and has determined my whole career;... I have always + felt that I owe to the voyage the first real training or education of my + mind; I was led to attend closely to several branches of natural history, + and thus my powers of observation were improved, though they were always + fairly developed." ("L.L." I. page 61.) + </p> + <p> + Referring to these general studies in natural history, however, Darwin + adds a very significant remark: "The investigation of the geology of the + places visited was far more important, as reasoning here comes into play. + On first examining a new district nothing can appear more hopeless than + the chaos of rocks; but by recording the stratification and nature of the + rocks and fossils at many points, always reasoning and predicting what + will be found elsewhere, light soon begins to dawn on the district, and + the structure of the whole becomes more or less intelligible." ("L.L." I. + page 62.) + </p> + <p> + The famous voyage began amid doubts, discouragements and disappointments. + Fearful of heart-disease, sad at parting from home and friends, depressed + by sea-sickness, the young explorer, after being twice driven back by + baffling winds, reached the great object of his ambition, the island of + Teneriffe, only to find that, owing to quarantine regulations, landing was + out of the question. + </p> + <p> + But soon this inauspicious opening of the voyage was forgotten. Henslow + had advised his pupil to take with him the first volume of Lyell's + "Principles of Geology", then just published—but cautioned him (as + nearly all the leaders in geological science at that day would certainly + have done) "on no account to accept the views therein advocated." ("L.L." + I. page 73.) It is probable that the days of waiting, discomfort and + sea-sickness at the beginning of the voyage were relieved by the reading + of this volume. For he says that when he landed, three weeks after setting + sail from Plymouth, in St Jago, the largest of the Cape de Verde Islands, + the volume had already been "studied attentively; and the book was of the + highest service to me in many ways... " His first original geological + work, he declares, "showed me clearly the wonderful superiority of Lyell's + manner of treating geology, compared with that of any other author, whose + works I had with me or ever afterwards read." ("L.L." I. page 62.) + </p> + <p> + At St Jago Darwin first experienced the joy of making new discoveries, and + his delight was unbounded. Writing to his father he says, "Geologising in + a volcanic country is most delightful; besides the interest attached to + itself, it leads you into most beautiful and retired spots." ("L.L." I. + page 228.) To Henslow he wrote of St Jago: "Here we spent three most + delightful weeks... St Jago is singularly barren, and produces few plants + or insects, so that my hammer was my usual companion, and in its company + most delightful hours I spent." "The geology was pre-eminently + interesting, and I believe quite new; there are some facts on a large + scale of upraised coast (which is an excellent epoch for all the volcanic + rocks to date from), that would interest Mr Lyell." ("L.L." I. page 235.) + After more than forty years the memory of this, his first geological work, + seems as fresh as ever, and he wrote in 1876, "The geology of St Jago is + very striking, yet simple: a stream of lava formerly flowed over the bed + of the sea, formed of triturated recent shells and corals, which it has + baked into a hard white rock. Since then the whole island has been + upheaved. But the line of white rock revealed to me a new and important + fact, namely, that there had been afterwards subsidence round the craters, + which had since been in action, and had poured forth lava." ("L.L." I. + page 65.) + </p> + <p> + It was at this time, probably, that Darwin made his first attempt at + drawing a sketch-map and section to illustrate the observations he had + made (see his "Volcanic Islands", pages 1 and 9). His first important + geological discovery, that of the subsidence of strata around volcanic + vents (which has since been confirmed by Mr Heaphy in New Zealand and + other authors) awakened an intense enthusiasm, and he writes: "It then + first dawned on me that I might perhaps write a book on the geology of the + various countries visited, and this made me thrill with delight. That was + a memorable hour to me, and how distinctly I can call to mind the low + cliff of lava beneath which I rested, with the sun glaring hot, a few + strange desert plants growing near, and with living corals in the tidal + pools at my feet." ("L.L." I. page 66.) + </p> + <p> + But it was when the "Beagle", after touching at St Paul's rock and Tristan + d'Acunha (for a sufficient time only to collect specimens), reached the + shores of South America, that Darwin's real work began; and he was able, + while the marine surveys were in progress, to make many extensive journeys + on land. His letters at this time show that geology had become his chief + delight, and such exclamations as "Geology carries the day," "I find in + Geology a never failing interest," etc. abound in his correspondence. + </p> + <p> + Darwin's time was divided between the study of the great deposits of red + mud—the Pampean formation—with its interesting fossil bones + and shells affording proofs of slow and constant movements of the land, + and the underlying masses of metamorphic and plutonic rocks. Writing to + Henslow in March, 1834, he says: "I am quite charmed with Geology, but, + like the wise animal between two bundles of hay, I do not know which to + like best; the old crystalline groups of rocks, or the softer and + fossiliferous beds. When puzzling about stratification, etc., I feel + inclined to cry 'a fig for your big oysters, and your bigger + megatheriums.' But then when digging out some fine bones, I wonder how any + man can tire his arms with hammering granite." ("L.L." I. page 249.) We + are told by Darwin that he loved to reason about and attempt to predict + the nature of the rocks in each new district before he arrived at it. + </p> + <p> + This love of guessing as to the geology of a district he was about to + visit is amusingly expressed by him in a letter (of May, 1832) to his + cousin and old college-friend, Fox. After alluding to the beetles he had + been collecting—a taste his friend had in common with himself—he + writes of geology that "It is like the pleasure of gambling. Speculating + on first arriving, what the rocks may be, I often mentally cry out 3 to 1 + tertiary against primitive; but the latter have hitherto won all the + bets." ("L.L." I. page 233.) + </p> + <p> + Not the least important of the educational results of the voyage to Darwin + was the acquirement by him of those habits of industry and method which + enabled him in after life to accomplish so much—in spite of constant + failures of health. From the outset, he daily undertook and resolutely + accomplished, in spite of sea-sickness and other distractions, four + important tasks. In the first place he regularly wrote up the pages of his + Journal, in which, paying great attention to literary style and + composition, he recorded only matters that would be of general interest, + such as remarks on scenery and vegetation, on the peculiarities and habits + of animals, and on the characters, avocations and political institutions + of the various races of men with whom he was brought in contact. It was + the freshness of these observations that gave his "Narrative" so much + charm. Only in those cases in which his ideas had become fully + crystallised, did he attempt to deal with scientific matters in this + journal. His second task was to write in voluminous note-books facts + concerning animals and plants, collected on sea or land, which could not + be well made out from specimens preserved in spirit; but he tells us that, + owing to want of skill in dissecting and drawing, much of the time spent + in this work was entirely thrown away, "a great pile of MS. which I made + during the voyage has proved almost useless." ("L.L." I. page 62.) Huxley + confirmed this judgment on his biological work, declaring that "all his + zeal and industry resulted, for the most part, in a vast accumulation of + useless manuscript." ("Proc. Roy. Soc." Vol. XLIV. (1888), page IX.) + Darwin's third task was of a very different character and of infinitely + greater value. It consisted in writing notes of his journeys on land—the + notes being devoted to the geology of the districts visited by him. These + formed the basis, not only of a number of geological papers published on + his return, but also of the three important volumes forming "The Geology + of the voyage of the 'Beagle'". On July 24th, 1834, when little more than + half of the voyage had been completed, Darwin wrote to Henslow, "My notes + are becoming bulky. I have about 600 small quarto pages full; about half + of this is Geology." ("M.L." I. page 14.) The last, and certainly not the + least important of all his duties, consisted in numbering, cataloguing, + and packing his specimens for despatch to Henslow, who had undertaken the + care of them. In his letters he often expresses the greatest solicitude + lest the value of these specimens should be impaired by the removal of the + numbers corresponding to his manuscript lists. Science owes much to + Henslow's patient care of the collections sent to him by Darwin. The + latter wrote in Henslow's biography, "During the five years' voyage, he + regularly corresponded with me and guided my efforts; he received, opened, + and took care of all the specimens sent home in many large boxes." ("Life + of Henslow", by L. Jenyns (Blomefield), London, 1862, page 53.) + </p> + <p> + Darwin's geological specimens are now very appropriately lodged for the + most part in the Sedgwick Museum, Cambridge, his original Catalogue with + subsequent annotations being preserved with them. From an examination of + these catalogues and specimens we are able to form a fair notion of the + work done by Darwin in his little cabin in the "Beagle", in the intervals + between his land journeys. + </p> + <p> + Besides writing up his notes, it is evident that he was able to accomplish + a considerable amount of study of his specimens, before they were packed + up for despatch to Henslow. Besides hand-magnifiers and a microscope, + Darwin had an equipment for blowpipe-analysis, a contact-goniometer and + magnet; and these were in constant use by him. His small library of + reference (now included in the Collection of books placed by Mr F. Darwin + in the Botany School at Cambridge ("Catalogue of the Library of Charles + Darwin now in the Botany School, Cambridge". Compiled by H.W. Rutherford; + with an introduction by Francis Darwin. Cambridge, 1908.)) appears to have + been admirably selected, and in all probability contained (in addition to + a good many works relating to South America) a fair number of excellent + books of reference. Among those relating to mineralogy, he possessed the + manuals of Phillips, Alexander Brongniart, Beudant, von Kobell and + Jameson: all the "Cristallographie" of Brochant de Villers and, for + blowpipe work, Dr Children's translation of the book of Berzelius on the + subject. In addition to these, he had Henry's "Experimental Chemistry" and + Ure's "Dictionary" (of Chemistry). A work, he evidently often employed, + was P. Syme's book on "Werner's Nomenclature of Colours"; while, for + Petrology, he used Macculloch's "Geological Classification of Rocks". How + diligently and well he employed his instruments and books is shown by the + valuable observations recorded in the annotated Catalogues drawn up on + board ship. + </p> + <p> + These catalogues have on the right-hand pages numbers and descriptions of + the specimens, and on the opposite pages notes on the specimens—the + result of experiments made at the time and written in a very small hand. + Of the subsequently made pencil notes, I shall have to speak later. (I am + greatly indebted to my friend Mr A. Harker, F.R.S., for his assistance in + examining these specimens and catalogues. He has also arranged the + specimens in the Sedgwick Museum, so as to make reference to them easy. + The specimens from Ascension and a few others are however in the Museum at + Jermyn Street.) + </p> + <p> + It is a question of great interest to determine the period and the + occasion of Darwin's first awakening to the great problem of the + transmutation of species. He tells us himself that his grandfather's + "Zoonomia" had been read by him "but without producing any effect," and + that his friend Grant's rhapsodies on Lamarck and his views on evolution + only gave rise to "astonishment." ("L.L." I. page 38.) + </p> + <p> + Huxley, who had probably never seen the privately printed volume of + letters to Henslow, expressed the opinion that Darwin could not have + perceived the important bearing of his discovery of bones in the Pampean + Formation, until they had been studied in England, and their analogies + pronounced upon by competent comparative anatomists. And this seemed to be + confirmed by Darwin's own entry in his pocket-book for 1837, "In July + opened first notebook on Transmutation of Species. Had been greatly struck + from about the month of previous March on character of South American + fossils... " ("L.L." I. page 276.) + </p> + <p> + The second volume of Lyell's "Principles of Geology" was published in + January, 1832, and Darwin's copy (like that of the other two volumes, in a + sadly dilapidated condition from constant use) has in it the inscription, + "Charles Darwin, Monte Video. Nov. 1832." As everyone knows, Darwin in + dedicating the second edition of his Journal of the Voyage to Lyell + declared, "the chief part of whatever scientific merit this journal and + the other works of the author may possess, has been derived from studying + the well-known and admirable 'Principles of Geology'". + </p> + <p> + In the first chapter of this second volume of the "Principles", Lyell + insists on the importance of the species question to the geologist, but + goes on to point out the difficulty of accepting the only serious attempt + at a transmutation theory which had up to that time appeared—that of + Lamarck. In subsequent chapters he discusses the questions of the + modification and variability of species, of hybridity, and of the + geographical distribution of plants and animals. He then gives vivid + pictures of the struggle for existence, ever going on between various + species, and of the causes which lead to their extinction—not by + overwhelming catastrophes, but by the silent and almost unobserved action + of natural causes. This leads him to consider theories with regard to the + introduction of new species, and, rejecting the fanciful notions of + "centres or foci of creation," he argues strongly in favour of the view, + as most reconcileable with observed facts, that "each species may have had + its origin in a single pair, or individual, where an individual was + sufficient, and species may have been created in succession at such times + and in such places as to enable them to multiply and endure for an + appointed period, and occupy an appointed space on the globe." + ("Principles of Geology", Vol. II. (1st edition 1832), page 124. We now + know, as has been so well pointed out by Huxley, that Lyell, as early as + 1827, was prepared to accept the doctrine of the transmutation of species. + In that year he wrote to Mantell, "What changes species may really + undergo! How impossible will it be to distinguish and lay down a line, + beyond which some of the so-called extinct species may have never passed + into recent ones" (Lyell's "Life and Letters" Vol. I. page 168). To Sir + John Herschel in 1836, he wrote, "In regard to the origination of new + species, I am very glad to find that you think it probable that it may be + carried on through the intervention of intermediate causes. I left this + rather to be inferred, not thinking it worth while to offend a certain + class of persons by embodying in words what would only be a speculation" + (Ibid. page 467). He expressed the same views to Whewell in 1837 (Ibid. + Vol. II. page 5.), and to Sedgwick (Ibid. Vol. II. page 36) to whom he + says, of "the theory, that the creation of new species is going on at the + present day"—"I really entertain it," but "I have studiously avoided + laying the doctrine down dogmatically as capable of proof" (see Huxley in + "L.L." II. pages 190-195.)) + </p> + <p> + After pointing out how impossible it would be for a naturalist to prove + that a newly DISCOVERED species was really newly CREATED (Mr F. Darwin has + pointed out that his father (like Lyell) often used the term "Creation" in + speaking of the origin of new species ("L.L." II. chapter 1.)), Lyell + argued that no satisfactory evidence OF THE WAY in which these new forms + were created, had as yet been discovered, but that he entertained the hope + of a possible solution of the problem being found in the study of the + geological record. + </p> + <p> + It is not difficult, in reading these chapters of Lyell's great work, to + realise what an effect they would have on the mind of Darwin, as new facts + were collected and fresh observations concerning extinct and recent forms + were made in his travels. We are not surprised to find him writing home, + "I am become a zealous disciple of Mr Lyell's views, as known in his + admirable book. Geologising in South America, I am tempted to carry parts + to a greater extent even than he does." ("L.L." I. page 263.) + </p> + <p> + Lyell's anticipation that the study of the geological record might afford + a clue to the discovery of how new species originate was remarkably + fulfilled, within a few months, by Darwin's discovery of fossil bones in + the red Pampean mud. + </p> + <p> + It is very true that, as Huxley remarked, Darwin's knowledge of + comparative anatomy must have been, at that time, slight; but that he + recognised the remarkable resemblances between the extinct and existing + mammals of South America is proved beyond all question by a passage in his + letter to Henslow, written November 24th, 1832: "I have been very lucky + with fossil bones; I have fragments of at least six distinct animals... I + found a large surface of osseous polygonal plates... Immediately I saw + them I thought they must belong to an enormous armadillo, living species + of which genus are so abundant here," and he goes on to say that he has + "the lower jaw of some large animal which, from the molar teeth, I should + think belonged to the Edentata." ("M.L." I. pages 11, 12. See "Extracts of + Letters addressed to Prof. Henslow by C. Darwin" (1835), page 7.) + </p> + <p> + Having found this important clue, Darwin followed it up with + characteristic perseverance. In his quest for more fossil bones he was + indefatigable. Mr Francis Darwin tells us, "I have often heard him speak + of the despair with which he had to break off the projecting extremity of + a huge, partly excavated bone, when the boat waiting for him would wait no + longer." ("L.L." I. page 276 (footnote).) Writing to Haeckel in 1864, + Darwin says: "I shall never forget my astonishment when I dug out a + gigantic piece of armour, like that of the living armadillo." (Haeckel, + "History of Creation", Vol. I. page 134, London, 1876.) + </p> + <p> + In a letter to Henslow in 1834 Darwin says: "I have just got scent of some + fossil bones... what they may be I do not know, but if gold or galloping + will get them they shall be mine." ("M.L." I. page 15.) + </p> + <p> + Darwin also showed his sense of the importance of the discovery of these + bones by his solicitude about their safe arrival and custody. From the + Falkland Isles (March, 1834), he writes to Henslow: "I have been alarmed + by your expression 'cleaning all the bones' as I am afraid the printed + numbers will be lost: the reason I am so anxious they should not be, is, + that a part were found in a gravel with recent shells, but others in a + very different bed. Now with these latter there were bones of an Agouti, a + genus of animals, I believe, peculiar to America, and it would be curious + to prove that some one of the genus co-existed with the Megatherium: such + and many other points depend on the numbers being carefully preserved." + ("Extracts from Letters etc.", pages 13-14.) In the abstract of the notes + read to the Geological Society in 1835, we read: "In the gravel of + Patagonia he (Darwin) also found many bones of the Megatherium and of five + or six other species of quadrupeds, among which he has detected the bones + of a species of Agouti. He also met with several examples of the polygonal + plates, etc." ("Proc. Geol. Soc." Vol. II. pages 211-212.) + </p> + <p> + Darwin's own recollections entirely bear out the conclusion that he fully + recognised, WHILE IN SOUTH AMERICA, the wonderful significance of the + resemblances between the extinct and recent mammalian faunas. He wrote in + his "Autobiography": "During the voyage of the 'Beagle' I had been deeply + impressed by discovering in the Pampean formation great fossil animals + covered with armour like that on the existing armadillos." ("L.L." I. page + 82.) + </p> + <p> + The impression made on Darwin's mind by the discovery of these fossil + bones, was doubtless deepened as, in his progress southward from Brazil to + Patagonia, he found similar species of Edentate animals everywhere + replacing one another among the living forms, while, whenever fossils + occurred, they also were seen to belong to the same remarkable group of + animals. (While Darwin was making these observations in South America, a + similar generalisation to that at which he arrived was being reached, + quite independently and almost simultaneously, with respect to the fossil + and recent mammals of Australia. In the year 1831, Clift gave to Jameson a + list of bones occurring in the caves and breccias of Australia, and in + publishing this list the latter referred to the fact that the forms + belonged to marsupials, similar to those of the existing Australian fauna. + But he also stated that, as a skull had been identified (doubtless + erroneously) as having belonged to a hippopotamus, other mammals than + marsupials must have spread over the island in late Tertiary times. It is + not necessary to point out that this paper was quite unknown to Darwin + while in South America. Lyell first noticed it in the third edition of his + "Principles", which was published in May, 1834 (see "Edinb. New Phil. + Journ." Vol. X. (1831), pages 394-6, and Lyell's "Principles" (3rd + edition), Vol. III. page 421). Darwin referred to this discovery in 1839 + (see his "Journal", page 210.)) + </p> + <p> + That the passage in Darwin's pocket-book for 1837 can only refer to an + AWAKENING of Darwin's interest in the subject—probably resulting + from a sight of the bones when they were being unpacked—I think + there cannot be the smallest doubt; AND WE MAY THEREFORE CONFIDENTLY FIX + UPON NOVEMBER, 1832, AS THE DATE AT WHICH DARWIN COMMENCED THAT LONG + SERIES OF OBSERVATIONS AND REASONINGS WHICH EVENTUALLY CULMINATED IN THE + PREPARATION OF THE "ORIGIN OF SPECIES". Equally certain is it, that it was + his geological work that led Darwin into those paths of research which in + the end conducted him to his great discoveries. I quite agree with the + view expressed by Mr F. Darwin and Professor Seward, that Darwin, like + Lyell, "thought it 'almost useless' to try to prove the truth of evolution + until the cause of change was discovered" ("M.L." I. page 38.), and that + possibly he may at times have vacillated in his opinions, but I believe + there is evidence that, from the date mentioned, the "species question" + was always more or less present in Darwin's mind. (Although we admit with + Huxley that Darwin's training in comparative anatomy was very small, yet + it may be remembered that he was a medical student for two years, and, if + he hated the lectures, he enjoyed the society of naturalists. He had with + him in the little "Beagle" library a fair number of zoological books, + including works on Osteology by Cuvier, Desmarest and Lesson, as well as + two French Encyclopaedias of Natural History. As a sportsman, he would + obtain specimens of recent mammals in South America, and would thus have + opportunities of studying their teeth and general anatomy. Keen observer, + as he undoubtedly was, we need not then be surprised that he was able to + make out the resemblances between the recent and fossil forms.) + </p> + <p> + It is clear that, as time went on, Darwin became more and more absorbed in + his geological work. One very significant fact was that the once ardent + sportsman, when he found that shooting the necessary game and zoological + specimens interfered with his work with the hammer, gave up his gun to his + servant. ("L.L." I. page 63.) There is clear evidence that Darwin + gradually became aware how futile were his attempts to add to zoological + knowledge by dissection and drawing, while he felt ever increasing + satisfaction with his geological work. + </p> + <p> + The voyage fortunately extended to a much longer period (five years) than + the two originally intended, but after being absent nearly three years, + Darwin wrote to his sister in November, 1834, "Hurrah! hurrah! it is fixed + that the 'Beagle' shall not go one mile south of Cape Tres Montes (about + 200 miles south of Chiloe), and from that point to Valparaiso will be + finished in about five months. We shall examine the Chonos Archipelago, + entirely unknown, and the curious inland sea behind Chiloe. For me it is + glorious. Cape Tres Montes is the most southern point where there is much + geological interest, as there the modern beds end. The Captain then talks + of crossing the Pacific; but I think we shall persuade him to finish the + coast of Peru, where the climate is delightful, the country hideously + sterile, but abounding with the highest interest to the geologist... I + have long been grieved and most sorry at the interminable length of the + voyage (though I never would have quitted it)... I could not make up my + mind to return. I could not give up all the geological castles in the air + I had been building up for the last two years." ("L.L." I. pages 257-58.) + </p> + <p> + In April, 1835, he wrote to another sister: "I returned a week ago from my + excursion across the Andes to Mendoza. Since leaving England I have never + made so successful a journey... how deeply I have enjoyed it; it was + something more than enjoyment; I cannot express the delight which I felt + at such a famous winding-up of all my geology in South America. I + literally could hardly sleep at nights for thinking over my day's work. + The scenery was so new, and so majestic; everything at an elevation of + 12,000 feet bears so different an aspect from that in the lower country... + To a geologist, also, there are such manifest proofs of excessive + violence; the strata of the highest pinnacles are tossed about like the + crust of a broken pie." ("L.L." I. pages 259-60.) + </p> + <p> + Darwin anticipated with intense pleasure his visit to the Galapagos + Islands. On July 12th, 1835, he wrote to Henslow: "In a few days' time the + "Beagle" will sail for the Galapagos Islands. I look forward with joy and + interest to this, both as being somewhat nearer to England and for the + sake of having a good look at an active volcano. Although we have seen + lava in abundance, I have never yet beheld the crater." ("M.L." I. page + 26.) He could little anticipate, as he wrote these lines, the important + aid in the solution of the "species question" that would ever after make + his visit to the Galapagos Islands so memorable. In 1832, as we have seen, + the great discovery of the relations of living to extinct mammals in the + same area had dawned upon his mind; in 1835 he was to find a second key + for opening up the great mystery, by recognising the variations of similar + types in adjoining islands among the Galapagos. + </p> + <p> + The final chapter in the second volume of the "Principles" had aroused in + Darwin's mind a desire to study coral-reefs, which was gratified during + his voyage across the Pacific and Indian Oceans. His theory on the subject + was suggested about the end of 1834 or the beginning of 1835, as he + himself tells us, before he had seen a coral-reef, and resulted from his + work during two years in which he had "been incessantly attending to the + effects on the shores of South America of the intermittent elevation of + the land, together with denudation and the deposition of sediment." + ("L.L." I. page 70.) + </p> + <p> + On arriving at the Cape of Good Hope in July, 1836, Darwin was greatly + gratified by hearing that Sedgwick had spoken to his father in high terms + of praise concerning the work done by him in South America. Referring to + the news from home, when he reached Bahia once more, on the return voyage + (August, 1836), he says: "The desert, volcanic rocks, and wild sea of + Ascension... suddenly wore a pleasing aspect, and I set to work with a + good-will at my old work of Geology." ("L.L." I. page 265.) Writing fifty + years later, he says: "I clambered over the mountains of Ascension with a + bounding step and made the volcanic rocks resound under my geological + hammer!" ("L.L." I. page 66.) + </p> + <p> + That his determination was now fixed to devote his own labours to the task + of working out the geological results of the voyage, and that he was + prepared to leave to more practised hands the study of his biological + collections, is clear from the letters he sent home at this time. From St + Helena he wrote to Henslow asking that he would propose him as a Fellow of + the Geological Society; and his Certificate, in Henslow's handwriting, is + dated September 8th, 1836, being signed from personal knowledge by Henslow + and Sedgwick. He was proposed on November 2nd and elected November 30th, + being formally admitted to the Society by Lyell, who was then President, + on January 4th, 1837, on which date he also read his first paper. Darwin + did not become a Fellow of the Linnean Society till eighteen years later + (in 1854). + </p> + <p> + An estimate of the value and importance of Darwin's geological discoveries + during the voyage of the "Beagle" can best be made when considering the + various memoirs and books in which the author described them. He was too + cautious to allow himself to write his first impressions in his Journal, + and wisely waited till he could study his specimens under better + conditions and with help from others on his return. The extracts published + from his correspondence with Henslow and others, while he was still + abroad, showed, nevertheless, how great was the mass of observation, how + suggestive and pregnant with results were the reasonings of the young + geologist. + </p> + <p> + Two sets of these extracts from Darwin's letters to Henslow were printed + while he was still abroad. The first of these was the series of + "Geological Notes made during a survey of the East and West Coasts of + South America, in the years 1832, 1833, 1834 and 1835, with an account of + a transverse section of the Cordilleras of the Andes between Valparaiso + and Mendoza". Professor Sedgwick, who read these notes to the Geological + Society on November 18th, 1835, stated that "they were extracted from a + series of letters (addressed to Professor Henslow), containing a great + mass of information connected with almost every branch of natural + history," and that he (Sedgwick) had made a selection of the remarks which + he thought would be more especially interesting to the Geological Society. + An abstract of three pages was published in the "Proceedings of the + Geological Society" (Vol. II. pages 210-12.), but so unknown was the + author at this time that he was described as F. Darwin, Esq., of St John's + College, Cambridge! Almost simultaneously (on November 16th, 1835) a + second set of extracts from these letters—this time of a general + character—were read to the Philosophical Society at Cambridge, and + these excited so much interest that they were privately printed in + pamphlet form for circulation among the members. + </p> + <p> + Many expeditions and "scientific missions" have been despatched to various + parts of the world since the return of the "Beagle" in 1836, but it is + doubtful whether any, even the most richly endowed of them, has brought + back such stores of new information and fresh discoveries as did that + little "ten-gun brig"—certainly no cabin or laboratory was the + birth-place of ideas of such fruitful character as was that narrow end of + a chart-room, where the solitary naturalist could climb into his hammock + and indulge in meditation. + </p> + <p> + The third and most active portion of Darwin's career as a geologist was + the period which followed his return to England at the end of 1836. His + immediate admission to the Geological Society, at the beginning of 1837, + coincided with an important crisis in the history of geological science. + </p> + <p> + The band of enthusiasts who nearly thirty years before had inaugurated the + Geological Society—weary of the fruitless conflicts between + "Neptunists" and "Plutonists"—had determined to eschew theory and + confine their labours to the collection of facts, their publications to + the careful record of observations. Greenough, the actual founder of the + Society, was an ardent Wernerian, and nearly all his fellow-workers had + come, more or less directly, under the Wernerian teaching. Macculloch + alone gave valuable support to the Huttonian doctrines, so far as they + related to the influence of igneous activity—but the most important + portion of the now celebrated "Theory of the Earth"—that dealing + with the competency of existing agencies to account for changes in past + geological times—was ignored by all alike. Macculloch's influence on + the development of geology, which might have had far-reaching effects, was + to a great extent neutralised by his peculiarities of mind and temper; + and, after a stormy and troublous career, he retired from the society in + 1832. In all the writings of the great pioneers in English geology, Hutton + and his splendid generalisation are scarcely ever referred to. The great + doctrines of Uniformitarianism, which he had foreshadowed, were completely + ignored, and only his extravagances of "anti-Wernerianism" seem to have + been remembered. + </p> + <p> + When between 1830 and 1832, Lyell, taking up the almost forgotten ideas of + Hutton, von Hoff and Prevost, published that bold challenge to the + Catastrophists—the "Principles of Geology"—he was met with the + strongest opposition, not only from the outside world, which was amused by + his "absurdities" and shocked by his "impiety"—but not less from his + fellow-workers and friends in the Geological Society. For Lyell's numerous + original observations, and his diligent collection of facts his + contemporaries had nothing but admiration, and they cheerfully admitted + him to the highest offices in the society, but they met his reasonings on + geological theory with vehement opposition and his conclusions with + coldness and contempt. + </p> + <p> + There is, indeed, a very striking parallelism between the reception of the + "Principles of Geology" by Lyell's contemporaries and the manner in which + the "Origin of Species" was met a quarter of a century later, as is so + vividly described by Huxley. ("L.L." II. pages 179-204.) Among Lyell's + fellow-geologists, two only—G. Poulett Scrope and John Herschel + (Both Lyell and Darwin fully realised the value of the support of these + two friends. Scrope in his appreciative reviews of the "Principles" justly + pointed out what was the weakest point, the inadequate recognition of + sub-aerial as compared with marine denudation. Darwin also admitted that + Scrope had to a great extent forestalled him in his theory of Foliation. + Herschel from the first insisted that the leading idea of the "Principles" + must be applied to organic as well as to inorganic nature and must explain + the appearance of new species (see Lyell's "Life and Letters", Vol. I. + page 467). Darwin tells us that Herschel's "Introduction to the Study of + Natural Philosophy" with Humboldt's "Personal Narrative" "stirred up in me + a burning zeal" in his undergraduate days. I once heard Lyell exclaim with + fervour "If ever there was a heaven-born genius it was John Herschel!")—declared + themselves from the first his strong supporters. Scrope in two luminous + articles in the "Quarterly Review" did for Lyell what Huxley accomplished + for Darwin in his famous review in the "Times"; but Scrope unfortunately + was at that time immersed in the stormy sea of politics, and devoted his + great powers of exposition to the preparation of fugitive pamphlets. + Herschel, like Scrope, was unable to support Lyell at the Geological + Society, owing to his absence on the important astronomical mission to the + Cape. + </p> + <p> + It thus came about that, in the frequent conflicts of opinion within the + walls of the Geological Society, Lyell had to bear the brunt of battle for + Uniformitarianism quite alone, and it is to be feared that he found + himself sadly overmatched when opposed by the eloquence of Sedgwick, the + sarcasm of Buckland, and the dead weight of incredulity on the part of + Greenough, Conybeare, Murchison and other members of the band of pioneer + workers. As time went on there is evidence that the opposition of De la + Beche and Whewell somewhat relaxed; the brilliant "Paddy" Fitton (as his + friends called him) was sometimes found in alliance with Lyell, but was + characteristically apt to turn his weapon, as occasion served, on friend + or foe alike; the amiable John Phillips "sat upon the fence." Only when a + new generation arose—including Jukes, Ramsay, Forbes and Hooker—did + Lyell find his teachings received with anything like favour. + </p> + <p> + We can well understand, then, how Lyell would welcome such a recruit as + young Darwin—a man who had declared himself more Lyellian than + Lyell, and who brought to his support facts and observations gleaned from + so wide a field. + </p> + <p> + The first meeting of Lyell and Darwin was characteristic of the two men. + Darwin at once explained to Lyell that, with respect to the origin of + coral-reefs, he had arrived at views directly opposed to those published + by "his master." To give up his own theory, cost Lyell, as he told + Herschel, a "pang at first," but he was at once convinced of the + immeasurable superiority of Darwin's theory. I have heard members of + Lyell's family tell of the state of wild excitement and sustained + enthusiasm, which lasted for days with Lyell after this interview, and his + letters to Herschel, Whewell and others show his pleasure at the new light + thrown upon the subject and his impatience to have the matter laid before + the Geological Society. + </p> + <p> + Writing forty years afterwards, Darwin, speaking of the time of the return + of the "Beagle", says: "I saw a great deal of Lyell. One of his chief + characteristics was his sympathy with the work of others, and I was as + much astonished as delighted at the interest which he showed when, on my + return to England, I explained to him my views on coral-reefs. This + encouraged me greatly, and his advice and example had much influence on + me." ("L.L." I. page 68.) Darwin further states that he saw more of Lyell + at this time than of any other scientific man, and at his request sent his + first communication to the Geological Society. ("L.L." I. page 67.) + </p> + <p> + "Mr Lonsdale" (the able curator of the Geological Society), Darwin wrote + to Henslow, "with whom I had much interesting conversation," "gave me a + most cordial reception," and he adds, "If I was not much more inclined for + geology than the other branches of Natural History, I am sure Mr Lyell's + and Lonsdale's kindness ought to fix me. You cannot conceive anything more + thoroughly good-natured than the heart-and-soul manner in which he put + himself in my place and thought what would be best to do." ("L.L." I. page + 275.) + </p> + <p> + Within a few days of Darwin's arrival in London we find Lyell writing to + Owen as follows: + </p> + <p> + "Mrs Lyell and I expect a few friends here on Saturday next, 29th + (October), to an early tea party at eight o'clock, and it will give us + great pleasure if you can join it. Among others you will meet Mr Charles + Darwin, whom I believe you have seen, just returned from South America, + where he has laboured for zoologists as well as for hammer-bearers. I have + also asked your friend Broderip." ("The Life of Richard Owen", London, + 1894, Vol. I. page 102.) It would probably be on this occasion that the + services of Owen were secured for the work on the fossil bones sent home + by Darwin. + </p> + <p> + On November 2nd, we find Lyell introducing Darwin as his guest at the + Geological Society Club; on December 14th, Lyell and Stokes proposed + Darwin as a member of the Club; between that date and May 3rd of the + following year, when his election to the Club took place, he was several + times dining as a guest. + </p> + <p> + On January 4th, 1837, as we have already seen, Darwin was formally + admitted to the Geological Society, and on the same evening he read his + first paper (I have already pointed out that the notes read at the + Geological Society on Nov. 18, 1835 were extracts made by Sedgwick from + letters sent to Henslow, and not a paper sent home for publication by + Darwin.) before the Society, "Observations of proofs of recent elevation + on the coast of Chili, made during the Survey of H.M.S. "Beagle", + commanded by Captain FitzRoy, R.N." By C. Darwin, F.G.S. This paper was + preceded by one on the same subject by Mr A. Caldcleugh, and the reading + of a letter and other communications from the Foreign Office also relating + to the earthquakes in Chili. + </p> + <p> + At the meeting of the Council of the Geological Society on February 1st, + Darwin was nominated as a member of the new Council, and he was elected on + February 17th. + </p> + <p> + The meeting of the Geological Society on April 19th was devoted to the + reading by Owen of his paper on Toxodon, perhaps the most remarkable of + the fossil mammals found by Darwin in South America; and at the next + meeting, on May 3rd, Darwin himself read "A Sketch of the Deposits + containing extinct Mammalia in the neighbourhood of the Plata". The next + following meeting, on May 17th, was devoted to Darwin's Coral-reef paper, + entitled "On certain areas of elevation and subsidence in the Pacific and + Indian Oceans, as deduced from the study of Coral Formations". Neither of + these three early papers of Darwin were published in the Transactions of + the Geological Society, but the minutes of the Council show that they were + "withdrawn by the author by permission of the Council." + </p> + <p> + Darwin's activity during this session led to some rather alarming effects + upon his health, and he was induced to take a holiday in Staffordshire and + the Isle of Wight. He was not idle, however, for a remark of his uncle, Mr + Wedgwood, led him to make those interesting observations on the work done + by earthworms, that resulted in his preparing a short memoir on the + subject, and this paper, "On the Formation of Mould", was read at the + Society on November 1st, 1837, being the first of Darwin's papers + published in full; it appeared in Vol. V. of the "Geological + Transactions", pages 505-510. + </p> + <p> + During this session, Darwin attended nearly all the Council meetings, and + took such an active part in the work of the Society that it is not + surprising to find that he was now requested to accept the position of + Secretary. After some hesitation, in which he urged his inexperience and + want of knowledge of foreign languages, he consented to accept the + appointment. ("L.L." I. page 285.) + </p> + <p> + At the anniversary meeting on February 16th, 1838, the Wollaston Medal was + given to Owen in recognition of his services in describing the fossil + mammals sent home by Darwin. In his address, the President, Professor + Whewell, dwelt at length on the great value of the papers which Darwin had + laid before the Society during the preceding session. + </p> + <p> + On March 7th, Darwin read before the Society the most important perhaps of + all his geological papers, "On the Connexion of certain Volcanic Phenomena + in South America, and on the Formation of Mountain-Chains and Volcanoes as + the effect of Continental Elevations". In this paper he boldly attacked + the tenets of the Catastrophists. It is evident that Darwin at this time, + taking advantage of the temporary improvement in his health, was throwing + himself into the breach of Uniformitarianism with the greatest ardour. + Lyell wrote to Sedgwick on April 21st, 1837, "Darwin is a glorious + addition to any society of geologists, and is working hard and making way, + both in his book and in our discussions." ("The Life and Letters of the + Reverend Adam Sedgwick", Vol. I. page 484, Cambridge, 1890.) + </p> + <p> + We have unfortunately few records of the animated debates which took place + at this time between the old and new schools of geologists. I have often + heard Lyell tell how Lockhart would bring down a party of friends from the + Athenaeum Club to Somerset House on Geological nights, not, as he + carefully explained, that "he cared for geology, but because he liked to + while the fellows fight." But it fortunately happens that a few days after + this last of Darwin's great field-days, at the Geological Society, Lyell, + in a friendly letter to his father-in-law, Leonard Horner, wrote a very + lively account of the proceedings while his impressions were still fresh; + and this gives us an excellent idea of the character of these discussions. + </p> + <p> + Neither Sedgwick nor Buckland were present on this occasion, but we can + imagine how they would have chastised their two "erring pupils"—more + in sorrow than in anger—had they been there. Greenough, too, was + absent—possibly unwilling to countenance even by his presence such + outrageous doctrines. + </p> + <p> + Darwin, after describing the great earthquakes which he had experienced in + South America, and the evidence of their connection with volcanic + outbursts, proceeded to show that earthquakes originated in fractures, + gradually formed in the earth's crust, and were accompanied by movements + of the land on either side of the fracture. In conclusion he boldly + advanced the view "that continental elevations, and the action of + volcanoes, are phenomena now in progress, caused by some great but slow + change in the interior of the earth; and, therefore, that it might be + anticipated, that the formation of mountain chains is likewise in + progress: and at a rate which may be judged of by either actions, but most + clearly by the growth of volcanoes." ("Proc. Geol. Soc." Vol. II. pages + 654-60.) + </p> + <p> + Lyell's account ("Life, Letters and Journals of Sir Charles Lyell, Bart.", + edited by his sister-in-law, Mrs Lyell, Vol. II. pages 40, 41 (Letter to + Leonard Horner, 1838), 2 vols. London, 1881.) of the discussion was as + follows: "In support of my heretical notions," Darwin "opened upon De la + Beche, Phillips and others his whole battery of the earthquakes and + volcanoes of the Andes, and argued that spaces at least a thousand miles + long were simultaneously subject to earthquakes and volcanic eruptions, + and that the elevation of the Pampas, Patagonia, etc., all depended on a + common cause; also that the greater the contortions of strata in a + mountain chain, the smaller must have been each separate and individual + movement of that long series which was necessary to upheave the chain. Had + they been more violent, he contended that the subterraneous fluid matter + would have gushed out and overflowed, and the strata would have been blown + up and annihilated. (It is interesting to compare this with what Darwin + wrote to Henslow seven years earlier.) He therefore introduces a cooling + of one small underground injection, and then the pumping in of other lava, + or porphyry, or granite, into the previously consolidated and first-formed + mass of igneous rock. (Ideas somewhat similar to this suggestion have + recently been revived by Dr See ("Proc. Am. Phil. Soc." Vol. XLVII. 1908, + page 262.).) When he had done his description of the reiterated strokes of + his volcanic pump, De la Beche gave us a long oration about the + impossibility of strata of the Alps, etc., remaining flexible for such a + time as they must have done, if they were to be tilted, convoluted, or + overturned by gradual small shoves. He never, however, explained his + theory of original flexibility, and therefore I am as unable as ever to + comprehend why flexiblility is a quality so limited in time. + </p> + <p> + "Phillips then got up and pronounced a panegyric upon the "Principles of + Geology", and although he still differed, thought the actual cause + doctrine had been so well put, that it had advanced the science and formed + a date or era, and that for centuries the two opposite doctrines would + divide geologists, some contending for greater pristine forces, others + satisfied, like Lyell and Darwin, with the same intensity as nature now + employs. + </p> + <p> + "Fitton quizzed Phillips a little for the warmth of his eulogy, saying + that he (Fitton) and others, who had Mr Lyell always with them, were in + the habit of admiring and quarrelling with him every day, as one might do + with a sister or cousin, whom one would only kiss and embrace fervently + after a long absence. This seemed to be Mr Phillips' case, coming up + occasionally from the provinces. Fitton then finished this drollery by + charging me with not having done justice to Hutton, who he said was for + gradual elevation. + </p> + <p> + "I replied, that most of the critics had attacked me for overrating + Hutton, and that Playfair understood him as I did. + </p> + <p> + "Whewell concluded by considering Hopkins' mathematical calculations, to + which Darwin had often referred. He also said that we ought not to try and + make out what Hutton would have taught and thought, if he had known the + facts which we now know." + </p> + <p> + It may be necessary to point out, in explanation of the above narrative, + that while it was perfectly clear from Hutton's rather obscure and + involved writings that he advocated slow and gradual change on the earth's + surface, his frequent references to violent action and earthquakes led + many—including Playfair, Lyell and Whewell—to believe that he + held the changes going on in the earth's interior to be of a catastrophic + nature. Fitton, however, maintained that Hutton was consistently + uniformitarian. Before the idea of the actual "flowing" of solid bodies + under intense pressure had been grasped by geologists, De la Beche, like + Playfair before him, maintained that the bending and folding of rocks must + have been effected before their complete consolidation. + </p> + <p> + In concluding his account of this memorable discussion, Lyell adds: "I was + much struck with the different tone in which my gradual causes was treated + by all, even including De la Beche, from that which they experienced in + the same room four years ago, when Buckland, De la Beche(?), Sedgwick, + Whewell, and some others treated them with as much ridicule as was + consistent with politeness in my presence." + </p> + <p> + This important paper was, in spite of its theoretical character, published + in full in the "Transactions of the Geological Society" (Ser. 2, Vol. V. + pages 601-630). It did not however appear till 1840, and possibly some + changes may have been made in it during the long interval between reading + and printing. During the year 1839, Darwin continued his regular + attendance at the Council meetings, but there is no record of any + discussions in which he may have taken part, and he contributed no papers + himself to the Society. At the beginning of 1840, he was re-elected for + the third time as Secretary, but the results of failing health are + indicated by the circumstance that, only at one meeting early in the + session, was he able to attend the Council. At the beginning of the next + session (Feb. 1841) Bunbury succeeded him as Secretary, Darwin still + remaining on the Council. It may be regarded as a striking indication of + the esteem in which he was held by his fellow geologists, that Darwin + remained on the Council for 14 consecutive years down to 1849, though his + attendances were in some years very few. In 1843 and 1844 he was a + Vice-president, but after his retirement at the beginning of 1850, he + never again accepted re-nomination. He continued, however, to contribute + papers to the Society, as we shall see, down to the end of 1862. + </p> + <p> + Although Darwin early became a member of the Geological Dining Club, it is + to be feared that he scarcely found himself in a congenial atmosphere at + those somewhat hilarious gatherings, where the hardy wielders of the + hammer not only drank port—and plenty of it—but wound up their + meal with a mixture of Scotch ale and soda water, a drink which, as + reminiscent of the "field," was regarded as especially appropriate to + geologists. Even after the meetings, which followed the dinners, they + reassembled for suppers, at which geological dainties, like "pterodactyle + pie" figured in the bill of fare, and fines of bumpers were inflicted on + those who talked the "ologies." + </p> + <p> + After being present at a fair number of meetings in 1837 and 1838, + Darwin's attendances at the Club fell off to two in 1839, and by 1841 he + had ceased to be a member. In a letter to Lyell on Dec. 2nd, 1841, Leonard + Horner wrote that the day before "At the Council, I had the satisfaction + of seeing Darwin again in his place and looking well. He tried the last + evening meeting, but found it too much, but I hope before the end of the + season he will find himself equal to that also. I hail Darwin's recovery + as a vast gain to science." Darwin's probably last attendance, this time + as a guest, was in 1851, when Horner again wrote to Lyell, "Charles Darwin + was at the Geological Society's Club yesterday, where he had not been for + ten years—remarkably well, and grown quite stout." ("Memoirs of + Leonard Horner" (privately printed), Vol. II. pages 39 and 195.) + </p> + <p> + It may be interesting to note that at the somewhat less lively dining Club—the + Philosophical—in the founding of which his friends Lyell and Hooker + had taken so active a part, Darwin found himself more at home, and he was + a frequent attendant—in spite of his residence being at Down—from + 1853 to 1864. He even made contributions on scientific questions after + these dinners. In a letter to Hooker he states that he was deeply + interested in the reforms of the Royal Society, which the Club was founded + to promote. He says also that he had arranged to come to town every Club + day "and then my head, I think, will allow me on an average to go to every + other meeting. But it is grievous how often any change knocks me up." + ("L.L." II. pages 42, 43.) + </p> + <p> + Of the years 1837 and 1838 Darwin himself says they were "the most active + ones which I ever spent, though I was occasionally unwell, and so lost + some time... I also went a little into society." ("L.L." I. pages 67, 68.) + But of the four years from 1839 to 1842 he has to confess sadly "I did + less scientific work, though I worked as hard as I could, than during any + other equal length of time in my life. This was owing to frequently + recurring unwellness, and to one long and serious illness." ("L.L." I. + page 69.) + </p> + <p> + Darwin's work at the Geological Society did not by any means engage the + whole of his energies, during the active years 1837 and 1838. In June of + the latter year, leaving town in somewhat bad health, he found himself at + Edinburgh again, and engaged in examining the Salisbury Craigs, in a very + different spirit to that excited by Jameson's discourse. ("L.L." I. page + 290.) Proceeding to the Highlands he then had eight days of hard work at + the famous "Parallel Roads of Glen Roy", being favoured with glorious + weather. + </p> + <p> + He says of the writing of the paper on the subject—the only memoir + contributed by Darwin to the Royal Society, to which he had been recently + elected—that it was "one of the most difficult and instructive tasks + I was ever engaged on." The paper extends to 40 quarto pages and is + illustrated by two plates. Though it is full of the records of careful + observation and acute reasoning, yet the theory of marine beaches which he + propounded was, as he candidly admitted in after years ("M.L." II page + 188.), altogether wrong. The alternative lake-theory he found himself + unable to accept at the time, for he could not understand how barriers + could be formed at successive levels across the valleys; and until the + following year, when the existence of great glaciers in the district was + proved by the researches of Agassiz, Buckland and others, the difficulty + appeared to him an insuperable one. Although Darwin said of this paper in + after years that it "was a great failure and I am ashamed of it"—yet + he retained his interest in the question ever afterwards, and he says "my + error has been a good lesson to me never to trust in science to the + principle of exclusion." ("M.L." II. pages 171-93.) + </p> + <p> + Although Darwin had not realised in 1838 that large parts of the British + Islands had been occupied by great glaciers, he had by no means failed + while in South America to recognise the importance of ice-action. His + observations, as recorded in his Journal, on glaciers coming down to the + sea-level, on the west coast of South America, in a latitude corresponding + to a much lower one than that of the British Islands, profoundly + interested geologists; and the same work contains many valuable notes on + the boulders and unstratified beds in South America in which they were + included. + </p> + <p> + But in 1840 Agassiz read his startling paper on the evidence of the former + existence of glaciers in the British Islands, and this was followed by + Buckland's memoir on the same subject. On April 14, 1841, Darwin + contributed to the Geological Society his important paper "On the + Distribution of Erratic Boulders and the Contemporaneous Unstratified + Deposits of South America", a paper full of suggestiveness for those + studying the glacial deposits of this country. It was published in the + "Transactions" in 1842. + </p> + <p> + The description of traces of glacial action in North Wales, by Buckland, + appears to have greatly excited the interest of Darwin. With Sedgwick he + had, in 1831, worked at the stratigraphy of that district, but neither of + them had noticed the very interesting surface features. ("L.L." I. page + 58.) Darwin was able to make a journey to North Wales in June, 1842 (alas! + it was his last effort in field-geology) and as a result he published his + most able and convincing paper on the subject in the September number of + the "Philosophical Magazine" for 1842. Thus the mystery of the bell-stone + was at last solved and Darwin, writing many years afterwards, said "I felt + the keenest delight when I first read of the action of icebergs in + transporting boulders, and I gloried in the progress of Geology." ("L.L." + I. page 41.) To the "Geographical Journal" he had sent in 1839 a note "On + a Rock seen on an Iceberg in 16 deg S. Latitude." For the subject of + ice-action, indeed, Darwin retained the greatest interest to the end of + his life. ("M.L." II. pages 148-71.) + </p> + <p> + In 1846, Darwin read two papers to the Geological Society "On the dust + which falls on vessels in the Atlantic, and On the Geology of the Falkland + Islands"; in 1848 he contributed a note on the transport of boulders from + lower to higher levels; and in 1862 another note on the thickness of the + Pampean formation, as shown by recent borings at Buenos Ayres. An account + of the "British Fossil Lepadidae" read in 1850, was withdrawn by him. + </p> + <p> + At the end of 1836 Darwin had settled himself in lodgings in Fitzwilliam + Street, Cambridge, and devoted three months to the work of unpacking his + specimens and studying his collection of rocks. The pencilled notes on the + Manuscript Catalogue in the Sedgwick Museum enable us to realise his mode + of work, and the diligence with which it was carried on. The letters M and + H, indicate the assistance he received from time to time from Professor + Miller, the crystallographer, and from his friend Henslow. Miller not only + measured many of the crystals submitted to him, but evidently taught + Darwin to use the reflecting goniometer himself with considerable success. + The "book of measurements" in which the records were kept, appears to have + been lost, but the pencilled notes in the catalogue show how thoroughly + the work was done. The letter R attached to some of the numbers in the + catalogue evidently refers to the fact that they were submitted to Mr + Trenham Reeks (who analysed some of his specimens) at the Geological + Survey quarters in Craig's Court. This was at a later date when Darwin was + writing the "Volcanic Islands" and "South America". + </p> + <p> + It was about the month of March, 1837, that Darwin completed this work + upon his rocks, and also the unpacking and distribution of his fossil + bones and other specimens. We have seen that November, 1832, must + certainly be regarded as the date when he FIRST realised the important + fact that the fossil mammals of the Pampean formation were all closely + related to the existing forms in South America; while October, 1835, was, + as undoubtedly, the date when the study of the birds and other forms of + life in the several islands of the Galapagos Islands gave him his SECOND + impulse towards abandoning the prevalent view of the immutability of + species. When then in his pocket-book for 1837 Darwin wrote the often + quoted passage: "In July opened first note-book on Transmutation of + Species. Had been greatly struck from about the month of previous March on + character of South American fossils, and species on Galapagos Archipelago. + These facts (especially latter), origin of all my views" ("L.L." I. page + 276.), it is clear that he must refer, not to his first inception of the + idea of evolution, but to the flood of recollections, the reawakening of + his interest in the subject, which could not fail to result from the sight + of his specimens and the reference to his notes. + </p> + <p> + Except during the summer vacation, when he was visiting his father and + uncle, and with the latter making his first observations upon the work of + earthworms, Darwin was busy with his arrangements for the publication of + the five volumes of the "Zoology of the 'Beagle'" and in getting the + necessary financial aid from the government for the preparation of the + plates. He was at the same time preparing his "Journal" for publication. + During the years 1837 to 1843, Darwin worked intermittently on the volumes + of Zoology, all of which he edited, while he wrote introductions to those + by Owen and Waterhouse and supplied notes to the others. + </p> + <p> + Although Darwin says of his Journal that the preparation of the book "was + not hard work, as my MS. Journal had been written with care." Yet from the + time that he settled at 36, Great Marlborough Street in March, 1837, to + the following November he was occupied with this book. He tells us that + the account of his scientific observations was added at this time. The + work was not published till March, 1839, when it appeared as the third + volume of the "Narrative of the Surveying Voyages of H.M. Ships + 'Adventure' and 'Beagle' between the years 1826 and 1836". The book was + probably a long time in the press, for there are no less than 20 pages of + addenda in small print. Even in this, its first form, the work is + remarkable for its freshness and charm, and excited a great amount of + attention and interest. In addition to matters treated of in greater + detail in his other works, there are many geological notes of extreme + value in this volume, such as his account of lightning tubes, of the + organisms found in dust, and of the obsidian bombs of Australia. + </p> + <p> + Having thus got out of hand a number of preliminary duties, Darwin was + ready to set to work upon the three volumes which were designed by him to + constitute "The Geology of the Voyage of the 'Beagle'". The first of these + was to be on "The Structure and Distribution of Coral-reefs". He commenced + the writing of the book on October 5, 1838, and the last proof was + corrected on May 6, 1842. Allowing for the frequent interruptions through + illness, Darwin estimated that it cost him twenty months of hard work. + </p> + <p> + Darwin has related how his theory of Coral-reefs which was begun in a more + "deductive spirit" than any of his other work, for in 1834 or 1835 it "was + thought out on the west coast of South America, before I had seen a true + coral-reef." ("L.L." I. page 70.) The final chapter in Lyell's second + volume of the "Principles" was devoted to the subject of Coral-reefs, and + a theory was suggested to account for the peculiar phenomena of "atolls." + Darwin at once saw the difficulty of accepting the view that the numerous + and diverse atolls all represent submerged volcanic craters. His own work + had for two years been devoted to the evidence of land movements over + great areas in South America, and thus he was led to announce his theory + of subsidence to account for barrier and encircling reefs as well as + atolls. + </p> + <p> + Fortunately, during his voyage across the Pacific and Indian Oceans, in + his visit to Australia and his twelve days' hard work at Keeling Island, + he had opportunities for putting his theory to the test of observation. + </p> + <p> + On his return to England, Darwin appears to have been greatly surprised at + the amount of interest that his new theory excited. Urged by Lyell, he + read to the Geological Society a paper on the subject, as we have seen, + with as little delay as possible, but this paper was "withdrawn by + permission of the Council." An abstract of three pages however appeared in + the "Proceedings of the Geological Society". (Vol. II. pages 552-554 (May + 31, 1837).) A full account of the observations and the theory was given in + the "Journal" (1839) in the 40 pages devoted to Keeling Island in + particular and to Coral formations generally. ("Journal" (1st edition), + pages 439-69.) + </p> + <p> + It will be readily understood what an amount of labour the book on Coral + reefs cost Darwin when we reflect on the number of charts, sailing + directions, narratives of voyages and other works which, with the friendly + assistance of the authorities at the Admiralty, he had to consult before + he could draw up his sketch of the nature and distribution of the reefs, + and this was necessary before the theory, in all its important bearings, + could be clearly enunciated. Very pleasing is it to read how Darwin, + although arriving at a different conclusion to Lyell, shows, by quoting a + very suggestive passage in the "Principles" (1st edition Vol. II. page + 296.), how the latter only just missed the true solution. This passage is + cited, both in the "Journal" and the volume on Coral-reefs. Lyell, as we + have seen, received the new theory not merely ungrudgingly, but with the + utmost enthusiasm. + </p> + <p> + In 1849 Darwin was gratified by receiving the support of Dana, after his + prolonged investigation in connection with the U.S. Exploring Expedition + ("M.L." II. pages 226-8.), and in 1874 he prepared a second edition of his + book, in which some objections which had been raised to the theory were + answered. A third edition, edited by Professor Bonney, appeared in 1880, + and a fourth (a reprint of the first edition, with introduction by myself) + in 1890. + </p> + <p> + Although Professor Semper, in his account of the Pelew Islands, had + suggested difficulties in the acceptance of Darwin's theory, it was not + till after the return of the "Challenger" expedition in 1875 that a rival + theory was propounded, and somewhat heated discussions were raised as to + the respective merits of the two theories. While geologists have, nearly + without exception, strongly supported Darwin's views, the notes of dissent + have come almost entirely from zoologists. At the height of the + controversy unfounded charges of unfairness were made against Darwin's + supporters and the authorities of the Geological Society, but this + unpleasant subject has been disposed of, once for all, by Huxley. ("Essays + upon some Controverted Questions", London, 1892, pages 314-328 and + 623-625.) + </p> + <p> + Darwin's final and very characteristic utterance on the coral-reef + controversy is found in a letter which he wrote to Professor Alexander + Agassiz, May 5th, 1881: less than a year before his death: "If I am wrong, + the sooner I am knocked on the head and annihilated so much the better. It + still seems to me a marvellous thing that there should not have been much, + and long-continued, subsidence in the beds of the great oceans. I wish + that some doubly rich millionaire would take it into his head to have + borings made in some of the Pacific and Indian atolls, and bring home + cores for slicing from a depth of 500 or 600 feet." ("L.L." III. page + 184.) + </p> + <p> + Though the "doubly rich millionaire" has not been forthcoming, the energy, + in England, of Professor Sollas, and in New South Wales of Professor + Anderson Stuart served to set on foot a project, which, aided at first by + the British Association for the Advancement of Science, and afterwards + taken up jointly by the Royal Society, the New South Wales Government, and + the Admiralty, has led to the most definite and conclusive results. + </p> + <p> + The Committee appointed by the Royal Society to carry out the undertaking + included representatives of all the views that had been put forward on the + subject. The place for the experiment was, with the consent of every + member of the Committee, selected by the late Admiral Sir W.J. Wharton—who + was not himself an adherent of Darwin's views—and no one has + ventured to suggest that his selection, the splendid atoll of Funafuti, + was not a most judicious one. + </p> + <p> + By the pluck and perseverance of Professor Sollas in the preliminary + expedition, and of Professor T. Edgeworth David and his pupils, in + subsequent investigations of the island, the rather difficult piece of + work was brought to a highly satisfactory conclusion. The New South Wales + Government lent boring apparatus and workmen, and the Admiralty carried + the expedition to its destination in a surveying ship which, under Captain + (now Admiral) A. Mostyn Field, made the most complete survey of the atoll + and its surrounding seas that has ever been undertaken in the case of a + coral formation. + </p> + <p> + After some failures and many interruptions, the boring was carried to the + depth of 1114 feet, and the cores obtained were sent to England. Here the + examination of the materials was fortunately undertaken by a zoologist of + the highest repute, Dr G.J. Hinde—who has a wide experience in the + study of organisms by sections—and he was aided at all points by + specialists in the British Museum of Natural History and by other + naturalists. Nor were the chemical and other problems neglected. + </p> + <p> + The verdict arrived at, after this most exhaustive study of a series of + cores obtained from depths twice as great as that thought necessary by + Darwin, was as follows:—"The whole of the cores are found to be + built up of those organisms which are seen forming coral-reefs near the + surface of the ocean—many of them evidently in situ; and not the + slightest indication could be detected, by chemical or microscopic means, + which suggested the proximity of non-calcareous rocks, even in the lowest + portions brought up." + </p> + <p> + But this was not all. Professor David succeeded in obtaining the aid of a + very skilful engineer from Australia, while the Admiralty allowed + Commander F.C.D. Sturdee to take a surveying ship into the lagoon for + further investigations. By very ingenious methods, and with great + perseverance, two borings were put down in the midst of the lagoon to the + depth of nearly 200 feet. The bottom of the lagoon, at the depth of 101 + 1/2 feet from sea-level, was found to be covered with remains of the + calcareous, green sea-weed Halimeda, mingled with many foraminifera; but + at a depth of 163 feet from the surface of the lagoon the boring tools + encountered great masses of coral, which were proved from the fragments + brought up to belong to species that live within AT MOST 120 feet from the + surface of the ocean, as admitted by all zoologists. ("The Atoll of + Funafuti; Report of the Coral Reef Committee of the Royal Society", + London, 1904.) + </p> + <p> + Darwin's theory, as is well known, is based on the fact that the + temperature of the ocean at any considerable depth does not permit of the + existence and luxuriant growth of the organisms that form the reefs. He + himself estimated this limit of depth to be from 120 to 130 feet; Dana, as + an extreme, 150 feet; while the recent very prolonged and successful + investigations of Professor Alexander Agassiz in the Pacific and Indian + Oceans lead him also to assign a limiting depth of 150 feet; the + EFFECTIVE, REEF-FORMING CORALS, however, flourishing at a much smaller + depth. Mr Stanley Gardiner gives for the most important reef-forming + corals depths between 30 and 90 feet, while a few are found as low as 120 + feet or even 180 feet. + </p> + <p> + It will thus be seen that the verdict of Funafuti is clearly and + unmistakeably in favour of Darwin's theory. It is true that some + zoologists find a difficulty in realising a slow sinking of parts of the + ocean floor, and have suggested new and alternative explanations: but + geologists generally, accepting the proofs of slow upheaval in some areas—as + shown by the admirable researches of Alexander Agassiz—consider that + it is absolutely necessary to admit that this elevation is balanced by + subsidence in other areas. If atolls and barrier-reefs did not exist we + should indeed be at a great loss to frame a theory to account for their + absence. + </p> + <p> + After finishing his book on Coral-reefs, Darwin made his summer excursion + to North Wales, and prepared his important memoir on the glaciers of that + district: but by October (1842) we find him fairly settled at work upon + the second volume of his "Geology of the 'Beagle'—Geological + Observations on the Volcanic Islands, visited during the Voyage of H.M.S. + 'Beagle'". The whole of the year 1843 was devoted to this work, but he + tells his friend Fox that he could "manage only a couple of hours per day, + and that not very regularly." ("L.L." I. page 321.) Darwin's work on the + various volcanic islands examined by him had given him the most intense + pleasure, but the work of writing the book by the aid of his notes and + specimens he found "uphill work," especially as he feared the book would + not be read, "even by geologists." (Loc. cit.) + </p> + <p> + As a matter of fact the work is full of the most interesting observations + and valuable suggestions, and the three editions (or reprints) which have + appeared have proved a most valuable addition to geological literature. It + is not necessary to refer to the novel and often very striking discoveries + described in this well-known work. The subsidence beneath volcanic vents, + the enormous denudation of volcanic cones reducing them to "basal wrecks," + the effects of solfatarric action and the formation of various minerals in + the cavities of rocks—all of these subjects find admirable + illustration from his graphic descriptions. One of the most important + discussions in this volume is that dealing with the "lamination" of lavas + as especially well seen in the rocks of Ascension. Like Scrope, Darwin + recognised the close analogy between the structure of these rocks and + those of metamorphic origin—a subject which he followed out in the + volume "Geological Observations on South America". + </p> + <p> + Of course in these days, since the application of the microscope to the + study of rocks in thin sections, Darwin's nomenclature and descriptions of + the petrological characters of the lavas appear to us somewhat crude. But + it happened that the "Challenger" visited most of the volcanic islands + described by Darwin, and the specimens brought home were examined by the + eminent petrologist Professor Renard. Renard was so struck with the work + done by Darwin, under disadvantageous conditions, that he undertook a + translation of Darwin's work into French, and I cannot better indicate the + manner in which the book is regarded by geologists than by quoting a + passage from Renard's preface. Referring to his own work in studying the + rocks brought home by the "Challenger" (Renard's descriptions of these + rocks are contained in the "Challenger Reports". Mr Harker is + supplementing these descriptions by a series of petrological memoirs on + Darwin's specimens, the first of which appeared in the "Geological + Magazine" for March, 1907.), he says: + </p> + <p> + "Je dus, en me livrant a ces recherches, suivre ligne par ligne les divers + chapitres des "Observations geologiques" consacrees aux iles de + l'Atlantique, oblige que j'etais de comparer d'une maniere suivie les + resultats auxquels j'etais conduit avec ceux de Darwin, qui servaient de + controle a mes constatations. Je ne tardai pas a eprouver une vive + admiration pour ce chercheur qui, sans autre appareil que la loupe, sans + autre reaction que quelques essais pyrognostiques, plus rarement quelques + mesures au goniometre, parvenait a discerner la nature des agregats + mineralogiques les plue complexes et les plus varies. Ce coup d'oeil qui + savait embrasser de si vastes horizons, penetre ici profondement tous les + details lithologiques. Avec quelle surete et quelle exactitude la + structure et la composition des roches ne sont'elles pas determinees, + l'origne de ces masses minerales deduite et confirmee par l'etude comparee + des manifestations volcaniques d'autres regions; avec quelle science les + relations entre les faits qu'il decouvre et ceux signales ailleurs par ses + devanciers ne sont'elles pas etablies, et comme voici ebranlees les + hypotheses regnantes, admises sans preuves, celles, par exemple, des + crateres de soulevement et de la differenciation radicale des phenomenes + plutoniques et volcaniques! Ce qui acheve de donner a ce livre un + incomparable merite, ce sont les idees nouvelles qui s'y trouvent en germe + et jetees la comme au hasard ainsi qu'un superflu d'abondance + intellectuelle inepuisable." ("Observations Geologiques sur les Iles + Volcaniques... ", Paris, 1902, pages vi., vii.) + </p> + <p> + While engaged in his study of banded lavas, Darwin was struck with the + analogy of their structure with that of glacier ice, and a note on the + subject, in the form of a letter addressed to Professor J.D. Forbes, was + published in the "Proceedings of the Royal Society of Edinburgh". (Vol. + II. (1844-5), pages 17, 18.) + </p> + <p> + From April, 1832, to September, 1835, Darwin had been occupied in + examining the coast or making inland journeys in the interior of the South + American continent. Thus while eighteen months were devoted, at the + beginning and end of the voyage to the study of volcanic islands and + coral-reefs, no less than three and a half years were given to South + American geology. The heavy task of dealing with the notes and specimens + accumulated during that long period was left by Darwin to the last. + Finishing the "Volcanic Islands" on February 14th, 1844, he, in July of + the same year, commenced the preparation of two important works which + engaged him till near the end of the year 1846. The first was his + "Geological Observations on South America", the second a recast of his + "Journal", published under the short title of "A Naturalist's Voyage round + the World". + </p> + <p> + The first of these works contains an immense amount of information + collected by the author under great difficulties and not unfrequently at + considerable risk to life and health. No sooner had Darwin landed in South + America than two sets of phenomena powerfully arrested his attention. The + first of these was the occurrence of great masses of red mud containing + bones and shells, which afforded striking evidence that the whole + continent had shared in a series of slow and gradual but often interrupted + movements. The second related to the great masses of crystalline rocks + which, underlying the muds, cover so great a part of the continent. + Darwin, almost as soon as he landed, was struck by the circumstance that + the direction, as shown by his compass, of the prominent features of these + great crystalline rock-masses—their cleavage, master-joints, + foliation and pegmatite veins—was the same as the orientation + described by Humboldt (whose works he had so carefully studied) on the + west of the same great continent. + </p> + <p> + The first five chapters of the book on South America were devoted to + formations of recent date and to the evidence collected on the east and + west coasts of the continent in regard to those grand earth-movements, + some of which could be shown to have been accompanied by + earthquake-shocks. The fossil bones, which had given him the first hint + concerning the mutability of species, had by this time been studied and + described by comparative anatomists, and Darwin was able to elaborate much + more fully the important conclusion that the existing fauna of South + America has a close analogy with that of the period immediately preceding + our own. + </p> + <p> + The remaining three chapters of the book dealt with the metamorphic and + plutonic rocks, and in them Darwin announced his important conclusions + concerning the relations of cleavage and foliation, and on the close + analogy of the latter structure with the banding found in rock-masses of + igneous origin. With respect to the first of these conclusions, he + received the powerful support of Daniel Sharpe, who in the years 1852 and + 1854 published two papers on the structure of the Scottish Highlands, + supplying striking confirmation of the correctness of Darwin's views. + Although Darwin's and Sharpe's conclusions were contested by Murchison and + other geologists, they are now universally accepted. In his theory + concerning the origin of foliation, Darwin had been to some extent + anticipated by Scrope, but he supplied many facts and illustrations + leading to the gradual acceptance of a doctrine which, when first + enunciated, was treated with neglect, if not with contempt. + </p> + <p> + The whole of this volume on South American geology is crowded with the + records of patient observations and suggestions of the greatest value; + but, as Darwin himself saw, it was a book for the working geologist and + "caviare to the general." Its author, indeed, frequently expressed his + sense of the "dryness" of the book; he even says "I long hesitated whether + I would publish it or not," and he wrote to Leonard Horner "I am + astonished that you should have had the courage to go right through my + book." ("M.L." II. page 221.) + </p> + <p> + Fortunately the second book, on which Darwin was engaged at this time, was + of a very different character. His "Journal", almost as he had written it + on board ship, with facts and observations fresh in his mind, had been + published in 1839 and attracted much attention. In 1845, he says, "I took + much pains in correcting a new edition," and the work which was commenced + in April, 1845, was not finished till August of that year. The volume + contains a history of the voyage with "a sketch of those observations in + Natural History and Geology, which I think will possess some interest for + the general reader." It is not necessary to speak of the merits of this + scientific classic. It became a great favourite with the general public—having + passed through many editions—it was, moreover, translated into a + number of different languages. Darwin was much gratified by these + evidences of popularity, and naively remarks in his "Autobiography", "The + success of this my first literary child tickles my vanity more than that + of any of my other books" ("L.L." I. page 80.)—and this was written + after the "Origin of Species" had become famous! + </p> + <p> + In Darwin's letters there are many evidences that his labours during these + ten years devoted to the working out of the geological results of the + voyage often made many demands on his patience and indomitable courage. + Most geologists have experience of the contrast between the pleasures felt + when wielding the hammer in the field, and the duller labour of plying the + pen in the study. But in Darwin's case, innumerable interruptions from + sickness and other causes, and the oft-deferred hope of reaching the end + of his task were not the only causes operating to make the work irksome. + The great project, which was destined to become the crowning achievement + of his life, was now gradually assuming more definite shape, and absorbing + more of his time and energies. + </p> + <p> + Nevertheless, during all this period, Darwin so far regarded his + geological pursuits as his PROPER "work," that attention to other matters + was always spoken of by him as "indulging in idleness." If at the end of + this period the world had sustained the great misfortune of losing Darwin + by death before the age of forty—and several times that event seemed + only too probable—he might have been remembered only as a very able + geologist of most advanced views, and a traveller who had written a + scientific narrative of more than ordinary excellence! + </p> + <p> + The completion of the "Geology of the 'Beagle'" and the preparation of a + revised narrative of the voyage mark the termination of that period of + fifteen years of Darwin's life during which geological studies were his + principal occupation. Henceforth, though his interest in geological + questions remained ever keen, biological problems engaged more and more of + his attention to the partial exclusion of geology. + </p> + <p> + The eight years from October, 1846, to October, 1854, were mainly devoted + to the preparation of his two important monographs on the recent and + fossil Cirripedia. Apart from the value of his description of the fossil + forms, this work of Darwin's had an important influence on the progress of + geological science. Up to that time a practice had prevailed for the + student of a particular geological formation to take up the description of + the plant and animal remains in it—often without having anything + more than a rudimentary knowledge of the living forms corresponding to + them. Darwin in his monograph gave a very admirable illustration of the + enormous advantage to be gained—alike for biology and geology—by + undertaking the study of the living and fossil forms of a natural group of + organisms in connection with one another. Of the advantage of these eight + years of work to Darwin himself, in preparing for the great task lying + before him, Huxley has expressed a very strong opinion indeed. ("L.L." II. + pages 247-48.) + </p> + <p> + But during these eight years of "species work," Darwin found opportunities + for not a few excursions into the field of geology. He occasionally + attended the Geological Society, and, as we have already seen, read + several papers there during this period. His friend, Dr Hooker, then + acting as botanist to the Geological Survey, was engaged in studying the + Carboniferous flora, and many discussions on Palaezoic plants and on the + origin of coal took place at this period. On this last subject he felt the + deepest interest and told Hooker, "I shall never rest easy in Down + churchyard without the problem be solved by some one before I die." + ("M.L." I. pages 63, 64.) + </p> + <p> + As at all times, conversations and letters with Lyell on every branch of + geological science continued with unabated vigour, and in spite of the + absorbing character of the work on the Cirripedes, time was found for all. + In 1849 his friend Herschel induced him to supply a chapter of forty pages + on Geology to the Admiralty "Manual of Scientific Inquiry" which he was + editing. This is Darwin's single contribution to books of an "educational" + kind. It is remarkable for its clearness and simplicity and attention to + minute details. It may be read by the student of Darwin's life with much + interest, for the directions he gives to an explorer are without doubt + those which he, as a self-taught geologist, proved to be serviceable + during his life on the "Beagle". + </p> + <p> + On the completion of the Cirripede volumes, in 1854, Darwin was able to + grapple with the immense pile of MS. notes which he had accumulated on the + species question. The first sketch of 35 pages (1842), had been enlarged + in 1844 into one of 230 pages ([The first draft of the "Origin" is being + prepared for Press by Mr Francis Darwin and will be published by the + Cambridge University Press this year (1909). A.C.S.]); but in 1856 was + commenced the work (never to be completed) which was designed on a scale + three or four times more extensive than that on which the "Origin of + Species" was in the end written. + </p> + <p> + In drawing up those two masterly chapters of the "Origin", "On the + Imperfection of the Geological Record," and "On the Geological Succession + of Organic Beings", Darwin had need of all the experience and knowledge he + had been gathering during thirty years, the first half of which had been + almost wholly devoted to geological study. The most enlightened geologists + of the day found much that was new, and still more that was startling from + the manner of its presentation, in these wonderful essays. Of Darwin's own + sense of the importance of the geological evidence in any presentation of + his theory a striking proof will be found in a passage of the touching + letter to his wife, enjoining the publication of his sketch of 1844. "In + case of my sudden death," he wrote, "... the editor must be a geologist as + well as a naturalist." ("L.L." II. pages 16, 17.) + </p> + <p> + In spite of the numerous and valuable palaeontological discoveries made + since the publication of "The Origin of Species", the importance of the + first of these two geological chapters is as great as ever. It still + remains true that "Those who believe that the geological record is in any + degree perfect, will at once reject the theory"—as indeed they must + reject any theory of evolution. The striking passage with which Darwin + concludes this chapter—in which he compares the record of the rocks + to the much mutilated volumes of a human history—remains as apt an + illustration as it did when first written. + </p> + <p> + And the second geological chapter, on the Succession of Organic Beings—though + it has been strengthened in a thousand ways, by the discoveries concerning + the pedigrees of the horse, the elephant and many other aberrant types, + though new light has been thrown even on the origin of great groups like + the mammals, and the gymnosperms, though not a few fresh links have been + discovered in the chains of evidence, concerning the order of appearance + of new forms of life—we would not wish to have re-written. Only the + same line of argument could be adopted, though with innumerable fresh + illustrations. Those who reject the reasonings of this chapter, neither + would they be persuaded if a long and complete succession of "ancestral + forms" could rise from the dead and pass in procession before them. + </p> + <p> + Among the geological discussions, which so frequently occupied Darwin's + attention during the later years of his life, there was one concerning + which his attitude seemed somewhat remarkable—I allude to his views + on "the permanence of Continents and Ocean-basins." In a letter to Mr + Mellard Reade, written at the end of 1880, he wrote: "On the whole, I lean + to the side that the continents have since Cambrian times occupied + approximately their present positions. But, as I have said, the question + seems a difficult one, and the more it is discussed the better." ("M.L." + II. page 147.) Since this was written, the important contribution to the + subject by the late Dr W.T. Blanford (himself, like Darwin, a naturalist + and geologist) has appeared in an address to the Geological Society in + 1890; and many discoveries, like that of Dr Woolnough in Fiji, have led to + considerable qualifications of the generalisation that all the islands in + the great ocean are wholly of volcanic or coral origin. + </p> + <p> + I remember once expressing surprise to Darwin that, after the views which + he had originated concerning the existence of areas of elevation and + others of subsidence in the Pacific Ocean, and in face of the admitted + difficulty of accounting for the distribution of certain terrestrial + animals and plants, if the land and sea areas had been permanent in + position, he still maintained that theory. Looking at me with a whimsical + smile, he said: "I have seen many of my old friends make fools of + themselves, by putting forward new theoretical views or revising old ones, + AFTER THEY WERE SIXTY YEARS OF AGE; so, long ago, I determined that on + reaching that age I would write nothing more of a speculative character." + </p> + <p> + Though Darwin's letters and conversations on geology during these later + years were the chief manifestations of the interest he preserved in his + "old love," as he continued to call it, yet in the sunset of that active + life a gleam of the old enthusiasm for geology broke forth once more. + There can be no doubt that Darwin's inability to occupy himself with + field-work proved an insuperable difficulty to any attempt on his part to + resume active geological research. But, as is shown by the series of + charming volumes on plant-life, Darwin had found compensation in making + patient and persevering experiment take the place of enterprising and + exact observation; and there was one direction in which he could indulge + the "old love" by employment of the new faculty. + </p> + <p> + We have seen that the earliest memoir written by Darwin, which was + published in full, was a paper "On the Formation of Mould" which was read + at the Geological Society on November 1st, 1837, but did not appear in the + "Transactions" of the Society till 1840, where it occupied four and a half + quarto pages, including some supplementary matter, obtained later, and a + woodcut. This little paper was confined to observations made in his + uncle's fields in Staffordshire, where burnt clay, cinders, and sand were + found to be buried under a layer of black earth, evidently brought from + below by earthworms, and to a recital of similar facts from Scotland + obtained through the agency of Lyell. The subsequent history of Darwin's + work on this question affords a striking example of the tenacity of + purpose with which he continued his enquiries on any subject that + interested him. + </p> + <p> + In 1842, as soon as he was settled at Down, he began a series of + observations on a foot-path and in his fields, that continued with + intermissions during his whole life, and he extended his enquiries from + time to time to the neighbouring parks of Knole and Holwood. In 1844 we + find him making a communication to the "Gardener's Chronicle" on the + subject. About 1870, his attention to the question was stimulated by the + circumstance that his niece (Miss L. Wedgwood) undertook to collect and + weigh the worm-casts thrown up, during a whole year, on measured squares + selected for the purpose, at Leith Hill Place. He also obtained + information from Professor Ramsay concerning observations made by him on a + pavement near his house in 1871. Darwin at this time began to realise the + great importance of the action of worms to the archaeologist. At an + earlier date he appears to have obtained some information concerning + articles found buried on the battle-field of Shrewsbury, and the old Roman + town of Uriconium, near his early home; between 1871 and 1878 Mr + (afterwards Lord) Farrer carried on a series of investigations at the + Roman Villa discovered on his land at Abinger; Darwin's son William + examined for his father the evidence at Beaulieu Abbey, Brading, + Stonehenge and other localities in the neighbourhood of his home; his sons + Francis and Horace were enlisted to make similar enquiries at Chideock and + Silchester; while Francis Galton contributed facts noticed in his walks in + Hyde Park. By correspondence with Fritz Muller and Dr Ernst, Darwin + obtained information concerning the worm-casts found in South America; + from Dr Kreft those of Australia; and from Mr Scott and Dr (afterwards Sir + George) King, those of India; the last-named correspondent also supplied + him with much valuable information obtained in the South of Europe. Help + too was obtained from the memoirs on Earthworms published by Perrier in + 1874 and van Hensen in 1877, while Professor Ray Lankester supplied + important facts with regard to their anatomy. + </p> + <p> + When therefore the series of interesting monographs on plant-life had been + completed, Darwin set to work in bringing the information that he had + gradually accumulated during forty-four years to bear on the subject of + his early paper. He also utilised the skill and ingenuity he had acquired + in botanical work to aid in the elucidation of many of the difficulties + that presented themselves. I well remember a visit which I paid to Down at + this period. At the side of the little study stood flower-pots containing + earth with worms, and, without interrupting our conversation, Darwin would + from time to time lift the glass plate covering a pot to watch what was + going on. Occasionally, with a humorous smile, he would murmur something + about a book in another room, and slip away; returning shortly, without + the book but with unmistakeable signs of having visited the snuff-jar + outside. After working about a year at the worms, he was able at the end + of 1881 to publish the charming little book—"The Formation of + Vegetable Mould through the Action of Worms, with Observations on their + Habits". This was the last of his books, and its reception by reviewers + and the public alike afforded the patient old worker no little + gratification. Darwin's scientific career, which had begun with geological + research, most appropriately ended with a return to it. + </p> + <p> + It has been impossible to sketch the origin and influence of Darwin's + geological work without, at almost every step, referring to the part + played by Lyell and the "Principles of Geology". Haeckel, in the chapters + on Lyell and Darwin in his "History of Creation", and Huxley in his + striking essay "On the Reception of the Origin of Species" ("L.L." II. + pages 179-204.) have both strongly insisted on the fact that the "Origin" + of Darwin was a necessary corollary to the "Principles" of Lyell. + </p> + <p> + It is true that, in an earlier essay, Huxley had spoken of the doctrine of + Uniformitarianism as being, in a certain sense, opposed to that of + Evolution (Huxley's Address to the Geological Society, 1869. "Collected + Essays", Vol. VIII. page 305, London, 1896.); but in his later years he + took up a very different and more logical position, and maintained that + "Consistent uniformitarianism postulates evolution as much in the organic + as in the inorganic world. The origin of a new species by other than + ordinary agencies would be a vastly greater 'catastrophe' than any of + those which Lyell success fully eliminated from sober geological + speculation." ("L.L." II. page 190.) + </p> + <p> + Huxley's admiration for the "Principles of Geology", and his conviction of + the greatness of the revolution of thought brought about by Lyell, was + almost as marked as in the case of Darwin himself. (See his Essay on + "Science and Pseudo Science". "Collected Essays", Vol. V. page 90, London, + 1902.) He felt, however, as many others have done, that in one respect the + very success of Lyell's masterpiece has been the reason why its + originality and influence have not been so fully recognised as they + deserved to be. Written as the book was before its author had arrived at + the age of thirty, no less than eleven editions of the "Principles" were + called for in his lifetime. With the most scrupulous care, Lyell, devoting + all his time and energies to the task of collecting and sifting all + evidence bearing on the subjects of his work, revised and re-revised it; + and as in each edition, eliminations, modifications, corrections, and + additions were made, the book, while it increased in value as a storehouse + of facts, lost much of its freshness, vigour and charm as a piece of + connected reasoning. + </p> + <p> + Darwin undoubtedly realised this when he wrote concerning the + "Principles", "the first edition, my old true love, which I never deserted + for the later editions." ("M.L." II. page 222.) Huxley once told me that + when, in later life, he read the first edition, he was both surprised and + delighted, feeling as if it were a new book to him. (I have before me a + letter which illustrates this feeling on Huxley's part. He had lamented to + me that he did not possess a copy of the first edition of the + "Principles", when, shortly afterwards, I picked up a dilapidated copy on + a bookstall; this I had bound and sent to my old teacher and colleague. + His reply is characteristic: + </p> + <p> + October 8, 1884. + </p> + <p> + My Dear Judd, + </p> + <p> + You could not have made me a more agreeable present than the copy of the + first edition of Lyell, which I find on my table. I have never been able + to meet with the book, and your copy is, as the old woman said of her + Bible, "the best of books in the best of bindings." + </p> + <p> + Ever yours sincerely, + </p> + <p> + T.H. Huxley. + </p> + <p> + (I cannot refrain from relating an incident which very strikingly + exemplifies the affection for one another felt by Lyell and Huxley. In his + last illness, when confined to his bed, Lyell heard that Huxley was to + lecture at the Royal Institution on the "Results of the 'Challenger' + expedition": he begged me to attend the lecture and bring him an account + of it. Happening to mention this to Huxley, he at once undertook to go to + Lyell in my place, and he did so on the morning following his lecture. I + shall never forget the look of gratitude on the face of the invalid when + he told me, shortly afterwards, how Huxley had sat by his bedside and + "repeated the whole lecture to him.") + </p> + <p> + Darwin's generous nature seems often to have made him experience a fear + lest he should do less than justice to his "dear old master," and to the + influence that the "Principles of Geology" had in moulding his mind. In + 1845 he wrote to Lyell, "I have long wished, not so much for your sake, as + for my own feelings of honesty, to acknowledge more plainly than by mere + reference, how much I geologically owe you. Those authors, however, who + like you, educate people's minds as well as teach them special facts, can + never, I should think, have full justice done them except by posterity, + for the mind thus insensibly improved can hardly perceive its own upward + ascent." ("L.L." I. pages 337-8.) In another letter, to Leonard Horner, he + says: "I always feel as if my books came half out of Lyell's brain, and + that I never acknowledge this sufficiently." ("M.L." II. page 117.) + Darwin's own most favourite book, the "Narrative of the Voyage", was + dedicated to Lyell in glowing terms; and in the "Origin of Species" he + wrote of "Lyell's grand work on the "Principles of Geology", which the + future historian will recognise as having produced a revolution in Natural + Science." "What glorious good that work has done" he fervently exclaims on + another occasion. ("L.L." I. page 342.) + </p> + <p> + To the very end of his life, as all who were in the habit of talking with + Darwin can testify, this sense of his indebtedness to Lyell remained with + him. In his "Autobiography", written in 1876, the year after Lyell's + death, he spoke in the warmest terms of the value to him of the + "Principles" while on the voyage and of the aid afforded to him by Lyell + on his return to England. ("L.L." I. page 62.) But the year before his own + death, Darwin felt constrained to return to the subject and to place on + record a final appreciation—one as honourable to the writer as it is + to his lost friend: + </p> + <p> + "I saw more of Lyell than of any other man, both before and after my + marriage. His mind was characterised, as it appeared to me, by clearness, + caution, sound judgment, and a good deal of originality. When I made any + remark to him on Geology, he never rested until he saw the whole case + clearly, and often made me see it more clearly than I had done before. He + would advance all possible objections to my suggestion, and even after + these were exhausted would remain long dubious. A second characteristic + was his hearty sympathy with the work of other scientific men... His + delight in science was ardent, and he felt the keenest interest in the + future progress of mankind. He was very kind-hearted... His candour was + highly remarkable. He exhibited this by becoming a convert to the Descent + theory, though he had gained much fame by opposing Lamarck's views, and + this after he had grown old." + </p> + <p> + "THE SCIENCE OF GEOLOGY IS ENORMOUSLY INDEBTED TO LYELL—MORE SO, AS + I BELIEVE, THAN TO ANY OTHER MAN WHO EVER LIVED." ("L.L." I. pages 71-2 + (the italics are mine.)) + </p> + <p> + Those who knew Lyell intimately will recognise the truth of the portrait + drawn by his dearest friend, and I believe that posterity will endorse + Darwin's deliberate verdict concerning the value of his labours. + </p> + <p> + It was my own good fortune, to be brought into close contact with these + two great men during the later years of their life, and I may perhaps be + permitted to put on record the impressions made upon me during friendly + intercourse with both. + </p> + <p> + In some respects, there was an extraordinary resemblance in their modes + and habits of thought, between Lyell and Darwin; and this likeness was + also seen in their modesty, their deference to the opinion of younger men, + their enthusiasm for science, their freedom from petty jealousies and + their righteous indignation for what was mean and unworthy in others. But + yet there was a difference. Both Lyell and Darwin were cautious, but + perhaps Lyell carried his caution to the verge of timidity. I think Darwin + possessed, and Lyell lacked, what I can only describe by the theological + term, "faith—the substance of things hoped for, the evidence of + things not seen." Both had been constrained to feel that the immutability + of species could not be maintained. Both, too, recognised the fact that it + would be useless to proclaim this conviction, unless prepared with a + satisfactory alternative to what Huxley called "the Miltonic hypothesis." + But Darwin's conviction was so far vital and operative that it sustained + him while working unceasingly for twenty-two years in collecting evidence + bearing on the question, till at last he was in the position of being able + to justify that conviction to others. + </p> + <p> + And yet Lyell's attitude—and that of Hooker, which was very similar—proved + of inestimable service to science, as Darwin often acknowledged. One of + the greatest merits of the "Origin of Species" is that so many + difficulties and objections are anticipated and fairly met; and this was + to a great extent the result of the persistent and very candid—if + always friendly—criticism of Lyell and Hooker. + </p> + <p> + I think the divergence of mental attitude in Lyell and Darwin must be + attributed to a difference in temperament, the evidence of which sometimes + appears in a very striking manner in their correspondence. Thus in 1838, + while they were in the thick of the fight with the Catastrophists of the + Geological Society, Lyell wrote characteristically: "I really find, when + bringing up my Preliminary Essays in "Principles" to the science of the + present day, so far as I know it, that the great outline, and even most of + the details, stand so uninjured, and in many cases they are so much + strengthened by new discoveries, especially by yours, that we may begin to + hope that the great principles there insisted on will stand the test of + new discoveries." (Lyell's "Life, Letters and Journals", Vol. II. page + 44.) To which the more youthful and impetuous Darwin replies: "BEGIN TO + HOPE: why the POSSIBILITY of a doubt has never crossed my mind for many a + day. This may be very unphilosophical, but my geological salvation is + staked on it... it makes me quite indignant that you should talk of + HOPING." ("L.L." I. page 296.) + </p> + <p> + It was not only Darwin's "geological salvation" that was at stake, when he + surrendered himself to his enthusiasm for an idea. To his firm faith in + the doctrine of continuity we owe the "Origin of Species"; and while + Darwin became the "Paul" of evolution, Lyell long remained the "doubting + Thomas." + </p> + <p> + Many must have felt like H.C. Watson when he wrote: "How could Sir C. + Lyell... for thirty years read, write, and think, on the subject of + species AND THEIR SUCCESSION, and yet constantly look down the wrong + road!" ("L.L." II. page 227.) Huxley attributed this hesitation of Lyell + to his "profound antipathy" to the doctrine of the "pithecoid origin of + man." ("L.L." II. page 193.) Without denying that this had considerable + influence (and those who knew Lyell and his great devotion to his wife and + her memory, are aware that he and she felt much stronger convictions + concerning such subjects as the immortality of the soul than Darwin was + able to confess to) yet I think Darwin had divined the real + characteristics of his friend's mind, when he wrote: "He would advance all + possible objections... AND EVEN AFTER THESE WERE EXHAUSTED, WOULD REMAIN + LONG DUBIOUS." + </p> + <p> + Very touching indeed was the friendship maintained to the end between + these two leaders of thought—free as their intercourse was from any + smallest trace of self-seeking or jealousy. When in 1874 I spent some time + with Lyell in his Forfarshire home, a communication from Darwin was always + an event which made a "red-letter day," as Lyell used to say; and he gave + me many indications in his conversation of how strongly he relied upon the + opinion of Darwin—more indeed than on the judgment of any other man—this + confidence not being confined to questions of science, but extending to + those of morals, politics, and religion. + </p> + <p> + I have heard those who knew Lyell only slightly, speak of his manners as + cold and reserved. His complete absorption in his scientific work, coupled + with extreme short-sightedness, almost in the end amounting to blindness, + may have permitted those having but a casual acquaintance with him to + accept such a view. But those privileged to know him intimately recognised + the nobleness of his character and can realise the justice and force of + Hooker's words when he heard of his death: "My loved, my best friend, for + well nigh forty years of my life. The most generous sharer of my own and + my family's hopes, joys and sorrows, whose affection for me was truly that + of a father and brother combined." + </p> + <p> + But the strongest of all testimonies to the grandeur of Lyell's character + is the lifelong devotion to him of such a man as Darwin. Before the two + met, we find Darwin constantly writing of facts and observations that he + thinks "will interest Mr Lyell"; and when they came together the mutual + esteem rapidly ripened into the warmest affection. Both having the + advantage of a moderate independence, permitting of an entire devotion of + their lives to scientific research, they had much in common, and the elder + man—who had already achieved both scientific and literary + distinction—was able to give good advice and friendly help to the + younger one. The warmth of their friendship comes out very strikingly in + their correspondence. When Darwin first conceived the idea of writing a + book on the "species question," soon after his return from the voyage, it + was "by following the example of Lyell in Geology" that he hoped to + succeed ("L.L." I. page 83.); when in 1844, Darwin had finished his first + sketch of the work, and, fearing that his life might not be spared to + complete his great undertaking, committed the care of it in a touching + letter to his wife, it was his friend Lyell whom he named as her adviser + and the possible editor of the book ("L.L." II. pages 17-18.); it was + Lyell who, in 1856, induced Darwin to lay the foundations of a treatise + ("L.L." I. page 84.) for which the author himself selected the + "Principles" as his model; and when the dilemma arose from the receipt of + Wallace's essay, it was to Lyell jointly with Hooker that Darwin turned, + not in vain, for advice and help. + </p> + <p> + During the later years of his life, I never heard Darwin allude to his + lost friend—and he did so very often—without coupling his name + with some term of affection. For a brief period, it is true, Lyell's + excessive caution when the "Origin" was published, seemed to try even the + patience of Darwin; but when "the master" was at last able to declare + himself fully convinced, he was the occasion of more rejoicing on the part + of Darwin, than any other convert to his views. The latter was never tired + of talking of Lyell's "magnanimity" and asserted that, "To have maintained + in the position of a master, one side of a question for thirty years, and + then deliberately give it up, is a fact to which I much doubt whether the + records of science offer a parallel." ("L.L." II. pages 229-30.) + </p> + <p> + Of Darwin himself, I can safely affirm that I never knew anyone who had + met him, even for the briefest period, who was not charmed by his + personality. Who could forget the hearty hand-grip at meeting, the gentle + and lingering pressure of the palm at parting, and above all that winning + smile which transformed his countenance—so as to make portraits, and + even photographs, seem ever afterwards unsatisfying! Looking back, one is + indeed tempted to forget the profoundness of the philosopher, in + recollection of the loveableness of the man. + </p> + <p> + <a name="link2H_4_0021" id="link2H_4_0021"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + XIX. DARWIN'S WORK ON THE MOVEMENTS OF PLANTS. By Francis Darwin, + </h2> + <h3> + Honorary Fellow of Christ's College, Cambridge. + </h3> + <p> + My father's interest in plants was of two kinds, which may be roughly + distinguished as EVOLUTIONARY and PHYSIOLOGICAL. Thus in his purely + evolutionary work, for instance in "The Origin of Species" and in his book + on "Variation under Domestication", plants as well as animals served as + material for his generalisations. He was largely dependent on the work of + others for the facts used in the evolutionary work, and despised himself + for belonging to the "blessed gang" of compilers. And he correspondingly + rejoiced in the employment of his wonderful power of observation in the + physiological problems which occupied so much of his later life. But + inasmuch as he felt evolution to be his life's work, he regarded himself + as something of an idler in observing climbing plants, insectivorous + plants, orchids, etc. In this physiological work he was to a large extent + urged on by his passionate desire to understand the machinery of all + living things. But though it is true that he worked at physiological + problems in the naturalist's spirit of curiosity, yet there was always + present to him the bearing of his facts on the problem of evolution. His + interests, physiological and evolutionary, were indeed so interwoven that + they cannot be sharply separated. Thus his original interest in the + fertilisation of flowers was evolutionary. "I was led" ("Life and + Letters", I. page 90.), he says, "to attend to the cross-fertilisation of + flowers by the aid of insects, from having come to the conclusion in my + speculations on the origin of species, that crossing played an important + part in keeping specific forms constant." In the same way the value of his + experimental work on heterostyled plants crystalised out in his mind into + the conclusion that the product of illegitimate unions are equivalent to + hybrids—a conclusion of the greatest interest from an evolutionary + point of view. And again his work "Cross and Self Fertilisation" may be + condensed to a point of view of great importance in reference to the + meaning and origin of sexual reproduction. (See Professor Goebel's article + in the present volume.) + </p> + <p> + The whole of his physiological work may be looked at as an illustration of + the potency of his theory as an "instrument for the extension of the realm + of natural knowledge." (Huxley in Darwin's "Life and Letters." II. page + 204.) + </p> + <p> + His doctrine of natural selection gave, as is well known, an impulse to + the investigation of the use of organs—and thus created the great + school of what is known in Germany as Biology—a department of + science for which no English word exists except the rather vague term + Natural History. This was especially the case in floral biology, and it is + interesting to see with what hesitation he at first expressed the value of + his book on Orchids ("Life and Letters", III. page 254.), "It will perhaps + serve to illustrate how Natural History may be worked under the belief of + the modification of species" (1861). And in 1862 he speaks (Loc. cit.) + more definitely of the relation of his work to natural selection: "I can + show the meaning of some of the apparently meaningless ridges (and) horns; + who will now venture to say that this or that structure is useless?" It is + the fashion now to minimise the value of this class of work, and we even + find it said by a modern writer that to inquire into the ends subserved by + organs is not a scientific problem. Those who take this view surely forget + that the structure of all living things is, as a whole, adaptive, and that + a knowledge of how the present forms come to be what they are includes a + knowledge of why they survived. They forget that the SUMMATION of + variations on which divergence depends is under the rule of the + environment considered as a selective force. They forget that the + scientific study of the interdependence of organisms is only possible + through a knowledge of the machinery of the units. And that, therefore, + the investigation of such widely interesting subjects as extinction and + distribution must include a knowledge of function. It is only those who + follow this line of work who get to see the importance of minute points of + structure and understand as my father did even in 1842, as shown in his + sketch of the "Origin" (Now being prepared for publication.), that every + grain of sand counts for something in the balance. Much that is + confidently stated about the uselessness of different organs would never + have been written if the naturalist spirit were commoner nowadays. This + spirit is strikingly shown in my father's work on the movements of plants. + The circumstance that botanists had not, as a class, realised the interest + of the subject accounts for the fact that he was able to gather such a + rich harvest of results from such a familiar object as a twining plant. + The subject had been investigated by H. von Mohl, Palm, and Dutrochet, but + they failed not only to master the problem but (which here concerns us) to + give the absorbing interest of Darwin's book to what they discovered. + </p> + <p> + His work on climbing plants was his first sustained piece of work on the + physiology of movement, and he remarks in 1864: "This has been new sort of + work for me." ("Life and Letters", III. page 315. He had, however, made a + beginning on the movements of Drosera.) He goes on to remark with + something of surprise, "I have been pleased to find what a capital guide + for observations a full conviction of the change of species is." + </p> + <p> + It was this point of view that enabled him to develop a broad conception + of the power of climbing as an adaptation by means of which plants are + enabled to reach the light. Instead of being compelled to construct a stem + of sufficient strength to stand alone, they succeed in the struggle by + making use of other plants as supports. He showed that the great class of + tendril- and root-climbers which do not depend on twining round a pole, + like a scarlet-runner, but on attaching themselves as they grow upwards, + effect an economy. Thus a Phaseolus has to manufacture a stem three feet + in length to reach a height of two feet above the ground, whereas a pea + "which had ascended to the same height by the aid of its tendrils, was but + little longer than the height reached." ("Climbing Plants" (2nd edition + 1875), page 193.) + </p> + <p> + Thus he was led on to the belief that TWINING is the more ancient form of + climbing, and that tendril-climbers have been developed from twiners. In + accordance with this view we find LEAF-CLIMBERS, which may be looked on as + incipient tendril-bearers, occurring in the same genera with simple + twiners. (Loc. cit. page 195.) He called attention to the case of + Maurandia semperflorens in which the young flower-stalks revolve + spontaneously and are sensitive to a touch, but neither of these qualities + is of any perceptible value to the species. This forced him to believe + that in other young plants the rudiments of the faculty needed for twining + would be found—a prophecy which he made good in his "Power of + Movement" many years later. + </p> + <p> + In "Climbing Plants" he did little more than point out the remarkable fact + that the habit of climbing is widely scattered through the vegetable + kingdom. Thus climbers are to be found in 35 out of the 59 Phanerogamic + Alliances of Lindley, so that "the conclusion is forced on our minds that + the capacity of revolving (If a twining plant, e.g. a hop, is observed + before it has begun to ascend a pole, it will be noticed that, owing to + the curvature of the stem, the tip is not vertical but hangs over in a + roughly horizontal position. If such a shoot is watched it will be found + that if, for instance, it points to the north at a given hour, it will be + found after a short interval pointing north-east, then east, and after + about two hours it will once more be looking northward. The curvature of + the stem depends on one side growing quicker than the opposite side, and + the revolving movement, i.e. circumnutation, depends on the region of + quickest growth creeping gradually round the stem from south through west + to south again. Other plants, e.g. Phaseolus, revolve in the opposite + direction.), on which most climbers depend, is inherent, though + undeveloped, in almost every plant in the vegetable kingdom." ("Climbing + Plants", page 205.) + </p> + <p> + In the "Origin" (Edition I. page 427, Edition VI. page 374.) Darwin speaks + of the "apparent paradox, that the very same characters are analogical + when one class or order is compared with another, but give true affinities + when the members of the same class or order are compared one with + another." In this way we might perhaps say that the climbing of an ivy and + a hop are analogical; the resemblance depending on the adaptive result + rather than on community of blood; whereas the relation between a + leaf-climber and a true tendril-bearer reveals descent. This particular + resemblance was one in which my father took especial delight. He has + described an interesting case occurring in the Fumariaceae. ("Climbing + Plants", page 195.) "The terminal leaflets of the leaf-climbing Fumaria + officinalis are not smaller than the other leaflets; those of the + leaf-climbing Adlumia cirrhosa are greatly reduced; those of Corydalis + claviculata (a plant which may be indifferently called a leaf-climber or a + tendril-bearer) are either reduced to microscopical dimensions or have + their blades wholly aborted, so that this plant is actually in a state of + transition; and finally in the Dicentra the tendrils are perfectly + characterized." + </p> + <p> + It is a remarkable fact that the quality which, broadly speaking, forms + the basis of the climbing habit (namely revolving nutation, otherwise + known as circumnutation) subserves two distinct ends. One of these is the + finding of a support, and this is common to twiners and tendrils. Here the + value ends as far as tendril-climbers are concerned, but in twiners Darwin + believed that the act of climbing round a support is a continuation of the + revolving movement (circumnutation). If we imagine a man swinging a rope + round his head and if we suppose the rope to strike a vertical post, the + free end will twine round it. This may serve as a rough model of twining + as explained in the "Movements and Habits of Climbing Plants". It is on + these points—the nature of revolving nutation and the mechanism of + twining—that modern physiologists differ from Darwin. (See the + discussion in Pfeffer's "The Physiology of Plants" Eng. Tr. (Oxford, + 1906), III. page 34, where the literature is given. Also Jost, + "Vorlesungen uber Pflanzenphysiologie", page 562, Jena, 1904.) + </p> + <p> + Their criticism originated in observations made on a revolving shoot which + is removed from the action of gravity by keeping the plant slowly rotating + about a horizontal axis by means of the instrument known as a klinostat. + Under these conditions circumnutation becomes irregular or ceases + altogether. When the same experiment is made with a plant which has twined + spirally up a stick, the process of climbing is checked and the last few + turns become loosened or actually untwisted. From this it has been argued + that Darwin was wrong in his description of circumnutation as an automatic + change in the region of quickest growth. When the free end of a revolving + shoot points towards the north there is no doubt that the south side has + been elongating more than the north; after a time it is plain from the + shoot hanging over to the east that the west side of the plant has grown + most, and so on. This rhythmic change of the position of the region of + greatest growth Darwin ascribes to an unknown internal regulating power. + Some modern physiologists, however, attempt to explain the revolving + movement as due to a particular form of sensitiveness to gravitation which + it is not necessary to discuss in detail in this place. It is sufficient + for my purpose to point out that Darwin's explanation of circumnutation is + not universally accepted. Personally I believe that circumnutation is + automatic—is primarily due to internal stimuli. It is however in + some way connected with gravitational sensitiveness, since the movement + normally occurs round a vertical line. It is not unnatural that, when the + plant has no external stimulus by which the vertical can be recognised, + the revolving movement should be upset. + </p> + <p> + Very much the same may be said of the act of twining, namely that most + physiologists refuse to accept Darwin's view (above referred to) that + twining is the direct result of circumnutation. Everyone must allow that + the two phenomena are in some way connected, since a plant which + circumnutates clockwise, i.e. with the sun, twines in the same direction, + and vice versa. It must also be granted that geotropism has a bearing on + the problem, since all plants twine upwards, and cannot twine along a + horizontal support. But how these two factors are combined, and whether + any (and if so what) other factors contribute, we cannot say. If we give + up Darwin's explanation, we must at the same time say with Pfeffer that + "the causes of twining are... unknown." ("The Physiology of Plants", Eng. + Tr. (Oxford, 1906), III. page 37.) + </p> + <p> + Let us leave this difficult question and consider some other points made + out in the progress of the work on climbing plants. One result of what he + called his "niggling" ("Life and Letters", III. page 312.) work on + tendrils was the discovery of the delicacy of their sense of touch, and + the rapidity of their movement. Thus in a passion-flower tendril, a bit of + platinum wire weighing 1.2 mg. produced curvature ("Climbing Plants", page + 171.), as did a loop of cotton weighing 2 mg. Pfeffer ("Untersuchungen + a.d. Bot. Inst. z. Tubingen", Bd. I. 1881-85, page 506.), however, + subsequently found much greater sensitiveness: thus the tendril of Sicyos + angulatus reacted to 0.00025 mg., but this only occurred when the delicate + rider of cottonwool fibre was disturbed by the wind. The same author + expanded and explained in a most interesting way the meaning of Darwin's + observation that tendrils are not stimulated to movement by drops of water + resting on them. Pfeffer showed that DIRTY water containing minute + particles of clay in suspension acts as a stimulus. He also showed that + gelatine acts like pure water; if a smooth glass rod is coated with a 10 + per cent solution of gelatine and is then applied to a tendril, no + movement occurs in spite of the fact that the gelatine is solid when cold. + Pfeffer ("Physiology", Eng. Tr. III. page 52. Pfeffer has pointed out the + resemblance between the contact irritability of plants and the human sense + of touch. Our skin is not sensitive to uniform pressure such as is + produced when the finger is dipped into mercury (Tubingen + "Untersuchungen", I. page 504.) generalises the result in the statement + that the tendril has a special form of irritability and only reacts to + "differences of pressure or variations of pressure in contiguous... + regions." Darwin was especially interested in such cases of specialised + irritability. For instance in May, 1864, he wrote to Asa Gray ("Life and + Letters", III. page 314.) describing the tendrils of Bignonia capreolata, + which "abhor a simple stick, do not much relish rough bark, but delight in + wool or moss." He received, from Gray, information as to the natural + habitat of the species, and finally concluded that the tendrils "are + specially adapted to climb trees clothed with lichens, mosses, or other + such productions." ("Climbing Plants", page 102.) + </p> + <p> + Tendrils were not the only instance discovered by Darwin of delicacy of + touch in plants. In 1860 he had already begun to observe Sundew (Drosera), + and was full of astonishment at its behaviour. He wrote to Sir Joseph + Hooker ("Life and Letters", III. page 319.): "I have been working like a + madman at Drosera. Here is a fact for you which is certain as you stand + where you are, though you won't believe it, that a bit of hair 1/78000 of + one grain in weight placed on gland, will cause ONE of the gland-bearing + hairs of Drosera to curve inwards." Here again Pfeffer (Pfeffer in + "Untersuchungen a. d. Bot. Inst. z. Tubingen", I. page 491.) has, as in so + many cases, added important facts to my father's observations. He showed + that if the leaf of Drosera is entirely freed from such vibrations as + would reach it if observed on an ordinary table, it does not react to + small weights, so that in fact it was the vibration of the minute fragment + of hair on the gland that produced movement. We may fancifully see an + adaptation to the capture of insects—to the dancing of a gnat's foot + on the sensitive surface. + </p> + <p> + Darwin was fond of telling how when he demonstrated the sensitiveness of + Drosera to Mr Huxley and (I think) to Sir John Burdon Sanderson, he could + perceive (in spite of their courtesy) that they thought the whole thing a + delusion. And the story ended with his triumph when Mr Huxley cried out, + "It IS moving." + </p> + <p> + Darwin's work on tendrils has led to some interesting investigations on + the mechanisms by which plants perceive stimuli. Thus Pfeffer (Tubingen + "Untersuchungen" I. page 524.) showed that certain epidermic cells + occurring in tendrils are probably organs of touch. In these cells the + protoplasm burrows as it were into cavities in the thickness of the + external cell-walls and thus comes close to the surface, being separated + from an object touching the tendril merely by a very thin layer of + cell-wall substance. Haberlandt ("Physiologische Pflanzenanatomie", + Edition III. Leipzig, 1904. "Sinnesorgane im Pflanzenreich", Leipzig, + 1901, and other publications.) has greatly extended our knowledge of + vegetable structure in relation to mechanical stimulation. He defines a + sense-organ as a contrivance by which the DEFORMATION or forcible change + of form in the protoplasm—on which mechanical stimulation depends—is + rendered rapid and considerable in amplitude ("Sinnesorgane", page 10). He + has shown that in certain papillose and bristle-like contrivances, plants + possess such sense-organs; and moreover that these contrivances show a + remarkable similarity to corresponding sense-organs in animals. + </p> + <p> + Haberlandt and Nemec ("Ber. d. Deutschen bot. Gesellschaft", XVIII. 1900. + See F. Darwin, Presidential Address to Section K, British Association, + 1904.) published independently and simultaneously a theory of the + mechanism by which plants are orientated in relation to gravitation. And + here again we find an arrangement identical in principle with that by + which certain animals recognise the vertical, namely the pressure of free + particles on the irritable wall of a cavity. In the higher plants, Nemec + and Haberlandt believe that special loose and freely movable starch-grains + play the part of the otoliths or statoliths of the crustacea, while the + protoplasm lining the cells in which they are contained corresponds to the + sensitive membrane lining the otocyst of the animal. What is of special + interest in our present connection is that according to this ingenious + theory (The original conception was due to Noll ("Heterogene Induction", + Leipzig, 1892), but his view differed in essential points from those here + given.) the sense of verticality in a plant is a form of + contact-irritability. The vertical position is distinguished from the + horizontal by the fact that, in the latter case, the loose starch-grains + rest on the lateral walls of the cells instead of on the terminal walls as + occurs in the normal upright position. It should be added that the + statolith theory is still sub judice; personally I cannot doubt that it is + in the main a satisfactory explanation of the facts. + </p> + <p> + With regard to the RAPIDITY of the reaction of tendrils, Darwin records + ("Climbing Plants", page 155. Others have observed movement after about + 6".) that a Passion-Flower tendril moved distinctly within 25 seconds of + stimulation. It was this fact, more than any other, that made him doubt + the current explanation, viz. that the movement is due to unequal growth + on the two sides of the tendril. The interesting work of Fitting + (Pringsheim's "Jahrb." XXXVIII. 1903, page 545.) has shown, however, that + the primary cause is not (as Darwin supposed) contraction on the concave, + but an astonishingly rapid increase in growth-rate on the convex side. + </p> + <p> + On the last page of "Climbing Plants" Darwin wrote: "It has often been + vaguely asserted that plants are distinguished from animals by not having + the power of movement. It should rather be said that plants acquire and + display this power only when it is of some advantage to them." + </p> + <p> + He gradually came to realise the vividness and variety of vegetable life, + and that a plant like an animal has capacities of behaving in different + ways under different circumstances, in a manner that may be compared to + the instinctive movements of animals. This point of view is expressed in + well-known passages in the "Power of Movement". ("The Power of Movement in + Plants", 1880, pages 571-3.) "It is impossible not to be struck with the + resemblance between the... movements of plants and many of the actions + performed unconsciously by the lower animals." And again, "It is hardly an + exaggeration to say that the tip of the radicle... having the power of + directing the movements of the adjoining parts, acts like the brain of one + of the lower animals; the brain being seated within the anterior end of + the body, receiving impressions from the sense-organs, and directing the + several movements." + </p> + <p> + The conception of a region of perception distinct from a region of + movement is perhaps the most fruitful outcome of his work on the movements + of plants. But many years before its publication, viz. in 1861, he had + made out the wonderful fact that in the Orchid Catasetum ("Life and + Letters", III. page 268.) the projecting organs or antennae are sensitive + to a touch, and transmit an influence "for more than one inch + INSTANTANEOUSLY," which leads to the explosion or violent ejection of the + pollinia. And as we have already seen a similar transmission of a stimulus + was discovered by him in Sundew in 1860, so that in 1862 he could write to + Hooker ("Life and Letters", III. page 321.): "I cannot avoid the + conclusion, that Drosera possesses matter at least in some degree + analogous in constitution and function to nervous matter." I propose in + what follows to give some account of the observations on the transmission + of stimuli given in the "Power of Movement". It is impossible within the + space at my command to give anything like a complete account of the + matter, and I must necessarily omit all mention of much interesting work. + One well-known experiment consisted in putting opaque caps on the tips of + seedling grasses (e.g. oat and canary-grass) and then exposing them to + light from one side. The difference, in the amount of curvature towards + the light, between the blinded and unblinded specimens, was so great that + it was concluded that the light-sensitiveness resided exclusively in the + tip. The experiment undoubtedly proves that the sensitiveness is much + greater in the tip than elsewhere, and that there is a transmission of + stimulus from the tip to the region of curvature. But Rothert (Rothert, + Cohn's "Beitrage", VII. 1894.) has conclusively proved that the basal part + where the curvature occurs is also DIRECTLY sensitive to light. He has + shown, however, that in other grasses (Setaria, Panicum) the cotyledon is + the only part which is sensitive, while the hypocotyl, where the movement + occurs, is not directly sensitive. + </p> + <p> + It was however the question of the localisation of the gravitational sense + in the tip of the seedling root or radicle that aroused most attention, + and it was on this question that a controversy arose which has continued + to the present day. + </p> + <p> + The experiment on which Darwin's conclusion was based consisted simply in + cutting off the tip, and then comparing the behaviour of roots so treated + with that of normal specimens. An uninjured root when placed horizontally + regains the vertical by means of a sharp downward curve; not so a + decapitated root which continues to grow more or less horizontally. It was + argued that this depends on the loss of an organ specialised for the + perception of gravity, and residing in the tip of the root; and the + experiment (together with certain important variants) was claimed as + evidence of the existence of such an organ. + </p> + <p> + It was at once objected that the amputation of the tip might check + curvature by interfering with longitudinal growth, on the distribution of + which curvature depends. This objection was met by showing that an injury, + e.g. splitting the root longitudinally (See F. Darwin, "Linnean Soc. + Journal (Bot)." XIX. 1882, page 218.), which does not remove the tip, but + seriously checks growth, does not prevent geotropism. This was of some + interest in another and more general way, in showing that curvature and + longitudinal growth must be placed in different categories as regards the + conditions on which they depend. + </p> + <p> + Another objection of a much more serious kind was that the amputation of + the tip acts as a shock. It was shown by Rothert (See his excellent + summary of the subject in "Flora" 1894 (Erganzungsband), page 199.) that + the removal of a small part of the cotyledon of Setaria prevents the plant + curving towards the light, and here there is no question of removing the + sense-organ since the greater part of the sensitive cotyledon is intact. + In view of this result it was impossible to rely on the amputations + performed on roots as above described. + </p> + <p> + At this juncture a new and brilliant method originated in Pfeffer's + laboratory. (See Pfeffer, "Annals of Botany", VIII. 1894, page 317, and + Czapek, Pringsheim's "Jahrb." XXVII. 1895, page 243.) Pfeffer and Czapek + showed that it is possible to bend the root of a lupine so that, for + instance, the supposed sense-organ at the tip is vertical while the motile + region is horizontal. If the motile region is directly sensitive to + gravity the root ought to curve downwards, but this did not occur: on the + contrary it continued to grow horizontally. This is precisely what should + happen if Darwin's theory is the right one: for if the tip is kept + vertical, the sense-organ is in its normal position and receives no + stimulus from gravitation, and therefore can obviously transmit none to + the region of curvature. Unfortunately this method did not convince the + botanical world because some of those who repeated Czapek's experiment + failed to get his results. + </p> + <p> + Czapek ("Berichte d. Deutsch. bot. Ges." XV. 1897, page 516, and numerous + subsequent papers. English readers should consult Czapek in the "Annals of + Botany", XIX. 1905, page 75.) has devised another interesting method which + throws light on the problem. He shows that roots, which have been placed + in a horizontal position and have therefore been geotropically stimulated, + can be distinguished by a chemical test from vertical, i.e. unstimulated + roots. The chemical change in the root can be detected before any + curvature has occurred and must therefore be a symptom of stimulation, not + of movement. It is particularly interesting to find that the change in the + root, on which Czapek's test depends, takes place in the tip, i.e. in the + region which Darwin held to be the centre for gravitational sensitiveness. + </p> + <p> + In 1899 I devised a method (F. Darwin, "Annals of Botany", XIII. 1899, + page 567.) by which I sought to prove that the cotyledon of Setaria is not + only the organ for light-perception, but also for gravitation. If a + seedling is supported horizontally by pushing the apical part (cotyledon) + into a horizontal tube, the cotyledon will, according to my supposition, + be stimulated gravitationally and a stimulus will be transmitted to the + basal part of the stem (hypocotyl) causing it to bend. But this curvature + merely raises the basal end of the seedling, the sensitive cotyledon + remains horizontal, imprisoned in its tube; it will therefore be + continually stimulated and will continue to transmit influences to the + bending region, which should therefore curl up into a helix or + corkscrew-like form,—and this is precisely what occurred. + </p> + <p> + I have referred to this work principally because the same method was + applied to roots by Massart (Massart, "Mem. Couronnes Acad. R. Belg." + LXII. 1902.) and myself (F. Darwin, "Linnean Soc. Journ." XXXV. 1902, page + 266.) with a similar though less striking result. Although these + researches confirmed Darwin's work on roots, much stress cannot be laid on + them as there are several objections to them, and they are not easily + repeated. + </p> + <p> + The method which—as far as we can judge at present—seems + likely to solve the problem of the root-tip is most ingenious and is due + to Piccard. (Pringsheim's "Jahrb." XL. 1904, page 94.) + </p> + <p> + Andrew Knight's celebrated experiment showed that roots react to + centrifugal force precisely as they do to gravity. So that if a bean root + is fixed to a wheel revolving rapidly on a horizontal axis, it tends to + curve away from the centre in the line of a radius of the wheel. In + ordinary demonstrations of Knight's experiment the seed is generally fixed + so that the root is at right angles to a radius, and as far as convenient + from the centre of rotation. Piccard's experiment is arranged differently. + (A seed is depicted below a horizontal dotted line AA, projecting a root + upwards.) The root is oblique to the axis of rotation, and the extreme tip + projects beyond that axis. Line AA represents the axis of rotation, T is + the tip of the root just above the line AA, and B is the region just below + line AA in which curvature takes place. If the motile region B is directly + sensitive to gravitation (and is the only part which is sensitive) the + root will curve (down and away from the vertical) away from the axis of + rotation, just as in Knight's experiment. But if the tip T is alone + sensitive to gravitation the result will be exactly reversed, the stimulus + originating in T and conveyed to B will produce curvature (up towards the + vertical). We may think of the line AA as a plane dividing two worlds. In + the lower one gravity is of the earthly type and is shown by bodies + falling and roots curving downwards: in the upper world bodies fall + upwards and roots curve in the same direction. The seedling is in the + lower world, but its tip containing the supposed sense-organ is in the + strange world where roots curve upwards. By observing whether the root + bends up or down we can decide whether the impulse to bend originates in + the tip or in the motile region. + </p> + <p> + Piccard's results showed that both curvatures occurred and he concluded + that the sensitive region is not confined to the tip. (Czapek + (Pringsheim's "Jahrb." XXXV. 1900, page 362) had previously given reasons + for believing that, in the root, there is no sharp line of separation + between the regions of perception and movement.) + </p> + <p> + Haberlandt (Pringsheim's "Jahrb." XLV. 1908, page 575.) has recently + repeated the experiment with the advantage of better apparatus and more + experience in dealing with plants, and has found as Piccard did that both + the tip and the curving region are sensitive to gravity, but with the + important addition that the sensitiveness of the tip is much greater than + that of the motile region. The case is in fact similar to that of the oat + and canary-grass. In both instances my father and I were wrong in assuming + that the sensitiveness is confined to the tip, yet there is a + concentration of irritability in that region and transmission of stimulus + is as true for geotropism as it is for heliotropism. Thus after nearly + thirty years the controversy of the root-tip has apparently ended somewhat + after the fashion of the quarrels at the "Rainbow" in "Silas Marner"—"you're + both right and you're both wrong." But the "brain-function" of the + root-tip at which eminent people laughed in early days turns out to be an + important part of the truth. (By using Piccard's method I have succeeded + in showing that the gravitational sensitiveness of the cotyledon of + Sorghum is certainly much greater than the sensitiveness of the hypocotyl—if + indeed any such sensitiveness exists. See Wiesner's "Festschrift", Vienna, + 1908.) + </p> + <p> + Another observation of Darwin's has given rise to much controversy. + ("Power of Movement", page 133.) If a minute piece of card is fixed + obliquely to the tip of a root some influence is transmitted to the region + of curvature and the root bends away from the side to which the card was + attached. It was thought at the time that this proved the root-tip to be + sensitive to contact, but this is not necessarily the case. It seems + possible that the curvature is a reaction to the injury caused by the + alcoholic solution of shellac with which the cards were cemented to the + tip. This agrees with the fact given in the "Power of Movement" that + injuring the root-tip on one side, by cutting or burning it, induced a + similar curvature. On the other hand it was shown that curvature could be + produced in roots by cementing cards, not to the naked surface of the + root-tip, but to pieces of gold-beaters skin applied to the root; + gold-beaters skin being by itself almost without effect. But it must be + allowed that, as regards touch, it is not clear how the addition of + shellac and card can increase the degree of contact. There is however some + evidence that very close contact from a solid body, such as a curved + fragment of glass, produces curvature: and this may conceivably be the + explanation of the effect of gold-beaters skin covered with shellac. But + on the whole it is perhaps safer to classify the shellac experiments with + the results of undoubted injury rather than with those of contact. + </p> + <p> + Another subject on which a good deal of labour was expended is the sleep + of leaves, or as Darwin called it their NYCTITROPIC movement. He showed + for the first time how widely spread this phenomenon is, and attempted to + give an explanation of the use to the plant of the power of sleeping. His + theory was that by becoming more or less vertical at night the leaves + escape the chilling effect of radiation. Our method of testing this view + was to fix some of the leaves of a sleeping plant so that they remained + horizontal at night and therefore fully exposed to radiation, while their + fellows were partly protected by assuming the nocturnal position. The + experiments showed clearly that the horizontal leaves were more injured + than the sleeping, i.e. more or less vertical, ones. It may be objected + that the danger from cold is very slight in warm countries where sleeping + plants abound. But it is quite possible that a lowering of the temperature + which produces no visible injury may nevertheless be hurtful by checking + the nutritive processes (e.g. translocation of carbohydrates), which go on + at night. Stahl ("Bot. Zeitung", 1897, page 81.) however has ingeniously + suggested that the exposure of the leaves to radiation is not DIRECTLY + hurtful because it lowers the temperature of the leaf, but INDIRECTLY + because it leads to the deposition of dew on the leaf-surface. He gives + reasons for believing that dew-covered leaves are unable to transpire + efficiently, and that the absorption of mineral food-material is + correspondingly checked. Stahl's theory is in no way destructive of + Darwin's, and it is possible that nyctitropic leaves are adapted to avoid + the indirect as well as the direct results of cooling by radiation. + </p> + <p> + In what has been said I have attempted to give an idea of some of the + discoveries brought before the world in the "Power of Movement" (In 1881 + Professor Wiesner published his "Das Bewegungsvermogen der Pflanzen", a + book devoted to the criticism of "The Power of Movement in Plants". A + letter to Wiesner, published in "Life and Letters", III. page 336, shows + Darwin's warm appreciation of his critic's work, and of the spirit in + which it is written.) and of the subsequent history of the problems. We + must now pass on to a consideration of the central thesis of the book,—the + relation of circumnutation to the adaptive curvatures of plants. + </p> + <p> + Darwin's view is plainly stated on pages 3-4 of the "Power of Movement". + Speaking of circumnutation he says, "In this universally present movement + we have the basis or groundwork for the acquirement, according to the + requirements of the plant, of the most diversified movements." He then + points out that curvatures such as those towards the light or towards the + centre of the earth can be shown to be exaggerations of circumnutation in + the given directions. He finally points out that the difficulty of + conceiving how the capacities of bending in definite directions were + acquired is diminished by his conception. "We know that there is always + movement in progress, and its amplitude, or direction, or both, have only + to be modified for the good of the plant in relation with internal or + external stimuli." + </p> + <p> + It may at once be allowed that the view here given has not been accepted + by physiologists. The bare fact that circumnutation is a general property + of plants (other than climbing species) is not generally rejected. But the + botanical world is no nearer to believing in the theory of reaction built + on it. + </p> + <p> + If we compare the movements of plants with those of the lower animals we + find a certain resemblance between the two. According to Jennings (H.S. + Jennings, "The Behavior of the Lower Animals". Columbia U. Press, N.Y. + 1906.) a Paramoecium constantly tends to swerve towards the aboral side of + its body owing to certain peculiarities in the set and power of its cilia. + But the tendency to swim in a circle, thus produced, is neutralised by the + rotation of the creature about its longitudinal axis. Thus the direction + of the swerves IN RELATION TO THE PATH of the organism is always changing, + with the result that the creature moves in what approximates to a straight + line, being however actually a spiral about the general line of progress. + This method of motion is strikingly like the circumnutation of a plant, + the apex of which also describes a spiral about the general line of + growth. A rooted plant obviously cannot rotate on its axis, but the + regular series of curvatures of which its growth consists correspond to + the aberrations of Paramoecium distributed regularly about its course by + means of rotation. (In my address to the Biological Section of the British + Association at Cardiff (1891) I have attempted to show the connection + between circumnutation and RECTIPETALITY, i.e. the innate capacity of + growing in a straight line.) Just as a plant changes its direction of + growth by an exaggeration of one of the curvature-elements of which + circumnutation consists, so does a Paramoecium change its course by the + accentuation of one of the deviations of which its path is built. Jennings + has shown that the infusoria, etc., react to stimuli by what is known as + the "method of trial." If an organism swims into a region where the + temperature is too high or where an injurious substance is present, it + changes its course. It then moves forward again, and if it is fortunate + enough to escape the influence, it continues to swim in the given + direction. If however its change of direction leads it further into the + heated or poisonous region it repeats the movement until it emerges from + its difficulties. Jennings finds in the movements of the lower organisms + an analogue with what is known as pain in conscious organisms. There is + certainly this much resemblance that a number of quite different + sub-injurious agencies produce in the lower organisms a form of reaction + by the help of which they, in a partly fortuitous way, escape from the + threatening element in their environment. The higher animals are + stimulated in a parallel manner to vague and originally purposeless + movements, one of which removes the discomfort under which they suffer, + and the organism finally learns to perform the appropriate movement + without going through the tentative series of actions. + </p> + <p> + I am tempted to recognise in circumnutation a similar groundwork of + tentative movements out of which the adaptive ones were originally + selected by a process rudely representative of learning by experience. + </p> + <p> + It is, however, simpler to confine ourselves to the assumption that those + plants have survived which have acquired through unknown causes the power + of reacting in appropriate ways to the external stimuli of light, gravity, + etc. It is quite possible to conceive this occurring in plants which have + no power of circumnutating—and, as already pointed out, + physiologists do as a fact neglect circumnutation as a factor in the + evolution of movements. Whatever may be the fate of Darwin's theory of + circumnutation there is no doubt that the research he carried out in + support of, and by the light of, this hypothesis has had a powerful + influence in guiding the modern theories of the behaviour of plants. + Pfeffer ("The Physiology of Plants", Eng. Tr. III. page 11.), who more + than any one man has impressed on the world a rational view of the + reactions of plants, has acknowledged in generous words the great value of + Darwin's work in the same direction. The older view was that, for + instance, curvature towards the light is the direct mechanical result of + the difference of illumination on the lighted and shaded surfaces of the + plant. This has been proved to be an incorrect explanation of the fact, + and Darwin by his work on the transmission of stimuli has greatly + contributed to the current belief that stimuli act indirectly. Thus we now + believe that in a root and a stem the mechanism for the perception of + gravitation is identical, but the resulting movements are different + because the motor-irritabilities are dissimilar in the two cases. We must + come back, in fact, to Darwin's comparison of plants to animals. In both + there is perceptive machinery by which they are made delicately alive to + their environment, in both the existing survivors are those whose internal + constitution has enabled them to respond in a beneficial way to the + disturbance originating in their sense-organs. + </p> + <p> + <a name="link2H_4_0022" id="link2H_4_0022"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + XX. THE BIOLOGY OF FLOWERS. By K. Goebel, Ph.D. + </h2> + <h3> + Professor of Botany in the University of Munich. + </h3> + <p> + There is scarcely any subject to which Darwin devoted so much time and + work as to his researches into the biology of flowers, or, in other words, + to the consideration of the question to what extent the structural and + physiological characters of flowers are correlated with their function of + producing fruits and seeds. We know from his own words what fascination + these studies possessed for him. We repeatedly find, for example, in his + letters expressions such as this:—"Nothing in my life has ever + interested me more than the fertilisation of such plants as Primula and + Lythrum, or again Anacamptis or Listera." ("More Letters of Charles + Darwin", Vol. II. page 419.) + </p> + <p> + Expressions of this kind coming from a man whose theories exerted an + epoch-making influence, would be unintelligible if his researches into the + biology of flowers had been concerned only with records of isolated facts, + however interesting these might be. We may at once take it for granted + that the investigations were undertaken with the view of following up + important problems of general interest, problems which are briefly dealt + with in this essay. + </p> + <p> + Darwin published the results of his researches in several papers and in + three larger works, (i) "On the various contrivances by which British and + Foreign Orchids are fertilised by insects" (First edition, London, 1862; + second edition, 1877; popular edition, 1904.) (ii) "The effects of Cross + and Self fertilisation in the vegetable kingdom" (First edition, 1876; + second edition, 1878). (iii) "The different forms of Flowers on plants of + the same species" (First edition, 1877; second edition, 1880). + </p> + <p> + Although the influence of his work is considered later, we may here point + out that it was almost without a parallel; not only does it include a mass + of purely scientific observations, but it awakened interest in very wide + circles, as is shown by the fact that we find the results of Darwin's + investigations in floral biology universally quoted in school books; they + are even willingly accepted by those who, as regards other questions, are + opposed to Darwin's views. + </p> + <p> + The works which we have mentioned are, however, not only of special + interest because of the facts they contribute, but because of the MANNER + in which the facts are expressed. A superficial reader seeking merely for + catch-words will, for instance, probably find the book on cross and + self-fertilisation rather dry because of the numerous details which it + contains: it is, indeed, not easy to compress into a few words the general + conclusions of this volume. But on closer examination, we cannot be + sufficiently grateful to the author for the exactness and objectivity with + which he enables us to participate in the scheme of his researches. He + never tries to persuade us, but only to convince us that his conclusions + are based on facts; he always gives prominence to such facts as appear to + be in opposition to his opinions,—a feature of his work in + accordance with a maxim which he laid down:—"It is a golden rule, + which I try to follow, to put every fact which is opposed to one's + preconceived opinion in the strongest light." ("More Letters", Vol. II. + page 324.) + </p> + <p> + The result of this method of presentation is that the works mentioned + above represent a collection of most valuable documents even for those who + feel impelled to draw from the data other conclusions than those of the + author. Each investigation is the outcome of a definite question, a + "preconceived opinion," which is either supported by the facts or must be + abandoned. "How odd it is that anyone should not see that all observation + must be for or against some view if it is to be of any service!" (Ibid. + Vol. I. page 195.) + </p> + <p> + The points of view which Darwin had before him were principally the + following. In the first place the proof that a large number of the + peculiarities in the structure of flowers are not useless, but of the + greatest significance in pollination must be of considerable importance + for the interpretation of adaptations; "The use of each trifling detail of + structure is far from a barren search to those who believe in natural + selection." ("Fertilisation of Orchids" (1st edition), page 351; (2nd + edition 1904) page 286.) Further, if these structural relations are shown + to be useful, they may have been acquired because from the many variations + which have occurred along different lines, those have been preserved by + natural selection "which are beneficial to the organism under the complex + and ever-varying conditions of life." (Ibid. page 351.) But in the case of + flowers there is not only the question of adaptation to fertilisation to + be considered. Darwin, indeed, soon formed the opinion which he has + expressed in the following sentence,—"From my own observations on + plants, guided to a certain extent by the experience of the breeders of + animals, I became convinced many years ago that it is a general law of + nature that flowers are adapted to be crossed, at least occasionally, by + pollen from a distinct plant." ("Cross and Self fertilisation" (1st + edition), page 6.) + </p> + <p> + The experience of animal breeders pointed to the conclusion that continual + in-breeding is injurious. If this is correct, it raises the question + whether the same conclusion holds for plants. As most flowers are + hermaphrodite, plants afford much more favourable material than animals + for an experimental solution of the question, what results follow from the + union of nearly related sexual cells as compared with those obtained by + the introduction of new blood. The answer to this question must, moreover, + possess the greatest significance for the correct understanding of sexual + reproduction in general. + </p> + <p> + We see, therefore, that the problems which Darwin had before him in his + researches into the biology of flowers were of the greatest importance, + and at the same time that the point of view from which he attacked the + problems was essentially a teleological one. + </p> + <p> + We may next inquire in what condition he found the biology of flowers at + the time of his first researches, which were undertaken about the year + 1838. In his autobiography he writes,—"During the summer of 1839, + and, I believe, during the previous summer, I was led to attend to the + cross-fertilisation of flowers by the aid of insects, from having come to + the conclusion in my speculations on the origin of species, that crossing + played an important part in keeping specific forms constant." ("The Life + and Letters of Charles Darwin", Vol. I. page 90, London, 1888.) In 1841 he + became acquainted with Sprengel's work: his researches into the biology of + flowers were thus continued for about forty years. + </p> + <p> + It is obvious that there could only be a biology of flowers after it had + been demonstrated that the formation of seeds and fruit in the flower is + dependent on pollination and subsequent fertilisation. This proof was + supplied at the end of the seventeenth century by R.J. Camerarius + (1665-1721). He showed that normally seeds and fruits are developed only + when the pollen reaches the stigma. The manner in which this happens was + first thoroughly investigated by J.G. Kolreuter (1733-1806 (Kolreuter, + "Vorlaufige Nachricht von einigen das Geschlecht der Planzen betreffenden + Versuchen und Beobachtungen", Leipzig, 1761; with three supplements, + 1763-66. Also, "Mem. de l'acad. St Petersbourg", Vol. XV. 1809.)), the + same observer to whom we owe the earliest experiments in hybridisation of + real scientific interest. Kolreuter mentioned that pollen may be carried + from one flower to another partly by wind and partly by insects. But he + held the view, and that was, indeed, the natural assumption, that + self-fertilisation usually occurs in a flower, in other words that the + pollen of a flower reaches the stigma of the same flower. He demonstrated, + however, certain cases in which cross-pollination occurs, that is in which + the pollen of another flower of the same species is conveyed to the + stigma. He was familiar with the phenomenon, exhibited by numerous + flowers, to which Sprengel afterwards applied the term Dichogamy, + expressing the fact that the anthers and stigmas of a flower often ripen + at different times, a peculiarity which is now recognised as one of the + commonest means of ensuring cross-pollination. + </p> + <p> + With far greater thoroughness and with astonishing power of observation + C.K. Sprengel (1750-1816) investigated the conditions of pollination of + flowers. Darwin was introduced by that eminent botanist Robert Brown to + Sprengel's then but little appreciated work,—"Das entdeckte + Geheimniss der Natur im Bau und in der Befruchtung der Blumen" (Berlin, + 1793); this is by no means the least service to Botany rendered by Robert + Brown. + </p> + <p> + Sprengel proceeded from a naive teleological point of view. He firmly + believed "that the wise Author of nature had not created a single hair + without a definite purpose." He succeeded in demonstrating a number of + beautiful adaptations in flowers for ensuring pollination; but his work + exercised but little influence on his contemporaries and indeed for a long + time after his death. It was through Darwin that Sprengel's work first + achieved a well deserved though belated fame. Even such botanists as + concerned themselves with researches into the biology of flowers appear to + have formerly attached much less value to Sprengel's work than it has + received since Darwin's time. In illustration of this we may quote C.F. + Gartner whose name is rightly held in the highest esteem as that of one of + the most eminent hybridologists. In his work "Versuche und Beobachtungen + uder die Befruchtungsorgane der vollkommeneren Gewachse und uber die + naturliche und kunstliche Befruchtung durch den eigenen Pollen" he also + deals with flower-pollination. He recognised the action of the wind, but + he believed, in spite of the fact that he both knew and quoted Kolreuter + and Sprengel, that while insects assist pollination, they do so only + occasionally, and he held that insects are responsible for the conveyance + of pollen; thorough investigations would show "that a very small + proportion of the plants included in this category require this assistance + in their native habitat." (Gartner, "Versucher und Beobachtungen... ", + page 335, Stuttgart, 1844.) In the majority of plants self-pollination + occurs. + </p> + <p> + Seeing that even investigators who had worked for several decades at + fertilisation-phenomena had not advanced the biology of flowers beyond the + initial stage, we cannot be surprised that other botanists followed to + even a less extent the lines laid down by Kolreuter and Sprengel. This was + in part the result of Sprengel's supernatural teleology and in part due to + the fact that his book appeared at a time when other lines of inquiry + exerted a dominating influence. + </p> + <p> + At the hands of Linnaeus systematic botany reached a vigorous development, + and at the beginning of the nineteenth century the anatomy and physiology + of plants grew from small beginnings to a flourishing branch of science. + Those who concerned themselves with flowers endeavoured to investigate + their development and structure or the most minute phenomena connected + with fertilisation and the formation of the embryo. No room was left for + the extension of the biology of flowers on the lines marked out by + Kolreuter and Sprengel. Darwin was the first to give new life and a deeper + significance to this subject, chiefly because he took as his + starting-point the above-mentioned problems, the importance of which is at + once admitted by all naturalists. + </p> + <p> + The further development of floral biology by Darwin is in the first place + closely connected with the book on the fertilisation of Orchids. It is + noteworthy that the title includes the sentence,—"and on the good + effects of intercrossing." + </p> + <p> + The purpose of the book is clearly stated in the introduction:—"The + object of the following work is to show that the contrivances by which + Orchids are fertilised, are as varied and almost as perfect as any of the + most beautiful adaptations in the animal kingdom; and, secondly, to show + that these contrivances have for their main object the fertilisation of + each flower by the pollen of another flower." ("Fertilisation of Orchids", + page 1.) Orchids constituted a particularly suitable family for such + researches. Their flowers exhibit a striking wealth of forms; the + question, therefore, whether the great variety in floral structure bears + any relation to fertilisation (In the older botanical literature the word + fertilisation is usually employed in cases where POLLINATION is really in + question: as Darwin used it in this sense it is so used here.) must in + this case possess special interest. + </p> + <p> + Darwin succeeded in showing that in most of the orchids examined + self-fertilisation is either an impossibility, or, under natural + conditions, occurs only exceptionally. On the other hand these plants + present a series of extraordinarily beautiful and remarkable adaptations + which ensure the transference of pollen by insects from one flower to + another. It is impossible to describe adequately in a few words the wealth + of facts contained in the Orchid book. A few examples may, however, be + quoted in illustration of the delicacy of the observations and of the + perspicuity employed in interpreting the facts. + </p> + <p> + The majority of orchids differ from other seed plants (with the exception + of the Asclepiads) in having no dust-like pollen. The pollen, or more + correctly, the pollen-tetrads, remain fastened together as club-shaped + pollinia usually borne on a slender pedicel. At the base of the pedicel is + a small viscid disc by which the pollinium is attached to the head or + proboscis of one of the insects which visit the flower. Darwin + demonstrated that in Orchis and other flowers the pedicel of the + pollinium, after its removal from the anther, undergoes a curving + movement. If the pollinium was originally vertical, after a time it + assumed a horizontal position. In the latter position, if the insect + visited another flower, the pollinium would exactly hit the sticky + stigmatic surface and thus effect fertilisation. The relation between the + behaviour of the viscid disc and the secretion of nectar by the flower is + especially remarkable. The flowers possess a spur which in some species + (e.g. Gymnadenia conopsea, Platanthera bifolia, etc.) contains honey + (nectar), which serves as an attractive bait for insects, but in others + (e.g. our native species of Orchis) the spur is empty. Darwin held the + opinion, confirmed by later investigations, that in the case of flowers + without honey the insects must penetrate the wall of the nectarless spurs + in order to obtain a nectar-like substance. The glands behave differently + in the nectar-bearing and in the nectarless flowers. In the former they + are so sticky that they at once adhere to the body of the insect; in the + nectarless flowers firm adherence only occurs after the viscid disc has + hardened. It is, therefore, adaptively of value that the insects should be + detained longer in the nectarless flowers (by having to bore into the + spur),—than in flowers in which the nectar is freely exposed. "If + this relation, on the one hand, between the viscid matter requiring some + little time to set hard, and the nectar being so lodged that moths are + delayed in getting it; and, on the other hand, between the viscid matter + being at first as viscid as ever it will become, and the nectar lying all + ready for rapid suction, be accidental, it is a fortunate accident for the + plant. If not accidental, and I cannot believe it to be accidental, what a + singular case of adaptation!" ("Fertilisation of Orchids" (1st edition), + page 53.) + </p> + <p> + Among exotic orchids Catasetum is particularly remarkable. One and the + same species bears different forms of flowers. The species known as + Catasetum tridentatum has pollinia with very large viscid discs; on + touching one of the two filaments (antennae) which occur on the + gynostemium of the flower the pollinia are shot out to a fairly long + distance (as far as 1 metre) and in such manner that they alight on the + back of the insect, where they are held. The antennae have, moreover, + acquired an importance, from the point of view of the physiology of + stimulation, as stimulus-perceiving organs. Darwin had shown that it is + only a touch on the antennae that causes the explosion, while contact, + blows, wounding, etc. on other places produce no effect. This form of + flower proved to be the male. The second form, formerly regarded as a + distinct species and named Monachanthus viridis, is shown to be the female + flower. The anthers have only rudimentary pollinia and do not open; there + are no antennae, but on the other hand numerous seeds are produced. + Another type of flower, known as Myanthus barbatus, was regarded by Darwin + as a third form: this was afterwards recognised by Rolfe (Rolfe, R.A. "On + the sexual forms of Catasetum with special reference to the researches of + Darwin and others," "Journ. Linn. Soc." Vol. XXVII. (Botany), 1891, pages + 206-225.) as the male flower of another species, Catasetum barbatum Link, + an identification in accordance with the discovery made by Cruger in + Trinidad that it always remains sterile. + </p> + <p> + Darwin had noticed that the flowers of Catasetum do not secrete nectar, + and he conjectured that in place of it the insects gnaw a tissue in the + cavity of the labellum which has a "slightly sweet, pleasant and + nutritious taste." This conjecture as well as other conclusions drawn by + Darwin from Catasetum have been confirmed by Cruger—assuredly the + best proof of the acumen with which the wonderful floral structure of this + "most remarkable of the Orchids" was interpretated far from its native + habitat. + </p> + <p> + As is shown by what we have said about Catasetum, other problems in + addition to those concerned with fertilisation are dealt with in the + Orchid book. This is especially the case in regard to flower morphology. + The scope of flower morphology cannot be more clearly and better expressed + than by these words: "He will see how curiously a flower may be moulded + out of many separate organs—how perfect the cohesion of primordially + distinct parts may become,—how organs may be used for purposes + widely different from their proper function,—how other organs may be + entirely suppressed, or leave mere useless emblems of their former + existence." ("Fertilisation of Orchids", page 289.) + </p> + <p> + In attempting, from this point of view, to refer the floral structure of + orchids to their original form, Darwin employed a much more thorough + method than that of Robert Brown and others. The result of this was the + production of a considerable literature, especially in France, along the + lines suggested by Darwin's work. This is the so-called anatomical method, + which seeks to draw conclusions as to the morphology of the flower from + the course of the vascular bundles in the several parts. (He wrote in one + of his letters, "... the destiny of the whole human race is as nothing to + the course of vessels of orchids" ("More Letters", Vol. II. page 275.) + Although the interpretation of the orchid flower given by Darwin has not + proved satisfactory in one particular point—the composition of the + labellum—the general results have received universal assent, namely + "that all Orchids owe what they have in common to descent from some + monocotyledonous plant, which, like so many other plants of the same + division, possessed fifteen organs arranged alternately three within three + in five whorls." ("Fertilisation of Orchids" (1st edition), page 307.) The + alterations which their original form has undergone have persisted so far + as they were found to be of use. + </p> + <p> + We see also that the remarkable adaptations of which we have given some + examples are directed towards cross-fertilisation. In only a few of the + orchids investigated by Darwin—other similar cases have since been + described—was self-fertilisation found to occur regularly or + usually. The former is the case in the Bee Ophrys (Ophrys apifera), the + mechanism of which greatly surprised Darwin. He once remarked to a friend + that one of the things that made him wish to live a few thousand years was + his desire to see the extinction of the Bee Ophrys, an end to which he + believed its self-fertilising habit was leading. ("Life and Letters", Vol. + III. page 276 (footnote).) But, he wrote, "the safest conclusion, as it + seems to me, is, that under certain unknown circumstances, and perhaps at + very long intervals of time, one individual of the Bee Ophrys is crossed + by another." ("Fertilisation of Orchids" page 71.) + </p> + <p> + If, on the one hand, we remember how much more sure self-fertilisation + would be than cross-fertilisation, and, on the other hand, if we call to + mind the numerous contrivances for cross-fertilisation, the conclusion is + naturally reached that "it is an astonishing fact that self-fertilisation + should not have been an habitual occurrence. It apparently demonstrates to + us that there must be something injurious in the process. Nature thus + tells us, in the most emphatic manner, that she abhors perpetual + self-fertilisation... For may we not further infer as probable, in + accordance with the belief of the vast majority of the breeders of our + domestic productions, that marriage between near relations is likewise in + some way injurious, that some unknown great good is derived from the union + of individuals which have been kept distinct for many generations?" + (Ibid., page 359.) + </p> + <p> + This view was supported by observations on plants of other families, e.g. + Papilionaceae; it could, however, in the absence of experimental proof, be + regarded only as a "working hypothesis." + </p> + <p> + All adaptations to cross-pollination might also be of use simply because + they made pollination possible when for any reason self-pollination had + become difficult or impossible. Cross-pollination would, therefore, be of + use, not as such, but merely as a means of pollination in general; it + would to some extent serve as a remedy for a method unsuitable in itself, + such as a modification standing in the way of self-pollination, and on the + other hand as a means of increasing the chance of pollination in the case + of flowers in which self-pollination was possible, but which might, in + accidental circumstances, be prevented. It was, therefore, very important + to obtain experimental proof of the conclusion to which Darwin was led by + the belief of the majority of breeders and by the evidence of the + widespread occurrence of cross-pollination and of the remarkable + adaptations thereto. + </p> + <p> + This was supplied by the researches which are described in the two other + works named above. The researches on which the conclusions rest had, in + part at least, been previously published in separate papers: this is the + case as regards the heterostyled plants. The discoveries which Darwin made + in the course of his investigations of these plants belong to the most + brilliant in biological science. + </p> + <p> + The case of Primula is now well known. C.K. Sprengel and others were + familiar with the remarkable fact that different individuals of the + European species of Primula bear differently constructed flowers; some + plants possess flowers in which the styles project beyond the stamens + attached to the corolla-tube (long-styled form), while in others the + stamens are inserted above the stigma which is borne on a short style + (short-styled form). It has been shown by Breitenbach that both forms of + flower may occur on the same plant, though this happens very rarely. An + analogous case is occasionally met with in hybrids, which bear flowers of + different colour on the same plant (e.g. Dianthus caryophyllus). Darwin + showed that the external differences are correlated with others in the + structure of the stigma and in the nature of the pollen. The long-styled + flowers have a spherical stigma provided with large stigmatic papillae; + the pollen grains are oblong and smaller than those of the short-styled + flowers. The number of the seeds produced is smaller and the ovules + larger, probably also fewer in number. The short-styled flowers have a + smooth compressed stigma and a corolla of somewhat different form; they + produce a greater number of seeds. + </p> + <p> + These different forms of flowers were regarded as merely a case of + variation, until Darwin showed "that these heterostyled plants are adapted + for reciprocal fertilisation; so that the two or three forms, though all + are hermaphrodites, are related to one another almost like the males and + females of ordinary unisexual animals." ("Forms of Flowers" (1st edition), + page 2.) We have here an example of hermaphrodite flowers which are + sexually different. There are essential differences in the manner in which + fertilisation occurs. This may be effected in four different ways; there + are two legitimate and two illegitimate types of fertilisation. The + fertilisation is legitimate if pollen from the long-styled flowers reaches + the stigma of the short-styled form or if pollen of the short-styled + flowers is brought to the stigma of the long-styled flower, that is the + organs of the same length of the two different kinds of flower react on + one another. Illegitimate fertilisation is represented by the two kinds of + self-fertilisation, also by cross-fertilisation, in which the pollen of + the long-styled form reaches the stigma of the same type of flower and, + similarly, by cross-pollination in the case of the short-styled flowers. + </p> + <p> + The applicability of the terms legitimate and illegitimate depends, on the + one hand, upon the fact that insects which visit the different forms of + flowers pollinate them in the manner suggested; the pollen of the + short-styled flowers adhere to that part of the insect's body which + touches the stigma of the long-styled flower and vice versa. On the other + hand, it is based also on the fact that experiment shows that artificial + pollination produces a very different result according as this is + legitimate or illegitimate; only the legitimate union ensures complete + fertility, the plants thus produced being stronger than those which are + produced illegitimately. + </p> + <p> + If we take 100 as the number of flowers which produce seeds as the result + of legitimate fertilisation, we obtain the following numbers from + illegitimate fertilisation: + </p> + <p> + Primula officinalis (P. veris) (Cowslip)... 69 Primula elatior + (Oxlip).................... 27 Primula acaulis (P. vulgaris) (Primrose)... + 60 + </p> + <p> + Further, the plants produced by the illegitimate method of fertilisation + showed, e.g. in P. officinalis, a decrease in fertility in later + generations, sterile pollen and in the open a feebler growth. (Under very + favourable conditions (in a greenhouse) the fertility of the plants of the + fourth generation increases—a point, which in view of various + theoretical questions, deserves further investigation.) They behave in + fact precisely in the same way as hybrids between species of different + genera. This result is important, "for we thus learn that the difficulty + in sexually uniting two organic forms and the sterility of their + offspring, afford no sure criterion of so-called specific distinctness" + ("Forms of Flowers", page 242): the relative or absolute sterility of the + illegitimate unions and that of their illegitimate descendants depend + exclusively on the nature of the sexual elements and on their inability to + combine in a particular manner. This functional difference of sexual cells + is characteristic of the behaviour of hybrids as of the illegitimate + unions of heterostyled plants. The agreement becomes even closer if we + regard the Primula plants bearing different forms of flowers not as + belonging to a systematic entity or "species," but as including several + elementary species. The legitimately produced plants are thus true hybrids + (When Darwin wrote in reference to the different forms of heterostyled + plants, "which all belong to the same species as certainly as do the two + sexes of the same species" ("Cross and Self fertilisation", page 466), he + adopted the term species in a comprehensive sense. The recent researches + of Bateson and Gregory ("On the inheritance of Heterostylism in Primula"; + "Proc. Roy. Soc." Ser. B, Vol. LXXVI. 1905, page 581) appear to me also to + support the view that the results of illegitimate crossing of heterostyled + Primulas correspond with those of hybridisation. The fact that legitimate + pollen effects fertilisation, even if illegitimate pollen reaches the + stigma a short time previously, also points to this conclusion. + Self-pollination in the case of the short-styled form, for example, is not + excluded. In spite of this, the numerical proportion of the two forms + obtained in the open remains approximately the same as when the + pollination was exclusively legitimate, presumably because legitimate + pollen is prepotent.), with which their behaviour in other respects, as + Darwin showed, presents so close an agreement. This view receives support + also from the fact that descendants of a flower fertilised illegitimately + by pollen from another plant with the same form of flower belong, with few + exceptions, to the same type as that of their parents. The two forms of + flower, however, behave differently in this respect. Among 162 seedlings + of the long-styled illegitimately pollinated plants of Primula + officinalis, including five generations, there were 156 long-styled and + only six short-styled forms, while as the result of legitimate + fertilisation nearly half of the offspring were long-styled and half + short-styled. The short-styled illegitimately pollinated form gave five + long-styled and nine short-styled; the cause of this difference requires + further explanation. The significance of heterostyly, whether or not we + now regard it as an arrangement for the normal production of hybrids, is + comprehensively expressed by Darwin: "We may feel sure that plants have + been rendered heterostyled to ensure cross-fertilisation, for we now know + that a cross between the distinct individuals of the same species is + highly important for the vigour and fertility of the offspring." ("Forms + of Flowers", page 258.) If we remember how important the interpretation of + heterostyly has become in all general problems as, for example, those + connected with the conditions of the formation of hybrids, a fact which + was formerly overlooked, we can appreciate how Darwin was able to say in + his autobiography: "I do not think anything in my scientific life has + given me so much satisfaction as making out the meaning of the structure + of these plants." ("Life and Letters", Vol. I. page 91.) + </p> + <p> + The remarkable conditions represented in plants with three kinds of + flowers, such as Lythrum and Oxalis, agree in essentials with those in + Primula. These cannot be considered in detail here; it need only be noted + that the investigation of these cases was still more laborious. In order + to establish the relative fertility of the different unions in Lythrum + salicaria 223 different fertilisations were made, each flower being + deprived of its male organs and then dusted with the appropriate pollen. + </p> + <p> + In the book containing the account of heterostyled plants other species + are dealt with which, in addition to flowers opening normally + (chasmogamous), also possess flowers which remain closed but are capable + of producing fruit. These cleistogamous flowers afford a striking example + of habitual self-pollination, and H. von Mohl drew special attention to + them as such shortly after the appearance of Darwin's Orchid book. If it + were only a question of producing seed in the simplest way, cleistogamous + flowers would be the most conveniently constructed. The corolla and + frequently other parts of the flower are reduced; the development of the + seed may, therefore, be accomplished with a smaller expenditure of + building material than in chasmogamous flowers; there is also no loss of + pollen, and thus a smaller amount suffices for fertilisation. + </p> + <p> + Almost all these plants, as Darwin pointed out, have also chasmogamous + flowers which render cross-fertilisation possible. His view that + cleistogamous flowers are derived from originally chasmogamous flowers has + been confirmed by more recent researches. Conditions of nutrition in the + broader sense are the factors which determine whether chasmogamous or + cleistogamous flowers are produced, assuming, of course, that the plants + in question have the power of developing both forms of flower. The former + may fail to appear for some time, but are eventually developed under + favourable conditions of nourishment. The belief of many authors that + there are plants with only cleistogamous flowers cannot therefore be + accepted as authoritative without thorough experimental proof, as we are + concerned with extra-european plants for which it is often difficult to + provide appropriate conditions in cultivation. + </p> + <p> + Darwin sees in cleistogamous flowers an adaptation to a good supply of + seeds with a small expenditure of material, while chasmogamous flowers of + the same species are usually cross-fertilised and "their offspring will + thus be invigorated, as we may infer from a wide-spread analogy." ("Forms + of Flowers" (1st edition), page 341.) Direct proof in support of this has + hitherto been supplied in a few cases only; we shall often find that the + example set by Darwin in solving such problems as these by laborious + experiment has unfortunately been little imitated. + </p> + <p> + Another chapter of this book treats of the distribution of the sexes in + polygamous, dioecious, and gyno-dioecious plants (the last term, now in + common use, we owe to Darwin). It contains a number of important facts and + discussions and has inspired the experimental researches of Correns and + others. + </p> + <p> + The most important of Darwin's work on floral biology is, however, that on + cross and self-fertilisation, chiefly because it states the results of + experimental investigations extending over many years. Only such + experiments, as we have pointed out, could determine whether + cross-fertilisation is in itself beneficial, and self-fertilisation on the + other hand injurious; a conclusion which a merely comparative examination + of pollination-mechanisms renders in the highest degree probable. Later + floral biologists have unfortunately almost entirely confined themselves + to observations on floral mechanisms. But there is little more to be + gained by this kind of work than an assumption long ago made by C.K. + Sprengel that "very many flowers have the sexes separate and probably at + least as many hermaphrodite flowers are dichogamous; it would thus appear + that Nature was unwilling that any flower should be fertilised by its own + pollen." + </p> + <p> + It was an accidental observation which inspired Darwin's experiments on + the effect of cross and self-fertilisation. Plants of Linaria vulgaris + were grown in two adjacent beds; in the one were plants produced by + cross-fertilisation, that is, from seeds obtained after fertilisation by + pollen of another plant of the same species; in the other grew plants + produced by self-fertilisation, that is from seed produced as the result + of pollination of the same flower. The first were obviously superior to + the latter. + </p> + <p> + Darwin was surprised by this observation, as he had expected a prejudicial + influence of self-fertilisation to manifest itself after a series of + generations: "I always supposed until lately that no evil effects would be + visible until after several generations of self-fertilisation, but now I + see that one generation sometimes suffices and the existence of dimorphic + plants and all the wonderful contrivances of orchids are quite + intelligible to me." ("More Letters", Vol. II. page 373.) + </p> + <p> + The observations on Linaria and the investigations of the results of + legitimate and illegitimate fertilisation in heterostyled plants were + apparently the beginning of a long series of experiments. These were + concerned with plants of different families and led to results which are + of fundamental importance for a true explanation of sexual reproduction. + </p> + <p> + The experiments were so arranged that plants were shielded from + insect-visits by a net. Some flowers were then pollinated with their own + pollen, others with pollen from another plant of the same species. The + seeds were germinated on moist sand; two seedlings of the same age, one + from a cross and the other from a self-fertilised flower, were selected + and planted on opposite sides of the same pot. They grew therefore under + identical external conditions; it was thus possible to compare their + peculiarities such as height, weight, fruiting capacity, etc. In other + cases the seedlings were placed near to one another in the open and in + this way their capacity of resisting unfavourable external conditions was + tested. The experiments were in some cases continued to the tenth + generation and the flowers were crossed in different ways. We see, + therefore, that this book also represents an enormous amount of most + careful and patient original work. + </p> + <p> + The general result obtained is that plants produced as the result of + cross-fertilisation are superior, in the majority of cases, to those + produced as the result of self-fertilisation, in height, resistance to + external injurious influences, and in seed-production. + </p> + <p> + Ipomoea purpurea may be quoted as an example. If we express the result of + cross-fertilisation by 100, we obtain the following numbers for the + fertilised plants. + </p> +<pre xml:space="preserve"> + Generation. Height. Number of seeds. + + 1 100: 76 100: 64 + 2 100: 79 - + 3 100: 68 100: 94 + 4 100: 86 100: 94 + 5 100: 75 100: 89 + 6 100: 72 - + 7 100: 81 - + 8 100: 85 - + 9 100: 79 100: 26 (Number of capsules) + 10 100: 54 - +</pre> + <p> + Taking the average, the ratio as regards growth is 100:77. The + considerable superiority of the crossed plants is apparent in the first + generation and is not increased in the following generations; but there is + some fluctuation about the average ratio. The numbers representing the + fertility of crossed and self-fertilised plants are more difficult to + compare with accuracy; the superiority of the crossed plants is chiefly + explained by the fact that they produce a much larger number of capsules, + not because there are on the average more seeds in each capsule. The ratio + of the capsules was, e.g. in the third generation, 100:38, that of the + seeds in the capsules 100:94. It is also especially noteworthy that in the + self-fertilised plants the anthers were smaller and contained a smaller + amount of pollen, and in the eighth generation the reduced fertility + showed itself in a form which is often found in hybrids, that is the first + flowers were sterile. (Complete sterility was not found in any of the + plants investigated by Darwin. Others appear to be more sensitive; Cluer + found Zea Mais "almost sterile" after three generations of + self-fertilisation. (Cf. Fruwirth, "Die Zuchtung der Landwirtschaftlichen + Kulturpflanzen", Berlin, 1904, II. page 6.)) + </p> + <p> + The superiority of crossed individuals is not exhibited in the same way in + all plants. For example in Eschscholzia californica the crossed seedlings + do not exceed the self-fertilised in height and vigour, but the crossing + considerably increases the plant's capacity for flower-production, and the + seedlings from such a mother-plant are more fertile. + </p> + <p> + The conception implied by the term crossing requires a closer analysis. As + in the majority of plants, a large number of flowers are in bloom at the + same time on one and the same plant, it follows that insects visiting the + flowers often carry pollen from one flower to another of the same stock. + Has this method, which is spoken of as Geitonogamy, the same influence as + crossing with pollen from another plant? The results of Darwin's + experiments with different plants (Ipomoea purpurea, Digitalis purpurea, + Mimulus luteus, Pelargonium, Origanum) were not in complete agreement; but + on the whole they pointed to the conclusion that Geitonogamy shows no + superiority over self-fertilisation (Autogamy). (Similarly crossing in the + case of flowers of Pelargonium zonale, which belong to plants raised from + cuttings from the same parent, shows no superiority over + self-fertilisation.) Darwin, however, considered it possible that this may + sometimes be the case. "The sexual elements in the flowers on the same + plant can rarely have been differentiated, though this is possible, as + flower-buds are in one sense distinct individuals, sometimes varying and + differing from one another in structure or constitution." ("Cross and Self + fertilisation" (1st edition), page 444.) + </p> + <p> + As regards the importance of this question from the point of view of the + significance of cross-fertilisation in general, it may be noted that later + observers have definitely discovered a difference between the results of + autogamy and geitonogamy. Gilley and Fruwirth found that in Brassica + Napus, the length and weight of the fruits as also the total weight of the + seeds in a single fruit were less in the case of autogamy than in + geitonogamy. With Sinapis alba a better crop of seeds was obtained after + geitonogamy, and in the Sugar Beet the average weight of a fruit in the + case of a self-fertilised plant was 0.009 gr., from geitonogamy 0.012 gr., + and on cross-fertilisation 0.013 gr. + </p> + <p> + On the whole, however, the results of geitonogamy show that the favourable + effects of cross-fertilisation do not depend simply on the fact that the + pollen of one flower is conveyed to the stigma of another. But the plants + which are crossed must in some way be different. If plants of Ipomoea + purpurea (and Mimulus luteus) which have been self-fertilised for seven + generations and grown under the same conditions of cultivation are crossed + together, the plants so crossed would not be superior to the + self-fertilised; on the other hand crossing with a fresh stock at once + proves very advantageous. The favourable effect of crossing is only + apparent, therefore, if the parent plants are grown under different + conditions or if they belong to different varieties. "It is really + wonderful what an effect pollen from a distinct seedling plant, which has + been exposed to different conditions of life, has on the offspring in + comparison with pollen from the same flower or from a distinct individual, + but which has been long subjected to the same conditions. The subject + bears on the very principle of life, which seems almost to require changes + in the conditions." ("More Letters", Vol. II. page 406.) + </p> + <p> + The fertility—measured by the number or weight of the seeds produced + by an equal number of plants—noticed under different conditions of + fertilisation may be quoted in illustration. + </p> +<pre xml:space="preserve"> + On crossing On crossing On self- + with a fresh plants of the fertilisation + stock same stock + Mimuleus luteus + (First and ninth generation) 100 4 3 + + Eschscholzia californica + (second generation) 100 45 40 + + Dianthus caryophyllus + (third and fourth generation) 100 45 33 + + Petunia violacea 100 54 46 +</pre> + <p> + Crossing under very similar conditions shows, therefore, that the + difference between the sexual cells is smaller and thus the result of + crossing is only slightly superior to that given by self-fertilisation. + Is, then, the favourable result of crossing with a foreign stock to be + attributed to the fact that this belongs to another systematic entity or + to the fact that the plants, though belonging to the same entity were + exposed to different conditions? This is a point on which further + researches must be taken into account, especially since the analysis of + the systematic entities has been much more thorough than formerly. (In the + case of garden plants, as Darwin to a large extent claimed, it is not easy + to say whether two individuals really belong to the same variety, as they + are usually of hybrid origin. In some instances (Petunia, Iberis) the + fresh stock employed by Darwin possessed flowers differing in colour from + those of the plant crossed with it.) We know that most of Linneaus's + species are compound species, frequently consisting of a very large number + of smaller or elementary species formerly included under the comprehensive + term varieties. Hybridisation has in most cases affected our garden and + cultivated plants so that they do not represent pure species but a mixture + of species. + </p> + <p> + But this consideration has no essential bearing on Darwin's point of view, + according to which the nature of the sexual cells is influenced by + external conditions. Even individuals growing close to one another are + only apparently exposed to identical conditions. Their sexual cells may + therefore be differently influenced and thus give favourable results on + crossing, as "the benefits which so generally follow from a cross between + two plants apparently depend on the two differing somewhat in constitution + or character." As a matter of fact we are familiar with a large number of + cases in which the condition of the reproductive organs is influenced by + external conditions. Darwin has himself demonstrated this for self-sterile + plants, that is plants in which self-fertilisation produces no result. + This self-sterility is affected by climatic conditions: thus in Brazil + Eschscholzia californica is absolutely sterile to the pollen of its own + flowers; the descendants of Brazilian plants in Darwin's cultures were + partially self-fertile in one generation and in a second generation still + more so. If one has any doubt in this case whether it is a question of the + condition of the style and stigma, which possibly prevents the entrance of + the pollen-tube or even its development, rather than that of the actual + sexual cells, in other cases there is no doubt that an influence is + exerted on the latter. + </p> + <p> + Janczewski (Janczewski, "Sur les antheres steriles des Groseilliers", + "Bull. de l'acad. des sciences de Cracovie", June, 1908.) has recently + shown that species of Ribes cultivated under unnatural conditions + frequently produce a mixed (i.e. partly useless) or completely sterile + pollen, precisely as happens with hybrids. There are, therefore, + substantial reasons for the conclusion that conditions of life exert an + influence on the sexual cells. "Thus the proposition that the benefit from + cross-fertilisation depends on the plants which are crossed having been + subjected during previous generations to somewhat different conditions, or + to their having varied from some unknown cause as if they had been thus + subjected, is securely fortified on all sides." ("Cross and Self + fertilisation" (1st edition), page 444.) + </p> + <p> + We thus obtain an insight into the significance of sexuality. If an + occasional and slight alteration in the conditions under which plants and + animals live is beneficial (Reasons for this are given by Darwin in + "Variation under Domestication" (2nd edition), Vol. II. page 127.), + crossing between organisms which have been exposed to different conditions + becomes still more advantageous. The entire constitution is in this way + influenced from the beginning, at a time when the whole organisation is in + a highly plastic state. The total life-energy, so to speak, is increased, + a gain which is not produced by asexual reproduction or by the union of + sexual cells of plants which have lived under the same or only slightly + different conditions. All the wonderful arrangements for + cross-fertilisation now appear to be useful adaptations. Darwin was, + however, far from giving undue prominence to this point of view, though + this has been to some extent done by others. He particularly emphasised + the following consideration:—"But we should always keep in mind that + two somewhat opposed ends have to be gained; the first and more important + one being the production of seeds by any means, and the second, + cross-fertilisation." ("Cross and Self fertilisation" (1st edition), page + 371.) Just as in some orchids and cleistogamic flowers self-pollination + regularly occurs, so it may also occur in other cases. Darwin showed that + Pisum sativum and Lathyrus odoratus belong to plants in which + self-pollination is regularly effected, and that this accounts for the + constancy of certain sorts of these plants, while a variety of form is + produced by crossing. Indeed among his culture plants were some which + derived no benefit from crossing. Thus in the sixth self-fertilised + generation of his Ipomoea cultures the "Hero" made its appearance, a form + slightly exceeding its crossed companion in height; this was in the + highest degree self-fertile and handed on its characteristics to both + children and grandchildren. Similar forms were found in Mimulus luteus and + Nicotiana (In Pisum sativum also the crossing of two individuals of the + same variety produced no advantage; Darwin attributed this to the fact + that the plants had for several generations been self-fertilised and in + each generation cultivated under almost the same conditions. Tschermak + ("Ueber kunstliche Kreuzung an Pisum sativum") afterwards recorded the + same result; but he found on crossing different varieties that usually + there was no superiority as regards height over the products of + self-fertilisation, while Darwin found a greater height represented by the + ratios 100:75 and 100:60.), types which, after self-fertilisation, have an + enhanced power of seed-production and of attaining a greater height than + the plants of the corresponding generation which are crossed together and + self-fertilised and grown under the same conditions. "Some observations + made on other plants lead me to suspect that self-fertilisation is in some + respects beneficial; although the benefit thus derived is as a rule very + small compared with that from a cross with a distinct plant." ("Cross and + Self fertilisation", page 350.) We are as ignorant of the reason why + plants behave differently when crossed and self-fertilised as we are in + regard to the nature of the differentiation of the sexual cells, which + determines whether a union of the sexual cells will prove favourable or + unfavourable. + </p> + <p> + It is impossible to discuss the different results of cross-fertilisation; + one point must, however, be emphasised, because Darwin attached + considerable importance to it. It is inevitable that pollen of different + kinds must reach the stigma. It was known that pollen of the same + "species" is dominant over the pollen of another species, that, in other + words, it is prepotent. Even if the pollen of the same species reaches the + stigma rather later than that of another species, the latter does not + effect fertilisation. + </p> + <p> + Darwin showed that the fertilising power of the pollen of another variety + or of another individual is greater than that of the plant's own pollen. + ("Cross and Self fertilisation", page 391.) This has been demonstrated in + the case of Mimulus luteus (for the fixed white-flowering variety) and + Iberis umbellata with pollen of another variety, and observations on + cultivated plants, such as cabbage, horseradish, etc. gave similar + results. It is, however, especially remarkable that pollen of another + individual of the same variety may be prepotent over the plant's own + pollen. This results from the superiority of plants crossed in this manner + over self-fertilised plants. "Scarcely any result from my experiments has + surprised me so much as this of the prepotency of pollen from a distinct + individual over each plant's own pollen, as proved by the greater + constitutional vigour of the crossed seedlings." (Ibid. page 397.) + Similarly, in self-fertile plants the flowers of which have not been + deprived of the male organs, pollen brought to the stigma by the wind or + by insects from another plant effects fertilisation, even if the plant's + own pollen has reached the stigma somewhat earlier. + </p> + <p> + Have the results of his experimental investigations modified the point of + view from which Darwin entered on his researches, or not? In the first + place the question is, whether or not the opinion expressed in the Orchid + book that there is "Something injurious" connected with + self-fertilisation, has been confirmed. We can, at all events, affirm that + Darwin adhered in essentials to his original position; but + self-fertilisation afterwards assumed a greater importance than it + formerly possessed. Darwin emphasised the fact that "the difference + between the self-fertilised and crossed plants raised by me cannot be + attributed to the superiority of the crossed, but to the inferiority of + the self-fertilised seedlings, due to the injurious effects of + self-fertilisation." (Ibid. page 437.) But he had no doubt that in + favourable circumstances self-fertilised plants were able to persist for + several generations without crossing. An occasional crossing appears to be + useful but not indispensable in all cases; its sporadic occurrence in + plants in which self-pollination habitually occurs is not excluded. + Self-fertilisation is for the most part relatively and not absolutely + injurious and always better than no fertilisation. "Nature abhors + perpetual self-fertilisation" (It is incorrect to say, as a writer has + lately said, that the aphorism expressed by Darwin in 1859 and 1862, + "Nature abhors perpetual self-fertilisation," is not repeated in his later + works. The sentence is repeated in "Cross and Self fertilisation" (page + 8), with the addition, "If the word perpetual had been omitted, the + aphorism would have been false. As it stands, I believe that it is true, + though perhaps rather too strongly expressed.") is, however, a pregnant + expression of the fact that cross-fertilisation is exceedingly widespread + and has been shown in the majority of cases to be beneficial, and that in + those plants in which we find self-pollination regularly occurring + cross-pollination may occasionally take place. + </p> + <p> + An attempt has been made to express in brief the main results of Darwin's + work on the biology of flowers. We have seen that his object was to + elucidate important general questions, particularly the question of the + significance of sexual reproduction. + </p> + <p> + It remains to consider what influence his work has had on botanical + science. That this influence has been very considerable, is shown by a + glance at the literature on the biology of flowers published since Darwin + wrote. Before the book on orchids was published there was nothing but the + old and almost forgotten works of Kolreuter and Sprengel with the + exception of a few scattered references. Darwin's investigations gave the + first stimulus to the development of an extensive literature on floral + biology. In Knuth's "Handbuch der Blutenbiologie" ("Handbook of Flower + Pollination", Oxford, 1906) as many as 3792 papers on this subject are + enumerated as having been published before January 1, 1904. These describe + not only the different mechanisms of flowers, but deal also with a series + of remarkable adaptations in the pollinating insects. As a fertilising + rain quickly calls into existence the most varied assortment of plants on + a barren steppe, so activity now reigns in a field which men formerly left + deserted. This development of the biology of flowers is of importance not + only on theoretical grounds but also from a practical point of view. The + rational breeding of plants is possible only if the flower-biology of the + plants in question (i.e. the question of the possibility of + self-pollination, self-sterility, etc.) is accurately known. And it is + also essential for plant-breeders that they should have "the power of + fixing each fleeting variety of colour, if they will fertilise the flowers + of the desired kind with their own pollen for half-a-dozen generations, + and grow the seedlings under the same conditions." ("Cross and Self + fertilisation" (1st edition), page 460.) + </p> + <p> + But the influence of Darwin on floral biology was not confined to the + development of this branch of Botany. Darwin's activity in this domain has + brought about (as Asa Gray correctly pointed out) the revival of teleology + in Botany and Zoology. Attempts were now made to determine, not only in + the case of flowers but also in vegetative organs, in what relation the + form and function of organs stand to one another and to what extent their + morphological characters exhibit adaptation to environment. A branch of + Botany, which has since been called Ecology (not a very happy term) has + been stimulated to vigorous growth by floral biology. + </p> + <p> + While the influence of the work on the biology of flowers was + extraordinarily great, it could not fail to elicit opinions at variance + with Darwin's conclusions. The opposition was based partly on reasons + valueless as counterarguments, partly on problems which have still to be + solved; to some extent also on that tendency against teleological + conceptions which has recently become current. This opposing trend of + thought is due to the fact that many biologists are content with + teleological explanations, unsupported by proof; it is also closely + connected with the fact that many authors estimate the importance of + natural selection less highly than Darwin did. We may describe the + objections which are based on the widespread occurrence of + self-fertilisation and geitonogamy as of little importance. Darwin did not + deny the occurrence of self-fertilisation, even for a long series of + generations; his law states only that "Nature abhors PERPETUAL + self-fertilisation." (It is impossible (as has been attempted) to express + Darwin's point of view in a single sentence, such as H. Muller's statement + of the "Knight-Darwin law." The conditions of life in organisms are so + various and complex that laws, such as are formulated in physics and + chemistry, can hardly be conceived.) An exception to this rule would + therefore occur only in the case of plants in which the possibility of + cross-pollination is excluded. Some of the plants with cleistogamous + flowers might afford examples of such cases. We have already seen, + however, that such a case has not as yet been shown to occur. Burck + believed that he had found an instance in certain tropical plants + (Anonaceae, Myrmecodia) of the complete exclusion of cross-fertilisation. + The flowers of these plants, in which, however,—in contrast to the + cleistogamous flowers—the corolla is well developed, remain closed + and fruit is produced. + </p> + <p> + Loew (E. Loew, "Bemerkungen zu Burck... ", "Biolog. Centralbl." XXVI. + (1906).) has shown that cases occur in which cross-fertilisation may be + effected even in these "cleistopetalous" flowers: humming birds visit the + permanently closed flowers of certain species of Nidularium and transport + the pollen. The fact that the formation of hybrids may occur as the result + of this shows that pollination may be accomplished. + </p> + <p> + The existence of plants for which self-pollination is of greater + importance than it is for others is by no means contradictory to Darwin's + view. Self-fertilisation is, for example, of greater importance for + annuals than for perennials as without it seeds might fail to be produced. + Even in the case of annual plants with small inconspicuous flowers in + which self-fertilisation usually occurs, such as Senecio vulgaris, + Capsella bursa-pastoris and Stellaria media, A. Bateson (Anna Bateson, + "The effects of cross-fertilisation on inconspicuous flowers", "Annals of + Botany", Vol. I. 1888, page 255.) found that cross-fertilisation gave a + beneficial result, although only in a slight degree. If the favourable + effects of sexual reproduction, according to Darwin's view, are correlated + with change of environment, it is quite possible that this is of less + importance in plants which die after ripening their seeds ("hapaxanthic") + and which in any case constantly change their situation. Objections which + are based on the proof of the prevalence of self-fertilisation are not, + therefore, pertinent. At first sight another point of view, which has been + more recently urged, appears to have more weight. + </p> + <p> + W. Burck (Burck, "Darwin's Kreuzeungsgesetz... ", "Biol. Centralbl". + XXVIII. 1908, page 177.) has expressed the opinion that the beneficial + results of cross-fertilisation demonstrated by Darwin concern only hybrid + plants. These alone become weaker by self-pollination; while pure species + derive no advantage from crossing and no disadvantage from + self-fertilisation. It is certain that some of the plants used by Darwin + were of hybrid origin. (It is questionable if this was always the case.) + This is evident from his statements, which are models of clearness and + precision; he says that his Ipomoea plants "were probably the offspring of + a cross." ("Cross and Self fertilisation" (1st edition), page 55.) The + fixed forms of this plant, such as Hero, which was produced by + self-fertilisation, and a form of Mimulus with white flowers spotted with + red probably resulted from splitting of the hybrids. It is true that the + phenomena observed in self-pollination, e.g. in Ipomoea, agree with those + which are often noticed in hybrids; Darwin himself drew attention to this. + </p> + <p> + Let us next call to mind some of the peculiarities connected with + hybridisation. We know that hybrids are often characterized by their large + size, rapidity of growth, earlier production of flowers, wealth of + flower-production and a longer life; hybrids, if crossed with one of the + two parent forms, are usually more fertile than when they are crossed + together or with another hybrid. But the characters which hybrids exhibit + on self-fertilisation are rather variable. The following instance may be + quoted from Gartner: "There are many hybrids which retain the + self-fertility of the first generation during the second and later + generations, but very often in a less degree; a considerable number, + however, become sterile." But the hybrid varieties may be more fertile in + the second generation than in the first, and in some hybrids the fertility + with their own pollen increases in the second, third, and following + generations. (K.F. Gartner, "Versuche uber die Bastarderzeugung", + Stuttgart, 1849, page 149.) As yet it is impossible to lay down rules of + general application for the self-fertility of hybrids. That the beneficial + influence of crossing with a fresh stock rests on the same ground—a + union of sexual cells possessing somewhat different characters—as + the fact that many hybrids are distinguished by greater luxuriance, wealth + of flowers, etc. corresponds entirely with Darwin's conclusions. It seems + to me to follow clearly from his investigations that there is no essential + difference between cross-fertilisation and hybridisation. The heterostyled + plants are normally dependent on a process corresponding to hybridisation. + The view that specifically distinct species could at best produce sterile + hybrids was always opposed by Darwin. But if the good results of crossing + were EXCLUSIVELY dependent on the fact that we are concerned with hybrids, + there must then be a demonstration of two distinct things. First, that + crossing with a fresh stock belonging to the same systematic entity or to + the same hybrid, but cultivated for a considerable time under different + conditions, shows no superiority over self-fertilisation, and that in pure + species crossing gives no better results than self-pollination. If this + were the case, we should be better able to understand why in one plant + crossing is advantageous while in others, such as Darwin's Hero and the + forms of Mimulus and Nicotiana no advantage is gained; these would then be + pure species. But such a proof has not been supplied; the inference drawn + from cleistogamous and cleistopetalous plants is not supported by + evidence, and the experiments on geitonogamy and on the advantage of + cross-fertilisation in species which are usually self-fertilised are + opposed to this view. There are still but few researches on this point; + Darwin found that in Ononis minutissima, which produces cleistogamous as + well as self-fertile chasmogamous flowers, the crossed and self-fertilised + capsules produced seed in the proportion of 100:65 and that the average + bore the proportion 100:86. Facts previously mentioned are also applicable + to this case. Further, it is certain that the self-sterility exhibited by + many plants has nothing to do with hybridisation. Between self-sterility + and reduced fertility as the result of self-fertilisation there is + probably no fundamental difference. + </p> + <p> + It is certain that so difficult a problem as that of the significance of + sexual reproduction requires much more investigation. Darwin was anything + but dogmatic and always ready to alter an opinion when it was not based on + definite proof: he wrote, "But the veil of secrecy is as yet far from + lifted; nor will it be, until we can say why it is beneficial that the + sexual elements should be differentiated to a certain extent, and why, if + the differentiation be carried still further, injury follows." He has also + shown us the way along which to follow up this problem; it is that of + carefully planned and exact experimental research. It may be that + eventually many things will be viewed in a different light, but Darwin's + investigations will always form the foundation of Floral Biology on which + the future may continue to build. + </p> + <p> + <a name="link2H_4_0023" id="link2H_4_0023"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + XXI. MENTAL FACTORS IN EVOLUTION. By C. Lloyd Morgan, LL.D., F.R.S. + </h2> + <p> + In developing his conception of organic evolution Charles Darwin was of + necessity brought into contact with some of the problems of mental + evolution. In "The Origin of Species" he devoted a chapter to "the + diversities of instinct and of the other mental faculties in animals of + the same class." ("Origin of Species" (6th edition), page 205.) When he + passed to the detailed consideration of "The Descent of Man", it was part + of his object to show "that there is no fundamental difference between man + and the higher mammals in their mental faculties." ("Descent of Man" (2nd + edition 1888), Vol. I. page 99; Popular edition page 99.) "If no organic + being excepting man," he said, "had possessed any mental power, or if his + powers had been of a wholly different nature from those of the lower + animals, then we should never have been able to convince ourselves that + our high faculties had been gradually developed." (Ibid. page 99.) In his + discussion of "The Expression of the Emotions" it was important for his + purpose "fully to recognise that actions readily become associated with + other actions and with various states of the mind." ("The Expression of + the Emotions" (2nd edition), page 32.) His hypothesis of sexual selection + is largely dependent upon the exercise of choice on the part of the female + and her preference for "not only the more attractive but at the same time + the more vigorous and victorious males." ("Descent of Man", Vol. II. page + 435.) Mental processes and physiological processes were for Darwin closely + correlated; and he accepted the conclusion "that the nervous system not + only regulates most of the existing functions of the body, but has + indirectly influenced the progressive development of various bodily + structures and of certain mental qualities." (Ibid. pages 437, 438.) + </p> + <p> + Throughout his treatment, mental evolution was for Darwin incidental to + and contributory to organic evolution. For specialised research in + comparative and genetic psychology, as an independent field of + investigation, he had neither the time nor the requisite training. None + the less his writings and the spirit of his work have exercised a profound + influence on this department of evolutionary thought. And, for those who + follow Darwin's lead, mental evolution is still in a measure subservient + to organic evolution. Mental processes are the accompaniments or + concomitants of the functional activity of specially differentiated parts + of the organism. They are in some way dependent on physiological and + physical conditions. But though they are not physical in their nature, and + though it is difficult or impossible to conceive that they are physical in + their origin, they are, for Darwin and his followers, factors in the + evolutionary process in its physical or organic aspect. By the + physiologist within his special and well-defined universe of discourse + they may be properly regarded as epiphenomena; but by the naturalist in + his more catholic survey of nature they cannot be so regarded, and were + not so regarded by Darwin. Intelligence has contributed to evolution of + which it is in a sense a product. + </p> + <p> + The facts of observation or of inference which Darwin accepted are these: + Conscious experience accompanies some of the modes of animal behaviour; it + is concomitant with certain physiological processes; these processes are + the outcome of development in the individual and evolution in the race; + the accompanying mental processes undergo a like development. Into the + subtle philosophical questions which arise out of the naive acceptance of + such a creed it was not Darwin's province to enter; "I have nothing to + do," he said ("Origin of Species" (6th edition), page 205.), "with the + origin of the mental powers, any more than I have with that of life + itself." He dealt with the natural history of organisms, including not + only their structure but their modes of behaviour; with the natural + history of the states of consciousness which accompany some of their + actions; and with the relation of behaviour to experience. We will + endeavour to follow Darwin in his modesty and candour in making no + pretence to give ultimate explanations. But we must note one of the + implications of this self-denying ordinance of science. Development and + evolution imply continuity. For Darwin and his followers the continuity is + organic through physical heredity. Apart from speculative hypothesis, + legitimate enough in its proper place but here out of court, we know + nothing of continuity of mental evolution as such: consciousness appears + afresh in each succeeding generation. Hence it is that for those who + follow Darwin's lead, mental evolution is and must ever be, within his + universe of discourse, subservient to organic evolution. Only in so far as + conscious experience, or its neural correlate, effects some changes in + organic structure can it influence the course of heredity; and conversely + only in so far as changes in organic structure are transmitted through + heredity, is mental evolution rendered possible. Such is the logical + outcome of Darwin's teaching. + </p> + <p> + Those who abide by the cardinal results of this teaching are bound to + regard all behaviour as the expression of the functional activities of the + living tissues of the organism, and all conscious experience as correlated + with such activities. For the purposes of scientific treatment, mental + processes are one mode of expression of the same changes of which the + physiological processes accompanying behaviour are another mode of + expression. This is simply accepted as a fact which others may seek to + explain. The behaviour itself is the adaptive application of the energies + of the organism; it is called forth by some form of presentation or + stimulation brought to bear on the organism by the environment. This + presentation is always an individual or personal matter. But in order that + the organism may be fitted to respond to the presentation of the + environment it must have undergone in some way a suitable preparation. + According to the theory of evolution this preparation is primarily racial + and is transmitted through heredity. Darwin's main thesis was that the + method of preparation is predominantly by natural selection. Subordinate + to racial preparation, and always dependent thereon, is individual or + personal preparation through some kind of acquisition; of which the + guidance of behaviour through individually won experience is a typical + example. We here introduce the mental factor because the facts seem to + justify the inference. Thus there are some modes of behaviour which are + wholly and solely dependent upon inherited racial preparation; there are + other modes of behaviour which are also dependent, in part at least, on + individual preparation. In the former case the behaviour is adaptive on + the first occurrence of the appropriate presentation; in the latter case + accommodation to circumstances is only reached after a greater or less + amount of acquired organic modification of structure, often accompanied + (as we assume) in the higher animals by acquired experience. Logically and + biologically the two classes of behaviour are clearly distinguishable: but + the analysis of complex cases of behaviour where the two factors + cooperate, is difficult and requires careful and critical study of + life-history. + </p> + <p> + The foundations of the mental life are laid in the conscious experience + that accompanies those modes of behaviour, dependent entirely on racial + preparation, which may broadly be described as instinctive. In the eighth + chapter of "The Origin of Species" Darwin says ("Origin of Species" (6th + edition), page 205.), "I will not attempt any definition of instinct... + Every one understands what is meant, when it is said that instinct impels + the cuckoo to migrate and to lay her eggs in other birds' nests. An + action, which we ourselves require experience to enable us to perform, + when performed by an animal, more especially by a very young one, without + experience, and when performed by many individuals in the same way, + without their knowing for what purpose it is performed, is usually said to + be instinctive." And in the summary at the close of the chapter he says + ("Origin of Species" (6th edition), page 233.), "I have endeavoured + briefly to show that the mental qualities of our domestic animals vary, + and that the variations are inherited. Still more briefly I have attempted + to show that instincts vary slightly in a state of nature. No one will + dispute that instincts are of the highest importance to each animal. + Therefore there is no real difficulty, under changing conditions of life, + in natural selection accumulating to any extent slight modifications of + instinct which are in any way useful. In many cases habit or use and + disuse have probably come into play." + </p> + <p> + Into the details of Darwin's treatment there is neither space nor need to + enter. There are some ambiguous passages; but it may be said that for him, + as for his followers to-day, instinctive behaviour is wholly the result of + racial preparation transmitted through organic heredity. For the + performance of the instinctive act no individual preparation under the + guidance of personal experience is necessary. It is true that Darwin + quotes with approval Huber's saying that "a little dose of judgment or + reason often comes into play, even with animals low in the scale of + nature." (Ibid. page 205.) But we may fairly interpret his meaning to be + that in behaviour, which is commonly called instinctive, some element of + intelligent guidance is often combined. If this be conceded the strictly + instinctive performance (or part of the performance) is the outcome of + heredity and due to the direct transmission of parental or ancestral + aptitudes. Hence the instinctive response as such depends entirely on how + the nervous mechanism has been built up through heredity; while + intelligent behaviour, or the intelligent factor in behaviour, depends + also on how the nervous mechanism has been modified and moulded by use + during its development and concurrently with the growth of individual + experience in the customary situations of daily life. Of course it is + essential to the Darwinian thesis that what Sir E. Ray Lankester has + termed "educability," not less than instinct, is hereditary. But it is + also essential to the understanding of this thesis that the differentiae + of the hereditary factors should be clearly grasped. + </p> + <p> + For Darwin there were two modes of racial preparation, (1) natural + selection, and (2) the establishment of individually acquired habit. He + showed that instincts are subject to hereditary variation; he saw that + instincts are also subject to modification through acquisition in the + course of individual life. He believed that not only the variations but + also, to some extent, the modifications are inherited. He therefore held + that some instincts (the greater number) are due to natural selection but + that others (less numerous) are due, or partly due, to the inheritance of + acquired habits. The latter involve Lamarckian inheritance, which of late + years has been the centre of so much controversy. It is noteworthy however + that Darwin laid especial emphasis on the fact that many of the most + typical and also the most complex instincts—those of neuter insects—do + not admit of such an interpretation. "I am surprised," he says ("Origin of + Species" (6th edition), page 233.), "that no one has hitherto advanced + this demonstrative case of neuter insects, against the well-known doctrine + of inherited habit, as advanced by Lamarck." None the less Darwin admitted + this doctrine as supplementary to that which was more distinctively his + own—for example in the case of the instincts of domesticated + animals. Still, even in such cases, "it may be doubted," he says (Ibid. + pages 210, 211.), "whether any one would have thought of training a dog to + point, had not some one dog naturally shown a tendency in this line... so + that habit and some degree of selection have probably concurred in + civilising by inheritance our dogs." But in the interpretation of the + instincts of domesticated animals, a more recently suggested hypothesis, + that of organic selection (Independently suggested, on somewhat different + lines, by Profs. J. Mark Baldwin, Henry F. Osborn and the writer.), may be + helpful. According to this hypothesis any intelligent modification of + behaviour which is subject to selection is probably coincident in + direction with an inherited tendency to behave in this fashion. Hence in + such behaviour there are two factors: (1) an incipient variation in the + line of such behaviour, and (2) an acquired modification by which the + behaviour is carried further along the same line. Under natural selection + those organisms in which the two factors cooperate are likely to survive. + Under artificial selection they are deliberately chosen out from among the + rest. + </p> + <p> + Organic selection has been termed a compromise between the more strictly + Darwinian and the Lamarckian principles of interpretation. But it is not + in any sense a compromise. The principle of interpretation of that which + is instinctive and hereditary is wholly Darwinian. It is true that some of + the facts of observation relied upon by Lamarckians are introduced. For + Lamarckians however the modifications which are admittedly factors in + survival, are regarded as the parents of inherited variations; for + believers in organic selection they are only the foster parents or nurses. + It is because organic selection is the direct outcome of and a natural + extension of Darwin's cardinal thesis that some reference to it here is + justifiable. The matter may be put with the utmost brevity as follows. (1) + Variations (V) occur, some of which are in the direction of increased + adaptation (+), others in the direction of decreased adaptation (-). (2) + Acquired modifications (M) also occur. Some of these are in the direction + of increased accommodation to circumstances (+), while others are in the + direction of diminished accommodation (-). Four major combinations are + </p> +<pre xml:space="preserve"> + (a) + V with + M, + (b) + V with - M, + (c) - V with + M, + (d) - V with - M. +</pre> + <p> + Of these (d) must inevitably be eliminated while (a) are selected. The + predominant survival of (a) entails the survival of the adaptive + variations which are inherited. The contributory acquisitions (+M) are not + inherited; but they are none the less factors in determining the survival + of the coincident variations. It is surely abundantly clear that this is + Darwinism and has no tincture of Lamarck's essential principle, the + inheritance of acquired characters. + </p> + <p> + Whether Darwin himself would have accepted this interpretation of some at + least of the evidence put forward by Lamarckians is unfortunately a matter + of conjecture. The fact remains that in his interpretation of instinct and + in allied questions he accepted the inheritance of individually acquired + modifications of behaviour and structure. + </p> + <p> + Darwin was chiefly concerned with instinct from the biological rather than + from the psychological point of view. Indeed it must be confessed that, + from the latter standpoint, his conception of instinct as a "mental + faculty" which "impels" an animal to the performance of certain actions, + scarcely affords a satisfactory basis for genetic treatment. To carry out + the spirit of Darwin's teaching it is necessary to link more closely + biological and psychological evolution. The first step towards this is to + interpret the phenomena of instinctive behaviour in terms of stimulation + and response. It may be well to take a particular case. Swimming on the + part of a duckling is, from the biological point of view, a typical + example of instinctive behaviour. Gently lower a recently hatched bird + into water: coordinated movements of the limbs follow in rhythmical + sequence. The behaviour is new to the individual though it is no doubt + closely related to that of walking, which is no less instinctive. There is + a group of stimuli afforded by the "presentation" which results from + partial immersion: upon this there follows as a complex response an + application of the functional activities in swimming; the sequence of + adaptive application on the appropriate presentation is determined by + racial preparation. We know, it is true, but little of the physiological + details of what takes place in the central nervous system; but in broad + outline the nature of the organic mechanism and the manner of its + functioning may at least be provisionally conjectured in the present state + of physiological knowledge. Similarly in the case of the pecking of + newly-hatched chicks; there is a visual presentation, there is probably a + cooperating group of stimuli from the alimentary tract in need of food, + there is an adaptive application of the activities in a definite mode of + behaviour. Like data are afforded in a great number of cases of + instinctive procedure, sometimes occurring very early in life, not + infrequently deferred until the organism is more fully developed, but all + of them dependent upon racial preparation. No doubt there is some range of + variation in the behaviour, just such variation as the theory of natural + selection demands. But there can be no question that the higher animals + inherit a bodily organisation and a nervous system, the functional working + of which gives rise to those inherited modes of behaviour which are termed + instinctive. + </p> + <p> + It is to be noted that the term "instinctive" is here employed in the + adjectival form as a descriptive heading under which may be grouped many + and various modes of behaviour due to racial preparation. We speak of + these as inherited; but in strictness what is transmitted through heredity + is the complex of anatomical and physiological conditions under which, in + appropriate circumstances, the organism so behaves. So far the term + "instinctive" has a restricted biological connotation in terms of + behaviour. But the connecting link between biological evolution and + psychological evolution is to be sought,—as Darwin fully realised,—in + the phenomena of instinct, broadly considered. The term "instinctive" has + also a psychological connotation. What is that connotation? + </p> + <p> + Let us take the case of the swimming duckling or the pecking chick, and + fix our attention on the first instinctive performance. Grant that just as + there is, strictly speaking, no inherited behaviour, but only the + conditions which render such behaviour under appropriate circumstances + possible; so too there is no inherited experience, but only the conditions + which render such experience possible; then the cerebral conditions in + both cases are the same. The biological behaviour-complex, including the + total stimulation and the total response with the intervening or resultant + processes in the sensorium, is accompanied by an experience-complex + including the initial stimulation-consciousness and resulting + response-consciousness. In the experience-complex are comprised data which + in psychological analysis are grouped under the headings of cognition, + affective tone and conation. But the complex is probably experienced as an + unanalysed whole. If then we use the term "instinctive" so as to comprise + all congenital modes of behaviour which contribute to experience, we are + in a position to grasp the view that the net result in consciousness + constitutes what we may term the primary tissue of experience. To the + development of this experience each instinctive act contributes. The + nature and manner of organisation of this primary tissue of experience are + dependent on inherited biological aptitudes; but they are from the outset + onwards subject to secondary development dependent on acquired aptitudes. + Biological values are supplemented by psychological values in terms of + satisfaction or the reverse. + </p> + <p> + In our study of instinct we have to select some particular phase of animal + behaviour and isolate it so far as is possible from the life of which it + is a part. But the animal is a going concern, restlessly active in many + ways. Many instinctive performances, as Darwin pointed out ("Origin of + Species" (6th edition), page 206.), are serial in their nature. But the + whole of active life is a serial and coordinated business. The particular + instinctive performance is only an episode in a life-history, and every + mode of behaviour is more or less closely correlated with other modes. + This coordination of behaviour is accompanied by a correlation of the + modes of primary experience. We may classify the instinctive modes of + behaviour and their accompanying modes of instinctive experience under as + many heads as may be convenient for our purposes of interpretation, and + label them instincts of self-preservation, of pugnacity, of acquisition, + the reproductive instincts, the parental instincts, and so forth. An + instinct, in this sense of the term (for example the parental instinct), + may be described as a specialised part of the primary tissue of experience + differentiated in relation to some definite biological end. Under such an + instinct will fall a large number of particular and often well-defined + modes of behaviour, each with its own peculiar mode of experience. + </p> + <p> + It is no doubt exceedingly difficult as a matter of observation and of + inference securely based thereon to distinguish what is primary from what + is in part due to secondary acquisition—a fact which Darwin fully + appreciated. Animals are educable in different degrees; but where they are + educable they begin to profit by experience from the first. Only, + therefore, on the occasion of the first instinctive act of a given type + can the experience gained be weighed as WHOLLY primary; all subsequent + performance is liable to be in some degree, sometimes more, sometimes + less, modified by the acquired disposition which the initial behaviour + engenders. But the early stages of acquisition are always along the lines + predetermined by instinctive differentiation. It is the task of + comparative psychology to distinguish the primary tissue of experience + from its secondary and acquired modifications. We cannot follow up the + matter in further detail. It must here suffice to suggest that this + conception of instinct as a primary form of experience lends itself better + to natural history treatment than Darwin's conception of an impelling + force, and that it is in line with the main trend of Darwin's thought. + </p> + <p> + In a characteristic work,—characteristic in wealth of detail, in + closeness and fidelity of observation, in breadth of outlook, in candour + and modesty,—Darwin dealt with "The Expression of the Emotions in + Man and Animals". Sir Charles Bell in his "Anatomy of Expression" had + contended that many of man's facial muscles had been specially created for + the sole purpose of being instrumental in the expression of his emotions. + Darwin claimed that a natural explanation, consistent with the doctrine of + evolution, could in many cases be given and would in other cases be + afforded by an extension of the principles he advocated. "No doubt," he + said ("Expression of the Emotions", page 13. The passage is here somewhat + condensed.), "as long as man and all other animals are viewed as + independent creations, an effectual stop is put to our natural desire to + investigate as far as possible the causes of Expression. By this doctrine, + anything and everything can be equally well explained... With mankind, + some expressions... can hardly be understood, except on the belief that + man once existed in a much lower and animal-like condition. The community + of certain expressions in distinct though allied species... is rendered + somewhat more intelligible, if we believe in their descent from a common + progenitor. He who admits on general grounds that the structure and habits + of all animals have been gradually evolved, will look at the whole subject + of Expression in a new and interesting light." + </p> + <p> + Darwin relied on three principles of explanation. "The first of these + principles is, that movements which are serviceable in gratifying some + desire, or in relieving some sensation, if often repeated, become so + habitual that they are performed, whether or not of any service, whenever + the same desire or sensation is felt, even in a very weak degree." (Ibid. + page 368.) The modes of expression which fall under this head have become + instinctive through the hereditary transmission of acquired habit. "As far + as we can judge, only a few expressive movements are learnt by each + individual; that is, were consciously and voluntarily performed during the + early years of life for some definite object, or in imitation of others, + and then became habitual. The far greater number of the movements of + expression, and all the more important ones, are innate or inherited; and + such cannot be said to depend on the will of the individual. Nevertheless, + all those included under our first principle were at first voluntarily + performed for a definite object,—namely, to escape some danger, to + relieve some distress, or to gratify some desire." (Ibid. pages 373, 374.) + </p> + <p> + "Our second principle is that of antithesis. The habit of voluntarily + performing opposite movements under opposite impulses has become firmly + established in us by the practice of our whole lives. Hence, if certain + actions have been regularly performed, in accordance with our first + principle, under a certain frame of mind, there will be a strong and + involuntary tendency to the performance of directly opposite actions, + whether or not these are of any use, under the excitement of an opposite + frame of mind." ("Expression of the Emotions", page 368.) This principle + of antithesis has not been widely accepted. Nor is Darwin's own position + easy to grasp. + </p> + <p> + "Our third principle," he says (Ibid. page 369.), "is the direct action of + the excited nervous system on the body, independently of the will, and + independently, in large part, of habit. Experience shows that nerve-force + is generated and set free whenever the cerebro-spinal system is excited. + The direction which this nerve-force follows is necessarily determined by + the lines of connection between the nerve-cells, with each other and with + various parts of the body." + </p> + <p> + Lack of space prevents our following up the details of Darwin's treatment + of expression. Whether we accept or do not accept his three principles of + explanation we must regard his work as a masterpiece of descriptive + analysis, packed full of observations possessing lasting value. For a + further development of the subject it is essential that the instinctive + factors in expression should be more fully distinguished from those which + are individually acquired—a difficult task—and that the + instinctive factors should be rediscussed in the light of modern doctrines + of heredity, with a view to determining whether Lamarckian inheritance, on + which Darwin so largely relied, is necessary for an interpretation of the + facts. + </p> + <p> + The whole subject as Darwin realised is very complex. Even the term + "expression" has a certain amount of ambiguity. When the emotion is in + full flood the animal fights, flees, or faints. Is this full-tide effect + to be regarded as expression; or are we to restrict the term to the + premonitory or residual effects—the bared canine when the fighting + mood is being roused, the ruffled fur when reminiscent representations of + the object inducing anger cross the mind? Broadly considered both should + be included. The activity of premonitory expression as a means of + communication was recognised by Darwin; he might, perhaps, have emphasised + it more strongly in dealing with the lower animals. Man so largely relies + on a special means of communication, that of language, that he sometimes + fails to realise that for animals with their keen powers of perception, + and dependent as they are on such means of communication, the more + strictly biological means of expression are full of subtle suggestiveness. + Many modes of expression, otherwise useless, are signs of behaviour that + may be anticipated,—signs which stimulate the appropriate attitude + of response. This would not, however, serve to account for the utility of + the organic accompaniments—heart-affection, respiratory changes, + vaso-motor effects and so forth, together with heightened muscular tone,—on + all of which Darwin lays stress ("Expression of the Emotions", pages 65 + ff.) under his third principle. The biological value of all this is, + however, of great importance, though Darwin was hardly in a position to + take it fully into account. + </p> + <p> + Having regard to the instinctive and hereditary factors of emotional + expression we may ask whether Darwin's third principle does not alone + suffice as an explanation. Whether we admit or reject Lamarckian + inheritance it would appear that all hereditary expression must be due to + pre-established connections within the central nervous system and to a + transmitted provision for coordinated response under the appropriate + stimulation. If this be so, Darwin's first and second principles are + subordinate and ancillary to the third, an expression, so far as it is + instinctive or hereditary, being "the direct result of the constitution of + the nervous system." + </p> + <p> + Darwin accepted the emotions themselves as hereditary or acquired states + of mind and devoted his attention to their expression. But these emotions + themselves are genetic products and as such dependent on organic + conditions. It remained, therefore, for psychologists who accepted + evolution and sought to build on biological foundations to trace the + genesis of these modes of animal and human experience. The subject has + been independently developed by Professors Lange and James (Cf. William + James, "Principles of Psychology", Vol. II. Chap. XXV, London, 1890.); and + some modification of their view is regarded by many evolutionists as + affording the best explanation of the facts. We must fix our attention on + the lower emotions, such as anger or fear, and on their first occurrence + in the life of the individual organism. It is a matter of observation that + if a group of young birds which have been hatched in an incubator are + frightened by an appropriate presentation, auditory or visual, they + instinctively respond in special ways. If we speak of this response as the + expression, we find that there are many factors. There are certain visible + modes of behaviour, crouching at once, scattering and then crouching, + remaining motionless, the braced muscles sustaining an attitude of arrest, + and so forth. There are also certain visceral or organic effects, such as + affections of the heart and respiration. These can be readily observed by + taking the young bird in the hand. Other effects cannot be readily + observed; vaso-motor changes, affections of the alimentary canal, the skin + and so forth. Now the essence of the James-Lange view, as applied to these + congenital effects, is that though we are justified in speaking of them as + effects of the stimulation, we are not justified, without further + evidence, in speaking of them as effects of the emotional state. May it + not rather be that the emotion as a primary mode of experience is the + concomitant of the net result of the organic situation—the initial + presentation, the instinctive mode of behaviour, the visceral + disturbances? According to this interpretation the primary tissue of + experience of the emotional order, felt as an unanalysed complex, is + generated by the stimulation of the sensorium by afferent or incoming + physiological impulses from the special senses, from the organs concerned + in the responsive behaviour, from the viscera and vaso-motor system. + </p> + <p> + Some psychologists, however, contend that the emotional experience is + generated in the sensorium prior to, and not subsequent to, the + behaviour-response and the visceral disturbances. It is a direct and not + an indirect outcome of the presentation to the special senses. Be this as + it may, there is a growing tendency to bring into the closest possible + relation, or even to identify, instinct and emotion in their primary + genesis. The central core of all such interpretations is that instinctive + behaviour and experience, its emotional accompaniments, and its + expression, are but different aspects of the outcome of the same organic + occurrences. Such emotions are, therefore, only a distinguishable aspect + of the primary tissue of experience and exhibit a like differentiation. + Here again a biological foundation is laid for a psychological doctrine of + the mental development of the individual. + </p> + <p> + The intimate relation between emotion as a psychological mode of + experience and expression as a group of organic conditions has an + important bearing on biological interpretation. The emotion, as the + psychological accompaniment of orderly disturbances in the central nervous + system profoundly influences behaviour and often renders it more vigorous + and more effective. The utility of the emotions in the struggle for + existence can, therefore, scarcely be over-estimated. Just as keenness of + perception has survival-value; just as it is obviously subject to + variation; just as it must be enhanced under natural selection, whether + individually acquired increments are inherited or not; and just as its + value lies not only in this or that special perceptive act but in its + importance for life as a whole; so the vigorous effectiveness of activity + has survival-value; it is subject to variation; it must be enhanced under + natural selection; and its importance lies not only in particular modes of + behaviour but in its value for life as a whole. If emotion and its + expression as a congenital endowment are but different aspects of the same + biological occurrence; and if this is a powerful supplement to vigour + effectiveness and persistency of behaviour, it must on Darwin's principles + be subject to natural selection. + </p> + <p> + If we include under the expression of the emotions not only the + premonitory symptoms of the initial phases of the organic and mental + state, not only the signs or conditions of half-tide emotion, but the + full-tide manifestation of an emotion which dominates the situation, we + are naturally led on to the consideration of many of the phenomena which + are discussed under the head of sexual selection. The subject is difficult + and complex, and it was treated by Darwin with all the strength he could + summon to the task. It can only be dealt with here from a special point of + view—that which may serve to illustrate the influence of certain + mental factors on the course of evolution. From this point of view too + much stress can scarcely be laid on the dominance of emotion during the + period of courtship and pairing in the more highly organised animals. It + is a period of maximum vigour, maximum activity, and, correlated with + special modes of behaviour and special organic and visceral + accompaniments, a period also of maximum emotional excitement. The combats + of males, their dances and aerial evolutions, their elaborate behaviour + and display, or the flood of song in birds, are emotional expressions + which are at any rate coincident in time with sexual periodicity. From the + combat of the males there follows on Darwin's principles the elimination + of those which are deficient in bodily vigour, deficient in special + structures, offensive or protective, which contribute to success, + deficient in the emotional supplement of which persistent and + whole-hearted fighting is the expression, and deficient in alertness and + skill which are the outcome of the psychological development of the powers + of perception. Few biologists question that we have here a mode of + selection of much importance, though its influence on psychological + evolution often fails to receive its due emphasis. Mr Wallace + ("Darwinism", pages 282, 283, London, 1889.) regards it as "a form of + natural selection"; "to it," he says, "we must impute the development of + the exceptional strength, size, and activity of the male, together with + the possession of special offensive and defensive weapons, and of all + other characters which arise from the development of these or are + correlated with them." So far there is little disagreement among the + followers of Darwin—for Mr Wallace, with fine magnanimity, has + always preferred to be ranked as such, notwithstanding his right, on which + a smaller man would have constantly insisted, to the claim of independent + originator of the doctrine of natural selection. So far with regard to + sexual selection Darwin and Mr Wallace are agreed; so far and no farther. + For Darwin, says Mr Wallace (Ibid. page 283.), "has extended the principle + into a totally different field of action, which has none of that character + of constancy and of inevitable result that attaches to natural selection, + including male rivalry; for by far the larger portion of the phenomena, + which he endeavours to explain by the direct action of sexual selection, + can only be so explained on the hypothesis that the immediate agency is + female choice or preference. It is to this that he imputes the origin of + all secondary sexual characters other than weapons of offence and + defence... In this extension of sexual selection to include the action of + female choice or preference, and in the attempt to give to that choice + such wide-reaching effects, I am unable to follow him more than a very + little way." + </p> + <p> + Into the details of Mr Wallace's criticisms it is impossible to enter + here. We cannot discuss either the mode of origin of the variations in + structure which have rendered secondary sexual characters possible or the + modes of selection other than sexual which have rendered them, within + narrow limits, specifically constant. Mendelism and mutation theories may + have something to say on the subject when these theories have been more + fully correlated with the basal principles of selection. It is noteworthy + that Mr Wallace says ("Darwinism", pages 283, 284.): "Besides the + acquisition of weapons by the male for the purpose of fighting with other + males, there are some other sexual characters which may have been produced + by natural selection. Such are the various sounds and odours which are + peculiar to the male, and which serve as a call to the female or as an + indication of his presence. These are evidently a valuable addition to the + means of recognition of the two sexes, and are a further indication that + the pairing season has arrived; and the production, intensification, and + differentiation of these sounds and odours are clearly within the power of + natural selection. The same remark will apply to the peculiar calls of + birds, and even to the singing of the males." Why the same remark should + not apply to their colours and adornments is not obvious. What is obvious + is that "means of recognition" and "indication that the pairing season has + arrived" are dependent on the perceptive powers of the female who + recognises and for whom the indication has meaning. The hypothesis of + female preference, stripped of the aesthetic surplusage which is + psychologically both unnecessary and unproven, is really only different in + degree from that which Mr Wallace admits in principle when he says that it + is probable that the female is pleased or excited by the display. + </p> + <p> + Let us for our present purpose leave on one side and regard as sub judice + the question whether the specific details of secondary sexual characters + are the outcome of female choice. For us the question is whether certain + psychological accompaniments of the pairing situation have influenced the + course of evolution and whether these psychological accompaniments are + themselves the outcome of evolution. As a matter of observation, specially + differentiated modes of behaviour, often very elaborate, frequently + requiring highly developed skill, and apparently highly charged with + emotional tone, are the precursors of pairing. They are generally confined + to the males, whose fierce combats during the period of sexual activity + are part of the emotional manifestation. It is inconceivable that they + have no biological meaning; and it is difficult to conceive that they have + any other biological end than to evoke in the generally more passive + female the pairing impulse. They are based on instinctive foundations + ingrained in the nervous constitution through natural (or may we not say + sexual?) selection in virtue of their profound utility. They are called + into play by a specialised presentation such as the sight or the scent of + the female at, or a little in advance of, a critical period of the + physiological rhythm. There is no necessity that the male should have any + knowledge of the end to which his strenuous activity leads up. In presence + of the female there is an elaborate application of all the energies of + behaviour, just because ages of racial preparation have made him + biologically and emotionally what he is—a functionally sexual male + that must dance or sing or go through hereditary movements of display, + when the appropriate stimulation comes. Of course after the first + successful courtship his future behaviour will be in some degree modified + by his previous experience. No doubt during his first courtship he is + gaining the primary data of a peculiarly rich experience, instinctive and + emotional. But the biological foundations of the behaviour of courtship + are laid in the hereditary coordinations. It would seem that in some + cases, not indeed in all, but perhaps especially in those cases in which + secondary sexual behaviour is most highly evolved,—correlative with + the ardour of the male is a certain amount of reluctance in the female. + The pairing act on her part only takes place after prolonged stimulation, + for affording which the behaviour of male courtship is the requisite + presentation. The most vigorous, defiant and mettlesome male is preferred + just because he alone affords a contributory stimulation adequate to evoke + the pairing impulse with its attendant emotional tone. + </p> + <p> + It is true that this places female preference or choice on a much lower + psychological plane than Darwin in some passages seems to contemplate + where, for example, he says that the female appreciates the display of the + male and places to her credit a taste for the beautiful. But Darwin + himself distinctly states ("Descent of Man" (2nd edition), Vol. II. pages + 136, 137; (Popular edition), pages 642, 643.) that "it is not probable + that she consciously deliberates; but she is most excited or attracted by + the most beautiful, or melodious, or gallant males." The view here put + forward, which has been developed by Prof. Groos ("The Play of Animals", + page 244, London, 1898.), therefore seems to have Darwin's own sanction. + The phenomena are not only biological; there are psychological elements as + well. One can hardly suppose that the female is unconscious of the male's + presence; the final yielding must surely be accompanied by heightened + emotional tone. Whether we call it choice or not is merely a matter of + definition of terms. The behaviour is in part determined by supplementary + psychological values. Prof. Groos regards the coyness of females as "a + most efficient means of preventing the too early and too frequent yielding + to the sexual impulse." (Ibid. page 283.) Be that as it may, it is, in any + case, if we grant the facts, a means through which male sexual behaviour + with all its biological and psychological implications, is raised to a + level otherwise perhaps unattainable by natural means, while in the female + it affords opportunities for the development in the individual and + evolution in the race of what we may follow Darwin in calling + appreciation, if we empty this word of the aesthetic implications which + have gathered round it in the mental life of man. + </p> + <p> + Regarded from this standpoint sexual selection, broadly considered, has + probably been of great importance. The psychological accompaniments of the + pairing situation have profoundly influenced the course of biological + evolution and are themselves the outcome of that evolution. + </p> + <p> + Darwin makes only passing reference to those modes of behaviour in animals + which go by the name of play. "Nothing," he says ("Descent of Man", Vol. + II. page 60; (Popular edition), page 566.), "is more common than for + animals to take pleasure in practising whatever instinct they follow at + other times for some real good." This is one of the very numerous cases in + which a hint of the master has served to stimulate research in his + disciples. It was left to Prof. Groos to develop this subject on + evolutionary lines and to elaborate in a masterly manner Darwin's + suggestion. "The utility of play," he says ("The Play of Animals", page + 76.), "is incalculable. This utility consists in the practice and exercise + it affords for some of the more important duties of life,"—that is + to say, for the performance of activities which will in adult life be + essential to survival. He urges (Ibid. page 75.) that "the play of young + animals has its origin in the fact that certain very important instincts + appear at a time when the animal does not seriously need them." It is, + however, questionable whether any instincts appear at a time when they are + not needed. And it is questionable whether the instinctive and emotional + attitude of the play-fight, to take one example, can be identified with + those which accompany fighting in earnest, though no doubt they are + closely related and have some common factors. It is probable that play, as + preparatory behaviour, differs in biological detail (as it almost + certainly does in emotional attributes) from the earnest of after-life and + that it has been evolved through differentiation and integration of the + primary tissue of experience, as a preparation through which certain + essential modes of skill may be acquired—those animals in which the + preparatory play-propensity was not inherited in due force and requisite + amount being subsequently eliminated in the struggle for existence. In any + case there is little question that Prof. Groos is right in basing the + play-propensity on instinctive foundations. ("The Play of Animals" page + 24.) None the less, as he contends, the essential biological value of play + is that it is a means of training the educable nerve-tissue, of developing + that part of the brain which is modified by experience and which thus + acquires new characters, of elaborating the secondary tissue of experience + on the predetermined lines of instinctive differentiation and thus + furthering the psychological activities which are included under the + comprehensive term "intelligent." + </p> + <p> + In "The Descent of Man" Darwin dealt at some length with intelligence and + the higher mental faculties. ("Descent of Man" (1st edition), Chapters II, + III, V; (2nd edition), Chapters III, IV, V.) His object, he says, is to + show that there is no fundamental difference between man and the higher + mammals in their mental faculties; that these faculties are variable and + the variations tend to be inherited; and that under natural selection + beneficial variations of all kinds will have been preserved and injurious + ones eliminated. + </p> + <p> + Darwin was too good an observer and too honest a man to minimise the + "enormous difference" between the level of mental attainment of civilised + man and that reached by any animal. His contention was that the + difference, great as it is, is one of degree and not of kind. He realised + that, in the development of the mental faculties of man, new factors in + evolution have supervened—factors which play but a subordinate and + subsidiary part in animal intelligence. Intercommunication by means of + language, approbation and blame, and all that arises out of reflective + thought, are but foreshadowed in the mental life of animals. Still he + contends that these may be explained on the doctrine of evolution. He + urges (Ibid. Vol. I. pages 70, 71; (Popular edition), pages 70, 71.)" that + man is variable in body and mind; and that the variations are induced, + either directly or indirectly, by the same general causes, and obey the + same general laws, as with the lower animals." He correlates mental + development with the evolution of the brain. (Ibid. page 81.) "As the + various mental faculties gradually developed themselves, the brain would + almost certainly become larger. No one, I presume, doubts that the large + proportion which the size of man's brain bears to his body, compared to + the same proportion in the gorilla or orang, is closely connected with his + higher mental powers." "With respect to the lower animals," he says + ("Descent of Man" (Popular edition), page 82.), "M.E. Lartet ("Comptes + Rendus des Sciences", June 1, 1868.), by comparing the crania of tertiary + and recent mammals belonging to the same groups, has come to the + remarkable conclusion that the brain is generally larger and the + convolutions are more complex in the more recent form." + </p> + <p> + Sir E. Ray Lankester has sought to express in the simplest terms the + implications of the increase in size of the cerebrum. "In what," he asks, + "does the advantage of a larger cerebral mass consist?" "Man," he replies + "is born with fewer ready-made tricks of the nerve-centres—these + performances of an inherited nervous mechanism so often called by the + ill-defined term 'instincts'—than are the monkeys or any other + animal. Correlated with the absence of inherited ready-made mechanism, man + has a greater capacity of developing in the course of his individual + growth similar nervous mechanisms (similar to but not identical with those + of 'instinct') than any other animal... The power of being educated—'educability' + as we may term it—is what man possesses in excess as compared with + the apes. I think we are justified in forming the hypothesis that it is + this 'educability' which is the correlative of the increased size of the + cerebrum." There has been natural selection of the more educable animals, + for "the character which we describe as 'educability' can be transmitted, + it is a congenital character. But the RESULTS of education can NOT be + transmitted. In each generation they have to be acquired afresh, and with + increased 'educability' they are more readily acquired and a larger + variety of them... The fact is that there is no community between the + mechanisms of instinct and the mechanisms of intelligence, and that the + latter are later in the history of the evolution of the brain than the + former and can only develop in proportion as the former become feeble and + defective." ("Nature", Vol. LXI. pages 624, 625 (1900).) + </p> + <p> + In this statement we have a good example of the further development of + views which Darwin foreshadowed but did not thoroughly work out. It states + the biological case clearly and tersely. Plasticity of behaviour in + special accommodation to special circumstances is of survival value; it + depends upon acquired characters; it is correlated with increase in size + and complexity of the cerebrum; under natural selection therefore the + larger and more complex cerebrum as the organ of plastic behaviour has + been the outcome of natural selection. We have thus the biological + foundations for a further development of genetic psychology. + </p> + <p> + There are diversities of opinion, as Darwin showed, with regard to the + range of instinct in man and the higher animals as contrasted with lower + types. Darwin himself said ("Descent of Man", Vol. I. page 100.) that + "Man, perhaps, has somewhat fewer instincts than those possessed by the + animals which come next to him in the series." On the other hand, Prof. + Wm. James says ("Principles of Psychology," Vol. II. page 289.) that man + is probably the animal with most instincts. The true position is that man + and the higher animals have fewer complete and self-sufficing instincts + than those which stand lower in the scale of mental evolution, but that + they have an equally large or perhaps larger mass of instinctive raw + material which may furnish the stuff to be elaborated by intelligent + processes. There is, perhaps, a greater abundance of the primary tissue of + experience to be refashioned and integrated by secondary modification; + there is probably the same differentiation in relation to the determining + biological ends, but there is at the outset less differentiation of the + particular and specific modes of behaviour. The specialised instinctive + performances and their concomitant experience-complexes are at the outset + more indefinite. Only through acquired connections, correlated with + experience, do they become definitely organised. + </p> + <p> + The full working-out of the delicate and subtle relationship of instinct + and educability—that is, of the hereditary and the acquired factors + in the mental life—is the task which lies before genetic and + comparative psychology. They interact throughout the whole of life, and + their interactions are very complex. No one can read the chapters of "The + Descent of Man" which Darwin devotes to a consideration of the mental + characters of man and animals without noticing, on the one hand, how + sedulous he is in his search for hereditary foundations, and, on the other + hand, how fully he realises the importance of acquired habits of mind. The + fact that educability itself has innate tendencies—is in fact a + partially differentiated educability—renders the unravelling of the + factors of mental progress all the more difficult. + </p> + <p> + In his comparison of the mental powers of men and animals it was essential + that Darwin should lay stress on points of similarity rather than on + points of difference. Seeking to establish a doctrine of evolution, with + its basal concept of continuity of process and community of character, he + was bound to render clear and to emphasise the contention that the + difference in mind between man and the higher animals, great as it is, is + one of degree and not of kind. To this end Darwin not only recorded a + large number of valuable observations of his own, and collected a + considerable body of information from reliable sources, he presented the + whole subject in a new light and showed that a natural history of mind + might be written and that this method of study offered a wide and rich + field for investigation. Of course those who regarded the study of mind + only as a branch of metaphysics smiled at the philosophical ineptitude of + the mere man of science. But the investigation, on natural history lines, + has been prosecuted with a large measure of success. Much indeed still + remains to be done; for special training is required, and the workers are + still few. Promise for the future is however afforded by the fact that + investigation is prosecuted on experimental lines and that something like + organised methods of research are taking form. There is now but little + reliance on casual observations recorded by those who have not undergone + the necessary discipline in these methods. There is also some change of + emphasis in formulating conclusions. Now that the general evolutionary + thesis is fully and freely accepted by those who carry on such researches, + more stress is laid on the differentiation of the stages of evolutionary + advance than on the fact of their underlying community of nature. The + conceptual intelligence which is especially characteristic of the higher + mental procedure of man is more firmly distinguished from the perceptual + intelligence which he shares with the lower animals—distinguished + now as a higher product of evolution, no longer as differing in origin or + different in kind. Some progress has been made, on the one hand in + rendering an account of intelligent profiting by experience under the + guidance of pleasure and pain in the perceptual field, on lines + predetermined by instinctive differentiation for biological ends, and on + the other hand in elucidating the method of conceptual thought employed, + for example, by the investigator himself in interpreting the perceptual + experience of the lower animals. + </p> + <p> + Thus there is a growing tendency to realise more fully that there are two + orders of educability—first an educability of the perceptual + intelligence based on the biological foundation of instinct, and secondly + an educability of the conceptual intelligence which refashions and + rearranges the data afforded by previous inheritance and acquisition. It + is in relation to this second and higher order of educability that the + cerebrum of man shows so large an increase of mass and a yet larger + increase of effective surface through its rich convolutions. It is through + educability of this order that the human child is brought intellectually + and affectively into touch with the ideal constructions by means of which + man has endeavoured, with more or less success, to reach an interpretation + of nature, and to guide the course of the further evolution of his race—ideal + constructions which form part of man's environment. + </p> + <p> + It formed no part of Darwin's purpose to consider, save in broad outline, + the methods, or to discuss in any fulness of detail the results of the + process by which a differentiation of the mental faculties of man from + those of the lower animals has been brought about—a differentiation + the existence of which he again and again acknowledges. His purpose was + rather to show that, notwithstanding this differentiation, there is basal + community in kind. This must be remembered in considering his treatment of + the biological foundations on which man's systems of ethics are built. He + definitely stated that he approached the subject "exclusively from the + side of natural history." ("Descent of Man", Vol. I. page 149.) His + general conclusion is that the moral sense is fundamentally identical with + the social instincts, which have been developed for the good of the + community; and he suggests that the concept which thus enables us to + interpret the biological ground-plan of morals also enables us to frame a + rational ideal of the moral end. "As the social instincts," he says (Ibid. + page 185.), "both of man and the lower animals have no doubt been + developed by nearly the same steps, it would be advisable, if found + practicable, to use the same definition in both cases, and to take as the + standard of morality, the general good or welfare of the community, rather + than the general happiness." But the kind of community for the good of + which the social instincts of animals and primitive men were biologically + developed may be different from that which is the product of civilisation, + as Darwin no doubt realised. Darwin's contention was that conscience is a + social instinct and has been evolved because it is useful to the tribe in + the struggle for existence against other tribes. On the other hand, J.S. + Mill urged that the moral feelings are not innate but acquired, and Bain + held the same view, believing that the moral sense is acquired by each + individual during his life-time. Darwin, who notes (Ibid. page 150 + (footnote).) their opinion with his usual candour, adds that "on the + general theory of evolution this is at least extremely improbable. It is + impossible to enter into the question here: much turns on the exact + connotation of the terms "conscience" and "moral sense," and on the + meaning we attach to the statement that the moral sense is fundamentally + identical with the social instincts." + </p> + <p> + Presumably the majority of those who approach the subjects discussed in + the third, fourth and fifth chapters of "The Descent of Man" in the full + conviction that mental phenomena, not less than organic phenomena, have a + natural genesis, would, without hesitation, admit that the intellectual + and moral systems of civilised man are ideal constructions, the products + of conceptual thought, and that as such they are, in their developed form, + acquired. The moral sentiments are the emotional analogues of highly + developed concepts. This does not however imply that they are outside the + range of natural history treatment. Even though it may be desirable to + differentiate the moral conduct of men from the social behaviour of + animals (to which some such term as "pre-moral" or "quasi-moral" may be + applied), still the fact remains that, as Darwin showed, there is abundant + evidence of the occurrence of such social behaviour—social behaviour + which, even granted that it is in large part intelligently acquired, and + is itself so far a product of educability, is of survival value. It makes + for that integration without which no social group could hold together and + escape elimination. Furthermore, even if we grant that such behaviour is + intelligently acquired, that is to say arises through the modification of + hereditary instincts and emotions, the fact remains that only through + these instinctive and emotional data is afforded the primary tissue of the + experience which is susceptible of such modification. + </p> + <p> + Darwin sought to show, and succeeded in showing, that for the intellectual + and moral life there are instinctive foundations which a biological + treatment alone can disclose. It is true that he did not in all cases + analytically distinguish the foundations from the superstructure. Even + to-day we are scarcely in a position to do so adequately. But his + treatment was of great value in giving an impetus to further research. + This value indeed can scarcely be overestimated. And when the natural + history of the mental operations shall have been written, the cardinal + fact will stand forth, that the instinctive and emotional foundations are + the outcome of biological evolution and have been ingrained in the race + through natural selection. We shall more clearly realise that educability + itself is a product of natural selection, though the specific results + acquired through cerebral modifications are not transmitted through + heredity. It will, perhaps, also be realised that the instinctive + foundations of social behaviour are, for us, somewhat out of date and have + undergone but little change throughout the progress of civilisation, + because natural selection has long since ceased to be the dominant factor + in human progress. The history of human progress has been mainly the + history of man's higher educability, the products of which he has + projected on to his environment. This educability remains on the average + what it was a dozen generations ago; but the thought-woven tapestry of his + surroundings is refashioned and improved by each succeeding generation. + Few men have in greater measure enriched the thought-environment with + which it is the aim of education to bring educable human beings into vital + contact, than has Charles Darwin. His special field of work was the wide + province of biology; but he did much to help us realise that mental + factors have contributed to organic evolution and that in man, the highest + product of Evolution, they have reached a position of unquestioned + supremacy. + </p> + <p> + <a name="link2H_4_0024" id="link2H_4_0024"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + XXII. THE INFLUENCE OF THE CONCEPTION OF EVOLUTION ON MODERN PHILOSOPHY. + By H. Hoffding. + </h2> + <h3> + Professor of Philosophy in the University of Copenhagen. + </h3> + <p> + I. + </p> + <p> + It is difficult to draw a sharp line between philosophy and natural + science. The naturalist who introduces a new principle, or demonstrates a + fact which throws a new light on existence, not only renders an important + service to philosophy but is himself a philosopher in the broader sense of + the word. The aim of philosophy in the stricter sense is to attain points + of view from which the fundamental phenomena and the principles of the + special sciences can be seen in their relative importance and connection. + But philosophy in this stricter sense has always been influenced by + philosophy in the broader sense. Greek philosophy came under the influence + of logic and mathematics, modern philosophy under the influence of natural + science. The name of Charles Darwin stands with those of Galileo, Newton, + and Robert Mayer—names which denote new problems and great + alterations in our conception of the universe. + </p> + <p> + First of all we must lay stress on Darwin's own personality. His deep love + of truth, his indefatigable inquiry, his wide horizon, and his steady + self-criticism make him a scientific model, even if his results and + theories should eventually come to possess mainly an historical interest. + In the intellectual domain the primary object is to reach high summits + from which wide surveys are possible, to reach them toiling honestly + upwards by way of experience, and then not to turn dizzy when a summit is + gained. Darwinians have sometimes turned dizzy, but Darwin never. He saw + from the first the great importance of his hypothesis, not only because of + its solution of the old problem as to the value of the concept of species, + not only because of the grand picture of natural evolution which it + unrolls, but also because of the life and inspiration its method would + impart to the study of comparative anatomy, of instinct and of heredity, + and finally because of the influence it would exert on the whole + conception of existence. He wrote in his note-book in the year 1837: "My + theory would give zest to recent and fossil comparative anatomy; it would + lead to the study of instinct, heredity, and mind-heredity, whole (of) + metaphysics." ("Life and Letters of Charles Darwin", Vol. I. page 8.) + </p> + <p> + We can distinguish four main points in which Darwin's investigations + possess philosophical importance. + </p> + <p> + The evolution hypothesis is much older than Darwin; it is, indeed, one of + the oldest guessings of human thought. In the eighteenth century it was + put forward by Diderot and Lamettrie and suggested by Kant (1786). As we + shall see later, it was held also by several philosophers in the first + half of the nineteenth century. In his preface to "The Origin of Species", + Darwin mentions the naturalists who were his forerunners. But he has set + forth the hypothesis of evolution in so energetic and thorough a manner + that it perforce attracts the attention of all thoughtful men in a much + higher degree than it did before the publication of the "Origin". + </p> + <p> + And further, the importance of his teaching rests on the fact that he, + much more than his predecessors, even than Lamarck, sought a foundation + for his hypothesis in definite facts. Modern science began by demanding—with + Kepler and Newton—evidence of verae causae; this demand Darwin + industriously set himself to satisfy—hence the wealth of material + which he collected by his observations and his experiments. He not only + revived an old hypothesis, but he saw the necessity of verifying it by + facts. Whether the special cause on which he founded the explanation of + the origin of species—Natural Selection—is sufficient, is now + a subject of discussion. He himself had some doubt in regard to this + question, and the criticisms which are directed against his hypothesis hit + Darwinism rather than Darwin. In his indefatigable search for empirical + evidence he is a model even for his antagonists: he has compelled them to + approach the problems of life along other lines than those which were + formerly followed. + </p> + <p> + Whether the special cause to which Darwin appealed is sufficient or not, + at least to it is probably due the greater part of the influence which he + has exerted on the general trend of thought. "Struggle for existence" and + "natural selection" are principles which have been applied, more or less, + in every department of thought. Recent research, it is true, has + discovered greater empirical discontinuity—leaps, "mutations"—whereas + Darwin believed in the importance of small variations slowly accumulated. + It has also been shown by the experimental method, which in recent + biological work has succeeded Darwin's more historical method, that types + once constituted possess great permanence, the fluctuations being + restricted within clearly defined boundaries. The problem has become more + precise, both as to variation and as to heredity. The inner conditions of + life have in both respects shown a greater independence than Darwin had + supposed in his theory, though he always admitted that the cause of + variation was to him a great enigma, "a most perplexing problem," and that + the struggle for life could only occur where variation existed. But, at + any rate, it was of the greatest importance that Darwin gave a living + impression of the struggle for life which is everywhere going on, and to + which even the highest forms of existence must be amenable. The + philosophical importance of these ideas does not stand or fall with the + answer to the question, whether natural selection is a sufficient + explanation of the origin of species or not: it has an independent, + positive value for everyone who will observe life and reality with an + unbiassed mind. + </p> + <p> + In accentuating the struggle for life Darwin stands as a + characteristically English thinker: he continues a train of ideas which + Hobbes and Malthus had already begun. Moreover in his critical views as to + the conception of species he had English forerunners; in the middle ages + Occam and Duns Scotus, in the eighteenth century Berkeley and Hume. In his + moral philosophy, as we shall see later, he is an adherent of the school + which is represented by Hutcheson, Hume and Adam Smith. Because he is no + philosopher in the stricter sense of the term, it is of great interest to + see that his attitude of mind is that of the great thinkers of his nation. + </p> + <p> + In considering Darwin's influence on philosophy we will begin with an + examination of the attitude of philosophy to the conception of evolution + at the time when "The Origin of Species" appeared. We will then examine + the effects which the theory of evolution, and especially the idea of the + struggle for life, has had, and naturally must have, on the discussion of + philosophical problems. + </p> + <p> + II. + </p> + <p> + When "The Origin of Species" appeared fifty years ago Romantic + speculation, Schelling's and Hegel's philosophy, still reigned on the + continent, while in England Positivism, the philosophy of Comte and Stuart + Mill, represented the most important trend of thought. German speculation + had much to say on evolution, it even pretended to be a philosophy of + evolution. But then the word "evolution" was to be taken in an ideal, not + in a real, sense. To speculative thought the forms and types of nature + formed a system of ideas, within which any form could lead us by + continuous transitions to any other. It was a classificatory system which + was regarded as a divine world of thought or images, within which + metamorphoses could go on—a condition comparable with that in the + mind of the poet when one image follows another with imperceptible + changes. Goethe's ideas of evolution, as expressed in his "Metamorphosen + der Pflanzen und der Thiere", belong to this category; it is, therefore, + incorrect to call him a forerunner of Darwin. Schelling and Hegel held the + same idea; Hegel expressly rejected the conception of a real evolution in + time as coarse and materialistic. "Nature," he says, "is to be considered + as a SYSTEM OF STAGES, the one necessarily arising from the other, and + being the nearest truth of that from which it proceeds; but not in such a + way that the one is NATURALLY generated by the other; on the contrary + (their connection lies) in the inner idea which is the ground of nature. + The METAMORPHOSIS can be ascribed only to the notion as such, because it + alone is evolution... It has been a clumsy idea in the older as well as in + the newer philosophy of nature, to regard the transformation and the + transition from one natural form and sphere to a higher as an outward and + actual production." ("Encyclopaedie der philosophischen Wissenschaften" + (4th edition), Berlin, 1845, paragraph 249.) + </p> + <p> + The only one of the philosophers of Romanticism who believed in a real, + historical evolution, a real production of new species, was Oken. + ("Lehrbuch der Naturphilosophie", Jena, 1809.) Danish philosophers, such + as Treschow (1812) and Sibbern (1846), have also broached the idea of an + historical evolution of all living beings from the lowest to the highest. + Schopenhauer's philosophy has a more realistic character than that of + Schelling's and Hegel's, his diametrical opposites, though he also belongs + to the romantic school of thought. His philosophical and psychological + views were greatly influenced by French naturalists and philosophers, + especially by Cabanis and Lamarck. He praises the "ever memorable + Lamarck," because he laid so much stress on the "will to live." But he + repudiates as a "wonderful error" the idea that the organs of animals + should have reached their present perfection through a development in + time, during the course of innumerable generations. It was, he said, a + consequence of the low standard of contemporary French philosophy, that + Lamarck came to the idea of the construction of living beings in time + through succession! ("Ueber den Willen in der Natur" (2nd edition), + Frankfurt a. M., 1854, pages 41-43.) + </p> + <p> + The positivistic stream of thought was not more in favour of a real + evolution than was the Romantic school. Its aim was to adhere to positive + facts: it looked with suspicion on far-reaching speculation. Comte laid + great stress on the discontinuity found between the different kingdoms of + nature, as well as within each single kingdom. As he regarded as + unscientific every attempt to reduce the number of physical forces, so he + rejected entirely the hypothesis of Lamarck concerning the evolution of + species; the idea of species would in his eyes absolutely lose its + importance if a transition from species to species under the influence of + conditions of life were admitted. His disciples (Littre, Robin) continued + to direct against Darwin the polemics which their master had employed + against Lamarck. Stuart Mill, who, in the theory of knowledge, represented + the empirical or positivistic movement in philosophy—like his + English forerunners from Locke to Hume—founded his theory of + knowledge and morals on the experience of the single individual. He + sympathised with the theory of the original likeness of all individuals + and derived their differences, on which he practically and theoretically + laid much stress, from the influence both of experience and education, + and, generally, of physical and social causes. He admitted an individual + evolution, and, in the human species, an evolution based on social + progress; but no physiological evolution of species. He was afraid that + the hypothesis of heredity would carry us back to the old theory of + "innate" ideas. + </p> + <p> + Darwin was more empirical than Comte and Mill; experience disclosed to him + a deeper continuity than they could find; closer than before the nature + and fate of the single individual were shown to be interwoven in the great + web binding the life of the species with nature as a whole. And the + continuity which so many idealistic philosophers could find only in the + world of thought, he showed to be present in the world of reality. + </p> + <p> + III. + </p> + <p> + Darwin's energetic renewal of the old idea of evolution had its chief + importance in strengthening the conviction of this real continuity in the + world, of continuity in the series of form and events. It was a great + support for all those who were prepared to base their conception of life + on scientific grounds. Together with the recently discovered law of the + conservation of energy, it helped to produce the great realistic movement + which characterises the last third of the nineteenth century. After the + decline of the Romantic movement people wished to have firmer ground under + their feet and reality now asserted itself in a more emphatic manner than + in the period of Romanticism. It was easy for Hegel to proclaim that "the + real" was "the rational," and that "the rational" was "the real": reality + itself existed for him only in the interpretation of ideal reason, and if + there was anything which could not be merged in the higher unity of + thought, then it was only an example of the "impotence of nature to hold + to the idea." But now concepts are to be founded on nature and not on any + system of categories too confidently deduced a priori. The new devotion to + nature had its recompense in itself, because the new points of view made + us see that nature could indeed "hold to ideas," though perhaps not to + those which we had cogitated beforehand. + </p> + <p> + A most important question for philosophers to answer was whether the new + views were compatible with an idealistic conception of life and existence. + Some proclaimed that we have now no need of any philosophy beyond the + principles of the conservation of matter and energy and the principle of + natural evolution: existence should and could be definitely and completely + explained by the laws of material nature. But abler thinkers saw that the + thing was not so simple. They were prepared to give the new views their + just place and to examine what alterations the old views must undergo in + order to be brought into harmony with the new data. + </p> + <p> + The realistic character of Darwin's theory was shown not only in the idea + of natural continuity, but also, and not least, in the idea of the cause + whereby organic life advances step by step. This idea—the idea of + the struggle for life—implied that nothing could persist, if it had + no power to maintain itself under the given conditions. Inner value alone + does not decide. Idealism was here put to its hardest trial. In continuous + evolution it could perhaps still find an analogy to the inner evolution of + ideas in the mind; but in the demand for power in order to struggle with + outward conditions Realism seemed to announce itself in its most brutal + form. Every form of Idealism had to ask itself seriously how it was going + to "struggle for life" with this new Realism. + </p> + <p> + We will now give a short account of the position which leading thinkers in + different countries have taken up in regard to this question. + </p> + <p> + I. Herbert Spencer was the philosopher whose mind was best prepared by his + own previous thinking to admit the theory of Darwin to a place in his + conception of the world. His criticism of the arguments which had been put + forward against the hypothesis of Lamarck, showed that Spencer, as a young + man, was an adherent to the evolution idea. In his "Social Statics" (1850) + he applied this idea to human life and moral civilisation. In 1852 he + wrote an essay on "The Development Hypothesis", in which he definitely + stated his belief that the differentiation of species, like the + differentiation within a single organism, was the result of development. + In the first edition of his "Psychology" (1855) he took a step which put + him in opposition to the older English school (from Locke to Mill): he + acknowledged "innate ideas" so far as to admit the tendency of acquired + habits to be inherited in the course of generations, so that the nature + and functions of the individual are only to be understood through its + connection with the life of the species. In 1857, in his essay on + "Progress", he propounded the law of differentiation as a general law of + evolution, verified by examples from all regions of experience, the + evolution of species being only one of these examples. On the effect which + the appearance of "The Origin of Species" had on his mind he writes in his + "Autobiography": "Up to that time... I held that the sole cause of organic + evolution is the inheritance of functionally-produced modifications. The + "Origin of Species" made it clear to me that I was wrong, and that the + larger part of the facts cannot be due to any such cause... To have the + theory of organic evolution justified was of course to get further support + for that theory of evolution at large with which... all my conceptions + were bound up." (Spencer, "Autobiography", Vol. II. page 50, London, + 1904.) Instead of the metaphorical expression "natural selection," Spencer + introduced the term "survival of the fittest," which found favour with + Darwin as well as with Wallace. + </p> + <p> + In working out his ideas of evolution, Spencer found that differentiation + was not the only form of evolution. In its simplest form evolution is + mainly a concentration, previously scattered elements being integrated and + losing independent movement. Differentiation is only forthcoming when + minor wholes arise within a greater whole. And the highest form of + evolution is reached when there is a harmony between concentration and + differentiation, a harmony which Spencer calls equilibration and which he + defines as a moving equilibrium. At the same time this definition enables + him to illustrate the expression "survival of the fittest." "Every living + organism exhibits such a moving equilibrium—a balanced set of + functions constituting its life; and the overthrow of this balanced set of + functions or moving equilibrium is what we call death. Some individuals in + a species are so constituted that their moving equilibria are less easily + overthrown than those of other individuals; and these are the fittest + which survive, or, in Mr Darwin's language, they are the select which + nature preserves." (Ibid. page 100.) Not only in the domain of organic + life, but in all domains, the summit of evolution is, according to + Spencer, characterised by such a harmony—by a moving equilibrium. + </p> + <p> + Spencer's analysis of the concept of evolution, based on a great variety + of examples, has made this concept clearer and more definite than before. + It contains the three elements; integration, differentiation and + equilibration. It is true that a concept which is to be valid for all + domains of experience must have an abstract character, and between the + several domains there is, strictly speaking, only a relation of analogy. + So there is only analogy between psychical and physical evolution. But + this is no serious objection, because general concepts do not express more + than analogies between the phenomena which they represent. Spencer takes + his leading terms from the material world in defining evolution (in the + simplest form) as integration of matter and dissipation of movement; but + as he—not always quite consistently (Cf. my letter to him, 1876, now + printed in Duncan's "Life and Letters of Herbert Spencer", page 178, + London, 1908.)—assumed a correspondence of mind and matter, he could + very well give these terms an indirect importance for psychical evolution. + Spencer has always, in my opinion with full right, repudiated the + ascription of materialism. He is no more a materialist than Spinoza. In + his "Principles of Psychology" (paragraph 63) he expressed himself very + clearly: "Though it seems easier to translate so-called matter into + so-called spirit, than to translate so-called spirit into so-called matter—which + latter is indeed wholly impossible—yet no translation can carry us + beyond our symbols." These words lead us naturally to a group of thinkers + whose starting-point was psychical evolution. But we have still one aspect + of Spencer's philosophy to mention. + </p> + <p> + Spencer founded his "laws of evolution" on an inductive basis, but he was + convinced that they could be deduced from the law of the conservation of + energy. Such a deduction is, perhaps, possible for the more elementary + forms of evolution, integration and differentiation; but it is not + possible for the highest form, the equilibration, which is a harmony of + integration and differentiation. Spencer can no more deduce the necessity + for the eventual appearance of "moving equilibria" of harmonious + totalities than Hegel could guarantee the "higher unities" in which all + contradictions should be reconciled. In Spencer's hands the theory of + evolution acquired a more decidedly optimistic character than in Darwin's; + but I shall deal later with the relation of Darwin's hypothesis to the + opposition of optimism and pessimism. + </p> + <p> + II. While the starting-point of Spencer was biological or cosmological, + psychical evolution being conceived as in analogy with physical, a group + of eminent thinkers—in Germany Wundt, in France Fouillee, in Italy + Ardigo—took, each in his own manner, their starting-point in + psychical evolution as an original fact and as a type of all evolution, + the hypothesis of Darwin coming in as a corroboration and as a special + example. They maintain the continuity of evolution; they find this + character most prominent in psychical evolution, and this is for them a + motive to demand a corresponding continuity in the material, especially in + the organic domain. + </p> + <p> + To Wundt and Fouillee the concept of will is prominent. They see the type + of all evolution in the transformation of the life of will from blind + impulse to conscious choice; the theories of Lamarck and Darwin are used + to support the view that there is in nature a tendency to evolution in + steady reciprocity with external conditions. The struggle for life is here + only a secondary fact. Its apparent prominence is explained by the + circumstance that the influence of external conditions is easily made out, + while inner conditions can be verified only through their effects. For + Ardigo the evolution of thought was the starting-point and the type: in + the evolution of a scientific hypothesis we see a progress from the + indefinite (indistinto) to the definite (distinto), and this is a + characteristic of all evolution, as Ardigo has pointed out in a series of + works. The opposition between indistinto and distinto corresponds to + Spencer's opposition between homogeneity and heterogeneity. The hypothesis + of the origin of differences of species from more simple forms is a + special example of the general law of evolution. + </p> + <p> + In the views of Wundt and Fouillee we find the fundamental idea of + idealism: psychical phenomena as expressions of the innermost nature of + existence. They differ from the older Idealism in the great stress which + they lay on evolution as a real, historical process which is going on + through steady conflict with external conditions. The Romantic dread of + reality is broken. It is beyond doubt that Darwin's emphasis on the + struggle for life as a necessary condition of evolution has been a very + important factor in carrying philosophy back to reality from the heaven of + pure ideas. The philosophy of Ardigo, on the other side, appears more as a + continuation and deepening of positivism, though the Italian thinker + arrived at his point of view independently of French-English positivism. + The idea of continuous evolution is here maintained in opposition to + Comte's and Mill's philosophy of discontinuity. From Wundt and Fouillee + Ardigo differs in conceiving psychical evolution not as an immediate + revelation of the innermost nature of existence, but only as a single, + though the most accessible example, of evolution. + </p> + <p> + III. To the French philosophers Boutroux and Bergson, evolution proper is + continuous and qualitative, while outer experience and physical science + give us fragments only, sporadic processes and mechanical combinations. To + Bergson, in his recent work "L'Evolution Creatrice", evolution consists in + an elan de vie which to our fragmentary observation and analytic reflexion + appears as broken into a manifold of elements and processes. The concept + of matter in its scientific form is the result of this breaking asunder, + essential for all scientific reflexion. In these conceptions the strongest + opposition between inner and outer conditions of evolution is expressed: + in the domain of internal conditions spontaneous development of + qualitative forms—in the domain of external conditions discontinuity + and mechanical combination. + </p> + <p> + We see, then, that the theory of evolution has influenced philosophy in a + variety of forms. It has made idealistic thinkers revise their relation to + the real world; it has led positivistic thinkers to find a closer + connection between the facts on which they based their views; it has made + us all open our eyes for new possibilities to arise through the prima + facie inexplicable "spontaneous" variations which are the condition of all + evolution. This last point is one of peculiar interest. Deeper than + speculative philosophy and mechanical science saw in the days of their + triumph, we catch sight of new streams, whose sources and laws we have + still to discover. Most sharply does this appear in the theory of + mutation, which is only a stronger accentuation of a main point in + Darwinism. It is interesting to see that an analogous problem comes into + the foreground in physics through the discovery of radioactive phenomena, + and in psychology through the assumption of psychical new formations (as + held by Boutroux, William James and Bergson). From this side, Darwin's + ideas, as well as the analogous ideas in other domains, incite us to + renewed examination of our first principles, their rationality and their + value. On the other hand, his theory of the struggle for existence + challenges us to examine the conditions and discuss the outlook as to the + persistence of human life and society and of the values that belong to + them. It is not enough to hope (or fear?) the rising of new forms; we have + also to investigate the possibility of upholding the forms and ideals + which have hitherto been the bases of human life. Darwin has here given + his age the most earnest and most impressive lesson. This side of Darwin's + theory is of peculiar interest to some special philosophical problems to + which I now pass. + </p> + <p> + IV. + </p> + <p> + Among philosophical problems the problem of knowledge has in the last + century occupied a foremost place. It is natural, then, to ask how Darwin + and the hypothesis whose most eminent representative he is, stand to this + problem. + </p> + <p> + Darwin started an hypothesis. But every hypothesis is won by inference + from certain presuppositions, and every inference is based on the general + principles of human thought. The evolution hypothesis presupposes, then, + human thought and its principles. And not only the abstract logical + principles are thus presupposed. The evolution hypothesis purports to be + not only a formal arrangement of phenomena, but to express also the law of + a real process. It supposes, then, that the real data—all that in + our knowledge which we do not produce ourselves, but which we in the main + simply receive—are subjected to laws which are at least analogous to + the logical relations of our thoughts; in other words, it assumes the + validity of the principle of causality. If organic species could arise + without cause there would be no use in framing hypotheses. Only if we + assume the principle of causality, is there a problem to solve. + </p> + <p> + Though Darwinism has had a great influence on philosophy considered as a + striving after a scientific view of the world, yet here is a point of view—the + epistemological—where philosophy is not only independent but reaches + beyond any result of natural science. Perhaps it will be said: the powers + and functions of organic beings only persist (perhaps also only arise) + when they correspond sufficiently to the conditions under which the + struggle of life is to go on. Human thought itself is, then, a variation + (or a mutation) which has been able to persist and to survive. Is not, + then, the problem of knowledge solved by the evolution hypothesis? Spencer + had given an affirmative answer to this question before the appearance of + "The Origin of Species". For the individual, he said, there is an a + priori, original, basis (or Anlage) for all mental life; but in the + species all powers have developed in reciprocity with external conditions. + Knowledge is here considered from the practical point of view, as a weapon + in the struggle for life, as an "organon" which has been continuously in + use for generations. In recent years the economic or pragmatic + epistemology, as developed by Avenarius and Mach in Germany, and by James + in America, points in the same direction. Science, it is said, only + maintains those principles and presuppositions which are necessary to the + simplest and clearest orientation in the world of experience. All + assumptions which cannot be applied to experience and to practical work, + will successively be eliminated. + </p> + <p> + In these views a striking and important application is made of the idea of + struggle for life to the development of human thought. Thought must, as + all other things in the world, struggle for life. But this whole + consideration belongs to psychology, not to the theory of knowledge + (epistemology), which is concerned only with the validity of knowledge, + not with its historical origin. Every hypothesis to explain the origin of + knowledge must submit to cross-examination by the theory of knowledge, + because it works with the fundamental forms and principles of human + thought. We cannot go further back than these forms and principles, which + it is the aim of epistemology to ascertain and for which no further reason + can be given. (The present writer, many years ago, in his "Psychology" + (Copenhagen, 1882; English translation London, 1891), criticised the + evolutionistic treatment of the problem of knowledge from the Kantian + point of view.) + </p> + <p> + But there is another side of the problem which is, perhaps, of more + importance and which epistemology generally overlooks. If new variations + can arise, not only in organic but perhaps also in inorganic nature, new + tasks are placed before the human mind. The question is, then, if it has + forms in which there is room for the new matter? We are here touching a + possibility which the great master of epistemology did not bring to light. + Kant supposed confidently that no other matter of knowledge could stream + forth from the dark source which he called "the thing-in-itself," than + such as could be synthesised in our existing forms of knowledge. He + mentions the possibility of other forms than the human, and warns us + against the dogmatic assumption that the human conception of existence + should be absolutely adequate. But he seems to be quite sure that the + thing-in-itself works constantly, and consequently always gives us only + what our powers can master. This assumption was a consequence of Kant's + rationalistic tendency, but one for which no warrant can be given. + Evolutionism and systematism are opposing tendencies which can never be + absolutely harmonised one with the other. Evolution may at any time break + some form which the system-monger regards as finally established. Darwin + himself felt a great difference in looking at variation as an evolutionist + and as a systematist. When he was working at his evolution theory, he was + very glad to find variations; but they were a hindrance to him when he + worked as a systematist, in preparing his work on Cirripedia. He says in a + letter: "I had thought the same parts of the same species more resemble + (than they do anyhow in Cirripedia) objects cast in the same mould. + Systematic work would be easy were it not for this confounded variation, + which, however, is pleasant to me as a speculatist, though odious to me as + a systematist." ("Life and Letters", Vol. II. page 37.) He could indeed be + angry with variations even as an evolutionist; but then only because he + could not explain them, not because he could not classify them. "If, as I + must think, external conditions produce little DIRECT effect, what the + devil determines each particular variation?" (Ibid. page 232.) What Darwin + experienced in his particular domain holds good of all knowledge. All + knowledge is systematic, in so far as it strives to put phenomena in quite + definite relations, one to another. But the systematisation can never be + complete. And here Darwin has contributed much to widen the world for us. + He has shown us forces and tendencies in nature which make absolute + systems impossible, at the same time that they give us new objects and + problems. There is still a place for what Lessing called "the unceasing + striving after truth," while "absolute truth" (in the sense of a closed + system) is unattainable so long as life and experience are going on. + </p> + <p> + There is here a special remark to be made. As we have seen above, recent + research has shown that natural selection or struggle for life is no + explanation of variations. Hugo de Vries distinguishes between partial and + embryonal variations, or between variations and mutations, only the + last-named being heritable, and therefore of importance for the origin of + new species. But the existence of variations is not only of interest for + the problem of the origin of species; it has also a more general interest. + An individual does not lose its importance for knowledge, because its + qualities are not heritable. On the contrary, in higher beings at least, + individual peculiarities will become more and more independent objects of + interest. Knowledge takes account of the biographies not only of species, + but also of individuals: it seeks to find the law of development of the + single individual. (The new science of Ecology occupies an intermediate + position between the biography of species and the biography of + individuals. Compare "Congress of Arts and Science", St Louis, Vol. V. + 1906 (the Reports of Drude and Robinson) and the work of my colleague E. + Warming.) As Leibniz said long ago, individuality consists in the law of + the changes of a being. "La loi du changement fait l'individualite de + chaque substance." Here is a world which is almost new for science, which + till now has mainly occupied itself with general laws and forms. But these + are ultimately only means to understand the individual phenomena, in whose + nature and history a manifold of laws and forms always cooperate. The + importance of this remark will appear in the sequel. + </p> + <p> + V. + </p> + <p> + To many people the Darwinian theory of natural selection or struggle for + existence seemed to change the whole conception of life, and particularly + all the conditions on which the validity of ethical ideas depends. If only + that has persistence which can be adapted to a given condition, what will + then be the fate of our ideals, of our standards of good and evil? Blind + force seems to reign, and the only thing that counts seems to be the most + heedless use of power. Darwinism, it was said, has proclaimed brutality. + No other difference seems permanent save that between the sound, powerful + and happy on the one side, the sick, feeble and unhappy on the other; and + every attempt to alleviate this difference seems to lead to general + enervation. Some of those who interpreted Darwinism in this manner felt an + aesthetic delight in contemplating the heedlessness and energy of the + great struggle for existence and anticipated the realisation of a higher + human type as the outcome of it: so Nietzsche and his followers. Others + recognising the same consequences in Darwinism regarded these as one of + the strongest objections against it; so Duhring and Kropotkin (in his + earlier works). + </p> + <p> + This interpretation of Darwinism was frequent in the interval between the + two main works of Darwin—"The Origin of Species" and "The Descent of + Man". But even during this interval it was evident to an attentive reader + that Darwin himself did not found his standard of good and evil on the + features of the life of nature he had emphasised so strongly. He did not + justify the ways along which nature reached its ends; he only pointed them + out. The "real" was not to him, as to Hegel, one with the "rational." + Darwin has, indeed, by his whole conception of nature, rendered a great + service to ethics in making the difference between the life of nature and + the ethical life appear in so strong a light. The ethical problem could + now be stated in a sharper form than before. But this was not the first + time that the idea of the struggle for life was put in relation to the + ethical problem. In the seventeenth century Thomas Hobbes gave the first + impulse to the whole modern discussion of ethical principles in his theory + of bellum omnium contra omnes. Men, he taught, are in the state of nature + enemies one of another, and they live either in fright or in the glory of + power. But it was not the opinion of Hobbes that this made ethics + impossible. On the contrary, he found a standard for virtue and vice in + the fact that some qualities and actions have a tendency to bring us out + of the state of war and to secure peace, while other qualities have a + contrary tendency. In the eighteenth century even Immanuel Kant's ideal + ethics had—so far as can be seen—a similar origin. Shortly + before the foundation of his definitive ethics, Kant wrote his "Idee zu + einer allgemeinen Weltgeschichte" (1784), where—in a way which + reminds us of Hobbes, and is prophetic of Darwin—he describes the + forward-driving power of struggle in the human world. It is here as with + the struggle of the trees for light and air, through which they compete + with one another in height. Anxiety about war can only be allayed by an + ordinance which gives everyone his full liberty under acknowledgment of + the equal liberty of others. And such ordinance and acknowledgment are + also attributes of the content of the moral law, as Kant proclaimed it in + the year after the publication of his essay (1785) (Cf. my "History of + Modern Philosophy" (English translation London, 1900), I. pages 76-79.) + Kant really came to his ethics by the way of evolution, though he + afterwards disavowed it. Similarly the same line of thought may be traced + in Hegel though it has been disguised in the form of speculative + dialectics. ("Herrschaft und Knechtschaft", "Phanomenologie des Geistes", + IV. A., Leiden, 1907.) And in Schopenhauer's theory of the blind will to + live and its abrogation by the ethical feeling, which is founded on + universal sympathy, we have a more individualistic form of the same idea. + </p> + <p> + It was, then, not entirely a foreign point of view which Darwin introduced + into ethical thought, even if we take no account of the poetical character + of the word "struggle" and of the more direct adaptation, through the use + and non-use of power, which Darwin also emphasised. In "The Descent of + Man" he has devoted a special chapter ("The Descent of Man", Vol. I. Ch. + iii.) to a discussion of the origin of the ethical consciousness. The + characteristic expression of this consciousness he found, just as Kant + did, in the idea of "ought"; it was the origin of this new idea which + should be explained. His hypothesis was that the ethical "ought" has its + origin in the social and parental instincts, which, as well as other + instincts (e.g. the instinct of self-preservation), lie deeper than + pleasure and pain. In many species, not least in the human species, these + instincts are fostered by natural selection; and when the powers of memory + and comparison are developed, so that single acts can be valued according + to the claims of the deep social instinct, then consciousness of duty and + remorse are possible. Blind instinct has developed to conscious ethical + will. + </p> + <p> + As already stated, Darwin, as a moral philosopher belongs to the school + that was founded by Shaftesbury, and was afterwards represented by + Hutcheson, Hume, Adam Smith, Comte and Spencer. His merit is, first, that + he has given this tendency of thought a biological foundation, and that he + has stamped on it a doughty character in showing that ethical ideas and + sentiments, rightly conceived, are forces which are at work in the + struggle for life. + </p> + <p> + There are still many questions to solve. Not only does the ethical + development within the human species contain features still unexplained + (The works of Westermarck and Hobhouse throw new light on many of these + features.); but we are confronted by the great problem whether after all a + genetic historical theory can be of decisive importance here. To every + consequent ethical consciousness there is a standard of value, a + primordial value which determines the single ethical judgments as their + last presupposition, and the "rightness" of this basis, the "value" of + this value can as little be discussed as the "rationality" of our logical + principles. There is here revealed a possibility of ethical scepticism + which evolutionistic ethics (as well as intuitive or rationalistic ethics) + has overlooked. No demonstration can show that the results of the ethical + development are definitive and universal. We meet here again with the + important opposition of systematisation and evolution. There will, I + think, always be an open question here, though comparative ethics, of + which we have so far only the first attempts, can do much to throw light + on it. + </p> + <p> + It would carry us too far to discuss all the philosophical works on + ethics, which have been influenced directly or indirectly by evolutionism. + I may, however, here refer to the book of C.M. Williams, "A Review of the + Systems of Ethics founded on the Theory of Evolution" (New York and + London, 1893.), in which, besides Darwin, the following authors are + reviewed: Wallace, Haeckel, Spencer, Fiske, Rolph, Barratt, Stephen, + Carneri, Hoffding, Gizycki, Alexander, Ree. As works which criticise + evolutionistic ethics from an intuitive point of view and in an + instructive way, may be cited: Guyau "La morale anglaise contemporaine" + (Paris, 1879.), and Sorley, "Ethics of Naturalism". I will only mention + some interesting contributions to ethical discussion which can be found in + Darwinism besides the idea of struggle for life. + </p> + <p> + The attention which Darwin has directed to variations has opened our eyes + to the differences in human nature as well as in nature generally. There + is here a fact of great importance for ethical thought, no matter from + what ultimate premiss it starts. Only from a very abstract point of view + can different individuals be treated in the same manner. The most eminent + ethical thinkers, men such as Jeremy Bentham and Immanuel Kant, who + discussed ethical questions from very opposite standpoints, agreed in + regarding all men as equal in respect of ethical endowment. In regard to + Bentham, Leslie Stephen remarks: "He is determined to be thoroughly + empirical, to take men as he found them. But his utilitarianism supposed + that men's views of happiness and utility were uniform and clear, and that + all that was wanted was to show them the means by which their ends could + be reached." ("English literature and society in the eighteenth century", + London, 1904, page 187.) And Kant supposed that every man would find the + "categorical imperative" in his consciousness, when he came to sober + reflexion, and that all would have the same qualifications to follow it. + But if continual variations, great or small, are going on in human nature, + it is the duty of ethics to make allowance for them, both in making + claims, and in valuing what is done. A new set of ethical problems have + their origin here. (Cf. my paper, "The law of relativity in Ethics," + "International Journal of Ethics", Vol. I. 1891, pages 37-62.) It is an + interesting fact that Stuart Mill's book "On Liberty" appeared in the same + year as "The Origin of Species". Though Mill agreed with Bentham about the + original equality of all men's endowments, he regarded individual + differences as a necessary result of physical and social influences, and + he claimed that free play shall be allowed to differences of character so + far as is possible without injury to other men. It is a condition of + individual and social progress that a man's mode of action should be + determined by his own character and not by tradition and custom, nor by + abstract rules. This view was to be corroborated by the theory of Darwin. + </p> + <p> + But here we have reached a point of view from which the criticism, which + in recent years has often been directed against Darwin—that small + variations are of no importance in the struggle for life—is of no + weight. From an ethical standpoint, and particularly from the ethical + standpoint of Darwin himself, it is a duty to foster individual + differences that can be valuable, even though they can neither be of + service for physical preservation nor be physically inherited. The + distinction between variation and mutation is here without importance. It + is quite natural that biologists should be particularly interested in such + variations as can be inherited and produce new species. But in the human + world there is not only a physical, but also a mental and social heredity. + When an ideal human character has taken form, then there is shaped a type, + which through imitation and influence can become an important factor in + subsequent development, even if it cannot form a species in the biological + sense of the word. Spiritually strong men often succumb in the physical + struggle for life; but they can nevertheless be victorious through the + typical influence they exert, perhaps on very distant generations, if the + remembrance of them is kept alive, be it in legendary or in historical + form. Their very failure can show that a type has taken form which is + maintained at all risks, a standard of life which is adhered to in spite + of the strongest opposition. The question "to be or not to be" can be put + from very different levels of being: it has too often been considered a + consequence of Darwinism that this question is only to be put from the + lowest level. When a stage is reached, where ideal (ethical, intellectual, + aesthetic) interests are concerned, the struggle for life is a struggle + for the preservation of this stage. The giving up of a higher standard of + life is a sort of death; for there is not only a physical, there is also a + spiritual, death. + </p> + <p> + VI. + </p> + <p> + The Socratic character of Darwin's mind appears in his wariness in drawing + the last consequences of his doctrine, in contrast both with the audacious + theories of so many of his followers and with the consequences which his + antagonists were busy in drawing. Though he, as we have seen, saw from the + beginning that his hypothesis would occasion "a whole of metaphysics," he + was himself very reserved as to the ultimate questions, and his answers to + such questions were extorted from him. + </p> + <p> + As to the question of optimism and pessimism, Darwin held that though pain + and suffering were very often the ways by which animals were led to pursue + that course of action which is most beneficial to the species, yet + pleasurable feelings were the most habitual guides. "We see this in the + pleasure from exertion, even occasionally from great exertion of the body + or mind, in the pleasure of our daily meals, and especially in the + pleasure derived from sociability, and from loving our families." But + there was to him so much suffering in the world that it was a strong + argument against the existence of an intelligent First Cause. ("Life and + Letters" Vol. I. page 310.) + </p> + <p> + It seems to me that Darwin was not so clear on another question, that of + the relation between improvement and adaptation. He wrote to Lyell: "When + you contrast natural selection and 'improvement,' you seem always to + overlook... that every step in the natural selection of each species + implies improvement in that species IN RELATION TO ITS CONDITION OF + LIFE... Improvement implies, I suppose, EACH FORM OBTAINING MANY PARTS OR + ORGANS, all excellently adapted for their functions." "All this," he adds, + "seems to me quite compatible with certain forms fitted for simple + conditions, remaining unaltered, or being degraded." (Ibid. Vol. II. page + 177.) But the great question is, if the conditions of life will in the + long run favour "improvement" in the sense of differentiation (or harmony + of differentiation and integration). Many beings are best adapted to their + conditions of life if they have few organs and few necessities. Pessimism + would not only be the consequence, if suffering outweighed happiness, but + also if the most elementary forms of happiness were predominant, or if + there were a tendency to reduce the standard of life to the simplest + possible, the contentment of inertia or stable equilibrium. There are + animals which are very highly differentiated and active in their young + state, but later lose their complex organisation and concentrate + themselves on the one function of nutrition. In the human world analogies + to this sort of adaptation are not wanting. Young "idealists" very often + end as old "Philistines." Adaptation and progress are not the same. + </p> + <p> + Another question of great importance in respect to human evolution is, + whether there will be always a possibility for the existence of an impulse + to progress, an impulse to make great claims on life, to be active and to + alter the conditions of life instead of adapting to them in a passive + manner. Many people do not develop because they have too few necessities, + and because they have no power to imagine other conditions of life than + those under which they live. In his remarks on "the pleasure from + exertion" Darwin has a point of contact with the practical idealism of + former times—with the ideas of Lessing and Goethe, of Condorcet and + Fichte. The continual striving which was the condition of salvation to + Faust's soul, is also the condition of salvation to mankind. There is a + holy fire which we ought to keep burning, if adaptation is really to be + improvement. If, as I have tried to show in my "Philosophy of Religion", + the innermost core of all religion is faith in the persistence of value in + the world, and if the highest values express themselves in the cry + "Excelsior!" then the capital point is, that this cry should always be + heard and followed. We have here a corollary of the theory of evolution in + its application to human life. + </p> + <p> + Darwin declared himself an agnostic, not only because he could not + harmonise the large amount of suffering in the world with the idea of a + God as its first cause, but also because he "was aware that if we admit a + first cause, the mind still craves to know whence it came and how it + arose." ("Life and Letters", Vol. I. page 306.) He saw, as Kant had seen + before him and expressed in his "Kritik der Urtheilskraft", that we cannot + accept either of the only two possibilities which we are able to conceive: + chance (or brute force) and design. Neither mechanism nor teleology can + give an absolute answer to ultimate questions. The universe, and + especially the organic life in it, can neither be explained as a mere + combination of absolute elements nor as the effect of a constructing + thought. Darwin concluded, as Kant, and before him Spinoza, that the + oppositions and distinctions which our experience presents, cannot safely + be regarded as valid for existence in itself. And, with Kant and Fichte, + he found his stronghold in the conviction that man has something to do, + even if he cannot solve all enigmas. "The safest conclusion seems to me + that the whole subject is beyond the scope of man's intellect; but man can + do his duty." (Ibid. page 307.) + </p> + <p> + Is this the last word of human thought? Does not the possibility, that man + can do his duty, suppose that the conditions of life allow of continuous + ethical striving, so that there is a certain harmony between cosmic order + and human ideals? Darwin himself has shown how the consciousness of duty + can arise as a natural result of evolution. Moreover there are lines of + evolution which have their end in ethical idealism, in a kingdom of + values, which must struggle for life as all things in the world must do, + but a kingdom which has its firm foundation in reality. + </p> + <p> + <a name="link2H_4_0025" id="link2H_4_0025"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + XXIII. DARWINISM AND SOCIOLOGY. By C. Bougle. + </h2> + <h3> + Professor of Social Philosophy in the University of Toulouse and + Deputy-Professor at the Sorbonne, Paris. + </h3> + <p> + How has our conception of social phenomena, and of their history, been + affected by Darwin's conception of Nature and the laws of its + transformations? To what extent and in what particular respects have the + discoveries and hypotheses of the author of "The Origin of Species" aided + the efforts of those who have sought to construct a science of society? + </p> + <p> + To such a question it is certainly not easy to give any brief or precise + answer. We find traces of Darwinism almost everywhere. Sociological + systems differing widely from each other have laid claim to its authority; + while, on the other hand, its influence has often made itself felt only in + combination with other influences. The Darwinian thread is worked into a + hundred patterns along with other threads. + </p> + <p> + To deal with the problem, we must, it seems, first of all distinguish the + more general conclusions in regard to the evolution of living beings, + which are the outcome of Darwinism, from the particular explanations it + offers of the ways and means by which that evolution is effected. That is + to say, we must, as far as possible, estimate separately the influence of + Darwin as an evolutionist and Darwin as a selectionist. + </p> + <p> + The nineteenth century, said Cournot, has witnessed a mighty effort to + "reintegrer l'homme dans la nature." From divers quarters there has been a + methodical reaction against the persistent dualism of the Cartesian + tradition, which was itself the unconscious heir of the Christian + tradition. Even the philosophy of the eighteenth century, materialistic as + were for the most part the tendencies of its leaders, seemed to revere man + as a being apart, concerning whom laws might be formulated a priori. To + bring him down from his pedestal there was needed the marked predominance + of positive researches wherein no account was taken of the "pride of man." + There can be no doubt that Darwin has done much to familiarise us with + this attitude. Take for instance the first part of "The Descent of Man": + it is an accumulation of typical facts, all tending to diminish the + distance between us and our brothers, the lower animals. One might say + that the naturalist had here taken as his motto, "Whosoever shall exalt + himself shall be abased; and he that shall humble himself shall be + exalted." Homologous structures, the survival in man of certain organs of + animals, the rudiments in the animal of certain human faculties, a + multitude of facts of this sort, led Darwin to the conclusion that there + is no ground for supposing that the "king of the universe" is exempt from + universal laws. Thus belief in the imperium in imperio has been, as it + were, whittled away by the progress of the naturalistic spirit, itself + continually strengthened by the conquests of the natural sciences. The + tendency may, indeed, drag the social sciences into overstrained + analogies, such, for instance, as the assimilation of societies to + organisms. But it will, at least, have had the merit of helping sociology + to shake off the pre-conception that the groups formed by men are + artificial, and that history is completely at the mercy of chance. Some + years before the appearance of "The Origin of Species", Auguste Comte had + pointed out the importance, as regards the unification of positive + knowledge, of the conviction that the social world, the last refuge of + spiritualism, is itself subject to determininism. It cannot be doubted + that the movement of thought which Darwin's discoveries promoted + contributed to the spread of this conviction, by breaking down the + traditional barrier which cut man off from Nature. + </p> + <p> + But Nature, according to modern naturalists, is no immutable thing: it is + rather perpetual movement, continual progression. Their discoveries batter + a breach directly into the Aristotelian notion of species; they refuse to + see in the animal world a collection of immutable types, distinct from all + eternity, and corresponding, as Cuvier said, to so many particular + thoughts of the Creator. Darwin especially congratulated himself upon + having been able to deal this doctrine the coup de grace: immutability is, + he says, his chief enemy; and he is concerned to show—therein + following up Lyell's work—that everything in the organic world, as + in the inorganic, is explained by insensible but incessant + transformations. "Nature makes no leaps"—"Nature knows no gaps": + these two dicta form, as it were, the two landmarks between which Darwin's + idea of transformation is worked out. That is to say, the development of + Darwinism is calculated to further the application of the philosophy of + Becoming to the study of human institutions. + </p> + <p> + The progress of the natural sciences thus brings unexpected reinforcements + to the revolution which the progress of historical discipline had begun. + The first attempt to constitute an actual science of social phenomena—that, + namely, of the economists—had resulted in laws which were called + natural, and which were believed to be eternal and universal, valid for + all times and all places. But this perpetuality, brother, as Knies said, + of the immutability of the old zoology, did not long hold out against the + ever swelling tide of the historical movement. Knowledge of the + transformations that had taken place in language, of the early phases of + the family, of religion, of property, had all favoured the revival of the + Heraclitean view: panta rei. As to the categories of political economy, it + was soon to be recognised, as by Lassalle, that they too are only + historical. The philosophy of history, moreover, gave expression under + various forms to the same tendency. Hegel declares that "all that is real + is rational," but at the same time he shows that all that is real is + ephemeral, and that for history there is nothing fixed beneath the sun. It + is this sense of universal evolution that Darwin came with fresh authority + to enlarge. It was in the name of biological facts themselves that he + taught us to see only slow metamorphoses in the history of institutions, + and to be always on the outlook for survivals side by side with + rudimentary forms. Anyone who reads "Primitive Culture", by Tylor,—a + writer closely connected with Darwin—will be able to estimate the + services which these cardinal ideas were to render to the social sciences + when the age of comparative research had succeeded to that of a priori + construction. + </p> + <p> + Let us note, moreover, that the philosophy of Becoming in passing through + the Darwinian biology became, as it were, filtered: it got rid of those + traces of finalism, which, under different forms, it had preserved through + all the systems of German Romanticism. Even in Herbert Spencer, it has + been plausibly argued, one can detect something of that sort of mystic + confidence in forces spontaneously directing life, which forms the very + essence of those systems. But Darwin's observations were precisely + calculated to render such an hypothesis futile. At first people may have + failed to see this; and we call to mind the ponderous sarcasms of Flourens + when he objected to the theory of Natural Selection that it attributed to + nature a power of free choice. "Nature endowed with will! That was the + final error of last century; but the nineteenth no longer deals in + personifications." (P. Flourens, "Examen du Livre de M. Darwin sur + l'Origine des Especes", page 53, Paris, 1864. See also Huxley, "Criticisms + on the 'Origin of Species'", "Collected Essays", Vol. II, page 102, + London, 1902.) In fact Darwin himself put his readers on their guard + against the metaphors he was obliged to use. The processes by which he + explains the survival of the fittest are far from affording any indication + of the design of some transcendent breeder. Nor, if we look closely, do + they even imply immanent effort in the animal; the sorting out can be + brought about mechanically, simply by the action of the environment. In + this connection Huxley could with good reason maintain that Darwin's + originality consisted in showing how harmonies which hitherto had been + taken to imply the agency of intelligence and will could be explained + without any such intervention. So, when later on, objective sociology + declares that, even when social phenomena are in question, all finalist + preconceptions must be distrusted if a science is to be constituted, it is + to Darwin that its thanks are due; he had long been clearing paths for it + which lay well away from the old familiar road trodden by so many theories + of evolution. + </p> + <p> + This anti-finalist doctrine, when fully worked out, was, moreover, + calculated to aid in the needful dissociation of two notions: that of + evolution and that of progress. In application to society these had long + been confounded; and, as a consequence, the general idea seemed to be that + only one type of evolution was here possible. Do we not detect such a view + in Comte's sociology, and perhaps even in Herbert Spencer's? Whoever, + indeed, assumes an end for evolution is naturally inclined to think that + only one road leads to that end. But those whose minds the Darwinian + theory has enlightened are aware that the transformations of living beings + depend primarily upon their conditions, and that it is these conditions + which are the agents of selection from among individual variations. Hence, + it immediately follows that transformations are not necessarily + improvements. Here, Darwin's thought hesitated. Logically his theory + proves, as Ray Lankester pointed out, that the struggle for existence may + have as its outcome degeneration as well as amelioration: evolution may be + regressive as well as progressive. Then, too—and this is especially + to be borne in mind—each species takes its good where it finds it, + seeks its own path and survives as best it can. Apply this notion to + society and you arrive at the theory of multilinear evolution. + Divergencies will no longer surprise you. You will be forewarned not to + apply to all civilisations the same measure of progress, and you will + recognise that types of evolution may differ just as social species + themselves differ. Have we not here one of the conceptions which mark off + sociology proper from the old philosophy of history? + </p> + <p> + But if we are to estimate the influence of Darwinism upon sociological + conceptions, we must not dwell only upon the way in which Darwin impressed + the general notion of evolution upon the minds of thinkers. We must go + into details. We must consider the influence of the particular theories by + which he explained the mechanism of this evolution. The name of the author + of "The Origin of Species" has been especially attached, as everyone + knows, to the doctrines of "natural selection" and of "struggle for + existence," completed by the notion of "individual variation." These + doctrines were turned to account by very different schools of social + philosophy. Pessimistic and optimistic, aristocratic and democratic, + individualistic and socialistic systems were to war with each other for + years by casting scraps of Darwinism at each other's heads. + </p> + <p> + It was the spectacle of human contrivance that suggested to Darwin his + conception of natural selection. It was in studying the methods of pigeon + breeders that he divined the processes by which nature, in the absence of + design, obtains analogous results in the differentiation of types. As soon + as the importance of artificial selection in the transformation of species + of animals was understood, reflection naturally turned to the human + species, and the question arose, How far do men observe, in connection + with themselves, those laws of which they make practical application in + the case of animals? Here we come upon one of the ideas which guided the + researches of Galton, Darwin's cousin. The author of "Inquiries into Human + Faculty and its Development" ("Inquiries into Human Faculty", pages 1, 2, + 3 sq., London, 1883.), has often expressed his surprise that, considering + all the precautions taken, for example, in the breeding of horses, none + whatever are taken in the breeding of the human species. It seems to be + forgotten that the species suffers when the "fittest" are not able to + perpetuate their type. Ritchie, in his "Darwinism and Politics" + ("Darwinism and Politics" pages 9, 22, London, 1889.) reminds us of + Darwin's remark that the institution of the peerage might be defended on + the ground that peers, owing to the prestige they enjoy, are enabled to + select as wives "the most beautiful and charming women out of the lower + ranks." ("Life and Letters of Charles Darwin", II. page 385.) But, says + Galton, it is as often as not "heiresses" that they pick out, and birth + statistics seem to show that these are either less robust or less fecund + than others. The truth is that considerations continue to preside over + marriage which are entirely foreign to the improvement of type, much as + this is a condition of general progress. Hence the importance of + completing Odin's and De Candolle's statistics which are designed to show + how characters are incorporated in organisms, how they are transmitted, + how lost, and according to what law eugenic elements depart from the mean + or return to it. + </p> + <p> + But thinkers do not always content themselves with undertaking merely the + minute researches which the idea of Selection suggests. They are eager to + defend this or that thesis. In the name of this idea certain social + anthropologists have recast the conception of the process of civilisation, + and have affirmed that Social Selection generally works against the trend + of Natural Selection. Vacher de Lapouge—following up an observation + by Broca on the point—enumerates the various institutions, or + customs, such as the celibacy of priests and military conscription, which + cause elimination or sterilisation of the bearers of certain superior + qualities, intellectual or physical. In a more general way he attacks the + democratic movement, a movement, as P. Bourget says, which is + "anti-physical" and contrary to the natural laws of progress; though it + has been inspired "by the dreams of that most visionary of all centuries, + the eighteenth." (V. de Lapouge, "Les Selections sociales", page 259, + Paris, 1896.) The "Equality" which levels down and mixes (justly + condemned, he holds, by the Comte de Gobineau), prevents the aristocracy + of the blond dolichocephales from holding the position and playing the + part which, in the interests of all, should belong to them. Otto Ammon, in + his "Natural Selection in Man", and in "The Social Order and its Natural + Bases" ("Die naturliche Auslese beim Menschen", Jena, 1893; "Die + Gesellschaftsordnung und ihre naturlichen Grundlagen". "Entwurf einer + Sozialanthropologie", Jena, 1896.), defended analogous doctrines in + Germany; setting the curve representing frequency of talent over against + that of income, he attempted to show that all democratic measures which + aim at promoting the rise in the social scale of the talented are useless, + if not dangerous; that they only increase the panmixia, to the great + detriment of the species and of society. + </p> + <p> + Among the aristocratic theories which Darwinism has thus inspired we must + reckon that of Nietzsche. It is well known that in order to complete his + philosophy he added biological studies to his philological; and more than + once in his remarks upon the "Wille zur Macht" he definitely alludes to + Darwin; though it must be confessed that it is generally in order to + proclaim the in sufficiency of the processes by which Darwin seeks to + explain the genesis of species. Nevertheless, Nietzsche's mind is + completely possessed by an ideal of Selection. He, too, has a horror of + panmixia. The naturalists' conception of "the fittest" is joined by him to + that of the "hero" of romance to furnish a basis for his doctrine of the + Superman. Let us hasten to add, moreover, that at the very moment when + support was being sought in the theory of Selection for the various forms + of the aristocratic doctrine, those same forms were being battered down on + another side by means of that very theory. Attention was drawn to the fact + that by virtue of the laws which Darwin himself had discovered isolation + leads to etiolation. There is a risk that the privilege which withdraws + the privileged elements of Society from competition will cause them to + degenerate. In fact, Jacoby in his "Studies in Selection, in connexion + with Heredity in Man", ("Etudes sur la Selection dans ses rapports avec + l'heredite chez l'homme", Paris, page 481, 1881.), concludes that + "sterility, mental debility, premature death and, finally, the extinction + of the stock were not specially and exclusively the fate of sovereign + dynasties; all privileged classes, all families in exclusively elevated + positions share the fate of reigning families, although in a minor degree + and in direct proportion to the loftiness of their social standing. From + the mass of human beings spring individuals, families, races, which tend + to raise themselves above the common level; painfully they climb the + rugged heights, attain the summits of power, of wealth, of intelligence, + of talent, and then, no sooner are they there than they topple down and + disappear in gulfs of mental and physical degeneracy." The demographical + researches of Hansen ("Die drei Bevolkerungsstufen", Munich, 1889.) + (following up and completing Dumont's) tended, indeed, to show that urban + as well as feudal aristocracies, burgher classes as well as noble castes, + were liable to become effete. Hence it might well be concluded that the + democratic movement, operating as it does to break down class barriers, + was promoting instead of impeding human selection. + </p> + <p> + So we see that, according to the point of view, very different conclusions + have been drawn from the application of the Darwinian idea of Selection to + human society. Darwin's other central idea, closely bound up with this, + that, namely, of the "struggle for existence" also has been diversely + utilised. But discussion has chiefly centered upon its signification. And + while some endeavour to extend its application to everything, we find + others trying to limit its range. The conception of a "struggle for + existence" has in the present day been taken up into the social sciences + from natural science, and adopted. But originally it descended from social + science to natural. Darwin's law is, as he himself said, only Malthus' law + generalised and extended to the animal world: a growing disproportion + between the supply of food and the number of the living is the fatal order + whence arises the necessity of universal struggle, a struggle which, to + the great advantage of the species, allows only the best equipped + individuals to survive. Nature is regarded by Huxley as an immense arena + where all living beings are gladiators. ("Evolution and Ethics", page 200; + "Collected Essays", Vol. IX, London, 1894.) + </p> + <p> + Such a generalisation was well adapted to feed the stream of pessimistic + thought; and it furnished to the apologists of war, in particular, new + arguments, weighted with all the authority which in these days attaches to + scientific deliverances. If people no longer say, as Bonald did, and + Moltke after him, that war is a providential fact, they yet lay stress on + the point that it is a natural fact. To the peace party Dragomirov's + objection is urged that its attempts are contrary to the fundamental laws + of nature, and that no sea wall can hold against breakers that come with + such gathered force. + </p> + <p> + But in yet another quarter Darwinism was represented as opposed to + philanthropic intervention. The defenders of the orthodox political + economy found in it support for their tenets. Since in the organic world + universal struggle is the condition of progress, it seemed obvious that + free competition must be allowed to reign unchecked in the economic world. + Attempts to curb it were in the highest degree imprudent. The spirit of + Liberalism here seemed in conformity with the trend of nature: in this + respect, at least, contemporary naturalism, offspring of the discoveries + of the nineteenth century, brought reinforcements to the individualist + doctrine, begotten of the speculations of the eighteenth: but only, it + appeared, to turn mankind away for ever from humanitarian dreams. Would + those whom such conclusions repelled be content to oppose to nature's + imperatives only the protests of the heart? There were some who declared, + like Brunetiere, that the laws in question, valid though they might be for + the animal kingdom, were not applicable to the human. And so a return was + made to the classic dualism. This indeed seems to be the line that Huxley + took, when, for instance, he opposed to the cosmic process an ethical + process which was its reverse. + </p> + <p> + But the number of thinkers whom this antithesis does not satisfy grows + daily. Although the pessimism which claims authorisation from Darwin's + doctrines is repugnant to them, they still are unable to accept the + dualism which leaves a gulf between man and nature. And their endeavour is + to link the two by showing that while Darwin's laws obtain in both + kingdoms, the conditions of their application are not the same: their + forms, and, consequently, their results, vary with the varying mediums in + which the struggle of living beings takes place, with the means these + beings have at disposal, with the ends even which they propose to + themselves. + </p> + <p> + Here we have the explanation of the fact that among determined opponents + of war partisans of the "struggle for existence" can be found: there are + disciples of Darwin in the peace party. Novicow, for example, admits the + "combat universel" of which Le Dantec ("Les Luttes entre Societies + humaines et leurs phases successives", Paris, 1893,) speaks; but he + remarks that at different stages of evolution, at different stages of life + the same weapons are not necessarily employed. Struggles of brute force, + armed hand to hand conflicts, may have been a necessity in the early + phases of human societies. Nowadays, although competition may remain + inevitable and indispensable, it can assume milder forms. Economic + rivalries, struggles between intellectual influences, suffice to stimulate + progress: the processes which these admit are, in the actual state of + civilisation, the only ones which attain their end without waste, the only + ones logical. From one end to the other of the ladder of life, struggle is + the order of the day; but more and more as the higher rungs are reached, + it takes on characters which are proportionately more "humane." + </p> + <p> + Reflections of this kind permit the introduction into the economic order + of limitations to the doctrine of "laisser faire, laisser passer." This + appeals, it is said, to the example of nature where creatures, left to + themselves, struggle without truce and without mercy; but the fact is + forgotten that upon industrial battlefields the conditions are different. + The competitors here are not left simply to their natural energies: they + are variously handicapped. A rich store of artificial resources exists in + which some participate and others do not. The sides then are unequal; and + as a consequence the result of the struggle is falsified. "In the animal + world," said De Laveleye ("Le socialisme contemporain", page 384 (6th + edition), Paris, 1891.), criticising Spencer, "the fate of each creature + is determined by its individual qualities; whereas in civilised societies + a man may obtain the highest position and the most beautiful wife because + he is rich and well-born, although he may be ugly, idle or improvident; + and then it is he who will perpetuate the species. The wealthy man, ill + constituted, incapable, sickly, enjoys his riches and establishes his + stock under the protection of the laws." Haycraft in England and Jentsch + in Germany have strongly emphasised these "anomalies," which nevertheless + are the rule. That is to say that even from a Darwinian point of view all + social reforms can readily be justified which aim at diminishing, as + Wallace said, inequalities at the start. + </p> + <p> + But we can go further still. Whence comes the idea that all measures + inspired by the sentiment of solidarity are contrary to Nature's trend? + Observe her carefully, and she will not give lessons only in + individualism. Side by side with the struggle for existence do we not find + in operation what Lanessan calls "association for existence." Long ago, + Espinas had drawn attention to "societies of animals," temporary or + permanent, and to the kind of morality that arose in them. Since then, + naturalists have often insisted upon the importance of various forms of + symbiosis. Kropotkin in "Mutual Aid" has chosen to enumerate many examples + of altruism furnished by animals to mankind. Geddes and Thomson went so + far as to maintain that "Each of the greater steps of progress is in fact + associated with an increased measure of subordination of individual + competition to reproductive or social ends, and of interspecific + competition to co-operative association." (Geddes and Thomson, "The + Evolution of Sex", page 311, London, 1889.) Experience shows, according to + Geddes, that the types which are fittest to surmount great obstacles are + not so much those who engage in the fiercest competitive struggle for + existence, as those who contrive to temper it. From all these observations + there resulted, along with a limitation of Darwinian pessimism, some + encouragement for the aspirations of the collectivists. + </p> + <p> + And Darwin himself would, doubtless, have subscribed to these + rectifications. He never insisted, like his rival, Wallace, upon the + necessity of the solitary struggle of creatures in a state of nature, each + for himself and against all. On the contrary, in "The Descent of Man", he + pointed out the serviceableness of the social instincts, and corroborated + Bagehot's statements when the latter, applying laws of physics to + politics, showed the great advantage societies derived from intercourse + and communion. Again, the theory of sexual evolution which makes the + evolution of types depend increasingly upon preferences, judgments, mental + factors, surely offers something to qualify what seems hard and brutal in + the theory of natural selection. + </p> + <p> + But, as often happens with disciples, the Darwinians had out-Darwined + Darwin. The extravagancies of social Darwinism provoked a useful reaction; + and thus people were led to seek, even in the animal kingdom, for facts of + solidarity which would serve to justify humane effort. + </p> + <p> + On quite another line, however, an attempt has been made to connect + socialist tendencies with Darwinian principles. Marx and Darwin have been + confronted; and writers have undertaken to show that the work of the + German philosopher fell readily into line with that of the English + naturalist and was a development of it. Such has been the endeavour of + Ferri in Italy and of Woltmann in Germany, not to mention others. The + founders of "scientific socialism" had, moreover, themselves thought of + this reconciliation. They make more than one allusion to Darwin in works + which appeared after 1859. And sometimes they use his theory to define by + contrast their own ideal. They remark that the capitalist system, by + giving free course to individual competition, ends indeed in a bellum + omnium contra omnes; and they make it clear that Darwinism, thus + understood, is as repugnant to them as to Duhring. + </p> + <p> + But it is at the scientific and not at the moral point of view that they + place themselves when they connect their economic history with Darwin's + work. Thanks to this unifying hypothesis, they claim to have constructed—as + Marx does in his preface to "Das Kapital"—a veritable natural + history of social evolution. Engels speaks in praise of his friend Marx as + having discovered the true mainspring of history hidden under the veil of + idealism and sentimentalism, and as having proclaimed in the primum vivere + the inevitableness of the struggle for existence. Marx himself, in "Das + Kapital", indicated another analogy when he dwelt upon the importance of a + general technology for the explanation of this psychology:—a history + of tools which would be to social organs what Darwinism is to the organs + of animal species. And the very importance they attach to tools, to + apparatus, to machines, abundantly proves that neither Marx nor Engels + were likely to forget the special characters which mark off the human + world from the animal. The former always remains to a great extent an + artificial world. Inventions change the face of its institutions. New + modes of production revolutionise not only modes of government, but modes + even of collective thought. Therefore it is that the evolution of society + is controlled by laws special to it, of which the spectacle of nature + offers no suggestion. + </p> + <p> + If, however, even in this special sphere, it can still be urged that the + evolution of the material conditions of society is in accord with Darwin's + theory, it is because the influence of the methods of production is itself + to be explained by the incessant strife of the various classes with each + other. So that in the end Marx, like Darwin, finds the source of all + progress in struggle. Both are grandsons of Heraclitus:—polemos + pater panton. It sometimes happens, in these days, that the doctrine of + revolutionary socialism is contrasted as rude and healthy with what may + seem to be the enervating tendency of "solidarist" philanthropy: the + apologists of the doctrine then pride themselves above all upon their + faithfulness to Darwinian principles. + </p> + <p> + So far we have been mainly concerned to show the use that social + philosophies have made of the Darwinian laws for practical purposes: in + order to orientate society towards their ideals each school tries to show + that the authority of natural science is on its side. But even in the most + objective of theories, those which systematically make abstraction of all + political tendencies in order to study the social reality in itself, + traces of Darwinism are readily to be found. + </p> + <p> + Let us take for example Durkheim's theory of Division of Labour ("De la + Division du Travail social", Paris, 1893.) The conclusions he derives from + it are that whenever professional specialisation causes multiplication of + distinct branches of activity, we get organic solidarity—implying + differences—substituted for mechanical solidarity, based upon + likenesses. The umbilical cord, as Marx said, which connects the + individual consciousness with the collective consciousness is cut. The + personality becomes more and more emancipated. But on what does this + phenomenon, so big with consequences, itself depend? The author goes to + social morphology for the answer: it is, he says, the growing density of + population which brings with it this increasing differentiation of + activities. But, again, why? Because the greater density, in thrusting men + up against each other, augments the intensity of their competition for the + means of existence; and for the problems which society thus has to face + differentiation of functions presents itself as the gentlest solution. + </p> + <p> + Here one sees that the writer borrows directly from Darwin. Competition is + at its maximum between similars, Darwin had declared; different species, + not laying claim to the same food, could more easily coexist. Here lay the + explanation of the fact that upon the same oak hundreds of different + insects might be found. Other things being equal, the same applies to + society. He who finds some unadopted speciality possesses a means of his + own for getting a living. It is by this division of their manifold tasks + that men contrive not to crush each other. Here we obviously have a + Darwinian law serving as intermediary in the explanation of that progress + of division of labour which itself explains so much in the social + evolution. + </p> + <p> + And we might take another example, at the other end of the series of + sociological systems. G. Tarde is a sociologist with the most pronounced + anti-naturalistic views. He has attempted to show that all application of + the laws of natural science to society is misleading. In his "Opposition + Universelle" he has directly combatted all forms of sociological + Darwinism. According to him the idea that the evolution of society can be + traced on the same plan as the evolution of species is chimerical. Social + evolution is at the mercy of all kinds of inventions, which by virtue of + the laws of imitation modify, through individual to individual, through + neighbourhood to neighbourhood, the general state of those beliefs and + desires which are the only "quantities" whose variation matters to the + sociologist. But, it may be rejoined, that however psychical the forces + may be, they are none the less subject to Darwinian laws. They compete + with each other; they struggle for the mastery of minds. Between types of + ideas, as between organic forms, selection operates. And though it may be + that these types are ushered into the arena by unexpected discoveries, we + yet recognise in the psychological accidents, which Tarde places at the + base of everything, near relatives of those small accidental variations + upon which Darwin builds. Thus, accepting Tarde's own representations, it + is quite possible to express in Darwinian terms, with the necessary + transpositions, one of the most idealistic sociologies that have ever been + constructed. + </p> + <p> + These few examples suffice. They enable us to estimate the extent of the + field of influence of Darwinism. It affects sociology not only through the + agency of its advocates but through that of its opponents. The + questionings to which it has given rise have proved no less fruitful than + the solutions it has suggested. In short, few doctrines, in the history of + social philosophy, will have produced on their passage a finer outcrop of + ideas. + </p> + <p> + <a name="link2H_4_0026" id="link2H_4_0026"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + XXIV. THE INFLUENCE OF DARWIN UPON RELIGIOUS THOUGHT. By P.N. Waggett, + M.A., S.S.J.E. + </h2> + <p> + I. + </p> + <p> + The object of this paper is first to point out certain elements of the + Darwinian influence upon Religious thought, and then to show reason for + the conclusion that it has been, from a Christian point of view, + satisfactory. I shall not proceed further to urge that the Christian + apologetic in relation to biology has been successful. A variety of + opinions may be held on this question, without disturbing the conclusion + that the movements of readjustment have been beneficial to those who + remain Christians, and this by making them more Christian and not only + more liberal. The theologians may sometimes have retreated, but there has + been an advance of theology. I know that this account incurs the charge of + optimism. It is not the worst that could be made. The influence has been + limited in personal range, unequal, even divergent, in operation, and + accompanied by the appearance of waste and mischievous products. The + estimate which follows requires for due balance a full development of many + qualifying considerations. For this I lack space, but I must at least + distinguish my view from the popular one that our difficulties about + religion and natural science have come to an end. + </p> + <p> + Concerning the older questions about origins—the origin of the + world, of species, of man, of reason, conscience, religion—a large + measure of understanding has been reached by some thoughtful men. But + meanwhile new questions have arisen, questions about conduct, regarding + both the reality of morals and the rule of right action for individuals + and societies. And these problems, still far from solution, may also be + traced to the influence of Darwin. For they arise from the renewed + attention to heredity, brought about by the search for the causes of + variation, without which the study of the selection of variations has no + sufficient basis. + </p> + <p> + Even the existing understanding about origins is very far from universal. + On these points there were always thoughtful men who denied the necessity + of conflict, and there are still thoughtful men who deny the possibility + of a truce. + </p> + <p> + It must further be remembered that the earlier discussion now, as I hope + to show, producing favourable results, created also for a time grave + damage, not only in the disturbance of faith and the loss of men—a + loss not repaired by a change in the currents of debate—but in what + I believe to be a still more serious respect. I mean the introduction of a + habit of facile and untested hypothesis in religious as in other + departments of thought. + </p> + <p> + Darwin is not responsible for this, but he is in part the cause of it. + Great ideas are dangerous guests in narrow minds; and thus it has happened + that Darwin—the most patient of scientific workers, in whom + hypothesis waited upon research, or if it provisionally outstepped it did + so only with the most scrupulously careful acknowledgment—has led + smaller and less conscientious men in natural science, in history, and in + theology to an over-eager confidence in probable conjecture and a loose + grip upon the facts of experience. It is not too much to say that in many + quarters the age of materialism was the least matter-of-fact age + conceivable, and the age of science the age which showed least of the + patient temper of inquiry. + </p> + <p> + I have indicated, as shortly as I could, some losses and dangers which in + a balanced account of Darwin's influence would be discussed at length. + </p> + <p> + One other loss must be mentioned. It is a defect in our thought which, in + some quarters, has by itself almost cancelled all the advantages secured. + I mean the exaggerated emphasis on uniformity or continuity; the + unwillingness to rest any part of faith or of our practical expectation + upon anything that from any point of view can be called exceptional. The + high degree of success reached by naturalists in tracing, or reasonably + conjecturing, the small beginnings of great differences, has led the + inconsiderate to believe that anything may in time become anything else. + </p> + <p> + It is true that this exaggeration of the belief in uniformity has produced + in turn its own perilous reaction. From refusing to believe whatever can + be called exceptional, some have come to believe whatever can be called + wonderful. + </p> + <p> + But, on the whole, the discontinuous or highly various character of + experience received for many years too little deliberate attention. The + conception of uniformity which is a necessity of scientific description + has been taken for the substance of history. We have accepted a postulate + of scientific method as if it were a conclusion of scientific + demonstration. In the name of a generalisation which, however just on the + lines of a particular method, is the prize of a difficult exploit of + reflexion, we have discarded the direct impressions of experience; or, + perhaps it is more true to say, we have used for the criticism of alleged + experiences a doctrine of uniformity which is only valid in the region of + abstract science. For every science depends for its advance upon + limitation of attention, upon the selection out of the whole content of + consciousness of that part or aspect which is measurable by the method of + the science. Accordingly there is a science of life which rightly displays + the unity underlying all its manifestations. But there is another view of + life, equally valid, and practically sometimes more important, which + recognises the immediate and lasting effect of crisis, difference, and + revolution. Our ardour for the demonstration of uniformity of process and + of minute continuous change needs to be balanced by a recognition of the + catastrophic element in experience, and also by a recognition of the + exceptional significance for us of events which may be perfectly regular + from an impersonal point of view. + </p> + <p> + An exorbitant jealousy of miracle, revelation, and ultimate moral + distinctions has been imported from evolutionary science into religious + thought. And it has been a damaging influence, because it has taken men's + attention from facts, and fixed them upon theories. + </p> + <p> + II. + </p> + <p> + With this acknowledgment of important drawbacks, requiring many words for + their proper description, I proceed to indicate certain results of + Darwin's doctrine which I believe to be in the long run wholly beneficial + to Christian thought. These are: + </p> + <p> + The encouragement in theology of that evolutionary method of observation + and study, which has shaped all modern research: + </p> + <p> + The recoil of Christian apologetics towards the ground of religious + experience, a recoil produced by the pressure of scientific criticism upon + other supports of faith: + </p> + <p> + The restatement, or the recovery of ancient forms of statement, of the + doctrines of Creation and of divine Design in Nature, consequent upon the + discussion of evolution and of natural selection as its guiding factor. + </p> + <p> + (1) The first of these is quite possibly the most important of all. It was + well defined in a notable paper read by Dr Gore, now Bishop of Birmingham, + to the Church Congress at Shrewsbury in 1896. We have learnt a new caution + both in ascribing and in denying significance to items of evidence, in + utterance or in event. There has been, as in art, a study of values, which + secures perspective and solidity in our representation of facts. On the + one hand, a given utterance or event cannot be drawn into evidence as if + all items were of equal consequence, like sovereigns in a bag. The + question whence and whither must be asked, and the particular thing + measured as part of a series. Thus measured it is not less truly + important, but it may be important in a lower degree. On the other hand, + and for exactly the same reason, nothing that is real is unimportant. The + "failures" are not mere mistakes. We see them, in St Augustine's words, as + "scholar's faults which men praise in hope of fruit." + </p> + <p> + We cannot safely trace the origin of the evolutionistic method to the + influence of natural science. The view is tenable that theology led the + way. Probably this is a case of alternate and reciprocal debt. Quite + certainly the evolutionist method in theology, in Christian history, and + in the estimate of scripture, has received vast reinforcement from + biology, in which evolution has been the ever present and ever victorious + conception. + </p> + <p> + (2) The second effect named is the new willingness of Christian thinkers + to take definite account of religious experience. This is related to + Darwin through the general pressure upon religious faith of scientific + criticism. The great advance of our knowledge of organisms has been an + important element in the general advance of science. It has acted, by the + varied requirements of the theory of organisms, upon all other branches of + natural inquiry, and it held for a long time that leading place in public + attention which is now occupied by speculative physics. Consequently it + contributed largely to our present estimation of science as the supreme + judge in all matters of inquiry (F.R. Tennant: "The Being of God in the + light of Physical Science", in "Essays on some theological questions of + the day". London, 1905.), to the supposed destruction of mystery and the + disparagement of metaphysic which marked the last age, as well as to the + just recommendation of scientific method in branches of learning where the + direct acquisitions of natural science had no place. + </p> + <p> + Besides this, the new application of the idea of law and mechanical + regularity to the organic world seemed to rob faith of a kind of refuge. + The romantics had, as Berthelot ("Evolutionisme et Platonisme", pages 45, + 46, 47. Paris, 1908.) shows, appealed to life to redress the judgments + drawn from mechanism. Now, in Spencer, evolution gave us a vitalist + mechanic or mechanical vitalism, and the appeal seemed cut off. We may + return to this point later when we consider evolution; at present I only + endeavour to indicate that general pressure of scientific criticism which + drove men of faith to seek the grounds of reassurance in a science of + their own; in a method of experiment, of observation, of hypothesis + checked by known facts. It is impossible for me to do more than glance + across the threshold of this subject. But it is necessary to say that the + method is in an elementary stage of revival. The imposing success that + belongs to natural science is absent: we fall short of the unchallengeable + unanimity of the Biologists on fundamentals. The experimental method with + its sure repetitions cannot be applied to our subject-matter. But we have + something like the observational method of palaeontology and geographical + distribution; and in biology there are still men who think that the large + examination of varieties by way of geography and the search of strata is + as truly scientific, uses as genuinely the logical method of difference, + and is as fruitful in sure conclusions as the quasi-chemical analysis of + Mendelian laboratory work, of which last I desire to express my humble + admiration. Religion also has its observational work in the larger and + possibly more arduous manner. + </p> + <p> + But the scientific work in religion makes its way through difficulties and + dangers. We are far from having found the formula of its combination with + the historical elements of our apologetic. It is exposed, therefore, to a + damaging fire not only from unspiritualist psychology and pathology but + also from the side of scholastic dogma. It is hard to admit on equal terms + a partner to the old undivided rule of books and learning. With Charles + Lamb, we cry in some distress, "must knowledge come to me, if it come at + all, by some awkward experiment of intuition, and no longer by this + familiar process of reading?" ("Essays of Elia", "New Year's Eve", page + 41; Ainger's edition. London, 1899.) and we are answered that the old + process has an imperishable value, only we have not yet made clear its + connection with other contributions. And all the work is young, liable to + be drawn into unprofitable excursions, side-tracked by self-deceit and + pretence; and it fatally attracts, like the older mysticism, the curiosity + and the expository powers of those least in sympathy with it, ready + writers who, with all the air of extended research, have been content with + narrow grounds for induction. There is a danger, besides, which + accompanies even the most genuine work of this science and must be + provided against by all its serious students. I mean the danger of + unbalanced introspection both for individuals and for societies; of a + preoccupation comparable to our modern social preoccupation with bodily + health; of reflection upon mental states not accompanied by exercise and + growth of the mental powers; the danger of contemplating will and + neglecting work, of analysing conviction and not criticising evidence. + </p> + <p> + Still, in spite of dangers and mistakes, the work remains full of hopeful + indications, and, in the best examples (Such an example is given in Baron + F. von Hugel's recently finished book, the result of thirty years' + research: "The Mystical Element of Religion, as studied in Saint Catherine + of Genoa and her Friends". London, 1908.), it is truly scientific in its + determination to know the very truth, to tell what we think, not what we + think we ought to think. (G. Tyrrell, in "Mediaevalism", has a chapter + which is full of the important MORAL element in a scientific attitude. + "The only infallible guardian of truth is the spirit of truthfulness." + "Mediaevalism" page 182, London, 1908.), truly scientific in its + employment of hypothesis and verification, and in growing conviction of + the reality of its subject-matter through the repeated victories of a + mastery which advances, like science, in the Baconian road of obedience. + It is reasonable to hope that progress in this respect will be more rapid + and sure when religious study enlists more men affected by scientific + desire and endowed with scientific capacity. + </p> + <p> + The class of investigating minds is a small one, possibly even smaller + than that of reflecting minds. Very few persons at any period are able to + find out anything whatever. There are few observers, few discoverers, few + who even wish to discover truth. In how many societies the problems of + philology which face every person who speaks English are left unattempted! + And if the inquiring or the successfully inquiring class of minds is + small, much smaller, of course, is the class of those possessing the + scientific aptitude in an eminent degree. During the last age this most + distinguished class was to a very great extent absorbed in the study of + phenomena, a study which had fallen into arrears. For we stood possessed, + in rudiment, of means of observation, means for travelling and + acquisition, qualifying men for a larger knowledge than had yet been + attempted. These were now to be directed with new accuracy and ardour upon + the fabric and behaviour of the world of sense. Our debt to the great + masters in physical science who overtook and almost out-stripped the task + cannot be measured; and, under the honourable leadership of Ruskin, we may + all well do penance if we have failed "in the respect due to their great + powers of thought, or in the admiration due to the far scope of their + discovery." ("Queen of the Air", Preface, page vii. London, 1906.) With + what miraculous mental energy and divine good fortune—as Romans said + of their soldiers—did our men of curiosity face the apparently + impenetrable mysteries of nature! And how natural it was that immense + accessions of knowledge, unrelated to the spiritual facts of life, should + discredit Christian faith, by the apparent superiority of the new work to + the feeble and unprogressive knowledge of Christian believers! The day is + coming when men of this mental character and rank, of this curiosity, this + energy and this good fortune in investigation, will be employed in opening + mysteries of a spiritual nature. They will silence with masterful witness + the over-confident denials of naturalism. They will be in danger of the + widespread recognition which thirty years ago accompanied every utterance + of Huxley, Tyndall, Spencer. They will contribute, in spite of adulation, + to the advance of sober religious and moral science. + </p> + <p> + And this result will be due to Darwin, first because by raising the + dignity of natural science, he encouraged the development of the + scientific mind; secondly because he gave to religious students the + example of patient and ardent investigation; and thirdly because by the + pressure of naturalistic criticism the religious have been driven to + ascertain the causes of their own convictions, a work in which they were + not without the sympathy of men of science. (The scientific rank of its + writer justifies the insertion of the following letter from the late Sir + John Burdon-Sanderson to me. In the lecture referred to I had described + the methods of Professor Moseley in teaching Biology as affording a + suggestion of the scientific treatment of religion.) + </p> + <p> + Oxford, April 30, 1902. + </p> + <p> + Dear Sir, + </p> + <p> + I feel that I must express to you my thanks for the discourse which I had + the pleasure of listening to yesterday afternoon. + </p> + <p> + I do not mean to say that I was able to follow all that you said as to the + identity of Method in the two fields of Science and Religion, but I + recognise that the "mysticism" of which you spoke gives us the only way by + which the two fields can be brought into relation. + </p> + <p> + Among much that was memorable, nothing interested me more than what you + said of Moseley. + </p> + <p> + No one, I am sure, knew better than you the value of his teaching and in + what that value consisted. + </p> + <p> + Yours faithfully + </p> + <p> + J. Burdon-Sanderson. 31-2.) + </p> + <p> + In leaving the subject of scientific religious inquiry, I will only add + that I do not believe it receives any important help—and certainly + it suffers incidentally much damaging interruption—from the study of + abnormal manifestations or abnormal conditions of personality. + </p> + <p> + (3) Both of the above effects seem to me of high, perhaps the very + highest, importance to faith and to thought. But, under the third head, I + name two which are more directly traceable to the personal work of Darwin, + and more definitely characteristic of the age in which his influence was + paramount: viz. the influence of the two conceptions of evolution and + natural selection upon the doctrine of creation and of design + respectively. + </p> + <p> + It is impossible here, though it is necessary for a complete sketch of the + matter, to distinguish the different elements and channels of this + Darwinian influence; in Darwin's own writings, in the vigorous polemic of + Huxley, and strangely enough, but very actually for popular thought, in + the teaching of the definitely anti-Darwinian evolutionist Spencer. + </p> + <p> + Under the head of the directly and purely Darwinian elements I should + class as preeminent the work of Wallace and of Bates; for no two sets of + facts have done more to fix in ordinary intelligent minds a belief in + organic evolution and in natural selection as its guiding factor than the + facts of geographical distribution and of protective colour and mimicry. + The facts of geology were difficult to grasp and the public and + theologians heard more often of the imperfection than of the extent of the + geological record. The witness of embryology, depending to a great extent + upon microscopic work, was and is beyond the appreciation of persons + occupied in fields of work other than biology. + </p> + <p> + III. + </p> + <p> + From the influence in religion of scientific modes of thought we pass to + the influence of particular biological conceptions. The former effect + comes by way of analogy, example, encouragement and challenge; inspiring + or provoking kindred or similar modes of thought in the field of theology; + the latter by a collision of opinions upon matters of fact or conjecture + which seem to concern both science and religion. + </p> + <p> + In the case of Darwinism the story of this collision is familiar, and + falls under the heads of evolution and natural selection, the doctrine of + descent with modification, and the doctrine of its guidance or + determination by the struggle for existence between related varieties. + These doctrines, though associated and interdependent, and in popular + thought not only combined but confused, must be considered separately. It + is true that the ancient doctrine of Evolution, in spite of the ingenuity + and ardour of Lamarck, remained a dream tantalising the intellectual + ambition of naturalists, until the day when Darwin made it conceivable by + suggesting the machinery of its guidance. And, further, the idea of + natural selection has so effectively opened the door of research and + stimulated observation in a score of principal directions that, even if + the Darwinian explanation became one day much less convincing than, in + spite of recent criticism, it now is, yet its passing, supposing it to + pass, would leave the doctrine of Evolution immeasurably and permanently + strengthened. For in the interests of the theory of selection, "Fur + Darwin," as Muller wrote, facts have been collected which remain in any + case evidence of the reality of descent with modification. + </p> + <p> + But still, though thus united in the modern history of convictions, though + united and confused in the collision of biological and traditional + opinion, yet evolution and natural selection must be separated in + theological no less than in biological estimation. Evolution seemed + inconsistent with Creation; natural selection with Providence and Divine + design. + </p> + <p> + Discussion was maintained about these points for many years and with much + dark heat. It ranged over many particular topics and engaged minds + different in tone, in quality, and in accomplishment. There was at most + times a degree of misconception. Some naturalists attributed to + theologians in general a poverty of thought which belonged really to men + of a particular temper or training. The "timid theism" discerned in Darwin + by so cautious a theologian as Liddon (H.P. Liddon, "The Recovery of S. + Thomas"; a sermon preached in St Paul's, London, on April 23rd, 1882 (the + Sunday after Darwin's death).) was supposed by many biologists to be the + necessary foundation of an honest Christianity. It was really more + characteristic of devout NATURALISTS like Philip Henry Gosse, than of + religious believers as such. (Dr Pusey ("Unscience not Science adverse to + Faith" 1878) writes: "The questions as to 'species,' of what variations + the animal world is capable, whether the species be more or fewer, whether + accidental variations may become hereditary... and the like, naturally + fall under the province of science. In all these questions Mr Darwin's + careful observations gained for him a deserved approbation and + confidence.") The study of theologians more considerable and even more + typically conservative than Liddon does not confirm the description of + religious intolerance given in good faith, but in serious ignorance, by a + disputant so acute, so observant and so candid as Huxley. Something hid + from each other's knowledge the devoted pilgrims in two great ways of + thought. The truth may be, that naturalists took their view of what + creation was from Christian men of science who naturally looked in their + own special studies for the supports and illustrations of their religious + belief. Of almost every laborious student it may be said "Hic ab arte sua + non recessit." And both the believing and the denying naturalists, + confining habitual attention to a part of experience, are apt to affirm + and deny with trenchant vigour and something of a narrow clearness "Qui + respiciunt ad pauca, de facili pronunciant." (Aristotle, in Bacon, quoted + by Newman in his "Idea of a University", page 78. London, 1873.) + </p> + <p> + Newman says of some secular teachers that "they persuade the world of what + is false by urging upon it what is true." Of some early opponents of + Darwin it might be said by a candid friend that, in all sincerity of + devotion to truth, they tried to persuade the world of what is true by + urging upon it what is false. If naturalists took their version of + orthodoxy from amateurs in theology, some conservative Christians, instead + of learning what evolution meant to its regular exponents, took their view + of it from celebrated persons, not of the front rank in theology or in + thought, but eager to take account of public movements and able to arrest + public attention. + </p> + <p> + Cleverness and eloquence on both sides certainly had their share in + producing the very great and general disturbance of men's minds in the + early days of Darwinian teaching. But by far the greater part of that + disturbance was due to the practical novelty and the profound importance + of the teaching itself, and to the fact that the controversy about + evolution quickly became much more public than any controversy of equal + seriousness had been for many generations. + </p> + <p> + We must not think lightly of that great disturbance because it has, in + some real sense, done its work, and because it is impossible in days of + more coolness and light, to recover a full sense of its very real + difficulties. + </p> + <p> + Those who would know them better should add to the calm records of Darwin + ("Life and Letters" and "More Letters of Charles Darwin".) and to the + story of Huxley's impassioned championship, all that they can learn of + George Romanes. ("Life and Letters", London, 1896. "Thoughts on Religion", + London, 1895. "Candid Examination of Theism", London, 1878.) For his life + was absorbed in this very struggle and reproduced its stages. It began in + a certain assured simplicity of biblical interpretation; it went on, + through the glories and adventures of a paladin in Darwin's train, to the + darkness and dismay of a man who saw all his most cherished beliefs + rendered, as he thought, incredible. ("Never in the history of man has so + terrific a calamity befallen the race as that which all who look may now + (viz. in consequence of the scientific victory of Darwin) behold advancing + as a deluge, black with destruction, resistless in might, uprooting our + most cherished hopes, engulphing our most precious creed, and burying our + highest life in mindless destruction."—"A Candid Examination of + Theism", page 51.) He lived to find the freer faith for which process and + purpose are not irreconcilable, but necessary to one another. His + development, scientific, intellectual and moral, was itself of high + significance; and its record is of unique value to our own generation, so + near the age of that doubt and yet so far from it; certainly still much in + need of the caution and courage by which past endurance prepares men for + new emergencies. We have little enough reason to be sure that in the + discussions awaiting us we shall do as well as our predecessors in theirs. + Remembering their endurance of mental pain, their ardour in mental labour, + the heroic temper and the high sincerity of controversialists on either + side, we may well speak of our fathers in such words of modesty and + self-judgment as Drayton used when he sang the victors of Agincourt. The + progress of biblical study, in the departments of Introduction and + Exegesis, resulting in the recovery of a point of view anciently tolerated + if not prevalent, has altered some of the conditions of that discussion. + In the years near 1858, the witness of Scripture was adduced both by + Christian advocates and their critics as if unmistakeably irreconcilable + with Evolution. + </p> + <p> + Huxley ("Science and Christian Tradition". London, 1904.) found the path + of the blameless naturalist everywhere blocked by "Moses": the believer in + revelation was generally held to be forced to a choice between revealed + cosmogony and the scientific account of origins. It is not clear how far + the change in Biblical interpretation is due to natural science, and how + far to the vital movements of theological study which have been quite + independent of the controversy about species. It belongs to a general + renewal of Christian movement, the recovery of a heritage. "Special + Creation"—really a biological rather than a theological conception,—seems + in its rigid form to have been a recent element even in English biblical + orthodoxy. + </p> + <p> + The Middle Ages had no suspicion that religious faith forbad inquiry into + the natural origination of the different forms of life. Bartholomaeus + Anglicus, an English Franciscan of the thirteenth century, was a + mutationist in his way, as Aristotle, "the Philosopher" of the Christian + Schoolmen, had been in his. So late as the seventeenth century, as we + learn not only from early proceedings of the Royal Society, but from a + writer so homely and so regularly pious as Walton, the variation of + species and "spontaneous" generations had no theological bearing, except + as instances of that various wonder of the world which in devout minds is + food for devotion. + </p> + <p> + It was in the eighteenth century that the harder statement took shape. + Something in the preciseness of that age, its exaltation of law, its cold + passion for a stable and measured universe, its cold denial, its cold + affirmation of the power of God, a God of ice, is the occasion of that + rigidity of religious thought about the living world which Darwin by + accident challenged, or rather by one of those movements of genius which, + Goethe ("No productiveness of the highest kind... is in the power of + anyone."—"Conversations of Goethe with Eckermann and Soret". London, + 1850.) declares, are "elevated above all earthly control." + </p> + <p> + If religious thought in the eighteenth century was aimed at a fixed and + nearly finite world of spirit, it followed in all these respects the + secular and critical lead. ("La philosophie reformatrice du XVIIIe siecle" + (Berthelot, "Evolutionisme et Platonisme", Paris, 1908, page 45.) ramenait + la nature et la societe a des mecanismes que la pensee reflechie peut + concevoir et recomposer." In fact, religion in a mechanical age is + condemned if it takes any but a mechanical tone. Butler's thought was too + moving, too vital, too evolutionary, for the sceptics of his time. In a + rationalist, encyclopaedic period, religion also must give hard outline to + its facts, it must be able to display its secret to any sensible man in + the language used by all sensible men. Milton's prophetic genius furnished + the eighteenth century, out of the depth of the passionate age before it, + with the theological tone it was to need. In spite of the austere + magnificence of his devotion, he gives to smaller souls a dangerous lead. + The rigidity of Scripture exegesis belonged to this stately but + imperfectly sensitive mode of thought. It passed away with the influence + of the older rationalists whose precise denials matched the precise and + limited affirmations of the static orthodoxy. + </p> + <p> + I shall, then, leave the specially biblical aspect of the debate—interesting + as it is and even useful, as in Huxley's correspondence with the Duke of + Argyll and others in 1892 ("Times", 1892, passim.)—in order to + consider without complication the permanent elements of Christian thought + brought into question by the teaching of evolution. + </p> + <p> + Such permanent elements are the doctrine of God as Creator of the + universe, and the doctrine of man as spiritual and unique. Upon both the + doctrine of evolution seemed to fall with crushing force. + </p> + <p> + With regard to Man I leave out, acknowledging a grave omission, the + doctrine of the Fall and of Sin. And I do so because these have not yet, + as I believe, been adequately treated: here the fruitful reaction to the + stimulus of evolution is yet to come. The doctrine of sin, indeed, falls + principally within the scope of that discussion which has followed or + displaced the Darwinian; and without it the Fall cannot be usefully + considered. For the question about the Fall is a question not merely of + origins, but of the interpretation of moral facts whose moral reality must + first be established. + </p> + <p> + I confine myself therefore to Creation and the dignity of man. + </p> + <p> + The meaning of evolution, in the most general terms, is that the + differentiation of forms is not essentially separate from their behaviour + and use; that if these are within the scope of study, that is also; that + the world has taken the form we see by movements not unlike those we now + see in progress; that what may be called proximate origins are continuous + in the way of force and matter, continuous in the way of life, with actual + occurrences and actual characteristics. All this has no revolutionary + bearing upon the question of ultimate origins. The whole is a statement + about process. It says nothing to metaphysicians about cause. It simply + brings within the scope of observation or conjecture that series of + changes which has given their special characters to the different parts of + the world we see. In particular, evolutionary science aspires to the + discovery of the process or order of the appearance of life itself: if it + were to achieve its aim it could say nothing of the cause of this or + indeed of the most familiar occurrences. We should have become spectators + or convinced historians of an event which, in respect of its cause and + ultimate meaning, would be still impenetrable. + </p> + <p> + With regard to the origin of species, supposing life already established, + biological science has the well founded hopes and the measure of success + with which we are all familiar. All this has, it would seem, little chance + of collision with a consistent theism, a doctrine which has its own + difficulties unconnected with any particular view of order or process. But + when it was stated that species had arisen by processes through which new + species were still being made, evolutionism came into collision with a + statement, traditionally religious, that species were formed and fixed + once for all and long ago. + </p> + <p> + What is the theological import of such a statement when it is regarded as + essential to belief in God? Simply that God's activity, with respect to + the formation of living creatures, ceased at some point in past time. + </p> + <p> + "God rested" is made the touchstone of orthodoxy. And when, under the + pressure of the evidences, we found ourselves obliged to acknowledge and + assert the present and persistent power of God, in the maintenance and in + the continued formation of "types," what happened was the abolition of a + time-limit. We were forced only to a bolder claim, to a theistic language + less halting, more consistent, more thorough in its own line, as well as + better qualified to assimilate and modify such schemes as Von Hartmann's + philosophy of the unconscious—a philosophy, by the way, quite + intolerant of a merely mechanical evolution. (See Von Hartmann's "Wahrheit + und Irrthum in Darwinismus". Berlin, 1875.) + </p> + <p> + Here was not the retrenchment of an extravagant assertion, but the + expansion of one which was faltering and inadequate. The traditional + statement did not need paring down so as to pass the meshes of a new and + exacting criticism. It was itself a net meant to surround and enclose + experience; and we must increase its size and close its mesh to hold newly + disclosed facts of life. The world, which had seemed a fixed picture or + model, gained first perspective and then solidity and movement. We had a + glimpse of organic HISTORY; and Christian thought became more living and + more assured as it met the larger view of life. + </p> + <p> + However unsatisfactory the new attitude might be to our critics, to + Christians the reform was positive. What was discarded was a limitation, a + negation. The movement was essentially conservative, even actually + reconstructive. For the language disused was a language inconsistent with + the definitions of orthodoxy; it set bounds to the infinite, and by + implication withdrew from the creative rule all such processes as could be + brought within the descriptions of research. It ascribed fixity and + finality to that "creature" in which an apostle taught us to recognise the + birth-struggles of an unexhausted progress. It tended to banish mystery + from the world we see, and to confine it to a remote first age. + </p> + <p> + In the reformed, the restored, language of religion, Creation became again + not a link in a rational series to complete a circle of the sciences, but + the mysterious and permanent relation between the infinite and the finite, + between the moving changes we know in part, and the Power, after the + fashion of that observation, unknown, which is itself "unmoved all + motion's source." (Hymn of the Church— Rerum Deus tenax vigor, + Immotus in te permanens.) + </p> + <p> + With regard to man it is hardly necessary, even were it possible, to + illustrate the application of this bolder faith. When the record of his + high extraction fell under dispute, we were driven to a contemplation of + the whole of his life, rather than of a part and that part out of sight. + We remembered again, out of Aristotle, that the result of a process + interprets its beginnings. We were obliged to read the title of such + dignity as we may claim, in results and still more in aspirations. + </p> + <p> + Some men still measure the value of great present facts in life—reason + and virtue and sacrifice—by what a self-disparaged reason can + collect of the meaner rudiments of these noble gifts. Mr Balfour has + admirably displayed the discrepancy, in this view, between the alleged + origin and the alleged authority of reason. Such an argument ought to be + used not to discredit the confident reason, but to illuminate and dignify + its dark beginnings, and to show that at every step in the long course of + growth a Power was at work which is not included in any term or in all the + terms of the series. + </p> + <p> + I submit that the more men know of actual Christian teaching, its fidelity + to the past, and its sincerity in face of discovery, the more certainly + they will judge that the stimulus of the doctrine of evolution has + produced in the long run vigour as well as flexibility in the doctrine of + Creation and of man. + </p> + <p> + I pass from Evolution in general to Natural Selection. + </p> + <p> + The character in religious language which I have for short called + mechanical was not absent in the argument from design as stated before + Darwin. It seemed to have reference to a world conceived as fixed. It + pointed, not to the plastic capacity and energy of living matter, but to + the fixed adaptation of this and that organ to an unchanging place or + function. + </p> + <p> + Mr Hobhouse has given us the valuable phrase "a niche of organic + opportunity." Such a phrase would have borne a different sense in + non-evolutionary thought. In that thought, the opportunity was an + opportunity for the Creative Power, and Design appeared in the preparation + of the organism to fit the niche. The idea of the niche and its occupant + growing together from simpler to more complex mutual adjustment was + unwelcome to this teleology. If the adaptation was traced to the + influence, through competition, of the environment, the old teleology lost + an illustration and a proof. For the cogency of the proof in every + instance depended upon the absence of explanation. Where the process of + adaptation was discerned, the evidence of Purpose or Design was weak. It + was strong only when the natural antecedents were not discovered, + strongest when they could be declared undiscoverable. + </p> + <p> + Paley's favourite word is "Contrivance"; and for him contrivance is most + certain where production is most obscure. He points out the physiological + advantage of the valvulae conniventes to man, and the advantage for + teleology of the fact that they cannot have been formed by "action and + pressure." What is not due to pressure may be attributed to design, and + when a "mechanical" process more subtle than pressure was suggested, the + case for design was so far weakened. The cumulative proof from the + multitude of instances began to disappear when, in selection, a natural + sequence was suggested in which all the adaptations might be reached by + the motive power of life, and especially when, as in Darwin's teaching, + there was full recognition of the reactions of life to the stimulus of + circumstance. "The organism fits the niche," said the teleologist, + "because the Creator formed it so as to fit." "The organism fits the + niche," said the naturalist, "because unless it fitted it could not + exist." "It was fitted to survive," said the theologian. "It survives + because it fits," said the selectionist. The two forms of statement are + not incompatible; but the new statement, by provision of an ideally + universal explanation of process, was hostile to a doctrine of purpose + which relied upon evidences always exceptional however numerous. Science + persistently presses on to find the universal machinery of adaptation in + this planet; and whether this be found in selection, or in direct-effect, + or in vital reactions resulting in large changes, or in a combination of + these and other factors, it must always be opposed to the conception of a + Divine Power here and there but not everywhere active. + </p> + <p> + For science, the Divine must be constant, operative everywhere and in + every quality and power, in environment and in organism, in stimulus and + in reaction, in variation and in struggle, in hereditary equilibrium, and + in "the unstable state of species"; equally present on both sides of every + strain, in all pressures and in all resistances, in short in the general + wonder of life and the world. And this is exactly what the Divine Power + must be for religious faith. + </p> + <p> + The point I wish once more to make is that the necessary readjustment of + teleology, so as to make it depend upon the contemplation of the whole + instead of a part, is advantageous quite as much to theology as to + science. For the older view failed in courage. Here again our theism was + not sufficiently theistic. + </p> + <p> + Where results seemed inevitable, it dared not claim them as God-given. In + the argument from Design it spoke not of God in the sense of theology, but + of a Contriver, immensely, not infinitely wise and good, working within a + world, the scene, rather than the ever dependent outcome, of His Wisdom; + working in such emergencies and opportunities as occurred, by forces not + altogether within His control, towards an end beyond Himself. It gave us, + instead of the awful reverence due to the Cause of all substance and form, + all love and wisdom, a dangerously detached appreciation of an ingenuity + and benevolence meritorious in aim and often surprisingly successful in + contrivance. + </p> + <p> + The old teleology was more useful to science than to religion, and the + design-naturalists ought to be gratefully remembered by Biologists. Their + search for evidences led them to an eager study of adaptations and of + minute forms, a study such as we have now an incentive to in the theory of + Natural Selection. One hardly meets with the same ardour in microscopical + research until we come to modern workers. But the argument from Design was + never of great importance to faith. Still, to rid it of this character was + worth all the stress and anxiety of the gallant old war. If Darwin had + done nothing else for us, we are to-day deeply in his debt for this. The + world is not less venerable to us now, not less eloquent of the causing + mind, rather much more eloquent and sacred. But our wonder is not that + "the underjaw of the swine works under the ground" or in any or all of + those particular adaptations which Paley collected with so much skill, but + that a purpose transcending, though resembling, our own purposes, is + everywhere manifest; that what we live in is a whole, mutually sustaining, + eventful and beautiful, where the "dead" forces feed the energies of life, + and life sustains a stranger existence, able in some real measure to + contemplate the whole, of which, mechanically considered, it is a minor + product and a rare ingredient. Here, again, the change was altogether + positive. It was not the escape of a vessel in a storm with loss of spars + and rigging, not a shortening of sail to save the masts and make a port of + refuge. It was rather the emergence from narrow channels to an open sea. + We had propelled the great ship, finding purchase here and there for slow + and uncertain movement. Now, in deep water, we spread large canvas to a + favouring breeze. + </p> + <p> + The scattered traces of design might be forgotten or obliterated. But the + broad impression of Order became plainer when seen at due distance and in + sufficient range of effect, and the evidence of love and wisdom in the + universe could be trusted more securely for the loss of the particular + calculation of their machinery. + </p> + <p> + Many other topics of faith are affected by modern biology. In some of + these we have learnt at present only a wise caution, a wise uncertainty. + We stand before the newly unfolded spectacle of suffering, silenced; with + faith not scientifically reassured but still holding fast certain other + clues of conviction. In many important topics we are at a loss. But in + others, and among them those I have mentioned, we have passed beyond this + negative state and find faith positively strengthened and more fully + expressed. + </p> + <p> + We have gained also a language and a habit of thought more fit for the + great and dark problems that remain, less liable to damaging conflicts, + equipped for more rapid assimilation of knowledge. And by this change + biology itself is a gainer. For, relieved of fruitless encounters with + popular religion, it may advance with surer aim along the path of really + scientific life-study which was reopened for modern men by the publication + of "The Origin of Species". + </p> + <p> + Charles Darwin regretted that, in following science, he had not done "more + direct good" ("Life and Letters", Vol. III. page 359.) to his + fellow-creatures. He has, in fact, rendered substantial service to + interests bound up with the daily conduct and hopes of common men; for his + work has led to improvements in the preaching of the Christian faith. + </p> + <p> + <a name="link2H_4_0027" id="link2H_4_0027"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + XXV. THE INFLUENCE OF DARWINISM ON THE STUDY OF RELIGIONS. By Jane Ellen + Harrison. + </h2> + <h3> + Hon. D.Litt. (Durham), Hon. LL.D. (Aberdeen), Staff Lecturer and sometime + Fellow of Newnham College, Cambridge. + </h3> + <p> + Corresponding member of the German Archaeological Institute. + </p> + <p> + The title of my paper might well have been "the creation by Darwinism of + the scientific study of Religions," but that I feared to mar my tribute to + a great name by any shadow of exaggeration. Before the publication of "The + Origin of Species" and "The Descent of Man", even in the eighteenth + century, isolated thinkers, notably Hume and Herder, had conjectured that + the orthodox beliefs of their own day were developments from the cruder + superstitions of the past. These were however only particular speculations + of individual sceptics. Religion was not yet generally regarded as a + proper subject for scientific study, with facts to be collected and + theories to be deduced. A Congress of Religions such as that recently held + at Oxford would have savoured of impiety. + </p> + <p> + In the brief space allotted me I can attempt only two things; first, and + very briefly, I shall try to indicate the normal attitude towards religion + in the early part of the last century; second, and in more detail, I shall + try to make clear what is the outlook of advanced thinkers to-day. (To be + accurate I ought to add "in Europe." I advisedly omit from consideration + the whole immense field of Oriental mysticism, because it has remained + practically untouched by the influence of Darwinism.) From this second + inquiry it will, I hope, be abundantly manifest that it is the doctrine of + evolution that has made this outlook possible and even necessary. + </p> + <p> + The ultimate and unchallenged presupposition of the old view was that + religion was a DOCTRINE, a body of supposed truths. It was in fact what we + should now call Theology, and what the ancients called Mythology. Ritual + was scarcely considered at all, and, when considered, it was held to be a + form in which beliefs, already defined and fixed as dogma, found a natural + mode of expression. This, it will be later shown, is a profound error or + rather a most misleading half-truth. Creeds, doctrines, theology and the + like are only a part, and at first the least important part, of religion. + </p> + <p> + Further, and the fact is important, this DOGMA, thus supposed to be the + essential content of the "true" religion, was a teleological scheme + complete and unalterable, which had been revealed to man once and for all + by a highly anthropomorphic God, whose existence was assumed. The duty of + man towards this revelation was to accept its doctrines and obey its + precepts. The notion that this revelation had grown bit by bit out of + man's consciousness and that his business was to better it would have + seemed rank blasphemy. Religion, so conceived, left no place for + development. "The Truth" might be learnt, but never critically examined; + being thus avowedly complete and final, it was doomed to stagnation. + </p> + <p> + The details of this supposed revelation seem almost too naive for + enumeration. As Hume observed, "popular theology has a positive appetite + for absurdity." It is sufficient to recall that "revelation" included such + items as the Creation (It is interesting to note that the very word + "Creator" has nowadays almost passed into the region of mythology. Instead + we have "L'Evolution Creatrice".) of the world out of nothing in six days; + the making of Eve from one of Adam's ribs; the Temptation by a talking + snake; the confusion of tongues at the tower of Babel; the doctrine of + Original Sin; a scheme of salvation which demanded the Virgin Birth, + Vicarious Atonement, and the Resurrection of the material body. The scheme + was unfolded in an infallible Book, or, for one section of Christians, + guarded by the tradition of an infallible Church, and on the acceptance or + refusal of this scheme depended an eternity of weal or woe. There is not + one of these doctrines that has not now been recast, softened down, + mysticised, allegorised into something more conformable with modern + thinking. It is hard for the present generation, unless their breeding has + been singularly archaic, to realise that these amazing doctrines were + literally held and believed to constitute the very essence of religion; to + doubt them was a moral delinquency. + </p> + <p> + It had not, however, escaped the notice of travellers and missionaries + that savages carried on some sort of practices that seemed to be + religious, and believed in some sort of spirits or demons. Hence, beyond + the confines illuminated by revealed truth, a vague region was assigned to + NATURAL Religion. The original revelation had been kept intact only by one + chosen people, the Jews, by them to be handed on to Christianity. Outside + the borders of this Goshen the world had sunk into the darkness of Egypt. + Where analogies between savage cults and the Christian religions were + observed, they were explained as degradations; the heathen had somehow + wilfully "lost the light." Our business was not to study but, exclusively, + to convert them, to root out superstition and carry the torch of + revelation to "Souls in heathen darkness lying." To us nowadays it is a + commonplace of anthropological research that we must seek for the + beginnings of religion in the religions of primitive peoples, but in the + last century the orthodox mind was convinced that it possessed a complete + and luminous ready-made revelation; the study of what was held to be a + mere degradation seemed idle and superfluous. + </p> + <p> + But, it may be asked, if, to the orthodox, revealed religion was + sacrosanct and savage religion a thing beneath consideration, why did not + the sceptics show a more liberal spirit, and pursue to their logical issue + the conjectures they had individually hazarded? The reason is simple and + significant. The sceptics too had not worked free from the presupposition + that the essence of religion is dogma. Their intellectualism, expressive + of the whole eighteenth century, was probably in England strengthened by + the Protestant doctrine of an infallible Book. Hume undoubtedly confused + religion with dogmatic theology. The attention of orthodox and sceptics + alike was focussed on the truth or falsity of certain propositions. Only a + few minds of rare quality were able dimly to conceive that religion might + be a necessary step in the evolution of human thought. + </p> + <p> + It is not a little interesting to note that Darwin, who was leader and + intellectual king of his generation, was also in this matter to some + extent its child. His attitude towards religion is stated clearly, in + Chapter VIII. of the "Life and Letters". (Vol. I. page 304. For Darwin's + religious views see also "Descent of Man", 1871, Vol. I. page 65; 2nd + edition. Vol. I. page 142.) On board the "Beagle" he was simply orthodox + and was laughed at by several of the officers for quoting the Bible as an + unanswerable authority on some point of morality. By 1839 he had come to + see that the Old Testament was no more to be trusted than the sacred books + of the Hindoos. Next went the belief in miracles, and next Paley's + "argument from design" broke down before the law of natural selection; the + suffering so manifest in nature is seen to be compatible rather with + Natural Selection than with the goodness and omnipotence of God. Darwin + felt to the full all the ignorance that lay hidden under specious phrases + like "the plan of creation" and "Unity of design." Finally, he tells us + "the mystery of the beginning of all things is insoluble by us; and I for + one must be content to remain an Agnostic." + </p> + <p> + The word Agnostic is significant not only of the humility of the man + himself but also of the attitude of his age. Religion, it is clear, is + still conceived as something to be KNOWN, a matter of true or false + OPINION. Orthodox religion was to Darwin a series of erroneous hypotheses + to be bit by bit discarded when shown to be untenable. The ACTS of + religion which may result from such convictions, i.e. devotion in all its + forms, prayer, praise, sacraments, are left unmentioned. It is clear that + they are not, as now to us, sociological survivals of great interest and + importance, but rather matters too private, too personal, for discussion. + </p> + <p> + Huxley, writing in the "Contemporary Review" (1871.), says, "In a dozen + years "The Origin of Species" has worked as complete a revolution in + biological science as the "Principia" did in astronomy." It has done so + because, in the words of Helmholtz, it contained "an essentially new + creative thought," that of the continuity of life, the absence of breaks. + In the two most conservative subjects, Religion and Classics, this + creative ferment was slow indeed to work. Darwin himself felt strongly + "that a man should not publish on a subject to which he has not given + special and continuous thought," and hence wrote little on religion and + with manifest reluctance, though, as already seen, in answer to + pertinacious inquiry he gave an outline of his own views. But none the + less he foresaw that his doctrine must have, for the history of man's + mental evolution, issues wider than those with which he was prepared + personally to deal. He writes, in "The Origin of Species" (6th edition, + page 428.), "In the future I see open fields for far more important + researches. Psychology will be securely based on the foundation already + well laid by Mr Herbert Spencer, that of the necessary acquirement of each + mental power and capacity by gradation." + </p> + <p> + Nowhere, it is true, does Darwin definitely say that he regarded religion + as a set of phenomena, the development of which may be studied from the + psychological standpoint. Rather we infer from his PIETY—in the + beautiful Roman sense—towards tradition and association, that + religion was to him in some way sacrosanct. But it is delightful to see + how his heart went out towards the new method in religious study which he + had himself, if half-unconsciously, inaugurated. Writing in 1871 to Dr + Tylor, on the publication of his "Primitive Culture", he says ("Life and + Letters", Vol. III. page 151.), "It is wonderful how you trace animism + from the lower races up the religious belief of the highest races. It will + make me for the future look at religion—a belief in the soul, etc.—from + a new point of view." + </p> + <p> + Psychology was henceforth to be based on "the necessary acquirement of + each mental capacity by gradation." With these memorable words the door + closes on the old and opens on the new horizon. The mental focus + henceforth is not on the maintaining or refuting of an orthodoxy but on + the genesis and evolution of a capacity, not on perfection but on process. + Continuous evolution leaves no gap for revelation sudden and complete. We + have henceforth to ask, not when was religion revealed or what was the + revelation, but how did religious phenomena arise and develop. For an + answer to this we turn with new and reverent eyes to study "the heathen in + his blindness" and the child "born in sin." We still indeed send out + missionaries to convert the heathen, but here at least in Cambridge before + they start they attend lectures on anthropology and comparative religion. + The "decadence" theory is dead and should be buried. + </p> + <p> + The study of primitive religions then has been made possible and even + inevitable by the theory of Evolution. We have now to ask what new facts + and theories have resulted from that study. This brings us to our second + point, the advanced outlook on religion to-day. + </p> + <p> + The view I am about to state is no mere personal opinion of my own. To my + present standpoint I have been led by the investigations of such masters + as Drs Wundt, Lehmann, Preuss, Bergson, Beck and in our own country Drs + Tylor and Frazer. (I can only name here the books that have specially + influenced my own views. They are W. Wundt, "Volkerpsychologie", Leipzig, + 1900, P. Beck, "Die Nachahmung", Leipzig, 1904, and "Erkenntnisstheorie + des primitiven Denkens" in "Zeitschrift f. Philos. und Philos. Kritik", + 1903, page 172, and 1904, page 9. Henri Bergson, "L'Evolution Creatrice" + and "Matiere et Memoire", 1908, K. Th. Preuss, various articles published + in the "Globus" (see page 507, note 1), and in the "Archiv. f. + Religionswissenschaft", and for the subject of magic, MM. Hubert et Mauss, + "Theorie generale de la Magie", in "L'Annee Sociologique", VII.) + </p> + <p> + Religion always contains two factors. First, a theoretical factor, what a + man THINKS about the unseen—his theology, or, if we prefer so to + call it, his mythology. Second, what he DOES in relation to this unseen—his + ritual. These factors rarely if ever occur in complete separation; they + are blended in very varying proportions. Religion we have seen was in the + last century regarded mainly in its theoretical aspect as a doctrine. + Greek religion for example meant to most educated persons Greek mythology. + Yet even a cursory examination shows that neither Greek nor Roman had any + creed or dogma, any hard and fast formulation of belief. In the Greek + Mysteries (See my "Prolegomena to the Study of Greek Religion", page 155, + Cambridge, 1903.) only we find what we should call a Confiteor; and this + is not a confession of faith, but an avowal of rites performed. When the + religion of primitive peoples came to be examined it was speedily seen + that though vague beliefs necessarily abound, definite creeds are + practically non-existent. Ritual is dominant and imperative. + </p> + <p> + This predominance and priority of ritual over definite creed was first + forced upon our notice by the study of savages, but it promptly and + happily joined hands with modern psychology. Popular belief says, I think, + therefore I act; modern scientific psychology says, I act (or rather, + REact to outside stimulus), and so I come to think. Thus there is set + going a recurrent series: act and thought become in their turn stimuli to + fresh acts and thoughts. In examining religion as envisaged to-day it + would therefore be more correct to begin with the practice of religion, + i.e. ritual, and then pass to its theory, theology or mythology. But it + will be more convenient to adopt the reverse method. The theoretical + content of religion is to those of us who are Protestants far more + familiar and we shall thus proceed from the known to the comparatively + unknown. + </p> + <p> + I shall avoid all attempt at rigid definition. The problem before the + modern investigator is, not to determine the essence and definition of + religion but to inquire how religious phenomena, religious ideas and + practices arose. Now the theoretical content of religion, the domain of + theology or mythology, is broadly familiar to all. It is the world of the + unseen, the supersensuous; it is the world of what we call the soul and + the supposed objects of the soul's perception, sprites, demons, ghosts and + gods. How did this world grow up? + </p> + <p> + We turn to our savages. Intelligent missionaries of bygone days used to + ply savages with questions such as these: Had they any belief in God? Did + they believe in the immortality of the soul? Taking their own clear-cut + conceptions, discriminated by a developed terminology, these missionaries + tried to translate them into languages that had neither the words nor the + thoughts, only a vague, inchoate, tangled substratum, out of which these + thoughts and words later differentiated themselves. Let us examine this + substratum. + </p> + <p> + Nowadays we popularly distinguish between objective and subjective; and + further, we regard the two worlds as in some sense opposed. To the + objective world we commonly attribute some reality independent of + consciousness, while we think of the subjective as dependent for its + existence on the mind. The objective world consists of perceptible things, + or of the ultimate constituents to which matter is reduced by physical + speculation. The subjective world is the world of beliefs, hallucinations, + dreams, abstract ideas, imaginations and the like. Psychology of course + knows that the objective and subjective worlds are interdependent, + inextricably intertwined, but for practical purposes the distinction is + convenient. + </p> + <p> + But primitive man has not yet drawn the distinction between objective and + subjective. Nay, more, it is foreign to almost the whole of ancient + philosophy. Plato's Ideas (I owe this psychological analysis of the + elements of the primitive supersensuous world mainly to Dr Beck, + "Erkenntnisstheorie des primitiven Denkens", see page 498, note 1.), his + Goodness, Truth, Beauty, his class-names, horse, table, are it is true + dematerialised as far as possible, but they have outside existence, apart + from the mind of the thinker, they have in some shadowy way spatial + extension. Yet ancient philosophies and primitive man alike needed and + possessed for practical purposes a distinction which served as well as our + subjective and objective. To the primitive savage all his thoughts, every + object of which he was conscious, whether by perception or conception, had + reality, that is, it had existence outside himself, but it might have + reality of various kinds or different degrees. + </p> + <p> + It is not hard to see how this would happen. A man's senses may mislead + him. He sees the reflection of a bird in a pond. To his eyes it is a real + bird. He touches it, HE PUTS IT TO THE TOUCH, and to his touch it is not a + bird at all. It is real then, but surely not quite so real as a bird that + you can touch. Again, he sees smoke. It is real to his eyes. He tries to + grasp it, it vanishes. The wind touches him, but he cannot see it, which + makes him feel uncanny. The most real thing is that which affects most + senses and especially what affects the sense of touch. Apparently touch is + the deepest down, most primitive, of senses. The rest are specialisations + and complications. Primitive man has no formal rubric "optical delusion," + but he learns practically to distinguish between things that affect only + one sense and things that affect two or more—if he did not he would + not survive. But both classes of things are real to him. Percipi est esse. + </p> + <p> + So far, primitive man has made a real observation; there are things that + appeal to one sense only. But very soon creeps in confusion fraught with + disaster. He passes naturally enough, being economical of any mental + effort, from what he really sees but cannot feel to what he thinks he + sees, and gives to it the same secondary reality. He has dreams, visions, + hallucinations, nightmares. He dreams that an enemy is beating him, and he + wakes rubbing his head. Then further he remembers things; that is, for + him, he sees them. A great chief died the other day and they buried him, + but he sees him still in his mind, sees him in his war-paint, splendid, + victorious. So the image of the past goes together with his dreams and + visions to the making of this other less real, but still real world, his + other-world of the supersensuous, the supernatural, a world, the outside + existence of which, independent of himself, he never questions. + </p> + <p> + And, naturally enough, the future joins the past in this supersensuous + world. He can hope, he can imagine, he can prophesy. And again the images + of his hope are real; he sees them with that mind's eye which as yet he + has not distinguished from his bodily eye. And so the supersensuous world + grows and grows big with the invisible present, and big also with the past + and the future, crowded with the ghosts of the dead and shadowed with + oracles and portents. It is this supersensuous, supernatural world which + is the eternity, the other-world, of primitive religion, not an + endlessness of time, but a state removed from full sensuous reality, a + world in which anything and everything may happen, a world peopled by + demonic ancestors and liable to a splendid vagueness, to a "once upon a + time-ness" denied to the present. It not unfrequently happens that people + who know that the world nowadays obeys fixed laws have no difficulty in + believing that six thousand years ago man was made direct from a lump of + clay, and woman was made from one of man's superfluous ribs. + </p> + <p> + The fashioning of the supersensuous world comes out very clearly in + primitive man's views about the soul and life after death. Herbert Spencer + noted long ago the influence of dreams in forming a belief in immortality, + but being very rational himself, he extended to primitive man a quite + alien quality of rationality. Herbert Spencer argued that when a savage + has a dream he seeks to account for it, and in so doing invents a spirit + world. The mistake here lies in the "seeks to account for it." (Primitive + man, as Dr Beck observes, is not impelled by an Erkenntnisstrieb. Dr Beck + says he has counted upwards of 30 of these mythological Triebe + (tendencies) with which primitive man has been endowed.) Man is at first + too busy LIVING to have any time for disinterested THINKING. He dreams a + dream and it is real for him. He does not seek to account for it any more + than for his hands and feet. He cannot distinguish between a CONception + and a PERception, that is all. He remembers his ancestors or they appear + to him in a dream; therefore they are alive still, but only as a rule to + about the third generation. Then he remembers them no more and they cease + to be. + </p> + <p> + Next as regards his own soul. He feels something within him, his + life-power, his will to live, his power to act, his personality—whatever + we like to call it. He cannot touch this thing that is himself, but it is + real. His friend too is alive and one day he is dead; he cannot move, he + cannot act. Well, something has gone that was his friend's self. He has + stopped breathing. Was it his breath? or he is bleeding; is it his blood? + This life-power IS something; does it live in his heart or his lungs or + his midriff? He did not see it go; perhaps it is like wind, an anima, a + Geist, a ghost. But again it comes back in a dream, only looking shadowy; + it is not the man's life, it is a thin copy of the man; it is an "image" + (eidolon). It is like that shifting distorted thing that dogs the living + man's footsteps in the sunshine; it is a "shade" (skia). (The two + conceptions of the soul, as a life-essence, inseparable from the body, and + as a separable phantom seem to occur in most primitive systems. They are + distinct conceptions but are inextricably blended in savage thought. The + two notions Korperseele and Psyche have been very fully discussed in + Wundt's "Volkerpsychologie" II. pages 1-142, Leipzig, 1900.) + </p> + <p> + Ghosts and sprites, ancestor worship, the soul, oracles, prophecy; all + these elements of the primitive supersensuous world we willingly admit to + be the proper material of religion; but other elements are more + surprising; such are class-names, abstract ideas, numbers, geometrical + figures. We do not nowadays think of these as of religious content, but to + primitive men they were all part of the furniture of his supernatural + world. + </p> + <p> + With respect to class-names, Dr Tylor ("Primitive Culture", Vol. II. page + 245 (4th edition), 1903.) has shown how instructive are the first attempts + of the savage to get at the idea of a class. Things in which similarity is + observed, things indeed which can be related at all are to the savage + KINDRED. A species is a family or a number of individuals with a common + god to look after them. Such for example is the Finn doctrine of the + haltia. Every object has its haltia, but the haltiat were not tied to the + individual, they interested themselves in every member of the species. + Each stone had its haltia, but that haltia was interested in other stones; + the individuals disappeared, the haltia remained. + </p> + <p> + Nor was it only class-names that belonged to the supersensuous world. A + man's own proper-name is a sort of spiritual essence of him, a kind of + soul to be carefully concealed. By pronouncing a name you bring the thing + itself into being. When Elohim would create Day "he called out to the + Light 'Day,' and to the Darkness he called out 'Night'"; the great + magician pronounced the magic Names and the Things came into being. "In + the beginning was the Word" is literally true, and this reflects the fact + that our CONCEPTUAL world comes into being by the mental process of + naming. (For a full discussion of this point see Beck, "Nachahmung" page + 41, "Die Sprache".) In old times people went further; they thought that by + naming events they could bring them to be, and custom even to-day keeps up + the inveterate magical habit of wishing people "Good Morning" and a "Happy + Christmas." + </p> + <p> + Number, too, is part of the supersensuous world that is thoroughly + religious. We can see and touch seven apples, but seven itself, that + wonderful thing that shifts from object to object, giving it its + SEVENness, that living thing, for it begets itself anew in multiplication—surely + seven is a fit denizen of the upper-world. Originally all numbers dwelt + there, and a certain supersensuous sanctity still clings to seven and + three. We still say "Holy, Holy, Holy," and in some mystic way feel the + holier. + </p> + <p> + The soul and the supersensuous world get thinner and thinner, rarer and + more rarified, but they always trail behind them clouds of smoke and + vapour from the world of sense and space whence they have come. It is + difficult for us even nowadays to use the word "soul" without lapsing into + a sensuous mythology. The Cartesians' sharp distinction between res + extensa non cogitans and res cogitans non extansa is remote. + </p> + <p> + So far then man, through the processes of his thinking, has provided + himself with a supersensuous world, the world of sense-delusion, of smoke + and cloud, of dream and phantom, of imagination, of name and number and + image. The natural course would now seem to be that this supersensuous + world should develop into the religious world as we know it, that out of a + vague animism with ghosts of ancestors, demons, and the like, there should + develop in due order momentary gods (Augenblicks-Gotter), tribal gods, + polytheism, and finally a pure monotheism. + </p> + <p> + This course of development is usually assumed, but it is not I think quite + what really happens. The supersensuous world as we have got it so far is + too theoretic to be complete material of religion. It is indeed only one + factor, or rather it is as it were a lifeless body that waits for a living + spirit to possess and inform it. Had the theoretic factor remained + uninformed it would eventually have separated off into its constituent + elements of error and truth, the error dying down as a belated metaphysic, + the truth developing into a correct and scientific psychology of the + subjective. But man has ritual as well as mythology; that is, he feels and + acts as well as thinks; nay more he probably feels and acts long before he + definitely thinks. This contradicts all our preconceived notions of + theology. Man, we imagine, believes in a god or gods and then worships. + The real order seems to be that, in a sense presently to be explained, he + worships, he feels and acts, and out of his feeling and action, projected + into his confused thinking, he develops a god. We pass therefore to our + second factor in religion:—ritual. + </p> + <p> + The word "ritual" brings to our modern minds the notion of a church with a + priesthood and organised services. Instinctively we think of a + congregation meeting to confess sins, to receive absolution, to pray, to + praise, to listen to sermons, and possibly to partake of sacraments. Were + we to examine these fully developed phenomena we should hardly get further + in the analysis of our religious conceptions than the notion of a highly + anthropomorphic god approached by purely human methods of personal + entreaty and adulation. + </p> + <p> + Further, when we first come to the study of primitive religions we expect + a priori to find the same elements, though in a ruder form. We expect to + see "The heathen in his blindness bow down to wood and stone," but the + facts that actually confront us are startlingly dissimilar. Bowing down to + wood and stone is an occupation that exists mainly in the minds of + hymn-writers. The real savage is more actively engaged. Instead of asking + a god to do what he wants done, he does it or tries to do it himself; + instead of prayers he utters spells. In a word he is busy practising + magic, and above all he is strenuously engaged in dancing magical dances. + When the savage wants rain or wind or sunshine, he does not go to church; + he summons his tribe and they dance a rain-dance or wind-dance or + sun-dance. When a savage goes to war we must not picture his wife on her + knees at home praying for the absent; instead we must picture her dancing + the whole night long; not for mere joy of heart or to pass the weary + hours; she is dancing his war-dance to bring him victory. + </p> + <p> + Magic is nowadays condemned alike by science and by religion; it is both + useless and impious. It is obsolete, and only practised by malign + sorcerers in obscure holes and corners. Undoubtedly magic is neither + religion nor science, but in all probability it is the spiritual + protoplasm from which religion and science ultimately differentiated. As + such the doctrine of evolution bids us scan it closely. Magic may be + malign and private; nowadays it is apt to be both. But in early days magic + was as much for good as for evil; it was publicly practised for the common + weal. + </p> + <p> + The gist of magic comes out most clearly in magical dances. We think of + dancing as a light form of recreation, practised by the young from sheer + joie de vivre and unsuitable for the mature. But among the Tarahumares + (Carl Lumholtz, "Unknown Mexico", page 330, London, 1903.) in Mexico the + word for dancing, nolavoa, means "to work." Old men will reproach young + men saying "Why do you not go to work?" meaning why do you not dance + instead of only looking on. The chief religious sin of which the + Tarahumare is conscious is that he has not danced enough and not made + enough tesvino, his cereal intoxicant. + </p> + <p> + Dancing then is to the savage WORKING, DOING, and the dance is in its + origin an imitation or perhaps rather an intensification of processes of + work. (Karl Bucher, "Arbeit und Rhythmus", Leipzig (3rd edition), 1902, + passim.) Repetition, regular and frequent, constitutes rhythm and rhythm + heightens the sense of will power in action. Rhythmical action may even, + as seen in the dances of Dervishes, produce a condition of ecstasy. + Ecstasy among primitive peoples is a condition much valued; it is often, + though not always, enhanced by the use of intoxicants. Psychologically the + savage starts from the sense of his own will power, he stimulates it by + every means at his command. Feeling his will strongly and knowing nothing + of natural law he recognises no limits to his own power; he feels himself + a magician, a god; he does not pray, he WILLS. Moreover he wills + collectively (The subject of collective hallucination as an element in + magic has been fully worked out by MM. Hubert and Mauss. "Theorie generale + de la Magie", In "L'Annee Sociologique", 1902—3, page 140.), + reinforced by the will and action of his whole tribe. Truly of him it may + be said "La vie deborde l'intelligence, l'intelligence c'est un + retrecissement." (Henri Bergson, "L'Evolution Creatrice", page 50.) + </p> + <p> + The magical extension and heightening of personality come out very clearly + in what are rather unfortunately known as MIMETIC dances. Animal dances + occur very frequently among primitive peoples. The dancers dress up as + birds, beasts, or fishes, and reproduce the characteristic movements and + habits of the animals impersonated. (So characteristic is this + impersonation in magical dancing that among the Mexicans the word for + magic, navali, means "disguise." K. Th. Preuss, "Archiv f. + Religionswissenschaft", 1906, page 97.) A very common animal dance is the + frog-dance. When it rains the frogs croak. If you desire rain you dress up + like a frog and croak and jump. We think of such a performance as a + conscious imitation. The man, we think, is more or less LIKE a frog. That + is not how primitive man thinks; indeed, he scarcely thinks at all; what + HE wants done the frog can do by croaking and jumping, so he croaks and + jumps and, for all he can, BECOMES a frog. "L'intelligence animale JOUE + sans doute les representations plutot qu'elle ne les pense." (Bergson, + "L'Evolution Creatrice", page 205.) + </p> + <p> + We shall best understand this primitive state of mind if we study the + child "born in sin." If a child is "playing at lions" he does not IMITATE + a lion, i.e. he does not consciously try to be a thing more or less like a + lion, he BECOMES one. His reaction, his terror, is the same as if the real + lion were there. It is this childlike power of utter impersonation, of + BEING the thing we act or even see acted, this extension and + intensification of our own personality that lives deep down in all of us + and is the very seat and secret of our joy in the drama. + </p> + <p> + A child's mind is indeed throughout the best clue to the understanding of + savage magic. A young and vital child knows no limit to his own will, and + it is the only reality to him. It is not that he wants at the outset to + fight other wills, but that they simply do not exist for him. Like the + artist he goes forth to the work of creation, gloriously alone. His + attitude towards other recalcitrant wills is "they simply must." Let even + a grown man be intoxicated, be in love, or subject to an intense + excitement, the limitations of personality again fall away. Like the + omnipotent child he is again a god, and to him all things are possible. + Only when he is old and weary does he cease to command fate. + </p> + <p> + The Iroquois (Hewitt, "American Anthropologist", IV. I. page 32, 1902, + N.S.) of North America have a word, orenda, the meaning of which is easier + to describe than to define, but it seems to express the very soul of + magic. This orenda is your power to do things, your force, sometimes + almost your personality. A man who hunts well has much and good orenda; + the shy bird who escapes his snares has a fine orenda. The orenda of the + rabbit controls the snow and fixes the depth to which it will fall. When a + storm is brewing the magician is said to be making its orenda. When you + yourself are in a rage, great is your orenda. The notes of birds are + utterances of their orenda. When the maize is ripening, the Iroquois know + it is the sun's heat that ripens it, but they know more; it is the cigala + makes the sun to shine and he does it by chirping, by uttering his orenda. + This orenda is sometimes very like the Greek thumos, your bodily life, + your vigour, your passion, your power, the virtue that is in you to feel + and do. This notion of orenda, a sort of pan-vitalism, is more fluid than + animism, and probably precedes it. It is the projection of man's inner + experience, vague and unanalysed, into the outer world. + </p> + <p> + The mana of the Melanesians (Codrington, "The Melanesians", pages 118, + 119, 192, Oxford, 1891.) is somewhat more specialised—all men do not + possess mana—but substantially it is the same idea. Mana is not only + a force, it is also an action, a quality, a state, at once a substantive, + an adjective, and a verb. It is very closely neighboured by the idea of + sanctity. Things that have mana are tabu. Like orenda it manifests itself + in noises, but specially mysterious ones, it is mana that is rustling in + the trees. Mana is highly contagious, it can pass from a holy stone to a + man or even to his shadow if it cross the stone. "All Melanesian + religion," Dr Codrington says, "consists in getting mana for oneself or + getting it used for one's benefit." (Codrington, "The Melanesians", page + 120, Oxford, 1891.) + </p> + <p> + Specially instructive is a word in use among the Omaka (See Prof. Haddon, + "Magic and Fetishism", page 60, London, 1906. Dr Vierkandt ("Globus", + July, 1907, page 41) thinks that "Fernzauber" is a later development from + Nahzauber.), wazhin-dhedhe, "directive energy, to send." This word means + roughly what we should call telepathy, sending out your thought or + will-power to influence another and affect his action. Here we seem to get + light on what has always been a puzzle, the belief in magic exercised at a + distance. For the savage will, distance is practically non-existent, his + intense desire feels itself as non-spatial. (This notion of mana, orenda, + wazhin-dhedhe and the like lives on among civilised peoples in such words + as the Vedic brahman in the neuter, familiar to us in its masculine form + Brahman. The neuter, brahman, means magic power of a rite, a rite itself, + formula, charm, also first principle, essence of the universe. It is own + cousin to the Greek dunamis and phusis. See MM. Hubert et Mauss, "Theorie + generale de la Magie", page 117, in "L'Annee Sociologique", VII.) + </p> + <p> + Through the examination of primitive ritual we have at last got at one + tangible, substantial factor in religion, a real live experience, the + sense, that is, of will, desire, power actually experienced in person by + the individual, and by him projected, extended into the rest of the world. + </p> + <p> + At this stage it may fairly be asked, though the question cannot with any + certainty be answered, "at what point in the evolution of man does this + religious experience come in?" + </p> + <p> + So long as an organism reacts immediately to outside stimulus, with a + certainty and conformity that is almost chemical, there is, it would seem, + no place, no possibility for magical experience. But when the germ appears + of an intellect that can foresee an end not immediately realised, or + rather when a desire arises that we feel and recognise as not satisfied, + then comes in the sense of will and the impulse magically to intensify + that will. The animal it would seem is preserved by instinct from drawing + into his horizon things which do not immediately subserve the conservation + of his species. But the moment man's life-power began to make on the + outside world demands not immediately and inevitably realised in action (I + owe this observation to Dr K. Th. Preuss. He writes ("Archiv f. Relig." + 1906, page 98), "Die Betonung des Willens in den Zauberakten ist der + richtige Kern. In der Tat muss der Mensch den Willen haben, sich selbst + und seiner Umgebung besondere Fahigkeiten zuzuschreiben, und den Willen + hat er, sobald sein Verstand ihn befahigt, EINE UBER DEN INSTINKT + HINAUSGEHEN DER FURSORGE fur sich zu zeigen. SO LANGE IHN DER INSTINKT + ALLEIN LEITET, KONNEN ZAUBERHANDLUNGEN NICHT ENSTEHEN." For more detailed + analysis of the origin of magic, see Dr Preuss "Ursprung der Religion und + Kunst", "Globus", LXXXVI. and LXXXVII.), then a door was opened to magic, + and in the train of magic followed errors innumerable, but also religion, + philosophy, science and art. + </p> + <p> + The world of mana, orenda, brahman is a world of feeling, desiring, + willing, acting. What element of thinking there may be in it is not yet + differentiated out. But we have already seen that a supersensuous world of + thought grew up very early in answer to other needs, a world of + sense-illusions, shadows, dreams, souls, ghosts, ancestors, names, + numbers, images, a world only wanting as it were the impulse of mana to + live as a religion. Which of the two worlds, the world of thinking or the + world of doing, developed first it is probably idle to inquire. (If + external stimuli leave on organisms a trace or record such as is known as + an Engram, this physical basis of memory and hence of thought is almost + coincident with reaction of the most elementary kind. See Mr Francis + Darwin's Presidential Address to the British Association, Dublin, 1908, + page 8, and again Bergson places memory at the very root of conscious + existence, see "L'Evolution Creatrice", page 18, "le fond meme de notre + existence consciente est memoire, c'est a dire prolongation du passee dans + le present," and again "la duree mord dans le temps et y laisse l'enpreint + de son dent," and again, "l'Evolution implique une continuation reelle du + passee par le present.") + </p> + <p> + It is more important to ask, Why do these two worlds join? Because, it + would seem, mana, the egomaniac or megalomaniac element, cannot get + satisfied with real things, and therefore goes eagerly out to a false + world, the supersensuous other-world whose growth we have sketched. This + junction of the two is fact, not fancy. Among all primitive peoples dead + men, ghosts, spirits of all kinds, become the chosen vehicle of mana. Even + to this day it is sometimes urged that religion, i.e. belief in the + immortality of the soul, is true "because it satisfies the deepest craving + of human nature." The two worlds, of mana and magic on the one hand, of + ghosts and other-world on the other, combine so easily because they have + the same laws, or rather the same comparative absence of law. As in the + world of dreams and ghosts, so in the world of mana, space and time offer + no obstacles; with magic all things are possible. In the one world what + you imagine is real; in the other what you desire is ipso facto + accomplished. Both worlds are egocentric, megalomaniac, filled to the full + with unbridled human will and desire. + </p> + <p> + We are all of us born in sin, in that sin which is to science "the seventh + and deadliest," anthropomorphism, we are egocentric, ego-projective. Hence + necessarily we make our gods in our own image. Anthropomorphism is often + spoken of in books on religion and mythology as if it were a last climax, + a splendid final achievement in religious thought. First, we are told, we + have the lifeless object as god (fetichism), then the plant or animal + (phytomorphism, theriomorphism), and last God is incarnate in the human + form divine. This way of putting things is misleading. Anthropomorphism + lies at the very beginning of our consciousness. Man's first achievement + in thought is to realise that there is anything at all not himself, any + object to his subject. When he has achieved however dimly this + distinction, still for long, for very long he can only think of those + other things in terms of himself; plants and animals are people with ways + of their own, stronger or weaker than himself but to all intents and + purposes human. + </p> + <p> + Again the child helps us to understand our own primitive selves. To + children animals are always people. You promise to take a child for a + drive. The child comes up beaming with a furry bear in her arms. You say + the bear cannot go. The child bursts into tears. You think it is because + the child cannot endure to be separated from a toy. It is no such thing. + It is the intolerable hurt done to the bear's human heart—a hurt not + to be healed by any proffer of buns. He wanted to go, but he was a shy, + proud bear, and he would not say so. + </p> + <p> + The relation of magic to religion has been much disputed. According to one + school religion develops out of magic, according to another, though they + ultimately blend, they are at the outset diametrically opposed, magic + being a sort of rudimentary and mistaken science (This view held by Dr + Frazer is fully set forth in his "Golden Bough" (2nd edition), pages + 73-79, London, 1900. It is criticised by Mr R.R. Marett in "From Spell to + Prayer", "Folk-Lore" XI. 1900, page 132, also very fully by MM. Hubert and + Mauss, "Theorie generale de la Magie", in "L'Annee Sociologique", VII. + page 1, with Mr Marett's view and with that of MM. Hubert and Mauss I am + in substantial agreement.), religion having to do from the outset with + spirits. + </p> + <p> + But, setting controversy aside, at the present stage of our inquiry their + relation becomes, I think, fairly clear. Magic is, if my view (This view + as explained above is, I believe, my own most serious contribution to the + subject. In thinking it out I was much helped by Prof. Gilbert Murray.) be + correct, the active element which informs a supersensuous world fashioned + to meet other needs. This blend of theory and practice it is convenient to + call religion. In practice the transition from magic to religion, from + Spell to Prayer, has always been found easy. So long as mana remains + impersonal you order it about; when it is personified and bulks to the + shape of an overgrown man, you drop the imperative and cringe before it. + "My will be done" is magic, "Thy Will be done" is the last word in + religion. The moral discipline involved in the second is momentous, the + intellectual advance not striking. + </p> + <p> + I have spoken of magical ritual as though it were the informing + life-spirit without which religion was left as an empty shell. Yet the + word ritual does not, as normally used, convey to our minds this notion of + intense vitalism. Rather we associate ritual with something cut and dried, + a matter of prescribed form and monotonous repetition. The association is + correct; ritual tends to become less and less informed by the + life-impulse, more and more externalised. Dr Beck ("Die Nachahmung und + ihre Bedeutung fur Psychologie und Volkerkunde", Leipzig, 1904.) in his + brilliant monograph on "Imitation" has laid stress on the almost boundless + influence of the imitation of one man by another in the evolution of + civilisation. Imitation is one of the chief spurs to action. Imitation + begets custom, custom begets sanctity. At first all custom is sacred. To + the savage it is as much a religious duty to tattoo himself as to + sacrifice to his gods. But certain customs naturally survive, because they + are really useful; they actually have good effects, and so need no social + sanction. Others are really useless; but man is too conservative and + imitative to abandon them. These become ritual. Custom is cautious, but la + vie est aleatoire. (Bergson, op. cit. page 143.) + </p> + <p> + Dr Beck's remarks on ritual are I think profoundly true and suggestive, + but with this reservation—they are true of ritual only when + uninformed by personal experience. The very elements in ritual on which Dr + Beck lays such stress, imitation, repetition, uniformity and social + collectivity, have been found by the experience of all time to have a + twofold influence—they inhibit the intellect, they stimulate and + suggest emotion, ecstasy, trance. The Church of Rome knows what she is + about when she prescribes the telling of the rosary. Mystery-cults and + sacraments, the lineal descendants of magic, all contain rites charged + with suggestion, with symbols, with gestures, with half-understood + formularies, with all the apparatus of appeal to emotion and will—the + more unintelligible they are the better they serve their purpose of + inhibiting thought. Thus ritual deadens the intellect and stimulates will, + desire, emotion. "Les operations magiques... sont le resultat d'une + science et d'une habitude qui exaltent la volonte humaine au-dessus de ses + limites habituelles." (Eliphas Levi, "Dogme et Rituel de la haute Magie", + II. page 32, Paris, 1861, and "A defence of Magic", by Evelyn Underhill, + "Fortnightly Review", 1907.) It is this personal EXPERIENCE, this + exaltation, this sense of immediate, non-intellectual revelation, of + mystical oneness with all things, that again and again rehabilitates a + ritual otherwise moribund. + </p> + <p> + To resume. The outcome of our examination of ORIGINES seems to be that + religious phenomena result from two delusive processes—a delusion of + the non-critical intellect, a delusion of the over-confident will. Is + religion then entirely a delusion? I think not. (I am deeply conscious + that what I say here is a merely personal opinion or sentiment, + unsupported and perhaps unsupportable by reason, and very possibly quite + worthless, but for fear of misunderstanding I prefer to state it.) Every + dogma religion has hitherto produced is probably false, but for all that + the religious or mystical spirit may be the only way of apprehending some + things and these of enormous importance. It may also be that the contents + of this mystical apprehension cannot be put into language without being + falsified and misstated, that they have rather to be felt and lived than + uttered and intellectually analysed, and thus do not properly fall under + the category of true or false, in the sense in which these words are + applied to propositions; yet they may be something for which "true" is our + nearest existing word and are often, if not necessary at least highly + advantageous to life. That is why man through a series of more or less + grossly anthropomorphic mythologies and theologies with their concomitant + rituals tries to restate them. Meantime we need not despair. Serious + psychology is yet young and has only just joined hands with physiology. + Religious students are still hampered by mediaevalisms such as Body and + Soul, and by the perhaps scarcely less mythological segregations of + Intellect, Emotion, Will. But new facts (See the "Proceedings" of the + Society for Psychical Research, London, passim, and especially Vols. + VII.-XV. For a valuable collection of the phenomena of mysticism, see + William James, "Varieties of Religious Experience", Edinburgh, 1901-2.) + are accumulating, facts about the formation and flux of personality, and + the relations between the conscious and the sub-conscious. Any moment some + great imagination may leap out into the dark, touch the secret places of + life, lay bare the cardinal mystery of the marriage of the spatial with + the non-spatial. It is, I venture to think, towards the apprehension of + such mysteries, not by reason only, but by man's whole personality, that + the religious spirit in the course of its evolution through ancient magic + and modern mysticism is ever blindly yet persistently moving. + </p> + <p> + Be this as it may, it is by thinking of religion in the light of + evolution, not as a revelation given, not as a realite faite but as a + process, and it is so only, I think, that we attain to a spirit of real + patience and tolerance. We have ourselves perhaps learnt laboriously + something of the working of natural law, something of the limitations of + our human will, and we have therefore renounced the practice of magic. Yet + we are bidden by those in high places to pray "Sanctify this water to the + mystical washing away of sin." Mystical in this connection spells magical, + and we have no place for a god-magician: the prayer is to us unmeaning, + irreverent. Or again, after much toil we have ceased, or hope we have + ceased, to think anthropomorphically. Yet we are invited to offer formal + thanks to God for a meal of flesh whose sanctity is the last survival of + that sacrifice of bulls and goats he has renounced. Such a ritual confuses + our intellect and fails to stir our emotion. But to others this ritual, + magical or anthropomorphic as it is, is charged with emotional impulse, + and others, a still larger number, think that they act by reason when + really they are hypnotised by suggestion and tradition; their fathers did + this or that and at all costs they must do it. It was good that primitive + man in his youth should bear the yoke of conservative custom; from each + man's neck that yoke will fall, when and because he has outgrown it. + Science teaches us to await that moment with her own inward and abiding + patience. Such a patience, such a gentleness we may well seek to practise + in the spirit and in the memory of Darwin. + </p> + <p> + <a name="link2H_4_0028" id="link2H_4_0028"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + XXVI. EVOLUTION AND THE SCIENCE OF LANGUAGE. By P. Giles, M.A., LL.D. + (Aberdeen), + </h2> + <h3> + Reader in Comparative Philology in the University of Cambridge. + </h3> + <p> + In no study has the historical method had a more salutary influence than + in the Science of Language. Even the earliest records show that the + meaning of the names of persons, places, and common objects was then, as + it has always been since, a matter of interest to mankind. And in every + age the common man has regarded himself as competent without special + training to explain by inspection (if one may use a mathematical phrase) + the meaning of any words that attracted his attention. Out of this amateur + etymologising has sprung a great amount of false history, a kind of + historical mythology invented to explain familiar names. A single example + will illustrate the tendency. According to the local legend the ancestor + of the Earl of Erroll—a husbandman who stayed the flight of his + countrymen in the battle of Luncarty and won the victory over the Danes by + the help of the yoke of his oxen—exhausted with the fray uttered the + exclamation "Hoch heigh!" The grateful king about to ennoble the + victorious ploughman at once replied: + </p> +<pre xml:space="preserve"> + "Hoch heigh! said ye + And Hay shall ye be." +</pre> + <p> + The Norman origin of the name Hay is well-known, and the battle of + Luncarty long preceded the appearance of Normans in Scotland, but the + legend nevertheless persists. + </p> + <p> + Though the earliest European treatise on philological questions which is + now extant—the "Cratylus" of Plato,—as might be expected from + its authorship, contains some acute thinking and some shrewd guesses, yet + the work as a whole is infantine in its handling of language, and it has + been doubted whether Plato was more than half serious in some of the + suggestions which he puts forward. (For an account of the "Cratylus" with + references to other literature see Sandys' "History of Classical + Scholarship", I. page 92 ff., Cambridge, 1903.) In the hands of the Romans + things were worse even than they had been in the hands of Plato and his + Greek successors. The lack of success on the part of Varro and later Roman + writers may have been partly due to the fact that, from the etymological + point of view, Latin is a much more difficult language than Greek; it is + by no means so closely connected with Greek as the ancients imagined, and + they had no knowledge of the Celtic languages from which, on some sides at + least, much greater light on the history of the Latin language might have + been obtained. Roman civilisation was a late development compared with + Greek, and its records dating earlier than 300 B.C.—a period when + the best of Greek literature was already in existence—are very few + and scanty. Varro it is true was much more of an antiquary than Plato, but + his extant works seem to show that he was rather a "dungeon of learning" + than an original thinker. + </p> + <p> + A scientific knowledge of language can be obtained only by comparison of + different languages of the same family and the contrasting of their + characteristics with those of another family or other families. It never + occurred to the Greeks that any foreign language was worthy of serious + study. Herodotus and other travellers and antiquaries indeed picked up + individual words from various languages, either as being necessary in + communication with the inhabitants of the countries where they sojourned, + or because of some point which interested them personally. Plato and + others noticed the similarity of some Phrygian words to Greek, but no + systematic comparison seems ever to have been instituted. + </p> + <p> + In the Middle Ages the treatment of language was in a sense more + historical. The Middle Ages started with the hypothesis, derived from the + book of Genesis, that in the early world all men were of one language and + of one speech. Though on the same authority they believed that the plain + of Shinar has seen that confusion of tongues whence sprang all the + languages upon earth, they seem to have considered that the words of each + separate language were nevertheless derived from this original tongue. And + as Hebrew was the language of the Chosen People, it was naturally assumed + that this original tongue was Hebrew. Hence we find Dante declaring in his + treatise on the Vulgar Tongue (Dante "de Vulgari Eloquio", I. 4.) that the + first word man uttered in Paradise must have been "El," the Hebrew name of + his Maker, while as a result of the fall of Adam, the first utterance of + every child now born into this world of sin and misery is "heu," Alas! + After the splendidly engraved bronze plates containing, as we now know, + ritual regulations for certain cults, were discovered in 1444 at the town + of Gubbio, in Umbria, they were declared, by some authorities, to be + written in excellent Hebrew. The study of them has been the fascination + and the despair of many a philologist. Thanks to the devoted labours of + numerous scholars, mainly in the last sixty years, the general drift of + these inscriptions is now known. They are the only important records of + the ancient Umbrian language, which was related closely to that of the + Samnites and, though not so closely, to that of the Romans on the other + side of the Apennines. Yet less than twenty years ago a book was published + in Germany, which boasts itself the home of Comparative Philology, wherein + the German origin of the Umbrian language was no less solemnly + demonstrated than had been its Celtic origin by Sir William Betham in + 1842. + </p> + <p> + It is good that the study of language should be historical, but the first + requisite is that the history should be sound. How little had been learnt + of the true history of language a century ago may be seen from a little + book by Stephen Weston first published in 1802 and several times + reprinted, where accidental assonance is considered sufficient to + establish connection. Is there not a word "bad" in English and a word + "bad" in Persian which mean the same thing? Clearly therefore Persian and + English must be connected. The conclusion is true, but it is drawn from + erroneous premises. As stated, this identity has no more value than the + similar assonance between the English "cover" and the Hebrew "kophar", + where the history of "cover" as coming through French from a Latin + "co-operire" was even in 1802 well-known to many. To this day, in spite of + recent elaborate attempts (Most recently in H. Moller's "Semitisch und + Indogermanisch", Erster Teil, Kopenhagen, 1907.) to establish connection + between the Indo-Germanic and the Semitic families of languages, there is + no satisfactory evidence of such relation between these families. This is + not to deny the possibility of such a connection at a very early period; + it is merely to say that through the lapse of long ages all trustworthy + record of such relationship, if it ever existed, has been, so far as + present knowledge extends, obliterated. + </p> + <p> + But while Stephen Weston was publishing, with much public approval, his + collection of amusing similarities between languages—similarities + which proved nothing—the key to the historical study of at least one + family of languages had already been found by a learned Englishman in a + distant land. In 1783 Sir William Jones had been sent out as a judge in + the supreme court of judicature in Bengal. While still a young man at + Oxford he was noted as a linguist; his reputation as a Persian scholar had + preceded him to the East. In the intervals of his professional duties he + made a careful study of the language which was held sacred by the natives + of the country in which he was living. He was mainly instrumental in + establishing a society for the investigation of language and related + subjects. He was himself the first president of the society, and in the + "third anniversary discourse" delivered on February 2, 1786, he made the + following observations: "The Sanscrit language, whatever be its antiquity, + is of a wonderful structure; more perfect than the GREEK, more copious + than the LATIN, and more exquisitely refined than either, yet bearing to + both of them a stronger affinity, both in the roots of verbs and in the + forms of grammar, than could possibly have been produced by accident; so + strong indeed, that no philologer could examine them all three, without + believing them to have sprung from some common source, which, perhaps, no + longer exists: there is a similar reason, though not quite so forcible, + for supposing that both the Gothick and the Celtick, though blended with a + very different idiom, had the same origin with the Sanscrit; and the old + Persian might be added to the same family, if this was the place for + discussing any question concerning the antiquities of Persia." ("Asiatic + Researches", I. page 422, "Works of Sir W. Jones", I. page 26, London, + 1799.) + </p> + <p> + No such epoch-making discovery was probably ever announced with less + flourish of trumpets. Though Sir William Jones lived for eight years more + and delivered other anniversary discourses, he added nothing of importance + to this utterance. He had neither the time nor the health that was needed + for the prosecution of so arduous an undertaking. + </p> + <p> + But the good seed did not fall upon stony ground. The news was speedily + conveyed to Europe. By a happy chance, the sudden renewal of war between + France and England in 1803 gave Friedrich Schlegel the opportunity of + learning Sanscrit from Alexander Hamilton, an Englishman who, like many + others, was confined in Paris during the long struggle with Napoleon. The + influence of Schlegel was not altogether for good in the history of this + research, but he was inspiring. Not upon him but upon Franz Bopp, a + struggling German student who spent some time in Paris and London a dozen + years later, fell the mantle of Sir William Jones. In Bopp's Comparative + Grammar of the Indo-Germanic languages which appeared in 1833, + three-quarters of a century ago, the foundations of Comparative Philology + were laid. Since that day the literature of the subject has grown till it + is almost, if not altogether, beyond the power of any single man to cope + with it. But long as the discourse may be, it is but the elaboration of + the text that Sir William Jones supplied. + </p> + <p> + With the publication of Bopp's Comparative Grammar the historical study of + language was put upon a stable footing. Needless to say much remained to + be done, much still remains to be done. More than once there has been + danger of the study following erroneous paths. Its terminology and its + point of view have in some degree changed. But nothing can shake the truth + of the statement that the Indo-Germanic languages constitute in themselves + a family sprung from the same source, marked by the same characteristics, + and differentiated from all other languages by formation, by vocabulary, + and by syntax. The historical method was applied to language long before + it reached biology. Nearly a quarter of a century before Charles Darwin + was born, Sir William Jones had made the first suggestion of a comparative + study of languages. Bopp's Comparative Grammar began to be published nine + years before the first draft of Darwin's treatise on the Origin of Species + was put on paper in 1842. + </p> + <p> + It is not therefore on the history of Comparative Philology in general + that the ideas of Darwin have had most influence. Unfortunately, as Jowett + has said in the introduction to his translation of Plato's "Republic", + most men live in a corner. The specialisation of knowledge has many + advantages, but it has also disadvantages, none worse perhaps than that it + tends to narrow the specialist's horizon and to make it more difficult for + one worker to follow the advances that are being made by workers in other + departments. No longer is it possible as in earlier days for an + intellectual prophet to survey from a Pisgah height all the Promised Land. + And the case of linguistic research has been specially hard. This study + has, if the metaphor may be allowed, a very extended frontier. On one side + it touches the domain of literature, on other sides it is conterminous + with history, with ethnology and anthropology, with physiology in so far + as language is the production of the brain and tissues of a living being, + with physics in questions of pitch and stress accent, with mental science + in so far as the principles of similarity, contrast, and contiguity affect + the forms and the meanings of words through association of ideas. The + territory of linguistic study is immense, and it has much to supply which + might be useful to the neighbours who border on that territory. But they + have not regarded her even with that interest which is called benevolent + because it is not actively maleficent. As Horne Tooke remarked a century + ago, Locke had found a whole philosophy in language. What have the + philosophers done for language since? The disciples of Kant and of Wilhelm + von Humboldt supplied her plentifully with the sour grapes of metaphysics; + otherwise her neighbours have left her severely alone save for an + occasional "Ausflug," on which it was clear they had sadly lost their + bearings. Some articles in Psychological Journals, Wundt's great work on + "Volkerpsychologie" (Erster Band: "Die Sprache", Leipzig, 1900. New + edition, 1904. This work has been fertile in producing both opponents and + supporters. Delbruck, "Grundfragen der Sprachforschung", Strassburg, 1901, + with a rejoinder by Wundt, "Sprachgeschichte" and "Sprachpsychologie", + Leipzig, 1901; L. Sutterlin, "Das Wesen der Sprachgebilde", Heidelberg, + 1902; von Rozwadowski, "Wortbildung und Wortbedeutung", Heidelberg, 1904; + O. Dittrich, "Grundzuge der Sprachpsychologie", Halle, 1904, Ch. A. + Sechehaye, "Programme et methodes de la linguistique theorique", Paris, + 1908.), and Mauthner's brilliantly written "Beitrage zu einer Kritik der + Sprache" (In three parts: (i) "Sprache und Psychologie, (ii) "Zur + Sprachwissenschaft", both Stuttgart 1901, (iii) "Zur Grammatic und Logik" + (with index to all three volumes), Stuttgart and Berlin, 1902.) give some + reason to hope that, on one side at least, the future may be better than + the past. + </p> + <p> + Where Charles Darwin's special studies came in contact with the Science of + Language was over the problem of the origin and development of language. + It is curious to observe that, where so many fields of linguistic research + have still to be reclaimed—many as yet can hardly be said to be + mapped out,—the least accessible field of all—that of the + Origin of Language—has never wanted assiduous tillers. Unfortunately + it is a field beyond most others where it may be said that + </p> + <p> + "Wilding oats and luckless darnel grow." + </p> + <p> + If Comparative Philology is to work to purpose here, it must be on results + derived from careful study of individual languages and groups of + languages. But as yet the group which Sir William Jones first mapped out + and which Bopp organised is the only one where much has been achieved. + Investigation of the Semitic group, in some respects of no less moment in + the history of civilisation and religion, where perhaps the labour of + comparison is not so difficult, as the languages differ less among + themselves, has for some reason strangely lagged behind. Some years ago in + the "American Journal of Philology" Paul Haupt pointed out that if advance + was to be made, it must be made according to the principles which had + guided the investigation of the Indo-Germanic languages to success, and at + last a Comparative Grammar of an elaborate kind is in progress also for + the Semitic languages. (Brockelmann, "Vergleichende Grammatik der + semitischen Sprachen", Berlin, 1907 ff. Brockelmann and Zimmern had + earlier produced two small hand-books. The only large work was William + Wright's "Lectures on the Comparative Grammar of the Semitic Languages", + Cambridge, 1890.) For the great group which includes Finnish, Hungarian, + Turkish and many languages of northern Asia, a beginning, but only a + beginning has been made. It may be presumed from the great discoveries + which are in progress in Turkestan that presently much more will be + achieved in this field. But for a certain utterance to be given by + Comparative Philology on the question of the origin of language it is + necessary that not merely for these languages but also for those in other + quarters of the globe, the facts should be collected, sifted and + tabulated. England rules an empire which contains a greater variety of + languages by far than were ever held under one sway before. The Government + of India is engaged in producing, under the editorship of Dr Grierson, a + linguistic survey of India, a remarkable undertaking and, so far as it has + gone, a remarkable achievement. Is it too much to ask that, with the + support of the self-governing colonies, a similar survey should be + undertaken for the whole of the British Empire? + </p> + <p> + Notwithstanding the great number of books that have been written on the + origin of language in the last three and twenty centuries, the results of + the investigation which can be described as certain are very meagre. The + question originally raised was whether language came into being thesei or + phusei, by convention or by nature. The first alternative, in its baldest + form at least, has passed from out the field of controversy. No one now + claims that names were given to living things or objects or activities by + formal agreement among the members of an early community, or that the + first father of mankind passed in review every living thing and gave it + its name. Even if the record of Adam's action were to be taken literally + there would still remain the question, whence had he this power? Did he + develop it himself or was it a miraculous gift with which he was endowed + at his creation? If the latter, then as Wundt says ("Volkerpsychologie", + I. 2, page 585.), "the miracle of language is subsumed in the miracle of + creation." If Adam developed language of himself, we are carried over to + the alternative origin of phusei. On this hypothesis we must assume that + the natural growth which modern theories of development regard as the + painful progress of multitudinous generations was contracted into the + experience of a single individual. + </p> + <p> + But even if the origin of language is admitted to be NATURAL there may + still be much variety of signification attached to the word: NATURE, like + most words which are used by philosophers, has accumulated many meanings, + and as research into the natural world proceeds, is accumulating more. + </p> + <p> + Forty years ago an animated controversy raged among the supporters of the + theories which were named for short the bow-wow, the pooh-pooh and the + ding-dong theories of the origin of language. The third, which was the + least tenacious of life, was made known to the English-speaking world by + the late Professor Max Muller who, however, when questioned, repudiated it + as his own belief. ("Science of Thought", London, 1887, page 211.) It was + taken by him from Heyse's lectures on language which were published + posthumously by Steinthal. Put shortly the theory is that "everything + which is struck, rings. Each substance has its peculiar ring. We can tell + the more or less perfect structure of metals by their vibrations, by the + answer which they give. Gold rings differently from tin, wood rings + differently from stone; and different sounds are produced according to the + nature of each percussion. It may be the same with man, the most highly + organised of nature's work." (Max Muller as above, translating from + Heyse.) Max Muller's repudiation of this theory was, however, not very + whole-hearted for he proceeds later in the same argument: "Heyse's theory, + which I neither adopted nor rejected, but which, as will be seen, is by no + means incompatible with that which for many years has been gaining on me, + and which of late has been so clearly formulated by Professor Noire, has + been assailed with ridicule and torn to pieces, often by persons who did + not even suspect how much truth was hidden behind its paradoxical + appearance. We are still very far from being able to identify roots with + nervous vibrations, but if it should appear hereafter that sensuous + vibrations supply at least the raw material of roots, it is quite possible + that the theory, proposed by Oken and Heyse, will retain its place in the + history of the various attempts at solving the problem of the origin of + language, when other theories, which in our own days were received with + popular applause, will be completely forgotten." ("Science of Thought", + page 212.) + </p> + <p> + Like a good deal else that has been written on the origin of language, + this statement perhaps is not likely to be altogether clear to the plain + man, who may feel that even the "raw material of roots" is some distance + removed from nervous vibrations, though obviously without the existence of + afferent and efferent nerves articulate speech would be impossible. But + Heyse's theory undoubtedly was that every thought or idea which occurred + to the mind of man for the first time had its own special phonetic + expression, and that this responsive faculty, when its object was thus + fulfilled, became extinct. Apart from the philosophical question whether + the mind acts without external stimulus, into which it is not necessary to + enter here, it is clear that this theory can neither be proved nor + disproved, because it postulates that this faculty existed only when + language first began, and later altogether disappeared. As we have already + seen, it is impossible for us to know what happened at the first + beginnings of language, because we have no information from any period + even approximately so remote; nor are we likely to attain it. Even in + their earliest stages the great families of language which possess a + history extending over many centuries—the Indo-Germanic and the + Semitic—have very little in common. With the exception of Chinese, + the languages which are apparently of a simpler or more primitive + formation have either a history which, compared with that of the families + mentioned, is very short, or, as in the case of the vast majority, have no + history beyond the time extending only over a few years or, at most, a few + centuries when they have been observed by competent scholars of European + origin. But, if we may judge by the history of geology and other studies, + it is well to be cautious in assuming for the first stages of development + forces which do not operate in the later, unless we have direct evidence + of their existence. + </p> + <p> + It is unnecessary here to enter into a prolonged discussion of the other + views christened by Max Muller, not without energetic protest from their + supporters, the bow-wow and pooh-pooh theories of language. Suffice it to + say that the former recognises as a source of language the imitation of + the sounds made by animals, the fall of bodies into water or on to solid + substances and the like, while the latter, also called the interjectional + theory, looks to the natural ejaculations produced by particular forms of + effort for the first beginnings of speech. It would be futile to deny that + some words in most languages come from imitation, and that others, + probably fewer in number, can be traced to ejaculations. But if either of + these sources alone or both in combination gave rise to primitive speech, + it clearly must have been a simple form of language and very limited in + amount. There is no reason to think that it was otherwise. Presumably in + its earliest stages language only indicated the most elementary ideas, + demands for food or the gratification of other appetites, indications of + danger, useful animals and plants. Some of these, such as animals or + indications of danger, could often be easily represented by imitative + sounds: the need for food and the like could be indicated by gesture and + natural cries. Both sources are verae causae; to them Noire, supported by + Max Muller, has added another which has sometimes been called the + Yo-heave-ho theory. Noire contends that the real crux in the early stages + of language is for primitive man to make other primitive men understand + what he means. The vocal signs which commend themselves to one may not + have occurred to another, and may therefore be unintelligible. It may be + admitted that this difficulty exists, but it is not insuperable. The old + story of the European in China who, sitting down to a meal and being + doubtful what the meat in the dish might be, addressed an interrogative + Quack-quack? to the waiter and was promptly answered by Bow-wow, + illustrates a simple situation where mutual understanding was easy. But + obviously many situations would be more complex than this, and to grapple + with them Noire has introduced his theory of communal action. "It was + common effort directed to a common object, it was the most primitive + (uralteste) labour of our ancestors, from which sprang language and the + life of reason." (Noire "Der Ursprung der Sprache", page 331, Mainz, + 1877.) As illustrations of such common effort he cites battle cries, the + rescue of a ship running on shore (a situation not likely to occur very + early in the history of man), and others. Like Max Muller he holds that + language is the utterance and the organ of thought for mankind, the one + characteristic which separates man from the brute. "In common action the + word was first produced; for long it was inseparably connected with + action; through long-continued connection it gradually became the firm, + intelligible symbol of action, and then in its development indicated also + things of the external world in so far as the action affected them and + finally the sound began to enter into a connexion with them also." (Op. + cit. page 339.) In so far as this theory recognises language as a social + institution it is undoubtedly correct. Darwin some years before Noire had + pointed to the same social origin of language in the fourth chapter of his + work on "The Expression of the Emotions in Man and Animals". "Naturalists + have remarked, I believe with truth, that social animals, from habitually + using their vocal organs as a means of intercommunication, use them on + other occasions much more freely than other animals... The principle, + also, of association, which is so widely extended in its power, has + likewise played its part. Hence it allows that the voice, from having been + employed as a serviceable aid under certain conditions, inducing pleasure, + pain, rage, etc., is commonly used whenever the same sensations or + emotions are excited, under quite different conditions, or in a lesser + degree." ("The Expression of the Emotions", page 84 (Popular Edition, + 1904). + </p> + <p> + Darwin's own views on language which are set forth most fully in "The + Descent of Man" (page 131 ff. (Popular Edition, 1906).) are characterised + by great modesty and caution. He did not profess to be a philologist and + the facts are naturally taken from the best known works of the day (1871). + In the notes added to the second edition he remarks on Max Muller's denial + of thought without words, "what a strange definition must here be given to + the word thought!" (Op. cit. page 135, footnote 63.) He naturally finds + the origin of language in "the imitation and modification of various + natural sounds, the voices of other animals, and man's own instinctive + cries aided by signs and gestures (op. cit. page 132.)... As the voice was + used more and more, the vocal organs would have been strengthened and + perfected through the principle of the inherited effects of use; and this + would have reacted on the power of speech." (Op. cit. page 133.) On man's + own instinctive cries, he has more to say in "The Expression of the + Emotions". (Page 93 (Popular Edition, 1904) and elsewhere.) These remarks + have been utilised by Prof. Jespersen of Copenhagen in propounding an + ingenious theory of his own to the effect that speech develops out of + singing. ("Progress in Language", page 361, London, 1894.) + </p> + <p> + For many years and in many books Max Muller argued against Darwin's views + on evolution on the one ground that thought is impossible without speech; + consequently as speech is confined to the human race, there is a gulf + which cannot be bridged between man and all other creatures. (Some + interesting comments on the theory will be found in a lecture on "Thought + and Language" in Samuel Butler's "Essays on Life, Art and Science", + London, 1908.) On the title-page of his "Science of Thought" he put the + two sentences "No Reason without Language: No Language without Reason." It + may be readily admitted that the second dictum is true, that no language + properly so-called can exist without reason. Various birds can learn to + repeat words or sentences used by their masters or mistresses. In most + cases probably the birds do not attach their proper meaning to the words + they have learnt; they repeat them in season and out of season, sometimes + apparently for their own amusement, generally in the expectation, raised + by past experience, of being rewarded for their proficiency. But even here + it is difficult to prove a universal negative, and most possessors of such + pets would repudiate indignantly the statement that the bird did not + understand what was said to it, and would also contend that in many cases + the words which it used were employed in their ordinary meaning. The first + dictum seems to be inconsistent with fact. The case of deaf mutes, such as + Laura Bridgeman, who became well educated, or the still more extraordinary + case of Helen Keller, deaf, dumb, and blind, who in spite of these + disadvantages has learnt not only to reason but to reason better than the + average of persons possessed of all their senses, goes to show that + language and reason are not necessarily always in combination. Reason is + but the conscious adaptation of means to ends, and so defined is a faculty + which cannot be denied to many of the lower animals. In these days when so + many books on Animal Intelligence are issued from the press, it seems + unnecessary to labour the point. Yet none of these animals, except by + parrot-imitation, makes use of speech, because man alone possesses in a + sufficient degree of development the centres of nervous energy which are + required for the working of articulation in speech. On this subject much + investigation was carried on during the last years of Darwin's life and + much more in the period since his death. As early as 1861 Broca, following + up observations made by earlier French writers, located the centre of + articulate speech in the third left frontal convolution of the brain. In + 1876 he more definitely fixed the organ of speech in "the posterior + two-fifths of the third frontal convolution" (Macnamara, "Human Speech", + page 197, London, 1908.), both sides and not merely the left being + concerned in speech production. Owing however to the greater use by most + human beings of the right side of the body, the left side of the brain, + which is the motor centre for the right side of the body, is more highly + developed than its right side, which moves the left side of the body. The + investigations of Professors Ferrier, Sherrington and Grunbaum have still + more precisely defined the relations between brain areas and certain + groups of muscles. One form of aphasia is the result of injury to or + disease in the third frontal convolution because the motor centre is no + longer equal to the task of setting the necessary muscles in motion. In + the brain of idiots who are unable to speak, the centre for speech is not + developed. (Op. cit. page 226.) In the anthropoid apes the brain is + similarly defective, though it has been demonstrated by Professors + Cunningham and Marchand "that there is a tendency, especially in the + gorilla's brain, for the third frontal convolution to assume the human + form... But if they possessed a centre for speech, those parts of the + hemispheres of their brains which form the mechanism by which intelligence + is elaborated are so ill-developed, as compared with the rest of their + bodies, that we can not conceive, even with more perfect frontal + convolutions, that these animals could formulate ideas expressible in + intelligent speech." (Op. cit. page 223.) + </p> + <p> + While Max Muller's theory is Shelley's + </p> + <p> + "He gave man speech, and speech created thought, Which is the measure of + the universe" ("Prometheus Unbound" II. 4.), + </p> + <p> + it seems more probable that the development was just the opposite—that + the development of new activities originated new thoughts which required + new symbols to express them, symbols which may at first have been, even to + a greater extent than with some of the lower races at present, sign + language as much as articulation. When once the faculty of articulation + was developed, which, though we cannot trace the process, was probably a + very gradual growth, there is no reason to suppose that words developed in + any other way then they do at present. An erroneous notion of the + development of language has become widely spread through the adoption of + the metaphorical term "roots" for the irreducible elements of human + speech. Men never talked in roots; they talked in words. Many words of + kindred meaning have a part in common, and a root is nothing but that + common part stripped of all additions. In some cases it is obvious that + one word is derived from another by the addition of a fresh element; in + other cases it is impossible to say which of two kindred words is the more + primitive. A root is merely a convenient term for an abstraction. The + simplest word may be called a root, but it is nevertheless a word. How are + new words added to a language in the present day? Some communities, like + the Germans, prefer to construct new words for new ideas out of the old + material existing in the language; others, like the English, prefer to go + to the ancient languages of Greece and Rome for terms to express new + ideas. The same chemical element is described in the two languages as sour + stuff (Sauerstoff) and as oxygen. Both terms mean the same thing + etymologically as well as in fact. On behalf of the German method, it may + be contended that the new idea is more closely attached to already + existing ideas, by being expressed in elements of the language which are + intelligible even to the meanest capacity. For the English practice it may + be argued that, if we coin a new word which means one thing, and one thing + only, the idea which it expresses is more clearly defined than if it were + expressed in popularly intelligible elements like "sour stuff." If the + etymological value of words were always present in the minds of their + users, "oxygen" would undoubtedly have an advantage over "sour stuff" as a + technical term. But the tendency in language is to put two words of this + kind which express but one idea under a single accent, and when this has + taken place, no one but the student of language any longer observes what + the elements really mean. When the ordinary man talks of a "blackbird" it + is certainly not present to his consciousness that he is talking of a + black bird, unless for some reason conversation has been dwelling upon the + colour rather than other characteristics of the species. + </p> + <p> + But, it may be said, words like "oxygen" are introduced by learned men, + and do not represent the action of the man in the street, who, after all, + is the author of most additions to the stock of human language. We may go + back therefore some four centuries to a period, when scientific study was + only in its infancy, and see what process was followed. With the discovery + of America new products never seen before reached Europe, and these + required names. Three of the most characteristic were tobacco, the potato, + and the turkey. How did these come to be so named? The first people to + import these products into Europe were naturally the Spanish discoverers. + The first of these words—tobacco—appears in forms which differ + only slightly in the languages of all civilised countries: Spanish tabaco, + Italian tabacco, French tabac, Dutch and German tabak, Swedish tobak, etc. + The word in the native dialect of Hayti is said to have been tabaco, but + to have meant not the plant (According to William Barclay, "Nepenthes, or + the Virtue of Tobacco", Edinburgh, 1614, "the countrey which God hath + honoured and blessed with this happie and holy herbe doth call it in their + native language 'Petum'.") but the pipe in which it was smoked. It thus + illustrates a frequent feature of borrowing—that the word is not + borrowed in its proper signification, but in some sense closely allied + thereto, which a foreigner, understanding the language with difficulty, + might readily mistake for the real meaning. Thus the Hindu practice of + burning a wife upon the funeral pyre of her husband is called in English + "suttee", this word being in fact but the phonetic spelling of the + Sanskrit "sati", "a virtuous woman," and passing into its English meaning + because formerly the practice of self-immolation by a wife was regarded as + the highest virtue. + </p> + <p> + The name of the potato exhibits greater variety. The English name was + borrowed from the Spanish "patata", which was itself borrowed from a + native word for the "yam" in the dialect of Hayti. The potato appeared + early in Italy, for the mariners of Genoa actively followed the footsteps + of their countryman Columbus in exploring America. In Italian generally + the form "patata" has survived. The tubers, however, also suggested a + resemblance to truffles, so that the Italian word "tartufolo", a + diminutive of the Italian modification of the Latin "terrae tuber" was + applied to them. In the language of the Rhaetian Alps this word appears as + "tartufel". From there it seems to have passed into Germany where potatoes + were not cultivated extensively till the eighteenth century, and + "tartufel" has in later times through some popular etymology been + metamorphosed into "Kartoffel". In France the shape of the tubers + suggested the name of earth-apple (pomme de terre), a name also adopted in + Dutch (aard-appel), while dialectically in German a form "Grumbire" + appears, which is a corruption of "Grund-birne", "ground pear". (Kluge + "Etymologisches Worterbuch der deutschen Sprache" (Strassburg), s.v. + "Kartoffel".) Here half the languages have adopted the original American + word for an allied plant, while others have adopted a name originating in + some more or less fanciful resemblance discovered in the tubers; the + Germans alone in Western Europe, failing to see any meaning in their + borrowed name, have modified it almost beyond recognition. To this English + supplies an exact parallel in "parsnep" which, though representing the + Latin "pastinaca" through the Old French "pastenaque", was first + assimilated in the last syllable to the "nep" of "turnep" ("pasneppe" in + Elizabethan English), and later had an "r" introduced into the first + syllable, apparently on the analogy of "parsley". + </p> + <p> + The turkey on the other hand seems never to be found with its original + American name. In England, as the name implies, the turkey cock was + regarded as having come from the land of the Turks. The bird no doubt + spread over Europe from the Italian seaports. The mistake, therefore, was + not unnatural, seeing that these towns conducted a great trade with the + Levant, while the fact that America when first discovered was identified + with India helped to increase the confusion. Thus in French the "coq + d'Inde" was abbreviated to "d'Inde" much as "turkey cock" was to "turkey"; + the next stage was to identify "dinde" as a feminine word and create a new + "dindon" on the analogy of "chapon" as the masculine. In Italian the name + "gallo d'India" besides survives, while in German the name "Truthahn" + seems to be derived onomatopoetically from the bird's cry, though a + dialectic "Calecutischer Hahn" specifies erroneously an origin for the + bird from the Indian Calicut. In the Spanish "pavo", on the other hand, + there is a curious confusion with the peacock. Thus in these names for + objects of common knowledge, the introduction of which into Europe can be + dated with tolerable definiteness, we see evinced the methods by which in + remoter ages objects were named. The words were borrowed from the + community whence came the new object, or the real or fancied resemblance + to some known object gave the name, or again popular etymology might + convert the unknown term into something that at least approached in sound + a well-known word. + </p> + <p> + "The Origin of Species" had not long been published when the parallelism + of development in natural species and in languages struck investigators. + At the time, one of the foremost German philologists was August + Schleicher, Professor at Jena. He was himself keenly interested in the + natural sciences, and amongst his colleagues was Ernst Haeckel, the + protagonist in Germany of the Darwinian theory. How the new ideas struck + Schleicher may be seen from the following sentences by his colleague + Haeckel. "Speech is a physiological function of the human organism, and + has been developed simultaneously with its organs, the larynx and tongue, + and with the functions of the brain. Hence it will be quite natural to + find in the evolution and classification of languages the same features as + in the evolution and classification of organic species. The various groups + of languages that are distinguished in philology as primitive, + fundamental, parent, and daughter languages, dialects, etc., correspond + entirely in their development to the different categories which we + classify in zoology and botany as stems, classes, orders, families, + genera, species and varieties. The relation of these groups, partly + coordinate and partly subordinate, in the general scheme is just the same + in both cases; and the evolution follows the same lines in both." + (Haeckel, "The Evolution of Man", page 485, London, 1905. This represents + Schleicher's own words: Was die Naturforscher als Gattung bezeichnen + wurden, heisst bei den Glottikern Sprachstamm, auch Sprachsippe; naher + verwandte Gattungen bezeichnen sie wohl auch als Sprachfamilien einer + Sippe oder eines Sprachstammes... Die Arten einer Gattung nennen wir + Sprachen eines Stammes; die Unterarten einer Art sind bei uns die Dialekte + oder Mundarten einer Sprache; den Varietaten und Spielarten entsprechen + die Untermundarten oder Nebenmundarten und endlich den einzelnen + Individuen die Sprechweise der einzelnen die Sprachen redenden Menschen. + "Die Darwinische Theorie und die Sprachwissenschaft", Weimar, 1863, page + 12 f. Darwin makes a more cautious statement about the classification of + languages in "The Origin of Species", page 578, (Popular Edition, 1900).) + These views were set forth in an open letter addressed to Haeckel in 1863 + by Schleicher entitled, "The Darwinian theory and the science of + language". Unfortunately Schleicher's views went a good deal farther than + is indicated in the extract given above. He appended to the pamphlet a + genealogical tree of the Indo-Germanic languages which, though to a large + extent confirmed by later research, by the dichotomy of each branch into + two other branches, led the unwary reader to suppose their phylogeny (to + use Professor Haeckel's term) was more regular than our evidence warrants. + </p> + <p> + Without qualification Schleicher declared languages to be "natural + organisms which originated unconditioned by the human will, developed + according to definite laws, grow old and die; they also are characterised + by that series of phenomena which we designate by the term 'Life.' + Consequently Glottic, the science of language, is a natural science; its + method is in general the same as that of the other natural sciences." + ("Die Darwinische Theorie", page 6 f.) In accordance with this view he + declared (op. cit. page 23.) that the root in language might be compared + with the simple cell in physiology, the linguistic simple cell or root + being as yet not differentiated into special organs for the function of + noun, verb, etc. + </p> + <p> + In this probably all recent philologists admit that Schleicher went too + far. One of the most fertile theories in the modern science of language + originated with him, and was further developed by his pupil, August + Leskien ("Die Declination im Slavisch-litanischen und Germanischen", + Leipzig, 1876; Osthoff and Brugmann, "Morphologische Untersuchungen", I. + (Introduction), 1878. The general principles of this school were + formulated (1880) in a fuller form in H. Paul's "Prinzipien der + Sprachgeschichte", Halle (3rd edition, 1898). Paul and Wundt (in his + "Volkerpsychologie") deal largely with the same matter, but begin their + investigations from different points of view, Paul being a philologist + with leanings to philosophy and Wundt a philosopher interested in + language.), and by Leskien's colleagues and friends, Brugmann and Osthoff. + This was the principle that phonetic laws have no exceptions. Under the + influence of this generalisation much greater precision in etymology was + insisted upon, and a new and remarkably active period in the study of + language began. Stated broadly in the fashion given above the principle is + not true. A more accurate statement would be that an original sound is + represented in a given dialect at a given time and in a given environment + only in one way; provided that the development of the original sound into + its representation in the given dialect has not been influenced by the + working of analogy. + </p> + <p> + It is this proviso that is most important for the characterisation of the + science of language. As I have said elsewhere, it is at this point that + this science parts company with the natural sciences. "If the chemist + compounds two pure simple elements, there can be but one result, and no + power of the chemist can prevent it. But the minds of men do act upon the + sounds which they produce. The result is that, when this happens, the + phonetic law which would have acted in the case is stopped, and this + particular form enters on the same course of development as other forms to + which it does not belong." (P. Giles, "Short Manual of Comparative + Philology", 2nd edition, page 57, London, 1901.) + </p> + <p> + Schleicher was wrong in defining a language to be an organism in the sense + in which a living being is an organism. Regarded physiologically, language + is a function or potentiality of certain human organs; regarded from the + point of view of the community it is of the nature of an institution. + (This view of language is worked out at some length by Prof. W.D. Whitney + in an article in the "Contemporary Review" for 1875, page 713 ff. This + article forms part of a controversy with Max Muller, which is partly + concerned with Darwin's views on language. He criticises Schleicher's + views severely in his "Oriental and Linguistic Studies", page 298 ff., New + York, 1873. In this volume will be found criticisms of various other views + mentioned in this essay.) More than most influences it conduces to the + binding together of the elements that form a state. That geographical or + other causes may effectively counteract the influence of identity of + language is obvious. One need only read the history of ancient Greece, or + observe the existing political separation of Germany and Austria, of Great + Britain and the United States of America. But however analogous to an + organism, language is not an organism. In a less degree Schleicher, by + defining languages as such, committed the same mistake which Bluntschli + made regarding the State, and which led him to declare that the State is + by nature masculine and the Church feminine. (Bluntschli, "Theory of the + State", page 24, Second English Edition, Oxford, 1892.) The views of + Schleicher were to some extent injurious to the proper methods of + linguistic study. But this misfortune was much more than fully compensated + by the inspiration which his ideas, collected and modified by his + disciples, had upon the science. In spite of the difference which the + psychological element represented by analogy makes between the science of + language and the natural sciences, we are entitled to say of it as + Schleicher said of Darwin's theory of the origin of species, "it depends + upon observation, and is essentially an attempt at a history of + development." + </p> + <p> + Other questions there are in connection with language and evolution which + require investigation—the survival of one amongst several competing + words (e.g. why German keeps only as a high poetic word "ross", which is + identical in origin with the English work-a-day "horse", and replaces it + by "pferd", whose congener the English "palfrey" is almost confined to + poetry and romance), the persistence of evolution till it becomes + revolution in languages like English or Persian which have practically + ceased to be inflectional languages, and many other problems. Into these + Darwin did not enter, and they require a fuller investigation than is + possible within the limits of the present paper. + </p> + <p> + <a name="link2H_4_0029" id="link2H_4_0029"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + XXVII. DARWINISM AND HISTORY. By J.B. Bury, Litt.D., LL.D. + </h2> + <h3> + Regius Professor of Modern History in the University of Cambridge. + </h3> + <p> + 1. Evolution, and the principles associated with the Darwinian theory, + could not fail to exert a considerable influence on the studies connected + with the history of civilised man. The speculations which are known as + "philosophy of history," as well as the sciences of anthropology, + ethnography, and sociology (sciences which though they stand on their own + feet are for the historian auxiliary), have been deeply affected by these + principles. Historiographers, indeed, have with few exceptions made little + attempt to apply them; but the growth of historical study in the + nineteenth century has been determined and characterised by the same + general principle which has underlain the simultaneous developments of the + study of nature, namely the GENETIC idea. The "historical" conception of + nature, which has produced the history of the solar system, the story of + the earth, the genealogies of telluric organisms, and has revolutionised + natural science, belongs to the same order of thought as the conception of + human history as a continuous, genetic, causal process—a conception + which has revolutionised historical research and made it scientific. + Before proceeding to consider the application of evolutional principles, + it will be pertinent to notice the rise of this new view. + </p> + <p> + 2. With the Greeks and Romans history had been either a descriptive record + or had been written in practical interests. The most eminent of the + ancient historians were pragmatical; that is, they regarded history as an + instructress in statesmanship, or in the art of war, or in morals. Their + records reached back such a short way, their experience was so brief, that + they never attained to the conception of continuous process, or realised + the significance of time; and they never viewed the history of human + societies as a phenomenon to be investigated for its own sake. In the + middle ages there was still less chance of the emergence of the ideas of + progress and development. Such notions were excluded by the fundamental + doctrines of the dominant religion which bounded and bound men's minds. As + the course of history was held to be determined from hour to hour by the + arbitrary will of an extra-cosmic person, there could be no self-contained + causal development, only a dispensation imposed from without. And as it + was believed that the world was within no great distance from the end of + this dispensation, there was no motive to take much interest in + understanding the temporal, which was to be only temporary. + </p> + <p> + The intellectual movements of the fifteenth and sixteenth centuries + prepared the way for a new conception, but it did not emerge immediately. + The historians of the Renaissance period simply reverted to the ancient + pragmatical view. For Machiavelli, exactly as for Thucydides and Polybius, + the use of studying history was instruction in the art of politics. The + Renaissance itself was the appearance of a new culture, different from + anything that had gone before; but at the time men were not conscious of + this; they saw clearly that the traditions of classical antiquity had been + lost for a long period, and they were seeking to revive them, but + otherwise they did not perceive that the world had moved, and that their + own spirit, culture, and conditions were entirely unlike those of the + thirteenth century. It was hardly till the seventeenth century that the + presence of a new age, as different from the middle ages as from the ages + of Greece and Rome, was fully realised. It was then that the triple + division of ancient, medieval, and modern was first applied to the history + of western civilisation. Whatever objections may be urged against this + division, which has now become almost a category of thought, it marks a + most significant advance in man's view of his own past. He has become + conscious of the immense changes in civilisation which have come about + slowly in the course of time, and history confronts him with a new aspect. + He has to explain how those changes have been produced, how the + transformations were effected. The appearance of this problem was almost + simultaneous with the rise of rationalism, and the great historians and + thinkers of the eighteenth century, such as Montesquieu, Voltaire, Gibbon, + attempted to explain the movement of civilisation by purely natural + causes. These brilliant writers prepared the way for the genetic history + of the following century. But in the spirit of the Aufklarung, that + eighteenth-century Enlightenment to which they belonged, they were + concerned to judge all phenomena before the tribunal of reason; and the + apotheosis of "reason" tended to foster a certain superior a priori + attitude, which was not favourable to objective treatment and was + incompatible with a "historical sense." Moreover the traditions of + pragmatical historiography had by no means disappeared. + </p> + <p> + 3. In the first quarter of the nineteenth century the meaning of genetic + history was fully realised. "Genetic" perhaps is as good a word as can be + found for the conception which in this century was applied to so many + branches of knowledge in the spheres both of nature and of mind. It does + not commit us to the doctrine proper of evolution, nor yet to any + teleological hypothesis such as is implied in "progress." For history it + meant that the present condition of the human race is simply and strictly + the result of a causal series (or set of causal series)—a continuous + succession of changes, where each state arises causally out of the + preceding; and that the business of historians is to trace this genetic + process, to explain each change, and ultimately to grasp the complete + development of the life of humanity. Three influential writers, who + appeared at this stage and helped to initiate a new period of research, + may specially be mentioned. Ranke in 1824 definitely repudiated the + pragmatical view which ascribes to history the duties of an instructress, + and with no less decision renounced the function, assumed by the + historians of the Aufklarung, to judge the past; it was his business, he + said, merely to show how things really happened. Niebuhr was already + working in the same spirit and did more than any other writer to establish + the principle that historical transactions must be related to the ideas + and conditions of their age. Savigny about the same time founded the + "historical school" of law. He sought to show that law was not the + creation of an enlightened will, but grew out of custom and was developed + by a series of adaptations and rejections, thus applying the conception of + evolution. He helped to diffuse the notion that all the institutions of a + society or a notion are as closely interconnected as the parts of a living + organism. + </p> + <p> + 4. The conception of the history of man as a causal development meant the + elevation of historical inquiry to the dignity of a science. Just as the + study of bees cannot become scientific so long as the student's interest + in them is only to procure honey or to derive moral lessons from the + labours of "the little busy bee," so the history of human societies cannot + become the object of pure scientific investigation so long as man + estimates its value in pragmatical scales. Nor can it become a science + until it is conceived as lying entirely within a sphere in which the law + of cause and effect has unreserved and unrestricted dominion. On the other + hand, once history is envisaged as a causal process, which contains within + itself the explanation of the development of man from his primitive state + to the point which he has reached, such a process necessarily becomes the + object of scientific investigation and the interest in it is scientific + curiosity. + </p> + <p> + At the same time, the instruments were sharpened and refined. Here Wolf, a + philologist with historical instinct, was a pioneer. His "Prolegomena" to + Homer (1795) announced new modes of attack. Historical investigation was + soon transformed by the elaboration of new methods. + </p> + <p> + 5. "Progress" involves a judgment of value, which is not involved in the + conception of history as a genetic process. It is also an idea distinct + from that of evolution. Nevertheless it is closely related to the ideas + which revolutionised history at the beginning of the last century; it swam + into men's ken simultaneously; and it helped effectively to establish the + notion of history as a continuous process and to emphasise the + significance of time. Passing over earlier anticipations, I may point to a + "Discours" of Turgot (1750), where history is presented as a process in + which "the total mass of the human race" "marches continually though + sometimes slowly to an ever increasing perfection." That is a clear + statement of the conception which Turgot's friend Condorcet elaborated in + the famous work, published in 1795, "Esquisse d'un tableau historique des + progres de l'esprit humain". This work first treated with explicit fulness + the idea to which a leading role was to fall in the ideology of the + nineteenth century. Condorcet's book reflects the triumphs of the Tiers + etat, whose growing importance had also inspired Turgot; it was the + political changes in the eighteenth century which led to the doctrine, + emphatically formulated by Condorcet, that the masses are the most + important element in the historical process. I dwell on this because, + though Condorcet had no idea of evolution, the pre-dominant importance of + the masses was the assumption which made it possible to apply evolutional + principles to history. And it enabled Condorcet himself to maintain that + the history of civilisation, a progress still far from being complete, was + a development conditioned by general laws. + </p> + <p> + 6. The assimilation of society to an organism, which was a governing + notion in the school of Savigny, and the conception of progress, combined + to produce the idea of an organic development, in which the historian has + to determine the central principle or leading character. This is + illustrated by the apotheosis of democracy in Tocqueville's "Democratie en + Amerique", where the theory is maintained that "the gradual and + progressive development of equality is at once the past and the future of + the history of men." The same two principles are combined in the doctrine + of Spencer (who held that society is an organism, though he also + contemplated its being what he calls a "super-organic aggregate") (A + society presents suggestive analogies with an organism, but it certainly + is not an organism, and sociologists who draw inferences from the + assumption of its organic nature must fall into error. A vital organism + and a society are radically distinguished by the fact that the individual + components of the former, namely the cells, are morphologically as well as + functionally differentiated, whereas the individuals which compose a + society are morphologically homogeneous and only functionally + differentiated. The resemblances and the differences are worked out in E. + de Majewski's striking book "La Science de la Civilisation", Paris, + 1908.), that social evolution is a progressive change from militarism to + industrialism. + </p> + <p> + 7. the idea of development assumed another form in the speculations of + German idealism. Hegel conceived the successive periods of history as + corresponding to the ascending phases or ideas in the self-evolution of + his Absolute Being. His "Lectures on the Philosophy of History" were + published in 1837 after his death. His philosophy had a considerable + effect, direct and indirect, on the treatment of history by historians, + and although he was superficial and unscientific himself in dealing with + historical phenomena, he contributed much towards making the idea of + historical development familiar. Ranke was influenced, if not by Hegel + himself, at least by the Idealistic philosophies of which Hegel's was the + greatest. He was inclined to conceive the stages in the process of history + as marked by incarnations, as it were, of ideas, and sometimes speaks as + if the ideas were independent forces, with hands and feet. But while Hegel + determined his ideas by a priori logic, Ranke obtained his by induction—by + a strict investigation of the phenomena; so that he was scientific in his + method and work, and was influenced by Hegelian prepossessions only in the + kind of significance which he was disposed to ascribe to his results. It + is to be noted that the theory of Hegel implied a judgment of value; the + movement was a progress towards perfection. + </p> + <p> + 8. In France, Comte approached the subject from a different side, and + exercised, outside Germany, a far wider influence than Hegel. The 4th + volume of his "Cours de philosophie positive", which appeared in 1839, + created sociology and treated history as a part of this new science, + namely as "social dynamics." Comte sought the key for unfolding historical + development, in what he called the social-psychological point of view, and + he worked out the two ideas which had been enunciated by Condorcet: that + the historian's attention should be directed not, as hitherto, principally + to eminent individuals, but to the collective behaviour of the masses, as + being the most important element in the process; and that, as in nature, + so in history, there are general laws, necessary and constant, which + condition the development. The two points are intimately connected, for it + is only when the masses are moved into the foreground that regularity, + uniformity, and law can be conceived as applicable. To determine the + social-psychological laws which have controlled the development is, + according to Comte, the task of sociologists and historians. + </p> + <p> + 9. The hypothesis of general laws operative in history was carried further + in a book which appeared in England twenty years later and exercised an + influence in Europe far beyond its intrinsic merit, Buckle's "History of + Civilisation in England" (1857-61). Buckle owed much to Comte, and + followed him, or rather outdid him, in regarding intellect as the most + important factor conditioning the upward development of man, so that + progress, according to him, consisted in the victory of the intellectual + over the moral laws. + </p> + <p> + 10. The tendency of Comte and Buckle to assimilate history to the sciences + of nature by reducing it to general "laws," derived stimulus and + plausibility from the vista offered by the study of statistics, in which + the Belgian Quetelet, whose book "Sur l'homme" appeared in 1835, discerned + endless possibilities. The astonishing uniformities which statistical + inquiry disclosed led to the belief that it was only a question of + collecting a sufficient amount of statistical material, to enable us to + predict how a given social group will act in a particular case. Bourdeau, + a disciple of this school, looks forward to the time when historical + science will become entirely quantitative. The actions of prominent + individuals, which are generally considered to have altered or determined + the course of things, are obviously not amenable to statistical + computation or explicable by general laws. Thinkers like Buckle sought to + minimise their importance or explain them away. + </p> + <p> + 11. These indications may suffice to show that the new efforts to + interpret history which marked the first half of the nineteenth century + were governed by conceptions closely related to those which were current + in the field of natural science and which resulted in the doctrine of + evolution. The genetic principle, progressive development, general laws, + the significance of time, the conception of society as an organic + aggregate, the metaphysical theory of history as the self-evolution of + spirit,—all these ideas show that historical inquiry had been + advancing independently on somewhat parallel lines to the sciences of + nature. It was necessary to bring this out in order to appreciate the + influence of Darwinism. + </p> + <p> + 12. In the course of the dozen years which elapsed between the appearances + of "The Origin of Species" (observe that the first volume of Buckle's work + was published just two years before) and of "The Descent of Man" (1871), + the hypothesis of Lamarck that man is the co-descendant with other species + of some lower extinct form was admitted to have been raised to the rank of + an established fact by most thinkers whose brains were not working under + the constraint of theological authority. + </p> + <p> + One important effect of the discovery of this fact (I am not speaking now + of the Darwinian explanation) was to assign to history a definite place in + the coordinated whole of knowledge, and relate it more closely to other + sciences. It had indeed a defined logical place in systems such as Hegel's + and Comte's; but Darwinism certified its standing convincingly and without + more ado. The prevailing doctrine that man was created ex abrupto had + placed history in an isolated position, disconnected with the sciences of + nature. Anthropology, which deals with the animal anthropos, now comes + into line with zoology, and brings it into relation with history. (It is + to be observed that history is not only different in scope but) not + coextensive with anthropology IN TIME. For it deals only with the + development of man in societies, whereas anthropology includes in its + definition the proto-anthropic period when anthropos was still non-social, + whether he lived in herds like the chimpanzee, or alone like the male + ourang-outang. (It has been well shown by Majewski that congregations—herds, + flocks, packs, etc.—of animals are not SOCIETIES; the characteristic + of a society is differentiation of function. Bee hives, ant hills, may be + called quasi-societies; but in their case the classes which perform + distinct functions are morphologically different.) Man's condition at the + present day is the result of a series of transformations, going back to + the most primitive phase of society, which is the ideal (unattainable) + beginning of history. But that beginning had emerged without any breach of + continuity from a development which carries us back to a quadrimane + ancestor, still further back (according to Darwin's conjecture) to a + marine animal of the ascidian type, and then through remoter periods to + the lowest form of organism. It is essential in this theory that though + links have been lost there was no break in the gradual development; and + this conception of a continuous progress in the evolution of life, + resulting in the appearance of uncivilised Anthropos, helped to reinforce, + and increase a belief in, the conception of the history of civilised + Anthropos as itself also a continuous progressive development. + </p> + <p> + 13. Thus the diffusion of the Darwinian theory of the origin of man, by + emphasising the idea of continuity and breaking down the barriers between + the human and animal kingdoms, has had an important effect in establishing + the position of history among the sciences which deal with telluric + development. The perspective of history is merged in a larger perspective + of development. As one of the objects of biology is to find the exact + steps in the genealogy of man from the lowest organic form, so the scope + of history is to determine the stages in the unique causal series from the + most rudimentary to the present state of human civilisation. + </p> + <p> + It is to be observed that the interest in historical research implied by + this conception need not be that of Comte. In the Positive Philosophy + history is part of sociology; the interest in it is to discover the + sociological laws. In the view of which I have just spoken, history is + permitted to be an end in itself; the reconstruction of the genetic + process is an independent interest. For the purpose of the reconstruction, + sociology, as well as physical geography, biology, psychology, is + necessary; the sociologist and the historian play into each other's hands; + but the object of the former is to establish generalisations; the aim of + the latter is to trace in detail a singular causal sequence. + </p> + <p> + 14. The success of the evolutional theory helped to discredit the + assumption or at least the invocation of transcendent causes. + Philosophically of course it is compatible with theism, but historians + have for the most part desisted from invoking the naive conception of a + "god in history" to explain historical movements. A historian may be a + theist; but, so far as his work is concerned, this particular belief is + otiose. Otherwise indeed (as was remarked above) history could not be a + science; for with a deus ex machina who can be brought on the stage to + solve difficulties scientific treatment is a farce. The transcendent + element had appeared in a more subtle form through the influence of German + philosophy. I noticed how Ranke is prone to refer to ideas as if they were + transcendent existences manifesting themselves in the successive movements + of history. It is intelligible to speak of certain ideas as controlling, + in a given period,—for instance, the idea of nationality; but from + the scientific point of view, such ideas have no existence outside the + minds of individuals and are purely psychical forces; and a historical + "idea," if it does not exist in this form, is merely a way of expressing a + synthesis of the historian himself. + </p> + <p> + 15. From the more general influence of Darwinism on the place of history + in the system of human knowledge, we may turn to the influence of the + principles and methods by which Darwin explained development. It had been + recognised even by ancient writers (such as Aristotle and Polybius) that + physical circumstances (geography, climate) were factors conditioning the + character and history of a race or society. In the sixteenth century Bodin + emphasised these factors, and many subsequent writers took them into + account. The investigations of Darwin, which brought them into the + foreground, naturally promoted attempts to discover in them the chief key + to the growth of civilisation. Comte had expressly denounced the notion + that the biological methods of Lamarck could be applied to social man. + Buckle had taken account of natural influences, but had relegated them to + a secondary plane, compared with psychological factors. But the Darwinian + theory made it tempting to explain the development of civilisation in + terms of "adaptation to environment," "struggle for existence," "natural + selection," "survival of the fittest," etc. (Recently O. Seeck has applied + these principles to the decline of Graeco-Roman civilisation in his + "Untergang der antiken Welt", 2 volumes, Berlin, 1895, 1901.) + </p> + <p> + The operation of these principles cannot be denied. Man is still an + animal, subject to zoological as well as mechanical laws. The dark + influence of heredity continues to be effective; and psychical development + had begun in lower organic forms,—perhaps with life itself. The + organic and the social struggles for existence are manifestations of the + same principle. Environment and climatic influence must be called in to + explain not only the differentiation of the great racial sections of + humanity, but also the varieties within these sub-species and, it may be, + the assimilation of distinct varieties. Ritter's "Anthropogeography" has + opened a useful line of research. But on the other hand, it is urged that, + in explaining the course of history, these principles do not take us very + far, and that it is chiefly for the primitive ultra-prehistoric period + that they can account for human development. It may be said that, so far + as concerns the actions and movements of men which are the subject of + recorded history, physical environment has ceased to act mechanically, and + in order to affect their actions must affect their wills first; and that + this psychical character of the causal relations substantially alters the + problem. The development of human societies, it may be argued, derives a + completely new character from the dominance of the conscious psychical + element, creating as it does new conditions (inventions, social + institutions, etc.) which limit and counteract the operation of natural + selection, and control and modify the influence of physical environment. + Most thinkers agree now that the chief clews to the growth of civilisation + must be sought in the psychological sphere. Imitation, for instance, is a + principle which is probably more significant for the explanation of human + development than natural selection. Darwin himself was conscious that his + principles had only a very restricted application in this sphere, as is + evident from his cautious and tentative remarks in the 5th chapter of his + "Descent of Man". He applied natural selection to the growth of the + intellectual faculties and of the fundamental social instincts, and also + to the differentiation of the great races or "sub-species" (Caucasian, + African, etc.) which differ in anthropological character. (Darwinian + formulae may be suggestive by way of analogy. For instance, it is + characteristic of social advance that a multitude of inventions, schemes + and plans are framed which are never carried out, similar to, or designed + for the same end as, an invention or plan which is actually adopted + because it has chanced to suit better the particular conditions of the + hour (just as the works accomplished by an individual statesman, artist or + savant are usually only a residue of the numerous projects conceived by + his brain). This process in which so much abortive production occurs is + analogous to elimination by natural selection.) + </p> + <p> + 16. But if it is admitted that the governing factors which concern the + student of social development are of the psychical order, the preliminary + success of natural science in explaining organic evolution by general + principles encouraged sociologists to hope that social evolution could be + explained on general principles also. The idea of Condorcet, Buckle, and + others, that history could be assimilated to the natural sciences was + powerfully reinforced, and the notion that the actual historical process, + and every social movement involved in it, can be accounted for by + sociological generalisations, so-called "laws," is still entertained by + many, in one form or another. Dissentients from this view do not deny that + the generalisations at which the sociologist arrives by the comparative + method, by the analysis of social factors, and by psychological deduction + may be an aid to the historian; but they deny that such uniformities are + laws or contain an explanation of the phenomena. They can point to the + element of chance coincidence. This element must have played a part in the + events of organic evolution, but it has probably in a larger measure + helped to determine events in social evolution. The collision of two + unconnected sequences may be fraught with great results. The sudden death + of a leader or a marriage without issue, to take simple cases, has again + and again led to permanent political consequences. More emphasis is laid + on the decisive actions of individuals, which cannot be reduced under + generalisations and which deflect the course of events. If the + significance of the individual will had been exaggerated to the neglect of + the collective activity of the social aggregate before Condorcet, his + doctrine tended to eliminate as unimportant the roles of prominent men, + and by means of this elimination it was possible to found sociology. But + it may be urged that it is patent on the face of history that its course + has constantly been shaped and modified by the wills of individuals (We + can ignore here the metaphysical question of freewill and determinism. For + the character of the individual's brain depends in any case on ante-natal + accidents and coincidences, and so it may be said that the role of + individuals ultimately depends on chance,—the accidental coincidence + of independent sequences.), which are by no means always the expression of + the collective will; and that the appearance of such personalities at the + given moments is not a necessary outcome of the conditions and cannot be + deduced. Nor is there any proof that, if such and such an individual had + not been born, some one else would have arisen to do what he did. In some + cases there is no reason to think that what happened need ever have come + to pass. In other cases, it seems evident that the actual change was + inevitable, but in default of the man who initiated and guided it, it + might have been postponed, and, postponed or not, might have borne a + different cachet. I may illustrate by an instance which has just come + under my notice. Modern painting was founded by Giotto, and the Italian + expedition of Charles VIII, near the close of the sixteenth century, + introduced into France the fashion of imitating Italian painters. But for + Giotto and Charles VIII, French painting might have been very different. + It may be said that "if Giotto had not appeared, some other great + initiator would have played a role analogous to his, and that without + Charles VIII there would have been the commerce with Italy, which in the + long run would have sufficed to place France in relation with Italian + artists. But the equivalent of Giotto might have been deferred for a + century and probably would have been different; and commercial relations + would have required ages to produce the rayonnement imitatif of Italian + art in France, which the expedition of the royal adventurer provoked in a + few years." (I have taken this example from G. Tarde's "La logique + sociale" 2 (page 403), Paris, 1904, where it is used for quite a different + purpose.) Instances furnished by political history are simply endless. Can + we conjecture how events would have moved if the son of Philip of Macedon + had been an incompetent? The aggressive action of Prussia which astonished + Europe in 1740 determined the subsequent history of Germany; but that + action was anything but inevitable; it depended entirely on the + personality of Frederick the Great. + </p> + <p> + Hence it may be argued that the action of individual wills is a + determining and disturbing factor, too significant and effective to allow + history to be grasped by sociological formulae. The types and general + forms of development which the sociologist attempts to disengage can only + assist the historian in understanding the actual course of events. It is + in the special domains of economic history and Culturgeschichte which have + come to the front in modern times that generalisation is most fruitful, + but even in these it may be contended that it furnishes only partial + explanations. + </p> + <p> + 17. The truth is that Darwinism itself offers the best illustration of the + insufficiency of general laws to account for historical development. The + part played by coincidence, and the part played by individuals—limited + by, and related to, general social conditions—render it impossible + to deduce the course of the past history of man or to predict the future. + But it is just the same with organic development. Darwin (or any other + zoologist) could not deduce the actual course of evolution from general + principles. Given an organism and its environment, he could not show that + it must evolve into a more complex organism of a definite pre-determined + type; knowing what it has evolved into, he could attempt to discover and + assign the determining causes. General principles do not account for a + particular sequence; they embody necessary conditions; but there is a + chapter of accidents too. It is the same in the case of history. + </p> + <p> + 18. Among the evolutional attempts to subsume the course of history under + general syntheses, perhaps the most important is that of Lamprecht, whose + "kulturhistorische Methode," which he has deduced from and applied to + German history, exhibits the (indirect) influence of the Comtist school. + It is based upon psychology, which, in his view, holds among the sciences + of mind (Geisteswissenschaften) the same place (that of a + Grundwissenschaft) which mechanics holds among the sciences of nature. + History, by the same comparison, corresponds to biology, and, according to + him, it can only become scientific if it is reduced to general concepts + (Begriffe). Historical movements and events are of a psychical character, + and Lamprecht conceives a given phase of civilisation as "a collective + psychical condition (seelischer Gesamtzustand)" controlling the period, "a + diapason which penetrates all psychical phenomena and thereby all + historical events of the time." ("Die kulturhistorische Methode", Berlin, + 1900, page 26.) He has worked out a series of such phases, "ages of + changing psychical diapason," in his "Deutsche Geschichte" with the aim of + showing that all the feelings and actions of each age can be explained by + the diapason; and has attempted to prove that these diapasons are + exhibited in other social developments, and are consequently not singular + but typical. He maintains further that these ages succeed each other in a + definite order; the principle being that the collective psychical + development begins with the homogeneity of all the individual members of a + society and, through heightened psychical activity, advances in the form + of a continually increasing differentiation of the individuals (this is + akin to the Spencerian formula). This process, evolving psychical freedom + from psychical constraint, exhibits a series of psychical phenomena which + define successive periods of civilisation. The process depends on two + simple principles, that no idea can disappear without leaving behind it an + effect or influence, and that all psychical life, whether in a person or a + society, means change, the acquisition of new mental contents. It follows + that the new have to come to terms with the old, and this leads to a + synthesis which determines the character of a new age. Hence the ages of + civilisation are defined as the "highest concepts for subsuming without + exception all psychical phenomena of the development of human societies, + that is, of all historical events." (Ibid. pages 28, 29.) Lamprecht + deduces the idea of a special historical science, which might be called + "historical ethnology," dealing with the ages of civilisation, and bearing + the same relation to (descriptive or narrative) history as ethnology to + ethnography. Such a science obviously corresponds to Comte's social + dynamics, and the comparative method, on which Comte laid so much + emphasis, is the principal instrument of Lamprecht. + </p> + <p> + 19. I have dwelt on the fundamental ideas of Lamprecht, because they are + not yet widely known in England, and because his system is the ablest + product of the sociological school of historians. It carries the more + weight as its author himself is a historical specialist, and his + historical syntheses deserve the most careful consideration. But there is + much in the process of development which on such assumptions is not + explained, especially the initiative of individuals. Historical + development does not proceed in a right line, without the choice of + diverging. Again and again, several roads are open to it, of which it + chooses one—why? On Lamprecht's method, we may be able to assign the + conditions which limit the psychical activity of men at a particular stage + of evolution, but within those limits the individual has so many options, + such a wide room for moving, that the definition of those conditions, the + "psychical diapasons," is only part of the explanation of the particular + development. The heel of Achilles in all historical speculations of this + class has been the role of the individual. + </p> + <p> + The increasing prominence of economic history has tended to encourage the + view that history can be explained in terms of general concepts or types. + Marx and his school based their theory of human development on the + conditions of production, by which, according to them, all social + movements and historical changes are entirely controlled. The leading part + which economic factors play in Lamprecht's system is significant, + illustrating the fact that economic changes admit most readily this kind + of treatment, because they have been less subject to direction or + interference by individual pioneers. + </p> + <p> + Perhaps it may be thought that the conception of SOCIAL ENVIRONMENT + (essentially psychical), on which Lamprecht's "psychical diapasons" + depend, is the most valuable and fertile conception that the historian + owes to the suggestion of the science of biology—the conception of + all particular historical actions and movements as (1) related to and + conditioned by the social environment, and (2) gradually bringing about a + transformation of that environment. But no given transformation can be + proved to be necessary (pre-determined). And types of development do not + represent laws; their meaning and value lie in the help they may give to + the historian, in investigating a certain period of civilisation, to + enable him to discover the interrelations among the diverse features which + it presents. They are, as some one has said, an instrument of heuretic + method. + </p> + <p> + 20. The men engaged in special historical researches—which have been + pursued unremittingly for a century past, according to scientific methods + of investigating evidence (initiated by Wolf, Niebuhr, Ranke)—have + for the most part worked on the assumptions of genetic history or at least + followed in the footsteps of those who fully grasped the genetic point of + view. But their aim has been to collect and sift evidence, and determine + particular facts; comparatively few have given serious thought to the + lines of research and the speculations which have been considered in this + paper. They have been reasonably shy of compromising their work by + applying theories which are still much debated and immature. But + historiography cannot permanently evade the questions raised by these + theories. One may venture to say that no historical change or + transformation will be fully understood until it is explained how social + environment acted on the individual components of the society (both + immediately and by heredity), and how the individuals reacted upon their + environment. The problem is psychical, but it is analogous to the main + problem of the biologist. + </p> + <p> + <a name="link2H_4_0030" id="link2H_4_0030"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + XXVIII. THE GENESIS OF DOUBLE STARS. By Sir George Darwin, K.C.B., F.R.S. + </h2> + <h3> + Plumian Professor of Astronomy and Experimental Philosophy in the + University of Cambridge. + </h3> + <p> + In ordinary speech a system of any sort is said to be stable when it + cannot be upset easily, but the meaning attached to the word is usually + somewhat vague. It is hardly surprising that this should be the case, when + it is only within the last thirty years, and principally through the + investigations of M. Poincare, that the conception of stability has, even + for physicists, assumed a definiteness and clearness in which it was + previously lacking. The laws which govern stability hold good in regions + of the greatest diversity; they apply to the motion of planets round the + sun, to the internal arrangement of those minute corpuscles of which each + chemical atom is constructed, and to the forms of celestial bodies. In the + present essay I shall attempt to consider the laws of stability as + relating to the last case, and shall discuss the succession of shapes + which may be assumed by celestial bodies in the course of their evolution. + I believe further that homologous conceptions are applicable in the + consideration of the transmutations of the various forms of animal and of + vegetable life and in other regions of thought. Even if some of my readers + should think that what I shall say on this head is fanciful, yet at least + the exposition will serve to illustrate the meaning to be attached to the + laws of stability in the physical universe. + </p> + <p> + I propose, therefore, to begin this essay by a sketch of the principles of + stability as they are now formulated by physicists. + </p> + <p> + I. + </p> + <p> + If a slight impulse be imparted to a system in equilibrium one of two + consequences must ensue; either small oscillations of the system will be + started, or the disturbance will increase without limit and the + arrangement of the system will be completely changed. Thus a stick may be + in equilibrium either when it hangs from a peg or when it is balanced on + its point. If in the first case the stick is touched it will swing to and + fro, but in the second case it will topple over. The first position is a + stable one, the second is unstable. But this case is too simple to + illustrate all that is implied by stability, and we must consider cases of + stable and of unstable motion. Imagine a satellite and its planet, and + consider each of them to be of indefinitely small size, in fact particles; + then the satellite revolves round its planet in an ellipse. A small + disturbance imparted to the satellite will only change the ellipse to a + small amount, and so the motion is said to be stable. If, on the other + hand, the disturbance were to make the satellite depart from its initial + elliptic orbit in ever widening circuits, the motion would be unstable. + This case affords an example of stable motion, but I have adduced it + principally with the object of illustrating another point not immediately + connected with stability, but important to a proper comprehension of the + theory of stability. + </p> + <p> + The motion of a satellite about its planet is one of revolution or + rotation. When the satellite moves in an ellipse of any given degree of + eccentricity, there is a certain amount of rotation in the system, + technically called rotational momentum, and it is always the same at every + part of the orbit. (Moment of momentum or rotational momentum is measured + by the momentum of the satellite multiplied by the perpendicular from the + planet on to the direction of the path of the satellite at any instant.) + </p> + <p> + Now if we consider all the possible elliptic orbits of a satellite about + its planet which have the same amount of "rotational momentum," we find + that the major axis of the ellipse described will be different according + to the amount of flattening (or the eccentricity) of the ellipse + described. A figure titled "A 'family' of elliptic orbits with constant + rotational momentum" (Fig. 1) illustrates for a given planet and satellite + all such orbits with constant rotational momentum, and with all the major + axes in the same direction. It will be observed that there is a continuous + transformation from one orbit to the next, and that the whole forms a + consecutive group, called by mathematicians "a family" of orbits. In this + case the rotational momentum is constant and the position of any orbit in + the family is determined by the length of the major axis of the ellipse; + the classification is according to the major axis, but it might have been + made according to anything else which would cause the orbit to be exactly + determinate. + </p> + <p> + I shall come later to the classification of all possible forms of ideal + liquid stars, which have the same amount of rotational momentum, and the + classification will then be made according to their densities, but the + idea of orderly arrangement in a "family" is just the same. + </p> + <p> + We thus arrive at the conception of a definite type of motion, with a + constant amount of rotational momentum, and a classification of all + members of the family, formed by all possible motions of that type, + according to the value of some measurable quantity (this will hereafter be + density) which determines the motion exactly. In the particular case of + the elliptic motion used for illustration the motion was stable, but other + cases of motion might be adduced in which the motion would be unstable, + and it would be found that classification in a family and specification by + some measurable quantity would be equally applicable. + </p> + <p> + A complex mechanical system may be capable of motion in several distinct + modes or types, and the motions corresponding to each such type may be + arranged as before in families. For the sake of simplicity I will suppose + that only two types are possible, so that there will only be two families; + and the rotational momentum is to be constant. The two types of motion + will have certain features in common which we denote in a sort of + shorthand by the letter A. Similarly the two types may be described as A + + a and A + b, so that a and b denote the specific differences which + discriminate the families from one another. Now following in imagination + the family of the type A + a, let us begin with the case where the + specific difference a is well marked. As we cast our eyes along the series + forming the family, we find the difference a becoming less conspicuous. It + gradually dwindles until it disappears; beyond this point it either + becomes reversed, or else the type has ceased to be a possible one. In our + shorthand we have started with A + a, and have watched the characteristic + a dwindling to zero. When it vanishes we have reached a type which may be + specified as A; beyond this point the type would be A - a or would be + impossible. + </p> + <p> + Following the A + b type in the same way, b is at first well marked, it + dwindles to zero, and finally may become negative. Hence in shorthand this + second family may be described as A + b,... A,... A - b. + </p> + <p> + In each family there is one single member which is indistinguishable from + a member of the other family; it is called by Poincare a form of + bifurcation. It is this conception of a form of bifurcation which forms + the important consideration in problems dealing with the forms of liquid + or gaseous bodies in rotation. + </p> + <p> + But to return to the general question,—thus far the stability of + these families has not been considered, and it is the stability which + renders this way of looking at the matter so valuable. It may be proved + that if before the point of bifurcation the type A + a was stable, then A + + b must have been unstable. Further as a and b each diminish A + a + becomes less pronouncedly stable, and A + b less unstable. On reaching the + point of bifurcation A + a has just ceased to be stable, or what amounts + to the same thing is just becoming unstable, and the converse is true of + the A + b family. After passing the point of bifurcation A + a has become + definitely unstable and A + b has become stable. Hence the point of + bifurcation is also a point of "exchange of stabilities between the two + types." (In order not to complicate unnecessarily this explanation of a + general principle I have not stated fully all the cases that may occur. + Thus: firstly, after bifurcation A + a may be an impossible type and A + a + will then stop at this point; or secondly, A + b may have been an + impossible type before bifurcation, and will only begin to be a real one + after it; or thirdly, both A + a and A + b may be impossible after the + point of bifurcation, in which case they coalesce and disappear. This last + case shows that types arise and disappear in pairs, and that on appearance + or before disappearance one must be stable and the other unstable.) + </p> + <p> + In nature it is of course only the stable types of motion which can + persist for more than a short time. Thus the task of the physical + evolutionist is to determine the forms of bifurcation, at which he must, + as it were, change carriages in the evolutionary journey so as always to + follow the stable route. He must besides be able to indicate some natural + process which shall correspond in effect to the ideal arrangement of the + several types of motion in families with gradually changing specific + differences. Although, as we shall see hereafter, it may frequently or + even generally be impossible to specify with exactness the forms of + bifurcation in the process of evolution, yet the conception is one of + fundamental importance. + </p> + <p> + The ideas involved in this sketch are no doubt somewhat recondite, but I + hope to render them clearer to the non-mathematical reader by homologous + considerations in other fields of thought (I considered this subject in my + Presidential address to the British Association in 1905, "Report of the + 75th Meeting of the British Assoc." (S. Africa, 1905), London, 1906, page + 3. Some reviewers treated my speculations as fanciful, but as I believe + that this was due generally to misapprehension, and as I hold that + homologous considerations as to stability and instability are really + applicable to evolution of all sorts, I have thought it well to return to + the subject in the present paper.), and I shall pass on thence to + illustrations which will teach us something of the evolution of stellar + systems. + </p> + <p> + States or governments are organised schemes of action amongst groups of + men, and they belong to various types to which generic names, such as + autocracy, aristocracy or democracy, are somewhat loosely applied. A + definite type of government corresponds to one of our types of motion, and + while retaining its type it undergoes a slow change as the civilisation + and character of the people change, and as the relationship of the nation + to other nations changes. In the language used before, the government + belongs to a family, and as time advances we proceed through the + successive members of the family. A government possesses a certain degree + of stability—hardly measurable in numbers however—to resist + disintegrating influences such as may arise from wars, famines, and + internal dissensions. This stability gradually rises to a maximum and + gradually declines. The degree of stability at any epoch will depend on + the fitness of some leading feature of the government to suit the slowly + altering circumstances, and that feature corresponds to the characteristic + denoted by a in the physical problem. A time at length arrives when the + stability vanishes, and the slightest shock will overturn the government. + At this stage we have reached the crisis of a point of bifurcation, and + there will then be some circumstance, apparently quite insignificant and + almost unnoticed, which is such as to prevent the occurrence of anarchy. + This circumstance or condition is what we typified as b. Insignificant + although it may seem, it has started the government on a new career of + stability by imparting to it a new type. It grows in importance, the form + of government becomes obviously different, and its stability increases. + Then in its turn this newly acquired stability declines, and we pass on to + a new crisis or revolution. There is thus a series of "points of + bifurcation" in history at which the continuity of political history is + maintained by means of changes in the type of government. These ideas + seem, to me at least, to give a true account of the history of states, and + I contend that it is no mere fanciful analogy but a true homology, when in + both realms of thought—the physical and the political—we + perceive the existence of forms of bifurcation and of exchanges of + stability. + </p> + <p> + Further than this, I would ask whether the same train of ideas does not + also apply to the evolution of animals? A species is well adapted to its + environment when the individual can withstand the shocks of famine or the + attacks and competition of other animals; it then possesses a high degree + of stability. Most of the casual variations of individuals are + indifferent, for they do not tell much either for or against success in + life; they are small oscillations which leave the type unchanged. As + circumstances change, the stability of the species may gradually dwindle + through the insufficiency of some definite quality, on which in earlier + times no such insistent demands were made. The individual animals will + then tend to fail in the struggle for life, the numbers will dwindle and + extinction may ensue. But it may be that some new variation, at first of + insignificant importance, may just serve to turn the scale. A new type may + be formed in which the variation in question is preserved and augmented; + its stability may increase and in time a new species may be produced. + </p> + <p> + At the risk of condemnation as a wanderer beyond my province into the + region of biological evolution, I would say that this view accords with + what I understand to be the views of some naturalists, who recognise the + existence of critical periods in biological history at which extinction + occurs or which form the starting-point for the formation of new species. + Ought we not then to expect that long periods will elapse during which a + type of animal will remain almost constant, followed by other periods, + enormously long no doubt as measured in the life of man, of acute struggle + for existence when the type will change more rapidly? This at least is the + view suggested by the theory of stability in the physical universe. (I + make no claim to extensive reading on this subject, but refer the reader + for example to a paper by Professor A.A.W. Hubrecht on "De Vries's theory + of Mutations", "Popular Science Monthly", July 1904, especially to page + 213.) + </p> + <p> + And now I propose to apply these ideas of stability to the theory of + stellar evolution, and finally to illustrate them by certain recent + observations of a very remarkable character. + </p> + <p> + Stars and planets are formed of materials which yield to the enormous + forces called into play by gravity and rotation. This is obviously true if + they are gaseous or fluid, and even solid matter becomes plastic under + sufficiently great stresses. Nothing approaching a complete study of the + equilibrium of a heterogeneous star has yet been found possible, and we + are driven to consider only bodies of simpler construction. I shall begin + therefore by explaining what is known about the shapes which may be + assumed by a mass of incompressible liquid of uniform density under the + influences of gravity and of rotation. Such a liquid mass may be regarded + as an ideal star, which resembles a real star in the fact that it is + formed of gravitating and rotating matter, and because its shape results + from the forces to which it is subject. It is unlike a star in that it + possesses the attributes of incompressibility and of uniform density. The + difference between the real and the ideal is doubtless great, yet the + similarity is great enough to allow us to extend many of the conclusions + as to ideal liquid stars to the conditions which must hold good in + reality. Thus with the object of obtaining some insight into actuality, it + is justifiable to discuss an avowedly ideal problem at some length. + </p> + <p> + The attraction of gravity alone tends to make a mass of liquid assume the + shape of a sphere, and the effects of rotation, summarised under the name + of centrifugal force, are such that the liquid seeks to spread itself + outwards from the axis of rotation. It is a singular fact that it is + unnecessary to take any account of the size of the mass of liquid under + consideration, because the shape assumed is exactly the same whether the + mass be small or large, and this renders the statement of results much + easier than would otherwise be the case. + </p> + <p> + A mass of liquid at rest will obviously assume the shape of a sphere, + under the influence of gravitation, and it is a stable form, because any + oscillation of the liquid which might be started would gradually die away + under the influence of friction, however small. If now we impart to the + whole mass of liquid a small speed of rotation about some axis, which may + be called the polar axis, in such a way that there are no internal + currents and so that it spins in the same way as if it were solid, the + shape will become slightly flattened like an orange. Although the earth + and the other planets are not homogeneous they behave in the same way, and + are flattened at the poles and protuberant at the equator. This shape may + therefore conveniently be described as planetary. + </p> + <p> + If the planetary body be slightly deformed the forces of restitution are + slightly less than they were for the sphere; the shape is stable but + somewhat less so than the sphere. We have then a planetary spheroid, + rotating slowly, slightly flattened at the poles, with a high degree of + stability, and possessing a certain amount of rotational momentum. Let us + suppose this ideal liquid star to be somewhere in stellar space far + removed from all other bodies; then it is subject to no external forces, + and any change which ensues must come from inside. Now the amount of + rotational momentum existing in a system in motion can neither be created + nor destroyed by any internal causes, and therefore, whatever happens, the + amount of rotational momentum possessed by the star must remain absolutely + constant. + </p> + <p> + A real star radiates heat, and as it cools it shrinks. Let us suppose then + that our ideal star also radiates and shrinks, but let the process proceed + so slowly that any internal currents generated in the liquid by the + cooling are annulled so quickly by fluid friction as to be insignificant; + further let the liquid always remain at any instant incompressible and + homogeneous. All that we are concerned with is that, as time passes, the + liquid star shrinks, rotates in one piece as if it were solid, and remains + incompressible and homogeneous. The condition is of course artificial, but + it represents the actual processes of nature as well as may be, + consistently with the postulated incompressibility and homogeneity. + (Mathematicians are accustomed to regard the density as constant and the + rotational momentum as increasing. But the way of looking at the matter, + which I have adopted, is easier of comprehension, and it comes to the same + in the end.) + </p> + <p> + The shrinkage of a constant mass of matter involves an increase of its + density, and we have therefore to trace the changes which supervene as the + star shrinks, and as the liquid of which it is composed increases in + density. The shrinkage will, in ordinary parlance, bring the weights + nearer to the axis of rotation. Hence in order to keep up the rotational + momentum, which as we have seen must remain constant, the mass must rotate + quicker. The greater speed of rotation augments the importance of + centrifugal force compared with that of gravity, and as the flattening of + the planetary spheroid was due to centrifugal force, that flattening is + increased; in other words the ellipticity of the planetary spheroid + increases. + </p> + <p> + As the shrinkage and corresponding increase of density proceed, the + planetary spheroid becomes more and more elliptic, and the succession of + forms constitutes a family classified according to the density of the + liquid. The specific mark of this family is the flattening or ellipticity. + </p> + <p> + Now consider the stability of the system, we have seen that the spheroid + with a slow rotation, which forms our starting-point, was slightly less + stable than the sphere, and as we proceed through the family of ever + flatter ellipsoids the stability continues to diminish. At length when it + has assumed the shape shown in a figure titled "Planetary spheroid just + becoming unstable" (Fig. 2.) where the equatorial and polar axes are + proportional to the numbers 1000 and 583, the stability has just + disappeared. According to the general principle explained above this is a + form of bifurcation, and corresponds to the form denoted A. The specific + difference a of this family must be regarded as the excess of the + ellipticity of this figure above that of all the earlier ones, beginning + with the slightly flattened planetary spheroid. Accordingly the specific + difference a of the family has gradually diminished from the beginning and + vanishes at this stage. + </p> + <p> + According to Poincare's principle the vanishing of the stability serves us + with notice that we have reached a figure of bifurcation, and it becomes + necessary to inquire what is the nature of the specific difference of the + new family of figures which must be coalescent with the old one at this + stage. This difference is found to reside in the fact that the equator, + which in the planetary family has hitherto been circular in section, tends + to become elliptic. Hitherto the rotational momentum has been kept up to + its constant value partly by greater speed of rotation and partly by a + symmetrical bulging of the equator. But now while the speed of rotation + still increases (The mathematician familiar with Jacobi's ellipsoid will + find that this is correct, although in the usual mode of exposition, + alluded to above in a footnote, the speed diminishes.), the equator tends + to bulge outwards at two diametrically opposite points and to be flattened + midway between these protuberances. The specific difference in the new + family, denoted in the general sketch by b, is this ellipticity of the + equator. If we had traced the planetary figures with circular equators + beyond this stage A, we should have found them to have become unstable, + and the stability has been shunted off along the A + b family of forms + with elliptic equators. + </p> + <p> + This new series of figures, generally named after the great mathematician + Jacobi, is at first only just stable, but as the density increases the + stability increases, reaches a maximum and then declines. As this goes on + the equator of these Jacobian figures becomes more and more elliptic, so + that the shape is considerably elongated in a direction at right angles to + the axis of rotation. + </p> + <p> + At length when the longest axis of the three has become about three times + as long as the shortest (The three axes of the ellipsoid are then + proportional to 1000, 432, 343.), the stability of this family of figures + vanishes, and we have reached a new form of bifurcation and must look for + a new type of figure along which the stable development will presumably + extend. Two sections of this critical Jacobian figure, which is a figure + of bifurcation, are shown by the dotted lines in a figure titled "The + 'pear-shaped figure' and the Jocobian figure from which it is derived" + (Fig. 3.) comprising two figures, one above the other: the upper figure is + the equatorial section at right angles to the axis of rotation, the lower + figure is a section through the axis. + </p> + <p> + Now Poincare has proved that the new type of figure is to be derived from + the figure of bifurcation by causing one of the ends to be prolonged into + a snout and by bluntening the other end. The snout forms a sort of stalk, + and between the stalk and the axis of rotation the surface is somewhat + flattened. These are the characteristics of a pear, and the figure has + therefore been called the "pear-shaped figure of equilibrium." The firm + line shows this new type of figure, whilst, as already explained, the + dotted line shows the form of bifurcation from which it is derived. The + specific mark of this new family is the protrusion of the stalk together + with the other corresponding smaller differences. If we denote this + difference by c, while A + b denotes the Jacobian figure of bifurcation + from which it is derived, the new family may be called A + b + c, and c is + zero initially. According to my calculations this series of figures is + stable (M. Liapounoff contends that for constant density the new series of + figures, which M. Poincare discovered, has less rotational momentum than + that of the figure of bifurcation. If he is correct, the figure of + bifurcation is a limit of stable figures, and none can exist with + stability for greater rotational momentum. My own work seems to indicate + that the opposite is true, and, notwithstanding M. Liapounoff's deservedly + great authority, I venture to state the conclusions in accordance with my + own work.), but I do not know at what stage of its development it becomes + unstable. + </p> + <p> + Professor Jeans has solved a problem which is of interest as throwing + light on the future development of the pear-shaped figure, although it is + of a still more ideal character than the one which has been discussed. He + imagines an INFINITELY long circular cylinder of liquid to be in rotation + about its central axis. The existence is virtually postulated of a demon + who is always occupied in keeping the axis of the cylinder straight, so + that Jeans has only to concern himself with the stability of the form of + the section of the cylinder, which as I have said is a circle with the + axis of rotation at the centre. He then supposes the liquid forming the + cylinder to shrink in diameter, just as we have done, and finds that the + speed of rotation must increase so as to keep up the constancy of the + rotational momentum. The circularity of section is at first stable, but as + the shrinkage proceeds the stability diminishes and at length vanishes. + This stage in the process is a form of bifurcation, and the stability + passes over to a new series consisting of cylinders which are elliptic in + section. The circular cylinders are exactly analogous with our planetary + spheroids, and the elliptic ones with the Jacobian ellipsoids. + </p> + <p> + With further shrinkage the elliptic cylinders become unstable, a new form + of bifurcation is reached, and the stability passes over to a series of + cylinders whose section is pear-shaped. Thus far the analogy is complete + between our problem and Jeans's, and in consequence of the greater + simplicity of the conditions, he is able to carry his investigation + further. He finds that the stalk end of the pear-like section continues to + protrude more and more, and the flattening between it and the axis of + rotation becomes a constriction. Finally the neck breaks and a satellite + cylinder is born. Jeans's figure for an advanced stage of development is + shown in a figure titled "Section of a rotating cylinder of liquid" (Fig. + 4.), but his calculations do not enable him actually to draw the state of + affairs after the rupture of the neck. + </p> + <p> + There are certain difficulties in admitting the exact parallelism between + this problem and ours, and thus the final development of our pear-shaped + figure and the end of its stability in a form of bifurcation remain hidden + from our view, but the successive changes as far as they have been + definitely traced are very suggestive in the study of stellar evolution. + </p> + <p> + Attempts have been made to attack this problem from the other end. If we + begin with a liquid satellite revolving about a liquid planet and proceed + backwards in time, we must make the two masses expand so that their + density will be diminished. Various figures have been drawn exhibiting the + shapes of two masses until their surfaces approach close to one another + and even until they just coalesce, but the discussion of their stability + is not easy. At present it would seem to be impossible to reach + coalescence by any series of stable transformations, and if this is so + Professor Jeans's investigation has ceased to be truly analogous to our + problem at some undetermined stage. However this may be this line of + research throws an instructive light on what we may expect to find in the + evolution of real stellar systems. + </p> + <p> + In the second part of this paper I shall point out the bearing which this + investigation of the evolution of an ideal liquid star may have on the + genesis of double stars. + </p> + <p> + II. + </p> + <p> + There are in the heavens many stars which shine with a variable + brilliancy. Amongst these there is a class which exhibits special + peculiarities; the members of this class are generally known as Algol + Variables, because the variability of the star Beta Persei or Algol was + the first of such cases to attract the attention of astronomers, and + because it is perhaps still the most remarkable of the whole class. But + the circumstances which led to this discovery were so extraordinary that + it seems worth while to pause a moment before entering on the subject. + </p> + <p> + John Goodricke, a deaf-mute, was born in 1764; he was grandson and heir of + Sir John Goodricke of Ribston Hall, Yorkshire. In November 1782, he noted + that the brilliancy of Algol waxed and waned (It is said that Georg + Palitzch, a farmer of Prohlis near Dresden, had about 1758 already noted + the variability of Algol with the naked eye. "Journ. Brit. Astron. Assoc." + Vol. XV. (1904-5), page 203.), and devoted himself to observing it on + every fine night from the 28th December 1782 to the 12th May 1783. He + communicated his observations to the Royal Society, and suggested that the + variation in brilliancy was due to periodic eclipses by a dark companion + star, a theory now universally accepted as correct. The Royal Society + recognised the importance of the discovery by awarding to Goodricke, then + only 19 years of age, their highest honour, the Copley medal. His later + observations of Beta Lyrae and of Delta Cephei were almost as remarkable + as those of Algol, but unfortunately a career of such extraordinary + promise was cut short by death, only a fortnight after his election to the + Royal Society. ("Dict. of National Biography"; article Goodricke (John). + The article is by Miss Agnes Clerke. It is strange that she did not then + seem to be aware that he was a deaf-mute, but she notes the fact in her + "Problems of Astrophysics", page 337, London, 1903.) + </p> + <p> + It was not until 1889 that Goodricke's theory was verified, when it was + proved by Vogel that the star was moving in an orbit, and in such a manner + that it was only possible to explain the rise and fall in the luminosity + by the partial eclipse of a bright star by a dark companion. + </p> + <p> + The whole mass of the system of Algol is found to be half as great again + as that of our sun, yet the two bodies complete their orbit in the short + period of 2d 20h 48m 55s. The light remains constant during each period, + except for 9h 20m when it exhibits a considerable fall in brightness + (Clerke, "Problems of Astrophysics" page 302 and chapter XVIII.); the + curve which represents the variation in the light is shown in a figure + titled "The light-curve and system of Beta Lyrae" (Fig. 7.). + </p> + <p> + The spectroscope has enabled astronomers to prove that many stars, + although apparently single, really consist of two stars circling around + one another (If a source of light is approaching with a great velocity the + waves of light are crowded together, and conversely they are spaced out + when the source is receding. Thus motion in the line of sight virtually + produces an infinitesimal change of colour. The position of certain dark + lines in the spectrum affords an exceedingly accurate measurement of + colour. Thus displacements of these spectral lines enables us to measure + the velocity of the source of light towards or away from the observer.); + they are known as spectroscopic binaries. Campbell of the Lick Observatory + believes that about one star in six is a binary ("Astrophysical Journ." + Vol. XIII. page 89, 1901. See also A. Roberts, "Nature", Sept. 12, 1901, + page 468.); thus there must be many thousand such stars within the reach + of our spectroscopes. + </p> + <p> + The orientation of the planes of the orbits of binary stars appears to be + quite arbitrary, and in general the star does not vary in brightness. + Amongst all such orbits there must be some whose planes pass nearly + through the sun, and in these cases the eclipse of one of the stars by the + other becomes inevitable, and in each circuit there will occur two + eclipses of unequal intensities. + </p> + <p> + It is easy to see that in the majority of such cases the two components + must move very close to one another. + </p> + <p> + The coincidence between the spectroscopic and the photometric evidence + permits us to feel complete confidence in the theory of eclipses. When + then we find a star with a light-curve of perfect regularity and with a + characteristics of that of Algol, we are justified in extending the theory + of eclipses to it, although it may be too faint to permit of adequate + spectroscopic examination. This extension of the theory secures a + considerable multiplication of the examples available for observation, and + some 30 have already been discovered. + </p> + <p> + Dr Alexander Roberts, of Lovedale in Cape Colony, truly remarks that the + study of Algol variables "brings us to the very threshold of the question + of stellar evolution." ("Proc. Roy. Soc. Edinburgh", XXIV. Part II. + (1902), page 73.) It is on this account that I propose to explain in some + detail the conclusion to which he and some other observers have been led. + </p> + <p> + Although these variable stars are mere points of light, it has been proved + by means of the spectroscope that the law of gravitation holds good in the + remotest regions of stellar space, and further it seems now to have become + possible even to examine the shapes of stars by indirect methods, and thus + to begin the study of their evolution. The chain of reasoning which I + shall explain must of necessity be open to criticism, yet the explanation + of the facts by the theory is so perfect that it is not easy to resist the + conviction that we are travelling along the path of truth. + </p> + <p> + The brightness of a star is specified by what is called its "magnitude." + The average brightness of all the stars which can just be seen with the + naked eye defines the sixth magnitude. A star which only gives two-fifths + as much light is said to be of the seventh magnitude; while one which + gives 2 1/2 times as much light is of the fifth magnitude, and successive + multiplications or divisions by 2 1/2 define the lower or higher + magnitudes. Negative magnitudes have clearly to be contemplated; thus + Sirius is of magnitude minus 1.4, and the sun is of magnitude minus 26. + </p> + <p> + The definition of magnitude is also extended to fractions; for example, + the lights given by two candles which are placed at 100 feet and 100 feet + 6 inches from the observer differ in brightness by one-hundredth of a + magnitude. + </p> + <p> + A great deal of thought has been devoted to the measurement of the + brightness of stars, but I will only describe one of the methods used, + that of the great astronomer Argelander. In the neighbourhood of the star + under observation some half dozen standard stars are selected of known + invariable magnitudes, some being brighter and some fainter than the star + to be measured; so that these stars afford a visible scale of brightness. + Suppose we number them in order of increasing brightness from 1 to 6; then + the observer estimates that on a given night his star falls between stars + 2 and 3, on the next night, say between 3 and 4, and then again perhaps it + may return to between 2 and 3, and so forth. With practice he learns to + evaluate the brightness down to small fractions of a magnitude, even a + hundredth part of a magnitude is not quite negligible. + </p> + <p> + For example, in observing the star RR Centauri five stars were in general + used for comparison by Dr Roberts, and in course of three months he + secured thereby 300 complete observations. When the period of the cycle + had been ascertained exactly, these 300 values were reduced to mean values + which appertained to certain mean places in the cycle, and a mean + light-curve was obtained in this way. Figures titled "Light curve of RR + Centauri" (Fig. 5) and "The light-curve and system of Beta Lyrae" (Fig. 7) + show examples of light curves. + </p> + <p> + I shall now follow out the results of the observation of RR Centauri not + only because it affords the easiest way of explaining these + investigations, but also because it is one of the stars which furnishes + the most striking results in connection with the object of this essay. + (See "Monthly notices R.A.S." Vol. 63, 1903, page 527.) This star has a + mean magnitude of about 7 1/2, and it is therefore invisible to the naked + eye. Its period of variability is 14h 32m 10s.76, the last refinement of + precision being of course only attained in the final stages of reduction. + Twenty-nine mean values of the magnitude were determined, and they were + nearly equally spaced over the whole cycle of changes. The black dots in + Fig. 5 exhibit the mean values determined by Dr Roberts. The last three + dots on the extreme right are merely the same as the first three on the + extreme left, and are repeated to show how the next cycle would begin. The + smooth dotted curve will be explained hereafter, but, by reference to the + scale of magnitudes on the margins of the figure, it may be used to note + that the dots might be brought into a perfectly smooth curve by shifting + some few of the dots by about a hundredth of a magnitude. + </p> + <p> + This light-curve presents those characteristics which are due to + successive eclipses, but the exact form of the curve must depend on the + nature of the two mutually eclipsing stars. If we are to interpret the + curve with all possible completeness, it is necessary to make certain + assumptions as to the stars. It is assumed then that the stars are equally + bright all over their disks, and secondly that they are not surrounded by + an extensive absorptive atmosphere. This last appears to me to be the most + dangerous assumption involved in the whole theory. + </p> + <p> + Making these assumptions, however, it is found that if each of the + eclipsing stars were spherical it would not be possible to generate such a + curve with the closest accuracy. The two stars are certainly close + together, and it is obvious that in such a case the tidal forces exercised + by each on the other must be such as to elongate the figure of each + towards the other. Accordingly it is reasonable to adopt the hypothesis + that the system consists of a pair of elongated ellipsoids, with their + longest axes pointed towards one another. No supposition is adopted a + priori as to the ratio of the two masses, or as to their relative size or + brightness, and the orbit may have any degree of eccentricity. These last + are all to be determined from the nature of the light-curve. + </p> + <p> + In the case of RR Centauri, however, Dr Roberts finds the conditions are + best satisfied by supposing the orbit to be circular, and the sizes and + masses of the components to be equal, while their luminosities are to one + another in the ratio of 4 to 3. As to their shapes he finds them to be so + much elongated that they overlap, as exhibited in his figure titled "The + shape of the star RR Centauri" (Fig. 6.). The dotted curve shows a form of + equilibrium of rotating liquid as computed by me some years before, and it + was added for the sake of comparison. + </p> + <p> + On turning back to Fig. 5 the reader will see in the smooth dotted curve + the light variation which would be exhibited by such a binary system as + this. The curve is the result of computation and it is impossible not to + be struck by the closeness of the coincidence with the series of black + dots which denote the observations. + </p> + <p> + It is virtually certain that RR Centauri is a case of an eclipsing binary + system, and that the two stars are close together. It is not of course + proved that the figures of the stars are ellipsoids, but gravitation must + deform them into a pair of elongated bodies, and, on the assumptions that + they are not enveloped in an absorptive atmosphere and that they are + ellipsoidal, their shapes must be as shown in the figure. + </p> + <p> + This light-curve gives an excellent illustration of what we have reason to + believe to be a stage in the evolution of stars, when a single star is + proceeding to separate into a binary one. + </p> + <p> + As the star is faint, there is as yet no direct spectroscopic evidence of + orbital motion. Let us turn therefore to the case of another star, namely + V Puppis, in which such evidence does already exist. I give an account of + it, because it presents a peculiarly interesting confirmation of the + correctness of the theory. + </p> + <p> + In 1895 Pickering announced in the "Harvard Circular" No. 14 that the + spectroscopic observations at Arequipa proved V Puppis to be a double star + with a period of 3d 2h 46m. Now when Roberts discussed its light-curve he + found that the period was 1d 10h 54m 27s, and on account of this serious + discrepancy he effected the reduction only on the simple assumption that + the two stars were spherical, and thus obtained a fairly good + representation of the light-curve. It appeared that the orbit was circular + and that the two spheres were not quite in contact. Obviously if the stars + had been assumed to be ellipsoids they would have been found to overlap, + as was the case for RR Centauri. ("Astrophysical Journ." Vol. XIII. + (1901), page 177.) The matter rested thus for some months until the + spectroscopic evidence was re-examined by Miss Cannon on behalf of + Professor Pickering, and we find in the notes on page 177 of Vol. XXVIII. + of the "Annals of the Harvard Observatory" the following: "A.G.C. 10534. + This star, which is the Algol variable V Puppis, has been found to be a + spectroscopic binary. The period 1d.454 (i.e. 1d 10h 54m) satisfies the + observations of the changes in light, and of the varying separation of the + lines of the spectrum. The spectrum has been examined on 61 plates, on 23 + of which the lines are double." Thus we have valuable evidence in + confirmation of the correctness of the conclusions drawn from the + light-curve. In the circumstances, however, I have not thought it worth + while to reproduce Dr Roberts's provisional figure. + </p> + <p> + I now turn to the conclusions drawn a few years previously by another + observer, where we shall find the component stars not quite in contact. + This is the star Beta Lyrae which was observed by Goodricke, Argelander, + Belopolsky, Schur, Markwick and by many others. The spectroscopic method + has been successfully applied in this case, and the component stars are + proved to move in an orbit about one another. In 1897, Mr. G.W. Myers + applied the theory of eclipses to the light-curve, on the hypothesis that + the stars are elongated ellipsoids, and he obtained the interesting + results exhibited in Fig. 7. ("Astrophysical Journ." Vol. VII. (1898), + page 1.) + </p> + <p> + The period of Beta Lyrae is relatively long, being 12d 21h 47m, the orbit + is sensibly eccentric, and the two spheroids are not so much elongated as + was the case with RR Centauri. The mass of the system is enormous, one of + the two stars being 10 times and the other 21 times as heavy as our sun. + </p> + <p> + Further illustrations of this subject might be given, but enough has been + said to explain the nature of the conclusions which have been drawn from + this class of observation. + </p> + <p> + In my account of these remarkable systems the consideration of one very + important conclusion has been purposely deferred. Since the light-curve is + explicable by eclipses, it follows that the sizes of the two stars are + determinable relatively to the distance between them. The period of their + orbital motion is known, being identical with the complete period of the + variability of their light, and an easy application of Kepler's law of + periodic times enables us to compute the sum of the masses of the two + stars divided by the cube of the distance between their centres. Now the + sizes of the bodies being known, the mean density of the whole system may + be calculated. In every case that density has been found to be much less + than the sun's, and indeed the average of a number of mean densities which + have been determined only amounts to one-eighth of that of the sun. In + some cases the density is extremely small, and in no case is it quite so + great as half the solar density. + </p> + <p> + It would be absurd to suppose that these stars can be uniform in density + throughout, and from all that is known of celestial bodies it is probable + that they are gaseous in their external parts with great condensation + towards their centres. This conclusion is confirmed by arguments drawn + from the theory of rotating masses of liquid. (See J.H. Jeans, "On the + density of Algol variables", "Astrophysical Journ." Vol. XXII. (1905), + page 97.) + </p> + <p> + Although, as already explained, a good deal is known about the shapes and + the stability of figures consisting of homogeneous incompressible liquid + in rotation, yet comparatively little has hitherto been discovered about + the equilibrium of rotating gaseous stars. The figures calculated for + homogeneous liquid can obviously only be taken to afford a general + indication of the kind of figure which we might expect to find in the + stellar universe. Thus the dotted curve in Fig. 5, which exhibits one of + the figures which I calculated, has some interest when placed alongside + the figures of the stars in RR Centauri, as computed from the + observations, but it must not be accepted as the calculated form of such a + system. I have moreover proved more recently that such a figure of + homogeneous liquid is unstable. Notwithstanding this instability it does + not necessarily follow that the analogous figure for compressible fluid is + also unstable, as will be pointed out more fully hereafter. + </p> + <p> + Professor Jeans has discussed in a paper of great ability the difficult + problems offered by the conditions of equilibrium and of stability of a + spherical nebula. ("Phil. Trans. R.S." Vol. CXCIX. A (1902), page 1. See + also A. Roberts, "S. African Assoc. Adv. Sci." Vol. I. (1903), page 6.) In + a later paper ("Astrophysical Journ." Vol. XXII. (1905), page 97.), in + contrasting the conditions which must govern the fission of a star into + two parts when the star is gaseous and compressible with the corresponding + conditions in the case of incompressible liquid, he points out that for a + gaseous star (the agency which effects the separation will no longer be + rotation alone; gravitation also will tend towards separation... From + numerical results obtained in the various papers of my own,... I have been + led to the conclusion that a gravitational instability of the kind + described must be regarded as the primary agent at work in the actual + evolution of the universe, Laplace's rotation playing only the secondary + part of separating the primary and satellite after the birth of the + satellite.) + </p> + <p> + It is desirable to add a word in explanation of the expression + "gravitational instability" in this passage. It means that when the + concentration of a gaseous nebula (without rotation) has proceeded to a + certain stage, the arrangement in spherical layers of equal density + becomes unstable, and a form of bifurcation has been reached. For further + concentration concentric spherical layers become unstable, and the new + stable form involves a concentration about two centres. The first sign of + this change is that the spherical layers cease to be quite concentric and + then the layers of equal density begin to assume a somewhat pear-shaped + form analogous to that which we found to occur under rotation for an + incompressible liquid. Accordingly it appears that while a sphere of + liquid is stable a sphere of gas may become unstable. Thus the conditions + of stability are different in these two simple cases, and it is likely + that while certain forms of rotating liquid are unstable the analogous + forms for gas may be stable. This furnishes a reason why it is worth while + to consider the unstable forms of rotating liquid. + </p> + <p> + There can I think be little doubt but that Jeans is right in looking to + gravitational instability as the primary cause of fission, but when we + consider that a binary system, with a mass larger than the sun's, is found + to rotate in a few hours, there seems reason to look to rotation as a + contributory cause scarcely less important than the primary one. + </p> + <p> + With the present extent of our knowledge it is only possible to + reconstruct the processes of the evolution of stars by means of inferences + drawn from several sources. We have first to rely on the general + principles of stability, according to which we are to look for a series of + families of forms, each terminating in an unstable form, which itself + becomes the starting-point of the next family of stable forms. Secondly we + have as a guide the analogy of the successive changes in the evolution of + ideal liquid stars; and thirdly we already possess some slender knowledge + as to the equilibrium of gaseous stars. + </p> + <p> + From these data it is possible to build up in outline the probable history + of binary stars. Originally the star must have been single, it must have + been widely diffused, and must have been endowed with a slow rotation. In + this condition the strata of equal density must have been of the planetary + form. As it cooled and contracted the symmetry round the axis of rotation + must have become unstable, through the effects of gravitation, assisted + perhaps by the increasing speed of rotation. (I learn from Professor Jeans + that he now (December 1908) believes that he can prove that some small + amount of rotation is necessary to induce instability in the symmetrical + arrangement.) The strata of equal density must then become somewhat + pear-shaped, and afterwards like an hour-glass, with the constriction more + pronounced in the internal than in the external strata. The constrictions + of the successive strata then begin to rupture from the inside + progressively outwards, and when at length all are ruptured we have the + twin stars portrayed by Roberts and by others. + </p> + <p> + As we have seen, the study of the forms of equilibrium of rotating liquid + is almost complete, and Jeans has made a good beginning in the + investigation of the equilibrium of gaseous stars, but much more remains + to be discovered. The field for the mathematician is a wide one, and in + proportion as the very arduous exploration of that field is attained so + will our knowledge of the processes of cosmical evolution increase. + </p> + <p> + From the point of view of observation, improved methods in the use of the + spectroscope and increase of accuracy in photometry will certainly lead to + a great increase in our knowledge within the next few years. Probably the + observational advance will be more rapid than that of theory, for we know + how extraordinary has been the success attained within the last few years, + and the theory is one of extreme difficulty; but the two ought to proceed + together hand in hand. Human life is too short to permit us to watch the + leisurely procedure of cosmical evolution, but the celestial museum + contains so many exhibits that it may become possible, by the aid of + theory, to piece together bit by bit the processes through which stars + pass in the course of their evolution. + </p> + <p> + In the sketch which I have endeavoured to give of this fascinating + subject, I have led my reader to the very confines of our present + knowledge. It is not much more than a quarter of a century since this + class of observation has claimed the close attention of astronomers; + something considerable has been discovered already and there seems + scarcely a discernible limit to what will be known in this field a century + from now. Some of the results which I have set forth may then be shown to + be false, but it seems profoundly improbable that we are being led astray + by a Will-of-the-Wisp. + </p> + <p> + <a name="link2H_4_0031" id="link2H_4_0031"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + XXIX. THE EVOLUTION OF MATTER. By W.C.D. Whetham, M.A., F.R.S. + </h2> + <h3> + Trinity College, Cambridge. + </h3> + <p> + The idea of evolution in the organic world, made intelligible by the work + of Charles Darwin, has little in common with the recent conception of + change in certain types of matter. The discovery that a process of + disintegration may take place in some at least of the chemical atoms, + previously believed to be indestructible and unalterable, has modified our + view of the physical universe, even as Darwin's scheme of the mode of + evolution changed the trend of thought concerning the organic world. Both + conceptions have in common the idea of change throughout extended realms + of space and time, and, therefore, it is perhaps not unfitting that some + account of the most recent physical discoveries should be included in the + present volume. + </p> + <p> + The earliest conception of the evolution of matter is found in the + speculation of the Greeks. Leucippus and Democritus imagined unchanging + eternal atoms, Heracleitus held that all things were in a continual state + of flux—Panta rei. + </p> + <p> + But no one in the Ancient World—no one till quite modern times—could + appreciate the strength of the position which the theory of the evolution + of matter must carry before it wins the day. Vague speculation, even by + the acute minds of philosophers, is of little use in physical science + before experimental facts are available. The true problems at issue cannot + even be formulated, much less solved, till the humble task of the observer + and experimenter has given us a knowledge of the phenomena to be + explained. + </p> + <p> + It was only through the atomic theory, at first apparently diametrically + opposed to it, that the conception of evolution in the physical world was + to gain an established place. For a century the atomic theory, when put + into a modern form by Dalton, led farther and farther away from the idea + of change in matter. The chemical elements seemed quite unalterable, and + the atoms, of which each element in modern view is composed, bore to Clerk + Maxwell, writing about 1870, "the stamp of manufactured articles" exactly + similar in kind, unchanging, eternal. + </p> + <p> + Nevertheless throughout these years, on the whole so unfavourable to its + existence, there persisted the idea of a common origin of the distinct + kinds of matter known to chemists. Indeed, this idea of unity in substance + in nature seems to accord with some innate desire or intimate structure of + the human mind. As Mr Arthur Balfour well puts it, "There is no a priori + reason that I know of for expecting that the material world should be a + modification of a single medium, rather than a composite structure built + out of sixty or seventy elementary substances, eternal and eternally + different. Why then should we feel content with the first hypothesis and + not with the second? Yet so it is. Men of science have always been restive + under the multiplication of entities. They have eagerly watched for any + sign that the different chemical elements own a common origin, and are all + compounded out of some primordial substance. Nor, for my part, do I think + that such instincts should be ignored... that they exist is certain; that + they modify the indifferent impartiality of pure empiricism can hardly be + denied." ("Report of the 74th Meeting of the British Association" + (Presidential Address, Cambridge 1904), page 9, London, 1905.) + </p> + <p> + When Dalton's atomic theory had been in existence some half century, it + was noted that certain numerical relations held good between the atomic + weights of elements chemically similar to one another. Thus the weight + (88) of an atom of strontium compared with that of hydrogen as unity, is + about the mean of those of calcium (40) and barium (137). Such relations, + in this and other chemical groups, were illustrated by Beguyer de + Chancourtois in 1862 by the construction of a spiral diagram in which the + atomic weights are placed in order round a cylinder and elements + chemically similar are found to fall on vertical lines. + </p> + <p> + Newlands seems to have been the first to see the significance of such a + diagram. In his "law of octaves," formulated in 1864, he advanced the + hypothesis that, if arranged in order of rising atomic weight, the + elements fell into groups, so that each eighth element was chemically + similar. Stated thus, the law was too definite; no room was left for + newly-discovered elements, and some dissimilar elements were perforce + grouped together. + </p> + <p> + But in 1869 Mendeleeff developed Newland's hypothesis in a form that + attracted at once general attention. Placing the elements in order of + rising atomic weight, but leaving a gap where necessary to bring similar + elements into vertical columns, he obtained a periodic table with natural + vacancies to be filled as new elements were discovered, and with a certain + amount of flexibility at the ends of the horizontal lines. From the + position of the vacancies, the general chemical and physical properties of + undiscovered elements could be predicted, and the success of such + predictions gave a striking proof of the usefulness of Mendeleeff's + generalisation. + </p> + <p> + When the chemical and physical properties of the elements were known to be + periodic functions of their atomic weights, the idea of a common origin + and common substance became much more credible. Differences in atomic + weight and differences in properties alike might reasonably be explained + by the differences in the amount of the primordial substance present in + the various atoms; an atom of oxygen being supposed to be composed of + sixteen times as much stuff as the atom of hydrogen, but to be made of the + same ultimate material. Speculations about the mode of origin of the + elements now began to appear, and put on a certain air of reality. Of + these speculations perhaps the most detailed was that of Crookes, who + imagined an initial chaos of a primordial medium he named protyle, and a + process of periodic change in which the chemical elements successively + were precipitated. + </p> + <p> + From another side too, suggestions were put forward by Sir Norman Lockyer + and others that the differences in spectra observed in different classes + of stars, and produced by different conditions in the laboratory, were to + be explained by changes in the structure of the vibrating atoms. + </p> + <p> + The next step in advance gave a theoretical basis for the idea of a common + structure of matter, and was taken in an unexpected direction. Clerk + Maxwell's electromagnetic theory of light, accepted in England, was driven + home to continental minds by the confirmatory experiments of Hertz, who in + 1888 detected and measured the electromagnetic waves that Maxwell had + described twenty years earlier. But, if light be an electromagnetic + phenomenon, the light waves radiated by hot bodies must take their origin + in the vibrations of electric systems. Hence within the atoms must exist + electric charges capable of vibration. On these lines Lorentz and Larmor + have developed an electronic theory of matter, which is imagined in its + essence to be a conglomerate of electric charges, with electro-magnetic + inertia to explain mechanical inertia. (Larmor, "Aether and Matter", + Cambridge, 1900.) The movement of electric charges would be affected by a + magnetic field, and hence the discovery by Zeeman that the spectral lines + of sodium were doubled by a strong magnetic force gave confirmatory + evidence to the theory of electrons. + </p> + <p> + Then came J.J. Thomson's great discovery of minute particles, much smaller + than any chemical atom, forming a common constituent of many different + kinds of matter. (Thomson, "Conduction of Electricity through Gases" (2nd + edition), Cambridge, 1906.) If an electric discharge be passed between + metallic terminals through a glass vessel containing air at very low + pressure, it is found that rectilinear rays, known as cathode rays, + proceed from the surface of the cathode or negative terminal. Where these + rays strike solid objects, they give rise to the Rontgen rays now so well + known; but it is with the cathode rays themselves that we are concerned. + When they strike an insulated conductor, they impart to it a negative + charge, and Thomson found that they were deflected from their path both by + magnetic and electric forces in the direction in which negatively + electrified particles would be deflected. Cathode rays then were accepted + as flights of negatively charged particles, moving with high velocities. + The electric and magnetic deflections give two independent measurements + which may be made on a cathode ray, and both the deflections involve + theoretically three unknown quantities, the mass of the particles, their + electric charge and their velocity. There is strong cumulative evidence + that all such particles possess the same charge, which is identical with + that associated with a univalent atom in electrolytic liquids. The number + of unknown quantities was thus reduced to two—the mass and the + velocity. The measurement of the magnetic and electric deflections gave + two independent relations between the unknowns, which could therefore be + determined. The velocities of the cathode ray particles were found to vary + round a value about one-tenth that of light, but the mass was found always + to be the same within the limits of error, whatever the nature of the + terminals, of the residual gas in the vessel, and of the conditions of the + experiment. The mass of a cathode ray particle, or corpuscle, as Thomson, + adopting Newton's name, called it, is about the eight-hundredth part of + the mass of a hydrogen atom. + </p> + <p> + These corpuscles, found in so many different kinds of substance, are + inevitably regarded as a common constituent of matter. They are associated + each with a unit of negative electricity. Now electricity in motion + possesses electromagnetic energy, and produces effects like those of + mechanical inertia. In other words, an electric charge possesses mass, and + there is evidence to show that the effective mass of a corpuscle increases + as its velocity approaches that of light in the way it would do if all its + mass were electromagnetic. We are led therefore to regard the corpuscle + from one aspect as a disembodied charge of electricity, and to identify it + with the electron of Lorentz and Larmor. + </p> + <p> + Thus, on this theory, matter and electricity are identified; and a great + simplification of our conception of the physical structure of Nature is + reached. Moreover, from our present point of view, a common basis for + matter suggests or implies a common origin, and a process of development + possibly intelligible to our minds. The idea of the evolution of matter + becomes much more probable. + </p> + <p> + The question of the nature and physical meaning of a corpuscle or electron + remains for consideration. On the hypothesis of a universal luminiferous + aether, Larmor has suggested a centre of aethereal strain "a place where + the continuity of the medium has been broken and cemented together again + (to use a crude but effective image) without accurately fitting the parts, + so that there is a residual strain all round the place." (Larmor, loc. + cit.) Thus he explains in quasi-mechanical terms the properties of an + electron. But whether we remain content for the time with our + identification of matter and electricity, or attempt to express both of + them in terms of hypothetical aether, we have made a great step in advance + on the view that matter is made up of chemical atoms fundamentally + distinct and eternally isolated. + </p> + <p> + Such was the position when the phenomena of radio-activity threw a new + light on the problem, and, for the first time in the history of science, + gave definite experimental evidence of the transmutation of matter from + one chemical element to another. + </p> + <p> + In 1896 H. Becquerel discovered that compounds of the metal uranium + continually emitted rays capable of penetrating opaque screens and + affecting photographic plates. Like cathode and Rontgen rays, the rays + from uranium make the air through which they pass a conductor of + electricity, and this property gives the most convenient method of + detecting the rays and of measuring their intensity. An electroscope may + be made of a strip of gold-leaf attached to an insulated brass plate and + confined in a brass vessel with glass windows. When the gold-leaf is + electrified, it is repelled from the similarly electrified brass plate, + and the angle at which it stands out measures the electrification. Such a + system, if well insulated, holds its charge for hours, the leakage of + electricity through the air being very slow. But, if radio-active + radiation reach the air within, the gold-leaf falls, and the rate of its + fall, as watched through a microscope with a scale in the eye-piece, + measures the intensity of the radiation. With some form of this simple + instrument, or with the more complicated quadrant electrometer, most + radio-active measurements have been made. + </p> + <p> + It was soon discovered that the activity of uranium compounds was + proportional to the amount of uranium present in them. Thus radio-activity + is an atomic property dependent on the amount of an element and + independent of its state of chemical combination. + </p> + <p> + In a search for radio-activity in different minerals, M. and Mme Curie + found a greater effect in pitch-blende than its contents of uranium + warranted, and, led by the radio-active property alone, they succeeded, by + a long series of chemical separations, in isolating compounds of a new and + intensely radio-active substance which they named radium. + </p> + <p> + Radium resembles barium in its chemical properties, and is precipitated + with barium in the ordinary course of chemical analysis. It is separated + by a prolonged course of successive crystallisation, the chloride of + radium being less soluble than that of barium, and therefore sooner + separated from an evaporating solution. When isolated, radium chloride has + a composition, which, on the assumption that one atom of metal combines + with two of chlorine as in barium chloride, indicates that the relative + weight of the atom of radium is about 225. As thus prepared, radium is a + well-marked chemical element, forming a series of compounds analogous to + those of barium and showing a characteristic line spectrum. But, unlike + most other chemical elements, it is intensely radio-active, and produces + effects some two million times greater than those of uranium. + </p> + <p> + In 1899 E. Rutherford, then of Montreal, discovered that the radiation + from uranium, thorium and radium was complex. (Rutherford, + "Radio-activity" (2nd edition), Cambridge, 1905.) Three types of rays were + soon distinguished. The first, named by Rutherford alpha-rays, are + absorbed by thin metal foil or a few centimetres of air. When examined by + measurements of the deflections caused by magnetic and electric fields, + the alpha-rays are found to behave as would positively electrified + particles of the magnitude of helium atoms possessing a double ionic + charge and travelling with a velocity about one-tenth that of light. The + second or beta type of radiation is much more penetrating. It will pass + through a considerable thickness of metallic foil, or many centimetres of + air, and still affect photographic plates or discharge electroscopes. + Magnetic and electric forces deflect beta-rays much more than alpha-rays, + indicating that, although the speed is greater, approaching in some cases + within five per cent. that of light, the mass is very much less. The + beta-rays must be streams of particles, identical with those of cathode + rays, possessing the minute mass of J.J. Thomson's corpuscle, some + eight-hundredth part of that of a hydrogen atom. A third or gamma type of + radiation was also detected. More penetrating even than beta-rays, the + gamma-rays have never been deflected by any magnetic or electric force yet + applied. Like Rontgen rays, it is probable that gamma-rays are wave-pulses + in the luminiferous aether, though the possibility of explaining them as + flights of non-electrified particles is before the minds of some + physicists. + </p> + <p> + Still another kind of radiation has been discovered more recently by + Thomson, who has found that in high vacua, rays become apparent which are + absorbed at once by air at any ordinary pressure. + </p> + <p> + The emission of all these different types of radiation involves a + continual drain of energy from the radio-active body. When M. and Mme + Curie had prepared as much as a gramme of radium chloride, the energy of + the radiation became apparent as an evolution of heat. The radium salt + itself, and the case containing it, absorbed the major part of the + radiation, and were thus maintained at a temperature measurably higher + than that of the surroundings. The rate of thermal evolution was such that + it appeared that one gramme of pure radium must emit about 100 + gramme-calories of heat in an hour. This observation, naturally as it + follows from the phenomena previously discovered, first called attention + to the question of the source of the energy which maintains indefinitely + and without apparent diminution the wonderful stream of radiation + proceeding from a radio-active substance. In the solution of this problem + lies the point of the present essay. + </p> + <p> + In order to appreciate the evidence which bears on the question we must + now describe two other series of phenomena. + </p> + <p> + It is a remarkable fact that the intensity of the radiation from a + radio-active body is independent of the external conditions of + temperature, pressure, etc. which modify so profoundly almost all other + physical and chemical processes. Exposure to the extreme cold of liquid + air, or to the great heat of a furnace, leaves the radio-activity of a + substance unchanged, apparent exceptions to this statement having been + traced to secondary causes. + </p> + <p> + Then, it is found that radio-activity is always accompanied by some + chemical change; a new substance always appears as the parent substance + emits these radiations. Thus by chemical reactions it is possible to + separate from uranium and thorium minute quantities of radio-active + materials to which the names of uranium-X and thorium-X have been given. + These bodies behave differently from their parents uranium and thorium, + and show all the signs of distinct chemical individuality. They are + strongly radio-active, while, after the separation, the parents uranium + and thorium are found to have lost some of their radio-activity. If the + X-substances be kept, their radio-activity decays, while that of the + uranium or thorium from which they were obtained gradually rises to the + initial value it had before the separation. At any moment, the sum of the + radio-activity is constant, the activity lost by the product being equal + to that gained by the parent substance. These phenomena are explained if + we suppose that the X-product is slowly produced in the substance of the + parent, and decays at a constant rate. Uranium, as usually seen, contains + a certain amount of uranium-X, and its radio-activity consists of two + parts—that of the uranium itself, and that of the X product. When + the latter is separated by means of its chemical reactions, its + radio-activity is separated also, and the rates of decay and recovery may + be examined. + </p> + <p> + Radium and thorium, but not uranium, give rise to radio-active gases which + have been called emanations. Rutherford has shown that their + radio-activity, like that of the X products, suffers decay, while the + walls of the vessel in which the emanation is confined, become themselves + radio-active. If washed with certain acids, however, the walls lose their + activity, which is transferred to the acid, and can be deposited by + evaporation from it on to a solid surface. Here again it is clear that the + emanation gives rise to a radio-active substance which clings to the walls + of the vessel, and is soluble in certain liquids, but not in others. + </p> + <p> + We shall return to this point, and trace farther the history of the + radio-active matter. At present we wish to emphasise the fact that, as in + other cases, the radio-activity of the emanation is accompanied by the + appearance of a new kind of substance with distinct chemical properties. + </p> + <p> + We are now in a position to consider as a whole the evidence on the + question of the source of radio-active energy. + </p> + <p> + (1) Radio-activity is accompanied by the appearance of new chemical + substances. The energy liberated is therefore probably due to the + associated chemical change. (2) The activity of a series of compounds is + found to accompany the presence of a radio-active element, the activity of + each compound depends only on the contents of the element, and is + independent of the nature of its combination. Thus radio-activity is a + property of the element, and is not affected by its state of isolation or + chemical combination. (3) The radio-activity of a simple transient product + decays in a geometrical progression, the loss per second being + proportional to the mass of substance still left at the moment, and + independent of its state of concentration or dilution. This type of + reaction is well known in chemistry to mark a mono-molecular change, where + each molecule is dissociated or altered in structure independently. If two + or more molecules were concerned simultaneously, the rate of reaction + would depend on the nearness of the molecules to each other, that is, to + the concentration of the material. (4) The amount of energy liberated by + the change of a given mass of material far transcends the amount set free + by any known ordinary chemical action. The activity of radium decays so + slowly that it would not sink to half its initial value in less than some + two thousand years, and yet one gramme of radium emits about 100 calories + of heat during each hour of its existence. + </p> + <p> + The energy of radio-activity is due to chemical change, but clearly to no + chemical change hitherto familiar to science. It is an atomic property, + characteristic of a given element, and the atoms undergo the change + individually, not by means of interaction among each other. The conclusion + is irresistible that we are dealing with a fundamental change in the + structure of the individual atoms, which, one by one, are dissociating + into simpler parts. We are watching the disintegration of the "atoms" of + the chemist, hitherto believed indestructible and eternal, and measuring + the liberation of some of the long-suspected store of internal atomic + energy. We have stumbled on the transmutation dreamed by the alchemist, + and discovered the process of a veritable evolution of matter. + </p> + <p> + The transmutation theory of radio-activity was formulated by Rutherford + (Rutherford, "Radio-activity" (2nd edition), Cambridge, 1905, page 307.) + and Soddy in 1903. By its light, all recent work on the subject has been + guided; it has stood the supreme test of a hypothesis, and shown power to + suggest new investigations and to co-ordinate and explain them, when + carried out. We have summarised the evidence which led to the conception + of the theory; we have now to consider the progress which has been made in + tracing the successive disintegration of radio-active atoms. + </p> + <p> + Soon after the statement of the transmutation theory, a striking + verification of one of its consequences appeared. The measurement of the + magnetic and electric deflection of the alpha-rays suggested to Rutherford + the idea that the stream of projectiles of which they consisted was a + flight of helium atoms. Ramsay and Soddy, confining a minute bubble of + radium emanation in a fine glass tube, were able to watch the development + of the helium spectrum as, day by day, the emanation decayed. By isolating + a very narrow pencil of alpha-rays, and watching through a microscope + their impact on a fluorescent screen, Rutherford has lately counted the + individual alpha-projectiles, and confirmed his original conclusion that + their mass corresponded to that of helium atoms and their charge to double + that on a univalent atom. ("Proc. Roy. Soc." A, page 141, 1908.) Still + more recently, he has collected the alpha-particles shot through an + extremely thin wall of glass, and demonstrated by direct spectroscopic + evidence the presence of helium. ("Phil. Mag." February 1909.) + </p> + <p> + But the most thorough investigation of a radio-active pedigree is found in + Rutherford's classical researches on the successive disintegration + products of radium, in order to follow the evidence on which his results + are founded, we must describe more fully the process of decay of the + activity of a simple radio-active substance. The decay of activity of the + body known as uranium-X is shown in a falling curve (Fig. 1.). It will be + seen that, in each successive 22 days, the activity falls to half the + value it possessed at the beginning. + </p> + <p> + This change in a geometrical progression is characteristic of simple + radio-active processes, and can be expressed mathematically by a simple + exponential formula. + </p> + <p> + As we have said above, solid bodies exposed to the emanations of radium or + thorium become coated with a radio-active deposit. The rate of decay of + this activity depends on the time of exposure to the emanation, and does + not always show the usual simple type of curve. Thus the activity of a rod + exposed to radium emanation for 1 minute decays in accordance with a curve + (Fig. 2) which represents the activity as measured by the alpha-rays. If + the electroscope be screened from the alpha-rays, it is found that the + activity of the rod in beta- an gamma-rays increases for some 35 minutes + and then diminishes (Fig. 3.). + </p> + <p> + These complicated relations have been explained satisfactorily and + completely by Rutherford on the hypothesis of successive changes of the + radio-active matter into one new body after another. (Rutherford, + "Radio-activity" (2nd edition), Cambridge, 1905, page 379.) The + experimental curve represents the resultant activity of all the matter + present at a given moment, and the process of disentangling the component + effects consists in finding a number of curves, which express the rise and + fall of activity of each kind of matter as it is produced and decays, and, + fitted together, give the curve of the experiments. + </p> + <p> + Other methods of investigation also are open. They have enabled Rutherford + to complete the life-history of radium and its products, and to clear up + doubtful points left by the analysis of the curves. By the removal of the + emanation, the activity of radium itself has been shown to consist solely + of alpha-rays. This removal can be effected by passing air through the + solution of a radium salt. The emanation comes away, and the activity of + the deposit which it leaves behind decays rapidly to a small fraction of + its initial value. Again, some of the active deposits of the emanation are + more volatile than others, and can be separated from them by the agency of + heat. + </p> + <p> + From such evidence Rutherford has traced a long series of disintegration + products of radium, all but the first of which exist in much too minute + quantities to be detected otherwise than by their radio-activities. + Moreover, two of these products are not themselves appreciably + radio-active, though they are born from radio-active parents, and give + rise to a series of radio-active descendants. Their presence is inferred + from such evidence as the rise of beta and gamma radio-activity in the + solid newly deposited by the emanation; this rise measuring the growth of + the first radio-active offspring of one of the non-active bodies. Some of + the radium products give out alpha-rays only, one beta- and gamma-rays, + while one yields all three types of radiation. The pedigree of the radium + family may be expressed in the following table, the time noted in the + second column being the time required for a given quantity to be half + transformed into its next derivative. + </p> +<pre xml:space="preserve"> + Time of half Radio- Properties + decay activity + + Radium About 2600 years alpha rays Element chemically analogous + to barium. + + Emanation 3.8 days alpha rays Chemically inert gas; + condenses at -150 deg C. + + Radium-A 3 minutes alpha rays Behaves as a solid deposited on + surfaces; concentrated on a + negative electrode. + + Radium-B 21 minutes no rays Soluble in strong acids; + volatile at a white heat; more + volatile than A or C. + + Radium-C 28 minutes alpha, beta, Soluble in strong acids; less + gamma rays volatile than B. + + Radium-D about 40 years no rays Soluble in strong acids; volatile + below 1000 deg C. + + Radium-E 6 days beta, gamma Non-volatile at 1000 deg C. + rays + + Radium-F 143 days alpha rays Volatile at 1000 deg C. + Deposited from solution on a + bismuth plate. +</pre> + <p> + Of these products, A, B, and C constitute that part of the active deposit + of the emanation which suffers rapid decay and nearly disappears in a few + hours. Radium-D, continually producing its short-lived descendants E and + F, remains for years on surfaces once exposed to the emanation, and makes + delicate radio-active researches impossible in laboratories which have + been contaminated by an escape of radium emanation. + </p> + <p> + A somewhat similar pedigree has been made out in the case of thorium. Here + thorium-X is interposed between thorium and its short-lived emanation, + which decays to half its initial quantity in 54 seconds. Two active + deposits, thorium A and B, arise successively from the emanation. In + uranium, we have the one obvious derivative uranium-X, and the question + remains whether this one descent can be connected with any other + individual or family. Uranium is long-lived, and emits only alpha-rays. + Uranium-X decays to half value in 22 days, giving out beta- and + gamma-rays. Since our evidence goes to show that radio-activity is + generally accompanied by the production of new elements, it is natural to + search for the substance of uranium-X in other forms, and perhaps under + other names, rather than to surrender immediately our belief in the + conservation of matter. + </p> + <p> + With this idea in mind we see at once the significance of the constitution + of uranium minerals. Formed in the remote antiquity of past geological + ages, these minerals must become store-houses of all the products of + uranium except those which may have escaped as gases or possibly liquids. + Even gases may be expected to some extent to be retained by occlusion. + Among the contents of uranium minerals, then, we may look for the + descendants of the parent uranium. If the descendants are permanent or + more long-lived than uranium, they will accumulate continually. If they + are short-lived, they will accumulate at a steady rate till enough is + formed for the quantity disintegrating to be equal to the quantity + developed. A state of mobile equilibrium will then be reached, and the + amount of the product will remain constant. This constant amount of + substance will depend only on the amount of uranium which is its source, + and, for different minerals, if all the product is retained, the quantity + of the product will be proportional to the quantity of uranium. In a + series of analyses of uranium minerals, therefore, we ought to be able to + pick out its more short-lived descendants by seeking for instances of such + proportionality. + </p> + <p> + Now radium itself is a constituent of uranium minerals, and two series of + experiments by R.J. Strutt and B.B. Boltwood have shown that the content + of radium, as measured by the radio-activity of the emanation, is directly + proportional to the content of uranium. (Strutt, "Proc. Roy. Soc." A, + February 1905; Boltwood, "Phil. Mag." April, 1905.) In Boltwood's + investigation, some twenty minerals, with amounts of uranium varying from + that in a specimen of uraninite with 74.65 per cent., to that in a + monazite with 0.30 per cent., gave a ratio of uranium to radium, constant + within about one part in ten. + </p> + <p> + The conclusion is irresistible that radium is a descendant of uranium, + though whether uranium is its parent or a more remote ancestor requires + further investigation by the radio-active genealogist. On the hypothesis + of direct parentage, it is easy to calculate that the amount of radium + produced in a month by a kilogramme of a uranium salt would be enough to + be detected easily by the radio-activity of its emanation. The + investigation has been attempted by several observers, and the results, + especially those of a careful experiment of Boltwood, show that from + purified uranium salts the growth of radium, if appreciable at all, is + much less than would be found if the radium was the first product of + change of the uranium. It is necessary, therefore, to look for one or more + intermediate substances. + </p> + <p> + While working in 1899 with the uranium residues used by M. and Mme Curie + for the preparation of radium, Debierne discovered and partially separated + another radio-active element which he called actinium. It gives rise to an + intermediate product actinium-X, which yields an emanation with the short + half-life of 3.9 seconds. The emanation deposits two successive + disintegration products actinium-A and actinium-B. + </p> + <p> + Evidence gradually accumulated that the amounts of actinium in + radio-active minerals were, roughly at any rate, proportional to the + amounts of uranium. This result pointed to a lineal connection between + them, and led Boltwood to undertake a direct attack on the problem. + Separating a quantity of actinium from a kilogramme of ore, Boltwood + observed a growth of 8.5 x (10 to the power -9) gramme of radium in 193 + days, agreeing with that indicated by theory within the limits of + experimental error. ("American Journal of Science", December, 1906.) We + may therefore insert provisionally actinium and its series of derivatives + between uranium and radium in the radio-active pedigree. + </p> + <p> + Turning to the other end of the radium series we are led to ask what + becomes of radium-F when in turn it disintegrates? What is the final + non-active product of the series of changes we have traced from uranium + through actinium and radium? + </p> + <p> + One such product has been indicated above. The alpha-ray particles appear + to possess the mass of helium atoms, and the growth of helium has been + detected by its spectrum in a tube of radium emanation. Moreover, helium + is found occluded in most if not all radio-active minerals in amount which + approaches, but never exceeds, the quantity suggested by theory. We may + safely regard such helium as formed by the accumulation of alpha-ray + particles given out by successive radio-active changes. + </p> + <p> + In considering the nature of the residue left after the expulsion of the + five alpha-particles, and the consequent passage of radium to radium-F we + are faced by the fact that lead is a general constituent of uranium + minerals. Five alpha-particles, each of atomic weight 4, taken from the + atomic weight (about 225) of radium gives 205—a number agreeing + fairly well with the 207 of lead. Since lead is more permanent than + uranium, it must steadily accumulate, no radio-active equilibrium will be + reached, and the amount of lead will depend on the age of the mineral as + well as on the quantity of uranium present in it. In primary minerals from + the same locality, Boltwood has shown that the contents of lead are + proportional to the amounts of uranium, while, accepting this theory, the + age of minerals with a given content of uranium may be calculated from the + amount of lead they contain. The results vary from 400 to 2000 million + years. ("American Journal of Science", October, 1905, and February, 1907.) + </p> + <p> + We can now exhibit in tabular form the amazing pedigree of radio-active + change shown by this one family of elements. An immediate descent is + indicated by >, while one which may either be immediate or involve an + intermediate step is shown by.... No place is found in this pedigree for + thorium and its derivatives. They seem to form a separate and independent + radio-active family. + </p> +<pre xml:space="preserve"> + Atomic Weight Time of half Radio-Activity + decay + + Uranium 238.5 alpha + + Uranium-X ? 22 days beta, gamma + ... + Actinium ? ? no rays + + Actinium-X ? 10.2 days alpha (beta, gamma) + + Actinium Emanation ? 3.9 seconds alpha + + Actinium-A ? 35.7 minutes no rays + + Actinium-B ? 2.15 minutes alpha, beta, gamma + ... + Radium 225 about 2600 years alpha + + Radium Emanation ? 3.8 days alpha + + Radium-A ? 3 minutes alpha + + Radium-B ? 21 minutes no rays + + Radium-C ? 28 minutes alpha, beta, gamma + + Radium-D ? about 40 years no rays + + Radium-E ? 6 days beta (gamma) + + Radium-F ? 143 days alpha + ... + Lead 207 ? no rays +</pre> + <p> + As soon as the transmutation theory of radio-activity was accepted, it + became natural to speculate about the intimate structure of the + radio-active atoms, and the mode in which they broke up with the + liberation of some of their store of internal energy. How could we imagine + an atomic structure which would persist unchanged for long periods of + time, and yet eventually spontaneously explode, as here an atom and there + an atom reached a condition of instability? + </p> + <p> + The atomic theory of corpuscles or electrons fortunately was ready to be + applied to this new problem. Of the resulting speculations the most + detailed and suggestive is that of J.J. Thomson. ("Phil. Mag." March, + 1904.) Thomson regards the atom as composed of a number of mutually + repelling negative corpuscles or electrons held together by some central + attractive force which he represents by supposing them immersed in a + uniform sphere of positive electricity. Under the action of the two + forces, the electrons space themselves in symmetrical patterns, which + depend on the number of electrons. Three place themselves at the corner of + an equilateral triangle, four at those of a square, and five form a + pentagon. With six, however, the single ring becomes unstable, one + corpuscle moves to the middle and five lie round it. But if we imagine the + system rapidly to rotate, the centrifugal force would enable the six + corpuscles to remain in a single ring. Thus internal kinetic energy would + maintain a configuration which would become unstable as the energy drained + away. Now in a system of electrons, electromagnetic radiation would result + in a loss of energy, and at one point of instability we might well have a + sudden spontaneous redistribution of the constituents, taking place with + an explosive violence, and accompanied by the ejection of a corpuscle as a + beta-ray, or of a large fragment of the atom as an alpha-ray. + </p> + <p> + The discovery of the new property of radio-activity in a small number of + chemical elements led physicists to ask whether the property might not be + found in other elements, though in a much less striking form. Are ordinary + materials slightly radio-active? Does the feeble electric conductivity + always observed in the air contained within the walls of an electroscope + depend on ionizing radiations from the material of the walls themselves? + The question is very difficult, owing to the wide distribution of slight + traces of radium. Contact with radium emanation results in a deposit of + the fatal radium-D, which in 40 years is but half removed. Is the + "natural" leak of a brass electroscope due to an intrinsic radio-activity + of brass, or to traces of a radio-active impurity on its surface? Long and + laborious researches have succeeded in establishing the existence of + slight intrinsic radio-activity in a few metals such as potassium, and + have left the wider problem still unsolved. + </p> + <p> + It should be noted, however, that, even if ordinary elements are not + radio-active, they may still be undergoing spontaneous disintegration. The + detection of ray-less changes by Rutherford, when those changes are + interposed between two radio-active transformations which can be followed, + show that spontaneous transmutation is possible without measureable + radio-activity. And, indeed, any theory of disintegration, such as + Thomson's corpuscular hypothesis, would suggest that atomic rearrangements + are of much more general occurrence than would be apparent to one who + could observe them only by the effect of the projectiles, which, in + special cases, owing to some peculiarity of atomic configuration, happened + to be shot out with the enormous velocity needed to ionize the surrounding + gas. No evidence for such ray-less changes in ordinary elements is yet + known, perhaps none may ever be obtained; but the possibility should not + be forgotten. + </p> + <p> + In the strict sense of the word, the process of atomic disintegration + revealed to us by the new science of radio-activity can hardly be called + evolution. In each case radio-active change involves the breaking up of a + heavier, more complex atom into lighter and simpler fragments. Are we to + regard this process as characteristic of the tendencies in accord with + which the universe has reached its present state, and is passing to its + unknown future? Or have we chanced upon an eddy in a backwater, opposed to + the main stream of advance? In the chaos from which the present universe + developed, was matter composed of large highly complex atoms, which have + formed the simpler elements by radio-active or ray-less disintegration? Or + did the primaeval substance consist of isolated electrons, which have + slowly come together to form the elements, and yet have left here and + there an anomaly such as that illustrated by the unstable family of + uranium and radium, or by some such course are returning to their state of + primaeval simplicity? + </p> + <p> + <a name="link2H_4_0032" id="link2H_4_0032"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + INDEX. + </h2> + <h3> + Abraxas grossulariata. + </h3> + <p> + Acquired characters, transmission of. + </p> + <p> + Acraea johnstoni. + </p> + <p> + Adaptation. + </p> + <p> + Adloff. + </p> + <p> + Adlumia cirrhosa. + </p> + <p> + Agassiz, A. + </p> + <p> + Agassiz, L. + </p> + <p> + Alexander. + </p> + <p> + Allen, C.A. + </p> + <p> + Alternation of generations. + </p> + <p> + Ameghino. + </p> + <p> + Ammon, O., Works of. + </p> + <p> + Ammonites, Descent of. + </p> + <p> + Amphidesmus analis. + </p> + <p> + Anaea divina. + </p> + <p> + Andrews, C.W. + </p> + <p> + Angiosperms, evolution of. + </p> + <p> + Anglicus, Bartholomaeus. + </p> + <p> + Ankyroderma. + </p> + <p> + Anomma. + </p> + <p> + Antedon rosacea. + </p> + <p> + Antennularia antennina. + </p> + <p> + Anthropops. + </p> + <p> + Ants, modifications of. + </p> + <p> + Arber, E.A.N.,—and J. Parkin, on the origin of Angiosperms. + </p> + <p> + Archaeopteryx. + </p> + <p> + Arctic regions, velocity of development of life in. + </p> + <p> + Ardigo. + </p> + <p> + Argelander. + </p> + <p> + Argyll, Huxley and the Duke of. + </p> + <p> + Aristotle. + </p> + <p> + Arrhenius. + </p> + <p> + Asterias, Loeb on hybridisation of. + </p> + <p> + Autogamy. + </p> + <p> + Avena fatua. + </p> + <p> + Avenarius. + </p> + <p> + Bacon, on mutability of species. + </p> + <p> + Baehr, von, on Cytology. + </p> + <p> + Baer, law of von. + </p> + <p> + Bain. + </p> + <p> + Baldwin, J.M. + </p> + <p> + Balfour, A.J. + </p> + <p> + Ball, J. + </p> + <p> + Barber, Mrs M.E., on Papilio nireus. + </p> + <p> + Barclay, W. + </p> + <p> + Barratt. + </p> + <p> + Bary, de. + </p> + <p> + Bates, H.W., on Mimicry.—Letters from Darwin to.—elsewhere. + </p> + <p> + Bateson, A. + </p> + <p> + BATESON, W., on "Heredity and Variation in Modern lights".—on + discontinuous evolution.—on hybridisation. + </p> + <p> + Bateson, W. and R.P. Gregory. + </p> + <p> + Bathmism. + </p> + <p> + Beche, de la. + </p> + <p> + Beck, P. + </p> + <p> + Becquerel, H. + </p> + <p> + Beebe, C.W., on the plumage of birds.—on sexual selection. + </p> + <p> + Beguyer de Chancourtois. + </p> + <p> + Bell's (Sir Charles) "Anatomy of Expression". + </p> + <p> + Belopolsky. + </p> + <p> + Belt, T., on Mimicry. + </p> + <p> + Beneden, E. van. + </p> + <p> + Benson, M. + </p> + <p> + Bentham, G., on Darwin's species-theory.—on geographical + distribution. + </p> + <p> + Bentham, Jeremy. + </p> + <p> + Bergson, H. + </p> + <p> + Berkeley. + </p> + <p> + Berthelot. + </p> + <p> + Betham, Sir W. + </p> + <p> + Bickford, E., experiments on degeneration by. + </p> + <p> + Bignonia capreolata. + </p> + <p> + Biophores. + </p> + <p> + Birds, geological history of. + </p> + <p> + Blanford, W.T. + </p> + <p> + Blaringhem, on wounding. + </p> + <p> + Blumenbach. + </p> + <p> + Bodin. + </p> + <p> + Boltwood, B.B. + </p> + <p> + Bonald, on war. + </p> + <p> + Bonnet. + </p> + <p> + Bonney, T.G. + </p> + <p> + Bonnier, G. + </p> + <p> + Bopp, F., on language. + </p> + <p> + BOUGLE C., on "Darwinism and Sociology". + </p> + <p> + Bourdeau. + </p> + <p> + Bourget, P. + </p> + <p> + Boutroux. + </p> + <p> + Boveri, T. + </p> + <p> + Brachiopods, history of. + </p> + <p> + Brassica, hybrids of. + </p> + <p> + Brassica Napus. + </p> + <p> + Broca. + </p> + <p> + Brock, on Kant. + </p> + <p> + Brown, Robert. + </p> + <p> + Brugmann and Osthoff. + </p> + <p> + Brugmann. + </p> + <p> + Brunetiere. + </p> + <p> + Bruno, on Evolution. + </p> + <p> + Buch, von. + </p> + <p> + Bucher, K. + </p> + <p> + Buckland. + </p> + <p> + Buckle. + </p> + <p> + Buffon. + </p> + <p> + Burchell, W.J. + </p> + <p> + Burck, W. + </p> + <p> + Burdon-Sanderson, J., letter from. + </p> + <p> + BURY, J.B., on "Darwinism and History". + </p> + <p> + Butler, A.G. + </p> + <p> + Butler, Samuel. + </p> + <p> + Butschli, O. + </p> + <p> + Butterflies, mimicry in.—sexual characters in. + </p> + <p> + Cabanis. + </p> + <p> + Campbell. + </p> + <p> + Camels, geological history of. + </p> + <p> + Camerarius, R.J. + </p> + <p> + Candolle, A. de. + </p> + <p> + Cannon and Davenport, experiments on Daphniae by. + </p> + <p> + Capsella bursapastoris. + </p> + <p> + Carneri. + </p> + <p> + Castnia linus. + </p> + <p> + Catasetum barbatum. + </p> + <p> + Catasetum tridentatum. + </p> + <p> + Caterpillars, variation in. + </p> + <p> + Celosia, variability of. + </p> + <p> + Cereals, variability in. + </p> + <p> + Cesnola, experiments on Mantis by. + </p> + <p> + Chaerocampa, colouring of. + </p> + <p> + Chambers, R., "The Vestiges of Creation" by. + </p> + <p> + Chromosomes and Chromomeres. + </p> + <p> + Chun. + </p> + <p> + Cieslar, experiments by. + </p> + <p> + Circumnutation, Darwin on. + </p> + <p> + Claus. + </p> + <p> + Cleistogamy. + </p> + <p> + Clerke, Miss A. + </p> + <p> + Clodd, E. + </p> + <p> + Cluer. + </p> + <p> + Clytus arietis. + </p> + <p> + Coadaptation. + </p> + <p> + Codrington. + </p> + <p> + Cohen and Peter. + </p> + <p> + Collingwood. + </p> + <p> + Colobopsis truncata. + </p> + <p> + Colour, E.B. Poulton on The Value in the Struggle for life of.—influence + and temperature on changes in.—in relation to Sexual Selection. + </p> + <p> + Colours, incidental.—warning. + </p> + <p> + Comte, A. + </p> + <p> + Condorcet. + </p> + <p> + Cope. + </p> + <p> + Coral reefs, Darwin's work on. + </p> + <p> + Correlation of organisms, Darwin's idea of the. + </p> + <p> + Correlation of parts. + </p> + <p> + Corydalis claviculata. + </p> + <p> + Cournot. + </p> + <p> + Couteur, Col. Le. + </p> + <p> + Crooks, Sir William. + </p> + <p> + Cruger, on Orchids. + </p> + <p> + Cunningham and Marchand, on the brain. + </p> + <p> + Curie, M. and Mme. + </p> + <p> + Cuvier. + </p> + <p> + Cycadeoidea dacotensis. + </p> + <p> + Cycads, geological history of. + </p> + <p> + Cystidea, an ancient group. + </p> + <p> + Cytology and heredity. + </p> + <p> + Cytolysis and fertilisation. + </p> + <p> + Czapek. + </p> + <p> + Dalton's atomic theory. + </p> + <p> + Dana, J.D., on marine faunas. + </p> + <p> + Danaida chrysippus. + </p> + <p> + Danaida genutia. + </p> + <p> + Danaida plexippus. + </p> + <p> + Dante. + </p> + <p> + Dantec, Le, + </p> + <p> + Darwin, Charles, as an Anthropologist.—on ants.—and the + "Beagle" Voyage.—on the Biology of Flowers.—as a Botanist.—his + influence on Botany.—and S. Butler.—at Cambridge.—on + Cirripedia.—on climbing plants.—on colour.—on coral + reefs.—on the Descent of Man.—his work on Drosera.—at + Edinburgh.—his influence on Animal Embryology.—on Geographical + Distribution.—his work on Earthworms.—evolutionist authors + referred to in the "Origin" by.—and E. Forbes.—on the + geological record.—and Geology.—his early love for geology.—his + connection with the Geological Society of London.—and Haeckel.—and + Henslow.—and History.—and Hooker.—and Huxley.—on + ice-action.—on igneous rocks.—on Lamarck.—on Language.—his + Scientific Library.—and the Linnean Society.—and Lyell.—and + Malthus.—on Patrick Matthew.—on mental evolution.—on + Mimicry.—a "Monistic Philosopher."—on the movements of plants.—on + Natural Selection.—a "Naturalist for Naturalists."—on Paley. + </p> + <p> + Darwin, Charles, his Pangenesis hypothesis.—on the permanence of + continents.—his personality.—his influence on Philosophy.—predecessors + of.—his views on religion, etc.—his influence on religious + thought.—his influence on the study of religions.—his methods + of research.—and Sedgwick.—on Sexual Selection.—the + first germ of his species theory.—on H. Spencer.—causes of his + success.—on Variation.—on the "Vestiges of Creation".—on + volcanic islands.—and Wallace.—letter to Wallace from.—letter + to E.B. Wilson from. + </p> + <p> + Darwin, E., on the colour of animals.—Charles Darwin's reference to.—on + evolution. + </p> + <p> + DARWIN, F., on "Darwin's work on the Movements of Plants".—on Darwin + as a botanist.—observations on Earthworms by.—on Lamarckism.—on + Memory.—on Prichard's "Anticipations".—various. + </p> + <p> + DARWIN, SIR G., on "The Genesis of Double Stars".—on the earth's + mass. + </p> + <p> + Darwin, H. + </p> + <p> + Darwin, W. + </p> + <p> + Darwinism, Sociology, Evolution and. + </p> + <p> + Davenport and Cannon, experiments on Daphniae by. + </p> + <p> + David, T.E., his work on Funafuti. + </p> + <p> + Death, cause of natural. + </p> + <p> + Debey, on Cretaceous plants. + </p> + <p> + Debierne. + </p> + <p> + Degeneration. + </p> + <p> + Delage, experiments on parthenogenesis by. + </p> + <p> + Delbruck. + </p> + <p> + Democritus. + </p> + <p> + Deniker. + </p> + <p> + Descartes. + </p> + <p> + Descent, history of doctrine of. + </p> + <p> + "Descent of Man", G. Schwalbe on "The".—Darwin on Sexual Selection + in "The".—rejection in Germany of "The". + </p> + <p> + Desmatippus. + </p> + <p> + Desmoulins, A., on Geographical Distribution. + </p> + <p> + Detto. + </p> + <p> + Development, effect of environment on. + </p> + <p> + Dianthus caryophyllus. + </p> + <p> + Diderot. + </p> + <p> + Digitalis purpurea. + </p> + <p> + Dimorphism, seasonal. + </p> + <p> + Dismorphia astynome. + </p> + <p> + Dismorphia orise. + </p> + <p> + Distribution, H. Gadow on Geographical.—Sir W. Thiselton-Dyer on. + </p> + <p> + Dittrick, O. + </p> + <p> + Dixey, F.A., on the scent of Butterflies. + </p> + <p> + Dolichonyx oryzivorus. + </p> + <p> + Dorfmeister. + </p> + <p> + Down, Darwin at. + </p> + <p> + Draba verna. + </p> + <p> + Dragomirov. + </p> + <p> + Driesch, experiments by.—elsewhere. + </p> + <p> + Drosera, Darwin's work on. + </p> + <p> + Dryopithecus. + </p> + <p> + Dubois, E., on Pithecanthropus. + </p> + <p> + Duhring. + </p> + <p> + Duhamel. + </p> + <p> + Duncan, J.S. + </p> + <p> + Duncan, P.B. + </p> + <p> + Duns Scotus. + </p> + <p> + Duret, C. + </p> + <p> + Durkheim, on division of labour. + </p> + <p> + Dutrochet. + </p> + <p> + Echinoderms, ancestry of. + </p> + <p> + Ecology. + </p> + <p> + Eimer. + </p> + <p> + Ekstam. + </p> + <p> + Elephants, geological history of. + </p> + <p> + Elymnias phegea. + </p> + <p> + E. undularis. + </p> + <p> + Embleton, A.L. + </p> + <p> + Embryology, A. Sedgwick on the influence of Darwin on. + </p> + <p> + Embryology, as a clue to Phylogeny.—the Origin of Species and. + </p> + <p> + Empedocles. + </p> + <p> + Engles. + </p> + <p> + Environment, action of.—Klebs on the influence on plants of.—Loeb + on experimental study in relation to. + </p> + <p> + Eohippus. + </p> + <p> + Epicurus, a poet of Evolution. + </p> + <p> + Eristalis. + </p> + <p> + Ernst. + </p> + <p> + Ernst, A., on the Flora of Krakatau. + </p> + <p> + Eschscholzia californica. + </p> + <p> + Espinas. + </p> + <p> + Eudendrium racemosum. + </p> + <p> + Evolution, in relation to Astronomy.—and creation.—conception + of.—discontinuous.—experimental.—factors of.—fossil + plants as evidence of.—and language.—of matter, W.C.D. Whetham + on.—mental.—Lloyd Morgan on mental factors in.—Darwinism + and Social.—Saltatory.—Herbert Spencer on.—Uniformitarian.—Philosophers + and modern methods of studying. + </p> + <p> + Expression of the Emotions. + </p> + <p> + Fabricius, J.C., on geographical distribution. + </p> + <p> + Farmer, J.B. + </p> + <p> + Farrer, Lord. + </p> + <p> + Fearnsides, W.G. + </p> + <p> + Felton, S., on protective resemblance. + </p> + <p> + Ferri. + </p> + <p> + Ferrier, his work on the brain. + </p> + <p> + Fertilisation, experimental work on animal-. + </p> + <p> + Fertilisation of Flowers. + </p> + <p> + Fichte. + </p> + <p> + Field, Admiral A.M. + </p> + <p> + Fischer, experiments on Butterflies by. + </p> + <p> + Fitting. + </p> + <p> + Flemming, W. + </p> + <p> + Flourens. + </p> + <p> + Flowering plants, ancestry of. + </p> + <p> + Flowers, K. Goebel on the Biology of. + </p> + <p> + Flowers and Insects. + </p> + <p> + Flowers, relation of external influences to the production of. + </p> + <p> + Fol, H. + </p> + <p> + Forbes, E.—and C. Darwin. + </p> + <p> + Ford, S.O. and A.C. Seward, on the Araucarieae. + </p> + <p> + Fossil Animals, W.B. Scott on their bearing on evolution. + </p> + <p> + Fossil Plants, D.H. Scott on their bearing on evolution. + </p> + <p> + Fouillee. + </p> + <p> + Fraipont, on skulls from Spy. + </p> + <p> + FRAZER, J.G., on "Some Primitive Theories of the Origin of Man".—various. + </p> + <p> + Fruwirth. + </p> + <p> + Fumaria officinalis. + </p> + <p> + Funafuti, coral atoll of. + </p> + <p> + Fundulus. + </p> + <p> + F. heteroclitus. + </p> + <p> + GADOW, H., on "Geographical Distribution of Animals".—elsewhere. + </p> + <p> + Gartner, K.F. + </p> + <p> + Gallus bankiva. + </p> + <p> + Galton, F. + </p> + <p> + Gamble, F.W. and F.W. Keeble. + </p> + <p> + Gasca, La. + </p> + <p> + Geddes, P. + </p> + <p> + Geddes, P. and A.W. Thomson. + </p> + <p> + Gegenbauer. + </p> + <p> + Geikie, Sir A. + </p> + <p> + Geitonogamy. + </p> + <p> + Genetics. + </p> + <p> + Geographical Distribution of Animals.—of Plants.—influence of + "The Origin of Species" on.—Wallace's contribution to. + </p> + <p> + Geography of former periods, reconstruction of. + </p> + <p> + Geology, Darwin and. + </p> + <p> + Geranium spinosum. + </p> + <p> + Germ-plasm, continuity of.—Weismann on. + </p> + <p> + Germinal Selection. + </p> + <p> + Gibbon. + </p> + <p> + Gilbert. + </p> + <p> + GILES, P., on "Evolution and the Science of Language". + </p> + <p> + Giuffrida-Ruggeri. + </p> + <p> + Giotto. + </p> + <p> + Gizycki. + </p> + <p> + Glossopteris Flora. + </p> + <p> + Gmelin. + </p> + <p> + Godlewski, on hybridisation. + </p> + <p> + GOEBEL, K., on "The Biology of Flowers".—his work on Morphology. + </p> + <p> + Goethe and Evolution.—on the relation between Man and Mammals.—elsewhere. + </p> + <p> + Goldfarb. + </p> + <p> + Gondwana Land. + </p> + <p> + Goodricke, J. + </p> + <p> + Gore, Dr. + </p> + <p> + Gorjanovic-Kramberger. + </p> + <p> + Gosse, P.H. + </p> + <p> + Grabau, A.W., on Fusus. + </p> + <p> + Grand'Eury, F.C., on fossil plants. + </p> + <p> + Grapta C. album. + </p> + <p> + Gravitation, effect on life-phenomena of. + </p> + <p> + Gray, Asa. + </p> + <p> + Gregoire, V. + </p> + <p> + Groom, T.T., on heliotropism. + </p> + <p> + Groos. + </p> + <p> + Grunbaum, on the brain. + </p> + <p> + Guignard, L. + </p> + <p> + Gulick. + </p> + <p> + Guppy, on plant-distribution. + </p> + <p> + Guyau. + </p> + <p> + Gwynne-Vaughan, D.T., on Osmundaceae. + </p> + <p> + Gymnadenia conopsea. + </p> + <p> + Haberlandt, G. + </p> + <p> + Haddon, A.C. + </p> + <p> + HAECKEL, E., on "Charles Darwin as an Anthropologist".—on Colour.—and + Darwin.—on the Descent of Man.—contributions to Evolution by. + </p> + <p> + Haeckel, E., on Lamarck.—on Language.—a leader in the + Darwinian controversy.—on Lyell's influence on Darwin.—various. + </p> + <p> + Hacker. + </p> + <p> + Hagedoorn, on hybridisation. + </p> + <p> + Hales, S. + </p> + <p> + Hansen. + </p> + <p> + Harker, A. + </p> + <p> + HARRISON, J.E., on "The Influence of Darwinism on the Study of Religions". + </p> + <p> + Hartmann, von. + </p> + <p> + Harvey. + </p> + <p> + Haupt, P., on Language. + </p> + <p> + Haycraft. + </p> + <p> + Hays, W.M. + </p> + <p> + Hegel. + </p> + <p> + Heliconius narcaea. + </p> + <p> + Heliotropism in animals. + </p> + <p> + Henslow, Rev. J.S. and Darwin. + </p> + <p> + Hensen, Van. + </p> + <p> + Herbst, his experiments on sea urchins. + </p> + <p> + Heracleitus. + </p> + <p> + Herder. + </p> + <p> + Heredity and Cytology.—Haeckel on.—and Variation.—various. + </p> + <p> + Hering, E., on Memory. + </p> + <p> + Herschel, J. + </p> + <p> + Hertwig, R. + </p> + <p> + Hertwig, O. + </p> + <p> + Hertz. + </p> + <p> + Heteromorphosis. + </p> + <p> + Heterostylism. + </p> + <p> + Heuser, E. + </p> + <p> + Hewitt. + </p> + <p> + Heyse's theory of language. + </p> + <p> + Hinde, G.J., his work on Funafuti. + </p> + <p> + Hipparion. + </p> + <p> + Hippolyte cranchii. + </p> + <p> + Hirase. + </p> + <p> + History, Darwin and. + </p> + <p> + Hobbes, T. + </p> + <p> + Hobhouse. + </p> + <p> + HOFFDING, H., on "The Influence of the Conception of Evolution on Modern + Philosophy". + </p> + <p> + Hofmeister, W. + </p> + <p> + Holmes, S.J., on Arthropods. + </p> + <p> + Holothurians, calcareous bodies in skin of. + </p> + <p> + Homo heidelbergensis. + </p> + <p> + Homo neandertalensis. + </p> + <p> + Homo pampaeus. + </p> + <p> + Homo primigenius. + </p> + <p> + Homunculus. + </p> + <p> + Hooker, Sir J.D., and Darwin.—on Distribution of Plants.—on + Ferns.—Letter to the Editor from. + </p> + <p> + Horner, L. + </p> + <p> + Horse, Geological history of the. + </p> + <p> + Huber. + </p> + <p> + Hubert and Mauss. + </p> + <p> + Hubrecht, A.R.W. + </p> + <p> + Hugel, F. von. + </p> + <p> + Humboldt, A. von. + </p> + <p> + Humboldt, W. von. + </p> + <p> + Hume. + </p> + <p> + Hutcheson. + </p> + <p> + Hutton. + </p> + <p> + Huxley, T.H., and Darwin.—and the Duke of Argyll.—on + Embryology.—on Geographical Distribution.—on Lamarck.—Letter + to J.W. Judd from.—on Lyell.—on Man.—on "The Origin of + Species".—on Selection.—on Teleology.—on transmission of + acquired characters.—various. + </p> + <p> + Hybridisation. + </p> + <p> + Hybrids, Sterility of. + </p> + <p> + Hyracodon. + </p> + <p> + Iberis umbellata. + </p> + <p> + Ikeno. + </p> + <p> + Imperfection of the Geological Record. + </p> + <p> + Ingenhousz, on plant physiology. + </p> + <p> + Inheritance of acquired characters. + </p> + <p> + Insects and Flowers. + </p> + <p> + Instinct. + </p> + <p> + Instincts, experimental control of animal. + </p> + <p> + Ipomaea purpurea. + </p> + <p> + Irish Elk, an example of co-adaptation. + </p> + <p> + Jacobian figures. + </p> + <p> + Jacoby, "Studies in Selection" by. + </p> + <p> + James, W. + </p> + <p> + Janczewski. + </p> + <p> + Jeans, J.H. + </p> + <p> + Jennings, H.S., on Paramoecium. + </p> + <p> + Jentsch. + </p> + <p> + Jespersen, Prof., Theory of. + </p> + <p> + Johannsen, on Species. + </p> + <p> + Jones, Sir William, on Language. + </p> + <p> + Jordan. + </p> + <p> + JUDD, J.W., on "Darwin and Geology". + </p> + <p> + Kallima, protective colouring of. + </p> + <p> + Kallima inachis. + </p> + <p> + Kammerer's experiments on Salamanders. + </p> + <p> + Kant, I. + </p> + <p> + Keane, on the Primates. + </p> + <p> + Keeble, F.W. and F.W. Gamble, on Colour-change. + </p> + <p> + Keith, on Anthropoid Apes. + </p> + <p> + Kellogg, V., on heliotropism. + </p> + <p> + Kepler. + </p> + <p> + Kerguelen Island. + </p> + <p> + Kidd. + </p> + <p> + Kidston, R., on fossil plants. + </p> + <p> + Killmann, on origin of human races. + </p> + <p> + King, Sir George. + </p> + <p> + Klaatsch, on Ancestry of Man. + </p> + <p> + Klaatsch and Hauser. + </p> + <p> + KLEBS, G., on "The influence of Environment on the forms of plants". + </p> + <p> + Kniep. + </p> + <p> + Knies. + </p> + <p> + Knight, A., experiments on plants by.—on Geotropism. + </p> + <p> + Knight-Darwin law. + </p> + <p> + Knuth. + </p> + <p> + Kolliker, his views on Evolution. + </p> + <p> + Kolreuter, J.G. + </p> + <p> + Kohl. + </p> + <p> + Korschinsky. + </p> + <p> + Kowalevsky, on fossil horses. + </p> + <p> + Krakatau, Ernst on the Flora of. + </p> + <p> + Krause, E. + </p> + <p> + Kreft, Dr. + </p> + <p> + Kropotkin. + </p> + <p> + Kupelwieser, on hybridisation. + </p> + <p> + Lagopus hyperboreus. + </p> + <p> + Lamarck, his division of the Animal Kingdom.—Darwin's opinion of.—on + Evolution.—on Man.—various. + </p> + <p> + Lamarckian principle. + </p> + <p> + Lamb, C. + </p> + <p> + Lamettrie. + </p> + <p> + Lamprecht. + </p> + <p> + Lanessan, J.L. de. + </p> + <p> + Lang. + </p> + <p> + Lange. + </p> + <p> + Language, Darwin on.—Evolution and the Science of.—various. + </p> + <p> + Lankester, Sir E. Ray, on degeneration.—on educability.—on the + germ-plasm theory.—elsewhere. + </p> + <p> + Lapouge, Vacher de. + </p> + <p> + Larmor, J. + </p> + <p> + Lartet, M.E. + </p> + <p> + Lassalle. + </p> + <p> + Lathyrus odoratus. + </p> + <p> + Lavelaye, de. + </p> + <p> + Lawrence, W. + </p> + <p> + Lehmann. + </p> + <p> + Lehmann-Nitsche. + </p> + <p> + Leibnitz. + </p> + <p> + Lepidium Draba. + </p> + <p> + Lepidoptera, variation in. + </p> + <p> + Leskien, A., on language. + </p> + <p> + Lessing. + </p> + <p> + Leucippus. + </p> + <p> + Levi, E. + </p> + <p> + Lewes, G.H. + </p> + <p> + Lewin, Capt. + </p> + <p> + Liapounoff. + </p> + <p> + Liddon, H.P. + </p> + <p> + Light, effect on organisms of. + </p> + <p> + Limenitis archippus.—arthemis. + </p> + <p> + Linnaeus. + </p> + <p> + Livingstone, on plant-forms. + </p> + <p> + Llamas, geological history of. + </p> + <p> + Lockyer, Sir N. + </p> + <p> + Locy, W.A. + </p> + <p> + LOEB, J., on "The Experimental Study of the influence of environment on + Animals. + </p> + <p> + Loew, E. + </p> + <p> + Longstaff, G.B., on the Scents of Butterflies. + </p> + <p> + Lorentz. + </p> + <p> + Lotsy, J.P. + </p> + <p> + Love, A.E.W. + </p> + <p> + Lovejoy. + </p> + <p> + Lubbock. + </p> + <p> + Lucas, K. + </p> + <p> + Lucretius, a poet of Evolution. + </p> + <p> + Lumholtz, C. + </p> + <p> + Luteva macrophthalma. + </p> + <p> + Lycorea halia. + </p> + <p> + Lyell, Sir Charles, and Darwin.—the influence of.—on + geographical distribution.—on "The Origin of Species".—on the + permanence of Ocean-basins.—publication of the "Principles" by.—the + uniformitarian teaching of. + </p> + <p> + Lythrum salicaria. + </p> + <p> + Macacus, ear of. + </p> + <p> + MacDougal, on wounding. + </p> + <p> + Mach, E. + </p> + <p> + Macromytis flexuosa, colour-change in. + </p> + <p> + Magic and religion. + </p> + <p> + Mahoudeau. + </p> + <p> + Maillet, de. + </p> + <p> + Majewski. + </p> + <p> + Malthus, his influence on Darwin.—various. + </p> + <p> + Mammalia, history of. + </p> + <p> + Man, Descent of.—J.G. Frazer on some primitive theories of the + origin of.—mental and moral qualities of animals and.—pre-Darwinian + views on the Descent of.—religious views of primitive.—Tertiary + flints worked by. + </p> + <p> + "Man", G. Schwalbe on Darwin's "Descent of". + </p> + <p> + Manouvrier. + </p> + <p> + Mantis religiosa, colour experiments on. + </p> + <p> + Marett, R.R. + </p> + <p> + Markwick. + </p> + <p> + Marshall, G.A.K. + </p> + <p> + Marx. + </p> + <p> + Massart. + </p> + <p> + Masters, M. + </p> + <p> + Matonia pectinata. + </p> + <p> + Matthew, P., and Natural Selection. + </p> + <p> + Maupertuis. + </p> + <p> + Maurandia semperflorens. + </p> + <p> + Mauss and Herbert. + </p> + <p> + Mauthner. + </p> + <p> + Maxwell. + </p> + <p> + Maxwell, Clerk. + </p> + <p> + Mayer, R. + </p> + <p> + Mechanitis lysimnia. + </p> + <p> + Meehan, T. + </p> + <p> + Meldola, R., Letters from Darwin to. + </p> + <p> + Melinaea ethra. + </p> + <p> + Mendel. + </p> + <p> + Mendeleeff. + </p> + <p> + Merrifield. + </p> + <p> + Merz, J.T. + </p> + <p> + Mesembryanthemum truncatum. + </p> + <p> + Mesohippus. + </p> + <p> + Mesopithecus. + </p> + <p> + Metschnikoff. + </p> + <p> + Mill, J.S. + </p> + <p> + Mimicry.—H.W. Bates on.—F. Muller on. + </p> + <p> + Mimulus luteus. + </p> + <p> + Miquel, F.W.A. + </p> + <p> + Mobius. + </p> + <p> + Mohl, H. von. + </p> + <p> + Moltke, on war. + </p> + <p> + Monachanthus viridis. + </p> + <p> + Monkeys, fossil. + </p> + <p> + Montesquieu. + </p> + <p> + Montgomery, T.H. + </p> + <p> + Monstrosoties. + </p> + <p> + Monticelli. + </p> + <p> + Moore, J.E.S. + </p> + <p> + MORGAN, C. LLOYD, on "Mental Factors in Evolution".—on Organic + Selection. + </p> + <p> + Morgan, T.H. + </p> + <p> + Morse, E.S., on colour. + </p> + <p> + Morselli. + </p> + <p> + Mortillet. + </p> + <p> + Moseley. + </p> + <p> + Mottier, M. + </p> + <p> + Muller, Fritz, "Fur Darwin" by.—on Mimicry. + </p> + <p> + Muller, Fritz. + </p> + <p> + Muller, J. + </p> + <p> + Muller, Max, on language. + </p> + <p> + Murray, A., on geographical distribution. + </p> + <p> + Murray, G. + </p> + <p> + Mutability. + </p> + <p> + Mutation. + </p> + <p> + Myanthus barbatus. + </p> + <p> + Myers, G.W., on Eclipses. + </p> + <p> + Nageli. + </p> + <p> + Nathorst, A.G. + </p> + <p> + Nathusius. + </p> + <p> + Natural Selection, and adaptation.—Darwin's views on.—Darwin + and Wallace on.—and design.—and educability.—Fossil + plants in relation to.—and human development.—and Mimicry.—and + Mutability.—various. + </p> + <p> + Naudin. + </p> + <p> + Neandertal skulls. + </p> + <p> + Nemec. + </p> + <p> + Neoclytus curvatus. + </p> + <p> + Neodarwinism. + </p> + <p> + Neumayr, M. + </p> + <p> + Newton, A. + </p> + <p> + Newton, I. + </p> + <p> + Niebuhr. + </p> + <p> + Nietzsche. + </p> + <p> + Nilsson, on cereals. + </p> + <p> + Nitsche. + </p> + <p> + Noire. + </p> + <p> + Noll. + </p> + <p> + Novicow. + </p> + <p> + Nuclear division. + </p> + <p> + Nussbaum, M. + </p> + <p> + Nuttall, G.H.F. + </p> + <p> + Occam. + </p> + <p> + Odin. + </p> + <p> + Oecology, see Ecology. + </p> + <p> + Oenothera biennis. + </p> + <p> + Oenothera gigas. + </p> + <p> + Oenothera Lamarckiana. + </p> + <p> + Oenothera muricata. + </p> + <p> + Oenothera nanella. + </p> + <p> + Oestergren, on Holothurians. + </p> + <p> + Oken, L. + </p> + <p> + Oliver, F.W., on Palaeozoic Seeds. + </p> + <p> + Ononis minutissima. + </p> + <p> + Ophyrs apifera. + </p> + <p> + Orchids, Darwin's work on the fertilisation of. + </p> + <p> + Organic Selection. + </p> + <p> + "Origin of Species", first draft of the.—geological chapter in the. + </p> + <p> + Orthogenesis. + </p> + <p> + Ortmann, A.E. + </p> + <p> + Osborn, H.F.—"From the Greeks to Darwin" by. + </p> + <p> + Osthoff and Brugmann. + </p> + <p> + Ostwald, W. + </p> + <p> + Ovibos moschatus. + </p> + <p> + Owen, Sir Richard. + </p> + <p> + Oxford, Ashmolean Museum at. + </p> + <p> + Packard, A.S. + </p> + <p> + Palaeontological Record, D.H. Scott on the.—W.B. Scott on the. + </p> + <p> + Palaeopithecus. + </p> + <p> + Paley. + </p> + <p> + Palitzch, G. + </p> + <p> + Palm. + </p> + <p> + Pangenesis. + </p> + <p> + Panmixia, Weismann's principle of. + </p> + <p> + Papilio dardanus. + </p> + <p> + Papilio meriones. + </p> + <p> + Papilio merope. + </p> + <p> + Papilio nireus. + </p> + <p> + Paramoecium, Jennings on. + </p> + <p> + Parker, G.H., on Butterflies. + </p> + <p> + Parkin, J. and E.A.N. Arber, on the origin of Angiosperms. + </p> + <p> + Parthenogenesis, artificial. + </p> + <p> + Paul, H. and Wundt. + </p> + <p> + Pearson, K. + </p> + <p> + Peckham, Dr and Mrs, on the Attidae. + </p> + <p> + Penck. + </p> + <p> + Penzig. + </p> + <p> + Peripatus, distribution of. + </p> + <p> + Peridineae. + </p> + <p> + Permanence of continents. + </p> + <p> + Perrier, E. + </p> + <p> + Perrhybris pyrrha. + </p> + <p> + Perthes, B. de. + </p> + <p> + Peter, on sea urchin's eggs. + </p> + <p> + Petunia violacea. + </p> + <p> + Pfeffer, W. + </p> + <p> + Pfitzner, W. + </p> + <p> + Pflueger. + </p> + <p> + Phillips. + </p> + <p> + Philosophy, influence of the conception of evolution on modern. + </p> + <p> + Phryniscus nigricans. + </p> + <p> + Phylogeny, embryology as a clue to.—Palaeontological evidence on. + </p> + <p> + Physiology of plants, development of. + </p> + <p> + Piccard, on Geotropism. + </p> + <p> + Pickering, spectroscopic observations by. + </p> + <p> + Piranga erythromelas. + </p> + <p> + Pisum sativum. + </p> + <p> + Pithecanthropus. + </p> + <p> + Pitheculites. + </p> + <p> + Planema epaea. + </p> + <p> + Plants, Darwin's work on the movements of.—geographical distribution + of.—Palaeontological record of fossil. + </p> + <p> + Platanthera bifolia. + </p> + <p> + Plate. + </p> + <p> + Plato. + </p> + <p> + Playfair. + </p> + <p> + Pliopithecus. + </p> + <p> + Pocock, R.I. + </p> + <p> + Poincare. + </p> + <p> + Polarity, Vochting on. + </p> + <p> + Polymorphic species.—variability in cereals. + </p> + <p> + Polypodium incanum. + </p> + <p> + Porthesia chrysorrhoea. + </p> + <p> + Potonie, R. + </p> + <p> + Pouchet, G. + </p> + <p> + POULTON, E.B., on "The Value of Colour in the Struggle for Life".—experiments + on Butterflies by.—on J.C. Prichard.—on Mimicry.—various. + </p> + <p> + Pratt. + </p> + <p> + Pratz, du. + </p> + <p> + Premutation. + </p> + <p> + Preuss, K. Th. + </p> + <p> + Prichard, J.C. + </p> + <p> + Primula, heterostylism in. + </p> + <p> + Primula acaulis. + </p> + <p> + Primula elatior. + </p> + <p> + Primula officinalis. + </p> + <p> + Promeces viridis. + </p> + <p> + Pronuba yuccasella. + </p> + <p> + Protective resemblance. + </p> + <p> + Protocetus. + </p> + <p> + Protohippus. + </p> + <p> + Psychology. + </p> + <p> + Pteridophytes, history of. + </p> + <p> + Pteridospermeae. + </p> + <p> + Pucheran. + </p> + <p> + Pusey. + </p> + <p> + Quatrefages, A. de. + </p> + <p> + Quetelet, statistical investigations by. + </p> + <p> + Rabl, C. + </p> + <p> + Radio-activity. + </p> + <p> + Radiolarians. + </p> + <p> + Raimannia odorata. + </p> + <p> + Ramsay, Sir W. and Soddy. + </p> + <p> + Ranke. + </p> + <p> + Rau, A. + </p> + <p> + Ray, J. + </p> + <p> + Reade, Mellard. + </p> + <p> + Recapitulation, the theory of. + </p> + <p> + Reduction. + </p> + <p> + Regeneration. + </p> + <p> + Reid, C. + </p> + <p> + Reinke. + </p> + <p> + Religion, Darwin's attitude towards.—Darwin's influence on the study + of.—and Magic. + </p> + <p> + Religious thought, Darwin's influence on. + </p> + <p> + Renard, on Darwin's work on volcanic islands. + </p> + <p> + Reproduction, effect of environment on. + </p> + <p> + Reptiles, history of. + </p> + <p> + Reversion. + </p> + <p> + Rhinoceros, the history of the. + </p> + <p> + Ridley, H.N. + </p> + <p> + Riley, C.V. + </p> + <p> + Ritchie. + </p> + <p> + Ritual. + </p> + <p> + Roberts, A. + </p> + <p> + Robertson, T.B. + </p> + <p> + Robinet. + </p> + <p> + Rolfe, R.A. + </p> + <p> + Rolph. + </p> + <p> + Romanes, G.J. + </p> + <p> + Rothert. + </p> + <p> + Roux. + </p> + <p> + Rozwadowski, von. + </p> + <p> + Ruskin. + </p> + <p> + Rutherford, E. + </p> + <p> + Rutot. + </p> + <p> + Sachs, J. + </p> + <p> + St Hilaire, E.G. de. + </p> + <p> + Salamandra atra. + </p> + <p> + Salamandra maculosa. + </p> + <p> + Saltatory Evolution, (see also Mutations). + </p> + <p> + Sanders, experiments on Vanessa by. + </p> + <p> + Saporta, on the Evolution of Angiosperms. + </p> + <p> + Sargant, Ethel, on the Evolution of Angiosperms. + </p> + <p> + Savigny. + </p> + <p> + Scardafella inca. + </p> + <p> + Scent, in relation to Sexual Selection. + </p> + <p> + Scharff, R.F. + </p> + <p> + Schelling. + </p> + <p> + Schlegel. + </p> + <p> + Schleicher, A., on language. + </p> + <p> + Schleiden and Schwann, Cell-theory of. + </p> + <p> + Schmarda, L.K., on geographical distribution. + </p> + <p> + Schoetensack, on Homo heidelbergensis. + </p> + <p> + Schreiner, K.E. + </p> + <p> + Schubler, on cereals. + </p> + <p> + Schultze, O., experiments on Frogs. + </p> + <p> + Schur. + </p> + <p> + Schutt. + </p> + <p> + SCHWALBE, G., on "The Descent of Man". + </p> + <p> + Sclater, P.L., on geographical distribution. + </p> + <p> + SCOTT, D.H., on "The Palaeontological Record (Plants)".—elsewhere. + </p> + <p> + SCOTT, W.B., on "The Palaeontological Record (Animals)". + </p> + <p> + Scrope. + </p> + <p> + Scyllaea. + </p> + <p> + Sechehaye, C.A. + </p> + <p> + SEDGWICK, A., on "The Influence of Darwin on Animal Embryology". + </p> + <p> + Sedgwick, A., Darwin's Geological Expedition with. + </p> + <p> + Seeck, O. + </p> + <p> + Seed-plants, origin of. + </p> + <p> + Segregation. + </p> + <p> + Selection, artificial.—germinal. + </p> + <p> + Selection, natural (see Natural Selection).—organic.—sexual.—social + and natural.—various. + </p> + <p> + Selenka. + </p> + <p> + Semnopithecus. + </p> + <p> + Semon, R. + </p> + <p> + Semper. + </p> + <p> + Senebier. + </p> + <p> + Senecio vulgaris. + </p> + <p> + Sergi. + </p> + <p> + Seward, A.C.—and S.O. Ford.—and J. Gowan. + </p> + <p> + Sex, recent investigations on. + </p> + <p> + Sharpe, D. + </p> + <p> + Sherrington, C.S. + </p> + <p> + Shirreff, P. + </p> + <p> + Shrewsbury, Darwin's recollections of. + </p> + <p> + Sibbern. + </p> + <p> + Sinapis alba. + </p> + <p> + Smerinthus ocellata. + </p> + <p> + Smerinthus populi. + </p> + <p> + Smerinthus tiliae. + </p> + <p> + Smith, A. + </p> + <p> + Smith, W. + </p> + <p> + Snyder. + </p> + <p> + Sociology, Darwinism and.—History and. + </p> + <p> + Soddy. + </p> + <p> + Sollas, W.J. + </p> + <p> + Sorley, W.R. + </p> + <p> + Species, Darwin's early work on transmutation of.—geographical + distribution and origin of.—immutability of.—influence on + environment on.—Lamarck on.—multiple origin of.—the + nature of a.—polymorphic.—production by physico-chemical means + of.—and varieties.—de Vries's work on. + </p> + <p> + Spencer, H., on evolution.—on Lyell's "Principles".—on the + nature of the living cell.—on primitive man.—on the theory of + Selection.—on Sociology. + </p> + <p> + Spencer, H., on the transmission of acquired characters.—on + Weismann.—various. + </p> + <p> + Sphingidae, variation in. + </p> + <p> + Spinoza. + </p> + <p> + Sports. + </p> + <p> + Sprengel, C.K. + </p> + <p> + Stability, principle of. + </p> + <p> + Stahl. + </p> + <p> + Standfuss. + </p> + <p> + Stars, evolution of double. + </p> + <p> + Stellaria media. + </p> + <p> + Stephen, L. + </p> + <p> + Sterility in hybrids. + </p> + <p> + Sterne, C. + </p> + <p> + Stockard, his experiments on fish embryos. + </p> + <p> + STRASBURBER, E., on "The Minute Structure of Cells in relation to + Heredity". + </p> + <p> + Strongylocentrotus franciscanus. + </p> + <p> + Strongylocentrotus purpuratus. + </p> + <p> + Struggle for existence. + </p> + <p> + Strutt, R.J. + </p> + <p> + Stuart, A. + </p> + <p> + Sturdee, F.C.D. + </p> + <p> + Sutterlin, L. + </p> + <p> + Sully. + </p> + <p> + Sutton, A.W. + </p> + <p> + Sutton, W.S. + </p> + <p> + Svalof, agricultural station of. + </p> + <p> + Swainson, W. + </p> + <p> + Synapta, calcareous bodies in skin of. + </p> + <p> + S. lappa. + </p> + <p> + Syrphus. + </p> + <p> + Tarde, G. + </p> + <p> + Teleology and adaptation. + </p> + <p> + Tennant, F.R. + </p> + <p> + Teratology. + </p> + <p> + Tetraprothomo. + </p> + <p> + THISELTON-DYER, SIR WILLIAM, on "Geographical distribution of Plants".—on + Burchell.—on protective resemblance.—elsewhere. + </p> + <p> + THOMSON, J.A., on "Darwin's Predecessors.—elsewhere.—and P. + Geddes. + </p> + <p> + Thomson, Sir J.J. + </p> + <p> + Theology, Darwin and. + </p> + <p> + Tiedemann, F. + </p> + <p> + Tooke, Horne. + </p> + <p> + Totemism. + </p> + <p> + Treschow. + </p> + <p> + Treviranus. + </p> + <p> + Trifolium pratense quinquefolium. + </p> + <p> + Trigonias. + </p> + <p> + Trilobites, phylogeny of. + </p> + <p> + Tschermack. + </p> + <p> + Turgot. + </p> + <p> + Turner, Sir W. + </p> + <p> + Twins, artificial production of. + </p> + <p> + Tylor. + </p> + <p> + Tyndall, W. + </p> + <p> + Tyrrell, G. + </p> + <p> + Uhlenhuth, on blood reactions. + </p> + <p> + Underhill, E. + </p> + <p> + Use and disuse. + </p> + <p> + Vanessa. + </p> + <p> + Vanessa antiope. + </p> + <p> + Vanessa levana. + </p> + <p> + Vanessa polychloros. + </p> + <p> + Vanessa urticae. + </p> + <p> + Van 't Hoff. + </p> + <p> + Varanus Salvator. + </p> + <p> + Variability, Darwin's attention directed to.—W. Bateson on.—and + cultivation.—causes of.—polymorphic. + </p> + <p> + Variation, continuous and discontinuous.—Darwin's views as an + evolutionist, and as a systematist, on.—definite and indefinite.—environment + and.—and heredity.—as seen in the life-history of an organism.—minute.—mutability + and.—in relation to species.—H. de Vries on. + </p> + <p> + Varigny, H. de. + </p> + <p> + Varro, on language. + </p> + <p> + Veronica chamaedrys. + </p> + <p> + Verworn. + </p> + <p> + "Vestiges of Creation", Darwin on "The". + </p> + <p> + Vierkandt. + </p> + <p> + Vilmorin, L. de. + </p> + <p> + Virchow, his opposition to Darwin. + </p> + <p> + Virchow, on the transmission of acquired characters. + </p> + <p> + Vochting. + </p> + <p> + Vogt, C. + </p> + <p> + Voltaire. + </p> + <p> + Volvox. + </p> + <p> + VRIES, H. de, on "Variation"—the Mutation theory of. + </p> + <p> + WAGGETT, REV. P.N., on "The Influence of Darwin upon religious thought". + </p> + <p> + Wagner. + </p> + <p> + Waldeyer, W. + </p> + <p> + Wallace, A.R., on Malayan Butterflies.—on Colour.—and Darwin.—on + the Descent of Man.—on distribution.—on Malthus.—on + Natural Selection.—on the permanence of continents.—on social + reforms.—on Sexual Selection. + </p> + <p> + Waller, A.D. + </p> + <p> + Walton. + </p> + <p> + Watson, H.C. + </p> + <p> + Watson, S. + </p> + <p> + Watt, J., and Natural Selection. + </p> + <p> + Watts, W.W. + </p> + <p> + Wedgwood, L. + </p> + <p> + Weir, J.J. + </p> + <p> + WEISMANN, A., on "The Selection Theory".—on Amphimixis. + </p> + <p> + Weismann, A., his germ-plasm theory.—on ontogeny.—and + Prichard.—and Spencer.—on the transmission of acquired + characters.—various. + </p> + <p> + Wells, W.C., and Natural Selection. + </p> + <p> + Weston, S., on language. + </p> + <p> + WHETHAM, W.C.D., on "The Evolution of Matter". + </p> + <p> + Whewell. + </p> + <p> + White, G. + </p> + <p> + Wichmann. + </p> + <p> + Wieland, G.R., on fossil Cycads. + </p> + <p> + Wiesner, on Darwin's work on plant movements. + </p> + <p> + Williams, C.M. + </p> + <p> + Williamson, W.C. + </p> + <p> + Wilson, E.B., on cytology.—letter from Darwin to. + </p> + <p> + Wolf. + </p> + <p> + Wollaston's, T.V. "Variation of Species". + </p> + <p> + Woltmann. + </p> + <p> + Woolner. + </p> + <p> + Wundt, on language. + </p> + <p> + Xylina vetusta. + </p> + <p> + Yucca, fertilisation of. + </p> + <p> + Zeiller, R., on Fossil Plants. + </p> + <p> + Zeller, E. + </p> + <p> + Zimmermann, E.A.W. + </p> + <p> + Zittel, on palaeontological research. + </p> + <p> + "Zoonomia", Erasmus Darwin's. + </p> + <p> + <br /><br /><br /><br /> + </p> +<pre xml:space="preserve"> + + + + + +End of the Project Gutenberg EBook of Darwin and Modern Science, by +A.C. Seward and Others + +*** END OF THIS PROJECT GUTENBERG EBOOK DARWIN AND MODERN SCIENCE *** + +***** This file should be named 1909-h.htm or 1909-h.zip ***** +This and all associated files of various formats will be found in: + http://www.gutenberg.org/1/9/0/1909/ + +Produced by Sue Asscher, and David Widger + + +Updated editions will replace the previous one--the old editions +will be renamed. + +Creating the works from public domain print editions means that no +one owns a United States copyright in these works, so the Foundation +(and you!) can copy and distribute it in the United States without +permission and without paying copyright royalties. Special rules, +set forth in the General Terms of Use part of this license, apply to +copying and distributing Project Gutenberg-tm electronic works to +protect the PROJECT GUTENBERG-tm concept and trademark. Project +Gutenberg is a registered trademark, and may not be used if you +charge for the eBooks, unless you receive specific permission. If you +do not charge anything for copies of this eBook, complying with the +rules is very easy. You may use this eBook for nearly any purpose +such as creation of derivative works, reports, performances and +research. They may be modified and printed and given away--you may do +practically ANYTHING with public domain eBooks. Redistribution is +subject to the trademark license, especially commercial +redistribution. + + + +*** START: FULL LICENSE *** + +THE FULL PROJECT GUTENBERG LICENSE +PLEASE READ THIS BEFORE YOU DISTRIBUTE OR USE THIS WORK + +To protect the Project Gutenberg-tm mission of promoting the free +distribution of electronic works, by using or distributing this work +(or any other work associated in any way with the phrase "Project +Gutenberg"), you agree to comply with all the terms of the Full Project +Gutenberg-tm License (available with this file or online at +http://gutenberg.org/license). + + +Section 1. General Terms of Use and Redistributing Project Gutenberg-tm +electronic works + +1.A. By reading or using any part of this Project Gutenberg-tm +electronic work, you indicate that you have read, understand, agree to +and accept all the terms of this license and intellectual property +(trademark/copyright) agreement. If you do not agree to abide by all +the terms of this agreement, you must cease using and return or destroy +all copies of Project Gutenberg-tm electronic works in your possession. +If you paid a fee for obtaining a copy of or access to a Project +Gutenberg-tm electronic work and you do not agree to be bound by the +terms of this agreement, you may obtain a refund from the person or +entity to whom you paid the fee as set forth in paragraph 1.E.8. + +1.B. "Project Gutenberg" is a registered trademark. It may only be +used on or associated in any way with an electronic work by people who +agree to be bound by the terms of this agreement. There are a few +things that you can do with most Project Gutenberg-tm electronic works +even without complying with the full terms of this agreement. See +paragraph 1.C below. There are a lot of things you can do with Project +Gutenberg-tm electronic works if you follow the terms of this agreement +and help preserve free future access to Project Gutenberg-tm electronic +works. See paragraph 1.E below. + +1.C. The Project Gutenberg Literary Archive Foundation ("the Foundation" +or PGLAF), owns a compilation copyright in the collection of Project +Gutenberg-tm electronic works. Nearly all the individual works in the +collection are in the public domain in the United States. If an +individual work is in the public domain in the United States and you are +located in the United States, we do not claim a right to prevent you from +copying, distributing, performing, displaying or creating derivative +works based on the work as long as all references to Project Gutenberg +are removed. Of course, we hope that you will support the Project +Gutenberg-tm mission of promoting free access to electronic works by +freely sharing Project Gutenberg-tm works in compliance with the terms of +this agreement for keeping the Project Gutenberg-tm name associated with +the work. You can easily comply with the terms of this agreement by +keeping this work in the same format with its attached full Project +Gutenberg-tm License when you share it without charge with others. + +1.D. The copyright laws of the place where you are located also govern +what you can do with this work. Copyright laws in most countries are in +a constant state of change. If you are outside the United States, check +the laws of your country in addition to the terms of this agreement +before downloading, copying, displaying, performing, distributing or +creating derivative works based on this work or any other Project +Gutenberg-tm work. The Foundation makes no representations concerning +the copyright status of any work in any country outside the United +States. + +1.E. Unless you have removed all references to Project Gutenberg: + +1.E.1. The following sentence, with active links to, or other immediate +access to, the full Project Gutenberg-tm License must appear prominently +whenever any copy of a Project Gutenberg-tm work (any work on which the +phrase "Project Gutenberg" appears, or with which the phrase "Project +Gutenberg" is associated) is accessed, displayed, performed, viewed, +copied or distributed: + +This eBook is for the use of anyone anywhere at no cost and with +almost no restrictions whatsoever. You may copy it, give it away or +re-use it under the terms of the Project Gutenberg License included +with this eBook or online at www.gutenberg.org + +1.E.2. If an individual Project Gutenberg-tm electronic work is derived +from the public domain (does not contain a notice indicating that it is +posted with permission of the copyright holder), the work can be copied +and distributed to anyone in the United States without paying any fees +or charges. If you are redistributing or providing access to a work +with the phrase "Project Gutenberg" associated with or appearing on the +work, you must comply either with the requirements of paragraphs 1.E.1 +through 1.E.7 or obtain permission for the use of the work and the +Project Gutenberg-tm trademark as set forth in paragraphs 1.E.8 or +1.E.9. + +1.E.3. If an individual Project Gutenberg-tm electronic work is posted +with the permission of the copyright holder, your use and distribution +must comply with both paragraphs 1.E.1 through 1.E.7 and any additional +terms imposed by the copyright holder. Additional terms will be linked +to the Project Gutenberg-tm License for all works posted with the +permission of the copyright holder found at the beginning of this work. + +1.E.4. Do not unlink or detach or remove the full Project Gutenberg-tm +License terms from this work, or any files containing a part of this +work or any other work associated with Project Gutenberg-tm. + +1.E.5. Do not copy, display, perform, distribute or redistribute this +electronic work, or any part of this electronic work, without +prominently displaying the sentence set forth in paragraph 1.E.1 with +active links or immediate access to the full terms of the Project +Gutenberg-tm License. + +1.E.6. You may convert to and distribute this work in any binary, +compressed, marked up, nonproprietary or proprietary form, including any +word processing or hypertext form. However, if you provide access to or +distribute copies of a Project Gutenberg-tm work in a format other than +"Plain Vanilla ASCII" or other format used in the official version +posted on the official Project Gutenberg-tm web site (www.gutenberg.org), +you must, at no additional cost, fee or expense to the user, provide a +copy, a means of exporting a copy, or a means of obtaining a copy upon +request, of the work in its original "Plain Vanilla ASCII" or other +form. Any alternate format must include the full Project Gutenberg-tm +License as specified in paragraph 1.E.1. + +1.E.7. Do not charge a fee for access to, viewing, displaying, +performing, copying or distributing any Project Gutenberg-tm works +unless you comply with paragraph 1.E.8 or 1.E.9. + +1.E.8. You may charge a reasonable fee for copies of or providing +access to or distributing Project Gutenberg-tm electronic works provided +that + +- You pay a royalty fee of 20% of the gross profits you derive from + the use of Project Gutenberg-tm works calculated using the method + you already use to calculate your applicable taxes. The fee is + owed to the owner of the Project Gutenberg-tm trademark, but he + has agreed to donate royalties under this paragraph to the + Project Gutenberg Literary Archive Foundation. Royalty payments + must be paid within 60 days following each date on which you + prepare (or are legally required to prepare) your periodic tax + returns. Royalty payments should be clearly marked as such and + sent to the Project Gutenberg Literary Archive Foundation at the + address specified in Section 4, "Information about donations to + the Project Gutenberg Literary Archive Foundation." + +- You provide a full refund of any money paid by a user who notifies + you in writing (or by e-mail) within 30 days of receipt that s/he + does not agree to the terms of the full Project Gutenberg-tm + License. You must require such a user to return or + destroy all copies of the works possessed in a physical medium + and discontinue all use of and all access to other copies of + Project Gutenberg-tm works. + +- You provide, in accordance with paragraph 1.F.3, a full refund of any + money paid for a work or a replacement copy, if a defect in the + electronic work is discovered and reported to you within 90 days + of receipt of the work. + +- You comply with all other terms of this agreement for free + distribution of Project Gutenberg-tm works. + +1.E.9. If you wish to charge a fee or distribute a Project Gutenberg-tm +electronic work or group of works on different terms than are set +forth in this agreement, you must obtain permission in writing from +both the Project Gutenberg Literary Archive Foundation and Michael +Hart, the owner of the Project Gutenberg-tm trademark. Contact the +Foundation as set forth in Section 3 below. + +1.F. + +1.F.1. Project Gutenberg volunteers and employees expend considerable +effort to identify, do copyright research on, transcribe and proofread +public domain works in creating the Project Gutenberg-tm +collection. Despite these efforts, Project Gutenberg-tm electronic +works, and the medium on which they may be stored, may contain +"Defects," such as, but not limited to, incomplete, inaccurate or +corrupt data, transcription errors, a copyright or other intellectual +property infringement, a defective or damaged disk or other medium, a +computer virus, or computer codes that damage or cannot be read by +your equipment. + +1.F.2. LIMITED WARRANTY, DISCLAIMER OF DAMAGES - Except for the "Right +of Replacement or Refund" described in paragraph 1.F.3, the Project +Gutenberg Literary Archive Foundation, the owner of the Project +Gutenberg-tm trademark, and any other party distributing a Project +Gutenberg-tm electronic work under this agreement, disclaim all +liability to you for damages, costs and expenses, including legal +fees. YOU AGREE THAT YOU HAVE NO REMEDIES FOR NEGLIGENCE, STRICT +LIABILITY, BREACH OF WARRANTY OR BREACH OF CONTRACT EXCEPT THOSE +PROVIDED IN PARAGRAPH F3. YOU AGREE THAT THE FOUNDATION, THE +TRADEMARK OWNER, AND ANY DISTRIBUTOR UNDER THIS AGREEMENT WILL NOT BE +LIABLE TO YOU FOR ACTUAL, DIRECT, INDIRECT, CONSEQUENTIAL, PUNITIVE OR +INCIDENTAL DAMAGES EVEN IF YOU GIVE NOTICE OF THE POSSIBILITY OF SUCH +DAMAGE. + +1.F.3. LIMITED RIGHT OF REPLACEMENT OR REFUND - If you discover a +defect in this electronic work within 90 days of receiving it, you can +receive a refund of the money (if any) you paid for it by sending a +written explanation to the person you received the work from. If you +received the work on a physical medium, you must return the medium with +your written explanation. The person or entity that provided you with +the defective work may elect to provide a replacement copy in lieu of a +refund. If you received the work electronically, the person or entity +providing it to you may choose to give you a second opportunity to +receive the work electronically in lieu of a refund. If the second copy +is also defective, you may demand a refund in writing without further +opportunities to fix the problem. + +1.F.4. Except for the limited right of replacement or refund set forth +in paragraph 1.F.3, this work is provided to you 'AS-IS' WITH NO OTHER +WARRANTIES OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO +WARRANTIES OF MERCHANTIBILITY OR FITNESS FOR ANY PURPOSE. + +1.F.5. Some states do not allow disclaimers of certain implied +warranties or the exclusion or limitation of certain types of damages. +If any disclaimer or limitation set forth in this agreement violates the +law of the state applicable to this agreement, the agreement shall be +interpreted to make the maximum disclaimer or limitation permitted by +the applicable state law. The invalidity or unenforceability of any +provision of this agreement shall not void the remaining provisions. + +1.F.6. INDEMNITY - You agree to indemnify and hold the Foundation, the +trademark owner, any agent or employee of the Foundation, anyone +providing copies of Project Gutenberg-tm electronic works in accordance +with this agreement, and any volunteers associated with the production, +promotion and distribution of Project Gutenberg-tm electronic works, +harmless from all liability, costs and expenses, including legal fees, +that arise directly or indirectly from any of the following which you do +or cause to occur: (a) distribution of this or any Project Gutenberg-tm +work, (b) alteration, modification, or additions or deletions to any +Project Gutenberg-tm work, and (c) any Defect you cause. + + +Section 2. Information about the Mission of Project Gutenberg-tm + +Project Gutenberg-tm is synonymous with the free distribution of +electronic works in formats readable by the widest variety of computers +including obsolete, old, middle-aged and new computers. It exists +because of the efforts of hundreds of volunteers and donations from +people in all walks of life. + +Volunteers and financial support to provide volunteers with the +assistance they need, are critical to reaching Project Gutenberg-tm's +goals and ensuring that the Project Gutenberg-tm collection will +remain freely available for generations to come. In 2001, the Project +Gutenberg Literary Archive Foundation was created to provide a secure +and permanent future for Project Gutenberg-tm and future generations. +To learn more about the Project Gutenberg Literary Archive Foundation +and how your efforts and donations can help, see Sections 3 and 4 +and the Foundation web page at http://www.pglaf.org. + + +Section 3. Information about the Project Gutenberg Literary Archive +Foundation + +The Project Gutenberg Literary Archive Foundation is a non profit +501(c)(3) educational corporation organized under the laws of the +state of Mississippi and granted tax exempt status by the Internal +Revenue Service. The Foundation's EIN or federal tax identification +number is 64-6221541. Its 501(c)(3) letter is posted at +http://pglaf.org/fundraising. Contributions to the Project Gutenberg +Literary Archive Foundation are tax deductible to the full extent +permitted by U.S. federal laws and your state's laws. + +The Foundation's principal office is located at 4557 Melan Dr. S. +Fairbanks, AK, 99712., but its volunteers and employees are scattered +throughout numerous locations. Its business office is located at +809 North 1500 West, Salt Lake City, UT 84116, (801) 596-1887, email +business@pglaf.org. Email contact links and up to date contact +information can be found at the Foundation's web site and official +page at http://pglaf.org + +For additional contact information: + Dr. Gregory B. Newby + Chief Executive and Director + gbnewby@pglaf.org + + +Section 4. Information about Donations to the Project Gutenberg +Literary Archive Foundation + +Project Gutenberg-tm depends upon and cannot survive without wide +spread public support and donations to carry out its mission of +increasing the number of public domain and licensed works that can be +freely distributed in machine readable form accessible by the widest +array of equipment including outdated equipment. Many small donations +($1 to $5,000) are particularly important to maintaining tax exempt +status with the IRS. + +The Foundation is committed to complying with the laws regulating +charities and charitable donations in all 50 states of the United +States. Compliance requirements are not uniform and it takes a +considerable effort, much paperwork and many fees to meet and keep up +with these requirements. We do not solicit donations in locations +where we have not received written confirmation of compliance. To +SEND DONATIONS or determine the status of compliance for any +particular state visit http://pglaf.org + +While we cannot and do not solicit contributions from states where we +have not met the solicitation requirements, we know of no prohibition +against accepting unsolicited donations from donors in such states who +approach us with offers to donate. + +International donations are gratefully accepted, but we cannot make +any statements concerning tax treatment of donations received from +outside the United States. U.S. laws alone swamp our small staff. + +Please check the Project Gutenberg Web pages for current donation +methods and addresses. Donations are accepted in a number of other +ways including checks, online payments and credit card donations. +To donate, please visit: http://pglaf.org/donate + + +Section 5. General Information About Project Gutenberg-tm electronic +works. + +Professor Michael S. Hart is the originator of the Project Gutenberg-tm +concept of a library of electronic works that could be freely shared +with anyone. For thirty years, he produced and distributed Project +Gutenberg-tm eBooks with only a loose network of volunteer support. + + +Project Gutenberg-tm eBooks are often created from several printed +editions, all of which are confirmed as Public Domain in the U.S. +unless a copyright notice is included. Thus, we do not necessarily +keep eBooks in compliance with any particular paper edition. + + +Most people start at our Web site which has the main PG search facility: + + http://www.gutenberg.org + +This Web site includes information about Project Gutenberg-tm, +including how to make donations to the Project Gutenberg Literary +Archive Foundation, how to help produce our new eBooks, and how to +subscribe to our email newsletter to hear about new eBooks. + + +</pre> + </body> +</html> diff --git a/1909.txt b/1909.txt new file mode 100644 index 0000000..dccccaf --- /dev/null +++ b/1909.txt @@ -0,0 +1,28456 @@ +Project Gutenberg's Darwin and Modern Science, by A.C. Seward and Others + +This eBook is for the use of anyone anywhere at no cost and with +almost no restrictions whatsoever. You may copy it, give it away or +re-use it under the terms of the Project Gutenberg License included +with this eBook or online at www.gutenberg.org + + +Title: Darwin and Modern Science + +Author: A.C. Seward and Others + +Release Date: September, 1999 [Etext #1909] +Posting Date: November 20, 2009 + +Language: English + +Character set encoding: ASCII + +*** START OF THIS PROJECT GUTENBERG EBOOK DARWIN AND MODERN SCIENCE *** + + + + +Produced by Sue Asscher + + + + + +DARWIN AND MODERN SCIENCE + +ESSAYS IN COMMEMORATION OF THE CENTENARY OF THE BIRTH OF CHARLES DARWIN +AND OF THE FIFTIETH ANNIVERSARY OF THE PUBLICATION OF "THE ORIGIN OF +SPECIES" + + +By A.C. Seward + + + +"My success as a man of science, whatever this may have amounted to, +has been determined, as far as I can judge, by complex and diversified +mental qualities and conditions. Of these, the most important have +been--the love of science--unbounded patience in long reflecting over +any subject--industry in observing and collecting facts--and a fair +share of invention as well as of common sense. With such moderate +abilities as I possess, it is truly surprising that I should have +influenced to a considerable extent the belief of scientific men on some +important points." + +Autobiography (1881); "The Life and Letters of Charles Darwin", Vol. 1. +page 107. + + + + +PREFACE + +At the suggestion of the Cambridge Philosophical Society, the Syndics +of the University Press decided in March, 1908, to arrange for the +publication of a series of Essays in commemoration of the Centenary +of the birth of Charles Darwin and of the Fiftieth anniversary of the +publication of "The Origin of Species". The preliminary arrangements +were made by a committee consisting of the following representatives of +the Council of the Philosophical Society and of the Press Syndicate: +Dr H.K. Anderson, Prof. Bateson, Mr Francis Darwin, Dr Hobson, Dr Marr, +Prof. Sedgwick, Mr David Sharp, Mr Shipley, Prof. Sorley, Prof. Seward. +In the course of the preparation of the volume, the original scheme and +list of authors have been modified: a few of those invited to contribute +essays were, for various reasons, unable to do so, and some alterations +have been made in the titles of articles. For the selection of authors +and for the choice of subjects, the committee are mainly responsible, +but for such share of the work in the preparation of the volume as +usually falls to the lot of an editor I accept full responsibility. + +Authors were asked to address themselves primarily to the educated +layman rather than to the expert. It was hoped that the publication +of the essays would serve the double purpose of illustrating the +far-reaching influence of Darwin's work on the progress of knowledge and +the present attitude of original investigators and thinkers towards the +views embodied in Darwin's works. + +In regard to the interpretation of a passage in "The Origin of Species" +quoted by Hugo de Vries, it seemed advisable to add an editorial +footnote; but, with this exception, I have not felt it necessary to +record any opinion on views stated in the essays. + +In reading the essays in proof I have availed myself freely of the +willing assistance of several Cambridge friends, among whom I wish more +especially to thank Mr Francis Darwin for the active interest he +has taken in the preparation of the volume. Mrs J.A. Thomson kindly +undertook the translation of the essays by Prof. Weismann and Prof. +Schwalbe; Mrs James Ward was good enough to assist me by translating +Prof. Bougle's article on Sociology, and to Mr McCabe I am indebted for +the translation of the essay by Prof. Haeckel. For the translation +of the botanical articles by Prof. Goebel, Prof. Klebs and Prof. +Strasburger, I am responsible; in the revision of the translation of +Prof. Strasburger's essay Madame Errera of Brussels rendered valuable +help. Mr Wright, the Secretary of the Press Syndicate, and Mr Waller, +the Assistant Secretary, have cordially cooperated with me in my +editorial work; nor can I omit to thank the readers of the University +Press for keeping watchful eyes on my shortcomings in the correction of +proofs. + +The two portraits of Darwin are reproduced by permission of Messrs Maull +and Fox and Messrs Elliott and Fry. The photogravure of the study at +Down is reproduced from an etching by Mr Axel Haig, lent by Mr Francis +Darwin; the coloured plate illustrating Prof. Weismann's essay was +originally published by him in his "Vortrage uber Descendenztheorie" +which afterwards appeared (1904) in English under the title "The +Evolution Theory". Copies of this plate were supplied by Messrs Fischer +of Jena. + +The Syndics of the University Press have agreed, in the event of +this volume being a financial success, to hand over the profits to a +University fund for the endowment of biological research. + +It is clearly impossible to express adequately in a single volume of +Essays the influence of Darwin's contributions to knowledge on the +subsequent progress of scientific inquiry. As Huxley said in 1885: +"Whatever be the ultimate verdict of posterity upon this or that opinion +which Mr Darwin has propounded; whatever adumbrations or anticipations +of his doctrines may be found in the writings of his predecessors; the +broad fact remains that, since the publication and by reason of the +publication of "The Origin of Species" the fundamental conceptions +and the aims of the students of living Nature have been completely +changed... But the impulse thus given to scientific thought rapidly +spread beyond the ordinarily recognised limits of Biology. Psychology, +Ethics, Cosmology were stirred to their foundations, and 'The Origin of +Species' proved itself to be the fixed point which the general doctrine +needed in order to move the world." + +In the contributions to this Memorial Volume, some of the authors +have more especially concerned themselves with the results achieved by +Darwin's own work, while others pass in review the progress of research +on lines which, though unknown or but little followed in his day, are +the direct outcome of his work. + +The divergence of views among biologists in regard to the origin of +species and as to the most promising directions in which to seek for +truth is illustrated by the different opinions of contributors. Whether +Darwin's views on the modus operandi of evolutionary forces receive +further confirmation in the future, or whether they are materially +modified, in no way affects the truth of the statement that, by +employing his life "in adding a little to Natural Science," he +revolutionised the world of thought. Darwin wrote in 1872 to Alfred +Russel Wallace: "How grand is the onward rush of science: it is enough +to console us for the many errors which we have committed, and for our +efforts being overlaid and forgotten in the mass of new facts and new +views which are daily turning up." In the onward rush, it is easy for +students convinced of the correctness of their own views and equally +convinced of the falsity of those of their fellow-workers to forget the +lessons of Darwin's life. In his autobiographical sketch, he tells us, +"I have steadily endeavoured to keep my mind free so as to give up any +hypothesis, however much beloved...as soon as facts are shown to be +opposed to it." Writing to Mr J. Scott, he says, "It is a golden rule, +which I try to follow, to put every fact which is opposed to one's +preconceived opinion in the strongest light. Absolute accuracy is the +hardest merit to attain, and the highest merit. Any deviation is ruin." + +He acted strictly in accordance with his determination expressed in a +letter to Lyell in 1844, "I shall keep out of controversy, and just +give my own facts." As was said of another son of Cambridge, Sir George +Stokes, "He would no more have thought of disputing about priority, +or the authorship of an idea, than of writing a report for a company +promoter." Darwin's life affords a striking confirmation of the truth +of Hazlitt's aphorism, "Where the pursuit of truth has been the habitual +study of any man's life, the love of truth will be his ruling passion." +Great as was the intellect of Darwin, his character, as Huxley wrote, +was even nobler than his intellect. + +A.C. SEWARD. + +Botany School, Cambridge, March 20, 1909. + + + +CONTENTS +I. INTRODUCTORY LETTER TO THE EDITOR from SIR JOSEPH DALTON HOOKER, O.M. + +II. DARWIN'S PREDECESSORS: J. ARTHUR THOMSON, Professor of Natural +History in the University of Aberdeen. + +III. THE SELECTION THEORY: AUGUST WEISMANN, Professor of Zoology in the +University of Freiburg (Baden). + +IV. VARIATION: HUGO DE VRIES, Professor of Botany in the University of +Amsterdam. + +V. HEREDITY AND VARIATION IN MODERN LIGHTS: W. BATESON, Professor of +Biology in the University of Cambridge. + +VI. THE MINUTE STRUCTURE OF CELLS IN RELATION TO HEREDITY: EDUARD +STRASBURGER, Professor of Botany in the University of Bonn. + +VII. "THE DESCENT OF MAN": G. SCHWALBE, Professor of Anatomy in the +University of Strassburg. + +VIII. CHARLES DARWIN AS AN ANTHROPOLOGIST: ERNST HAECKEL, Professor of +Zoology in the University of Jena. + +IX. SOME PRIMITIVE THEORIES OF THE ORIGIN OF MAN: J.G. FRAZER, Fellow +of Trinity College, Cambridge. + +X. THE INFLUENCE OF DARWIN ON THE STUDY OF ANIMAL EMBRYOLOGY: A. +SEDGWICK, Professor of Zoology and Comparative Anatomy in the University +of Cambridge. + +XI. THE PALAEONTOLOGICAL RECORD. I. ANIMALS: W.B. SCOTT, Professor of +Geology in the University of Princeton. + +XII. THE PALAEONTOLOGICAL RECORD. II. PLANTS: D.H. SCOTT, President of +the Linnean Society of London. + +XIII. THE INFLUENCE OF ENVIRONMENT ON THE FORMS OF PLANTS: GEORG KLEBS, +Professor of Botany in the University of Heidelberg. + +XIV. EXPERIMENTAL STUDY OF THE INFLUENCE OF ENVIRONMENT ON ANIMALS: +JACQUES LOEB, Professor of Physiology in the University of California. + +XV. THE VALUE OF COLOUR IN THE STRUGGLE FOR LIFE: E.B. POULTON, Hope +Professor of Zoology in the University of Oxford. + +XVI. GEOGRAPHICAL DISTRIBUTION OF PLANTS: SIR WILLIAM THISELTON-DYER. + +XVII. GEOGRAPHICAL DISTRIBUTION OF ANIMALS: HANS GADOW, Strickland +Curator and Lecturer on Zoology in the University of Cambridge. + +XVIII. DARWIN AND GEOLOGY: J.W. JUDD. + +XIX. DARWIN'S WORK ON THE MOVEMENTS OF PLANTS: FRANCIS DARWIN. + +XX. THE BIOLOGY OF FLOWERS: K. GOEBEL, Professor of Botany in the +University of Munich. + +XXI. MENTAL FACTORS IN EVOLUTION: C. LLOYD MORGAN, Professor of +Psychology at University College, Bristol. + +XXII. THE INFLUENCE OF THE CONCEPTION OF EVOLUTION ON MODERN PHILOSOPHY: +H. HOFFDING, Professor of Philosophy in the University of Copenhagen. + +XXIII. DARWINISM AND SOCIOLOGY: C. BOUGLE, Professor of Social +Philosophy in the University of Toulouse, and Deputy-Professor at the +Sorbonne, Paris. + +XXIV. THE INFLUENCE OF DARWIN UPON RELIGIOUS THOUGHT: REV. P.N. +WAGGETT. + +XXV. THE INFLUENCE OF DARWINISM ON THE STUDY OF RELIGIONS: JANE ELLEN +HARRISON, Staff-Lecturer and sometime Fellow of Newnham College, +Cambridge. + +XXVI. EVOLUTION AND THE SCIENCE OF LANGUAGE: P. GILES, Reader in +Comparative Philology in the University of Cambridge. + +XXVII. DARWINISM AND HISTORY: J.B. BURY, Regius Professor of Modern +History in the University of Cambridge. + +XXVIII. THE GENESIS OF DOUBLE STARS: SIR GEORGE DARWIN, Plumian +Professor of Astronomy and Experimental Philosophy in the University of +Cambridge. + +XXIX. THE EVOLUTION OF MATTER: W.C.D. WHETHAM, Fellow of Trinity +College, Cambridge. + +INDEX. + + + + +DATES OF THE PUBLICATION Of CHARLES DARWIN'S BOOKS AND OF THE PRINCIPAL +EVENTS IN HIS LIFE + +1809: + +Charles Darwin born at Shrewsbury, February 12. + +1817: + +"At 8 1/2 years old I went to Mr Case's school." (A day-school at +Shrewsbury kept by the Rev G. Case, Minister of the Unitarian Chapel.) + +1818: + +"I was at school at Shrewsbury under a great scholar, Dr Butler; I +learnt absolutely nothing, except by amusing myself by reading and +experimenting in Chemistry." + +1825: + +"As I was doing no good at school, my father wisely took me away at +a rather earlier age than usual, and sent me (Oct. 1825) to Edinburgh +University with my brother, where I stayed for two years." + +1828: + +Began residence at Christ's College, Cambridge. + +"I went to Cambridge early in the year 1828, and soon became acquainted +with Professor Henslow...Nothing could be more simple, cordial and +unpretending than the encouragement which he afforded to all young +naturalists." + +"During the three years which I spent at Cambridge my time was wasted, +as far as the academical studies were concerned, as completely as at +Edinburgh and at school." + +"In order to pass the B.A. Examination, it was...necessary to get up +Paley's 'Evidences of Christianity,' and his 'Moral Philosophy'... The +careful study of these works, without attempting to learn any part by +rote, was the only part of the academical course which...was of the +least use to me in the education of my mind." + +1831: + +Passed the examination for the B.A. degree in January and kept the +following terms. + +"I gained a good place among the oi polloi or crowd of men who do not go +in for honours." + +"I am very busy,...and see a great deal of Henslow, whom I do not know +whether I love or respect most." + +Dec. 27. "Sailed from England on our circumnavigation," in H.M.S. +"Beagle", a barque of 235 tons carrying 6 guns, under Capt. FitzRoy. + +"There is indeed a tide in the affairs of men." + +1836: + +Oct. 4. "Reached Shrewsbury after absence of 5 years and 2 days." + +"You cannot imagine how gloriously delightful my first visit was at +home; it was worth the banishment." + +Dec. 13. Went to live at Cambridge (Fitzwilliam Street). + +"The only evil I found in Cambridge was its being too pleasant." + +1837: + +"On my return home (in the 'Beagle') in the autumn of 1836 I immediately +began to prepare my journal for publication, and then saw how many facts +indicated the common descent of species... In July (1837) I opened my +first note-book for facts in relation to the Origin of Species, about +which I had long reflected, and never ceased working for the next twenty +years... Had been greatly struck from about the month of previous +March on character of South American fossils, and species on Galapagos +Archipelago. These facts (especially latter), origin of all my views." + +"On March 7, 1837 I took lodgings in (36) Great Marlborough Street in +London, and remained there for nearly two years, until I was married." + +1838: + +"In October, that is fifteen months after I had begun my systematic +enquiry, I happened to read for amusement 'Malthus on Population,' +and being well prepared to appreciate the struggle for existence which +everywhere goes on from long-continued observation of the habits of +animals and plants, it at once struck me that under these circumstances +favourable variations would tend to be preserved, and unfavourable +ones to be destroyed. The result of this would be the formation of new +species. Here then I had at last got a theory by which to work; but I +was so anxious to avoid prejudice, that I determined not for some time +to write even the briefest sketch of it." + +1839: + +Married at Maer (Staffordshire) to his first cousin Emma Wedgwood, +daughter of Josiah Wedgwood. + +"I marvel at my good fortune that she, so infinitely my superior in +every single moral quality, consented to be my wife. She has been my +wise adviser and cheerful comforter throughout life, which without +her would have been during a very long period a miserable one +from ill-health. She has earned the love of every soul near her" +(Autobiography). + +Dec. 31. "Entered 12 Upper Gower street" (now 110 Gower street, London). +"There never was so good a house for me, and I devoutly trust you (his +future wife) will approve of it equally. The little garden is worth its +weight in gold." + +Published "Journal and Researches", being Vol. III. of the "Narrative of +the Surveying Voyage of H.M.S. 'Adventure' and 'Beagle'"... + +Publication of the "Zoology of the Voyage of H.M.S. 'Beagle'", Part +II., "Mammalia", by G.R. Waterhouse, with a "Notice of their habits and +ranges", by Charles Darwin. + +1840: + +Contributed Geological Introduction to Part I. ("Fossil Mammalia") of +the "Zoology of the Voyage of H.M.S. 'Beagle'" by Richard Owen. + +1842: + +"In June 1842 I first allowed myself the satisfaction of writing a very +brief abstract of my (species) theory in pencil in 35 pages; and this +was enlarged during the summer of 1844 into one of 230 pages, which I +had fairly copied out and still (1876) possess." (The first draft of +"The Origin of Species", edited by Mr Francis Darwin, will be published +this year (1909) by the Syndics of the Cambridge University Press.) + +Sept. 14. Settled at the village of Down in Kent. + +"I think I was never in a more perfectly quiet country." + +Publication of "The Structure and Distribution of Coral Reefs"; being +Part I. of the "Geology of the Voyage of the Beagle". + +1844: + +Publication of "Geological Observations on the Volcanic Islands visited +during the Voyage of H.M.S. 'Beagle'"; being Part II. of the "Geology of +the Voyage of the 'Beagle'". + +"I think much more highly of my book on Volcanic Islands since Mr Judd, +by far the best judge on the subject in England, has, as I hear, learnt +much from it." (Autobiography, 1876.) + +1845: + +Publication of the "Journal of Researches" as a separate book. + +1846: + +Publication of "Geological Observations on South America"; being Part +III. of the "Geology of the Voyage of the 'Beagle'". + +1851: + +Publication of a "Monograph of the Fossil Lepadidae" and of a "Monograph +of the sub-class Cirripedia". + +"I fear the study of the Cirripedia will ever remain 'wholly unapplied,' +and yet I feel that such study is better than castle-building." + +1854: + +Publication of Monographs of the Balanidae and Verrucidae. + +"I worked steadily on this subject for...eight years, and ultimately +published two thick volumes, describing all the known living +species, and two thin quartos on the extinct species... My work was of +considerable use to me, when I had to discuss in the "Origin of Species" +the principles of a natural classification. Nevertheless, I doubt +whether the work was worth the consumption of so much time." + +"From September 1854 I devoted my whole time to arranging my huge +pile of notes, to observing, and to experimenting in relation to the +transmutation of species." + +1856: + +"Early in 1856 Lyell advised me to write out my views pretty fully, and +I began at once to do so on a scale three or four times as extensive as +that which was afterwards followed in my 'Origin of Species'." + +1858: + +Joint paper by Charles Darwin and Alfred Russel Wallace "On the Tendency +of Species to form Varieties; and on the perpetuation of Varieties and +Species by Natural Means of Selection," communicated to the Linnean +Society by Sir Charles Lyell and Sir Joseph Hooker. + +"I was at first very unwilling to consent (to the communication of his +MS. to the Society) as I thought Mr Wallace might consider my doing so +unjustifiable, for I did not then know how generous and noble was his +disposition." + +"July 20 to Aug. 12 at Sandown (Isle of Wight) began abstract of Species +book." + +1859: + +Nov. 24. Publication of "The Origin of Species" (1250 copies). + +"Oh, good heavens, the relief to my head and body to banish the whole +subject from my mind!... But, alas, how frequent, how almost universal it +is in an author to persuade himself of the truth of his own dogmas. +My only hope is that I certainly see many difficulties of gigantic +stature." + +1860: + +Publication of the second edition of the "Origin" (3000 copies). + +Publication of a "Naturalist's Voyage". + +1861: + +Publication of the third edition of the "Origin" (2000 copies). + +"I am going to write a little book... on Orchids, and to-day I hate them +worse than everything." + +1862: + +Publication of the book "On the various contrivances by which Orchids +are fertilised by Insects". + +1865: + +Read paper before the Linnean Society "On the Movements and Habits of +Climbing plants". (Published as a book in 1875.) + +1866: + +Publication of the fourth edition of the "Origin" (1250 copies). + +1868: + +"I have sent the MS. of my big book, and horridly, disgustingly big it +will be, to the printers." + +Publication of the "Variation of Animals and Plants under +Domestication". + +"About my book, I will give you (Sir Joseph Hooker) a bit of advice. +Skip the whole of Vol. I, except the last chapter, (and that need only +be skimmed), and skip largely in the 2nd volume; and then you will say +it is a very good book." + +"Towards the end of the work I give my well-abused hypothesis of +Pangenesis. An unverified hypothesis is of little or no value; but if +anyone should hereafter be led to make observations by which some such +hypothesis could be established, I shall have done good service, as an +astonishing number of isolated facts can be thus connected together and +rendered intelligible." + +1869: + +Publication of the fifth edition of the "Origin". + +1871: + +Publication of "The Descent of Man". + +"Although in the 'Origin of Species' the derivation of any particular +species is never discussed, yet I thought it best, in order that no +honourable man should accuse me of concealing my views, to add that by +the work 'light would be thrown on the origin of man and his history'." + +1872: + +Publication of the sixth edition of the "Origin". + +Publication of "The Expression of the Emotions in Man and Animals". + +1874: + +Publication of the second edition of "The Descent of Man". + +"The new edition of the "Descent" has turned out an awful job. It took +me ten days merely to glance over letters and reviews with criticisms +and new facts. It is a devil of a job." + +Publication of the second edition of "The Structure and Distribution of +Coral Reefs". + +1875: + +Publication of "Insectivorous Plants". + +"I begin to think that every one who publishes a book is a fool." + +Publication of the second edition of "Variation in Animals and Plants". + +Publication of "The Movements and Habits of Climbing Plants" as a +separate book. + +1876: + +Wrote Autobiographical Sketch ("Life and Letters", Vol. I., Chap II.). + +Publication of "The Effects of Cross and Self fertilisation". + +"I now (1881) believe, however,...that I ought to have insisted more +strongly than I did on the many adaptations for self-fertilisation." + +Publication of the second edition of "Observations on Volcanic Islands". + +1877: + +Publication of "The Different Forms of Flowers on Plants of the same +species". + +"I do not suppose that I shall publish any more books... I cannot endure +being idle, but heaven knows whether I am capable of any more good +work." + +Publication of the second edition of the Orchid book. + +1878: + +Publication of the second edition of "The Effects of Cross and Self +fertilisation". + +1879: + +Publication of an English translation of Ernst Krause's "Erasmus +Darwin", with a notice by Charles Darwin. "I am EXTREMELY glad that +you approve of the little 'Life' of our Grandfather, for I have been +repenting that I ever undertook it, as the work was quite beyond my +tether." (To Mr Francis Galton, Nov. 14, 1879.) + +1880: + +Publication of "The Power of Movement in Plants". + +"It has always pleased me to exalt plants in the scale of organised +beings." + +Publication of the second edition of "The Different Forms of Flowers". + +1881: + +Wrote a continuation of the Autobiography. + +Publication of "The Formation of Vegetable Mould, through the Action of +Worms". + +"It is the completion of a short paper read before the Geological +Society more than forty years ago, and has revived old geological +thoughts... As far as I can judge it will be a curious little book." + +1882: + +Charles Darwin died at Down, April 19, and was buried in Westminster +Abbey, April 26, in the north aisle of the Nave a few feet from the +grave of Sir Isaac Newton. + +"As for myself, I believe that I have acted rightly in steadily +following and devoting my life to Science. I feel no remorse from having +committed any great sin, but have often and often regretted that I have +not done more direct good to my fellow creatures." + +The quotations in the above Epitome are taken from the Autobiography and +published Letters:-- + +"The Life and Letters of Charles Darwin", including an Autobiographical +Chapter. Edited by his son, Francis Darwin, 3 Vols., London, 1887. + +"Charles Darwin": His life told in an Autobiographical Chapter, and in +a selected series of his published Letters. Edited by his son, Francis +Darwin, London, 1902. + +"More Letters of Charles Darwin". A record of his work in a series of +hitherto unpublished Letters. Edited by Francis Darwin and A.C. Seward, +2 Vols., London, 1903. + + + + +I. INTRODUCTORY LETTER From Sir Joseph Dalton Hooker, O.M., G.C.S.I., +C.B., M.D., D.C.L., LL.D., F.R.S., ETC. + + +The Camp, + +near Sunningdale, + +January 15, 1909. + +Dear Professor Seward, + +The publication of a Series of Essays in Commemoration of the century +of the birth of Charles Darwin and of the fiftieth anniversary of the +publication of "The Origin of Species" is assuredly welcome and is a +subject of congratulation to all students of Science. + +These Essays on the progress of Science and Philosophy as affected by +Darwin's labours have been written by men known for their ability to +discuss the problems which he so successfully worked to solve. They +cannot but prove to be of enduring value, whether for the information of +the general reader or as guides to investigators occupied with problems +similar to those which engaged the attention of Darwin. + +The essayists have been fortunate in having for reference the five +published volumes of Charles Darwin's Life and Correspondence. For there +is set forth in his own words the inception in his mind of the problems, +geological, zoological and botanical, hypothetical and theoretical, +which he set himself to solve and the steps by which he proceeded to +investigate them with the view of correlating the phenomena of life with +the evolution of living things. In his letters he expressed himself in +language so lucid and so little burthened with technical terms that they +may be regarded as models for those who were asked to address themselves +primarily to the educated reader rather than to the expert. + +I may add that by no one can the perusal of the Essays be more vividly +appreciated than by the writer of these lines. It was my privilege for +forty years to possess the intimate friendship of Charles Darwin and to +be his companion during many of his working hours in Study, Laboratory, +and Garden. I was the recipient of letters from him, relating mainly to +the progress of his researches, the copies of which (the originals are +now in the possession of his family) cover upwards of a thousand pages +of foolscap, each page containing, on an average, three hundred words. + +That the editorship of these Essays has been entrusted to a Cambridge +Professor of Botany must be gratifying to all concerned in their +production and in their perusal, recalling as it does the fact that +Charles Darwin's instructor in scientific methods was his lifelong +friend the late Rev. J.S. Henslow at that time Professor of Botany in +the University. It was owing to his recommendation that his pupil was +appointed Naturalist to H.M.S. "Beagle", a service which Darwin himself +regarded as marking the dawn of his scientific career. + +Very sincerely yours, + +J.D. HOOKER. + + + + +II. DARWIN'S PREDECESSORS. By J. Arthur Thomson. + +Professor of Natural History in the University of Aberdeen. + + +In seeking to discover Darwin's relation to his predecessors it is +useful to distinguish the various services which he rendered to the +theory of organic evolution. + +(I) As everyone knows, the general idea of the Doctrine of Descent +is that the plants and animals of the present-day are the lineal +descendants of ancestors on the whole somewhat simpler, that these again +are descended from yet simpler forms, and so on backwards towards the +literal "Protozoa" and "Protophyta" about which we unfortunately know +nothing. Now no one supposes that Darwin originated this idea, which in +rudiment at least is as old as Aristotle. What Darwin did was to make +it current intellectual coin. He gave it a form that commended itself +to the scientific and public intelligence of the day, and he won +wide-spread conviction by showing with consummate skill that it was +an effective formula to work with, a key which no lock refused. In +a scholarly, critical, and pre-eminently fair-minded way, admitting +difficulties and removing them, foreseeing objections and forestalling +them, he showed that the doctrine of descent supplied a modal +interpretation of how our present-day fauna and flora have come to be. + +(II) In the second place, Darwin applied the evolution-idea to +particular problems, such as the descent of man, and showed what a +powerful organon it is, introducing order into masses of uncorrelated +facts, interpreting enigmas both of structure and function, both +bodily and mental, and, best of all, stimulating and guiding further +investigation. But here again it cannot be claimed that Darwin was +original. The problem of the descent or ascent of man, and other +particular cases of evolution, had attracted not a few naturalists +before Darwin's day, though no one (except Herbert Spencer in the +psychological domain (1855)) had come near him in precision and +thoroughness of inquiry. + +(III) In the third place, Darwin contributed largely to a knowledge of +the factors in the evolution-process, especially by his analysis of what +occurs in the case of domestic animals and cultivated plants, and by +his elaboration of the theory of Natural Selection, which Alfred Russel +Wallace independently stated at the same time, and of which there had +been a few previous suggestions of a more or less vague description. +It was here that Darwin's originality was greatest, for he revealed to +naturalists the many different forms--often very subtle--which natural +selection takes, and with the insight of a disciplined scientific +imagination he realised what a mighty engine of progress it has been and +is. + +(IV) As an epoch-marking contribution, not only to Aetiology but to +Natural History in the widest sense, we rank the picture which +Darwin gave to the world of the web of life, that is to say, of +the inter-relations and linkages in Nature. For the Biology of the +individual--if that be not a contradiction in terms--no idea is more +fundamental than that of the correlation of organs, but Darwin's most +characteristic contribution was not less fundamental,--it was the idea +of the correlation of organisms. This, again, was not novel; we find +it in the works of naturalist like Christian Conrad Sprengel, Gilbert +White, and Alexander von Humboldt, but the realisation of its full +import was distinctively Darwinian. + +AS REGARDS THE GENERAL IDEA OF ORGANIC EVOLUTION. + +While it is true, as Prof. H.F. Osborn puts it, that "'Before and after +Darwin' will always be the ante et post urbem conditam of biological +history," it is also true that the general idea of organic evolution +is very ancient. In his admirable sketch "From the Greeks to Darwin" +("Columbia University Biological Series", Vol. I. New York and London, +1894. We must acknowledge our great indebtness to this fine piece of +work.), Prof. Osborn has shown that several of the ancient philosophers +looked upon Nature as a gradual development and as still in process of +change. In the suggestions of Empedocles, to take the best instance, +there were "four sparks of truth,--first, that the development of life +was a gradual process; second, that plants were evolved before animals; +third, that imperfect forms were gradually replaced (not succeeded) +by perfect forms; fourth, that the natural cause of the production of +perfect forms was the extinction of the imperfect." (Op. cit. page +41.) But the fundamental idea of one stage giving origin to another was +absent. As the blue Aegean teemed with treasures of beauty and threw +many upon its shores, so did Nature produce like a fertile artist what +had to be rejected as well as what was able to survive, but the idea of +one species emerging out of another was not yet conceived. + +Aristotle's views of Nature (See G.J. Romanes, "Aristotle as a +Naturalist", "Contemporary Review", Vol. LIX. page 275, 1891; G. Pouchet +"La Biologie Aristotelique", Paris, 1885; E. Zeller, "A History of +Greek Philosophy", London, 1881, and "Ueber die griechischen Vorganger +Darwin's", "Abhandl. Berlin Akad." 1878, pages 111-124.) seem to have +been more definitely evolutionist than those of his predecessors, in +this sense, at least, that he recognised not only an ascending scale, +but a genetic series from polyp to man and an age-long movement towards +perfection. "It is due to the resistance of matter to form that Nature +can only rise by degrees from lower to higher types." "Nature produces +those things which, being continually moved by a certain principle +contained in themselves, arrive at a certain end." + +To discern the outcrop of evolution-doctrine in the long interval +between Aristotle and Bacon seems to be very difficult, and some of +the instances that have been cited strike one as forced. Epicurus and +Lucretius, often called poets of evolution, both pictured animals as +arising directly out of the earth, very much as Milton's lion long +afterwards pawed its way out. Even when we come to Bruno who wrote that +"to the sound of the harp of the Universal Apollo (the World Spirit), +the lower organisms are called by stages to higher, and the lower stages +are connected by intermediate forms with the higher," there is great +room, as Prof. Osborn points out (op. cit. page 81.), for difference of +opinion as to how far he was an evolutionist in our sense of the term. + +The awakening of natural science in the sixteenth century brought the +possibility of a concrete evolution theory nearer, and in the early +seventeenth century we find evidences of a new spirit--in the embryology +of Harvey and the classifications of Ray. Besides sober naturalists +there were speculative dreamers in the sixteenth and seventeenth +centuries who had at least got beyond static formulae, but, as Professor +Osborn points out (op. cit. page 87.), "it is a very striking fact, that +the basis of our modern methods of studying the Evolution problem was +established not by the early naturalists nor by the speculative writers, +but by the Philosophers." He refers to Bacon, Descartes, Leibnitz, Hume, +Kant, Lessing, Herder, and Schelling. "They alone were upon the main +track of modern thought. It is evident that they were groping in the +dark for a working theory of the Evolution of life, and it is remarkable +that they clearly perceived from the outset that the point to which +observation should be directed was not the past but the present +mutability of species, and further, that this mutability was simply the +variation of individuals on an extended scale." + +Bacon seems to have been one of the first to think definitely about the +mutability of species, and he was far ahead of his age in his suggestion +of what we now call a Station of Experimental Evolution. Leibnitz +discusses in so many words how the species of animals may be changed +and how intermediate species may once have linked those that now seem +discontinuous. "All natural orders of beings present but a single +chain"... "All advances by degrees in Nature, and nothing by leaps." +Similar evolutionist statements are to be found in the works of the +other "philosophers," to whom Prof. Osborn refers, who were, indeed, +more scientific than the naturalists of their day. It must be borne in +mind that the general idea of organic evolution--that the present is +the child of the past--is in great part just the idea of human history +projected upon the natural world, differentiated by the qualification +that the continuous "Becoming" has been wrought out by forces inherent +in the organisms themselves and in their environment. + +A reference to Kant (See Brock, "Die Stellung Kant's zur +Deszendenztheorie," "Biol. Centralbl." VIII. 1889, pages 641-648. Fritz +Schultze, "Kant und Darwin", Jena, 1875.) should come in historical +order after Buffon, with whose writings he was acquainted, but he seems, +along with Herder and Schelling, to be best regarded as the culmination +of the evolutionist philosophers--of those at least who interested +themselves in scientific problems. In a famous passage he speaks of +"the agreement of so many kinds of animals in a certain common plan of +structure"... an "analogy of forms" which "strengthens the supposition +that they have an actual blood-relationship, due to derivation from a +common parent." He speaks of "the great Family of creatures, for as +a Family we must conceive it, if the above-mentioned continuous and +connected relationship has a real foundation." Prof. Osborn alludes to +the scientific caution which led Kant, biology being what it was, to +refuse to entertain the hope "that a Newton may one day arise even to +make the production of a blade of grass comprehensible, according +to natural laws ordained by no intention." As Prof. Haeckel finely +observes, Darwin rose up as Kant's Newton. (Mr Alfred Russel Wallace +writes: "We claim for Darwin that he is the Newton of natural history, +and that, just so surely as that the discovery and demonstration by +Newton of the law of gravitation established order in place of chaos and +laid a sure foundation for all future study of the starry heavens, so +surely has Darwin, by his discovery of the law of natural selection and +his demonstration of the great principle of the preservation of useful +variations in the struggle for life, not only thrown a flood of light +on the process of development of the whole organic world, but +also established a firm foundation for all future study of nature." +("Darwinism", London, 1889, page 9). See also Prof. Karl Pearson's +"Grammar of Science" (2nd edition), London, 1900, page 32. See Osborn, +op. cit. Page 100.)) + +The scientific renaissance brought a wealth of fresh impressions and +some freedom from the tyranny of tradition, and the twofold stimulus +stirred the speculative activity of a great variety of men from old +Claude Duret of Moulins, of whose weird transformism (1609) Dr Henry +de Varigny ("Experimental Evolution". London, 1892. Chap. 1. page 14.) +gives us a glimpse, to Lorenz Oken (1799-1851) whose writings are such +mixtures of sense and nonsense that some regard him as a +far-seeing prophet and others as a fatuous follower of intellectual +will-o'-the-wisps. Similarly, for De Maillet, Maupertuis, Diderot, +Bonnet, and others, we must agree with Professor Osborn that they were +not actually in the main Evolution movement. Some have been included in +the roll of honour on very slender evidence, Robinet for instance, whose +evolutionism seems to us extremely dubious. (See J. Arthur Thomson, +"The Science of Life". London, 1899. Chap. XVI. "Evolution of Evolution +Theory".) + +The first naturalist to give a broad and concrete expression to the +evolutionist doctrine of descent was Buffon (1707-1788), but it +is interesting to recall the fact that his contemporary Linnaeus +(1707-1778), protagonist of the counter-doctrine of the fixity +of species (See Carus Sterne (Ernest Krause), "Die allgemeine +Weltanschauung in ihrer historischen Entwickelung". Stuttgart, 1889. +Chapter entitled "Bestandigkeit oder Veranderlichkeit der Naturwesen".), +went the length of admitting (in 1762) that new species might arise +by intercrossing. Buffon's position among the pioneers of the +evolution-doctrine is weakened by his habit of vacillating between his +own conclusions and the orthodoxy of the Sorbonne, but there is no doubt +that he had a firm grasp of the general idea of "l'enchainement des +etres." + +Erasmus Darwin (1731-1802), probably influenced by Buffon, was another +firm evolutionist, and the outline of his argument in the "Zoonomia" +("Zoonomia, or the Laws of Organic Life", 2 vols. London, 1794; Osborn +op. cit. page 145.) might serve in part at least to-day. "When we +revolve in our minds the metamorphoses of animals, as from the tadpole +to the frog; secondly, the changes produced by artificial cultivation, +as in the breeds of horses, dogs, and sheep; thirdly, the changes +produced by conditions of climate and of season, as in the sheep of +warm climates being covered with hair instead of wool, and the hares and +partridges of northern climates becoming white in winter: when, +further, we observe the changes of structure produced by habit, as seen +especially in men of different occupations; or the changes produced by +artificial mutilation and prenatal influences, as in the crossing +of species and production of monsters; fourth, when we observe the +essential unity of plan in all warm-blooded animals,--we are led to +conclude that they have been alike produced from a similar living +filament"... "From thus meditating upon the minute portion of time in +which many of the above changes have been produced, would it be too bold +to imagine, in the great length of time since the earth began to exist, +perhaps millions of years before the commencement of the history of +mankind, that all warm-blooded animals have arisen from one living +filament?"... "This idea of the gradual generation of all things seems to +have been as familiar to the ancient philosophers as to the modern +ones, and to have given rise to the beautiful hieroglyphic figure of the +proton oon, or first great egg, produced by night, that is, whose origin +is involved in obscurity, and animated by Eros, that is, by Divine Love; +from whence proceeded all things which exist." + +Lamarck (1744-1829) seems to have become an evolutionist independently +of Erasmus Darwin's influence, though the parallelism between them is +striking. He probably owed something to Buffon, but he developed his +theory along a different line. Whatever view be held in regard to that +theory there is no doubt that Lamarck was a thorough-going evolutionist. +Professor Haeckel speaks of the "Philosophie Zoologique" as "the first +connected and thoroughly logical exposition of the theory of descent." +(See Alpheus S. Packard, "Lamarck, the Founder of Evolution, His Life +and Work, with Translations of his writings on Organic Evolution". +London, 1901.) + +Besides the three old masters, as we may call them, Buffon, Erasmus +Darwin, and Lamarck, there were other quite convinced pre-Darwinian +evolutionists. The historian of the theory of descent must take account +of Treviranus whose "Biology or Philosophy of Animate Nature" is full of +evolutionary suggestions; of Etienne Geoffroy St Hilaire, who in +1830, before the French Academy of Sciences, fought with Cuvier, the +fellow-worker of his youth, an intellectual duel on the question of +descent; of Goethe, one of the founders of morphology and the greatest +poet of Evolution--who, in his eighty-first year, heard the tidings +of Geoffroy St Hilaire's defeat with an interest which transcended the +political anxieties of the time; and of many others who had gained with +more or less confidence and clearness a new outlook on Nature. It +will be remembered that Darwin refers to thirty-four more or less +evolutionist authors in his Historical Sketch, and the list might be +added to. Especially when we come near to 1858 do the numbers increase, +and one of the most remarkable, as also most independent champions of +the evolution-idea before that date was Herbert Spencer, who not only +marshalled the arguments in a very forcible way in 1852, but applied the +formula in detail in his "Principles of Psychology" in 1855. (See Edward +Clodd, "Pioneers of Evolution", London, page 161, 1897.) + +It is right and proper that we should shake ourselves free from all +creationist appreciations of Darwin, and that we should recognise the +services of pre-Darwinian evolutionists who helped to make the time +ripe, yet one cannot help feeling that the citation of them is apt to +suggest two fallacies. It may suggest that Darwin simply entered into +the labours of his predecessors, whereas, as a matter of fact, he knew +very little about them till after he had been for years at work. To +write, as Samuel Butler did, "Buffon planted, Erasmus Darwin and Lamarck +watered, but it was Mr Darwin who said 'That fruit is ripe,' and shook +it into his lap"... seems to us a quite misleading version of the facts +of the case. The second fallacy which the historical citation is +a little apt to suggest is that the filiation of ideas is a simple +problem. On the contrary, the history of an idea, like the pedigree +of an organism, is often very intricate, and the evolution of the +evolution-idea is bound up with the whole progress of the world. Thus +in order to interpret Darwin's clear formulation of the idea of organic +evolution and his convincing presentation of it, we have to do more than +go back to his immediate predecessors, such as Buffon, Erasmus Darwin, +and Lamarck; we have to inquire into the acceptance of evolutionary +conceptions in regard to other orders of facts, such as the earth and +the solar system (See Chapter IX. "The Genetic View of Nature" in J.T. +Merz's "History of European Thought in the Nineteenth Century", Vol. 2, +Edinburgh and London, 1903.); we have to realise how the growing success +of scientific interpretation along other lines gave confidence to those +who refused to admit that there was any domain from which science could +be excluded as a trespasser; we have to take account of the development +of philosophical thought, and even of theological and religious +movements; we should also, if we are wise enough, consider social +changes. In short, we must abandon the idea that we can understand +the history of any science as such, without reference to contemporary +evolution in other departments of activity. + +While there were many evolutionists before Darwin, few of them were +expert naturalists and few were known outside a small circle; what +was of much more importance was that the genetic view of nature was +insinuating itself in regard to other than biological orders of facts, +here a little and there a little, and that the scientific spirit had +ripened since the days when Cuvier laughed Lamarck out of court. How was +it that Darwin succeeded where others had failed? Because, in the first +place, he had clear visions--"pensees de la jeunesse, executees par +l'age mur"--which a University curriculum had not made impossible, which +the "Beagle" voyage made vivid, which an unrivalled British doggedness +made real--visions of the web of life, of the fountain of change within +the organism, of the struggle for existence and its winnowing, and of +the spreading genealogical tree. Because, in the second place, he put +so much grit into the verification of his visions, putting them to the +proof in an argument which is of its kind--direct demonstration being +out of the question--quite unequalled. Because, in the third place, +he broke down the opposition which the most scientific had felt to +the seductive modal formula of evolution by bringing forward a more +plausible theory of the process than had been previously suggested. +Nor can one forget, since questions of this magnitude are human and not +merely academic, that he wrote so that all men could understand. + +AS REGARDS THE FACTORS OF EVOLUTION. + +It is admitted by all who are acquainted with the history of biology +that the general idea of organic evolution as expressed in the Doctrine +of Descent was quite familiar to Darwin's grandfather, and to others +before and after him, as we have briefly indicated. It must also be +admitted that some of these pioneers of evolutionism did more than apply +the evolution-idea as a modal formula of becoming, they began to inquire +into the factors in the process. Thus there were pre-Darwinian theories +of evolution, and to these we must now briefly refer. (See Prof. W.A. +Locy's "Biology and its Makers". New York, 1908. Part II. "The Doctrine +of Organic Evolution".) + +In all biological thinking we have to work with the categories +Organism--Function--Environment, and theories of evolution may be +classified in relation to these. To some it has always seemed that the +fundamental fact is the living organism,--a creative agent, a striving +will, a changeful Proteus, selecting its environment, adjusting +itself to it, self-differentiating and self-adaptive. The necessity of +recognising the importance of the organism is admitted by all Darwinians +who start with inborn variations, but it is open to question whether the +whole truth of what we might call the Goethian position is exhausted in +the postulate of inherent variability. + +To others it has always seemed that the emphasis should be laid on +Function,--on use and disuse, on doing and not doing. Practice makes +perfect; c'est a force de forger qu'on devient forgeron. This is one of +the fundamental ideas of Lamarckism; to some extent it met with Darwin's +approval; and it finds many supporters to-day. One of the ablest +of these--Mr Francis Darwin--has recently given strong reasons for +combining a modernised Lamarckism with what we usually regard as sound +Darwinism. (Presidential Address to the British Association meeting at +Dublin in 1908.) + +To others it has always seemed that the emphasis should be laid on the +Environment, which wakes the organism to action, prompts it to change, +makes dints upon it, moulds it, prunes it, and finally, perhaps, kills +it. It is again impossible to doubt that there is truth in this +view, for even if environmentally induced "modifications" be not +transmissible, environmentally induced "variations" are; and even if +the direct influence of the environment be less important than +many enthusiastic supporters of this view--may we call them +Buffonians--think, there remains the indirect influence which Darwinians +in part rely on,--the eliminative process. Even if the extreme view +be held that the only form of discriminate elimination that counts is +inter-organismal competition, this might be included under the rubric of +the animate environment. + +In many passages Buffon (See in particular Samuel Butler, "Evolution +Old and New", London, 1879; J.L. de Lanessan, "Buffon et Darwin", +"Revue Scientifique", XLIII. pages 385-391, 425-432, 1889.) definitely +suggested that environmental influences--especially of climate and +food--were directly productive of changes in organisms, but he did not +discuss the question of the transmissibility of the modifications so +induced, and it is difficult to gather from his inconsistent writings +what extent of transformation he really believed in. Prof. Osborn +says of Buffon: "The struggle for existence, the elimination of the +least-perfected species, the contest between the fecundity of certain +species and their constant destruction, are all clearly expressed in +various passages." He quotes two of these (op. cit. page 136.): + +"Le cours ordinaire de la nature vivante, est en general toujours +constant, toujours le meme; son mouvement, toujours regulier, roule +sur deux points inebranlables: l'un, la fecondite sans bornes donnee +a toutes les especes; l'autre, les obstacles sans nombre qui reduisent +cette fecondite a une mesure determinee et ne laissent en tout temps +qu'a peu pres la meme quantite d'individus de chaque espece"... "Les +especes les moins parfaites, les plus delicates, les plus pesantes, +les moins agissantes, les moins armees, etc., ont deja disparu ou +disparaitront." + +Erasmus Darwin (See Ernst Krause and Charles Darwin, "Erasmus Darwin", +London, 1879.) had a firm grip of the "idea of the gradual formation and +improvement of the Animal world," and he had his theory of the process. +No sentence is more characteristic than this: "All animals undergo +transformations which are in part produced by their own exertions, in +response to pleasures and pains, and many of these acquired forms or +propensities are transmitted to their posterity." This is Lamarckism +before Lamarck, as his grandson pointed out. His central idea is that +wants stimulate efforts and that these result in improvements, which +subsequent generations make better still. He realised something of the +struggle for existence and even pointed out that this advantageously +checks the rapid multiplication. "As Dr Krause points out, Darwin just +misses the connection between this struggle and the Survival of the +Fittest." (Osborn op. cit. page 142.) + +Lamarck (1744-1829) (See E. Perrier "La Philosophie Zoologique avant +Darwin", Paris, 1884; A. de Quatrefages, "Darwin et ses Precurseurs +Francais", Paris, 1870; Packard op. cit.; also Claus, "Lamarck als +Begrunder der Descendenzlehre", Wien, 1888; Haeckel, "Natural History +of Creation", English translation London, 1879; Lang "Zur Charakteristik +der Forschungswege von Lamarck und Darwin", Jena, 1889.) seems to have +thought out his theory of evolution without any knowledge of Erasmus +Darwin's which it closely resembled. The central idea of his theory +was the cumulative inheritance of functional modifications. "Changes +in environment bring about changes in the habits of animals. Changes in +their wants necessarily bring about parallel changes in their habits. If +new wants become constant or very lasting, they form new habits, the new +habits involve the use of new parts, or a different use of old +parts, which results finally in the production of new organs and the +modification of old ones." He differed from Buffon in not attaching +importance, as far as animals are concerned, to the direct influence of +the environment, "for environment can effect no direct change whatever +upon the organisation of animals," but in regard to plants he agreed +with Buffon that external conditions directly moulded them. + +Treviranus (1776-1837) (See Huxley's article "Evolution in Biology", +"Encyclopaedia Britannica" (9th edit.), 1878, pages 744-751, and Sully's +article, "Evolution in Philosophy", ibid. pages 751-772.), whom Huxley +ranked beside Lamarck, was on the whole Buffonian, attaching chief +importance to the influence of a changeful environment both in modifying +and in eliminating, but he was also Goethian, for instance in his idea +that species like individuals pass through periods of growth, full +bloom, and decline. "Thus, it is not only the great catastrophes of +Nature which have caused extinction, but the completion of cycles +of existence, out of which new cycles have begun." A characteristic +sentence is quoted by Prof. Osborn: "In every living being there exists +a capability of an endless variety of form-assumption; each possesses +the power to adapt its organisation to the changes of the outer world, +and it is this power, put into action by the change of the universe, +that has raised the simple zoophytes of the primitive world to +continually higher stages of organisation, and has introduced a +countless variety of species into animate Nature." + +Goethe (1749-1832) (See Haeckel, "Die Naturanschauung von Darwin, Goethe +und Lamarck", Jena, 1882.), who knew Buffon's work but not Lamarck's, is +peculiarly interesting as one of the first to use the evolution-idea as +a guiding hypothesis, e.g. in the interpretation of vestigial structures +in man, and to realise that organisms express an attempt to make a +compromise between specific inertia and individual change. He gave the +finest expression that science has yet known--if it has known it--of +the kernel-idea of what is called "bathmism," the idea of an "inherent +growth-force"--and at the same time he held that "the way of life +powerfully reacts upon all form" and that the orderly growth of form +"yields to change from externally acting causes." + +Besides Buffon, Erasmus Darwin, Lamarck, Treviranus, and Goethe, +there were other "pioneers of evolution," whose views have been often +discussed and appraised. Etienne Geoffroy Saint-Hilaire (1772-1844), +whose work Goethe so much admired, was on the whole Buffonian, +emphasising the direct action of the changeful milieu. "Species +vary with their environment, and existing species have descended by +modification from earlier and somewhat simpler species." He had a +glimpse of the selection idea, and believed in mutations or sudden +leaps--induced in the embryonic condition by external influences. The +complete history of evolution-theories will include many instances +of guesses at truth which were afterwards substantiated, thus the +geographer von Buch (1773-1853) detected the importance of the Isolation +factor on which Wagner, Romanes, Gulick and others have laid great +stress, but we must content ourselves with recalling one other pioneer, +the author of the "Vestiges of Creation" (1844), a work which passed +through ten editions in nine years and certainly helped to harrow the +soil for Darwin's sowing. As Darwin said, "it did excellent service in +this country in calling attention to the subject, in removing prejudice, +and in thus preparing the ground for the reception of analogous views." +("Origin of Species" (6th edition), page xvii.) Its author, Robert +Chambers (1802-1871) was in part a Buffonian--maintaining +that environment moulded organisms adaptively, and in part a +Goethian--believing in an inherent progressive impulse which lifted +organisms from one grade of organisation to another. + +AS REGARDS NATURAL SELECTION. + +The only thinker to whom Darwin was directly indebted, so far as the +theory of Natural Selection is concerned, was Malthus, and we may once +more quote the well-known passage in the Autobiography: "In October, +1838, that is, fifteen months after I had begun my systematic enquiry, +I happened to read for amusement 'Malthus on Population', and being well +prepared to appreciate the struggle for existence which everywhere goes +on from long-continued observation of the habits of animals and +plants, it at once struck me that under these circumstances favourable +variations would tend to be preserved, and unfavourable ones to be +destroyed. The result of this would be the formation of new species." +("The Life and Letters of Charles Darwin", Vol. 1. page 83. London, +1887.) + +Although Malthus gives no adumbration of the idea of Natural Selection +in his exposition of the eliminative processes which go on in mankind, +the suggestive value of his essay is undeniable, as is strikingly +borne out by the fact that it gave to Alfred Russel Wallace also "the +long-sought clue to the effective agent in the evolution of organic +species." (A.R. Wallace, "My Life, A Record of Events and Opinions", +London, 1905, Vol. 1. page 232.) One day in Ternate when he was resting +between fits of fever, something brought to his recollection the work of +Malthus which he had read twelve years before. "I thought of his clear +exposition of 'the positive checks to increase'--disease, accidents, +war, and famine--which keep down the population of savage races to +so much lower an average than that of more civilized peoples. It then +occurred to me that these causes or their equivalents are continually +acting in the case of animals also; and as animals usually breed much +more rapidly than does mankind, the destruction every year from these +causes must be enormous in order to keep down the numbers of each +species, since they evidently do not increase regularly from year to +year, as otherwise the world would long ago have been densely crowded +with those that breed most quickly. Vaguely thinking over the enormous +and constant destruction which this implied, it occurred to me to ask +the question, Why do some die and some live? And the answer was clearly, +that on the whole the best fitted live. From the effects of disease the +most healthy escaped; from enemies the strongest, the swiftest, or +the most cunning; from famine the best hunters or those with the +best digestion; and so on. Then it suddenly flashed upon me that this +self-acting process would necessarily IMPROVE THE RACE, because in every +generation the inferior would inevitably be killed off and the superior +would remain--that is, THE FITTEST WOULD SURVIVE." (Ibid. Vol. 1. page +361.) We need not apologise for this long quotation, it is a tribute +to Darwin's magnanimous colleague, the Nestor of the evolutionist +camp,--and it probably indicates the line of thought which Darwin +himself followed. It is interesting also to recall the fact that in +1852, when Herbert Spencer wrote his famous "Leader" article on "The +Development Hypothesis" in which he argued powerfully for the thesis +that the whole animate world is the result of an age-long process of +natural transformation, he wrote for "The Westminster Review" another +important essay, "A Theory of Population deduced from the General Law of +Animal Fertility", towards the close of which he came within an ace +of recognising that the struggle for existence was a factor in organic +evolution. At a time when pressure of population was practically +interesting men's minds, Darwin, Wallace, and Spencer were being +independently led from a social problem to a biological theory. There +could be no better illustration, as Prof. Patrick Geddes has pointed +out, of the Comtian thesis that science is a "social phenomenon." + +Therefore, as far more important than any further ferreting out of vague +hints of Natural Selection in books which Darwin never read, we would +indicate by a quotation the view that the central idea in Darwinism +is correlated with contemporary social evolution. "The substitution +of Darwin for Paley as the chief interpreter of the order of nature is +currently regarded as the displacement of an anthropomorphic view by a +purely scientific one: a little reflection, however, will show that +what has actually happened has been merely the replacement of the +anthropomorphism of the eighteenth century by that of the nineteenth. +For the place vacated by Paley's theological and metaphysical +explanation has simply been occupied by that suggested to Darwin and +Wallace by Malthus in terms of the prevalent severity of industrial +competition, and those phenomena of the struggle for existence which the +light of contemporary economic theory has enabled us to discern, have +thus come to be temporarily exalted into a complete explanation +of organic progress." (P. Geddes, article "Biology", "Chambers's +Encyclopaedia".) It goes without saying that the idea suggested by +Malthus was developed by Darwin into a biological theory which was then +painstakingly verified by being used as an interpretative formula, and +that the validity of a theory so established is not affected by what +suggested it, but the practical question which this line of thought +raises in the mind is this: if Biology did thus borrow with such +splendid results from social theory, why should we not more deliberately +repeat the experiment? + +Darwin was characteristically frank and generous in admitting that the +principle of Natural Selection had been independently recognised by +Dr W.C. Wells in 1813 and by Mr Patrick Matthew in 1831, but he had no +knowledge of these anticipations when he published the first edition +of "The Origin of Species". Wells, whose "Essay on Dew" is still +remembered, read in 1813 before the Royal Society a short paper entitled +"An account of a White Female, part of whose skin resembles that of a +Negro" (published in 1818). In this communication, as Darwin said, "he +observes, firstly, that all animals tend to vary in some degree, and, +secondly, that agriculturists improve their domesticated animals by +selection; and then, he adds, but what is done in this latter case +'by art, seems to be done with equal efficacy, though more slowly, by +nature, in the formation of varieties of mankind, fitted for the country +which they inhabit.'" ("Origin of Species" (6th edition) page xv.) +Thus Wells had the clear idea of survival dependent upon a favourable +variation, but he makes no more use of the idea and applies it only +to man. There is not in the paper the least hint that the author ever +thought of generalising the remarkable sentence quoted above. + +Of Mr Patrick Matthew, who buried his treasure in an appendix to a work +on "Naval Timber and Arboriculture", Darwin said that "he clearly saw +the full force of the principle of natural selection." In 1860 Darwin +wrote--very characteristically--about this to Lyell: "Mr Patrick +Matthew publishes a long extract from his work on "Naval Timber and +Arboriculture", published in 1831, in which he briefly but completely +anticipates the theory of Natural Selection. I have ordered the book, +as some passages are rather obscure, but it is certainly, I think, a +complete but not developed anticipation. Erasmus always said that surely +this would be shown to be the case some day. Anyhow, one may be excused +in not having discovered the fact in a work on Naval Timber." ("Life and +Letters" II. page 301.) + +De Quatrefages and De Varigny have maintained that the botanist Naudin +stated the theory of evolution by natural selection in 1852. He explains +very clearly the process of artificial selection, and says that in the +garden we are following Nature's method. "We do not think that Nature +has made her species in a different fashion from that in which we +proceed ourselves in order to make our variations." But, as Darwin said, +"he does not show how selection acts under nature." Similarly it must +be noted in regard to several pre-Darwinian pictures of the struggle +for existence (such as Herder's, who wrote in 1790 "All is in +struggle... each one for himself" and so on), that a recognition of this +is only the first step in Darwinism. + +Profs. E. Perrier and H.F. Osborn have called attention to a remarkable +anticipation of the selection-idea which is to be found in the +speculations of Etienne Geoffroy St Hilaire (1825-1828) on the evolution +of modern Crocodilians from the ancient Teleosaurs. Changing environment +induced changes in the respiratory system and far-reaching consequences +followed. The atmosphere, acting upon the pulmonary cells, brings about +"modifications which are favourable or destructive ('funestes'); these +are inherited, and they influence all the rest of the organisation of +the animal because if these modifications lead to injurious effects, +the animals which exhibit them perish and are replaced by others of a +somewhat different form, a form changed so as to be adapted to (a la +convenance) the new environment." + +Prof. E.B. Poulton ("Science Progress", New Series, Vol. I. 1897. "A +Remarkable Anticipation of Modern Views on Evolution". See also +Chap. VI. in "Essays on Evolution", Oxford, 1908.) has shown that the +anthropologist James Cowles Prichard (1786-1848) must be included, even +in spite of himself, among the precursors of Darwin. In some passages +of the second edition of his "Researches into the Physical History of +Mankind" (1826), he certainly talks evolution and anticipates Prof. +Weismann in denying the transmission of acquired characters. He is, +however, sadly self-contradictory and his evolutionism weakens in +subsequent editions--the only ones that Darwin saw. Prof. Poulton finds +in Prichard's work a recognition of the operation of Natural Selection. +"After enquiring how it is that 'these varieties are developed and +preserved in connection with particular climates and differences of +local situation,' he gives the following very significant answer: 'One +cause which tends to maintain this relation is obvious. Individuals and +families, and even whole colonies, perish and disappear in climates for +which they are, by peculiarity of constitution, not adapted. Of this +fact proofs have been already mentioned.'" Mr Francis Darwin and Prof. +A.C. Seward discuss Prichard's "anticipations" in "More Letters of +Charles Darwin", Vol. I. page 43, and come to the conclusion that the +evolutionary passages are entirely neutralised by others of an opposite +trend. There is the same difficulty with Buffon. + +Hints of the idea of Natural Selection have been detected elsewhere. +James Watt (See Prof. Patrick Geddes's article "Variation and +Selection", "Encyclopaedia Britannica (9th edition) 1888.), for +instance, has been reported as one of the anticipators (1851). But we +need not prolong the inquiry further, since Darwin did not know of any +anticipations until after he had published the immortal work of 1859, +and since none of those who got hold of the idea made any use of it. +What Darwin did was to follow the clue which Malthus gave him, to +realise, first by genius and afterwards by patience, how the complex +and subtle struggle for existence works out a natural selection of +those organisms which vary in the direction of fitter adaptation to the +conditions of their life. So much success attended his application of +the Selection-formula that for a time he regarded Natural Selection +as almost the sole factor in evolution, variations being pre-supposed; +gradually, however, he came to recognise that there was some validity in +the factors which had been emphasized by Lamarck and by Buffon, and in +his well-known summing up in the sixth edition of the "Origin" he +says of the transformation of species: "This has been effected chiefly +through the natural selection of numerous successive, slight, favourable +variations; aided in an important manner by the inherited effects of +the use and disuse of parts; and in an unimportant manner, that is, in +relation to adaptive structures, whether past or present, by the direct +action of external conditions, and by variations which seem to us in our +ignorance to arise spontaneously." + +To sum up: the idea of organic evolution, older than Aristotle, slowly +developed from the stage of suggestion to the stage of verification, and +the first convincing verification was Darwin's; from being an a priori +anticipation it has become an interpretation of nature, and Darwin is +still the chief interpreter; from being a modal interpretation it has +advanced to the rank of a causal theory, the most convincing part of +which men will never cease to call Darwinism. + + + + +III. THE SELECTION THEORY, By August Weismann. + +Professor of Zoology in the University of Freiburg (Baden). + + +I. THE IDEA OF SELECTION. + +Many and diverse were the discoveries made by Charles Darwin in the +course of a long and strenuous life, but none of them has had so +far-reaching an influence on the science and thought of his time as the +theory of selection. I do not believe that the theory of evolution would +have made its way so easily and so quickly after Darwin took up the +cudgels in favour of it, if he had not been able to support it by a +principle which was capable of solving, in a simple manner, the greatest +riddle that living nature presents to us,--I mean the purposiveness +of every living form relative to the conditions of its life and its +marvellously exact adaptation to these. + +Everyone knows that Darwin was not alone in discovering the principle +of selection, and that the same idea occurred simultaneously and +independently to Alfred Russel Wallace. At the memorable meeting of the +Linnean Society on 1st July, 1858, two papers were read (communicated by +Lyell and Hooker) both setting forth the same idea of selection. One +was written by Charles Darwin in Kent, the other by Alfred Wallace +in Ternate, in the Malay Archipelago. It was a splendid proof of +the magnanimity of these two investigators, that they thus, in all +friendliness and without envy, united in laying their ideas before a +scientific tribunal: their names will always shine side by side as two +of the brightest stars in the scientific sky. + +But it is with Charles Darwin that I am here chiefly concerned, since +this paper is intended to aid in the commemoration of the hundredth +anniversary of his birth. + +The idea of selection set forth by the two naturalists was at the time +absolutely new, but it was also so simple that Huxley could say of it +later, "How extremely stupid not to have thought of that." As Darwin was +led to the general doctrine of descent, not through the labours of +his predecessors in the early years of the century, but by his own +observations, so it was in regard to the principle of selection. He was +struck by the innumerable cases of adaptation, as, for instance, that +of the woodpeckers and tree-frogs to climbing, or the hooks and +feather-like appendages of seeds, which aid in the distribution of +plants, and he said to himself that an explanation of adaptations was +the first thing to be sought for in attempting to formulate a theory of +evolution. + +But since adaptations point to CHANGES which have been undergone by the +ancestral forms of existing species, it is necessary, first of all, to +inquire how far species in general are VARIABLE. Thus Darwin's attention +was directed in the first place to the phenomenon of variability, and +the use man has made of this, from very early times, in the breeding of +his domesticated animals and cultivated plants. He inquired carefully +how breeders set to work, when they wished to modify the structure and +appearance of a species to their own ends, and it was soon clear to him +that SELECTION FOR BREEDING PURPOSES played the chief part. + +But how was it possible that such processes should occur in free +nature? Who is here the breeder, making the selection, choosing out one +individual to bring forth offspring and rejecting others? That was the +problem that for a long time remained a riddle to him. + +Darwin himself relates how illumination suddenly came to him. He had +been reading, for his own pleasure, Malthus' book on Population, and, as +he had long known from numerous observations, that every species gives +rise to many more descendants than ever attain to maturity, and that, +therefore, the greater number of the descendants of a species perish +without reproducing, the idea came to him that the decision as to which +member of a species was to perish, and which was to attain to maturity +and reproduction might not be a matter of chance, but might be +determined by the constitution of the individuals themselves, according +as they were more or less fitted for survival. With this idea the +foundation of the theory of selection was laid. + +In ARTIFICIAL SELECTION the breeder chooses out for pairing only such +individuals as possess the character desired by him in a somewhat higher +degree than the rest of the race. Some of the descendants inherit this +character, often in a still higher degree, and if this method be pursued +throughout several generations, the race is transformed in respect of +that particular character. + +NATURAL SELECTION depends on the same three factors as ARTIFICIAL +SELECTION: on VARIABILITY, INHERITANCE, and SELECTION FOR BREEDING, but +this last is here carried out not by a breeder but by what Darwin called +the "struggle for existence." This last factor is one of the special +features of the Darwinian conception of nature. That there are +carnivorous animals which take heavy toll in every generation of the +progeny of the animals on which they prey, and that there are herbivores +which decimate the plants in every generation had long been known, but +it is only since Darwin's time that sufficient attention has been paid +to the facts that, in addition to this regular destruction, there exists +between the members of a species a keen competition for space and food, +which limits multiplication, and that numerous individuals of each +species perish because of unfavourable climatic conditions. The +"struggle for existence," which Darwin regarded as taking the place +of the human breeder in free nature, is not a direct struggle between +carnivores and their prey, but is the assumed competition for survival +between individuals OF THE SAME species, of which, on an average, only +those survive to reproduce which have the greatest power of resistance, +while the others, less favourably constituted, perish early. This +struggle is so keen, that, within a limited area, where the conditions +of life have long remained unchanged, of every species, whatever be the +degree of fertility, only two, ON AN AVERAGE, of the descendants of each +pair survive; the others succumb either to enemies, or to disadvantages +of climate, or to accident. A high degree of fertility is thus not an +indication of the special success of a species, but of the numerous +dangers that have attended its evolution. Of the six young brought forth +by a pair of elephants in the course of their lives only two survive in +a given area; similarly, of the millions of eggs which two thread-worms +leave behind them only two survive. It is thus possible to estimate the +dangers which threaten a species by its ratio of elimination, or, since +this cannot be done directly, by its fertility. + +Although a great number of the descendants of each generation fall +victims to accident, among those that remain it is still the greater +or lesser fitness of the organism that determines the "selection +for breeding purposes," and it would be incomprehensible if, in this +competition, it were not ultimately, that is, on an average, the best +equipped which survive, in the sense of living long enough to reproduce. + +Thus the principle of natural selection is THE SELECTION OF THE BEST FOR +REPRODUCTION, whether the "best" refers to the whole constitution, +to one or more parts of the organism, or to one or more stages of +development. Every organ, every part, every character of an animal, +fertility and intelligence included, must be improved in this manner, +and be gradually brought up in the course of generations to its highest +attainable state of perfection. And not only may improvement of parts +be brought about in this way, but new parts and organs may arise, +since, through the slow and minute steps of individual or "fluctuating" +variations, a part may be added here or dropped out there, and thus +something new is produced. + +The principle of selection solved the riddle as to how what was +purposive could conceivably be brought about without the intervention +of a directing power, the riddle which animate nature presents to our +intelligence at every turn, and in face of which the mind of a Kant +could find no way out, for he regarded a solution of it as not to be +hoped for. For, even if we were to assume an evolutionary force that is +continually transforming the most primitive and the simplest forms of +life into ever higher forms, and the homogeneity of primitive times into +the infinite variety of the present, we should still be unable to infer +from this alone how each of the numberless forms adapted to particular +conditions of life should have appeared PRECISELY AT THE RIGHT MOMENT +IN THE HISTORY OF THE EARTH to which their adaptations were appropriate, +and precisely at the proper place in which all the conditions of life to +which they were adapted occurred: the humming-birds at the same time as +the flowers; the trichina at the same time as the pig; the bark-coloured +moth at the same time as the oak, and the wasp-like moth at the same +time as the wasp which protects it. Without processes of selection we +should be obliged to assume a "pre-established harmony" after the famous +Leibnitzian model, by means of which the clock of the evolution of +organisms is so regulated as to strike in exact synchronism with that of +the history of the earth! All forms of life are strictly adapted to the +conditions of their life, and can persist under these conditions alone. + +There must therefore be an intrinsic connection between the conditions +and the structural adaptations of the organism, and, SINCE THE +CONDITIONS OF LIFE CANNOT BE DETERMINED BY THE ANIMAL ITSELF, THE +ADAPTATIONS MUST BE CALLED FORTH BY THE CONDITIONS. + +The selection theory teaches us how this is conceivable, since it +enables us to understand that there is a continual production of what is +non-purposive as well as of what is purposive, but the purposive alone +survives, while the non-purposive perishes in the very act of arising. +This is the old wisdom taught long ago by Empedocles. + +II. THE LAMARCKIAN PRINCIPLE. + +Lamarck, as is well known, formulated a definite theory of evolution at +the beginning of the nineteenth century, exactly fifty years before +the Darwin-Wallace principle of selection was given to the world. +This brilliant investigator also endeavoured to support his theory by +demonstrating forces which might have brought about the transformations +of the organic world in the course of the ages. In addition to other +factors, he laid special emphasis on the increased or diminished use +of the parts of the body, assuming that the strengthening or weakening +which takes place from this cause during the individual life, could be +handed on to the offspring, and thus intensified and raised to the rank +of a specific character. Darwin also regarded this LAMARCKIAN PRINCIPLE, +as it is now generally called, as a factor in evolution, but he was not +fully convinced of the transmissibility of acquired characters. + +As I have here to deal only with the theory of selection, I need not +discuss the Lamarckian hypothesis, but I must express my opinion that +there is room for much doubt as to the cooperation of this principle in +evolution. Not only is it difficult to imagine how the transmission of +functional modifications could take place, but, up to the present time, +notwithstanding the endeavours of many excellent investigators, not +a single actual proof of such inheritance has been brought forward. +Semon's experiments on plants are, according to the botanist Pfeffer, +not to be relied on, and even the recent, beautiful experiments made +by Dr Kammerer on salamanders, cannot, as I hope to show elsewhere, +be regarded as proof, if only because they do not deal at all with +functional modifications, that is, with modifications brought about by +use, and it is to these ALONE that the Lamarckian principle refers. + +III. OBJECTIONS TO THE THEORY OF SELECTION. + +(a) Saltatory evolution. + +The Darwinian doctrine of evolution depends essentially on THE +CUMULATIVE AUGMENTATION of minute variations in the direction of +utility. But can such minute variations, which are undoubtedly +continually appearing among the individuals of the same species, +possess any selection-value; can they determine which individuals are +to survive, and which are to succumb; can they be increased by natural +selection till they attain to the highest development of a purposive +variation? + +To many this seems so improbable that they have urged a theory of +evolution by leaps from species to species. Kolliker, in 1872, compared +the evolution of species with the processes which we can observe in the +individual life in cases of alternation of generations. But a polyp only +gives rise to a medusa because it has itself arisen from one, and there +can be no question of a medusa ever having arisen suddenly and de +novo from a polyp-bud, if only because both forms are adapted in their +structure as a whole, and in every detail to the conditions of their +life. A sudden origin, in a natural way, of numerous adaptations is +inconceivable. Even the degeneration of a medusoid from a free-swimming +animal to a mere brood-sac (gonophore) is not sudden and saltatory, but +occurs by imperceptible modifications throughout hundreds of years, as +we can learn from the numerous stages of the process of degeneration +persisting at the same time in different species. + +If, then, the degeneration to a simple brood-sac takes place only by +very slow transitions, each stage of which may last for centuries, how +could the much more complex ASCENDING evolution possibly have taken +place by sudden leaps? I regard this argument as capable of further +extension, for wherever in nature we come upon degeneration, it is +taking place by minute steps and with a slowness that makes it not +directly perceptible, and I believe that this in itself justifies us in +concluding that THE SAME MUST BE TRUE OF ASCENDING evolution. But in the +latter case the goal can seldom be distinctly recognised while in cases +of degeneration the starting-point of the process can often be inferred, +because several nearly related species may represent different stages. + +In recent years Bateson in particular has championed the idea of +saltatory, or so-called discontinuous evolution, and has collected a +number of cases in which more or less marked variations have suddenly +appeared. These are taken for the most part from among domesticated +animals which have been bred and crossed for a long time, and it is +hardly to be wondered at that their much mixed and much influenced +germ-plasm should, under certain conditions, give rise to remarkable +phenomena, often indeed producing forms which are strongly suggestive of +monstrosities, and which would undoubtedly not survive in free nature, +unprotected by man. I should regard such cases as due to an intensified +germinal selection--though this is to anticipate a little--and from this +point of view it cannot be denied that they have a special interest. But +they seem to me to have no significance as far as the transformation +of species is concerned, if only because of the extreme rarity of their +occurrence. + +There are, however, many variations which have appeared in a sudden and +saltatory manner, and some of these Darwin pointed out and discussed +in detail: the copper beech, the weeping trees, the oak with "fern-like +leaves," certain garden-flowers, etc. But none of them have persisted in +free nature, or evolved into permanent types. + +On the other hand, wherever enduring types have arisen, we find traces +of a gradual origin by successive stages, even if, at first sight, their +origin may appear to have been sudden. This is the case with SEASONAL +DIMORPHISM, the first known cases of which exhibited marked differences +between the two generations, the winter and the summer brood. Take +for instance the much discussed and studied form Vanessa (Araschnia) +levana-prorsa. Here the differences between the two forms are so great +and so apparently disconnected, that one might almost believe it to be +a sudden mutation, were it not that old transition-stages can be called +forth by particular temperatures, and we know other butterflies, as for +instance our Garden Whites, in which the differences between the +two generations are not nearly so marked; indeed, they are so little +apparent that they are scarcely likely to be noticed except by experts. +Thus here again there are small initial steps, some of which, indeed, +must be regarded as adaptations, such as the green-sprinkled or lightly +tinted under-surface which gives them a deceptive resemblance to parsley +or to Cardamine leaves. + +Even if saltatory variations do occur, we cannot assume that these HAVE +EVER LED TO FORMS WHICH ARE CAPABLE OF SURVIVAL UNDER THE CONDITIONS +OF WILD LIFE. Experience has shown that in plants which have suddenly +varied the power of persistence is diminished. Korschinksky attributes +to them weaknesses of organisation in general; "they bloom late, ripen +few of their seeds, and show great sensitiveness to cold." These are not +the characters which make for success in the struggle for existence. + +We must briefly refer here to the views--much discussed in the last +decade--of H. de Vries, who believes that the roots of transformation +must be sought for in SALTATORY VARIATIONS ARISING FROM INTERNAL CAUSES, +and distinguishes such MUTATIONS, as he has called them, from ordinary +individual variations, in that they breed true, that is, with strict +inbreeding they are handed on pure to the next generation. I have +elsewhere endeavoured to point out the weaknesses of this theory +("Vortrage uber Descendenztheorie", Jena, 1904, II. 269. English +Translation London, 1904, II. page 317.), and I am the less inclined +to return to it here that it now appears (See Poulton, "Essays on +Evolution", Oxford, 1908, pages xix-xxii.) that the far-reaching +conclusions drawn by de Vries from his observations on the Evening +Primrose, Oenothera lamarckiana, rest upon a very insecure +foundation. The plant from which de Vries saw numerous "species"--his +"mutations"--arise was not, as he assumed, a WILD SPECIES that had been +introduced to Europe from America, but was probably a hybrid form which +was first discovered in the Jardin des Plantes in Paris, and which does +not appear to exist anywhere in America as a wild species. + +This gives a severe shock to the "Mutation theory," for the other +ACTUALLY WILD species with which de Vries experimented showed no +"mutations" but yielded only negative results. + +Thus we come to the conclusion that Darwin ("Origin of Species" (6th +edition), pages 176 et seq.) was right in regarding transformations as +taking place by minute steps, which, if useful, are augmented in +the course of innumerable generations, because their possessors more +frequently survive in the struggle for existence. + +(b) SELECTION-VALUE OF THE INITIAL STEPS. + +Is it possible that the significant deviations which we know as +"individual variations" can form the beginning of a process of +selection? Can they decide which is to perish and which to survive? To +use a phrase of Romanes, can they have SELECTION-VALUE? + +Darwin himself answered this question, and brought together many +excellent examples to show that differences, apparently insignificant +because very small, might be of decisive importance for the life of the +possessor. But it is by no means enough to bring forward cases of this +kind, for the question is not merely whether finished adaptations have +selection-value, but whether the first beginnings of these, and whether +the small, I might almost say minimal increments, which have led up +from these beginnings to the perfect adaptation, have also had +selection-value. To this question even one who, like myself, has been +for many years a convinced adherent of the theory of selection, can only +reply: WE MUST ASSUME SO, BUT WE CANNOT PROVE IT IN ANY CASE. It is not +upon demonstrative evidence that we rely when we champion the doctrine +of selection as a scientific truth; we base our argument on quite other +grounds. Undoubtedly there are many apparently insignificant features, +which can nevertheless be shown to be adaptations--for instance, the +thickness of the basin-shaped shell of the limpets that live among the +breakers on the shore. There can be no doubt that the thickness of these +shells, combined with their flat form, protects the animals from the +force of the waves breaking upon them,--but how have they become so +thick? What proportion of thickness was sufficient to decide that of two +variants of a limpet one should survive, the other be eliminated? We can +say nothing more than that we infer from the present state of the shell, +that it must have varied in regard to differences in shell-thickness, +and that these differences must have had selection-value,--no proof +therefore, but an assumption which we must show to be convincing. + +For a long time the marvellously complex RADIATE and LATTICE-WORK +skeletons of Radiolarians were regarded as a mere outflow of "Nature's +infinite wealth of form," as an instance of a purely morphological +character with no biological significance. But recent investigations +have shown that these, too, have an adaptive significance (Hacker). The +same thing has been shown by Schutt in regard to the lowly unicellular +plants, the Peridineae, which abound alike on the surface of the ocean +and in its depths. It has been shown that the long skeletal processes +which grow out from these organisms have significance not merely as a +supporting skeleton, but also as an extension of the superficial area, +which increases the contact with the water-particles, and prevents +the floating organisms from sinking. It has been established that the +processes are considerably shorter in the colder layers of the ocean, +and that they may be twelve times as long (Chun, "Reise der Valdivia", +Leipzig, 1904.) in the warmer layers, thus corresponding to the greater +or smaller amount of friction which takes place in the denser and less +dense layers of the water. + +The Peridineae of the warmer ocean layers have thus become long-rayed, +those of the colder layers short-rayed, not through the direct effect +of friction on the protoplasm, but through processes of selection, which +favoured the longer rays in warm water, since they kept the organism +afloat, while those with short rays sank and were eliminated. If we put +the question as to selection-value in this case, and ask how great +the variations in the length of processes must be in order to possess +selection-value; what can we answer except that these variations must +have been minimal, and yet sufficient to prevent too rapid sinking +and consequent elimination? Yet this very case would give the +ideal opportunity for a mathematical calculation of the minimal +selection-value, although of course it is not feasible from lack of data +to carry out the actual calculation. + +But even in organisms of more than microscopic size there must +frequently be minute, even microscopic differences which set going the +process of selection, and regulate its progress to the highest possible +perfection. + +Many tropical trees possess thick, leathery leaves, as a protection +against the force of the tropical rain drops. The DIRECT influence +of the rain cannot be the cause of this power of resistance, for the +leaves, while they were still thin, would simply have been torn to +pieces. Their toughness must therefore be referred to selection, which +would favour the trees with slightly thicker leaves, though we cannot +calculate with any exactness how great the first stages of increase in +thickness must have been. Our hypothesis receives further support from +the fact that, in many such trees, the leaves are drawn out into a +beak-like prolongation (Stahl and Haberlandt) which facilitates the +rapid falling off of the rain water, and also from the fact that the +leaves, while they are still young, hang limply down in bunches which +offer the least possible resistance to the rain. Thus there are here +three adaptations which can only be interpreted as due to selection. +The initial stages of these adaptations must undoubtedly have had +selection-value. + +But even in regard to this case we are reasoning in a circle, not giving +"proofs," and no one who does not wish to believe in the selection-value +of the initial stages can be forced to do so. Among the many pieces of +presumptive evidence a particularly weighty one seems to me to be THE +SMALLNESS OF THE STEPS OF PROGRESS which we can observe in certain +cases, as for instance in leaf-imitation among butterflies, and +in mimicry generally. The resemblance to a leaf, for instance of a +particular Kallima, seems to us so close as to be deceptive, and yet we +find in another individual, or it may be in many others, a spot added +which increases the resemblance, and which could not have become fixed +unless the increased deceptiveness so produced had frequently led to +the overlooking of its much persecuted possessor. But if we take the +selection-value of the initial stages for granted, we are confronted +with the further question which I myself formulated many years ago: How +does it happen THAT THE NECESSARY BEGINNINGS OF A USEFUL VARIATION ARE +ALWAYS PRESENT? How could insects which live upon or among green leaves +become all green, while those that live on bark become brown? How have +the desert animals become yellow and the Arctic animals white? Why were +the necessary variations always present? How could the green locust lay +brown eggs, or the privet caterpillar develop white and lilac-coloured +lines on its green skin? + +It is of no use answering to this that the question is wrongly +formulated (Plate, "Selektionsprinzip u. Probleme der Artbildung" (3rd +edition), Leipzig, 1908.) and that it is the converse that is true; that +the process of selection takes place in accordance with the variations +that present themselves. This proposition is undeniably true, but so +also is another, which apparently negatives it: the variation required +has in the majority of cases actually presented itself. Selection cannot +solve this contradiction; it does not call forth the useful variation, +but simply works upon it. The ultimate reason why one and the same +insect should occur in green and in brown, as often happens in +caterpillars and locusts, lies in the fact that variations towards brown +presented themselves, and so also did variations towards green: THE +KERNEL OF THE RIDDLE LIES IN THE VARYING, and for the present we +can only say, that small variations in different directions present +themselves in every species. Otherwise so many different kinds of +variations could not have arisen. I have endeavoured to explain this +remarkable fact by means of the intimate processes that must take place +within the germ-plasm, and I shall return to the problem when dealing +with "germinal selection." + +We have, however, to make still greater demands on variation, for it +is not enough that the necessary variation should occur in isolated +individuals, because in that case there would be small prospect of its +being preserved, notwithstanding its utility. Darwin at first believed, +that even single variations might lead to transformation of the species, +but later he became convinced that this was impossible, at least +without the cooperation of other factors, such as isolation and sexual +selection. + +In the case of the GREEN CATERPILLARS WITH BRIGHT LONGITUDINAL STRIPES, +numerous individuals exhibiting this useful variation must have been +produced to start with. In all higher, that is, multicellular organisms, +the germ-substance is the source of all transmissible variations, and +this germ-plasm is not a simple substance but is made up of many primary +constituents. The question can therefore be more precisely stated thus: +How does it come about that in so many cases the useful variations +present themselves in numbers just where they are required, the white +oblique lines in the leaf-caterpillar on the under surface of the body, +the accompanying coloured stripes just above them? And, further, how has +it come about that in grass caterpillars, not oblique but longitudinal +stripes, which are more effective for concealment among grass and +plants, have been evolved? And finally, how is it that the same +Hawk-moth caterpillars, which to-day show oblique stripes, possessed +longitudinal stripes in Tertiary times? We can read this fact from the +history of their development, and I have before attempted to show +the biological significance of this change of colour. ("Studien +zur Descendenz-Theorie" II., "Die Enstehung der Zeichnung bei den +Schmetterlings-raupen," Leipzig, 1876.) + +For the present I need only draw the conclusion that one and the same +caterpillar may exhibit the initial stages of both, and that it depends +on the manner in which these marking elements are INTENSIFIED and +COMBINED by natural selection whether whitish longitudinal or oblique +stripes should result. In this case then the "useful variations" +were actually "always there," and we see that in the same group of +Lepidoptera, e.g. species of Sphingidae, evolution has occurred in both +directions according to whether the form lived among grass or on broad +leaves with oblique lateral veins, and we can observe even now that the +species with oblique stripes have longitudinal stripes when young, that +is to say, while the stripes have no biological significance. The white +places in the skin which gave rise, probably first as small spots, +to this protective marking could be combined in one way or another +according to the requirements of the species. They must therefore either +have possessed selection-value from the first, or, if this was not +the case at their earliest occurrence, there must have been SOME OTHER +FACTORS which raised them to the point of selection-value. I shall +return to this in discussing germinal selection. But the case may be +followed still farther, and leads us to the same alternative on a still +more secure basis. + +Many years ago I observed in caterpillars of Smerinthus populi (the +poplar hawk-moth), which also possess white oblique stripes, that +certain individuals showed RED SPOTS above these stripes; these spots +occurred only on certain segments, and never flowed together to form +continuous stripes. In another species (Smerinthus tiliae) similar +blood-red spots unite to form a line-like coloured seam in the last +stage of larval life, while in S. ocellata rust-red spots appear in +individual caterpillars, but more rarely than in S. Populi, and they +show no tendency to flow together. + +Thus we have here the origin of a new character, arising from small +beginnings, at least in S. tiliae, in which species the coloured stripes +are a normal specific character. In the other species, S. populi and +S. ocellata, we find the beginnings of the same variation, in one more +rarely than in the other, and we can imagine that, in the course of +time, in these two species, coloured lines over the oblique stripes will +arise. In any case these spots are the elements of variation, out +of which coloured lines MAY be evolved, if they are combined in this +direction through the agency of natural selection. In S. populi the +spots are often small, but sometimes it seems as though several had +united to form large spots. Whether a process of selection in this +direction will arise in S. populi and S. ocellata, or whether it is +now going on cannot be determined, since we cannot tell in advance what +biological value the marking might have for these two species. It is +conceivable that the spots may have no selection-value as far as these +species are concerned, and may therefore disappear again in the course +of phylogeny, or, on the other hand, that they may be changed in another +direction, for instance towards imitation of the rust-red fungoid +patches on poplar and willow leaves. In any case we may regard the +smallest spots as the initial stages of variation, the larger as a +cumulative summation of these. Therefore either these initial stages +must already possess selection-value, or, as I said before: THERE MUST +BE SOME OTHER REASON FOR THEIR CUMULATIVE SUMMATION. I should like to +give one more example, in which we can infer, though we cannot directly +observe, the initial stages. + +All the Holothurians or sea-cucumbers have in the skin calcareous bodies +of different forms, usually thick and irregular, which make the +skin tough and resistant. In a small group of them--the species of +Synapta--the calcareous bodies occur in the form of delicate anchors of +microscopic size. Up till 1897 these anchors, like many other delicate +microscopic structures, were regarded as curiosities, as natural +marvels. But a Swedish observer, Oestergren, has recently shown that +they have a biological significance: they serve the footless Synapta as +auxiliary organs of locomotion, since, when the body swells up in the +act of creeping, they press firmly with their tips, which are embedded +in the skin, against the substratum on which the animal creeps, and thus +prevent slipping backwards. In other Holothurians this slipping is +made impossible by the fixing of the tube-feet. The anchors act +automatically, sinking their tips towards the ground when the +corresponding part of the body thickens, and returning to the original +position at an angle of 45 degrees to the upper surface when the part +becomes thin again. The arms of the anchor do not lie in the same plane +as the shaft, and thus the curve of the arms forms the outermost part +of the anchor, and offers no further resistance to the gliding of the +animal. Every detail of the anchor, the curved portion, the little teeth +at the head, the arms, etc., can be interpreted in the most beautiful +way, above all the form of the anchor itself, for the two arms prevent +it from swaying round to the side. The position of the anchors, too, is +definite and significant; they lie obliquely to the longitudinal axis of +the animal, and therefore they act alike whether the animal is creeping +backwards or forwards. Moreover, the tips would pierce through the skin +if the anchors lay in the longitudinal direction. Synapta burrows in the +sand; it first pushes in the thin anterior end, and thickens this again, +thus enlarging the hole, then the anterior tentacles displace more sand, +the body is worked in a little farther, and the process begins anew. In +the first act the anchors are passive, but they begin to take an +active share in the forward movement when the body is contracted again. +Frequently the animal retains only the posterior end buried in the sand, +and then the anchors keep it in position, and make rapid withdrawal +possible. + +Thus we have in these apparently random forms of the calcareous bodies, +complex adaptations in which every little detail as to direction, curve, +and pointing is exactly determined. That they have selection-value in +their present perfected form is beyond all doubt, since the animals +are enabled by means of them to bore rapidly into the ground and so to +escape from enemies. We do not know what the initial stages were, but we +cannot doubt that the little improvements, which occurred as variations +of the originally simple slimy bodies of the Holothurians, were +preserved because they already possessed selection-value for the +Synaptidae. For such minute microscopic structures whose form is so +delicately adapted to the role they have to play in the life of the +animal, cannot have arisen suddenly and as a whole, and every new +variation of the anchor, that is, in the direction of the development +of the two arms, and every curving of the shaft which prevented the tips +from projecting at the wrong time, in short, every little adaptation +in the modelling of the anchor must have possessed selection-value. And +that such minute changes of form fall within the sphere of fluctuating +variations, that is to say, THAT THEY OCCUR is beyond all doubt. + +In many of the Synaptidae the anchors are replaced by calcareous rods +bent in the form of an S, which are said to act in the same way. Others, +such as those of the genus Ankyroderma, have anchors which project +considerably beyond the skin, and, according to Oestergren, serve "to +catch plant-particles and other substances" and so mask the animal. Thus +we see that in the Synaptidae the thick and irregular calcareous bodies +of the Holothurians have been modified and transformed in various ways +in adaptation to the footlessness of these animals, and to the peculiar +conditions of their life, and we must conclude that the earlier stages +of these changes presented themselves to the processes of selection in +the form of microscopic variations. For it is as impossible to think of +any origin other than through selection in this case as in the case of +the toughness, and the "drip-tips" of tropical leaves. And as these +last could not have been produced directly by the beating of the heavy +rain-drops upon them, so the calcareous anchors of Synapta cannot have +been produced directly by the friction of the sand and mud at the bottom +of the sea, and, since they are parts whose function is PASSIVE the +Lamarckian factor of use and disuse does not come into question. The +conclusion is unavoidable, that the microscopically small variations of +the calcareous bodies in the ancestral forms have been intensified +and accumulated in a particular direction, till they have led to the +formation of the anchor. Whether this has taken place by the action +of natural selection alone, or whether the laws of variation and the +intimate processes within the germ-plasm have cooperated will become +clear in the discussion of germinal selection. This whole process of +adaptation has obviously taken place within the time that has +elapsed since this group of sea-cucumbers lost their tube-feet, those +characteristic organs of locomotion which occur in no group except the +Echinoderms, and yet have totally disappeared in the Synaptidae. +And after all what would animals that live in sand and mud do with +tube-feet? + +(c) COADAPTATION. + +Darwin pointed out that one of the essential differences between +artificial and natural selection lies in the fact that the former can +modify only a few characters, usually only one at a time, while Nature +preserves in the struggle for existence all the variations of a species, +at the same time and in a purely mechanical way, if they possess +selection-value. + +Herbert Spencer, though himself an adherent of the theory of selection, +declared in the beginning of the nineties that in his opinion the range +of this principle was greatly over-estimated, if the great changes which +have taken place in so many organisms in the course of ages are to +be interpreted as due to this process of selection alone, since no +transformation of any importance can be evolved by itself; it is always +accompanied by a host of secondary changes. He gives the familiar +example of the Giant Stag of the Irish peat, the enormous antlers of +which required not only a much stronger skull cap, but also greater +strength of the sinews, muscles, nerves and bones of the whole anterior +half of the animal, if their mass was not to weigh down the animal +altogether. It is inconceivable, he says, that so many processes of +selection should take place SIMULTANEOUSLY, and we are therefore +forced to fall back on the Lamarckian factor of the use and disuse of +functional parts. And how, he asks, could natural selection follow two +opposite directions of evolution in different parts of the body at the +same time, as for instance in the case of the kangaroo, in which the +forelegs must have become shorter, while the hind legs and the tail were +becoming longer and stronger? + +Spencer's main object was to substantiate the validity of the Lamarckian +principle, the cooperation of which with selection had been doubted +by many. And it does seem as though this principle, if it operates +in nature at all, offers a ready and simple explanation of all such +secondary variations. Not only muscles, but nerves, bones, sinews, +in short all tissues which function actively, increase in strength +in proportion as they are used, and conversely they decrease when the +claims on them diminish. All the parts, therefore, which depend on the +part that varied first, as for instance the enlarged antlers of the +Irish Elk, must have been increased or decreased in strength, in exact +proportion to the claims made upon them,--just as is actually the case. + +But beautiful as this explanation would be, I regard it as untenable, +because it assumes the TRANSMISSIBILITY OF FUNCTIONAL MODIFICATIONS +(so-called "acquired" characters), and this is not only undemonstrable, +but is scarcely theoretically conceivable, for the secondary variations +which accompany or follow the first as correlative variations, occur +also in cases in which the animals concerned are sterile and THEREFORE +CANNOT TRANSMIT ANYTHING TO THEIR DESCENDANTS. This is true of WORKER +BEES, and particularly of ANTS, and I shall here give a brief survey of +the present state of the problem as it appears to me. + +Much has been written on both sides of this question since the published +controversy on the subject in the nineties between Herbert Spencer and +myself. I should like to return to the matter in detail, if the space +at my disposal permitted, because it seems to me that the arguments I +advanced at that time are equally cogent to-day, notwithstanding all the +objections that have since been urged against them. Moreover, the matter +is by no means one of subordinate interest; it is the very kernel of the +whole question of the reality and value of the principle of selection. +For if selection alone does not suffice to explain "HARMONIOUS +ADAPTATION" as I have called Spencer's COADAPTATION, and if we require +to call in the aid of the Lamarckian factor it would be questionable +whether selection could explain any adaptations whatever. In this +particular case--of worker bees--the Lamarckian factor may be excluded +altogether, for it can be demonstrated that here at any rate the effects +of use and disuse cannot be transmitted. + +But if it be asked why we are unwilling to admit the cooperation of +the Darwinian factor of selection and the Lamarckian factor, since this +would afford us an easy and satisfactory explanation of the phenomena, +I answer: BECAUSE THE LAMARCKIAN PRINCIPLE IS FALLACIOUS, AND BECAUSE BY +ACCEPTING IT WE CLOSE THE WAY TOWARDS DEEPER INSIGHT. It is not a spirit +of combativeness or a desire for self-vindication that induces me to +take the field once more against the Lamarckian principle, it is the +conviction that the progress of our knowledge is being obstructed by the +acceptance of this fallacious principle, since the facile explanation it +apparently affords prevents our seeking after a truer explanation and a +deeper analysis. + +The workers in the various species of ants are sterile, that is to say, +they take no regular part in the reproduction of the species, although +individuals among them may occasionally lay eggs. In addition to this +they have lost the wings, and the receptaculum seminis, and their +compound eyes have degenerated to a few facets. How could this last +change have come about through disuse, since the eyes of workers are +exposed to light in the same way as are those of the sexual insects and +thus in this particular case are not liable to "disuse" at all? The same +is true of the receptaculum seminis, which can only have been disused +as far as its glandular portion and its stalk are concerned, and also +of the wings, the nerves tracheae and epidermal cells of which could +not cease to function until the whole wing had degenerated, for the +chitinous skeleton of the wing does not function at all in the active +sense. + +But, on the other hand, the workers in all species have undergone +modifications in a positive direction, as, for instance, the greater +development of brain. In many species large workers have evolved,--the +so-called SOLDIERS, with enormous jaws and teeth, which defend the +colony,--and in others there are SMALL workers which have taken over +other special functions, such as the rearing of the young Aphides. This +kind of division of the workers into two castes occurs among several +tropical species of ants, but it is also present in the Italian species, +Colobopsis truncata. Beautifully as the size of the jaws could be +explained as due to the increased use made of them by the "soldiers," or +the enlarged brain as due to the mental activities of the workers, the +fact of the infertility of these forms is an insurmountable obstacle +to accepting such an explanation. Neither jaws nor brain can have been +evolved on the Lamarckian principle. + +The problem of coadaptation is no easier in the case of the ant than in +the case of the Giant Stag. Darwin himself gave a pretty illustration to +show how imposing the difference between the two kinds of workers in one +species would seem if we translated it into human terms. In regard to +the Driver ants (Anomma) we must picture to ourselves a piece of work, +"for instance the building of a house, being carried on by two kinds of +workers, of which one group was five feet four inches high, the other +sixteen feet high." ("Origin of Species" (6th edition), page 232.) + +Although the ant is a small animal as compared with man or with the +Irish Elk, the "soldier" with its relatively enormous jaws is hardly +less heavily burdened than the Elk with its antlers, and in the ant's +case, too, a strengthening of the skeleton, of the muscles, the nerves +of the head, and of the legs must have taken place parallel with the +enlargement of the jaws. HARMONIOUS ADAPTATION (coadaptation) has here +been active in a high degree, and yet these "soldiers" are sterile! +There thus remains nothing for it but to refer all their adaptations, +positive and negative alike, to processes of selection which have taken +place in the rudiments of the workers within the egg and sperm-cells +of their parents. There is no way out of the difficulty except the one +Darwin pointed out. He himself did not find the solution of the riddle +at once. At first he believed that the case of the workers among social +insects presented "the most serious special difficulty" in the way of +his theory of natural selection; and it was only after it had become +clear to him, that it was not the sterile insects themselves but their +parents that were selected, according as they produced more or less +well adapted workers, that he was able to refer to this very case of the +conditions among ants "IN ORDER TO SHOW THE POWER OF NATURAL SELECTION" +("Origin of Species", page 233; see also edition 1, page 242.). He +explains his view by a simple but interesting illustration. Gardeners +have produced, by means of long continued artificial selection, a +variety of Stock, which bears entirely double, and therefore infertile +flowers (Ibid. page 230.). Nevertheless the variety continues to be +reproduced from seed, because in addition to the double and infertile +flowers, the seeds always produce a certain number of single, fertile +blossoms, and these are used to reproduce the double variety. These +single and fertile plants correspond "to the males and females of an +ant-colony, the infertile plants, which are regularly produced in large +numbers, to the neuter workers of the colony." + +This illustration is entirely apt, the only difference between the two +cases consisting in the fact that the variation in the flower is not +a useful, but a disadvantageous one, which can only be preserved +by artificial selection on the part of the gardener, while the +transformations that have taken place parallel with the sterility of the +ants are useful, since they procure for the colony an advantage in the +struggle for existence, and they are therefore preserved by +natural selection. Even the sterility itself in this case is not +disadvantageous, since the fertility of the true females has at the same +time considerably increased. We may therefore regard the sterile forms +of ants, which have gradually been adapted in several directions to +varying functions, AS A CERTAIN PROOF that selection really takes place +in the germ-cells of the fathers and mothers of the workers, and that +SPECIAL COMPLEXES OF PRIMORDIA (IDS) are present in the workers and in +the males and females, and these complexes contain the primordia of the +individual parts (DETERMINANTS). But since all living entities vary, the +determinants must also vary, now in a favourable, now in an unfavourable +direction. If a female produces eggs, which contain favourably varying +determinants in the worker-ids, then these eggs will give rise to +workers modified in the favourable direction, and if this happens with +many females, the colony concerned will contain a better kind of worker +than other colonies. + +I digress here in order to give an account of the intimate processes, +which, according to my view, take place within the germ-plasm, and which +I have called "GERMINAL SELECTION." These processes are of importance +since they form the roots of variation, which in its turn is the root +of natural selection. I cannot here do more than give a brief outline of +the theory in order to show how the Darwin-Wallace theory of selection +has gained support from it. + +With others, I regard the minimal amount of substance which is contained +within the nucleus of the germ-cells, in the form of rods, bands, or +granules, as the GERM-SUBSTANCE or GERM-PLASM, and I call the individual +granules IDS. There is always a multiplicity of such ids present in the +nucleus, either occurring individually, or united in the form of rods +or bands (chromosomes). Each id contains the primary constituents of a +WHOLE individual, so that several ids are concerned in the development +of a new individual. + +In every being of complex structure thousands of primary constituents +must go to make up a single id; these I call DETERMINANTS, and I mean +by this name very small individual particles, far below the limits of +microscopic visibility, vital units which feed, grow, and multiply +by division. These determinants control the parts of the developing +embryo,--in what manner need not here concern us. The determinants +differ among themselves, those of a muscle are differently constituted +from those of a nerve-cell or a glandular cell, etc., and every +determinant is in its turn made up of minute vital units, which I +call BIOPHORS, or the bearers of life. According to my view, these +determinants not only assimilate, like every other living unit, but they +VARY in the course of their growth, as every living unit does; they may +vary qualitatively if the elements of which they are composed vary, they +may grow and divide more or less rapidly, and their variations give rise +to CORRESPONDING variations of the organ, cell, or cell-group which they +determine. That they are undergoing ceaseless fluctuations in regard to +size and quality seems to me the inevitable consequence of their unequal +nutrition; for although the germ-cell as a whole usually receives +sufficient nutriment, minute fluctuations in the amount carried to +different parts within the germ-plasm cannot fail to occur. + +Now, if a determinant, for instance of a sensory cell, receives for a +considerable time more abundant nutriment than before, it will grow more +rapidly--become bigger, and divide more quickly, and, later, when the +id concerned develops into an embryo, this sensory cell will become +stronger than in the parents, possibly even twice as strong. This is an +instance of a HEREDITARY INDIVIDUAL VARIATION, arising from the germ. + +The nutritive stream which, according to our hypothesis, favours the +determinant N by chance, that is, for reasons unknown to us, may remain +strong for a considerable time, or may decrease again; but even in +the latter case it is conceivable that the ascending movement of the +determinant may continue, because the strengthened determinant now +ACTIVELY nourishes itself more abundantly,--that is to say, it attracts +the nutriment to itself, and to a certain extent withdraws it from its +fellow-determinants. In this way, it may--as it seems to me--get into +PERMANENT UPWARD MOVEMENT, AND ATTAIN A DEGREE OF STRENGTH FROM WHICH +THERE IS NO FALLING BACK. Then positive or negative selection sets in, +favouring the variations which are advantageous, setting aside those +which are disadvantageous. + +In a similar manner a DOWNWARD variation of the determinants may take +place, if its progress be started by a diminished flow of nutriment. The +determinants which are weakened by this diminished flow will have less +affinity for attracting nutriment because of their diminished strength, +and they will assimilate more feebly and grow more slowly, unless chance +streams of nutriment help them to recover themselves. But, as will +presently be shown, a change of direction cannot take place at EVERY +stage of the degenerative process. If a certain critical stage of +downward progress be passed, even favourable conditions of food-supply +will no longer suffice permanently to change the direction of +the variation. Only two cases are conceivable; if the determinant +corresponds to a USEFUL organ, only its removal can bring back the +germ-plasm to its former level; therefore personal selection removes the +id in question, with its determinants, from the germ-plasm, by causing +the elimination of the individual in the struggle for existence. But +there is another conceivable case; the determinants concerned may be +those of an organ which has become USELESS, and they will then continue +unobstructed, but with exceeding slowness, along the downward path, +until the organ becomes vestigial, and finally disappears altogether. + +The fluctuations of the determinants hither and thither may thus be +transformed into a lasting ascending or descending movement; and THIS IS +THE CRUCIAL POINT OF THESE GERMINAL PROCESSES. + +This is not a fantastic assumption; we can read it in the fact of the +degeneration of disused parts. USELESS ORGANS ARE THE ONLY ONES WHICH +ARE NOT HELPED TO ASCEND AGAIN BY PERSONAL SELECTION, AND THEREFORE IN +THEIR CASE ALONE CAN WE FORM ANY IDEA OF HOW THE PRIMARY CONSTITUENTS +BEHAVE, WHEN THEY ARE SUBJECT SOLELY TO INTRA-GERMINAL FORCES. + +The whole determinant system of an id, as I conceive it, is in a state +of continual fluctuation upwards and downwards. In most cases the +fluctuations will counteract one another, because the passive streams of +nutriment soon change, but in many cases the limit from which a return +is possible will be passed, and then the determinants concerned will +continue to vary in the same direction, till they attain positive or +negative selection-value. At this stage personal selection intervenes +and sets aside the variation if it is disadvantageous, or favours--that +is to say, preserves--it if it is advantageous. Only THE DETERMINANT +OF A USELESS ORGAN IS UNINFLUENCED BY PERSONAL SELECTION, and, +as experience shows, it sinks downwards; that is, the organ that +corresponds to it degenerates very slowly but uninterruptedly till, +after what must obviously be an immense stretch of time, it disappears +from the germ-plasm altogether. + +Thus we find in the fact of the degeneration of disused parts the proof +that not all the fluctuations of a determinant return to equilibrium +again, but that, when the movement has attained to a certain strength, +it continues IN THE SAME DIRECTION. We have entire certainty in regard +to this as far as the downward progress is concerned, and we must +assume it also in regard to ascending variations, as the phenomena of +artificial selection certainly justify us in doing. If the Japanese +breeders were able to lengthen the tail feathers of the cock to +six feet, it can only have been because the determinants of the +tail-feathers in the germ-plasm had already struck out a path of +ascending variation, and this movement was taken advantage of by the +breeder, who continually selected for reproduction the individuals in +which the ascending variation was most marked. For all breeding depends +upon the unconscious selection of germinal variations. + +Of course these germinal processes cannot be proved mathematically, +since we cannot actually see the play of forces of the passive +fluctuations and their causes. We cannot say how great these +fluctuations are, and how quickly or slowly, how regularly or +irregularly they change. Nor do we know how far a determinant must be +strengthened by the passive flow of the nutritive stream if it is to +be beyond the danger of unfavourable variations, or how far it must be +weakened passively before it loses the power of recovering itself by its +own strength. It is no more possible to bring forward actual proofs in +this case than it was in regard to the selection-value of the initial +stages of an adaptation. But if we consider that all heritable +variations must have their roots in the germ-plasm, and further, that +when personal selection does not intervene, that is to say, in the case +of parts which have become useless, a degeneration of the part, and +therefore also of its determinant must inevitably take place; then we +must conclude that processes such as I have assumed are running their +course within the germ-plasm, and we can do this with as much certainty +as we were able to infer, from the phenomena of adaptation, the +selection-value of their initial stages. The fact of the degeneration +of disused parts seems to me to afford irrefutable proof that the +fluctuations within the germ-plasm ARE THE REAL ROOT OF ALL HEREDITARY +VARIATION, and the preliminary condition for the occurrence of the +Darwin-Wallace factor of selection. Germinal selection supplies the +stones out of which personal selection builds her temples and +palaces: ADAPTATIONS. The importance for the theory of the process of +degeneration of disused parts cannot be over-estimated, especially when +it occurs in sterile animal forms, where we are free from the doubt as +to the alleged LAMARCKIAN FACTOR which is apt to confuse our ideas in +regard to other cases. + +If we regard the variation of the many determinants concerned in the +transformation of the female into the sterile worker as having come +about through the gradual transformation of the ids into worker-ids, +we shall see that the germ-plasm of the sexual ants must contain three +kinds of ids, male, female, and worker ids, or if the workers have +diverged into soldiers and nest-builders, then four kinds. We understand +that the worker-ids arose because their determinants struck out a useful +path of variation, whether upward or downward, and that they continued +in this path until the highest attainable degree of utility of the parts +determined was reached. But in addition to the organs of positive or +negative selection-value, there were some which were indifferent as far +as the success and especially the functional capacity of the workers was +concerned: wings, ovarian tubes, receptaculum seminis, a number of the +facets of the eye, perhaps even the whole eye. As to the ovarian tubes +it is possible that their degeneration was an advantage for the workers, +in saving energy, and if so selection would favour the degeneration; but +how could the presence of eyes diminish the usefulness of the workers to +the colony? or the minute receptaculum seminis, or even the wings? These +parts have therefore degenerated BECAUSE THEY WERE OF NO FURTHER VALUE +TO THE INSECT. But if selection did not influence the setting aside of +these parts because they were neither of advantage nor of disadvantage +to the species, then the Darwinian factor of selection is here +confronted with a puzzle which it cannot solve alone, but which at once +becomes clear when germinal selection is added. For the determinants +of organs that have no further value for the organism, must, as we have +already explained, embark on a gradual course of retrograde development. + +In ants the degeneration has gone so far that there are no +wing-rudiments present in ANY species, as is the case with so many +butterflies, flies, and locusts, but in the larvae the imaginal discs of +the wings are still laid down. With regard to the ovaries, degeneration +has reached different levels in different species of ants, as has been +shown by the researches of my former pupil, Elizabeth Bickford. In many +species there are twelve ovarian tubes, and they decrease from that +number to one; indeed, in one species no ovarian tube at all is present. +So much at least is certain from what has been said, that in this +case EVERYTHING depends on the fluctuations of the elements of the +germ-plasm. Germinal selection, here as elsewhere, presents the +variations of the determinants, and personal selection favours or +rejects these, or,--if it be a question of organs which have become +useless,--it does not come into play at all, and allows the descending +variation free course. + +It is obvious that even the problem of COADAPTATION IN STERILE +ANIMALS can thus be satisfactorily explained. If the determinants are +oscillating upwards and downwards in continual fluctuation, and +varying more pronouncedly now in one direction now in the other, useful +variations of every determinant will continually present themselves +anew, and may, in the course of generations, be combined with one +another in various ways. But there is one character of the determinants +that greatly facilitates this complex process of selection, that, +after a certain limit has been reached, they go on varying in the same +direction. From this it follows that development along a path once +struck out may proceed without the continual intervention of personal +selection. This factor only operates, so to speak, at the beginning, +when it selects the determinants which are varying in the right +direction, and again at the end, when it is necessary to put a check +upon further variation. In addition to this, enormously long periods +have been available for all these adaptations, as the very gradual +transition stages between females and workers in many species plainly +show, and thus this process of transformation loses the marvellous and +mysterious character that seemed at the first glance to invest it, +and takes rank, without any straining, among the other processes of +selection. It seems to me that, from the facts that sterile animal forms +can adapt themselves to new vital functions, their superfluous parts +degenerate, and the parts more used adapt themselves in an ascending +direction, those less used in a descending direction, we must draw +the conclusion that harmonious adaptation here comes about WITHOUT +THE COOPERATION OF THE LAMARCKIAN PRINCIPLE. This conclusion once +established, however, we have no reason to refer the thousands of cases +of harmonious adaptation, which occur in exactly the same way among +other animals or plants, to a principle, the ACTIVE INTERVENTION OF +WHICH IN THE TRANSFORMATION OF SPECIES IS NOWHERE PROVED. WE DO NOT +REQUIRE IT TO EXPLAIN THE FACTS, AND THEREFORE WE MUST NOT ASSUME IT. + +The fact of coadaptation, which was supposed to furnish the strongest +argument against the principle of selection, in reality yields the +clearest evidence in favour of it. We MUST assume it, BECAUSE NO OTHER +POSSIBILITY OF EXPLANATION IS OPEN TO US, AND BECAUSE THESE ADAPTATIONS +ACTUALLY EXIST, THAT IS TO SAY, HAVE REALLY TAKEN PLACE. With this +conviction I attempted, as far back as 1894, when the idea of germinal +selection had not yet occurred to me, to make "harmonious adaptation" +(coadaptation) more easily intelligible in some way or other, and so +I was led to the idea, which was subsequently expounded in detail by +Baldwin, and Lloyd Morgan, and also by Osborn, and Gulick as ORGANIC +SELECTION. It seemed to me that it was not necessary that all the +germinal variations required for secondary variations should have +occurred SIMULTANEOUSLY, since, for instance, in the case of the +stag, the bones, muscles, sinews, and nerves would be incited by +the increasing heaviness of the antlers to greater activity in THE +INDIVIDUAL LIFE, and so would be strengthened. The antlers can only have +increased in size by very slow degrees, so that the muscles and bones +may have been able to keep pace with their growth in the individual +life, until the requisite germinal variations presented themselves. In +this way a disharmony between the increasing weight of the antlers and +the parts which support and move them would be avoided, since time would +be given for the appropriate germinal variations to occur, and so to set +agoing the HEREDITARY variation of the muscles, sinews, and bones. +("The Effect of External Influences upon Development", Romanes Lecture, +Oxford, 1894.) + +I still regard this idea as correct, but I attribute less importance +to "organic selection" than I did at that time, in so far that I do +not believe that it ALONE could effect complex harmonious adaptations. +Germinal selection now seems to me to play the chief part in bringing +about such adaptations. Something the same is true of the principle +I have called "Panmixia". As I became more and more convinced, in the +course of years, that the LAMARCKIAN PRINCIPLE ought not to be called in +to explain the dwindling of disused parts, I believed that this process +might be simply explained as due to the cessation of the conservative +effect of natural selection. I said to myself that, from the moment in +which a part ceases to be of use, natural selection withdraws its +hand from it, and then it must inevitably fall from the height of its +adaptiveness, because inferior variants would have as good a chance of +persisting as better ones, since all grades of fitness of the part in +question would be mingled with one another indiscriminately. This is +undoubtedly true, as Romanes pointed out ten years before I did, and +this mingling of the bad with the good probably does bring about a +deterioration of the part concerned. But it cannot account for the +steady diminution, which always occurs when a part is in process of +becoming rudimentary, and which goes on until it ultimately disappears +altogether. The process of dwindling cannot therefore be explained as +due to panmixia alone; we can only find a sufficient explanation in +germinal selection. + +IV. DERIVATIVES OF THE THEORY OF SELECTION. + +The impetus in all directions given by Darwin through his theory of +selection has been an immeasurable one, and its influence is still felt. +It falls within the province of the historian of science to enumerate +all the ideas which, in the last quarter of the nineteenth century, grew +out of Darwin's theories, in the endeavour to penetrate more deeply into +the problem of the evolution of the organic world. Within the narrow +limits to which this paper is restricted, I cannot attempt to discuss +any of these. + +V. ARGUMENTS FOR THE REALITY OF THE PROCESSES OF SELECTION. + +(a) SEXUAL SELECTION. + +Sexual selection goes hand in hand with natural selection. From the +very first I have regarded sexual selection as affording an extremely +important and interesting corroboration of natural selection, but, +singularly enough, it is precisely against this theory that an adverse +judgment has been pronounced in so many quarters, and it is only quite +recently, and probably in proportion as the wealth of facts in proof of +it penetrates into a wider circle, that we seem to be approaching a +more general recognition of this side of the problem of adaptation. Thus +Darwin's words in his preface to the second edition (1874) of his book, +"The Descent of Man and Sexual Selection", are being justified: "My +conviction as to the operation of natural selection remains unshaken," +and further, "If naturalists were to become more familiar with the idea +of sexual selection, it would, I think, be accepted to a much greater +extent, and already it is fully and favourably accepted by many +competent judges." Darwin was able to speak thus because he was already +acquainted with an immense mass of facts, which, taken together, +yield overwhelming evidence of the validity of the principle of sexual +selection. + +NATURAL SELECTION chooses out for reproduction the individuals that are +best equipped for the struggle for existence, and it does so at every +stage of development; it thus improves the species in all its stages and +forms. SEXUAL SELECTION operates only on individuals that are already +capable of reproduction, and does so only in relation to the attainment +of reproduction. It arises from the rivalry of one sex, usually the +male, for the possession of the other, usually the female. Its influence +can therefore only DIRECTLY affect one sex, in that it equips it +better for attaining possession of the other. But the effect may +extend indirectly to the female sex, and thus the whole species may be +modified, without, however, becoming any more capable of resistance +in the struggle for existence, for sexual selection only gives rise to +adaptations which are likely to give their possessor the victory over +rivals in the struggle for possession of the female, and which are +therefore peculiar to the wooing sex: the manifold "secondary sexual +characters." The diversity of these characters is so great that I cannot +here attempt to give anything approaching a complete treatment of them, +but I should like to give a sufficient number of examples to make the +principle itself, in its various modes of expression, quite clear. + +One of the chief preliminary postulates of sexual selection is the +unequal number of individuals in the two sexes, for if every male +immediately finds his mate there can be no competition for the +possession of the female. Darwin has shown that, for the most part, the +inequality between the sexes is due simply to the fact that there are +more males than females, and therefore the males must take some pains +to secure a mate. But the inequality does not always depend on the +numerical preponderance of the males, it is often due to polygamy; for, +if one male claims several females, the number of females in proportion +to the rest of the males will be reduced. Since it is almost always +the males that are the wooers, we must expect to find the occurrence +of secondary sexual characters chiefly among them, and to find it +especially frequent in polygamous species. And this is actually the +case. + +If we were to try to guess--without knowing the facts--what means the +male animals make use of to overcome their rivals in the struggle for +the possession of the female, we might name many kinds of means, but it +would be difficult to suggest any which is not actually employed in some +animal group or other. I begin with the mere difference in strength, +through which the male of many animals is so sharply distinguished from +the female, as, for instance, the lion, walrus, "sea-elephant," and +others. Among these the males fight violently for the possession of the +female, who falls to the victor in the combat. In this simple case no +one can doubt the operation of selection, and there is just as little +room for doubt as to the selection-value of the initial stages of the +variation. Differences in bodily strength are apparent even among human +beings, although in their case the struggle for the possession of the +female is no longer decided by bodily strength alone. + +Combats between male animals are often violent and obstinate, and the +employment of the natural weapons of the species in this way has led +to perfecting of these, e.g. the tusks of the boar, the antlers of the +stag, and the enormous, antler-like jaws of the stag-beetle. Here again +it is impossible to doubt that variations in these organs presented +themselves, and that these were considerable enough to be decisive in +combat, and so to lead to the improvement of the weapon. + +Among many animals, however, the females at first withdraw from the +males; they are coy, and have to be sought out, and sometimes held by +force. This tracking and grasping of the females by the males has given +rise to many different characters in the latter, as, for instance, +the larger eyes of the male bee, and especially of the males of the +Ephemerids (May-flies), some species of which show, in addition to the +usual compound eyes, large, so-called turban-eyes, so that the whole +head is covered with seeing surfaces. In these species the females are +very greatly in the minority (1-100), and it is easy to understand that +a keen competition for them must take place, and that, when the insects +of both sexes are floating freely in the air, an unusually wide range +of vision will carry with it a decided advantage. Here again the actual +adaptations are in accordance with the preliminary postulates of the +theory. We do not know the stages through which the eye has passed +to its present perfected state, but, since the number of simple eyes +(facets) has become very much greater in the male than in the female, +we may assume that their increase is due to a gradual duplication of +the determinants of the ommatidium in the germ-plasm, as I have already +indicated in regard to sense-organs in general. In this case, again, +the selection-value of the initial stages hardly admits of doubt; better +vision DIRECTLY secures reproduction. + +In many cases THE ORGAN OF SMELL shows a similar improvement. Many lower +Crustaceans (Daphnidae) have better developed organs of smell in the +male sex. The difference is often slight and amounts only to one or two +olfactory filaments, but certain species show a difference of nearly +a hundred of these filaments (Leptodora). The same thing occurs among +insects. + +We must briefly consider the clasping or grasping organs which have +developed in the males among many lower Crustaceans, but here natural +selection plays its part along with sexual selection, for the union +of the sexes is an indispensable condition for the maintenance of the +species, and as Darwin himself pointed out, in many cases the two forms +of selection merge into each other. This fact has always seemed to me to +be a proof of natural selection, for, in regard to sexual selection, +it is quite obvious that the victory of the best-equipped could have +brought about the improvement only of the organs concerned, the factors +in the struggle, such as the eye and the olfactory organ. + +We come now to the EXCITANTS; that is, to the group of sexual characters +whose origin through processes of selection has been most frequently +called in question. We may cite the LOVE-CALLS produced by many male +insects, such as crickets and cicadas. These could only have arisen in +animal groups in which the female did not rapidly flee from the male, +but was inclined to accept his wooing from the first. Thus, notes like +the chirping of the male cricket serve to entice the females. At first +they were merely the signal which showed the presence of a male in the +neighbourhood, and the female was gradually enticed nearer and nearer +by the continued chirping. The male that could make himself heard to the +greatest distance would obtain the largest following, and would transmit +the beginnings, and, later, the improvement of his voice to the greatest +number of descendants. But sexual excitement in the female +became associated with the hearing of the love-call, and then the +sound-producing organ of the male began to improve, until it attained to +the emission of the long-drawn-out soft notes of the mole-cricket or +the maenad-like cry of the cicadas. I cannot here follow the process +of development in detail, but will call attention to the fact that the +original purpose of the voice, the announcing of the male's presence, +became subsidiary, and the exciting of the female became the chief goal +to be aimed at. The loudest singers awakened the strongest excitement, +and the improvement resulted as a matter of course. I conceive of the +origin of bird-song in a somewhat similar manner, first as a means of +enticing, then of exciting the female. + +One more kind of secondary sexual character must here be mentioned: the +odour which emanates from so many animals at the breeding season. It is +possible that this odour also served at first merely to give notice +of the presence of individuals of the other sex, but it soon became an +excitant, and as the individuals which caused the greatest degree of +excitement were preferred, it reached as high a pitch of perfection as +was possible to it. I shall confine myself here to the comparatively +recently discovered fragrance of butterflies. Since Fritz Muller found +out that certain Brazilian butterflies gave off fragrance "like a +flower," we have become acquainted with many such cases, and we now know +that in all lands, not only many diurnal Lepidoptera but nocturnal ones +also give off a delicate odour, which is agreeable even to man. +The ethereal oil to which this fragrance is due is secreted by the +skin-cells, usually of the wing, as I showed soon after the discovery +of the SCENT-SCALES. This is the case in the males; the females have no +SPECIAL scent-scales recognisable as such by their form, but they must, +nevertheless, give off an extremely delicate fragrance, although our +imperfect organ of smell cannot perceive it, for the males become aware +of the presence of a female, even at night, from a long distance off, +and gather round her. We may therefore conclude, that both sexes have +long given forth a very delicate perfume, which announced their presence +to others of the same species, and that in many species (NOT IN ALL) +these small beginnings became, in the males, particularly strong +scent-scales of characteristic form (lute, brush, or lyre-shaped). At +first these scales were scattered over the surface of the wing, but +gradually they concentrated themselves, and formed broad, velvety bands, +or strong, prominent brushes, and they attained their highest pitch of +evolution when they became enclosed within pits or folds of the skin, +which could be opened to let the delicious fragrance stream forth +suddenly towards the female. Thus in this case also we see that +characters, the original use of which was to bring the sexes together, +and so to maintain the species, have been evolved in the males into +means for exciting the female. And we can hardly doubt, that the females +are most readily enticed to yield to the butterfly that sends out the +strongest fragrance,--that is to say, that excites them to the highest +degree. It is a pity that our organs of smell are not fine enough to +examine the fragrance of male Lepidoptera in general, and to compare it +with other perfumes which attract these insects. (See Poulton, "Essays +on Evolution", 1908, pages 316, 317.) As far as we can perceive them +they resemble the fragrance of flowers, but there are Lepidoptera +whose scent suggests musk. A smell of musk is also given off by several +plants: it is a sexual excitant in the musk-deer, the musk-sheep, and +the crocodile. + +As far as we know, then, it is perfumes similar to those of flowers that +the male Lepidoptera give off in order to entice their mates, and this +is a further indication that animals, like plants, can to a large extent +meet the claims made upon them by life, and produce the adaptations +which are most purposive,--a further proof, too, of my proposition +that the useful variations, so to speak, are ALWAYS THERE. The flowers +developed the perfumes which entice their visitors, and the male +Lepidoptera developed the perfumes which entice and excite their mates. + +There are many pretty little problems to be solved in this connection, +for there are insects, such as some flies, that are attracted by smells +which are unpleasant to us, like those from decaying flesh and carrion. +But there are also certain flowers, some orchids for instance, which +give forth no very agreeable odour, but one which is to us repulsive +and disgusting; and we should therefore expect that the males of such +insects would give off a smell unpleasant to us, but there is no case +known to me in which this has been demonstrated. + +In cases such as we have discussed, it is obvious that there is no +possible explanation except through selection. This brings us to the +last kind of secondary sexual characters, and the one in regard to +which doubt has been most frequently expressed,--decorative colours +and decorative forms, the brilliant plumage of the male pheasant, the +humming-birds, and the bird of Paradise, as well as the bright colours +of many species of butterfly, from the beautiful blue of our little +Lycaenidae to the magnificent azure of the large Morphinae of Brazil. In +a great many cases, though not by any means in all, the male butterflies +are "more beautiful" than the females, and in the Tropics in particular +they shine and glow in the most superb colours. I really see no reason +why we should doubt the power of sexual selection, and I myself stand +wholly on Darwin's side. Even though we certainly cannot assume that +the females exercise a conscious choice of the "handsomest" mate, and +deliberate like the judges in a court of justice over the perfections +of their wooers, we have no reason to doubt that distinctive forms +(decorative feathers) and colours have a particularly exciting effect +upon the female, just as certain odours have among animals of so many +different groups, including the butterflies. The doubts which existed +for a considerable time, as a result of fallacious experiments, as to +whether the colours of flowers really had any influence in attracting +butterflies have now been set at rest through a series of more careful +investigations; we now know that the colours of flowers are there on +account of the butterflies, as Sprengel first showed, and that the +blossoms of Phanerogams are selected in relation to them, as Darwin +pointed out. + +Certainly it is not possible to bring forward any convincing proof of +the origin of decorative colours through sexual selection, but there +are many weighty arguments in favour of it, and these form a body of +presumptive evidence so strong that it almost amounts to certainty. + +In the first place, there is the analogy with other secondary sexual +characters. If the song of birds and the chirping of the cricket have +been evolved through sexual selection, if the penetrating odours of male +animals,--the crocodile, the musk-deer, the beaver, the carnivores, and, +finally, the flower-like fragrances of the butterflies have been evolved +to their present pitch in this way, why should decorative colours +have arisen in some other way? Why should the eye be less sensitive +to SPECIFICALLY MALE colours and other VISIBLE signs ENTICING TO THE +FEMALE, than the olfactory sense to specifically male odours, or the +sense of hearing to specifically male sounds? Moreover, the decorative +feathers of birds are almost always spread out and displayed before +the female during courtship. I have elsewhere ("The Evolution Theory", +London, 1904, I. page 219.) pointed out that decorative colouring and +sweet-scentedness may replace one another in Lepidoptera as well as +in flowers, for just as some modestly coloured flowers (mignonette and +violet) have often a strong perfume, while strikingly coloured ones are +sometimes quite devoid of fragrance, so we find that the most beautiful +and gaily-coloured of our native Lepidoptera, the species of Vanessa, +have no scent-scales, while these are often markedly developed in grey +nocturnal Lepidoptera. Both attractions may, however, be combined in +butterflies, just as in flowers. Of course, we cannot explain why both +means of attraction should exist in one genus, and only one of them in +another, since we do not know the minutest details of the conditions +of life of the genera concerned. But from the sporadic distribution of +scent-scales in Lepidoptera, and from their occurrence or absence in +nearly related species, we may conclude that fragrance is a relatively +MODERN acquirement, more recent than brilliant colouring. + +One thing in particular that stamps decorative colouring as a product of +selection is ITS GRADUAL INTENSIFICATION by the addition of new spots, +which we can quite well observe, because in many cases the colours have +been first acquired by the males, and later transmitted to the females +by inheritance. The scent-scales are never thus transmitted, probably +for the same reason that the decorative colours of many birds are often +not transmitted to the females: because with these they would be exposed +to too great elimination by enemies. Wallace was the first to point out +that in species with concealed nests the beautiful feathers of the male +occurred in the female also, as in the parrots, for instance, but +this is not the case in species which brood on an exposed nest. In the +parrots one can often observe that the general brilliant colouring of +the male is found in the female, but that certain spots of colour are +absent, and these have probably been acquired comparatively recently by +the male and have not yet been transmitted to the female. + +Isolation of the group of individuals which is in process of varying +is undoubtedly of great value in sexual selection, for even a solitary +conspicuous variation will become dominant much sooner in a small +isolated colony, than among a large number of members of a species. + +Anyone who agrees with me in deriving variations from germinal selection +will regard that process as an essential aid towards explaining the +selection of distinctive courtship-characters, such as coloured spots, +decorative feathers, horny outgrowths in birds and reptiles, combs, +feather-tufts, and the like, since the beginnings of these would +be presented with relative frequency in the struggle between the +determinants within the germ-plasm. The process of transmission of +decorative feathers to the female results, as Darwin pointed out and +illustrated by interesting examples, in the COLOUR-TRANSFORMATION OF A +WHOLE SPECIES, and this process, as the phyletically older colouring +of young birds shows, must, in the course of thousands of years, have +repeated itself several times in a line of descent. + +If we survey the wealth of phenomena presented to us by secondary sexual +characters, we can hardly fail to be convinced of the truth of the +principle of sexual selection. And certainly no one who has accepted +natural selection should reject sexual selection, for, not only do the +two processes rest upon the same basis, but they merge into one another, +so that it is often impossible to say how much of a particular character +depends on one and how much on the other form of selection. + +(b) NATURAL SELECTION. + +An actual proof of the theory of sexual selection is out of the +question, if only because we cannot tell when a variation attains to +selection-value. It is certain that a delicate sense of smell is of +value to the male moth in his search for the female, but whether the +possession of one additional olfactory hair, or of ten, or of twenty +additional hairs leads to the success of its possessor we are unable +to tell. And we are groping even more in the dark when we discuss the +excitement caused in the female by agreeable perfumes, or by striking +and beautiful colours. That these do make an impression is beyond doubt; +but we can only assume that slight intensifications of them give any +advantage, and we MUST assume this SINCE OTHERWISE SECONDARY SEXUAL +CHARACTERS REMAIN INEXPLICABLE. + +The same thing is true in regard to natural selection. It is not +possible to bring forward any actual proof of the selection-value of +the initial stages, and the stages in the increase of variations, as has +been already shown. But the selection-value of a finished adaptation can +in many cases be statistically determined. Cesnola and Poulton have made +valuable experiments in this direction. The former attached forty-five +individuals of the green, and sixty-five of the brown variety of the +praying mantis (Mantis religiosa), by a silk thread to plants, and +watched them for seventeen days. The insects which were on a surface of +a colour similar to their own remained uneaten, while twenty-five green +insects on brown parts of plants had all disappeared in eleven days. + +The experiments of Poulton and Sanders ("Report of the British +Association" (Bristol, 1898), London, 1899, pages 906-909.) were made +with 600 pupae of Vanessa urticae, the "tortoise-shell butterfly." The +pupae were artificially attached to nettles, tree-trunks, fences, walls, +and to the ground, some at Oxford, some at St Helens in the Isle of +Wight. In the course of a month 93 per cent of the pupae at Oxford were +killed, chiefly by small birds, while at St Helens 68 per cent perished. +The experiments showed very clearly that the colour and character of the +surface on which the pupa rests--and thus its own conspicuousness--are +of the greatest importance. At Oxford only the four pupae which were +fastened to nettles emerged; all the rest--on bark, stones and the +like--perished. At St Helens the elimination was as follows: on fences +where the pupae were conspicuous, 92 per cent; on bark, 66 per cent; on +walls, 54 per cent; and among nettles, 57 per cent. These interesting +experiments confirm our views as to protective coloration, and show +further, THAT THE RATIO OF ELIMINATION IN THE SPECIES IS A VERY HIGH +ONE, AND THAT THEREFORE SELECTION MUST BE VERY KEEN. + +We may say that the process of selection follows as a logical necessity +from the fulfilment of the three preliminary postulates of the theory: +variability, heredity, and the struggle for existence, with its enormous +ratio of elimination in all species. To this we must add a fourth +factor, the INTENSIFICATION of variations which Darwin established as +a fact, and which we are now able to account for theoretically on +the basis of germinal selection. It may be objected that there is +considerable uncertainty about this LOGICAL proof, because of our +inability to demonstrate the selection-value of the initial stages and +the individual stages of increase. We have therefore to fall back on +PRESUMPTIVE EVIDENCE. This is to be found in THE INTERPRETATIVE VALUE OF +THE THEORY. Let us consider this point in greater detail. + +In the first place, it is necessary to emphasise what is often +overlooked, namely, that the theory not only explains the +TRANSFORMATIONS of species, it also explains THEIR REMAINING THE SAME; +in addition to the principle of varying, it contains within itself that +of PERSISTING. It is part of the essence of selection, that it not +only causes a part to VARY till it has reached its highest pitch of +adaptation, but that it MAINTAINS IT AT THIS PITCH. THIS CONSERVING +INFLUENCE OF NATURAL SELECTION is of great importance, and was early +recognised by Darwin; it follows naturally from the principle of the +survival of the fittest. + +We understand from this how it is that a species which has become +fully adapted to certain conditions of life ceases to vary, but remains +"constant," as long as the conditions of life FOR IT remain unchanged, +whether this be for thousands of years, or for whole geological epochs. +But the most convincing proof of the power of the principle of selection +lies in the innumerable multitude of phenomena which cannot be explained +in any other way. To this category belong all structures which are only +PASSIVELY of advantage to the organism, because none of these can have +arisen by the alleged LAMARCKIAN PRINCIPLE. These have been so often +discussed that we need do no more than indicate them here. Until quite +recently the sympathetic coloration of animals--for instance, the +whiteness of Arctic animals--was referred, at least in part, to +the DIRECT influence of external factors, but the facts can best be +explained by referring them to the processes of selection, for then it +is unnecessary to make the gratuitous assumption that many species are +sensitive to the stimulus of cold and that others are not. The great +majority of Arctic land-animals, mammals and birds, are white, and this +proves that they were all able to present the variation which was most +useful for them. The sable is brown, but it lives in trees, where +the brown colouring protects and conceals it more effectively. The +musk-sheep (Ovibos moschatus) is also brown, and contrasts sharply +with the ice and snow, but it is protected from beasts of prey by its +gregarious habit, and therefore it is of advantage to be visible from +as great a distance as possible. That so many species have been able to +give rise to white varieties does not depend on a special sensitiveness +of the skin to the influence of cold, but to the fact that Mammals and +Birds have a general tendency to vary towards white. Even with us, many +birds--starlings, blackbirds, swallows, etc.--occasionally produce white +individuals, but the white variety does not persist, because it readily +falls a victim to the carnivores. This is true of white fawns, foxes, +deer, etc. The whiteness, therefore, arises from internal causes, and +only persists when it is useful. A great many animals living in a +GREEN ENVIRONMENT have become clothed in green, especially insects, +caterpillars, and Mantidae, both persecuted and persecutors. + +That it is not the direct effect of the environment which calls forth +the green colour is shown by the many kinds of caterpillar which rest on +leaves and feed on them, but are nevertheless brown. These feed by night +and betake themselves through the day to the trunk of the tree, and hide +in the furrows of the bark. We cannot, however, conclude from this that +they were UNABLE to vary towards green, for there are Arctic animals +which are white only in winter and brown in summer (Alpine hare, and +the ptarmigan of the Alps), and there are also green leaf-insects which +remain green only while they are young and difficult to see on the leaf, +but which become brown again in the last stage of larval life, when they +have outgrown the leaf. They then conceal themselves by day, sometimes +only among withered leaves on the ground, sometimes in the earth itself. +It is interesting that in one genus, Chaerocampa, one species is brown +in the last stage of larval life, another becomes brown earlier, and in +many species the last stage is not wholly brown, a part remaining green. +Whether this is a case of a double adaptation, or whether the green is +being gradually crowded out by the brown, the fact remains that the same +species, even the same individual, can exhibit both variations. The case +is the same with many of the leaf-like Orthoptera, as, for instance, the +praying mantis (Mantis religiosa) which we have already mentioned. + +But the best proofs are furnished by those often-cited cases in which +the insect bears a deceptive resemblance to another object. We now know +many such cases, such as the numerous imitations of green or withered +leaves, which are brought about in the most diverse ways, sometimes by +mere variations in the form of the insect and in its colour, sometimes +by an elaborate marking, like that which occurs in the Indian +leaf-butterflies, Kallima inachis. In the single butterfly-genus Anaea, +in the woods of South America, there are about a hundred species which +are all gaily coloured on the upper surface, and on the reverse side +exhibit the most delicate imitation of the colouring and pattern of a +leaf, generally without any indication of the leaf-ribs, but extremely +deceptive nevertheless. Anyone who has seen only one such butterfly +may doubt whether many of the insignificant details of the marking can +really be of advantage to the insect. Such details are for instance the +apparent holes and splits in the apparently dry or half-rotten leaf, +which are usually due to the fact that the scales are absent on a +circular or oval patch so that the colourless wing-membrane lies bare, +and one can look through the spot as through a window. Whether the +bird which is seeking or pursuing the butterflies takes these holes for +dewdrops, or for the work of a devouring insect, does not affect +the question; the mirror-like spot undoubtedly increases the general +deceptiveness, for the same thing occurs in many leaf-butterflies, +though not in all, and in some cases it is replaced in quite a peculiar +manner. In one species of Anaea (A. divina), the resting butterfly looks +exactly like a leaf out of the outer edge of which a large semicircular +piece has been eaten, possibly by a caterpillar; but if we look more +closely it is obvious that there is no part of the wing absent, and that +the semicircular piece is of a clear, pale yellow colour, while the rest +of the wing is of a strongly contrasted dark brown. + +But the deceptive resemblance may be caused in quite a different manner. +I have often speculated as to what advantage the brilliant white C +could give to the otherwise dusky-coloured "Comma butterfly" (Grapta C. +album). Poulton's recent observations ("Proc. Ent. Soc"., London, May 6, +1903.) have shown that this represents the imitation of a crack such as +is often seen in dry leaves, and is very conspicuous because the light +shines through it. + +The utility obviously lies in presenting to the bird the very familiar +picture of a broken leaf with a clear shining slit, and we may conclude, +from the imitation of such small details, that the birds are very sharp +observers and that the smallest deviation from the usual arrests their +attention and incites them to closer investigation. It is obvious that +such detailed--we might almost say such subtle--deceptive resemblances +could only have come about in the course of long ages through the +acquirement from time to time of something new which heightened the +already existing resemblance. + +In face of facts like these there can be no question of chance, and no +one has succeeded so far in finding any other explanation to replace +that by selection. For the rest, the apparent leaves are by no means +perfect copies of a leaf; many of them only represent the torn or +broken piece, or the half or two-thirds of a leaf, but then the leaves +themselves frequently do not present themselves to the eye as a whole, +but partially concealed among other leaves. Even those butterflies +which, like the species of Kallima and Anaea, represent the whole of +a leaf with stalk, ribs, apex, and the whole breadth, are not actual +copies which would satisfy a botanist; there is often much wanting. +In Kallima the lateral ribs of the leaf are never all included in the +markings; there are only two or three on the left side and at most four +or five on the right, and in many individuals these are rather obscure, +while in others they are comparatively distinct. This furnishes us with +fresh evidence in favour of their origin through processes of selection, +for a botanically perfect picture could not arise in this way; there +could only be a fixing of such details as heightened the deceptive +resemblance. + +Our postulate of origin through selection also enables us to understand +why the leaf-imitation is on the lower surface of the wing in the +diurnal Lepidoptera, and on the upper surface in the nocturnal forms, +corresponding to the attitude of the wings in the resting position of +the two groups. + +The strongest of all proofs of the theory, however, is afforded by +cases of true "mimicry," those adaptations discovered by Bates in 1861, +consisting in the imitation of one species by another, which becomes +more and more like its model. The model is always a species that enjoys +some special protection from enemies, whether because it is unpleasant +to taste, or because it is in some way dangerous. + +It is chiefly among insects and especially among butterflies that we +find the greatest number of such cases. Several of these have been +minutely studied, and every detail has been investigated, so that it is +difficult to understand how there can still be disbelief in regard +to them. If the many and exact observations which have been carefully +collected and critically discussed, for instance by Poulton ("Essays +on Evolution", 1889-1907, Oxford, 1908, passim, e.g. page 269.) were +thoroughly studied, the arguments which are still frequently urged +against mimicry would be found untenable; we can hardly hope to find +more convincing proof of the actuality of the processes of selection +than these cases put into our hands. The preliminary postulates of +the theory of mimicry have been disputed, for instance, that diurnal +butterflies are persecuted and eaten by birds, but observations +specially directed towards this point in India, Africa, America and +Europe have placed it beyond all doubt. If it were necessary I could +myself furnish an account of my own observations on this point. + +In the same way it has been established by experiment and observation +in the field that in all the great regions of distribution there +are butterflies which are rejected by birds and lizards, their +chief enemies, on account of their unpleasant smell or taste. These +butterflies are usually gaily and conspicuously coloured and thus--as +Wallace first interpreted it--are furnished with an easily recognisable +sign: a sign of unpalatableness or WARNING COLOURS. If they were not +thus recognisable easily and from a distance, they would frequently be +pecked at by birds, and then rejected because of their unpleasant taste; +but as it is, the insect-eaters recognise them at once as unpalatable +booty and ignore them. Such IMMUNE (The expression does not refer to all +the enemies of this butterfly; against ichneumon-flies, for instance, +their unpleasant smell usually gives no protection.) species, wherever +they occur, are imitated by other palatable species, which thus acquire +a certain degree of protection. + +It is true that this explanation of the bright, conspicuous colours +is only a hypothesis, but its foundations,--unpalatableness, and the +liability of other butterflies to be eaten,--are certain, and its +consequences--the existence of mimetic palatable forms--confirm it in +the most convincing manner. Of the many cases now known I select +one, which is especially remarkable, and which has been thoroughly +investigated, Papilio dardanus (merope), a large, beautiful, diurnal +butterfly which ranges from Abyssinia throughout the whole of Africa to +the south coast of Cape Colony. + +The males of this form are everywhere ALMOST the same in colour and in +form of wings, save for a few variations in the sparse black markings on +the pale yellow ground. But the females occur in several quite different +forms and colourings, and one of these only, the Abyssinian form, is +like the male, while the other three or four are MIMETIC, that is to +say, they copy a butterfly of quite a different family the Danaids, +which are among the IMMUNE forms. In each region the females have thus +copied two or three different immune species. There is much that is +interesting to be said in regard to these species, but it would be out +of keeping with the general tenor of this paper to give details of this +very complicated case of polymorphism in P. dardanus. Anyone who is +interested in the matter will find a full and exact statement of the +case in as far as we know it, in Poulton's "Essays on Evolution" (pages +373-375). (Professor Poulton has corrected some wrong descriptions which +I had unfortunately overlooked in the Plates of my book "Vortrage uber +Descendenztheorie", and which refer to Papilio dardanus (merope). +These mistakes are of no importance as far as and understanding of the +mimicry-theory is concerned, but I hope shortly to be able to correct +them in a later edition.) I need only add that three different mimetic +female forms have been reared from the eggs of a single female in South +Africa. The resemblance of these forms to their immune models goes so +far that even the details of the LOCAL forms of the models are copied by +the mimetic species. + +It remains to be said that in Madagascar a butterfly, Papilio meriones, +occurs, of which both sexes are very similar in form and markings to +the non-mimetic male of P. dardanus, so that it probably represents the +ancestor of this latter species. + +In face of such facts as these every attempt at another explanation must +fail. Similarly all the other details of the case fulfil the preliminary +postulates of selection, and leave no room for any other interpretation. +That the males do not take on the protective colouring is easily +explained, because they are in general more numerous, and the females +are more important for the preservation of the species, and must also +live longer in order to deposit their eggs. We find the same state of +things in many other species, and in one case (Elymnias undularis) +in which the male is also mimetically coloured, it copies quite a +differently coloured immune species from the model followed by the +female. This is quite intelligible when we consider that if there were +TOO MANY false immune types, the birds would soon discover that there +were palatable individuals among those with unpalatable warning colours. +Hence the imitation of different immune species by Papilio dardanus! + +I regret that lack of space prevents my bringing forward more examples +of mimicry and discussing them fully. But from the case of Papilio +dardanus alone there is much to be learnt which is of the highest +importance for our understanding of transformations. It shows us chiefly +what I once called, somewhat strongly perhaps, THE OMNIPOTENCE OF +NATURAL SELECTION in answer to an opponent who had spoken of its +"inadequacy." We here see that one and the same species is capable of +producing four or five different patterns of colouring and marking; +thus the colouring and marking are not, as has often been supposed, +a necessary outcome of the specific nature of the species, but a +true adaptation, which cannot arise as a direct effect of climatic +conditions, but solely through what I may call the sorting out of the +variations produced by the species, according to their utility. That +caterpillars may be either green or brown is already something more than +could have been expected according to the old conception of species, but +that one and the same butterfly should be now pale yellow, with black; +now red with black and pure white; now deep black with large, pure white +spots; and again black with a large ochreous-yellow spot, and many small +white and yellow spots; that in one sub-species it may be tailed like +the ancestral form, and in another tailless like its Danaid model,--all +this shows a far-reaching capacity for variation and adaptation that +wide never have expected if we did not see the facts before us. How +it is possible that the primary colour-variations should thus be +intensified and combined remains a puzzle even now; we are reminded of +the modern three-colour printing,--perhaps similar combinations of the +primary colours take place in this case; in any case the direction of +these primary variations is determined by the artist whom we know as +natural selection, for there is no other conceivable way in which the +model could affect the butterfly that is becoming more and more like it. +The same climate surrounds all four forms of female; they are subject +to the same conditions of nutrition. Moreover, Papilio dardanus is by +no means the only species of butterfly which exhibits different kinds of +colour-pattern on its wings. Many species of the Asiatic genus Elymnias +have on the upper surface a very good imitation of an immune Euploeine +(Danainae), often with a steel-blue ground-colour, while the under +surface is well concealed when the butterfly is at rest,--thus there are +two kinds of protective coloration each with a different meaning! The +same thing may be observed in many non-mimetic butterflies, for +instance in all our species of Vanessa, in which the under side shows +a grey-brown or brownish-black protective coloration, but we do not yet +know with certainty what may be the biological significance of the gaily +coloured upper surface. + +In general it may be said that mimetic butterflies are comparatively +rare species, but there are exceptions, for instance Limenitis archippus +in North America, of which the immune model (Danaida plexippus) also +occurs in enormous numbers. + +In another mimicry-category the imitators are often more numerous than +the models, namely in the case of the imitation of DANGEROUS INSECTS by +harmless species. Bees and wasps are dreaded for their sting, and they +are copied by harmless flies of the genera Eristalis and Syrphus, and +these mimics often occur in swarms about flowering plants without damage +to themselves or to their models; they are feared and are therefore left +unmolested. + +In regard also to the FAITHFULNESS OF THE COPY the facts are quite in +harmony with the theory, according to which the resemblance must have +arisen and increased BY DEGREES. We can recognise this in many +cases, for even now the mimetic species show very VARYING DEGREES OF +RESEMBLANCE to their immune model. If we compare, for instance, the +many different imitators of Danaida chrysippus we find that, with their +brownish-yellow ground-colour, and the position and size, and more or +less sharp limitation of their clear marginal spots, they have reached +very different degrees of nearness to their model. Or compare the female +of Elymnias undularis with its model Danaida genutia; there is a general +resemblance, but the marking of the Danaida is very roughly imitated in +Elymnias. + +Another fact that bears out the theory of mimicry is, that even when the +resemblance in colour-pattern is very great, the WING-VENATION, which is +so constant, and so important in determining the systematic position +of butterflies, is never affected by the variation. The pursuers of the +butterfly have no time to trouble about entomological intricacies. + +I must not pass over a discovery of Poulton's which is of great +theoretical importance--that mimetic butterflies may reach the same +effect by very different means. ("Journ. Linn. Soc. London (Zool.)", +Vol. XXVI. 1898, pages 598-602.) Thus the glass-like transparency of the +wing of a certain Ithomiine (Methona) and its Pierine mimic (Dismorphia +orise) depends on a diminution in the size of the scales; in the Danaine +genus Ituna it is due to the fewness of the scales, and in a third +imitator, a moth (Castnia linus var. heliconoides) the glass-like +appearance of the wing is due neither to diminution nor to absence of +scales, but to their absolute colourlessness and transparency, and to +the fact that they stand upright. In another moth mimic (Anthomyza) the +arrangement of the transparent scales is normal. Thus it is not some +unknown external influence that has brought about the transparency of +the wing in these five forms, as has sometimes been supposed. Nor is it +a hypothetical INTERNAL evolutionary tendency, for all three vary in a +different manner. The cause of this agreement can only lie in selection, +which preserves and intensifies in each species the favourable +variations that present themselves. The great faithfulness of the copy +is astonishing in these cases, for it is not THE WHOLE wing which is +transparent; certain markings are black in colour, and these contrast +sharply with the glass-like ground. It is obvious that the pursuers +of these butterflies must be very sharp-sighted, for otherwise the +agreement between the species could never have been pushed so far. The +less the enemies see and observe, the more defective must the imitation +be, and if they had been blind, no visible resemblance between the +species which required protection could ever have arisen. + +A seemingly irreconcilable contradiction to the mimicry theory is +presented in the following cases, which were known to Bates, who, +however, never succeeded in bringing them into line with the principle +of mimicry. + +In South America there are, as we have already said, many mimics of the +immune Ithomiinae (or as Bates called them Heliconidae). Among these +there occur not merely species which are edible, and thus require the +protection of a disguise, but others which are rejected on account of +their unpalatableness. How could the Ithomiine dress have developed in +their case, and of what use is it, since the species would in any case +be immune? In Eastern Brazil, for instance, there are four butterflies, +which bear a most confusing resemblance to one another in colour, +marking, and form of wing, and all four are unpalatable to birds. They +belong to four different genera and three sub-families, and we have to +inquire: Whence came this resemblance and what end does it serve? For +a long time no satisfactory answer could be found, but Fritz Muller +(In "Kosmos", 1879, page 100.), seventeen years after Bates, offered a +solution to the riddle, when he pointed out that young birds could not +have an instinctive knowledge of the unpalatableness of the Ithomiines, +but must learn by experience which species were edible and which +inedible. Thus each young bird must have tasted at least one individual +of each inedible species and discovered its unpalatability, before it +learnt to avoid, and thus to spare the species. But if the four species +resemble each other very closely the bird will regard them all as of +the same kind, and avoid them all. Thus there developed a process +of selection which resulted in the survival of the Ithomiine-like +individuals, and in so great an increase of resemblance between the four +species, that they are difficult to distinguish one from another even in +a collection. The advantage for the four species, living side by side +as they do e.g. in Bahia, lies in the fact that only one individual +from the MIMICRY-RING ("inedible association") need be tasted by a young +bird, instead of at least four individuals, as would otherwise be the +case. As the number of young birds is great, this makes a considerable +difference in the ratio of elimination. + +These interesting mimicry-rings (trusts), which have much significance +for the theory, have been the subject of numerous and careful +investigations, and at least their essential features are now fully +established. Muller took for granted, without making any investigations, +that young birds only learn by experience to distinguish between +different kinds of victims. But Lloyd Morgan's ("Habit and Instinct", +London, 1896.) experiments with young birds proved that this is really +the case, and at the same time furnished an additional argument against +the LAMARCKIAN PRINCIPLE. + +In addition to the mimicry-rings first observed in South America, others +have been described from Tropical India by Moore, and by Poulton and +Dixey from Africa, and we may expect to learn many more interesting +facts in this connection. Here again the preliminary postulates of the +theory are satisfied. And how much more that would lead to the same +conclusion might be added! + +As in the case of mimicry many species have come to resemble one another +through processes of selection, so we know whole classes of phenomena +in which plants and animals have become adapted to one another, and have +thus been modified to a considerable degree. I refer particularly to the +relation between flowers and insects; but as there is an article on "The +Biology of Flowers" in this volume, I need not discuss the subject, but +will confine myself to pointing out the significance of these remarkable +cases for the theory of selection. Darwin has shown that the originally +inconspicuous blossoms of the phanerogams were transformed into flowers +through the visits of insects, and that, conversely, several large +orders of insects have been gradually modified by their association +with flowers, especially as regards the parts of their body actively +concerned. Bees and butterflies in particular have become what they +are through their relation to flowers. In this case again all that is +apparently contradictory to the theory can, on closer investigation, be +beautifully interpreted in corroboration of it. Selection can give rise +only to what is of use to the organism actually concerned, never to what +is of use to some other organism, and we must therefore expect to find +that in flowers only characters of use to THEMSELVES have arisen, never +characters which are of use to insects only, and conversely that in the +insects characters useful to them and not merely to the plants would +have originated. For a long time it seemed as if an exception to this +rule existed in the case of the fertilisation of the yucca blossoms by +a little moth, Pronuba yuccasella. This little moth has a sickle-shaped +appendage to its mouth-parts which occurs in no other Lepidopteron, +and which is used for pushing the yellow pollen into the opening of +the pistil, thus fertilising the flower. Thus it appears as if a new +structure, which is useful only to the plant, has arisen in the insect. +But the difficulty is solved as soon as we learn that the moth lays +its eggs in the fruit-buds of the Yucca, and that the larvae, when they +emerge, feed on the developing seeds. In effecting the fertilisation +of the flower the moth is at the same time making provision for its own +offspring, since it is only after fertilisation that the seeds begin to +develop. There is thus nothing to prevent our referring this structural +adaptation in Pronuba yuccasella to processes of selection, which +have gradually transformed the maxillary palps of the female into the +sickle-shaped instrument for collecting the pollen, and which have at +the same time developed in the insect the instinct to press the pollen +into the pistil. + +In this domain, then, the theory of selection finds nothing but +corroboration, and it would be impossible to substitute for it any +other explanation, which, now that the facts are so well known, could +be regarded as a serious rival to it. That selection is a factor, and +a very powerful factor in the evolution of organisms, can no longer be +doubted. Even although we cannot bring forward formal proofs of it IN +DETAIL, cannot calculate definitely the size of the variations which +present themselves, and their selection-value, cannot, in short, +reduce the whole process to a mathematical formula, yet we must assume +selection, because it is the only possible explanation applicable to +whole classes of phenomena, and because, on the other hand, it is made +up of factors which we know can be proved actually to exist, and +which, IF they exist, must of logical necessity cooperate in the manner +required by the theory. WE MUST ACCEPT IT BECAUSE THE PHENOMENA OF +EVOLUTION AND ADAPTATION MUST HAVE A NATURAL BASIS, AND BECAUSE IT IS +THE ONLY POSSIBLE EXPLANATION OF THEM. (This has been discussed in many +of my earlier works. See for instance "The All-Sufficiency of Natural +Selection, a reply to Herbert Spencer", London, 1893.) + +Many people are willing to admit that selection explains adaptations, +but they maintain that only a part of the phenomena are thus explained, +because everything does not depend upon adaptation. They regard +adaptation as, so to speak, a special effort on the part of Nature, +which she keeps in readiness to meet particularly difficult claims +of the external world on organisms. But if we look at the matter more +carefully we shall find that adaptations are by no means exceptional, +but that they are present everywhere in such enormous numbers, that it +would be difficult in regard to any structure whatever, to prove that +adaptation had NOT played a part in its evolution. + +How often has the senseless objection been urged against selection that +it can create nothing, it can only reject. It is true that it cannot +create either the living substance or the variations of it; both must be +given. But in rejecting one thing it preserves another, intensifies +it, combines it, and in this way CREATES what is new. EVERYTHING in +organisms depends on adaptation; that is to say, everything must be +admitted through the narrow door of selection, otherwise it can take +no part in the building up of the whole. But, it is asked, what of the +direct effect of external conditions, temperature, nutrition, climate +and the like? Undoubtedly these can give rise to variations, but they +too must pass through the door of selection, and if they cannot do this +they are rejected, eliminated from the constitution of the species. + +It may, perhaps, be objected that such external influences are often of +a compelling power, and that every animal MUST submit to them, and that +thus selection has no choice and can neither select nor reject. There +may be such cases; let us assume for instance that the effect of the +cold of the Arctic regions was to make all the mammals become black; the +result would be that they would all be eliminated by selection, and +that no mammals would be able to live there at all. But in most cases a +certain percentage of animals resists these strong influences, and +thus selection secures a foothold on which to work, eliminating the +unfavourable variation, and establishing a useful colouring, consistent +with what is required for the maintenance of the species. + +Everything depends upon adaptation! We have spoken much of adaptation +in colouring, in connection with the examples brought into prominence by +Darwin, because these are conspicuous, easily verified, and at the same +time convincing for the theory of selection. But is it only desert and +polar animals whose colouring is determined through adaptation? Or the +leaf-butterflies, and the mimetic species, or the terrifying markings, +and "warning-colours" and a thousand other kinds of sympathetic +colouring? It is, indeed, never the colouring alone which makes up +the adaptation; the structure of the animal plays a part, often a very +essential part, in the protective disguise, and thus MANY variations may +cooperate towards ONE common end. And it is to be noted that it is by +no means only external parts that are changed; internal parts are ALWAYS +modified at the same time--for instance, the delicate elements of the +nervous system on which depend the INSTINCT of the insect to hold its +wings, when at rest, in a perfectly definite position, which, in the +leaf-butterfly, has the effect of bringing the two pieces on which +the marking occurs on the anterior and posterior wing into the same +direction, and thus displaying as a whole the fine curve of the midrib +on the seeming leaf. But the wing-holding instinct is not regulated in +the same way in all leaf-butterflies; even our indigenous species +of Vanessa, with their protective ground-colouring, have quite a +distinctive way of holding their wings so that the greater part of the +anterior wing is covered by the posterior when the butterfly is at rest. +But the protective colouring appears on the posterior wing and on the +tip of the anterior, TO PRECISELY THE DISTANCE TO WHICH IT IS LEFT +UNCOVERED. This occurs, as Standfuss has shown, in different degree in +our two most nearly allied species, the uncovered portion being +smaller in V. urticae than in V. polychloros. In this case, as in most +leaf-butterflies, the holding of the wing was probably the primary +character; only after that was thoroughly established did the protective +marking develop. In any case, the instinctive manner of holding the +wings is associated with the protective colouring, and must remain as it +is if the latter is to be effective. How greatly instincts may change, +that is to say, may be adapted, is shown by the case of the Noctuid +"shark" moth, Xylina vetusta. This form bears a most deceptive +resemblance to a piece of rotten wood, and the appearance is greatly +increased by the modification of the innate impulse to flight common to +so many animals, which has here been transformed into an almost contrary +instinct. This moth does not fly away from danger, but "feigns death," +that is, it draws antennae, legs and wings close to the body, and +remains perfectly motionless. It may be touched, picked up, and thrown +down again, and still it does not move. This remarkable instinct must +surely have developed simultaneously with the wood-colouring; at all +events, both cooperating variations are now present, and prove that both +the external and the most minute internal structure have undergone a +process of adaptation. + +The case is the same with all structural variations of animal parts, +which are not absolutely insignificant. When the insects acquired wings +they must also have acquired the mechanism with which to move them--the +musculature, and the nervous apparatus necessary for its automatic +regulation. All instincts depend upon compound reflex mechanisms and are +just as indispensable as the parts they have to set in motion, and all +may have arisen through processes of selection if the reasons which I +have elsewhere given for this view are correct. ("The Evolution Theory", +London, 1904, page 144.) + +Thus there is no lack of adaptations within the organism, and +particularly in its most important and complicated parts, so that we may +say that there is no actively functional organ that has not undergone a +process of adaptation relative to its function and the requirements of +the organism. Not only is every gland structurally adapted, down to the +very minutest histological details, to its function, but the function +is equally minutely adapted to the needs of the body. Every cell in the +mucous lining of the intestine is exactly regulated in its relation to +the different nutritive substances, and behaves in quite a different way +towards the fats, and towards nitrogenous substances, or peptones. + +I have elsewhere called attention to the many adaptations of the whale +to the surrounding medium, and have pointed out--what has long been +known, but is not universally admitted, even now--that in it a great +number of important organs have been transformed in adaptation to the +peculiar conditions of aquatic life, although the ancestors of the whale +must have lived, like other hair-covered mammals, on land. I cited a +number of these transformations--the fish-like form of the body, the +hairlessness of the skin, the transformation of the fore-limbs to fins, +the disappearance of the hind-limbs and the development of a tail fin, +the layer of blubber under the skin, which affords the protection +from cold necessary to a warm-blooded animal, the disappearance of the +ear-muscles and the auditory passages, the displacement of the external +nares to the forehead for the greater security of the breathing-hole +during the brief appearance at the surface, and certain remarkable +changes in the respiratory and circulatory organs which enable the +animal to remain for a long time under water. I might have added many +more, for the list of adaptations in the whale to aquatic life is by no +means exhausted; they are found in the histological structure and in the +minutest combinations in the nervous system. For it is obvious that a +tail-fin must be used in quite a different way from a tail, which serves +as a fly-brush in hoofed animals, or as an aid to springing in the +kangaroo or as a climbing organ; it will require quite different +reflex-mechanisms and nerve-combinations in the motor centres. + +I used this example in order to show how unnecessary it is to assume a +special internal evolutionary power for the phylogenesis of species, for +this whole order of whales is, so to speak, MADE UP OF ADAPTATIONS; it +deviates in many essential respects from the usual mammalian type, and +all the deviations are adaptations to aquatic life. But if precisely the +most essential features of the organisation thus depend upon adaptation, +what is left for a phyletic force to do, since it is these essential +features of the structure it would have to determine? There are few +people now who believe in a phyletic evolutionary power, which is not +made up of the forces known to us--adaptation and heredity--but the +conviction that EVERY part of an organism depends upon adaptation has +not yet gained a firm footing. Nevertheless, I must continue to regard +this conception as the correct one, as I have long done. + +I may be permitted one more example. The feather of a bird is a +marvellous structure, and no one will deny that as a whole it depends +upon adaptation. But what part of it DOES NOT depend upon adaptation? +The hollow quill, the shaft with its hard, thin, light cortex, and the +spongy substance within it, its square section compared with the round +section of the quill, the flat barbs, their short, hooked barbules +which, in the flight-feathers, hook into one another with just +sufficient firmness to resist the pressure of the air at each wing-beat, +the lightness and firmness of the whole apparatus, the elasticity of +the vane, and so on. And yet all this belongs to an organ which is only +passively functional, and therefore can have nothing to do with the +LAMARCKIAN PRINCIPLE. Nor can the feather have arisen through some +magical effect of temperature, moisture, electricity, or specific +nutrition, and thus selection is again our only anchor of safety. + +But--it will be objected--the substance of which the feather consists, +this peculiar kind of horny substance, did not first arise through +selection in the course of the evolution of the birds, for it formed the +covering of the scales of their reptilian ancestors. It is quite true +that a similar substance covered the scales of the Reptiles, but why +should it not have arisen among them through selection? Or in what other +way could it have arisen, since scales are also passively useful parts? +It is true that if we are only to call adaptation what has been acquired +by the species we happen to be considering, there would remain a great +deal that could not be referred to selection; but we are postulating an +evolution which has stretched back through aeons, and in the course of +which innumerable adaptations took place, which had not merely ephemeral +persistence in a genus, a family or a class, but which was continued +into whole Phyla of animals, with continual fresh adaptations to +the special conditions of each species, family, or class, yet with +persistence of the fundamental elements. Thus the feather, once +acquired, persisted in all birds, and the vertebral column, once gained +by adaptation in the lowest forms, has persisted in all the Vertebrates, +from Amphioxus upwards, although with constant readaptation to the +conditions of each particular group. Thus everything we can see in +animals is adaptation, whether of to-day, or of yesterday, or of ages +long gone by; every kind of cell, whether glandular, muscular, nervous, +epidermic, or skeletal, is adapted to absolutely definite and specific +functions, and every organ which is composed of these different kinds +of cells contains them in the proper proportions, and in the particular +arrangement which best serves the function of the organ; it is thus +adapted to its function. + +All parts of the organism are tuned to one another, that is, THEY ARE +ADAPTED TO ONE ANOTHER, and in the same way THE ORGANISM AS A WHOLE IS +ADAPTED TO THE CONDITIONS OF ITS LIFE, AND IT IS SO AT EVERY STAGE OF +ITS EVOLUTION. + +But all adaptations CAN be referred to selection; the only point that +remains doubtful is whether they all MUST be referred to it. + +However that may be, whether the LAMARCKIAN PRINCIPLE is a factor that +has cooperated with selection in evolution, or whether it is altogether +fallacious, the fact remains, that selection is the cause of a great +part of the phyletic evolution of organisms on our earth. Those +who agree with me in rejecting the LAMARCKIAN PRINCIPLE will regard +selection as the only GUIDING factor in evolution, which creates what +is new out of the transmissible variations, by ordering and arranging +these, selecting them in relation to their number and size, as the +architect does his building-stones so that a particular style must +result. ("Variation under Domestication", 1875 II. pages 426, 427.) But +the building-stones themselves, the variations, have their basis in the +influences which cause variation in those vital units which are handed +on from one generation to another, whether, taken together they form the +WHOLE organism, as in Bacteria and other low forms of life, or only +a germ-substance, as in unicellular and multicellular organisms. (The +Author and Editor are indebted to Professor Poulton for kindly assisting +in the revision of the proof of this Essay.) + + + + +IV. VARIATION. By HUGO DE VRIES. + +Professor of Botany in the University of Amsterdam. + + +I. DIFFERENT KINDS OF VARIABILITY. + +Before Darwin, little was known concerning the phenomena of variability. +The fact, that hardly two leaves on a tree were exactly the same, could +not escape observation: small deviations of the same kind were met with +everywhere, among individuals as well as among the organs of the same +plant. Larger aberrations, spoken of as monstrosities, were for a +long time regarded as lying outside the range of ordinary phenomena. A +special branch of inquiry, that of Teratology, was devoted to them, but +it constituted a science by itself, sometimes connected with morphology, +but having scarcely any bearing on the processes of evolution and +heredity. + +Darwin was the first to take a broad survey of the whole range of +variations in the animal and vegetable kingdoms. His theory of Natural +Selection is based on the fact of variability. In order that this +foundation should be as strong as possible he collected all the facts, +scattered in the literature of his time, and tried to arrange them in a +scientific way. He succeeded in showing that variations may be grouped +along a line of almost continuous gradations, beginning with simple +differences in size and ending with monstrosities. He was struck by the +fact that, as a rule, the smaller the deviations, the more frequently +they appear, very abrupt breaks in characters being of rare occurrence. + +Among these numerous degrees of variability Darwin was always on the +look out for those which might, with the greatest probability, be +considered as affording material for natural selection to act upon in +the development of new species. Neither of the extremes complied with +his conceptions. He often pointed out, that there are a good many small +fluctuations, which in this respect must be absolutely useless. On the +other hand, he strongly combated the belief, that great changes would be +necessary to explain the origin of species. Some authors had propounded +the idea that highly adapted organs, e.g. the wings of a bird, could +not have been developed in any other way than by a comparatively sudden +modification of a well defined and important kind. Such a conception +would allow of great breaks or discontinuity in the evolution of highly +differentiated animals and plants, shortening the time for the evolution +of the whole organic kingdom and getting over numerous difficulties +inherent in the theory of slow and gradual progress. It would, moreover, +account for the genetic relation of the larger groups of both animals +and plants. It would, in a word, undoubtedly afford an easy means of +simplifying the problem of descent with modification. + +Darwin, however, considered such hypotheses as hardly belonging to the +domain of science; they belong, he said, to the realm of miracles. That +species have a capacity for change is admitted by all evolutionists; but +there is no need to invoke modifications other than those represented by +ordinary variability. It is well known that in artificial selection this +tendency to vary has given rise to numerous distinct races, and there is +no reason for denying that it can do the same in nature, by the aid of +natural selection. On both lines an advance may be expected with equal +probability. + +His main argument, however, is that the most striking and most highly +adapted modifications may be acquired by successive variations. Each +of these may be slight, and they may affect different organs, gradually +adapting them to the same purpose. The direction of the adaptations +will be determined by the needs in the struggle for life, and natural +selection will simply exclude all such changes as occur on opposite +or deviating lines. In this way, it is not variability itself which is +called upon to explain beautiful adaptations, but it is quite sufficient +to suppose that natural selection has operated during long periods in +the same way. Eventually, all the acquired characters, being transmitted +together, would appear to us, as if they had all been simultaneously +developed. + +Correlations must play a large part in such special evolutions: when +one part is modified, so will be other parts. The distribution of +nourishment will come in as one of the causes, the reactions of +different organs to the same external influences as another. But no +doubt the more effective cause is that of the internal correlations, +which, however, are still but dimly understood. Darwin repeatedly laid +great stress on this view, although a definite proof of its correctness +could not be given in his time. Such proof requires the direct +observation of a mutation, and it should be stated here that even +the first observations made in this direction have clearly confirmed +Darwin's ideas. The new evening primroses which have sprung in my garden +from the old form of Oenothera Lamarckiana, and which have evidently +been derived from it, in each case, by a single mutation, do not differ +from their parent species in one character only, but in almost all their +organs and qualities. Oenothera gigas, for example, has stouter stems +and denser foliage; the leaves are larger and broader; its thick +flower-buds produce gigantic flowers, but only small fruits with large +seeds. Correlative changes of this kind are seen in all my new forms, +and they lend support to the view that in the gradual development of +highly adapted structures, analogous correlations may have played a +large part. They easily explain large deviations from an original type, +without requiring the assumption of too many steps. + +Monstrosities, as their name implies, are widely different in character +from natural species; they cannot, therefore, be adduced as evidence in +the investigation of the origin of species. There is no doubt that they +may have much in common as regards their manner of origin, and that the +origin of species, once understood, may lead to a better understanding +of the monstrosities. But the reverse is not true, at least not as +regards the main lines of development. Here, it is clear, monstrosities +cannot have played a part of any significance. + +Reversions, or atavistic changes, would seem to give a better support +to the theory of descent through modifications. These have been of +paramount importance on many lines of evolution of the animal as well +as of the vegetable kingdom. It is often assumed that monocotyledons are +descended from some lower group of dicotyledons, probably allied to that +which includes the buttercup family. On this view the monocotyledons +must be assumed to have lost the cambium and all its influence on +secondary growth, the differentiation of the flower into calyx and +corolla, the second cotyledon or seed-leaf and several other characters. +Losses of characters such as these may have been the result of abrupt +changes, but this does not prove that the characters themselves have +been produced with equal suddenness. On the contrary, Darwin shows very +convincingly that a modification may well be developed by a series of +steps, and afterwards suddenly disappear. Many monstrosities, such as +those represented by twisted stems, furnish direct proofs in support of +this view, since they are produced by the loss of one character and this +loss implies secondary changes in a large number of other organs and +qualities. + +Darwin criticises in detail the hypothesis of great and abrupt changes +and comes to the conclusion that it does not give even a shadow of +an explanation of the origin of species. It is as improbable as it is +unnecessary. + +Sports and spontaneous variations must now be considered. It is well +known that they have produced a large number of fine horticultural +varieties. The cut-leaved maple and many other trees and shrubs with +split leaves are known to have been produced at a single step; this +is true in the case of the single-leaf strawberry plant and of the +laciniate variety of the greater celandine: many white flowers, white +or yellow berries and numerous other forms had a similar origin. But +changes such as these do not come under the head of adaptations, as they +consist for the most part in the loss of some quality or organ belonging +to the species from which they were derived. Darwin thinks it impossible +to attribute to this cause the innumerable structures, which are so well +adapted to the habits of life of each species. At the present time we +should say that such adaptations require progressive modifications, +which are additions to the stock of qualities already possessed by +the ancestors, and cannot, therefore, be explained on the ground of +a supposed analogy with sports, which are for the most part of a +retrogressive nature. + +Excluding all these more or less sudden changes, there remains a long +series of gradations of variability, but all of these are not assumed by +Darwin to be equally fit for the production of new species. In the +first place, he disregards all mere temporary variations, such as size, +albinism, etc.; further, he points out that very many species have +almost certainly been produced by steps, not greater, and probably not +very much smaller, than those separating closely related varieties. For +varieties are only small species. Next comes the question of polymorphic +species: their occurrence seems to have been a source of much doubt and +difficulty in Darwin's mind, although at present it forms one of +the main supports of the prevailing explanation of the origin of new +species. Darwin simply states that this kind of variability seems to +be of a peculiar nature; since polymorphic species are now in a stable +condition their occurrence gives no clue as to the mode of origin of +new species. Polymorphic species are the expression of the result +of previous variability acting on a large scale; but they now simply +consist of more or less numerous elementary species, which, as far as we +know, do not at present exhibit a larger degree of variability than any +other more uniform species. The vernal whitlow-grass (Draba verna) and +the wild pansy are the best known examples; both have spread over almost +the whole of Europe and are split up into hundreds of elementary +forms. These sub-species show no signs of any extraordinary degree +of variability, when cultivated under conditions necessary for the +exclusion of inter-crossing. Hooker has shown, in the case of some ferns +distributed over still wider areas, that the extinction of some of the +intermediate forms in such groups would suffice to justify the elevation +of the remaining types to the rank of distinct species. Polymorphic +species may now be regarded as the link which unites ordinary +variability with the historical production of species. But it does not +appear that they had this significance for Darwin; and, in fact, they +exhibit no phenomena which could explain the processes by which one +species has been derived from another. By thus narrowing the limits +of the species-producing variability Darwin was led to regard small +deviations as the source from which natural selection derives material +upon which to act. But even these are not all of the same type, and +Darwin was well aware of the fact. + +It should here be pointed out that in order to be selected, a change +must first have been produced. This proposition, which now seems +self-evident, has, however, been a source of much difference of opinion +among Darwin's followers. The opinion that natural selection produces +changes in useful directions has prevailed for a long time. In other +words, it was assumed that natural selection, by the simple means of +singling out, could induce small and useful changes to increase and +to reach any desired degree of deviation from the original type. In +my opinion this view was never actually held by Darwin. It is +in contradiction with the acknowledged aim of all his work,--the +explanation of the origin of species by means of natural forces and +phenomena only. Natural selection acts as a sieve; it does not single +out the best variations, but it simply destroys the larger number of +those which are, from some cause or another, unfit for their present +environment. In this way it keeps the strains up to the required +standard, and, in special circumstances, may even improve them. + +Returning to the variations which afford the material for the +sieving-action of natural selection, we may distinguish two main kinds. +It is true that the distinction between these was not clear at the time +of Darwin, and that he was unable to draw a sharp line between them. +Nevertheless, in many cases, he was able to separate them, and he often +discussed the question which of the two would be the real source of +the differentiation of species. Certain variations constantly occur, +especially such as are connected with size, weight, colour, etc. They +are usually too small for natural selection to act upon, having hardly +any influence in the struggle for life: others are more rare, occurring +only from time to time, perhaps once or twice in a century, perhaps even +only once in a thousand years. Moreover, these are of another type, not +simply affecting size, number or weight, but bringing about something +new, which may be useful or not. Whenever the variation is useful +natural selection will take hold of it and preserve it; in other cases +the variation may either persist or disappear. + +In his criticism of miscellaneous objections brought forward against the +theory of natural selection after the publication of the first edition +of "The Origin of Species", Darwin stated his view on this point very +clearly:--"The doctrine of natural selection or the survival of the +fittest, which implies that when variations or individual differences of +a beneficial nature happen to arise, these will be preserved." ("Origin +of Species" (6th edition), page 169, 1882.) In this sentence the words +"HAPPEN TO ARISE" appear to me of prominent significance. They are +evidently due to the same general conception which prevailed in Darwin's +Pangenesis hypothesis. (Cf. de Vries, "Intracellulare Pangenesis", page +73, Jena, 1889, and "Die Mutationstheorie", I. page 63. Leipzig, 1901.) + +A distinction is indicated between ordinary fluctuations which are +always present, and such variations as "happen to arise" from time to +time. ((I think it right to point out that the interpretation of this +passage from the "Origin" by Professor de Vries is not accepted as +correct either by Mr Francis Darwin or by myself. We do not believe that +Darwin intended to draw any distinction between TWO TYPES of variation; +the words "when variations or individual differences of a beneficial +nature happen to arise" are not in our opinion meant to imply a +distinction between ordinary fluctuations and variations which "happen +to arise," but we believe that "or" is here used in the sense of ALIAS. +With the permission of Professor de Vries, the following extract is +quoted from a letter in which he replied to the objection raised to his +reading of the passage in question: + +"As to your remarks on the passage on page 6, I agree that it is now +impossible to see clearly how far Darwin went in his distinction of the +different kinds of variability. Distinctions were only dimly guessed at +by him. But in our endeavour to arrive at a true conception of his view +I think that the chapter on Pangenesis should be our leading guide, +and that we should try to interpret the more difficult passages by that +chapter. A careful and often repeated study of the Pangenesis hypothesis +has convinced me that Darwin, when he wrote that chapter, was well aware +that ordinary variability has nothing to do with evolution, but that +other kinds of variation were necessary. In some chapters he comes +nearer to a clear distinction than in others. To my mind the expression +'happen to arise' is the sharpest indication of his inclining in this +direction. I am quite convinced that numerous expressions in his book +become much clearer when looked at in this way." + +The statement in this passage that "Darwin was well aware that ordinary +variability has nothing to do with evolution, but that other kinds +of variation were necessary" is contradicted by many passages in the +"Origin". A.C.S.)) The latter afford the material for natural selection +to act upon on the broad lines of organic development, but the first +do not. Fortuitous variations are the species-producing kind, which the +theory requires; continuous fluctuations constitute, in this respect, a +useless type. + +Of late, the study of variability has returned to the recognition of +this distinction. Darwin's variations, which from time to time happen +to arise, are MUTATIONS, the opposite type being commonly designed +fluctuations. A large mass of facts, collected during the last few +decades, has confirmed this view, which in Darwin's time could only be +expressed with much reserve, and everyone knows that Darwin was always +very careful in statements of this kind. + +From the same chapter I may here cite the following paragraph: "Thus +as I am inclined to believe, morphological differences,... such as +the arrangement of the leaves, the divisions of the flower or of the +ovarium, the position of the ovules, etc.--first appeared in many cases +as fluctuating variations, which sooner or later became constant through +the nature of the organism and of the surrounding conditions... but NOT +THROUGH NATURAL SELECTION (The italics are mine (H. de V.).); for as +these morphological characters do not affect the welfare of the species, +any slight deviation in them could not have been governed or accumulated +through this latter agency." ("Origin of Species" (6th edition), page +176.) We thus see that in Darwin's opinion, all small variations had +not the same importance. In favourable circumstances some could become +constant, but others could not. + +Since the appearance of the first edition of "The Origin of Species" +fluctuating variability has been thoroughly studied by Quetelet. He +discovered the law, which governs all phenomena of organic life falling +under this head. It is a very simple law, and states that individual +variations follow the laws of probability. He proved it, in the first +place, for the size of the human body, using the measurements published +for Belgian recruits; he then extended it to various other measurements +of parts of the body, and finally concluded that it must be of universal +validity for all organic beings. It must hold true for all characters in +man, physical as well as intellectual and moral qualities; it must hold +true for the plant kingdom as well as for the animal kingdom; in short, +it must include the whole living world. + +Quetelet's law may be most easily studied in those cases where the +variability relates to measure, number and weight, and a vast number of +facts have since confirmed its exactness and its validity for all kinds +of organisms, organs and qualities. But if we examine it more closely, +we find that it includes just those minute variations, which, as Darwin +repeatedly pointed out, have often no significance for the origin of +species. In the phenomena, described by Quetelet's law nothing "happens +to arise"; all is governed by the common law, which states that small +deviations from the mean type are frequent, but that larger aberrations +are rare, the rarer as they are larger. Any degree of variation will +be found to occur, if only the number of individuals studied is large +enough: it is even possible to calculate before hand, how many +specimens must be compared in order to find a previously fixed degree of +deviation. + +The variations, which from time to time happen to appear, are evidently +not governed by this law. They cannot, as yet, be produced at will: no +sowings of thousands or even of millions of plants will induce them, +although by such means the chance of their occurring will obviously +be increased. But they are known to occur, and to occur suddenly and +abruptly. They have been observed especially in horticulture, where they +are ranged in the large and ill-defined group called sports. Korschinsky +has collected all the evidence which horticultural literature affords +on this point. (S. Korschinsky, "Heterogenesis und Evolution", "Flora", +Vol. LXXXIX. pages 240-363, 1901.) Several cases of the first appearance +of a horticultural novelty have been recorded: this has always happened +in the same way; it appeared suddenly and unexpectedly without any +definite relation to previously existing variability. Dwarf types are +one of the commonest and most favourite varieties of flowering plants; +they are not originated by a repeated selection of the smallest +specimens, but appear at once, without intermediates and without any +previous indication. In many instances they are only about half the +height of the original type, thus constituting obvious novelties. So it +is in other cases described by Korschinsky: these sports or mutations +are now recognised to be the main source of varieties of horticultural +plants. + +As already stated, I do not pretend that the production of horticultural +novelties is the prototype of the origin of new species in nature. I +assume that they are, as a rule, derived from the parent species by the +loss of some organ or quality, whereas the main lines of the evolution +of the animal and vegetable kingdom are of course determined by +progressive changes. Darwin himself has often pointed out this +difference. But the saltatory origin of horticultural novelties is as +yet the simplest parallel for natural mutations, since it relates to +forms and phenomena, best known to the general student of evolution. + +The point which I wish to insist upon is this. The difference between +small and ever present fluctuations and rare and more sudden variations +was clear to Darwin, although the facts known at his time were too +meagre to enable a sharp line to be drawn between these two great +classes of variability. Since Darwin's time evidence, which proves +the correctness of his view, has accumulated with increasing rapidity. +Fluctuations constitute one type; they are never absent and follow the +law of chance, but they do not afford the material from which to build +new species. Mutations, on the other hand, only happen to occur from +time to time. They do not necessarily produce greater changes than +fluctuations, but such as may become, or rather are from their very +nature, constant. It is this constancy which is the mark of specific +characters, and on this basis every new specific character may be +assumed to have arisen by mutation. + +Some authors have tried to show that the theory of mutation is opposed +to Darwin's views. But this is erroneous. On the contrary, it is in +fullest harmony with the great principle laid down by Darwin. In order +to be acted upon by that complex of environmental forces, which Darwin +has called natural selection, the changes must obviously first be there. +The manner in which they are produced is of secondary importance and has +hardly any bearing on the theory of descent with modification. ("Life +and Letters" II. 125.) + +A critical survey of all the facts of variability of plants in nature as +well as under cultivation has led me to the conviction, that Darwin was +right in stating that those rare beneficial variations, which from time +to time happen to arise,--the now so-called mutations--are the real +source of progress in the whole realm of the organic world. + +II. EXTERNAL AND INTERNAL CAUSES OF VARIABILITY. + +All phenomena of animal and plant life are governed by two sets of +causes; one of these is external, the other internal. As a rule the +internal causes determine the nature of a phenomenon--what an organism +can do and what it cannot do. The external causes, on the other hand, +decide when a certain variation will occur, and to what extent its +features may be developed. + +As a very clear and wholly typical instance I cite the cocks-combs +(Celosia). This race is distinguished from allied forms by its faculty +of producing the well-known broad and much twisted combs. Every single +individual possesses this power, but all individuals do not exhibit +it in its most complete form. In some cases this faculty may not be +exhibited at the top of the main stem, although developed in lateral +branches: in others it begins too late for full development. Much +depends upon nourishment and cultivation, but almost always the +horticulturist has to single out the best individuals and to reject +those which do not come up to the standard. + +The internal causes are of a historical nature. The external ones may be +defined as nourishment and environment. In some cases nutrition is +the main factor, as, for instance, in fluctuating variability, but in +natural selection environment usually plays the larger part. + +The internal or historical causes are constant during the life-time of +a species, using the term species in its most limited sense, as +designating the so-called elementary species or the units out of which +the ordinary species are built up. These historical causes are simply +the specific characters, since in the origin of a species one or more of +these must have been changed, thus producing the characters of the new +type. These changes must, of course, also be due partly to internal and +partly to external causes. + +In contrast to these changes of the internal causes, the ordinary +variability which is exhibited during the life-time of a species +is called fluctuating variability. The name mutations or mutating +variability is then given to the changes in the specific characters. +It is desirable to consider these two main divisions of variability +separately. + +In the case of fluctuations the internal causes, as well as the external +ones, are often apparent. The specific characters may be designated as +the mean about which the observed forms vary. Almost every character may +be developed to a greater or a less degree, but the variations of the +single characters producing a small deviation from the mean are usually +the commonest. The limits of these fluctuations may be called wide or +narrow, according to the way we look at them, but in numerous cases the +extreme on the favoured side hardly surpasses double the value of that +on the other side. The degree of this development, for every individual +and for every organ, is dependent mainly on nutrition. Better +nourishment or an increased supply of food produces a higher +development; only it is not always easy to determine which direction +is the fuller and which is the poorer one. The differences among +individuals grown from different seeds are described as examples of +individual variability, but those which may be observed on the same +plant, or on cuttings, bulbs or roots derived from one individual +are referred to as cases of partial variability. Partial variability, +therefore, determines the differences among the flowers, fruits, leaves +or branches of one individual: in the main, it follows the same laws +as individual variability, but the position of a branch on a plant also +determines its strength, and the part it may take in the nourishment of +the whole. Composite flowers and umbels therefore have, as a rule, +fewer rays on weak branches than on the strong main ones. The number of +carpels in the fruits of poppies becomes very small on the weak lateral +branches, which are produced towards the autumn, as well as on crowded, +and therefore on weakened individuals. Double flowers follow the same +rule, and numerous other instances could easily be adduced. + +Mutating variability occurs along three main lines. Either a character +may disappear, or, as we now say, become latent; or a latent character +may reappear, reproducing thereby a character which was once prominent +in more or less remote ancestors. The third and most interesting case +is that of the production of quite new characters which never existed in +the ancestors. Upon this progressive mutability the main development of +the animal and vegetable kingdom evidently depends. In contrast to this, +the two other cases are called retrogressive and degressive mutability. +In nature retrogressive mutability plays a large part; in agriculture +and in horticulture it gives rise to numerous varieties, which have +in the past been preserved, either on account of their usefulness or +beauty, or simply as fancy-types. In fact the possession of numbers +of varieties may be considered as the main character of domesticated +animals and cultivated plants. + +In the case of retrogressive and degressive mutability the internal +cause is at once apparent, for it is this which causes the disappearance +or reappearance of some character. With progressive mutations the case +is not so simple, since the new character must first be produced and +then displayed. These two processes are theoretically different, but +they may occur together or after long intervals. The production of the +new character I call premutation, and the displaying mutation. Both of +course must have their external as well as their internal causes, as +I have repeatedly pointed out in my work on the Mutation Theory. ("Die +Mutationstheorie", 2 vols., Leipzig, 1901.) + +It is probable that nutrition plays as important a part among the +external causes of mutability as it does among those of fluctuating +variability. Observations in support of this view, however, are too +scanty to allow of a definite judgment. Darwin assumed an accumulative +influence of external causes in the case of the production of new +varieties or species. The accumulation might be limited to the life-time +of a single individual, or embrace that of two or more generations. +In the end a degree of instability in the equilibrium of one or more +characters might be attained, great enough for a character to give +way under a small shock produced by changed conditions of life. The +character would then be thrown over from the old state of equilibrium +into a new one. + +Characters which happen to be in this state of unstable equilibrium are +called mutable. They may be either latent or active, being in the +former case derived from old active ones or produced as new ones (by the +process, designated premutation). They may be inherited in this mutable +condition during a long series of generations. I have shown that in the +case of the evening primrose of Lamarck this state of mutability +must have existed for at least half a century, for this species was +introduced from Texas into England about the year 1860, and since then +all the strains derived from its first distribution over the several +countries of Europe show the same phenomena in producing new forms. +The production of the dwarf evening primrose, or Oenothera nanella, +is assumed to be due to one of the factors, which determines the tall +stature of the parent form, becoming latent; this would, therefore, +afford an example of retrogressive mutation. Most of the other types +of my new mutants, on the other hand, seem to be due to progressive +mutability. + +The external causes of this curious period of mutability are as yet +wholly unknown and can hardly be guessed at, since the origin of the +Oenothera Lamarckiana is veiled in mystery. The seeds, introduced into +England about 1860, were said to have come from Texas, but whether from +wild or from cultivated plants we do not know. Nor has the species been +recorded as having been observed in the wild condition. This, however, +is nothing peculiar. The European types of Oenothera biennis and O. +muricata are in the same condition. The first is said to have been +introduced from Virginia, and the second from Canada, but both probably +from plants cultivated in the gardens of these countries. Whether the +same elementary species are still growing on those spots is unknown, +mainly because the different sub-species of the species mentioned have +not been systematically studied and distinguished. + +The origin of new species, which is in part the effect of mutability, +is, however, due mainly to natural selection. Mutability provides the +new characters and new elementary species. Natural selection, on the +other hand, decides what is to live and what to die. Mutability seems to +be free, and not restricted to previously determined lines. Selection, +however, may take place along the same main lines in the course of long +geological epochs, thus directing the development of large branches of +the animal and vegetable kingdom. In natural selection it is evident +that nutrition and environment are the main factors. But it is probable +that, while nutrition may be one of the main causes of mutability, +environment may play the chief part in the decisions ascribed to natural +selection. Relations to neighbouring plants and to injurious or useful +animals, have been considered the most important determining factors +ever since the time when Darwin pointed out their prevailing influence. + +From this discussion of the main causes of variability we may derive the +proposition that the study of every phenomenon in the field of heredity, +of variability, and of the origin of new species will have to be +considered from two standpoints; on one hand we have the internal +causes, on the other the external ones. Sometimes the first are more +easily detected, in other cases the latter are more accessible to +investigation. But the complete elucidation of any phenomenon of life +must always combine the study of the influence of internal with that of +external causes. + +III. POLYMORPHIC VARIABILITY IN CEREALS. + +One of the propositions of Darwin's theory of the struggle for life +maintains that the largest amount of life can be supported on any area, +by great diversification or divergence in the structure and constitution +of its inhabitants. Every meadow and every forest affords a proof of +this thesis. The numerical proportion of the different species of the +flora is always changing according to external influences. Thus, in a +given meadow, some species will flower abundantly in one year and then +almost disappear, until, after a series of years, circumstances allow +them again to multiply rapidly. Other species, which have taken their +places, will then become rare. It follows from this principle, that +notwithstanding the constantly changing conditions, a suitable +selection from the constituents of a meadow will ensure a continued +high production. But, although the principle is quite clear, artificial +selection has, as yet, done very little towards reaching a really high +standard. + +The same holds good for cereals. In ordinary circumstances a field +will give a greater yield, if the crop grown consists of a number of +sufficiently differing types. Hence it happens that almost all older +varieties of wheat are mixtures of more or less diverging forms. In the +same variety the numerical composition will vary from year to year, and +in oats this may, in bad years, go so far as to destroy more than half +of the harvest, the wind-oats (Avena fatua), which scatter their grain +to the winds as soon as it ripens, increasing so rapidly that they +assume the dominant place. A severe winter, a cold spring and other +extreme conditions of life will destroy one form more completely +than another, and it is evident that great changes in the numerical +composition of the mixture may thus be brought about. + +This mixed condition of the common varieties of cereals was well known +to Darwin. For him it constituted one of the many types of variability. +It is of that peculiar nature to which, in describing other groups, +he applies the term polymorphy. It does not imply that the single +constituents of the varieties are at present really changing their +characters. On the other hand, it does not exclude the possibility of +such changes. It simply states that observation shows the existence of +different forms; how these have originated is a question which it +does not deal with. In his well-known discussion of the variability of +cereals, Darwin is mainly concerned with the question, whether under +cultivation they have undergone great changes or only small ones. +The decision ultimately depends on the question, how many forms have +originally been taken into cultivation. Assuming five or six initial +species, the variability must be assumed to have been very large, but +on the assumption that there were between ten and fifteen types, the +necessary range of variability is obviously much smaller. But in regard +to this point, we are of course entirely without historical data. + +Few of the varieties of wheat show conspicuous differences, although +their number is great. If we compare the differentiating characters of +the smaller types of cereals with those of ordinary wild species, even +within the same genus or family, they are obviously much less marked. +All these small characters, however, are strictly inherited, and this +fact makes it very probable that the less obvious constituents of the +mixtures in ordinary fields must be constant and pure as long as they do +not intercross. Natural crossing is in most cereals a phenomenon of rare +occurrence, common enough to admit of the production of all possible +hybrid combinations, but requiring the lapse of a long series of years +to reach its full effect. + +Darwin laid great stress on this high amount of variability in the +plants of the same variety, and illustrated it by the experience of +Colonel Le Couteur ("On the Varieties, Properties, and Classification of +Wheat", Jersey, 1837.) on his farm on the isle of Jersey, who cultivated +upwards of 150 varieties of wheat, which he claimed were as pure as +those of any other agriculturalist. But Professor La Gasca of Madrid, +who visited him, drew attention to aberrant ears, and pointed out, that +some of them might be better yielders than the majority of plants in the +crop, whilst others might be poor types. Thence he concluded that the +isolation of the better ones might be a means of increasing his crops. +Le Couteur seems to have considered the constancy of such smaller types +after isolation as absolutely probable, since he did not even discuss +the possibility of their being variable or of their yielding a +changeable or mixed progeny. This curious fact proves that he considered +the types, discovered in his fields by La Gasca to be of the same kind +as his other varieties, which until that time he had relied upon as +being pure and uniform. Thus we see, that for him, the variability of +cereals was what we now call polymorphy. He looked through his fields +for useful aberrations, and collected twenty-three new types of wheat. +He was, moreover, clear about one point, which, on being rediscovered +after half a century, has become the starting-point for the new Swedish +principle of selecting agricultural plants. It was the principle of +single-ear sowing, instead of mixing the grains of all the selected ears +together. By sowing each ear on a separate plot he intended not only +to multiply them, but also to compare their value. This comparison +ultimately led him to the choice of some few valuable sorts, one of +which, the "Bellevue de Talavera," still holds its place among the +prominent sorts of wheat cultivated in France. This variety seems to be +really a uniform type, a quality very useful under favourable conditions +of cultivation, but which seems to have destroyed its capacity for +further improvement by selection. + +The principle of single-ear sowing, with a view to obtain pure and +uniform strains without further selection, has, until a few years ago, +been almost entirely lost sight of. Only a very few agriculturists have +applied it: among these are Patrick Shirreff ("Die Verbesserung der +Getreide-Arten", translated by R. Hesse, Halle, 1880.) in Scotland +and Willet M. Hays ("Wheat, varieties, breeding, cultivation", Univ. +Minnesota, Agricultural Experimental Station, Bull. no. 62, 1899.) in +Minnesota. Patrick Shirreff observed the fact, that in large fields of +cereals, single plants may from time to time be found with larger ears, +which justify the expectation of a far greater yield. In the course of +about twenty-five years he isolated in this way two varieties of wheat +and two of oats. He simply multiplied them as fast as possible, without +any selection, and put them on the market. + +Hays was struck by the fact that the yield of wheat in Minnesota was far +beneath that in the neighbouring States. The local varieties were Fife +and Blue Stem. They gave him, on inspection, some better specimens, +"phenomenal yielders" as he called them. These were simply isolated and +propagated, and, after comparison with the parent-variety and with some +other selected strains of less value, were judged to be of sufficient +importance to be tested by cultivation all over the State of Minnesota. +They have since almost supplanted the original types, at least in most +parts of the State, with the result that the total yield of wheat in +Minnesota is said to have been increased by about a million dollars +yearly. + +Definite progress in the method of single-ear sowing has, however, been +made only recently. It had been foreshadowed by Patrick Shirreff, who +after the production of the four varieties already mentioned, tried +to carry out his work on a larger scale, by including numerous minor +deviations from the main type. He found by doing so that the chances +of obtaining a better form were sufficiently increased to justify +the trial. But it was Nilsson who discovered the almost inexhaustible +polymorphy of cereals and other agricultural crops and made it the +starting-point for a new and entirely trustworthy method of the highest +utility. By this means he has produced during the last fifteen years a +number of new and valuable races, which have already supplanted the old +types on numerous farms in Sweden and which are now being introduced on +a large scale into Germany and other European countries. + +It is now twenty years since the station at Svalof was founded. During +the first period of its work, embracing about five years, selection was +practised on the principle which was then generally used in Germany. In +order to improve a race a sample of the best ears was carefully selected +from the best fields of the variety. These ears were considered as +representatives of the type under cultivation, and it was assumed that +by sowing their grains on a small plot a family could be obtained, which +could afterwards be improved by a continuous selection. Differences +between the collected ears were either not observed or disregarded. At +Svalof this method of selection was practised on a far larger scale than +on any German farm, and the result was, broadly speaking, the same. +This may be stated in the following words: improvement in a few cases, +failure in all the others. Some few varieties could be improved and +yielded excellent new types, some of which have since been introduced +into Swedish agriculture and are now prominent races in the southern +and middle parts of the country. But the station had definite aims, and +among them was the improvement of the Chevalier barley. This, in +Middle Sweden, is a fine brewer's barley, but liable to failure during +unfavourable summers on account of its slender stems. It was selected +with a view of giving it stiffer stems, but in spite of all the care and +work bestowed upon it no satisfactory result was obtained. + +This experience, combined with a number of analogous failures, could +not fail to throw doubt upon the whole method. It was evident that good +results were only exceptions, and that in most cases the principle +was not one that could be relied upon. The exceptions might be due +to unknown causes, and not to the validity of the method; it became +therefore of much more interest to search for the causes than to +continue the work along these lines. + +In the year 1892 a number of different varieties of cereals were +cultivated on a large scale and a selection was again made from +them. About two hundred samples of ears were chosen, each apparently +constituting a different type. Their seeds were sown on separate plots +and manured and treated as much as possible in the same manner. The +plots were small and arranged in rows so as to facilitate the comparison +of allied types. During the whole period of growth and during the +ripening of the ears the plots were carefully studied and compared: they +were harvested separately; ears and kernels were counted and weighed, +and notes were made concerning layering, rust and other cereal pests. + +The result of this experiment was, in the main, no distinct improvement. +Nilsson was especially struck by the fact that the plots, which should +represent distinct types, were far from uniform. Many of them were as +multiform as the fields from which the parent-ears were taken. Others +showed variability in a less degree, but in almost all of them it was +clear that a pure race had not been obtained. The experiment was a fair +one, inasmuch as it demonstrated the polymorphic variability of cereals +beyond all doubt and in a degree hitherto unsuspected; but from the +standpoint of the selectionist it was a failure. Fortunately there were, +however, one or two exceptions. A few lots showed a perfect uniformity +in regard to all the stalks and ears: these were small families. This +fact suggested the idea that each might have been derived from a single +ear. During the selection in the previous summer, Nilsson had tried to +find as many ears as possible of each new type which he recognised in +his fields. But the variability of his crops was so great, that he was +rarely able to include more than two or three ears in the same group, +and, in a few cases, he found only one representative of the supposed +type. It might, therefore, be possible that those small uniform plots +were the direct progeny of ears, the grains of which had not been mixed +with those from other ears before sowing. Exact records had, of course, +been kept of the chosen samples, and the number of ears had been noted +in each case. It was, therefore, possible to answer the question and it +was found that those plots alone were uniform on which the kernels of +one single ear only had been sown. Nilsson concluded that the mixture +of two or more ears in a single sowing might be the cause of the lack of +uniformity in the progeny. Apparently similar ears might be different in +their progeny. + +Once discovered, this fact was elevated to the rank of a leading +principle and tested on as large a scale as possible. The fields were +again carefully investigated and every single ear, which showed a +distinct divergence from the main type in one character or another, +was selected. A thousand samples were chosen, but this time each sample +consisted of one ear only. Next year, the result corresponded to the +expectation. Uniformity prevailed almost everywhere; only a few +lots showed a discrepancy, which might be ascribed to the accidental +selection of hybrid ears. It was now clear that the progeny of single +ears was, as a rule, pure, whereas that of mixed ears was impure. +The single-ear selection or single-ear sowing, which had fallen into +discredit in Germany and elsewhere in Europe, was rediscovered. It +proved to be the only trustworthy principle of selection. Once isolated, +such single-parent races are constant from seed and remain true to their +type. No further selection is needed; they have simply to be multiplied +and their real value tested. + +Patrick Shirreff, in his early experiments, Le Couteur, Hays and others +had observed the rare occurrence of exceptionally good yielders and the +value of their isolation to the agriculturist. The possibility of error +in the choice of such striking specimens and the necessity of judging +their value by their progeny were also known to these investigators, but +they had not the slightest idea of all the possibilities suggested by +their principle. Nilsson, who is a botanist as well as an agriculturist, +discovered that, besides these exceptionably good yielders, every +variety of a cereal consists of hundreds of different types, which find +the best conditions for success when grown together, but which, after +isolation, prove to be constant. Their preference for mixed growth is so +definite, that once isolated, their claims on manure and treatment +are found to be much higher than those of the original mixed variety. +Moreover, the greatest care is necessary to enable them to retain +their purity, and as soon as they are left to themselves they begin to +deteriorate through accidental crosses and admixtures and rapidly return +to the mixed condition. + +Reverting now to Darwin's discussion of the variability of cereals, we +may conclude that subsequent investigation has proved it to be exactly +of the kind which he describes. The only difference is that in reality +it reaches a degree, quite unexpected by Darwin and his contemporaries. +But it is polymorphic variability in the strictest sense of the word. +How the single constituents of a variety originate we do not see. We +may assume, and there can hardly be a doubt about the truth of the +assumption, that a new character, once produced, will slowly but surely +be combined through accidental crosses with a large number of +previously existing types, and so will tend to double the number of the +constituents of the variety. But whether it first appears suddenly or +whether it is only slowly evolved we cannot determine. It would, of +course, be impossible to observe either process in such a mixture. Only +cultures of pure races, of single-parent races as we have called them, +can afford an opportunity for this kind of observation. In the fields of +Svalof new and unexpected qualities have recently been seen, from time +to time, to appear suddenly. These characters are as distinct as the +older ones and appear to be constant from the moment of their origin. + +Darwin has repeatedly insisted that man does not cause variability. He +simply selects the variations given to him by the hand of nature. He may +repeat this process in order to accumulate different new characters +in the same family, thus producing varieties of a higher order. This +process of accumulation would, if continued for a longer time, lead to +the augmentation of the slight differences characteristic of varieties +into the greater differences characteristic of species and genera. It is +in this way that horticultural and agricultural experience contribute +to the problem of the conversion of varieties into species, and to the +explanation of the admirable adaptations of each organism to its complex +conditions of life. In the long run new forms, distinguished from their +allies by quite a number of new characters, would, by the extermination +of the older intermediates, become distinct species. + +Thus we see that the theory of the origin of species by means of natural +selection is quite independent of the question, how the variations to +be selected arise. They may arise slowly, from simple fluctuations, or +suddenly, by mutations; in both cases natural selection will take hold +of them, will multiply them if they are beneficial, and in the course of +time accumulate them, so as to produce that great diversity of organic +life, which we so highly admire. + +Darwin has left the decision of this difficult and obviously subordinate +point to his followers. But in his Pangenesis hypothesis he has given us +the clue for a close study and ultimate elucidation of the subject under +discussion. + + + + +V. HEREDITY AND VARIATION IN MODERN LIGHTS. By W. Bateson, M.A., F.R.S. + +Professor of Biology in the University of Cambridge. + + +Darwin's work has the property of greatness in that it may be admired +from more aspects than one. For some the perception of the principle of +Natural Selection stands out as his most wonderful achievement to which +all the rest is subordinate. Others, among whom I would range myself, +look up to him rather as the first who plainly distinguished, collected, +and comprehensively studied that new class of evidence from which +hereafter a true understanding of the process of Evolution may be +developed. We each prefer our own standpoint of admiration; but I think +that it will be in their wider aspect that his labours will most command +the veneration of posterity. + +A treatise written to advance knowledge may be read in two moods. The +reader may keep his mind passive, willing merely to receive the impress +of the writer's thought; or he may read with his attention strained and +alert, asking at every instant how the new knowledge can be used in a +further advance, watching continually for fresh footholds by which to +climb higher still. Of Shelley it has been said that he was a poet +for poets: so Darwin was a naturalist for naturalists. It is when his +writings are used in the critical and more exacting spirit with which +we test the outfit for our own enterprise that we learn their full value +and strength. Whether we glance back and compare his performance with +the efforts of his predecessors, or look forward along the course which +modern research is disclosing, we shall honour most in him not the +rounded merit of finite accomplishment, but the creative power by which +he inaugurated a line of discovery endless in variety and extension. +Let us attempt thus to see his work in true perspective between the past +from which it grew, and the present which is its consequence. Darwin +attacked the problem of Evolution by reference to facts of three +classes: Variation; Heredity; Natural Selection. His work was not as the +laity suppose, a sudden and unheralded revelation, but the first fruit +of a long and hitherto barren controversy. The occurrence of variation +from type, and the hereditary transmission of such variation had of +course been long familiar to practical men, and inferences as to the +possible bearing of those phenomena on the nature of specific difference +had been from time to time drawn by naturalists. Maupertuis, for +example, wrote "Ce qui nous reste a examiner, c'est comment d'un seul +individu, il a pu naitre tant d'especes si differentes." And again "La +Nature contient le fonds de toutes ces varietes: mais le hasard ou l'art +les mettent en oeuvre. C'est ainsi que ceux dont l'industrie s'applique +a satisfaire le gout des curieux, sont, pour ainsi dire, creatures +d'especes nouvelles." ("Venus Physique, contenant deux Dissertations, +l'une sur l'origine des Hommes et des Animaux: Et l'autre sur l'origine +des Noirs" La Haye, 1746, pages 124 and 129. For an introduction to the +writings of Maupertuis I am indebted to an article by Professor Lovejoy +in "Popular Sci. Monthly", 1902.) + +Such passages, of which many (though few so emphatic) can be found in +eighteenth century writers, indicate a true perception of the mode of +Evolution. The speculations hinted at by Buffon (For the fullest account +of the views of these pioneers of Evolution, see the works of Samuel +Butler, especially "Evolution, Old and New" (2nd edition) 1882. Butler's +claims on behalf of Buffon have met with some acceptance; but after +reading what Butler has said, and a considerable part of Buffon's own +works, the word "hinted" seems to me a sufficiently correct description +of the part he played. It is interesting to note that in the chapter on +the Ass, which contains some of his evolutionary passages, there is a +reference to "plusieurs idees tres-elevees sur la generation" contained +in the Letters of Maupertuis.), developed by Erasmus Darwin, and +independently proclaimed above all by Lamarck, gave to the doctrine of +descent a wide renown. The uniformitarian teaching which Lyell deduced +from geological observation had gained acceptance. The facts of +geographical distribution (See especially W. Lawrence, "Lectures on +Physiology", London, 1823, pages 213 f.) had been shown to be obviously +inconsistent with the Mosaic legend. Prichard, and Lawrence, following +the example of Blumenbach, had successfully demonstrated that the races +of Man could be regarded as different forms of one species, contrary +to the opinion up till then received. These treatises all begin, it is +true, with a profound obeisance to the sons of Noah, but that performed, +they continue on strictly modern lines. The question of the mutability +of species was thus prominently raised. + +Those who rate Lamarck no higher than did Huxley in his contemptuous +phrase "buccinator tantum," will scarcely deny that the sound of the +trumpet had carried far, or that its note was clear. If then there were +few who had already turned to evolution with positive conviction, +all scientific men must at least have known that such views had been +promulgated; and many must, as Huxley says, have taken up his own +position of "critical expectancy." (See the chapter contributed to the +"Life and Letters of Charles Darwin" II. page 195. I do not clearly +understand the sense in which Darwin wrote (Autobiography, ibid. I. page +87): "It has sometimes been said that the success of the "Origin" proved +'that the subject was in the air,' or 'that men's minds were prepared +for it.' I do not think that this is strictly true, for I occasionally +sounded not a few naturalists, and never happened to come across a +single one who seemed to doubt about the permanence of species." This +experience may perhaps have been an accident due to Darwin's isolation. +The literature of the period abounds with indications of "critical +expectancy." A most interesting expression of that feeling is given in +the charming account of the "Early Days of Darwinism" by Alfred Newton, +"Macmillan's Magazine", LVII. 1888, page 241. He tells how in 1858 +when spending a dreary summer in Iceland, he and his friend, the +ornithologist John Wolley, in default of active occupation, spent +their days in discussion. "Both of us taking a keen interest in Natural +History, it was but reasonable that a question, which in those days +was always coming up wherever two or more naturalists were gathered +together, should be continually recurring. That question was, 'What is +a species?' and connected therewith was the other question, 'How did a +species begin?'... Now we were of course fairly well acquainted with what +had been published on these subjects." He then enumerates some of these +publications, mentioning among others T. Vernon Wollaston's "Variation +of Species"--a work which has in my opinion never been adequately +appreciated. He proceeds: "Of course we never arrived at anything like +a solution of these problems, general or special, but we felt very +strongly that a solution ought to be found, and that quickly, if the +study of Botany and Zoology was to make any great advance." He then +describes how on his return home he received the famous number of the +"Linnean Journal" on a certain evening. "I sat up late that night to +read it; and never shall I forget the impression it made upon me. Herein +was contained a perfectly simple solution of all the difficulties which +had been troubling me for months past... I went to bed satisfied that a +solution had been found.") + +Why, then, was it, that Darwin succeeded where the rest had failed? +The cause of that success was two-fold. First, and obviously, in the +principle of Natural Selection he had a suggestion which would work. It +might not go the whole way, but it was true as far as it went. Evolution +could thus in great measure be fairly represented as a consequence of +demonstrable processes. Darwin seldom endangers the mechanism he devised +by putting on it strains much greater than it can bear. He at least was +under no illusion as to the omnipotence of Selection; and he introduces +none of the forced pleading which in recent years has threatened to +discredit that principle. + +For example, in the latest text of the "Origin" ("Origin", (6th edition +(1882), page 421.)) we find him saying: + +"But as my conclusions have lately been much misrepresented, and it has +been stated that I attribute the modification of species exclusively +to natural selection, I may be permitted to remark that in the first +edition of this work, and subsequently, I placed in a most conspicuous +position--namely, at the close of the Introduction--the following words: +'I am convinced that natural selection has been the main but not the +exclusive means of modification.'" + +But apart from the invention of this reasonable hypothesis, which may +well, as Huxley estimated, "be the guide of biological and psychological +speculation for the next three or four generations," Darwin made a more +significant and imperishable contribution. Not for a few generations, +but through all ages he should be remembered as the first who showed +clearly that the problems of Heredity and Variation are soluble by +observation, and laid down the course by which we must proceed to +their solution. (Whatever be our estimate of the importance of Natural +Selection, in this we all agree. Samuel Butler, the most brilliant, and +by far the most interesting of Darwin's opponents--whose works are at +length emerging from oblivion--in his Preface (1882) to the 2nd edition +of "Evolution, Old and New", repeats his earlier expression of homage to +one whom he had come to regard as an enemy: "To the end of time, if +the question be asked, 'Who taught people to believe in Evolution?' the +answer must be that it was Mr. Darwin. This is true, and it is hard to +see what palm of higher praise can be awarded to any philosopher.") The +moment of inspiration did not come with the reading of Malthus, but with +the opening of the "first note-book on Transmutation of Species." ("Life +and Letters", I. pages 276 and 83.) Evolution is a process of Variation +and Heredity. The older writers, though they had some vague idea that +it must be so, did not study Variation and Heredity. Darwin did, and so +begat not a theory, but a science. + +The extent to which this is true, the scientific world is only beginning +to realise. So little was the fact appreciated in Darwin's own time that +the success of his writings was followed by an almost total cessation of +work in that special field. Of the causes which led to this remarkable +consequence I have spoken elsewhere. They proceeded from circumstances +peculiar to the time; but whatever the causes there is no doubt that +this statement of the result is historically exact, and those who +make it their business to collect facts elucidating the physiology of +Heredity and Variation are well aware that they will find little to +reward their quest in the leading scientific Journals of the Darwinian +epoch. + +In those thirty years the original stock of evidence current and in +circulation even underwent a process of attrition. As in the story of +the Eastern sage who first wrote the collected learning of the universe +for his sons in a thousand volumes, and by successive compression and +burning reduced them to one, and from this by further burning distilled +the single ejaculation of the Faith, "There is no god but God and +Mohamed is the Prophet of God," which was all his maturer wisdom deemed +essential:--so in the books of that period do we find the corpus of +genetic knowledge dwindle to a few prerogative instances, and these at +last to the brief formula of an unquestioned creed. + +And yet in all else that concerns biological science this period was, +in very truth, our Golden Age, when the natural history of the earth was +explored as never before; morphology and embryology were exhaustively +ransacked; the physiology of plants and animals began to rival chemistry +and physics in precision of method and in the rapidity of its advances; +and the foundations of pathology were laid. + +In contrast with this immense activity elsewhere the neglect which befel +the special physiology of Descent, or Genetics as we now call it, is +astonishing. This may of course be interpreted as meaning that the +favoured studies seemed to promise a quicker return for effort, but it +would be more true to say that those who chose these other pursuits did +so without making any such comparison; for the idea that the physiology +of Heredity and Variation was a coherent science, offering possibilities +of extraordinary discovery, was not present to their minds at all. In +a word, the existence of such a science was well nigh forgotten. It is +true that in ancillary periodicals, as for example those that treat of +entomology or horticulture, or in the writings of the already isolated +systematists (This isolation of the systematists is the one most +melancholy sequela of Darwinism. It seems an irony that we should +read in the peroration to the "Origin" that when the Darwinian view +is accepted "Systematists will be able to pursue their labours as at +present; but they will not be incessantly haunted by the shadowy doubt +whether this or that form be a true species. This, I feel sure, and I +speak after experience, will be no slight relief. The endless disputes +whether or not some fifty species of British brambles are good species +will cease." "Origin", 6th edition (1882), page 425. True they have +ceased to attract the attention of those who lead opinion, but anyone +who will turn to the literature of systematics will find that they have +not ceased in any other sense. Should there not be something disquieting +in the fact that among the workers who come most into contact with +specific differences, are to be found the only men who have failed to +be persuaded of the unreality of those differences?), observations with +this special bearing were from time to time related, but the class of +fact on which Darwin built his conceptions of Heredity and Variation was +not seen in the highways of biology. It formed no part of the official +curriculum of biological students, and found no place among the subjects +which their teachers were investigating. + +During this period nevertheless one distinct advance was made, that +with which Weismann's name is prominently connected. In Darwin's genetic +scheme the hereditary transmission of parental experience and its +consequences played a considerable role. Exactly how great that role was +supposed to be, he with his habitual caution refrained from specifying, +for the sufficient reason that he did not know. Nevertheless much of +the process of Evolution, especially that by which organs have become +degenerate and rudimentary, was certainly attributed by Darwin to +such inheritance, though since belief in the inheritance of acquired +characters fell into disrepute, the fact has been a good deal +overlooked. The "Origin" without "use and disuse" would be a materially +different book. A certain vacillation is discernible in Darwin's +utterances on this question, and the fact gave to the astute Butler +an opportunity for his most telling attack. The discussion which best +illustrates the genetic views of the period arose in regard to the +production of the rudimentary condition of the wings of many beetles +in the Madeira group of islands, and by comparing passages from the +"Origin" (6th edition pages 109 and 401. See Butler, "Essays on Life, +Art, and Science", page 265, reprinted 1908, and "Evolution, Old and +New", chapter XXII. (2nd edition), 1882.) Butler convicts Darwin +of saying first that this condition was in the main the result of +Selection, with disuse aiding, and in another place that the main cause +of degeneration was disuse, but that Selection had aided. To Darwin +however I think the point would have seemed one of dialectics merely. To +him the one paramount purpose was to show that somehow an Evolution +by means of Variation and Heredity might have brought about the facts +observed, and whether they had come to pass in the one way or the other +was a matter of subordinate concern. + + +To us moderns the question at issue has a diminished significance. For +over all such debates a change has been brought by Weismann's challenge +for evidence that use and disuse have any transmitted effects at all. +Hitherto the transmission of many acquired characteristics had seemed +to most naturalists so obvious as not to call for demonstration. (W. +Lawrence was one of the few who consistently maintained the contrary +opinion. Prichard, who previously had expressed himself in the same +sense, does not, I believe repeat these views in his later writings, and +there are signs that he came to believe in the transmission of acquired +habits. See Lawrence, "Lect. Physiol." 1823, pages 436-437, 447 +Prichard, Edin. Inaug. Disp. 1808 (not seen by me), quoted ibid. and +"Nat. Hist. Man", 1843, pages 34 f.) Weismann's demand for facts in +support of the main proposition revealed at once that none having real +cogency could be produced. The time-honoured examples were easily shown +to be capable of different explanations. A few certainly remain +which cannot be so summarily dismissed, but--though it is manifestly +impossible here to do justice to such a subject--I think no one will +dispute that these residual and doubtful phenomena, whatever be their +true nature, are not of a kind to help us much in the interpretation +of any of those complex cases of adaptation which on the hypothesis of +unguided Natural Selection are especially difficult to understand. Use +and disuse were invoked expressly to help us over these hard places; but +whatever changes can be induced in offspring by direct treatment of the +parents, they are not of a kind to encourage hope of real assistance +from that quarter. It is not to be denied that through the collapse of +this second line of argument the Selection hypothesis has had to take +an increased and perilous burden. Various ways of meeting the difficulty +have been proposed, but these mostly resolve themselves into improbable +attempts to expand or magnify the powers of Natural Selection. + +Weismann's interpellation, though negative in purpose, has had a lasting +and beneficial effect, for through his thorough demolition of the old +loose and distracting notions of inherited experience, the ground has +been cleared for the construction of a true knowledge of heredity based +on experimental fact. + +In another way he made a contribution of a more positive character, +for his elaborate speculations as to the genetic meaning of cytological +appearances have led to a minute investigation of the visible phenomena +occurring in those divisions by which germ-cells arise. Though the +particular views he advocated have very largely proved incompatible +with the observed facts of heredity, yet we must acknowledge that it was +chiefly through the stimulus of Weismann's ideas that those advances +in cytology were made; and though the doctrine of the continuity of +germ-plasm cannot be maintained in the form originally propounded, it is +in the main true and illuminating. (It is interesting to see how nearly +Butler was led by natural penetration, and from absolutely opposite +conclusions, back to this underlying truth: "So that each ovum when +impregnate should be considered not as descended from its ancestors, but +as being a continuation of the personality of every ovum in the chain +of its ancestry, which every ovum IT ACTUALLY IS quite as truly as the +octogenarian IS the same identity with the ovum from which he has been +developed. This process cannot stop short of the primordial cell, +which again will probably turn out to be but a brief resting-place. We +therefore prove each one of us to BE ACTUALLY the primordial cell which +never died nor dies, but has differentiated itself into the life of the +world, all living beings whatever, being one with it and members one of +another," "Life and Habit", 1878, page 86.) Nevertheless in the present +state of knowledge we are still as a rule quite unable to connect +cytological appearances with any genetic consequence and save in one +respect (obviously of extreme importance--to be spoken of later) the two +sets of phenomena might, for all we can see, be entirely distinct. + +I cannot avoid attaching importance to this want of connection between +the nuclear phenomena and the features of bodily organisation. All +attempts to investigate Heredity by cytological means lie under +the disadvantage that it is the nuclear changes which can alone be +effectively observed. Important as they must surely be, I have never +been persuaded that the rest of the cell counts for nothing. What we +know of the behaviour and variability of chromosomes seems in my opinion +quite incompatible with the belief that they alone govern form, and are +the sole agents responsible in heredity. (This view is no doubt contrary +to the received opinion. I am however interested to see it lately +maintained by Driesch ("Science and Philosophy of the Organism", London, +1907, page 233), and from the recent observations of Godlewski it has +received distinct experimental support.) + +If, then, progress was to be made in Genetics, work of a different kind +was required. To learn the laws of Heredity and Variation there is +no other way than that which Darwin himself followed, the direct +examination of the phenomena. A beginning could be made by collecting +fortuitous observations of this class, which have often thrown a +suggestive light, but such evidence can be at best but superficial and +some more penetrating instrument of research is required. This can only +be provided by actual experiments in breeding. + +The truth of these general considerations was becoming gradually clear +to many of us when in 1900 Mendel's work was rediscovered. Segregation, +a phenomenon of the utmost novelty, was thus revealed. From that moment +not only in the problem of the origin of species, but in all the great +problems of biology a new era began. So unexpected was the discovery +that many naturalists were convinced it was untrue, and at once +proclaimed Mendel's conclusions as either altogether mistaken, or if +true, of very limited application. Many fantastic notions about the +workings of Heredity had been asserted as general principles before: +this was probably only another fancy of the same class. + +Nevertheless those who had a preliminary acquaintance with the facts +of Variation were not wholly unprepared for some such revelation. The +essential deduction from the discovery of segregation was that the +characters of living things are dependent on the presence of definite +elements or factors, which are treated as units in the processes of +Heredity. These factors can thus be recombined in various ways. They act +sometimes separately, and sometimes they interact in conjunction with +each other, producing their various effects. All this indicates a +definiteness and specific order in heredity, and therefore in variation. +This order cannot by the nature of the case be dependent on Natural +Selection for its existence, but must be a consequence of the +fundamental chemical and physical nature of living things. The study of +Variation had from the first shown that an orderliness of this kind was +present. The bodies and the properties of living things are cosmic, +not chaotic. No matter how low in the scale we go, never do we find the +slightest hint of a diminution in that all-pervading orderliness, nor +can we conceive an organism existing for a moment in any other state. +Moreover not only does this order prevail in normal forms, but again +and again it is to be seen in newly-sprung varieties, which by general +consent cannot have been subjected to a prolonged Selection. The +discovery of Mendelian elements admirably coincided with and at once +gave a rationale of these facts. Genetic Variation is then primarily the +consequence of additions to, or omissions from, the stock of +elements which the species contains. The further investigation of +the species-problem must thus proceed by the analytical method which +breeding experiments provide. + +In the nine years which have elapsed since Mendel's clue became +generally known, progress has been rapid. We now understand the process +by which a polymorphic race maintains its polymorphism. When a family +consists of dissimilar members, given the numerical proportions in +which these members are occurring, we can represent their composition +symbolically and state what types can be transmitted by the various +members. The difficulty of the "swamping effects of intercrossing" is +practically at an end. Even the famous puzzle of sex-limited inheritance +is solved, at all events in its more regular manifestations, and we know +now how it is brought about that the normal sisters of a colour-blind +man can transmit the colour-blindness while his normal brothers cannot +transmit it. + +We are still only on the fringe of the inquiry. It can be seen extending +and ramifying in many directions. To enumerate these here would be +impossible. A whole new range of possibilities is being brought into +view by study of the interrelations between the simple factors. By +following up the evidence as to segregation, indications have been +obtained which can only be interpreted as meaning that when many factors +are being simultaneously redistributed among the germ-cells, certain of +them exert what must be described as a repulsion upon other factors. We +cannot surmise whither this discovery may lead. + +In the new light all the old problems wear a fresh aspect. Upon the +question of the nature of Sex, for example, the bearing of Mendelian +evidence is close. Elsewhere I have shown that from several sets of +parallel experiments the conclusion is almost forced upon us that, in +the types investigated, of the two sexes the female is to be regarded as +heterozygous in sex, containing one unpaired dominant element, while the +male is similarly homozygous in the absence of that element. (In other +words, the ova are each EITHER female, OR male (i.e. non-female), but +the sperms are all non-female.) It is not a little remarkable that on +this point--which is the only one where observations of the nuclear +processes of gameto-genesis have yet been brought into relation with +the visible characteristics of the organisms themselves--there should be +diametrical opposition between the results of breeding experiments and +those derived from cytology. + +Those who have followed the researches of the American school will +be aware that, after it had been found in certain insects that the +spermatozoa were of two kinds according as they contained or did not +contain the accessory chromosome, E.B. Wilson succeeded in proving that +the sperms possessing this accessory body were destined to form FEMALES +on fertilisation, while sperms without it form males, the eggs being +apparently indifferent. Perhaps the most striking of all this series +of observations is that lately made by T.H. Morgan (Morgan, "Proc. Soc. +Exp. Biol. Med." V. 1908, and von Baehr, "Zool. Anz." XXXII. page 507, +1908.), since confirmed by von Baehr, that in a Phylloxeran two kinds +of spermatids are formed, respectively with and without an accessory +(in this case, DOUBLE) chromosome. Of these, only those possessing the +accessory body become functional spermatozoa, the others degenerating. +We have thus an elucidation of the puzzling fact that in these forms +fertilisation results in the formation of FEMALES only. How the +males are formed--for of course males are eventually produced by the +parthenogenetic females--we do not know. + +If the accessory body is really to be regarded as bearing the factor +for femaleness, then in Mendelian terms female is DD and male is DR. The +eggs are indifferent and the spermatozoa are each male, OR female. +But according to the evidence derived from a study of the sex-limited +descent of certain features in other animals the conclusion seems +equally clear that in them female must be regarded as DR and male as +RR. The eggs are thus each either male or female and the spermatozoa are +indifferent. How this contradictory evidence is to be reconciled we +do not yet know. The breeding work concerns fowls, canaries, and the +Currant moth (Abraxas grossulariata). The accessory chromosome has been +now observed in most of the great divisions of insects (As Wilson has +proved, the unpaired body is not a universal feature even in those +orders in which it has been observed. Nearly allied types may differ. +In some it is altogether unpaired. In others it is paired with a body of +much smaller size, and by selection of various types all gradations can +be demonstrated ranging to the condition in which the members of the +pair are indistinguishable from each other.), except, as it happens, +Lepidoptera. At first sight it seems difficult to suppose that a feature +apparently so fundamental as sex should be differently constituted +in different animals, but that seems at present the least improbable +inference. I mention these two groups of facts as illustrating the +nature and methods of modern genetic work. We must proceed by minute and +specific analytical investigation. Wherever we look we find traces of +the operation of precise and specific rules. + +In the light of present knowledge it is evident that before we can +attack the Species-problem with any hope of success there are vast +arrears to be made up. He would be a bold man who would now assert that +there was no sense in which the term Species might not have a strict and +concrete meaning in contradistinction to the term Variety. We have been +taught to regard the difference between species and variety as one of +degree. I think it unlikely that this conclusion will bear the test of +further research. To Darwin the question, What is a variation? presented +no difficulties. Any difference between parent and offspring was a +variation. Now we have to be more precise. First we must, as de Vries +has shown, distinguish real, genetic, variation from FLUCTUATIONAL +variations, due to environmental and other accidents, which cannot +be transmitted. Having excluded these sources of error the variations +observed must be expressed in terms of the factors to which they are due +before their significance can be understood. For example, numbers of the +variations seen under domestication, and not a few witnessed in nature, +are simply the consequence of some ingredient being in an unknown way +omitted from the composition of the varying individual. The variation +may on the contrary be due to the addition of some new element, but to +prove that it is so is by no means an easy matter. Casual observation +is useless, for though these latter variations will always be dominants, +yet many dominant characteristics may arise from another cause, namely +the meeting of complementary factors, and special study of each case +in two generations at least is needed before these two phenomena can be +distinguished. + +When such considerations are fully appreciated it will be realised that +medleys of most dissimilar occurrences are all confused together under +the term Variation. One of the first objects of genetic analysis is to +disentangle this mass of confusion. + +To those who have made no study of heredity it sometimes appears that +the question of the effect of conditions in causing variation is one +which we should immediately investigate, but a little thought will +show that before any critical inquiry into such possibilities can be +attempted, a knowledge of the working of heredity under conditions as +far as possible uniform must be obtained. At the time when Darwin was +writing, if a plant brought into cultivation gave off an albino variety, +such an event was without hesitation ascribed to the change of life. Now +we see that albino GAMETES, germs, that is to say, which are destitute +of the pigment-forming factor, may have been originally produced by +individuals standing an indefinite number of generations back in the +ancestry of the actual albino, and it is indeed almost certain that the +variation to which the appearance of the albino is due cannot have taken +place in a generation later than that of the grandparents. It is true +that when a new DOMINANT appears we should feel greater confidence +that we were witnessing the original variation, but such events are +of extreme rarity, and no such case has come under the notice of an +experimenter in modern times, as far as I am aware. That they must have +appeared is clear enough. Nothing corresponding to the Brown-breasted +Game fowl is known wild, yet that colour is a most definite dominant, +and at some moment since Gallus bankiva was domesticated, the element on +which that special colour depends must have at least once been formed in +the germ-cell of a fowl; but we need harder evidence than any which has +yet been produced before we can declare that this novelty came through +over-feeding, or change of climate, or any other disturbance consequent +on domestication. When we reflect on the intricacies of genetic problems +as we must now conceive them there come moments when we feel almost +thankful that the Mendelian principles were unknown to Darwin. The time +called for a bold pronouncement, and he made it, to our lasting profit +and delight. With fuller knowledge we pass once more into a period of +cautious expectation and reserve. + +In every arduous enterprise it is pleasanter to look back at +difficulties overcome than forward to those which still seem +insurmountable, but in the next stage there is nothing to be gained by +disguising the fact that the attributes of living things are not what +we used to suppose. If they are more complex in the sense that the +properties they display are throughout so regular (I have in view, for +example, the marvellous and specific phenomena of regeneration, +and those discovered by the students of "Entwicklungsmechanik". The +circumstances of its occurrence here preclude any suggestion that this +regularity has been brought about by the workings of Selection. The +attempts thus to represent the phenomena have resulted in mere parodies +of scientific reasoning.) that the Selection of minute random variations +is an unacceptable account of the origin of their diversity, yet by +virtue of that very regularity the problem is limited in scope and thus +simplified. + +To begin with, we must relegate Selection to its proper place. Selection +permits the viable to continue and decides that the non-viable shall +perish; just as the temperature of our atmosphere decides that no liquid +carbon shall be found on the face of the earth: but we do not suppose +that the form of the diamond has been gradually achieved by a process of +Selection. So again, as the course of descent branches in the successive +generations, Selection determines along which branch Evolution shall +proceed, but it does not decide what novelties that branch shall bring +forth. "La Nature contient le fonds de toutes ces varietes, mais le +hazard ou l'art les mettent en oeuvre," as Maupertuis most truly said. + +Not till knowledge of the genetic properties of organisms has attained +to far greater completeness can evolutionary speculations have more than +a suggestive value. By genetic experiment, cytology and physiological +chemistry aiding, we may hope to acquire such knowledge. In 1872 +Nathusius wrote ("Vortrage uber Viehzucht und Rassenerkenntniss", page +120, Berlin, 1872.): "Das Gesetz der Vererbung ist noch nicht erkannt; +der Apfel ist noch nicht vom Baum der Erkenntniss gefallen, welcher, +der Sage nach, Newton auf den rechten Weg zur Ergrundung der +Gravitationsgesetze fuhrte." We cannot pretend that the words are not +still true, but in Mendelian analysis the seeds of that apple-tree at +last are sown. + +If we were asked what discovery would do most to forward our inquiry, +what one bit of knowledge would more than any other illuminate the +problem, I think we may give the answer without hesitation. The greatest +advance that we can foresee will be made when it is found possible to +connect the geometrical phenomena of development with the chemical. The +geometrical symmetry of living things is the key to a knowledge of +their regularity, and the forces which cause it. In the symmetry of +the dividing cell the basis of that resemblance we call Heredity is +contained. To imitate the morphological phenomena of life we have to +devise a system which can divide. It must be able to divide, and to +segment as--grossly--a vibrating plate or rod does, or as an icicle can +do as it becomes ribbed in a continuous stream of water; but with +this distinction, that the distribution of chemical differences and +properties must simultaneously be decided and disposed in orderly +relation to the pattern of the segmentation. Even if a model which would +do this could be constructed it might prove to be a useful beginning. + +This may be looking too far ahead. If we had to choose some one piece of +more proximate knowledge which we would more especially like to acquire, +I suppose we should ask for the secret of interracial sterility. Nothing +has yet been discovered to remove the grave difficulty, by which Huxley +in particular was so much oppressed, that among the many varieties +produced under domestication--which we all regard as analogous to the +species seen in nature--no clear case of interracial sterility has +been demonstrated. The phenomenon is probably the only one to which the +domesticated products seem to afford no parallel. No solution of the +difficulty can be offered which has positive value, but it is perhaps +worth considering the facts in the light of modern ideas. It should be +observed that we are not discussing incompatibility of two species to +produce offspring (a totally distinct phenomenon), but the sterility of +the offspring which many of them do produce. + +When two species, both perfectly fertile severally, produce on crossing +a sterile progeny, there is a presumption that the sterility is due to +the development in the hybrid of some substance which can only be formed +by the meeting of two complementary factors. That some such account is +correct in essence may be inferred from the well-known observation that +if the hybrid is not totally sterile but only partially so, and thus is +able to form some good germ-cells which develop into new individuals, +the sterility of these daughter-individuals is sensibly reduced or may +be entirely absent. The fertility once re-established, the sterility +does not return in the later progeny, a fact strongly suggestive of +segregation. Now if the sterility of the cross-bred be really the +consequence of the meeting of two complementary factors, we see that the +phenomenon could only be produced among the divergent offspring of +one species by the acquisition of at least TWO new factors; for if the +acquisition of a single factor caused sterility the line would then +end. Moreover each factor must be separately acquired by distinct +individuals, for if both were present together, the possessors would by +hypothesis be sterile. And in order to imitate the case of species each +of these factors must be acquired by distinct breeds. The factors need +not, and probably would not, produce any other perceptible effects; +they might, like the colour-factors present in white flowers, make +no difference in the form or other characters. Not till the cross was +actually made between the two complementary individuals would either +factor come into play, and the effects even then might be unobserved +until an attempt was made to breed from the cross-bred. + +Next, if the factors responsible for sterility were acquired, they would +in all probability be peculiar to certain individuals and would not +readily be distributed to the whole breed. Any member of the breed +also into which BOTH the factors were introduced would drop out of the +pedigree by virtue of its sterility. Hence the evidence that the various +domesticated breeds say of dogs or fowls can when mated together produce +fertile offspring, is beside the mark. The real question is, Do they +ever produce sterile offspring? I think the evidence is clearly that +sometimes they do, oftener perhaps than is commonly supposed. These +suggestions are quite amenable to experimental tests. The most obvious +way to begin is to get a pair of parents which are known to have had any +sterile offspring, and to find the proportions in which these steriles +were produced. If, as I anticipate, these proportions are found to be +definite, the rest is simple. + +In passing, certain other considerations may be referred to. First, that +there are observations favouring the view that the production of totally +sterile cross-breds is seldom a universal property of two species, and +that it may be a matter of individuals, which is just what on the view +here proposed would be expected. Moreover, as we all know now, though +incompatibility may be dependent to some extent on the degree to which +the species are dissimilar, no such principle can be demonstrated to +determine sterility or fertility in general. For example, though all our +Finches can breed together, the hybrids are all sterile. Of Ducks some +species can breed together without producing the slightest sterility; +others have totally sterile offspring, and so on. The hybrids between +several genera of Orchids are perfectly fertile on the female side, and +some on the male side also, but the hybrids produced between the Turnip +(Brassica napus) and the Swede (Brassica campestris), which, according +to our estimates of affinity should be nearly allied forms, are totally +sterile. (See Sutton, A.W., "Journ. Linn. Soc." XXXVIII. page 341, +1908.) Lastly, it may be recalled that in sterility we are almost +certainly considering a meristic phenomenon. FAILURE TO DIVIDE is, +we may feel fairly sure, the immediate "cause" of the sterility. Now, +though we know very little about the heredity of meristic differences, +all that we do know points to the conclusion that the less-divided is +dominant to the more-divided, and we are thus justified in supposing +that there are factors which can arrest or prevent cell-division. My +conjecture therefore is that in the case of sterility of cross-breds we +see the effect produced by a complementary pair of such factors. This +and many similar problems are now open to our analysis. + +The question is sometimes asked, Do the new lights on Variation and +Heredity make the process of Evolution easier to understand? On the +whole the answer may be given that they do. There is some appearance of +loss of simplicity, but the gain is real. As was said above, the time +is not ripe for the discussion of the origin of species. With faith in +Evolution unshaken--if indeed the word faith can be used in application +to that which is certain--we look on the manner and causation of adapted +differentiation as still wholly mysterious. As Samuel Butler so truly +said: "To me it seems that the 'Origin of Variation,' whatever it is, is +the only true 'Origin of Species'" ("Life and Habit", London, page +263, 1878.), and of that Origin not one of us knows anything. But given +Variation--and it is given: assuming further that the variations are not +guided into paths of adaptation--and both to the Darwinian and to +the modern school this hypothesis appears to be sound if unproven--an +evolution of species proceeding by definite steps is more, rather than +less, easy to imagine than an evolution proceeding by the accumulation +of indefinite and insensible steps. Those who have lost themselves in +contemplating the miracles of Adaptation (whether real or spurious) have +not unnaturally fixed their hopes rather on the indefinite than on the +definite changes. The reasons are obvious. By suggesting that the +steps through which an adaptative mechanism arose were indefinite and +insensible, all further trouble is spared. While it could be said that +species arise by an insensible and imperceptible process of variation, +there was clearly no use in tiring ourselves by trying to perceive that +process. This labour-saving counsel found great favour. All that had +to be done to develop evolution-theory was to discover the good in +everything, a task which, in the complete absence of any control or test +whereby to check the truth of the discovery, is not very onerous. The +doctrine "que tout est au mieux" was therefore preached with fresh +vigour, and examples of that illuminating principle were discovered with +a facility that Pangloss himself might have envied, till at last even +the spectators wearied of such dazzling performances. + +But in all seriousness, why should indefinite and unlimited variation +have been regarded as a more probable account of the origin of +Adaptation? Only, I think, because the obstacle was shifted one plane +back, and so looked rather less prominent. The abundance of Adaptation, +we all grant, is an immense, almost an unsurpassable difficulty in +all non-Lamarckian views of Evolution; but if the steps by which +that adaptation arose were fortuitous, to imagine them insensible is +assuredly no help. In one most important respect indeed, as has often +been observed, it is a multiplication of troubles. For the smaller +the steps, the less could Natural Selection act upon them. Definite +variations--and of the occurrence of definite variations in abundance we +have now the most convincing proof--have at least the obvious merit +that they can make and often do make a real difference in the chances of +life. + +There is another aspect of the Adaptation problem to which I can only +allude very briefly. May not our present ideas of the universality and +precision of Adaptation be greatly exaggerated? The fit of organism to +its environment is not after all so very close--a proposition unwelcome +perhaps, but one which could be illustrated by very copious evidence. +Natural Selection is stern, but she has her tolerant moods. + +We have now most certain and irrefragable proof that much definiteness +exists in living things apart from Selection, and also much that +may very well have been preserved and so in a sense constituted by +Selection. Here the matter is likely to rest. There is a passage in the +sixth edition of the "Origin" which has I think been overlooked. On page +70 Darwin says "The tuft of hair on the breast of the wild turkey-cock +cannot be of any use, and it is doubtful whether it can be ornamental in +the eyes of the female bird." This tuft of hair is a most definite and +unusual structure, and I am afraid that the remark that it "cannot be +of any use" may have been made inadvertently; but it may have been +intended, for in the first edition the usual qualification was given and +must therefore have been deliberately excised. Anyhow I should like to +think that Darwin did throw over that tuft of hair, and that he felt +relief when he had done so. Whether however we have his great authority +for such a course or not, I feel quite sure that we shall be rightly +interpreting the facts of nature if we cease to expect to find +purposefulness wherever we meet with definite structures or patterns. +Such things are, as often as not, I suspect rather of the nature of +tool-marks, mere incidents of manufacture, benefiting their possessor +not more than the wire-marks in a sheet of paper, or the ribbing on the +bottom of an oriental plate renders those objects more attractive in our +eyes. + +If Variation may be in any way definite, the question once more arises, +may it not be definite in direction? The belief that it is has had many +supporters, from Lamarck onwards, who held that it was guided by need, +and others who, like Nageli, while laying no emphasis on need, yet were +convinced that there was guidance of some kind. The latter view under +the name of "Orthogenesis," devised I believe by Eimer, at the present +day commends itself to some naturalists. The objection to such a +suggestion is of course that no fragment of real evidence can be +produced in its support. On the other hand, with the experimental proof +that variation consists largely in the unpacking and repacking of an +original complexity, it is not so certain as we might like to think +that the order of these events is not pre-determined. For instance +the original "pack" may have been made in such a way that at the nth +division of the germ-cells of a Sweet Pea a colour-factor might be +dropped, and that at the n plus n prime division the hooded variety be +given off, and so on. I see no ground whatever for holding such a view, +but in fairness the possibility should not be forgotten, and in the +light of modern research it scarcely looks so absurdly improbable as +before. + +No one can survey the work of recent years without perceiving that +evolutionary orthodoxy developed too fast, and that a great deal has +got to come down; but this satisfaction at least remains, that in the +experimental methods which Mendel inaugurated, we have means of reaching +certainty in regard to the physiology of Heredity and Variation upon +which a more lasting structure may be built. + + + + +VI. THE MINUTE STRUCTURE OF CELLS IN RELATION TO HEREDITY. By Eduard +Strasburger. + +Professor of Botany in the University of Bonn. + +Since 1875 an unexpected insight has been gained into the internal +structure of cells. Those who are familiar with the results of +investigations in this branch of Science are convinced that any modern +theory of heredity must rest on a basis of cytology and cannot be at +variance with cytological facts. Many histological discoveries, both +such as have been proved correct and others which may be accepted as +probably well founded, have acquired a fundamental importance from the +point of view of the problems of heredity. + +My aim is to describe the present position of our knowledge of Cytology. +The account must be confined to essentials and cannot deal with +far-reaching and controversial questions. In cases where difference of +opinion exists, I adopt my own view for which I hold myself responsible. +I hope to succeed in making myself intelligible even without the aid of +illustrations: in order to convey to the uninitiated an adequate idea +of the phenomena connected with the life of a cell, a greater number +of figures would be required than could be included within the scope of +this article. + +So long as the most eminent investigators (As for example the +illustrious Wilhelm Hofmeister in his "Lehre von der Pflanzenzelle" +(1867).) believed that the nucleus of a cell was destroyed in the course +of each division and that the nuclei of the daughter-cells were produced +de novo, theories of heredity were able to dispense with the nucleus. +If they sought, as did Charles Darwin, who showed a correct grasp of +the problem in the enunciation of his Pangenesis hypothesis, for +histological connecting links, their hypotheses, or at least the best of +them, had reference to the cell as a whole. It was known to Darwin +that the cell multiplied by division and was derived from a similar +pre-existing cell. Towards 1870 it was first demonstrated that +cell-nuclei do not arise de novo, but are invariably the result of +division of pre-existing nuclei. Better methods of investigation +rendered possible a deeper insight into the phenomena accompanying cell +and nuclear divisions and at the same time disclosed the existence of +remarkable structures. The work of O. Butschli, O. Hertwig, W. Flemming +H. Fol and of the author of this article (For further reference to +literature, see my article on "Die Ontogenie der Zelle seit 1875", +in the "Progressus Rei Botanicae", Vol. I. page 1, Jena, 1907.), have +furnished conclusive evidence in favour of these facts. It was found +that when the reticular framework of a nucleus prepares to divide, it +separates into single segments. These then become thicker and denser, +taking up with avidity certain stains, which are used as aids to +investigation, and finally form longer or shorter, variously bent, +rodlets of uniform thickness. In these organs which, on account of their +special property of absorbing certain stains, were styled Chromosomes +(By W. Waldeyer in 1888.), there may usually be recognised a separation +into thicker and thinner discs; the former are often termed Chromomeres. +(Discovered by W. Pfitzner in 1880.) In the course of division of the +nucleus, the single rows of chromomeres in the chromosomes are doubled +and this produces a band-like flattening and leads to the longitudinal +splitting by which each chromosome is divided into two exactly equal +halves. The nuclear membrane then disappears and fibrillar cell-plasma +or cytoplasm invades the nuclear area. In animal cells these fibrillae +in the cytoplasm centre on definite bodies (Their existence and their +multiplication by fission were demonstrated by E. van Beneden and Th. +Boveri in 1887.), which it is customary to speak of as Centrosomes. +Radiating lines in the adjacent cell-plasma suggest that these bodies +constitute centres of force. The cells of the higher plants do not +possess such individualised centres; they have probably disappeared in +the course of phylogenetic development: in spite of this, however, in +the nuclear division-figures the fibrillae of the cell-plasma are seen +to radiate from two opposite poles. In both animal and plant cells a +fibrillar bipolar spindle is formed, the fibrillae of which grasp the +longitudinally divided chromosomes from two opposite sides and arrange +them on the equatorial plane of the spindle as the so-called nuclear +or equatorial plate. Each half-chromosome is connected with one of the +spindle poles only and is then drawn towards that pole. (These important +facts, suspected by W. Flemming in 1882, were demonstrated by E. Heuser, +L. Guignard, E. van Beneden, M. Nussbaum, and C. Rabl.) + +The formation of the daughter-nuclei is then effected. The changes +which the daughter-chromosomes undergo in the process of producing the +daughter-nuclei repeat in the reverse order the changes which they went +through in the course of their progressive differentiation from the +mother-nucleus. The division of the cell-body is completed midway +between the two daughter-nuclei. In animal cells, which possess no +chemically differentiated membrane, separation is effected by simple +constriction, while in the case of plant cells provided with a definite +wall, the process begins with the formation of a cytoplasmic separating +layer. + +The phenomena observed in the course of the division of the nucleus show +beyond doubt that an exact halving of its substance is of the greatest +importance. (First shown by W. Roux in 1883.) Compared with the method +of division of the nucleus, that of the cytoplasm appears to be very +simple. This led to the conception that the cell-nucleus must be the +chief if not the sole carrier of hereditary characters in the organism. +It is for this reason that the detailed investigation of fertilisation +phenomena immediately followed researches into the nucleus. The +fundamental discovery of the union of two nuclei in the sexual act was +then made (By O. Hertwig in 1875.) and this afforded a new support for +the correct conception of the nuclear functions. The minute study of the +behaviour of the other constituents of sexual cells during fertilisation +led to the result, that the nucleus alone is concerned with handing on +hereditary characters (This was done by O. Hertwig and the author of +this essay simultaneously in 1884.) from one generation to another. +Especially important, from the point of view of this conclusion, is +the study of fertilisation in Angiosperms (Flowering plants); in these +plants the male sexual cells lose their cell-body in the pollen-tube and +the nucleus only--the sperm-nucleus--reaches the egg. The cytoplasm of +the male sexual cell is therefore not necessary to ensure a transference +of hereditary characters from parents to offspring. I lay stress on the +case of the Angiosperms because researches recently repeated with +the help of the latest methods failed to obtain different results. +As regards the descendants of angiospermous plants, the same laws of +heredity hold good as for other sexually differentiated organisms; we +may, therefore, extend to the latter what the Angiosperms so clearly +teach us. + +The next advance in the hitherto rapid progress in our knowledge of +nuclear division was delayed, because it was not at once recognised that +there are two absolutely different methods of nuclear division. All +such nuclear divisions were united under the head of indirect or +mitotic divisions; these were also spoken of as karyo-kineses, and +were distinguished from the direct or amitotic divisions which are +characterised by a simple constriction of the nuclear body. So long +as the two kinds of indirect nuclear division were not clearly +distinguished, their correct interpretation was impossible. This was +accomplished after long and laborious research, which has recently +been carried out and with results which should, perhaps, be regarded as +provisional. + +Soon after the new study of the nucleus began, investigators were struck +by the fact that the course of nuclear division in the mother-cells, or +more correctly in the grandmother-cells, of spores, pollen-grains, and +embryo-sacs of the more highly organised plants and in the spermatozoids +and eggs of the higher animals, exhibits similar phenomena, distinct +from those which occur in the somatic cells. + +In the nuclei of all those cells which we may group together as +gonotokonts (At the suggestion of J.P. Lotsy in 1904.) (i.e. cells +concerned in reproduction) there are fewer chromosomes than in the +adjacent body-cells (somatic cells). It was noticed also that there is a +peculiarity characteristic of the gonotokonts, namely the occurrence of +two nuclear divisions rapidly succeeding one another. It was afterwards +recognised that in the first stage of nuclear division in +the gonotokonts the chromosomes unite in pairs: it is these +chromosome-pairs, and not the two longitudinal halves of single +chromosomes, which form the nuclear plate in the equatorial plane of +the nuclear spindle. It has been proposed to call these pairs gemini. +(J.E.S. Moore and A.L. Embleton, "Proc. Roy. Soc." London, Vol. LXXVII. +page 555, 1906; V. Gregoire, 1907.) In the course of this division +the spindle-fibrillae attach themselves to the gemini, i.e. to entire +chromosomes and direct them to the points where the new daughter-nuclei +are formed, that is to those positions towards which the longitudinal +halves of the chromosomes travel in ordinary nuclear divisions. It +is clear that in this way the number of chromosomes which the +daughter-nuclei contain, as the result of the first stage in division +in the gonotokonts, will be reduced by one half, while in ordinary +divisions the number of chromosomes always remains the same. The first +stage in the division of the nucleus in the gonotokonts has therefore +been termed the reduction division. (In 1887 W. Flemming termed this the +heterotypic form of nuclear division.) This stage in division determines +the conditions for the second division which rapidly ensues. Each of the +paired chromosomes of the mother-nucleus has already, as in an ordinary +nuclear division, completed the longitudinal fission, but in this case +it is not succeeded by the immediate separation of the longitudinal +halves and their allotment to different nuclei. Each chromosome, +therefore, takes its two longitudinal halves into the same +daughter-nucleus. Thus, in each daughter-nucleus the longitudinal halves +of the chromosomes are present ready for the next stage in the +division; they only require to be arranged in the nuclear plate and then +distributed among the granddaughter-nuclei. This method of division, +which takes place with chromosomes already split, and which have only +to provide for the distribution of their longitudinal halves to the next +nuclear generation, has been called homotypic nuclear division. (The +name was proposed by W. Flemming in 1887; the nature of this type of +division was, however, not explained until later.) + +Reduction division and homotypic nuclear division are included together +under the term allotypic nuclear division and are distinguished from the +ordinary or typical nuclear division. The name Meiosis (By J. Bretland +Farmer and J.E.S. Moore in 1905.) has also been proposed for these two +allotypic nuclear divisions. The typical divisions are often spoken of +as somatic. + +Observers who were actively engaged in this branch of recent +histological research soon noticed that the chromosomes of a given +organism are differentiated in definite numbers from the nuclear +network in the course of division. This is especially striking in the +gonotokonts, but it applies also to the somatic tissues. In the latter, +one usually finds twice as many chromosomes as in the gonotokonts. Thus +the conclusion was gradually reached that the doubling of chromosomes, +which necessarily accompanies fertilisation, is maintained in the +product of fertilisation, to be again reduced to one half in the +gonotokonts at the stage of reduction-division. This enabled us to form +a conception as to the essence of true alternation of generations, in +which generations containing single and double chromosomes alternate +with one another. + +The single-chromosome generation, which I will call the HAPLOID, must +have been the primitive generation in all organisms; it might also +persist as the only generation. Every sexual differentiation in +organisms, which occurred in the course of phylogenetic development, was +followed by fertilisation and therefore by the creation of a diploid or +double-chromosome product. So long as the germination of the product +of fertilisation, the zygote, began with a reducing process, a special +DIPLOID generation was not represented. This, however, appeared later +as a product of the further evolution of the zygote, and the reduction +division was correspondingly postponed. In animals, as in plants, the +diploid generation attained the higher development and gradually assumed +the dominant position. The haploid generation suffered a proportional +reduction, until it finally ceased to have an independent existence and +became restricted to the role of producing the sexual products within +the body of the diploid generation. Those who do not possess the +necessary special knowledge are unable to realise what remains of the +first haploid generation in a phanerogamic plant or in a vertebrate +animal. In Angiosperms this is actually represented only by the short +developmental stages which extend from the pollen mother-cells to the +sperm-nucleus of the pollen-tube, and from the embryo-sac mother-cell to +the egg and the endosperm tissue. The embryo-sac remains enclosed in +the diploid ovule, and within this from the fertilised egg is formed +the embryo which introduces the new diploid generation. On the full +development of the diploid embryo of the next generation, the diploid +ovule of the preceding diploid generation is separated from the latter +as a ripe seed. The uninitiated sees in the more highly organised plants +only a succession of diploid generations. Similarly all the higher +animals appear to us as independent organisms with diploid nuclei only. +The haploid generation is confined in them to the cells produced as the +result of the reduction division of the gonotokonts; the development of +these is completed with the homotypic stage of division which succeeds +the reduction division and produces the sexual products. + +The constancy of the numbers in which the chromosomes separate +themselves from the nuclear network during division gave rise to the +conception that, in a certain degree, chromosomes possess individuality. +Indeed the most careful investigations (Particularly those of V. +Gregoire and his pupils.) have shown that the segments of the nuclear +network, which separate from one another and condense so as to produce +chromosomes for a new division, correspond to the segments produced from +the chromosomes of the preceding division. The behaviour of such nuclei +as possess chromosomes of unequal size affords confirmatory evidence of +the permanence of individual chromosomes in corresponding sections of an +apparently uniform nuclear network. Moreover at each stage in division +chromosomes with the same differences in size reappear. Other cases are +known in which thicker portions occur in the substance of the resting +nucleus, and these agree in number with the chromosomes. In this +network, therefore, the individual chromosomes must have retained +their original position. But the chromosomes cannot be regarded as the +ultimate hereditary units in the nuclei, as their number is too small. +Moreover, related species not infrequently show a difference in the +number of their chromosomes, whereas the number of hereditary units +must approximately agree. We thus picture to ourselves the carriers of +hereditary characters as enclosed in the chromosomes; the transmitted +fixed number of chromosomes is for us only the visible expression of +the conception that the number of hereditary units which the chromosomes +carry must be also constant. The ultimate hereditary units may, like +the chromosomes themselves, retain a definite position in the resting +nucleus. Further, it may be assumed that during the separation of the +chromosomes from one another and during their assumption of the rod-like +form, the hereditary units become aggregated in the chromomeres and +that these are characterised by a constant order of succession. +The hereditary units then grow, divide into two and are uniformly +distributed by the fission of the chromosomes between their longitudinal +halves. + +As the contraction and rod-like separation of the chromosomes serve +to isnure the transmission of all hereditary units in the products of +division of a nucleus, so, on the other hand, the reticular distension +of each chromosome in the so-called resting nucleus may effect a +separation of the carriers of hereditary units from each other and +facilitate the specific activity of each of them. + +In the stages preliminary to their division, the chromosomes become +denser and take up a substance which increases their staining capacity; +this is called chromatin. This substance collects in the chromomeres +and may form the nutritive material for the carriers of hereditary units +which we now believe to be enclosed in them. The chromatin cannot itself +be the hereditary substance, as it afterwards leaves the chromosomes, +and the amount of it is subject to considerable variation in the +nucleus, according to its stage of development. Conjointly with the +materials which take part in the formation of the nuclear spindle and +other processes in the cell, the chromatin accumulates in the resting +nucleus to form the nucleoli. + +Naturally connected with the conclusion that the nuclei are the carriers +of hereditary characters in the organism, is the question whether +enucleate organisms can also exist. Phylogenetic considerations give an +affirmative answer to this question. The differentiation into nucleus +and cytoplasm represents a division of labour in the protoplast. A +study of organisms which belong to the lowest class of the organic world +teaches us how this was accomplished. Instead of well-defined nuclei, +scattered granules have been described in the protoplasm of several of +these organisms (Bacteria, Cyanophyceae, Protozoa.), characterised by +the same reactions as nuclear material, provided also with a nuclear +network, but without a limiting membrane. (This is the result of the +work of R. Hertwig and of the most recently published investigations.) +Thus the carriers of hereditary characters may originally have been +distributed in the common protoplasm, afterwards coming together and +eventually assuming a definite form as special organs of the cell. It +may be also assumed that in the protoplasm and in the primitive types +of nucleus, the carriers of the same hereditary unit were represented in +considerable quantity; they became gradually differentiated to an extent +commensurate with newly acquired characters. It was also necessary that, +in proportion as this happened, the mechanism of nuclear division must +be refined. At first processes resembling a simple constriction would +suffice to provide for the distribution of all hereditary units to each +of the products of division, but eventually in both organic kingdoms +nuclear division, which alone insured the qualitative identity of the +products of division, became a more marked feature in the course of +cell-multiplication. + +Where direct nuclear division occurs by constriction in the higher +organisms, it does not result in the halving of hereditary units. So far +as my observations go, direct nuclear division occurs in the more highly +organised plants only in cells which have lost their specific +functions. Such cells are no longer capable of specific reproduction. An +interesting case in this connection is afforded by the internodal cells +of the Characeae, which possess only vegetative functions. These cells +grow vigorously and their cytoplasm increases, their growth being +accompanied by a correspondingly direct multiplication of the nuclei. +They serve chiefly to nourish the plant, but, unlike the other +cells, they are incapable of producing any offspring. This is a very +instructive case, because it clearly shows that the nuclei are not only +carriers of hereditary characters, but that they also play a definite +part in the metabolism of the protoplasts. + +Attention was drawn to the fact that during the reducing division of +nuclei which contain chromosomes of unequal size, gemini are constantly +produced by the pairing of chromosomes of the same size. This led to +the conclusion that the pairing chromosomes are homologous, and that one +comes from the father, the other from the mother. (First stated by T.H. +Montgomery in 1901 and by W.S. Sutton in 1902.) This evidently applies +also to the pairing of chromosomes in those reduction-divisions in +which differences in size do not enable us to distinguish the individual +chromosomes. In this case also each pair would be formed by two +homologous chromosomes, the one of paternal, the other of maternal +origin. When the separation of these chromosomes and their distribution +to both daughter-nuclei occur a chromosome of each kind is provided for +each of these nuclei. It would seem that the components of each pair +might pass to either pole of the nuclear spindle, so that the paternal +and maternal chromosomes would be distributed in varying proportion +between the daughter-nuclei; and it is not impossible that one +daughter-nucleus might occasionally contain paternal chromosomes only +and its sister-nucleus exclusively maternal chromosomes. + +The fact that in nuclei containing chromosomes of various sizes, the +chromosomes which pair together in reduction-division are always of +equal size, constitutes a further and more important proof of their +qualitative difference. This is supported also by ingenious experiments +which led to an unequal distribution of chromosomes in the products of +division of a sea-urchin's egg, with the result that a difference was +induced in their further development. (Demonstrated by Th. Boveri in +1902.) + +The recently discovered fact that in diploid nuclei the chromosomes are +arranged in pairs affords additional evidence in favour of the unequal +value of the chromosomes. This is still more striking in the case of +chromosomes of different sizes. It has been shown that in the first +division-figure in the nucleus of the fertilised egg the chromosomes of +corresponding size form pairs. They appear with this arrangement in all +subsequent nuclear divisions in the diploid generation. The longitudinal +fissions of the chromosomes provide for the unaltered preservation +of this condition. In the reduction nucleus of the gonotokonts the +homologous chromosomes being near together need not seek out one +another; they are ready to form gemini. The next stage is their +separation to the haploid daughter-nuclei, which have resulted from the +reduction process. + +Peculiar phenomena in the reduction nucleus accompany the formation of +gemini in both organic kingdoms. (This has been shown more particularly +by the work of L. Guignard, M. Mottier, J.B. Farmer, C.B. Wilson, V. +Hacker and more recently by V. Gregoire and his pupil C.A. Allen, by the +researches conducted in the Bonn Botanical Institute, and by A. and +K.E. Schreiner.) Probably for the purpose of entering into most +intimate relation, the pairs are stretched to long threads in which the +chromomeres come to lie opposite one another. (C.A. Allen, A. and K.E. +Schreiner, and Strasburger.) It seems probable that these are homologous +chromomeres, and that the pairs afterwards unite for a short time, so +that an exchange of hereditary units is rendered possible. (H. de Vries +and Strasburger.) This cannot be actually seen, but certain facts of +heredity point to the conclusion that this occurs. It follows from +these phenomena that any exchange which may be effected must be one of +homologous carriers of hereditary units only. These units continue to +form exchangeable segments after they have undergone unequal changes; +they then constitute allelotropic pairs. We may thus calculate what sum +of possible combinations the exchange of homologous hereditary units +between the pairing chromosomes provides for before the reduction +division and the subsequent distribution of paternal and maternal +chromosomes in the haploid daughter-nuclei. These nuclei then transmit +their characters to the sexual cells, the conjugation of which in +fertilization again produces the most varied combinations. (A. Weismann +gave the impulse to these ideas in his theory on "Amphimixis".) In this +way all the cooperations which the carriers of hereditary characters are +capable of in a species are produced; this must give it an appreciable +advantage in the struggle for life. + +The admirers of Charles Darwin must deeply regret that he did not live +to see the results achieved by the new Cytology. What service would they +have been to him in the presentation of his hypothesis of Pangenesis; +what an outlook into the future would they have given to his active +mind! + +The Darwinian hypothesis of Pangenesis rests on the conception that all +inheritable properties are represented in the cells by small invisible +particles or gemmules and that these gemmules increase by division. +Cytology began to develop on new lines some years after the publication +in 1868 of Charles Darwin's "Provisional hypothesis of Pangenesis" +("Animals and Plants under Domestication", London, 1868, Chapter +XXVII.), and when he died in 1882 it was still in its infancy. Darwin +would have soon suggested the substitution of the nuclei for his +gemmules. At least the great majority of present-day investigators in +the domain of cytology have been led to the conclusion that the nucleus +is the carrier of hereditary characters, and they also believe that +hereditary characters are represented in the nucleus as distinct units. +Such would be Darwin's gemmules, which in conformity with the name +of his hypothesis may be called pangens (So called by H. de Vries in +1889.): these pangens multiply by division. All recently adopted +views may be thus linked on to this part of Darwin's hypothesis. It is +otherwise with Darwin's conception to which Pangenesis owes its name, +namely the view that all cells continually give off gemmules, which +migrate to other places in the organism, where they unite to form +reproductive cells. When Darwin foresaw this possibility, the continuity +of the germinal substance was still unknown (Demonstrated by Nussbaum in +1880, by Sachs in 1882, and by Weismann in 1885.), a fact which excludes +a transference of gemmules. + +But even Charles Darwin's genius was confined within finite boundaries +by the state of science in his day. + +It is not my province to deal with other theories of development which +followed from Darwin's Pangenesis, or to discuss their histological +probabilities. We can, however, affirm that Charles Darwin's idea that +invisible gemmules are the carriers of hereditary characters and that +they multiply by division has been removed from the position of a +provisional hypothesis to that of a well-founded theory. It is supported +by histology, and the results of experimental work in heredity, which +are now assuming extraordinary prominence, are in close agreement with +it. + + + + +VII. "THE DESCENT OF MAN". By G. Schwalbe. + +Professor of Anatomy in the University of Strassburg. + +The problem of the origin of the human race, of the descent of man, is +ranked by Huxley in his epoch-making book "Man's Place in Nature", as +the deepest with which biology has to concern itself, "the question +of questions,"--the problem which underlies all others. In the same +brilliant and lucid exposition, which appeared in 1863, soon after the +publication of Darwin's "Origin of Species", Huxley stated his own views +in regard to this great problem. He tells us how the idea of a natural +descent of man gradually grew up in his mind, it was especially the +assertions of Owen in regard to the total difference between the human +and the simian brain that called forth strong dissent from the great +anatomist Huxley, and he easily succeeded in showing that Owen's +supposed differences had no real existence; he even established, on the +basis of his own anatomical investigations, the proposition that the +anatomical differences between the Marmoset and the Chimpanzee are much +greater than those between the Chimpanzee and Man. + +But why do we thus introduce the study of Darwin's "Descent of Man", +which is to occupy us here, by insisting on the fact that Huxley had +taken the field in defence of the descent of man in 1863, while Darwin's +book on the subject did not appear till 1871? It is in order that we may +clearly understand how it happened that from this time onwards Darwin +and Huxley followed the same great aim in the most intimate association. + +Huxley and Darwin working at the same Problema maximum! Huxley fiery, +impetuous, eager for battle, contemptuous of the resistance of a dull +world, or energetically triumphing over it. Darwin calm, weighing every +problem slowly, letting it mature thoroughly,--not a fighter, yet having +the greater and more lasting influence by virtue of his immense mass of +critically sifted proofs. Darwin's friend, Huxley, was the first to do +him justice, to understand his nature, and to find in it the reason why +the detailed and carefully considered book on the descent of man made +its appearance so late. Huxley, always generous, never thought of +claiming priority for himself. In enthusiastic language he tells how +Darwin's immortal work, "The Origin of Species", first shed light for +him on the problem of the descent of man; the recognition of a vera +causa in the transformation of species illuminated his thoughts as with +a flash. He was now content to leave what perplexed him, what he could +not yet solve, as he says himself, "in the mighty hands of Darwin." +Happy in the bustle of strife against old and deep-rooted prejudices, +against intolerance and superstition, he wielded his sharp weapons on +Darwin's behalf; wearing Darwin's armour he joyously overthrew adversary +after adversary. Darwin spoke of Huxley as his "general agent." ("Life +and Letters of Thomas Henry Huxley", Vol. I. page 171, London, 1900.) +Huxley says of himself "I am Darwin's bulldog." (Ibid. page 363.) + +Thus Huxley openly acknowledged that it was Darwin's "Origin of Species" +that first set the problem of the descent of man in its true light, that +made the question of the origin of the human race a pressing one. That +this was the logical consequence of his book Darwin himself had long +felt. He had been reproached with intentionally shirking the application +of his theory to Man. Let us hear what he says on this point in his +autobiography: "As soon as I had become, in the year 1837 or 1838, +convinced that species were mutable productions, I could not avoid the +belief that man must come under the same law. Accordingly I collected +notes on the subject for my own satisfaction, and not for a long time +with any intention of publishing. Although in the 'Origin of Species' +the derivation of any particular species is never discussed, yet I +thought it best, in order THAT NO HONOURABLE MAN SHOULD ACCUSE ME OF +CONCEALING MY VIEWS (No italics in original.), to add that by the work +'light would be thrown on the origin of man and his history.' It would +have been useless and injurious to the success of the book to have +paraded, without giving any evidence, my conviction with respect to his +origin." ("Life and Letters of Charles Darwin", Vol. 1. page 93.) + +In a letter written in January, 1860, to the Rev. L. Blomefield, Darwin +expresses himself in similar terms. "With respect to man, I am very far +from wishing to obtrude my belief; but I thought it dishonest to quite +conceal my opinion." (Ibid. Vol. II. page 263.) + +The brief allusion in the "Origin of Species" is so far from prominent +and so incidental that it was excusable to assume that Darwin had not +touched upon the descent of man in this work. It was solely the desire +to have his mass of evidence sufficiently complete, solely Darwin's +great characteristic of never publishing till he had carefully weighed +all aspects of his subject for years, solely, in short, his most +fastidious scientific conscience that restrained him from challenging +the world in 1859 with a book in which the theory of the descent of man +was fully set forth. Three years, frequently interrupted by ill-health, +were needed for the actual writing of the book ("Life and Letters", Vol. +I. page 94.): the first edition, which appeared in 1871, was followed in +1874 by a much improved second edition, the preparation of which he very +reluctantly undertook. (Ibid. Vol. III. page 175.) + +This, briefly, is the history of the work, which, with the "Origin of +Species", marks an epoch in the history of biological sciences--the work +with which the cautious, peace-loving investigator ventured forth from +his contemplative life into the arena of strife and unrest, and +laid himself open to all the annoyances that deep-rooted belief and +prejudice, and the prevailing tendency of scientific thought at the time +could devise. + +Darwin did not take this step lightly. Of great interest in this +connection is a letter written to Wallace on Dec. 22, 1857 (Ibid. Vol. +II. page 109.), in which he says "You ask whether I shall discuss +'man.' I think I shall avoid the whole subject, as so surrounded +with prejudices; though I fully admit that it is the highest and most +interesting problem for the naturalist." But his conscientiousness +compelled him to state briefly his opinion on the subject in the "Origin +of Species" in 1859. Nevertheless he did not escape reproaches for +having been so reticent. This is unmistakably apparent from a letter to +Fritz Muller dated February 22 (1869?), in which he says: "I am thinking +of writing a little essay on the Origin of Mankind, as I have been +taunted with concealing my opinions." (Ibid. Vol. III. page 112.) + +It might be thought that Darwin behaved thus hesitatingly, and was so +slow in deciding on the full publication of his collected material in +regard to the descent of man, because he had religious difficulties to +overcome. + +But this was not the case, as we can see from his admirable confession +of faith, the publication of which we owe to his son Francis. (Ibid. +Vol. I. pages 304-317.) Whoever wishes really to understand the lofty +character of this great man should read these immortal lines in which he +unfolds to us in simple and straightforward words the development of his +conception of the universe. He describes how, though he was still quite +orthodox during his voyage round the world on board the "Beagle", he +came gradually to see, shortly afterwards (1836-1839) that the Old +Testament was no more to be trusted than the Sacred Books of the +Hindoos; the miracles by which Christianity is supported, the +discrepancies between the accounts in the different Gospels, gradually +led him to disbelieve in Christianity as a divine revelation. "Thus," he +writes ("Life and Letters", Vol. 1. page 309.), "disbelief crept over me +at a very slow rate, but was at last complete. The rate was so slow that +I felt no distress." But Darwin was too modest to presume to go beyond +the limits laid down by science. He wanted nothing more than to be able +to go, freely and unhampered by belief in authority or in the Bible, as +far as human knowledge could lead him. We learn this from the concluding +words of his chapter on religion: "The mystery of the beginning of all +things is insoluble by us; and I for one must be content to remain an +Agnostic." (Loc. cit. page 313.) + +Darwin was always very unwilling to give publicity to his views in +regard to religion. In a letter to Asa Gray on May 22, 1860 (Ibid. Vol. +II. page 310.), he declares that it is always painful to him to have +to enter into discussion of religious problems. He had, he said, no +intention of writing atheistically. + +Finally, let us cite one characteristic sentence from a letter from +Darwin to C. Ridley (Ibid. Vol. III. page. 236. ("C. Ridley," Mr Francis +Darwin points out to me, should be H.N. Ridley. A.C.S.)) (Nov. 28, +1878.) A clergyman, Dr Pusey, had asserted that Darwin had written +the "Origin of Species" with some relation to theology. Darwin writes +emphatically, "Many years ago, when I was collecting facts for the +'Origin', my belief in what is called a personal God was as firm as that +of Dr Pusey himself, and as to the eternity of matter I never troubled +myself about such insoluble questions." The expression "many years ago" +refers to the time of his voyage round the world, as has already been +pointed out. Darwin means by this utterance that the views which had +gradually developed in his mind in regard to the origin of species were +quite compatible with the faith of the Church. + +If we consider all these utterances of Darwin in regard to religion and +to his outlook on life (Weltanschauung), we shall see at least so much, +that religious reflection could in no way have influenced him in regard +to the writing and publishing of his book on "The Descent of Man". +Darwin had early won for himself freedom of thought, and to this freedom +he remained true to the end of his life, uninfluenced by the customs and +opinions of the world around him. + +Darwin was thus inwardly fortified and armed against the host of +calumnies, accusations, and attacks called forth by the publication of +the "Origin of Species", and to an even greater extent by the appearance +of the "Descent of Man". But in his defence he could rely on the aid of +a band of distinguished auxiliaries of the rarest ability. His faithful +confederate, Huxley, was joined by the botanist Hooker, and, after +longer resistance, by the famous geologist Lyell, whose "conversion" +afforded Darwin peculiar satisfaction. All three took the field with +enthusiasm in defence of the natural descent of man. From Wallace, on +the other hand, though he shared with him the idea of natural selection, +Darwin got no support in this matter. Wallace expressed himself in a +strange manner. He admitted everything in regard to the morphological +descent of man, but maintained, in a mystic way, that something else, +something of a spiritual nature must have been added to what man +inherited from his animal ancestors. Darwin, whose esteem for Wallace +was extraordinarily high, could not understand how he could give +utterance to such a mystical view in regard to man; the idea seemed +to him so "incredibly strange" that he thought some one else must have +added these sentences to Wallace's paper. + +Even now there are thinkers who, like Wallace, shrink from applying to +man the ultimate consequences of the theory of descent. The idea +that man is derived from ape-like forms is to them unpleasant and +humiliating. + +So far I have been depicting the development of Darwin's work on the +descent of man. In what follows I shall endeavour to give a condensed +survey of the contents of the book. + +It must at once be said that the contents of Darwin's work fall into two +parts, dealing with entirely different subjects. "The Descent of Man" +includes a very detailed investigation in regard to secondary sexual +characters in the animal series, and on this investigation Darwin +founded a new theory, that of sexual selection. With astonishing +patience he gathered together an immense mass of material, and showed, +in regard to Arthropods and Vertebrates, the wide distribution of +secondary characters, which develop almost exclusively in the male, and +which enable him, on the one hand, to get the better of his rivals in +the struggle for the female by the greater perfection of his weapons, +and on the other hand, to offer greater allurements to the female +through the higher development of decorative characters, of song, or of +scent-producing glands. The best equipped males will thus crowd out the +less well-equipped in the matter of reproduction, and thus the relevant +characters will be increased and perfected through sexual selection. +It is, of course, a necessary assumption that these secondary sexual +characters may be transmitted to the female, although perhaps in +rudimentary form. + +As we have said, this theory of sexual selection takes up a great deal +of space in Darwin's book, and it need only be considered here in so far +as Darwin applied it to the descent of man. To this latter problem the +whole of Part I is devoted, while Part III contains a discussion of +sexual selection in relation to man, and a general summary. Part II +treats of sexual selection in general, and may be disregarded in our +present study. Moreover, many interesting details must necessarily be +passed over in what follows, for want of space. + +The first part of the "Descent of Man" begins with an enumeration of +the proofs of the animal descent of man taken from the structure of +the human body. Darwin chiefly emphasises the fact that the human body +consists of the same organs and of the same tissues as those of the +other mammals; he shows also that man is subject to the same diseases +and tormented by the same parasites as the apes. He further dwells +on the general agreement exhibited by young, embryonic forms, and +he illustrates this by two figures placed one above the other, one +representing a human embryo, after Eaker, the other a dog embryo, after +Bischoff. ("Descent of Man" (Popular Edition, 1901), fig. 1, page 14.) + +Darwin finds further proofs of the animal origin of man in the +reduced structures, in themselves extremely variable, which are either +absolutely useless to their possessors, or of so little use that they +could never have developed under existing conditions. Of such vestiges +he enumerates: the defective development of the panniculus carnosus +(muscle of the skin) so widely distributed among mammals, the +ear-muscles, the occasional persistence of the animal ear-point in man, +the rudimentary nictitating membrane (plica semilunaris) in the human +eye, the slight development of the organ of smell, the general hairiness +of the human body, the frequently defective development or entire +absence of the third molar (the wisdom tooth), the vermiform appendix, +the occasional reappearance of a bony canal (foramen supracondyloideum) +at the lower end of the humerus, the rudimentary tail of man (the +so-called taillessness), and so on. Of these rudimentary structures +the occasional occurrence of the animal ear-point in man is most fully +discussed. Darwin's attention was called to this interesting structure +by the sculptor Woolner. He figures such a case observed in man, and +also the head of an alleged orang-foetus, the photograph of which he +received from Nitsche. + +Darwin's interpretation of Woolner's case as having arisen through a +folding over of the free edge of a pointed ear has been fully borne out +by my investigations on the external ear. (G. Schwalbe, "Das Darwin'sche +Spitzohr beim menschlichen Embryo", "Anatom. Anzeiger", 1889, pages +176-189, and other papers.) In particular, it was established by these +investigations that the human foetus, about the middle of its embryonic +life, possesses a pointed ear somewhat similar to that of the monkey +genus Macacus. One of Darwin's statements in regard to the head of the +orang-foetus must be corrected. A LARGE ear with a point is shown in +the photograph ("Descent of Man", fig.3, page 24.), but it can easily be +demonstrated--and Deniker has already pointed this out--that the figure +is not that of an orang-foetus at all, for that form has much smaller +ears with no point; nor can it be a gibbon-foetus, as Deniker supposes, +for the gibbon ear is also without a point. I myself regard it as that +of a Macacus-embryo. But this mistake, which is due to Nitsche, in no +way affects the fact recognised by Darwin, that ear-forms showing the +point characteristic of the animal ear occur in man with extraordinary +frequency. + +Finally, there is a discussion of those rudimentary structures which +occur only in ONE sex, such as the rudimentary mammary glands in the +male, the vesicula prostatica, which corresponds to the uterus of the +female, and others. All these facts tell in favour of the common descent +of man and all other vertebrates. The conclusion of this section is +characteristic: "IT IS ONLY OUR NATURAL PREJUDICE, AND THAT ARROGANCE +WHICH MADE OUR FOREFATHERS DECLARE THAT THEY WERE DESCENDED FROM +DEMI-GODS, WHICH LEADS US TO DEMUR TO THIS CONCLUSION. BUT THE TIME WILL +BEFORE LONG COME, WHEN IT WILL BE THOUGHT WONDERFUL THAT NATURALISTS, +WHO WERE WELL ACQUAINTED WITH THE COMPARATIVE STRUCTURE AND DEVELOPMENT +OF MAN, AND OTHER MAMMALS, SHOULD HAVE BELIEVED THAT EACH WAS THE WORK +OF A SEPARATE ACT OF CREATION." (Ibid. page 36.) + +In the second chapter there is a more detailed discussion, again based +upon an extraordinary wealth of facts, of the problem as to the manner +in which, and the causes through which, man evolved from a lower form. +Precisely the same causes are here suggested for the origin of man, as +for the origin of species in general. Variability, which is a necessary +assumption in regard to all transformations, occurs in man to a high +degree. Moreover, the rapid multiplication of the human race creates +conditions which necessitate an energetic struggle for existence, and +thus afford scope for the intervention of natural selection. Of the +exercise of ARTIFICIAL selection in the human race, there is nothing +to be said, unless we cite such cases as the grenadiers of Frederick +William I, or the population of ancient Sparta. In the passages already +referred to and in those which follow, the transmission of acquired +characters, upon which Darwin does not dwell, is taken for granted. +In man, direct effects of changed conditions can be demonstrated (for +instance in regard to bodily size), and there are also proofs of the +influence exerted on his physical constitution by increased use or +disuse. Reference is here made to the fact, established by Forbes, +that the Quechua-Indians of the high plateaus of Peru show a striking +development of lungs and thorax, as a result of living constantly at +high altitudes. + +Such special forms of variation as arrests of development +(microcephalism) and reversion to lower forms are next discussed. Darwin +himself felt ("Descent of Man", page 54.) that these subjects are so +nearly related to the cases mentioned in the first chapter, that many +of them might as well have been dealt with there. It seems to me that it +would have been better so, for the citation of additional instances +of reversion at this place rather disturbs the logical sequence of his +ideas as to the conditions which have brought about the evolution of +man from lower forms. The instances of reversion here discussed +are microcephalism, which Darwin wrongly interpreted as atavistic, +supernumerary mammae, supernumerary digits, bicornuate uterus, the +development of abnormal muscles, and so on. Brief mention is also made +of correlative variations observed in man. + +Darwin next discusses the question as to the manner in which man +attained to the erect position from the state of a climbing quadruped. +Here again he puts the influence of Natural Selection in the first +rank. The immediate progenitors of man had to maintain a struggle for +existence in which success was to the more intelligent, and to those +with social instincts. The hand of these climbing ancestors, which +had little skill and served mainly for locomotion, could only undergo +further development when some early member of the Primate series came to +live more on the ground and less among trees. + +A bipedal existence thus became possible, and with it the liberation +of the hand from locomotion, and the one-sided development of the human +foot. The upright position brought about correlated variations in the +bodily structure; with the free use of the hand it became possible +to manufacture weapons and to use them; and this again resulted in a +degeneration of the powerful canine teeth and the jaws, which were then +no longer necessary for defence. Above all, however, the intelligence +immediately increased, and with it skull and brain. The nakedness of +man, and the absence of a tail (rudimentariness of the tail vertebrae) +are next discussed. Darwin is inclined to attribute the nakedness of +man, not to the action of natural selection on ancestors who originally +inhabited a tropical land, but to sexual selection, which, for aesthetic +reasons, brought about the loss of the hairy covering in man, or +primarily in woman. An interesting discussion of the loss of the tail, +which, however, man shares with the anthropoid apes, some other monkeys +and lemurs, forms the conclusion of the almost superabundant material +which Darwin worked up in the second chapter. His object was to +show that some of the most distinctive human characters are in all +probability directly or indirectly due to natural selection. With +characteristic modesty he adds ("Descent of Man", page 92.): "Hence, if +I have erred in giving to natural selection great power, which I am +very far from admitting, or in having exaggerated its power, which is in +itself probable, I have at least, as I hope, done good service in aiding +to overthrow the dogma of separate creations." At the end of the chapter +he touches upon the objection as to man's helpless and defenceless +condition. Against this he urges his intelligence and social instincts. + +The two following chapters contain a detailed discussion of the +objections drawn from the supposed great differences between the mental +powers of men and animals. Darwin at once admits that the differences +are enormous, but not that any fundamental difference between the two +can be found. Very characteristic of him is the following passage: +"In what manner the mental powers were first developed in the +lowest organisms, is as hopeless an enquiry as how life itself first +originated. These are problems for the distant future, if they are ever +to be solved by man." (Ibid. page 100.) + +After some brief observations on instinct and intelligence, Darwin +brings forward evidence to show that the greater number of the emotional +states, such as pleasure and pain, happiness and misery, love and hate +are common to man and the higher animals. He goes on to give various +examples showing that wonder and curiosity, imitation, attention, memory +and imagination (dreams of animals), can also be observed in the higher +mammals, especially in apes. In regard even to reason there are +no sharply defined limits. A certain faculty of deliberation is +characteristic of some animals, and the more thoroughly we know an +animal the more intelligence we are inclined to credit it with. Examples +are brought forward of the intelligent and deliberate actions of apes, +dogs and elephants. But although no sharply defined differences exist +between man and animals, there is, nevertheless, a series of other +mental powers which are characteristics usually regarded as absolutely +peculiar to man. Some of these characteristics are examined in detail, +and it is shown that the arguments drawn from them are not conclusive. +Man alone is said to be capable of progressive improvement; but against +this must be placed as something analogous in animals, the fact that +they learn cunning and caution through long continued persecution. Even +the use of tools is not in itself peculiar to man (monkeys use sticks, +stones and twigs), but man alone fashions and uses implements DESIGNED +FOR A SPECIAL PURPOSE. In this connection the remarks taken from Lubbock +in regard to the origin and gradual development of the earliest +flint implements will be read with interest; these are similar to the +observations on modern eoliths, and their bearing on the development of +the stone-industry. It is interesting to learn from a letter to Hooker +("Life and Letters", Vol. II. page 161, June 22, 1859.), that Darwin +himself at first doubted whether the stone implements discovered +by Boucher de Perthes were really of the nature of tools. With the +relentless candour as to himself which characterised him, he writes four +years later in a letter to Lyell in regard to this view of Boucher de +Perthes' discoveries: "I know something about his errors, and looked at +his book many years ago, and am ashamed to think that I concluded the +whole was rubbish! Yet he has done for man something like what Agassiz +did for glaciers." (Ibid. Vol. III. page 15, March 17, 1863.) + +To return to Darwin's further comparisons between the higher mental +powers of man and animals. He takes much of the force from the argument +that man alone is capable of abstraction and self-consciousness by his +own observations on dogs. One of the main differences between man and +animals, speech, receives detailed treatment. He points out that various +animals (birds, monkeys, dogs) have a large number of different sounds +for different emotions, that, further, man produces in common with +animals a whole series of inarticulate cries combined with gestures, and +that dogs learn to understand whole sentences of human speech. In regard +to human language, Darwin expresses a view contrary to that held by Max +Muller ("Descent of Man", page 132.): "I cannot doubt that language owes +its origin to the imitation and modification of various natural sounds, +the voices of other animals, and man's own instinctive cries, aided by +signs and gestures." The development of actual language presupposes a +higher degree of intelligence than is found in any kind of ape. Darwin +remarks on this point (Ibid. pages 136, 137.): "The fact of the higher +apes not using their vocal organs for speech no doubt depends on their +intelligence not having been sufficiently advanced." + +The sense of beauty, too, has been alleged to be peculiar to man. In +refutation of this assertion Darwin points to the decorative colours of +birds, which are used for display. And to the last objection, that man +alone has religion, that he alone has a belief in God, it is answered +"that numerous races have existed, and still exist, who have no idea of +one or more gods, and who have no words in their languages to express +such an idea." (Ibid. page 143.) + +The result of the investigations recorded in this chapter is to show +that, great as the difference in mental powers between man and the +higher animals may be, it is undoubtedly only a difference "of degree +and not of kind." ("Descent of Man", page 193.) + +In the fourth chapter Darwin deals with the MORAL SENSE or CONSCIENCE, +which is the most important of all differences between man and animals. +It is a result of social instincts, which lead to sympathy for other +members of the same society, to non-egoistic actions for the good +of others. Darwin shows that social tendencies are found among many +animals, and that among these love and kin-sympathy exist, and he gives +examples of animals (especially dogs) which may exhibit characters that +we should call moral in man (e.g. disinterested self-sacrifice for the +sake of others). The early ape-like progenitors of the human race were +undoubtedly social. With the increase of intelligence the moral sense +develops farther; with the acquisition of speech public opinion arises, +and finally, moral sense becomes habit. The rest of Darwin's detailed +discussions on moral philosophy may be passed over. + +The fifth chapter may be very briefly summarised. In it Darwin shows +that the intellectual and moral faculties are perfected through natural +selection. He inquires how it can come about that a tribe at a low level +of evolution attains to a higher, although the best and bravest among +them often pay for their fidelity and courage with their lives without +leaving any descendants. In this case it is the sentiment of glory, +praise and blame, the admiration of others, which bring about the +increase of the better members of the tribe. Property, fixed dwellings, +and the association of families into a community are also indispensable +requirements for civilisation. In the longer second section of the +fifth chapter Darwin acts mainly as recorder. On the basis of numerous +investigations, especially those of Greg, Wallace, and Galton, he +inquires how far the influence of natural selection can be demonstrated +in regard to civilised nations. In the final section, which deals with +the proofs that all civilised nations were once barbarians, Darwin again +uses the results gained by other investigators, such as Lubbock and +Tylor. There are two sets of facts which prove the proposition in +question. In the first place, we find traces of a former lower state +in the customs and beliefs of all civilised nations, and in the second +place, there are proofs to show that savage races are independently able +to raise themselves a few steps in the scale of civilisation, and that +they have thus raised themselves. + +In the sixth chapter of the work, Morphology comes into the foreground +once more. Darwin first goes back, however, to the argument based on the +great difference between the mental powers of the highest animals and +those of man. That this is only quantitative, not qualitative, he has +already shown. Very instructive in this connection is the reference to +the enormous difference in mental powers in another class. No one +would draw from the fact that the cochineal insect (Coccus) and the ant +exhibit enormous differences in their mental powers, the conclusion that +the ant should therefore be regarded as something quite distinct, and +withdrawn from the class of insects altogether. + +Darwin next attempts to establish the SPECIFIC genealogical tree of +man, and carefully weighs the differences and resemblances between the +different families of the Primates. The erect position of man is an +adaptive character, just as are the various characters referable to +aquatic life in the seals, which, notwithstanding these, are ranked as +a mere family of the Carnivores. The following utterance is very +characteristic of Darwin ("Descent of Man", page 231.): "If man had +not been his own classifier, he would never have thought of founding +a separate order for his own reception." In numerous characters not +mentioned in systematic works, in the features of the face, in the form +of the nose, in the structure of the external ear, man resembles the +apes. The arrangement of the hair in man has also much in common with +the apes; as also the occurrence of hair on the forehead of the human +embryo, the beard, the convergence of the hair of the upper and under +arm towards the elbow, which occurs not only in the anthropoid apes, but +also in some American monkeys. Darwin here adopts Wallace's explanation +of the origin of the ascending direction of the hair in the forearm of +the orang,--that it has arisen through the habit of holding the hands +over the head in rain. But this explanation cannot be maintained when we +consider that this disposition of the hair is widely distributed among +the most different mammals, being found in the dog, in the sloth, and in +many of the lower monkeys. + +After further careful analysis of the anatomical characters Darwin +reaches the conclusion that the New World monkeys (Platyrrhine) may +be excluded from the genealogical tree altogether, but that man is +an offshoot from the Old World monkeys (Catarrhine) whose progenitors +existed as far back as the Miocene period. Among these Old World monkeys +the forms to which man shows the greatest resemblance are the anthropoid +apes, which, like him, possess neither tail nor ischial callosities. The +platyrrhine and catarrhine monkeys have their primitive ancestor among +extinct forms of the Lemuridae. Darwin also touches on the question of +the original home of the human race and supposes that it may have been +in Africa, because it is there that man's nearest relatives, the gorilla +and the chimpanzee, are found. But he regards speculation on this point +as useless. It is remarkable that, in this connection, Darwin regards +the loss of the hair-covering in man as having some relation to a +warm climate, while elsewhere he is inclined to make sexual selection +responsible for it. Darwin recognises the great gap between man and +his nearest relatives, but similar gaps exist at other parts of the +mammalian genealogical tree: the allied forms have become extinct. After +the extermination of the lower races of mankind, on the one hand, and of +the anthropoid apes on the other, which will undoubtedly take place, the +gulf will be greater than ever, since the baboons will then bound it on +the one side, and the white races on the other. Little weight need be +attached to the lack of fossil remains to fill up this gap, since the +discovery of these depends upon chance. The last part of the chapter is +devoted to a discussion of the earlier stages in the genealogy of +man. Here Darwin accepts in the main the genealogical tree, which had +meantime been published by Haeckel, who traces the pedigree back through +Monotremes, Reptiles, Amphibians, and Fishes, to Amphioxus. + +Then follows an attempt to reconstruct, from the atavistic characters, +a picture of our primitive ancestor who was undoubtedly an arboreal +animal. The occurrence of rudiments of parts in one sex which only come +to full development in the other is next discussed. This state of things +Darwin regards as derived from an original hermaphroditism. In regard to +the mammary glands of the male he does not accept the theory that they +are vestigial, but considers them rather as not fully developed. + +The last chapter of Part I deals with the question whether the different +races of man are to be regarded as different species, or as sub-species +of a race of monophyletic origin. The striking differences between +the races are first emphasised, and the question of the fertility or +infertility of hybrids is discussed. That fertility is the more usual +is shown by the excessive fertility of the hybrid population of Brazil. +This, and the great variability of the distinguishing characters of +the different races, as well as the fact that all grades of transition +stages are found between these, while considerable general agreement +exists, tell in favour of the unity of the races and lead to the +conclusion that they all had a common primitive ancestor. + +Darwin therefore classifies all the different races as sub-species of +ONE AND THE SAME SPECIES. Then follows an interesting inquiry into the +reasons for the extinction of human races. He recognises as the ultimate +reason the injurious effects of a change of the conditions of life, +which may bring about an increase in infantile mortality, and a +diminished fertility. It is precisely the reproductive system, among +animals also, which is most susceptible to changes in the environment. + +The final section of this chapter deals with the formation of the races +of mankind. Darwin discusses the question how far the direct effect of +different conditions of life, or the inherited effects of increased use +or disuse may have brought about the characteristic differences between +the different races. Even in regard to the origin of the colour of the +skin he rejects the transmitted effects of an original difference of +climate as an explanation. In so doing he is following his tendency to +exclude Lamarckian explanations as far as possible. But here he makes +gratuitous difficulties from which, since natural selection fails, there +is no escape except by bringing in the principle of sexual selection, to +which, he regarded it as possible, skin-colouring, arrangement of +hair, and form of features might be traced. But with his characteristic +conscientiousness he guards himself thus: "I do not intend to assert +that sexual selection will account for all the differences between the +races." ("Descent of Man", page 308.) + +I may be permitted a remark as to Darwin's attitude towards Lamarck. +While, at an earlier stage, when he was engaged in the preliminary +labours for his immortal work, "The Origin of Species", Darwin expresses +himself very forcibly against the views of Lamarck, speaking of +Lamarckian "nonsense," ("Life and Letters", Vol. II. page 23.), and +of Lamarck's "absurd, though clever work" (Loc. cit. page 39.) and +expressly declaring, "I attribute very little to the direct action of +climate, etc." (Loc. cit. (1856), page 82.) yet in later life he became +more and more convinced of the influence of external conditions. In +1876, that is, two years after the appearance of the second edition of +"The Descent of Man", he writes with his usual candid honesty: "In my +opinion the greatest error which I have committed, has been not allowing +sufficient weight to the direct action of the environment, i.e. food, +climate, etc. independently of natural selection." (Ibid. Vol. III. page +159.) It is certain from this change of opinion that, if he had been +able to make up his mind to issue a third edition of "The Descent of +Man", he would have ascribed a much greater influence to the effect of +external conditions in explaining the different characters of the races +of man than he did in the second edition. He would also undoubtedly have +attributed less influence to sexual selection as a factor in the origin +of the different bodily characteristics, if indeed he would not have +excluded it altogether. + +In Part III of the "Descent" two additional chapters are devoted to the +discussion of sexual selection in relation to man. These may be very +briefly referred to. Darwin here seeks to show that sexual selection has +been operative on man and his primitive progenitor. Space fails me to +follow out his interesting arguments. I can only mention that he is +inclined to trace back hairlessness, the development of the beard in +man, and the characteristic colour of the different human races to +sexual selection. Since bareness of the skin could be no advantage, but +rather a disadvantage, this character cannot have been brought about by +natural selection. Darwin also rejected a direct influence of climate as +a cause of the origin of the skin-colour. I have already expressed the +opinion, based on the development of his views as shown in his letters, +that in a third edition Darwin would probably have laid more stress on +the influence of external environment. He himself feels that there are +gaps in his proofs here, and says in self-criticism: "The views here +advanced, on the part which sexual selection has played in the history +of man, want scientific precision." ("Descent of Man", page 924.) I +need here only point out that it is impossible to explain the graduated +stages of skin-colour by sexual selection, since it would have produced +races sharply defined by their colour and not united to other races +by transition stages, and this, it is well known, is not the case. +Moreover, the fact established by me ("Die Hautfarbe des Menschen", +"Mitteilungen der Anthropologischen Gesellschaft in Wien", Vol. XXXIV. +pages 331-352.), that in all races the ventral side of the trunk is +paler than the dorsal side, and the inner surface of the extremities +paler than the outer side, cannot be explained by sexual selection in +the Darwinian sense. + +With this I conclude my brief survey of the rich contents of Darwin's +book. I may be permitted to conclude by quoting the magnificent final +words of "The Descent of Man": "We must, however, acknowledge, as it +seems to me, that man, with all his noble qualities, with sympathy which +feels for the most debased, with benevolence which extends not only +to other men but to the humblest living creature, with his god-like +intellect which has penetrated into the movements and constitution of +the solar system--with all these exalted powers--Man still bears in his +bodily frame the indelible stamp of his lowly origin." (Ibid. page 947.) + +What has been the fate of Darwin's doctrines since his great +achievement? How have they been received and followed up by the +scientific and lay world? And what do the successors of the mighty hero +and genius think now in regard to the origin of the human race? + +At the present time we are incomparably more favourably placed than +Darwin was for answering this question of all questions. We have at our +command an incomparably greater wealth of material than he had at his +disposal. And we are more fortunate than he in this respect, that we +now know transition-forms which help to fill up the gap, still great, +between the lowest human races and the highest apes. Let us consider +for a little the more essential additions to our knowledge since the +publication of "The Descent of Man". + +Since that time our knowledge of animal embryos has increased +enormously. While Darwin was obliged to content himself with comparing +a human embryo with that of a dog, there are now available the youngest +embryos of monkeys of all possible groups (Orang, Gibbon, Semnopithecus, +Macacus), thanks to Selenka's most successful tour in the East Indies in +search of such material. We can now compare corresponding stages of +the lower monkeys and of the Anthropoid apes with human embryos, and +convince ourselves of their great resemblance to one another, thus +strengthening enormously the armour prepared by Darwin in defence of his +view on man's nearest relatives. It may be said that Selenka's material +fils up the blanks in Darwin's array of proofs in the most satisfactory +manner. + +The deepening of our knowledge of comparative anatomy also gives us much +surer foundations than those on which Darwin was obliged to build. Just +of late there have been many workers in the domain of the anatomy of +apes and lemurs, and their investigations extend to the most different +organs. Our knowledge of fossil apes and lemurs has also become much +wider and more exact since Darwin's time: the fossil lemurs have been +especially worked up by Cope, Forsyth Major, Ameghino, and others. +Darwin knew very little about fossil monkeys. He mentions two or three +anthropoid apes as occurring in the Miocene of Europe ("Descent of +Man", page 240.), but only names Dryopithecus, the largest form from +the Miocene of France. It was erroneously supposed that this form was +related to Hylobates. We now know not only a form that actually stands +near to the gibbon (Pliopithecus), and remains of other anthropoids +(Pliohylobates and the fossil chimpanzee, Palaeopithecus), but also +several lower catarrhine monkeys, of which Mesopithecus, a form nearly +related to the modern Sacred Monkeys (a species of Semnopithecus) and +found in strata of the Miocene period in Greece, is the most important. +Quite recently, too, Ameghino's investigations have made us acquainted +with fossil monkeys from South America (Anthropops, Homunculus), which, +according to their discoverer, are to be regarded as in the line of +human descent. + +What Darwin missed most of all--intermediate forms between apes +and man--has been recently furnished. (E. Dubois, as is well known, +discovered in 1893, near Trinil in Java, in the alluvial deposits of +the river Bengawan, an important form represented by a skull-cap, some +molars, and a femur. His opinion--much disputed as it has been--that in +this form, which he named Pithecanthropus, he has found a long-desired +transition-form is shared by the present writer. And although the +geological age of these fossils, which, according to Dubois, belong to +the uppermost Tertiary series, the Pliocene, has recently been fixed +at a later date (the older Diluvium)), the MORPHOLOGICAL VALUE of +these interesting remains, that is, the intermediate position of +Pithecanthropus, still holds good. Volz says with justice ("Das +geologische Alter der Pithecanthropus-Schichten bei Trinil, Ost-Java". +"Neues Jahrb. f.Mineralogie". Festband, 1907.), that even if +Pithecanthropus is not THE missing link, it is undoubtedly _A_ missing +link. + +As on the one hand there has been found in Pithecanthropus a form which, +though intermediate between apes and man, is nevertheless more closely +allied to the apes, so on the other hand, much progress has been made +since Darwin's day in the discovery and description of the older +human remains. Since the famous roof of a skull and the bones of the +extremities belonging to it were found in 1856 in the Neandertal near +Dusseldorf, the most varied judgments have been expressed in regard +to the significance of the remains and of the skull in particular. +In Darwin's "Descent of Man" there is only a passing allusion to them +("Descent of Man", page 82.) in connection with the discussion of the +skull-capacity, although the investigations of Schaaffhausen, King, and +Huxley were then known. I believe I have shown, in a series of papers, +that the skull in question belongs to a form different from any of the +races of man now living, and, with King and Cope, I regard it as at +least a different species from living man, and have therefore designated +it Homo primigenius. The form unquestionably belongs to the older +Diluvium, and in the later Diluvium human forms already appear, which +agree in all essential points with existing human races. + +As far back as 1886 the value of the Neandertal skull was greatly +enhanced by Fraipont's discovery of two skulls and skeletons from Spy in +Belgium. These are excellently described by their discoverer ("La race +humaine de Neanderthal ou de Canstatt en Belgique". "Arch. de Biologie", +VII. 1887.), and are regarded as belonging to the same group of forms +as the Neandertal remains. In 1899 and the following years came the +discovery by Gorjanovic-Kramberger of different skeletal parts of +at least ten individuals in a cave near Krapina in Croatia. +(Gorjanovic-Kramberger "Der diluviale Mensch von Krapina in Kroatien", +1906.) It is in particular the form of the lower jaw which is different +from that of all recent races of man, and which clearly indicates +the lowly position of Homo primigenius, while, on the other hand, the +long-known skull from Gibraltar, which I ("Studien zur Vorgeschichte des +Menschen", 1906, pages 154 ff.) have referred to Homo primigenius, and +which has lately been examined in detail by Sollas ("On the cranial and +facial characters of the Neandertal Race". "Trans. R. Soc." London, vol. +199, 1908, page 281.), has made us acquainted with the surprising shape +of the eye-orbit, of the nose, and of the whole upper part of the face. +Isolated lower jaws found at La Naulette in Belgium, and at Malarnaud +in France, increase our material which is now as abundant as could be +desired. The most recent discovery of all is that of a skull dug up in +August of this year (1908) by Klaatsch and Hauser in the lower grotto +of the Le Moustier in Southern France, but this skull has not yet +been fully described. Thus Homo primigenius must also be regarded as +occupying a position in the gap existing between the highest apes and +the lowest human races, Pithecanthropus, standing in the lower part of +it, and Homo primigenius in the higher, near man. In order to prevent +misunderstanding, I should like here to emphasise that in arranging this +structural series--anthropoid apes, Pithecanthropus, Homo primigenius, +Homo sapiens--I have no intention of establishing it as a direct +genealogical series. I shall have something to say in regard to the +genetic relations of these forms, one to another, when discussing the +different theories of descent current at the present day. ((Since +this essay was written Schoetensack has discovered near Heidelberg +and briefly described an exceedingly interesting lower jaw from rocks +between the Pliocene and Diluvial beds. This exhibits interesting +differences from the forms of lower jaw of Homo primigenius. +(Schoetensack "Der Unterkiefer des Homo heidelbergensis". Leipzig, +1908.) G.S.)) + +In quite a different domain from that of morphological relationship, +namely in the physiological study of the blood, results have recently +been gained which are of the highest importance to the doctrine of +descent. Uhlenhuth, Nuttall, and others have established the fact +that the blood-serum of a rabbit which has previously had human blood +injected into it, forms a precipitate with human blood. This biological +reaction was tried with a great variety of mammalian species, and it was +found that those far removed from man gave no precipitate under these +conditions. But as in other cases among mammals all nearly related forms +yield an almost equally marked precipitate, so the serum of a rabbit +treated with human blood and then added to the blood of an anthropoid +ape gives ALMOST as marked a precipitate as in human blood; the reaction +to the blood of the lower Eastern monkeys is weaker, that to the Western +monkeys weaker still; indeed in this last case there is only a slight +clouding after a considerable time and no actual precipitate. The blood +of the Lemuridae (Nuttall) gives no reaction or an extremely weak one, +that of the other mammals none whatever. We have in this not only a +proof of the literal blood-relationship between man and apes, but the +degree of relationship with the different main groups of apes can be +determined beyond possibility of mistake. + +Finally, it must be briefly mentioned that in regard to remains of human +handicraft also, the material at our disposal has greatly increased of +late years, that, as a result of this, the opinions of archaeologists +have undergone many changes, and that, in particular, their views in +regard to the age of the human race have been greatly influenced. There +is a tendency at the present time to refer the origin of man back to +Tertiary times. It is true that no remains of Tertiary man have been +found, but flints have been discovered which, according to the opinion +of most investigators, bear traces either of use, or of very primitive +workmanship. Since Rutot's time, following Mortillet's example, +investigators have called these "eoliths," and they have been traced +back by Verworn to the Miocene of the Auvergne, and by Rutot even to the +upper Oligocene. Although these eoliths are even nowadays the subject of +many different views, the preoccupation with them has kept the problem +of the age of the human race continually before us. + +Geology, too, has made great progress since the days of Darwin and +Lyell, and has endeavoured with satisfactory results to arrange the +human remains of the Diluvial period in chronological order (Penck). I +do not intend to enter upon the question of the primitive home of the +human race; since the space at my disposal will not allow of my +touching even very briefly upon all the departments of science which are +concerned in the problem of the descent of man. How Darwin would have +rejoiced over each of the discoveries here briefly outlined! What use +he would have made of the new and precious material, which would have +prevented the discouragement from which he suffered when preparing the +second edition of "The Descent of Man"! But it was not granted to him to +see this progress towards filling up the gaps in his edifice of which he +was so painfully conscious. + +He did, however, have the satisfaction of seeing his ideas steadily +gaining ground, notwithstanding much hostility and deep-rooted +prejudice. Even in the years between the appearance of "The Origin +of Species" and of the first edition of the "Descent", the idea of a +natural descent of man, which was only briefly indicated in the work of +1859, had been eagerly welcomed in some quarters. It has been already +pointed out how brilliantly Huxley contributed to the defence and +diffusion of Darwin's doctrines, and how in "Man's Place in Nature" +he has given us a classic work as a foundation for the doctrine of +the descent of man. As Huxley was Darwin's champion in England, so in +Germany Carl Vogt, in particular, made himself master of the Darwinian +ideas. But above all it was Haeckel who, in energy, eagerness for +battle, and knowledge may be placed side by side with Huxley, who took +over the leadership in the controversy over the new conception of the +universe. As far back as 1866, in his "Generelle Morphologie", he had +inquired minutely into the question of the descent of man, and not +content with urging merely the general theory of descent from lower +animal forms, he drew up for the first time genealogical trees showing +the close relationships of the different animal groups; the last of +these illustrated the relationships of Mammals, and among them of all +groups of the Primates, including man. It was Haeckel's genealogical +trees that formed the basis of the special discussion of the +relationships of man, in the sixth chapter of Darwin's "Descent of Man". + +In the last section of this essay I shall return to Haeckel's conception +of the special descent of man, the main features of which he still +upholds, and rightly so. Haeckel has contributed more than any one else +to the spread of the Darwinian doctrine. + +I can only allow myself a few words as to the spread of the theory +of the natural descent of man in other countries. The Parisian +anthropological school, founded and guided by the genius of Broca, took +up the idea of the descent of man, and made many notable contributions +to it (Broca, Manouvrier, Mahoudeau, Deniker and others). In England +itself Darwin's work did not die. Huxley took care of that, for he, with +his lofty and unprejudiced mind, dominated and inspired English biology +until his death on June 29, 1895. He had the satisfaction shortly before +his death of learning of Dubois' discovery, which he illustrated by a +humorous sketch. ("Life and Letters of Thomas Henry Huxley", Vol. II. +page 394.) But there are still many followers in Darwin's footsteps +in England. Keane has worked at the special genealogical tree of the +Primates; Keith has inquired which of the anthropoid apes has the +greatest number of characters in common with man; Morris concerns +himself with the evolution of man in general, especially with +his acquisition of the erect position. The recent discoveries of +Pithecanthropus and Homo primigenius are being vigorously discussed; but +the present writer is not in a position to form an opinion of the +extent to which the idea of descent has penetrated throughout England +generally. + +In Italy independent work in the domain of the descent of man is being +produced, especially by Morselli; with him are associated, in the +investigation of related problems, Sergi and Giuffrida-Ruggeri. From +the ranks of American investigators we may single out in particular the +eminent geologist Cope, who championed with much decision the idea +of the specific difference of Homo neandertalensis (primigenius) and +maintained a more direct descent of man from the fossil Lemuridae. In +South America too, in Argentina, new life is stirring in this department +of science. Ameghino in Buenos Ayres has awakened the fossil primates +of the Pampas formation to new life; he even believes that in +Tetraprothomo, represented by a femur, he has discovered a direct +ancestor of man. Lehmann-Nitsche is working at the other side of the +gulf between apes and men, and he describes a remarkable first cervical +vertebra (atlas) from Monte Hermoso as belonging to a form which +may bear the same relation to Homo sapiens in South America as Homo +primigenius does in the Old World. After a minute investigation he +establishes a human species Homo neogaeus, while Ameghino ascribes this +atlas vertebra to his Tetraprothomo. + +Thus throughout the whole scientific world there is arising a new +life, an eager endeavour to get nearer to Huxley's problema maximum, +to penetrate more deeply into the origin of the human race. There are +to-day very few experts in anatomy and zoology who deny the animal +descent of man in general. Religious considerations, old prejudices, +the reluctance to accept man, who so far surpasses mentally all +other creatures, as descended from "soulless" animals, prevent a few +investigators from giving full adherence to the doctrine. But there are +very few of these who still postulate a special act of creation for +man. Although the majority of experts in anatomy and zoology accept +unconditionally the descent of man from lower forms, there is much +diversity of opinion among them in regard to the special line of +descent. + +In trying to establish any special hypothesis of descent, whether by +the graphic method of drawing up genealogical trees or otherwise, let us +always bear in mind Darwin's words ("Descent of Man", page 229.) and use +them as a critical guiding line: "As we have no record of the lines of +descent, the pedigree can be discovered only by observing the degrees of +resemblance between the beings which are to be classed." Darwin carries +this further by stating "that resemblances in several unimportant +structures, in useless and rudimentary organs, or not now functionally +active, or in an embryological condition, are by far the most +serviceable for classification." (Loc. cit.) It has also to be +remembered that NUMEROUS separate points of agreement are of much +greater importance than the amount of similarity or dissimilarity in a +few points. + +The hypotheses as to descent current at the present day may be divided +into two main groups. The first group seeks for the roots of the human +race not among any of the families of the apes--the anatomically nearest +forms--nor among their very similar but less specialised ancestral +forms, the fossil representatives of which we can know only in part, +but, setting the monkeys on one side, it seeks for them lower down among +the fossil Eocene Pseudo-lemuridae or Lemuridae (Cope), or even among +the primitive pentadactylous Eocene forms, which may either have led +directly to the evolution of man (Adloff), or have given rise to an +ancestral form common to apes and men (Klaatsch (Klaatsch in his last +publications speaks in the main only of an ancestral form common to men +and anthropoid apes.), Giuffrida-Ruggeri). The common ancestral form, +from which man and apes are thus supposed to have arisen independently, +may explain the numerous resemblances which actually exist between +them. That is to say, all the characters upon which the great structural +resemblance between apes and man depends must have been present in their +common ancestor. Let us take an example of such a common character. The +bony external ear-passage is in general as highly developed in the lower +Eastern monkeys and the anthropoid apes as in man. This character must, +therefore, have already been present in the common primitive form. In +that case it is not easy to understand why the Western monkeys have +not also inherited the character, instead of possessing only a tympanic +ring. But it becomes more intelligible if we assume that forms with a +primitive tympanic ring were the original type, and that from these were +evolved, on the one hand, the existing New World monkeys with persistent +tympanic ring, and on the other an ancestral form common to the lower +Old World monkeys, the anthropoid apes and man. For man shares with +these the character in question, and it is also one of the "unimportant" +characters required by Darwin. Thus we have two divergent lines arising +from the ancestral form, the Western monkeys (Platyrrhine) on the one +hand, and an ancestral form common to the lower Eastern monkeys, the +anthropoid apes, and man, on the other. But considerations similar to +those which showed it to be impossible that man should have developed +from an ancestor common to him and the monkeys, yet outside of and +parallel with these, may be urged also against the likelihood of a +parallel evolution of the lower Eastern monkeys, the anthropoid apes, +and man. The anthropoid apes have in common with man many characters +which are not present in the lower Old World monkeys. These characters +must therefore have been present in the ancestral form common to the +three groups. But here, again, it is difficult to understand why the +lower Eastern monkeys should not also have inherited these characters. +As this is not the case, there remains no alternative but to assume +divergent evolution from an indifferent form. The lower Eastern monkeys +are carrying on the evolution in one direction--I might almost say +towards a blind alley--while anthropoids and men have struck out a +progressive path, at first in common, which explains the many points of +resemblance between them, without regarding man as derived directly +from the anthropoids. Their many striking points of agreement indicate a +common descent, and cannot be explained as phenomena of convergence. + +I believe I have shown in the above sketch that a theory which derives +man directly from lower forms without regarding apes as transition-types +leads ad absurdum. The close structural relationship between man and +monkeys can only be understood if both are brought into the same line +of evolution. To trace man's line of descent directly back to the old +Eocene mammals, alongside of, but with no relation to these very similar +forms, is to abandon the method of exact comparison, which, as Darwin +rightly recognised, alone justifies us in drawing up genealogical trees +on the basis of resemblances and differences. The farther down we go the +more does the ground slip from beneath our feet. Even the Lemuridae +show very numerous divergent conditions, much more so the Eocene +mammals (Creodonta, Condylarthra), the chief resemblance of which to man +consists in the possession of pentadactylous hands and feet! Thus the +farther course of the line of descent disappears in the darkness of the +ancestry of the mammals. With just as much reason we might pass by the +Vertebrates altogether, and go back to the lower Invertebrates, but +in that case it would be much easier to say that man has arisen +independently, and has evolved, without relation to any animals, from +the lowest primitive form to his present isolated and dominant position. +But this would be to deny all value to classification, which must after +all be the ultimate basis of a genealogical tree. We can, as Darwin +rightly observed, only infer the line of descent from the degree of +resemblance between single forms. If we regard man as directly derived +from primitive forms very far back, we have no way of explaining the +many points of agreement between him and the monkeys in general, and the +anthropoid apes in particular. These must remain an inexplicable marvel. + +I have thus, I trust, shown that the first class of special theories +of descent, which assumes that man has developed, parallel with the +monkeys, but without relation to them, from very low primitive forms +cannot be upheld, because it fails to take into account the close +structural affinity of man and monkeys. I cannot but regard this +hypothesis as lamentably retrograde, for it makes impossible any +application of the facts that have been discovered in the course of +the anatomical and embryological study of man and monkeys, and indeed +prejudges investigations of that class as pointless. The whole method is +perverted; an unjustifiable theory of descent is first formulated with +the aid of the imagination, and then we are asked to declare that all +structural relations between man and monkeys, and between the different +groups of the latter, are valueless,--the fact being that they are the +only true basis on which a genealogical tree can be constructed. + +So much for this most modern method of classification, which has +probably found adherents because it would deliver us from the +relationship to apes which many people so much dislike. In contrast +to it we have the second class of special hypotheses of descent, which +keeps strictly to the nearest structural relationships. This is the only +basis that justifies the drawing up of a special hypothesis of descent. +If this fundamental proposition be recognised, it will be admitted that +the doctrine of special descent upheld by Haeckel, and set forth in +Darwin's "Descent of Man", is still valid to-day. In the genealogical +tree, man's place is quite close to the anthropoid apes; these again +have as their nearest relatives the lower Old World monkeys, and their +progenitors must be sought among the less differentiated Platyrrhine +monkeys, whose most important characters have been handed on to the +present day New World monkeys. How the different genera are to be +arranged within the general scheme indicated depends in the main on +the classificatory value attributed to individual characters. This is +particularly true in regard to Pithecanthropus, which I consider as the +root of a branch which has sprung from the anthropoid ape root and has +led up to man; the latter I have designated the family of the Hominidae. + +For the rest, there are, as we have said, various possible ways of +constructing the narrower genealogy within the limits of this branch +including men and apes, and these methods will probably continue to +change with the accumulation of new facts. Haeckel himself has modified +his genealogical tree of the Primates in certain details since the +publication of his "Generelle Morphologie" in 1866, but its general +basis remains the same. (Haeckel's latest genealogical tree is to be +found in his most recent work, "Unsere Ahnenreihe". Jena, 1908.) All the +special genealogical trees drawn up on the lines laid down by Haeckel +and Darwin--and that of Dubois may be specially mentioned--are based, in +general, on the close relationship of monkeys and men, although they may +vary in detail. Various hypotheses have been formulated on these lines, +with special reference to the evolution of man. "Pithecanthropus" is +regarded by some authorities as the direct ancestor of man, by others as +a side-track failure in the attempt at the evolution of man. The problem +of the monophyletic or polyphyletic origin of the human race has also +been much discussed. Sergi (Sergi G. "Europa", 1908.) inclines towards +the assumption of a polyphyletic origin of the three main races of man, +the African primitive form of which has given rise also to the +gorilla and chimpanzee, the Asiatic to the Orang, the Gibbon, and +Pithecanthropus. Kollmann regards existing human races as derived from +small primitive races (pigmies), and considers that Homo primigenius +must have arisen in a secondary and degenerative manner. + +But this is not the place, nor have I the space to criticise the various +special theories of descent. One, however, must receive particular +notice. According to Ameghino, the South American monkeys (Pitheculites) +from the oldest Tertiary of the Pampas are the forms from which have +arisen the existing American monkeys on the one hand, and on the other, +the extinct South American Homunculidae, which are also small forms. +From these last, anthropoid apes and man have, he believes, been +evolved. Among the progenitors of man, Ameghino reckons the form +discovered by him (Tetraprothomo), from which a South American primitive +man, Homo pampaeus, might be directly evolved, while on the other hand +all the lower Old World monkeys may have arisen from older fossil +South American forms (Clenialitidae), the distribution of which may +be explained by the bridge formerly existing between South America and +Africa, as may be the derivation of all existing human races from Homo +pampaeus. (See Ameghino's latest paper, "Notas preliminares sobre el +Tetraprothomo argentinus", etc. "Anales del Museo nacional de Buenos +Aires", XVI. pages 107-242, 1907.) The fossil forms discovered by +Ameghino deserve the most minute investigation, as does also the fossil +man from South America of which Lehmann-Nitsche ("Nouvelles recherches +sur la formation pampeenne et l'homme fossile de la Republique +Argentine". "Rivista del Museo de la Plata", T. XIV. pages 193-488.) has +made a thorough study. + +It is obvious that, notwithstanding the necessity for fitting man's line +of descent into the genealogical tree of the Primates, especially the +apes, opinions in regard to it differ greatly in detail. This could not +be otherwise, since the different Primate forms, especially the fossil +forms, are still far from being exhaustively known. But one thing +remains certain,--the idea of the close relationship between man and +monkeys set forth in Darwin's "Descent of Man". Only those who deny the +many points of agreement, the sole basis of classification, and thus of +a natural genealogical tree, can look upon the position of Darwin and +Haeckel as antiquated, or as standing on an insufficient foundation. +For such a genealogical tree is nothing more than a summarised +representation of what is known in regard to the degree of resemblance +between the different forms. + +Darwin's work in regard to the descent of man has not been surpassed; +the more we immerse ourselves in the study of the structural +relationships between apes and man, the more is our path illumined by +the clear light radiating from him, and through his calm and deliberate +investigation, based on a mass of material in the accumulation of which +he has never had an equal. Darwin's fame will be bound up for all time +with the unprejudiced investigation of the question of all questions, +the descent of the human race. + + + + +VIII. CHARLES DARWIN AS AN ANTHROPOLOGIST. By Ernst Haeckel. + +Professor of Zoology in the University of Jena. + +The great advance that anthropology has made in the second half of the +nineteenth century is due in the first place, to Darwin's discovery of +the origin of man. No other problem in the whole field of research is so +momentous as that of "Man's place in nature," which was justly described +by Huxley (1863) as the most fundamental of all questions. Yet the +scientific solution of this problem was impossible until the theory of +descent had been established. + +It is now a hundred years since the great French biologist Jean Lamarck +published his "Philosophie Zoologique". By a remarkable coincidence the +year in which that work was issued, 1809, was the year of the birth of +his most distinguished successor, Charles Darwin. Lamarck had +already recognised that the descent of man from a series of other +Vertebrates--that is, from a series of Ape-like Primates--was +essentially involved in the general theory of transformation which +he had erected on a broad inductive basis; and he had sufficient +penetration to detect the agencies that had been at work in the +evolution of the erect bimanous man from the arboreal and quadrumanous +ape. He had, however, few empirical arguments to advance in support +of his hypothesis, and it could not be established until the further +development of the biological sciences--the founding of comparative +embryology by Baer (1828) and of the cell-theory by Schleiden and +Schwann (1838), the advance of physiology under Johannes Muller (1833), +and the enormous progress of palaeontology and comparative anatomy +between 1820 and 1860--provided this necessary foundation. Darwin was +the first to coordinate the ample results of these lines of research. +With no less comprehensiveness than discrimination he consolidated them +as a basis of a modified theory of descent, and associated with them +his own theory of natural selection, which we take to be distinctive +of "Darwinism" in the stricter sense. The illuminating truth of these +cumulative arguments was so great in every branch of biology that, +in spite of the most vehement opposition, the battle was won within a +single decade, and Darwin secured the general admiration and recognition +that had been denied to his forerunner, Lamarck, up to the hour of his +death (1829). + +Before, however, we consider the momentous influence that Darwinism has +had in anthropology, we shall find it useful to glance at its history +in the course of the last half century, and notice the various theories +that have contributed to its advance. The first attempt to give +extensive expression to the reform of biology by Darwin's work will be +found in my "Generelle Morphologie" (1866) ("Generelle Morphologie +der Organismen", 2 vols., Berlin, 1866.) which was followed by a more +popular treatment of the subject in my "Naturliche Schopfungsgeschichte" +(1868) (English translation; "The History of Creation", London, +1876.), a compilation from the earlier work. In the first volume of the +"Generelle Morphologie" I endeavoured to show the great importance +of evolution in settling the fundamental questions of biological +philosophy, especially in regard to comparative anatomy. In the second +volume I dealt broadly with the principle of evolution, distinguishing +ontogeny and phylogeny as its two coordinate main branches, and +associating the two in the Biogenetic Law. The Law may be formulated +thus: "Ontogeny (embryology or the development of the individual) is a +concise and compressed recapitulation of phylogeny (the palaeontological +or genealogical series) conditioned by laws of heredity and adaptation." +The "Systematic introduction to general evolution," with which the +second volume of the "Generelle Morphologie" opens, was the first +attempt to draw up a natural system of organisms (in harmony with +the principles of Lamarck and Darwin) in the form of a hypothetical +pedigree, and was provisionally set forth in eight genealogical tables. + +In the nineteenth chapter of the "Generelle Morphologie"--a part of +which has been republished, without any alteration, after a lapse of +forty years--I made a critical study of Lamarck's theory of descent and +of Darwin's theory of selection, and endeavoured to bring the complex +phenomena of heredity and adaptation under definite laws for the first +time. Heredity I divided into conservative and progressive: adaptation +into indirect (or potential) and direct (or actual). I then found +it possible to give some explanation of the correlation of the two +physiological functions in the struggle for life (selection), and to +indicate the important laws of divergence (or differentiation) and +complexity (or division of labour), which are the direct and inevitable +outcome of selection. Finally, I marked off dysteleology as the science +of the aimless (vestigial, abortive, atrophied, and useless) organs +and parts of the body. In all this I worked from a strictly monistic +standpoint, and sought to explain all biological phenomena on the +mechanical and naturalistic lines that had long been recognised in the +study of inorganic nature. Then (1866), as now, being convinced of the +unity of nature, the fundamental identity of the agencies at work in the +inorganic and the organic worlds, I discarded vitalism, teleology, and +all hypotheses of a mystic character. + +It was clear from the first that it was essential, in the monistic +conception of evolution, to distinguish between the laws of conservative +and progressive heredity. Conservative heredity maintains from +generation to generation the enduring characters of the species. Each +organism transmits to its descendants a part of the morphological +and physiological qualities that it has received from its parents and +ancestors. On the other hand, progressive heredity brings new characters +to the species--characters that were not found in preceding generations. +Each organism may transmit to its offspring a part of the morphological +and physiological features that it has itself acquired, by adaptation, +in the course of its individual career, through the use or disuse of +particular organs, the influence of environment, climate, nutrition, +etc. At that time I gave the name of "progressive heredity" to +this inheritance of acquired characters, as a short and convenient +expression, but have since changed the term to "transformative heredity" +(as distinguished from conservative). This term is preferable, +as inherited regressive modifications (degeneration, retrograde +metamorphisis, etc.) come under the same head. + +Transformative heredity--or the transmission of acquired characters--is +one of the most important principles in evolutionary science. Unless +we admit it most of the facts of comparative anatomy and physiology are +inexplicable. That was the conviction of Darwin no less than of Lamarck, +of Spencer as well as Virchow, of Huxley as well as Gegenbaur, indeed of +the great majority of speculative biologists. This fundamental principle +was for the first time called in question and assailed in 1885 by +August Weismann of Freiburg, the eminent zoologist to whom the theory +of evolution owes a great deal of valuable support, and who has attained +distinction by his extension of the theory of selection. In explanation +of the phenomena of heredity he introduced a new theory, the "theory of +the continuity of the germ-plasm." According to him the living substance +in all organisms consists of two quite distinct kinds of plasm, somatic +and germinal. The permanent germ-plasm, or the active substance of the +two germ-cells (egg-cell and sperm-cell), passes unchanged through a +series of generations, and is not affected by environmental influences. +The environment modifies only the soma-plasm, the organs and tissues +of the body. The modifications that these parts undergo through the +influence of the environment or their own activity (use and habit), do +not affect the germ-plasm, and cannot therefore be transmitted. + +This theory of the continuity of the germ-plasm has been expounded by +Weismann during the last twenty-four years in a number of able volumes, +and is regarded by many biologists, such as Mr Francis Galton, Sir E. +Ray Lankester, and Professor J. Arthur Thomson (who has recently made +a thoroughgoing defence of it in his important work "Heredity" (London, +1908.)), as the most striking advance in evolutionary science. On the +other hand, the theory has been rejected by Herbert Spencer, Sir W. +Turner, Gegenbaur, Kolliker, Hertwig, and many others. For my part I +have, with all respect for the distinguished Darwinian, contested +the theory from the first, because its whole foundation seems to me +erroneous, and its deductions do not seem to be in accord with the main +facts of comparative morphology and physiology. Weismann's theory in its +entirety is a finely conceived molecular hypothesis, but it is devoid of +empirical basis. The notion of the absolute and permanent independence +of the germ-plasm, as distinguished from the soma-plasm, is purely +speculative; as is also the theory of germinal selection. The +determinants, ids, and idants, are purely hypothetical elements. The +experiments that have been devised to demonstrate their existence really +prove nothing. + +It seems to me quite improper to describe this hypothetical structure +as "Neodarwinism." Darwin was just as convinced as Lamarck of the +transmission of acquired characters and its great importance in the +scheme of evolution. I had the good fortune to visit Darwin at Down +three times and discuss with him the main principles of his system, and +on each occasion we were fully agreed as to the incalculable importance +of what I call transformative inheritance. It is only proper to point +out that Weismann's theory of the germ-plasm is in express contradiction +to the fundamental principles of Darwin and Lamarck. Nor is it more +acceptable in what one may call its "ultradarwinism"--the idea that the +theory of selection explains everything in the evolution of the organic +world. This belief in the "omnipotence of natural selection" was not +shared by Darwin himself. Assuredly, I regard it as of the utmost +value, as the process of natural selection through the struggle for +life affords an explanation of the mechanical origin of the adapted +organisation. It solves the great problem: how could the finely adapted +structure of the animal or plant body be formed unless it was built on a +preconceived plan? It thus enables us to dispense with the teleology of +the metaphysician and the dualist, and to set aside the old mythological +and poetic legends of creation. The idea had occurred in vague form to +the great Empedocles 2000 years before the time of Darwin, but it was +reserved for modern research to give it ample expression. Nevertheless, +natural selection does not of itself give the solution of all our +evolutionary problems. It has to be taken in conjunction with the +transformism of Lamarck, with which it is in complete harmony. + +The monumental greatness of Charles Darwin, who surpasses every other +student of science in the nineteenth century by the loftiness of his +monistic conception of nature and the progressive influence of his +ideas, is perhaps best seen in the fact that not one of his many +successors has succeeded in modifying his theory of descent in any +essential point or in discovering an entirely new standpoint in the +interpretation of the organic world. Neither Nageli nor Weismann, +neither De Vries nor Roux, has done this. Nageli, in his +"Mechanisch-Physiologische Theorie der Abstammungslehre" (Munich, +1884.), which is to a great extent in agreement with Weismann, +constructed a theory of the idioplasm, that represents it (like the +germ-plasm) as developing continuously in a definite direction from +internal causes. But his internal "principle of progress" is at the +bottom just as teleological as the vital force of the Vitalists, and +the micellar structure of the idioplasm is just as hypothetical as the +"dominant" structure of the germ-plasm. In 1889 Moritz Wagner sought to +explain the origin of species by migration and isolation, and on that +basis constructed a special "migration-theory." This, however, is not +out of harmony with the theory of selection. It merely elevates one +single factor in the theory to a predominant position. Isolation is +only a special case of selection, as I had pointed out in the fifteenth +chapter of my "Natural history of creation". The "mutation-theory" of De +Vries ("Die Mutationstheorie", Leipzig, 1903.), that would explain the +origin of species by sudden and saltatory variations rather than by +gradual modification, is regarded by many botanists as a great step +in advance, but it is generally rejected by zoologists. It affords no +explanation of the facts of adaptation, and has no causal value. + +Much more important than these theories is that of Wilhelm Roux ("Der +Kampf der Theile im Organismus", Leipzig, 1881.) of "the struggle of +parts within the organism, a supplementation of the theory of mechanical +adaptation." He explains the functional autoformation of the purposive +structure by a combination of Darwin's principle of selection with +Lamarck's idea of transformative heredity, and applies the two +in conjunction to the facts of histology. He lays stress on the +significance of functional adaptation, which I had described in 1866, +under the head of cumulative adaptation, as the most important factor in +evolution. Pointing out its influence in the cell-life of the tissues, +he puts "cellular selection" above "personal selection," and shows how +the finest conceivable adaptations in the structure of the tissue may +be brought about quite mechanically, without preconceived plan. This +"mechanical teleology" is a valuable extension of Darwin's monistic +principle of selection to the whole field of cellular physiology and +histology, and is wholly destructive of dualistic vitalism. + +The most important advance that evolution has made since Darwin and +the most valuable amplification of his theory of selection is, in my +opinion, the work of Richard Semon: "Die Mneme als erhaltendes Prinzip +im Wechsel des organischen Geschehens" (Leipzig, 1904.). He offers a +psychological explanation of the facts of heredity by reducing them to a +process of (unconscious) memory. The physiologist Ewald Hering had shown +in 1870 that memory must be regarded as a general function of organic +matter, and that we are quite unable to explain the chief vital +phenomena, especially those of reproduction and inheritance, unless +we admit this unconscious memory. In my essay "Die Perigenesis der +Plastidule" (Berlin, 1876.) I elaborated this far-reaching idea, and +applied the physical principle of transmitted motion to the plastidules, +or active molecules of plasm. I concluded that "heredity is the memory +of the plastidules, and variability their power of comprehension." This +"provisional attempt to give a mechanical explanation of the elementary +processes of evolution" I afterwards extended by showing that +sensitiveness is (as Carl Nageli, Ernst Mach, and Albrecht Rau express +it) a general quality of matter. This form of panpsychism finds its +simplest expression in the "trinity of substance." + +To the two fundamental attributes that Spinoza ascribed to +substance--Extension (matter as occupying space) and Cogitation +(energy, force)--we now add the third fundamental quality of Psychoma +(sensitiveness, soul). I further elaborated this trinitarian conception +of substance in the nineteenth chapter of my "Die Lebenswunder" (1904) +("Wonders of Life", London, 1904.), and it seems to me well calculated +to afford a monistic solution of many of the antitheses of philosophy. + +This important Mneme-theory of Semon and the luminous physiological +experiments and observations associated with it not only throw +considerable light on transformative inheritance, but provide a sound +physiological foundation for the biogenetic law. I had endeavoured +to show in 1874, in the first chapter of my "Anthropogenie" (English +translation; "The Evolution of Man", 2 volumes, London, 1879 and 1905.), +that this fundamental law of organic evolution holds good generally, and +that there is everywhere a direct causal connection between ontogeny +and phylogeny. "Phylogenesis is the mechanical cause of ontogenesis"; in +other words, "The evolution of the stem or race is--in accordance with +the laws of heredity and adaptation--the real cause of all the changes +that appear, in a condensed form, in the development of the individual +organism from the ovum, in either the embryo or the larva." + +It is now fifty years since Charles Darwin pointed out, in the +thirteenth chapter of his epoch-making "Origin of Species", the +fundamental importance of embryology in connection with his theory of +descent: + +"The leading facts in embryology, which are second to none in +importance, are explained on the principle of variations in the many +descendants from some one ancient progenitor, having appeared at a not +very early period of life, and having been inherited at a corresponding +period." ("Origin of Species" (6th edition), page 396.) + +He then shows that the striking resemblance of the embryos and larvae +of closely related animals, which in the mature stage belong to widely +different species and genera, can only be explained by their descent +from a common progenitor. Fritz Muller made a closer study of these +important phenomena in the instructive instance of the Crustacean larva, +as given in his able work "Fur Darwin" (1864). (English translation; +"Facts and Arguments for Darwin", London, 1869.) I then, in 1872, +extended the range so as to include all animals (with the exception +of the unicellular Protozoa) and showed, by means of the theory of +the Gastraea, that all multicellular, tissue-forming animals--all +the Metazoa--develop in essentially the same way from the primary +germ-layers. I conceived the embryonic form, in which the whole +structure consists of only two layers of cells, and is known as the +gastrula, to be the ontogenetic recapitulation, maintained by tenacious +heredity, of a primitive common progenitor of all the Metazoa, the +Gastraea. At a later date (1895) Monticelli discovered that this +conjectural ancestral form is still preserved in certain primitive +Coelenterata--Pemmatodiscus, Kunstleria, and the nearly-related +Orthonectida. + +The general application of the biogenetic law to all classes of animals +and plants has been proved in my "Systematische Phylogenie". (3 volumes, +Berlin, 1894-96.) It has, however, been frequently challenged, both +by botanists and zoologists, chiefly owing to the fact that many have +failed to distinguish its two essential elements, palingenesis and +cenogenesis. As early as 1874 I had emphasised, in the first chapter +of my "Evolution of Man", the importance of discriminating carefully +between these two sets of phenomena: + +"In the evolutionary appreciation of the facts of embryology we must +take particular care to distinguish sharply and clearly between +the primary, palingenetic evolutionary processes and the secondary, +cenogenetic processes. The palingenetic phenomena, or embryonic +RECAPITULATIONS, are due to heredity, to the transmission of characters +from one generation to another. They enable us to draw direct inferences +in regard to corresponding structures in the development of the species +(e.g. the chorda or the branchial arches in all vertebrate embryos). The +cenogenetic phenomena, on the other hand, or the embryonic VARIATIONS, +cannot be traced to inheritance from a mature ancestor, but are due to +the adaptation of the embryo or the larva to certain conditions of +its individual development (e.g. the amnion, the allantois, and the +vitelline arteries in the embryos of the higher vertebrates). These +cenogenetic phenomena are later additions; we must not infer from them +that there were corresponding processes in the ancestral history, and +hence they are apt to mislead." + +The fundamental importance of these facts of comparative anatomy, +atavism, and the rudimentary organs, was pointed out by Darwin in the +first part of his classic work, "The Descent of Man and Selection in +Relation to Sex" (1871). ("Descent of Man" (Popular Edition), page 927.) +In the "General summary and conclusion" (chapter XXI.) he was able +to say, with perfect justice: "He who is not content to look, like a +savage, at the phenomena of nature as disconnected, cannot any longer +believe that man is the work of a separate act of creation. He will be +forced to admit that the close resemblance of the embryo of man to that, +for instance, of a dog--the construction of his skull, limbs, and whole +frame on the same plan with that of other mammals, independently of +the uses to which the parts may be put--the occasional reappearance of +various structures, for instance of several muscles, which man does not +normally possess, but which are common to the Quadrumana--and a crowd of +analogous facts--all point in the plainest manner to the conclusion that +man is the co-descendant with other mammals of a common progenitor." + +These few lines of Darwin's have a greater scientific value than +hundreds of those so-called "anthropological treatises," which give +detailed descriptions of single organs, or mathematical tables with +series of numbers and what are claimed to be "exact analyses," but are +devoid of synoptic conclusions and a philosophical spirit. + +Charles Darwin is not generally recognised as a great anthropologist, +nor does the school of modern anthropologists regard him as a leading +authority. In Germany, especially, the great majority of the members of +the anthropological societies took up an attitude of hostility to him +from the very beginning of the controversy in 1860. "The Descent of Man" +was not merely rejected, but even the discussion of it was forbidden on +the ground that it was "unscientific." + +The centre of this inveterate hostility for thirty years--especially +after 1877--was Rudolph Virchow of Berlin, the leading investigator in +pathological anatomy, who did so much for the reform of medicine by +his establishment of cellular pathology in 1858. As a prominent +representative of "exact" or "descriptive" anthropology, and lacking a +broad equipment in comparative anatomy and ontogeny, he was unable to +accept the theory of descent. In earlier years, and especially during +his splendid period of activity at Wurzburg (1848-1856), he had been a +consistent free-thinker, and had in a number of able articles (collected +in his "Gesammelte Abhandlungen") ("Gesammelte Abhandlungen zur +wissenschaftlichen Medizin", Berlin, 1856.) upheld the unity of human +nature, the inseparability of body and spirit. In later years at Berlin, +where he was more occupied with political work and sociology (especially +after 1866), he abandoned the positive monistic position for one of +agnosticism and scepticism, and made concessions to the dualistic dogma +of a spiritual world apart from the material frame. + +In the course of a Scientific Congress at Munich in 1877 the conflict +of these antithetic views of nature came into sharp relief. At this +memorable Congress I had undertaken to deliver the first address +(September 18th) on the subject of "Modern evolution in relation to the +whole of science." I maintained that Darwin's theory not only solved +the great problem of the origin of species, but that its implications, +especially in regard to the nature of man, threw considerable light on +the whole of science, and on anthropology in particular. The discovery +of the real origin of man by evolution from a long series of mammal +ancestors threw light on his place in nature in every aspect, as Huxley +had already shown in his excellent lectures of 1863. Just as all the +organs and tissues of the human body had originated from those of the +nearest related mammals, certain ape-like forms, so we were bound to +conclude that his mental qualities also had been derived from those of +his extinct primate ancestor. + +This monistic view of the origin and nature of man, which is now +admitted by nearly all who have the requisite acquaintance with +biology, and approach the subject without prejudice, encountered a sharp +opposition at that time. The opposition found its strongest expression +in an address that Virchow delivered at Munich four days afterwards +(September 22nd), on "The freedom of science in the modern State." He +spoke of the theory of evolution as an unproved hypothesis, and declared +that it ought not to be taught in the schools, because it was dangerous +to the State. "We must not," he said, "teach that man has descended from +the ape or any other animal." When Darwin, usually so lenient in his +judgment, read the English translation of Virchow's speech, he expressed +his disapproval in strong terms. But the great authority that Virchow +had--an authority well founded in pathology and sociology--and his +prestige as President of the German Anthropological Society, had the +effect of preventing any member of the Society from raising serious +opposition to him for thirty years. Numbers of journals and treatises +repeated his dogmatic statement: "It is quite certain that man has +descended neither from the ape nor from any other animal." In this he +persisted till his death in 1902. Since that time the whole position of +German anthropology has changed. The question is no longer whether +man was created by a distinct supernatural act or evolved from other +mammals, but to which line of the animal hierarchy we must look for the +actual series of ancestors. The interested reader will find an account +of this "battle of Munich" (1877) in my three Berlin lectures (April, +1905) ("Der Kampf um die Entwickelungs-Gedanken". (English translation; +"Last Words on Evolution", London, 1906.)) + +The main points in our genealogical tree were clearly recognised by +Darwin in the sixth chapter of the "Descent of Man". Lowly organised +fishes, like the lancelet (Amphioxus), are descended from lower +invertebrates resembling the larvae of an existing Tunicate +(Appendicularia). From these primitive fishes were evolved higher fishes +of the ganoid type and others of the type of Lepidosiren (Dipneusta). It +is a very small step from these to the Amphibia: + +"In the class of mammals the steps are not difficult to conceive which +led from the ancient Monotremata to the ancient Marsupials; and from +these to the early progenitors of the placental mammals. We may thus +ascend to the Lemuridae; and the interval is not very wide from these to +the Simiadae. The Simiadae then branched off into two great stems, +the New World and Old World monkeys; and from the latter, at a remote +period, Man, the wonder and glory of the Universe, proceeded." ("Descent +of Man" (Popular Edition), page 255.) + +In these few lines Darwin clearly indicated the way in which we were +to conceive our ancestral series within the vertebrates. It is fully +confirmed by all the arguments of comparative anatomy and embryology, +of palaeontology and physiology; and all the research of the subsequent +forty years has gone to establish it. The deep interest in geology which +Darwin maintained throughout his life and his complete knowledge of +palaeontology enabled him to grasp the fundamental importance of the +palaeontological record more clearly than anthropologists and zoologists +usually do. + +There has been much debate in subsequent decades whether Darwin himself +maintained that man was descended from the ape, and many writers +have sought to deny it. But the lines I have quoted verbatim from the +conclusion of the sixth chapter of the "Descent of Man" (1871) leave no +doubt that he was as firmly convinced of it as was his great +precursor Jean Lamarck in 1809. Moreover, Darwin adds, with particular +explicitness, in the "general summary and conclusion" (chapter XXI.) of +that standard work ("Descent of Man", page 930.): + +"By considering the embryological structure of man--the homologies +which he presents with the lower animals,--the rudiments which he +retains,--and the reversions to which he is liable, we can partly recall +in imagination the former condition of our early progenitors; and can +approximately place them in their proper place in the zoological series. +We thus learn that man is descended from a hairy, tailed quadruped, +probably arboreal in its habits, and an inhabitant of the Old World. +This creature, if its whole structure had been examined by a naturalist, +would have been classed amongst the Quadrumana, as surely as the still +more ancient progenitor of the Old and New World monkeys." + +These clear and definite lines leave no doubt that Darwin--so critical +and cautious in regard to important conclusions--was quite as firmly +convinced of the descent of man from the apes (the Catarrhinae, in +particular) as Lamarck was in 1809 and Huxley in 1863. + +It is to be noted particularly that, in these and other observations +on the subject, Darwin decidedly assumes the monophyletic origin of +the mammals, including man. It is my own conviction that this is of the +greatest importance. A number of difficult questions in regard to the +development of man, in respect of anatomy, physiology, psychology, +and embryology, are easily settled if we do not merely extend our +progonotaxis to our nearest relatives, the anthropoid apes and the +tailed monkeys from which these have descended, but go further back and +find an ancestor in the group of the Lemuridae, and still further back +to the Marsupials and Monotremata. The essential identity of all the +Mammals in point of anatomical structure and embryonic development--in +spite of their astonishing differences in external appearance and habits +of life--is so palpably significant that modern zoologists are agreed +in the hypothesis that they have all sprung from a common root, and that +this root may be sought in the earlier Palaeozoic Amphibia. + +The fundamental importance of this comparative morphology of the +Mammals, as a sound basis of scientific anthropology, was recognised +just before the beginning of the nineteenth century, when Lamarck first +emphasised (1794) the division of the animal kingdom into Vertebrates +and Invertebrates. Even thirteen years earlier (1781), when Goethe made +a close study of the mammal skeleton in the Anatomical Institute at +Jena, he was intensely interested to find that the composition of the +skull was the same in man as in the other mammals. His discovery of the +os intermaxillare in man (1784), which was contradicted by most of +the anatomists of the time, and his ingenious "vertebral theory of +the skull," were the splendid fruit of his morphological studies. They +remind us how Germany's greatest philosopher and poet was for many years +ardently absorbed in the comparative anatomy of man and the mammals, and +how he divined that their wonderful identity in structure was no mere +superficial resemblance, but pointed to a deep internal connection. +In my "Generelle Morphologie" (1866), in which I published the first +attempts to construct phylogenetic trees, I have given a number of +remarkable theses of Goethe, which may be called "phyletic prophecies." +They justify us in regarding him as a precursor of Darwin. + +In the ensuing forty years I have made many conscientious efforts to +penetrate further along that line of anthropological research that was +opened up by Goethe, Lamarck, and Darwin. I have brought together the +many valuable results that have constantly been reached in comparative +anatomy, physiology, ontogeny, and palaeontology, and maintained +the effort to reform the classification of animals and plants in an +evolutionary sense. The first rough drafts of pedigrees that were +published in the "Generelle Morphologie" have been improved time after +time in the ten editions of my "Naturaliche Schopfungsgeschichte" +(1868-1902). (English translation; "The History of Creation", London, +1876.) A sounder basis for my phyletic hypotheses, derived from a +discriminating combination of the three great records--morphology, +ontogeny, and palaeontology--was provided in the three volumes of my +"Systematische Phylogenie" (Berlin, 1894-96.) (1894 Protists and Plants, +1895 Vertebrates, 1896 Invertebrates). In my "Anthropogenie" (Leipzig, +1874, 5th edition 1905. English translation; "The Evolution of +Man", London, 1905.) I endeavoured to employ all the known facts of +comparative ontogeny (embryology) for the purpose of completing my +scheme of human phylogeny (evolution). I attempted to sketch the +historical development of each organ of the body, beginning with the +most elementary structures in the germ-layers of the Gastraea. At the +same time I drew up a corrected statement of the most important steps in +the line of our ancestral series. + +At the fourth International Congress of Zoology at Cambridge (August +26th, 1898) I delivered an address on "Our present knowledge of the +Descent of Man." It was translated into English, enriched with many +valuable notes and additions, by my friend and pupil in earlier days Dr +Hans Gadow (Cambridge), and published under the title: "The Last Link; +our present knowledge of the Descent of Man". (London, 1898.) The +determination of the chief animal forms that occur in the line of our +ancestry is there restricted to thirty types, and these are distributed +in six main groups. + +The first half of this "Progonotaxis hominis," which has no support +from fossil evidence, comprises three groups: (i) Protista (unicellular +organisms, 1-5: (ii) Invertebrate Metazoa (Coelenteria 6-8, Vermalia +9-11): (iii) Monorrhine Vertebrates (Acrania 12-13, Cyclostoma 14-15). +The second half, which is based on fossil records, also comprises three +groups: (iv) Palaeozoic cold-blooded Craniota (Fishes 16-18, Amphibia +19, Reptiles 20: (v) Mesozoic Mammals (Monotrema 21, Marsupialia 22, +Mallotheria 23): (vi) Cenozoic Primates (Lemuridae 24-25, Tailed Apes +26-27, Anthropomorpha 28-30). An improved and enlarged edition of this +hypothetic "Progonotaxis hominis" was published in 1908, in my essay +"Unsere Ahnenreihe". ("Festschrift zur 350-jahrigen Jubelfeier der +Thuringer Universitat Jena". Jena, 1908.) + +If I have succeeded in furthering, in some degree, by these +anthropological works, the solution of the great problem of Man's place +in nature, and particularly in helping to trace the definite stages in +our ancestral series, I owe the success, not merely to the vast progress +that biology has made in the last half century, but largely to the +luminous example of the great investigators who have applied themselves +to the problem, with so much assiduity and genius, for a century and +a quarter--I mean Goethe and Lamarck, Gegenbaur and Huxley, but, above +all, Charles Darwin. It was the great genius of Darwin that first +brought together the scattered material of biology and shaped it into +that symmetrical temple of scientific knowledge, the theory of descent. +It was Darwin who put the crown on the edifice by his theory of natural +selection. Not until this broad inductive law was firmly established was +it possible to vindicate the special conclusion, the descent of man from +a series of other Vertebrates. By his illuminating discovery Darwin +did more for anthropology than thousands of those writers, who are +more specifically titled anthropologists, have done by their technical +treatises. We may, indeed, say that it is not merely as an exact +observer and ingenious experimenter, but as a distinguished +anthropologist and far-seeing thinker, that Darwin takes his place among +the greatest men of science of the nineteenth century. + +To appreciate fully the immortal merit of Darwin in connection with +anthropology, we must remember that not only did his chief work, "The +Origin of Species", which opened up a new era in natural history in +1859, sustain the most virulent and widespread opposition for a lengthy +period, but even thirty years later, when its principles were generally +recognised and adopted, the application of them to man was energetically +contested by many high scientific authorities. Even Alfred Russel +Wallace, who discovered the principle of natural selection independently +in 1858, did not concede that it was applicable to the higher mental +and moral qualities of man. Dr Wallace still holds a spiritualist and +dualist view of the nature of man, contending that he is composed of a +material frame (descended from the apes) and an immortal immaterial soul +(infused by a higher power). This dual conception, moreover, is still +predominant in the wide circles of modern theology and metaphysics, +and has the general and influential adherence of the more conservative +classes of society. + +In strict contradiction to this mystical dualism, which is generally +connected with teleology and vitalism, Darwin always maintained the +complete unity of human nature, and showed convincingly that the +psychological side of man was developed, in the same way as the body, +from the less advanced soul of the anthropoid ape, and, at a still more +remote period, from the cerebral functions of the older vertebrates. The +eighth chapter of the "Origin of Species", which is devoted to instinct, +contains weighty evidence that the instincts of animals are subject, +like all other vital processes, to the general laws of historic +development. The special instincts of particular species were formed +by adaptation, and the modifications thus acquired were handed on to +posterity by heredity; in their formation and preservation natural +selection plays the same part as in the transformation of every other +physiological function. The higher moral qualities of civilised man +have been derived from the lower mental functions of the uncultivated +barbarians and savages, and these in turn from the social instincts +of the mammals. This natural and monistic psychology of Darwin's was +afterwards more fully developed by his friend George Romanes in his +excellent works "Mental Evolution in Animals" and "Mental Evolution in +Man". (London, 1885; 1888.) + +Many valuable and most interesting contributions to this monistic +psychology of man were made by Darwin in his fine work on "The Descent +of Man and Selection in Relation to Sex", and again in his supplementary +work, "The Expression of the Emotions in Man and Animals". To understand +the historical development of Darwin's anthropology one must read his +life and the introduction to "The Descent of Man". From the moment that +he was convinced of the truth of the principle of descent--that is to +say, from his thirtieth year, in 1838--he recognised clearly that +man could not be excluded from its range. He recognised as a logical +necessity the important conclusion that "man is the co-descendant with +other species of some ancient, lower, and extinct form." For many years +he gathered notes and arguments in support of this thesis, and for the +purpose of showing the probable line of man's ancestry. But in the first +edition of "The Origin of Species" (1859) he restricted himself to the +single line, that by this work "light would be thrown on the origin of +man and his history." In the fifty years that have elapsed since that +time the science of the origin and nature of man has made astonishing +progress, and we are now fairly agreed in a monistic conception of +nature that regards the whole universe, including man, as a wonderful +unity, governed by unalterable and eternal laws. In my philosophical +book "Die Weltratsel" (1899) ("The Riddle of the Universe", London, +1900.) and in the supplementary volume "Die Lebenswunder" (1904) "The +Wonders of Life", London, (1904.), I have endeavoured to show that this +pure monism is securely established, and that the admission of the +all-powerful rule of the same principle of evolution throughout the +universe compels us to formulate a single supreme law--the all-embracing +"Law of Substance," or the united laws of the constancy of matter and +the conservation of energy. We should never have reached this supreme +general conception if Charles Darwin--a "monistic philosopher" in +the true sense of the word--had not prepared the way by his theory of +descent by natural selection, and crowned the great work of his life by +the association of this theory with a naturalistic anthropology. + + +IX. SOME PRIMITIVE THEORIES OF THE ORIGIN OF MAN. + +By J.G. FRAZER. Fellow of Trinity College, Cambridge. + +On a bright day in late autumn a good many years ago I had ascended the +hill of Panopeus in Phocis to examine the ancient Greek fortifications +which crest its brow. It was the first of November, but the weather was +very hot; and when my work among the ruins was done, I was glad to +rest under the shade of a clump of fine holly-oaks, to inhale the sweet +refreshing perfume of the wild thyme which scented all the air, and +to enjoy the distant prospects, rich in natural beauty, rich too in +memories of the legendary and historic past. To the south the finely-cut +peak of Helicon peered over the low intervening hills. In the west +loomed the mighty mass of Parnassus, its middle slopes darkened by +pine-woods like shadows of clouds brooding on the mountain-side; while +at its skirts nestled the ivy-mantled walls of Daulis overhanging the +deep glen, whose romantic beauty accords so well with the loves and +sorrows of Procne and Philomela, which Greek tradition associated +with the spot. Northwards, across the broad plain to which the hill +of Panopeus descends, steep and bare, the eye rested on the gap in the +hills through which the Cephissus winds his tortuous way to flow under +grey willows, at the foot of barren stony hills, till his turbid waters +lose themselves, no longer in the vast reedy swamps of the now vanished +Copaic Lake, but in the darkness of a cavern in the limestone rock. +Eastward, clinging to the slopes of the bleak range of which the hill +of Panopeus forms part, were the ruins of Chaeronea, the birthplace of +Plutarch; and out there in the plain was fought the disastrous battle +which laid Greece at the feet of Macedonia. There, too, in a later age +East and West met in deadly conflict, when the Roman armies under Sulla +defeated the Asiatic hosts of Mithridates. Such was the landscape spread +out before me on one of those farewell autumn days of almost pathetic +splendour, when the departing summer seems to linger fondly, as if loth +to resign to winter the enchanted mountains of Greece. Next day the +scene had changed: summer was gone. A grey November mist hung low on the +hills which only yesterday had shone resplendent in the sun, and under +its melancholy curtain the dead flat of the Chaeronean plain, a wide +treeless expanse shut in by desolate slopes, wore an aspect of chilly +sadness befitting the battlefield where a nation's freedom was lost. + +But crowded as the prospect from Panopeus is with memories of the past, +the place itself, now so still and deserted, was once the scene of an +event even more ancient and memorable, if Greek story-tellers can be +trusted. For here, they say, the sage Prometheus created our first +parents by fashioning them, like a potter, out of clay. (Pausanias X. +4.4. Compare Apollodorus, "Bibliotheca", I. 7. 1; Ovid, "Metamorph." +I. 82 sq.; Juvenal, "Sat". XIV. 35. According to another version of +the tale, this creation of mankind took place not at Panopeus, but +at Iconium in Lycaonia. After the original race of mankind had been +destroyed in the great flood of Deucalion, the Greek Noah, Zeus +commanded Prometheus and Athena to create men afresh by moulding images +out of clay, breathing the winds into them, and making them live. See +"Etymologicum Magnum", s.v. "'Ikonion", pages 470 sq. It is said that +Prometheus fashioned the animals as well as men, giving to each kind of +beast its proper nature. See Philemon, quoted by Stobaeus, "Florilegium" +II. 27. The creation of man by Prometheus is figured on ancient works of +art. See J. Toutain, "Etudes de Mythologie et d'Histoire des Religions +Antiques" (Paris, 1909), page 190. According to Hesiod ("Works and +Days", 60 sqq.) it was Hephaestus who at the bidding of Zeus moulded the +first woman out of moist earth.) The very spot where he did so can still +be seen. It is a forlorn little glen or rather hollow behind the hill +of Panopeus, below the ruined but still stately walls and towers which +crown the grey rocks of the summit. The glen, when I visited it that hot +day after the long drought of summer, was quite dry; no water trickled +down its bushy sides, but in the bottom I found a reddish crumbling +earth, a relic perhaps of the clay out of which the potter Prometheus +moulded the Greek Adam and Eve. In a volume dedicated to the honour of +one who has done more than any other in modern times to shape the ideas +of mankind as to their origin it may not be out of place to recall this +crude Greek notion of the creation of the human race, and to compare or +contrast it with other rudimentary speculations of primitive peoples +on the same subject, if only for the sake of marking the interval which +divides the childhood from the maturity of science. + +The simple notion that the first man and woman were modelled out of clay +by a god or other superhuman being is found in the traditions of many +peoples. This is the Hebrew belief recorded in Genesis: "The Lord God +formed man of the dust of the ground, and breathed into his nostrils the +breath of life; and man became a living soul." (Genesis ii.7.) To the +Hebrews this derivation of our species suggested itself all the more +naturally because in their language the word for "ground" (adamah) is +in form the feminine of the word for man (adam). (S.R. Driver and +W.H.Bennett, in their commentaries on Genesis ii. 7.) From various +allusions in Babylonian literature it would seem that the Babylonians +also conceived man to have been moulded out of clay. (H. Zimmern, in E. +Schrader's "Die Keilinschriften und das Alte Testament" 3 (Berlin, 1902), +page 506.) According to Berosus, the Babylonian priest whose account of +creation has been preserved in a Greek version, the god Bel cut off his +own head, and the other gods caught the flowing blood, mixed it with +earth, and fashioned men out of the bloody paste; and that, they said, +is why men are so wise, because their mortal clay is tempered with +divine blood. (Eusebius, "Chronicon", ed. A. Schoene, Vol. I. (Berlin, +1875), col. 16.) In Egyptian mythology Khnoumou, the Father of the gods, +is said to have moulded men out of clay. (G. Maspero, "Histoire Ancienne +des Peuples de l'Orient Classique", I. (Paris, 1895), page 128.) We +cannot doubt that such crude conceptions of the origin of our race were +handed down to the civilised peoples of antiquity by their savage or +barbarous forefathers. Certainly stories of the same sort are known to +be current among savages and barbarians. + +Thus the Australian blacks in the neighbourhood of Melbourne said that +Pund-jel, the creator, cut three large sheets of bark with his big +knife. On one of these he placed some clay and worked it up with his +knife into a proper consistence. He then laid a portion of the clay on +one of the other pieces of bark and shaped it into a human form; first +he made the feet, then the legs, then the trunk, the arms, and the head. +Thus he made a clay man on each of the two pieces of bark; and being +well pleased with them he danced round them for joy. Next he took +stringy bark from the Eucalyptus tree, made hair of it, and stuck it +on the heads of his clay men. Then he looked at them again, was pleased +with his work, and again danced round them for joy. He then lay down +on them, blew his breath hard into their mouths, their noses, and their +navels; and presently they stirred, spoke, and rose up as full-grown +men. (R. Brough Smyth, "The Aborigines of Victoria" (Melbourne, 1878), +I. 424. This and many of the following legends of creation have been +already cited by me in a note on Pausanias X. 4. 4 ("Pausanias's +Description of Greece, translated with a Commentary" (London, 1898), +Vol V. pages 220 sq.).) The Maoris of New Zealand say that Tiki made man +after his own image. He took red clay, kneaded it, like the Babylonian +Bel, with his own blood, fashioned it in human form, and gave the image +breath. As he had made man in his own likeness he called him Tiki-ahua +or Tiki's likeness. (R. Taylor "Te Ika A Maui, or New Zealand and +its Inhabitants", Second Edition (London, 1870), page 117. Compare E. +Shortland, "Maori Religion and Mythology" (London, 1882), pages 21 sq.) +A very generally received tradition in Tahiti was that the first human +pair was made by Taaroa, the chief god. They say that after he had +formed the world he created man out of red earth, which was also the +food of mankind until bread-fruit was produced. Further, some say that +one day Taaroa called for the man by name, and when he came he made him +fall asleep. As he slept, the creator took out one of his bones (ivi) +and made a woman of it, whom he gave to the man to be his wife, and the +pair became the progenitors of mankind. This narrative was taken down +from the lips of the natives in the early years of the mission to +Tahiti. The missionary who records it observes: "This always appeared +to me a mere recital of the Mosaic account of creation, which they +had heard from some European, and I never placed any reliance on it, +although they have repeatedly told me it was a tradition among them +before any foreigner arrived. Some have also stated that the woman's +name was Ivi, which would be by them pronounced as if written "Eve". +"Ivi" is an aboriginal word, and not only signifies a bone, but also a +widow, and a victim slain in war. Notwithstanding the assertion of +the natives, I am disposed to think that "Ivi", or Eve, is the only +aboriginal part of the story, as far as it respects the mother of the +human race. (W. Ellis, "Polynesian Researches", Second Edition (London, +1832), I. 110 sq. "Ivi" or "iwi" is the regular word for "bone" in the +various Polynesian languages. See E. Tregear, "The Maori-Polynesian +Comparative Dictionary" (Wellington, New Zealand, 1891), page 109.) +However, the same tradition has been recorded in other parts of +Polynesia besides Tahiti. Thus the natives of Fakaofo or Bowditch Island +say that the first man was produced out of a stone. After a time he +bethought him of making a woman. So he gathered earth and moulded the +figure of a woman out of it, and having done so he took a rib out of his +left side and thrust it into the earthen figure, which thereupon started +up a live woman. He called her Ivi (Eevee) or "rib" and took her to +wife, and the whole human race sprang from this pair. (G. Turner, +"Samoa" (London, 1884), pages 267 sq.) The Maoris also are reported to +believe that the first woman was made out of the first man's ribs. (J.L. +Nicholas, "Narrative of a Voyage to New Zealand" (London, 1817), I. +59, who writes "and to add still more to this strange coincidence, the +general term for bone is 'Hevee'.") This wide diffusion of the story +in Polynesia raises a doubt whether it is merely, as Ellis thought, a +repetition of the Biblical narrative learned from Europeans. In Nui, or +Netherland Island, it was the god Aulialia who made earthen models of +a man and woman, raised them up, and made them live. He called the man +Tepapa and the woman Tetata. (G. Turner, "Samoa", pages 300 sq.) + +In the Pelew Islands they say that a brother and sister made men out of +clay kneaded with the blood of various animals, and that the characters +of these first men and of their descendants were determined by the +characters of the animals whose blood had been kneaded with the +primordial clay; for instance, men who have rat's blood in them are +thieves, men who have serpent's blood in them are sneaks, and men who +have cock's blood in them are brave. (J. Kubary, "Die Religion der +Pelauer", in A. Bastian's "Allerlei aus Volks- und Menschenkunde" +(Berlin, 1888), I. 3, 56.) According to a Melanesian legend, told in +Mota, one of the Banks Islands, the hero Qat moulded men of clay, the +red clay from the marshy river-side at Vanua Lava. At first he made men +and pigs just alike, but his brothers remonstrated with him, so he +beat down the pigs to go on all fours and made men walk upright. Qat +fashioned the first woman out of supple twigs, and when she smiled +he knew she was a living woman. (R.H. Codrington, "The Melanesians" +(Oxford, 1891), page 158.) A somewhat different version of the +Melanesian story is told at Lakona, in Santa Maria. There they say that +Qat and another spirit ("vui") called Marawa both made men. Qat made +them out of the wood of dracaena-trees. Six days he worked at them, +carving their limbs and fitting them together. Then he allowed them six +days to come to life. Three days he hid them away, and three days more +he worked to make them live. He set them up and danced to them and beat +his drum, and little by little they stirred, till at last they could +stand all by themselves. Then Qat divided them into pairs and called +each pair husband and wife. Marawa also made men out of a tree, but it +was a different tree, the tavisoviso. He likewise worked at them six +days, beat his drum, and made them live, just as Qat did. But when he +saw them move, he dug a pit and buried them in it for six days, and +then, when he scraped away the earth to see what they were doing, he +found them all rotten and stinking. That was the origin of death. (R.H. +Codrington op. cit., pages 157 sq.) + +The inhabitants of Noo-Hoo-roa, in the Kei Islands say that their +ancestors were fashioned out of clay by the supreme god, Dooadlera, +who breathed life into the clay figures. (C.M. Pleyte, "Ethnographische +Beschrijving der Kei-Eilanden", "Tijdschrift van het Nederlandsch +Aardrijkskundig Genootschap", Tweede Serie X. (1893), page 564.) The +aborigines of Minahassa, in the north of Celebes, say that two beings +called Wailan Wangko and Wangi were alone on an island, on which grew +a cocoa-nut tree. Said Wailan Wangko to Wangi, "Remain on earth while +I climb up the tree." Said Wangi to Wailan Wangko, "Good." But then +a thought occurred to Wangi and he climbed up the tree to ask Wailan +Wangko why he, Wangi, should remain down there all alone. Said Wailan +Wangko to Wangi, "Return and take earth and make two images, a man and a +woman." Wangi did so, and both images were men who could move but could +not speak. So Wangi climbed up the tree to ask Wailan Wangko, "How now? +The two images are made, but they cannot speak." Said Wailan Wangko to +Wangi, "Take this ginger and go and blow it on the skulls and the ears +of these two images, that they may be able to speak; call the man Adam +and the woman Ewa." (N. Graafland "De Minahassa" (Rotterdam, 1869), I. +pages 96 sq.) In this narrative the names of the man and woman betray +European influence, but the rest of the story may be aboriginal. The +Dyaks of Sakarran in British Borneo say that the first man was made by +two large birds. At first they tried to make men out of trees, but +in vain. Then they hewed them out of rocks, but the figures could not +speak. Then they moulded a man out of damp earth and infused into his +veins the red gum of the kumpang-tree. After that they called to him and +he answered; they cut him and blood flowed from his wounds. (Horsburgh, +quoted by H. Ling Roth, "The Natives of Sarawak and of British North +Borneo" (London, 1896), I. pages 299 sq. Compare The Lord Bishop +of Labuan, "On the Wild Tribes of the North-West Coast of Borneo," +"Transactions of the Ethnological Society of London", New Series, II. +(1863), page 27.) + +The Kumis of South-Eastern India related to Captain Lewin, the Deputy +Commissioner of Hill Tracts, the following tradition of the creation of +man. "God made the world and the trees and the creeping things first, +and after that he set to work to make one man and one woman, forming +their bodies of clay; but each night, on the completion of his work, +there came a great snake, which, while God was sleeping, devoured the +two images. This happened twice or thrice, and God was at his wit's end, +for he had to work all day, and could not finish the pair in less than +twelve hours; besides, if he did not sleep, he would be no good," said +Captain Lewin's informant. "If he were not obliged to sleep, there would +be no death, nor would mankind be afflicted with illness. It is when +he rests that the snake carries us off to this day. Well, he was at his +wit's end, so at last he got up early one morning and first made a dog +and put life into it, and that night, when he had finished the images, +he set the dog to watch them, and when the snake came, the dog barked +and frightened it away. This is the reason at this day that when a +man is dying the dogs begin to howl; but I suppose God sleeps heavily +now-a-days, or the snake is bolder, for men die all the same." (Capt. +T.H. Lewin, "Wild Races of South-Eastern India" (London, 1870), +pages 224-26.) The Khasis of Assam tell a similar tale. (A. Bastian, +"Volkerstamme am Brahmaputra und verwandtschaftliche Nachbarn" (Berlin, +1883), page 8; Major P.R.T. Gurdon, "The Khasis" (London, 1907), page +106.) + +The Ewe-speaking tribes of Togo-land, in West Africa, think that God +still makes men out of clay. When a little of the water with which he +moistens the clay remains over, he pours it on the ground and out of +that he makes the bad and disobedient people. When he wishes to make a +good man he makes him out of good clay; but when he wishes to make a +bad man, he employs only bad clay for the purpose. In the beginning +God fashioned a man and set him on the earth; after that he fashioned +a woman. The two looked at each other and began to laugh, whereupon +God sent them into the world. (J. Spieth, "Die Ewe-Stamme, Material zur +Kunde des Ewe-Volkes in Deutsch-Togo" (Berlin, 1906), pages 828, 840.) +The Innuit or Esquimaux of Point Barrow, in Alaska, tell of a time when +there was no man in the land, till a spirit named "a se lu", who resided +at Point Barrow, made a clay man, set him up on the shore to dry, +breathed into him and gave him life. ("Report of the International +Expedition to Point Barrow" (Washington, 1885), page 47.) Other +Esquimaux of Alaska relate how the Raven made the first woman out of +clay to be a companion to the first man; he fastened water-grass to the +back of the head to be hair, flapped his wings over the clay figure, +and it arose, a beautiful young woman. (E.W. Nelson, "The Eskimo about +Bering Strait", "Eighteenth Annual Report of the Bureau of American +Ethnology", Part I. (Washington, 1899), page 454.) The Acagchemem +Indians of California said that a powerful being called Chinigchinich +created man out of clay which he found on the banks of a lake; male and +female created he them, and the Indians of the present day are their +descendants. (Friar Geronimo Boscana, "Chinigchinich", appended to (A. +Robinson's) "Life in California" (New York, 1846), page 247.) A priest +of the Natchez Indians in Louisiana told Du Pratz "that God had kneaded +some clay, such as that which potters use and had made it into a little +man; and that after examining it, and finding it well formed, he blew up +his work, and forthwith that little man had life, grew, acted, walked, +and found himself a man perfectly well shaped." As to the mode in which +the first woman was created, the priest had no information, but thought +she was probably made in the same way as the first man; so Du Pratz +corrected his imperfect notions by reference to Scripture. (M. Le Page +Du Pratz, "The History of Louisiana" (London, 1774), page 330.) The +Michoacans of Mexico said that the great god Tucapacha first made man +and woman out of clay, but that when the couple went to bathe in a river +they absorbed so much water that the clay of which they were composed +all fell to pieces. Then the creator went to work again and moulded them +afresh out of ashes, and after that he essayed a third time and made +them of metal. This last attempt succeeded. The metal man and woman +bathed in the river without falling to pieces, and by their union they +became the progenitors of mankind. (A. de Herrera, "General History of +the vast Continent and Islands of America", translated into English by +Capt. J. Stevens (London, 1725, 1726), III. 254; Brasseur de Bourbourg, +"Histoire des Nations Civilisees du Mexique et de l'Amerique-Centrale" +(Paris, 1857--1859), III. 80 sq; compare id. I. 54 sq.) + +According to a legend of the Peruvian Indians, which was told to a +Spanish priest in Cuzco about half a century after the conquest, it was +in Tiahuanaco that man was first created, or at least was created afresh +after the deluge. "There (in Tiahuanaco)," so runs the legend, "the +Creator began to raise up the people and nations that are in that +region, making one of each nation of clay, and painting the dresses that +each one was to wear; those that were to wear their hair, with hair, and +those that were to be shorn, with hair cut. And to each nation was given +the language, that was to be spoken, and the songs to be sung, and the +seeds and food that they were to sow. When the Creator had finished +painting and making the said nations and figures of clay, he gave life +and soul to each one, as well men as women, and ordered that they should +pass under the earth. Thence each nation came up in the places to which +he ordered them to go." (E.J. Payne, "History of the New World called +America", I. (Oxford, 1892), page 462.) + +These examples suffice to prove that the theory of the creation of man +out of dust or clay has been current among savages in many parts of +the world. But it is by no means the only explanation which the savage +philosopher has given of the beginnings of human life on earth. Struck +by the resemblances which may be traced between himself and the beasts, +he has often supposed, like Darwin himself, that mankind has been +developed out of lower forms of animal life. For the simple savage has +none of that high notion of the transcendant dignity of man which makes +so many superior persons shrink with horror from the suggestion that +they are distant cousins of the brutes. He on the contrary is not too +proud to own his humble relations; indeed his difficulty often is +to perceive the distinction between him and them. Questioned by a +missionary, a Bushman of more than average intelligence "could not state +any difference between a man and a brute--he did not know but a buffalo +might shoot with bows and arrows as well as man, if it had them." +(Reverend John Campbell, "Travels in South Africa" (London, 1822, II. +page 34.) When the Russians first landed on one of the Alaskan islands, +the natives took them for cuttle-fish "on account of the buttons on +their clothes." (I. Petroff, "Report on the Population, Industries, and +Resources of Alaska", page 145.) The Giliaks of the Amoor think that the +outward form and size of an animal are only apparent; in substance every +beast is a real man, just like a Giliak himself, only endowed with an +intelligence and strength, which often surpass those of mere ordinary +human beings. (L. Sternberg, "Die Religion der Giljaken", "Archiv fur +Religionswissenschaft", VIII. (1905), page 248.) The Borororos, an +Indian tribe of Brazil, will have it that they are parrots of a gorgeous +red plumage which live in their native forests. Accordingly they treat +the birds as their fellow-tribesmen, keeping them in captivity, refusing +to eat their flesh, and mourning for them when they die. (K. von den +Steinen, "Unter den Naturvolkern Zentral-Brasiliens" (Berlin, 1894), +pages 352 sq., 512.)) + +This sense of the close relationship of man to the lower creation is the +essence of totemism, that curious system of superstition which unites +by a mystic bond a group of human kinsfolk to a species of animals or +plants. Where that system exists in full force, the members of a totem +clan identify themselves with their totem animals in a way and to an +extent which we find it hard even to imagine. For example, men of the +Cassowary clan in Mabuiag think that cassowaries are men or nearly so. +"Cassowary, he all same as relation, he belong same family," is the +account they give of their relationship with the long-legged bird. +Conversely they hold that they themselves are cassowaries for all +practical purposes. They pride themselves on having long thin legs like +a cassowary. This reflection affords them peculiar satisfaction when +they go out to fight, or to run away, as the case may be; for at such +times a Cassowary man will say to himself, "My leg is long and thin, I +can run and not feel tired; my legs will go quickly and the grass will +not entangle them." Members of the Cassowary clan are reputed to be +pugnacious, because the cassowary is a bird of very uncertain temper and +can kick with extreme violence. (A.C. Haddon, "The Ethnography of +the Western Tribe of Torres Straits", "Journal of the Anthropological +Institute", XIX. (1890), page 393; "Reports of the Cambridge +Anthropological Expedition to Torres Straits", V. (Cambridge, 1904), +pages 166, 184.) So among the Ojibways men of the Bear clan are reputed +to be surly and pugnacious like bears, and men of the Crane clan to +have clear ringing voices like cranes. (W.W. Warren, "History of the +Ojibways", "Collections of the Minnesota Historical Society", V. (Saint +Paul, Minn. 1885), pages 47, 49.) Hence the savage will often speak of +his totem animal as his father or his brother, and will neither kill it +himself nor allow others to do so, if he can help it. For example, if +somebody were to kill a bird in the presence of a native Australian who +had the bird for his totem, the black might say, "What for you kill +that fellow? that my father!" or "That brother belonging to me you +have killed; why did you do it?" (E. Palmer, "Notes on some Australian +Tribes", "Journal of the Anthropological Institute", XIII. (1884), page +300.) Bechuanas of the Porcupine clan are greatly afflicted if anybody +hurts or kills a porcupine in their presence. They say, "They have +killed our brother, our master, one of ourselves, him whom we sing of"; +and so saying they piously gather the quills of their murdered brother, +spit on them, and rub their eyebrows with them. They think they would +die if they touched its flesh. In like manner Bechuanas of the Crocodile +clan call the crocodile one of themselves, their master, their +brother; and they mark the ears of their cattle with a long slit like a +crocodile's mouth by way of a family crest. Similarly Bechuanas of the +Lion clan would not, like the members of other clans, partake of lion's +flesh; for how, say they, could they eat their grandfather? If they are +forced in self-defence to kill a lion, they do so with great regret and +rub their eyes carefully with its skin, fearing to lose their sight if +they neglected this precaution. (T. Arbousset et F. Daumas, "Relation +d'un Voyage d'Exploration au Nord-Est de la Colonie du Cap de +Bonne-Esperance" (Paris, 1842), pages 349 sq., 422-24.) A Mandingo +porter has been known to offer the whole of his month's pay to save +the life of a python, because the python was his totem and he therefore +regarded the reptile as his relation; he thought that if he allowed +the creature to be killed, the whole of his own family would perish, +probably through the vengeance to be taken by the reptile kinsfolk of +the murdered serpent. (M. le Docteur Tautain, "Notes sur les Croyances +et Pratiques Religieuses des Banmanas", "Revue d'Ethnographie", +III. (1885), pages 396 sq.; A. Rancon, "Dans la Haute-Gambie, Voyage +d'Exploration Scientifique" (Paris, 1894), page 445.) + +Sometimes, indeed, the savage goes further and identifies the revered +animal not merely with a kinsman but with himself; he imagines that one +of his own more or less numerous souls, or at all events that a vital +part of himself, is in the beast, so that if it is killed he must die. +Thus, the Balong tribe of the Cameroons, in West Africa, think that +every man has several souls, of which one is lodged in an elephant, a +wild boar, a leopard, or what not. When any one comes home, feels ill, +and says, "I shall soon die," and is as good as his word, his friends +are of opinion that one of his souls has been shot by a hunter in a wild +boar or a leopard, for example, and that that is the real cause of his +death. (J. Keller, "Ueber das Land und Volk der Balong", "Deutsches +Kolonialblatt", 1 October, 1895, page 484.) A Catholic missionary, +sleeping in the hut of a chief of the Fan negroes, awoke in the middle +of the night to see a huge black serpent of the most dangerous sort +in the act of darting at him. He was about to shoot it when the chief +stopped him, saying, "In killing that serpent, it is me that you would +have killed. Fear nothing, the serpent is my elangela." (Father Trilles, +"Chez les Fang, leurs Moeurs, leur Langue, leur Religion", "Les Missions +Catholiques", XXX. (1898), page 322.) At Calabar there used to be some +years ago a huge old crocodile which was well known to contain the +spirit of a chief who resided in the flesh at Duke Town. Sporting +Vice-Consuls, with a reckless disregard of human life, from time to time +made determined attempts to injure the animal, and once a peculiarly +active officer succeeded in hitting it. The chief was immediately laid +up with a wound in his leg. He SAID that a dog had bitten him, but +few people perhaps were deceived by so flimsy a pretext. (Miss Mary H. +Kingsley, "Travels in West Africa" (London, 1897), pages 538 sq. As to +the external or bush souls of human beings, which in this part of Africa +are supposed to be lodged in the bodies of animals, see Miss Mary H. +Kingsley op. cit. pages 459-461; R. Henshaw, "Notes on the Efik belief +in 'bush soul'", "Man", VI.(1906), pages 121 sq.; J. Parkinson, +"Notes on the Asaba people (Ibos) of the Niger", "Journal of the +Anthropological Institute", XXXVI. (1906), pages 314 sq.) Once when Mr +Partridge's canoe-men were about to catch fish near an Assiga town in +Southern Nigeria, the natives of the town objected, saying, "Our +souls live in those fish, and if you kill them we shall die." (Charles +Partridge, "Cross River Natives" (London, 1905), pages 225 sq.) On +another occasion, in the same region, an Englishman shot a hippopotamus +near a native village. The same night a woman died in the village, +and her friends demanded and obtained from the marksman five pounds as +compensation for the murder of the woman, whose soul or second self had +been in that hippopotamus. (C.H. Robinson, "Hausaland" (London, 1896), +pages 36 sq.) Similarly at Ndolo, in the Congo region, we hear of a +chief whose life was bound up with a hippopotamus, but he prudently +suffered no one to fire at the animal. ("Notes Analytiques sur les +Collections Ethnographiques du Musee du Congo", I. (Brussels, 1902-06), +page 150.) + +Amongst people who thus fail to perceive any sharp line of distinction +between beasts and men it is not surprising to meet with the belief that +human beings are directly descended from animals. Such a belief is often +found among totemic tribes who imagine that their ancestors sprang from +their totemic animals or plants; but it is by no means confined to +them. Thus, to take instances, some of the Californian Indians, in whose +mythology the coyote or prairie-wolf is a leading personage, think that +they are descended from coyotes. At first they walked on all fours; then +they began to have some members of the human body, one finger, one toe, +one eye, one ear, and so on; then they got two fingers, two toes, two +eyes, two ears, and so forth; till at last, progressing from period to +period, they became perfect human beings. The loss of their tails, which +they still deplore, was produced by the habit of sitting upright. (H.R. +Schoolcraft, "Indian Tribes of the United States", IV. (Philadelphia, +1856), pages 224 sq.; compare id. V. page 217. The descent of some, not +all, Indians from coyotes is mentioned also by Friar Boscana, in (A. +Robinson's) "Life in California" (New York, 1846), page 299.) +Similarly Darwin thought that "the tail has disappeared in man and the +anthropomorphous apes, owing to the terminal portion having been injured +by friction during a long lapse of time; the basal and embedded portion +having been reduced and modified, so as to become suitable to the erect +or semi-erect position." (Charles Darwin, "The Descent of Man", Second +Edition (London, 1879), page 60.) The Turtle clam of the Iroquois think +that they are descended from real mud turtles which used to live in a +pool. One hot summer the pool dried up, and the mud turtles set out to +find another. A very fat turtle, waddling after the rest in the heat, +was much incommoded by the weight of his shell, till by a great effort +he heaved it off altogether. After that he gradually developed into a +man and became the progenitor of the Turtle clan. (E.A. Smith, "Myths +of the Iroquois", "Second Annual Report of the Bureau of Ethnology" +(Washington, 1883), page 77.) The Crawfish band of the Choctaws are +in like manner descended from real crawfish, which used to live under +ground, only coming up occasionally through the mud to the surface. Once +a party of Choctaws smoked them out, taught them the Choctaw language, +taught them to walk on two legs, made them cut off their toe nails and +pluck the hair from their bodies, after which they adopted them into the +tribe. But the rest of their kindred, the crawfish, are crawfish under +ground to this day. (Geo. Catlin, "North American Indians" 4 (London, +1844), II. page 128.) The Osage Indians universally believed that they +were descended from a male snail and a female beaver. A flood swept the +snail down to the Missouri and left him high and dry on the bank, where +the sun ripened him into a man. He met and married a beaver maid, and +from the pair the tribe of the Osages is descended. For a long time +these Indians retained a pious reverence for their animal ancestors and +refrained from hunting beavers, because in killing a beaver they killed +a brother of the Osages. But when white men came among them and offered +high prices for beaver skins, the Osages yielded to the temptation and +took the lives of their furry brethren. (Lewis and Clarke, "Travels to +the Source of the Missouri River" (London, 1815), I. 12 (Vol. I. pages +44 sq. of the London reprint, 1905).) The Carp clan of the Ootawak +Indians are descended from the eggs of a carp which had been deposited +by the fish on the banks of a stream and warmed by the sun. ("Lettres +Edifiantes et Curieuses", Nouvelle Edition, VI. (Paris, 1781), page +171.) The Crane clan of the Ojibways are sprung originally from a pair +of cranes, which after long wanderings settled on the rapids at the +outlet of Lake Superior, where they were changed by the Great Spirit +into a man and woman. (L.H. Morgan, "Ancient Society" (London, 1877), +page 180.) The members of two Omaha clans were originally buffaloes and +lived, oddly enough, under water, which they splashed about, making it +muddy. And at death all the members of these clans went back to their +ancestors the buffaloes. So when one of them lay adying, his friends +used to wrap him up in a buffalo skin with the hair outside and say to +him, "You came hither from the animals and you are going back thither. +Do not face this way again. When you go, continue walking. (J. Owen +Dorsey, "Omaha Sociology", "Third Annual Report of the Bureau of +Ethnology" (Washington, 1884), pages 229, 233.) The Haida Indians of +Queen Charlotte Islands believe that long ago the raven, who is the +chief figure in the mythology of North-West America, took a cockle from +the beach and married it; the cockle gave birth to a female child, whom +the raven took to wife, and from their union the Indians were produced. +(G.M. Dawson, "Report on the Queen Charlotte Islands" (Montreal, +1880), pages 149B sq. ("Geological Survey of Canada"); F. Poole, +"Queen Charlotte Islands", page 136.) The Delaware Indians called the +rattle-snake their grandfather and would on no account destroy one of +these reptiles, believing that were they to do so the whole race of +rattle-snakes would rise up and bite them. Under the influence of the +white man, however, their respect for their grandfather the rattle-snake +gradually died away, till at last they killed him without compunction +or ceremony whenever they met him. The writer who records the old custom +observes that he had often reflected on the curious connection which +appears to subsist in the mind of an Indian between man and the brute +creation; "all animated nature," says he, "in whatever degree, is in +their eyes a great whole, from which they have not yet ventured to +separate themselves." (Rev. John Heckewelder, "An Account of the +History, Manners, and Customs, of the Indian Nations, who once inhabited +Pennsylvania and the Neighbouring States", "Transactions of the +Historical and Literary Committee of the American Philosophical +Society", I. (Philadelphia, 1819), pages 245, 247, 248.) + +Some of the Indians of Peru boasted of being descended from the puma +or American lion; hence they adored the lion as a god and appeared at +festivals like Hercules dressed in the skins of lions with the heads +of the beasts fixed over their own. Others claimed to be sprung from +condors and attired themselves in great black and white wings, like +that enormous bird. (Garcilasso de la Vega, "First Part of the Royal +Commentaries of the Yncas", Vol. I. page 323, Vol. II. page 156 +(Markham's translation).) The Wanika of East Africa look upon the hyaena +as one of their ancestors or as associated in some way with their origin +and destiny. The death of a hyaena is mourned by the whole people, and +the greatest funeral ceremonies which they perform are performed for +this brute. The wake held over a chief is as nothing compared to the +wake held over a hyaena; one tribe only mourns the death of its chief, +but all the tribes unite to celebrate the obsequies of a hyaena. +(Charles New, "Life, Wanderings, and Labours in Eastern Africa" (London, +1873) page 122.) Some Malagasy families claim to be descended from the +babacoote (Lichanotus brevicaudatus), a large lemur of grave appearance +and staid demeanour, which lives in the depth of the forest. When +they find one of these creatures dead, his human descendants bury it +solemnly, digging a grave for it, wrapping it in a shroud, and weeping +and lamenting over its carcase. A doctor who had shot a babacoote was +accused by the inhabitants of a Betsimisaraka village of having +killed "one of their grandfathers in the forest," and to appease their +indignation he had to promise not to skin the animal in the village +but in a solitary place where nobody could see him. (Father Abinal, +"Croyances fabuleuses des Malgaches", "Les Missions Catholiques", XII. +(1880), page 526; G.H. Smith, "Some Betsimisaraka superstitions", "The +Antananarivo Annual and Madagascar Magazine", No. 10 (Antananarivo, +1886), page 239; H.W. Little, "Madagascar, its History and People" +(London, 1884), pages 321 sq; A. van Gennep, "Tabou et Totemisme a +Madagascar" (Paris, 1904), pages 214 sqq.) Many of the Betsimisaraka +believe that the curious nocturnal animal called the aye-aye (Cheiromys +madagascariensis) "is the embodiment of their forefathers, and hence +will not touch it, much less do it an injury. It is said that when one +is discovered dead in the forest, these people make a tomb for it and +bury it with all the forms of a funeral. They think that if they attempt +to entrap it, they will surely die in consequence." (G.A. Shaw, "The +Aye-aye", "Antananarivo Annual and Madagascar Magazine", Vol. II. +(Antananarivo, 1896), pages 201, 203 (Reprint of the Second four +Numbers). Compare A. van Gennep, "Tabou et Totemisme a Madagascar", +pages 223 sq.) Some Malagasy tribes believe themselves descended from +crocodiles and accordingly they deem the formidable reptiles their +brothers. If one of these scaly brothers so far forgets the ties of +kinship as to devour a man, the chief of the tribe, or in his absence +an old man familiar with the tribal customs, repairs at the head of the +people to the edge of the water, and summons the family of the culprit +to deliver him up to the arm of justice. A hook is then baited and cast +into the river or lake. Next day the guilty brother or one of his family +is dragged ashore, formally tried, sentenced to death, and executed. The +claims of justice being thus satisfied, the dead animal is lamented +and buried like a kinsman; a mound is raised over his grave and a stone +marks the place of his head. (Father Abinal, "Croyances fabuleuses des +Malgaches", "Les Missions Catholiques", XII. (1880), page 527; A. van +Gennep, "Tabou et Totemisme a Madagascar", pages 281 sq.) + +Amongst the Tshi-speaking tribes of the Gold Coast in West Africa the +Horse-mackerel family traces its descent from a real horse-mackerel whom +an ancestor of theirs once took to wife. She lived with him happily +in human shape on shore till one day a second wife, whom the man had +married, cruelly taunted her with being nothing but a fish. That hurt +her so much that bidding her husband farewell she returned to her old +home in the sea, with her youngest child in her arms, and never came +back again. But ever since the Horse-mackerel people have refrained from +eating horse-mackerels, because the lost wife and mother was a fish of +that sort. (A.B. Ellis, "The Tshi-speaking Peoples of the Gold Coast +of West Africa" (London, 1887), pages 208-11. A similar tale is told by +another fish family who abstain from eating the fish (appei) from which +they take their name (A.B. Ellis op. cit. pages 211 sq.).) Some of the +Land Dyaks of Borneo tell a similar tale to explain a similar custom. +"There is a fish which is taken in their rivers called a puttin, which +they would on no account touch, under the idea that if they did they +would be eating their relations. The tradition respecting it is, that a +solitary old man went out fishing and caught a puttin, which he dragged +out of the water and laid down in his boat. On turning round, he found +it had changed into a very pretty little girl. Conceiving the idea she +would make, what he had long wished for, a charming wife for his son, +he took her home and educated her until she was fit to be married. She +consented to be the son's wife cautioning her husband to use her well. +Some time after their marriage, however, being out of temper, he struck +her, when she screamed, and rushed away into the water; but not without +leaving behind her a beautiful daughter, who became afterwards the +mother of the race." (The Lord Bishop of Labuan, "On the Wild Tribes +of the North-West Coast of Borneo", "Transactions of the Ethnological +Society of London", New Series II. (London, 1863), pages 26 sq. Such +stories conform to a well-known type which may be called the Swan-Maiden +type of story, or Beauty and the Beast, or Cupid and Psyche. The +occurrence of stories of this type among totemic peoples, such as the +Tshi-speaking negroes of the Gold Coast, who tell them to explain their +totemic taboos, suggests that all such tales may have originated in +totemism. I shall deal with this question elsewhere.) + +Members of a clan in Mandailing, on the west coast of Sumatra, assert +that they are descended from a tiger, and at the present day, when a +tiger is shot, the women of the clan are bound to offer betel to the +dead beast. When members of this clan come upon the tracks of a tiger, +they must, as a mark of homage, enclose them with three little sticks. +Further, it is believed that the tiger will not attack or lacerate his +kinsmen, the members of the clan. (H. Ris, "De Onderafdeeling Klein +Mandailing Oeloe en Pahantan en hare Bevolking met uitzondering van +de Oeloes", "Bijdragen tot de Tall- Land- en Volkenkunde van +Nederlansch-Indie, XLVI." (1896), page 473.) The Battas of Central +Sumatra are divided into a number of clans which have for their totems +white buffaloes, goats, wild turtle-doves, dogs, cats, apes, tigers, and +so forth; and one of the explanations which they give of their totems +is that these creatures were their ancestors, and that their own souls +after death can transmigrate into the animals. (J.B. Neumann, "Het +Pane en Bila-stroomgebied op het eiland Sumatra", "Tijdschrift van het +Nederlandsch Aardrijkskundig Genootschap", Tweede Serie, III. Afdeeling, +Meer uitgebreide Artikelen, No. 2 (Amsterdam, 1886), pages 311 sq.; +id. ib. Tweede Serie, IV. Afdeeling, Meer uitgebreide Artikelen, No. 1 +(Amsterdam, 1887), pages 8 sq.) In Amboyna and the neighbouring islands +the inhabitants of some villages aver that they are descended from +trees, such as the Capellenia moluccana, which had been fertilised by +the Pandion Haliaetus. Others claim to be sprung from pigs, octopuses, +crocodiles, sharks, and eels. People will not burn the wood of the trees +from which they trace their descent, nor eat the flesh of the animals +which they regard as their ancestors. Sicknesses of all sorts are +believed to result from disregarding these taboos. (J.G.F. Riedel, "De +sluik- en kroesharige rassen tusschen Selebes en Papua" (The Hague, +1886), pages 32, 61; G.W.W.C. Baron van Hoevell, "Ambon en meer +bepaaldelijk de Oeliasers" (Dordrecht, 1875), page 152.) Similarly in +Ceram persons who think they are descended from crocodiles, serpents, +iguanas, and sharks will not eat the flesh of these animals. (J.G.F. +Riedel op. cit. page 122.) Many other peoples of the Molucca Islands +entertain similar beliefs and observe similar taboos. (J.G.F. Riedel +"De sluik- en kroesharige rassen tusschen Selebes en Papua" (The Hague, +1886), pages 253, 334, 341, 348, 412, 414, 432.) Again, in Ponape, one +of the Caroline Islands, "The different families suppose themselves to +stand in a certain relation to animals, and especially to fishes, and +believe in their descent from them. They actually name these animals +'mothers'; the creatures are sacred to the family and may not be +injured. Great dances, accompanied with the offering of prayers, are +performed in their honour. Any person who killed such an animal would +expose himself to contempt and punishment, certainly also to the +vengeance of the insulted deity." Blindness is commonly supposed to +be the consequence of such a sacrilege. (Dr Hahl, "Mittheilungen +uber Sitten und rechtliche Verhaltnisse auf Ponape", "Ethnologisches +Notizblatt", Vol. II. Heft 2 (Berlin, 1901), page 10.) + +Some of the aborigines of Western Australia believe that their ancestors +were swans, ducks, or various other species of water-fowl before they +were transformed into men. (Captain G. Grey, "A Vocabulary of the +Dialects of South Western Australia", Second Edition (London, 1840), +pages 29, 37, 61, 63, 66, 71.) The Dieri tribe of Central Australia, who +are divided into totemic clans, explain their origin by the following +legend. They say that in the beginning the earth opened in the midst of +Perigundi Lake, and the totems (murdus or madas) came trooping out one +after the other. Out came the crow, and the shell parakeet, and the emu, +and all the rest. Being as yet imperfectly formed and without members +or organs of sense, they laid themselves down on the sandhills which +surrounded the lake then just as they do now. It was a bright day and +the totems lay basking in the sunshine, till at last, refreshed and +invigorated by it, they stood up as human beings and dispersed in all +directions. That is why people of the same totem are now scattered all +over the country. You may still see the island in the lake out of which +the totems came trooping long ago. (A.W. Howitt, "Native Tribes of +South-East Australia" (London, 1904), pages 476, 779 sq.) Another +Dieri legend relates how Paralina, one of the Mura-Muras or mythical +predecessors of the Dieri, perfected mankind. He was out hunting +kangaroos, when he saw four incomplete beings cowering together. So he +went up to them, smoothed their bodies, stretched out their limbs, slit +up their fingers and toes, formed their mouths, noses, and eyes, stuck +ears on them, and blew into their ears in order that they might hear. +Having perfected their organs and so produced mankind out of these +rudimentary beings, he went about making men everywhere. (A.W. Howitt +op. cit., pages 476, 780 sq.) Yet another Dieri tradition sets forth how +the Mura-Mura produced the race of man out of a species of small black +lizards, which may still be met with under dry bark. To do this he +divided the feet of the lizards into fingers and toes, and, applying +his forefinger to the middle of their faces, created a nose; likewise he +gave them human eyes, mouths and ears. He next set one of them upright, +but it fell down again because of its tail; so he cut off its tail and +the lizard then walked on its hind legs. That is the origin of mankind. +(S. Gason, "The Manners and Customs of the Dieyerie tribe of Australian +Aborigines", "Native Tribes of South Australia" (Adelaide, 1879), +page 260. This writer fell into the mistake of regarding the Mura-Mura +(Mooramoora) as a Good-Spirit instead of as one of the mythical but more +or less human predecessors of the Dieri in the country. See A.W. Howitt, +"Native Tribes of South-East Australia", pages 475 sqq.) + +The Arunta tribe of Central Australia similarly tell how in the +beginning mankind was developed out of various rudimentary forms of +animal life. They say that in those days two beings called Ungambikula, +that is, "out of nothing," or "self-existing," dwelt in the western sky. +From their lofty abode they could see, far away to the east, a number +of inapertwa creatures, that is, rudimentary human beings or incomplete +men, whom it was their mission to make into real men and women. For at +that time there were no real men and women; the rudimentary creatures +(inapertwa) were of various shapes and dwelt in groups along the shore +of the salt water which covered the country. These embryos, as we may +call them, had no distinct limbs or organs of sight, hearing, and smell; +they did not eat food, and they presented the appearance of human beings +all doubled up into a rounded mass, in which only the outline of the +different parts of the body could be vaguely perceived. Coming down +from their home in the western sky, armed with great stone knives, the +Ungambikula took hold of the embryos, one after the other. First of all +they released the arms from the bodies, then making four clefts at the +end of each arm they fashioned hands and fingers; afterwards legs, feet, +and toes were added in the same way. The figure could now stand; a nose +was then moulded and the nostrils bored with the fingers. A cut with the +knife made the mouth, which was pulled open several times to render it +flexible. A slit on each side of the face separated the upper and lower +eye-lids, disclosing the eyes, which already existed behind them; and +a few strokes more completed the body. Thus out of the rudimentary +creatures were formed men and women. These rudimentary creatures or +embryos, we are told, "were in reality stages in the transformation +of various animals and plants into human beings, and thus they were +naturally, when made into human beings, intimately associated with the +particular animal or plant, as the case may be, of which they were the +transformations--in other words, each individual of necessity belonged +to a totem, the name of which was of course that of the animal or plant +of which he or she was a transformation." However, it is not said +that all the totemic clans of the Arunta were thus developed; no such +tradition, for example, is told to explain the origin of the important +Witchetty Grub clan. The clans which are positively known, or at least +said, to have originated out of embryos in the way described are the +Plum Tree, the Grass Seed, the Large Lizard, the Small Lizard, the +Alexandra Parakeet, and the Small Rat clans. When the Ungambikula had +thus fashioned people of these totems, they circumcised them all, except +the Plum Tree men, by means of a fire-stick. After that, having done the +work of creation or evolution, the Ungambikula turned themselves +into little lizards which bear a name meaning "snappers-up of flies." +(Baldwin Spencer and F.J. Gillen, "Native Tribes of Central Australia" +(London, 1899), pages 388 sq.; compare id., "Northern Tribes of Central +Australia" (London, 1904), page 150.) + +This Arunta tradition of the origin of man, as Messrs Spencer and +Gillen, who have recorded it, justly observe, "is of considerable +interest; it is in the first place evidently a crude attempt to describe +the origin of human beings out of non-human creatures who were of +various forms; some of them were representatives of animals, others of +plants, but in all cases they are to be regarded as intermediate stages +in the transition of an animal or plant ancestor into a human individual +who bore its name as that of his or her totem." (Baldwin Spencer and +F.J. Gillen, "Native Tribes of Central Australia", pages 391 sq.) In a +sense these speculations of the Arunta on their own origin may be said +to combine the theory of creation with the theory of evolution; for +while they represent men as developed out of much simpler forms of life, +they at the same time assume that this development was effected by the +agency of two powerful beings, whom so far we may call creators. It is +well known that at a far higher stage of culture a crude form of +the evolutionary hypothesis was propounded by the Greek philosopher +Empedocles. He imagined that shapeless lumps of earth and water, thrown +up by the subterranean fires, developed into monstrous animals, bulls +with the heads of men, men with the heads of bulls, and so forth; till +at last, these hybrid forms being gradually eliminated, the various +existing species of animals and men were evolved. (E. Zeller, "Die +Philosophie der Griechen", I.4 (Leipsic, 1876), pages 718 sq.; H. Ritter +et L. Preller, "Historia Philosophiae Graecae et Romanae ex fontium +locis contexta" 5, pages 102 sq. H. Diels, "Die Fragmente der +Vorsokratiker" 2, I. (Berlin, 1906), pages 190 sqq. Compare Lucretius "De +rerum natura", V. 837 sqq.) The theory of the civilised Greek of Sicily +may be set beside the similar theory of the savage Arunta of Central +Australia. Both represent gropings of the human mind in the dark abyss +of the past; both were in a measure grotesque anticipations of the +modern theory of evolution. + +In this essay I have made no attempt to illustrate all the many various +and divergent views which primitive man has taken of his own origin. I +have confined myself to collecting examples of two radically different +views, which may be distinguished as the theory of creation and the +theory of evolution. According to the one, man was fashioned in his +existing shape by a god or other powerful being; according to the other +he was evolved by a natural process out of lower forms of animal life. +Roughly speaking, these two theories still divide the civilised world +between them. The partisans of each can appeal in support of their view +to a large consensus of opinion; and if truth were to be decided by +weighing the one consensus against the other, with "Genesis" in the +one scale and "The Origin of Species" in the other, it might perhaps be +found, when the scales were finally trimmed, that the balance hung very +even between creation and evolution. + + + + +X. THE INFLUENCE OF DARWIN ON THE STUDY OF ANIMAL EMBRYOLOGY. By A. +Sedgwick, M.A., F.R.S. + +Professor of Zoology and Comparative Anatomy in the University of +Cambridge. + +The publication of "The Origin of Species" ushered in a new era in the +study of Embryology. Whereas, before the year 1859 the facts of anatomy +and development were loosely held together by the theory of types, which +owed its origin to the great anatomists of the preceding generation, +to Cuvier, L. Agassiz, J. Muller, and R. Owen, they were now combined +together into one organic whole by the theory of descent and by the +hypothesis of recapitulation which was deduced from that theory. The +view (First clearly enunciated by Fritz Muller in his well-known work, +"Fur Darwin", Leipzig, 1864; (English Edition, "Facts for Darwin", +1869).) that a knowledge of embryonic and larval histories would lay +bare the secrets of race-history and enable the course of evolution +to be traced, and so lead to the discovery of the natural system of +classification, gave a powerful stimulus to morphological study in +general and to embryological investigation in particular. In Darwin's +words: "Embryology rises greatly in interest, when we look at the embryo +as a picture, more or less obscured, of the progenitor, either in its +adult or larval state, of all the members of the same great class." +("Origin" (6th edition), page 396.) In the period under consideration +the output of embryological work has been enormous. No group of the +animal kingdom has escaped exhaustive examination and no effort has been +spared to obtain the embryos of isolated and out of the way forms, the +development of which might have an important bearing upon questions +of phylogeny and classification. Marine zoological stations have been +established, expeditions have been sent to distant countries, and the +methods of investigation have been greatly improved. The result of this +activity has been that the main features of the developmental history +of all the most important animals are now known and the curiosity as to +developmental processes, so greatly excited by the promulgation of the +Darwinian theory, has to a considerable extent been satisfied. + +To what extent have the results of this vast activity fulfilled the +expectations of the workers who have achieved them? The Darwin centenary +is a fitting moment at which to take stock of our position. In this +inquiry we shall leave out of consideration the immense and intensely +interesting additions to our knowledge of Natural History. These may be +said to constitute a capital fund upon which philosophers, poets and +men of science will draw for many generations. The interest of Natural +History existed long before Darwinian evolution was thought of and +will endure without any reference to philosophic speculations. She is +a mistress in whose face are beauties and in whose arms are delights +elsewhere unattainable. She is and always has been pursued for her own +sake without any reference to philosophy, science, or utility. + +Darwin's own views of the bearing of the facts of embryology upon +questions of wide scientific interest are perfectly clear. He writes +("Origin" (6th edition), page 395.): + +"On the other hand it is highly probable that with many animals the +embryonic or larval stages show us, more or less completely, the +condition of the progenitor of the whole group in its adult state. In +the great class of the Crustacea, forms wonderfully distinct from each +other, namely, suctorial parasites, cirripedes, entomostraca, and even +the malacostraca, appear at first as larvae under the nauplius-form; and +as these larvae live and feed in the open sea, and are not adapted for +any peculiar habits of life, and from other reasons assigned by Fritz +Muller, it is probable that at some very remote period an independent +adult animal, resembling the Nauplius, existed, and subsequently +produced, along several divergent lines of descent, the above-named +great Crustacean groups. So again it is probable, from what we know of +the embryos of mammals, birds, fishes, and reptiles, that these animals +are the modified descendants of some ancient progenitor, which was +furnished in its adult state with branchiae, a swim-bladder, four +fin-like limbs, and a long tail, all fitted for an aquatic life. + +"As all the organic beings, extinct and recent, which have ever lived, +can be arranged within a few great classes; and as all within each +class have, according to our theory, been connected together by fine +gradations, the best, and, if our collections were nearly perfect, the +only possible arrangement, would be genealogical; descent being the +hidden bond of connexion which naturalists have been seeking under the +term of the Natural System. On this view we can understand how it is +that, in the eyes of most naturalists, the structure of the embryo is +even more important for classification than that of the adult. In two or +more groups of animals, however much they may differ from each other +in structure and habits in their adult condition, if they pass through +closely similar embryonic stages, we may feel assured that they all are +descended from one parent-form, and are therefore closely related. +Thus, community in embryonic structure reveals community of descent; but +dissimilarity in embryonic development does not prove discommunity of +descent, for in one of two groups the developmental stages may have been +suppressed, or may have been so greatly modified through adaptation to +new habits of life, as to be no longer recognisable. Even in groups, in +which the adults have been modified to an extreme degree, community of +origin is often revealed by the structure of the larvae; we have seen, +for instance, that cirripedes, though externally so like shell-fish, +are at once known by their larvae to belong to the great class of +crustaceans. As the embryo often shows us more or less plainly the +structure of the less modified and ancient progenitor of the group, we +can see why ancient and extinct forms so often resemble in their +adult state the embryos of existing species of the same class. Agassiz +believes this to be a universal law of nature; and we may hope hereafter +to see the law proved true. It can, however, be proved true only in +those cases in which the ancient state of the progenitor of the group +has not been wholly obliterated, either by successive variations having +supervened at a very early period of growth, or by such variations +having been inherited at an earlier stage than that at which they first +appeared. It should also be borne in mind, that the law may be true, +but yet, owing to the geological record not extending far enough back +in time, may remain for a long period, or for ever, incapable of +demonstration. The law will not strictly hold good in those cases in +which an ancient form became adapted in its larval state to some special +line of life, and transmitted the same larval state to a whole group of +descendants; for such larvae will not resemble any still more ancient +form in its adult state." + +As this passage shows, Darwin held that embryology was of interest +because of the light it seems to throw upon ancestral history +(phylogeny) and because of the help it would give in enabling us to +arrive at a natural system of classification. With regard to the latter +point, he quotes with approval the opinion that "the structure of +the embryo is even more important for classification than that of the +adult." What justification is there for this view? The phase of life +chosen for the ordinary anatomical and physiological studies, namely, +the adult phase, is merely one of the large number of stages of +structure through which the organism passes. By far the greater number +of these are included in what is specially called the developmental +or (if we include larvae with embryos) embryonic period, for the +developmental changes are more numerous and take place with greater +rapidity at the beginning of life than in its later periods. As each of +these stages is equal in value, for our present purpose, to the adult +phase, it clearly follows that if there is anything in the view that +the anatomical study of organisms is of importance in determining their +mutual relations, the study of the organism in its various embryonic +(and larval) stages must have a greater importance than the study of the +single and arbitrarily selected stage of life called the adult. + +But a deeper reason than this has been assigned for the importance of +embryology in classification. It has been asserted, and is implied by +Darwin in the passage quoted, that the ancestral history is repeated +in a condensed form in the embryonic, and that a study of the latter +enables us to form a picture of the stages of structure through which +the organism has passed in its evolution. It enables us on this view to +reconstruct the pedigrees of animals and so to form a genealogical tree +which shall be the true expression of their natural relations. + +The real question which we have to consider is to what extent the +embryological studies of the last 50 years have confirmed or rendered +probable this "theory of recapitulation." In the first place it must +be noted that the recapitulation theory is itself a deduction from the +theory of evolution. The facts of embryology, particularly of vertebrate +embryology, and of larval history receive, it is argued, an explanation +on the view that the successive stages of development are, on the +whole, records of adult stages of structure which the species has passed +through in its evolution. Whether this statement will bear a critical +verbal examination I will not now pause to inquire, for it is more +important to determine whether any independent facts can be alleged in +favour of the theory. If it could be shown, as was stated to be the case +by L. Agassiz, that ancient and extinct forms of life present features +of structure now only found in embryos, we should have a body of facts +of the greatest importance in the present discussion. But as Huxley (See +Huxley's "Scientific Memoirs", London, 1898, Vol. I. page 303: "There is +no real parallel between the successive forms assumed in the development +of the life of the individual at present, and those which have appeared +at different epochs in the past." See also his Address to the +Geological Society of London (1862) 'On the Palaeontological Evidence of +Evolution', ibid. Vol. II. page 512.) has shown and as the whole course +of palaeontological and embryological investigation has demonstrated, no +such statement can be made. The extinct forms of life are very similar +to those now existing and there is nothing specially embryonic about +them. So that the facts, as we know them, lend no support to theory. + +But there is another class of facts which have been alleged in favour +of the theory, viz. the facts which have been included in the +generalisation known as the Law of v. Baer. The law asserts that embryos +of different species of animals of the same group are more alike +than the adults and that, the younger the embryo, the greater are the +resemblances. If this law could be established it would undoubtedly be +a strong argument in favour of the "recapitulation" explanation of the +facts of embryology. But its truth has been seriously disputed. If it +were true we should expect to find that the embryos of closely similar +species would be indistinguishable from one another, but this is +notoriously not the case. It is more difficult to meet the assertion +when it is made in the form given above, for here we are dealing with +matters of opinion. For instance, no one would deny that the embryo of a +dogfish is different from the embryo of a rabbit, but there is room for +difference of opinion when it is asserted that the difference is less +than the difference between an adult dogfish and an adult rabbit. It +would be perfectly true to say that the differences between the embryos +concern other organs more than do the differences between the adults, +but who is prepared to affirm that the presence of a cephalic coelom and +of cranial segments, of external gills, of six gill slits, of the kidney +tubes opening into the muscle-plate coelom, of an enormous yolk-sac, of +a neurenteric canal, and the absence of any trace of an amnion, of an +allantois and of a primitive streak are not morphological facts of as +high an import as those implied by the differences between the adults? +The generalisation undoubtedly had its origin in the fact that there is +what may be called a family resemblance between embryos and larvae, but +this resemblance, which is by no means exact, is largely superficial and +does not extend to anatomical detail. + +It is useless to say, as Weismann has stated ("The Evolution Theory", +by A. Weismann, English Translation, Vol. II. page 176, London, 1904.), +that "it cannot be disputed that the rudiments [vestiges his translator +means] of gill-arches and gill-clefts, which are peculiar to one stage +of human ontogeny, give us every ground for concluding that we possessed +fish-like ancestors." The question at issue is: did the pharyngeal +arches and clefts of mammalian embryos ever discharge a branchial +function in an adult ancestor of the mammalia? We cannot therefore, +without begging the question at issue in the grossest manner, apply to +them the terms "gill-arches" and "gill-clefts". That they are homologous +with the "gill-arches" and "gill-clefts" of fishes is true; but there +is no evidence to show that they ever discharged a branchial function. +Until such evidence is forthcoming, it is beside the point to say that +it "cannot be disputed" that they are evidence of a piscine ancestry. + +It must, therefore, be admitted that one outcome of the progress of +embryological and palaeontological research for the last 50 years is +negative. The recapitulation theory originated as a deduction from the +evolution theory and as a deduction it still remains. + +Let us before leaving the subject apply another test. If the evolution +theory and the recapitulation theory are both true, how is it that +living birds are not only without teeth but have no rudiments of teeth +at any stage of their existence? How is it that the missing digits in +birds and mammals, the missing or reduced limb of snakes and whales, the +reduced mandibulo-hyoid cleft of elasmobranch fishes are not present or +relatively more highly developed in the embryo than in the adult? How +is it that when a marked variation, such as an extra digit, or a reduced +limb, or an extra segment, makes its appearance, it is not confined to +the adult but can be seen all through the development? All the clear +evidence we can get tends to show that marked variations, whether of +reduction or increase, of organs are manifest during the whole of the +development of the organ and do not merely affect the adult. And on +reflection we see that it could hardly be otherwise. All such evidence +is distinctly at variance with the theory of recapitulation, at least +as applied to embryos. In the case of larvae of course the case will be +different, for in them the organs are functional, and reduction in the +adult will not be accompanied by reduction in the larva unless a change +in the conditions of life of the larva enables it to occur. + +If after 50 years of research and close examination of the facts of +embryology the recapitulation theory is still without satisfactory +proof, it seems desirable to take a wider sweep and to inquire whether +the facts of embryology cannot be included in a larger category. + +As has been pointed out by Huxley, development and life are +co-extensive, and it is impossible to point to any period in the life of +an organism when the developmental changes cease. It is true that these +changes take place more rapidly at the commencement of life, but they +are never wholly absent, and those which occur in the later or so-called +adult stages of life do not differ in their essence, however much they +may differ in their degree, from those which occur during the embryonic +and larval periods. This consideration at once brings the changes of +the embryonic period into the same category as those of the adult and +suggests that an explanation which will account for the one will account +for the other. What then is the problem we are dealing with? Surely +it is this: Why does an organism as soon as it is established at the +fertilisation of the ovum enter upon a cycle of transformations which +never cease until death puts an end to them? In other words what is +the meaning of that cycle of changes which all organisms present in a +greater or less degree and which constitute the very essence of life? +It is impossible to give an answer to this question so long as we remain +within the precincts of Biology--and it is not my present purpose to +penetrate beyond those precincts into the realms of philosophy. We have +to do with an ultimate biological fact, with a fundamental property of +living matter, which governs and includes all its other properties. How +may this property be stated? Thus: it is a property of living matter +to react in a remarkable way to external forces without undergoing +destruction. The life-cycle, of which the embryonic and larval periods +are a part, consists of the orderly interaction between the organism +and its environment. The action of the environment produces certain +morphological changes in the organism. These changes enable the organism +to come into relation with new external forces, to move into what +is practically a new environment, which in its turn produces further +structural changes in the organism. These in their turn enable, indeed +necessitate, the organism to move again into a new environment, and so +the process continues until the structural changes are of such a nature +that the organism is unable to adapt itself to the environment in which +it finds itself. The essential condition of success in this process is +that the organism should always shift into the environment to which its +new structure is suited--any failure in this leading to the impairment +of the organism. In most cases the shifting of the environment is a +very gradual process (whether consisting in the very slight and gradual +alteration in the relation of the embryo as a whole to the egg-shell or +uterine wall, or in the relations of its parts to each other, or in +the successive phases of adult life), and the morphological changes in +connection with each step of it are but slight. But in some cases jumps +are made such as we find in the phenomena known as hatching, birth, and +metamorphosis. + +This property of reacting to the environment without undergoing +destruction is, as has been stated, a fundamental property of organisms. +It is impossible to conceive of any matter, to which the term living +could be applied, being without it. And with this property of reacting +to the environment goes the further property of undergoing a change +which alters the relation of the organism to the old environment +and places it in a new environment. If this reasoning is correct, it +necessarily follows that this property must have been possessed by +living matter at its first appearance on the earth. In other words +living matter must always have presented a life-cycle, and the question +arises what kind of modification has that cycle undergone? Has it +increased or diminished in duration and complexity since organisms first +appeared on the earth? The current view is that the cycle was at first +very short and that it has increased in length by the evolutionary +creation of new adult phases, that these new phases are in addition to +those already existing and that each of them as it appears takes +over from the preceding adult phase the functional condition of the +reproductive organs. According to the same view the old adult phases are +not obliterated but persist in a more or less modified form as larval +stages. It is further supposed that as the life-history lengthens at one +end by the addition of new adult phases, it is shortened at the other by +the abbreviation of embryonic development and by the absorption of some +of the early larval stages into the embryonic period; but on the whole +the lengthening process has exceeded that of shortening, so that the +whole life-history has, with the progress of evolution, become longer +and more complicated. + +Now there can be no doubt that the life-history of organisms has been +shortened in the way above suggested, for cases are known in which this +can practically be seen to occur at the present day. But the process +of lengthening by the creation of new stages at the other end of the +life-cycle is more difficult to conceive and moreover there is no +evidence for its having occurred. This, indeed, may have occurred, as +is suggested below, but the evidence we have seems to indicate +that evolutionary modification has proceeded by ALTERING and not by +SUPERSEDING: that is to say that each stage in the life-history, as we +see it to-day, has proceeded from a corresponding stage in a former era +by the modification of that stage and not by the creation of a new one. +Let me, at the risk of repetition, explain my meaning more fully by +taking a concrete illustration. The mandibulo-hyoid cleft (spiracle) +of the elasmobranch fishes, the lateral digits of the pig's foot, the +hind-limbs of whales, the enlarged digit of the ostrich's foot +are supposed to be organs which have been recently modified. +This modification is not confined to the final adult stage of the +life-history but characterises them throughout the whole of their +development. A stage with a reduced spiracle does not proceed in +development from a preceding stage in which the spiracle shows no +reduction: it is reduced at its first appearance. The same statement may +be made of organs which have entirely disappeared in the adult, such as +bird's teeth and snake's fore-limbs: the adult stage in which they have +disappeared is not preceded by embryonic stages in which the teeth and +limbs or rudiments of them are present. In fact the evidence indicates +that adult variations of any part are accompanied by precedent +variations in the same direction in the embryo. The evidence seems to +show, not that a stage is added on at the end of the life-history, but +only that some of the stages in the life-history are modified. Indeed, +on the wider view of development taken in this essay, a view which makes +it coincident with life, one would not expect often to find, even if new +stages are added in the course of evolution, that they are added at the +end of the series when the organism has passed through its reproductive +period. It is possible of course that new stages have been intercalated +in the course of the life-history, though it is difficult to see +how this has occurred. It is much more likely, if we may judge from +available evidence, that every stage has had its counterpart in +the ancestral form from which it has been derived by descent with +modification. Just as the adult phase of the living form differs, owing +to evolutionary modification, from the adult phase of the ancestor from +which it has proceeded, so each larval phase will differ for the same +reason from the corresponding larval phase in the life-history of the +ancestor. Inasmuch as the organism is variable at every stage of its +independent existence and is exposed to the action of natural selection +there is no reason why it should escape modification at any stage. + +If there is any truth in these considerations it would seem to follow +that at the dawn of life the life-cycle must have been, either in posse +or in esse, at least as long as it is at the present time, and that +the peculiarity of passing through a series of stages in which new +characters are successively evolved is a primordial quality of living +matter. + +Before leaving this part of the subject, it is necessary to touch upon +another aspect of it. What are these variations in structure which +succeed one another in the life-history of an organism? I am conscious +that I am here on the threshold of a chamber which contains the clue to +some of our difficulties, and that I cannot enter it. Looked at from +one point of view they belong to the class of genetic variations, which +depend upon the structure or constitution of the protoplasm; but instead +of appearing in different zygotes (A zygote is a fertilised ovum, i.e. a +new organism resulting from the fusion of an ovum and a spermatozoon.), +they are present in the same zygote though at different times in its +life-history. They are of the same order as the mutational variations +of the modern biologist upon which the appearance of a new character +depends. What is a genetic or mutational variation? It is a genetic +character which was not present in either of the parents. But these +"growth variations" were present in the parents, and in this they differ +from mutational variations. But what are genetic characters? They are +characters which must appear if any development occurs. They are usually +contrasted with "acquired characters," using the expression "acquired +character" in the Lamarckian sense. But strictly speaking they ARE +acquired characters, for the zygote at first has none of the characters +which it subsequently acquires, but only the power of acquiring them +in response to the action of the environment. But the characters so +acquired are not what we technically understand and what Lamarck meant +by "acquired characters." They are genetic characters, as defined above. +What then are Lamarck's "acquired characters"? They are variations in +genetic characters caused in a particular way. There are, in fact, +two kinds of variation in genetic characters depending on the mode +of causation. Firstly, there are those variations consequent upon a +variation in the constitution of the protoplasm of a particular zygote, +and independent of the environment in which the organism develops, +save in so far as this simply calls them forth: these are the so-called +genetic or mutational variations. Secondly, there are those variations +which occur in zygotes of similar germinal constitution and which are +caused solely by differences in the environment to which the individuals +are respectively exposed: these are the "acquired characters" of Lamarck +and of authors generally. In consequence of this double sense in which +the term "acquired characters" may be used, great confusion may and +does occur. If the protoplasm be compared to a machine, and the external +conditions to the hand that works the machine, then it may be said that, +as the machine can only work in one way, it can only produce one kind +of result (genetic character), but the particular form or quality +(Lamarckian "acquired character") of the result will depend upon the +hand that works the machine (environment), just as the quality of the +sound produced by a fiddle depends entirely upon the hand which plays +upon it. It would be improper to apply the term "mutation" to those +genetic characters which are not new characters or new variants of old +characters, but such genetic characters are of the same nature as +those characters to which the term mutation has been applied. It may be +noticed in passing that it is very questionable if the modern biologist +has acted in the real interests of science in applying the term mutation +in the sense in which he has applied it. The genetic characters of +organisms come from one of two sources: either they are old characters +and are due to the action of what we call inheritance or they are new +and are due to what we call variation. If the term mutation is applied +to the actual alteration of the machinery of the protoplasm, no +objection can be felt to its use; but if it be applied, as it is, to the +product of the action of the altered machine, viz. to the new genetic +character, it leads to confusion. Inheritance is the persistence of the +structure of the machine; characters are the products of the working of +the machine; variation in genetic characters is due to the alteration +(mutation) in the arrangement of the machinery, while variation in +acquired characters (Lamarckian) is due to differences in the mode of +working the machinery. The machinery when it starts (in the new zygote) +has the power of grinding out certain results, which we call the +characters of the organism. These appear at successive intervals +of time, and the orderly manifestation of them is what we call the +life-history of the organism. This brings us back to the question with +which we started this discussion, viz. what is the relation of these +variations in structure, which successively appear in an organism and +constitute its life-history, to the mutational variations which appear +in different organisms of the same brood or species. The question is +brought home to us when we ask what is a bud-sport, such as a nectarine +appearing on a peach-tree? From one point of view, it is simply a +mutation appearing in asexual reproduction; from another it is one of +these successional characters ("growth variations") which constitute +the life-history of the zygote, for it appears in the same zygote which +first produces a peach. Here our analogy of a machine which only works +in one way seems to fail us, for these bud-sports do not appear in all +parts of the organism, only in certain buds or parts of it, so that one +part of the zygotic machine would appear to work differently to another. +To discuss this question further would take us too far from our subject. +Suffice it to say that we cannot answer it, any more than we can this +further question of burning interest at the present day, viz. to +what extent and in what manner is the machine itself altered by the +particular way in which it is worked. In connection with this question +we can only submit one consideration: the zygotic machine can, by +its nature, only work once, so that any alteration in it can only be +ascertained by studying the replicas of it which are produced in the +reproductive organs. + +It is a peculiarity that the result which we call the ripening of the +generative organs nearly always appears among the final products of the +action of the zygotic machine. It is remarkable that this should be +the case. What is the reason of it? The late appearance of functional +reproductive organs is almost a universal law, and the explanation of it +is suggested by expressing the law in another way, viz. that the machine +is almost always so constituted that it ceases to work efficiently +soon after the reproductive organs have sufficiently discharged their +function. Why this should occur we cannot explain: it is an ultimate +fact of nature, and cannot be included in any wider category. The +period during which the reproductive organs can act may be short as +in ephemerids or long as in man and trees, and there is no reason to +suppose that their action damages the vital machinery, though sometimes, +as in the case of annual plants (Metschnikoff), it may incidentally +do so; but, long or short, the cessation of their actions is always +a prelude to the end. When they and their action are impaired, the +organism ceases to react with precision to the environment, and the +organism as a whole undergoes retrogressive changes. + +It has been pointed out above that there is reason to believe that at +the dawn of life the life-cycle was, EITHER IN ESSE OR IN POSSE, at +least as long as it is at the present time. The qualification implied by +the words in italics is necessary, for it is clearly possible that the +external conditions then existing were not suitable for the production +of all the stages of the potential life-history, and that what we +call organic evolution has consisted in a gradual evolution of new +environments to which the organism's innate capacity of change has +enabled it to adapt itself. We have warrant for this possibility in the +case of the Axolotl and in other similar cases of neoteny. And these +cases further bring home to us the fact, to which I have already +referred, that the full development of the functional reproductive +organs is nearly always associated with the final stages of the +life-history. + +On this view of the succession of characters in the life-history of +organisms, how shall we explain the undoubted fact that the development +of buds hardly ever presents any phenomena corresponding to the +embryonic and larval changes? The reason is clearly this, that budding +usually occurs after the embryonic stage is past; when the characters of +embryonic life have been worked out by the machine. When it takes place +at an early stage in embryonic life, as it does in cases of so-called +embryonic fission, the product shows, either partly or entirely, +phenomena similar to those of embryonic development. The only case known +to me in which budding by the adult is accompanied by morphological +features similar to those displayed by embryos is furnished by the +budding of the medusiform spore-sacs of hydrozoon polyps. But this case +is exceptional, for here we have to do with an attempt, which fails, to +form a free-swimming organism, the medusa; and the vestiges which appear +in the buds are the umbrella-cavity, marginal tentacles, circular canal, +etc., of the medusa arrested in development. + +But the question still remains, are there no cases in which, as implied +by the recapitulation theory, variations in any organ are confined to +the period in which the organ is functional and do not affect it in the +embryonic stages? The teeth of the whalebone whales may be cited as +a case in which this is said to occur; but here the teeth are only +imperfectly developed in the embryo and are soon absorbed. They have +been affected by the change which has produced their disappearance in +the adult, but not to complete extinction. Nor are they now likely to be +extinguished, for having become exclusively embryonic they are largely +protected from the action of natural selection. This consideration +brings up a most important aspect of the question, so far as +disappearing organs are concerned. Every organ is laid down at a certain +period in the embryo and undergoes a certain course of growth until +it obtains full functional development. When for any cause reduction +begins, it is affected at all stages of its growth, unless it has +functional importance in the larva, and in some cases its life is +shortened at one or both ends. In cases, as in that of the whale's +teeth, in which it entirely disappears in the adult, the latter part +of its life is cut off; in others, the beginning of its life may +be deferred. This happens, for instance, with the spiracle of many +Elasmobranchs, which makes its appearance after the hyobranchial cleft, +not before it as it should do, being anterior to it in position, and +as it does in the Amniota in which it shows no reduction in size as +compared with the other pharyngeal clefts. In those Elasmobranchs +in which it is absent in the adult but present in the embryo (e.g. +Carcharias) its life is shortened at both ends. Many more instances +of organs, of which the beginning and end have been cut off, might be +mentioned; e.g. the muscle-plate coelom of Aves, the primitive streak +and the neurenteric canal of amniote blastoderms. In yet other cases in +which the reduced organ is almost on the verge of disappearance, it +may appear for a moment and disappear more than once in the course of +development. As an instance of this striking phenomenon I may mention +the neurenteric canal of avine embryos, and the anterior neuropore of +Ascidians. Lastly the reduced organ may disappear in the developing +stages before it does so in the adult. As an instance of this may be +mentioned the mandibular palp of those Crustacea with zoaea larvae. This +structure disappears in the larva only to reappear in a reduced form in +later stages. In all these cases we are dealing with an organ which, we +imagine, attained a fuller functional development at some previous stage +in race-history, but in most of them we have no proof that it did so. It +may be, and the possibility must not be lost sight of, that these organs +never were anything else than functionless and that though they have +been got rid of in the adult by elimination in the course of time, they +have been able to persist in embryonic stages which are protected from +the full action of natural selection. There is no reason to suppose that +living matter at its first appearance differed from non-living matter +in possessing only properties conducive to its well-being and prolonged +existence. No one thinks that the properties of the various forms of +inorganic matter are all strictly related to external conditions. +Of what use to the diamond is its high specific gravity and high +refrangibility, and to gold of its yellow colour and great weight? These +substances continue to exist in virtue of other properties than these. +It is impossible to suppose that the properties of living matter at +its first appearance were all useful to it, for even now after aeons of +elimination we find that it possesses many useless organs and that +many of its relations to the external world are capable of considerable +improvement. + +In writing this essay I have purposely refrained from taking a definite +position with regard to the problems touched. My desire has been +to write a chapter showing the influence of Darwin's work so far as +Embryology is concerned, and the various points which come up for +consideration in discussing his views. Darwin was the last man who would +have claimed finality for any of his doctrines, but he might fairly have +claimed to have set going a process of intellectual fermentation which +is still very far from completion. + + + + +XI. THE PALAEONTOLOGICAL RECORD. By W.B. Scott. + +Professor of Geology in the University of Princeton, U.S.A. + + +I. ANIMALS. + +To no branch of science did the publication of "The Origin of Species" +prove to be a more vivifying and transforming influence than to +Palaeontology. This science had suffered, and to some extent, still +suffers from its rather anomalous position between geology and biology, +each of which makes claim to its territory, and it was held in strict +bondage to the Linnean and Cuvierian dogma that species were immutable +entities. There is, however, reason to maintain that this strict bondage +to a dogma now abandoned, was not without its good side, and served the +purpose of keeping the infant science in leading-strings until it was +able to walk alone, and preventing a flood of premature generalisations +and speculations. + +As Zittel has said: "Two directions were from the first apparent +in palaeontological research--a stratigraphical and a biological. +Stratigraphers wished from palaeontology mainly confirmation regarding +the true order or relative age of zones of rock-deposits in the field. +Biologists had, theoretically at least, the more genuine interest in +fossil organisms as individual forms of life." (Zittel, "History of +Geology and Palaeontology", page 363, London, 1901.) The geological +or stratigraphical direction of the science was given by the work of +William Smith, "the father of historical geology," in the closing decade +of the eighteenth century. Smith was the first to make a systematic use +of fossils in determining the order of succession of the rocks which +make up the accessible crust of the earth, and this use has continued, +without essential change, to the present day. It is true that the +theory of evolution has greatly modified our conceptions concerning the +introduction of new species and the manner in which palaeontological +data are to be interpreted in terms of stratigraphy, but, broadly +speaking, the method remains fundamentally the same as that introduced +by Smith. + +The biological direction of palaeontology was due to Cuvier and his +associates, who first showed that fossils were not merely varieties +of existing organisms, but belonged to extinct species and genera, +an altogether revolutionary conception, which startled the scientific +world. Cuvier made careful studies, especially of fossil vertebrates, +from the standpoint of zoology and was thus the founder of palaeontology +as a biological science. His great work on "Ossements Fossiles" (Paris, +1821) has never been surpassed as a masterpiece of the comparative +method of anatomical investigation, and has furnished to the +palaeontologist the indispensable implements of research. + +On the other hand, Cuvier's theoretical views regarding the history +of the earth and its successive faunas and floras are such as no one +believes to-day. He held that the earth had been repeatedly devastated +by great cataclysms, which destroyed every living thing, necessitating +an entirely new creation, thus regarding the geological periods as +sharply demarcated and strictly contemporaneous for the whole earth, +and each species of animal and plant as confined to a single period. +Cuvier's immense authority and his commanding personality dominated +scientific thought for more than a generation and marked out the line +which the development of palaeontology was to follow. The work was +enthusiastically taken up by many very able men in the various European +countries and in the United States, but, controlled as it was by the +belief in the fixity of species, it remained almost entirely descriptive +and consisted in the description and classification of the different +groups of fossil organisms. As already intimated, this narrowness of +view had its compensations, for it deferred generalisations until some +adequate foundations for these had been laid. + +Dominant as it was, Cuvier's authority was slowly undermined by the +progress of knowledge and the way was prepared for the introduction of +more rational conceptions. The theory of "Catastrophism" was attacked by +several geologists, most effectively by Sir Charles Lyell, who greatly +amplified the principles enunciated by Hutton and Playfair in the +preceding century, and inaugurated a new era in geology. Lyell's +uniformitarian views of the earth's history and of the agencies which +had wrought its changes, had undoubted effect in educating men's minds +for the acceptance of essentially similar views regarding the organic +world. In palaeontology too the doctrine of the immutability of species, +though vehemently maintained and reasserted, was gradually weakening. In +reviewing long series of fossils, relations were observed which pointed +to genetic connections and yet were interpreted as purely ideal. +Agassiz, for example, who never accepted the evolutionary theory, drew +attention to facts which could be satisfactorily interpreted only in +terms of that theory. Among the fossils he indicated "progressive," +"synthetic," "prophetic," and "embryonic" types, and pointed out the +parallelism which obtains between the geological succession of ancient +animals and the ontogenetic development of recent forms. In Darwin's +words: "This view accords admirably well with our theory." ("Origin of +Species" (6th edition), page 310.) Of similar import were Owen's views +on "generalised types" and "archetypes." + +The appearance of "The Origin of Species" in 1859 revolutionised all +the biological sciences. From the very nature of the case, Darwin +was compelled to give careful consideration to the palaeontological +evidence; indeed, it was the palaeontology and modern distribution of +animals in South America which first led him to reflect upon the great +problem. In his own words: "I had been deeply impressed by discovering +in the Pampean formation great fossil animals covered with armour +like that on the existing armadillos; secondly, by the manner in which +closely allied animals replace one another in proceeding southward over +the Continent; and thirdly, by the South American character of most of +the productions of the Galapagos archipelago, and more especially by +the manner in which they differ slightly on each island of the group." +("Life and Letters of Charles Darwin", I. page 82.) In the famous tenth +and eleventh chapters of the "Origin", the palaeontological evidence +is examined at length and the imperfection of the geological record is +strongly emphasised. The conclusion is reached, that, in view of this +extreme imperfection, palaeontology could not reasonably be expected to +yield complete and convincing proof of the evolutionary theory. "I look +at the geological record as a history of the world imperfectly kept, +and written in a changing dialect; of this history we possess the last +volume alone, relating only to two or three countries. Of this volume, +only here and there a short chapter has been preserved; and of each +page, only here and there a few lines." ("Origin of Species", page 289.) +Yet, aside from these inevitable difficulties, he concludes, that "the +other great leading facts in palaeontology agree admirably with the +theory of descent with modification through variation and natural +selection." (Ibid. page 313.) + +Darwin's theory gave an entirely new significance and importance to +palaeontology. Cuvier's conception of the science had been a limited, +though a lofty one. "How glorious it would be if we could arrange the +organised products of the universe in their chronological order!... The +chronological succession of organised forms, the exact determination +of those types which appeared first, the simultaneous origin of certain +species and their gradual decay, would perhaps teach us as much +about the mysteries of organisation as we can possibly learn through +experiments with living organisms." (Zittel op. cit. page 140.) This, +however, was rather the expression of a hope for the distant future than +an account of what was attainable, and in practice the science remained +almost purely descriptive, until Darwin gave it a new standpoint, new +problems and an altogether fresh interest and charm. The revolution +thus accomplished is comparable only to that produced by the Copernican +astronomy. + +From the first it was obvious that one of the most searching tests +of the evolutionary theory would be given by the advance of +palaeontological discovery. However imperfect the geological record +might be, its ascertained facts would necessarily be consistent, under +any reasonable interpretation, with the demands of a true theory; +otherwise the theory would eventually be overwhelmed by the mass of +irreconcilable data. A very great stimulus was thus given to geological +investigation and to the exploration of new lands. In the last forty +years, the examination of North and South America, of Africa and Asia +has brought to light many chapters in the history of life, which are +astonishingly full and complete. The flood of new material continues to +accumulate at such a rate that it is impossible to keep abreast of it, +and the very wealth of the collections is a source of difficulty and +embarrassment. In modern palaeontology phylogenetic questions and +problems occupy a foremost place and, as a result of the labours of many +eminent investigators in many lands, it may be said that this science +has proved to be one of the most solid supports of Darwin's theory. +True, there are very many unsolved problems, and the discouraged worker +is often tempted to believe that the fossils raise more questions than +they answer. Yet, on the other hand, the whole trend of the evidence +is so strongly in favour of the evolutionary doctrine, that no other +interpretation seems at all rational. + +To present any adequate account of the palaeontological record from the +evolutionary standpoint, would require a large volume and a singularly +unequal, broken and disjointed history it would be. Here the record is +scanty, interrupted, even unintelligible, while there it is crowded with +embarrassing wealth of material, but too often these full chapters are +separated by such stretches of unrecorded time, that it is difficult to +connect them. It will be more profitable to present a few illustrative +examples than to attempt an outline of the whole history. + +At the outset, the reader should be cautioned not to expect too +much, for the task of determining phylogenies fairly bristles with +difficulties and encounters many unanswered questions. Even when the +evidence seems to be as copious and as complete as could be wished, +different observers will put different interpretations upon it, as in +the notorious case of the Steinheim shells. (In the Miocene beds of +Steinheim, Wurtemberg, occur countless fresh-water shells, which show +numerous lines of modification, but these have been very differently +interpreted by different writers.) The ludicrous discrepances which +often appear between the phylogenetic "trees" of various writers have +cast an undue discredit upon the science and have led many zoologists +to ignore palaeontology altogether as unworthy of serious attention. One +principal cause of these discrepant and often contradictory results is +our ignorance concerning the exact modes of developmental change. +What one writer postulates as almost axiomatic, another will reject as +impossible and absurd. Few will be found to agree as to how far a given +resemblance is offset by a given unlikeness, and so long as the question +is one of weighing evidence and balancing probabilities, complete +harmony is not to be looked for. These formidable difficulties confront +us even in attempting to work out from abundant material a brief chapter +in the phylogenetic history of some small and clearly limited group, +and they become disproportionately greater, when we extend our view over +vast periods of time and undertake to determine the mutual relationships +of classes and types. If the evidence were complete and available, we +should hardly be able to unravel its infinite complexity, or to find +a clue through the mazes of the labyrinth. "Our ideas of the course of +descent must of necessity be diagrammatic." (D.H. Scott, "Studies in +Fossil Botany", page 524. London, 1900.) + +Some of the most complete and convincing examples of descent with +modification are to be found among the mammals, and nowhere more +abundantly than in North America, where the series of continental +formations, running through the whole Tertiary period, is remarkably +full. Most of these formations contain a marvellous wealth of mammalian +remains and in an unusual state of preservation. The oldest Eocene +(Paleocene) has yielded a mammalian fauna which is still of prevailingly +Mesozoic character, and contains but few forms which can be regarded +as ancestral to those of later times. The succeeding fauna of the lower +Eocene proper (Wasatch stage) is radically different and, while a few +forms continue over from the Paleocene, the majority are evidently +recent immigrants from some region not yet identified. From the Wasatch +onward, the development of many phyla may be traced in almost unbroken +continuity, though from time to time the record is somewhat obscured by +migrations from the Old World and South America. As a rule, however, it +is easy to distinguish between the immigrant and the indigenous elements +of the fauna. + +From their gregarious habits and individual abundance, the history of +many hoofed animals is preserved with especial clearness. So well known +as to have become a commonplace, is the phylogeny of the horses, which, +contrary to all that would have been expected, ran the greater part of +its course in North America. So far as it has yet been traced, the line +begins in the lower Eocene with the genus Eohippus, a little creature +not much larger than a cat, which has a short neck, relatively short +limbs, and in particular, short feet, with four functional digits and +a splint-like rudiment in the fore-foot, three functional digits and +a rudiment in the hind-foot. The forearm bones (ulna and radius) are +complete and separate, as are also the bones of the lower leg (fibula +and tibia). The skull has a short face, with the orbit, or eye-socket, +incompletely enclosed with bone, and the brain-case is slender and +of small capacity. The teeth are short-crowned, the incisors without +"mark," or enamel pit, on the cutting edge; the premolars are all +smaller and simpler than the molars. The pattern of the upper molars is +so entirely different from that seen in the modern horses that, without +the intermediate connecting steps, no one would have ventured to derive +the later from the earlier plan. This pattern is quadritubercular, with +four principal, conical cusps arranged in two transverse pairs, forming +a square, and two minute cuspules between each transverse pair, a tooth +which is much more pig-like than horse-like. In the lower molars the +cusps have already united to form two crescents, one behind the other, +forming a pattern which is extremely common in the early representatives +of many different families, both of the Perissodactyla and the +Artiodactyla. In spite of the manifold differences in all parts of the +skeleton between Eohippus and the recent horses, the former has stamped +upon it an equine character which is unmistakable, though it can hardly +be expressed in words. + +Each one of the different Eocene and Oligocene horizons has its +characteristic genus of horses, showing a slow, steady progress in a +definite direction, all parts of the structure participating in the +advance. It is not necessary to follow each of these successive steps +of change, but it should be emphasised that the changes are gradual and +uninterrupted. The genus Mesohippus, of the middle Oligocene, may be +selected as a kind of half-way stage in the long progression. Comparing +Mesohippus with Eohippus, we observe that the former is much larger, +some species attaining the size of a sheep, and has a relatively longer +neck, longer limbs and much more elongate feet, which are tridactyl, and +the middle toe is so enlarged that it bears most of the weight, while +the lateral digits are very much more slender. The fore-arm bones have +begun to co-ossify and the ulna is greatly reduced, while the fibula, +though still complete, is hardly more than a thread of bone. The skull +has a longer face and a nearly enclosed orbit, and the brain-case is +fuller and more capacious, the internal cast of which shows that the +brain was richly convoluted. The teeth are still very short-crowned, +but the upper incisors plainly show the beginning of the "mark"; the +premolars have assumed the molar form, and the upper molars, though +plainly derived from those of Eohippus, have made a long stride toward +the horse pattern, in that the separate cusps have united to form a +continuous outer wall and two transverse crests. + +In the lower Miocene the interesting genus Desmatippus shows a further +advance in the development of the teeth, which are beginning to assume +the long-crowned shape, delaying the formation of roots; a thin layer +of cement covers the crowns, and the transverse crests of the upper +grinding teeth display an incipient degree of their modern complexity. +This tooth-pattern is strictly intermediate between the recent type +and the ancient type seen in Mesohippus and its predecessors. The +upper Miocene genera, Protohippus and Hipparion are, to all intents and +purposes, modern in character, but their smaller size, tridactyl feet +and somewhat shorter-crowned teeth are reminiscences of their ancestry. + +From time to time, when a land-connection between North America and +Eurasia was established, some of the successive equine genera migrated +to the Old World, but they do not seem to have gained a permanent +footing there until the end of the Miocene or beginning of the Pliocene, +eventually diversifying into the horses, asses, and zebras of Africa, +Asia and Europe. At about the same period, the family extended its range +to South America and there gave rise to a number of species and genera, +some of them extremely peculiar. For some unknown reason, all the horse +tribe had become extinct in the western hemisphere before the European +discovery, but not until after the native race of man had peopled the +continents. + +In addition to the main stem of equine descent, briefly considered +in the foregoing paragraphs, several side-branches were given off at +successive levels of the stem. Most of these branches were short-lived, +but some of them flourished for a considerable period and ramified into +many species. + +Apparently related to the horses and derived from the same root-stock is +the family of the Palaeotheres, confined to the Eocene and Oligocene of +Europe, dying out without descendants. In the earlier attempts to work +out the history of the horses, as in the famous essay of Kowalevsky +("Sur l'Anchitherium aurelianense Cuv. et sur l'histoire paleontologique +des Chevaux", "Mem. de l'Acad. Imp. des Sc. de St Petersbourg", XX. no. +5, 1873.), the Palaeotheres were placed in the direct line, because +the number of adequately known Eocene mammals was then so small, that +Cuvier's types were forced into various incongruous positions, to serve +as ancestors for unrelated series. + +The American family of the Titanotheres may also be distantly related +to the horses, but passed through an entirely different course of +development. From the lower Eocene to the lower sub-stage of the middle +Oligocene the series is complete, beginning with small and rather +lightly built animals. Gradually the stature and massiveness increase, +a transverse pair of nasal horns make their appearance and, as +these increase in size, the canine tusks and incisors diminish +correspondingly. Already in the oldest known genus the number of digits +had been reduced to four in the fore-foot and three in the hind, but +there the reduction stops, for the increasing body-weight made necessary +the development of broad and heavy feet. The final members of the +series comprise only large, almost elephantine animals, with immensely +developed and very various nasal horns, huge and massive heads, and +altogether a grotesque appearance. The growth of the brain did not +at all keep pace with the increase of the head and body, and the +ludicrously small brain may will have been one of the factors which +determined the startlingly sudden disappearance and extinction of the +group. + +Less completely known, but of unusual interest, is the genealogy of the +rhinoceros family, which probably, though not certainly, was likewise +of American origin. The group in North America at least, comprised three +divisions, or sub-families, of very different proportions, appearance +and habits, representing three divergent lines from the same stem. +Though the relationship between the three lines seems hardly open +to question, yet the form ancestral to all of them has not yet been +identified. This is because of our still very incomplete knowledge +of several perissodactyl genera of the Eocene, any one of which may +eventually prove to be the ancestor sought for. + +The first sub-family is the entirely extinct group of Hyracodonts, which +may be traced in successive modifications through the upper Eocene, +lower and middle Oligocene, then disappearing altogether. As yet, the +hyracodonts have been found only in North America, and the last genus of +the series, Hyracodon, was a cursorial animal. Very briefly stated, +the modifications consist in a gradual increase in size, with greater +slenderness of proportions, accompanied by elongation of the neck, +limbs, and feet, which become tridactyl and very narrow. The grinding +teeth have assumed the rhinoceros-like pattern and the premolars +resemble the molars in form; on the other hand, the front teeth, +incisors and canines, have become very small and are useless as weapons. +As the animal had no horns, it was quite defenceless and must have found +its safety in its swift running, for Hyracodon displays many superficial +resemblances to the contemporary Oligocene horses, and was evidently +adapted for speed. It may well have been the competition of the horses +which led to the extinction of these cursorial rhinoceroses. + +The second sub-family, that of the Amynodonts, followed a totally +different course of development, becoming short-legged and short-footed, +massive animals, the proportions of which suggest aquatic habits; they +retained four digits in the front foot. The animal was well provided +with weapons in the large canine tusks, but was without horns. Some +members of this group extended their range to the Old World, but they +all died out in the middle Oligocene, leaving no successors. + +The sub-family of the true rhinoceroses cannot yet be certainly traced +farther back than to the base of the middle Oligocene, though some +fragmentary remains found in the lower Oligocene are probably also +referable to it. The most ancient and most primitive member of +this series yet discovered, the genus Trigonias, is unmistakably a +rhinoceros, yet much less massive, having more the proportions of a +tapir; it had four toes in the front foot, three in the hind, and had a +full complement of teeth, except for the lower canines, though the upper +canines are about to disappear, and the peculiar modification of the +incisors, characteristic of the true rhinoceroses, is already apparent; +the skull is hornless. Representatives of this sub-family continue +through the Oligocene and Miocene of North America, becoming rare and +localised in the Pliocene and then disappearing altogether. In the Old +World, on the other hand, where the line appeared almost as early as it +did in America, this group underwent a great expansion and ramification, +giving rise not only to the Asiatic and African forms, but also to +several extinct series. + +Turning now to the Artiodactyla, we find still another group of mammals, +that of the camels and llamas, which has long vanished from North +America, yet took its rise and ran the greater part of its course in +that continent. From the lower Eocene onward the history of this series +is substantially complete, though much remains to be learned concerning +the earlier members of the family. The story is very like that of the +horses, to which in many respects it runs curiously parallel. Beginning +with very small, five-toed animals, we observe in the successive genera +a gradual transformation in all parts of the skeleton, an elongation of +the neck, limbs and feet, a reduction of the digits from five to two, +and eventually the coalescence of the remaining two digits into a +"cannon-bone." The grinding teeth, by equally gradual steps, take on +the ruminant pattern. In the upper Miocene the line divides into the two +branches of the camels and llamas, the former migrating to Eurasia +and the latter to South America, though representatives of both lines +persisted in North America until a very late period. Interesting +side-branches of this line have also been found, one of which ended in +the upper Miocene in animals which had almost the proportions of the +giraffes and must have resembled them in appearance. + +The American Tertiary has yielded several other groups of ruminant-like +animals, some of which form beautifully complete evolutionary series, +but space forbids more than this passing mention of them. + +It was in Europe that the Artiodactyla had their principal development, +and the upper Eocene, Oligocene and Miocene are crowded with such an +overwhelming number and variety of forms that it is hardly possible to +marshal them in orderly array and determine their mutual relationships. +Yet in this chaotic exuberance of life, certain important facts stand +out clearly, among these none is of greater interest and importance than +the genealogy of the true Ruminants, or Pecora, which may be traced from +the upper Eocene onward. The steps of modification and change are very +similar to those through which the camel phylum passed in North America, +but it is instructive to note that, despite their many resemblances, the +two series can be connected only in their far distant beginnings. The +pecoran stock became vastly more expanded and diversified than did +the camel line and was evidently more plastic and adaptable, spreading +eventually over all the continents except Australia, and forming to-day +one of the dominant types of mammals, while the camels are on the +decline and not far from extinction. The Pecora successively ramified +into the deer, antelopes, sheep, goats and oxen, and did not reach +North America till the Miocene, when they were already far advanced in +specialisation. To this invasion of the Pecora, or true ruminants, it +seems probable that the decline and eventual disappearance of the camels +is to be ascribed. + +Recent discoveries in Egypt have thrown much light upon a problem which +long baffled the palaeontologist, namely, the origin of the elephants. +(C.W. Andrews, "On the Evolution of the Proboscidea", "Phil. Trans. Roy. +Soc." London, Vol. 196, 1904, page 99.) Early representatives of this +order, Mastodons, had appeared almost simultaneously (in the geological +sense of that word) in the upper Miocene of Europe and North America, +but in neither continent was any more ancient type known which +could plausibly be regarded as ancestral to them. Evidently, these +problematical animals had reached the northern continents by migrating +from some other region, but no one could say where that region lay. The +Eocene and Oligocene beds of the Fayoum show us that the region sought +for is Africa, and that the elephants form just such a series of gradual +modifications as we have found among other hoofed animals. The later +steps of the transformation, by which the mastodons lost their lower +tusks, and their relatively small and simple grinding teeth acquired the +great size and highly complex structure of the true elephants, may be +followed in the uppermost Miocene and Pliocene fossils of India and +southern Europe. + +Egypt has also of late furnished some very welcome material which +contributes to the solution of another unsolved problem which had quite +eluded research, the origin of the whales. The toothed-whales may be +traced back in several more or less parallel lines as far as the +lower Miocene, but their predecessors in the Oligocene are still so +incompletely known that safe conclusions can hardly be drawn from +them. In the middle Eocene of Egypt, however, has been found a +small, whale-like animal (Protocetus), which shows what the ancestral +toothed-whale was like, and at the same time seems to connect these +thoroughly marine mammals with land-animals. Though already entirely +adapted to an aquatic mode of life, the teeth, skull and backbone of +Protocetus display so many differences from those of the later +whales and so many approximations to those of primitive, carnivorous +land-mammals, as, in a large degree, to bridge over the gap between the +two groups. Thus one of the most puzzling of palaeontological questions +is in a fair way to receive a satisfactory answer. The origin of the +whalebone-whales and their relations to the toothed-whales cannot yet be +determined, since the necessary fossils have not been discovered. + +Among the carnivorous mammals, phylogenetic series are not so clear and +distinct as among the hoofed animals, chiefly because the carnivores are +individually much less abundant, and well-preserved skeletons are among +the prizes of the collector. Nevertheless, much has already been learned +concerning the mutual relations of the carnivorous families, and several +phylogenetic series, notably that of the dogs, are quite complete. It +has been made extremely probable that the primitive dogs of the Eocene +represent the central stock, from which nearly or quite all the other +families branched off, though the origin and descent of the cats have +not yet been determined. + +It should be clearly understood that the foregoing account of mammalian +descent is merely a selection of a few representative cases and might be +almost indefinitely extended. Nothing has been said, for example, of +the wonderful museum of ancient mammalian life which is entombed in the +rocks of South America, especially of Patagonia, and which opens a +world so entirely different from that of the northern continents, +yet exemplifying the same laws of "descent with modification." Very +beautiful phylogenetic series have already been established among these +most interesting and marvellously preserved fossils, but lack of space +forbids a consideration of them. + +The origin of the mammalia, as a class, offers a problem of which +palaeontology can as yet present no definitive solution. Many +morphologists regard the early amphibia as the ancestral group from +which the mammals were derived, while most palaeontologists believe +that the mammals are descended from the reptiles. The most ancient known +mammals, those from the upper Triassic of Europe and North America, are +so extremely rare and so very imperfectly known, that they give little +help in determining the descent of the class, but, on the other +hand, certain reptilian orders of the Permian period, especially +well represented in South Africa, display so many and such close +approximations to mammalian structure, as strongly to suggest a genetic +relationship. It is difficult to believe that all those likenesses +should have been independently acquired and are without phylogenetic +significance. + +Birds are comparatively rare as fossils and we should therefore look in +vain among them for any such long and closely knit series as the +mammals display in abundance. Nevertheless, a few extremely fortunate +discoveries have made it practically certain that birds are descended +from reptiles, of which they represent a highly specialised branch. The +most ancient representative of this class is the extraordinary genus +Archaeopteryx from the upper Jurassic of Bavaria, which, though +an unmistakable bird, retains so many reptilian structures and +characteristics as to make its derivation plain. Not to linger over +anatomical minutiae, it may suffice to mention the absence of a horny +beak, which is replaced by numerous true teeth, and the long lizard-like +tail, which is made up of numerous distinct vertebrae, each with a pair +of quill-like feathers attached to it. Birds with teeth are also found +in the Cretaceous, though in most other respects the birds of that +period had attained a substantially modern structure. Concerning +the interrelations of the various orders and families of birds, +palaeontology has as yet little to tell us. + +The life of the Mesozoic era was characterised by an astonishing number +and variety of reptiles, which were adapted to every mode of life, +and dominated the air, the sea and the land, and many of which were +of colossal proportions. Owing to the conditions of preservation which +obtained during the Mesozoic period, the history of the reptiles is a +broken and interrupted one, so that we can make out many short series, +rather than any one of considerable length. While the relations of +several reptilian orders can be satisfactorily determined, others still +baffle us entirely, making their first known appearance in a fully +differentiated state. We can trace the descent of the sea-dragons, the +Ichthyosaurs and Plesiosaurs, from terrestrial ancestors, but the most +ancient turtles yet discovered show us no closer approximation to any +other order than do the recent turtles; and the oldest known Pterosaurs, +the flying dragons of the Jurassic, are already fully differentiated. +There is, however, no ground for discouragement in this, for the +progress of discovery has been so rapid of late years, and our knowledge +of Mesozoic life has increased with such leaps and bounds, that there is +every reason to expect a solution of many of the outstanding problems in +the near future. + +Passing over the lower vertebrates, for lack of space to give them +any adequate consideration, we may briefly take up the record of +invertebrate life. From the overwhelming mass of material it is +difficult to make a representative selection and even more difficult +to state the facts intelligibly without the use of unduly technical +language and without the aid of illustrations. + +Several groups of the Mollusca, or shell-fish, yield very full and +convincing evidence of their descent from earlier and simpler forms, +and of these none is of greater interest than the Ammonites, an extinct +order of the cephalopoda. The nearest living ally of the ammonites is +the pearly nautilus, the other existing cephalopods, such as the squids, +cuttle-fish, octopus, etc., are much more distantly related. Like the +nautilus, the ammonites all possess a coiled and chambered shell, but +their especial characteristic is the complexity of the "sutures." By +sutures is meant the edges of the transverse partitions, or septa, where +these join the shell-wall, and their complexity in the fully developed +genera is extraordinary, forming patterns like the most elaborate +oak-leaf embroidery, while in the nautiloids the sutures form simple +curves. In the rocks of the Mesozoic era, wherever conditions of +preservation are favourable, these beautiful shells are stored in +countless multitudes, of an incredible variety of form, size and +ornamentation, as is shown by the fact that nearly 5000 species have +already been described. The ammonites are particularly well adapted for +phylogenetic studies, because, by removing the successive whorls of the +coiled shell, the individual development may be followed back in inverse +order, to the microscopic "protoconch," or embryonic shell, which lies +concealed in the middle of the coil. Thus the valuable aid of embryology +is obtained in determining relationships. + +The descent of the ammonites, taken as a group, is simple and clear; +they arose as a branch of the nautiloids in the lower Devonian, the +shells known as goniatites having zigzag, angulated sutures. Late in +the succeeding Carboniferous period appear shells with a truly ammonoid +complexity of sutures, and in the Permian their number and variety +cause them to form a striking element of the marine faunas. It is in the +Mesozoic era, however, that these shells attain their full development; +increasing enormously in the Triassic, they culminate in the Jurassic +in the number of families, genera and species, in the complexity of +the sutures, and in the variety of shell-ornamentation. A slow decline +begins in the Cretaceous, ending in the complete extinction of the whole +group at the end of that period. As a final phase in the history of the +ammonites, there appear many so-called "abnormal" genera, in which the +shell is irregularly coiled, or more or less uncoiled, in some forms +becoming actually straight. It is interesting to observe that some of +these genera are not natural groups, but are "polyphyletic," i.e. +are each derived from several distinct ancestral genera, which have +undergone a similar kind of degeneration. + +In the huge assembly of ammonites it is not yet possible to arrange all +the forms in a truly natural classification, which shall express the +various interrelations of the genera, yet several beautiful series have +already been determined. In these series the individual development +of the later general shows transitory stages which are permanent in +antecedent genera. To give a mere catalogue of names without figures +would not make these series more intelligible. + +The Brachiopoda, or "lamp-shells," are a phylum of which comparatively +few survive to the present day; their shells have a superficial likeness +to those of the bivalved Mollusca, but are not homologous with the +latter, and the phylum is really very distinct from the molluscs. While +greatly reduced now, these animals were incredibly abundant throughout +the Palaeozoic era, great masses of limestone being often composed +almost exclusively of their shells, and their variety is in keeping with +their individual abundance. As in the case of the ammonites, the problem +is to arrange this great multitude of forms in an orderly array that +shall express the ramifications of the group according to a genetic +system. For many brachiopods, both recent and fossil, the individual +development, or ontogeny, has been worked out and has proved to be +of great assistance in the problems of classification and phylogeny. +Already very encouraging progress has been made in the solution of these +problems. All brachiopods form first a tiny, embryonic shell, called +the protegulum, which is believed to represent the ancestral form of the +whole group, and in the more advanced genera the developmental stages +clearly indicate the ancestral genera of the series, the succession +of adult forms in time corresponding to the order of the ontogenetic +stages. The transformation of the delicate calcareous supports of the +arms, often exquisitely preserved, are extremely interesting. Many of +the Palaeozoic genera had these supports coiled like a pair of spiral +springs, and it has been shown that these genera were derived from types +in which the supports were simply shelly loops. + +The long extinct class of crustacea known as the Trilobites are likewise +very favourable subjects for phylogenetic studies. So far as the known +record can inform us, the trilobites are exclusively Palaeozoic in +distribution, but their course must have begun long before that era, as +is shown by the number of distinct types among the genera of the +lower Cambrian. The group reached the acme of abundance and relative +importance in the Cambrian and Ordovician; then followed a long, slow +decline, ending in complete and final disappearance before the end of +the Permian. The newly-hatched and tiny trilobite larva, known as +the protaspis, is very near to the primitive larval form of all the +crustacea. By the aid of the correlated ontogenetic stages and the +succession of the adult forms in the rocks, many phylogenetic series +have been established and a basis for the natural arrangement of the +whole class has been laid. + +Very instructive series may also be observed among the Echinoderms and, +what is very rare, we are able in this sub-kingdom to demonstrate the +derivation of one class from another. Indeed, there is much reason to +believe that the extinct class Cystidea of the Cambrian is the ancestral +group, from which all the other Echinoderms, star-fishes, brittle-stars, +sea-urchins, feather-stars, etc., are descended. + +The foregoing sketch of the palaeontological record is, of necessity, +extremely meagre, and does not represent even an outline of the +evidence, but merely a few illustrative examples, selected almost +at random from an immense body of material. However, it will perhaps +suffice to show that the geological record is not so hopelessly +incomplete as Darwin believed it to be. Since "The Origin of Species" +was written, our knowledge of that record has been enormously extended +and we now possess, no complete volumes, it is true, but some remarkably +full and illuminating chapters. The main significance of the whole lies +in the fact, that JUST IN PROPORTION TO THE COMPLETENESS OF THE RECORD +IS THE UNEQUIVOCAL CHARACTER OF ITS TESTIMONY TO THE TRUTH OF THE +EVOLUTIONARY THEORY. + +The test of a true, as distinguished from a false, theory is the manner +in which newly discovered and unanticipated facts arrange themselves +under it. No more striking illustration of this can be found than in the +contrasted fates of Cuvier's theory and of that of Darwin. Even before +Cuvier's death his views had been undermined and the progress of +discovery soon laid them in irreparable ruin, while the activity of +half-a-century in many different lines of inquiry has established the +theory of evolution upon a foundation of ever growing solidity. It is +Darwin's imperishable glory that he prescribed the lines along which all +the biological sciences were to advance to conquests not dreamed of when +he wrote. + + + + +XII. THE PALAEONTOLOGICAL RECORD. By D.H. Scott, F.R.S. + +President of the Linnean Society. + + +II. PLANTS. + +There are several points of view from which the subject of the present +essay may be regarded. We may consider the fossil record of plants +in its bearing: I. on the truth of the doctrine of Evolution; II. on +Phylogeny, or the course of Evolution; III. on the theory of Natural +Selection. The remarks which follow, illustrating certain aspects only +of an extensive subject, may conveniently be grouped under these three +headings. + +I. THE TRUTH OF EVOLUTION. + +When "The Origin of Species" was written, it was necessary to show that +the Geological Record was favourable to, or at least consistent with, +the Theory of Descent. The point is argued, closely and fully, in +Chapter X. "On the Imperfection of the Geological Record," and Chapter +XI. "On the Geological Succession of Organic Beings"; there is, however, +little about plants in these chapters. At the present time the truth +of Evolution is no longer seriously disputed, though there are writers, +like Reinke, who insist, and rightly so, that the doctrine is still +only a belief, rather than an established fact of science. (J. Reinke, +"Kritische Abstammungslehre", "Wiesner-Festschrift", page 11, Vienna, +1908.) Evidently, then, however little the Theory of Descent may be +questioned in our own day, it is desirable to assure ourselves how the +case stands, and in particular how far the evidence from fossil plants +has grown stronger with time. + +As regards direct evidence for the derivation of one species from +another, there has probably been little advance since Darwin wrote, at +least so we must infer from the emphasis laid on the discontinuity +of successive fossil species by great systematic authorities like +Grand'Eury and Zeiller in their most recent writings. We must either +adopt the mutationist views of those authors (referred to in the last +section of this essay) or must still rely on Darwin's explanation of the +absence of numerous intermediate varieties. The attempts which have been +made to trace, in the Tertiary rocks, the evolution of recent species, +cannot, owing to the imperfect character of the evidence, be regarded as +wholly satisfactory. + +When we come to groups of a somewhat higher order we have an interesting +history of the evolution of a recent family in the work, not yet +completed, of Kidston and Gwynne-Vaughan on the fossil Osmundaceae. +("Trans. Royal Soc. Edinburgh", Vol. 45, Part III. 1907, Vol. 46, Part +II. 1908, Vol. 46, Part III. 1909.) The authors are able, mainly on +anatomical evidence, to trace back this now limited group of Ferns, +through the Tertiary and Mesozoic to the Permian, and to show, with +great probability, how their structure has been derived from that of +early Palaeozoic types. + +The history of the Ginkgoaceae, now represented only by the isolated +maidenhair tree, scarcely known in a wild state, offers another striking +example of a family which can be traced with certainty to the older +Mesozoic and perhaps further back still. (See Seward and Gowan, "The +Maidenhair Tree (Gingko biloba)", "Annals of Botany", Vol. XIV. 1900, +page 109; also A. Sprecher "Le Ginkgo biloba", L., Geneva, 1907.) + +On the wider question of the derivation of the great groups of plants, +a very considerable advance has been made, and, so far as the higher +plants are concerned, we are now able to form a far better conception +than before of the probable course of evolution. This is a matter +of phylogeny, and the facts will be considered under that head; our +immediate point is that the new knowledge of the relations between the +classes of plants in question materially strengthens the case for the +theory of descent. The discoveries of the last few years throw light +especially on the relation of the Angiosperms to the Gymnosperms, +on that of the Seed-plants generally to the Ferns, and on the +interrelations between the various classes of the higher Cryptogams. + +That the fossil record has not done still more for Evolution is due to +the fact that it begins too late--a point on which Darwin laid stress +("Origin of Species" (6th edition), page 286.) and which has more +recently been elaborated by Poulton. ("Essays on Evolution", pages 46 +et seq., Oxford, 1908.) An immense proportion of the whole evolutionary +history lies behind the lowest fossiliferous rocks, and the case is +worse for plants than for animals, as the record for the former begins, +for all practical purposes, much higher up in the rocks. + +It may be well here to call attention to a question, often overlooked, +which has lately been revived by Reinke. (Reinke, loc. cit. page 13.) As +all admit, we know nothing of the origin of life; consequently, for all +we can tell, it is as probable that life began, on this planet, with +many living things, as with one. If the first organic beings were many, +they may have been heterogeneous, or at least exposed to different +conditions, from their origin; in either case there would have been a +number of distinct series from the beginning, and if so we should not +be justified in assuming that all organisms are related to one another. +There may conceivably be several of the original lines of descent still +surviving, or represented among extinct forms--to reverse the remark +of a distinguished botanist, there may be several Vegetable Kingdoms! +However improbable this may sound, the possibility is one to be borne in +mind. + +That all VASCULAR plants really belong to one stock seems certain, and +here the palaeontological record has materially strengthened the +case for a monophyletic history. The Bryophyta are not likely to be +absolutely distinct, for their sexual organs, and the stomata of the +Mosses strongly suggest community of descent with the higher plants; if +this be so it no doubt establishes a certain presumption in favour of +a common origin for plants generally, for the gap between "Mosses and +Ferns" has been regarded as the widest in the Vegetable Kingdom. The +direct evidence of consanguinity is however much weaker when we come to +the Algae, and it is conceivable (even if improbable) that the higher +plants may have had a distinct ancestry (now wholly lost) from the +beginning. The question had been raised in Darwin's time, and he +referred to it in these words: "No doubt it is possible, as Mr G.H. +Lewes has urged, that at the first commencement of life many different +forms were evolved; but if so, we may conclude that only a very few +have left modified descendants." ("Origin of Species", page 425.) This +question, though it deserves attention, does not immediately affect the +subject of the palaeontological record of plants, for there can be no +reasonable doubt as to the interrelationship of those groups on which +the record at present throws light. + +The past history of plants by no means shows a regular progression from +the simple to the complex, but often the contrary. This apparent anomaly +is due to two causes. + +1. The palaeobotanical record is essentially the story of the successive +ascendancy of a series of dominant families, each of which attained +its maximum, in organisation as well as in extent, and then sank into +comparative obscurity, giving place to other families, which under new +conditions were better able to take a leading place. As each family ran +its downward course, either its members underwent an actual reduction in +structure as they became relegated to herbaceous or perhaps aquatic life +(this may have happened with the Horsetails and with Isoetes if derived +from Lepidodendreae), or the higher branches of the family were crowded +out altogether and only the "poor relations" were able to maintain their +position by evading the competition of the ascendant races; this is also +illustrated by the history of the Lycopod phylum. In either case there +would result a lowering of the type of organisation within the group. + +2. The course of real progress is often from the complex to the simple. +If, as we shall find some grounds for believing, the Angiosperms came +from a type with a flower resembling in its complexity that of Mesozoic +"Cycads," almost the whole evolution of the flower in the highest +plants has been a process of reduction. The stamen, in particular, has +undoubtedly become extremely simplified during evolution; in the most +primitive known seed-plants it was a highly compound leaf or pinna; its +reduction has gone on in the Conifers and modern Cycads, as well as in +the Angiosperms, though in different ways and to a varying extent. + +The seed offers another striking example; the Palaeozoic seeds (if we +leave the seed-like organs of certain Lycopods out of consideration) +were always, so far as we know, highly complex structures, with +an elaborate vascular system, a pollen-chamber, and often a +much-differentiated testa. In the present day such seeds exist only in a +few Gymnosperms which retain their ancient characters--in all the higher +Spermophytes the structure is very much simplified, and this holds good +even in the Coniferae, where there is no countervailing complication of +ovary and stigma. + +Reduction, in fact, is not always, or even generally, the same thing as +degeneration. Simplification of parts is one of the most usual means of +advance for the organism as a whole. A large proportion of the higher +plants are microphyllous in comparison with the highly megaphyllous +fern-like forms from which they appear to have been derived. + +Darwin treated the general question of advance in organisation with much +caution, saying: "The geological record... does not extend far enough +back, to show with unmistakeable clearness that within the known history +of the world organisation has largely advanced." ("Origin of Species", +page 308.) Further on (Ibid. page 309.) he gives two standards by which +advance may be measured: "We ought not solely to compare the highest +members of a class at any two periods... but we ought to compare all the +members, high and low, at the two periods." Judged by either standard +the Horsetails and Club Mosses of the Carboniferous were higher than +those of our own day, and the same is true of the Mesozoic Cycads. There +is a general advance in the succession of classes, but not within each +class. + +Darwin's argument that "the inhabitants of the world at each successive +period in its history have beaten their predecessors in the race for +life, and are, in so far, higher in the scale" ("Origin of Species", +page 315.) is unanswerable, but we must remember that "higher in the +scale" only means "better adapted to the existing conditions." Darwin +points out (Ibid. page 279.) that species have remained unchanged for +long periods, probably longer than the periods of modification, and only +underwent change when the conditions of their life were altered. Higher +organisation, judged by the test of success, is thus purely relative to +the changing conditions, a fact of which we have a striking illustration +in the sudden incoming of the Angiosperms with all their wonderful +floral adaptations to fertilisation by the higher families of Insects. + +II. PHYLOGENY. + +The question of phylogeny is really inseparable from that of the truth +of the doctrine of evolution, for we cannot have historical evidence +that evolution has actually taken place without at the same time having +evidence of the course it has followed. + +As already pointed out, the progress hitherto made has been rather in +the way of joining up the great classes of plants than in tracing the +descent of particular species or genera of the recent flora. There +appears to be a difference in this respect from the Animal record, +which tells us so much about the descent of living species, such as the +elephant or the horse. The reason for this difference is no doubt to be +found in the fact that the later part of the palaeontological record +is the most satisfactory in the case of animals and the least so in the +case of plants. The Tertiary plant-remains, in the great majority of +instances, are impressions of leaves, the conclusions to be drawn from +which are highly precarious; until the whole subject of Angiospermous +palaeobotany has been reinvestigated, it would be rash to venture on +any statements as to the descent of the families of Dicotyledons or +Monocotyledons. + +Our attention will be concentrated on the following questions, all +relating to the phylogeny of main groups of plants: i. The Origin of the +Angiosperms. ii. The Origin of the Seed-plants. iii. The Origin of the +different classes of the Higher Cryptogamia. + +i. THE ORIGIN OF THE ANGIOSPERMS. + +The first of these questions has long been the great crux of botanical +phylogeny, and until quite recently no light had been thrown upon the +difficulty. The Angiosperms are the Flowering Plants, par excellence, +and form, beyond comparison, the dominant sub-kingdom in the flora of +our own age, including, apart from a few Conifers and Ferns, all the +most familiar plants of our fields and gardens, and practically all +plants of service to man. All recent work has tended to separate the +Angiosperms more widely from the other seed-plants now living, the +Gymnosperms. Vast as is the range of organisation presented by the great +modern sub-kingdom, embracing forms adapted to every environment, there +is yet a marked uniformity in certain points of structure, as in the +development of the embryo-sac and its contents, the pollination +through the intervention of a stigma, the strange phenomenon of double +fertilisation (One sperm fertilising the egg, while the other unites +with the embryo-sac nucleus, itself the product of a nuclear fusion, to +give rise to a nutritive tissue, the endosperm.), the structure of +the stamens, and the arrangement of the parts of the flower. All these +points are common to Monocotyledons and Dicotyledons, and separate the +Angiosperms collectively from all other plants. + +In geological history the Angiosperms first appear in the Lower +Cretaceous, and by Upper Cretaceous times had already swamped all other +vegetation and seized the dominant position which they still hold. Thus +they are isolated structurally from the rest of the Vegetable Kingdom, +while historically they suddenly appear, almost in full force, and +apparently without intermediaries with other groups. To quote Darwin's +vigorous words: "The rapid development, as far as we can judge, of +all the higher plants within recent geological times is an abominable +mystery." ("More Letters of Charles Darwin", Vol. II. page 20, letter +to J.D. Hooker, 1879.) A couple of years later he made a bold suggestion +(which he only called an "idle thought") to meet this difficulty. He +says: "I have been so astonished at the apparently sudden coming in of +the higher phanerogams, that I have sometimes fancied that development +might have slowly gone on for an immense period in some isolated +continent or large island, perhaps near the South Pole." (Ibid, page +26, letter to Hooker, 1881.) This idea of an Angiospermous invasion from +some lost southern land has sometimes been revived since, but has not, +so far as the writer is aware, been supported by evidence. Light on the +problem has come from a different direction. + +The immense development of plants with the habit of Cycads, during the +Mesozoic Period up to the Lower Cretaceous, has long been known. The +existing Order Cycadaceae is a small family, with 9 genera and perhaps +100 species, occurring in the tropical and sub-tropical zones of both +the Old and New World, but nowhere forming a dominant feature in the +vegetation. Some few attain the stature of small trees, while in the +majority the stem is short, though often living to a great age. The +large pinnate or rarely bipinnate leaves give the Cycads a superficial +resemblance in habit to Palms. Recent Cycads are dioecious; throughout +the family the male fructification is in the form of a cone, each scale +of the cone representing a stamen, and bearing on its lower surface +numerous pollen-sacs, grouped in sori like the sporangia of Ferns. In +all the genera, except Cycas itself, the female fructifications are +likewise cones, each carpel bearing two ovules on its margin. In Cycas, +however, no female cone is produced, but the leaf-like carpels, bearing +from two to six ovules each, are borne directly on the main stem of the +plant in rosettes alternating with those of the ordinary leaves--the +most primitive arrangement known in any living seed-plant. The +whole Order is relatively primitive, as shown most strikingly in its +cryptogamic mode of fertilisation, by means of spermatozoids, which it +shares with the maidenhair tree alone, among recent seed-plants. + +In all the older Mesozoic rocks, from the Trias to the Lower Cretaceous, +plants of the Cycad class (Cycadophyta, to use Nathorst's comprehensive +name) are extraordinarily abundant in all parts of the world; in +fact they were almost as prominent in the flora of those ages as the +Dicotyledons are in that of our own day. In habit and to a great extent +in anatomy, the Mesozoic Cycadophyta for the most part much resemble the +recent Cycadaceae. But, strange to say, it is only in the rarest +cases that the fructification has proved to be of the simple type +characteristic of the recent family; the vast majority of the abundant +fertile specimens yielded by the Mesozoic rocks possess a type of +reproductive apparatus far more elaborate than anything known in +Cycadaceae or other Gymnosperms. The predominant Mesozoic family, +characterised by this advanced reproductive organisation, is known +as the Bennettiteae; in habit these plants resembled the more stunted +Cycads of the recent flora, but differed from them in the presence of +numerous lateral fructifications, like large buds, borne on the stem +among the crowded bases of the leaves. The organisation of these +fructifications was first worked out on European specimens by +Carruthers, Solms-Laubach, Lignier and others, but these observers had +only more or less ripe fruits to deal with; the complete structure of +the flower has only been elucidated within the last few years by the +researches of Wieland on the magnificent American material, derived from +the Upper Jurassic and Lower Cretaceous beds of Maryland, Dakota and +Wyoming. (G.R. Wieland, "American Fossil Cycads", Carnegie Institution, +Washington, 1906.) The word "flower" is used deliberately, for reasons +which will be apparent from the following brief description, based on +Wieland's observations. + +The fructification is attached to the stem by a thick stalk, which, +in its upper part, bears a large number of spirally arranged bracts, +forming collectively a kind of perianth and completely enclosing the +essential organs of reproduction. The latter consist of a whorl of +stamens, of extremely elaborate structure, surrounding a central cone +or receptacle bearing numerous ovules. The stamens resemble the fertile +fronds of a fern; they are of a compound, pinnate form, and bear +very large numbers of pollen-sacs, each of which is itself a compound +structure consisting of a number of compartments in which the pollen +was formed. In their lower part the stamens are fused together by their +stalks, like the "monadelphous" stamens of a mallow. The numerous ovules +borne on the central receptacle are stalked, and are intermixed with +sterile scales; the latter are expanded at their outer ends, which are +united to form a kind of pericarp or ovary-wall, only interrupted by the +protruding micropyles of the ovules. There is thus an approach to +the closed pistil of an Angiosperm, but it is evident that the ovules +received the pollen directly. The whole fructification is of large size; +in the case of Cycadeoidea dacotensis, one of the species investigated +by Wieland, the total length, in the bud condition, is about 12 cm., +half of which belongs to the peduncle. + +The general arrangement of the organs is manifestly the same as in a +typical Angiospermous flower, with a central pistil, a surrounding whorl +of stamens and an enveloping perianth; there is, as we have seen, some +approach to the closed ovary of an Angiosperm; another point, first +discovered nearly 20 years ago by Solms-Laubach in his investigation of +a British species, is that the seed was practically "exalbuminous," its +cavity being filled by the large, dicotyledonous embryo, whereas in all +known Gymnosperms a large part of the sac is occupied by a nutritive +tissue, the prothallus or endosperm; here also we have a condition only +met with elsewhere among the higher Flowering Plants. + +Taking all the characters into account, the indications of affinity +between the Mesozoic Cycadophyta and the Angiosperms appear extremely +significant, as was recognised by Wieland when he first discovered the +hermaphrodite nature of the Bennettitean flower. The Angiosperm +with which he specially compared the fossil type was the Tulip tree +(Liriodendron) and certainly there is a remarkable analogy with +the Magnoliaceous flowers, and with those of related orders such as +Ranunculaceae and the Water-lilies. It cannot, of course, be maintained +that the Bennettiteae, or any other Mesozoic Cycadophyta at present +known, were on the direct line of descent of the Angiosperms, for there +are some important points of difference, as, for example, in the great +complexity of the stamens, and in the fact that the ovary-wall +or pericarp was not formed by the carpels themselves, but by the +accompanying sterile scale-leaves. Botanists, since the discovery of the +bisexual flowers of the Bennettiteae, have expressed different views as +to the nearness of their relation to the higher Flowering Plants, but +the points of agreement are so many that it is difficult to resist the +conviction that a real relation exists, and that the ancestry of the +Angiosperms, so long shrouded in complete obscurity, is to be sought +among the great plexus of Cycad-like plants which dominated the flora +of the world in Mesozoic times. (On this subject see, in addition +to Wieland's great work above cited, F.W. Oliver, "Pteridosperms +and Angiosperms", "New Phytologist", Vol. V. 1906; D.H. Scott, +"The Flowering Plants of the Mesozoic Age in the Light of Recent +Discoveries", "Journal R. Microscop. Soc." 1907, and especially E.A.N. +Arber and J. Parkin, "On the Origin of Angiosperms", "Journal Linn. +Soc." (Bot.) Vol. XXXVIII. page 29, 1907.) + +The great complexity of the Bennettitean flower, the earliest known +fructification to which the word "flower" can be applied without forcing +the sense, renders it probable, as Wieland and others have pointed +out, that the evolution of the flower in Angiosperms has consisted +essentially in a process of reduction, and that the simplest forms +of flower are not to be regarded as the most primitive. The older +morphologists generally took the view that such simple flowers were to +be explained as reductions from a more perfect type, and this opinion, +though abandoned by many later writers, appears likely to be true when +we consider the elaboration of floral structure attained among the +Mesozoic Cycadophyta, which preceded the Angiosperms in evolution. + +If, as now seems probable, the Angiosperms were derived from ancestors +allied to the Cycads, it would naturally follow that the Dicotyledons +were first evolved, for their structure has most in common with that of +the Cycadophyta. We should then have to regard the Monocotyledons as +a side-line, diverging probably at a very early stage from the main +dicotyledonous stock, a view which many botanists have maintained, +of late, on other grounds. (See especially Ethel Sargant, "The +Reconstruction of a Race of Primitive Angiosperms", "Annals of Botany", +Vol. XXII. page 121, 1908.) So far, however, as the palaeontological +record shows, the Monocotyledons were little if at all later in their +appearance than the Dicotyledons, though always subordinate in numbers. +The typical and beautifully preserved Palm-wood from Cretaceous rocks +is striking evidence of the early evolution of a characteristic +monocotyledonous family. It must be admitted that the whole question of +the evolution of Monocotyledons remains to be solved. + +Accepting, provisionally, the theory of the cycadophytic origin of +Angiosperms, it is interesting to see to what further conclusions we +are led. The Bennettiteae, at any rate, were still at the gymnospermous +level as regards their pollination, for the exposed micropyles of the +ovules were in a position to receive the pollen directly, without the +intervention of a stigma. It is thus indicated that the Angiosperms +sprang from a gymnospermous source, and that the two great phyla of +Seed-plants have not been distinct from the first, though no doubt the +great majority of known Gymnosperms, especially the Coniferae, represent +branch-lines of their own. + +The stamens of the Bennettiteae are arranged precisely as in an +angiospermous flower, but in form and structure they are like the +fertile fronds of a Fern, in fact the compound pollen-sacs, or synangia +as they are technically called, almost exactly agree with the spore-sacs +of a particular family of Ferns--the Marattiaceae, a limited group, +now mainly tropical, which was probably more prominent in the later +Palaeozoic times than at present. The scaly hairs, or ramenta, which +clothe every part of the plant, are also like those of Ferns. + +It is not likely that the characters in which the Bennettiteae resemble +the Ferns came to them directly from ancestors belonging to that class; +an extensive group of Seed-plants, the Pteridospermeae, existed in +Palaeozoic times and bear evident marks of affinity with the Fern +phylum. The fern-like characters so remarkably persistent in the highly +organised Cycadophyta of the Mesozoic were in all likelihood derived +through the Pteridosperms, plants which show an unmistakable approach to +the cycadophytic type. + +The family Bennettiteae thus presents an extraordinary association +of characters, exhibiting, side by side, features which belong to the +Angiosperms, the Gymnosperms and the Ferns. + +ii. ORIGIN OF SEED-PLANTS. + +The general relation of the gymnospermous Seed-plants to the Higher +Cryptogamia was cleared up, independently of fossil evidence, by the +brilliant researches of Hofmeister, dating from the middle of the +past century. (W. Hofmeister, "On the Germination, Development and +Fructification of the Higher Cryptogamia", Ray Society, London, 1862. +The original German treatise appeared in 1851.) He showed that "the +embryo-sac of the Coniferae may be looked upon as a spore remaining +enclosed in its sporangium; the prothallium which it forms does not come +to the light." (Ibid. page 438.) He thus determined the homologies on +the female side. Recognising, as some previous observers had already +done, that the microspores of those Cryptogams in which two kinds of +spore are developed, are equivalent to the pollen-grains of the higher +plants, he further pointed out that fertilisation "in the Rhizocarpeae +and Selaginellae takes place by free spermatozoa, and in the Coniferae +by a pollen-tube, in the interior of which spermatozoa are probably +formed"--a remarkable instance of prescience, for though spermatozoids +have not been found in the Conifers proper, they were demonstrated +in the allied groups Cycadaceae and Ginkgo, in 1896, by the Japanese +botanists Ikeno and Hirase. A new link was thus established between the +Gymnosperms and the Cryptogams. + +It remained uncertain, however, from which line of Cryptogams the +gymnospermous Seed-plants had sprung. The great point of morphological +comparison was the presence of two kinds of spore, and this was known to +occur in the recent Lycopods and Water-ferns (Rhizocarpeae) and was +also found in fossil representatives of the third phylum, that of the +Horsetails. As a matter of fact all the three great Cryptogamic classes +have found champions to maintain their claim to the ancestry of the +Seed-plants, and in every case fossil evidence was called in. For a long +time the Lycopods were the favourites, while the Ferns found the least +support. The writer remembers, however, in the year 1881, hearing the +late Prof. Sachs maintain, in a lecture to his class, that the descent +of the Cycads could be traced, not merely from Ferns, but from a +definite family of Ferns, the Marattiaceae, a view which, though in a +somewhat crude form, anticipated more modern ideas. + +Williamson appears to have been the first to recognise the presence, in +the Carboniferous flora, of plants combining the characters of Ferns and +Cycads. (See especially his "Organisation of the Fossil Plants of the +Coal-Measures", Part XIII. "Phil. Trans. Royal Soc." 1887 B. page 299.) +This conclusion was first reached in the case of the genera Heterangium +and Lyginodendron, plants, which with a wholly fern-like habit, were +found to unite an anatomical structure holding the balance between +that of Ferns and Cycads, Heterangium inclining more to the former +and Lyginodendron to the latter. Later researches placed Williamson's +original suggestion on a firmer basis, and clearly proved the +intermediate nature of these genera, and of a number of others, so far +as their vegetative organs were concerned. This stage in our knowledge +was marked by the institution of the class Cycadofilices by Potonie in +1897. + +Nothing, however, was known of the organs of reproduction of the +Cycadofilices, until F.W. Oliver, in 1903, identified a fossil seed, +Lagenostoma Lomaxi, as belonging to Lyginodendron, the identification +depending, in the first instance, on the recognition of an identical +form of gland, of very characteristic structure, on the vegetative +organs of Lyginodendron and on the cupule enveloping the seed. This +evidence was supported by the discovery of a close anatomical agreement +in other respects, as well as by constant association between the seed +and the plant. (F.W. Oliver and D.H. Scott, "On the Structure of the +Palaeozoic Seed, Lagenostoma Lomaxi, etc." "Phil. Trans. Royal Soc." +Vol. 197 B. 1904.) The structure of the seed of Lyginodendron, proved to +be of the same general type as that of the Cycads, as shown especially +by the presence of a pollen-chamber or special cavity for the reception +of the pollen-grains, an organ only known in the Cycads and Ginkgo among +recent plants. + +Within a few months after the discovery of the seed of Lyginodendron, +Kidston found the large, nut-like seed of a Neuropteris, another +fern-like Carboniferous plant, in actual connection with the pinnules +of the frond, and since then seeds have been observed on the frond in +species of Aneimites and Pecopteris, and a vast body of evidence, direct +or indirect, has accumulated, showing that a large proportion of the +Palaeozoic plants formerly classed as Ferns were in reality reproduced +by seeds of the same type as those of recent Cycadaceae. (A summary +of the evidence will be found in the writer's article "On the present +position of Palaeozoic Botany", "Progressus Rei Botanicae", 1907, page +139, and "Studies in Fossil Botany", Vol. II. (2nd edition) London, +1909.) At the same time, the anatomical structure, where it is open to +investigation, confirms the suggestion given by the habit, and shows +that these early seed-bearing plants had a real affinity with Ferns. +This conclusion received strong corroboration when Kidston, in 1905, +discovered the male organs of Lyginodendron, and showed that they were +identical with a fructification of the genus Crossotheca, hitherto +regarded as belonging to Marattiaceous Ferns. (Kidston, "On the +Microsporangia of the Pteridospermeae, etc." "Phil. Trans. Royal Soc." +Vol. 198, B. 1906.) + +The general conclusion which follows from the various observations +alluded to, is that in Palaeozoic times there was a great body of plants +(including, as it appears, a large majority of the fossils previously +regarded as Ferns) which had attained the rank of Spermophyta, +bearing seeds of a Cycadean type on fronds scarcely differing from the +vegetative foliage, and in other respects, namely anatomy, habit and the +structure of the pollen-bearing organs, retaining many of the characters +of Ferns. From this extensive class of plants, to which the name +Pteridospermeae has been given, it can scarcely be doubted that the +abundant Cycadophyta, of the succeeding Mesozoic period, were derived. +This conclusion is of far-reaching significance, for we have already +found reason to think that the Angiosperms themselves sprang, in +later times, from the Cycadophytic stock; it thus appears that the +Fern-phylum, taken in a broad sense, ultimately represents the source +from which the main line of descent of the Phanerogams took its rise. + +It must further be borne in mind that in the Palaeozoic period there +existed another group of seed-bearing plants, the Cordaiteae, far more +advanced than the Pteridospermeae, and in many respects approaching the +Coniferae, which themselves begin to appear in the latest Palaeozoic +rocks. The Cordaiteae, while wholly different in habit from the +contemporary fern-like Seed-plants, show unmistakable signs of a common +origin with them. Not only is there a whole series of forms +connecting the anatomical structure of the Cordaiteae with that of the +Lyginodendreae among Pteridosperms, but a still more important point is +that the seeds of the Cordaiteae, which have long been known, are of +the same Cycadean type as those of the Pteridosperms, so that it is not +always possible, as yet, to discriminate between the seeds of the two +groups. These facts indicate that the same fern-like stock which gave +rise to the Cycadophyta and through them, as appears probable, to the +Angiosperms, was also the source of the Cordaiteae, which in their turn +show manifest affinity with some at least of the Coniferae. Unless the +latter are an artificial group, a view which does not commend itself to +the writer, it would appear probable that the Gymnosperms generally, +as well as the Angiosperms, were derived from an ancient race of +Cryptogams, most nearly related to the Ferns. (Some botanists, however, +believe that the Coniferae, or some of them, are probably more nearly +related to the Lycopods. See Seward and Ford, "The Araucarieae, Recent +and Extinct", "Phil. Trans. Royal Soc." Vol. 198 B. 1906.) + +It may be mentioned here that the small gymnospermous group Gnetales +(including the extraordinary West African plant Welwitschia) which were +formerly regarded by some authorities as akin to the Equisetales, have +recently been referred, on better grounds, to a common origin with the +Angiosperms, from the Mesozoic Cycadophyta. + +The tendency, therefore, of modern work on the palaeontological record +of the Seed-plants has been to exalt the importance of the Fern-phylum, +which, on present evidence, appears to be that from which the great +majority, possibly the whole, of the Spermophyta have been derived. + +One word of caution, however, is necessary. The Seed-plants are of +enormous antiquity; both the Pteridosperms and the more highly organised +family Cordaiteae, go back as far in geological history (namely to the +Devonian) as the Ferns themselves or any other Vascular Cryptogams. It +must therefore be understood that in speaking of the derivation of the +Spermophyta from the Fern-phylum, we refer to that phylum at a very +early stage, probably earlier than the most ancient period to which +our record of land-plants extends. The affinity between the oldest +Seed-plants and the Ferns, in the widest sense, seems established, but +the common stock from which they actually arose is still unknown; though +no doubt nearer to the Ferns than to any other group, it must have +differed widely from the Ferns as we now know them, or perhaps even from +any which the fossil record has yet revealed to us. + +iii. THE ORIGIN OF THE HIGHER CRYPTOGAMIA. + +The Sub-kingdom of the higher Spore-plants, the Cryptogamia possessing a +vascular system, was more prominent in early geological periods than at +present. It is true that the dominance of the Pteridophyta in Palaeozoic +times has been much exaggerated owing to the assumption that everything +which looked like a Fern really was a Fern. But, allowing for the fact, +now established, that most of the Palaeozoic fern-like plants were +already Spermophyta, there remains a vast mass of Cryptogamic forms +of that period, and the familiar statement that they formed the main +constituent of the Coal-forests still holds good. The three +classes, Ferns (Filicales), Horsetails (Equisetales) and Club-mosses +(Lycopodiales), under which we now group the Vascular Cryptogams, all +extend back in geological history as far as we have any record of the +flora of the land; in the Palaeozoic, however, a fourth class, the +Sphenophyllales, was present. + +As regards the early history of the Ferns, which are of special interest +from their relation to the Seed-plants, it is impossible to speak quite +positively, owing to the difficulty of discriminating between true +fossil Ferns and the Pteridosperms which so closely simulated them. +The difficulty especially affects the question of the position of +Marattiaceous Ferns in the Palaeozoic Floras. This family, now so +restricted, was until recently believed to have been one of the +most important groups of Palaeozoic plants, especially during later +Carboniferous and Permian times. Evidence both from anatomy and from +sporangial characters appeared to establish this conclusion. Of late, +however, doubts have arisen, owing to the discovery that some +supposed members of the Marattiaceae bore seeds, and that a form of +fructification previously referred to that family (Crossotheca) was +really the pollen-bearing apparatus of a Pteridosperm (Lyginodendron). +The question presents much difficulty; though it seems certain that our +ideas of the extent of the family in Palaeozoic times will have to be +restricted, there is still a decided balance of evidence in favour +of the view that a considerable body of Marattiaceous Ferns actually +existed. The plants in question were of large size (often arborescent) +and highly organised--they represent, in fact, one of the highest +developments of the Fern-stock, rather than a primitive type of the +class. + +There was, however, in the Palaeozoic period, a considerable group of +comparatively simple Ferns (for which Arber has proposed the collective +name Primofilices); the best known of these are referred to the family +Botryopterideae, consisting of plants of small or moderate dimensions, +with, on the whole, a simple anatomical structure, in certain cases +actually simpler than that of any recent Ferns. On the other hand the +sporangia of these plants were usually borne on special fertile fronds, +a mark of rather high differentiation. This group goes back to the +Devonian and includes some of the earliest types of Fern with which we +are acquainted. It is probable that the Primofilices (though not the +particular family Botryopterideae) represent the stock from which the +various families of modern Ferns, already developed in the Mesozoic +period, may have sprung. + +None of the early Ferns show any clear approach to other classes of +Vascular Cryptogams; so far as the fossil record affords any evidence, +Ferns have always been plants with relatively large and usually compound +leaves. There is no indication of their derivation from a microphyllous +ancestry, though, as we shall see, there is some slight evidence for the +converse hypothesis. Whatever the origin of the Ferns may have been it +is hidden in the older rocks. + +It has, however, been held that certain other Cryptogamic phyla had +a common origin with the Ferns. The Equisetales are at present a +well-defined group; even in the rich Palaeozoic floras the habit, +anatomy and reproductive characters usually render the members of this +class unmistakable, in spite of the great development and stature which +they then attained. It is interesting, however, to find that in the +oldest known representatives of the Equisetales the leaves were highly +developed and dichotomously divided, thus differing greatly from the +mere scale-leaves of the recent Horsetails, or even from the simple +linear leaves of the later Calamites. The early members of the class, in +their forked leaves, and in anatomical characters, show an approximation +to the Sphenophyllales, which are chiefly represented by the large genus +Sphenophyllum, ranging through the Palaeozoic from the Middle Devonian +onwards. These were plants with rather slender, ribbed stems, bearing +whorls of wedge-shaped or deeply forked leaves, six being the typical +number in each whorl. From their weak habit it has been conjectured, +with much probability, that they may have been climbing plants, like the +scrambling Bedstraws of our hedgerows. The anatomy of the stem is simple +and root-like; the cones are remarkable for the fact that each scale or +sporophyll is a double structure, consisting of a lower, usually sterile +lobe and one or more upper lobes bearing the sporangia; in one species +both parts of the sporophyll were fertile. Sphenophyllum was evidently +much specialised; the only other known genus is based on an isolated +cone, Cheirostrobus, of Lower Carboniferous age, with an extraordinarily +complex structure. In this genus especially, but also in the entire +group, there is an evident relation to the Equisetales; hence it is of +great interest that Nathorst has described, from the Devonian of Bear +Island in the Arctic regions, a new genus Pseudobornia, consisting of +large plants, remarkable for their highly compound leaves which, +when found detached, were taken for the fronds of a Fern. The whorled +arrangement of the leaves, and the habit of the plant, suggest +affinities either with the Equisetales or the Sphenophyllales; Nathorst +makes the genus the type of a new class, the Pseudoborniales. (A.G. +Nathorst, "Zur Oberdevonischen Flora der Baren-Insel", "Kongl. Svenska +Vetenskaps-Akademiens Handlingar" Bd. 36, No. 3, Stockholm, 1902.) + +The available data, though still very fragmentary, certainly suggest +that both Equisetales and Sphenophyllales may have sprung from a +common stock having certain fern-like characters. On the other hand the +Sphenophylls, and especially the peculiar genus Cheirostrobus, have in +their anatomy a good deal in common with the Lycopods, and of late years +they have been regarded as the derivatives of a stock common to +that class and the Equisetales. At any rate the characters of the +Sphenophyllales and of the new group Pseudoborniales suggest the +existence, at a very early period, of a synthetic race of plants, +combining the characters of various phyla of the Vascular Cryptogams. +It may further be mentioned that the Psilotaceae, an isolated epiphytic +family hitherto referred to the Lycopods, have been regarded by several +recent authors as the last survivors of the Sphenophyllales, which they +resemble both in their anatomy and in the position of their sporangia. + +The Lycopods, so far as their early history is known, are remarkable +rather for their high development in Palaeozoic times than for any +indications of a more primitive ancestry. In the recent Flora, two +of the four living genera (Excluding Psilotaceae.) (Selaginella and +Isoetes) have spores of two kinds, while the other two (Lycopodium and +Phylloglossum) are homosporous. Curiously enough, no certain instance +of a homosporous Palaeozoic Lycopod has yet been discovered, though +well-preserved fructifications are numerous. Wherever the facts have +been definitely ascertained, we find two kinds of spore, differentiated +quite as sharply as in any living members of the group. Some of the +Palaeozoic Lycopods, in fact, went further, and produced bodies of the +nature of seeds, some of which were actually regarded, for many +years, as the seeds of Gymnosperms. This specially advanced form of +fructification goes back at least as far as the Lower Carboniferous, +while the oldest known genus of Lycopods, Bothrodendron, which is found +in the Devonian, though not seed-bearing, was typically heterosporous, +if we may judge from the Coal-measure species. No doubt homosporous +Lycopods existed, but the great prevalence of the higher mode of +reproduction in days which to us appear ancient, shows how long a course +of evolution must have already been passed through before the oldest +known members of the group came into being. The other characters of +the Palaeozoic Lycopods tell the same tale; most of them attained +the stature of trees, with a corresponding elaboration of anatomical +structure, and even the herbaceous forms show no special simplicity. +It appears from recent work that herbaceous Lycopods, indistinguishable +from our recent Selaginellas, already existed in the time of the +Coal-measures, while one herbaceous form (Miadesmia) is known to have +borne seeds. + +The utmost that can be said for primitiveness of character in Palaeozoic +Lycopods is that the anatomy of the stem, in its primary ground-plan, as +distinguished from its secondary growth, was simpler than that of most +Lycopodiums and Selaginellas at the present day. There are also some +peculiarities in the underground organs (Stigmaria) which suggest the +possibility of a somewhat imperfect differentiation between root and +stem, but precisely parallel difficulties are met with in the case of +the living Selaginellas, and in some degree in species of Lycopodium. + +In spite of their high development in past ages the Lycopods, recent +and fossil, constitute, on the whole, a homogeneous group, and there is +little at present to connect them with other phyla. Anatomically some +relation to the Sphenophylls is indicated, and perhaps the recent +Psilotaceae give some support to this connection, for while their +nearest alliance appears to be with the Sphenophylls, they approach the +Lycopods in anatomy, habit, and mode of branching. + +The typically microphyllous character of the Lycopods, and the simple +relation between sporangium and sporophyll which obtains throughout the +class, have led various botanists to regard them as the most primitive +phylum of the Vascular Cryptogams. There is nothing in the fossil record +to disprove this view, but neither is there anything to support it, for +this class so far as we know is no more ancient than the megaphyllous +Cryptogams, and its earliest representatives show no special simplicity. +If the indications of affinity with Sphenophylls are of any value +the Lycopods are open to suspicion of reduction from a megaphyllous +ancestry, but there is no direct palaeontological evidence for such a +history. + +The general conclusions to which we are led by a consideration of the +fossil record of the Vascular Cryptogams are still very hypothetical, +but may be provisionally stated as follows: + +The Ferns go back to the earliest known period. In Mesozoic times +practically all the existing families had appeared; in the Palaeozoic +the class was less extensive than formerly believed, a majority of the +supposed Ferns of that age having proved to be seed-bearing plants. The +oldest authentic representatives of the Ferns were megaphyllous plants, +broadly speaking, of the same type as those of later epochs, though +differing much in detail. As far back as the record extends they show no +sign of becoming merged with other phyla in any synthetic group. + +The Equisetales likewise have a long history, and manifestly attained +their greatest development in Palaeozoic times. Their oldest forms show +an approach to the extinct class Sphenophyllales, which connects them +to some extent, by anatomical characters, with the Lycopods. At the +same time the oldest Equisetales show a somewhat megaphyllous character, +which was more marked in the Devonian Pseudoborniales. Some remote +affinity with the Ferns (which has also been upheld on other grounds) +may thus be indicated. It is possible that in the Sphenophyllales we +may have the much-modified representatives of a very ancient synthetic +group. + +The Lycopods likewise attained their maximum in the Palaeozoic, and +show, on the whole, a greater elaboration of structure in their early +forms than at any later period, while at the same time maintaining a +considerable degree of uniformity in morphological characters throughout +their history. The Sphenophyllales are the only other class with which +they show any relation; if such a connection existed, the common point +of origin must lie exceedingly far back. + +The fossil record, as at present known, cannot, in the nature of things, +throw any direct light on what is perhaps the most disputed question in +the morphology of plants--the origin of the alternating generations of +the higher Cryptogams and the Spermophyta. At the earliest period +to which terrestrial plants have been traced back all the groups of +Vascular Cryptogams were in a highly advanced stage of evolution, while +innumerable Seed-plants--presumably the descendants of Cryptogamic +ancestors--were already flourishing. On the other hand we know +practically nothing of Palaeozoic Bryophyta, and the evidence even for +their existence at that period cannot be termed conclusive. While +there are thus no palaeontological grounds for the hypothesis that the +Vascular plants came of a Bryophytic stock, the question of their actual +origin remains unsolved. + +III. NATURAL SELECTION. + +Hitherto we have considered the palaeontological record of plants in +relation to Evolution. The question remains, whether the record +throws any light on the theory of which Darwin and Wallace were the +authors--that of Natural Selection. The subject is clearly one which +must be investigated by other methods than those of the palaeontologist; +still there are certain important points involved, on which the +palaeontological record appears to bear. + +One of these points is the supposed distinction between morphological +and adaptive characters, on which Nageli, in particular, laid so much +stress. The question is a difficult one; it was discussed by Darwin +("Origin of Species" (6th edition), pages 170-176.), who, while +showing that the apparent distinction is in part to be explained by our +imperfect knowledge of function, recognised the existence of important +morphological characters which are not adaptations. The following +passage expresses his conclusion. "Thus, as I am inclined to believe, +morphological differences, which we consider as important--such as +the arrangement of the leaves, the divisions of the flower or of the +ovarium, the position of the ovules, etc.--first appeared in many cases +as fluctuating variations, which sooner or later became constant through +the nature of the organism and of the surrounding conditions, as well +as through the inter-crossing of distinct individuals, but not through +natural selection; for as these morphological characters do not affect +the welfare of the species, any slight deviations in them could not have +been governed or accumulated through this latter agency." (Ibid. page +176.) + +This is a sufficiently liberal concession; Nageli, however, went much +further when he said: "I do not know among plants a morphological +modification which can be explained on utilitarian principles." (See +"More Letters", Vol. II. page 375 (footnote).) If this were true the +field of Natural Selection would be so seriously restricted, as to leave +the theory only a very limited importance. + +It can be shown, as the writer believes, that many typical +"morphological characters," on which the distinction between great +classes of plants is based, were adaptive in origin, and even that their +constancy is due to their functional importance. Only one or two cases +will be mentioned, where the fossil evidence affects the question. + +The pollen-tube is one of the most important morphological characters of +the Spermophyta as now existing--in fact the name Siphonogama is used +by Engler in his classification, as expressing a peculiarly constant +character of the Seed-plants. Yet the pollen-tube is a manifest +adaptation, following on the adoption of the seed-habit, and serving +first to bring the spermatozoids with greater precision to their +goal, and ultimately to relieve them of the necessity for independent +movement. The pollen-tube is constant because it has proved to be +indispensable. + +In the Palaeozoic Seed-plants there are a number of instances in which +the pollen-grains, contained in the pollen-chamber of a seed, are so +beautifully preserved that the presence of a group of cells within the +grain can be demonstrated; sometimes we can even see how the cell-walls +broke down to emit the sperms, and quite lately it is said that the +sperms themselves have been recognised. (F.W. Oliver, "On Physostoma +elegans, an archaic type of seed from the Palaeozoic Rocks", "Annals of +Botany", January, 1909. See also the earlier papers there cited.) In +no case, however, is there as yet any satisfactory evidence for +the formation of a pollen-tube; it is probable that in these early +Seed-plants the pollen-grains remained at about the evolutionary level +of the microspores in Pilularia or Selaginella, and discharged their +spermatozoids directly, leaving them to find their own way to the +female cells. It thus appears that there were once Spermophyta without +pollen-tubes. The pollen-tube method ultimately prevailed, becoming a +constant "morphological character," for no other reason than because, +under the new conditions, it provided a more perfect mechanism for the +accomplishment of the act of fertilisation. We have still, in the Cycads +and Ginkgo, the transitional case, where the tube remains short, serves +mainly as an anchor and water-reservoir, but yet is able, by its slight +growth, to give the spermatozoids a "lift" in the right direction. In +other Seed-plants the sperms are mere passengers, carried all the way by +the pollen-tube; this fact has alone rendered the Angiospermous method +of fertilisation through a stigma possible. + +We may next take the seed itself--the very type of a morphological +character. Our fossil record does not go far enough back to tell us the +origin of the seed in the Cycadophyta and Pteridosperms (the main line +of its development) but some interesting sidelights may be obtained from +the Lycopod phylum. In two Palaeozoic genera, as we have seen, seed-like +organs are known to have been developed, resembling true seeds in the +presence of an integument and of a single functional embryo-sac, as well +as in some other points. We will call these organs "seeds" for the sake +of shortness. In one genus (Lepidocarpon) the seeds were borne on a cone +indistinguishable from that of the ordinary cryptogamic Lepidodendreae, +the typical Lycopods of the period, while the seed itself retained +much of the detailed structure of the sporangium of that family. In the +second genus, Miadesmia, the seed-bearing plant was herbaceous, and much +like a recent Selaginella. (See Margaret Benson, "Miadesmia membranacea, +a new Palaeozoic Lycopod with a seed-like structure", "Phil. Trans. +Royal Soc. Vol." 199, B. 1908.) The seeds of the two genera are +differently constructed, and evidently had an independent origin. Here, +then, we have seeds arising casually, as it were, at different points +among plants which otherwise retain all the characters of their +cryptogamic fellows; the seed is not yet a morphological character of +importance. To suppose that in these isolated cases the seed sprang into +being in obedience to a Law of Advance ("Vervollkommungsprincip"), +from which other contemporary Lycopods were exempt, involves us in +unnecessary mysticism. On the other hand it is not difficult to see how +these seeds may have arisen, as adaptive structures, under the influence +of Natural Selection. The seed-like structure afforded protection to the +prothallus, and may have enabled the embryo to be launched on the world +in greater security. There was further, as we may suppose, a gain in +certainty of fertilisation. As the writer has pointed out elsewhere, +the chances against the necessary association of the small male with the +large female spores must have been enormously great when the cones were +borne high up on tall trees. The same difficulty may have existed in the +case of the herbaceous Miadesmia, if, as Miss Benson conjectures, it was +an epiphyte. One way of solving the problem was for pollination to take +place while the megaspore was still on the parent plant, and this is +just what the formation of an ovule or seed was likely to secure. + +The seeds of the Pteridosperms, unlike those of the Lycopod stock, +have not yet been found in statu nascendi--in all known cases they were +already highly developed organs and far removed from the cryptogamic +sporangium. But in two respects we find that these seeds, or some +of them, had not yet realised their possibilities. In the seed +of Lyginodendron and other cases the micropyle, or orifice of the +integument, was not the passage through which the pollen entered; the +open neck of the pollen-chamber protruded through the micropyle and +itself received the pollen. We have met with an analogous case, at a +more advanced stage of evolution, in the Bennettiteae, where the wall +of the gynaecium, though otherwise closed, did not provide a stigma to +catch the pollen, but allowed the micropyles of the ovules to protrude +and receive the pollen in the old gymnospermous fashion. The integument +in the one case and the pistil in the other had not yet assumed all +the functions to which the organ ultimately became adapted. Again, no +Palaeozoic seed has yet been found to contain an embryo, though the +preservation is often good enough for it to have been recognised if +present. It is probable that the nursing of the embryo had not yet come +to be one of the functions of the seed, and that the whole embryonic +development was relegated to the germination stage. + +In these two points, the reception of the pollen by the micropyle and +the nursing of the embryo, it appears that many Palaeozoic seeds +were imperfect, as compared with the typical seeds of later times. +As evolution went on, one function was superadded on another, and +it appears impossible to resist the conclusion that the whole +differentiation of the seed was a process of adaptation, and +consequently governed by Natural Selection, just as much as the +specialisation of the rostellum in an Orchid, or of the pappus in a +Composite. + +Did space allow, other examples might be added. We may venture to +maintain that the glimpses which the fossil record allows us into early +stages in the evolution of organs now of high systematic importance, +by no means justify the belief in any essential distinction between +morphological and adaptive characters. + +Another point, closely connected with Darwin's theory, on which the +fossil history of plants has been supposed to have some bearing, is +the question of Mutation, as opposed to indefinite variation. Arber and +Parkin, in their interesting memoir on the Origin of Angiosperms, +have suggested calling in Mutation to explain the apparently sudden +transition from the cycadean to the angiospermous type of foliage, in +late Mesozoic times, though they express themselves with much caution, +and point out "a distinct danger that Mutation may become the last +resort of the phylogenetically destitute"! + +The distinguished French palaeobotanists, Grand'Eury (C. Grand'Eury, +"Sur les mutations de quelques Plantes fossiles du Terrain houiller". +"Comptes Rendus", CXLII. page 25, 1906.) and Zeiller (R. Zeiller +"Les Vegetaux fossiles et leurs Enchainements", "Revue du Mois", III. +February, 1907.), are of opinion, to quote the words of the latter +writer, that the facts of fossil Botany are in agreement with the sudden +appearance of new forms, differing by marked characters from those that +have given them birth; he adds that these results give more amplitude +to this idea of Mutation, extending it to groups of a higher order, +and even revealing the existence of discontinuous series between the +successive terms of which we yet recognise bonds of filiation. (Loc. +cit. page 23.) + +If Zeiller's opinion should be confirmed, it would no doubt be a serious +blow to the Darwinian theory. As Darwin said: "Under a scientific point +of view, and as leading to further investigation, but little advantage +is gained by believing that new forms are suddenly developed in an +inexplicable manner from old and widely different forms, over the old +belief in the creation of species from the dust of the earth." ("Origin +of Species", page 424.) + +It most however be pointed out, that such mutations as Zeiller, and to +some extent Arber and Parkin, appear to have in view, bridging the gulf +between different Orders and Classes, bear no relation to any mutations +which have been actually observed, such as the comparatively small +changes, of sub-specific value, described by De Vries in the type-case +of Oenothera Lamarckiana. The results of palaeobotanical research have +undoubtedly tended to fill up gaps in the Natural System of plants--that +many such gaps still persist is not surprising; their presence may well +serve as an incentive to further research but does not, as it seems +to the writer, justify the assumption of changes in the past, wholly +without analogy among living organisms. + +As regards the succession of species, there are no greater authorities +than Grand'Eury and Zeiller, and great weight must be attached to their +opinion that the evidence from continuous deposits favours a somewhat +sudden change from one specific form to another. At the same time +it will be well to bear in mind that the subject of the "absence of +numerous intermediate varieties in any single formation" was fully +discussed by Darwin. ("Origin of Species", pages 275-282, and page +312.); the explanation which he gave may go a long way to account for +the facts which recent writers have regarded as favouring the theory of +saltatory mutation. + +The rapid sketch given in the present essay can do no more than call +attention to a few salient points, in which the palaeontological records +of plants has an evident bearing on the Darwinian theory. At the present +day the whole subject of palaeobotany is a study in evolution, and +derives its chief inspiration from the ideas of Darwin and Wallace. In +return it contributes something to the verification of their teaching; +the recent progress of the subject, in spite of the immense difficulties +which still remain, has added fresh force to Darwin's statement that +"the great leading facts in palaeontology agree admirably with the +theory of descent with modification through variation and natural +selection." (Ibid. page 313.) + + + + +XIII. THE INFLUENCE OF ENVIRONMENT ON THE FORMS OF PLANTS. By Georg +Klebs, PH.D. + +Professor of Botany in the University of Heidelberg. + + +The dependence of plants on their environment became the object of +scientific research when the phenomena of life were first investigated +and physiology took its place as a special branch of science. This +occurred in the course of the eighteenth century as the result of the +pioneer work of Hales, Duhamel, Ingenhousz, Senebier and others. In +the nineteenth century, particularly in the second half, physiology +experienced an unprecedented development in that it began to concern +itself with the experimental study of nutrition and growth, and with +the phenomena associated with stimulus and movement; on the other hand, +physiology neglected phenomena connected with the production of form, a +department of knowledge which was the province of morphology, a purely +descriptive science. It was in the middle of the last century that the +growth of comparative morphology and the study of phases of development +reached their highest point. + +The forms of plants appeared to be the expression of their inscrutable +inner nature; the stages passed through in the development of the +individual were regarded as the outcome of purely internal and hidden +laws. The feasibility of experimental inquiry seemed therefore remote. +Meanwhile, the recognition of the great importance of such a causal +morphology emerged from the researches of the physiologists of that +time, more especially from those of Hofmeister (Hofmeister, "Allgemeine +Morphologie", Leipzig, 1868, page 579.), and afterwards from the work of +Sachs. (Sachs, "Stoff und Form der Pflanzenorgane", Vol. I. 1880; Vol. +II. 1882. "Gesammelte Abhandlungen uber Pflanzen-Physiologie", II. +Leipzig, 1893.) Hofmeister, in speaking of this line of inquiry, +described it as "the most pressing and immediate aim of the investigator +to discover to what extent external forces acting on the organism are of +importance in determining its form." This advance was the outcome of the +influence of that potent force in biology which was created by Darwin's +"Origin of Species" (1859). + +The significance of the splendid conception of the transformation of +species was first recognised and discussed by Lamarck (1809); as an +explanation of transformation he at once seized upon the idea--an +intelligible view--that the external world is the determining factor. +Lamarck (Lamarck, "Philosophie zoologique", pages 223-227. Paris, 1809.) +endeavoured, more especially, to demonstrate from the behaviour +of plants that changes in environment induce change in form which +eventually leads to the production of new species. In the case of +animals, Lamarck adopted the teleological view that alterations in the +environment first lead to alterations in the needs of the organisms, +which, as the result of a kind of conscious effort of will, induce +useful modifications and even the development of new organs. His work +has not exercised any influence on the progress of science: Darwin +himself confessed in regard to Lamarck's work--"I got not a fact or idea +from it." ("Life and Letters", Vol. II. page 215.) + +On a mass of incomparably richer and more essential data Darwin +based his view of the descent of organisms and gained for it general +acceptance; as an explanation of modification he elaborated the +ingeniously conceived selection theory. The question of special interest +in this connection, namely what is the importance of the influence +of the environment, Darwin always answered with some hesitation and +caution, indeed with a certain amount of indecision. + +The fundamental principle underlying his theory is that of general +variability as a whole, the nature and extent of which, especially +in cultivated organisms, are fully dealt with in his well-known book. +(Darwin, "The variation of Animals and Plants under domestication", +2 vols., edition 1, 1868; edition 2, 1875; popular edition 1905.) In +regard to the question as to the cause of variability Darwin adopts a +consistently mechanical view. He says: "These several considerations +alone render it probable that variability of every kind is directly or +indirectly caused by changed conditions of life. Or, to put the case +under another point of view, if it were possible to expose all the +individuals of a species during many generations to absolutely uniform +conditions of life, there would be no variability." ("The variation of +Animals and Plants" (2nd edition), Vol. II. page 242.) Darwin did not +draw further conclusions from this general principle. + +Variations produced in organisms by the environment are distinguished by +Darwin as "the definite" and "the indefinite." (Ibid. II. page 260. See +also "Origin of Species" (6th edition), page 6.) The first occur "when +all or nearly all the offspring of an individual exposed to certain +conditions during several generations are modified in the same manner." +Indefinite variation is much more general and a more important factor in +the production of new species; as a result of this, single individuals +are distinguished from one another by "slight" differences, first in +one then in another character. There may also occur, though this is very +rare, more marked modifications, "variations which seem to us in our +ignorance to arise spontaneously." ("Origin of Species" (6th edition), +page 421.) The selection theory demands the further postulate that such +changes, "whether extremely slight or strongly marked," are inherited. +Darwin was no nearer to an experimental proof of this assumption than to +the discovery of the actual cause of variability. It was not until the +later years of his life that Darwin was occupied with the "perplexing +problem... what causes almost every cultivated plant to vary" ("Life +and Letters", Vol. III. page 342.): he began to make experiments on the +influence of the soil, but these were soon given up. + +In the course of the violent controversy which was the outcome of +Darwin's work the fundamental principles of his teaching were not +advanced by any decisive observations. Among the supporters and +opponents, Nageli (Nageli, "Theorie der Abstammungslehre", Munich, 1884; +cf. Chapter III.) was one of the few who sought to obtain proofs by +experimental methods. His extensive cultural experiments with alpine +Hieracia led him to form the opinion that the changes which are induced +by an alteration in the food-supply, in climate or in habitat, are not +inherited and are therefore of no importance from the point of view of +the production of species. And yet Nageli did attribute an important +influence to the external world; he believed that adaptations of plants +arise as reactions to continuous stimuli, which supply a need and are +therefore useful. These opinions, which recall the teleological +aspect of Lamarckism, are entirely unsupported by proof. While other +far-reaching attempts at an explanation of the theory of descent were +formulated both in Nageli's time and afterwards, some in support of, +others in opposition to Darwin, the necessity of investigating, from +different standpoints, the underlying causes, variability and heredity, +was more and more realised. To this category belong the statistical +investigations undertaken by Quetelet and Galton, the researches into +hybridisation, to which an impetus was given by the re-discovery of +the Mendelian law of segregation, as also by the culture experiments +on mutating species following the work of de Vries, and lastly the +consideration of the question how far variation and heredity are +governed by external influences. These latter problems, which +are concerned in general with the causes of form-production and +form-modification, may be treated in a short summary which falls under +two heads, one having reference to the conditions of form-production in +single species, the other being concerned with the conditions governing +the transformation of species. + +I. THE INFLUENCE OF EXTERNAL CONDITIONS ON FORM-PRODUCTION IN SINGLE +SPECIES. + +The members of plants, which we express by the terms stem, leaf, flower, +etc. are capable of modification within certain limits; since Lamarck's +time this power of modification has been brought more or less into +relation with the environment. We are concerned not only with the +question of experimental demonstration of this relationship, but, more +generally, with an examination of the origin of forms, the sequences of +stages in development that are governed by recognisable causes. We have +to consider the general problem; to study the conditions of all typical +as well as of atypic forms, in other words, to found a physiology of +form. + +If we survey the endless variety of plant-forms and consider the highly +complex and still little known processes in the interior of cells, and +if we remember that the whole of this branch of investigation came into +existence only a few decades ago, we are able to grasp the fact that +a satisfactory explanation of the factors determining form cannot be +discovered all at once. The goal is still far away. We are not concerned +now with the controversial question, whether, on the whole, the +fundamental processes in the development of form can be recognised by +physiological means. A belief in the possibility of this can in any case +do no harm. What we may and must attempt is this--to discover points +of attack on one side or another, which may enable us by means of +experimental methods to come into closer touch with these elusive +and difficult problems. While we are forced to admit that there is at +present much that is insoluble there remains an inexhaustible supply of +problems capable of solution. + +The object of our investigations is the species; but as regards the +question, what is a species, science of to-day takes up a position +different from that of Darwin. For him it was the Linnean species which +illustrates variation: we now know, thanks to the work of Jordan, +de Bary, and particularly to that of de Vries (de Vries, "Die +Mutationstheorie", Leipzig, 1901, Vol. I. page 33.), that the Linnean +species consists of a large or small number of entities, elementary +species. In experimental investigation it is essential that observations +be made on a pure species, or, as Johannsen (Johannsen, "Ueber +Erblichkeit in Populationen und reinen Linien", Jena, 1903.) says, on +a pure "line." What has long been recognised as necessary in the +investigation of fungi, bacteria and algae must also be insisted on in +the case of flowering plants; we must start with a single individual +which is reproduced vegetatively or by strict self-fertilisation. +In dioecious plants we must aim at the reproduction of brothers and +sisters. + +We may at the outset take it for granted that a pure species remains the +same under similar external conditions; it varies as these vary. IT IS +CHARACTERISTIC OF A SPECIES THAT IT ALWAYS EXHIBITS A CONSTANT RELATION +TO A PARTICULAR ENVIRONMENT. In the case of two different species, e.g. +the hay and anthrax bacilli or two varieties of Campanula with blue and +white flowers respectively, a similar environment produces a constant +difference. The cause of this is a mystery. + +According to the modern standpoint, the living cell is a complex +chemico-physical system which is regarded as a dynamical system of +equilibrium, a conception suggested by Herbert Spencer and which has +acquired a constantly increasing importance in the light of modern +developments in physical chemistry. The various chemical compounds, +proteids, carbohydrates, fats, the whole series of different ferments, +etc. occur in the cell in a definite physical arrangement. The two +systems of two species must as a matter of fact possess a constant +difference, which it is necessary to define by a special term. We say, +therefore, that the SPECIFIC STRUCTURE is different. + +By way of illustrating this provisionally, we may assume that the +proteids of the two species possess a constant chemical difference. This +conception of specific structure is specially important in its bearing +on a further treatment of the subject. In the original cell, eventually +also in every cell of a plant, the characters which afterwards +become apparent must exist somewhere; they are integral parts of the +capabilities or potentialities of specific structure. Thus not only the +characters which are exhibited under ordinary conditions in nature, but +also many others which become apparent only under special conditions (In +this connection I leave out of account, as before, the idea of material +carriers of heredity which since the publication of Darwin's Pangenesis +hypothesis has been frequently suggested. See my remarks in "Variationen +der Bluten", "Pringsheim's Jahrb. Wiss. Bot." 1905, page 298; also +Detto, "Biol. Centralbl." 1907, page 81, "Die Erklarbarkeit der +Ontogenese durch materielle Anlagen".), are to be included as such +potentialities in cells; the conception of specific structure includes +the WHOLE OF THE POTENTIALITIES OF A SPECIES; specific structure +comprises that which we must always assume without being able to explain +it. + +A relatively simple substance, such as oxalate of lime, is known under +a great number of different crystalline forms belonging to different +systems (Compare Kohl's work on "Anatomisch-phys. Untersuchungen uber +Kalksalze", etc. Marburg, 1889.); these may occur as single crystals, +concretions or as concentric sphaerites. The power to assume this +variety of form is in some way inherent in the molecular structure, +though we cannot, even in this case, explain the necessary connection +between structure and crystalline form. These potentialities can only +become operative under the influence of external conditions; their +stimulation into activity depends on the degree of concentration of the +various solutions, on the nature of the particular calcium salt, on the +acid or alkaline reactions. Broadly speaking, the plant cell behaves in +a similar way. The manifestation of each form, which is inherent as a +potentiality in the specific structure, is ultimately to be referred to +external conditions. + +An insight into this connection is, however, rendered exceedingly +difficult, often quite impossible, because the environment never +directly calls into action the potentialities. Its influence is exerted +on what we may call the inner world of the organism, the importance of +which increases with the degree of differentiation. The production of +form in every plant depends upon processes in the interior of the cells, +and the nature of these determines which among the possible characters +is to be brought to light. In no single case are we acquainted with the +internal process responsible for the production of a particular +form. All possible factors may play a part, such as osmotic pressure, +permeability of the protoplasm, the degree of concentration of the +various chemical substances, etc.; all these factors should be included +in the category of INTERNAL CONDITIONS. This inner world appears the +more hidden from our ken because it is always represented by a certain +definite state, whether we are dealing with a single cell or with a +small group of cells. These have been produced from pre-existing cells +and they in turn from others; the problem is constantly pushed back +through a succession of generations until it becomes identified with +that of the origin of species. + +A way, however, is opened for investigation; experience teaches us that +this inner world is not a constant factor: on the contrary, it appears +to be very variable. The dependence of VARIABLE INTERNAL on VARIABLE +EXTERNAL conditions gives us the key with which research may open the +door. In the lower plants this dependence is at once apparent, each cell +is directly subject to external influences. In the higher plants with +their different organs, these influences were transmitted to cells in +course of development along exceedingly complex lines. In the case of +the growing-point of a bud, which is capable of producing a complete +plant, direct influences play a much less important part than those +exerted through other organs, particularly through the roots and leaves, +which are essential in nutrition. These correlations, as we may call +them, are of the greatest importance as aids to an understanding of +form-production. When a bud is produced on a particular part of a plant, +it undergoes definite internal modifications induced by the influence of +other organs, the activity of which is governed by the environment, and +as the result of this it develops along a certain direction; it may, +for example, become a flower. The particular direction of development +is determined before the rudiment is differentiated and is exerted so +strongly that further development ensues without interruption, even +though the external conditions vary considerably and exert a positively +inimical influence: this produces the impression that development +proceeds entirely independently of the outer world. The widespread +belief that such independence exists is very premature and at all events +unproven. + +The state of the young rudiment is the outcome of previous influences of +the external world communicated through other organs. Experiments show +that in certain cases, if the efficiency of roots and leaves as organs +concerned with nutrition is interfered with, the production of flowers +is affected, and their characters, which are normally very constant, +undergo far-reaching modifications. To find the right moment at which to +make the necessary alteration in the environment is indeed difficult +and in many cases not yet possible. This is especially the case with +fertilised eggs, which in a higher degree than buds have acquired, +through parental influences, an apparently fixed internal organisation, +and this seems to have pre-determined their development. It is, however, +highly probable that it will be possible, by influencing the parents, +to alter the internal organisation and to switch off development on to +other lines. + +Having made these general observations I will now cite a few of the many +facts at our disposal, in order to illustrate the methods and aim of the +experimental methods of research. As a matter of convenience I will deal +separately with modification of development and with modification of +single organs. + +I. EFFECT OF ENVIRONMENT UPON THE COURSE OF DEVELOPMENT. + +Every plant, whether an alga or a flowering plant passes, under natural +conditions, through a series of developmental stages characteristic of +each species, and these consist in a regular sequence of definite +forms. It is impossible to form an opinion from mere observation and +description as to what inner changes are essential for the production of +the several forms. We must endeavour to influence the inner factors by +known external conditions in such a way that the individual stages in +development are separately controlled and the order of their sequence +determined at will by experimental treatment. Such control over the +course of development may be gained with special certainty in the case +of the lower organisms. + +With these it is practicable to control the principal conditions of +cultivation and to vary them in various ways. By this means it has been +demonstrated that each developmental stage depends upon special external +conditions, and in cases where our knowledge is sufficient, a particular +stage may be obtained at will. In the Green Algae (See Klebs, "Die +Bedingung der Fortpflanzung... ", Jena, 1896; also "Jahrb. fur +Wiss. Bot." 1898 and 1900; "Probleme der Entwickelung, III." "Biol. +Centralbl." 1904, page 452.), as in the case of Fungi, we may classify +the stages of development into purely vegetative growth (growth, +cell-division, branching), asexual reproduction (formation of zoospores, +conidia) and sexual processes (formation of male and female sexual +organs). By modifying the external conditions it is possible to induce +algae or fungi (Vaucheria, Saprolegnia) to grow continuously for +several years or, in the course of a few days, to die after an enormous +production of asexual or sexual cells. In some instances even an almost +complete stoppage of growth may be caused, reproductive cells being +scarcely formed before the organism is again compelled to resort to +reproduction. Thus the sequence of the different stages in development +can be modified as we may desire. + +The result of a more thorough investigation of the determining +conditions appears to produce at first sight a confused impression +of all sorts of possibilities. Even closely allied species exhibit +differences in regard to the connection between their development and +external conditions. It is especially noteworthy that the same form in +development may be produced as the result of very different alterations +in the environment. At the same time we can undoubtedly detect a certain +unity in the multiplicity of the individual phenomena. + +If we compare the factors essential for the different stages in +development, we see that the question always resolves itself into one +of modification of similar conditions common to all life-processes. We +should rather have inferred that there exist specific external stimuli +for each developmental stage, for instance, certain chemical agencies. +Experiments hitherto made support the conclusion that QUANTITATIVE +alterations in the general conditions of life produce different types of +development. An alga or a fungus grows so long as all the conditions +of nutrition remain at a certain optimum for growth. In order to bring +about asexual reproduction, e.g. the formation of zoospores, it is +sometimes necessary to increase the degree of intensity of external +factors; sometimes, on the other hand, these must be reduced in +intensity. In the case of many algae a decrease in light-intensity or +in the amount of salts in the culture solution, or in the temperature, +induces asexual reproduction, while in others, on the contrary, an +increase in regard to each of these factors is required to produce +the same result. This holds good for the quantitative variations which +induce sexual reproduction in algae. The controlling factor is found to +be a reduction in the supply of nutritive salts and the exposure of the +plants to prolonged illumination or, better still, an increase in the +intensity of the light, the efficiency of illumination depending on the +consequent formation of organic substances such as carbohydrates. + +The quantitative alterations of external conditions may be spoken of as +releasing stimuli. They produce, in the complex equilibrium of the cell, +quantitative modifications in the arrangement and distribution of mass, +by means of which other chemical processes are at once set in motion, +and finally a new condition of equilibrium is attained. But the +commonly expressed view that the environment can as a rule act only as +a releasing agent is incorrect, because it overlooks an essential point. +The power of a cell to receive stimuli is only acquired as the result +of previous nutrition, which has produced a definite condition of +concentration of different substances. Quantities are in this case +the determining factors. The distribution of quantities is especially +important in the sexual reproduction of algae, for which a vigorous +production of the materials formed during carbon-assimilation appears to +be essential. + +In the Flowering plants, on the other hand, for reasons already +mentioned, the whole problem is more complicated. Investigations on +changes in the course of development of fertilised eggs have hitherto +been unsuccessful; the difficulty of influencing egg-cells deeply +immersed in tissue constitutes a serious obstacle. Other parts of plants +are, however, convenient objects of experiment; e.g. the growing apices +of buds which serve as cuttings for reproductive purposes, or buds on +tubers, runners, rhizomes, etc. A growing apex consists of cells capable +of division in which, as in egg-cells, a complete series of latent +possibilities of development is embodied. Which of these possibilities +becomes effective depends upon the action of the outer world transmitted +by organs concerned with nutrition. + +Of the different stages which a flowering plant passes through in the +course of its development we will deal only with one in order to show +that, in spite of its great complexity, the problem is, in essentials, +equally open to attack in the higher plants and in the simplest +organisms. The most important stage in the life of a flowering plant +is the transition from purely vegetative growth to sexual +reproduction--that is, the production of flowers. In certain cases it +can be demonstrated that there is no internal cause, dependent simply +on the specific structure, which compels a plant to produce its flowers +after a definite period of vegetative growth. (Klebs, "Willkurliche +Entwickelungsanderungen", Jena 1903; see also "Probleme der +Entwickelung", I. II. "Centralbl." 1904.) + +One extreme case, that of exceptionally early flowering, has been +observed in nature and more often in cultivation. A number of plants +under certain conditions are able to flower soon after germination. +(Cf. numerous records of this kind by Diels, "Jugendformen und Bluten", +Berlin, 1906.) This shortening of the period of development is exhibited +in the most striking form in trees, as in the oak (Mobius, "Beitrage zur +Lehre von der Fortpflanzung", Jena, 1897, page 89.), flowering seedlings +of which have been observed from one to three years old, whereas +normally the tree does not flower until it is sixty or eighty years old. + +Another extreme case is represented by prolonged vegetative growth +leading to the complete suppression of flower-production. This result +may be obtained with several plants, such as Glechoma, the sugar beet, +Digitalis, and others, if they are kept during the winter in a warm, +damp atmosphere, and in rich soil; in the following spring or summer +they fail to flower. (Klebs, "Willkurliche Aenderungen", etc. Jena, +1903, page 130.) Theoretically, however, experiments are of greater +importance in which the production of flowers is inhibited by +very favourable conditions of nutrition (Klebs, "Ueber kunstliche +Metamorphosen", Stuttgart, 1906, page 115) ("Abh. Naturf. Ges. Halle", +XXV.) occurring at the normal flowering period. Even in the case of +plants of Sempervivum several years old, which, as is shown by control +experiments on precisely similar plants, are on the point of flowering, +flowering is rendered impossible if they are forced to very vigorous +growth by an abundant supply of water and salts in the spring. +Flowering, however, occurs, if such plants are cultivated in relatively +dry sandy soil and in the presence of strong light. Careful researches +into the conditions of growth have led, in the cases Sempervivum, to +the following results: (1) With a strong light and vigorous +carbon-assimilation a considerably increased supply of water and +nutritive salts produces active vegetative growth. (2) With a vigorous +carbon-assimilation in strong light, and a decrease in the supply of +water and salts active flower-production is induced. (3) If an average +supply of water and salts is given both processes are possible; +the intensity of carbon-assimilation determines which of the two is +manifested. A diminution in the production of organic substances, +particularly of carbohydrates, induces vegetative growth. This can +be effected by culture in feeble light or in light deprived of the +yellow-red rays: on the other hand, flower-production follows an +increase in light-intensity. These results are essentially in agreement +with well-known observations on cultivated plants, according to which, +the application of much moisture, after a plentiful supply of manure +composed of inorganic salts, hinders the flower-production of many +vegetables, while a decrease in the supply of water and salts favours +flowering. + +ii. INFLUENCE OF THE ENVIRONMENT ON THE FORM OF SINGLE ORGANS. (A +considerable number of observations bearing on this question are given +by Goebel in his "Experimentelle Morphologie der Pflanzen", Leipzig, +1908. It is not possible to deal here with the alteration in anatomical +structure; cf. Kuster, "Pathologische Pflanzenanatomie", Jena, 1903.) + +If we look closely into the development of a flowering plant, we notice +that in a given species differently formed organs occur in definite +positions. In a potato plant colourless runners are formed from the +base of the main stem which grow underground and produce tubers at their +tips: from a higher level foliage shoots arise nearer the apex. External +appearances suggest that both the place of origin and the form of these +organs were predetermined in the egg-cell or in the tuber. But it was +shown experimentally by the well-known investigator Knight (Knight, +"Selection from the Physiological and Horticultural Papers", London, +1841.) that tubers may be developed on the aerial stem in place of +foliage shoots. These observations were considerably extended by +Vochting. (Vochting, "Ueber die Bildung der Knollen", Cassel, 1887; see +also "Bot. Zeit." 1902, 87.) In one kind of potato, germinating tubers +were induced to form foliage shoots under the influence of a higher +temperature; at a lower temperature they formed tuber-bearing shoots. +Many other examples of the conversion of foliage-shoots into runners and +rhizomes, or vice versa, have been described by Goebel and others. As in +the asexual reproduction of algae quantitative alteration in the amount +of moisture, light, temperature, etc. determines whether this or that +form of shoot is produced. If the primordia of these organs are exposed +to altered conditions of nutrition at a sufficiently early stage a +complete substitution of one organ for another is effected. If the +rudiment has reached a certain stage in development before it is exposed +to these influences, extraordinary intermediate forms are obtained, +bearing the characters of both organs. + +The study of regeneration following injury is of greater importance as +regards the problem of the development and place of origin of organs. +(Reference may be made to the full summary of results given by Goebel in +his "Experimentelle Morphologie", Leipzig and Berlin, 1908, Section IV.) +Only in relatively very rare cases is there a complete re-formation +of the injured organ itself, as e.g. in the growing-apex. Much more +commonly injury leads to the development of complementary formations, it +may be the rejuvenescence of a hitherto dormant rudiment, or it may be +the formation of such ab initio. In all organs, stems, roots, leaves, +as well as inflorescences, this kind of regeneration, which occurs in +a great variety of ways according to the species, may be observed on +detached pieces of the plant. Cases are also known, such, for example, +as the leaves of many plants which readily form roots but not shoots, +where a complete regeneration does not occur. + +The widely spread power of reacting to wounding affords a very valuable +means of inducing a fresh development of buds and roots on places +where they do not occur in normal circumstances. Injury creates special +conditions, but little is known as yet in regard to alterations directly +produced in this way. Where the injury consists in the separation of +an organ from its normal connections, the factors concerned are more +comprehensible. A detached leaf, e.g., is at once cut off from a supply +of water and salts, and is deprived of the means of getting rid of +organic substances which it produces; the result is a considerable +alteration in the degree of concentration. No experimental investigation +on these lines has yet been made. Our ignorance has often led to the +view that we are dealing with a force whose specific quality is the +restitution of the parts lost by operation; the proof, therefore, +that in certain cases a similar production of new roots or buds may +be induced without previous injury and simply by a change in external +conditions assumes an importance. (Klebs, "Willkurliche Entwickelung", +page 100; also, "Probleme der Entwickelung", "Biol. Centralbl." 1904, +page 610.) + +A specially striking phenomenon of regeneration, exhibited also by +uninjured plants, is afforded by polarity, which was discovered by +Vochting. (See the classic work of Vochting, "Ueber Organbildung im +Pflanzenreich", I. Bonn, 1888; also "Bot. Zeit." 1906, page 101; cf. +Goebel, "Experimentelle Morphologie", Leipzig and Berlin, 1908, Section +V, Polaritat.) It is found, for example, that roots are formed from the +base of a detached piece of stem and shoots from the apex. Within +the limits of this essay it is impossible to go into this difficult +question; it is, however, important from the point of view of our +general survey to emphasise the fact that the physiological distinctions +between base and apex of pieces of stem are only of a quantitative +kind, that is, they consist in the inhibition of certain phenomena or +in favouring them. As a matter of fact roots may be produced from the +apices of willows and cuttings of other plants; the distinction is thus +obliterated under the influence of environment. The fixed polarity of +cuttings from full grown stems cannot be destroyed; it is the expression +of previous development. Vochting speaks of polarity as a fixed +inherited character. This is an unconvincing conclusion, as nothing can +be deduced from our present knowledge as to the causes which led up to +polarity. We know that the fertilised egg, like the embryo, is fixed at +one end by which it hangs freely in the embryo-sac and afterwards in +the endosperm. From the first, therefore, the two ends have different +natures, and these are revealed in the differentiation into root-apex +and stem-apex. A definite direction in the flow of food-substances +is correlated with this arrangement, and this eventually leads to a +polarity in the tissues. This view requires experimental proof, which in +the case of the egg-cells of flowering plants hardly appears possible; +but it derives considerable support from the fact that in herbaceous +plants, e.g. Sempervivum (Klebs, "Variationen der Bluten", "Jahrb. Wiss. +Bot." 1905, page 260.), rosettes or flower-shoots are formed in response +to external conditions at the base, in the middle, or at the apex of the +stem, so that polarity as it occurs under normal conditions cannot be +the result of unalterable hereditary factors. On the other hand, the +lower plants should furnish decisive evidence on this question, and +the experiments of Stahl, Winkler, Kniep, and others indicate the right +method of attacking the problem. + +The relation of leaf-form to environment has often been investigated and +is well known. The leaves of bog and water plants (Cf.Goebel, loc. +cit. chapter II.; also Gluck, "Untersuchungen uber Wasser- und +Sumpfgewachse", Jena, Vols. I.-II. 1905-06.) afford the most striking +examples of modifications: according as they are grown in water, moist +or dry air, the form of the species characteristic of the particular +habitat is produced, since the stems are also modified. To the same +group of phenomena belongs the modification of the forms of leaves and +stems in plants on transplantation from the plains to the mountains +(Bonnier, "Recherches sur l'Anatomie experimentale des Vegetaux", +Corbeil, 1895.) or vice versa. Such variations are by no means isolated +examples. All plants exhibit a definite alteration in form as the result +of prolonged cultivation in moist or dry air, in strong or feeble +light, or in darkness, or in salt solutions of different composition and +strength. + +Every individual which is exposed to definite combinations of external +factors exhibits eventually the same type of modification. This is the +type of variation which Darwin termed "definite." It is easy to realise +that indefinite or fluctuating variations belong essentially to the same +class of phenomena; both are reactions to changes in environment. In the +production of individual variations two different influences undoubtedly +cooperate. One set of variations is caused by different external +conditions, during the production, either of sexual cells or of +vegetative primordia; another set is the result of varying external +conditions during the development of the embryo into an adult plant. The +two sets of influences cannot as yet be sharply differentiated. If, +for purposes of vegetative reproduction, we select pieces of the +same parent-plant of a pure species, the second type of variation +predominates. Individual fluctuations depend essentially in such cases +on small variations in environment during development. + +These relations must be borne in mind if we wish to understand the +results of statistical methods. Since the work of Quetelet, Galton, and +others the statistical examination of individual differences in animals +and plants has become a special science, which is primarily based on the +consideration that the application of the theory of probability renders +possible mathematical statement and control of the results. The facts +show that any character, size of leaf, length of stem, the number of +members in a flower, etc. do not vary haphazard but in a very regular +manner. In most cases it is found that there is a value which occurs +most commonly, the average or medium value, from which the larger and +smaller deviations, the so-called plus and minus variations fall away in +a continuous series and end in a limiting value. In the simpler cases +a falling off occurs equally on both sides of the curve; the curve +constructed from such data agrees very closely with the Gaussian curve +of error. In more complicated cases irregular curves of different kinds +are obtained which may be calculated on certain suppositions. + +The regular fluctuations about a mean according to the rule of +probability is often attributed to some law underlying variability. (de +Vries, "Mutationstheorie", Vol. I. page 35, Leipzig, 1901.) But there is +no such law which compels a plant to vary in a particular manner. Every +experimental investigation shows, as we have already remarked, that +the fluctuation of characters depends on fluctuation in the external +factors. The applicability of the method of probability follows from +the fact that the numerous individuals of a species are influenced by +a limited number of variable conditions. (Klebs, "Willkurl. Ent." Jena, +1903, page 141.) As each of these conditions includes within certain +limits all possible values and exhibits all possible combinations, it +follows that, according to the rules of probability, there must be +a mean value, about which the larger and smaller deviations are +distributed. Any character will be found to have the mean value which +corresponds with that combination of determining factors which occurs +most frequently. Deviations towards plus and minus values will be +correspondingly produced by rarer conditions. + +A conclusion of fundamental importance may be drawn from this +conception, which is, to a certain extent, supported by experimental +investigation. (Klebs, "Studien uber Variation", "Arch. fur Entw." +1907.) There is no normal curve for a particular CHARACTER, there is +only a curve for the varying combinations of conditions occurring in +nature or under cultivation. Under other conditions entirely different +curves may be obtained with other variants as a mean value. If, for +example, under ordinary conditions the number 10 is the most frequent +variant for the stamens of Sedum spectabile, in special circumstances +(red light) this is replaced by the number 5. The more accurately we +know the conditions for a particular form or number, and are able to +reproduce it by experiment, the nearer we are to achieving our aim of +rendering a particular variation impossible or of making it dominant. + +In addition to the individual variations of a species, more pronounced +fluctuations occur relatively rarely and sporadically which are spoken +of as "single variations," or if specially striking as abnormalities +or monstrosities. These forms have long attracted the attention of +morphologists; a large number of observations of this kind are given +in the handbooks of Masters (Masters, "Vegetable Teratology", London, +1869.) and Penzig (Penzig, "Pflanzen-Teratologie", Vols I. and II. Genua, +1890-94.) These variations, which used to be regarded as curiosities, +have now assumed considerable importance in connection with the causes +of form-development. They also possess special interest in relation to +the question of heredity, a subject which does not at present concern +us, as such deviations from normal development undoubtedly arise as +individual variations induced by the influence of environment. + +Abnormal developments of all kinds in stems, leaves, and flowers, may +be produced by parasites, insects, or fungi. They may also be induced +by injury, as Blaringhem (Blaringhem, "Mutation et traumatismes", Paris, +1907.) has more particularly demonstrated, which, by cutting away the +leading shoots of branches in an early stage of development, caused +fasciation, torsion, anomalous flowers, etc. The experiments of +Blaringhem point to the probability that disturbances in the conditions +of food-supply consequent on injury are the cause of the production of +monstrosities. This is certainly the case in my experiments with species +of Sempervivum (Klebs, "Kunstliche Metamorphosen", Stuttgart, 1906.); +individuals, which at first formed normal flowers, produced a great +variety of abnormalities as the result of changes in nutrition, we +may call to mind the fact that the formation of inflorescences occurs +normally when a vigorous production of organic compounds, such as +starch, sugar, etc. follows a diminution in the supply of mineral +salts. On the other hand, the development of inflorescences is entirely +suppressed if, at a suitable moment before the actual foundations have +been laid, water and mineral salts are supplied to the roots. If, during +the week when the inflorescence has just been laid down and is growing +very slowly, the supply of water and salts is increased, the internal +conditions of the cells are essentially changed. At a later stage, after +the elongation of the inflorescence, rosettes of leaves are produced +instead of flowers, and structures intermediate between the two kinds of +organs; a number of peculiar plant-forms are thus obtained (Cf. Lotsy, +"Vorlesungen uber Deszendenztheorien", Vol. II. pl. 3, Jena, 1908.) +Abnormalities in the greatest variety are produced in flowers by varying +the time at which the stimulus is applied, and by the cooperation +of other factors such as temperature, darkness, etc. In number and +arrangement the several floral members vary within wide limits; +sepals, petals, stamens, and carpels are altered in form and colour, a +transformation of stamens to carpels and from carpels to stamens occurs +in varying degrees. The majority of the deviations observed had not +previously been seen either under natural conditions or in cultivation; +they were first brought to light through the influence of external +factors. + +Such transformations of flowers become apparent at a time, which is +separated by about two months from the period at which the particular +cause began to act. There is, therefore, no close connection between +the appearance of the modifications and the external conditions which +prevail at the moment. When we are ignorant of the causes which are +operative so long before the results are seen, we gain the impression +that such variations as occur are spontaneous or autonomous expressions +of the inner nature of the plant. It is much more likely that, as in +Sempervivum, they were originally produced by an external stimulus which +had previously reached the sexual cells or the young embryo. In any case +abnormalities of this kind appear to be of a special type as compared +with ordinary fluctuating variations. Darwin pointed out this +difference; Bateson (Bateson, "Materials for the study of Variation", +London, 1894, page 5.) has attempted to make the distinction sharper, at +the same time emphasising its importance in heredity. + +Bateson applies the term CONTINUOUS to small variations connected with +one another by transitional stages, while those which are more striking +and characterised from the first by a certain completeness, he names +DISCONTINUOUS. He drew attention to a great difficulty which stands in +the way of Lamarck's hypothesis, as also of Darwin's view. "According to +both theories, specific diversity of form is consequent upon diversity +of environment, and diversity of environment is thus the ultimate +measure of diversity of specific form. Here then we meet the difficulty +that diverse environments often shade into each other insensibly and +form a continuous series, whereas the Specific Forms of life which +are subject to them on the whole form a Discontinuous Series." +This difficulty is, however, not of fundamental importance as well +authenticated facts have been adduced showing that by alteration of the +environment discontinuous variations, such as alterations in the number +and form of members of a flower, may be produced. We can as yet no more +explain how this happens than we can explain the existence of continuous +variations. We can only assert that both kinds of variation arise +in response to quantitative alterations in external conditions. The +question as to which kind of variation is produced depends on the +greater or less degree of alteration; it is correlated with the state of +the particular cells at the moment. + +In this short sketch it is only possible to deal superficially with a +small part of the subject. It has been clearly shown that in view of the +general dependence of development on the factors of the environment +a number of problems are ready for experimental treatment. One must, +however, not forget that the science of the physiology of form has not +progressed beyond its initial stages. Just now our first duty is to +demonstrate the dependence on external factors in as many forms of +plants as possible, in order to obtain a more thorough control of all +the different plant-forms. The problem is not only to produce at will +(and independently of their normal mode of life) forms which occur +in nature, but also to stimulate into operation potentialities which +necessarily lie dormant under the conditions which prevail in nature. +The constitution of a species is much richer in possibilities of +development than would appear to be the case under normal conditions. It +remains for man to stimulate into activity all the potentialities. + +But the control of plant-form is only a preliminary step--the foundation +stones on which to erect a coherent scientific structure. We must +discover what are the internal processes in the cell produced by +external factors, which as a necessary consequence result in the +appearance of a definite form. We are here brought into contact with the +most obscure problem of life. Progress can only be made pari passu with +progress in physics and chemistry, and with the growth of our knowledge +of nutrition, growth, etc. + +Let us take one of the simplest cases--an alteration in form. A +cylindrical cell of the alga Stigeoclonium assumes, as Livingstone +(Livingstone, "On the nature of the stimulus which causes the change +of form, etc." "Botanical Gazette", XXX. 1900; also XXXII. 1901.) has +shown, a spherical form when the osmotic pressure of the culture fluid +is increased; or a spore of Mucor, which, in a sugar solution grows +into a branched filament, in the presence of a small quantity of acid +(hydrogen ions) becomes a comparatively large sphere. (Ritter, "Ueber +Kugelhefe, etc." "Ber. bot. Gesell." Berlin, XXV. page 255, 1907.) +In both cases there has undoubtedly been an alteration in the osmotic +pressure of the cell-sap, but this does not suffice to explain the +alteration in form, since the unknown alterations, which are induced in +the protoplasm, must in their turn influence the cell-membrane. In +the case of the very much more complex alterations in form, such as we +encounter in the course of development of plants, there do not appear +to be any clues which lead us to a deeper insight into the phenomena. +Nevertheless we continue the attempt, seeking with the help of any +available hypothesis for points of attack, which may enable us to +acquire a more complete mastery of physiological methods. To quote a +single example; I may put the question, what internal changes produce a +transition from vegetative growth to sexual reproduction? + +The facts, which are as clearly established from the lower as for the +higher plants, teach us that quantitative alteration in the environment +produces such a transition. This suggests the conclusion that +quantitative internal changes in the cells, and with them disturbances +in the degree of concentration, are induced, through which the chemical +reactions are led in the direction of sexual reproduction. An increase +in the production of organic substances in the presence of light, +chiefly of the carbohydrates, with a simultaneous decrease in the amount +of inorganic salts and water, are the cause of the disturbance and +at the same time of the alteration in the direction of development. +Possibly indeed mineral salts as such are not in question, but only in +the form of other organic combinations, particularly proteid material, +so that we are concerned with an alteration in the relation of the +carbohydrates and proteids. The difficulties of such researches are very +great because the methods are not yet sufficiently exact to demonstrate +the frequently small quantitative differences in chemical composition. +Questions relating to the enzymes, which are of the greatest importance +in all these life-processes, are especially complicated. In any case +it is the necessary result of such an hypothesis that we must employ +chemical methods of investigation in dealing with problems connected +with the physiology of form. + +II. INFLUENCE OF ENVIRONMENT ON THE TRANSFORMATION OF SPECIES. + +The study of the physiology of form-development in a pure species has +already yielded results and makes slow but sure progress. The physiology +of the possibility of the transformation of one species into another is +based, as yet, rather on pious hope than on accomplished fact. From +the first it appeared to be hopeless to investigate physiologically +the origin of Linnean species and at the same time that of the natural +system, an aim which Darwin had before him in his enduring work. The +historical sequence of events, of which an organism is the expression, +can only be treated hypothetically with the help of facts supplied +by comparative morphology, the history of development, geographical +distribution, and palaeontology. (See Lotsy, "Vorlesungen" (Jena, I. +1906, II. 1908), for summary of the facts.) A glance at the controversy +which is going on today in regard to different hypotheses shows that +the same material may lead different investigators to form entirely +different opinions. Our ultimate aim is to find a solution of the +problem as to the cause of the origin of species. Indeed such +attempts are now being made: they are justified by the fact that under +cultivation new and permanent strains are produced; the fundamental +importance of this was first grasped by Darwin. New points of view in +regard to these lines of inquiry have been adopted by H. de Vries +who has succeeded in obtaining from Oenothera Lamarckiana a number of +constant "elementary" species. Even if it is demonstrated that he was +simply dealing with the complex splitting up of a hybrid (Bateson, +"Reports to the Evolution Committee of the Royal Society", London, 1902; +cf. also Lotsy, "Vorlesungen", Vol. I. page 234.), the facts adduced in +no sense lose their very great value. + +We must look at the problem in its simplest form; we find it in every +case where a new race differs essentially from the original type in a +single character only; for example, in the colour of the flowers or in +the petalody of the stamens (doubling of flowers). In this connection +we must keep in view the fact that every visible character in a plant is +the resultant of the cooperation of specific structure, with its various +potentialities, and the influence of the environment. We know, that in +a pure species all characters vary, that a blue-flowering Campanula or +a red Sempervivum can be converted by experiment into white-flowering +forms, that a transformation of stamens into petals may be caused by +fungi or by the influence of changed conditions of nutrition, or +that plants in dry and poor soil become dwarfed. But so far as the +experiments justify a conclusion, it would appear that such alterations +are not inherited by the offspring. Like all other variations they +appear only so long as special conditions prevail in the surroundings. + +It has been shown that the case is quite different as regards the +white-flowering, double or dwarf races, because these retain their +characters when cultivated under practically identical conditions, and +side by side with the blue, single-flowering or tall races. The problem +may therefore be stated thus: how can a character, which appears in the +one case only under the strictly limited conditions of the experiment, +in other cases become apparent under the very much wider conditions of +ordinary cultivation? If a character appears, in these circumstances, +in the case of all individuals, we then speak of constant races. In such +simple cases the essential point is not the creation of a new character +but rather an ALTERATION OF THIS CHARACTER IN ACCORDANCE WITH THE +ENVIRONMENT. In the examples mentioned the modified character in the +simple varieties (or a number of characters in elementary species) +appears more or less suddenly and is constant in the above sense. The +result is what de Vries has termed a Mutation. In this connection we +must bear in mind the fact that no difference, recognisable externally, +need exist between individual variation and mutation. Even the most +minute quantitative difference between two plants may be of specific +value if it is preserved under similar external conditions during many +successive generations. We do not know how this happens. We may state +the problem in other terms; by saying that the specific structure must +be altered. It is possible, to some extent, to explain this sudden +alteration, if we regard it as a chemical alteration of structure either +in the specific qualities of the proteids or of the unknown carriers +of life. In the case of many organic compounds their morphological +characters (the physical condition, crystalline form, etc.) are at once +changed by alteration of atomic relations or by incorporation of new +radicals. (For instance ethylchloride (C2H5Cl) is a gas at 21 deg +C., ethylenechloride (C2H4Cl2) a fluid boiling at 84 deg C., beta +trichlorethane (C2H3Cl3) a fluid boiling at 113 deg C., +perchlorethane (C2Cl6) a crystalline substance. Klebs, ("Willkurliche +Entwickelungsanderungen" page 158.) Much more important, however, would +be an answer to the question, whether an individual variation can be +converted experimentally into an inherited character--a mutation in de +Vries's sense. + +In all circumstances we may recognise as a guiding principle the +assumption adopted by Lamarck, Darwin, and many others, that the +inheritance of any one character, or in more general terms, the +transformation of one species into another, is, in the last instance, +to be referred to a change in the environment. From a causal-mechanical +point of view it is not a priori conceivable that one species can +ever become changed into another so long as external conditions remain +constant. The inner structure of a species must be essentially altered +by external influences. Two methods of experimental research may be +adopted, the effect of crossing distinct species and, secondly, the +effect of definite factors of the environment. + +The subject of hybridisation is dealt with in another part of this +essay. It is enough to refer here to the most important fact, that as +the result of combinations of characters of different species new and +constant forms are produced. Further, Tschermack, Bateson and others +have demonstrated the possibility that hitherto unknown inheritable +characters may be produced by hybridisation. + +The other method of producing constant races by the influence of special +external conditions has often been employed. The sporeless races of +Bacteria and Yeasts (Cf. Detto, "Die Theorie der direkten Anpassung... ", +pages 98 et seq., Jena, 1904; see also Lotsy, "Vorlesungen", II. pages +636 et seq., where other similar cases are described.) are well known, +in which an internal alteration of the cells is induced by the influence +of poison or higher temperature, so that the power of producing spores +even under normal conditions appears to be lost. A similar state of +things is found in some races which under certain definite conditions +lose their colour or their virulence. Among the phanerogams the +investigations of Schubler on cereals afford parallel cases, in which +the influence of a northern climate produces individuals which ripen +their seeds early; these seeds produce plants which seed early in +southern countries. Analogous results were obtained by Cieslar in his +experiments; seeds of conifers from the Alps when planted in the plains +produced plants of slow growth and small diameter. + +All these observations are of considerable interest theoretically; they +show that the action of environment certainly induces such internal +changes, and that these are transmitted to the next generation. But as +regards the main question, whether constant races may be obtained by +this means, the experiments cannot as yet supply a definite answer. In +phanerogams, the influence very soon dies out in succeeding generations; +in the case of bacteria, in which it is only a question of the loss of +a character it is relatively easy for this to reappear. It is not +impossible, that in all such cases there is a material hanging-on of +certain internal conditions, in consequence of which the modification +of the character persists for a time in the descendants, although the +original external conditions are no longer present. + +Thus a slow dying-out of the effect of a stimulus was seen in my +experiments on Veronica chamaedrys. (Klebs, "Kunstliche Metamorphosen", +Stuttgart, 1906, page 132.) During the cultivation of an artificially +modified inflorescence I obtained a race showing modifications in +different directions, among which twisting was especially conspicuous. +This plant, however, does not behave as the twisted race of Dipsacus +isolated by de Vries (de Vries, "Mutationstheorie", Vol. II. Leipzig, +1903, page 573.), which produced each year a definite percentage of +twisted individuals. In the vegetative reproduction of this Veronica the +torsion appeared in the first, also in the second and third year, but +with diminishing intensity. In spite of good cultivation this character +has apparently now disappeared; it disappeared still more quickly in +seedlings. In another character of the same Veronica chamaedrys the +influence of the environment was stronger. The transformation of the +inflorescences to foliage-shoots formed the starting-point; it occurred +only under narrowly defined conditions, namely on cultivation as a +cutting in moist air and on removal of all other leaf-buds. In the +majority (7/10) of the plants obtained from the transformed shoots, the +modification appeared in the following year without any interference. +Of the three plants which were under observation several years the first +lost the character in a short time, while the two others still retain +it, after vegetative propagation, in varying degrees. The same character +occurs also in some of the seedlings; but anything approaching a +constant race has not been produced. + +Another means of producing new races has been attempted by Blaringhem. +(Blaringhem, "Mutation et Traumatisme", Paris, 1907.) On removing at +an early stage the main shoots of different plants he observed various +abnormalities in the newly formed basal shoots. From the seeds of such +plants he obtained races, a large percentage of which exhibited these +abnormalities. Starting from a male Maize plant with a fasciated +inflorescence, on which a proportion of the flowers had become male, +a new race was bred in which hermaphrodite flowers were frequently +produced. In the same way Blaringhem obtained, among other similar +results, a race of barley with branched ears. These races, however, +behaved in essentials like those which have been demonstrated by de +Vries to be inconstant, e.g. Trifolium pratense quinquefolium and +others. The abnormality appears in a proportion of the individuals +and only under very special conditions. It must be remembered too that +Blaringhem worked with old cultivated plants, which from the first had +been disposed to split into a great variety of races. It is possible, +but difficult to prove, that injury contributed to this result. + +A third method has been adopted by MacDougal (MacDougal, "Heredity and +Origin of species", "Monist", 1906; "Report of department of botanical +research", "Fifth Year-book of the Carnegie Institution of Washington", +page 119, 1907.) who injected strong (10 percent) sugar solution or weak +solutions of calcium nitrate and zinc sulphate into young carpels of +different plants. From the seeds of a plant of Raimannia odorata the +carpels of which had been thus treated he obtained several plants +distinguished from the parent-forms by the absence of hairs and by +distinct forms of leaves. Further examination showed that he had here to +do with a new elementary species. MacDougal also obtained a more or less +distinct mutant of Oenothera biennis. We cannot as yet form an opinion +as to how far the effect is due to the wound or to the injection of +fluid as such, or to its chemical properties. This, however, is not so +essential as to decide whether the mutant stands in any relation to the +influence of external factors. It is at any rate very important that +this kind of investigation should be carried further. + +If it could be shown that new and inherited races were obtained by +MacDougal's method, it would be safe to conclude that the same end might +be gained by altering the conditions of the food-stuff conducted to the +sexual cells. New races or elementary species, however, arise without +wounding or injection. This at once raises the much discussed question, +how far garden-cultivation has led to the creation of new races? +Contrary to the opinion expressed by Darwin and others, de Vries +("Mutationstheorie", Vol. I. pages 412 et seq.) tried to show that +garden-races have been produced only from spontaneous types which occur +in a wild state or from sub-races, which the breeder has accidentally +discovered but not originated. In a small number of cases only has de +Vries adduced definite proof. On the other side we have the work of +Korschinsky (Korschinsky, "Heterogenesis und Evolution", "Flora", 1901.) +which shows that whole series of garden-races have made their appearance +only after years of cultivation. In the majority of races we are +entirely ignorant of their origin. + +It is, however, a fact that if a plant is removed from natural +conditions into cultivation, a well-marked variation occurs. The +well-known plant-breeder L. de Vilmorin (L. de Vilmorin, "Notices sur +l'amelioration des plantes", Paris, 1886, page 36.), speaking from his +own experience, states that a plant is induced to "affoler," that is +to exhibit all possible variations from which the breeder may make a +further selection only after cultivation for several generations. The +effect of cultivation was particularly striking in Veronica chamaedrys +(Klebs, "Kunstliche Metamorphosen", Stuttgart, 1906, page 152.) which, +in spite of its wide distribution in nature, varies very little. After a +few years of cultivation this "good" and constant species becomes highly +variable. The specimens on which the experiments were made were three +modified inflorescence cuttings, the parent-plants of which certainly +exhibited no striking abnormalities. In a short time many hitherto +latent potentialities became apparent, so that characters, never +previously observed, or at least very rarely, were exhibited, such +as scattered leaf-arrangement, torsion, terminal or branched +inflorescences, the conversion of the inflorescence into foliage-shoots, +every conceivable alteration in the colour of flowers, the assumption of +a green colour by parts of the flowers, the proliferation of flowers. + +All this points to some disturbance in the species resulting from +methods of cultivation. It has, however, not yet been possible to +produce constant races with any one of these modified characters. But +variations appeared among the seedlings, some of which, e.g. yellow +variegation, were not inheritable, while others have proved constant. +This holds good, so far as we know at present, for a small rose-coloured +form which is to be reckoned as a mutation. Thus the prospect of +producing new races by cultivation appears to be full of promise. + +So long as the view is held that good nourishment, i.e. a plentiful +supply of water and salts, constitutes the essential characteristic of +garden-cultivation, we can hardly conceive that new mutations can be +thus produced. But perhaps the view here put forward in regard to the +production of form throws new light on this puzzling problem. + +Good manuring is in the highest degree favourable to vegetative growth, +but is in no way equally favourable to the formation of flowers. The +constantly repeated expression, good or favourable nourishment, is not +only vague but misleading, because circumstances favourable to growth +differ from those which promote reproduction; for the production of +every form there are certain favourable conditions of nourishment, which +may be defined for each species. Experience shows that, within definite +and often very wide limits, it does not depend upon the ABSOLUTE AMOUNT +of the various food substances, but upon their respective degrees of +concentration. As we have already stated, the production of flowers +follows a relative increase in the amount of carbohydrates formed in +the presence of light, as compared with the inorganic salts on which +the formation of albuminous substances depends. (Klebs, "Kunstliche +Metamorphosen", page 117.) The various modifications of flowers are due +to the fact that a relatively too strong solution of salts is supplied +to the rudiments of these organs. As a general rule every plant +form depends upon a certain relation between the different chemical +substances in the cells and is modified by an alteration of that +relation. + +During long cultivation under conditions which vary in very different +degrees, such as moisture, the amount of salts, light intensity, +temperature, oxygen, it is possible that sudden and special disturbances +in the relations of the cell substances have a directive influence on +the inner organisation of the sexual cells, so that not only inconstant +but also constant varieties will be formed. + +Definite proof in support of this view has not yet been furnished, and +we must admit that the question as to the cause of heredity remains, +fundamentally, as far from solution as it was in Darwin's time. As the +result of the work of many investigators, particularly de Vries, +the problem is constantly becoming clearer and more definite. The +penetration into this most difficult and therefore most interesting +problem of life and the creation by experiment of new races or +elementary species are no longer beyond the region of possibility. + + + + +XIV. EXPERIMENTAL STUDY OF THE INFLUENCE OF ENVIRONMENT ON ANIMALS. +By Jacques Loeb, M.D. Professor of Physiology in the University of +California. + + +I. INTRODUCTORY REMARKS. + +What the biologist calls the natural environment of an animal is from a +physical point of view a rather rigid combination of definite forces. It +is obvious that by a purposeful and systematic variation of these and +by the application of other forces in the laboratory, results must be +obtainable which do not appear in the natural environment. This is the +reasoning underlying the modern development of the study of the effects +of environment upon animal life. It was perhaps not the least important +of Darwin's services to science that the boldness of his conceptions +gave to the experimental biologist courage to enter upon the attempt of +controlling at will the life-phenomena of animals, and of bringing about +effects which cannot be expected in Nature. + +The systematic physico-chemical analysis of the effect of outside +forces upon the form and reactions of animals is also our only means of +unravelling the mechanism of heredity beyond the scope of the Mendelian +law. The manner in which a germ-cell can force upon the adult certain +characters will not be understood until we succeed in varying +and controlling hereditary characteristics; and this can only be +accomplished on the basis of a systematic study of the effects of +chemical and physical forces upon living matter. + +Owing to limitation of space this sketch is necessarily very incomplete, +and it must not be inferred that studies which are not mentioned here +were considered to be of minor importance. All the writer could hope to +do was to bring together a few instances of the experimental analysis of +the effect of environment, which indicate the nature and extent of our +control over life-phenomena and which also have some relation to the +work of Darwin. In the selection of these instances preference is given +to those problems which are not too technical for the general reader. + +The forces, the influence of which we shall discuss, are in succession +chemical agencies, temperature, light, and gravitation. We shall also +treat separately the effect of these forces upon form and instinctive +reactions. + + +II. THE EFFECTS OF CHEMICAL AGENCIES. + +(a) HETEROGENEOUS HYBRIDISATION. + +It was held until recently that hybridisation is not possible except +between closely related species and that even among these a successful +hybridisation cannot always be counted upon. This view was well +supported by experience. It is, for instance, well known that the +majority of marine animals lay their unfertilised eggs in the ocean and +that the males shed their sperm also into the sea-water. The numerical +excess of the spermatozoa over the ova in the sea-water is the only +guarantee that the eggs are fertilised, for the spermatozoa are +carried to the eggs by chance and are not attracted by the latter. This +statement is the result of numerous experiments by various authors, +and is contrary to common belief. As a rule all or the majority of +individuals of a species in a given region spawn on the same day, and +when this occurs the sea-water constitutes a veritable suspension of +sperm. It has been shown by experiment that in fresh sea-water the sperm +may live and retain its fertilising power for several days. It is thus +unavoidable that at certain periods more than one kind of spermatozoon +is suspended in the sea-water and it is a matter of surprise that the +most heterogeneous hybridisations do not constantly occur. The reason +for this becomes obvious if we bring together mature eggs and equally +mature and active sperm of a different family. When this is done no egg +is, as a rule, fertilised. The eggs of a sea-urchin can be fertilised by +sperm of their own species, or, though in smaller numbers, by the sperm +of other species of sea-urchins, but not by the sperm of other groups of +echinoderms, e.g. starfish, brittle-stars, holothurians or crinoids, and +still less by the sperm of more distant groups of animals. The consensus +of opinion seemed to be that the spermatozoon must enter the egg +through a narrow opening or canal, the so-called micropyle, and that +the micropyle allowed only the spermatozoa of the same or of a closely +related species to enter the egg. + +It seemed to the writer that the cause of this limitation of +hybridisation might be of another kind and that by a change in the +constitution of the sea-water it might be possible to bring about +heterogenous hybridisations, which in normal sea-water are impossible. +This assumption proved correct. Sea-water has a faintly alkaline +reaction (in terms of the physical chemist its concentration of hydroxyl +ions is about (10 to the power minus six)N at Pacific Grove, California, +and about (10 to the power minus 5)N at Woods Hole, Massachusetts). +If we slightly raise the alkalinity of the sea-water by adding to it a +small but definite quantity of sodium hydroxide or some other alkali, +the eggs of the sea-urchin can be fertilised with the sperm of widely +different groups of animals, possibly with the sperm of any marine +animal which sheds it into the ocean. In 1903 it was shown that if we +add from about 0.5 to 0.8 cubic centimetre N/10 sodium hydroxide to +50 cubic centimetres of sea-water, the eggs of Strongylocentrotus +purpuratus (a sea-urchin which is found on the coast of California) +can be fertilised in large quantities by the sperm of various kinds of +starfish, brittle-stars and holothurians; while in normal sea-water or +with less sodium hydroxide not a single egg of the same female could +be fertilised with the starfish sperm which proved effective in the +hyper-alkaline sea-water. The sperm of the various forms of starfish was +not equally effective for these hybridisations; the sperm of Asterias +ochracea and A. capitata gave the best results, since it was possible to +fertilise 50 per cent or more of the sea-urchin eggs, while the sperm of +Pycnopodia and Asterina fertilised only 2 per cent of the same eggs. + +Godlewski used the same method for the hybridisation of the sea-urchin +eggs with the sperm of a crinoid (Antedon rosacea). Kupelwieser +afterwards obtained results which seemed to indicate the possibility of +fertilising the eggs of Strongylocentrotus with the sperm of a mollusc +(Mytilus.) Recently, the writer succeeded in fertilising the +eggs of Strongylocentrotus franciscanus with the sperm of a +mollusc--Chlorostoma. This result could only be obtained in sea-water +the alkalinity of which had been increased (through the addition of +0.8 cubic centimetre N/10 sodium hydroxide to 50 cubic centimetres +of sea-water). We thus see that by increasing the alkalinity of the +sea-water it is possible to effect heterogeneous hybridisations which +are at present impossible in the natural environment of these animals. + +It is, however, conceivable that in former periods of the earth's +history such heterogeneous hybridisations were possible. It is known +that in solutions like sea-water the degree of alkalinity must increase +when the amount of carbon-dioxide in the atmosphere is diminished. If it +be true, as Arrhenius assumes, that the Ice age was caused or preceded +by a diminution in the amount of carbon-dioxide in the air, such a +diminution must also have resulted in an increase of the alkalinity +of the sea-water, and one result of such an increase must have been to +render possible heterogeneous hybridisations in the ocean which in the +present state of alkalinity are practically excluded. + +But granted that such hybridisations were possible, would they have +influenced the character of the fauna? In other words, are the hybrids +between sea-urchin and starfish, or better still, between sea-urchin and +mollusc, capable of development, and if so, what is their character? +The first experiment made it appear doubtful whether these heterogeneous +hybrids could live. The sea-urchin eggs which were fertilised in the +laboratory by the spermatozoa of the starfish, as a rule, died earlier +than those of the pure breeds. But more recent results indicate that +this was due merely to deficiencies in the technique of the earlier +experiments. The writer has recently obtained hybrid larvae between the +sea-urchin egg and the sperm of a mollusc (Chlorostoma) which, in the +laboratory, developed as well and lived as long as the pure breeds of +the sea-urchin, and there was nothing to indicate any difference in the +vitality of the two breeds. + +So far as the question of heredity is concerned, all the experiments on +heterogeneous hybridisation of the egg of the sea-urchin with the sperm +of starfish, brittle-stars, crinoids and molluscs, have led to the same +result, namely, that the larvae have purely maternal characteristics and +differ in no way from the pure breed of the form from which the egg +is taken. By way of illustration it may be said that the larvae of the +sea-urchin reach on the third day or earlier (according to species +and temperature) the so-called pluteus stage, in which they possess a +typical skeleton; while neither the larvae of the starfish nor those +of the mollusc form a skeleton at the corresponding stage. It was, +therefore, a matter of some interest to find out whether or not the +larvae produced by the fertilisation of the sea-urchin egg with the +sperm of starfish or mollusc would form the normal and typical pluteus +skeleton. This was invariably the case in the experiments of Godlewski, +Kupelwieser, Hagedoorn, and the writer. These hybrid larvae were +exclusively maternal in character. + +It might be argued that in the case of heterogeneous hybridisation the +sperm-nucleus does not fuse with the egg-nucleus, and that, therefore, +the spermatozoon cannot transmit its hereditary substances to the +larvae. But these objections are refuted by Godlewski's experiments, +in which he showed definitely that if the egg of the sea-urchin is +fertilised with the sperm of a crinoid the fusion of the egg-nucleus +and sperm-nucleus takes place in the normal way. It remains for further +experiments to decide what the character of the adult hybrids would be. + +(b). ARTIFICIAL PARTHENOGENESIS. + +Possibly in no other field of Biology has our ability to control +life-phenomena by outside conditions been proved to such an extent as +in the domain of fertilisation. The reader knows that the eggs of the +overwhelming majority of animals cannot develop unless a spermatozoon +enters them. In this case a living agency is the cause of development +and the problem arises whether it is possible to accomplish the same +result through the application of well-known physico-chemical agencies. +This is, indeed, true, and during the last ten years living larvae +have been produced by chemical agencies from the unfertilised eggs +of sea-urchins, starfish, holothurians and a number of annelids and +molluscs; in fact this holds true in regard to the eggs of practically +all forms of animals with which such experiments have been tried long +enough. In each form the method of procedure is somewhat different and +a long series of experiments is often required before the successful +method is found. + +The facts of Artificial Parthenogenesis, as the chemical fertilisation +of the egg is called, have, perhaps, some bearing on the problem of +evolution. If we wish to form a mental image of the process of evolution +we have to reckon with the possibility that parthenogenetic propagation +may have preceded sexual reproduction. This suggests also the +possibility that at that period outside forces may have supplied +the conditions for the development of the egg which at present the +spermatozoon has to supply. For this, if for no other reason, a brief +consideration of the means of artificial parthenogenesis may be of +interest to the student of evolution. + +It seemed necessary in these experiments to imitate as completely as +possible by chemical agencies the effects of the spermatozoon upon +the egg. When a spermatozoon enters the egg of a sea-urchin or certain +starfish or annelids, the immediate effect is a characteristic change of +the surface of the egg, namely the formation of the so-called membrane +of fertilisation. The writer found that we can produce this membrane in +the unfertilised egg by certain acids, especially the monobasic acids +of the fatty series, e.g. formic, acetic, propionic, butyric, etc. +Carbon-dioxide is also very efficient in this direction. It was also +found that the higher acids are more efficient than the lower ones, +and it is possible that the spermatozoon induces membrane-formation by +carrying into the egg a higher fatty acid, namely oleic acid or one of +its salts or esters. + +The physico-chemical process which underlies the formation of the +membrane seems to be the cause of the development of the egg. In all +cases in which the unfertilised egg has been treated in such a way as +to cause it to form a membrane it begins to develop. For the eggs of +certain animals membrane-formation is all that is required to induce a +complete development of the unfertilised egg, e.g. in the starfish and +certain annelids. For the eggs of other animals a second treatment is +necessary, presumably to overcome some of the injurious effects of +acid treatment. Thus the unfertilised eggs of the sea-urchin +Strongylocentrotus purpuratus of the Californian coast begin to develop +when membrane-formation has been induced by treatment with a fatty acid, +e.g. butyric acid; but the development soon ceases and the eggs +perish in the early stages of segmentation, or after the first nuclear +division. But if we treat the same eggs, after membrane-formation, for +from 35 to 55 minutes (at 15 deg C.) with sea-water the concentration +(osmotic pressure) of which has been raised through the addition of a +definite amount of some salt or sugar, the eggs will segment and develop +normally, when transferred back to normal sea-water. If care is taken, +practically all the eggs can be caused to develop into plutei, the +majority of which may be perfectly normal and may live as long as larvae +produced from eggs fertilised with sperm. + +It is obvious that the sea-urchin egg is injured in the process of +membrane-formation and that the subsequent treatment with a hypertonic +solution only acts as a remedy. The nature of this injury became clear +when it was discovered that all the agencies which cause haemolysis, +i.e. the destruction of the red blood corpuscles, also cause +membrane-formation in unfertilised eggs, e.g. fatty acids or ether, +alcohols or chloroform, etc., or saponin, solanin, digitalin, bile +salts and alkali. It thus happens that the phenomena of artificial +parthenogenesis are linked together with the phenomena of haemolysis +which at present play so important a role in the study of immunity. The +difference between cytolysis (or haemolysis) and fertilisation seems to +be this, that the latter is caused by a superficial or slight cytolysis +of the egg, while if the cytolytic agencies have time to act on the +whole egg the latter is completely destroyed. If we put unfertilised +eggs of a sea-urchin into sea-water which contains a trace of saponin we +notice that, after a few minutes, all the eggs form the typical +membrane of fertilisation. If the eggs are then taken out of the saponin +solution, freed from all traces of saponin by repeated washing in normal +sea-water, and transferred to the hypertonic sea-water for from 35 to +55 minutes, they develop into larvae. If, however, they are left in +the sea-water containing the saponin they undergo, a few minutes after +membrane-formation, the disintegration known in pathology as CYTOLYSIS. +Membrane-formation is, therefore, caused by a superficial or incomplete +cytolysis. The writer believes that the subsequent treatment of the egg +with hypertonic sea-water is needed only to overcome the destructive +effects of this partial cytolysis. The full reasons for this belief +cannot be given in a short essay. + +Many pathologists assume that haemolysis or cytolysis is due to a +liquefaction of certain fatty or fat-like compounds, the so-called +lipoids, in the cell. If this view is correct, it would be necessary to +ascribe the fertilisation of the egg to the same process. + +The analogy between haemolysis and fertilisation throws, possibly, +some light on a curious observation. It is well known that the blood +corpuscles, as a rule, undergo cytolysis if injected into the blood of +an animal which belongs to a different family. The writer found last +year that the blood of mammals, e.g. the rabbit, pig, and cattle, causes +the egg of Strongylocentrotus to form a typical fertilisation-membrane. +If such eggs are afterwards treated for a short period with hypertonic +sea-water they develop into normal larvae (plutei). Some substance +contained in the blood causes, presumably, a superficial cytolysis of +the egg and thus starts its development. + +We can also cause the development of the sea-urchin egg without +membrane-formation. The early experiments of the writer were done in +this way and many experimenters still use such methods. It is probable +that in this case the mechanism of fertilisation is essentially the same +as in the case where the membrane-formation is brought about, with +this difference only, that the cytolytic effect is less when no +fertilisation-membrane is formed. This inference is corroborated by +observations on the fertilisation of the sea-urchin egg with ox blood. +It very frequently happens that not all of the eggs form membranes in +this process. Those eggs which form membranes begin to develop, but +perish if they are not treated with hypertonic sea-water. Some of the +other eggs, however, which do not form membranes, develop directly into +normal larvae without any treatment with hypertonic sea-water, provided +they are exposed to the blood for only a few minutes. Presumably some +blood enters the eggs and causes the cytolytic effects in a less degree +than is necessary for membrane-formation, but in a sufficient degree to +cause their development. The slightness of the cytolytic effect allows +the egg to develop without treatment with hypertonic sea-water. + +Since the entrance of the spermatozoon causes that degree of cytolysis +which leads to membrane-formation, it is probable that, in addition to +the cytolytic or membrane-forming substance (presumably a higher fatty +acid), it carries another substance into the egg which counteracts the +deleterious cytolytic effects underlying membrane-formation. + +The question may be raised whether the larvae produced by artificial +parthenogenesis can reach the mature stage. This question may be +answered in the affirmative, since Delage has succeeded in raising +several parthenogenetic sea-urchin larvae beyond the metamorphosis into +the adult stage and since in all the experiments made by the writer +the parthenogenetic plutei lived as long as the plutei produced from +fertilised eggs. + +(c). ON THE PRODUCTION OF TWINS FROM ONE EGG THROUGH A CHANGE IN THE +CHEMICAL CONSTITUTION OF THE SEA-WATER. + +The reader is probably familiar with the fact that there exist two +different types of human twins. In the one type the twins differ as much +as two children of the same parents born at different periods; they +may or may not have the same sex. In the second type the twins have +invariably the same sex and resemble each other most closely. Twins +of the latter type are produced from the same egg, while twins of the +former type are produced from two different eggs. + +The experiments of Driesch and others have taught us that twins +originate from one egg in this manner, namely, that the first two cells +into which the egg divides after fertilisation become separated from +each other. This separation can be brought about by a change in the +chemical constitution of the sea-water. Herbst observed that if the +fertilised eggs of the sea-urchin are put into sea-water which is freed +from calcium, the cells into which the egg divides have a tendency +to fall apart. Driesch afterwards noticed that eggs of the sea-urchin +treated with sea-water which is free from lime have a tendency to give +rise to twins. The writer has recently found that twins can be produced +not only by the absence of lime, but also through the absence of sodium +or of potassium; in other words, through the absence of one or two of +the three important metals in the sea-water. There is, however, a second +condition, namely, that the solution used for the production of twins +must have a neutral or at least not an alkaline reaction. + +The procedure for the production of twins in the sea-urchin egg consists +simply in this:--the eggs are fertilised as usual in normal sea-water +and then, after repeated washing in a neutral solution of sodium +chloride (of the concentration of the sea-water), are placed in a +neutral mixture of potassium chloride and calcium chloride, or of sodium +chloride and potassium chloride, or of sodium chloride and calcium +chloride, or of sodium chloride and magnesium chloride. The eggs must +remain in this solution until half an hour or an hour after they have +reached the two-cell stage. They are then transferred into normal +sea-water and allowed to develop. From 50 to 90 per cent of the eggs of +Strongylocentrotus purpuratus treated in this manner may develop into +twins. These twins may remain separate or grow partially together and +form double monsters, or heal together so completely that only slight or +even no imperfections indicate that the individual started its career +as a pair of twins. It is also possible to control the tendency of such +twins to grow together by a change in the constitution of the sea-water. +If we use as a twin-producing solution a mixture of sodium, magnesium +and potassium chlorides (in the proportion in which these salts exist in +the sea-water) the tendency of the twins to grow together is much +more pronounced than if we use simply a mixture of sodium chloride and +magnesium chloride. + +The mechanism of the origin of twins, as the result of altering the +composition of the sea-water, is revealed by observation of the first +segmentation of the egg in these solutions. This cell-division is +modified in a way which leads to a separation of the first two cells. +If the egg is afterwards transferred back into normal sea-water, each +of these two cells develops into an independent embryo. Since normal +sea-water contains all three metals, sodium, calcium, and potassium, and +since it has besides an alkaline reaction, we perceive the reason why +twins are not normally produced from one egg. These experiments suggest +the possibility of a chemical cause for the origin of twins from one egg +or of double monstrosities in mammals. If, for some reason, the liquids +which surround the human egg a short time before and after the first +cell-division are slightly acid, and at the same time lacking in one +of the three important metals, the conditions for the separation of the +first two cells and the formation of identical twins are provided. + +In conclusion it may be pointed out that the reverse result, namely, +the fusion of normally double organs, can also be brought about +experimentally through a change in the chemical constitution of the +sea-water. Stockard succeeded in causing the eyes of fish embryos +(Fundulus heteroclitus) to fuse into a single cyclopean eye through the +addition of magnesium chloride to the sea-water. When he added about 6 +grams of magnesium chloride to 100 cubic centimetres of sea-water and +placed the fertilised eggs in the mixture, about 50 per cent of the +eggs gave rise to one-eyed embryos. "When the embryos were studied the +one-eyed condition was found to result from the union or fusion of the +'anlagen' of the two eyes. Cases were observed which showed various +degrees in this fusion; it appeared as though the optic vessels were +formed too far forward and ventral, so that their antero-ventro-median +surfaces fused. This produces one large optic cup, which in all cases +gives more or less evidence of its double nature." (Stockard, "Archiv f. +Entwickelungsmechanik", Vol. 23, page 249, 1907.) + +We have confined ourselves to a discussion of rather simple effects of +the change in the constitution of the sea-water upon development. It +is a priori obvious, however, that an unlimited number of pathological +variations might be produced by a variation in the concentration and +constitution of the sea-water, and experience confirms this statement. +As an example we may mention the abnormalities observed by Herbst in the +development of sea-urchins through the addition of lithium to sea-water. +It is, however, as yet impossible to connect in a rational way the +effects produced in this and similar cases with the cause which produced +them; and it is also impossible to define in a simple way the character +of the change produced. + +III. THE INFLUENCE OF TEMPERATURE. + +(a) THE INFLUENCE OF TEMPERATURE UPON THE DENSITY OF PELAGIC ORGANISMS +AND THE DURATION OF LIFE. + +It has often been noticed by explorers who have had a chance to compare +the faunas in different climates that in polar seas such species as +thrive at all in those regions occur, as a rule, in much greater density +than they do in the moderate or warmer regions of the ocean. This refers +to those members of the fauna which live at or near the surface, since +they alone lend themselves to a statistical comparison. In his account +of the Valdivia expedition, Chun (Chun, "Aus den Tiefen des Weltmeeres", +page 225, Jena, 1903.) calls especial attention to this quantitative +difference in the surface fauna and flora of different regions. "In the +icy water of the Antarctic, the temperature of which is below 0 deg C., +we find an astonishingly rich animal and plant life. The same condition +with which we are familiar in the Arctic seas is repeated here, namely, +that the quantity of plankton material exceeds that of the temperate and +warm seas." And again, in regard to the pelagic fauna in the region of +the Kerguelen Islands, he states: "The ocean is alive with transparent +jelly fish, Ctenophores (Bolina and Callianira) and of Siphonophore +colonies of the genus Agalma." + +The paradoxical character of this general observation lies in the fact +that a low temperature retards development, and hence should be +expected to have the opposite effect from that mentioned by Chun. Recent +investigations have led to the result that life-phenomena are affected +by temperature in the same sense as the velocity of chemical reactions. +In the case of the latter van't Hoff had shown that a decrease in +temperature by 10 degrees reduces their velocity to one half or less, +and the same has been found for the influence of temperature on the +velocity of physiological processes. Thus Snyder and T.B. Robertson +found that the rate of heartbeat in the tortoise and in Daphnia is +reduced to about one-half if the temperature is lowered 10 deg C., and +Maxwell, Keith Lucas, and Snyder found the same influence of temperature +for the rate with which an impulse travels in the nerve. Peter observed +that the rate of development in a sea-urchin's egg is reduced to less +than one-half if the temperature (within certain limits) is reduced by +10 degrees. The same effect of temperature upon the rate of development +holds for the egg of the frog, as Cohen and Peter calculated from +the experiments of O. Hertwig. The writer found the same +temperature-coefficient for the rate of maturation of the egg of a +mollusc (Lottia). + +All these facts prove that the velocity of development of animal life +in Arctic regions, where the temperature is near the freezing point of +water, must be from two to three times smaller than in regions where the +temperature of the ocean is about 10 deg C. and from four to nine times +smaller than in seas the temperature of which is about 20 deg C. It is, +therefore, exactly the reverse of what we should expect when authors +state that the density of organisms at or near the surface of the ocean +in polar regions is greater than in more temperate regions. + +The writer believes that this paradox finds its explanation in +experiments which he has recently made on the influence of temperature +on the duration of life of cold-blooded marine animals. The experiments +were made on the fertilised and unfertilised eggs of the sea-urchin, and +yielded the result that for the lowering of temperature by 1 deg C. +the duration of life was about doubled. Lowering the temperature by 10 +degrees therefore prolongs the life of the organism 2 to the power 10, +i.e. over a thousand times, and a lowering by 20 degrees prolongs it +about one million times. Since this prolongation of life is far +in excess of the retardation of development through a lowering of +temperature, it is obvious that, in spite of the retardation of +development in Arctic seas, animal life must be denser there than in +temperate or tropical seas. The excessive increase of the duration of +life at the poles will necessitate the simultaneous existence of more +successive generations of the same species in these regions than in the +temperate or tropical regions. + +The writer is inclined to believe that these results have some bearing +upon a problem which plays an important role in theories of evolution, +namely, the cause of natural death. It has been stated that the +processes of differentiation and development lead also to the natural +death of the individual. If we express this in chemical terms it means +that the chemical processes which underlie development also determine +natural death. Physical chemistry has taught us to identify two chemical +processes even if only certain of their features are known. One of +these means of identification is the temperature coefficient. When two +chemical processes are identical, their velocity must be reduced by +the same amount if the temperature is lowered to the same extent. +The temperature coefficient for the duration of life of cold-blooded +organisms seems, however, to differ enormously from the temperature +coefficient for their rate of development. For a difference in +temperature of 10 deg C. the duration of life is altered five hundred +times as much as the rate of development; and, for a change of 20 deg +C., it is altered more than a hundred thousand times as much. From this +we may conclude that, at least for the sea-urchin eggs and embryo, +the chemical processes which determine natural death are certainly not +identical with the processes which underlie their development. T.B. +Robertson has also arrived at the conclusion, for quite different +reasons, that the process of senile decay is essentially different from +that of growth and development. + +(b) CHANGES IN THE COLOUR OF BUTTERFLIES PRODUCED THROUGH THE INFLUENCE +OF TEMPERATURE. + +The experiments of Dorfmeister, Weismann, Merrifield, Standfuss, +and Fischer, on seasonal dimorphism and the aberration of colour in +butterflies have so often been discussed in biological literature that +a short reference to them will suffice. By seasonal dimorphism is meant +the fact that species may appear at different seasons of the year in a +somewhat different form or colour. Vanessa prorsa is the summer form, +Vanessa levana the winter form of the same species. By keeping the pupae +of Vanessa prorsa several weeks at a temperature of from 0 deg to 1 deg +Weismann succeeded in obtaining from the summer chrysalids specimens +which resembled the winter variety, Vanessa levana. + +If we wish to get a clear understanding of the causes of variation in +the colour and pattern of butterflies, we must direct our attention to +the experiments of Fischer, who worked with more extreme temperatures +than his predecessors, and found that almost identical aberrations +of colour could be produced by both extremely high and extremely low +temperatures. This can be clearly seen from the following tabulated +results of his observations. At the head of each column the reader +finds the temperature to which Fischer submitted the pupae, and in the +vertical column below are found the varieties that were produced. In the +vertical column A are given the normal forms: + +(Temperatures in deg C.) + + 0 to -20 0 to +10 A. +35 to +37 +36 to +41 +42 to +46 + (Normal forms) + + ichnusoides polaris urticae ichnusa polaris ichnusoides + (nigrita) (nigrita) + + antigone fischeri io - fischeri antigone + (iokaste) (iokaste) + + testudo dixeyi polychloros erythromelas dixeyi testudo + + hygiaea artemis antiopa epione artemis hygiaea + + elymi wiskotti cardui - wiskotti elymi + + klymene merrifieldi atalanta - merrifieldi klymene + + weismanni porima prorsa - porima weismanni + +The reader will notice that the aberrations produced at a very low +temperature (from 0 to -20 deg C.) are absolutely identical with +the aberrations produced by exposing the pupae to extremely high +temperatures (42 to 46 deg C.). Moreover the aberrations produced by a +moderately low temperature (from 0 to 10 deg C.) are identical with the +aberrations produced by a moderately high temperature (36 to 41 deg C.) + +From these observations Fischer concludes that it is erroneous to speak +of a specific effect of high and of low temperatures, but that there +must be a common cause for the aberration found at the high as well +as at the low temperature limits. This cause he seems to find in the +inhibiting effects of extreme temperatures upon development. + +If we try to analyse such results as Fischer's from a physico-chemical +point of view, we must realise that what we call life consists of a +series of chemical reactions, which are connected in a catenary way; +inasmuch as one reaction or group of reactions (a) (e.g. hydrolyses) +causes or furnishes the material for a second reaction or group +of reactions (b) (e.g. oxydations). We know that the temperature +coefficient for physiological processes varies slightly at various parts +of the scale; as a rule it is higher near 0 and lower near 30 deg. But +we know also that the temperature coefficients do not vary equally from +the various physiological processes. It is, therefore, to be expected +that the temperature coefficients for the group of reactions of the type +(a) will not be identical through the whole scale with the temperature +coefficients for the reactions of the type (b). If therefore a certain +substance is formed at the normal temperature of the animal in such +quantities as are needed for the catenary reaction (b), it is not to be +expected that this same perfect balance will be maintained for extremely +high or extremely low temperatures; it is more probable that one group +of reactions will exceed the other and thus produce aberrant chemical +effects, which may underlie the colour aberrations observed by Fischer +and other experimenters. + +It is important to notice that Fischer was also able to produce +aberrations through the application of narcotics. Wolfgang Ostwald has +produced experimentally, through variation of temperature, dimorphism of +form in Daphnia. Lack of space precludes an account of these important +experiments, as of so many others. + +IV. THE EFFECTS OF LIGHT. + +At the present day nobody seriously questions the statement that the +action of light upon organisms is primarily one of a chemical character. +While this chemical action is of the utmost importance for organisms, +the nutrition of which depends upon the action of chlorophyll, it +becomes of less importance for organisms devoid of chlorophyll. +Nevertheless, we find animals in which the formation of organs by +regeneration is not possible unless they are exposed to light. An +observation made by the writer on the regeneration of polyps in a +hydroid, Eudendrium racemosum, at Woods Hole, may be mentioned as an +instance of this. If the stem of this hydroid, which is usually covered +with polyps, is put into an aquarium the polyps soon fall off. If the +stems are kept in an aquarium where light strikes them during the day, a +regeneration of numerous polyps takes place in a few days. If, however, +the stems of Eudendrium are kept permanently in the dark, no polyps are +formed even after an interval of some weeks; but they are formed in a +few days after the same stems have been transferred from the dark to +the light. Diffused daylight suffices for this effect. Goldfarb, who +repeated these experiments, states that an exposure of comparatively +short duration is sufficient for this effect, it is possible that the +light favours the formation of substances which are a prerequisite for +the origin of polyps and their growth. + +Of much greater significance than this observation are the facts which +show that a large number of animals assume, to some extent, the +colour of the ground on which they are placed. Pouchet found through +experiments upon crustaceans and fish that this influence of the ground +on the colour of animals is produced through the medium of the eyes. +If the eyes are removed or the animals made blind in another way these +phenomena cease. The second general fact found by Pouchet was that the +variation in the colour of the animal is brought about through an action +of the nerves on the pigment-cells of the skin; the nerve-action being +induced through the agency of the eye. + +The mechanism and the conditions for the change in colouration were made +clear through the beautiful investigations of Keeble and Gamble, on +the colour-change in crustaceans. According to these authors the +pigment-cells can, as a rule, be considered as consisting of a central +body from which a system of more or less complicated ramifications or +processes spreads out in all directions. As a rule, the centre of the +cell contains one or more different pigments which under the influence +of nerves can spread out separately or together into the ramifications. +These phenomena of spreading and retraction of the pigments into or from +the ramifications of the pigment-cells form on the whole the basis for +the colour changes under the influence of environment. Thus Keeble +and Gamble observed that Macromysis flexuosa appears transparent and +colourless or grey on sandy ground. On a dark ground their colour +becomes darker. These animals have two pigments in their chromatophores, +a brown pigment and a whitish or yellow pigment; the former is much more +plentiful than the latter. When the animal appears transparent all the +pigment is contained in the centre of the cells, while the ramifications +are free from pigment. When the animal appears brown both pigments are +spread out into the ramifications. In the condition of maximal spreading +the animals appear black. + +This is a comparatively simple case. Much more complicated conditions +were found by Keeble and Gamble in other crustaceans, e.g. in Hippolyte +cranchii, but the influence of the surroundings upon the colouration of +this form was also satisfactorily analysed by these authors. + +While many animals show transitory changes in colour under the influence +of their surroundings, in a few cases permanent changes can be produced. +The best examples of this are those which were observed by Poulton +in the chrysalids of various butterflies, especially the small +tortoise-shell. These experiments are so well known that a short +reference to them will suffice. Poulton (Poulton, E.B., "Colours of +Animals" (The International Scientific Series), London, 1890, page 121.) +found that in gilt or white surroundings the pupae became light coloured +and there was often an immense development of the golden spots, "so that +in many cases the whole surface of the pupae glittered with an apparent +metallic lustre. So remarkable was the appearance that a physicist to +whom I showed the chrysalids, suggested that I had played a trick and +had covered them with goldleaf." When black surroundings were used "the +pupae were as a rule extremely dark, with only the smallest trace, and +often no trace at all, of the golden spots which are so conspicuous in +the lighter form." The susceptibility of the animal to this influence of +its surroundings was found to be greatest during a definite period when +the caterpillar undergoes the metamorphosis into the chrysalis stage. +As far as the writer is aware, no physico-chemical explanation, except +possibly Wiener's suggestion of colour-photography by mechanical colour +adaptation, has ever been offered for the results of the type of those +observed by Poulton. + + +V. EFFECTS OF GRAVITATION. + +(a) EXPERIMENTS ON THE EGG OF THE FROG. + +Gravitation can only indirectly affect life-phenomena; namely, when we +have in a cell two different non-miscible liquids (or a liquid and a +solid) of different specific gravity, so that a change in the position +of the cell or the organ may give results which can be traced to a +change in the position of the two substances. This is very nicely +illustrated by the frog's egg, which has two layers of very viscous +protoplasm one of which is black and one white. The dark one occupies +normally the upper position in the egg and may therefore be assumed to +possess a smaller specific gravity than the white substance. When +the egg is turned with the white pole upwards a tendency of the white +protoplasm to flow down again manifests itself. It is, however, possible +to prevent or retard this rotation of the highly viscous protoplasm, by +compressing the eggs between horizontal glass plates. Such compression +experiments may lead to rather interesting results, as O. Schultze first +pointed out. Pflueger had already shown that the first plane of division +in a fertilised frog's egg is vertical and Roux established the fact +that the first plane of division is identical with the plane of symmetry +of the later embryo. Schultze found that if the frog's egg is turned +upside down at the time of its first division and kept in this abnormal +position, through compression between two glass plates for about 20 +hours, a small number of eggs may give rise to twins. It is possible, +in this case, that the tendency of the black part of the egg to rotate +upwards along the surface of the egg leads to a separation of its first +cells, such a separation leading to the formation of twins. + +T.H. Morgan made an interesting additional observation. He destroyed +one half of the egg after the first segmentation and found that the +half which remained alive gave rise to only one half of an embryo, thus +confirming an older observation of Roux. When, however, Morgan put the +egg upside down after the destruction of one of the first two cells, and +compressed the eggs between two glass plates, the surviving half of the +egg gave rise to a perfect embryo of half size (and not to a half embryo +of normal size as before.) Obviously in this case the tendency of the +protoplasm to flow back to its normal position was partially successful +and led to a partial or complete separation of the living from the dead +half; whereby the former was enabled to form a whole embryo, which, of +course, possessed only half the size of an embryo originating from a +whole egg. + +(b) EXPERIMENTS ON HYDROIDS. + +A striking influence of gravitation can be observed in a hydroid, +Antennularia antennina, from the bay of Naples. This hydroid consists of +a long straight main stem which grows vertically upwards and which has +at regular intervals very fine and short bristle-like lateral branches, +on the upper side of which the polyps grow. The main stem is negatively +geotropic, i.e. its apex continues to grow vertically upwards when we +put it obliquely into the aquarium, while the roots grow vertically +downwards. The writer observed that when the stem is put horizontally +into the water the short lateral branches on the lower side give rise to +an altogether different kind of organ, namely, to roots, and these roots +grow indefinitely in length and attach themselves to solid bodies; while +if the stem had remained in its normal position no further growth +would have occurred in the lateral branches. From the upper side of the +horizontal stem new stems grow out, mostly directly from the original +stem, occasionally also from the short lateral branches. It is thus +possible to force upon this hydroid an arrangement of organs which is +altogether different from the hereditary arrangement. The writer +had called the change in the hereditary arrangement of organs or the +transformation of organs by external forces HETEROMORPHOSIS. We cannot +now go any further into this subject, which should, however, prove of +interest in relation to the problem of heredity. + +If it is correct to apply inferences drawn from the observation on the +frog's egg to the behaviour of Antennularia, one might conclude that the +cells of Antennularia also contain non-miscible substances of different +specific gravity, and that wherever the specifically lighter substance +comes in contact with the sea-water (or gets near the surface of the +cell) the growth of a stem is favoured; while contact with the sea-water +of the specifically heavier of the substances, will favour the formation +of roots. + +VI. THE EXPERIMENTAL CONTROL OF ANIMAL INSTINCTS. + +(a) EXPERIMENTS ON THE MECHANISM OF HELIOTROPIC REACTIONS IN ANIMALS. + +Since the instinctive reactions of animals are as hereditary as +their morphological character, a discussion of experiments on the +physico-chemical character of the instinctive reactions of animals +should not be entirely omitted from this sketch. It is obvious that such +experiments must begin with the simplest type of instincts, if they are +expected to lead to any results; and it is also obvious that only such +animals must be selected for this purpose, the reactions of which are +not complicated by associative memory, or, as it may preferably be +termed, associative hysteresis. + +The simplest type of instincts is represented by the purposeful motions +of animals to or from a source of energy, e.g. light; and it is with +some of these that we intend to deal here. When we expose winged aphides +(after they have flown away from the plant), or young caterpillars of +Porthesia chrysorrhoea (when they are aroused from their winter sleep) +or marine or freshwater copepods and many other animals, to diffused +daylight falling in from a window, we notice a tendency among these +animals to move towards the source of light. If the animals are +naturally sensitive, or if they are rendered sensitive through the +agencies which we shall mention later, and if the light is strong +enough, they move towards the source of light in as straight a line as +the imperfections and peculiarities of their locomotor apparatus will +permit. It is also obvious that we are here dealing with a forced +reaction in which the animals have no more choice in the direction +of their motion than have the iron filings in their arrangement in a +magnetic field. This can be proved very nicely in the case of starving +caterpillars of Porthesia. The writer put such caterpillars into a glass +tube the axis of which was at right angles to the plane of the window: +the caterpillars went to the window side of the tube and remained there, +even if leaves of their food-plant were put into the tube directly +behind them. Under such conditions the animals actually died from +starvation, the light preventing them from turning to the food, which +they eagerly ate when the light allowed them to do so. One cannot say +that these animals, which we call positively helioptropic, are attracted +by the light, since it can be shown that they go towards the source +of the light even if in so doing they move from places of a higher to +places of a lower degree of illumination. + +The writer has advanced the following theory of these instinctive +reactions. Animals of the type of those mentioned are automatically +orientated by the light in such a way that symmetrical elements of their +retina (or skin) are struck by the rays of light at the same angle. +In this case the intensity of light is the same for both retinae or +symmetrical parts of the skin. + +This automatic orientation is determined by two factors, first a +peculiar photo-sensitiveness of the retina (or skin), and second +a peculiar nervous connection between the retina and the muscular +apparatus. In symmetrically built heliotropic animals in which the +symmetrical muscles participate equally in locomotion, the symmetrical +muscles work with equal energy as long as the photo-chemical processes +in both eyes are identical. If, however, one eye is struck by stronger +light than the other, the symmetrical muscles will work unequally and +in positively heliotropic animals those muscles will work with greater +energy which bring the plane of symmetry back into the direction of the +rays of light and the head towards the source of light. As soon as both +eyes are struck by the rays of light at the same angle, there is no more +reason for the animal to deviate from this direction and it will move in +a straight line. All this holds good on the supposition that the animals +are exposed to only one source of light and are very sensitive to light. + +Additional proof for the correctness of this theory was furnished +through the experiments of G.H. Parker and S.J. Holmes. The former +worked on a butterfly, Vanessa antiope, the latter on other arthropods. +All the animals were in a marked degree positively heliotropic. These +authors found that if one cornea is blackened in such an animal, it +moves continually in a circle when it is exposed to a source of light, +and in these motions the eye which is not covered with paint is directed +towards the centre of the circle. The animal behaves, therefore, as if +the darkened eye were in the shade. + +(b) THE PRODUCTION OF POSITIVE HELIOTROPISM BY ACIDS AND OTHER MEANS AND +THE PERIODIC DEPTH-MIGRATIONS OF PELAGIC ANIMALS. + +When we observe a dense mass of copepods collected from a freshwater +pond, we notice that some have a tendency to go to the light while +others go in the opposite direction and many, if not the majority, +are indifferent to light. It is an easy matter to make the negatively +heliotropic or the indifferent copepods almost instantly positively +heliotropic by adding a small but definite amount of carbon-dioxide +in the form of carbonated water to the water in which the animals are +contained. If the animals are contained in 50 cubic centimetres of water +it suffices to add from three to six cubic centimetres of carbonated +water to make all the copepods energetically positively heliotropic. +This heliotropism lasts about half an hour (probably until all the +carbon-dioxide has again diffused into the air.) Similar results may be +obtained with any other acid. + +The same experiments may be made with another freshwater crustacean, +namely Daphnia, with this difference, however, that it is as a rule +necessary to lower the temperature of the water also. If the water +containing the Daphniae is cooled and at the same time carbon-dioxide +added, the animals which were before indifferent to light now become +most strikingly positively heliotropic. Marine copepods can be made +positively heliotropic by the lowering of the temperature alone, or by a +sudden increase in the concentration of the sea-water. + +These data have a bearing upon the depth-migrations of pelagic animals, +as was pointed out years ago by Theo. T. Groom and the writer. It is +well known that many animals living near the surface of the ocean or +freshwater lakes, have a tendency to migrate upwards towards evening and +downwards in the morning and during the day. These periodic motions are +determined to a large extent, if not exclusively, by the heliotropism +of these animals. Since the consumption of carbon-dioxide by the green +plants ceases towards evening, the tension of this gas in the water must +rise and this must have the effect of inducing positive heliotropism or +increasing its intensity. At the same time the temperature of the +water near the surface is lowered and this also increases the positive +heliotropism in the organisms. + +The faint light from the sky is sufficient to cause animals which are in +a high degree positively heliotropic to move vertically upwards towards +the light, as experiments with such pelagic animals, e.g. copepods, have +shown. When, in the morning, the absorption of carbon-dioxide by the +green algae begins again and the temperature of the water rises, the +animals lose their positive heliotropism, and slowly sink down or become +negatively heliotropic and migrate actively downwards. + +These experiments have also a bearing upon the problem of the +inheritance of instincts. The character which is transmitted in this +case is not the tendency to migrate periodically upwards and downwards, +but the positive heliotropism. The tendency to migrate is the outcome of +the fact that periodically varying external conditions induce a periodic +change in the sense and intensity of the heliotropism of these animals. +It is of course immaterial for the result, whether the carbon-dioxide or +any other acid diffuse into the animal from the outside or whether they +are produced inside in the tissue cells of the animals. Davenport and +Cannon found that Daphniae, which at the beginning of the experiment, +react sluggishly to light react much more quickly after they have been +made to go to the light a few times. The writer is inclined to attribute +this result to the effect of acids, e.g. carbon-dioxide, produced in the +animals themselves in consequence of their motion. A similar effect of +the acids was shown by A.D. Waller in the case of the response of nerve +to stimuli. + +The writer observed many years ago that winged male and female ants +are positively helioptropic and that their heliotropic sensitiveness +increases and reaches its maximum towards the period of nuptial flight. +Since the workers show no heliotropism it looks as if an internal +secretion from the sexual glands were the cause of their heliotropic +sensitiveness. V. Kellogg has observed that bees also become intensely +positively heliotropic at the period of their wedding flight, in fact so +much so that by letting light fall into the observation hive from above, +the bees are prevented from leaving the hive through the exit at the +lower end. + +We notice also the reverse phenomenon, namely, that chemical changes +produced in the animal destroy its heliotropism. The caterpillars of +Porthesia chrysorrhoea are very strongly positively heliotropic when +they are first aroused from their winter sleep. This heliotropic +sensitiveness lasts only as long as they are not fed. If they are kept +permanently without food they remain permanently positively heliotropic +until they die from starvation. It is to be inferred that as soon as +these animals take up food, a substance or substances are formed +in their bodies which diminish or annihilate their heliotropic +sensitiveness. + +The heliotropism of animals is identical with the heliotropism of +plants. The writer has shown that the experiments on the effect of acids +on the heliotropism of copepods can be repeated with the same result in +Volvox. It is therefore erroneous to try to explain these heliotropic +reactions of animals on the basis of peculiarities (e.g. vision) which +are not found in plants. + +We may briefly discuss the question of the transmission through the sex +cells of such instincts as are based upon heliotropism. This problem +reduces itself simply to that of the method whereby the gametes transmit +heliotropism to the larvae or to the adult. The writer has expressed the +idea that all that is necessary for this transmission is the presence in +the eyes (or in the skin) of the animal of a photo-sensitive substance. +For the transmission of this the gametes need not contain anything more +than a catalyser or ferment for the synthesis of the photo-sensitive +substance in the body of the animal. What has been said in regard to +animal heliotropism might, if space permitted, be extended, mutatis +mutandis, to geotropism and stereotropism. + +(c) THE TROPIC REACTIONS OF CERTAIN TISSUE-CELLS AND THE MORPHOGENETIC +EFFECTS OF THESE REACTIONS. + +Since plant-cells show heliotropic reactions identical with those +of animals, it is not surprising that certain tissue-cells also show +reactions which belong to the class of tropisms. These reactions of +tissue-cells are of special interest by reason of their bearing upon the +inheritance of morphological characters. An example of this is found in +the tiger-like marking of the yolk-sac of the embryo of Fundulus and in +the marking of the young fish itself. The writer found that the former +is entirely, and the latter at least in part, due to the creeping of the +chromatophores upon the blood-vessels. The chromatophores are at first +scattered irregularly over the yolk-sac and show their characteristic +ramifications. There is at that time no definite relation between +blood-vessels and chromatophores. As soon as a ramification of a +chromatophore comes in contact with a blood-vessel the whole mass of the +chromatophore creeps gradually on the blood-vessel and forms a complete +sheath around the vessel, until finally all the chromatophores form a +sheath around the vessels and no more pigment cells are found in the +meshes between the vessels. Nobody who has not actually watched the +process of the creeping of the chromatophores upon the blood-vessels +would anticipate that the tiger-like colouration of the yolk-sac in the +later stages of the development was brought about in this way. Similar +facts can be observed in regard to the first marking of the embryo +itself. The writer is inclined to believe that we are here dealing with +a case of chemotropism, and that the oxygen of the blood may be the +cause of the spreading of the chromatophores around the blood-vessels. +Certain observations seem to indicate the possibility that in the adult +the chromatophores have, in some forms at least, a more rigid structure +and are prevented from acting in the way indicated. It seems to the +writer that such observations as those made on Fundulus might simplify +the problem of the hereditary transmission of certain markings. + +Driesch has found that a tropism underlies the arrangement of the +skeleton in the pluteus larvae of the sea-urchin. The position of this +skeleton is predetermined by the arrangement of the mesenchyme cells, +and Driesch has shown that these cells migrate actively to the place +of their destination, possibly led there under the influence of certain +chemical substances. When Driesch scattered these cells mechanically +before their migration, they nevertheless reached their destination. + +In the developing eggs of insects the nuclei, together with some +cytoplasm, migrate to the periphery of the egg. Herbst pointed out that +this might be a case of chemotropism, caused by the oxygen surrounding +the egg. The writer has expressed the opinion that the formation of +the blastula may be caused generally by a tropic reaction of the +blastomeres, the latter being forced by an outside influence to creep to +the surface of the egg. + +These examples may suffice to indicate that the arrangement of definite +groups of cells and the morphological effects resulting therefrom may +be determined by forces lying outside the cells. Since these forces are +ubiquitous and constant it appears as if we were dealing exclusively +with the influence of a gamete; while in reality all that it is +necessary for the gamete to transmit is a certain form of irritability. + +(d) FACTORS WHICH DETERMINE PLACE AND TIME FOR THE DEPOSITION OF EGGS. + +For the preservation of species the instinct of animals to lay their +eggs in places in which the young larvae find their food and can develop +is of paramount importance. A simple example of this instinct is the +fact that the common fly lays its eggs on putrid material which serves +as food for the young larvae. When a piece of meat and of fat of the +same animal are placed side by side, the fly will deposit its eggs upon +the meat on which the larvae can grow, and not upon the fat, on which +they would starve. Here we are dealing with the effect of a volatile +nitrogenous substance which reflexly causes the peristaltic motions for +the laying of the egg in the female fly. + +Kammerer has investigated the conditions for the laying of eggs in two +forms of salamanders, e.g. Salamandra atra and S. maculosa. In both +forms the eggs are fertilised in the body and begin to develop in the +uterus. Since there is room only for a few larvae in the uterus, a large +number of eggs perish and this number is the greater the longer the +period of gestation. It thus happens that when the animals retain their +eggs a long time, very few young ones are born; and these are in a +rather advanced stage of development, owing to the long time which +elapsed since they were fertilised. When the animal lays its eggs +comparatively soon after copulation, many eggs (from 12 to 72) are +produced and the larvae are of course in an early stage of development. +In the early stage the larvae possess gills and can therefore live in +water, while in later stages they have no gills and breathe through +their lungs. Kammerer showed that both forms of Salamandra can be +induced to lay their eggs early or late, according to the physical +conditions surrounding them. If they are kept in water or in proximity +to water and in a moist atmosphere they have a tendency to lay their +eggs earlier and a comparatively high temperature enhances the tendency +to shorten the period of gestation. If the salamanders are kept in +comparative dryness they show a tendency to lay their eggs rather late +and a low temperature enhances this tendency. + +Since Salamandra atra is found in rather dry alpine regions with a +relatively low temperature and Salamandra maculosa in lower regions with +plenty of water and a higher temperature, the fact that S. atra bears +young which are already developed and beyond the stage of aquatic life, +while S. maculosa bears young ones in an earlier stage, has been termed +adaptation. Kammerer's experiments, however, show that we are dealing +with the direct effects of definite outside forces. While we may speak +of adaptation when all or some of the variables which determine a +reaction are unknown, it is obviously in the interest of further +scientific progress to connect cause and effect directly whenever our +knowledge allows us to do so. + +VII. CONCLUDING REMARKS. + +The discovery of De Vries, that new species may arise by mutation and +the wide if not universal applicability of Mendel's Law to phenomena of +heredity, as shown especially by Bateson and his pupils, must, for +the time being, if not permanently, serve as a basis for theories of +evolution. These discoveries place before the experimental biologist the +definite task of producing mutations by physico-chemical means. It +is true that certain authors claim to have succeeded in this, but +the writer wishes to apologise to these authors for his inability to +convince himself of the validity of their claims at the present moment. +He thinks that only continued breeding of these apparent mutants through +several generations can afford convincing evidence that we are here +dealing with mutants rather than with merely pathological variations. + +What was said in regard to the production of new species by +physico-chemical means may be repeated with still more justification +in regard to the second problem of transformation, namely the making +of living from inanimate matter. The purely morphological imitations +of bacteria or cells which physicists have now and then proclaimed as +artificially produced living beings; or the plays on words by which, +e.g. the regeneration of broken crystals and the regeneration of lost +limbs by a crustacean were declared identical, will not appeal to the +biologist. We know that growth and development in animals and plants are +determined by definite although complicated series of catenary chemical +reactions, which result in the synthesis of a DEFINITE compound or group +of compounds, namely, NUCLEINS. + +The nucleins have the peculiarity of acting as ferments or enzymes +for their own synthesis. Thus a given type of nucleus will continue to +synthesise other nuclein of its own kind. This determines the continuity +of a species; since each species has, probably, its own specific nuclein +or nuclear material. But it also shows us that whoever claims to have +succeeded in making living matter from inanimate will have to prove that +he has succeeded in producing nuclein material which acts as a ferment +for its own synthesis and thus reproduces itself. Nobody has thus far +succeeded in this, although nothing warrants us in taking it for granted +that this task is beyond the power of science. + + + + +XV. THE VALUE OF COLOUR IN THE STRUGGLE FOR LIFE. By E.B. Poulton. + +Hope Professor of Zoology in the University of Oxford. + + +INTRODUCTION. + +The following pages have been written almost entirely from the +historical stand-point. Their principal object has been to give some +account of the impressions produced on the mind of Darwin and his great +compeer Wallace by various difficult problems suggested by the colours +of living nature. In order to render the brief summary of Darwin's +thoughts and opinions on the subject in any way complete, it was found +necessary to say again much that has often been said before. No attempt +has been made to display as a whole the vast contribution of Wallace; +but certain of its features are incidentally revealed in passages quoted +from Darwin's letters. It is assumed that the reader is familiar with +the well-known theories of Protective Resemblance, Warning Colours, and +Mimicry both Batesian and Mullerian. It would have been superfluous to +explain these on the present occasion; for a far more detailed account +than could have been attempted in these pages has recently appeared. +(Poulton, "Essays on Evolution" Oxford, 1908, pages 293-382.) Among the +older records I have made a point of bringing together the principal +observations scattered through the note-books and collections of W.J. +Burchell. These have never hitherto found a place in any memoir dealing +with the significance of the colours of animals. + +INCIDENTAL COLOURS. + +Darwin fully recognised that the colours of living beings are not +necessarily of value as colours, but that they may be an incidental +result of chemical or physical structure. Thus he wrote to T. Meehan, +Oct. 9, 1874: "I am glad that you are attending to the colours of +dioecious flowers; but it is well to remember that their colours may be +as unimportant to them as those of a gall, or, indeed, as the colour +of an amethyst or ruby is to these gems." ("More Letters of Charles +Darwin", Vol. I. pages 354, 355. See also the admirable account of +incidental colours in "Descent of Man" (2nd edition), 1874, pages 261, +262.) + +Incidental colours remain as available assets of the organism ready to +be turned to account by natural selection. It is a probable speculation +that all pigmentary colours were originally incidental; but now and for +immense periods of time the visible tints of animals have been modified +and arranged so as to assist in the struggle with other organisms or in +courtship. The dominant colouring of plants, on the other hand, is +an essential element in the paramount physiological activity of +chlorophyll. In exceptional instances, however, the shapes and visible +colours of plants may be modified in order to promote concealment. + +TELEOLOGY AND ADAPTATION. + +In the department of Biology which forms the subject of this essay, +the adaptation of means to an end is probably more evident than in +any other; and it is therefore of interest to compare, in a brief +introductory section, the older with the newer teleological views. + +The distinctive feature of Natural Selection as contrasted with other +attempts to explain the process of Evolution is the part played by the +struggle for existence. All naturalists in all ages must have known +something of the operations of "Nature red in tooth and claw"; but it +was left for this great theory to suggest that vast extermination is +a necessary condition of progress, and even of maintaining the ground +already gained. + +Realising that fitness is the outcome of this fierce struggle, thus +turned to account for the first time, we are sometimes led to associate +the recognition of adaptation itself too exclusively with Natural +Selection. Adaptation had been studied with the warmest enthusiasm +nearly forty years before this great theory was given to the scientific +world, and it is difficult now to realise the impetus which the works +of Paley gave to the study of Natural History. That they did inspire the +naturalists of the early part of the last century is clearly shown in +the following passages. + +In the year 1824 the Ashmolean Museum at Oxford was intrusted to the +care of J.S. Duncan of New College. He was succeeded in this office by +his brother, P.B. Duncan, of the same College, author of a History of +the Museum, which shows very clearly the influence of Paley upon the +study of nature, and the dominant position given to his teachings: +"Happily at this time (1824) a taste for the study of natural history +had been excited in the University by Dr Paley's very interesting +work on Natural Theology, and the very popular lectures of Dr Kidd on +Comparative Anatomy, and Dr Buckland on Geology." In the arrangement of +the contents of the Museum the illustration of Paley's work was given +the foremost place by J.S. Duncan: "The first division proposes to +familiarize the eye to those relations of all natural objects which form +the basis of argument in Dr Paley's Natural Theology; to induce a mental +habit of associating the view of natural phenomena with the conviction +that they are the media of Divine manifestation; and by such association +to give proper dignity to every branch of natural science." (From +"History and Arrangement of the Ashmolean Museum" by P.B. Duncan: see +pages vi, vii of "A Catalogue of the Ashmolean Museum", Oxford, 1836.) + +The great naturalist, W.J. Burchell, in his classical work shows the +same recognition of adaptation in nature at a still earlier date. +Upon the subject of collections he wrote ("Travels in the Interior of +Southern Africa", London, Vol. I. 1822, page 505. The references to +Burchell's observations in the present essay are adapted from +the author's article in "Report of the British and South African +Associations", 1905, Vol. III. pages 57-110.): "It must not be supposed +that these charms (the pleasures of Nature) are produced by the mere +discovery of new objects: it is the harmony with which they have been +adapted by the Creator to each other, and to the situations in which +they are found, which delights the observer in countries where Art has +not yet introduced her discords." The remainder of the passage is so +admirable that I venture to quote it: "To him who is satisfied with +amassing collections of curious objects, simply for the pleasure of +possessing them, such objects can afford, at best, but a childish +gratification, faint and fleeting; while he who extends his view beyond +the narrow field of nomenclature, beholds a boundless expanse, the +exploring of which is worthy of the philosopher, and of the best talents +of a reasonable being." + +On September 14, 1811, Burchell was at Zand Valley (Vlei), or Sand Pool, +a few miles south-west of the site of Prieska, on the Orange River. Here +he found a Mesembryanthemum (M. turbiniforme, now M. truncatum) and also +a "Gryllus" (Acridian), closely resembling the pebbles with which their +locality was strewn. He says of both of these, "The intention of Nature, +in these instances, seems to have been the same as when she gave to the +Chameleon the power of accommodating its color, in a certain degree, +to that of the object nearest to it, in order to compensate for the +deficiency of its locomotive powers. By their form and colour, this +insect may pass unobserved by those birds, which otherwise would soon +extirpate a species so little able to elude its pursuers, and this juicy +little Mesembryanthemum may generally escape the notice of cattle and +wild animals." (Loc. cit. pages 310, 311. See Sir William Thiselton-Dyer +"Morphological Notes", XI.; "Protective Adaptations", I.; "Annals of +Botany", Vol. XX. page 124. In plates VII., VIII. and IX. accompanying +this article the author represents the species observed by Burchell, +together with others in which analogous adaptations exist. He writes: +"Burchell was clearly on the track on which Darwin reached the goal. +But the time had not come for emancipation from the old teleology. This, +however, in no respect detracts from the merit or value of his work. +For, as Huxley has pointed out ("Life and Letters of Thomas Henry +Huxley", London, 1900, I. page 457), the facts of the old teleology are +immediately transferable to Darwinism, which simply supplies them with a +natural in place of a supernatural explanation.") Burchell here seems +to miss, at least in part, the meaning of the relationship between the +quiescence of the Acridian and its cryptic colouring. Quiescence is an +essential element in the protective resemblance to a stone--probably +even more indispensable than the details of the form and colouring. +Although Burchell appears to overlook this point he fully recognised the +community between protection by concealment and more aggressive modes +of defence; for, in the passage of which a part is quoted above, he +specially refers to some earlier remarks on page 226 of his Vol. I. We +here find that even when the oxen were resting by the Juk rivier (Yoke +river), on July 19, 1811, Burchell observed "Geranium spinosum, with +a fleshy stem and large white flowers...; and a succulent species of +Pelargonium... so defended by the old panicles, grown to hard woody +thorns, that no cattle could browze upon it." He goes on to say, "In +this arid country, where every juicy vegetable would soon be eaten up by +the wild animals, the Great Creating Power, with all-provident wisdom, +has given to such plants either an acrid or poisonous juice, or sharp +thorns, to preserve the species from annihilation... " All these modes +of defence, especially adapted to a desert environment, have since +been generally recognised, and it is very interesting to place beside +Burchell's statement the following passage from a letter written by +Darwin, Aug. 7, 1868, to G.H. Lewes; "That Natural Selection would tend +to produce the most formidable thorns will be admitted by every one +who has observed the distribution in South America and Africa (vide +Livingstone) of thorn-bearing plants, for they always appear where the +bushes grow isolated and are exposed to the attacks of mammals. Even +in England it has been noticed that all spine-bearing and sting-bearing +plants are palatable to quadrupeds, when the thorns are crushed." ("More +Letters", I. page 308.) + +ADAPTATION AND NATURAL SELECTION. + +I have preferred to show the influence of the older teleology upon +Natural History by quotations from a single great and insufficiently +appreciated naturalist. It might have been seen equally well in the +pages of Kirby and Spence and those of many other writers. If the older +naturalists who thought and spoke with Burchell of "the intention +of Nature" and the adaptation of beings "to each other, and to +the situations in which they are found," could have conceived the +possibility of evolution, they must have been led, as Darwin was, by the +same considerations to Natural Selection. This was impossible for them, +because the philosophy which they followed contemplated the phenomena of +adaptation as part of a static immutable system. Darwin, convinced that +the system is dynamic and mutable, was prevented by these very phenomena +from accepting anything short of the crowning interpretation offered by +Natural Selection. ("I had always been much struck by such adaptations +(e.g. woodpecker and tree-frog for climbing, seeds for dispersal), +and until these could be explained it seemed to me almost useless +to endeavour to prove by indirect evidence that species have been +modified." "Autobiography" in "Life and Letters of Charles Darwin", Vol. +I. page 82. The same thought is repeated again and again in Darwin's +letters to his friends. It is forcibly urged in the Introduction to +the "Origin" (1859), page 3.) And the birth of Darwin's unalterable +conviction that adaptation is of dominant importance in the organic +world,--a conviction confirmed and ever again confirmed by his +experience as a naturalist--may probably be traced to the influence of +the great theologian. Thus Darwin, speaking of his Undergraduate days, +tells us in his "Autobiography" that the logic of Paley's "Evidences +of Christianity" and "Moral Philosophy" gave him as much delight as did +Euclid. + +"The careful study of these works, without attempting to learn any part +by rote, was the only part of the academical course which, as I then +felt and as I still believe, was of the least use to me in the education +of my mind. I did not at that time trouble myself about Paley's +premises; and taking these on trust, I was charmed and convinced by the +long line of argumentation." ("Life and Letters", I. page 47.) + +When Darwin came to write the "Origin" he quoted in relation to Natural +Selection one of Paley's conclusions. "No organ will be formed, as Paley +has remarked, for the purpose of causing pain or for doing an injury to +its possessor." ("Origin of Species" (1st edition) 1859, page 201.) + +The study of adaptation always had for Darwin, as it has for many, +a peculiar charm. His words, written Nov. 28, 1880, to Sir W. +Thiselton-Dyer, are by no means inapplicable to-day: "Many of the +Germans are very contemptuous about making out use of organs; but they +may sneer the souls out of their bodies, and I for one shall think it +the most interesting part of natural history." ("More Letters" II. page +428.) + +PROTECTIVE AND AGGRESSIVE RESEMBLANCE: PROCRYPTIC AND ANTICRYPTIC +COLOURING. + +Colouring for the purpose of concealment is sometimes included under the +head Mimicry, a classification adopted by H.W. Bates in his classical +paper. Such an arrangement is inconvenient, and I have followed Wallace +in keeping the two categories distinct. + +The visible colours of animals are far more commonly adapted for +Protective Resemblance than for any other purpose. The concealment of +animals by their colours, shapes and attitudes, must have been well +known from the period at which human beings first began to take an +intelligent interest in Nature. An interesting early record is that of +Samuel Felton, who (Dec. 2, 1763) figured and gave some account of an +Acridian (Phyllotettix) from Jamaica. Of this insect he says "THE THORAX +is like a leaf that is raised perpendicularly from the body." ("Phil. +Trans. Roy. Soc." Vol. LIV. Tab. VI. page 55.) + +Both Protective and Aggressive Resemblances were appreciated and clearly +explained by Erasmus Darwin in 1794: "The colours of many animals seem +adapted to their purposes of concealing themselves either to avoid +danger, or to spring upon their prey." ("Zoonomia", Vol. I. page 509, +London, 1794.) + +Protective Resemblance of a very marked and beautiful kind is found +in certain plants, inhabitants of desert areas. Examples observed by +Burchell almost exactly a hundred years ago have already been mentioned. +In addition to the resemblance to stones Burchell observed, although +he did not publish the fact, a South African plant concealed by its +likeness to the dung of birds. (Sir William Thiselton-Dyer has suggested +the same method of concealment ("Annals of Botany", Vol. XX. page 123). +Referring to Anacampseros papyracea, figured on plate IX., the author +says of its adaptive resemblance: "At the risk of suggesting one perhaps +somewhat far-fetched, I must confess that the aspect of the plant always +calls to my mind the dejecta of some bird, and the more so owing to the +whitening of the branches towards the tips" (loc. cit. page 126). The +student of insects, who is so familiar with this very form of protective +resemblance in larvae, and even perfect insects, will not be inclined to +consider the suggestion far-fetched.) The observation is recorded in +one of the manuscript journals kept by the great explorer during his +journey. I owe the opportunity of studying it to the kindness of Mr +Francis A. Burchell of the Rhodes University College, Grahamstown. The +following account is given under the date July 5, 1812, when Burchell +was at the Makkwarin River, about half-way between the Kuruman River and +Litakun the old capital of the Bachapins (Bechuanas): "I found a curious +little Crassula (not in flower) so snow white, that I should never has +(have) distinguished it from the white limestones... It was an inch high +and a little branchy,... and was at first mistaken for the dung of birds +of the passerine order. I have often had occasion to remark that in +stony place(s) there grow many small succulent plants and abound insects +(chiefly Grylli) which have exactly the same colour as the ground and +must for ever escape observation unless a person sit on the ground and +observe very attentively." + +The cryptic resemblances of animals impressed Darwin and Wallace in +very different degrees, probably in part due to the fact that Wallace's +tropical experiences were so largely derived from the insect world, in +part to the importance assigned by Darwin to Sexual Selection "a +subject which had always greatly interested me," as he says in his +"Autobiography", ("Life and Letters", Vol. I. page 94.) There is no +reference to Cryptic Resemblance in Darwin's section of the Joint Essay, +although he gives an excellent short account of Sexual Selection (see +page 295). Wallace's section on the other hand contains the following +statement: "Even the peculiar colours of many animals, especially +insects, so closely resembling the soil or the leaves or the trunks on +which they habitually reside, are explained on the same principle; for +though in the course of ages varieties of many tints may have occurred, +YET THOSE RACES HAVING COLOURS BEST ADAPTED TO CONCEALMENT FROM THEIR +ENEMIES WOULD INEVITABLY SURVIVE THE LONGEST." ("Journ. Proc. Linn. +Soc." Vol. III. 1859, page 61. The italics are Wallace's.) + +It would occupy too much space to attempt any discussion of the +difference between the views of these two naturalists, but it is clear +that Darwin, although fully believing in the efficiency of protective +resemblance and replying to St George Mivart's contention that Natural +Selection was incompetent to produce it ("Origin" (6th edition) London, +1872, pages 181, 182; see also page 66.), never entirely agreed with +Wallace's estimate of its importance. Thus the following extract from a +letter to Sir Joseph Hooker, May 21, 1868, refers to Wallace: "I find +I must (and I always distrust myself when I differ from him) separate +rather widely from him all about birds' nests and protection; he is +riding that hobby to death." ("More Letters", I. page 304.) It is clear +from the account given in "The Descent of Man", (London, 1874, pages +452-458. See also "Life and Letters", III. pages 123-125, and "More +Letters", II. pages 59-63, 72-74, 76-78, 84-90, 92, 93.), that the +divergence was due to the fact that Darwin ascribed more importance +to Sexual Selection than did Wallace, and Wallace more importance to +Protective Resemblance than Darwin. Thus Darwin wrote to Wallace, +Oct. 12 and 13, 1867: "By the way, I cannot but think that you push +protection too far in some cases, as with the stripes on the tiger." +("More Letters", I. page 283.) Here too Darwin was preferring the +explanation offered by Sexual Selection ("Descent of Man" (2nd edition) +1874, pages 545, 546.), a preference which, considering the relation of +the colouring of the lion and tiger to their respective environments, +few naturalists will be found to share. It is also shown that Darwin +contemplated the possibility of cryptic colours such as those of +Patagonian animals being due to sexual selection influenced by the +aspect of surrounding nature. + +Nearly a year later Darwin in his letter of May 5, 1868?, expressed +his agreement with Wallace's views: "Expect that I should put sexual +selection as an equal, or perhaps as even a more important agent in +giving colour than Natural Selection for protection." ("More Letters", +II. pages 77, 78.) The conclusion expressed in the above quoted passage +is opposed by the extraordinary development of Protective Resemblance in +the immature stages of animals, especially insects. + +It must not be supposed, however, that Darwin ascribed an unimportant +role to Cryptic Resemblances, and as observations accumulated he came to +recognise their efficiency in fresh groups of the animal kingdom. Thus +he wrote to Wallace, May 5, 1867: "Haeckel has recently well shown that +the transparency and absence of colour in the lower oceanic animals, +belonging to the most different classes, may be well accounted for on +the principle of protection." ("More Letters", II. page 62. See also +"Descent of Man", page 261.) Darwin also admitted the justice of +Professor E.S. Morse's contention that the shells of molluscs are often +adaptively coloured. ("More Letters", II. page 95.) But he looked +upon cryptic colouring and also mimicry as more especially Wallace's +departments, and sent to him and to Professor Meldola observations and +notes bearing upon these subjects. Thus the following letter given to me +by Dr A.R. Wallace and now, by kind permission, published for the first +time, accompanied a photograph of the chrysalis of Papilio sarpedon +choredon, Feld., suspended from a leaf of its food-plant: + +July 9th, Down, Beckenham, Kent. + +My Dear Wallace, + +Dr G. Krefft has sent me the enclosed from Sydney. A nurseryman saw a +caterpillar feeding on a plant and covered the whole up, but when he +searched for the cocoon (pupa), was long before he could find it, so +good was its imitation in colour and form to the leaf to which it was +attached. I hope that the world goes well with you. Do not trouble +yourself by acknowledging this. + +Ever yours + +Ch. Darwin. + +Another deeply interesting letter of Darwin's bearing upon protective +resemblance, has only recently been shown to me by my friend Professor +E.B. Wilson, the great American Cytologist. With his kind consent and +that of Mr Francis Darwin, this letter, written four months before +Darwin's death on April 19, 1882, is reproduced here (The letter is +addressed: "Edmund B. Wilson, Esq., Assistant in Biology, John Hopkins +University, Baltimore Md, U. States."): + +December 21, 1881. + +Dear Sir, + +I thank you much for having taken so much trouble in describing fully +your interesting and curious case of mimickry. + +I am in the habit of looking through many scientific Journals, and +though my memory is now not nearly so good as it was, I feel pretty sure +that no such case as yours has been described (amongst the nudibranch) +molluscs. You perhaps know the case of a fish allied to Hippocampus, +(described some years ago by Dr Gunther in "Proc. Zoolog. Socy.") which +clings by its tail to sea-weeds, and is covered with waving filaments +so as itself to look like a piece of the same sea-weed. The parallelism +between your and Dr Gunther's case makes both of them the more +interesting; considering how far a fish and a mollusc stand apart. It +would be difficult for anyone to explain such cases by the direct +action of the environment.--I am glad that you intend to make further +observations on this mollusc, and I hope that you will give a figure and +if possible a coloured figure. + +With all good wishes from an old brother naturalist, + +I remain, Dear Sir, + +Yours faithfully, + +Charles Darwin. + +Professor E.B. Wilson has kindly given the following account of the +circumstances under which he had written to Darwin: "The case to which +Darwin's letter refers is that of the nudibranch mollusc Scyllaea, +which lives on the floating Sargassum and shows a really astonishing +resemblance to the plant, having leaf-shaped processes very closely +similar to the fronds of the sea-weed both in shape and in colour. The +concealment of the animal may be judged from the fact that we found +the animal quite by accident on a piece of Sargassum that had been in a +glass jar in the laboratory for some time and had been closely examined +in the search for hydroids and the like without disclosing the presence +upon it of two large specimens of the Scyllaea (the animal, as I recall +it, is about two inches long). It was first detected by its movements +alone, by someone (I think a casual visitor to the laboratory) who was +looking closely at the Sargassum and exclaimed 'Why, the sea-weed is +moving its leaves'! We found the example in the summer of 1880 or 1881 +at Beaufort, N.C., where the Johns Hopkins laboratory was located for +the time being. It must have been seen by many others, before or since. + +"I wrote and sent to Darwin a short description of the case at the +suggestion of Brooks, with whom I was at the time a student. I was, of +course, entirely unknown to Darwin (or to anyone else) and to me the +principal interest of Darwin's letter is the evidence that it gives of +his extraordinary kindness and friendliness towards an obscure youngster +who had of course absolutely no claim upon his time or attention. The +little incident made an indelible impression upon my memory and taught +me a lesson that was worth learning." + +VARIABLE PROTECTIVE RESEMBLANCE. + +The wonderful power of rapid colour adjustment possessed by the +cuttle-fish was observed by Darwin in 1832 at St Jago, Cape de Verd +Islands, the first place visited during the voyage of the "Beagle". +From Rio he wrote to Henslow, giving the following account of his +observations, May 18, 1832: "I took several specimens of an Octopus +which possessed a most marvellous power of changing its colours, +equalling any chameleon, and evidently accommodating the changes to the +colour of the ground which it passed over. Yellowish green, dark brown, +and red, were the prevailing colours; this fact appears to be new, as +far as I can find out." ("Life and Letters", I. pages 235, 236. See +also Darwin's "Journal of Researches", 1876, pages 6-8, where a far more +detailed account is given together with a reference to "Encycl. of Anat. +and Physiol.") + +Darwin was well aware of the power of individual colour adjustment, +now known to be possessed by large numbers of lepidopterous pupae and +larvae. An excellent example was brought to his notice by C.V. Riley +("More Letters" II, pages 385, 386.), while the most striking of the +early results obtained with the pupae of butterflies--those of Mrs M.E. +Barber upon Papilio nireus--was communicated by him to the Entomological +Society of London. ("Trans. Ent. Soc. Lond." 1874, page 519. See also +"More Letters", II. page 403.) + +It is also necessary to direct attention to C.W. Beebe's ("Zoologica: +N.Y. Zool. Soc." Vol. I. No. 1, Sept. 25, 1907: "Geographic variation +in birds with especial reference to the effects of humidity".) recent +discovery that the pigmentation of the plumage of certain birds is +increased by confinement in a superhumid atmosphere. In Scardafella +inca, on which the most complete series of experiments was made, the +changes took place only at the moults, whether normal and annual or +artificially induced at shorter periods. There was a corresponding +increase in the choroidal pigment of the eye. At a certain advanced +stage of feather pigmentation a brilliant iridescent bronze or green +tint made its appearance on those areas where iridescence most often +occurs in allied genera. Thus in birds no less than in insects, +characters previously regarded as of taxonomic value, can be evoked or +withheld by the forces of the environment. + +WARNING OR APOSEMATIC COLOURS. + +From Darwin's description of the colours and habits it is evident that +he observed, in 1833, an excellent example of warning colouring in a +little South American toad (Phryniscus nigricans). He described it in a +letter to Henslow, written from Monte Video, Nov. 24, 1832: "As for +one little toad, I hope it may be new, that it may be christened +'diabolicus.' Milton must allude to this very individual when he talks +of 'squat like a toad'; its colours are by Werner ("Nomenclature of +Colours", 1821) ink black, vermilion red and buff orange." ("More +Letters", I. page 12.) In the "Journal of Researches" (1876, page 97.) +its colours are described as follows: "If we imagine, first, that it had +been steeped in the blackest ink, and then, when dry, allowed to crawl +over a board, freshly painted with the brightest vermilion, so as to +colour the soles of its feet and parts of its stomach, a good idea +of its appearance will be gained." "Instead of being nocturnal in its +habits, as other toads are, and living in damp obscure recesses, it +crawls during the heat of the day about the dry sand-hillocks and +arid plains,... " The appearance and habits recall T. Belt's well-known +description of the conspicuous little Nicaraguan frog which he found to +be distasteful to a duck. ("The Naturalist in Nicaragua" (2nd edition) +London, 1888, page 321.) + +The recognition of the Warning Colours of caterpillars is due in the +first instance to Darwin, who, reflecting on Sexual Selection, was +puzzled by the splendid colours of sexually immature organisms. He +applied to Wallace "who has an innate genius for solving difficulties." +("Descent of Man", page 325. On this and the following page an excellent +account of the discovery will be found, as well as in Wallace's "Natural +Selection", London, 1875, pages 117-122.) Darwin's original letter +exists ("Life and Letters", III. pages 93, 94.), and in it we are +told that he had taken the advice given by Bates: "You had better ask +Wallace." After some consideration Wallace replied that he believed the +colours of conspicuous caterpillars and perfect insects were a warning +of distastefulness and that such forms would be refused by birds. +Darwin's reply ("Life and Letters", III. pages 94, 95.) is extremely +interesting both for its enthusiasm at the brilliancy of the hypothesis +and its caution in acceptance without full confirmation: + +"Bates was quite right; you are the man to apply to in a difficulty. I +never heard anything more ingenious than your suggestion, and I hope you +may be able to prove it true. That is a splendid fact about the white +moths (A single white moth which was rejected by young turkeys, while +other moths were greedily devoured: "Natural Selection", 1875, page +78.); it warms one's very blood to see a theory thus almost proved to be +true." + +Two years later the hypothesis was proved to hold for caterpillars of +many kinds by J. Jenner Weir and A.G. Butler, whose observations have +since been abundantly confirmed by many naturalists. Darwin wrote to +Weir, May 13, 1869: "Your verification of Wallace's suggestion seems +to me to amount to quite a discovery." ("More Letters", II. page 71 +(footnote).) + +RECOGNITION OR EPISEMATIC CHARACTERS. + +This principle does not appear to have been in any way foreseen by +Darwin, although he draws special attention to several elements of +pattern which would now be interpreted by many naturalists as epismes. +He believed that the markings in question interfered with the cryptic +effect, and came to the conclusion that, even when common to both sexes, +they "are the result of sexual selection primarily applied to the male." +("Descent of Man", page 544.) The most familiar of all recognition +characters was carefully explained by him, although here too explained +as an ornamental feature now equally transmitted to both sexes: "The +hare on her form is a familiar instance of concealment through colour; +yet this principle partly fails in a closely-allied species, the rabbit, +for when running to its burrow, it is made conspicuous to the sportsman, +and no doubt to all beasts of prey, by its upturned white tail." +("Descent of Man", page 542.) + +The analogous episematic use of the bright colours of flowers to attract +insects for effecting cross-fertilisation and of fruits to attract +vertebrates for effecting dispersal is very clearly explained in the +"Origin". (Edition 1872, page 161. For a good example of Darwin's +caution in dealing with exceptions see the allusion to brightly coloured +fruit in "More Letters", II. page 348.) + +It is not, at this point, necessary to treat sematic characters at +any greater length. They will form the subject of a large part of +the following section, where the models of Batesian (Pseudaposematic) +mimicry are considered as well as the Mullerian (Synaposematic) +combinations of Warning Colours. + +MIMICRY,--BATESIAN OR PSEUDAPOSEMATIC, MULLERIAN OR SYNAPOSEMATIC. + +The existence of superficial resemblances between animals of various +degrees of affinity must have been observed for hundreds of years. +Among the early examples, the best known to me have been found in +the manuscript note-books and collections of W.J. Burchell, the great +traveller in Africa (1810-15) and Brazil (1825-30). The most interesting +of his records on this subject are brought together in the following +paragraphs. + +Conspicuous among well-defended insects are the dark steely or +iridescent greenish blue fossorial wasps or sand-wasps, Sphex and the +allied genera. Many Longicorn beetles mimic these in colour, slender +shape of body and limbs, rapid movements, and the readiness with which +they take to flight. On Dec. 21, 1812, Burchell captured one such beetle +(Promeces viridis) at Kosi Fountain on the journey from the source +of the Kuruman River to Klaarwater. It is correctly placed among the +Longicorns in his catalogue, but opposite to its number is the comment +"Sphex! totus purpureus." + +In our own country the black-and-yellow colouring of many stinging +insects, especially the ordinary wasps, affords perhaps the commonest +model for mimicry. It is reproduced with more or less accuracy on moths, +flies and beetles. Among the latter it is again a Longicorn which offers +one of the best-known, although by no means one of the most perfect, +examples. The appearance of the well-known "wasp-beetle" (Clytus +arietis) in the living state is sufficiently suggestive to prevent +the great majority of people from touching it. In Burchell's Brazilian +collection there is a nearly allied species (Neoclytus curvatus) which +appears to be somewhat less wasp-like than the British beetle. The +specimen bears the number "1188," and the date March 27, 1827, when +Burchell was collecting in the neighbourhood of San Paulo. Turning to +the corresponding number in the Brazilian note-book we find this +record: "It runs rapidly like an ichneumon or wasp, of which it has the +appearance." + +The formidable, well-defended ants are as freely mimicked by other +insects as the sand-wasps, ordinary wasps and bees. Thus on February +17, 1901, Guy A.K. Marshall captured, near Salisbury, Mashonaland, +three similar species of ants (Hymenoptera) with a bug (Hemiptera) and +a Locustid (Orthoptera), the two latter mimicking the former. All the +insects, seven in number, were caught on a single plant, a small bushy +vetch. ("Trans. Ent. Soc. Lond." 1902, page 535, plate XIX. figs. +53-59.) + +This is an interesting recent example from South Africa, and large +numbers of others might be added--the observations of many naturalists +in many lands; but nearly all of them known since that general awakening +of interest in the subject which was inspired by the great hypotheses +of H.W. Bates and Fritz Muller. We find, however, that Burchell had +more than once recorded the mimetic resemblance to ants. An extremely +ant-like bug (the larva of a species of Alydus) in his Brazilian +collection is labelled "1141," with the date December 8, 1826, when +Burchell was at the Rio das Pedras, Cubatao, near Santos. In the +note-book the record is as follows: "1141 Cimex. I collected this for a +Formica." + +Some of the chief mimics of ants are the active little hunting spiders +belonging to the family Attidae. Examples have been brought forward +during many recent years, especially by my friends Dr and Mrs Peckham, +of Milwaukee, the great authorities on this group of Araneae. Here too +we find an observation of the mimetic resemblance recorded by Burchell, +and one which adds in the most interesting manner to our knowledge +of the subject. A fragment, all that is now left, of an Attid spider, +captured on June 30, 1828, at Goyaz, Brazil, bears the following note, +in this case on the specimen and not in the note-book: "Black... runs and +seems like an ant with large extended jaws." My friend Mr R.I. Pocock, +to whom I have submitted the specimen, tells me that it is not one of +the group of species hitherto regarded as ant-like, and he adds, "It is +most interesting that Burchell should have noticed the resemblance to an +ant in its movements. This suggests that the perfect imitation in shape, +as well as in movement, seen in many species was started in forms of an +appropriate size and colour by the mimicry of movement alone." Up to the +present time Burchell is the only naturalist who has observed an example +which still exhibits this ancestral stage in the evolution of mimetic +likeness. + +Following the teachings of his day, Burchell was driven to believe that +it was part of the fixed and inexorable scheme of things that these +strange superficial resemblances existed. Thus, when he found other +examples of Hemipterous mimics, including one (Luteva macrophthalma) +with "exactly the manners of a Mantis," he added the sentence, "In the +genus Cimex (Linn.) are to be found the outward resemblances of insects +of many other genera and orders" (February 15, 1829). Of another +Brazilian bug, which is not to be found in his collection, and cannot +therefore be precisely identified, he wrote: "Cimex... Nature seems +to have intended it to imitate a Sphex, both in colour and the rapid +palpitating and movement of the antennae" (November 15, 1826). At the +same time it is impossible not to feel the conviction that Burchell felt +the advantage of a likeness to stinging insects and to aggressive ants, +just as he recognised the benefits conferred on desert plants by spines +and by concealment. Such an interpretation of mimicry was perfectly +consistent with the theological doctrines of his day. (See Kirby and +Spence, "An Introduction to Entomology" (1st edition), London, Vol. II. +1817, page 223.) + +The last note I have selected from Burchell's manuscript refers to one +of the chief mimics of the highly protected Lycid beetles. The whole +assemblage of African insects with a Lycoid colouring forms a most +important combination and one which has an interesting bearing upon the +theories of Bates and Fritz Muller. This most wonderful set of +mimetic forms, described in 1902 by Guy A.K. Marshall, is composed +of flower-haunting beetles belonging to the family Lycidae, and the +heterogeneous group of varied insects which mimic their conspicuous and +simple scheme of colouring. The Lycid beetles, forming the centre or +"models" of the whole company, are orange-brown in front for about +two-thirds of the exposed surface, black behind for the remaining third. +They are undoubtedly protected by qualities which make them excessively +unpalatable to the bulk of insect-eating animals. Some experimental +proof of this has been obtained by Mr Guy Marshall. What are the forms +which surround them? According to the hypothesis of Bates they would be, +at any rate mainly, palatable hard-pressed insects which only hold their +own in the struggle for life by a fraudulent imitation of the trade-mark +of the successful and powerful Lycidae. According to Fritz Muller's +hypothesis we should expect that the mimickers would be highly +protected, successful and abundant species, which (metaphorically +speaking) have found it to their advantage to possess an advertisement, +a danger-signal, in common with each other, and in common with the +beetles in the centre of the group. + +How far does the constitution of this wonderful combination--the largest +and most complicated as yet known in all the world--convey to us the +idea of mimicry working along the lines supposed by Bates or those +suggested by Muller? Figures 1 to 52 of Mr Marshall's coloured plate +("Trans. Ent. Soc. Lond." 1902, plate XVIII. See also page 517, where +the group is analysed.) represent a set of forty-two or forty-three +species or forms of insects captured in Mashonaland, and all except two +in the neighbourhood of Salisbury. The combination includes six species +of Lycidae; nine beetles of five groups all specially protected by +nauseous qualities, Telephoridae, Melyridae, Phytophaga, Lagriidae, +Cantharidae; six Longicorn beetles; one Coprid beetle; eight stinging +Hymenoptera; three or four parasitic Hymenoptera (Braconidae, a group +much mimicked and shown by some experiments to be distasteful); five +bugs (Hemiptera, a largely unpalatable group); three moths (Arctiidae +and Zygaenidae, distasteful families); one fly. In fact the whole +combination, except perhaps one Phytophagous, one Coprid and the +Longicorn beetles, and the fly, fall under the hypothesis of Muller +and not under that of Bates. And it is very doubtful whether these +exceptions will be sustained: indeed the suspicion of unpalatability +already besets the Longicorns and is always on the heels,--I should say +the hind tarsi--of a Phytophagous beetle. + +This most remarkable group which illustrates so well the problem of +mimicry and the alternative hypotheses proposed for its solution, was, +as I have said, first described in 1902. Among the most perfect of +the mimetic resemblances in it is that between the Longicorn beetle, +Amphidesmus analis, and the Lycidae. It was with the utmost astonishment +and pleasure that I found this very resemblance had almost certainly +been observed by Burchell. A specimen of the Amphidesmus exists in his +collection and it bears "651." Turning to the same number in the +African Catalogue we find that the beetle is correctly placed among the +Longicorns, that it was captured at Uitenhage on Nov. 18, 1813, and that +it was found associated with Lycid beetles in flowers ("consocians cum +Lycis 78-87 in floribus"). Looking up Nos. 78-87 in the collection and +catalogue, three species of Lycidae are found, all captured on Nov. 18, +1813, at Uitenhage. Burchell recognised the wide difference in affinity, +shown by the distance between the respective numbers; for his catalogue +is arranged to represent relationships. He observed, what students of +mimicry are only just beginning to note and record, the coincidence +between model and mimic in time and space and in habits. We are +justified in concluding that he observed the close superficial likeness +although he does not in this case expressly allude to it. + +One of the most interesting among the early observations of superficial +resemblance between forms remote in the scale of classification was made +by Darwin himself, as described in the following passage from his letter +to Henslow, written from Monte Video, Aug. 15, 1832: "Amongst the lower +animals nothing has so much interested me as finding two species of +elegantly coloured true Planaria inhabiting the dewy forest! The false +relation they bear to snails is the most extraordinary thing of the kind +I have ever seen." ("More Letters", I. page 9.) + +Many years later, in 1867, he wrote to Fritz Muller suggesting that the +resemblance of a soberly coloured British Planarian to a slug might be +due to mimicry. ("Life and Letters", III. page 71.) + +The most interesting copy of Bates's classical memoir on Mimicry +("Contributions to an Insect Fauna of the Amazon Valley". "Trans. Linn. +Soc." Vol. XXIII. 1862, page 495.), read before the Linnean Society in +1861, is that given by him to the man who has done most to support and +extend the theory. My kind friend has given that copy to me; it bears +the inscription: + +"Mr A.R. Wallace from his old travelling companion the Author." + +Only a year and a half after the publication of the "Origin", we find +that Darwin wrote to Bates on the subject which was to provide such +striking evidence of the truth of Natural Selection: "I am glad to hear +that you have specially attended to 'mimetic' analogies--a most curious +subject; I hope you publish on it. I have for a long time wished to +know whether what Dr Collingwood asserts is true--that the most striking +cases generally occur between insects inhabiting the same country." (The +letter is dated April 4, 1861. "More Letters", I. page 183.) + +The next letter, written about six months later, reveals the remarkable +fact that the illustrious naturalist who had anticipated Edward Forbes +in the explanation of arctic forms on alpine heights ("I was forestalled +in only one important point, which my vanity has always made me regret, +namely, the explanation by means of the Glacial period of the presence +of the same species of plants and of some few animals on distant +mountain summits and in the arctic regions. This view pleased me so much +that I wrote it out in extenso, and I believe that it was read by Hooker +some years before E. Forbes published his celebrated memoir on the +subject. In the very few points in which we differed, I still think +that I was in the right. I have never, of course, alluded in print to +my having independently worked out this view." "Autobiography, Life and +Letters", I. page 88.), had also anticipated H.W. Bates in the theory +of Mimicry: "What a capital paper yours will be on mimetic resemblances! +You will make quite a new subject of it. I had thought of such cases +as a difficulty; and once, when corresponding with Dr Collingwood, I +thought of your explanation; but I drove it from my mind, for I felt +that I had not knowledge to judge one way or the other." (The letter is +dated Sept. 25, 1861: "More Letters", I. page 197.) + +Bates read his paper before the Linnean Society, Nov. 21, 1861, and +Darwin's impressions on hearing it were conveyed in a letter to +the author dated Dec. 3: "Under a general point of view, I am quite +convinced (Hooker and Huxley took the same view some months ago) that +a philosophic view of nature can solely be driven into naturalists by +treating special subjects as you have done. Under a special point of +view, I think you have solved one of the most perplexing problems which +could be given to solve." ("Life and Letters", II. page 378.) The memoir +appeared in the following year, and after reading it Darwin wrote +as follows, Nov. 20, 1862: "... In my opinion it is one of the most +remarkable and admirable papers I ever read in my life... I am rejoiced +that I passed over the whole subject in the "Origin", for I should have +made a precious mess of it. You have most clearly stated and solved a +wonderful problem... Your paper is too good to be largely appreciated by +the mob of naturalists without souls; but, rely on it, that it will +have LASTING value, and I cordially congratulate you on your first great +work. You will find, I should think, that Wallace will fully appreciate +it." ("Life and Letters", II. pages 391-393.) Four days later, Nov. 24, +Darwin wrote to Hooker on the same subject: "I have now finished his +paper...' it seems to me admirable. To my mind the act of segregation of +varieties into species was never so plainly brought forward, and there +are heaps of capital miscellaneous observations." ("More Letters", I. +page 214.) + +Darwin was here referring to the tendency of similar varieties of the +same species to pair together, and on Nov. 25 he wrote to Bates asking +for fuller information on this subject. ("More Letters", I. page 215. +See also parts of Darwin's letter to Bates in "Life and Letters", II. +page 392.) If Bates's opinion were well founded, sexual selection would +bear a most important part in the establishment of such species. (See +Poulton, "Essays on Evolution", 1908, pages 65, 85-88.) It must be +admitted, however, that the evidence is as yet quite insufficient to +establish this conclusion. It is interesting to observe how Darwin +at once fixed on the part of Bates's memoir which seemed to bear upon +sexual selection. A review of Bates's theory of Mimicry was contributed +by Darwin to the "Natural History Review" (New Ser. Vol. III. 1863, page +219.) and an account of it is to be found in the "Origin" (Edition +1872, pages 375-378.) and in "The Descent of Man". (Edition 1874, pages +323-325.) + +Darwin continually writes of the value of hypothesis as the inspiration +of inquiry. We find an example in his letter to Bates, Nov. 22, 1860: +"I have an old belief that a good observer really means a good theorist, +and I fully expect to find your observations most valuable." ("More +Letters", I. page 176.) Darwin's letter refers to many problems upon +which Bates had theorised and observed, but as regards Mimicry itself +the hypothesis was thought out after the return of the letter from the +Amazons, when he no longer had the opportunity of testing it by the +observation of living Nature. It is by no means improbable that, had +he been able to apply this test, Bates would have recognised that his +division of butterfly resemblances into two classes,--one due to +the theory of mimicry, the other to the influence of local +conditions,--could not be sustained. + +Fritz Muller's contributions to the problem of Mimicry were all made +in S.E. Brazil, and numbers of them were communicated, with other +observations on natural history, to Darwin, and by him sent to Professor +R. Meldola who published many of the facts. Darwin's letters to Meldola +(Poulton, "Charles Darwin and the theory of Natural Selection", London, +1896, pages 199-218.) contain abundant proofs of his interest in +Muller's work upon Mimicry. One deeply interesting letter (Loc. cit. +pages 201, 202.) dated Jan. 23, 1872, proves that Fritz Muller before +he originated the theory of Common Warning Colours (Synaposematic +Resemblance or Mullerian Mimicry), which will ever be associated with +his name, had conceived the idea of the production of mimetic likeness +by sexual selection. + +Darwin's letter to Meldola shows that he was by no means inclined to +dismiss the suggestion as worthless, although he considered it daring. +"You will also see in this letter a strange speculation, which I should +not dare to publish, about the appreciation of certain colours being +developed in those species which frequently behold other forms similarly +ornamented. I do not feel at all sure that this view is as incredible as +it may at first appear. Similar ideas have passed through my mind +when considering the dull colours of all the organisms which inhabit +dull-coloured regions, such as Patagonia and the Galapagos Is." A little +later, on April 5, he wrote to Professor August Weismann on the same +subject: "It may be suspected that even the habit of viewing differently +coloured surrounding objects would influence their taste, and +Fritz Muller even goes so far as to believe that the sight of gaudy +butterflies might influence the taste of distinct species." ("Life and +Letters", III. page 157.) + +This remarkable suggestion affords interesting evidence that F. Muller +was not satisfied with the sufficiency of Bates's theory. Nor is +this surprising when we think of the numbers of abundant conspicuous +butterflies which he saw exhibiting mimetic likenesses. The common +instances in his locality, and indeed everywhere in tropical America, +were anything but the hard-pressed struggling forms assumed by the +theory of Bates. They belonged to the groups which were themselves +mimicked by other butterflies. Fritz Muller's suggestion also shows +that he did not accept Bates's alternative explanation of a superficial +likeness between models themselves, based on some unknown influence of +local physico-chemical forces. At the same time Muller's own suggestion +was subject to this apparently fatal objection, that the sexual +selection he invoked would tend to produce resemblances in the males +rather than the females, while it is well known that when the sexes +differ the females are almost invariably more perfectly mimetic than the +males and in a high proportion of cases are mimetic while the males are +non-mimetic. + +The difficulty was met several years later by Fritz Muller's well-known +theory, published in 1879 ("Kosmos", May 1879, page 100.), and +immediately translated by Meldola and brought before the Entomological +Society. ("Proc. Ent. Soc. Lond." 1879, page xx.) Darwin's letter to +Meldola dated June 6, 1879, shows "that the first introduction of this +new and most suggestive hypothesis into this country was due to the +direct influence of Darwin himself, who brought it before the notice +of the one man who was likely to appreciate it at its true value and to +find the means for its presentation to English naturalists." ("Charles +Darwin and the Theory of Natural Selection", page 214.) Of the +hypothesis itself Darwin wrote "F. Muller's view of the mutual +protection was quite new to me." (Ibid. page 213.) The hypothesis of +Mullerian mimicry was at first strongly opposed. Bates himself could +never make up his mind to accept it. As the Fellows were walking out +of the meeting at which Professor Meldola explained the hypothesis, an +eminent entomologist, now deceased, was heard to say to Bates: "It's a +case of save me from my friends!" The new ideas encountered and still +encounter to a great extent the difficulty that the theory of Bates had +so completely penetrated the literature of natural history. The present +writer has observed that naturalists who have not thoroughly absorbed +the older hypothesis are usually far more impressed by the newer +one than are those whose allegiance has already been rendered. The +acceptance of Natural Selection itself was at first hindered by +similar causes, as Darwin clearly recognised: "If you argue about the +non-acceptance of Natural Selection, it seems to me a very striking fact +that the Newtonian theory of gravitation, which seems to every one now +so certain and plain, was rejected by a man so extraordinarily able as +Leibnitz. The truth will not penetrate a preoccupied mind." (To Sir J. +Hooker, July 28, 1868, "More Letters", I. page 305. See also the letter +to A.R. Wallace, April 30, 1868, in "More Letters" II. page 77, lines +6-8 from top.) + +There are many naturalists, especially students of insects, who appear +to entertain an inveterate hostility to any theory of mimicry. Some of +them are eager investigators in the fascinating field of geographical +distribution, so essential for the study of Mimicry itself. The changes +of pattern undergone by a species of Erebia as we follow it over +different parts of the mountain ranges of Europe is indeed a most +interesting inquiry, but not more so than the differences between e.g. +the Acraea johnstoni of S.E. Rhodesia and of Kilimanjaro. A naturalist +who is interested by the Erebia should be equally interested by the +Acraea; and so he would be if the student of mimicry did not also +record that the characteristics which distinguish the northern from +the southern individuals of the African species correspond with the +presence, in the north but not in the south, of certain entirely +different butterflies. That this additional information should so +greatly weaken, in certain minds, the appeal of a favourite study, is a +psychological problem of no little interest. This curious antagonism is +I believe confined to a few students of insects. Those naturalists who, +standing rather farther off, are able to see the bearings of the subject +more clearly, will usually admit the general support yielded by an +ever-growing mass of observations to the theories of Mimicry propounded +by H.W. Bates and Fritz Muller. In like manner natural selection itself +was in the early days often best understood and most readily accepted by +those who were not naturalists. Thus Darwin wrote to D.T. Ansted, Oct. +27, 1860: "I am often in despair in making the generality of NATURALISTS +even comprehend me. Intelligent men who are not naturalists and have not +a bigoted idea of the term species, show more clearness of mind." ("More +Letters", I. page 175.) + +Even before the "Origin" appeared Darwin anticipated the first results +upon the mind of naturalists. He wrote to Asa Gray, Dec. 21, 1859: "I +have made up my mind to be well abused; but I think it of importance +that my notions should be read by intelligent men, accustomed to +scientific argument, though NOT naturalists. It may seem absurd, but +I think such men will drag after them those naturalists who have too +firmly fixed in their heads that a species is an entity." ("Life and +Letters" II. page 245.) + +Mimicry was not only one of the first great departments of zoological +knowledge to be studied under the inspiration of natural Selection, +it is still and will always remain one of the most interesting +and important of subjects in relation to this theory as well as to +evolution. In mimicry we investigate the effect of environment in its +simplest form: we trace the effects of the pattern of a single species +upon that of another far removed from it in the scale of classification. +When there is reason to believe that the model is an invader from +another region and has only recently become an element in the +environment of the species native to its second home, the problem gains +a special interest and fascination. Although we are chiefly dealing with +the fleeting and changeable element of colour we expect to find and we +do find evidence of a comparatively rapid evolution. The invasion of +a fresh model is for certain species an unusually sudden change in the +forces of the environment and in some instances we have grounds for the +belief that the mimetic response has not been long delayed. + +MIMICRY AND SEX. + +Ever since Wallace's classical memoir on mimicry in the Malayan +Swallowtail butterflies, those naturalists who have written on the +subject have followed his interpretation of the marked prevalence of +mimetic resemblance in the female sex as compared with the male. They +have believed with Wallace that the greater dangers of the female, with +slower flight and often alighting for oviposition, have been in part +met by the high development of this special mode of protection. The fact +cannot be doubted. It is extremely common for a non-mimetic male to be +accompanied by a beautifully mimetic female and often by two or three +different forms of female, each mimicking a different model. The male +of a polymorphic mimetic female is, in fact, usually non-mimetic (e.g. +Papilio dardanus = merope), or if a mimic (e.g. the Nymphaline genus +Euripus), resembles a very different model. On the other hand a +non-mimetic female accompanied by a mimetic male is excessively rare. An +example is afforded by the Oriental Nymphaline, Cethosia, in which the +males of some species are rough mimics of the brown Danaines. In some +of the orb-weaving spiders the males mimic ants, while the much larger +females are non-mimetic. When both sexes mimic, it is very common in +butterflies and is also known in moths, for the females to be better and +often far better mimics than the males. + +Although still believing that Wallace's hypothesis in large part +accounts for the facts briefly summarised above, the present writer has +recently been led to doubt whether it offers a complete explanation. +Mimicry in the male, even though less beneficial to the species than +mimicry in the female, would still surely be advantageous. Why then is +it so often entirely restricted to the female? While the attempt to find +an answer to this question was haunting me, I re-read a letter +written by Darwin to Wallace, April 15, 1868, containing the following +sentences: "When female butterflies are more brilliant than their males +you believe that they have in most cases, or in all cases, been rendered +brilliant so as to mimic some other species, and thus escape danger. But +can you account for the males not having been rendered equally brilliant +and equally protected? Although it may be most for the welfare of +the species that the female should be protected, yet it would be some +advantage, certainly no disadvantage, for the unfortunate male to enjoy +an equal immunity from danger. For my part, I should say that the female +alone had happened to vary in the right manner, and that the beneficial +variations had been transmitted to the same sex alone. Believing in +this, I can see no improbability (but from analogy of domestic animals +a strong probability) that variations leading to beauty must often have +occurred in the males alone, and been transmitted to that sex alone. +Thus I should account in many cases for the greater beauty of the male +over the female, without the need of the protective principle." ("More +Letters", II. pages 73, 74. On the same subject--"the gay-coloured +females of Pieris" (Perrhybris (Mylothris) pyrrha of Brazil), Darwin +wrote to Wallace, May 5, 1868, as follows: "I believe I quite follow you +in believing that the colours are wholly due to mimicry; and I further +believe that the male is not brilliant from not having received through +inheritance colour from the female, and from not himself having varied; +in short, that he has not been influenced by selection." It should be +noted that the male of this species does exhibit a mimetic pattern on +the under surface. "More Letters" II. page 78.) + +The consideration of the facts of mimicry thus led Darwin to the +conclusion that the female happens to vary in the right manner more +commonly than the male, while the secondary sexual characters of males +supported the conviction "that from some unknown cause such characters +(viz. new characters arising in one sex and transmitted to it alone) +apparently appear oftener in the male than in the female." (Letter from +Darwin to Wallace, May 5, 1867, "More Letters", II. Page 61.) + +Comparing these conflicting arguments we are led to believe that the +first is the stronger. Mimicry in the male would be no disadvantage but +an advantage, and when it appears would be and is taken advantage of +by selection. The secondary sexual characters of males would be no +advantage but a disadvantage to females, and, as Wallace thinks, are +withheld from this sex by selection. It is indeed possible that mimicry +has been hindered and often prevented from passing to the males by +sexual selection. We know that Darwin was much impressed ("Descent of +Man", page 325.) by Thomas Belt's daring and brilliant suggestion that +the white patches which exist, although ordinarily concealed, on the +wings of mimetic males of certain Pierinae (Dismorphia), have been +preserved by preferential mating. He supposed this result to have been +brought about by the females exhibiting a deep-seated preference for +males that displayed the chief ancestral colour, inherited from periods +before any mimetic pattern had been evolved in the species. But it has +always appeared to me that Belt's deeply interesting suggestion requires +much solid evidence and repeated confirmation before it can be accepted +as a valid interpretation of the facts. In the present state of our +knowledge, at any rate of insects and especially of Lepidoptera, it is +probable that the female is more apt to vary than the male and that an +important element in the interpretation of prevalent female mimicry is +provided by this fact. + +In order adequately to discuss the question of mimicry and sex it would +be necessary to analyse the whole of the facts, so far as they are known +in butterflies. On the present occasion it is only possible to state the +inferences which have been drawn from general impressions,--inferences +which it is believed will be sustained by future inquiry. + +(1) Mimicry may occasionally arise in one sex because the differences +which distinguish it from the other sex happen to be such as to afford a +starting-point for the resemblance. Here the male is at no disadvantage +as compared with the female, and the rarity of mimicry in the male +alone (e.g. Cethosia) is evidence that the great predominance of female +mimicry is not to be thus explained. + +(2) The tendency of the female to dimorphism and polymorphism has been +of great importance in determining this predominance. Thus if the female +appear in two different forms and the male in only one it will be twice +as probable that she will happen to possess a sufficient foundation for +the evolution of mimicry. + +(3) The appearance of melanic or partially melanic forms in the female +has been of very great service, providing as it does a change of +ground-colour. Thus the mimicry of the black generally red-marked +American "Aristolochia swallowtails" (Pharmacophagus) by the females of +Papilio swallowtails was probably begun in this way. + +(4) It is probably incorrect to assume with Haase that mimicry always +arose in the female and was later acquired by the male. Both sexes of +the third section of swallowtails (Cosmodesmus) mimic Pharmacophagus in +America, far more perfectly than do the females of Papilio. But this is +not due to Cosmodesmus presenting us with a later stage of history begun +in Papilio; for in Africa Cosmodesmus is still mimetic (of Danainae) in +both sexes although the resemblances attained are imperfect, while +many African species of Papilio have non-mimetic males with beautifully +mimetic females. The explanation is probably to be sought in the fact +that the females of Papilio are more variable and more often tend to +become dimorphic than those of Cosmodesmus, while the latter group has +more often happened to possess a sufficient foundation for the origin of +the resemblance in patterns which, from the start, were common to male +and female. + +(5) In very variable species with sexes alike, mimicry can be rapidly +evolved in both sexes out of very small beginnings. Thus the reddish +marks which are common in many individuals of Limenitis arthemis were +almost certainly the starting-point for the evolution of the beautifully +mimetic L. archippus. Nevertheless in such cases, although there is +no reason to suspect any greater variability, the female is commonly a +somewhat better mimic than the male and often a very much better mimic. +Wallace's principle seems here to supply the obvious interpretation. + +(6) When the difference between the patterns of the model and presumed +ancestor of the mimic is very great, the female is often alone mimetic; +when the difference is comparatively small, both sexes are commonly +mimetic. The Nymphaline genus Hypolimnas is a good example. In +Hypolimnas itself the females mimic Danainae with patterns very +different from those preserved by the non-mimetic males: in the +sub-genus Euralia, both sexes resemble the black and white Ethiopian +Danaines with patterns not very dissimilar from that which we infer to +have existed in the non-mimetic ancestor. + +(7) Although a melanic form or other large variation may be of the +utmost importance in facilitating the start of a mimetic likeness, it is +impossible to explain the evolution of any detailed resemblance in +this manner. And even the large colour variation itself may well be +the expression of a minute and "continuous" change in the chemical and +physical constitution of pigments. + +SEXUAL SELECTION (EPIGAMIC CHARACTERS). + +We do not know the date at which the idea of Sexual Selection arose in +Darwin's mind, but it was probably not many years after the sudden flash +of insight which, in October 1838, gave to him the theory of Natural +Selection. An excellent account of Sexual Selection occupies the +concluding paragraph of Part I. of Darwin's Section of the Joint Essay +on Natural Selection, read July 1st, 1858, before the Linnean Society. +("Journ. Proc. Linn. Soc." Vol. III. 1859, page 50.) The principles are +so clearly and sufficiently stated in these brief sentences that it +is appropriate to quote the whole: "Besides this natural means of +selection, by which those individuals are preserved, whether in their +egg, or larval, or mature state, which are best adapted to the place +they fill in nature, there is a second agency at work in most unisexual +animals, tending to produce the same effect, namely, the struggle of the +males for the females. These struggles are generally decided by the law +of battle, but in the case of birds, apparently, by the charms of their +song, by their beauty or their power of courtship, as in the dancing +rock-thrush of Guiana. The most vigorous and healthy males, implying +perfect adaptation, must generally gain the victory in their contests. +This kind of selection, however, is less rigorous than the other; it +does not require the death of the less successful, but gives to them +fewer descendants. The struggle falls, moreover, at a time of year when +food is generally abundant, and perhaps the effect chiefly produced +would be the modification of the secondary sexual characters, which are +not related to the power of obtaining food, or to defence from enemies, +but to fighting with or rivalling other males. The result of this +struggle amongst the males may be compared in some respects to that +produced by those agriculturists who pay less attention to the careful +selection of all their young animals, and more to the occasional use of +a choice mate." + +A full exposition of Sexual Selection appeared in the "The Descent of +Man" in 1871, and in the greatly augmented second edition, in 1874. +It has been remarked that the two subjects, "The Descent of Man and +Selection in Relation to Sex", seem to fuse somewhat imperfectly into +the single work of which they form the title. The reason for their +association is clearly shown in a letter to Wallace, dated May 28, 1864: +"... I suspect that a sort of sexual selection has been the most powerful +means of changing the races of man." ("More Letters", II. page 33.) + +Darwin, as we know from his Autobiography ("Life and Letters", I. page +94.), was always greatly interested in this hypothesis, and it has been +shown in the preceding pages that he was inclined to look favourably +upon it as an interpretation of many appearances usually explained by +Natural Selection. Hence Sexual Selection, incidentally discussed in +other sections of the present essay, need not be considered at any +length, in the section specially allotted to it. + +Although so interested in the subject and notwithstanding his conviction +that the hypothesis was sound, Darwin was quite aware that it was +probably the most vulnerable part of the "Origin". Thus he wrote to H.W. +Bates, April 4, 1861: "If I had to cut up myself in a review I would +have (worried?) and quizzed sexual selection; therefore, though I am +fully convinced that it is largely true, you may imagine how pleased I +am at what you say on your belief." ("More Letters", I. page 183.) + +The existence of sound-producing organs in the males of insects was, +Darwin considered, the strongest evidence in favour of the operation +of sexual selection in this group. ("Life and Letters", III. pages 94, +138.) Such a conclusion has received strong support in recent years by +the numerous careful observations of Dr F.A. Dixey ("Proc. Ent. Soc. +Lond." 1904, page lvi; 1905, pages xxxvii, liv; 1906, page ii.) and Dr +G.B. Longstaff ("Proc. Ent. Soc. Lond." 1905, page xxxv; "Trans. Ent. +Soc. Lond." 1905, page 136; 1908, page 607.) on the scents of male +butterflies. The experience of these naturalists abundantly confirms and +extends the account given by Fritz Muller ("Jen. Zeit." Vol. XI. 1877, +page 99; "Trans. Ent. Soc. Lond." 1878, page 211.) of the scents +of certain Brazilian butterflies. It is a remarkable fact that the +apparently epigamic scents of male butterflies should be pleasing to +man while the apparently aposematic scents in both sexes of species with +warning colours should be displeasing to him. But the former is far more +surprising than the latter. It is not perhaps astonishing that a scent +which is ex hypothesi unpleasant to an insect-eating Vertebrate should +be displeasing to the human sense; but it is certainly wonderful that an +odour which is ex hypothesi agreeable to a female butterfly should also +be agreeable to man. + +Entirely new light upon the seasonal appearance of epigamic characters +is shed by the recent researches of C.W. Beebe ("The American +Naturalist", Vol. XLII. No. 493, Jan. 1908, page 34.), who caused the +scarlet tanager (Piranga erythromelas) and the bobolink (Dolichonyx +oryzivorus) to retain their breeding plumage through the whole year by +means of fattening food, dim illumination, and reduced activity. Gradual +restoration to the light and the addition of meal-worms to the diet +invariably brought back the spring song, even in the middle of winter. +A sudden alteration of temperature, either higher or lower, caused the +birds nearly to stop feeding, and one tanager lost weight rapidly and in +two weeks moulted into the olive-green winter plumage. After a year, and +at the beginning of the normal breeding season, "individual tanagers +and bobolinks were gradually brought under normal conditions and +activities," and in every case moulted from nuptial plumage to nuptial +plumage. "The dull colours of the winter season had been skipped." The +author justly claims to have established "that the sequence of plumage +in these birds is not in any way predestined through inheritance..., +but that it may be interrupted by certain factors in the environmental +complex." + + + + +XVI. GEOGRAPHICAL DISTRIBUTION OF PLANTS. By Sir William Thiselton-Dyer, +K.C.M.G., C.I.E. Sc.D., F.R.S. + +The publication of "The Origin of Species" placed the study of Botanical +Geography on an entirely new basis. It is only necessary to study the +monumental "Geographie Botanique raisonnee" of Alphonse De Candolle, +published four years earlier (1855), to realise how profound and +far-reaching was the change. After a masterly and exhaustive discussion +of all available data De Candolle in his final conclusions could only +arrive at a deadlock. It is sufficient to quote a few sentences:-- + +"L'opinion de Lamarck est aujourd'hui abandonee par tous les +naturalistes qui ont etudie sagement les modifications possibles des +etres organises... + +"Et si l'on s'ecarte des exagerations de Lamarck, si l'on suppose un +premier type de chaque genre, de chaque famille tout au moins, on se +trouve encore a l'egard de l'origine de ces types en presence de la +grande question de la creation. + +"Le seul parti a prendre est donc d'envisager les etres organises comme +existant depuis certaines epoques, avec leurs qualites particulieres." +(Vol. II. page 1107.) + +Reviewing the position fourteen years afterwards, Bentham +remarked:--"These views, generally received by the great majority of +naturalists at the time De Candolle wrote, and still maintained by a +few, must, if adhered to, check all further enquiry into any connection +of facts with causes," and he added, "there is little doubt but that if +De Candolle were to revise his work, he would follow the example of +so many other eminent naturalists, and... insist that the present +geographical distribution of plants was in most instances a derivative +one, altered from a very different former distribution." ("Pres. Addr." +(1869) "Proc. Linn. Soc." 1868-69, page lxviii.) + +Writing to Asa Gray in 1856, Darwin gave a brief preliminary account +of his ideas as to the origin of species, and said that geographical +distribution must be one of the tests of their validity. ("Life and +Letters", II. page 78.) What is of supreme interest is that it was also +their starting-point. He tells us:--"When I visited, during the voyage +of H.M.S. "Beagle", the Galapagos Archipelago,... I fancied myself +brought near to the very act of creation. I often asked myself how these +many peculiar animals and plants had been produced: the simplest answer +seemed to be that the inhabitants of the several islands had descended +from each other, undergoing modification in the course of their +descent." ("The Variation of Animals and Plants" (2nd edition), 1890, I. +pages 9, 10.) We need not be surprised then, that in writing in 1845 +to Sir Joseph Hooker, he speaks of "that grand subject, that almost +keystone of the laws of creation, Geographical Distribution." ("Life and +Letters", I. page 336.) + +Yet De Candolle was, as Bentham saw, unconsciously feeling his way, +like Lyell, towards evolution, without being able to grasp it. They both +strove to explain phenomena by means of agencies which they saw actually +at work. If De Candolle gave up the ultimate problem as insoluble:--"La +creation ou premiere formation des etres organises echappe, par sa +nature et par son anciennete, a nos moyens d'observation" (Loc. cit. +page 1106.), he steadily endeavoured to minimise its scope. At least +half of his great work is devoted to the researches by which he +extricated himself from a belief in species having had a multiple +origin, the view which had been held by successive naturalists from +Gmelin to Agassiz. To account for the obvious fact that species +constantly occupy dissevered areas, De Candolle made a minute study of +their means of transport. This was found to dispose of the vast majority +of cases, and the remainder he accounted for by geographical change. +(Loc. cit. page 1116.) + +But Darwin strenuously objected to invoking geographical change as a +solution of every difficulty. He had apparently long satisfied himself +as to the "permanence of continents and great oceans." Dana, he tells us +"was, I believe, the first man who maintained" this ("Life and Letters", +III. page 247. Dana says:--"The continents and oceans had their general +outline or form defined in earliest time," "Manual of Geology", revised +edition. Philadelphia, 1869, page 732. I have no access to an earlier +edition.), but he had himself probably arrived at it independently. +Modern physical research tends to confirm it. The earth's centre of +gravity, as pointed out by Pratt from the existence of the Pacific +Ocean, does not coincide with its centre of figure, and it has been +conjectured that the Pacific Ocean dates its origin from the separation +of the moon from the earth. + +The conjecture appears to be unnecessary. Love shows that "the force +that keeps the Pacific Ocean on one side of the earth is gravity, +directed more towards the centre of gravity than the centre of the +figure." ("Report of the 77th Meeting of the British Association" +(Leicester, 1907), London, 1908, page 431.) I can only summarise the +conclusions of a technical but masterly discussion. "The broad general +features of the distribution of continent and ocean can be regarded +as the consequences of simple causes of a dynamical character," and +finally, "As regards the contour of the great ocean basins, we seem +to be justified in saying that the earth is approximately an oblate +spheroid, but more nearly an ellipsoid with three unequal axes, having +its surface furrowed according to the formula for a certain spherical +harmonic of the third degree" (Ibid. page 436.), and he shows that this +furrowed surface must be produced "if the density is greater in one +hemispheroid than in the other, so that the position of the centre of +gravity is eccentric." (Ibid. page 431.) Such a modelling of the earth's +surface can only be referred to a primitive period of plasticity. If +the furrows account for the great ocean basins, the disposition of the +continents seems equally to follow. Sir George Darwin has pointed out +that they necessarily "arise from a supposed primitive viscosity or +plasticity of the earth's mass. For during this course of evolution the +earth's mass must have suffered a screwing motion, so that the polar +regions have travelled a little from west to east relatively to the +equator. This affords a possible explanation of the north and south +trend of our great continents." ("Encycl. Brit." (9th edition), Vol. +XXIII. "Tides", page 379.) + +It would be trespassing on the province of the geologist to pursue the +subject at any length. But as Wallace ("Island Life" (2nd edition), +1895, page 103.), who has admirably vindicated Darwin's position, points +out, the "question of the permanence of our continents... lies at the +root of all our inquiries into the great changes of the earth and its +inhabitants." But he proceeds: "The very same evidence which has been +adduced to prove the GENERAL stability and permanence of our continental +areas also goes to prove that they have been subjected to wonderful +and repeated changes in DETAIL." (Loc. cit. page 101.) Darwin of course +would have admitted this, for with a happy expression he insisted +to Lyell (1856) that "the skeletons, at least, of our continents are +ancient." ("More Letters", II. page 135.) It is impossible not to +admire the courage and tenacity with which he carried on the conflict +single-handed. But he failed to convince Lyell. For we still find +him maintaining in the last edition of the "Principles": "Continents +therefore, although permanent for whole geological epochs, shift their +positions entirely in the course of ages." (Lyell's "Principles of +Geology" (11th edition), London, 1872, I. page 258.) + +Evidence, however, steadily accumulates in Darwin's support. His +position still remains inexpugnable that it is not permissible to invoke +geographical change to explain difficulties in distribution without +valid geological and physical support. Writing to Mellard Reade, who in +1878 had said, "While believing that the ocean-depths are of enormous +age, it is impossible to reject other evidences that they have once +been land," he pointed out "the statement from the 'Challenger' that all +sediment is deposited within one or two hundred miles from the shores." +("More Letters", II. page 146.) The following year Sir Archibald Geikie +("Geographical Evolution", "Proc. R. Geogr. Soc." 1879, page 427.) +informed the Royal Geographical Society that "No part of the results +obtained by the 'Challenger' expedition has a profounder interest for +geologists and geographers than the proof which they furnish that the +floor of the ocean basins has no real analogy among the sedimentary +formations which form most of the framework of the land." + +Nor has Darwin's earlier argument ever been upset. "The fact which +I pointed out many years ago, that all oceanic islands are volcanic +(except St Paul's, and now that is viewed by some as the nucleus of an +ancient volcano), seem to me a strong argument that no continent ever +occupied the great oceans." ("More Letters", II. page 146.) + +Dr Guppy, who devoted several years to geological and botanical +investigations in the Pacific, found himself forced to similar +conclusions. "It may be at once observed," he says, "that my belief in +the general principle that islands have always been islands has not +been shaken," and he entirely rejects "the hypothesis of a Pacific +continent." He comes back, in full view of the problems on the spot, +to the position from which, as has been seen, Darwin started: "If the +distribution of a particular group of plants or animals does not seem to +accord with the present arrangement of the land, it is by far the safest +plan, even after exhausting all likely modes of explanation, not to +invoke the intervention of geographical changes; and I scarcely think +that our knowledge of any one group of organisms is ever sufficiently +precise to justify a recourse to hypothetical alterations in the present +relations of land and sea." ("Observations of a Naturalist in the +Pacific between 1896 and 1899", London, 1903, I. page 380.) Wallace +clinches the matter when he finds "almost the whole of the vast areas of +the Atlantic, Pacific, Indian, and Southern Oceans, without a solitary +relic of the great islands or continents supposed to have sunk beneath +their waves." ("Island Life", page 105.) + +Writing to Wallace (1876), Darwin warmly approves the former's "protest +against sinking imaginary continents in a quite reckless manner, as +was stated by Forbes, followed, alas, by Hooker, and caricatured by +Wollaston and (Andrew) Murray." ("Life and Letters", III. page 230.) +The transport question thus became of enormously enhanced importance. We +need not be surprised then at his writing to Lyell in 1856:--"I cannot +avoid thinking that Forbes's 'Atlantis' was an ill-service to science, +as checking a close study of means of dissemination" (Ibid. II. page +78.), and Darwin spared no pains to extend our knowledge of them. He +implores Hooker, ten years later, to "admit how little is known on the +subject," and summarises with some satisfaction what he had himself +achieved:--"Remember how recently you and others thought that salt +water would soon kill seeds... Remember that no one knew that seeds would +remain for many hours in the crops of birds and retain their vitality; +that fish eat seeds, and that when the fish are devoured by birds the +seeds can germinate, etc. Remember that every year many birds are blown +to Madeira and to the Bermudas. Remember that dust is blown 1000 miles +across the Atlantic." ("More Letters", I. page 483.) + +It has always been the fashion to minimise Darwin's conclusions, and +these have not escaped objection. The advocatus diaboli has a useful +function in science. But in attacking Darwin his brief is generally +found to be founded on a slender basis of facts. Thus Winge and Knud +Andersen have examined many thousands of migratory birds and found "that +their crops and stomachs were always empty. They never observed any +seeds adhering to the feathers, beaks or feet of the birds." (R.F. +Scharff, "European Animals", page 64, London, 1907.) The most +considerable investigation of the problem of Plant Dispersal since +Darwin is that of Guppy. He gives a striking illustration of how easily +an observer may be led into error by relying on negative evidence. + +"When Ekstam published, in 1895, the results of his observations on the +plants of Nova Zembla, he observed that he possessed no data to show +whether swimming and wading birds fed on berries; and he attached all +importance to dispersal by winds. On subsequently visiting Spitzbergen +he must have been at first inclined, therefore, to the opinion +of Nathorst, who, having found only a solitary species of bird (a +snow-sparrow) in that region, naturally concluded that birds had been +of no importance as agents in the plant-stocking. However, Ekstam's +opportunities were greater, and he tells us that in the craws of six +specimens of Lagopus hyperboreus shot in Spitzbergen in August he found +represented almost 25 per cent. of the usual phanerogamic flora of that +region in the form of fruits, seeds, bulbils, flower-buds, leaf-buds, +etc... " + +"The result of Ekstam's observations in Spitzbergen was to lead him to +attach a very considerable importance in plant dispersal to the agency +of birds; and when in explanation of the Scandinavian elements in the +Spitzbergen flora he had to choose between a former land connection and +the agency of birds, he preferred the bird." (Guppy, op. cit. II. pages +511, 512.) + +Darwin objected to "continental extensions" on geological grounds, +but he also objected to Lyell that they do not "account for all the +phenomena of distribution on islands" ("Life and Letters", II. page +77.), such for example as the absence of Acacias and Banksias in New +Zealand. He agreed with De Candolle that "it is poor work putting +together the merely POSSIBLE means of distribution." But he also +agreed with him that they were the only practicable door of escape from +multiple origins. If they would not work then "every one who believes +in single centres will have to admit continental extensions" (Ibid. II. +page 82.), and that he regarded as a mere counsel of despair:--"to make +continents, as easily as a cook does pancakes." (Ibid. II. page 74.) + +The question of multiple origins however presented itself in another +shape where the solution was much more difficult. The problem, as +stated by Darwin, is this:--"The identity of many plants and animals, +on mountain-summits, separated from each other by hundreds of miles of +lowlands... without the apparent possibility of their having migrated +from one point to the other." He continues, "even as long ago as 1747, +such facts led Gmelin to conclude that the same species must have been +independently created at several distinct points; and we might have +remained in this same belief, had not Agassiz and others called vivid +attention to the Glacial period, which affords... a simple explanation of +the facts." ("Origin of Species" (6th edition) page 330.) + +The "simple explanation" was substantially given by E. Forbes in 1846. +It is scarcely too much to say that it belongs to the same class of +fertile and far-reaching ideas as "natural selection" itself. It is +an extraordinary instance, if one were wanted at all, of Darwin's +magnanimity and intense modesty that though he had arrived at the theory +himself, he acquiesced in Forbes receiving the well-merited credit. +"I have never," he says, "of course alluded in print to my having +independently worked out this view." But he would have been more than +human if he had not added:--"I was forestalled in... one important point, +which my vanity has always made me regret." ("Life and Letters", I. page +88.) + +Darwin, however, by applying the theory to trans-tropical migration, +went far beyond Forbes. The first enunciation to this is apparently +contained in a letter to Asa Gray in 1858. The whole is too long +to quote, but the pith is contained in one paragraph. "There is a +considerable body of geological evidence that during the Glacial epoch +the whole world was colder; I inferred that,... from erratic boulder +phenomena carefully observed by me on both the east and west coast of +South America. Now I am so bold as to believe that at the height of +the Glacial epoch, AND WHEN ALL TROPICAL PRODUCTIONS MUST HAVE BEEN +CONSIDERABLY DISTRESSED, several temperate forms slowly travelled into +the heart of the Tropics, and even reached the southern hemisphere; and +some few southern forms penetrated in a reverse direction northward." +("Life and Letters", II. page 136.) Here again it is clear that though +he credits Agassiz with having called vivid attention to the Glacial +period, he had himself much earlier grasped the idea of periods of +refrigeration. + +Putting aside the fact, which has only been made known to us since +Darwin's death, that he had anticipated Forbes, it is clear that he gave +the theory a generality of which the latter had no conception. This is +pointed out by Hooker in his classical paper "On the Distribution of +Arctic Plants" (1860). "The theory of a southern migration of northern +types being due to the cold epochs preceding and during the glacial, +originated, I believe, with the late Edward Forbes; the extended one, +of the trans-tropical migration, is Mr Darwin's." ("Linn. Trans." +XXIII. page 253. The attempt appears to have been made to claim for Heer +priority in what I may term for short the arctic-alpine theory (Scharff, +"European Animals", page 128). I find no suggestion of his having hit +upon it in his correspondence with Darwin or Hooker. Nor am I aware +of any reference to his having done so in his later publications. I +am indebted to his biographer, Professor Schroter, of Zurich, for an +examination of his earlier papers with an equally negative result.) +Assuming that local races have derived from a common ancestor, Hooker's +great paper placed the fact of the migration on an impregnable basis. +And, as he pointed out, Darwin has shown that "such an explanation meets +the difficulty of accounting for the restriction of so many American and +Asiatic arctic types to their own peculiar longitudinal zones, and for +what is a far greater difficulty, the representation of the same arctic +genera by most closely allied species in different longitudes." + +The facts of botanical geography were vital to Darwin's argument. He +had to show that they admitted of explanation without assuming multiple +origins for species, which would be fatal to the theory of Descent. He +had therefore to strengthen and extend De Candolle's work as to means +of transport. He refused to supplement them by hypothetical geographical +changes for which there was no independent evidence: this was simply to +attempt to explain ignotum per ignotius. He found a real and, as it has +turned out, a far-reaching solution in climatic change due to cosmical +causes which compelled the migration of species as a condition of their +existence. The logical force of the argument consists in dispensing with +any violent assumption, and in showing that the principle of descent is +adequate to explain the ascertained facts. + +It does not, I think, detract from the merit of Darwin's conclusions +that the tendency of modern research has been to show that the effects +of the Glacial period were less simple, more localised and less +general than he perhaps supposed. He admitted that "equatorial +refrigeration... must have been small." ("More Letters", I. page 177.) It +may prove possible to dispense with it altogether. One cannot but regret +that as he wrote to Bates:--"the sketch in the 'Origin' gives a very +meagre account of my fuller MS. essay on this subject." (Loc. cit.) +Wallace fully accepted "the effect of the Glacial epoch in bringing +about the present distribution of Alpine and Arctic plants in the +NORTHERN HEMISPHERE," but rejected "the lowering of the temperature of +the tropical regions during the Glacial period" in order to account for +their presence in the SOUTHERN hemisphere. ("More Letters", II. page 25 +(footnote 1).) The divergence however does not lie very deep. Wallace +attaches more importance to ordinary means of transport. "If plants can +pass in considerable numbers and variety over wide seas and oceans, it +must be yet more easy for them to traverse continuous areas of land, +wherever mountain-chains offer suitable stations." ("Island Life" (2nd +edition), London, 1895, page 512.) And he argues that such periodical +changes of climate, of which the Glacial period may be taken as a type, +would facilitate if not stimulate the process. (Loc. cit. page 518.) + +It is interesting to remark that Darwin drew from the facts of plant +distribution one of his most ingenious arguments in support of this +theory. (See "More Letters", I. page 424.) He tells us, "I was led to +anticipate that the species of the larger genera in each country would +oftener present varieties, than the species of the smaller genera." +("Origin", page 44.) He argues "where, if we may use the expression, the +manufactory of species has been active, we ought generally to find the +manufactory still in action." (Ibid. page 45.) This proved to be the +case. But the labour imposed upon him in the study was immense. He +tabulated local floras "belting the whole northern hemisphere" ("More +Letters", I. page 107.), besides voluminous works such as De Candolle's +"Prodromus". The results scarcely fill a couple of pages. This is a good +illustration of the enormous pains which he took to base any statement +on a secure foundation of evidence, and for this the world, till the +publication of his letters, could not do him justice. He was a great +admirer of Herbert Spencer, whose "prodigality of original thought" +astonished him. "But," he says, "the reflection constantly recurred to +me that each suggestion, to be of real value to service, would require +years of work." (Ibid. II. page 235.) + +At last the ground was cleared and we are led to the final conclusion. +"If the difficulties be not insuperable in admitting that in the long +course of time all the individuals of the same species belonging to +the same genus, have proceeded from some one source; then all the grand +leading facts of geographical distribution are explicable on the +theory of migration, together with subsequent modification and the +multiplication of new forms." ("Origin", page 360.) In this single +sentence Darwin has stated a theory which, as his son F. Darwin has said +with justice, has "revolutionized botanical geography." ("The Botanical +Work of Darwin", "Ann. Bot." 1899, page xi.) It explains how physical +barriers separate and form botanical regions; how allied species become +concentrated in the same areas; how, under similar physical conditions, +plants may be essentially dissimilar, showing that descent and not the +surroundings is the controlling factor; how insular floras have acquired +their peculiarities; in short how the most various and apparently +uncorrelated problems fall easily and inevitably into line. + +The argument from plant distribution was in fact irresistible. A proof, +if one were wanted, was the immediate conversion of what Hooker called +"the stern keen intellect" ("More Letters", I. page 134.) of Bentham, by +general consent the leading botanical systematist at the time. It is a +striking historical fact that a paper of his own had been set down for +reading at the Linnean Society on the same day as Darwin's, but had to +give way. In this he advocated the fixity of species. He withdrew it +after hearing Darwin's. We can hardly realise now the momentous effect +on the scientific thought of the day of the announcement of the new +theory. Years afterwards (1882) Bentham, notwithstanding his habitual +restraint, could not write of it without emotion. "I was forced, however +reluctantly, to give up my long-cherished convictions, the results of +much labour and study." The revelation came without preparation. Darwin, +he wrote, "never made any communications to me in relation to his +views and labours." But, he adds, "I... fully adopted his theories and +conclusions, notwithstanding the severe pain and disappointment they +at first occasioned me." ("Life and Letters", II. page 294.) Scientific +history can have few incidents more worthy. I do not know what is most +striking in the story, the pathos or the moral dignity of Bentham's +attitude. + +Darwin necessarily restricted himself in the "Origin" to establishing +the general principles which would account for the facts of +distribution, as a part of his larger argument, without attempting +to illustrate them in particular cases. This he appears to have +contemplated doing in a separate work. But writing to Hooker in 1868 +he said:--"I shall to the day of my death keep up my full interest +in Geographical Distribution, but I doubt whether I shall ever have +strength to come in any fuller detail than in the "Origin" to this grand +subject." ("More Letters", II. page 7.) This must be always a matter for +regret. But we may gather some indication of his later speculations from +the letters, the careful publication of which by F. Darwin has rendered +a service to science, the value of which it is difficult to exaggerate. +They admit us to the workshop, where we see a great theory, as it were, +in the making. The later ideas that they contain were not it is true +public property at the time. But they were communicated to the leading +biologists of the day and indirectly have had a large influence. + +If Darwin laid the foundation, the present fabric of Botanical Geography +must be credited to Hooker. It was a happy partnership. The far-seeing, +generalising power of the one was supplied with data and checked in +conclusions by the vast detailed knowledge of the other. It may be +permitted to quote Darwin's generous acknowledgment when writing the +"Origin":--"I never did pick any one's pocket, but whilst writing my +present chapter I keep on feeling (even when differing most from you) +just as if I were stealing from you, so much do I owe to your writings +and conversation, so much more than mere acknowledgements show." ("Life +and Letters", II. page 148 (footnote).) Fourteen years before he had +written to Hooker: "I know I shall live to see you the first authority +in Europe on... Geographical Distribution." (Ibid. I. page 336.) We owe +it to Hooker that no one now undertakes the flora of a country without +indicating the range of the species it contains. Bentham tells us: +"After De Candolle, independently of the great works of Darwin... the +first important addition to the science of geographical botany was that +made by Hooker in his "Introductory Essay to the Flora of Tasmania", +which, though contemporaneous only with the "Origin of Species", was +drawn up with a general knowledge of his friend's observations and +views." (Pres. Addr. (1869), "Proc. Linn. Soc." 1868-69, page lxxiv.) It +cannot be doubted that this and the great memoir on the "Distribution of +Arctic Plants" were only less epoch-making than the "Origin" itself, and +must have supplied a powerful support to the general theory of organic +evolution. + +Darwin always asserted his "entire ignorance of Botany." ("More +Letters", I. page 400.) But this was only part of his constant +half-humorous self-depreciation. He had been a pupil of Henslow, and it +is evident that he had a good working knowledge of systematic botany. He +could find his way about in the literature and always cites the names of +plants with scrupulous accuracy. It was because he felt the want of +such a work for his own researches that he urged the preparation of +the "Index Kewensis", and undertook to defray the expense. It has been +thought singular that he should have been elected a "correspondant" +of the Academie des Sciences in the section of Botany, but it is not +surprising that his work in Geographical Botany made the botanists +anxious to claim him. His heart went with them. "It has always pleased +me," he tells us, "to exalt plants in the scale of organised beings." +("Life and Letters", I. page 98.) And he declares that he finds "any +proposition more easily tested in botanical works (Ibid. II. page 99.) +than in zoological." + +In the "Introductory Essay" Hooker dwelt on the "continuous current of +vegetation from Scandinavia to Tasmania" ("Introductory Essay to the +Flora of Tasmania", London, 1859. Reprinted from the "Botany of the +Antarctic Expedition", Part III., "Flora of Tasmania", Vol I. page +ciii.), but finds little evidence of one in the reverse direction. +"In the New World, Arctic, Scandinavian, and North American genera and +species are continuously extended from the north to the south temperate +and even Antarctic zones; but scarcely one Antarctic species, or even +genus advances north beyond the Gulf of Mexico" (page civ.). Hooker +considered that this negatived "the idea that the Southern and Northern +Floras have had common origin within comparatively modern geological +epochs." (Loc. cit.) This is no doubt a correct conclusion. But it is +difficult to explain on Darwin's view alone, of alternating cold in the +two hemispheres, the preponderant migration from the north to the south. +He suggests, therefore, that it "is due to the greater extent of land +in the north and to the northern forms... having... been advanced through +natural selection and competition to a higher stage of perfection or +dominating power." ("Origin of Species" (6th edition), page 340; cf. +also "Life and Letters", II. page 142.) The present state of the Flora +of New Zealand affords a striking illustration of the correctness of +this view. It is poor in species, numbering only some 1400, of which +three-fourths are endemic. They seem however quite unable to resist the +invasion of new comers and already 600 species of foreign origin have +succeeded in establishing themselves. + +If we accept the general configuration of the earth's surface as +permanent a continuous and progressive dispersal of species from the +centre to the circumference, i.e. southwards, seems inevitable. If an +observer were placed above a point in St George's Channel from which +one half of the globe was visible he would see the greatest possible +quantity of land spread out in a sort of stellate figure. The maritime +supremacy of the English race has perhaps flowed from the central +position of its home. That such a disposition would facilitate a +centrifugal migration of land organisms is at any rate obvious, and +fluctuating conditions of climate operating from the pole would supply +an effective means of propulsion. As these became more rigorous animals +at any rate would move southwards to escape them. It would be equally +the case with plants if no insuperable obstacle interposed. This implies +a mobility in plants, notwithstanding what we know of means of transport +which is at first sight paradoxical. Bentham has stated this in a +striking way: "Fixed and immovable as is the individual plant, there is +no class in which the race is endowed with greater facilities for the +widest dispersion... Plants cast away their offspring in a dormant state, +ready to be carried to any distance by those external agencies which we +may deem fortuitous, but without which many a race might perish from the +exhaustion of the limited spot of soil in which it is rooted." (Pres. +Addr.(1869), "Proc. Linn. Soc." 1868-69, pages lxvi, lxvii.) + +I have quoted this passage from Bentham because it emphasises a point +which Darwin for his purpose did not find it necessary to dwell upon, +though he no doubt assumed it. Dispersal to a distance is, so to speak, +an accidental incident in the life of a species. Lepidium Draba, a +native of South-eastern Europe, owes its prevalence in the Isle of +Thanet to the disastrous Walcheren expedition; the straw-stuffing of the +mattresses of the fever-stricken soldiers who were landed there was used +by a farmer for manure. Sir Joseph Hooker ("Royal Institution Lecture", +April 12, 1878.) tells us that landing on Lord Auckland's Island, which +was uninhabited, "the first evidence I met with of its having been +previously visited by man was the English chickweed; and this I traced +to a mound that marked the grave of a British sailor, and that was +covered with the plant, doubtless the offspring of seed that had adhered +to the spade or mattock with which the grave had been dug." + +Some migration from the spot where the individuals of a species +have germinated is an essential provision against extinction. Their +descendants otherwise would be liable to suppression by more vigorous +competitors. But they would eventually be extinguished inevitably, +as pointed out by Bentham, by the exhaustion of at any rate some one +necessary constituent of the soil. Gilbert showed by actual analysis +that the production of a "fairy ring" is simply due to the using up +by the fungi of the available nitrogen in the enclosed area which +continually enlarges as they seek a fresh supply on the outside margin. +Anyone who cultivates a garden can easily verify the fact that every +plant has some adaptation for varying degrees of seed-dispersal. It +cannot be doubted that slow but persistent terrestrial migration has +played an enormous part in bringing about existing plant-distribution, +or that climatic changes would intensify the effect because they would +force the abandonment of a former area and the occupation of a new one. +We are compelled to admit that as an incident of the Glacial period a +whole flora may have moved down and up a mountain side, while only some +of its constituent species would be able to take advantage of means of +long-distance transport. + +I have dwelt on the importance of what I may call short-distance +dispersal as a necessary condition of plant life, because I think it +suggests the solution of a difficulty which leads Guppy to a conclusion +with which I am unable to agree. But the work which he has done taken as +a whole appears to me so admirable that I do so with the utmost respect. +He points out, as Bentham had already done, that long-distance dispersal +is fortuitous. And being so it cannot have been provided for by +previous adaptation. He says (Guppy, op. cit. II. page 99.): "It is not +conceivable that an organism can be adapted to conditions outside +its environment." To this we must agree; but, it may be asked, do the +general means of plant dispersal violate so obvious a principle? He +proceeds: "The great variety of the modes of dispersal of seeds is in +itself an indication that the dispersing agencies avail themselves in a +hap-hazard fashion of characters and capacities that have been developed +in other connections." (Loc. cit. page 102.) "Their utility in these +respects is an accident in the plant's life." (Loc. cit. page 100.) He +attributes this utility to a "determining agency," an influence which +constantly reappears in various shapes in the literature of Evolution +and is ultra-scientific in the sense that it bars the way to the search +for material causes. He goes so far as to doubt whether fleshy fruits +are an adaptation for the dispersal of their contained seeds. (Loc. cit. +page 102.) Writing as I am from a hillside which is covered by hawthorn +bushes sown by birds, I confess I can feel little doubt on the subject +myself. The essential fact which Guppy brings out is that long-distance +unlike short-distance dispersal is not universal and purposeful, but +selective and in that sense accidental. But it is not difficult to see +how under favouring conditions one must merge into the other. + +Guppy has raised one novel point which can only be briefly referred to +but which is of extreme interest. There are grounds for thinking that +flowers and insects have mutually reacted upon one another in their +evolution. Guppy suggests that something of the same kind may be true +of birds. I must content myself with the quotation of a single sentence. +"With the secular drying of the globe and the consequent differentiation +of climate is to be connected the suspension to a great extent of the +agency of birds as plant dispersers in later ages, not only in the +Pacific Islands but all over the tropics. The changes of climate, birds +and plants have gone on together, the range of the bird being controlled +by the climate, and the distribution of the plant being largely +dependent on the bird." (Loc.cit. II. page 221.) + +Darwin was clearly prepared to go further than Hooker in accounting for +the southern flora by dispersion from the north. Thus he says: "We must, +I suppose, admit that every yard of land has been successively covered +with a beech-forest between the Caucasus and Japan." ("More Letters", +II. page 9.) Hooker accounted for the dissevered condition of the +southern flora by geographical change, but this Darwin could not admit. +He suggested to Hooker that the Australian and Cape floras might have +had a point of connection through Abyssinia (Ibid. I. page 447.), an +idea which was promptly snuffed out. Similarly he remarked to Bentham +(1869): "I suppose you think that the Restiaceae, Proteaceae, etc., etc. +once extended over the whole world, leaving fragments in the south." +(Ibid. I. page 380.) Eventually he conjectured "that there must have +been a Tertiary Antarctic continent, from which various forms radiated +to the southern extremities of our present continents." ("Life and +Letters", III. page 231.) But characteristically he could not admit any +land connections and trusted to "floating ice for transporting seed." +("More Letters", I. page 116.) I am far from saying that this theory is +not deserving of serious attention, though there seems to be no positive +evidence to support it, and it immediately raises the difficulty how did +such a continent come to be stocked? + +We must, however, agree with Hooker that the common origin of the +northern and southern floras must be referred to a remote past. That +Darwin had this in his mind at the time of the publication of the +"Origin" is clear from a letter to Hooker. "The view which I should have +looked at as perhaps most probable (though it hardly differs from yours) +is that the whole world during the Secondary ages was inhabited by +marsupials, araucarias (Mem.--Fossil wood of this nature in South +America), Banksia, etc.; and that these were supplanted and exterminated +in the greater area of the north, but were left alive in the south." +(Ibid. I. page 453.) Remembering that Araucaria, unlike Banksia, belongs +to the earlier Jurassic not to the angiospermous flora, this view is a +germinal idea of the widest generality. + +The extraordinary congestion in species of the peninsulas of the Old +World points to the long-continued action of a migration southwards. +Each is in fact a cul-de-sac into which they have poured and from which +there is no escape. On the other hand the high degree of specialisation +in the southern floras and the little power the species possess of +holding their own in competition or in adaptation to new conditions +point to long-continued isolation. "An island... will prevent free +immigration and competition, hence a greater number of ancient forms +will survive." (Ibid. I. page 481.) But variability is itself subject to +variation. The nemesis of a high degree of protected specialisation is +the loss of adaptability. (See Lyell, "The Geological Evidences of the +Antiquity of Man", London, 1863, page 446.) It is probable that many +elements of the southern flora are doomed: there is, for example, reason +to think that the singular Stapelieae of S. Africa are a disappearing +group. The tree Lobelias which linger in the mountains of Central +Africa, in Tropical America and in the Sandwich Islands have the aspect +of extreme antiquity. I may add a further striking illustration from +Professor Seward: "The tall, graceful fronds of Matonia pectinata, +forming miniature forests on the slopes of Mount Ophir and other +districts in the Malay Peninsula in association with Dipteris conjugata +and Dipteris lobbiana, represent a phase of Mesozoic life which survives +'Like a dim picture of the drowned past.'" ("Report of the 73rd Meeting +of the British Assoc." (Southport, 1903), London, 1904, page 844.) + +The Matonineae are ferns with an unusually complex vascular system and +were abundant "in the northern hemisphere during the earlier part of the +Mesozoic era." + +It was fortunate for science that Wallace took up the task which his +colleague had abandoned. Writing to him on the publication of his +"Geographical Distribution of Animals" Darwin said: "I feel sure +that you have laid a broad and safe foundation for all future work on +Distribution. How interesting it will be to see hereafter plants treated +in strict relation to your views." ("More Letters", II. page 12.) This +hope was fulfilled in "Island Life". I may quote a passage from it which +admirably summarises the contrast between the northern and the southern +floras. + +"Instead of the enormous northern area, in which highly organised +and dominant groups of plants have been developed gifted with +great colonising and aggressive powers, we have in the south three +comparatively small and detached areas, in which rich floras have +been developed with SPECIAL adaptations to soil, climate, and organic +environment, but comparatively impotent and inferior beyond their own +domain." (Wallace, "Island Life", pages 527, 528.) + +It will be noticed that in the summary I have attempted to give of the +history of the subject, efforts have been concentrated on bringing into +relation the temperate floras of the northern and southern hemispheres, +but no account has been taken of the rich tropical vegetation which +belts the world and little to account for the original starting-point +of existing vegetation generally. It must be remembered on the one hand +that our detailed knowledge of the floras of the tropics is still very +incomplete and far inferior to that of temperate regions; on the other +hand palaeontological discoveries have put the problem in an entirely +new light. Well might Darwin, writing to Heer in 1875, say: "Many +as have been the wonderful discoveries in Geology during the last +half-century, I think none have exceeded in interest your results with +respect to the plants which formerly existed in the arctic regions." +("More Letters", II. page 240.) + +As early as 1848 Debey had described from the Upper Cretaceous rocks of +Aix-la-Chapelle Flowering plants of as high a degree of development +as those now existing. The fact was commented upon by Hooker ("Introd. +Essay to the Flora of Tasmania", page xx.), but its full significance +seems to have been scarcely appreciated. For it implied not merely that +their evolution must have taken place but the foundations of existing +distribution must have been laid in a preceding age. We now know +from the discoveries of the last fifty years that the remains of the +Neocomian flora occur over an area extending through 30 deg of latitude. +The conclusion is irresistible that within this was its centre of +distribution and probably of origin. + +Darwin was immensely impressed with the outburst on the world of a +fully fledged angiospermous vegetation. He warmly approved the brilliant +theory of Saporta that this happened "as soon (as) flower-frequenting +insects were developed and favoured intercrossing." ("More Letters", II. +page 21.) Writing to him in 1877 he says: "Your idea that dicotyledonous +plants were not developed in force until sucking insects had been +evolved seems to me a splendid one. I am surprised that the idea never +occurred to me, but this is always the case when one first hears a +new and simple explanation of some mysterious phenomenon." ("Life +and Letters", III. page 285. Substantially the same idea had +occurred earlier to F.W.A. Miquel. Remarking that "sucking insects +(Haustellata)... perform in nature the important duty of maintaining the +existence of the vegetable kingdom, at least as far as the higher orders +are concerned," he points our that "the appearance in great numbers of +haustellate insects occurs at and after the Cretaceous epoch, when +the plants with pollen and closed carpels (Angiosperms) are found, and +acquire little by little the preponderance in the vegetable kingdom." +"Archives Neerlandaises", III. (1868). English translation in "Journ. of +Bot." 1869, page 101.) + +Even with this help the abruptness still remains an almost insoluble +problem, though a forecast of floral structure is now recognised in some +Jurassic and Lower Cretaceous plants. But the gap between this and the +structural complexity and diversity of angiosperms is enormous. Darwin +thought that the evolution might have been accomplished during a period +of prolonged isolation. Writing to Hooker (1881) he says: "Nothing is +more extraordinary in the history of the Vegetable Kingdom, as it seems +to me, than the APPARENTLY very sudden or abrupt development of the +higher plants. I have sometimes speculated whether there did not exist +somewhere during long ages an extremely isolated continent, perhaps near +the South Pole." ("Life and Letters", III. page 248.) + +The present trend of evidence is, however, all in favour of a northern +origin for flowering plants, and we can only appeal to the imperfection +of the geological record as a last resource to extricate us from the +difficulty of tracing the process. But Darwin's instinct that at some +time or other the southern hemisphere had played an important part in +the evolution of the vegetable kingdom did not mislead him. Nothing +probably would have given him greater satisfaction than the masterly +summary in which Seward has brought together the evidence for the origin +of the Glossopteris flora in Gondwana land. + +"A vast continental area, of which remnants are preserved in Australia, +South Africa and South America... A tract of enormous extent occupying +an area, part of which has since given place to a southern ocean, while +detached masses persist as portions of more modern continents, which +have enabled us to read in their fossil plants and ice-scratched +boulders the records of a lost continent, in which the Mesozoic +vegetation of the northern continent had its birth." ("Encycl. Brit." +(10th edition 1902), Vol. XXXI. ("Palaeobotany; Mesozoic"), page 422.) +Darwin would probably have demurred on physical grounds to the extent +of the continent, and preferred to account for the transoceanic +distribution of its flora by the same means which must have accomplished +it on land. + +It must in fairness be added that Guppy's later views give some support +to the conjectural existence of the "lost continent." "The distribution +of the genus Dammara" (Agathis) led him to modify his earlier +conclusions. He tells us:--"In my volume on the geology of Vanua Levu +it was shown that the Tertiary period was an age of submergence in the +Western Pacific, and a disbelief in any previous continental condition +was expressed. My later view is more in accordance with that of +Wichmann, who, on geological grounds, contended that the islands of the +Western Pacific were in a continental condition during the Palaeozoic +and Mesozoic periods, and that their submergence and subsequent +emergence took place in Tertiary times." (Guppy, op. cit. II. page 304.) + +The weight of the geological evidence I am unable to scrutinise. But +though I must admit the possibility of some unconscious bias in my +own mind on the subject, I am impressed with the fact that the known +distribution of the Glossopteris flora in the southern hemisphere is +precisely paralleled by that of Proteaceae and Restiaceae in it at the +present time. It is not unreasonable to suppose that both phenomena, +so similar, may admit of the same explanation. I confess it would not +surprise me if fresh discoveries in the distribution of the Glossopteris +flora were to point to the possibility of its also having migrated +southwards from a centre of origin in the northern hemisphere. + +Darwin, however, remained sceptical "about the travelling of plants +from the north EXCEPT DURING THE TERTIARY PERIOD." But he added, "such +speculations seem to me hardly scientific, seeing how little we know +of the old floras." ("Life and Letters", III. page 247.) That in later +geological times the south has been the grave of the weakened offspring +of the aggressive north can hardly be doubted. But if we look to the +Glossopteris flora for the ancestry of Angiosperms during the Secondary +period, Darwin's prevision might be justified, though he has given us no +clue as to how he arrived at it. + +It may be true that technically Darwin was not a botanist. But in two +pages of the "Origin" he has given us a masterly explanation of "the +relationship, with very little identity, between the productions of +North America and Europe." (Pages 333, 334.) He showed that this could +be accounted for by their migration southwards from a common area, and +he told Wallace that he "doubted much whether the now called Palaearctic +and Neartic regions ought to be separated." ("Life and Letters", III. +page 230.) Catkin-bearing deciduous trees had long been seen to justify +Darwin's doubt: oaks, chestnuts, beeches, hazels, hornbeams, birches, +alders, willows and poplars are common both to the Old and New World. +Newton found that the separate regions could not be sustained for birds, +and he is now usually followed in uniting them as the Holartic. One +feels inclined to say in reading the two pages, as Lord Kelvin did to +a correspondent who asked for some further development of one of his +papers, It is all there. We have only to apply the principle to previous +geological ages to understand why the flora of the Southern United +States preserves a Cretaceous facies. Applying it still further we can +understand why, when the northern hemisphere gradually cooled through +the Tertiary period, the plants of the Eocene "suggest a comparison of +the climate and forests with those of the Malay Archipelago and Tropical +America." (Clement Reid, "Encycl. Brit." (10th edition), Vol. XXXI. +("Palaeobotany; Tertiary"), page 435.) Writing to Asa Gray in 1856 +with respect to the United States flora, Darwin said that "nothing has +surprised me more than the greater generic and specific affinity with +East Asia than with West America." ("More Letters", I. page 434.) The +recent discoveries of a Tulip tree and a Sassafras in China afford fresh +illustrations. A few years later Asa Gray found the explanation in +both areas being centres of preservation of the Cretaceous flora from +a common origin. It is interesting to note that the paper in which this +was enunciated at once established his reputation. + +In Europe the latitudinal range of the great mountain chains gave the +Miocene flora no chance of escape during the Glacial period, and the +Mediterranean appears to have equally intercepted the flow of alpine +plants to the Atlas. (John Ball in Appendix G, page 438, in "Journal of +a Tour in Morocco and the Great Atlas", J.D. Hooker and J. Ball, London, +1878.) In Southern Europe the myrtle, the laurel, the fig and the +dwarf-palm are the sole representatives of as many great tropical +families. Another great tropical family, the Gesneraceae has left single +representatives from the Pyrenees to the Balkans; and in the former +a diminutive yam still lingers. These are only illustrations of the +evidence which constantly accumulates and which finds no rational +explanation except that which Darwin has given to it. + +The theory of southward migration is the key to the interpretation of +the geographical distribution of plants. It derived enormous support +from the researches of Heer and has now become an accepted commonplace. +Saporta in 1888 described the vegetable kingdom as "emigrant pour suivre +une direction determinee et marcher du nord au sud, a la recherche +de regions et de stations plus favorables, mieux appropriees aux +adaptations acquises, a meme que la temperature terrestre perd ses +conditions premieres." ("Origine Paleontologique des arbres", Paris, +1888, page 28.) If, as is so often the case, the theory now seems to be +a priori inevitable, the historian of science will not omit to record +that the first germ sprang from the brain of Darwin. + +In attempting this sketch of Darwin's influence on Geographical +Distribution, I have found it impossible to treat it from an external +point of view. His interest in it was unflagging; all I could say became +necessarily a record of that interest and could not be detached from it. +He was in more or less intimate touch with everyone who was working +at it. In reading the letters we move amongst great names. With an +extraordinary charm of persuasive correspondence he was constantly +suggesting, criticising and stimulating. It is hardly an exaggeration +to say that from the quiet of his study at Down he was founding and +directing a wide-world school. + +POSTSCRIPTUM. + +Since this essay was put in type Dr Ernst's striking account of the "New +Flora of the Volcanic Island of Krakatau" (Cambridge, 1909.) has reached +me. All botanists must feel a debt of gratitude to Prof. Seward for +his admirable translation of a memoir which in its original form +is practically unprocurable and to the liberality of the Cambridge +University Press for its publication. In the preceding pages I have +traced the laborious research by which the methods of Plant Dispersal +were established by Darwin. In the island of Krakatau nature has +supplied a crucial experiment which, if it had occurred earlier, would +have at once secured conviction of their efficiency. A quarter of a +century ago every trace of organic life in the island was "destroyed +and buried under a thick covering of glowing stones." Now, it is "again +covered with a mantle of green, the growth being in places so +luxuriant that it is necessary to cut one's way laboriously through the +vegetation." (Op. cit. page 4.) Ernst traces minutely how this has been +brought about by the combined action of wind, birds and sea currents, +as means of transport. The process will continue, and he concludes:--"At +last after a long interval the vegetation on the desolated island will +again acquire that wealth of variety and luxuriance which we see in the +fullest development which Nature has reached in the primaeval forest +in the tropics." (Op. cit. page 72.) The possibility of such a result +revealed itself to the insight of Darwin with little encouragement or +support from contemporary opinion. + +One of the most remarkable facts established by Ernst is that this has +not been accomplished by the transport of seeds alone. "Tree stems and +branches played an important part in the colonisation of Krakatau by +plants and animals. Large piles of floating trees, stems, branches and +bamboos are met with everywhere on the beach above high-water mark and +often carried a considerable distance inland. Some of the animals on the +island, such as the fat Iguana (Varanus salvator) which suns itself in +the beds of streams, may have travelled on floating wood, possibly also +the ancestors of the numerous ants, but certainly plants." (Op. cit. +page 56.) Darwin actually had a prevision of this. Writing to Hooker he +says:--"Would it not be a prodigy if an unstocked island did not in the +course of ages receive colonists from coasts whence the currents flow, +trees are drifted and birds are driven by gales?" ("More Letters", I. +page 483.) And ten years earlier:--"I must believe in the... whole +plant or branch being washed into the sea; with floods and slips and +earthquakes; this must continually be happening." ("Life and Letters", +II. pages 56, 57.) If we give to "continually" a cosmic measure, can the +fact be doubted? All this, in the light of our present knowledge, is too +obvious to us to admit of discussion. But it seems to me nothing less +than pathetic to see how in the teeth of the obsession as to continental +extension, Darwin fought single-handed for what we now know to be the +truth. + +Guppy's heart failed him when he had to deal with the isolated case of +Agathis which alone seemed inexplicable by known means of transport. But +when we remember that it is a relic of the pre-Angiospermous flora, and +is of Araucarian ancestry, it cannot be said that the impossibility, +in so prolonged a history, of the bodily transference of cone-bearing +branches or even of trees, compels us as a last resort to fall back on +continental extension to account for its existing distribution. + +When Darwin was in the Galapagos Archipelago, he tells us that he +fancied himself "brought near to the very act of creation." He saw +how new species might arise from a common stock. Krakatau shows us an +earlier stage and how by simple agencies, continually at work, that +stock might be supplied. It also shows us how the mixed and casual +elements of a new colony enter into competition for the ground and +become mutually adjusted. The study of Plant Distribution from a +Darwinian standpoint has opened up a new field of research in Ecology. +The means of transport supply the materials for a flora, but their +ultimate fate depends on their equipment for the "struggle for +existence." The whole subject can no longer be regarded as a mere +statistical inquiry which has seemed doubtless to many of somewhat arid +interest. The fate of every element of the earth's vegetation has sooner +or later depended on its ability to travel and to hold its own under +new conditions. And the means by which it has secured success is an +each case a biological problem which demands and will reward the most +attentive study. This is the lesson which Darwin has bequeathed to us. +It is summed up in the concluding paragraph of the "Origin" ("Origin of +Species" (6th edition), page 429.):--"It is interesting to contemplate a +tangled bank, clothed with many plants of many kinds, with birds singing +on the bushes, with various insects flitting about, and with worms +crawling through the damp earth, and to reflect that these elaborately +constructed forms, so different from each other, and dependent upon +each other in so complex a manner, have all been produced by laws acting +around us." + + + + +XVII. GEOGRAPHICAL DISTRIBUTION OF ANIMALS. By Hans Gadow, M.A., Ph.D., +F.R.S. + +Strickland Curator and Lecturer on Zoology in the University of +Cambridge. + + +The first general ideas about geographical distribution may be found +in some of the brilliant speculations contained in Buffon's "Histoire +Naturelle". The first special treatise on the subject was however +written in 1777 by E.A.W. Zimmermann, Professor of Natural Science +at Brunswick, whose large volume, "Specimen Zoologiae Geographicae +Quadrupedum"..., deals in a statistical way with the mammals; important +features of the large accompanying map of the world are the ranges +of mountains and the names of hundreds of genera indicating their +geographical range. In a second work he laid special stress on +domesticated animals with reference to the spreading of the various +races of Mankind. + +In the following year appeared the "Philosophia Entomologica" by J.C. +Fabricius, who was the first to divide the world into eight regions. In +1803 G.R. Treviranus ("Biologie oder Philosophie der lebenden Natur", +Vol. II. Gottingen, 1803.) devoted a long chapter of his great work on +"Biologie" to a philosophical and coherent treatment of the distribution +of the whole animal kingdom. Remarkable progress was made in 1810 by F. +Tiedemann ("Anatomie und Naturgeschichte der Vogel". Heidelberg, 1810.) +of Heidelberg. Few, if any, of the many subsequent Ornithologists seem +to have appreciated, or known of, the ingenious way in which Tiedemann +marshalled his statistics in order to arrive at general conclusions. +There are, for instance, long lists of birds arranged in accordance +with their occurrence in one or more continents: by correlating the +distribution of the birds with their food he concludes "that the +countries of the East Indian flora have no vegetable feeders in common +with America," and "that it is probably due to the great peculiarity of +the African flora that Africa has few phytophagous kinds in common with +other countries, whilst zoophagous birds have a far more independent, +often cosmopolitan, distribution." There are also remarkable chapters +on the influence of environment, distribution, and migration, upon the +structure of the Birds! In short, this anatomist dealt with some of the +fundamental causes of distribution. + +Whilst Tiedemann restricted himself to Birds, A. Desmoulins in 1822 +wrote a short but most suggestive paper on the Vertebrata, omitting +the birds; he combated the view recently proposed by the entomologist +Latreille that temperature was the main factor in distribution. Some of +his ten main conclusions show a peculiar mixture of evolutionary ideas +coupled with the conception of the stability of species: whilst each +species must have started from but one creative centre, there may be +several "analogous centres of creation" so far as genera and families +are concerned. Countries with different faunas, but lying within the +same climatic zones, are proof of the effective and permanent existence +of barriers preventing an exchange between the original creative +centres. + +The first book dealing with the "geography and classification" of the +whole animal kingdom was written by W. Swainson ("A Treatise on +the Geography and Classification of Animals", Lardner's "Cabinet +Cyclopaedia" London, 1835.) in 1835. He saw in the five races of Man +the clue to the mapping of the world into as many "true zoological +divisions," and he reconciled the five continents with his mystical +quinary circles. + +Lyell's "Principles of Geology" should have marked a new epoch, since +in his "Elements" he treats of the past history of the globe and the +distribution of animals in time, and in his "Principles" of their +distribution in space in connection with the actual changes undergone by +the surface of the world. But as the sub-title of his great work "Modern +changes of the Earth and its inhabitants" indicates, he restricted +himself to comparatively minor changes, and, emphatically believing +in the permanency of the great oceans, his numerous and careful +interpretations of the effect of the geological changes upon the +dispersal of animals did after all advance the problem but little. + +Hitherto the marine faunas had been neglected. This was remedied by E. +Forbes, who established nine homozoic zones, based mainly on the study +of the mollusca, the determining factors being to a great extent +the isotherms of the sea, whilst the 25 provinces were given by the +configuration of the land. He was followed by J.D. Dana, who, taking +principally the Crustacea as a basis, and as leading factors the mean +temperatures of the coldest and of the warmest months, established +five latitudinal zones. By using these as divisors into an American, +Afro-European, Oriental, Arctic and Antarctic realm, most of which were +limited by an eastern and western land-boundary, he arrived at about +threescore provinces. + +In 1853 appeared L.K. Schmarda's ("Die geographische Verbreitung der +Thiere", Wien, 1853.) two volumes, embracing the whole subject. Various +centres of creation being, according to him, still traceable, he formed +the hypothesis that these centres were originally islands, which later +became enlarged and joined together to form the great continents, so +that the original faunas could overlap and mix whilst still remaining +pure at their respective centres. After devoting many chapters to the +possible physical causes and modes of dispersal, he divided the land +into 21 realms which he shortly characterises, e.g. Australia as the +only country inhabited by marsupials, monotremes and meliphagous birds. +Ten main marine divisions were diagnosed in a similar way. Although some +of these realms were not badly selected from the point of view of being +applicable to more than one class of animals, they were obviously too +numerous for general purposes, and this drawback was overcome, in 1857, +by P.L. Sclater. ("On the general Geographical Distribution of the +members of the class Aves", "Proc. Linn. Soc." (Zoology II. 1858, pages +130-145.)) Starting with the idea, that "each species must have been +created within and over the geographical area, which it now occupies," +he concluded "that the most natural primary ontological divisions of the +Earth's surface" were those six regions, which since their adoption +by Wallace in his epoch-making work, have become classical. Broadly +speaking, these six regions are equivalent to the great masses of land; +they are convenient terms for geographical facts, especially since the +Palaearctic region expresses the unity of Europe with the bulk of Asia. +Sclater further brigaded the regions of the Old World as Palaeogaea and +the two Americas as Neogaea, a fundamental mistake, justifiable to a +certain extent only since he based his regions mainly upon the present +distribution of the Passerine birds. + +Unfortunately these six regions are not of equal value. The Indian +countries and the Ethiopian region (Africa south of the Sahara) are +obviously nothing but the tropical, southern continuations or appendages +of one greater complex. Further, the great eastern mass of land is so +intimately connected with North America that this continent has much +more in common with Europe and Asia than with South America. Therefore, +instead of dividing the world longitudinally as Sclater had done, +Huxley, in 1868 ("On the classification and distribution of the +Alectoromorphae and Heteromorphae", "Proc. Zool. Soc." 1868, page +294.), gave weighty reasons for dividing it transversely. Accordingly +he established two primary divisions, Arctogaea or the North world in +a wider sense, comprising Sclater's Indian, African, Palaearctic and +Neartic regions; and Notogaea, the Southern world, which he divided +into (1) Austro-Columbia (an unfortunate substitute for the neotropical +region), (2) Australasia, and (3) New Zealand, the number of big regions +thus being reduced to three but for the separation of New Zealand upon +rather negative characters. Sclater was the first to accept these four +great regions and showed, in 1874 ("The geographical distribution of +Mammals", "Manchester Science Lectures", 1874.), that they were well +borne out by the present distribution of the Mammals. + +Although applicable to various other groups of animals, for instance to +the tailless Amphibia and to Birds (Huxley himself had been led to found +his two fundamental divisions on the distribution of the Gallinaceous +birds), the combination of South America with Australia was gradually +found to be too sweeping a measure. The obvious and satisfactory +solution was provided by W.T. Blanford (Anniversary address (Geological +Society, 1889), "Proc. Geol. Soc." 1889-90, page 67; "Quart. Journ." +XLVI 1890.), who in 1890 recognised three main divisions, namely +Australian, South American, and the rest, for which the already existing +terms (although used partly in a new sense, as proposed by an anonymous +writer in "Natural Science", III. page 289) "Notogaea," "Neogaea" and +"Arctogaea" have been gladly accepted by a number of English writers. + +After this historical survey of the search for larger and largest or +fundamental centres of animal creation, which resulted in the mapping +of the world into zoological regions and realms of after all doubtful +value, we have to return to the year 1858. The eleventh and twelfth +chapters of "The Origin of Species" (1859), dealing with "Geographical +Distribution," are based upon a great amount of observation, experiment +and reading. As Darwin's main problem was the origin of species, +nature's way of making species by gradual changes from others previously +existing, he had to dispose of the view, held universally, of the +independent creation of each species and at the same time to insist upon +a single centre of creation for each species; and in order to emphasise +his main point, the theory of descent, he had to disallow convergent, or +as they were then called, analogous forms. To appreciate the difficulty +of his position we have to take the standpoint of fifty years ago, when +the immutability of the species was an axiom and each was supposed to +have been created within or over the geographical area which it now +occupies. If he once admitted that a species could arise from many +individuals instead of from one pair, there was no way of shutting the +door against the possibility that these individuals may have been so +numerous that they occupied a very large district, even so large that +it had become as discontinuous as the distribution of many a species +actually is. Such a concession would at once be taken as an admission of +multiple, independent, origin instead of descent in Darwin's sense. + +For the so-called multiple, independently repeated creation of species +as an explanation of their very wide and often quite discontinuous +distribution, he substituted colonisation from the nearest and readiest +source together with subsequent modification and better adaptation to +their new home. + +He was the first seriously to call attention to the many accidental +means, "which more properly should be called occasional means of +distribution," especially to oceanic islands. His specific, even +individual, centres of creation made migrations all the more necessary, +but their extent was sadly baulked by the prevailing dogma of the +permanency of the oceans. Any number of small changes ("many islands +having existed as halting places, of which not a wreck now remains" +("The Origin of Species" (1st edition), page 396.).) were conceded +freely, but few, if any, great enough to permit migration of truly +terrestrial creatures. The only means of getting across the gaps was by +the principle of the "flotsam and jetsam," a theory which Darwin took +over from Lyell and further elaborated so as to make it applicable to +many kinds of plants and animals, but sadly deficient, often grotesque, +in the case of most terrestrial creatures. + +Another very fertile source was Darwin's strong insistence upon the +great influence which the last glacial epoch must have had upon the +distribution of animals and plants. Why was the migration of northern +creatures southwards of far-reaching and most significant importance? +More northerners have established themselves in southern lands than +vice versa, because there is such a great mass of land in the north +and greater continents imply greater intensity of selection. "The +productions of real islands have everywhere largely yielded to +continental forms." (Ibid. page 380.)... "The Alpine forms have almost +everywhere largely yielded to the more dominant forms generated in the +larger areas and more efficient workshops of the North." + +Let us now pass in rapid survey the influence of the publication of "The +Origin of Species" upon the study of Geographical Distribution in its +wider sense. + +Hitherto the following thought ran through the minds of most writers: +Wherever we examine two or more widely separated countries their +respective faunas are very different, but where two faunas can come into +contact with each other, they intermingle. Consequently these faunas +represent centres of creation, whence the component creatures have +spread peripherally so far as existing boundaries allowed them to do so. +This is of course the fundamental idea of "regions." There is not one +of the numerous writers who considered the possibility that these +intermediate belts might represent not a mixture of species but +transitional forms, the result of changes undergone by the most +peripheral migrants in adaptation to their new surroundings. The usual +standpoint was also that of Pucheran ("Note sur l'equateur zoologique", +"Rev. et Mag. de Zoologie", 1855; also several other papers, ibid. 1865, +1866, and 1867.) in 1855. But what a change within the next ten years! +Pucheran explains the agreement in coloration between the desert and +its fauna as "une harmonie post-etablie"; the Sahara, formerly a marine +basin, was peopled by immigrants from the neighbouring countries, and +these new animals adapted themselves to the new environment. He also +discusses, among other similar questions, the Isthmus of Panama with +regard to its having once been a strait. From the same author may be +quoted the following passage as a strong proof of the new influence: +"By the radiation of the contemporaneous faunas, each from one centre, +whence as the various parts of the world successively were formed and +became habitable, they spread and became modified according to the local +physical conditions." + +The "multiple" origin of each species as advocated by Sclater and +Murray, although giving the species a broader basis, suffered from the +same difficulties. There was only one alternative to the old +orthodox view of independent creation, namely the bold acceptance of +land-connections to an extent for which geological and palaeontological +science was not yet ripe. Those who shrank from either view, gave up +the problem as mysterious and beyond the human intellect. This was the +expressed opinion of men like Swainson, Lyell and Humboldt. Only Darwin +had the courage to say that the problem was not insoluble. If we admit +"that in the long course of time the individuals of the same species, +and likewise of allied species, have proceeded from some one source; +then I think all the grand leading facts of geographical distribution +are explicable on the theory of migration... together with subsequent +modification and the multiplication of new forms." We can thus +understand how it is that in some countries the inhabitants "are linked +to the extinct beings which formerly inhabited the same continent." +We can see why two areas, having nearly the same physical conditions, +should often be inhabited by very different forms of life,... and "we can +see why in two areas, however distant from each other, there should be a +correlation, in the presence of identical species... and of distinct but +representative species." ("The Origin of Species" (1st edition), pages +408, 409.) + +Darwin's reluctance to assume great geological changes, such as a +land-connection of Europe with North America, is easily explained by the +fact that he restricted himself to the distribution of the present and +comparatively recent species. "I do not believe that it will ever be +proved that within the recent period continents which are now quite +separate, have been continuously, or almost continuously, united with +each other, and with the many existing oceanic islands." (Ibid. page +357.) Again, "believing... that our continents have long remained in +nearly the same relative position, though subjected to large, but +partial oscillations of level," that means to say within the period of +existing species, or "within the recent period." (Ibid. page. 370.) The +difficulty was to a great extent one of his own making. Whilst almost +everybody else believed in the immutability of the species, which +implies an enormous age, logically since the dawn of creation, to him +the actually existing species as the latest results of evolution, were +necessarily something very new, so young that only the very latest of +the geological epochs could have affected them. It has since come to +our knowledge that a great number of terrestrial "recent" species, even +those of the higher classes of Vertebrates, date much farther back than +had been thought possible. Many of them reach well into the Miocene, a +time since which the world seems to have assumed the main outlines of +the present continents. + +In the year 1866 appeared A. Murray's work on the "Geographical +Distribution of Mammals", a book which has perhaps received less +recognition than it deserves. His treatment of the general introductory +questions marks a considerable advance of our problem, although, and +partly because, he did not entirely agree with Darwin's views as laid +down in the first edition of "The Origin of Species", which after all +was the great impulse given to Murray's work. Like Forbes he did not +shrink from assuming enormous changes in the configuration of the +continents and oceans because the theory of descent, with its necessary +postulate of great migrations, required them. He stated, for instance, +"that a Miocene Atlantis sufficiently explains the common distribution +of animals and plants in Europe and America up to the glacial epoch." +And next he considers how, and by what changes, the rehabilitation and +distribution of these lands themselves were effected subsequent to +that period. Further, he deserves credit for having cleared up a +misunderstanding of the idea of specific centres of creation. Whilst for +instance Schmarda assumed without hesitation that the same species, +if occurring at places separated by great distances, or apparently +insurmountable barriers, had been there created independently (multiple +centres), Lyell and Darwin held that each species had only one single +centre, and with this view most of us agree, but their starting point +was to them represented by one individual, or rather one single pair. +According to Murray, on the other hand, this centre of a species is +formed by all the individuals of a species, all of which equally undergo +those changes which new conditions may impose upon them. In this respect +a new species has a multiple origin, but this in a sense very different +from that which was upheld by L. Agassiz. As Murray himself puts it: "To +my multiple origin, communication and direct derivation is essential. +The species is compounded of many influences brought together through +many individuals, and distilled by Nature into one species; and, being +once established it may roam and spread wherever it finds the conditions +of life not materially different from those of its original centre." +(Murray, "The Geographical Distribution of Mammals", page 14. London, +1866.) This declaration fairly agrees with more modern views, and +it must be borne in mind that the application of the single-centre +principle to the genera, families and larger groups in the search for +descent inevitably leads to one creative centre for the whole animal +kingdom, a condition as unwarrantable as the myth of Adam and Eve being +the first representatives of Mankind. + +It looks as if it had required almost ten years for "The Origin +of Species" to show its full effect, since the year 1868 marks the +publication of Haeckel's "Naturliche Schoepfungsgeschichte" in addition +to other great works. The terms "Oecology" (the relation of organisms +to their environment) and "Chorology" (their distribution in space) had +been given us in his "Generelle Morphologie" in 1866. The fourteenth +chapter of the "History of Creation" is devoted to the distribution of +organisms, their chorology, with the emphatic assertion that "not +until Darwin can chorology be spoken of as a separate science, since +he supplied the acting causes for the elucidation of the hitherto +accumulated mass of facts." A map (a "hypothetical sketch") shows the +monophyletic origin and the routes of distribution of Man. + +Natural Selection may be all-mighty, all-sufficient, but it requires +time, so much that the countless aeons required for the evolution of the +present fauna were soon felt to be one of the most serious drawbacks of +the theory. Therefore every help to ease and shorten this process should +have been welcomed. In 1868 M. Wagner (The first to formulate clearly +the fundamental idea of a theory of migration and its importance in +the origin of new species was L. von Buch, who in his "Physikalische +Beschreibung der Canarischen Inseln", written in 1825, wrote as follows: +"Upon the continents the individuals of the genera by spreading far, +form, through differences of the locality, food and soil, varieties +which finally become constant as new species, since owing to the +distances they could never be crossed with other varieties and thus +be brought back to the main type. Next they may again, perhaps upon +different roads, return to the old home where they find the old +type likewise changed, both having become so different that they can +interbreed no longer. Not so upon islands, where the individuals shut +up in narrow valleys or within narrow districts, can always meet one +another and thereby destroy every new attempt towards the fixing of a +new variety." Clearly von Buch explains here why island types remain +fixed, and why these types themselves have become so different from +their continental congeners.--Actually von Buch is aware of a most +important point, the difference in the process of development which +exists between a new species b, which is the result of an ancestral +species a having itself changed into b and thereby vanished itself, and +a new species c which arose through separation out of the same ancestral +a, which itself persists as such unaltered. Von Buch's prophetic view +seems to have escaped Lyell's and even Wagner's notice.) came to the +rescue with his "Darwin'sche Theorie und das Migrations-Gesetz der +Organismen". (Leipzig, 1868.) He shows that migration, i.e. change of +locality, implies new environmental conditions (never mind whether +these be new stimuli to variation, or only acting as their selectors or +censors), and moreover secures separation from the original stock and +thus eliminates or lessens the reactionary dangers of panmixia. Darwin +accepted Wagner's theory as "advantageous." Through the heated polemics +of the more ardent selectionists Wagner's theory came to grow into an +alternative instead of a help to the theory of selectional evolution. +Separation is now rightly considered a most important factor by modern +students of geographical distribution. + +For the same year, 1868, we have to mention Huxley, whose Arctogaea and +Notogaea are nothing less than the reconstructed main masses of land +of the Mesozoic period. Beyond doubt the configuration of land at that +remote period has left recognisable traces in the present continents, +but whether they can account for the distribution of such a much later +group as the Gallinaceous birds is more than questionable. In any case +he took for his text a large natural group of birds, cosmopolitan as +a whole, but with a striking distribution. The Peristeropodes, or +pigeon-footed division, are restricted to the Australian and Neotropical +regions, in distinction to the Alectoropodes (with the hallux inserted +at a level above the front toes) which inhabit the whole of the +Arctogaea, only a few members having spread into the South World. +Further, as Asia alone has its Pheasants and allies, so is Africa +characterised by its Guinea-fowls and relations, America has the Turkey +as an endemic genus, and the Grouse tribe in a wider sense has its +centre in the holarctic region: a splendid object lesson of descent, +world-wide spreading and subsequent differentiation. Huxley, by the way, +was the first--at least in private talk--to state that it will be for +the morphologist, the well-trained anatomist, to give the casting vote +in questions of geographical distribution, since he alone can determine +whether we have to deal with homologous, or analogous, convergent, +representative forms. + +It seems late to introduce Wallace's name in 1876, the year of the +publication of his standard work. ("The Geographical Distribution of +Animals", 2 vols. London, 1876.) We cannot do better than quote the +author's own words, expressing the hope that his "book should bear a +similar relation to the eleventh and twelfth chapters of the "Origin of +Species" as Darwin's "Animals and Plants under Domestication" does to +the first chapter of that work," and to add that he has amply succeeded. +Pleading for a few primary centres he accepts Sclater's six regions and +does not follow Huxley's courageous changes which Sclater himself had +accepted in 1874. Holding the view of the permanence of the oceans he +accounts for the colonisation of outlying islands by further elaborating +the views of Lyell and Darwin, especially in his fascinating "Island +Life", with remarkable chapters on the Ice Age, Climate and Time and +other fundamental factors. His method of arriving at the degree +of relationship of the faunas of the various regions is eminently +statistical. Long lists of genera determine by their numbers the +affinity and hence the source of colonisation. In order to make sure +of his material he performed the laborious task of evolving a new +classification of the host of Passerine birds. This statistical method +has been followed by many authors, who, relying more upon quantity than +quality, have obscured the fact that the key to the present distribution +lies in the past changes of the earth's surface. However, with Wallace +begins the modern study of the geographical distribution of animals and +the sudden interest taken in this subject by an ever widening circle of +enthusiasts far beyond the professional brotherhood. + +A considerable literature has since grown up, almost bewildering in its +range, diversity of aims and style of procedure. It is a chaos, with +many paths leading into the maze, but as yet very few take us to a +position commanding a view of the whole intricate terrain with its +impenetrable tangle and pitfalls. + +One line of research, not initiated but greatly influenced by Wallace's +works, became so prominent as to almost constitute a period which may +be characterised as that of the search by specialists for either the +justification or the amending of his regions. As class after class of +animals was brought up to reveal the secret of the true regions, some +authors saw in their different results nothing but the faultiness of +previously established regions; others looked upon eventual agreements +as their final corroboration, especially when for instance such diverse +groups as mammals and scorpions could, with some ingenuity, be made to +harmonise. But the obvious result of all these efforts was the growing +knowledge that almost every class seemed to follow principles of its +own. The regions tallied neither in extent nor in numbers, although +most of them gravitated more and more towards three centres, namely +Australia, South America and the rest of the world. Still zoologists +persisted in the search, and the various modes and capabilities of +dispersal of the respective groups were thought sufficient explanation +of the divergent results in trying to bring the mapping of the world +under one scheme. + +Contemporary literature is full of devices for the mechanical dispersal +of animals. Marine currents, warm and cold, were favoured all the +more since they showed the probable original homes of the creatures in +question. If these could not stand sea-water, they floated upon logs or +icebergs, or they were blown across by storms; fishes were lifted over +barriers by waterspouts, and there is on record even an hypothetical +land tortoise, full of eggs, which colonised an oceanic island after a +perilous sea voyage upon a tree trunk. Accidents will happen, and beyond +doubt many freaks of discontinuous distribution have to be accounted +for by some such means. But whilst sufficient for the scanty settlers of +true oceanic islands, they cannot be held seriously to account for the +rich fauna of a large continent, over which palaeontology shows us that +the immigrants have passed like waves. It should also be borne in mind +that there is a great difference between flotsam and jetsam. A current +is an extension of the same medium and the animals in it may suffer no +change during even a long voyage, since they may be brought from one +litoral to another where they will still be in the same or but slightly +altered environment. But the jetsam is in the position of a passenger +who has been carried off by the wrong train. Almost every year some +American land birds arrive at our western coasts and none of them have +gained a permanent footing although such visits must have taken place +since prehistoric times. It was therefore argued that only those groups +of animals should be used for locating and defining regions which were +absolutely bound to the soil. This method likewise gave results not +reconcilable with each other, even when the distribution of fossils +was taken into account, but it pointed to the absolute necessity of +searching for former land-connections regardless of their extent and the +present depths to which they may have sunk. + +That the key to the present distribution lies in the past had been felt +long ago, but at last it was appreciated that the various classes of +animals and plants have appeared in successive geological epochs and +also at many places remote from each other. The key to the distribution +of any group lies in the configuration of land and water of that epoch +in which it made its first appearance. Although this sounds like a +platitude, it has frequently been ignored. If, for argument's sake, +Amphibia were evolved somewhere upon the great southern land-mass of +Carboniferous times (supposed by some to have stretched from South +America across Africa to Australia), the distribution of this developing +class must have proceeded upon lines altogether different from that of +the mammals which dated perhaps from lower Triassic times, when the old +south continental belt was already broken up. The broad lines of this +distribution could never coincide with that of the other, older class, +no matter whether the original mammalian centre was in the Afro-Indian, +Australian, or Brazilian portion. If all the various groups of animals +had come into existence at the same time and at the same place, then it +would be possible, with sufficient geological data, to construct a map +showing the generalised results applicable to the whole animal kingdom. +But the premises are wrong. Whatever regions we may seek to establish +applicable to all classes, we are necessarily mixing up several +principles, namely geological, historical, i.e. evolutionary, with +present day statistical facts. We might as well attempt one compound +picture representing a chick's growth into an adult bird and a child's +growth into manhood. + +In short there are no general regions, not even for each class +separately, unless this class be one which is confined to a +comparatively short geological period. Most of the great classes have +far too long a history and have evolved many successive main groups. +Let us take the mammals. Marsupials live now in Australia and in both +Americas, because they already existed in Mesozoic times; Ungulata +existed at one time or other all over the world except in Australia, +because they are post-Cretaceous; Insectivores, although as old as any +Placentalia, are cosmopolitan excepting South America and Australia; +Stags and Bears, as examples of comparatively recent Arctogaeans, are +found everywhere with the exception of Ethiopia and Australia. Each of +these groups teaches a valuable historical lesson, but when these are +combined into the establishment of a few mammalian "realms," they mean +nothing but statistical majorities. If there is one at all, Australia is +such a realm backed against the rest of the world, but as certainly it +is not a mammalian creative centre! + +Well then, if the idea of generally applicable regions is a mare's nest, +as was the search for the Holy Grail, what is the object of the study +of geographical distribution? It is nothing less than the history of the +evolution of life in space and time in the widest sense. The attempt to +account for the present distribution of any group of organisms involves +the aid of every branch of science. It bids fair to become a history of +the world. It started in a mild, statistical way, restricting itself to +the present fauna and flora and to the present configuration of land +and water. Next came Oceanography concerned with the depths of the seas, +their currents and temperatures; then enquiries into climatic changes, +culminating in irreconcilable astronomical hypotheses as to glacial +epochs; theories about changes of the level of the seas, mainly from the +point of view of the physicist and astronomer. Then came more and more +to the front the importance of the geological record, hand in hand with +the palaeontological data and the search for the natural affinities, the +genetic system of the organisms. Now and then it almost seems as if the +biologists had done their share by supplying the problems and that the +physicists and geologists would settle them, but in reality it is not +so. The biologists not only set the problems, they alone can check the +offered solutions. The mere fact of palms having flourished in Miocene +Spitzbergen led to an hypothetical shifting of the axis of the world +rather than to the assumption, by way of explanation, that the palms +themselves might have changed their nature. One of the most valuable +aids in geological research, often the only means for reconstructing the +face of the earth in by-gone periods, is afforded by fossils, but only +the morphologist can pronounce as to their trustworthiness as witnesses, +because of the danger of mistaking analogous for homologous forms. This +difficulty applies equally to living groups, and it is so important that +a few instances may not be amiss. + +There is undeniable similarity between the faunas of Madagascar and +South America. This was supported by the Centetidae and Dendrobatidae, +two entire "families," as also by other facts. The value of the +Insectivores, Solenodon in Cuba, Centetes in Madagascar, has been much +lessened by their recognition as an extremely ancient group and as a +case of convergence, but if they are no longer put into the same +family, this amendment is really to a great extent due to their widely +discontinuous distribution. The only systematic difference of the +Dendrobatidae from the Ranidae is the absence of teeth, morphologically +a very unimportant character, and it is now agreed, on the strength of +their distribution, that these little arboreal, conspicuously coloured +frogs, Dendrobates in South America, Mantella in Madagascar, do not form +a natural group, although a third genus, Cardioglossa in West Africa, +seems also to belong to them. If these creatures lived all on the +same continent, we should unhesitatingly look upon them as forming a +well-defined, natural little group. On the other hand the Aglossa, with +their three very divergent genera, namely Pipa in South America, Xenopus +and Hymenochirus in Africa, are so well characterised as one ancient +group that we use their distribution unhesitatingly as a hint of a +former connection between the two continents. We are indeed arguing in +vicious circles. The Ratitae as such are absolutely worthless since they +are a most heterogeneous assembly, and there are untold groups, of +the artificiality of which many a zoo-geographer had not the slightest +suspicion when he took his statistical material, the genera and +families, from some systematic catalogues or similar lists. A lamentable +instance is that of certain flightless Rails, recently extinct or +sub-fossil, on the isalnds of Mauritius, Rodriguez and Chatham. Being +flightless they have been used in support of a former huge Antarctic +continent, instead of ruling them out of court as Rails which, each in +its island, have lost the power of flight, a process which must have +taken place so recently that it is difficult, upon morphological +grounds, to justify their separation into Aphanapteryx in Mauritius, +Erythromachus in Rodriguez and Diaphorapteryx on Chatham Island. +Morphologically they may well form but one genus, since they have sprung +from the same stock and have developed upon the same lines; they are +therefore monogenetic: but since we know that they have become what they +are independently of each other (now unlike any other Rails), they are +polygenetic and therefore could not form one genus in the old Darwinian +sense. Further, they are not a case of convergence, since their ancestry +is not divergent but leads into the same stratum. + +THE RECONSTRUCTION OF THE GEOGRAPHY OF SUCCESSIVE EPOCHS. + +A promising method is the study by the specialist of a large, widely +distributed group of animals from an evolutionary point of view. +Good examples of this method are afforded by A.E. Ortmann's ("The +geographical distribution of Freshwater Decapods and its bearing upon +ancient geography", "Proc. Amer. Phil. Soc." Vol. 41, 1902.) exhaustive +paper and by A.W. Grabau's "Phylogeny of Fusus and its Allies" +("Smithsonian Misc. Coll." 44, 1904.) After many important groups of +animals have been treated in this way--as yet sparingly attempted--the +results as to hypothetical land-connections etc. are sure to be +corrective and supplementary, and their problems will be solved, since +they are not imaginary. + +The same problems are attacked, in the reverse way, by starting with the +whole fauna of a country and thence, so to speak, letting the research +radiate. Some groups will be considered as autochthonous, others as +immigrants, and the directions followed by them will be inquired into; +the search may lead far and in various directions, and by comparison of +results, by making compound maps, certain routes will assume definite +shape, and if they lead across straits and seas they are warrants to +search for land-connections in the past. (A fair sample of this method +is C.H. Eigenmann's "The Freshwater Fishes of South and Middle America", +"Popular Science Monthly", Vol. 68, 1906.) There are now not a few maps +purporting to show the outlines of land and water at various epochs. +Many of these attempts do not tally with each other, owing to the +lamentable deficiencies of geological and fossil data, but the bolder +the hypothetical outlines are drawn, the better, and this is preferable +to the insertion of bays and similar detail which give such maps a +fallacious look of certainty where none exists. Moreover it must be +borne in mind that, when we draw a broad continental belt across an +ocean, this belt need never have existed in its entirety at any one +time. The features of dispersal, intended to be explained by it, would +be accomplished just as well by an unknown number of islands which have +joined into larger complexes while elsewhere they subsided again: +like pontoon-bridges which may be opened anywhere, or like a series +of superimposed dissolving views of land and sea-scapes. Hence the +reconstructed maps of Europe, the only continent tolerably known, show +a considerable number of islands in puzzling changes, while elsewhere, +e.g. in Asia, we have to be satisfied with sweeping generalisations. + +At present about half-a-dozen big connections are engaging our +attention, leaving as comparatively settled the extent and the duration +of such minor "bridges" as that between Africa and Madagascar, Tasmania +and Australia, the Antilles and Central America, Europe and North +Africa. (Not a few of those who are fascinated by, and satisfied with, +the statistical aspect of distribution still have a strong dislike to +the use of "bridges" if these lead over deep seas, and they get +over present discontinuous occurrences by a former "universal or +sub-universal distribution" of their groups.) This is indeed an easy +method of cutting the knot, but in reality they shunt the question only +a stage or two back, never troubling to explain how their groups managed +to attain to that sub-universal range; or do they still suppose that the +whole world was originally one paradise where everything lived side by +side, until sin and strife and glacial epochs left nothing but scattered +survivors? + +The permanence of the great ocean-basins had become a dogma since it +was found that a universal elevation of the land to the extent of 100 +fathoms would produce but little changes, and when it was shown that +even the 1000 fathom-line followed the great masses of land rather +closely, and still leaving the great basins (although transgression +of the sea to the same extent would change the map of the world beyond +recognition), by general consent one mile was allowed as the utmost +speculative limit of subsidence. Naturally two or three miles, the +average depth of the oceans, seems enormous, and yet such a difference +in level is as nothing in comparison with the size of the Earth. On +a clay model globe ten feet in diameter an ocean bed three miles deep +would scarcely be detected, and the highest mountains would be smaller +than the unavoidable grains in the glazed surface of our model. There +are but few countries which have not be submerged at some time or +other. + +CONNECTION OF SOUTH EASTERN ASIA WITH AUSTRALIA. Neumayr's +Sino-Australian continent during mid-Mesozoic times was probably a +much changing Archipelago, with final separations subsequent to the +Cretaceous period. Henceforth Australasia was left to its own fate, but +for a possible connection with the antarctic continent. + +AFRICA, MADAGASCAR, INDIA. The "Lemuria" of Sclater and Haeckel cannot +have been more than a broad bridge in Jurassic times; whether it was +ever available for the Lemurs themselves must depend upon the time of +its duration, the more recent the better, but it is difficult to show +that it lasted into the Miocene. + +AFRICA AND SOUTH AMERICA. Since the opposite coasts show an entire +absence of marine fossils and deposits during the Mesozoic period, +whilst further north and south such are known to exist and are mostly +identical on either side, Neumayr suggested the existence of a great +Afro-Son American mass of land during the Jurassic epoch. Such land +is almost a necessity and is supported by many facts; it would easily +explain the distribution of numerous groups of terrestrial creatures. +Moreover to the north of this hypothetical land, somewhere across +from the Antilles and Guiana to North Africa and South Western Europe, +existed an almost identical fauna of Corals and Molluscs, indicating +either a coast-line or a series of islands interrupted by shallow seas, +just as one would expect if, and when, a Brazil-Ethiopian mass of land +were breaking up. Lastly from Central America to the Mediterranean +stretches one of the Tertiary tectonic lines of the geologists. Here +also the great question is how long this continent lasted. Apparently +the South Atlantic began to encroach from the south so that by the +later Cretaceous epoch the land was reduced to a comparatively narrow +Brazil-West Africa, remnants of which persisted certainly into the early +Tertiary, until the South Atlantic joined across the equator with the +Atlantic portion of the "Thetys," leaving what remained of South America +isolated from the rest of the world. + +ANTARCTIC CONNECTIONS. Patagonia and Argentina seem to have joined +Antartica during the Cretaceous epoch, and this South Georgian bridge +had broken down again by mid-Tertiary times when South America became +consolidated. The Antarctic continent, presuming that it existed, seems +also to have been joined, by way of Tasmania, with Australia, +also during the Cretaceous epoch, and it is assumed that the great +Australia-Antarctic-Patagonian land was severed first to the south of +Tasmania and then at the South Georgian bridge. No connection, and +this is important, is indicated between Antarctica and either Africa or +Madagascar. + +So far we have followed what may be called the vicissitudes of the great +Permo-Carboniferous Gondwana land in its fullest imaginary extent, +an enormous equatorial and south temperate belt from South America to +Africa, South India and Australia, which seems to have provided the +foundation of the present Southern continents, two of which temporarily +joined Antarctica, of which however we know nothing except that it +exists now. + +Let us next consider the Arctic and periarctic lands. Unfortunately very +little is known about the region within the arctic circle. If it was all +land, or more likely great changing archipelagoes, faunistic exchange +between North America, Europe and Siberia would present no difficulties, +but there is one connection which engages much attention, namely a land +where now lies the North temperate and Northern part of the Atlantic +ocean. How far south did it ever extend and what is the latest date of +a direct practicable communication, say from North Western Europe +to Greenland? Connections, perhaps often interrupted, e.g. between +Greenland and Labrador, at another time between Greenland and +Scandinavia, seem to have existed at least since the Permo-Carboniferous +epoch. If they existed also in late Cretaceous and in Tertiary times, +they would of course easily explain exchanges which we know to have +repeatedly taken place between America and Europe, but they are not +proved thereby, since most of these exchanges can almost as easily +have occurred across the polar regions, and others still more easily by +repeated junction of Siberia with Alaska. + +Let us now describe a hypothetical case based on the supposition of +connecting bridges. Not to work in a circle, we select an important +group which has not served as a basis for the reconstruction of bridges; +and it must be a group which we feel justified in assuming to be old +enough to have availed itself of ancient land-connections. + +The occurrence of one species of Peripatus in the whole of Australia, +Tasmania and New Zealand (the latter being joined to Australia by way of +New Britain in Cretaceous times but not later) puts the genus back +into this epoch, no unsatisfactory assumption to the morphologist. The +apparent absence of Peripatus in Madagascar indicates that it did not +come from the east into Africa, that it was neither Afro-Indian, nor +Afro-Australian; nor can it have started in South America. We therefore +assume as its creative centre Australia or Malaya in the Cretaceous +epoch, whence its occurrence in Sumatra, Malay Peninsula, New Britain, +New Zealand and Australia is easily explained. Then extension across +Antarctica to Patagonia and Chile, whence it could spread into the rest +of South America as this became consolidated in early Tertiary times. +For getting to the Antilles and into Mexico it would have to wait until +the Miocene, but long before that time it could arrive in Africa, there +surviving as a Congolese and a Cape species. This story is unsupported +by a single fossil. Peripatus may have been "sub-universal" all over +greater Gondwana land in Carboniferous times, and then its absence from +Madagascar would be difficult to explain, but the migrations suggested +above amount to little considering that the distance from Tasmania to +South America could be covered in far less time than that represented by +the whole of the Eocene epoch alone. + +There is yet another field, essentially the domain of geographical +distribution, the cultivation of which promises fair to throw much light +upon Nature's way of making species. This is the study of the organisms +with regard to their environment. Instead of revealing pedigrees or +of showing how and when the creatures got to a certain locality, it +investigates how they behaved to meet the ever changing conditions of +their habitats. There is a facies, characteristic of, and often peculiar +to, the fauna of tropical moist forests, another of deserts, of high +mountains, of underground life and so forth; these same facies are +stamped upon whole associations of animals and plants, although these +may be--and in widely separated countries generally are--drawn from +totally different families of their respective orders. It does not go to +the root of the matter to say that these facies have been brought about +by the extermination of all the others which did not happen to fit into +their particular environment. One might almost say that tropical moist +forests must have arboreal frogs and that these are made out of whatever +suitable material happened to be available; in Australia and South +America Hylidae, in Africa Ranidae, since there Hylas are absent. The +deserts must have lizards capable of standing the glare, the great +changes of temperature, of running over or burrowing into the loose +sand. When as in America Iguanids are available, some of these are thus +modified, while in Africa and Asia the Agamids are drawn upon. Both in +the Damara and in the Transcaspian deserts, a Gecko has been turned into +a runner upon sand! + +We cannot assume that at various epochs deserts, and at others moist +forests were continuous all over the world. The different facies and +associations were developed at various times and places. Are we to +suppose that, wherever tropical forests came into existence, amongst +the stock of humivagous lizards were always some which presented those +nascent variations which made them keep step with the similarly nascent +forests, the overwhelming rest being eliminated? This principle would +imply that the same stratum of lizards always had variations ready to +fit any changed environment, forests and deserts, rocks and swamps. +The study of Ecology indicates a different procedure, a great, almost +boundless plasticity of the organism, not in the sense of an exuberant +moulding force, but of a readiness to be moulded, and of this the +"variations" are the visible outcome. In most cases identical facies +are produced by heterogeneous convergences and these may seem to be but +superficial, affecting only what some authors are pleased to call the +physiological characters; but environment presumably affects first those +parts by which the organism comes into contact with it most directly, +and if the internal structures remain unchanged, it is not because these +are less easily modified but because they are not directly affected. +When they are affected, they too change deeply enough. + +That the plasticity should react so quickly--indeed this very quickness +seems to have initiated our mistaking the variations called forth for +something performed--and to the point, is itself the outcome of the long +training which protoplasm has undergone since its creation. + +In Nature's workshop he does not succeed who has ready an arsenal of +tools for every conceivable emergency, but he who can make a tool at the +spur of the moment. The ordeal of the practical test is Charles Darwin's +glorious conception of Natural Selection. + + + + +XVIII. DARWIN AND GEOLOGY. By J.W. Judd, C.B., LL.D., F.R.S. + + +(Mr Francis Darwin has related how his father occasionally came up from +Down to spend a few days with his brother Erasmus in London, and, +after his brother's death, with his daughter, Mrs Litchfield. On these +occasions, it was his habit to arrange meetings with Huxley, to talk +over zoological questions, with Hooker, to discuss botanical problems, +and with Lyell to hold conversations on geology. After the death of +Lyell, Darwin, knowing my close intimacy with his friend during his +later years, used to ask me to meet him when he came to town, and "talk +geology." The "talks" took place sometimes at Jermyn Street Museum, at +other times in the Royal College of Science, South Kensington; but +more frequently, after having lunch with him, at his brother's or his +daughter's house. On several occasions, however, I had the pleasure of +visiting him at Down. In the postscript of a letter (of April 15, 1880) +arranging one of these visits, he writes: "Since poor, dear Lyell's +death, I rarely have the pleasure of geological talk with anyone.") + +In one of the very interesting conversations which I had with Charles +Darwin during the last seven years of his life, he asked me in a very +pointed manner if I were able to recall the circumstances, accidental or +otherwise, which had led me to devote myself to geological studies. He +informed me that he was making similar inquiries of other friends, and I +gathered from what he said that he contemplated at that time a study +of the causes producing SCIENTIFIC BIAS in individual minds. I have +no means of knowing how far this project ever assumed anything like +concrete form, but certain it is that Darwin himself often indulged +in the processes of mental introspection and analysis; and he has +thus fortunately left us--in his fragments of autobiography and in his +correspondence--the materials from which may be reconstructed a fairly +complete history of his own mental development. + +There are two perfectly distinct inquiries which we have to undertake +in connection with the development of Darwin's ideas on the subject of +evolution: + +FIRST. How, when, and under what conditions was Darwin led to a +conviction that species were not immutable, but were derived from +pre-existing forms? + +SECONDLY. By what lines of reasoning and research was he brought to +regard "natural selection" as a vera causa in the process of evolution? + +It is the first of these inquiries which specially interests the +geologist; though geology undoubtedly played a part--and by no means an +insignificant part--in respect to the second inquiry. + +When, indeed, the history comes to be written of that great revolution +of thought in the nineteenth century, by which the doctrine of +evolution, from being the dream of poets and visionaries, gradually grew +to be the accepted creed of naturalists, the paramount influence exerted +by the infant science of geology--and especially that resulting from +the publication of Lyell's epoch-making work, the "Principles of +Geology"--cannot fail to be regarded as one of the leading factors. +Herbert Spencer in his "Autobiography" bears testimony to the effect +produced on his mind by the recently published "Principles", when, at +the age of twenty, he had already begun to speculate on the subject +of evolution (Herbert Spencer's "Autobiography", London, 1904, Vol. I. +pages 175-177.); and Alfred Russel Wallace is scarcely less emphatic +concerning the part played by Lyell's teaching in his scientific +education. (See "My Life; a record of Events and Opinions", London, +1905, Vol. I. page 355, etc. Also his review of Lyell's "Principles" +in "Quarterly Review" (Vol. 126), 1869, pages 359-394. See also "The +Darwin-Wallace Celebration by the Linnean Society" (1909), page 118.) +Huxley wrote in 1887 "I owe more than I can tell to the careful study +of the "Principles of Geology" in my young days." ("Science and Pseudo +Science"; "Collected Essays", London, 1902, Vol. V. page 101.) As for +Charles Darwin, he never tired--either in his published writings, his +private correspondence or his most intimate conversations--of ascribing +the awakening of his enthusiasm and the direction of his energies +towards the elucidation of the problem of development to the "Principles +of Geology" and the personal influence of its author. Huxley has well +expressed what the author of the "Origin of Species" so constantly +insisted upon, in the statements "Darwin's greatest work is the outcome +of the unflinching application to Biology of the leading idea and the +method applied in the "Principles" to Geology ("Proc. Roy. Soc." Vol. +XLIV. (1888), page viii.; "Collected Essays" II. page 268, 1902.), and +"Lyell, for others, as for myself, was the chief agent in smoothing the +road for Darwin." ("Life and Letters of Charles Darwin" II. page 190.) + +We propose therefore to consider, first, what Darwin owed to geology and +its cultivators, and in the second place how he was able in the end so +fully to pay a great debt which he never failed to acknowledge. Thanks +to the invaluable materials contained in the "Life and Letters of +Charles Darwin" (3 vols.) published by Mr Francis Darwin in 1887; and to +"More Letters of Charles Darwin" (2 vols.) issued by the same author, +in conjunction with Professor A.C. Seward, in 1903, we are permitted to +follow the various movements in Darwin's mind, and are able to record +the story almost entirely in his own words. (The first of these works +is indicated in the following pages by the letters "L.L."; the second by +"M.L.") + +From the point of view of the geologist, Darwin's life naturally divides +itself into four periods. In the first, covering twenty-two years, +various influences were at work militating, now for and now against, +his adoption of a geological career; in the second period--the five +memorable years of the voyage of the "Beagle"--the ardent sportsman with +some natural-history tastes, gradually became the most enthusiastic and +enlightened of geologists; in the third period, lasting ten years, the +valuable geological recruit devoted nearly all his energies and time +to geological study and discussion and to preparing for publication the +numerous observations made by him during the voyage; the fourth period, +which covers the latter half of his life, found Darwin gradually drawn +more and more from geological to biological studies, though always +retaining the deepest interest in the progress and fortunes of his "old +love." But geologists gladly recognise the fact that Darwin immeasurably +better served their science by this biological work, than he could +possibly have done by confining himself to purely geological questions. + +From his earliest childhood, Darwin was a collector, though up to the +time when, at eight years of age, he went to a preparatory school, +seals, franks and similar trifles appear to have been the only objects +of his quest. But a stone, which one of his schoolfellows at that time +gave to him, seems to have attracted his attention and set him seeking +for pebbles and minerals; as the result of this newly acquired taste, he +says (writing in 1838) "I distinctly recollect the desire I had of being +able to know something about every pebble in front of the hall door--it +was my earliest and only geological aspiration at that time." ("M.L." +I. page 3.) He further suspects that while at Mr Case's school "I do +not remember any mental pursuits except those of collecting stones," +etc... "I was born a naturalist." ("M.L." I. page 4.) + +The court-yard in front of the hall door at the Mount House, Darwin's +birthplace and the home of his childhood, is surrounded by beds or +rockeries on which lie a number of pebbles. Some of these pebbles (in +quite recent times as I am informed) have been collected to form a +"cobbled" space in front of the gate in the outer wall, which fronts the +hall door; and a similar "cobbled area," there is reason to believe, may +have existed in Darwin's childhood before the door itself. The pebbles, +which were obtained from a neighbouring gravel-pit, being derived from +the glacial drift, exhibit very striking differences in colour and form. +It was probably this circumstance which awakened in the child his +love of observation and speculation. It is certainly remarkable that +"aspirations" of the kind should have arisen in the mind of a child of 9 +or 10! + +When he went to Shrewsbury School, he relates "I continued collecting +minerals with much zeal, but quite unscientifically,--all that I cared +about was a new-NAMED mineral, and I hardly attempted to classify them." +("L.L." I. page 34.) + +There has stood from very early times in Darwin's native town of +Shrewsbury, a very notable boulder which has probably marked a boundary +and is known as the "Bell-stone"--giving its name to a house and street. +Darwin tells us in his "Autobiography" that while he was at Shrewsbury +School at the age of 13 or 14 "an old Mr Cotton in Shropshire, who knew +a good deal about rocks" pointed out to me "... the 'bell-stone'; he told +me that there was no rock of the same kind nearer than Cumberland or +Scotland, and he solemnly assured me that the world would come to an end +before anyone would be able to explain how this stone came where it +now lay"! Darwin adds "This produced a deep impression on me, and I +meditated over this wonderful stone." ("L.L." I. page 41.) + +The "bell-stone" has now, owing to the necessities of building, been +removed a short distance from its original site, and is carefully +preserved within the walls of a bank. It is a block of irregular shape 3 +feet long and 2 feet wide, and about 1 foot thick, weighing probably not +less than one-third of a ton. By the courtesy of the directors of the +National Provincial Bank of England, I have been able to make a minute +examination of it, and Professors Bonney and Watts, with Mr Harker and +Mr Fearnsides have given me their valuable assistance. The rock is a +much altered andesite and was probably derived from the Arenig district +in North Wales, or possibly from a point nearer the Welsh Border. (I +am greatly indebted to the Managers of the Bank at Shrewsbury for kind +assistance in the examination of this interesting memorial: and Mr +H.T. Beddoes, the Curator of the Shrewsbury Museum, has given me some +archaeological information concerning the stone. Mr Richard Cotton was +a good local naturalist, a Fellow both of the Geological and Linnean +Societies; and to the officers of these societies I am indebted for +information concerning him. He died in 1839, and although he does not +appear to have published any scientific papers, he did far more for +science by influencing the career of the school boy!) It was of course +brought to where Shrewsbury now stands by the agency of a glacier--as +Darwin afterwards learnt. + +We can well believe from the perusal of these reminiscences that, +at this time, Darwin's mind was, as he himself says, "prepared for a +philosophical treatment of the subject" of Geology. ("L.L." I. page 41.) +When at the age of 16, however, he was entered as a medical student at +Edinburgh University, he not only did not get any encouragement of +his scientific tastes, but was positively repelled by the ordinary +instruction given there. Dr Hope's lectures on Chemistry, it is true, +interested the boy, who with his brother Erasmus had made a laboratory +in the toolhouse, and was nicknamed "Gas" by his schoolfellows, while +undergoing solemn and public reprimand from Dr Butler at Shrewsbury +School for thus wasting his time. ("L.L." I. page 35.) But most of +the other Edinburgh lectures were "intolerably dull," "as dull as the +professors" themselves, "something fearful to remember." In after life +the memory of these lectures was like a nightmare to him. He speaks in +1840 of Jameson's lectures as something "I... for my sins experienced!" +("L.L." I. page 340.) Darwin especially signalises these lectures on +Geology and Zoology, which he attended in his second year, as being +worst of all "incredibly dull. The sole effect they produced on me was +the determination never so long as I lived to read a book on Geology, or +in any way to study the science!" ("L.L." I. page 41.) + +The misfortune was that Edinburgh at that time had become the cockpit in +which the barren conflict between "Neptunism" and "Plutonism" was being +waged with blind fury and theological bitterness. Jameson and his +pupils, on the one hand, and the friends and disciples of Hutton, on the +other, went to the wildest extremes in opposing each other's peculiar +tenets. Darwin tells us that he actually heard Jameson "in a field +lecture at Salisbury Craigs, discoursing on a trap-dyke, with +amygdaloidal margins and the strata indurated on each side, with +volcanic rocks all around us, say that it was a fissure filled with +sediment from above, adding with a sneer that there were men who +maintained that it had been injected from beneath in a molten +condition." ("L.L." I. pages 41-42.) "When I think of this lecture," +added Darwin, "I do not wonder that I determined never to attend to +Geology." (This was written in 1876 and Darwin had in the summer of 1839 +revisited and carefully studied the locality ("L.L." I. page 290.) It is +probable that most of Jameson's teaching was of the same controversial +and unilluminating character as this field-lecture at Salisbury Craigs. + +There can be no doubt that, while at Edinburgh, Darwin must have become +acquainted with the doctrines of the Huttonian School. Though so young, +he mixed freely with the scientific society of the city, Macgillivray, +Grant, Leonard Horner, Coldstream, Ainsworth and others being among +his acquaintances, while he attended and even read papers at the local +scientific societies. It is to be feared, however, that what Darwin +would hear most of, as characteristic of the Huttonian teaching, would +be assertions that chalk-flints were intrusions of molten silica, that +fossil wood and other petrifactions had been impregnated with fused +materials, that heat--but never water--was always the agent by which +the induration and crystallisation of rock-materials (even siliceous +conglomerate, limestone and rock-salt) had been effected! These +extravagant "anti-Wernerian" views the young student might well regard +as not one whit less absurd and repellant than the doctrine of the +"aqueous precipitation" of basalt. There is no evidence that Darwin, +even if he ever heard of them, was in any way impressed, in his early +career, by the suggestive passages in Hutton and Playfair, to which +Lyell afterwards called attention, and which foreshadowed the main +principles of Uniformitarianism. + +As a matter of fact, I believe that the influence of Hutton and Playfair +in the development of a philosophical theory of geology has been very +greatly exaggerated by later writers on the subject. Just as Wells +and Matthew anticipated the views of Darwin on Natural Selection, +but without producing any real influence on the course of biological +thought, so Hutton and Playfair adumbrated doctrines which only became +the basis of vivifying theory in the hands of Lyell. Alfred Russel +Wallace has very justly remarked that when Lyell wrote the "Principles +of Geology", "the doctrines of Hutton and Playfair, so much in advance +of their age, seemed to be utterly forgotten." ("Quarterly Review", Vol. +CXXVI. (1869), page 363.) In proof of this it is only necessary to +point to the works of the great masters of English geology, who preceded +Lyell, in which the works of Hutton and his followers are scarcely ever +mentioned. This is true even of the "Researches in Theoretical Geology" +and the other works of the sagacious De la Beche. (Of the strength +and persistence of the prejudice felt against Lyell's views by his +contemporaries, I had a striking illustration some little time after +Lyell's death. One of the old geologists who in the early years of the +century had done really good work in connection with the Geological +Society expressed a hope that I was not "one of those who had been +carried away by poor Lyell's fads." My surprise was indeed great when +further conversation showed me that the whole of the "Principles" were +included in the "fads"!) Darwin himself possessed a copy of Playfair's +"Illustrations of the Huttonian Theory", and occasionally quotes it; +but I have met with only one reference to Hutton, and that a somewhat +enigmatical one, in all Darwin's writings. In a letter to Lyell in 1841, +when his mind was much exercised concerning glacial questions, he says +"What a grand new feature all this ice work is in Geology! How old +Hutton would have stared!" ("M.L." II. page 149.) + +As a consequence of the influences brought to bear on his mind during +his two years' residence in Edinburgh, Darwin, who had entered that +University with strong geological aspirations, left it and proceeded to +Cambridge with a pronounced distaste for the whole subject. The result +of this was that, during his career as an under-graduate, he neglected +all the opportunities for geological study. During that important period +of life, when he was between eighteen and twenty years of age, Darwin +spent his time in riding, shooting and beetle-hunting, pursuits which +were undoubtedly an admirable preparation for his future work as an +explorer; but in none of his letters of this period does he even mention +geology. He says, however, "I was so sickened with lectures at +Edinburgh that I did not even attend Sedgwick's eloquent and interesting +lectures." ("L.L." I. page 48.) + +It was only after passing his examination, and when he went up to spend +two extra terms at Cambridge, that geology again began to attract his +attention. The reading of Sir John Herschel's "Introduction to the Study +of Natural Philosophy", and of Humboldt's "Personal Narrative", a +copy of which last had been given to him by his good friend and mentor +Henslow, roused his dormant enthusiasm for science, and awakened in his +mind a passionate desire for travel. And it was from Henslow, whom +he had accompanied in his excursions, but without imbibing any marked +taste, at that time, for botany, that the advice came to think of and to +"begin the study of geology." ("L.L." I. page 56.) This was in 1831, and +in the summer vacation of that year we find him back again at Shrewsbury +"working like a tiger" at geology and endeavouring to make a map +and section of Shropshire--work which he says was not "as easy as I +expected." ("L.L." I. page 189.) No better field for geological studies +could possibly be found than Darwin's native county. + +Writing to Henslow at this time, and referring to a form of the +instrument devised by his friend, Darwin says: "I am very glad to say I +think the clinometer will answer admirably. I put all the tables in my +bedroom at every conceivable angle and direction. I will venture to say +that I have measured them as accurately as any geologist going could +do." But he adds: "I have been working at so many things that I have +not got on much with geology. I suspect the first expedition I take, +clinometer and hammer in hand, will send me back very little wiser and +a good deal more puzzled than when I started." ("L.L." I. page 189.) +Valuable aid was, however, at hand, for at this time Sedgwick, to whom +Darwin had been introduced by the ever-helpful Henslow, was making one +of his expeditions into Wales, and consented to accept the young student +as his companion during the geological tour. ("L.L." I. page 56.) We +find Darwin looking forward to this privilege with the keenest interest. +("L.L." I. page 189.) + +When at the beginning of August (1831), Sedgwick arrived at his father's +house in Shrewsbury, where he spent a night, Darwin began to receive his +first and only instruction as a field-geologist. The journey they took +together led them through Llangollen, Conway, Bangor, and Capel Curig, +at which latter place they parted after spending many hours in examining +the rocks at Cwm Idwal with extreme care, seeking for fossils but +without success. Sedgwick's mode of instruction was admirable--he from +time to time sent the pupil off on a line parallel to his own, "telling +me to bring back specimens of the rocks and to mark the stratification +on a map." ("L.L." I. page 57.) On his return to Shrewsbury, Darwin +wrote to Henslow, "My trip with Sedgwick answered most perfectly," +("L.L." I. page 195.), and in the following year he wrote again from +South America to the same friend, "Tell Professor Sedgwick he does not +know how much I am indebted to him for the Welsh expedition; it has +given me an interest in Geology which I would not give up for any +consideration. I do not think I ever spent a more delightful three weeks +than pounding the north-west mountains." ("L.L." I. pages 237-8.) + +It would be a mistake, however, to suppose that at this time Darwin +had acquired anything like the affection for geological study, which +he afterwards developed. After parting with Sedgwick, he walked in a +straight line by compass and map across the mountains to Barmouth to +visit a reading party there, but taking care to return to Shropshire +before September 1st, in order to be ready for the shooting. For as +he candidly tells us, "I should have thought myself mad to give up the +first days of partridge-shooting for geology or any other science!" +("L.L." I. page 58.) + +Any regret we may be disposed to feel that Darwin did not use his +opportunities at Edinburgh and Cambridge to obtain systematic and +practical instruction in mineralogy and geology, will be mitigated, +however, when we reflect on the danger which he would run of being +indoctrinated with the crude "catastrophic" views of geology, which were +at that time prevalent in all the centres of learning. + +Writing to Henslow in the summer of 1831, Darwin says "As yet I have +only indulged in hypotheses, but they are such powerful ones that I +suppose, if they were put into action but for one day, the world would +come to an end." ("L.L." I. page 189.) + +May we not read in this passage an indication that the self-taught +geologist had, even at this early stage, begun to feel a distrust for +the prevalent catastrophism, and that his mind was becoming a field in +which the seeds which Lyell was afterwards to sow would "fall on good +ground"? + +The second period of Darwin's geological career--the five years spent +by him on board the "Beagle"--was the one in which by far the most +important stage in his mental development was accomplished. He left +England a healthy, vigorous and enthusiastic collector; he returned five +years later with unique experiences, the germs of great ideas, and +a knowledge which placed him at once in the foremost ranks of the +geologists of that day. Huxley has well said that "Darwin found on board +the "Beagle" that which neither the pedagogues of Shrewsbury, nor the +professoriate of Edinburgh, nor the tutors of Cambridge had managed +to give him." ("Proc. Roy. Soc." Vol. XLIV. (1888), page IX.) Darwin +himself wrote, referring to the date at which the voyage was expected to +begin: "My second life will then commence, and it shall be as a birthday +for the rest of my life." ("L.L." I. page 214.); and looking back on the +voyage after forty years, he wrote; "The voyage of the 'Beagle' has been +by far the most important event in my life, and has determined my whole +career;... I have always felt that I owe to the voyage the first real +training or education of my mind; I was led to attend closely to several +branches of natural history, and thus my powers of observation were +improved, though they were always fairly developed." ("L.L." I. page +61.) + +Referring to these general studies in natural history, however, Darwin +adds a very significant remark: "The investigation of the geology of +the places visited was far more important, as reasoning here comes into +play. On first examining a new district nothing can appear more hopeless +than the chaos of rocks; but by recording the stratification and nature +of the rocks and fossils at many points, always reasoning and predicting +what will be found elsewhere, light soon begins to dawn on the district, +and the structure of the whole becomes more or less intelligible." +("L.L." I. page 62.) + +The famous voyage began amid doubts, discouragements and +disappointments. Fearful of heart-disease, sad at parting from home +and friends, depressed by sea-sickness, the young explorer, after being +twice driven back by baffling winds, reached the great object of +his ambition, the island of Teneriffe, only to find that, owing to +quarantine regulations, landing was out of the question. + +But soon this inauspicious opening of the voyage was forgotten. Henslow +had advised his pupil to take with him the first volume of Lyell's +"Principles of Geology", then just published--but cautioned him (as +nearly all the leaders in geological science at that day would certainly +have done) "on no account to accept the views therein advocated." +("L.L." I. page 73.) It is probable that the days of waiting, discomfort +and sea-sickness at the beginning of the voyage were relieved by the +reading of this volume. For he says that when he landed, three weeks +after setting sail from Plymouth, in St Jago, the largest of the Cape de +Verde Islands, the volume had already been "studied attentively; and +the book was of the highest service to me in many ways... " His first +original geological work, he declares, "showed me clearly the wonderful +superiority of Lyell's manner of treating geology, compared with that +of any other author, whose works I had with me or ever afterwards read." +("L.L." I. page 62.) + +At St Jago Darwin first experienced the joy of making new discoveries, +and his delight was unbounded. Writing to his father he says, +"Geologising in a volcanic country is most delightful; besides the +interest attached to itself, it leads you into most beautiful and +retired spots." ("L.L." I. page 228.) To Henslow he wrote of St Jago: +"Here we spent three most delightful weeks... St Jago is singularly +barren, and produces few plants or insects, so that my hammer was my +usual companion, and in its company most delightful hours I spent." "The +geology was pre-eminently interesting, and I believe quite new; there +are some facts on a large scale of upraised coast (which is an excellent +epoch for all the volcanic rocks to date from), that would interest Mr +Lyell." ("L.L." I. page 235.) After more than forty years the memory of +this, his first geological work, seems as fresh as ever, and he wrote in +1876, "The geology of St Jago is very striking, yet simple: a stream +of lava formerly flowed over the bed of the sea, formed of triturated +recent shells and corals, which it has baked into a hard white rock. +Since then the whole island has been upheaved. But the line of white +rock revealed to me a new and important fact, namely, that there had +been afterwards subsidence round the craters, which had since been in +action, and had poured forth lava." ("L.L." I. page 65.) + +It was at this time, probably, that Darwin made his first attempt at +drawing a sketch-map and section to illustrate the observations he had +made (see his "Volcanic Islands", pages 1 and 9). His first important +geological discovery, that of the subsidence of strata around volcanic +vents (which has since been confirmed by Mr Heaphy in New Zealand and +other authors) awakened an intense enthusiasm, and he writes: "It then +first dawned on me that I might perhaps write a book on the geology of +the various countries visited, and this made me thrill with delight. +That was a memorable hour to me, and how distinctly I can call to mind +the low cliff of lava beneath which I rested, with the sun glaring hot, +a few strange desert plants growing near, and with living corals in the +tidal pools at my feet." ("L.L." I. page 66.) + +But it was when the "Beagle", after touching at St Paul's rock and +Tristan d'Acunha (for a sufficient time only to collect specimens), +reached the shores of South America, that Darwin's real work began; and +he was able, while the marine surveys were in progress, to make many +extensive journeys on land. His letters at this time show that geology +had become his chief delight, and such exclamations as "Geology carries +the day," "I find in Geology a never failing interest," etc. abound in +his correspondence. + +Darwin's time was divided between the study of the great deposits of red +mud--the Pampean formation--with its interesting fossil bones and shells +affording proofs of slow and constant movements of the land, and the +underlying masses of metamorphic and plutonic rocks. Writing to Henslow +in March, 1834, he says: "I am quite charmed with Geology, but, like +the wise animal between two bundles of hay, I do not know which to +like best; the old crystalline groups of rocks, or the softer and +fossiliferous beds. When puzzling about stratification, etc., I +feel inclined to cry 'a fig for your big oysters, and your bigger +megatheriums.' But then when digging out some fine bones, I wonder how +any man can tire his arms with hammering granite." ("L.L." I. page +249.) We are told by Darwin that he loved to reason about and attempt to +predict the nature of the rocks in each new district before he arrived +at it. + +This love of guessing as to the geology of a district he was about to +visit is amusingly expressed by him in a letter (of May, 1832) to his +cousin and old college-friend, Fox. After alluding to the beetles he +had been collecting--a taste his friend had in common with himself--he +writes of geology that "It is like the pleasure of gambling. Speculating +on first arriving, what the rocks may be, I often mentally cry out 3 to +1 tertiary against primitive; but the latter have hitherto won all the +bets." ("L.L." I. page 233.) + +Not the least important of the educational results of the voyage to +Darwin was the acquirement by him of those habits of industry and method +which enabled him in after life to accomplish so much--in spite of +constant failures of health. From the outset, he daily undertook +and resolutely accomplished, in spite of sea-sickness and other +distractions, four important tasks. In the first place he regularly +wrote up the pages of his Journal, in which, paying great attention to +literary style and composition, he recorded only matters that would be +of general interest, such as remarks on scenery and vegetation, on the +peculiarities and habits of animals, and on the characters, avocations +and political institutions of the various races of men with whom he was +brought in contact. It was the freshness of these observations that gave +his "Narrative" so much charm. Only in those cases in which his ideas +had become fully crystallised, did he attempt to deal with scientific +matters in this journal. His second task was to write in voluminous +note-books facts concerning animals and plants, collected on sea or +land, which could not be well made out from specimens preserved in +spirit; but he tells us that, owing to want of skill in dissecting and +drawing, much of the time spent in this work was entirely thrown away, +"a great pile of MS. which I made during the voyage has proved almost +useless." ("L.L." I. page 62.) Huxley confirmed this judgment on his +biological work, declaring that "all his zeal and industry resulted, for +the most part, in a vast accumulation of useless manuscript." ("Proc. +Roy. Soc." Vol. XLIV. (1888), page IX.) Darwin's third task was of a +very different character and of infinitely greater value. It consisted +in writing notes of his journeys on land--the notes being devoted to +the geology of the districts visited by him. These formed the basis, not +only of a number of geological papers published on his return, but also +of the three important volumes forming "The Geology of the voyage of the +'Beagle'". On July 24th, 1834, when little more than half of the voyage +had been completed, Darwin wrote to Henslow, "My notes are becoming +bulky. I have about 600 small quarto pages full; about half of this is +Geology." ("M.L." I. page 14.) The last, and certainly not the least +important of all his duties, consisted in numbering, cataloguing, and +packing his specimens for despatch to Henslow, who had undertaken the +care of them. In his letters he often expresses the greatest solicitude +lest the value of these specimens should be impaired by the removal of +the numbers corresponding to his manuscript lists. Science owes much +to Henslow's patient care of the collections sent to him by Darwin. The +latter wrote in Henslow's biography, "During the five years' voyage, +he regularly corresponded with me and guided my efforts; he received, +opened, and took care of all the specimens sent home in many large +boxes." ("Life of Henslow", by L. Jenyns (Blomefield), London, 1862, +page 53.) + +Darwin's geological specimens are now very appropriately lodged for the +most part in the Sedgwick Museum, Cambridge, his original Catalogue with +subsequent annotations being preserved with them. From an examination of +these catalogues and specimens we are able to form a fair notion of +the work done by Darwin in his little cabin in the "Beagle", in the +intervals between his land journeys. + +Besides writing up his notes, it is evident that he was able to +accomplish a considerable amount of study of his specimens, before they +were packed up for despatch to Henslow. Besides hand-magnifiers and +a microscope, Darwin had an equipment for blowpipe-analysis, a +contact-goniometer and magnet; and these were in constant use by him. +His small library of reference (now included in the Collection of books +placed by Mr F. Darwin in the Botany School at Cambridge ("Catalogue +of the Library of Charles Darwin now in the Botany School, Cambridge". +Compiled by H.W. Rutherford; with an introduction by Francis Darwin. +Cambridge, 1908.)) appears to have been admirably selected, and in all +probability contained (in addition to a good many works relating to +South America) a fair number of excellent books of reference. Among +those relating to mineralogy, he possessed the manuals of Phillips, +Alexander Brongniart, Beudant, von Kobell and Jameson: all the +"Cristallographie" of Brochant de Villers and, for blowpipe work, Dr +Children's translation of the book of Berzelius on the subject. In +addition to these, he had Henry's "Experimental Chemistry" and Ure's +"Dictionary" (of Chemistry). A work, he evidently often employed, was P. +Syme's book on "Werner's Nomenclature of Colours"; while, for Petrology, +he used Macculloch's "Geological Classification of Rocks". How +diligently and well he employed his instruments and books is shown by +the valuable observations recorded in the annotated Catalogues drawn up +on board ship. + +These catalogues have on the right-hand pages numbers and descriptions +of the specimens, and on the opposite pages notes on the specimens--the +result of experiments made at the time and written in a very small hand. +Of the subsequently made pencil notes, I shall have to speak later. +(I am greatly indebted to my friend Mr A. Harker, F.R.S., for his +assistance in examining these specimens and catalogues. He has also +arranged the specimens in the Sedgwick Museum, so as to make reference +to them easy. The specimens from Ascension and a few others are however +in the Museum at Jermyn Street.) + +It is a question of great interest to determine the period and the +occasion of Darwin's first awakening to the great problem of the +transmutation of species. He tells us himself that his grandfather's +"Zoonomia" had been read by him "but without producing any effect," and +that his friend Grant's rhapsodies on Lamarck and his views on evolution +only gave rise to "astonishment." ("L.L." I. page 38.) + +Huxley, who had probably never seen the privately printed volume of +letters to Henslow, expressed the opinion that Darwin could not have +perceived the important bearing of his discovery of bones in the Pampean +Formation, until they had been studied in England, and their analogies +pronounced upon by competent comparative anatomists. And this seemed to +be confirmed by Darwin's own entry in his pocket-book for 1837, "In +July opened first notebook on Transmutation of Species. Had been greatly +struck from about the month of previous March on character of South +American fossils... " ("L.L." I. page 276.) + +The second volume of Lyell's "Principles of Geology" was published in +January, 1832, and Darwin's copy (like that of the other two volumes, +in a sadly dilapidated condition from constant use) has in it the +inscription, "Charles Darwin, Monte Video. Nov. 1832." As everyone +knows, Darwin in dedicating the second edition of his Journal of the +Voyage to Lyell declared, "the chief part of whatever scientific merit +this journal and the other works of the author may possess, has been +derived from studying the well-known and admirable 'Principles of +Geology'". + +In the first chapter of this second volume of the "Principles", Lyell +insists on the importance of the species question to the geologist, +but goes on to point out the difficulty of accepting the only +serious attempt at a transmutation theory which had up to that time +appeared--that of Lamarck. In subsequent chapters he discusses the +questions of the modification and variability of species, of hybridity, +and of the geographical distribution of plants and animals. He then +gives vivid pictures of the struggle for existence, ever going +on between various species, and of the causes which lead to their +extinction--not by overwhelming catastrophes, but by the silent and +almost unobserved action of natural causes. This leads him to consider +theories with regard to the introduction of new species, and, rejecting +the fanciful notions of "centres or foci of creation," he argues +strongly in favour of the view, as most reconcileable with observed +facts, that "each species may have had its origin in a single pair, or +individual, where an individual was sufficient, and species may have +been created in succession at such times and in such places as to enable +them to multiply and endure for an appointed period, and occupy an +appointed space on the globe." ("Principles of Geology", Vol. II. (1st +edition 1832), page 124. We now know, as has been so well pointed out +by Huxley, that Lyell, as early as 1827, was prepared to accept the +doctrine of the transmutation of species. In that year he wrote to +Mantell, "What changes species may really undergo! How impossible will +it be to distinguish and lay down a line, beyond which some of the +so-called extinct species may have never passed into recent ones" +(Lyell's "Life and Letters" Vol. I. page 168). To Sir John Herschel in +1836, he wrote, "In regard to the origination of new species, I am +very glad to find that you think it probable that it may be carried on +through the intervention of intermediate causes. I left this rather to +be inferred, not thinking it worth while to offend a certain class of +persons by embodying in words what would only be a speculation" (Ibid. +page 467). He expressed the same views to Whewell in 1837 (Ibid. Vol. +II. page 5.), and to Sedgwick (Ibid. Vol. II. page 36) to whom he says, +of "the theory, that the creation of new species is going on at the +present day"--"I really entertain it," but "I have studiously avoided +laying the doctrine down dogmatically as capable of proof" (see Huxley +in "L.L." II. pages 190-195.)) + +After pointing out how impossible it would be for a naturalist to prove +that a newly DISCOVERED species was really newly CREATED (Mr F. Darwin +has pointed out that his father (like Lyell) often used the term +"Creation" in speaking of the origin of new species ("L.L." II. chapter +1.)), Lyell argued that no satisfactory evidence OF THE WAY in which +these new forms were created, had as yet been discovered, but that he +entertained the hope of a possible solution of the problem being found +in the study of the geological record. + +It is not difficult, in reading these chapters of Lyell's great work, +to realise what an effect they would have on the mind of Darwin, as +new facts were collected and fresh observations concerning extinct and +recent forms were made in his travels. We are not surprised to find him +writing home, "I am become a zealous disciple of Mr Lyell's views, as +known in his admirable book. Geologising in South America, I am tempted +to carry parts to a greater extent even than he does." ("L.L." I. page +263.) + +Lyell's anticipation that the study of the geological record might +afford a clue to the discovery of how new species originate was +remarkably fulfilled, within a few months, by Darwin's discovery of +fossil bones in the red Pampean mud. + +It is very true that, as Huxley remarked, Darwin's knowledge of +comparative anatomy must have been, at that time, slight; but that he +recognised the remarkable resemblances between the extinct and existing +mammals of South America is proved beyond all question by a passage in +his letter to Henslow, written November 24th, 1832: "I have been very +lucky with fossil bones; I have fragments of at least six +distinct animals... I found a large surface of osseous polygonal +plates... Immediately I saw them I thought they must belong to an +enormous armadillo, living species of which genus are so abundant here," +and he goes on to say that he has "the lower jaw of some large animal +which, from the molar teeth, I should think belonged to the Edentata." +("M.L." I. pages 11, 12. See "Extracts of Letters addressed to Prof. +Henslow by C. Darwin" (1835), page 7.) + +Having found this important clue, Darwin followed it up with +characteristic perseverance. In his quest for more fossil bones he was +indefatigable. Mr Francis Darwin tells us, "I have often heard him speak +of the despair with which he had to break off the projecting extremity +of a huge, partly excavated bone, when the boat waiting for him would +wait no longer." ("L.L." I. page 276 (footnote).) Writing to Haeckel in +1864, Darwin says: "I shall never forget my astonishment when I dug +out a gigantic piece of armour, like that of the living armadillo." +(Haeckel, "History of Creation", Vol. I. page 134, London, 1876.) + +In a letter to Henslow in 1834 Darwin says: "I have just got scent +of some fossil bones... what they may be I do not know, but if gold or +galloping will get them they shall be mine." ("M.L." I. page 15.) + +Darwin also showed his sense of the importance of the discovery of these +bones by his solicitude about their safe arrival and custody. From the +Falkland Isles (March, 1834), he writes to Henslow: "I have been alarmed +by your expression 'cleaning all the bones' as I am afraid the printed +numbers will be lost: the reason I am so anxious they should not be, is, +that a part were found in a gravel with recent shells, but others in a +very different bed. Now with these latter there were bones of an Agouti, +a genus of animals, I believe, peculiar to America, and it would +be curious to prove that some one of the genus co-existed with the +Megatherium: such and many other points depend on the numbers being +carefully preserved." ("Extracts from Letters etc.", pages 13-14.) In +the abstract of the notes read to the Geological Society in 1835, we +read: "In the gravel of Patagonia he (Darwin) also found many bones of +the Megatherium and of five or six other species of quadrupeds, among +which he has detected the bones of a species of Agouti. He also met with +several examples of the polygonal plates, etc." ("Proc. Geol. Soc." Vol. +II. pages 211-212.) + +Darwin's own recollections entirely bear out the conclusion that he +fully recognised, WHILE IN SOUTH AMERICA, the wonderful significance +of the resemblances between the extinct and recent mammalian faunas. He +wrote in his "Autobiography": "During the voyage of the 'Beagle' I had +been deeply impressed by discovering in the Pampean formation +great fossil animals covered with armour like that on the existing +armadillos." ("L.L." I. page 82.) + +The impression made on Darwin's mind by the discovery of these fossil +bones, was doubtless deepened as, in his progress southward from Brazil +to Patagonia, he found similar species of Edentate animals everywhere +replacing one another among the living forms, while, whenever fossils +occurred, they also were seen to belong to the same remarkable group of +animals. (While Darwin was making these observations in South America, +a similar generalisation to that at which he arrived was being reached, +quite independently and almost simultaneously, with respect to the +fossil and recent mammals of Australia. In the year 1831, Clift gave +to Jameson a list of bones occurring in the caves and breccias of +Australia, and in publishing this list the latter referred to the fact +that the forms belonged to marsupials, similar to those of the +existing Australian fauna. But he also stated that, as a skull had been +identified (doubtless erroneously) as having belonged to a hippopotamus, +other mammals than marsupials must have spread over the island in late +Tertiary times. It is not necessary to point out that this paper was +quite unknown to Darwin while in South America. Lyell first noticed it +in the third edition of his "Principles", which was published in May, +1834 (see "Edinb. New Phil. Journ." Vol. X. (1831), pages 394-6, and +Lyell's "Principles" (3rd edition), Vol. III. page 421). Darwin referred +to this discovery in 1839 (see his "Journal", page 210.)) + +That the passage in Darwin's pocket-book for 1837 can only refer to an +AWAKENING of Darwin's interest in the subject--probably resulting from +a sight of the bones when they were being unpacked--I think there +cannot be the smallest doubt; AND WE MAY THEREFORE CONFIDENTLY FIX UPON +NOVEMBER, 1832, AS THE DATE AT WHICH DARWIN COMMENCED THAT LONG SERIES +OF OBSERVATIONS AND REASONINGS WHICH EVENTUALLY CULMINATED IN THE +PREPARATION OF THE "ORIGIN OF SPECIES". Equally certain is it, that it +was his geological work that led Darwin into those paths of research +which in the end conducted him to his great discoveries. I quite agree +with the view expressed by Mr F. Darwin and Professor Seward, that +Darwin, like Lyell, "thought it 'almost useless' to try to prove the +truth of evolution until the cause of change was discovered" ("M.L." +I. page 38.), and that possibly he may at times have vacillated in his +opinions, but I believe there is evidence that, from the date mentioned, +the "species question" was always more or less present in Darwin's mind. +(Although we admit with Huxley that Darwin's training in comparative +anatomy was very small, yet it may be remembered that he was a medical +student for two years, and, if he hated the lectures, he enjoyed the +society of naturalists. He had with him in the little "Beagle" library a +fair number of zoological books, including works on Osteology by Cuvier, +Desmarest and Lesson, as well as two French Encyclopaedias of Natural +History. As a sportsman, he would obtain specimens of recent mammals in +South America, and would thus have opportunities of studying their teeth +and general anatomy. Keen observer, as he undoubtedly was, we need not +then be surprised that he was able to make out the resemblances between +the recent and fossil forms.) + +It is clear that, as time went on, Darwin became more and more absorbed +in his geological work. One very significant fact was that the once +ardent sportsman, when he found that shooting the necessary game and +zoological specimens interfered with his work with the hammer, gave up +his gun to his servant. ("L.L." I. page 63.) There is clear evidence +that Darwin gradually became aware how futile were his attempts to add +to zoological knowledge by dissection and drawing, while he felt ever +increasing satisfaction with his geological work. + +The voyage fortunately extended to a much longer period (five years) +than the two originally intended, but after being absent nearly three +years, Darwin wrote to his sister in November, 1834, "Hurrah! hurrah! +it is fixed that the 'Beagle' shall not go one mile south of Cape +Tres Montes (about 200 miles south of Chiloe), and from that point to +Valparaiso will be finished in about five months. We shall examine the +Chonos Archipelago, entirely unknown, and the curious inland sea behind +Chiloe. For me it is glorious. Cape Tres Montes is the most southern +point where there is much geological interest, as there the modern beds +end. The Captain then talks of crossing the Pacific; but I think we +shall persuade him to finish the coast of Peru, where the climate +is delightful, the country hideously sterile, but abounding with the +highest interest to the geologist... I have long been grieved and most +sorry at the interminable length of the voyage (though I never would +have quitted it)... I could not make up my mind to return. I could not +give up all the geological castles in the air I had been building up for +the last two years." ("L.L." I. pages 257-58.) + +In April, 1835, he wrote to another sister: "I returned a week ago from +my excursion across the Andes to Mendoza. Since leaving England I have +never made so successful a journey... how deeply I have enjoyed it; it +was something more than enjoyment; I cannot express the delight which I +felt at such a famous winding-up of all my geology in South America. I +literally could hardly sleep at nights for thinking over my day's work. +The scenery was so new, and so majestic; everything at an elevation +of 12,000 feet bears so different an aspect from that in the lower +country... To a geologist, also, there are such manifest proofs of +excessive violence; the strata of the highest pinnacles are tossed about +like the crust of a broken pie." ("L.L." I. pages 259-60.) + +Darwin anticipated with intense pleasure his visit to the Galapagos +Islands. On July 12th, 1835, he wrote to Henslow: "In a few days' time +the "Beagle" will sail for the Galapagos Islands. I look forward with +joy and interest to this, both as being somewhat nearer to England and +for the sake of having a good look at an active volcano. Although +we have seen lava in abundance, I have never yet beheld the crater." +("M.L." I. page 26.) He could little anticipate, as he wrote these +lines, the important aid in the solution of the "species question" that +would ever after make his visit to the Galapagos Islands so memorable. +In 1832, as we have seen, the great discovery of the relations of living +to extinct mammals in the same area had dawned upon his mind; in 1835 +he was to find a second key for opening up the great mystery, by +recognising the variations of similar types in adjoining islands among +the Galapagos. + +The final chapter in the second volume of the "Principles" had aroused +in Darwin's mind a desire to study coral-reefs, which was gratified +during his voyage across the Pacific and Indian Oceans. His theory on +the subject was suggested about the end of 1834 or the beginning of +1835, as he himself tells us, before he had seen a coral-reef, +and resulted from his work during two years in which he had "been +incessantly attending to the effects on the shores of South America of +the intermittent elevation of the land, together with denudation and the +deposition of sediment." ("L.L." I. page 70.) + +On arriving at the Cape of Good Hope in July, 1836, Darwin was greatly +gratified by hearing that Sedgwick had spoken to his father in high +terms of praise concerning the work done by him in South America. +Referring to the news from home, when he reached Bahia once more, on the +return voyage (August, 1836), he says: "The desert, volcanic rocks, and +wild sea of Ascension... suddenly wore a pleasing aspect, and I set to +work with a good-will at my old work of Geology." ("L.L." I. page 265.) +Writing fifty years later, he says: "I clambered over the mountains of +Ascension with a bounding step and made the volcanic rocks resound under +my geological hammer!" ("L.L." I. page 66.) + +That his determination was now fixed to devote his own labours to the +task of working out the geological results of the voyage, and that +he was prepared to leave to more practised hands the study of his +biological collections, is clear from the letters he sent home at this +time. From St Helena he wrote to Henslow asking that he would propose +him as a Fellow of the Geological Society; and his Certificate, in +Henslow's handwriting, is dated September 8th, 1836, being signed from +personal knowledge by Henslow and Sedgwick. He was proposed on November +2nd and elected November 30th, being formally admitted to the Society +by Lyell, who was then President, on January 4th, 1837, on which date he +also read his first paper. Darwin did not become a Fellow of the Linnean +Society till eighteen years later (in 1854). + +An estimate of the value and importance of Darwin's geological +discoveries during the voyage of the "Beagle" can best be made when +considering the various memoirs and books in which the author +described them. He was too cautious to allow himself to write his first +impressions in his Journal, and wisely waited till he could study his +specimens under better conditions and with help from others on his +return. The extracts published from his correspondence with Henslow and +others, while he was still abroad, showed, nevertheless, how great was +the mass of observation, how suggestive and pregnant with results were +the reasonings of the young geologist. + +Two sets of these extracts from Darwin's letters to Henslow were +printed while he was still abroad. The first of these was the series of +"Geological Notes made during a survey of the East and West Coasts of +South America, in the years 1832, 1833, 1834 and 1835, with an account +of a transverse section of the Cordilleras of the Andes between +Valparaiso and Mendoza". Professor Sedgwick, who read these notes to +the Geological Society on November 18th, 1835, stated that "they were +extracted from a series of letters (addressed to Professor Henslow), +containing a great mass of information connected with almost every +branch of natural history," and that he (Sedgwick) had made a selection +of the remarks which he thought would be more especially interesting to +the Geological Society. An abstract of three pages was published in the +"Proceedings of the Geological Society" (Vol. II. pages 210-12.), but so +unknown was the author at this time that he was described as F. Darwin, +Esq., of St John's College, Cambridge! Almost simultaneously (on +November 16th, 1835) a second set of extracts from these letters--this +time of a general character--were read to the Philosophical Society at +Cambridge, and these excited so much interest that they were privately +printed in pamphlet form for circulation among the members. + +Many expeditions and "scientific missions" have been despatched to +various parts of the world since the return of the "Beagle" in 1836, but +it is doubtful whether any, even the most richly endowed of them, has +brought back such stores of new information and fresh discoveries as +did that little "ten-gun brig"--certainly no cabin or laboratory was the +birth-place of ideas of such fruitful character as was that narrow end +of a chart-room, where the solitary naturalist could climb into his +hammock and indulge in meditation. + +The third and most active portion of Darwin's career as a geologist was +the period which followed his return to England at the end of 1836. His +immediate admission to the Geological Society, at the beginning of 1837, +coincided with an important crisis in the history of geological science. + +The band of enthusiasts who nearly thirty years before had inaugurated +the Geological Society--weary of the fruitless conflicts between +"Neptunists" and "Plutonists"--had determined to eschew theory and +confine their labours to the collection of facts, their publications to +the careful record of observations. Greenough, the actual founder of the +Society, was an ardent Wernerian, and nearly all his fellow-workers had +come, more or less directly, under the Wernerian teaching. Macculloch +alone gave valuable support to the Huttonian doctrines, so far as they +related to the influence of igneous activity--but the most important +portion of the now celebrated "Theory of the Earth"--that dealing with +the competency of existing agencies to account for changes in past +geological times--was ignored by all alike. Macculloch's influence on +the development of geology, which might have had far-reaching effects, +was to a great extent neutralised by his peculiarities of mind and +temper; and, after a stormy and troublous career, he retired from the +society in 1832. In all the writings of the great pioneers in English +geology, Hutton and his splendid generalisation are scarcely ever +referred to. The great doctrines of Uniformitarianism, which he had +foreshadowed, were completely ignored, and only his extravagances of +"anti-Wernerianism" seem to have been remembered. + +When between 1830 and 1832, Lyell, taking up the almost forgotten ideas +of Hutton, von Hoff and Prevost, published that bold challenge to +the Catastrophists--the "Principles of Geology"--he was met with the +strongest opposition, not only from the outside world, which was amused +by his "absurdities" and shocked by his "impiety"--but not less from +his fellow-workers and friends in the Geological Society. For Lyell's +numerous original observations, and his diligent collection of facts his +contemporaries had nothing but admiration, and they cheerfully admitted +him to the highest offices in the society, but they met his reasonings +on geological theory with vehement opposition and his conclusions with +coldness and contempt. + +There is, indeed, a very striking parallelism between the reception of +the "Principles of Geology" by Lyell's contemporaries and the manner in +which the "Origin of Species" was met a quarter of a century later, as +is so vividly described by Huxley. ("L.L." II. pages 179-204.) Among +Lyell's fellow-geologists, two only--G. Poulett Scrope and John Herschel +(Both Lyell and Darwin fully realised the value of the support of these +two friends. Scrope in his appreciative reviews of the "Principles" +justly pointed out what was the weakest point, the inadequate +recognition of sub-aerial as compared with marine denudation. Darwin +also admitted that Scrope had to a great extent forestalled him in his +theory of Foliation. Herschel from the first insisted that the leading +idea of the "Principles" must be applied to organic as well as to +inorganic nature and must explain the appearance of new species (see +Lyell's "Life and Letters", Vol. I. page 467). Darwin tells us that +Herschel's "Introduction to the Study of Natural Philosophy" with +Humboldt's "Personal Narrative" "stirred up in me a burning zeal" in +his undergraduate days. I once heard Lyell exclaim with fervour "If +ever there was a heaven-born genius it was John Herschel!")--declared +themselves from the first his strong supporters. Scrope in two +luminous articles in the "Quarterly Review" did for Lyell what Huxley +accomplished for Darwin in his famous review in the "Times"; but Scrope +unfortunately was at that time immersed in the stormy sea of politics, +and devoted his great powers of exposition to the preparation of +fugitive pamphlets. Herschel, like Scrope, was unable to support +Lyell at the Geological Society, owing to his absence on the important +astronomical mission to the Cape. + +It thus came about that, in the frequent conflicts of opinion within the +walls of the Geological Society, Lyell had to bear the brunt of battle +for Uniformitarianism quite alone, and it is to be feared that he found +himself sadly overmatched when opposed by the eloquence of Sedgwick, the +sarcasm of Buckland, and the dead weight of incredulity on the part of +Greenough, Conybeare, Murchison and other members of the band of pioneer +workers. As time went on there is evidence that the opposition of De la +Beche and Whewell somewhat relaxed; the brilliant "Paddy" Fitton (as his +friends called him) was sometimes found in alliance with Lyell, but was +characteristically apt to turn his weapon, as occasion served, on friend +or foe alike; the amiable John Phillips "sat upon the fence." Only when +a new generation arose--including Jukes, Ramsay, Forbes and Hooker--did +Lyell find his teachings received with anything like favour. + +We can well understand, then, how Lyell would welcome such a recruit as +young Darwin--a man who had declared himself more Lyellian than Lyell, +and who brought to his support facts and observations gleaned from so +wide a field. + +The first meeting of Lyell and Darwin was characteristic of the two men. +Darwin at once explained to Lyell that, with respect to the origin of +coral-reefs, he had arrived at views directly opposed to those published +by "his master." To give up his own theory, cost Lyell, as he told +Herschel, a "pang at first," but he was at once convinced of the +immeasurable superiority of Darwin's theory. I have heard members +of Lyell's family tell of the state of wild excitement and sustained +enthusiasm, which lasted for days with Lyell after this interview, and +his letters to Herschel, Whewell and others show his pleasure at the new +light thrown upon the subject and his impatience to have the matter laid +before the Geological Society. + +Writing forty years afterwards, Darwin, speaking of the time of the +return of the "Beagle", says: "I saw a great deal of Lyell. One of his +chief characteristics was his sympathy with the work of others, and +I was as much astonished as delighted at the interest which he +showed when, on my return to England, I explained to him my views on +coral-reefs. This encouraged me greatly, and his advice and example had +much influence on me." ("L.L." I. page 68.) Darwin further states that +he saw more of Lyell at this time than of any other scientific man, and +at his request sent his first communication to the Geological Society. +("L.L." I. page 67.) + +"Mr Lonsdale" (the able curator of the Geological Society), Darwin wrote +to Henslow, "with whom I had much interesting conversation," "gave me a +most cordial reception," and he adds, "If I was not much more inclined +for geology than the other branches of Natural History, I am sure Mr +Lyell's and Lonsdale's kindness ought to fix me. You cannot conceive +anything more thoroughly good-natured than the heart-and-soul manner in +which he put himself in my place and thought what would be best to do." +("L.L." I. page 275.) + +Within a few days of Darwin's arrival in London we find Lyell writing to +Owen as follows: + +"Mrs Lyell and I expect a few friends here on Saturday next, 29th +(October), to an early tea party at eight o'clock, and it will give us +great pleasure if you can join it. Among others you will meet Mr Charles +Darwin, whom I believe you have seen, just returned from South America, +where he has laboured for zoologists as well as for hammer-bearers. +I have also asked your friend Broderip." ("The Life of Richard Owen", +London, 1894, Vol. I. page 102.) It would probably be on this occasion +that the services of Owen were secured for the work on the fossil bones +sent home by Darwin. + +On November 2nd, we find Lyell introducing Darwin as his guest at the +Geological Society Club; on December 14th, Lyell and Stokes proposed +Darwin as a member of the Club; between that date and May 3rd of the +following year, when his election to the Club took place, he was several +times dining as a guest. + +On January 4th, 1837, as we have already seen, Darwin was formally +admitted to the Geological Society, and on the same evening he read +his first paper (I have already pointed out that the notes read at the +Geological Society on Nov. 18, 1835 were extracts made by Sedgwick from +letters sent to Henslow, and not a paper sent home for publication by +Darwin.) before the Society, "Observations of proofs of recent elevation +on the coast of Chili, made during the Survey of H.M.S. "Beagle", +commanded by Captain FitzRoy, R.N." By C. Darwin, F.G.S. This paper was +preceded by one on the same subject by Mr A. Caldcleugh, and the reading +of a letter and other communications from the Foreign Office also +relating to the earthquakes in Chili. + +At the meeting of the Council of the Geological Society on February 1st, +Darwin was nominated as a member of the new Council, and he was elected +on February 17th. + +The meeting of the Geological Society on April 19th was devoted to the +reading by Owen of his paper on Toxodon, perhaps the most remarkable +of the fossil mammals found by Darwin in South America; and at the +next meeting, on May 3rd, Darwin himself read "A Sketch of the Deposits +containing extinct Mammalia in the neighbourhood of the Plata". The +next following meeting, on May 17th, was devoted to Darwin's Coral-reef +paper, entitled "On certain areas of elevation and subsidence in +the Pacific and Indian Oceans, as deduced from the study of Coral +Formations". Neither of these three early papers of Darwin were +published in the Transactions of the Geological Society, but the +minutes of the Council show that they were "withdrawn by the author by +permission of the Council." + +Darwin's activity during this session led to some rather alarming +effects upon his health, and he was induced to take a holiday in +Staffordshire and the Isle of Wight. He was not idle, however, for a +remark of his uncle, Mr Wedgwood, led him to make those interesting +observations on the work done by earthworms, that resulted in his +preparing a short memoir on the subject, and this paper, "On the +Formation of Mould", was read at the Society on November 1st, 1837, +being the first of Darwin's papers published in full; it appeared in +Vol. V. of the "Geological Transactions", pages 505-510. + +During this session, Darwin attended nearly all the Council meetings, +and took such an active part in the work of the Society that it is not +surprising to find that he was now requested to accept the position of +Secretary. After some hesitation, in which he urged his inexperience +and want of knowledge of foreign languages, he consented to accept the +appointment. ("L.L." I. page 285.) + +At the anniversary meeting on February 16th, 1838, the Wollaston Medal +was given to Owen in recognition of his services in describing the +fossil mammals sent home by Darwin. In his address, the President, +Professor Whewell, dwelt at length on the great value of the papers +which Darwin had laid before the Society during the preceding session. + +On March 7th, Darwin read before the Society the most important perhaps +of all his geological papers, "On the Connexion of certain Volcanic +Phenomena in South America, and on the Formation of Mountain-Chains and +Volcanoes as the effect of Continental Elevations". In this paper he +boldly attacked the tenets of the Catastrophists. It is evident that +Darwin at this time, taking advantage of the temporary improvement in +his health, was throwing himself into the breach of Uniformitarianism +with the greatest ardour. Lyell wrote to Sedgwick on April 21st, 1837, +"Darwin is a glorious addition to any society of geologists, and is +working hard and making way, both in his book and in our discussions." +("The Life and Letters of the Reverend Adam Sedgwick", Vol. I. page 484, +Cambridge, 1890.) + +We have unfortunately few records of the animated debates which took +place at this time between the old and new schools of geologists. I have +often heard Lyell tell how Lockhart would bring down a party of friends +from the Athenaeum Club to Somerset House on Geological nights, not, as +he carefully explained, that "he cared for geology, but because he liked +to while the fellows fight." But it fortunately happens that a few days +after this last of Darwin's great field-days, at the Geological Society, +Lyell, in a friendly letter to his father-in-law, Leonard Horner, wrote +a very lively account of the proceedings while his impressions were +still fresh; and this gives us an excellent idea of the character of +these discussions. + +Neither Sedgwick nor Buckland were present on this occasion, but we can +imagine how they would have chastised their two "erring pupils"--more +in sorrow than in anger--had they been there. Greenough, too, was +absent--possibly unwilling to countenance even by his presence such +outrageous doctrines. + +Darwin, after describing the great earthquakes which he had experienced +in South America, and the evidence of their connection with volcanic +outbursts, proceeded to show that earthquakes originated in fractures, +gradually formed in the earth's crust, and were accompanied by movements +of the land on either side of the fracture. In conclusion he boldly +advanced the view "that continental elevations, and the action of +volcanoes, are phenomena now in progress, caused by some great but slow +change in the interior of the earth; and, therefore, that it might +be anticipated, that the formation of mountain chains is likewise in +progress: and at a rate which may be judged of by either actions, but +most clearly by the growth of volcanoes." ("Proc. Geol. Soc." Vol. II. +pages 654-60.) + +Lyell's account ("Life, Letters and Journals of Sir Charles Lyell, +Bart.", edited by his sister-in-law, Mrs Lyell, Vol. II. pages 40, +41 (Letter to Leonard Horner, 1838), 2 vols. London, 1881.) of the +discussion was as follows: "In support of my heretical notions," Darwin +"opened upon De la Beche, Phillips and others his whole battery of the +earthquakes and volcanoes of the Andes, and argued that spaces at least +a thousand miles long were simultaneously subject to earthquakes and +volcanic eruptions, and that the elevation of the Pampas, Patagonia, +etc., all depended on a common cause; also that the greater the +contortions of strata in a mountain chain, the smaller must have been +each separate and individual movement of that long series which was +necessary to upheave the chain. Had they been more violent, he +contended that the subterraneous fluid matter would have gushed out and +overflowed, and the strata would have been blown up and annihilated. (It +is interesting to compare this with what Darwin wrote to Henslow +seven years earlier.) He therefore introduces a cooling of one small +underground injection, and then the pumping in of other lava, or +porphyry, or granite, into the previously consolidated and first-formed +mass of igneous rock. (Ideas somewhat similar to this suggestion have +recently been revived by Dr See ("Proc. Am. Phil. Soc." Vol. XLVII. +1908, page 262.).) When he had done his description of the reiterated +strokes of his volcanic pump, De la Beche gave us a long oration about +the impossibility of strata of the Alps, etc., remaining flexible +for such a time as they must have done, if they were to be tilted, +convoluted, or overturned by gradual small shoves. He never, however, +explained his theory of original flexibility, and therefore I am as +unable as ever to comprehend why flexiblility is a quality so limited in +time. + +"Phillips then got up and pronounced a panegyric upon the "Principles +of Geology", and although he still differed, thought the actual cause +doctrine had been so well put, that it had advanced the science and +formed a date or era, and that for centuries the two opposite doctrines +would divide geologists, some contending for greater pristine forces, +others satisfied, like Lyell and Darwin, with the same intensity as +nature now employs. + +"Fitton quizzed Phillips a little for the warmth of his eulogy, saying +that he (Fitton) and others, who had Mr Lyell always with them, were in +the habit of admiring and quarrelling with him every day, as one +might do with a sister or cousin, whom one would only kiss and embrace +fervently after a long absence. This seemed to be Mr Phillips' case, +coming up occasionally from the provinces. Fitton then finished this +drollery by charging me with not having done justice to Hutton, who he +said was for gradual elevation. + +"I replied, that most of the critics had attacked me for overrating +Hutton, and that Playfair understood him as I did. + +"Whewell concluded by considering Hopkins' mathematical calculations, to +which Darwin had often referred. He also said that we ought not to try +and make out what Hutton would have taught and thought, if he had known +the facts which we now know." + +It may be necessary to point out, in explanation of the above narrative, +that while it was perfectly clear from Hutton's rather obscure and +involved writings that he advocated slow and gradual change on +the earth's surface, his frequent references to violent action and +earthquakes led many--including Playfair, Lyell and Whewell--to believe +that he held the changes going on in the earth's interior to be of +a catastrophic nature. Fitton, however, maintained that Hutton was +consistently uniformitarian. Before the idea of the actual "flowing" of +solid bodies under intense pressure had been grasped by geologists, +De la Beche, like Playfair before him, maintained that the bending +and folding of rocks must have been effected before their complete +consolidation. + +In concluding his account of this memorable discussion, Lyell adds: "I +was much struck with the different tone in which my gradual causes +was treated by all, even including De la Beche, from that which they +experienced in the same room four years ago, when Buckland, De la +Beche(?), Sedgwick, Whewell, and some others treated them with as much +ridicule as was consistent with politeness in my presence." + +This important paper was, in spite of its theoretical character, +published in full in the "Transactions of the Geological Society" (Ser. +2, Vol. V. pages 601-630). It did not however appear till 1840, and +possibly some changes may have been made in it during the long interval +between reading and printing. During the year 1839, Darwin continued his +regular attendance at the Council meetings, but there is no record of +any discussions in which he may have taken part, and he contributed +no papers himself to the Society. At the beginning of 1840, he was +re-elected for the third time as Secretary, but the results of failing +health are indicated by the circumstance that, only at one meeting early +in the session, was he able to attend the Council. At the beginning of +the next session (Feb. 1841) Bunbury succeeded him as Secretary, +Darwin still remaining on the Council. It may be regarded as a striking +indication of the esteem in which he was held by his fellow geologists, +that Darwin remained on the Council for 14 consecutive years down to +1849, though his attendances were in some years very few. In 1843 and +1844 he was a Vice-president, but after his retirement at the beginning +of 1850, he never again accepted re-nomination. He continued, however, +to contribute papers to the Society, as we shall see, down to the end of +1862. + +Although Darwin early became a member of the Geological Dining Club, it +is to be feared that he scarcely found himself in a congenial atmosphere +at those somewhat hilarious gatherings, where the hardy wielders of the +hammer not only drank port--and plenty of it--but wound up their +meal with a mixture of Scotch ale and soda water, a drink which, as +reminiscent of the "field," was regarded as especially appropriate to +geologists. Even after the meetings, which followed the dinners, +they reassembled for suppers, at which geological dainties, like +"pterodactyle pie" figured in the bill of fare, and fines of bumpers +were inflicted on those who talked the "ologies." + +After being present at a fair number of meetings in 1837 and 1838, +Darwin's attendances at the Club fell off to two in 1839, and by 1841 +he had ceased to be a member. In a letter to Lyell on Dec. 2nd, 1841, +Leonard Horner wrote that the day before "At the Council, I had the +satisfaction of seeing Darwin again in his place and looking well. He +tried the last evening meeting, but found it too much, but I hope before +the end of the season he will find himself equal to that also. I hail +Darwin's recovery as a vast gain to science." Darwin's probably last +attendance, this time as a guest, was in 1851, when Horner again +wrote to Lyell, "Charles Darwin was at the Geological Society's Club +yesterday, where he had not been for ten years--remarkably well, and +grown quite stout." ("Memoirs of Leonard Horner" (privately printed), +Vol. II. pages 39 and 195.) + +It may be interesting to note that at the somewhat less lively dining +Club--the Philosophical--in the founding of which his friends Lyell and +Hooker had taken so active a part, Darwin found himself more at home, +and he was a frequent attendant--in spite of his residence being at +Down--from 1853 to 1864. He even made contributions on scientific +questions after these dinners. In a letter to Hooker he states that he +was deeply interested in the reforms of the Royal Society, which the +Club was founded to promote. He says also that he had arranged to come +to town every Club day "and then my head, I think, will allow me on an +average to go to every other meeting. But it is grievous how often any +change knocks me up." ("L.L." II. pages 42, 43.) + +Of the years 1837 and 1838 Darwin himself says they were "the most +active ones which I ever spent, though I was occasionally unwell, and +so lost some time... I also went a little into society." ("L.L." I. pages +67, 68.) But of the four years from 1839 to 1842 he has to confess sadly +"I did less scientific work, though I worked as hard as I could, than +during any other equal length of time in my life. This was owing to +frequently recurring unwellness, and to one long and serious illness." +("L.L." I. page 69.) + +Darwin's work at the Geological Society did not by any means engage the +whole of his energies, during the active years 1837 and 1838. In June of +the latter year, leaving town in somewhat bad health, he found himself +at Edinburgh again, and engaged in examining the Salisbury Craigs, in a +very different spirit to that excited by Jameson's discourse. ("L.L." +I. page 290.) Proceeding to the Highlands he then had eight days of hard +work at the famous "Parallel Roads of Glen Roy", being favoured with +glorious weather. + +He says of the writing of the paper on the subject--the only memoir +contributed by Darwin to the Royal Society, to which he had been +recently elected--that it was "one of the most difficult and instructive +tasks I was ever engaged on." The paper extends to 40 quarto pages +and is illustrated by two plates. Though it is full of the records +of careful observation and acute reasoning, yet the theory of marine +beaches which he propounded was, as he candidly admitted in after years +("M.L." II page 188.), altogether wrong. The alternative lake-theory he +found himself unable to accept at the time, for he could not understand +how barriers could be formed at successive levels across the valleys; +and until the following year, when the existence of great glaciers +in the district was proved by the researches of Agassiz, Buckland and +others, the difficulty appeared to him an insuperable one. Although +Darwin said of this paper in after years that it "was a great failure +and I am ashamed of it"--yet he retained his interest in the question +ever afterwards, and he says "my error has been a good lesson to me +never to trust in science to the principle of exclusion." ("M.L." II. +pages 171-93.) + +Although Darwin had not realised in 1838 that large parts of the British +Islands had been occupied by great glaciers, he had by no means failed +while in South America to recognise the importance of ice-action. His +observations, as recorded in his Journal, on glaciers coming down to +the sea-level, on the west coast of South America, in a latitude +corresponding to a much lower one than that of the British Islands, +profoundly interested geologists; and the same work contains many +valuable notes on the boulders and unstratified beds in South America in +which they were included. + +But in 1840 Agassiz read his startling paper on the evidence of the +former existence of glaciers in the British Islands, and this was +followed by Buckland's memoir on the same subject. On April 14, 1841, +Darwin contributed to the Geological Society his important paper "On the +Distribution of Erratic Boulders and the Contemporaneous Unstratified +Deposits of South America", a paper full of suggestiveness for those +studying the glacial deposits of this country. It was published in the +"Transactions" in 1842. + +The description of traces of glacial action in North Wales, by Buckland, +appears to have greatly excited the interest of Darwin. With Sedgwick he +had, in 1831, worked at the stratigraphy of that district, but neither +of them had noticed the very interesting surface features. ("L.L." I. +page 58.) Darwin was able to make a journey to North Wales in June, +1842 (alas! it was his last effort in field-geology) and as a result +he published his most able and convincing paper on the subject in the +September number of the "Philosophical Magazine" for 1842. Thus the +mystery of the bell-stone was at last solved and Darwin, writing many +years afterwards, said "I felt the keenest delight when I first read of +the action of icebergs in transporting boulders, and I gloried in the +progress of Geology." ("L.L." I. page 41.) To the "Geographical Journal" +he had sent in 1839 a note "On a Rock seen on an Iceberg in 16 deg S. +Latitude." For the subject of ice-action, indeed, Darwin retained the +greatest interest to the end of his life. ("M.L." II. pages 148-71.) + +In 1846, Darwin read two papers to the Geological Society "On the +dust which falls on vessels in the Atlantic, and On the Geology of the +Falkland Islands"; in 1848 he contributed a note on the transport of +boulders from lower to higher levels; and in 1862 another note on the +thickness of the Pampean formation, as shown by recent borings at Buenos +Ayres. An account of the "British Fossil Lepadidae" read in 1850, was +withdrawn by him. + +At the end of 1836 Darwin had settled himself in lodgings in Fitzwilliam +Street, Cambridge, and devoted three months to the work of unpacking his +specimens and studying his collection of rocks. The pencilled notes on +the Manuscript Catalogue in the Sedgwick Museum enable us to realise +his mode of work, and the diligence with which it was carried on. The +letters M and H, indicate the assistance he received from time to +time from Professor Miller, the crystallographer, and from his friend +Henslow. Miller not only measured many of the crystals submitted to him, +but evidently taught Darwin to use the reflecting goniometer himself +with considerable success. The "book of measurements" in which the +records were kept, appears to have been lost, but the pencilled notes +in the catalogue show how thoroughly the work was done. The letter R +attached to some of the numbers in the catalogue evidently refers to the +fact that they were submitted to Mr Trenham Reeks (who analysed some of +his specimens) at the Geological Survey quarters in Craig's Court. This +was at a later date when Darwin was writing the "Volcanic Islands" and +"South America". + +It was about the month of March, 1837, that Darwin completed this work +upon his rocks, and also the unpacking and distribution of his fossil +bones and other specimens. We have seen that November, 1832, must +certainly be regarded as the date when he FIRST realised the important +fact that the fossil mammals of the Pampean formation were all closely +related to the existing forms in South America; while October, 1835, +was, as undoubtedly, the date when the study of the birds and other +forms of life in the several islands of the Galapagos Islands gave +him his SECOND impulse towards abandoning the prevalent view of the +immutability of species. When then in his pocket-book for 1837 Darwin +wrote the often quoted passage: "In July opened first note-book on +Transmutation of Species. Had been greatly struck from about the month +of previous March on character of South American fossils, and species on +Galapagos Archipelago. These facts (especially latter), origin of all my +views" ("L.L." I. page 276.), it is clear that he must refer, not to +his first inception of the idea of evolution, but to the flood of +recollections, the reawakening of his interest in the subject, which +could not fail to result from the sight of his specimens and the +reference to his notes. + +Except during the summer vacation, when he was visiting his father and +uncle, and with the latter making his first observations upon the work +of earthworms, Darwin was busy with his arrangements for the publication +of the five volumes of the "Zoology of the 'Beagle'" and in getting the +necessary financial aid from the government for the preparation of the +plates. He was at the same time preparing his "Journal" for publication. +During the years 1837 to 1843, Darwin worked intermittently on the +volumes of Zoology, all of which he edited, while he wrote introductions +to those by Owen and Waterhouse and supplied notes to the others. + +Although Darwin says of his Journal that the preparation of the book +"was not hard work, as my MS. Journal had been written with care." Yet +from the time that he settled at 36, Great Marlborough Street in March, +1837, to the following November he was occupied with this book. He tells +us that the account of his scientific observations was added at this +time. The work was not published till March, 1839, when it appeared +as the third volume of the "Narrative of the Surveying Voyages of H.M. +Ships 'Adventure' and 'Beagle' between the years 1826 and 1836". The +book was probably a long time in the press, for there are no less than +20 pages of addenda in small print. Even in this, its first form, the +work is remarkable for its freshness and charm, and excited a great +amount of attention and interest. In addition to matters treated of in +greater detail in his other works, there are many geological notes of +extreme value in this volume, such as his account of lightning tubes, of +the organisms found in dust, and of the obsidian bombs of Australia. + +Having thus got out of hand a number of preliminary duties, Darwin was +ready to set to work upon the three volumes which were designed by him +to constitute "The Geology of the Voyage of the 'Beagle'". The first of +these was to be on "The Structure and Distribution of Coral-reefs". He +commenced the writing of the book on October 5, 1838, and the last proof +was corrected on May 6, 1842. Allowing for the frequent interruptions +through illness, Darwin estimated that it cost him twenty months of hard +work. + +Darwin has related how his theory of Coral-reefs which was begun in a +more "deductive spirit" than any of his other work, for in 1834 or 1835 +it "was thought out on the west coast of South America, before I had +seen a true coral-reef." ("L.L." I. page 70.) The final chapter in +Lyell's second volume of the "Principles" was devoted to the subject +of Coral-reefs, and a theory was suggested to account for the peculiar +phenomena of "atolls." Darwin at once saw the difficulty of accepting +the view that the numerous and diverse atolls all represent submerged +volcanic craters. His own work had for two years been devoted to the +evidence of land movements over great areas in South America, and thus +he was led to announce his theory of subsidence to account for barrier +and encircling reefs as well as atolls. + +Fortunately, during his voyage across the Pacific and Indian Oceans, in +his visit to Australia and his twelve days' hard work at Keeling Island, +he had opportunities for putting his theory to the test of observation. + +On his return to England, Darwin appears to have been greatly surprised +at the amount of interest that his new theory excited. Urged by Lyell, +he read to the Geological Society a paper on the subject, as we have +seen, with as little delay as possible, but this paper was "withdrawn by +permission of the Council." An abstract of three pages however appeared +in the "Proceedings of the Geological Society". (Vol. II. pages 552-554 +(May 31, 1837).) A full account of the observations and the theory was +given in the "Journal" (1839) in the 40 pages devoted to Keeling +Island in particular and to Coral formations generally. ("Journal" (1st +edition), pages 439-69.) + +It will be readily understood what an amount of labour the book on +Coral reefs cost Darwin when we reflect on the number of charts, sailing +directions, narratives of voyages and other works which, with the +friendly assistance of the authorities at the Admiralty, he had +to consult before he could draw up his sketch of the nature and +distribution of the reefs, and this was necessary before the theory, in +all its important bearings, could be clearly enunciated. Very pleasing +is it to read how Darwin, although arriving at a different conclusion to +Lyell, shows, by quoting a very suggestive passage in the "Principles" +(1st edition Vol. II. page 296.), how the latter only just missed the +true solution. This passage is cited, both in the "Journal" and the +volume on Coral-reefs. Lyell, as we have seen, received the new theory +not merely ungrudgingly, but with the utmost enthusiasm. + +In 1849 Darwin was gratified by receiving the support of Dana, after his +prolonged investigation in connection with the U.S. Exploring Expedition +("M.L." II. pages 226-8.), and in 1874 he prepared a second edition of +his book, in which some objections which had been raised to the theory +were answered. A third edition, edited by Professor Bonney, appeared in +1880, and a fourth (a reprint of the first edition, with introduction by +myself) in 1890. + +Although Professor Semper, in his account of the Pelew Islands, had +suggested difficulties in the acceptance of Darwin's theory, it was +not till after the return of the "Challenger" expedition in 1875 that a +rival theory was propounded, and somewhat heated discussions were raised +as to the respective merits of the two theories. While geologists have, +nearly without exception, strongly supported Darwin's views, the notes +of dissent have come almost entirely from zoologists. At the height +of the controversy unfounded charges of unfairness were made against +Darwin's supporters and the authorities of the Geological Society, but +this unpleasant subject has been disposed of, once for all, by Huxley. +("Essays upon some Controverted Questions", London, 1892, pages 314-328 +and 623-625.) + +Darwin's final and very characteristic utterance on the coral-reef +controversy is found in a letter which he wrote to Professor Alexander +Agassiz, May 5th, 1881: less than a year before his death: "If I am +wrong, the sooner I am knocked on the head and annihilated so much the +better. It still seems to me a marvellous thing that there should not +have been much, and long-continued, subsidence in the beds of the great +oceans. I wish that some doubly rich millionaire would take it into his +head to have borings made in some of the Pacific and Indian atolls, and +bring home cores for slicing from a depth of 500 or 600 feet." ("L.L." +III. page 184.) + +Though the "doubly rich millionaire" has not been forthcoming, the +energy, in England, of Professor Sollas, and in New South Wales of +Professor Anderson Stuart served to set on foot a project, which, aided +at first by the British Association for the Advancement of Science, and +afterwards taken up jointly by the Royal Society, the New South +Wales Government, and the Admiralty, has led to the most definite and +conclusive results. + +The Committee appointed by the Royal Society to carry out the +undertaking included representatives of all the views that had been +put forward on the subject. The place for the experiment was, with the +consent of every member of the Committee, selected by the late Admiral +Sir W.J. Wharton--who was not himself an adherent of Darwin's views--and +no one has ventured to suggest that his selection, the splendid atoll of +Funafuti, was not a most judicious one. + +By the pluck and perseverance of Professor Sollas in the preliminary +expedition, and of Professor T. Edgeworth David and his pupils, in +subsequent investigations of the island, the rather difficult piece +of work was brought to a highly satisfactory conclusion. The New South +Wales Government lent boring apparatus and workmen, and the Admiralty +carried the expedition to its destination in a surveying ship which, +under Captain (now Admiral) A. Mostyn Field, made the most complete +survey of the atoll and its surrounding seas that has ever been +undertaken in the case of a coral formation. + +After some failures and many interruptions, the boring was carried to +the depth of 1114 feet, and the cores obtained were sent to England. +Here the examination of the materials was fortunately undertaken by +a zoologist of the highest repute, Dr G.J. Hinde--who has a wide +experience in the study of organisms by sections--and he was aided at +all points by specialists in the British Museum of Natural History +and by other naturalists. Nor were the chemical and other problems +neglected. + +The verdict arrived at, after this most exhaustive study of a series of +cores obtained from depths twice as great as that thought necessary by +Darwin, was as follows:--"The whole of the cores are found to be built +up of those organisms which are seen forming coral-reefs near the +surface of the ocean--many of them evidently in situ; and not the +slightest indication could be detected, by chemical or microscopic +means, which suggested the proximity of non-calcareous rocks, even in +the lowest portions brought up." + +But this was not all. Professor David succeeded in obtaining the aid +of a very skilful engineer from Australia, while the Admiralty allowed +Commander F.C.D. Sturdee to take a surveying ship into the lagoon +for further investigations. By very ingenious methods, and with great +perseverance, two borings were put down in the midst of the lagoon to +the depth of nearly 200 feet. The bottom of the lagoon, at the depth of +101 1/2 feet from sea-level, was found to be covered with remains of the +calcareous, green sea-weed Halimeda, mingled with many foraminifera; but +at a depth of 163 feet from the surface of the lagoon the boring tools +encountered great masses of coral, which were proved from the fragments +brought up to belong to species that live within AT MOST 120 feet from +the surface of the ocean, as admitted by all zoologists. ("The Atoll +of Funafuti; Report of the Coral Reef Committee of the Royal Society", +London, 1904.) + +Darwin's theory, as is well known, is based on the fact that the +temperature of the ocean at any considerable depth does not permit of +the existence and luxuriant growth of the organisms that form the reefs. +He himself estimated this limit of depth to be from 120 to 130 feet; +Dana, as an extreme, 150 feet; while the recent very prolonged and +successful investigations of Professor Alexander Agassiz in the Pacific +and Indian Oceans lead him also to assign a limiting depth of 150 feet; +the EFFECTIVE, REEF-FORMING CORALS, however, flourishing at a much +smaller depth. Mr Stanley Gardiner gives for the most important +reef-forming corals depths between 30 and 90 feet, while a few are found +as low as 120 feet or even 180 feet. + +It will thus be seen that the verdict of Funafuti is clearly and +unmistakeably in favour of Darwin's theory. It is true that some +zoologists find a difficulty in realising a slow sinking of parts of the +ocean floor, and have suggested new and alternative explanations: but +geologists generally, accepting the proofs of slow upheaval in +some areas--as shown by the admirable researches of Alexander +Agassiz--consider that it is absolutely necessary to admit that this +elevation is balanced by subsidence in other areas. If atolls and +barrier-reefs did not exist we should indeed be at a great loss to frame +a theory to account for their absence. + +After finishing his book on Coral-reefs, Darwin made his summer +excursion to North Wales, and prepared his important memoir on the +glaciers of that district: but by October (1842) we find him fairly +settled at work upon the second volume of his "Geology of the +'Beagle'--Geological Observations on the Volcanic Islands, visited +during the Voyage of H.M.S. 'Beagle'". The whole of the year 1843 was +devoted to this work, but he tells his friend Fox that he could "manage +only a couple of hours per day, and that not very regularly." ("L.L." I. +page 321.) Darwin's work on the various volcanic islands examined by +him had given him the most intense pleasure, but the work of writing +the book by the aid of his notes and specimens he found "uphill +work," especially as he feared the book would not be read, "even by +geologists." (Loc. cit.) + +As a matter of fact the work is full of the most interesting +observations and valuable suggestions, and the three editions (or +reprints) which have appeared have proved a most valuable addition to +geological literature. It is not necessary to refer to the novel and +often very striking discoveries described in this well-known work. The +subsidence beneath volcanic vents, the enormous denudation of volcanic +cones reducing them to "basal wrecks," the effects of solfatarric action +and the formation of various minerals in the cavities of rocks--all +of these subjects find admirable illustration from his graphic +descriptions. One of the most important discussions in this volume is +that dealing with the "lamination" of lavas as especially well seen in +the rocks of Ascension. Like Scrope, Darwin recognised the close analogy +between the structure of these rocks and those of metamorphic origin--a +subject which he followed out in the volume "Geological Observations on +South America". + +Of course in these days, since the application of the microscope to the +study of rocks in thin sections, Darwin's nomenclature and descriptions +of the petrological characters of the lavas appear to us somewhat crude. +But it happened that the "Challenger" visited most of the volcanic +islands described by Darwin, and the specimens brought home were +examined by the eminent petrologist Professor Renard. Renard was so +struck with the work done by Darwin, under disadvantageous conditions, +that he undertook a translation of Darwin's work into French, and I +cannot better indicate the manner in which the book is regarded by +geologists than by quoting a passage from Renard's preface. Referring +to his own work in studying the rocks brought home by the "Challenger" +(Renard's descriptions of these rocks are contained in the "Challenger +Reports". Mr Harker is supplementing these descriptions by a series of +petrological memoirs on Darwin's specimens, the first of which appeared +in the "Geological Magazine" for March, 1907.), he says: + +"Je dus, en me livrant a ces recherches, suivre ligne par ligne les +divers chapitres des "Observations geologiques" consacrees aux iles de +l'Atlantique, oblige que j'etais de comparer d'une maniere suivie les +resultats auxquels j'etais conduit avec ceux de Darwin, qui servaient +de controle a mes constatations. Je ne tardai pas a eprouver une vive +admiration pour ce chercheur qui, sans autre appareil que la loupe, +sans autre reaction que quelques essais pyrognostiques, plus rarement +quelques mesures au goniometre, parvenait a discerner la nature des +agregats mineralogiques les plue complexes et les plus varies. Ce +coup d'oeil qui savait embrasser de si vastes horizons, penetre ici +profondement tous les details lithologiques. Avec quelle surete +et quelle exactitude la structure et la composition des roches ne +sont'elles pas determinees, l'origne de ces masses minerales deduite et +confirmee par l'etude comparee des manifestations volcaniques d'autres +regions; avec quelle science les relations entre les faits qu'il +decouvre et ceux signales ailleurs par ses devanciers ne sont'elles pas +etablies, et comme voici ebranlees les hypotheses regnantes, admises +sans preuves, celles, par exemple, des crateres de soulevement et de la +differenciation radicale des phenomenes plutoniques et volcaniques! +Ce qui acheve de donner a ce livre un incomparable merite, ce sont les +idees nouvelles qui s'y trouvent en germe et jetees la comme au +hasard ainsi qu'un superflu d'abondance intellectuelle inepuisable." +("Observations Geologiques sur les Iles Volcaniques... ", Paris, 1902, +pages vi., vii.) + +While engaged in his study of banded lavas, Darwin was struck with the +analogy of their structure with that of glacier ice, and a note on the +subject, in the form of a letter addressed to Professor J.D. Forbes, was +published in the "Proceedings of the Royal Society of Edinburgh". (Vol. +II. (1844-5), pages 17, 18.) + +From April, 1832, to September, 1835, Darwin had been occupied in +examining the coast or making inland journeys in the interior of the +South American continent. Thus while eighteen months were devoted, at +the beginning and end of the voyage to the study of volcanic islands +and coral-reefs, no less than three and a half years were given to South +American geology. The heavy task of dealing with the notes and specimens +accumulated during that long period was left by Darwin to the last. +Finishing the "Volcanic Islands" on February 14th, 1844, he, in July of +the same year, commenced the preparation of two important works which +engaged him till near the end of the year 1846. The first was his +"Geological Observations on South America", the second a recast of his +"Journal", published under the short title of "A Naturalist's Voyage +round the World". + +The first of these works contains an immense amount of information +collected by the author under great difficulties and not unfrequently +at considerable risk to life and health. No sooner had Darwin landed +in South America than two sets of phenomena powerfully arrested his +attention. The first of these was the occurrence of great masses of red +mud containing bones and shells, which afforded striking evidence that +the whole continent had shared in a series of slow and gradual but +often interrupted movements. The second related to the great masses of +crystalline rocks which, underlying the muds, cover so great a part of +the continent. Darwin, almost as soon as he landed, was struck by +the circumstance that the direction, as shown by his compass, of +the prominent features of these great crystalline rock-masses--their +cleavage, master-joints, foliation and pegmatite veins--was the same as +the orientation described by Humboldt (whose works he had so carefully +studied) on the west of the same great continent. + +The first five chapters of the book on South America were devoted to +formations of recent date and to the evidence collected on the east and +west coasts of the continent in regard to those grand earth-movements, +some of which could be shown to have been accompanied by +earthquake-shocks. The fossil bones, which had given him the first hint +concerning the mutability of species, had by this time been studied and +described by comparative anatomists, and Darwin was able to elaborate +much more fully the important conclusion that the existing fauna of +South America has a close analogy with that of the period immediately +preceding our own. + +The remaining three chapters of the book dealt with the metamorphic and +plutonic rocks, and in them Darwin announced his important conclusions +concerning the relations of cleavage and foliation, and on the close +analogy of the latter structure with the banding found in rock-masses +of igneous origin. With respect to the first of these conclusions, he +received the powerful support of Daniel Sharpe, who in the years +1852 and 1854 published two papers on the structure of the Scottish +Highlands, supplying striking confirmation of the correctness of +Darwin's views. Although Darwin's and Sharpe's conclusions were +contested by Murchison and other geologists, they are now universally +accepted. In his theory concerning the origin of foliation, Darwin had +been to some extent anticipated by Scrope, but he supplied many facts +and illustrations leading to the gradual acceptance of a doctrine which, +when first enunciated, was treated with neglect, if not with contempt. + +The whole of this volume on South American geology is crowded with the +records of patient observations and suggestions of the greatest value; +but, as Darwin himself saw, it was a book for the working geologist and +"caviare to the general." Its author, indeed, frequently expressed +his sense of the "dryness" of the book; he even says "I long hesitated +whether I would publish it or not," and he wrote to Leonard Horner "I am +astonished that you should have had the courage to go right through my +book." ("M.L." II. page 221.) + +Fortunately the second book, on which Darwin was engaged at this time, +was of a very different character. His "Journal", almost as he had +written it on board ship, with facts and observations fresh in his mind, +had been published in 1839 and attracted much attention. In 1845, he +says, "I took much pains in correcting a new edition," and the work +which was commenced in April, 1845, was not finished till August of +that year. The volume contains a history of the voyage with "a sketch +of those observations in Natural History and Geology, which I think will +possess some interest for the general reader." It is not necessary +to speak of the merits of this scientific classic. It became a +great favourite with the general public--having passed through many +editions--it was, moreover, translated into a number of different +languages. Darwin was much gratified by these evidences of popularity, +and naively remarks in his "Autobiography", "The success of this my +first literary child tickles my vanity more than that of any of my other +books" ("L.L." I. page 80.)--and this was written after the "Origin of +Species" had become famous! + +In Darwin's letters there are many evidences that his labours during +these ten years devoted to the working out of the geological results +of the voyage often made many demands on his patience and indomitable +courage. Most geologists have experience of the contrast between the +pleasures felt when wielding the hammer in the field, and the duller +labour of plying the pen in the study. But in Darwin's case, innumerable +interruptions from sickness and other causes, and the oft-deferred hope +of reaching the end of his task were not the only causes operating to +make the work irksome. The great project, which was destined to become +the crowning achievement of his life, was now gradually assuming more +definite shape, and absorbing more of his time and energies. + +Nevertheless, during all this period, Darwin so far regarded his +geological pursuits as his PROPER "work," that attention to other +matters was always spoken of by him as "indulging in idleness." If at +the end of this period the world had sustained the great misfortune of +losing Darwin by death before the age of forty--and several times that +event seemed only too probable--he might have been remembered only as +a very able geologist of most advanced views, and a traveller who had +written a scientific narrative of more than ordinary excellence! + +The completion of the "Geology of the 'Beagle'" and the preparation of +a revised narrative of the voyage mark the termination of that period of +fifteen years of Darwin's life during which geological studies were +his principal occupation. Henceforth, though his interest in geological +questions remained ever keen, biological problems engaged more and more +of his attention to the partial exclusion of geology. + +The eight years from October, 1846, to October, 1854, were mainly +devoted to the preparation of his two important monographs on the recent +and fossil Cirripedia. Apart from the value of his description of the +fossil forms, this work of Darwin's had an important influence on the +progress of geological science. Up to that time a practice had prevailed +for the student of a particular geological formation to take up the +description of the plant and animal remains in it--often without +having anything more than a rudimentary knowledge of the living forms +corresponding to them. Darwin in his monograph gave a very admirable +illustration of the enormous advantage to be gained--alike for biology +and geology--by undertaking the study of the living and fossil forms +of a natural group of organisms in connection with one another. Of the +advantage of these eight years of work to Darwin himself, in preparing +for the great task lying before him, Huxley has expressed a very strong +opinion indeed. ("L.L." II. pages 247-48.) + +But during these eight years of "species work," Darwin found +opportunities for not a few excursions into the field of geology. He +occasionally attended the Geological Society, and, as we have already +seen, read several papers there during this period. His friend, Dr +Hooker, then acting as botanist to the Geological Survey, was engaged +in studying the Carboniferous flora, and many discussions on Palaezoic +plants and on the origin of coal took place at this period. On this last +subject he felt the deepest interest and told Hooker, "I shall never +rest easy in Down churchyard without the problem be solved by some one +before I die." ("M.L." I. pages 63, 64.) + +As at all times, conversations and letters with Lyell on every branch of +geological science continued with unabated vigour, and in spite of the +absorbing character of the work on the Cirripedes, time was found for +all. In 1849 his friend Herschel induced him to supply a chapter of +forty pages on Geology to the Admiralty "Manual of Scientific Inquiry" +which he was editing. This is Darwin's single contribution to books of +an "educational" kind. It is remarkable for its clearness and simplicity +and attention to minute details. It may be read by the student of +Darwin's life with much interest, for the directions he gives to an +explorer are without doubt those which he, as a self-taught geologist, +proved to be serviceable during his life on the "Beagle". + +On the completion of the Cirripede volumes, in 1854, Darwin was able to +grapple with the immense pile of MS. notes which he had accumulated +on the species question. The first sketch of 35 pages (1842), had been +enlarged in 1844 into one of 230 pages ([The first draft of the "Origin" +is being prepared for Press by Mr Francis Darwin and will be published +by the Cambridge University Press this year (1909). A.C.S.]); but in +1856 was commenced the work (never to be completed) which was designed +on a scale three or four times more extensive than that on which the +"Origin of Species" was in the end written. + +In drawing up those two masterly chapters of the "Origin", "On +the Imperfection of the Geological Record," and "On the Geological +Succession of Organic Beings", Darwin had need of all the experience and +knowledge he had been gathering during thirty years, the first half +of which had been almost wholly devoted to geological study. The most +enlightened geologists of the day found much that was new, and still +more that was startling from the manner of its presentation, in these +wonderful essays. Of Darwin's own sense of the importance of the +geological evidence in any presentation of his theory a striking proof +will be found in a passage of the touching letter to his wife, enjoining +the publication of his sketch of 1844. "In case of my sudden death," +he wrote, "... the editor must be a geologist as well as a naturalist." +("L.L." II. pages 16, 17.) + +In spite of the numerous and valuable palaeontological discoveries made +since the publication of "The Origin of Species", the importance of the +first of these two geological chapters is as great as ever. It still +remains true that "Those who believe that the geological record is in +any degree perfect, will at once reject the theory"--as indeed they must +reject any theory of evolution. The striking passage with which Darwin +concludes this chapter--in which he compares the record of the rocks +to the much mutilated volumes of a human history--remains as apt an +illustration as it did when first written. + +And the second geological chapter, on the Succession of Organic +Beings--though it has been strengthened in a thousand ways, by the +discoveries concerning the pedigrees of the horse, the elephant and +many other aberrant types, though new light has been thrown even on the +origin of great groups like the mammals, and the gymnosperms, though +not a few fresh links have been discovered in the chains of evidence, +concerning the order of appearance of new forms of life--we would +not wish to have re-written. Only the same line of argument could be +adopted, though with innumerable fresh illustrations. Those who reject +the reasonings of this chapter, neither would they be persuaded if a +long and complete succession of "ancestral forms" could rise from the +dead and pass in procession before them. + +Among the geological discussions, which so frequently occupied Darwin's +attention during the later years of his life, there was one concerning +which his attitude seemed somewhat remarkable--I allude to his views +on "the permanence of Continents and Ocean-basins." In a letter to Mr +Mellard Reade, written at the end of 1880, he wrote: "On the whole, I +lean to the side that the continents have since Cambrian times occupied +approximately their present positions. But, as I have said, the question +seems a difficult one, and the more it is discussed the better." ("M.L." +II. page 147.) Since this was written, the important contribution to the +subject by the late Dr W.T. Blanford (himself, like Darwin, a naturalist +and geologist) has appeared in an address to the Geological Society in +1890; and many discoveries, like that of Dr Woolnough in Fiji, have +led to considerable qualifications of the generalisation that all the +islands in the great ocean are wholly of volcanic or coral origin. + +I remember once expressing surprise to Darwin that, after the views +which he had originated concerning the existence of areas of elevation +and others of subsidence in the Pacific Ocean, and in face of the +admitted difficulty of accounting for the distribution of certain +terrestrial animals and plants, if the land and sea areas had been +permanent in position, he still maintained that theory. Looking at me +with a whimsical smile, he said: "I have seen many of my old friends +make fools of themselves, by putting forward new theoretical views or +revising old ones, AFTER THEY WERE SIXTY YEARS OF AGE; so, long ago, +I determined that on reaching that age I would write nothing more of a +speculative character." + +Though Darwin's letters and conversations on geology during these later +years were the chief manifestations of the interest he preserved in his +"old love," as he continued to call it, yet in the sunset of that active +life a gleam of the old enthusiasm for geology broke forth once more. +There can be no doubt that Darwin's inability to occupy himself with +field-work proved an insuperable difficulty to any attempt on his part +to resume active geological research. But, as is shown by the series of +charming volumes on plant-life, Darwin had found compensation in making +patient and persevering experiment take the place of enterprising and +exact observation; and there was one direction in which he could indulge +the "old love" by employment of the new faculty. + +We have seen that the earliest memoir written by Darwin, which was +published in full, was a paper "On the Formation of Mould" which was +read at the Geological Society on November 1st, 1837, but did not appear +in the "Transactions" of the Society till 1840, where it occupied four +and a half quarto pages, including some supplementary matter, obtained +later, and a woodcut. This little paper was confined to observations +made in his uncle's fields in Staffordshire, where burnt clay, cinders, +and sand were found to be buried under a layer of black earth, evidently +brought from below by earthworms, and to a recital of similar facts from +Scotland obtained through the agency of Lyell. The subsequent history +of Darwin's work on this question affords a striking example of the +tenacity of purpose with which he continued his enquiries on any subject +that interested him. + +In 1842, as soon as he was settled at Down, he began a series of +observations on a foot-path and in his fields, that continued with +intermissions during his whole life, and he extended his enquiries from +time to time to the neighbouring parks of Knole and Holwood. In 1844 +we find him making a communication to the "Gardener's Chronicle" on the +subject. About 1870, his attention to the question was stimulated by the +circumstance that his niece (Miss L. Wedgwood) undertook to collect and +weigh the worm-casts thrown up, during a whole year, on measured +squares selected for the purpose, at Leith Hill Place. He also obtained +information from Professor Ramsay concerning observations made by him on +a pavement near his house in 1871. Darwin at this time began to realise +the great importance of the action of worms to the archaeologist. At +an earlier date he appears to have obtained some information concerning +articles found buried on the battle-field of Shrewsbury, and the old +Roman town of Uriconium, near his early home; between 1871 and 1878 Mr +(afterwards Lord) Farrer carried on a series of investigations at the +Roman Villa discovered on his land at Abinger; Darwin's son William +examined for his father the evidence at Beaulieu Abbey, Brading, +Stonehenge and other localities in the neighbourhood of his home; his +sons Francis and Horace were enlisted to make similar enquiries at +Chideock and Silchester; while Francis Galton contributed facts noticed +in his walks in Hyde Park. By correspondence with Fritz Muller and Dr +Ernst, Darwin obtained information concerning the worm-casts found in +South America; from Dr Kreft those of Australia; and from Mr Scott +and Dr (afterwards Sir George) King, those of India; the last-named +correspondent also supplied him with much valuable information obtained +in the South of Europe. Help too was obtained from the memoirs on +Earthworms published by Perrier in 1874 and van Hensen in 1877, while +Professor Ray Lankester supplied important facts with regard to their +anatomy. + +When therefore the series of interesting monographs on plant-life had +been completed, Darwin set to work in bringing the information that he +had gradually accumulated during forty-four years to bear on the subject +of his early paper. He also utilised the skill and ingenuity he had +acquired in botanical work to aid in the elucidation of many of the +difficulties that presented themselves. I well remember a visit which +I paid to Down at this period. At the side of the little study stood +flower-pots containing earth with worms, and, without interrupting +our conversation, Darwin would from time to time lift the glass plate +covering a pot to watch what was going on. Occasionally, with a humorous +smile, he would murmur something about a book in another room, and slip +away; returning shortly, without the book but with unmistakeable signs +of having visited the snuff-jar outside. After working about a year at +the worms, he was able at the end of 1881 to publish the charming little +book--"The Formation of Vegetable Mould through the Action of Worms, +with Observations on their Habits". This was the last of his books, and +its reception by reviewers and the public alike afforded the patient old +worker no little gratification. Darwin's scientific career, which had +begun with geological research, most appropriately ended with a return +to it. + +It has been impossible to sketch the origin and influence of Darwin's +geological work without, at almost every step, referring to the part +played by Lyell and the "Principles of Geology". Haeckel, in the +chapters on Lyell and Darwin in his "History of Creation", and Huxley in +his striking essay "On the Reception of the Origin of Species" ("L.L." +II. pages 179-204.) have both strongly insisted on the fact that the +"Origin" of Darwin was a necessary corollary to the "Principles" of +Lyell. + +It is true that, in an earlier essay, Huxley had spoken of the doctrine +of Uniformitarianism as being, in a certain sense, opposed to that of +Evolution (Huxley's Address to the Geological Society, 1869. "Collected +Essays", Vol. VIII. page 305, London, 1896.); but in his later years he +took up a very different and more logical position, and maintained +that "Consistent uniformitarianism postulates evolution as much in the +organic as in the inorganic world. The origin of a new species by other +than ordinary agencies would be a vastly greater 'catastrophe' than +any of those which Lyell success fully eliminated from sober geological +speculation." ("L.L." II. page 190.) + +Huxley's admiration for the "Principles of Geology", and his conviction +of the greatness of the revolution of thought brought about by Lyell, +was almost as marked as in the case of Darwin himself. (See his Essay +on "Science and Pseudo Science". "Collected Essays", Vol. V. page 90, +London, 1902.) He felt, however, as many others have done, that in one +respect the very success of Lyell's masterpiece has been the reason why +its originality and influence have not been so fully recognised as they +deserved to be. Written as the book was before its author had arrived at +the age of thirty, no less than eleven editions of the "Principles" +were called for in his lifetime. With the most scrupulous care, Lyell, +devoting all his time and energies to the task of collecting and sifting +all evidence bearing on the subjects of his work, revised and re-revised +it; and as in each edition, eliminations, modifications, corrections, +and additions were made, the book, while it increased in value as a +storehouse of facts, lost much of its freshness, vigour and charm as a +piece of connected reasoning. + +Darwin undoubtedly realised this when he wrote concerning the +"Principles", "the first edition, my old true love, which I never +deserted for the later editions." ("M.L." II. page 222.) Huxley once +told me that when, in later life, he read the first edition, he was both +surprised and delighted, feeling as if it were a new book to him. (I +have before me a letter which illustrates this feeling on Huxley's +part. He had lamented to me that he did not possess a copy of the first +edition of the "Principles", when, shortly afterwards, I picked up a +dilapidated copy on a bookstall; this I had bound and sent to my old +teacher and colleague. His reply is characteristic: + +October 8, 1884. + +My Dear Judd, + +You could not have made me a more agreeable present than the copy of the +first edition of Lyell, which I find on my table. I have never been able +to meet with the book, and your copy is, as the old woman said of her +Bible, "the best of books in the best of bindings." + +Ever yours sincerely, + +T.H. Huxley. + +(I cannot refrain from relating an incident which very strikingly +exemplifies the affection for one another felt by Lyell and Huxley. In +his last illness, when confined to his bed, Lyell heard that Huxley was +to lecture at the Royal Institution on the "Results of the 'Challenger' +expedition": he begged me to attend the lecture and bring him an account +of it. Happening to mention this to Huxley, he at once undertook to +go to Lyell in my place, and he did so on the morning following his +lecture. I shall never forget the look of gratitude on the face of the +invalid when he told me, shortly afterwards, how Huxley had sat by his +bedside and "repeated the whole lecture to him.") + +Darwin's generous nature seems often to have made him experience a fear +lest he should do less than justice to his "dear old master," and to the +influence that the "Principles of Geology" had in moulding his mind. In +1845 he wrote to Lyell, "I have long wished, not so much for your sake, +as for my own feelings of honesty, to acknowledge more plainly than by +mere reference, how much I geologically owe you. Those authors, however, +who like you, educate people's minds as well as teach them special +facts, can never, I should think, have full justice done them except by +posterity, for the mind thus insensibly improved can hardly perceive +its own upward ascent." ("L.L." I. pages 337-8.) In another letter, to +Leonard Horner, he says: "I always feel as if my books came half out of +Lyell's brain, and that I never acknowledge this sufficiently." ("M.L." +II. page 117.) Darwin's own most favourite book, the "Narrative of the +Voyage", was dedicated to Lyell in glowing terms; and in the "Origin of +Species" he wrote of "Lyell's grand work on the "Principles of +Geology", which the future historian will recognise as having produced a +revolution in Natural Science." "What glorious good that work has done" +he fervently exclaims on another occasion. ("L.L." I. page 342.) + +To the very end of his life, as all who were in the habit of talking +with Darwin can testify, this sense of his indebtedness to Lyell +remained with him. In his "Autobiography", written in 1876, the year +after Lyell's death, he spoke in the warmest terms of the value to him +of the "Principles" while on the voyage and of the aid afforded to him +by Lyell on his return to England. ("L.L." I. page 62.) But the year +before his own death, Darwin felt constrained to return to the subject +and to place on record a final appreciation--one as honourable to the +writer as it is to his lost friend: + +"I saw more of Lyell than of any other man, both before and after +my marriage. His mind was characterised, as it appeared to me, by +clearness, caution, sound judgment, and a good deal of originality. When +I made any remark to him on Geology, he never rested until he saw the +whole case clearly, and often made me see it more clearly than I had +done before. He would advance all possible objections to my suggestion, +and even after these were exhausted would remain long dubious. A second +characteristic was his hearty sympathy with the work of other scientific +men... His delight in science was ardent, and he felt the +keenest interest in the future progress of mankind. He was very +kind-hearted... His candour was highly remarkable. He exhibited this by +becoming a convert to the Descent theory, though he had gained much fame +by opposing Lamarck's views, and this after he had grown old." + +"THE SCIENCE OF GEOLOGY IS ENORMOUSLY INDEBTED TO LYELL--MORE SO, AS I +BELIEVE, THAN TO ANY OTHER MAN WHO EVER LIVED." ("L.L." I. pages 71-2 +(the italics are mine.)) + +Those who knew Lyell intimately will recognise the truth of the portrait +drawn by his dearest friend, and I believe that posterity will endorse +Darwin's deliberate verdict concerning the value of his labours. + +It was my own good fortune, to be brought into close contact with these +two great men during the later years of their life, and I may perhaps be +permitted to put on record the impressions made upon me during friendly +intercourse with both. + +In some respects, there was an extraordinary resemblance in their modes +and habits of thought, between Lyell and Darwin; and this likeness was +also seen in their modesty, their deference to the opinion of younger +men, their enthusiasm for science, their freedom from petty jealousies +and their righteous indignation for what was mean and unworthy in +others. But yet there was a difference. Both Lyell and Darwin were +cautious, but perhaps Lyell carried his caution to the verge of +timidity. I think Darwin possessed, and Lyell lacked, what I can only +describe by the theological term, "faith--the substance of things hoped +for, the evidence of things not seen." Both had been constrained to feel +that the immutability of species could not be maintained. Both, +too, recognised the fact that it would be useless to proclaim this +conviction, unless prepared with a satisfactory alternative to what +Huxley called "the Miltonic hypothesis." But Darwin's conviction was so +far vital and operative that it sustained him while working unceasingly +for twenty-two years in collecting evidence bearing on the question, +till at last he was in the position of being able to justify that +conviction to others. + +And yet Lyell's attitude--and that of Hooker, which was very +similar--proved of inestimable service to science, as Darwin often +acknowledged. One of the greatest merits of the "Origin of Species" is +that so many difficulties and objections are anticipated and fairly met; +and this was to a great extent the result of the persistent and very +candid--if always friendly--criticism of Lyell and Hooker. + +I think the divergence of mental attitude in Lyell and Darwin must +be attributed to a difference in temperament, the evidence of which +sometimes appears in a very striking manner in their correspondence. +Thus in 1838, while they were in the thick of the fight with +the Catastrophists of the Geological Society, Lyell wrote +characteristically: "I really find, when bringing up my Preliminary +Essays in "Principles" to the science of the present day, so far as I +know it, that the great outline, and even most of the details, stand +so uninjured, and in many cases they are so much strengthened by new +discoveries, especially by yours, that we may begin to hope that +the great principles there insisted on will stand the test of new +discoveries." (Lyell's "Life, Letters and Journals", Vol. II. page 44.) +To which the more youthful and impetuous Darwin replies: "BEGIN TO HOPE: +why the POSSIBILITY of a doubt has never crossed my mind for many a day. +This may be very unphilosophical, but my geological salvation is staked +on it... it makes me quite indignant that you should talk of HOPING." +("L.L." I. page 296.) + +It was not only Darwin's "geological salvation" that was at stake, when +he surrendered himself to his enthusiasm for an idea. To his firm faith +in the doctrine of continuity we owe the "Origin of Species"; and while +Darwin became the "Paul" of evolution, Lyell long remained the "doubting +Thomas." + +Many must have felt like H.C. Watson when he wrote: "How could Sir +C. Lyell... for thirty years read, write, and think, on the subject of +species AND THEIR SUCCESSION, and yet constantly look down the wrong +road!" ("L.L." II. page 227.) Huxley attributed this hesitation of Lyell +to his "profound antipathy" to the doctrine of the "pithecoid origin of +man." ("L.L." II. page 193.) Without denying that this had considerable +influence (and those who knew Lyell and his great devotion to his wife +and her memory, are aware that he and she felt much stronger convictions +concerning such subjects as the immortality of the soul than Darwin +was able to confess to) yet I think Darwin had divined the real +characteristics of his friend's mind, when he wrote: "He would advance +all possible objections... AND EVEN AFTER THESE WERE EXHAUSTED, WOULD +REMAIN LONG DUBIOUS." + +Very touching indeed was the friendship maintained to the end between +these two leaders of thought--free as their intercourse was from any +smallest trace of self-seeking or jealousy. When in 1874 I spent some +time with Lyell in his Forfarshire home, a communication from Darwin was +always an event which made a "red-letter day," as Lyell used to say; +and he gave me many indications in his conversation of how strongly he +relied upon the opinion of Darwin--more indeed than on the judgment +of any other man--this confidence not being confined to questions of +science, but extending to those of morals, politics, and religion. + +I have heard those who knew Lyell only slightly, speak of his manners +as cold and reserved. His complete absorption in his scientific work, +coupled with extreme short-sightedness, almost in the end amounting to +blindness, may have permitted those having but a casual acquaintance +with him to accept such a view. But those privileged to know him +intimately recognised the nobleness of his character and can realise +the justice and force of Hooker's words when he heard of his death: "My +loved, my best friend, for well nigh forty years of my life. The most +generous sharer of my own and my family's hopes, joys and sorrows, whose +affection for me was truly that of a father and brother combined." + +But the strongest of all testimonies to the grandeur of Lyell's +character is the lifelong devotion to him of such a man as Darwin. +Before the two met, we find Darwin constantly writing of facts and +observations that he thinks "will interest Mr Lyell"; and when they came +together the mutual esteem rapidly ripened into the warmest affection. +Both having the advantage of a moderate independence, permitting of an +entire devotion of their lives to scientific research, they had much in +common, and the elder man--who had already achieved both scientific and +literary distinction--was able to give good advice and friendly help +to the younger one. The warmth of their friendship comes out very +strikingly in their correspondence. When Darwin first conceived the idea +of writing a book on the "species question," soon after his return from +the voyage, it was "by following the example of Lyell in Geology" that +he hoped to succeed ("L.L." I. page 83.); when in 1844, Darwin had +finished his first sketch of the work, and, fearing that his life might +not be spared to complete his great undertaking, committed the care of +it in a touching letter to his wife, it was his friend Lyell whom he +named as her adviser and the possible editor of the book ("L.L." II. +pages 17-18.); it was Lyell who, in 1856, induced Darwin to lay the +foundations of a treatise ("L.L." I. page 84.) for which the author +himself selected the "Principles" as his model; and when the dilemma +arose from the receipt of Wallace's essay, it was to Lyell jointly with +Hooker that Darwin turned, not in vain, for advice and help. + +During the later years of his life, I never heard Darwin allude to his +lost friend--and he did so very often--without coupling his name +with some term of affection. For a brief period, it is true, Lyell's +excessive caution when the "Origin" was published, seemed to try even +the patience of Darwin; but when "the master" was at last able to +declare himself fully convinced, he was the occasion of more rejoicing +on the part of Darwin, than any other convert to his views. The latter +was never tired of talking of Lyell's "magnanimity" and asserted that, +"To have maintained in the position of a master, one side of a question +for thirty years, and then deliberately give it up, is a fact to which I +much doubt whether the records of science offer a parallel." ("L.L." II. +pages 229-30.) + +Of Darwin himself, I can safely affirm that I never knew anyone who +had met him, even for the briefest period, who was not charmed by his +personality. Who could forget the hearty hand-grip at meeting, the +gentle and lingering pressure of the palm at parting, and above all +that winning smile which transformed his countenance--so as to make +portraits, and even photographs, seem ever afterwards unsatisfying! +Looking back, one is indeed tempted to forget the profoundness of the +philosopher, in recollection of the loveableness of the man. + + + + +XIX. DARWIN'S WORK ON THE MOVEMENTS OF PLANTS. By Francis Darwin, + +Honorary Fellow of Christ's College, Cambridge. + + +My father's interest in plants was of two kinds, which may be roughly +distinguished as EVOLUTIONARY and PHYSIOLOGICAL. Thus in his purely +evolutionary work, for instance in "The Origin of Species" and in his +book on "Variation under Domestication", plants as well as animals +served as material for his generalisations. He was largely dependent +on the work of others for the facts used in the evolutionary work, and +despised himself for belonging to the "blessed gang" of compilers. And +he correspondingly rejoiced in the employment of his wonderful power of +observation in the physiological problems which occupied so much of his +later life. But inasmuch as he felt evolution to be his life's work, he +regarded himself as something of an idler in observing climbing plants, +insectivorous plants, orchids, etc. In this physiological work he was +to a large extent urged on by his passionate desire to understand the +machinery of all living things. But though it is true that he worked +at physiological problems in the naturalist's spirit of curiosity, yet +there was always present to him the bearing of his facts on the problem +of evolution. His interests, physiological and evolutionary, were indeed +so interwoven that they cannot be sharply separated. Thus his original +interest in the fertilisation of flowers was evolutionary. "I was +led" ("Life and Letters", I. page 90.), he says, "to attend to the +cross-fertilisation of flowers by the aid of insects, from having come +to the conclusion in my speculations on the origin of species, that +crossing played an important part in keeping specific forms constant." +In the same way the value of his experimental work on heterostyled +plants crystalised out in his mind into the conclusion that the product +of illegitimate unions are equivalent to hybrids--a conclusion of the +greatest interest from an evolutionary point of view. And again his work +"Cross and Self Fertilisation" may be condensed to a point of view +of great importance in reference to the meaning and origin of sexual +reproduction. (See Professor Goebel's article in the present volume.) + +The whole of his physiological work may be looked at as an illustration +of the potency of his theory as an "instrument for the extension of the +realm of natural knowledge." (Huxley in Darwin's "Life and Letters." II. +page 204.) + +His doctrine of natural selection gave, as is well known, an impulse +to the investigation of the use of organs--and thus created the great +school of what is known in Germany as Biology--a department of science +for which no English word exists except the rather vague term Natural +History. This was especially the case in floral biology, and it is +interesting to see with what hesitation he at first expressed the value +of his book on Orchids ("Life and Letters", III. page 254.), "It will +perhaps serve to illustrate how Natural History may be worked under the +belief of the modification of species" (1861). And in 1862 he speaks +(Loc. cit.) more definitely of the relation of his work to natural +selection: "I can show the meaning of some of the apparently meaningless +ridges (and) horns; who will now venture to say that this or that +structure is useless?" It is the fashion now to minimise the value of +this class of work, and we even find it said by a modern writer that to +inquire into the ends subserved by organs is not a scientific problem. +Those who take this view surely forget that the structure of all living +things is, as a whole, adaptive, and that a knowledge of how the +present forms come to be what they are includes a knowledge of why +they survived. They forget that the SUMMATION of variations on which +divergence depends is under the rule of the environment considered as +a selective force. They forget that the scientific study of the +interdependence of organisms is only possible through a knowledge of the +machinery of the units. And that, therefore, the investigation of such +widely interesting subjects as extinction and distribution must include +a knowledge of function. It is only those who follow this line of +work who get to see the importance of minute points of structure and +understand as my father did even in 1842, as shown in his sketch of the +"Origin" (Now being prepared for publication.), that every grain of sand +counts for something in the balance. Much that is confidently stated +about the uselessness of different organs would never have been +written if the naturalist spirit were commoner nowadays. This spirit +is strikingly shown in my father's work on the movements of plants. The +circumstance that botanists had not, as a class, realised the interest +of the subject accounts for the fact that he was able to gather such a +rich harvest of results from such a familiar object as a twining plant. +The subject had been investigated by H. von Mohl, Palm, and Dutrochet, +but they failed not only to master the problem but (which here concerns +us) to give the absorbing interest of Darwin's book to what they +discovered. + +His work on climbing plants was his first sustained piece of work on the +physiology of movement, and he remarks in 1864: "This has been new sort +of work for me." ("Life and Letters", III. page 315. He had, however, +made a beginning on the movements of Drosera.) He goes on to remark with +something of surprise, "I have been pleased to find what a capital guide +for observations a full conviction of the change of species is." + +It was this point of view that enabled him to develop a broad conception +of the power of climbing as an adaptation by means of which plants are +enabled to reach the light. Instead of being compelled to construct a +stem of sufficient strength to stand alone, they succeed in the struggle +by making use of other plants as supports. He showed that the great +class of tendril- and root-climbers which do not depend on twining round +a pole, like a scarlet-runner, but on attaching themselves as they grow +upwards, effect an economy. Thus a Phaseolus has to manufacture a stem +three feet in length to reach a height of two feet above the ground, +whereas a pea "which had ascended to the same height by the aid of its +tendrils, was but little longer than the height reached." ("Climbing +Plants" (2nd edition 1875), page 193.) + +Thus he was led on to the belief that TWINING is the more ancient form +of climbing, and that tendril-climbers have been developed from twiners. +In accordance with this view we find LEAF-CLIMBERS, which may be looked +on as incipient tendril-bearers, occurring in the same genera with +simple twiners. (Loc. cit. page 195.) He called attention to the case +of Maurandia semperflorens in which the young flower-stalks revolve +spontaneously and are sensitive to a touch, but neither of these +qualities is of any perceptible value to the species. This forced him to +believe that in other young plants the rudiments of the faculty needed +for twining would be found--a prophecy which he made good in his "Power +of Movement" many years later. + +In "Climbing Plants" he did little more than point out the remarkable +fact that the habit of climbing is widely scattered through the +vegetable kingdom. Thus climbers are to be found in 35 out of the 59 +Phanerogamic Alliances of Lindley, so that "the conclusion is forced +on our minds that the capacity of revolving (If a twining plant, e.g. +a hop, is observed before it has begun to ascend a pole, it will +be noticed that, owing to the curvature of the stem, the tip is not +vertical but hangs over in a roughly horizontal position. If such a +shoot is watched it will be found that if, for instance, it points +to the north at a given hour, it will be found after a short interval +pointing north-east, then east, and after about two hours it will once +more be looking northward. The curvature of the stem depends on one side +growing quicker than the opposite side, and the revolving movement, +i.e. circumnutation, depends on the region of quickest growth creeping +gradually round the stem from south through west to south again. Other +plants, e.g. Phaseolus, revolve in the opposite direction.), on which +most climbers depend, is inherent, though undeveloped, in almost every +plant in the vegetable kingdom." ("Climbing Plants", page 205.) + +In the "Origin" (Edition I. page 427, Edition VI. page 374.) Darwin +speaks of the "apparent paradox, that the very same characters are +analogical when one class or order is compared with another, but give +true affinities when the members of the same class or order are compared +one with another." In this way we might perhaps say that the climbing +of an ivy and a hop are analogical; the resemblance depending on the +adaptive result rather than on community of blood; whereas the relation +between a leaf-climber and a true tendril-bearer reveals descent. This +particular resemblance was one in which my father took especial delight. +He has described an interesting case occurring in the Fumariaceae. +("Climbing Plants", page 195.) "The terminal leaflets of the +leaf-climbing Fumaria officinalis are not smaller than the other +leaflets; those of the leaf-climbing Adlumia cirrhosa are greatly +reduced; those of Corydalis claviculata (a plant which may be +indifferently called a leaf-climber or a tendril-bearer) are either +reduced to microscopical dimensions or have their blades wholly aborted, +so that this plant is actually in a state of transition; and finally in +the Dicentra the tendrils are perfectly characterized." + +It is a remarkable fact that the quality which, broadly speaking, forms +the basis of the climbing habit (namely revolving nutation, otherwise +known as circumnutation) subserves two distinct ends. One of these is +the finding of a support, and this is common to twiners and tendrils. +Here the value ends as far as tendril-climbers are concerned, but in +twiners Darwin believed that the act of climbing round a support is a +continuation of the revolving movement (circumnutation). If we imagine a +man swinging a rope round his head and if we suppose the rope to strike +a vertical post, the free end will twine round it. This may serve as +a rough model of twining as explained in the "Movements and Habits +of Climbing Plants". It is on these points--the nature of revolving +nutation and the mechanism of twining--that modern physiologists differ +from Darwin. (See the discussion in Pfeffer's "The Physiology of Plants" +Eng. Tr. (Oxford, 1906), III. page 34, where the literature is given. +Also Jost, "Vorlesungen uber Pflanzenphysiologie", page 562, Jena, +1904.) + +Their criticism originated in observations made on a revolving shoot +which is removed from the action of gravity by keeping the plant slowly +rotating about a horizontal axis by means of the instrument known as a +klinostat. Under these conditions circumnutation becomes irregular or +ceases altogether. When the same experiment is made with a plant which +has twined spirally up a stick, the process of climbing is checked and +the last few turns become loosened or actually untwisted. From this +it has been argued that Darwin was wrong in his description of +circumnutation as an automatic change in the region of quickest growth. +When the free end of a revolving shoot points towards the north there +is no doubt that the south side has been elongating more than the north; +after a time it is plain from the shoot hanging over to the east that +the west side of the plant has grown most, and so on. This rhythmic +change of the position of the region of greatest growth Darwin ascribes +to an unknown internal regulating power. Some modern physiologists, +however, attempt to explain the revolving movement as due to a +particular form of sensitiveness to gravitation which it is not +necessary to discuss in detail in this place. It is sufficient for my +purpose to point out that Darwin's explanation of circumnutation is +not universally accepted. Personally I believe that circumnutation is +automatic--is primarily due to internal stimuli. It is however in some +way connected with gravitational sensitiveness, since the movement +normally occurs round a vertical line. It is not unnatural that, +when the plant has no external stimulus by which the vertical can be +recognised, the revolving movement should be upset. + +Very much the same may be said of the act of twining, namely that most +physiologists refuse to accept Darwin's view (above referred to) that +twining is the direct result of circumnutation. Everyone must allow +that the two phenomena are in some way connected, since a plant +which circumnutates clockwise, i.e. with the sun, twines in the same +direction, and vice versa. It must also be granted that geotropism has a +bearing on the problem, since all plants twine upwards, and cannot twine +along a horizontal support. But how these two factors are combined, and +whether any (and if so what) other factors contribute, we cannot say. +If we give up Darwin's explanation, we must at the same time say with +Pfeffer that "the causes of twining are... unknown." ("The Physiology of +Plants", Eng. Tr. (Oxford, 1906), III. page 37.) + +Let us leave this difficult question and consider some other points made +out in the progress of the work on climbing plants. One result of what +he called his "niggling" ("Life and Letters", III. page 312.) work on +tendrils was the discovery of the delicacy of their sense of touch, and +the rapidity of their movement. Thus in a passion-flower tendril, a bit +of platinum wire weighing 1.2 mg. produced curvature ("Climbing +Plants", page 171.), as did a loop of cotton weighing 2 mg. Pfeffer +("Untersuchungen a.d. Bot. Inst. z. Tubingen", Bd. I. 1881-85, page +506.), however, subsequently found much greater sensitiveness: thus +the tendril of Sicyos angulatus reacted to 0.00025 mg., but this only +occurred when the delicate rider of cottonwool fibre was disturbed by +the wind. The same author expanded and explained in a most interesting +way the meaning of Darwin's observation that tendrils are not stimulated +to movement by drops of water resting on them. Pfeffer showed that +DIRTY water containing minute particles of clay in suspension acts as a +stimulus. He also showed that gelatine acts like pure water; if a smooth +glass rod is coated with a 10 per cent solution of gelatine and is then +applied to a tendril, no movement occurs in spite of the fact that the +gelatine is solid when cold. Pfeffer ("Physiology", Eng. Tr. III. +page 52. Pfeffer has pointed out the resemblance between the contact +irritability of plants and the human sense of touch. Our skin is not +sensitive to uniform pressure such as is produced when the finger +is dipped into mercury (Tubingen "Untersuchungen", I. page 504.) +generalises the result in the statement that the tendril has a special +form of irritability and only reacts to "differences of pressure or +variations of pressure in contiguous... regions." Darwin was especially +interested in such cases of specialised irritability. For instance in +May, 1864, he wrote to Asa Gray ("Life and Letters", III. page 314.) +describing the tendrils of Bignonia capreolata, which "abhor a simple +stick, do not much relish rough bark, but delight in wool or moss." +He received, from Gray, information as to the natural habitat of the +species, and finally concluded that the tendrils "are specially adapted +to climb trees clothed with lichens, mosses, or other such productions." +("Climbing Plants", page 102.) + +Tendrils were not the only instance discovered by Darwin of delicacy +of touch in plants. In 1860 he had already begun to observe Sundew +(Drosera), and was full of astonishment at its behaviour. He wrote to +Sir Joseph Hooker ("Life and Letters", III. page 319.): "I have been +working like a madman at Drosera. Here is a fact for you which is +certain as you stand where you are, though you won't believe it, that a +bit of hair 1/78000 of one grain in weight placed on gland, will cause +ONE of the gland-bearing hairs of Drosera to curve inwards." Here again +Pfeffer (Pfeffer in "Untersuchungen a. d. Bot. Inst. z. Tubingen", +I. page 491.) has, as in so many cases, added important facts to my +father's observations. He showed that if the leaf of Drosera is entirely +freed from such vibrations as would reach it if observed on an ordinary +table, it does not react to small weights, so that in fact it was the +vibration of the minute fragment of hair on the gland that produced +movement. We may fancifully see an adaptation to the capture of +insects--to the dancing of a gnat's foot on the sensitive surface. + +Darwin was fond of telling how when he demonstrated the sensitiveness +of Drosera to Mr Huxley and (I think) to Sir John Burdon Sanderson, he +could perceive (in spite of their courtesy) that they thought the whole +thing a delusion. And the story ended with his triumph when Mr Huxley +cried out, "It IS moving." + +Darwin's work on tendrils has led to some interesting investigations on +the mechanisms by which plants perceive stimuli. Thus Pfeffer (Tubingen +"Untersuchungen" I. page 524.) showed that certain epidermic cells +occurring in tendrils are probably organs of touch. In these cells the +protoplasm burrows as it were into cavities in the thickness of the +external cell-walls and thus comes close to the surface, being separated +from an object touching the tendril merely by a very thin layer of +cell-wall substance. Haberlandt ("Physiologische Pflanzenanatomie", +Edition III. Leipzig, 1904. "Sinnesorgane im Pflanzenreich", Leipzig, +1901, and other publications.) has greatly extended our knowledge of +vegetable structure in relation to mechanical stimulation. He defines a +sense-organ as a contrivance by which the DEFORMATION or forcible change +of form in the protoplasm--on which mechanical stimulation depends--is +rendered rapid and considerable in amplitude ("Sinnesorgane", page 10). +He has shown that in certain papillose and bristle-like contrivances, +plants possess such sense-organs; and moreover that these contrivances +show a remarkable similarity to corresponding sense-organs in animals. + +Haberlandt and Nemec ("Ber. d. Deutschen bot. Gesellschaft", XVIII. +1900. See F. Darwin, Presidential Address to Section K, British +Association, 1904.) published independently and simultaneously a +theory of the mechanism by which plants are orientated in relation +to gravitation. And here again we find an arrangement identical in +principle with that by which certain animals recognise the vertical, +namely the pressure of free particles on the irritable wall of a cavity. +In the higher plants, Nemec and Haberlandt believe that special loose +and freely movable starch-grains play the part of the otoliths or +statoliths of the crustacea, while the protoplasm lining the cells in +which they are contained corresponds to the sensitive membrane lining +the otocyst of the animal. What is of special interest in our present +connection is that according to this ingenious theory (The original +conception was due to Noll ("Heterogene Induction", Leipzig, 1892), but +his view differed in essential points from those here given.) the +sense of verticality in a plant is a form of contact-irritability. The +vertical position is distinguished from the horizontal by the fact that, +in the latter case, the loose starch-grains rest on the lateral walls +of the cells instead of on the terminal walls as occurs in the normal +upright position. It should be added that the statolith theory is +still sub judice; personally I cannot doubt that it is in the main a +satisfactory explanation of the facts. + +With regard to the RAPIDITY of the reaction of tendrils, Darwin records +("Climbing Plants", page 155. Others have observed movement after about +6".) that a Passion-Flower tendril moved distinctly within 25 seconds of +stimulation. It was this fact, more than any other, that made him doubt +the current explanation, viz. that the movement is due to unequal +growth on the two sides of the tendril. The interesting work of Fitting +(Pringsheim's "Jahrb." XXXVIII. 1903, page 545.) has shown, however, +that the primary cause is not (as Darwin supposed) contraction on the +concave, but an astonishingly rapid increase in growth-rate on the +convex side. + +On the last page of "Climbing Plants" Darwin wrote: "It has often been +vaguely asserted that plants are distinguished from animals by not +having the power of movement. It should rather be said that plants +acquire and display this power only when it is of some advantage to +them." + +He gradually came to realise the vividness and variety of vegetable +life, and that a plant like an animal has capacities of behaving in +different ways under different circumstances, in a manner that may be +compared to the instinctive movements of animals. This point of view is +expressed in well-known passages in the "Power of Movement". ("The Power +of Movement in Plants", 1880, pages 571-3.) "It is impossible not to be +struck with the resemblance between the... movements of plants and many +of the actions performed unconsciously by the lower animals." And +again, "It is hardly an exaggeration to say that the tip of the +radicle... having the power of directing the movements of the adjoining +parts, acts like the brain of one of the lower animals; the brain being +seated within the anterior end of the body, receiving impressions from +the sense-organs, and directing the several movements." + +The conception of a region of perception distinct from a region of +movement is perhaps the most fruitful outcome of his work on the +movements of plants. But many years before its publication, viz. in +1861, he had made out the wonderful fact that in the Orchid Catasetum +("Life and Letters", III. page 268.) the projecting organs or antennae +are sensitive to a touch, and transmit an influence "for more than one +inch INSTANTANEOUSLY," which leads to the explosion or violent ejection +of the pollinia. And as we have already seen a similar transmission of +a stimulus was discovered by him in Sundew in 1860, so that in 1862 he +could write to Hooker ("Life and Letters", III. page 321.): "I cannot +avoid the conclusion, that Drosera possesses matter at least in some +degree analogous in constitution and function to nervous matter." I +propose in what follows to give some account of the observations on +the transmission of stimuli given in the "Power of Movement". It is +impossible within the space at my command to give anything like a +complete account of the matter, and I must necessarily omit all mention +of much interesting work. One well-known experiment consisted in putting +opaque caps on the tips of seedling grasses (e.g. oat and canary-grass) +and then exposing them to light from one side. The difference, in the +amount of curvature towards the light, between the blinded and +unblinded specimens, was so great that it was concluded that the +light-sensitiveness resided exclusively in the tip. The experiment +undoubtedly proves that the sensitiveness is much greater in the tip +than elsewhere, and that there is a transmission of stimulus from the +tip to the region of curvature. But Rothert (Rothert, Cohn's "Beitrage", +VII. 1894.) has conclusively proved that the basal part where the +curvature occurs is also DIRECTLY sensitive to light. He has shown, +however, that in other grasses (Setaria, Panicum) the cotyledon is the +only part which is sensitive, while the hypocotyl, where the movement +occurs, is not directly sensitive. + +It was however the question of the localisation of the gravitational +sense in the tip of the seedling root or radicle that aroused most +attention, and it was on this question that a controversy arose which +has continued to the present day. + +The experiment on which Darwin's conclusion was based consisted simply +in cutting off the tip, and then comparing the behaviour of roots so +treated with that of normal specimens. An uninjured root when placed +horizontally regains the vertical by means of a sharp downward +curve; not so a decapitated root which continues to grow more or less +horizontally. It was argued that this depends on the loss of an organ +specialised for the perception of gravity, and residing in the tip of +the root; and the experiment (together with certain important variants) +was claimed as evidence of the existence of such an organ. + +It was at once objected that the amputation of the tip might check +curvature by interfering with longitudinal growth, on the distribution +of which curvature depends. This objection was met by showing that an +injury, e.g. splitting the root longitudinally (See F. Darwin, "Linnean +Soc. Journal (Bot)." XIX. 1882, page 218.), which does not remove the +tip, but seriously checks growth, does not prevent geotropism. This +was of some interest in another and more general way, in showing that +curvature and longitudinal growth must be placed in different categories +as regards the conditions on which they depend. + +Another objection of a much more serious kind was that the amputation +of the tip acts as a shock. It was shown by Rothert (See his excellent +summary of the subject in "Flora" 1894 (Erganzungsband), page 199.) that +the removal of a small part of the cotyledon of Setaria prevents the +plant curving towards the light, and here there is no question of +removing the sense-organ since the greater part of the sensitive +cotyledon is intact. In view of this result it was impossible to rely on +the amputations performed on roots as above described. + +At this juncture a new and brilliant method originated in Pfeffer's +laboratory. (See Pfeffer, "Annals of Botany", VIII. 1894, page 317, and +Czapek, Pringsheim's "Jahrb." XXVII. 1895, page 243.) Pfeffer and Czapek +showed that it is possible to bend the root of a lupine so that, for +instance, the supposed sense-organ at the tip is vertical while the +motile region is horizontal. If the motile region is directly sensitive +to gravity the root ought to curve downwards, but this did not occur: on +the contrary it continued to grow horizontally. This is precisely what +should happen if Darwin's theory is the right one: for if the tip is +kept vertical, the sense-organ is in its normal position and receives no +stimulus from gravitation, and therefore can obviously transmit none to +the region of curvature. Unfortunately this method did not convince the +botanical world because some of those who repeated Czapek's experiment +failed to get his results. + +Czapek ("Berichte d. Deutsch. bot. Ges." XV. 1897, page 516, and +numerous subsequent papers. English readers should consult Czapek in the +"Annals of Botany", XIX. 1905, page 75.) has devised another interesting +method which throws light on the problem. He shows that roots, which +have been placed in a horizontal position and have therefore been +geotropically stimulated, can be distinguished by a chemical test from +vertical, i.e. unstimulated roots. The chemical change in the root can +be detected before any curvature has occurred and must therefore be a +symptom of stimulation, not of movement. It is particularly interesting +to find that the change in the root, on which Czapek's test depends, +takes place in the tip, i.e. in the region which Darwin held to be the +centre for gravitational sensitiveness. + +In 1899 I devised a method (F. Darwin, "Annals of Botany", XIII. 1899, +page 567.) by which I sought to prove that the cotyledon of Setaria is +not only the organ for light-perception, but also for gravitation. If +a seedling is supported horizontally by pushing the apical part +(cotyledon) into a horizontal tube, the cotyledon will, according to +my supposition, be stimulated gravitationally and a stimulus will be +transmitted to the basal part of the stem (hypocotyl) causing it to +bend. But this curvature merely raises the basal end of the seedling, +the sensitive cotyledon remains horizontal, imprisoned in its tube; it +will therefore be continually stimulated and will continue to transmit +influences to the bending region, which should therefore curl up into a +helix or corkscrew-like form,--and this is precisely what occurred. + +I have referred to this work principally because the same method was +applied to roots by Massart (Massart, "Mem. Couronnes Acad. R. Belg." +LXII. 1902.) and myself (F. Darwin, "Linnean Soc. Journ." XXXV. 1902, +page 266.) with a similar though less striking result. Although these +researches confirmed Darwin's work on roots, much stress cannot be laid +on them as there are several objections to them, and they are not easily +repeated. + +The method which--as far as we can judge at present--seems likely +to solve the problem of the root-tip is most ingenious and is due to +Piccard. (Pringsheim's "Jahrb." XL. 1904, page 94.) + +Andrew Knight's celebrated experiment showed that roots react to +centrifugal force precisely as they do to gravity. So that if a bean +root is fixed to a wheel revolving rapidly on a horizontal axis, it +tends to curve away from the centre in the line of a radius of the +wheel. In ordinary demonstrations of Knight's experiment the seed is +generally fixed so that the root is at right angles to a radius, and as +far as convenient from the centre of rotation. Piccard's experiment is +arranged differently. (A seed is depicted below a horizontal dotted +line AA, projecting a root upwards.) The root is oblique to the axis +of rotation, and the extreme tip projects beyond that axis. Line AA +represents the axis of rotation, T is the tip of the root just above the +line AA, and B is the region just below line AA in which curvature takes +place. If the motile region B is directly sensitive to gravitation (and +is the only part which is sensitive) the root will curve (down and away +from the vertical) away from the axis of rotation, just as in Knight's +experiment. But if the tip T is alone sensitive to gravitation the +result will be exactly reversed, the stimulus originating in T and +conveyed to B will produce curvature (up towards the vertical). We may +think of the line AA as a plane dividing two worlds. In the lower one +gravity is of the earthly type and is shown by bodies falling and roots +curving downwards: in the upper world bodies fall upwards and roots +curve in the same direction. The seedling is in the lower world, but its +tip containing the supposed sense-organ is in the strange world where +roots curve upwards. By observing whether the root bends up or down we +can decide whether the impulse to bend originates in the tip or in the +motile region. + +Piccard's results showed that both curvatures occurred and he +concluded that the sensitive region is not confined to the tip. (Czapek +(Pringsheim's "Jahrb." XXXV. 1900, page 362) had previously given +reasons for believing that, in the root, there is no sharp line of +separation between the regions of perception and movement.) + +Haberlandt (Pringsheim's "Jahrb." XLV. 1908, page 575.) has recently +repeated the experiment with the advantage of better apparatus and more +experience in dealing with plants, and has found as Piccard did that +both the tip and the curving region are sensitive to gravity, but with +the important addition that the sensitiveness of the tip is much greater +than that of the motile region. The case is in fact similar to that of +the oat and canary-grass. In both instances my father and I were wrong +in assuming that the sensitiveness is confined to the tip, yet there +is a concentration of irritability in that region and transmission of +stimulus is as true for geotropism as it is for heliotropism. Thus after +nearly thirty years the controversy of the root-tip has apparently ended +somewhat after the fashion of the quarrels at the "Rainbow" in +"Silas Marner"--"you're both right and you're both wrong." But the +"brain-function" of the root-tip at which eminent people laughed in +early days turns out to be an important part of the truth. (By using +Piccard's method I have succeeded in showing that the gravitational +sensitiveness of the cotyledon of Sorghum is certainly much greater than +the sensitiveness of the hypocotyl--if indeed any such sensitiveness +exists. See Wiesner's "Festschrift", Vienna, 1908.) + +Another observation of Darwin's has given rise to much controversy. +("Power of Movement", page 133.) If a minute piece of card is fixed +obliquely to the tip of a root some influence is transmitted to the +region of curvature and the root bends away from the side to which +the card was attached. It was thought at the time that this proved the +root-tip to be sensitive to contact, but this is not necessarily the +case. It seems possible that the curvature is a reaction to the injury +caused by the alcoholic solution of shellac with which the cards were +cemented to the tip. This agrees with the fact given in the "Power of +Movement" that injuring the root-tip on one side, by cutting or burning +it, induced a similar curvature. On the other hand it was shown that +curvature could be produced in roots by cementing cards, not to the +naked surface of the root-tip, but to pieces of gold-beaters skin +applied to the root; gold-beaters skin being by itself almost without +effect. But it must be allowed that, as regards touch, it is not clear +how the addition of shellac and card can increase the degree of contact. +There is however some evidence that very close contact from a solid +body, such as a curved fragment of glass, produces curvature: and this +may conceivably be the explanation of the effect of gold-beaters skin +covered with shellac. But on the whole it is perhaps safer to classify +the shellac experiments with the results of undoubted injury rather than +with those of contact. + +Another subject on which a good deal of labour was expended is the sleep +of leaves, or as Darwin called it their NYCTITROPIC movement. He showed +for the first time how widely spread this phenomenon is, and attempted +to give an explanation of the use to the plant of the power of sleeping. +His theory was that by becoming more or less vertical at night the +leaves escape the chilling effect of radiation. Our method of testing +this view was to fix some of the leaves of a sleeping plant so that they +remained horizontal at night and therefore fully exposed to radiation, +while their fellows were partly protected by assuming the nocturnal +position. The experiments showed clearly that the horizontal leaves were +more injured than the sleeping, i.e. more or less vertical, ones. It may +be objected that the danger from cold is very slight in warm countries +where sleeping plants abound. But it is quite possible that a lowering +of the temperature which produces no visible injury may nevertheless +be hurtful by checking the nutritive processes (e.g. translocation of +carbohydrates), which go on at night. Stahl ("Bot. Zeitung", 1897, page +81.) however has ingeniously suggested that the exposure of the leaves +to radiation is not DIRECTLY hurtful because it lowers the temperature +of the leaf, but INDIRECTLY because it leads to the deposition of dew on +the leaf-surface. He gives reasons for believing that dew-covered leaves +are unable to transpire efficiently, and that the absorption of mineral +food-material is correspondingly checked. Stahl's theory is in no way +destructive of Darwin's, and it is possible that nyctitropic leaves are +adapted to avoid the indirect as well as the direct results of cooling +by radiation. + +In what has been said I have attempted to give an idea of some of the +discoveries brought before the world in the "Power of Movement" (In 1881 +Professor Wiesner published his "Das Bewegungsvermogen der Pflanzen", +a book devoted to the criticism of "The Power of Movement in Plants". A +letter to Wiesner, published in "Life and Letters", III. page 336, shows +Darwin's warm appreciation of his critic's work, and of the spirit in +which it is written.) and of the subsequent history of the problems. +We must now pass on to a consideration of the central thesis of the +book,--the relation of circumnutation to the adaptive curvatures of +plants. + +Darwin's view is plainly stated on pages 3-4 of the "Power of Movement". +Speaking of circumnutation he says, "In this universally present +movement we have the basis or groundwork for the acquirement, according +to the requirements of the plant, of the most diversified movements." +He then points out that curvatures such as those towards the light or +towards the centre of the earth can be shown to be exaggerations of +circumnutation in the given directions. He finally points out that +the difficulty of conceiving how the capacities of bending in definite +directions were acquired is diminished by his conception. "We know that +there is always movement in progress, and its amplitude, or direction, +or both, have only to be modified for the good of the plant in relation +with internal or external stimuli." + +It may at once be allowed that the view here given has not been accepted +by physiologists. The bare fact that circumnutation is a general +property of plants (other than climbing species) is not generally +rejected. But the botanical world is no nearer to believing in the +theory of reaction built on it. + +If we compare the movements of plants with those of the lower animals we +find a certain resemblance between the two. According to Jennings (H.S. +Jennings, "The Behavior of the Lower Animals". Columbia U. Press, N.Y. +1906.) a Paramoecium constantly tends to swerve towards the aboral side +of its body owing to certain peculiarities in the set and power of +its cilia. But the tendency to swim in a circle, thus produced, is +neutralised by the rotation of the creature about its longitudinal +axis. Thus the direction of the swerves IN RELATION TO THE PATH of the +organism is always changing, with the result that the creature moves in +what approximates to a straight line, being however actually a spiral +about the general line of progress. This method of motion is strikingly +like the circumnutation of a plant, the apex of which also describes a +spiral about the general line of growth. A rooted plant obviously cannot +rotate on its axis, but the regular series of curvatures of which its +growth consists correspond to the aberrations of Paramoecium distributed +regularly about its course by means of rotation. (In my address to the +Biological Section of the British Association at Cardiff (1891) I +have attempted to show the connection between circumnutation and +RECTIPETALITY, i.e. the innate capacity of growing in a straight line.) +Just as a plant changes its direction of growth by an exaggeration of +one of the curvature-elements of which circumnutation consists, so +does a Paramoecium change its course by the accentuation of one of +the deviations of which its path is built. Jennings has shown that the +infusoria, etc., react to stimuli by what is known as the "method of +trial." If an organism swims into a region where the temperature is too +high or where an injurious substance is present, it changes its course. +It then moves forward again, and if it is fortunate enough to escape the +influence, it continues to swim in the given direction. If however its +change of direction leads it further into the heated or poisonous region +it repeats the movement until it emerges from its difficulties. Jennings +finds in the movements of the lower organisms an analogue with what +is known as pain in conscious organisms. There is certainly this much +resemblance that a number of quite different sub-injurious agencies +produce in the lower organisms a form of reaction by the help of which +they, in a partly fortuitous way, escape from the threatening element +in their environment. The higher animals are stimulated in a parallel +manner to vague and originally purposeless movements, one of which +removes the discomfort under which they suffer, and the organism finally +learns to perform the appropriate movement without going through the +tentative series of actions. + +I am tempted to recognise in circumnutation a similar groundwork of +tentative movements out of which the adaptive ones were originally +selected by a process rudely representative of learning by experience. + +It is, however, simpler to confine ourselves to the assumption that +those plants have survived which have acquired through unknown causes +the power of reacting in appropriate ways to the external stimuli of +light, gravity, etc. It is quite possible to conceive this occurring in +plants which have no power of circumnutating--and, as already pointed +out, physiologists do as a fact neglect circumnutation as a factor in +the evolution of movements. Whatever may be the fate of Darwin's theory +of circumnutation there is no doubt that the research he carried out +in support of, and by the light of, this hypothesis has had a powerful +influence in guiding the modern theories of the behaviour of plants. +Pfeffer ("The Physiology of Plants", Eng. Tr. III. page 11.), who more +than any one man has impressed on the world a rational view of the +reactions of plants, has acknowledged in generous words the great value +of Darwin's work in the same direction. The older view was that, for +instance, curvature towards the light is the direct mechanical result of +the difference of illumination on the lighted and shaded surfaces of the +plant. This has been proved to be an incorrect explanation of the +fact, and Darwin by his work on the transmission of stimuli has greatly +contributed to the current belief that stimuli act indirectly. Thus we +now believe that in a root and a stem the mechanism for the perception +of gravitation is identical, but the resulting movements are different +because the motor-irritabilities are dissimilar in the two cases. We +must come back, in fact, to Darwin's comparison of plants to animals. +In both there is perceptive machinery by which they are made delicately +alive to their environment, in both the existing survivors are those +whose internal constitution has enabled them to respond in a beneficial +way to the disturbance originating in their sense-organs. + + + + +XX. THE BIOLOGY OF FLOWERS. By K. Goebel, Ph.D. + +Professor of Botany in the University of Munich. + + +There is scarcely any subject to which Darwin devoted so much time and +work as to his researches into the biology of flowers, or, in other +words, to the consideration of the question to what extent the +structural and physiological characters of flowers are correlated with +their function of producing fruits and seeds. We know from his own words +what fascination these studies possessed for him. We repeatedly find, +for example, in his letters expressions such as this:--"Nothing in my +life has ever interested me more than the fertilisation of such plants +as Primula and Lythrum, or again Anacamptis or Listera." ("More Letters +of Charles Darwin", Vol. II. page 419.) + +Expressions of this kind coming from a man whose theories exerted an +epoch-making influence, would be unintelligible if his researches into +the biology of flowers had been concerned only with records of isolated +facts, however interesting these might be. We may at once take it +for granted that the investigations were undertaken with the view of +following up important problems of general interest, problems which are +briefly dealt with in this essay. + +Darwin published the results of his researches in several papers and in +three larger works, (i) "On the various contrivances by which British +and Foreign Orchids are fertilised by insects" (First edition, London, +1862; second edition, 1877; popular edition, 1904.) (ii) "The effects of +Cross and Self fertilisation in the vegetable kingdom" (First edition, +1876; second edition, 1878). (iii) "The different forms of Flowers on +plants of the same species" (First edition, 1877; second edition, 1880). + +Although the influence of his work is considered later, we may here +point out that it was almost without a parallel; not only does it +include a mass of purely scientific observations, but it awakened +interest in very wide circles, as is shown by the fact that we find the +results of Darwin's investigations in floral biology universally quoted +in school books; they are even willingly accepted by those who, as +regards other questions, are opposed to Darwin's views. + +The works which we have mentioned are, however, not only of special +interest because of the facts they contribute, but because of the MANNER +in which the facts are expressed. A superficial reader seeking merely +for catch-words will, for instance, probably find the book on cross and +self-fertilisation rather dry because of the numerous details which +it contains: it is, indeed, not easy to compress into a few words the +general conclusions of this volume. But on closer examination, we cannot +be sufficiently grateful to the author for the exactness and objectivity +with which he enables us to participate in the scheme of his researches. +He never tries to persuade us, but only to convince us that his +conclusions are based on facts; he always gives prominence to such facts +as appear to be in opposition to his opinions,--a feature of his work in +accordance with a maxim which he laid down:--"It is a golden rule, +which I try to follow, to put every fact which is opposed to one's +preconceived opinion in the strongest light." ("More Letters", Vol. II. +page 324.) + +The result of this method of presentation is that the works mentioned +above represent a collection of most valuable documents even for those +who feel impelled to draw from the data other conclusions than those of +the author. Each investigation is the outcome of a definite question, a +"preconceived opinion," which is either supported by the facts or +must be abandoned. "How odd it is that anyone should not see that all +observation must be for or against some view if it is to be of any +service!" (Ibid. Vol. I. page 195.) + +The points of view which Darwin had before him were principally the +following. In the first place the proof that a large number of the +peculiarities in the structure of flowers are not useless, but of the +greatest significance in pollination must be of considerable importance +for the interpretation of adaptations; "The use of each trifling detail +of structure is far from a barren search to those who believe in natural +selection." ("Fertilisation of Orchids" (1st edition), page 351; (2nd +edition 1904) page 286.) Further, if these structural relations are +shown to be useful, they may have been acquired because from the many +variations which have occurred along different lines, those have been +preserved by natural selection "which are beneficial to the organism +under the complex and ever-varying conditions of life." (Ibid. page +351.) But in the case of flowers there is not only the question of +adaptation to fertilisation to be considered. Darwin, indeed, +soon formed the opinion which he has expressed in the following +sentence,--"From my own observations on plants, guided to a certain +extent by the experience of the breeders of animals, I became convinced +many years ago that it is a general law of nature that flowers are +adapted to be crossed, at least occasionally, by pollen from a distinct +plant." ("Cross and Self fertilisation" (1st edition), page 6.) + +The experience of animal breeders pointed to the conclusion that +continual in-breeding is injurious. If this is correct, it raises the +question whether the same conclusion holds for plants. As most flowers +are hermaphrodite, plants afford much more favourable material than +animals for an experimental solution of the question, what results +follow from the union of nearly related sexual cells as compared with +those obtained by the introduction of new blood. The answer to this +question must, moreover, possess the greatest significance for the +correct understanding of sexual reproduction in general. + +We see, therefore, that the problems which Darwin had before him in his +researches into the biology of flowers were of the greatest importance, +and at the same time that the point of view from which he attacked the +problems was essentially a teleological one. + +We may next inquire in what condition he found the biology of flowers at +the time of his first researches, which were undertaken about the year +1838. In his autobiography he writes,--"During the summer of 1839, +and, I believe, during the previous summer, I was led to attend to the +cross-fertilisation of flowers by the aid of insects, from having come +to the conclusion in my speculations on the origin of species, that +crossing played an important part in keeping specific forms constant." +("The Life and Letters of Charles Darwin", Vol. I. page 90, London, +1888.) In 1841 he became acquainted with Sprengel's work: his researches +into the biology of flowers were thus continued for about forty years. + +It is obvious that there could only be a biology of flowers after it had +been demonstrated that the formation of seeds and fruit in the flower +is dependent on pollination and subsequent fertilisation. This proof +was supplied at the end of the seventeenth century by R.J. Camerarius +(1665-1721). He showed that normally seeds and fruits are developed only +when the pollen reaches the stigma. The manner in which this happens was +first thoroughly investigated by J.G. Kolreuter (1733-1806 (Kolreuter, +"Vorlaufige Nachricht von einigen das Geschlecht der Planzen +betreffenden Versuchen und Beobachtungen", Leipzig, 1761; with three +supplements, 1763-66. Also, "Mem. de l'acad. St Petersbourg", Vol. XV. +1809.)), the same observer to whom we owe the earliest experiments in +hybridisation of real scientific interest. Kolreuter mentioned that +pollen may be carried from one flower to another partly by wind and +partly by insects. But he held the view, and that was, indeed, the +natural assumption, that self-fertilisation usually occurs in a flower, +in other words that the pollen of a flower reaches the stigma of +the same flower. He demonstrated, however, certain cases in which +cross-pollination occurs, that is in which the pollen of another flower +of the same species is conveyed to the stigma. He was familiar with the +phenomenon, exhibited by numerous flowers, to which Sprengel afterwards +applied the term Dichogamy, expressing the fact that the anthers and +stigmas of a flower often ripen at different times, a peculiarity +which is now recognised as one of the commonest means of ensuring +cross-pollination. + +With far greater thoroughness and with astonishing power of observation +C.K. Sprengel (1750-1816) investigated the conditions of pollination of +flowers. Darwin was introduced by that eminent botanist Robert Brown to +Sprengel's then but little appreciated work,--"Das entdeckte Geheimniss +der Natur im Bau und in der Befruchtung der Blumen" (Berlin, 1793); this +is by no means the least service to Botany rendered by Robert Brown. + +Sprengel proceeded from a naive teleological point of view. He firmly +believed "that the wise Author of nature had not created a single hair +without a definite purpose." He succeeded in demonstrating a number of +beautiful adaptations in flowers for ensuring pollination; but his work +exercised but little influence on his contemporaries and indeed for a +long time after his death. It was through Darwin that Sprengel's work +first achieved a well deserved though belated fame. Even such botanists +as concerned themselves with researches into the biology of flowers +appear to have formerly attached much less value to Sprengel's work +than it has received since Darwin's time. In illustration of this we may +quote C.F. Gartner whose name is rightly held in the highest esteem as +that of one of the most eminent hybridologists. In his work "Versuche +und Beobachtungen uder die Befruchtungsorgane der vollkommeneren +Gewachse und uber die naturliche und kunstliche Befruchtung durch den +eigenen Pollen" he also deals with flower-pollination. He recognised the +action of the wind, but he believed, in spite of the fact that he +both knew and quoted Kolreuter and Sprengel, that while insects assist +pollination, they do so only occasionally, and he held that insects are +responsible for the conveyance of pollen; thorough investigations +would show "that a very small proportion of the plants included in this +category require this assistance in their native habitat." (Gartner, +"Versucher und Beobachtungen... ", page 335, Stuttgart, 1844.) In the +majority of plants self-pollination occurs. + +Seeing that even investigators who had worked for several decades at +fertilisation-phenomena had not advanced the biology of flowers beyond +the initial stage, we cannot be surprised that other botanists followed +to even a less extent the lines laid down by Kolreuter and Sprengel. +This was in part the result of Sprengel's supernatural teleology and in +part due to the fact that his book appeared at a time when other lines +of inquiry exerted a dominating influence. + +At the hands of Linnaeus systematic botany reached a vigorous +development, and at the beginning of the nineteenth century the anatomy +and physiology of plants grew from small beginnings to a flourishing +branch of science. Those who concerned themselves with flowers +endeavoured to investigate their development and structure or the most +minute phenomena connected with fertilisation and the formation of the +embryo. No room was left for the extension of the biology of flowers on +the lines marked out by Kolreuter and Sprengel. Darwin was the first to +give new life and a deeper significance to this subject, chiefly +because he took as his starting-point the above-mentioned problems, the +importance of which is at once admitted by all naturalists. + +The further development of floral biology by Darwin is in the first +place closely connected with the book on the fertilisation of Orchids. +It is noteworthy that the title includes the sentence,--"and on the good +effects of intercrossing." + +The purpose of the book is clearly stated in the introduction:--"The +object of the following work is to show that the contrivances by which +Orchids are fertilised, are as varied and almost as perfect as any of +the most beautiful adaptations in the animal kingdom; and, secondly, +to show that these contrivances have for their main object the +fertilisation of each flower by the pollen of another flower." +("Fertilisation of Orchids", page 1.) Orchids constituted a particularly +suitable family for such researches. Their flowers exhibit a striking +wealth of forms; the question, therefore, whether the great variety +in floral structure bears any relation to fertilisation (In the older +botanical literature the word fertilisation is usually employed in cases +where POLLINATION is really in question: as Darwin used it in this sense +it is so used here.) must in this case possess special interest. + +Darwin succeeded in showing that in most of the orchids examined +self-fertilisation is either an impossibility, or, under natural +conditions, occurs only exceptionally. On the other hand these plants +present a series of extraordinarily beautiful and remarkable adaptations +which ensure the transference of pollen by insects from one flower to +another. It is impossible to describe adequately in a few words the +wealth of facts contained in the Orchid book. A few examples may, +however, be quoted in illustration of the delicacy of the observations +and of the perspicuity employed in interpreting the facts. + +The majority of orchids differ from other seed plants (with the +exception of the Asclepiads) in having no dust-like pollen. The pollen, +or more correctly, the pollen-tetrads, remain fastened together as +club-shaped pollinia usually borne on a slender pedicel. At the base of +the pedicel is a small viscid disc by which the pollinium is attached +to the head or proboscis of one of the insects which visit the flower. +Darwin demonstrated that in Orchis and other flowers the pedicel of +the pollinium, after its removal from the anther, undergoes a curving +movement. If the pollinium was originally vertical, after a time it +assumed a horizontal position. In the latter position, if the insect +visited another flower, the pollinium would exactly hit the sticky +stigmatic surface and thus effect fertilisation. The relation between +the behaviour of the viscid disc and the secretion of nectar by the +flower is especially remarkable. The flowers possess a spur which in +some species (e.g. Gymnadenia conopsea, Platanthera bifolia, etc.) +contains honey (nectar), which serves as an attractive bait for insects, +but in others (e.g. our native species of Orchis) the spur is empty. +Darwin held the opinion, confirmed by later investigations, that in the +case of flowers without honey the insects must penetrate the wall of the +nectarless spurs in order to obtain a nectar-like substance. The glands +behave differently in the nectar-bearing and in the nectarless flowers. +In the former they are so sticky that they at once adhere to the body of +the insect; in the nectarless flowers firm adherence only occurs after +the viscid disc has hardened. It is, therefore, adaptively of value +that the insects should be detained longer in the nectarless flowers (by +having to bore into the spur),--than in flowers in which the nectar is +freely exposed. "If this relation, on the one hand, between the viscid +matter requiring some little time to set hard, and the nectar being so +lodged that moths are delayed in getting it; and, on the other hand, +between the viscid matter being at first as viscid as ever it will +become, and the nectar lying all ready for rapid suction, be accidental, +it is a fortunate accident for the plant. If not accidental, and I +cannot believe it to be accidental, what a singular case of adaptation!" +("Fertilisation of Orchids" (1st edition), page 53.) + +Among exotic orchids Catasetum is particularly remarkable. One and the +same species bears different forms of flowers. The species known as +Catasetum tridentatum has pollinia with very large viscid discs; +on touching one of the two filaments (antennae) which occur on the +gynostemium of the flower the pollinia are shot out to a fairly long +distance (as far as 1 metre) and in such manner that they alight on the +back of the insect, where they are held. The antennae have, moreover, +acquired an importance, from the point of view of the physiology of +stimulation, as stimulus-perceiving organs. Darwin had shown that it is +only a touch on the antennae that causes the explosion, while contact, +blows, wounding, etc. on other places produce no effect. This form of +flower proved to be the male. The second form, formerly regarded as +a distinct species and named Monachanthus viridis, is shown to be the +female flower. The anthers have only rudimentary pollinia and do not +open; there are no antennae, but on the other hand numerous seeds +are produced. Another type of flower, known as Myanthus barbatus, was +regarded by Darwin as a third form: this was afterwards recognised +by Rolfe (Rolfe, R.A. "On the sexual forms of Catasetum with special +reference to the researches of Darwin and others," "Journ. Linn. Soc." +Vol. XXVII. (Botany), 1891, pages 206-225.) as the male flower +of another species, Catasetum barbatum Link, an identification in +accordance with the discovery made by Cruger in Trinidad that it always +remains sterile. + +Darwin had noticed that the flowers of Catasetum do not secrete nectar, +and he conjectured that in place of it the insects gnaw a tissue in +the cavity of the labellum which has a "slightly sweet, pleasant and +nutritious taste." This conjecture as well as other conclusions drawn by +Darwin from Catasetum have been confirmed by Cruger--assuredly the best +proof of the acumen with which the wonderful floral structure of this +"most remarkable of the Orchids" was interpretated far from its native +habitat. + +As is shown by what we have said about Catasetum, other problems in +addition to those concerned with fertilisation are dealt with in the +Orchid book. This is especially the case in regard to flower morphology. +The scope of flower morphology cannot be more clearly and better +expressed than by these words: "He will see how curiously a flower may +be moulded out of many separate organs--how perfect the cohesion of +primordially distinct parts may become,--how organs may be used for +purposes widely different from their proper function,--how other organs +may be entirely suppressed, or leave mere useless emblems of their +former existence." ("Fertilisation of Orchids", page 289.) + +In attempting, from this point of view, to refer the floral structure +of orchids to their original form, Darwin employed a much more thorough +method than that of Robert Brown and others. The result of this was the +production of a considerable literature, especially in France, along +the lines suggested by Darwin's work. This is the so-called anatomical +method, which seeks to draw conclusions as to the morphology of the +flower from the course of the vascular bundles in the several parts. (He +wrote in one of his letters, "... the destiny of the whole human race is +as nothing to the course of vessels of orchids" ("More Letters", Vol. +II. page 275.) Although the interpretation of the orchid flower given +by Darwin has not proved satisfactory in one particular point--the +composition of the labellum--the general results have received universal +assent, namely "that all Orchids owe what they have in common to descent +from some monocotyledonous plant, which, like so many other plants of +the same division, possessed fifteen organs arranged alternately three +within three in five whorls." ("Fertilisation of Orchids" (1st edition), +page 307.) The alterations which their original form has undergone have +persisted so far as they were found to be of use. + +We see also that the remarkable adaptations of which we have given some +examples are directed towards cross-fertilisation. In only a few of +the orchids investigated by Darwin--other similar cases have since been +described--was self-fertilisation found to occur regularly or usually. +The former is the case in the Bee Ophrys (Ophrys apifera), the mechanism +of which greatly surprised Darwin. He once remarked to a friend that one +of the things that made him wish to live a few thousand years was his +desire to see the extinction of the Bee Ophrys, an end to which he +believed its self-fertilising habit was leading. ("Life and Letters", +Vol. III. page 276 (footnote).) But, he wrote, "the safest conclusion, +as it seems to me, is, that under certain unknown circumstances, and +perhaps at very long intervals of time, one individual of the Bee Ophrys +is crossed by another." ("Fertilisation of Orchids" page 71.) + +If, on the one hand, we remember how much more sure self-fertilisation +would be than cross-fertilisation, and, on the other hand, if we call to +mind the numerous contrivances for cross-fertilisation, the +conclusion is naturally reached that "it is an astonishing fact that +self-fertilisation should not have been an habitual occurrence. It +apparently demonstrates to us that there must be something injurious in +the process. Nature thus tells us, in the most emphatic manner, that she +abhors perpetual self-fertilisation... For may we not further infer as +probable, in accordance with the belief of the vast majority of the +breeders of our domestic productions, that marriage between near +relations is likewise in some way injurious, that some unknown great +good is derived from the union of individuals which have been kept +distinct for many generations?" (Ibid., page 359.) + +This view was supported by observations on plants of other families, +e.g. Papilionaceae; it could, however, in the absence of experimental +proof, be regarded only as a "working hypothesis." + +All adaptations to cross-pollination might also be of use simply because +they made pollination possible when for any reason self-pollination had +become difficult or impossible. Cross-pollination would, therefore, be +of use, not as such, but merely as a means of pollination in general; +it would to some extent serve as a remedy for a method unsuitable in +itself, such as a modification standing in the way of self-pollination, +and on the other hand as a means of increasing the chance of pollination +in the case of flowers in which self-pollination was possible, but which +might, in accidental circumstances, be prevented. It was, therefore, +very important to obtain experimental proof of the conclusion to which +Darwin was led by the belief of the majority of breeders and by the +evidence of the widespread occurrence of cross-pollination and of the +remarkable adaptations thereto. + +This was supplied by the researches which are described in the two other +works named above. The researches on which the conclusions rest had, in +part at least, been previously published in separate papers: this is the +case as regards the heterostyled plants. The discoveries which Darwin +made in the course of his investigations of these plants belong to the +most brilliant in biological science. + +The case of Primula is now well known. C.K. Sprengel and others were +familiar with the remarkable fact that different individuals of the +European species of Primula bear differently constructed flowers; some +plants possess flowers in which the styles project beyond the stamens +attached to the corolla-tube (long-styled form), while in others the +stamens are inserted above the stigma which is borne on a short style +(short-styled form). It has been shown by Breitenbach that both forms of +flower may occur on the same plant, though this happens very rarely. An +analogous case is occasionally met with in hybrids, which bear flowers +of different colour on the same plant (e.g. Dianthus caryophyllus). +Darwin showed that the external differences are correlated with others +in the structure of the stigma and in the nature of the pollen. +The long-styled flowers have a spherical stigma provided with large +stigmatic papillae; the pollen grains are oblong and smaller than those +of the short-styled flowers. The number of the seeds produced is smaller +and the ovules larger, probably also fewer in number. The short-styled +flowers have a smooth compressed stigma and a corolla of somewhat +different form; they produce a greater number of seeds. + +These different forms of flowers were regarded as merely a case of +variation, until Darwin showed "that these heterostyled plants are +adapted for reciprocal fertilisation; so that the two or three forms, +though all are hermaphrodites, are related to one another almost +like the males and females of ordinary unisexual animals." ("Forms +of Flowers" (1st edition), page 2.) We have here an example of +hermaphrodite flowers which are sexually different. There are essential +differences in the manner in which fertilisation occurs. This may +be effected in four different ways; there are two legitimate and two +illegitimate types of fertilisation. The fertilisation is legitimate +if pollen from the long-styled flowers reaches the stigma of the +short-styled form or if pollen of the short-styled flowers is brought +to the stigma of the long-styled flower, that is the organs of the +same length of the two different kinds of flower react on one +another. Illegitimate fertilisation is represented by the two kinds of +self-fertilisation, also by cross-fertilisation, in which the pollen of +the long-styled form reaches the stigma of the same type of flower and, +similarly, by cross-pollination in the case of the short-styled flowers. + +The applicability of the terms legitimate and illegitimate depends, on +the one hand, upon the fact that insects which visit the different forms +of flowers pollinate them in the manner suggested; the pollen of the +short-styled flowers adhere to that part of the insect's body which +touches the stigma of the long-styled flower and vice versa. On the +other hand, it is based also on the fact that experiment shows that +artificial pollination produces a very different result according as +this is legitimate or illegitimate; only the legitimate union ensures +complete fertility, the plants thus produced being stronger than those +which are produced illegitimately. + +If we take 100 as the number of flowers which produce seeds as the +result of legitimate fertilisation, we obtain the following numbers from +illegitimate fertilisation: + +Primula officinalis (P. veris) (Cowslip)... 69 Primula elatior +(Oxlip).................... 27 Primula acaulis (P. vulgaris) +(Primrose)... 60 + +Further, the plants produced by the illegitimate method of fertilisation +showed, e.g. in P. officinalis, a decrease in fertility in later +generations, sterile pollen and in the open a feebler growth. (Under +very favourable conditions (in a greenhouse) the fertility of the plants +of the fourth generation increases--a point, which in view of various +theoretical questions, deserves further investigation.) They behave in +fact precisely in the same way as hybrids between species of different +genera. This result is important, "for we thus learn that the difficulty +in sexually uniting two organic forms and the sterility of their +offspring, afford no sure criterion of so-called specific distinctness" +("Forms of Flowers", page 242): the relative or absolute sterility +of the illegitimate unions and that of their illegitimate descendants +depend exclusively on the nature of the sexual elements and on their +inability to combine in a particular manner. This functional difference +of sexual cells is characteristic of the behaviour of hybrids as of the +illegitimate unions of heterostyled plants. The agreement becomes +even closer if we regard the Primula plants bearing different forms of +flowers not as belonging to a systematic entity or "species," but as +including several elementary species. The legitimately produced plants +are thus true hybrids (When Darwin wrote in reference to the different +forms of heterostyled plants, "which all belong to the same species +as certainly as do the two sexes of the same species" ("Cross and +Self fertilisation", page 466), he adopted the term species in a +comprehensive sense. The recent researches of Bateson and Gregory ("On +the inheritance of Heterostylism in Primula"; "Proc. Roy. Soc." Ser. B, +Vol. LXXVI. 1905, page 581) appear to me also to support the view that +the results of illegitimate crossing of heterostyled Primulas correspond +with those of hybridisation. The fact that legitimate pollen effects +fertilisation, even if illegitimate pollen reaches the stigma a short +time previously, also points to this conclusion. Self-pollination in the +case of the short-styled form, for example, is not excluded. In spite +of this, the numerical proportion of the two forms obtained in the open +remains approximately the same as when the pollination was exclusively +legitimate, presumably because legitimate pollen is prepotent.), with +which their behaviour in other respects, as Darwin showed, presents so +close an agreement. This view receives support also from the fact that +descendants of a flower fertilised illegitimately by pollen from another +plant with the same form of flower belong, with few exceptions, to the +same type as that of their parents. The two forms of flower, however, +behave differently in this respect. Among 162 seedlings of the +long-styled illegitimately pollinated plants of Primula officinalis, +including five generations, there were 156 long-styled and only six +short-styled forms, while as the result of legitimate fertilisation +nearly half of the offspring were long-styled and half short-styled. The +short-styled illegitimately pollinated form gave five long-styled +and nine short-styled; the cause of this difference requires further +explanation. The significance of heterostyly, whether or not we now +regard it as an arrangement for the normal production of hybrids, is +comprehensively expressed by Darwin: "We may feel sure that plants have +been rendered heterostyled to ensure cross-fertilisation, for we now +know that a cross between the distinct individuals of the same species +is highly important for the vigour and fertility of the offspring." +("Forms of Flowers", page 258.) If we remember how important the +interpretation of heterostyly has become in all general problems as, +for example, those connected with the conditions of the formation of +hybrids, a fact which was formerly overlooked, we can appreciate how +Darwin was able to say in his autobiography: "I do not think anything in +my scientific life has given me so much satisfaction as making out the +meaning of the structure of these plants." ("Life and Letters", Vol. I. +page 91.) + +The remarkable conditions represented in plants with three kinds of +flowers, such as Lythrum and Oxalis, agree in essentials with those +in Primula. These cannot be considered in detail here; it need only be +noted that the investigation of these cases was still more laborious. +In order to establish the relative fertility of the different unions in +Lythrum salicaria 223 different fertilisations were made, each flower +being deprived of its male organs and then dusted with the appropriate +pollen. + +In the book containing the account of heterostyled plants other +species are dealt with which, in addition to flowers opening normally +(chasmogamous), also possess flowers which remain closed but are capable +of producing fruit. These cleistogamous flowers afford a striking +example of habitual self-pollination, and H. von Mohl drew special +attention to them as such shortly after the appearance of Darwin's +Orchid book. If it were only a question of producing seed in the +simplest way, cleistogamous flowers would be the most conveniently +constructed. The corolla and frequently other parts of the flower are +reduced; the development of the seed may, therefore, be accomplished +with a smaller expenditure of building material than in chasmogamous +flowers; there is also no loss of pollen, and thus a smaller amount +suffices for fertilisation. + +Almost all these plants, as Darwin pointed out, have also chasmogamous +flowers which render cross-fertilisation possible. His view that +cleistogamous flowers are derived from originally chasmogamous flowers +has been confirmed by more recent researches. Conditions of nutrition in +the broader sense are the factors which determine whether chasmogamous +or cleistogamous flowers are produced, assuming, of course, that the +plants in question have the power of developing both forms of flower. +The former may fail to appear for some time, but are eventually +developed under favourable conditions of nourishment. The belief of many +authors that there are plants with only cleistogamous flowers cannot +therefore be accepted as authoritative without thorough experimental +proof, as we are concerned with extra-european plants for which it is +often difficult to provide appropriate conditions in cultivation. + +Darwin sees in cleistogamous flowers an adaptation to a good supply of +seeds with a small expenditure of material, while chasmogamous flowers +of the same species are usually cross-fertilised and "their offspring +will thus be invigorated, as we may infer from a wide-spread analogy." +("Forms of Flowers" (1st edition), page 341.) Direct proof in support of +this has hitherto been supplied in a few cases only; we shall often +find that the example set by Darwin in solving such problems as these by +laborious experiment has unfortunately been little imitated. + +Another chapter of this book treats of the distribution of the sexes in +polygamous, dioecious, and gyno-dioecious plants (the last term, now in +common use, we owe to Darwin). It contains a number of important facts +and discussions and has inspired the experimental researches of Correns +and others. + +The most important of Darwin's work on floral biology is, however, that +on cross and self-fertilisation, chiefly because it states the results +of experimental investigations extending over many years. Only +such experiments, as we have pointed out, could determine whether +cross-fertilisation is in itself beneficial, and self-fertilisation +on the other hand injurious; a conclusion which a merely comparative +examination of pollination-mechanisms renders in the highest degree +probable. Later floral biologists have unfortunately almost entirely +confined themselves to observations on floral mechanisms. But there is +little more to be gained by this kind of work than an assumption +long ago made by C.K. Sprengel that "very many flowers have the sexes +separate and probably at least as many hermaphrodite flowers are +dichogamous; it would thus appear that Nature was unwilling that any +flower should be fertilised by its own pollen." + +It was an accidental observation which inspired Darwin's experiments on +the effect of cross and self-fertilisation. Plants of Linaria vulgaris +were grown in two adjacent beds; in the one were plants produced by +cross-fertilisation, that is, from seeds obtained after fertilisation +by pollen of another plant of the same species; in the other grew plants +produced by self-fertilisation, that is from seed produced as the result +of pollination of the same flower. The first were obviously superior to +the latter. + +Darwin was surprised by this observation, as he had expected a +prejudicial influence of self-fertilisation to manifest itself after +a series of generations: "I always supposed until lately that no +evil effects would be visible until after several generations of +self-fertilisation, but now I see that one generation sometimes suffices +and the existence of dimorphic plants and all the wonderful contrivances +of orchids are quite intelligible to me." ("More Letters", Vol. II. page +373.) + +The observations on Linaria and the investigations of the results of +legitimate and illegitimate fertilisation in heterostyled plants were +apparently the beginning of a long series of experiments. These were +concerned with plants of different families and led to results which are +of fundamental importance for a true explanation of sexual reproduction. + +The experiments were so arranged that plants were shielded from +insect-visits by a net. Some flowers were then pollinated with their own +pollen, others with pollen from another plant of the same species. The +seeds were germinated on moist sand; two seedlings of the same age, one +from a cross and the other from a self-fertilised flower, were selected +and planted on opposite sides of the same pot. They grew therefore under +identical external conditions; it was thus possible to compare their +peculiarities such as height, weight, fruiting capacity, etc. In other +cases the seedlings were placed near to one another in the open and in +this way their capacity of resisting unfavourable external conditions +was tested. The experiments were in some cases continued to the tenth +generation and the flowers were crossed in different ways. We see, +therefore, that this book also represents an enormous amount of most +careful and patient original work. + +The general result obtained is that plants produced as the result of +cross-fertilisation are superior, in the majority of cases, to those +produced as the result of self-fertilisation, in height, resistance to +external injurious influences, and in seed-production. + +Ipomoea purpurea may be quoted as an example. If we express the result +of cross-fertilisation by 100, we obtain the following numbers for the +fertilised plants. + + Generation. Height. Number of seeds. + + 1 100: 76 100: 64 + 2 100: 79 - + 3 100: 68 100: 94 + 4 100: 86 100: 94 + 5 100: 75 100: 89 + 6 100: 72 - + 7 100: 81 - + 8 100: 85 - + 9 100: 79 100: 26 (Number of capsules) + 10 100: 54 - + + +Taking the average, the ratio as regards growth is 100:77. The +considerable superiority of the crossed plants is apparent in the first +generation and is not increased in the following generations; but there +is some fluctuation about the average ratio. The numbers representing +the fertility of crossed and self-fertilised plants are more difficult +to compare with accuracy; the superiority of the crossed plants is +chiefly explained by the fact that they produce a much larger number +of capsules, not because there are on the average more seeds in each +capsule. The ratio of the capsules was, e.g. in the third generation, +100:38, that of the seeds in the capsules 100:94. It is also especially +noteworthy that in the self-fertilised plants the anthers were smaller +and contained a smaller amount of pollen, and in the eighth generation +the reduced fertility showed itself in a form which is often found in +hybrids, that is the first flowers were sterile. (Complete sterility was +not found in any of the plants investigated by Darwin. Others appear +to be more sensitive; Cluer found Zea Mais "almost sterile" after three +generations of self-fertilisation. (Cf. Fruwirth, "Die Zuchtung der +Landwirtschaftlichen Kulturpflanzen", Berlin, 1904, II. page 6.)) + +The superiority of crossed individuals is not exhibited in the same +way in all plants. For example in Eschscholzia californica the crossed +seedlings do not exceed the self-fertilised in height and vigour, +but the crossing considerably increases the plant's capacity for +flower-production, and the seedlings from such a mother-plant are more +fertile. + +The conception implied by the term crossing requires a closer analysis. +As in the majority of plants, a large number of flowers are in bloom +at the same time on one and the same plant, it follows that insects +visiting the flowers often carry pollen from one flower to another of +the same stock. Has this method, which is spoken of as Geitonogamy, the +same influence as crossing with pollen from another plant? The results +of Darwin's experiments with different plants (Ipomoea purpurea, +Digitalis purpurea, Mimulus luteus, Pelargonium, Origanum) were not in +complete agreement; but on the whole they pointed to the conclusion that +Geitonogamy shows no superiority over self-fertilisation (Autogamy). +(Similarly crossing in the case of flowers of Pelargonium zonale, which +belong to plants raised from cuttings from the same parent, shows no +superiority over self-fertilisation.) Darwin, however, considered it +possible that this may sometimes be the case. "The sexual elements +in the flowers on the same plant can rarely have been differentiated, +though this is possible, as flower-buds are in one sense distinct +individuals, sometimes varying and differing from one another in +structure or constitution." ("Cross and Self fertilisation" (1st +edition), page 444.) + +As regards the importance of this question from the point of view of +the significance of cross-fertilisation in general, it may be noted +that later observers have definitely discovered a difference between the +results of autogamy and geitonogamy. Gilley and Fruwirth found that in +Brassica Napus, the length and weight of the fruits as also the total +weight of the seeds in a single fruit were less in the case of autogamy +than in geitonogamy. With Sinapis alba a better crop of seeds was +obtained after geitonogamy, and in the Sugar Beet the average weight +of a fruit in the case of a self-fertilised plant was 0.009 gr., from +geitonogamy 0.012 gr., and on cross-fertilisation 0.013 gr. + +On the whole, however, the results of geitonogamy show that the +favourable effects of cross-fertilisation do not depend simply on the +fact that the pollen of one flower is conveyed to the stigma of another. +But the plants which are crossed must in some way be different. +If plants of Ipomoea purpurea (and Mimulus luteus) which have been +self-fertilised for seven generations and grown under the same +conditions of cultivation are crossed together, the plants so crossed +would not be superior to the self-fertilised; on the other hand crossing +with a fresh stock at once proves very advantageous. The favourable +effect of crossing is only apparent, therefore, if the parent plants +are grown under different conditions or if they belong to different +varieties. "It is really wonderful what an effect pollen from a distinct +seedling plant, which has been exposed to different conditions of life, +has on the offspring in comparison with pollen from the same flower or +from a distinct individual, but which has been long subjected to the +same conditions. The subject bears on the very principle of life, which +seems almost to require changes in the conditions." ("More Letters", +Vol. II. page 406.) + +The fertility--measured by the number or weight of the seeds produced +by an equal number of plants--noticed under different conditions of +fertilisation may be quoted in illustration. + + + On crossing On crossing On self- + with a fresh plants of the fertilisation + stock same stock + Mimuleus luteus + (First and ninth generation) 100 4 3 + + Eschscholzia californica + (second generation) 100 45 40 + + Dianthus caryophyllus + (third and fourth generation) 100 45 33 + + Petunia violacea 100 54 46 + + +Crossing under very similar conditions shows, therefore, that the +difference between the sexual cells is smaller and thus the result of +crossing is only slightly superior to that given by self-fertilisation. +Is, then, the favourable result of crossing with a foreign stock to be +attributed to the fact that this belongs to another systematic entity +or to the fact that the plants, though belonging to the same entity +were exposed to different conditions? This is a point on which further +researches must be taken into account, especially since the analysis of +the systematic entities has been much more thorough than formerly. (In +the case of garden plants, as Darwin to a large extent claimed, it +is not easy to say whether two individuals really belong to the same +variety, as they are usually of hybrid origin. In some instances +(Petunia, Iberis) the fresh stock employed by Darwin possessed flowers +differing in colour from those of the plant crossed with it.) We +know that most of Linneaus's species are compound species, frequently +consisting of a very large number of smaller or elementary species +formerly included under the comprehensive term varieties. Hybridisation +has in most cases affected our garden and cultivated plants so that they +do not represent pure species but a mixture of species. + +But this consideration has no essential bearing on Darwin's point of +view, according to which the nature of the sexual cells is influenced by +external conditions. Even individuals growing close to one another are +only apparently exposed to identical conditions. Their sexual cells may +therefore be differently influenced and thus give favourable results +on crossing, as "the benefits which so generally follow from a cross +between two plants apparently depend on the two differing somewhat in +constitution or character." As a matter of fact we are familiar with a +large number of cases in which the condition of the reproductive organs +is influenced by external conditions. Darwin has himself demonstrated +this for self-sterile plants, that is plants in which self-fertilisation +produces no result. This self-sterility is affected by climatic +conditions: thus in Brazil Eschscholzia californica is absolutely +sterile to the pollen of its own flowers; the descendants of Brazilian +plants in Darwin's cultures were partially self-fertile in one +generation and in a second generation still more so. If one has any +doubt in this case whether it is a question of the condition of +the style and stigma, which possibly prevents the entrance of the +pollen-tube or even its development, rather than that of the actual +sexual cells, in other cases there is no doubt that an influence is +exerted on the latter. + +Janczewski (Janczewski, "Sur les antheres steriles des Groseilliers", +"Bull. de l'acad. des sciences de Cracovie", June, 1908.) has recently +shown that species of Ribes cultivated under unnatural conditions +frequently produce a mixed (i.e. partly useless) or completely sterile +pollen, precisely as happens with hybrids. There are, therefore, +substantial reasons for the conclusion that conditions of life exert an +influence on the sexual cells. "Thus the proposition that the benefit +from cross-fertilisation depends on the plants which are crossed +having been subjected during previous generations to somewhat different +conditions, or to their having varied from some unknown cause as if they +had been thus subjected, is securely fortified on all sides." ("Cross +and Self fertilisation" (1st edition), page 444.) + +We thus obtain an insight into the significance of sexuality. If an +occasional and slight alteration in the conditions under which plants +and animals live is beneficial (Reasons for this are given by Darwin +in "Variation under Domestication" (2nd edition), Vol. II. page +127.), crossing between organisms which have been exposed to different +conditions becomes still more advantageous. The entire constitution +is in this way influenced from the beginning, at a time when the whole +organisation is in a highly plastic state. The total life-energy, so +to speak, is increased, a gain which is not produced by asexual +reproduction or by the union of sexual cells of plants which have lived +under the same or only slightly different conditions. All the +wonderful arrangements for cross-fertilisation now appear to be useful +adaptations. Darwin was, however, far from giving undue prominence to +this point of view, though this has been to some extent done by others. +He particularly emphasised the following consideration:--"But we should +always keep in mind that two somewhat opposed ends have to be gained; +the first and more important one being the production of seeds by +any means, and the second, cross-fertilisation." ("Cross and Self +fertilisation" (1st edition), page 371.) Just as in some orchids and +cleistogamic flowers self-pollination regularly occurs, so it may also +occur in other cases. Darwin showed that Pisum sativum and Lathyrus +odoratus belong to plants in which self-pollination is regularly +effected, and that this accounts for the constancy of certain sorts of +these plants, while a variety of form is produced by crossing. Indeed +among his culture plants were some which derived no benefit from +crossing. Thus in the sixth self-fertilised generation of his Ipomoea +cultures the "Hero" made its appearance, a form slightly exceeding its +crossed companion in height; this was in the highest degree self-fertile +and handed on its characteristics to both children and grandchildren. +Similar forms were found in Mimulus luteus and Nicotiana (In Pisum +sativum also the crossing of two individuals of the same variety +produced no advantage; Darwin attributed this to the fact that the +plants had for several generations been self-fertilised and in each +generation cultivated under almost the same conditions. Tschermak +("Ueber kunstliche Kreuzung an Pisum sativum") afterwards recorded the +same result; but he found on crossing different varieties that usually +there was no superiority as regards height over the products of +self-fertilisation, while Darwin found a greater height represented by +the ratios 100:75 and 100:60.), types which, after self-fertilisation, +have an enhanced power of seed-production and of attaining a greater +height than the plants of the corresponding generation which are crossed +together and self-fertilised and grown under the same conditions. +"Some observations made on other plants lead me to suspect that +self-fertilisation is in some respects beneficial; although the benefit +thus derived is as a rule very small compared with that from a cross +with a distinct plant." ("Cross and Self fertilisation", page 350.) We +are as ignorant of the reason why plants behave differently when +crossed and self-fertilised as we are in regard to the nature of the +differentiation of the sexual cells, which determines whether a union of +the sexual cells will prove favourable or unfavourable. + +It is impossible to discuss the different results of +cross-fertilisation; one point must, however, be emphasised, because +Darwin attached considerable importance to it. It is inevitable that +pollen of different kinds must reach the stigma. It was known that +pollen of the same "species" is dominant over the pollen of another +species, that, in other words, it is prepotent. Even if the pollen of +the same species reaches the stigma rather later than that of another +species, the latter does not effect fertilisation. + +Darwin showed that the fertilising power of the pollen of another +variety or of another individual is greater than that of the plant's +own pollen. ("Cross and Self fertilisation", page 391.) This has +been demonstrated in the case of Mimulus luteus (for the fixed +white-flowering variety) and Iberis umbellata with pollen of another +variety, and observations on cultivated plants, such as cabbage, +horseradish, etc. gave similar results. It is, however, especially +remarkable that pollen of another individual of the same variety may be +prepotent over the plant's own pollen. This results from the superiority +of plants crossed in this manner over self-fertilised plants. "Scarcely +any result from my experiments has surprised me so much as this of the +prepotency of pollen from a distinct individual over each plant's own +pollen, as proved by the greater constitutional vigour of the crossed +seedlings." (Ibid. page 397.) Similarly, in self-fertile plants the +flowers of which have not been deprived of the male organs, pollen +brought to the stigma by the wind or by insects from another plant +effects fertilisation, even if the plant's own pollen has reached the +stigma somewhat earlier. + +Have the results of his experimental investigations modified the point +of view from which Darwin entered on his researches, or not? In the +first place the question is, whether or not the opinion expressed in +the Orchid book that there is "Something injurious" connected with +self-fertilisation, has been confirmed. We can, at all events, affirm +that Darwin adhered in essentials to his original position; but +self-fertilisation afterwards assumed a greater importance than it +formerly possessed. Darwin emphasised the fact that "the difference +between the self-fertilised and crossed plants raised by me cannot be +attributed to the superiority of the crossed, but to the inferiority +of the self-fertilised seedlings, due to the injurious effects of +self-fertilisation." (Ibid. page 437.) But he had no doubt that in +favourable circumstances self-fertilised plants were able to persist for +several generations without crossing. An occasional crossing appears to +be useful but not indispensable in all cases; its sporadic occurrence +in plants in which self-pollination habitually occurs is not excluded. +Self-fertilisation is for the most part relatively and not absolutely +injurious and always better than no fertilisation. "Nature abhors +perpetual self-fertilisation" (It is incorrect to say, as a writer has +lately said, that the aphorism expressed by Darwin in 1859 and 1862, +"Nature abhors perpetual self-fertilisation," is not repeated in his +later works. The sentence is repeated in "Cross and Self fertilisation" +(page 8), with the addition, "If the word perpetual had been omitted, +the aphorism would have been false. As it stands, I believe that it is +true, though perhaps rather too strongly expressed.") is, however, a +pregnant expression of the fact that cross-fertilisation is exceedingly +widespread and has been shown in the majority of cases to be beneficial, +and that in those plants in which we find self-pollination regularly +occurring cross-pollination may occasionally take place. + +An attempt has been made to express in brief the main results of +Darwin's work on the biology of flowers. We have seen that his object +was to elucidate important general questions, particularly the question +of the significance of sexual reproduction. + +It remains to consider what influence his work has had on botanical +science. That this influence has been very considerable, is shown by +a glance at the literature on the biology of flowers published since +Darwin wrote. Before the book on orchids was published there was nothing +but the old and almost forgotten works of Kolreuter and Sprengel with +the exception of a few scattered references. Darwin's investigations +gave the first stimulus to the development of an extensive literature on +floral biology. In Knuth's "Handbuch der Blutenbiologie" ("Handbook +of Flower Pollination", Oxford, 1906) as many as 3792 papers on this +subject are enumerated as having been published before January 1, 1904. +These describe not only the different mechanisms of flowers, but deal +also with a series of remarkable adaptations in the pollinating insects. +As a fertilising rain quickly calls into existence the most varied +assortment of plants on a barren steppe, so activity now reigns in a +field which men formerly left deserted. This development of the biology +of flowers is of importance not only on theoretical grounds but also +from a practical point of view. The rational breeding of plants is +possible only if the flower-biology of the plants in question (i.e. the +question of the possibility of self-pollination, self-sterility, etc.) +is accurately known. And it is also essential for plant-breeders that +they should have "the power of fixing each fleeting variety of colour, +if they will fertilise the flowers of the desired kind with their own +pollen for half-a-dozen generations, and grow the seedlings under the +same conditions." ("Cross and Self fertilisation" (1st edition), page +460.) + +But the influence of Darwin on floral biology was not confined to the +development of this branch of Botany. Darwin's activity in this domain +has brought about (as Asa Gray correctly pointed out) the revival of +teleology in Botany and Zoology. Attempts were now made to determine, +not only in the case of flowers but also in vegetative organs, in what +relation the form and function of organs stand to one another and +to what extent their morphological characters exhibit adaptation to +environment. A branch of Botany, which has since been called Ecology +(not a very happy term) has been stimulated to vigorous growth by floral +biology. + +While the influence of the work on the biology of flowers was +extraordinarily great, it could not fail to elicit opinions at variance +with Darwin's conclusions. The opposition was based partly on reasons +valueless as counterarguments, partly on problems which have still to +be solved; to some extent also on that tendency against teleological +conceptions which has recently become current. This opposing trend +of thought is due to the fact that many biologists are content with +teleological explanations, unsupported by proof; it is also closely +connected with the fact that many authors estimate the importance of +natural selection less highly than Darwin did. We may describe +the objections which are based on the widespread occurrence of +self-fertilisation and geitonogamy as of little importance. Darwin did +not deny the occurrence of self-fertilisation, even for a long series +of generations; his law states only that "Nature abhors PERPETUAL +self-fertilisation." (It is impossible (as has been attempted) to +express Darwin's point of view in a single sentence, such as H. +Muller's statement of the "Knight-Darwin law." The conditions of life in +organisms are so various and complex that laws, such as are formulated +in physics and chemistry, can hardly be conceived.) An exception to +this rule would therefore occur only in the case of plants in which the +possibility of cross-pollination is excluded. Some of the plants with +cleistogamous flowers might afford examples of such cases. We have +already seen, however, that such a case has not as yet been shown to +occur. Burck believed that he had found an instance in certain +tropical plants (Anonaceae, Myrmecodia) of the complete exclusion of +cross-fertilisation. The flowers of these plants, in which, however,--in +contrast to the cleistogamous flowers--the corolla is well developed, +remain closed and fruit is produced. + +Loew (E. Loew, "Bemerkungen zu Burck... ", "Biolog. Centralbl." XXVI. +(1906).) has shown that cases occur in which cross-fertilisation may be +effected even in these "cleistopetalous" flowers: humming birds visit +the permanently closed flowers of certain species of Nidularium and +transport the pollen. The fact that the formation of hybrids may occur +as the result of this shows that pollination may be accomplished. + +The existence of plants for which self-pollination is of greater +importance than it is for others is by no means contradictory to +Darwin's view. Self-fertilisation is, for example, of greater importance +for annuals than for perennials as without it seeds might fail to be +produced. Even in the case of annual plants with small inconspicuous +flowers in which self-fertilisation usually occurs, such as Senecio +vulgaris, Capsella bursa-pastoris and Stellaria media, A. Bateson (Anna +Bateson, "The effects of cross-fertilisation on inconspicuous +flowers", "Annals of Botany", Vol. I. 1888, page 255.) found that +cross-fertilisation gave a beneficial result, although only in a slight +degree. If the favourable effects of sexual reproduction, according to +Darwin's view, are correlated with change of environment, it is quite +possible that this is of less importance in plants which die after +ripening their seeds ("hapaxanthic") and which in any case constantly +change their situation. Objections which are based on the proof of the +prevalence of self-fertilisation are not, therefore, pertinent. At first +sight another point of view, which has been more recently urged, appears +to have more weight. + +W. Burck (Burck, "Darwin's Kreuzeungsgesetz... ", "Biol. Centralbl". +XXVIII. 1908, page 177.) has expressed the opinion that the beneficial +results of cross-fertilisation demonstrated by Darwin concern only +hybrid plants. These alone become weaker by self-pollination; while +pure species derive no advantage from crossing and no disadvantage from +self-fertilisation. It is certain that some of the plants used by Darwin +were of hybrid origin. (It is questionable if this was always the case.) +This is evident from his statements, which are models of clearness and +precision; he says that his Ipomoea plants "were probably the offspring +of a cross." ("Cross and Self fertilisation" (1st edition), page 55.) +The fixed forms of this plant, such as Hero, which was produced by +self-fertilisation, and a form of Mimulus with white flowers spotted +with red probably resulted from splitting of the hybrids. It is true +that the phenomena observed in self-pollination, e.g. in Ipomoea, agree +with those which are often noticed in hybrids; Darwin himself drew +attention to this. + +Let us next call to mind some of the peculiarities connected with +hybridisation. We know that hybrids are often characterized by their +large size, rapidity of growth, earlier production of flowers, wealth of +flower-production and a longer life; hybrids, if crossed with one of the +two parent forms, are usually more fertile than when they are crossed +together or with another hybrid. But the characters which hybrids +exhibit on self-fertilisation are rather variable. The following +instance may be quoted from Gartner: "There are many hybrids which +retain the self-fertility of the first generation during the second +and later generations, but very often in a less degree; a considerable +number, however, become sterile." But the hybrid varieties may be more +fertile in the second generation than in the first, and in some hybrids +the fertility with their own pollen increases in the second, third, +and following generations. (K.F. Gartner, "Versuche uber die +Bastarderzeugung", Stuttgart, 1849, page 149.) As yet it is impossible +to lay down rules of general application for the self-fertility of +hybrids. That the beneficial influence of crossing with a fresh stock +rests on the same ground--a union of sexual cells possessing somewhat +different characters--as the fact that many hybrids are distinguished +by greater luxuriance, wealth of flowers, etc. corresponds entirely +with Darwin's conclusions. It seems to me to follow clearly from +his investigations that there is no essential difference between +cross-fertilisation and hybridisation. The heterostyled plants are +normally dependent on a process corresponding to hybridisation. The view +that specifically distinct species could at best produce sterile hybrids +was always opposed by Darwin. But if the good results of crossing were +EXCLUSIVELY dependent on the fact that we are concerned with hybrids, +there must then be a demonstration of two distinct things. First, that +crossing with a fresh stock belonging to the same systematic entity +or to the same hybrid, but cultivated for a considerable time under +different conditions, shows no superiority over self-fertilisation, +and that in pure species crossing gives no better results than +self-pollination. If this were the case, we should be better able to +understand why in one plant crossing is advantageous while in others, +such as Darwin's Hero and the forms of Mimulus and Nicotiana no +advantage is gained; these would then be pure species. But such a +proof has not been supplied; the inference drawn from cleistogamous and +cleistopetalous plants is not supported by evidence, and the experiments +on geitonogamy and on the advantage of cross-fertilisation in species +which are usually self-fertilised are opposed to this view. There are +still but few researches on this point; Darwin found that in Ononis +minutissima, which produces cleistogamous as well as self-fertile +chasmogamous flowers, the crossed and self-fertilised capsules +produced seed in the proportion of 100:65 and that the average bore the +proportion 100:86. Facts previously mentioned are also applicable to +this case. Further, it is certain that the self-sterility exhibited by +many plants has nothing to do with hybridisation. Between self-sterility +and reduced fertility as the result of self-fertilisation there is +probably no fundamental difference. + +It is certain that so difficult a problem as that of the significance +of sexual reproduction requires much more investigation. Darwin was +anything but dogmatic and always ready to alter an opinion when it was +not based on definite proof: he wrote, "But the veil of secrecy is +as yet far from lifted; nor will it be, until we can say why it is +beneficial that the sexual elements should be differentiated to a +certain extent, and why, if the differentiation be carried still +further, injury follows." He has also shown us the way along which +to follow up this problem; it is that of carefully planned and exact +experimental research. It may be that eventually many things will be +viewed in a different light, but Darwin's investigations will always +form the foundation of Floral Biology on which the future may continue +to build. + + + + +XXI. MENTAL FACTORS IN EVOLUTION. By C. Lloyd Morgan, LL.D., F.R.S. + +In developing his conception of organic evolution Charles Darwin was +of necessity brought into contact with some of the problems of mental +evolution. In "The Origin of Species" he devoted a chapter to "the +diversities of instinct and of the other mental faculties in animals of +the same class." ("Origin of Species" (6th edition), page 205.) When +he passed to the detailed consideration of "The Descent of Man", it +was part of his object to show "that there is no fundamental difference +between man and the higher mammals in their mental faculties." ("Descent +of Man" (2nd edition 1888), Vol. I. page 99; Popular edition page 99.) +"If no organic being excepting man," he said, "had possessed any mental +power, or if his powers had been of a wholly different nature from those +of the lower animals, then we should never have been able to convince +ourselves that our high faculties had been gradually developed." (Ibid. +page 99.) In his discussion of "The Expression of the Emotions" it +was important for his purpose "fully to recognise that actions readily +become associated with other actions and with various states of the +mind." ("The Expression of the Emotions" (2nd edition), page 32.) His +hypothesis of sexual selection is largely dependent upon the exercise +of choice on the part of the female and her preference for "not only the +more attractive but at the same time the more vigorous and victorious +males." ("Descent of Man", Vol. II. page 435.) Mental processes and +physiological processes were for Darwin closely correlated; and he +accepted the conclusion "that the nervous system not only regulates most +of the existing functions of the body, but has indirectly influenced +the progressive development of various bodily structures and of certain +mental qualities." (Ibid. pages 437, 438.) + +Throughout his treatment, mental evolution was for Darwin incidental +to and contributory to organic evolution. For specialised research +in comparative and genetic psychology, as an independent field of +investigation, he had neither the time nor the requisite training. +None the less his writings and the spirit of his work have exercised a +profound influence on this department of evolutionary thought. And, for +those who follow Darwin's lead, mental evolution is still in a +measure subservient to organic evolution. Mental processes are the +accompaniments or concomitants of the functional activity of specially +differentiated parts of the organism. They are in some way dependent on +physiological and physical conditions. But though they are not physical +in their nature, and though it is difficult or impossible to conceive +that they are physical in their origin, they are, for Darwin and his +followers, factors in the evolutionary process in its physical or +organic aspect. By the physiologist within his special and well-defined +universe of discourse they may be properly regarded as epiphenomena; but +by the naturalist in his more catholic survey of nature they cannot +be so regarded, and were not so regarded by Darwin. Intelligence has +contributed to evolution of which it is in a sense a product. + +The facts of observation or of inference which Darwin accepted are +these: Conscious experience accompanies some of the modes of animal +behaviour; it is concomitant with certain physiological processes; these +processes are the outcome of development in the individual and +evolution in the race; the accompanying mental processes undergo a like +development. Into the subtle philosophical questions which arise out +of the naive acceptance of such a creed it was not Darwin's province +to enter; "I have nothing to do," he said ("Origin of Species" (6th +edition), page 205.), "with the origin of the mental powers, any more +than I have with that of life itself." He dealt with the natural history +of organisms, including not only their structure but their modes of +behaviour; with the natural history of the states of consciousness which +accompany some of their actions; and with the relation of behaviour +to experience. We will endeavour to follow Darwin in his modesty and +candour in making no pretence to give ultimate explanations. But we must +note one of the implications of this self-denying ordinance of science. +Development and evolution imply continuity. For Darwin and his followers +the continuity is organic through physical heredity. Apart from +speculative hypothesis, legitimate enough in its proper place but here +out of court, we know nothing of continuity of mental evolution as such: +consciousness appears afresh in each succeeding generation. Hence it is +that for those who follow Darwin's lead, mental evolution is and must +ever be, within his universe of discourse, subservient to organic +evolution. Only in so far as conscious experience, or its neural +correlate, effects some changes in organic structure can it influence +the course of heredity; and conversely only in so far as changes in +organic structure are transmitted through heredity, is mental evolution +rendered possible. Such is the logical outcome of Darwin's teaching. + +Those who abide by the cardinal results of this teaching are bound to +regard all behaviour as the expression of the functional activities +of the living tissues of the organism, and all conscious experience +as correlated with such activities. For the purposes of scientific +treatment, mental processes are one mode of expression of the same +changes of which the physiological processes accompanying behaviour +are another mode of expression. This is simply accepted as a fact +which others may seek to explain. The behaviour itself is the adaptive +application of the energies of the organism; it is called forth by some +form of presentation or stimulation brought to bear on the organism by +the environment. This presentation is always an individual or personal +matter. But in order that the organism may be fitted to respond to the +presentation of the environment it must have undergone in some way +a suitable preparation. According to the theory of evolution this +preparation is primarily racial and is transmitted through heredity. +Darwin's main thesis was that the method of preparation is predominantly +by natural selection. Subordinate to racial preparation, and always +dependent thereon, is individual or personal preparation through +some kind of acquisition; of which the guidance of behaviour through +individually won experience is a typical example. We here introduce +the mental factor because the facts seem to justify the inference. Thus +there are some modes of behaviour which are wholly and solely dependent +upon inherited racial preparation; there are other modes of behaviour +which are also dependent, in part at least, on individual preparation. +In the former case the behaviour is adaptive on the first occurrence +of the appropriate presentation; in the latter case accommodation to +circumstances is only reached after a greater or less amount of acquired +organic modification of structure, often accompanied (as we assume) in +the higher animals by acquired experience. Logically and biologically +the two classes of behaviour are clearly distinguishable: but the +analysis of complex cases of behaviour where the two factors cooperate, +is difficult and requires careful and critical study of life-history. + +The foundations of the mental life are laid in the conscious experience +that accompanies those modes of behaviour, dependent entirely on racial +preparation, which may broadly be described as instinctive. In the +eighth chapter of "The Origin of Species" Darwin says ("Origin of +Species" (6th edition), page 205.), "I will not attempt any definition +of instinct... Every one understands what is meant, when it is said +that instinct impels the cuckoo to migrate and to lay her eggs in other +birds' nests. An action, which we ourselves require experience to enable +us to perform, when performed by an animal, more especially by a very +young one, without experience, and when performed by many individuals in +the same way, without their knowing for what purpose it is performed, is +usually said to be instinctive." And in the summary at the close of the +chapter he says ("Origin of Species" (6th edition), page 233.), "I have +endeavoured briefly to show that the mental qualities of our domestic +animals vary, and that the variations are inherited. Still more briefly +I have attempted to show that instincts vary slightly in a state of +nature. No one will dispute that instincts are of the highest importance +to each animal. Therefore there is no real difficulty, under changing +conditions of life, in natural selection accumulating to any extent +slight modifications of instinct which are in any way useful. In many +cases habit or use and disuse have probably come into play." + +Into the details of Darwin's treatment there is neither space nor need +to enter. There are some ambiguous passages; but it may be said that for +him, as for his followers to-day, instinctive behaviour is wholly the +result of racial preparation transmitted through organic heredity. For +the performance of the instinctive act no individual preparation under +the guidance of personal experience is necessary. It is true that Darwin +quotes with approval Huber's saying that "a little dose of judgment +or reason often comes into play, even with animals low in the scale of +nature." (Ibid. page 205.) But we may fairly interpret his meaning to be +that in behaviour, which is commonly called instinctive, some element of +intelligent guidance is often combined. If this be conceded the strictly +instinctive performance (or part of the performance) is the outcome of +heredity and due to the direct transmission of parental or ancestral +aptitudes. Hence the instinctive response as such depends entirely on +how the nervous mechanism has been built up through heredity; while +intelligent behaviour, or the intelligent factor in behaviour, depends +also on how the nervous mechanism has been modified and moulded by use +during its development and concurrently with the growth of individual +experience in the customary situations of daily life. Of course it is +essential to the Darwinian thesis that what Sir E. Ray Lankester has +termed "educability," not less than instinct, is hereditary. But it is +also essential to the understanding of this thesis that the differentiae +of the hereditary factors should be clearly grasped. + +For Darwin there were two modes of racial preparation, (1) natural +selection, and (2) the establishment of individually acquired habit. He +showed that instincts are subject to hereditary variation; he saw that +instincts are also subject to modification through acquisition in the +course of individual life. He believed that not only the variations but +also, to some extent, the modifications are inherited. He therefore held +that some instincts (the greater number) are due to natural selection +but that others (less numerous) are due, or partly due, to the +inheritance of acquired habits. The latter involve Lamarckian +inheritance, which of late years has been the centre of so much +controversy. It is noteworthy however that Darwin laid especial emphasis +on the fact that many of the most typical and also the most +complex instincts--those of neuter insects--do not admit of such an +interpretation. "I am surprised," he says ("Origin of Species" +(6th edition), page 233.), "that no one has hitherto advanced this +demonstrative case of neuter insects, against the well-known doctrine of +inherited habit, as advanced by Lamarck." None the less Darwin admitted +this doctrine as supplementary to that which was more distinctively his +own--for example in the case of the instincts of domesticated animals. +Still, even in such cases, "it may be doubted," he says (Ibid. pages +210, 211.), "whether any one would have thought of training a dog to +point, had not some one dog naturally shown a tendency in this line... so +that habit and some degree of selection have probably concurred in +civilising by inheritance our dogs." But in the interpretation of the +instincts of domesticated animals, a more recently suggested hypothesis, +that of organic selection (Independently suggested, on somewhat +different lines, by Profs. J. Mark Baldwin, Henry F. Osborn and the +writer.), may be helpful. According to this hypothesis any intelligent +modification of behaviour which is subject to selection is probably +coincident in direction with an inherited tendency to behave in this +fashion. Hence in such behaviour there are two factors: (1) an +incipient variation in the line of such behaviour, and (2) an acquired +modification by which the behaviour is carried further along the same +line. Under natural selection those organisms in which the two factors +cooperate are likely to survive. Under artificial selection they are +deliberately chosen out from among the rest. + +Organic selection has been termed a compromise between the more strictly +Darwinian and the Lamarckian principles of interpretation. But it is not +in any sense a compromise. The principle of interpretation of that which +is instinctive and hereditary is wholly Darwinian. It is true that some +of the facts of observation relied upon by Lamarckians are introduced. +For Lamarckians however the modifications which are admittedly factors +in survival, are regarded as the parents of inherited variations; for +believers in organic selection they are only the foster parents or +nurses. It is because organic selection is the direct outcome of and a +natural extension of Darwin's cardinal thesis that some reference to it +here is justifiable. The matter may be put with the utmost brevity as +follows. (1) Variations (V) occur, some of which are in the direction +of increased adaptation (+), others in the direction of decreased +adaptation (-). (2) Acquired modifications (M) also occur. Some of these +are in the direction of increased accommodation to circumstances (+), +while others are in the direction of diminished accommodation (-). Four +major combinations are + + (a) + V with + M, + (b) + V with - M, + (c) - V with + M, + (d) - V with - M. + +Of these (d) must inevitably be eliminated while (a) are selected. +The predominant survival of (a) entails the survival of the adaptive +variations which are inherited. The contributory acquisitions (+M) are +not inherited; but they are none the less factors in determining the +survival of the coincident variations. It is surely abundantly clear +that this is Darwinism and has no tincture of Lamarck's essential +principle, the inheritance of acquired characters. + +Whether Darwin himself would have accepted this interpretation of some +at least of the evidence put forward by Lamarckians is unfortunately +a matter of conjecture. The fact remains that in his interpretation +of instinct and in allied questions he accepted the inheritance of +individually acquired modifications of behaviour and structure. + +Darwin was chiefly concerned with instinct from the biological rather +than from the psychological point of view. Indeed it must be confessed +that, from the latter standpoint, his conception of instinct as a +"mental faculty" which "impels" an animal to the performance of certain +actions, scarcely affords a satisfactory basis for genetic treatment. To +carry out the spirit of Darwin's teaching it is necessary to link more +closely biological and psychological evolution. The first step towards +this is to interpret the phenomena of instinctive behaviour in terms +of stimulation and response. It may be well to take a particular case. +Swimming on the part of a duckling is, from the biological point +of view, a typical example of instinctive behaviour. Gently lower a +recently hatched bird into water: coordinated movements of the limbs +follow in rhythmical sequence. The behaviour is new to the individual +though it is no doubt closely related to that of walking, which is +no less instinctive. There is a group of stimuli afforded by the +"presentation" which results from partial immersion: upon this +there follows as a complex response an application of the functional +activities in swimming; the sequence of adaptive application on the +appropriate presentation is determined by racial preparation. We know, +it is true, but little of the physiological details of what takes place +in the central nervous system; but in broad outline the nature of the +organic mechanism and the manner of its functioning may at least +be provisionally conjectured in the present state of physiological +knowledge. Similarly in the case of the pecking of newly-hatched chicks; +there is a visual presentation, there is probably a cooperating group of +stimuli from the alimentary tract in need of food, there is an adaptive +application of the activities in a definite mode of behaviour. Like +data are afforded in a great number of cases of instinctive procedure, +sometimes occurring very early in life, not infrequently deferred until +the organism is more fully developed, but all of them dependent upon +racial preparation. No doubt there is some range of variation in the +behaviour, just such variation as the theory of natural selection +demands. But there can be no question that the higher animals inherit +a bodily organisation and a nervous system, the functional working of +which gives rise to those inherited modes of behaviour which are termed +instinctive. + +It is to be noted that the term "instinctive" is here employed in the +adjectival form as a descriptive heading under which may be grouped many +and various modes of behaviour due to racial preparation. We speak +of these as inherited; but in strictness what is transmitted through +heredity is the complex of anatomical and physiological conditions under +which, in appropriate circumstances, the organism so behaves. So far the +term "instinctive" has a restricted biological connotation in terms +of behaviour. But the connecting link between biological evolution and +psychological evolution is to be sought,--as Darwin fully realised,--in +the phenomena of instinct, broadly considered. The term "instinctive" +has also a psychological connotation. What is that connotation? + +Let us take the case of the swimming duckling or the pecking chick, and +fix our attention on the first instinctive performance. Grant that just +as there is, strictly speaking, no inherited behaviour, but only the +conditions which render such behaviour under appropriate circumstances +possible; so too there is no inherited experience, but only the +conditions which render such experience possible; then the cerebral +conditions in both cases are the same. The biological behaviour-complex, +including the total stimulation and the total response with the +intervening or resultant processes in the sensorium, is accompanied by +an experience-complex including the initial stimulation-consciousness +and resulting response-consciousness. In the experience-complex are +comprised data which in psychological analysis are grouped under the +headings of cognition, affective tone and conation. But the complex is +probably experienced as an unanalysed whole. If then we use the term +"instinctive" so as to comprise all congenital modes of behaviour which +contribute to experience, we are in a position to grasp the view that +the net result in consciousness constitutes what we may term the +primary tissue of experience. To the development of this experience each +instinctive act contributes. The nature and manner of organisation of +this primary tissue of experience are dependent on inherited biological +aptitudes; but they are from the outset onwards subject to secondary +development dependent on acquired aptitudes. Biological values are +supplemented by psychological values in terms of satisfaction or the +reverse. + +In our study of instinct we have to select some particular phase of +animal behaviour and isolate it so far as is possible from the life of +which it is a part. But the animal is a going concern, restlessly active +in many ways. Many instinctive performances, as Darwin pointed out +("Origin of Species" (6th edition), page 206.), are serial in their +nature. But the whole of active life is a serial and coordinated +business. The particular instinctive performance is only an episode in +a life-history, and every mode of behaviour is more or less closely +correlated with other modes. This coordination of behaviour is +accompanied by a correlation of the modes of primary experience. We may +classify the instinctive modes of behaviour and their accompanying modes +of instinctive experience under as many heads as may be convenient +for our purposes of interpretation, and label them instincts of +self-preservation, of pugnacity, of acquisition, the reproductive +instincts, the parental instincts, and so forth. An instinct, in this +sense of the term (for example the parental instinct), may be described +as a specialised part of the primary tissue of experience differentiated +in relation to some definite biological end. Under such an instinct +will fall a large number of particular and often well-defined modes of +behaviour, each with its own peculiar mode of experience. + +It is no doubt exceedingly difficult as a matter of observation and of +inference securely based thereon to distinguish what is primary from +what is in part due to secondary acquisition--a fact which Darwin fully +appreciated. Animals are educable in different degrees; but where they +are educable they begin to profit by experience from the first. Only, +therefore, on the occasion of the first instinctive act of a given type +can the experience gained be weighed as WHOLLY primary; all subsequent +performance is liable to be in some degree, sometimes more, sometimes +less, modified by the acquired disposition which the initial behaviour +engenders. But the early stages of acquisition are always along the +lines predetermined by instinctive differentiation. It is the task of +comparative psychology to distinguish the primary tissue of experience +from its secondary and acquired modifications. We cannot follow up the +matter in further detail. It must here suffice to suggest that this +conception of instinct as a primary form of experience lends itself +better to natural history treatment than Darwin's conception of an +impelling force, and that it is in line with the main trend of Darwin's +thought. + +In a characteristic work,--characteristic in wealth of detail, in +closeness and fidelity of observation, in breadth of outlook, in candour +and modesty,--Darwin dealt with "The Expression of the Emotions in +Man and Animals". Sir Charles Bell in his "Anatomy of Expression" had +contended that many of man's facial muscles had been specially created +for the sole purpose of being instrumental in the expression of his +emotions. Darwin claimed that a natural explanation, consistent with the +doctrine of evolution, could in many cases be given and would in other +cases be afforded by an extension of the principles he advocated. "No +doubt," he said ("Expression of the Emotions", page 13. The passage is +here somewhat condensed.), "as long as man and all other animals are +viewed as independent creations, an effectual stop is put to our natural +desire to investigate as far as possible the causes of Expression. +By this doctrine, anything and everything can be equally well +explained... With mankind, some expressions... can hardly be understood, +except on the belief that man once existed in a much lower and +animal-like condition. The community of certain expressions in distinct +though allied species... is rendered somewhat more intelligible, if we +believe in their descent from a common progenitor. He who admits on +general grounds that the structure and habits of all animals have been +gradually evolved, will look at the whole subject of Expression in a new +and interesting light." + +Darwin relied on three principles of explanation. "The first of these +principles is, that movements which are serviceable in gratifying some +desire, or in relieving some sensation, if often repeated, become +so habitual that they are performed, whether or not of any service, +whenever the same desire or sensation is felt, even in a very weak +degree." (Ibid. page 368.) The modes of expression which fall under +this head have become instinctive through the hereditary transmission of +acquired habit. "As far as we can judge, only a few expressive movements +are learnt by each individual; that is, were consciously and voluntarily +performed during the early years of life for some definite object, or in +imitation of others, and then became habitual. The far greater number of +the movements of expression, and all the more important ones, are innate +or inherited; and such cannot be said to depend on the will of the +individual. Nevertheless, all those included under our first principle +were at first voluntarily performed for a definite object,--namely, +to escape some danger, to relieve some distress, or to gratify some +desire." (Ibid. pages 373, 374.) + +"Our second principle is that of antithesis. The habit of voluntarily +performing opposite movements under opposite impulses has become firmly +established in us by the practice of our whole lives. Hence, if certain +actions have been regularly performed, in accordance with our first +principle, under a certain frame of mind, there will be a strong and +involuntary tendency to the performance of directly opposite actions, +whether or not these are of any use, under the excitement of an opposite +frame of mind." ("Expression of the Emotions", page 368.) This principle +of antithesis has not been widely accepted. Nor is Darwin's own position +easy to grasp. + +"Our third principle," he says (Ibid. page 369.), "is the direct action +of the excited nervous system on the body, independently of the will, +and independently, in large part, of habit. Experience shows that +nerve-force is generated and set free whenever the cerebro-spinal system +is excited. The direction which this nerve-force follows is necessarily +determined by the lines of connection between the nerve-cells, with each +other and with various parts of the body." + +Lack of space prevents our following up the details of Darwin's +treatment of expression. Whether we accept or do not accept his three +principles of explanation we must regard his work as a masterpiece of +descriptive analysis, packed full of observations possessing lasting +value. For a further development of the subject it is essential that +the instinctive factors in expression should be more fully distinguished +from those which are individually acquired--a difficult task--and that +the instinctive factors should be rediscussed in the light of modern +doctrines of heredity, with a view to determining whether Lamarckian +inheritance, on which Darwin so largely relied, is necessary for an +interpretation of the facts. + +The whole subject as Darwin realised is very complex. Even the term +"expression" has a certain amount of ambiguity. When the emotion is in +full flood the animal fights, flees, or faints. Is this full-tide effect +to be regarded as expression; or are we to restrict the term to the +premonitory or residual effects--the bared canine when the fighting mood +is being roused, the ruffled fur when reminiscent representations of the +object inducing anger cross the mind? Broadly considered both should +be included. The activity of premonitory expression as a means of +communication was recognised by Darwin; he might, perhaps, have +emphasised it more strongly in dealing with the lower animals. Man so +largely relies on a special means of communication, that of language, +that he sometimes fails to realise that for animals with their keen +powers of perception, and dependent as they are on such means of +communication, the more strictly biological means of expression are full +of subtle suggestiveness. Many modes of expression, otherwise useless, +are signs of behaviour that may be anticipated,--signs which stimulate +the appropriate attitude of response. This would not, however, serve to +account for the utility of the organic accompaniments--heart-affection, +respiratory changes, vaso-motor effects and so forth, together +with heightened muscular tone,--on all of which Darwin lays stress +("Expression of the Emotions", pages 65 ff.) under his third principle. +The biological value of all this is, however, of great importance, +though Darwin was hardly in a position to take it fully into account. + +Having regard to the instinctive and hereditary factors of emotional +expression we may ask whether Darwin's third principle does not alone +suffice as an explanation. Whether we admit or reject Lamarckian +inheritance it would appear that all hereditary expression must be due +to pre-established connections within the central nervous system and to +a transmitted provision for coordinated response under the appropriate +stimulation. If this be so, Darwin's first and second principles are +subordinate and ancillary to the third, an expression, so far as it is +instinctive or hereditary, being "the direct result of the constitution +of the nervous system." + +Darwin accepted the emotions themselves as hereditary or acquired +states of mind and devoted his attention to their expression. But +these emotions themselves are genetic products and as such dependent +on organic conditions. It remained, therefore, for psychologists who +accepted evolution and sought to build on biological foundations to +trace the genesis of these modes of animal and human experience. The +subject has been independently developed by Professors Lange and James +(Cf. William James, "Principles of Psychology", Vol. II. Chap. XXV, +London, 1890.); and some modification of their view is regarded by many +evolutionists as affording the best explanation of the facts. We must +fix our attention on the lower emotions, such as anger or fear, and on +their first occurrence in the life of the individual organism. It is +a matter of observation that if a group of young birds which have been +hatched in an incubator are frightened by an appropriate presentation, +auditory or visual, they instinctively respond in special ways. If we +speak of this response as the expression, we find that there are many +factors. There are certain visible modes of behaviour, crouching at +once, scattering and then crouching, remaining motionless, the braced +muscles sustaining an attitude of arrest, and so forth. There are also +certain visceral or organic effects, such as affections of the heart and +respiration. These can be readily observed by taking the young bird in +the hand. Other effects cannot be readily observed; vaso-motor changes, +affections of the alimentary canal, the skin and so forth. Now the +essence of the James-Lange view, as applied to these congenital effects, +is that though we are justified in speaking of them as effects of the +stimulation, we are not justified, without further evidence, in speaking +of them as effects of the emotional state. May it not rather be that the +emotion as a primary mode of experience is the concomitant of the +net result of the organic situation--the initial presentation, the +instinctive mode of behaviour, the visceral disturbances? According to +this interpretation the primary tissue of experience of the emotional +order, felt as an unanalysed complex, is generated by the stimulation +of the sensorium by afferent or incoming physiological impulses from the +special senses, from the organs concerned in the responsive behaviour, +from the viscera and vaso-motor system. + +Some psychologists, however, contend that the emotional experience +is generated in the sensorium prior to, and not subsequent to, the +behaviour-response and the visceral disturbances. It is a direct and not +an indirect outcome of the presentation to the special senses. Be +this as it may, there is a growing tendency to bring into the closest +possible relation, or even to identify, instinct and emotion in their +primary genesis. The central core of all such interpretations is that +instinctive behaviour and experience, its emotional accompaniments, and +its expression, are but different aspects of the outcome of the +same organic occurrences. Such emotions are, therefore, only a +distinguishable aspect of the primary tissue of experience and exhibit +a like differentiation. Here again a biological foundation is laid for a +psychological doctrine of the mental development of the individual. + +The intimate relation between emotion as a psychological mode of +experience and expression as a group of organic conditions has an +important bearing on biological interpretation. The emotion, as the +psychological accompaniment of orderly disturbances in the central +nervous system profoundly influences behaviour and often renders it more +vigorous and more effective. The utility of the emotions in the struggle +for existence can, therefore, scarcely be over-estimated. Just as +keenness of perception has survival-value; just as it is obviously +subject to variation; just as it must be enhanced under natural +selection, whether individually acquired increments are inherited +or not; and just as its value lies not only in this or that special +perceptive act but in its importance for life as a whole; so the +vigorous effectiveness of activity has survival-value; it is subject +to variation; it must be enhanced under natural selection; and its +importance lies not only in particular modes of behaviour but in its +value for life as a whole. If emotion and its expression as a congenital +endowment are but different aspects of the same biological occurrence; +and if this is a powerful supplement to vigour effectiveness and +persistency of behaviour, it must on Darwin's principles be subject to +natural selection. + +If we include under the expression of the emotions not only the +premonitory symptoms of the initial phases of the organic and mental +state, not only the signs or conditions of half-tide emotion, but the +full-tide manifestation of an emotion which dominates the situation, we +are naturally led on to the consideration of many of the phenomena +which are discussed under the head of sexual selection. The subject +is difficult and complex, and it was treated by Darwin with all the +strength he could summon to the task. It can only be dealt with here +from a special point of view--that which may serve to illustrate the +influence of certain mental factors on the course of evolution. From +this point of view too much stress can scarcely be laid on the dominance +of emotion during the period of courtship and pairing in the more highly +organised animals. It is a period of maximum vigour, maximum activity, +and, correlated with special modes of behaviour and special organic and +visceral accompaniments, a period also of maximum emotional excitement. +The combats of males, their dances and aerial evolutions, their +elaborate behaviour and display, or the flood of song in birds, are +emotional expressions which are at any rate coincident in time with +sexual periodicity. From the combat of the males there follows on +Darwin's principles the elimination of those which are deficient in +bodily vigour, deficient in special structures, offensive or protective, +which contribute to success, deficient in the emotional supplement +of which persistent and whole-hearted fighting is the expression, +and deficient in alertness and skill which are the outcome of the +psychological development of the powers of perception. Few biologists +question that we have here a mode of selection of much importance, +though its influence on psychological evolution often fails to receive +its due emphasis. Mr Wallace ("Darwinism", pages 282, 283, London, +1889.) regards it as "a form of natural selection"; "to it," he says, +"we must impute the development of the exceptional strength, size, and +activity of the male, together with the possession of special offensive +and defensive weapons, and of all other characters which arise from +the development of these or are correlated with them." So far there is +little disagreement among the followers of Darwin--for Mr Wallace, +with fine magnanimity, has always preferred to be ranked as such, +notwithstanding his right, on which a smaller man would have constantly +insisted, to the claim of independent originator of the doctrine of +natural selection. So far with regard to sexual selection Darwin and Mr +Wallace are agreed; so far and no farther. For Darwin, says Mr Wallace +(Ibid. page 283.), "has extended the principle into a totally different +field of action, which has none of that character of constancy and of +inevitable result that attaches to natural selection, including male +rivalry; for by far the larger portion of the phenomena, which he +endeavours to explain by the direct action of sexual selection, can only +be so explained on the hypothesis that the immediate agency is female +choice or preference. It is to this that he imputes the origin of +all secondary sexual characters other than weapons of offence and +defence... In this extension of sexual selection to include the action of +female choice or preference, and in the attempt to give to that choice +such wide-reaching effects, I am unable to follow him more than a very +little way." + +Into the details of Mr Wallace's criticisms it is impossible to enter +here. We cannot discuss either the mode of origin of the variations in +structure which have rendered secondary sexual characters possible +or the modes of selection other than sexual which have rendered them, +within narrow limits, specifically constant. Mendelism and mutation +theories may have something to say on the subject when these theories +have been more fully correlated with the basal principles of selection. +It is noteworthy that Mr Wallace says ("Darwinism", pages 283, 284.): +"Besides the acquisition of weapons by the male for the purpose of +fighting with other males, there are some other sexual characters which +may have been produced by natural selection. Such are the various sounds +and odours which are peculiar to the male, and which serve as a call to +the female or as an indication of his presence. These are evidently a +valuable addition to the means of recognition of the two sexes, and +are a further indication that the pairing season has arrived; and the +production, intensification, and differentiation of these sounds and +odours are clearly within the power of natural selection. The same +remark will apply to the peculiar calls of birds, and even to the +singing of the males." Why the same remark should not apply to their +colours and adornments is not obvious. What is obvious is that "means +of recognition" and "indication that the pairing season has arrived" are +dependent on the perceptive powers of the female who recognises and for +whom the indication has meaning. The hypothesis of female preference, +stripped of the aesthetic surplusage which is psychologically both +unnecessary and unproven, is really only different in degree from that +which Mr Wallace admits in principle when he says that it is probable +that the female is pleased or excited by the display. + +Let us for our present purpose leave on one side and regard as sub +judice the question whether the specific details of secondary sexual +characters are the outcome of female choice. For us the question is +whether certain psychological accompaniments of the pairing situation +have influenced the course of evolution and whether these psychological +accompaniments are themselves the outcome of evolution. As a matter of +observation, specially differentiated modes of behaviour, often very +elaborate, frequently requiring highly developed skill, and apparently +highly charged with emotional tone, are the precursors of pairing. They +are generally confined to the males, whose fierce combats during the +period of sexual activity are part of the emotional manifestation. It is +inconceivable that they have no biological meaning; and it is difficult +to conceive that they have any other biological end than to evoke in +the generally more passive female the pairing impulse. They are based +on instinctive foundations ingrained in the nervous constitution +through natural (or may we not say sexual?) selection in virtue of +their profound utility. They are called into play by a specialised +presentation such as the sight or the scent of the female at, or a +little in advance of, a critical period of the physiological rhythm. +There is no necessity that the male should have any knowledge of the +end to which his strenuous activity leads up. In presence of the female +there is an elaborate application of all the energies of behaviour, +just because ages of racial preparation have made him biologically and +emotionally what he is--a functionally sexual male that must dance or +sing or go through hereditary movements of display, when the appropriate +stimulation comes. Of course after the first successful courtship +his future behaviour will be in some degree modified by his previous +experience. No doubt during his first courtship he is gaining the +primary data of a peculiarly rich experience, instinctive and emotional. +But the biological foundations of the behaviour of courtship are laid +in the hereditary coordinations. It would seem that in some cases, not +indeed in all, but perhaps especially in those cases in which secondary +sexual behaviour is most highly evolved,--correlative with the ardour +of the male is a certain amount of reluctance in the female. The pairing +act on her part only takes place after prolonged stimulation, for +affording which the behaviour of male courtship is the requisite +presentation. The most vigorous, defiant and mettlesome male is +preferred just because he alone affords a contributory stimulation +adequate to evoke the pairing impulse with its attendant emotional tone. + +It is true that this places female preference or choice on a much lower +psychological plane than Darwin in some passages seems to contemplate +where, for example, he says that the female appreciates the display of +the male and places to her credit a taste for the beautiful. But Darwin +himself distinctly states ("Descent of Man" (2nd edition), Vol. II. +pages 136, 137; (Popular edition), pages 642, 643.) that "it is not +probable that she consciously deliberates; but she is most excited or +attracted by the most beautiful, or melodious, or gallant males." The +view here put forward, which has been developed by Prof. Groos ("The +Play of Animals", page 244, London, 1898.), therefore seems to have +Darwin's own sanction. The phenomena are not only biological; there are +psychological elements as well. One can hardly suppose that the female +is unconscious of the male's presence; the final yielding must surely be +accompanied by heightened emotional tone. Whether we call it choice or +not is merely a matter of definition of terms. The behaviour is in part +determined by supplementary psychological values. Prof. Groos regards +the coyness of females as "a most efficient means of preventing the +too early and too frequent yielding to the sexual impulse." (Ibid. page +283.) Be that as it may, it is, in any case, if we grant the facts, a +means through which male sexual behaviour with all its biological and +psychological implications, is raised to a level otherwise perhaps +unattainable by natural means, while in the female it affords +opportunities for the development in the individual and evolution in the +race of what we may follow Darwin in calling appreciation, if we empty +this word of the aesthetic implications which have gathered round it in +the mental life of man. + +Regarded from this standpoint sexual selection, broadly considered, has +probably been of great importance. The psychological accompaniments +of the pairing situation have profoundly influenced the course of +biological evolution and are themselves the outcome of that evolution. + +Darwin makes only passing reference to those modes of behaviour in +animals which go by the name of play. "Nothing," he says ("Descent of +Man", Vol. II. page 60; (Popular edition), page 566.), "is more common +than for animals to take pleasure in practising whatever instinct they +follow at other times for some real good." This is one of the very +numerous cases in which a hint of the master has served to stimulate +research in his disciples. It was left to Prof. Groos to develop this +subject on evolutionary lines and to elaborate in a masterly manner +Darwin's suggestion. "The utility of play," he says ("The Play of +Animals", page 76.), "is incalculable. This utility consists in the +practice and exercise it affords for some of the more important duties +of life,"--that is to say, for the performance of activities which will +in adult life be essential to survival. He urges (Ibid. page 75.) that +"the play of young animals has its origin in the fact that certain very +important instincts appear at a time when the animal does not seriously +need them." It is, however, questionable whether any instincts appear +at a time when they are not needed. And it is questionable whether +the instinctive and emotional attitude of the play-fight, to take +one example, can be identified with those which accompany fighting in +earnest, though no doubt they are closely related and have some common +factors. It is probable that play, as preparatory behaviour, differs in +biological detail (as it almost certainly does in emotional attributes) +from the earnest of after-life and that it has been evolved through +differentiation and integration of the primary tissue of experience, +as a preparation through which certain essential modes of skill may be +acquired--those animals in which the preparatory play-propensity was +not inherited in due force and requisite amount being subsequently +eliminated in the struggle for existence. In any case there is little +question that Prof. Groos is right in basing the play-propensity on +instinctive foundations. ("The Play of Animals" page 24.) None the less, +as he contends, the essential biological value of play is that it is a +means of training the educable nerve-tissue, of developing that part of +the brain which is modified by experience and which thus acquires new +characters, of elaborating the secondary tissue of experience on the +predetermined lines of instinctive differentiation and thus furthering +the psychological activities which are included under the comprehensive +term "intelligent." + +In "The Descent of Man" Darwin dealt at some length with intelligence +and the higher mental faculties. ("Descent of Man" (1st edition), +Chapters II, III, V; (2nd edition), Chapters III, IV, V.) His object, he +says, is to show that there is no fundamental difference between man and +the higher mammals in their mental faculties; that these faculties are +variable and the variations tend to be inherited; and that under natural +selection beneficial variations of all kinds will have been preserved +and injurious ones eliminated. + +Darwin was too good an observer and too honest a man to minimise +the "enormous difference" between the level of mental attainment of +civilised man and that reached by any animal. His contention was that +the difference, great as it is, is one of degree and not of kind. He +realised that, in the development of the mental faculties of man, +new factors in evolution have supervened--factors which play but +a subordinate and subsidiary part in animal intelligence. +Intercommunication by means of language, approbation and blame, and +all that arises out of reflective thought, are but foreshadowed in the +mental life of animals. Still he contends that these may be explained +on the doctrine of evolution. He urges (Ibid. Vol. I. pages 70, 71; +(Popular edition), pages 70, 71.)" that man is variable in body +and mind; and that the variations are induced, either directly or +indirectly, by the same general causes, and obey the same general laws, +as with the lower animals." He correlates mental development with +the evolution of the brain. (Ibid. page 81.) "As the various mental +faculties gradually developed themselves, the brain would almost +certainly become larger. No one, I presume, doubts that the large +proportion which the size of man's brain bears to his body, compared to +the same proportion in the gorilla or orang, is closely connected with +his higher mental powers." "With respect to the lower animals," he says +("Descent of Man" (Popular edition), page 82.), "M.E. Lartet ("Comptes +Rendus des Sciences", June 1, 1868.), by comparing the crania of +tertiary and recent mammals belonging to the same groups, has come to +the remarkable conclusion that the brain is generally larger and the +convolutions are more complex in the more recent form." + +Sir E. Ray Lankester has sought to express in the simplest terms the +implications of the increase in size of the cerebrum. "In what," he +asks, "does the advantage of a larger cerebral mass consist?" "Man," +he replies "is born with fewer ready-made tricks of the +nerve-centres--these performances of an inherited nervous mechanism so +often called by the ill-defined term 'instincts'--than are the monkeys +or any other animal. Correlated with the absence of inherited ready-made +mechanism, man has a greater capacity of developing in the course of +his individual growth similar nervous mechanisms (similar to but not +identical with those of 'instinct') than any other animal... The power of +being educated--'educability' as we may term it--is what man possesses +in excess as compared with the apes. I think we are justified in forming +the hypothesis that it is this 'educability' which is the correlative of +the increased size of the cerebrum." There has been natural selection +of the more educable animals, for "the character which we describe as +'educability' can be transmitted, it is a congenital character. But the +RESULTS of education can NOT be transmitted. In each generation they +have to be acquired afresh, and with increased 'educability' they are +more readily acquired and a larger variety of them... The fact is +that there is no community between the mechanisms of instinct and the +mechanisms of intelligence, and that the latter are later in the history +of the evolution of the brain than the former and can only develop in +proportion as the former become feeble and defective." ("Nature", Vol. +LXI. pages 624, 625 (1900).) + +In this statement we have a good example of the further development +of views which Darwin foreshadowed but did not thoroughly work out. It +states the biological case clearly and tersely. Plasticity of behaviour +in special accommodation to special circumstances is of survival value; +it depends upon acquired characters; it is correlated with increase in +size and complexity of the cerebrum; under natural selection therefore +the larger and more complex cerebrum as the organ of plastic behaviour +has been the outcome of natural selection. We have thus the biological +foundations for a further development of genetic psychology. + +There are diversities of opinion, as Darwin showed, with regard to the +range of instinct in man and the higher animals as contrasted with lower +types. Darwin himself said ("Descent of Man", Vol. I. page 100.) that +"Man, perhaps, has somewhat fewer instincts than those possessed by the +animals which come next to him in the series." On the other hand, Prof. +Wm. James says ("Principles of Psychology," Vol. II. page 289.) that man +is probably the animal with most instincts. The true position is that +man and the higher animals have fewer complete and self-sufficing +instincts than those which stand lower in the scale of mental +evolution, but that they have an equally large or perhaps larger mass of +instinctive raw material which may furnish the stuff to be elaborated +by intelligent processes. There is, perhaps, a greater abundance of +the primary tissue of experience to be refashioned and integrated by +secondary modification; there is probably the same differentiation in +relation to the determining biological ends, but there is at the outset +less differentiation of the particular and specific modes of behaviour. +The specialised instinctive performances and their concomitant +experience-complexes are at the outset more indefinite. Only through +acquired connections, correlated with experience, do they become +definitely organised. + +The full working-out of the delicate and subtle relationship of instinct +and educability--that is, of the hereditary and the acquired factors in +the mental life--is the task which lies before genetic and comparative +psychology. They interact throughout the whole of life, and their +interactions are very complex. No one can read the chapters of "The +Descent of Man" which Darwin devotes to a consideration of the mental +characters of man and animals without noticing, on the one hand, how +sedulous he is in his search for hereditary foundations, and, on the +other hand, how fully he realises the importance of acquired habits of +mind. The fact that educability itself has innate tendencies--is in fact +a partially differentiated educability--renders the unravelling of the +factors of mental progress all the more difficult. + +In his comparison of the mental powers of men and animals it was +essential that Darwin should lay stress on points of similarity rather +than on points of difference. Seeking to establish a doctrine of +evolution, with its basal concept of continuity of process and community +of character, he was bound to render clear and to emphasise the +contention that the difference in mind between man and the higher +animals, great as it is, is one of degree and not of kind. To this end +Darwin not only recorded a large number of valuable observations of +his own, and collected a considerable body of information from reliable +sources, he presented the whole subject in a new light and showed that +a natural history of mind might be written and that this method of study +offered a wide and rich field for investigation. Of course those who +regarded the study of mind only as a branch of metaphysics smiled at +the philosophical ineptitude of the mere man of science. But the +investigation, on natural history lines, has been prosecuted with a +large measure of success. Much indeed still remains to be done; for +special training is required, and the workers are still few. Promise +for the future is however afforded by the fact that investigation is +prosecuted on experimental lines and that something like organised +methods of research are taking form. There is now but little reliance +on casual observations recorded by those who have not undergone the +necessary discipline in these methods. There is also some change of +emphasis in formulating conclusions. Now that the general evolutionary +thesis is fully and freely accepted by those who carry on such +researches, more stress is laid on the differentiation of the stages of +evolutionary advance than on the fact of their underlying community of +nature. The conceptual intelligence which is especially characteristic +of the higher mental procedure of man is more firmly distinguished +from the perceptual intelligence which he shares with the lower +animals--distinguished now as a higher product of evolution, no longer +as differing in origin or different in kind. Some progress has been +made, on the one hand in rendering an account of intelligent profiting +by experience under the guidance of pleasure and pain in the perceptual +field, on lines predetermined by instinctive differentiation for +biological ends, and on the other hand in elucidating the method of +conceptual thought employed, for example, by the investigator himself in +interpreting the perceptual experience of the lower animals. + +Thus there is a growing tendency to realise more fully that there +are two orders of educability--first an educability of the perceptual +intelligence based on the biological foundation of instinct, and +secondly an educability of the conceptual intelligence which +refashions and rearranges the data afforded by previous inheritance +and acquisition. It is in relation to this second and higher order of +educability that the cerebrum of man shows so large an increase of +mass and a yet larger increase of effective surface through its rich +convolutions. It is through educability of this order that the human +child is brought intellectually and affectively into touch with the +ideal constructions by means of which man has endeavoured, with more +or less success, to reach an interpretation of nature, and to guide the +course of the further evolution of his race--ideal constructions which +form part of man's environment. + +It formed no part of Darwin's purpose to consider, save in broad +outline, the methods, or to discuss in any fulness of detail the results +of the process by which a differentiation of the mental faculties of +man from those of the lower animals has been brought about--a +differentiation the existence of which he again and again +acknowledges. His purpose was rather to show that, notwithstanding +this differentiation, there is basal community in kind. This must be +remembered in considering his treatment of the biological foundations +on which man's systems of ethics are built. He definitely stated that he +approached the subject "exclusively from the side of natural history." +("Descent of Man", Vol. I. page 149.) His general conclusion is that the +moral sense is fundamentally identical with the social instincts, which +have been developed for the good of the community; and he suggests +that the concept which thus enables us to interpret the biological +ground-plan of morals also enables us to frame a rational ideal of the +moral end. "As the social instincts," he says (Ibid. page 185.), "both +of man and the lower animals have no doubt been developed by nearly the +same steps, it would be advisable, if found practicable, to use the same +definition in both cases, and to take as the standard of morality, +the general good or welfare of the community, rather than the general +happiness." But the kind of community for the good of which the social +instincts of animals and primitive men were biologically developed may +be different from that which is the product of civilisation, as Darwin +no doubt realised. Darwin's contention was that conscience is a social +instinct and has been evolved because it is useful to the tribe in the +struggle for existence against other tribes. On the other hand, J.S. +Mill urged that the moral feelings are not innate but acquired, and Bain +held the same view, believing that the moral sense is acquired by each +individual during his life-time. Darwin, who notes (Ibid. page 150 +(footnote).) their opinion with his usual candour, adds that "on the +general theory of evolution this is at least extremely improbable. It +is impossible to enter into the question here: much turns on the exact +connotation of the terms "conscience" and "moral sense," and on the +meaning we attach to the statement that the moral sense is fundamentally +identical with the social instincts." + +Presumably the majority of those who approach the subjects discussed in +the third, fourth and fifth chapters of "The Descent of Man" in the full +conviction that mental phenomena, not less than organic phenomena, +have a natural genesis, would, without hesitation, admit that the +intellectual and moral systems of civilised man are ideal constructions, +the products of conceptual thought, and that as such they are, in +their developed form, acquired. The moral sentiments are the emotional +analogues of highly developed concepts. This does not however imply that +they are outside the range of natural history treatment. Even though +it may be desirable to differentiate the moral conduct of men from the +social behaviour of animals (to which some such term as "pre-moral" or +"quasi-moral" may be applied), still the fact remains that, as Darwin +showed, there is abundant evidence of the occurrence of such social +behaviour--social behaviour which, even granted that it is in large part +intelligently acquired, and is itself so far a product of educability, +is of survival value. It makes for that integration without which no +social group could hold together and escape elimination. Furthermore, +even if we grant that such behaviour is intelligently acquired, that +is to say arises through the modification of hereditary instincts and +emotions, the fact remains that only through these instinctive and +emotional data is afforded the primary tissue of the experience which is +susceptible of such modification. + +Darwin sought to show, and succeeded in showing, that for the +intellectual and moral life there are instinctive foundations which a +biological treatment alone can disclose. It is true that he did not +in all cases analytically distinguish the foundations from the +superstructure. Even to-day we are scarcely in a position to do so +adequately. But his treatment was of great value in giving an impetus to +further research. This value indeed can scarcely be overestimated. +And when the natural history of the mental operations shall have been +written, the cardinal fact will stand forth, that the instinctive and +emotional foundations are the outcome of biological evolution and have +been ingrained in the race through natural selection. We shall more +clearly realise that educability itself is a product of natural +selection, though the specific results acquired through cerebral +modifications are not transmitted through heredity. It will, perhaps, +also be realised that the instinctive foundations of social behaviour +are, for us, somewhat out of date and have undergone but little change +throughout the progress of civilisation, because natural selection +has long since ceased to be the dominant factor in human progress. The +history of human progress has been mainly the history of man's +higher educability, the products of which he has projected on to his +environment. This educability remains on the average what it was a dozen +generations ago; but the thought-woven tapestry of his surroundings is +refashioned and improved by each succeeding generation. Few men have in +greater measure enriched the thought-environment with which it is the +aim of education to bring educable human beings into vital contact, than +has Charles Darwin. His special field of work was the wide province of +biology; but he did much to help us realise that mental factors have +contributed to organic evolution and that in man, the highest product of +Evolution, they have reached a position of unquestioned supremacy. + + + + +XXII. THE INFLUENCE OF THE CONCEPTION OF EVOLUTION ON MODERN PHILOSOPHY. +By H. Hoffding. + +Professor of Philosophy in the University of Copenhagen. + + +I. + +It is difficult to draw a sharp line between philosophy and natural +science. The naturalist who introduces a new principle, or demonstrates +a fact which throws a new light on existence, not only renders an +important service to philosophy but is himself a philosopher in the +broader sense of the word. The aim of philosophy in the stricter sense +is to attain points of view from which the fundamental phenomena and +the principles of the special sciences can be seen in their relative +importance and connection. But philosophy in this stricter sense +has always been influenced by philosophy in the broader sense. Greek +philosophy came under the influence of logic and mathematics, modern +philosophy under the influence of natural science. The name of Charles +Darwin stands with those of Galileo, Newton, and Robert Mayer--names +which denote new problems and great alterations in our conception of the +universe. + +First of all we must lay stress on Darwin's own personality. His deep +love of truth, his indefatigable inquiry, his wide horizon, and his +steady self-criticism make him a scientific model, even if his results +and theories should eventually come to possess mainly an historical +interest. In the intellectual domain the primary object is to reach +high summits from which wide surveys are possible, to reach them toiling +honestly upwards by way of experience, and then not to turn dizzy when +a summit is gained. Darwinians have sometimes turned dizzy, but Darwin +never. He saw from the first the great importance of his hypothesis, not +only because of its solution of the old problem as to the value of the +concept of species, not only because of the grand picture of natural +evolution which it unrolls, but also because of the life and inspiration +its method would impart to the study of comparative anatomy, of instinct +and of heredity, and finally because of the influence it would exert on +the whole conception of existence. He wrote in his note-book in the +year 1837: "My theory would give zest to recent and fossil comparative +anatomy; it would lead to the study of instinct, heredity, and +mind-heredity, whole (of) metaphysics." ("Life and Letters of Charles +Darwin", Vol. I. page 8.) + +We can distinguish four main points in which Darwin's investigations +possess philosophical importance. + +The evolution hypothesis is much older than Darwin; it is, indeed, one +of the oldest guessings of human thought. In the eighteenth century it +was put forward by Diderot and Lamettrie and suggested by Kant (1786). +As we shall see later, it was held also by several philosophers in the +first half of the nineteenth century. In his preface to "The Origin of +Species", Darwin mentions the naturalists who were his forerunners. +But he has set forth the hypothesis of evolution in so energetic +and thorough a manner that it perforce attracts the attention of +all thoughtful men in a much higher degree than it did before the +publication of the "Origin". + +And further, the importance of his teaching rests on the fact that he, +much more than his predecessors, even than Lamarck, sought a foundation +for his hypothesis in definite facts. Modern science began by +demanding--with Kepler and Newton--evidence of verae causae; this +demand Darwin industriously set himself to satisfy--hence the wealth of +material which he collected by his observations and his experiments. +He not only revived an old hypothesis, but he saw the necessity of +verifying it by facts. Whether the special cause on which he founded the +explanation of the origin of species--Natural Selection--is sufficient, +is now a subject of discussion. He himself had some doubt in regard +to this question, and the criticisms which are directed against his +hypothesis hit Darwinism rather than Darwin. In his indefatigable search +for empirical evidence he is a model even for his antagonists: he has +compelled them to approach the problems of life along other lines than +those which were formerly followed. + +Whether the special cause to which Darwin appealed is sufficient or not, +at least to it is probably due the greater part of the influence which +he has exerted on the general trend of thought. "Struggle for existence" +and "natural selection" are principles which have been applied, more or +less, in every department of thought. Recent research, it is true, has +discovered greater empirical discontinuity--leaps, "mutations"--whereas +Darwin believed in the importance of small variations slowly +accumulated. It has also been shown by the experimental method, which +in recent biological work has succeeded Darwin's more historical method, +that types once constituted possess great permanence, the fluctuations +being restricted within clearly defined boundaries. The problem has +become more precise, both as to variation and as to heredity. The inner +conditions of life have in both respects shown a greater independence +than Darwin had supposed in his theory, though he always admitted that +the cause of variation was to him a great enigma, "a most perplexing +problem," and that the struggle for life could only occur where +variation existed. But, at any rate, it was of the greatest importance +that Darwin gave a living impression of the struggle for life which is +everywhere going on, and to which even the highest forms of existence +must be amenable. The philosophical importance of these ideas does not +stand or fall with the answer to the question, whether natural selection +is a sufficient explanation of the origin of species or not: it has +an independent, positive value for everyone who will observe life and +reality with an unbiassed mind. + +In accentuating the struggle for life Darwin stands as a +characteristically English thinker: he continues a train of ideas which +Hobbes and Malthus had already begun. Moreover in his critical views as +to the conception of species he had English forerunners; in the middle +ages Occam and Duns Scotus, in the eighteenth century Berkeley and Hume. +In his moral philosophy, as we shall see later, he is an adherent of the +school which is represented by Hutcheson, Hume and Adam Smith. Because +he is no philosopher in the stricter sense of the term, it is of great +interest to see that his attitude of mind is that of the great thinkers +of his nation. + +In considering Darwin's influence on philosophy we will begin with an +examination of the attitude of philosophy to the conception of evolution +at the time when "The Origin of Species" appeared. We will then examine +the effects which the theory of evolution, and especially the idea +of the struggle for life, has had, and naturally must have, on the +discussion of philosophical problems. + +II. + +When "The Origin of Species" appeared fifty years ago Romantic +speculation, Schelling's and Hegel's philosophy, still reigned on the +continent, while in England Positivism, the philosophy of Comte and +Stuart Mill, represented the most important trend of thought. German +speculation had much to say on evolution, it even pretended to be a +philosophy of evolution. But then the word "evolution" was to be taken +in an ideal, not in a real, sense. To speculative thought the forms and +types of nature formed a system of ideas, within which any form could +lead us by continuous transitions to any other. It was a classificatory +system which was regarded as a divine world of thought or images, within +which metamorphoses could go on--a condition comparable with that in +the mind of the poet when one image follows another with imperceptible +changes. Goethe's ideas of evolution, as expressed in his "Metamorphosen +der Pflanzen und der Thiere", belong to this category; it is, therefore, +incorrect to call him a forerunner of Darwin. Schelling and Hegel +held the same idea; Hegel expressly rejected the conception of a real +evolution in time as coarse and materialistic. "Nature," he says, "is +to be considered as a SYSTEM OF STAGES, the one necessarily arising from +the other, and being the nearest truth of that from which it proceeds; +but not in such a way that the one is NATURALLY generated by the other; +on the contrary (their connection lies) in the inner idea which is the +ground of nature. The METAMORPHOSIS can be ascribed only to the notion +as such, because it alone is evolution... It has been a clumsy idea in +the older as well as in the newer philosophy of nature, to regard the +transformation and the transition from one natural form and sphere to +a higher as an outward and actual production." ("Encyclopaedie der +philosophischen Wissenschaften" (4th edition), Berlin, 1845, paragraph +249.) + +The only one of the philosophers of Romanticism who believed in a +real, historical evolution, a real production of new species, was Oken. +("Lehrbuch der Naturphilosophie", Jena, 1809.) Danish philosophers, such +as Treschow (1812) and Sibbern (1846), have also broached the idea of +an historical evolution of all living beings from the lowest to the +highest. Schopenhauer's philosophy has a more realistic character than +that of Schelling's and Hegel's, his diametrical opposites, though he +also belongs to the romantic school of thought. His philosophical and +psychological views were greatly influenced by French naturalists and +philosophers, especially by Cabanis and Lamarck. He praises the "ever +memorable Lamarck," because he laid so much stress on the "will to +live." But he repudiates as a "wonderful error" the idea that the +organs of animals should have reached their present perfection through +a development in time, during the course of innumerable generations. It +was, he said, a consequence of the low standard of contemporary French +philosophy, that Lamarck came to the idea of the construction of living +beings in time through succession! ("Ueber den Willen in der Natur" (2nd +edition), Frankfurt a. M., 1854, pages 41-43.) + +The positivistic stream of thought was not more in favour of a real +evolution than was the Romantic school. Its aim was to adhere to +positive facts: it looked with suspicion on far-reaching speculation. +Comte laid great stress on the discontinuity found between the different +kingdoms of nature, as well as within each single kingdom. As he +regarded as unscientific every attempt to reduce the number of physical +forces, so he rejected entirely the hypothesis of Lamarck concerning the +evolution of species; the idea of species would in his eyes absolutely +lose its importance if a transition from species to species under the +influence of conditions of life were admitted. His disciples (Littre, +Robin) continued to direct against Darwin the polemics which their +master had employed against Lamarck. Stuart Mill, who, in the theory +of knowledge, represented the empirical or positivistic movement in +philosophy--like his English forerunners from Locke to Hume--founded +his theory of knowledge and morals on the experience of the single +individual. He sympathised with the theory of the original likeness of +all individuals and derived their differences, on which he practically +and theoretically laid much stress, from the influence both of +experience and education, and, generally, of physical and social causes. +He admitted an individual evolution, and, in the human species, an +evolution based on social progress; but no physiological evolution of +species. He was afraid that the hypothesis of heredity would carry us +back to the old theory of "innate" ideas. + +Darwin was more empirical than Comte and Mill; experience disclosed to +him a deeper continuity than they could find; closer than before the +nature and fate of the single individual were shown to be interwoven in +the great web binding the life of the species with nature as a whole. +And the continuity which so many idealistic philosophers could find +only in the world of thought, he showed to be present in the world of +reality. + +III. + +Darwin's energetic renewal of the old idea of evolution had its chief +importance in strengthening the conviction of this real continuity in +the world, of continuity in the series of form and events. It was a +great support for all those who were prepared to base their conception +of life on scientific grounds. Together with the recently discovered law +of the conservation of energy, it helped to produce the great realistic +movement which characterises the last third of the nineteenth century. +After the decline of the Romantic movement people wished to have firmer +ground under their feet and reality now asserted itself in a more +emphatic manner than in the period of Romanticism. It was easy for Hegel +to proclaim that "the real" was "the rational," and that "the +rational" was "the real": reality itself existed for him only in the +interpretation of ideal reason, and if there was anything which could +not be merged in the higher unity of thought, then it was only an +example of the "impotence of nature to hold to the idea." But now +concepts are to be founded on nature and not on any system of categories +too confidently deduced a priori. The new devotion to nature had its +recompense in itself, because the new points of view made us see that +nature could indeed "hold to ideas," though perhaps not to those which +we had cogitated beforehand. + +A most important question for philosophers to answer was whether the +new views were compatible with an idealistic conception of life and +existence. Some proclaimed that we have now no need of any philosophy +beyond the principles of the conservation of matter and energy and the +principle of natural evolution: existence should and could be definitely +and completely explained by the laws of material nature. But abler +thinkers saw that the thing was not so simple. They were prepared to +give the new views their just place and to examine what alterations the +old views must undergo in order to be brought into harmony with the new +data. + +The realistic character of Darwin's theory was shown not only in the +idea of natural continuity, but also, and not least, in the idea of the +cause whereby organic life advances step by step. This idea--the idea of +the struggle for life--implied that nothing could persist, if it had no +power to maintain itself under the given conditions. Inner value +alone does not decide. Idealism was here put to its hardest trial. In +continuous evolution it could perhaps still find an analogy to the inner +evolution of ideas in the mind; but in the demand for power in order to +struggle with outward conditions Realism seemed to announce itself in +its most brutal form. Every form of Idealism had to ask itself seriously +how it was going to "struggle for life" with this new Realism. + +We will now give a short account of the position which leading thinkers +in different countries have taken up in regard to this question. + +I. Herbert Spencer was the philosopher whose mind was best prepared by +his own previous thinking to admit the theory of Darwin to a place in +his conception of the world. His criticism of the arguments which had +been put forward against the hypothesis of Lamarck, showed that Spencer, +as a young man, was an adherent to the evolution idea. In his +"Social Statics" (1850) he applied this idea to human life and moral +civilisation. In 1852 he wrote an essay on "The Development Hypothesis", +in which he definitely stated his belief that the differentiation of +species, like the differentiation within a single organism, was the +result of development. In the first edition of his "Psychology" (1855) +he took a step which put him in opposition to the older English school +(from Locke to Mill): he acknowledged "innate ideas" so far as to +admit the tendency of acquired habits to be inherited in the course of +generations, so that the nature and functions of the individual are only +to be understood through its connection with the life of the species. +In 1857, in his essay on "Progress", he propounded the law of +differentiation as a general law of evolution, verified by examples from +all regions of experience, the evolution of species being only one of +these examples. On the effect which the appearance of "The Origin of +Species" had on his mind he writes in his "Autobiography": "Up to +that time... I held that the sole cause of organic evolution is the +inheritance of functionally-produced modifications. The "Origin of +Species" made it clear to me that I was wrong, and that the larger part +of the facts cannot be due to any such cause... To have the theory of +organic evolution justified was of course to get further support for +that theory of evolution at large with which... all my conceptions were +bound up." (Spencer, "Autobiography", Vol. II. page 50, London, 1904.) +Instead of the metaphorical expression "natural selection," Spencer +introduced the term "survival of the fittest," which found favour with +Darwin as well as with Wallace. + +In working out his ideas of evolution, Spencer found that +differentiation was not the only form of evolution. In its simplest form +evolution is mainly a concentration, previously scattered elements being +integrated and losing independent movement. Differentiation is only +forthcoming when minor wholes arise within a greater whole. And the +highest form of evolution is reached when there is a harmony between +concentration and differentiation, a harmony which Spencer calls +equilibration and which he defines as a moving equilibrium. At the same +time this definition enables him to illustrate the expression "survival +of the fittest." "Every living organism exhibits such a moving +equilibrium--a balanced set of functions constituting its life; and the +overthrow of this balanced set of functions or moving equilibrium is +what we call death. Some individuals in a species are so constituted +that their moving equilibria are less easily overthrown than those of +other individuals; and these are the fittest which survive, or, in Mr +Darwin's language, they are the select which nature preserves." (Ibid. +page 100.) Not only in the domain of organic life, but in all domains, +the summit of evolution is, according to Spencer, characterised by such +a harmony--by a moving equilibrium. + +Spencer's analysis of the concept of evolution, based on a great variety +of examples, has made this concept clearer and more definite than +before. It contains the three elements; integration, differentiation and +equilibration. It is true that a concept which is to be valid for all +domains of experience must have an abstract character, and between the +several domains there is, strictly speaking, only a relation of analogy. +So there is only analogy between psychical and physical evolution. But +this is no serious objection, because general concepts do not express +more than analogies between the phenomena which they represent. Spencer +takes his leading terms from the material world in defining evolution +(in the simplest form) as integration of matter and dissipation of +movement; but as he--not always quite consistently (Cf. my letter +to him, 1876, now printed in Duncan's "Life and Letters of Herbert +Spencer", page 178, London, 1908.)--assumed a correspondence of mind and +matter, he could very well give these terms an indirect importance for +psychical evolution. Spencer has always, in my opinion with full right, +repudiated the ascription of materialism. He is no more a materialist +than Spinoza. In his "Principles of Psychology" (paragraph 63) he +expressed himself very clearly: "Though it seems easier to translate +so-called matter into so-called spirit, than to translate so-called +spirit into so-called matter--which latter is indeed wholly +impossible--yet no translation can carry us beyond our symbols." These +words lead us naturally to a group of thinkers whose starting-point +was psychical evolution. But we have still one aspect of Spencer's +philosophy to mention. + +Spencer founded his "laws of evolution" on an inductive basis, but +he was convinced that they could be deduced from the law of the +conservation of energy. Such a deduction is, perhaps, possible for the +more elementary forms of evolution, integration and differentiation; but +it is not possible for the highest form, the equilibration, which is a +harmony of integration and differentiation. Spencer can no more deduce +the necessity for the eventual appearance of "moving equilibria" of +harmonious totalities than Hegel could guarantee the "higher unities" +in which all contradictions should be reconciled. In Spencer's hands the +theory of evolution acquired a more decidedly optimistic character +than in Darwin's; but I shall deal later with the relation of Darwin's +hypothesis to the opposition of optimism and pessimism. + +II. While the starting-point of Spencer was biological or cosmological, +psychical evolution being conceived as in analogy with physical, a group +of eminent thinkers--in Germany Wundt, in France Fouillee, in Italy +Ardigo--took, each in his own manner, their starting-point in psychical +evolution as an original fact and as a type of all evolution, the +hypothesis of Darwin coming in as a corroboration and as a special +example. They maintain the continuity of evolution; they find this +character most prominent in psychical evolution, and this is for them a +motive to demand a corresponding continuity in the material, especially +in the organic domain. + +To Wundt and Fouillee the concept of will is prominent. They see the +type of all evolution in the transformation of the life of will from +blind impulse to conscious choice; the theories of Lamarck and Darwin +are used to support the view that there is in nature a tendency to +evolution in steady reciprocity with external conditions. The struggle +for life is here only a secondary fact. Its apparent prominence is +explained by the circumstance that the influence of external conditions +is easily made out, while inner conditions can be verified only +through their effects. For Ardigo the evolution of thought was the +starting-point and the type: in the evolution of a scientific hypothesis +we see a progress from the indefinite (indistinto) to the definite +(distinto), and this is a characteristic of all evolution, as Ardigo has +pointed out in a series of works. The opposition between indistinto and +distinto corresponds to Spencer's opposition between homogeneity and +heterogeneity. The hypothesis of the origin of differences of species +from more simple forms is a special example of the general law of +evolution. + +In the views of Wundt and Fouillee we find the fundamental idea of +idealism: psychical phenomena as expressions of the innermost nature of +existence. They differ from the older Idealism in the great stress which +they lay on evolution as a real, historical process which is going on +through steady conflict with external conditions. The Romantic dread +of reality is broken. It is beyond doubt that Darwin's emphasis on the +struggle for life as a necessary condition of evolution has been a very +important factor in carrying philosophy back to reality from the heaven +of pure ideas. The philosophy of Ardigo, on the other side, appears +more as a continuation and deepening of positivism, though the Italian +thinker arrived at his point of view independently of French-English +positivism. The idea of continuous evolution is here maintained in +opposition to Comte's and Mill's philosophy of discontinuity. From Wundt +and Fouillee Ardigo differs in conceiving psychical evolution not as an +immediate revelation of the innermost nature of existence, but only as a +single, though the most accessible example, of evolution. + +III. To the French philosophers Boutroux and Bergson, evolution proper +is continuous and qualitative, while outer experience and physical +science give us fragments only, sporadic processes and mechanical +combinations. To Bergson, in his recent work "L'Evolution Creatrice", +evolution consists in an elan de vie which to our fragmentary +observation and analytic reflexion appears as broken into a manifold of +elements and processes. The concept of matter in its scientific form +is the result of this breaking asunder, essential for all scientific +reflexion. In these conceptions the strongest opposition between +inner and outer conditions of evolution is expressed: in the domain of +internal conditions spontaneous development of qualitative forms--in the +domain of external conditions discontinuity and mechanical combination. + +We see, then, that the theory of evolution has influenced philosophy +in a variety of forms. It has made idealistic thinkers revise their +relation to the real world; it has led positivistic thinkers to find a +closer connection between the facts on which they based their views; it +has made us all open our eyes for new possibilities to arise through +the prima facie inexplicable "spontaneous" variations which are the +condition of all evolution. This last point is one of peculiar interest. +Deeper than speculative philosophy and mechanical science saw in the +days of their triumph, we catch sight of new streams, whose sources and +laws we have still to discover. Most sharply does this appear in the +theory of mutation, which is only a stronger accentuation of a main +point in Darwinism. It is interesting to see that an analogous +problem comes into the foreground in physics through the discovery +of radioactive phenomena, and in psychology through the assumption +of psychical new formations (as held by Boutroux, William James and +Bergson). From this side, Darwin's ideas, as well as the analogous +ideas in other domains, incite us to renewed examination of our first +principles, their rationality and their value. On the other hand, +his theory of the struggle for existence challenges us to examine the +conditions and discuss the outlook as to the persistence of human life +and society and of the values that belong to them. It is not enough to +hope (or fear?) the rising of new forms; we have also to investigate the +possibility of upholding the forms and ideals which have hitherto been +the bases of human life. Darwin has here given his age the most earnest +and most impressive lesson. This side of Darwin's theory is of peculiar +interest to some special philosophical problems to which I now pass. + +IV. + +Among philosophical problems the problem of knowledge has in the last +century occupied a foremost place. It is natural, then, to ask how +Darwin and the hypothesis whose most eminent representative he is, stand +to this problem. + +Darwin started an hypothesis. But every hypothesis is won by inference +from certain presuppositions, and every inference is based on +the general principles of human thought. The evolution hypothesis +presupposes, then, human thought and its principles. And not only +the abstract logical principles are thus presupposed. The evolution +hypothesis purports to be not only a formal arrangement of phenomena, +but to express also the law of a real process. It supposes, then, +that the real data--all that in our knowledge which we do not produce +ourselves, but which we in the main simply receive--are subjected +to laws which are at least analogous to the logical relations of our +thoughts; in other words, it assumes the validity of the principle of +causality. If organic species could arise without cause there would +be no use in framing hypotheses. Only if we assume the principle of +causality, is there a problem to solve. + +Though Darwinism has had a great influence on philosophy considered as +a striving after a scientific view of the world, yet here is a point of +view--the epistemological--where philosophy is not only independent but +reaches beyond any result of natural science. Perhaps it will be said: +the powers and functions of organic beings only persist (perhaps also +only arise) when they correspond sufficiently to the conditions under +which the struggle of life is to go on. Human thought itself is, then, a +variation (or a mutation) which has been able to persist and to +survive. Is not, then, the problem of knowledge solved by the evolution +hypothesis? Spencer had given an affirmative answer to this question +before the appearance of "The Origin of Species". For the individual, he +said, there is an a priori, original, basis (or Anlage) for all mental +life; but in the species all powers have developed in reciprocity with +external conditions. Knowledge is here considered from the practical +point of view, as a weapon in the struggle for life, as an "organon" +which has been continuously in use for generations. In recent years the +economic or pragmatic epistemology, as developed by Avenarius and Mach +in Germany, and by James in America, points in the same direction. +Science, it is said, only maintains those principles and presuppositions +which are necessary to the simplest and clearest orientation in +the world of experience. All assumptions which cannot be applied to +experience and to practical work, will successively be eliminated. + +In these views a striking and important application is made of the idea +of struggle for life to the development of human thought. Thought must, +as all other things in the world, struggle for life. But this whole +consideration belongs to psychology, not to the theory of knowledge +(epistemology), which is concerned only with the validity of knowledge, +not with its historical origin. Every hypothesis to explain the +origin of knowledge must submit to cross-examination by the theory of +knowledge, because it works with the fundamental forms and principles +of human thought. We cannot go further back than these forms and +principles, which it is the aim of epistemology to ascertain and for +which no further reason can be given. (The present writer, many years +ago, in his "Psychology" (Copenhagen, 1882; English translation London, +1891), criticised the evolutionistic treatment of the problem of +knowledge from the Kantian point of view.) + +But there is another side of the problem which is, perhaps, of more +importance and which epistemology generally overlooks. If new variations +can arise, not only in organic but perhaps also in inorganic nature, new +tasks are placed before the human mind. The question is, then, if it has +forms in which there is room for the new matter? We are here touching +a possibility which the great master of epistemology did not bring to +light. Kant supposed confidently that no other matter of knowledge could +stream forth from the dark source which he called "the thing-in-itself," +than such as could be synthesised in our existing forms of knowledge. +He mentions the possibility of other forms than the human, and warns us +against the dogmatic assumption that the human conception of existence +should be absolutely adequate. But he seems to be quite sure that the +thing-in-itself works constantly, and consequently always gives us only +what our powers can master. This assumption was a consequence of Kant's +rationalistic tendency, but one for which no warrant can be given. +Evolutionism and systematism are opposing tendencies which can never +be absolutely harmonised one with the other. Evolution may at any time +break some form which the system-monger regards as finally established. +Darwin himself felt a great difference in looking at variation as an +evolutionist and as a systematist. When he was working at his evolution +theory, he was very glad to find variations; but they were a hindrance +to him when he worked as a systematist, in preparing his work on +Cirripedia. He says in a letter: "I had thought the same parts of the +same species more resemble (than they do anyhow in Cirripedia) objects +cast in the same mould. Systematic work would be easy were it not +for this confounded variation, which, however, is pleasant to me as a +speculatist, though odious to me as a systematist." ("Life and Letters", +Vol. II. page 37.) He could indeed be angry with variations even as +an evolutionist; but then only because he could not explain them, not +because he could not classify them. "If, as I must think, external +conditions produce little DIRECT effect, what the devil determines each +particular variation?" (Ibid. page 232.) What Darwin experienced in +his particular domain holds good of all knowledge. All knowledge is +systematic, in so far as it strives to put phenomena in quite definite +relations, one to another. But the systematisation can never be +complete. And here Darwin has contributed much to widen the world for +us. He has shown us forces and tendencies in nature which make absolute +systems impossible, at the same time that they give us new objects and +problems. There is still a place for what Lessing called "the unceasing +striving after truth," while "absolute truth" (in the sense of a closed +system) is unattainable so long as life and experience are going on. + +There is here a special remark to be made. As we have seen above, recent +research has shown that natural selection or struggle for life is no +explanation of variations. Hugo de Vries distinguishes between partial +and embryonal variations, or between variations and mutations, only the +last-named being heritable, and therefore of importance for the origin +of new species. But the existence of variations is not only of interest +for the problem of the origin of species; it has also a more general +interest. An individual does not lose its importance for knowledge, +because its qualities are not heritable. On the contrary, in higher +beings at least, individual peculiarities will become more and more +independent objects of interest. Knowledge takes account of the +biographies not only of species, but also of individuals: it seeks to +find the law of development of the single individual. (The new science +of Ecology occupies an intermediate position between the biography of +species and the biography of individuals. Compare "Congress of Arts and +Science", St Louis, Vol. V. 1906 (the Reports of Drude and Robinson) +and the work of my colleague E. Warming.) As Leibniz said long ago, +individuality consists in the law of the changes of a being. "La loi du +changement fait l'individualite de chaque substance." Here is a world +which is almost new for science, which till now has mainly occupied +itself with general laws and forms. But these are ultimately only means +to understand the individual phenomena, in whose nature and history +a manifold of laws and forms always cooperate. The importance of this +remark will appear in the sequel. + +V. + +To many people the Darwinian theory of natural selection or struggle +for existence seemed to change the whole conception of life, and +particularly all the conditions on which the validity of ethical ideas +depends. If only that has persistence which can be adapted to a given +condition, what will then be the fate of our ideals, of our standards +of good and evil? Blind force seems to reign, and the only thing that +counts seems to be the most heedless use of power. Darwinism, it was +said, has proclaimed brutality. No other difference seems permanent save +that between the sound, powerful and happy on the one side, the sick, +feeble and unhappy on the other; and every attempt to alleviate this +difference seems to lead to general enervation. Some of those who +interpreted Darwinism in this manner felt an aesthetic delight in +contemplating the heedlessness and energy of the great struggle for +existence and anticipated the realisation of a higher human type as the +outcome of it: so Nietzsche and his followers. Others recognising the +same consequences in Darwinism regarded these as one of the strongest +objections against it; so Duhring and Kropotkin (in his earlier works). + +This interpretation of Darwinism was frequent in the interval between +the two main works of Darwin--"The Origin of Species" and "The Descent +of Man". But even during this interval it was evident to an attentive +reader that Darwin himself did not found his standard of good and evil +on the features of the life of nature he had emphasised so strongly. He +did not justify the ways along which nature reached its ends; he only +pointed them out. The "real" was not to him, as to Hegel, one with +the "rational." Darwin has, indeed, by his whole conception of nature, +rendered a great service to ethics in making the difference between the +life of nature and the ethical life appear in so strong a light. The +ethical problem could now be stated in a sharper form than before. But +this was not the first time that the idea of the struggle for life +was put in relation to the ethical problem. In the seventeenth century +Thomas Hobbes gave the first impulse to the whole modern discussion of +ethical principles in his theory of bellum omnium contra omnes. Men, he +taught, are in the state of nature enemies one of another, and they live +either in fright or in the glory of power. But it was not the opinion +of Hobbes that this made ethics impossible. On the contrary, he found a +standard for virtue and vice in the fact that some qualities and actions +have a tendency to bring us out of the state of war and to secure +peace, while other qualities have a contrary tendency. In the eighteenth +century even Immanuel Kant's ideal ethics had--so far as can be seen--a +similar origin. Shortly before the foundation of his definitive ethics, +Kant wrote his "Idee zu einer allgemeinen Weltgeschichte" (1784), +where--in a way which reminds us of Hobbes, and is prophetic of +Darwin--he describes the forward-driving power of struggle in the human +world. It is here as with the struggle of the trees for light and air, +through which they compete with one another in height. Anxiety about +war can only be allayed by an ordinance which gives everyone his full +liberty under acknowledgment of the equal liberty of others. And such +ordinance and acknowledgment are also attributes of the content of the +moral law, as Kant proclaimed it in the year after the publication +of his essay (1785) (Cf. my "History of Modern Philosophy" (English +translation London, 1900), I. pages 76-79.) Kant really came to his +ethics by the way of evolution, though he afterwards disavowed it. +Similarly the same line of thought may be traced in Hegel though it has +been disguised in the form of speculative dialectics. ("Herrschaft und +Knechtschaft", "Phanomenologie des Geistes", IV. A., Leiden, 1907.) And +in Schopenhauer's theory of the blind will to live and its abrogation by +the ethical feeling, which is founded on universal sympathy, we have a +more individualistic form of the same idea. + +It was, then, not entirely a foreign point of view which Darwin +introduced into ethical thought, even if we take no account of the +poetical character of the word "struggle" and of the more direct +adaptation, through the use and non-use of power, which Darwin also +emphasised. In "The Descent of Man" he has devoted a special chapter +("The Descent of Man", Vol. I. Ch. iii.) to a discussion of the origin +of the ethical consciousness. The characteristic expression of this +consciousness he found, just as Kant did, in the idea of "ought"; it was +the origin of this new idea which should be explained. His hypothesis +was that the ethical "ought" has its origin in the social and parental +instincts, which, as well as other instincts (e.g. the instinct of +self-preservation), lie deeper than pleasure and pain. In many species, +not least in the human species, these instincts are fostered by natural +selection; and when the powers of memory and comparison are developed, +so that single acts can be valued according to the claims of the deep +social instinct, then consciousness of duty and remorse are possible. +Blind instinct has developed to conscious ethical will. + +As already stated, Darwin, as a moral philosopher belongs to the school +that was founded by Shaftesbury, and was afterwards represented by +Hutcheson, Hume, Adam Smith, Comte and Spencer. His merit is, first, +that he has given this tendency of thought a biological foundation, and +that he has stamped on it a doughty character in showing that ethical +ideas and sentiments, rightly conceived, are forces which are at work in +the struggle for life. + +There are still many questions to solve. Not only does the ethical +development within the human species contain features still unexplained +(The works of Westermarck and Hobhouse throw new light on many of these +features.); but we are confronted by the great problem whether after all +a genetic historical theory can be of decisive importance here. To +every consequent ethical consciousness there is a standard of value, a +primordial value which determines the single ethical judgments as their +last presupposition, and the "rightness" of this basis, the "value" +of this value can as little be discussed as the "rationality" of our +logical principles. There is here revealed a possibility of ethical +scepticism which evolutionistic ethics (as well as intuitive or +rationalistic ethics) has overlooked. No demonstration can show that the +results of the ethical development are definitive and universal. We +meet here again with the important opposition of systematisation and +evolution. There will, I think, always be an open question here, though +comparative ethics, of which we have so far only the first attempts, can +do much to throw light on it. + +It would carry us too far to discuss all the philosophical works +on ethics, which have been influenced directly or indirectly by +evolutionism. I may, however, here refer to the book of C.M. Williams, +"A Review of the Systems of Ethics founded on the Theory of Evolution" +(New York and London, 1893.), in which, besides Darwin, the following +authors are reviewed: Wallace, Haeckel, Spencer, Fiske, Rolph, Barratt, +Stephen, Carneri, Hoffding, Gizycki, Alexander, Ree. As works which +criticise evolutionistic ethics from an intuitive point of view and +in an instructive way, may be cited: Guyau "La morale anglaise +contemporaine" (Paris, 1879.), and Sorley, "Ethics of Naturalism". I +will only mention some interesting contributions to ethical discussion +which can be found in Darwinism besides the idea of struggle for life. + +The attention which Darwin has directed to variations has opened our +eyes to the differences in human nature as well as in nature generally. +There is here a fact of great importance for ethical thought, no matter +from what ultimate premiss it starts. Only from a very abstract point of +view can different individuals be treated in the same manner. The most +eminent ethical thinkers, men such as Jeremy Bentham and Immanuel Kant, +who discussed ethical questions from very opposite standpoints, agreed +in regarding all men as equal in respect of ethical endowment. In regard +to Bentham, Leslie Stephen remarks: "He is determined to be thoroughly +empirical, to take men as he found them. But his utilitarianism supposed +that men's views of happiness and utility were uniform and clear, and +that all that was wanted was to show them the means by which their ends +could be reached." ("English literature and society in the eighteenth +century", London, 1904, page 187.) And Kant supposed that every man +would find the "categorical imperative" in his consciousness, when he +came to sober reflexion, and that all would have the same qualifications +to follow it. But if continual variations, great or small, are going on +in human nature, it is the duty of ethics to make allowance for them, +both in making claims, and in valuing what is done. A new set of ethical +problems have their origin here. (Cf. my paper, "The law of relativity +in Ethics," "International Journal of Ethics", Vol. I. 1891, pages +37-62.) It is an interesting fact that Stuart Mill's book "On Liberty" +appeared in the same year as "The Origin of Species". Though Mill agreed +with Bentham about the original equality of all men's endowments, he +regarded individual differences as a necessary result of physical and +social influences, and he claimed that free play shall be allowed to +differences of character so far as is possible without injury to other +men. It is a condition of individual and social progress that a man's +mode of action should be determined by his own character and not +by tradition and custom, nor by abstract rules. This view was to be +corroborated by the theory of Darwin. + +But here we have reached a point of view from which the criticism, +which in recent years has often been directed against Darwin--that +small variations are of no importance in the struggle for life--is of +no weight. From an ethical standpoint, and particularly from the +ethical standpoint of Darwin himself, it is a duty to foster individual +differences that can be valuable, even though they can neither be of +service for physical preservation nor be physically inherited. The +distinction between variation and mutation is here without importance. +It is quite natural that biologists should be particularly interested in +such variations as can be inherited and produce new species. But in the +human world there is not only a physical, but also a mental and social +heredity. When an ideal human character has taken form, then there +is shaped a type, which through imitation and influence can become an +important factor in subsequent development, even if it cannot form a +species in the biological sense of the word. Spiritually strong +men often succumb in the physical struggle for life; but they can +nevertheless be victorious through the typical influence they exert, +perhaps on very distant generations, if the remembrance of them is kept +alive, be it in legendary or in historical form. Their very failure +can show that a type has taken form which is maintained at all risks, +a standard of life which is adhered to in spite of the strongest +opposition. The question "to be or not to be" can be put from +very different levels of being: it has too often been considered a +consequence of Darwinism that this question is only to be put from +the lowest level. When a stage is reached, where ideal (ethical, +intellectual, aesthetic) interests are concerned, the struggle for life +is a struggle for the preservation of this stage. The giving up of a +higher standard of life is a sort of death; for there is not only a +physical, there is also a spiritual, death. + +VI. + +The Socratic character of Darwin's mind appears in his wariness in +drawing the last consequences of his doctrine, in contrast both with the +audacious theories of so many of his followers and with the consequences +which his antagonists were busy in drawing. Though he, as we have seen, +saw from the beginning that his hypothesis would occasion "a whole of +metaphysics," he was himself very reserved as to the ultimate questions, +and his answers to such questions were extorted from him. + +As to the question of optimism and pessimism, Darwin held that though +pain and suffering were very often the ways by which animals were led +to pursue that course of action which is most beneficial to the species, +yet pleasurable feelings were the most habitual guides. "We see this in +the pleasure from exertion, even occasionally from great exertion of the +body or mind, in the pleasure of our daily meals, and especially in the +pleasure derived from sociability, and from loving our families." But +there was to him so much suffering in the world that it was a strong +argument against the existence of an intelligent First Cause. ("Life and +Letters" Vol. I. page 310.) + +It seems to me that Darwin was not so clear on another question, that +of the relation between improvement and adaptation. He wrote to Lyell: +"When you contrast natural selection and 'improvement,' you seem always +to overlook... that every step in the natural selection of each species +implies improvement in that species IN RELATION TO ITS CONDITION OF +LIFE... Improvement implies, I suppose, EACH FORM OBTAINING MANY PARTS +OR ORGANS, all excellently adapted for their functions." "All this," he +adds, "seems to me quite compatible with certain forms fitted for simple +conditions, remaining unaltered, or being degraded." (Ibid. Vol. II. +page 177.) But the great question is, if the conditions of life will in +the long run favour "improvement" in the sense of differentiation +(or harmony of differentiation and integration). Many beings are best +adapted to their conditions of life if they have few organs and few +necessities. Pessimism would not only be the consequence, if suffering +outweighed happiness, but also if the most elementary forms of happiness +were predominant, or if there were a tendency to reduce the standard +of life to the simplest possible, the contentment of inertia or stable +equilibrium. There are animals which are very highly differentiated and +active in their young state, but later lose their complex organisation +and concentrate themselves on the one function of nutrition. In the +human world analogies to this sort of adaptation are not wanting. Young +"idealists" very often end as old "Philistines." Adaptation and progress +are not the same. + +Another question of great importance in respect to human evolution +is, whether there will be always a possibility for the existence of +an impulse to progress, an impulse to make great claims on life, to be +active and to alter the conditions of life instead of adapting to them +in a passive manner. Many people do not develop because they have +too few necessities, and because they have no power to imagine other +conditions of life than those under which they live. In his remarks +on "the pleasure from exertion" Darwin has a point of contact with +the practical idealism of former times--with the ideas of Lessing and +Goethe, of Condorcet and Fichte. The continual striving which was +the condition of salvation to Faust's soul, is also the condition +of salvation to mankind. There is a holy fire which we ought to keep +burning, if adaptation is really to be improvement. If, as I have +tried to show in my "Philosophy of Religion", the innermost core of all +religion is faith in the persistence of value in the world, and if +the highest values express themselves in the cry "Excelsior!" then the +capital point is, that this cry should always be heard and followed. We +have here a corollary of the theory of evolution in its application to +human life. + +Darwin declared himself an agnostic, not only because he could not +harmonise the large amount of suffering in the world with the idea of a +God as its first cause, but also because he "was aware that if we admit +a first cause, the mind still craves to know whence it came and how it +arose." ("Life and Letters", Vol. I. page 306.) He saw, as Kant had +seen before him and expressed in his "Kritik der Urtheilskraft", that we +cannot accept either of the only two possibilities which we are able +to conceive: chance (or brute force) and design. Neither mechanism +nor teleology can give an absolute answer to ultimate questions. +The universe, and especially the organic life in it, can neither be +explained as a mere combination of absolute elements nor as the effect +of a constructing thought. Darwin concluded, as Kant, and before him +Spinoza, that the oppositions and distinctions which our experience +presents, cannot safely be regarded as valid for existence in itself. +And, with Kant and Fichte, he found his stronghold in the conviction +that man has something to do, even if he cannot solve all enigmas. "The +safest conclusion seems to me that the whole subject is beyond the scope +of man's intellect; but man can do his duty." (Ibid. page 307.) + +Is this the last word of human thought? Does not the possibility, +that man can do his duty, suppose that the conditions of life allow of +continuous ethical striving, so that there is a certain harmony +between cosmic order and human ideals? Darwin himself has shown how +the consciousness of duty can arise as a natural result of evolution. +Moreover there are lines of evolution which have their end in ethical +idealism, in a kingdom of values, which must struggle for life as all +things in the world must do, but a kingdom which has its firm foundation +in reality. + + + + +XXIII. DARWINISM AND SOCIOLOGY. By C. Bougle. + +Professor of Social Philosophy in the University of Toulouse and +Deputy-Professor at the Sorbonne, Paris. + + +How has our conception of social phenomena, and of their history, +been affected by Darwin's conception of Nature and the laws of its +transformations? To what extent and in what particular respects have +the discoveries and hypotheses of the author of "The Origin of Species" +aided the efforts of those who have sought to construct a science of +society? + +To such a question it is certainly not easy to give any brief or precise +answer. We find traces of Darwinism almost everywhere. Sociological +systems differing widely from each other have laid claim to its +authority; while, on the other hand, its influence has often made itself +felt only in combination with other influences. The Darwinian thread is +worked into a hundred patterns along with other threads. + +To deal with the problem, we must, it seems, first of all distinguish +the more general conclusions in regard to the evolution of living +beings, which are the outcome of Darwinism, from the particular +explanations it offers of the ways and means by which that evolution +is effected. That is to say, we must, as far as possible, estimate +separately the influence of Darwin as an evolutionist and Darwin as a +selectionist. + +The nineteenth century, said Cournot, has witnessed a mighty effort to +"reintegrer l'homme dans la nature." From divers quarters there has been +a methodical reaction against the persistent dualism of the Cartesian +tradition, which was itself the unconscious heir of the Christian +tradition. Even the philosophy of the eighteenth century, materialistic +as were for the most part the tendencies of its leaders, seemed to +revere man as a being apart, concerning whom laws might be formulated a +priori. To bring him down from his pedestal there was needed the marked +predominance of positive researches wherein no account was taken of +the "pride of man." There can be no doubt that Darwin has done much to +familiarise us with this attitude. Take for instance the first part +of "The Descent of Man": it is an accumulation of typical facts, all +tending to diminish the distance between us and our brothers, the lower +animals. One might say that the naturalist had here taken as his motto, +"Whosoever shall exalt himself shall be abased; and he that shall humble +himself shall be exalted." Homologous structures, the survival in man of +certain organs of animals, the rudiments in the animal of certain +human faculties, a multitude of facts of this sort, led Darwin to the +conclusion that there is no ground for supposing that the "king of the +universe" is exempt from universal laws. Thus belief in the imperium +in imperio has been, as it were, whittled away by the progress of the +naturalistic spirit, itself continually strengthened by the conquests of +the natural sciences. The tendency may, indeed, drag the social sciences +into overstrained analogies, such, for instance, as the assimilation +of societies to organisms. But it will, at least, have had the merit of +helping sociology to shake off the pre-conception that the groups formed +by men are artificial, and that history is completely at the mercy of +chance. Some years before the appearance of "The Origin of Species", +Auguste Comte had pointed out the importance, as regards the unification +of positive knowledge, of the conviction that the social world, the last +refuge of spiritualism, is itself subject to determininism. It cannot be +doubted that the movement of thought which Darwin's discoveries promoted +contributed to the spread of this conviction, by breaking down the +traditional barrier which cut man off from Nature. + +But Nature, according to modern naturalists, is no immutable thing: it +is rather perpetual movement, continual progression. Their discoveries +batter a breach directly into the Aristotelian notion of species; they +refuse to see in the animal world a collection of immutable types, +distinct from all eternity, and corresponding, as Cuvier said, to so +many particular thoughts of the Creator. Darwin especially congratulated +himself upon having been able to deal this doctrine the coup de grace: +immutability is, he says, his chief enemy; and he is concerned to +show--therein following up Lyell's work--that everything in the organic +world, as in the inorganic, is explained by insensible but incessant +transformations. "Nature makes no leaps"--"Nature knows no gaps": these +two dicta form, as it were, the two landmarks between which Darwin's +idea of transformation is worked out. That is to say, the development of +Darwinism is calculated to further the application of the philosophy of +Becoming to the study of human institutions. + +The progress of the natural sciences thus brings unexpected +reinforcements to the revolution which the progress of historical +discipline had begun. The first attempt to constitute an actual science +of social phenomena--that, namely, of the economists--had resulted in +laws which were called natural, and which were believed to be +eternal and universal, valid for all times and all places. But this +perpetuality, brother, as Knies said, of the immutability of the old +zoology, did not long hold out against the ever swelling tide of the +historical movement. Knowledge of the transformations that had taken +place in language, of the early phases of the family, of religion, of +property, had all favoured the revival of the Heraclitean view: panta +rei. As to the categories of political economy, it was soon to be +recognised, as by Lassalle, that they too are only historical. The +philosophy of history, moreover, gave expression under various forms to +the same tendency. Hegel declares that "all that is real is rational," +but at the same time he shows that all that is real is ephemeral, and +that for history there is nothing fixed beneath the sun. It is this +sense of universal evolution that Darwin came with fresh authority +to enlarge. It was in the name of biological facts themselves that he +taught us to see only slow metamorphoses in the history of institutions, +and to be always on the outlook for survivals side by side with +rudimentary forms. Anyone who reads "Primitive Culture", by Tylor,--a +writer closely connected with Darwin--will be able to estimate the +services which these cardinal ideas were to render to the social +sciences when the age of comparative research had succeeded to that of a +priori construction. + +Let us note, moreover, that the philosophy of Becoming in passing +through the Darwinian biology became, as it were, filtered: it got +rid of those traces of finalism, which, under different forms, it had +preserved through all the systems of German Romanticism. Even in Herbert +Spencer, it has been plausibly argued, one can detect something of that +sort of mystic confidence in forces spontaneously directing life, which +forms the very essence of those systems. But Darwin's observations +were precisely calculated to render such an hypothesis futile. At first +people may have failed to see this; and we call to mind the ponderous +sarcasms of Flourens when he objected to the theory of Natural Selection +that it attributed to nature a power of free choice. "Nature endowed +with will! That was the final error of last century; but the nineteenth +no longer deals in personifications." (P. Flourens, "Examen du Livre +de M. Darwin sur l'Origine des Especes", page 53, Paris, 1864. See also +Huxley, "Criticisms on the 'Origin of Species'", "Collected Essays", +Vol. II, page 102, London, 1902.) In fact Darwin himself put his +readers on their guard against the metaphors he was obliged to use. The +processes by which he explains the survival of the fittest are far from +affording any indication of the design of some transcendent breeder. +Nor, if we look closely, do they even imply immanent effort in the +animal; the sorting out can be brought about mechanically, simply by +the action of the environment. In this connection Huxley could with +good reason maintain that Darwin's originality consisted in showing +how harmonies which hitherto had been taken to imply the agency of +intelligence and will could be explained without any such intervention. +So, when later on, objective sociology declares that, even when +social phenomena are in question, all finalist preconceptions must be +distrusted if a science is to be constituted, it is to Darwin that its +thanks are due; he had long been clearing paths for it which lay +well away from the old familiar road trodden by so many theories of +evolution. + +This anti-finalist doctrine, when fully worked out, was, moreover, +calculated to aid in the needful dissociation of two notions: that of +evolution and that of progress. In application to society these had long +been confounded; and, as a consequence, the general idea seemed to be +that only one type of evolution was here possible. Do we not detect +such a view in Comte's sociology, and perhaps even in Herbert Spencer's? +Whoever, indeed, assumes an end for evolution is naturally inclined to +think that only one road leads to that end. But those whose minds the +Darwinian theory has enlightened are aware that the transformations of +living beings depend primarily upon their conditions, and that it is +these conditions which are the agents of selection from among individual +variations. Hence, it immediately follows that transformations are not +necessarily improvements. Here, Darwin's thought hesitated. Logically +his theory proves, as Ray Lankester pointed out, that the struggle for +existence may have as its outcome degeneration as well as amelioration: +evolution may be regressive as well as progressive. Then, too--and this +is especially to be borne in mind--each species takes its good where +it finds it, seeks its own path and survives as best it can. Apply this +notion to society and you arrive at the theory of multilinear evolution. +Divergencies will no longer surprise you. You will be forewarned not to +apply to all civilisations the same measure of progress, and you will +recognise that types of evolution may differ just as social species +themselves differ. Have we not here one of the conceptions which mark +off sociology proper from the old philosophy of history? + +But if we are to estimate the influence of Darwinism upon sociological +conceptions, we must not dwell only upon the way in which Darwin +impressed the general notion of evolution upon the minds of thinkers. We +must go into details. We must consider the influence of the particular +theories by which he explained the mechanism of this evolution. The name +of the author of "The Origin of Species" has been especially attached, +as everyone knows, to the doctrines of "natural selection" and of +"struggle for existence," completed by the notion of "individual +variation." These doctrines were turned to account by very different +schools of social philosophy. Pessimistic and optimistic, aristocratic +and democratic, individualistic and socialistic systems were to war +with each other for years by casting scraps of Darwinism at each other's +heads. + +It was the spectacle of human contrivance that suggested to Darwin +his conception of natural selection. It was in studying the methods of +pigeon breeders that he divined the processes by which nature, in the +absence of design, obtains analogous results in the differentiation +of types. As soon as the importance of artificial selection in the +transformation of species of animals was understood, reflection +naturally turned to the human species, and the question arose, How far +do men observe, in connection with themselves, those laws of which they +make practical application in the case of animals? Here we come upon one +of the ideas which guided the researches of Galton, Darwin's cousin. The +author of "Inquiries into Human Faculty and its Development" ("Inquiries +into Human Faculty", pages 1, 2, 3 sq., London, 1883.), has often +expressed his surprise that, considering all the precautions taken, +for example, in the breeding of horses, none whatever are taken in the +breeding of the human species. It seems to be forgotten that the species +suffers when the "fittest" are not able to perpetuate their type. +Ritchie, in his "Darwinism and Politics" ("Darwinism and Politics" pages +9, 22, London, 1889.) reminds us of Darwin's remark that the institution +of the peerage might be defended on the ground that peers, owing to the +prestige they enjoy, are enabled to select as wives "the most beautiful +and charming women out of the lower ranks." ("Life and Letters of +Charles Darwin", II. page 385.) But, says Galton, it is as often as not +"heiresses" that they pick out, and birth statistics seem to show that +these are either less robust or less fecund than others. The truth is +that considerations continue to preside over marriage which are entirely +foreign to the improvement of type, much as this is a condition of +general progress. Hence the importance of completing Odin's and De +Candolle's statistics which are designed to show how characters are +incorporated in organisms, how they are transmitted, how lost, and +according to what law eugenic elements depart from the mean or return to +it. + +But thinkers do not always content themselves with undertaking merely +the minute researches which the idea of Selection suggests. They are +eager to defend this or that thesis. In the name of this idea certain +social anthropologists have recast the conception of the process of +civilisation, and have affirmed that Social Selection generally works +against the trend of Natural Selection. Vacher de Lapouge--following +up an observation by Broca on the point--enumerates the various +institutions, or customs, such as the celibacy of priests and military +conscription, which cause elimination or sterilisation of the bearers of +certain superior qualities, intellectual or physical. In a more general +way he attacks the democratic movement, a movement, as P. Bourget says, +which is "anti-physical" and contrary to the natural laws of progress; +though it has been inspired "by the dreams of that most visionary of all +centuries, the eighteenth." (V. de Lapouge, "Les Selections sociales", +page 259, Paris, 1896.) The "Equality" which levels down and mixes +(justly condemned, he holds, by the Comte de Gobineau), prevents the +aristocracy of the blond dolichocephales from holding the position and +playing the part which, in the interests of all, should belong to them. +Otto Ammon, in his "Natural Selection in Man", and in "The Social Order +and its Natural Bases" ("Die naturliche Auslese beim Menschen", Jena, +1893; "Die Gesellschaftsordnung und ihre naturlichen Grundlagen". +"Entwurf einer Sozialanthropologie", Jena, 1896.), defended analogous +doctrines in Germany; setting the curve representing frequency of talent +over against that of income, he attempted to show that all democratic +measures which aim at promoting the rise in the social scale of the +talented are useless, if not dangerous; that they only increase the +panmixia, to the great detriment of the species and of society. + +Among the aristocratic theories which Darwinism has thus inspired +we must reckon that of Nietzsche. It is well known that in order to +complete his philosophy he added biological studies to his philological; +and more than once in his remarks upon the "Wille zur Macht" he +definitely alludes to Darwin; though it must be confessed that it is +generally in order to proclaim the in sufficiency of the processes by +which Darwin seeks to explain the genesis of species. Nevertheless, +Nietzsche's mind is completely possessed by an ideal of Selection. +He, too, has a horror of panmixia. The naturalists' conception of "the +fittest" is joined by him to that of the "hero" of romance to furnish a +basis for his doctrine of the Superman. Let us hasten to add, moreover, +that at the very moment when support was being sought in the theory of +Selection for the various forms of the aristocratic doctrine, those same +forms were being battered down on another side by means of that very +theory. Attention was drawn to the fact that by virtue of the laws which +Darwin himself had discovered isolation leads to etiolation. There is +a risk that the privilege which withdraws the privileged elements of +Society from competition will cause them to degenerate. In fact, Jacoby +in his "Studies in Selection, in connexion with Heredity in Man", +("Etudes sur la Selection dans ses rapports avec l'heredite chez +l'homme", Paris, page 481, 1881.), concludes that "sterility, mental +debility, premature death and, finally, the extinction of the stock +were not specially and exclusively the fate of sovereign dynasties; all +privileged classes, all families in exclusively elevated positions share +the fate of reigning families, although in a minor degree and in direct +proportion to the loftiness of their social standing. From the mass of +human beings spring individuals, families, races, which tend to raise +themselves above the common level; painfully they climb the rugged +heights, attain the summits of power, of wealth, of intelligence, of +talent, and then, no sooner are they there than they topple down and +disappear in gulfs of mental and physical degeneracy." The demographical +researches of Hansen ("Die drei Bevolkerungsstufen", Munich, 1889.) +(following up and completing Dumont's) tended, indeed, to show that +urban as well as feudal aristocracies, burgher classes as well as noble +castes, were liable to become effete. Hence it might well be concluded +that the democratic movement, operating as it does to break down class +barriers, was promoting instead of impeding human selection. + +So we see that, according to the point of view, very different +conclusions have been drawn from the application of the Darwinian idea +of Selection to human society. Darwin's other central idea, closely +bound up with this, that, namely, of the "struggle for existence" also +has been diversely utilised. But discussion has chiefly centered upon +its signification. And while some endeavour to extend its application to +everything, we find others trying to limit its range. The conception of +a "struggle for existence" has in the present day been taken up into +the social sciences from natural science, and adopted. But originally it +descended from social science to natural. Darwin's law is, as he himself +said, only Malthus' law generalised and extended to the animal world: a +growing disproportion between the supply of food and the number of +the living is the fatal order whence arises the necessity of universal +struggle, a struggle which, to the great advantage of the species, +allows only the best equipped individuals to survive. Nature is regarded +by Huxley as an immense arena where all living beings are gladiators. +("Evolution and Ethics", page 200; "Collected Essays", Vol. IX, London, +1894.) + +Such a generalisation was well adapted to feed the stream of pessimistic +thought; and it furnished to the apologists of war, in particular, new +arguments, weighted with all the authority which in these days attaches +to scientific deliverances. If people no longer say, as Bonald did, and +Moltke after him, that war is a providential fact, they yet lay stress +on the point that it is a natural fact. To the peace party Dragomirov's +objection is urged that its attempts are contrary to the fundamental +laws of nature, and that no sea wall can hold against breakers that come +with such gathered force. + +But in yet another quarter Darwinism was represented as opposed to +philanthropic intervention. The defenders of the orthodox political +economy found in it support for their tenets. Since in the organic world +universal struggle is the condition of progress, it seemed obvious that +free competition must be allowed to reign unchecked in the economic +world. Attempts to curb it were in the highest degree imprudent. The +spirit of Liberalism here seemed in conformity with the trend of nature: +in this respect, at least, contemporary naturalism, offspring of the +discoveries of the nineteenth century, brought reinforcements to the +individualist doctrine, begotten of the speculations of the eighteenth: +but only, it appeared, to turn mankind away for ever from humanitarian +dreams. Would those whom such conclusions repelled be content to oppose +to nature's imperatives only the protests of the heart? There were some +who declared, like Brunetiere, that the laws in question, valid though +they might be for the animal kingdom, were not applicable to the human. +And so a return was made to the classic dualism. This indeed seems to be +the line that Huxley took, when, for instance, he opposed to the cosmic +process an ethical process which was its reverse. + +But the number of thinkers whom this antithesis does not satisfy grows +daily. Although the pessimism which claims authorisation from Darwin's +doctrines is repugnant to them, they still are unable to accept the +dualism which leaves a gulf between man and nature. And their endeavour +is to link the two by showing that while Darwin's laws obtain in both +kingdoms, the conditions of their application are not the same: their +forms, and, consequently, their results, vary with the varying mediums +in which the struggle of living beings takes place, with the means +these beings have at disposal, with the ends even which they propose to +themselves. + +Here we have the explanation of the fact that among determined opponents +of war partisans of the "struggle for existence" can be found: there are +disciples of Darwin in the peace party. Novicow, for example, admits +the "combat universel" of which Le Dantec ("Les Luttes entre Societies +humaines et leurs phases successives", Paris, 1893,) speaks; but he +remarks that at different stages of evolution, at different stages of +life the same weapons are not necessarily employed. Struggles of brute +force, armed hand to hand conflicts, may have been a necessity in the +early phases of human societies. Nowadays, although competition may +remain inevitable and indispensable, it can assume milder forms. +Economic rivalries, struggles between intellectual influences, suffice +to stimulate progress: the processes which these admit are, in the +actual state of civilisation, the only ones which attain their end +without waste, the only ones logical. From one end to the other of the +ladder of life, struggle is the order of the day; but more and more +as the higher rungs are reached, it takes on characters which are +proportionately more "humane." + +Reflections of this kind permit the introduction into the economic order +of limitations to the doctrine of "laisser faire, laisser passer." This +appeals, it is said, to the example of nature where creatures, left to +themselves, struggle without truce and without mercy; but the fact +is forgotten that upon industrial battlefields the conditions are +different. The competitors here are not left simply to their natural +energies: they are variously handicapped. A rich store of artificial +resources exists in which some participate and others do not. The sides +then are unequal; and as a consequence the result of the struggle is +falsified. "In the animal world," said De Laveleye ("Le socialisme +contemporain", page 384 (6th edition), Paris, 1891.), criticising +Spencer, "the fate of each creature is determined by its individual +qualities; whereas in civilised societies a man may obtain the highest +position and the most beautiful wife because he is rich and well-born, +although he may be ugly, idle or improvident; and then it is he who will +perpetuate the species. The wealthy man, ill constituted, incapable, +sickly, enjoys his riches and establishes his stock under the protection +of the laws." Haycraft in England and Jentsch in Germany have strongly +emphasised these "anomalies," which nevertheless are the rule. That is +to say that even from a Darwinian point of view all social reforms +can readily be justified which aim at diminishing, as Wallace said, +inequalities at the start. + +But we can go further still. Whence comes the idea that all measures +inspired by the sentiment of solidarity are contrary to Nature's +trend? Observe her carefully, and she will not give lessons only in +individualism. Side by side with the struggle for existence do we not +find in operation what Lanessan calls "association for existence." Long +ago, Espinas had drawn attention to "societies of animals," temporary or +permanent, and to the kind of morality that arose in them. Since then, +naturalists have often insisted upon the importance of various forms +of symbiosis. Kropotkin in "Mutual Aid" has chosen to enumerate many +examples of altruism furnished by animals to mankind. Geddes and Thomson +went so far as to maintain that "Each of the greater steps of progress +is in fact associated with an increased measure of subordination +of individual competition to reproductive or social ends, and of +interspecific competition to co-operative association." (Geddes and +Thomson, "The Evolution of Sex", page 311, London, 1889.) Experience +shows, according to Geddes, that the types which are fittest to surmount +great obstacles are not so much those who engage in the fiercest +competitive struggle for existence, as those who contrive to temper it. +From all these observations there resulted, along with a limitation +of Darwinian pessimism, some encouragement for the aspirations of the +collectivists. + +And Darwin himself would, doubtless, have subscribed to these +rectifications. He never insisted, like his rival, Wallace, upon the +necessity of the solitary struggle of creatures in a state of nature, +each for himself and against all. On the contrary, in "The Descent of +Man", he pointed out the serviceableness of the social instincts, and +corroborated Bagehot's statements when the latter, applying laws of +physics to politics, showed the great advantage societies derived from +intercourse and communion. Again, the theory of sexual evolution which +makes the evolution of types depend increasingly upon preferences, +judgments, mental factors, surely offers something to qualify what seems +hard and brutal in the theory of natural selection. + +But, as often happens with disciples, the Darwinians had out-Darwined +Darwin. The extravagancies of social Darwinism provoked a useful +reaction; and thus people were led to seek, even in the animal kingdom, +for facts of solidarity which would serve to justify humane effort. + +On quite another line, however, an attempt has been made to connect +socialist tendencies with Darwinian principles. Marx and Darwin have +been confronted; and writers have undertaken to show that the work of +the German philosopher fell readily into line with that of the English +naturalist and was a development of it. Such has been the endeavour of +Ferri in Italy and of Woltmann in Germany, not to mention others. The +founders of "scientific socialism" had, moreover, themselves thought of +this reconciliation. They make more than one allusion to Darwin in works +which appeared after 1859. And sometimes they use his theory to define +by contrast their own ideal. They remark that the capitalist system, by +giving free course to individual competition, ends indeed in a bellum +omnium contra omnes; and they make it clear that Darwinism, thus +understood, is as repugnant to them as to Duhring. + +But it is at the scientific and not at the moral point of view that they +place themselves when they connect their economic history with +Darwin's work. Thanks to this unifying hypothesis, they claim to have +constructed--as Marx does in his preface to "Das Kapital"--a veritable +natural history of social evolution. Engels speaks in praise of his +friend Marx as having discovered the true mainspring of history hidden +under the veil of idealism and sentimentalism, and as having proclaimed +in the primum vivere the inevitableness of the struggle for existence. +Marx himself, in "Das Kapital", indicated another analogy when he dwelt +upon the importance of a general technology for the explanation of this +psychology:--a history of tools which would be to social organs what +Darwinism is to the organs of animal species. And the very importance +they attach to tools, to apparatus, to machines, abundantly proves that +neither Marx nor Engels were likely to forget the special characters +which mark off the human world from the animal. The former always +remains to a great extent an artificial world. Inventions change the +face of its institutions. New modes of production revolutionise not only +modes of government, but modes even of collective thought. Therefore it +is that the evolution of society is controlled by laws special to it, of +which the spectacle of nature offers no suggestion. + +If, however, even in this special sphere, it can still be urged that +the evolution of the material conditions of society is in accord +with Darwin's theory, it is because the influence of the methods of +production is itself to be explained by the incessant strife of the +various classes with each other. So that in the end Marx, like Darwin, +finds the source of all progress in struggle. Both are grandsons of +Heraclitus:--polemos pater panton. It sometimes happens, in these days, +that the doctrine of revolutionary socialism is contrasted as rude and +healthy with what may seem to be the enervating tendency of "solidarist" +philanthropy: the apologists of the doctrine then pride themselves above +all upon their faithfulness to Darwinian principles. + +So far we have been mainly concerned to show the use that social +philosophies have made of the Darwinian laws for practical purposes: +in order to orientate society towards their ideals each school tries to +show that the authority of natural science is on its side. But even +in the most objective of theories, those which systematically make +abstraction of all political tendencies in order to study the social +reality in itself, traces of Darwinism are readily to be found. + +Let us take for example Durkheim's theory of Division of Labour ("De la +Division du Travail social", Paris, 1893.) The conclusions he +derives from it are that whenever professional specialisation causes +multiplication of distinct branches of activity, we get organic +solidarity--implying differences--substituted for mechanical solidarity, +based upon likenesses. The umbilical cord, as Marx said, which connects +the individual consciousness with the collective consciousness is cut. +The personality becomes more and more emancipated. But on what does this +phenomenon, so big with consequences, itself depend? The author goes to +social morphology for the answer: it is, he says, the growing density +of population which brings with it this increasing differentiation of +activities. But, again, why? Because the greater density, in thrusting +men up against each other, augments the intensity of their competition +for the means of existence; and for the problems which society thus has +to face differentiation of functions presents itself as the gentlest +solution. + +Here one sees that the writer borrows directly from Darwin. Competition +is at its maximum between similars, Darwin had declared; different +species, not laying claim to the same food, could more easily coexist. +Here lay the explanation of the fact that upon the same oak hundreds +of different insects might be found. Other things being equal, the same +applies to society. He who finds some unadopted speciality possesses a +means of his own for getting a living. It is by this division of their +manifold tasks that men contrive not to crush each other. Here +we obviously have a Darwinian law serving as intermediary in the +explanation of that progress of division of labour which itself explains +so much in the social evolution. + +And we might take another example, at the other end of the series of +sociological systems. G. Tarde is a sociologist with the most pronounced +anti-naturalistic views. He has attempted to show that all application +of the laws of natural science to society is misleading. In his +"Opposition Universelle" he has directly combatted all forms of +sociological Darwinism. According to him the idea that the evolution of +society can be traced on the same plan as the evolution of species is +chimerical. Social evolution is at the mercy of all kinds of inventions, +which by virtue of the laws of imitation modify, through individual to +individual, through neighbourhood to neighbourhood, the general state +of those beliefs and desires which are the only "quantities" whose +variation matters to the sociologist. But, it may be rejoined, that +however psychical the forces may be, they are none the less subject +to Darwinian laws. They compete with each other; they struggle for the +mastery of minds. Between types of ideas, as between organic forms, +selection operates. And though it may be that these types are ushered +into the arena by unexpected discoveries, we yet recognise in the +psychological accidents, which Tarde places at the base of everything, +near relatives of those small accidental variations upon which Darwin +builds. Thus, accepting Tarde's own representations, it is +quite possible to express in Darwinian terms, with the necessary +transpositions, one of the most idealistic sociologies that have ever +been constructed. + +These few examples suffice. They enable us to estimate the extent of the +field of influence of Darwinism. It affects sociology not only through +the agency of its advocates but through that of its opponents. The +questionings to which it has given rise have proved no less fruitful +than the solutions it has suggested. In short, few doctrines, in the +history of social philosophy, will have produced on their passage a +finer outcrop of ideas. + + + + +XXIV. THE INFLUENCE OF DARWIN UPON RELIGIOUS THOUGHT. By P.N. Waggett, +M.A., S.S.J.E. + + +I. + +The object of this paper is first to point out certain elements of the +Darwinian influence upon Religious thought, and then to show reason +for the conclusion that it has been, from a Christian point of view, +satisfactory. I shall not proceed further to urge that the Christian +apologetic in relation to biology has been successful. A variety of +opinions may be held on this question, without disturbing the conclusion +that the movements of readjustment have been beneficial to those who +remain Christians, and this by making them more Christian and not only +more liberal. The theologians may sometimes have retreated, but there +has been an advance of theology. I know that this account incurs +the charge of optimism. It is not the worst that could be made. The +influence has been limited in personal range, unequal, even divergent, +in operation, and accompanied by the appearance of waste and mischievous +products. The estimate which follows requires for due balance a full +development of many qualifying considerations. For this I lack space, +but I must at least distinguish my view from the popular one that our +difficulties about religion and natural science have come to an end. + +Concerning the older questions about origins--the origin of the world, +of species, of man, of reason, conscience, religion--a large measure of +understanding has been reached by some thoughtful men. But meanwhile +new questions have arisen, questions about conduct, regarding both +the reality of morals and the rule of right action for individuals and +societies. And these problems, still far from solution, may also be +traced to the influence of Darwin. For they arise from the renewed +attention to heredity, brought about by the search for the causes of +variation, without which the study of the selection of variations has no +sufficient basis. + +Even the existing understanding about origins is very far from +universal. On these points there were always thoughtful men who denied +the necessity of conflict, and there are still thoughtful men who deny +the possibility of a truce. + +It must further be remembered that the earlier discussion now, as I hope +to show, producing favourable results, created also for a time grave +damage, not only in the disturbance of faith and the loss of men--a +loss not repaired by a change in the currents of debate--but in what I +believe to be a still more serious respect. I mean the introduction of +a habit of facile and untested hypothesis in religious as in other +departments of thought. + +Darwin is not responsible for this, but he is in part the cause of +it. Great ideas are dangerous guests in narrow minds; and thus it has +happened that Darwin--the most patient of scientific workers, in whom +hypothesis waited upon research, or if it provisionally outstepped it +did so only with the most scrupulously careful acknowledgment--has led +smaller and less conscientious men in natural science, in history, and +in theology to an over-eager confidence in probable conjecture and a +loose grip upon the facts of experience. It is not too much to say that +in many quarters the age of materialism was the least matter-of-fact age +conceivable, and the age of science the age which showed least of the +patient temper of inquiry. + +I have indicated, as shortly as I could, some losses and dangers which +in a balanced account of Darwin's influence would be discussed at +length. + +One other loss must be mentioned. It is a defect in our thought which, +in some quarters, has by itself almost cancelled all the advantages +secured. I mean the exaggerated emphasis on uniformity or continuity; +the unwillingness to rest any part of faith or of our practical +expectation upon anything that from any point of view can be called +exceptional. The high degree of success reached by naturalists in +tracing, or reasonably conjecturing, the small beginnings of great +differences, has led the inconsiderate to believe that anything may in +time become anything else. + +It is true that this exaggeration of the belief in uniformity has +produced in turn its own perilous reaction. From refusing to believe +whatever can be called exceptional, some have come to believe whatever +can be called wonderful. + +But, on the whole, the discontinuous or highly various character of +experience received for many years too little deliberate attention. The +conception of uniformity which is a necessity of scientific description +has been taken for the substance of history. We have accepted a +postulate of scientific method as if it were a conclusion of scientific +demonstration. In the name of a generalisation which, however just on +the lines of a particular method, is the prize of a difficult exploit of +reflexion, we have discarded the direct impressions of experience; +or, perhaps it is more true to say, we have used for the criticism of +alleged experiences a doctrine of uniformity which is only valid in the +region of abstract science. For every science depends for its advance +upon limitation of attention, upon the selection out of the whole +content of consciousness of that part or aspect which is measurable by +the method of the science. Accordingly there is a science of life which +rightly displays the unity underlying all its manifestations. But there +is another view of life, equally valid, and practically sometimes more +important, which recognises the immediate and lasting effect of +crisis, difference, and revolution. Our ardour for the demonstration +of uniformity of process and of minute continuous change needs to be +balanced by a recognition of the catastrophic element in experience, and +also by a recognition of the exceptional significance for us of events +which may be perfectly regular from an impersonal point of view. + +An exorbitant jealousy of miracle, revelation, and ultimate moral +distinctions has been imported from evolutionary science into religious +thought. And it has been a damaging influence, because it has taken +men's attention from facts, and fixed them upon theories. + +II. + +With this acknowledgment of important drawbacks, requiring many words +for their proper description, I proceed to indicate certain results +of Darwin's doctrine which I believe to be in the long run wholly +beneficial to Christian thought. These are: + +The encouragement in theology of that evolutionary method of observation +and study, which has shaped all modern research: + +The recoil of Christian apologetics towards the ground of religious +experience, a recoil produced by the pressure of scientific criticism +upon other supports of faith: + +The restatement, or the recovery of ancient forms of statement, of the +doctrines of Creation and of divine Design in Nature, consequent upon +the discussion of evolution and of natural selection as its guiding +factor. + +(1) The first of these is quite possibly the most important of all. +It was well defined in a notable paper read by Dr Gore, now Bishop of +Birmingham, to the Church Congress at Shrewsbury in 1896. We have learnt +a new caution both in ascribing and in denying significance to items of +evidence, in utterance or in event. There has been, as in art, a study +of values, which secures perspective and solidity in our representation +of facts. On the one hand, a given utterance or event cannot be drawn +into evidence as if all items were of equal consequence, like sovereigns +in a bag. The question whence and whither must be asked, and the +particular thing measured as part of a series. Thus measured it is not +less truly important, but it may be important in a lower degree. On the +other hand, and for exactly the same reason, nothing that is real is +unimportant. The "failures" are not mere mistakes. We see them, in St +Augustine's words, as "scholar's faults which men praise in hope of +fruit." + +We cannot safely trace the origin of the evolutionistic method to the +influence of natural science. The view is tenable that theology led the +way. Probably this is a case of alternate and reciprocal debt. Quite +certainly the evolutionist method in theology, in Christian history, +and in the estimate of scripture, has received vast reinforcement +from biology, in which evolution has been the ever present and ever +victorious conception. + +(2) The second effect named is the new willingness of Christian thinkers +to take definite account of religious experience. This is related to +Darwin through the general pressure upon religious faith of scientific +criticism. The great advance of our knowledge of organisms has been an +important element in the general advance of science. It has acted, +by the varied requirements of the theory of organisms, upon all other +branches of natural inquiry, and it held for a long time that leading +place in public attention which is now occupied by speculative physics. +Consequently it contributed largely to our present estimation of science +as the supreme judge in all matters of inquiry (F.R. Tennant: "The Being +of God in the light of Physical Science", in "Essays on some theological +questions of the day". London, 1905.), to the supposed destruction of +mystery and the disparagement of metaphysic which marked the last age, +as well as to the just recommendation of scientific method in branches +of learning where the direct acquisitions of natural science had no +place. + +Besides this, the new application of the idea of law and mechanical +regularity to the organic world seemed to rob faith of a kind of refuge. +The romantics had, as Berthelot ("Evolutionisme et Platonisme", pages +45, 46, 47. Paris, 1908.) shows, appealed to life to redress the +judgments drawn from mechanism. Now, in Spencer, evolution gave us a +vitalist mechanic or mechanical vitalism, and the appeal seemed cut off. +We may return to this point later when we consider evolution; at +present I only endeavour to indicate that general pressure of scientific +criticism which drove men of faith to seek the grounds of reassurance +in a science of their own; in a method of experiment, of observation, +of hypothesis checked by known facts. It is impossible for me to do more +than glance across the threshold of this subject. But it is necessary to +say that the method is in an elementary stage of revival. The imposing +success that belongs to natural science is absent: we fall short of +the unchallengeable unanimity of the Biologists on fundamentals. The +experimental method with its sure repetitions cannot be applied to our +subject-matter. But we have something like the observational method of +palaeontology and geographical distribution; and in biology there are +still men who think that the large examination of varieties by way +of geography and the search of strata is as truly scientific, uses as +genuinely the logical method of difference, and is as fruitful in sure +conclusions as the quasi-chemical analysis of Mendelian laboratory work, +of which last I desire to express my humble admiration. Religion also +has its observational work in the larger and possibly more arduous +manner. + +But the scientific work in religion makes its way through difficulties +and dangers. We are far from having found the formula of its combination +with the historical elements of our apologetic. It is exposed, +therefore, to a damaging fire not only from unspiritualist psychology +and pathology but also from the side of scholastic dogma. It is hard to +admit on equal terms a partner to the old undivided rule of books and +learning. With Charles Lamb, we cry in some distress, "must knowledge +come to me, if it come at all, by some awkward experiment of intuition, +and no longer by this familiar process of reading?" ("Essays of Elia", +"New Year's Eve", page 41; Ainger's edition. London, 1899.) and we are +answered that the old process has an imperishable value, only we have +not yet made clear its connection with other contributions. And all +the work is young, liable to be drawn into unprofitable excursions, +side-tracked by self-deceit and pretence; and it fatally attracts, like +the older mysticism, the curiosity and the expository powers of those +least in sympathy with it, ready writers who, with all the air of +extended research, have been content with narrow grounds for induction. +There is a danger, besides, which accompanies even the most genuine +work of this science and must be provided against by all its serious +students. I mean the danger of unbalanced introspection both for +individuals and for societies; of a preoccupation comparable to our +modern social preoccupation with bodily health; of reflection upon +mental states not accompanied by exercise and growth of the mental +powers; the danger of contemplating will and neglecting work, of +analysing conviction and not criticising evidence. + +Still, in spite of dangers and mistakes, the work remains full of +hopeful indications, and, in the best examples (Such an example is given +in Baron F. von Hugel's recently finished book, the result of thirty +years' research: "The Mystical Element of Religion, as studied in +Saint Catherine of Genoa and her Friends". London, 1908.), it is truly +scientific in its determination to know the very truth, to tell what +we think, not what we think we ought to think. (G. Tyrrell, in +"Mediaevalism", has a chapter which is full of the important MORAL +element in a scientific attitude. "The only infallible guardian of truth +is the spirit of truthfulness." "Mediaevalism" page 182, London, 1908.), +truly scientific in its employment of hypothesis and verification, and +in growing conviction of the reality of its subject-matter through the +repeated victories of a mastery which advances, like science, in the +Baconian road of obedience. It is reasonable to hope that progress in +this respect will be more rapid and sure when religious study enlists +more men affected by scientific desire and endowed with scientific +capacity. + +The class of investigating minds is a small one, possibly even smaller +than that of reflecting minds. Very few persons at any period are able +to find out anything whatever. There are few observers, few discoverers, +few who even wish to discover truth. In how many societies the problems +of philology which face every person who speaks English are left +unattempted! And if the inquiring or the successfully inquiring class +of minds is small, much smaller, of course, is the class of those +possessing the scientific aptitude in an eminent degree. During the last +age this most distinguished class was to a very great extent absorbed +in the study of phenomena, a study which had fallen into arrears. For +we stood possessed, in rudiment, of means of observation, means for +travelling and acquisition, qualifying men for a larger knowledge than +had yet been attempted. These were now to be directed with new accuracy +and ardour upon the fabric and behaviour of the world of sense. Our +debt to the great masters in physical science who overtook and almost +out-stripped the task cannot be measured; and, under the honourable +leadership of Ruskin, we may all well do penance if we have failed "in +the respect due to their great powers of thought, or in the admiration +due to the far scope of their discovery." ("Queen of the Air", Preface, +page vii. London, 1906.) With what miraculous mental energy and divine +good fortune--as Romans said of their soldiers--did our men of curiosity +face the apparently impenetrable mysteries of nature! And how natural +it was that immense accessions of knowledge, unrelated to the spiritual +facts of life, should discredit Christian faith, by the apparent +superiority of the new work to the feeble and unprogressive knowledge of +Christian believers! The day is coming when men of this mental character +and rank, of this curiosity, this energy and this good fortune in +investigation, will be employed in opening mysteries of a spiritual +nature. They will silence with masterful witness the over-confident +denials of naturalism. They will be in danger of the widespread +recognition which thirty years ago accompanied every utterance of +Huxley, Tyndall, Spencer. They will contribute, in spite of adulation, +to the advance of sober religious and moral science. + +And this result will be due to Darwin, first because by raising the +dignity of natural science, he encouraged the development of the +scientific mind; secondly because he gave to religious students the +example of patient and ardent investigation; and thirdly because by the +pressure of naturalistic criticism the religious have been driven to +ascertain the causes of their own convictions, a work in which they were +not without the sympathy of men of science. (The scientific rank of its +writer justifies the insertion of the following letter from the late Sir +John Burdon-Sanderson to me. In the lecture referred to I had described +the methods of Professor Moseley in teaching Biology as affording a +suggestion of the scientific treatment of religion.) + +Oxford, April 30, 1902. + +Dear Sir, + +I feel that I must express to you my thanks for the discourse which I +had the pleasure of listening to yesterday afternoon. + +I do not mean to say that I was able to follow all that you said as to +the identity of Method in the two fields of Science and Religion, but I +recognise that the "mysticism" of which you spoke gives us the only way +by which the two fields can be brought into relation. + +Among much that was memorable, nothing interested me more than what you +said of Moseley. + +No one, I am sure, knew better than you the value of his teaching and in +what that value consisted. + +Yours faithfully + +J. Burdon-Sanderson. 31-2.) + +In leaving the subject of scientific religious inquiry, I will only add +that I do not believe it receives any important help--and certainly +it suffers incidentally much damaging interruption--from the study of +abnormal manifestations or abnormal conditions of personality. + +(3) Both of the above effects seem to me of high, perhaps the very +highest, importance to faith and to thought. But, under the third head, +I name two which are more directly traceable to the personal work of +Darwin, and more definitely characteristic of the age in which his +influence was paramount: viz. the influence of the two conceptions of +evolution and natural selection upon the doctrine of creation and of +design respectively. + +It is impossible here, though it is necessary for a complete sketch of +the matter, to distinguish the different elements and channels of this +Darwinian influence; in Darwin's own writings, in the vigorous polemic +of Huxley, and strangely enough, but very actually for popular thought, +in the teaching of the definitely anti-Darwinian evolutionist Spencer. + +Under the head of the directly and purely Darwinian elements I should +class as preeminent the work of Wallace and of Bates; for no two sets +of facts have done more to fix in ordinary intelligent minds a belief +in organic evolution and in natural selection as its guiding factor +than the facts of geographical distribution and of protective colour and +mimicry. The facts of geology were difficult to grasp and the public and +theologians heard more often of the imperfection than of the extent of +the geological record. The witness of embryology, depending to a great +extent upon microscopic work, was and is beyond the appreciation of +persons occupied in fields of work other than biology. + +III. + +From the influence in religion of scientific modes of thought we pass +to the influence of particular biological conceptions. The former effect +comes by way of analogy, example, encouragement and challenge; inspiring +or provoking kindred or similar modes of thought in the field of +theology; the latter by a collision of opinions upon matters of fact or +conjecture which seem to concern both science and religion. + +In the case of Darwinism the story of this collision is familiar, and +falls under the heads of evolution and natural selection, the doctrine +of descent with modification, and the doctrine of its guidance or +determination by the struggle for existence between related varieties. +These doctrines, though associated and interdependent, and in popular +thought not only combined but confused, must be considered separately. +It is true that the ancient doctrine of Evolution, in spite of the +ingenuity and ardour of Lamarck, remained a dream tantalising the +intellectual ambition of naturalists, until the day when Darwin made it +conceivable by suggesting the machinery of its guidance. And, further, +the idea of natural selection has so effectively opened the door of +research and stimulated observation in a score of principal directions +that, even if the Darwinian explanation became one day much less +convincing than, in spite of recent criticism, it now is, yet its +passing, supposing it to pass, would leave the doctrine of Evolution +immeasurably and permanently strengthened. For in the interests of the +theory of selection, "Fur Darwin," as Muller wrote, facts have been +collected which remain in any case evidence of the reality of descent +with modification. + +But still, though thus united in the modern history of convictions, +though united and confused in the collision of biological and +traditional opinion, yet evolution and natural selection must be +separated in theological no less than in biological estimation. +Evolution seemed inconsistent with Creation; natural selection with +Providence and Divine design. + +Discussion was maintained about these points for many years and with +much dark heat. It ranged over many particular topics and engaged minds +different in tone, in quality, and in accomplishment. There was at +most times a degree of misconception. Some naturalists attributed to +theologians in general a poverty of thought which belonged really to +men of a particular temper or training. The "timid theism" discerned in +Darwin by so cautious a theologian as Liddon (H.P. Liddon, "The Recovery +of S. Thomas"; a sermon preached in St Paul's, London, on April 23rd, +1882 (the Sunday after Darwin's death).) was supposed by many biologists +to be the necessary foundation of an honest Christianity. It was really +more characteristic of devout NATURALISTS like Philip Henry Gosse, +than of religious believers as such. (Dr Pusey ("Unscience not Science +adverse to Faith" 1878) writes: "The questions as to 'species,' of what +variations the animal world is capable, whether the species be more or +fewer, whether accidental variations may become hereditary... and +the like, naturally fall under the province of science. In all these +questions Mr Darwin's careful observations gained for him a deserved +approbation and confidence.") The study of theologians more considerable +and even more typically conservative than Liddon does not confirm the +description of religious intolerance given in good faith, but in serious +ignorance, by a disputant so acute, so observant and so candid as +Huxley. Something hid from each other's knowledge the devoted pilgrims +in two great ways of thought. The truth may be, that naturalists took +their view of what creation was from Christian men of science who +naturally looked in their own special studies for the supports and +illustrations of their religious belief. Of almost every laborious +student it may be said "Hic ab arte sua non recessit." And both the +believing and the denying naturalists, confining habitual attention to a +part of experience, are apt to affirm and deny with trenchant vigour +and something of a narrow clearness "Qui respiciunt ad pauca, de facili +pronunciant." (Aristotle, in Bacon, quoted by Newman in his "Idea of a +University", page 78. London, 1873.) + +Newman says of some secular teachers that "they persuade the world of +what is false by urging upon it what is true." Of some early opponents +of Darwin it might be said by a candid friend that, in all sincerity of +devotion to truth, they tried to persuade the world of what is true +by urging upon it what is false. If naturalists took their version +of orthodoxy from amateurs in theology, some conservative Christians, +instead of learning what evolution meant to its regular exponents, +took their view of it from celebrated persons, not of the front rank in +theology or in thought, but eager to take account of public movements +and able to arrest public attention. + +Cleverness and eloquence on both sides certainly had their share in +producing the very great and general disturbance of men's minds in the +early days of Darwinian teaching. But by far the greater part of that +disturbance was due to the practical novelty and the profound importance +of the teaching itself, and to the fact that the controversy about +evolution quickly became much more public than any controversy of equal +seriousness had been for many generations. + +We must not think lightly of that great disturbance because it has, in +some real sense, done its work, and because it is impossible in days +of more coolness and light, to recover a full sense of its very real +difficulties. + +Those who would know them better should add to the calm records of +Darwin ("Life and Letters" and "More Letters of Charles Darwin".) and to +the story of Huxley's impassioned championship, all that they can learn +of George Romanes. ("Life and Letters", London, 1896. "Thoughts on +Religion", London, 1895. "Candid Examination of Theism", London, 1878.) +For his life was absorbed in this very struggle and reproduced +its stages. It began in a certain assured simplicity of biblical +interpretation; it went on, through the glories and adventures of a +paladin in Darwin's train, to the darkness and dismay of a man who saw +all his most cherished beliefs rendered, as he thought, incredible. +("Never in the history of man has so terrific a calamity befallen the +race as that which all who look may now (viz. in consequence of the +scientific victory of Darwin) behold advancing as a deluge, black with +destruction, resistless in might, uprooting our most cherished hopes, +engulphing our most precious creed, and burying our highest life in +mindless destruction."--"A Candid Examination of Theism", page 51.) +He lived to find the freer faith for which process and purpose are +not irreconcilable, but necessary to one another. His development, +scientific, intellectual and moral, was itself of high significance; and +its record is of unique value to our own generation, so near the age of +that doubt and yet so far from it; certainly still much in need of +the caution and courage by which past endurance prepares men for +new emergencies. We have little enough reason to be sure that in the +discussions awaiting us we shall do as well as our predecessors in +theirs. Remembering their endurance of mental pain, their ardour +in mental labour, the heroic temper and the high sincerity of +controversialists on either side, we may well speak of our fathers in +such words of modesty and self-judgment as Drayton used when he sang the +victors of Agincourt. The progress of biblical study, in the departments +of Introduction and Exegesis, resulting in the recovery of a point +of view anciently tolerated if not prevalent, has altered some of the +conditions of that discussion. In the years near 1858, the witness of +Scripture was adduced both by Christian advocates and their critics as +if unmistakeably irreconcilable with Evolution. + +Huxley ("Science and Christian Tradition". London, 1904.) found the path +of the blameless naturalist everywhere blocked by "Moses": the believer +in revelation was generally held to be forced to a choice between +revealed cosmogony and the scientific account of origins. It is not +clear how far the change in Biblical interpretation is due to natural +science, and how far to the vital movements of theological study which +have been quite independent of the controversy about species. It belongs +to a general renewal of Christian movement, the recovery of a heritage. +"Special Creation"--really a biological rather than a theological +conception,--seems in its rigid form to have been a recent element even +in English biblical orthodoxy. + +The Middle Ages had no suspicion that religious faith forbad +inquiry into the natural origination of the different forms of life. +Bartholomaeus Anglicus, an English Franciscan of the thirteenth century, +was a mutationist in his way, as Aristotle, "the Philosopher" of +the Christian Schoolmen, had been in his. So late as the seventeenth +century, as we learn not only from early proceedings of the Royal +Society, but from a writer so homely and so regularly pious as +Walton, the variation of species and "spontaneous" generations had no +theological bearing, except as instances of that various wonder of the +world which in devout minds is food for devotion. + +It was in the eighteenth century that the harder statement took shape. +Something in the preciseness of that age, its exaltation of law, its +cold passion for a stable and measured universe, its cold denial, its +cold affirmation of the power of God, a God of ice, is the occasion of +that rigidity of religious thought about the living world which Darwin +by accident challenged, or rather by one of those movements of genius +which, Goethe ("No productiveness of the highest kind... is in the power +of anyone."--"Conversations of Goethe with Eckermann and Soret". London, +1850.) declares, are "elevated above all earthly control." + +If religious thought in the eighteenth century was aimed at a fixed and +nearly finite world of spirit, it followed in all these respects the +secular and critical lead. ("La philosophie reformatrice du XVIIIe +siecle" (Berthelot, "Evolutionisme et Platonisme", Paris, 1908, page +45.) ramenait la nature et la societe a des mecanismes que la pensee +reflechie peut concevoir et recomposer." In fact, religion in a +mechanical age is condemned if it takes any but a mechanical tone. +Butler's thought was too moving, too vital, too evolutionary, for the +sceptics of his time. In a rationalist, encyclopaedic period, religion +also must give hard outline to its facts, it must be able to display +its secret to any sensible man in the language used by all sensible men. +Milton's prophetic genius furnished the eighteenth century, out of the +depth of the passionate age before it, with the theological tone it was +to need. In spite of the austere magnificence of his devotion, he gives +to smaller souls a dangerous lead. The rigidity of Scripture exegesis +belonged to this stately but imperfectly sensitive mode of thought. It +passed away with the influence of the older rationalists whose precise +denials matched the precise and limited affirmations of the static +orthodoxy. + +I shall, then, leave the specially biblical aspect of the +debate--interesting as it is and even useful, as in Huxley's +correspondence with the Duke of Argyll and others in 1892 ("Times", +1892, passim.)--in order to consider without complication the permanent +elements of Christian thought brought into question by the teaching of +evolution. + +Such permanent elements are the doctrine of God as Creator of the +universe, and the doctrine of man as spiritual and unique. Upon both the +doctrine of evolution seemed to fall with crushing force. + +With regard to Man I leave out, acknowledging a grave omission, the +doctrine of the Fall and of Sin. And I do so because these have not yet, +as I believe, been adequately treated: here the fruitful reaction to the +stimulus of evolution is yet to come. The doctrine of sin, indeed, falls +principally within the scope of that discussion which has followed or +displaced the Darwinian; and without it the Fall cannot be usefully +considered. For the question about the Fall is a question not merely of +origins, but of the interpretation of moral facts whose moral reality +must first be established. + +I confine myself therefore to Creation and the dignity of man. + +The meaning of evolution, in the most general terms, is that the +differentiation of forms is not essentially separate from their +behaviour and use; that if these are within the scope of study, that is +also; that the world has taken the form we see by movements not unlike +those we now see in progress; that what may be called proximate origins +are continuous in the way of force and matter, continuous in the way of +life, with actual occurrences and actual characteristics. All this has +no revolutionary bearing upon the question of ultimate origins. The +whole is a statement about process. It says nothing to metaphysicians +about cause. It simply brings within the scope of observation or +conjecture that series of changes which has given their special +characters to the different parts of the world we see. In particular, +evolutionary science aspires to the discovery of the process or order +of the appearance of life itself: if it were to achieve its aim it +could say nothing of the cause of this or indeed of the most familiar +occurrences. We should have become spectators or convinced historians of +an event which, in respect of its cause and ultimate meaning, would be +still impenetrable. + +With regard to the origin of species, supposing life already +established, biological science has the well founded hopes and the +measure of success with which we are all familiar. All this has, it +would seem, little chance of collision with a consistent theism, a +doctrine which has its own difficulties unconnected with any particular +view of order or process. But when it was stated that species had +arisen by processes through which new species were still being made, +evolutionism came into collision with a statement, traditionally +religious, that species were formed and fixed once for all and long ago. + +What is the theological import of such a statement when it is regarded +as essential to belief in God? Simply that God's activity, with respect +to the formation of living creatures, ceased at some point in past time. + +"God rested" is made the touchstone of orthodoxy. And when, under the +pressure of the evidences, we found ourselves obliged to acknowledge and +assert the present and persistent power of God, in the maintenance and +in the continued formation of "types," what happened was the abolition +of a time-limit. We were forced only to a bolder claim, to a theistic +language less halting, more consistent, more thorough in its own line, +as well as better qualified to assimilate and modify such schemes as +Von Hartmann's philosophy of the unconscious--a philosophy, by the way, +quite intolerant of a merely mechanical evolution. (See Von Hartmann's +"Wahrheit und Irrthum in Darwinismus". Berlin, 1875.) + +Here was not the retrenchment of an extravagant assertion, but the +expansion of one which was faltering and inadequate. The traditional +statement did not need paring down so as to pass the meshes of a new and +exacting criticism. It was itself a net meant to surround and enclose +experience; and we must increase its size and close its mesh to hold +newly disclosed facts of life. The world, which had seemed a fixed +picture or model, gained first perspective and then solidity and +movement. We had a glimpse of organic HISTORY; and Christian thought +became more living and more assured as it met the larger view of life. + +However unsatisfactory the new attitude might be to our critics, to +Christians the reform was positive. What was discarded was a limitation, +a negation. The movement was essentially conservative, even actually +reconstructive. For the language disused was a language inconsistent +with the definitions of orthodoxy; it set bounds to the infinite, and by +implication withdrew from the creative rule all such processes as could +be brought within the descriptions of research. It ascribed fixity and +finality to that "creature" in which an apostle taught us to recognise +the birth-struggles of an unexhausted progress. It tended to banish +mystery from the world we see, and to confine it to a remote first age. + +In the reformed, the restored, language of religion, Creation became +again not a link in a rational series to complete a circle of the +sciences, but the mysterious and permanent relation between the infinite +and the finite, between the moving changes we know in part, and the +Power, after the fashion of that observation, unknown, which is itself +"unmoved all motion's source." (Hymn of the Church-- Rerum Deus tenax +vigor, Immotus in te permanens.) + +With regard to man it is hardly necessary, even were it possible, to +illustrate the application of this bolder faith. When the record of his +high extraction fell under dispute, we were driven to a contemplation of +the whole of his life, rather than of a part and that part out of sight. +We remembered again, out of Aristotle, that the result of a process +interprets its beginnings. We were obliged to read the title of such +dignity as we may claim, in results and still more in aspirations. + +Some men still measure the value of great present facts in life--reason +and virtue and sacrifice--by what a self-disparaged reason can collect +of the meaner rudiments of these noble gifts. Mr Balfour has admirably +displayed the discrepancy, in this view, between the alleged origin and +the alleged authority of reason. Such an argument ought to be used not +to discredit the confident reason, but to illuminate and dignify its +dark beginnings, and to show that at every step in the long course of +growth a Power was at work which is not included in any term or in all +the terms of the series. + +I submit that the more men know of actual Christian teaching, its +fidelity to the past, and its sincerity in face of discovery, the more +certainly they will judge that the stimulus of the doctrine of evolution +has produced in the long run vigour as well as flexibility in the +doctrine of Creation and of man. + +I pass from Evolution in general to Natural Selection. + +The character in religious language which I have for short called +mechanical was not absent in the argument from design as stated before +Darwin. It seemed to have reference to a world conceived as fixed. It +pointed, not to the plastic capacity and energy of living matter, but +to the fixed adaptation of this and that organ to an unchanging place or +function. + +Mr Hobhouse has given us the valuable phrase "a niche of organic +opportunity." Such a phrase would have borne a different sense in +non-evolutionary thought. In that thought, the opportunity was +an opportunity for the Creative Power, and Design appeared in the +preparation of the organism to fit the niche. The idea of the niche +and its occupant growing together from simpler to more complex mutual +adjustment was unwelcome to this teleology. If the adaptation was traced +to the influence, through competition, of the environment, the old +teleology lost an illustration and a proof. For the cogency of the proof +in every instance depended upon the absence of explanation. Where the +process of adaptation was discerned, the evidence of Purpose or Design +was weak. It was strong only when the natural antecedents were not +discovered, strongest when they could be declared undiscoverable. + +Paley's favourite word is "Contrivance"; and for him contrivance is +most certain where production is most obscure. He points out the +physiological advantage of the valvulae conniventes to man, and the +advantage for teleology of the fact that they cannot have been formed by +"action and pressure." What is not due to pressure may be attributed to +design, and when a "mechanical" process more subtle than pressure was +suggested, the case for design was so far weakened. The cumulative proof +from the multitude of instances began to disappear when, in selection, +a natural sequence was suggested in which all the adaptations might be +reached by the motive power of life, and especially when, as in Darwin's +teaching, there was full recognition of the reactions of life to the +stimulus of circumstance. "The organism fits the niche," said the +teleologist, "because the Creator formed it so as to fit." "The organism +fits the niche," said the naturalist, "because unless it fitted it +could not exist." "It was fitted to survive," said the theologian. +"It survives because it fits," said the selectionist. The two forms of +statement are not incompatible; but the new statement, by provision of +an ideally universal explanation of process, was hostile to a doctrine +of purpose which relied upon evidences always exceptional however +numerous. Science persistently presses on to find the universal +machinery of adaptation in this planet; and whether this be found in +selection, or in direct-effect, or in vital reactions resulting in large +changes, or in a combination of these and other factors, it must always +be opposed to the conception of a Divine Power here and there but not +everywhere active. + +For science, the Divine must be constant, operative everywhere and in +every quality and power, in environment and in organism, in stimulus and +in reaction, in variation and in struggle, in hereditary equilibrium, +and in "the unstable state of species"; equally present on both sides of +every strain, in all pressures and in all resistances, in short in +the general wonder of life and the world. And this is exactly what the +Divine Power must be for religious faith. + +The point I wish once more to make is that the necessary readjustment of +teleology, so as to make it depend upon the contemplation of the whole +instead of a part, is advantageous quite as much to theology as to +science. For the older view failed in courage. Here again our theism was +not sufficiently theistic. + +Where results seemed inevitable, it dared not claim them as God-given. +In the argument from Design it spoke not of God in the sense of +theology, but of a Contriver, immensely, not infinitely wise and good, +working within a world, the scene, rather than the ever dependent +outcome, of His Wisdom; working in such emergencies and opportunities +as occurred, by forces not altogether within His control, towards an end +beyond Himself. It gave us, instead of the awful reverence due to the +Cause of all substance and form, all love and wisdom, a dangerously +detached appreciation of an ingenuity and benevolence meritorious in aim +and often surprisingly successful in contrivance. + +The old teleology was more useful to science than to religion, and the +design-naturalists ought to be gratefully remembered by Biologists. +Their search for evidences led them to an eager study of adaptations +and of minute forms, a study such as we have now an incentive to in the +theory of Natural Selection. One hardly meets with the same ardour in +microscopical research until we come to modern workers. But the argument +from Design was never of great importance to faith. Still, to rid it of +this character was worth all the stress and anxiety of the gallant old +war. If Darwin had done nothing else for us, we are to-day deeply in +his debt for this. The world is not less venerable to us now, not less +eloquent of the causing mind, rather much more eloquent and sacred. +But our wonder is not that "the underjaw of the swine works under the +ground" or in any or all of those particular adaptations which Paley +collected with so much skill, but that a purpose transcending, though +resembling, our own purposes, is everywhere manifest; that what we live +in is a whole, mutually sustaining, eventful and beautiful, where the +"dead" forces feed the energies of life, and life sustains a stranger +existence, able in some real measure to contemplate the whole, of which, +mechanically considered, it is a minor product and a rare ingredient. +Here, again, the change was altogether positive. It was not the escape +of a vessel in a storm with loss of spars and rigging, not a shortening +of sail to save the masts and make a port of refuge. It was rather the +emergence from narrow channels to an open sea. We had propelled the +great ship, finding purchase here and there for slow and uncertain +movement. Now, in deep water, we spread large canvas to a favouring +breeze. + +The scattered traces of design might be forgotten or obliterated. But +the broad impression of Order became plainer when seen at due distance +and in sufficient range of effect, and the evidence of love and wisdom +in the universe could be trusted more securely for the loss of the +particular calculation of their machinery. + +Many other topics of faith are affected by modern biology. In some of +these we have learnt at present only a wise caution, a wise uncertainty. +We stand before the newly unfolded spectacle of suffering, silenced; +with faith not scientifically reassured but still holding fast certain +other clues of conviction. In many important topics we are at a loss. +But in others, and among them those I have mentioned, we have passed +beyond this negative state and find faith positively strengthened and +more fully expressed. + +We have gained also a language and a habit of thought more fit for the +great and dark problems that remain, less liable to damaging conflicts, +equipped for more rapid assimilation of knowledge. And by this change +biology itself is a gainer. For, relieved of fruitless encounters with +popular religion, it may advance with surer aim along the path of +really scientific life-study which was reopened for modern men by the +publication of "The Origin of Species". + +Charles Darwin regretted that, in following science, he had not done +"more direct good" ("Life and Letters", Vol. III. page 359.) to his +fellow-creatures. He has, in fact, rendered substantial service to +interests bound up with the daily conduct and hopes of common men; +for his work has led to improvements in the preaching of the Christian +faith. + + + + +XXV. THE INFLUENCE OF DARWINISM ON THE STUDY OF RELIGIONS. By Jane Ellen +Harrison. + +Hon. D.Litt. (Durham), Hon. LL.D. (Aberdeen), Staff Lecturer and +sometime Fellow of Newnham College, Cambridge. + +Corresponding member of the German Archaeological Institute. + +The title of my paper might well have been "the creation by Darwinism of +the scientific study of Religions," but that I feared to mar my tribute +to a great name by any shadow of exaggeration. Before the publication of +"The Origin of Species" and "The Descent of Man", even in the eighteenth +century, isolated thinkers, notably Hume and Herder, had conjectured +that the orthodox beliefs of their own day were developments from the +cruder superstitions of the past. These were however only particular +speculations of individual sceptics. Religion was not yet generally +regarded as a proper subject for scientific study, with facts to be +collected and theories to be deduced. A Congress of Religions such as +that recently held at Oxford would have savoured of impiety. + +In the brief space allotted me I can attempt only two things; first, +and very briefly, I shall try to indicate the normal attitude towards +religion in the early part of the last century; second, and in more +detail, I shall try to make clear what is the outlook of advanced +thinkers to-day. (To be accurate I ought to add "in Europe." I advisedly +omit from consideration the whole immense field of Oriental mysticism, +because it has remained practically untouched by the influence of +Darwinism.) From this second inquiry it will, I hope, be abundantly +manifest that it is the doctrine of evolution that has made this outlook +possible and even necessary. + +The ultimate and unchallenged presupposition of the old view was that +religion was a DOCTRINE, a body of supposed truths. It was in fact what +we should now call Theology, and what the ancients called Mythology. +Ritual was scarcely considered at all, and, when considered, it was held +to be a form in which beliefs, already defined and fixed as dogma, +found a natural mode of expression. This, it will be later shown, is +a profound error or rather a most misleading half-truth. Creeds, +doctrines, theology and the like are only a part, and at first the least +important part, of religion. + +Further, and the fact is important, this DOGMA, thus supposed to be +the essential content of the "true" religion, was a teleological scheme +complete and unalterable, which had been revealed to man once and for +all by a highly anthropomorphic God, whose existence was assumed. The +duty of man towards this revelation was to accept its doctrines and obey +its precepts. The notion that this revelation had grown bit by bit out +of man's consciousness and that his business was to better it would +have seemed rank blasphemy. Religion, so conceived, left no place for +development. "The Truth" might be learnt, but never critically examined; +being thus avowedly complete and final, it was doomed to stagnation. + +The details of this supposed revelation seem almost too naive for +enumeration. As Hume observed, "popular theology has a positive appetite +for absurdity." It is sufficient to recall that "revelation" included +such items as the Creation (It is interesting to note that the very +word "Creator" has nowadays almost passed into the region of mythology. +Instead we have "L'Evolution Creatrice".) of the world out of nothing in +six days; the making of Eve from one of Adam's ribs; the Temptation by +a talking snake; the confusion of tongues at the tower of Babel; the +doctrine of Original Sin; a scheme of salvation which demanded the +Virgin Birth, Vicarious Atonement, and the Resurrection of the material +body. The scheme was unfolded in an infallible Book, or, for one section +of Christians, guarded by the tradition of an infallible Church, and on +the acceptance or refusal of this scheme depended an eternity of weal or +woe. There is not one of these doctrines that has not now been recast, +softened down, mysticised, allegorised into something more conformable +with modern thinking. It is hard for the present generation, unless +their breeding has been singularly archaic, to realise that these +amazing doctrines were literally held and believed to constitute the +very essence of religion; to doubt them was a moral delinquency. + +It had not, however, escaped the notice of travellers and missionaries +that savages carried on some sort of practices that seemed to be +religious, and believed in some sort of spirits or demons. Hence, beyond +the confines illuminated by revealed truth, a vague region was assigned +to NATURAL Religion. The original revelation had been kept intact only +by one chosen people, the Jews, by them to be handed on to Christianity. +Outside the borders of this Goshen the world had sunk into the darkness +of Egypt. Where analogies between savage cults and the Christian +religions were observed, they were explained as degradations; the +heathen had somehow wilfully "lost the light." Our business was not to +study but, exclusively, to convert them, to root out superstition and +carry the torch of revelation to "Souls in heathen darkness lying." To +us nowadays it is a commonplace of anthropological research that we +must seek for the beginnings of religion in the religions of primitive +peoples, but in the last century the orthodox mind was convinced that +it possessed a complete and luminous ready-made revelation; the study of +what was held to be a mere degradation seemed idle and superfluous. + +But, it may be asked, if, to the orthodox, revealed religion was +sacrosanct and savage religion a thing beneath consideration, why did +not the sceptics show a more liberal spirit, and pursue to their logical +issue the conjectures they had individually hazarded? The reason is +simple and significant. The sceptics too had not worked free from +the presupposition that the essence of religion is dogma. Their +intellectualism, expressive of the whole eighteenth century, was +probably in England strengthened by the Protestant doctrine of an +infallible Book. Hume undoubtedly confused religion with dogmatic +theology. The attention of orthodox and sceptics alike was focussed on +the truth or falsity of certain propositions. Only a few minds of rare +quality were able dimly to conceive that religion might be a necessary +step in the evolution of human thought. + +It is not a little interesting to note that Darwin, who was leader and +intellectual king of his generation, was also in this matter to some +extent its child. His attitude towards religion is stated clearly, in +Chapter VIII. of the "Life and Letters". (Vol. I. page 304. For Darwin's +religious views see also "Descent of Man", 1871, Vol. I. page 65; 2nd +edition. Vol. I. page 142.) On board the "Beagle" he was simply orthodox +and was laughed at by several of the officers for quoting the Bible as +an unanswerable authority on some point of morality. By 1839 he had come +to see that the Old Testament was no more to be trusted than the sacred +books of the Hindoos. Next went the belief in miracles, and next Paley's +"argument from design" broke down before the law of natural selection; +the suffering so manifest in nature is seen to be compatible rather with +Natural Selection than with the goodness and omnipotence of God. Darwin +felt to the full all the ignorance that lay hidden under specious +phrases like "the plan of creation" and "Unity of design." Finally, he +tells us "the mystery of the beginning of all things is insoluble by us; +and I for one must be content to remain an Agnostic." + +The word Agnostic is significant not only of the humility of the man +himself but also of the attitude of his age. Religion, it is clear, +is still conceived as something to be KNOWN, a matter of true or +false OPINION. Orthodox religion was to Darwin a series of erroneous +hypotheses to be bit by bit discarded when shown to be untenable. The +ACTS of religion which may result from such convictions, i.e. devotion +in all its forms, prayer, praise, sacraments, are left unmentioned. +It is clear that they are not, as now to us, sociological survivals +of great interest and importance, but rather matters too private, too +personal, for discussion. + +Huxley, writing in the "Contemporary Review" (1871.), says, "In a dozen +years "The Origin of Species" has worked as complete a revolution in +biological science as the "Principia" did in astronomy." It has done +so because, in the words of Helmholtz, it contained "an essentially +new creative thought," that of the continuity of life, the absence of +breaks. In the two most conservative subjects, Religion and Classics, +this creative ferment was slow indeed to work. Darwin himself felt +strongly "that a man should not publish on a subject to which he has +not given special and continuous thought," and hence wrote little on +religion and with manifest reluctance, though, as already seen, in +answer to pertinacious inquiry he gave an outline of his own views. But +none the less he foresaw that his doctrine must have, for the history +of man's mental evolution, issues wider than those with which he was +prepared personally to deal. He writes, in "The Origin of Species" +(6th edition, page 428.), "In the future I see open fields for far +more important researches. Psychology will be securely based on +the foundation already well laid by Mr Herbert Spencer, that of the +necessary acquirement of each mental power and capacity by gradation." + +Nowhere, it is true, does Darwin definitely say that he regarded +religion as a set of phenomena, the development of which may be studied +from the psychological standpoint. Rather we infer from his PIETY--in +the beautiful Roman sense--towards tradition and association, that +religion was to him in some way sacrosanct. But it is delightful to see +how his heart went out towards the new method in religious study which +he had himself, if half-unconsciously, inaugurated. Writing in 1871 to +Dr Tylor, on the publication of his "Primitive Culture", he says ("Life +and Letters", Vol. III. page 151.), "It is wonderful how you trace +animism from the lower races up the religious belief of the highest +races. It will make me for the future look at religion--a belief in the +soul, etc.--from a new point of view." + +Psychology was henceforth to be based on "the necessary acquirement of +each mental capacity by gradation." With these memorable words the +door closes on the old and opens on the new horizon. The mental focus +henceforth is not on the maintaining or refuting of an orthodoxy but +on the genesis and evolution of a capacity, not on perfection but on +process. Continuous evolution leaves no gap for revelation sudden and +complete. We have henceforth to ask, not when was religion revealed +or what was the revelation, but how did religious phenomena arise and +develop. For an answer to this we turn with new and reverent eyes to +study "the heathen in his blindness" and the child "born in sin." We +still indeed send out missionaries to convert the heathen, but here +at least in Cambridge before they start they attend lectures on +anthropology and comparative religion. The "decadence" theory is dead +and should be buried. + +The study of primitive religions then has been made possible and even +inevitable by the theory of Evolution. We have now to ask what new facts +and theories have resulted from that study. This brings us to our second +point, the advanced outlook on religion to-day. + +The view I am about to state is no mere personal opinion of my own. +To my present standpoint I have been led by the investigations of such +masters as Drs Wundt, Lehmann, Preuss, Bergson, Beck and in our own +country Drs Tylor and Frazer. (I can only name here the books that +have specially influenced my own views. They are W. Wundt, +"Volkerpsychologie", Leipzig, 1900, P. Beck, "Die Nachahmung", Leipzig, +1904, and "Erkenntnisstheorie des primitiven Denkens" in "Zeitschrift +f. Philos. und Philos. Kritik", 1903, page 172, and 1904, page 9. Henri +Bergson, "L'Evolution Creatrice" and "Matiere et Memoire", 1908, K. Th. +Preuss, various articles published in the "Globus" (see page 507, note +1), and in the "Archiv. f. Religionswissenschaft", and for the subject +of magic, MM. Hubert et Mauss, "Theorie generale de la Magie", in +"L'Annee Sociologique", VII.) + +Religion always contains two factors. First, a theoretical factor, what +a man THINKS about the unseen--his theology, or, if we prefer so to call +it, his mythology. Second, what he DOES in relation to this unseen--his +ritual. These factors rarely if ever occur in complete separation; they +are blended in very varying proportions. Religion we have seen was +in the last century regarded mainly in its theoretical aspect as a +doctrine. Greek religion for example meant to most educated persons +Greek mythology. Yet even a cursory examination shows that neither +Greek nor Roman had any creed or dogma, any hard and fast formulation +of belief. In the Greek Mysteries (See my "Prolegomena to the Study of +Greek Religion", page 155, Cambridge, 1903.) only we find what we should +call a Confiteor; and this is not a confession of faith, but an avowal +of rites performed. When the religion of primitive peoples came to be +examined it was speedily seen that though vague beliefs necessarily +abound, definite creeds are practically non-existent. Ritual is dominant +and imperative. + +This predominance and priority of ritual over definite creed was first +forced upon our notice by the study of savages, but it promptly and +happily joined hands with modern psychology. Popular belief says, I +think, therefore I act; modern scientific psychology says, I act (or +rather, REact to outside stimulus), and so I come to think. Thus there +is set going a recurrent series: act and thought become in their turn +stimuli to fresh acts and thoughts. In examining religion as envisaged +to-day it would therefore be more correct to begin with the practice +of religion, i.e. ritual, and then pass to its theory, theology or +mythology. But it will be more convenient to adopt the reverse +method. The theoretical content of religion is to those of us who are +Protestants far more familiar and we shall thus proceed from the known +to the comparatively unknown. + +I shall avoid all attempt at rigid definition. The problem before the +modern investigator is, not to determine the essence and definition of +religion but to inquire how religious phenomena, religious ideas and +practices arose. Now the theoretical content of religion, the domain of +theology or mythology, is broadly familiar to all. It is the world of +the unseen, the supersensuous; it is the world of what we call the soul +and the supposed objects of the soul's perception, sprites, demons, +ghosts and gods. How did this world grow up? + +We turn to our savages. Intelligent missionaries of bygone days used to +ply savages with questions such as these: Had they any belief in God? +Did they believe in the immortality of the soul? Taking their own +clear-cut conceptions, discriminated by a developed terminology, these +missionaries tried to translate them into languages that had neither the +words nor the thoughts, only a vague, inchoate, tangled substratum, out +of which these thoughts and words later differentiated themselves. Let +us examine this substratum. + +Nowadays we popularly distinguish between objective and subjective; +and further, we regard the two worlds as in some sense opposed. To +the objective world we commonly attribute some reality independent of +consciousness, while we think of the subjective as dependent for its +existence on the mind. The objective world consists of perceptible +things, or of the ultimate constituents to which matter is reduced by +physical speculation. The subjective world is the world of beliefs, +hallucinations, dreams, abstract ideas, imaginations and the like. +Psychology of course knows that the objective and subjective worlds are +interdependent, inextricably intertwined, but for practical purposes the +distinction is convenient. + +But primitive man has not yet drawn the distinction between objective +and subjective. Nay, more, it is foreign to almost the whole of ancient +philosophy. Plato's Ideas (I owe this psychological analysis of the +elements of the primitive supersensuous world mainly to Dr Beck, +"Erkenntnisstheorie des primitiven Denkens", see page 498, note 1.), his +Goodness, Truth, Beauty, his class-names, horse, table, are it is true +dematerialised as far as possible, but they have outside existence, +apart from the mind of the thinker, they have in some shadowy way +spatial extension. Yet ancient philosophies and primitive man alike +needed and possessed for practical purposes a distinction which served +as well as our subjective and objective. To the primitive savage all his +thoughts, every object of which he was conscious, whether by perception +or conception, had reality, that is, it had existence outside himself, +but it might have reality of various kinds or different degrees. + +It is not hard to see how this would happen. A man's senses may mislead +him. He sees the reflection of a bird in a pond. To his eyes it is a +real bird. He touches it, HE PUTS IT TO THE TOUCH, and to his touch it +is not a bird at all. It is real then, but surely not quite so real as +a bird that you can touch. Again, he sees smoke. It is real to his eyes. +He tries to grasp it, it vanishes. The wind touches him, but he cannot +see it, which makes him feel uncanny. The most real thing is that which +affects most senses and especially what affects the sense of touch. +Apparently touch is the deepest down, most primitive, of senses. The +rest are specialisations and complications. Primitive man has no formal +rubric "optical delusion," but he learns practically to distinguish +between things that affect only one sense and things that affect two or +more--if he did not he would not survive. But both classes of things are +real to him. Percipi est esse. + +So far, primitive man has made a real observation; there are things that +appeal to one sense only. But very soon creeps in confusion fraught with +disaster. He passes naturally enough, being economical of any mental +effort, from what he really sees but cannot feel to what he thinks +he sees, and gives to it the same secondary reality. He has dreams, +visions, hallucinations, nightmares. He dreams that an enemy is beating +him, and he wakes rubbing his head. Then further he remembers things; +that is, for him, he sees them. A great chief died the other day and +they buried him, but he sees him still in his mind, sees him in his +war-paint, splendid, victorious. So the image of the past goes together +with his dreams and visions to the making of this other less real, +but still real world, his other-world of the supersensuous, the +supernatural, a world, the outside existence of which, independent of +himself, he never questions. + +And, naturally enough, the future joins the past in this supersensuous +world. He can hope, he can imagine, he can prophesy. And again the +images of his hope are real; he sees them with that mind's eye which +as yet he has not distinguished from his bodily eye. And so the +supersensuous world grows and grows big with the invisible present, and +big also with the past and the future, crowded with the ghosts of the +dead and shadowed with oracles and portents. It is this supersensuous, +supernatural world which is the eternity, the other-world, of primitive +religion, not an endlessness of time, but a state removed from full +sensuous reality, a world in which anything and everything may happen, +a world peopled by demonic ancestors and liable to a splendid vagueness, +to a "once upon a time-ness" denied to the present. It not unfrequently +happens that people who know that the world nowadays obeys fixed laws +have no difficulty in believing that six thousand years ago man was +made direct from a lump of clay, and woman was made from one of man's +superfluous ribs. + +The fashioning of the supersensuous world comes out very clearly in +primitive man's views about the soul and life after death. Herbert +Spencer noted long ago the influence of dreams in forming a belief in +immortality, but being very rational himself, he extended to primitive +man a quite alien quality of rationality. Herbert Spencer argued that +when a savage has a dream he seeks to account for it, and in so doing +invents a spirit world. The mistake here lies in the "seeks to account +for it." (Primitive man, as Dr Beck observes, is not impelled by an +Erkenntnisstrieb. Dr Beck says he has counted upwards of 30 of these +mythological Triebe (tendencies) with which primitive man has been +endowed.) Man is at first too busy LIVING to have any time for +disinterested THINKING. He dreams a dream and it is real for him. He +does not seek to account for it any more than for his hands and feet. He +cannot distinguish between a CONception and a PERception, that is all. +He remembers his ancestors or they appear to him in a dream; therefore +they are alive still, but only as a rule to about the third generation. +Then he remembers them no more and they cease to be. + +Next as regards his own soul. He feels something within him, +his life-power, his will to live, his power to act, his +personality--whatever we like to call it. He cannot touch this thing +that is himself, but it is real. His friend too is alive and one day he +is dead; he cannot move, he cannot act. Well, something has gone that +was his friend's self. He has stopped breathing. Was it his breath? or +he is bleeding; is it his blood? This life-power IS something; does it +live in his heart or his lungs or his midriff? He did not see it go; +perhaps it is like wind, an anima, a Geist, a ghost. But again it comes +back in a dream, only looking shadowy; it is not the man's life, it is +a thin copy of the man; it is an "image" (eidolon). It is like that +shifting distorted thing that dogs the living man's footsteps in the +sunshine; it is a "shade" (skia). (The two conceptions of the soul, as a +life-essence, inseparable from the body, and as a separable phantom seem +to occur in most primitive systems. They are distinct conceptions but +are inextricably blended in savage thought. The two notions Korperseele +and Psyche have been very fully discussed in Wundt's "Volkerpsychologie" +II. pages 1-142, Leipzig, 1900.) + +Ghosts and sprites, ancestor worship, the soul, oracles, prophecy; all +these elements of the primitive supersensuous world we willingly admit +to be the proper material of religion; but other elements are more +surprising; such are class-names, abstract ideas, numbers, geometrical +figures. We do not nowadays think of these as of religious content, but +to primitive men they were all part of the furniture of his supernatural +world. + +With respect to class-names, Dr Tylor ("Primitive Culture", Vol. II. +page 245 (4th edition), 1903.) has shown how instructive are the first +attempts of the savage to get at the idea of a class. Things in which +similarity is observed, things indeed which can be related at all are +to the savage KINDRED. A species is a family or a number of individuals +with a common god to look after them. Such for example is the Finn +doctrine of the haltia. Every object has its haltia, but the haltiat +were not tied to the individual, they interested themselves in every +member of the species. Each stone had its haltia, but that haltia was +interested in other stones; the individuals disappeared, the haltia +remained. + +Nor was it only class-names that belonged to the supersensuous world. A +man's own proper-name is a sort of spiritual essence of him, a kind +of soul to be carefully concealed. By pronouncing a name you bring the +thing itself into being. When Elohim would create Day "he called out to +the Light 'Day,' and to the Darkness he called out 'Night'"; the great +magician pronounced the magic Names and the Things came into being. "In +the beginning was the Word" is literally true, and this reflects the +fact that our CONCEPTUAL world comes into being by the mental process of +naming. (For a full discussion of this point see Beck, "Nachahmung" page +41, "Die Sprache".) In old times people went further; they thought that +by naming events they could bring them to be, and custom even to-day +keeps up the inveterate magical habit of wishing people "Good Morning" +and a "Happy Christmas." + +Number, too, is part of the supersensuous world that is thoroughly +religious. We can see and touch seven apples, but seven itself, that +wonderful thing that shifts from object to object, giving it +its SEVENness, that living thing, for it begets itself anew in +multiplication--surely seven is a fit denizen of the upper-world. +Originally all numbers dwelt there, and a certain supersensuous sanctity +still clings to seven and three. We still say "Holy, Holy, Holy," and in +some mystic way feel the holier. + +The soul and the supersensuous world get thinner and thinner, rarer and +more rarified, but they always trail behind them clouds of smoke and +vapour from the world of sense and space whence they have come. It is +difficult for us even nowadays to use the word "soul" without lapsing +into a sensuous mythology. The Cartesians' sharp distinction between res +extensa non cogitans and res cogitans non extansa is remote. + +So far then man, through the processes of his thinking, has provided +himself with a supersensuous world, the world of sense-delusion, of +smoke and cloud, of dream and phantom, of imagination, of name and +number and image. The natural course would now seem to be that this +supersensuous world should develop into the religious world as we know +it, that out of a vague animism with ghosts of ancestors, demons, +and the like, there should develop in due order momentary gods +(Augenblicks-Gotter), tribal gods, polytheism, and finally a pure +monotheism. + +This course of development is usually assumed, but it is not I think +quite what really happens. The supersensuous world as we have got it so +far is too theoretic to be complete material of religion. It is indeed +only one factor, or rather it is as it were a lifeless body that waits +for a living spirit to possess and inform it. Had the theoretic factor +remained uninformed it would eventually have separated off into its +constituent elements of error and truth, the error dying down as a +belated metaphysic, the truth developing into a correct and scientific +psychology of the subjective. But man has ritual as well as mythology; +that is, he feels and acts as well as thinks; nay more he probably feels +and acts long before he definitely thinks. This contradicts all our +preconceived notions of theology. Man, we imagine, believes in a god +or gods and then worships. The real order seems to be that, in a sense +presently to be explained, he worships, he feels and acts, and out +of his feeling and action, projected into his confused thinking, +he develops a god. We pass therefore to our second factor in +religion:--ritual. + +The word "ritual" brings to our modern minds the notion of a church +with a priesthood and organised services. Instinctively we think of a +congregation meeting to confess sins, to receive absolution, to pray, +to praise, to listen to sermons, and possibly to partake of sacraments. +Were we to examine these fully developed phenomena we should hardly get +further in the analysis of our religious conceptions than the notion +of a highly anthropomorphic god approached by purely human methods of +personal entreaty and adulation. + +Further, when we first come to the study of primitive religions we +expect a priori to find the same elements, though in a ruder form. We +expect to see "The heathen in his blindness bow down to wood and stone," +but the facts that actually confront us are startlingly dissimilar. +Bowing down to wood and stone is an occupation that exists mainly in the +minds of hymn-writers. The real savage is more actively engaged. Instead +of asking a god to do what he wants done, he does it or tries to do +it himself; instead of prayers he utters spells. In a word he is busy +practising magic, and above all he is strenuously engaged in dancing +magical dances. When the savage wants rain or wind or sunshine, he does +not go to church; he summons his tribe and they dance a rain-dance or +wind-dance or sun-dance. When a savage goes to war we must not picture +his wife on her knees at home praying for the absent; instead we must +picture her dancing the whole night long; not for mere joy of heart +or to pass the weary hours; she is dancing his war-dance to bring him +victory. + +Magic is nowadays condemned alike by science and by religion; it is +both useless and impious. It is obsolete, and only practised by malign +sorcerers in obscure holes and corners. Undoubtedly magic is neither +religion nor science, but in all probability it is the spiritual +protoplasm from which religion and science ultimately differentiated. +As such the doctrine of evolution bids us scan it closely. Magic may +be malign and private; nowadays it is apt to be both. But in early days +magic was as much for good as for evil; it was publicly practised for +the common weal. + +The gist of magic comes out most clearly in magical dances. We think of +dancing as a light form of recreation, practised by the young from sheer +joie de vivre and unsuitable for the mature. But among the Tarahumares +(Carl Lumholtz, "Unknown Mexico", page 330, London, 1903.) in Mexico the +word for dancing, nolavoa, means "to work." Old men will reproach young +men saying "Why do you not go to work?" meaning why do you not dance +instead of only looking on. The chief religious sin of which the +Tarahumare is conscious is that he has not danced enough and not made +enough tesvino, his cereal intoxicant. + +Dancing then is to the savage WORKING, DOING, and the dance is in its +origin an imitation or perhaps rather an intensification of processes of +work. (Karl Bucher, "Arbeit und Rhythmus", Leipzig (3rd edition), 1902, +passim.) Repetition, regular and frequent, constitutes rhythm and rhythm +heightens the sense of will power in action. Rhythmical action may even, +as seen in the dances of Dervishes, produce a condition of ecstasy. +Ecstasy among primitive peoples is a condition much valued; it is often, +though not always, enhanced by the use of intoxicants. Psychologically +the savage starts from the sense of his own will power, he stimulates +it by every means at his command. Feeling his will strongly and knowing +nothing of natural law he recognises no limits to his own power; he +feels himself a magician, a god; he does not pray, he WILLS. Moreover +he wills collectively (The subject of collective hallucination as an +element in magic has been fully worked out by MM. Hubert and Mauss. +"Theorie generale de la Magie", In "L'Annee Sociologique", 1902--3, page +140.), reinforced by the will and action of his whole tribe. Truly of +him it may be said "La vie deborde l'intelligence, l'intelligence c'est +un retrecissement." (Henri Bergson, "L'Evolution Creatrice", page 50.) + +The magical extension and heightening of personality come out very +clearly in what are rather unfortunately known as MIMETIC dances. Animal +dances occur very frequently among primitive peoples. The dancers +dress up as birds, beasts, or fishes, and reproduce the characteristic +movements and habits of the animals impersonated. (So characteristic is +this impersonation in magical dancing that among the Mexicans the +word for magic, navali, means "disguise." K. Th. Preuss, "Archiv f. +Religionswissenschaft", 1906, page 97.) A very common animal dance is +the frog-dance. When it rains the frogs croak. If you desire rain you +dress up like a frog and croak and jump. We think of such a performance +as a conscious imitation. The man, we think, is more or less LIKE a +frog. That is not how primitive man thinks; indeed, he scarcely thinks +at all; what HE wants done the frog can do by croaking and jumping, so +he croaks and jumps and, for all he can, BECOMES a frog. "L'intelligence +animale JOUE sans doute les representations plutot qu'elle ne les +pense." (Bergson, "L'Evolution Creatrice", page 205.) + +We shall best understand this primitive state of mind if we study +the child "born in sin." If a child is "playing at lions" he does not +IMITATE a lion, i.e. he does not consciously try to be a thing more or +less like a lion, he BECOMES one. His reaction, his terror, is the same +as if the real lion were there. It is this childlike power of utter +impersonation, of BEING the thing we act or even see acted, this +extension and intensification of our own personality that lives deep +down in all of us and is the very seat and secret of our joy in the +drama. + +A child's mind is indeed throughout the best clue to the understanding +of savage magic. A young and vital child knows no limit to his own will, +and it is the only reality to him. It is not that he wants at the outset +to fight other wills, but that they simply do not exist for him. Like +the artist he goes forth to the work of creation, gloriously alone. His +attitude towards other recalcitrant wills is "they simply must." Let +even a grown man be intoxicated, be in love, or subject to an intense +excitement, the limitations of personality again fall away. Like the +omnipotent child he is again a god, and to him all things are possible. +Only when he is old and weary does he cease to command fate. + +The Iroquois (Hewitt, "American Anthropologist", IV. I. page 32, 1902, +N.S.) of North America have a word, orenda, the meaning of which is +easier to describe than to define, but it seems to express the very soul +of magic. This orenda is your power to do things, your force, sometimes +almost your personality. A man who hunts well has much and good orenda; +the shy bird who escapes his snares has a fine orenda. The orenda of the +rabbit controls the snow and fixes the depth to which it will fall. When +a storm is brewing the magician is said to be making its orenda. When +you yourself are in a rage, great is your orenda. The notes of birds +are utterances of their orenda. When the maize is ripening, the Iroquois +know it is the sun's heat that ripens it, but they know more; it is the +cigala makes the sun to shine and he does it by chirping, by uttering +his orenda. This orenda is sometimes very like the Greek thumos, your +bodily life, your vigour, your passion, your power, the virtue that is +in you to feel and do. This notion of orenda, a sort of pan-vitalism, is +more fluid than animism, and probably precedes it. It is the projection +of man's inner experience, vague and unanalysed, into the outer world. + +The mana of the Melanesians (Codrington, "The Melanesians", pages 118, +119, 192, Oxford, 1891.) is somewhat more specialised--all men do not +possess mana--but substantially it is the same idea. Mana is not only a +force, it is also an action, a quality, a state, at once a substantive, +an adjective, and a verb. It is very closely neighboured by the idea +of sanctity. Things that have mana are tabu. Like orenda it manifests +itself in noises, but specially mysterious ones, it is mana that is +rustling in the trees. Mana is highly contagious, it can pass from a +holy stone to a man or even to his shadow if it cross the stone. "All +Melanesian religion," Dr Codrington says, "consists in getting mana +for oneself or getting it used for one's benefit." (Codrington, "The +Melanesians", page 120, Oxford, 1891.) + +Specially instructive is a word in use among the Omaka (See Prof. +Haddon, "Magic and Fetishism", page 60, London, 1906. Dr Vierkandt +("Globus", July, 1907, page 41) thinks that "Fernzauber" is a later +development from Nahzauber.), wazhin-dhedhe, "directive energy, to +send." This word means roughly what we should call telepathy, sending +out your thought or will-power to influence another and affect his +action. Here we seem to get light on what has always been a puzzle, the +belief in magic exercised at a distance. For the savage will, distance +is practically non-existent, his intense desire feels itself as +non-spatial. (This notion of mana, orenda, wazhin-dhedhe and the like +lives on among civilised peoples in such words as the Vedic brahman in +the neuter, familiar to us in its masculine form Brahman. The neuter, +brahman, means magic power of a rite, a rite itself, formula, charm, +also first principle, essence of the universe. It is own cousin to the +Greek dunamis and phusis. See MM. Hubert et Mauss, "Theorie generale de +la Magie", page 117, in "L'Annee Sociologique", VII.) + +Through the examination of primitive ritual we have at last got at one +tangible, substantial factor in religion, a real live experience, the +sense, that is, of will, desire, power actually experienced in person +by the individual, and by him projected, extended into the rest of the +world. + +At this stage it may fairly be asked, though the question cannot with +any certainty be answered, "at what point in the evolution of man does +this religious experience come in?" + +So long as an organism reacts immediately to outside stimulus, with a +certainty and conformity that is almost chemical, there is, it would +seem, no place, no possibility for magical experience. But when the +germ appears of an intellect that can foresee an end not immediately +realised, or rather when a desire arises that we feel and recognise as +not satisfied, then comes in the sense of will and the impulse magically +to intensify that will. The animal it would seem is preserved by +instinct from drawing into his horizon things which do not immediately +subserve the conservation of his species. But the moment man's +life-power began to make on the outside world demands not immediately +and inevitably realised in action (I owe this observation to Dr K. Th. +Preuss. He writes ("Archiv f. Relig." 1906, page 98), "Die Betonung des +Willens in den Zauberakten ist der richtige Kern. In der Tat muss der +Mensch den Willen haben, sich selbst und seiner Umgebung besondere +Fahigkeiten zuzuschreiben, und den Willen hat er, sobald sein Verstand +ihn befahigt, EINE UBER DEN INSTINKT HINAUSGEHEN DER FURSORGE fur +sich zu zeigen. SO LANGE IHN DER INSTINKT ALLEIN LEITET, KONNEN +ZAUBERHANDLUNGEN NICHT ENSTEHEN." For more detailed analysis of the +origin of magic, see Dr Preuss "Ursprung der Religion und Kunst", +"Globus", LXXXVI. and LXXXVII.), then a door was opened to magic, and +in the train of magic followed errors innumerable, but also religion, +philosophy, science and art. + +The world of mana, orenda, brahman is a world of feeling, desiring, +willing, acting. What element of thinking there may be in it is not yet +differentiated out. But we have already seen that a supersensuous world +of thought grew up very early in answer to other needs, a world of +sense-illusions, shadows, dreams, souls, ghosts, ancestors, names, +numbers, images, a world only wanting as it were the impulse of mana to +live as a religion. Which of the two worlds, the world of thinking or +the world of doing, developed first it is probably idle to inquire. (If +external stimuli leave on organisms a trace or record such as is known +as an Engram, this physical basis of memory and hence of thought is +almost coincident with reaction of the most elementary kind. See Mr +Francis Darwin's Presidential Address to the British Association, +Dublin, 1908, page 8, and again Bergson places memory at the very root +of conscious existence, see "L'Evolution Creatrice", page 18, "le +fond meme de notre existence consciente est memoire, c'est a dire +prolongation du passee dans le present," and again "la duree mord dans +le temps et y laisse l'enpreint de son dent," and again, "l'Evolution +implique une continuation reelle du passee par le present.") + +It is more important to ask, Why do these two worlds join? Because, +it would seem, mana, the egomaniac or megalomaniac element, cannot get +satisfied with real things, and therefore goes eagerly out to a false +world, the supersensuous other-world whose growth we have sketched. This +junction of the two is fact, not fancy. Among all primitive peoples dead +men, ghosts, spirits of all kinds, become the chosen vehicle of mana. +Even to this day it is sometimes urged that religion, i.e. belief in +the immortality of the soul, is true "because it satisfies the deepest +craving of human nature." The two worlds, of mana and magic on the one +hand, of ghosts and other-world on the other, combine so easily because +they have the same laws, or rather the same comparative absence of law. +As in the world of dreams and ghosts, so in the world of mana, space and +time offer no obstacles; with magic all things are possible. In the one +world what you imagine is real; in the other what you desire is ipso +facto accomplished. Both worlds are egocentric, megalomaniac, filled to +the full with unbridled human will and desire. + +We are all of us born in sin, in that sin which is to science +"the seventh and deadliest," anthropomorphism, we are egocentric, +ego-projective. Hence necessarily we make our gods in our own image. +Anthropomorphism is often spoken of in books on religion and mythology +as if it were a last climax, a splendid final achievement in religious +thought. First, we are told, we have the lifeless object as god +(fetichism), then the plant or animal (phytomorphism, theriomorphism), +and last God is incarnate in the human form divine. This way of putting +things is misleading. Anthropomorphism lies at the very beginning of +our consciousness. Man's first achievement in thought is to realise that +there is anything at all not himself, any object to his subject. When +he has achieved however dimly this distinction, still for long, for very +long he can only think of those other things in terms of himself; plants +and animals are people with ways of their own, stronger or weaker than +himself but to all intents and purposes human. + +Again the child helps us to understand our own primitive selves. To +children animals are always people. You promise to take a child for a +drive. The child comes up beaming with a furry bear in her arms. You say +the bear cannot go. The child bursts into tears. You think it is because +the child cannot endure to be separated from a toy. It is no such thing. +It is the intolerable hurt done to the bear's human heart--a hurt not +to be healed by any proffer of buns. He wanted to go, but he was a shy, +proud bear, and he would not say so. + +The relation of magic to religion has been much disputed. According to +one school religion develops out of magic, according to another, though +they ultimately blend, they are at the outset diametrically opposed, +magic being a sort of rudimentary and mistaken science (This view held +by Dr Frazer is fully set forth in his "Golden Bough" (2nd edition), +pages 73-79, London, 1900. It is criticised by Mr R.R. Marett in "From +Spell to Prayer", "Folk-Lore" XI. 1900, page 132, also very fully by +MM. Hubert and Mauss, "Theorie generale de la Magie", in "L'Annee +Sociologique", VII. page 1, with Mr Marett's view and with that of MM. +Hubert and Mauss I am in substantial agreement.), religion having to do +from the outset with spirits. + +But, setting controversy aside, at the present stage of our inquiry +their relation becomes, I think, fairly clear. Magic is, if my view +(This view as explained above is, I believe, my own most serious +contribution to the subject. In thinking it out I was much helped by +Prof. Gilbert Murray.) be correct, the active element which informs a +supersensuous world fashioned to meet other needs. This blend of +theory and practice it is convenient to call religion. In practice the +transition from magic to religion, from Spell to Prayer, has always been +found easy. So long as mana remains impersonal you order it about; when +it is personified and bulks to the shape of an overgrown man, you drop +the imperative and cringe before it. "My will be done" is magic, +"Thy Will be done" is the last word in religion. The moral discipline +involved in the second is momentous, the intellectual advance not +striking. + +I have spoken of magical ritual as though it were the informing +life-spirit without which religion was left as an empty shell. Yet the +word ritual does not, as normally used, convey to our minds this notion +of intense vitalism. Rather we associate ritual with something cut +and dried, a matter of prescribed form and monotonous repetition. The +association is correct; ritual tends to become less and less informed by +the life-impulse, more and more externalised. Dr Beck ("Die Nachahmung +und ihre Bedeutung fur Psychologie und Volkerkunde", Leipzig, 1904.) +in his brilliant monograph on "Imitation" has laid stress on the almost +boundless influence of the imitation of one man by another in the +evolution of civilisation. Imitation is one of the chief spurs to +action. Imitation begets custom, custom begets sanctity. At first all +custom is sacred. To the savage it is as much a religious duty to tattoo +himself as to sacrifice to his gods. But certain customs naturally +survive, because they are really useful; they actually have good +effects, and so need no social sanction. Others are really useless; +but man is too conservative and imitative to abandon them. These become +ritual. Custom is cautious, but la vie est aleatoire. (Bergson, op. cit. +page 143.) + +Dr Beck's remarks on ritual are I think profoundly true and suggestive, +but with this reservation--they are true of ritual only when uninformed +by personal experience. The very elements in ritual on which Dr +Beck lays such stress, imitation, repetition, uniformity and social +collectivity, have been found by the experience of all time to have +a twofold influence--they inhibit the intellect, they stimulate and +suggest emotion, ecstasy, trance. The Church of Rome knows what she is +about when she prescribes the telling of the rosary. Mystery-cults and +sacraments, the lineal descendants of magic, all contain rites charged +with suggestion, with symbols, with gestures, with half-understood +formularies, with all the apparatus of appeal to emotion and will--the +more unintelligible they are the better they serve their purpose of +inhibiting thought. Thus ritual deadens the intellect and stimulates +will, desire, emotion. "Les operations magiques... sont le resultat d'une +science et d'une habitude qui exaltent la volonte humaine au-dessus de +ses limites habituelles." (Eliphas Levi, "Dogme et Rituel de la haute +Magie", II. page 32, Paris, 1861, and "A defence of Magic", by Evelyn +Underhill, "Fortnightly Review", 1907.) It is this personal EXPERIENCE, +this exaltation, this sense of immediate, non-intellectual revelation, +of mystical oneness with all things, that again and again rehabilitates +a ritual otherwise moribund. + +To resume. The outcome of our examination of ORIGINES seems to be that +religious phenomena result from two delusive processes--a delusion of +the non-critical intellect, a delusion of the over-confident will. Is +religion then entirely a delusion? I think not. (I am deeply conscious +that what I say here is a merely personal opinion or sentiment, +unsupported and perhaps unsupportable by reason, and very possibly quite +worthless, but for fear of misunderstanding I prefer to state it.) Every +dogma religion has hitherto produced is probably false, but for all that +the religious or mystical spirit may be the only way of apprehending +some things and these of enormous importance. It may also be that the +contents of this mystical apprehension cannot be put into language +without being falsified and misstated, that they have rather to be felt +and lived than uttered and intellectually analysed, and thus do not +properly fall under the category of true or false, in the sense in which +these words are applied to propositions; yet they may be something +for which "true" is our nearest existing word and are often, if not +necessary at least highly advantageous to life. That is why man through +a series of more or less grossly anthropomorphic mythologies and +theologies with their concomitant rituals tries to restate them. +Meantime we need not despair. Serious psychology is yet young and has +only just joined hands with physiology. Religious students are still +hampered by mediaevalisms such as Body and Soul, and by the perhaps +scarcely less mythological segregations of Intellect, Emotion, Will. But +new facts (See the "Proceedings" of the Society for Psychical Research, +London, passim, and especially Vols. VII.-XV. For a valuable collection +of the phenomena of mysticism, see William James, "Varieties of +Religious Experience", Edinburgh, 1901-2.) are accumulating, facts about +the formation and flux of personality, and the relations between the +conscious and the sub-conscious. Any moment some great imagination may +leap out into the dark, touch the secret places of life, lay bare the +cardinal mystery of the marriage of the spatial with the non-spatial. It +is, I venture to think, towards the apprehension of such mysteries, +not by reason only, but by man's whole personality, that the religious +spirit in the course of its evolution through ancient magic and modern +mysticism is ever blindly yet persistently moving. + +Be this as it may, it is by thinking of religion in the light of +evolution, not as a revelation given, not as a realite faite but as a +process, and it is so only, I think, that we attain to a spirit of real +patience and tolerance. We have ourselves perhaps learnt laboriously +something of the working of natural law, something of the limitations of +our human will, and we have therefore renounced the practice of magic. +Yet we are bidden by those in high places to pray "Sanctify this water +to the mystical washing away of sin." Mystical in this connection spells +magical, and we have no place for a god-magician: the prayer is to us +unmeaning, irreverent. Or again, after much toil we have ceased, or +hope we have ceased, to think anthropomorphically. Yet we are invited +to offer formal thanks to God for a meal of flesh whose sanctity is the +last survival of that sacrifice of bulls and goats he has renounced. +Such a ritual confuses our intellect and fails to stir our emotion. But +to others this ritual, magical or anthropomorphic as it is, is charged +with emotional impulse, and others, a still larger number, think that +they act by reason when really they are hypnotised by suggestion and +tradition; their fathers did this or that and at all costs they must do +it. It was good that primitive man in his youth should bear the yoke of +conservative custom; from each man's neck that yoke will fall, when and +because he has outgrown it. Science teaches us to await that moment with +her own inward and abiding patience. Such a patience, such a gentleness +we may well seek to practise in the spirit and in the memory of Darwin. + + + + +XXVI. EVOLUTION AND THE SCIENCE OF LANGUAGE. By P. Giles, M.A., LL.D. +(Aberdeen), + +Reader in Comparative Philology in the University of Cambridge. + + +In no study has the historical method had a more salutary influence +than in the Science of Language. Even the earliest records show that the +meaning of the names of persons, places, and common objects was then, as +it has always been since, a matter of interest to mankind. And in every +age the common man has regarded himself as competent without special +training to explain by inspection (if one may use a mathematical phrase) +the meaning of any words that attracted his attention. Out of this +amateur etymologising has sprung a great amount of false history, a kind +of historical mythology invented to explain familiar names. A single +example will illustrate the tendency. According to the local legend the +ancestor of the Earl of Erroll--a husbandman who stayed the flight of +his countrymen in the battle of Luncarty and won the victory over the +Danes by the help of the yoke of his oxen--exhausted with the fray +uttered the exclamation "Hoch heigh!" The grateful king about to ennoble +the victorious ploughman at once replied: + + "Hoch heigh! said ye + And Hay shall ye be." + +The Norman origin of the name Hay is well-known, and the battle of +Luncarty long preceded the appearance of Normans in Scotland, but the +legend nevertheless persists. + +Though the earliest European treatise on philological questions which +is now extant--the "Cratylus" of Plato,--as might be expected from its +authorship, contains some acute thinking and some shrewd guesses, yet +the work as a whole is infantine in its handling of language, and it +has been doubted whether Plato was more than half serious in some of +the suggestions which he puts forward. (For an account of the "Cratylus" +with references to other literature see Sandys' "History of Classical +Scholarship", I. page 92 ff., Cambridge, 1903.) In the hands of the +Romans things were worse even than they had been in the hands of Plato +and his Greek successors. The lack of success on the part of Varro and +later Roman writers may have been partly due to the fact that, from the +etymological point of view, Latin is a much more difficult language than +Greek; it is by no means so closely connected with Greek as the ancients +imagined, and they had no knowledge of the Celtic languages from which, +on some sides at least, much greater light on the history of the +Latin language might have been obtained. Roman civilisation was a late +development compared with Greek, and its records dating earlier than +300 B.C.--a period when the best of Greek literature was already in +existence--are very few and scanty. Varro it is true was much more of +an antiquary than Plato, but his extant works seem to show that he was +rather a "dungeon of learning" than an original thinker. + +A scientific knowledge of language can be obtained only by comparison +of different languages of the same family and the contrasting of their +characteristics with those of another family or other families. It never +occurred to the Greeks that any foreign language was worthy of serious +study. Herodotus and other travellers and antiquaries indeed picked up +individual words from various languages, either as being necessary +in communication with the inhabitants of the countries where they +sojourned, or because of some point which interested them personally. +Plato and others noticed the similarity of some Phrygian words to Greek, +but no systematic comparison seems ever to have been instituted. + +In the Middle Ages the treatment of language was in a sense more +historical. The Middle Ages started with the hypothesis, derived +from the book of Genesis, that in the early world all men were of one +language and of one speech. Though on the same authority they believed +that the plain of Shinar has seen that confusion of tongues whence +sprang all the languages upon earth, they seem to have considered that +the words of each separate language were nevertheless derived from this +original tongue. And as Hebrew was the language of the Chosen People, +it was naturally assumed that this original tongue was Hebrew. Hence +we find Dante declaring in his treatise on the Vulgar Tongue (Dante "de +Vulgari Eloquio", I. 4.) that the first word man uttered in Paradise +must have been "El," the Hebrew name of his Maker, while as a result of +the fall of Adam, the first utterance of every child now born into this +world of sin and misery is "heu," Alas! After the splendidly engraved +bronze plates containing, as we now know, ritual regulations for certain +cults, were discovered in 1444 at the town of Gubbio, in Umbria, they +were declared, by some authorities, to be written in excellent Hebrew. +The study of them has been the fascination and the despair of many a +philologist. Thanks to the devoted labours of numerous scholars, mainly +in the last sixty years, the general drift of these inscriptions is +now known. They are the only important records of the ancient Umbrian +language, which was related closely to that of the Samnites and, +though not so closely, to that of the Romans on the other side of +the Apennines. Yet less than twenty years ago a book was published in +Germany, which boasts itself the home of Comparative Philology, +wherein the German origin of the Umbrian language was no less solemnly +demonstrated than had been its Celtic origin by Sir William Betham in +1842. + +It is good that the study of language should be historical, but the +first requisite is that the history should be sound. How little had been +learnt of the true history of language a century ago may be seen from a +little book by Stephen Weston first published in 1802 and several +times reprinted, where accidental assonance is considered sufficient to +establish connection. Is there not a word "bad" in English and a word +"bad" in Persian which mean the same thing? Clearly therefore Persian +and English must be connected. The conclusion is true, but it is drawn +from erroneous premises. As stated, this identity has no more value +than the similar assonance between the English "cover" and the Hebrew +"kophar", where the history of "cover" as coming through French from a +Latin "co-operire" was even in 1802 well-known to many. To this day, +in spite of recent elaborate attempts (Most recently in H. Moller's +"Semitisch und Indogermanisch", Erster Teil, Kopenhagen, 1907.) to +establish connection between the Indo-Germanic and the Semitic families +of languages, there is no satisfactory evidence of such relation between +these families. This is not to deny the possibility of such a connection +at a very early period; it is merely to say that through the lapse +of long ages all trustworthy record of such relationship, if it ever +existed, has been, so far as present knowledge extends, obliterated. + +But while Stephen Weston was publishing, with much public approval, his +collection of amusing similarities between languages--similarities which +proved nothing--the key to the historical study of at least one family +of languages had already been found by a learned Englishman in a distant +land. In 1783 Sir William Jones had been sent out as a judge in the +supreme court of judicature in Bengal. While still a young man at Oxford +he was noted as a linguist; his reputation as a Persian scholar had +preceded him to the East. In the intervals of his professional duties +he made a careful study of the language which was held sacred by +the natives of the country in which he was living. He was mainly +instrumental in establishing a society for the investigation of language +and related subjects. He was himself the first president of the society, +and in the "third anniversary discourse" delivered on February 2, 1786, +he made the following observations: "The Sanscrit language, whatever be +its antiquity, is of a wonderful structure; more perfect than the GREEK, +more copious than the LATIN, and more exquisitely refined than either, +yet bearing to both of them a stronger affinity, both in the roots +of verbs and in the forms of grammar, than could possibly have been +produced by accident; so strong indeed, that no philologer could examine +them all three, without believing them to have sprung from some common +source, which, perhaps, no longer exists: there is a similar reason, +though not quite so forcible, for supposing that both the Gothick and +the Celtick, though blended with a very different idiom, had the same +origin with the Sanscrit; and the old Persian might be added to the same +family, if this was the place for discussing any question concerning the +antiquities of Persia." ("Asiatic Researches", I. page 422, "Works of +Sir W. Jones", I. page 26, London, 1799.) + +No such epoch-making discovery was probably ever announced with less +flourish of trumpets. Though Sir William Jones lived for eight years +more and delivered other anniversary discourses, he added nothing of +importance to this utterance. He had neither the time nor the health +that was needed for the prosecution of so arduous an undertaking. + +But the good seed did not fall upon stony ground. The news was speedily +conveyed to Europe. By a happy chance, the sudden renewal of war between +France and England in 1803 gave Friedrich Schlegel the opportunity of +learning Sanscrit from Alexander Hamilton, an Englishman who, like many +others, was confined in Paris during the long struggle with Napoleon. +The influence of Schlegel was not altogether for good in the history of +this research, but he was inspiring. Not upon him but upon Franz Bopp, +a struggling German student who spent some time in Paris and London +a dozen years later, fell the mantle of Sir William Jones. In Bopp's +Comparative Grammar of the Indo-Germanic languages which appeared in +1833, three-quarters of a century ago, the foundations of Comparative +Philology were laid. Since that day the literature of the subject has +grown till it is almost, if not altogether, beyond the power of any +single man to cope with it. But long as the discourse may be, it is but +the elaboration of the text that Sir William Jones supplied. + +With the publication of Bopp's Comparative Grammar the historical study +of language was put upon a stable footing. Needless to say much remained +to be done, much still remains to be done. More than once there has been +danger of the study following erroneous paths. Its terminology and its +point of view have in some degree changed. But nothing can shake the +truth of the statement that the Indo-Germanic languages constitute in +themselves a family sprung from the same source, marked by the same +characteristics, and differentiated from all other languages by +formation, by vocabulary, and by syntax. The historical method was +applied to language long before it reached biology. Nearly a quarter of +a century before Charles Darwin was born, Sir William Jones had made the +first suggestion of a comparative study of languages. Bopp's Comparative +Grammar began to be published nine years before the first draft of +Darwin's treatise on the Origin of Species was put on paper in 1842. + +It is not therefore on the history of Comparative Philology in general +that the ideas of Darwin have had most influence. Unfortunately, as +Jowett has said in the introduction to his translation of Plato's +"Republic", most men live in a corner. The specialisation of knowledge +has many advantages, but it has also disadvantages, none worse perhaps +than that it tends to narrow the specialist's horizon and to make it +more difficult for one worker to follow the advances that are being made +by workers in other departments. No longer is it possible as in earlier +days for an intellectual prophet to survey from a Pisgah height all the +Promised Land. And the case of linguistic research has been specially +hard. This study has, if the metaphor may be allowed, a very extended +frontier. On one side it touches the domain of literature, on other +sides it is conterminous with history, with ethnology and anthropology, +with physiology in so far as language is the production of the brain and +tissues of a living being, with physics in questions of pitch and stress +accent, with mental science in so far as the principles of similarity, +contrast, and contiguity affect the forms and the meanings of words +through association of ideas. The territory of linguistic study +is immense, and it has much to supply which might be useful to the +neighbours who border on that territory. But they have not regarded her +even with that interest which is called benevolent because it is not +actively maleficent. As Horne Tooke remarked a century ago, Locke had +found a whole philosophy in language. What have the philosophers done +for language since? The disciples of Kant and of Wilhelm von Humboldt +supplied her plentifully with the sour grapes of metaphysics; otherwise +her neighbours have left her severely alone save for an occasional +"Ausflug," on which it was clear they had sadly lost their bearings. +Some articles in Psychological Journals, Wundt's great work on +"Volkerpsychologie" (Erster Band: "Die Sprache", Leipzig, 1900. New +edition, 1904. This work has been fertile in producing both opponents +and supporters. Delbruck, "Grundfragen der Sprachforschung", +Strassburg, 1901, with a rejoinder by Wundt, "Sprachgeschichte" and +"Sprachpsychologie", Leipzig, 1901; L. Sutterlin, "Das Wesen der +Sprachgebilde", Heidelberg, 1902; von Rozwadowski, "Wortbildung +und Wortbedeutung", Heidelberg, 1904; O. Dittrich, "Grundzuge der +Sprachpsychologie", Halle, 1904, Ch. A. Sechehaye, "Programme et +methodes de la linguistique theorique", Paris, 1908.), and Mauthner's +brilliantly written "Beitrage zu einer Kritik der Sprache" (In three +parts: (i) "Sprache und Psychologie, (ii) "Zur Sprachwissenschaft", both +Stuttgart 1901, (iii) "Zur Grammatic und Logik" (with index to all three +volumes), Stuttgart and Berlin, 1902.) give some reason to hope that, on +one side at least, the future may be better than the past. + +Where Charles Darwin's special studies came in contact with the Science +of Language was over the problem of the origin and development of +language. It is curious to observe that, where so many fields of +linguistic research have still to be reclaimed--many as yet can hardly +be said to be mapped out,--the least accessible field of all--that +of the Origin of Language--has never wanted assiduous tillers. +Unfortunately it is a field beyond most others where it may be said that + +"Wilding oats and luckless darnel grow." + +If Comparative Philology is to work to purpose here, it must be on +results derived from careful study of individual languages and groups of +languages. But as yet the group which Sir William Jones first mapped out +and which Bopp organised is the only one where much has been achieved. +Investigation of the Semitic group, in some respects of no less moment +in the history of civilisation and religion, where perhaps the labour +of comparison is not so difficult, as the languages differ less among +themselves, has for some reason strangely lagged behind. Some years ago +in the "American Journal of Philology" Paul Haupt pointed out that if +advance was to be made, it must be made according to the principles +which had guided the investigation of the Indo-Germanic languages to +success, and at last a Comparative Grammar of an elaborate kind is in +progress also for the Semitic languages. (Brockelmann, "Vergleichende +Grammatik der semitischen Sprachen", Berlin, 1907 ff. Brockelmann and +Zimmern had earlier produced two small hand-books. The only large work +was William Wright's "Lectures on the Comparative Grammar of the +Semitic Languages", Cambridge, 1890.) For the great group which includes +Finnish, Hungarian, Turkish and many languages of northern Asia, a +beginning, but only a beginning has been made. It may be presumed from +the great discoveries which are in progress in Turkestan that presently +much more will be achieved in this field. But for a certain utterance +to be given by Comparative Philology on the question of the origin of +language it is necessary that not merely for these languages but also +for those in other quarters of the globe, the facts should be collected, +sifted and tabulated. England rules an empire which contains a greater +variety of languages by far than were ever held under one sway before. +The Government of India is engaged in producing, under the editorship of +Dr Grierson, a linguistic survey of India, a remarkable undertaking and, +so far as it has gone, a remarkable achievement. Is it too much to ask +that, with the support of the self-governing colonies, a similar survey +should be undertaken for the whole of the British Empire? + +Notwithstanding the great number of books that have been written on the +origin of language in the last three and twenty centuries, the results +of the investigation which can be described as certain are very meagre. +The question originally raised was whether language came into being +thesei or phusei, by convention or by nature. The first alternative, in +its baldest form at least, has passed from out the field of controversy. +No one now claims that names were given to living things or objects or +activities by formal agreement among the members of an early community, +or that the first father of mankind passed in review every living thing +and gave it its name. Even if the record of Adam's action were to be +taken literally there would still remain the question, whence had he +this power? Did he develop it himself or was it a miraculous gift with +which he was endowed at his creation? If the latter, then as Wundt says +("Volkerpsychologie", I. 2, page 585.), "the miracle of language is +subsumed in the miracle of creation." If Adam developed language of +himself, we are carried over to the alternative origin of phusei. On +this hypothesis we must assume that the natural growth which modern +theories of development regard as the painful progress of multitudinous +generations was contracted into the experience of a single individual. + +But even if the origin of language is admitted to be NATURAL there may +still be much variety of signification attached to the word: NATURE, +like most words which are used by philosophers, has accumulated +many meanings, and as research into the natural world proceeds, is +accumulating more. + +Forty years ago an animated controversy raged among the supporters of +the theories which were named for short the bow-wow, the pooh-pooh and +the ding-dong theories of the origin of language. The third, which was +the least tenacious of life, was made known to the English-speaking +world by the late Professor Max Muller who, however, when questioned, +repudiated it as his own belief. ("Science of Thought", London, 1887, +page 211.) It was taken by him from Heyse's lectures on language which +were published posthumously by Steinthal. Put shortly the theory is +that "everything which is struck, rings. Each substance has its peculiar +ring. We can tell the more or less perfect structure of metals by their +vibrations, by the answer which they give. Gold rings differently +from tin, wood rings differently from stone; and different sounds are +produced according to the nature of each percussion. It may be the same +with man, the most highly organised of nature's work." (Max Muller as +above, translating from Heyse.) Max Muller's repudiation of this theory +was, however, not very whole-hearted for he proceeds later in the same +argument: "Heyse's theory, which I neither adopted nor rejected, but +which, as will be seen, is by no means incompatible with that which for +many years has been gaining on me, and which of late has been so clearly +formulated by Professor Noire, has been assailed with ridicule and torn +to pieces, often by persons who did not even suspect how much truth was +hidden behind its paradoxical appearance. We are still very far from +being able to identify roots with nervous vibrations, but if it should +appear hereafter that sensuous vibrations supply at least the raw +material of roots, it is quite possible that the theory, proposed by +Oken and Heyse, will retain its place in the history of the various +attempts at solving the problem of the origin of language, when other +theories, which in our own days were received with popular applause, +will be completely forgotten." ("Science of Thought", page 212.) + +Like a good deal else that has been written on the origin of language, +this statement perhaps is not likely to be altogether clear to the plain +man, who may feel that even the "raw material of roots" is some distance +removed from nervous vibrations, though obviously without the existence +of afferent and efferent nerves articulate speech would be impossible. +But Heyse's theory undoubtedly was that every thought or idea which +occurred to the mind of man for the first time had its own special +phonetic expression, and that this responsive faculty, when its object +was thus fulfilled, became extinct. Apart from the philosophical +question whether the mind acts without external stimulus, into which it +is not necessary to enter here, it is clear that this theory can neither +be proved nor disproved, because it postulates that this faculty existed +only when language first began, and later altogether disappeared. As we +have already seen, it is impossible for us to know what happened at the +first beginnings of language, because we have no information from any +period even approximately so remote; nor are we likely to attain it. +Even in their earliest stages the great families of language which +possess a history extending over many centuries--the Indo-Germanic and +the Semitic--have very little in common. With the exception of Chinese, +the languages which are apparently of a simpler or more primitive +formation have either a history which, compared with that of the +families mentioned, is very short, or, as in the case of the vast +majority, have no history beyond the time extending only over a few +years or, at most, a few centuries when they have been observed by +competent scholars of European origin. But, if we may judge by the +history of geology and other studies, it is well to be cautious in +assuming for the first stages of development forces which do not operate +in the later, unless we have direct evidence of their existence. + +It is unnecessary here to enter into a prolonged discussion of the other +views christened by Max Muller, not without energetic protest from their +supporters, the bow-wow and pooh-pooh theories of language. Suffice it +to say that the former recognises as a source of language the imitation +of the sounds made by animals, the fall of bodies into water or on +to solid substances and the like, while the latter, also called the +interjectional theory, looks to the natural ejaculations produced by +particular forms of effort for the first beginnings of speech. It would +be futile to deny that some words in most languages come from +imitation, and that others, probably fewer in number, can be traced +to ejaculations. But if either of these sources alone or both in +combination gave rise to primitive speech, it clearly must have been a +simple form of language and very limited in amount. There is no reason +to think that it was otherwise. Presumably in its earliest stages +language only indicated the most elementary ideas, demands for food +or the gratification of other appetites, indications of danger, useful +animals and plants. Some of these, such as animals or indications of +danger, could often be easily represented by imitative sounds: the need +for food and the like could be indicated by gesture and natural cries. +Both sources are verae causae; to them Noire, supported by Max Muller, +has added another which has sometimes been called the Yo-heave-ho +theory. Noire contends that the real crux in the early stages of +language is for primitive man to make other primitive men understand +what he means. The vocal signs which commend themselves to one may not +have occurred to another, and may therefore be unintelligible. It may be +admitted that this difficulty exists, but it is not insuperable. The +old story of the European in China who, sitting down to a meal and being +doubtful what the meat in the dish might be, addressed an interrogative +Quack-quack? to the waiter and was promptly answered by Bow-wow, +illustrates a simple situation where mutual understanding was easy. +But obviously many situations would be more complex than this, and to +grapple with them Noire has introduced his theory of communal action. +"It was common effort directed to a common object, it was the most +primitive (uralteste) labour of our ancestors, from which sprang +language and the life of reason." (Noire "Der Ursprung der Sprache", +page 331, Mainz, 1877.) As illustrations of such common effort he cites +battle cries, the rescue of a ship running on shore (a situation not +likely to occur very early in the history of man), and others. Like Max +Muller he holds that language is the utterance and the organ of thought +for mankind, the one characteristic which separates man from the +brute. "In common action the word was first produced; for long it was +inseparably connected with action; through long-continued connection it +gradually became the firm, intelligible symbol of action, and then in +its development indicated also things of the external world in so far +as the action affected them and finally the sound began to enter into a +connexion with them also." (Op. cit. page 339.) In so far as this theory +recognises language as a social institution it is undoubtedly correct. +Darwin some years before Noire had pointed to the same social origin +of language in the fourth chapter of his work on "The Expression of the +Emotions in Man and Animals". "Naturalists have remarked, I believe with +truth, that social animals, from habitually using their vocal organs +as a means of intercommunication, use them on other occasions much more +freely than other animals... The principle, also, of association, which +is so widely extended in its power, has likewise played its part. Hence +it allows that the voice, from having been employed as a serviceable +aid under certain conditions, inducing pleasure, pain, rage, etc., is +commonly used whenever the same sensations or emotions are excited, +under quite different conditions, or in a lesser degree." ("The +Expression of the Emotions", page 84 (Popular Edition, 1904). + +Darwin's own views on language which are set forth most fully in +"The Descent of Man" (page 131 ff. (Popular Edition, 1906).) are +characterised by great modesty and caution. He did not profess to be a +philologist and the facts are naturally taken from the best known works +of the day (1871). In the notes added to the second edition he remarks +on Max Muller's denial of thought without words, "what a strange +definition must here be given to the word thought!" (Op. cit. page +135, footnote 63.) He naturally finds the origin of language in "the +imitation and modification of various natural sounds, the voices of +other animals, and man's own instinctive cries aided by signs and +gestures (op. cit. page 132.)... As the voice was used more and more, +the vocal organs would have been strengthened and perfected through the +principle of the inherited effects of use; and this would have reacted +on the power of speech." (Op. cit. page 133.) On man's own instinctive +cries, he has more to say in "The Expression of the Emotions". (Page 93 +(Popular Edition, 1904) and elsewhere.) These remarks have been utilised +by Prof. Jespersen of Copenhagen in propounding an ingenious theory of +his own to the effect that speech develops out of singing. ("Progress in +Language", page 361, London, 1894.) + +For many years and in many books Max Muller argued against Darwin's +views on evolution on the one ground that thought is impossible without +speech; consequently as speech is confined to the human race, there is a +gulf which cannot be bridged between man and all other creatures. +(Some interesting comments on the theory will be found in a lecture +on "Thought and Language" in Samuel Butler's "Essays on Life, Art and +Science", London, 1908.) On the title-page of his "Science of Thought" +he put the two sentences "No Reason without Language: No Language +without Reason." It may be readily admitted that the second dictum is +true, that no language properly so-called can exist without reason. +Various birds can learn to repeat words or sentences used by their +masters or mistresses. In most cases probably the birds do not attach +their proper meaning to the words they have learnt; they repeat them in +season and out of season, sometimes apparently for their own amusement, +generally in the expectation, raised by past experience, of being +rewarded for their proficiency. But even here it is difficult to prove +a universal negative, and most possessors of such pets would repudiate +indignantly the statement that the bird did not understand what was said +to it, and would also contend that in many cases the words which it used +were employed in their ordinary meaning. The first dictum seems to be +inconsistent with fact. The case of deaf mutes, such as Laura Bridgeman, +who became well educated, or the still more extraordinary case of Helen +Keller, deaf, dumb, and blind, who in spite of these disadvantages +has learnt not only to reason but to reason better than the average of +persons possessed of all their senses, goes to show that language and +reason are not necessarily always in combination. Reason is but the +conscious adaptation of means to ends, and so defined is a faculty which +cannot be denied to many of the lower animals. In these days when so +many books on Animal Intelligence are issued from the press, it seems +unnecessary to labour the point. Yet none of these animals, except by +parrot-imitation, makes use of speech, because man alone possesses in a +sufficient degree of development the centres of nervous energy which are +required for the working of articulation in speech. On this subject much +investigation was carried on during the last years of Darwin's life +and much more in the period since his death. As early as 1861 Broca, +following up observations made by earlier French writers, located the +centre of articulate speech in the third left frontal convolution of +the brain. In 1876 he more definitely fixed the organ of speech in +"the posterior two-fifths of the third frontal convolution" (Macnamara, +"Human Speech", page 197, London, 1908.), both sides and not merely the +left being concerned in speech production. Owing however to the greater +use by most human beings of the right side of the body, the left side of +the brain, which is the motor centre for the right side of the body, is +more highly developed than its right side, which moves the left side +of the body. The investigations of Professors Ferrier, Sherrington and +Grunbaum have still more precisely defined the relations between brain +areas and certain groups of muscles. One form of aphasia is the result +of injury to or disease in the third frontal convolution because the +motor centre is no longer equal to the task of setting the necessary +muscles in motion. In the brain of idiots who are unable to speak, +the centre for speech is not developed. (Op. cit. page 226.) In the +anthropoid apes the brain is similarly defective, though it has been +demonstrated by Professors Cunningham and Marchand "that there is a +tendency, especially in the gorilla's brain, for the third frontal +convolution to assume the human form... But if they possessed a centre +for speech, those parts of the hemispheres of their brains which form +the mechanism by which intelligence is elaborated are so ill-developed, +as compared with the rest of their bodies, that we can not conceive, +even with more perfect frontal convolutions, that these animals could +formulate ideas expressible in intelligent speech." (Op. cit. page 223.) + +While Max Muller's theory is Shelley's + +"He gave man speech, and speech created thought, Which is the measure of +the universe" ("Prometheus Unbound" II. 4.), + +it seems more probable that the development was just the opposite--that +the development of new activities originated new thoughts which required +new symbols to express them, symbols which may at first have been, even +to a greater extent than with some of the lower races at present, sign +language as much as articulation. When once the faculty of articulation +was developed, which, though we cannot trace the process, was probably a +very gradual growth, there is no reason to suppose that words developed +in any other way then they do at present. An erroneous notion of the +development of language has become widely spread through the adoption +of the metaphorical term "roots" for the irreducible elements of human +speech. Men never talked in roots; they talked in words. Many words of +kindred meaning have a part in common, and a root is nothing but that +common part stripped of all additions. In some cases it is obvious that +one word is derived from another by the addition of a fresh element; in +other cases it is impossible to say which of two kindred words is the +more primitive. A root is merely a convenient term for an abstraction. +The simplest word may be called a root, but it is nevertheless a +word. How are new words added to a language in the present day? Some +communities, like the Germans, prefer to construct new words for new +ideas out of the old material existing in the language; others, like the +English, prefer to go to the ancient languages of Greece and Rome for +terms to express new ideas. The same chemical element is described in +the two languages as sour stuff (Sauerstoff) and as oxygen. Both terms +mean the same thing etymologically as well as in fact. On behalf of the +German method, it may be contended that the new idea is more closely +attached to already existing ideas, by being expressed in elements of +the language which are intelligible even to the meanest capacity. For +the English practice it may be argued that, if we coin a new word which +means one thing, and one thing only, the idea which it expresses is +more clearly defined than if it were expressed in popularly intelligible +elements like "sour stuff." If the etymological value of words were +always present in the minds of their users, "oxygen" would undoubtedly +have an advantage over "sour stuff" as a technical term. But the +tendency in language is to put two words of this kind which express but +one idea under a single accent, and when this has taken place, no one +but the student of language any longer observes what the elements really +mean. When the ordinary man talks of a "blackbird" it is certainly not +present to his consciousness that he is talking of a black bird, unless +for some reason conversation has been dwelling upon the colour rather +than other characteristics of the species. + +But, it may be said, words like "oxygen" are introduced by learned men, +and do not represent the action of the man in the street, who, after +all, is the author of most additions to the stock of human language. We +may go back therefore some four centuries to a period, when scientific +study was only in its infancy, and see what process was followed. With +the discovery of America new products never seen before reached Europe, +and these required names. Three of the most characteristic were tobacco, +the potato, and the turkey. How did these come to be so named? The first +people to import these products into Europe were naturally the Spanish +discoverers. The first of these words--tobacco--appears in forms which +differ only slightly in the languages of all civilised countries: +Spanish tabaco, Italian tabacco, French tabac, Dutch and German tabak, +Swedish tobak, etc. The word in the native dialect of Hayti is said to +have been tabaco, but to have meant not the plant (According to William +Barclay, "Nepenthes, or the Virtue of Tobacco", Edinburgh, 1614, "the +countrey which God hath honoured and blessed with this happie and holy +herbe doth call it in their native language 'Petum'.") but the pipe +in which it was smoked. It thus illustrates a frequent feature of +borrowing--that the word is not borrowed in its proper signification, +but in some sense closely allied thereto, which a foreigner, +understanding the language with difficulty, might readily mistake for +the real meaning. Thus the Hindu practice of burning a wife upon the +funeral pyre of her husband is called in English "suttee", this word +being in fact but the phonetic spelling of the Sanskrit "sati", "a +virtuous woman," and passing into its English meaning because formerly +the practice of self-immolation by a wife was regarded as the highest +virtue. + +The name of the potato exhibits greater variety. The English name was +borrowed from the Spanish "patata", which was itself borrowed from a +native word for the "yam" in the dialect of Hayti. The potato appeared +early in Italy, for the mariners of Genoa actively followed the +footsteps of their countryman Columbus in exploring America. In Italian +generally the form "patata" has survived. The tubers, however, +also suggested a resemblance to truffles, so that the Italian word +"tartufolo", a diminutive of the Italian modification of the Latin +"terrae tuber" was applied to them. In the language of the Rhaetian Alps +this word appears as "tartufel". From there it seems to have passed +into Germany where potatoes were not cultivated extensively till the +eighteenth century, and "tartufel" has in later times through some +popular etymology been metamorphosed into "Kartoffel". In France the +shape of the tubers suggested the name of earth-apple (pomme de terre), +a name also adopted in Dutch (aard-appel), while dialectically in German +a form "Grumbire" appears, which is a corruption of "Grund-birne", +"ground pear". (Kluge "Etymologisches Worterbuch der deutschen Sprache" +(Strassburg), s.v. "Kartoffel".) Here half the languages have adopted +the original American word for an allied plant, while others have +adopted a name originating in some more or less fanciful resemblance +discovered in the tubers; the Germans alone in Western Europe, failing +to see any meaning in their borrowed name, have modified it almost +beyond recognition. To this English supplies an exact parallel in +"parsnep" which, though representing the Latin "pastinaca" through the +Old French "pastenaque", was first assimilated in the last syllable to +the "nep" of "turnep" ("pasneppe" in Elizabethan English), and later had +an "r" introduced into the first syllable, apparently on the analogy of +"parsley". + +The turkey on the other hand seems never to be found with its original +American name. In England, as the name implies, the turkey cock was +regarded as having come from the land of the Turks. The bird no doubt +spread over Europe from the Italian seaports. The mistake, therefore, +was not unnatural, seeing that these towns conducted a great trade +with the Levant, while the fact that America when first discovered was +identified with India helped to increase the confusion. Thus in French +the "coq d'Inde" was abbreviated to "d'Inde" much as "turkey cock" was +to "turkey"; the next stage was to identify "dinde" as a feminine word +and create a new "dindon" on the analogy of "chapon" as the masculine. +In Italian the name "gallo d'India" besides survives, while in German +the name "Truthahn" seems to be derived onomatopoetically from +the bird's cry, though a dialectic "Calecutischer Hahn" specifies +erroneously an origin for the bird from the Indian Calicut. In the +Spanish "pavo", on the other hand, there is a curious confusion with +the peacock. Thus in these names for objects of common knowledge, +the introduction of which into Europe can be dated with tolerable +definiteness, we see evinced the methods by which in remoter ages +objects were named. The words were borrowed from the community whence +came the new object, or the real or fancied resemblance to some known +object gave the name, or again popular etymology might convert the +unknown term into something that at least approached in sound a +well-known word. + +"The Origin of Species" had not long been published when the parallelism +of development in natural species and in languages struck investigators. +At the time, one of the foremost German philologists was August +Schleicher, Professor at Jena. He was himself keenly interested in the +natural sciences, and amongst his colleagues was Ernst Haeckel, the +protagonist in Germany of the Darwinian theory. How the new ideas struck +Schleicher may be seen from the following sentences by his colleague +Haeckel. "Speech is a physiological function of the human organism, +and has been developed simultaneously with its organs, the larynx and +tongue, and with the functions of the brain. Hence it will be quite +natural to find in the evolution and classification of languages the +same features as in the evolution and classification of organic species. +The various groups of languages that are distinguished in philology as +primitive, fundamental, parent, and daughter languages, dialects, etc., +correspond entirely in their development to the different categories +which we classify in zoology and botany as stems, classes, orders, +families, genera, species and varieties. The relation of these groups, +partly coordinate and partly subordinate, in the general scheme is just +the same in both cases; and the evolution follows the same lines in +both." (Haeckel, "The Evolution of Man", page 485, London, 1905. This +represents Schleicher's own words: Was die Naturforscher als Gattung +bezeichnen wurden, heisst bei den Glottikern Sprachstamm, auch +Sprachsippe; naher verwandte Gattungen bezeichnen sie wohl auch als +Sprachfamilien einer Sippe oder eines Sprachstammes... Die Arten einer +Gattung nennen wir Sprachen eines Stammes; die Unterarten einer Art sind +bei uns die Dialekte oder Mundarten einer Sprache; den Varietaten +und Spielarten entsprechen die Untermundarten oder Nebenmundarten und +endlich den einzelnen Individuen die Sprechweise der einzelnen +die Sprachen redenden Menschen. "Die Darwinische Theorie und die +Sprachwissenschaft", Weimar, 1863, page 12 f. Darwin makes a more +cautious statement about the classification of languages in "The Origin +of Species", page 578, (Popular Edition, 1900).) These views were set +forth in an open letter addressed to Haeckel in 1863 by Schleicher +entitled, "The Darwinian theory and the science of language". +Unfortunately Schleicher's views went a good deal farther than is +indicated in the extract given above. He appended to the pamphlet a +genealogical tree of the Indo-Germanic languages which, though to a +large extent confirmed by later research, by the dichotomy of each +branch into two other branches, led the unwary reader to suppose their +phylogeny (to use Professor Haeckel's term) was more regular than our +evidence warrants. + +Without qualification Schleicher declared languages to be "natural +organisms which originated unconditioned by the human will, +developed according to definite laws, grow old and die; they also are +characterised by that series of phenomena which we designate by the +term 'Life.' Consequently Glottic, the science of language, is a natural +science; its method is in general the same as that of the other natural +sciences." ("Die Darwinische Theorie", page 6 f.) In accordance with +this view he declared (op. cit. page 23.) that the root in language +might be compared with the simple cell in physiology, the linguistic +simple cell or root being as yet not differentiated into special organs +for the function of noun, verb, etc. + +In this probably all recent philologists admit that Schleicher went too +far. One of the most fertile theories in the modern science of language +originated with him, and was further developed by his pupil, August +Leskien ("Die Declination im Slavisch-litanischen und Germanischen", +Leipzig, 1876; Osthoff and Brugmann, "Morphologische Untersuchungen", +I. (Introduction), 1878. The general principles of this school were +formulated (1880) in a fuller form in H. Paul's "Prinzipien der +Sprachgeschichte", Halle (3rd edition, 1898). Paul and Wundt (in his +"Volkerpsychologie") deal largely with the same matter, but begin their +investigations from different points of view, Paul being a philologist +with leanings to philosophy and Wundt a philosopher interested in +language.), and by Leskien's colleagues and friends, Brugmann and +Osthoff. This was the principle that phonetic laws have no exceptions. +Under the influence of this generalisation much greater precision in +etymology was insisted upon, and a new and remarkably active period in +the study of language began. Stated broadly in the fashion given above +the principle is not true. A more accurate statement would be that an +original sound is represented in a given dialect at a given time and in +a given environment only in one way; provided that the development of +the original sound into its representation in the given dialect has not +been influenced by the working of analogy. + +It is this proviso that is most important for the characterisation of +the science of language. As I have said elsewhere, it is at this point +that this science parts company with the natural sciences. "If the +chemist compounds two pure simple elements, there can be but one result, +and no power of the chemist can prevent it. But the minds of men do +act upon the sounds which they produce. The result is that, when this +happens, the phonetic law which would have acted in the case is stopped, +and this particular form enters on the same course of development as +other forms to which it does not belong." (P. Giles, "Short Manual of +Comparative Philology", 2nd edition, page 57, London, 1901.) + +Schleicher was wrong in defining a language to be an organism in the +sense in which a living being is an organism. Regarded physiologically, +language is a function or potentiality of certain human organs; regarded +from the point of view of the community it is of the nature of an +institution. (This view of language is worked out at some length by +Prof. W.D. Whitney in an article in the "Contemporary Review" for 1875, +page 713 ff. This article forms part of a controversy with Max Muller, +which is partly concerned with Darwin's views on language. He criticises +Schleicher's views severely in his "Oriental and Linguistic Studies", +page 298 ff., New York, 1873. In this volume will be found criticisms of +various other views mentioned in this essay.) More than most influences +it conduces to the binding together of the elements that form a state. +That geographical or other causes may effectively counteract the +influence of identity of language is obvious. One need only read the +history of ancient Greece, or observe the existing political separation +of Germany and Austria, of Great Britain and the United States of +America. But however analogous to an organism, language is not an +organism. In a less degree Schleicher, by defining languages as such, +committed the same mistake which Bluntschli made regarding the State, +and which led him to declare that the State is by nature masculine and +the Church feminine. (Bluntschli, "Theory of the State", page 24, Second +English Edition, Oxford, 1892.) The views of Schleicher were to some +extent injurious to the proper methods of linguistic study. But this +misfortune was much more than fully compensated by the inspiration +which his ideas, collected and modified by his disciples, had upon the +science. In spite of the difference which the psychological element +represented by analogy makes between the science of language and the +natural sciences, we are entitled to say of it as Schleicher said of +Darwin's theory of the origin of species, "it depends upon observation, +and is essentially an attempt at a history of development." + +Other questions there are in connection with language and evolution +which require investigation--the survival of one amongst several +competing words (e.g. why German keeps only as a high poetic word +"ross", which is identical in origin with the English work-a-day +"horse", and replaces it by "pferd", whose congener the English +"palfrey" is almost confined to poetry and romance), the persistence +of evolution till it becomes revolution in languages like English or +Persian which have practically ceased to be inflectional languages, and +many other problems. Into these Darwin did not enter, and they require +a fuller investigation than is possible within the limits of the present +paper. + + + + +XXVII. DARWINISM AND HISTORY. By J.B. Bury, Litt.D., LL.D. + +Regius Professor of Modern History in the University of Cambridge. + + +1. Evolution, and the principles associated with the Darwinian theory, +could not fail to exert a considerable influence on the studies +connected with the history of civilised man. The speculations which +are known as "philosophy of history," as well as the sciences of +anthropology, ethnography, and sociology (sciences which though they +stand on their own feet are for the historian auxiliary), have been +deeply affected by these principles. Historiographers, indeed, have +with few exceptions made little attempt to apply them; but the growth +of historical study in the nineteenth century has been determined and +characterised by the same general principle which has underlain the +simultaneous developments of the study of nature, namely the GENETIC +idea. The "historical" conception of nature, which has produced the +history of the solar system, the story of the earth, the genealogies of +telluric organisms, and has revolutionised natural science, belongs +to the same order of thought as the conception of human history as +a continuous, genetic, causal process--a conception which has +revolutionised historical research and made it scientific. Before +proceeding to consider the application of evolutional principles, it +will be pertinent to notice the rise of this new view. + +2. With the Greeks and Romans history had been either a descriptive +record or had been written in practical interests. The most eminent of +the ancient historians were pragmatical; that is, they regarded history +as an instructress in statesmanship, or in the art of war, or in morals. +Their records reached back such a short way, their experience was so +brief, that they never attained to the conception of continuous process, +or realised the significance of time; and they never viewed the history +of human societies as a phenomenon to be investigated for its own sake. +In the middle ages there was still less chance of the emergence of the +ideas of progress and development. Such notions were excluded by the +fundamental doctrines of the dominant religion which bounded and bound +men's minds. As the course of history was held to be determined from +hour to hour by the arbitrary will of an extra-cosmic person, there +could be no self-contained causal development, only a dispensation +imposed from without. And as it was believed that the world was within +no great distance from the end of this dispensation, there was no motive +to take much interest in understanding the temporal, which was to be +only temporary. + +The intellectual movements of the fifteenth and sixteenth centuries +prepared the way for a new conception, but it did not emerge +immediately. The historians of the Renaissance period simply reverted to +the ancient pragmatical view. For Machiavelli, exactly as for Thucydides +and Polybius, the use of studying history was instruction in the art of +politics. The Renaissance itself was the appearance of a new culture, +different from anything that had gone before; but at the time men were +not conscious of this; they saw clearly that the traditions of classical +antiquity had been lost for a long period, and they were seeking to +revive them, but otherwise they did not perceive that the world had +moved, and that their own spirit, culture, and conditions were +entirely unlike those of the thirteenth century. It was hardly till the +seventeenth century that the presence of a new age, as different from +the middle ages as from the ages of Greece and Rome, was fully realised. +It was then that the triple division of ancient, medieval, and modern +was first applied to the history of western civilisation. Whatever +objections may be urged against this division, which has now become +almost a category of thought, it marks a most significant advance in +man's view of his own past. He has become conscious of the immense +changes in civilisation which have come about slowly in the course of +time, and history confronts him with a new aspect. He has to explain how +those changes have been produced, how the transformations were effected. +The appearance of this problem was almost simultaneous with the rise +of rationalism, and the great historians and thinkers of the eighteenth +century, such as Montesquieu, Voltaire, Gibbon, attempted to explain +the movement of civilisation by purely natural causes. These brilliant +writers prepared the way for the genetic history of the following +century. But in the spirit of the Aufklarung, that eighteenth-century +Enlightenment to which they belonged, they were concerned to judge all +phenomena before the tribunal of reason; and the apotheosis of "reason" +tended to foster a certain superior a priori attitude, which was +not favourable to objective treatment and was incompatible with +a "historical sense." Moreover the traditions of pragmatical +historiography had by no means disappeared. + +3. In the first quarter of the nineteenth century the meaning of genetic +history was fully realised. "Genetic" perhaps is as good a word as can +be found for the conception which in this century was applied to so many +branches of knowledge in the spheres both of nature and of mind. It +does not commit us to the doctrine proper of evolution, nor yet to any +teleological hypothesis such as is implied in "progress." For history +it meant that the present condition of the human race is simply and +strictly the result of a causal series (or set of causal series)--a +continuous succession of changes, where each state arises causally out +of the preceding; and that the business of historians is to trace this +genetic process, to explain each change, and ultimately to grasp the +complete development of the life of humanity. Three influential writers, +who appeared at this stage and helped to initiate a new period +of research, may specially be mentioned. Ranke in 1824 definitely +repudiated the pragmatical view which ascribes to history the duties +of an instructress, and with no less decision renounced the function, +assumed by the historians of the Aufklarung, to judge the past; it +was his business, he said, merely to show how things really happened. +Niebuhr was already working in the same spirit and did more than any +other writer to establish the principle that historical transactions +must be related to the ideas and conditions of their age. Savigny about +the same time founded the "historical school" of law. He sought to show +that law was not the creation of an enlightened will, but grew out of +custom and was developed by a series of adaptations and rejections, thus +applying the conception of evolution. He helped to diffuse the notion +that all the institutions of a society or a notion are as closely +interconnected as the parts of a living organism. + +4. The conception of the history of man as a causal development meant +the elevation of historical inquiry to the dignity of a science. Just +as the study of bees cannot become scientific so long as the student's +interest in them is only to procure honey or to derive moral lessons +from the labours of "the little busy bee," so the history of human +societies cannot become the object of pure scientific investigation so +long as man estimates its value in pragmatical scales. Nor can it become +a science until it is conceived as lying entirely within a sphere +in which the law of cause and effect has unreserved and unrestricted +dominion. On the other hand, once history is envisaged as a causal +process, which contains within itself the explanation of the development +of man from his primitive state to the point which he has reached, such +a process necessarily becomes the object of scientific investigation and +the interest in it is scientific curiosity. + +At the same time, the instruments were sharpened and refined. Here Wolf, +a philologist with historical instinct, was a pioneer. His "Prolegomena" +to Homer (1795) announced new modes of attack. Historical investigation +was soon transformed by the elaboration of new methods. + +5. "Progress" involves a judgment of value, which is not involved in the +conception of history as a genetic process. It is also an idea distinct +from that of evolution. Nevertheless it is closely related to the ideas +which revolutionised history at the beginning of the last century; +it swam into men's ken simultaneously; and it helped effectively to +establish the notion of history as a continuous process and to emphasise +the significance of time. Passing over earlier anticipations, I may +point to a "Discours" of Turgot (1750), where history is presented as a +process in which "the total mass of the human race" "marches continually +though sometimes slowly to an ever increasing perfection." That is +a clear statement of the conception which Turgot's friend Condorcet +elaborated in the famous work, published in 1795, "Esquisse d'un tableau +historique des progres de l'esprit humain". This work first treated with +explicit fulness the idea to which a leading role was to fall in the +ideology of the nineteenth century. Condorcet's book reflects the +triumphs of the Tiers etat, whose growing importance had also inspired +Turgot; it was the political changes in the eighteenth century which led +to the doctrine, emphatically formulated by Condorcet, that the masses +are the most important element in the historical process. I dwell +on this because, though Condorcet had no idea of evolution, the +pre-dominant importance of the masses was the assumption which made +it possible to apply evolutional principles to history. And it enabled +Condorcet himself to maintain that the history of civilisation, a +progress still far from being complete, was a development conditioned by +general laws. + +6. The assimilation of society to an organism, which was a governing +notion in the school of Savigny, and the conception of progress, +combined to produce the idea of an organic development, in which the +historian has to determine the central principle or leading character. +This is illustrated by the apotheosis of democracy in Tocqueville's +"Democratie en Amerique", where the theory is maintained that "the +gradual and progressive development of equality is at once the past and +the future of the history of men." The same two principles are combined +in the doctrine of Spencer (who held that society is an organism, +though he also contemplated its being what he calls a "super-organic +aggregate") (A society presents suggestive analogies with an organism, +but it certainly is not an organism, and sociologists who draw +inferences from the assumption of its organic nature must fall into +error. A vital organism and a society are radically distinguished by the +fact that the individual components of the former, namely the cells, +are morphologically as well as functionally differentiated, whereas the +individuals which compose a society are morphologically homogeneous and +only functionally differentiated. The resemblances and the differences +are worked out in E. de Majewski's striking book "La Science de la +Civilisation", Paris, 1908.), that social evolution is a progressive +change from militarism to industrialism. + +7. the idea of development assumed another form in the speculations of +German idealism. Hegel conceived the successive periods of history as +corresponding to the ascending phases or ideas in the self-evolution +of his Absolute Being. His "Lectures on the Philosophy of History" were +published in 1837 after his death. His philosophy had a considerable +effect, direct and indirect, on the treatment of history by historians, +and although he was superficial and unscientific himself in dealing with +historical phenomena, he contributed much towards making the idea of +historical development familiar. Ranke was influenced, if not by Hegel +himself, at least by the Idealistic philosophies of which Hegel's was +the greatest. He was inclined to conceive the stages in the process of +history as marked by incarnations, as it were, of ideas, and sometimes +speaks as if the ideas were independent forces, with hands and feet. But +while Hegel determined his ideas by a priori logic, Ranke obtained his +by induction--by a strict investigation of the phenomena; so that he +was scientific in his method and work, and was influenced by Hegelian +prepossessions only in the kind of significance which he was disposed +to ascribe to his results. It is to be noted that the theory of Hegel +implied a judgment of value; the movement was a progress towards +perfection. + +8. In France, Comte approached the subject from a different side, and +exercised, outside Germany, a far wider influence than Hegel. The 4th +volume of his "Cours de philosophie positive", which appeared in 1839, +created sociology and treated history as a part of this new science, +namely as "social dynamics." Comte sought the key for unfolding +historical development, in what he called the social-psychological point +of view, and he worked out the two ideas which had been enunciated by +Condorcet: that the historian's attention should be directed not, as +hitherto, principally to eminent individuals, but to the collective +behaviour of the masses, as being the most important element in the +process; and that, as in nature, so in history, there are general laws, +necessary and constant, which condition the development. The two points +are intimately connected, for it is only when the masses are moved into +the foreground that regularity, uniformity, and law can be conceived +as applicable. To determine the social-psychological laws which +have controlled the development is, according to Comte, the task of +sociologists and historians. + +9. The hypothesis of general laws operative in history was carried +further in a book which appeared in England twenty years later and +exercised an influence in Europe far beyond its intrinsic merit, +Buckle's "History of Civilisation in England" (1857-61). Buckle owed +much to Comte, and followed him, or rather outdid him, in regarding +intellect as the most important factor conditioning the upward +development of man, so that progress, according to him, consisted in the +victory of the intellectual over the moral laws. + +10. The tendency of Comte and Buckle to assimilate history to the +sciences of nature by reducing it to general "laws," derived stimulus +and plausibility from the vista offered by the study of statistics, in +which the Belgian Quetelet, whose book "Sur l'homme" appeared in 1835, +discerned endless possibilities. The astonishing uniformities which +statistical inquiry disclosed led to the belief that it was only a +question of collecting a sufficient amount of statistical material, to +enable us to predict how a given social group will act in a particular +case. Bourdeau, a disciple of this school, looks forward to the time +when historical science will become entirely quantitative. The actions +of prominent individuals, which are generally considered to have altered +or determined the course of things, are obviously not amenable to +statistical computation or explicable by general laws. Thinkers like +Buckle sought to minimise their importance or explain them away. + +11. These indications may suffice to show that the new efforts to +interpret history which marked the first half of the nineteenth century +were governed by conceptions closely related to those which were current +in the field of natural science and which resulted in the doctrine of +evolution. The genetic principle, progressive development, general +laws, the significance of time, the conception of society as an organic +aggregate, the metaphysical theory of history as the self-evolution of +spirit,--all these ideas show that historical inquiry had been advancing +independently on somewhat parallel lines to the sciences of nature. It +was necessary to bring this out in order to appreciate the influence of +Darwinism. + +12. In the course of the dozen years which elapsed between the +appearances of "The Origin of Species" (observe that the first volume of +Buckle's work was published just two years before) and of "The Descent +of Man" (1871), the hypothesis of Lamarck that man is the co-descendant +with other species of some lower extinct form was admitted to have been +raised to the rank of an established fact by most thinkers whose brains +were not working under the constraint of theological authority. + +One important effect of the discovery of this fact (I am not speaking +now of the Darwinian explanation) was to assign to history a definite +place in the coordinated whole of knowledge, and relate it more closely +to other sciences. It had indeed a defined logical place in systems +such as Hegel's and Comte's; but Darwinism certified its standing +convincingly and without more ado. The prevailing doctrine that man +was created ex abrupto had placed history in an isolated position, +disconnected with the sciences of nature. Anthropology, which deals with +the animal anthropos, now comes into line with zoology, and brings it +into relation with history. (It is to be observed that history is not +only different in scope but) not coextensive with anthropology IN TIME. +For it deals only with the development of man in societies, whereas +anthropology includes in its definition the proto-anthropic period +when anthropos was still non-social, whether he lived in herds like +the chimpanzee, or alone like the male ourang-outang. (It has been well +shown by Majewski that congregations--herds, flocks, packs, etc.--of +animals are not SOCIETIES; the characteristic of a society is +differentiation of function. Bee hives, ant hills, may be called +quasi-societies; but in their case the classes which perform distinct +functions are morphologically different.) Man's condition at the present +day is the result of a series of transformations, going back to the most +primitive phase of society, which is the ideal (unattainable) beginning +of history. But that beginning had emerged without any breach of +continuity from a development which carries us back to a quadrimane +ancestor, still further back (according to Darwin's conjecture) to a +marine animal of the ascidian type, and then through remoter periods to +the lowest form of organism. It is essential in this theory that though +links have been lost there was no break in the gradual development; +and this conception of a continuous progress in the evolution of +life, resulting in the appearance of uncivilised Anthropos, helped to +reinforce, and increase a belief in, the conception of the history of +civilised Anthropos as itself also a continuous progressive development. + +13. Thus the diffusion of the Darwinian theory of the origin of man, +by emphasising the idea of continuity and breaking down the barriers +between the human and animal kingdoms, has had an important effect in +establishing the position of history among the sciences which deal with +telluric development. The perspective of history is merged in a larger +perspective of development. As one of the objects of biology is to find +the exact steps in the genealogy of man from the lowest organic form, +so the scope of history is to determine the stages in the unique +causal series from the most rudimentary to the present state of human +civilisation. + +It is to be observed that the interest in historical research implied +by this conception need not be that of Comte. In the Positive Philosophy +history is part of sociology; the interest in it is to discover the +sociological laws. In the view of which I have just spoken, history +is permitted to be an end in itself; the reconstruction of the +genetic process is an independent interest. For the purpose of the +reconstruction, sociology, as well as physical geography, biology, +psychology, is necessary; the sociologist and the historian play +into each other's hands; but the object of the former is to establish +generalisations; the aim of the latter is to trace in detail a singular +causal sequence. + +14. The success of the evolutional theory helped to discredit +the assumption or at least the invocation of transcendent causes. +Philosophically of course it is compatible with theism, but historians +have for the most part desisted from invoking the naive conception of a +"god in history" to explain historical movements. A historian may be a +theist; but, so far as his work is concerned, this particular belief is +otiose. Otherwise indeed (as was remarked above) history could not be a +science; for with a deus ex machina who can be brought on the stage to +solve difficulties scientific treatment is a farce. The transcendent +element had appeared in a more subtle form through the influence of +German philosophy. I noticed how Ranke is prone to refer to ideas as +if they were transcendent existences manifesting themselves in the +successive movements of history. It is intelligible to speak of certain +ideas as controlling, in a given period,--for instance, the idea of +nationality; but from the scientific point of view, such ideas have +no existence outside the minds of individuals and are purely psychical +forces; and a historical "idea," if it does not exist in this form, is +merely a way of expressing a synthesis of the historian himself. + +15. From the more general influence of Darwinism on the place of history +in the system of human knowledge, we may turn to the influence of the +principles and methods by which Darwin explained development. It had +been recognised even by ancient writers (such as Aristotle and +Polybius) that physical circumstances (geography, climate) were factors +conditioning the character and history of a race or society. In the +sixteenth century Bodin emphasised these factors, and many subsequent +writers took them into account. The investigations of Darwin, which +brought them into the foreground, naturally promoted attempts to +discover in them the chief key to the growth of civilisation. Comte had +expressly denounced the notion that the biological methods of Lamarck +could be applied to social man. Buckle had taken account of natural +influences, but had relegated them to a secondary plane, compared with +psychological factors. But the Darwinian theory made it tempting to +explain the development of civilisation in terms of "adaptation to +environment," "struggle for existence," "natural selection," "survival +of the fittest," etc. (Recently O. Seeck has applied these principles to +the decline of Graeco-Roman civilisation in his "Untergang der antiken +Welt", 2 volumes, Berlin, 1895, 1901.) + +The operation of these principles cannot be denied. Man is still an +animal, subject to zoological as well as mechanical laws. The dark +influence of heredity continues to be effective; and psychical +development had begun in lower organic forms,--perhaps with life itself. +The organic and the social struggles for existence are manifestations of +the same principle. Environment and climatic influence must be called in +to explain not only the differentiation of the great racial sections of +humanity, but also the varieties within these sub-species and, it may +be, the assimilation of distinct varieties. Ritter's "Anthropogeography" +has opened a useful line of research. But on the other hand, it is urged +that, in explaining the course of history, these principles do not take +us very far, and that it is chiefly for the primitive ultra-prehistoric +period that they can account for human development. It may be said +that, so far as concerns the actions and movements of men which are +the subject of recorded history, physical environment has ceased to act +mechanically, and in order to affect their actions must affect their +wills first; and that this psychical character of the causal relations +substantially alters the problem. The development of human societies, it +may be argued, derives a completely new character from the dominance +of the conscious psychical element, creating as it does new conditions +(inventions, social institutions, etc.) which limit and counteract the +operation of natural selection, and control and modify the influence of +physical environment. Most thinkers agree now that the chief clews to +the growth of civilisation must be sought in the psychological +sphere. Imitation, for instance, is a principle which is probably +more significant for the explanation of human development than natural +selection. Darwin himself was conscious that his principles had only +a very restricted application in this sphere, as is evident from his +cautious and tentative remarks in the 5th chapter of his "Descent of +Man". He applied natural selection to the growth of the intellectual +faculties and of the fundamental social instincts, and also to the +differentiation of the great races or "sub-species" (Caucasian, African, +etc.) which differ in anthropological character. (Darwinian formulae may +be suggestive by way of analogy. For instance, it is characteristic of +social advance that a multitude of inventions, schemes and plans are +framed which are never carried out, similar to, or designed for the same +end as, an invention or plan which is actually adopted because it has +chanced to suit better the particular conditions of the hour (just as +the works accomplished by an individual statesman, artist or savant are +usually only a residue of the numerous projects conceived by his brain). +This process in which so much abortive production occurs is analogous to +elimination by natural selection.) + +16. But if it is admitted that the governing factors which concern +the student of social development are of the psychical order, the +preliminary success of natural science in explaining organic evolution +by general principles encouraged sociologists to hope that social +evolution could be explained on general principles also. The idea of +Condorcet, Buckle, and others, that history could be assimilated to +the natural sciences was powerfully reinforced, and the notion that the +actual historical process, and every social movement involved in it, can +be accounted for by sociological generalisations, so-called "laws," is +still entertained by many, in one form or another. Dissentients from +this view do not deny that the generalisations at which the sociologist +arrives by the comparative method, by the analysis of social factors, +and by psychological deduction may be an aid to the historian; but they +deny that such uniformities are laws or contain an explanation of the +phenomena. They can point to the element of chance coincidence. This +element must have played a part in the events of organic evolution, but +it has probably in a larger measure helped to determine events in social +evolution. The collision of two unconnected sequences may be fraught +with great results. The sudden death of a leader or a marriage without +issue, to take simple cases, has again and again led to permanent +political consequences. More emphasis is laid on the decisive actions +of individuals, which cannot be reduced under generalisations and which +deflect the course of events. If the significance of the individual will +had been exaggerated to the neglect of the collective activity of the +social aggregate before Condorcet, his doctrine tended to eliminate as +unimportant the roles of prominent men, and by means of this elimination +it was possible to found sociology. But it may be urged that it is +patent on the face of history that its course has constantly been +shaped and modified by the wills of individuals (We can ignore here the +metaphysical question of freewill and determinism. For the character of +the individual's brain depends in any case on ante-natal accidents +and coincidences, and so it may be said that the role of individuals +ultimately depends on chance,--the accidental coincidence of independent +sequences.), which are by no means always the expression of the +collective will; and that the appearance of such personalities at the +given moments is not a necessary outcome of the conditions and cannot be +deduced. Nor is there any proof that, if such and such an individual +had not been born, some one else would have arisen to do what he did. In +some cases there is no reason to think that what happened need ever have +come to pass. In other cases, it seems evident that the actual change +was inevitable, but in default of the man who initiated and guided it, +it might have been postponed, and, postponed or not, might have borne +a different cachet. I may illustrate by an instance which has just come +under my notice. Modern painting was founded by Giotto, and the Italian +expedition of Charles VIII, near the close of the sixteenth century, +introduced into France the fashion of imitating Italian painters. +But for Giotto and Charles VIII, French painting might have been very +different. It may be said that "if Giotto had not appeared, some other +great initiator would have played a role analogous to his, and that +without Charles VIII there would have been the commerce with Italy, +which in the long run would have sufficed to place France in relation +with Italian artists. But the equivalent of Giotto might have been +deferred for a century and probably would have been different; and +commercial relations would have required ages to produce the rayonnement +imitatif of Italian art in France, which the expedition of the royal +adventurer provoked in a few years." (I have taken this example from G. +Tarde's "La logique sociale" 2 (page 403), Paris, 1904, where it is used +for quite a different purpose.) Instances furnished by political history +are simply endless. Can we conjecture how events would have moved if the +son of Philip of Macedon had been an incompetent? The aggressive action +of Prussia which astonished Europe in 1740 determined the subsequent +history of Germany; but that action was anything but inevitable; it +depended entirely on the personality of Frederick the Great. + +Hence it may be argued that the action of individual wills is a +determining and disturbing factor, too significant and effective to +allow history to be grasped by sociological formulae. The types and +general forms of development which the sociologist attempts to disengage +can only assist the historian in understanding the actual course +of events. It is in the special domains of economic history and +Culturgeschichte which have come to the front in modern times that +generalisation is most fruitful, but even in these it may be contended +that it furnishes only partial explanations. + +17. The truth is that Darwinism itself offers the best illustration of +the insufficiency of general laws to account for historical +development. The part played by coincidence, and the part played +by individuals--limited by, and related to, general social +conditions--render it impossible to deduce the course of the past +history of man or to predict the future. But it is just the same with +organic development. Darwin (or any other zoologist) could not deduce +the actual course of evolution from general principles. Given an +organism and its environment, he could not show that it must evolve into +a more complex organism of a definite pre-determined type; knowing +what it has evolved into, he could attempt to discover and assign the +determining causes. General principles do not account for a particular +sequence; they embody necessary conditions; but there is a chapter of +accidents too. It is the same in the case of history. + +18. Among the evolutional attempts to subsume the course of history +under general syntheses, perhaps the most important is that of +Lamprecht, whose "kulturhistorische Methode," which he has deduced from +and applied to German history, exhibits the (indirect) influence of the +Comtist school. It is based upon psychology, which, in his view, holds +among the sciences of mind (Geisteswissenschaften) the same place (that +of a Grundwissenschaft) which mechanics holds among the sciences of +nature. History, by the same comparison, corresponds to biology, and, +according to him, it can only become scientific if it is reduced to +general concepts (Begriffe). Historical movements and events are of +a psychical character, and Lamprecht conceives a given phase of +civilisation as "a collective psychical condition (seelischer +Gesamtzustand)" controlling the period, "a diapason which penetrates +all psychical phenomena and thereby all historical events of the time." +("Die kulturhistorische Methode", Berlin, 1900, page 26.) He has worked +out a series of such phases, "ages of changing psychical diapason," in +his "Deutsche Geschichte" with the aim of showing that all the feelings +and actions of each age can be explained by the diapason; and has +attempted to prove that these diapasons are exhibited in other social +developments, and are consequently not singular but typical. He +maintains further that these ages succeed each other in a definite +order; the principle being that the collective psychical development +begins with the homogeneity of all the individual members of a society +and, through heightened psychical activity, advances in the form of a +continually increasing differentiation of the individuals (this is akin +to the Spencerian formula). This process, evolving psychical freedom +from psychical constraint, exhibits a series of psychical phenomena +which define successive periods of civilisation. The process depends on +two simple principles, that no idea can disappear without leaving behind +it an effect or influence, and that all psychical life, whether in +a person or a society, means change, the acquisition of new mental +contents. It follows that the new have to come to terms with the old, +and this leads to a synthesis which determines the character of a new +age. Hence the ages of civilisation are defined as the "highest +concepts for subsuming without exception all psychical phenomena of +the development of human societies, that is, of all historical events." +(Ibid. pages 28, 29.) Lamprecht deduces the idea of a special historical +science, which might be called "historical ethnology," dealing with the +ages of civilisation, and bearing the same relation to (descriptive or +narrative) history as ethnology to ethnography. Such a science obviously +corresponds to Comte's social dynamics, and the comparative method, +on which Comte laid so much emphasis, is the principal instrument of +Lamprecht. + +19. I have dwelt on the fundamental ideas of Lamprecht, because they are +not yet widely known in England, and because his system is the ablest +product of the sociological school of historians. It carries the +more weight as its author himself is a historical specialist, and his +historical syntheses deserve the most careful consideration. But there +is much in the process of development which on such assumptions is +not explained, especially the initiative of individuals. Historical +development does not proceed in a right line, without the choice of +diverging. Again and again, several roads are open to it, of which it +chooses one--why? On Lamprecht's method, we may be able to assign the +conditions which limit the psychical activity of men at a particular +stage of evolution, but within those limits the individual has so many +options, such a wide room for moving, that the definition of those +conditions, the "psychical diapasons," is only part of the explanation +of the particular development. The heel of Achilles in all historical +speculations of this class has been the role of the individual. + +The increasing prominence of economic history has tended to encourage +the view that history can be explained in terms of general concepts or +types. Marx and his school based their theory of human development on +the conditions of production, by which, according to them, all social +movements and historical changes are entirely controlled. The leading +part which economic factors play in Lamprecht's system is significant, +illustrating the fact that economic changes admit most readily this +kind of treatment, because they have been less subject to direction or +interference by individual pioneers. + +Perhaps it may be thought that the conception of SOCIAL ENVIRONMENT +(essentially psychical), on which Lamprecht's "psychical diapasons" +depend, is the most valuable and fertile conception that the historian +owes to the suggestion of the science of biology--the conception of +all particular historical actions and movements as (1) related to and +conditioned by the social environment, and (2) gradually bringing about +a transformation of that environment. But no given transformation can be +proved to be necessary (pre-determined). And types of development do not +represent laws; their meaning and value lie in the help they may give +to the historian, in investigating a certain period of civilisation, +to enable him to discover the interrelations among the diverse features +which it presents. They are, as some one has said, an instrument of +heuretic method. + +20. The men engaged in special historical researches--which have been +pursued unremittingly for a century past, according to scientific +methods of investigating evidence (initiated by Wolf, Niebuhr, +Ranke)--have for the most part worked on the assumptions of genetic +history or at least followed in the footsteps of those who fully grasped +the genetic point of view. But their aim has been to collect and sift +evidence, and determine particular facts; comparatively few have given +serious thought to the lines of research and the speculations which +have been considered in this paper. They have been reasonably shy +of compromising their work by applying theories which are still much +debated and immature. But historiography cannot permanently evade the +questions raised by these theories. One may venture to say that no +historical change or transformation will be fully understood until it is +explained how social environment acted on the individual components of +the society (both immediately and by heredity), and how the individuals +reacted upon their environment. The problem is psychical, but it is +analogous to the main problem of the biologist. + + + + +XXVIII. THE GENESIS OF DOUBLE STARS. By Sir George Darwin, K.C.B., +F.R.S. + +Plumian Professor of Astronomy and Experimental Philosophy in the +University of Cambridge. + +In ordinary speech a system of any sort is said to be stable when it +cannot be upset easily, but the meaning attached to the word is usually +somewhat vague. It is hardly surprising that this should be the case, +when it is only within the last thirty years, and principally through +the investigations of M. Poincare, that the conception of stability has, +even for physicists, assumed a definiteness and clearness in which it +was previously lacking. The laws which govern stability hold good in +regions of the greatest diversity; they apply to the motion of planets +round the sun, to the internal arrangement of those minute corpuscles of +which each chemical atom is constructed, and to the forms of celestial +bodies. In the present essay I shall attempt to consider the laws of +stability as relating to the last case, and shall discuss the succession +of shapes which may be assumed by celestial bodies in the course of +their evolution. I believe further that homologous conceptions are +applicable in the consideration of the transmutations of the various +forms of animal and of vegetable life and in other regions of thought. +Even if some of my readers should think that what I shall say on this +head is fanciful, yet at least the exposition will serve to illustrate +the meaning to be attached to the laws of stability in the physical +universe. + +I propose, therefore, to begin this essay by a sketch of the principles +of stability as they are now formulated by physicists. + +I. + +If a slight impulse be imparted to a system in equilibrium one of two +consequences must ensue; either small oscillations of the system will +be started, or the disturbance will increase without limit and the +arrangement of the system will be completely changed. Thus a stick may +be in equilibrium either when it hangs from a peg or when it is balanced +on its point. If in the first case the stick is touched it will swing to +and fro, but in the second case it will topple over. The first position +is a stable one, the second is unstable. But this case is too simple to +illustrate all that is implied by stability, and we must consider cases +of stable and of unstable motion. Imagine a satellite and its planet, +and consider each of them to be of indefinitely small size, in fact +particles; then the satellite revolves round its planet in an ellipse. A +small disturbance imparted to the satellite will only change the ellipse +to a small amount, and so the motion is said to be stable. If, on the +other hand, the disturbance were to make the satellite depart from its +initial elliptic orbit in ever widening circuits, the motion would be +unstable. This case affords an example of stable motion, but I have +adduced it principally with the object of illustrating another point +not immediately connected with stability, but important to a proper +comprehension of the theory of stability. + +The motion of a satellite about its planet is one of revolution or +rotation. When the satellite moves in an ellipse of any given degree +of eccentricity, there is a certain amount of rotation in the system, +technically called rotational momentum, and it is always the same at +every part of the orbit. (Moment of momentum or rotational momentum +is measured by the momentum of the satellite multiplied by the +perpendicular from the planet on to the direction of the path of the +satellite at any instant.) + +Now if we consider all the possible elliptic orbits of a satellite about +its planet which have the same amount of "rotational momentum," we find +that the major axis of the ellipse described will be different according +to the amount of flattening (or the eccentricity) of the ellipse +described. A figure titled "A 'family' of elliptic orbits with constant +rotational momentum" (Fig. 1) illustrates for a given planet and +satellite all such orbits with constant rotational momentum, and with +all the major axes in the same direction. It will be observed that there +is a continuous transformation from one orbit to the next, and that the +whole forms a consecutive group, called by mathematicians "a family" +of orbits. In this case the rotational momentum is constant and the +position of any orbit in the family is determined by the length of the +major axis of the ellipse; the classification is according to the major +axis, but it might have been made according to anything else which would +cause the orbit to be exactly determinate. + +I shall come later to the classification of all possible forms of ideal +liquid stars, which have the same amount of rotational momentum, and the +classification will then be made according to their densities, but the +idea of orderly arrangement in a "family" is just the same. + +We thus arrive at the conception of a definite type of motion, with +a constant amount of rotational momentum, and a classification of all +members of the family, formed by all possible motions of that type, +according to the value of some measurable quantity (this will hereafter +be density) which determines the motion exactly. In the particular case +of the elliptic motion used for illustration the motion was stable, +but other cases of motion might be adduced in which the motion would +be unstable, and it would be found that classification in a family and +specification by some measurable quantity would be equally applicable. + +A complex mechanical system may be capable of motion in several distinct +modes or types, and the motions corresponding to each such type may +be arranged as before in families. For the sake of simplicity I will +suppose that only two types are possible, so that there will only be two +families; and the rotational momentum is to be constant. The two types +of motion will have certain features in common which we denote in a sort +of shorthand by the letter A. Similarly the two types may be described +as A + a and A + b, so that a and b denote the specific differences +which discriminate the families from one another. Now following in +imagination the family of the type A + a, let us begin with the case +where the specific difference a is well marked. As we cast our eyes +along the series forming the family, we find the difference a becoming +less conspicuous. It gradually dwindles until it disappears; beyond this +point it either becomes reversed, or else the type has ceased to be +a possible one. In our shorthand we have started with A + a, and have +watched the characteristic a dwindling to zero. When it vanishes we have +reached a type which may be specified as A; beyond this point the type +would be A - a or would be impossible. + +Following the A + b type in the same way, b is at first well marked, it +dwindles to zero, and finally may become negative. Hence in shorthand +this second family may be described as A + b,... A,... A - b. + +In each family there is one single member which is indistinguishable +from a member of the other family; it is called by Poincare a form of +bifurcation. It is this conception of a form of bifurcation which forms +the important consideration in problems dealing with the forms of liquid +or gaseous bodies in rotation. + +But to return to the general question,--thus far the stability of these +families has not been considered, and it is the stability which renders +this way of looking at the matter so valuable. It may be proved that if +before the point of bifurcation the type A + a was stable, then A + b +must have been unstable. Further as a and b each diminish A + a becomes +less pronouncedly stable, and A + b less unstable. On reaching the point +of bifurcation A + a has just ceased to be stable, or what amounts to +the same thing is just becoming unstable, and the converse is true +of the A + b family. After passing the point of bifurcation A + a has +become definitely unstable and A + b has become stable. Hence the point +of bifurcation is also a point of "exchange of stabilities between the +two types." (In order not to complicate unnecessarily this explanation +of a general principle I have not stated fully all the cases that may +occur. Thus: firstly, after bifurcation A + a may be an impossible type +and A + a will then stop at this point; or secondly, A + b may have been +an impossible type before bifurcation, and will only begin to be a real +one after it; or thirdly, both A + a and A + b may be impossible after +the point of bifurcation, in which case they coalesce and disappear. +This last case shows that types arise and disappear in pairs, and that +on appearance or before disappearance one must be stable and the other +unstable.) + +In nature it is of course only the stable types of motion which can +persist for more than a short time. Thus the task of the physical +evolutionist is to determine the forms of bifurcation, at which he must, +as it were, change carriages in the evolutionary journey so as always +to follow the stable route. He must besides be able to indicate +some natural process which shall correspond in effect to the ideal +arrangement of the several types of motion in families with gradually +changing specific differences. Although, as we shall see hereafter, it +may frequently or even generally be impossible to specify with exactness +the forms of bifurcation in the process of evolution, yet the conception +is one of fundamental importance. + +The ideas involved in this sketch are no doubt somewhat recondite, but I +hope to render them clearer to the non-mathematical reader by homologous +considerations in other fields of thought (I considered this subject in +my Presidential address to the British Association in 1905, "Report of +the 75th Meeting of the British Assoc." (S. Africa, 1905), London, 1906, +page 3. Some reviewers treated my speculations as fanciful, but as I +believe that this was due generally to misapprehension, and as I hold +that homologous considerations as to stability and instability are +really applicable to evolution of all sorts, I have thought it well to +return to the subject in the present paper.), and I shall pass on thence +to illustrations which will teach us something of the evolution of +stellar systems. + +States or governments are organised schemes of action amongst groups of +men, and they belong to various types to which generic names, such as +autocracy, aristocracy or democracy, are somewhat loosely applied. A +definite type of government corresponds to one of our types of +motion, and while retaining its type it undergoes a slow change as the +civilisation and character of the people change, and as the relationship +of the nation to other nations changes. In the language used before, the +government belongs to a family, and as time advances we proceed through +the successive members of the family. A government possesses a certain +degree of stability--hardly measurable in numbers however--to resist +disintegrating influences such as may arise from wars, famines, and +internal dissensions. This stability gradually rises to a maximum and +gradually declines. The degree of stability at any epoch will depend on +the fitness of some leading feature of the government to suit the +slowly altering circumstances, and that feature corresponds to the +characteristic denoted by a in the physical problem. A time at length +arrives when the stability vanishes, and the slightest shock will +overturn the government. At this stage we have reached the crisis of +a point of bifurcation, and there will then be some circumstance, +apparently quite insignificant and almost unnoticed, which is such as +to prevent the occurrence of anarchy. This circumstance or condition +is what we typified as b. Insignificant although it may seem, it has +started the government on a new career of stability by imparting to it +a new type. It grows in importance, the form of government becomes +obviously different, and its stability increases. Then in its turn this +newly acquired stability declines, and we pass on to a new crisis or +revolution. There is thus a series of "points of bifurcation" in history +at which the continuity of political history is maintained by means of +changes in the type of government. These ideas seem, to me at least, to +give a true account of the history of states, and I contend that it is +no mere fanciful analogy but a true homology, when in both realms of +thought--the physical and the political--we perceive the existence of +forms of bifurcation and of exchanges of stability. + +Further than this, I would ask whether the same train of ideas does not +also apply to the evolution of animals? A species is well adapted to its +environment when the individual can withstand the shocks of famine or +the attacks and competition of other animals; it then possesses a high +degree of stability. Most of the casual variations of individuals are +indifferent, for they do not tell much either for or against success +in life; they are small oscillations which leave the type unchanged. As +circumstances change, the stability of the species may gradually dwindle +through the insufficiency of some definite quality, on which in earlier +times no such insistent demands were made. The individual animals will +then tend to fail in the struggle for life, the numbers will dwindle and +extinction may ensue. But it may be that some new variation, at first of +insignificant importance, may just serve to turn the scale. A new +type may be formed in which the variation in question is preserved and +augmented; its stability may increase and in time a new species may be +produced. + +At the risk of condemnation as a wanderer beyond my province into the +region of biological evolution, I would say that this view accords with +what I understand to be the views of some naturalists, who recognise the +existence of critical periods in biological history at which extinction +occurs or which form the starting-point for the formation of new +species. Ought we not then to expect that long periods will elapse +during which a type of animal will remain almost constant, followed by +other periods, enormously long no doubt as measured in the life of man, +of acute struggle for existence when the type will change more rapidly? +This at least is the view suggested by the theory of stability in +the physical universe. (I make no claim to extensive reading on this +subject, but refer the reader for example to a paper by Professor A.A.W. +Hubrecht on "De Vries's theory of Mutations", "Popular Science Monthly", +July 1904, especially to page 213.) + +And now I propose to apply these ideas of stability to the theory of +stellar evolution, and finally to illustrate them by certain recent +observations of a very remarkable character. + +Stars and planets are formed of materials which yield to the enormous +forces called into play by gravity and rotation. This is obviously true +if they are gaseous or fluid, and even solid matter becomes plastic +under sufficiently great stresses. Nothing approaching a complete study +of the equilibrium of a heterogeneous star has yet been found possible, +and we are driven to consider only bodies of simpler construction. I +shall begin therefore by explaining what is known about the shapes which +may be assumed by a mass of incompressible liquid of uniform density +under the influences of gravity and of rotation. Such a liquid mass may +be regarded as an ideal star, which resembles a real star in the fact +that it is formed of gravitating and rotating matter, and because its +shape results from the forces to which it is subject. It is unlike a +star in that it possesses the attributes of incompressibility and +of uniform density. The difference between the real and the ideal is +doubtless great, yet the similarity is great enough to allow us +to extend many of the conclusions as to ideal liquid stars to the +conditions which must hold good in reality. Thus with the object of +obtaining some insight into actuality, it is justifiable to discuss an +avowedly ideal problem at some length. + +The attraction of gravity alone tends to make a mass of liquid assume +the shape of a sphere, and the effects of rotation, summarised under +the name of centrifugal force, are such that the liquid seeks to spread +itself outwards from the axis of rotation. It is a singular fact that +it is unnecessary to take any account of the size of the mass of liquid +under consideration, because the shape assumed is exactly the same +whether the mass be small or large, and this renders the statement of +results much easier than would otherwise be the case. + +A mass of liquid at rest will obviously assume the shape of a sphere, +under the influence of gravitation, and it is a stable form, because +any oscillation of the liquid which might be started would gradually die +away under the influence of friction, however small. If now we impart +to the whole mass of liquid a small speed of rotation about some axis, +which may be called the polar axis, in such a way that there are no +internal currents and so that it spins in the same way as if it were +solid, the shape will become slightly flattened like an orange. Although +the earth and the other planets are not homogeneous they behave in the +same way, and are flattened at the poles and protuberant at the equator. +This shape may therefore conveniently be described as planetary. + +If the planetary body be slightly deformed the forces of restitution +are slightly less than they were for the sphere; the shape is stable +but somewhat less so than the sphere. We have then a planetary spheroid, +rotating slowly, slightly flattened at the poles, with a high degree of +stability, and possessing a certain amount of rotational momentum. Let +us suppose this ideal liquid star to be somewhere in stellar space far +removed from all other bodies; then it is subject to no external forces, +and any change which ensues must come from inside. Now the amount +of rotational momentum existing in a system in motion can neither be +created nor destroyed by any internal causes, and therefore, whatever +happens, the amount of rotational momentum possessed by the star must +remain absolutely constant. + +A real star radiates heat, and as it cools it shrinks. Let us suppose +then that our ideal star also radiates and shrinks, but let the process +proceed so slowly that any internal currents generated in the liquid +by the cooling are annulled so quickly by fluid friction as to be +insignificant; further let the liquid always remain at any instant +incompressible and homogeneous. All that we are concerned with is that, +as time passes, the liquid star shrinks, rotates in one piece as if it +were solid, and remains incompressible and homogeneous. The condition is +of course artificial, but it represents the actual processes of nature +as well as may be, consistently with the postulated incompressibility +and homogeneity. (Mathematicians are accustomed to regard the density +as constant and the rotational momentum as increasing. But the way of +looking at the matter, which I have adopted, is easier of comprehension, +and it comes to the same in the end.) + +The shrinkage of a constant mass of matter involves an increase of its +density, and we have therefore to trace the changes which supervene as +the star shrinks, and as the liquid of which it is composed increases +in density. The shrinkage will, in ordinary parlance, bring the weights +nearer to the axis of rotation. Hence in order to keep up the rotational +momentum, which as we have seen must remain constant, the mass must +rotate quicker. The greater speed of rotation augments the importance of +centrifugal force compared with that of gravity, and as the flattening +of the planetary spheroid was due to centrifugal force, that flattening +is increased; in other words the ellipticity of the planetary spheroid +increases. + +As the shrinkage and corresponding increase of density proceed, the +planetary spheroid becomes more and more elliptic, and the succession +of forms constitutes a family classified according to the density of +the liquid. The specific mark of this family is the flattening or +ellipticity. + +Now consider the stability of the system, we have seen that the spheroid +with a slow rotation, which forms our starting-point, was slightly less +stable than the sphere, and as we proceed through the family of ever +flatter ellipsoids the stability continues to diminish. At length when +it has assumed the shape shown in a figure titled "Planetary spheroid +just becoming unstable" (Fig. 2.) where the equatorial and polar axes +are proportional to the numbers 1000 and 583, the stability has just +disappeared. According to the general principle explained above this +is a form of bifurcation, and corresponds to the form denoted A. The +specific difference a of this family must be regarded as the excess +of the ellipticity of this figure above that of all the earlier ones, +beginning with the slightly flattened planetary spheroid. Accordingly +the specific difference a of the family has gradually diminished from +the beginning and vanishes at this stage. + +According to Poincare's principle the vanishing of the stability serves +us with notice that we have reached a figure of bifurcation, and +it becomes necessary to inquire what is the nature of the specific +difference of the new family of figures which must be coalescent with +the old one at this stage. This difference is found to reside in the +fact that the equator, which in the planetary family has hitherto been +circular in section, tends to become elliptic. Hitherto the rotational +momentum has been kept up to its constant value partly by greater speed +of rotation and partly by a symmetrical bulging of the equator. But now +while the speed of rotation still increases (The mathematician familiar +with Jacobi's ellipsoid will find that this is correct, although in +the usual mode of exposition, alluded to above in a footnote, the speed +diminishes.), the equator tends to bulge outwards at two diametrically +opposite points and to be flattened midway between these protuberances. +The specific difference in the new family, denoted in the general sketch +by b, is this ellipticity of the equator. If we had traced the planetary +figures with circular equators beyond this stage A, we should have found +them to have become unstable, and the stability has been shunted off +along the A + b family of forms with elliptic equators. + +This new series of figures, generally named after the great +mathematician Jacobi, is at first only just stable, but as the density +increases the stability increases, reaches a maximum and then declines. +As this goes on the equator of these Jacobian figures becomes more +and more elliptic, so that the shape is considerably elongated in a +direction at right angles to the axis of rotation. + +At length when the longest axis of the three has become about three +times as long as the shortest (The three axes of the ellipsoid are +then proportional to 1000, 432, 343.), the stability of this family of +figures vanishes, and we have reached a new form of bifurcation and must +look for a new type of figure along which the stable development will +presumably extend. Two sections of this critical Jacobian figure, which +is a figure of bifurcation, are shown by the dotted lines in a figure +titled "The 'pear-shaped figure' and the Jocobian figure from which it +is derived" (Fig. 3.) comprising two figures, one above the other: the +upper figure is the equatorial section at right angles to the axis of +rotation, the lower figure is a section through the axis. + +Now Poincare has proved that the new type of figure is to be derived +from the figure of bifurcation by causing one of the ends to be +prolonged into a snout and by bluntening the other end. The snout forms +a sort of stalk, and between the stalk and the axis of rotation the +surface is somewhat flattened. These are the characteristics of a pear, +and the figure has therefore been called the "pear-shaped figure of +equilibrium." The firm line shows this new type of figure, whilst, as +already explained, the dotted line shows the form of bifurcation +from which it is derived. The specific mark of this new family is the +protrusion of the stalk together with the other corresponding smaller +differences. If we denote this difference by c, while A + b denotes the +Jacobian figure of bifurcation from which it is derived, the new family +may be called A + b + c, and c is zero initially. According to my +calculations this series of figures is stable (M. Liapounoff contends +that for constant density the new series of figures, which M. Poincare +discovered, has less rotational momentum than that of the figure of +bifurcation. If he is correct, the figure of bifurcation is a limit of +stable figures, and none can exist with stability for greater rotational +momentum. My own work seems to indicate that the opposite is true, and, +notwithstanding M. Liapounoff's deservedly great authority, I venture +to state the conclusions in accordance with my own work.), but I do not +know at what stage of its development it becomes unstable. + +Professor Jeans has solved a problem which is of interest as throwing +light on the future development of the pear-shaped figure, although +it is of a still more ideal character than the one which has been +discussed. He imagines an INFINITELY long circular cylinder of liquid +to be in rotation about its central axis. The existence is virtually +postulated of a demon who is always occupied in keeping the axis of the +cylinder straight, so that Jeans has only to concern himself with the +stability of the form of the section of the cylinder, which as I have +said is a circle with the axis of rotation at the centre. He then +supposes the liquid forming the cylinder to shrink in diameter, just as +we have done, and finds that the speed of rotation must increase so as +to keep up the constancy of the rotational momentum. The circularity of +section is at first stable, but as the shrinkage proceeds the stability +diminishes and at length vanishes. This stage in the process is a form +of bifurcation, and the stability passes over to a new series consisting +of cylinders which are elliptic in section. The circular cylinders are +exactly analogous with our planetary spheroids, and the elliptic ones +with the Jacobian ellipsoids. + +With further shrinkage the elliptic cylinders become unstable, a new +form of bifurcation is reached, and the stability passes over to a +series of cylinders whose section is pear-shaped. Thus far the analogy +is complete between our problem and Jeans's, and in consequence of +the greater simplicity of the conditions, he is able to carry his +investigation further. He finds that the stalk end of the pear-like +section continues to protrude more and more, and the flattening between +it and the axis of rotation becomes a constriction. Finally the neck +breaks and a satellite cylinder is born. Jeans's figure for an advanced +stage of development is shown in a figure titled "Section of a rotating +cylinder of liquid" (Fig. 4.), but his calculations do not enable him +actually to draw the state of affairs after the rupture of the neck. + +There are certain difficulties in admitting the exact parallelism +between this problem and ours, and thus the final development of our +pear-shaped figure and the end of its stability in a form of bifurcation +remain hidden from our view, but the successive changes as far as they +have been definitely traced are very suggestive in the study of stellar +evolution. + +Attempts have been made to attack this problem from the other end. If +we begin with a liquid satellite revolving about a liquid planet and +proceed backwards in time, we must make the two masses expand so that +their density will be diminished. Various figures have been drawn +exhibiting the shapes of two masses until their surfaces approach close +to one another and even until they just coalesce, but the discussion of +their stability is not easy. At present it would seem to be impossible +to reach coalescence by any series of stable transformations, and +if this is so Professor Jeans's investigation has ceased to be truly +analogous to our problem at some undetermined stage. However this may be +this line of research throws an instructive light on what we may expect +to find in the evolution of real stellar systems. + +In the second part of this paper I shall point out the bearing which +this investigation of the evolution of an ideal liquid star may have on +the genesis of double stars. + +II. + +There are in the heavens many stars which shine with a variable +brilliancy. Amongst these there is a class which exhibits special +peculiarities; the members of this class are generally known as Algol +Variables, because the variability of the star Beta Persei or Algol was +the first of such cases to attract the attention of astronomers, and +because it is perhaps still the most remarkable of the whole class. But +the circumstances which led to this discovery were so extraordinary that +it seems worth while to pause a moment before entering on the subject. + +John Goodricke, a deaf-mute, was born in 1764; he was grandson and heir +of Sir John Goodricke of Ribston Hall, Yorkshire. In November 1782, +he noted that the brilliancy of Algol waxed and waned (It is said that +Georg Palitzch, a farmer of Prohlis near Dresden, had about 1758 already +noted the variability of Algol with the naked eye. "Journ. Brit. Astron. +Assoc." Vol. XV. (1904-5), page 203.), and devoted himself to observing +it on every fine night from the 28th December 1782 to the 12th May 1783. +He communicated his observations to the Royal Society, and suggested +that the variation in brilliancy was due to periodic eclipses by a dark +companion star, a theory now universally accepted as correct. The +Royal Society recognised the importance of the discovery by awarding to +Goodricke, then only 19 years of age, their highest honour, the Copley +medal. His later observations of Beta Lyrae and of Delta Cephei were +almost as remarkable as those of Algol, but unfortunately a career of +such extraordinary promise was cut short by death, only a fortnight +after his election to the Royal Society. ("Dict. of National Biography"; +article Goodricke (John). The article is by Miss Agnes Clerke. It is +strange that she did not then seem to be aware that he was a deaf-mute, +but she notes the fact in her "Problems of Astrophysics", page 337, +London, 1903.) + +It was not until 1889 that Goodricke's theory was verified, when it +was proved by Vogel that the star was moving in an orbit, and in such +a manner that it was only possible to explain the rise and fall in the +luminosity by the partial eclipse of a bright star by a dark companion. + +The whole mass of the system of Algol is found to be half as great again +as that of our sun, yet the two bodies complete their orbit in the short +period of 2d 20h 48m 55s. The light remains constant during each period, +except for 9h 20m when it exhibits a considerable fall in brightness +(Clerke, "Problems of Astrophysics" page 302 and chapter XVIII.); the +curve which represents the variation in the light is shown in a figure +titled "The light-curve and system of Beta Lyrae" (Fig. 7.). + +The spectroscope has enabled astronomers to prove that many stars, +although apparently single, really consist of two stars circling around +one another (If a source of light is approaching with a great velocity +the waves of light are crowded together, and conversely they are spaced +out when the source is receding. Thus motion in the line of sight +virtually produces an infinitesimal change of colour. The position +of certain dark lines in the spectrum affords an exceedingly accurate +measurement of colour. Thus displacements of these spectral lines +enables us to measure the velocity of the source of light towards or +away from the observer.); they are known as spectroscopic binaries. +Campbell of the Lick Observatory believes that about one star in six is +a binary ("Astrophysical Journ." Vol. XIII. page 89, 1901. See also A. +Roberts, "Nature", Sept. 12, 1901, page 468.); thus there must be many +thousand such stars within the reach of our spectroscopes. + +The orientation of the planes of the orbits of binary stars appears to +be quite arbitrary, and in general the star does not vary in brightness. +Amongst all such orbits there must be some whose planes pass nearly +through the sun, and in these cases the eclipse of one of the stars by +the other becomes inevitable, and in each circuit there will occur two +eclipses of unequal intensities. + +It is easy to see that in the majority of such cases the two components +must move very close to one another. + +The coincidence between the spectroscopic and the photometric evidence +permits us to feel complete confidence in the theory of eclipses. When +then we find a star with a light-curve of perfect regularity and with +a characteristics of that of Algol, we are justified in extending the +theory of eclipses to it, although it may be too faint to permit of +adequate spectroscopic examination. This extension of the theory secures +a considerable multiplication of the examples available for observation, +and some 30 have already been discovered. + +Dr Alexander Roberts, of Lovedale in Cape Colony, truly remarks that +the study of Algol variables "brings us to the very threshold of the +question of stellar evolution." ("Proc. Roy. Soc. Edinburgh", XXIV. Part +II. (1902), page 73.) It is on this account that I propose to explain +in some detail the conclusion to which he and some other observers have +been led. + +Although these variable stars are mere points of light, it has been +proved by means of the spectroscope that the law of gravitation holds +good in the remotest regions of stellar space, and further it seems now +to have become possible even to examine the shapes of stars by indirect +methods, and thus to begin the study of their evolution. The chain of +reasoning which I shall explain must of necessity be open to criticism, +yet the explanation of the facts by the theory is so perfect that it is +not easy to resist the conviction that we are travelling along the path +of truth. + +The brightness of a star is specified by what is called its "magnitude." +The average brightness of all the stars which can just be seen with +the naked eye defines the sixth magnitude. A star which only gives +two-fifths as much light is said to be of the seventh magnitude; while +one which gives 2 1/2 times as much light is of the fifth magnitude, +and successive multiplications or divisions by 2 1/2 define the lower or +higher magnitudes. Negative magnitudes have clearly to be contemplated; +thus Sirius is of magnitude minus 1.4, and the sun is of magnitude minus +26. + +The definition of magnitude is also extended to fractions; for example, +the lights given by two candles which are placed at 100 feet and 100 +feet 6 inches from the observer differ in brightness by one-hundredth of +a magnitude. + +A great deal of thought has been devoted to the measurement of the +brightness of stars, but I will only describe one of the methods used, +that of the great astronomer Argelander. In the neighbourhood of the +star under observation some half dozen standard stars are selected of +known invariable magnitudes, some being brighter and some fainter than +the star to be measured; so that these stars afford a visible scale of +brightness. Suppose we number them in order of increasing brightness +from 1 to 6; then the observer estimates that on a given night his star +falls between stars 2 and 3, on the next night, say between 3 and 4, and +then again perhaps it may return to between 2 and 3, and so forth. With +practice he learns to evaluate the brightness down to small fractions +of a magnitude, even a hundredth part of a magnitude is not quite +negligible. + +For example, in observing the star RR Centauri five stars were in +general used for comparison by Dr Roberts, and in course of three months +he secured thereby 300 complete observations. When the period of the +cycle had been ascertained exactly, these 300 values were reduced to +mean values which appertained to certain mean places in the cycle, and +a mean light-curve was obtained in this way. Figures titled "Light curve +of RR Centauri" (Fig. 5) and "The light-curve and system of Beta Lyrae" +(Fig. 7) show examples of light curves. + +I shall now follow out the results of the observation of RR Centauri +not only because it affords the easiest way of explaining these +investigations, but also because it is one of the stars which furnishes +the most striking results in connection with the object of this essay. +(See "Monthly notices R.A.S." Vol. 63, 1903, page 527.) This star has +a mean magnitude of about 7 1/2, and it is therefore invisible to +the naked eye. Its period of variability is 14h 32m 10s.76, the last +refinement of precision being of course only attained in the final +stages of reduction. Twenty-nine mean values of the magnitude were +determined, and they were nearly equally spaced over the whole cycle of +changes. The black dots in Fig. 5 exhibit the mean values determined by +Dr Roberts. The last three dots on the extreme right are merely the same +as the first three on the extreme left, and are repeated to show how +the next cycle would begin. The smooth dotted curve will be explained +hereafter, but, by reference to the scale of magnitudes on the margins +of the figure, it may be used to note that the dots might be brought +into a perfectly smooth curve by shifting some few of the dots by about +a hundredth of a magnitude. + +This light-curve presents those characteristics which are due to +successive eclipses, but the exact form of the curve must depend on the +nature of the two mutually eclipsing stars. If we are to interpret the +curve with all possible completeness, it is necessary to make certain +assumptions as to the stars. It is assumed then that the stars are +equally bright all over their disks, and secondly that they are not +surrounded by an extensive absorptive atmosphere. This last appears to +me to be the most dangerous assumption involved in the whole theory. + +Making these assumptions, however, it is found that if each of the +eclipsing stars were spherical it would not be possible to generate such +a curve with the closest accuracy. The two stars are certainly close +together, and it is obvious that in such a case the tidal forces +exercised by each on the other must be such as to elongate the figure +of each towards the other. Accordingly it is reasonable to adopt the +hypothesis that the system consists of a pair of elongated ellipsoids, +with their longest axes pointed towards one another. No supposition +is adopted a priori as to the ratio of the two masses, or as to their +relative size or brightness, and the orbit may have any degree of +eccentricity. These last are all to be determined from the nature of the +light-curve. + +In the case of RR Centauri, however, Dr Roberts finds the conditions are +best satisfied by supposing the orbit to be circular, and the sizes and +masses of the components to be equal, while their luminosities are to +one another in the ratio of 4 to 3. As to their shapes he finds them +to be so much elongated that they overlap, as exhibited in his figure +titled "The shape of the star RR Centauri" (Fig. 6.). The dotted curve +shows a form of equilibrium of rotating liquid as computed by me some +years before, and it was added for the sake of comparison. + +On turning back to Fig. 5 the reader will see in the smooth dotted curve +the light variation which would be exhibited by such a binary system as +this. The curve is the result of computation and it is impossible not to +be struck by the closeness of the coincidence with the series of black +dots which denote the observations. + +It is virtually certain that RR Centauri is a case of an eclipsing +binary system, and that the two stars are close together. It is not +of course proved that the figures of the stars are ellipsoids, but +gravitation must deform them into a pair of elongated bodies, and, on +the assumptions that they are not enveloped in an absorptive atmosphere +and that they are ellipsoidal, their shapes must be as shown in the +figure. + +This light-curve gives an excellent illustration of what we have reason +to believe to be a stage in the evolution of stars, when a single star +is proceeding to separate into a binary one. + +As the star is faint, there is as yet no direct spectroscopic evidence +of orbital motion. Let us turn therefore to the case of another star, +namely V Puppis, in which such evidence does already exist. I give an +account of it, because it presents a peculiarly interesting confirmation +of the correctness of the theory. + +In 1895 Pickering announced in the "Harvard Circular" No. 14 that the +spectroscopic observations at Arequipa proved V Puppis to be a double +star with a period of 3d 2h 46m. Now when Roberts discussed its +light-curve he found that the period was 1d 10h 54m 27s, and on account +of this serious discrepancy he effected the reduction only on the simple +assumption that the two stars were spherical, and thus obtained a fairly +good representation of the light-curve. It appeared that the orbit was +circular and that the two spheres were not quite in contact. Obviously +if the stars had been assumed to be ellipsoids they would have been +found to overlap, as was the case for RR Centauri. ("Astrophysical +Journ." Vol. XIII. (1901), page 177.) The matter rested thus for some +months until the spectroscopic evidence was re-examined by Miss Cannon +on behalf of Professor Pickering, and we find in the notes on page +177 of Vol. XXVIII. of the "Annals of the Harvard Observatory" the +following: "A.G.C. 10534. This star, which is the Algol variable V +Puppis, has been found to be a spectroscopic binary. The period 1d.454 +(i.e. 1d 10h 54m) satisfies the observations of the changes in light, +and of the varying separation of the lines of the spectrum. The spectrum +has been examined on 61 plates, on 23 of which the lines are double." +Thus we have valuable evidence in confirmation of the correctness of the +conclusions drawn from the light-curve. In the circumstances, however, +I have not thought it worth while to reproduce Dr Roberts's provisional +figure. + +I now turn to the conclusions drawn a few years previously by another +observer, where we shall find the component stars not quite in contact. +This is the star Beta Lyrae which was observed by Goodricke, Argelander, +Belopolsky, Schur, Markwick and by many others. The spectroscopic method +has been successfully applied in this case, and the component stars are +proved to move in an orbit about one another. In 1897, Mr. G.W. Myers +applied the theory of eclipses to the light-curve, on the hypothesis +that the stars are elongated ellipsoids, and he obtained the interesting +results exhibited in Fig. 7. ("Astrophysical Journ." Vol. VII. (1898), +page 1.) + +The period of Beta Lyrae is relatively long, being 12d 21h 47m, the +orbit is sensibly eccentric, and the two spheroids are not so much +elongated as was the case with RR Centauri. The mass of the system is +enormous, one of the two stars being 10 times and the other 21 times as +heavy as our sun. + +Further illustrations of this subject might be given, but enough has +been said to explain the nature of the conclusions which have been drawn +from this class of observation. + +In my account of these remarkable systems the consideration of one very +important conclusion has been purposely deferred. Since the light-curve +is explicable by eclipses, it follows that the sizes of the two stars +are determinable relatively to the distance between them. The period of +their orbital motion is known, being identical with the complete period +of the variability of their light, and an easy application of Kepler's +law of periodic times enables us to compute the sum of the masses of the +two stars divided by the cube of the distance between their centres. +Now the sizes of the bodies being known, the mean density of the whole +system may be calculated. In every case that density has been found to +be much less than the sun's, and indeed the average of a number of mean +densities which have been determined only amounts to one-eighth of that +of the sun. In some cases the density is extremely small, and in no case +is it quite so great as half the solar density. + +It would be absurd to suppose that these stars can be uniform in +density throughout, and from all that is known of celestial bodies it +is probable that they are gaseous in their external parts with great +condensation towards their centres. This conclusion is confirmed by +arguments drawn from the theory of rotating masses of liquid. (See J.H. +Jeans, "On the density of Algol variables", "Astrophysical Journ." Vol. +XXII. (1905), page 97.) + +Although, as already explained, a good deal is known about the shapes +and the stability of figures consisting of homogeneous incompressible +liquid in rotation, yet comparatively little has hitherto been +discovered about the equilibrium of rotating gaseous stars. The figures +calculated for homogeneous liquid can obviously only be taken to afford +a general indication of the kind of figure which we might expect to find +in the stellar universe. Thus the dotted curve in Fig. 5, which exhibits +one of the figures which I calculated, has some interest when placed +alongside the figures of the stars in RR Centauri, as computed from the +observations, but it must not be accepted as the calculated form of such +a system. I have moreover proved more recently that such a figure of +homogeneous liquid is unstable. Notwithstanding this instability it does +not necessarily follow that the analogous figure for compressible fluid +is also unstable, as will be pointed out more fully hereafter. + +Professor Jeans has discussed in a paper of great ability the difficult +problems offered by the conditions of equilibrium and of stability of a +spherical nebula. ("Phil. Trans. R.S." Vol. CXCIX. A (1902), page 1. See +also A. Roberts, "S. African Assoc. Adv. Sci." Vol. I. (1903), page 6.) +In a later paper ("Astrophysical Journ." Vol. XXII. (1905), page 97.), +in contrasting the conditions which must govern the fission of a star +into two parts when the star is gaseous and compressible with the +corresponding conditions in the case of incompressible liquid, he points +out that for a gaseous star (the agency which effects the separation +will no longer be rotation alone; gravitation also will tend towards +separation... From numerical results obtained in the various papers of +my own,... I have been led to the conclusion that a gravitational +instability of the kind described must be regarded as the primary agent +at work in the actual evolution of the universe, Laplace's rotation +playing only the secondary part of separating the primary and satellite +after the birth of the satellite.) + +It is desirable to add a word in explanation of the expression +"gravitational instability" in this passage. It means that when the +concentration of a gaseous nebula (without rotation) has proceeded to +a certain stage, the arrangement in spherical layers of equal density +becomes unstable, and a form of bifurcation has been reached. For +further concentration concentric spherical layers become unstable, and +the new stable form involves a concentration about two centres. The +first sign of this change is that the spherical layers cease to be +quite concentric and then the layers of equal density begin to assume +a somewhat pear-shaped form analogous to that which we found to occur +under rotation for an incompressible liquid. Accordingly it appears that +while a sphere of liquid is stable a sphere of gas may become unstable. +Thus the conditions of stability are different in these two simple +cases, and it is likely that while certain forms of rotating liquid are +unstable the analogous forms for gas may be stable. This furnishes a +reason why it is worth while to consider the unstable forms of rotating +liquid. + +There can I think be little doubt but that Jeans is right in looking to +gravitational instability as the primary cause of fission, but when we +consider that a binary system, with a mass larger than the sun's, is +found to rotate in a few hours, there seems reason to look to rotation +as a contributory cause scarcely less important than the primary one. + +With the present extent of our knowledge it is only possible to +reconstruct the processes of the evolution of stars by means of +inferences drawn from several sources. We have first to rely on the +general principles of stability, according to which we are to look for a +series of families of forms, each terminating in an unstable form, which +itself becomes the starting-point of the next family of stable forms. +Secondly we have as a guide the analogy of the successive changes in +the evolution of ideal liquid stars; and thirdly we already possess some +slender knowledge as to the equilibrium of gaseous stars. + +From these data it is possible to build up in outline the probable +history of binary stars. Originally the star must have been single, it +must have been widely diffused, and must have been endowed with a slow +rotation. In this condition the strata of equal density must have been +of the planetary form. As it cooled and contracted the symmetry round +the axis of rotation must have become unstable, through the effects of +gravitation, assisted perhaps by the increasing speed of rotation. (I +learn from Professor Jeans that he now (December 1908) believes that +he can prove that some small amount of rotation is necessary to induce +instability in the symmetrical arrangement.) The strata of equal +density must then become somewhat pear-shaped, and afterwards like an +hour-glass, with the constriction more pronounced in the internal than +in the external strata. The constrictions of the successive strata then +begin to rupture from the inside progressively outwards, and when at +length all are ruptured we have the twin stars portrayed by Roberts and +by others. + +As we have seen, the study of the forms of equilibrium of rotating +liquid is almost complete, and Jeans has made a good beginning in the +investigation of the equilibrium of gaseous stars, but much more remains +to be discovered. The field for the mathematician is a wide one, and in +proportion as the very arduous exploration of that field is attained so +will our knowledge of the processes of cosmical evolution increase. + +From the point of view of observation, improved methods in the use of +the spectroscope and increase of accuracy in photometry will certainly +lead to a great increase in our knowledge within the next few years. +Probably the observational advance will be more rapid than that of +theory, for we know how extraordinary has been the success attained +within the last few years, and the theory is one of extreme difficulty; +but the two ought to proceed together hand in hand. Human life is +too short to permit us to watch the leisurely procedure of cosmical +evolution, but the celestial museum contains so many exhibits that it +may become possible, by the aid of theory, to piece together bit by bit +the processes through which stars pass in the course of their evolution. + +In the sketch which I have endeavoured to give of this fascinating +subject, I have led my reader to the very confines of our present +knowledge. It is not much more than a quarter of a century since this +class of observation has claimed the close attention of astronomers; +something considerable has been discovered already and there seems +scarcely a discernible limit to what will be known in this field a +century from now. Some of the results which I have set forth may then be +shown to be false, but it seems profoundly improbable that we are being +led astray by a Will-of-the-Wisp. + + + + +XXIX. THE EVOLUTION OF MATTER. By W.C.D. Whetham, M.A., F.R.S. + +Trinity College, Cambridge. + + +The idea of evolution in the organic world, made intelligible by the +work of Charles Darwin, has little in common with the recent conception +of change in certain types of matter. The discovery that a process of +disintegration may take place in some at least of the chemical atoms, +previously believed to be indestructible and unalterable, has modified +our view of the physical universe, even as Darwin's scheme of the mode +of evolution changed the trend of thought concerning the organic world. +Both conceptions have in common the idea of change throughout extended +realms of space and time, and, therefore, it is perhaps not unfitting +that some account of the most recent physical discoveries should be +included in the present volume. + +The earliest conception of the evolution of matter is found in the +speculation of the Greeks. Leucippus and Democritus imagined unchanging +eternal atoms, Heracleitus held that all things were in a continual +state of flux--Panta rei. + +But no one in the Ancient World--no one till quite modern times--could +appreciate the strength of the position which the theory of the +evolution of matter must carry before it wins the day. Vague +speculation, even by the acute minds of philosophers, is of little use +in physical science before experimental facts are available. The true +problems at issue cannot even be formulated, much less solved, till the +humble task of the observer and experimenter has given us a knowledge of +the phenomena to be explained. + +It was only through the atomic theory, at first apparently diametrically +opposed to it, that the conception of evolution in the physical world +was to gain an established place. For a century the atomic theory, when +put into a modern form by Dalton, led farther and farther away from +the idea of change in matter. The chemical elements seemed quite +unalterable, and the atoms, of which each element in modern view is +composed, bore to Clerk Maxwell, writing about 1870, "the stamp of +manufactured articles" exactly similar in kind, unchanging, eternal. + +Nevertheless throughout these years, on the whole so unfavourable to its +existence, there persisted the idea of a common origin of the distinct +kinds of matter known to chemists. Indeed, this idea of unity in +substance in nature seems to accord with some innate desire or intimate +structure of the human mind. As Mr Arthur Balfour well puts it, "There +is no a priori reason that I know of for expecting that the material +world should be a modification of a single medium, rather than a +composite structure built out of sixty or seventy elementary substances, +eternal and eternally different. Why then should we feel content with +the first hypothesis and not with the second? Yet so it is. Men of +science have always been restive under the multiplication of entities. +They have eagerly watched for any sign that the different chemical +elements own a common origin, and are all compounded out of some +primordial substance. Nor, for my part, do I think that such instincts +should be ignored... that they exist is certain; that they modify the +indifferent impartiality of pure empiricism can hardly be denied." +("Report of the 74th Meeting of the British Association" (Presidential +Address, Cambridge 1904), page 9, London, 1905.) + +When Dalton's atomic theory had been in existence some half century, it +was noted that certain numerical relations held good between the atomic +weights of elements chemically similar to one another. Thus the weight +(88) of an atom of strontium compared with that of hydrogen as unity, +is about the mean of those of calcium (40) and barium (137). Such +relations, in this and other chemical groups, were illustrated by +Beguyer de Chancourtois in 1862 by the construction of a spiral diagram +in which the atomic weights are placed in order round a cylinder and +elements chemically similar are found to fall on vertical lines. + +Newlands seems to have been the first to see the significance of such +a diagram. In his "law of octaves," formulated in 1864, he advanced +the hypothesis that, if arranged in order of rising atomic weight, the +elements fell into groups, so that each eighth element was chemically +similar. Stated thus, the law was too definite; no room was left for +newly-discovered elements, and some dissimilar elements were perforce +grouped together. + +But in 1869 Mendeleeff developed Newland's hypothesis in a form that +attracted at once general attention. Placing the elements in order of +rising atomic weight, but leaving a gap where necessary to bring similar +elements into vertical columns, he obtained a periodic table with +natural vacancies to be filled as new elements were discovered, and with +a certain amount of flexibility at the ends of the horizontal lines. +From the position of the vacancies, the general chemical and physical +properties of undiscovered elements could be predicted, and the +success of such predictions gave a striking proof of the usefulness of +Mendeleeff's generalisation. + +When the chemical and physical properties of the elements were known +to be periodic functions of their atomic weights, the idea of a common +origin and common substance became much more credible. Differences in +atomic weight and differences in properties alike might reasonably be +explained by the differences in the amount of the primordial substance +present in the various atoms; an atom of oxygen being supposed to be +composed of sixteen times as much stuff as the atom of hydrogen, but to +be made of the same ultimate material. Speculations about the mode of +origin of the elements now began to appear, and put on a certain air +of reality. Of these speculations perhaps the most detailed was that of +Crookes, who imagined an initial chaos of a primordial medium he named +protyle, and a process of periodic change in which the chemical elements +successively were precipitated. + +From another side too, suggestions were put forward by Sir Norman +Lockyer and others that the differences in spectra observed in +different classes of stars, and produced by different conditions in +the laboratory, were to be explained by changes in the structure of the +vibrating atoms. + +The next step in advance gave a theoretical basis for the idea of a +common structure of matter, and was taken in an unexpected direction. +Clerk Maxwell's electromagnetic theory of light, accepted in England, +was driven home to continental minds by the confirmatory experiments of +Hertz, who in 1888 detected and measured the electromagnetic waves +that Maxwell had described twenty years earlier. But, if light be an +electromagnetic phenomenon, the light waves radiated by hot bodies must +take their origin in the vibrations of electric systems. Hence within +the atoms must exist electric charges capable of vibration. On these +lines Lorentz and Larmor have developed an electronic theory of matter, +which is imagined in its essence to be a conglomerate of electric +charges, with electro-magnetic inertia to explain mechanical inertia. +(Larmor, "Aether and Matter", Cambridge, 1900.) The movement of electric +charges would be affected by a magnetic field, and hence the discovery +by Zeeman that the spectral lines of sodium were doubled by a strong +magnetic force gave confirmatory evidence to the theory of electrons. + +Then came J.J. Thomson's great discovery of minute particles, much +smaller than any chemical atom, forming a common constituent of many +different kinds of matter. (Thomson, "Conduction of Electricity through +Gases" (2nd edition), Cambridge, 1906.) If an electric discharge be +passed between metallic terminals through a glass vessel containing +air at very low pressure, it is found that rectilinear rays, known +as cathode rays, proceed from the surface of the cathode or negative +terminal. Where these rays strike solid objects, they give rise to +the Rontgen rays now so well known; but it is with the cathode rays +themselves that we are concerned. When they strike an insulated +conductor, they impart to it a negative charge, and Thomson found that +they were deflected from their path both by magnetic and electric forces +in the direction in which negatively electrified particles would be +deflected. Cathode rays then were accepted as flights of negatively +charged particles, moving with high velocities. The electric and +magnetic deflections give two independent measurements which may be made +on a cathode ray, and both the deflections involve theoretically three +unknown quantities, the mass of the particles, their electric charge +and their velocity. There is strong cumulative evidence that all +such particles possess the same charge, which is identical with that +associated with a univalent atom in electrolytic liquids. The number of +unknown quantities was thus reduced to two--the mass and the velocity. +The measurement of the magnetic and electric deflections gave two +independent relations between the unknowns, which could therefore be +determined. The velocities of the cathode ray particles were found to +vary round a value about one-tenth that of light, but the mass was found +always to be the same within the limits of error, whatever the nature of +the terminals, of the residual gas in the vessel, and of the conditions +of the experiment. The mass of a cathode ray particle, or corpuscle, as +Thomson, adopting Newton's name, called it, is about the eight-hundredth +part of the mass of a hydrogen atom. + +These corpuscles, found in so many different kinds of substance, +are inevitably regarded as a common constituent of matter. They are +associated each with a unit of negative electricity. Now electricity in +motion possesses electromagnetic energy, and produces effects like those +of mechanical inertia. In other words, an electric charge possesses +mass, and there is evidence to show that the effective mass of a +corpuscle increases as its velocity approaches that of light in the way +it would do if all its mass were electromagnetic. We are led therefore +to regard the corpuscle from one aspect as a disembodied charge of +electricity, and to identify it with the electron of Lorentz and Larmor. + +Thus, on this theory, matter and electricity are identified; and a great +simplification of our conception of the physical structure of Nature is +reached. Moreover, from our present point of view, a common basis for +matter suggests or implies a common origin, and a process of development +possibly intelligible to our minds. The idea of the evolution of matter +becomes much more probable. + +The question of the nature and physical meaning of a corpuscle or +electron remains for consideration. On the hypothesis of a universal +luminiferous aether, Larmor has suggested a centre of aethereal strain +"a place where the continuity of the medium has been broken and cemented +together again (to use a crude but effective image) without accurately +fitting the parts, so that there is a residual strain all round the +place." (Larmor, loc. cit.) Thus he explains in quasi-mechanical terms +the properties of an electron. But whether we remain content for the +time with our identification of matter and electricity, or attempt to +express both of them in terms of hypothetical aether, we have made a +great step in advance on the view that matter is made up of chemical +atoms fundamentally distinct and eternally isolated. + +Such was the position when the phenomena of radio-activity threw a new +light on the problem, and, for the first time in the history of science, +gave definite experimental evidence of the transmutation of matter from +one chemical element to another. + +In 1896 H. Becquerel discovered that compounds of the metal uranium +continually emitted rays capable of penetrating opaque screens and +affecting photographic plates. Like cathode and Rontgen rays, the +rays from uranium make the air through which they pass a conductor +of electricity, and this property gives the most convenient method of +detecting the rays and of measuring their intensity. An electroscope may +be made of a strip of gold-leaf attached to an insulated brass plate +and confined in a brass vessel with glass windows. When the gold-leaf is +electrified, it is repelled from the similarly electrified brass plate, +and the angle at which it stands out measures the electrification. Such +a system, if well insulated, holds its charge for hours, the leakage +of electricity through the air being very slow. But, if radio-active +radiation reach the air within, the gold-leaf falls, and the rate of +its fall, as watched through a microscope with a scale in the eye-piece, +measures the intensity of the radiation. With some form of this simple +instrument, or with the more complicated quadrant electrometer, most +radio-active measurements have been made. + +It was soon discovered that the activity of uranium compounds +was proportional to the amount of uranium present in them. Thus +radio-activity is an atomic property dependent on the amount of an +element and independent of its state of chemical combination. + +In a search for radio-activity in different minerals, M. and Mme Curie +found a greater effect in pitch-blende than its contents of uranium +warranted, and, led by the radio-active property alone, they succeeded, +by a long series of chemical separations, in isolating compounds of a +new and intensely radio-active substance which they named radium. + +Radium resembles barium in its chemical properties, and is precipitated +with barium in the ordinary course of chemical analysis. It is separated +by a prolonged course of successive crystallisation, the chloride of +radium being less soluble than that of barium, and therefore sooner +separated from an evaporating solution. When isolated, radium chloride +has a composition, which, on the assumption that one atom of metal +combines with two of chlorine as in barium chloride, indicates that the +relative weight of the atom of radium is about 225. As thus prepared, +radium is a well-marked chemical element, forming a series of compounds +analogous to those of barium and showing a characteristic line spectrum. +But, unlike most other chemical elements, it is intensely radio-active, +and produces effects some two million times greater than those of +uranium. + +In 1899 E. Rutherford, then of Montreal, discovered that the +radiation from uranium, thorium and radium was complex. (Rutherford, +"Radio-activity" (2nd edition), Cambridge, 1905.) Three types of rays +were soon distinguished. The first, named by Rutherford alpha-rays, are +absorbed by thin metal foil or a few centimetres of air. When examined +by measurements of the deflections caused by magnetic and electric +fields, the alpha-rays are found to behave as would positively +electrified particles of the magnitude of helium atoms possessing a +double ionic charge and travelling with a velocity about one-tenth that +of light. The second or beta type of radiation is much more penetrating. +It will pass through a considerable thickness of metallic foil, or many +centimetres of air, and still affect photographic plates or discharge +electroscopes. Magnetic and electric forces deflect beta-rays much +more than alpha-rays, indicating that, although the speed is greater, +approaching in some cases within five per cent. that of light, the mass +is very much less. The beta-rays must be streams of particles, identical +with those of cathode rays, possessing the minute mass of J.J. Thomson's +corpuscle, some eight-hundredth part of that of a hydrogen atom. A third +or gamma type of radiation was also detected. More penetrating even than +beta-rays, the gamma-rays have never been deflected by any magnetic +or electric force yet applied. Like Rontgen rays, it is probable that +gamma-rays are wave-pulses in the luminiferous aether, though the +possibility of explaining them as flights of non-electrified particles +is before the minds of some physicists. + +Still another kind of radiation has been discovered more recently by +Thomson, who has found that in high vacua, rays become apparent which +are absorbed at once by air at any ordinary pressure. + +The emission of all these different types of radiation involves a +continual drain of energy from the radio-active body. When M. and Mme +Curie had prepared as much as a gramme of radium chloride, the energy of +the radiation became apparent as an evolution of heat. The radium salt +itself, and the case containing it, absorbed the major part of the +radiation, and were thus maintained at a temperature measurably higher +than that of the surroundings. The rate of thermal evolution was such +that it appeared that one gramme of pure radium must emit about 100 +gramme-calories of heat in an hour. This observation, naturally as it +follows from the phenomena previously discovered, first called attention +to the question of the source of the energy which maintains indefinitely +and without apparent diminution the wonderful stream of radiation +proceeding from a radio-active substance. In the solution of this +problem lies the point of the present essay. + +In order to appreciate the evidence which bears on the question we must +now describe two other series of phenomena. + +It is a remarkable fact that the intensity of the radiation from +a radio-active body is independent of the external conditions of +temperature, pressure, etc. which modify so profoundly almost all other +physical and chemical processes. Exposure to the extreme cold of liquid +air, or to the great heat of a furnace, leaves the radio-activity of a +substance unchanged, apparent exceptions to this statement having been +traced to secondary causes. + +Then, it is found that radio-activity is always accompanied by some +chemical change; a new substance always appears as the parent substance +emits these radiations. Thus by chemical reactions it is possible to +separate from uranium and thorium minute quantities of radio-active +materials to which the names of uranium-X and thorium-X have been given. +These bodies behave differently from their parents uranium and thorium, +and show all the signs of distinct chemical individuality. They are +strongly radio-active, while, after the separation, the parents uranium +and thorium are found to have lost some of their radio-activity. If the +X-substances be kept, their radio-activity decays, while that of the +uranium or thorium from which they were obtained gradually rises to the +initial value it had before the separation. At any moment, the sum of +the radio-activity is constant, the activity lost by the product being +equal to that gained by the parent substance. These phenomena are +explained if we suppose that the X-product is slowly produced in the +substance of the parent, and decays at a constant rate. Uranium, +as usually seen, contains a certain amount of uranium-X, and its +radio-activity consists of two parts--that of the uranium itself, and +that of the X product. When the latter is separated by means of its +chemical reactions, its radio-activity is separated also, and the rates +of decay and recovery may be examined. + +Radium and thorium, but not uranium, give rise to radio-active gases +which have been called emanations. Rutherford has shown that their +radio-activity, like that of the X products, suffers decay, while +the walls of the vessel in which the emanation is confined, become +themselves radio-active. If washed with certain acids, however, the +walls lose their activity, which is transferred to the acid, and can be +deposited by evaporation from it on to a solid surface. Here again it +is clear that the emanation gives rise to a radio-active substance which +clings to the walls of the vessel, and is soluble in certain liquids, +but not in others. + +We shall return to this point, and trace farther the history of the +radio-active matter. At present we wish to emphasise the fact that, as +in other cases, the radio-activity of the emanation is accompanied +by the appearance of a new kind of substance with distinct chemical +properties. + +We are now in a position to consider as a whole the evidence on the +question of the source of radio-active energy. + +(1) Radio-activity is accompanied by the appearance of new chemical +substances. The energy liberated is therefore probably due to the +associated chemical change. (2) The activity of a series of compounds is +found to accompany the presence of a radio-active element, the activity +of each compound depends only on the contents of the element, and is +independent of the nature of its combination. Thus radio-activity is a +property of the element, and is not affected by its state of isolation +or chemical combination. (3) The radio-activity of a simple transient +product decays in a geometrical progression, the loss per second being +proportional to the mass of substance still left at the moment, and +independent of its state of concentration or dilution. This type of +reaction is well known in chemistry to mark a mono-molecular +change, where each molecule is dissociated or altered in structure +independently. If two or more molecules were concerned simultaneously, +the rate of reaction would depend on the nearness of the molecules +to each other, that is, to the concentration of the material. (4) The +amount of energy liberated by the change of a given mass of material far +transcends the amount set free by any known ordinary chemical action. +The activity of radium decays so slowly that it would not sink to half +its initial value in less than some two thousand years, and yet one +gramme of radium emits about 100 calories of heat during each hour of +its existence. + +The energy of radio-activity is due to chemical change, but clearly +to no chemical change hitherto familiar to science. It is an atomic +property, characteristic of a given element, and the atoms undergo the +change individually, not by means of interaction among each other. The +conclusion is irresistible that we are dealing with a fundamental +change in the structure of the individual atoms, which, one by one, are +dissociating into simpler parts. We are watching the disintegration +of the "atoms" of the chemist, hitherto believed indestructible and +eternal, and measuring the liberation of some of the long-suspected +store of internal atomic energy. We have stumbled on the transmutation +dreamed by the alchemist, and discovered the process of a veritable +evolution of matter. + +The transmutation theory of radio-activity was formulated by Rutherford +(Rutherford, "Radio-activity" (2nd edition), Cambridge, 1905, page 307.) +and Soddy in 1903. By its light, all recent work on the subject has been +guided; it has stood the supreme test of a hypothesis, and shown power +to suggest new investigations and to co-ordinate and explain them, when +carried out. We have summarised the evidence which led to the conception +of the theory; we have now to consider the progress which has been made +in tracing the successive disintegration of radio-active atoms. + +Soon after the statement of the transmutation theory, a striking +verification of one of its consequences appeared. The measurement of +the magnetic and electric deflection of the alpha-rays suggested +to Rutherford the idea that the stream of projectiles of which they +consisted was a flight of helium atoms. Ramsay and Soddy, confining a +minute bubble of radium emanation in a fine glass tube, were able +to watch the development of the helium spectrum as, day by day, the +emanation decayed. By isolating a very narrow pencil of alpha-rays, +and watching through a microscope their impact on a fluorescent screen, +Rutherford has lately counted the individual alpha-projectiles, and +confirmed his original conclusion that their mass corresponded to that +of helium atoms and their charge to double that on a univalent atom. +("Proc. Roy. Soc." A, page 141, 1908.) Still more recently, he has +collected the alpha-particles shot through an extremely thin wall of +glass, and demonstrated by direct spectroscopic evidence the presence of +helium. ("Phil. Mag." February 1909.) + +But the most thorough investigation of a radio-active pedigree is found +in Rutherford's classical researches on the successive disintegration +products of radium, in order to follow the evidence on which his results +are founded, we must describe more fully the process of decay of the +activity of a simple radio-active substance. The decay of activity of +the body known as uranium-X is shown in a falling curve (Fig. 1.). It +will be seen that, in each successive 22 days, the activity falls to +half the value it possessed at the beginning. + +This change in a geometrical progression is characteristic of simple +radio-active processes, and can be expressed mathematically by a simple +exponential formula. + +As we have said above, solid bodies exposed to the emanations of radium +or thorium become coated with a radio-active deposit. The rate of decay +of this activity depends on the time of exposure to the emanation, and +does not always show the usual simple type of curve. Thus the activity +of a rod exposed to radium emanation for 1 minute decays in accordance +with a curve (Fig. 2) which represents the activity as measured by the +alpha-rays. If the electroscope be screened from the alpha-rays, it is +found that the activity of the rod in beta- an gamma-rays increases for +some 35 minutes and then diminishes (Fig. 3.). + +These complicated relations have been explained satisfactorily and +completely by Rutherford on the hypothesis of successive changes of +the radio-active matter into one new body after another. (Rutherford, +"Radio-activity" (2nd edition), Cambridge, 1905, page 379.) The +experimental curve represents the resultant activity of all the +matter present at a given moment, and the process of disentangling the +component effects consists in finding a number of curves, which express +the rise and fall of activity of each kind of matter as it is produced +and decays, and, fitted together, give the curve of the experiments. + +Other methods of investigation also are open. They have enabled +Rutherford to complete the life-history of radium and its products, and +to clear up doubtful points left by the analysis of the curves. By the +removal of the emanation, the activity of radium itself has been shown +to consist solely of alpha-rays. This removal can be effected by passing +air through the solution of a radium salt. The emanation comes away, and +the activity of the deposit which it leaves behind decays rapidly to a +small fraction of its initial value. Again, some of the active deposits +of the emanation are more volatile than others, and can be separated +from them by the agency of heat. + +From such evidence Rutherford has traced a long series of disintegration +products of radium, all but the first of which exist in much too minute +quantities to be detected otherwise than by their radio-activities. +Moreover, two of these products are not themselves appreciably +radio-active, though they are born from radio-active parents, and give +rise to a series of radio-active descendants. Their presence is inferred +from such evidence as the rise of beta and gamma radio-activity in the +solid newly deposited by the emanation; this rise measuring the growth +of the first radio-active offspring of one of the non-active bodies. +Some of the radium products give out alpha-rays only, one beta- and +gamma-rays, while one yields all three types of radiation. The pedigree +of the radium family may be expressed in the following table, the time +noted in the second column being the time required for a given quantity +to be half transformed into its next derivative. + + + Time of half Radio- Properties + decay activity + + Radium About 2600 years alpha rays Element chemically analogous + to barium. + + Emanation 3.8 days alpha rays Chemically inert gas; + condenses at -150 deg C. + + Radium-A 3 minutes alpha rays Behaves as a solid deposited on + surfaces; concentrated on a + negative electrode. + + Radium-B 21 minutes no rays Soluble in strong acids; + volatile at a white heat; more + volatile than A or C. + + Radium-C 28 minutes alpha, beta, Soluble in strong acids; less + gamma rays volatile than B. + + Radium-D about 40 years no rays Soluble in strong acids; volatile + below 1000 deg C. + + Radium-E 6 days beta, gamma Non-volatile at 1000 deg C. + rays + + Radium-F 143 days alpha rays Volatile at 1000 deg C. + Deposited from solution on a + bismuth plate. + + +Of these products, A, B, and C constitute that part of the active +deposit of the emanation which suffers rapid decay and nearly disappears +in a few hours. Radium-D, continually producing its short-lived +descendants E and F, remains for years on surfaces once exposed to the +emanation, and makes delicate radio-active researches impossible +in laboratories which have been contaminated by an escape of radium +emanation. + +A somewhat similar pedigree has been made out in the case of thorium. +Here thorium-X is interposed between thorium and its short-lived +emanation, which decays to half its initial quantity in 54 seconds. Two +active deposits, thorium A and B, arise successively from the emanation. +In uranium, we have the one obvious derivative uranium-X, and the +question remains whether this one descent can be connected with any +other individual or family. Uranium is long-lived, and emits only +alpha-rays. Uranium-X decays to half value in 22 days, giving out beta- +and gamma-rays. Since our evidence goes to show that radio-activity is +generally accompanied by the production of new elements, it is natural +to search for the substance of uranium-X in other forms, and perhaps +under other names, rather than to surrender immediately our belief in +the conservation of matter. + +With this idea in mind we see at once the significance of the +constitution of uranium minerals. Formed in the remote antiquity of +past geological ages, these minerals must become store-houses of all +the products of uranium except those which may have escaped as gases +or possibly liquids. Even gases may be expected to some extent to be +retained by occlusion. Among the contents of uranium minerals, then, we +may look for the descendants of the parent uranium. If the descendants +are permanent or more long-lived than uranium, they will accumulate +continually. If they are short-lived, they will accumulate at a steady +rate till enough is formed for the quantity disintegrating to be equal +to the quantity developed. A state of mobile equilibrium will then +be reached, and the amount of the product will remain constant. This +constant amount of substance will depend only on the amount of uranium +which is its source, and, for different minerals, if all the product +is retained, the quantity of the product will be proportional to the +quantity of uranium. In a series of analyses of uranium minerals, +therefore, we ought to be able to pick out its more short-lived +descendants by seeking for instances of such proportionality. + +Now radium itself is a constituent of uranium minerals, and two series +of experiments by R.J. Strutt and B.B. Boltwood have shown that the +content of radium, as measured by the radio-activity of the emanation, +is directly proportional to the content of uranium. (Strutt, "Proc. +Roy. Soc." A, February 1905; Boltwood, "Phil. Mag." April, 1905.) In +Boltwood's investigation, some twenty minerals, with amounts of uranium +varying from that in a specimen of uraninite with 74.65 per cent., +to that in a monazite with 0.30 per cent., gave a ratio of uranium to +radium, constant within about one part in ten. + +The conclusion is irresistible that radium is a descendant of uranium, +though whether uranium is its parent or a more remote ancestor requires +further investigation by the radio-active genealogist. On the hypothesis +of direct parentage, it is easy to calculate that the amount of radium +produced in a month by a kilogramme of a uranium salt would be enough +to be detected easily by the radio-activity of its emanation. The +investigation has been attempted by several observers, and the results, +especially those of a careful experiment of Boltwood, show that from +purified uranium salts the growth of radium, if appreciable at all, is +much less than would be found if the radium was the first product of +change of the uranium. It is necessary, therefore, to look for one or +more intermediate substances. + +While working in 1899 with the uranium residues used by M. and Mme +Curie for the preparation of radium, Debierne discovered and partially +separated another radio-active element which he called actinium. It +gives rise to an intermediate product actinium-X, which yields an +emanation with the short half-life of 3.9 seconds. The emanation +deposits two successive disintegration products actinium-A and +actinium-B. + +Evidence gradually accumulated that the amounts of actinium in +radio-active minerals were, roughly at any rate, proportional to the +amounts of uranium. This result pointed to a lineal connection between +them, and led Boltwood to undertake a direct attack on the problem. +Separating a quantity of actinium from a kilogramme of ore, Boltwood +observed a growth of 8.5 x (10 to the power -9) gramme of radium in +193 days, agreeing with that indicated by theory within the limits of +experimental error. ("American Journal of Science", December, 1906.) +We may therefore insert provisionally actinium and its series of +derivatives between uranium and radium in the radio-active pedigree. + +Turning to the other end of the radium series we are led to ask what +becomes of radium-F when in turn it disintegrates? What is the final +non-active product of the series of changes we have traced from uranium +through actinium and radium? + +One such product has been indicated above. The alpha-ray particles +appear to possess the mass of helium atoms, and the growth of helium has +been detected by its spectrum in a tube of radium emanation. Moreover, +helium is found occluded in most if not all radio-active minerals in +amount which approaches, but never exceeds, the quantity suggested by +theory. We may safely regard such helium as formed by the accumulation +of alpha-ray particles given out by successive radio-active changes. + +In considering the nature of the residue left after the expulsion of the +five alpha-particles, and the consequent passage of radium to radium-F +we are faced by the fact that lead is a general constituent of uranium +minerals. Five alpha-particles, each of atomic weight 4, taken from the +atomic weight (about 225) of radium gives 205--a number agreeing fairly +well with the 207 of lead. Since lead is more permanent than uranium, it +must steadily accumulate, no radio-active equilibrium will be reached, +and the amount of lead will depend on the age of the mineral as well as +on the quantity of uranium present in it. In primary minerals from +the same locality, Boltwood has shown that the contents of lead are +proportional to the amounts of uranium, while, accepting this theory, +the age of minerals with a given content of uranium may be calculated +from the amount of lead they contain. The results vary from 400 to +2000 million years. ("American Journal of Science", October, 1905, and +February, 1907.) + +We can now exhibit in tabular form the amazing pedigree of radio-active +change shown by this one family of elements. An immediate descent is +indicated by >, while one which may either be immediate or involve an +intermediate step is shown by.... No place is found in this pedigree +for thorium and its derivatives. They seem to form a separate and +independent radio-active family. + + + Atomic Weight Time of half Radio-Activity + decay + + Uranium 238.5 alpha + + Uranium-X ? 22 days beta, gamma + ... + Actinium ? ? no rays + + Actinium-X ? 10.2 days alpha (beta, gamma) + + Actinium Emanation ? 3.9 seconds alpha + + Actinium-A ? 35.7 minutes no rays + + Actinium-B ? 2.15 minutes alpha, beta, gamma + ... + Radium 225 about 2600 years alpha + + Radium Emanation ? 3.8 days alpha + + Radium-A ? 3 minutes alpha + + Radium-B ? 21 minutes no rays + + Radium-C ? 28 minutes alpha, beta, gamma + + Radium-D ? about 40 years no rays + + Radium-E ? 6 days beta (gamma) + + Radium-F ? 143 days alpha + ... + Lead 207 ? no rays + + +As soon as the transmutation theory of radio-activity was accepted, +it became natural to speculate about the intimate structure of the +radio-active atoms, and the mode in which they broke up with the +liberation of some of their store of internal energy. How could we +imagine an atomic structure which would persist unchanged for long +periods of time, and yet eventually spontaneously explode, as here an +atom and there an atom reached a condition of instability? + +The atomic theory of corpuscles or electrons fortunately was ready to +be applied to this new problem. Of the resulting speculations the most +detailed and suggestive is that of J.J. Thomson. ("Phil. Mag." March, +1904.) Thomson regards the atom as composed of a number of mutually +repelling negative corpuscles or electrons held together by some central +attractive force which he represents by supposing them immersed in a +uniform sphere of positive electricity. Under the action of the two +forces, the electrons space themselves in symmetrical patterns, which +depend on the number of electrons. Three place themselves at the corner +of an equilateral triangle, four at those of a square, and five form +a pentagon. With six, however, the single ring becomes unstable, one +corpuscle moves to the middle and five lie round it. But if we imagine +the system rapidly to rotate, the centrifugal force would enable the +six corpuscles to remain in a single ring. Thus internal kinetic energy +would maintain a configuration which would become unstable as the energy +drained away. Now in a system of electrons, electromagnetic radiation +would result in a loss of energy, and at one point of instability we +might well have a sudden spontaneous redistribution of the constituents, +taking place with an explosive violence, and accompanied by the ejection +of a corpuscle as a beta-ray, or of a large fragment of the atom as an +alpha-ray. + +The discovery of the new property of radio-activity in a small number of +chemical elements led physicists to ask whether the property might not +be found in other elements, though in a much less striking form. Are +ordinary materials slightly radio-active? Does the feeble electric +conductivity always observed in the air contained within the walls of +an electroscope depend on ionizing radiations from the material of the +walls themselves? The question is very difficult, owing to the wide +distribution of slight traces of radium. Contact with radium emanation +results in a deposit of the fatal radium-D, which in 40 years is but +half removed. Is the "natural" leak of a brass electroscope due to +an intrinsic radio-activity of brass, or to traces of a radio-active +impurity on its surface? Long and laborious researches have succeeded in +establishing the existence of slight intrinsic radio-activity in a +few metals such as potassium, and have left the wider problem still +unsolved. + +It should be noted, however, that, even if ordinary elements are not +radio-active, they may still be undergoing spontaneous disintegration. +The detection of ray-less changes by Rutherford, when those changes +are interposed between two radio-active transformations which can +be followed, show that spontaneous transmutation is possible without +measureable radio-activity. And, indeed, any theory of disintegration, +such as Thomson's corpuscular hypothesis, would suggest that atomic +rearrangements are of much more general occurrence than would be +apparent to one who could observe them only by the effect of the +projectiles, which, in special cases, owing to some peculiarity of +atomic configuration, happened to be shot out with the enormous velocity +needed to ionize the surrounding gas. No evidence for such ray-less +changes in ordinary elements is yet known, perhaps none may ever be +obtained; but the possibility should not be forgotten. + +In the strict sense of the word, the process of atomic disintegration +revealed to us by the new science of radio-activity can hardly be called +evolution. In each case radio-active change involves the breaking up of +a heavier, more complex atom into lighter and simpler fragments. Are +we to regard this process as characteristic of the tendencies in accord +with which the universe has reached its present state, and is passing +to its unknown future? Or have we chanced upon an eddy in a backwater, +opposed to the main stream of advance? In the chaos from which the +present universe developed, was matter composed of large highly complex +atoms, which have formed the simpler elements by radio-active or +ray-less disintegration? Or did the primaeval substance consist +of isolated electrons, which have slowly come together to form the +elements, and yet have left here and there an anomaly such as that +illustrated by the unstable family of uranium and radium, or by some +such course are returning to their state of primaeval simplicity? + + + + +INDEX. + +Abraxas grossulariata. + +Acquired characters, transmission of. + +Acraea johnstoni. + +Adaptation. + +Adloff. + +Adlumia cirrhosa. + +Agassiz, A. + +Agassiz, L. + +Alexander. + +Allen, C.A. + +Alternation of generations. + +Ameghino. + +Ammon, O., Works of. + +Ammonites, Descent of. + +Amphidesmus analis. + +Anaea divina. + +Andrews, C.W. + +Angiosperms, evolution of. + +Anglicus, Bartholomaeus. + +Ankyroderma. + +Anomma. + +Antedon rosacea. + +Antennularia antennina. + +Anthropops. + +Ants, modifications of. + +Arber, E.A.N.,--and J. Parkin, on the origin of Angiosperms. + +Archaeopteryx. + +Arctic regions, velocity of development of life in. + +Ardigo. + +Argelander. + +Argyll, Huxley and the Duke of. + +Aristotle. + +Arrhenius. + +Asterias, Loeb on hybridisation of. + +Autogamy. + +Avena fatua. + +Avenarius. + +Bacon, on mutability of species. + +Baehr, von, on Cytology. + +Baer, law of von. + +Bain. + +Baldwin, J.M. + +Balfour, A.J. + +Ball, J. + +Barber, Mrs M.E., on Papilio nireus. + +Barclay, W. + +Barratt. + +Bary, de. + +Bates, H.W., on Mimicry.--Letters from Darwin to.--elsewhere. + +Bateson, A. + +BATESON, W., on "Heredity and Variation in Modern lights".--on +discontinuous evolution.--on hybridisation. + +Bateson, W. and R.P. Gregory. + +Bathmism. + +Beche, de la. + +Beck, P. + +Becquerel, H. + +Beebe, C.W., on the plumage of birds.--on sexual selection. + +Beguyer de Chancourtois. + +Bell's (Sir Charles) "Anatomy of Expression". + +Belopolsky. + +Belt, T., on Mimicry. + +Beneden, E. van. + +Benson, M. + +Bentham, G., on Darwin's species-theory.--on geographical distribution. + +Bentham, Jeremy. + +Bergson, H. + +Berkeley. + +Berthelot. + +Betham, Sir W. + +Bickford, E., experiments on degeneration by. + +Bignonia capreolata. + +Biophores. + +Birds, geological history of. + +Blanford, W.T. + +Blaringhem, on wounding. + +Blumenbach. + +Bodin. + +Boltwood, B.B. + +Bonald, on war. + +Bonnet. + +Bonney, T.G. + +Bonnier, G. + +Bopp, F., on language. + +BOUGLE C., on "Darwinism and Sociology". + +Bourdeau. + +Bourget, P. + +Boutroux. + +Boveri, T. + +Brachiopods, history of. + +Brassica, hybrids of. + +Brassica Napus. + +Broca. + +Brock, on Kant. + +Brown, Robert. + +Brugmann and Osthoff. + +Brugmann. + +Brunetiere. + +Bruno, on Evolution. + +Buch, von. + +Bucher, K. + +Buckland. + +Buckle. + +Buffon. + +Burchell, W.J. + +Burck, W. + +Burdon-Sanderson, J., letter from. + +BURY, J.B., on "Darwinism and History". + +Butler, A.G. + +Butler, Samuel. + +Butschli, O. + +Butterflies, mimicry in.--sexual characters in. + +Cabanis. + +Campbell. + +Camels, geological history of. + +Camerarius, R.J. + +Candolle, A. de. + +Cannon and Davenport, experiments on Daphniae by. + +Capsella bursapastoris. + +Carneri. + +Castnia linus. + +Catasetum barbatum. + +Catasetum tridentatum. + +Caterpillars, variation in. + +Celosia, variability of. + +Cereals, variability in. + +Cesnola, experiments on Mantis by. + +Chaerocampa, colouring of. + +Chambers, R., "The Vestiges of Creation" by. + +Chromosomes and Chromomeres. + +Chun. + +Cieslar, experiments by. + +Circumnutation, Darwin on. + +Claus. + +Cleistogamy. + +Clerke, Miss A. + +Clodd, E. + +Cluer. + +Clytus arietis. + +Coadaptation. + +Codrington. + +Cohen and Peter. + +Collingwood. + +Colobopsis truncata. + +Colour, E.B. Poulton on The Value in the Struggle for life +of.--influence and temperature on changes in.--in relation to Sexual +Selection. + +Colours, incidental.--warning. + +Comte, A. + +Condorcet. + +Cope. + +Coral reefs, Darwin's work on. + +Correlation of organisms, Darwin's idea of the. + +Correlation of parts. + +Corydalis claviculata. + +Cournot. + +Couteur, Col. Le. + +Crooks, Sir William. + +Cruger, on Orchids. + +Cunningham and Marchand, on the brain. + +Curie, M. and Mme. + +Cuvier. + +Cycadeoidea dacotensis. + +Cycads, geological history of. + +Cystidea, an ancient group. + +Cytology and heredity. + +Cytolysis and fertilisation. + +Czapek. + +Dalton's atomic theory. + +Dana, J.D., on marine faunas. + +Danaida chrysippus. + +Danaida genutia. + +Danaida plexippus. + +Dante. + +Dantec, Le, + +Darwin, Charles, as an Anthropologist.--on ants.--and the "Beagle" +Voyage.--on the Biology of Flowers.--as a Botanist.--his influence on +Botany.--and S. Butler.--at Cambridge.--on Cirripedia.--on climbing +plants.--on colour.--on coral reefs.--on the Descent of Man.--his work +on Drosera.--at Edinburgh.--his influence on Animal Embryology.--on +Geographical Distribution.--his work on Earthworms.--evolutionist +authors referred to in the "Origin" by.--and E. Forbes.--on the +geological record.--and Geology.--his early love for geology.--his +connection with the Geological Society of London.--and Haeckel.--and +Henslow.--and History.--and Hooker.--and Huxley.--on ice-action.--on +igneous rocks.--on Lamarck.--on Language.--his Scientific Library.--and +the Linnean Society.--and Lyell.--and Malthus.--on Patrick Matthew.--on +mental evolution.--on Mimicry.--a "Monistic Philosopher."--on the +movements of plants.--on Natural Selection.--a "Naturalist for +Naturalists."--on Paley. + +Darwin, Charles, his Pangenesis hypothesis.--on the permanence +of continents.--his personality.--his influence on +Philosophy.--predecessors of.--his views on religion, etc.--his +influence on religious thought.--his influence on the study of +religions.--his methods of research.--and Sedgwick.--on Sexual +Selection.--the first germ of his species theory.--on H. +Spencer.--causes of his success.--on Variation.--on the "Vestiges +of Creation".--on volcanic islands.--and Wallace.--letter to Wallace +from.--letter to E.B. Wilson from. + +Darwin, E., on the colour of animals.--Charles Darwin's reference +to.--on evolution. + +DARWIN, F., on "Darwin's work on the Movements of Plants".--on Darwin +as a botanist.--observations on Earthworms by.--on Lamarckism.--on +Memory.--on Prichard's "Anticipations".--various. + +DARWIN, SIR G., on "The Genesis of Double Stars".--on the earth's mass. + +Darwin, H. + +Darwin, W. + +Darwinism, Sociology, Evolution and. + +Davenport and Cannon, experiments on Daphniae by. + +David, T.E., his work on Funafuti. + +Death, cause of natural. + +Debey, on Cretaceous plants. + +Debierne. + +Degeneration. + +Delage, experiments on parthenogenesis by. + +Delbruck. + +Democritus. + +Deniker. + +Descartes. + +Descent, history of doctrine of. + +"Descent of Man", G. Schwalbe on "The".--Darwin on Sexual Selection in +"The".--rejection in Germany of "The". + +Desmatippus. + +Desmoulins, A., on Geographical Distribution. + +Detto. + +Development, effect of environment on. + +Dianthus caryophyllus. + +Diderot. + +Digitalis purpurea. + +Dimorphism, seasonal. + +Dismorphia astynome. + +Dismorphia orise. + +Distribution, H. Gadow on Geographical.--Sir W. Thiselton-Dyer on. + +Dittrick, O. + +Dixey, F.A., on the scent of Butterflies. + +Dolichonyx oryzivorus. + +Dorfmeister. + +Down, Darwin at. + +Draba verna. + +Dragomirov. + +Driesch, experiments by.--elsewhere. + +Drosera, Darwin's work on. + +Dryopithecus. + +Dubois, E., on Pithecanthropus. + +Duhring. + +Duhamel. + +Duncan, J.S. + +Duncan, P.B. + +Duns Scotus. + +Duret, C. + +Durkheim, on division of labour. + +Dutrochet. + +Echinoderms, ancestry of. + +Ecology. + +Eimer. + +Ekstam. + +Elephants, geological history of. + +Elymnias phegea. + +E. undularis. + +Embleton, A.L. + +Embryology, A. Sedgwick on the influence of Darwin on. + +Embryology, as a clue to Phylogeny.--the Origin of Species and. + +Empedocles. + +Engles. + +Environment, action of.--Klebs on the influence on plants of.--Loeb on +experimental study in relation to. + +Eohippus. + +Epicurus, a poet of Evolution. + +Eristalis. + +Ernst. + +Ernst, A., on the Flora of Krakatau. + +Eschscholzia californica. + +Espinas. + +Eudendrium racemosum. + +Evolution, in relation to Astronomy.--and creation.--conception +of.--discontinuous.--experimental.--factors of.--fossil plants +as evidence of.--and language.--of matter, W.C.D. Whetham +on.--mental.--Lloyd Morgan on mental factors in.--Darwinism and +Social.--Saltatory.--Herbert Spencer on.--Uniformitarian.--Philosophers +and modern methods of studying. + +Expression of the Emotions. + +Fabricius, J.C., on geographical distribution. + +Farmer, J.B. + +Farrer, Lord. + +Fearnsides, W.G. + +Felton, S., on protective resemblance. + +Ferri. + +Ferrier, his work on the brain. + +Fertilisation, experimental work on animal-. + +Fertilisation of Flowers. + +Fichte. + +Field, Admiral A.M. + +Fischer, experiments on Butterflies by. + +Fitting. + +Flemming, W. + +Flourens. + +Flowering plants, ancestry of. + +Flowers, K. Goebel on the Biology of. + +Flowers and Insects. + +Flowers, relation of external influences to the production of. + +Fol, H. + +Forbes, E.--and C. Darwin. + +Ford, S.O. and A.C. Seward, on the Araucarieae. + +Fossil Animals, W.B. Scott on their bearing on evolution. + +Fossil Plants, D.H. Scott on their bearing on evolution. + +Fouillee. + +Fraipont, on skulls from Spy. + +FRAZER, J.G., on "Some Primitive Theories of the Origin of +Man".--various. + +Fruwirth. + +Fumaria officinalis. + +Funafuti, coral atoll of. + +Fundulus. + +F. heteroclitus. + +GADOW, H., on "Geographical Distribution of Animals".--elsewhere. + +Gartner, K.F. + +Gallus bankiva. + +Galton, F. + +Gamble, F.W. and F.W. Keeble. + +Gasca, La. + +Geddes, P. + +Geddes, P. and A.W. Thomson. + +Gegenbauer. + +Geikie, Sir A. + +Geitonogamy. + +Genetics. + +Geographical Distribution of Animals.--of Plants.--influence of "The +Origin of Species" on.--Wallace's contribution to. + +Geography of former periods, reconstruction of. + +Geology, Darwin and. + +Geranium spinosum. + +Germ-plasm, continuity of.--Weismann on. + +Germinal Selection. + +Gibbon. + +Gilbert. + +GILES, P., on "Evolution and the Science of Language". + +Giuffrida-Ruggeri. + +Giotto. + +Gizycki. + +Glossopteris Flora. + +Gmelin. + +Godlewski, on hybridisation. + +GOEBEL, K., on "The Biology of Flowers".--his work on Morphology. + +Goethe and Evolution.--on the relation between Man and +Mammals.--elsewhere. + +Goldfarb. + +Gondwana Land. + +Goodricke, J. + +Gore, Dr. + +Gorjanovic-Kramberger. + +Gosse, P.H. + +Grabau, A.W., on Fusus. + +Grand'Eury, F.C., on fossil plants. + +Grapta C. album. + +Gravitation, effect on life-phenomena of. + +Gray, Asa. + +Gregoire, V. + +Groom, T.T., on heliotropism. + +Groos. + +Grunbaum, on the brain. + +Guignard, L. + +Gulick. + +Guppy, on plant-distribution. + +Guyau. + +Gwynne-Vaughan, D.T., on Osmundaceae. + +Gymnadenia conopsea. + +Haberlandt, G. + +Haddon, A.C. + +HAECKEL, E., on "Charles Darwin as an Anthropologist".--on Colour.--and +Darwin.--on the Descent of Man.--contributions to Evolution by. + +Haeckel, E., on Lamarck.--on Language.--a leader in the Darwinian +controversy.--on Lyell's influence on Darwin.--various. + +Hacker. + +Hagedoorn, on hybridisation. + +Hales, S. + +Hansen. + +Harker, A. + +HARRISON, J.E., on "The Influence of Darwinism on the Study of +Religions". + +Hartmann, von. + +Harvey. + +Haupt, P., on Language. + +Haycraft. + +Hays, W.M. + +Hegel. + +Heliconius narcaea. + +Heliotropism in animals. + +Henslow, Rev. J.S. and Darwin. + +Hensen, Van. + +Herbst, his experiments on sea urchins. + +Heracleitus. + +Herder. + +Heredity and Cytology.--Haeckel on.--and Variation.--various. + +Hering, E., on Memory. + +Herschel, J. + +Hertwig, R. + +Hertwig, O. + +Hertz. + +Heteromorphosis. + +Heterostylism. + +Heuser, E. + +Hewitt. + +Heyse's theory of language. + +Hinde, G.J., his work on Funafuti. + +Hipparion. + +Hippolyte cranchii. + +Hirase. + +History, Darwin and. + +Hobbes, T. + +Hobhouse. + +HOFFDING, H., on "The Influence of the Conception of Evolution on Modern +Philosophy". + +Hofmeister, W. + +Holmes, S.J., on Arthropods. + +Holothurians, calcareous bodies in skin of. + +Homo heidelbergensis. + +Homo neandertalensis. + +Homo pampaeus. + +Homo primigenius. + +Homunculus. + +Hooker, Sir J.D., and Darwin.--on Distribution of Plants.--on +Ferns.--Letter to the Editor from. + +Horner, L. + +Horse, Geological history of the. + +Huber. + +Hubert and Mauss. + +Hubrecht, A.R.W. + +Hugel, F. von. + +Humboldt, A. von. + +Humboldt, W. von. + +Hume. + +Hutcheson. + +Hutton. + +Huxley, T.H., and Darwin.--and the Duke of Argyll.--on Embryology.--on +Geographical Distribution.--on Lamarck.--Letter to J.W. Judd from.--on +Lyell.--on Man.--on "The Origin of Species".--on Selection.--on +Teleology.--on transmission of acquired characters.--various. + +Hybridisation. + +Hybrids, Sterility of. + +Hyracodon. + +Iberis umbellata. + +Ikeno. + +Imperfection of the Geological Record. + +Ingenhousz, on plant physiology. + +Inheritance of acquired characters. + +Insects and Flowers. + +Instinct. + +Instincts, experimental control of animal. + +Ipomaea purpurea. + +Irish Elk, an example of co-adaptation. + +Jacobian figures. + +Jacoby, "Studies in Selection" by. + +James, W. + +Janczewski. + +Jeans, J.H. + +Jennings, H.S., on Paramoecium. + +Jentsch. + +Jespersen, Prof., Theory of. + +Johannsen, on Species. + +Jones, Sir William, on Language. + +Jordan. + +JUDD, J.W., on "Darwin and Geology". + +Kallima, protective colouring of. + +Kallima inachis. + +Kammerer's experiments on Salamanders. + +Kant, I. + +Keane, on the Primates. + +Keeble, F.W. and F.W. Gamble, on Colour-change. + +Keith, on Anthropoid Apes. + +Kellogg, V., on heliotropism. + +Kepler. + +Kerguelen Island. + +Kidd. + +Kidston, R., on fossil plants. + +Killmann, on origin of human races. + +King, Sir George. + +Klaatsch, on Ancestry of Man. + +Klaatsch and Hauser. + +KLEBS, G., on "The influence of Environment on the forms of plants". + +Kniep. + +Knies. + +Knight, A., experiments on plants by.--on Geotropism. + +Knight-Darwin law. + +Knuth. + +Kolliker, his views on Evolution. + +Kolreuter, J.G. + +Kohl. + +Korschinsky. + +Kowalevsky, on fossil horses. + +Krakatau, Ernst on the Flora of. + +Krause, E. + +Kreft, Dr. + +Kropotkin. + +Kupelwieser, on hybridisation. + +Lagopus hyperboreus. + +Lamarck, his division of the Animal Kingdom.--Darwin's opinion of.--on +Evolution.--on Man.--various. + +Lamarckian principle. + +Lamb, C. + +Lamettrie. + +Lamprecht. + +Lanessan, J.L. de. + +Lang. + +Lange. + +Language, Darwin on.--Evolution and the Science of.--various. + +Lankester, Sir E. Ray, on degeneration.--on educability.--on the +germ-plasm theory.--elsewhere. + +Lapouge, Vacher de. + +Larmor, J. + +Lartet, M.E. + +Lassalle. + +Lathyrus odoratus. + +Lavelaye, de. + +Lawrence, W. + +Lehmann. + +Lehmann-Nitsche. + +Leibnitz. + +Lepidium Draba. + +Lepidoptera, variation in. + +Leskien, A., on language. + +Lessing. + +Leucippus. + +Levi, E. + +Lewes, G.H. + +Lewin, Capt. + +Liapounoff. + +Liddon, H.P. + +Light, effect on organisms of. + +Limenitis archippus.--arthemis. + +Linnaeus. + +Livingstone, on plant-forms. + +Llamas, geological history of. + +Lockyer, Sir N. + +Locy, W.A. + +LOEB, J., on "The Experimental Study of the influence of environment on +Animals. + +Loew, E. + +Longstaff, G.B., on the Scents of Butterflies. + +Lorentz. + +Lotsy, J.P. + +Love, A.E.W. + +Lovejoy. + +Lubbock. + +Lucas, K. + +Lucretius, a poet of Evolution. + +Lumholtz, C. + +Luteva macrophthalma. + +Lycorea halia. + +Lyell, Sir Charles, and Darwin.--the influence of.--on geographical +distribution.--on "The Origin of Species".--on the permanence of +Ocean-basins.--publication of the "Principles" by.--the uniformitarian +teaching of. + +Lythrum salicaria. + +Macacus, ear of. + +MacDougal, on wounding. + +Mach, E. + +Macromytis flexuosa, colour-change in. + +Magic and religion. + +Mahoudeau. + +Maillet, de. + +Majewski. + +Malthus, his influence on Darwin.--various. + +Mammalia, history of. + +Man, Descent of.--J.G. Frazer on some primitive theories of the origin +of.--mental and moral qualities of animals and.--pre-Darwinian views on +the Descent of.--religious views of primitive.--Tertiary flints worked +by. + +"Man", G. Schwalbe on Darwin's "Descent of". + +Manouvrier. + +Mantis religiosa, colour experiments on. + +Marett, R.R. + +Markwick. + +Marshall, G.A.K. + +Marx. + +Massart. + +Masters, M. + +Matonia pectinata. + +Matthew, P., and Natural Selection. + +Maupertuis. + +Maurandia semperflorens. + +Mauss and Herbert. + +Mauthner. + +Maxwell. + +Maxwell, Clerk. + +Mayer, R. + +Mechanitis lysimnia. + +Meehan, T. + +Meldola, R., Letters from Darwin to. + +Melinaea ethra. + +Mendel. + +Mendeleeff. + +Merrifield. + +Merz, J.T. + +Mesembryanthemum truncatum. + +Mesohippus. + +Mesopithecus. + +Metschnikoff. + +Mill, J.S. + +Mimicry.--H.W. Bates on.--F. Muller on. + +Mimulus luteus. + +Miquel, F.W.A. + +Mobius. + +Mohl, H. von. + +Moltke, on war. + +Monachanthus viridis. + +Monkeys, fossil. + +Montesquieu. + +Montgomery, T.H. + +Monstrosoties. + +Monticelli. + +Moore, J.E.S. + +MORGAN, C. LLOYD, on "Mental Factors in Evolution".--on Organic +Selection. + +Morgan, T.H. + +Morse, E.S., on colour. + +Morselli. + +Mortillet. + +Moseley. + +Mottier, M. + +Muller, Fritz, "Fur Darwin" by.--on Mimicry. + +Muller, Fritz. + +Muller, J. + +Muller, Max, on language. + +Murray, A., on geographical distribution. + +Murray, G. + +Mutability. + +Mutation. + +Myanthus barbatus. + +Myers, G.W., on Eclipses. + +Nageli. + +Nathorst, A.G. + +Nathusius. + +Natural Selection, and adaptation.--Darwin's views on.--Darwin and +Wallace on.--and design.--and educability.--Fossil plants in relation +to.--and human development.--and Mimicry.--and Mutability.--various. + +Naudin. + +Neandertal skulls. + +Nemec. + +Neoclytus curvatus. + +Neodarwinism. + +Neumayr, M. + +Newton, A. + +Newton, I. + +Niebuhr. + +Nietzsche. + +Nilsson, on cereals. + +Nitsche. + +Noire. + +Noll. + +Novicow. + +Nuclear division. + +Nussbaum, M. + +Nuttall, G.H.F. + +Occam. + +Odin. + +Oecology, see Ecology. + +Oenothera biennis. + +Oenothera gigas. + +Oenothera Lamarckiana. + +Oenothera muricata. + +Oenothera nanella. + +Oestergren, on Holothurians. + +Oken, L. + +Oliver, F.W., on Palaeozoic Seeds. + +Ononis minutissima. + +Ophyrs apifera. + +Orchids, Darwin's work on the fertilisation of. + +Organic Selection. + +"Origin of Species", first draft of the.--geological chapter in the. + +Orthogenesis. + +Ortmann, A.E. + +Osborn, H.F.--"From the Greeks to Darwin" by. + +Osthoff and Brugmann. + +Ostwald, W. + +Ovibos moschatus. + +Owen, Sir Richard. + +Oxford, Ashmolean Museum at. + +Packard, A.S. + +Palaeontological Record, D.H. Scott on the.--W.B. Scott on the. + +Palaeopithecus. + +Paley. + +Palitzch, G. + +Palm. + +Pangenesis. + +Panmixia, Weismann's principle of. + +Papilio dardanus. + +Papilio meriones. + +Papilio merope. + +Papilio nireus. + +Paramoecium, Jennings on. + +Parker, G.H., on Butterflies. + +Parkin, J. and E.A.N. Arber, on the origin of Angiosperms. + +Parthenogenesis, artificial. + +Paul, H. and Wundt. + +Pearson, K. + +Peckham, Dr and Mrs, on the Attidae. + +Penck. + +Penzig. + +Peripatus, distribution of. + +Peridineae. + +Permanence of continents. + +Perrier, E. + +Perrhybris pyrrha. + +Perthes, B. de. + +Peter, on sea urchin's eggs. + +Petunia violacea. + +Pfeffer, W. + +Pfitzner, W. + +Pflueger. + +Phillips. + +Philosophy, influence of the conception of evolution on modern. + +Phryniscus nigricans. + +Phylogeny, embryology as a clue to.--Palaeontological evidence on. + +Physiology of plants, development of. + +Piccard, on Geotropism. + +Pickering, spectroscopic observations by. + +Piranga erythromelas. + +Pisum sativum. + +Pithecanthropus. + +Pitheculites. + +Planema epaea. + +Plants, Darwin's work on the movements of.--geographical distribution +of.--Palaeontological record of fossil. + +Platanthera bifolia. + +Plate. + +Plato. + +Playfair. + +Pliopithecus. + +Pocock, R.I. + +Poincare. + +Polarity, Vochting on. + +Polymorphic species.--variability in cereals. + +Polypodium incanum. + +Porthesia chrysorrhoea. + +Potonie, R. + +Pouchet, G. + +POULTON, E.B., on "The Value of Colour in the Struggle for +Life".--experiments on Butterflies by.--on J.C. Prichard.--on +Mimicry.--various. + +Pratt. + +Pratz, du. + +Premutation. + +Preuss, K. Th. + +Prichard, J.C. + +Primula, heterostylism in. + +Primula acaulis. + +Primula elatior. + +Primula officinalis. + +Promeces viridis. + +Pronuba yuccasella. + +Protective resemblance. + +Protocetus. + +Protohippus. + +Psychology. + +Pteridophytes, history of. + +Pteridospermeae. + +Pucheran. + +Pusey. + +Quatrefages, A. de. + +Quetelet, statistical investigations by. + +Rabl, C. + +Radio-activity. + +Radiolarians. + +Raimannia odorata. + +Ramsay, Sir W. and Soddy. + +Ranke. + +Rau, A. + +Ray, J. + +Reade, Mellard. + +Recapitulation, the theory of. + +Reduction. + +Regeneration. + +Reid, C. + +Reinke. + +Religion, Darwin's attitude towards.--Darwin's influence on the study +of.--and Magic. + +Religious thought, Darwin's influence on. + +Renard, on Darwin's work on volcanic islands. + +Reproduction, effect of environment on. + +Reptiles, history of. + +Reversion. + +Rhinoceros, the history of the. + +Ridley, H.N. + +Riley, C.V. + +Ritchie. + +Ritual. + +Roberts, A. + +Robertson, T.B. + +Robinet. + +Rolfe, R.A. + +Rolph. + +Romanes, G.J. + +Rothert. + +Roux. + +Rozwadowski, von. + +Ruskin. + +Rutherford, E. + +Rutot. + +Sachs, J. + +St Hilaire, E.G. de. + +Salamandra atra. + +Salamandra maculosa. + +Saltatory Evolution, (see also Mutations). + +Sanders, experiments on Vanessa by. + +Saporta, on the Evolution of Angiosperms. + +Sargant, Ethel, on the Evolution of Angiosperms. + +Savigny. + +Scardafella inca. + +Scent, in relation to Sexual Selection. + +Scharff, R.F. + +Schelling. + +Schlegel. + +Schleicher, A., on language. + +Schleiden and Schwann, Cell-theory of. + +Schmarda, L.K., on geographical distribution. + +Schoetensack, on Homo heidelbergensis. + +Schreiner, K.E. + +Schubler, on cereals. + +Schultze, O., experiments on Frogs. + +Schur. + +Schutt. + +SCHWALBE, G., on "The Descent of Man". + +Sclater, P.L., on geographical distribution. + +SCOTT, D.H., on "The Palaeontological Record (Plants)".--elsewhere. + +SCOTT, W.B., on "The Palaeontological Record (Animals)". + +Scrope. + +Scyllaea. + +Sechehaye, C.A. + +SEDGWICK, A., on "The Influence of Darwin on Animal Embryology". + +Sedgwick, A., Darwin's Geological Expedition with. + +Seeck, O. + +Seed-plants, origin of. + +Segregation. + +Selection, artificial.--germinal. + +Selection, natural (see Natural Selection).--organic.--sexual.--social +and natural.--various. + +Selenka. + +Semnopithecus. + +Semon, R. + +Semper. + +Senebier. + +Senecio vulgaris. + +Sergi. + +Seward, A.C.--and S.O. Ford.--and J. Gowan. + +Sex, recent investigations on. + +Sharpe, D. + +Sherrington, C.S. + +Shirreff, P. + +Shrewsbury, Darwin's recollections of. + +Sibbern. + +Sinapis alba. + +Smerinthus ocellata. + +Smerinthus populi. + +Smerinthus tiliae. + +Smith, A. + +Smith, W. + +Snyder. + +Sociology, Darwinism and.--History and. + +Soddy. + +Sollas, W.J. + +Sorley, W.R. + +Species, Darwin's early work on transmutation of.--geographical +distribution and origin of.--immutability of.--influence on +environment on.--Lamarck on.--multiple origin of.--the nature of +a.--polymorphic.--production by physico-chemical means of.--and +varieties.--de Vries's work on. + +Spencer, H., on evolution.--on Lyell's "Principles".--on the nature of +the living cell.--on primitive man.--on the theory of Selection.--on +Sociology. + +Spencer, H., on the transmission of acquired characters.--on +Weismann.--various. + +Sphingidae, variation in. + +Spinoza. + +Sports. + +Sprengel, C.K. + +Stability, principle of. + +Stahl. + +Standfuss. + +Stars, evolution of double. + +Stellaria media. + +Stephen, L. + +Sterility in hybrids. + +Sterne, C. + +Stockard, his experiments on fish embryos. + +STRASBURBER, E., on "The Minute Structure of Cells in relation to +Heredity". + +Strongylocentrotus franciscanus. + +Strongylocentrotus purpuratus. + +Struggle for existence. + +Strutt, R.J. + +Stuart, A. + +Sturdee, F.C.D. + +Sutterlin, L. + +Sully. + +Sutton, A.W. + +Sutton, W.S. + +Svalof, agricultural station of. + +Swainson, W. + +Synapta, calcareous bodies in skin of. + +S. lappa. + +Syrphus. + +Tarde, G. + +Teleology and adaptation. + +Tennant, F.R. + +Teratology. + +Tetraprothomo. + +THISELTON-DYER, SIR WILLIAM, on "Geographical distribution of +Plants".--on Burchell.--on protective resemblance.--elsewhere. + +THOMSON, J.A., on "Darwin's Predecessors.--elsewhere.--and P. Geddes. + +Thomson, Sir J.J. + +Theology, Darwin and. + +Tiedemann, F. + +Tooke, Horne. + +Totemism. + +Treschow. + +Treviranus. + +Trifolium pratense quinquefolium. + +Trigonias. + +Trilobites, phylogeny of. + +Tschermack. + +Turgot. + +Turner, Sir W. + +Twins, artificial production of. + +Tylor. + +Tyndall, W. + +Tyrrell, G. + +Uhlenhuth, on blood reactions. + +Underhill, E. + +Use and disuse. + +Vanessa. + +Vanessa antiope. + +Vanessa levana. + +Vanessa polychloros. + +Vanessa urticae. + +Van 't Hoff. + +Varanus Salvator. + +Variability, Darwin's attention directed to.--W. Bateson on.--and +cultivation.--causes of.--polymorphic. + +Variation, continuous and discontinuous.--Darwin's views as +an evolutionist, and as a systematist, on.--definite and +indefinite.--environment and.--and heredity.--as seen in the +life-history of an organism.--minute.--mutability and.--in relation to +species.--H. de Vries on. + +Varigny, H. de. + +Varro, on language. + +Veronica chamaedrys. + +Verworn. + +"Vestiges of Creation", Darwin on "The". + +Vierkandt. + +Vilmorin, L. de. + +Virchow, his opposition to Darwin. + +Virchow, on the transmission of acquired characters. + +Vochting. + +Vogt, C. + +Voltaire. + +Volvox. + +VRIES, H. de, on "Variation"--the Mutation theory of. + +WAGGETT, REV. P.N., on "The Influence of Darwin upon religious thought". + +Wagner. + +Waldeyer, W. + +Wallace, A.R., on Malayan Butterflies.--on Colour.--and Darwin.--on +the Descent of Man.--on distribution.--on Malthus.--on Natural +Selection.--on the permanence of continents.--on social reforms.--on +Sexual Selection. + +Waller, A.D. + +Walton. + +Watson, H.C. + +Watson, S. + +Watt, J., and Natural Selection. + +Watts, W.W. + +Wedgwood, L. + +Weir, J.J. + +WEISMANN, A., on "The Selection Theory".--on Amphimixis. + +Weismann, A., his germ-plasm theory.--on ontogeny.--and Prichard.--and +Spencer.--on the transmission of acquired characters.--various. + +Wells, W.C., and Natural Selection. + +Weston, S., on language. + +WHETHAM, W.C.D., on "The Evolution of Matter". + +Whewell. + +White, G. + +Wichmann. + +Wieland, G.R., on fossil Cycads. + +Wiesner, on Darwin's work on plant movements. + +Williams, C.M. + +Williamson, W.C. + +Wilson, E.B., on cytology.--letter from Darwin to. + +Wolf. + +Wollaston's, T.V. "Variation of Species". + +Woltmann. + +Woolner. + +Wundt, on language. + +Xylina vetusta. + +Yucca, fertilisation of. + +Zeiller, R., on Fossil Plants. + +Zeller, E. + +Zimmermann, E.A.W. + +Zittel, on palaeontological research. + +"Zoonomia", Erasmus Darwin's. + + + + + + +End of the Project Gutenberg EBook of Darwin and Modern Science, by +A.C. Seward and Others + +*** END OF THIS PROJECT GUTENBERG EBOOK DARWIN AND MODERN SCIENCE *** + +***** This file should be named 1909.txt or 1909.zip ***** +This and all associated files of various formats will be found in: + http://www.gutenberg.org/1/9/0/1909/ + +Produced by Sue Asscher + +Updated editions will replace the previous one--the old editions +will be renamed. + +Creating the works from public domain print editions means that no +one owns a United States copyright in these works, so the Foundation +(and you!) can copy and distribute it in the United States without +permission and without paying copyright royalties. Special rules, +set forth in the General Terms of Use part of this license, apply to +copying and distributing Project Gutenberg-tm electronic works to +protect the PROJECT GUTENBERG-tm concept and trademark. Project +Gutenberg is a registered trademark, and may not be used if you +charge for the eBooks, unless you receive specific permission. If you +do not charge anything for copies of this eBook, complying with the +rules is very easy. You may use this eBook for nearly any purpose +such as creation of derivative works, reports, performances and +research. They may be modified and printed and given away--you may do +practically ANYTHING with public domain eBooks. Redistribution is +subject to the trademark license, especially commercial +redistribution. + + + +*** START: FULL LICENSE *** + +THE FULL PROJECT GUTENBERG LICENSE +PLEASE READ THIS BEFORE YOU DISTRIBUTE OR USE THIS WORK + +To protect the Project Gutenberg-tm mission of promoting the free +distribution of electronic works, by using or distributing this work +(or any other work associated in any way with the phrase "Project +Gutenberg"), you agree to comply with all the terms of the Full Project +Gutenberg-tm License (available with this file or online at +http://gutenberg.org/license). + + +Section 1. General Terms of Use and Redistributing Project Gutenberg-tm +electronic works + +1.A. By reading or using any part of this Project Gutenberg-tm +electronic work, you indicate that you have read, understand, agree to +and accept all the terms of this license and intellectual property +(trademark/copyright) agreement. If you do not agree to abide by all +the terms of this agreement, you must cease using and return or destroy +all copies of Project Gutenberg-tm electronic works in your possession. +If you paid a fee for obtaining a copy of or access to a Project +Gutenberg-tm electronic work and you do not agree to be bound by the +terms of this agreement, you may obtain a refund from the person or +entity to whom you paid the fee as set forth in paragraph 1.E.8. + +1.B. "Project Gutenberg" is a registered trademark. It may only be +used on or associated in any way with an electronic work by people who +agree to be bound by the terms of this agreement. There are a few +things that you can do with most Project Gutenberg-tm electronic works +even without complying with the full terms of this agreement. See +paragraph 1.C below. There are a lot of things you can do with Project +Gutenberg-tm electronic works if you follow the terms of this agreement +and help preserve free future access to Project Gutenberg-tm electronic +works. See paragraph 1.E below. + +1.C. The Project Gutenberg Literary Archive Foundation ("the Foundation" +or PGLAF), owns a compilation copyright in the collection of Project +Gutenberg-tm electronic works. Nearly all the individual works in the +collection are in the public domain in the United States. If an +individual work is in the public domain in the United States and you are +located in the United States, we do not claim a right to prevent you from +copying, distributing, performing, displaying or creating derivative +works based on the work as long as all references to Project Gutenberg +are removed. Of course, we hope that you will support the Project +Gutenberg-tm mission of promoting free access to electronic works by +freely sharing Project Gutenberg-tm works in compliance with the terms of +this agreement for keeping the Project Gutenberg-tm name associated with +the work. You can easily comply with the terms of this agreement by +keeping this work in the same format with its attached full Project +Gutenberg-tm License when you share it without charge with others. + +1.D. The copyright laws of the place where you are located also govern +what you can do with this work. Copyright laws in most countries are in +a constant state of change. If you are outside the United States, check +the laws of your country in addition to the terms of this agreement +before downloading, copying, displaying, performing, distributing or +creating derivative works based on this work or any other Project +Gutenberg-tm work. The Foundation makes no representations concerning +the copyright status of any work in any country outside the United +States. + +1.E. Unless you have removed all references to Project Gutenberg: + +1.E.1. The following sentence, with active links to, or other immediate +access to, the full Project Gutenberg-tm License must appear prominently +whenever any copy of a Project Gutenberg-tm work (any work on which the +phrase "Project Gutenberg" appears, or with which the phrase "Project +Gutenberg" is associated) is accessed, displayed, performed, viewed, +copied or distributed: + +This eBook is for the use of anyone anywhere at no cost and with +almost no restrictions whatsoever. You may copy it, give it away or +re-use it under the terms of the Project Gutenberg License included +with this eBook or online at www.gutenberg.org + +1.E.2. If an individual Project Gutenberg-tm electronic work is derived +from the public domain (does not contain a notice indicating that it is +posted with permission of the copyright holder), the work can be copied +and distributed to anyone in the United States without paying any fees +or charges. If you are redistributing or providing access to a work +with the phrase "Project Gutenberg" associated with or appearing on the +work, you must comply either with the requirements of paragraphs 1.E.1 +through 1.E.7 or obtain permission for the use of the work and the +Project Gutenberg-tm trademark as set forth in paragraphs 1.E.8 or +1.E.9. + +1.E.3. If an individual Project Gutenberg-tm electronic work is posted +with the permission of the copyright holder, your use and distribution +must comply with both paragraphs 1.E.1 through 1.E.7 and any additional +terms imposed by the copyright holder. Additional terms will be linked +to the Project Gutenberg-tm License for all works posted with the +permission of the copyright holder found at the beginning of this work. + +1.E.4. Do not unlink or detach or remove the full Project Gutenberg-tm +License terms from this work, or any files containing a part of this +work or any other work associated with Project Gutenberg-tm. + +1.E.5. Do not copy, display, perform, distribute or redistribute this +electronic work, or any part of this electronic work, without +prominently displaying the sentence set forth in paragraph 1.E.1 with +active links or immediate access to the full terms of the Project +Gutenberg-tm License. + +1.E.6. You may convert to and distribute this work in any binary, +compressed, marked up, nonproprietary or proprietary form, including any +word processing or hypertext form. However, if you provide access to or +distribute copies of a Project Gutenberg-tm work in a format other than +"Plain Vanilla ASCII" or other format used in the official version +posted on the official Project Gutenberg-tm web site (www.gutenberg.org), +you must, at no additional cost, fee or expense to the user, provide a +copy, a means of exporting a copy, or a means of obtaining a copy upon +request, of the work in its original "Plain Vanilla ASCII" or other +form. Any alternate format must include the full Project Gutenberg-tm +License as specified in paragraph 1.E.1. + +1.E.7. Do not charge a fee for access to, viewing, displaying, +performing, copying or distributing any Project Gutenberg-tm works +unless you comply with paragraph 1.E.8 or 1.E.9. + +1.E.8. You may charge a reasonable fee for copies of or providing +access to or distributing Project Gutenberg-tm electronic works provided +that + +- You pay a royalty fee of 20% of the gross profits you derive from + the use of Project Gutenberg-tm works calculated using the method + you already use to calculate your applicable taxes. The fee is + owed to the owner of the Project Gutenberg-tm trademark, but he + has agreed to donate royalties under this paragraph to the + Project Gutenberg Literary Archive Foundation. Royalty payments + must be paid within 60 days following each date on which you + prepare (or are legally required to prepare) your periodic tax + returns. Royalty payments should be clearly marked as such and + sent to the Project Gutenberg Literary Archive Foundation at the + address specified in Section 4, "Information about donations to + the Project Gutenberg Literary Archive Foundation." + +- You provide a full refund of any money paid by a user who notifies + you in writing (or by e-mail) within 30 days of receipt that s/he + does not agree to the terms of the full Project Gutenberg-tm + License. You must require such a user to return or + destroy all copies of the works possessed in a physical medium + and discontinue all use of and all access to other copies of + Project Gutenberg-tm works. + +- You provide, in accordance with paragraph 1.F.3, a full refund of any + money paid for a work or a replacement copy, if a defect in the + electronic work is discovered and reported to you within 90 days + of receipt of the work. + +- You comply with all other terms of this agreement for free + distribution of Project Gutenberg-tm works. + +1.E.9. If you wish to charge a fee or distribute a Project Gutenberg-tm +electronic work or group of works on different terms than are set +forth in this agreement, you must obtain permission in writing from +both the Project Gutenberg Literary Archive Foundation and Michael +Hart, the owner of the Project Gutenberg-tm trademark. Contact the +Foundation as set forth in Section 3 below. + +1.F. + +1.F.1. Project Gutenberg volunteers and employees expend considerable +effort to identify, do copyright research on, transcribe and proofread +public domain works in creating the Project Gutenberg-tm +collection. Despite these efforts, Project Gutenberg-tm electronic +works, and the medium on which they may be stored, may contain +"Defects," such as, but not limited to, incomplete, inaccurate or +corrupt data, transcription errors, a copyright or other intellectual +property infringement, a defective or damaged disk or other medium, a +computer virus, or computer codes that damage or cannot be read by +your equipment. + +1.F.2. LIMITED WARRANTY, DISCLAIMER OF DAMAGES - Except for the "Right +of Replacement or Refund" described in paragraph 1.F.3, the Project +Gutenberg Literary Archive Foundation, the owner of the Project +Gutenberg-tm trademark, and any other party distributing a Project +Gutenberg-tm electronic work under this agreement, disclaim all +liability to you for damages, costs and expenses, including legal +fees. YOU AGREE THAT YOU HAVE NO REMEDIES FOR NEGLIGENCE, STRICT +LIABILITY, BREACH OF WARRANTY OR BREACH OF CONTRACT EXCEPT THOSE +PROVIDED IN PARAGRAPH F3. YOU AGREE THAT THE FOUNDATION, THE +TRADEMARK OWNER, AND ANY DISTRIBUTOR UNDER THIS AGREEMENT WILL NOT BE +LIABLE TO YOU FOR ACTUAL, DIRECT, INDIRECT, CONSEQUENTIAL, PUNITIVE OR +INCIDENTAL DAMAGES EVEN IF YOU GIVE NOTICE OF THE POSSIBILITY OF SUCH +DAMAGE. + +1.F.3. LIMITED RIGHT OF REPLACEMENT OR REFUND - If you discover a +defect in this electronic work within 90 days of receiving it, you can +receive a refund of the money (if any) you paid for it by sending a +written explanation to the person you received the work from. If you +received the work on a physical medium, you must return the medium with +your written explanation. The person or entity that provided you with +the defective work may elect to provide a replacement copy in lieu of a +refund. If you received the work electronically, the person or entity +providing it to you may choose to give you a second opportunity to +receive the work electronically in lieu of a refund. If the second copy +is also defective, you may demand a refund in writing without further +opportunities to fix the problem. + +1.F.4. Except for the limited right of replacement or refund set forth +in paragraph 1.F.3, this work is provided to you 'AS-IS' WITH NO OTHER +WARRANTIES OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO +WARRANTIES OF MERCHANTIBILITY OR FITNESS FOR ANY PURPOSE. + +1.F.5. Some states do not allow disclaimers of certain implied +warranties or the exclusion or limitation of certain types of damages. +If any disclaimer or limitation set forth in this agreement violates the +law of the state applicable to this agreement, the agreement shall be +interpreted to make the maximum disclaimer or limitation permitted by +the applicable state law. The invalidity or unenforceability of any +provision of this agreement shall not void the remaining provisions. + +1.F.6. INDEMNITY - You agree to indemnify and hold the Foundation, the +trademark owner, any agent or employee of the Foundation, anyone +providing copies of Project Gutenberg-tm electronic works in accordance +with this agreement, and any volunteers associated with the production, +promotion and distribution of Project Gutenberg-tm electronic works, +harmless from all liability, costs and expenses, including legal fees, +that arise directly or indirectly from any of the following which you do +or cause to occur: (a) distribution of this or any Project Gutenberg-tm +work, (b) alteration, modification, or additions or deletions to any +Project Gutenberg-tm work, and (c) any Defect you cause. + + +Section 2. Information about the Mission of Project Gutenberg-tm + +Project Gutenberg-tm is synonymous with the free distribution of +electronic works in formats readable by the widest variety of computers +including obsolete, old, middle-aged and new computers. It exists +because of the efforts of hundreds of volunteers and donations from +people in all walks of life. + +Volunteers and financial support to provide volunteers with the +assistance they need, are critical to reaching Project Gutenberg-tm's +goals and ensuring that the Project Gutenberg-tm collection will +remain freely available for generations to come. In 2001, the Project +Gutenberg Literary Archive Foundation was created to provide a secure +and permanent future for Project Gutenberg-tm and future generations. +To learn more about the Project Gutenberg Literary Archive Foundation +and how your efforts and donations can help, see Sections 3 and 4 +and the Foundation web page at http://www.pglaf.org. + + +Section 3. Information about the Project Gutenberg Literary Archive +Foundation + +The Project Gutenberg Literary Archive Foundation is a non profit +501(c)(3) educational corporation organized under the laws of the +state of Mississippi and granted tax exempt status by the Internal +Revenue Service. The Foundation's EIN or federal tax identification +number is 64-6221541. Its 501(c)(3) letter is posted at +http://pglaf.org/fundraising. Contributions to the Project Gutenberg +Literary Archive Foundation are tax deductible to the full extent +permitted by U.S. federal laws and your state's laws. + +The Foundation's principal office is located at 4557 Melan Dr. S. +Fairbanks, AK, 99712., but its volunteers and employees are scattered +throughout numerous locations. Its business office is located at +809 North 1500 West, Salt Lake City, UT 84116, (801) 596-1887, email +business@pglaf.org. Email contact links and up to date contact +information can be found at the Foundation's web site and official +page at http://pglaf.org + +For additional contact information: + Dr. Gregory B. Newby + Chief Executive and Director + gbnewby@pglaf.org + + +Section 4. Information about Donations to the Project Gutenberg +Literary Archive Foundation + +Project Gutenberg-tm depends upon and cannot survive without wide +spread public support and donations to carry out its mission of +increasing the number of public domain and licensed works that can be +freely distributed in machine readable form accessible by the widest +array of equipment including outdated equipment. Many small donations +($1 to $5,000) are particularly important to maintaining tax exempt +status with the IRS. + +The Foundation is committed to complying with the laws regulating +charities and charitable donations in all 50 states of the United +States. Compliance requirements are not uniform and it takes a +considerable effort, much paperwork and many fees to meet and keep up +with these requirements. We do not solicit donations in locations +where we have not received written confirmation of compliance. To +SEND DONATIONS or determine the status of compliance for any +particular state visit http://pglaf.org + +While we cannot and do not solicit contributions from states where we +have not met the solicitation requirements, we know of no prohibition +against accepting unsolicited donations from donors in such states who +approach us with offers to donate. + +International donations are gratefully accepted, but we cannot make +any statements concerning tax treatment of donations received from +outside the United States. U.S. laws alone swamp our small staff. + +Please check the Project Gutenberg Web pages for current donation +methods and addresses. Donations are accepted in a number of other +ways including checks, online payments and credit card donations. +To donate, please visit: http://pglaf.org/donate + + +Section 5. General Information About Project Gutenberg-tm electronic +works. + +Professor Michael S. Hart is the originator of the Project Gutenberg-tm +concept of a library of electronic works that could be freely shared +with anyone. For thirty years, he produced and distributed Project +Gutenberg-tm eBooks with only a loose network of volunteer support. + + +Project Gutenberg-tm eBooks are often created from several printed +editions, all of which are confirmed as Public Domain in the U.S. +unless a copyright notice is included. Thus, we do not necessarily +keep eBooks in compliance with any particular paper edition. + + +Most people start at our Web site which has the main PG search facility: + + http://www.gutenberg.org + +This Web site includes information about Project Gutenberg-tm, +including how to make donations to the Project Gutenberg Literary +Archive Foundation, how to help produce our new eBooks, and how to +subscribe to our email newsletter to hear about new eBooks. diff --git a/1909.zip b/1909.zip Binary files differnew file mode 100644 index 0000000..1b09bc7 --- /dev/null +++ b/1909.zip diff --git a/LICENSE.txt b/LICENSE.txt new file mode 100644 index 0000000..6312041 --- /dev/null +++ b/LICENSE.txt @@ -0,0 +1,11 @@ +This eBook, including all associated images, markup, improvements, +metadata, and any other content or labor, has been confirmed to be +in the PUBLIC DOMAIN IN THE UNITED STATES. + +Procedures for determining public domain status are described in +the "Copyright How-To" at https://www.gutenberg.org. + +No investigation has been made concerning possible copyrights in +jurisdictions other than the United States. Anyone seeking to utilize +this eBook outside of the United States should confirm copyright +status under the laws that apply to them. diff --git a/README.md b/README.md new file mode 100644 index 0000000..37b47cc --- /dev/null +++ b/README.md @@ -0,0 +1,2 @@ +Project Gutenberg (https://www.gutenberg.org) public repository for +eBook #1909 (https://www.gutenberg.org/ebooks/1909) diff --git a/old/drwnm10.txt b/old/drwnm10.txt new file mode 100644 index 0000000..9ab4082 --- /dev/null +++ b/old/drwnm10.txt @@ -0,0 +1,27636 @@ +Project Gutenberg Etext Darwin and Modern Science, by A C Seward + + +Copyright laws are changing all over the world, be sure to check +the copyright laws for your country before posting these files!! + +Please take a look at the important information in this header. +We encourage you to keep this file on your own disk, keeping an +electronic path open for the next readers. Do not remove this. + + +**Welcome To The World of Free Plain Vanilla Electronic Texts** + +**Etexts Readable By Both Humans and By Computers, Since 1971** + +*These Etexts Prepared By Hundreds of Volunteers and Donations* + +Information on contacting Project Gutenberg to get Etexts, and +further information is included below. We need your donations. + + +Darwin and Modern Science + +by A.C. Seward + +September, 1999 [Etext #1909] + + +Project Gutenberg Etext Darwin and Modern Science, by A C Seward +******This file should be named drwnm10.txt or drwnm10.zip****** + +Corrected EDITIONS of our etexts get a new NUMBER, drwnm11.txt +VERSIONS based on separate sources get new LETTER, drwnm10a.txt + + +This etext was prepared by Sue Asscher <asschers@aia.net.au> + + +Project Gutenberg Etexts are usually created from multiple editions, +all of which are in the Public Domain in the United States, unless a +copyright notice is included. Therefore, we usually do NOT keep +these books in compliance with any particular paper edition. + + +We are now trying to release all our books one month in advance +of the official release dates, for time for better editing. + +Please note: neither this list nor its contents are final till +midnight of the last day of the month of any such announcement. +The official release date of all Project Gutenberg Etexts is at +Midnight, Central Time, of the last day of the stated month. A +preliminary version may often be posted for suggestion, comment +and editing by those who wish to do so. To be sure you have an +up to date first edition [xxxxx10x.xxx] please check file sizes +in the first week of the next month. Since our ftp program has +a bug in it that scrambles the date [tried to fix and failed] a +look at the file size will have to do, but we will try to see a +new copy has at least one byte more or less. + + +Information about Project Gutenberg (one page) + +We produce about two million dollars for each hour we work. The +fifty hours is one conservative estimate for how long it we take +to get any etext selected, entered, proofread, edited, copyright +searched and analyzed, the copyright letters written, etc. This +projected audience is one hundred million readers. If our value +per text is nominally estimated at one dollar then we produce $2 +million dollars per hour this year as we release thirty-six text +files per month, or 432 more Etexts in 1999 for a total of 2000+ +If these reach just 10% of the computerized population, then the +total should reach over 200 billion Etexts given away this year. + +The Goal of Project Gutenberg is to Give Away One Trillion Etext +Files by the December 31, 2001. [10,000 x 100,000,000=Trillion] +This is ten thousand titles each to one hundred million readers, +which is only ~5% of the present number of computer users. + +At our revised rates of production, we will reach only one-third +of that goal by the end of 2001, or about 3,333 Etexts unless we +manage to get some real funding; currently our funding is mostly +from Michael Hart's salary at Carnegie-Mellon University, and an +assortment of sporadic gifts; this salary is only good for a few +more years, so we are looking for something to replace it, as we +don't want Project Gutenberg to be so dependent on one person. + +We need your donations more than ever! + + +All donations should be made to "Project Gutenberg/CMU": and are +tax deductible to the extent allowable by law. (CMU = Carnegie- +Mellon University). + +For these and other matters, please mail to: + +Project Gutenberg +P. O. Box 2782 +Champaign, IL 61825 + +When all other email fails try our Executive Director: +Michael S. Hart <hart@pobox.com> + +We would prefer to send you this information by email. + +****** + +To access Project Gutenberg etexts, use any Web browser +to view http://promo.net/pg. This site lists Etexts by +author and by title, and includes information about how +to get involved with Project Gutenberg. You could also +download our past Newsletters, or subscribe here. This +is one of our major sites, please email hart@pobox.com, +for a more complete list of our various sites. + +To go directly to the etext collections, use FTP or any +Web browser to visit a Project Gutenberg mirror (mirror +sites are available on 7 continents; mirrors are listed +at http://promo.net/pg). + +Mac users, do NOT point and click, typing works better. + +Example FTP session: + +ftp sunsite.unc.edu +login: anonymous +password: your@login +cd pub/docs/books/gutenberg +cd etext90 through etext99 +dir [to see files] +get or mget [to get files. . .set bin for zip files] +GET GUTINDEX.?? [to get a year's listing of books, e.g., GUTINDEX.99] +GET GUTINDEX.ALL [to get a listing of ALL books] + +*** + +**Information prepared by the Project Gutenberg legal advisor** + +(Three Pages) + + +***START**THE SMALL PRINT!**FOR PUBLIC DOMAIN ETEXTS**START*** +Why is this "Small Print!" statement here? You know: lawyers. +They tell us you might sue us if there is something wrong with +your copy of this etext, even if you got it for free from +someone other than us, and even if what's wrong is not our +fault. So, among other things, this "Small Print!" statement +disclaims most of our liability to you. It also tells you how +you can distribute copies of this etext if you want to. + +*BEFORE!* YOU USE OR READ THIS ETEXT +By using or reading any part of this PROJECT GUTENBERG-tm +etext, you indicate that you understand, agree to and accept +this "Small Print!" statement. If you do not, you can receive +a refund of the money (if any) you paid for this etext by +sending a request within 30 days of receiving it to the person +you got it from. If you received this etext on a physical +medium (such as a disk), you must return it with your request. + +ABOUT PROJECT GUTENBERG-TM ETEXTS +This PROJECT GUTENBERG-tm etext, like most PROJECT GUTENBERG- +tm etexts, is a "public domain" work distributed by Professor +Michael S. Hart through the Project Gutenberg Association at +Carnegie-Mellon University (the "Project"). Among other +things, this means that no one owns a United States copyright +on or for this work, so the Project (and you!) can copy and +distribute it in the United States without permission and +without paying copyright royalties. Special rules, set forth +below, apply if you wish to copy and distribute this etext +under the Project's "PROJECT GUTENBERG" trademark. + +To create these etexts, the Project expends considerable +efforts to identify, transcribe and proofread public domain +works. Despite these efforts, the Project's etexts and any +medium they may be on may contain "Defects". Among other +things, Defects may take the form of incomplete, inaccurate or +corrupt data, transcription errors, a copyright or other +intellectual property infringement, a defective or damaged +disk or other etext medium, a computer virus, or computer +codes that damage or cannot be read by your equipment. + +LIMITED WARRANTY; DISCLAIMER OF DAMAGES +But for the "Right of Replacement or Refund" described below, +[1] the Project (and any other party you may receive this +etext from as a PROJECT GUTENBERG-tm etext) disclaims all +liability to you for damages, costs and expenses, including +legal fees, and [2] YOU HAVE NO REMEDIES FOR NEGLIGENCE OR +UNDER STRICT LIABILITY, OR FOR BREACH OF WARRANTY OR CONTRACT, +INCLUDING BUT NOT LIMITED TO INDIRECT, CONSEQUENTIAL, PUNITIVE +OR INCIDENTAL DAMAGES, EVEN IF YOU GIVE NOTICE OF THE +POSSIBILITY OF SUCH DAMAGES. + +If you discover a Defect in this etext within 90 days of +receiving it, you can receive a refund of the money (if any) +you paid for it by sending an explanatory note within that +time to the person you received it from. If you received it +on a physical medium, you must return it with your note, and +such person may choose to alternatively give you a replacement +copy. If you received it electronically, such person may +choose to alternatively give you a second opportunity to +receive it electronically. + +THIS ETEXT IS OTHERWISE PROVIDED TO YOU "AS-IS". NO OTHER +WARRANTIES OF ANY KIND, EXPRESS OR IMPLIED, ARE MADE TO YOU AS +TO THE ETEXT OR ANY MEDIUM IT MAY BE ON, INCLUDING BUT NOT +LIMITED TO WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A +PARTICULAR PURPOSE. + +Some states do not allow disclaimers of implied warranties or +the exclusion or limitation of consequential damages, so the +above disclaimers and exclusions may not apply to you, and you +may have other legal rights. + +INDEMNITY +You will indemnify and hold the Project, its directors, +officers, members and agents harmless from all liability, cost +and expense, including legal fees, that arise directly or +indirectly from any of the following that you do or cause: +[1] distribution of this etext, [2] alteration, modification, +or addition to the etext, or [3] any Defect. + +DISTRIBUTION UNDER "PROJECT GUTENBERG-tm" +You may distribute copies of this etext electronically, or by +disk, book or any other medium if you either delete this +"Small Print!" and all other references to Project Gutenberg, +or: + +[1] Only give exact copies of it. Among other things, this + requires that you do not remove, alter or modify the + etext or this "small print!" statement. You may however, + if you wish, distribute this etext in machine readable + binary, compressed, mark-up, or proprietary form, + including any form resulting from conversion by word pro- + cessing or hypertext software, but only so long as + *EITHER*: + + [*] The etext, when displayed, is clearly readable, and + does *not* contain characters other than those + intended by the author of the work, although tilde + (~), asterisk (*) and underline (_) characters may + be used to convey punctuation intended by the + author, and additional characters may be used to + indicate hypertext links; OR + + [*] The etext may be readily converted by the reader at + no expense into plain ASCII, EBCDIC or equivalent + form by the program that displays the etext (as is + the case, for instance, with most word processors); + OR + + [*] You provide, or agree to also provide on request at + no additional cost, fee or expense, a copy of the + etext in its original plain ASCII form (or in EBCDIC + or other equivalent proprietary form). + +[2] Honor the etext refund and replacement provisions of this + "Small Print!" statement. + +[3] Pay a trademark license fee to the Project of 20% of the + net profits you derive calculated using the method you + already use to calculate your applicable taxes. If you + don't derive profits, no royalty is due. Royalties are + payable to "Project Gutenberg Association/Carnegie-Mellon + University" within the 60 days following each + date you prepare (or were legally required to prepare) + your annual (or equivalent periodic) tax return. + +WHAT IF YOU *WANT* TO SEND MONEY EVEN IF YOU DON'T HAVE TO? +The Project gratefully accepts contributions in money, time, +scanning machines, OCR software, public domain etexts, royalty +free copyright licenses, and every other sort of contribution +you can think of. Money should be paid to "Project Gutenberg +Association / Carnegie-Mellon University". + +*END*THE SMALL PRINT! FOR PUBLIC DOMAIN ETEXTS*Ver.04.29.93*END* + + + + + +This etext was prepared by Sue Asscher <asschers@aia.net.au> + + + + + +DARWIN AND MODERN SCIENCE + +ESSAYS IN COMMEMORATION OF THE CENTENARY OF THE BIRTH OF CHARLES DARWIN AND +OF THE FIFTIETH ANNIVERSARY OF THE PUBLICATION OF "THE ORIGIN OF SPECIES" + + +BY + +A.C. SEWARD + + + + +"My success as a man of science, whatever this may have amounted to, has +been determined, as far as I can judge, by complex and diversified mental +qualities and conditions. Of these, the most important have been--the love +of science--unbounded patience in long reflecting over any subject-- +industry in observing and collecting facts--and a fair share of invention +as well as of common sense. With such moderate abilities as I possess, it +is truly surprising that I should have influenced to a considerable extent +the belief of scientific men on some important points." + +Autobiography (1881); "The Life and Letters of Charles Darwin", Vol. 1. +page 107. + + +PREFACE + +At the suggestion of the Cambridge Philosophical Society, the Syndics of +the University Press decided in March, 1908, to arrange for the publication +of a series of Essays in commemoration of the Centenary of the birth of +Charles Darwin and of the Fiftieth anniversary of the publication of "The +Origin of Species". The preliminary arrangements were made by a committee +consisting of the following representatives of the Council of the +Philosophical Society and of the Press Syndicate: Dr H.K. Anderson, Prof. +Bateson, Mr Francis Darwin, Dr Hobson, Dr Marr, Prof. Sedgwick, Mr David +Sharp, Mr Shipley, Prof. Sorley, Prof. Seward. In the course of the +preparation of the volume, the original scheme and list of authors have +been modified: a few of those invited to contribute essays were, for +various reasons, unable to do so, and some alterations have been made in +the titles of articles. For the selection of authors and for the choice of +subjects, the committee are mainly responsible, but for such share of the +work in the preparation of the volume as usually falls to the lot of an +editor I accept full responsibility. + +Authors were asked to address themselves primarily to the educated layman +rather than to the expert. It was hoped that the publication of the essays +would serve the double purpose of illustrating the far-reaching influence +of Darwin's work on the progress of knowledge and the present attitude of +original investigators and thinkers towards the views embodied in Darwin's +works. + +In regard to the interpretation of a passage in "The Origin of Species" +quoted by Hugo de Vries, it seemed advisable to add an editorial footnote; +but, with this exception, I have not felt it necessary to record any +opinion on views stated in the essays. + +In reading the essays in proof I have availed myself freely of the willing +assistance of several Cambridge friends, among whom I wish more especially +to thank Mr Francis Darwin for the active interest he has taken in the +preparation of the volume. Mrs J.A. Thomson kindly undertook the +translation of the essays by Prof. Weismann and Prof. Schwalbe; Mrs James +Ward was good enough to assist me by translating Prof. Bougle's article on +Sociology, and to Mr McCabe I am indebted for the translation of the essay +by Prof. Haeckel. For the translation of the botanical articles by Prof. +Goebel, Prof. Klebs and Prof. Strasburger, I am responsible; in the +revision of the translation of Prof. Strasburger's essay Madame Errera of +Brussels rendered valuable help. Mr Wright, the Secretary of the Press +Syndicate, and Mr Waller, the Assistant Secretary, have cordially +cooperated with me in my editorial work; nor can I omit to thank the +readers of the University Press for keeping watchful eyes on my +shortcomings in the correction of proofs. + +The two portraits of Darwin are reproduced by permission of Messrs Maull +and Fox and Messrs Elliott and Fry. The photogravure of the study at Down +is reproduced from an etching by Mr Axel Haig, lent by Mr Francis Darwin; +the coloured plate illustrating Prof. Weismann's essay was originally +published by him in his "Vortrage uber Descendenztheorie" which afterwards +appeared (1904) in English under the title "The Evolution Theory". Copies +of this plate were supplied by Messrs Fischer of Jena. + +The Syndics of the University Press have agreed, in the event of this +volume being a financial success, to hand over the profits to a University +fund for the endowment of biological research. + +It is clearly impossible to express adequately in a single volume of Essays +the influence of Darwin's contributions to knowledge on the subsequent +progress of scientific inquiry. As Huxley said in 1885: "Whatever be the +ultimate verdict of posterity upon this or that opinion which Mr Darwin has +propounded; whatever adumbrations or anticipations of his doctrines may be +found in the writings of his predecessors; the broad fact remains that, +since the publication and by reason of the publication of "The Origin of +Species" the fundamental conceptions and the aims of the students of living +Nature have been completely changed...But the impulse thus given to +scientific thought rapidly spread beyond the ordinarily recognised limits +of Biology. Psychology, Ethics, Cosmology were stirred to their +foundations, and 'The Origin of Species' proved itself to be the fixed +point which the general doctrine needed in order to move the world." + +In the contributions to this Memorial Volume, some of the authors have more +especially concerned themselves with the results achieved by Darwin's own +work, while others pass in review the progress of research on lines which, +though unknown or but little followed in his day, are the direct outcome of +his work. + +The divergence of views among biologists in regard to the origin of species +and as to the most promising directions in which to seek for truth is +illustrated by the different opinions of contributors. Whether Darwin's +views on the modus operandi of evolutionary forces receive further +confirmation in the future, or whether they are materially modified, in no +way affects the truth of the statement that, by employing his life "in +adding a little to Natural Science," he revolutionised the world of +thought. Darwin wrote in 1872 to Alfred Russel Wallace: "How grand is the +onward rush of science: it is enough to console us for the many errors +which we have committed, and for our efforts being overlaid and forgotten +in the mass of new facts and new views which are daily turning up." In the +onward rush, it is easy for students convinced of the correctness of their +own views and equally convinced of the falsity of those of their fellow- +workers to forget the lessons of Darwin's life. In his autobiographical +sketch, he tells us, "I have steadily endeavoured to keep my mind free so +as to give up any hypothesis, however much beloved...as soon as facts are +shown to be opposed to it." Writing to Mr J. Scott, he says, "It is a +golden rule, which I try to follow, to put every fact which is opposed to +one's preconceived opinion in the strongest light. Absolute accuracy is +the hardest merit to attain, and the highest merit. Any deviation is +ruin." + +He acted strictly in accordance with his determination expressed in a +letter to Lyell in 1844, "I shall keep out of controversy, and just give my +own facts." As was said of another son of Cambridge, Sir George Stokes, +"He would no more have thought of disputing about priority, or the +authorship of an idea, than of writing a report for a company promoter." +Darwin's life affords a striking confirmation of the truth of Hazlitt's +aphorism, "Where the pursuit of truth has been the habitual study of any +man's life, the love of truth will be his ruling passion." Great as was +the intellect of Darwin, his character, as Huxley wrote, was even nobler +than his intellect. + +A.C. SEWARD. + +Botany School, Cambridge, +March 20, 1909. + + +CONTENTS + +I. INTRODUCTORY LETTER TO THE EDITOR from SIR JOSEPH DALTON HOOKER, O.M. + +II. DARWIN'S PREDECESSORS: + J. ARTHUR THOMSON, Professor of Natural History in the University of +Aberdeen. + +III. THE SELECTION THEORY: + AUGUST WEISMANN, Professor of Zoology in the University of Freiburg +(Baden). + +IV. VARIATION: + HUGO DE VRIES, Professor of Botany in the University of Amsterdam. + +V. HEREDITY AND VARIATION IN MODERN LIGHTS: + W. BATESON, Professor of Biology in the University of Cambridge. + +VI. THE MINUTE STRUCTURE OF CELLS IN RELATION TO HEREDITY: + EDUARD STRASBURGER, Professor of Botany in the University of Bonn. + +VII. "THE DESCENT OF MAN": + G. SCHWALBE, Professor of Anatomy in the University of Strassburg. + +VIII. CHARLES DARWIN AS AN ANTHROPOLOGIST: + ERNST HAECKEL, Professor of Zoology in the University of Jena. + +IX. SOME PRIMITIVE THEORIES OF THE ORIGIN OF MAN: + J.G. FRAZER, Fellow of Trinity College, Cambridge. + +X. THE INFLUENCE OF DARWIN ON THE STUDY OF ANIMAL EMBRYOLOGY: + A. SEDGWICK, Professor of Zoology and Comparative Anatomy in the +University of Cambridge. + +XI. THE PALAEONTOLOGICAL RECORD. I. ANIMALS: + W.B. SCOTT, Professor of Geology in the University of Princeton. + +XII. THE PALAEONTOLOGICAL RECORD. II. PLANTS: + D.H. SCOTT, President of the Linnean Society of London. + +XIII. THE INFLUENCE OF ENVIRONMENT ON THE FORMS OF PLANTS: + GEORG KLEBS, Professor of Botany in the University of Heidelberg. + +XIV. EXPERIMENTAL STUDY OF THE INFLUENCE OF ENVIRONMENT ON ANIMALS: + JACQUES LOEB, Professor of Physiology in the University of California. + +XV. THE VALUE OF COLOUR IN THE STRUGGLE FOR LIFE: + E.B. POULTON, Hope Professor of Zoology in the University of Oxford. + +XVI. GEOGRAPHICAL DISTRIBUTION OF PLANTS: + SIR WILLIAM THISELTON-DYER. + +XVII. GEOGRAPHICAL DISTRIBUTION OF ANIMALS: + HANS GADOW, Strickland Curator and Lecturer on Zoology in the University +of Cambridge. + +XVIII. DARWIN AND GEOLOGY: + J.W. JUDD. + +XIX. DARWIN'S WORK ON THE MOVEMENTS OF PLANTS: + FRANCIS DARWIN. + +XX. THE BIOLOGY OF FLOWERS: + K. GOEBEL, Professor of Botany in the University of Munich. + +XXI. MENTAL FACTORS IN EVOLUTION: + C. LLOYD MORGAN, Professor of Psychology at University College, Bristol. + +XXII. THE INFLUENCE OF THE CONCEPTION OF EVOLUTION ON MODERN PHILOSOPHY: + H. HOFFDING, Professor of Philosophy in the University of Copenhagen. + +XXIII. DARWINISM AND SOCIOLOGY: + C. BOUGLE, Professor of Social Philosophy in the University of Toulouse, +and Deputy-Professor at the Sorbonne, Paris. + +XXIV. THE INFLUENCE OF DARWIN UPON RELIGIOUS THOUGHT: + REV. P.N. WAGGETT. + +XXV. THE INFLUENCE OF DARWINISM ON THE STUDY OF RELIGIONS: + JANE ELLEN HARRISON, Staff-Lecturer and sometime Fellow of Newnham +College, Cambridge. + +XXVI. EVOLUTION AND THE SCIENCE OF LANGUAGE: + P. GILES, Reader in Comparative Philology in the University of Cambridge. + +XXVII. DARWINISM AND HISTORY: + J.B. BURY, Regius Professor of Modern History in the University of +Cambridge. + +XXVIII. THE GENESIS OF DOUBLE STARS: + SIR GEORGE DARWIN, Plumian Professor of Astronomy and Experimental +Philosophy in the University of Cambridge. + +XXIX. THE EVOLUTION OF MATTER: + W.C.D. WHETHAM, Fellow of Trinity College, Cambridge. + +INDEX. + + +DATES OF THE PUBLICATION Of CHARLES DARWIN'S BOOKS AND OF THE PRINCIPAL +EVENTS IN HIS LIFE + +1809: + +Charles Darwin born at Shrewsbury, February 12. + +1817: + +"At 8 1/2 years old I went to Mr Case's school." (A day-school at +Shrewsbury kept by the Rev G. Case, Minister of the Unitarian Chapel.) + +1818: + +"I was at school at Shrewsbury under a great scholar, Dr Butler; I learnt +absolutely nothing, except by amusing myself by reading and experimenting +in Chemistry." + +1825: + +"As I was doing no good at school, my father wisely took me away at a +rather earlier age than usual, and sent me (Oct. 1825) to Edinburgh +University with my brother, where I stayed for two years." + +1828: + +Began residence at Christ's College, Cambridge. + +"I went to Cambridge early in the year 1828, and soon became acquainted +with Professor Henslow...Nothing could be more simple, cordial and +unpretending than the encouragement which he afforded to all young +naturalists." + +"During the three years which I spent at Cambridge my time was wasted, as +far as the academical studies were concerned, as completely as at Edinburgh +and at school." + +"In order to pass the B.A. Examination, it was...necessary to get up +Paley's 'Evidences of Christianity,' and his 'Moral Philosophy'...The +careful study of these works, without attempting to learn any part by rote, +was the only part of the academical course which...was of the least use to +me in the education of my mind." + +1831: + +Passed the examination for the B.A. degree in January and kept the +following terms. + +"I gained a good place among the oi polloi or crowd of men who do not go in +for honours." + +"I am very busy,...and see a great deal of Henslow, whom I do not know +whether I love or respect most." + +Dec. 27. "Sailed from England on our circumnavigation," in H.M.S. +"Beagle", a barque of 235 tons carrying 6 guns, under Capt. FitzRoy. + +"There is indeed a tide in the affairs of men." + +1836: + +Oct. 4. "Reached Shrewsbury after absence of 5 years and 2 days." + +"You cannot imagine how gloriously delightful my first visit was at home; +it was worth the banishment." + +Dec. 13. Went to live at Cambridge (Fitzwilliam Street). + +"The only evil I found in Cambridge was its being too pleasant." + +1837: + +"On my return home (in the 'Beagle') in the autumn of 1836 I immediately +began to prepare my journal for publication, and then saw how many facts +indicated the common descent of species...In July (1837) I opened my first +note-book for facts in relation to the Origin of Species, about which I had +long reflected, and never ceased working for the next twenty years...Had +been greatly struck from about the month of previous March on character of +South American fossils, and species on Galapagos Archipelago. These facts +(especially latter), origin of all my views." + +"On March 7, 1837 I took lodgings in (36) Great Marlborough Street in +London, and remained there for nearly two years, until I was married." + +1838: + +"In October, that is fifteen months after I had begun my systematic +enquiry, I happened to read for amusement 'Malthus on Population,' and +being well prepared to appreciate the struggle for existence which +everywhere goes on from long-continued observation of the habits of animals +and plants, it at once struck me that under these circumstances favourable +variations would tend to be preserved, and unfavourable ones to be +destroyed. The result of this would be the formation of new species. Here +then I had at last got a theory by which to work; but I was so anxious to +avoid prejudice, that I determined not for some time to write even the +briefest sketch of it." + +1839: + +Married at Maer (Staffordshire) to his first cousin Emma Wedgwood, daughter +of Josiah Wedgwood. + +"I marvel at my good fortune that she, so infinitely my superior in every +single moral quality, consented to be my wife. She has been my wise +adviser and cheerful comforter throughout life, which without her would +have been during a very long period a miserable one from ill-health. She +has earned the love of every soul near her" (Autobiography). + +Dec. 31. "Entered 12 Upper Gower street" (now 110 Gower street, London). +"There never was so good a house for me, and I devoutly trust you (his +future wife) will approve of it equally. The little garden is worth its +weight in gold." + +Published "Journal and Researches", being Vol. III. of the "Narrative of +the Surveying Voyage of H.M.S. 'Adventure' and 'Beagle'"... + +Publication of the "Zoology of the Voyage of H.M.S. 'Beagle'", Part II., +"Mammalia", by G.R. Waterhouse, with a "Notice of their habits and ranges", +by Charles Darwin. + +1840: + +Contributed Geological Introduction to Part I. ("Fossil Mammalia") of the +"Zoology of the Voyage of H.M.S. 'Beagle'" by Richard Owen. + +1842: + +"In June 1842 I first allowed myself the satisfaction of writing a very +brief abstract of my (species) theory in pencil in 35 pages; and this was +enlarged during the summer of 1844 into one of 230 pages, which I had +fairly copied out and still (1876) possess." (The first draft of "The +Origin of Species", edited by Mr Francis Darwin, will be published this +year (1909) by the Syndics of the Cambridge University Press.) + +Sept. 14. Settled at the village of Down in Kent. + +"I think I was never in a more perfectly quiet country." + +Publication of "The Structure and Distribution of Coral Reefs"; being Part +I. of the "Geology of the Voyage of the Beagle". + +1844: + +Publication of "Geological Observations on the Volcanic Islands visited +during the Voyage of H.M.S. 'Beagle'"; being Part II. of the "Geology of +the Voyage of the 'Beagle'". + +"I think much more highly of my book on Volcanic Islands since Mr Judd, by +far the best judge on the subject in England, has, as I hear, learnt much +from it." (Autobiography, 1876.) + +1845: + +Publication of the "Journal of Researches" as a separate book. + +1846: + +Publication of "Geological Observations on South America"; being Part III. +of the "Geology of the Voyage of the 'Beagle'". + +1851: + +Publication of a "Monograph of the Fossil Lepadidae" and of a "Monograph of +the sub-class Cirripedia". + +"I fear the study of the Cirripedia will ever remain 'wholly unapplied,' +and yet I feel that such study is better than castle-building." + +1854: + +Publication of Monographs of the Balanidae and Verrucidae. + +"I worked steadily on this subject for...eight years, and ultimately +published two thick volumes, describing all the known living species, and +two thin quartos on the extinct species...My work was of considerable use +to me, when I had to discuss in the "Origin of Species" the principles of a +natural classification. Nevertheless, I doubt whether the work was worth +the consumption of so much time." + +"From September 1854 I devoted my whole time to arranging my huge pile of +notes, to observing, and to experimenting in relation to the transmutation +of species." + +1856: + +"Early in 1856 Lyell advised me to write out my views pretty fully, and I +began at once to do so on a scale three or four times as extensive as that +which was afterwards followed in my 'Origin of Species'." + +1858: + +Joint paper by Charles Darwin and Alfred Russel Wallace "On the Tendency of +Species to form Varieties; and on the perpetuation of Varieties and Species +by Natural Means of Selection," communicated to the Linnean Society by Sir +Charles Lyell and Sir Joseph Hooker. + +"I was at first very unwilling to consent (to the communication of his MS. +to the Society) as I thought Mr Wallace might consider my doing so +unjustifiable, for I did not then know how generous and noble was his +disposition." + +"July 20 to Aug. 12 at Sandown (Isle of Wight) began abstract of Species +book." + +1859: + +Nov. 24. Publication of "The Origin of Species" (1250 copies). + +"Oh, good heavens, the relief to my head and body to banish the whole +subject from my mind!...But, alas, how frequent, how almost universal it is +in an author to persuade himself of the truth of his own dogmas. My only +hope is that I certainly see many difficulties of gigantic stature." + +1860: + +Publication of the second edition of the "Origin" (3000 copies). + +Publication of a "Naturalist's Voyage". + +1861: + +Publication of the third edition of the "Origin" (2000 copies). + +"I am going to write a little book...on Orchids, and to-day I hate them +worse than everything." + +1862: + +Publication of the book "On the various contrivances by which Orchids are +fertilised by Insects". + +1865: + +Read paper before the Linnean Society "On the Movements and Habits of +Climbing plants". (Published as a book in 1875.) + +1866: + +Publication of the fourth edition of the "Origin" (1250 copies). + +1868: + +"I have sent the MS. of my big book, and horridly, disgustingly big it will +be, to the printers." + +Publication of the "Variation of Animals and Plants under Domestication". + +"About my book, I will give you (Sir Joseph Hooker) a bit of advice. Skip +the whole of Vol. I, except the last chapter, (and that need only be +skimmed), and skip largely in the 2nd volume; and then you will say it is a +very good book." + +"Towards the end of the work I give my well-abused hypothesis of +Pangenesis. An unverified hypothesis is of little or no value; but if +anyone should hereafter be led to make observations by which some such +hypothesis could be established, I shall have done good service, as an +astonishing number of isolated facts can be thus connected together and +rendered intelligible." + +1869: + +Publication of the fifth edition of the "Origin". + +1871: + +Publication of "The Descent of Man". + +"Although in the 'Origin of Species' the derivation of any particular +species is never discussed, yet I thought it best, in order that no +honourable man should accuse me of concealing my views, to add that by the +work 'light would be thrown on the origin of man and his history'." + +1872: + +Publication of the sixth edition of the "Origin". + +Publication of "The Expression of the Emotions in Man and Animals". + +1874: + +Publication of the second edition of "The Descent of Man". + +"The new edition of the "Descent" has turned out an awful job. It took me +ten days merely to glance over letters and reviews with criticisms and new +facts. It is a devil of a job." + +Publication of the second edition of "The Structure and Distribution of +Coral Reefs". + +1875: + +Publication of "Insectivorous Plants". + +"I begin to think that every one who publishes a book is a fool." + +Publication of the second edition of "Variation in Animals and Plants". + +Publication of "The Movements and Habits of Climbing Plants" as a separate +book. + +1876: + +Wrote Autobiographical Sketch ("Life and Letters", Vol. I., Chap II.). + +Publication of "The Effects of Cross and Self fertilisation". + +"I now (1881) believe, however,...that I ought to have insisted more +strongly than I did on the many adaptations for self-fertilisation." + +Publication of the second edition of "Observations on Volcanic Islands". + +1877: + +Publication of "The Different Forms of Flowers on Plants of the same +species". + +"I do not suppose that I shall publish any more books...I cannot endure +being idle, but heaven knows whether I am capable of any more good work." + +Publication of the second edition of the Orchid book. + +1878: + +Publication of the second edition of "The Effects of Cross and Self +fertilisation". + +1879: + +Publication of an English translation of Ernst Krause's "Erasmus Darwin", +with a notice by Charles Darwin. "I am EXTREMELY glad that you approve of +the little 'Life' of our Grandfather, for I have been repenting that I ever +undertook it, as the work was quite beyond my tether." (To Mr Francis +Galton, Nov. 14, 1879.) + +1880: + +Publication of "The Power of Movement in Plants". + +"It has always pleased me to exalt plants in the scale of organised +beings." + +Publication of the second edition of "The Different Forms of Flowers". + +1881: + +Wrote a continuation of the Autobiography. + +Publication of "The Formation of Vegetable Mould, through the Action of +Worms". + +"It is the completion of a short paper read before the Geological Society +more than forty years ago, and has revived old geological thoughts...As far +as I can judge it will be a curious little book." + +1882: + +Charles Darwin died at Down, April 19, and was buried in Westminster Abbey, +April 26, in the north aisle of the Nave a few feet from the grave of Sir +Isaac Newton. + +"As for myself, I believe that I have acted rightly in steadily following +and devoting my life to Science. I feel no remorse from having committed +any great sin, but have often and often regretted that I have not done more +direct good to my fellow creatures." + +The quotations in the above Epitome are taken from the Autobiography and +published Letters:-- + +"The Life and Letters of Charles Darwin", including an Autobiographical +Chapter. Edited by his son, Francis Darwin, 3 Vols., London, 1887. + +"Charles Darwin": His life told in an Autobiographical Chapter, and in a +selected series of his published Letters. Edited by his son, Francis +Darwin, London, 1902. + +"More Letters of Charles Darwin". A record of his work in a series of +hitherto unpublished Letters. Edited by Francis Darwin and A.C. Seward, 2 +Vols., London, 1903. + + +I. INTRODUCTORY LETTER + +FROM SIR JOSEPH DALTON HOOKER, + +O.M., G.C.S.I., C.B., M.D., D.C.L., LL.D., F.R.S., ETC. + + +The Camp, + +near Sunningdale, + +January 15, 1909. + +Dear Professor Seward, + +The publication of a Series of Essays in Commemoration of the century of +the birth of Charles Darwin and of the fiftieth anniversary of the +publication of "The Origin of Species" is assuredly welcome and is a +subject of congratulation to all students of Science. + +These Essays on the progress of Science and Philosophy as affected by +Darwin's labours have been written by men known for their ability to +discuss the problems which he so successfully worked to solve. They cannot +but prove to be of enduring value, whether for the information of the +general reader or as guides to investigators occupied with problems similar +to those which engaged the attention of Darwin. + +The essayists have been fortunate in having for reference the five +published volumes of Charles Darwin's Life and Correspondence. For there +is set forth in his own words the inception in his mind of the problems, +geological, zoological and botanical, hypothetical and theoretical, which +he set himself to solve and the steps by which he proceeded to investigate +them with the view of correlating the phenomena of life with the evolution +of living things. In his letters he expressed himself in language so lucid +and so little burthened with technical terms that they may be regarded as +models for those who were asked to address themselves primarily to the +educated reader rather than to the expert. + +I may add that by no one can the perusal of the Essays be more vividly +appreciated than by the writer of these lines. It was my privilege for +forty years to possess the intimate friendship of Charles Darwin and to be +his companion during many of his working hours in Study, Laboratory, and +Garden. I was the recipient of letters from him, relating mainly to the +progress of his researches, the copies of which (the originals are now in +the possession of his family) cover upwards of a thousand pages of +foolscap, each page containing, on an average, three hundred words. + +That the editorship of these Essays has been entrusted to a Cambridge +Professor of Botany must be gratifying to all concerned in their production +and in their perusal, recalling as it does the fact that Charles Darwin's +instructor in scientific methods was his lifelong friend the late Rev. J.S. +Henslow at that time Professor of Botany in the University. It was owing +to his recommendation that his pupil was appointed Naturalist to H.M.S. +"Beagle", a service which Darwin himself regarded as marking the dawn of +his scientific career. + +Very sincerely yours, + +J.D. HOOKER. + + +II. DARWIN'S PREDECESSORS. + +By J. ARTHUR THOMSON. +Professor of Natural History in the University of Aberdeen. + +In seeking to discover Darwin's relation to his predecessors it is useful +to distinguish the various services which he rendered to the theory of +organic evolution. + +(I) As everyone knows, the general idea of the Doctrine of Descent is that +the plants and animals of the present-day are the lineal descendants of +ancestors on the whole somewhat simpler, that these again are descended +from yet simpler forms, and so on backwards towards the literal "Protozoa" +and "Protophyta" about which we unfortunately know nothing. Now no one +supposes that Darwin originated this idea, which in rudiment at least is as +old as Aristotle. What Darwin did was to make it current intellectual +coin. He gave it a form that commended itself to the scientific and public +intelligence of the day, and he won wide-spread conviction by showing with +consummate skill that it was an effective formula to work with, a key which +no lock refused. In a scholarly, critical, and pre-eminently fair-minded +way, admitting difficulties and removing them, foreseeing objections and +forestalling them, he showed that the doctrine of descent supplied a modal +interpretation of how our present-day fauna and flora have come to be. + +(II) In the second place, Darwin applied the evolution-idea to particular +problems, such as the descent of man, and showed what a powerful organon it +is, introducing order into masses of uncorrelated facts, interpreting +enigmas both of structure and function, both bodily and mental, and, best +of all, stimulating and guiding further investigation. But here again it +cannot be claimed that Darwin was original. The problem of the descent or +ascent of man, and other particular cases of evolution, had attracted not a +few naturalists before Darwin's day, though no one (except Herbert Spencer +in the psychological domain (1855)) had come near him in precision and +thoroughness of inquiry. + +(III) In the third place, Darwin contributed largely to a knowledge of the +factors in the evolution-process, especially by his analysis of what occurs +in the case of domestic animals and cultivated plants, and by his +elaboration of the theory of Natural Selection, which Alfred Russel Wallace +independently stated at the same time, and of which there had been a few +previous suggestions of a more or less vague description. It was here that +Darwin's originality was greatest, for he revealed to naturalists the many +different forms--often very subtle--which natural selection takes, and with +the insight of a disciplined scientific imagination he realised what a +mighty engine of progress it has been and is. + +(IV) As an epoch-marking contribution, not only to Aetiology but to +Natural History in the widest sense, we rank the picture which Darwin gave +to the world of the web of life, that is to say, of the inter-relations and +linkages in Nature. For the Biology of the individual--if that be not a +contradiction in terms--no idea is more fundamental than that of the +correlation of organs, but Darwin's most characteristic contribution was +not less fundamental,--it was the idea of the correlation of organisms. +This, again, was not novel; we find it in the works of naturalist like +Christian Conrad Sprengel, Gilbert White, and Alexander von Humboldt, but +the realisation of its full import was distinctively Darwinian. + +AS REGARDS THE GENERAL IDEA OF ORGANIC EVOLUTION. + +While it is true, as Prof. H.F. Osborn puts it, that "'Before and after +Darwin' will always be the ante et post urbem conditam of biological +history," it is also true that the general idea of organic evolution is +very ancient. In his admirable sketch "From the Greeks to Darwin" +("Columbia University Biological Series", Vol. I. New York and London, +1894. We must acknowledge our great indebtness to this fine piece of +work.), Prof. Osborn has shown that several of the ancient philosophers +looked upon Nature as a gradual development and as still in process of +change. In the suggestions of Empedocles, to take the best instance, there +were "four sparks of truth,--first, that the development of life was a +gradual process; second, that plants were evolved before animals; third, +that imperfect forms were gradually replaced (not succeeded) by perfect +forms; fourth, that the natural cause of the production of perfect forms +was the extinction of the imperfect." (Op. cit. page 41.) But the +fundamental idea of one stage giving origin to another was absent. As the +blue Aegean teemed with treasures of beauty and threw many upon its shores, +so did Nature produce like a fertile artist what had to be rejected as well +as what was able to survive, but the idea of one species emerging out of +another was not yet conceived. + +Aristotle's views of Nature (See G.J. Romanes, "Aristotle as a Naturalist", +"Contemporary Review", Vol. LIX. page 275, 1891; G. Pouchet "La Biologie +Aristotelique", Paris, 1885; E. Zeller, "A History of Greek Philosophy", +London, 1881, and "Ueber die griechischen Vorganger Darwin's", "Abhandl. +Berlin Akad." 1878, pages 111-124.) seem to have been more definitely +evolutionist than those of his predecessors, in this sense, at least, that +he recognised not only an ascending scale, but a genetic series from polyp +to man and an age-long movement towards perfection. "It is due to the +resistance of matter to form that Nature can only rise by degrees from +lower to higher types." "Nature produces those things which, being +continually moved by a certain principle contained in themselves, arrive at +a certain end." + +To discern the outcrop of evolution-doctrine in the long interval between +Aristotle and Bacon seems to be very difficult, and some of the instances +that have been cited strike one as forced. Epicurus and Lucretius, often +called poets of evolution, both pictured animals as arising directly out of +the earth, very much as Milton's lion long afterwards pawed its way out. +Even when we come to Bruno who wrote that "to the sound of the harp of the +Universal Apollo (the World Spirit), the lower organisms are called by +stages to higher, and the lower stages are connected by intermediate forms +with the higher," there is great room, as Prof. Osborn points out (op. cit. +page 81.), for difference of opinion as to how far he was an evolutionist +in our sense of the term. + +The awakening of natural science in the sixteenth century brought the +possibility of a concrete evolution theory nearer, and in the early +seventeenth century we find evidences of a new spirit--in the embryology of +Harvey and the classifications of Ray. Besides sober naturalists there +were speculative dreamers in the sixteenth and seventeenth centuries who +had at least got beyond static formulae, but, as Professor Osborn points +out (op. cit. page 87.), "it is a very striking fact, that the basis of our +modern methods of studying the Evolution problem was established not by the +early naturalists nor by the speculative writers, but by the Philosophers." +He refers to Bacon, Descartes, Leibnitz, Hume, Kant, Lessing, Herder, and +Schelling. "They alone were upon the main track of modern thought. It is +evident that they were groping in the dark for a working theory of the +Evolution of life, and it is remarkable that they clearly perceived from +the outset that the point to which observation should be directed was not +the past but the present mutability of species, and further, that this +mutability was simply the variation of individuals on an extended scale." + +Bacon seems to have been one of the first to think definitely about the +mutability of species, and he was far ahead of his age in his suggestion of +what we now call a Station of Experimental Evolution. Leibnitz discusses +in so many words how the species of animals may be changed and how +intermediate species may once have linked those that now seem +discontinuous. "All natural orders of beings present but a single +chain"..."All advances by degrees in Nature, and nothing by leaps." +Similar evolutionist statements are to be found in the works of the other +"philosophers," to whom Prof. Osborn refers, who were, indeed, more +scientific than the naturalists of their day. It must be borne in mind +that the general idea of organic evolution--that the present is the child +of the past--is in great part just the idea of human history projected upon +the natural world, differentiated by the qualification that the continuous +"Becoming" has been wrought out by forces inherent in the organisms +themselves and in their environment. + +A reference to Kant (See Brock, "Die Stellung Kant's zur +Deszendenztheorie," "Biol. Centralbl." VIII. 1889, pages 641-648. Fritz +Schultze, "Kant und Darwin", Jena, 1875.) should come in historical order +after Buffon, with whose writings he was acquainted, but he seems, along +with Herder and Schelling, to be best regarded as the culmination of the +evolutionist philosophers--of those at least who interested themselves in +scientific problems. In a famous passage he speaks of "the agreement of so +many kinds of animals in a certain common plan of structure"...an "analogy +of forms" which "strengthens the supposition that they have an actual +blood-relationship, due to derivation from a common parent." He speaks of +"the great Family of creatures, for as a Family we must conceive it, if the +above-mentioned continuous and connected relationship has a real +foundation." Prof. Osborn alludes to the scientific caution which led +Kant, biology being what it was, to refuse to entertain the hope "that a +Newton may one day arise even to make the production of a blade of grass +comprehensible, according to natural laws ordained by no intention." As +Prof. Haeckel finely observes, Darwin rose up as Kant's Newton. (Mr Alfred +Russel Wallace writes: "We claim for Darwin that he is the Newton of +natural history, and that, just so surely as that the discovery and +demonstration by Newton of the law of gravitation established order in +place of chaos and laid a sure foundation for all future study of the +starry heavens, so surely has Darwin, by his discovery of the law of +natural selection and his demonstration of the great principle of the +preservation of useful variations in the struggle for life, not only thrown +a flood of light on the process of development of the whole organic world, +but also established a firm foundation for all future study of nature" +("Darwinism", London, 1889, page 9). See also Prof. Karl Pearson's +"Grammar of Science" (2nd edition), London, 1900, page 32. See Osborn, op. +cit. Page 100.)) + +The scientific renaissance brought a wealth of fresh impressions and some +freedom from the tyranny of tradition, and the twofold stimulus stirred the +speculative activity of a great variety of men from old Claude Duret of +Moulins, of whose weird transformism (1609) Dr Henry de Varigny +("Experimental Evolution". London, 1892. Chap. 1. page 14.) gives us a +glimpse, to Lorenz Oken (1799-1851) whose writings are such mixtures of +sense and nonsense that some regard him as a far-seeing prophet and others +as a fatuous follower of intellectual will-o'-the-wisps. Similarly, for De +Maillet, Maupertuis, Diderot, Bonnet, and others, we must agree with +Professor Osborn that they were not actually in the main Evolution +movement. Some have been included in the roll of honour on very slender +evidence, Robinet for instance, whose evolutionism seems to us extremely +dubious. (See J. Arthur Thomson, "The Science of Life". London, 1899. +Chap. XVI. "Evolution of Evolution Theory".) + +The first naturalist to give a broad and concrete expression to the +evolutionist doctrine of descent was Buffon (1707-1788), but it is +interesting to recall the fact that his contemporary Linnaeus (1707-1778), +protagonist of the counter-doctrine of the fixity of species (See Carus +Sterne (Ernest Krause), "Die allgemeine Weltanschauung in ihrer +historischen Entwickelung". Stuttgart, 1889. Chapter entitled +"Bestandigkeit oder Veranderlichkeit der Naturwesen".), went the length of +admitting (in 1762) that new species might arise by intercrossing. +Buffon's position among the pioneers of the evolution-doctrine is weakened +by his habit of vacillating between his own conclusions and the orthodoxy +of the Sorbonne, but there is no doubt that he had a firm grasp of the +general idea of "l'enchainement des etres." + +Erasmus Darwin (1731-1802), probably influenced by Buffon, was another firm +evolutionist, and the outline of his argument in the "Zoonomia" ("Zoonomia, +or the Laws of Organic Life", 2 vols. London, 1794; Osborn op. cit. page +145.) might serve in part at least to-day. "When we revolve in our minds +the metamorphoses of animals, as from the tadpole to the frog; secondly, +the changes produced by artificial cultivation, as in the breeds of horses, +dogs, and sheep; thirdly, the changes produced by conditions of climate and +of season, as in the sheep of warm climates being covered with hair instead +of wool, and the hares and partridges of northern climates becoming white +in winter: when, further, we observe the changes of structure produced by +habit, as seen especially in men of different occupations; or the changes +produced by artificial mutilation and prenatal influences, as in the +crossing of species and production of monsters; fourth, when we observe the +essential unity of plan in all warm-blooded animals,--we are led to +conclude that they have been alike produced from a similar living +filament"..."From thus meditating upon the minute portion of time in which +many of the above changes have been produced, would it be too bold to +imagine, in the great length of time since the earth began to exist, +perhaps millions of years before the commencement of the history of +mankind, that all warm-blooded animals have arisen from one living +filament?"..."This idea of the gradual generation of all things seems to +have been as familiar to the ancient philosophers as to the modern ones, +and to have given rise to the beautiful hieroglyphic figure of the proton +oon, or first great egg, produced by night, that is, whose origin is +involved in obscurity, and animated by Eros, that is, by Divine Love; from +whence proceeded all things which exist." + +Lamarck (1744-1829) seems to have become an evolutionist independently of +Erasmus Darwin's influence, though the parallelism between them is +striking. He probably owed something to Buffon, but he developed his +theory along a different line. Whatever view be held in regard to that +theory there is no doubt that Lamarck was a thorough-going evolutionist. +Professor Haeckel speaks of the "Philosophie Zoologique" as "the first +connected and thoroughly logical exposition of the theory of descent." +(See Alpheus S. Packard, "Lamarck, the Founder of Evolution, His Life and +Work, with Translations of his writings on Organic Evolution". London, +1901.) + +Besides the three old masters, as we may call them, Buffon, Erasmus Darwin, +and Lamarck, there were other quite convinced pre-Darwinian evolutionists. +The historian of the theory of descent must take account of Treviranus +whose "Biology or Philosophy of Animate Nature" is full of evolutionary +suggestions; of Etienne Geoffroy St Hilaire, who in 1830, before the French +Academy of Sciences, fought with Cuvier, the fellow-worker of his youth, an +intellectual duel on the question of descent; of Goethe, one of the +founders of morphology and the greatest poet of Evolution--who, in his +eighty-first year, heard the tidings of Geoffroy St Hilaire's defeat with +an interest which transcended the political anxieties of the time; and of +many others who had gained with more or less confidence and clearness a new +outlook on Nature. It will be remembered that Darwin refers to thirty-four +more or less evolutionist authors in his Historical Sketch, and the list +might be added to. Especially when we come near to 1858 do the numbers +increase, and one of the most remarkable, as also most independent +champions of the evolution-idea before that date was Herbert Spencer, who +not only marshalled the arguments in a very forcible way in 1852, but +applied the formula in detail in his "Principles of Psychology" in 1855. +(See Edward Clodd, "Pioneers of Evolution", London, page 161, 1897.) + +It is right and proper that we should shake ourselves free from all +creationist appreciations of Darwin, and that we should recognise the +services of pre-Darwinian evolutionists who helped to make the time ripe, +yet one cannot help feeling that the citation of them is apt to suggest two +fallacies. It may suggest that Darwin simply entered into the labours of +his predecessors, whereas, as a matter of fact, he knew very little about +them till after he had been for years at work. To write, as Samuel Butler +did, "Buffon planted, Erasmus Darwin and Lamarck watered, but it was Mr +Darwin who said 'That fruit is ripe,' and shook it into his lap"...seems to +us a quite misleading version of the facts of the case. The second fallacy +which the historical citation is a little apt to suggest is that the +filiation of ideas is a simple problem. On the contrary, the history of an +idea, like the pedigree of an organism, is often very intricate, and the +evolution of the evolution-idea is bound up with the whole progress of the +world. Thus in order to interpret Darwin's clear formulation of the idea +of organic evolution and his convincing presentation of it, we have to do +more than go back to his immediate predecessors, such as Buffon, Erasmus +Darwin, and Lamarck; we have to inquire into the acceptance of evolutionary +conceptions in regard to other orders of facts, such as the earth and the +solar system (See Chapter IX. "The Genetic View of Nature" in J.T. Merz's +"History of European Thought in the Nineteenth Century", Vol. 2, Edinburgh +and London, 1903.); we have to realise how the growing success of +scientific interpretation along other lines gave confidence to those who +refused to admit that there was any domain from which science could be +excluded as a trespasser; we have to take account of the development of +philosophical thought, and even of theological and religious movements; we +should also, if we are wise enough, consider social changes. In short, we +must abandon the idea that we can understand the history of any science as +such, without reference to contemporary evolution in other departments of +activity. + +While there were many evolutionists before Darwin, few of them were expert +naturalists and few were known outside a small circle; what was of much +more importance was that the genetic view of nature was insinuating itself +in regard to other than biological orders of facts, here a little and there +a little, and that the scientific spirit had ripened since the days when +Cuvier laughed Lamarck out of court. How was it that Darwin succeeded +where others had failed? Because, in the first place, he had clear +visions--"pensees de la jeunesse, executees par l'age mur"--which a +University curriculum had not made impossible, which the "Beagle" voyage +made vivid, which an unrivalled British doggedness made real--visions of +the web of life, of the fountain of change within the organism, of the +struggle for existence and its winnowing, and of the spreading genealogical +tree. Because, in the second place, he put so much grit into the +verification of his visions, putting them to the proof in an argument which +is of its kind--direct demonstration being out of the question--quite +unequalled. Because, in the third place, he broke down the opposition +which the most scientific had felt to the seductive modal formula of +evolution by bringing forward a more plausible theory of the process than +had been previously suggested. Nor can one forget, since questions of this +magnitude are human and not merely academic, that he wrote so that all men +could understand. + +AS REGARDS THE FACTORS OF EVOLUTION. + +It is admitted by all who are acquainted with the history of biology that +the general idea of organic evolution as expressed in the Doctrine of +Descent was quite familiar to Darwin's grandfather, and to others before +and after him, as we have briefly indicated. It must also be admitted that +some of these pioneers of evolutionism did more than apply the evolution- +idea as a modal formula of becoming, they began to inquire into the factors +in the process. Thus there were pre-Darwinian theories of evolution, and +to these we must now briefly refer. (See Prof. W.A. Locy's "Biology and +its Makers". New York, 1908. Part II. "The Doctrine of Organic +Evolution". + +In all biological thinking we have to work with the categories Organism-- +Function--Environment, and theories of evolution may be classified in +relation to these. To some it has always seemed that the fundamental fact +is the living organism,--a creative agent, a striving will, a changeful +Proteus, selecting its environment, adjusting itself to it, self- +differentiating and self-adaptive. The necessity of recognising the +importance of the organism is admitted by all Darwinians who start with +inborn variations, but it is open to question whether the whole truth of +what we might call the Goethian position is exhausted in the postulate of +inherent variability. + +To others it has always seemed that the emphasis should be laid on +Function,--on use and disuse, on doing and not doing. Practice makes +perfect; c'est a force de forger qu'on devient forgeron. This is one of +the fundamental ideas of Lamarckism; to some extent it met with Darwin's +approval; and it finds many supporters to-day. One of the ablest of these +--Mr Francis Darwin--has recently given strong reasons for combining a +modernised Lamarckism with what we usually regard as sound Darwinism. +(Presidential Address to the British Association meeting at Dublin in +1908.) + +To others it has always seemed that the emphasis should be laid on the +Environment, which wakes the organism to action, prompts it to change, +makes dints upon it, moulds it, prunes it, and finally, perhaps, kills it. +It is again impossible to doubt that there is truth in this view, for even +if environmentally induced "modifications" be not transmissible, +environmentally induced "variations" are; and even if the direct influence +of the environment be less important than many enthusiastic supporters of +this view--may we call them Buffonians--think, there remains the indirect +influence which Darwinians in part rely on,--the eliminative process. Even +if the extreme view be held that the only form of discriminate elimination +that counts is inter-organismal competition, this might be included under +the rubric of the animate environment. + +In many passages Buffon (See in particular Samuel Butler, "Evolution Old +and New", London, 1879; J.L. de Lanessan, "Buffon et Darwin", "Revue +Scientifique", XLIII. pages 385-391, 425-432, 1889.) definitely suggested +that environmental influences--especially of climate and food--were +directly productive of changes in organisms, but he did not discuss the +question of the transmissibility of the modifications so induced, and it is +difficult to gather from his inconsistent writings what extent of +transformation he really believed in. Prof. Osborn says of Buffon: "The +struggle for existence, the elimination of the least-perfected species, the +contest between the fecundity of certain species and their constant +destruction, are all clearly expressed in various passages." He quotes two +of these (op. cit. page 136.): + +"Le cours ordinaire de la nature vivante, est en general toujours constant, +toujours le meme; son mouvement, toujours regulier, roule sur deux points +inebranlables: l'un, la fecondite sans bornes donnee a toutes les especes; +l'autre, les obstacles sans nombre qui reduisent cette fecondite a une +mesure determinee et ne laissent en tout temps qu'a peu pres la meme +quantite d'individus de chaque espece"..."Les especes les moins parfaites, +les plus delicates, les plus pesantes, les moins agissantes, les moins +armees, etc., ont deja disparu ou disparaitront." + +Erasmus Darwin (See Ernst Krause and Charles Darwin, "Erasmus Darwin", +London, 1879.) had a firm grip of the "idea of the gradual formation and +improvement of the Animal world," and he had his theory of the process. No +sentence is more characteristic than this: "All animals undergo +transformations which are in part produced by their own exertions, in +response to pleasures and pains, and many of these acquired forms or +propensities are transmitted to their posterity." This is Lamarckism +before Lamarck, as his grandson pointed out. His central idea is that +wants stimulate efforts and that these result in improvements, which +subsequent generations make better still. He realised something of the +struggle for existence and even pointed out that this advantageously checks +the rapid multiplication. "As Dr Krause points out, Darwin just misses the +connection between this struggle and the Survival of the Fittest." (Osborn +op. cit. page 142.) + +Lamarck (1744-1829) (See E. Perrier "La Philosophie Zoologique avant +Darwin", Paris, 1884; A. de Quatrefages, "Darwin et ses Precurseurs +Francais", Paris, 1870; Packard op. cit.; also Claus, "Lamarck als +Begrunder der Descendenzlehre", Wien, 1888; Haeckel, "Natural History of +Creation", English translation London, 1879; Lang "Zur Charakteristik der +Forschungswege von Lamarck und Darwin", Jena, 1889.) seems to have thought +out his theory of evolution without any knowledge of Erasmus Darwin's which +it closely resembled. The central idea of his theory was the cumulative +inheritance of functional modifications. "Changes in environment bring +about changes in the habits of animals. Changes in their wants necessarily +bring about parallel changes in their habits. If new wants become constant +or very lasting, they form new habits, the new habits involve the use of +new parts, or a different use of old parts, which results finally in the +production of new organs and the modification of old ones." He differed +from Buffon in not attaching importance, as far as animals are concerned, +to the direct influence of the environment, "for environment can effect no +direct change whatever upon the organisation of animals," but in regard to +plants he agreed with Buffon that external conditions directly moulded +them. + +Treviranus (1776-1837) (See Huxley's article "Evolution in Biology", +"Encyclopaedia Britannica" (9th edit.), 1878, pages 744-751, and Sully's +article, "Evolution in Philosophy", ibid. pages 751-772.), whom Huxley +ranked beside Lamarck, was on the whole Buffonian, attaching chief +importance to the influence of a changeful environment both in modifying +and in eliminating, but he was also Goethian, for instance in his idea that +species like individuals pass through periods of growth, full bloom, and +decline. "Thus, it is not only the great catastrophes of Nature which have +caused extinction, but the completion of cycles of existence, out of which +new cycles have begun." A characteristic sentence is quoted by Prof. +Osborn: "In every living being there exists a capability of an endless +variety of form-assumption; each possesses the power to adapt its +organisation to the changes of the outer world, and it is this power, put +into action by the change of the universe, that has raised the simple +zoophytes of the primitive world to continually higher stages of +organisation, and has introduced a countless variety of species into +animate Nature." + +Goethe (1749-1832) (See Haeckel, "Die Naturanschauung von Darwin, Goethe +und Lamarck", Jena, 1882.), who knew Buffon's work but not Lamarck's, is +peculiarly interesting as one of the first to use the evolution-idea as a +guiding hypothesis, e.g. in the interpretation of vestigial structures in +man, and to realise that organisms express an attempt to make a compromise +between specific inertia and individual change. He gave the finest +expression that science has yet known--if it has known it--of the kernel- +idea of what is called "bathmism," the idea of an "inherent growth-force"-- +and at the same time he held that "the way of life powerfully reacts upon +all form" and that the orderly growth of form "yields to change from +externally acting causes." + +Besides Buffon, Erasmus Darwin, Lamarck, Treviranus, and Goethe, there were +other "pioneers of evolution," whose views have been often discussed and +appraised. Etienne Geoffroy Saint-Hilaire (1772-1844), whose work Goethe +so much admired, was on the whole Buffonian, emphasising the direct action +of the changeful milieu. "Species vary with their environment, and +existing species have descended by modification from earlier and somewhat +simpler species." He had a glimpse of the selection idea, and believed in +mutations or sudden leaps--induced in the embryonic condition by external +influences. The complete history of evolution-theories will include many +instances of guesses at truth which were afterwards substantiated, thus the +geographer von Buch (1773-1853) detected the importance of the Isolation +factor on which Wagner, Romanes, Gulick and others have laid great stress, +but we must content ourselves with recalling one other pioneer, the author +of the "Vestiges of Creation" (1844), a work which passed through ten +editions in nine years and certainly helped to harrow the soil for Darwin's +sowing. As Darwin said, "it did excellent service in this country in +calling attention to the subject, in removing prejudice, and in thus +preparing the ground for the reception of analogous views." ("Origin of +Species" (6th edition), page xvii.) Its author, Robert Chambers (1802- +1871) was in part a Buffonian--maintaining that environment moulded +organisms adaptively, and in part a Goethian--believing in an inherent +progressive impulse which lifted organisms from one grade of organisation +to another. + +AS REGARDS NATURAL SELECTION. + +The only thinker to whom Darwin was directly indebted, so far as the theory +of Natural Selection is concerned, was Malthus, and we may once more quote +the well-known passage in the Autobiography: "In October, 1838, that is, +fifteen months after I had begun my systematic enquiry, I happened to read +for amusement 'Malthus on Population', and being well prepared to +appreciate the struggle for existence which everywhere goes on from long- +continued observation of the habits of animals and plants, it at once +struck me that under these circumstances favourable variations would tend +to be preserved, and unfavourable ones to be destroyed. The result of this +would be the formation of new species." ("The Life and Letters of Charles +Darwin", Vol. 1. page 83. London, 1887.) + +Although Malthus gives no adumbration of the idea of Natural Selection in +his exposition of the eliminative processes which go on in mankind, the +suggestive value of his essay is undeniable, as is strikingly borne out by +the fact that it gave to Alfred Russel Wallace also "the long-sought clue +to the effective agent in the evolution of organic species." (A.R. +Wallace, "My Life, A Record of Events and Opinions", London, 1905, Vol. 1. +page 232.) One day in Ternate when he was resting between fits of fever, +something brought to his recollection the work of Malthus which he had read +twelve years before. "I thought of his clear exposition of 'the positive +checks to increase'--disease, accidents, war, and famine--which keep down +the population of savage races to so much lower an average than that of +more civilized peoples. It then occurred to me that these causes or their +equivalents are continually acting in the case of animals also; and as +animals usually breed much more rapidly than does mankind, the destruction +every year from these causes must be enormous in order to keep down the +numbers of each species, since they evidently do not increase regularly +from year to year, as otherwise the world would long ago have been densely +crowded with those that breed most quickly. Vaguely thinking over the +enormous and constant destruction which this implied, it occurred to me to +ask the question, Why do some die and some live? And the answer was +clearly, that on the whole the best fitted live. From the effects of +disease the most healthy escaped; from enemies the strongest, the swiftest, +or the most cunning; from famine the best hunters or those with the best +digestion; and so on. Then it suddenly flashed upon me that this self- +acting process would necessarily IMPROVE THE RACE, because in every +generation the inferior would inevitably be killed off and the superior +would remain--that is, THE FITTEST WOULD SURVIVE." (Ibid. Vol. 1. page +361.) We need not apologise for this long quotation, it is a tribute to +Darwin's magnanimous colleague, the Nestor of the evolutionist camp,--and +it probably indicates the line of thought which Darwin himself followed. +It is interesting also to recall the fact that in 1852, when Herbert +Spencer wrote his famous "Leader" article on "The Development Hypothesis" +in which he argued powerfully for the thesis that the whole animate world +is the result of an age-long process of natural transformation, he wrote +for "The Westminster Review" another important essay, "A Theory of +Population deduced from the General Law of Animal Fertility", towards the +close of which he came within an ace of recognising that the struggle for +existence was a factor in organic evolution. At a time when pressure of +population was practically interesting men's minds, Darwin, Wallace, and +Spencer were being independently led from a social problem to a biological +theory. There could be no better illustration, as Prof. Patrick Geddes has +pointed out, of the Comtian thesis that science is a "social phenomenon." + +Therefore, as far more important than any further ferreting out of vague +hints of Natural Selection in books which Darwin never read, we would +indicate by a quotation the view that the central idea in Darwinism is +correlated with contemporary social evolution. "The substitution of Darwin +for Paley as the chief interpreter of the order of nature is currently +regarded as the displacement of an anthropomorphic view by a purely +scientific one: a little reflection, however, will show that what has +actually happened has been merely the replacement of the anthropomorphism +of the eighteenth century by that of the nineteenth. For the place vacated +by Paley's theological and metaphysical explanation has simply been +occupied by that suggested to Darwin and Wallace by Malthus in terms of the +prevalent severity of industrial competition, and those phenomena of the +struggle for existence which the light of contemporary economic theory has +enabled us to discern, have thus come to be temporarily exalted into a +complete explanation of organic progress." (P. Geddes, article "Biology", +"Chambers's Encyclopaedia".) It goes without saying that the idea +suggested by Malthus was developed by Darwin into a biological theory which +was then painstakingly verified by being used as an interpretative formula, +and that the validity of a theory so established is not affected by what +suggested it, but the practical question which this line of thought raises +in the mind is this: if Biology did thus borrow with such splendid results +from social theory, why should we not more deliberately repeat the +experiment? + +Darwin was characteristically frank and generous in admitting that the +principle of Natural Selection had been independently recognised by Dr W.C. +Wells in 1813 and by Mr Patrick Matthew in 1831, but he had no knowledge of +these anticipations when he published the first edition of "The Origin of +Species". Wells, whose "Essay on Dew" is still remembered, read in 1813 +before the Royal Society a short paper entitled "An account of a White +Female, part of whose skin resembles that of a Negro" (published in 1818). +In this communication, as Darwin said, "he observes, firstly, that all +animals tend to vary in some degree, and, secondly, that agriculturists +improve their domesticated animals by selection; and then, he adds, but +what is done in this latter case 'by art, seems to be done with equal +efficacy, though more slowly, by nature, in the formation of varieties of +mankind, fitted for the country which they inhabit.'" ("Origin of Species" +(6th edition) page xv.) Thus Wells had the clear idea of survival +dependent upon a favourable variation, but he makes no more use of the idea +and applies it only to man. There is not in the paper the least hint that +the author ever thought of generalising the remarkable sentence quoted +above. + +Of Mr Patrick Matthew, who buried his treasure in an appendix to a work on +"Naval Timber and Arboriculture", Darwin said that "he clearly saw the full +force of the principle of natural selection." In 1860 Darwin wrote--very +characteristically--about this to Lyell: "Mr Patrick Matthew publishes a +long extract from his work on "Naval Timber and Arboriculture", published +in 1831, in which he briefly but completely anticipates the theory of +Natural Selection. I have ordered the book, as some passages are rather +obscure, but it is certainly, I think, a complete but not developed +anticipation. Erasmus always said that surely this would be shown to be +the case some day. Anyhow, one may be excused in not having discovered the +fact in a work on Naval Timber." ("Life and Letters" II. page 301.) + +De Quatrefages and De Varigny have maintained that the botanist Naudin +stated the theory of evolution by natural selection in 1852. He explains +very clearly the process of artificial selection, and says that in the +garden we are following Nature's method. "We do not think that Nature has +made her species in a different fashion from that in which we proceed +ourselves in order to make our variations." But, as Darwin said, "he does +not show how selection acts under nature." Similarly it must be noted in +regard to several pre-Darwinian pictures of the struggle for existence +(such as Herder's, who wrote in 1790 "All is in struggle...each one for +himself" and so on), that a recognition of this is only the first step in +Darwinism. + +Profs. E. Perrier and H.F. Osborn have called attention to a remarkable +anticipation of the selection-idea which is to be found in the speculations +of Etienne Geoffroy St Hilaire (1825-1828) on the evolution of modern +Crocodilians from the ancient Teleosaurs. Changing environment induced +changes in the respiratory system and far-reaching consequences followed. +The atmosphere, acting upon the pulmonary cells, brings about +"modifications which are favourable or destructive ('funestes'); these are +inherited, and they influence all the rest of the organisation of the +animal because if these modifications lead to injurious effects, the +animals which exhibit them perish and are replaced by others of a somewhat +different form, a form changed so as to be adapted to (a la convenance) the +new environment." + +Prof. E.B. Poulton ("Science Progress", New Series, Vol. I. 1897. "A +Remarkable Anticipation of Modern Views on Evolution". See also Chap. VI. +in "Essays on Evolution", Oxford, 1908.) has shown that the anthropologist +James Cowles Prichard (1786-1848) must be included, even in spite of +himself, among the precursors of Darwin. In some passages of the second +edition of his "Researches into the Physical History of Mankind" (1826), he +certainly talks evolution and anticipates Prof. Weismann in denying the +transmission of acquired characters. He is, however, sadly self- +contradictory and his evolutionism weakens in subsequent editions--the only +ones that Darwin saw. Prof. Poulton finds in Prichard's work a recognition +of the operation of Natural Selection. "After enquiring how it is that +'these varieties are developed and preserved in connection with particular +climates and differences of local situation,' he gives the following very +significant answer: 'One cause which tends to maintain this relation is +obvious. Individuals and families, and even whole colonies, perish and +disappear in climates for which they are, by peculiarity of constitution, +not adapted. Of this fact proofs have been already mentioned.'" Mr +Francis Darwin and Prof. A.C. Seward discuss Prichard's "anticipations" in +"More Letters of Charles Darwin", Vol. I. page 43, and come to the +conclusion that the evolutionary passages are entirely neutralised by +others of an opposite trend. There is the same difficulty with Buffon. + +Hints of the idea of Natural Selection have been detected elsewhere. James +Watt (See Prof. Patrick Geddes's article "Variation and Selection", +"Encyclopaedia Britannica (9th edition) 1888.), for instance, has been +reported as one of the anticipators (1851). But we need not prolong the +inquiry further, since Darwin did not know of any anticipations until after +he had published the immortal work of 1859, and since none of those who got +hold of the idea made any use of it. What Darwin did was to follow the +clue which Malthus gave him, to realise, first by genius and afterwards by +patience, how the complex and subtle struggle for existence works out a +natural selection of those organisms which vary in the direction of fitter +adaptation to the conditions of their life. So much success attended his +application of the Selection-formula that for a time he regarded Natural +Selection as almost the sole factor in evolution, variations being pre- +supposed; gradually, however, he came to recognise that there was some +validity in the factors which had been emphasized by Lamarck and by Buffon, +and in his well-known summing up in the sixth edition of the "Origin" he +says of the transformation of species: "This has been effected chiefly +through the natural selection of numerous successive, slight, favourable +variations; aided in an important manner by the inherited effects of the +use and disuse of parts; and in an unimportant manner, that is, in relation +to adaptive structures, whether past or present, by the direct action of +external conditions, and by variations which seem to us in our ignorance to +arise spontaneously." + +To sum up: the idea of organic evolution, older than Aristotle, slowly +developed from the stage of suggestion to the stage of verification, and +the first convincing verification was Darwin's; from being an a priori +anticipation it has become an interpretation of nature, and Darwin is still +the chief interpreter; from being a modal interpretation it has advanced to +the rank of a causal theory, the most convincing part of which men will +never cease to call Darwinism. + + +III. THE SELECTION THEORY + +By August Weismann. +Professor of Zoology in the University of Freiburg (Baden). + +I. THE IDEA OF SELECTION. + +Many and diverse were the discoveries made by Charles Darwin in the course +of a long and strenuous life, but none of them has had so far-reaching an +influence on the science and thought of his time as the theory of +selection. I do not believe that the theory of evolution would have made +its way so easily and so quickly after Darwin took up the cudgels in favour +of it, if he had not been able to support it by a principle which was +capable of solving, in a simple manner, the greatest riddle that living +nature presents to us,--I mean the purposiveness of every living form +relative to the conditions of its life and its marvellously exact +adaptation to these. + +Everyone knows that Darwin was not alone in discovering the principle of +selection, and that the same idea occurred simultaneously and independently +to Alfred Russel Wallace. At the memorable meeting of the Linnean Society +on 1st July, 1858, two papers were read (communicated by Lyell and Hooker) +both setting forth the same idea of selection. One was written by Charles +Darwin in Kent, the other by Alfred Wallace in Ternate, in the Malay +Archipelago. It was a splendid proof of the magnanimity of these two +investigators, that they thus, in all friendliness and without envy, united +in laying their ideas before a scientific tribunal: their names will +always shine side by side as two of the brightest stars in the scientific +sky. + +But it is with Charles Darwin that I am here chiefly concerned, since this +paper is intended to aid in the commemoration of the hundredth anniversary +of his birth. + +The idea of selection set forth by the two naturalists was at the time +absolutely new, but it was also so simple that Huxley could say of it +later, "How extremely stupid not to have thought of that." As Darwin was +led to the general doctrine of descent, not through the labours of his +predecessors in the early years of the century, but by his own +observations, so it was in regard to the principle of selection. He was +struck by the innumerable cases of adaptation, as, for instance, that of +the woodpeckers and tree-frogs to climbing, or the hooks and feather-like +appendages of seeds, which aid in the distribution of plants, and he said +to himself that an explanation of adaptations was the first thing to be +sought for in attempting to formulate a theory of evolution. + +But since adaptations point to CHANGES which have been undergone by the +ancestral forms of existing species, it is necessary, first of all, to +inquire how far species in general are VARIABLE. Thus Darwin's attention +was directed in the first place to the phenomenon of variability, and the +use man has made of this, from very early times, in the breeding of his +domesticated animals and cultivated plants. He inquired carefully how +breeders set to work, when they wished to modify the structure and +appearance of a species to their own ends, and it was soon clear to him +that SELECTION FOR BREEDING PURPOSES played the chief part. + +But how was it possible that such processes should occur in free nature? +Who is here the breeder, making the selection, choosing out one individual +to bring forth offspring and rejecting others? That was the problem that +for a long time remained a riddle to him. + +Darwin himself relates how illumination suddenly came to him. He had been +reading, for his own pleasure, Malthus' book on Population, and, as he had +long known from numerous observations, that every species gives rise to +many more descendants than ever attain to maturity, and that, therefore, +the greater number of the descendants of a species perish without +reproducing, the idea came to him that the decision as to which member of a +species was to perish, and which was to attain to maturity and reproduction +might not be a matter of chance, but might be determined by the +constitution of the individuals themselves, according as they were more or +less fitted for survival. With this idea the foundation of the theory of +selection was laid. + +In ARTIFICIAL SELECTION the breeder chooses out for pairing only such +individuals as possess the character desired by him in a somewhat higher +degree than the rest of the race. Some of the descendants inherit this +character, often in a still higher degree, and if this method be pursued +throughout several generations, the race is transformed in respect of that +particular character. + +NATURAL SELECTION depends on the same three factors as ARTIFICIAL +SELECTION: on VARIABILITY, INHERITANCE, and SELECTION FOR BREEDING, but +this last is here carried out not by a breeder but by what Darwin called +the "struggle for existence." This last factor is one of the special +features of the Darwinian conception of nature. That there are carnivorous +animals which take heavy toll in every generation of the progeny of the +animals on which they prey, and that there are herbivores which decimate +the plants in every generation had long been known, but it is only since +Darwin's time that sufficient attention has been paid to the facts that, in +addition to this regular destruction, there exists between the members of a +species a keen competition for space and food, which limits multiplication, +and that numerous individuals of each species perish because of +unfavourable climatic conditions. The "struggle for existence," which +Darwin regarded as taking the place of the human breeder in free nature, is +not a direct struggle between carnivores and their prey, but is the assumed +competition for survival between individuals OF THE SAME species, of which, +on an average, only those survive to reproduce which have the greatest +power of resistance, while the others, less favourably constituted, perish +early. This struggle is so keen, that, within a limited area, where the +conditions of life have long remained unchanged, of every species, whatever +be the degree of fertility, only two, ON AN AVERAGE, of the descendants of +each pair survive; the others succumb either to enemies, or to +disadvantages of climate, or to accident. A high degree of fertility is +thus not an indication of the special success of a species, but of the +numerous dangers that have attended its evolution. Of the six young +brought forth by a pair of elephants in the course of their lives only two +survive in a given area; similarly, of the millions of eggs which two +thread-worms leave behind them only two survive. It is thus possible to +estimate the dangers which threaten a species by its ratio of elimination, +or, since this cannot be done directly, by its fertility. + +Although a great number of the descendants of each generation fall victims +to accident, among those that remain it is still the greater or lesser +fitness of the organism that determines the "selection for breeding +purposes," and it would be incomprehensible if, in this competition, it +were not ultimately, that is, on an average, the best equipped which +survive, in the sense of living long enough to reproduce. + +Thus the principle of natural selection is THE SELECTION OF THE BEST FOR +REPRODUCTION, whether the "best" refers to the whole constitution, to one +or more parts of the organism, or to one or more stages of development. +Every organ, every part, every character of an animal, fertility and +intelligence included, must be improved in this manner, and be gradually +brought up in the course of generations to its highest attainable state of +perfection. And not only may improvement of parts be brought about in this +way, but new parts and organs may arise, since, through the slow and minute +steps of individual or "fluctuating" variations, a part may be added here +or dropped out there, and thus something new is produced. + +The principle of selection solved the riddle as to how what was purposive +could conceivably be brought about without the intervention of a directing +power, the riddle which animate nature presents to our intelligence at +every turn, and in face of which the mind of a Kant could find no way out, +for he regarded a solution of it as not to be hoped for. For, even if we +were to assume an evolutionary force that is continually transforming the +most primitive and the simplest forms of life into ever higher forms, and +the homogeneity of primitive times into the infinite variety of the +present, we should still be unable to infer from this alone how each of the +numberless forms adapted to particular conditions of life should have +appeared PRECISELY AT THE RIGHT MOMENT IN THE HISTORY OF THE EARTH to which +their adaptations were appropriate, and precisely at the proper place in +which all the conditions of life to which they were adapted occurred: the +humming-birds at the same time as the flowers; the trichina at the same +time as the pig; the bark-coloured moth at the same time as the oak, and +the wasp-like moth at the same time as the wasp which protects it. Without +processes of selection we should be obliged to assume a "pre-established +harmony" after the famous Leibnitzian model, by means of which the clock of +the evolution of organisms is so regulated as to strike in exact +synchronism with that of the history of the earth! All forms of life are +strictly adapted to the conditions of their life, and can persist under +these conditions alone. + +There must therefore be an intrinsic connection between the conditions and +the structural adaptations of the organism, and, SINCE THE CONDITIONS OF +LIFE CANNOT BE DETERMINED BY THE ANIMAL ITSELF, THE ADAPTATIONS MUST BE +CALLED FORTH BY THE CONDITIONS. + +The selection theory teaches us how this is conceivable, since it enables +us to understand that there is a continual production of what is non- +purposive as well as of what is purposive, but the purposive alone +survives, while the non-purposive perishes in the very act of arising. +This is the old wisdom taught long ago by Empedocles. + +II. THE LAMARCKIAN PRINCIPLE. + +Lamarck, as is well known, formulated a definite theory of evolution at the +beginning of the nineteenth century, exactly fifty years before the Darwin- +Wallace principle of selection was given to the world. This brilliant +investigator also endeavoured to support his theory by demonstrating forces +which might have brought about the transformations of the organic world in +the course of the ages. In addition to other factors, he laid special +emphasis on the increased or diminished use of the parts of the body, +assuming that the strengthening or weakening which takes place from this +cause during the individual life, could be handed on to the offspring, and +thus intensified and raised to the rank of a specific character. Darwin +also regarded this LAMARCKIAN PRINCIPLE, as it is now generally called, as +a factor in evolution, but he was not fully convinced of the +transmissibility of acquired characters. + +As I have here to deal only with the theory of selection, I need not +discuss the Lamarckian hypothesis, but I must express my opinion that there +is room for much doubt as to the cooperation of this principle in +evolution. Not only is it difficult to imagine how the transmission of +functional modifications could take place, but, up to the present time, +notwithstanding the endeavours of many excellent investigators, not a +single actual proof of such inheritance has been brought forward. Semon's +experiments on plants are, according to the botanist Pfeffer, not to be +relied on, and even the recent, beautiful experiments made by Dr Kammerer +on salamanders, cannot, as I hope to show elsewhere, be regarded as proof, +if only because they do not deal at all with functional modifications, that +is, with modifications brought about by use, and it is to these ALONE that +the Lamarckian principle refers. + +III. OBJECTIONS TO THE THEORY OF SELECTION. + +(a) Saltatory evolution. + +The Darwinian doctrine of evolution depends essentially on THE CUMULATIVE +AUGMENTATION of minute variations in the direction of utility. But can +such minute variations, which are undoubtedly continually appearing among +the individuals of the same species, possess any selection-value; can they +determine which individuals are to survive, and which are to succumb; can +they be increased by natural selection till they attain to the highest +development of a purposive variation? + +To many this seems so improbable that they have urged a theory of evolution +by leaps from species to species. Kolliker, in 1872, compared the +evolution of species with the processes which we can observe in the +individual life in cases of alternation of generations. But a polyp only +gives rise to a medusa because it has itself arisen from one, and there can +be no question of a medusa ever having arisen suddenly and de novo from a +polyp-bud, if only because both forms are adapted in their structure as a +whole, and in every detail to the conditions of their life. A sudden +origin, in a natural way, of numerous adaptations is inconceivable. Even +the degeneration of a medusoid from a free-swimming animal to a mere brood- +sac (gonophore) is not sudden and saltatory, but occurs by imperceptible +modifications throughout hundreds of years, as we can learn from the +numerous stages of the process of degeneration persisting at the same time +in different species. + +If, then, the degeneration to a simple brood-sac takes place only by very +slow transitions, each stage of which may last for centuries, how could the +much more complex ASCENDING evolution possibly have taken place by sudden +leaps? I regard this argument as capable of further extension, for +wherever in nature we come upon degeneration, it is taking place by minute +steps and with a slowness that makes it not directly perceptible, and I +believe that this in itself justifies us in concluding that THE SAME MUST +BE TRUE OF ASCENDING evolution. But in the latter case the goal can seldom +be distinctly recognised while in cases of degeneration the starting-point +of the process can often be inferred, because several nearly related +species may represent different stages. + +In recent years Bateson in particular has championed the idea of saltatory, +or so-called discontinuous evolution, and has collected a number of cases +in which more or less marked variations have suddenly appeared. These are +taken for the most part from among domesticated animals which have been +bred and crossed for a long time, and it is hardly to be wondered at that +their much mixed and much influenced germ-plasm should, under certain +conditions, give rise to remarkable phenomena, often indeed producing forms +which are strongly suggestive of monstrosities, and which would undoubtedly +not survive in free nature, unprotected by man. I should regard such cases +as due to an intensified germinal selection--though this is to anticipate a +little--and from this point of view it cannot be denied that they have a +special interest. But they seem to me to have no significance as far as +the transformation of species is concerned, if only because of the extreme +rarity of their occurrence. + +There are, however, many variations which have appeared in a sudden and +saltatory manner, and some of these Darwin pointed out and discussed in +detail: the copper beech, the weeping trees, the oak with "fern-like +leaves," certain garden-flowers, etc. But none of them have persisted in +free nature, or evolved into permanent types. + +On the other hand, wherever enduring types have arisen, we find traces of a +gradual origin by successive stages, even if, at first sight, their origin +may appear to have been sudden. This is the case with SEASONAL DIMORPHISM, +the first known cases of which exhibited marked differences between the two +generations, the winter and the summer brood. Take for instance the much +discussed and studied form Vanessa (Araschnia) levana-prorsa. Here the +differences between the two forms are so great and so apparently +disconnected, that one might almost believe it to be a sudden mutation, +were it not that old transition-stages can be called forth by particular +temperatures, and we know other butterflies, as for instance our Garden +Whites, in which the differences between the two generations are not nearly +so marked; indeed, they are so little apparent that they are scarcely +likely to be noticed except by experts. Thus here again there are small +initial steps, some of which, indeed, must be regarded as adaptations, such +as the green-sprinkled or lightly tinted under-surface which gives them a +deceptive resemblance to parsley or to Cardamine leaves. + +Even if saltatory variations do occur, we cannot assume that these HAVE +EVER LED TO FORMS WHICH ARE CAPABLE OF SURVIVAL UNDER THE CONDITIONS OF +WILD LIFE. Experience has shown that in plants which have suddenly varied +the power of persistence is diminished. Korschinksky attributes to them +weaknesses of organisation in general; "they bloom late, ripen few of their +seeds, and show great sensitiveness to cold." These are not the characters +which make for success in the struggle for existence. + +We must briefly refer here to the views--much discussed in the last decade +--of H. de Vries, who believes that the roots of transformation must be +sought for in SALTATORY VARIATIONS ARISING FROM INTERNAL CAUSES, and +distinguishes such MUTATIONS, as he has called them, from ordinary +individual variations, in that they breed true, that is, with strict +inbreeding they are handed on pure to the next generation. I have +elsewhere endeavoured to point out the weaknesses of this theory ("Vortrage +uber Descendenztheorie", Jena, 1904, II. 269. English Translation London, +1904, II. page 317.), and I am the less inclined to return to it here that +it now appears (See Poulton, "Essays on Evolution", Oxford, 1908, pages +xix-xxii.) that the far-reaching conclusions drawn by de Vries from his +observations on the Evening Primrose, Oenothera lamarckiana, rest upon a +very insecure foundation. The plant from which de Vries saw numerous +"species"--his "mutations"--arise was not, as he assumed, a WILD SPECIES +that had been introduced to Europe from America, but was probably a hybrid +form which was first discovered in the Jardin des Plantes in Paris, and +which does not appear to exist anywhere in America as a wild species. + +This gives a severe shock to the "Mutation theory," for the other ACTUALLY +WILD species with which de Vries experimented showed no "mutations" but +yielded only negative results. + +Thus we come to the conclusion that Darwin ("Origin of Species" (6th +edition), pages 176 et seq.) was right in regarding transformations as +taking place by minute steps, which, if useful, are augmented in the course +of innumerable generations, because their possessors more frequently +survive in the struggle for existence. + +(b) SELECTION-VALUE OF THE INITIAL STEPS. + +Is it possible that the significant deviations which we know as "individual +variations" can form the beginning of a process of selection? Can they +decide which is to perish and which to survive? To use a phrase of +Romanes, can they have SELECTION-VALUE? + +Darwin himself answered this question, and brought together many excellent +examples to show that differences, apparently insignificant because very +small, might be of decisive importance for the life of the possessor. But +it is by no means enough to bring forward cases of this kind, for the +question is not merely whether finished adaptations have selection-value, +but whether the first beginnings of these, and whether the small, I might +almost say minimal increments, which have led up from these beginnings to +the perfect adaptation, have also had selection-value. To this question +even one who, like myself, has been for many years a convinced adherent of +the theory of selection, can only reply: WE MUST ASSUME SO, BUT WE CANNOT +PROVE IT IN ANY CASE. It is not upon demonstrative evidence that we rely +when we champion the doctrine of selection as a scientific truth; we base +our argument on quite other grounds. Undoubtedly there are many apparently +insignificant features, which can nevertheless be shown to be adaptations-- +for instance, the thickness of the basin-shaped shell of the limpets that +live among the breakers on the shore. There can be no doubt that the +thickness of these shells, combined with their flat form, protects the +animals from the force of the waves breaking upon them,--but how have they +become so thick? What proportion of thickness was sufficient to decide +that of two variants of a limpet one should survive, the other be +eliminated? We can say nothing more than that we infer from the present +state of the shell, that it must have varied in regard to differences in +shell-thickness, and that these differences must have had selection-value, +--no proof therefore, but an assumption which we must show to be +convincing. + +For a long time the marvellously complex RADIATE and LATTICE-WORK skeletons +of Radiolarians were regarded as a mere outflow of "Nature's infinite +wealth of form," as an instance of a purely morphological character with no +biological significance. But recent investigations have shown that these, +too, have an adaptive significance (Hacker). The same thing has been shown +by Schutt in regard to the lowly unicellular plants, the Peridineae, which +abound alike on the surface of the ocean and in its depths. It has been +shown that the long skeletal processes which grow out from these organisms +have significance not merely as a supporting skeleton, but also as an +extension of the superficial area, which increases the contact with the +water-particles, and prevents the floating organisms from sinking. It has +been established that the processes are considerably shorter in the colder +layers of the ocean, and that they may be twelve times as long (Chun, +"Reise der Valdivia", Leipzig, 1904.) in the warmer layers, thus +corresponding to the greater or smaller amount of friction which takes +place in the denser and less dense layers of the water. + +The Peridineae of the warmer ocean layers have thus become long-rayed, +those of the colder layers short-rayed, not through the direct effect of +friction on the protoplasm, but through processes of selection, which +favoured the longer rays in warm water, since they kept the organism +afloat, while those with short rays sank and were eliminated. If we put +the question as to selection-value in this case, and ask how great the +variations in the length of processes must be in order to possess +selection-value; what can we answer except that these variations must have +been minimal, and yet sufficient to prevent too rapid sinking and +consequent elimination? Yet this very case would give the ideal +opportunity for a mathematical calculation of the minimal selection-value, +although of course it is not feasible from lack of data to carry out the +actual calculation. + +But even in organisms of more than microscopic size there must frequently +be minute, even microscopic differences which set going the process of +selection, and regulate its progress to the highest possible perfection. + +Many tropical trees possess thick, leathery leaves, as a protection against +the force of the tropical rain drops. The DIRECT influence of the rain +cannot be the cause of this power of resistance, for the leaves, while they +were still thin, would simply have been torn to pieces. Their toughness +must therefore be referred to selection, which would favour the trees with +slightly thicker leaves, though we cannot calculate with any exactness how +great the first stages of increase in thickness must have been. Our +hypothesis receives further support from the fact that, in many such trees, +the leaves are drawn out into a beak-like prolongation (Stahl and +Haberlandt) which facilitates the rapid falling off of the rain water, and +also from the fact that the leaves, while they are still young, hang limply +down in bunches which offer the least possible resistance to the rain. +Thus there are here three adaptations which can only be interpreted as due +to selection. The initial stages of these adaptations must undoubtedly +have had selection-value. + +But even in regard to this case we are reasoning in a circle, not giving +"proofs," and no one who does not wish to believe in the selection-value of +the initial stages can be forced to do so. Among the many pieces of +presumptive evidence a particularly weighty one seems to me to be THE +SMALLNESS OF THE STEPS OF PROGRESS which we can observe in certain cases, +as for instance in leaf-imitation among butterflies, and in mimicry +generally. The resemblance to a leaf, for instance of a particular +Kallima, seems to us so close as to be deceptive, and yet we find in +another individual, or it may be in many others, a spot added which +increases the resemblance, and which could not have become fixed unless the +increased deceptiveness so produced had frequently led to the overlooking +of its much persecuted possessor. But if we take the selection-value of +the initial stages for granted, we are confronted with the further question +which I myself formulated many years ago: How does it happen THAT THE +NECESSARY BEGINNINGS OF A USEFUL VARIATION ARE ALWAYS PRESENT? How could +insects which live upon or among green leaves become all green, while those +that live on bark become brown? How have the desert animals become yellow +and the Arctic animals white? Why were the necessary variations always +present? How could the green locust lay brown eggs, or the privet +caterpillar develop white and lilac-coloured lines on its green skin? + +It is of no use answering to this that the question is wrongly formulated +(Plate, "Selektionsprinzip u. Probleme der Artbildung" (3rd edition), +Leipzig, 1908.) and that it is the converse that is true; that the process +of selection takes place in accordance with the variations that present +themselves. This proposition is undeniably true, but so also is another, +which apparently negatives it: the variation required has in the majority +of cases actually presented itself. Selection cannot solve this +contradiction; it does not call forth the useful variation, but simply +works upon it. The ultimate reason why one and the same insect should +occur in green and in brown, as often happens in caterpillars and locusts, +lies in the fact that variations towards brown presented themselves, and so +also did variations towards green: THE KERNEL OF THE RIDDLE LIES IN THE +VARYING, and for the present we can only say, that small variations in +different directions present themselves in every species. Otherwise so +many different kinds of variations could not have arisen. I have +endeavoured to explain this remarkable fact by means of the intimate +processes that must take place within the germ-plasm, and I shall return to +the problem when dealing with "germinal selection." + +We have, however, to make still greater demands on variation, for it is not +enough that the necessary variation should occur in isolated individuals, +because in that case there would be small prospect of its being preserved, +notwithstanding its utility. Darwin at first believed, that even single +variations might lead to transformation of the species, but later he became +convinced that this was impossible, at least without the cooperation of +other factors, such as isolation and sexual selection. + +In the case of the GREEN CATERPILLARS WITH BRIGHT LONGITUDINAL STRIPES, +numerous individuals exhibiting this useful variation must have been +produced to start with. In all higher, that is, multicellular organisms, +the germ-substance is the source of all transmissible variations, and this +germ-plasm is not a simple substance but is made up of many primary +constituents. The question can therefore be more precisely stated thus: +How does it come about that in so many cases the useful variations present +themselves in numbers just where they are required, the white oblique lines +in the leaf-caterpillar on the under surface of the body, the accompanying +coloured stripes just above them? And, further, how has it come about that +in grass caterpillars, not oblique but longitudinal stripes, which are more +effective for concealment among grass and plants, have been evolved? And +finally, how is it that the same Hawk-moth caterpillars, which to-day show +oblique stripes, possessed longitudinal stripes in Tertiary times? We can +read this fact from the history of their development, and I have before +attempted to show the biological significance of this change of colour. +("Studien zur Descendenz-Theorie" II., "Die Enstehung der Zeichnung bei den +Schmetterlings-raupen," Leipzig, 1876.) + +For the present I need only draw the conclusion that one and the same +caterpillar may exhibit the initial stages of both, and that it depends on +the manner in which these marking elements are INTENSIFIED and COMBINED by +natural selection whether whitish longitudinal or oblique stripes should +result. In this case then the "useful variations" were actually "always +there," and we see that in the same group of Lepidoptera, e.g. species of +Sphingidae, evolution has occurred in both directions according to whether +the form lived among grass or on broad leaves with oblique lateral veins, +and we can observe even now that the species with oblique stripes have +longitudinal stripes when young, that is to say, while the stripes have no +biological significance. The white places in the skin which gave rise, +probably first as small spots, to this protective marking could be combined +in one way or another according to the requirements of the species. They +must therefore either have possessed selection-value from the first, or, if +this was not the case at their earliest occurrence, there must have been +SOME OTHER FACTORS which raised them to the point of selection-value. I +shall return to this in discussing germinal selection. But the case may be +followed still farther, and leads us to the same alternative on a still +more secure basis. + +Many years ago I observed in caterpillars of Smerinthus populi (the poplar +hawk-moth), which also possess white oblique stripes, that certain +individuals showed RED SPOTS above these stripes; these spots occurred only +on certain segments, and never flowed together to form continuous stripes. +In another species (Smerinthus tiliae) similar blood-red spots unite to +form a line-like coloured seam in the last stage of larval life, while in +S. ocellata rust-red spots appear in individual caterpillars, but more +rarely than in S. Populi, and they show no tendency to flow together. + +Thus we have here the origin of a new character, arising from small +beginnings, at least in S. tiliae, in which species the coloured stripes +are a normal specific character. In the other species, S. populi and S. +ocellata, we find the beginnings of the same variation, in one more rarely +than in the other, and we can imagine that, in the course of time, in these +two species, coloured lines over the oblique stripes will arise. In any +case these spots are the elements of variation, out of which coloured lines +MAY be evolved, if they are combined in this direction through the agency +of natural selection. In S. populi the spots are often small, but +sometimes it seems as though several had united to form large spots. +Whether a process of selection in this direction will arise in S. populi +and S. ocellata, or whether it is now going on cannot be determined, since +we cannot tell in advance what biological value the marking might have for +these two species. It is conceivable that the spots may have no selection- +value as far as these species are concerned, and may therefore disappear +again in the course of phylogeny, or, on the other hand, that they may be +changed in another direction, for instance towards imitation of the rust- +red fungoid patches on poplar and willow leaves. In any case we may regard +the smallest spots as the initial stages of variation, the larger as a +cumulative summation of these. Therefore either these initial stages must +already possess selection-value, or, as I said before: THERE MUST BE SOME +OTHER REASON FOR THEIR CUMULATIVE SUMMATION. I should like to give one +more example, in which we can infer, though we cannot directly observe, the +initial stages. + +All the Holothurians or sea-cucumbers have in the skin calcareous bodies of +different forms, usually thick and irregular, which make the skin tough and +resistant. In a small group of them--the species of Synapta--the +calcareous bodies occur in the form of delicate anchors of microscopic +size. Up till 1897 these anchors, like many other delicate microscopic +structures, were regarded as curiosities, as natural marvels. But a +Swedish observer, Oestergren, has recently shown that they have a +biological significance: they serve the footless Synapta as auxiliary +organs of locomotion, since, when the body swells up in the act of +creeping, they press firmly with their tips, which are embedded in the +skin, against the substratum on which the animal creeps, and thus prevent +slipping backwards. In other Holothurians this slipping is made impossible +by the fixing of the tube-feet. The anchors act automatically, sinking +their tips towards the ground when the corresponding part of the body +thickens, and returning to the original position at an angle of 45 degrees +to the upper surface when the part becomes thin again. The arms of the +anchor do not lie in the same plane as the shaft, and thus the curve of the +arms forms the outermost part of the anchor, and offers no further +resistance to the gliding of the animal. Every detail of the anchor, the +curved portion, the little teeth at the head, the arms, etc., can be +interpreted in the most beautiful way, above all the form of the anchor +itself, for the two arms prevent it from swaying round to the side. The +position of the anchors, too, is definite and significant; they lie +obliquely to the longitudinal axis of the animal, and therefore they act +alike whether the animal is creeping backwards or forwards. Moreover, the +tips would pierce through the skin if the anchors lay in the longitudinal +direction. Synapta burrows in the sand; it first pushes in the thin +anterior end, and thickens this again, thus enlarging the hole, then the +anterior tentacles displace more sand, the body is worked in a little +farther, and the process begins anew. In the first act the anchors are +passive, but they begin to take an active share in the forward movement +when the body is contracted again. Frequently the animal retains only the +posterior end buried in the sand, and then the anchors keep it in position, +and make rapid withdrawal possible. + +Thus we have in these apparently random forms of the calcareous bodies, +complex adaptations in which every little detail as to direction, curve, +and pointing is exactly determined. That they have selection-value in +their present perfected form is beyond all doubt, since the animals are +enabled by means of them to bore rapidly into the ground and so to escape +from enemies. We do not know what the initial stages were, but we cannot +doubt that the little improvements, which occurred as variations of the +originally simple slimy bodies of the Holothurians, were preserved because +they already possessed selection-value for the Synaptidae. For such minute +microscopic structures whose form is so delicately adapted to the role they +have to play in the life of the animal, cannot have arisen suddenly and as +a whole, and every new variation of the anchor, that is, in the direction +of the development of the two arms, and every curving of the shaft which +prevented the tips from projecting at the wrong time, in short, every +little adaptation in the modelling of the anchor must have possessed +selection-value. And that such minute changes of form fall within the +sphere of fluctuating variations, that is to say, THAT THEY OCCUR is beyond +all doubt. + +In many of the Synaptidae the anchors are replaced by calcareous rods bent +in the form of an S, which are said to act in the same way. Others, such +as those of the genus Ankyroderma, have anchors which project considerably +beyond the skin, and, according to Oestergren, serve "to catch plant- +particles and other substances" and so mask the animal. Thus we see that +in the Synaptidae the thick and irregular calcareous bodies of the +Holothurians have been modified and transformed in various ways in +adaptation to the footlessness of these animals, and to the peculiar +conditions of their life, and we must conclude that the earlier stages of +these changes presented themselves to the processes of selection in the +form of microscopic variations. For it is as impossible to think of any +origin other than through selection in this case as in the case of the +toughness, and the "drip-tips" of tropical leaves. And as these last could +not have been produced directly by the beating of the heavy rain-drops upon +them, so the calcareous anchors of Synapta cannot have been produced +directly by the friction of the sand and mud at the bottom of the sea, and, +since they are parts whose function is PASSIVE the Lamarckian factor of use +and disuse does not come into question. The conclusion is unavoidable, +that the microscopically small variations of the calcareous bodies in the +ancestral forms have been intensified and accumulated in a particular +direction, till they have led to the formation of the anchor. Whether this +has taken place by the action of natural selection alone, or whether the +laws of variation and the intimate processes within the germ-plasm have +cooperated will become clear in the discussion of germinal selection. This +whole process of adaptation has obviously taken place within the time that +has elapsed since this group of sea-cucumbers lost their tube-feet, those +characteristic organs of locomotion which occur in no group except the +Echinoderms, and yet have totally disappeared in the Synaptidae. And after +all what would animals that live in sand and mud do with tube-feet? + +(c) COADAPTATION. + +Darwin pointed out that one of the essential differences between artificial +and natural selection lies in the fact that the former can modify only a +few characters, usually only one at a time, while Nature preserves in the +struggle for existence all the variations of a species, at the same time +and in a purely mechanical way, if they possess selection-value. + +Herbert Spencer, though himself an adherent of the theory of selection, +declared in the beginning of the nineties that in his opinion the range of +this principle was greatly over-estimated, if the great changes which have +taken place in so many organisms in the course of ages are to be +interpreted as due to this process of selection alone, since no +transformation of any importance can be evolved by itself; it is always +accompanied by a host of secondary changes. He gives the familiar example +of the Giant Stag of the Irish peat, the enormous antlers of which required +not only a much stronger skull cap, but also greater strength of the +sinews, muscles, nerves and bones of the whole anterior half of the animal, +if their mass was not to weigh down the animal altogether. It is +inconceivable, he says, that so many processes of selection should take +place SIMULTANEOUSLY, and we are therefore forced to fall back on the +Lamarckian factor of the use and disuse of functional parts. And how, he +asks, could natural selection follow two opposite directions of evolution +in different parts of the body at the same time, as for instance in the +case of the kangaroo, in which the forelegs must have become shorter, while +the hind legs and the tail were becoming longer and stronger? + +Spencer's main object was to substantiate the validity of the Lamarckian +principle, the cooperation of which with selection had been doubted by +many. And it does seem as though this principle, if it operates in nature +at all, offers a ready and simple explanation of all such secondary +variations. Not only muscles, but nerves, bones, sinews, in short all +tissues which function actively, increase in strength in proportion as they +are used, and conversely they decrease when the claims on them diminish. +All the parts, therefore, which depend on the part that varied first, as +for instance the enlarged antlers of the Irish Elk, must have been +increased or decreased in strength, in exact proportion to the claims made +upon them,--just as is actually the case. + +But beautiful as this explanation would be, I regard it as untenable, +because it assumes the TRANSMISSIBILITY OF FUNCTIONAL MODIFICATIONS (so- +called "acquired" characters), and this is not only undemonstrable, but is +scarcely theoretically conceivable, for the secondary variations which +accompany or follow the first as correlative variations, occur also in +cases in which the animals concerned are sterile and THEREFORE CANNOT +TRANSMIT ANYTHING TO THEIR DESCENDANTS. This is true of WORKER BEES, and +particularly of ANTS, and I shall here give a brief survey of the present +state of the problem as it appears to me. + +Much has been written on both sides of this question since the published +controversy on the subject in the nineties between Herbert Spencer and +myself. I should like to return to the matter in detail, if the space at +my disposal permitted, because it seems to me that the arguments I advanced +at that time are equally cogent to-day, notwithstanding all the objections +that have since been urged against them. Moreover, the matter is by no +means one of subordinate interest; it is the very kernel of the whole +question of the reality and value of the principle of selection. For if +selection alone does not suffice to explain "HARMONIOUS ADAPTATION" as I +have called Spencer's COADAPTATION, and if we require to call in the aid of +the Lamarckian factor it would be questionable whether selection could +explain any adaptations whatever. In this particular case--of worker bees +--the Lamarckian factor may be excluded altogether, for it can be +demonstrated that here at any rate the effects of use and disuse cannot be +transmitted. + +But if it be asked why we are unwilling to admit the cooperation of the +Darwinian factor of selection and the Lamarckian factor, since this would +afford us an easy and satisfactory explanation of the phenomena, I answer: +BECAUSE THE LAMARCKIAN PRINCIPLE IS FALLACIOUS, AND BECAUSE BY ACCEPTING IT +WE CLOSE THE WAY TOWARDS DEEPER INSIGHT. It is not a spirit of +combativeness or a desire for self-vindication that induces me to take the +field once more against the Lamarckian principle, it is the conviction that +the progress of our knowledge is being obstructed by the acceptance of this +fallacious principle, since the facile explanation it apparently affords +prevents our seeking after a truer explanation and a deeper analysis. + +The workers in the various species of ants are sterile, that is to say, +they take no regular part in the reproduction of the species, although +individuals among them may occasionally lay eggs. In addition to this they +have lost the wings, and the receptaculum seminis, and their compound eyes +have degenerated to a few facets. How could this last change have come +about through disuse, since the eyes of workers are exposed to light in the +same way as are those of the sexual insects and thus in this particular +case are not liable to "disuse" at all? The same is true of the +receptaculum seminis, which can only have been disused as far as its +glandular portion and its stalk are concerned, and also of the wings, the +nerves tracheae and epidermal cells of which could not cease to function +until the whole wing had degenerated, for the chitinous skeleton of the +wing does not function at all in the active sense. + +But, on the other hand, the workers in all species have undergone +modifications in a positive direction, as, for instance, the greater +development of brain. In many species large workers have evolved,--the so- +called SOLDIERS, with enormous jaws and teeth, which defend the colony,-- +and in others there are SMALL workers which have taken over other special +functions, such as the rearing of the young Aphides. This kind of division +of the workers into two castes occurs among several tropical species of +ants, but it is also present in the Italian species, Colobopsis truncata. +Beautifully as the size of the jaws could be explained as due to the +increased use made of them by the "soldiers," or the enlarged brain as due +to the mental activities of the workers, the fact of the infertility of +these forms is an insurmountable obstacle to accepting such an explanation. +Neither jaws nor brain can have been evolved on the Lamarckian principle. + +The problem of coadaptation is no easier in the case of the ant than in the +case of the Giant Stag. Darwin himself gave a pretty illustration to show +how imposing the difference between the two kinds of workers in one species +would seem if we translated it into human terms. In regard to the Driver +ants (Anomma) we must picture to ourselves a piece of work, "for instance +the building of a house, being carried on by two kinds of workers, of which +one group was five feet four inches high, the other sixteen feet high." +("Origin of Species" (6th edition), page 232.) + +Although the ant is a small animal as compared with man or with the Irish +Elk, the "soldier" with its relatively enormous jaws is hardly less heavily +burdened than the Elk with its antlers, and in the ant's case, too, a +strengthening of the skeleton, of the muscles, the nerves of the head, and +of the legs must have taken place parallel with the enlargement of the +jaws. HARMONIOUS ADAPTATION (coadaptation) has here been active in a high +degree, and yet these "soldiers" are sterile! There thus remains nothing +for it but to refer all their adaptations, positive and negative alike, to +processes of selection which have taken place in the rudiments of the +workers within the egg and sperm-cells of their parents. There is no way +out of the difficulty except the one Darwin pointed out. He himself did +not find the solution of the riddle at once. At first he believed that the +case of the workers among social insects presented "the most serious +special difficulty" in the way of his theory of natural selection; and it +was only after it had become clear to him, that it was not the sterile +insects themselves but their parents that were selected, according as they +produced more or less well adapted workers, that he was able to refer to +this very case of the conditions among ants "IN ORDER TO SHOW THE POWER OF +NATURAL SELECTION" ("Origin of Species", page 233; see also edition 1, page +242.). He explains his view by a simple but interesting illustration. +Gardeners have produced, by means of long continued artificial selection, a +variety of Stock, which bears entirely double, and therefore infertile +flowers (Ibid. page 230.). Nevertheless the variety continues to be +reproduced from seed, because in addition to the double and infertile +flowers, the seeds always produce a certain number of single, fertile +blossoms, and these are used to reproduce the double variety. These single +and fertile plants correspond "to the males and females of an ant-colony, +the infertile plants, which are regularly produced in large numbers, to the +neuter workers of the colony." + +This illustration is entirely apt, the only difference between the two +cases consisting in the fact that the variation in the flower is not a +useful, but a disadvantageous one, which can only be preserved by +artificial selection on the part of the gardener, while the transformations +that have taken place parallel with the sterility of the ants are useful, +since they procure for the colony an advantage in the struggle for +existence, and they are therefore preserved by natural selection. Even the +sterility itself in this case is not disadvantageous, since the fertility +of the true females has at the same time considerably increased. We may +therefore regard the sterile forms of ants, which have gradually been +adapted in several directions to varying functions, AS A CERTAIN PROOF that +selection really takes place in the germ-cells of the fathers and mothers +of the workers, and that SPECIAL COMPLEXES OF PRIMORDIA (IDS) are present +in the workers and in the males and females, and these complexes contain +the primordia of the individual parts (DETERMINANTS). But since all living +entities vary, the determinants must also vary, now in a favourable, now in +an unfavourable direction. If a female produces eggs, which contain +favourably varying determinants in the worker-ids, then these eggs will +give rise to workers modified in the favourable direction, and if this +happens with many females, the colony concerned will contain a better kind +of worker than other colonies. + +I digress here in order to give an account of the intimate processes, +which, according to my view, take place within the germ-plasm, and which I +have called "GERMINAL SELECTION." These processes are of importance since +they form the roots of variation, which in its turn is the root of natural +selection. I cannot here do more than give a brief outline of the theory +in order to show how the Darwin-Wallace theory of selection has gained +support from it. + +With others, I regard the minimal amount of substance which is contained +within the nucleus of the germ-cells, in the form of rods, bands, or +granules, as the GERM-SUBSTANCE or GERM-PLASM, and I call the individual +granules IDS. There is always a multiplicity of such ids present in the +nucleus, either occurring individually, or united in the form of rods or +bands (chromosomes). Each id contains the primary constituents of a WHOLE +individual, so that several ids are concerned in the development of a new +individual. + +In every being of complex structure thousands of primary constituents must +go to make up a single id; these I call DETERMINANTS, and I mean by this +name very small individual particles, far below the limits of microscopic +visibility, vital units which feed, grow, and multiply by division. These +determinants control the parts of the developing embryo,--in what manner +need not here concern us. The determinants differ among themselves, those +of a muscle are differently constituted from those of a nerve-cell or a +glandular cell, etc., and every determinant is in its turn made up of +minute vital units, which I call BIOPHORS, or the bearers of life. +According to my view, these determinants not only assimilate, like every +other living unit, but they VARY in the course of their growth, as every +living unit does; they may vary qualitatively if the elements of which they +are composed vary, they may grow and divide more or less rapidly, and their +variations give rise to CORRESPONDING variations of the organ, cell, or +cell-group which they determine. That they are undergoing ceaseless +fluctuations in regard to size and quality seems to me the inevitable +consequence of their unequal nutrition; for although the germ-cell as a +whole usually receives sufficient nutriment, minute fluctuations in the +amount carried to different parts within the germ-plasm cannot fail to +occur. + +Now, if a determinant, for instance of a sensory cell, receives for a +considerable time more abundant nutriment than before, it will grow more +rapidly--become bigger, and divide more quickly, and, later, when the id +concerned develops into an embryo, this sensory cell will become stronger +than in the parents, possibly even twice as strong. This is an instance of +a HEREDITARY INDIVIDUAL VARIATION, arising from the germ. + +The nutritive stream which, according to our hypothesis, favours the +determinant N by chance, that is, for reasons unknown to us, may remain +strong for a considerable time, or may decrease again; but even in the +latter case it is conceivable that the ascending movement of the +determinant may continue, because the strengthened determinant now ACTIVELY +nourishes itself more abundantly,--that is to say, it attracts the +nutriment to itself, and to a certain extent withdraws it from its fellow- +determinants. In this way, it may--as it seems to me--get into PERMANENT +UPWARD MOVEMENT, AND ATTAIN A DEGREE OF STRENGTH FROM WHICH THERE IS NO +FALLING BACK. Then positive or negative selection sets in, favouring the +variations which are advantageous, setting aside those which are +disadvantageous. + +In a similar manner a DOWNWARD variation of the determinants may take +place, if its progress be started by a diminished flow of nutriment. The +determinants which are weakened by this diminished flow will have less +affinity for attracting nutriment because of their diminished strength, and +they will assimilate more feebly and grow more slowly, unless chance +streams of nutriment help them to recover themselves. But, as will +presently be shown, a change of direction cannot take place at EVERY stage +of the degenerative process. If a certain critical stage of downward +progress be passed, even favourable conditions of food-supply will no +longer suffice permanently to change the direction of the variation. Only +two cases are conceivable; if the determinant corresponds to a USEFUL +organ, only its removal can bring back the germ-plasm to its former level; +therefore personal selection removes the id in question, with its +determinants, from the germ-plasm, by causing the elimination of the +individual in the struggle for existence. But there is another conceivable +case; the determinants concerned may be those of an organ which has become +USELESS, and they will then continue unobstructed, but with exceeding +slowness, along the downward path, until the organ becomes vestigial, and +finally disappears altogether. + +The fluctuations of the determinants hither and thither may thus be +transformed into a lasting ascending or descending movement; and THIS IS +THE CRUCIAL POINT OF THESE GERMINAL PROCESSES. + +This is not a fantastic assumption; we can read it in the fact of the +degeneration of disused parts. USELESS ORGANS ARE THE ONLY ONES WHICH ARE +NOT HELPED TO ASCEND AGAIN BY PERSONAL SELECTION, AND THEREFORE IN THEIR +CASE ALONE CAN WE FORM ANY IDEA OF HOW THE PRIMARY CONSTITUENTS BEHAVE, +WHEN THEY ARE SUBJECT SOLELY TO INTRA-GERMINAL FORCES. + +The whole determinant system of an id, as I conceive it, is in a state of +continual fluctuation upwards and downwards. In most cases the +fluctuations will counteract one another, because the passive streams of +nutriment soon change, but in many cases the limit from which a return is +possible will be passed, and then the determinants concerned will continue +to vary in the same direction, till they attain positive or negative +selection-value. At this stage personal selection intervenes and sets +aside the variation if it is disadvantageous, or favours--that is to say, +preserves--it if it is advantageous. Only THE DETERMINANT OF A USELESS +ORGAN IS UNINFLUENCED BY PERSONAL SELECTION, and, as experience shows, it +sinks downwards; that is, the organ that corresponds to it degenerates very +slowly but uninterruptedly till, after what must obviously be an immense +stretch of time, it disappears from the germ-plasm altogether. + +Thus we find in the fact of the degeneration of disused parts the proof +that not all the fluctuations of a determinant return to equilibrium again, +but that, when the movement has attained to a certain strength, it +continues IN THE SAME DIRECTION. We have entire certainty in regard to +this as far as the downward progress is concerned, and we must assume it +also in regard to ascending variations, as the phenomena of artificial +selection certainly justify us in doing. If the Japanese breeders were +able to lengthen the tail feathers of the cock to six feet, it can only +have been because the determinants of the tail-feathers in the germ-plasm +had already struck out a path of ascending variation, and this movement was +taken advantage of by the breeder, who continually selected for +reproduction the individuals in which the ascending variation was most +marked. For all breeding depends upon the unconscious selection of +germinal variations. + +Of course these germinal processes cannot be proved mathematically, since +we cannot actually see the play of forces of the passive fluctuations and +their causes. We cannot say how great these fluctuations are, and how +quickly or slowly, how regularly or irregularly they change. Nor do we +know how far a determinant must be strengthened by the passive flow of the +nutritive stream if it is to be beyond the danger of unfavourable +variations, or how far it must be weakened passively before it loses the +power of recovering itself by its own strength. It is no more possible to +bring forward actual proofs in this case than it was in regard to the +selection-value of the initial stages of an adaptation. But if we consider +that all heritable variations must have their roots in the germ-plasm, and +further, that when personal selection does not intervene, that is to say, +in the case of parts which have become useless, a degeneration of the part, +and therefore also of its determinant must inevitably take place; then we +must conclude that processes such as I have assumed are running their +course within the germ-plasm, and we can do this with as much certainty as +we were able to infer, from the phenomena of adaptation, the selection- +value of their initial stages. The fact of the degeneration of disused +parts seems to me to afford irrefutable proof that the fluctuations within +the germ-plasm ARE THE REAL ROOT OF ALL HEREDITARY VARIATION, and the +preliminary condition for the occurrence of the Darwin-Wallace factor of +selection. Germinal selection supplies the stones out of which personal +selection builds her temples and palaces: ADAPTATIONS. The importance for +the theory of the process of degeneration of disused parts cannot be over- +estimated, especially when it occurs in sterile animal forms, where we are +free from the doubt as to the alleged LAMARCKIAN FACTOR which is apt to +confuse our ideas in regard to other cases. + +If we regard the variation of the many determinants concerned in the +transformation of the female into the sterile worker as having come about +through the gradual transformation of the ids into worker-ids, we shall see +that the germ-plasm of the sexual ants must contain three kinds of ids, +male, female, and worker ids, or if the workers have diverged into soldiers +and nest-builders, then four kinds. We understand that the worker-ids +arose because their determinants struck out a useful path of variation, +whether upward or downward, and that they continued in this path until the +highest attainable degree of utility of the parts determined was reached. +But in addition to the organs of positive or negative selection-value, +there were some which were indifferent as far as the success and especially +the functional capacity of the workers was concerned: wings, ovarian +tubes, receptaculum seminis, a number of the facets of the eye, perhaps +even the whole eye. As to the ovarian tubes it is possible that their +degeneration was an advantage for the workers, in saving energy, and if so +selection would favour the degeneration; but how could the presence of eyes +diminish the usefulness of the workers to the colony? or the minute +receptaculum seminis, or even the wings? These parts have therefore +degenerated BECAUSE THEY WERE OF NO FURTHER VALUE TO THE INSECT. But if +selection did not influence the setting aside of these parts because they +were neither of advantage nor of disadvantage to the species, then the +Darwinian factor of selection is here confronted with a puzzle which it +cannot solve alone, but which at once becomes clear when germinal selection +is added. For the determinants of organs that have no further value for +the organism, must, as we have already explained, embark on a gradual +course of retrograde development. + +In ants the degeneration has gone so far that there are no wing-rudiments +present in ANY species, as is the case with so many butterflies, flies, and +locusts, but in the larvae the imaginal discs of the wings are still laid +down. With regard to the ovaries, degeneration has reached different +levels in different species of ants, as has been shown by the researches of +my former pupil, Elizabeth Bickford. In many species there are twelve +ovarian tubes, and they decrease from that number to one; indeed, in one +species no ovarian tube at all is present. So much at least is certain +from what has been said, that in this case EVERYTHING depends on the +fluctuations of the elements of the germ-plasm. Germinal selection, here +as elsewhere, presents the variations of the determinants, and personal +selection favours or rejects these, or,--if it be a question of organs +which have become useless,--it does not come into play at all, and allows +the descending variation free course. + +It is obvious that even the problem of COADAPTATION IN STERILE ANIMALS can +thus be satisfactorily explained. If the determinants are oscillating +upwards and downwards in continual fluctuation, and varying more +pronouncedly now in one direction now in the other, useful variations of +every determinant will continually present themselves anew, and may, in the +course of generations, be combined with one another in various ways. But +there is one character of the determinants that greatly facilitates this +complex process of selection, that, after a certain limit has been reached, +they go on varying in the same direction. From this it follows that +development along a path once struck out may proceed without the continual +intervention of personal selection. This factor only operates, so to +speak, at the beginning, when it selects the determinants which are varying +in the right direction, and again at the end, when it is necessary to put a +check upon further variation. In addition to this, enormously long periods +have been available for all these adaptations, as the very gradual +transition stages between females and workers in many species plainly show, +and thus this process of transformation loses the marvellous and mysterious +character that seemed at the first glance to invest it, and takes rank, +without any straining, among the other processes of selection. It seems to +me that, from the facts that sterile animal forms can adapt themselves to +new vital functions, their superfluous parts degenerate, and the parts more +used adapt themselves in an ascending direction, those less used in a +descending direction, we must draw the conclusion that harmonious +adaptation here comes about WITHOUT THE COOPERATION OF THE LAMARCKIAN +PRINCIPLE. This conclusion once established, however, we have no reason to +refer the thousands of cases of harmonious adaptation, which occur in +exactly the same way among other animals or plants, to a principle, the +ACTIVE INTERVENTION OF WHICH IN THE TRANSFORMATION OF SPECIES IS NOWHERE +PROVED. WE DO NOT REQUIRE IT TO EXPLAIN THE FACTS, AND THEREFORE WE MUST +NOT ASSUME IT. + +The fact of coadaptation, which was supposed to furnish the strongest +argument against the principle of selection, in reality yields the clearest +evidence in favour of it. We MUST assume it, BECAUSE NO OTHER POSSIBILITY +OF EXPLANATION IS OPEN TO US, AND BECAUSE THESE ADAPTATIONS ACTUALLY EXIST, +THAT IS TO SAY, HAVE REALLY TAKEN PLACE. With this conviction I attempted, +as far back as 1894, when the idea of germinal selection had not yet +occurred to me, to make "harmonious adaptation" (coadaptation) more easily +intelligible in some way or other, and so I was led to the idea, which was +subsequently expounded in detail by Baldwin, and Lloyd Morgan, and also by +Osborn, and Gulick as ORGANIC SELECTION. It seemed to me that it was not +necessary that all the germinal variations required for secondary +variations should have occurred SIMULTANEOUSLY, since, for instance, in the +case of the stag, the bones, muscles, sinews, and nerves would be incited +by the increasing heaviness of the antlers to greater activity in THE +INDIVIDUAL LIFE, and so would be strengthened. The antlers can only have +increased in size by very slow degrees, so that the muscles and bones may +have been able to keep pace with their growth in the individual life, until +the requisite germinal variations presented themselves. In this way a +disharmony between the increasing weight of the antlers and the parts which +support and move them would be avoided, since time would be given for the +appropriate germinal variations to occur, and so to set agoing the +HEREDITARY variation of the muscles, sinews, and bones. ("The Effect of +External Influences upon Development", Romanes Lecture, Oxford, 1894.) + +I still regard this idea as correct, but I attribute less importance to +"organic selection" than I did at that time, in so far that I do not +believe that it ALONE could effect complex harmonious adaptations. +Germinal selection now seems to me to play the chief part in bringing about +such adaptations. Something the same is true of the principle I have +called "Panmixia". As I became more and more convinced, in the course of +years, that the LAMARCKIAN PRINCIPLE ought not to be called in to explain +the dwindling of disused parts, I believed that this process might be +simply explained as due to the cessation of the conservative effect of +natural selection. I said to myself that, from the moment in which a part +ceases to be of use, natural selection withdraws its hand from it, and then +it must inevitably fall from the height of its adaptiveness, because +inferior variants would have as good a chance of persisting as better ones, +since all grades of fitness of the part in question would be mingled with +one another indiscriminately. This is undoubtedly true, as Romanes pointed +out ten years before I did, and this mingling of the bad with the good +probably does bring about a deterioration of the part concerned. But it +cannot account for the steady diminution, which always occurs when a part +is in process of becoming rudimentary, and which goes on until it +ultimately disappears altogether. The process of dwindling cannot +therefore be explained as due to panmixia alone; we can only find a +sufficient explanation in germinal selection. + +IV. DERIVATIVES OF THE THEORY OF SELECTION. + +The impetus in all directions given by Darwin through his theory of +selection has been an immeasurable one, and its influence is still felt. It +falls within the province of the historian of science to enumerate all the +ideas which, in the last quarter of the nineteenth century, grew out of +Darwin's theories, in the endeavour to penetrate more deeply into the +problem of the evolution of the organic world. Within the narrow limits to +which this paper is restricted, I cannot attempt to discuss any of these. + +V. ARGUMENTS FOR THE REALITY OF THE PROCESSES OF SELECTION. + +(a) SEXUAL SELECTION. + +Sexual selection goes hand in hand with natural selection. From the very +first I have regarded sexual selection as affording an extremely important +and interesting corroboration of natural selection, but, singularly enough, +it is precisely against this theory that an adverse judgment has been +pronounced in so many quarters, and it is only quite recently, and probably +in proportion as the wealth of facts in proof of it penetrates into a wider +circle, that we seem to be approaching a more general recognition of this +side of the problem of adaptation. Thus Darwin's words in his preface to +the second edition (1874) of his book, "The Descent of Man and Sexual +Selection", are being justified: "My conviction as to the operation of +natural selection remains unshaken," and further, "If naturalists were to +become more familiar with the idea of sexual selection, it would, I think, +be accepted to a much greater extent, and already it is fully and +favourably accepted by many competent judges." Darwin was able to speak +thus because he was already acquainted with an immense mass of facts, +which, taken together, yield overwhelming evidence of the validity of the +principle of sexual selection. + +NATURAL SELECTION chooses out for reproduction the individuals that are +best equipped for the struggle for existence, and it does so at every stage +of development; it thus improves the species in all its stages and forms. +SEXUAL SELECTION operates only on individuals that are already capable of +reproduction, and does so only in relation to the attainment of +reproduction. It arises from the rivalry of one sex, usually the male, for +the possession of the other, usually the female. Its influence can +therefore only DIRECTLY affect one sex, in that it equips it better for +attaining possession of the other. But the effect may extend indirectly to +the female sex, and thus the whole species may be modified, without, +however, becoming any more capable of resistance in the struggle for +existence, for sexual selection only gives rise to adaptations which are +likely to give their possessor the victory over rivals in the struggle for +possession of the female, and which are therefore peculiar to the wooing +sex: the manifold "secondary sexual characters." The diversity of these +characters is so great that I cannot here attempt to give anything +approaching a complete treatment of them, but I should like to give a +sufficient number of examples to make the principle itself, in its various +modes of expression, quite clear. + +One of the chief preliminary postulates of sexual selection is the unequal +number of individuals in the two sexes, for if every male immediately finds +his mate there can be no competition for the possession of the female. +Darwin has shown that, for the most part, the inequality between the sexes +is due simply to the fact that there are more males than females, and +therefore the males must take some pains to secure a mate. But the +inequality does not always depend on the numerical preponderance of the +males, it is often due to polygamy; for, if one male claims several +females, the number of females in proportion to the rest of the males will +be reduced. Since it is almost always the males that are the wooers, we +must expect to find the occurrence of secondary sexual characters chiefly +among them, and to find it especially frequent in polygamous species. And +this is actually the case. + +If we were to try to guess--without knowing the facts--what means the male +animals make use of to overcome their rivals in the struggle for the +possession of the female, we might name many kinds of means, but it would +be difficult to suggest any which is not actually employed in some animal +group or other. I begin with the mere difference in strength, through +which the male of many animals is so sharply distinguished from the female, +as, for instance, the lion, walrus, "sea-elephant," and others. Among +these the males fight violently for the possession of the female, who falls +to the victor in the combat. In this simple case no one can doubt the +operation of selection, and there is just as little room for doubt as to +the selection-value of the initial stages of the variation. Differences in +bodily strength are apparent even among human beings, although in their +case the struggle for the possession of the female is no longer decided by +bodily strength alone. + +Combats between male animals are often violent and obstinate, and the +employment of the natural weapons of the species in this way has led to +perfecting of these, e.g. the tusks of the boar, the antlers of the stag, +and the enormous, antler-like jaws of the stag-beetle. Here again it is +impossible to doubt that variations in these organs presented themselves, +and that these were considerable enough to be decisive in combat, and so to +lead to the improvement of the weapon. + +Among many animals, however, the females at first withdraw from the males; +they are coy, and have to be sought out, and sometimes held by force. This +tracking and grasping of the females by the males has given rise to many +different characters in the latter, as, for instance, the larger eyes of +the male bee, and especially of the males of the Ephemerids (May-flies), +some species of which show, in addition to the usual compound eyes, large, +so-called turban-eyes, so that the whole head is covered with seeing +surfaces. In these species the females are very greatly in the minority (1- +100), and it is easy to understand that a keen competition for them must +take place, and that, when the insects of both sexes are floating freely in +the air, an unusually wide range of vision will carry with it a decided +advantage. Here again the actual adaptations are in accordance with the +preliminary postulates of the theory. We do not know the stages through +which the eye has passed to its present perfected state, but, since the +number of simple eyes (facets) has become very much greater in the male +than in the female, we may assume that their increase is due to a gradual +duplication of the determinants of the ommatidium in the germ-plasm, as I +have already indicated in regard to sense-organs in general. In this case, +again, the selection-value of the initial stages hardly admits of doubt; +better vision DIRECTLY secures reproduction. + +In many cases THE ORGAN OF SMELL shows a similar improvement. Many lower +Crustaceans (Daphnidae) have better developed organs of smell in the male +sex. The difference is often slight and amounts only to one or two +olfactory filaments, but certain species show a difference of nearly a +hundred of these filaments (Leptodora). The same thing occurs among +insects. + +We must briefly consider the clasping or grasping organs which have +developed in the males among many lower Crustaceans, but here natural +selection plays its part along with sexual selection, for the union of the +sexes is an indispensable condition for the maintenance of the species, and +as Darwin himself pointed out, in many cases the two forms of selection +merge into each other. This fact has always seemed to me to be a proof of +natural selection, for, in regard to sexual selection, it is quite obvious +that the victory of the best-equipped could have brought about the +improvement only of the organs concerned, the factors in the struggle, such +as the eye and the olfactory organ. + +We come now to the EXCITANTS; that is, to the group of sexual characters +whose origin through processes of selection has been most frequently called +in question. We may cite the LOVE-CALLS produced by many male insects, +such as crickets and cicadas. These could only have arisen in animal +groups in which the female did not rapidly flee from the male, but was +inclined to accept his wooing from the first. Thus, notes like the +chirping of the male cricket serve to entice the females. At first they +were merely the signal which showed the presence of a male in the +neighbourhood, and the female was gradually enticed nearer and nearer by +the continued chirping. The male that could make himself heard to the +greatest distance would obtain the largest following, and would transmit +the beginnings, and, later, the improvement of his voice to the greatest +number of descendants. But sexual excitement in the female became +associated with the hearing of the love-call, and then the sound-producing +organ of the male began to improve, until it attained to the emission of +the long-drawn-out soft notes of the mole-cricket or the maenad-like cry of +the cicadas. I cannot here follow the process of development in detail, +but will call attention to the fact that the original purpose of the voice, +the announcing of the male's presence, became subsidiary, and the exciting +of the female became the chief goal to be aimed at. The loudest singers +awakened the strongest excitement, and the improvement resulted as a matter +of course. I conceive of the origin of bird-song in a somewhat similar +manner, first as a means of enticing, then of exciting the female. + +One more kind of secondary sexual character must here be mentioned: the +odour which emanates from so many animals at the breeding season. It is +possible that this odour also served at first merely to give notice of the +presence of individuals of the other sex, but it soon became an excitant, +and as the individuals which caused the greatest degree of excitement were +preferred, it reached as high a pitch of perfection as was possible to it. +I shall confine myself here to the comparatively recently discovered +fragrance of butterflies. Since Fritz Muller found out that certain +Brazilian butterflies gave off fragrance "like a flower," we have become +acquainted with many such cases, and we now know that in all lands, not +only many diurnal Lepidoptera but nocturnal ones also give off a delicate +odour, which is agreeable even to man. The ethereal oil to which this +fragrance is due is secreted by the skin-cells, usually of the wing, as I +showed soon after the discovery of the SCENT-SCALES. This is the case in +the males; the females have no SPECIAL scent-scales recognisable as such by +their form, but they must, nevertheless, give off an extremely delicate +fragrance, although our imperfect organ of smell cannot perceive it, for +the males become aware of the presence of a female, even at night, from a +long distance off, and gather round her. We may therefore conclude, that +both sexes have long given forth a very delicate perfume, which announced +their presence to others of the same species, and that in many species (NOT +IN ALL) these small beginnings became, in the males, particularly strong +scent-scales of characteristic form (lute, brush, or lyre-shaped). At +first these scales were scattered over the surface of the wing, but +gradually they concentrated themselves, and formed broad, velvety bands, or +strong, prominent brushes, and they attained their highest pitch of +evolution when they became enclosed within pits or folds of the skin, which +could be opened to let the delicious fragrance stream forth suddenly +towards the female. Thus in this case also we see that characters, the +original use of which was to bring the sexes together, and so to maintain +the species, have been evolved in the males into means for exciting the +female. And we can hardly doubt, that the females are most readily enticed +to yield to the butterfly that sends out the strongest fragrance,--that is +to say, that excites them to the highest degree. It is a pity that our +organs of smell are not fine enough to examine the fragrance of male +Lepidoptera in general, and to compare it with other perfumes which attract +these insects. (See Poulton, "Essays on Evolution", 1908, pages 316, 317.) +As far as we can perceive them they resemble the fragrance of flowers, but +there are Lepidoptera whose scent suggests musk. A smell of musk is also +given off by several plants: it is a sexual excitant in the musk-deer, the +musk-sheep, and the crocodile. + +As far as we know, then, it is perfumes similar to those of flowers that +the male Lepidoptera give off in order to entice their mates, and this is a +further indication that animals, like plants, can to a large extent meet +the claims made upon them by life, and produce the adaptations which are +most purposive,--a further proof, too, of my proposition that the useful +variations, so to speak, are ALWAYS THERE. The flowers developed the +perfumes which entice their visitors, and the male Lepidoptera developed +the perfumes which entice and excite their mates. + +There are many pretty little problems to be solved in this connection, for +there are insects, such as some flies, that are attracted by smells which +are unpleasant to us, like those from decaying flesh and carrion. But +there are also certain flowers, some orchids for instance, which give forth +no very agreeable odour, but one which is to us repulsive and disgusting; +and we should therefore expect that the males of such insects would give +off a smell unpleasant to us, but there is no case known to me in which +this has been demonstrated. + +In cases such as we have discussed, it is obvious that there is no possible +explanation except through selection. This brings us to the last kind of +secondary sexual characters, and the one in regard to which doubt has been +most frequently expressed,--decorative colours and decorative forms, the +brilliant plumage of the male pheasant, the humming-birds, and the bird of +Paradise, as well as the bright colours of many species of butterfly, from +the beautiful blue of our little Lycaenidae to the magnificent azure of the +large Morphinae of Brazil. In a great many cases, though not by any means +in all, the male butterflies are "more beautiful" than the females, and in +the Tropics in particular they shine and glow in the most superb colours. +I really see no reason why we should doubt the power of sexual selection, +and I myself stand wholly on Darwin's side. Even though we certainly +cannot assume that the females exercise a conscious choice of the +"handsomest" mate, and deliberate like the judges in a court of justice +over the perfections of their wooers, we have no reason to doubt that +distinctive forms (decorative feathers) and colours have a particularly +exciting effect upon the female, just as certain odours have among animals +of so many different groups, including the butterflies. The doubts which +existed for a considerable time, as a result of fallacious experiments, as +to whether the colours of flowers really had any influence in attracting +butterflies have now been set at rest through a series of more careful +investigations; we now know that the colours of flowers are there on +account of the butterflies, as Sprengel first showed, and that the blossoms +of Phanerogams are selected in relation to them, as Darwin pointed out. + +Certainly it is not possible to bring forward any convincing proof of the +origin of decorative colours through sexual selection, but there are many +weighty arguments in favour of it, and these form a body of presumptive +evidence so strong that it almost amounts to certainty. + +In the first place, there is the analogy with other secondary sexual +characters. If the song of birds and the chirping of the cricket have been +evolved through sexual selection, if the penetrating odours of male +animals,--the crocodile, the musk-deer, the beaver, the carnivores, and, +finally, the flower-like fragrances of the butterflies have been evolved to +their present pitch in this way, why should decorative colours have arisen +in some other way? Why should the eye be less sensitive to SPECIFICALLY +MALE colours and other VISIBLE signs ENTICING TO THE FEMALE, than the +olfactory sense to specifically male odours, or the sense of hearing to +specifically male sounds? Moreover, the decorative feathers of birds are +almost always spread out and displayed before the female during courtship. +I have elsewhere ("The Evolution Theory", London, 1904, I. page 219.) +pointed out that decorative colouring and sweet-scentedness may replace one +another in Lepidoptera as well as in flowers, for just as some modestly +coloured flowers (mignonette and violet) have often a strong perfume, while +strikingly coloured ones are sometimes quite devoid of fragrance, so we +find that the most beautiful and gaily-coloured of our native Lepidoptera, +the species of Vanessa, have no scent-scales, while these are often +markedly developed in grey nocturnal Lepidoptera. Both attractions may, +however, be combined in butterflies, just as in flowers. Of course, we +cannot explain why both means of attraction should exist in one genus, and +only one of them in another, since we do not know the minutest details of +the conditions of life of the genera concerned. But from the sporadic +distribution of scent-scales in Lepidoptera, and from their occurrence or +absence in nearly related species, we may conclude that fragrance is a +relatively MODERN acquirement, more recent than brilliant colouring. + +One thing in particular that stamps decorative colouring as a product of +selection is ITS GRADUAL INTENSIFICATION by the addition of new spots, +which we can quite well observe, because in many cases the colours have +been first acquired by the males, and later transmitted to the females by +inheritance. The scent-scales are never thus transmitted, probably for the +same reason that the decorative colours of many birds are often not +transmitted to the females: because with these they would be exposed to +too great elimination by enemies. Wallace was the first to point out that +in species with concealed nests the beautiful feathers of the male occurred +in the female also, as in the parrots, for instance, but this is not the +case in species which brood on an exposed nest. In the parrots one can +often observe that the general brilliant colouring of the male is found in +the female, but that certain spots of colour are absent, and these have +probably been acquired comparatively recently by the male and have not yet +been transmitted to the female. + +Isolation of the group of individuals which is in process of varying is +undoubtedly of great value in sexual selection, for even a solitary +conspicuous variation will become dominant much sooner in a small isolated +colony, than among a large number of members of a species. + +Anyone who agrees with me in deriving variations from germinal selection +will regard that process as an essential aid towards explaining the +selection of distinctive courtship-characters, such as coloured spots, +decorative feathers, horny outgrowths in birds and reptiles, combs, +feather-tufts, and the like, since the beginnings of these would be +presented with relative frequency in the struggle between the determinants +within the germ-plasm. The process of transmission of decorative feathers +to the female results, as Darwin pointed out and illustrated by interesting +examples, in the COLOUR-TRANSFORMATION OF A WHOLE SPECIES, and this +process, as the phyletically older colouring of young birds shows, must, in +the course of thousands of years, have repeated itself several times in a +line of descent. + +If we survey the wealth of phenomena presented to us by secondary sexual +characters, we can hardly fail to be convinced of the truth of the +principle of sexual selection. And certainly no one who has accepted +natural selection should reject sexual selection, for, not only do the two +processes rest upon the same basis, but they merge into one another, so +that it is often impossible to say how much of a particular character +depends on one and how much on the other form of selection. + +(b) NATURAL SELECTION. + +An actual proof of the theory of sexual selection is out of the question, +if only because we cannot tell when a variation attains to selection-value. +It is certain that a delicate sense of smell is of value to the male moth +in his search for the female, but whether the possession of one additional +olfactory hair, or of ten, or of twenty additional hairs leads to the +success of its possessor we are unable to tell. And we are groping even +more in the dark when we discuss the excitement caused in the female by +agreeable perfumes, or by striking and beautiful colours. That these do +make an impression is beyond doubt; but we can only assume that slight +intensifications of them give any advantage, and we MUST assume this SINCE +OTHERWISE SECONDARY SEXUAL CHARACTERS REMAIN INEXPLICABLE. + +The same thing is true in regard to natural selection. It is not possible +to bring forward any actual proof of the selection-value of the initial +stages, and the stages in the increase of variations, as has been already +shown. But the selection-value of a finished adaptation can in many cases +be statistically determined. Cesnola and Poulton have made valuable +experiments in this direction. The former attached forty-five individuals +of the green, and sixty-five of the brown variety of the praying mantis +(Mantis religiosa), by a silk thread to plants, and watched them for +seventeen days. The insects which were on a surface of a colour similar to +their own remained uneaten, while twenty-five green insects on brown parts +of plants had all disappeared in eleven days. + +The experiments of Poulton and Sanders ("Report of the British Association" +(Bristol, 1898), London, 1899, pages 906-909.) were made with 600 pupae of +Vanessa urticae, the "tortoise-shell butterfly." The pupae were +artificially attached to nettles, tree-trunks, fences, walls, and to the +ground, some at Oxford, some at St Helens in the Isle of Wight. In the +course of a month 93 per cent of the pupae at Oxford were killed, chiefly +by small birds, while at St Helens 68 per cent perished. The experiments +showed very clearly that the colour and character of the surface on which +the pupa rests--and thus its own conspicuousness--are of the greatest +importance. At Oxford only the four pupae which were fastened to nettles +emerged; all the rest--on bark, stones and the like--perished. At St +Helens the elimination was as follows: on fences where the pupae were +conspicuous, 92 per cent; on bark, 66 per cent; on walls, 54 per cent; and +among nettles, 57 per cent. These interesting experiments confirm our +views as to protective coloration, and show further, THAT THE RATIO OF +ELIMINATION IN THE SPECIES IS A VERY HIGH ONE, AND THAT THEREFORE SELECTION +MUST BE VERY KEEN. + +We may say that the process of selection follows as a logical necessity +from the fulfilment of the three preliminary postulates of the theory: +variability, heredity, and the struggle for existence, with its enormous +ratio of elimination in all species. To this we must add a fourth factor, +the INTENSIFICATION of variations which Darwin established as a fact, and +which we are now able to account for theoretically on the basis of germinal +selection. It may be objected that there is considerable uncertainty about +this LOGICAL proof, because of our inability to demonstrate the selection- +value of the initial stages and the individual stages of increase. We have +therefore to fall back on PRESUMPTIVE EVIDENCE. This is to be found in THE +INTERPRETATIVE VALUE OF THE THEORY. Let us consider this point in greater +detail. + +In the first place, it is necessary to emphasise what is often overlooked, +namely, that the theory not only explains the TRANSFORMATIONS of species, +it also explains THEIR REMAINING THE SAME; in addition to the principle of +varying, it contains within itself that of PERSISTING. It is part of the +essence of selection, that it not only causes a part to VARY till it has +reached its highest pitch of adaptation, but that it MAINTAINS IT AT THIS +PITCH. THIS CONSERVING INFLUENCE OF NATURAL SELECTION is of great +importance, and was early recognised by Darwin; it follows naturally from +the principle of the survival of the fittest. + +We understand from this how it is that a species which has become fully +adapted to certain conditions of life ceases to vary, but remains +"constant," as long as the conditions of life FOR IT remain unchanged, +whether this be for thousands of years, or for whole geological epochs. +But the most convincing proof of the power of the principle of selection +lies in the innumerable multitude of phenomena which cannot be explained in +any other way. To this category belong all structures which are only +PASSIVELY of advantage to the organism, because none of these can have +arisen by the alleged LAMARCKIAN PRINCIPLE. These have been so often +discussed that we need do no more than indicate them here. Until quite +recently the sympathetic coloration of animals--for instance, the whiteness +of Arctic animals--was referred, at least in part, to the DIRECT influence +of external factors, but the facts can best be explained by referring them +to the processes of selection, for then it is unnecessary to make the +gratuitous assumption that many species are sensitive to the stimulus of +cold and that others are not. The great majority of Arctic land-animals, +mammals and birds, are white, and this proves that they were all able to +present the variation which was most useful for them. The sable is brown, +but it lives in trees, where the brown colouring protects and conceals it +more effectively. The musk-sheep (Ovibos moschatus) is also brown, and +contrasts sharply with the ice and snow, but it is protected from beasts of +prey by its gregarious habit, and therefore it is of advantage to be +visible from as great a distance as possible. That so many species have +been able to give rise to white varieties does not depend on a special +sensitiveness of the skin to the influence of cold, but to the fact that +Mammals and Birds have a general tendency to vary towards white. Even with +us, many birds--starlings, blackbirds, swallows, etc.--occasionally produce +white individuals, but the white variety does not persist, because it +readily falls a victim to the carnivores. This is true of white fawns, +foxes, deer, etc. The whiteness, therefore, arises from internal causes, +and only persists when it is useful. A great many animals living in a +GREEN ENVIRONMENT have become clothed in green, especially insects, +caterpillars, and Mantidae, both persecuted and persecutors. + +That it is not the direct effect of the environment which calls forth the +green colour is shown by the many kinds of caterpillar which rest on leaves +and feed on them, but are nevertheless brown. These feed by night and +betake themselves through the day to the trunk of the tree, and hide in the +furrows of the bark. We cannot, however, conclude from this that they were +UNABLE to vary towards green, for there are Arctic animals which are white +only in winter and brown in summer (Alpine hare, and the ptarmigan of the +Alps), and there are also green leaf-insects which remain green only while +they are young and difficult to see on the leaf, but which become brown +again in the last stage of larval life, when they have outgrown the leaf. +They then conceal themselves by day, sometimes only among withered leaves +on the ground, sometimes in the earth itself. It is interesting that in +one genus, Chaerocampa, one species is brown in the last stage of larval +life, another becomes brown earlier, and in many species the last stage is +not wholly brown, a part remaining green. Whether this is a case of a +double adaptation, or whether the green is being gradually crowded out by +the brown, the fact remains that the same species, even the same +individual, can exhibit both variations. The case is the same with many of +the leaf-like Orthoptera, as, for instance, the praying mantis (Mantis +religiosa) which we have already mentioned. + +But the best proofs are furnished by those often-cited cases in which the +insect bears a deceptive resemblance to another object. We now know many +such cases, such as the numerous imitations of green or withered leaves, +which are brought about in the most diverse ways, sometimes by mere +variations in the form of the insect and in its colour, sometimes by an +elaborate marking, like that which occurs in the Indian leaf-butterflies, +Kallima inachis. In the single butterfly-genus Anaea, in the woods of +South America, there are about a hundred species which are all gaily +coloured on the upper surface, and on the reverse side exhibit the most +delicate imitation of the colouring and pattern of a leaf, generally +without any indication of the leaf-ribs, but extremely deceptive +nevertheless. Anyone who has seen only one such butterfly may doubt +whether many of the insignificant details of the marking can really be of +advantage to the insect. Such details are for instance the apparent holes +and splits in the apparently dry or half-rotten leaf, which are usually due +to the fact that the scales are absent on a circular or oval patch so that +the colourless wing-membrane lies bare, and one can look through the spot +as through a window. Whether the bird which is seeking or pursuing the +butterflies takes these holes for dewdrops, or for the work of a devouring +insect, does not affect the question; the mirror-like spot undoubtedly +increases the general deceptiveness, for the same thing occurs in many +leaf-butterflies, though not in all, and in some cases it is replaced in +quite a peculiar manner. In one species of Anaea (A. divina), the resting +butterfly looks exactly like a leaf out of the outer edge of which a large +semicircular piece has been eaten, possibly by a caterpillar; but if we +look more closely it is obvious that there is no part of the wing absent, +and that the semicircular piece is of a clear, pale yellow colour, while +the rest of the wing is of a strongly contrasted dark brown. + +But the deceptive resemblance may be caused in quite a different manner. I +have often speculated as to what advantage the brilliant white C could give +to the otherwise dusky-coloured "Comma butterfly" (Grapta C. album). +Poulton's recent observations ("Proc. Ent. Soc"., London, May 6, 1903.) +have shown that this represents the imitation of a crack such as is often +seen in dry leaves, and is very conspicuous because the light shines +through it. + +The utility obviously lies in presenting to the bird the very familiar +picture of a broken leaf with a clear shining slit, and we may conclude, +from the imitation of such small details, that the birds are very sharp +observers and that the smallest deviation from the usual arrests their +attention and incites them to closer investigation. It is obvious that +such detailed--we might almost say such subtle--deceptive resemblances +could only have come about in the course of long ages through the +acquirement from time to time of something new which heightened the already +existing resemblance. + +In face of facts like these there can be no question of chance, and no one +has succeeded so far in finding any other explanation to replace that by +selection. For the rest, the apparent leaves are by no means perfect +copies of a leaf; many of them only represent the torn or broken piece, or +the half or two-thirds of a leaf, but then the leaves themselves frequently +do not present themselves to the eye as a whole, but partially concealed +among other leaves. Even those butterflies which, like the species of +Kallima and Anaea, represent the whole of a leaf with stalk, ribs, apex, +and the whole breadth, are not actual copies which would satisfy a +botanist; there is often much wanting. In Kallima the lateral ribs of the +leaf are never all included in the markings; there are only two or three on +the left side and at most four or five on the right, and in many +individuals these are rather obscure, while in others they are +comparatively distinct. This furnishes us with fresh evidence in favour of +their origin through processes of selection, for a botanically perfect +picture could not arise in this way; there could only be a fixing of such +details as heightened the deceptive resemblance. + +Our postulate of origin through selection also enables us to understand why +the leaf-imitation is on the lower surface of the wing in the diurnal +Lepidoptera, and on the upper surface in the nocturnal forms, corresponding +to the attitude of the wings in the resting position of the two groups. + +The strongest of all proofs of the theory, however, is afforded by cases of +true "mimicry," those adaptations discovered by Bates in 1861, consisting +in the imitation of one species by another, which becomes more and more +like its model. The model is always a species that enjoys some special +protection from enemies, whether because it is unpleasant to taste, or +because it is in some way dangerous. + +It is chiefly among insects and especially among butterflies that we find +the greatest number of such cases. Several of these have been minutely +studied, and every detail has been investigated, so that it is difficult to +understand how there can still be disbelief in regard to them. If the many +and exact observations which have been carefully collected and critically +discussed, for instance by Poulton ("Essays on Evolution", 1889-1907, +Oxford, 1908, passim, e.g. page 269.) were thoroughly studied, the +arguments which are still frequently urged against mimicry would be found +untenable; we can hardly hope to find more convincing proof of the +actuality of the processes of selection than these cases put into our +hands. The preliminary postulates of the theory of mimicry have been +disputed, for instance, that diurnal butterflies are persecuted and eaten +by birds, but observations specially directed towards this point in India, +Africa, America and Europe have placed it beyond all doubt. If it were +necessary I could myself furnish an account of my own observations on this +point. + +In the same way it has been established by experiment and observation in +the field that in all the great regions of distribution there are +butterflies which are rejected by birds and lizards, their chief enemies, +on account of their unpleasant smell or taste. These butterflies are +usually gaily and conspicuously coloured and thus--as Wallace first +interpreted it--are furnished with an easily recognisable sign: a sign of +unpalatableness or WARNING COLOURS. If they were not thus recognisable +easily and from a distance, they would frequently be pecked at by birds, +and then rejected because of their unpleasant taste; but as it is, the +insect-eaters recognise them at once as unpalatable booty and ignore them. +Such IMMUNE (The expression does not refer to all the enemies of this +butterfly; against ichneumon-flies, for instance, their unpleasant smell +usually gives no protection.) species, wherever they occur, are imitated by +other palatable species, which thus acquire a certain degree of protection. + +It is true that this explanation of the bright, conspicuous colours is only +a hypothesis, but its foundations,--unpalatableness, and the liability of +other butterflies to be eaten,--are certain, and its consequences--the +existence of mimetic palatable forms--confirm it in the most convincing +manner. Of the many cases now known I select one, which is especially +remarkable, and which has been thoroughly investigated, Papilio dardanus +(merope), a large, beautiful, diurnal butterfly which ranges from Abyssinia +throughout the whole of Africa to the south coast of Cape Colony. + +The males of this form are everywhere ALMOST the same in colour and in form +of wings, save for a few variations in the sparse black markings on the +pale yellow ground. But the females occur in several quite different forms +and colourings, and one of these only, the Abyssinian form, is like the +male, while the other three or four are MIMETIC, that is to say, they copy +a butterfly of quite a different family the Danaids, which are among the +IMMUNE forms. In each region the females have thus copied two or three +different immune species. There is much that is interesting to be said in +regard to these species, but it would be out of keeping with the general +tenor of this paper to give details of this very complicated case of +polymorphism in P. dardanus. Anyone who is interested in the matter will +find a full and exact statement of the case in as far as we know it, in +Poulton's "Essays on Evolution" (pages 373-375). (Professor Poulton has +corrected some wrong descriptions which I had unfortunately overlooked in +the Plates of my book "Vortrage uber Descendenztheorie", and which refer to +Papilio dardanus (merope). These mistakes are of no importance as far as +and understanding of the mimicry-theory is concerned, but I hope shortly to +be able to correct them in a later edition.) I need only add that three +different mimetic female forms have been reared from the eggs of a single +female in South Africa. The resemblance of these forms to their immune +models goes so far that even the details of the LOCAL forms of the models +are copied by the mimetic species. + +It remains to be said that in Madagascar a butterfly, Papilio meriones, +occurs, of which both sexes are very similar in form and markings to the +non-mimetic male of P. dardanus, so that it probably represents the +ancestor of this latter species. + +In face of such facts as these every attempt at another explanation must +fail. Similarly all the other details of the case fulfil the preliminary +postulates of selection, and leave no room for any other interpretation. +That the males do not take on the protective colouring is easily explained, +because they are in general more numerous, and the females are more +important for the preservation of the species, and must also live longer in +order to deposit their eggs. We find the same state of things in many +other species, and in one case (Elymnias undularis) in which the male is +also mimetically coloured, it copies quite a differently coloured immune +species from the model followed by the female. This is quite intelligible +when we consider that if there were TOO MANY false immune types, the birds +would soon discover that there were palatable individuals among those with +unpalatable warning colours. Hence the imitation of different immune +species by Papilio dardanus! + +I regret that lack of space prevents my bringing forward more examples of +mimicry and discussing them fully. But from the case of Papilio dardanus +alone there is much to be learnt which is of the highest importance for our +understanding of transformations. It shows us chiefly what I once called, +somewhat strongly perhaps, THE OMNIPOTENCE OF NATURAL SELECTION in answer +to an opponent who had spoken of its "inadequacy." We here see that one +and the same species is capable of producing four or five different +patterns of colouring and marking; thus the colouring and marking are not, +as has often been supposed, a necessary outcome of the specific nature of +the species, but a true adaptation, which cannot arise as a direct effect +of climatic conditions, but solely through what I may call the sorting out +of the variations produced by the species, according to their utility. +That caterpillars may be either green or brown is already something more +than could have been expected according to the old conception of species, +but that one and the same butterfly should be now pale yellow, with black; +now red with black and pure white; now deep black with large, pure white +spots; and again black with a large ochreous-yellow spot, and many small +white and yellow spots; that in one sub-species it may be tailed like the +ancestral form, and in another tailless like its Danaid model,--all this +shows a far-reaching capacity for variation and adaptation that wide never +have expected if we did not see the facts before us. How it is possible +that the primary colour-variations should thus be intensified and combined +remains a puzzle even now; we are reminded of the modern three-colour +printing,--perhaps similar combinations of the primary colours take place +in this case; in any case the direction of these primary variations is +determined by the artist whom we know as natural selection, for there is no +other conceivable way in which the model could affect the butterfly that is +becoming more and more like it. The same climate surrounds all four forms +of female; they are subject to the same conditions of nutrition. Moreover, +Papilio dardanus is by no means the only species of butterfly which +exhibits different kinds of colour-pattern on its wings. Many species of +the Asiatic genus Elymnias have on the upper surface a very good imitation +of an immune Euploeine (Danainae), often with a steel-blue ground-colour, +while the under surface is well concealed when the butterfly is at rest,-- +thus there are two kinds of protective coloration each with a different +meaning! The same thing may be observed in many non-mimetic butterflies, +for instance in all our species of Vanessa, in which the under side shows a +grey-brown or brownish-black protective coloration, but we do not yet know +with certainty what may be the biological significance of the gaily +coloured upper surface. + +In general it may be said that mimetic butterflies are comparatively rare +species, but there are exceptions, for instance Limenitis archippus in +North America, of which the immune model (Danaida plexippus) also occurs in +enormous numbers. + +In another mimicry-category the imitators are often more numerous than the +models, namely in the case of the imitation of DANGEROUS INSECTS by +harmless species. Bees and wasps are dreaded for their sting, and they are +copied by harmless flies of the genera Eristalis and Syrphus, and these +mimics often occur in swarms about flowering plants without damage to +themselves or to their models; they are feared and are therefore left +unmolested. + +In regard also to the FAITHFULNESS OF THE COPY the facts are quite in +harmony with the theory, according to which the resemblance must have +arisen and increased BY DEGREES. We can recognise this in many cases, for +even now the mimetic species show very VARYING DEGREES OF RESEMBLANCE to +their immune model. If we compare, for instance, the many different +imitators of Danaida chrysippus we find that, with their brownish-yellow +ground-colour, and the position and size, and more or less sharp limitation +of their clear marginal spots, they have reached very different degrees of +nearness to their model. Or compare the female of Elymnias undularis with +its model Danaida genutia; there is a general resemblance, but the marking +of the Danaida is very roughly imitated in Elymnias. + +Another fact that bears out the theory of mimicry is, that even when the +resemblance in colour-pattern is very great, the WING-VENATION, which is +so constant, and so important in determining the systematic position of +butterflies, is never affected by the variation. The pursuers of the +butterfly have no time to trouble about entomological intricacies. + +I must not pass over a discovery of Poulton's which is of great theoretical +importance--that mimetic butterflies may reach the same effect by very +different means. ("Journ. Linn. Soc. London (Zool.)", Vol. XXVI. 1898, +pages 598-602.) Thus the glass-like transparency of the wing of a certain +Ithomiine (Methona) and its Pierine mimic (Dismorphia orise) depends on a +diminution in the size of the scales; in the Danaine genus Ituna it is due +to the fewness of the scales, and in a third imitator, a moth (Castnia +linus var. heliconoides) the glass-like appearance of the wing is due +neither to diminution nor to absence of scales, but to their absolute +colourlessness and transparency, and to the fact that they stand upright. +In another moth mimic (Anthomyza) the arrangement of the transparent scales +is normal. Thus it is not some unknown external influence that has brought +about the transparency of the wing in these five forms, as has sometimes +been supposed. Nor is it a hypothetical INTERNAL evolutionary tendency, +for all three vary in a different manner. The cause of this agreement can +only lie in selection, which preserves and intensifies in each species the +favourable variations that present themselves. The great faithfulness of +the copy is astonishing in these cases, for it is not THE WHOLE wing which +is transparent; certain markings are black in colour, and these contrast +sharply with the glass-like ground. It is obvious that the pursuers of +these butterflies must be very sharp-sighted, for otherwise the agreement +between the species could never have been pushed so far. The less the +enemies see and observe, the more defective must the imitation be, and if +they had been blind, no visible resemblance between the species which +required protection could ever have arisen. + +A seemingly irreconcilable contradiction to the mimicry theory is presented +in the following cases, which were known to Bates, who, however, never +succeeded in bringing them into line with the principle of mimicry. + +In South America there are, as we have already said, many mimics of the +immune Ithomiinae (or as Bates called them Heliconidae). Among these there +occur not merely species which are edible, and thus require the protection +of a disguise, but others which are rejected on account of their +unpalatableness. How could the Ithomiine dress have developed in their +case, and of what use is it, since the species would in any case be immune? +In Eastern Brazil, for instance, there are four butterflies, which bear a +most confusing resemblance to one another in colour, marking, and form of +wing, and all four are unpalatable to birds. They belong to four different +genera and three sub-families, and we have to inquire: Whence came this +resemblance and what end does it serve? For a long time no satisfactory +answer could be found, but Fritz Muller (In "Kosmos", 1879, page 100.), +seventeen years after Bates, offered a solution to the riddle, when he +pointed out that young birds could not have an instinctive knowledge of the +unpalatableness of the Ithomiines, but must learn by experience which +species were edible and which inedible. Thus each young bird must have +tasted at least one individual of each inedible species and discovered its +unpalatability, before it learnt to avoid, and thus to spare the species. +But if the four species resemble each other very closely the bird will +regard them all as of the same kind, and avoid them all. Thus there +developed a process of selection which resulted in the survival of the +Ithomiine-like individuals, and in so great an increase of resemblance +between the four species, that they are difficult to distinguish one from +another even in a collection. The advantage for the four species, living +side by side as they do e.g. in Bahia, lies in the fact that only one +individual from the MIMICRY-RING ("inedible association") need be tasted by +a young bird, instead of at least four individuals, as would otherwise be +the case. As the number of young birds is great, this makes a considerable +difference in the ratio of elimination. + +These interesting mimicry-rings (trusts), which have much significance for +the theory, have been the subject of numerous and careful investigations, +and at least their essential features are now fully established. Muller +took for granted, without making any investigations, that young birds only +learn by experience to distinguish between different kinds of victims. But +Lloyd Morgan's ("Habit and Instinct", London, 1896.) experiments with young +birds proved that this is really the case, and at the same time furnished +an additional argument against the LAMARCKIAN PRINCIPLE. + +In addition to the mimicry-rings first observed in South America, others +have been described from Tropical India by Moore, and by Poulton and Dixey +from Africa, and we may expect to learn many more interesting facts in this +connection. Here again the preliminary postulates of the theory are +satisfied. And how much more that would lead to the same conclusion might +be added! + +As in the case of mimicry many species have come to resemble one another +through processes of selection, so we know whole classes of phenomena in +which plants and animals have become adapted to one another, and have thus +been modified to a considerable degree. I refer particularly to the +relation between flowers and insects; but as there is an article on "The +Biology of Flowers" in this volume, I need not discuss the subject, but +will confine myself to pointing out the significance of these remarkable +cases for the theory of selection. Darwin has shown that the originally +inconspicuous blossoms of the phanerogams were transformed into flowers +through the visits of insects, and that, conversely, several large orders +of insects have been gradually modified by their association with flowers, +especially as regards the parts of their body actively concerned. Bees and +butterflies in particular have become what they are through their relation +to flowers. In this case again all that is apparently contradictory to the +theory can, on closer investigation, be beautifully interpreted in +corroboration of it. Selection can give rise only to what is of use to the +organism actually concerned, never to what is of use to some other +organism, and we must therefore expect to find that in flowers only +characters of use to THEMSELVES have arisen, never characters which are of +use to insects only, and conversely that in the insects characters useful +to them and not merely to the plants would have originated. For a long +time it seemed as if an exception to this rule existed in the case of the +fertilisation of the yucca blossoms by a little moth, Pronuba yuccasella. +This little moth has a sickle-shaped appendage to its mouth-parts which +occurs in no other Lepidopteron, and which is used for pushing the yellow +pollen into the opening of the pistil, thus fertilising the flower. Thus +it appears as if a new structure, which is useful only to the plant, has +arisen in the insect. But the difficulty is solved as soon as we learn +that the moth lays its eggs in the fruit-buds of the Yucca, and that the +larvae, when they emerge, feed on the developing seeds. In effecting the +fertilisation of the flower the moth is at the same time making provision +for its own offspring, since it is only after fertilisation that the seeds +begin to develop. There is thus nothing to prevent our referring this +structural adaptation in Pronuba yuccasella to processes of selection, +which have gradually transformed the maxillary palps of the female into the +sickle-shaped instrument for collecting the pollen, and which have at the +same time developed in the insect the instinct to press the pollen into the +pistil. + +In this domain, then, the theory of selection finds nothing but +corroboration, and it would be impossible to substitute for it any other +explanation, which, now that the facts are so well known, could be regarded +as a serious rival to it. That selection is a factor, and a very powerful +factor in the evolution of organisms, can no longer be doubted. Even +although we cannot bring forward formal proofs of it IN DETAIL, cannot +calculate definitely the size of the variations which present themselves, +and their selection-value, cannot, in short, reduce the whole process to a +mathematical formula, yet we must assume selection, because it is the only +possible explanation applicable to whole classes of phenomena, and because, +on the other hand, it is made up of factors which we know can be proved +actually to exist, and which, IF they exist, must of logical necessity +cooperate in the manner required by the theory. WE MUST ACCEPT IT BECAUSE +THE PHENOMENA OF EVOLUTION AND ADAPTATION MUST HAVE A NATURAL BASIS, AND +BECAUSE IT IS THE ONLY POSSIBLE EXPLANATION OF THEM. (This has been +discussed in many of my earlier works. See for instance "The All- +Sufficiency of Natural Selection, a reply to Herbert Spencer", London, +1893.) + +Many people are willing to admit that selection explains adaptations, but +they maintain that only a part of the phenomena are thus explained, because +everything does not depend upon adaptation. They regard adaptation as, so +to speak, a special effort on the part of Nature, which she keeps in +readiness to meet particularly difficult claims of the external world on +organisms. But if we look at the matter more carefully we shall find that +adaptations are by no means exceptional, but that they are present +everywhere in such enormous numbers, that it would be difficult in regard +to any structure whatever, to prove that adaptation had NOT played a part +in its evolution. + +How often has the senseless objection been urged against selection that it +can create nothing, it can only reject. It is true that it cannot create +either the living substance or the variations of it; both must be given. +But in rejecting one thing it preserves another, intensifies it, combines +it, and in this way CREATES what is new. EVERYTHING in organisms depends +on adaptation; that is to say, everything must be admitted through the +narrow door of selection, otherwise it can take no part in the building up +of the whole. But, it is asked, what of the direct effect of external +conditions, temperature, nutrition, climate and the like? Undoubtedly +these can give rise to variations, but they too must pass through the door +of selection, and if they cannot do this they are rejected, eliminated from +the constitution of the species. + +It may, perhaps, be objected that such external influences are often of a +compelling power, and that every animal MUST submit to them, and that thus +selection has no choice and can neither select nor reject. There may be +such cases; let us assume for instance that the effect of the cold of the +Arctic regions was to make all the mammals become black; the result would +be that they would all be eliminated by selection, and that no mammals +would be able to live there at all. But in most cases a certain percentage +of animals resists these strong influences, and thus selection secures a +foothold on which to work, eliminating the unfavourable variation, and +establishing a useful colouring, consistent with what is required for the +maintenance of the species. + +Everything depends upon adaptation! We have spoken much of adaptation in +colouring, in connection with the examples brought into prominence by +Darwin, because these are conspicuous, easily verified, and at the same +time convincing for the theory of selection. But is it only desert and +polar animals whose colouring is determined through adaptation? Or the +leaf-butterflies, and the mimetic species, or the terrifying markings, and +"warning-colours" and a thousand other kinds of sympathetic colouring? It +is, indeed, never the colouring alone which makes up the adaptation; the +structure of the animal plays a part, often a very essential part, in the +protective disguise, and thus MANY variations may cooperate towards ONE +common end. And it is to be noted that it is by no means only external +parts that are changed; internal parts are ALWAYS modified at the same +time--for instance, the delicate elements of the nervous system on which +depend the INSTINCT of the insect to hold its wings, when at rest, in a +perfectly definite position, which, in the leaf-butterfly, has the effect +of bringing the two pieces on which the marking occurs on the anterior and +posterior wing into the same direction, and thus displaying as a whole the +fine curve of the midrib on the seeming leaf. But the wing-holding instinct +is not regulated in the same way in all leaf-butterflies; even our +indigenous species of Vanessa, with their protective ground-colouring, have +quite a distinctive way of holding their wings so that the greater part of +the anterior wing is covered by the posterior when the butterfly is at +rest. But the protective colouring appears on the posterior wing and on +the tip of the anterior, TO PRECISELY THE DISTANCE TO WHICH IT IS LEFT +UNCOVERED. This occurs, as Standfuss has shown, in different degree in our +two most nearly allied species, the uncovered portion being smaller in V. +urticae than in V. polychloros. In this case, as in most leaf-butterflies, +the holding of the wing was probably the primary character; only after that +was thoroughly established did the protective marking develop. In any +case, the instinctive manner of holding the wings is associated with the +protective colouring, and must remain as it is if the latter is to be +effective. How greatly instincts may change, that is to say, may be +adapted, is shown by the case of the Noctuid "shark" moth, Xylina vetusta. +This form bears a most deceptive resemblance to a piece of rotten wood, and +the appearance is greatly increased by the modification of the innate +impulse to flight common to so many animals, which has here been +transformed into an almost contrary instinct. This moth does not fly away +from danger, but "feigns death," that is, it draws antennae, legs and wings +close to the body, and remains perfectly motionless. It may be touched, +picked up, and thrown down again, and still it does not move. This +remarkable instinct must surely have developed simultaneously with the +wood-colouring; at all events, both cooperating variations are now present, +and prove that both the external and the most minute internal structure +have undergone a process of adaptation. + +The case is the same with all structural variations of animal parts, which +are not absolutely insignificant. When the insects acquired wings they +must also have acquired the mechanism with which to move them--the +musculature, and the nervous apparatus necessary for its automatic +regulation. All instincts depend upon compound reflex mechanisms and are +just as indispensable as the parts they have to set in motion, and all may +have arisen through processes of selection if the reasons which I have +elsewhere given for this view are correct. ("The Evolution Theory", +London, 1904, page 144.) + +Thus there is no lack of adaptations within the organism, and particularly +in its most important and complicated parts, so that we may say that there +is no actively functional organ that has not undergone a process of +adaptation relative to its function and the requirements of the organism. +Not only is every gland structurally adapted, down to the very minutest +histological details, to its function, but the function is equally minutely +adapted to the needs of the body. Every cell in the mucous lining of the +intestine is exactly regulated in its relation to the different nutritive +substances, and behaves in quite a different way towards the fats, and +towards nitrogenous substances, or peptones. + +I have elsewhere called attention to the many adaptations of the whale to +the surrounding medium, and have pointed out--what has long been known, but +is not universally admitted, even now--that in it a great number of +important organs have been transformed in adaptation to the peculiar +conditions of aquatic life, although the ancestors of the whale must have +lived, like other hair-covered mammals, on land. I cited a number of these +transformations--the fish-like form of the body, the hairlessness of the +skin, the transformation of the fore-limbs to fins, the disappearance of +the hind-limbs and the development of a tail fin, the layer of blubber +under the skin, which affords the protection from cold necessary to a warm- +blooded animal, the disappearance of the ear-muscles and the auditory +passages, the displacement of the external nares to the forehead for the +greater security of the breathing-hole during the brief appearance at the +surface, and certain remarkable changes in the respiratory and circulatory +organs which enable the animal to remain for a long time under water. I +might have added many more, for the list of adaptations in the whale to +aquatic life is by no means exhausted; they are found in the histological +structure and in the minutest combinations in the nervous system. For it +is obvious that a tail-fin must be used in quite a different way from a +tail, which serves as a fly-brush in hoofed animals, or as an aid to +springing in the kangaroo or as a climbing organ; it will require quite +different reflex-mechanisms and nerve-combinations in the motor centres. + +I used this example in order to show how unnecessary it is to assume a +special internal evolutionary power for the phylogenesis of species, for +this whole order of whales is, so to speak, MADE UP OF ADAPTATIONS; it +deviates in many essential respects from the usual mammalian type, and all +the deviations are adaptations to aquatic life. But if precisely the most +essential features of the organisation thus depend upon adaptation, what is +left for a phyletic force to do, since it is these essential features of +the structure it would have to determine? There are few people now who +believe in a phyletic evolutionary power, which is not made up of the +forces known to us--adaptation and heredity--but the conviction that EVERY +part of an organism depends upon adaptation has not yet gained a firm +footing. Nevertheless, I must continue to regard this conception as the +correct one, as I have long done. + +I may be permitted one more example. The feather of a bird is a marvellous +structure, and no one will deny that as a whole it depends upon adaptation. +But what part of it DOES NOT depend upon adaptation? The hollow quill, the +shaft with its hard, thin, light cortex, and the spongy substance within +it, its square section compared with the round section of the quill, the +flat barbs, their short, hooked barbules which, in the flight-feathers, +hook into one another with just sufficient firmness to resist the pressure +of the air at each wing-beat, the lightness and firmness of the whole +apparatus, the elasticity of the vane, and so on. And yet all this belongs +to an organ which is only passively functional, and therefore can have +nothing to do with the LAMARCKIAN PRINCIPLE. Nor can the feather have +arisen through some magical effect of temperature, moisture, electricity, +or specific nutrition, and thus selection is again our only anchor of +safety. + +But--it will be objected--the substance of which the feather consists, this +peculiar kind of horny substance, did not first arise through selection in +the course of the evolution of the birds, for it formed the covering of the +scales of their reptilian ancestors. It is quite true that a similar +substance covered the scales of the Reptiles, but why should it not have +arisen among them through selection? Or in what other way could it have +arisen, since scales are also passively useful parts? It is true that if +we are only to call adaptation what has been acquired by the species we +happen to be considering, there would remain a great deal that could not be +referred to selection; but we are postulating an evolution which has +stretched back through aeons, and in the course of which innumerable +adaptations took place, which had not merely ephemeral persistence in a +genus, a family or a class, but which was continued into whole Phyla of +animals, with continual fresh adaptations to the special conditions of each +species, family, or class, yet with persistence of the fundamental +elements. Thus the feather, once acquired, persisted in all birds, and the +vertebral column, once gained by adaptation in the lowest forms, has +persisted in all the Vertebrates, from Amphioxus upwards, although with +constant readaptation to the conditions of each particular group. Thus +everything we can see in animals is adaptation, whether of to-day, or of +yesterday, or of ages long gone by; every kind of cell, whether glandular, +muscular, nervous, epidermic, or skeletal, is adapted to absolutely +definite and specific functions, and every organ which is composed of these +different kinds of cells contains them in the proper proportions, and in +the particular arrangement which best serves the function of the organ; it +is thus adapted to its function. + +All parts of the organism are tuned to one another, that is, THEY ARE +ADAPTED TO ONE ANOTHER, and in the same way THE ORGANISM AS A WHOLE IS +ADAPTED TO THE CONDITIONS OF ITS LIFE, AND IT IS SO AT EVERY STAGE OF ITS +EVOLUTION. + +But all adaptations CAN be referred to selection; the only point that +remains doubtful is whether they all MUST be referred to it. + +However that may be, whether the LAMARCKIAN PRINCIPLE is a factor that has +cooperated with selection in evolution, or whether it is altogether +fallacious, the fact remains, that selection is the cause of a great part +of the phyletic evolution of organisms on our earth. Those who agree with +me in rejecting the LAMARCKIAN PRINCIPLE will regard selection as the only +GUIDING factor in evolution, which creates what is new out of the +transmissible variations, by ordering and arranging these, selecting them +in relation to their number and size, as the architect does his building- +stones so that a particular style must result. ("Variation under +Domestication", 1875 II. pages 426, 427.) But the building-stones +themselves, the variations, have their basis in the influences which cause +variation in those vital units which are handed on from one generation to +another, whether, taken together they form the WHOLE organism, as in +Bacteria and other low forms of life, or only a germ-substance, as in +unicellular and multicellular organisms. (The Author and Editor are +indebted to Professor Poulton for kindly assisting in the revision of the +proof of this Essay.) + + +IV. VARIATION. + +By HUGO DE VRIES, +Professor of Botany in the University of Amsterdam. + +I. DIFFERENT KINDS OF VARIABILITY. + +Before Darwin, little was known concerning the phenomena of variability. +The fact, that hardly two leaves on a tree were exactly the same, could not +escape observation: small deviations of the same kind were met with +everywhere, among individuals as well as among the organs of the same +plant. Larger aberrations, spoken of as monstrosities, were for a long +time regarded as lying outside the range of ordinary phenomena. A special +branch of inquiry, that of Teratology, was devoted to them, but it +constituted a science by itself, sometimes connected with morphology, but +having scarcely any bearing on the processes of evolution and heredity. + +Darwin was the first to take a broad survey of the whole range of +variations in the animal and vegetable kingdoms. His theory of Natural +Selection is based on the fact of variability. In order that this +foundation should be as strong as possible he collected all the facts, +scattered in the literature of his time, and tried to arrange them in a +scientific way. He succeeded in showing that variations may be grouped +along a line of almost continuous gradations, beginning with simple +differences in size and ending with monstrosities. He was struck by the +fact that, as a rule, the smaller the deviations, the more frequently they +appear, very abrupt breaks in characters being of rare occurrence. + +Among these numerous degrees of variability Darwin was always on the look +out for those which might, with the greatest probability, be considered as +affording material for natural selection to act upon in the development of +new species. Neither of the extremes complied with his conceptions. He +often pointed out, that there are a good many small fluctuations, which in +this respect must be absolutely useless. On the other hand, he strongly +combated the belief, that great changes would be necessary to explain the +origin of species. Some authors had propounded the idea that highly +adapted organs, e.g. the wings of a bird, could not have been developed in +any other way than by a comparatively sudden modification of a well defined +and important kind. Such a conception would allow of great breaks or +discontinuity in the evolution of highly differentiated animals and plants, +shortening the time for the evolution of the whole organic kingdom and +getting over numerous difficulties inherent in the theory of slow and +gradual progress. It would, moreover, account for the genetic relation of +the larger groups of both animals and plants. It would, in a word, +undoubtedly afford an easy means of simplifying the problem of descent with +modification. + +Darwin, however, considered such hypotheses as hardly belonging to the +domain of science; they belong, he said, to the realm of miracles. That +species have a capacity for change is admitted by all evolutionists; but +there is no need to invoke modifications other than those represented by +ordinary variability. It is well known that in artificial selection this +tendency to vary has given rise to numerous distinct races, and there is no +reason for denying that it can do the same in nature, by the aid of natural +selection. On both lines an advance may be expected with equal +probability. + +His main argument, however, is that the most striking and most highly +adapted modifications may be acquired by successive variations. Each of +these may be slight, and they may affect different organs, gradually +adapting them to the same purpose. The direction of the adaptations will +be determined by the needs in the struggle for life, and natural selection +will simply exclude all such changes as occur on opposite or deviating +lines. In this way, it is not variability itself which is called upon to +explain beautiful adaptations, but it is quite sufficient to suppose that +natural selection has operated during long periods in the same way. +Eventually, all the acquired characters, being transmitted together, would +appear to us, as if they had all been simultaneously developed. + +Correlations must play a large part in such special evolutions: when one +part is modified, so will be other parts. The distribution of nourishment +will come in as one of the causes, the reactions of different organs to the +same external influences as another. But no doubt the more effective cause +is that of the internal correlations, which, however, are still but dimly +understood. Darwin repeatedly laid great stress on this view, although a +definite proof of its correctness could not be given in his time. Such +proof requires the direct observation of a mutation, and it should be +stated here that even the first observations made in this direction have +clearly confirmed Darwin's ideas. The new evening primroses which have +sprung in my garden from the old form of Oenothera Lamarckiana, and which +have evidently been derived from it, in each case, by a single mutation, do +not differ from their parent species in one character only, but in almost +all their organs and qualities. Oenothera gigas, for example, has stouter +stems and denser foliage; the leaves are larger and broader; its thick +flower-buds produce gigantic flowers, but only small fruits with large +seeds. Correlative changes of this kind are seen in all my new forms, and +they lend support to the view that in the gradual development of highly +adapted structures, analogous correlations may have played a large part. +They easily explain large deviations from an original type, without +requiring the assumption of too many steps. + +Monstrosities, as their name implies, are widely different in character +from natural species; they cannot, therefore, be adduced as evidence in the +investigation of the origin of species. There is no doubt that they may +have much in common as regards their manner of origin, and that the origin +of species, once understood, may lead to a better understanding of the +monstrosities. But the reverse is not true, at least not as regards the +main lines of development. Here, it is clear, monstrosities cannot have +played a part of any significance. + +Reversions, or atavistic changes, would seem to give a better support to +the theory of descent through modifications. These have been of paramount +importance on many lines of evolution of the animal as well as of the +vegetable kingdom. It is often assumed that monocotyledons are descended +from some lower group of dicotyledons, probably allied to that which +includes the buttercup family. On this view the monocotyledons must be +assumed to have lost the cambium and all its influence on secondary growth, +the differentiation of the flower into calyx and corolla, the second +cotyledon or seed-leaf and several other characters. Losses of characters +such as these may have been the result of abrupt changes, but this does not +prove that the characters themselves have been produced with equal +suddenness. On the contrary, Darwin shows very convincingly that a +modification may well be developed by a series of steps, and afterwards +suddenly disappear. Many monstrosities, such as those represented by +twisted stems, furnish direct proofs in support of this view, since they +are produced by the loss of one character and this loss implies secondary +changes in a large number of other organs and qualities. + +Darwin criticises in detail the hypothesis of great and abrupt changes and +comes to the conclusion that it does not give even a shadow of an +explanation of the origin of species. It is as improbable as it is +unnecessary. + +Sports and spontaneous variations must now be considered. It is well known +that they have produced a large number of fine horticultural varieties. +The cut-leaved maple and many other trees and shrubs with split leaves are +known to have been produced at a single step; this is true in the case of +the single-leaf strawberry plant and of the laciniate variety of the +greater celandine: many white flowers, white or yellow berries and +numerous other forms had a similar origin. But changes such as these do +not come under the head of adaptations, as they consist for the most part +in the loss of some quality or organ belonging to the species from which +they were derived. Darwin thinks it impossible to attribute to this cause +the innumerable structures, which are so well adapted to the habits of life +of each species. At the present time we should say that such adaptations +require progressive modifications, which are additions to the stock of +qualities already possessed by the ancestors, and cannot, therefore, be +explained on the ground of a supposed analogy with sports, which are for +the most part of a retrogressive nature. + +Excluding all these more or less sudden changes, there remains a long +series of gradations of variability, but all of these are not assumed by +Darwin to be equally fit for the production of new species. In the first +place, he disregards all mere temporary variations, such as size, albinism, +etc.; further, he points out that very many species have almost certainly +been produced by steps, not greater, and probably not very much smaller, +than those separating closely related varieties. For varieties are only +small species. Next comes the question of polymorphic species: their +occurrence seems to have been a source of much doubt and difficulty in +Darwin's mind, although at present it forms one of the main supports of the +prevailing explanation of the origin of new species. Darwin simply states +that this kind of variability seems to be of a peculiar nature; since +polymorphic species are now in a stable condition their occurrence gives no +clue as to the mode of origin of new species. Polymorphic species are the +expression of the result of previous variability acting on a large scale; +but they now simply consist of more or less numerous elementary species, +which, as far as we know, do not at present exhibit a larger degree of +variability than any other more uniform species. The vernal whitlow-grass +(Draba verna) and the wild pansy are the best known examples; both have +spread over almost the whole of Europe and are split up into hundreds of +elementary forms. These sub-species show no signs of any extraordinary +degree of variability, when cultivated under conditions necessary for the +exclusion of inter-crossing. Hooker has shown, in the case of some ferns +distributed over still wider areas, that the extinction of some of the +intermediate forms in such groups would suffice to justify the elevation of +the remaining types to the rank of distinct species. Polymorphic species +may now be regarded as the link which unites ordinary variability with the +historical production of species. But it does not appear that they had +this significance for Darwin; and, in fact, they exhibit no phenomena which +could explain the processes by which one species has been derived from +another. By thus narrowing the limits of the species-producing variability +Darwin was led to regard small deviations as the source from which natural +selection derives material upon which to act. But even these are not all +of the same type, and Darwin was well aware of the fact. + +It should here be pointed out that in order to be selected, a change must +first have been produced. This proposition, which now seems self-evident, +has, however, been a source of much difference of opinion among Darwin's +followers. The opinion that natural selection produces changes in useful +directions has prevailed for a long time. In other words, it was assumed +that natural selection, by the simple means of singling out, could induce +small and useful changes to increase and to reach any desired degree of +deviation from the original type. In my opinion this view was never +actually held by Darwin. It is in contradiction with the acknowledged aim +of all his work,--the explanation of the origin of species by means of +natural forces and phenomena only. Natural selection acts as a sieve; it +does not single out the best variations, but it simply destroys the larger +number of those which are, from some cause or another, unfit for their +present environment. In this way it keeps the strains up to the required +standard, and, in special circumstances, may even improve them. + +Returning to the variations which afford the material for the sieving- +action of natural selection, we may distinguish two main kinds. It is true +that the distinction between these was not clear at the time of Darwin, and +that he was unable to draw a sharp line between them. Nevertheless, in +many cases, he was able to separate them, and he often discussed the +question which of the two would be the real source of the differentiation +of species. Certain variations constantly occur, especially such as are +connected with size, weight, colour, etc. They are usually too small for +natural selection to act upon, having hardly any influence in the struggle +for life: others are more rare, occurring only from time to time, perhaps +once or twice in a century, perhaps even only once in a thousand years. +Moreover, these are of another type, not simply affecting size, number or +weight, but bringing about something new, which may be useful or not. +Whenever the variation is useful natural selection will take hold of it and +preserve it; in other cases the variation may either persist or disappear. + +In his criticism of miscellaneous objections brought forward against the +theory of natural selection after the publication of the first edition of +"The Origin of Species", Darwin stated his view on this point very +clearly:--"The doctrine of natural selection or the survival of the +fittest, which implies that when variations or individual differences of a +beneficial nature happen to arise, these will be preserved." ("Origin of +Species" (6th edition), page 169, 1882.) In this sentence the words +"HAPPEN TO ARISE" appear to me of prominent significance. They are +evidently due to the same general conception which prevailed in Darwin's +Pangenesis hypothesis. (Cf. de Vries, "Intracellulare Pangenesis", page +73, Jena, 1889, and "Die Mutationstheorie", I. page 63. Leipzig, 1901.) + +A distinction is indicated between ordinary fluctuations which are always +present, and such variations as "happen to arise" from time to time. ((I +think it right to point out that the interpretation of this passage from +the "Origin" by Professor de Vries is not accepted as correct either by Mr +Francis Darwin or by myself. We do not believe that Darwin intended to +draw any distinction between TWO TYPES of variation; the words "when +variations or individual differences of a beneficial nature happen to +arise" are not in our opinion meant to imply a distinction between ordinary +fluctuations and variations which "happen to arise," but we believe that +"or" is here used in the sense of ALIAS. With the permission of Professor +de Vries, the following extract is quoted from a letter in which he replied +to the objection raised to his reading of the passage in question: + +"As to your remarks on the passage on page 6, I agree that it is now +impossible to see clearly how far Darwin went in his distinction of the +different kinds of variability. Distinctions were only dimly guessed at by +him. But in our endeavour to arrive at a true conception of his view I +think that the chapter on Pangenesis should be our leading guide, and that +we should try to interpret the more difficult passages by that chapter. A +careful and often repeated study of the Pangenesis hypothesis has convinced +me that Darwin, when he wrote that chapter, was well aware that ordinary +variability has nothing to do with evolution, but that other kinds of +variation were necessary. In some chapters he comes nearer to a clear +distinction than in others. To my mind the expression 'happen to arise' is +the sharpest indication of his inclining in this direction. I am quite +convinced that numerous expressions in his book become much clearer when +looked at in this way." + +The statement in this passage that "Darwin was well aware that ordinary +variability has nothing to do with evolution, but that other kinds of +variation were necessary" is contradicted by many passages in the "Origin". +A.C.S.)) The latter afford the material for natural selection to act upon +on the broad lines of organic development, but the first do not. +Fortuitous variations are the species-producing kind, which the theory +requires; continuous fluctuations constitute, in this respect, a useless +type. + +Of late, the study of variability has returned to the recognition of this +distinction. Darwin's variations, which from time to time happen to arise, +are MUTATIONS, the opposite type being commonly designed fluctuations. A +large mass of facts, collected during the last few decades, has confirmed +this view, which in Darwin's time could only be expressed with much +reserve, and everyone knows that Darwin was always very careful in +statements of this kind. + +From the same chapter I may here cite the following paragraph: "Thus as I +am inclined to believe, morphological differences,...such as the +arrangement of the leaves, the divisions of the flower or of the ovarium, +the position of the ovules, etc.--first appeared in many cases as +fluctuating variations, which sooner or later became constant through the +nature of the organism and of the surrounding conditions...but NOT THROUGH +NATURAL SELECTION (The italics are mine (H. de V.).); for as these +morphological characters do not affect the welfare of the species, any +slight deviation in them could not have been governed or accumulated +through this latter agency." ("Origin of Species" (6th edition), page +176.) We thus see that in Darwin's opinion, all small variations had not +the same importance. In favourable circumstances some could become +constant, but others could not. + +Since the appearance of the first edition of "The Origin of Species" +fluctuating variability has been thoroughly studied by Quetelet. He +discovered the law, which governs all phenomena of organic life falling +under this head. It is a very simple law, and states that individual +variations follow the laws of probability. He proved it, in the first +place, for the size of the human body, using the measurements published for +Belgian recruits; he then extended it to various other measurements of +parts of the body, and finally concluded that it must be of universal +validity for all organic beings. It must hold true for all characters in +man, physical as well as intellectual and moral qualities; it must hold +true for the plant kingdom as well as for the animal kingdom; in short, it +must include the whole living world. + +Quetelet's law may be most easily studied in those cases where the +variability relates to measure, number and weight, and a vast number of +facts have since confirmed its exactness and its validity for all kinds of +organisms, organs and qualities. But if we examine it more closely, we +find that it includes just those minute variations, which, as Darwin +repeatedly pointed out, have often no significance for the origin of +species. In the phenomena, described by Quetelet's law nothing "happens to +arise"; all is governed by the common law, which states that small +deviations from the mean type are frequent, but that larger aberrations are +rare, the rarer as they are larger. Any degree of variation will be found +to occur, if only the number of individuals studied is large enough: it is +even possible to calculate before hand, how many specimens must be compared +in order to find a previously fixed degree of deviation. + +The variations, which from time to time happen to appear, are evidently not +governed by this law. They cannot, as yet, be produced at will: no +sowings of thousands or even of millions of plants will induce them, +although by such means the chance of their occurring will obviously be +increased. But they are known to occur, and to occur suddenly and +abruptly. They have been observed especially in horticulture, where they +are ranged in the large and ill-defined group called sports. Korschinsky +has collected all the evidence which horticultural literature affords on +this point. (S. Korschinsky, "Heterogenesis und Evolution", "Flora", Vol. +LXXXIX. pages 240-363, 1901.) Several cases of the first appearance of a +horticultural novelty have been recorded: this has always happened in the +same way; it appeared suddenly and unexpectedly without any definite +relation to previously existing variability. Dwarf types are one of the +commonest and most favourite varieties of flowering plants; they are not +originated by a repeated selection of the smallest specimens, but appear at +once, without intermediates and without any previous indication. In many +instances they are only about half the height of the original type, thus +constituting obvious novelties. So it is in other cases described by +Korschinsky: these sports or mutations are now recognised to be the main +source of varieties of horticultural plants. + +As already stated, I do not pretend that the production of horticultural +novelties is the prototype of the origin of new species in nature. I +assume that they are, as a rule, derived from the parent species by the +loss of some organ or quality, whereas the main lines of the evolution of +the animal and vegetable kingdom are of course determined by progressive +changes. Darwin himself has often pointed out this difference. But the +saltatory origin of horticultural novelties is as yet the simplest parallel +for natural mutations, since it relates to forms and phenomena, best known +to the general student of evolution. + +The point which I wish to insist upon is this. The difference between +small and ever present fluctuations and rare and more sudden variations was +clear to Darwin, although the facts known at his time were too meagre to +enable a sharp line to be drawn between these two great classes of +variability. Since Darwin's time evidence, which proves the correctness of +his view, has accumulated with increasing rapidity. Fluctuations +constitute one type; they are never absent and follow the law of chance, +but they do not afford the material from which to build new species. +Mutations, on the other hand, only happen to occur from time to time. They +do not necessarily produce greater changes than fluctuations, but such as +may become, or rather are from their very nature, constant. It is this +constancy which is the mark of specific characters, and on this basis every +new specific character may be assumed to have arisen by mutation. + +Some authors have tried to show that the theory of mutation is opposed to +Darwin's views. But this is erroneous. On the contrary, it is in fullest +harmony with the great principle laid down by Darwin. In order to be acted +upon by that complex of environmental forces, which Darwin has called +natural selection, the changes must obviously first be there. The manner +in which they are produced is of secondary importance and has hardly any +bearing on the theory of descent with modification. ("Life and Letters" +II. 125.) + +A critical survey of all the facts of variability of plants in nature as +well as under cultivation has led me to the conviction, that Darwin was +right in stating that those rare beneficial variations, which from time to +time happen to arise,--the now so-called mutations--are the real source of +progress in the whole realm of the organic world. + +II. EXTERNAL AND INTERNAL CAUSES OF VARIABILITY. + +All phenomena of animal and plant life are governed by two sets of causes; +one of these is external, the other internal. As a rule the internal +causes determine the nature of a phenomenon--what an organism can do and +what it cannot do. The external causes, on the other hand, decide when a +certain variation will occur, and to what extent its features may be +developed. + +As a very clear and wholly typical instance I cite the cocks-combs +(Celosia). This race is distinguished from allied forms by its faculty of +producing the well-known broad and much twisted combs. Every single +individual possesses this power, but all individuals do not exhibit it in +its most complete form. In some cases this faculty may not be exhibited at +the top of the main stem, although developed in lateral branches: in +others it begins too late for full development. Much depends upon +nourishment and cultivation, but almost always the horticulturist has to +single out the best individuals and to reject those which do not come up to +the standard. + +The internal causes are of a historical nature. The external ones may be +defined as nourishment and environment. In some cases nutrition is the +main factor, as, for instance, in fluctuating variability, but in natural +selection environment usually plays the larger part. + +The internal or historical causes are constant during the life-time of a +species, using the term species in its most limited sense, as designating +the so-called elementary species or the units out of which the ordinary +species are built up. These historical causes are simply the specific +characters, since in the origin of a species one or more of these must have +been changed, thus producing the characters of the new type. These changes +must, of course, also be due partly to internal and partly to external +causes. + +In contrast to these changes of the internal causes, the ordinary +variability which is exhibited during the life-time of a species is called +fluctuating variability. The name mutations or mutating variability is +then given to the changes in the specific characters. It is desirable to +consider these two main divisions of variability separately. + +In the case of fluctuations the internal causes, as well as the external +ones, are often apparent. The specific characters may be designated as the +mean about which the observed forms vary. Almost every character may be +developed to a greater or a less degree, but the variations of the single +characters producing a small deviation from the mean are usually the +commonest. The limits of these fluctuations may be called wide or narrow, +according to the way we look at them, but in numerous cases the extreme on +the favoured side hardly surpasses double the value of that on the other +side. The degree of this development, for every individual and for every +organ, is dependent mainly on nutrition. Better nourishment or an +increased supply of food produces a higher development; only it is not +always easy to determine which direction is the fuller and which is the +poorer one. The differences among individuals grown from different seeds +are described as examples of individual variability, but those which may be +observed on the same plant, or on cuttings, bulbs or roots derived from one +individual are referred to as cases of partial variability. Partial +variability, therefore, determines the differences among the flowers, +fruits, leaves or branches of one individual: in the main, it follows the +same laws as individual variability, but the position of a branch on a +plant also determines its strength, and the part it may take in the +nourishment of the whole. Composite flowers and umbels therefore have, as +a rule, fewer rays on weak branches than on the strong main ones. The +number of carpels in the fruits of poppies becomes very small on the weak +lateral branches, which are produced towards the autumn, as well as on +crowded, and therefore on weakened individuals. Double flowers follow the +same rule, and numerous other instances could easily be adduced. + +Mutating variability occurs along three main lines. Either a character may +disappear, or, as we now say, become latent; or a latent character may +reappear, reproducing thereby a character which was once prominent in more +or less remote ancestors. The third and most interesting case is that of +the production of quite new characters which never existed in the +ancestors. Upon this progressive mutability the main development of the +animal and vegetable kingdom evidently depends. In contrast to this, the +two other cases are called retrogressive and degressive mutability. In +nature retrogressive mutability plays a large part; in agriculture and in +horticulture it gives rise to numerous varieties, which have in the past +been preserved, either on account of their usefulness or beauty, or simply +as fancy-types. In fact the possession of numbers of varieties may be +considered as the main character of domesticated animals and cultivated +plants. + +In the case of retrogressive and degressive mutability the internal cause +is at once apparent, for it is this which causes the disappearance or +reappearance of some character. With progressive mutations the case is not +so simple, since the new character must first be produced and then +displayed. These two processes are theoretically different, but they may +occur together or after long intervals. The production of the new +character I call premutation, and the displaying mutation. Both of course +must have their external as well as their internal causes, as I have +repeatedly pointed out in my work on the Mutation Theory. ("Die +Mutationstheorie", 2 vols., Leipzig, 1901.) + +It is probable that nutrition plays as important a part among the external +causes of mutability as it does among those of fluctuating variability. +Observations in support of this view, however, are too scanty to allow of a +definite judgment. Darwin assumed an accumulative influence of external +causes in the case of the production of new varieties or species. The +accumulation might be limited to the life-time of a single individual, or +embrace that of two or more generations. In the end a degree of +instability in the equilibrium of one or more characters might be attained, +great enough for a character to give way under a small shock produced by +changed conditions of life. The character would then be thrown over from +the old state of equilibrium into a new one. + +Characters which happen to be in this state of unstable equilibrium are +called mutable. They may be either latent or active, being in the former +case derived from old active ones or produced as new ones (by the process, +designated premutation). They may be inherited in this mutable condition +during a long series of generations. I have shown that in the case of the +evening primrose of Lamarck this state of mutability must have existed for +at least half a century, for this species was introduced from Texas into +England about the year 1860, and since then all the strains derived from +its first distribution over the several countries of Europe show the same +phenomena in producing new forms. The production of the dwarf evening +primrose, or Oenothera nanella, is assumed to be due to one of the factors, +which determines the tall stature of the parent form, becoming latent; this +would, therefore, afford an example of retrogressive mutation. Most of the +other types of my new mutants, on the other hand, seem to be due to +progressive mutability. + +The external causes of this curious period of mutability are as yet wholly +unknown and can hardly be guessed at, since the origin of the Oenothera +Lamarckiana is veiled in mystery. The seeds, introduced into England about +1860, were said to have come from Texas, but whether from wild or from +cultivated plants we do not know. Nor has the species been recorded as +having been observed in the wild condition. This, however, is nothing +peculiar. The European types of Oenothera biennis and O. muricata are in +the same condition. The first is said to have been introduced from +Virginia, and the second from Canada, but both probably from plants +cultivated in the gardens of these countries. Whether the same elementary +species are still growing on those spots is unknown, mainly because the +different sub-species of the species mentioned have not been systematically +studied and distinguished. + +The origin of new species, which is in part the effect of mutability, is, +however, due mainly to natural selection. Mutability provides the new +characters and new elementary species. Natural selection, on the other +hand, decides what is to live and what to die. Mutability seems to be +free, and not restricted to previously determined lines. Selection, +however, may take place along the same main lines in the course of long +geological epochs, thus directing the development of large branches of the +animal and vegetable kingdom. In natural selection it is evident that +nutrition and environment are the main factors. But it is probable that, +while nutrition may be one of the main causes of mutability, environment +may play the chief part in the decisions ascribed to natural selection. +Relations to neighbouring plants and to injurious or useful animals, have +been considered the most important determining factors ever since the time +when Darwin pointed out their prevailing influence. + +From this discussion of the main causes of variability we may derive the +proposition that the study of every phenomenon in the field of heredity, of +variability, and of the origin of new species will have to be considered +from two standpoints; on one hand we have the internal causes, on the other +the external ones. Sometimes the first are more easily detected, in other +cases the latter are more accessible to investigation. But the complete +elucidation of any phenomenon of life must always combine the study of the +influence of internal with that of external causes. + +III. POLYMORPHIC VARIABILITY IN CEREALS. + +One of the propositions of Darwin's theory of the struggle for life +maintains that the largest amount of life can be supported on any area, by +great diversification or divergence in the structure and constitution of +its inhabitants. Every meadow and every forest affords a proof of this +thesis. The numerical proportion of the different species of the flora is +always changing according to external influences. Thus, in a given meadow, +some species will flower abundantly in one year and then almost disappear, +until, after a series of years, circumstances allow them again to multiply +rapidly. Other species, which have taken their places, will then become +rare. It follows from this principle, that notwithstanding the constantly +changing conditions, a suitable selection from the constituents of a meadow +will ensure a continued high production. But, although the principle is +quite clear, artificial selection has, as yet, done very little towards +reaching a really high standard. + +The same holds good for cereals. In ordinary circumstances a field will +give a greater yield, if the crop grown consists of a number of +sufficiently differing types. Hence it happens that almost all older +varieties of wheat are mixtures of more or less diverging forms. In the +same variety the numerical composition will vary from year to year, and in +oats this may, in bad years, go so far as to destroy more than half of the +harvest, the wind-oats (Avena fatua), which scatter their grain to the +winds as soon as it ripens, increasing so rapidly that they assume the +dominant place. A severe winter, a cold spring and other extreme +conditions of life will destroy one form more completely than another, and +it is evident that great changes in the numerical composition of the +mixture may thus be brought about. + +This mixed condition of the common varieties of cereals was well known to +Darwin. For him it constituted one of the many types of variability. It +is of that peculiar nature to which, in describing other groups, he applies +the term polymorphy. It does not imply that the single constituents of the +varieties are at present really changing their characters. On the other +hand, it does not exclude the possibility of such changes. It simply +states that observation shows the existence of different forms; how these +have originated is a question which it does not deal with. In his well- +known discussion of the variability of cereals, Darwin is mainly concerned +with the question, whether under cultivation they have undergone great +changes or only small ones. The decision ultimately depends on the +question, how many forms have originally been taken into cultivation. +Assuming five or six initial species, the variability must be assumed to +have been very large, but on the assumption that there were between ten and +fifteen types, the necessary range of variability is obviously much +smaller. But in regard to this point, we are of course entirely without +historical data. + +Few of the varieties of wheat show conspicuous differences, although their +number is great. If we compare the differentiating characters of the +smaller types of cereals with those of ordinary wild species, even within +the same genus or family, they are obviously much less marked. All these +small characters, however, are strictly inherited, and this fact makes it +very probable that the less obvious constituents of the mixtures in +ordinary fields must be constant and pure as long as they do not +intercross. Natural crossing is in most cereals a phenomenon of rare +occurrence, common enough to admit of the production of all possible hybrid +combinations, but requiring the lapse of a long series of years to reach +its full effect. + +Darwin laid great stress on this high amount of variability in the plants +of the same variety, and illustrated it by the experience of Colonel Le +Couteur ("On the Varieties, Properties, and Classification of Wheat", +Jersey, 1837.) on his farm on the isle of Jersey, who cultivated upwards of +150 varieties of wheat, which he claimed were as pure as those of any other +agriculturalist. But Professor La Gasca of Madrid, who visited him, drew +attention to aberrant ears, and pointed out, that some of them might be +better yielders than the majority of plants in the crop, whilst others +might be poor types. Thence he concluded that the isolation of the better +ones might be a means of increasing his crops. Le Couteur seems to have +considered the constancy of such smaller types after isolation as +absolutely probable, since he did not even discuss the possibility of their +being variable or of their yielding a changeable or mixed progeny. This +curious fact proves that he considered the types, discovered in his fields +by La Gasca to be of the same kind as his other varieties, which until that +time he had relied upon as being pure and uniform. Thus we see, that for +him, the variability of cereals was what we now call polymorphy. He looked +through his fields for useful aberrations, and collected twenty-three new +types of wheat. He was, moreover, clear about one point, which, on being +rediscovered after half a century, has become the starting-point for the +new Swedish principle of selecting agricultural plants. It was the +principle of single-ear sowing, instead of mixing the grains of all the +selected ears together. By sowing each ear on a separate plot he intended +not only to multiply them, but also to compare their value. This +comparison ultimately led him to the choice of some few valuable sorts, one +of which, the "Bellevue de Talavera," still holds its place among the +prominent sorts of wheat cultivated in France. This variety seems to be +really a uniform type, a quality very useful under favourable conditions of +cultivation, but which seems to have destroyed its capacity for further +improvement by selection. + +The principle of single-ear sowing, with a view to obtain pure and uniform +strains without further selection, has, until a few years ago, been almost +entirely lost sight of. Only a very few agriculturists have applied it: +among these are Patrick Shirreff ("Die Verbesserung der Getreide-Arten", +translated by R. Hesse, Halle, 1880.) in Scotland and Willet M. Hays +("Wheat, varieties, breeding, cultivation", Univ. Minnesota, Agricultural +Experimental Station, Bull. no. 62, 1899.) in Minnesota. Patrick Shirreff +observed the fact, that in large fields of cereals, single plants may from +time to time be found with larger ears, which justify the expectation of a +far greater yield. In the course of about twenty-five years he isolated in +this way two varieties of wheat and two of oats. He simply multiplied them +as fast as possible, without any selection, and put them on the market. + +Hays was struck by the fact that the yield of wheat in Minnesota was far +beneath that in the neighbouring States. The local varieties were Fife and +Blue Stem. They gave him, on inspection, some better specimens, +"phenomenal yielders" as he called them. These were simply isolated and +propagated, and, after comparison with the parent-variety and with some +other selected strains of less value, were judged to be of sufficient +importance to be tested by cultivation all over the State of Minnesota. +They have since almost supplanted the original types, at least in most +parts of the State, with the result that the total yield of wheat in +Minnesota is said to have been increased by about a million dollars yearly. + +Definite progress in the method of single-ear sowing has, however, been +made only recently. It had been foreshadowed by Patrick Shirreff, who +after the production of the four varieties already mentioned, tried to +carry out his work on a larger scale, by including numerous minor +deviations from the main type. He found by doing so that the chances of +obtaining a better form were sufficiently increased to justify the trial. +But it was Nilsson who discovered the almost inexhaustible polymorphy of +cereals and other agricultural crops and made it the starting-point for a +new and entirely trustworthy method of the highest utility. By this means +he has produced during the last fifteen years a number of new and valuable +races, which have already supplanted the old types on numerous farms in +Sweden and which are now being introduced on a large scale into Germany and +other European countries. + +It is now twenty years since the station at Svalof was founded. During the +first period of its work, embracing about five years, selection was +practised on the principle which was then generally used in Germany. In +order to improve a race a sample of the best ears was carefully selected +from the best fields of the variety. These ears were considered as +representatives of the type under cultivation, and it was assumed that by +sowing their grains on a small plot a family could be obtained, which could +afterwards be improved by a continuous selection. Differences between the +collected ears were either not observed or disregarded. At Svalof this +method of selection was practised on a far larger scale than on any German +farm, and the result was, broadly speaking, the same. This may be stated +in the following words: improvement in a few cases, failure in all the +others. Some few varieties could be improved and yielded excellent new +types, some of which have since been introduced into Swedish agriculture +and are now prominent races in the southern and middle parts of the +country. But the station had definite aims, and among them was the +improvement of the Chevalier barley. This, in Middle Sweden, is a fine +brewer's barley, but liable to failure during unfavourable summers on +account of its slender stems. It was selected with a view of giving it +stiffer stems, but in spite of all the care and work bestowed upon it no +satisfactory result was obtained. + +This experience, combined with a number of analogous failures, could not +fail to throw doubt upon the whole method. It was evident that good +results were only exceptions, and that in most cases the principle was not +one that could be relied upon. The exceptions might be due to unknown +causes, and not to the validity of the method; it became therefore of much +more interest to search for the causes than to continue the work along +these lines. + +In the year 1892 a number of different varieties of cereals were cultivated +on a large scale and a selection was again made from them. About two +hundred samples of ears were chosen, each apparently constituting a +different type. Their seeds were sown on separate plots and manured and +treated as much as possible in the same manner. The plots were small and +arranged in rows so as to facilitate the comparison of allied types. +During the whole period of growth and during the ripening of the ears the +plots were carefully studied and compared: they were harvested separately; +ears and kernels were counted and weighed, and notes were made concerning +layering, rust and other cereal pests. + +The result of this experiment was, in the main, no distinct improvement. +Nilsson was especially struck by the fact that the plots, which should +represent distinct types, were far from uniform. Many of them were as +multiform as the fields from which the parent-ears were taken. Others +showed variability in a less degree, but in almost all of them it was clear +that a pure race had not been obtained. The experiment was a fair one, +inasmuch as it demonstrated the polymorphic variability of cereals beyond +all doubt and in a degree hitherto unsuspected; but from the standpoint of +the selectionist it was a failure. Fortunately there were, however, one or +two exceptions. A few lots showed a perfect uniformity in regard to all +the stalks and ears: these were small families. This fact suggested the +idea that each might have been derived from a single ear. During the +selection in the previous summer, Nilsson had tried to find as many ears as +possible of each new type which he recognised in his fields. But the +variability of his crops was so great, that he was rarely able to include +more than two or three ears in the same group, and, in a few cases, he +found only one representative of the supposed type. It might, therefore, +be possible that those small uniform plots were the direct progeny of ears, +the grains of which had not been mixed with those from other ears before +sowing. Exact records had, of course, been kept of the chosen samples, and +the number of ears had been noted in each case. It was, therefore, +possible to answer the question and it was found that those plots alone +were uniform on which the kernels of one single ear only had been sown. +Nilsson concluded that the mixture of two or more ears in a single sowing +might be the cause of the lack of uniformity in the progeny. Apparently +similar ears might be different in their progeny. + +Once discovered, this fact was elevated to the rank of a leading principle +and tested on as large a scale as possible. The fields were again +carefully investigated and every single ear, which showed a distinct +divergence from the main type in one character or another, was selected. A +thousand samples were chosen, but this time each sample consisted of one +ear only. Next year, the result corresponded to the expectation. +Uniformity prevailed almost everywhere; only a few lots showed a +discrepancy, which might be ascribed to the accidental selection of hybrid +ears. It was now clear that the progeny of single ears was, as a rule, +pure, whereas that of mixed ears was impure. The single-ear selection or +single-ear sowing, which had fallen into discredit in Germany and elsewhere +in Europe, was rediscovered. It proved to be the only trustworthy +principle of selection. Once isolated, such single-parent races are +constant from seed and remain true to their type. No further selection is +needed; they have simply to be multiplied and their real value tested. + +Patrick Shirreff, in his early experiments, Le Couteur, Hays and others had +observed the rare occurrence of exceptionally good yielders and the value +of their isolation to the agriculturist. The possibility of error in the +choice of such striking specimens and the necessity of judging their value +by their progeny were also known to these investigators, but they had not +the slightest idea of all the possibilities suggested by their principle. +Nilsson, who is a botanist as well as an agriculturist, discovered that, +besides these exceptionably good yielders, every variety of a cereal +consists of hundreds of different types, which find the best conditions for +success when grown together, but which, after isolation, prove to be +constant. Their preference for mixed growth is so definite, that once +isolated, their claims on manure and treatment are found to be much higher +than those of the original mixed variety. Moreover, the greatest care is +necessary to enable them to retain their purity, and as soon as they are +left to themselves they begin to deteriorate through accidental crosses and +admixtures and rapidly return to the mixed condition. + +Reverting now to Darwin's discussion of the variability of cereals, we may +conclude that subsequent investigation has proved it to be exactly of the +kind which he describes. The only difference is that in reality it reaches +a degree, quite unexpected by Darwin and his contemporaries. But it is +polymorphic variability in the strictest sense of the word. How the single +constituents of a variety originate we do not see. We may assume, and +there can hardly be a doubt about the truth of the assumption, that a new +character, once produced, will slowly but surely be combined through +accidental crosses with a large number of previously existing types, and so +will tend to double the number of the constituents of the variety. But +whether it first appears suddenly or whether it is only slowly evolved we +cannot determine. It would, of course, be impossible to observe either +process in such a mixture. Only cultures of pure races, of single-parent +races as we have called them, can afford an opportunity for this kind of +observation. In the fields of Svalof new and unexpected qualities have +recently been seen, from time to time, to appear suddenly. These +characters are as distinct as the older ones and appear to be constant from +the moment of their origin. + +Darwin has repeatedly insisted that man does not cause variability. He +simply selects the variations given to him by the hand of nature. He may +repeat this process in order to accumulate different new characters in the +same family, thus producing varieties of a higher order. This process of +accumulation would, if continued for a longer time, lead to the +augmentation of the slight differences characteristic of varieties into the +greater differences characteristic of species and genera. It is in this +way that horticultural and agricultural experience contribute to the +problem of the conversion of varieties into species, and to the explanation +of the admirable adaptations of each organism to its complex conditions of +life. In the long run new forms, distinguished from their allies by quite +a number of new characters, would, by the extermination of the older +intermediates, become distinct species. + +Thus we see that the theory of the origin of species by means of natural +selection is quite independent of the question, how the variations to be +selected arise. They may arise slowly, from simple fluctuations, or +suddenly, by mutations; in both cases natural selection will take hold of +them, will multiply them if they are beneficial, and in the course of time +accumulate them, so as to produce that great diversity of organic life, +which we so highly admire. + +Darwin has left the decision of this difficult and obviously subordinate +point to his followers. But in his Pangenesis hypothesis he has given us +the clue for a close study and ultimate elucidation of the subject under +discussion. + + +V. HEREDITY AND VARIATION IN MODERN LIGHTS. + +By W. BATESON, M.A., F.R.S. + +Professor of Biology in the University of Cambridge. + +Darwin's work has the property of greatness in that it may be admired from +more aspects than one. For some the perception of the principle of Natural +Selection stands out as his most wonderful achievement to which all the +rest is subordinate. Others, among whom I would range myself, look up to +him rather as the first who plainly distinguished, collected, and +comprehensively studied that new class of evidence from which hereafter a +true understanding of the process of Evolution may be developed. We each +prefer our own standpoint of admiration; but I think that it will be in +their wider aspect that his labours will most command the veneration of +posterity. + +A treatise written to advance knowledge may be read in two moods. The +reader may keep his mind passive, willing merely to receive the impress of +the writer's thought; or he may read with his attention strained and alert, +asking at every instant how the new knowledge can be used in a further +advance, watching continually for fresh footholds by which to climb higher +still. Of Shelley it has been said that he was a poet for poets: so +Darwin was a naturalist for naturalists. It is when his writings are used +in the critical and more exacting spirit with which we test the outfit for +our own enterprise that we learn their full value and strength. Whether we +glance back and compare his performance with the efforts of his +predecessors, or look forward along the course which modern research is +disclosing, we shall honour most in him not the rounded merit of finite +accomplishment, but the creative power by which he inaugurated a line of +discovery endless in variety and extension. Let us attempt thus to see his +work in true perspective between the past from which it grew, and the +present which is its consequence. Darwin attacked the problem of Evolution +by reference to facts of three classes: Variation; Heredity; Natural +Selection. His work was not as the laity suppose, a sudden and unheralded +revelation, but the first fruit of a long and hitherto barren controversy. +The occurrence of variation from type, and the hereditary transmission of +such variation had of course been long familiar to practical men, and +inferences as to the possible bearing of those phenomena on the nature of +specific difference had been from time to time drawn by naturalists. +Maupertuis, for example, wrote "Ce qui nous reste a examiner, c'est comment +d'un seul individu, il a pu naitre tant d'especes si differentes." And +again "La Nature contient le fonds de toutes ces varietes: mais le hasard +ou l'art les mettent en oeuvre. C'est ainsi que ceux dont l'industrie +s'applique a satisfaire le gout des curieux, sont, pour ainsi dire, +creatures d'especes nouvelles." ("Venus Physique, contenant deux +Dissertations, l'une sur l'origine des Hommes et des Animaux: Et l'autre +sur l'origine des Noirs" La Haye, 1746, pages 124 and 129. For an +introduction to the writings of Maupertuis I am indebted to an article by +Professor Lovejoy in "Popular Sci. Monthly", 1902.) + +Such passages, of which many (though few so emphatic) can be found in +eighteenth century writers, indicate a true perception of the mode of +Evolution. The speculations hinted at by Buffon (For the fullest account +of the views of these pioneers of Evolution, see the works of Samuel +Butler, especially "Evolution, Old and New" (2nd edition) 1882. Butler's +claims on behalf of Buffon have met with some acceptance; but after reading +what Butler has said, and a considerable part of Buffon's own works, the +word "hinted" seems to me a sufficiently correct description of the part he +played. It is interesting to note that in the chapter on the Ass, which +contains some of his evolutionary passages, there is a reference to +"plusieurs idees tres-elevees sur la generation" contained in the Letters +of Maupertuis.), developed by Erasmus Darwin, and independently proclaimed +above all by Lamarck, gave to the doctrine of descent a wide renown. The +uniformitarian teaching which Lyell deduced from geological observation had +gained acceptance. The facts of geographical distribution (See especially +W. Lawrence, "Lectures on Physiology", London, 1823, pages 213 f.) had been +shown to be obviously inconsistent with the Mosaic legend. Prichard, and +Lawrence, following the example of Blumenbach, had successfully +demonstrated that the races of Man could be regarded as different forms of +one species, contrary to the opinion up till then received. These +treatises all begin, it is true, with a profound obeisance to the sons of +Noah, but that performed, they continue on strictly modern lines. The +question of the mutability of species was thus prominently raised. + +Those who rate Lamarck no higher than did Huxley in his contemptuous phrase +"buccinator tantum," will scarcely deny that the sound of the trumpet had +carried far, or that its note was clear. If then there were few who had +already turned to evolution with positive conviction, all scientific men +must at least have known that such views had been promulgated; and many +must, as Huxley says, have taken up his own position of "critical +expectancy." (See the chapter contributed to the "Life and Letters of +Charles Darwin" II. page 195. I do not clearly understand the sense in +which Darwin wrote (Autobiography, ibid. I. page 87): "It has sometimes +been said that the success of the "Origin" proved 'that the subject was in +the air,' or 'that men's minds were prepared for it.' I do not think that +this is strictly true, for I occasionally sounded not a few naturalists, +and never happened to come across a single one who seemed to doubt about +the permanence of species." This experience may perhaps have been an +accident due to Darwin's isolation. The literature of the period abounds +with indications of "critical expectancy." A most interesting expression +of that feeling is given in the charming account of the "Early Days of +Darwinism" by Alfred Newton, "Macmillan's Magazine", LVII. 1888, page 241. +He tells how in 1858 when spending a dreary summer in Iceland, he and his +friend, the ornithologist John Wolley, in default of active occupation, +spent their days in discussion. "Both of us taking a keen interest in +Natural History, it was but reasonable that a question, which in those days +was always coming up wherever two or more naturalists were gathered +together, should be continually recurring. That question was, 'What is a +species?' and connected therewith was the other question, 'How did a +species begin?'...Now we were of course fairly well acquainted with what +had been published on these subjects." He then enumerates some of these +publications, mentioning among others T. Vernon Wollaston's "Variation of +Species"--a work which has in my opinion never been adequately appreciated. +He proceeds: "Of course we never arrived at anything like a solution of +these problems, general or special, but we felt very strongly that a +solution ought to be found, and that quickly, if the study of Botany and +Zoology was to make any great advance." He then describes how on his +return home he received the famous number of the "Linnean Journal" on a +certain evening. "I sat up late that night to read it; and never shall I +forget the impression it made upon me. Herein was contained a perfectly +simple solution of all the difficulties which had been troubling me for +months past...I went to bed satisfied that a solution had been found.") + +Why, then, was it, that Darwin succeeded where the rest had failed? The +cause of that success was two-fold. First, and obviously, in the principle +of Natural Selection he had a suggestion which would work. It might not go +the whole way, but it was true as far as it went. Evolution could thus in +great measure be fairly represented as a consequence of demonstrable +processes. Darwin seldom endangers the mechanism he devised by putting on +it strains much greater than it can bear. He at least was under no +illusion as to the omnipotence of Selection; and he introduces none of the +forced pleading which in recent years has threatened to discredit that +principle. + +For example, in the latest text of the "Origin" ("Origin", (6th edition +(1882), page 421.) we find him saying: + +"But as my conclusions have lately been much misrepresented, and it has +been stated that I attribute the modification of species exclusively to +natural selection, I may be permitted to remark that in the first edition +of this work, and subsequently, I placed in a most conspicuous position-- +namely, at the close of the Introduction--the following words: 'I am +convinced that natural selection has been the main but not the exclusive +means of modification.'" + +But apart from the invention of this reasonable hypothesis, which may well, +as Huxley estimated, "be the guide of biological and psychological +speculation for the next three or four generations," Darwin made a more +significant and imperishable contribution. Not for a few generations, but +through all ages he should be remembered as the first who showed clearly +that the problems of Heredity and Variation are soluble by observation, and +laid down the course by which we must proceed to their solution. (Whatever +be our estimate of the importance of Natural Selection, in this we all +agree. Samuel Butler, the most brilliant, and by far the most interesting +of Darwin's opponents--whose works are at length emerging from oblivion--in +his Preface (1882) to the 2nd edition of "Evolution, Old and New", repeats +his earlier expression of homage to one whom he had come to regard as an +enemy: "To the end of time, if the question be asked, 'Who taught people +to believe in Evolution?' the answer must be that it was Mr. Darwin. This +is true, and it is hard to see what palm of higher praise can be awarded to +any philosopher.") The moment of inspiration did not come with the reading +of Malthus, but with the opening of the "first note-book on Transmutation +of Species." ("Life and Letters", I. pages 276 and 83.) Evolution is a +process of Variation and Heredity. The older writers, though they had some +vague idea that it must be so, did not study Variation and Heredity. +Darwin did, and so begat not a theory, but a science. + +The extent to which this is true, the scientific world is only beginning to +realise. So little was the fact appreciated in Darwin's own time that the +success of his writings was followed by an almost total cessation of work +in that special field. Of the causes which led to this remarkable +consequence I have spoken elsewhere. They proceeded from circumstances +peculiar to the time; but whatever the causes there is no doubt that this +statement of the result is historically exact, and those who make it their +business to collect facts elucidating the physiology of Heredity and +Variation are well aware that they will find little to reward their quest +in the leading scientific Journals of the Darwinian epoch. + +In those thirty years the original stock of evidence current and in +circulation even underwent a process of attrition. As in the story of the +Eastern sage who first wrote the collected learning of the universe for his +sons in a thousand volumes, and by successive compression and burning +reduced them to one, and from this by further burning distilled the single +ejaculation of the Faith, "There is no god but God and Mohamed is the +Prophet of God," which was all his maturer wisdom deemed essential:--so in +the books of that period do we find the corpus of genetic knowledge dwindle +to a few prerogative instances, and these at last to the brief formula of +an unquestioned creed. + +And yet in all else that concerns biological science this period was, in +very truth, our Golden Age, when the natural history of the earth was +explored as never before; morphology and embryology were exhaustively +ransacked; the physiology of plants and animals began to rival chemistry +and physics in precision of method and in the rapidity of its advances; and +the foundations of pathology were laid. + +In contrast with this immense activity elsewhere the neglect which befel +the special physiology of Descent, or Genetics as we now call it, is +astonishing. This may of course be interpreted as meaning that the +favoured studies seemed to promise a quicker return for effort, but it +would be more true to say that those who chose these other pursuits did so +without making any such comparison; for the idea that the physiology of +Heredity and Variation was a coherent science, offering possibilities of +extraordinary discovery, was not present to their minds at all. In a word, +the existence of such a science was well nigh forgotten. It is true that +in ancillary periodicals, as for example those that treat of entomology or +horticulture, or in the writings of the already isolated systematists (This +isolation of the systematists is the one most melancholy sequela of +Darwinism. It seems an irony that we should read in the peroration to the +"Origin" that when the Darwinian view is accepted "Systematists will be +able to pursue their labours as at present; but they will not be +incessantly haunted by the shadowy doubt whether this or that form be a +true species. This, I feel sure, and I speak after experience, will be no +slight relief. The endless disputes whether or not some fifty species of +British brambles are good species will cease." "Origin", 6th edition +(1882), page 425. True they have ceased to attract the attention of those +who lead opinion, but anyone who will turn to the literature of systematics +will find that they have not ceased in any other sense. Should there not +be something disquieting in the fact that among the workers who come most +into contact with specific differences, are to be found the only men who +have failed to be persuaded of the unreality of those differences?), +observations with this special bearing were from time to time related, but +the class of fact on which Darwin built his conceptions of Heredity and +Variation was not seen in the highways of biology. It formed no part of +the official curriculum of biological students, and found no place among +the subjects which their teachers were investigating. + +During this period nevertheless one distinct advance was made, that with +which Weismann's name is prominently connected. In Darwin's genetic scheme +the hereditary transmission of parental experience and its consequences +played a considerable role. Exactly how great that role was supposed to +be, he with his habitual caution refrained from specifying, for the +sufficient reason that he did not know. Nevertheless much of the process +of Evolution, especially that by which organs have become degenerate and +rudimentary, was certainly attributed by Darwin to such inheritance, though +since belief in the inheritance of acquired characters fell into disrepute, +the fact has been a good deal overlooked. The "Origin" without "use and +disuse" would be a materially different book. A certain vacillation is +discernible in Darwin's utterances on this question, and the fact gave to +the astute Butler an opportunity for his most telling attack. The +discussion which best illustrates the genetic views of the period arose in +regard to the production of the rudimentary condition of the wings of many +beetles in the Madeira group of islands, and by comparing passages from the +"Origin" (6th edition pages 109 and 401. See Butler, "Essays on Life, Art, +and Science", page 265, reprinted 1908, and "Evolution, Old and New", +chapter XXII. (2nd edition), 1882.) Butler convicts Darwin of saying first +that this condition was in the main the result of Selection, with disuse +aiding, and in another place that the main cause of degeneration was +disuse, but that Selection had aided. To Darwin however I think the point +would have seemed one of dialectics merely. To him the one paramount +purpose was to show that somehow an Evolution by means of Variation and +Heredity might have brought about the facts observed, and whether they had +come to pass in the one way or the other was a matter of subordinate +concern. + + +To us moderns the question at issue has a diminished significance. For +over all such debates a change has been brought by Weismann's challenge for +evidence that use and disuse have any transmitted effects at all. Hitherto +the transmission of many acquired characteristics had seemed to most +naturalists so obvious as not to call for demonstration. (W. Lawrence was +one of the few who consistently maintained the contrary opinion. Prichard, +who previously had expressed himself in the same sense, does not, I believe +repeat these views in his later writings, and there are signs that he came +to believe in the transmission of acquired habits. See Lawrence, "Lect. +Physiol." 1823, pages 436-437, 447 Prichard, Edin. Inaug. Disp. 1808 (not +seen by me), quoted ibid. and "Nat. Hist. Man", 1843, pages 34 f.) +Weismann's demand for facts in support of the main proposition revealed at +once that none having real cogency could be produced. The time-honoured +examples were easily shown to be capable of different explanations. A few +certainly remain which cannot be so summarily dismissed, but--though it is +manifestly impossible here to do justice to such a subject--I think no one +will dispute that these residual and doubtful phenomena, whatever be their +true nature, are not of a kind to help us much in the interpretation of any +of those complex cases of adaptation which on the hypothesis of unguided +Natural Selection are especially difficult to understand. Use and disuse +were invoked expressly to help us over these hard places; but whatever +changes can be induced in offspring by direct treatment of the parents, +they are not of a kind to encourage hope of real assistance from that +quarter. It is not to be denied that through the collapse of this second +line of argument the Selection hypothesis has had to take an increased and +perilous burden. Various ways of meeting the difficulty have been +proposed, but these mostly resolve themselves into improbable attempts to +expand or magnify the powers of Natural Selection. + +Weismann's interpellation, though negative in purpose, has had a lasting +and beneficial effect, for through his thorough demolition of the old loose +and distracting notions of inherited experience, the ground has been +cleared for the construction of a true knowledge of heredity based on +experimental fact. + +In another way he made a contribution of a more positive character, for his +elaborate speculations as to the genetic meaning of cytological appearances +have led to a minute investigation of the visible phenomena occurring in +those divisions by which germ-cells arise. Though the particular views he +advocated have very largely proved incompatible with the observed facts of +heredity, yet we must acknowledge that it was chiefly through the stimulus +of Weismann's ideas that those advances in cytology were made; and though +the doctrine of the continuity of germ-plasm cannot be maintained in the +form originally propounded, it is in the main true and illuminating. (It +is interesting to see how nearly Butler was led by natural penetration, and +from absolutely opposite conclusions, back to this underlying truth: "So +that each ovum when impregnate should be considered not as descended from +its ancestors, but as being a continuation of the personality of every ovum +in the chain of its ancestry, which every ovum IT ACTUALLY IS quite as +truly as the octogenarian IS the same identity with the ovum from which he +has been developed. This process cannot stop short of the primordial cell, +which again will probably turn out to be but a brief resting-place. We +therefore prove each one of us to BE ACTUALLY the primordial cell which +never died nor dies, but has differentiated itself into the life of the +world, all living beings whatever, being one with it and members one of +another," "Life and Habit", 1878, page 86.) Nevertheless in the present +state of knowledge we are still as a rule quite unable to connect +cytological appearances with any genetic consequence and save in one +respect (obviously of extreme importance--to be spoken of later) the two +sets of phenomena might, for all we can see, be entirely distinct. + +I cannot avoid attaching importance to this want of connection between the +nuclear phenomena and the features of bodily organisation. All attempts to +investigate Heredity by cytological means lie under the disadvantage that +it is the nuclear changes which can alone be effectively observed. +Important as they must surely be, I have never been persuaded that the rest +of the cell counts for nothing. What we know of the behaviour and +variability of chromosomes seems in my opinion quite incompatible with the +belief that they alone govern form, and are the sole agents responsible in +heredity. (This view is no doubt contrary to the received opinion. I am +however interested to see it lately maintained by Driesch ("Science and +Philosophy of the Organism", London, 1907, page 233), and from the recent +observations of Godlewski it has received distinct experimental support.) + +If, then, progress was to be made in Genetics, work of a different kind was +required. To learn the laws of Heredity and Variation there is no other +way than that which Darwin himself followed, the direct examination of the +phenomena. A beginning could be made by collecting fortuitous observations +of this class, which have often thrown a suggestive light, but such +evidence can be at best but superficial and some more penetrating +instrument of research is required. This can only be provided by actual +experiments in breeding. + +The truth of these general considerations was becoming gradually clear to +many of us when in 1900 Mendel's work was rediscovered. Segregation, a +phenomenon of the utmost novelty, was thus revealed. From that moment not +only in the problem of the origin of species, but in all the great problems +of biology a new era began. So unexpected was the discovery that many +naturalists were convinced it was untrue, and at once proclaimed Mendel's +conclusions as either altogether mistaken, or if true, of very limited +application. Many fantastic notions about the workings of Heredity had +been asserted as general principles before: this was probably only another +fancy of the same class. + +Nevertheless those who had a preliminary acquaintance with the facts of +Variation were not wholly unprepared for some such revelation. The +essential deduction from the discovery of segregation was that the +characters of living things are dependent on the presence of definite +elements or factors, which are treated as units in the processes of +Heredity. These factors can thus be recombined in various ways. They act +sometimes separately, and sometimes they interact in conjunction with each +other, producing their various effects. All this indicates a definiteness +and specific order in heredity, and therefore in variation. This order +cannot by the nature of the case be dependent on Natural Selection for its +existence, but must be a consequence of the fundamental chemical and +physical nature of living things. The study of Variation had from the +first shown that an orderliness of this kind was present. The bodies and +the properties of living things are cosmic, not chaotic. No matter how low +in the scale we go, never do we find the slightest hint of a diminution in +that all-pervading orderliness, nor can we conceive an organism existing +for a moment in any other state. Moreover not only does this order prevail +in normal forms, but again and again it is to be seen in newly-sprung +varieties, which by general consent cannot have been subjected to a +prolonged Selection. The discovery of Mendelian elements admirably +coincided with and at once gave a rationale of these facts. Genetic +Variation is then primarily the consequence of additions to, or omissions +from, the stock of elements which the species contains. The further +investigation of the species-problem must thus proceed by the analytical +method which breeding experiments provide. + +In the nine years which have elapsed since Mendel's clue became generally +known, progress has been rapid. We now understand the process by which a +polymorphic race maintains its polymorphism. When a family consists of +dissimilar members, given the numerical proportions in which these members +are occurring, we can represent their composition symbolically and state +what types can be transmitted by the various members. The difficulty of +the "swamping effects of intercrossing" is practically at an end. Even the +famous puzzle of sex-limited inheritance is solved, at all events in its +more regular manifestations, and we know now how it is brought about that +the normal sisters of a colour-blind man can transmit the colour-blindness +while his normal brothers cannot transmit it. + +We are still only on the fringe of the inquiry. It can be seen extending +and ramifying in many directions. To enumerate these here would be +impossible. A whole new range of possibilities is being brought into view +by study of the interrelations between the simple factors. By following up +the evidence as to segregation, indications have been obtained which can +only be interpreted as meaning that when many factors are being +simultaneously redistributed among the germ-cells, certain of them exert +what must be described as a repulsion upon other factors. We cannot +surmise whither this discovery may lead. + +In the new light all the old problems wear a fresh aspect. Upon the +question of the nature of Sex, for example, the bearing of Mendelian +evidence is close. Elsewhere I have shown that from several sets of +parallel experiments the conclusion is almost forced upon us that, in the +types investigated, of the two sexes the female is to be regarded as +heterozygous in sex, containing one unpaired dominant element, while the +male is similarly homozygous in the absence of that element. (In other +words, the ova are each EITHER female, OR male (i.e. non-female), but the +sperms are all non-female.) It is not a little remarkable that on this +point--which is the only one where observations of the nuclear processes of +gameto-genesis have yet been brought into relation with the visible +characteristics of the organisms themselves--there should be diametrical +opposition between the results of breeding experiments and those derived +from cytology. + +Those who have followed the researches of the American school will be aware +that, after it had been found in certain insects that the spermatozoa were +of two kinds according as they contained or did not contain the accessory +chromosome, E.B. Wilson succeeded in proving that the sperms possessing +this accessory body were destined to form FEMALES on fertilisation, while +sperms without it form males, the eggs being apparently indifferent. +Perhaps the most striking of all this series of observations is that lately +made by T.H. Morgan (Morgan, "Proc. Soc. Exp. Biol. Med." V. 1908, and von +Baehr, "Zool. Anz." XXXII. page 507, 1908.), since confirmed by von Baehr, +that in a Phylloxeran two kinds of spermatids are formed, respectively with +and without an accessory (in this case, DOUBLE) chromosome. Of these, only +those possessing the accessory body become functional spermatozoa, the +others degenerating. We have thus an elucidation of the puzzling fact that +in these forms fertilisation results in the formation of FEMALES only. How +the males are formed--for of course males are eventually produced by the +parthenogenetic females--we do not know. + +If the accessory body is really to be regarded as bearing the factor for +femaleness, then in Mendelian terms female is DD and male is DR. The eggs +are indifferent and the spermatozoa are each male, OR female. But +according to the evidence derived from a study of the sex-limited descent +of certain features in other animals the conclusion seems equally clear +that in them female must be regarded as DR and male as RR. The eggs are +thus each either male or female and the spermatozoa are indifferent. How +this contradictory evidence is to be reconciled we do not yet know. The +breeding work concerns fowls, canaries, and the Currant moth (Abraxas +grossulariata). The accessory chromosome has been now observed in most of +the great divisions of insects (As Wilson has proved, the unpaired body is +not a universal feature even in those orders in which it has been observed. +Nearly allied types may differ. In some it is altogether unpaired. In +others it is paired with a body of much smaller size, and by selection of +various types all gradations can be demonstrated ranging to the condition +in which the members of the pair are indistinguishable from each other.), +except, as it happens, Lepidoptera. At first sight it seems difficult to +suppose that a feature apparently so fundamental as sex should be +differently constituted in different animals, but that seems at present the +least improbable inference. I mention these two groups of facts as +illustrating the nature and methods of modern genetic work. We must +proceed by minute and specific analytical investigation. Wherever we look +we find traces of the operation of precise and specific rules. + +In the light of present knowledge it is evident that before we can attack +the Species-problem with any hope of success there are vast arrears to be +made up. He would be a bold man who would now assert that there was no +sense in which the term Species might not have a strict and concrete +meaning in contradistinction to the term Variety. We have been taught to +regard the difference between species and variety as one of degree. I +think it unlikely that this conclusion will bear the test of further +research. To Darwin the question, What is a variation? presented no +difficulties. Any difference between parent and offspring was a variation. +Now we have to be more precise. First we must, as de Vries has shown, +distinguish real, genetic, variation from FLUCTUATIONAL variations, due to +environmental and other accidents, which cannot be transmitted. Having +excluded these sources of error the variations observed must be expressed +in terms of the factors to which they are due before their significance can +be understood. For example, numbers of the variations seen under +domestication, and not a few witnessed in nature, are simply the +consequence of some ingredient being in an unknown way omitted from the +composition of the varying individual. The variation may on the contrary +be due to the addition of some new element, but to prove that it is so is +by no means an easy matter. Casual observation is useless, for though +these latter variations will always be dominants, yet many dominant +characteristics may arise from another cause, namely the meeting of +complementary factors, and special study of each case in two generations at +least is needed before these two phenomena can be distinguished. + +When such considerations are fully appreciated it will be realised that +medleys of most dissimilar occurrences are all confused together under the +term Variation. One of the first objects of genetic analysis is to +disentangle this mass of confusion. + +To those who have made no study of heredity it sometimes appears that the +question of the effect of conditions in causing variation is one which we +should immediately investigate, but a little thought will show that before +any critical inquiry into such possibilities can be attempted, a knowledge +of the working of heredity under conditions as far as possible uniform must +be obtained. At the time when Darwin was writing, if a plant brought into +cultivation gave off an albino variety, such an event was without +hesitation ascribed to the change of life. Now we see that albino GAMETES, +germs, that is to say, which are destitute of the pigment-forming factor, +may have been originally produced by individuals standing an indefinite +number of generations back in the ancestry of the actual albino, and it is +indeed almost certain that the variation to which the appearance of the +albino is due cannot have taken place in a generation later than that of +the grandparents. It is true that when a new DOMINANT appears we should +feel greater confidence that we were witnessing the original variation, but +such events are of extreme rarity, and no such case has come under the +notice of an experimenter in modern times, as far as I am aware. That they +must have appeared is clear enough. Nothing corresponding to the Brown- +breasted Game fowl is known wild, yet that colour is a most definite +dominant, and at some moment since Gallus bankiva was domesticated, the +element on which that special colour depends must have at least once been +formed in the germ-cell of a fowl; but we need harder evidence than any +which has yet been produced before we can declare that this novelty came +through over-feeding, or change of climate, or any other disturbance +consequent on domestication. When we reflect on the intricacies of genetic +problems as we must now conceive them there come moments when we feel +almost thankful that the Mendelian principles were unknown to Darwin. The +time called for a bold pronouncement, and he made it, to our lasting profit +and delight. With fuller knowledge we pass once more into a period of +cautious expectation and reserve. + +In every arduous enterprise it is pleasanter to look back at difficulties +overcome than forward to those which still seem insurmountable, but in the +next stage there is nothing to be gained by disguising the fact that the +attributes of living things are not what we used to suppose. If they are +more complex in the sense that the properties they display are throughout +so regular (I have in view, for example, the marvellous and specific +phenomena of regeneration, and those discovered by the students of +"Entwicklungsmechanik". The circumstances of its occurrence here preclude +any suggestion that this regularity has been brought about by the workings +of Selection. The attempts thus to represent the phenomena have resulted +in mere parodies of scientific reasoning.) that the Selection of minute +random variations is an unacceptable account of the origin of their +diversity, yet by virtue of that very regularity the problem is limited in +scope and thus simplified. + +To begin with, we must relegate Selection to its proper place. Selection +permits the viable to continue and decides that the non-viable shall +perish; just as the temperature of our atmosphere decides that no liquid +carbon shall be found on the face of the earth: but we do not suppose that +the form of the diamond has been gradually achieved by a process of +Selection. So again, as the course of descent branches in the successive +generations, Selection determines along which branch Evolution shall +proceed, but it does not decide what novelties that branch shall bring +forth. "La Nature contient le fonds de toutes ces varietes, mais le hazard +ou l'art les mettent en oeuvre," as Maupertuis most truly said. + +Not till knowledge of the genetic properties of organisms has attained to +far greater completeness can evolutionary speculations have more than a +suggestive value. By genetic experiment, cytology and physiological +chemistry aiding, we may hope to acquire such knowledge. In 1872 Nathusius +wrote ("Vortrage uber Viehzucht und Rassenerkenntniss", page 120, Berlin, +1872.): "Das Gesetz der Vererbung ist noch nicht erkannt; der Apfel ist +noch nicht vom Baum der Erkenntniss gefallen, welcher, der Sage nach, +Newton auf den rechten Weg zur Ergrundung der Gravitationsgesetze fuhrte." +We cannot pretend that the words are not still true, but in Mendelian +analysis the seeds of that apple-tree at last are sown. + +If we were asked what discovery would do most to forward our inquiry, what +one bit of knowledge would more than any other illuminate the problem, I +think we may give the answer without hesitation. The greatest advance that +we can foresee will be made when it is found possible to connect the +geometrical phenomena of development with the chemical. The geometrical +symmetry of living things is the key to a knowledge of their regularity, +and the forces which cause it. In the symmetry of the dividing cell the +basis of that resemblance we call Heredity is contained. To imitate the +morphological phenomena of life we have to devise a system which can +divide. It must be able to divide, and to segment as--grossly--a vibrating +plate or rod does, or as an icicle can do as it becomes ribbed in a +continuous stream of water; but with this distinction, that the +distribution of chemical differences and properties must simultaneously be +decided and disposed in orderly relation to the pattern of the +segmentation. Even if a model which would do this could be constructed it +might prove to be a useful beginning. + +This may be looking too far ahead. If we had to choose some one piece of +more proximate knowledge which we would more especially like to acquire, I +suppose we should ask for the secret of interracial sterility. Nothing has +yet been discovered to remove the grave difficulty, by which Huxley in +particular was so much oppressed, that among the many varieties produced +under domestication--which we all regard as analogous to the species seen +in nature--no clear case of interracial sterility has been demonstrated. +The phenomenon is probably the only one to which the domesticated products +seem to afford no parallel. No solution of the difficulty can be offered +which has positive value, but it is perhaps worth considering the facts in +the light of modern ideas. It should be observed that we are not +discussing incompatibility of two species to produce offspring (a totally +distinct phenomenon), but the sterility of the offspring which many of them +do produce. + +When two species, both perfectly fertile severally, produce on crossing a +sterile progeny, there is a presumption that the sterility is due to the +development in the hybrid of some substance which can only be formed by the +meeting of two complementary factors. That some such account is correct in +essence may be inferred from the well-known observation that if the hybrid +is not totally sterile but only partially so, and thus is able to form some +good germ-cells which develop into new individuals, the sterility of these +daughter-individuals is sensibly reduced or may be entirely absent. The +fertility once re-established, the sterility does not return in the later +progeny, a fact strongly suggestive of segregation. Now if the sterility +of the cross-bred be really the consequence of the meeting of two +complementary factors, we see that the phenomenon could only be produced +among the divergent offspring of one species by the acquisition of at least +TWO new factors; for if the acquisition of a single factor caused sterility +the line would then end. Moreover each factor must be separately acquired +by distinct individuals, for if both were present together, the possessors +would by hypothesis be sterile. And in order to imitate the case of +species each of these factors must be acquired by distinct breeds. The +factors need not, and probably would not, produce any other perceptible +effects; they might, like the colour-factors present in white flowers, make +no difference in the form or other characters. Not till the cross was +actually made between the two complementary individuals would either factor +come into play, and the effects even then might be unobserved until an +attempt was made to breed from the cross-bred. + +Next, if the factors responsible for sterility were acquired, they would in +all probability be peculiar to certain individuals and would not readily be +distributed to the whole breed. Any member of the breed also into which +BOTH the factors were introduced would drop out of the pedigree by virtue +of its sterility. Hence the evidence that the various domesticated breeds +say of dogs or fowls can when mated together produce fertile offspring, is +beside the mark. The real question is, Do they ever produce sterile +offspring? I think the evidence is clearly that sometimes they do, oftener +perhaps than is commonly supposed. These suggestions are quite amenable to +experimental tests. The most obvious way to begin is to get a pair of +parents which are known to have had any sterile offspring, and to find the +proportions in which these steriles were produced. If, as I anticipate, +these proportions are found to be definite, the rest is simple. + +In passing, certain other considerations may be referred to. First, that +there are observations favouring the view that the production of totally +sterile cross-breds is seldom a universal property of two species, and that +it may be a matter of individuals, which is just what on the view here +proposed would be expected. Moreover, as we all know now, though +incompatibility may be dependent to some extent on the degree to which the +species are dissimilar, no such principle can be demonstrated to determine +sterility or fertility in general. For example, though all our Finches can +breed together, the hybrids are all sterile. Of Ducks some species can +breed together without producing the slightest sterility; others have +totally sterile offspring, and so on. The hybrids between several genera +of Orchids are perfectly fertile on the female side, and some on the male +side also, but the hybrids produced between the Turnip (Brassica napus) and +the Swede (Brassica campestris), which, according to our estimates of +affinity should be nearly allied forms, are totally sterile. (See Sutton, +A.W., "Journ. Linn. Soc." XXXVIII. page 341, 1908.) Lastly, it may be +recalled that in sterility we are almost certainly considering a meristic +phenomenon. FAILURE TO DIVIDE is, we may feel fairly sure, the immediate +"cause" of the sterility. Now, though we know very little about the +heredity of meristic differences, all that we do know points to the +conclusion that the less-divided is dominant to the more-divided, and we +are thus justified in supposing that there are factors which can arrest or +prevent cell-division. My conjecture therefore is that in the case of +sterility of cross-breds we see the effect produced by a complementary pair +of such factors. This and many similar problems are now open to our +analysis. + +The question is sometimes asked, Do the new lights on Variation and +Heredity make the process of Evolution easier to understand? On the whole +the answer may be given that they do. There is some appearance of loss of +simplicity, but the gain is real. As was said above, the time is not ripe +for the discussion of the origin of species. With faith in Evolution +unshaken--if indeed the word faith can be used in application to that which +is certain--we look on the manner and causation of adapted differentiation +as still wholly mysterious. As Samuel Butler so truly said: "To me it +seems that the 'Origin of Variation,' whatever it is, is the only true +'Origin of Species'" ("Life and Habit", London, page 263, 1878.), and of +that Origin not one of us knows anything. But given Variation--and it is +given: assuming further that the variations are not guided into paths of +adaptation--and both to the Darwinian and to the modern school this +hypothesis appears to be sound if unproven--an evolution of species +proceeding by definite steps is more, rather than less, easy to imagine +than an evolution proceeding by the accumulation of indefinite and +insensible steps. Those who have lost themselves in contemplating the +miracles of Adaptation (whether real or spurious) have not unnaturally +fixed their hopes rather on the indefinite than on the definite changes. +The reasons are obvious. By suggesting that the steps through which an +adaptative mechanism arose were indefinite and insensible, all further +trouble is spared. While it could be said that species arise by an +insensible and imperceptible process of variation, there was clearly no use +in tiring ourselves by trying to perceive that process. This labour-saving +counsel found great favour. All that had to be done to develop evolution- +theory was to discover the good in everything, a task which, in the +complete absence of any control or test whereby to check the truth of the +discovery, is not very onerous. The doctrine "que tout est au mieux" was +therefore preached with fresh vigour, and examples of that illuminating +principle were discovered with a facility that Pangloss himself might have +envied, till at last even the spectators wearied of such dazzling +performances. + +But in all seriousness, why should indefinite and unlimited variation have +been regarded as a more probable account of the origin of Adaptation? +Only, I think, because the obstacle was shifted one plane back, and so +looked rather less prominent. The abundance of Adaptation, we all grant, +is an immense, almost an unsurpassable difficulty in all non-Lamarckian +views of Evolution; but if the steps by which that adaptation arose were +fortuitous, to imagine them insensible is assuredly no help. In one most +important respect indeed, as has often been observed, it is a +multiplication of troubles. For the smaller the steps, the less could +Natural Selection act upon them. Definite variations--and of the +occurrence of definite variations in abundance we have now the most +convincing proof--have at least the obvious merit that they can make and +often do make a real difference in the chances of life. + +There is another aspect of the Adaptation problem to which I can only +allude very briefly. May not our present ideas of the universality and +precision of Adaptation be greatly exaggerated? The fit of organism to its +environment is not after all so very close--a proposition unwelcome +perhaps, but one which could be illustrated by very copious evidence. +Natural Selection is stern, but she has her tolerant moods. + +We have now most certain and irrefragable proof that much definiteness +exists in living things apart from Selection, and also much that may very +well have been preserved and so in a sense constituted by Selection. Here +the matter is likely to rest. There is a passage in the sixth edition of +the "Origin" which has I think been overlooked. On page 70 Darwin says +"The tuft of hair on the breast of the wild turkey-cock cannot be of any +use, and it is doubtful whether it can be ornamental in the eyes of the +female bird." This tuft of hair is a most definite and unusual structure, +and I am afraid that the remark that it "cannot be of any use" may have +been made inadvertently; but it may have been intended, for in the first +edition the usual qualification was given and must therefore have been +deliberately excised. Anyhow I should like to think that Darwin did throw +over that tuft of hair, and that he felt relief when he had done so. +Whether however we have his great authority for such a course or not, I +feel quite sure that we shall be rightly interpreting the facts of nature +if we cease to expect to find purposefulness wherever we meet with definite +structures or patterns. Such things are, as often as not, I suspect rather +of the nature of tool-marks, mere incidents of manufacture, benefiting +their possessor not more than the wire-marks in a sheet of paper, or the +ribbing on the bottom of an oriental plate renders those objects more +attractive in our eyes. + +If Variation may be in any way definite, the question once more arises, may +it not be definite in direction? The belief that it is has had many +supporters, from Lamarck onwards, who held that it was guided by need, and +others who, like Nageli, while laying no emphasis on need, yet were +convinced that there was guidance of some kind. The latter view under the +name of "Orthogenesis," devised I believe by Eimer, at the present day +commends itself to some naturalists. The objection to such a suggestion is +of course that no fragment of real evidence can be produced in its support. +On the other hand, with the experimental proof that variation consists +largely in the unpacking and repacking of an original complexity, it is not +so certain as we might like to think that the order of these events is not +pre-determined. For instance the original "pack" may have been made in +such a way that at the nth division of the germ-cells of a Sweet Pea a +colour-factor might be dropped, and that at the n plus n prime division the +hooded variety be given off, and so on. I see no ground whatever for +holding such a view, but in fairness the possibility should not be +forgotten, and in the light of modern research it scarcely looks so +absurdly improbable as before. + +No one can survey the work of recent years without perceiving that +evolutionary orthodoxy developed too fast, and that a great deal has got to +come down; but this satisfaction at least remains, that in the experimental +methods which Mendel inaugurated, we have means of reaching certainty in +regard to the physiology of Heredity and Variation upon which a more +lasting structure may be built. + + +VI. THE MINUTE STRUCTURE OF CELLS IN RELATION TO HEREDITY. + +By EDUARD STRASBURGER, +Professor of Botany in the University of Bonn. + +Since 1875 an unexpected insight has been gained into the internal +structure of cells. Those who are familiar with the results of +investigations in this branch of Science are convinced that any modern +theory of heredity must rest on a basis of cytology and cannot be at +variance with cytological facts. Many histological discoveries, both such +as have been proved correct and others which may be accepted as probably +well founded, have acquired a fundamental importance from the point of view +of the problems of heredity. + +My aim is to describe the present position of our knowledge of Cytology. +The account must be confined to essentials and cannot deal with far- +reaching and controversial questions. In cases where difference of opinion +exists, I adopt my own view for which I hold myself responsible. I hope to +succeed in making myself intelligible even without the aid of +illustrations: in order to convey to the uninitiated an adequate idea of +the phenomena connected with the life of a cell, a greater number of +figures would be required than could be included within the scope of this +article. + +So long as the most eminent investigators (As for example the illustrious +Wilhelm Hofmeister in his "Lehre von der Pflanzenzelle" (1867).) believed +that the nucleus of a cell was destroyed in the course of each division and +that the nuclei of the daughter-cells were produced de novo, theories of +heredity were able to dispense with the nucleus. If they sought, as did +Charles Darwin, who showed a correct grasp of the problem in the +enunciation of his Pangenesis hypothesis, for histological connecting +links, their hypotheses, or at least the best of them, had reference to the +cell as a whole. It was known to Darwin that the cell multiplied by +division and was derived from a similar pre-existing cell. Towards 1870 it +was first demonstrated that cell-nuclei do not arise de novo, but are +invariably the result of division of pre-existing nuclei. Better methods +of investigation rendered possible a deeper insight into the phenomena +accompanying cell and nuclear divisions and at the same time disclosed the +existence of remarkable structures. The work of O. Butschli, O. Hertwig, +W. Flemming H. Fol and of the author of this article (For further reference +to literature, see my article on "Die Ontogenie der Zelle seit 1875", in +the "Progressus Rei Botanicae", Vol. I. page 1, Jena, 1907.), have +furnished conclusive evidence in favour of these facts. It was found that +when the reticular framework of a nucleus prepares to divide, it separates +into single segments. These then become thicker and denser, taking up with +avidity certain stains, which are used as aids to investigation, and +finally form longer or shorter, variously bent, rodlets of uniform +thickness. In these organs which, on account of their special property of +absorbing certain stains, were styled Chromosomes (By W. Waldeyer in +1888.), there may usually be recognised a separation into thicker and +thinner discs; the former are often termed Chromomeres. (Discovered by W. +Pfitzner in 1880.) In the course of division of the nucleus, the single +rows of chromomeres in the chromosomes are doubled and this produces a +band-like flattening and leads to the longitudinal splitting by which each +chromosome is divided into two exactly equal halves. The nuclear membrane +then disappears and fibrillar cell-plasma or cytoplasm invades the nuclear +area. In animal cells these fibrillae in the cytoplasm centre on definite +bodies (Their existence and their multiplication by fission were +demonstrated by E. van Beneden and Th. Boveri in 1887.), which it is +customary to speak of as Centrosomes. Radiating lines in the adjacent +cell-plasma suggest that these bodies constitute centres of force. The +cells of the higher plants do not possess such individualised centres; they +have probably disappeared in the course of phylogenetic development: in +spite of this, however, in the nuclear division-figures the fibrillae of +the cell-plasma are seen to radiate from two opposite poles. In both +animal and plant cells a fibrillar bipolar spindle is formed, the fibrillae +of which grasp the longitudinally divided chromosomes from two opposite +sides and arrange them on the equatorial plane of the spindle as the so- +called nuclear or equatorial plate. Each half-chromosome is connected with +one of the spindle poles only and is then drawn towards that pole. (These +important facts, suspected by W. Flemming in 1882, were demonstrated by E. +Heuser, L. Guignard, E. van Beneden, M. Nussbaum, and C. Rabl.) + +The formation of the daughter-nuclei is then effected. The changes which +the daughter-chromosomes undergo in the process of producing the daughter- +nuclei repeat in the reverse order the changes which they went through in +the course of their progressive differentiation from the mother-nucleus. +The division of the cell-body is completed midway between the two daughter- +nuclei. In animal cells, which possess no chemically differentiated +membrane, separation is effected by simple constriction, while in the case +of plant cells provided with a definite wall, the process begins with the +formation of a cytoplasmic separating layer. + +The phenomena observed in the course of the division of the nucleus show +beyond doubt that an exact halving of its substance is of the greatest +importance. (First shown by W. Roux in 1883.) Compared with the method of +division of the nucleus, that of the cytoplasm appears to be very simple. +This led to the conception that the cell-nucleus must be the chief if not +the sole carrier of hereditary characters in the organism. It is for this +reason that the detailed investigation of fertilisation phenomena +immediately followed researches into the nucleus. The fundamental +discovery of the union of two nuclei in the sexual act was then made (By O. +Hertwig in 1875.) and this afforded a new support for the correct +conception of the nuclear functions. The minute study of the behaviour of +the other constituents of sexual cells during fertilisation led to the +result, that the nucleus alone is concerned with handing on hereditary +characters (This was done by O. Hertwig and the author of this essay +simultaneously in 1884.) from one generation to another. Especially +important, from the point of view of this conclusion, is the study of +fertilisation in Angiosperms (Flowering plants); in these plants the male +sexual cells lose their cell-body in the pollen-tube and the nucleus only-- +the sperm-nucleus--reaches the egg. The cytoplasm of the male sexual cell +is therefore not necessary to ensure a transference of hereditary +characters from parents to offspring. I lay stress on the case of the +Angiosperms because researches recently repeated with the help of the +latest methods failed to obtain different results. As regards the +descendants of angiospermous plants, the same laws of heredity hold good as +for other sexually differentiated organisms; we may, therefore, extend to +the latter what the Angiosperms so clearly teach us. + +The next advance in the hitherto rapid progress in our knowledge of nuclear +division was delayed, because it was not at once recognised that there are +two absolutely different methods of nuclear division. All such nuclear +divisions were united under the head of indirect or mitotic divisions; +these were also spoken of as karyo-kineses, and were distinguished from the +direct or amitotic divisions which are characterised by a simple +constriction of the nuclear body. So long as the two kinds of indirect +nuclear division were not clearly distinguished, their correct +interpretation was impossible. This was accomplished after long and +laborious research, which has recently been carried out and with results +which should, perhaps, be regarded as provisional. + +Soon after the new study of the nucleus began, investigators were struck by +the fact that the course of nuclear division in the mother-cells, or more +correctly in the grandmother-cells, of spores, pollen-grains, and embryo- +sacs of the more highly organised plants and in the spermatozoids and eggs +of the higher animals, exhibits similar phenomena, distinct from those +which occur in the somatic cells. + +In the nuclei of all those cells which we may group together as gonotokonts +(At the suggestion of J.P. Lotsy in 1904.) (i.e. cells concerned in +reproduction) there are fewer chromosomes than in the adjacent body-cells +(somatic cells). It was noticed also that there is a peculiarity +characteristic of the gonotokonts, namely the occurrence of two nuclear +divisions rapidly succeeding one another. It was afterwards recognised +that in the first stage of nuclear division in the gonotokonts the +chromosomes unite in pairs: it is these chromosome-pairs, and not the two +longitudinal halves of single chromosomes, which form the nuclear plate in +the equatorial plane of the nuclear spindle. It has been proposed to call +these pairs gemini. (J.E.S. Moore and A.L. Embleton, "Proc. Roy. Soc." +London, Vol. LXXVII. page 555, 1906; V. Gregoire, 1907.) In the course of +this division the spindle-fibrillae attach themselves to the gemini, i.e. +to entire chromosomes and direct them to the points where the new daughter- +nuclei are formed, that is to those positions towards which the +longitudinal halves of the chromosomes travel in ordinary nuclear +divisions. It is clear that in this way the number of chromosomes which +the daughter-nuclei contain, as the result of the first stage in division +in the gonotokonts, will be reduced by one half, while in ordinary +divisions the number of chromosomes always remains the same. The first +stage in the division of the nucleus in the gonotokonts has therefore been +termed the reduction division. (In 1887 W. Flemming termed this the +heterotypic form of nuclear division.) This stage in division determines +the conditions for the second division which rapidly ensues. Each of the +paired chromosomes of the mother-nucleus has already, as in an ordinary +nuclear division, completed the longitudinal fission, but in this case it +is not succeeded by the immediate separation of the longitudinal halves and +their allotment to different nuclei. Each chromosome, therefore, takes its +two longitudinal halves into the same daughter-nucleus. Thus, in each +daughter-nucleus the longitudinal halves of the chromosomes are present +ready for the next stage in the division; they only require to be arranged +in the nuclear plate and then distributed among the granddaughter-nuclei. +This method of division, which takes place with chromosomes already split, +and which have only to provide for the distribution of their longitudinal +halves to the next nuclear generation, has been called homotypic nuclear +division. (The name was proposed by W. Flemming in 1887; the nature of +this type of division was, however, not explained until later.) + +Reduction division and homotypic nuclear division are included together +under the term allotypic nuclear division and are distinguished from the +ordinary or typical nuclear division. The name Meiosis (By J. Bretland +Farmer and J.E.S. Moore in 1905.) has also been proposed for these two +allotypic nuclear divisions. The typical divisions are often spoken of as +somatic. + +Observers who were actively engaged in this branch of recent histological +research soon noticed that the chromosomes of a given organism are +differentiated in definite numbers from the nuclear network in the course +of division. This is especially striking in the gonotokonts, but it +applies also to the somatic tissues. In the latter, one usually finds +twice as many chromosomes as in the gonotokonts. Thus the conclusion was +gradually reached that the doubling of chromosomes, which necessarily +accompanies fertilisation, is maintained in the product of fertilisation, +to be again reduced to one half in the gonotokonts at the stage of +reduction-division. This enabled us to form a conception as to the essence +of true alternation of generations, in which generations containing single +and double chromosomes alternate with one another. + +The single-chromosome generation, which I will call the HAPLOID, must have +been the primitive generation in all organisms; it might also persist as +the only generation. Every sexual differentiation in organisms, which +occurred in the course of phylogenetic development, was followed by +fertilisation and therefore by the creation of a diploid or double- +chromosome product. So long as the germination of the product of +fertilisation, the zygote, began with a reducing process, a special DIPLOID +generation was not represented. This, however, appeared later as a product +of the further evolution of the zygote, and the reduction division was +correspondingly postponed. In animals, as in plants, the diploid +generation attained the higher development and gradually assumed the +dominant position. The haploid generation suffered a proportional +reduction, until it finally ceased to have an independent existence and +became restricted to the role of producing the sexual products within the +body of the diploid generation. Those who do not possess the necessary +special knowledge are unable to realise what remains of the first haploid +generation in a phanerogamic plant or in a vertebrate animal. In +Angiosperms this is actually represented only by the short developmental +stages which extend from the pollen mother-cells to the sperm-nucleus of +the pollen-tube, and from the embryo-sac mother-cell to the egg and the +endosperm tissue. The embryo-sac remains enclosed in the diploid ovule, +and within this from the fertilised egg is formed the embryo which +introduces the new diploid generation. On the full development of the +diploid embryo of the next generation, the diploid ovule of the preceding +diploid generation is separated from the latter as a ripe seed. The +uninitiated sees in the more highly organised plants only a succession of +diploid generations. Similarly all the higher animals appear to us as +independent organisms with diploid nuclei only. The haploid generation is +confined in them to the cells produced as the result of the reduction +division of the gonotokonts; the development of these is completed with the +homotypic stage of division which succeeds the reduction division and +produces the sexual products. + +The constancy of the numbers in which the chromosomes separate themselves +from the nuclear network during division gave rise to the conception that, +in a certain degree, chromosomes possess individuality. Indeed the most +careful investigations (Particularly those of V. Gregoire and his pupils.) +have shown that the segments of the nuclear network, which separate from +one another and condense so as to produce chromosomes for a new division, +correspond to the segments produced from the chromosomes of the preceding +division. The behaviour of such nuclei as possess chromosomes of unequal +size affords confirmatory evidence of the permanence of individual +chromosomes in corresponding sections of an apparently uniform nuclear +network. Moreover at each stage in division chromosomes with the same +differences in size reappear. Other cases are known in which thicker +portions occur in the substance of the resting nucleus, and these agree in +number with the chromosomes. In this network, therefore, the individual +chromosomes must have retained their original position. But the +chromosomes cannot be regarded as the ultimate hereditary units in the +nuclei, as their number is too small. Moreover, related species not +infrequently show a difference in the number of their chromosomes, whereas +the number of hereditary units must approximately agree. We thus picture +to ourselves the carriers of hereditary characters as enclosed in the +chromosomes; the transmitted fixed number of chromosomes is for us only the +visible expression of the conception that the number of hereditary units +which the chromosomes carry must be also constant. The ultimate hereditary +units may, like the chromosomes themselves, retain a definite position in +the resting nucleus. Further, it may be assumed that during the separation +of the chromosomes from one another and during their assumption of the rod- +like form, the hereditary units become aggregated in the chromomeres and +that these are characterised by a constant order of succession. The +hereditary units then grow, divide into two and are uniformly distributed +by the fission of the chromosomes between their longitudinal halves. + +As the contraction and rod-like separation of the chromosomes serve to +isnure the transmission of all hereditary units in the products of division +of a nucleus, so, on the other hand, the reticular distension of each +chromosome in the so-called resting nucleus may effect a separation of the +carriers of hereditary units from each other and facilitate the specific +activity of each of them. + +In the stages preliminary to their division, the chromosomes become denser +and take up a substance which increases their staining capacity; this is +called chromatin. This substance collects in the chromomeres and may form +the nutritive material for the carriers of hereditary units which we now +believe to be enclosed in them. The chromatin cannot itself be the +hereditary substance, as it afterwards leaves the chromosomes, and the +amount of it is subject to considerable variation in the nucleus, according +to its stage of development. Conjointly with the materials which take part +in the formation of the nuclear spindle and other processes in the cell, +the chromatin accumulates in the resting nucleus to form the nucleoli. + +Naturally connected with the conclusion that the nuclei are the carriers of +hereditary characters in the organism, is the question whether enucleate +organisms can also exist. Phylogenetic considerations give an affirmative +answer to this question. The differentiation into nucleus and cytoplasm +represents a division of labour in the protoplast. A study of organisms +which belong to the lowest class of the organic world teaches us how this +was accomplished. Instead of well-defined nuclei, scattered granules have +been described in the protoplasm of several of these organisms (Bacteria, +Cyanophyceae, Protozoa.), characterised by the same reactions as nuclear +material, provided also with a nuclear network, but without a limiting +membrane. (This is the result of the work of R. Hertwig and of the most +recently published investigations.) Thus the carriers of hereditary +characters may originally have been distributed in the common protoplasm, +afterwards coming together and eventually assuming a definite form as +special organs of the cell. It may be also assumed that in the protoplasm +and in the primitive types of nucleus, the carriers of the same hereditary +unit were represented in considerable quantity; they became gradually +differentiated to an extent commensurate with newly acquired characters. +It was also necessary that, in proportion as this happened, the mechanism +of nuclear division must be refined. At first processes resembling a +simple constriction would suffice to provide for the distribution of all +hereditary units to each of the products of division, but eventually in +both organic kingdoms nuclear division, which alone insured the qualitative +identity of the products of division, became a more marked feature in the +course of cell-multiplication. + +Where direct nuclear division occurs by constriction in the higher +organisms, it does not result in the halving of hereditary units. So far +as my observations go, direct nuclear division occurs in the more highly +organised plants only in cells which have lost their specific functions. +Such cells are no longer capable of specific reproduction. An interesting +case in this connection is afforded by the internodal cells of the +Characeae, which possess only vegetative functions. These cells grow +vigorously and their cytoplasm increases, their growth being accompanied by +a correspondingly direct multiplication of the nuclei. They serve chiefly +to nourish the plant, but, unlike the other cells, they are incapable of +producing any offspring. This is a very instructive case, because it +clearly shows that the nuclei are not only carriers of hereditary +characters, but that they also play a definite part in the metabolism of +the protoplasts. + +Attention was drawn to the fact that during the reducing division of nuclei +which contain chromosomes of unequal size, gemini are constantly produced +by the pairing of chromosomes of the same size. This led to the conclusion +that the pairing chromosomes are homologous, and that one comes from the +father, the other from the mother. (First stated by T.H. Montgomery in +1901 and by W.S. Sutton in 1902.) This evidently applies also to the +pairing of chromosomes in those reduction-divisions in which differences in +size do not enable us to distinguish the individual chromosomes. In this +case also each pair would be formed by two homologous chromosomes, the one +of paternal, the other of maternal origin. When the separation of these +chromosomes and their distribution to both daughter-nuclei occur a +chromosome of each kind is provided for each of these nuclei. It would +seem that the components of each pair might pass to either pole of the +nuclear spindle, so that the paternal and maternal chromosomes would be +distributed in varying proportion between the daughter-nuclei; and it is +not impossible that one daughter-nucleus might occasionally contain +paternal chromosomes only and its sister-nucleus exclusively maternal +chromosomes. + +The fact that in nuclei containing chromosomes of various sizes, the +chromosomes which pair together in reduction-division are always of equal +size, constitutes a further and more important proof of their qualitative +difference. This is supported also by ingenious experiments which led to +an unequal distribution of chromosomes in the products of division of a +sea-urchin's egg, with the result that a difference was induced in their +further development. (Demonstrated by Th. Boveri in 1902.) + +The recently discovered fact that in diploid nuclei the chromosomes are +arranged in pairs affords additional evidence in favour of the unequal +value of the chromosomes. This is still more striking in the case of +chromosomes of different sizes. It has been shown that in the first +division-figure in the nucleus of the fertilised egg the chromosomes of +corresponding size form pairs. They appear with this arrangement in all +subsequent nuclear divisions in the diploid generation. The longitudinal +fissions of the chromosomes provide for the unaltered preservation of this +condition. In the reduction nucleus of the gonotokonts the homologous +chromosomes being near together need not seek out one another; they are +ready to form gemini. The next stage is their separation to the haploid +daughter-nuclei, which have resulted from the reduction process. + +Peculiar phenomena in the reduction nucleus accompany the formation of +gemini in both organic kingdoms. (This has been shown more particularly by +the work of L. Guignard, M. Mottier, J.B. Farmer, C.B. Wilson, V. Hacker +and more recently by V. Gregoire and his pupil C.A. Allen, by the +researches conducted in the Bonn Botanical Institute, and by A. and K.E. +Schreiner.) Probably for the purpose of entering into most intimate +relation, the pairs are stretched to long threads in which the chromomeres +come to lie opposite one another. (C.A. Allen, A. and K.E. Schreiner, and +Strasburger.) It seems probable that these are homologous chromomeres, and +that the pairs afterwards unite for a short time, so that an exchange of +hereditary units is rendered possible. (H. de Vries and Strasburger.) +This cannot be actually seen, but certain facts of heredity point to the +conclusion that this occurs. It follows from these phenomena that any +exchange which may be effected must be one of homologous carriers of +hereditary units only. These units continue to form exchangeable segments +after they have undergone unequal changes; they then constitute +allelotropic pairs. We may thus calculate what sum of possible +combinations the exchange of homologous hereditary units between the +pairing chromosomes provides for before the reduction division and the +subsequent distribution of paternal and maternal chromosomes in the haploid +daughter-nuclei. These nuclei then transmit their characters to the sexual +cells, the conjugation of which in fertilization again produces the most +varied combinations. (A. Weismann gave the impulse to these ideas in his +theory on "Amphimixis".) In this way all the cooperations which the +carriers of hereditary characters are capable of in a species are produced; +this must give it an appreciable advantage in the struggle for life. + +The admirers of Charles Darwin must deeply regret that he did not live to +see the results achieved by the new Cytology. What service would they have +been to him in the presentation of his hypothesis of Pangenesis; what an +outlook into the future would they have given to his active mind! + +The Darwinian hypothesis of Pangenesis rests on the conception that all +inheritable properties are represented in the cells by small invisible +particles or gemmules and that these gemmules increase by division. +Cytology began to develop on new lines some years after the publication in +1868 of Charles Darwin's "Provisional hypothesis of Pangenesis" ("Animals +and Plants under Domestication", London, 1868, Chapter XXVII.), and when he +died in 1882 it was still in its infancy. Darwin would have soon suggested +the substitution of the nuclei for his gemmules. At least the great +majority of present-day investigators in the domain of cytology have been +led to the conclusion that the nucleus is the carrier of hereditary +characters, and they also believe that hereditary characters are +represented in the nucleus as distinct units. Such would be Darwin's +gemmules, which in conformity with the name of his hypothesis may be called +pangens (So called by H. de Vries in 1889.): these pangens multiply by +division. All recently adopted views may be thus linked on to this part of +Darwin's hypothesis. It is otherwise with Darwin's conception to which +Pangenesis owes its name, namely the view that all cells continually give +off gemmules, which migrate to other places in the organism, where they +unite to form reproductive cells. When Darwin foresaw this possibility, +the continuity of the germinal substance was still unknown (Demonstrated by +Nussbaum in 1880, by Sachs in 1882, and by Weismann in 1885.), a fact which +excludes a transference of gemmules. + +But even Charles Darwin's genius was confined within finite boundaries by +the state of science in his day. + +It is not my province to deal with other theories of development which +followed from Darwin's Pangenesis, or to discuss their histological +probabilities. We can, however, affirm that Charles Darwin's idea that +invisible gemmules are the carriers of hereditary characters and that they +multiply by division has been removed from the position of a provisional +hypothesis to that of a well-founded theory. It is supported by histology, +and the results of experimental work in heredity, which are now assuming +extraordinary prominence, are in close agreement with it. + + +VII. "THE DESCENT OF MAN" + +By G. SCHWALBE. +Professor of Anatomy in the University of Strassburg. + +The problem of the origin of the human race, of the descent of man, is +ranked by Huxley in his epoch-making book "Man's Place in Nature", as the +deepest with which biology has to concern itself, "the question of +questions,"--the problem which underlies all others. In the same brilliant +and lucid exposition, which appeared in 1863, soon after the publication of +Darwin's "Origin of Species", Huxley stated his own views in regard to this +great problem. He tells us how the idea of a natural descent of man +gradually grew up in his mind, it was especially the assertions of Owen in +regard to the total difference between the human and the simian brain that +called forth strong dissent from the great anatomist Huxley, and he easily +succeeded in showing that Owen's supposed differences had no real +existence; he even established, on the basis of his own anatomical +investigations, the proposition that the anatomical differences between the +Marmoset and the Chimpanzee are much greater than those between the +Chimpanzee and Man. + +But why do we thus introduce the study of Darwin's "Descent of Man", which +is to occupy us here, by insisting on the fact that Huxley had taken the +field in defence of the descent of man in 1863, while Darwin's book on the +subject did not appear till 1871? It is in order that we may clearly +understand how it happened that from this time onwards Darwin and Huxley +followed the same great aim in the most intimate association. + +Huxley and Darwin working at the same Problema maximum! Huxley fiery, +impetuous, eager for battle, contemptuous of the resistance of a dull +world, or energetically triumphing over it. Darwin calm, weighing every +problem slowly, letting it mature thoroughly,--not a fighter, yet having +the greater and more lasting influence by virtue of his immense mass of +critically sifted proofs. Darwin's friend, Huxley, was the first to do him +justice, to understand his nature, and to find in it the reason why the +detailed and carefully considered book on the descent of man made its +appearance so late. Huxley, always generous, never thought of claiming +priority for himself. In enthusiastic language he tells how Darwin's +immortal work, "The Origin of Species", first shed light for him on the +problem of the descent of man; the recognition of a vera causa in the +transformation of species illuminated his thoughts as with a flash. He was +now content to leave what perplexed him, what he could not yet solve, as he +says himself, "in the mighty hands of Darwin." Happy in the bustle of +strife against old and deep-rooted prejudices, against intolerance and +superstition, he wielded his sharp weapons on Darwin's behalf; wearing +Darwin's armour he joyously overthrew adversary after adversary. Darwin +spoke of Huxley as his "general agent." ("Life and Letters of Thomas Henry +Huxley", Vol. I. page 171, London, 1900.) Huxley says of himself "I am +Darwin's bulldog." (Ibid. page 363.) + +Thus Huxley openly acknowledged that it was Darwin's "Origin of Species" +that first set the problem of the descent of man in its true light, that +made the question of the origin of the human race a pressing one. That +this was the logical consequence of his book Darwin himself had long felt. +He had been reproached with intentionally shirking the application of his +theory to Man. Let us hear what he says on this point in his +autobiography: "As soon as I had become, in the year 1837 or 1838, +convinced that species were mutable productions, I could not avoid the +belief that man must come under the same law. Accordingly I collected +notes on the subject for my own satisfaction, and not for a long time with +any intention of publishing. Although in the 'Origin of Species' the +derivation of any particular species is never discussed, yet I thought it +best, in order THAT NO HONOURABLE MAN SHOULD ACCUSE ME OF CONCEALING MY +VIEWS (No italics in original.), to add that by the work 'light would be +thrown on the origin of man and his history.' It would have been useless +and injurious to the success of the book to have paraded, without giving +any evidence, my conviction with respect to his origin." ("Life and +Letters of Charles Darwin", Vol. 1. page 93.) + +In a letter written in January, 1860, to the Rev. L. Blomefield, Darwin +expresses himself in similar terms. "With respect to man, I am very far +from wishing to obtrude my belief; but I thought it dishonest to quite +conceal my opinion." (Ibid. Vol. II. page 263.) + +The brief allusion in the "Origin of Species" is so far from prominent and +so incidental that it was excusable to assume that Darwin had not touched +upon the descent of man in this work. It was solely the desire to have his +mass of evidence sufficiently complete, solely Darwin's great +characteristic of never publishing till he had carefully weighed all +aspects of his subject for years, solely, in short, his most fastidious +scientific conscience that restrained him from challenging the world in +1859 with a book in which the theory of the descent of man was fully set +forth. Three years, frequently interrupted by ill-health, were needed for +the actual writing of the book ("Life and Letters", Vol. I. page 94.): the +first edition, which appeared in 1871, was followed in 1874 by a much +improved second edition, the preparation of which he very reluctantly +undertook. (Ibid. Vol. III. page 175.) + +This, briefly, is the history of the work, which, with the "Origin of +Species", marks an epoch in the history of biological sciences--the work +with which the cautious, peace-loving investigator ventured forth from his +contemplative life into the arena of strife and unrest, and laid himself +open to all the annoyances that deep-rooted belief and prejudice, and the +prevailing tendency of scientific thought at the time could devise. + +Darwin did not take this step lightly. Of great interest in this +connection is a letter written to Wallace on Dec. 22, 1857 (Ibid. Vol. II. +page 109.), in which he says "You ask whether I shall discuss 'man.' I +think I shall avoid the whole subject, as so surrounded with prejudices; +though I fully admit that it is the highest and most interesting problem +for the naturalist." But his conscientiousness compelled him to state +briefly his opinion on the subject in the "Origin of Species" in 1859. +Nevertheless he did not escape reproaches for having been so reticent. +This is unmistakably apparent from a letter to Fritz Muller dated February +22 (1869?), in which he says: "I am thinking of writing a little essay on +the Origin of Mankind, as I have been taunted with concealing my opinions." +(Ibid. Vol. III. page 112.) + +It might be thought that Darwin behaved thus hesitatingly, and was so slow +in deciding on the full publication of his collected material in regard to +the descent of man, because he had religious difficulties to overcome. + +But this was not the case, as we can see from his admirable confession of +faith, the publication of which we owe to his son Francis. (Ibid. Vol. I. +pages 304-317.) Whoever wishes really to understand the lofty character of +this great man should read these immortal lines in which he unfolds to us +in simple and straightforward words the development of his conception of +the universe. He describes how, though he was still quite orthodox during +his voyage round the world on board the "Beagle", he came gradually to see, +shortly afterwards (1836-1839) that the Old Testament was no more to be +trusted than the Sacred Books of the Hindoos; the miracles by which +Christianity is supported, the discrepancies between the accounts in the +different Gospels, gradually led him to disbelieve in Christianity as a +divine revelation. "Thus," he writes ("Life and Letters", Vol. 1. page +309.), "disbelief crept over me at a very slow rate, but was at last +complete. The rate was so slow that I felt no distress." But Darwin was +too modest to presume to go beyond the limits laid down by science. He +wanted nothing more than to be able to go, freely and unhampered by belief +in authority or in the Bible, as far as human knowledge could lead him. We +learn this from the concluding words of his chapter on religion: "The +mystery of the beginning of all things is insoluble by us; and I for one +must be content to remain an Agnostic." (Loc. cit. page 313.) + +Darwin was always very unwilling to give publicity to his views in regard +to religion. In a letter to Asa Gray on May 22, 1860 (Ibid. Vol. II. page +310.), he declares that it is always painful to him to have to enter into +discussion of religious problems. He had, he said, no intention of writing +atheistically. + +Finally, let us cite one characteristic sentence from a letter from Darwin +to C. Ridley (Ibid. Vol. III. page. 236. ("C. Ridley," Mr Francis Darwin +points out to me, should be H.N. Ridley. A.C.S.)) (Nov. 28, 1878.) A +clergyman, Dr Pusey, had asserted that Darwin had written the "Origin of +Species" with some relation to theology. Darwin writes emphatically, "Many +years ago, when I was collecting facts for the 'Origin', my belief in what +is called a personal God was as firm as that of Dr Pusey himself, and as to +the eternity of matter I never troubled myself about such insoluble +questions." The expression "many years ago" refers to the time of his +voyage round the world, as has already been pointed out. Darwin means by +this utterance that the views which had gradually developed in his mind in +regard to the origin of species were quite compatible with the faith of the +Church. + +If we consider all these utterances of Darwin in regard to religion and to +his outlook on life (Weltanschauung), we shall see at least so much, that +religious reflection could in no way have influenced him in regard to the +writing and publishing of his book on "The Descent of Man". Darwin had +early won for himself freedom of thought, and to this freedom he remained +true to the end of his life, uninfluenced by the customs and opinions of +the world around him. + +Darwin was thus inwardly fortified and armed against the host of calumnies, +accusations, and attacks called forth by the publication of the "Origin of +Species", and to an even greater extent by the appearance of the "Descent +of Man". But in his defence he could rely on the aid of a band of +distinguished auxiliaries of the rarest ability. His faithful confederate, +Huxley, was joined by the botanist Hooker, and, after longer resistance, by +the famous geologist Lyell, whose "conversion" afforded Darwin peculiar +satisfaction. All three took the field with enthusiasm in defence of the +natural descent of man. From Wallace, on the other hand, though he shared +with him the idea of natural selection, Darwin got no support in this +matter. Wallace expressed himself in a strange manner. He admitted +everything in regard to the morphological descent of man, but maintained, +in a mystic way, that something else, something of a spiritual nature must +have been added to what man inherited from his animal ancestors. Darwin, +whose esteem for Wallace was extraordinarily high, could not understand how +he could give utterance to such a mystical view in regard to man; the idea +seemed to him so "incredibly strange" that he thought some one else must +have added these sentences to Wallace's paper. + +Even now there are thinkers who, like Wallace, shrink from applying to man +the ultimate consequences of the theory of descent. The idea that man is +derived from ape-like forms is to them unpleasant and humiliating. + +So far I have been depicting the development of Darwin's work on the +descent of man. In what follows I shall endeavour to give a condensed +survey of the contents of the book. + +It must at once be said that the contents of Darwin's work fall into two +parts, dealing with entirely different subjects. "The Descent of Man" +includes a very detailed investigation in regard to secondary sexual +characters in the animal series, and on this investigation Darwin founded a +new theory, that of sexual selection. With astonishing patience he +gathered together an immense mass of material, and showed, in regard to +Arthropods and Vertebrates, the wide distribution of secondary characters, +which develop almost exclusively in the male, and which enable him, on the +one hand, to get the better of his rivals in the struggle for the female by +the greater perfection of his weapons, and on the other hand, to offer +greater allurements to the female through the higher development of +decorative characters, of song, or of scent-producing glands. The best +equipped males will thus crowd out the less well-equipped in the matter of +reproduction, and thus the relevant characters will be increased and +perfected through sexual selection. It is, of course, a necessary +assumption that these secondary sexual characters may be transmitted to the +female, although perhaps in rudimentary form. + +As we have said, this theory of sexual selection takes up a great deal of +space in Darwin's book, and it need only be considered here in so far as +Darwin applied it to the descent of man. To this latter problem the whole +of Part I is devoted, while Part III contains a discussion of sexual +selection in relation to man, and a general summary. Part II treats of +sexual selection in general, and may be disregarded in our present study. +Moreover, many interesting details must necessarily be passed over in what +follows, for want of space. + +The first part of the "Descent of Man" begins with an enumeration of the +proofs of the animal descent of man taken from the structure of the human +body. Darwin chiefly emphasises the fact that the human body consists of +the same organs and of the same tissues as those of the other mammals; he +shows also that man is subject to the same diseases and tormented by the +same parasites as the apes. He further dwells on the general agreement +exhibited by young, embryonic forms, and he illustrates this by two figures +placed one above the other, one representing a human embryo, after Eaker, +the other a dog embryo, after Bischoff. ("Descent of Man" (Popular +Edition, 1901), fig. 1, page 14.) + +Darwin finds further proofs of the animal origin of man in the reduced +structures, in themselves extremely variable, which are either absolutely +useless to their possessors, or of so little use that they could never have +developed under existing conditions. Of such vestiges he enumerates: the +defective development of the panniculus carnosus (muscle of the skin) so +widely distributed among mammals, the ear-muscles, the occasional +persistence of the animal ear-point in man, the rudimentary nictitating +membrane (plica semilunaris) in the human eye, the slight development of +the organ of smell, the general hairiness of the human body, the frequently +defective development or entire absence of the third molar (the wisdom +tooth), the vermiform appendix, the occasional reappearance of a bony canal +(foramen supracondyloideum) at the lower end of the humerus, the +rudimentary tail of man (the so-called taillessness), and so on. Of these +rudimentary structures the occasional occurrence of the animal ear-point in +man is most fully discussed. Darwin's attention was called to this +interesting structure by the sculptor Woolner. He figures such a case +observed in man, and also the head of an alleged orang-foetus, the +photograph of which he received from Nitsche. + +Darwin's interpretation of Woolner's case as having arisen through a +folding over of the free edge of a pointed ear has been fully borne out by +my investigations on the external ear. (G. Schwalbe, "Das Darwin'sche +Spitzohr beim menschlichen Embryo", "Anatom. Anzeiger", 1889, pages 176- +189, and other papers.) In particular, it was established by these +investigations that the human foetus, about the middle of its embryonic +life, possesses a pointed ear somewhat similar to that of the monkey genus +Macacus. One of Darwin's statements in regard to the head of the orang- +foetus must be corrected. A LARGE ear with a point is shown in the +photograph ("Descent of Man", fig.3, page 24.), but it can easily be +demonstrated--and Deniker has already pointed this out--that the figure is +not that of an orang-foetus at all, for that form has much smaller ears +with no point; nor can it be a gibbon-foetus, as Deniker supposes, for the +gibbon ear is also without a point. I myself regard it as that of a +Macacus-embryo. But this mistake, which is due to Nitsche, in no way +affects the fact recognised by Darwin, that ear-forms showing the point +characteristic of the animal ear occur in man with extraordinary frequency. + +Finally, there is a discussion of those rudimentary structures which occur +only in ONE sex, such as the rudimentary mammary glands in the male, the +vesicula prostatica, which corresponds to the uterus of the female, and +others. All these facts tell in favour of the common descent of man and +all other vertebrates. The conclusion of this section is characteristic: +"IT IS ONLY OUR NATURAL PREJUDICE, AND THAT ARROGANCE WHICH MADE OUR +FOREFATHERS DECLARE THAT THEY WERE DESCENDED FROM DEMI-GODS, WHICH LEADS US +TO DEMUR TO THIS CONCLUSION. BUT THE TIME WILL BEFORE LONG COME, WHEN IT +WILL BE THOUGHT WONDERFUL THAT NATURALISTS, WHO WERE WELL ACQUAINTED WITH +THE COMPARATIVE STRUCTURE AND DEVELOPMENT OF MAN, AND OTHER MAMMALS, SHOULD +HAVE BELIEVED THAT EACH WAS THE WORK OF A SEPARATE ACT OF CREATION." +(Ibid. page 36.) + +In the second chapter there is a more detailed discussion, again based upon +an extraordinary wealth of facts, of the problem as to the manner in which, +and the causes through which, man evolved from a lower form. Precisely the +same causes are here suggested for the origin of man, as for the origin of +species in general. Variability, which is a necessary assumption in regard +to all transformations, occurs in man to a high degree. Moreover, the +rapid multiplication of the human race creates conditions which necessitate +an energetic struggle for existence, and thus afford scope for the +intervention of natural selection. Of the exercise of ARTIFICIAL selection +in the human race, there is nothing to be said, unless we cite such cases +as the grenadiers of Frederick William I, or the population of ancient +Sparta. In the passages already referred to and in those which follow, the +transmission of acquired characters, upon which Darwin does not dwell, is +taken for granted. In man, direct effects of changed conditions can be +demonstrated (for instance in regard to bodily size), and there are also +proofs of the influence exerted on his physical constitution by increased +use or disuse. Reference is here made to the fact, established by Forbes, +that the Quechua-Indians of the high plateaus of Peru show a striking +development of lungs and thorax, as a result of living constantly at high +altitudes. + +Such special forms of variation as arrests of development (microcephalism) +and reversion to lower forms are next discussed. Darwin himself felt +("Descent of Man", page 54.) that these subjects are so nearly related to +the cases mentioned in the first chapter, that many of them might as well +have been dealt with there. It seems to me that it would have been better +so, for the citation of additional instances of reversion at this place +rather disturbs the logical sequence of his ideas as to the conditions +which have brought about the evolution of man from lower forms. The +instances of reversion here discussed are microcephalism, which Darwin +wrongly interpreted as atavistic, supernumerary mammae, supernumerary +digits, bicornuate uterus, the development of abnormal muscles, and so on. +Brief mention is also made of correlative variations observed in man. + +Darwin next discusses the question as to the manner in which man attained +to the erect position from the state of a climbing quadruped. Here again +he puts the influence of Natural Selection in the first rank. The +immediate progenitors of man had to maintain a struggle for existence in +which success was to the more intelligent, and to those with social +instincts. The hand of these climbing ancestors, which had little skill +and served mainly for locomotion, could only undergo further development +when some early member of the Primate series came to live more on the +ground and less among trees. + +A bipedal existence thus became possible, and with it the liberation of the +hand from locomotion, and the one-sided development of the human foot. The +upright position brought about correlated variations in the bodily +structure; with the free use of the hand it became possible to manufacture +weapons and to use them; and this again resulted in a degeneration of the +powerful canine teeth and the jaws, which were then no longer necessary for +defence. Above all, however, the intelligence immediately increased, and +with it skull and brain. The nakedness of man, and the absence of a tail +(rudimentariness of the tail vertebrae) are next discussed. Darwin is +inclined to attribute the nakedness of man, not to the action of natural +selection on ancestors who originally inhabited a tropical land, but to +sexual selection, which, for aesthetic reasons, brought about the loss of +the hairy covering in man, or primarily in woman. An interesting +discussion of the loss of the tail, which, however, man shares with the +anthropoid apes, some other monkeys and lemurs, forms the conclusion of the +almost superabundant material which Darwin worked up in the second chapter. +His object was to show that some of the most distinctive human characters +are in all probability directly or indirectly due to natural selection. +With characteristic modesty he adds ("Descent of Man", page 92.): "Hence, +if I have erred in giving to natural selection great power, which I am very +far from admitting, or in having exaggerated its power, which is in itself +probable, I have at least, as I hope, done good service in aiding to +overthrow the dogma of separate creations." At the end of the chapter he +touches upon the objection as to man's helpless and defenceless condition. +Against this he urges his intelligence and social instincts. + +The two following chapters contain a detailed discussion of the objections +drawn from the supposed great differences between the mental powers of men +and animals. Darwin at once admits that the differences are enormous, but +not that any fundamental difference between the two can be found. Very +characteristic of him is the following passage: "In what manner the mental +powers were first developed in the lowest organisms, is as hopeless an +enquiry as how life itself first originated. These are problems for the +distant future, if they are ever to be solved by man." (Ibid. page 100.) + +After some brief observations on instinct and intelligence, Darwin brings +forward evidence to show that the greater number of the emotional states, +such as pleasure and pain, happiness and misery, love and hate are common +to man and the higher animals. He goes on to give various examples showing +that wonder and curiosity, imitation, attention, memory and imagination +(dreams of animals), can also be observed in the higher mammals, especially +in apes. In regard even to reason there are no sharply defined limits. A +certain faculty of deliberation is characteristic of some animals, and the +more thoroughly we know an animal the more intelligence we are inclined to +credit it with. Examples are brought forward of the intelligent and +deliberate actions of apes, dogs and elephants. But although no sharply +defined differences exist between man and animals, there is, nevertheless, +a series of other mental powers which are characteristics usually regarded +as absolutely peculiar to man. Some of these characteristics are examined +in detail, and it is shown that the arguments drawn from them are not +conclusive. Man alone is said to be capable of progressive improvement; +but against this must be placed as something analogous in animals, the fact +that they learn cunning and caution through long continued persecution. +Even the use of tools is not in itself peculiar to man (monkeys use sticks, +stones and twigs), but man alone fashions and uses implements DESIGNED FOR +A SPECIAL PURPOSE. In this connection the remarks taken from Lubbock in +regard to the origin and gradual development of the earliest flint +implements will be read with interest; these are similar to the +observations on modern eoliths, and their bearing on the development of the +stone-industry. It is interesting to learn from a letter to Hooker ("Life +and Letters", Vol. II. page 161, June 22, 1859.), that Darwin himself at +first doubted whether the stone implements discovered by Boucher de Perthes +were really of the nature of tools. With the relentless candour as to +himself which characterised him, he writes four years later in a letter to +Lyell in regard to this view of Boucher de Perthes' discoveries: "I know +something about his errors, and looked at his book many years ago, and am +ashamed to think that I concluded the whole was rubbish! Yet he has done +for man something like what Agassiz did for glaciers." (Ibid. Vol. III. +page 15, March 17, 1863.) + +To return to Darwin's further comparisons between the higher mental powers +of man and animals. He takes much of the force from the argument that man +alone is capable of abstraction and self-consciousness by his own +observations on dogs. One of the main differences between man and animals, +speech, receives detailed treatment. He points out that various animals +(birds, monkeys, dogs) have a large number of different sounds for +different emotions, that, further, man produces in common with animals a +whole series of inarticulate cries combined with gestures, and that dogs +learn to understand whole sentences of human speech. In regard to human +language, Darwin expresses a view contrary to that held by Max Muller +("Descent of Man", page 132.): "I cannot doubt that language owes its +origin to the imitation and modification of various natural sounds, the +voices of other animals, and man's own instinctive cries, aided by signs +and gestures." The development of actual language presupposes a higher +degree of intelligence than is found in any kind of ape. Darwin remarks on +this point (Ibid. pages 136, 137.): "The fact of the higher apes not using +their vocal organs for speech no doubt depends on their intelligence not +having been sufficiently advanced." + +The sense of beauty, too, has been alleged to be peculiar to man. In +refutation of this assertion Darwin points to the decorative colours of +birds, which are used for display. And to the last objection, that man +alone has religion, that he alone has a belief in God, it is answered "that +numerous races have existed, and still exist, who have no idea of one or +more gods, and who have no words in their languages to express such an +idea." (Ibid. page 143.) + +The result of the investigations recorded in this chapter is to show that, +great as the difference in mental powers between man and the higher animals +may be, it is undoubtedly only a difference "of degree and not of kind." +("Descent of Man", page 193.) + +In the fourth chapter Darwin deals with the MORAL SENSE or CONSCIENCE, +which is the most important of all differences between man and animals. It +is a result of social instincts, which lead to sympathy for other members +of the same society, to non-egoistic actions for the good of others. +Darwin shows that social tendencies are found among many animals, and that +among these love and kin-sympathy exist, and he gives examples of animals +(especially dogs) which may exhibit characters that we should call moral in +man (e.g. disinterested self-sacrifice for the sake of others). The early +ape-like progenitors of the human race were undoubtedly social. With the +increase of intelligence the moral sense develops farther; with the +acquisition of speech public opinion arises, and finally, moral sense +becomes habit. The rest of Darwin's detailed discussions on moral +philosophy may be passed over. + +The fifth chapter may be very briefly summarised. In it Darwin shows that +the intellectual and moral faculties are perfected through natural +selection. He inquires how it can come about that a tribe at a low level +of evolution attains to a higher, although the best and bravest among them +often pay for their fidelity and courage with their lives without leaving +any descendants. In this case it is the sentiment of glory, praise and +blame, the admiration of others, which bring about the increase of the +better members of the tribe. Property, fixed dwellings, and the +association of families into a community are also indispensable +requirements for civilisation. In the longer second section of the fifth +chapter Darwin acts mainly as recorder. On the basis of numerous +investigations, especially those of Greg, Wallace, and Galton, he inquires +how far the influence of natural selection can be demonstrated in regard to +civilised nations. In the final section, which deals with the proofs that +all civilised nations were once barbarians, Darwin again uses the results +gained by other investigators, such as Lubbock and Tylor. There are two +sets of facts which prove the proposition in question. In the first place, +we find traces of a former lower state in the customs and beliefs of all +civilised nations, and in the second place, there are proofs to show that +savage races are independently able to raise themselves a few steps in the +scale of civilisation, and that they have thus raised themselves. + +In the sixth chapter of the work, Morphology comes into the foreground once +more. Darwin first goes back, however, to the argument based on the great +difference between the mental powers of the highest animals and those of +man. That this is only quantitative, not qualitative, he has already +shown. Very instructive in this connection is the reference to the +enormous difference in mental powers in another class. No one would draw +from the fact that the cochineal insect (Coccus) and the ant exhibit +enormous differences in their mental powers, the conclusion that the ant +should therefore be regarded as something quite distinct, and withdrawn +from the class of insects altogether. + +Darwin next attempts to establish the SPECIFIC genealogical tree of man, +and carefully weighs the differences and resemblances between the different +families of the Primates. The erect position of man is an adaptive +character, just as are the various characters referable to aquatic life in +the seals, which, notwithstanding these, are ranked as a mere family of the +Carnivores. The following utterance is very characteristic of Darwin +("Descent of Man", page 231.): "If man had not been his own classifier, he +would never have thought of founding a separate order for his own +reception." In numerous characters not mentioned in systematic works, in +the features of the face, in the form of the nose, in the structure of the +external ear, man resembles the apes. The arrangement of the hair in man +has also much in common with the apes; as also the occurrence of hair on +the forehead of the human embryo, the beard, the convergence of the hair of +the upper and under arm towards the elbow, which occurs not only in the +anthropoid apes, but also in some American monkeys. Darwin here adopts +Wallace's explanation of the origin of the ascending direction of the hair +in the forearm of the orang,--that it has arisen through the habit of +holding the hands over the head in rain. But this explanation cannot be +maintained when we consider that this disposition of the hair is widely +distributed among the most different mammals, being found in the dog, in +the sloth, and in many of the lower monkeys. + +After further careful analysis of the anatomical characters Darwin reaches +the conclusion that the New World monkeys (Platyrrhine) may be excluded +from the genealogical tree altogether, but that man is an offshoot from the +Old World monkeys (Catarrhine) whose progenitors existed as far back as the +Miocene period. Among these Old World monkeys the forms to which man shows +the greatest resemblance are the anthropoid apes, which, like him, possess +neither tail nor ischial callosities. The platyrrhine and catarrhine +monkeys have their primitive ancestor among extinct forms of the Lemuridae. +Darwin also touches on the question of the original home of the human race +and supposes that it may have been in Africa, because it is there that +man's nearest relatives, the gorilla and the chimpanzee, are found. But he +regards speculation on this point as useless. It is remarkable that, in +this connection, Darwin regards the loss of the hair-covering in man as +having some relation to a warm climate, while elsewhere he is inclined to +make sexual selection responsible for it. Darwin recognises the great gap +between man and his nearest relatives, but similar gaps exist at other +parts of the mammalian genealogical tree: the allied forms have become +extinct. After the extermination of the lower races of mankind, on the one +hand, and of the anthropoid apes on the other, which will undoubtedly take +place, the gulf will be greater than ever, since the baboons will then +bound it on the one side, and the white races on the other. Little weight +need be attached to the lack of fossil remains to fill up this gap, since +the discovery of these depends upon chance. The last part of the chapter +is devoted to a discussion of the earlier stages in the genealogy of man. +Here Darwin accepts in the main the genealogical tree, which had meantime +been published by Haeckel, who traces the pedigree back through Monotremes, +Reptiles, Amphibians, and Fishes, to Amphioxus. + +Then follows an attempt to reconstruct, from the atavistic characters, a +picture of our primitive ancestor who was undoubtedly an arboreal animal. +The occurrence of rudiments of parts in one sex which only come to full +development in the other is next discussed. This state of things Darwin +regards as derived from an original hermaphroditism. In regard to the +mammary glands of the male he does not accept the theory that they are +vestigial, but considers them rather as not fully developed. + +The last chapter of Part I deals with the question whether the different +races of man are to be regarded as different species, or as sub-species of +a race of monophyletic origin. The striking differences between the races +are first emphasised, and the question of the fertility or infertility of +hybrids is discussed. That fertility is the more usual is shown by the +excessive fertility of the hybrid population of Brazil. This, and the +great variability of the distinguishing characters of the different races, +as well as the fact that all grades of transition stages are found between +these, while considerable general agreement exists, tell in favour of the +unity of the races and lead to the conclusion that they all had a common +primitive ancestor. + +Darwin therefore classifies all the different races as sub-species of ONE +AND THE SAME SPECIES. Then follows an interesting inquiry into the reasons +for the extinction of human races. He recognises as the ultimate reason +the injurious effects of a change of the conditions of life, which may +bring about an increase in infantile mortality, and a diminished fertility. +It is precisely the reproductive system, among animals also, which is most +susceptible to changes in the environment. + +The final section of this chapter deals with the formation of the races of +mankind. Darwin discusses the question how far the direct effect of +different conditions of life, or the inherited effects of increased use or +disuse may have brought about the characteristic differences between the +different races. Even in regard to the origin of the colour of the skin he +rejects the transmitted effects of an original difference of climate as an +explanation. In so doing he is following his tendency to exclude +Lamarckian explanations as far as possible. But here he makes gratuitous +difficulties from which, since natural selection fails, there is no escape +except by bringing in the principle of sexual selection, to which, he +regarded it as possible, skin-colouring, arrangement of hair, and form of +features might be traced. But with his characteristic conscientiousness he +guards himself thus: "I do not intend to assert that sexual selection will +account for all the differences between the races." ("Descent of Man", +page 308.) + +I may be permitted a remark as to Darwin's attitude towards Lamarck. +While, at an earlier stage, when he was engaged in the preliminary labours +for his immortal work, "The Origin of Species", Darwin expresses himself +very forcibly against the views of Lamarck, speaking of Lamarckian +"nonsense," ("Life and Letters", Vol. II. page 23.), and of Lamarck's +"absurd, though clever work" (Loc. cit. page 39.) and expressly declaring, +"I attribute very little to the direct action of climate, etc." (Loc. cit. +(1856), page 82.) yet in later life he became more and more convinced of +the influence of external conditions. In 1876, that is, two years after +the appearance of the second edition of "The Descent of Man", he writes +with his usual candid honesty: "In my opinion the greatest error which I +have committed, has been not allowing sufficient weight to the direct +action of the environment, i.e. food, climate, etc. independently of +natural selection." (Ibid. Vol. III. page 159.) It is certain from this +change of opinion that, if he had been able to make up his mind to issue a +third edition of "The Descent of Man", he would have ascribed a much +greater influence to the effect of external conditions in explaining the +different characters of the races of man than he did in the second edition. +He would also undoubtedly have attributed less influence to sexual +selection as a factor in the origin of the different bodily +characteristics, if indeed he would not have excluded it altogether. + +In Part III of the "Descent" two additional chapters are devoted to the +discussion of sexual selection in relation to man. These may be very +briefly referred to. Darwin here seeks to show that sexual selection has +been operative on man and his primitive progenitor. Space fails me to +follow out his interesting arguments. I can only mention that he is +inclined to trace back hairlessness, the development of the beard in man, +and the characteristic colour of the different human races to sexual +selection. Since bareness of the skin could be no advantage, but rather a +disadvantage, this character cannot have been brought about by natural +selection. Darwin also rejected a direct influence of climate as a cause +of the origin of the skin-colour. I have already expressed the opinion, +based on the development of his views as shown in his letters, that in a +third edition Darwin would probably have laid more stress on the influence +of external environment. He himself feels that there are gaps in his +proofs here, and says in self-criticism: "The views here advanced, on the +part which sexual selection has played in the history of man, want +scientific precision." ("Descent of Man", page 924.) I need here only +point out that it is impossible to explain the graduated stages of skin- +colour by sexual selection, since it would have produced races sharply +defined by their colour and not united to other races by transition stages, +and this, it is well known, is not the case. Moreover, the fact +established by me ("Die Hautfarbe des Menschen", "Mitteilungen der +Anthropologischen Gesellschaft in Wien", Vol. XXXIV. pages 331-352.), that +in all races the ventral side of the trunk is paler than the dorsal side, +and the inner surface of the extremities paler than the outer side, cannot +be explained by sexual selection in the Darwinian sense. + +With this I conclude my brief survey of the rich contents of Darwin's book. +I may be permitted to conclude by quoting the magnificent final words of +"The Descent of Man": "We must, however, acknowledge, as it seems to me, +that man, with all his noble qualities, with sympathy which feels for the +most debased, with benevolence which extends not only to other men but to +the humblest living creature, with his god-like intellect which has +penetrated into the movements and constitution of the solar system--with +all these exalted powers--Man still bears in his bodily frame the indelible +stamp of his lowly origin." (Ibid. page 947.) + +What has been the fate of Darwin's doctrines since his great achievement? +How have they been received and followed up by the scientific and lay +world? And what do the successors of the mighty hero and genius think now +in regard to the origin of the human race? + +At the present time we are incomparably more favourably placed than Darwin +was for answering this question of all questions. We have at our command +an incomparably greater wealth of material than he had at his disposal. +And we are more fortunate than he in this respect, that we now know +transition-forms which help to fill up the gap, still great, between the +lowest human races and the highest apes. Let us consider for a little the +more essential additions to our knowledge since the publication of "The +Descent of Man". + +Since that time our knowledge of animal embryos has increased enormously. +While Darwin was obliged to content himself with comparing a human embryo +with that of a dog, there are now available the youngest embryos of monkeys +of all possible groups (Orang, Gibbon, Semnopithecus, Macacus), thanks to +Selenka's most successful tour in the East Indies in search of such +material. We can now compare corresponding stages of the lower monkeys and +of the Anthropoid apes with human embryos, and convince ourselves of their +great resemblance to one another, thus strengthening enormously the armour +prepared by Darwin in defence of his view on man's nearest relatives. It +may be said that Selenka's material fils up the blanks in Darwin's array of +proofs in the most satisfactory manner. + +The deepening of our knowledge of comparative anatomy also gives us much +surer foundations than those on which Darwin was obliged to build. Just of +late there have been many workers in the domain of the anatomy of apes and +lemurs, and their investigations extend to the most different organs. Our +knowledge of fossil apes and lemurs has also become much wider and more +exact since Darwin's time: the fossil lemurs have been especially worked +up by Cope, Forsyth Major, Ameghino, and others. Darwin knew very little +about fossil monkeys. He mentions two or three anthropoid apes as +occurring in the Miocene of Europe ("Descent of Man", page 240.), but only +names Dryopithecus, the largest form from the Miocene of France. It was +erroneously supposed that this form was related to Hylobates. We now know +not only a form that actually stands near to the gibbon (Pliopithecus), and +remains of other anthropoids (Pliohylobates and the fossil chimpanzee, +Palaeopithecus), but also several lower catarrhine monkeys, of which +Mesopithecus, a form nearly related to the modern Sacred Monkeys (a species +of Semnopithecus) and found in strata of the Miocene period in Greece, is +the most important. Quite recently, too, Ameghino's investigations have +made us acquainted with fossil monkeys from South America (Anthropops, +Homunculus), which, according to their discoverer, are to be regarded as in +the line of human descent. + +What Darwin missed most of all--intermediate forms between apes and man-- +has been recently furnished. (E. Dubois, as is well known, discovered in +1893, near Trinil in Java, in the alluvial deposits of the river Bengawan, +an important form represented by a skull-cap, some molars, and a femur. +His opinion--much disputed as it has been--that in this form, which he +named Pithecanthropus, he has found a long-desired transition-form is +shared by the present writer. And although the geological age of these +fossils, which, according to Dubois, belong to the uppermost Tertiary +series, the Pliocene, has recently been fixed at a later date (the older +Diluvium), the MORPHOLOGICAL VALUE of these interesting remains, that is, +the intermediate position of Pithecanthropus, still holds good. Volz says +with justice ("Das geologische Alter der Pithecanthropus-Schichten bei +Trinil, Ost-Java". "Neues Jahrb. f.Mineralogie". Festband, 1907.), that +even if Pithecanthropus is not THE missing link, it is undoubtedly _A_ +missing link. + +As on the one hand there has been found in Pithecanthropus a form which, +though intermediate between apes and man, is nevertheless more closely +allied to the apes, so on the other hand, much progress has been made since +Darwin's day in the discovery and description of the older human remains. +Since the famous roof of a skull and the bones of the extremities belonging +to it were found in 1856 in the Neandertal near Dusseldorf, the most varied +judgments have been expressed in regard to the significance of the remains +and of the skull in particular. In Darwin's "Descent of Man" there is only +a passing allusion to them ("Descent of Man", page 82.) in connection with +the discussion of the skull-capacity, although the investigations of +Schaaffhausen, King, and Huxley were then known. I believe I have shown, +in a series of papers, that the skull in question belongs to a form +different from any of the races of man now living, and, with King and Cope, +I regard it as at least a different species from living man, and have +therefore designated it Homo primigenius. The form unquestionably belongs +to the older Diluvium, and in the later Diluvium human forms already +appear, which agree in all essential points with existing human races. + +As far back as 1886 the value of the Neandertal skull was greatly enhanced +by Fraipont's discovery of two skulls and skeletons from Spy in Belgium. +These are excellently described by their discoverer ("La race humaine de +Neanderthal ou de Canstatt en Belgique". "Arch. de Biologie", VII. 1887.), +and are regarded as belonging to the same group of forms as the Neandertal +remains. In 1899 and the following years came the discovery by Gorjanovic- +Kramberger of different skeletal parts of at least ten individuals in a +cave near Krapina in Croatia. (Gorjanovic-Kramberger "Der diluviale Mensch +von Krapina in Kroatien", 1906.) It is in particular the form of the lower +jaw which is different from that of all recent races of man, and which +clearly indicates the lowly position of Homo primigenius, while, on the +other hand, the long-known skull from Gibraltar, which I ("Studien zur +Vorgeschichte des Menschen", 1906, pages 154 ff.) have referred to Homo +primigenius, and which has lately been examined in detail by Sollas ("On +the cranial and facial characters of the Neandertal Race". "Trans. R. +Soc." London, vol. 199, 1908, page 281.), has made us acquainted with the +surprising shape of the eye-orbit, of the nose, and of the whole upper part +of the face. Isolated lower jaws found at La Naulette in Belgium, and at +Malarnaud in France, increase our material which is now as abundant as +could be desired. The most recent discovery of all is that of a skull dug +up in August of this year (1908) by Klaatsch and Hauser in the lower grotto +of the Le Moustier in Southern France, but this skull has not yet been +fully described. Thus Homo primigenius must also be regarded as occupying +a position in the gap existing between the highest apes and the lowest +human races, Pithecanthropus, standing in the lower part of it, and Homo +primigenius in the higher, near man. In order to prevent misunderstanding, +I should like here to emphasise that in arranging this structural series-- +anthropoid apes, Pithecanthropus, Homo primigenius, Homo sapiens--I have no +intention of establishing it as a direct genealogical series. I shall have +something to say in regard to the genetic relations of these forms, one to +another, when discussing the different theories of descent current at the +present day. ((Since this essay was written Schoetensack has discovered +near Heidelberg and briefly described an exceedingly interesting lower jaw +from rocks between the Pliocene and Diluvial beds. This exhibits +interesting differences from the forms of lower jaw of Homo primigenius. +(Schoetensack "Der Unterkiefer des Homo heidelbergensis". Leipzig, 1908.) +G.S.)) + +In quite a different domain from that of morphological relationship, namely +in the physiological study of the blood, results have recently been gained +which are of the highest importance to the doctrine of descent. Uhlenhuth, +Nuttall, and others have established the fact that the blood-serum of a +rabbit which has previously had human blood injected into it, forms a +precipitate with human blood. This biological reaction was tried with a +great variety of mammalian species, and it was found that those far removed +from man gave no precipitate under these conditions. But as in other cases +among mammals all nearly related forms yield an almost equally marked +precipitate, so the serum of a rabbit treated with human blood and then +added to the blood of an anthropoid ape gives ALMOST as marked a +precipitate as in human blood; the reaction to the blood of the lower +Eastern monkeys is weaker, that to the Western monkeys weaker still; indeed +in this last case there is only a slight clouding after a considerable time +and no actual precipitate. The blood of the Lemuridae (Nuttall) gives no +reaction or an extremely weak one, that of the other mammals none whatever. +We have in this not only a proof of the literal blood-relationship between +man and apes, but the degree of relationship with the different main groups +of apes can be determined beyond possibility of mistake. + +Finally, it must be briefly mentioned that in regard to remains of human +handicraft also, the material at our disposal has greatly increased of late +years, that, as a result of this, the opinions of archaeologists have +undergone many changes, and that, in particular, their views in regard to +the age of the human race have been greatly influenced. There is a +tendency at the present time to refer the origin of man back to Tertiary +times. It is true that no remains of Tertiary man have been found, but +flints have been discovered which, according to the opinion of most +investigators, bear traces either of use, or of very primitive workmanship. +Since Rutot's time, following Mortillet's example, investigators have +called these "eoliths," and they have been traced back by Verworn to the +Miocene of the Auvergne, and by Rutot even to the upper Oligocene. +Although these eoliths are even nowadays the subject of many different +views, the preoccupation with them has kept the problem of the age of the +human race continually before us. + +Geology, too, has made great progress since the days of Darwin and Lyell, +and has endeavoured with satisfactory results to arrange the human remains +of the Diluvial period in chronological order (Penck). I do not intend to +enter upon the question of the primitive home of the human race; since the +space at my disposal will not allow of my touching even very briefly upon +all the departments of science which are concerned in the problem of the +descent of man. How Darwin would have rejoiced over each of the +discoveries here briefly outlined! What use he would have made of the new +and precious material, which would have prevented the discouragement from +which he suffered when preparing the second edition of "The Descent of +Man"! But it was not granted to him to see this progress towards filling +up the gaps in his edifice of which he was so painfully conscious. + +He did, however, have the satisfaction of seeing his ideas steadily gaining +ground, notwithstanding much hostility and deep-rooted prejudice. Even in +the years between the appearance of "The Origin of Species" and of the +first edition of the "Descent", the idea of a natural descent of man, which +was only briefly indicated in the work of 1859, had been eagerly welcomed +in some quarters. It has been already pointed out how brilliantly Huxley +contributed to the defence and diffusion of Darwin's doctrines, and how in +"Man's Place in Nature" he has given us a classic work as a foundation for +the doctrine of the descent of man. As Huxley was Darwin's champion in +England, so in Germany Carl Vogt, in particular, made himself master of the +Darwinian ideas. But above all it was Haeckel who, in energy, eagerness +for battle, and knowledge may be placed side by side with Huxley, who took +over the leadership in the controversy over the new conception of the +universe. As far back as 1866, in his "Generelle Morphologie", he had +inquired minutely into the question of the descent of man, and not content +with urging merely the general theory of descent from lower animal forms, +he drew up for the first time genealogical trees showing the close +relationships of the different animal groups; the last of these illustrated +the relationships of Mammals, and among them of all groups of the Primates, +including man. It was Haeckel's genealogical trees that formed the basis +of the special discussion of the relationships of man, in the sixth chapter +of Darwin's "Descent of Man". + +In the last section of this essay I shall return to Haeckel's conception of +the special descent of man, the main features of which he still upholds, +and rightly so. Haeckel has contributed more than any one else to the +spread of the Darwinian doctrine. + +I can only allow myself a few words as to the spread of the theory of the +natural descent of man in other countries. The Parisian anthropological +school, founded and guided by the genius of Broca, took up the idea of the +descent of man, and made many notable contributions to it (Broca, +Manouvrier, Mahoudeau, Deniker and others). In England itself Darwin's +work did not die. Huxley took care of that, for he, with his lofty and +unprejudiced mind, dominated and inspired English biology until his death +on June 29, 1895. He had the satisfaction shortly before his death of +learning of Dubois' discovery, which he illustrated by a humorous sketch. +("Life and Letters of Thomas Henry Huxley", Vol. II. page 394.) But there +are still many followers in Darwin's footsteps in England. Keane has +worked at the special genealogical tree of the Primates; Keith has inquired +which of the anthropoid apes has the greatest number of characters in +common with man; Morris concerns himself with the evolution of man in +general, especially with his acquisition of the erect position. The recent +discoveries of Pithecanthropus and Homo primigenius are being vigorously +discussed; but the present writer is not in a position to form an opinion +of the extent to which the idea of descent has penetrated throughout +England generally. + +In Italy independent work in the domain of the descent of man is being +produced, especially by Morselli; with him are associated, in the +investigation of related problems, Sergi and Giuffrida-Ruggeri. From the +ranks of American investigators we may single out in particular the eminent +geologist Cope, who championed with much decision the idea of the specific +difference of Homo neandertalensis (primigenius) and maintained a more +direct descent of man from the fossil Lemuridae. In South America too, in +Argentina, new life is stirring in this department of science. Ameghino in +Buenos Ayres has awakened the fossil primates of the Pampas formation to +new life; he even believes that in Tetraprothomo, represented by a femur, +he has discovered a direct ancestor of man. Lehmann-Nitsche is working at +the other side of the gulf between apes and men, and he describes a +remarkable first cervical vertebra (atlas) from Monte Hermoso as belonging +to a form which may bear the same relation to Homo sapiens in South America +as Homo primigenius does in the Old World. After a minute investigation he +establishes a human species Homo neogaeus, while Ameghino ascribes this +atlas vertebra to his Tetraprothomo. + +Thus throughout the whole scientific world there is arising a new life, an +eager endeavour to get nearer to Huxley's problema maximum, to penetrate +more deeply into the origin of the human race. There are to-day very few +experts in anatomy and zoology who deny the animal descent of man in +general. Religious considerations, old prejudices, the reluctance to +accept man, who so far surpasses mentally all other creatures, as descended +from "soulless" animals, prevent a few investigators from giving full +adherence to the doctrine. But there are very few of these who still +postulate a special act of creation for man. Although the majority of +experts in anatomy and zoology accept unconditionally the descent of man +from lower forms, there is much diversity of opinion among them in regard +to the special line of descent. + +In trying to establish any special hypothesis of descent, whether by the +graphic method of drawing up genealogical trees or otherwise, let us always +bear in mind Darwin's words ("Descent of Man", page 229.) and use them as a +critical guiding line: "As we have no record of the lines of descent, the +pedigree can be discovered only by observing the degrees of resemblance +between the beings which are to be classed." Darwin carries this further +by stating "that resemblances in several unimportant structures, in useless +and rudimentary organs, or not now functionally active, or in an +embryological condition, are by far the most serviceable for +classification." (Loc. cit.) It has also to be remembered that NUMEROUS +separate points of agreement are of much greater importance than the amount +of similarity or dissimilarity in a few points. + +The hypotheses as to descent current at the present day may be divided into +two main groups. The first group seeks for the roots of the human race not +among any of the families of the apes--the anatomically nearest forms--nor +among their very similar but less specialised ancestral forms, the fossil +representatives of which we can know only in part, but, setting the monkeys +on one side, it seeks for them lower down among the fossil Eocene Pseudo- +lemuridae or Lemuridae (Cope), or even among the primitive pentadactylous +Eocene forms, which may either have led directly to the evolution of man +(Adloff), or have given rise to an ancestral form common to apes and men +(Klaatsch (Klaatsch in his last publications speaks in the main only of an +ancestral form common to men and anthropoid apes.), Giuffrida-Ruggeri). +The common ancestral form, from which man and apes are thus supposed to +have arisen independently, may explain the numerous resemblances which +actually exist between them. That is to say, all the characters upon which +the great structural resemblance between apes and man depends must have +been present in their common ancestor. Let us take an example of such a +common character. The bony external ear-passage is in general as highly +developed in the lower Eastern monkeys and the anthropoid apes as in man. +This character must, therefore, have already been present in the common +primitive form. In that case it is not easy to understand why the Western +monkeys have not also inherited the character, instead of possessing only a +tympanic ring. But it becomes more intelligible if we assume that forms +with a primitive tympanic ring were the original type, and that from these +were evolved, on the one hand, the existing New World monkeys with +persistent tympanic ring, and on the other an ancestral form common to the +lower Old World monkeys, the anthropoid apes and man. For man shares with +these the character in question, and it is also one of the "unimportant" +characters required by Darwin. Thus we have two divergent lines arising +from the ancestral form, the Western monkeys (Platyrrhine) on the one hand, +and an ancestral form common to the lower Eastern monkeys, the anthropoid +apes, and man, on the other. But considerations similar to those which +showed it to be impossible that man should have developed from an ancestor +common to him and the monkeys, yet outside of and parallel with these, may +be urged also against the likelihood of a parallel evolution of the lower +Eastern monkeys, the anthropoid apes, and man. The anthropoid apes have in +common with man many characters which are not present in the lower Old +World monkeys. These characters must therefore have been present in the +ancestral form common to the three groups. But here, again, it is +difficult to understand why the lower Eastern monkeys should not also have +inherited these characters. As this is not the case, there remains no +alternative but to assume divergent evolution from an indifferent form. +The lower Eastern monkeys are carrying on the evolution in one direction--I +might almost say towards a blind alley--while anthropoids and men have +struck out a progressive path, at first in common, which explains the many +points of resemblance between them, without regarding man as derived +directly from the anthropoids. Their many striking points of agreement +indicate a common descent, and cannot be explained as phenomena of +convergence. + +I believe I have shown in the above sketch that a theory which derives man +directly from lower forms without regarding apes as transition-types leads +ad absurdum. The close structural relationship between man and monkeys can +only be understood if both are brought into the same line of evolution. To +trace man's line of descent directly back to the old Eocene mammals, +alongside of, but with no relation to these very similar forms, is to +abandon the method of exact comparison, which, as Darwin rightly +recognised, alone justifies us in drawing up genealogical trees on the +basis of resemblances and differences. The farther down we go the more +does the ground slip from beneath our feet. Even the Lemuridae show very +numerous divergent conditions, much more so the Eocene mammals (Creodonta, +Condylarthra), the chief resemblance of which to man consists in the +possession of pentadactylous hands and feet! Thus the farther course of +the line of descent disappears in the darkness of the ancestry of the +mammals. With just as much reason we might pass by the Vertebrates +altogether, and go back to the lower Invertebrates, but in that case it +would be much easier to say that man has arisen independently, and has +evolved, without relation to any animals, from the lowest primitive form to +his present isolated and dominant position. But this would be to deny all +value to classification, which must after all be the ultimate basis of a +genealogical tree. We can, as Darwin rightly observed, only infer the line +of descent from the degree of resemblance between single forms. If we +regard man as directly derived from primitive forms very far back, we have +no way of explaining the many points of agreement between him and the +monkeys in general, and the anthropoid apes in particular. These must +remain an inexplicable marvel. + +I have thus, I trust, shown that the first class of special theories of +descent, which assumes that man has developed, parallel with the monkeys, +but without relation to them, from very low primitive forms cannot be +upheld, because it fails to take into account the close structural affinity +of man and monkeys. I cannot but regard this hypothesis as lamentably +retrograde, for it makes impossible any application of the facts that have +been discovered in the course of the anatomical and embryological study of +man and monkeys, and indeed prejudges investigations of that class as +pointless. The whole method is perverted; an unjustifiable theory of +descent is first formulated with the aid of the imagination, and then we +are asked to declare that all structural relations between man and monkeys, +and between the different groups of the latter, are valueless,--the fact +being that they are the only true basis on which a genealogical tree can be +constructed. + +So much for this most modern method of classification, which has probably +found adherents because it would deliver us from the relationship to apes +which many people so much dislike. In contrast to it we have the second +class of special hypotheses of descent, which keeps strictly to the nearest +structural relationships. This is the only basis that justifies the +drawing up of a special hypothesis of descent. If this fundamental +proposition be recognised, it will be admitted that the doctrine of special +descent upheld by Haeckel, and set forth in Darwin's "Descent of Man", is +still valid to-day. In the genealogical tree, man's place is quite close +to the anthropoid apes; these again have as their nearest relatives the +lower Old World monkeys, and their progenitors must be sought among the +less differentiated Platyrrhine monkeys, whose most important characters +have been handed on to the present day New World monkeys. How the +different genera are to be arranged within the general scheme indicated +depends in the main on the classificatory value attributed to individual +characters. This is particularly true in regard to Pithecanthropus, which +I consider as the root of a branch which has sprung from the anthropoid ape +root and has led up to man; the latter I have designated the family of the +Hominidae. + +For the rest, there are, as we have said, various possible ways of +constructing the narrower genealogy within the limits of this branch +including men and apes, and these methods will probably continue to change +with the accumulation of new facts. Haeckel himself has modified his +genealogical tree of the Primates in certain details since the publication +of his "Generelle Morphologie" in 1866, but its general basis remains the +same. (Haeckel's latest genealogical tree is to be found in his most +recent work, "Unsere Ahnenreihe". Jena, 1908.) All the special +genealogical trees drawn up on the lines laid down by Haeckel and Darwin-- +and that of Dubois may be specially mentioned--are based, in general, on +the close relationship of monkeys and men, although they may vary in +detail. Various hypotheses have been formulated on these lines, with +special reference to the evolution of man. "Pithecanthropus" is regarded +by some authorities as the direct ancestor of man, by others as a side- +track failure in the attempt at the evolution of man. The problem of the +monophyletic or polyphyletic origin of the human race has also been much +discussed. Sergi (Sergi G. "Europa", 1908.) inclines towards the +assumption of a polyphyletic origin of the three main races of man, the +African primitive form of which has given rise also to the gorilla and +chimpanzee, the Asiatic to the Orang, the Gibbon, and Pithecanthropus. +Kollmann regards existing human races as derived from small primitive races +(pigmies), and considers that Homo primigenius must have arisen in a +secondary and degenerative manner. + +But this is not the place, nor have I the space to criticise the various +special theories of descent. One, however, must receive particular notice. +According to Ameghino, the South American monkeys (Pitheculites) from the +oldest Tertiary of the Pampas are the forms from which have arisen the +existing American monkeys on the one hand, and on the other, the extinct +South American Homunculidae, which are also small forms. From these last, +anthropoid apes and man have, he believes, been evolved. Among the +progenitors of man, Ameghino reckons the form discovered by him +(Tetraprothomo), from which a South American primitive man, Homo pampaeus, +might be directly evolved, while on the other hand all the lower Old World +monkeys may have arisen from older fossil South American forms +(Clenialitidae), the distribution of which may be explained by the bridge +formerly existing between South America and Africa, as may be the +derivation of all existing human races from Homo pampaeus. (See Ameghino's +latest paper, "Notas preliminares sobre el Tetraprothomo argentinus", etc. +"Anales del Museo nacional de Buenos Aires", XVI. pages 107-242, 1907.) +The fossil forms discovered by Ameghino deserve the most minute +investigation, as does also the fossil man from South America of which +Lehmann-Nitsche ("Nouvelles recherches sur la formation pampeenne et +l'homme fossile de la Republique Argentine". "Rivista del Museo de la +Plata", T. XIV. pages 193-488.) has made a thorough study. + +It is obvious that, notwithstanding the necessity for fitting man's line of +descent into the genealogical tree of the Primates, especially the apes, +opinions in regard to it differ greatly in detail. This could not be +otherwise, since the different Primate forms, especially the fossil forms, +are still far from being exhaustively known. But one thing remains +certain,--the idea of the close relationship between man and monkeys set +forth in Darwin's "Descent of Man". Only those who deny the many points of +agreement, the sole basis of classification, and thus of a natural +genealogical tree, can look upon the position of Darwin and Haeckel as +antiquated, or as standing on an insufficient foundation. For such a +genealogical tree is nothing more than a summarised representation of what +is known in regard to the degree of resemblance between the different +forms. + +Darwin's work in regard to the descent of man has not been surpassed; the +more we immerse ourselves in the study of the structural relationships +between apes and man, the more is our path illumined by the clear light +radiating from him, and through his calm and deliberate investigation, +based on a mass of material in the accumulation of which he has never had +an equal. Darwin's fame will be bound up for all time with the +unprejudiced investigation of the question of all questions, the descent of +the human race. + + +VIII. CHARLES DARWIN AS AN ANTHROPOLOGIST. + +By ERNST HAECKEL. +Professor of Zoology in the University of Jena. + +The great advance that anthropology has made in the second half of the +nineteenth century is due in the first place, to Darwin's discovery of the +origin of man. No other problem in the whole field of research is so +momentous as that of "Man's place in nature," which was justly described by +Huxley (1863) as the most fundamental of all questions. Yet the scientific +solution of this problem was impossible until the theory of descent had +been established. + +It is now a hundred years since the great French biologist Jean Lamarck +published his "Philosophie Zoologique". By a remarkable coincidence the +year in which that work was issued, 1809, was the year of the birth of his +most distinguished successor, Charles Darwin. Lamarck had already +recognised that the descent of man from a series of other Vertebrates--that +is, from a series of Ape-like Primates--was essentially involved in the +general theory of transformation which he had erected on a broad inductive +basis; and he had sufficient penetration to detect the agencies that had +been at work in the evolution of the erect bimanous man from the arboreal +and quadrumanous ape. He had, however, few empirical arguments to advance +in support of his hypothesis, and it could not be established until the +further development of the biological sciences--the founding of comparative +embryology by Baer (1828) and of the cell-theory by Schleiden and Schwann +(1838), the advance of physiology under Johannes Muller (1833), and the +enormous progress of palaeontology and comparative anatomy between 1820 and +1860--provided this necessary foundation. Darwin was the first to +coordinate the ample results of these lines of research. With no less +comprehensiveness than discrimination he consolidated them as a basis of a +modified theory of descent, and associated with them his own theory of +natural selection, which we take to be distinctive of "Darwinism" in the +stricter sense. The illuminating truth of these cumulative arguments was +so great in every branch of biology that, in spite of the most vehement +opposition, the battle was won within a single decade, and Darwin secured +the general admiration and recognition that had been denied to his +forerunner, Lamarck, up to the hour of his death (1829). + +Before, however, we consider the momentous influence that Darwinism has had +in anthropology, we shall find it useful to glance at its history in the +course of the last half century, and notice the various theories that have +contributed to its advance. The first attempt to give extensive expression +to the reform of biology by Darwin's work will be found in my "Generelle +Morphologie" (1866) ("Generelle Morphologie der Organismen", 2 vols., +Berlin, 1866.) which was followed by a more popular treatment of the +subject in my "Naturliche Schopfungsgeschichte (1868) (English translation; +"The History of Creation", London, 1876.), a compilation from the earlier +work. In the first volume of the "Generelle Morphologie" I endeavoured to +show the great importance of evolution in settling the fundamental +questions of biological philosophy, especially in regard to comparative +anatomy. In the second volume I dealt broadly with the principle of +evolution, distinguishing ontogeny and phylogeny as its two coordinate main +branches, and associating the two in the Biogenetic Law. The Law may be +formulated thus: "Ontogeny (embryology or the development of the +individual) is a concise and compressed recapitulation of phylogeny (the +palaeontological or genealogical series) conditioned by laws of heredity +and adaptation." The "Systematic introduction to general evolution," with +which the second volume of the "Generelle Morphologie" opens, was the first +attempt to draw up a natural system of organisms (in harmony with the +principles of Lamarck and Darwin) in the form of a hypothetical pedigree, +and was provisionally set forth in eight genealogical tables. + +In the nineteenth chapter of the "Generelle Morphologie"--a part of which +has been republished, without any alteration, after a lapse of forty years +--I made a critical study of Lamarck's theory of descent and of Darwin's +theory of selection, and endeavoured to bring the complex phenomena of +heredity and adaptation under definite laws for the first time. Heredity I +divided into conservative and progressive: adaptation into indirect (or +potential) and direct (or actual). I then found it possible to give some +explanation of the correlation of the two physiological functions in the +struggle for life (selection), and to indicate the important laws of +divergence (or differentiation) and complexity (or division of labour), +which are the direct and inevitable outcome of selection. Finally, I +marked off dysteleology as the science of the aimless (vestigial, abortive, +atrophied, and useless) organs and parts of the body. In all this I worked +from a strictly monistic standpoint, and sought to explain all biological +phenomena on the mechanical and naturalistic lines that had long been +recognised in the study of inorganic nature. Then (1866), as now, being +convinced of the unity of nature, the fundamental identity of the agencies +at work in the inorganic and the organic worlds, I discarded vitalism, +teleology, and all hypotheses of a mystic character. + +It was clear from the first that it was essential, in the monistic +conception of evolution, to distinguish between the laws of conservative +and progressive heredity. Conservative heredity maintains from generation +to generation the enduring characters of the species. Each organism +transmits to its descendants a part of the morphological and physiological +qualities that it has received from its parents and ancestors. On the +other hand, progressive heredity brings new characters to the species-- +characters that were not found in preceding generations. Each organism may +transmit to its offspring a part of the morphological and physiological +features that it has itself acquired, by adaptation, in the course of its +individual career, through the use or disuse of particular organs, the +influence of environment, climate, nutrition, etc. At that time I gave the +name of "progressive heredity" to this inheritance of acquired characters, +as a short and convenient expression, but have since changed the term to +"transformative heredity" (as distinguished from conservative). This term +is preferable, as inherited regressive modifications (degeneration, +retrograde metamorphisis, etc.) come under the same head. + +Transformative heredity--or the transmission of acquired characters--is one +of the most important principles in evolutionary science. Unless we admit +it most of the facts of comparative anatomy and physiology are +inexplicable. That was the conviction of Darwin no less than of Lamarck, +of Spencer as well as Virchow, of Huxley as well as Gegenbaur, indeed of +the great majority of speculative biologists. This fundamental principle +was for the first time called in question and assailed in 1885 by August +Weismann of Freiburg, the eminent zoologist to whom the theory of evolution +owes a great deal of valuable support, and who has attained distinction by +his extension of the theory of selection. In explanation of the phenomena +of heredity he introduced a new theory, the "theory of the continuity of +the germ-plasm." According to him the living substance in all organisms +consists of two quite distinct kinds of plasm, somatic and germinal. The +permanent germ-plasm, or the active substance of the two germ-cells (egg- +cell and sperm-cell), passes unchanged through a series of generations, and +is not affected by environmental influences. The environment modifies only +the soma-plasm, the organs and tissues of the body. The modifications that +these parts undergo through the influence of the environment or their own +activity (use and habit), do not affect the germ-plasm, and cannot +therefore be transmitted. + +This theory of the continuity of the germ-plasm has been expounded by +Weismann during the last twenty-four years in a number of able volumes, and +is regarded by many biologists, such as Mr Francis Galton, Sir E. Ray +Lankester, and Professor J. Arthur Thomson (who has recently made a +thoroughgoing defence of it in his important work "Heredity" (London, +1908.)), as the most striking advance in evolutionary science. On the +other hand, the theory has been rejected by Herbert Spencer, Sir W. Turner, +Gegenbaur, Kolliker, Hertwig, and many others. For my part I have, with +all respect for the distinguished Darwinian, contested the theory from the +first, because its whole foundation seems to me erroneous, and its +deductions do not seem to be in accord with the main facts of comparative +morphology and physiology. Weismann's theory in its entirety is a finely +conceived molecular hypothesis, but it is devoid of empirical basis. The +notion of the absolute and permanent independence of the germ-plasm, as +distinguished from the soma-plasm, is purely speculative; as is also the +theory of germinal selection. The determinants, ids, and idants, are +purely hypothetical elements. The experiments that have been devised to +demonstrate their existence really prove nothing. + +It seems to me quite improper to describe this hypothetical structure as +"Neodarwinism." Darwin was just as convinced as Lamarck of the +transmission of acquired characters and its great importance in the scheme +of evolution. I had the good fortune to visit Darwin at Down three times +and discuss with him the main principles of his system, and on each +occasion we were fully agreed as to the incalculable importance of what I +call transformative inheritance. It is only proper to point out that +Weismann's theory of the germ-plasm is in express contradiction to the +fundamental principles of Darwin and Lamarck. Nor is it more acceptable in +what one may call its "ultradarwinism"--the idea that the theory of +selection explains everything in the evolution of the organic world. This +belief in the "omnipotence of natural selection" was not shared by Darwin +himself. Assuredly, I regard it as of the utmost value, as the process of +natural selection through the struggle for life affords an explanation of +the mechanical origin of the adapted organisation. It solves the great +problem: how could the finely adapted structure of the animal or plant +body be formed unless it was built on a preconceived plan? It thus enables +us to dispense with the teleology of the metaphysician and the dualist, and +to set aside the old mythological and poetic legends of creation. The idea +had occurred in vague form to the great Empedocles 2000 years before the +time of Darwin, but it was reserved for modern research to give it ample +expression. Nevertheless, natural selection does not of itself give the +solution of all our evolutionary problems. It has to be taken in +conjunction with the transformism of Lamarck, with which it is in complete +harmony. + +The monumental greatness of Charles Darwin, who surpasses every other +student of science in the nineteenth century by the loftiness of his +monistic conception of nature and the progressive influence of his ideas, +is perhaps best seen in the fact that not one of his many successors has +succeeded in modifying his theory of descent in any essential point or in +discovering an entirely new standpoint in the interpretation of the organic +world. Neither Nageli nor Weismann, neither De Vries nor Roux, has done +this. Nageli, in his "Mechanisch-Physiologische Theorie der +Abstammungslehre" (Munich, 1884.), which is to a great extent in agreement +with Weismann, constructed a theory of the idioplasm, that represents it +(like the germ-plasm) as developing continuously in a definite direction +from internal causes. But his internal "principle of progress" is at the +bottom just as teleological as the vital force of the Vitalists, and the +micellar structure of the idioplasm is just as hypothetical as the +"dominant" structure of the germ-plasm. In 1889 Moritz Wagner sought to +explain the origin of species by migration and isolation, and on that basis +constructed a special "migration-theory." This, however, is not out of +harmony with the theory of selection. It merely elevates one single factor +in the theory to a predominant position. Isolation is only a special case +of selection, as I had pointed out in the fifteenth chapter of my "Natural +history of creation". The "mutation-theory" of De Vries ("Die +Mutationstheorie", Leipzig, 1903.), that would explain the origin of +species by sudden and saltatory variations rather than by gradual +modification, is regarded by many botanists as a great step in advance, but +it is generally rejected by zoologists. It affords no explanation of the +facts of adaptation, and has no causal value. + +Much more important than these theories is that of Wilhelm Roux ("Der Kampf +der Theile im Organismus", Leipzig, 1881.) of "the struggle of parts within +the organism, a supplementation of the theory of mechanical adaptation." +He explains the functional autoformation of the purposive structure by a +combination of Darwin's principle of selection with Lamarck's idea of +transformative heredity, and applies the two in conjunction to the facts of +histology. He lays stress on the significance of functional adaptation, +which I had described in 1866, under the head of cumulative adaptation, as +the most important factor in evolution. Pointing out its influence in the +cell-life of the tissues, he puts "cellular selection" above "personal +selection," and shows how the finest conceivable adaptations in the +structure of the tissue may be brought about quite mechanically, without +preconceived plan. This "mechanical teleology" is a valuable extension of +Darwin's monistic principle of selection to the whole field of cellular +physiology and histology, and is wholly destructive of dualistic vitalism. + +The most important advance that evolution has made since Darwin and the +most valuable amplification of his theory of selection is, in my opinion, +the work of Richard Semon: "Die Mneme als erhaltendes Prinzip im Wechsel +des organischen Geschehens" (Leipzig, 1904.). He offers a psychological +explanation of the facts of heredity by reducing them to a process of +(unconscious) memory. The physiologist Ewald Hering had shown in 1870 that +memory must be regarded as a general function of organic matter, and that +we are quite unable to explain the chief vital phenomena, especially those +of reproduction and inheritance, unless we admit this unconscious memory. +In my essay "Die Perigenesis der Plastidule" (Berlin, 1876.) I elaborated +this far-reaching idea, and applied the physical principle of transmitted +motion to the plastidules, or active molecules of plasm. I concluded that +"heredity is the memory of the plastidules, and variability their power of +comprehension." This "provisional attempt to give a mechanical explanation +of the elementary processes of evolution" I afterwards extended by showing +that sensitiveness is (as Carl Nageli, Ernst Mach, and Albrecht Rau express +it) a general quality of matter. This form of panpsychism finds its +simplest expression in the "trinity of substance." + +To the two fundamental attributes that Spinoza ascribed to substance-- +Extension (matter as occupying space) and Cogitation (energy, force)--we +now add the third fundamental quality of Psychoma (sensitiveness, soul). I +further elaborated this trinitarian conception of substance in the +nineteenth chapter of my "Die Lebenswunder" (1904) ("Wonders of Life", +London, 1904.), and it seems to me well calculated to afford a monistic +solution of many of the antitheses of philosophy. + +This important Mneme-theory of Semon and the luminous physiological +experiments and observations associated with it not only throw considerable +light on transformative inheritance, but provide a sound physiological +foundation for the biogenetic law. I had endeavoured to show in 1874, in +the first chapter of my "Anthropogenie" (English translation; "The +Evolution of Man", 2 volumes, London, 1879 and 1905.), that this +fundamental law of organic evolution holds good generally, and that there +is everywhere a direct causal connection between ontogeny and phylogeny. +"Phylogenesis is the mechanical cause of ontogenesis"; in other words, "The +evolution of the stem or race is--in accordance with the laws of heredity +and adaptation--the real cause of all the changes that appear, in a +condensed form, in the development of the individual organism from the +ovum, in either the embryo or the larva." + +It is now fifty years since Charles Darwin pointed out, in the thirteenth +chapter of his epoch-making "Origin of Species", the fundamental importance +of embryology in connection with his theory of descent: + +"The leading facts in embryology, which are second to none in importance, +are explained on the principle of variations in the many descendants from +some one ancient progenitor, having appeared at a not very early period of +life, and having been inherited at a corresponding period." ("Origin of +Species" (6th edition), page 396.) + +He then shows that the striking resemblance of the embryos and larvae of +closely related animals, which in the mature stage belong to widely +different species and genera, can only be explained by their descent from a +common progenitor. Fritz Muller made a closer study of these important +phenomena in the instructive instance of the Crustacean larva, as given in +his able work "Fur Darwin" (1864). (English translation; "Facts and +Arguments for Darwin", London, 1869.) I then, in 1872, extended the range +so as to include all animals (with the exception of the unicellular +Protozoa) and showed, by means of the theory of the Gastraea, that all +multicellular, tissue-forming animals--all the Metazoa--develop in +essentially the same way from the primary germ-layers. I conceived the +embryonic form, in which the whole structure consists of only two layers of +cells, and is known as the gastrula, to be the ontogenetic recapitulation, +maintained by tenacious heredity, of a primitive common progenitor of all +the Metazoa, the Gastraea. At a later date (1895) Monticelli discovered +that this conjectural ancestral form is still preserved in certain +primitive Coelenterata--Pemmatodiscus, Kunstleria, and the nearly-related +Orthonectida. + +The general application of the biogenetic law to all classes of animals and +plants has been proved in my "Systematische Phylogenie". (3 volumes, +Berlin, 1894-96.) It has, however, been frequently challenged, both by +botanists and zoologists, chiefly owing to the fact that many have failed +to distinguish its two essential elements, palingenesis and cenogenesis. +As early as 1874 I had emphasised, in the first chapter of my "Evolution of +Man", the importance of discriminating carefully between these two sets of +phenomena: + +"In the evolutionary appreciation of the facts of embryology we must take +particular care to distinguish sharply and clearly between the primary, +palingenetic evolutionary processes and the secondary, cenogenetic +processes. The palingenetic phenomena, or embryonic RECAPITULATIONS, are +due to heredity, to the transmission of characters from one generation to +another. They enable us to draw direct inferences in regard to +corresponding structures in the development of the species (e.g. the chorda +or the branchial arches in all vertebrate embryos). The cenogenetic +phenomena, on the other hand, or the embryonic VARIATIONS, cannot be traced +to inheritance from a mature ancestor, but are due to the adaptation of the +embryo or the larva to certain conditions of its individual development +(e.g. the amnion, the allantois, and the vitelline arteries in the embryos +of the higher vertebrates). These cenogenetic phenomena are later +additions; we must not infer from them that there were corresponding +processes in the ancestral history, and hence they are apt to mislead." + +The fundamental importance of these facts of comparative anatomy, atavism, +and the rudimentary organs, was pointed out by Darwin in the first part of +his classic work, "The Descent of Man and Selection in Relation to Sex" +(1871). ("Descent of Man" (Popular Edition), page 927.) In the "General +summary and conclusion" (chapter XXI.) he was able to say, with perfect +justice: "He who is not content to look, like a savage, at the phenomena +of nature as disconnected, cannot any longer believe that man is the work +of a separate act of creation. He will be forced to admit that the close +resemblance of the embryo of man to that, for instance, of a dog--the +construction of his skull, limbs, and whole frame on the same plan with +that of other mammals, independently of the uses to which the parts may be +put--the occasional reappearance of various structures, for instance of +several muscles, which man does not normally possess, but which are common +to the Quadrumana--and a crowd of analogous facts--all point in the +plainest manner to the conclusion that man is the co-descendant with other +mammals of a common progenitor." + +These few lines of Darwin's have a greater scientific value than hundreds +of those so-called "anthropological treatises," which give detailed +descriptions of single organs, or mathematical tables with series of +numbers and what are claimed to be "exact analyses," but are devoid of +synoptic conclusions and a philosophical spirit. + +Charles Darwin is not generally recognised as a great anthropologist, nor +does the school of modern anthropologists regard him as a leading +authority. In Germany, especially, the great majority of the members of +the anthropological societies took up an attitude of hostility to him from +the very beginning of the controversy in 1860. "The Descent of Man" was +not merely rejected, but even the discussion of it was forbidden on the +ground that it was "unscientific." + +The centre of this inveterate hostility for thirty years--especially after +1877--was Rudolph Virchow of Berlin, the leading investigator in +pathological anatomy, who did so much for the reform of medicine by his +establishment of cellular pathology in 1858. As a prominent representative +of "exact" or "descriptive" anthropology, and lacking a broad equipment in +comparative anatomy and ontogeny, he was unable to accept the theory of +descent. In earlier years, and especially during his splendid period of +activity at Wurzburg (1848-1856), he had been a consistent free-thinker, +and had in a number of able articles (collected in his "Gesammelte +Abhandlungen") ("Gesammelte Abhandlungen zur wissenschaftlichen Medizin", +Berlin, 1856.) upheld the unity of human nature, the inseparability of body +and spirit. In later years at Berlin, where he was more occupied with +political work and sociology (especially after 1866), he abandoned the +positive monistic position for one of agnosticism and scepticism, and made +concessions to the dualistic dogma of a spiritual world apart from the +material frame. + +In the course of a Scientific Congress at Munich in 1877 the conflict of +these antithetic views of nature came into sharp relief. At this memorable +Congress I had undertaken to deliver the first address (September 18th) on +the subject of "Modern evolution in relation to the whole of science." I +maintained that Darwin's theory not only solved the great problem of the +origin of species, but that its implications, especially in regard to the +nature of man, threw considerable light on the whole of science, and on +anthropology in particular. The discovery of the real origin of man by +evolution from a long series of mammal ancestors threw light on his place +in nature in every aspect, as Huxley had already shown in his excellent +lectures of 1863. Just as all the organs and tissues of the human body had +originated from those of the nearest related mammals, certain ape-like +forms, so we were bound to conclude that his mental qualities also had been +derived from those of his extinct primate ancestor. + +This monistic view of the origin and nature of man, which is now admitted +by nearly all who have the requisite acquaintance with biology, and +approach the subject without prejudice, encountered a sharp opposition at +that time. The opposition found its strongest expression in an address +that Virchow delivered at Munich four days afterwards (September 22nd), on +"The freedom of science in the modern State." He spoke of the theory of +evolution as an unproved hypothesis, and declared that it ought not to be +taught in the schools, because it was dangerous to the State. "We must +not," he said, "teach that man has descended from the ape or any other +animal." When Darwin, usually so lenient in his judgment, read the English +translation of Virchow's speech, he expressed his disapproval in strong +terms. But the great authority that Virchow had--an authority well founded +in pathology and sociology--and his prestige as President of the German +Anthropological Society, had the effect of preventing any member of the +Society from raising serious opposition to him for thirty years. Numbers +of journals and treatises repeated his dogmatic statement: "It is quite +certain that man has descended neither from the ape nor from any other +animal." In this he persisted till his death in 1902. Since that time the +whole position of German anthropology has changed. The question is no +longer whether man was created by a distinct supernatural act or evolved +from other mammals, but to which line of the animal hierarchy we must look +for the actual series of ancestors. The interested reader will find an +account of this "battle of Munich" (1877) in my three Berlin lectures +(April, 1905) ("Der Kampf um die Entwickelungs-Gedanken". (English +translation; "Last Words on Evolution", London, 1906.) + +The main points in our genealogical tree were clearly recognised by Darwin +in the sixth chapter of the "Descent of Man". Lowly organised fishes, like +the lancelet (Amphioxus), are descended from lower invertebrates resembling +the larvae of an existing Tunicate (Appendicularia). From these primitive +fishes were evolved higher fishes of the ganoid type and others of the type +of Lepidosiren (Dipneusta). It is a very small step from these to the +Amphibia: + +"In the class of mammals the steps are not difficult to conceive which led +from the ancient Monotremata to the ancient Marsupials; and from these to +the early progenitors of the placental mammals. We may thus ascend to the +Lemuridae; and the interval is not very wide from these to the Simiadae. +The Simiadae then branched off into two great stems, the New World and Old +World monkeys; and from the latter, at a remote period, Man, the wonder and +glory of the Universe, proceeded." ("Descent of Man" (Popular Edition), +page 255.) + +In these few lines Darwin clearly indicated the way in which we were to +conceive our ancestral series within the vertebrates. It is fully +confirmed by all the arguments of comparative anatomy and embryology, of +palaeontology and physiology; and all the research of the subsequent forty +years has gone to establish it. The deep interest in geology which Darwin +maintained throughout his life and his complete knowledge of palaeontology +enabled him to grasp the fundamental importance of the palaeontological +record more clearly than anthropologists and zoologists usually do. + +There has been much debate in subsequent decades whether Darwin himself +maintained that man was descended from the ape, and many writers have +sought to deny it. But the lines I have quoted verbatim from the +conclusion of the sixth chapter of the "Descent of Man" (1871) leave no +doubt that he was as firmly convinced of it as was his great precursor Jean +Lamarck in 1809. Moreover, Darwin adds, with particular explicitness, in +the "general summary and conclusion" (chapter XXI.) of that standard work +("Descent of Man", page 930.): + +"By considering the embryological structure of man--the homologies which he +presents with the lower animals,--the rudiments which he retains,--and the +reversions to which he is liable, we can partly recall in imagination the +former condition of our early progenitors; and can approximately place them +in their proper place in the zoological series. We thus learn that man is +descended from a hairy, tailed quadruped, probably arboreal in its habits, +and an inhabitant of the Old World. This creature, if its whole structure +had been examined by a naturalist, would have been classed amongst the +Quadrumana, as surely as the still more ancient progenitor of the Old and +New World monkeys." + +These clear and definite lines leave no doubt that Darwin--so critical and +cautious in regard to important conclusions--was quite as firmly convinced +of the descent of man from the apes (the Catarrhinae, in particular) as +Lamarck was in 1809 and Huxley in 1863. + +It is to be noted particularly that, in these and other observations on the +subject, Darwin decidedly assumes the monophyletic origin of the mammals, +including man. It is my own conviction that this is of the greatest +importance. A number of difficult questions in regard to the development +of man, in respect of anatomy, physiology, psychology, and embryology, are +easily settled if we do not merely extend our progonotaxis to our nearest +relatives, the anthropoid apes and the tailed monkeys from which these have +descended, but go further back and find an ancestor in the group of the +Lemuridae, and still further back to the Marsupials and Monotremata. The +essential identity of all the Mammals in point of anatomical structure and +embryonic development--in spite of their astonishing differences in +external appearance and habits of life--is so palpably significant that +modern zoologists are agreed in the hypothesis that they have all sprung +from a common root, and that this root may be sought in the earlier +Palaeozoic Amphibia. + +The fundamental importance of this comparative morphology of the Mammals, +as a sound basis of scientific anthropology, was recognised just before the +beginning of the nineteenth century, when Lamarck first emphasised (1794) +the division of the animal kingdom into Vertebrates and Invertebrates. +Even thirteen years earlier (1781), when Goethe made a close study of the +mammal skeleton in the Anatomical Institute at Jena, he was intensely +interested to find that the composition of the skull was the same in man as +in the other mammals. His discovery of the os intermaxillare in man +(1784), which was contradicted by most of the anatomists of the time, and +his ingenious "vertebral theory of the skull," were the splendid fruit of +his morphological studies. They remind us how Germany's greatest +philosopher and poet was for many years ardently absorbed in the +comparative anatomy of man and the mammals, and how he divined that their +wonderful identity in structure was no mere superficial resemblance, but +pointed to a deep internal connection. In my "Generelle Morphologie" +(1866), in which I published the first attempts to construct phylogenetic +trees, I have given a number of remarkable theses of Goethe, which may be +called "phyletic prophecies." They justify us in regarding him as a +precursor of Darwin. + +In the ensuing forty years I have made many conscientious efforts to +penetrate further along that line of anthropological research that was +opened up by Goethe, Lamarck, and Darwin. I have brought together the many +valuable results that have constantly been reached in comparative anatomy, +physiology, ontogeny, and palaeontology, and maintained the effort to +reform the classification of animals and plants in an evolutionary sense. +The first rough drafts of pedigrees that were published in the "Generelle +Morphologie" have been improved time after time in the ten editions of my +"Naturaliche Schopfungsgeschichte" (1868-1902). (English translation; "The +History of Creation", London, 1876.) A sounder basis for my phyletic +hypotheses, derived from a discriminating combination of the three great +records--morphology, ontogeny, and palaeontology--was provided in the three +volumes of my "Systematische Phylogenie (Berlin, 1894-96.) (1894 Protists +and Plants, 1895 Vertebrates, 1896 Invertebrates). In my "Anthropogenie" +(Leipzig, 1874, 5th edition 1905. English translation; "The Evolution of +Man", London, 1905.) I endeavoured to employ all the known facts of +comparative ontogeny (embryology) for the purpose of completing my scheme +of human phylogeny (evolution). I attempted to sketch the historical +development of each organ of the body, beginning with the most elementary +structures in the germ-layers of the Gastraea. At the same time I drew up +a corrected statement of the most important steps in the line of our +ancestral series. + +At the fourth International Congress of Zoology at Cambridge (August 26th, +1898) I delivered an address on "Our present knowledge of the Descent of +Man." It was translated into English, enriched with many valuable notes +and additions, by my friend and pupil in earlier days Dr Hans Gadow +(Cambridge), and published under the title: "The Last Link; our present +knowledge of the Descent of Man". (London, 1898.) The determination of +the chief animal forms that occur in the line of our ancestry is there +restricted to thirty types, and these are distributed in six main groups. + +The first half of this "Progonotaxis hominis," which has no support from +fossil evidence, comprises three groups: (i) Protista (unicellular +organisms, 1-5: (ii) Invertebrate Metazoa (Coelenteria 6-8, Vermalia 9- +11): (iii) Monorrhine Vertebrates (Acrania 12-13, Cyclostoma 14-15). The +second half, which is based on fossil records, also comprises three groups: +(iv) Palaeozoic cold-blooded Craniota (Fishes 16-18, Amphibia 19, Reptiles +20: (v) Mesozoic Mammals (Monotrema 21, Marsupialia 22, Mallotheria 23): +(vi) Cenozoic Primates (Lemuridae 24-25, Tailed Apes 26-27, Anthropomorpha +28-30). An improved and enlarged edition of this hypothetic "Progonotaxis +hominis" was published in 1908, in my essay "Unsere Ahnenreihe". +("Festschrift zur 350-jahrigen Jubelfeier der Thuringer Universitat Jena". +Jena, 1908.) + +If I have succeeded in furthering, in some degree, by these anthropological +works, the solution of the great problem of Man's place in nature, and +particularly in helping to trace the definite stages in our ancestral +series, I owe the success, not merely to the vast progress that biology has +made in the last half century, but largely to the luminous example of the +great investigators who have applied themselves to the problem, with so +much assiduity and genius, for a century and a quarter--I mean Goethe and +Lamarck, Gegenbaur and Huxley, but, above all, Charles Darwin. It was the +great genius of Darwin that first brought together the scattered material +of biology and shaped it into that symmetrical temple of scientific +knowledge, the theory of descent. It was Darwin who put the crown on the +edifice by his theory of natural selection. Not until this broad inductive +law was firmly established was it possible to vindicate the special +conclusion, the descent of man from a series of other Vertebrates. By his +illuminating discovery Darwin did more for anthropology than thousands of +those writers, who are more specifically titled anthropologists, have done +by their technical treatises. We may, indeed, say that it is not merely as +an exact observer and ingenious experimenter, but as a distinguished +anthropologist and far-seeing thinker, that Darwin takes his place among +the greatest men of science of the nineteenth century. + +To appreciate fully the immortal merit of Darwin in connection with +anthropology, we must remember that not only did his chief work, "The +Origin of Species", which opened up a new era in natural history in 1859, +sustain the most virulent and widespread opposition for a lengthy period, +but even thirty years later, when its principles were generally recognised +and adopted, the application of them to man was energetically contested by +many high scientific authorities. Even Alfred Russel Wallace, who +discovered the principle of natural selection independently in 1858, did +not concede that it was applicable to the higher mental and moral qualities +of man. Dr Wallace still holds a spiritualist and dualist view of the +nature of man, contending that he is composed of a material frame +(descended from the apes) and an immortal immaterial soul (infused by a +higher power). This dual conception, moreover, is still predominant in the +wide circles of modern theology and metaphysics, and has the general and +influential adherence of the more conservative classes of society. + +In strict contradiction to this mystical dualism, which is generally +connected with teleology and vitalism, Darwin always maintained the +complete unity of human nature, and showed convincingly that the +psychological side of man was developed, in the same way as the body, from +the less advanced soul of the anthropoid ape, and, at a still more remote +period, from the cerebral functions of the older vertebrates. The eighth +chapter of the "Origin of Species", which is devoted to instinct, contains +weighty evidence that the instincts of animals are subject, like all other +vital processes, to the general laws of historic development. The special +instincts of particular species were formed by adaptation, and the +modifications thus acquired were handed on to posterity by heredity; in +their formation and preservation natural selection plays the same part as +in the transformation of every other physiological function. The higher +moral qualities of civilised man have been derived from the lower mental +functions of the uncultivated barbarians and savages, and these in turn +from the social instincts of the mammals. This natural and monistic +psychology of Darwin's was afterwards more fully developed by his friend +George Romanes in his excellent works "Mental Evolution in Animals" and +"Mental Evolution in Man". (London, 1885; 1888.) + +Many valuable and most interesting contributions to this monistic +psychology of man were made by Darwin in his fine work on "The Descent of +Man and Selection in Relation to Sex", and again in his supplementary work, +"The Expression of the Emotions in Man and Animals". To understand the +historical development of Darwin's anthropology one must read his life and +the introduction to "The Descent of Man". From the moment that he was +convinced of the truth of the principle of descent--that is to say, from +his thirtieth year, in 1838--he recognised clearly that man could not be +excluded from its range. He recognised as a logical necessity the +important conclusion that "man is the co-descendant with other species of +some ancient, lower, and extinct form." For many years he gathered notes +and arguments in support of this thesis, and for the purpose of showing the +probable line of man's ancestry. But in the first edition of "The Origin +of Species" (1859) he restricted himself to the single line, that by this +work "light would be thrown on the origin of man and his history." In the +fifty years that have elapsed since that time the science of the origin and +nature of man has made astonishing progress, and we are now fairly agreed +in a monistic conception of nature that regards the whole universe, +including man, as a wonderful unity, governed by unalterable and eternal +laws. In my philosophical book "Die Weltratsel" (1899) ("The Riddle of the +Universe", London, 1900.) and in the supplementary volume "Die +Lebenswunder" (1904) "The Wonders of Life", London, 1904.), I have +endeavoured to show that this pure monism is securely established, and that +the admission of the all-powerful rule of the same principle of evolution +throughout the universe compels us to formulate a single supreme law--the +all-embracing "Law of Substance," or the united laws of the constancy of +matter and the conservation of energy. We should never have reached this +supreme general conception if Charles Darwin--a "monistic philosopher" in +the true sense of the word--had not prepared the way by his theory of +descent by natural selection, and crowned the great work of his life by the +association of this theory with a naturalistic anthropology. + + +IX. SOME PRIMITIVE THEORIES OF THE ORIGIN OF MAN. + +By J.G. FRAZER. +Fellow of Trinity College, Cambridge. + +On a bright day in late autumn a good many years ago I had ascended the +hill of Panopeus in Phocis to examine the ancient Greek fortifications +which crest its brow. It was the first of November, but the weather was +very hot; and when my work among the ruins was done, I was glad to rest +under the shade of a clump of fine holly-oaks, to inhale the sweet +refreshing perfume of the wild thyme which scented all the air, and to +enjoy the distant prospects, rich in natural beauty, rich too in memories +of the legendary and historic past. To the south the finely-cut peak of +Helicon peered over the low intervening hills. In the west loomed the +mighty mass of Parnassus, its middle slopes darkened by pine-woods like +shadows of clouds brooding on the mountain-side; while at its skirts +nestled the ivy-mantled walls of Daulis overhanging the deep glen, whose +romantic beauty accords so well with the loves and sorrows of Procne and +Philomela, which Greek tradition associated with the spot. Northwards, +across the broad plain to which the hill of Panopeus descends, steep and +bare, the eye rested on the gap in the hills through which the Cephissus +winds his tortuous way to flow under grey willows, at the foot of barren +stony hills, till his turbid waters lose themselves, no longer in the vast +reedy swamps of the now vanished Copaic Lake, but in the darkness of a +cavern in the limestone rock. Eastward, clinging to the slopes of the +bleak range of which the hill of Panopeus forms part, were the ruins of +Chaeronea, the birthplace of Plutarch; and out there in the plain was +fought the disastrous battle which laid Greece at the feet of Macedonia. +There, too, in a later age East and West met in deadly conflict, when the +Roman armies under Sulla defeated the Asiatic hosts of Mithridates. Such +was the landscape spread out before me on one of those farewell autumn days +of almost pathetic splendour, when the departing summer seems to linger +fondly, as if loth to resign to winter the enchanted mountains of Greece. +Next day the scene had changed: summer was gone. A grey November mist +hung low on the hills which only yesterday had shone resplendent in the +sun, and under its melancholy curtain the dead flat of the Chaeronean +plain, a wide treeless expanse shut in by desolate slopes, wore an aspect +of chilly sadness befitting the battlefield where a nation's freedom was +lost. + +But crowded as the prospect from Panopeus is with memories of the past, the +place itself, now so still and deserted, was once the scene of an event +even more ancient and memorable, if Greek story-tellers can be trusted. +For here, they say, the sage Prometheus created our first parents by +fashioning them, like a potter, out of clay. (Pausanias X. 4.4. Compare +Apollodorus, "Bibliotheca", I. 7. 1; Ovid, "Metamorph." I. 82 sq.; Juvenal, +"Sat". XIV. 35. According to another version of the tale, this creation of +mankind took place not at Panopeus, but at Iconium in Lycaonia. After the +original race of mankind had been destroyed in the great flood of +Deucalion, the Greek Noah, Zeus commanded Prometheus and Athena to create +men afresh by moulding images out of clay, breathing the winds into them, +and making them live. See "Etymologicum Magnum", s.v. "'Ikonion", pages +470 sq. It is said that Prometheus fashioned the animals as well as men, +giving to each kind of beast its proper nature. See Philemon, quoted by +Stobaeus, "Florilegium" II. 27. The creation of man by Prometheus is +figured on ancient works of art. See J. Toutain, "Etudes de Mythologie et +d'Histoire des Religions Antiques" (Paris, 1909), page 190. According to +Hesiod ("Works and Days", 60 sqq.) it was Hephaestus who at the bidding of +Zeus moulded the first woman out of moist earth.) The very spot where he +did so can still be seen. It is a forlorn little glen or rather hollow +behind the hill of Panopeus, below the ruined but still stately walls and +towers which crown the grey rocks of the summit. The glen, when I visited +it that hot day after the long drought of summer, was quite dry; no water +trickled down its bushy sides, but in the bottom I found a reddish +crumbling earth, a relic perhaps of the clay out of which the potter +Prometheus moulded the Greek Adam and Eve. In a volume dedicated to the +honour of one who has done more than any other in modern times to shape the +ideas of mankind as to their origin it may not be out of place to recall +this crude Greek notion of the creation of the human race, and to compare +or contrast it with other rudimentary speculations of primitive peoples on +the same subject, if only for the sake of marking the interval which +divides the childhood from the maturity of science. + +The simple notion that the first man and woman were modelled out of clay by +a god or other superhuman being is found in the traditions of many peoples. +This is the Hebrew belief recorded in Genesis: "The Lord God formed man of +the dust of the ground, and breathed into his nostrils the breath of life; +and man became a living soul." (Genesis ii.7.) To the Hebrews this +derivation of our species suggested itself all the more naturally because +in their language the word for "ground" (adamah) is in form the feminine of +the word for man (adam). (S.R. Driver and W.H.Bennett, in their +commentaries on Genesis ii. 7.) From various allusions in Babylonian +literature it would seem that the Babylonians also conceived man to have +been moulded out of clay. (H. Zimmern, in E. Schrader's "Die +Keilinschriften und das Alte Testament"3 (Berlin, 1902), page 506.) +According to Berosus, the Babylonian priest whose account of creation has +been preserved in a Greek version, the god Bel cut off his own head, and +the other gods caught the flowing blood, mixed it with earth, and fashioned +men out of the bloody paste; and that, they said, is why men are so wise, +because their mortal clay is tempered with divine blood. (Eusebius, +"Chronicon", ed. A. Schoene, Vol. I. (Berlin, 1875), col. 16.) In Egyptian +mythology Khnoumou, the Father of the gods, is said to have moulded men out +of clay. (G. Maspero, "Histoire Ancienne des Peuples de l'Orient +Classique", I. (Paris, 1895), page 128.) We cannot doubt that such crude +conceptions of the origin of our race were handed down to the civilised +peoples of antiquity by their savage or barbarous forefathers. Certainly +stories of the same sort are known to be current among savages and +barbarians. + +Thus the Australian blacks in the neighbourhood of Melbourne said that +Pund-jel, the creator, cut three large sheets of bark with his big knife. +On one of these he placed some clay and worked it up with his knife into a +proper consistence. He then laid a portion of the clay on one of the other +pieces of bark and shaped it into a human form; first he made the feet, +then the legs, then the trunk, the arms, and the head. Thus he made a clay +man on each of the two pieces of bark; and being well pleased with them he +danced round them for joy. Next he took stringy bark from the Eucalyptus +tree, made hair of it, and stuck it on the heads of his clay men. Then he +looked at them again, was pleased with his work, and again danced round +them for joy. He then lay down on them, blew his breath hard into their +mouths, their noses, and their navels; and presently they stirred, spoke, +and rose up as full-grown men. (R. Brough Smyth, "The Aborigines of +Victoria" (Melbourne, 1878), I. 424. This and many of the following +legends of creation have been already cited by me in a note on Pausanias X. +4. 4 ("Pausanias's Description of Greece, translated with a Commentary" +(London, 1898), Vol V. pages 220 sq.).) The Maoris of New Zealand say that +Tiki made man after his own image. He took red clay, kneaded it, like the +Babylonian Bel, with his own blood, fashioned it in human form, and gave +the image breath. As he had made man in his own likeness he called him +Tiki-ahua or Tiki's likeness. (R. Taylor "Te Ika A Maui, or New Zealand +and its Inhabitants", Second Edition (London, 1870), page 117. Compare E. +Shortland, "Maori Religion and Mythology" (London, 1882), pages 21 sq.) A +very generally received tradition in Tahiti was that the first human pair +was made by Taaroa, the chief god. They say that after he had formed the +world he created man out of red earth, which was also the food of mankind +until bread-fruit was produced. Further, some say that one day Taaroa +called for the man by name, and when he came he made him fall asleep. As +he slept, the creator took out one of his bones (ivi) and made a woman of +it, whom he gave to the man to be his wife, and the pair became the +progenitors of mankind. This narrative was taken down from the lips of the +natives in the early years of the mission to Tahiti. The missionary who +records it observes: "This always appeared to me a mere recital of the +Mosaic account of creation, which they had heard from some European, and I +never placed any reliance on it, although they have repeatedly told me it +was a tradition among them before any foreigner arrived. Some have also +stated that the woman's name was Ivi, which would be by them pronounced as +if written "Eve". "Ivi" is an aboriginal word, and not only signifies a +bone, but also a widow, and a victim slain in war. Notwithstanding the +assertion of the natives, I am disposed to think that "Ivi", or Eve, is the +only aboriginal part of the story, as far as it respects the mother of the +human race. (W. Ellis, "Polynesian Researches", Second Edition (London, +1832), I. 110 sq. "Ivi" or "iwi" is the regular word for "bone" in the +various Polynesian languages. See E. Tregear, "The Maori-Polynesian +Comparative Dictionary" (Wellington, New Zealand, 1891), page 109.) +However, the same tradition has been recorded in other parts of Polynesia +besides Tahiti. Thus the natives of Fakaofo or Bowditch Island say that +the first man was produced out of a stone. After a time he bethought him +of making a woman. So he gathered earth and moulded the figure of a woman +out of it, and having done so he took a rib out of his left side and thrust +it into the earthen figure, which thereupon started up a live woman. He +called her Ivi (Eevee) or "rib" and took her to wife, and the whole human +race sprang from this pair. (G. Turner, "Samoa" (London, 1884), pages 267 +sq.) The Maoris also are reported to believe that the first woman was made +out of the first man's ribs. (J.L. Nicholas, "Narrative of a Voyage to New +Zealand" (London, 1817), I. 59, who writes "and to add still more to this +strange coincidence, the general term for bone is 'Hevee'.") This wide +diffusion of the story in Polynesia raises a doubt whether it is merely, as +Ellis thought, a repetition of the Biblical narrative learned from +Europeans. In Nui, or Netherland Island, it was the god Aulialia who made +earthen models of a man and woman, raised them up, and made them live. He +called the man Tepapa and the woman Tetata. (G. Turner, "Samoa", pages 300 +sq.) + +In the Pelew Islands they say that a brother and sister made men out of +clay kneaded with the blood of various animals, and that the characters of +these first men and of their descendants were determined by the characters +of the animals whose blood had been kneaded with the primordial clay; for +instance, men who have rat's blood in them are thieves, men who have +serpent's blood in them are sneaks, and men who have cock's blood in them +are brave. (J. Kubary, "Die Religion der Pelauer", in A. Bastian's +"Allerlei aus Volks- und Menschenkunde" (Berlin, 1888), I. 3, 56.) +According to a Melanesian legend, told in Mota, one of the Banks Islands, +the hero Qat moulded men of clay, the red clay from the marshy river-side +at Vanua Lava. At first he made men and pigs just alike, but his brothers +remonstrated with him, so he beat down the pigs to go on all fours and made +men walk upright. Qat fashioned the first woman out of supple twigs, and +when she smiled he knew she was a living woman. (R.H. Codrington, "The +Melanesians" (Oxford, 1891), page 158.) A somewhat different version of +the Melanesian story is told at Lakona, in Santa Maria. There they say +that Qat and another spirit ("vui") called Marawa both made men. Qat made +them out of the wood of dracaena-trees. Six days he worked at them, +carving their limbs and fitting them together. Then he allowed them six +days to come to life. Three days he hid them away, and three days more he +worked to make them live. He set them up and danced to them and beat his +drum, and little by little they stirred, till at last they could stand all +by themselves. Then Qat divided them into pairs and called each pair +husband and wife. Marawa also made men out of a tree, but it was a +different tree, the tavisoviso. He likewise worked at them six days, beat +his drum, and made them live, just as Qat did. But when he saw them move, +he dug a pit and buried them in it for six days, and then, when he scraped +away the earth to see what they were doing, he found them all rotten and +stinking. That was the origin of death. (R.H. Codrington op. cit., pages +157 sq.) + +The inhabitants of Noo-Hoo-roa, in the Kei Islands say that their ancestors +were fashioned out of clay by the supreme god, Dooadlera, who breathed life +into the clay figures. (C.M. Pleyte, "Ethnographische Beschrijving der +Kei-Eilanden", "Tijdschrift van het Nederlandsch Aardrijkskundig +Genootschap", Tweede Serie X. (1893), page 564.) The aborigines of +Minahassa, in the north of Celebes, say that two beings called Wailan +Wangko and Wangi were alone on an island, on which grew a cocoa-nut tree. +Said Wailan Wangko to Wangi, "Remain on earth while I climb up the tree." +Said Wangi to Wailan Wangko, "Good." But then a thought occurred to Wangi +and he climbed up the tree to ask Wailan Wangko why he, Wangi, should +remain down there all alone. Said Wailan Wangko to Wangi, "Return and take +earth and make two images, a man and a woman." Wangi did so, and both +images were men who could move but could not speak. So Wangi climbed up +the tree to ask Wailan Wangko, "How now? The two images are made, but they +cannot speak." Said Wailan Wangko to Wangi, "Take this ginger and go and +blow it on the skulls and the ears of these two images, that they may be +able to speak; call the man Adam and the woman Ewa." (N. Graafland "De +Minahassa" (Rotterdam, 1869), I. pages 96 sq.) In this narrative the names +of the man and woman betray European influence, but the rest of the story +may be aboriginal. The Dyaks of Sakarran in British Borneo say that the +first man was made by two large birds. At first they tried to make men out +of trees, but in vain. Then they hewed them out of rocks, but the figures +could not speak. Then they moulded a man out of damp earth and infused +into his veins the red gum of the kumpang-tree. After that they called to +him and he answered; they cut him and blood flowed from his wounds. +(Horsburgh, quoted by H. Ling Roth, "The Natives of Sarawak and of British +North Borneo" (London, 1896), I. pages 299 sq. Compare The Lord Bishop of +Labuan, "On the Wild Tribes of the North-West Coast of Borneo," +"Transactions of the Ethnological Society of London", New Series, II. +(1863), page 27.) + +The Kumis of South-Eastern India related to Captain Lewin, the Deputy +Commissioner of Hill Tracts, the following tradition of the creation of +man. "God made the world and the trees and the creeping things first, and +after that he set to work to make one man and one woman, forming their +bodies of clay; but each night, on the completion of his work, there came a +great snake, which, while God was sleeping, devoured the two images. This +happened twice or thrice, and God was at his wit's end, for he had to work +all day, and could not finish the pair in less than twelve hours; besides, +if he did not sleep, he would be no good," said Captain Lewin's informant. +"If he were not obliged to sleep, there would be no death, nor would +mankind be afflicted with illness. It is when he rests that the snake +carries us off to this day. Well, he was at his wit's end, so at last he +got up early one morning and first made a dog and put life into it, and +that night, when he had finished the images, he set the dog to watch them, +and when the snake came, the dog barked and frightened it away. This is +the reason at this day that when a man is dying the dogs begin to howl; but +I suppose God sleeps heavily now-a-days, or the snake is bolder, for men +die all the same." (Capt. T.H. Lewin, "Wild Races of South-Eastern India" +(London, 1870), pages 224-26.) The Khasis of Assam tell a similar tale. +(A. Bastian, "Volkerstamme am Brahmaputra und verwandtschaftliche Nachbarn" +(Berlin, 1883), page 8; Major P.R.T. Gurdon, "The Khasis" (London, 1907), +page 106.) + +The Ewe-speaking tribes of Togo-land, in West Africa, think that God still +makes men out of clay. When a little of the water with which he moistens +the clay remains over, he pours it on the ground and out of that he makes +the bad and disobedient people. When he wishes to make a good man he makes +him out of good clay; but when he wishes to make a bad man, he employs only +bad clay for the purpose. In the beginning God fashioned a man and set him +on the earth; after that he fashioned a woman. The two looked at each +other and began to laugh, whereupon God sent them into the world. (J. +Spieth, "Die Ewe-Stamme, Material zur Kunde des Ewe-Volkes in Deutsch-Togo" +(Berlin, 1906), pages 828, 840.) The Innuit or Esquimaux of Point Barrow, +in Alaska, tell of a time when there was no man in the land, till a spirit +named "a se lu", who resided at Point Barrow, made a clay man, set him up +on the shore to dry, breathed into him and gave him life. ("Report of the +International Expedition to Point Barrow" (Washington, 1885), page 47.) +Other Esquimaux of Alaska relate how the Raven made the first woman out of +clay to be a companion to the first man; he fastened water-grass to the +back of the head to be hair, flapped his wings over the clay figure, and it +arose, a beautiful young woman. (E.W. Nelson, "The Eskimo about Bering +Strait", "Eighteenth Annual Report of the Bureau of American Ethnology", +Part I. (Washington, 1899), page 454.) The Acagchemem Indians of +California said that a powerful being called Chinigchinich created man out +of clay which he found on the banks of a lake; male and female created he +them, and the Indians of the present day are their descendants. (Friar +Geronimo Boscana, "Chinigchinich", appended to (A. Robinson's) "Life in +California" (New York, 1846), page 247.) A priest of the Natchez Indians +in Louisiana told Du Pratz "that God had kneaded some clay, such as that +which potters use and had made it into a little man; and that after +examining it, and finding it well formed, he blew up his work, and +forthwith that little man had life, grew, acted, walked, and found himself +a man perfectly well shaped." As to the mode in which the first woman was +created, the priest had no information, but thought she was probably made +in the same way as the first man; so Du Pratz corrected his imperfect +notions by reference to Scripture. (M. Le Page Du Pratz, "The History of +Louisiana" (London, 1774), page 330.) The Michoacans of Mexico said that +the great god Tucapacha first made man and woman out of clay, but that when +the couple went to bathe in a river they absorbed so much water that the +clay of which they were composed all fell to pieces. Then the creator went +to work again and moulded them afresh out of ashes, and after that he +essayed a third time and made them of metal. This last attempt succeeded. +The metal man and woman bathed in the river without falling to pieces, and +by their union they became the progenitors of mankind. (A. de Herrera, +"General History of the vast Continent and Islands of America", translated +into English by Capt. J. Stevens (London, 1725, 1726), III. 254; Brasseur +de Bourbourg, "Histoire des Nations Civilisees du Mexique et de l'Amerique- +Centrale" (Paris, 1857--1859), III. 80 sq; compare id. I. 54 sq.) + +According to a legend of the Peruvian Indians, which was told to a Spanish +priest in Cuzco about half a century after the conquest, it was in +Tiahuanaco that man was first created, or at least was created afresh after +the deluge. "There (in Tiahuanaco)," so runs the legend, "the Creator +began to raise up the people and nations that are in that region, making +one of each nation of clay, and painting the dresses that each one was to +wear; those that were to wear their hair, with hair, and those that were to +be shorn, with hair cut. And to each nation was given the language, that +was to be spoken, and the songs to be sung, and the seeds and food that +they were to sow. When the Creator had finished painting and making the +said nations and figures of clay, he gave life and soul to each one, as +well men as women, and ordered that they should pass under the earth. +Thence each nation came up in the places to which he ordered them to go." +(E.J. Payne, "History of the New World called America", I. (Oxford, 1892), +page 462.) + +These examples suffice to prove that the theory of the creation of man out +of dust or clay has been current among savages in many parts of the world. +But it is by no means the only explanation which the savage philosopher has +given of the beginnings of human life on earth. Struck by the resemblances +which may be traced between himself and the beasts, he has often supposed, +like Darwin himself, that mankind has been developed out of lower forms of +animal life. For the simple savage has none of that high notion of the +transcendant dignity of man which makes so many superior persons shrink +with horror from the suggestion that they are distant cousins of the +brutes. He on the contrary is not too proud to own his humble relations; +indeed his difficulty often is to perceive the distinction between him and +them. Questioned by a missionary, a Bushman of more than average +intelligence "could not state any difference between a man and a brute--he +did not know but a buffalo might shoot with bows and arrows as well as man, +if it had them." (Reverend John Campbell, "Travels in South Africa" +(London, 1822, II. page 34.) When the Russians first landed on one of the +Alaskan islands, the natives took them for cuttle-fish "on account of the +buttons on their clothes." (I. Petroff, "Report on the Population, +Industries, and Resources of Alaska", page 145.) The Giliaks of the Amoor +think that the outward form and size of an animal are only apparent; in +substance every beast is a real man, just like a Giliak himself, only +endowed with an intelligence and strength, which often surpass those of +mere ordinary human beings. (L. Sternberg, "Die Religion der Giljaken", +"Archiv fur Religionswissenschaft", VIII. (1905), page 248.) The +Borororos, an Indian tribe of Brazil, will have it that they are parrots of +a gorgeous red plumage which live in their native forests. Accordingly +they treat the birds as their fellow-tribesmen, keeping them in captivity, +refusing to eat their flesh, and mourning for them when they die. (K. von +den Steinen, "Unter den Naturvolkern Zentral-Brasiliens" (Berlin, 1894), +pages 352 sq., 512.) + +This sense of the close relationship of man to the lower creation is the +essence of totemism, that curious system of superstition which unites by a +mystic bond a group of human kinsfolk to a species of animals or plants. +Where that system exists in full force, the members of a totem clan +identify themselves with their totem animals in a way and to an extent +which we find it hard even to imagine. For example, men of the Cassowary +clan in Mabuiag think that cassowaries are men or nearly so. "Cassowary, +he all same as relation, he belong same family," is the account they give +of their relationship with the long-legged bird. Conversely they hold that +they themselves are cassowaries for all practical purposes. They pride +themselves on having long thin legs like a cassowary. This reflection +affords them peculiar satisfaction when they go out to fight, or to run +away, as the case may be; for at such times a Cassowary man will say to +himself, "My leg is long and thin, I can run and not feel tired; my legs +will go quickly and the grass will not entangle them." Members of the +Cassowary clan are reputed to be pugnacious, because the cassowary is a +bird of very uncertain temper and can kick with extreme violence. (A.C. +Haddon, "The Ethnography of the Western Tribe of Torres Straits", "Journal +of the Anthropological Institute", XIX. (1890), page 393; "Reports of the +Cambridge Anthropological Expedition to Torres Straits", V. (Cambridge, +1904), pages 166, 184.) So among the Ojibways men of the Bear clan are +reputed to be surly and pugnacious like bears, and men of the Crane clan to +have clear ringing voices like cranes. (W.W. Warren, "History of the +Ojibways", "Collections of the Minnesota Historical Society", V. (Saint +Paul, Minn. 1885), pages 47, 49.) Hence the savage will often speak of his +totem animal as his father or his brother, and will neither kill it himself +nor allow others to do so, if he can help it. For example, if somebody +were to kill a bird in the presence of a native Australian who had the bird +for his totem, the black might say, "What for you kill that fellow? that my +father!" or "That brother belonging to me you have killed; why did you do +it?" (E. Palmer, "Notes on some Australian Tribes", "Journal of the +Anthropological Institute", XIII. (1884), page 300.) Bechuanas of the +Porcupine clan are greatly afflicted if anybody hurts or kills a porcupine +in their presence. They say, "They have killed our brother, our master, +one of ourselves, him whom we sing of"; and so saying they piously gather +the quills of their murdered brother, spit on them, and rub their eyebrows +with them. They think they would die if they touched its flesh. In like +manner Bechuanas of the Crocodile clan call the crocodile one of +themselves, their master, their brother; and they mark the ears of their +cattle with a long slit like a crocodile's mouth by way of a family crest. +Similarly Bechuanas of the Lion clan would not, like the members of other +clans, partake of lion's flesh; for how, say they, could they eat their +grandfather? If they are forced in self-defence to kill a lion, they do so +with great regret and rub their eyes carefully with its skin, fearing to +lose their sight if they neglected this precaution. (T. Arbousset et F. +Daumas, "Relation d'un Voyage d'Exploration au Nord-Est de la Colonie du +Cap de Bonne-Esperance" (Paris, 1842), pages 349 sq., 422-24.) A Mandingo +porter has been known to offer the whole of his month's pay to save the +life of a python, because the python was his totem and he therefore +regarded the reptile as his relation; he thought that if he allowed the +creature to be killed, the whole of his own family would perish, probably +through the vengeance to be taken by the reptile kinsfolk of the murdered +serpent. (M. le Docteur Tautain, "Notes sur les Croyances et Pratiques +Religieuses des Banmanas", "Revue d'Ethnographie", III. (1885), pages 396 +sq.; A. Rancon, "Dans la Haute-Gambie, Voyage d'Exploration Scientifique" +(Paris, 1894), page 445.) + +Sometimes, indeed, the savage goes further and identifies the revered +animal not merely with a kinsman but with himself; he imagines that one of +his own more or less numerous souls, or at all events that a vital part of +himself, is in the beast, so that if it is killed he must die. Thus, the +Balong tribe of the Cameroons, in West Africa, think that every man has +several souls, of which one is lodged in an elephant, a wild boar, a +leopard, or what not. When any one comes home, feels ill, and says, "I +shall soon die," and is as good as his word, his friends are of opinion +that one of his souls has been shot by a hunter in a wild boar or a +leopard, for example, and that that is the real cause of his death. (J. +Keller, "Ueber das Land und Volk der Balong", "Deutsches Kolonialblatt", 1 +October, 1895, page 484.) A Catholic missionary, sleeping in the hut of a +chief of the Fan negroes, awoke in the middle of the night to see a huge +black serpent of the most dangerous sort in the act of darting at him. He +was about to shoot it when the chief stopped him, saying, "In killing that +serpent, it is me that you would have killed. Fear nothing, the serpent is +my elangela." (Father Trilles, "Chez les Fang, leurs Moeurs, leur Langue, +leur Religion", "Les Missions Catholiques", XXX. (1898), page 322.) At +Calabar there used to be some years ago a huge old crocodile which was well +known to contain the spirit of a chief who resided in the flesh at Duke +Town. Sporting Vice-Consuls, with a reckless disregard of human life, from +time to time made determined attempts to injure the animal, and once a +peculiarly active officer succeeded in hitting it. The chief was +immediately laid up with a wound in his leg. He SAID that a dog had bitten +him, but few people perhaps were deceived by so flimsy a pretext. (Miss +Mary H. Kingsley, "Travels in West Africa" (London, 1897), pages 538 sq. +As to the external or bush souls of human beings, which in this part of +Africa are supposed to be lodged in the bodies of animals, see Miss Mary H. +Kingsley op. cit. pages 459-461; R. Henshaw, "Notes on the Efik belief in +'bush soul'", "Man", VI.(1906), pages 121 sq.; J. Parkinson, "Notes on the +Asaba people (Ibos) of the Niger", "Journal of the Anthropological +Institute", XXXVI. (1906), pages 314 sq.) Once when Mr Partridge's canoe- +men were about to catch fish near an Assiga town in Southern Nigeria, the +natives of the town objected, saying, "Our souls live in those fish, and if +you kill them we shall die." (Charles Partridge, "Cross River Natives" +(London, 1905), pages 225 sq.) On another occasion, in the same region, an +Englishman shot a hippopotamus near a native village. The same night a +woman died in the village, and her friends demanded and obtained from the +marksman five pounds as compensation for the murder of the woman, whose +soul or second self had been in that hippopotamus. (C.H. Robinson, +"Hausaland" (London, 1896), pages 36 sq.) Similarly at Ndolo, in the Congo +region, we hear of a chief whose life was bound up with a hippopotamus, but +he prudently suffered no one to fire at the animal. ("Notes Analytiques +sur les Collections Ethnographiques du Musee du Congo", I. (Brussels, 1902- +06), page 150. + +Amongst people who thus fail to perceive any sharp line of distinction +between beasts and men it is not surprising to meet with the belief that +human beings are directly descended from animals. Such a belief is often +found among totemic tribes who imagine that their ancestors sprang from +their totemic animals or plants; but it is by no means confined to them. +Thus, to take instances, some of the Californian Indians, in whose +mythology the coyote or prairie-wolf is a leading personage, think that +they are descended from coyotes. At first they walked on all fours; then +they began to have some members of the human body, one finger, one toe, one +eye, one ear, and so on; then they got two fingers, two toes, two eyes, two +ears, and so forth; till at last, progressing from period to period, they +became perfect human beings. The loss of their tails, which they still +deplore, was produced by the habit of sitting upright. (H.R. Schoolcraft, +"Indian Tribes of the United States", IV. (Philadelphia, 1856), pages 224 +sq.; compare id. V. page 217. The descent of some, not all, Indians from +coyotes is mentioned also by Friar Boscana, in (A. Robinson's) "Life in +California" (New York, 1846), page 299.) Similarly Darwin thought that +"the tail has disappeared in man and the anthropomorphous apes, owing to +the terminal portion having been injured by friction during a long lapse of +time; the basal and embedded portion having been reduced and modified, so +as to become suitable to the erect or semi-erect position." (Charles +Darwin, "The Descent of Man", Second Edition (London, 1879), page 60.) The +Turtle clam of the Iroquois think that they are descended from real mud +turtles which used to live in a pool. One hot summer the pool dried up, +and the mud turtles set out to find another. A very fat turtle, waddling +after the rest in the heat, was much incommoded by the weight of his shell, +till by a great effort he heaved it off altogether. After that he +gradually developed into a man and became the progenitor of the Turtle +clan. (E.A. Smith, "Myths of the Iroquois", "Second Annual Report of the +Bureau of Ethnology" (Washington, 1883), page 77.) The Crawfish band of +the Choctaws are in like manner descended from real crawfish, which used to +live under ground, only coming up occasionally through the mud to the +surface. Once a party of Choctaws smoked them out, taught them the Choctaw +language, taught them to walk on two legs, made them cut off their toe +nails and pluck the hair from their bodies, after which they adopted them +into the tribe. But the rest of their kindred, the crawfish, are crawfish +under ground to this day. (Geo. Catlin, "North American Indians"4 (London, +1844), II. page 128.) The Osage Indians universally believed that they +were descended from a male snail and a female beaver. A flood swept the +snail down to the Missouri and left him high and dry on the bank, where the +sun ripened him into a man. He met and married a beaver maid, and from the +pair the tribe of the Osages is descended. For a long time these Indians +retained a pious reverence for their animal ancestors and refrained from +hunting beavers, because in killing a beaver they killed a brother of the +Osages. But when white men came among them and offered high prices for +beaver skins, the Osages yielded to the temptation and took the lives of +their furry brethren. (Lewis and Clarke, "Travels to the Source of the +Missouri River" (London, 1815), I. 12 (Vol. I. pages 44 sq. of the London +reprint, 1905).) The Carp clan of the Ootawak Indians are descended from +the eggs of a carp which had been deposited by the fish on the banks of a +stream and warmed by the sun. ("Lettres Edifiantes et Curieuses", Nouvelle +Edition, VI. (Paris, 1781), page 171.) The Crane clan of the Ojibways are +sprung originally from a pair of cranes, which after long wanderings +settled on the rapids at the outlet of Lake Superior, where they were +changed by the Great Spirit into a man and woman. (L.H. Morgan, "Ancient +Society" (London, 1877), page 180.) The members of two Omaha clans were +originally buffaloes and lived, oddly enough, under water, which they +splashed about, making it muddy. And at death all the members of these +clans went back to their ancestors the buffaloes. So when one of them lay +adying, his friends used to wrap him up in a buffalo skin with the hair +outside and say to him, "You came hither from the animals and you are going +back thither. Do not face this way again. When you go, continue walking. +(J. Owen Dorsey, "Omaha Sociology", "Third Annual Report of the Bureau of +Ethnology" (Washington, 1884), pages 229, 233.) The Haida Indians of Queen +Charlotte Islands believe that long ago the raven, who is the chief figure +in the mythology of North-West America, took a cockle from the beach and +married it; the cockle gave birth to a female child, whom the raven took to +wife, and from their union the Indians were produced. (G.M. Dawson, +"Report on the Queen Charlotte Islands" (Montreal, 1880), pages 149B sq. +("Geological Survey of Canada"); F. Poole, "Queen Charlotte Islands", page +136.) The Delaware Indians called the rattle-snake their grandfather and +would on no account destroy one of these reptiles, believing that were they +to do so the whole race of rattle-snakes would rise up and bite them. +Under the influence of the white man, however, their respect for their +grandfather the rattle-snake gradually died away, till at last they killed +him without compunction or ceremony whenever they met him. The writer who +records the old custom observes that he had often reflected on the curious +connection which appears to subsist in the mind of an Indian between man +and the brute creation; "all animated nature," says he, "in whatever +degree, is in their eyes a great whole, from which they have not yet +ventured to separate themselves." (Rev. John Heckewelder, "An Account of +the History, Manners, and Customs, of the Indian Nations, who once +inhabited Pennsylvania and the Neighbouring States", "Transactions of the +Historical and Literary Committee of the American Philosophical Society", +I. (Philadelphia, 1819), pages 245, 247, 248.) + +Some of the Indians of Peru boasted of being descended from the puma or +American lion; hence they adored the lion as a god and appeared at +festivals like Hercules dressed in the skins of lions with the heads of the +beasts fixed over their own. Others claimed to be sprung from condors and +attired themselves in great black and white wings, like that enormous bird. +(Garcilasso de la Vega, "First Part of the Royal Commentaries of the +Yncas", Vol. I. page 323, Vol. II. page 156 (Markham's translation).) The +Wanika of East Africa look upon the hyaena as one of their ancestors or as +associated in some way with their origin and destiny. The death of a +hyaena is mourned by the whole people, and the greatest funeral ceremonies +which they perform are performed for this brute. The wake held over a +chief is as nothing compared to the wake held over a hyaena; one tribe only +mourns the death of its chief, but all the tribes unite to celebrate the +obsequies of a hyaena. (Charles New, "Life, Wanderings, and Labours in +Eastern Africa" (London, 1873) page 122.) Some Malagasy families claim to +be descended from the babacoote (Lichanotus brevicaudatus), a large lemur +of grave appearance and staid demeanour, which lives in the depth of the +forest. When they find one of these creatures dead, his human descendants +bury it solemnly, digging a grave for it, wrapping it in a shroud, and +weeping and lamenting over its carcase. A doctor who had shot a babacoote +was accused by the inhabitants of a Betsimisaraka village of having killed +"one of their grandfathers in the forest," and to appease their indignation +he had to promise not to skin the animal in the village but in a solitary +place where nobody could see him. (Father Abinal, "Croyances fabuleuses +des Malgaches", "Les Missions Catholiques", XII. (1880), page 526; G.H. +Smith, "Some Betsimisaraka superstitions", "The Antananarivo Annual and +Madagascar Magazine", No. 10 (Antananarivo, 1886), page 239; H.W. Little, +"Madagascar, its History and People" (London, 1884), pages 321 sq; A. van +Gennep, "Tabou et Totemisme a Madagascar" (Paris, 1904), pages 214 sqq.) +Many of the Betsimisaraka believe that the curious nocturnal animal called +the aye-aye (Cheiromys madagascariensis) "is the embodiment of their +forefathers, and hence will not touch it, much less do it an injury. It is +said that when one is discovered dead in the forest, these people make a +tomb for it and bury it with all the forms of a funeral. They think that +if they attempt to entrap it, they will surely die in consequence." (G.A. +Shaw, "The Aye-aye", "Antananarivo Annual and Madagascar Magazine", Vol. +II. (Antananarivo, 1896), pages 201, 203 (Reprint of the Second four +Numbers). Compare A. van Gennep, "Tabou et Totemisme a Madagascar", pages +223 sq.) Some Malagasy tribes believe themselves descended from crocodiles +and accordingly they deem the formidable reptiles their brothers. If one +of these scaly brothers so far forgets the ties of kinship as to devour a +man, the chief of the tribe, or in his absence an old man familiar with the +tribal customs, repairs at the head of the people to the edge of the water, +and summons the family of the culprit to deliver him up to the arm of +justice. A hook is then baited and cast into the river or lake. Next day +the guilty brother or one of his family is dragged ashore, formally tried, +sentenced to death, and executed. The claims of justice being thus +satisfied, the dead animal is lamented and buried like a kinsman; a mound +is raised over his grave and a stone marks the place of his head. (Father +Abinal, "Croyances fabuleuses des Malgaches", "Les Missions Catholiques", +XII. (1880), page 527; A. van Gennep, "Tabou et Totemisme a Madagascar", +pages 281 sq.) + +Amongst the Tshi-speaking tribes of the Gold Coast in West Africa the +Horse-mackerel family traces its descent from a real horse-mackerel whom an +ancestor of theirs once took to wife. She lived with him happily in human +shape on shore till one day a second wife, whom the man had married, +cruelly taunted her with being nothing but a fish. That hurt her so much +that bidding her husband farewell she returned to her old home in the sea, +with her youngest child in her arms, and never came back again. But ever +since the Horse-mackerel people have refrained from eating horse-mackerels, +because the lost wife and mother was a fish of that sort. (A.B. Ellis, +"The Tshi-speaking Peoples of the Gold Coast of West Africa" (London, +1887), pages 208-11. A similar tale is told by another fish family who +abstain from eating the fish (appei) from which they take their name (A.B. +Ellis op. cit. pages 211 sq.).) Some of the Land Dyaks of Borneo tell a +similar tale to explain a similar custom. "There is a fish which is taken +in their rivers called a puttin, which they would on no account touch, +under the idea that if they did they would be eating their relations. The +tradition respecting it is, that a solitary old man went out fishing and +caught a puttin, which he dragged out of the water and laid down in his +boat. On turning round, he found it had changed into a very pretty little +girl. Conceiving the idea she would make, what he had long wished for, a +charming wife for his son, he took her home and educated her until she was +fit to be married. She consented to be the son's wife cautioning her +husband to use her well. Some time after their marriage, however, being +out of temper, he struck her, when she screamed, and rushed away into the +water; but not without leaving behind her a beautiful daughter, who became +afterwards the mother of the race." (The Lord Bishop of Labuan, "On the +Wild Tribes of the North-West Coast of Borneo", "Transactions of the +Ethnological Society of London", New Series II. (London, 1863), pages 26 +sq. Such stories conform to a well-known type which may be called the +Swan-Maiden type of story, or Beauty and the Beast, or Cupid and Psyche. +The occurrence of stories of this type among totemic peoples, such as the +Tshi-speaking negroes of the Gold Coast, who tell them to explain their +totemic taboos, suggests that all such tales may have originated in +totemism. I shall deal with this question elsewhere.) + +Members of a clan in Mandailing, on the west coast of Sumatra, assert that +they are descended from a tiger, and at the present day, when a tiger is +shot, the women of the clan are bound to offer betel to the dead beast. +When members of this clan come upon the tracks of a tiger, they must, as a +mark of homage, enclose them with three little sticks. Further, it is +believed that the tiger will not attack or lacerate his kinsmen, the +members of the clan. (H. Ris, "De Onderafdeeling Klein Mandailing Oeloe en +Pahantan en hare Bevolking met uitzondering van de Oeloes", "Bijdragen tot +de Tall- Land- en Volkenkunde van Nederlansch-Indie, XLVI. (1896), page +473.) The Battas of Central Sumatra are divided into a number of clans +which have for their totems white buffaloes, goats, wild turtle-doves, +dogs, cats, apes, tigers, and so forth; and one of the explanations which +they give of their totems is that these creatures were their ancestors, and +that their own souls after death can transmigrate into the animals. (J.B. +Neumann, "Het Pane en Bila-stroomgebied op het eiland Sumatra", +"Tijdschrift van het Nederlandsch Aardrijkskundig Genootschap", Tweede +Serie, III. Afdeeling, Meer uitgebreide Artikelen, No. 2 (Amsterdam, 1886), +pages 311 sq.; id. ib. Tweede Serie, IV. Afdeeling, Meer uitgebreide +Artikelen, No. 1 (Amsterdam, 1887), pages 8 sq.) In Amboyna and the +neighbouring islands the inhabitants of some villages aver that they are +descended from trees, such as the Capellenia moluccana, which had been +fertilised by the Pandion Haliaetus. Others claim to be sprung from pigs, +octopuses, crocodiles, sharks, and eels. People will not burn the wood of +the trees from which they trace their descent, nor eat the flesh of the +animals which they regard as their ancestors. Sicknesses of all sorts are +believed to result from disregarding these taboos. (J.G.F. Riedel, "De +sluik- en kroesharige rassen tusschen Selebes en Papua" (The Hague, 1886), +pages 32, 61; G.W.W.C. Baron van Hoevell, "Ambon en meer bepaaldelijk de +Oeliasers" (Dordrecht, 1875), page 152.) Similarly in Ceram persons who +think they are descended from crocodiles, serpents, iguanas, and sharks +will not eat the flesh of these animals. (J.G.F. Riedel op. cit. page +122.) Many other peoples of the Molucca Islands entertain similar beliefs +and observe similar taboos. (J.G.F. Riedel "De sluik- en kroesharige +rassen tusschen Selebes en Papua" (The Hague, 1886), pages 253, 334, 341, +348, 412, 414, 432.) Again, in Ponape, one of the Caroline Islands, "The +different families suppose themselves to stand in a certain relation to +animals, and especially to fishes, and believe in their descent from them. +They actually name these animals 'mothers'; the creatures are sacred to the +family and may not be injured. Great dances, accompanied with the offering +of prayers, are performed in their honour. Any person who killed such an +animal would expose himself to contempt and punishment, certainly also to +the vengeance of the insulted deity." Blindness is commonly supposed to be +the consequence of such a sacrilege. (Dr Hahl, "Mittheilungen uber Sitten +und rechtliche Verhaltnisse auf Ponape", "Ethnologisches Notizblatt", Vol. +II. Heft 2 (Berlin, 1901), page 10.) + +Some of the aborigines of Western Australia believe that their ancestors +were swans, ducks, or various other species of water-fowl before they were +transformed into men. (Captain G. Grey, "A Vocabulary of the Dialects of +South Western Australia", Second Edition (London, 1840), pages 29, 37, 61, +63, 66, 71.) The Dieri tribe of Central Australia, who are divided into +totemic clans, explain their origin by the following legend. They say that +in the beginning the earth opened in the midst of Perigundi Lake, and the +totems (murdus or madas) came trooping out one after the other. Out came +the crow, and the shell parakeet, and the emu, and all the rest. Being as +yet imperfectly formed and without members or organs of sense, they laid +themselves down on the sandhills which surrounded the lake then just as +they do now. It was a bright day and the totems lay basking in the +sunshine, till at last, refreshed and invigorated by it, they stood up as +human beings and dispersed in all directions. That is why people of the +same totem are now scattered all over the country. You may still see the +island in the lake out of which the totems came trooping long ago. (A.W. +Howitt, "Native Tribes of South-East Australia" (London, 1904), pages 476, +779 sq.) Another Dieri legend relates how Paralina, one of the Mura-Muras +or mythical predecessors of the Dieri, perfected mankind. He was out +hunting kangaroos, when he saw four incomplete beings cowering together. +So he went up to them, smoothed their bodies, stretched out their limbs, +slit up their fingers and toes, formed their mouths, noses, and eyes, stuck +ears on them, and blew into their ears in order that they might hear. +Having perfected their organs and so produced mankind out of these +rudimentary beings, he went about making men everywhere. (A.W. Howitt op. +cit., pages 476, 780 sq.) Yet another Dieri tradition sets forth how the +Mura-Mura produced the race of man out of a species of small black lizards, +which may still be met with under dry bark. To do this he divided the feet +of the lizards into fingers and toes, and, applying his forefinger to the +middle of their faces, created a nose; likewise he gave them human eyes, +mouths and ears. He next set one of them upright, but it fell down again +because of its tail; so he cut off its tail and the lizard then walked on +its hind legs. That is the origin of mankind. (S. Gason, "The Manners and +Customs of the Dieyerie tribe of Australian Aborigines", "Native Tribes of +South Australia" (Adelaide, 1879), page 260. This writer fell into the +mistake of regarding the Mura-Mura (Mooramoora) as a Good-Spirit instead of +as one of the mythical but more or less human predecessors of the Dieri in +the country. See A.W. Howitt, "Native Tribes of South-East Australia", +pages 475 sqq.) + +The Arunta tribe of Central Australia similarly tell how in the beginning +mankind was developed out of various rudimentary forms of animal life. +They say that in those days two beings called Ungambikula, that is, "out of +nothing," or "self-existing," dwelt in the western sky. From their lofty +abode they could see, far away to the east, a number of inapertwa +creatures, that is, rudimentary human beings or incomplete men, whom it was +their mission to make into real men and women. For at that time there were +no real men and women; the rudimentary creatures (inapertwa) were of +various shapes and dwelt in groups along the shore of the salt water which +covered the country. These embryos, as we may call them, had no distinct +limbs or organs of sight, hearing, and smell; they did not eat food, and +they presented the appearance of human beings all doubled up into a rounded +mass, in which only the outline of the different parts of the body could be +vaguely perceived. Coming down from their home in the western sky, armed +with great stone knives, the Ungambikula took hold of the embryos, one +after the other. First of all they released the arms from the bodies, then +making four clefts at the end of each arm they fashioned hands and fingers; +afterwards legs, feet, and toes were added in the same way. The figure +could now stand; a nose was then moulded and the nostrils bored with the +fingers. A cut with the knife made the mouth, which was pulled open +several times to render it flexible. A slit on each side of the face +separated the upper and lower eye-lids, disclosing the eyes, which already +existed behind them; and a few strokes more completed the body. Thus out +of the rudimentary creatures were formed men and women. These rudimentary +creatures or embryos, we are told, "were in reality stages in the +transformation of various animals and plants into human beings, and thus +they were naturally, when made into human beings, intimately associated +with the particular animal or plant, as the case may be, of which they were +the transformations--in other words, each individual of necessity belonged +to a totem, the name of which was of course that of the animal or plant of +which he or she was a transformation." However, it is not said that all +the totemic clans of the Arunta were thus developed; no such tradition, for +example, is told to explain the origin of the important Witchetty Grub +clan. The clans which are positively known, or at least said, to have +originated out of embryos in the way described are the Plum Tree, the Grass +Seed, the Large Lizard, the Small Lizard, the Alexandra Parakeet, and the +Small Rat clans. When the Ungambikula had thus fashioned people of these +totems, they circumcised them all, except the Plum Tree men, by means of a +fire-stick. After that, having done the work of creation or evolution, the +Ungambikula turned themselves into little lizards which bear a name meaning +"snappers-up of flies." (Baldwin Spencer and F.J. Gillen, "Native Tribes +of Central Australia (London, 1899), pages 388 sq.; compare id., "Northern +Tribes of Central Australia" (London, 1904), page 150.) + +This Arunta tradition of the origin of man, as Messrs Spencer and Gillen, +who have recorded it, justly observe, "is of considerable interest; it is +in the first place evidently a crude attempt to describe the origin of +human beings out of non-human creatures who were of various forms; some of +them were representatives of animals, others of plants, but in all cases +they are to be regarded as intermediate stages in the transition of an +animal or plant ancestor into a human individual who bore its name as that +of his or her totem." (Baldwin Spencer and F.J. Gillen, "Native Tribes of +Central Australia", pages 391 sq.) In a sense these speculations of the +Arunta on their own origin may be said to combine the theory of creation +with the theory of evolution; for while they represent men as developed out +of much simpler forms of life, they at the same time assume that this +development was effected by the agency of two powerful beings, whom so far +we may call creators. It is well known that at a far higher stage of +culture a crude form of the evolutionary hypothesis was propounded by the +Greek philosopher Empedocles. He imagined that shapeless lumps of earth +and water, thrown up by the subterranean fires, developed into monstrous +animals, bulls with the heads of men, men with the heads of bulls, and so +forth; till at last, these hybrid forms being gradually eliminated, the +various existing species of animals and men were evolved. (E. Zeller, "Die +Philosophie der Griechen", I.4 (Leipsic, 1876), pages 718 sq.; H. Ritter et +L. Preller, "Historia Philosophiae Graecae et Romanae ex fontium locis +contexta"5, pages 102 sq. H. Diels, "Die Fragmente der Vorsokratiker"2, I. +(Berlin, 1906), pages 190 sqq. Compare Lucretius "De rerum natura", V. 837 +sqq.) The theory of the civilised Greek of Sicily may be set beside the +similar theory of the savage Arunta of Central Australia. Both represent +gropings of the human mind in the dark abyss of the past; both were in a +measure grotesque anticipations of the modern theory of evolution. + +In this essay I have made no attempt to illustrate all the many various and +divergent views which primitive man has taken of his own origin. I have +confined myself to collecting examples of two radically different views, +which may be distinguished as the theory of creation and the theory of +evolution. According to the one, man was fashioned in his existing shape +by a god or other powerful being; according to the other he was evolved by +a natural process out of lower forms of animal life. Roughly speaking, +these two theories still divide the civilised world between them. The +partisans of each can appeal in support of their view to a large consensus +of opinion; and if truth were to be decided by weighing the one consensus +against the other, with "Genesis" in the one scale and "The Origin of +Species" in the other, it might perhaps be found, when the scales were +finally trimmed, that the balance hung very even between creation and +evolution. + + +X. THE INFLUENCE OF DARWIN ON THE STUDY OF ANIMAL EMBRYOLOGY. + +By A. SEDGWICK, M.A., F.R.S. +Professor of Zoology and Comparative Anatomy in the University of +Cambridge. + +The publication of "The Origin of Species" ushered in a new era in the +study of Embryology. Whereas, before the year 1859 the facts of anatomy +and development were loosely held together by the theory of types, which +owed its origin to the great anatomists of the preceding generation, to +Cuvier, L. Agassiz, J. Muller, and R. Owen, they were now combined together +into one organic whole by the theory of descent and by the hypothesis of +recapitulation which was deduced from that theory. The view (First clearly +enunciated by Fritz Muller in his well-known work, "Fur Darwin", Leipzig, +1864; (English Edition, "Facts for Darwin", 1869).) that a knowledge of +embryonic and larval histories would lay bare the secrets of race-history +and enable the course of evolution to be traced, and so lead to the +discovery of the natural system of classification, gave a powerful stimulus +to morphological study in general and to embryological investigation in +particular. In Darwin's words: "Embryology rises greatly in interest, +when we look at the embryo as a picture, more or less obscured, of the +progenitor, either in its adult or larval state, of all the members of the +same great class." ("Origin" (6th edition), page 396.) In the period +under consideration the output of embryological work has been enormous. No +group of the animal kingdom has escaped exhaustive examination and no +effort has been spared to obtain the embryos of isolated and out of the way +forms, the development of which might have an important bearing upon +questions of phylogeny and classification. Marine zoological stations have +been established, expeditions have been sent to distant countries, and the +methods of investigation have been greatly improved. The result of this +activity has been that the main features of the developmental history of +all the most important animals are now known and the curiosity as to +developmental processes, so greatly excited by the promulgation of the +Darwinian theory, has to a considerable extent been satisfied. + +To what extent have the results of this vast activity fulfilled the +expectations of the workers who have achieved them? The Darwin centenary +is a fitting moment at which to take stock of our position. In this +inquiry we shall leave out of consideration the immense and intensely +interesting additions to our knowledge of Natural History. These may be +said to constitute a capital fund upon which philosophers, poets and men of +science will draw for many generations. The interest of Natural History +existed long before Darwinian evolution was thought of and will endure +without any reference to philosophic speculations. She is a mistress in +whose face are beauties and in whose arms are delights elsewhere +unattainable. She is and always has been pursued for her own sake without +any reference to philosophy, science, or utility. + +Darwin's own views of the bearing of the facts of embryology upon questions +of wide scientific interest are perfectly clear. He writes ("Origin" (6th +edition), page 395.): + +"On the other hand it is highly probable that with many animals the +embryonic or larval stages show us, more or less completely, the condition +of the progenitor of the whole group in its adult state. In the great +class of the Crustacea, forms wonderfully distinct from each other, namely, +suctorial parasites, cirripedes, entomostraca, and even the malacostraca, +appear at first as larvae under the nauplius-form; and as these larvae live +and feed in the open sea, and are not adapted for any peculiar habits of +life, and from other reasons assigned by Fritz Muller, it is probable that +at some very remote period an independent adult animal, resembling the +Nauplius, existed, and subsequently produced, along several divergent lines +of descent, the above-named great Crustacean groups. So again it is +probable, from what we know of the embryos of mammals, birds, fishes, and +reptiles, that these animals are the modified descendants of some ancient +progenitor, which was furnished in its adult state with branchiae, a swim- +bladder, four fin-like limbs, and a long tail, all fitted for an aquatic +life. + +"As all the organic beings, extinct and recent, which have ever lived, can +be arranged within a few great classes; and as all within each class have, +according to our theory, been connected together by fine gradations, the +best, and, if our collections were nearly perfect, the only possible +arrangement, would be genealogical; descent being the hidden bond of +connexion which naturalists have been seeking under the term of the Natural +System. On this view we can understand how it is that, in the eyes of most +naturalists, the structure of the embryo is even more important for +classification than that of the adult. In two or more groups of animals, +however much they may differ from each other in structure and habits in +their adult condition, if they pass through closely similar embryonic +stages, we may feel assured that they all are descended from one parent- +form, and are therefore closely related. Thus, community in embryonic +structure reveals community of descent; but dissimilarity in embryonic +development does not prove discommunity of descent, for in one of two +groups the developmental stages may have been suppressed, or may have been +so greatly modified through adaptation to new habits of life, as to be no +longer recognisable. Even in groups, in which the adults have been +modified to an extreme degree, community of origin is often revealed by the +structure of the larvae; we have seen, for instance, that cirripedes, +though externally so like shell-fish, are at once known by their larvae to +belong to the great class of crustaceans. As the embryo often shows us +more or less plainly the structure of the less modified and ancient +progenitor of the group, we can see why ancient and extinct forms so often +resemble in their adult state the embryos of existing species of the same +class. Agassiz believes this to be a universal law of nature; and we may +hope hereafter to see the law proved true. It can, however, be proved true +only in those cases in which the ancient state of the progenitor of the +group has not been wholly obliterated, either by successive variations +having supervened at a very early period of growth, or by such variations +having been inherited at an earlier stage than that at which they first +appeared. It should also be borne in mind, that the law may be true, but +yet, owing to the geological record not extending far enough back in time, +may remain for a long period, or for ever, incapable of demonstration. The +law will not strictly hold good in those cases in which an ancient form +became adapted in its larval state to some special line of life, and +transmitted the same larval state to a whole group of descendants; for such +larvae will not resemble any still more ancient form in its adult state." + +As this passage shows, Darwin held that embryology was of interest because +of the light it seems to throw upon ancestral history (phylogeny) and +because of the help it would give in enabling us to arrive at a natural +system of classification. With regard to the latter point, he quotes with +approval the opinion that "the structure of the embryo is even more +important for classification than that of the adult." What justification +is there for this view? The phase of life chosen for the ordinary +anatomical and physiological studies, namely, the adult phase, is merely +one of the large number of stages of structure through which the organism +passes. By far the greater number of these are included in what is +specially called the developmental or (if we include larvae with embryos) +embryonic period, for the developmental changes are more numerous and take +place with greater rapidity at the beginning of life than in its later +periods. As each of these stages is equal in value, for our present +purpose, to the adult phase, it clearly follows that if there is anything +in the view that the anatomical study of organisms is of importance in +determining their mutual relations, the study of the organism in its +various embryonic (and larval) stages must have a greater importance than +the study of the single and arbitrarily selected stage of life called the +adult. + +But a deeper reason than this has been assigned for the importance of +embryology in classification. It has been asserted, and is implied by +Darwin in the passage quoted, that the ancestral history is repeated in a +condensed form in the embryonic, and that a study of the latter enables us +to form a picture of the stages of structure through which the organism has +passed in its evolution. It enables us on this view to reconstruct the +pedigrees of animals and so to form a genealogical tree which shall be the +true expression of their natural relations. + +The real question which we have to consider is to what extent the +embryological studies of the last 50 years have confirmed or rendered +probable this "theory of recapitulation." In the first place it must be +noted that the recapitulation theory is itself a deduction from the theory +of evolution. The facts of embryology, particularly of vertebrate +embryology, and of larval history receive, it is argued, an explanation on +the view that the successive stages of development are, on the whole, +records of adult stages of structure which the species has passed through +in its evolution. Whether this statement will bear a critical verbal +examination I will not now pause to inquire, for it is more important to +determine whether any independent facts can be alleged in favour of the +theory. If it could be shown, as was stated to be the case by L. Agassiz, +that ancient and extinct forms of life present features of structure now +only found in embryos, we should have a body of facts of the greatest +importance in the present discussion. But as Huxley (See Huxley's +"Scientific Memoirs", London, 1898, Vol. I. page 303: "There is no real +parallel between the successive forms assumed in the development of the +life of the individual at present, and those which have appeared at +different epochs in the past." See also his Address to the Geological +Society of London (1862) 'On the Palaeontological Evidence of Evolution', +ibid. Vol. II. page 512.) has shown and as the whole course of +palaeontological and embryological investigation has demonstrated, no such +statement can be made. The extinct forms of life are very similar to those +now existing and there is nothing specially embryonic about them. So that +the facts, as we know them, lend no support to theory. + +But there is another class of facts which have been alleged in favour of +the theory, viz. the facts which have been included in the generalisation +known as the Law of v. Baer. The law asserts that embryos of different +species of animals of the same group are more alike than the adults and +that, the younger the embryo, the greater are the resemblances. If this +law could be established it would undoubtedly be a strong argument in +favour of the "recapitulation" explanation of the facts of embryology. But +its truth has been seriously disputed. If it were true we should expect to +find that the embryos of closely similar species would be indistinguishable +from one another, but this is notoriously not the case. It is more +difficult to meet the assertion when it is made in the form given above, +for here we are dealing with matters of opinion. For instance, no one +would deny that the embryo of a dogfish is different from the embryo of a +rabbit, but there is room for difference of opinion when it is asserted +that the difference is less than the difference between an adult dogfish +and an adult rabbit. It would be perfectly true to say that the +differences between the embryos concern other organs more than do the +differences between the adults, but who is prepared to affirm that the +presence of a cephalic coelom and of cranial segments, of external gills, +of six gill slits, of the kidney tubes opening into the muscle-plate +coelom, of an enormous yolk-sac, of a neurenteric canal, and the absence of +any trace of an amnion, of an allantois and of a primitive streak are not +morphological facts of as high an import as those implied by the +differences between the adults? The generalisation undoubtedly had its +origin in the fact that there is what may be called a family resemblance +between embryos and larvae, but this resemblance, which is by no means +exact, is largely superficial and does not extend to anatomical detail. + +It is useless to say, as Weismann has stated ("The Evolution Theory", by A. +Weismann, English Translation, Vol. II. page 176, London, 1904.), that "it +cannot be disputed that the rudiments [vestiges his translator means] of +gill-arches and gill-clefts, which are peculiar to one stage of human +ontogeny, give us every ground for concluding that we possessed fish-like +ancestors." The question at issue is: did the pharyngeal arches and +clefts of mammalian embryos ever discharge a branchial function in an adult +ancestor of the mammalia? We cannot therefore, without begging the +question at issue in the grossest manner, apply to them the terms "gill- +arches" and "gill-clefts". That they are homologous with the "gill-arches" +and "gill-clefts" of fishes is true; but there is no evidence to show that +they ever discharged a branchial function. Until such evidence is +forthcoming, it is beside the point to say that it "cannot be disputed" +that they are evidence of a piscine ancestry. + +It must, therefore, be admitted that one outcome of the progress of +embryological and palaeontological research for the last 50 years is +negative. The recapitulation theory originated as a deduction from the +evolution theory and as a deduction it still remains. + +Let us before leaving the subject apply another test. If the evolution +theory and the recapitulation theory are both true, how is it that living +birds are not only without teeth but have no rudiments of teeth at any +stage of their existence? How is it that the missing digits in birds and +mammals, the missing or reduced limb of snakes and whales, the reduced +mandibulo-hyoid cleft of elasmobranch fishes are not present or relatively +more highly developed in the embryo than in the adult? How is it that when +a marked variation, such as an extra digit, or a reduced limb, or an extra +segment, makes its appearance, it is not confined to the adult but can be +seen all through the development? All the clear evidence we can get tends +to show that marked variations, whether of reduction or increase, of organs +are manifest during the whole of the development of the organ and do not +merely affect the adult. And on reflection we see that it could hardly be +otherwise. All such evidence is distinctly at variance with the theory of +recapitulation, at least as applied to embryos. In the case of larvae of +course the case will be different, for in them the organs are functional, +and reduction in the adult will not be accompanied by reduction in the +larva unless a change in the conditions of life of the larva enables it to +occur. + +If after 50 years of research and close examination of the facts of +embryology the recapitulation theory is still without satisfactory proof, +it seems desirable to take a wider sweep and to inquire whether the facts +of embryology cannot be included in a larger category. + +As has been pointed out by Huxley, development and life are co-extensive, +and it is impossible to point to any period in the life of an organism when +the developmental changes cease. It is true that these changes take place +more rapidly at the commencement of life, but they are never wholly absent, +and those which occur in the later or so-called adult stages of life do not +differ in their essence, however much they may differ in their degree, from +those which occur during the embryonic and larval periods. This +consideration at once brings the changes of the embryonic period into the +same category as those of the adult and suggests that an explanation which +will account for the one will account for the other. What then is the +problem we are dealing with? Surely it is this: Why does an organism as +soon as it is established at the fertilisation of the ovum enter upon a +cycle of transformations which never cease until death puts an end to them? +In other words what is the meaning of that cycle of changes which all +organisms present in a greater or less degree and which constitute the very +essence of life? It is impossible to give an answer to this question so +long as we remain within the precincts of Biology--and it is not my present +purpose to penetrate beyond those precincts into the realms of philosophy. +We have to do with an ultimate biological fact, with a fundamental property +of living matter, which governs and includes all its other properties. How +may this property be stated? Thus: it is a property of living matter to +react in a remarkable way to external forces without undergoing +destruction. The life-cycle, of which the embryonic and larval periods are +a part, consists of the orderly interaction between the organism and its +environment. The action of the environment produces certain morphological +changes in the organism. These changes enable the organism to come into +relation with new external forces, to move into what is practically a new +environment, which in its turn produces further structural changes in the +organism. These in their turn enable, indeed necessitate, the organism to +move again into a new environment, and so the process continues until the +structural changes are of such a nature that the organism is unable to +adapt itself to the environment in which it finds itself. The essential +condition of success in this process is that the organism should always +shift into the environment to which its new structure is suited--any +failure in this leading to the impairment of the organism. In most cases +the shifting of the environment is a very gradual process (whether +consisting in the very slight and gradual alteration in the relation of the +embryo as a whole to the egg-shell or uterine wall, or in the relations of +its parts to each other, or in the successive phases of adult life), and +the morphological changes in connection with each step of it are but +slight. But in some cases jumps are made such as we find in the phenomena +known as hatching, birth, and metamorphosis. + +This property of reacting to the environment without undergoing destruction +is, as has been stated, a fundamental property of organisms. It is +impossible to conceive of any matter, to which the term living could be +applied, being without it. And with this property of reacting to the +environment goes the further property of undergoing a change which alters +the relation of the organism to the old environment and places it in a new +environment. If this reasoning is correct, it necessarily follows that +this property must have been possessed by living matter at its first +appearance on the earth. In other words living matter must always have +presented a life-cycle, and the question arises what kind of modification +has that cycle undergone? Has it increased or diminished in duration and +complexity since organisms first appeared on the earth? The current view +is that the cycle was at first very short and that it has increased in +length by the evolutionary creation of new adult phases, that these new +phases are in addition to those already existing and that each of them as +it appears takes over from the preceding adult phase the functional +condition of the reproductive organs. According to the same view the old +adult phases are not obliterated but persist in a more or less modified +form as larval stages. It is further supposed that as the life-history +lengthens at one end by the addition of new adult phases, it is shortened +at the other by the abbreviation of embryonic development and by the +absorption of some of the early larval stages into the embryonic period; +but on the whole the lengthening process has exceeded that of shortening, +so that the whole life-history has, with the progress of evolution, become +longer and more complicated. + +Now there can be no doubt that the life-history of organisms has been +shortened in the way above suggested, for cases are known in which this can +practically be seen to occur at the present day. But the process of +lengthening by the creation of new stages at the other end of the life- +cycle is more difficult to conceive and moreover there is no evidence for +its having occurred. This, indeed, may have occurred, as is suggested +below, but the evidence we have seems to indicate that evolutionary +modification has proceeded by ALTERING and not by SUPERSEDING: that is to +say that each stage in the life-history, as we see it to-day, has proceeded +from a corresponding stage in a former era by the modification of that +stage and not by the creation of a new one. Let me, at the risk of +repetition, explain my meaning more fully by taking a concrete +illustration. The mandibulo-hyoid cleft (spiracle) of the elasmobranch +fishes, the lateral digits of the pig's foot, the hind-limbs of whales, the +enlarged digit of the ostrich's foot are supposed to be organs which have +been recently modified. This modification is not confined to the final +adult stage of the life-history but characterises them throughout the whole +of their development. A stage with a reduced spiracle does not proceed in +development from a preceding stage in which the spiracle shows no +reduction: it is reduced at its first appearance. The same statement may +be made of organs which have entirely disappeared in the adult, such as +bird's teeth and snake's fore-limbs: the adult stage in which they have +disappeared is not preceded by embryonic stages in which the teeth and +limbs or rudiments of them are present. In fact the evidence indicates +that adult variations of any part are accompanied by precedent variations +in the same direction in the embryo. The evidence seems to show, not that +a stage is added on at the end of the life-history, but only that some of +the stages in the life-history are modified. Indeed, on the wider view of +development taken in this essay, a view which makes it coincident with +life, one would not expect often to find, even if new stages are added in +the course of evolution, that they are added at the end of the series when +the organism has passed through its reproductive period. It is possible of +course that new stages have been intercalated in the course of the life- +history, though it is difficult to see how this has occurred. It is much +more likely, if we may judge from available evidence, that every stage has +had its counterpart in the ancestral form from which it has been derived by +descent with modification. Just as the adult phase of the living form +differs, owing to evolutionary modification, from the adult phase of the +ancestor from which it has proceeded, so each larval phase will differ for +the same reason from the corresponding larval phase in the life-history of +the ancestor. Inasmuch as the organism is variable at every stage of its +independent existence and is exposed to the action of natural selection +there is no reason why it should escape modification at any stage. + +If there is any truth in these considerations it would seem to follow that +at the dawn of life the life-cycle must have been, either in posse or in +esse, at least as long as it is at the present time, and that the +peculiarity of passing through a series of stages in which new characters +are successively evolved is a primordial quality of living matter. + +Before leaving this part of the subject, it is necessary to touch upon +another aspect of it. What are these variations in structure which succeed +one another in the life-history of an organism? I am conscious that I am +here on the threshold of a chamber which contains the clue to some of our +difficulties, and that I cannot enter it. Looked at from one point of view +they belong to the class of genetic variations, which depend upon the +structure or constitution of the protoplasm; but instead of appearing in +different zygotes (A zygote is a fertilised ovum, i.e. a new organism +resulting from the fusion of an ovum and a spermatozoon.), they are present +in the same zygote though at different times in its life-history. They are +of the same order as the mutational variations of the modern biologist upon +which the appearance of a new character depends. What is a genetic or +mutational variation? It is a genetic character which was not present in +either of the parents. But these "growth variations" were present in the +parents, and in this they differ from mutational variations. But what are +genetic characters? They are characters which must appear if any +development occurs. They are usually contrasted with "acquired +characters," using the expression "acquired character" in the Lamarckian +sense. But strictly speaking they ARE acquired characters, for the zygote +at first has none of the characters which it subsequently acquires, but +only the power of acquiring them in response to the action of the +environment. But the characters so acquired are not what we technically +understand and what Lamarck meant by "acquired characters." They are +genetic characters, as defined above. What then are Lamarck's "acquired +characters"? They are variations in genetic characters caused in a +particular way. There are, in fact, two kinds of variation in genetic +characters depending on the mode of causation. Firstly, there are those +variations consequent upon a variation in the constitution of the +protoplasm of a particular zygote, and independent of the environment in +which the organism develops, save in so far as this simply calls them +forth: these are the so-called genetic or mutational variations. +Secondly, there are those variations which occur in zygotes of similar +germinal constitution and which are caused solely by differences in the +environment to which the individuals are respectively exposed: these are +the "acquired characters" of Lamarck and of authors generally. In +consequence of this double sense in which the term "acquired characters" +may be used, great confusion may and does occur. If the protoplasm be +compared to a machine, and the external conditions to the hand that works +the machine, then it may be said that, as the machine can only work in one +way, it can only produce one kind of result (genetic character), but the +particular form or quality (Lamarckian "acquired character") of the result +will depend upon the hand that works the machine (environment), just as the +quality of the sound produced by a fiddle depends entirely upon the hand +which plays upon it. It would be improper to apply the term "mutation" to +those genetic characters which are not new characters or new variants of +old characters, but such genetic characters are of the same nature as those +characters to which the term mutation has been applied. It may be noticed +in passing that it is very questionable if the modern biologist has acted +in the real interests of science in applying the term mutation in the sense +in which he has applied it. The genetic characters of organisms come from +one of two sources: either they are old characters and are due to the +action of what we call inheritance or they are new and are due to what we +call variation. If the term mutation is applied to the actual alteration +of the machinery of the protoplasm, no objection can be felt to its use; +but if it be applied, as it is, to the product of the action of the altered +machine, viz. to the new genetic character, it leads to confusion. +Inheritance is the persistence of the structure of the machine; characters +are the products of the working of the machine; variation in genetic +characters is due to the alteration (mutation) in the arrangement of the +machinery, while variation in acquired characters (Lamarckian) is due to +differences in the mode of working the machinery. The machinery when it +starts (in the new zygote) has the power of grinding out certain results, +which we call the characters of the organism. These appear at successive +intervals of time, and the orderly manifestation of them is what we call +the life-history of the organism. This brings us back to the question with +which we started this discussion, viz. what is the relation of these +variations in structure, which successively appear in an organism and +constitute its life-history, to the mutational variations which appear in +different organisms of the same brood or species. The question is brought +home to us when we ask what is a bud-sport, such as a nectarine appearing +on a peach-tree? From one point of view, it is simply a mutation appearing +in asexual reproduction; from another it is one of these successional +characters ("growth variations") which constitute the life-history of the +zygote, for it appears in the same zygote which first produces a peach. +Here our analogy of a machine which only works in one way seems to fail us, +for these bud-sports do not appear in all parts of the organism, only in +certain buds or parts of it, so that one part of the zygotic machine would +appear to work differently to another. To discuss this question further +would take us too far from our subject. Suffice it to say that we cannot +answer it, any more than we can this further question of burning interest +at the present day, viz. to what extent and in what manner is the machine +itself altered by the particular way in which it is worked. In connection +with this question we can only submit one consideration: the zygotic +machine can, by its nature, only work once, so that any alteration in it +can only be ascertained by studying the replicas of it which are produced +in the reproductive organs. + +It is a peculiarity that the result which we call the ripening of the +generative organs nearly always appears among the final products of the +action of the zygotic machine. It is remarkable that this should be the +case. What is the reason of it? The late appearance of functional +reproductive organs is almost a universal law, and the explanation of it is +suggested by expressing the law in another way, viz. that the machine is +almost always so constituted that it ceases to work efficiently soon after +the reproductive organs have sufficiently discharged their function. Why +this should occur we cannot explain: it is an ultimate fact of nature, and +cannot be included in any wider category. The period during which the +reproductive organs can act may be short as in ephemerids or long as in man +and trees, and there is no reason to suppose that their action damages the +vital machinery, though sometimes, as in the case of annual plants +(Metschnikoff), it may incidentally do so; but, long or short, the +cessation of their actions is always a prelude to the end. When they and +their action are impaired, the organism ceases to react with precision to +the environment, and the organism as a whole undergoes retrogressive +changes. + +It has been pointed out above that there is reason to believe that at the +dawn of life the life-cycle was, EITHER IN ESSE OR IN POSSE, at least as +long as it is at the present time. The qualification implied by the words +in italics is necessary, for it is clearly possible that the external +conditions then existing were not suitable for the production of all the +stages of the potential life-history, and that what we call organic +evolution has consisted in a gradual evolution of new environments to which +the organism's innate capacity of change has enabled it to adapt itself. +We have warrant for this possibility in the case of the Axolotl and in +other similar cases of neoteny. And these cases further bring home to us +the fact, to which I have already referred, that the full development of +the functional reproductive organs is nearly always associated with the +final stages of the life-history. + +On this view of the succession of characters in the life-history of +organisms, how shall we explain the undoubted fact that the development of +buds hardly ever presents any phenomena corresponding to the embryonic and +larval changes? The reason is clearly this, that budding usually occurs +after the embryonic stage is past; when the characters of embryonic life +have been worked out by the machine. When it takes place at an early stage +in embryonic life, as it does in cases of so-called embryonic fission, the +product shows, either partly or entirely, phenomena similar to those of +embryonic development. The only case known to me in which budding by the +adult is accompanied by morphological features similar to those displayed +by embryos is furnished by the budding of the medusiform spore-sacs of +hydrozoon polyps. But this case is exceptional, for here we have to do +with an attempt, which fails, to form a free-swimming organism, the medusa; +and the vestiges which appear in the buds are the umbrella-cavity, marginal +tentacles, circular canal, etc., of the medusa arrested in development. + +But the question still remains, are there no cases in which, as implied by +the recapitulation theory, variations in any organ are confined to the +period in which the organ is functional and do not affect it in the +embryonic stages? The teeth of the whalebone whales may be cited as a case +in which this is said to occur; but here the teeth are only imperfectly +developed in the embryo and are soon absorbed. They have been affected by +the change which has produced their disappearance in the adult, but not to +complete extinction. Nor are they now likely to be extinguished, for +having become exclusively embryonic they are largely protected from the +action of natural selection. This consideration brings up a most important +aspect of the question, so far as disappearing organs are concerned. Every +organ is laid down at a certain period in the embryo and undergoes a +certain course of growth until it obtains full functional development. +When for any cause reduction begins, it is affected at all stages of its +growth, unless it has functional importance in the larva, and in some cases +its life is shortened at one or both ends. In cases, as in that of the +whale's teeth, in which it entirely disappears in the adult, the latter +part of its life is cut off; in others, the beginning of its life may be +deferred. This happens, for instance, with the spiracle of many +Elasmobranchs, which makes its appearance after the hyobranchial cleft, not +before it as it should do, being anterior to it in position, and as it does +in the Amniota in which it shows no reduction in size as compared with the +other pharyngeal clefts. In those Elasmobranchs in which it is absent in +the adult but present in the embryo (e.g. Carcharias) its life is shortened +at both ends. Many more instances of organs, of which the beginning and +end have been cut off, might be mentioned; e.g. the muscle-plate coelom of +Aves, the primitive streak and the neurenteric canal of amniote +blastoderms. In yet other cases in which the reduced organ is almost on +the verge of disappearance, it may appear for a moment and disappear more +than once in the course of development. As an instance of this striking +phenomenon I may mention the neurenteric canal of avine embryos, and the +anterior neuropore of Ascidians. Lastly the reduced organ may disappear in +the developing stages before it does so in the adult. As an instance of +this may be mentioned the mandibular palp of those Crustacea with zoaea +larvae. This structure disappears in the larva only to reappear in a +reduced form in later stages. In all these cases we are dealing with an +organ which, we imagine, attained a fuller functional development at some +previous stage in race-history, but in most of them we have no proof that +it did so. It may be, and the possibility must not be lost sight of, that +these organs never were anything else than functionless and that though +they have been got rid of in the adult by elimination in the course of +time, they have been able to persist in embryonic stages which are +protected from the full action of natural selection. There is no reason to +suppose that living matter at its first appearance differed from non-living +matter in possessing only properties conducive to its well-being and +prolonged existence. No one thinks that the properties of the various +forms of inorganic matter are all strictly related to external conditions. +Of what use to the diamond is its high specific gravity and high +refrangibility, and to gold of its yellow colour and great weight? These +substances continue to exist in virtue of other properties than these. It +is impossible to suppose that the properties of living matter at its first +appearance were all useful to it, for even now after aeons of elimination +we find that it possesses many useless organs and that many of its +relations to the external world are capable of considerable improvement. + +In writing this essay I have purposely refrained from taking a definite +position with regard to the problems touched. My desire has been to write +a chapter showing the influence of Darwin's work so far as Embryology is +concerned, and the various points which come up for consideration in +discussing his views. Darwin was the last man who would have claimed +finality for any of his doctrines, but he might fairly have claimed to have +set going a process of intellectual fermentation which is still very far +from completion. + + +XI. THE PALAEONTOLOGICAL RECORD. + +I. ANIMALS. + +By W.B. SCOTT. +Professor of Geology in the University of Princeton, U.S.A. + +To no branch of science did the publication of "The Origin of Species" +prove to be a more vivifying and transforming influence than to +Palaeontology. This science had suffered, and to some extent, still +suffers from its rather anomalous position between geology and biology, +each of which makes claim to its territory, and it was held in strict +bondage to the Linnean and Cuvierian dogma that species were immutable +entities. There is, however, reason to maintain that this strict bondage +to a dogma now abandoned, was not without its good side, and served the +purpose of keeping the infant science in leading-strings until it was able +to walk alone, and preventing a flood of premature generalisations and +speculations. + +As Zittel has said: "Two directions were from the first apparent in +palaeontological research--a stratigraphical and a biological. +Stratigraphers wished from palaeontology mainly confirmation regarding the +true order or relative age of zones of rock-deposits in the field. +Biologists had, theoretically at least, the more genuine interest in fossil +organisms as individual forms of life." (Zittel, "History of Geology and +Palaeontology", page 363, London, 1901.) The geological or stratigraphical +direction of the science was given by the work of William Smith, "the +father of historical geology," in the closing decade of the eighteenth +century. Smith was the first to make a systematic use of fossils in +determining the order of succession of the rocks which make up the +accessible crust of the earth, and this use has continued, without +essential change, to the present day. It is true that the theory of +evolution has greatly modified our conceptions concerning the introduction +of new species and the manner in which palaeontological data are to be +interpreted in terms of stratigraphy, but, broadly speaking, the method +remains fundamentally the same as that introduced by Smith. + +The biological direction of palaeontology was due to Cuvier and his +associates, who first showed that fossils were not merely varieties of +existing organisms, but belonged to extinct species and genera, an +altogether revolutionary conception, which startled the scientific world. +Cuvier made careful studies, especially of fossil vertebrates, from the +standpoint of zoology and was thus the founder of palaeontology as a +biological science. His great work on "Ossements Fossiles" (Paris, 1821) +has never been surpassed as a masterpiece of the comparative method of +anatomical investigation, and has furnished to the palaeontologist the +indispensable implements of research. + +On the other hand, Cuvier's theoretical views regarding the history of the +earth and its successive faunas and floras are such as no one believes to- +day. He held that the earth had been repeatedly devastated by great +cataclysms, which destroyed every living thing, necessitating an entirely +new creation, thus regarding the geological periods as sharply demarcated +and strictly contemporaneous for the whole earth, and each species of +animal and plant as confined to a single period. Cuvier's immense +authority and his commanding personality dominated scientific thought for +more than a generation and marked out the line which the development of +palaeontology was to follow. The work was enthusiastically taken up by +many very able men in the various European countries and in the United +States, but, controlled as it was by the belief in the fixity of species, +it remained almost entirely descriptive and consisted in the description +and classification of the different groups of fossil organisms. As already +intimated, this narrowness of view had its compensations, for it deferred +generalisations until some adequate foundations for these had been laid. + +Dominant as it was, Cuvier's authority was slowly undermined by the +progress of knowledge and the way was prepared for the introduction of more +rational conceptions. The theory of "Catastrophism" was attacked by +several geologists, most effectively by Sir Charles Lyell, who greatly +amplified the principles enunciated by Hutton and Playfair in the preceding +century, and inaugurated a new era in geology. Lyell's uniformitarian +views of the earth's history and of the agencies which had wrought its +changes, had undoubted effect in educating men's minds for the acceptance +of essentially similar views regarding the organic world. In palaeontology +too the doctrine of the immutability of species, though vehemently +maintained and reasserted, was gradually weakening. In reviewing long +series of fossils, relations were observed which pointed to genetic +connections and yet were interpreted as purely ideal. Agassiz, for +example, who never accepted the evolutionary theory, drew attention to +facts which could be satisfactorily interpreted only in terms of that +theory. Among the fossils he indicated "progressive," "synthetic," +"prophetic," and "embryonic" types, and pointed out the parallelism which +obtains between the geological succession of ancient animals and the +ontogenetic development of recent forms. In Darwin's words: "This view +accords admirably well with our theory." ("Origin of Species" (6th +edition), page 310.) Of similar import were Owen's views on "generalised +types" and "archetypes." + +The appearance of "The Origin of Species" in 1859 revolutionised all the +biological sciences. From the very nature of the case, Darwin was +compelled to give careful consideration to the palaeontological evidence; +indeed, it was the palaeontology and modern distribution of animals in +South America which first led him to reflect upon the great problem. In +his own words: "I had been deeply impressed by discovering in the Pampean +formation great fossil animals covered with armour like that on the +existing armadillos; secondly, by the manner in which closely allied +animals replace one another in proceeding southward over the Continent; and +thirdly, by the South American character of most of the productions of the +Galapagos archipelago, and more especially by the manner in which they +differ slightly on each island of the group." ("Life and Letters of +Charles Darwin", I. page 82.) In the famous tenth and eleventh chapters of +the "Origin", the palaeontological evidence is examined at length and the +imperfection of the geological record is strongly emphasised. The +conclusion is reached, that, in view of this extreme imperfection, +palaeontology could not reasonably be expected to yield complete and +convincing proof of the evolutionary theory. "I look at the geological +record as a history of the world imperfectly kept, and written in a +changing dialect; of this history we possess the last volume alone, +relating only to two or three countries. Of this volume, only here and +there a short chapter has been preserved; and of each page, only here and +there a few lines." ("Origin of Species", page 289.) Yet, aside from +these inevitable difficulties, he concludes, that "the other great leading +facts in palaeontology agree admirably with the theory of descent with +modification through variation and natural selection." (Ibid. page 313.) + +Darwin's theory gave an entirely new significance and importance to +palaeontology. Cuvier's conception of the science had been a limited, +though a lofty one. "How glorious it would be if we could arrange the +organised products of the universe in their chronological order!...The +chronological succession of organised forms, the exact determination of +those types which appeared first, the simultaneous origin of certain +species and their gradual decay, would perhaps teach us as much about the +mysteries of organisation as we can possibly learn through experiments with +living organisms." (Zittel op. cit. page 140.) This, however, was rather +the expression of a hope for the distant future than an account of what was +attainable, and in practice the science remained almost purely descriptive, +until Darwin gave it a new standpoint, new problems and an altogether fresh +interest and charm. The revolution thus accomplished is comparable only to +that produced by the Copernican astronomy. + +From the first it was obvious that one of the most searching tests of the +evolutionary theory would be given by the advance of palaeontological +discovery. However imperfect the geological record might be, its +ascertained facts would necessarily be consistent, under any reasonable +interpretation, with the demands of a true theory; otherwise the theory +would eventually be overwhelmed by the mass of irreconcilable data. A very +great stimulus was thus given to geological investigation and to the +exploration of new lands. In the last forty years, the examination of +North and South America, of Africa and Asia has brought to light many +chapters in the history of life, which are astonishingly full and complete. +The flood of new material continues to accumulate at such a rate that it is +impossible to keep abreast of it, and the very wealth of the collections is +a source of difficulty and embarrassment. In modern palaeontology +phylogenetic questions and problems occupy a foremost place and, as a +result of the labours of many eminent investigators in many lands, it may +be said that this science has proved to be one of the most solid supports +of Darwin's theory. True, there are very many unsolved problems, and the +discouraged worker is often tempted to believe that the fossils raise more +questions than they answer. Yet, on the other hand, the whole trend of the +evidence is so strongly in favour of the evolutionary doctrine, that no +other interpretation seems at all rational. + +To present any adequate account of the palaeontological record from the +evolutionary standpoint, would require a large volume and a singularly +unequal, broken and disjointed history it would be. Here the record is +scanty, interrupted, even unintelligible, while there it is crowded with +embarrassing wealth of material, but too often these full chapters are +separated by such stretches of unrecorded time, that it is difficult to +connect them. It will be more profitable to present a few illustrative +examples than to attempt an outline of the whole history. + +At the outset, the reader should be cautioned not to expect too much, for +the task of determining phylogenies fairly bristles with difficulties and +encounters many unanswered questions. Even when the evidence seems to be +as copious and as complete as could be wished, different observers will put +different interpretations upon it, as in the notorious case of the +Steinheim shells. (In the Miocene beds of Steinheim, Wurtemberg, occur +countless fresh-water shells, which show numerous lines of modification, +but these have been very differently interpreted by different writers.) +The ludicrous discrepances which often appear between the phylogenetic +"trees" of various writers have cast an undue discredit upon the science +and have led many zoologists to ignore palaeontology altogether as unworthy +of serious attention. One principal cause of these discrepant and often +contradictory results is our ignorance concerning the exact modes of +developmental change. What one writer postulates as almost axiomatic, +another will reject as impossible and absurd. Few will be found to agree +as to how far a given resemblance is offset by a given unlikeness, and so +long as the question is one of weighing evidence and balancing +probabilities, complete harmony is not to be looked for. These formidable +difficulties confront us even in attempting to work out from abundant +material a brief chapter in the phylogenetic history of some small and +clearly limited group, and they become disproportionately greater, when we +extend our view over vast periods of time and undertake to determine the +mutual relationships of classes and types. If the evidence were complete +and available, we should hardly be able to unravel its infinite complexity, +or to find a clue through the mazes of the labyrinth. "Our ideas of the +course of descent must of necessity be diagrammatic." (D.H. Scott, +"Studies in Fossil Botany", page 524. London, 1900.) + +Some of the most complete and convincing examples of descent with +modification are to be found among the mammals, and nowhere more abundantly +than in North America, where the series of continental formations, running +through the whole Tertiary period, is remarkably full. Most of these +formations contain a marvellous wealth of mammalian remains and in an +unusual state of preservation. The oldest Eocene (Paleocene) has yielded a +mammalian fauna which is still of prevailingly Mesozoic character, and +contains but few forms which can be regarded as ancestral to those of later +times. The succeeding fauna of the lower Eocene proper (Wasatch stage) is +radically different and, while a few forms continue over from the +Paleocene, the majority are evidently recent immigrants from some region +not yet identified. From the Wasatch onward, the development of many phyla +may be traced in almost unbroken continuity, though from time to time the +record is somewhat obscured by migrations from the Old World and South +America. As a rule, however, it is easy to distinguish between the +immigrant and the indigenous elements of the fauna. + +From their gregarious habits and individual abundance, the history of many +hoofed animals is preserved with especial clearness. So well known as to +have become a commonplace, is the phylogeny of the horses, which, contrary +to all that would have been expected, ran the greater part of its course in +North America. So far as it has yet been traced, the line begins in the +lower Eocene with the genus Eohippus, a little creature not much larger +than a cat, which has a short neck, relatively short limbs, and in +particular, short feet, with four functional digits and a splint-like +rudiment in the fore-foot, three functional digits and a rudiment in the +hind-foot. The forearm bones (ulna and radius) are complete and separate, +as are also the bones of the lower leg (fibula and tibia). The skull has a +short face, with the orbit, or eye-socket, incompletely enclosed with bone, +and the brain-case is slender and of small capacity. The teeth are short- +crowned, the incisors without "mark," or enamel pit, on the cutting edge; +the premolars are all smaller and simpler than the molars. The pattern of +the upper molars is so entirely different from that seen in the modern +horses that, without the intermediate connecting steps, no one would have +ventured to derive the later from the earlier plan. This pattern is +quadritubercular, with four principal, conical cusps arranged in two +transverse pairs, forming a square, and two minute cuspules between each +transverse pair, a tooth which is much more pig-like than horse-like. In +the lower molars the cusps have already united to form two crescents, one +behind the other, forming a pattern which is extremely common in the early +representatives of many different families, both of the Perissodactyla and +the Artiodactyla. In spite of the manifold differences in all parts of the +skeleton between Eohippus and the recent horses, the former has stamped +upon it an equine character which is unmistakable, though it can hardly be +expressed in words. + +Each one of the different Eocene and Oligocene horizons has its +characteristic genus of horses, showing a slow, steady progress in a +definite direction, all parts of the structure participating in the +advance. It is not necessary to follow each of these successive steps of +change, but it should be emphasised that the changes are gradual and +uninterrupted. The genus Mesohippus, of the middle Oligocene, may be +selected as a kind of half-way stage in the long progression. Comparing +Mesohippus with Eohippus, we observe that the former is much larger, some +species attaining the size of a sheep, and has a relatively longer neck, +longer limbs and much more elongate feet, which are tridactyl, and the +middle toe is so enlarged that it bears most of the weight, while the +lateral digits are very much more slender. The fore-arm bones have begun +to co-ossify and the ulna is greatly reduced, while the fibula, though +still complete, is hardly more than a thread of bone. The skull has a +longer face and a nearly enclosed orbit, and the brain-case is fuller and +more capacious, the internal cast of which shows that the brain was richly +convoluted. The teeth are still very short-crowned, but the upper incisors +plainly show the beginning of the "mark"; the premolars have assumed the +molar form, and the upper molars, though plainly derived from those of +Eohippus, have made a long stride toward the horse pattern, in that the +separate cusps have united to form a continuous outer wall and two +transverse crests. + +In the lower Miocene the interesting genus Desmatippus shows a further +advance in the development of the teeth, which are beginning to assume the +long-crowned shape, delaying the formation of roots; a thin layer of cement +covers the crowns, and the transverse crests of the upper grinding teeth +display an incipient degree of their modern complexity. This tooth-pattern +is strictly intermediate between the recent type and the ancient type seen +in Mesohippus and its predecessors. The upper Miocene genera, Protohippus +and Hipparion are, to all intents and purposes, modern in character, but +their smaller size, tridactyl feet and somewhat shorter-crowned teeth are +reminiscences of their ancestry. + +From time to time, when a land-connection between North America and Eurasia +was established, some of the successive equine genera migrated to the Old +World, but they do not seem to have gained a permanent footing there until +the end of the Miocene or beginning of the Pliocene, eventually +diversifying into the horses, asses, and zebras of Africa, Asia and Europe. +At about the same period, the family extended its range to South America +and there gave rise to a number of species and genera, some of them +extremely peculiar. For some unknown reason, all the horse tribe had +become extinct in the western hemisphere before the European discovery, but +not until after the native race of man had peopled the continents. + +In addition to the main stem of equine descent, briefly considered in the +foregoing paragraphs, several side-branches were given off at successive +levels of the stem. Most of these branches were short-lived, but some of +them flourished for a considerable period and ramified into many species. + +Apparently related to the horses and derived from the same root-stock is +the family of the Palaeotheres, confined to the Eocene and Oligocene of +Europe, dying out without descendants. In the earlier attempts to work out +the history of the horses, as in the famous essay of Kowalevsky ("Sur +l'Anchitherium aurelianense Cuv. et sur l'histoire paleontologique des +Chevaux", "Mem. de l'Acad. Imp. des Sc. de St Petersbourg", XX. no. 5, +1873.), the Palaeotheres were placed in the direct line, because the number +of adequately known Eocene mammals was then so small, that Cuvier's types +were forced into various incongruous positions, to serve as ancestors for +unrelated series. + +The American family of the Titanotheres may also be distantly related to +the horses, but passed through an entirely different course of development. +From the lower Eocene to the lower sub-stage of the middle Oligocene the +series is complete, beginning with small and rather lightly built animals. +Gradually the stature and massiveness increase, a transverse pair of nasal +horns make their appearance and, as these increase in size, the canine +tusks and incisors diminish correspondingly. Already in the oldest known +genus the number of digits had been reduced to four in the fore-foot and +three in the hind, but there the reduction stops, for the increasing body- +weight made necessary the development of broad and heavy feet. The final +members of the series comprise only large, almost elephantine animals, with +immensely developed and very various nasal horns, huge and massive heads, +and altogether a grotesque appearance. The growth of the brain did not at +all keep pace with the increase of the head and body, and the ludicrously +small brain may will have been one of the factors which determined the +startlingly sudden disappearance and extinction of the group. + +Less completely known, but of unusual interest, is the genealogy of the +rhinoceros family, which probably, though not certainly, was likewise of +American origin. The group in North America at least, comprised three +divisions, or sub-families, of very different proportions, appearance and +habits, representing three divergent lines from the same stem. Though the +relationship between the three lines seems hardly open to question, yet the +form ancestral to all of them has not yet been identified. This is because +of our still very incomplete knowledge of several perissodactyl genera of +the Eocene, any one of which may eventually prove to be the ancestor sought +for. + +The first sub-family is the entirely extinct group of Hyracodonts, which +may be traced in successive modifications through the upper Eocene, lower +and middle Oligocene, then disappearing altogether. As yet, the +hyracodonts have been found only in North America, and the last genus of +the series, Hyracodon, was a cursorial animal. Very briefly stated, the +modifications consist in a gradual increase in size, with greater +slenderness of proportions, accompanied by elongation of the neck, limbs, +and feet, which become tridactyl and very narrow. The grinding teeth have +assumed the rhinoceros-like pattern and the premolars resemble the molars +in form; on the other hand, the front teeth, incisors and canines, have +become very small and are useless as weapons. As the animal had no horns, +it was quite defenceless and must have found its safety in its swift +running, for Hyracodon displays many superficial resemblances to the +contemporary Oligocene horses, and was evidently adapted for speed. It may +well have been the competition of the horses which led to the extinction of +these cursorial rhinoceroses. + +The second sub-family, that of the Amynodonts, followed a totally different +course of development, becoming short-legged and short-footed, massive +animals, the proportions of which suggest aquatic habits; they retained +four digits in the front foot. The animal was well provided with weapons +in the large canine tusks, but was without horns. Some members of this +group extended their range to the Old World, but they all died out in the +middle Oligocene, leaving no successors. + +The sub-family of the true rhinoceroses cannot yet be certainly traced +farther back than to the base of the middle Oligocene, though some +fragmentary remains found in the lower Oligocene are probably also +referable to it. The most ancient and most primitive member of this series +yet discovered, the genus Trigonias, is unmistakably a rhinoceros, yet much +less massive, having more the proportions of a tapir; it had four toes in +the front foot, three in the hind, and had a full complement of teeth, +except for the lower canines, though the upper canines are about to +disappear, and the peculiar modification of the incisors, characteristic of +the true rhinoceroses, is already apparent; the skull is hornless. +Representatives of this sub-family continue through the Oligocene and +Miocene of North America, becoming rare and localised in the Pliocene and +then disappearing altogether. In the Old World, on the other hand, where +the line appeared almost as early as it did in America, this group +underwent a great expansion and ramification, giving rise not only to the +Asiatic and African forms, but also to several extinct series. + +Turning now to the Artiodactyla, we find still another group of mammals, +that of the camels and llamas, which has long vanished from North America, +yet took its rise and ran the greater part of its course in that continent. +From the lower Eocene onward the history of this series is substantially +complete, though much remains to be learned concerning the earlier members +of the family. The story is very like that of the horses, to which in many +respects it runs curiously parallel. Beginning with very small, five-toed +animals, we observe in the successive genera a gradual transformation in +all parts of the skeleton, an elongation of the neck, limbs and feet, a +reduction of the digits from five to two, and eventually the coalescence of +the remaining two digits into a "cannon-bone." The grinding teeth, by +equally gradual steps, take on the ruminant pattern. In the upper Miocene +the line divides into the two branches of the camels and llamas, the former +migrating to Eurasia and the latter to South America, though +representatives of both lines persisted in North America until a very late +period. Interesting side-branches of this line have also been found, one +of which ended in the upper Miocene in animals which had almost the +proportions of the giraffes and must have resembled them in appearance. + +The American Tertiary has yielded several other groups of ruminant-like +animals, some of which form beautifully complete evolutionary series, but +space forbids more than this passing mention of them. + +It was in Europe that the Artiodactyla had their principal development, and +the upper Eocene, Oligocene and Miocene are crowded with such an +overwhelming number and variety of forms that it is hardly possible to +marshal them in orderly array and determine their mutual relationships. +Yet in this chaotic exuberance of life, certain important facts stand out +clearly, among these none is of greater interest and importance than the +genealogy of the true Ruminants, or Pecora, which may be traced from the +upper Eocene onward. The steps of modification and change are very similar +to those through which the camel phylum passed in North America, but it is +instructive to note that, despite their many resemblances, the two series +can be connected only in their far distant beginnings. The pecoran stock +became vastly more expanded and diversified than did the camel line and was +evidently more plastic and adaptable, spreading eventually over all the +continents except Australia, and forming to-day one of the dominant types +of mammals, while the camels are on the decline and not far from +extinction. The Pecora successively ramified into the deer, antelopes, +sheep, goats and oxen, and did not reach North America till the Miocene, +when they were already far advanced in specialisation. To this invasion of +the Pecora, or true ruminants, it seems probable that the decline and +eventual disappearance of the camels is to be ascribed. + +Recent discoveries in Egypt have thrown much light upon a problem which +long baffled the palaeontologist, namely, the origin of the elephants. +(C.W. Andrews, "On the Evolution of the Proboscidea", "Phil. Trans. Roy. +Soc." London, Vol. 196, 1904, page 99.) Early representatives of this +order, Mastodons, had appeared almost simultaneously (in the geological +sense of that word) in the upper Miocene of Europe and North America, but +in neither continent was any more ancient type known which could plausibly +be regarded as ancestral to them. Evidently, these problematical animals +had reached the northern continents by migrating from some other region, +but no one could say where that region lay. The Eocene and Oligocene beds +of the Fayoum show us that the region sought for is Africa, and that the +elephants form just such a series of gradual modifications as we have found +among other hoofed animals. The later steps of the transformation, by +which the mastodons lost their lower tusks, and their relatively small and +simple grinding teeth acquired the great size and highly complex structure +of the true elephants, may be followed in the uppermost Miocene and +Pliocene fossils of India and southern Europe. + +Egypt has also of late furnished some very welcome material which +contributes to the solution of another unsolved problem which had quite +eluded research, the origin of the whales. The toothed-whales may be +traced back in several more or less parallel lines as far as the lower +Miocene, but their predecessors in the Oligocene are still so incompletely +known that safe conclusions can hardly be drawn from them. In the middle +Eocene of Egypt, however, has been found a small, whale-like animal +(Protocetus), which shows what the ancestral toothed-whale was like, and at +the same time seems to connect these thoroughly marine mammals with land- +animals. Though already entirely adapted to an aquatic mode of life, the +teeth, skull and backbone of Protocetus display so many differences from +those of the later whales and so many approximations to those of primitive, +carnivorous land-mammals, as, in a large degree, to bridge over the gap +between the two groups. Thus one of the most puzzling of palaeontological +questions is in a fair way to receive a satisfactory answer. The origin of +the whalebone-whales and their relations to the toothed-whales cannot yet +be determined, since the necessary fossils have not been discovered. + +Among the carnivorous mammals, phylogenetic series are not so clear and +distinct as among the hoofed animals, chiefly because the carnivores are +individually much less abundant, and well-preserved skeletons are among the +prizes of the collector. Nevertheless, much has already been learned +concerning the mutual relations of the carnivorous families, and several +phylogenetic series, notably that of the dogs, are quite complete. It has +been made extremely probable that the primitive dogs of the Eocene +represent the central stock, from which nearly or quite all the other +families branched off, though the origin and descent of the cats have not +yet been determined. + +It should be clearly understood that the foregoing account of mammalian +descent is merely a selection of a few representative cases and might be +almost indefinitely extended. Nothing has been said, for example, of the +wonderful museum of ancient mammalian life which is entombed in the rocks +of South America, especially of Patagonia, and which opens a world so +entirely different from that of the northern continents, yet exemplifying +the same laws of "descent with modification." Very beautiful phylogenetic +series have already been established among these most interesting and +marvellously preserved fossils, but lack of space forbids a consideration +of them. + +The origin of the mammalia, as a class, offers a problem of which +palaeontology can as yet present no definitive solution. Many +morphologists regard the early amphibia as the ancestral group from which +the mammals were derived, while most palaeontologists believe that the +mammals are descended from the reptiles. The most ancient known mammals, +those from the upper Triassic of Europe and North America, are so extremely +rare and so very imperfectly known, that they give little help in +determining the descent of the class, but, on the other hand, certain +reptilian orders of the Permian period, especially well represented in +South Africa, display so many and such close approximations to mammalian +structure, as strongly to suggest a genetic relationship. It is difficult +to believe that all those likenesses should have been independently +acquired and are without phylogenetic significance. + +Birds are comparatively rare as fossils and we should therefore look in +vain among them for any such long and closely knit series as the mammals +display in abundance. Nevertheless, a few extremely fortunate discoveries +have made it practically certain that birds are descended from reptiles, of +which they represent a highly specialised branch. The most ancient +representative of this class is the extraordinary genus Archaeopteryx from +the upper Jurassic of Bavaria, which, though an unmistakable bird, retains +so many reptilian structures and characteristics as to make its derivation +plain. Not to linger over anatomical minutiae, it may suffice to mention +the absence of a horny beak, which is replaced by numerous true teeth, and +the long lizard-like tail, which is made up of numerous distinct vertebrae, +each with a pair of quill-like feathers attached to it. Birds with teeth +are also found in the Cretaceous, though in most other respects the birds +of that period had attained a substantially modern structure. Concerning +the interrelations of the various orders and families of birds, +palaeontology has as yet little to tell us. + +The life of the Mesozoic era was characterised by an astonishing number and +variety of reptiles, which were adapted to every mode of life, and +dominated the air, the sea and the land, and many of which were of colossal +proportions. Owing to the conditions of preservation which obtained during +the Mesozoic period, the history of the reptiles is a broken and +interrupted one, so that we can make out many short series, rather than any +one of considerable length. While the relations of several reptilian +orders can be satisfactorily determined, others still baffle us entirely, +making their first known appearance in a fully differentiated state. We +can trace the descent of the sea-dragons, the Ichthyosaurs and Plesiosaurs, +from terrestrial ancestors, but the most ancient turtles yet discovered +show us no closer approximation to any other order than do the recent +turtles; and the oldest known Pterosaurs, the flying dragons of the +Jurassic, are already fully differentiated. There is, however, no ground +for discouragement in this, for the progress of discovery has been so rapid +of late years, and our knowledge of Mesozoic life has increased with such +leaps and bounds, that there is every reason to expect a solution of many +of the outstanding problems in the near future. + +Passing over the lower vertebrates, for lack of space to give them any +adequate consideration, we may briefly take up the record of invertebrate +life. From the overwhelming mass of material it is difficult to make a +representative selection and even more difficult to state the facts +intelligibly without the use of unduly technical language and without the +aid of illustrations. + +Several groups of the Mollusca, or shell-fish, yield very full and +convincing evidence of their descent from earlier and simpler forms, and of +these none is of greater interest than the Ammonites, an extinct order of +the cephalopoda. The nearest living ally of the ammonites is the pearly +nautilus, the other existing cephalopods, such as the squids, cuttle-fish, +octopus, etc., are much more distantly related. Like the nautilus, the +ammonites all possess a coiled and chambered shell, but their especial +characteristic is the complexity of the "sutures." By sutures is meant the +edges of the transverse partitions, or septa, where these join the shell- +wall, and their complexity in the fully developed genera is extraordinary, +forming patterns like the most elaborate oak-leaf embroidery, while in the +nautiloids the sutures form simple curves. In the rocks of the Mesozoic +era, wherever conditions of preservation are favourable, these beautiful +shells are stored in countless multitudes, of an incredible variety of +form, size and ornamentation, as is shown by the fact that nearly 5000 +species have already been described. The ammonites are particularly well +adapted for phylogenetic studies, because, by removing the successive +whorls of the coiled shell, the individual development may be followed back +in inverse order, to the microscopic "protoconch," or embryonic shell, +which lies concealed in the middle of the coil. Thus the valuable aid of +embryology is obtained in determining relationships. + +The descent of the ammonites, taken as a group, is simple and clear; they +arose as a branch of the nautiloids in the lower Devonian, the shells known +as goniatites having zigzag, angulated sutures. Late in the succeeding +Carboniferous period appear shells with a truly ammonoid complexity of +sutures, and in the Permian their number and variety cause them to form a +striking element of the marine faunas. It is in the Mesozoic era, however, +that these shells attain their full development; increasing enormously in +the Triassic, they culminate in the Jurassic in the number of families, +genera and species, in the complexity of the sutures, and in the variety of +shell-ornamentation. A slow decline begins in the Cretaceous, ending in +the complete extinction of the whole group at the end of that period. As a +final phase in the history of the ammonites, there appear many so-called +"abnormal" genera, in which the shell is irregularly coiled, or more or +less uncoiled, in some forms becoming actually straight. It is interesting +to observe that some of these genera are not natural groups, but are +"polyphyletic," i.e. are each derived from several distinct ancestral +genera, which have undergone a similar kind of degeneration. + +In the huge assembly of ammonites it is not yet possible to arrange all the +forms in a truly natural classification, which shall express the various +interrelations of the genera, yet several beautiful series have already +been determined. In these series the individual development of the later +general shows transitory stages which are permanent in antecedent genera. +To give a mere catalogue of names without figures would not make these +series more intelligible. + +The Brachiopoda, or "lamp-shells," are a phylum of which comparatively few +survive to the present day; their shells have a superficial likeness to +those of the bivalved Mollusca, but are not homologous with the latter, and +the phylum is really very distinct from the molluscs. While greatly +reduced now, these animals were incredibly abundant throughout the +Palaeozoic era, great masses of limestone being often composed almost +exclusively of their shells, and their variety is in keeping with their +individual abundance. As in the case of the ammonites, the problem is to +arrange this great multitude of forms in an orderly array that shall +express the ramifications of the group according to a genetic system. For +many brachiopods, both recent and fossil, the individual development, or +ontogeny, has been worked out and has proved to be of great assistance in +the problems of classification and phylogeny. Already very encouraging +progress has been made in the solution of these problems. All brachiopods +form first a tiny, embryonic shell, called the protegulum, which is +believed to represent the ancestral form of the whole group, and in the +more advanced genera the developmental stages clearly indicate the +ancestral genera of the series, the succession of adult forms in time +corresponding to the order of the ontogenetic stages. The transformation +of the delicate calcareous supports of the arms, often exquisitely +preserved, are extremely interesting. Many of the Palaeozoic genera had +these supports coiled like a pair of spiral springs, and it has been shown +that these genera were derived from types in which the supports were simply +shelly loops. + +The long extinct class of crustacea known as the Trilobites are likewise +very favourable subjects for phylogenetic studies. So far as the known +record can inform us, the trilobites are exclusively Palaeozoic in +distribution, but their course must have begun long before that era, as is +shown by the number of distinct types among the genera of the lower +Cambrian. The group reached the acme of abundance and relative importance +in the Cambrian and Ordovician; then followed a long, slow decline, ending +in complete and final disappearance before the end of the Permian. The +newly-hatched and tiny trilobite larva, known as the protaspis, is very +near to the primitive larval form of all the crustacea. By the aid of the +correlated ontogenetic stages and the succession of the adult forms in the +rocks, many phylogenetic series have been established and a basis for the +natural arrangement of the whole class has been laid. + +Very instructive series may also be observed among the Echinoderms and, +what is very rare, we are able in this sub-kingdom to demonstrate the +derivation of one class from another. Indeed, there is much reason to +believe that the extinct class Cystidea of the Cambrian is the ancestral +group, from which all the other Echinoderms, star-fishes, brittle-stars, +sea-urchins, feather-stars, etc., are descended. + +The foregoing sketch of the palaeontological record is, of necessity, +extremely meagre, and does not represent even an outline of the evidence, +but merely a few illustrative examples, selected almost at random from an +immense body of material. However, it will perhaps suffice to show that +the geological record is not so hopelessly incomplete as Darwin believed it +to be. Since "The Origin of Species" was written, our knowledge of that +record has been enormously extended and we now possess, no complete +volumes, it is true, but some remarkably full and illuminating chapters. +The main significance of the whole lies in the fact, that JUST IN +PROPORTION TO THE COMPLETENESS OF THE RECORD IS THE UNEQUIVOCAL CHARACTER +OF ITS TESTIMONY TO THE TRUTH OF THE EVOLUTIONARY THEORY. + +The test of a true, as distinguished from a false, theory is the manner in +which newly discovered and unanticipated facts arrange themselves under it. +No more striking illustration of this can be found than in the contrasted +fates of Cuvier's theory and of that of Darwin. Even before Cuvier's death +his views had been undermined and the progress of discovery soon laid them +in irreparable ruin, while the activity of half-a-century in many different +lines of inquiry has established the theory of evolution upon a foundation +of ever growing solidity. It is Darwin's imperishable glory that he +prescribed the lines along which all the biological sciences were to +advance to conquests not dreamed of when he wrote. + + +XII. THE PALAEONTOLOGICAL RECORD. + +II. PLANTS. + +By D.H. SCOTT, F.R.S. +President of the Linnean Society. + +There are several points of view from which the subject of the present +essay may be regarded. We may consider the fossil record of plants in its +bearing: I. on the truth of the doctrine of Evolution; II. on Phylogeny, +or the course of Evolution; III. on the theory of Natural Selection. The +remarks which follow, illustrating certain aspects only of an extensive +subject, may conveniently be grouped under these three headings. + +I. THE TRUTH OF EVOLUTION. + +When "The Origin of Species" was written, it was necessary to show that the +Geological Record was favourable to, or at least consistent with, the +Theory of Descent. The point is argued, closely and fully, in Chapter X. +"On the Imperfection of the Geological Record," and Chapter XI. "On the +Geological Succession of Organic Beings"; there is, however, little about +plants in these chapters. At the present time the truth of Evolution is no +longer seriously disputed, though there are writers, like Reinke, who +insist, and rightly so, that the doctrine is still only a belief, rather +than an established fact of science. (J. Reinke, "Kritische +Abstammungslehre", "Wiesner-Festschrift", page 11, Vienna, 1908.) +Evidently, then, however little the Theory of Descent may be questioned in +our own day, it is desirable to assure ourselves how the case stands, and +in particular how far the evidence from fossil plants has grown stronger +with time. + +As regards direct evidence for the derivation of one species from another, +there has probably been little advance since Darwin wrote, at least so we +must infer from the emphasis laid on the discontinuity of successive fossil +species by great systematic authorities like Grand'Eury and Zeiller in +their most recent writings. We must either adopt the mutationist views of +those authors (referred to in the last section of this essay) or must still +rely on Darwin's explanation of the absence of numerous intermediate +varieties. The attempts which have been made to trace, in the Tertiary +rocks, the evolution of recent species, cannot, owing to the imperfect +character of the evidence, be regarded as wholly satisfactory. + +When we come to groups of a somewhat higher order we have an interesting +history of the evolution of a recent family in the work, not yet completed, +of Kidston and Gwynne-Vaughan on the fossil Osmundaceae. ("Trans. Royal +Soc. Edinburgh", Vol. 45, Part III. 1907, Vol. 46, Part II. 1908, Vol. 46, +Part III. 1909.) The authors are able, mainly on anatomical evidence, to +trace back this now limited group of Ferns, through the Tertiary and +Mesozoic to the Permian, and to show, with great probability, how their +structure has been derived from that of early Palaeozoic types. + +The history of the Ginkgoaceae, now represented only by the isolated +maidenhair tree, scarcely known in a wild state, offers another striking +example of a family which can be traced with certainty to the older +Mesozoic and perhaps further back still. (See Seward and Gowan, "The +Maidenhair Tree (Gingko biloba)", "Annals of Botany", Vol. XIV. 1900, page +109; also A. Sprecher "Le Ginkgo biloba", L., Geneva, 1907.) + +On the wider question of the derivation of the great groups of plants, a +very considerable advance has been made, and, so far as the higher plants +are concerned, we are now able to form a far better conception than before +of the probable course of evolution. This is a matter of phylogeny, and +the facts will be considered under that head; our immediate point is that +the new knowledge of the relations between the classes of plants in +question materially strengthens the case for the theory of descent. The +discoveries of the last few years throw light especially on the relation of +the Angiosperms to the Gymnosperms, on that of the Seed-plants generally to +the Ferns, and on the interrelations between the various classes of the +higher Cryptogams. + +That the fossil record has not done still more for Evolution is due to the +fact that it begins too late--a point on which Darwin laid stress ("Origin +of Species" (6th edition), page 286.) and which has more recently been +elaborated by Poulton. ("Essays on Evolution", pages 46 et seq., Oxford, +1908.) An immense proportion of the whole evolutionary history lies behind +the lowest fossiliferous rocks, and the case is worse for plants than for +animals, as the record for the former begins, for all practical purposes, +much higher up in the rocks. + +It may be well here to call attention to a question, often overlooked, +which has lately been revived by Reinke. (Reinke, loc. cit. page 13.) As +all admit, we know nothing of the origin of life; consequently, for all we +can tell, it is as probable that life began, on this planet, with many +living things, as with one. If the first organic beings were many, they +may have been heterogeneous, or at least exposed to different conditions, +from their origin; in either case there would have been a number of +distinct series from the beginning, and if so we should not be justified in +assuming that all organisms are related to one another. There may +conceivably be several of the original lines of descent still surviving, or +represented among extinct forms--to reverse the remark of a distinguished +botanist, there may be several Vegetable Kingdoms! However improbable this +may sound, the possibility is one to be borne in mind. + +That all VASCULAR plants really belong to one stock seems certain, and here +the palaeontological record has materially strengthened the case for a +monophyletic history. The Bryophyta are not likely to be absolutely +distinct, for their sexual organs, and the stomata of the Mosses strongly +suggest community of descent with the higher plants; if this be so it no +doubt establishes a certain presumption in favour of a common origin for +plants generally, for the gap between "Mosses and Ferns" has been regarded +as the widest in the Vegetable Kingdom. The direct evidence of +consanguinity is however much weaker when we come to the Algae, and it is +conceivable (even if improbable) that the higher plants may have had a +distinct ancestry (now wholly lost) from the beginning. The question had +been raised in Darwin's time, and he referred to it in these words: "No +doubt it is possible, as Mr G.H. Lewes has urged, that at the first +commencement of life many different forms were evolved; but if so, we may +conclude that only a very few have left modified descendants." ("Origin of +Species", page 425.) This question, though it deserves attention, does not +immediately affect the subject of the palaeontological record of plants, +for there can be no reasonable doubt as to the interrelationship of those +groups on which the record at present throws light. + +The past history of plants by no means shows a regular progression from the +simple to the complex, but often the contrary. This apparent anomaly is +due to two causes. + +1. The palaeobotanical record is essentially the story of the successive +ascendancy of a series of dominant families, each of which attained its +maximum, in organisation as well as in extent, and then sank into +comparative obscurity, giving place to other families, which under new +conditions were better able to take a leading place. As each family ran +its downward course, either its members underwent an actual reduction in +structure as they became relegated to herbaceous or perhaps aquatic life +(this may have happened with the Horsetails and with Isoetes if derived +from Lepidodendreae), or the higher branches of the family were crowded out +altogether and only the "poor relations" were able to maintain their +position by evading the competition of the ascendant races; this is also +illustrated by the history of the Lycopod phylum. In either case there +would result a lowering of the type of organisation within the group. + +2. The course of real progress is often from the complex to the simple. +If, as we shall find some grounds for believing, the Angiosperms came from +a type with a flower resembling in its complexity that of Mesozoic +"Cycads," almost the whole evolution of the flower in the highest plants +has been a process of reduction. The stamen, in particular, has +undoubtedly become extremely simplified during evolution; in the most +primitive known seed-plants it was a highly compound leaf or pinna; its +reduction has gone on in the Conifers and modern Cycads, as well as in the +Angiosperms, though in different ways and to a varying extent. + +The seed offers another striking example; the Palaeozoic seeds (if we leave +the seed-like organs of certain Lycopods out of consideration) were always, +so far as we know, highly complex structures, with an elaborate vascular +system, a pollen-chamber, and often a much-differentiated testa. In the +present day such seeds exist only in a few Gymnosperms which retain their +ancient characters--in all the higher Spermophytes the structure is very +much simplified, and this holds good even in the Coniferae, where there is +no countervailing complication of ovary and stigma. + +Reduction, in fact, is not always, or even generally, the same thing as +degeneration. Simplification of parts is one of the most usual means of +advance for the organism as a whole. A large proportion of the higher +plants are microphyllous in comparison with the highly megaphyllous fern- +like forms from which they appear to have been derived. + +Darwin treated the general question of advance in organisation with much +caution, saying: "The geological record...does not extend far enough back, +to show with unmistakeable clearness that within the known history of the +world organisation has largely advanced." ("Origin of Species", page 308.) +Further on (Ibid. page 309.) he gives two standards by which advance may be +measured: "We ought not solely to compare the highest members of a class +at any two periods...but we ought to compare all the members, high and low, +at the two periods." Judged by either standard the Horsetails and Club +Mosses of the Carboniferous were higher than those of our own day, and the +same is true of the Mesozoic Cycads. There is a general advance in the +succession of classes, but not within each class. + +Darwin's argument that "the inhabitants of the world at each successive +period in its history have beaten their predecessors in the race for life, +and are, in so far, higher in the scale" ("Origin of Species", page 315.) +is unanswerable, but we must remember that "higher in the scale" only means +"better adapted to the existing conditions." Darwin points out (Ibid. page +279.) that species have remained unchanged for long periods, probably +longer than the periods of modification, and only underwent change when the +conditions of their life were altered. Higher organisation, judged by the +test of success, is thus purely relative to the changing conditions, a fact +of which we have a striking illustration in the sudden incoming of the +Angiosperms with all their wonderful floral adaptations to fertilisation by +the higher families of Insects. + +II. PHYLOGENY. + +The question of phylogeny is really inseparable from that of the truth of +the doctrine of evolution, for we cannot have historical evidence that +evolution has actually taken place without at the same time having evidence +of the course it has followed. + +As already pointed out, the progress hitherto made has been rather in the +way of joining up the great classes of plants than in tracing the descent +of particular species or genera of the recent flora. There appears to be a +difference in this respect from the Animal record, which tells us so much +about the descent of living species, such as the elephant or the horse. +The reason for this difference is no doubt to be found in the fact that the +later part of the palaeontological record is the most satisfactory in the +case of animals and the least so in the case of plants. The Tertiary +plant-remains, in the great majority of instances, are impressions of +leaves, the conclusions to be drawn from which are highly precarious; until +the whole subject of Angiospermous palaeobotany has been reinvestigated, it +would be rash to venture on any statements as to the descent of the +families of Dicotyledons or Monocotyledons. + +Our attention will be concentrated on the following questions, all relating +to the phylogeny of main groups of plants: i. The Origin of the +Angiosperms. ii. The Origin of the Seed-plants. iii. The Origin of the +different classes of the Higher Cryptogamia. + +i. THE ORIGIN OF THE ANGIOSPERMS. + +The first of these questions has long been the great crux of botanical +phylogeny, and until quite recently no light had been thrown upon the +difficulty. The Angiosperms are the Flowering Plants, par excellence, and +form, beyond comparison, the dominant sub-kingdom in the flora of our own +age, including, apart from a few Conifers and Ferns, all the most familiar +plants of our fields and gardens, and practically all plants of service to +man. All recent work has tended to separate the Angiosperms more widely +from the other seed-plants now living, the Gymnosperms. Vast as is the +range of organisation presented by the great modern sub-kingdom, embracing +forms adapted to every environment, there is yet a marked uniformity in +certain points of structure, as in the development of the embryo-sac and +its contents, the pollination through the intervention of a stigma, the +strange phenomenon of double fertilisation (One sperm fertilising the egg, +while the other unites with the embryo-sac nucleus, itself the product of a +nuclear fusion, to give rise to a nutritive tissue, the endosperm.), the +structure of the stamens, and the arrangement of the parts of the flower. +All these points are common to Monocotyledons and Dicotyledons, and +separate the Angiosperms collectively from all other plants. + +In geological history the Angiosperms first appear in the Lower Cretaceous, +and by Upper Cretaceous times had already swamped all other vegetation and +seized the dominant position which they still hold. Thus they are isolated +structurally from the rest of the Vegetable Kingdom, while historically +they suddenly appear, almost in full force, and apparently without +intermediaries with other groups. To quote Darwin's vigorous words: "The +rapid development, as far as we can judge, of all the higher plants within +recent geological times is an abominable mystery." ("More Letters of +Charles Darwin", Vol. II. page 20, letter to J.D. Hooker, 1879.) A couple +of years later he made a bold suggestion (which he only called an "idle +thought") to meet this difficulty. He says: "I have been so astonished at +the apparently sudden coming in of the higher phanerogams, that I have +sometimes fancied that development might have slowly gone on for an immense +period in some isolated continent or large island, perhaps near the South +Pole." (Ibid, page 26, letter to Hooker, 1881.) This idea of an +Angiospermous invasion from some lost southern land has sometimes been +revived since, but has not, so far as the writer is aware, been supported +by evidence. Light on the problem has come from a different direction. + +The immense development of plants with the habit of Cycads, during the +Mesozoic Period up to the Lower Cretaceous, has long been known. The +existing Order Cycadaceae is a small family, with 9 genera and perhaps 100 +species, occurring in the tropical and sub-tropical zones of both the Old +and New World, but nowhere forming a dominant feature in the vegetation. +Some few attain the stature of small trees, while in the majority the stem +is short, though often living to a great age. The large pinnate or rarely +bipinnate leaves give the Cycads a superficial resemblance in habit to +Palms. Recent Cycads are dioecious; throughout the family the male +fructification is in the form of a cone, each scale of the cone +representing a stamen, and bearing on its lower surface numerous pollen- +sacs, grouped in sori like the sporangia of Ferns. In all the genera, +except Cycas itself, the female fructifications are likewise cones, each +carpel bearing two ovules on its margin. In Cycas, however, no female cone +is produced, but the leaf-like carpels, bearing from two to six ovules +each, are borne directly on the main stem of the plant in rosettes +alternating with those of the ordinary leaves--the most primitive +arrangement known in any living seed-plant. The whole Order is relatively +primitive, as shown most strikingly in its cryptogamic mode of +fertilisation, by means of spermatozoids, which it shares with the +maidenhair tree alone, among recent seed-plants. + +In all the older Mesozoic rocks, from the Trias to the Lower Cretaceous, +plants of the Cycad class (Cycadophyta, to use Nathorst's comprehensive +name) are extraordinarily abundant in all parts of the world; in fact they +were almost as prominent in the flora of those ages as the Dicotyledons are +in that of our own day. In habit and to a great extent in anatomy, the +Mesozoic Cycadophyta for the most part much resemble the recent Cycadaceae. +But, strange to say, it is only in the rarest cases that the fructification +has proved to be of the simple type characteristic of the recent family; +the vast majority of the abundant fertile specimens yielded by the Mesozoic +rocks possess a type of reproductive apparatus far more elaborate than +anything known in Cycadaceae or other Gymnosperms. The predominant +Mesozoic family, characterised by this advanced reproductive organisation, +is known as the Bennettiteae; in habit these plants resembled the more +stunted Cycads of the recent flora, but differed from them in the presence +of numerous lateral fructifications, like large buds, borne on the stem +among the crowded bases of the leaves. The organisation of these +fructifications was first worked out on European specimens by Carruthers, +Solms-Laubach, Lignier and others, but these observers had only more or +less ripe fruits to deal with; the complete structure of the flower has +only been elucidated within the last few years by the researches of Wieland +on the magnificent American material, derived from the Upper Jurassic and +Lower Cretaceous beds of Maryland, Dakota and Wyoming. (G.R. Wieland, +"American Fossil Cycads", Carnegie Institution, Washington, 1906.) The +word "flower" is used deliberately, for reasons which will be apparent from +the following brief description, based on Wieland's observations. + +The fructification is attached to the stem by a thick stalk, which, in its +upper part, bears a large number of spirally arranged bracts, forming +collectively a kind of perianth and completely enclosing the essential +organs of reproduction. The latter consist of a whorl of stamens, of +extremely elaborate structure, surrounding a central cone or receptacle +bearing numerous ovules. The stamens resemble the fertile fronds of a +fern; they are of a compound, pinnate form, and bear very large numbers of +pollen-sacs, each of which is itself a compound structure consisting of a +number of compartments in which the pollen was formed. In their lower part +the stamens are fused together by their stalks, like the "monadelphous" +stamens of a mallow. The numerous ovules borne on the central receptacle +are stalked, and are intermixed with sterile scales; the latter are +expanded at their outer ends, which are united to form a kind of pericarp +or ovary-wall, only interrupted by the protruding micropyles of the ovules. +There is thus an approach to the closed pistil of an Angiosperm, but it is +evident that the ovules received the pollen directly. The whole +fructification is of large size; in the case of Cycadeoidea dacotensis, one +of the species investigated by Wieland, the total length, in the bud +condition, is about 12 cm., half of which belongs to the peduncle. + +The general arrangement of the organs is manifestly the same as in a +typical Angiospermous flower, with a central pistil, a surrounding whorl of +stamens and an enveloping perianth; there is, as we have seen, some +approach to the closed ovary of an Angiosperm; another point, first +discovered nearly 20 years ago by Solms-Laubach in his investigation of a +British species, is that the seed was practically "exalbuminous," its +cavity being filled by the large, dicotyledonous embryo, whereas in all +known Gymnosperms a large part of the sac is occupied by a nutritive +tissue, the prothallus or endosperm; here also we have a condition only met +with elsewhere among the higher Flowering Plants. + +Taking all the characters into account, the indications of affinity between +the Mesozoic Cycadophyta and the Angiosperms appear extremely significant, +as was recognised by Wieland when he first discovered the hermaphrodite +nature of the Bennettitean flower. The Angiosperm with which he specially +compared the fossil type was the Tulip tree (Liriodendron) and certainly +there is a remarkable analogy with the Magnoliaceous flowers, and with +those of related orders such as Ranunculaceae and the Water-lilies. It +cannot, of course, be maintained that the Bennettiteae, or any other +Mesozoic Cycadophyta at present known, were on the direct line of descent +of the Angiosperms, for there are some important points of difference, as, +for example, in the great complexity of the stamens, and in the fact that +the ovary-wall or pericarp was not formed by the carpels themselves, but by +the accompanying sterile scale-leaves. Botanists, since the discovery of +the bisexual flowers of the Bennettiteae, have expressed different views as +to the nearness of their relation to the higher Flowering Plants, but the +points of agreement are so many that it is difficult to resist the +conviction that a real relation exists, and that the ancestry of the +Angiosperms, so long shrouded in complete obscurity, is to be sought among +the great plexus of Cycad-like plants which dominated the flora of the +world in Mesozoic times. (On this subject see, in addition to Wieland's +great work above cited, F.W. Oliver, "Pteridosperms and Angiosperms", "New +Phytologist", Vol. V. 1906; D.H. Scott, "The Flowering Plants of the +Mesozoic Age in the Light of Recent Discoveries", "Journal R. Microscop. +Soc." 1907, and especially E.A.N. Arber and J. Parkin, "On the Origin of +Angiosperms", "Journal Linn. Soc." (Bot.) Vol. XXXVIII. page 29, 1907.) + +The great complexity of the Bennettitean flower, the earliest known +fructification to which the word "flower" can be applied without forcing +the sense, renders it probable, as Wieland and others have pointed out, +that the evolution of the flower in Angiosperms has consisted essentially +in a process of reduction, and that the simplest forms of flower are not to +be regarded as the most primitive. The older morphologists generally took +the view that such simple flowers were to be explained as reductions from a +more perfect type, and this opinion, though abandoned by many later +writers, appears likely to be true when we consider the elaboration of +floral structure attained among the Mesozoic Cycadophyta, which preceded +the Angiosperms in evolution. + +If, as now seems probable, the Angiosperms were derived from ancestors +allied to the Cycads, it would naturally follow that the Dicotyledons were +first evolved, for their structure has most in common with that of the +Cycadophyta. We should then have to regard the Monocotyledons as a side- +line, diverging probably at a very early stage from the main dicotyledonous +stock, a view which many botanists have maintained, of late, on other +grounds. (See especially Ethel Sargant, "The Reconstruction of a Race of +Primitive Angiosperms", "Annals of Botany", Vol. XXII. page 121, 1908.) So +far, however, as the palaeontological record shows, the Monocotyledons were +little if at all later in their appearance than the Dicotyledons, though +always subordinate in numbers. The typical and beautifully preserved Palm- +wood from Cretaceous rocks is striking evidence of the early evolution of a +characteristic monocotyledonous family. It must be admitted that the whole +question of the evolution of Monocotyledons remains to be solved. + +Accepting, provisionally, the theory of the cycadophytic origin of +Angiosperms, it is interesting to see to what further conclusions we are +led. The Bennettiteae, at any rate, were still at the gymnospermous level +as regards their pollination, for the exposed micropyles of the ovules were +in a position to receive the pollen directly, without the intervention of a +stigma. It is thus indicated that the Angiosperms sprang from a +gymnospermous source, and that the two great phyla of Seed-plants have not +been distinct from the first, though no doubt the great majority of known +Gymnosperms, especially the Coniferae, represent branch-lines of their own. + +The stamens of the Bennettiteae are arranged precisely as in an +angiospermous flower, but in form and structure they are like the fertile +fronds of a Fern, in fact the compound pollen-sacs, or synangia as they are +technically called, almost exactly agree with the spore-sacs of a +particular family of Ferns--the Marattiaceae, a limited group, now mainly +tropical, which was probably more prominent in the later Palaeozoic times +than at present. The scaly hairs, or ramenta, which clothe every part of +the plant, are also like those of Ferns. + +It is not likely that the characters in which the Bennettiteae resemble the +Ferns came to them directly from ancestors belonging to that class; an +extensive group of Seed-plants, the Pteridospermeae, existed in Palaeozoic +times and bear evident marks of affinity with the Fern phylum. The fern- +like characters so remarkably persistent in the highly organised +Cycadophyta of the Mesozoic were in all likelihood derived through the +Pteridosperms, plants which show an unmistakable approach to the +cycadophytic type. + +The family Bennettiteae thus presents an extraordinary association of +characters, exhibiting, side by side, features which belong to the +Angiosperms, the Gymnosperms and the Ferns. + +ii. ORIGIN OF SEED-PLANTS. + +The general relation of the gymnospermous Seed-plants to the Higher +Cryptogamia was cleared up, independently of fossil evidence, by the +brilliant researches of Hofmeister, dating from the middle of the past +century. (W. Hofmeister, "On the Germination, Development and +Fructification of the Higher Cryptogamia", Ray Society, London, 1862. The +original German treatise appeared in 1851.) He showed that "the embryo-sac +of the Coniferae may be looked upon as a spore remaining enclosed in its +sporangium; the prothallium which it forms does not come to the light." +(Ibid. page 438.) He thus determined the homologies on the female side. +Recognising, as some previous observers had already done, that the +microspores of those Cryptogams in which two kinds of spore are developed, +are equivalent to the pollen-grains of the higher plants, he further +pointed out that fertilisation "in the Rhizocarpeae and Selaginellae takes +place by free spermatozoa, and in the Coniferae by a pollen-tube, in the +interior of which spermatozoa are probably formed"--a remarkable instance +of prescience, for though spermatozoids have not been found in the Conifers +proper, they were demonstrated in the allied groups Cycadaceae and Ginkgo, +in 1896, by the Japanese botanists Ikeno and Hirase. A new link was thus +established between the Gymnosperms and the Cryptogams. + +It remained uncertain, however, from which line of Cryptogams the +gymnospermous Seed-plants had sprung. The great point of morphological +comparison was the presence of two kinds of spore, and this was known to +occur in the recent Lycopods and Water-ferns (Rhizocarpeae) and was also +found in fossil representatives of the third phylum, that of the +Horsetails. As a matter of fact all the three great Cryptogamic classes +have found champions to maintain their claim to the ancestry of the Seed- +plants, and in every case fossil evidence was called in. For a long time +the Lycopods were the favourites, while the Ferns found the least support. +The writer remembers, however, in the year 1881, hearing the late Prof. +Sachs maintain, in a lecture to his class, that the descent of the Cycads +could be traced, not merely from Ferns, but from a definite family of +Ferns, the Marattiaceae, a view which, though in a somewhat crude form, +anticipated more modern ideas. + +Williamson appears to have been the first to recognise the presence, in the +Carboniferous flora, of plants combining the characters of Ferns and +Cycads. (See especially his "Organisation of the Fossil Plants of the +Coal-Measures", Part XIII. "Phil. Trans. Royal Soc." 1887 B. page 299.) +This conclusion was first reached in the case of the genera Heterangium and +Lyginodendron, plants, which with a wholly fern-like habit, were found to +unite an anatomical structure holding the balance between that of Ferns and +Cycads, Heterangium inclining more to the former and Lyginodendron to the +latter. Later researches placed Williamson's original suggestion on a +firmer basis, and clearly proved the intermediate nature of these genera, +and of a number of others, so far as their vegetative organs were +concerned. This stage in our knowledge was marked by the institution of +the class Cycadofilices by Potonie in 1897. + +Nothing, however, was known of the organs of reproduction of the +Cycadofilices, until F.W. Oliver, in 1903, identified a fossil seed, +Lagenostoma Lomaxi, as belonging to Lyginodendron, the identification +depending, in the first instance, on the recognition of an identical form +of gland, of very characteristic structure, on the vegetative organs of +Lyginodendron and on the cupule enveloping the seed. This evidence was +supported by the discovery of a close anatomical agreement in other +respects, as well as by constant association between the seed and the +plant. (F.W. Oliver and D.H. Scott, "On the Structure of the Palaeozoic +Seed, Lagenostoma Lomaxi, etc." "Phil. Trans. Royal Soc." Vol. 197 B. +1904.) The structure of the seed of Lyginodendron, proved to be of the +same general type as that of the Cycads, as shown especially by the +presence of a pollen-chamber or special cavity for the reception of the +pollen-grains, an organ only known in the Cycads and Ginkgo among recent +plants. + +Within a few months after the discovery of the seed of Lyginodendron, +Kidston found the large, nut-like seed of a Neuropteris, another fern-like +Carboniferous plant, in actual connection with the pinnules of the frond, +and since then seeds have been observed on the frond in species of +Aneimites and Pecopteris, and a vast body of evidence, direct or indirect, +has accumulated, showing that a large proportion of the Palaeozoic plants +formerly classed as Ferns were in reality reproduced by seeds of the same +type as those of recent Cycadaceae. (A summary of the evidence will be +found in the writer's article "On the present position of Palaeozoic +Botany", "Progressus Rei Botanicae", 1907, page 139, and "Studies in Fossil +Botany", Vol. II. (2nd edition) London, 1909.) At the same time, the +anatomical structure, where it is open to investigation, confirms the +suggestion given by the habit, and shows that these early seed-bearing +plants had a real affinity with Ferns. This conclusion received strong +corroboration when Kidston, in 1905, discovered the male organs of +Lyginodendron, and showed that they were identical with a fructification of +the genus Crossotheca, hitherto regarded as belonging to Marattiaceous +Ferns. (Kidston, "On the Microsporangia of the Pteridospermeae, etc." +"Phil. Trans. Royal Soc." Vol. 198, B. 1906.) + +The general conclusion which follows from the various observations alluded +to, is that in Palaeozoic times there was a great body of plants +(including, as it appears, a large majority of the fossils previously +regarded as Ferns) which had attained the rank of Spermophyta, bearing +seeds of a Cycadean type on fronds scarcely differing from the vegetative +foliage, and in other respects, namely anatomy, habit and the structure of +the pollen-bearing organs, retaining many of the characters of Ferns. From +this extensive class of plants, to which the name Pteridospermeae has been +given, it can scarcely be doubted that the abundant Cycadophyta, of the +succeeding Mesozoic period, were derived. This conclusion is of far- +reaching significance, for we have already found reason to think that the +Angiosperms themselves sprang, in later times, from the Cycadophytic stock; +it thus appears that the Fern-phylum, taken in a broad sense, ultimately +represents the source from which the main line of descent of the +Phanerogams took its rise. + +It must further be borne in mind that in the Palaeozoic period there +existed another group of seed-bearing plants, the Cordaiteae, far more +advanced than the Pteridospermeae, and in many respects approaching the +Coniferae, which themselves begin to appear in the latest Palaeozoic rocks. +The Cordaiteae, while wholly different in habit from the contemporary fern- +like Seed-plants, show unmistakable signs of a common origin with them. +Not only is there a whole series of forms connecting the anatomical +structure of the Cordaiteae with that of the Lyginodendreae among +Pteridosperms, but a still more important point is that the seeds of the +Cordaiteae, which have long been known, are of the same Cycadean type as +those of the Pteridosperms, so that it is not always possible, as yet, to +discriminate between the seeds of the two groups. These facts indicate +that the same fern-like stock which gave rise to the Cycadophyta and +through them, as appears probable, to the Angiosperms, was also the source +of the Cordaiteae, which in their turn show manifest affinity with some at +least of the Coniferae. Unless the latter are an artificial group, a view +which does not commend itself to the writer, it would appear probable that +the Gymnosperms generally, as well as the Angiosperms, were derived from an +ancient race of Cryptogams, most nearly related to the Ferns. (Some +botanists, however, believe that the Coniferae, or some of them, are +probably more nearly related to the Lycopods. See Seward and Ford, "The +Araucarieae, Recent and Extinct", "Phil. Trans. Royal Soc." Vol. 198 B. +1906.) + +It may be mentioned here that the small gymnospermous group Gnetales +(including the extraordinary West African plant Welwitschia) which were +formerly regarded by some authorities as akin to the Equisetales, have +recently been referred, on better grounds, to a common origin with the +Angiosperms, from the Mesozoic Cycadophyta. + +The tendency, therefore, of modern work on the palaeontological record of +the Seed-plants has been to exalt the importance of the Fern-phylum, which, +on present evidence, appears to be that from which the great majority, +possibly the whole, of the Spermophyta have been derived. + +One word of caution, however, is necessary. The Seed-plants are of +enormous antiquity; both the Pteridosperms and the more highly organised +family Cordaiteae, go back as far in geological history (namely to the +Devonian) as the Ferns themselves or any other Vascular Cryptogams. It +must therefore be understood that in speaking of the derivation of the +Spermophyta from the Fern-phylum, we refer to that phylum at a very early +stage, probably earlier than the most ancient period to which our record of +land-plants extends. The affinity between the oldest Seed-plants and the +Ferns, in the widest sense, seems established, but the common stock from +which they actually arose is still unknown; though no doubt nearer to the +Ferns than to any other group, it must have differed widely from the Ferns +as we now know them, or perhaps even from any which the fossil record has +yet revealed to us. + +iii. THE ORIGIN OF THE HIGHER CRYPTOGAMIA. + +The Sub-kingdom of the higher Spore-plants, the Cryptogamia possessing a +vascular system, was more prominent in early geological periods than at +present. It is true that the dominance of the Pteridophyta in Palaeozoic +times has been much exaggerated owing to the assumption that everything +which looked like a Fern really was a Fern. But, allowing for the fact, +now established, that most of the Palaeozoic fern-like plants were already +Spermophyta, there remains a vast mass of Cryptogamic forms of that period, +and the familiar statement that they formed the main constituent of the +Coal-forests still holds good. The three classes, Ferns (Filicales), +Horsetails (Equisetales) and Club-mosses (Lycopodiales), under which we now +group the Vascular Cryptogams, all extend back in geological history as far +as we have any record of the flora of the land; in the Palaeozoic, however, +a fourth class, the Sphenophyllales, was present. + +As regards the early history of the Ferns, which are of special interest +from their relation to the Seed-plants, it is impossible to speak quite +positively, owing to the difficulty of discriminating between true fossil +Ferns and the Pteridosperms which so closely simulated them. The +difficulty especially affects the question of the position of Marattiaceous +Ferns in the Palaeozoic Floras. This family, now so restricted, was until +recently believed to have been one of the most important groups of +Palaeozoic plants, especially during later Carboniferous and Permian times. +Evidence both from anatomy and from sporangial characters appeared to +establish this conclusion. Of late, however, doubts have arisen, owing to +the discovery that some supposed members of the Marattiaceae bore seeds, +and that a form of fructification previously referred to that family +(Crossotheca) was really the pollen-bearing apparatus of a Pteridosperm +(Lyginodendron). The question presents much difficulty; though it seems +certain that our ideas of the extent of the family in Palaeozoic times will +have to be restricted, there is still a decided balance of evidence in +favour of the view that a considerable body of Marattiaceous Ferns actually +existed. The plants in question were of large size (often arborescent) and +highly organised--they represent, in fact, one of the highest developments +of the Fern-stock, rather than a primitive type of the class. + +There was, however, in the Palaeozoic period, a considerable group of +comparatively simple Ferns (for which Arber has proposed the collective +name Primofilices); the best known of these are referred to the family +Botryopterideae, consisting of plants of small or moderate dimensions, +with, on the whole, a simple anatomical structure, in certain cases +actually simpler than that of any recent Ferns. On the other hand the +sporangia of these plants were usually borne on special fertile fronds, a +mark of rather high differentiation. This group goes back to the Devonian +and includes some of the earliest types of Fern with which we are +acquainted. It is probable that the Primofilices (though not the +particular family Botryopterideae) represent the stock from which the +various families of modern Ferns, already developed in the Mesozoic period, +may have sprung. + +None of the early Ferns show any clear approach to other classes of +Vascular Cryptogams; so far as the fossil record affords any evidence, +Ferns have always been plants with relatively large and usually compound +leaves. There is no indication of their derivation from a microphyllous +ancestry, though, as we shall see, there is some slight evidence for the +converse hypothesis. Whatever the origin of the Ferns may have been it is +hidden in the older rocks. + +It has, however, been held that certain other Cryptogamic phyla had a +common origin with the Ferns. The Equisetales are at present a well- +defined group; even in the rich Palaeozoic floras the habit, anatomy and +reproductive characters usually render the members of this class +unmistakable, in spite of the great development and stature which they then +attained. It is interesting, however, to find that in the oldest known +representatives of the Equisetales the leaves were highly developed and +dichotomously divided, thus differing greatly from the mere scale-leaves of +the recent Horsetails, or even from the simple linear leaves of the later +Calamites. The early members of the class, in their forked leaves, and in +anatomical characters, show an approximation to the Sphenophyllales, which +are chiefly represented by the large genus Sphenophyllum, ranging through +the Palaeozoic from the Middle Devonian onwards. These were plants with +rather slender, ribbed stems, bearing whorls of wedge-shaped or deeply +forked leaves, six being the typical number in each whorl. From their weak +habit it has been conjectured, with much probability, that they may have +been climbing plants, like the scrambling Bedstraws of our hedgerows. The +anatomy of the stem is simple and root-like; the cones are remarkable for +the fact that each scale or sporophyll is a double structure, consisting of +a lower, usually sterile lobe and one or more upper lobes bearing the +sporangia; in one species both parts of the sporophyll were fertile. +Sphenophyllum was evidently much specialised; the only other known genus is +based on an isolated cone, Cheirostrobus, of Lower Carboniferous age, with +an extraordinarily complex structure. In this genus especially, but also +in the entire group, there is an evident relation to the Equisetales; hence +it is of great interest that Nathorst has described, from the Devonian of +Bear Island in the Arctic regions, a new genus Pseudobornia, consisting of +large plants, remarkable for their highly compound leaves which, when found +detached, were taken for the fronds of a Fern. The whorled arrangement of +the leaves, and the habit of the plant, suggest affinities either with the +Equisetales or the Sphenophyllales; Nathorst makes the genus the type of a +new class, the Pseudoborniales. (A.G. Nathorst, "Zur Oberdevonischen Flora +der Baren-Insel", "Kongl. Svenska Vetenskaps-Akademiens Handlingar" Bd. 36, +No. 3, Stockholm, 1902.) + +The available data, though still very fragmentary, certainly suggest that +both Equisetales and Sphenophyllales may have sprung from a common stock +having certain fern-like characters. On the other hand the Sphenophylls, +and especially the peculiar genus Cheirostrobus, have in their anatomy a +good deal in common with the Lycopods, and of late years they have been +regarded as the derivatives of a stock common to that class and the +Equisetales. At any rate the characters of the Sphenophyllales and of the +new group Pseudoborniales suggest the existence, at a very early period, of +a synthetic race of plants, combining the characters of various phyla of +the Vascular Cryptogams. It may further be mentioned that the Psilotaceae, +an isolated epiphytic family hitherto referred to the Lycopods, have been +regarded by several recent authors as the last survivors of the +Sphenophyllales, which they resemble both in their anatomy and in the +position of their sporangia. + +The Lycopods, so far as their early history is known, are remarkable rather +for their high development in Palaeozoic times than for any indications of +a more primitive ancestry. In the recent Flora, two of the four living +genera (Excluding Psilotaceae.) (Selaginella and Isoetes) have spores of +two kinds, while the other two (Lycopodium and Phylloglossum) are +homosporous. Curiously enough, no certain instance of a homosporous +Palaeozoic Lycopod has yet been discovered, though well-preserved +fructifications are numerous. Wherever the facts have been definitely +ascertained, we find two kinds of spore, differentiated quite as sharply as +in any living members of the group. Some of the Palaeozoic Lycopods, in +fact, went further, and produced bodies of the nature of seeds, some of +which were actually regarded, for many years, as the seeds of Gymnosperms. +This specially advanced form of fructification goes back at least as far as +the Lower Carboniferous, while the oldest known genus of Lycopods, +Bothrodendron, which is found in the Devonian, though not seed-bearing, was +typically heterosporous, if we may judge from the Coal-measure species. No +doubt homosporous Lycopods existed, but the great prevalence of the higher +mode of reproduction in days which to us appear ancient, shows how long a +course of evolution must have already been passed through before the oldest +known members of the group came into being. The other characters of the +Palaeozoic Lycopods tell the same tale; most of them attained the stature +of trees, with a corresponding elaboration of anatomical structure, and +even the herbaceous forms show no special simplicity. It appears from +recent work that herbaceous Lycopods, indistinguishable from our recent +Selaginellas, already existed in the time of the Coal-measures, while one +herbaceous form (Miadesmia) is known to have borne seeds. + +The utmost that can be said for primitiveness of character in Palaeozoic +Lycopods is that the anatomy of the stem, in its primary ground-plan, as +distinguished from its secondary growth, was simpler than that of most +Lycopodiums and Selaginellas at the present day. There are also some +peculiarities in the underground organs (Stigmaria) which suggest the +possibility of a somewhat imperfect differentiation between root and stem, +but precisely parallel difficulties are met with in the case of the living +Selaginellas, and in some degree in species of Lycopodium. + +In spite of their high development in past ages the Lycopods, recent and +fossil, constitute, on the whole, a homogeneous group, and there is little +at present to connect them with other phyla. Anatomically some relation to +the Sphenophylls is indicated, and perhaps the recent Psilotaceae give some +support to this connection, for while their nearest alliance appears to be +with the Sphenophylls, they approach the Lycopods in anatomy, habit, and +mode of branching. + +The typically microphyllous character of the Lycopods, and the simple +relation between sporangium and sporophyll which obtains throughout the +class, have led various botanists to regard them as the most primitive +phylum of the Vascular Cryptogams. There is nothing in the fossil record +to disprove this view, but neither is there anything to support it, for +this class so far as we know is no more ancient than the megaphyllous +Cryptogams, and its earliest representatives show no special simplicity. +If the indications of affinity with Sphenophylls are of any value the +Lycopods are open to suspicion of reduction from a megaphyllous ancestry, +but there is no direct palaeontological evidence for such a history. + +The general conclusions to which we are led by a consideration of the +fossil record of the Vascular Cryptogams are still very hypothetical, but +may be provisionally stated as follows: + +The Ferns go back to the earliest known period. In Mesozoic times +practically all the existing families had appeared; in the Palaeozoic the +class was less extensive than formerly believed, a majority of the supposed +Ferns of that age having proved to be seed-bearing plants. The oldest +authentic representatives of the Ferns were megaphyllous plants, broadly +speaking, of the same type as those of later epochs, though differing much +in detail. As far back as the record extends they show no sign of becoming +merged with other phyla in any synthetic group. + +The Equisetales likewise have a long history, and manifestly attained their +greatest development in Palaeozoic times. Their oldest forms show an +approach to the extinct class Sphenophyllales, which connects them to some +extent, by anatomical characters, with the Lycopods. At the same time the +oldest Equisetales show a somewhat megaphyllous character, which was more +marked in the Devonian Pseudoborniales. Some remote affinity with the +Ferns (which has also been upheld on other grounds) may thus be indicated. +It is possible that in the Sphenophyllales we may have the much-modified +representatives of a very ancient synthetic group. + +The Lycopods likewise attained their maximum in the Palaeozoic, and show, +on the whole, a greater elaboration of structure in their early forms than +at any later period, while at the same time maintaining a considerable +degree of uniformity in morphological characters throughout their history. +The Sphenophyllales are the only other class with which they show any +relation; if such a connection existed, the common point of origin must lie +exceedingly far back. + +The fossil record, as at present known, cannot, in the nature of things, +throw any direct light on what is perhaps the most disputed question in the +morphology of plants--the origin of the alternating generations of the +higher Cryptogams and the Spermophyta. At the earliest period to which +terrestrial plants have been traced back all the groups of Vascular +Cryptogams were in a highly advanced stage of evolution, while innumerable +Seed-plants--presumably the descendants of Cryptogamic ancestors--were +already flourishing. On the other hand we know practically nothing of +Palaeozoic Bryophyta, and the evidence even for their existence at that +period cannot be termed conclusive. While there are thus no +palaeontological grounds for the hypothesis that the Vascular plants came +of a Bryophytic stock, the question of their actual origin remains +unsolved. + +III. NATURAL SELECTION. + +Hitherto we have considered the palaeontological record of plants in +relation to Evolution. The question remains, whether the record throws any +light on the theory of which Darwin and Wallace were the authors--that of +Natural Selection. The subject is clearly one which must be investigated +by other methods than those of the palaeontologist; still there are certain +important points involved, on which the palaeontological record appears to +bear. + +One of these points is the supposed distinction between morphological and +adaptive characters, on which Nageli, in particular, laid so much stress. +The question is a difficult one; it was discussed by Darwin ("Origin of +Species" (6th edition), pages 170-176.), who, while showing that the +apparent distinction is in part to be explained by our imperfect knowledge +of function, recognised the existence of important morphological characters +which are not adaptations. The following passage expresses his conclusion. +"Thus, as I am inclined to believe, morphological differences, which we +consider as important--such as the arrangement of the leaves, the divisions +of the flower or of the ovarium, the position of the ovules, etc.--first +appeared in many cases as fluctuating variations, which sooner or later +became constant through the nature of the organism and of the surrounding +conditions, as well as through the inter-crossing of distinct individuals, +but not through natural selection; for as these morphological characters do +not affect the welfare of the species, any slight deviations in them could +not have been governed or accumulated through this latter agency." (Ibid. +page 176.) + +This is a sufficiently liberal concession; Nageli, however, went much +further when he said: "I do not know among plants a morphological +modification which can be explained on utilitarian principles." (See "More +Letters", Vol. II. page 375 (footnote).) If this were true the field of +Natural Selection would be so seriously restricted, as to leave the theory +only a very limited importance. + +It can be shown, as the writer believes, that many typical "morphological +characters," on which the distinction between great classes of plants is +based, were adaptive in origin, and even that their constancy is due to +their functional importance. Only one or two cases will be mentioned, +where the fossil evidence affects the question. + +The pollen-tube is one of the most important morphological characters of +the Spermophyta as now existing--in fact the name Siphonogama is used by +Engler in his classification, as expressing a peculiarly constant character +of the Seed-plants. Yet the pollen-tube is a manifest adaptation, +following on the adoption of the seed-habit, and serving first to bring the +spermatozoids with greater precision to their goal, and ultimately to +relieve them of the necessity for independent movement. The pollen-tube is +constant because it has proved to be indispensable. + +In the Palaeozoic Seed-plants there are a number of instances in which the +pollen-grains, contained in the pollen-chamber of a seed, are so +beautifully preserved that the presence of a group of cells within the +grain can be demonstrated; sometimes we can even see how the cell-walls +broke down to emit the sperms, and quite lately it is said that the sperms +themselves have been recognised. (F.W. Oliver, "On Physostoma elegans, an +archaic type of seed from the Palaeozoic Rocks", "Annals of Botany", +January, 1909. See also the earlier papers there cited.) In no case, +however, is there as yet any satisfactory evidence for the formation of a +pollen-tube; it is probable that in these early Seed-plants the pollen- +grains remained at about the evolutionary level of the microspores in +Pilularia or Selaginella, and discharged their spermatozoids directly, +leaving them to find their own way to the female cells. It thus appears +that there were once Spermophyta without pollen-tubes. The pollen-tube +method ultimately prevailed, becoming a constant "morphological character," +for no other reason than because, under the new conditions, it provided a +more perfect mechanism for the accomplishment of the act of fertilisation. +We have still, in the Cycads and Ginkgo, the transitional case, where the +tube remains short, serves mainly as an anchor and water-reservoir, but yet +is able, by its slight growth, to give the spermatozoids a "lift" in the +right direction. In other Seed-plants the sperms are mere passengers, +carried all the way by the pollen-tube; this fact has alone rendered the +Angiospermous method of fertilisation through a stigma possible. + +We may next take the seed itself--the very type of a morphological +character. Our fossil record does not go far enough back to tell us the +origin of the seed in the Cycadophyta and Pteridosperms (the main line of +its development) but some interesting sidelights may be obtained from the +Lycopod phylum. In two Palaeozoic genera, as we have seen, seed-like +organs are known to have been developed, resembling true seeds in the +presence of an integument and of a single functional embryo-sac, as well as +in some other points. We will call these organs "seeds" for the sake of +shortness. In one genus (Lepidocarpon) the seeds were borne on a cone +indistinguishable from that of the ordinary cryptogamic Lepidodendreae, the +typical Lycopods of the period, while the seed itself retained much of the +detailed structure of the sporangium of that family. In the second genus, +Miadesmia, the seed-bearing plant was herbaceous, and much like a recent +Selaginella. (See Margaret Benson, "Miadesmia membranacea, a new +Palaeozoic Lycopod with a seed-like structure", "Phil. Trans. Royal Soc. +Vol. 199, B. 1908.) The seeds of the two genera are differently +constructed, and evidently had an independent origin. Here, then, we have +seeds arising casually, as it were, at different points among plants which +otherwise retain all the characters of their cryptogamic fellows; the seed +is not yet a morphological character of importance. To suppose that in +these isolated cases the seed sprang into being in obedience to a Law of +Advance ("Vervollkommungsprincip"), from which other contemporary Lycopods +were exempt, involves us in unnecessary mysticism. On the other hand it is +not difficult to see how these seeds may have arisen, as adaptive +structures, under the influence of Natural Selection. The seed-like +structure afforded protection to the prothallus, and may have enabled the +embryo to be launched on the world in greater security. There was further, +as we may suppose, a gain in certainty of fertilisation. As the writer has +pointed out elsewhere, the chances against the necessary association of the +small male with the large female spores must have been enormously great +when the cones were borne high up on tall trees. The same difficulty may +have existed in the case of the herbaceous Miadesmia, if, as Miss Benson +conjectures, it was an epiphyte. One way of solving the problem was for +pollination to take place while the megaspore was still on the parent +plant, and this is just what the formation of an ovule or seed was likely +to secure. + +The seeds of the Pteridosperms, unlike those of the Lycopod stock, have not +yet been found in statu nascendi--in all known cases they were already +highly developed organs and far removed from the cryptogamic sporangium. +But in two respects we find that these seeds, or some of them, had not yet +realised their possibilities. In the seed of Lyginodendron and other cases +the micropyle, or orifice of the integument, was not the passage through +which the pollen entered; the open neck of the pollen-chamber protruded +through the micropyle and itself received the pollen. We have met with an +analogous case, at a more advanced stage of evolution, in the Bennettiteae, +where the wall of the gynaecium, though otherwise closed, did not provide a +stigma to catch the pollen, but allowed the micropyles of the ovules to +protrude and receive the pollen in the old gymnospermous fashion. The +integument in the one case and the pistil in the other had not yet assumed +all the functions to which the organ ultimately became adapted. Again, no +Palaeozoic seed has yet been found to contain an embryo, though the +preservation is often good enough for it to have been recognised if +present. It is probable that the nursing of the embryo had not yet come to +be one of the functions of the seed, and that the whole embryonic +development was relegated to the germination stage. + +In these two points, the reception of the pollen by the micropyle and the +nursing of the embryo, it appears that many Palaeozoic seeds were +imperfect, as compared with the typical seeds of later times. As evolution +went on, one function was superadded on another, and it appears impossible +to resist the conclusion that the whole differentiation of the seed was a +process of adaptation, and consequently governed by Natural Selection, just +as much as the specialisation of the rostellum in an Orchid, or of the +pappus in a Composite. + +Did space allow, other examples might be added. We may venture to maintain +that the glimpses which the fossil record allows us into early stages in +the evolution of organs now of high systematic importance, by no means +justify the belief in any essential distinction between morphological and +adaptive characters. + +Another point, closely connected with Darwin's theory, on which the fossil +history of plants has been supposed to have some bearing, is the question +of Mutation, as opposed to indefinite variation. Arber and Parkin, in +their interesting memoir on the Origin of Angiosperms, have suggested +calling in Mutation to explain the apparently sudden transition from the +cycadean to the angiospermous type of foliage, in late Mesozoic times, +though they express themselves with much caution, and point out "a distinct +danger that Mutation may become the last resort of the phylogenetically +destitute"! + +The distinguished French palaeobotanists, Grand'Eury (C. Grand'Eury, "Sur +les mutations de quelques Plantes fossiles du Terrain houiller". "Comptes +Rendus", CXLII. page 25, 1906.) and Zeiller (R. Zeiller "Les Vegetaux +fossiles et leurs Enchainements", "Revue du Mois", III. February, 1907.), +are of opinion, to quote the words of the latter writer, that the facts of +fossil Botany are in agreement with the sudden appearance of new forms, +differing by marked characters from those that have given them birth; he +adds that these results give more amplitude to this idea of Mutation, +extending it to groups of a higher order, and even revealing the existence +of discontinuous series between the successive terms of which we yet +recognise bonds of filiation. (Loc. cit. page 23.) + +If Zeiller's opinion should be confirmed, it would no doubt be a serious +blow to the Darwinian theory. As Darwin said: "Under a scientific point +of view, and as leading to further investigation, but little advantage is +gained by believing that new forms are suddenly developed in an +inexplicable manner from old and widely different forms, over the old +belief in the creation of species from the dust of the earth." ("Origin of +Species", page 424.) + +It most however be pointed out, that such mutations as Zeiller, and to some +extent Arber and Parkin, appear to have in view, bridging the gulf between +different Orders and Classes, bear no relation to any mutations which have +been actually observed, such as the comparatively small changes, of sub- +specific value, described by De Vries in the type-case of Oenothera +Lamarckiana. The results of palaeobotanical research have undoubtedly +tended to fill up gaps in the Natural System of plants--that many such gaps +still persist is not surprising; their presence may well serve as an +incentive to further research but does not, as it seems to the writer, +justify the assumption of changes in the past, wholly without analogy among +living organisms. + +As regards the succession of species, there are no greater authorities than +Grand'Eury and Zeiller, and great weight must be attached to their opinion +that the evidence from continuous deposits favours a somewhat sudden change +from one specific form to another. At the same time it will be well to +bear in mind that the subject of the "absence of numerous intermediate +varieties in any single formation" was fully discussed by Darwin. ("Origin +of Species", pages 275-282, and page 312.); the explanation which he gave +may go a long way to account for the facts which recent writers have +regarded as favouring the theory of saltatory mutation. + +The rapid sketch given in the present essay can do no more than call +attention to a few salient points, in which the palaeontological records of +plants has an evident bearing on the Darwinian theory. At the present day +the whole subject of palaeobotany is a study in evolution, and derives its +chief inspiration from the ideas of Darwin and Wallace. In return it +contributes something to the verification of their teaching; the recent +progress of the subject, in spite of the immense difficulties which still +remain, has added fresh force to Darwin's statement that "the great leading +facts in palaeontology agree admirably with the theory of descent with +modification through variation and natural selection." (Ibid. page 313.) + + +XIII. THE INFLUENCE OF ENVIRONMENT ON THE FORMS OF PLANTS. + +By GEORG KLEBS, PH.D. +Professor of Botany in the University of Heidelberg. + +The dependence of plants on their environment became the object of +scientific research when the phenomena of life were first investigated and +physiology took its place as a special branch of science. This occurred in +the course of the eighteenth century as the result of the pioneer work of +Hales, Duhamel, Ingenhousz, Senebier and others. In the nineteenth +century, particularly in the second half, physiology experienced an +unprecedented development in that it began to concern itself with the +experimental study of nutrition and growth, and with the phenomena +associated with stimulus and movement; on the other hand, physiology +neglected phenomena connected with the production of form, a department of +knowledge which was the province of morphology, a purely descriptive +science. It was in the middle of the last century that the growth of +comparative morphology and the study of phases of development reached their +highest point. + +The forms of plants appeared to be the expression of their inscrutable +inner nature; the stages passed through in the development of the +individual were regarded as the outcome of purely internal and hidden laws. +The feasibility of experimental inquiry seemed therefore remote. +Meanwhile, the recognition of the great importance of such a causal +morphology emerged from the researches of the physiologists of that time, +more especially from those of Hofmeister (Hofmeister, "Allgemeine +Morphologie", Leipzig, 1868, page 579.), and afterwards from the work of +Sachs. (Sachs, "Stoff und Form der Pflanzenorgane", Vol. I. 1880; Vol. II. +1882. "Gesammelte Abhandlungen uber Pflanzen-Physiologie", II. Leipzig, +1893.) Hofmeister, in speaking of this line of inquiry, described it as +"the most pressing and immediate aim of the investigator to discover to +what extent external forces acting on the organism are of importance in +determining its form." This advance was the outcome of the influence of +that potent force in biology which was created by Darwin's "Origin of +Species" (1859). + +The significance of the splendid conception of the transformation of +species was first recognised and discussed by Lamarck (1809); as an +explanation of transformation he at once seized upon the idea--an +intelligible view--that the external world is the determining factor. +Lamarck (Lamarck, "Philosophie zoologique", pages 223-227. Paris, 1809.) +endeavoured, more especially, to demonstrate from the behaviour of plants +that changes in environment induce change in form which eventually leads to +the production of new species. In the case of animals, Lamarck adopted the +teleological view that alterations in the environment first lead to +alterations in the needs of the organisms, which, as the result of a kind +of conscious effort of will, induce useful modifications and even the +development of new organs. His work has not exercised any influence on the +progress of science: Darwin himself confessed in regard to Lamarck's work +--"I got not a fact or idea from it." ("Life and Letters", Vol. II. page +215.) + +On a mass of incomparably richer and more essential data Darwin based his +view of the descent of organisms and gained for it general acceptance; as +an explanation of modification he elaborated the ingeniously conceived +selection theory. The question of special interest in this connection, +namely what is the importance of the influence of the environment, Darwin +always answered with some hesitation and caution, indeed with a certain +amount of indecision. + +The fundamental principle underlying his theory is that of general +variability as a whole, the nature and extent of which, especially in +cultivated organisms, are fully dealt with in his well-known book. +(Darwin, "The variation of Animals and Plants under domestication", 2 +vols., edition 1, 1868; edition 2, 1875; popular edition 1905.) In regard +to the question as to the cause of variability Darwin adopts a consistently +mechanical view. He says: "These several considerations alone render it +probable that variability of every kind is directly or indirectly caused by +changed conditions of life. Or, to put the case under another point of +view, if it were possible to expose all the individuals of a species during +many generations to absolutely uniform conditions of life, there would be +no variability." ("The variation of Animals and Plants" (2nd edition), +Vol. II. page 242.) Darwin did not draw further conclusions from this +general principle. + +Variations produced in organisms by the environment are distinguished by +Darwin as "the definite" and "the indefinite." (Ibid. II. page 260. See +also "Origin of Species" (6th edition), page 6.) The first occur "when all +or nearly all the offspring of an individual exposed to certain conditions +during several generations are modified in the same manner." Indefinite +variation is much more general and a more important factor in the +production of new species; as a result of this, single individuals are +distinguished from one another by "slight" differences, first in one then +in another character. There may also occur, though this is very rare, more +marked modifications, "variations which seem to us in our ignorance to +arise spontaneously." ("Origin of Species" (6th edition), page 421.) The +selection theory demands the further postulate that such changes, "whether +extremely slight or strongly marked," are inherited. Darwin was no nearer +to an experimental proof of this assumption than to the discovery of the +actual cause of variability. It was not until the later years of his life +that Darwin was occupied with the "perplexing problem...what causes almost +every cultivated plant to vary" ("Life and Letters", Vol. III. page 342.): +he began to make experiments on the influence of the soil, but these were +soon given up. + +In the course of the violent controversy which was the outcome of Darwin's +work the fundamental principles of his teaching were not advanced by any +decisive observations. Among the supporters and opponents, Nageli (Nageli, +"Theorie der Abstammungslehre", Munich, 1884; cf. Chapter III.) was one of +the few who sought to obtain proofs by experimental methods. His extensive +cultural experiments with alpine Hieracia led him to form the opinion that +the changes which are induced by an alteration in the food-supply, in +climate or in habitat, are not inherited and are therefore of no importance +from the point of view of the production of species. And yet Nageli did +attribute an important influence to the external world; he believed that +adaptations of plants arise as reactions to continuous stimuli, which +supply a need and are therefore useful. These opinions, which recall the +teleological aspect of Lamarckism, are entirely unsupported by proof. +While other far-reaching attempts at an explanation of the theory of +descent were formulated both in Nageli's time and afterwards, some in +support of, others in opposition to Darwin, the necessity of investigating, +from different standpoints, the underlying causes, variability and +heredity, was more and more realised. To this category belong the +statistical investigations undertaken by Quetelet and Galton, the +researches into hybridisation, to which an impetus was given by the re- +discovery of the Mendelian law of segregation, as also by the culture +experiments on mutating species following the work of de Vries, and lastly +the consideration of the question how far variation and heredity are +governed by external influences. These latter problems, which are +concerned in general with the causes of form-production and form- +modification, may be treated in a short summary which falls under two +heads, one having reference to the conditions of form-production in single +species, the other being concerned with the conditions governing the +transformation of species. + +I. THE INFLUENCE OF EXTERNAL CONDITIONS ON FORM-PRODUCTION IN SINGLE +SPECIES. + +The members of plants, which we express by the terms stem, leaf, flower, +etc. are capable of modification within certain limits; since Lamarck's +time this power of modification has been brought more or less into relation +with the environment. We are concerned not only with the question of +experimental demonstration of this relationship, but, more generally, with +an examination of the origin of forms, the sequences of stages in +development that are governed by recognisable causes. We have to consider +the general problem; to study the conditions of all typical as well as of +atypic forms, in other words, to found a physiology of form. + +If we survey the endless variety of plant-forms and consider the highly +complex and still little known processes in the interior of cells, and if +we remember that the whole of this branch of investigation came into +existence only a few decades ago, we are able to grasp the fact that a +satisfactory explanation of the factors determining form cannot be +discovered all at once. The goal is still far away. We are not concerned +now with the controversial question, whether, on the whole, the fundamental +processes in the development of form can be recognised by physiological +means. A belief in the possibility of this can in any case do no harm. +What we may and must attempt is this--to discover points of attack on one +side or another, which may enable us by means of experimental methods to +come into closer touch with these elusive and difficult problems. While we +are forced to admit that there is at present much that is insoluble there +remains an inexhaustible supply of problems capable of solution. + +The object of our investigations is the species; but as regards the +question, what is a species, science of to-day takes up a position +different from that of Darwin. For him it was the Linnean species which +illustrates variation: we now know, thanks to the work of Jordan, de Bary, +and particularly to that of de Vries (de Vries, "Die Mutationstheorie", +Leipzig, 1901, Vol. I. page 33.), that the Linnean species consists of a +large or small number of entities, elementary species. In experimental +investigation it is essential that observations be made on a pure species, +or, as Johannsen (Johannsen, "Ueber Erblichkeit in Populationen und reinen +Linien", Jena, 1903.) says, on a pure "line." What has long been +recognised as necessary in the investigation of fungi, bacteria and algae +must also be insisted on in the case of flowering plants; we must start +with a single individual which is reproduced vegetatively or by strict +self-fertilisation. In dioecious plants we must aim at the reproduction of +brothers and sisters. + +We may at the outset take it for granted that a pure species remains the +same under similar external conditions; it varies as these vary. IT IS +CHARACTERISTIC OF A SPECIES THAT IT ALWAYS EXHIBITS A CONSTANT RELATION TO +A PARTICULAR ENVIRONMENT. In the case of two different species, e.g. the +hay and anthrax bacilli or two varieties of Campanula with blue and white +flowers respectively, a similar environment produces a constant difference. +The cause of this is a mystery. + +According to the modern standpoint, the living cell is a complex chemico- +physical system which is regarded as a dynamical system of equilibrium, a +conception suggested by Herbert Spencer and which has acquired a constantly +increasing importance in the light of modern developments in physical +chemistry. The various chemical compounds, proteids, carbohydrates, fats, +the whole series of different ferments, etc. occur in the cell in a +definite physical arrangement. The two systems of two species must as a +matter of fact possess a constant difference, which it is necessary to +define by a special term. We say, therefore, that the SPECIFIC STRUCTURE +is different. + +By way of illustrating this provisionally, we may assume that the proteids +of the two species possess a constant chemical difference. This conception +of specific structure is specially important in its bearing on a further +treatment of the subject. In the original cell, eventually also in every +cell of a plant, the characters which afterwards become apparent must exist +somewhere; they are integral parts of the capabilities or potentialities of +specific structure. Thus not only the characters which are exhibited under +ordinary conditions in nature, but also many others which become apparent +only under special conditions (In this connection I leave out of account, +as before, the idea of material carriers of heredity which since the +publication of Darwin's Pangenesis hypothesis has been frequently +suggested. See my remarks in "Variationen der Bluten", "Pringsheim's +Jahrb. Wiss. Bot." 1905, page 298; also Detto, "Biol. Centralbl." 1907, +page 81, "Die Erklarbarkeit der Ontogenese durch materielle Anlagen".), are +to be included as such potentialities in cells; the conception of specific +structure includes the WHOLE OF THE POTENTIALITIES OF A SPECIES; specific +structure comprises that which we must always assume without being able to +explain it. + +A relatively simple substance, such as oxalate of lime, is known under a +great number of different crystalline forms belonging to different systems +(Compare Kohl's work on "Anatomisch-phys. Untersuchungen uber Kalksalze", +etc. Marburg, 1889.); these may occur as single crystals, concretions or as +concentric sphaerites. The power to assume this variety of form is in some +way inherent in the molecular structure, though we cannot, even in this +case, explain the necessary connection between structure and crystalline +form. These potentialities can only become operative under the influence +of external conditions; their stimulation into activity depends on the +degree of concentration of the various solutions, on the nature of the +particular calcium salt, on the acid or alkaline reactions. Broadly +speaking, the plant cell behaves in a similar way. The manifestation of +each form, which is inherent as a potentiality in the specific structure, +is ultimately to be referred to external conditions. + +An insight into this connection is, however, rendered exceedingly +difficult, often quite impossible, because the environment never directly +calls into action the potentialities. Its influence is exerted on what we +may call the inner world of the organism, the importance of which increases +with the degree of differentiation. The production of form in every plant +depends upon processes in the interior of the cells, and the nature of +these determines which among the possible characters is to be brought to +light. In no single case are we acquainted with the internal process +responsible for the production of a particular form. All possible factors +may play a part, such as osmotic pressure, permeability of the protoplasm, +the degree of concentration of the various chemical substances, etc.; all +these factors should be included in the category of INTERNAL CONDITIONS. +This inner world appears the more hidden from our ken because it is always +represented by a certain definite state, whether we are dealing with a +single cell or with a small group of cells. These have been produced from +pre-existing cells and they in turn from others; the problem is constantly +pushed back through a succession of generations until it becomes identified +with that of the origin of species. + +A way, however, is opened for investigation; experience teaches us that +this inner world is not a constant factor: on the contrary, it appears to +be very variable. The dependence of VARIABLE INTERNAL on VARIABLE EXTERNAL +conditions gives us the key with which research may open the door. In the +lower plants this dependence is at once apparent, each cell is directly +subject to external influences. In the higher plants with their different +organs, these influences were transmitted to cells in course of development +along exceedingly complex lines. In the case of the growing-point of a +bud, which is capable of producing a complete plant, direct influences play +a much less important part than those exerted through other organs, +particularly through the roots and leaves, which are essential in +nutrition. These correlations, as we may call them, are of the greatest +importance as aids to an understanding of form-production. When a bud is +produced on a particular part of a plant, it undergoes definite internal +modifications induced by the influence of other organs, the activity of +which is governed by the environment, and as the result of this it develops +along a certain direction; it may, for example, become a flower. The +particular direction of development is determined before the rudiment is +differentiated and is exerted so strongly that further development ensues +without interruption, even though the external conditions vary considerably +and exert a positively inimical influence: this produces the impression +that development proceeds entirely independently of the outer world. The +widespread belief that such independence exists is very premature and at +all events unproven. + +The state of the young rudiment is the outcome of previous influences of +the external world communicated through other organs. Experiments show +that in certain cases, if the efficiency of roots and leaves as organs +concerned with nutrition is interfered with, the production of flowers is +affected, and their characters, which are normally very constant, undergo +far-reaching modifications. To find the right moment at which to make the +necessary alteration in the environment is indeed difficult and in many +cases not yet possible. This is especially the case with fertilised eggs, +which in a higher degree than buds have acquired, through parental +influences, an apparently fixed internal organisation, and this seems to +have pre-determined their development. It is, however, highly probable +that it will be possible, by influencing the parents, to alter the internal +organisation and to switch off development on to other lines. + +Having made these general observations I will now cite a few of the many +facts at our disposal, in order to illustrate the methods and aim of the +experimental methods of research. As a matter of convenience I will deal +separately with modification of development and with modification of single +organs. + +I. EFFECT OF ENVIRONMENT UPON THE COURSE OF DEVELOPMENT. + +Every plant, whether an alga or a flowering plant passes, under natural +conditions, through a series of developmental stages characteristic of each +species, and these consist in a regular sequence of definite forms. It is +impossible to form an opinion from mere observation and description as to +what inner changes are essential for the production of the several forms. +We must endeavour to influence the inner factors by known external +conditions in such a way that the individual stages in development are +separately controlled and the order of their sequence determined at will by +experimental treatment. Such control over the course of development may be +gained with special certainty in the case of the lower organisms. + +With these it is practicable to control the principal conditions of +cultivation and to vary them in various ways. By this means it has been +demonstrated that each developmental stage depends upon special external +conditions, and in cases where our knowledge is sufficient, a particular +stage may be obtained at will. In the Green Algae (See Klebs, "Die +Bedingung der Fortpflanzung...", Jena, 1896; also "Jahrb. fur Wiss. Bot." +1898 and 1900; "Probleme der Entwickelung, III." "Biol. Centralbl." 1904, +page 452.), as in the case of Fungi, we may classify the stages of +development into purely vegetative growth (growth, cell-division, +branching), asexual reproduction (formation of zoospores, conidia) and +sexual processes (formation of male and female sexual organs). By +modifying the external conditions it is possible to induce algae or fungi +(Vaucheria, Saprolegnia) to grow continuously for several years or, in the +course of a few days, to die after an enormous production of asexual or +sexual cells. In some instances even an almost complete stoppage of growth +may be caused, reproductive cells being scarcely formed before the organism +is again compelled to resort to reproduction. Thus the sequence of the +different stages in development can be modified as we may desire. + +The result of a more thorough investigation of the determining conditions +appears to produce at first sight a confused impression of all sorts of +possibilities. Even closely allied species exhibit differences in regard +to the connection between their development and external conditions. It is +especially noteworthy that the same form in development may be produced as +the result of very different alterations in the environment. At the same +time we can undoubtedly detect a certain unity in the multiplicity of the +individual phenomena. + +If we compare the factors essential for the different stages in +development, we see that the question always resolves itself into one of +modification of similar conditions common to all life-processes. We should +rather have inferred that there exist specific external stimuli for each +developmental stage, for instance, certain chemical agencies. Experiments +hitherto made support the conclusion that QUANTITATIVE alterations in the +general conditions of life produce different types of development. An alga +or a fungus grows so long as all the conditions of nutrition remain at a +certain optimum for growth. In order to bring about asexual reproduction, +e.g. the formation of zoospores, it is sometimes necessary to increase the +degree of intensity of external factors; sometimes, on the other hand, +these must be reduced in intensity. In the case of many algae a decrease +in light-intensity or in the amount of salts in the culture solution, or in +the temperature, induces asexual reproduction, while in others, on the +contrary, an increase in regard to each of these factors is required to +produce the same result. This holds good for the quantitative variations +which induce sexual reproduction in algae. The controlling factor is found +to be a reduction in the supply of nutritive salts and the exposure of the +plants to prolonged illumination or, better still, an increase in the +intensity of the light, the efficiency of illumination depending on the +consequent formation of organic substances such as carbohydrates. + +The quantitative alterations of external conditions may be spoken of as +releasing stimuli. They produce, in the complex equilibrium of the cell, +quantitative modifications in the arrangement and distribution of mass, by +means of which other chemical processes are at once set in motion, and +finally a new condition of equilibrium is attained. But the commonly +expressed view that the environment can as a rule act only as a releasing +agent is incorrect, because it overlooks an essential point. The power of +a cell to receive stimuli is only acquired as the result of previous +nutrition, which has produced a definite condition of concentration of +different substances. Quantities are in this case the determining factors. +The distribution of quantities is especially important in the sexual +reproduction of algae, for which a vigorous production of the materials +formed during carbon-assimilation appears to be essential. + +In the Flowering plants, on the other hand, for reasons already mentioned, +the whole problem is more complicated. Investigations on changes in the +course of development of fertilised eggs have hitherto been unsuccessful; +the difficulty of influencing egg-cells deeply immersed in tissue +constitutes a serious obstacle. Other parts of plants are, however, +convenient objects of experiment; e.g. the growing apices of buds which +serve as cuttings for reproductive purposes, or buds on tubers, runners, +rhizomes, etc. A growing apex consists of cells capable of division in +which, as in egg-cells, a complete series of latent possibilities of +development is embodied. Which of these possibilities becomes effective +depends upon the action of the outer world transmitted by organs concerned +with nutrition. + +Of the different stages which a flowering plant passes through in the +course of its development we will deal only with one in order to show that, +in spite of its great complexity, the problem is, in essentials, equally +open to attack in the higher plants and in the simplest organisms. The +most important stage in the life of a flowering plant is the transition +from purely vegetative growth to sexual reproduction--that is, the +production of flowers. In certain cases it can be demonstrated that there +is no internal cause, dependent simply on the specific structure, which +compels a plant to produce its flowers after a definite period of +vegetative growth. (Klebs, "Willkurliche Entwickelungsanderungen", Jena +1903; see also "Probleme der Entwickelung", I. II. "Centralbl." 1904.) + +One extreme case, that of exceptionally early flowering, has been observed +in nature and more often in cultivation. A number of plants under certain +conditions are able to flower soon after germination. (Cf. numerous +records of this kind by Diels, "Jugendformen und Bluten", Berlin, 1906.) +This shortening of the period of development is exhibited in the most +striking form in trees, as in the oak (Mobius, "Beitrage zur Lehre von der +Fortpflanzung", Jena, 1897, page 89.), flowering seedlings of which have +been observed from one to three years old, whereas normally the tree does +not flower until it is sixty or eighty years old. + +Another extreme case is represented by prolonged vegetative growth leading +to the complete suppression of flower-production. This result may be +obtained with several plants, such as Glechoma, the sugar beet, Digitalis, +and others, if they are kept during the winter in a warm, damp atmosphere, +and in rich soil; in the following spring or summer they fail to flower. +(Klebs, "Willkurliche Aenderungen", etc. Jena, 1903, page 130.) +Theoretically, however, experiments are of greater importance in which the +production of flowers is inhibited by very favourable conditions of +nutrition (Klebs, "Ueber kunstliche Metamorphosen", Stuttgart, 1906, page +115 ("Abh. Naturf. Ges. Halle", XXV.) occurring at the normal flowering +period. Even in the case of plants of Sempervivum several years old, +which, as is shown by control experiments on precisely similar plants, are +on the point of flowering, flowering is rendered impossible if they are +forced to very vigorous growth by an abundant supply of water and salts in +the spring. Flowering, however, occurs, if such plants are cultivated in +relatively dry sandy soil and in the presence of strong light. Careful +researches into the conditions of growth have led, in the cases +Sempervivum, to the following results: (1) With a strong light and +vigorous carbon-assimilation a considerably increased supply of water and +nutritive salts produces active vegetative growth. (2) With a vigorous +carbon-assimilation in strong light, and a decrease in the supply of water +and salts active flower-production is induced. (3) If an average supply +of water and salts is given both processes are possible; the intensity of +carbon-assimilation determines which of the two is manifested. A +diminution in the production of organic substances, particularly of +carbohydrates, induces vegetative growth. This can be effected by culture +in feeble light or in light deprived of the yellow-red rays: on the other +hand, flower-production follows an increase in light-intensity. These +results are essentially in agreement with well-known observations on +cultivated plants, according to which, the application of much moisture, +after a plentiful supply of manure composed of inorganic salts, hinders the +flower-production of many vegetables, while a decrease in the supply of +water and salts favours flowering. + +ii. INFLUENCE OF THE ENVIRONMENT ON THE FORM OF SINGLE ORGANS. (A +considerable number of observations bearing on this question are given by +Goebel in his "Experimentelle Morphologie der Pflanzen", Leipzig, 1908. It +is not possible to deal here with the alteration in anatomical structure; +cf. Kuster, "Pathologische Pflanzenanatomie", Jena, 1903.) + +If we look closely into the development of a flowering plant, we notice +that in a given species differently formed organs occur in definite +positions. In a potato plant colourless runners are formed from the base +of the main stem which grow underground and produce tubers at their tips: +from a higher level foliage shoots arise nearer the apex. External +appearances suggest that both the place of origin and the form of these +organs were predetermined in the egg-cell or in the tuber. But it was +shown experimentally by the well-known investigator Knight (Knight, +"Selection from the Physiological and Horticultural Papers", London, 1841.) +that tubers may be developed on the aerial stem in place of foliage shoots. +These observations were considerably extended by Vochting. (Vochting, +"Ueber die Bildung der Knollen", Cassel, 1887; see also "Bot. Zeit." 1902, +87.) In one kind of potato, germinating tubers were induced to form +foliage shoots under the influence of a higher temperature; at a lower +temperature they formed tuber-bearing shoots. Many other examples of the +conversion of foliage-shoots into runners and rhizomes, or vice versa, have +been described by Goebel and others. As in the asexual reproduction of +algae quantitative alteration in the amount of moisture, light, +temperature, etc. determines whether this or that form of shoot is +produced. If the primordia of these organs are exposed to altered +conditions of nutrition at a sufficiently early stage a complete +substitution of one organ for another is effected. If the rudiment has +reached a certain stage in development before it is exposed to these +influences, extraordinary intermediate forms are obtained, bearing the +characters of both organs. + +The study of regeneration following injury is of greater importance as +regards the problem of the development and place of origin of organs. +(Reference may be made to the full summary of results given by Goebel in +his "Experimentelle Morphologie", Leipzig and Berlin, 1908, Section IV.) +Only in relatively very rare cases is there a complete re-formation of the +injured organ itself, as e.g. in the growing-apex. Much more commonly +injury leads to the development of complementary formations, it may be the +rejuvenescence of a hitherto dormant rudiment, or it may be the formation +of such ab initio. In all organs, stems, roots, leaves, as well as +inflorescences, this kind of regeneration, which occurs in a great variety +of ways according to the species, may be observed on detached pieces of the +plant. Cases are also known, such, for example, as the leaves of many +plants which readily form roots but not shoots, where a complete +regeneration does not occur. + +The widely spread power of reacting to wounding affords a very valuable +means of inducing a fresh development of buds and roots on places where +they do not occur in normal circumstances. Injury creates special +conditions, but little is known as yet in regard to alterations directly +produced in this way. Where the injury consists in the separation of an +organ from its normal connections, the factors concerned are more +comprehensible. A detached leaf, e.g., is at once cut off from a supply of +water and salts, and is deprived of the means of getting rid of organic +substances which it produces; the result is a considerable alteration in +the degree of concentration. No experimental investigation on these lines +has yet been made. Our ignorance has often led to the view that we are +dealing with a force whose specific quality is the restitution of the parts +lost by operation; the proof, therefore, that in certain cases a similar +production of new roots or buds may be induced without previous injury and +simply by a change in external conditions assumes an importance. (Klebs, +"Willkurliche Entwickelung", page 100; also, "Probleme der Entwickelung", +"Biol. Centralbl." 1904, page 610.) + +A specially striking phenomenon of regeneration, exhibited also by +uninjured plants, is afforded by polarity, which was discovered by +Vochting. (See the classic work of Vochting, "Ueber Organbildung im +Pflanzenreich", I. Bonn, 1888; also "Bot. Zeit. 1906, page 101; cf. Goebel, +"Experimentelle Morphologie", Leipzig and Berlin, 1908, Section V, +Polaritat.) It is found, for example, that roots are formed from the base +of a detached piece of stem and shoots from the apex. Within the limits of +this essay it is impossible to go into this difficult question; it is, +however, important from the point of view of our general survey to +emphasise the fact that the physiological distinctions between base and +apex of pieces of stem are only of a quantitative kind, that is, they +consist in the inhibition of certain phenomena or in favouring them. As a +matter of fact roots may be produced from the apices of willows and +cuttings of other plants; the distinction is thus obliterated under the +influence of environment. The fixed polarity of cuttings from full grown +stems cannot be destroyed; it is the expression of previous development. +Vochting speaks of polarity as a fixed inherited character. This is an +unconvincing conclusion, as nothing can be deduced from our present +knowledge as to the causes which led up to polarity. We know that the +fertilised egg, like the embryo, is fixed at one end by which it hangs +freely in the embryo-sac and afterwards in the endosperm. From the first, +therefore, the two ends have different natures, and these are revealed in +the differentiation into root-apex and stem-apex. A definite direction in +the flow of food-substances is correlated with this arrangement, and this +eventually leads to a polarity in the tissues. This view requires +experimental proof, which in the case of the egg-cells of flowering plants +hardly appears possible; but it derives considerable support from the fact +that in herbaceous plants, e.g. Sempervivum (Klebs, "Variationen der +Bluten", "Jahrb. Wiss. Bot." 1905, page 260.), rosettes or flower-shoots +are formed in response to external conditions at the base, in the middle, +or at the apex of the stem, so that polarity as it occurs under normal +conditions cannot be the result of unalterable hereditary factors. On the +other hand, the lower plants should furnish decisive evidence on this +question, and the experiments of Stahl, Winkler, Kniep, and others indicate +the right method of attacking the problem. + +The relation of leaf-form to environment has often been investigated and is +well known. The leaves of bog and water plants (Cf.Goebel, loc. cit. +chapter II.; also Gluck, "Untersuchungen uber Wasser- und Sumpfgewachse", +Jena, Vols. I.-II. 1905-06.) afford the most striking examples of +modifications: according as they are grown in water, moist or dry air, the +form of the species characteristic of the particular habitat is produced, +since the stems are also modified. To the same group of phenomena belongs +the modification of the forms of leaves and stems in plants on +transplantation from the plains to the mountains (Bonnier, "Recherches sur +l'Anatomie experimentale des Vegetaux", Corbeil, 1895.) or vice versa. +Such variations are by no means isolated examples. All plants exhibit a +definite alteration in form as the result of prolonged cultivation in moist +or dry air, in strong or feeble light, or in darkness, or in salt solutions +of different composition and strength. + +Every individual which is exposed to definite combinations of external +factors exhibits eventually the same type of modification. This is the +type of variation which Darwin termed "definite." It is easy to realise +that indefinite or fluctuating variations belong essentially to the same +class of phenomena; both are reactions to changes in environment. In the +production of individual variations two different influences undoubtedly +cooperate. One set of variations is caused by different external +conditions, during the production, either of sexual cells or of vegetative +primordia; another set is the result of varying external conditions during +the development of the embryo into an adult plant. The two sets of +influences cannot as yet be sharply differentiated. If, for purposes of +vegetative reproduction, we select pieces of the same parent-plant of a +pure species, the second type of variation predominates. Individual +fluctuations depend essentially in such cases on small variations in +environment during development. + +These relations must be borne in mind if we wish to understand the results +of statistical methods. Since the work of Quetelet, Galton, and others the +statistical examination of individual differences in animals and plants has +become a special science, which is primarily based on the consideration +that the application of the theory of probability renders possible +mathematical statement and control of the results. The facts show that any +character, size of leaf, length of stem, the number of members in a flower, +etc. do not vary haphazard but in a very regular manner. In most cases it +is found that there is a value which occurs most commonly, the average or +medium value, from which the larger and smaller deviations, the so-called +plus and minus variations fall away in a continuous series and end in a +limiting value. In the simpler cases a falling off occurs equally on both +sides of the curve; the curve constructed from such data agrees very +closely with the Gaussian curve of error. In more complicated cases +irregular curves of different kinds are obtained which may be calculated on +certain suppositions. + +The regular fluctuations about a mean according to the rule of probability +is often attributed to some law underlying variability. (de Vries, +"Mutationstheorie", Vol. I. page 35, Leipzig, 1901.) But there is no such +law which compels a plant to vary in a particular manner. Every +experimental investigation shows, as we have already remarked, that the +fluctuation of characters depends on fluctuation in the external factors. +The applicability of the method of probability follows from the fact that +the numerous individuals of a species are influenced by a limited number of +variable conditions. (Klebs, "Willkurl. Ent." Jena, 1903, page 141.) As +each of these conditions includes within certain limits all possible values +and exhibits all possible combinations, it follows that, according to the +rules of probability, there must be a mean value, about which the larger +and smaller deviations are distributed. Any character will be found to +have the mean value which corresponds with that combination of determining +factors which occurs most frequently. Deviations towards plus and minus +values will be correspondingly produced by rarer conditions. + +A conclusion of fundamental importance may be drawn from this conception, +which is, to a certain extent, supported by experimental investigation. +(Klebs, "Studien uber Variation", "Arch. fur Entw." 1907.) There is no +normal curve for a particular CHARACTER, there is only a curve for the +varying combinations of conditions occurring in nature or under +cultivation. Under other conditions entirely different curves may be +obtained with other variants as a mean value. If, for example, under +ordinary conditions the number 10 is the most frequent variant for the +stamens of Sedum spectabile, in special circumstances (red light) this is +replaced by the number 5. The more accurately we know the conditions for a +particular form or number, and are able to reproduce it by experiment, the +nearer we are to achieving our aim of rendering a particular variation +impossible or of making it dominant. + +In addition to the individual variations of a species, more pronounced +fluctuations occur relatively rarely and sporadically which are spoken of +as "single variations," or if specially striking as abnormalities or +monstrosities. These forms have long attracted the attention of +morphologists; a large number of observations of this kind are given in the +handbooks of Masters (Masters, "Vegetable Teratology", London, 1869.) and +Penzig (Penzig, "Pflanzen-Teratologie, Vols I. and II. Genua, 1890-94.) +These variations, which used to be regarded as curiosities, have now +assumed considerable importance in connection with the causes of form- +development. They also possess special interest in relation to the +question of heredity, a subject which does not at present concern us, as +such deviations from normal development undoubtedly arise as individual +variations induced by the influence of environment. + +Abnormal developments of all kinds in stems, leaves, and flowers, may be +produced by parasites, insects, or fungi. They may also be induced by +injury, as Blaringhem (Blaringhem, "Mutation et traumatismes", Paris, +1907.) has more particularly demonstrated, which, by cutting away the +leading shoots of branches in an early stage of development, caused +fasciation, torsion, anomalous flowers, etc. The experiments of Blaringhem +point to the probability that disturbances in the conditions of food-supply +consequent on injury are the cause of the production of monstrosities. +This is certainly the case in my experiments with species of Sempervivum +(Klebs, "Kunstliche Metamorphosen", Stuttgart, 1906.); individuals, which +at first formed normal flowers, produced a great variety of abnormalities +as the result of changes in nutrition, we may call to mind the fact that +the formation of inflorescences occurs normally when a vigorous production +of organic compounds, such as starch, sugar, etc. follows a diminution in +the supply of mineral salts. On the other hand, the development of +inflorescences is entirely suppressed if, at a suitable moment before the +actual foundations have been laid, water and mineral salts are supplied to +the roots. If, during the week when the inflorescence has just been laid +down and is growing very slowly, the supply of water and salts is +increased, the internal conditions of the cells are essentially changed. +At a later stage, after the elongation of the inflorescence, rosettes of +leaves are produced instead of flowers, and structures intermediate between +the two kinds of organs; a number of peculiar plant-forms are thus obtained +(Cf. Lotsy, "Vorlesungen uber Deszendenztheorien", Vol. II. pl. 3, Jena, +1908.) Abnormalities in the greatest variety are produced in flowers by +varying the time at which the stimulus is applied, and by the cooperation +of other factors such as temperature, darkness, etc. In number and +arrangement the several floral members vary within wide limits; sepals, +petals, stamens, and carpels are altered in form and colour, a +transformation of stamens to carpels and from carpels to stamens occurs in +varying degrees. The majority of the deviations observed had not +previously been seen either under natural conditions or in cultivation; +they were first brought to light through the influence of external factors. + +Such transformations of flowers become apparent at a time, which is +separated by about two months from the period at which the particular cause +began to act. There is, therefore, no close connection between the +appearance of the modifications and the external conditions which prevail +at the moment. When we are ignorant of the causes which are operative so +long before the results are seen, we gain the impression that such +variations as occur are spontaneous or autonomous expressions of the inner +nature of the plant. It is much more likely that, as in Sempervivum, they +were originally produced by an external stimulus which had previously +reached the sexual cells or the young embryo. In any case abnormalities of +this kind appear to be of a special type as compared with ordinary +fluctuating variations. Darwin pointed out this difference; Bateson +(Bateson, "Materials for the study of Variation", London, 1894, page 5.) +has attempted to make the distinction sharper, at the same time emphasising +its importance in heredity. + +Bateson applies the term CONTINUOUS to small variations connected with one +another by transitional stages, while those which are more striking and +characterised from the first by a certain completeness, he names +DISCONTINUOUS. He drew attention to a great difficulty which stands in the +way of Lamarck's hypothesis, as also of Darwin's view. "According to both +theories, specific diversity of form is consequent upon diversity of +environment, and diversity of environment is thus the ultimate measure of +diversity of specific form. Here then we meet the difficulty that diverse +environments often shade into each other insensibly and form a continuous +series, whereas the Specific Forms of life which are subject to them on the +whole form a Discontinuous Series." This difficulty is, however, not of +fundamental importance as well authenticated facts have been adduced +showing that by alteration of the environment discontinuous variations, +such as alterations in the number and form of members of a flower, may be +produced. We can as yet no more explain how this happens than we can +explain the existence of continuous variations. We can only assert that +both kinds of variation arise in response to quantitative alterations in +external conditions. The question as to which kind of variation is +produced depends on the greater or less degree of alteration; it is +correlated with the state of the particular cells at the moment. + +In this short sketch it is only possible to deal superficially with a small +part of the subject. It has been clearly shown that in view of the general +dependence of development on the factors of the environment a number of +problems are ready for experimental treatment. One must, however, not +forget that the science of the physiology of form has not progressed beyond +its initial stages. Just now our first duty is to demonstrate the +dependence on external factors in as many forms of plants as possible, in +order to obtain a more thorough control of all the different plant-forms. +The problem is not only to produce at will (and independently of their +normal mode of life) forms which occur in nature, but also to stimulate +into operation potentialities which necessarily lie dormant under the +conditions which prevail in nature. The constitution of a species is much +richer in possibilities of development than would appear to be the case +under normal conditions. It remains for man to stimulate into activity all +the potentialities. + +But the control of plant-form is only a preliminary step--the foundation +stones on which to erect a coherent scientific structure. We must discover +what are the internal processes in the cell produced by external factors, +which as a necessary consequence result in the appearance of a definite +form. We are here brought into contact with the most obscure problem of +life. Progress can only be made pari passu with progress in physics and +chemistry, and with the growth of our knowledge of nutrition, growth, etc. + +Let us take one of the simplest cases--an alteration in form. A +cylindrical cell of the alga Stigeoclonium assumes, as Livingstone +(Livingstone, "On the nature of the stimulus which causes the change of +form, etc." "Botanical Gazette", XXX. 1900; also XXXII. 1901.) has shown, +a spherical form when the osmotic pressure of the culture fluid is +increased; or a spore of Mucor, which, in a sugar solution grows into a +branched filament, in the presence of a small quantity of acid (hydrogen +ions) becomes a comparatively large sphere. (Ritter, "Ueber Kugelhefe, +etc." "Ber. bot. Gesell." Berlin, XXV. page 255, 1907.) In both cases +there has undoubtedly been an alteration in the osmotic pressure of the +cell-sap, but this does not suffice to explain the alteration in form, +since the unknown alterations, which are induced in the protoplasm, must in +their turn influence the cell-membrane. In the case of the very much more +complex alterations in form, such as we encounter in the course of +development of plants, there do not appear to be any clues which lead us to +a deeper insight into the phenomena. Nevertheless we continue the attempt, +seeking with the help of any available hypothesis for points of attack, +which may enable us to acquire a more complete mastery of physiological +methods. To quote a single example; I may put the question, what internal +changes produce a transition from vegetative growth to sexual reproduction? + +The facts, which are as clearly established from the lower as for the +higher plants, teach us that quantitative alteration in the environment +produces such a transition. This suggests the conclusion that quantitative +internal changes in the cells, and with them disturbances in the degree of +concentration, are induced, through which the chemical reactions are led in +the direction of sexual reproduction. An increase in the production of +organic substances in the presence of light, chiefly of the carbohydrates, +with a simultaneous decrease in the amount of inorganic salts and water, +are the cause of the disturbance and at the same time of the alteration in +the direction of development. Possibly indeed mineral salts as such are +not in question, but only in the form of other organic combinations, +particularly proteid material, so that we are concerned with an alteration +in the relation of the carbohydrates and proteids. The difficulties of +such researches are very great because the methods are not yet sufficiently +exact to demonstrate the frequently small quantitative differences in +chemical composition. Questions relating to the enzymes, which are of the +greatest importance in all these life-processes, are especially +complicated. In any case it is the necessary result of such an hypothesis +that we must employ chemical methods of investigation in dealing with +problems connected with the physiology of form. + +II. INFLUENCE OF ENVIRONMENT ON THE TRANSFORMATION OF SPECIES. + +The study of the physiology of form-development in a pure species has +already yielded results and makes slow but sure progress. The physiology +of the possibility of the transformation of one species into another is +based, as yet, rather on pious hope than on accomplished fact. From the +first it appeared to be hopeless to investigate physiologically the origin +of Linnean species and at the same time that of the natural system, an aim +which Darwin had before him in his enduring work. The historical sequence +of events, of which an organism is the expression, can only be treated +hypothetically with the help of facts supplied by comparative morphology, +the history of development, geographical distribution, and palaeontology. +(See Lotsy, "Vorlesungen" (Jena, I. 1906, II. 1908), for summary of the +facts.) A glance at the controversy which is going on today in regard to +different hypotheses shows that the same material may lead different +investigators to form entirely different opinions. Our ultimate aim is to +find a solution of the problem as to the cause of the origin of species. +Indeed such attempts are now being made: they are justified by the fact +that under cultivation new and permanent strains are produced; the +fundamental importance of this was first grasped by Darwin. New points of +view in regard to these lines of inquiry have been adopted by H. de Vries +who has succeeded in obtaining from Oenothera Lamarckiana a number of +constant "elementary" species. Even if it is demonstrated that he was +simply dealing with the complex splitting up of a hybrid (Bateson, "Reports +to the Evolution Committee of the Royal Society", London, 1902; cf. also +Lotsy, "Vorlesungen", Vol. I. page 234.), the facts adduced in no sense +lose their very great value. + +We must look at the problem in its simplest form; we find it in every case +where a new race differs essentially from the original type in a single +character only; for example, in the colour of the flowers or in the +petalody of the stamens (doubling of flowers). In this connection we must +keep in view the fact that every visible character in a plant is the +resultant of the cooperation of specific structure, with its various +potentialities, and the influence of the environment. We know, that in a +pure species all characters vary, that a blue-flowering Campanula or a red +Sempervivum can be converted by experiment into white-flowering forms, that +a transformation of stamens into petals may be caused by fungi or by the +influence of changed conditions of nutrition, or that plants in dry and +poor soil become dwarfed. But so far as the experiments justify a +conclusion, it would appear that such alterations are not inherited by the +offspring. Like all other variations they appear only so long as special +conditions prevail in the surroundings. + +It has been shown that the case is quite different as regards the white- +flowering, double or dwarf races, because these retain their characters +when cultivated under practically identical conditions, and side by side +with the blue, single-flowering or tall races. The problem may therefore +be stated thus: how can a character, which appears in the one case only +under the strictly limited conditions of the experiment, in other cases +become apparent under the very much wider conditions of ordinary +cultivation? If a character appears, in these circumstances, in the case +of all individuals, we then speak of constant races. In such simple cases +the essential point is not the creation of a new character but rather an +ALTERATION OF THIS CHARACTER IN ACCORDANCE WITH THE ENVIRONMENT. In the +examples mentioned the modified character in the simple varieties (or a +number of characters in elementary species) appears more or less suddenly +and is constant in the above sense. The result is what de Vries has termed +a Mutation. In this connection we must bear in mind the fact that no +difference, recognisable externally, need exist between individual +variation and mutation. Even the most minute quantitative difference +between two plants may be of specific value if it is preserved under +similar external conditions during many successive generations. We do not +know how this happens. We may state the problem in other terms; by saying +that the specific structure must be altered. It is possible, to some +extent, to explain this sudden alteration, if we regard it as a chemical +alteration of structure either in the specific qualities of the proteids or +of the unknown carriers of life. In the case of many organic compounds +their morphological characters (the physical condition, crystalline form, +etc.) are at once changed by alteration of atomic relations or by +incorporation of new radicals. (For instance ethylchloride (C2H5Cl) is a +gas at 21 deg C., ethylenechloride (C2H4Cl2) a fluid boiling at 84 deg C., +beta trichlorethane (C2H3Cl3) a fluid boiling at 113 deg C., perchlorethane +(C2Cl6) a crystalline substance. Klebs, ("Willkurliche +Entwickelungsanderungen" page 158.) Much more important, however, would be +an answer to the question, whether an individual variation can be converted +experimentally into an inherited character--a mutation in de Vries's sense. + +In all circumstances we may recognise as a guiding principle the assumption +adopted by Lamarck, Darwin, and many others, that the inheritance of any +one character, or in more general terms, the transformation of one species +into another, is, in the last instance, to be referred to a change in the +environment. From a causal-mechanical point of view it is not a priori +conceivable that one species can ever become changed into another so long +as external conditions remain constant. The inner structure of a species +must be essentially altered by external influences. Two methods of +experimental research may be adopted, the effect of crossing distinct +species and, secondly, the effect of definite factors of the environment. + +The subject of hybridisation is dealt with in another part of this essay. +It is enough to refer here to the most important fact, that as the result +of combinations of characters of different species new and constant forms +are produced. Further, Tschermack, Bateson and others have demonstrated +the possibility that hitherto unknown inheritable characters may be +produced by hybridisation. + +The other method of producing constant races by the influence of special +external conditions has often been employed. The sporeless races of +Bacteria and Yeasts (Cf. Detto, "Die Theorie der direkten Anpassung...", +pages 98 et seq., Jena, 1904; see also Lotsy, "Vorlesungen", II. pages 636 +et seq., where other similar cases are described.) are well known, in which +an internal alteration of the cells is induced by the influence of poison +or higher temperature, so that the power of producing spores even under +normal conditions appears to be lost. A similar state of things is found +in some races which under certain definite conditions lose their colour or +their virulence. Among the phanerogams the investigations of Schubler on +cereals afford parallel cases, in which the influence of a northern climate +produces individuals which ripen their seeds early; these seeds produce +plants which seed early in southern countries. Analogous results were +obtained by Cieslar in his experiments; seeds of conifers from the Alps +when planted in the plains produced plants of slow growth and small +diameter. + +All these observations are of considerable interest theoretically; they +show that the action of environment certainly induces such internal +changes, and that these are transmitted to the next generation. But as +regards the main question, whether constant races may be obtained by this +means, the experiments cannot as yet supply a definite answer. In +phanerogams, the influence very soon dies out in succeeding generations; in +the case of bacteria, in which it is only a question of the loss of a +character it is relatively easy for this to reappear. It is not +impossible, that in all such cases there is a material hanging-on of +certain internal conditions, in consequence of which the modification of +the character persists for a time in the descendants, although the original +external conditions are no longer present. + +Thus a slow dying-out of the effect of a stimulus was seen in my +experiments on Veronica chamaedrys. (Klebs, "Kunstliche Metamorphosen", +Stuttgart, 1906, page 132.) During the cultivation of an artificially +modified inflorescence I obtained a race showing modifications in different +directions, among which twisting was especially conspicuous. This plant, +however, does not behave as the twisted race of Dipsacus isolated by de +Vries (de Vries, "Mutationstheorie", Vol. II. Leipzig, 1903, page 573.), +which produced each year a definite percentage of twisted individuals. In +the vegetative reproduction of this Veronica the torsion appeared in the +first, also in the second and third year, but with diminishing intensity. +In spite of good cultivation this character has apparently now disappeared; +it disappeared still more quickly in seedlings. In another character of +the same Veronica chamaedrys the influence of the environment was stronger. +The transformation of the inflorescences to foliage-shoots formed the +starting-point; it occurred only under narrowly defined conditions, namely +on cultivation as a cutting in moist air and on removal of all other leaf- +buds. In the majority (7/10) of the plants obtained from the transformed +shoots, the modification appeared in the following year without any +interference. Of the three plants which were under observation several +years the first lost the character in a short time, while the two others +still retain it, after vegetative propagation, in varying degrees. The +same character occurs also in some of the seedlings; but anything +approaching a constant race has not been produced. + +Another means of producing new races has been attempted by Blaringhem. +(Blaringhem, "Mutation et Traumatisme", Paris, 1907.) On removing at an +early stage the main shoots of different plants he observed various +abnormalities in the newly formed basal shoots. From the seeds of such +plants he obtained races, a large percentage of which exhibited these +abnormalities. Starting from a male Maize plant with a fasciated +inflorescence, on which a proportion of the flowers had become male, a new +race was bred in which hermaphrodite flowers were frequently produced. In +the same way Blaringhem obtained, among other similar results, a race of +barley with branched ears. These races, however, behaved in essentials +like those which have been demonstrated by de Vries to be inconstant, e.g. +Trifolium pratense quinquefolium and others. The abnormality appears in a +proportion of the individuals and only under very special conditions. It +must be remembered too that Blaringhem worked with old cultivated plants, +which from the first had been disposed to split into a great variety of +races. It is possible, but difficult to prove, that injury contributed to +this result. + +A third method has been adopted by MacDougal (MacDougal, "Heredity and +Origin of species", "Monist", 1906; "Report of department of botanical +research", "Fifth Year-book of the Carnegie Institution of Washington", +page 119, 1907.) who injected strong (10 percent) sugar solution or weak +solutions of calcium nitrate and zinc sulphate into young carpels of +different plants. From the seeds of a plant of Raimannia odorata the +carpels of which had been thus treated he obtained several plants +distinguished from the parent-forms by the absence of hairs and by distinct +forms of leaves. Further examination showed that he had here to do with a +new elementary species. MacDougal also obtained a more or less distinct +mutant of Oenothera biennis. We cannot as yet form an opinion as to how +far the effect is due to the wound or to the injection of fluid as such, or +to its chemical properties. This, however, is not so essential as to +decide whether the mutant stands in any relation to the influence of +external factors. It is at any rate very important that this kind of +investigation should be carried further. + +If it could be shown that new and inherited races were obtained by +MacDougal's method, it would be safe to conclude that the same end might be +gained by altering the conditions of the food-stuff conducted to the sexual +cells. New races or elementary species, however, arise without wounding or +injection. This at once raises the much discussed question, how far +garden-cultivation has led to the creation of new races? Contrary to the +opinion expressed by Darwin and others, de Vries ("Mutationstheorie", Vol. +I. pages 412 et seq.) tried to show that garden-races have been produced +only from spontaneous types which occur in a wild state or from sub-races, +which the breeder has accidentally discovered but not originated. In a +small number of cases only has de Vries adduced definite proof. On the +other side we have the work of Korschinsky (Korschinsky, "Heterogenesis und +Evolution", "Flora", 1901.) which shows that whole series of garden-races +have made their appearance only after years of cultivation. In the +majority of races we are entirely ignorant of their origin. + +It is, however, a fact that if a plant is removed from natural conditions +into cultivation, a well-marked variation occurs. The well-known plant- +breeder L. de Vilmorin (L. de Vilmorin, "Notices sur l'amelioration des +plantes", Paris, 1886, page 36.), speaking from his own experience, states +that a plant is induced to "affoler," that is to exhibit all possible +variations from which the breeder may make a further selection only after +cultivation for several generations. The effect of cultivation was +particularly striking in Veronica chamaedrys (Klebs, "Kunstliche +Metamorphosen", Stuttgart, 1906, page 152.) which, in spite of its wide +distribution in nature, varies very little. After a few years of +cultivation this "good" and constant species becomes highly variable. The +specimens on which the experiments were made were three modified +inflorescence cuttings, the parent-plants of which certainly exhibited no +striking abnormalities. In a short time many hitherto latent +potentialities became apparent, so that characters, never previously +observed, or at least very rarely, were exhibited, such as scattered leaf- +arrangement, torsion, terminal or branched inflorescences, the conversion +of the inflorescence into foliage-shoots, every conceivable alteration in +the colour of flowers, the assumption of a green colour by parts of the +flowers, the proliferation of flowers. + +All this points to some disturbance in the species resulting from methods +of cultivation. It has, however, not yet been possible to produce constant +races with any one of these modified characters. But variations appeared +among the seedlings, some of which, e.g. yellow variegation, were not +inheritable, while others have proved constant. This holds good, so far as +we know at present, for a small rose-coloured form which is to be reckoned +as a mutation. Thus the prospect of producing new races by cultivation +appears to be full of promise. + +So long as the view is held that good nourishment, i.e. a plentiful supply +of water and salts, constitutes the essential characteristic of garden- +cultivation, we can hardly conceive that new mutations can be thus +produced. But perhaps the view here put forward in regard to the +production of form throws new light on this puzzling problem. + +Good manuring is in the highest degree favourable to vegetative growth, but +is in no way equally favourable to the formation of flowers. The +constantly repeated expression, good or favourable nourishment, is not only +vague but misleading, because circumstances favourable to growth differ +from those which promote reproduction; for the production of every form +there are certain favourable conditions of nourishment, which may be +defined for each species. Experience shows that, within definite and often +very wide limits, it does not depend upon the ABSOLUTE AMOUNT of the +various food substances, but upon their respective degrees of +concentration. As we have already stated, the production of flowers +follows a relative increase in the amount of carbohydrates formed in the +presence of light, as compared with the inorganic salts on which the +formation of albuminous substances depends. (Klebs, "Kunstliche +Metamorphosen", page 117.) The various modifications of flowers are due to +the fact that a relatively too strong solution of salts is supplied to the +rudiments of these organs. As a general rule every plant form depends upon +a certain relation between the different chemical substances in the cells +and is modified by an alteration of that relation. + +During long cultivation under conditions which vary in very different +degrees, such as moisture, the amount of salts, light intensity, +temperature, oxygen, it is possible that sudden and special disturbances in +the relations of the cell substances have a directive influence on the +inner organisation of the sexual cells, so that not only inconstant but +also constant varieties will be formed. + +Definite proof in support of this view has not yet been furnished, and we +must admit that the question as to the cause of heredity remains, +fundamentally, as far from solution as it was in Darwin's time. As the +result of the work of many investigators, particularly de Vries, the +problem is constantly becoming clearer and more definite. The penetration +into this most difficult and therefore most interesting problem of life and +the creation by experiment of new races or elementary species are no longer +beyond the region of possibility. + + +XIV. EXPERIMENTAL STUDY OF THE INFLUENCE OF ENVIRONMENT ON ANIMALS. + +By JACQUES LOEB, M.D. +Professor of Physiology in the University of California. + +I. INTRODUCTORY REMARKS. + +What the biologist calls the natural environment of an animal is from a +physical point of view a rather rigid combination of definite forces. It +is obvious that by a purposeful and systematic variation of these and by +the application of other forces in the laboratory, results must be +obtainable which do not appear in the natural environment. This is the +reasoning underlying the modern development of the study of the effects of +environment upon animal life. It was perhaps not the least important of +Darwin's services to science that the boldness of his conceptions gave to +the experimental biologist courage to enter upon the attempt of controlling +at will the life-phenomena of animals, and of bringing about effects which +cannot be expected in Nature. + +The systematic physico-chemical analysis of the effect of outside forces +upon the form and reactions of animals is also our only means of +unravelling the mechanism of heredity beyond the scope of the Mendelian +law. The manner in which a germ-cell can force upon the adult certain +characters will not be understood until we succeed in varying and +controlling hereditary characteristics; and this can only be accomplished +on the basis of a systematic study of the effects of chemical and physical +forces upon living matter. + +Owing to limitation of space this sketch is necessarily very incomplete, +and it must not be inferred that studies which are not mentioned here were +considered to be of minor importance. All the writer could hope to do was +to bring together a few instances of the experimental analysis of the +effect of environment, which indicate the nature and extent of our control +over life-phenomena and which also have some relation to the work of +Darwin. In the selection of these instances preference is given to those +problems which are not too technical for the general reader. + +The forces, the influence of which we shall discuss, are in succession +chemical agencies, temperature, light, and gravitation. We shall also +treat separately the effect of these forces upon form and instinctive +reactions. + +II. THE EFFECTS OF CHEMICAL AGENCIES. + +(a) HETEROGENEOUS HYBRIDISATION. + +It was held until recently that hybridisation is not possible except +between closely related species and that even among these a successful +hybridisation cannot always be counted upon. This view was well supported +by experience. It is, for instance, well known that the majority of marine +animals lay their unfertilised eggs in the ocean and that the males shed +their sperm also into the sea-water. The numerical excess of the +spermatozoa over the ova in the sea-water is the only guarantee that the +eggs are fertilised, for the spermatozoa are carried to the eggs by chance +and are not attracted by the latter. This statement is the result of +numerous experiments by various authors, and is contrary to common belief. +As a rule all or the majority of individuals of a species in a given region +spawn on the same day, and when this occurs the sea-water constitutes a +veritable suspension of sperm. It has been shown by experiment that in +fresh sea-water the sperm may live and retain its fertilising power for +several days. It is thus unavoidable that at certain periods more than one +kind of spermatozoon is suspended in the sea-water and it is a matter of +surprise that the most heterogeneous hybridisations do not constantly +occur. The reason for this becomes obvious if we bring together mature +eggs and equally mature and active sperm of a different family. When this +is done no egg is, as a rule, fertilised. The eggs of a sea-urchin can be +fertilised by sperm of their own species, or, though in smaller numbers, by +the sperm of other species of sea-urchins, but not by the sperm of other +groups of echinoderms, e.g. starfish, brittle-stars, holothurians or +crinoids, and still less by the sperm of more distant groups of animals. +The consensus of opinion seemed to be that the spermatozoon must enter the +egg through a narrow opening or canal, the so-called micropyle, and that +the micropyle allowed only the spermatozoa of the same or of a closely +related species to enter the egg. + +It seemed to the writer that the cause of this limitation of hybridisation +might be of another kind and that by a change in the constitution of the +sea-water it might be possible to bring about heterogenous hybridisations, +which in normal sea-water are impossible. This assumption proved correct. +Sea-water has a faintly alkaline reaction (in terms of the physical chemist +its concentration of hydroxyl ions is about (10 to the power minus six)N at +Pacific Grove, California, and about (10 to the power minus 5)N at Woods +Hole, Massachusetts). If we slightly raise the alkalinity of the sea-water +by adding to it a small but definite quantity of sodium hydroxide or some +other alkali, the eggs of the sea-urchin can be fertilised with the sperm +of widely different groups of animals, possibly with the sperm of any +marine animal which sheds it into the ocean. In 1903 it was shown that if +we add from about 0.5 to 0.8 cubic centimetre N/10 sodium hydroxide to 50 +cubic centimetres of sea-water, the eggs of Strongylocentrotus purpuratus +(a sea-urchin which is found on the coast of California) can be fertilised +in large quantities by the sperm of various kinds of starfish, brittle- +stars and holothurians; while in normal sea-water or with less sodium +hydroxide not a single egg of the same female could be fertilised with the +starfish sperm which proved effective in the hyper-alkaline sea-water. The +sperm of the various forms of starfish was not equally effective for these +hybridisations; the sperm of Asterias ochracea and A. capitata gave the +best results, since it was possible to fertilise 50 per cent or more of the +sea-urchin eggs, while the sperm of Pycnopodia and Asterina fertilised only +2 per cent of the same eggs. + +Godlewski used the same method for the hybridisation of the sea-urchin eggs +with the sperm of a crinoid (Antedon rosacea). Kupelwieser afterwards +obtained results which seemed to indicate the possibility of fertilising +the eggs of Strongylocentrotus with the sperm of a mollusc (Mytilus.) +Recently, the writer succeeded in fertilising the eggs of +Strongylocentrotus franciscanus with the sperm of a mollusc--Chlorostoma. +This result could only be obtained in sea-water the alkalinity of which had +been increased (through the addition of 0.8 cubic centimetre N/10 sodium +hydroxide to 50 cubic centimetres of sea-water). We thus see that by +increasing the alkalinity of the sea-water it is possible to effect +heterogeneous hybridisations which are at present impossible in the natural +environment of these animals. + +It is, however, conceivable that in former periods of the earth's history +such heterogeneous hybridisations were possible. It is known that in +solutions like sea-water the degree of alkalinity must increase when the +amount of carbon-dioxide in the atmosphere is diminished. If it be true, +as Arrhenius assumes, that the Ice age was caused or preceded by a +diminution in the amount of carbon-dioxide in the air, such a diminution +must also have resulted in an increase of the alkalinity of the sea-water, +and one result of such an increase must have been to render possible +heterogeneous hybridisations in the ocean which in the present state of +alkalinity are practically excluded. + +But granted that such hybridisations were possible, would they have +influenced the character of the fauna? In other words, are the hybrids +between sea-urchin and starfish, or better still, between sea-urchin and +mollusc, capable of development, and if so, what is their character? The +first experiment made it appear doubtful whether these heterogeneous +hybrids could live. The sea-urchin eggs which were fertilised in the +laboratory by the spermatozoa of the starfish, as a rule, died earlier than +those of the pure breeds. But more recent results indicate that this was +due merely to deficiencies in the technique of the earlier experiments. +The writer has recently obtained hybrid larvae between the sea-urchin egg +and the sperm of a mollusc (Chlorostoma) which, in the laboratory, +developed as well and lived as long as the pure breeds of the sea-urchin, +and there was nothing to indicate any difference in the vitality of the two +breeds. + +So far as the question of heredity is concerned, all the experiments on +heterogeneous hybridisation of the egg of the sea-urchin with the sperm of +starfish, brittle-stars, crinoids and molluscs, have led to the same +result, namely, that the larvae have purely maternal characteristics and +differ in no way from the pure breed of the form from which the egg is +taken. By way of illustration it may be said that the larvae of the sea- +urchin reach on the third day or earlier (according to species and +temperature) the so-called pluteus stage, in which they possess a typical +skeleton; while neither the larvae of the starfish nor those of the mollusc +form a skeleton at the corresponding stage. It was, therefore, a matter of +some interest to find out whether or not the larvae produced by the +fertilisation of the sea-urchin egg with the sperm of starfish or mollusc +would form the normal and typical pluteus skeleton. This was invariably +the case in the experiments of Godlewski, Kupelwieser, Hagedoorn, and the +writer. These hybrid larvae were exclusively maternal in character. + +It might be argued that in the case of heterogeneous hybridisation the +sperm-nucleus does not fuse with the egg-nucleus, and that, therefore, the +spermatozoon cannot transmit its hereditary substances to the larvae. But +these objections are refuted by Godlewski's experiments, in which he showed +definitely that if the egg of the sea-urchin is fertilised with the sperm +of a crinoid the fusion of the egg-nucleus and sperm-nucleus takes place in +the normal way. It remains for further experiments to decide what the +character of the adult hybrids would be. + +(b). ARTIFICIAL PARTHENOGENESIS. + +Possibly in no other field of Biology has our ability to control life- +phenomena by outside conditions been proved to such an extent as in the +domain of fertilisation. The reader knows that the eggs of the +overwhelming majority of animals cannot develop unless a spermatozoon +enters them. In this case a living agency is the cause of development and +the problem arises whether it is possible to accomplish the same result +through the application of well-known physico-chemical agencies. This is, +indeed, true, and during the last ten years living larvae have been +produced by chemical agencies from the unfertilised eggs of sea-urchins, +starfish, holothurians and a number of annelids and molluscs; in fact this +holds true in regard to the eggs of practically all forms of animals with +which such experiments have been tried long enough. In each form the +method of procedure is somewhat different and a long series of experiments +is often required before the successful method is found. + +The facts of Artificial Parthenogenesis, as the chemical fertilisation of +the egg is called, have, perhaps, some bearing on the problem of evolution. +If we wish to form a mental image of the process of evolution we have to +reckon with the possibility that parthenogenetic propagation may have +preceded sexual reproduction. This suggests also the possibility that at +that period outside forces may have supplied the conditions for the +development of the egg which at present the spermatozoon has to supply. +For this, if for no other reason, a brief consideration of the means of +artificial parthenogenesis may be of interest to the student of evolution. + +It seemed necessary in these experiments to imitate as completely as +possible by chemical agencies the effects of the spermatozoon upon the egg. +When a spermatozoon enters the egg of a sea-urchin or certain starfish or +annelids, the immediate effect is a characteristic change of the surface of +the egg, namely the formation of the so-called membrane of fertilisation. +The writer found that we can produce this membrane in the unfertilised egg +by certain acids, especially the monobasic acids of the fatty series, e.g. +formic, acetic, propionic, butyric, etc. Carbon-dioxide is also very +efficient in this direction. It was also found that the higher acids are +more efficient than the lower ones, and it is possible that the +spermatozoon induces membrane-formation by carrying into the egg a higher +fatty acid, namely oleic acid or one of its salts or esters. + +The physico-chemical process which underlies the formation of the membrane +seems to be the cause of the development of the egg. In all cases in which +the unfertilised egg has been treated in such a way as to cause it to form +a membrane it begins to develop. For the eggs of certain animals membrane- +formation is all that is required to induce a complete development of the +unfertilised egg, e.g. in the starfish and certain annelids. For the eggs +of other animals a second treatment is necessary, presumably to overcome +some of the injurious effects of acid treatment. Thus the unfertilised +eggs of the sea-urchin Strongylocentrotus purpuratus of the Californian +coast begin to develop when membrane-formation has been induced by +treatment with a fatty acid, e.g. butyric acid; but the development soon +ceases and the eggs perish in the early stages of segmentation, or after +the first nuclear division. But if we treat the same eggs, after membrane- +formation, for from 35 to 55 minutes (at 15 deg C.) with sea-water the +concentration (osmotic pressure) of which has been raised through the +addition of a definite amount of some salt or sugar, the eggs will segment +and develop normally, when transferred back to normal sea-water. If care +is taken, practically all the eggs can be caused to develop into plutei, +the majority of which may be perfectly normal and may live as long as +larvae produced from eggs fertilised with sperm. + +It is obvious that the sea-urchin egg is injured in the process of +membrane-formation and that the subsequent treatment with a hypertonic +solution only acts as a remedy. The nature of this injury became clear +when it was discovered that all the agencies which cause haemolysis, i.e. +the destruction of the red blood corpuscles, also cause membrane-formation +in unfertilised eggs, e.g. fatty acids or ether, alcohols or chloroform, +etc., or saponin, solanin, digitalin, bile salts and alkali. It thus +happens that the phenomena of artificial parthenogenesis are linked +together with the phenomena of haemolysis which at present play so +important a role in the study of immunity. The difference between +cytolysis (or haemolysis) and fertilisation seems to be this, that the +latter is caused by a superficial or slight cytolysis of the egg, while if +the cytolytic agencies have time to act on the whole egg the latter is +completely destroyed. If we put unfertilised eggs of a sea-urchin into +sea-water which contains a trace of saponin we notice that, after a few +minutes, all the eggs form the typical membrane of fertilisation. If the +eggs are then taken out of the saponin solution, freed from all traces of +saponin by repeated washing in normal sea-water, and transferred to the +hypertonic sea-water for from 35 to 55 minutes, they develop into larvae. +If, however, they are left in the sea-water containing the saponin they +undergo, a few minutes after membrane-formation, the disintegration known +in pathology as CYTOLYSIS. Membrane-formation is, therefore, caused by a +superficial or incomplete cytolysis. The writer believes that the +subsequent treatment of the egg with hypertonic sea-water is needed only to +overcome the destructive effects of this partial cytolysis. The full +reasons for this belief cannot be given in a short essay. + +Many pathologists assume that haemolysis or cytolysis is due to a +liquefaction of certain fatty or fat-like compounds, the so-called lipoids, +in the cell. If this view is correct, it would be necessary to ascribe the +fertilisation of the egg to the same process. + +The analogy between haemolysis and fertilisation throws, possibly, some +light on a curious observation. It is well known that the blood +corpuscles, as a rule, undergo cytolysis if injected into the blood of an +animal which belongs to a different family. The writer found last year +that the blood of mammals, e.g. the rabbit, pig, and cattle, causes the egg +of Strongylocentrotus to form a typical fertilisation-membrane. If such +eggs are afterwards treated for a short period with hypertonic sea-water +they develop into normal larvae (plutei). Some substance contained in the +blood causes, presumably, a superficial cytolysis of the egg and thus +starts its development. + +We can also cause the development of the sea-urchin egg without membrane- +formation. The early experiments of the writer were done in this way and +many experimenters still use such methods. It is probable that in this +case the mechanism of fertilisation is essentially the same as in the case +where the membrane-formation is brought about, with this difference only, +that the cytolytic effect is less when no fertilisation-membrane is formed. +This inference is corroborated by observations on the fertilisation of the +sea-urchin egg with ox blood. It very frequently happens that not all of +the eggs form membranes in this process. Those eggs which form membranes +begin to develop, but perish if they are not treated with hypertonic sea- +water. Some of the other eggs, however, which do not form membranes, +develop directly into normal larvae without any treatment with hypertonic +sea-water, provided they are exposed to the blood for only a few minutes. +Presumably some blood enters the eggs and causes the cytolytic effects in a +less degree than is necessary for membrane-formation, but in a sufficient +degree to cause their development. The slightness of the cytolytic effect +allows the egg to develop without treatment with hypertonic sea-water. + +Since the entrance of the spermatozoon causes that degree of cytolysis +which leads to membrane-formation, it is probable that, in addition to the +cytolytic or membrane-forming substance (presumably a higher fatty acid), +it carries another substance into the egg which counteracts the deleterious +cytolytic effects underlying membrane-formation. + +The question may be raised whether the larvae produced by artificial +parthenogenesis can reach the mature stage. This question may be answered +in the affirmative, since Delage has succeeded in raising several +parthenogenetic sea-urchin larvae beyond the metamorphosis into the adult +stage and since in all the experiments made by the writer the +parthenogenetic plutei lived as long as the plutei produced from fertilised +eggs. + +(c). ON THE PRODUCTION OF TWINS FROM ONE EGG THROUGH A CHANGE IN THE +CHEMICAL CONSTITUTION OF THE SEA-WATER. + +The reader is probably familiar with the fact that there exist two +different types of human twins. In the one type the twins differ as much +as two children of the same parents born at different periods; they may or +may not have the same sex. In the second type the twins have invariably +the same sex and resemble each other most closely. Twins of the latter +type are produced from the same egg, while twins of the former type are +produced from two different eggs. + +The experiments of Driesch and others have taught us that twins originate +from one egg in this manner, namely, that the first two cells into which +the egg divides after fertilisation become separated from each other. This +separation can be brought about by a change in the chemical constitution of +the sea-water. Herbst observed that if the fertilised eggs of the sea- +urchin are put into sea-water which is freed from calcium, the cells into +which the egg divides have a tendency to fall apart. Driesch afterwards +noticed that eggs of the sea-urchin treated with sea-water which is free +from lime have a tendency to give rise to twins. The writer has recently +found that twins can be produced not only by the absence of lime, but also +through the absence of sodium or of potassium; in other words, through the +absence of one or two of the three important metals in the sea-water. +There is, however, a second condition, namely, that the solution used for +the production of twins must have a neutral or at least not an alkaline +reaction. + +The procedure for the production of twins in the sea-urchin egg consists +simply in this:--the eggs are fertilised as usual in normal sea-water and +then, after repeated washing in a neutral solution of sodium chloride (of +the concentration of the sea-water), are placed in a neutral mixture of +potassium chloride and calcium chloride, or of sodium chloride and +potassium chloride, or of sodium chloride and calcium chloride, or of +sodium chloride and magnesium chloride. The eggs must remain in this +solution until half an hour or an hour after they have reached the two-cell +stage. They are then transferred into normal sea-water and allowed to +develop. From 50 to 90 per cent of the eggs of Strongylocentrotus +purpuratus treated in this manner may develop into twins. These twins may +remain separate or grow partially together and form double monsters, or +heal together so completely that only slight or even no imperfections +indicate that the individual started its career as a pair of twins. It is +also possible to control the tendency of such twins to grow together by a +change in the constitution of the sea-water. If we use as a twin-producing +solution a mixture of sodium, magnesium and potassium chlorides (in the +proportion in which these salts exist in the sea-water) the tendency of the +twins to grow together is much more pronounced than if we use simply a +mixture of sodium chloride and magnesium chloride. + +The mechanism of the origin of twins, as the result of altering the +composition of the sea-water, is revealed by observation of the first +segmentation of the egg in these solutions. This cell-division is modified +in a way which leads to a separation of the first two cells. If the egg is +afterwards transferred back into normal sea-water, each of these two cells +develops into an independent embryo. Since normal sea-water contains all +three metals, sodium, calcium, and potassium, and since it has besides an +alkaline reaction, we perceive the reason why twins are not normally +produced from one egg. These experiments suggest the possibility of a +chemical cause for the origin of twins from one egg or of double +monstrosities in mammals. If, for some reason, the liquids which surround +the human egg a short time before and after the first cell-division are +slightly acid, and at the same time lacking in one of the three important +metals, the conditions for the separation of the first two cells and the +formation of identical twins are provided. + +In conclusion it may be pointed out that the reverse result, namely, the +fusion of normally double organs, can also be brought about experimentally +through a change in the chemical constitution of the sea-water. Stockard +succeeded in causing the eyes of fish embryos (Fundulus heteroclitus) to +fuse into a single cyclopean eye through the addition of magnesium chloride +to the sea-water. When he added about 6 grams of magnesium chloride to 100 +cubic centimetres of sea-water and placed the fertilised eggs in the +mixture, about 50 per cent of the eggs gave rise to one-eyed embryos. +"When the embryos were studied the one-eyed condition was found to result +from the union or fusion of the 'anlagen' of the two eyes. Cases were +observed which showed various degrees in this fusion; it appeared as though +the optic vessels were formed too far forward and ventral, so that their +antero-ventro-median surfaces fused. This produces one large optic cup, +which in all cases gives more or less evidence of its double nature." +(Stockard, "Archiv f. Entwickelungsmechanik", Vol. 23, page 249, 1907.) + +We have confined ourselves to a discussion of rather simple effects of the +change in the constitution of the sea-water upon development. It is a +priori obvious, however, that an unlimited number of pathological +variations might be produced by a variation in the concentration and +constitution of the sea-water, and experience confirms this statement. As +an example we may mention the abnormalities observed by Herbst in the +development of sea-urchins through the addition of lithium to sea-water. +It is, however, as yet impossible to connect in a rational way the effects +produced in this and similar cases with the cause which produced them; and +it is also impossible to define in a simple way the character of the change +produced. + +III. THE INFLUENCE OF TEMPERATURE. + +(a) THE INFLUENCE OF TEMPERATURE UPON THE DENSITY OF PELAGIC ORGANISMS AND +THE DURATION OF LIFE. + +It has often been noticed by explorers who have had a chance to compare the +faunas in different climates that in polar seas such species as thrive at +all in those regions occur, as a rule, in much greater density than they do +in the moderate or warmer regions of the ocean. This refers to those +members of the fauna which live at or near the surface, since they alone +lend themselves to a statistical comparison. In his account of the +Valdivia expedition, Chun (Chun, "Aus den Tiefen des Weltmeeres", page 225, +Jena, 1903.) calls especial attention to this quantitative difference in +the surface fauna and flora of different regions. "In the icy water of the +Antarctic, the temperature of which is below 0 deg C., we find an +astonishingly rich animal and plant life. The same condition with which we +are familiar in the Arctic seas is repeated here, namely, that the quantity +of plankton material exceeds that of the temperate and warm seas." And +again, in regard to the pelagic fauna in the region of the Kerguelen +Islands, he states: "The ocean is alive with transparent jelly fish, +Ctenophores (Bolina and Callianira) and of Siphonophore colonies of the +genus Agalma." + +The paradoxical character of this general observation lies in the fact that +a low temperature retards development, and hence should be expected to have +the opposite effect from that mentioned by Chun. Recent investigations +have led to the result that life-phenomena are affected by temperature in +the same sense as the velocity of chemical reactions. In the case of the +latter van't Hoff had shown that a decrease in temperature by 10 degrees +reduces their velocity to one half or less, and the same has been found for +the influence of temperature on the velocity of physiological processes. +Thus Snyder and T.B. Robertson found that the rate of heartbeat in the +tortoise and in Daphnia is reduced to about one-half if the temperature is +lowered 10 deg C., and Maxwell, Keith Lucas, and Snyder found the same +influence of temperature for the rate with which an impulse travels in the +nerve. Peter observed that the rate of development in a sea-urchin's egg +is reduced to less than one-half if the temperature (within certain limits) +is reduced by 10 degrees. The same effect of temperature upon the rate of +development holds for the egg of the frog, as Cohen and Peter calculated +from the experiments of O. Hertwig. The writer found the same temperature- +coefficient for the rate of maturation of the egg of a mollusc (Lottia). + +All these facts prove that the velocity of development of animal life in +Arctic regions, where the temperature is near the freezing point of water, +must be from two to three times smaller than in regions where the +temperature of the ocean is about 10 deg C. and from four to nine times +smaller than in seas the temperature of which is about 20 deg C. It is, +therefore, exactly the reverse of what we should expect when authors state +that the density of organisms at or near the surface of the ocean in polar +regions is greater than in more temperate regions. + +The writer believes that this paradox finds its explanation in experiments +which he has recently made on the influence of temperature on the duration +of life of cold-blooded marine animals. The experiments were made on the +fertilised and unfertilised eggs of the sea-urchin, and yielded the result +that for the lowering of temperature by 1 deg C. the duration of life was +about doubled. Lowering the temperature by 10 degrees therefore prolongs +the life of the organism 2 to the power 10, i.e. over a thousand times, and +a lowering by 20 degrees prolongs it about one million times. Since this +prolongation of life is far in excess of the retardation of development +through a lowering of temperature, it is obvious that, in spite of the +retardation of development in Arctic seas, animal life must be denser there +than in temperate or tropical seas. The excessive increase of the duration +of life at the poles will necessitate the simultaneous existence of more +successive generations of the same species in these regions than in the +temperate or tropical regions. + +The writer is inclined to believe that these results have some bearing upon +a problem which plays an important role in theories of evolution, namely, +the cause of natural death. It has been stated that the processes of +differentiation and development lead also to the natural death of the +individual. If we express this in chemical terms it means that the +chemical processes which underlie development also determine natural death. +Physical chemistry has taught us to identify two chemical processes even if +only certain of their features are known. One of these means of +identification is the temperature coefficient. When two chemical processes +are identical, their velocity must be reduced by the same amount if the +temperature is lowered to the same extent. The temperature coefficient for +the duration of life of cold-blooded organisms seems, however, to differ +enormously from the temperature coefficient for their rate of development. +For a difference in temperature of 10 deg C. the duration of life is +altered five hundred times as much as the rate of development; and, for a +change of 20 deg C., it is altered more than a hundred thousand times as +much. From this we may conclude that, at least for the sea-urchin eggs and +embryo, the chemical processes which determine natural death are certainly +not identical with the processes which underlie their development. T.B. +Robertson has also arrived at the conclusion, for quite different reasons, +that the process of senile decay is essentially different from that of +growth and development. + +(b) CHANGES IN THE COLOUR OF BUTTERFLIES PRODUCED THROUGH THE INFLUENCE OF +TEMPERATURE. + +The experiments of Dorfmeister, Weismann, Merrifield, Standfuss, and +Fischer, on seasonal dimorphism and the aberration of colour in butterflies +have so often been discussed in biological literature that a short +reference to them will suffice. By seasonal dimorphism is meant the fact +that species may appear at different seasons of the year in a somewhat +different form or colour. Vanessa prorsa is the summer form, Vanessa +levana the winter form of the same species. By keeping the pupae of +Vanessa prorsa several weeks at a temperature of from 0 deg to 1 deg +Weismann succeeded in obtaining from the summer chrysalids specimens which +resembled the winter variety, Vanessa levana. + +If we wish to get a clear understanding of the causes of variation in the +colour and pattern of butterflies, we must direct our attention to the +experiments of Fischer, who worked with more extreme temperatures than his +predecessors, and found that almost identical aberrations of colour could +be produced by both extremely high and extremely low temperatures. This +can be clearly seen from the following tabulated results of his +observations. At the head of each column the reader finds the temperature +to which Fischer submitted the pupae, and in the vertical column below are +found the varieties that were produced. In the vertical column A are given +the normal forms: + +(Temperatures in deg C.) +0 to -20 0 to +10 A. +35 to +37 +36 to +41 +42 to +46 + (Normal forms) + +ichnusoides polaris urticae ichnusa polaris ichnusoides + (nigrita) (nigrita) + +antigone fischeri io - fischeri antigone + (iokaste) (iokaste) + +testudo dixeyi polychloros erythromelas dixeyi testudo + +hygiaea artemis antiopa epione artemis hygiaea + +elymi wiskotti cardui - wiskotti elymi + +klymene merrifieldi atalanta - merrifieldi klymene + +weismanni porima prorsa - porima weismanni + +The reader will notice that the aberrations produced at a very low +temperature (from 0 to -20 deg C.) are absolutely identical with the +aberrations produced by exposing the pupae to extremely high temperatures +(42 to 46 deg C.). Moreover the aberrations produced by a moderately low +temperature (from 0 to 10 deg C.) are identical with the aberrations +produced by a moderately high temperature (36 to 41 deg C.) + +From these observations Fischer concludes that it is erroneous to speak of +a specific effect of high and of low temperatures, but that there must be a +common cause for the aberration found at the high as well as at the low +temperature limits. This cause he seems to find in the inhibiting effects +of extreme temperatures upon development. + +If we try to analyse such results as Fischer's from a physico-chemical +point of view, we must realise that what we call life consists of a series +of chemical reactions, which are connected in a catenary way; inasmuch as +one reaction or group of reactions (a) (e.g. hydrolyses) causes or +furnishes the material for a second reaction or group of reactions (b) +(e.g. oxydations). We know that the temperature coefficient for +physiological processes varies slightly at various parts of the scale; as a +rule it is higher near 0 and lower near 30 deg. But we know also that the +temperature coefficients do not vary equally from the various physiological +processes. It is, therefore, to be expected that the temperature +coefficients for the group of reactions of the type (a) will not be +identical through the whole scale with the temperature coefficients for the +reactions of the type (b). If therefore a certain substance is formed at +the normal temperature of the animal in such quantities as are needed for +the catenary reaction (b), it is not to be expected that this same perfect +balance will be maintained for extremely high or extremely low +temperatures; it is more probable that one group of reactions will exceed +the other and thus produce aberrant chemical effects, which may underlie +the colour aberrations observed by Fischer and other experimenters. + +It is important to notice that Fischer was also able to produce aberrations +through the application of narcotics. Wolfgang Ostwald has produced +experimentally, through variation of temperature, dimorphism of form in +Daphnia. Lack of space precludes an account of these important +experiments, as of so many others. + +IV. THE EFFECTS OF LIGHT. + +At the present day nobody seriously questions the statement that the action +of light upon organisms is primarily one of a chemical character. While +this chemical action is of the utmost importance for organisms, the +nutrition of which depends upon the action of chlorophyll, it becomes of +less importance for organisms devoid of chlorophyll. Nevertheless, we find +animals in which the formation of organs by regeneration is not possible +unless they are exposed to light. An observation made by the writer on the +regeneration of polyps in a hydroid, Eudendrium racemosum, at Woods Hole, +may be mentioned as an instance of this. If the stem of this hydroid, +which is usually covered with polyps, is put into an aquarium the polyps +soon fall off. If the stems are kept in an aquarium where light strikes +them during the day, a regeneration of numerous polyps takes place in a few +days. If, however, the stems of Eudendrium are kept permanently in the +dark, no polyps are formed even after an interval of some weeks; but they +are formed in a few days after the same stems have been transferred from +the dark to the light. Diffused daylight suffices for this effect. +Goldfarb, who repeated these experiments, states that an exposure of +comparatively short duration is sufficient for this effect, it is possible +that the light favours the formation of substances which are a prerequisite +for the origin of polyps and their growth. + +Of much greater significance than this observation are the facts which show +that a large number of animals assume, to some extent, the colour of the +ground on which they are placed. Pouchet found through experiments upon +crustaceans and fish that this influence of the ground on the colour of +animals is produced through the medium of the eyes. If the eyes are +removed or the animals made blind in another way these phenomena cease. +The second general fact found by Pouchet was that the variation in the +colour of the animal is brought about through an action of the nerves on +the pigment-cells of the skin; the nerve-action being induced through the +agency of the eye. + +The mechanism and the conditions for the change in colouration were made +clear through the beautiful investigations of Keeble and Gamble, on the +colour-change in crustaceans. According to these authors the pigment-cells +can, as a rule, be considered as consisting of a central body from which a +system of more or less complicated ramifications or processes spreads out +in all directions. As a rule, the centre of the cell contains one or more +different pigments which under the influence of nerves can spread out +separately or together into the ramifications. These phenomena of +spreading and retraction of the pigments into or from the ramifications of +the pigment-cells form on the whole the basis for the colour changes under +the influence of environment. Thus Keeble and Gamble observed that +Macromysis flexuosa appears transparent and colourless or grey on sandy +ground. On a dark ground their colour becomes darker. These animals have +two pigments in their chromatophores, a brown pigment and a whitish or +yellow pigment; the former is much more plentiful than the latter. When +the animal appears transparent all the pigment is contained in the centre +of the cells, while the ramifications are free from pigment. When the +animal appears brown both pigments are spread out into the ramifications. +In the condition of maximal spreading the animals appear black. + +This is a comparatively simple case. Much more complicated conditions were +found by Keeble and Gamble in other crustaceans, e.g. in Hippolyte +cranchii, but the influence of the surroundings upon the colouration of +this form was also satisfactorily analysed by these authors. + +While many animals show transitory changes in colour under the influence of +their surroundings, in a few cases permanent changes can be produced. The +best examples of this are those which were observed by Poulton in the +chrysalids of various butterflies, especially the small tortoise-shell. +These experiments are so well known that a short reference to them will +suffice. Poulton (Poulton, E.B., "Colours of Animals" (The International +Scientific Series), London, 1890, page 121.) found that in gilt or white +surroundings the pupae became light coloured and there was often an immense +development of the golden spots, "so that in many cases the whole surface +of the pupae glittered with an apparent metallic lustre. So remarkable was +the appearance that a physicist to whom I showed the chrysalids, suggested +that I had played a trick and had covered them with goldleaf." When black +surroundings were used "the pupae were as a rule extremely dark, with only +the smallest trace, and often no trace at all, of the golden spots which +are so conspicuous in the lighter form." The susceptibility of the animal +to this influence of its surroundings was found to be greatest during a +definite period when the caterpillar undergoes the metamorphosis into the +chrysalis stage. As far as the writer is aware, no physico-chemical +explanation, except possibly Wiener's suggestion of colour-photography by +mechanical colour adaptation, has ever been offered for the results of the +type of those observed by Poulton. + +V. EFFECTS OF GRAVITATION. + +(a) EXPERIMENTS ON THE EGG OF THE FROG. + +Gravitation can only indirectly affect life-phenomena; namely, when we have +in a cell two different non-miscible liquids (or a liquid and a solid) of +different specific gravity, so that a change in the position of the cell or +the organ may give results which can be traced to a change in the position +of the two substances. This is very nicely illustrated by the frog's egg, +which has two layers of very viscous protoplasm one of which is black and +one white. The dark one occupies normally the upper position in the egg +and may therefore be assumed to possess a smaller specific gravity than the +white substance. When the egg is turned with the white pole upwards a +tendency of the white protoplasm to flow down again manifests itself. It +is, however, possible to prevent or retard this rotation of the highly +viscous protoplasm, by compressing the eggs between horizontal glass +plates. Such compression experiments may lead to rather interesting +results, as O. Schultze first pointed out. Pflueger had already shown that +the first plane of division in a fertilised frog's egg is vertical and Roux +established the fact that the first plane of division is identical with the +plane of symmetry of the later embryo. Schultze found that if the frog's +egg is turned upside down at the time of its first division and kept in +this abnormal position, through compression between two glass plates for +about 20 hours, a small number of eggs may give rise to twins. It is +possible, in this case, that the tendency of the black part of the egg to +rotate upwards along the surface of the egg leads to a separation of its +first cells, such a separation leading to the formation of twins. + +T.H. Morgan made an interesting additional observation. He destroyed one +half of the egg after the first segmentation and found that the half which +remained alive gave rise to only one half of an embryo, thus confirming an +older observation of Roux. When, however, Morgan put the egg upside down +after the destruction of one of the first two cells, and compressed the +eggs between two glass plates, the surviving half of the egg gave rise to a +perfect embryo of half size (and not to a half embryo of normal size as +before.) Obviously in this case the tendency of the protoplasm to flow +back to its normal position was partially successful and led to a partial +or complete separation of the living from the dead half; whereby the former +was enabled to form a whole embryo, which, of course, possessed only half +the size of an embryo originating from a whole egg. + +(b) EXPERIMENTS ON HYDROIDS. + +A striking influence of gravitation can be observed in a hydroid, +Antennularia antennina, from the bay of Naples. This hydroid consists of a +long straight main stem which grows vertically upwards and which has at +regular intervals very fine and short bristle-like lateral branches, on the +upper side of which the polyps grow. The main stem is negatively +geotropic, i.e. its apex continues to grow vertically upwards when we put +it obliquely into the aquarium, while the roots grow vertically downwards. +The writer observed that when the stem is put horizontally into the water +the short lateral branches on the lower side give rise to an altogether +different kind of organ, namely, to roots, and these roots grow +indefinitely in length and attach themselves to solid bodies; while if the +stem had remained in its normal position no further growth would have +occurred in the lateral branches. From the upper side of the horizontal +stem new stems grow out, mostly directly from the original stem, +occasionally also from the short lateral branches. It is thus possible to +force upon this hydroid an arrangement of organs which is altogether +different from the hereditary arrangement. The writer had called the +change in the hereditary arrangement of organs or the transformation of +organs by external forces HETEROMORPHOSIS. We cannot now go any further +into this subject, which should, however, prove of interest in relation to +the problem of heredity. + +If it is correct to apply inferences drawn from the observation on the +frog's egg to the behaviour of Antennularia, one might conclude that the +cells of Antennularia also contain non-miscible substances of different +specific gravity, and that wherever the specifically lighter substance +comes in contact with the sea-water (or gets near the surface of the cell) +the growth of a stem is favoured; while contact with the sea-water of the +specifically heavier of the substances, will favour the formation of roots. + +VI. THE EXPERIMENTAL CONTROL OF ANIMAL INSTINCTS. + +(a) EXPERIMENTS ON THE MECHANISM OF HELIOTROPIC REACTIONS IN ANIMALS. + +Since the instinctive reactions of animals are as hereditary as their +morphological character, a discussion of experiments on the physico- +chemical character of the instinctive reactions of animals should not be +entirely omitted from this sketch. It is obvious that such experiments +must begin with the simplest type of instincts, if they are expected to +lead to any results; and it is also obvious that only such animals must be +selected for this purpose, the reactions of which are not complicated by +associative memory, or, as it may preferably be termed, associative +hysteresis. + +The simplest type of instincts is represented by the purposeful motions of +animals to or from a source of energy, e.g. light; and it is with some of +these that we intend to deal here. When we expose winged aphides (after +they have flown away from the plant), or young caterpillars of Porthesia +chrysorrhoea (when they are aroused from their winter sleep) or marine or +freshwater copepods and many other animals, to diffused daylight falling in +from a window, we notice a tendency among these animals to move towards the +source of light. If the animals are naturally sensitive, or if they are +rendered sensitive through the agencies which we shall mention later, and +if the light is strong enough, they move towards the source of light in as +straight a line as the imperfections and peculiarities of their locomotor +apparatus will permit. It is also obvious that we are here dealing with a +forced reaction in which the animals have no more choice in the direction +of their motion than have the iron filings in their arrangement in a +magnetic field. This can be proved very nicely in the case of starving +caterpillars of Porthesia. The writer put such caterpillars into a glass +tube the axis of which was at right angles to the plane of the window: the +caterpillars went to the window side of the tube and remained there, even +if leaves of their food-plant were put into the tube directly behind them. +Under such conditions the animals actually died from starvation, the light +preventing them from turning to the food, which they eagerly ate when the +light allowed them to do so. One cannot say that these animals, which we +call positively helioptropic, are attracted by the light, since it can be +shown that they go towards the source of the light even if in so doing they +move from places of a higher to places of a lower degree of illumination. + +The writer has advanced the following theory of these instinctive +reactions. Animals of the type of those mentioned are automatically +orientated by the light in such a way that symmetrical elements of their +retina (or skin) are struck by the rays of light at the same angle. In +this case the intensity of light is the same for both retinae or +symmetrical parts of the skin. + +This automatic orientation is determined by two factors, first a peculiar +photo-sensitiveness of the retina (or skin), and second a peculiar nervous +connection between the retina and the muscular apparatus. In symmetrically +built heliotropic animals in which the symmetrical muscles participate +equally in locomotion, the symmetrical muscles work with equal energy as +long as the photo-chemical processes in both eyes are identical. If, +however, one eye is struck by stronger light than the other, the +symmetrical muscles will work unequally and in positively heliotropic +animals those muscles will work with greater energy which bring the plane +of symmetry back into the direction of the rays of light and the head +towards the source of light. As soon as both eyes are struck by the rays +of light at the same angle, there is no more reason for the animal to +deviate from this direction and it will move in a straight line. All this +holds good on the supposition that the animals are exposed to only one +source of light and are very sensitive to light. + +Additional proof for the correctness of this theory was furnished through +the experiments of G.H. Parker and S.J. Holmes. The former worked on a +butterfly, Vanessa antiope, the latter on other arthropods. All the +animals were in a marked degree positively heliotropic. These authors +found that if one cornea is blackened in such an animal, it moves +continually in a circle when it is exposed to a source of light, and in +these motions the eye which is not covered with paint is directed towards +the centre of the circle. The animal behaves, therefore, as if the +darkened eye were in the shade. + +(b) THE PRODUCTION OF POSITIVE HELIOTROPISM BY ACIDS AND OTHER MEANS AND +THE PERIODIC DEPTH-MIGRATIONS OF PELAGIC ANIMALS. + +When we observe a dense mass of copepods collected from a freshwater pond, +we notice that some have a tendency to go to the light while others go in +the opposite direction and many, if not the majority, are indifferent to +light. It is an easy matter to make the negatively heliotropic or the +indifferent copepods almost instantly positively heliotropic by adding a +small but definite amount of carbon-dioxide in the form of carbonated water +to the water in which the animals are contained. If the animals are +contained in 50 cubic centimetres of water it suffices to add from three to +six cubic centimetres of carbonated water to make all the copepods +energetically positively heliotropic. This heliotropism lasts about half +an hour (probably until all the carbon-dioxide has again diffused into the +air.) Similar results may be obtained with any other acid. + +The same experiments may be made with another freshwater crustacean, namely +Daphnia, with this difference, however, that it is as a rule necessary to +lower the temperature of the water also. If the water containing the +Daphniae is cooled and at the same time carbon-dioxide added, the animals +which were before indifferent to light now become most strikingly +positively heliotropic. Marine copepods can be made positively heliotropic +by the lowering of the temperature alone, or by a sudden increase in the +concentration of the sea-water. + +These data have a bearing upon the depth-migrations of pelagic animals, as +was pointed out years ago by Theo. T. Groom and the writer. It is well +known that many animals living near the surface of the ocean or freshwater +lakes, have a tendency to migrate upwards towards evening and downwards in +the morning and during the day. These periodic motions are determined to a +large extent, if not exclusively, by the heliotropism of these animals. +Since the consumption of carbon-dioxide by the green plants ceases towards +evening, the tension of this gas in the water must rise and this must have +the effect of inducing positive heliotropism or increasing its intensity. +At the same time the temperature of the water near the surface is lowered +and this also increases the positive heliotropism in the organisms. + +The faint light from the sky is sufficient to cause animals which are in a +high degree positively heliotropic to move vertically upwards towards the +light, as experiments with such pelagic animals, e.g. copepods, have shown. +When, in the morning, the absorption of carbon-dioxide by the green algae +begins again and the temperature of the water rises, the animals lose their +positive heliotropism, and slowly sink down or become negatively +heliotropic and migrate actively downwards. + +These experiments have also a bearing upon the problem of the inheritance +of instincts. The character which is transmitted in this case is not the +tendency to migrate periodically upwards and downwards, but the positive +heliotropism. The tendency to migrate is the outcome of the fact that +periodically varying external conditions induce a periodic change in the +sense and intensity of the heliotropism of these animals. It is of course +immaterial for the result, whether the carbon-dioxide or any other acid +diffuse into the animal from the outside or whether they are produced +inside in the tissue cells of the animals. Davenport and Cannon found that +Daphniae, which at the beginning of the experiment, react sluggishly to +light react much more quickly after they have been made to go to the light +a few times. The writer is inclined to attribute this result to the effect +of acids, e.g. carbon-dioxide, produced in the animals themselves in +consequence of their motion. A similar effect of the acids was shown by +A.D. Waller in the case of the response of nerve to stimuli. + +The writer observed many years ago that winged male and female ants are +positively helioptropic and that their heliotropic sensitiveness increases +and reaches its maximum towards the period of nuptial flight. Since the +workers show no heliotropism it looks as if an internal secretion from the +sexual glands were the cause of their heliotropic sensitiveness. V. +Kellogg has observed that bees also become intensely positively heliotropic +at the period of their wedding flight, in fact so much so that by letting +light fall into the observation hive from above, the bees are prevented +from leaving the hive through the exit at the lower end. + +We notice also the reverse phenomenon, namely, that chemical changes +produced in the animal destroy its heliotropism. The caterpillars of +Porthesia chrysorrhoea are very strongly positively heliotropic when they +are first aroused from their winter sleep. This heliotropic sensitiveness +lasts only as long as they are not fed. If they are kept permanently +without food they remain permanently positively heliotropic until they die +from starvation. It is to be inferred that as soon as these animals take +up food, a substance or substances are formed in their bodies which +diminish or annihilate their heliotropic sensitiveness. + +The heliotropism of animals is identical with the heliotropism of plants. +The writer has shown that the experiments on the effect of acids on the +heliotropism of copepods can be repeated with the same result in Volvox. +It is therefore erroneous to try to explain these heliotropic reactions of +animals on the basis of peculiarities (e.g. vision) which are not found in +plants. + +We may briefly discuss the question of the transmission through the sex +cells of such instincts as are based upon heliotropism. This problem +reduces itself simply to that of the method whereby the gametes transmit +heliotropism to the larvae or to the adult. The writer has expressed the +idea that all that is necessary for this transmission is the presence in +the eyes (or in the skin) of the animal of a photo-sensitive substance. +For the transmission of this the gametes need not contain anything more +than a catalyser or ferment for the synthesis of the photo-sensitive +substance in the body of the animal. What has been said in regard to +animal heliotropism might, if space permitted, be extended, mutatis +mutandis, to geotropism and stereotropism. + +(c) THE TROPIC REACTIONS OF CERTAIN TISSUE-CELLS AND THE MORPHOGENETIC +EFFECTS OF THESE REACTIONS. + +Since plant-cells show heliotropic reactions identical with those of +animals, it is not surprising that certain tissue-cells also show reactions +which belong to the class of tropisms. These reactions of tissue-cells are +of special interest by reason of their bearing upon the inheritance of +morphological characters. An example of this is found in the tiger-like +marking of the yolk-sac of the embryo of Fundulus and in the marking of the +young fish itself. The writer found that the former is entirely, and the +latter at least in part, due to the creeping of the chromatophores upon the +blood-vessels. The chromatophores are at first scattered irregularly over +the yolk-sac and show their characteristic ramifications. There is at that +time no definite relation between blood-vessels and chromatophores. As +soon as a ramification of a chromatophore comes in contact with a blood- +vessel the whole mass of the chromatophore creeps gradually on the blood- +vessel and forms a complete sheath around the vessel, until finally all the +chromatophores form a sheath around the vessels and no more pigment cells +are found in the meshes between the vessels. Nobody who has not actually +watched the process of the creeping of the chromatophores upon the blood- +vessels would anticipate that the tiger-like colouration of the yolk-sac in +the later stages of the development was brought about in this way. Similar +facts can be observed in regard to the first marking of the embryo itself. +The writer is inclined to believe that we are here dealing with a case of +chemotropism, and that the oxygen of the blood may be the cause of the +spreading of the chromatophores around the blood-vessels. Certain +observations seem to indicate the possibility that in the adult the +chromatophores have, in some forms at least, a more rigid structure and are +prevented from acting in the way indicated. It seems to the writer that +such observations as those made on Fundulus might simplify the problem of +the hereditary transmission of certain markings. + +Driesch has found that a tropism underlies the arrangement of the skeleton +in the pluteus larvae of the sea-urchin. The position of this skeleton is +predetermined by the arrangement of the mesenchyme cells, and Driesch has +shown that these cells migrate actively to the place of their destination, +possibly led there under the influence of certain chemical substances. +When Driesch scattered these cells mechanically before their migration, +they nevertheless reached their destination. + +In the developing eggs of insects the nuclei, together with some cytoplasm, +migrate to the periphery of the egg. Herbst pointed out that this might be +a case of chemotropism, caused by the oxygen surrounding the egg. The +writer has expressed the opinion that the formation of the blastula may be +caused generally by a tropic reaction of the blastomeres, the latter being +forced by an outside influence to creep to the surface of the egg. + +These examples may suffice to indicate that the arrangement of definite +groups of cells and the morphological effects resulting therefrom may be +determined by forces lying outside the cells. Since these forces are +ubiquitous and constant it appears as if we were dealing exclusively with +the influence of a gamete; while in reality all that it is necessary for +the gamete to transmit is a certain form of irritability. + +(d) FACTORS WHICH DETERMINE PLACE AND TIME FOR THE DEPOSITION OF EGGS. + +For the preservation of species the instinct of animals to lay their eggs +in places in which the young larvae find their food and can develop is of +paramount importance. A simple example of this instinct is the fact that +the common fly lays its eggs on putrid material which serves as food for +the young larvae. When a piece of meat and of fat of the same animal are +placed side by side, the fly will deposit its eggs upon the meat on which +the larvae can grow, and not upon the fat, on which they would starve. +Here we are dealing with the effect of a volatile nitrogenous substance +which reflexly causes the peristaltic motions for the laying of the egg in +the female fly. + +Kammerer has investigated the conditions for the laying of eggs in two +forms of salamanders, e.g. Salamandra atra and S. maculosa. In both forms +the eggs are fertilised in the body and begin to develop in the uterus. +Since there is room only for a few larvae in the uterus, a large number of +eggs perish and this number is the greater the longer the period of +gestation. It thus happens that when the animals retain their eggs a long +time, very few young ones are born; and these are in a rather advanced +stage of development, owing to the long time which elapsed since they were +fertilised. When the animal lays its eggs comparatively soon after +copulation, many eggs (from 12 to 72) are produced and the larvae are of +course in an early stage of development. In the early stage the larvae +possess gills and can therefore live in water, while in later stages they +have no gills and breathe through their lungs. Kammerer showed that both +forms of Salamandra can be induced to lay their eggs early or late, +according to the physical conditions surrounding them. If they are kept in +water or in proximity to water and in a moist atmosphere they have a +tendency to lay their eggs earlier and a comparatively high temperature +enhances the tendency to shorten the period of gestation. If the +salamanders are kept in comparative dryness they show a tendency to lay +their eggs rather late and a low temperature enhances this tendency. + +Since Salamandra atra is found in rather dry alpine regions with a +relatively low temperature and Salamandra maculosa in lower regions with +plenty of water and a higher temperature, the fact that S. atra bears young +which are already developed and beyond the stage of aquatic life, while S. +maculosa bears young ones in an earlier stage, has been termed adaptation. +Kammerer's experiments, however, show that we are dealing with the direct +effects of definite outside forces. While we may speak of adaptation when +all or some of the variables which determine a reaction are unknown, it is +obviously in the interest of further scientific progress to connect cause +and effect directly whenever our knowledge allows us to do so. + +VII. CONCLUDING REMARKS. + +The discovery of De Vries, that new species may arise by mutation and the +wide if not universal applicability of Mendel's Law to phenomena of +heredity, as shown especially by Bateson and his pupils, must, for the time +being, if not permanently, serve as a basis for theories of evolution. +These discoveries place before the experimental biologist the definite task +of producing mutations by physico-chemical means. It is true that certain +authors claim to have succeeded in this, but the writer wishes to apologise +to these authors for his inability to convince himself of the validity of +their claims at the present moment. He thinks that only continued breeding +of these apparent mutants through several generations can afford convincing +evidence that we are here dealing with mutants rather than with merely +pathological variations. + +What was said in regard to the production of new species by physico- +chemical means may be repeated with still more justification in regard to +the second problem of transformation, namely the making of living from +inanimate matter. The purely morphological imitations of bacteria or cells +which physicists have now and then proclaimed as artificially produced +living beings; or the plays on words by which, e.g. the regeneration of +broken crystals and the regeneration of lost limbs by a crustacean were +declared identical, will not appeal to the biologist. We know that growth +and development in animals and plants are determined by definite although +complicated series of catenary chemical reactions, which result in the +synthesis of a DEFINITE compound or group of compounds, namely, NUCLEINS. + +The nucleins have the peculiarity of acting as ferments or enzymes for +their own synthesis. Thus a given type of nucleus will continue to +synthesise other nuclein of its own kind. This determines the continuity +of a species; since each species has, probably, its own specific nuclein or +nuclear material. But it also shows us that whoever claims to have +succeeded in making living matter from inanimate will have to prove that he +has succeeded in producing nuclein material which acts as a ferment for its +own synthesis and thus reproduces itself. Nobody has thus far succeeded in +this, although nothing warrants us in taking it for granted that this task +is beyond the power of science. + +XV. THE VALUE OF COLOUR IN THE STRUGGLE FOR LIFE. + +By E.B. POULTON. +Hope Professor of Zoology in the University of Oxford. + +INTRODUCTION. + +The following pages have been written almost entirely from the historical +stand-point. Their principal object has been to give some account of the +impressions produced on the mind of Darwin and his great compeer Wallace by +various difficult problems suggested by the colours of living nature. In +order to render the brief summary of Darwin's thoughts and opinions on the +subject in any way complete, it was found necessary to say again much that +has often been said before. No attempt has been made to display as a whole +the vast contribution of Wallace; but certain of its features are +incidentally revealed in passages quoted from Darwin's letters. It is +assumed that the reader is familiar with the well-known theories of +Protective Resemblance, Warning Colours, and Mimicry both Batesian and +Mullerian. It would have been superfluous to explain these on the present +occasion; for a far more detailed account than could have been attempted in +these pages has recently appeared. (Poulton, "Essays on Evolution" Oxford, +1908, pages 293-382.) Among the older records I have made a point of +bringing together the principal observations scattered through the note- +books and collections of W.J. Burchell. These have never hitherto found a +place in any memoir dealing with the significance of the colours of +animals. + +INCIDENTAL COLOURS. + +Darwin fully recognised that the colours of living beings are not +necessarily of value as colours, but that they may be an incidental result +of chemical or physical structure. Thus he wrote to T. Meehan, Oct. 9, +1874: "I am glad that you are attending to the colours of dioecious +flowers; but it is well to remember that their colours may be as +unimportant to them as those of a gall, or, indeed, as the colour of an +amethyst or ruby is to these gems." ("More Letters of Charles Darwin", +Vol. I. pages 354, 355. See also the admirable account of incidental +colours in "Descent of Man" (2nd edition), 1874, pages 261, 262.) + +Incidental colours remain as available assets of the organism ready to be +turned to account by natural selection. It is a probable speculation that +all pigmentary colours were originally incidental; but now and for immense +periods of time the visible tints of animals have been modified and +arranged so as to assist in the struggle with other organisms or in +courtship. The dominant colouring of plants, on the other hand, is an +essential element in the paramount physiological activity of chlorophyll. +In exceptional instances, however, the shapes and visible colours of plants +may be modified in order to promote concealment. + +TELEOLOGY AND ADAPTATION. + +In the department of Biology which forms the subject of this essay, the +adaptation of means to an end is probably more evident than in any other; +and it is therefore of interest to compare, in a brief introductory +section, the older with the newer teleological views. + +The distinctive feature of Natural Selection as contrasted with other +attempts to explain the process of Evolution is the part played by the +struggle for existence. All naturalists in all ages must have known +something of the operations of "Nature red in tooth and claw"; but it was +left for this great theory to suggest that vast extermination is a +necessary condition of progress, and even of maintaining the ground already +gained. + +Realising that fitness is the outcome of this fierce struggle, thus turned +to account for the first time, we are sometimes led to associate the +recognition of adaptation itself too exclusively with Natural Selection. +Adaptation had been studied with the warmest enthusiasm nearly forty years +before this great theory was given to the scientific world, and it is +difficult now to realise the impetus which the works of Paley gave to the +study of Natural History. That they did inspire the naturalists of the +early part of the last century is clearly shown in the following passages. + +In the year 1824 the Ashmolean Museum at Oxford was intrusted to the care +of J.S. Duncan of New College. He was succeeded in this office by his +brother, P.B. Duncan, of the same College, author of a History of the +Museum, which shows very clearly the influence of Paley upon the study of +nature, and the dominant position given to his teachings: "Happily at this +time (1824) a taste for the study of natural history had been excited in +the University by Dr Paley's very interesting work on Natural Theology, and +the very popular lectures of Dr Kidd on Comparative Anatomy, and Dr +Buckland on Geology." In the arrangement of the contents of the Museum the +illustration of Paley's work was given the foremost place by J.S. Duncan: +"The first division proposes to familiarize the eye to those relations of +all natural objects which form the basis of argument in Dr Paley's Natural +Theology; to induce a mental habit of associating the view of natural +phenomena with the conviction that they are the media of Divine +manifestation; and by such association to give proper dignity to every +branch of natural science." ((From "History and Arrangement of the +Ashmolean Museum" by P.B. Duncan: see pages vi, vii of "A Catalogue of the +Ashmolean Museum", Oxford, 1836.) + +The great naturalist, W.J. Burchell, in his classical work shows the same +recognition of adaptation in nature at a still earlier date. Upon the +subject of collections he wrote ("Travels in the Interior of Southern +Africa", London, Vol. I. 1822, page 505. The references to Burchell's +observations in the present essay are adapted from the author's article in +"Report of the British and South African Associations", 1905, Vol. III. +pages 57-110.): "It must not be supposed that these charms (the pleasures +of Nature) are produced by the mere discovery of new objects: it is the +harmony with which they have been adapted by the Creator to each other, and +to the situations in which they are found, which delights the observer in +countries where Art has not yet introduced her discords." The remainder of +the passage is so admirable that I venture to quote it: "To him who is +satisfied with amassing collections of curious objects, simply for the +pleasure of possessing them, such objects can afford, at best, but a +childish gratification, faint and fleeting; while he who extends his view +beyond the narrow field of nomenclature, beholds a boundless expanse, the +exploring of which is worthy of the philosopher, and of the best talents of +a reasonable being." + +On September 14, 1811, Burchell was at Zand Valley (Vlei), or Sand Pool, a +few miles south-west of the site of Prieska, on the Orange River. Here he +found a Mesembryanthemum (M. turbiniforme, now M. truncatum) and also a +"Gryllus" (Acridian), closely resembling the pebbles with which their +locality was strewn. He says of both of these, "The intention of Nature, +in these instances, seems to have been the same as when she gave to the +Chameleon the power of accommodating its color, in a certain degree, to +that of the object nearest to it, in order to compensate for the deficiency +of its locomotive powers. By their form and colour, this insect may pass +unobserved by those birds, which otherwise would soon extirpate a species +so little able to elude its pursuers, and this juicy little +Mesembryanthemum may generally escape the notice of cattle and wild +animals." (Loc. cit. pages 310, 311. See Sir William Thiselton-Dyer +"Morphological Notes", XI.; "Protective Adaptations", I.; "Annals of +Botany", Vol. XX. page 124. In plates VII., VIII. and IX. accompanying +this article the author represents the species observed by Burchell, +together with others in which analogous adaptations exist. He writes: +"Burchell was clearly on the track on which Darwin reached the goal. But +the time had not come for emancipation from the old teleology. This, +however, in no respect detracts from the merit or value of his work. For, +as Huxley has pointed out ("Life and Letters of Thomas Henry Huxley", +London, 1900, I. page 457), the facts of the old teleology are immediately +transferable to Darwinism, which simply supplies them with a natural in +place of a supernatural explanation.") Burchell here seems to miss, at +least in part, the meaning of the relationship between the quiescence of +the Acridian and its cryptic colouring. Quiescence is an essential element +in the protective resemblance to a stone--probably even more indispensable +than the details of the form and colouring. Although Burchell appears to +overlook this point he fully recognised the community between protection by +concealment and more aggressive modes of defence; for, in the passage of +which a part is quoted above, he specially refers to some earlier remarks +on page 226 of his Vol. I. We here find that even when the oxen were +resting by the Juk rivier (Yoke river), on July 19, 1811, Burchell observed +"Geranium spinosum, with a fleshy stem and large white flowers...; and a +succulent species of Pelargonium...so defended by the old panicles, grown +to hard woody thorns, that no cattle could browze upon it." He goes on to +say, "In this arid country, where every juicy vegetable would soon be eaten +up by the wild animals, the Great Creating Power, with all-provident +wisdom, has given to such plants either an acrid or poisonous juice, or +sharp thorns, to preserve the species from annihilation..." All these +modes of defence, especially adapted to a desert environment, have since +been generally recognised, and it is very interesting to place beside +Burchell's statement the following passage from a letter written by Darwin, +Aug. 7, 1868, to G.H. Lewes; "That Natural Selection would tend to produce +the most formidable thorns will be admitted by every one who has observed +the distribution in South America and Africa (vide Livingstone) of thorn- +bearing plants, for they always appear where the bushes grow isolated and +are exposed to the attacks of mammals. Even in England it has been noticed +that all spine-bearing and sting-bearing plants are palatable to +quadrupeds, when the thorns are crushed." ("More Letters", I. page 308.) + +ADAPTATION AND NATURAL SELECTION. + +I have preferred to show the influence of the older teleology upon Natural +History by quotations from a single great and insufficiently appreciated +naturalist. It might have been seen equally well in the pages of Kirby and +Spence and those of many other writers. If the older naturalists who +thought and spoke with Burchell of "the intention of Nature" and the +adaptation of beings "to each other, and to the situations in which they +are found," could have conceived the possibility of evolution, they must +have been led, as Darwin was, by the same considerations to Natural +Selection. This was impossible for them, because the philosophy which they +followed contemplated the phenomena of adaptation as part of a static +immutable system. Darwin, convinced that the system is dynamic and +mutable, was prevented by these very phenomena from accepting anything +short of the crowning interpretation offered by Natural Selection. ("I had +always been much struck by such adaptations (e.g. woodpecker and tree-frog +for climbing, seeds for dispersal), and until these could be explained it +seemed to me almost useless to endeavour to prove by indirect evidence that +species have been modified." "Autobiography" in "Life and Letters of +Charles Darwin", Vol. I. page 82. The same thought is repeated again and +again in Darwin's letters to his friends. It is forcibly urged in the +Introduction to the "Origin" (1859), page 3.) And the birth of Darwin's +unalterable conviction that adaptation is of dominant importance in the +organic world,--a conviction confirmed and ever again confirmed by his +experience as a naturalist--may probably be traced to the influence of the +great theologian. Thus Darwin, speaking of his Undergraduate days, tells +us in his "Autobiography" that the logic of Paley's "Evidences of +Christianity" and "Moral Philosophy" gave him as much delight as did +Euclid. + +"The careful study of these works, without attempting to learn any part by +rote, was the only part of the academical course which, as I then felt and +as I still believe, was of the least use to me in the education of my mind. +I did not at that time trouble myself about Paley's premises; and taking +these on trust, I was charmed and convinced by the long line of +argumentation." ("Life and Letters", I. page 47.) + +When Darwin came to write the "Origin" he quoted in relation to Natural +Selection one of Paley's conclusions. "No organ will be formed, as Paley +has remarked, for the purpose of causing pain or for doing an injury to its +possessor." ("Origin of Species" (1st edition) 1859, page 201.) + +The study of adaptation always had for Darwin, as it has for many, a +peculiar charm. His words, written Nov. 28, 1880, to Sir W. Thiselton- +Dyer, are by no means inapplicable to-day: "Many of the Germans are very +contemptuous about making out use of organs; but they may sneer the souls +out of their bodies, and I for one shall think it the most interesting part +of natural history." ("More Letters" II. page 428.) + +PROTECTIVE AND AGGRESSIVE RESEMBLANCE: PROCRYPTIC AND ANTICRYPTIC +COLOURING. + +Colouring for the purpose of concealment is sometimes included under the +head Mimicry, a classification adopted by H.W. Bates in his classical +paper. Such an arrangement is inconvenient, and I have followed Wallace in +keeping the two categories distinct. + +The visible colours of animals are far more commonly adapted for Protective +Resemblance than for any other purpose. The concealment of animals by +their colours, shapes and attitudes, must have been well known from the +period at which human beings first began to take an intelligent interest in +Nature. An interesting early record is that of Samuel Felton, who (Dec. 2, +1763) figured and gave some account of an Acridian (Phyllotettix) from +Jamaica. Of this insect he says "THE THORAX is like a leaf that is raised +perpendicularly from the body." ("Phil. Trans. Roy. Soc." Vol. LIV. Tab. +VI. page 55.) + +Both Protective and Aggressive Resemblances were appreciated and clearly +explained by Erasmus Darwin in 1794: "The colours of many animals seem +adapted to their purposes of concealing themselves either to avoid danger, +or to spring upon their prey." ("Zoonomia", Vol. I. page 509, London, +1794.) + +Protective Resemblance of a very marked and beautiful kind is found in +certain plants, inhabitants of desert areas. Examples observed by Burchell +almost exactly a hundred years ago have already been mentioned. In +addition to the resemblance to stones Burchell observed, although he did +not publish the fact, a South African plant concealed by its likeness to +the dung of birds. (Sir William Thiselton-Dyer has suggested the same +method of concealment ("Annals of Botany", Vol. XX. page 123). Referring +to Anacampseros papyracea, figured on plate IX., the author says of its +adaptive resemblance: "At the risk of suggesting one perhaps somewhat far- +fetched, I must confess that the aspect of the plant always calls to my +mind the dejecta of some bird, and the more so owing to the whitening of +the branches towards the tips" (loc. cit. page 126). The student of +insects, who is so familiar with this very form of protective resemblance +in larvae, and even perfect insects, will not be inclined to consider the +suggestion far-fetched.) The observation is recorded in one of the +manuscript journals kept by the great explorer during his journey. I owe +the opportunity of studying it to the kindness of Mr Francis A. Burchell of +the Rhodes University College, Grahamstown. The following account is given +under the date July 5, 1812, when Burchell was at the Makkwarin River, +about half-way between the Kuruman River and Litakun the old capital of the +Bachapins (Bechuanas): "I found a curious little Crassula (not in flower) +so snow white, that I should never has (have) distinguished it from the +white limestones...It was an inch high and a little branchy,...and was at +first mistaken for the dung of birds of the passerine order. I have often +had occasion to remark that in stony place(s) there grow many small +succulent plants and abound insects (chiefly Grylli) which have exactly the +same colour as the ground and must for ever escape observation unless a +person sit on the ground and observe very attentively." + +The cryptic resemblances of animals impressed Darwin and Wallace in very +different degrees, probably in part due to the fact that Wallace's tropical +experiences were so largely derived from the insect world, in part to the +importance assigned by Darwin to Sexual Selection "a subject which had +always greatly interested me," as he says in his "Autobiography", ("Life +and Letters", Vol. I. page 94.) There is no reference to Cryptic +Resemblance in Darwin's section of the Joint Essay, although he gives an +excellent short account of Sexual Selection (see page 295). Wallace's +section on the other hand contains the following statement: "Even the +peculiar colours of many animals, especially insects, so closely resembling +the soil or the leaves or the trunks on which they habitually reside, are +explained on the same principle; for though in the course of ages varieties +of many tints may have occurred, YET THOSE RACES HAVING COLOURS BEST +ADAPTED TO CONCEALMENT FROM THEIR ENEMIES WOULD INEVITABLY SURVIVE THE +LONGEST." ("Journ. Proc. Linn. Soc." Vol. III. 1859, page 61. The italics +are Wallace's.) + +It would occupy too much space to attempt any discussion of the difference +between the views of these two naturalists, but it is clear that Darwin, +although fully believing in the efficiency of protective resemblance and +replying to St George Mivart's contention that Natural Selection was +incompetent to produce it ("Origin" (6th edition) London, 1872, pages 181, +182; see also page 66.), never entirely agreed with Wallace's estimate of +its importance. Thus the following extract from a letter to Sir Joseph +Hooker, May 21, 1868, refers to Wallace: "I find I must (and I always +distrust myself when I differ from him) separate rather widely from him all +about birds' nests and protection; he is riding that hobby to death." +("More Letters", I. page 304.) It is clear from the account given in "The +Descent of Man", (London, 1874, pages 452-458. See also "Life and +Letters", III. pages 123-125, and "More Letters", II. pages 59-63, 72-74, +76-78, 84-90, 92, 93.), that the divergence was due to the fact that Darwin +ascribed more importance to Sexual Selection than did Wallace, and Wallace +more importance to Protective Resemblance than Darwin. Thus Darwin wrote +to Wallace, Oct. 12 and 13, 1867: "By the way, I cannot but think that you +push protection too far in some cases, as with the stripes on the tiger." +("More Letters", I. page 283.) Here too Darwin was preferring the +explanation offered by Sexual Selection ("Descent of Man" (2nd edition) +1874, pages 545, 546.), a preference which, considering the relation of the +colouring of the lion and tiger to their respective environments, few +naturalists will be found to share. It is also shown that Darwin +contemplated the possibility of cryptic colours such as those of Patagonian +animals being due to sexual selection influenced by the aspect of +surrounding nature. + +Nearly a year later Darwin in his letter of May 5, 1868?, expressed his +agreement with Wallace's views: "Expect that I should put sexual selection +as an equal, or perhaps as even a more important agent in giving colour +than Natural Selection for protection." ("More Letters", II. pages 77, +78.) The conclusion expressed in the above quoted passage is opposed by +the extraordinary development of Protective Resemblance in the immature +stages of animals, especially insects. + +It must not be supposed, however, that Darwin ascribed an unimportant role +to Cryptic Resemblances, and as observations accumulated he came to +recognise their efficiency in fresh groups of the animal kingdom. Thus he +wrote to Wallace, May 5, 1867: "Haeckel has recently well shown that the +transparency and absence of colour in the lower oceanic animals, belonging +to the most different classes, may be well accounted for on the principle +of protection." ("More Letters", II. page 62. See also "Descent of Man", +page 261.) Darwin also admitted the justice of Professor E.S. Morse's +contention that the shells of molluscs are often adaptively coloured. +("More Letters", II. page 95.) But he looked upon cryptic colouring and +also mimicry as more especially Wallace's departments, and sent to him and +to Professor Meldola observations and notes bearing upon these subjects. +Thus the following letter given to me by Dr A.R. Wallace and now, by kind +permission, published for the first time, accompanied a photograph of the +chrysalis of Papilio sarpedon choredon, Feld., suspended from a leaf of its +food-plant: + +July 9th, +Down, Beckenham, Kent. + +My Dear Wallace, + +Dr G. Krefft has sent me the enclosed from Sydney. A nurseryman saw a +caterpillar feeding on a plant and covered the whole up, but when he +searched for the cocoon (pupa), was long before he could find it, so good +was its imitation in colour and form to the leaf to which it was attached. +I hope that the world goes well with you. Do not trouble yourself by +acknowledging this. + +Ever yours + +Ch. Darwin. + +Another deeply interesting letter of Darwin's bearing upon protective +resemblance, has only recently been shown to me by my friend Professor E.B. +Wilson, the great American Cytologist. With his kind consent and that of +Mr Francis Darwin, this letter, written four months before Darwin's death +on April 19, 1882, is reproduced here (The letter is addressed: "Edmund B. +Wilson, Esq., Assistant in Biology, John Hopkins University, Baltimore Md, +U. States.": + +December 21, 1881. + +Dear Sir, + +I thank you much for having taken so much trouble in describing fully your +interesting and curious case of mimickry. + +I am in the habit of looking through many scientific Journals, and though +my memory is now not nearly so good as it was, I feel pretty sure that no +such case as yours has been described (amongst the nudibranch) molluscs. +You perhaps know the case of a fish allied to Hippocampus, (described some +years ago by Dr Gunther in "Proc. Zoolog. Socy.") which clings by its tail +to sea-weeds, and is covered with waving filaments so as itself to look +like a piece of the same sea-weed. The parallelism between your and Dr +Gunther's case makes both of them the more interesting; considering how far +a fish and a mollusc stand apart. It would be difficult for anyone to +explain such cases by the direct action of the environment.--I am glad that +you intend to make further observations on this mollusc, and I hope that +you will give a figure and if possible a coloured figure. + +With all good wishes from an old brother naturalist, + +I remain, Dear Sir, + +Yours faithfully, + +Charles Darwin. + +Professor E.B. Wilson has kindly given the following account of the +circumstances under which he had written to Darwin: "The case to which +Darwin's letter refers is that of the nudibranch mollusc Scyllaea, which +lives on the floating Sargassum and shows a really astonishing resemblance +to the plant, having leaf-shaped processes very closely similar to the +fronds of the sea-weed both in shape and in colour. The concealment of the +animal may be judged from the fact that we found the animal quite by +accident on a piece of Sargassum that had been in a glass jar in the +laboratory for some time and had been closely examined in the search for +hydroids and the like without disclosing the presence upon it of two large +specimens of the Scyllaea (the animal, as I recall it, is about two inches +long). It was first detected by its movements alone, by someone (I think a +casual visitor to the laboratory) who was looking closely at the Sargassum +and exclaimed 'Why, the sea-weed is moving its leaves'! We found the +example in the summer of 1880 or 1881 at Beaufort, N.C., where the Johns +Hopkins laboratory was located for the time being. It must have been seen +by many others, before or since. + +"I wrote and sent to Darwin a short description of the case at the +suggestion of Brooks, with whom I was at the time a student. I was, of +course, entirely unknown to Darwin (or to anyone else) and to me the +principal interest of Darwin's letter is the evidence that it gives of his +extraordinary kindness and friendliness towards an obscure youngster who +had of course absolutely no claim upon his time or attention. The little +incident made an indelible impression upon my memory and taught me a lesson +that was worth learning." + +VARIABLE PROTECTIVE RESEMBLANCE. + +The wonderful power of rapid colour adjustment possessed by the cuttle-fish +was observed by Darwin in 1832 at St Jago, Cape de Verd Islands, the first +place visited during the voyage of the "Beagle". From Rio he wrote to +Henslow, giving the following account of his observations, May 18, 1832: +"I took several specimens of an Octopus which possessed a most marvellous +power of changing its colours, equalling any chameleon, and evidently +accommodating the changes to the colour of the ground which it passed over. +Yellowish green, dark brown, and red, were the prevailing colours; this +fact appears to be new, as far as I can find out." ("Life and Letters", I. +pages 235, 236. See also Darwin's "Journal of Researches", 1876, pages 6- +8, where a far more detailed account is given together with a reference to +"Encycl. of Anat. and Physiol.") + +Darwin was well aware of the power of individual colour adjustment, now +known to be possessed by large numbers of lepidopterous pupae and larvae. +An excellent example was brought to his notice by C.V. Riley ("More +Letters" II, pages 385, 386.), while the most striking of the early results +obtained with the pupae of butterflies--those of Mrs M.E. Barber upon +Papilio nireus--was communicated by him to the Entomological Society of +London. ("Trans. Ent. Soc. Lond." 1874, page 519. See also "More +Letters", II. page 403.) + +It is also necessary to direct attention to C.W. Beebe's ("Zoologica: N.Y. +Zool. Soc." Vol. I. No. 1, Sept. 25, 1907: "Geographic variation in birds +with especial reference to the effects of humidity".) recent discovery that +the pigmentation of the plumage of certain birds is increased by +confinement in a superhumid atmosphere. In Scardafella inca, on which the +most complete series of experiments was made, the changes took place only +at the moults, whether normal and annual or artificially induced at shorter +periods. There was a corresponding increase in the choroidal pigment of +the eye. At a certain advanced stage of feather pigmentation a brilliant +iridescent bronze or green tint made its appearance on those areas where +iridescence most often occurs in allied genera. Thus in birds no less than +in insects, characters previously regarded as of taxonomic value, can be +evoked or withheld by the forces of the environment. + +WARNING OR APOSEMATIC COLOURS. + +From Darwin's description of the colours and habits it is evident that he +observed, in 1833, an excellent example of warning colouring in a little +South American toad (Phryniscus nigricans). He described it in a letter to +Henslow, written from Monte Video, Nov. 24, 1832: "As for one little toad, +I hope it may be new, that it may be christened 'diabolicus.' Milton must +allude to this very individual when he talks of 'squat like a toad'; its +colours are by Werner ("Nomenclature of Colours", 1821) ink black, +vermilion red and buff orange." ("More Letters", I. page 12.) In the +"Journal of Researches" (1876, page 97.) its colours are described as +follows: "If we imagine, first, that it had been steeped in the blackest +ink, and then, when dry, allowed to crawl over a board, freshly painted +with the brightest vermilion, so as to colour the soles of its feet and +parts of its stomach, a good idea of its appearance will be gained." +"Instead of being nocturnal in its habits, as other toads are, and living +in damp obscure recesses, it crawls during the heat of the day about the +dry sand-hillocks and arid plains,..." The appearance and habits recall T. +Belt's well-known description of the conspicuous little Nicaraguan frog +which he found to be distasteful to a duck. ("The Naturalist in Nicaragua" +(2nd edition) London, 1888, page 321.) + +The recognition of the Warning Colours of caterpillars is due in the first +instance to Darwin, who, reflecting on Sexual Selection, was puzzled by the +splendid colours of sexually immature organisms. He applied to Wallace +"who has an innate genius for solving difficulties." ("Descent of Man", +page 325. On this and the following page an excellent account of the +discovery will be found, as well as in Wallace's "Natural Selection", +London, 1875, pages 117-122.) Darwin's original letter exists ("Life and +Letters", III. pages 93, 94.), and in it we are told that he had taken the +advice given by Bates: "You had better ask Wallace." After some +consideration Wallace replied that he believed the colours of conspicuous +caterpillars and perfect insects were a warning of distastefulness and that +such forms would be refused by birds. Darwin's reply ("Life and Letters", +III. pages 94, 95.) is extremely interesting both for its enthusiasm at the +brilliancy of the hypothesis and its caution in acceptance without full +confirmation: + +"Bates was quite right; you are the man to apply to in a difficulty. I +never heard anything more ingenious than your suggestion, and I hope you +may be able to prove it true. That is a splendid fact about the white +moths (A single white moth which was rejected by young turkeys, while other +moths were greedily devoured: "Natural Selection", 1875, page 78.); it +warms one's very blood to see a theory thus almost proved to be true." + +Two years later the hypothesis was proved to hold for caterpillars of many +kinds by J. Jenner Weir and A.G. Butler, whose observations have since been +abundantly confirmed by many naturalists. Darwin wrote to Weir, May 13, +1869: "Your verification of Wallace's suggestion seems to me to amount to +quite a discovery." ("More Letters", II. page 71 (footnote).) + +RECOGNITION OR EPISEMATIC CHARACTERS. + +This principle does not appear to have been in any way foreseen by Darwin, +although he draws special attention to several elements of pattern which +would now be interpreted by many naturalists as epismes. He believed that +the markings in question interfered with the cryptic effect, and came to +the conclusion that, even when common to both sexes, they "are the result +of sexual selection primarily applied to the male." ("Descent of Man", +page 544.) The most familiar of all recognition characters was carefully +explained by him, although here too explained as an ornamental feature now +equally transmitted to both sexes: "The hare on her form is a familiar +instance of concealment through colour; yet this principle partly fails in +a closely-allied species, the rabbit, for when running to its burrow, it is +made conspicuous to the sportsman, and no doubt to all beasts of prey, by +its upturned white tail." ("Descent of Man", page 542.) + +The analogous episematic use of the bright colours of flowers to attract +insects for effecting cross-fertilisation and of fruits to attract +vertebrates for effecting dispersal is very clearly explained in the +"Origin". (Edition 1872, page 161. For a good example of Darwin's caution +in dealing with exceptions see the allusion to brightly coloured fruit in +"More Letters", II. page 348.) + +It is not, at this point, necessary to treat sematic characters at any +greater length. They will form the subject of a large part of the +following section, where the models of Batesian (Pseudaposematic) mimicry +are considered as well as the Mullerian (Synaposematic) combinations of +Warning Colours. + +MIMICRY,--BATESIAN OR PSEUDAPOSEMATIC, MULLERIAN OR SYNAPOSEMATIC. + +The existence of superficial resemblances between animals of various +degrees of affinity must have been observed for hundreds of years. Among +the early examples, the best known to me have been found in the manuscript +note-books and collections of W.J. Burchell, the great traveller in Africa +(1810-15) and Brazil (1825-30). The most interesting of his records on +this subject are brought together in the following paragraphs. + +Conspicuous among well-defended insects are the dark steely or iridescent +greenish blue fossorial wasps or sand-wasps, Sphex and the allied genera. +Many Longicorn beetles mimic these in colour, slender shape of body and +limbs, rapid movements, and the readiness with which they take to flight. +On Dec. 21, 1812, Burchell captured one such beetle (Promeces viridis) at +Kosi Fountain on the journey from the source of the Kuruman River to +Klaarwater. It is correctly placed among the Longicorns in his catalogue, +but opposite to its number is the comment "Sphex! totus purpureus." + +In our own country the black-and-yellow colouring of many stinging insects, +especially the ordinary wasps, affords perhaps the commonest model for +mimicry. It is reproduced with more or less accuracy on moths, flies and +beetles. Among the latter it is again a Longicorn which offers one of the +best-known, although by no means one of the most perfect, examples. The +appearance of the well-known "wasp-beetle" (Clytus arietis) in the living +state is sufficiently suggestive to prevent the great majority of people +from touching it. In Burchell's Brazilian collection there is a nearly +allied species (Neoclytus curvatus) which appears to be somewhat less wasp- +like than the British beetle. The specimen bears the number "1188," and +the date March 27, 1827, when Burchell was collecting in the neighbourhood +of San Paulo. Turning to the corresponding number in the Brazilian note- +book we find this record: "It runs rapidly like an ichneumon or wasp, of +which it has the appearance." + +The formidable, well-defended ants are as freely mimicked by other insects +as the sand-wasps, ordinary wasps and bees. Thus on February 17, 1901, Guy +A.K. Marshall captured, near Salisbury, Mashonaland, three similar species +of ants (Hymenoptera) with a bug (Hemiptera) and a Locustid (Orthoptera), +the two latter mimicking the former. All the insects, seven in number, +were caught on a single plant, a small bushy vetch. ("Trans. Ent. Soc. +Lond." 1902, page 535, plate XIX. figs. 53-59.) + +This is an interesting recent example from South Africa, and large numbers +of others might be added--the observations of many naturalists in many +lands; but nearly all of them known since that general awakening of +interest in the subject which was inspired by the great hypotheses of H.W. +Bates and Fritz Muller. We find, however, that Burchell had more than once +recorded the mimetic resemblance to ants. An extremely ant-like bug (the +larva of a species of Alydus) in his Brazilian collection is labelled +"1141," with the date December 8, 1826, when Burchell was at the Rio das +Pedras, Cubatao, near Santos. In the note-book the record is as follows: +"1141 Cimex. I collected this for a Formica." + +Some of the chief mimics of ants are the active little hunting spiders +belonging to the family Attidae. Examples have been brought forward during +many recent years, especially by my friends Dr and Mrs Peckham, of +Milwaukee, the great authorities on this group of Araneae. Here too we +find an observation of the mimetic resemblance recorded by Burchell, and +one which adds in the most interesting manner to our knowledge of the +subject. A fragment, all that is now left, of an Attid spider, captured on +June 30, 1828, at Goyaz, Brazil, bears the following note, in this case on +the specimen and not in the note-book: "Black...runs and seems like an ant +with large extended jaws." My friend Mr R.I. Pocock, to whom I have +submitted the specimen, tells me that it is not one of the group of species +hitherto regarded as ant-like, and he adds, "It is most interesting that +Burchell should have noticed the resemblance to an ant in its movements. +This suggests that the perfect imitation in shape, as well as in movement, +seen in many species was started in forms of an appropriate size and colour +by the mimicry of movement alone." Up to the present time Burchell is the +only naturalist who has observed an example which still exhibits this +ancestral stage in the evolution of mimetic likeness. + +Following the teachings of his day, Burchell was driven to believe that it +was part of the fixed and inexorable scheme of things that these strange +superficial resemblances existed. Thus, when he found other examples of +Hemipterous mimics, including one (Luteva macrophthalma) with "exactly the +manners of a Mantis," he added the sentence, "In the genus Cimex (Linn.) +are to be found the outward resemblances of insects of many other genera +and orders" (February 15, 1829). Of another Brazilian bug, which is not to +be found in his collection, and cannot therefore be precisely identified, +he wrote: "Cimex...Nature seems to have intended it to imitate a Sphex, +both in colour and the rapid palpitating and movement of the antennae" +(November 15, 1826). At the same time it is impossible not to feel the +conviction that Burchell felt the advantage of a likeness to stinging +insects and to aggressive ants, just as he recognised the benefits +conferred on desert plants by spines and by concealment. Such an +interpretation of mimicry was perfectly consistent with the theological +doctrines of his day. (See Kirby and Spence, "An Introduction to +Entomology" (1st edition), London, Vol. II. 1817, page 223.) + +The last note I have selected from Burchell's manuscript refers to one of +the chief mimics of the highly protected Lycid beetles. The whole +assemblage of African insects with a Lycoid colouring forms a most +important combination and one which has an interesting bearing upon the +theories of Bates and Fritz Muller. This most wonderful set of mimetic +forms, described in 1902 by Guy A.K. Marshall, is composed of flower- +haunting beetles belonging to the family Lycidae, and the heterogeneous +group of varied insects which mimic their conspicuous and simple scheme of +colouring. The Lycid beetles, forming the centre or "models" of the whole +company, are orange-brown in front for about two-thirds of the exposed +surface, black behind for the remaining third. They are undoubtedly +protected by qualities which make them excessively unpalatable to the bulk +of insect-eating animals. Some experimental proof of this has been +obtained by Mr Guy Marshall. What are the forms which surround them? +According to the hypothesis of Bates they would be, at any rate mainly, +palatable hard-pressed insects which only hold their own in the struggle +for life by a fraudulent imitation of the trade-mark of the successful and +powerful Lycidae. According to Fritz Muller's hypothesis we should expect +that the mimickers would be highly protected, successful and abundant +species, which (metaphorically speaking) have found it to their advantage +to possess an advertisement, a danger-signal, in common with each other, +and in common with the beetles in the centre of the group. + +How far does the constitution of this wonderful combination--the largest +and most complicated as yet known in all the world--convey to us the idea +of mimicry working along the lines supposed by Bates or those suggested by +Muller? Figures 1 to 52 of Mr Marshall's coloured plate ("Trans. Ent. Soc. +Lond." 1902, plate XVIII. See also page 517, where the group is analysed.) +represent a set of forty-two or forty-three species or forms of insects +captured in Mashonaland, and all except two in the neighbourhood of +Salisbury. The combination includes six species of Lycidae; nine beetles +of five groups all specially protected by nauseous qualities, Telephoridae, +Melyridae, Phytophaga, Lagriidae, Cantharidae; six Longicorn beetles; one +Coprid beetle; eight stinging Hymenoptera; three or four parasitic +Hymenoptera (Braconidae, a group much mimicked and shown by some +experiments to be distasteful); five bugs (Hemiptera, a largely unpalatable +group); three moths (Arctiidae and Zygaenidae, distasteful families); one +fly. In fact the whole combination, except perhaps one Phytophagous, one +Coprid and the Longicorn beetles, and the fly, fall under the hypothesis of +Muller and not under that of Bates. And it is very doubtful whether these +exceptions will be sustained: indeed the suspicion of unpalatability +already besets the Longicorns and is always on the heels,--I should say the +hind tarsi--of a Phytophagous beetle. + +This most remarkable group which illustrates so well the problem of mimicry +and the alternative hypotheses proposed for its solution, was, as I have +said, first described in 1902. Among the most perfect of the mimetic +resemblances in it is that between the Longicorn beetle, Amphidesmus +analis, and the Lycidae. It was with the utmost astonishment and pleasure +that I found this very resemblance had almost certainly been observed by +Burchell. A specimen of the Amphidesmus exists in his collection and it +bears "651." Turning to the same number in the African Catalogue we find +that the beetle is correctly placed among the Longicorns, that it was +captured at Uitenhage on Nov. 18, 1813, and that it was found associated +with Lycid beetles in flowers ("consocians cum Lycis 78-87 in floribus"). +Looking up Nos. 78-87 in the collection and catalogue, three species of +Lycidae are found, all captured on Nov. 18, 1813, at Uitenhage. Burchell +recognised the wide difference in affinity, shown by the distance between +the respective numbers; for his catalogue is arranged to represent +relationships. He observed, what students of mimicry are only just +beginning to note and record, the coincidence between model and mimic in +time and space and in habits. We are justified in concluding that he +observed the close superficial likeness although he does not in this case +expressly allude to it. + +One of the most interesting among the early observations of superficial +resemblance between forms remote in the scale of classification was made by +Darwin himself, as described in the following passage from his letter to +Henslow, written from Monte Video, Aug. 15, 1832: "Amongst the lower +animals nothing has so much interested me as finding two species of +elegantly coloured true Planaria inhabiting the dewy forest! The false +relation they bear to snails is the most extraordinary thing of the kind I +have ever seen." ("More Letters", I. page 9.) + +Many years later, in 1867, he wrote to Fritz Muller suggesting that the +resemblance of a soberly coloured British Planarian to a slug might be due +to mimicry. ("Life and Letters", III. page 71.) + +The most interesting copy of Bates's classical memoir on Mimicry +("Contributions to an Insect Fauna of the Amazon Valley". "Trans. Linn. +Soc." Vol. XXIII. 1862, page 495.), read before the Linnean Society in +1861, is that given by him to the man who has done most to support and +extend the theory. My kind friend has given that copy to me; it bears the +inscription: + +"Mr A.R. Wallace from his old travelling companion the Author." + +Only a year and a half after the publication of the "Origin", we find that +Darwin wrote to Bates on the subject which was to provide such striking +evidence of the truth of Natural Selection: "I am glad to hear that you +have specially attended to 'mimetic' analogies--a most curious subject; I +hope you publish on it. I have for a long time wished to know whether what +Dr Collingwood asserts is true--that the most striking cases generally +occur between insects inhabiting the same country." (The letter is dated +April 4, 1861. "More Letters", I. page 183.) + +The next letter, written about six months later, reveals the remarkable +fact that the illustrious naturalist who had anticipated Edward Forbes in +the explanation of arctic forms on alpine heights ("I was forestalled in +only one important point, which my vanity has always made me regret, +namely, the explanation by means of the Glacial period of the presence of +the same species of plants and of some few animals on distant mountain +summits and in the arctic regions. This view pleased me so much that I +wrote it out in extenso, and I believe that it was read by Hooker some +years before E. Forbes published his celebrated memoir on the subject. In +the very few points in which we differed, I still think that I was in the +right. I have never, of course, alluded in print to my having +independently worked out this view." "Autobiography, Life and Letters", I. +page 88.), had also anticipated H.W. Bates in the theory of Mimicry: "What +a capital paper yours will be on mimetic resemblances! You will make quite +a new subject of it. I had thought of such cases as a difficulty; and +once, when corresponding with Dr Collingwood, I thought of your +explanation; but I drove it from my mind, for I felt that I had not +knowledge to judge one way or the other." (The letter is dated Sept. 25, +1861: "More Letters", I. page 197.) + +Bates read his paper before the Linnean Society, Nov. 21, 1861, and +Darwin's impressions on hearing it were conveyed in a letter to the author +dated Dec. 3: "Under a general point of view, I am quite convinced (Hooker +and Huxley took the same view some months ago) that a philosophic view of +nature can solely be driven into naturalists by treating special subjects +as you have done. Under a special point of view, I think you have solved +one of the most perplexing problems which could be given to solve." ("Life +and Letters", II. page 378.) The memoir appeared in the following year, +and after reading it Darwin wrote as follows, Nov. 20, 1862: "...In my +opinion it is one of the most remarkable and admirable papers I ever read +in my life...I am rejoiced that I passed over the whole subject in the +"Origin", for I should have made a precious mess of it. You have most +clearly stated and solved a wonderful problem...Your paper is too good to +be largely appreciated by the mob of naturalists without souls; but, rely +on it, that it will have LASTING value, and I cordially congratulate you on +your first great work. You will find, I should think, that Wallace will +fully appreciate it." ("Life and Letters", II. pages 391-393.) Four days +later, Nov. 24, Darwin wrote to Hooker on the same subject: "I have now +finished his paper...' it seems to me admirable. To my mind the act of +segregation of varieties into species was never so plainly brought forward, +and there are heaps of capital miscellaneous observations." ("More +Letters", I. page 214.) + +Darwin was here referring to the tendency of similar varieties of the same +species to pair together, and on Nov. 25 he wrote to Bates asking for +fuller information on this subject. ("More Letters", I. page 215. See +also parts of Darwin's letter to Bates in "Life and Letters", II. page +392.) If Bates's opinion were well founded, sexual selection would bear a +most important part in the establishment of such species. (See Poulton, +"Essays on Evolution", 1908, pages 65, 85-88.) It must be admitted, +however, that the evidence is as yet quite insufficient to establish this +conclusion. It is interesting to observe how Darwin at once fixed on the +part of Bates's memoir which seemed to bear upon sexual selection. A +review of Bates's theory of Mimicry was contributed by Darwin to the +"Natural History Review" (New Ser. Vol. III. 1863, page 219.) and an +account of it is to be found in the "Origin" (Edition 1872, pages 375-378.) +and in "The Descent of Man". (Edition 1874, pages 323-325.) + +Darwin continually writes of the value of hypothesis as the inspiration of +inquiry. We find an example in his letter to Bates, Nov. 22, 1860: "I +have an old belief that a good observer really means a good theorist, and I +fully expect to find your observations most valuable." ("More Letters", I. +page 176.) Darwin's letter refers to many problems upon which Bates had +theorised and observed, but as regards Mimicry itself the hypothesis was +thought out after the return of the letter from the Amazons, when he no +longer had the opportunity of testing it by the observation of living +Nature. It is by no means improbable that, had he been able to apply this +test, Bates would have recognised that his division of butterfly +resemblances into two classes,--one due to the theory of mimicry, the other +to the influence of local conditions,--could not be sustained. + +Fritz Muller's contributions to the problem of Mimicry were all made in +S.E. Brazil, and numbers of them were communicated, with other observations +on natural history, to Darwin, and by him sent to Professor R. Meldola who +published many of the facts. Darwin's letters to Meldola (Poulton, +"Charles Darwin and the theory of Natural Selection", London, 1896, pages +199-218.) contain abundant proofs of his interest in Muller's work upon +Mimicry. One deeply interesting letter (Loc. cit. pages 201, 202.) dated +Jan. 23, 1872, proves that Fritz Muller before he originated the theory of +Common Warning Colours (Synaposematic Resemblance or Mullerian Mimicry), +which will ever be associated with his name, had conceived the idea of the +production of mimetic likeness by sexual selection. + +Darwin's letter to Meldola shows that he was by no means inclined to +dismiss the suggestion as worthless, although he considered it daring. +"You will also see in this letter a strange speculation, which I should not +dare to publish, about the appreciation of certain colours being developed +in those species which frequently behold other forms similarly ornamented. +I do not feel at all sure that this view is as incredible as it may at +first appear. Similar ideas have passed through my mind when considering +the dull colours of all the organisms which inhabit dull-coloured regions, +such as Patagonia and the Galapagos Is." A little later, on April 5, he +wrote to Professor August Weismann on the same subject: "It may be +suspected that even the habit of viewing differently coloured surrounding +objects would influence their taste, and Fritz Muller even goes so far as +to believe that the sight of gaudy butterflies might influence the taste of +distinct species." ("Life and Letters", III. page 157.) + +This remarkable suggestion affords interesting evidence that F. Muller was +not satisfied with the sufficiency of Bates's theory. Nor is this +surprising when we think of the numbers of abundant conspicuous butterflies +which he saw exhibiting mimetic likenesses. The common instances in his +locality, and indeed everywhere in tropical America, were anything but the +hard-pressed struggling forms assumed by the theory of Bates. They +belonged to the groups which were themselves mimicked by other butterflies. +Fritz Muller's suggestion also shows that he did not accept Bates's +alternative explanation of a superficial likeness between models +themselves, based on some unknown influence of local physico-chemical +forces. At the same time Muller's own suggestion was subject to this +apparently fatal objection, that the sexual selection he invoked would tend +to produce resemblances in the males rather than the females, while it is +well known that when the sexes differ the females are almost invariably +more perfectly mimetic than the males and in a high proportion of cases are +mimetic while the males are non-mimetic. + +The difficulty was met several years later by Fritz Muller's well-known +theory, published in 1879 ("Kosmos", May 1879, page 100.), and immediately +translated by Meldola and brought before the Entomological Society. +("Proc. Ent. Soc. Lond." 1879, page xx.) Darwin's letter to Meldola dated +June 6, 1879, shows "that the first introduction of this new and most +suggestive hypothesis into this country was due to the direct influence of +Darwin himself, who brought it before the notice of the one man who was +likely to appreciate it at its true value and to find the means for its +presentation to English naturalists." ("Charles Darwin and the Theory of +Natural Selection", page 214.) Of the hypothesis itself Darwin wrote "F. +Muller's view of the mutual protection was quite new to me." (Ibid. page +213.) The hypothesis of Mullerian mimicry was at first strongly opposed. +Bates himself could never make up his mind to accept it. As the Fellows +were walking out of the meeting at which Professor Meldola explained the +hypothesis, an eminent entomologist, now deceased, was heard to say to +Bates: "It's a case of save me from my friends!" The new ideas +encountered and still encounter to a great extent the difficulty that the +theory of Bates had so completely penetrated the literature of natural +history. The present writer has observed that naturalists who have not +thoroughly absorbed the older hypothesis are usually far more impressed by +the newer one than are those whose allegiance has already been rendered. +The acceptance of Natural Selection itself was at first hindered by similar +causes, as Darwin clearly recognised: "If you argue about the non- +acceptance of Natural Selection, it seems to me a very striking fact that +the Newtonian theory of gravitation, which seems to every one now so +certain and plain, was rejected by a man so extraordinarily able as +Leibnitz. The truth will not penetrate a preoccupied mind." (To Sir J. +Hooker, July 28, 1868, "More Letters", I. page 305. See also the letter to +A.R. Wallace, April 30, 1868, in "More Letters" II. page 77, lines 6-8 from +top.) + +There are many naturalists, especially students of insects, who appear to +entertain an inveterate hostility to any theory of mimicry. Some of them +are eager investigators in the fascinating field of geographical +distribution, so essential for the study of Mimicry itself. The changes of +pattern undergone by a species of Erebia as we follow it over different +parts of the mountain ranges of Europe is indeed a most interesting +inquiry, but not more so than the differences between e.g. the Acraea +johnstoni of S.E. Rhodesia and of Kilimanjaro. A naturalist who is +interested by the Erebia should be equally interested by the Acraea; and so +he would be if the student of mimicry did not also record that the +characteristics which distinguish the northern from the southern +individuals of the African species correspond with the presence, in the +north but not in the south, of certain entirely different butterflies. +That this additional information should so greatly weaken, in certain +minds, the appeal of a favourite study, is a psychological problem of no +little interest. This curious antagonism is I believe confined to a few +students of insects. Those naturalists who, standing rather farther off, +are able to see the bearings of the subject more clearly, will usually +admit the general support yielded by an ever-growing mass of observations +to the theories of Mimicry propounded by H.W. Bates and Fritz Muller. In +like manner natural selection itself was in the early days often best +understood and most readily accepted by those who were not naturalists. +Thus Darwin wrote to D.T. Ansted, Oct. 27, 1860: "I am often in despair in +making the generality of NATURALISTS even comprehend me. Intelligent men +who are not naturalists and have not a bigoted idea of the term species, +show more clearness of mind." ("More Letters", I. page 175.) + +Even before the "Origin" appeared Darwin anticipated the first results upon +the mind of naturalists. He wrote to Asa Gray, Dec. 21, 1859: "I have +made up my mind to be well abused; but I think it of importance that my +notions should be read by intelligent men, accustomed to scientific +argument, though NOT naturalists. It may seem absurd, but I think such men +will drag after them those naturalists who have too firmly fixed in their +heads that a species is an entity." ("Life and Letters" II. page 245.) + +Mimicry was not only one of the first great departments of zoological +knowledge to be studied under the inspiration of natural Selection, it is +still and will always remain one of the most interesting and important of +subjects in relation to this theory as well as to evolution. In mimicry we +investigate the effect of environment in its simplest form: we trace the +effects of the pattern of a single species upon that of another far removed +from it in the scale of classification. When there is reason to believe +that the model is an invader from another region and has only recently +become an element in the environment of the species native to its second +home, the problem gains a special interest and fascination. Although we +are chiefly dealing with the fleeting and changeable element of colour we +expect to find and we do find evidence of a comparatively rapid evolution. +The invasion of a fresh model is for certain species an unusually sudden +change in the forces of the environment and in some instances we have +grounds for the belief that the mimetic response has not been long delayed. + +MIMICRY AND SEX. + +Ever since Wallace's classical memoir on mimicry in the Malayan Swallowtail +butterflies, those naturalists who have written on the subject have +followed his interpretation of the marked prevalence of mimetic resemblance +in the female sex as compared with the male. They have believed with +Wallace that the greater dangers of the female, with slower flight and +often alighting for oviposition, have been in part met by the high +development of this special mode of protection. The fact cannot be +doubted. It is extremely common for a non-mimetic male to be accompanied +by a beautifully mimetic female and often by two or three different forms +of female, each mimicking a different model. The male of a polymorphic +mimetic female is, in fact, usually non-mimetic (e.g. Papilio dardanus = +merope), or if a mimic (e.g. the Nymphaline genus Euripus), resembles a +very different model. On the other hand a non-mimetic female accompanied +by a mimetic male is excessively rare. An example is afforded by the +Oriental Nymphaline, Cethosia, in which the males of some species are rough +mimics of the brown Danaines. In some of the orb-weaving spiders the males +mimic ants, while the much larger females are non-mimetic. When both sexes +mimic, it is very common in butterflies and is also known in moths, for the +females to be better and often far better mimics than the males. + +Although still believing that Wallace's hypothesis in large part accounts +for the facts briefly summarised above, the present writer has recently +been led to doubt whether it offers a complete explanation. Mimicry in the +male, even though less beneficial to the species than mimicry in the +female, would still surely be advantageous. Why then is it so often +entirely restricted to the female? While the attempt to find an answer to +this question was haunting me, I re-read a letter written by Darwin to +Wallace, April 15, 1868, containing the following sentences: "When female +butterflies are more brilliant than their males you believe that they have +in most cases, or in all cases, been rendered brilliant so as to mimic some +other species, and thus escape danger. But can you account for the males +not having been rendered equally brilliant and equally protected? Although +it may be most for the welfare of the species that the female should be +protected, yet it would be some advantage, certainly no disadvantage, for +the unfortunate male to enjoy an equal immunity from danger. For my part, +I should say that the female alone had happened to vary in the right +manner, and that the beneficial variations had been transmitted to the same +sex alone. Believing in this, I can see no improbability (but from analogy +of domestic animals a strong probability) that variations leading to beauty +must often have occurred in the males alone, and been transmitted to that +sex alone. Thus I should account in many cases for the greater beauty of +the male over the female, without the need of the protective principle." +("More Letters", II. pages 73, 74. On the same subject--"the gay-coloured +females of Pieris" (Perrhybris (Mylothris) pyrrha of Brazil), Darwin wrote +to Wallace, May 5, 1868, as follows: "I believe I quite follow you in +believing that the colours are wholly due to mimicry; and I further believe +that the male is not brilliant from not having received through inheritance +colour from the female, and from not himself having varied; in short, that +he has not been influenced by selection." It should be noted that the male +of this species does exhibit a mimetic pattern on the under surface. "More +Letters" II. page 78.) + +The consideration of the facts of mimicry thus led Darwin to the conclusion +that the female happens to vary in the right manner more commonly than the +male, while the secondary sexual characters of males supported the +conviction "that from some unknown cause such characters (viz. new +characters arising in one sex and transmitted to it alone) apparently +appear oftener in the male than in the female." (Letter from Darwin to +Wallace, May 5, 1867, "More Letters", II. Page 61.) + +Comparing these conflicting arguments we are led to believe that the first +is the stronger. Mimicry in the male would be no disadvantage but an +advantage, and when it appears would be and is taken advantage of by +selection. The secondary sexual characters of males would be no advantage +but a disadvantage to females, and, as Wallace thinks, are withheld from +this sex by selection. It is indeed possible that mimicry has been +hindered and often prevented from passing to the males by sexual selection. +We know that Darwin was much impressed ("Descent of Man", page 325.) by +Thomas Belt's daring and brilliant suggestion that the white patches which +exist, although ordinarily concealed, on the wings of mimetic males of +certain Pierinae (Dismorphia), have been preserved by preferential mating. +He supposed this result to have been brought about by the females +exhibiting a deep-seated preference for males that displayed the chief +ancestral colour, inherited from periods before any mimetic pattern had +been evolved in the species. But it has always appeared to me that Belt's +deeply interesting suggestion requires much solid evidence and repeated +confirmation before it can be accepted as a valid interpretation of the +facts. In the present state of our knowledge, at any rate of insects and +especially of Lepidoptera, it is probable that the female is more apt to +vary than the male and that an important element in the interpretation of +prevalent female mimicry is provided by this fact. + +In order adequately to discuss the question of mimicry and sex it would be +necessary to analyse the whole of the facts, so far as they are known in +butterflies. On the present occasion it is only possible to state the +inferences which have been drawn from general impressions,--inferences +which it is believed will be sustained by future inquiry. + +(1) Mimicry may occasionally arise in one sex because the differences +which distinguish it from the other sex happen to be such as to afford a +starting-point for the resemblance. Here the male is at no disadvantage as +compared with the female, and the rarity of mimicry in the male alone (e.g. +Cethosia) is evidence that the great predominance of female mimicry is not +to be thus explained. + +(2) The tendency of the female to dimorphism and polymorphism has been of +great importance in determining this predominance. Thus if the female +appear in two different forms and the male in only one it will be twice as +probable that she will happen to possess a sufficient foundation for the +evolution of mimicry. + +(3) The appearance of melanic or partially melanic forms in the female has +been of very great service, providing as it does a change of ground-colour. +Thus the mimicry of the black generally red-marked American "Aristolochia +swallowtails" (Pharmacophagus) by the females of Papilio swallowtails was +probably begun in this way. + +(4) It is probably incorrect to assume with Haase that mimicry always +arose in the female and was later acquired by the male. Both sexes of the +third section of swallowtails (Cosmodesmus) mimic Pharmacophagus in +America, far more perfectly than do the females of Papilio. But this is +not due to Cosmodesmus presenting us with a later stage of history begun in +Papilio; for in Africa Cosmodesmus is still mimetic (of Danainae) in both +sexes although the resemblances attained are imperfect, while many African +species of Papilio have non-mimetic males with beautifully mimetic females. +The explanation is probably to be sought in the fact that the females of +Papilio are more variable and more often tend to become dimorphic than +those of Cosmodesmus, while the latter group has more often happened to +possess a sufficient foundation for the origin of the resemblance in +patterns which, from the start, were common to male and female. + +(5) In very variable species with sexes alike, mimicry can be rapidly +evolved in both sexes out of very small beginnings. Thus the reddish marks +which are common in many individuals of Limenitis arthemis were almost +certainly the starting-point for the evolution of the beautifully mimetic +L. archippus. Nevertheless in such cases, although there is no reason to +suspect any greater variability, the female is commonly a somewhat better +mimic than the male and often a very much better mimic. Wallace's +principle seems here to supply the obvious interpretation. + +(6) When the difference between the patterns of the model and presumed +ancestor of the mimic is very great, the female is often alone mimetic; +when the difference is comparatively small, both sexes are commonly +mimetic. The Nymphaline genus Hypolimnas is a good example. In Hypolimnas +itself the females mimic Danainae with patterns very different from those +preserved by the non-mimetic males: in the sub-genus Euralia, both sexes +resemble the black and white Ethiopian Danaines with patterns not very +dissimilar from that which we infer to have existed in the non-mimetic +ancestor. + +(7) Although a melanic form or other large variation may be of the utmost +importance in facilitating the start of a mimetic likeness, it is +impossible to explain the evolution of any detailed resemblance in this +manner. And even the large colour variation itself may well be the +expression of a minute and "continuous" change in the chemical and physical +constitution of pigments. + +SEXUAL SELECTION (EPIGAMIC CHARACTERS). + +We do not know the date at which the idea of Sexual Selection arose in +Darwin's mind, but it was probably not many years after the sudden flash of +insight which, in October 1838, gave to him the theory of Natural +Selection. An excellent account of Sexual Selection occupies the +concluding paragraph of Part I. of Darwin's Section of the Joint Essay on +Natural Selection, read July 1st, 1858, before the Linnean Society. +("Journ. Proc. Linn. Soc." Vol. III. 1859, page 50.) The principles are so +clearly and sufficiently stated in these brief sentences that it is +appropriate to quote the whole: "Besides this natural means of selection, +by which those individuals are preserved, whether in their egg, or larval, +or mature state, which are best adapted to the place they fill in nature, +there is a second agency at work in most unisexual animals, tending to +produce the same effect, namely, the struggle of the males for the females. +These struggles are generally decided by the law of battle, but in the case +of birds, apparently, by the charms of their song, by their beauty or their +power of courtship, as in the dancing rock-thrush of Guiana. The most +vigorous and healthy males, implying perfect adaptation, must generally +gain the victory in their contests. This kind of selection, however, is +less rigorous than the other; it does not require the death of the less +successful, but gives to them fewer descendants. The struggle falls, +moreover, at a time of year when food is generally abundant, and perhaps +the effect chiefly produced would be the modification of the secondary +sexual characters, which are not related to the power of obtaining food, or +to defence from enemies, but to fighting with or rivalling other males. +The result of this struggle amongst the males may be compared in some +respects to that produced by those agriculturists who pay less attention to +the careful selection of all their young animals, and more to the +occasional use of a choice mate." + +A full exposition of Sexual Selection appeared in the "The Descent of Man" +in 1871, and in the greatly augmented second edition, in 1874. It has been +remarked that the two subjects, "The Descent of Man and Selection in +Relation to Sex", seem to fuse somewhat imperfectly into the single work of +which they form the title. The reason for their association is clearly +shown in a letter to Wallace, dated May 28, 1864: "...I suspect that a +sort of sexual selection has been the most powerful means of changing the +races of man." ("More Letters", II. page 33.) + +Darwin, as we know from his Autobiography ("Life and Letters", I. page +94.), was always greatly interested in this hypothesis, and it has been +shown in the preceding pages that he was inclined to look favourably upon +it as an interpretation of many appearances usually explained by Natural +Selection. Hence Sexual Selection, incidentally discussed in other +sections of the present essay, need not be considered at any length, in the +section specially allotted to it. + +Although so interested in the subject and notwithstanding his conviction +that the hypothesis was sound, Darwin was quite aware that it was probably +the most vulnerable part of the "Origin". Thus he wrote to H.W. Bates, +April 4, 1861: "If I had to cut up myself in a review I would have +(worried?) and quizzed sexual selection; therefore, though I am fully +convinced that it is largely true, you may imagine how pleased I am at what +you say on your belief." ("More Letters", I. page 183.) + +The existence of sound-producing organs in the males of insects was, Darwin +considered, the strongest evidence in favour of the operation of sexual +selection in this group. ("Life and Letters", III. pages 94, 138.) Such a +conclusion has received strong support in recent years by the numerous +careful observations of Dr F.A. Dixey ("Proc. Ent. Soc. Lond." 1904, page +lvi; 1905, pages xxxvii, liv; 1906, page ii.) and Dr G.B. Longstaff ("Proc. +Ent. Soc. Lond." 1905, page xxxv; "Trans. Ent. Soc. Lond." 1905, page 136; +1908, page 607.) on the scents of male butterflies. The experience of +these naturalists abundantly confirms and extends the account given by +Fritz Muller ("Jen. Zeit." Vol. XI. 1877, page 99; "Trans. Ent. Soc. Lond." +1878, page 211.) of the scents of certain Brazilian butterflies. It is a +remarkable fact that the apparently epigamic scents of male butterflies +should be pleasing to man while the apparently aposematic scents in both +sexes of species with warning colours should be displeasing to him. But +the former is far more surprising than the latter. It is not perhaps +astonishing that a scent which is ex hypothesi unpleasant to an insect- +eating Vertebrate should be displeasing to the human sense; but it is +certainly wonderful that an odour which is ex hypothesi agreeable to a +female butterfly should also be agreeable to man. + +Entirely new light upon the seasonal appearance of epigamic characters is +shed by the recent researches of C.W. Beebe ("The American Naturalist", +Vol. XLII. No. 493, Jan. 1908, page 34.), who caused the scarlet tanager +(Piranga erythromelas) and the bobolink (Dolichonyx oryzivorus) to retain +their breeding plumage through the whole year by means of fattening food, +dim illumination, and reduced activity. Gradual restoration to the light +and the addition of meal-worms to the diet invariably brought back the +spring song, even in the middle of winter. A sudden alteration of +temperature, either higher or lower, caused the birds nearly to stop +feeding, and one tanager lost weight rapidly and in two weeks moulted into +the olive-green winter plumage. After a year, and at the beginning of the +normal breeding season, "individual tanagers and bobolinks were gradually +brought under normal conditions and activities," and in every case moulted +from nuptial plumage to nuptial plumage. "The dull colours of the winter +season had been skipped." The author justly claims to have established +"that the sequence of plumage in these birds is not in any way predestined +through inheritance..., but that it may be interrupted by certain factors +in the environmental complex." + + +XVI. GEOGRAPHICAL DISTRIBUTION OF PLANTS. + +By SIR WILLIAM THISELTON-DYER, K.C.M.G., C.I.E. Sc.D., F.R.S. + +The publication of "The Origin of Species" placed the study of Botanical +Geography on an entirely new basis. It is only necessary to study the +monumental "Geographie Botanique raisonnee" of Alphonse De Candolle, +published four years earlier (1855), to realise how profound and far- +reaching was the change. After a masterly and exhaustive discussion of all +available data De Candolle in his final conclusions could only arrive at a +deadlock. It is sufficient to quote a few sentences:-- + +"L'opinion de Lamarck est aujourd'hui abandonee par tous les naturalistes +qui ont etudie sagement les modifications possibles des etres organises... + +"Et si l'on s'ecarte des exagerations de Lamarck, si l'on suppose un +premier type de chaque genre, de chaque famille tout au moins, on se trouve +encore a l'egard de l'origine de ces types en presence de la grande +question de la creation. + +"Le seul parti a prendre est donc d'envisager les etres organises comme +existant depuis certaines epoques, avec leurs qualites particulieres." +(Vol. II. page 1107.) + +Reviewing the position fourteen years afterwards, Bentham remarked:--"These +views, generally received by the great majority of naturalists at the time +De Candolle wrote, and still maintained by a few, must, if adhered to, +check all further enquiry into any connection of facts with causes," and he +added, "there is little doubt but that if De Candolle were to revise his +work, he would follow the example of so many other eminent naturalists, +and...insist that the present geographical distribution of plants was in +most instances a derivative one, altered from a very different former +distribution." ("Pres. Addr." (1869) "Proc. Linn. Soc." 1868-69, page +lxviii.) + +Writing to Asa Gray in 1856, Darwin gave a brief preliminary account of his +ideas as to the origin of species, and said that geographical distribution +must be one of the tests of their validity. ("Life and Letters", II. page +78.) What is of supreme interest is that it was also their starting-point. +He tells us:--"When I visited, during the voyage of H.M.S. "Beagle", the +Galapagos Archipelago,...I fancied myself brought near to the very act of +creation. I often asked myself how these many peculiar animals and plants +had been produced: the simplest answer seemed to be that the inhabitants +of the several islands had descended from each other, undergoing +modification in the course of their descent." ("The Variation of Animals +and Plants" (2nd edition), 1890, I. pages 9, 10.) We need not be surprised +then, that in writing in 1845 to Sir Joseph Hooker, he speaks of "that +grand subject, that almost keystone of the laws of creation, Geographical +Distribution." ("Life and Letters", I. page 336.) + +Yet De Candolle was, as Bentham saw, unconsciously feeling his way, like +Lyell, towards evolution, without being able to grasp it. They both strove +to explain phenomena by means of agencies which they saw actually at work. +If De Candolle gave up the ultimate problem as insoluble:--"La creation ou +premiere formation des etres organises echappe, par sa nature et par son +anciennete, a nos moyens d'observation" (Loc. cit. page 1106.), he steadily +endeavoured to minimise its scope. At least half of his great work is +devoted to the researches by which he extricated himself from a belief in +species having had a multiple origin, the view which had been held by +successive naturalists from Gmelin to Agassiz. To account for the obvious +fact that species constantly occupy dissevered areas, De Candolle made a +minute study of their means of transport. This was found to dispose of the +vast majority of cases, and the remainder he accounted for by geographical +change. (Loc. cit. page 1116.) + +But Darwin strenuously objected to invoking geographical change as a +solution of every difficulty. He had apparently long satisfied himself as +to the "permanence of continents and great oceans." Dana, he tells us +"was, I believe, the first man who maintained" this ("Life and Letters", +III. page 247. Dana says:--"The continents and oceans had their general +outline or form defined in earliest time," "Manual of Geology", revised +edition. Philadelphia, 1869, page 732. I have no access to an earlier +edition.), but he had himself probably arrived at it independently. Modern +physical research tends to confirm it. The earth's centre of gravity, as +pointed out by Pratt from the existence of the Pacific Ocean, does not +coincide with its centre of figure, and it has been conjectured that the +Pacific Ocean dates its origin from the separation of the moon from the +earth. + +The conjecture appears to be unnecessary. Love shows that "the force that +keeps the Pacific Ocean on one side of the earth is gravity, directed more +towards the centre of gravity than the centre of the figure." ("Report of +the 77th Meeting of the British Association" (Leicester, 1907), London, +1908, page 431.) I can only summarise the conclusions of a technical but +masterly discussion. "The broad general features of the distribution of +continent and ocean can be regarded as the consequences of simple causes of +a dynamical character," and finally, "As regards the contour of the great +ocean basins, we seem to be justified in saying that the earth is +approximately an oblate spheroid, but more nearly an ellipsoid with three +unequal axes, having its surface furrowed according to the formula for a +certain spherical harmonic of the third degree" (Ibid. page 436.), and he +shows that this furrowed surface must be produced "if the density is +greater in one hemispheroid than in the other, so that the position of the +centre of gravity is eccentric." (Ibid. page 431.) Such a modelling of +the earth's surface can only be referred to a primitive period of +plasticity. If the furrows account for the great ocean basins, the +disposition of the continents seems equally to follow. Sir George Darwin +has pointed out that they necessarily "arise from a supposed primitive +viscosity or plasticity of the earth's mass. For during this course of +evolution the earth's mass must have suffered a screwing motion, so that +the polar regions have travelled a little from west to east relatively to +the equator. This affords a possible explanation of the north and south +trend of our great continents." ("Encycl. Brit." (9th edition), Vol. +XXIII. "Tides", page 379.) + +It would be trespassing on the province of the geologist to pursue the +subject at any length. But as Wallace ("Island Life" (2nd edition), 1895, +page 103.), who has admirably vindicated Darwin's position, points out, the +"question of the permanence of our continents...lies at the root of all our +inquiries into the great changes of the earth and its inhabitants." But he +proceeds: "The very same evidence which has been adduced to prove the +GENERAL stability and permanence of our continental areas also goes to +prove that they have been subjected to wonderful and repeated changes in +DETAIL." (Loc. cit. page 101.) Darwin of course would have admitted this, +for with a happy expression he insisted to Lyell (1856) that "the +skeletons, at least, of our continents are ancient." ("More Letters", II. +page 135.) It is impossible not to admire the courage and tenacity with +which he carried on the conflict single-handed. But he failed to convince +Lyell. For we still find him maintaining in the last edition of the +"Principles": "Continents therefore, although permanent for whole +geological epochs, shift their positions entirely in the course of ages." +(Lyell's "Principles of Geology" (11th edition), London, 1872, I. page +258.) + +Evidence, however, steadily accumulates in Darwin's support. His position +still remains inexpugnable that it is not permissible to invoke +geographical change to explain difficulties in distribution without valid +geological and physical support. Writing to Mellard Reade, who in 1878 had +said, "While believing that the ocean-depths are of enormous age, it is +impossible to reject other evidences that they have once been land," he +pointed out "the statement from the 'Challenger' that all sediment is +deposited within one or two hundred miles from the shores." ("More +Letters", II. page 146.) The following year Sir Archibald Geikie +("Geographical Evolution", "Proc. R. Geogr. Soc." 1879, page 427.) informed +the Royal Geographical Society that "No part of the results obtained by the +'Challenger' expedition has a profounder interest for geologists and +geographers than the proof which they furnish that the floor of the ocean +basins has no real analogy among the sedimentary formations which form most +of the framework of the land." + +Nor has Darwin's earlier argument ever been upset. "The fact which I +pointed out many years ago, that all oceanic islands are volcanic (except +St Paul's, and now that is viewed by some as the nucleus of an ancient +volcano), seem to me a strong argument that no continent ever occupied the +great oceans." ("More Letters", II. page 146.) + +Dr Guppy, who devoted several years to geological and botanical +investigations in the Pacific, found himself forced to similar conclusions. +"It may be at once observed," he says, "that my belief in the general +principle that islands have always been islands has not been shaken," and +he entirely rejects "the hypothesis of a Pacific continent." He comes +back, in full view of the problems on the spot, to the position from which, +as has been seen, Darwin started: "If the distribution of a particular +group of plants or animals does not seem to accord with the present +arrangement of the land, it is by far the safest plan, even after +exhausting all likely modes of explanation, not to invoke the intervention +of geographical changes; and I scarcely think that our knowledge of any one +group of organisms is ever sufficiently precise to justify a recourse to +hypothetical alterations in the present relations of land and sea." +("Observations of a Naturalist in the Pacific between 1896 and 1899", +London, 1903, I. page 380.) Wallace clinches the matter when he finds +"almost the whole of the vast areas of the Atlantic, Pacific, Indian, and +Southern Oceans, without a solitary relic of the great islands or +continents supposed to have sunk beneath their waves." ("Island Life", +page 105.) + +Writing to Wallace (1876), Darwin warmly approves the former's "protest +against sinking imaginary continents in a quite reckless manner, as was +stated by Forbes, followed, alas, by Hooker, and caricatured by Wollaston +and (Andrew) Murray." ("Life and Letters", III. page 230.) The transport +question thus became of enormously enhanced importance. We need not be +surprised then at his writing to Lyell in 1856:--"I cannot avoid thinking +that Forbes's 'Atlantis' was an ill-service to science, as checking a close +study of means of dissemination" (Ibid. II. page 78.), and Darwin spared no +pains to extend our knowledge of them. He implores Hooker, ten years +later, to "admit how little is known on the subject," and summarises with +some satisfaction what he had himself achieved:--"Remember how recently you +and others thought that salt water would soon kill seeds...Remember that no +one knew that seeds would remain for many hours in the crops of birds and +retain their vitality; that fish eat seeds, and that when the fish are +devoured by birds the seeds can germinate, etc. Remember that every year +many birds are blown to Madeira and to the Bermudas. Remember that dust is +blown 1000 miles across the Atlantic." ("More Letters", I. page 483.) + +It has always been the fashion to minimise Darwin's conclusions, and these +have not escaped objection. The advocatus diaboli has a useful function in +science. But in attacking Darwin his brief is generally found to be +founded on a slender basis of facts. Thus Winge and Knud Andersen have +examined many thousands of migratory birds and found "that their crops and +stomachs were always empty. They never observed any seeds adhering to the +feathers, beaks or feet of the birds." (R.F. Scharff, "European Animals", +page 64, London, 1907.) The most considerable investigation of the problem +of Plant Dispersal since Darwin is that of Guppy. He gives a striking +illustration of how easily an observer may be led into error by relying on +negative evidence. + +"When Ekstam published, in 1895, the results of his observations on the +plants of Nova Zembla, he observed that he possessed no data to show +whether swimming and wading birds fed on berries; and he attached all +importance to dispersal by winds. On subsequently visiting Spitzbergen he +must have been at first inclined, therefore, to the opinion of Nathorst, +who, having found only a solitary species of bird (a snow-sparrow) in that +region, naturally concluded that birds had been of no importance as agents +in the plant-stocking. However, Ekstam's opportunities were greater, and +he tells us that in the craws of six specimens of Lagopus hyperboreus shot +in Spitzbergen in August he found represented almost 25 per cent. of the +usual phanerogamic flora of that region in the form of fruits, seeds, +bulbils, flower-buds, leaf-buds, etc..." + +"The result of Ekstam's observations in Spitzbergen was to lead him to +attach a very considerable importance in plant dispersal to the agency of +birds; and when in explanation of the Scandinavian elements in the +Spitzbergen flora he had to choose between a former land connection and the +agency of birds, he preferred the bird." (Guppy, op. cit. II. pages 511, +512.) + +Darwin objected to "continental extensions" on geological grounds, but he +also objected to Lyell that they do not "account for all the phenomena of +distribution on islands" ("Life and Letters", II. page 77.), such for +example as the absence of Acacias and Banksias in New Zealand. He agreed +with De Candolle that "it is poor work putting together the merely POSSIBLE +means of distribution." But he also agreed with him that they were the +only practicable door of escape from multiple origins. If they would not +work then "every one who believes in single centres will have to admit +continental extensions" (Ibid. II. page 82.), and that he regarded as a +mere counsel of despair:--"to make continents, as easily as a cook does +pancakes." (Ibid. II. page 74.) + +The question of multiple origins however presented itself in another shape +where the solution was much more difficult. The problem, as stated by +Darwin, is this:--"The identity of many plants and animals, on mountain- +summits, separated from each other by hundreds of miles of +lowlands...without the apparent possibility of their having migrated from +one point to the other." He continues, "even as long ago as 1747, such +facts led Gmelin to conclude that the same species must have been +independently created at several distinct points; and we might have +remained in this same belief, had not Agassiz and others called vivid +attention to the Glacial period, which affords...a simple explanation of +the facts." ("Origin of Species" (6th edition) page 330.) + +The "simple explanation" was substantially given by E. Forbes in 1846. It +is scarcely too much to say that it belongs to the same class of fertile +and far-reaching ideas as "natural selection" itself. It is an +extraordinary instance, if one were wanted at all, of Darwin's magnanimity +and intense modesty that though he had arrived at the theory himself, he +acquiesced in Forbes receiving the well-merited credit. "I have never," he +says, "of course alluded in print to my having independently worked out +this view." But he would have been more than human if he had not added:-- +"I was forestalled in...one important point, which my vanity has always +made me regret." ("Life and Letters", I. page 88.) + +Darwin, however, by applying the theory to trans-tropical migration, went +far beyond Forbes. The first enunciation to this is apparently contained +in a letter to Asa Gray in 1858. The whole is too long to quote, but the +pith is contained in one paragraph. "There is a considerable body of +geological evidence that during the Glacial epoch the whole world was +colder; I inferred that,...from erratic boulder phenomena carefully +observed by me on both the east and west coast of South America. Now I am +so bold as to believe that at the height of the Glacial epoch, AND WHEN ALL +TROPICAL PRODUCTIONS MUST HAVE BEEN CONSIDERABLY DISTRESSED, several +temperate forms slowly travelled into the heart of the Tropics, and even +reached the southern hemisphere; and some few southern forms penetrated in +a reverse direction northward." ("Life and Letters", II. page 136.) Here +again it is clear that though he credits Agassiz with having called vivid +attention to the Glacial period, he had himself much earlier grasped the +idea of periods of refrigeration. + +Putting aside the fact, which has only been made known to us since Darwin's +death, that he had anticipated Forbes, it is clear that he gave the theory +a generality of which the latter had no conception. This is pointed out by +Hooker in his classical paper "On the Distribution of Arctic Plants" +(1860). "The theory of a southern migration of northern types being due to +the cold epochs preceding and during the glacial, originated, I believe, +with the late Edward Forbes; the extended one, of the trans-tropical +migration, is Mr Darwin's." ("Linn. Trans." XXIII. page 253. The attempt +appears to have been made to claim for Heer priority in what I may term for +short the arctic-alpine theory (Scharff, "European Animals", page 128). I +find no suggestion of his having hit upon it in his correspondence with +Darwin or Hooker. Nor am I aware of any reference to his having done so in +his later publications. I am indebted to his biographer, Professor +Schroter, of Zurich, for an examination of his earlier papers with an +equally negative result.) Assuming that local races have derived from a +common ancestor, Hooker's great paper placed the fact of the migration on +an impregnable basis. And, as he pointed out, Darwin has shown that "such +an explanation meets the difficulty of accounting for the restriction of so +many American and Asiatic arctic types to their own peculiar longitudinal +zones, and for what is a far greater difficulty, the representation of the +same arctic genera by most closely allied species in different longitudes." + +The facts of botanical geography were vital to Darwin's argument. He had +to show that they admitted of explanation without assuming multiple origins +for species, which would be fatal to the theory of Descent. He had +therefore to strengthen and extend De Candolle's work as to means of +transport. He refused to supplement them by hypothetical geographical +changes for which there was no independent evidence: this was simply to +attempt to explain ignotum per ignotius. He found a real and, as it has +turned out, a far-reaching solution in climatic change due to cosmical +causes which compelled the migration of species as a condition of their +existence. The logical force of the argument consists in dispensing with +any violent assumption, and in showing that the principle of descent is +adequate to explain the ascertained facts. + +It does not, I think, detract from the merit of Darwin's conclusions that +the tendency of modern research has been to show that the effects of the +Glacial period were less simple, more localised and less general than he +perhaps supposed. He admitted that "equatorial refrigeration...must have +been small." ("More Letters", I. page 177.) It may prove possible to +dispense with it altogether. One cannot but regret that as he wrote to +Bates:--"the sketch in the 'Origin' gives a very meagre account of my +fuller MS. essay on this subject." (Loc. cit.) Wallace fully accepted +"the effect of the Glacial epoch in bringing about the present distribution +of Alpine and Arctic plants in the NORTHERN HEMISPHERE," but rejected "the +lowering of the temperature of the tropical regions during the Glacial +period" in order to account for their presence in the SOUTHERN hemisphere. +("More Letters", II. page 25 (footnote 1).) The divergence however does +not lie very deep. Wallace attaches more importance to ordinary means of +transport. "If plants can pass in considerable numbers and variety over +wide seas and oceans, it must be yet more easy for them to traverse +continuous areas of land, wherever mountain-chains offer suitable +stations." ("Island Life" (2nd edition), London, 1895, page 512.) And he +argues that such periodical changes of climate, of which the Glacial period +may be taken as a type, would facilitate if not stimulate the process. +(Loc. cit. page 518.) + +It is interesting to remark that Darwin drew from the facts of plant +distribution one of his most ingenious arguments in support of this theory. +(See "More Letters", I. page 424.) He tells us, "I was led to anticipate +that the species of the larger genera in each country would oftener present +varieties, than the species of the smaller genera." ("Origin", page 44.) +He argues "where, if we may use the expression, the manufactory of species +has been active, we ought generally to find the manufactory still in +action." (Ibid. page 45.) This proved to be the case. But the labour +imposed upon him in the study was immense. He tabulated local floras +"belting the whole northern hemisphere" ("More Letters", I. page 107.), +besides voluminous works such as De Candolle's "Prodromus". The results +scarcely fill a couple of pages. This is a good illustration of the +enormous pains which he took to base any statement on a secure foundation +of evidence, and for this the world, till the publication of his letters, +could not do him justice. He was a great admirer of Herbert Spencer, whose +"prodigality of original thought" astonished him. "But," he says, "the +reflection constantly recurred to me that each suggestion, to be of real +value to service, would require years of work." (Ibid. II. page 235.) + +At last the ground was cleared and we are led to the final conclusion. "If +the difficulties be not insuperable in admitting that in the long course of +time all the individuals of the same species belonging to the same genus, +have proceeded from some one source; then all the grand leading facts of +geographical distribution are explicable on the theory of migration, +together with subsequent modification and the multiplication of new forms." +("Origin", page 360.) In this single sentence Darwin has stated a theory +which, as his son F. Darwin has said with justice, has "revolutionized +botanical geography." ("The Botanical Work of Darwin", "Ann. Bot." 1899, +page xi.) It explains how physical barriers separate and form botanical +regions; how allied species become concentrated in the same areas; how, +under similar physical conditions, plants may be essentially dissimilar, +showing that descent and not the surroundings is the controlling factor; +how insular floras have acquired their peculiarities; in short how the most +various and apparently uncorrelated problems fall easily and inevitably +into line. + +The argument from plant distribution was in fact irresistible. A proof, if +one were wanted, was the immediate conversion of what Hooker called "the +stern keen intellect" ("More Letters", I. page 134.) of Bentham, by general +consent the leading botanical systematist at the time. It is a striking +historical fact that a paper of his own had been set down for reading at +the Linnean Society on the same day as Darwin's, but had to give way. In +this he advocated the fixity of species. He withdrew it after hearing +Darwin's. We can hardly realise now the momentous effect on the scientific +thought of the day of the announcement of the new theory. Years afterwards +(1882) Bentham, notwithstanding his habitual restraint, could not write of +it without emotion. "I was forced, however reluctantly, to give up my +long-cherished convictions, the results of much labour and study." The +revelation came without preparation. Darwin, he wrote, "never made any +communications to me in relation to his views and labours." But, he adds, +I...fully adopted his theories and conclusions, notwithstanding the severe +pain and disappointment they at first occasioned me." ("Life and Letters", +II. page 294.) Scientific history can have few incidents more worthy. I +do not know what is most striking in the story, the pathos or the moral +dignity of Bentham's attitude. + +Darwin necessarily restricted himself in the "Origin" to establishing the +general principles which would account for the facts of distribution, as a +part of his larger argument, without attempting to illustrate them in +particular cases. This he appears to have contemplated doing in a separate +work. But writing to Hooker in 1868 he said:--"I shall to the day of my +death keep up my full interest in Geographical Distribution, but I doubt +whether I shall ever have strength to come in any fuller detail than in the +"Origin" to this grand subject." ("More Letters", II. page 7.) This must +be always a matter for regret. But we may gather some indication of his +later speculations from the letters, the careful publication of which by F. +Darwin has rendered a service to science, the value of which it is +difficult to exaggerate. They admit us to the workshop, where we see a +great theory, as it were, in the making. The later ideas that they contain +were not it is true public property at the time. But they were +communicated to the leading biologists of the day and indirectly have had a +large influence. + +If Darwin laid the foundation, the present fabric of Botanical Geography +must be credited to Hooker. It was a happy partnership. The far-seeing, +generalising power of the one was supplied with data and checked in +conclusions by the vast detailed knowledge of the other. It may be +permitted to quote Darwin's generous acknowledgment when writing the +"Origin":--"I never did pick any one's pocket, but whilst writing my +present chapter I keep on feeling (even when differing most from you) just +as if I were stealing from you, so much do I owe to your writings and +conversation, so much more than mere acknowledgements show." ("Life and +Letters", II. page 148 (footnote).) Fourteen years before he had written +to Hooker: "I know I shall live to see you the first authority in Europe +on...Geographical Distribution." (Ibid. I. page 336.) We owe it to Hooker +that no one now undertakes the flora of a country without indicating the +range of the species it contains. Bentham tells us: "After De Candolle, +independently of the great works of Darwin...the first important addition +to the science of geographical botany was that made by Hooker in his +"Introductory Essay to the Flora of Tasmania", which, though +contemporaneous only with the "Origin of Species", was drawn up with a +general knowledge of his friend's observations and views." (Pres. Addr. +(1869), "Proc. Linn. Soc." 1868-69, page lxxiv.) It cannot be doubted that +this and the great memoir on the "Distribution of Arctic Plants" were only +less epoch-making than the "Origin" itself, and must have supplied a +powerful support to the general theory of organic evolution. + +Darwin always asserted his "entire ignorance of Botany." ("More Letters", +I. page 400.) But this was only part of his constant half-humorous self- +depreciation. He had been a pupil of Henslow, and it is evident that he +had a good working knowledge of systematic botany. He could find his way +about in the literature and always cites the names of plants with +scrupulous accuracy. It was because he felt the want of such a work for +his own researches that he urged the preparation of the "Index Kewensis", +and undertook to defray the expense. It has been thought singular that he +should have been elected a "correspondant" of the Academie des Sciences in +the section of Botany, but it is not surprising that his work in +Geographical Botany made the botanists anxious to claim him. His heart +went with them. "It has always pleased me," he tells us, "to exalt plants +in the scale of organised beings." ("Life and Letters", I. page 98.) And +he declares that he finds "any proposition more easily tested in botanical +works (Ibid. II. page 99.) than in zoological." + +In the "Introductory Essay" Hooker dwelt on the "continuous current of +vegetation from Scandinavia to Tasmania" ("Introductory Essay to the Flora +of Tasmania", London, 1859. Reprinted from the "Botany of the Antarctic +Expedition", Part III., "Flora of Tasmania", Vol I. page ciii.), but finds +little evidence of one in the reverse direction. "In the New World, +Arctic, Scandinavian, and North American genera and species are +continuously extended from the north to the south temperate and even +Antarctic zones; but scarcely one Antarctic species, or even genus advances +north beyond the Gulf of Mexico" (page civ.). Hooker considered that this +negatived "the idea that the Southern and Northern Floras have had common +origin within comparatively modern geological epochs." (Loc. cit.) This +is no doubt a correct conclusion. But it is difficult to explain on +Darwin's view alone, of alternating cold in the two hemispheres, the +preponderant migration from the north to the south. He suggests, +therefore, that it "is due to the greater extent of land in the north and +to the northern forms...having...been advanced through natural selection +and competition to a higher stage of perfection or dominating power." +("Origin of Species" (6th edition), page 340; cf. also "Life and Letters", +II. page 142.) The present state of the Flora of New Zealand affords a +striking illustration of the correctness of this view. It is poor in +species, numbering only some 1400, of which three-fourths are endemic. +They seem however quite unable to resist the invasion of new comers and +already 600 species of foreign origin have succeeded in establishing +themselves. + +If we accept the general configuration of the earth's surface as permanent +a continuous and progressive dispersal of species from the centre to the +circumference, i.e. southwards, seems inevitable. If an observer were +placed above a point in St George's Channel from which one half of the +globe was visible he would see the greatest possible quantity of land +spread out in a sort of stellate figure. The maritime supremacy of the +English race has perhaps flowed from the central position of its home. +That such a disposition would facilitate a centrifugal migration of land +organisms is at any rate obvious, and fluctuating conditions of climate +operating from the pole would supply an effective means of propulsion. As +these became more rigorous animals at any rate would move southwards to +escape them. It would be equally the case with plants if no insuperable +obstacle interposed. This implies a mobility in plants, notwithstanding +what we know of means of transport which is at first sight paradoxical. +Bentham has stated this in a striking way: "Fixed and immovable as is the +individual plant, there is no class in which the race is endowed with +greater facilities for the widest dispersion...Plants cast away their +offspring in a dormant state, ready to be carried to any distance by those +external agencies which we may deem fortuitous, but without which many a +race might perish from the exhaustion of the limited spot of soil in which +it is rooted." (Pres. Addr.(1869), "Proc. Linn. Soc." 1868-69, pages lxvi, +lxvii.) + +I have quoted this passage from Bentham because it emphasises a point which +Darwin for his purpose did not find it necessary to dwell upon, though he +no doubt assumed it. Dispersal to a distance is, so to speak, an +accidental incident in the life of a species. Lepidium Draba, a native of +South-eastern Europe, owes its prevalence in the Isle of Thanet to the +disastrous Walcheren expedition; the straw-stuffing of the mattresses of +the fever-stricken soldiers who were landed there was used by a farmer for +manure. Sir Joseph Hooker ("Royal Institution Lecture", April 12, 1878.) +tells us that landing on Lord Auckland's Island, which was uninhabited, +"the first evidence I met with of its having been previously visited by man +was the English chickweed; and this I traced to a mound that marked the +grave of a British sailor, and that was covered with the plant, doubtless +the offspring of seed that had adhered to the spade or mattock with which +the grave had been dug." + +Some migration from the spot where the individuals of a species have +germinated is an essential provision against extinction. Their descendants +otherwise would be liable to suppression by more vigorous competitors. But +they would eventually be extinguished inevitably, as pointed out by +Bentham, by the exhaustion of at any rate some one necessary constituent of +the soil. Gilbert showed by actual analysis that the production of a +"fairy ring" is simply due to the using up by the fungi of the available +nitrogen in the enclosed area which continually enlarges as they seek a +fresh supply on the outside margin. Anyone who cultivates a garden can +easily verify the fact that every plant has some adaptation for varying +degrees of seed-dispersal. It cannot be doubted that slow but persistent +terrestrial migration has played an enormous part in bringing about +existing plant-distribution, or that climatic changes would intensify the +effect because they would force the abandonment of a former area and the +occupation of a new one. We are compelled to admit that as an incident of +the Glacial period a whole flora may have moved down and up a mountain +side, while only some of its constituent species would be able to take +advantage of means of long-distance transport. + +I have dwelt on the importance of what I may call short-distance dispersal +as a necessary condition of plant life, because I think it suggests the +solution of a difficulty which leads Guppy to a conclusion with which I am +unable to agree. But the work which he has done taken as a whole appears +to me so admirable that I do so with the utmost respect. He points out, as +Bentham had already done, that long-distance dispersal is fortuitous. And +being so it cannot have been provided for by previous adaptation. He says +(Guppy, op. cit. II. page 99.): "It is not conceivable that an organism +can be adapted to conditions outside its environment." To this we must +agree; but, it may be asked, do the general means of plant dispersal +violate so obvious a principle? He proceeds: "The great variety of the +modes of dispersal of seeds is in itself an indication that the dispersing +agencies avail themselves in a hap-hazard fashion of characters and +capacities that have been developed in other connections." (Loc. cit. page +102.) "Their utility in these respects is an accident in the plant's +life." (Loc. cit. page 100.) He attributes this utility to a "determining +agency," an influence which constantly reappears in various shapes in the +literature of Evolution and is ultra-scientific in the sense that it bars +the way to the search for material causes. He goes so far as to doubt +whether fleshy fruits are an adaptation for the dispersal of their +contained seeds. (Loc. cit. page 102.) Writing as I am from a hillside +which is covered by hawthorn bushes sown by birds, I confess I can feel +little doubt on the subject myself. The essential fact which Guppy brings +out is that long-distance unlike short-distance dispersal is not universal +and purposeful, but selective and in that sense accidental. But it is not +difficult to see how under favouring conditions one must merge into the +other. + +Guppy has raised one novel point which can only be briefly referred to but +which is of extreme interest. There are grounds for thinking that flowers +and insects have mutually reacted upon one another in their evolution. +Guppy suggests that something of the same kind may be true of birds. I +must content myself with the quotation of a single sentence. "With the +secular drying of the globe and the consequent differentiation of climate +is to be connected the suspension to a great extent of the agency of birds +as plant dispersers in later ages, not only in the Pacific Islands but all +over the tropics. The changes of climate, birds and plants have gone on +together, the range of the bird being controlled by the climate, and the +distribution of the plant being largely dependent on the bird." (Loc.cit. +II. page 221.) + +Darwin was clearly prepared to go further than Hooker in accounting for the +southern flora by dispersion from the north. Thus he says: "We must, I +suppose, admit that every yard of land has been successively covered with a +beech-forest between the Caucasus and Japan." ("More Letters", II. page +9.) Hooker accounted for the dissevered condition of the southern flora by +geographical change, but this Darwin could not admit. He suggested to +Hooker that the Australian and Cape floras might have had a point of +connection through Abyssinia (Ibid. I. page 447.), an idea which was +promptly snuffed out. Similarly he remarked to Bentham (1869): "I suppose +you think that the Restiaceae, Proteaceae, etc., etc. once extended over +the whole world, leaving fragments in the south." (Ibid. I. page 380.) +Eventually he conjectured "that there must have been a Tertiary Antarctic +continent, from which various forms radiated to the southern extremities of +our present continents." ("Life and Letters", III. page 231.) But +characteristically he could not admit any land connections and trusted to +"floating ice for transporting seed." ("More Letters", I. page 116.) I am +far from saying that this theory is not deserving of serious attention, +though there seems to be no positive evidence to support it, and it +immediately raises the difficulty how did such a continent come to be +stocked? + +We must, however, agree with Hooker that the common origin of the northern +and southern floras must be referred to a remote past. That Darwin had +this in his mind at the time of the publication of the "Origin" is clear +from a letter to Hooker. "The view which I should have looked at as +perhaps most probable (though it hardly differs from yours) is that the +whole world during the Secondary ages was inhabited by marsupials, +araucarias (Mem.--Fossil wood of this nature in South America), Banksia, +etc.; and that these were supplanted and exterminated in the greater area +of the north, but were left alive in the south." (Ibid. I. page 453.) +Remembering that Araucaria, unlike Banksia, belongs to the earlier Jurassic +not to the angiospermous flora, this view is a germinal idea of the widest +generality. + +The extraordinary congestion in species of the peninsulas of the Old World +points to the long-continued action of a migration southwards. Each is in +fact a cul-de-sac into which they have poured and from which there is no +escape. On the other hand the high degree of specialisation in the +southern floras and the little power the species possess of holding their +own in competition or in adaptation to new conditions point to long- +continued isolation. "An island...will prevent free immigration and +competition, hence a greater number of ancient forms will survive." (Ibid. +I. page 481.) But variability is itself subject to variation. The nemesis +of a high degree of protected specialisation is the loss of adaptability. +(See Lyell, "The Geological Evidences of the Antiquity of Man", London, +1863, page 446.) It is probable that many elements of the southern flora +are doomed: there is, for example, reason to think that the singular +Stapelieae of S. Africa are a disappearing group. The tree Lobelias which +linger in the mountains of Central Africa, in Tropical America and in the +Sandwich Islands have the aspect of extreme antiquity. I may add a further +striking illustration from Professor Seward: "The tall, graceful fronds of +Matonia pectinata, forming miniature forests on the slopes of Mount Ophir +and other districts in the Malay Peninsula in association with Dipteris +conjugata and Dipteris lobbiana, represent a phase of Mesozoic life which +survives + +'Like a dim picture of the drowned past.'" ("Report of the 73rd Meeting of +the British Assoc." (Southport, 1903), London, 1904, page 844.) + +The Matonineae are ferns with an unusually complex vascular system and were +abundant "in the northern hemisphere during the earlier part of the +Mesozoic era." + +It was fortunate for science that Wallace took up the task which his +colleague had abandoned. Writing to him on the publication of his +"Geographical Distribution of Animals" Darwin said: "I feel sure that you +have laid a broad and safe foundation for all future work on Distribution. +How interesting it will be to see hereafter plants treated in strict +relation to your views." ("More Letters", II. page 12.) This hope was +fulfilled in "Island Life". I may quote a passage from it which admirably +summarises the contrast between the northern and the southern floras. + +"Instead of the enormous northern area, in which highly organised and +dominant groups of plants have been developed gifted with great colonising +and aggressive powers, we have in the south three comparatively small and +detached areas, in which rich floras have been developed with SPECIAL +adaptations to soil, climate, and organic environment, but comparatively +impotent and inferior beyond their own domain." (Wallace, "Island Life", +pages 527, 528.) + +It will be noticed that in the summary I have attempted to give of the +history of the subject, efforts have been concentrated on bringing into +relation the temperate floras of the northern and southern hemispheres, but +no account has been taken of the rich tropical vegetation which belts the +world and little to account for the original starting-point of existing +vegetation generally. It must be remembered on the one hand that our +detailed knowledge of the floras of the tropics is still very incomplete +and far inferior to that of temperate regions; on the other hand +palaeontological discoveries have put the problem in an entirely new light. +Well might Darwin, writing to Heer in 1875, say: "Many as have been the +wonderful discoveries in Geology during the last half-century, I think none +have exceeded in interest your results with respect to the plants which +formerly existed in the arctic regions." ("More Letters", II. page 240.) + +As early as 1848 Debey had described from the Upper Cretaceous rocks of +Aix-la-Chapelle Flowering plants of as high a degree of development as +those now existing. The fact was commented upon by Hooker ("Introd. Essay +to the Flora of Tasmania", page xx.), but its full significance seems to +have been scarcely appreciated. For it implied not merely that their +evolution must have taken place but the foundations of existing +distribution must have been laid in a preceding age. We now know from the +discoveries of the last fifty years that the remains of the Neocomian flora +occur over an area extending through 30 deg of latitude. The conclusion is +irresistible that within this was its centre of distribution and probably +of origin. + +Darwin was immensely impressed with the outburst on the world of a fully +fledged angiospermous vegetation. He warmly approved the brilliant theory +of Saporta that this happened "as soon (as) flower-frequenting insects were +developed and favoured intercrossing." ("More Letters", II. page 21.) +Writing to him in 1877 he says: "Your idea that dicotyledonous plants were +not developed in force until sucking insects had been evolved seems to me a +splendid one. I am surprised that the idea never occurred to me, but this +is always the case when one first hears a new and simple explanation of +some mysterious phenomenon." ("Life and Letters", III. page 285. +Substantially the same idea had occurred earlier to F.W.A. Miquel. +Remarking that "sucking insects (Haustellata)...perform in nature the +important duty of maintaining the existence of the vegetable kingdom, at +least as far as the higher orders are concerned," he points our that "the +appearance in great numbers of haustellate insects occurs at and after the +Cretaceous epoch, when the plants with pollen and closed carpels +(Angiosperms) are found, and acquire little by little the preponderance in +the vegetable kingdom." "Archives Neerlandaises", III. (1868). English +translation in "Journ. of Bot." 1869, page 101.) + +Even with this help the abruptness still remains an almost insoluble +problem, though a forecast of floral structure is now recognised in some +Jurassic and Lower Cretaceous plants. But the gap between this and the +structural complexity and diversity of angiosperms is enormous. Darwin +thought that the evolution might have been accomplished during a period of +prolonged isolation. Writing to Hooker (1881) he says: "Nothing is more +extraordinary in the history of the Vegetable Kingdom, as it seems to me, +than the APPARENTLY very sudden or abrupt development of the higher plants. +I have sometimes speculated whether there did not exist somewhere during +long ages an extremely isolated continent, perhaps near the South Pole." +("Life and Letters", III. page 248.) + +The present trend of evidence is, however, all in favour of a northern +origin for flowering plants, and we can only appeal to the imperfection of +the geological record as a last resource to extricate us from the +difficulty of tracing the process. But Darwin's instinct that at some time +or other the southern hemisphere had played an important part in the +evolution of the vegetable kingdom did not mislead him. Nothing probably +would have given him greater satisfaction than the masterly summary in +which Seward has brought together the evidence for the origin of the +Glossopteris flora in Gondwana land. + +"A vast continental area, of which remnants are preserved in Australia, +South Africa and South America...A tract of enormous extent occupying an +area, part of which has since given place to a southern ocean, while +detached masses persist as portions of more modern continents, which have +enabled us to read in their fossil plants and ice-scratched boulders the +records of a lost continent, in which the Mesozoic vegetation of the +northern continent had its birth." ("Encycl. Brit." (10th edition 1902), +Vol. XXXI. ("Palaeobotany; Mesozoic"), page 422.) Darwin would probably +have demurred on physical grounds to the extent of the continent, and +preferred to account for the transoceanic distribution of its flora by the +same means which must have accomplished it on land. + +It must in fairness be added that Guppy's later views give some support to +the conjectural existence of the "lost continent." "The distribution of +the genus Dammara" (Agathis) led him to modify his earlier conclusions. He +tells us:--"In my volume on the geology of Vanua Levu it was shown that the +Tertiary period was an age of submergence in the Western Pacific, and a +disbelief in any previous continental condition was expressed. My later +view is more in accordance with that of Wichmann, who, on geological +grounds, contended that the islands of the Western Pacific were in a +continental condition during the Palaeozoic and Mesozoic periods, and that +their submergence and subsequent emergence took place in Tertiary times." +(Guppy, op. cit. II. page 304.) + +The weight of the geological evidence I am unable to scrutinise. But +though I must admit the possibility of some unconscious bias in my own mind +on the subject, I am impressed with the fact that the known distribution of +the Glossopteris flora in the southern hemisphere is precisely paralleled +by that of Proteaceae and Restiaceae in it at the present time. It is not +unreasonable to suppose that both phenomena, so similar, may admit of the +same explanation. I confess it would not surprise me if fresh discoveries +in the distribution of the Glossopteris flora were to point to the +possibility of its also having migrated southwards from a centre of origin +in the northern hemisphere. + +Darwin, however, remained sceptical "about the travelling of plants from +the north EXCEPT DURING THE TERTIARY PERIOD." But he added, "such +speculations seem to me hardly scientific, seeing how little we know of the +old floras." ("Life and Letters", III. page 247.) That in later +geological times the south has been the grave of the weakened offspring of +the aggressive north can hardly be doubted. But if we look to the +Glossopteris flora for the ancestry of Angiosperms during the Secondary +period, Darwin's prevision might be justified, though he has given us no +clue as to how he arrived at it. + +It may be true that technically Darwin was not a botanist. But in two +pages of the "Origin" he has given us a masterly explanation of "the +relationship, with very little identity, between the productions of North +America and Europe." (Pages 333, 334.) He showed that this could be +accounted for by their migration southwards from a common area, and he told +Wallace that he "doubted much whether the now called Palaearctic and +Neartic regions ought to be separated." ("Life and Letters", III. page +230.) Catkin-bearing deciduous trees had long been seen to justify +Darwin's doubt: oaks, chestnuts, beeches, hazels, hornbeams, birches, +alders, willows and poplars are common both to the Old and New World. +Newton found that the separate regions could not be sustained for birds, +and he is now usually followed in uniting them as the Holartic. One feels +inclined to say in reading the two pages, as Lord Kelvin did to a +correspondent who asked for some further development of one of his papers, +It is all there. We have only to apply the principle to previous +geological ages to understand why the flora of the Southern United States +preserves a Cretaceous facies. Applying it still further we can understand +why, when the northern hemisphere gradually cooled through the Tertiary +period, the plants of the Eocene "suggest a comparison of the climate and +forests with those of the Malay Archipelago and Tropical America." +(Clement Reid, "Encycl. Brit." (10th edition), Vol. XXXI. ("Palaeobotany; +Tertiary"), page 435.) Writing to Asa Gray in 1856 with respect to the +United States flora, Darwin said that "nothing has surprised me more than +the greater generic and specific affinity with East Asia than with West +America." ("More Letters", I. page 434.) The recent discoveries of a +Tulip tree and a Sassafras in China afford fresh illustrations. A few +years later Asa Gray found the explanation in both areas being centres of +preservation of the Cretaceous flora from a common origin. It is +interesting to note that the paper in which this was enunciated at once +established his reputation. + +In Europe the latitudinal range of the great mountain chains gave the +Miocene flora no chance of escape during the Glacial period, and the +Mediterranean appears to have equally intercepted the flow of alpine plants +to the Atlas. (John Ball in Appendix G, page 438, in "Journal of a Tour in +Morocco and the Great Atlas", J.D. Hooker and J. Ball, London, 1878.) In +Southern Europe the myrtle, the laurel, the fig and the dwarf-palm are the +sole representatives of as many great tropical families. Another great +tropical family, the Gesneraceae has left single representatives from the +Pyrenees to the Balkans; and in the former a diminutive yam still lingers. +These are only illustrations of the evidence which constantly accumulates +and which finds no rational explanation except that which Darwin has given +to it. + +The theory of southward migration is the key to the interpretation of the +geographical distribution of plants. It derived enormous support from the +researches of Heer and has now become an accepted commonplace. Saporta in +1888 described the vegetable kingdom as "emigrant pour suivre une direction +determinee et marcher du nord au sud, a la recherche de regions et de +stations plus favorables, mieux appropriees aux adaptations acquises, a +meme que la temperature terrestre perd ses conditions premieres." +("Origine Paleontologique des arbres", Paris, 1888, page 28.) If, as is so +often the case, the theory now seems to be a priori inevitable, the +historian of science will not omit to record that the first germ sprang +from the brain of Darwin. + +In attempting this sketch of Darwin's influence on Geographical +Distribution, I have found it impossible to treat it from an external point +of view. His interest in it was unflagging; all I could say became +necessarily a record of that interest and could not be detached from it. +He was in more or less intimate touch with everyone who was working at it. +In reading the letters we move amongst great names. With an extraordinary +charm of persuasive correspondence he was constantly suggesting, +criticising and stimulating. It is hardly an exaggeration to say that from +the quiet of his study at Down he was founding and directing a wide-world +school. + +POSTSCRIPTUM. + +Since this essay was put in type Dr Ernst's striking account of the "New +Flora of the Volcanic Island of Krakatau" (Cambridge, 1909.) has reached +me. All botanists must feel a debt of gratitude to Prof. Seward for his +admirable translation of a memoir which in its original form is practically +unprocurable and to the liberality of the Cambridge University Press for +its publication. In the preceding pages I have traced the laborious +research by which the methods of Plant Dispersal were established by +Darwin. In the island of Krakatau nature has supplied a crucial experiment +which, if it had occurred earlier, would have at once secured conviction of +their efficiency. A quarter of a century ago every trace of organic life +in the island was "destroyed and buried under a thick covering of glowing +stones." Now, it is "again covered with a mantle of green, the growth +being in places so luxuriant that it is necessary to cut one's way +laboriously through the vegetation." (Op. cit. page 4.) Ernst traces +minutely how this has been brought about by the combined action of wind, +birds and sea currents, as means of transport. The process will continue, +and he concludes:--"At last after a long interval the vegetation on the +desolated island will again acquire that wealth of variety and luxuriance +which we see in the fullest development which Nature has reached in the +primaeval forest in the tropics." (Op. cit. page 72.) The possibility of +such a result revealed itself to the insight of Darwin with little +encouragement or support from contemporary opinion. + +One of the most remarkable facts established by Ernst is that this has not +been accomplished by the transport of seeds alone. "Tree stems and +branches played an important part in the colonisation of Krakatau by plants +and animals. Large piles of floating trees, stems, branches and bamboos +are met with everywhere on the beach above high-water mark and often +carried a considerable distance inland. Some of the animals on the island, +such as the fat Iguana (Varanus salvator) which suns itself in the beds of +streams, may have travelled on floating wood, possibly also the ancestors +of the numerous ants, but certainly plants." (Op. cit. page 56.) Darwin +actually had a prevision of this. Writing to Hooker he says:--"Would it +not be a prodigy if an unstocked island did not in the course of ages +receive colonists from coasts whence the currents flow, trees are drifted +and birds are driven by gales?" ("More Letters", I. page 483.) And ten +years earlier:--"I must believe in the...whole plant or branch being washed +into the sea; with floods and slips and earthquakes; this must continually +be happening." ("Life and Letters", II. pages 56, 57.) If we give to +"continually" a cosmic measure, can the fact be doubted? All this, in the +light of our present knowledge, is too obvious to us to admit of +discussion. But it seems to me nothing less than pathetic to see how in +the teeth of the obsession as to continental extension, Darwin fought +single-handed for what we now know to be the truth. + +Guppy's heart failed him when he had to deal with the isolated case of +Agathis which alone seemed inexplicable by known means of transport. But +when we remember that it is a relic of the pre-Angiospermous flora, and is +of Araucarian ancestry, it cannot be said that the impossibility, in so +prolonged a history, of the bodily transference of cone-bearing branches or +even of trees, compels us as a last resort to fall back on continental +extension to account for its existing distribution. + +When Darwin was in the Galapagos Archipelago, he tells us that he fancied +himself "brought near to the very act of creation." He saw how new species +might arise from a common stock. Krakatau shows us an earlier stage and +how by simple agencies, continually at work, that stock might be supplied. +It also shows us how the mixed and casual elements of a new colony enter +into competition for the ground and become mutually adjusted. The study of +Plant Distribution from a Darwinian standpoint has opened up a new field of +research in Ecology. The means of transport supply the materials for a +flora, but their ultimate fate depends on their equipment for the "struggle +for existence." The whole subject can no longer be regarded as a mere +statistical inquiry which has seemed doubtless to many of somewhat arid +interest. The fate of every element of the earth's vegetation has sooner +or later depended on its ability to travel and to hold its own under new +conditions. And the means by which it has secured success is an each case +a biological problem which demands and will reward the most attentive +study. This is the lesson which Darwin has bequeathed to us. It is summed +up in the concluding paragraph of the "Origin" ("Origin of Species" (6th +edition), page 429.):--"It is interesting to contemplate a tangled bank, +clothed with many plants of many kinds, with birds singing on the bushes, +with various insects flitting about, and with worms crawling through the +damp earth, and to reflect that these elaborately constructed forms, so +different from each other, and dependent upon each other in so complex a +manner, have all been produced by laws acting around us." + + +XVII. GEOGRAPHICAL DISTRIBUTION OF ANIMALS. + +By HANS GADOW, M.A., Ph.D., F.R.S. +Strickland Curator and Lecturer on Zoology in the University of Cambridge. + +The first general ideas about geographical distribution may be found in +some of the brilliant speculations contained in Buffon's "Histoire +Naturelle". The first special treatise on the subject was however written +in 1777 by E.A.W. Zimmermann, Professor of Natural Science at Brunswick, +whose large volume, "Specimen Zoologiae Geographicae Quadrupedum"..., deals +in a statistical way with the mammals; important features of the large +accompanying map of the world are the ranges of mountains and the names of +hundreds of genera indicating their geographical range. In a second work +he laid special stress on domesticated animals with reference to the +spreading of the various races of Mankind. + +In the following year appeared the "Philosophia Entomologica" by J.C. +Fabricius, who was the first to divide the world into eight regions. In +1803 G.R. Treviranus ("Biologie oder Philosophie der lebenden Natur", Vol. +II. Gottingen, 1803.) devoted a long chapter of his great work on +"Biologie" to a philosophical and coherent treatment of the distribution of +the whole animal kingdom. Remarkable progress was made in 1810 by F. +Tiedemann ("Anatomie und Naturgeschichte der Vogel". Heidelberg, 1810.) of +Heidelberg. Few, if any, of the many subsequent Ornithologists seem to +have appreciated, or known of, the ingenious way in which Tiedemann +marshalled his statistics in order to arrive at general conclusions. There +are, for instance, long lists of birds arranged in accordance with their +occurrence in one or more continents: by correlating the distribution of +the birds with their food he concludes "that the countries of the East +Indian flora have no vegetable feeders in common with America," and "that +it is probably due to the great peculiarity of the African flora that +Africa has few phytophagous kinds in common with other countries, whilst +zoophagous birds have a far more independent, often cosmopolitan, +distribution." There are also remarkable chapters on the influence of +environment, distribution, and migration, upon the structure of the Birds! +In short, this anatomist dealt with some of the fundamental causes of +distribution. + +Whilst Tiedemann restricted himself to Birds, A. Desmoulins in 1822 wrote a +short but most suggestive paper on the Vertebrata, omitting the birds; he +combated the view recently proposed by the entomologist Latreille that +temperature was the main factor in distribution. Some of his ten main +conclusions show a peculiar mixture of evolutionary ideas coupled with the +conception of the stability of species: whilst each species must have +started from but one creative centre, there may be several "analogous +centres of creation" so far as genera and families are concerned. +Countries with different faunas, but lying within the same climatic zones, +are proof of the effective and permanent existence of barriers preventing +an exchange between the original creative centres. + +The first book dealing with the "geography and classification" of the whole +animal kingdom was written by W. Swainson ("A Treatise on the Geography and +Classification of Animals", Lardner's "Cabinet Cyclopaedia" London, 1835.) +in 1835. He saw in the five races of Man the clue to the mapping of the +world into as many "true zoological divisions," and he reconciled the five +continents with his mystical quinary circles. + +Lyell's "Principles of Geology" should have marked a new epoch, since in +his "Elements" he treats of the past history of the globe and the +distribution of animals in time, and in his "Principles" of their +distribution in space in connection with the actual changes undergone by +the surface of the world. But as the sub-title of his great work "Modern +changes of the Earth and its inhabitants" indicates, he restricted himself +to comparatively minor changes, and, emphatically believing in the +permanency of the great oceans, his numerous and careful interpretations of +the effect of the geological changes upon the dispersal of animals did +after all advance the problem but little. + +Hitherto the marine faunas had been neglected. This was remedied by E. +Forbes, who established nine homozoic zones, based mainly on the study of +the mollusca, the determining factors being to a great extent the isotherms +of the sea, whilst the 25 provinces were given by the configuration of the +land. He was followed by J.D. Dana, who, taking principally the Crustacea +as a basis, and as leading factors the mean temperatures of the coldest and +of the warmest months, established five latitudinal zones. By using these +as divisors into an American, Afro-European, Oriental, Arctic and Antarctic +realm, most of which were limited by an eastern and western land-boundary, +he arrived at about threescore provinces. + +In 1853 appeared L.K. Schmarda's ("Die geographische Verbreitung der +Thiere", Wien, 1853.) two volumes, embracing the whole subject. Various +centres of creation being, according to him, still traceable, he formed the +hypothesis that these centres were originally islands, which later became +enlarged and joined together to form the great continents, so that the +original faunas could overlap and mix whilst still remaining pure at their +respective centres. After devoting many chapters to the possible physical +causes and modes of dispersal, he divided the land into 21 realms which he +shortly characterises, e.g. Australia as the only country inhabited by +marsupials, monotremes and meliphagous birds. Ten main marine divisions +were diagnosed in a similar way. Although some of these realms were not +badly selected from the point of view of being applicable to more than one +class of animals, they were obviously too numerous for general purposes, +and this drawback was overcome, in 1857, by P.L. Sclater. ("On the general +Geographical Distribution of the members of the class Aves", "Proc. Linn. +Soc." (Zoology II. 1858, pages 130-145.) Starting with the idea, that +"each species must have been created within and over the geographical area, +which it now occupies," he concluded "that the most natural primary +ontological divisions of the Earth's surface" were those six regions, which +since their adoption by Wallace in his epoch-making work, have become +classical. Broadly speaking, these six regions are equivalent to the great +masses of land; they are convenient terms for geographical facts, +especially since the Palaearctic region expresses the unity of Europe with +the bulk of Asia. Sclater further brigaded the regions of the Old World as +Palaeogaea and the two Americas as Neogaea, a fundamental mistake, +justifiable to a certain extent only since he based his regions mainly upon +the present distribution of the Passerine birds. + +Unfortunately these six regions are not of equal value. The Indian +countries and the Ethiopian region (Africa south of the Sahara) are +obviously nothing but the tropical, southern continuations or appendages of +one greater complex. Further, the great eastern mass of land is so +intimately connected with North America that this continent has much more +in common with Europe and Asia than with South America. Therefore, instead +of dividing the world longitudinally as Sclater had done, Huxley, in 1868 +("On the classification and distribution of the Alectoromorphae and +Heteromorphae", "Proc. Zool. Soc." 1868, page 294.), gave weighty reasons +for dividing it transversely. Accordingly he established two primary +divisions, Arctogaea or the North world in a wider sense, comprising +Sclater's Indian, African, Palaearctic and Neartic regions; and Notogaea, +the Southern world, which he divided into (1) Austro-Columbia (an +unfortunate substitute for the neotropical region), (2) Australasia, and +(3) New Zealand, the number of big regions thus being reduced to three but +for the separation of New Zealand upon rather negative characters. Sclater +was the first to accept these four great regions and showed, in 1874 ("The +geographical distribution of Mammals", "Manchester Science Lectures", +1874.), that they were well borne out by the present distribution of the +Mammals. + +Although applicable to various other groups of animals, for instance to the +tailless Amphibia and to Birds (Huxley himself had been led to found his +two fundamental divisions on the distribution of the Gallinaceous birds), +the combination of South America with Australia was gradually found to be +too sweeping a measure. The obvious and satisfactory solution was provided +by W.T. Blanford (Anniversary address (Geological Society, 1889), "Proc. +Geol. Soc." 1889-90, page 67; "Quart. Journ." XLVI 1890.), who in 1890 +recognised three main divisions, namely Australian, South American, and the +rest, for which the already existing terms (although used partly in a new +sense, as proposed by an anonymous writer in "Natural Science", III. page +289) "Notogaea," "Neogaea" and "Arctogaea" have been gladly accepted by a +number of English writers. + +After this historical survey of the search for larger and largest or +fundamental centres of animal creation, which resulted in the mapping of +the world into zoological regions and realms of after all doubtful value, +we have to return to the year 1858. The eleventh and twelfth chapters of +"The Origin of Species" (1859), dealing with "Geographical Distribution," +are based upon a great amount of observation, experiment and reading. As +Darwin's main problem was the origin of species, nature's way of making +species by gradual changes from others previously existing, he had to +dispose of the view, held universally, of the independent creation of each +species and at the same time to insist upon a single centre of creation for +each species; and in order to emphasise his main point, the theory of +descent, he had to disallow convergent, or as they were then called, +analogous forms. To appreciate the difficulty of his position we have to +take the standpoint of fifty years ago, when the immutability of the +species was an axiom and each was supposed to have been created within or +over the geographical area which it now occupies. If he once admitted that +a species could arise from many individuals instead of from one pair, there +was no way of shutting the door against the possibility that these +individuals may have been so numerous that they occupied a very large +district, even so large that it had become as discontinuous as the +distribution of many a species actually is. Such a concession would at +once be taken as an admission of multiple, independent, origin instead of +descent in Darwin's sense. + +For the so-called multiple, independently repeated creation of species as +an explanation of their very wide and often quite discontinuous +distribution, he substituted colonisation from the nearest and readiest +source together with subsequent modification and better adaptation to their +new home. + +He was the first seriously to call attention to the many accidental means, +"which more properly should be called occasional means of distribution," +especially to oceanic islands. His specific, even individual, centres of +creation made migrations all the more necessary, but their extent was sadly +baulked by the prevailing dogma of the permanency of the oceans. Any +number of small changes ("many islands having existed as halting places, of +which not a wreck now remains" ("The Origin of Species" (1st edition), page +396.).) were conceded freely, but few, if any, great enough to permit +migration of truly terrestrial creatures. The only means of getting across +the gaps was by the principle of the "flotsam and jetsam," a theory which +Darwin took over from Lyell and further elaborated so as to make it +applicable to many kinds of plants and animals, but sadly deficient, often +grotesque, in the case of most terrestrial creatures. + +Another very fertile source was Darwin's strong insistence upon the great +influence which the last glacial epoch must have had upon the distribution +of animals and plants. Why was the migration of northern creatures +southwards of far-reaching and most significant importance? More +northerners have established themselves in southern lands than vice versa, +because there is such a great mass of land in the north and greater +continents imply greater intensity of selection. "The productions of real +islands have everywhere largely yielded to continental forms." (Ibid. page +380.)..."The Alpine forms have almost everywhere largely yielded to the +more dominant forms generated in the larger areas and more efficient +workshops of the North." + +Let us now pass in rapid survey the influence of the publication of "The +Origin of Species" upon the study of Geographical Distribution in its wider +sense. + +Hitherto the following thought ran through the minds of most writers: +Wherever we examine two or more widely separated countries their respective +faunas are very different, but where two faunas can come into contact with +each other, they intermingle. Consequently these faunas represent centres +of creation, whence the component creatures have spread peripherally so far +as existing boundaries allowed them to do so. This is of course the +fundamental idea of "regions." There is not one of the numerous writers +who considered the possibility that these intermediate belts might +represent not a mixture of species but transitional forms, the result of +changes undergone by the most peripheral migrants in adaptation to their +new surroundings. The usual standpoint was also that of Pucheran ("Note +sur l'equateur zoologique", "Rev. et Mag. de Zoologie", 1855; also several +other papers, ibid. 1865, 1866, and 1867.) in 1855. But what a change +within the next ten years! Pucheran explains the agreement in coloration +between the desert and its fauna as "une harmonie post-etablie"; the +Sahara, formerly a marine basin, was peopled by immigrants from the +neighbouring countries, and these new animals adapted themselves to the new +environment. He also discusses, among other similar questions, the Isthmus +of Panama with regard to its having once been a strait. From the same +author may be quoted the following passage as a strong proof of the new +influence: "By the radiation of the contemporaneous faunas, each from one +centre, whence as the various parts of the world successively were formed +and became habitable, they spread and became modified according to the +local physical conditions." + +The "multiple" origin of each species as advocated by Sclater and Murray, +although giving the species a broader basis, suffered from the same +difficulties. There was only one alternative to the old orthodox view of +independent creation, namely the bold acceptance of land-connections to an +extent for which geological and palaeontological science was not yet ripe. +Those who shrank from either view, gave up the problem as mysterious and +beyond the human intellect. This was the expressed opinion of men like +Swainson, Lyell and Humboldt. Only Darwin had the courage to say that the +problem was not insoluble. If we admit "that in the long course of time +the individuals of the same species, and likewise of allied species, have +proceeded from some one source; then I think all the grand leading facts of +geographical distribution are explicable on the theory of +migration...together with subsequent modification and the multiplication of +new forms." We can thus understand how it is that in some countries the +inhabitants "are linked to the extinct beings which formerly inhabited the +same continent." We can see why two areas, having nearly the same physical +conditions, should often be inhabited by very different forms of +life,...and "we can see why in two areas, however distant from each other, +there should be a correlation, in the presence of identical species...and +of distinct but representative species." ("The Origin of Species" (1st +edition), pages 408, 409.) + +Darwin's reluctance to assume great geological changes, such as a land- +connection of Europe with North America, is easily explained by the fact +that he restricted himself to the distribution of the present and +comparatively recent species. "I do not believe that it will ever be +proved that within the recent period continents which are now quite +separate, have been continuously, or almost continuously, united with each +other, and with the many existing oceanic islands." (Ibid. page 357.) +Again, "believing...that our continents have long remained in nearly the +same relative position, though subjected to large, but partial oscillations +of level," that means to say within the period of existing species, or +"within the recent period." (Ibid. page. 370.) The difficulty was to a +great extent one of his own making. Whilst almost everybody else believed +in the immutability of the species, which implies an enormous age, +logically since the dawn of creation, to him the actually existing species +as the latest results of evolution, were necessarily something very new, so +young that only the very latest of the geological epochs could have +affected them. It has since come to our knowledge that a great number of +terrestrial "recent" species, even those of the higher classes of +Vertebrates, date much farther back than had been thought possible. Many +of them reach well into the Miocene, a time since which the world seems to +have assumed the main outlines of the present continents. + +In the year 1866 appeared A. Murray's work on the "Geographical +Distribution of Mammals", a book which has perhaps received less +recognition than it deserves. His treatment of the general introductory +questions marks a considerable advance of our problem, although, and partly +because, he did not entirely agree with Darwin's views as laid down in the +first edition of "The Origin of Species", which after all was the great +impulse given to Murray's work. Like Forbes he did not shrink from +assuming enormous changes in the configuration of the continents and oceans +because the theory of descent, with its necessary postulate of great +migrations, required them. He stated, for instance, "that a Miocene +Atlantis sufficiently explains the common distribution of animals and +plants in Europe and America up to the glacial epoch." And next he +considers how, and by what changes, the rehabilitation and distribution of +these lands themselves were effected subsequent to that period. Further, +he deserves credit for having cleared up a misunderstanding of the idea of +specific centres of creation. Whilst for instance Schmarda assumed without +hesitation that the same species, if occurring at places separated by great +distances, or apparently insurmountable barriers, had been there created +independently (multiple centres), Lyell and Darwin held that each species +had only one single centre, and with this view most of us agree, but their +starting point was to them represented by one individual, or rather one +single pair. According to Murray, on the other hand, this centre of a +species is formed by all the individuals of a species, all of which equally +undergo those changes which new conditions may impose upon them. In this +respect a new species has a multiple origin, but this in a sense very +different from that which was upheld by L. Agassiz. As Murray himself puts +it: "To my multiple origin, communication and direct derivation is +essential. The species is compounded of many influences brought together +through many individuals, and distilled by Nature into one species; and, +being once established it may roam and spread wherever it finds the +conditions of life not materially different from those of its original +centre." (Murray, "The Geographical Distribution of Mammals", page 14. +London, 1866.) This declaration fairly agrees with more modern views, and +it must be borne in mind that the application of the single-centre +principle to the genera, families and larger groups in the search for +descent inevitably leads to one creative centre for the whole animal +kingdom, a condition as unwarrantable as the myth of Adam and Eve being the +first representatives of Mankind. + +It looks as if it had required almost ten years for "The Origin of Species" +to show its full effect, since the year 1868 marks the publication of +Haeckel's "Naturliche Schoepfungsgeschichte" in addition to other great +works. The terms "Oecology" (the relation of organisms to their +environment) and "Chorology" (their distribution in space) had been given +us in his "Generelle Morphologie" in 1866. The fourteenth chapter of the +"History of Creation" is devoted to the distribution of organisms, their +chorology, with the emphatic assertion that "not until Darwin can chorology +be spoken of as a separate science, since he supplied the acting causes for +the elucidation of the hitherto accumulated mass of facts." A map (a +"hypothetical sketch") shows the monophyletic origin and the routes of +distribution of Man. + +Natural Selection may be all-mighty, all-sufficient, but it requires time, +so much that the countless aeons required for the evolution of the present +fauna were soon felt to be one of the most serious drawbacks of the theory. +Therefore every help to ease and shorten this process should have been +welcomed. In 1868 M. Wagner (The first to formulate clearly the +fundamental idea of a theory of migration and its importance in the origin +of new species was L. von Buch, who in his "Physikalische Beschreibung der +Canarischen Inseln", written in 1825, wrote as follows: "Upon the +continents the individuals of the genera by spreading far, form, through +differences of the locality, food and soil, varieties which finally become +constant as new species, since owing to the distances they could never be +crossed with other varieties and thus be brought back to the main type. +Next they may again, perhaps upon different roads, return to the old home +where they find the old type likewise changed, both having become so +different that they can interbreed no longer. Not so upon islands, where +the individuals shut up in narrow valleys or within narrow districts, can +always meet one another and thereby destroy every new attempt towards the +fixing of a new variety." Clearly von Buch explains here why island types +remain fixed, and why these types themselves have become so different from +their continental congeners.--Actually von Buch is aware of a most +important point, the difference in the process of development which exists +between a new species b, which is the result of an ancestral species a +having itself changed into b and thereby vanished itself, and a new species +c which arose through separation out of the same ancestral a, which itself +persists as such unaltered. Von Buch's prophetic view seems to have +escaped Lyell's and even Wagner's notice.) came to the rescue with his +"Darwin'sche Theorie und das Migrations-Gesetz der Organismen". (Leipzig, +1868.) He shows that migration, i.e. change of locality, implies new +environmental conditions (never mind whether these be new stimuli to +variation, or only acting as their selectors or censors), and moreover +secures separation from the original stock and thus eliminates or lessens +the reactionary dangers of panmixia. Darwin accepted Wagner's theory as +"advantageous." Through the heated polemics of the more ardent +selectionists Wagner's theory came to grow into an alternative instead of a +help to the theory of selectional evolution. Separation is now rightly +considered a most important factor by modern students of geographical +distribution. + +For the same year, 1868, we have to mention Huxley, whose Arctogaea and +Notogaea are nothing less than the reconstructed main masses of land of the +Mesozoic period. Beyond doubt the configuration of land at that remote +period has left recognisable traces in the present continents, but whether +they can account for the distribution of such a much later group as the +Gallinaceous birds is more than questionable. In any case he took for his +text a large natural group of birds, cosmopolitan as a whole, but with a +striking distribution. The Peristeropodes, or pigeon-footed division, are +restricted to the Australian and Neotropical regions, in distinction to the +Alectoropodes (with the hallux inserted at a level above the front toes) +which inhabit the whole of the Arctogaea, only a few members having spread +into the South World. Further, as Asia alone has its Pheasants and allies, +so is Africa characterised by its Guinea-fowls and relations, America has +the Turkey as an endemic genus, and the Grouse tribe in a wider sense has +its centre in the holarctic region: a splendid object lesson of descent, +world-wide spreading and subsequent differentiation. Huxley, by the way, +was the first--at least in private talk--to state that it will be for the +morphologist, the well-trained anatomist, to give the casting vote in +questions of geographical distribution, since he alone can determine +whether we have to deal with homologous, or analogous, convergent, +representative forms. + +It seems late to introduce Wallace's name in 1876, the year of the +publication of his standard work. ("The Geographical Distribution of +Animals", 2 vols. London, 1876.) We cannot do better than quote the +author's own words, expressing the hope that his "book should bear a +similar relation to the eleventh and twelfth chapters of the "Origin of +Species" as Darwin's "Animals and Plants under Domestication" does to the +first chapter of that work," and to add that he has amply succeeded. +Pleading for a few primary centres he accepts Sclater's six regions and +does not follow Huxley's courageous changes which Sclater himself had +accepted in 1874. Holding the view of the permanence of the oceans he +accounts for the colonisation of outlying islands by further elaborating +the views of Lyell and Darwin, especially in his fascinating "Island Life", +with remarkable chapters on the Ice Age, Climate and Time and other +fundamental factors. His method of arriving at the degree of relationship +of the faunas of the various regions is eminently statistical. Long lists +of genera determine by their numbers the affinity and hence the source of +colonisation. In order to make sure of his material he performed the +laborious task of evolving a new classification of the host of Passerine +birds. This statistical method has been followed by many authors, who, +relying more upon quantity than quality, have obscured the fact that the +key to the present distribution lies in the past changes of the earth's +surface. However, with Wallace begins the modern study of the geographical +distribution of animals and the sudden interest taken in this subject by an +ever widening circle of enthusiasts far beyond the professional +brotherhood. + +A considerable literature has since grown up, almost bewildering in its +range, diversity of aims and style of procedure. It is a chaos, with many +paths leading into the maze, but as yet very few take us to a position +commanding a view of the whole intricate terrain with its impenetrable +tangle and pitfalls. + +One line of research, not initiated but greatly influenced by Wallace's +works, became so prominent as to almost constitute a period which may be +characterised as that of the search by specialists for either the +justification or the amending of his regions. As class after class of +animals was brought up to reveal the secret of the true regions, some +authors saw in their different results nothing but the faultiness of +previously established regions; others looked upon eventual agreements as +their final corroboration, especially when for instance such diverse groups +as mammals and scorpions could, with some ingenuity, be made to harmonise. +But the obvious result of all these efforts was the growing knowledge that +almost every class seemed to follow principles of its own. The regions +tallied neither in extent nor in numbers, although most of them gravitated +more and more towards three centres, namely Australia, South America and +the rest of the world. Still zoologists persisted in the search, and the +various modes and capabilities of dispersal of the respective groups were +thought sufficient explanation of the divergent results in trying to bring +the mapping of the world under one scheme. + +Contemporary literature is full of devices for the mechanical dispersal of +animals. Marine currents, warm and cold, were favoured all the more since +they showed the probable original homes of the creatures in question. If +these could not stand sea-water, they floated upon logs or icebergs, or +they were blown across by storms; fishes were lifted over barriers by +waterspouts, and there is on record even an hypothetical land tortoise, +full of eggs, which colonised an oceanic island after a perilous sea voyage +upon a tree trunk. Accidents will happen, and beyond doubt many freaks of +discontinuous distribution have to be accounted for by some such means. +But whilst sufficient for the scanty settlers of true oceanic islands, they +cannot be held seriously to account for the rich fauna of a large +continent, over which palaeontology shows us that the immigrants have +passed like waves. It should also be borne in mind that there is a great +difference between flotsam and jetsam. A current is an extension of the +same medium and the animals in it may suffer no change during even a long +voyage, since they may be brought from one litoral to another where they +will still be in the same or but slightly altered environment. But the +jetsam is in the position of a passenger who has been carried off by the +wrong train. Almost every year some American land birds arrive at our +western coasts and none of them have gained a permanent footing although +such visits must have taken place since prehistoric times. It was +therefore argued that only those groups of animals should be used for +locating and defining regions which were absolutely bound to the soil. +This method likewise gave results not reconcilable with each other, even +when the distribution of fossils was taken into account, but it pointed to +the absolute necessity of searching for former land-connections regardless +of their extent and the present depths to which they may have sunk. + +That the key to the present distribution lies in the past had been felt +long ago, but at last it was appreciated that the various classes of +animals and plants have appeared in successive geological epochs and also +at many places remote from each other. The key to the distribution of any +group lies in the configuration of land and water of that epoch in which it +made its first appearance. Although this sounds like a platitude, it has +frequently been ignored. If, for argument's sake, Amphibia were evolved +somewhere upon the great southern land-mass of Carboniferous times +(supposed by some to have stretched from South America across Africa to +Australia), the distribution of this developing class must have proceeded +upon lines altogether different from that of the mammals which dated +perhaps from lower Triassic times, when the old south continental belt was +already broken up. The broad lines of this distribution could never +coincide with that of the other, older class, no matter whether the +original mammalian centre was in the Afro-Indian, Australian, or Brazilian +portion. If all the various groups of animals had come into existence at +the same time and at the same place, then it would be possible, with +sufficient geological data, to construct a map showing the generalised +results applicable to the whole animal kingdom. But the premises are +wrong. Whatever regions we may seek to establish applicable to all +classes, we are necessarily mixing up several principles, namely +geological, historical, i.e. evolutionary, with present day statistical +facts. We might as well attempt one compound picture representing a +chick's growth into an adult bird and a child's growth into manhood. + +In short there are no general regions, not even for each class separately, +unless this class be one which is confined to a comparatively short +geological period. Most of the great classes have far too long a history +and have evolved many successive main groups. Let us take the mammals. +Marsupials live now in Australia and in both Americas, because they already +existed in Mesozoic times; Ungulata existed at one time or other all over +the world except in Australia, because they are post-Cretaceous; +Insectivores, although as old as any Placentalia, are cosmopolitan +excepting South America and Australia; Stags and Bears, as examples of +comparatively recent Arctogaeans, are found everywhere with the exception +of Ethiopia and Australia. Each of these groups teaches a valuable +historical lesson, but when these are combined into the establishment of a +few mammalian "realms," they mean nothing but statistical majorities. If +there is one at all, Australia is such a realm backed against the rest of +the world, but as certainly it is not a mammalian creative centre! + +Well then, if the idea of generally applicable regions is a mare's nest, as +was the search for the Holy Grail, what is the object of the study of +geographical distribution? It is nothing less than the history of the +evolution of life in space and time in the widest sense. The attempt to +account for the present distribution of any group of organisms involves the +aid of every branch of science. It bids fair to become a history of the +world. It started in a mild, statistical way, restricting itself to the +present fauna and flora and to the present configuration of land and water. +Next came Oceanography concerned with the depths of the seas, their +currents and temperatures; then enquiries into climatic changes, +culminating in irreconcilable astronomical hypotheses as to glacial epochs; +theories about changes of the level of the seas, mainly from the point of +view of the physicist and astronomer. Then came more and more to the front +the importance of the geological record, hand in hand with the +palaeontological data and the search for the natural affinities, the +genetic system of the organisms. Now and then it almost seems as if the +biologists had done their share by supplying the problems and that the +physicists and geologists would settle them, but in reality it is not so. +The biologists not only set the problems, they alone can check the offered +solutions. The mere fact of palms having flourished in Miocene Spitzbergen +led to an hypothetical shifting of the axis of the world rather than to the +assumption, by way of explanation, that the palms themselves might have +changed their nature. One of the most valuable aids in geological +research, often the only means for reconstructing the face of the earth in +by-gone periods, is afforded by fossils, but only the morphologist can +pronounce as to their trustworthiness as witnesses, because of the danger +of mistaking analogous for homologous forms. This difficulty applies +equally to living groups, and it is so important that a few instances may +not be amiss. + +There is undeniable similarity between the faunas of Madagascar and South +America. This was supported by the Centetidae and Dendrobatidae, two +entire "families," as also by other facts. The value of the Insectivores, +Solenodon in Cuba, Centetes in Madagascar, has been much lessened by their +recognition as an extremely ancient group and as a case of convergence, but +if they are no longer put into the same family, this amendment is really to +a great extent due to their widely discontinuous distribution. The only +systematic difference of the Dendrobatidae from the Ranidae is the absence +of teeth, morphologically a very unimportant character, and it is now +agreed, on the strength of their distribution, that these little arboreal, +conspicuously coloured frogs, Dendrobates in South America, Mantella in +Madagascar, do not form a natural group, although a third genus, +Cardioglossa in West Africa, seems also to belong to them. If these +creatures lived all on the same continent, we should unhesitatingly look +upon them as forming a well-defined, natural little group. On the other +hand the Aglossa, with their three very divergent genera, namely Pipa in +South America, Xenopus and Hymenochirus in Africa, are so well +characterised as one ancient group that we use their distribution +unhesitatingly as a hint of a former connection between the two continents. +We are indeed arguing in vicious circles. The Ratitae as such are +absolutely worthless since they are a most heterogeneous assembly, and +there are untold groups, of the artificiality of which many a zoo- +geographer had not the slightest suspicion when he took his statistical +material, the genera and families, from some systematic catalogues or +similar lists. A lamentable instance is that of certain flightless Rails, +recently extinct or sub-fossil, on the isalnds of Mauritius, Rodriguez and +Chatham. Being flightless they have been used in support of a former huge +Antarctic continent, instead of ruling them out of court as Rails which, +each in its island, have lost the power of flight, a process which must +have taken place so recently that it is difficult, upon morphological +grounds, to justify their separation into Aphanapteryx in Mauritius, +Erythromachus in Rodriguez and Diaphorapteryx on Chatham Island. +Morphologically they may well form but one genus, since they have sprung +from the same stock and have developed upon the same lines; they are +therefore monogenetic: but since we know that they have become what they +are independently of each other (now unlike any other Rails), they are +polygenetic and therefore could not form one genus in the old Darwinian +sense. Further, they are not a case of convergence, since their ancestry +is not divergent but leads into the same stratum. + +THE RECONSTRUCTION OF THE GEOGRAPHY OF SUCCESSIVE EPOCHS. + +A promising method is the study by the specialist of a large, widely +distributed group of animals from an evolutionary point of view. Good +examples of this method are afforded by A.E. Ortmann's ("The geographical +distribution of Freshwater Decapods and its bearing upon ancient +geography", "Proc. Amer. Phil. Soc." Vol. 41, 1902.) exhaustive paper and +by A.W. Grabau's "Phylogeny of Fusus and its Allies" ("Smithsonian Misc. +Coll." 44, 1904.) After many important groups of animals have been treated +in this way--as yet sparingly attempted--the results as to hypothetical +land-connections etc. are sure to be corrective and supplementary, and +their problems will be solved, since they are not imaginary. + +The same problems are attacked, in the reverse way, by starting with the +whole fauna of a country and thence, so to speak, letting the research +radiate. Some groups will be considered as autochthonous, others as +immigrants, and the directions followed by them will be inquired into; the +search may lead far and in various directions, and by comparison of +results, by making compound maps, certain routes will assume definite +shape, and if they lead across straits and seas they are warrants to search +for land-connections in the past. (A fair sample of this method is C.H. +Eigenmann's "The Freshwater Fishes of South and Middle America", "Popular +Science Monthly", Vol. 68, 1906.) There are now not a few maps purporting +to show the outlines of land and water at various epochs. Many of these +attempts do not tally with each other, owing to the lamentable deficiencies +of geological and fossil data, but the bolder the hypothetical outlines are +drawn, the better, and this is preferable to the insertion of bays and +similar detail which give such maps a fallacious look of certainty where +none exists. Moreover it must be borne in mind that, when we draw a broad +continental belt across an ocean, this belt need never have existed in its +entirety at any one time. The features of dispersal, intended to be +explained by it, would be accomplished just as well by an unknown number of +islands which have joined into larger complexes while elsewhere they +subsided again: like pontoon-bridges which may be opened anywhere, or like +a series of superimposed dissolving views of land and sea-scapes. Hence +the reconstructed maps of Europe, the only continent tolerably known, show +a considerable number of islands in puzzling changes, while elsewhere, e.g. +in Asia, we have to be satisfied with sweeping generalisations. + +At present about half-a-dozen big connections are engaging our attention, +leaving as comparatively settled the extent and the duration of such minor +"bridges" as that between Africa and Madagascar, Tasmania and Australia, +the Antilles and Central America, Europe and North Africa. (Not a few of +those who are fascinated by, and satisfied with, the statistical aspect of +distribution still have a strong dislike to the use of "bridges" if these +lead over deep seas, and they get over present discontinuous occurrences by +a former "universal or sub-universal distribution" of their groups. This +is indeed an easy method of cutting the knot, but in reality they shunt the +question only a stage or two back, never troubling to explain how their +groups managed to attain to that sub-universal range; or do they still +suppose that the whole world was originally one paradise where everything +lived side by side, until sin and strife and glacial epochs left nothing +but scattered survivors? + +The permanence of the great ocean-basins had become a dogma since it was +found that a universal elevation of the land to the extent of 100 fathoms +would produce but little changes, and when it was shown that even the 1000 +fathom-line followed the great masses of land rather closely, and still +leaving the great basins (although transgression of the sea to the same +extent would change the map of the world beyond recognition), by general +consent one mile was allowed as the utmost speculative limit of subsidence. +Naturally two or three miles, the average depth of the oceans, seems +enormous, and yet such a difference in level is as nothing in comparison +with the size of the Earth. On a clay model globe ten feet in diameter an +ocean bed three miles deep would scarcely be detected, and the highest +mountains would be smaller than the unavoidable grains in the glazed +surface of our model. There are but few countries which have not be +submerged at some time or other.) + +CONNECTION OF SOUTH EASTERN ASIA WITH AUSTRALIA. Neumayr's Sino-Australian +continent during mid-Mesozoic times was probably a much changing +Archipelago, with final separations subsequent to the Cretaceous period. +Henceforth Australasia was left to its own fate, but for a possible +connection with the antarctic continent. + +AFRICA, MADAGASCAR, INDIA. The "Lemuria" of Sclater and Haeckel cannot +have been more than a broad bridge in Jurassic times; whether it was ever +available for the Lemurs themselves must depend upon the time of its +duration, the more recent the better, but it is difficult to show that it +lasted into the Miocene. + +AFRICA AND SOUTH AMERICA. Since the opposite coasts show an entire absence +of marine fossils and deposits during the Mesozoic period, whilst further +north and south such are known to exist and are mostly identical on either +side, Neumayr suggested the existence of a great Afro-Son American mass of +land during the Jurassic epoch. Such land is almost a necessity and is +supported by many facts; it would easily explain the distribution of +numerous groups of terrestrial creatures. Moreover to the north of this +hypothetical land, somewhere across from the Antilles and Guiana to North +Africa and South Western Europe, existed an almost identical fauna of +Corals and Molluscs, indicating either a coast-line or a series of islands +interrupted by shallow seas, just as one would expect if, and when, a +Brazil-Ethiopian mass of land were breaking up. Lastly from Central +America to the Mediterranean stretches one of the Tertiary tectonic lines +of the geologists. Here also the great question is how long this continent +lasted. Apparently the South Atlantic began to encroach from the south so +that by the later Cretaceous epoch the land was reduced to a comparatively +narrow Brazil-West Africa, remnants of which persisted certainly into the +early Tertiary, until the South Atlantic joined across the equator with the +Atlantic portion of the "Thetys," leaving what remained of South America +isolated from the rest of the world. + +ANTARCTIC CONNECTIONS. Patagonia and Argentina seem to have joined +Antartica during the Cretaceous epoch, and this South Georgian bridge had +broken down again by mid-Tertiary times when South America became +consolidated. The Antarctic continent, presuming that it existed, seems +also to have been joined, by way of Tasmania, with Australia, also during +the Cretaceous epoch, and it is assumed that the great Australia-Antarctic- +Patagonian land was severed first to the south of Tasmania and then at the +South Georgian bridge. No connection, and this is important, is indicated +between Antarctica and either Africa or Madagascar. + +So far we have followed what may be called the vicissitudes of the great +Permo-Carboniferous Gondwana land in its fullest imaginary extent, an +enormous equatorial and south temperate belt from South America to Africa, +South India and Australia, which seems to have provided the foundation of +the present Southern continents, two of which temporarily joined +Antarctica, of which however we know nothing except that it exists now. + +Let us next consider the Arctic and periarctic lands. Unfortunately very +little is known about the region within the arctic circle. If it was all +land, or more likely great changing archipelagoes, faunistic exchange +between North America, Europe and Siberia would present no difficulties, +but there is one connection which engages much attention, namely a land +where now lies the North temperate and Northern part of the Atlantic ocean. +How far south did it ever extend and what is the latest date of a direct +practicable communication, say from North Western Europe to Greenland? +Connections, perhaps often interrupted, e.g. between Greenland and +Labrador, at another time between Greenland and Scandinavia, seem to have +existed at least since the Permo-Carboniferous epoch. If they existed also +in late Cretaceous and in Tertiary times, they would of course easily +explain exchanges which we know to have repeatedly taken place between +America and Europe, but they are not proved thereby, since most of these +exchanges can almost as easily have occurred across the polar regions, and +others still more easily by repeated junction of Siberia with Alaska. + +Let us now describe a hypothetical case based on the supposition of +connecting bridges. Not to work in a circle, we select an important group +which has not served as a basis for the reconstruction of bridges; and it +must be a group which we feel justified in assuming to be old enough to +have availed itself of ancient land-connections. + +The occurrence of one species of Peripatus in the whole of Australia, +Tasmania and New Zealand (the latter being joined to Australia by way of +New Britain in Cretaceous times but not later) puts the genus back into +this epoch, no unsatisfactory assumption to the morphologist. The apparent +absence of Peripatus in Madagascar indicates that it did not come from the +east into Africa, that it was neither Afro-Indian, nor Afro-Australian; nor +can it have started in South America. We therefore assume as its creative +centre Australia or Malaya in the Cretaceous epoch, whence its occurrence +in Sumatra, Malay Peninsula, New Britain, New Zealand and Australia is +easily explained. Then extension across Antarctica to Patagonia and Chile, +whence it could spread into the rest of South America as this became +consolidated in early Tertiary times. For getting to the Antilles and into +Mexico it would have to wait until the Miocene, but long before that time +it could arrive in Africa, there surviving as a Congolese and a Cape +species. This story is unsupported by a single fossil. Peripatus may have +been "sub-universal" all over greater Gondwana land in Carboniferous times, +and then its absence from Madagascar would be difficult to explain, but the +migrations suggested above amount to little considering that the distance +from Tasmania to South America could be covered in far less time than that +represented by the whole of the Eocene epoch alone. + +There is yet another field, essentially the domain of geographical +distribution, the cultivation of which promises fair to throw much light +upon Nature's way of making species. This is the study of the organisms +with regard to their environment. Instead of revealing pedigrees or of +showing how and when the creatures got to a certain locality, it +investigates how they behaved to meet the ever changing conditions of their +habitats. There is a facies, characteristic of, and often peculiar to, the +fauna of tropical moist forests, another of deserts, of high mountains, of +underground life and so forth; these same facies are stamped upon whole +associations of animals and plants, although these may be--and in widely +separated countries generally are--drawn from totally different families of +their respective orders. It does not go to the root of the matter to say +that these facies have been brought about by the extermination of all the +others which did not happen to fit into their particular environment. One +might almost say that tropical moist forests must have arboreal frogs and +that these are made out of whatever suitable material happened to be +available; in Australia and South America Hylidae, in Africa Ranidae, since +there Hylas are absent. The deserts must have lizards capable of standing +the glare, the great changes of temperature, of running over or burrowing +into the loose sand. When as in America Iguanids are available, some of +these are thus modified, while in Africa and Asia the Agamids are drawn +upon. Both in the Damara and in the Transcaspian deserts, a Gecko has been +turned into a runner upon sand! + +We cannot assume that at various epochs deserts, and at others moist +forests were continuous all over the world. The different facies and +associations were developed at various times and places. Are we to suppose +that, wherever tropical forests came into existence, amongst the stock of +humivagous lizards were always some which presented those nascent +variations which made them keep step with the similarly nascent forests, +the overwhelming rest being eliminated? This principle would imply that +the same stratum of lizards always had variations ready to fit any changed +environment, forests and deserts, rocks and swamps. The study of Ecology +indicates a different procedure, a great, almost boundless plasticity of +the organism, not in the sense of an exuberant moulding force, but of a +readiness to be moulded, and of this the "variations" are the visible +outcome. In most cases identical facies are produced by heterogeneous +convergences and these may seem to be but superficial, affecting only what +some authors are pleased to call the physiological characters; but +environment presumably affects first those parts by which the organism +comes into contact with it most directly, and if the internal structures +remain unchanged, it is not because these are less easily modified but +because they are not directly affected. When they are affected, they too +change deeply enough. + +That the plasticity should react so quickly--indeed this very quickness +seems to have initiated our mistaking the variations called forth for +something performed--and to the point, is itself the outcome of the long +training which protoplasm has undergone since its creation. + +In Nature's workshop he does not succeed who has ready an arsenal of tools +for every conceivable emergency, but he who can make a tool at the spur of +the moment. The ordeal of the practical test is Charles Darwin's glorious +conception of Natural Selection. + + +XVIII. DARWIN AND GEOLOGY. + +By J.W. JUDD, C.B., LL.D., F.R.S. + +(Mr Francis Darwin has related how his father occasionally came up from +Down to spend a few days with his brother Erasmus in London, and, after his +brother's death, with his daughter, Mrs Litchfield. On these occasions, it +was his habit to arrange meetings with Huxley, to talk over zoological +questions, with Hooker, to discuss botanical problems, and with Lyell to +hold conversations on geology. After the death of Lyell, Darwin, knowing +my close intimacy with his friend during his later years, used to ask me to +meet him when he came to town, and "talk geology." The "talks" took place +sometimes at Jermyn Street Museum, at other times in the Royal College of +Science, South Kensington; but more frequently, after having lunch with +him, at his brother's or his daughter's house. On several occasions, +however, I had the pleasure of visiting him at Down. In the postscript of +a letter (of April 15, 1880) arranging one of these visits, he writes: +"Since poor, dear Lyell's death, I rarely have the pleasure of geological +talk with anyone.") + +In one of the very interesting conversations which I had with Charles +Darwin during the last seven years of his life, he asked me in a very +pointed manner if I were able to recall the circumstances, accidental or +otherwise, which had led me to devote myself to geological studies. He +informed me that he was making similar inquiries of other friends, and I +gathered from what he said that he contemplated at that time a study of the +causes producing SCIENTIFIC BIAS in individual minds. I have no means of +knowing how far this project ever assumed anything like concrete form, but +certain it is that Darwin himself often indulged in the processes of mental +introspection and analysis; and he has thus fortunately left us--in his +fragments of autobiography and in his correspondence--the materials from +which may be reconstructed a fairly complete history of his own mental +development. + +There are two perfectly distinct inquiries which we have to undertake in +connection with the development of Darwin's ideas on the subject of +evolution: + +FIRST. How, when, and under what conditions was Darwin led to a conviction +that species were not immutable, but were derived from pre-existing forms? + +SECONDLY. By what lines of reasoning and research was he brought to regard +"natural selection" as a vera causa in the process of evolution? + +It is the first of these inquiries which specially interests the geologist; +though geology undoubtedly played a part--and by no means an insignificant +part--in respect to the second inquiry. + +When, indeed, the history comes to be written of that great revolution of +thought in the nineteenth century, by which the doctrine of evolution, from +being the dream of poets and visionaries, gradually grew to be the accepted +creed of naturalists, the paramount influence exerted by the infant science +of geology--and especially that resulting from the publication of Lyell's +epoch-making work, the "Principles of Geology"--cannot fail to be regarded +as one of the leading factors. Herbert Spencer in his "Autobiography" +bears testimony to the effect produced on his mind by the recently +published "Principles", when, at the age of twenty, he had already begun to +speculate on the subject of evolution (Herbert Spencer's "Autobiography", +London, 1904, Vol. I. pages 175-177.); and Alfred Russel Wallace is +scarcely less emphatic concerning the part played by Lyell's teaching in +his scientific education. (See "My Life; a record of Events and Opinions", +London, 1905, Vol. I. page 355, etc. Also his review of Lyell's +"Principles" in "Quarterly Review" (Vol. 126), 1869, pages 359-394. See +also "The Darwin-Wallace Celebration by the Linnean Society" (1909), page +118.) Huxley wrote in 1887 "I owe more than I can tell to the careful +study of the "Principles of Geology" in my young days." ("Science and +Pseudo Science"; "Collected Essays", London, 1902, Vol. V. page 101.) As +for Charles Darwin, he never tired--either in his published writings, his +private correspondence or his most intimate conversations--of ascribing the +awakening of his enthusiasm and the direction of his energies towards the +elucidation of the problem of development to the "Principles of Geology" +and the personal influence of its author. Huxley has well expressed what +the author of the "Origin of Species" so constantly insisted upon, in the +statements "Darwin's greatest work is the outcome of the unflinching +application to Biology of the leading idea and the method applied in the +"Principles" to Geology ("Proc. Roy. Soc." Vol. XLIV. (1888), page viii.; +"Collected Essays" II. page 268, 1902.), and "Lyell, for others, as for +myself, was the chief agent in smoothing the road for Darwin." ("Life and +Letters of Charles Darwin" II. page 190.) + +We propose therefore to consider, first, what Darwin owed to geology and +its cultivators, and in the second place how he was able in the end so +fully to pay a great debt which he never failed to acknowledge. Thanks to +the invaluable materials contained in the "Life and Letters of Charles +Darwin" (3 vols.) published by Mr Francis Darwin in 1887; and to "More +Letters of Charles Darwin" (2 vols.) issued by the same author, in +conjunction with Professor A.C. Seward, in 1903, we are permitted to follow +the various movements in Darwin's mind, and are able to record the story +almost entirely in his own words. (The first of these works is indicated +in the following pages by the letters "L.L."; the second by "M.L.") + +From the point of view of the geologist, Darwin's life naturally divides +itself into four periods. In the first, covering twenty-two years, various +influences were at work militating, now for and now against, his adoption +of a geological career; in the second period--the five memorable years of +the voyage of the "Beagle"--the ardent sportsman with some natural-history +tastes, gradually became the most enthusiastic and enlightened of +geologists; in the third period, lasting ten years, the valuable geological +recruit devoted nearly all his energies and time to geological study and +discussion and to preparing for publication the numerous observations made +by him during the voyage; the fourth period, which covers the latter half +of his life, found Darwin gradually drawn more and more from geological to +biological studies, though always retaining the deepest interest in the +progress and fortunes of his "old love." But geologists gladly recognise +the fact that Darwin immeasurably better served their science by this +biological work, than he could possibly have done by confining himself to +purely geological questions. + +From his earliest childhood, Darwin was a collector, though up to the time +when, at eight years of age, he went to a preparatory school, seals, franks +and similar trifles appear to have been the only objects of his quest. But +a stone, which one of his schoolfellows at that time gave to him, seems to +have attracted his attention and set him seeking for pebbles and minerals; +as the result of this newly acquired taste, he says (writing in 1838) "I +distinctly recollect the desire I had of being able to know something about +every pebble in front of the hall door--it was my earliest and only +geological aspiration at that time." ("M.L." I. page 3.) He further +suspects that while at Mr Case's school "I do not remember any mental +pursuits except those of collecting stones," etc..."I was born a +naturalist." ("M.L." I. page 4.) + +The court-yard in front of the hall door at the Mount House, Darwin's +birthplace and the home of his childhood, is surrounded by beds or +rockeries on which lie a number of pebbles. Some of these pebbles (in +quite recent times as I am informed) have been collected to form a +"cobbled" space in front of the gate in the outer wall, which fronts the +hall door; and a similar "cobbled area," there is reason to believe, may +have existed in Darwin's childhood before the door itself. The pebbles, +which were obtained from a neighbouring gravel-pit, being derived from the +glacial drift, exhibit very striking differences in colour and form. It +was probably this circumstance which awakened in the child his love of +observation and speculation. It is certainly remarkable that "aspirations" +of the kind should have arisen in the mind of a child of 9 or 10! + +When he went to Shrewsbury School, he relates "I continued collecting +minerals with much zeal, but quite unscientifically,--all that I cared +about was a new-NAMED mineral, and I hardly attempted to classify them." +("L.L." I. page 34.) + +There has stood from very early times in Darwin's native town of +Shrewsbury, a very notable boulder which has probably marked a boundary and +is known as the "Bell-stone"--giving its name to a house and street. +Darwin tells us in his "Autobiography" that while he was at Shrewsbury +School at the age of 13 or 14 "an old Mr Cotton in Shropshire, who knew a +good deal about rocks" pointed out to me "...the 'bell-stone'; he told me +that there was no rock of the same kind nearer than Cumberland or Scotland, +and he solemnly assured me that the world would come to an end before +anyone would be able to explain how this stone came where it now lay"! +Darwin adds "This produced a deep impression on me, and I meditated over +this wonderful stone." ("L.L." I. page 41.) + +The "bell-stone" has now, owing to the necessities of building, been +removed a short distance from its original site, and is carefully preserved +within the walls of a bank. It is a block of irregular shape 3 feet long +and 2 feet wide, and about 1 foot thick, weighing probably not less than +one-third of a ton. By the courtesy of the directors of the National +Provincial Bank of England, I have been able to make a minute examination +of it, and Professors Bonney and Watts, with Mr Harker and Mr Fearnsides +have given me their valuable assistance. The rock is a much altered +andesite and was probably derived from the Arenig district in North Wales, +or possibly from a point nearer the Welsh Border. (I am greatly indebted +to the Managers of the Bank at Shrewsbury for kind assistance in the +examination of this interesting memorial: and Mr H.T. Beddoes, the Curator +of the Shrewsbury Museum, has given me some archaeological information +concerning the stone. Mr Richard Cotton was a good local naturalist, a +Fellow both of the Geological and Linnean Societies; and to the officers of +these societies I am indebted for information concerning him. He died in +1839, and although he does not appear to have published any scientific +papers, he did far more for science by influencing the career of the school +boy!" It was of course brought to where Shrewsbury now stands by the +agency of a glacier--as Darwin afterwards learnt. + +We can well believe from the perusal of these reminiscences that, at this +time, Darwin's mind was, as he himself says, "prepared for a philosophical +treatment of the subject" of Geology. ("L.L." I. page 41.) When at the +age of 16, however, he was entered as a medical student at Edinburgh +University, he not only did not get any encouragement of his scientific +tastes, but was positively repelled by the ordinary instruction given +there. Dr Hope's lectures on Chemistry, it is true, interested the boy, +who with his brother Erasmus had made a laboratory in the toolhouse, and +was nicknamed "Gas" by his schoolfellows, while undergoing solemn and +public reprimand from Dr Butler at Shrewsbury School for thus wasting his +time. ("L.L." I. page 35.) But most of the other Edinburgh lectures were +"intolerably dull," "as dull as the professors" themselves, "something +fearful to remember." In after life the memory of these lectures was like +a nightmare to him. He speaks in 1840 of Jameson's lectures as something +"I...for my sins experienced!" ("L.L." I. page 340.) Darwin especially +signalises these lectures on Geology and Zoology, which he attended in his +second year, as being worst of all "incredibly dull. The sole effect they +produced on me was the determination never so long as I lived to read a +book on Geology, or in any way to study the science!" ("L.L." I. page 41.) + +The misfortune was that Edinburgh at that time had become the cockpit in +which the barren conflict between "Neptunism" and Plutonism" was being +waged with blind fury and theological bitterness. Jameson and his pupils, +on the one hand, and the friends and disciples of Hutton, on the other, +went to the wildest extremes in opposing each other's peculiar tenets. +Darwin tells us that he actually heard Jameson "in a field lecture at +Salisbury Craigs, discoursing on a trap-dyke, with amygdaloidal margins and +the strata indurated on each side, with volcanic rocks all around us, say +that it was a fissure filled with sediment from above, adding with a sneer +that there were men who maintained that it had been injected from beneath +in a molten condition." ("L.L." I. pages 41-42.) "When I think of this +lecture," added Darwin, "I do not wonder that I determined never to attend +to Geology." (This was written in 1876 and Darwin had in the summer of +1839 revisited and carefully studied the locality ("L.L." I. page 290.) It +is probable that most of Jameson's teaching was of the same controversial +and unilluminating character as this field-lecture at Salisbury Craigs. + +There can be no doubt that, while at Edinburgh, Darwin must have become +acquainted with the doctrines of the Huttonian School. Though so young, he +mixed freely with the scientific society of the city, Macgillivray, Grant, +Leonard Horner, Coldstream, Ainsworth and others being among his +acquaintances, while he attended and even read papers at the local +scientific societies. It is to be feared, however, that what Darwin would +hear most of, as characteristic of the Huttonian teaching, would be +assertions that chalk-flints were intrusions of molten silica, that fossil +wood and other petrifactions had been impregnated with fused materials, +that heat--but never water--was always the agent by which the induration +and crystallisation of rock-materials (even siliceous conglomerate, +limestone and rock-salt) had been effected! These extravagant "anti- +Wernerian" views the young student might well regard as not one whit less +absurd and repellant than the doctrine of the "aqueous precipitation" of +basalt. There is no evidence that Darwin, even if he ever heard of them, +was in any way impressed, in his early career, by the suggestive passages +in Hutton and Playfair, to which Lyell afterwards called attention, and +which foreshadowed the main principles of Uniformitarianism. + +As a matter of fact, I believe that the influence of Hutton and Playfair in +the development of a philosophical theory of geology has been very greatly +exaggerated by later writers on the subject. Just as Wells and Matthew +anticipated the views of Darwin on Natural Selection, but without producing +any real influence on the course of biological thought, so Hutton and +Playfair adumbrated doctrines which only became the basis of vivifying +theory in the hands of Lyell. Alfred Russel Wallace has very justly +remarked that when Lyell wrote the "Principles of Geology", "the doctrines +of Hutton and Playfair, so much in advance of their age, seemed to be +utterly forgotten." ("Quarterly Review", Vol. CXXVI. (1869), page 363.) +In proof of this it is only necessary to point to the works of the great +masters of English geology, who preceded Lyell, in which the works of +Hutton and his followers are scarcely ever mentioned. This is true even of +the "Researches in Theoretical Geology" and the other works of the +sagacious De la Beche. (Of the strength and persistence of the prejudice +felt against Lyell's views by his contemporaries, I had a striking +illustration some little time after Lyell's death. One of the old +geologists who in the early years of the century had done really good work +in connection with the Geological Society expressed a hope that I was not +"one of those who had been carried away by poor Lyell's fads." My surprise +was indeed great when further conversation showed me that the whole of the +"Principles" were included in the "fads"!) Darwin himself possessed a copy +of Playfair's "Illustrations of the Huttonian Theory", and occasionally +quotes it; but I have met with only one reference to Hutton, and that a +somewhat enigmatical one, in all Darwin's writings. In a letter to Lyell +in 1841, when his mind was much exercised concerning glacial questions, he +says "What a grand new feature all this ice work is in Geology! How old +Hutton would have stared!" ("M.L." II. page 149.) + +As a consequence of the influences brought to bear on his mind during his +two years' residence in Edinburgh, Darwin, who had entered that University +with strong geological aspirations, left it and proceeded to Cambridge with +a pronounced distaste for the whole subject. The result of this was that, +during his career as an under-graduate, he neglected all the opportunities +for geological study. During that important period of life, when he was +between eighteen and twenty years of age, Darwin spent his time in riding, +shooting and beetle-hunting, pursuits which were undoubtedly an admirable +preparation for his future work as an explorer; but in none of his letters +of this period does he even mention geology. He says, however, "I was so +sickened with lectures at Edinburgh that I did not even attend Sedgwick's +eloquent and interesting lectures." ("L.L." I. page 48.) + +It was only after passing his examination, and when he went up to spend two +extra terms at Cambridge, that geology again began to attract his +attention. The reading of Sir John Herschel's "Introduction to the Study +of Natural Philosophy", and of Humboldt's "Personal Narrative", a copy of +which last had been given to him by his good friend and mentor Henslow, +roused his dormant enthusiasm for science, and awakened in his mind a +passionate desire for travel. And it was from Henslow, whom he had +accompanied in his excursions, but without imbibing any marked taste, at +that time, for botany, that the advice came to think of and to "begin the +study of geology." ("L.L." I. page 56.) This was in 1831, and in the +summer vacation of that year we find him back again at Shrewsbury "working +like a tiger" at geology and endeavouring to make a map and section of +Shropshire--work which he says was not "as easy as I expected." ("L.L." I. +page 189.) No better field for geological studies could possibly be found +than Darwin's native county. + +Writing to Henslow at this time, and referring to a form of the instrument +devised by his friend, Darwin says: "I am very glad to say I think the +clinometer will answer admirably. I put all the tables in my bedroom at +every conceivable angle and direction. I will venture to say that I have +measured them as accurately as any geologist going could do." But he adds: +"I have been working at so many things that I have not got on much with +geology. I suspect the first expedition I take, clinometer and hammer in +hand, will send me back very little wiser and a good deal more puzzled than +when I started." ("L.L." I. page 189.) Valuable aid was, however, at +hand, for at this time Sedgwick, to whom Darwin had been introduced by the +ever-helpful Henslow, was making one of his expeditions into Wales, and +consented to accept the young student as his companion during the +geological tour. ("L.L." I. page 56.) We find Darwin looking forward to +this privilege with the keenest interest. ("L.L." I. page 189.) + +When at the beginning of August (1831), Sedgwick arrived at his father's +house in Shrewsbury, where he spent a night, Darwin began to receive his +first and only instruction as a field-geologist. The journey they took +together led them through Llangollen, Conway, Bangor, and Capel Curig, at +which latter place they parted after spending many hours in examining the +rocks at Cwm Idwal with extreme care, seeking for fossils but without +success. Sedgwick's mode of instruction was admirable--he from time to +time sent the pupil off on a line parallel to his own, "telling me to bring +back specimens of the rocks and to mark the stratification on a map." +("L.L." I. page 57.) On his return to Shrewsbury, Darwin wrote to Henslow, +"My trip with Sedgwick answered most perfectly," ("L.L." I. page 195.), and +in the following year he wrote again from South America to the same friend, +"Tell Professor Sedgwick he does not know how much I am indebted to him for +the Welsh expedition; it has given me an interest in Geology which I would +not give up for any consideration. I do not think I ever spent a more +delightful three weeks than pounding the north-west mountains." ("L.L." I. +pages 237-8.) + +It would be a mistake, however, to suppose that at this time Darwin had +acquired anything like the affection for geological study, which he +afterwards developed. After parting with Sedgwick, he walked in a straight +line by compass and map across the mountains to Barmouth to visit a reading +party there, but taking care to return to Shropshire before September 1st, +in order to be ready for the shooting. For as he candidly tells us, "I +should have thought myself mad to give up the first days of partridge- +shooting for geology or any other science!" ("L.L." I. page 58.) + +Any regret we may be disposed to feel that Darwin did not use his +opportunities at Edinburgh and Cambridge to obtain systematic and practical +instruction in mineralogy and geology, will be mitigated, however, when we +reflect on the danger which he would run of being indoctrinated with the +crude "catastrophic" views of geology, which were at that time prevalent in +all the centres of learning. + +Writing to Henslow in the summer of 1831, Darwin says "As yet I have only +indulged in hypotheses, but they are such powerful ones that I suppose, if +they were put into action but for one day, the world would come to an end." +("L.L." I. page 189.) + +May we not read in this passage an indication that the self-taught +geologist had, even at this early stage, begun to feel a distrust for the +prevalent catastrophism, and that his mind was becoming a field in which +the seeds which Lyell was afterwards to sow would "fall on good ground"? + +The second period of Darwin's geological career--the five years spent by +him on board the "Beagle"--was the one in which by far the most important +stage in his mental development was accomplished. He left England a +healthy, vigorous and enthusiastic collector; he returned five years later +with unique experiences, the germs of great ideas, and a knowledge which +placed him at once in the foremost ranks of the geologists of that day. +Huxley has well said that "Darwin found on board the "Beagle" that which +neither the pedagogues of Shrewsbury, nor the professoriate of Edinburgh, +nor the tutors of Cambridge had managed to give him." ("Proc. Roy. Soc." +Vol. XLIV. (1888), page IX.) Darwin himself wrote, referring to the date +at which the voyage was expected to begin: "My second life will then +commence, and it shall be as a birthday for the rest of my life." ("L.L." +I. page 214.); and looking back on the voyage after forty years, he wrote; +"The voyage of the 'Beagle' has been by far the most important event in my +life, and has determined my whole career;...I have always felt that I owe +to the voyage the first real training or education of my mind; I was led to +attend closely to several branches of natural history, and thus my powers +of observation were improved, though they were always fairly developed." +("L.L." I. page 61.) + +Referring to these general studies in natural history, however, Darwin adds +a very significant remark: "The investigation of the geology of the places +visited was far more important, as reasoning here comes into play. On +first examining a new district nothing can appear more hopeless than the +chaos of rocks; but by recording the stratification and nature of the rocks +and fossils at many points, always reasoning and predicting what will be +found elsewhere, light soon begins to dawn on the district, and the +structure of the whole becomes more or less intelligible." ("L.L." I. page +62.) + +The famous voyage began amid doubts, discouragements and disappointments. +Fearful of heart-disease, sad at parting from home and friends, depressed +by sea-sickness, the young explorer, after being twice driven back by +baffling winds, reached the great object of his ambition, the island of +Teneriffe, only to find that, owing to quarantine regulations, landing was +out of the question. + +But soon this inauspicious opening of the voyage was forgotten. Henslow +had advised his pupil to take with him the first volume of Lyell's +"Principles of Geology", then just published--but cautioned him (as nearly +all the leaders in geological science at that day would certainly have +done) "on no account to accept the views therein advocated." ("L.L." I. +page 73.) It is probable that the days of waiting, discomfort and sea- +sickness at the beginning of the voyage were relieved by the reading of +this volume. For he says that when he landed, three weeks after setting +sail from Plymouth, in St Jago, the largest of the Cape de Verde Islands, +the volume had already been "studied attentively; and the book was of the +highest service to me in many ways..." His first original geological work, +he declares, "showed me clearly the wonderful superiority of Lyell's manner +of treating geology, compared with that of any other author, whose works I +had with me or ever afterwards read." ("L.L." I. page 62.) + +At St Jago Darwin first experienced the joy of making new discoveries, and +his delight was unbounded. Writing to his father he says, "Geologising in +a volcanic country is most delightful; besides the interest attached to +itself, it leads you into most beautiful and retired spots." ("L.L." I. +page 228.) To Henslow he wrote of St Jago: "Here we spent three most +delightful weeks...St Jago is singularly barren, and produces few plants or +insects, so that my hammer was my usual companion, and in its company most +delightful hours I spent." "The geology was pre-eminently interesting, and +I believe quite new; there are some facts on a large scale of upraised +coast (which is an excellent epoch for all the volcanic rocks to date +from), that would interest Mr Lyell." ("L.L." I. page 235.) After more +than forty years the memory of this, his first geological work, seems as +fresh as ever, and he wrote in 1876, "The geology of St Jago is very +striking, yet simple: a stream of lava formerly flowed over the bed of the +sea, formed of triturated recent shells and corals, which it has baked into +a hard white rock. Since then the whole island has been upheaved. But the +line of white rock revealed to me a new and important fact, namely, that +there had been afterwards subsidence round the craters, which had since +been in action, and had poured forth lava." ("L.L." I. page 65.) + +It was at this time, probably, that Darwin made his first attempt at +drawing a sketch-map and section to illustrate the observations he had made +(see his "Volcanic Islands", pages 1 and 9). His first important +geological discovery, that of the subsidence of strata around volcanic +vents (which has since been confirmed by Mr Heaphy in New Zealand and other +authors) awakened an intense enthusiasm, and he writes: "It then first +dawned on me that I might perhaps write a book on the geology of the +various countries visited, and this made me thrill with delight. That was +a memorable hour to me, and how distinctly I can call to mind the low cliff +of lava beneath which I rested, with the sun glaring hot, a few strange +desert plants growing near, and with living corals in the tidal pools at my +feet." ("L.L." I. page 66.) + +But it was when the "Beagle", after touching at St Paul's rock and Tristan +d'Acunha (for a sufficient time only to collect specimens), reached the +shores of South America, that Darwin's real work began; and he was able, +while the marine surveys were in progress, to make many extensive journeys +on land. His letters at this time show that geology had become his chief +delight, and such exclamations as "Geology carries the day," "I find in +Geology a never failing interest," etc. abound in his correspondence. + +Darwin's time was divided between the study of the great deposits of red +mud--the Pampean formation--with its interesting fossil bones and shells +affording proofs of slow and constant movements of the land, and the +underlying masses of metamorphic and plutonic rocks. Writing to Henslow in +March, 1834, he says: "I am quite charmed with Geology, but, like the wise +animal between two bundles of hay, I do not know which to like best; the +old crystalline groups of rocks, or the softer and fossiliferous beds. +When puzzling about stratification, etc., I feel inclined to cry 'a fig for +your big oysters, and your bigger megatheriums.' But then when digging out +some fine bones, I wonder how any man can tire his arms with hammering +granite." ("L.L." I. page 249.) We are told by Darwin that he loved to +reason about and attempt to predict the nature of the rocks in each new +district before he arrived at it. + +This love of guessing as to the geology of a district he was about to visit +is amusingly expressed by him in a letter (of May, 1832) to his cousin and +old college-friend, Fox. After alluding to the beetles he had been +collecting--a taste his friend had in common with himself--he writes of +geology that "It is like the pleasure of gambling. Speculating on first +arriving, what the rocks may be, I often mentally cry out 3 to 1 tertiary +against primitive; but the latter have hitherto won all the bets." ("L.L." +I. page 233.) + +Not the least important of the educational results of the voyage to Darwin +was the acquirement by him of those habits of industry and method which +enabled him in after life to accomplish so much--in spite of constant +failures of health. From the outset, he daily undertook and resolutely +accomplished, in spite of sea-sickness and other distractions, four +important tasks. In the first place he regularly wrote up the pages of his +Journal, in which, paying great attention to literary style and +composition, he recorded only matters that would be of general interest, +such as remarks on scenery and vegetation, on the peculiarities and habits +of animals, and on the characters, avocations and political institutions of +the various races of men with whom he was brought in contact. It was the +freshness of these observations that gave his "Narrative" so much charm. +Only in those cases in which his ideas had become fully crystallised, did +he attempt to deal with scientific matters in this journal. His second +task was to write in voluminous note-books facts concerning animals and +plants, collected on sea or land, which could not be well made out from +specimens preserved in spirit; but he tells us that, owing to want of skill +in dissecting and drawing, much of the time spent in this work was entirely +thrown away, "a great pile of MS. which I made during the voyage has proved +almost useless." ("L.L." I. page 62.) Huxley confirmed this judgment on +his biological work, declaring that "all his zeal and industry resulted, +for the most part, in a vast accumulation of useless manuscript." ("Proc. +Roy. Soc." Vol. XLIV. (1888), page IX.) Darwin's third task was of a very +different character and of infinitely greater value. It consisted in +writing notes of his journeys on land--the notes being devoted to the +geology of the districts visited by him. These formed the basis, not only +of a number of geological papers published on his return, but also of the +three important volumes forming "The Geology of the voyage of the +'Beagle'". On July 24th, 1834, when little more than half of the voyage +had been completed, Darwin wrote to Henslow, "My notes are becoming bulky. +I have about 600 small quarto pages full; about half of this is Geology." +("M.L." I. page 14.) The last, and certainly not the least important of +all his duties, consisted in numbering, cataloguing, and packing his +specimens for despatch to Henslow, who had undertaken the care of them. In +his letters he often expresses the greatest solicitude lest the value of +these specimens should be impaired by the removal of the numbers +corresponding to his manuscript lists. Science owes much to Henslow's +patient care of the collections sent to him by Darwin. The latter wrote in +Henslow's biography, "During the five years' voyage, he regularly +corresponded with me and guided my efforts; he received, opened, and took +care of all the specimens sent home in many large boxes." ("Life of +Henslow", by L. Jenyns (Blomefield), London, 1862, page 53.) + +Darwin's geological specimens are now very appropriately lodged for the +most part in the Sedgwick Museum, Cambridge, his original Catalogue with +subsequent annotations being preserved with them. From an examination of +these catalogues and specimens we are able to form a fair notion of the +work done by Darwin in his little cabin in the "Beagle", in the intervals +between his land journeys. + +Besides writing up his notes, it is evident that he was able to accomplish +a considerable amount of study of his specimens, before they were packed up +for despatch to Henslow. Besides hand-magnifiers and a microscope, Darwin +had an equipment for blowpipe-analysis, a contact-goniometer and magnet; +and these were in constant use by him. His small library of reference (now +included in the Collection of books placed by Mr F. Darwin in the Botany +School at Cambridge ("Catalogue of the Library of Charles Darwin now in the +Botany School, Cambridge". Compiled by H.W. Rutherford; with an +introduction by Francis Darwin. Cambridge, 1908.)) appears to have been +admirably selected, and in all probability contained (in addition to a good +many works relating to South America) a fair number of excellent books of +reference. Among those relating to mineralogy, he possessed the manuals of +Phillips, Alexander Brongniart, Beudant, von Kobell and Jameson: all the +"Cristallographie" of Brochant de Villers and, for blowpipe work, Dr +Children's translation of the book of Berzelius on the subject. In +addition to these, he had Henry's "Experimental Chemistry" and Ure's +"Dictionary" (of Chemistry). A work, he evidently often employed, was P. +Syme's book on "Werner's Nomenclature of Colours"; while, for Petrology, he +used Macculloch's "Geological Classification of Rocks". How diligently and +well he employed his instruments and books is shown by the valuable +observations recorded in the annotated Catalogues drawn up on board ship. + +These catalogues have on the right-hand pages numbers and descriptions of +the specimens, and on the opposite pages notes on the specimens--the result +of experiments made at the time and written in a very small hand. Of the +subsequently made pencil notes, I shall have to speak later. (I am greatly +indebted to my friend Mr A. Harker, F.R.S., for his assistance in examining +these specimens and catalogues. He has also arranged the specimens in the +Sedgwick Museum, so as to make reference to them easy. The specimens from +Ascension and a few others are however in the Museum at Jermyn Street.) + +It is a question of great interest to determine the period and the occasion +of Darwin's first awakening to the great problem of the transmutation of +species. He tells us himself that his grandfather's "Zoonomia" had been +read by him "but without producing any effect," and that his friend Grant's +rhapsodies on Lamarck and his views on evolution only gave rise to +"astonishment." ("L.L." I. page 38.) + +Huxley, who had probably never seen the privately printed volume of letters +to Henslow, expressed the opinion that Darwin could not have perceived the +important bearing of his discovery of bones in the Pampean Formation, until +they had been studied in England, and their analogies pronounced upon by +competent comparative anatomists. And this seemed to be confirmed by +Darwin's own entry in his pocket-book for 1837, "In July opened first +notebook on Transmutation of Species. Had been greatly struck from about +the month of previous March on character of South American fossils..." +("L.L." I. page 276.) + +The second volume of Lyell's "Principles of Geology" was published in +January, 1832, and Darwin's copy (like that of the other two volumes, in a +sadly dilapidated condition from constant use) has in it the inscription, +"Charles Darwin, Monte Video. Nov. 1832." As everyone knows, Darwin in +dedicating the second edition of his Journal of the Voyage to Lyell +declared, "the chief part of whatever scientific merit this journal and the +other works of the author may possess, has been derived from studying the +well-known and admirable "Principles of Geology". + +In the first chapter of this second volume of the "Principles", Lyell +insists on the importance of the species question to the geologist, but +goes on to point out the difficulty of accepting the only serious attempt +at a transmutation theory which had up to that time appeared--that of +Lamarck. In subsequent chapters he discusses the questions of the +modification and variability of species, of hybridity, and of the +geographical distribution of plants and animals. He then gives vivid +pictures of the struggle for existence, ever going on between various +species, and of the causes which lead to their extinction--not by +overwhelming catastrophes, but by the silent and almost unobserved action +of natural causes. This leads him to consider theories with regard to the +introduction of new species, and, rejecting the fanciful notions of +"centres or foci of creation," he argues strongly in favour of the view, as +most reconcileable with observed facts, that "each species may have had its +origin in a single pair, or individual, where an individual was sufficient, +and species may have been created in succession at such times and in such +places as to enable them to multiply and endure for an appointed period, +and occupy an appointed space on the globe." ("Principles of Geology", +Vol. II. (1st edition 1832), page 124. We now know, as has been so well +pointed out by Huxley, that Lyell, as early as 1827, was prepared to accept +the doctrine of the transmutation of species. In that year he wrote to +Mantell, "What changes species may really undergo! How impossible will it +be to distinguish and lay down a line, beyond which some of the so-called +extinct species may have never passed into recent ones" (Lyell's "Life and +Letters" Vol. I. page 168). To Sir John Herschel in 1836, he wrote, "In +regard to the origination of new species, I am very glad to find that you +think it probable that it may be carried on through the intervention of +intermediate causes. I left this rather to be inferred, not thinking it +worth while to offend a certain class of persons by embodying in words what +would only be a speculation" (Ibid. page 467). He expressed the same views +to Whewell in 1837 (Ibid. Vol. II. page 5.), and to Sedgwick (Ibid. Vol. +II. page 36) to whom he says, of "the theory, that the creation of new +species is going on at the present day"--"I really entertain it," but "I +have studiously avoided laying the doctrine down dogmatically as capable of +proof" (see Huxley in "L.L." II. pages 190-195.)) + +After pointing out how impossible it would be for a naturalist to prove +that a newly DISCOVERED species was really newly CREATED (Mr F. Darwin has +pointed out that his father (like Lyell) often used the term "Creation" in +speaking of the origin of new species ("L.L." II. chapter 1.)), Lyell +argued that no satisfactory evidence OF THE WAY in which these new forms +were created, had as yet been discovered, but that he entertained the hope +of a possible solution of the problem being found in the study of the +geological record. + +It is not difficult, in reading these chapters of Lyell's great work, to +realise what an effect they would have on the mind of Darwin, as new facts +were collected and fresh observations concerning extinct and recent forms +were made in his travels. We are not surprised to find him writing home, +"I am become a zealous disciple of Mr Lyell's views, as known in his +admirable book. Geologising in South America, I am tempted to carry parts +to a greater extent even than he does." ("L.L." I. page 263.) + +Lyell's anticipation that the study of the geological record might afford a +clue to the discovery of how new species originate was remarkably +fulfilled, within a few months, by Darwin's discovery of fossil bones in +the red Pampean mud. + +It is very true that, as Huxley remarked, Darwin's knowledge of comparative +anatomy must have been, at that time, slight; but that he recognised the +remarkable resemblances between the extinct and existing mammals of South +America is proved beyond all question by a passage in his letter to +Henslow, written November 24th, 1832: "I have been very lucky with fossil +bones; I have fragments of at least six distinct animals...I found a large +surface of osseous polygonal plates...Immediately I saw them I thought they +must belong to an enormous armadillo, living species of which genus are so +abundant here," and he goes on to say that he has "the lower jaw of some +large animal which, from the molar teeth, I should think belonged to the +Edentata." ("M.L." I. pages 11, 12. See "Extracts of Letters addressed to +Prof. Henslow by C. Darwin" (1835), page 7.) + +Having found this important clue, Darwin followed it up with characteristic +perseverance. In his quest for more fossil bones he was indefatigable. Mr +Francis Darwin tells us, "I have often heard him speak of the despair with +which he had to break off the projecting extremity of a huge, partly +excavated bone, when the boat waiting for him would wait no longer." +("L.L." I. page 276 (footnote).) Writing to Haeckel in 1864, Darwin says: +"I shall never forget my astonishment when I dug out a gigantic piece of +armour, like that of the living armadillo." (Haeckel, "History of +Creation", Vol. I. page 134, London, 1876.) + +In a letter to Henslow in 1834 Darwin says: "I have just got scent of some +fossil bones...what they may be I do not know, but if gold or galloping +will get them they shall be mine." ("M.L." I. page 15.) + +Darwin also showed his sense of the importance of the discovery of these +bones by his solicitude about their safe arrival and custody. From the +Falkland Isles (March, 1834), he writes to Henslow: "I have been alarmed +by your expression 'cleaning all the bones' as I am afraid the printed +numbers will be lost: the reason I am so anxious they should not be, is, +that a part were found in a gravel with recent shells, but others in a very +different bed. Now with these latter there were bones of an Agouti, a +genus of animals, I believe, peculiar to America, and it would be curious +to prove that some one of the genus co-existed with the Megatherium: such +and many other points depend on the numbers being carefully preserved." +("Extracts from Letters etc.", pages 13-14.) In the abstract of the notes +read to the Geological Society in 1835, we read: "In the gravel of +Patagonia he (Darwin) also found many bones of the Megatherium and of five +or six other species of quadrupeds, among which he has detected the bones +of a species of Agouti. He also met with several examples of the polygonal +plates, etc." ("Proc. Geol. Soc." Vol. II. pages 211-212.) + +Darwin's own recollections entirely bear out the conclusion that he fully +recognised, WHILE IN SOUTH AMERICA, the wonderful significance of the +resemblances between the extinct and recent mammalian faunas. He wrote in +his "Autobiography": "During the voyage of the 'Beagle' I had been deeply +impressed by discovering in the Pampean formation great fossil animals +covered with armour like that on the existing armadillos." ("L.L." I. page +82.) + +The impression made on Darwin's mind by the discovery of these fossil +bones, was doubtless deepened as, in his progress southward from Brazil to +Patagonia, he found similar species of Edentate animals everywhere +replacing one another among the living forms, while, whenever fossils +occurred, they also were seen to belong to the same remarkable group of +animals. (While Darwin was making these observations in South America, a +similar generalisation to that at which he arrived was being reached, quite +independently and almost simultaneously, with respect to the fossil and +recent mammals of Australia. In the year 1831, Clift gave to Jameson a +list of bones occurring in the caves and breccias of Australia, and in +publishing this list the latter referred to the fact that the forms +belonged to marsupials, similar to those of the existing Australian fauna. +But he also stated that, as a skull had been identified (doubtless +erroneously) as having belonged to a hippopotamus, other mammals than +marsupials must have spread over the island in late Tertiary times. It is +not necessary to point out that this paper was quite unknown to Darwin +while in South America. Lyell first noticed it in the third edition of his +"Principles", which was published in May, 1834 (see "Edinb. New Phil. +Journ." Vol. X. (1831), pages 394-6, and Lyell's "Principles" (3rd +edition), Vol. III. page 421). Darwin referred to this discovery in 1839 +(see his "Journal", page 210.) + +That the passage in Darwin's pocket-book for 1837 can only refer to an +AWAKENING of Darwin's interest in the subject--probably resulting from a +sight of the bones when they were being unpacked--I think there cannot be +the smallest doubt; AND WE MAY THEREFORE CONFIDENTLY FIX UPON NOVEMBER, +1832, AS THE DATE AT WHICH DARWIN COMMENCED THAT LONG SERIES OF +OBSERVATIONS AND REASONINGS WHICH EVENTUALLY CULMINATED IN THE PREPARATION +OF THE "ORIGIN OF SPECIES". Equally certain is it, that it was his +geological work that led Darwin into those paths of research which in the +end conducted him to his great discoveries. I quite agree with the view +expressed by Mr F. Darwin and Professor Seward, that Darwin, like Lyell, +"thought it 'almost useless' to try to prove the truth of evolution until +the cause of change was discovered" ("M.L." I. page 38.), and that possibly +he may at times have vacillated in his opinions, but I believe there is +evidence that, from the date mentioned, the "species question" was always +more or less present in Darwin's mind. (Although we admit with Huxley that +Darwin's training in comparative anatomy was very small, yet it may be +remembered that he was a medical student for two years, and, if he hated +the lectures, he enjoyed the society of naturalists. He had with him in +the little "Beagle" library a fair number of zoological books, including +works on Osteology by Cuvier, Desmarest and Lesson, as well as two French +Encyclopaedias of Natural History. As a sportsman, he would obtain +specimens of recent mammals in South America, and would thus have +opportunities of studying their teeth and general anatomy. Keen observer, +as he undoubtedly was, we need not then be surprised that he was able to +make out the resemblances between the recent and fossil forms.) + +It is clear that, as time went on, Darwin became more and more absorbed in +his geological work. One very significant fact was that the once ardent +sportsman, when he found that shooting the necessary game and zoological +specimens interfered with his work with the hammer, gave up his gun to his +servant. ("L.L." I. page 63.) There is clear evidence that Darwin +gradually became aware how futile were his attempts to add to zoological +knowledge by dissection and drawing, while he felt ever increasing +satisfaction with his geological work. + +The voyage fortunately extended to a much longer period (five years) than +the two originally intended, but after being absent nearly three years, +Darwin wrote to his sister in November, 1834, "Hurrah! hurrah! it is fixed +that the 'Beagle' shall not go one mile south of Cape Tres Montes (about +200 miles south of Chiloe), and from that point to Valparaiso will be +finished in about five months. We shall examine the Chonos Archipelago, +entirely unknown, and the curious inland sea behind Chiloe. For me it is +glorious. Cape Tres Montes is the most southern point where there is much +geological interest, as there the modern beds end. The Captain then talks +of crossing the Pacific; but I think we shall persuade him to finish the +coast of Peru, where the climate is delightful, the country hideously +sterile, but abounding with the highest interest to the geologist...I have +long been grieved and most sorry at the interminable length of the voyage +(though I never would have quitted it)...I could not make up my mind to +return. I could not give up all the geological castles in the air I had +been building up for the last two years." ("L.L." I. pages 257-58.) + +In April, 1835, he wrote to another sister: "I returned a week ago from my +excursion across the Andes to Mendoza. Since leaving England I have never +made so successful a journey...how deeply I have enjoyed it; it was +something more than enjoyment; I cannot express the delight which I felt at +such a famous winding-up of all my geology in South America. I literally +could hardly sleep at nights for thinking over my day's work. The scenery +was so new, and so majestic; everything at an elevation of 12,000 feet +bears so different an aspect from that in the lower country...To a +geologist, also, there are such manifest proofs of excessive violence; the +strata of the highest pinnacles are tossed about like the crust of a broken +pie." ("L.L." I. pages 259-60.) + +Darwin anticipated with intense pleasure his visit to the Galapagos +Islands. On July 12th, 1835, he wrote to Henslow: "In a few days' time +the "Beagle" will sail for the Galapagos Islands. I look forward with joy +and interest to this, both as being somewhat nearer to England and for the +sake of having a good look at an active volcano. Although we have seen +lava in abundance, I have never yet beheld the crater." ("M.L." I. page +26.) He could little anticipate, as he wrote these lines, the important +aid in the solution of the "species question" that would ever after make +his visit to the Galapagos Islands so memorable. In 1832, as we have seen, +the great discovery of the relations of living to extinct mammals in the +same area had dawned upon his mind; in 1835 he was to find a second key for +opening up the great mystery, by recognising the variations of similar +types in adjoining islands among the Galapagos. + +The final chapter in the second volume of the "Principles" had aroused in +Darwin's mind a desire to study coral-reefs, which was gratified during his +voyage across the Pacific and Indian Oceans. His theory on the subject was +suggested about the end of 1834 or the beginning of 1835, as he himself +tells us, before he had seen a coral-reef, and resulted from his work +during two years in which he had "been incessantly attending to the effects +on the shores of South America of the intermittent elevation of the land, +together with denudation and the deposition of sediment." ("L.L." I. page +70.) + +On arriving at the Cape of Good Hope in July, 1836, Darwin was greatly +gratified by hearing that Sedgwick had spoken to his father in high terms +of praise concerning the work done by him in South America. Referring to +the news from home, when he reached Bahia once more, on the return voyage +(August, 1836), he says: "The desert, volcanic rocks, and wild sea of +Ascension...suddenly wore a pleasing aspect, and I set to work with a good- +will at my old work of Geology." ("L.L." I. page 265.) Writing fifty +years later, he says: "I clambered over the mountains of Ascension with a +bounding step and made the volcanic rocks resound under my geological +hammer!" ("L.L." I. page 66.) + +That his determination was now fixed to devote his own labours to the task +of working out the geological results of the voyage, and that he was +prepared to leave to more practised hands the study of his biological +collections, is clear from the letters he sent home at this time. From St +Helena he wrote to Henslow asking that he would propose him as a Fellow of +the Geological Society; and his Certificate, in Henslow's handwriting, is +dated September 8th, 1836, being signed from personal knowledge by Henslow +and Sedgwick. He was proposed on November 2nd and elected November 30th, +being formally admitted to the Society by Lyell, who was then President, on +January 4th, 1837, on which date he also read his first paper. Darwin did +not become a Fellow of the Linnean Society till eighteen years later (in +1854). + +An estimate of the value and importance of Darwin's geological discoveries +during the voyage of the "Beagle" can best be made when considering the +various memoirs and books in which the author described them. He was too +cautious to allow himself to write his first impressions in his Journal, +and wisely waited till he could study his specimens under better conditions +and with help from others on his return. The extracts published from his +correspondence with Henslow and others, while he was still abroad, showed, +nevertheless, how great was the mass of observation, how suggestive and +pregnant with results were the reasonings of the young geologist. + +Two sets of these extracts from Darwin's letters to Henslow were printed +while he was still abroad. The first of these was the series of +"Geological Notes made during a survey of the East and West Coasts of South +America, in the years 1832, 1833, 1834 and 1835, with an account of a +transverse section of the Cordilleras of the Andes between Valparaiso and +Mendoza". Professor Sedgwick, who read these notes to the Geological +Society on November 18th, 1835, stated that "they were extracted from a +series of letters (addressed to Professor Henslow), containing a great mass +of information connected with almost every branch of natural history," and +that he (Sedgwick) had made a selection of the remarks which he thought +would be more especially interesting to the Geological Society. An +abstract of three pages was published in the "Proceedings of the Geological +Society" (Vol. II. pages 210-12.), but so unknown was the author at this +time that he was described as F. Darwin, Esq., of St John's College, +Cambridge"! Almost simultaneously (on November 16th, 1835) a second set of +extracts from these letters--this time of a general character--were read to +the Philosophical Society at Cambridge, and these excited so much interest +that they were privately printed in pamphlet form for circulation among the +members. + +Many expeditions and "scientific missions" have been despatched to various +parts of the world since the return of the "Beagle" in 1836, but it is +doubtful whether any, even the most richly endowed of them, has brought +back such stores of new information and fresh discoveries as did that +little "ten-gun brig"--certainly no cabin or laboratory was the birth-place +of ideas of such fruitful character as was that narrow end of a chart-room, +where the solitary naturalist could climb into his hammock and indulge in +meditation. + +The third and most active portion of Darwin's career as a geologist was the +period which followed his return to England at the end of 1836. His +immediate admission to the Geological Society, at the beginning of 1837, +coincided with an important crisis in the history of geological science. + +The band of enthusiasts who nearly thirty years before had inaugurated the +Geological Society--weary of the fruitless conflicts between "Neptunists" +and "Plutonists"--had determined to eschew theory and confine their labours +to the collection of facts, their publications to the careful record of +observations. Greenough, the actual founder of the Society, was an ardent +Wernerian, and nearly all his fellow-workers had come, more or less +directly, under the Wernerian teaching. Macculloch alone gave valuable +support to the Huttonian doctrines, so far as they related to the influence +of igneous activity--but the most important portion of the now celebrated +"Theory of the Earth"--that dealing with the competency of existing +agencies to account for changes in past geological times--was ignored by +all alike. Macculloch's influence on the development of geology, which +might have had far-reaching effects, was to a great extent neutralised by +his peculiarities of mind and temper; and, after a stormy and troublous +career, he retired from the society in 1832. In all the writings of the +great pioneers in English geology, Hutton and his splendid generalisation +are scarcely ever referred to. The great doctrines of Uniformitarianism, +which he had foreshadowed, were completely ignored, and only his +extravagances of "anti-Wernerianism" seem to have been remembered. + +When between 1830 and 1832, Lyell, taking up the almost forgotten ideas of +Hutton, von Hoff and Prevost, published that bold challenge to the +Catastrophists--the "Principles of Geology"--he was met with the strongest +opposition, not only from the outside world, which was amused by his +"absurdities" and shocked by his "impiety"--but not less from his fellow- +workers and friends in the Geological Society. For Lyell's numerous +original observations, and his diligent collection of facts his +contemporaries had nothing but admiration, and they cheerfully admitted him +to the highest offices in the society, but they met his reasonings on +geological theory with vehement opposition and his conclusions with +coldness and contempt. + +There is, indeed, a very striking parallelism between the reception of the +"Principles of Geology" by Lyell's contemporaries and the manner in which +the "Origin of Species" was met a quarter of a century later, as is so +vividly described by Huxley. ("L.L." II. pages 179-204.) Among Lyell's +fellow-geologists, two only--G. Poulett Scrope and John Herschel (Both +Lyell and Darwin fully realised the value of the support of these two +friends. Scrope in his appreciative reviews of the "Principles" justly +pointed out what was the weakest point, the inadequate recognition of sub- +aerial as compared with marine denudation. Darwin also admitted that +Scrope had to a great extent forestalled him in his theory of Foliation. +Herschel from the first insisted that the leading idea of the "Principles" +must be applied to organic as well as to inorganic nature and must explain +the appearance of new species (see Lyell's "Life and Letters", Vol. I. page +467). Darwin tells us that Herschel's "Introduction to the Study of +Natural Philosophy" with Humboldt's "Personal Narrative" "stirred up in me +a burning zeal" in his undergraduate days. I once heard Lyell exclaim with +fervour "If ever there was a heaven-born genius it was John Herschel!")-- +declared themselves from the first his strong supporters. Scrope in two +luminous articles in the "Quarterly Review" did for Lyell what Huxley +accomplished for Darwin in his famous review in the "Times"; but Scrope +unfortunately was at that time immersed in the stormy sea of politics, and +devoted his great powers of exposition to the preparation of fugitive +pamphlets. Herschel, like Scrope, was unable to support Lyell at the +Geological Society, owing to his absence on the important astronomical +mission to the Cape. + +It thus came about that, in the frequent conflicts of opinion within the +walls of the Geological Society, Lyell had to bear the brunt of battle for +Uniformitarianism quite alone, and it is to be feared that he found himself +sadly overmatched when opposed by the eloquence of Sedgwick, the sarcasm of +Buckland, and the dead weight of incredulity on the part of Greenough, +Conybeare, Murchison and other members of the band of pioneer workers. As +time went on there is evidence that the opposition of De la Beche and +Whewell somewhat relaxed; the brilliant "Paddy" Fitton (as his friends +called him) was sometimes found in alliance with Lyell, but was +characteristically apt to turn his weapon, as occasion served, on friend or +foe alike; the amiable John Phillips "sat upon the fence." Only when a new +generation arose--including Jukes, Ramsay, Forbes and Hooker--did Lyell +find his teachings received with anything like favour. + +We can well understand, then, how Lyell would welcome such a recruit as +young Darwin--a man who had declared himself more Lyellian than Lyell, and +who brought to his support facts and observations gleaned from so wide a +field. + +The first meeting of Lyell and Darwin was characteristic of the two men. +Darwin at once explained to Lyell that, with respect to the origin of +coral-reefs, he had arrived at views directly opposed to those published by +"his master." To give up his own theory, cost Lyell, as he told Herschel, +a "pang at first," but he was at once convinced of the immeasurable +superiority of Darwin's theory. I have heard members of Lyell's family +tell of the state of wild excitement and sustained enthusiasm, which lasted +for days with Lyell after this interview, and his letters to Herschel, +Whewell and others show his pleasure at the new light thrown upon the +subject and his impatience to have the matter laid before the Geological +Society. + +Writing forty years afterwards, Darwin, speaking of the time of the return +of the "Beagle", says: "I saw a great deal of Lyell. One of his chief +characteristics was his sympathy with the work of others, and I was as much +astonished as delighted at the interest which he showed when, on my return +to England, I explained to him my views on coral-reefs. This encouraged me +greatly, and his advice and example had much influence on me." ("L.L." I. +page 68.) Darwin further states that he saw more of Lyell at this time +than of any other scientific man, and at his request sent his first +communication to the Geological Society. ("L.L." I. page 67.) + +"Mr Lonsdale" (the able curator of the Geological Society), Darwin wrote to +Henslow, "with whom I had much interesting conversation," "gave me a most +cordial reception," and he adds, "If I was not much more inclined for +geology than the other branches of Natural History, I am sure Mr Lyell's +and Lonsdale's kindness ought to fix me. You cannot conceive anything more +thoroughly good-natured than the heart-and-soul manner in which he put +himself in my place and thought what would be best to do." ("L.L." I. page +275.) + +Within a few days of Darwin's arrival in London we find Lyell writing to +Owen as follows: + +"Mrs Lyell and I expect a few friends here on Saturday next, 29th +(October), to an early tea party at eight o'clock, and it will give us +great pleasure if you can join it. Among others you will meet Mr Charles +Darwin, whom I believe you have seen, just returned from South America, +where he has laboured for zoologists as well as for hammer-bearers. I have +also asked your friend Broderip." ("The Life of Richard Owen", London, +1894, Vol. I. page 102.) It would probably be on this occasion that the +services of Owen were secured for the work on the fossil bones sent home by +Darwin. + +On November 2nd, we find Lyell introducing Darwin as his guest at the +Geological Society Club; on December 14th, Lyell and Stokes proposed Darwin +as a member of the Club; between that date and May 3rd of the following +year, when his election to the Club took place, he was several times dining +as a guest. + +On January 4th, 1837, as we have already seen, Darwin was formally admitted +to the Geological Society, and on the same evening he read his first paper +(I have already pointed out that the notes read at the Geological Society +on Nov. 18, 1835 were extracts made by Sedgwick from letters sent to +Henslow, and not a paper sent home for publication by Darwin.) before the +Society, "Observations of proofs of recent elevation on the coast of Chili, +made during the Survey of H.M.S. "Beagle", commanded by Captain FitzRoy, +R.N." By C. Darwin, F.G.S. This paper was preceded by one on the same +subject by Mr A. Caldcleugh, and the reading of a letter and other +communications from the Foreign Office also relating to the earthquakes in +Chili. + +At the meeting of the Council of the Geological Society on February 1st, +Darwin was nominated as a member of the new Council, and he was elected on +February 17th. + +The meeting of the Geological Society on April 19th was devoted to the +reading by Owen of his paper on Toxodon, perhaps the most remarkable of the +fossil mammals found by Darwin in South America; and at the next meeting, +on May 3rd, Darwin himself read "A Sketch of the Deposits containing +extinct Mammalia in the neighbourhood of the Plata". The next following +meeting, on May 17th, was devoted to Darwin's Coral-reef paper, entitled +"On certain areas of elevation and subsidence in the Pacific and Indian +Oceans, as deduced from the study of Coral Formations". Neither of these +three early papers of Darwin were published in the Transactions of the +Geological Society, but the minutes of the Council show that they were +"withdrawn by the author by permission of the Council." + +Darwin's activity during this session led to some rather alarming effects +upon his health, and he was induced to take a holiday in Staffordshire and +the Isle of Wight. He was not idle, however, for a remark of his uncle, Mr +Wedgwood, led him to make those interesting observations on the work done +by earthworms, that resulted in his preparing a short memoir on the +subject, and this paper, "On the Formation of Mould", was read at the +Society on November 1st, 1837, being the first of Darwin's papers published +in full; it appeared in Vol. V. of the "Geological Transactions", pages +505-510.) + +During this session, Darwin attended nearly all the Council meetings, and +took such an active part in the work of the Society that it is not +surprising to find that he was now requested to accept the position of +Secretary. After some hesitation, in which he urged his inexperience and +want of knowledge of foreign languages, he consented to accept the +appointment. ("L.L." I. page 285.) + +At the anniversary meeting on February 16th, 1838, the Wollaston Medal was +given to Owen in recognition of his services in describing the fossil +mammals sent home by Darwin. In his address, the President, Professor +Whewell, dwelt at length on the great value of the papers which Darwin had +laid before the Society during the preceding session. + +On March 7th, Darwin read before the Society the most important perhaps of +all his geological papers, "On the Connexion of certain Volcanic Phenomena +in South America, and on the Formation of Mountain-Chains and Volcanoes as +the effect of Continental Elevations". In this paper he boldly attacked +the tenets of the Catastrophists. It is evident that Darwin at this time, +taking advantage of the temporary improvement in his health, was throwing +himself into the breach of Uniformitarianism with the greatest ardour. +Lyell wrote to Sedgwick on April 21st, 1837, "Darwin is a glorious addition +to any society of geologists, and is working hard and making way, both in +his book and in our discussions." ("The Life and Letters of the Reverend +Adam Sedgwick", Vol. I. page 484, Cambridge, 1890.) + +We have unfortunately few records of the animated debates which took place +at this time between the old and new schools of geologists. I have often +heard Lyell tell how Lockhart would bring down a party of friends from the +Athenaeum Club to Somerset House on Geological nights, not, as he carefully +explained, that "he cared for geology, but because he liked to while the +fellows fight." But it fortunately happens that a few days after this last +of Darwin's great field-days, at the Geological Society, Lyell, in a +friendly letter to his father-in-law, Leonard Horner, wrote a very lively +account of the proceedings while his impressions were still fresh; and this +gives us an excellent idea of the character of these discussions. + +Neither Sedgwick nor Buckland were present on this occasion, but we can +imagine how they would have chastised their two "erring pupils"--more in +sorrow than in anger--had they been there. Greenough, too, was absent-- +possibly unwilling to countenance even by his presence such outrageous +doctrines. + +Darwin, after describing the great earthquakes which he had experienced in +South America, and the evidence of their connection with volcanic +outbursts, proceeded to show that earthquakes originated in fractures, +gradually formed in the earth's crust, and were accompanied by movements of +the land on either side of the fracture. In conclusion he boldly advanced +the view "that continental elevations, and the action of volcanoes, are +phenomena now in progress, caused by some great but slow change in the +interior of the earth; and, therefore, that it might be anticipated, that +the formation of mountain chains is likewise in progress: and at a rate +which may be judged of by either actions, but most clearly by the growth of +volcanoes." ("Proc. Geol. Soc." Vol. II. pages 654-60.) + +Lyell's account ("Life, Letters and Journals of Sir Charles Lyell, Bart.", +edited by his sister-in-law, Mrs Lyell, Vol. II. pages 40, 41 (Letter to +Leonard Horner, 1838), 2 vols. London, 1881.) of the discussion was as +follows: "In support of my heretical notions," Darwin "opened upon De la +Beche, Phillips and others his whole battery of the earthquakes and +volcanoes of the Andes, and argued that spaces at least a thousand miles +long were simultaneously subject to earthquakes and volcanic eruptions, and +that the elevation of the Pampas, Patagonia, etc., all depended on a common +cause; also that the greater the contortions of strata in a mountain chain, +the smaller must have been each separate and individual movement of that +long series which was necessary to upheave the chain. Had they been more +violent, he contended that the subterraneous fluid matter would have gushed +out and overflowed, and the strata would have been blown up and +annihilated. (It is interesting to compare this with what Darwin wrote to +Henslow seven years earlier.) He therefore introduces a cooling of one +small underground injection, and then the pumping in of other lava, or +porphyry, or granite, into the previously consolidated and first-formed +mass of igneous rock. (Ideas somewhat similar to this suggestion have +recently been revived by Dr See ("Proc. Am. Phil. Soc." Vol. XLVII. 1908, +page 262.).) When he had done his description of the reiterated strokes of +his volcanic pump, De la Beche gave us a long oration about the +impossibility of strata of the Alps, etc., remaining flexible for such a +time as they must have done, if they were to be tilted, convoluted, or +overturned by gradual small shoves. He never, however, explained his +theory of original flexibility, and therefore I am as unable as ever to +comprehend why flexiblility is a quality so limited in time. + +"Phillips then got up and pronounced a panegyric upon the "Principles of +Geology", and although he still differed, thought the actual cause doctrine +had been so well put, that it had advanced the science and formed a date or +era, and that for centuries the two opposite doctrines would divide +geologists, some contending for greater pristine forces, others satisfied, +like Lyell and Darwin, with the same intensity as nature now employs. + +"Fitton quizzed Phillips a little for the warmth of his eulogy, saying that +he (Fitton) and others, who had Mr Lyell always with them, were in the +habit of admiring and quarrelling with him every day, as one might do with +a sister or cousin, whom one would only kiss and embrace fervently after a +long absence. This seemed to be Mr Phillips' case, coming up occasionally +from the provinces. Fitton then finished this drollery by charging me with +not having done justice to Hutton, who he said was for gradual elevation. + +"I replied, that most of the critics had attacked me for overrating Hutton, +and that Playfair understood him as I did. + +"Whewell concluded by considering Hopkins' mathematical calculations, to +which Darwin had often referred. He also said that we ought not to try and +make out what Hutton would have taught and thought, if he had known the +facts which we now know." + +It may be necessary to point out, in explanation of the above narrative, +that while it was perfectly clear from Hutton's rather obscure and involved +writings that he advocated slow and gradual change on the earth's surface, +his frequent references to violent action and earthquakes led many-- +including Playfair, Lyell and Whewell--to believe that he held the changes +going on in the earth's interior to be of a catastrophic nature. Fitton, +however, maintained that Hutton was consistently uniformitarian. Before +the idea of the actual "flowing" of solid bodies under intense pressure had +been grasped by geologists, De la Beche, like Playfair before him, +maintained that the bending and folding of rocks must have been effected +before their complete consolidation. + +In concluding his account of this memorable discussion, Lyell adds: "I was +much struck with the different tone in which my gradual causes was treated +by all, even including De la Beche, from that which they experienced in the +same room four years ago, when Buckland, De la Beche(?), Sedgwick, Whewell, +and some others treated them with as much ridicule as was consistent with +politeness in my presence." + +This important paper was, in spite of its theoretical character, published +in full in the "Transactions of the Geological Society" (Ser. 2, Vol. V. +pages 601-630). It did not however appear till 1840, and possibly some +changes may have been made in it during the long interval between reading +and printing. During the year 1839, Darwin continued his regular +attendance at the Council meetings, but there is no record of any +discussions in which he may have taken part, and he contributed no papers +himself to the Society. At the beginning of 1840, he was re-elected for +the third time as Secretary, but the results of failing health are +indicated by the circumstance that, only at one meeting early in the +session, was he able to attend the Council. At the beginning of the next +session (Feb. 1841) Bunbury succeeded him as Secretary, Darwin still +remaining on the Council. It may be regarded as a striking indication of +the esteem in which he was held by his fellow geologists, that Darwin +remained on the Council for 14 consecutive years down to 1849, though his +attendances were in some years very few. In 1843 and 1844 he was a Vice- +president, but after his retirement at the beginning of 1850, he never +again accepted re-nomination. He continued, however, to contribute papers +to the Society, as we shall see, down to the end of 1862. + +Although Darwin early became a member of the Geological Dining Club, it is +to be feared that he scarcely found himself in a congenial atmosphere at +those somewhat hilarious gatherings, where the hardy wielders of the hammer +not only drank port--and plenty of it--but wound up their meal with a +mixture of Scotch ale and soda water, a drink which, as reminiscent of the +"field," was regarded as especially appropriate to geologists. Even after +the meetings, which followed the dinners, they reassembled for suppers, at +which geological dainties, like "pterodactyle pie" figured in the bill of +fare, and fines of bumpers were inflicted on those who talked the +"ologies." + +After being present at a fair number of meetings in 1837 and 1838, Darwin's +attendances at the Club fell off to two in 1839, and by 1841 he had ceased +to be a member. In a letter to Lyell on Dec. 2nd, 1841, Leonard Horner +wrote that the day before "At the Council, I had the satisfaction of seeing +Darwin again in his place and looking well. He tried the last evening +meeting, but found it too much, but I hope before the end of the season he +will find himself equal to that also. I hail Darwin's recovery as a vast +gain to science." Darwin's probably last attendance, this time as a guest, +was in 1851, when Horner again wrote to Lyell, "Charles Darwin was at the +Geological Society's Club yesterday, where he had not been for ten years-- +remarkably well, and grown quite stout." ("Memoirs of Leonard Horner" +(privately printed), Vol. II. pages 39 and 195.) + +It may be interesting to note that at the somewhat less lively dining Club- +-the Philosophical--in the founding of which his friends Lyell and Hooker +had taken so active a part, Darwin found himself more at home, and he was a +frequent attendant--in spite of his residence being at Down--from 1853 to +1864. He even made contributions on scientific questions after these +dinners. In a letter to Hooker he states that he was deeply interested in +the reforms of the Royal Society, which the Club was founded to promote. +He says also that he had arranged to come to town every Club day "and then +my head, I think, will allow me on an average to go to every other meeting. +But it is grievous how often any change knocks me up." ("L.L." II. pages +42, 43.) + +Of the years 1837 and 1838 Darwin himself says they were "the most active +ones which I ever spent, though I was occasionally unwell, and so lost some +time...I also went a little into society." ("L.L." I. pages 67, 68.) But +of the four years from 1839 to 1842 he has to confess sadly "I did less +scientific work, though I worked as hard as I could, than during any other +equal length of time in my life. This was owing to frequently recurring +unwellness, and to one long and serious illness." ("L.L." I. page 69.) + +Darwin's work at the Geological Society did not by any means engage the +whole of his energies, during the active years 1837 and 1838. In June of +the latter year, leaving town in somewhat bad health, he found himself at +Edinburgh again, and engaged in examining the Salisbury Craigs, in a very +different spirit to that excited by Jameson's discourse. ("L.L." I. page +290.) Proceeding to the Highlands he then had eight days of hard work at +the famous "Parallel Roads of Glen Roy", being favoured with glorious +weather. + +He says of the writing of the paper on the subject--the only memoir +contributed by Darwin to the Royal Society, to which he had been recently +elected--that it was "one of the most difficult and instructive tasks I was +ever engaged on." The paper extends to 40 quarto pages and is illustrated +by two plates. Though it is full of the records of careful observation and +acute reasoning, yet the theory of marine beaches which he propounded was, +as he candidly admitted in after years ("M.L." II page 188.), altogether +wrong. The alternative lake-theory he found himself unable to accept at +the time, for he could not understand how barriers could be formed at +successive levels across the valleys; and until the following year, when +the existence of great glaciers in the district was proved by the +researches of Agassiz, Buckland and others, the difficulty appeared to him +an insuperable one. Although Darwin said of this paper in after years that +it "was a great failure and I am ashamed of it"--yet he retained his +interest in the question ever afterwards, and he says "my error has been a +good lesson to me never to trust in science to the principle of exclusion." +("M.L." II. pages 171-93.) + +Although Darwin had not realised in 1838 that large parts of the British +Islands had been occupied by great glaciers, he had by no means failed +while in South America to recognise the importance of ice-action. His +observations, as recorded in his Journal, on glaciers coming down to the +sea-level, on the west coast of South America, in a latitude corresponding +to a much lower one than that of the British Islands, profoundly interested +geologists; and the same work contains many valuable notes on the boulders +and unstratified beds in South America in which they were included. + +But in 1840 Agassiz read his startling paper on the evidence of the former +existence of glaciers in the British Islands, and this was followed by +Buckland's memoir on the same subject. On April 14, 1841, Darwin +contributed to the Geological Society his important paper "On the +Distribution of Erratic Boulders and the Contemporaneous Unstratified +Deposits of South America", a paper full of suggestiveness for those +studying the glacial deposits of this country. It was published in the +"Transactions" in 1842. + +The description of traces of glacial action in North Wales, by Buckland, +appears to have greatly excited the interest of Darwin. With Sedgwick he +had, in 1831, worked at the stratigraphy of that district, but neither of +them had noticed the very interesting surface features. ("L.L." I. page +58.) Darwin was able to make a journey to North Wales in June, 1842 (alas! +it was his last effort in field-geology) and as a result he published his +most able and convincing paper on the subject in the September number of +the "Philosophical Magazine" for 1842. Thus the mystery of the bell-stone +was at last solved and Darwin, writing many years afterwards, said "I felt +the keenest delight when I first read of the action of icebergs in +transporting boulders, and I gloried in the progress of Geology." ("L.L." +I. page 41.) To the "Geographical Journal" he had sent in 1839 a note "On +a Rock seen on an Iceberg in 16 deg S. Latitude." For the subject of ice- +action, indeed, Darwin retained the greatest interest to the end of his +life. ("M.L." II. pages 148-71.) + +In 1846, Darwin read two papers to the Geological Society "On the dust +which falls on vessels in the Atlantic, and On the Geology of the Falkland +Islands"; in 1848 he contributed a note on the transport of boulders from +lower to higher levels; and in 1862 another note on the thickness of the +Pampean formation, as shown by recent borings at Buenos Ayres. An account +of the "British Fossil Lepadidae" read in 1850, was withdrawn by him. + +At the end of 1836 Darwin had settled himself in lodgings in Fitzwilliam +Street, Cambridge, and devoted three months to the work of unpacking his +specimens and studying his collection of rocks. The pencilled notes on the +Manuscript Catalogue in the Sedgwick Museum enable us to realise his mode +of work, and the diligence with which it was carried on. The letters M and +H, indicate the assistance he received from time to time from Professor +Miller, the crystallographer, and from his friend Henslow. Miller not only +measured many of the crystals submitted to him, but evidently taught Darwin +to use the reflecting goniometer himself with considerable success. The +"book of measurements" in which the records were kept, appears to have been +lost, but the pencilled notes in the catalogue show how thoroughly the work +was done. The letter R attached to some of the numbers in the catalogue +evidently refers to the fact that they were submitted to Mr Trenham Reeks +(who analysed some of his specimens) at the Geological Survey quarters in +Craig's Court. This was at a later date when Darwin was writing the +"Volcanic Islands" and "South America". + +It was about the month of March, 1837, that Darwin completed this work upon +his rocks, and also the unpacking and distribution of his fossil bones and +other specimens. We have seen that November, 1832, must certainly be +regarded as the date when he FIRST realised the important fact that the +fossil mammals of the Pampean formation were all closely related to the +existing forms in South America; while October, 1835, was, as undoubtedly, +the date when the study of the birds and other forms of life in the several +islands of the Galapagos Islands gave him his SECOND impulse towards +abandoning the prevalent view of the immutability of species. When then in +his pocket-book for 1837 Darwin wrote the often quoted passage: "In July +opened first note-book on Transmutation of Species. Had been greatly +struck from about the month of previous March on character of South +American fossils, and species on Galapagos Archipelago. These facts +(especially latter), origin of all my views" ("L.L." I. page 276.), it is +clear that he must refer, not to his first inception of the idea of +evolution, but to the flood of recollections, the reawakening of his +interest in the subject, which could not fail to result from the sight of +his specimens and the reference to his notes. + +Except during the summer vacation, when he was visiting his father and +uncle, and with the latter making his first observations upon the work of +earthworms, Darwin was busy with his arrangements for the publication of +the five volumes of the "Zoology of the 'Beagle'" and in getting the +necessary financial aid from the government for the preparation of the +plates. He was at the same time preparing his "Journal" for publication. +During the years 1837 to 1843, Darwin worked intermittently on the volumes +of Zoology, all of which he edited, while he wrote introductions to those +by Owen and Waterhouse and supplied notes to the others. + +Although Darwin says of his Journal that the preparation of the book "was +not hard work, as my MS. Journal had been written with care." Yet from the +time that he settled at 36, Great Marlborough Street in March, 1837, to the +following November he was occupied with this book. He tells us that the +account of his scientific observations was added at this time. The work +was not published till March, 1839, when it appeared as the third volume of +the "Narrative of the Surveying Voyages of H.M. Ships 'Adventure' and +'Beagle' between the years 1826 and 1836". The book was probably a long +time in the press, for there are no less than 20 pages of addenda in small +print. Even in this, its first form, the work is remarkable for its +freshness and charm, and excited a great amount of attention and interest. +In addition to matters treated of in greater detail in his other works, +there are many geological notes of extreme value in this volume, such as +his account of lightning tubes, of the organisms found in dust, and of the +obsidian bombs of Australia. + +Having thus got out of hand a number of preliminary duties, Darwin was +ready to set to work upon the three volumes which were designed by him to +constitute "The Geology of the Voyage of the 'Beagle'". The first of these +was to be on "The Structure and Distribution of Coral-reefs". He commenced +the writing of the book on October 5, 1838, and the last proof was +corrected on May 6, 1842. Allowing for the frequent interruptions through +illness, Darwin estimated that it cost him twenty months of hard work. + +Darwin has related how his theory of Coral-reefs which was begun in a more +"deductive spirit" than any of his other work, for in 1834 or 1835 it "was +thought out on the west coast of South America, before I had seen a true +coral-reef." ("L.L." I. page 70.) The final chapter in Lyell's second +volume of the "Principles" was devoted to the subject of Coral-reefs, and a +theory was suggested to account for the peculiar phenomena of "atolls." +Darwin at once saw the difficulty of accepting the view that the numerous +and diverse atolls all represent submerged volcanic craters. His own work +had for two years been devoted to the evidence of land movements over great +areas in South America, and thus he was led to announce his theory of +subsidence to account for barrier and encircling reefs as well as atolls. + +Fortunately, during his voyage across the Pacific and Indian Oceans, in his +visit to Australia and his twelve days' hard work at Keeling Island, he had +opportunities for putting his theory to the test of observation. + +On his return to England, Darwin appears to have been greatly surprised at +the amount of interest that his new theory excited. Urged by Lyell, he +read to the Geological Society a paper on the subject, as we have seen, +with as little delay as possible, but this paper was "withdrawn by +permission of the Council." An abstract of three pages however appeared in +the "Proceedings of the Geological Society". (Vol. II. pages 552-554 (May +31, 1837).) A full account of the observations and the theory was given in +the "Journal" (1839) in the 40 pages devoted to Keeling Island in +particular and to Coral formations generally. ("Journal (1st edition), +pages 439-69.) + +It will be readily understood what an amount of labour the book on Coral +reefs cost Darwin when we reflect on the number of charts, sailing +directions, narratives of voyages and other works which, with the friendly +assistance of the authorities at the Admiralty, he had to consult before he +could draw up his sketch of the nature and distribution of the reefs, and +this was necessary before the theory, in all its important bearings, could +be clearly enunciated. Very pleasing is it to read how Darwin, although +arriving at a different conclusion to Lyell, shows, by quoting a very +suggestive passage in the "Principles" (1st edition Vol. II. page 296.), +how the latter only just missed the true solution. This passage is cited, +both in the "Journal" and the volume on Coral-reefs. Lyell, as we have +seen, received the new theory not merely ungrudgingly, but with the utmost +enthusiasm. + +In 1849 Darwin was gratified by receiving the support of Dana, after his +prolonged investigation in connection with the U.S. Exploring Expedition +("M.L." II. pages 226-8.), and in 1874 he prepared a second edition of his +book, in which some objections which had been raised to the theory were +answered. A third edition, edited by Professor Bonney, appeared in 1880, +and a fourth (a reprint of the first edition, with introduction by myself) +in 1890. + +Although Professor Semper, in his account of the Pelew Islands, had +suggested difficulties in the acceptance of Darwin's theory, it was not +till after the return of the "Challenger" expedition in 1875 that a rival +theory was propounded, and somewhat heated discussions were raised as to +the respective merits of the two theories. While geologists have, nearly +without exception, strongly supported Darwin's views, the notes of dissent +have come almost entirely from zoologists. At the height of the +controversy unfounded charges of unfairness were made against Darwin's +supporters and the authorities of the Geological Society, but this +unpleasant subject has been disposed of, once for all, by Huxley. ("Essays +upon some Controverted Questions", London, 1892, pages 314-328 and 623- +625.) + +Darwin's final and very characteristic utterance on the coral-reef +controversy is found in a letter which he wrote to Professor Alexander +Agassiz, May 5th, 1881: less than a year before his death: "If I am +wrong, the sooner I am knocked on the head and annihilated so much the +better. It still seems to me a marvellous thing that there should not have +been much, and long-continued, subsidence in the beds of the great oceans. +I wish that some doubly rich millionaire would take it into his head to +have borings made in some of the Pacific and Indian atolls, and bring home +cores for slicing from a depth of 500 or 600 feet." ("L.L." III. page +184.) + +Though the "doubly rich millionaire" has not been forthcoming, the energy, +in England, of Professor Sollas, and in New South Wales of Professor +Anderson Stuart served to set on foot a project, which, aided at first by +the British Association for the Advancement of Science, and afterwards +taken up jointly by the Royal Society, the New South Wales Government, and +the Admiralty, has led to the most definite and conclusive results. + +The Committee appointed by the Royal Society to carry out the undertaking +included representatives of all the views that had been put forward on the +subject. The place for the experiment was, with the consent of every +member of the Committee, selected by the late Admiral Sir W.J. Wharton--who +was not himself an adherent of Darwin's views--and no one has ventured to +suggest that his selection, the splendid atoll of Funafuti, was not a most +judicious one. + +By the pluck and perseverance of Professor Sollas in the preliminary +expedition, and of Professor T. Edgeworth David and his pupils, in +subsequent investigations of the island, the rather difficult piece of work +was brought to a highly satisfactory conclusion. The New South Wales +Government lent boring apparatus and workmen, and the Admiralty carried the +expedition to its destination in a surveying ship which, under Captain (now +Admiral) A. Mostyn Field, made the most complete survey of the atoll and +its surrounding seas that has ever been undertaken in the case of a coral +formation. + +After some failures and many interruptions, the boring was carried to the +depth of 1114 feet, and the cores obtained were sent to England. Here the +examination of the materials was fortunately undertaken by a zoologist of +the highest repute, Dr G.J. Hinde--who has a wide experience in the study +of organisms by sections--and he was aided at all points by specialists in +the British Museum of Natural History and by other naturalists. Nor were +the chemical and other problems neglected. + +The verdict arrived at, after this most exhaustive study of a series of +cores obtained from depths twice as great as that thought necessary by +Darwin, was as follows:--"The whole of the cores are found to be built up +of those organisms which are seen forming coral-reefs near the surface of +the ocean--many of them evidently in situ; and not the slightest indication +could be detected, by chemical or microscopic means, which suggested the +proximity of non-calcareous rocks, even in the lowest portions brought up." + +But this was not all. Professor David succeeded in obtaining the aid of a +very skilful engineer from Australia, while the Admiralty allowed Commander +F.C.D. Sturdee to take a surveying ship into the lagoon for further +investigations. By very ingenious methods, and with great perseverance, +two borings were put down in the midst of the lagoon to the depth of nearly +200 feet. The bottom of the lagoon, at the depth of 101 1/2 feet from sea- +level, was found to be covered with remains of the calcareous, green sea- +weed Halimeda, mingled with many foraminifera; but at a depth of 163 feet +from the surface of the lagoon the boring tools encountered great masses of +coral, which were proved from the fragments brought up to belong to species +that live within AT MOST 120 feet from the surface of the ocean, as +admitted by all zoologists. ("The Atoll of Funafuti; Report of the Coral +Reef Committee of the Royal Society", London, 1904.) + +Darwin's theory, as is well known, is based on the fact that the +temperature of the ocean at any considerable depth does not permit of the +existence and luxuriant growth of the organisms that form the reefs. He +himself estimated this limit of depth to be from 120 to 130 feet; Dana, as +an extreme, 150 feet; while the recent very prolonged and successful +investigations of Professor Alexander Agassiz in the Pacific and Indian +Oceans lead him also to assign a limiting depth of 150 feet; the EFFECTIVE, +REEF-FORMING CORALS, however, flourishing at a much smaller depth. Mr +Stanley Gardiner gives for the most important reef-forming corals depths +between 30 and 90 feet, while a few are found as low as 120 feet or even +180 feet. + +It will thus be seen that the verdict of Funafuti is clearly and +unmistakeably in favour of Darwin's theory. It is true that some +zoologists find a difficulty in realising a slow sinking of parts of the +ocean floor, and have suggested new and alternative explanations: but +geologists generally, accepting the proofs of slow upheaval in some areas-- +as shown by the admirable researches of Alexander Agassiz--consider that it +is absolutely necessary to admit that this elevation is balanced by +subsidence in other areas. If atolls and barrier-reefs did not exist we +should indeed be at a great loss to frame a theory to account for their +absence. + +After finishing his book on Coral-reefs, Darwin made his summer excursion +to North Wales, and prepared his important memoir on the glaciers of that +district: but by October (1842) we find him fairly settled at work upon +the second volume of his "Geology of the 'Beagle'--Geological Observations +on the Volcanic Islands, visited during the Voyage of H.M.S. 'Beagle'". +The whole of the year 1843 was devoted to this work, but he tells his +friend Fox that he could "manage only a couple of hours per day, and that +not very regularly." ("L.L." I. page 321.) Darwin's work on the various +volcanic islands examined by him had given him the most intense pleasure, +but the work of writing the book by the aid of his notes and specimens he +found "uphill work," especially as he feared the book would not be read, +"even by geologists." (Loc. cit.) + +As a matter of fact the work is full of the most interesting observations +and valuable suggestions, and the three editions (or reprints) which have +appeared have proved a most valuable addition to geological literature. It +is not necessary to refer to the novel and often very striking discoveries +described in this well-known work. The subsidence beneath volcanic vents, +the enormous denudation of volcanic cones reducing them to "basal wrecks," +the effects of solfatarric action and the formation of various minerals in +the cavities of rocks--all of these subjects find admirable illustration +from his graphic descriptions. One of the most important discussions in +this volume is that dealing with the "lamination" of lavas as especially +well seen in the rocks of Ascension. Like Scrope, Darwin recognised the +close analogy between the structure of these rocks and those of metamorphic +origin--a subject which he followed out in the volume "Geological +Observations on South America". + +Of course in these days, since the application of the microscope to the +study of rocks in thin sections, Darwin's nomenclature and descriptions of +the petrological characters of the lavas appear to us somewhat crude. But +it happened that the "Challenger" visited most of the volcanic islands +described by Darwin, and the specimens brought home were examined by the +eminent petrologist Professor Renard. Renard was so struck with the work +done by Darwin, under disadvantageous conditions, that he undertook a +translation of Darwin's work into French, and I cannot better indicate the +manner in which the book is regarded by geologists than by quoting a +passage from Renard's preface. Referring to his own work in studying the +rocks brought home by the "Challenger" (Renard's descriptions of these +rocks are contained in the "Challenger Reports". Mr Harker is +supplementing these descriptions by a series of petrological memoirs on +Darwin's specimens, the first of which appeared in the "Geological +Magazine" for March, 1907.), he says: + +"Je dus, en me livrant a ces recherches, suivre ligne par ligne les divers +chapitres des "Observations geologiques" consacrees aux iles de +l'Atlantique, oblige que j'etais de comparer d'une maniere suivie les +resultats auxquels j'etais conduit avec ceux de Darwin, qui servaient de +controle a mes constatations. Je ne tardai pas a eprouver une vive +admiration pour ce chercheur qui, sans autre appareil que la loupe, sans +autre reaction que quelques essais pyrognostiques, plus rarement quelques +mesures au goniometre, parvenait a discerner la nature des agregats +mineralogiques les plue complexes et les plus varies. Ce coup d'oeil qui +savait embrasser de si vastes horizons, penetre ici profondement tous les +details lithologiques. Avec quelle surete et quelle exactitude la +structure et la composition des roches ne sont'elles pas determinees, +l'origne de ces masses minerales deduite et confirmee par l'etude comparee +des manifestations volcaniques d'autres regions; avec quelle science les +relations entre les faits qu'il decouvre et ceux signales ailleurs par ses +devanciers ne sont'elles pas etablies, et comme voici ebranlees les +hypotheses regnantes, admises sans preuves, celles, par exemple, des +crateres de soulevement et de la differenciation radicale des phenomenes +plutoniques et volcaniques! Ce qui acheve de donner a ce livre un +incomparable merite, ce sont les idees nouvelles qui s'y trouvent en germe +et jetees la comme au hasard ainsi qu'un superflu d'abondance +intellectuelle inepuisable." ("Observations Geologiques sur les Iles +Volcaniques...", Paris, 1902, pages vi., vii.) + +While engaged in his study of banded lavas, Darwin was struck with the +analogy of their structure with that of glacier ice, and a note on the +subject, in the form of a letter addressed to Professor J.D. Forbes, was +published in the "Proceedings of the Royal Society of Edinburgh". (Vol. +II. (1844-5), pages 17, 18.) + +From April, 1832, to September, 1835, Darwin had been occupied in examining +the coast or making inland journeys in the interior of the South American +continent. Thus while eighteen months were devoted, at the beginning and +end of the voyage to the study of volcanic islands and coral-reefs, no less +than three and a half years were given to South American geology. The +heavy task of dealing with the notes and specimens accumulated during that +long period was left by Darwin to the last. Finishing the "Volcanic +Islands" on February 14th, 1844, he, in July of the same year, commenced +the preparation of two important works which engaged him till near the end +of the year 1846. The first was his "Geological Observations on South +America", the second a recast of his "Journal", published under the short +title of "A Naturalist's Voyage round the World". + +The first of these works contains an immense amount of information +collected by the author under great difficulties and not unfrequently at +considerable risk to life and health. No sooner had Darwin landed in South +America than two sets of phenomena powerfully arrested his attention. The +first of these was the occurrence of great masses of red mud containing +bones and shells, which afforded striking evidence that the whole continent +had shared in a series of slow and gradual but often interrupted movements. +The second related to the great masses of crystalline rocks which, +underlying the muds, cover so great a part of the continent. Darwin, +almost as soon as he landed, was struck by the circumstance that the +direction, as shown by his compass, of the prominent features of these +great crystalline rock-masses--their cleavage, master-joints, foliation and +pegmatite veins--was the same as the orientation described by Humboldt +(whose works he had so carefully studied) on the west of the same great +continent. + +The first five chapters of the book on South America were devoted to +formations of recent date and to the evidence collected on the east and +west coasts of the continent in regard to those grand earth-movements, some +of which could be shown to have been accompanied by earthquake-shocks. The +fossil bones, which had given him the first hint concerning the mutability +of species, had by this time been studied and described by comparative +anatomists, and Darwin was able to elaborate much more fully the important +conclusion that the existing fauna of South America has a close analogy +with that of the period immediately preceding our own. + +The remaining three chapters of the book dealt with the metamorphic and +plutonic rocks, and in them Darwin announced his important conclusions +concerning the relations of cleavage and foliation, and on the close +analogy of the latter structure with the banding found in rock-masses of +igneous origin. With respect to the first of these conclusions, he +received the powerful support of Daniel Sharpe, who in the years 1852 and +1854 published two papers on the structure of the Scottish Highlands, +supplying striking confirmation of the correctness of Darwin's views. +Although Darwin's and Sharpe's conclusions were contested by Murchison and +other geologists, they are now universally accepted. In his theory +concerning the origin of foliation, Darwin had been to some extent +anticipated by Scrope, but he supplied many facts and illustrations leading +to the gradual acceptance of a doctrine which, when first enunciated, was +treated with neglect, if not with contempt. + +The whole of this volume on South American geology is crowded with the +records of patient observations and suggestions of the greatest value; but, +as Darwin himself saw, it was a book for the working geologist and "caviare +to the general." Its author, indeed, frequently expressed his sense of the +"dryness" of the book; he even says "I long hesitated whether I would +publish it or not," and he wrote to Leonard Horner "I am astonished that +you should have had the courage to go right through my book." ("M.L." II. +page 221.) + +Fortunately the second book, on which Darwin was engaged at this time, was +of a very different character. His "Journal", almost as he had written it +on board ship, with facts and observations fresh in his mind, had been +published in 1839 and attracted much attention. In 1845, he says, "I took +much pains in correcting a new edition," and the work which was commenced +in April, 1845, was not finished till August of that year. The volume +contains a history of the voyage with "a sketch of those observations in +Natural History and Geology, which I think will possess some interest for +the general reader." It is not necessary to speak of the merits of this +scientific classic. It became a great favourite with the general public-- +having passed through many editions--it was, moreover, translated into a +number of different languages. Darwin was much gratified by these +evidences of popularity, and naively remarks in his "Autobiography", "The +success of this my first literary child tickles my vanity more than that of +any of my other books" ("L.L." I. page 80.)--and this was written after the +"Origin of Species" had become famous! + +In Darwin's letters there are many evidences that his labours during these +ten years devoted to the working out of the geological results of the +voyage often made many demands on his patience and indomitable courage. +Most geologists have experience of the contrast between the pleasures felt +when wielding the hammer in the field, and the duller labour of plying the +pen in the study. But in Darwin's case, innumerable interruptions from +sickness and other causes, and the oft-deferred hope of reaching the end of +his task were not the only causes operating to make the work irksome. The +great project, which was destined to become the crowning achievement of his +life, was now gradually assuming more definite shape, and absorbing more of +his time and energies. + +Nevertheless, during all this period, Darwin so far regarded his geological +pursuits as his PROPER "work," that attention to other matters was always +spoken of by him as "indulging in idleness." If at the end of this period +the world had sustained the great misfortune of losing Darwin by death +before the age of forty--and several times that event seemed only too +probable--he might have been remembered only as a very able geologist of +most advanced views, and a traveller who had written a scientific narrative +of more than ordinary excellence! + +The completion of the "Geology of the 'Beagle'" and the preparation of a +revised narrative of the voyage mark the termination of that period of +fifteen years of Darwin's life during which geological studies were his +principal occupation. Henceforth, though his interest in geological +questions remained ever keen, biological problems engaged more and more of +his attention to the partial exclusion of geology. + +The eight years from October, 1846, to October, 1854, were mainly devoted +to the preparation of his two important monographs on the recent and fossil +Cirripedia. Apart from the value of his description of the fossil forms, +this work of Darwin's had an important influence on the progress of +geological science. Up to that time a practice had prevailed for the +student of a particular geological formation to take up the description of +the plant and animal remains in it--often without having anything more than +a rudimentary knowledge of the living forms corresponding to them. Darwin +in his monograph gave a very admirable illustration of the enormous +advantage to be gained--alike for biology and geology--by undertaking the +study of the living and fossil forms of a natural group of organisms in +connection with one another. Of the advantage of these eight years of work +to Darwin himself, in preparing for the great task lying before him, Huxley +has expressed a very strong opinion indeed. ("L.L." II. pages 247-48.) + +But during these eight years of "species work," Darwin found opportunities +for not a few excursions into the field of geology. He occasionally +attended the Geological Society, and, as we have already seen, read several +papers there during this period. His friend, Dr Hooker, then acting as +botanist to the Geological Survey, was engaged in studying the +Carboniferous flora, and many discussions on Palaezoic plants and on the +origin of coal took place at this period. On this last subject he felt the +deepest interest and told Hooker, "I shall never rest easy in Down +churchyard without the problem be solved by some one before I die." +("M.L." I. pages 63, 64.) + +As at all times, conversations and letters with Lyell on every branch of +geological science continued with unabated vigour, and in spite of the +absorbing character of the work on the Cirripedes, time was found for all. +In 1849 his friend Herschel induced him to supply a chapter of forty pages +on Geology to the Admiralty "Manual of Scientific Inquiry" which he was +editing. This is Darwin's single contribution to books of an "educational" +kind. It is remarkable for its clearness and simplicity and attention to +minute details. It may be read by the student of Darwin's life with much +interest, for the directions he gives to an explorer are without doubt +those which he, as a self-taught geologist, proved to be serviceable during +his life on the "Beagle". + +On the completion of the Cirripede volumes, in 1854, Darwin was able to +grapple with the immense pile of MS. notes which he had accumulated on the +species question. The first sketch of 35 pages (1842), had been enlarged +in 1844 into one of 230 pages ([The first draft of the "Origin" is being +prepared for Press by Mr Francis Darwin and will be published by the +Cambridge University Press this year (1909). A.C.S.]); but in 1856 was +commenced the work (never to be completed) which was designed on a scale +three or four times more extensive than that on which the "Origin of +Species" was in the end written. + +In drawing up those two masterly chapters of the "Origin", "On the +Imperfection of the Geological Record," and "On the Geological Succession +of Organic Beings", Darwin had need of all the experience and knowledge he +had been gathering during thirty years, the first half of which had been +almost wholly devoted to geological study. The most enlightened geologists +of the day found much that was new, and still more that was startling from +the manner of its presentation, in these wonderful essays. Of Darwin's own +sense of the importance of the geological evidence in any presentation of +his theory a striking proof will be found in a passage of the touching +letter to his wife, enjoining the publication of his sketch of 1844. "In +case of my sudden death," he wrote, "...the editor must be a geologist as +well as a naturalist." ("L.L." II. pages 16, 17.) + +In spite of the numerous and valuable palaeontological discoveries made +since the publication of "The Origin of Species", the importance of the +first of these two geological chapters is as great as ever. It still +remains true that "Those who believe that the geological record is in any +degree perfect, will at once reject the theory"--as indeed they must reject +any theory of evolution. The striking passage with which Darwin concludes +this chapter--in which he compares the record of the rocks to the much +mutilated volumes of a human history--remains as apt an illustration as it +did when first written. + +And the second geological chapter, on the Succession of Organic Beings-- +though it has been strengthened in a thousand ways, by the discoveries +concerning the pedigrees of the horse, the elephant and many other aberrant +types, though new light has been thrown even on the origin of great groups +like the mammals, and the gymnosperms, though not a few fresh links have +been discovered in the chains of evidence, concerning the order of +appearance of new forms of life--we would not wish to have re-written. +Only the same line of argument could be adopted, though with innumerable +fresh illustrations. Those who reject the reasonings of this chapter, +neither would they be persuaded if a long and complete succession of +"ancestral forms" could rise from the dead and pass in procession before +them. + +Among the geological discussions, which so frequently occupied Darwin's +attention during the later years of his life, there was one concerning +which his attitude seemed somewhat remarkable--I allude to his views on +"the permanence of Continents and Ocean-basins." In a letter to Mr Mellard +Reade, written at the end of 1880, he wrote: "On the whole, I lean to the +side that the continents have since Cambrian times occupied approximately +their present positions. But, as I have said, the question seems a +difficult one, and the more it is discussed the better." ("M.L." II. page +147.) Since this was written, the important contribution to the subject by +the late Dr W.T. Blanford (himself, like Darwin, a naturalist and +geologist) has appeared in an address to the Geological Society in 1890; +and many discoveries, like that of Dr Woolnough in Fiji, have led to +considerable qualifications of the generalisation that all the islands in +the great ocean are wholly of volcanic or coral origin. + +I remember once expressing surprise to Darwin that, after the views which +he had originated concerning the existence of areas of elevation and others +of subsidence in the Pacific Ocean, and in face of the admitted difficulty +of accounting for the distribution of certain terrestrial animals and +plants, if the land and sea areas had been permanent in position, he still +maintained that theory. Looking at me with a whimsical smile, he said: "I +have seen many of my old friends make fools of themselves, by putting +forward new theoretical views or revising old ones, AFTER THEY WERE SIXTY +YEARS OF AGE; so, long ago, I determined that on reaching that age I would +write nothing more of a speculative character." + +Though Darwin's letters and conversations on geology during these later +years were the chief manifestations of the interest he preserved in his +"old love," as he continued to call it, yet in the sunset of that active +life a gleam of the old enthusiasm for geology broke forth once more. +There can be no doubt that Darwin's inability to occupy himself with field- +work proved an insuperable difficulty to any attempt on his part to resume +active geological research. But, as is shown by the series of charming +volumes on plant-life, Darwin had found compensation in making patient and +persevering experiment take the place of enterprising and exact +observation; and there was one direction in which he could indulge the "old +love" by employment of the new faculty. + +We have seen that the earliest memoir written by Darwin, which was +published in full, was a paper "On the Formation of Mould" which was read +at the Geological Society on November 1st, 1837, but did not appear in the +"Transactions" of the Society till 1840, where it occupied four and a half +quarto pages, including some supplementary matter, obtained later, and a +woodcut. This little paper was confined to observations made in his +uncle's fields in Staffordshire, where burnt clay, cinders, and sand were +found to be buried under a layer of black earth, evidently brought from +below by earthworms, and to a recital of similar facts from Scotland +obtained through the agency of Lyell. The subsequent history of Darwin's +work on this question affords a striking example of the tenacity of purpose +with which he continued his enquiries on any subject that interested him. + +In 1842, as soon as he was settled at Down, he began a series of +observations on a foot-path and in his fields, that continued with +intermissions during his whole life, and he extended his enquiries from +time to time to the neighbouring parks of Knole and Holwood. In 1844 we +find him making a communication to the "Gardener's Chronicle" on the +subject. About 1870, his attention to the question was stimulated by the +circumstance that his niece (Miss L. Wedgwood) undertook to collect and +weigh the worm-casts thrown up, during a whole year, on measured squares +selected for the purpose, at Leith Hill Place. He also obtained +information from Professor Ramsay concerning observations made by him on a +pavement near his house in 1871. Darwin at this time began to realise the +great importance of the action of worms to the archaeologist. At an +earlier date he appears to have obtained some information concerning +articles found buried on the battle-field of Shrewsbury, and the old Roman +town of Uriconium, near his early home; between 1871 and 1878 Mr +(afterwards Lord) Farrer carried on a series of investigations at the Roman +Villa discovered on his land at Abinger; Darwin's son William examined for +his father the evidence at Beaulieu Abbey, Brading, Stonehenge and other +localities in the neighbourhood of his home; his sons Francis and Horace +were enlisted to make similar enquiries at Chideock and Silchester; while +Francis Galton contributed facts noticed in his walks in Hyde Park. By +correspondence with Fritz Muller and Dr Ernst, Darwin obtained information +concerning the worm-casts found in South America; from Dr Kreft those of +Australia; and from Mr Scott and Dr (afterwards Sir George) King, those of +India; the last-named correspondent also supplied him with much valuable +information obtained in the South of Europe. Help too was obtained from +the memoirs on Earthworms published by Perrier in 1874 and van Hensen in +1877, while Professor Ray Lankester supplied important facts with regard to +their anatomy. + +When therefore the series of interesting monographs on plant-life had been +completed, Darwin set to work in bringing the information that he had +gradually accumulated during forty-four years to bear on the subject of his +early paper. He also utilised the skill and ingenuity he had acquired in +botanical work to aid in the elucidation of many of the difficulties that +presented themselves. I well remember a visit which I paid to Down at this +period. At the side of the little study stood flower-pots containing earth +with worms, and, without interrupting our conversation, Darwin would from +time to time lift the glass plate covering a pot to watch what was going +on. Occasionally, with a humorous smile, he would murmur something about a +book in another room, and slip away; returning shortly, without the book +but with unmistakeable signs of having visited the snuff-jar outside. +After working about a year at the worms, he was able at the end of 1881 to +publish the charming little book--"The Formation of Vegetable Mould through +the Action of Worms, with Observations on their Habits". This was the last +of his books, and its reception by reviewers and the public alike afforded +the patient old worker no little gratification. Darwin's scientific +career, which had begun with geological research, most appropriately ended +with a return to it. + +It has been impossible to sketch the origin and influence of Darwin's +geological work without, at almost every step, referring to the part played +by Lyell and the "Principles of Geology". Haeckel, in the chapters on +Lyell and Darwin in his "History of Creation", and Huxley in his striking +essay "On the Reception of the Origin of Species" ("L.L." II. pages 179- +204.) have both strongly insisted on the fact that the "Origin" of Darwin +was a necessary corollary to the "Principles" of Lyell. + +It is true that, in an earlier essay, Huxley had spoken of the doctrine of +Uniformitarianism as being, in a certain sense, opposed to that of +Evolution (Huxley's Address to the Geological Society, 1869. "Collected +Essays", Vol. VIII. page 305, London, 1896.); but in his later years he +took up a very different and more logical position, and maintained that +"Consistent uniformitarianism postulates evolution as much in the organic +as in the inorganic world. The origin of a new species by other than +ordinary agencies would be a vastly greater 'catastrophe' than any of those +which Lyell success fully eliminated from sober geological speculation." +("L.L." II. page 190.) + +Huxley's admiration for the "Principles of Geology", and his conviction of +the greatness of the revolution of thought brought about by Lyell, was +almost as marked as in the case of Darwin himself. (See his Essay on +"Science and Pseudo Science". "Collected Essays", Vol. V. page 90, London, +1902.) He felt, however, as many others have done, that in one respect the +very success of Lyell's masterpiece has been the reason why its originality +and influence have not been so fully recognised as they deserved to be. +Written as the book was before its author had arrived at the age of thirty, +no less than eleven editions of the "Principles" were called for in his +lifetime. With the most scrupulous care, Lyell, devoting all his time and +energies to the task of collecting and sifting all evidence bearing on the +subjects of his work, revised and re-revised it; and as in each edition, +eliminations, modifications, corrections, and additions were made, the +book, while it increased in value as a storehouse of facts, lost much of +its freshness, vigour and charm as a piece of connected reasoning. + +Darwin undoubtedly realised this when he wrote concerning the "Principles", +"the first edition, my old true love, which I never deserted for the later +editions." ("M.L." II. page 222.) Huxley once told me that when, in later +life, he read the first edition, he was both surprised and delighted, +feeling as if it were a new book to him. (I have before me a letter which +illustrates this feeling on Huxley's part. He had lamented to me that he +did not possess a copy of the first edition of the "Principles", when, +shortly afterwards, I picked up a dilapidated copy on a bookstall; this I +had bound and sent to my old teacher and colleague. His reply is +characteristic: + +October 8, 1884. + +My Dear Judd, + +You could not have made me a more agreeable present than the copy of the +first edition of Lyell, which I find on my table. I have never been able +to meet with the book, and your copy is, as the old woman said of her +Bible, "the best of books in the best of bindings." + +Ever yours sincerely, + +T.H. Huxley. + +I cannot refrain from relating an incident which very strikingly +exemplifies the affection for one another felt by Lyell and Huxley. In his +last illness, when confined to his bed, Lyell heard that Huxley was to +lecture at the Royal Institution on the "Results of the 'Challenger' +expedition": he begged me to attend the lecture and bring him an account +of it. Happening to mention this to Huxley, he at once undertook to go to +Lyell in my place, and he did so on the morning following his lecture. I +shall never forget the look of gratitude on the face of the invalid when he +told me, shortly afterwards, how Huxley had sat by his bedside and +"repeated the whole lecture to him.") + +Darwin's generous nature seems often to have made him experience a fear +lest he should do less than justice to his "dear old master," and to the +influence that the "Principles of Geology" had in moulding his mind. In +1845 he wrote to Lyell, "I have long wished, not so much for your sake, as +for my own feelings of honesty, to acknowledge more plainly than by mere +reference, how much I geologically owe you. Those authors, however, who +like you, educate people's minds as well as teach them special facts, can +never, I should think, have full justice done them except by posterity, for +the mind thus insensibly improved can hardly perceive its own upward +ascent." ("L.L." I. pages 337-8.) In another letter, to Leonard Horner, +he says: "I always feel as if my books came half out of Lyell's brain, and +that I never acknowledge this sufficiently." ("M.L." II. page 117.) +Darwin's own most favourite book, the "Narrative of the Voyage", was +dedicated to Lyell in glowing terms; and in the "Origin of Species" he +wrote of "Lyell's grand work on the "Principles of Geology", which the +future historian will recognise as having produced a revolution in Natural +Science." "What glorious good that work has done" he fervently exclaims on +another occasion. ("L.L." I. page 342.) + +To the very end of his life, as all who were in the habit of talking with +Darwin can testify, this sense of his indebtedness to Lyell remained with +him. In his "Autobiography", written in 1876, the year after Lyell's +death, he spoke in the warmest terms of the value to him of the +"Principles" while on the voyage and of the aid afforded to him by Lyell on +his return to England. ("L.L." I. page 62.) But the year before his own +death, Darwin felt constrained to return to the subject and to place on +record a final appreciation--one as honourable to the writer as it is to +his lost friend: + +"I saw more of Lyell than of any other man, both before and after my +marriage. His mind was characterised, as it appeared to me, by clearness, +caution, sound judgment, and a good deal of originality. When I made any +remark to him on Geology, he never rested until he saw the whole case +clearly, and often made me see it more clearly than I had done before. He +would advance all possible objections to my suggestion, and even after +these were exhausted would remain long dubious. A second characteristic +was his hearty sympathy with the work of other scientific men...His delight +in science was ardent, and he felt the keenest interest in the future +progress of mankind. He was very kind-hearted...His candour was highly +remarkable. He exhibited this by becoming a convert to the Descent theory, +though he had gained much fame by opposing Lamarck's views, and this after +he had grown old." + +"THE SCIENCE OF GEOLOGY IS ENORMOUSLY INDEBTED TO LYELL--MORE SO, AS I +BELIEVE, THAN TO ANY OTHER MAN WHO EVER LIVED." ("L.L." I. pages 71-2 (the +italics are mine.) + +Those who knew Lyell intimately will recognise the truth of the portrait +drawn by his dearest friend, and I believe that posterity will endorse +Darwin's deliberate verdict concerning the value of his labours. + +It was my own good fortune, to be brought into close contact with these two +great men during the later years of their life, and I may perhaps be +permitted to put on record the impressions made upon me during friendly +intercourse with both. + +In some respects, there was an extraordinary resemblance in their modes and +habits of thought, between Lyell and Darwin; and this likeness was also +seen in their modesty, their deference to the opinion of younger men, their +enthusiasm for science, their freedom from petty jealousies and their +righteous indignation for what was mean and unworthy in others. But yet +there was a difference. Both Lyell and Darwin were cautious, but perhaps +Lyell carried his caution to the verge of timidity. I think Darwin +possessed, and Lyell lacked, what I can only describe by the theological +term, "faith--the substance of things hoped for, the evidence of things not +seen." Both had been constrained to feel that the immutability of species +could not be maintained. Both, too, recognised the fact that it would be +useless to proclaim this conviction, unless prepared with a satisfactory +alternative to what Huxley called "the Miltonic hypothesis." But Darwin's +conviction was so far vital and operative that it sustained him while +working unceasingly for twenty-two years in collecting evidence bearing on +the question, till at last he was in the position of being able to justify +that conviction to others. + +And yet Lyell's attitude--and that of Hooker, which was very similar-- +proved of inestimable service to science, as Darwin often acknowledged. +One of the greatest merits of the "Origin of Species" is that so many +difficulties and objections are anticipated and fairly met; and this was to +a great extent the result of the persistent and very candid--if always +friendly--criticism of Lyell and Hooker. + +I think the divergence of mental attitude in Lyell and Darwin must be +attributed to a difference in temperament, the evidence of which sometimes +appears in a very striking manner in their correspondence. Thus in 1838, +while they were in the thick of the fight with the Catastrophists of the +Geological Society, Lyell wrote characteristically: "I really find, when +bringing up my Preliminary Essays in "Principles" to the science of the +present day, so far as I know it, that the great outline, and even most of +the details, stand so uninjured, and in many cases they are so much +strengthened by new discoveries, especially by yours, that we may begin to +hope that the great principles there insisted on will stand the test of new +discoveries." (Lyell's "Life, Letters and Journals", Vol. II. page 44.) +To which the more youthful and impetuous Darwin replies: "BEGIN TO HOPE: +why the POSSIBILITY of a doubt has never crossed my mind for many a day. +This may be very unphilosophical, but my geological salvation is staked on +it...it makes me quite indignant that you should talk of HOPING." ("L.L." +I. page 296.) + +It was not only Darwin's "geological salvation" that was at stake, when he +surrendered himself to his enthusiasm for an idea. To his firm faith in +the doctrine of continuity we owe the "Origin of Species"; and while Darwin +became the "Paul" of evolution, Lyell long remained the "doubting Thomas." + +Many must have felt like H.C. Watson when he wrote: "How could Sir C. +Lyell...for thirty years read, write, and think, on the subject of species +AND THEIR SUCCESSION, and yet constantly look down the wrong road!" ("L.L." +II. page 227.) Huxley attributed this hesitation of Lyell to his "profound +antipathy" to the doctrine of the "pithecoid origin of man." ("L.L." II. +page 193.) Without denying that this had considerable influence (and those +who knew Lyell and his great devotion to his wife and her memory, are aware +that he and she felt much stronger convictions concerning such subjects as +the immortality of the soul than Darwin was able to confess to) yet I think +Darwin had divined the real characteristics of his friend's mind, when he +wrote: "He would advance all possible objections...AND EVEN AFTER THESE +WERE EXHAUSTED, WOULD REMAIN LONG DUBIOUS." + +Very touching indeed was the friendship maintained to the end between these +two leaders of thought--free as their intercourse was from any smallest +trace of self-seeking or jealousy. When in 1874 I spent some time with +Lyell in his Forfarshire home, a communication from Darwin was always an +event which made a "red-letter day," as Lyell used to say; and he gave me +many indications in his conversation of how strongly he relied upon the +opinion of Darwin--more indeed than on the judgment of any other man--this +confidence not being confined to questions of science, but extending to +those of morals, politics, and religion. + +I have heard those who knew Lyell only slightly, speak of his manners as +cold and reserved. His complete absorption in his scientific work, coupled +with extreme short-sightedness, almost in the end amounting to blindness, +may have permitted those having but a casual acquaintance with him to +accept such a view. But those privileged to know him intimately recognised +the nobleness of his character and can realise the justice and force of +Hooker's words when he heard of his death: "My loved, my best friend, for +well nigh forty years of my life. The most generous sharer of my own and +my family's hopes, joys and sorrows, whose affection for me was truly that +of a father and brother combined." + +But the strongest of all testimonies to the grandeur of Lyell's character +is the lifelong devotion to him of such a man as Darwin. Before the two +met, we find Darwin constantly writing of facts and observations that he +thinks "will interest Mr Lyell"; and when they came together the mutual +esteem rapidly ripened into the warmest affection. Both having the +advantage of a moderate independence, permitting of an entire devotion of +their lives to scientific research, they had much in common, and the elder +man--who had already achieved both scientific and literary distinction--was +able to give good advice and friendly help to the younger one. The warmth +of their friendship comes out very strikingly in their correspondence. +When Darwin first conceived the idea of writing a book on the "species +question," soon after his return from the voyage, it was "by following the +example of Lyell in Geology" that he hoped to succeed ("L.L." I. page 83.); +when in 1844, Darwin had finished his first sketch of the work, and, +fearing that his life might not be spared to complete his great +undertaking, committed the care of it in a touching letter to his wife, it +was his friend Lyell whom he named as her adviser and the possible editor +of the book ("L.L." II. pages 17-18.); it was Lyell who, in 1856, induced +Darwin to lay the foundations of a treatise ("L.L." I. page 84.) for which +the author himself selected the "Principles" as his model; and when the +dilemma arose from the receipt of Wallace's essay, it was to Lyell jointly +with Hooker that Darwin turned, not in vain, for advice and help. + +During the later years of his life, I never heard Darwin allude to his lost +friend--and he did so very often--without coupling his name with some term +of affection. For a brief period, it is true, Lyell's excessive caution +when the "Origin" was published, seemed to try even the patience of Darwin; +but when "the master" was at last able to declare himself fully convinced, +he was the occasion of more rejoicing on the part of Darwin, than any other +convert to his views. The latter was never tired of talking of Lyell's +"magnanimity" and asserted that, "To have maintained in the position of a +master, one side of a question for thirty years, and then deliberately give +it up, is a fact to which I much doubt whether the records of science offer +a parallel." ("L.L." II. pages 229-30.) + +Of Darwin himself, I can safely affirm that I never knew anyone who had met +him, even for the briefest period, who was not charmed by his personality. +Who could forget the hearty hand-grip at meeting, the gentle and lingering +pressure of the palm at parting, and above all that winning smile which +transformed his countenance--so as to make portraits, and even photographs, +seem ever afterwards unsatisfying! Looking back, one is indeed tempted to +forget the profoundness of the philosopher, in recollection of the +loveableness of the man. + + +XIX. DARWIN'S WORK ON THE MOVEMENTS OF PLANTS. + +By FRANCIS DARWIN, +Honorary Fellow of Christ's College, Cambridge. + +My father's interest in plants was of two kinds, which may be roughly +distinguished as EVOLUTIONARY and PHYSIOLOGICAL. Thus in his purely +evolutionary work, for instance in "The Origin of Species" and in his book +on "Variation under Domestication", plants as well as animals served as +material for his generalisations. He was largely dependent on the work of +others for the facts used in the evolutionary work, and despised himself +for belonging to the "blessed gang" of compilers. And he correspondingly +rejoiced in the employment of his wonderful power of observation in the +physiological problems which occupied so much of his later life. But +inasmuch as he felt evolution to be his life's work, he regarded himself as +something of an idler in observing climbing plants, insectivorous plants, +orchids, etc. In this physiological work he was to a large extent urged on +by his passionate desire to understand the machinery of all living things. +But though it is true that he worked at physiological problems in the +naturalist's spirit of curiosity, yet there was always present to him the +bearing of his facts on the problem of evolution. His interests, +physiological and evolutionary, were indeed so interwoven that they cannot +be sharply separated. Thus his original interest in the fertilisation of +flowers was evolutionary. "I was led" ("Life and Letters", I. page 90.), +he says, "to attend to the cross-fertilisation of flowers by the aid of +insects, from having come to the conclusion in my speculations on the +origin of species, that crossing played an important part in keeping +specific forms constant." In the same way the value of his experimental +work on heterostyled plants crystalised out in his mind into the conclusion +that the product of illegitimate unions are equivalent to hybrids--a +conclusion of the greatest interest from an evolutionary point of view. +And again his work "Cross and Self Fertilisation" may be condensed to a +point of view of great importance in reference to the meaning and origin of +sexual reproduction. (See Professor Goebel's article in the present +volume.) + +The whole of his physiological work may be looked at as an illustration of +the potency of his theory as an "instrument for the extension of the realm +of natural knowledge." (Huxley in Darwin's "Life and Letters." II. page +204.) + +His doctrine of natural selection gave, as is well known, an impulse to the +investigation of the use of organs--and thus created the great school of +what is known in Germany as Biology--a department of science for which no +English word exists except the rather vague term Natural History. This was +especially the case in floral biology, and it is interesting to see with +what hesitation he at first expressed the value of his book on Orchids +("Life and Letters", III. page 254.), "It will perhaps serve to illustrate +how Natural History may be worked under the belief of the modification of +species" (1861). And in 1862 he speaks (Loc. cit.) more definitely of the +relation of his work to natural selection: "I can show the meaning of some +of the apparently meaningless ridges (and) horns; who will now venture to +say that this or that structure is useless?" It is the fashion now to +minimise the value of this class of work, and we even find it said by a +modern writer that to inquire into the ends subserved by organs is not a +scientific problem. Those who take this view surely forget that the +structure of all living things is, as a whole, adaptive, and that a +knowledge of how the present forms come to be what they are includes a +knowledge of why they survived. They forget that the SUMMATION of +variations on which divergence depends is under the rule of the environment +considered as a selective force. They forget that the scientific study of +the interdependence of organisms is only possible through a knowledge of +the machinery of the units. And that, therefore, the investigation of such +widely interesting subjects as extinction and distribution must include a +knowledge of function. It is only those who follow this line of work who +get to see the importance of minute points of structure and understand as +my father did even in 1842, as shown in his sketch of the "Origin" (Now +being prepared for publication.), that every grain of sand counts for +something in the balance. Much that is confidently stated about the +uselessness of different organs would never have been written if the +naturalist spirit were commoner nowadays. This spirit is strikingly shown +in my father's work on the movements of plants. The circumstance that +botanists had not, as a class, realised the interest of the subject +accounts for the fact that he was able to gather such a rich harvest of +results from such a familiar object as a twining plant. The subject had +been investigated by H. von Mohl, Palm, and Dutrochet, but they failed not +only to master the problem but (which here concerns us) to give the +absorbing interest of Darwin's book to what they discovered. + +His work on climbing plants was his first sustained piece of work on the +physiology of movement, and he remarks in 1864: "This has been new sort of +work for me." ("Life and Letters", III. page 315. He had, however, made a +beginning on the movements of Drosera.) He goes on to remark with +something of surprise, "I have been pleased to find what a capital guide +for observations a full conviction of the change of species is." + +It was this point of view that enabled him to develop a broad conception of +the power of climbing as an adaptation by means of which plants are enabled +to reach the light. Instead of being compelled to construct a stem of +sufficient strength to stand alone, they succeed in the struggle by making +use of other plants as supports. He showed that the great class of +tendril- and root-climbers which do not depend on twining round a pole, +like a scarlet-runner, but on attaching themselves as they grow upwards, +effect an economy. Thus a Phaseolus has to manufacture a stem three feet +in length to reach a height of two feet above the ground, whereas a pea +"which had ascended to the same height by the aid of its tendrils, was but +little longer than the height reached." ("Climbing Plants" (2nd edition +1875), page 193.) + +Thus he was led on to the belief that TWINING is the more ancient form of +climbing, and that tendril-climbers have been developed from twiners. In +accordance with this view we find LEAF-CLIMBERS, which may be looked on as +incipient tendril-bearers, occurring in the same genera with simple +twiners. (Loc. cit. page 195.) He called attention to the case of +Maurandia semperflorens in which the young flower-stalks revolve +spontaneously and are sensitive to a touch, but neither of these qualities +is of any perceptible value to the species. This forced him to believe +that in other young plants the rudiments of the faculty needed for twining +would be found--a prophecy which he made good in his "Power of Movement" +many years later. + +In "Climbing Plants" he did little more than point out the remarkable fact +that the habit of climbing is widely scattered through the vegetable +kingdom. Thus climbers are to be found in 35 out of the 59 Phanerogamic +Alliances of Lindley, so that "the conclusion is forced on our minds that +the capacity of revolving (If a twining plant, e.g. a hop, is observed +before it has begun to ascend a pole, it will be noticed that, owing to the +curvature of the stem, the tip is not vertical but hangs over in a roughly +horizontal position. If such a shoot is watched it will be found that if, +for instance, it points to the north at a given hour, it will be found +after a short interval pointing north-east, then east, and after about two +hours it will once more be looking northward. The curvature of the stem +depends on one side growing quicker than the opposite side, and the +revolving movement, i.e. circumnutation, depends on the region of quickest +growth creeping gradually round the stem from south through west to south +again. Other plants, e.g. Phaseolus, revolve in the opposite direction.), +on which most climbers depend, is inherent, though undeveloped, in almost +every plant in the vegetable kingdom." ("Climbing Plants", page 205.) + +In the "Origin" (Edition I. page 427, Edition VI. page 374.) Darwin speaks +of the "apparent paradox, that the very same characters are analogical when +one class or order is compared with another, but give true affinities when +the members of the same class or order are compared one with another." In +this way we might perhaps say that the climbing of an ivy and a hop are +analogical; the resemblance depending on the adaptive result rather than on +community of blood; whereas the relation between a leaf-climber and a true +tendril-bearer reveals descent. This particular resemblance was one in +which my father took especial delight. He has described an interesting +case occurring in the Fumariaceae. ("Climbing Plants", page 195.) "The +terminal leaflets of the leaf-climbing Fumaria officinalis are not smaller +than the other leaflets; those of the leaf-climbing Adlumia cirrhosa are +greatly reduced; those of Corydalis claviculata (a plant which may be +indifferently called a leaf-climber or a tendril-bearer) are either reduced +to microscopical dimensions or have their blades wholly aborted, so that +this plant is actually in a state of transition; and finally in the +Dicentra the tendrils are perfectly characterized." + +It is a remarkable fact that the quality which, broadly speaking, forms the +basis of the climbing habit (namely revolving nutation, otherwise known as +circumnutation) subserves two distinct ends. One of these is the finding +of a support, and this is common to twiners and tendrils. Here the value +ends as far as tendril-climbers are concerned, but in twiners Darwin +believed that the act of climbing round a support is a continuation of the +revolving movement (circumnutation). If we imagine a man swinging a rope +round his head and if we suppose the rope to strike a vertical post, the +free end will twine round it. This may serve as a rough model of twining +as explained in the "Movements and Habits of Climbing Plants". It is on +these points--the nature of revolving nutation and the mechanism of +twining--that modern physiologists differ from Darwin. (See the discussion +in Pfeffer's "The Physiology of Plants" Eng. Tr. (Oxford, 1906), III. page +34, where the literature is given. Also Jost, "Vorlesungen uber +Pflanzenphysiologie", page 562, Jena, 1904.) + +Their criticism originated in observations made on a revolving shoot which +is removed from the action of gravity by keeping the plant slowly rotating +about a horizontal axis by means of the instrument known as a klinostat. +Under these conditions circumnutation becomes irregular or ceases +altogether. When the same experiment is made with a plant which has twined +spirally up a stick, the process of climbing is checked and the last few +turns become loosened or actually untwisted. From this it has been argued +that Darwin was wrong in his description of circumnutation as an automatic +change in the region of quickest growth. When the free end of a revolving +shoot points towards the north there is no doubt that the south side has +been elongating more than the north; after a time it is plain from the +shoot hanging over to the east that the west side of the plant has grown +most, and so on. This rhythmic change of the position of the region of +greatest growth Darwin ascribes to an unknown internal regulating power. +Some modern physiologists, however, attempt to explain the revolving +movement as due to a particular form of sensitiveness to gravitation which +it is not necessary to discuss in detail in this place. It is sufficient +for my purpose to point out that Darwin's explanation of circumnutation is +not universally accepted. Personally I believe that circumnutation is +automatic--is primarily due to internal stimuli. It is however in some way +connected with gravitational sensitiveness, since the movement normally +occurs round a vertical line. It is not unnatural that, when the plant has +no external stimulus by which the vertical can be recognised, the revolving +movement should be upset. + +Very much the same may be said of the act of twining, namely that most +physiologists refuse to accept Darwin's view (above referred to) that +twining is the direct result of circumnutation. Everyone must allow that +the two phenomena are in some way connected, since a plant which +circumnutates clockwise, i.e. with the sun, twines in the same direction, +and vice versa. It must also be granted that geotropism has a bearing on +the problem, since all plants twine upwards, and cannot twine along a +horizontal support. But how these two factors are combined, and whether +any (and if so what) other factors contribute, we cannot say. If we give +up Darwin's explanation, we must at the same time say with Pfeffer that +"the causes of twining are...unknown." ("The Physiology of Plants", Eng. +Tr. (Oxford, 1906), III. page 37.) + +Let us leave this difficult question and consider some other points made +out in the progress of the work on climbing plants. One result of what he +called his "niggling" ("Life and Letters", III. page 312.) work on tendrils +was the discovery of the delicacy of their sense of touch, and the rapidity +of their movement. Thus in a passion-flower tendril, a bit of platinum +wire weighing 1.2 mg. produced curvature ("Climbing Plants", page 171.), as +did a loop of cotton weighing 2 mg. Pfeffer ("Untersuchungen a.d. Bot. +Inst. z. Tubingen", Bd. I. 1881-85, page 506.), however, subsequently found +much greater sensitiveness: thus the tendril of Sicyos angulatus reacted +to 0.00025 mg., but this only occurred when the delicate rider of +cottonwool fibre was disturbed by the wind. The same author expanded and +explained in a most interesting way the meaning of Darwin's observation +that tendrils are not stimulated to movement by drops of water resting on +them. Pfeffer showed that DIRTY water containing minute particles of clay +in suspension acts as a stimulus. He also showed that gelatine acts like +pure water; if a smooth glass rod is coated with a 10 per cent solution of +gelatine and is then applied to a tendril, no movement occurs in spite of +the fact that the gelatine is solid when cold. Pfeffer ("Physiology", Eng. +Tr. III. page 52. Pfeffer has pointed out the resemblance between the +contact irritability of plants and the human sense of touch. Our skin is +not sensitive to uniform pressure such as is produced when the finger is +dipped into mercury (Tubingen "Untersuchungen", I. page 504.) generalises +the result in the statement that the tendril has a special form of +irritability and only reacts to "differences of pressure or variations of +pressure in contiguous...regions." Darwin was especially interested in +such cases of specialised irritability. For instance in May, 1864, he +wrote to Asa Gray ("Life and Letters", III. page 314.) describing the +tendrils of Bignonia capreolata, which "abhor a simple stick, do not much +relish rough bark, but delight in wool or moss." He received, from Gray, +information as to the natural habitat of the species, and finally concluded +that the tendrils "are specially adapted to climb trees clothed with +lichens, mosses, or other such productions." ("Climbing Plants", page +102.) + +Tendrils were not the only instance discovered by Darwin of delicacy of +touch in plants. In 1860 he had already begun to observe Sundew (Drosera), +and was full of astonishment at its behaviour. He wrote to Sir Joseph +Hooker ("Life and Letters", III. page 319.): "I have been working like a +madman at Drosera. Here is a fact for you which is certain as you stand +where you are, though you won't believe it, that a bit of hair 1/78000 of +one grain in weight placed on gland, will cause ONE of the gland-bearing +hairs of Drosera to curve inwards." Here again Pfeffer (Pfeffer in +"Untersuchungen a. d. Bot. Inst. z. Tubingen", I. page 491.) has, as in so +many cases, added important facts to my father's observations. He showed +that if the leaf of Drosera is entirely freed from such vibrations as would +reach it if observed on an ordinary table, it does not react to small +weights, so that in fact it was the vibration of the minute fragment of +hair on the gland that produced movement. We may fancifully see an +adaptation to the capture of insects--to the dancing of a gnat's foot on +the sensitive surface. + +Darwin was fond of telling how when he demonstrated the sensitiveness of +Drosera to Mr Huxley and (I think) to Sir John Burdon Sanderson, he could +perceive (in spite of their courtesy) that they thought the whole thing a +delusion. And the story ended with his triumph when Mr Huxley cried out, +"It IS moving." + +Darwin's work on tendrils has led to some interesting investigations on the +mechanisms by which plants perceive stimuli. Thus Pfeffer (Tubingen +"Untersuchungen" I. page 524.) showed that certain epidermic cells +occurring in tendrils are probably organs of touch. In these cells the +protoplasm burrows as it were into cavities in the thickness of the +external cell-walls and thus comes close to the surface, being separated +from an object touching the tendril merely by a very thin layer of cell- +wall substance. Haberlandt ("Physiologische Pflanzenanatomie", Edition +III. Leipzig, 1904. "Sinnesorgane im Pflanzenreich", Leipzig, 1901, and +other publications.) has greatly extended our knowledge of vegetable +structure in relation to mechanical stimulation. He defines a sense-organ +as a contrivance by which the DEFORMATION or forcible change of form in the +protoplasm--on which mechanical stimulation depends--is rendered rapid and +considerable in amplitude ("Sinnesorgane", page 10). He has shown that in +certain papillose and bristle-like contrivances, plants possess such sense- +organs; and moreover that these contrivances show a remarkable similarity +to corresponding sense-organs in animals. + +Haberlandt and Nemec ("Ber. d. Deutschen bot. Gesellschaft", XVIII. 1900. +See F. Darwin, Presidential Address to Section K, British Association, +1904.) published independently and simultaneously a theory of the mechanism +by which plants are orientated in relation to gravitation. And here again +we find an arrangement identical in principle with that by which certain +animals recognise the vertical, namely the pressure of free particles on +the irritable wall of a cavity. In the higher plants, Nemec and Haberlandt +believe that special loose and freely movable starch-grains play the part +of the otoliths or statoliths of the crustacea, while the protoplasm lining +the cells in which they are contained corresponds to the sensitive membrane +lining the otocyst of the animal. What is of special interest in our +present connection is that according to this ingenious theory (The original +conception was due to Noll ("Heterogene Induction", Leipzig, 1892), but his +view differed in essential points from those here given.) the sense of +verticality in a plant is a form of contact-irritability. The vertical +position is distinguished from the horizontal by the fact that, in the +latter case, the loose starch-grains rest on the lateral walls of the cells +instead of on the terminal walls as occurs in the normal upright position. +It should be added that the statolith theory is still sub judice; +personally I cannot doubt that it is in the main a satisfactory explanation +of the facts. + +With regard to the RAPIDITY of the reaction of tendrils, Darwin records +("Climbing Plants", page 155. Others have observed movement after about +6".) that a Passion-Flower tendril moved distinctly within 25 seconds of +stimulation. It was this fact, more than any other, that made him doubt +the current explanation, viz. that the movement is due to unequal growth on +the two sides of the tendril. The interesting work of Fitting +(Pringsheim's "Jahrb." XXXVIII. 1903, page 545.) has shown, however, that +the primary cause is not (as Darwin supposed) contraction on the concave, +but an astonishingly rapid increase in growth-rate on the convex side. + +On the last page of "Climbing Plants" Darwin wrote: "It has often been +vaguely asserted that plants are distinguished from animals by not having +the power of movement. It should rather be said that plants acquire and +display this power only when it is of some advantage to them." + +He gradually came to realise the vividness and variety of vegetable life, +and that a plant like an animal has capacities of behaving in different +ways under different circumstances, in a manner that may be compared to the +instinctive movements of animals. This point of view is expressed in well- +known passages in the "Power of Movement". ("The Power of Movement in +Plants", 1880, pages 571-3.) "It is impossible not to be struck with the +resemblance between the...movements of plants and many of the actions +performed unconsciously by the lower animals." And again, "It is hardly an +exaggeration to say that the tip of the radicle...having the power of +directing the movements of the adjoining parts, acts like the brain of one +of the lower animals; the brain being seated within the anterior end of the +body, receiving impressions from the sense-organs, and directing the +several movements." + +The conception of a region of perception distinct from a region of movement +is perhaps the most fruitful outcome of his work on the movements of +plants. But many years before its publication, viz. in 1861, he had made +out the wonderful fact that in the Orchid Catasetum ("Life and Letters", +III. page 268.) the projecting organs or antennae are sensitive to a touch, +and transmit an influence "for more than one inch INSTANTANEOUSLY," which +leads to the explosion or violent ejection of the pollinia. And as we have +already seen a similar transmission of a stimulus was discovered by him in +Sundew in 1860, so that in 1862 he could write to Hooker ("Life and +Letters", III. page 321.): "I cannot avoid the conclusion, that Drosera +possesses matter at least in some degree analogous in constitution and +function to nervous matter." I propose in what follows to give some +account of the observations on the transmission of stimuli given in the +"Power of Movement". It is impossible within the space at my command to +give anything like a complete account of the matter, and I must necessarily +omit all mention of much interesting work. One well-known experiment +consisted in putting opaque caps on the tips of seedling grasses (e.g. oat +and canary-grass) and then exposing them to light from one side. The +difference, in the amount of curvature towards the light, between the +blinded and unblinded specimens, was so great that it was concluded that +the light-sensitiveness resided exclusively in the tip. The experiment +undoubtedly proves that the sensitiveness is much greater in the tip than +elsewhere, and that there is a transmission of stimulus from the tip to the +region of curvature. But Rothert (Rothert, Cohn's "Beitrage", VII. 1894.) +has conclusively proved that the basal part where the curvature occurs is +also DIRECTLY sensitive to light. He has shown, however, that in other +grasses (Setaria, Panicum) the cotyledon is the only part which is +sensitive, while the hypocotyl, where the movement occurs, is not directly +sensitive. + +It was however the question of the localisation of the gravitational sense +in the tip of the seedling root or radicle that aroused most attention, and +it was on this question that a controversy arose which has continued to the +present day. + +The experiment on which Darwin's conclusion was based consisted simply in +cutting off the tip, and then comparing the behaviour of roots so treated +with that of normal specimens. An uninjured root when placed horizontally +regains the vertical by means of a sharp downward curve; not so a +decapitated root which continues to grow more or less horizontally. It was +argued that this depends on the loss of an organ specialised for the +perception of gravity, and residing in the tip of the root; and the +experiment (together with certain important variants) was claimed as +evidence of the existence of such an organ. + +It was at once objected that the amputation of the tip might check +curvature by interfering with longitudinal growth, on the distribution of +which curvature depends. This objection was met by showing that an injury, +e.g. splitting the root longitudinally (See F. Darwin, "Linnean Soc. +Journal (Bot)." XIX. 1882, page 218.), which does not remove the tip, but +seriously checks growth, does not prevent geotropism. This was of some +interest in another and more general way, in showing that curvature and +longitudinal growth must be placed in different categories as regards the +conditions on which they depend. + +Another objection of a much more serious kind was that the amputation of +the tip acts as a shock. It was shown by Rothert (See his excellent +summary of the subject in "Flora" 1894 (Erganzungsband), page 199.) that +the removal of a small part of the cotyledon of Setaria prevents the plant +curving towards the light, and here there is no question of removing the +sense-organ since the greater part of the sensitive cotyledon is intact. +In view of this result it was impossible to rely on the amputations +performed on roots as above described. + +At this juncture a new and brilliant method originated in Pfeffer's +laboratory. (See Pfeffer, "Annals of Botany", VIII. 1894, page 317, and +Czapek, Pringsheim's "Jahrb." XXVII. 1895, page 243.) Pfeffer and Czapek +showed that it is possible to bend the root of a lupine so that, for +instance, the supposed sense-organ at the tip is vertical while the motile +region is horizontal. If the motile region is directly sensitive to +gravity the root ought to curve downwards, but this did not occur: on the +contrary it continued to grow horizontally. This is precisely what should +happen if Darwin's theory is the right one: for if the tip is kept +vertical, the sense-organ is in its normal position and receives no +stimulus from gravitation, and therefore can obviously transmit none to the +region of curvature. Unfortunately this method did not convince the +botanical world because some of those who repeated Czapek's experiment +failed to get his results. + +Czapek ("Berichte d. Deutsch. bot. Ges." XV. 1897, page 516, and numerous +subsequent papers. English readers should consult Czapek in the "Annals of +Botany", XIX. 1905, page 75.) has devised another interesting method which +throws light on the problem. He shows that roots, which have been placed +in a horizontal position and have therefore been geotropically stimulated, +can be distinguished by a chemical test from vertical, i.e. unstimulated +roots. The chemical change in the root can be detected before any +curvature has occurred and must therefore be a symptom of stimulation, not +of movement. It is particularly interesting to find that the change in the +root, on which Czapek's test depends, takes place in the tip, i.e. in the +region which Darwin held to be the centre for gravitational sensitiveness. + +In 1899 I devised a method (F. Darwin, "Annals of Botany", XIII. 1899, page +567.) by which I sought to prove that the cotyledon of Setaria is not only +the organ for light-perception, but also for gravitation. If a seedling is +supported horizontally by pushing the apical part (cotyledon) into a +horizontal tube, the cotyledon will, according to my supposition, be +stimulated gravitationally and a stimulus will be transmitted to the basal +part of the stem (hypocotyl) causing it to bend. But this curvature merely +raises the basal end of the seedling, the sensitive cotyledon remains +horizontal, imprisoned in its tube; it will therefore be continually +stimulated and will continue to transmit influences to the bending region, +which should therefore curl up into a helix or corkscrew-like form,--and +this is precisely what occurred. + +I have referred to this work principally because the same method was +applied to roots by Massart (Massart, "Mem. Couronnes Acad. R. Belg." LXII. +1902.) and myself (F. Darwin, "Linnean Soc. Journ." XXXV. 1902, page 266.) +with a similar though less striking result. Although these researches +confirmed Darwin's work on roots, much stress cannot be laid on them as +there are several objections to them, and they are not easily repeated. + +The method which--as far as we can judge at present--seems likely to solve +the problem of the root-tip is most ingenious and is due to Piccard. +(Pringsheim's "Jahrb." XL. 1904, page 94.) + +Andrew Knight's celebrated experiment showed that roots react to +centrifugal force precisely as they do to gravity. So that if a bean root +is fixed to a wheel revolving rapidly on a horizontal axis, it tends to +curve away from the centre in the line of a radius of the wheel. In +ordinary demonstrations of Knight's experiment the seed is generally fixed +so that the root is at right angles to a radius, and as far as convenient +from the centre of rotation. Piccard's experiment is arranged differently. +(A seed is depicted below a horizontal dotted line AA, projecting a root +upwards.) The root is oblique to the axis of rotation, and the extreme tip +projects beyond that axis. Line AA represents the axis of rotation, T is +the tip of the root just above the line AA, and B is the region just below +line AA in which curvature takes place. If the motile region B is directly +sensitive to gravitation (and is the only part which is sensitive) the root +will curve (down and away from the vertical) away from the axis of +rotation, just as in Knight's experiment. But if the tip T is alone +sensitive to gravitation the result will be exactly reversed, the stimulus +originating in T and conveyed to B will produce curvature (up towards the +vertical). We may think of the line AA as a plane dividing two worlds. In +the lower one gravity is of the earthly type and is shown by bodies falling +and roots curving downwards: in the upper world bodies fall upwards and +roots curve in the same direction. The seedling is in the lower world, but +its tip containing the supposed sense-organ is in the strange world where +roots curve upwards. By observing whether the root bends up or down we can +decide whether the impulse to bend originates in the tip or in the motile +region. + +Piccard's results showed that both curvatures occurred and he concluded +that the sensitive region is not confined to the tip. (Czapek +(Pringsheim's "Jahrb." XXXV. 1900, page 362) had previously given reasons +for believing that, in the root, there is no sharp line of separation +between the regions of perception and movement.) + +Haberlandt (Pringsheim's "Jahrb." XLV. 1908, page 575.) has recently +repeated the experiment with the advantage of better apparatus and more +experience in dealing with plants, and has found as Piccard did that both +the tip and the curving region are sensitive to gravity, but with the +important addition that the sensitiveness of the tip is much greater than +that of the motile region. The case is in fact similar to that of the oat +and canary-grass. In both instances my father and I were wrong in assuming +that the sensitiveness is confined to the tip, yet there is a concentration +of irritability in that region and transmission of stimulus is as true for +geotropism as it is for heliotropism. Thus after nearly thirty years the +controversy of the root-tip has apparently ended somewhat after the fashion +of the quarrels at the "Rainbow" in "Silas Marner"--"you're both right and +you're both wrong." But the "brain-function" of the root-tip at which +eminent people laughed in early days turns out to be an important part of +the truth. (By using Piccard's method I have succeeded in showing that the +gravitational sensitiveness of the cotyledon of Sorghum is certainly much +greater than the sensitiveness of the hypocotyl--if indeed any such +sensitiveness exists. See Wiesner's "Festschrift", Vienna, 1908.) + +Another observation of Darwin's has given rise to much controversy. +("Power of Movement", page 133.) If a minute piece of card is fixed +obliquely to the tip of a root some influence is transmitted to the region +of curvature and the root bends away from the side to which the card was +attached. It was thought at the time that this proved the root-tip to be +sensitive to contact, but this is not necessarily the case. It seems +possible that the curvature is a reaction to the injury caused by the +alcoholic solution of shellac with which the cards were cemented to the +tip. This agrees with the fact given in the "Power of Movement" that +injuring the root-tip on one side, by cutting or burning it, induced a +similar curvature. On the other hand it was shown that curvature could be +produced in roots by cementing cards, not to the naked surface of the root- +tip, but to pieces of gold-beaters skin applied to the root; gold-beaters +skin being by itself almost without effect. But it must be allowed that, +as regards touch, it is not clear how the addition of shellac and card can +increase the degree of contact. There is however some evidence that very +close contact from a solid body, such as a curved fragment of glass, +produces curvature: and this may conceivably be the explanation of the +effect of gold-beaters skin covered with shellac. But on the whole it is +perhaps safer to classify the shellac experiments with the results of +undoubted injury rather than with those of contact. + +Another subject on which a good deal of labour was expended is the sleep of +leaves, or as Darwin called it their NYCTITROPIC movement. He showed for +the first time how widely spread this phenomenon is, and attempted to give +an explanation of the use to the plant of the power of sleeping. His +theory was that by becoming more or less vertical at night the leaves +escape the chilling effect of radiation. Our method of testing this view +was to fix some of the leaves of a sleeping plant so that they remained +horizontal at night and therefore fully exposed to radiation, while their +fellows were partly protected by assuming the nocturnal position. The +experiments showed clearly that the horizontal leaves were more injured +than the sleeping, i.e. more or less vertical, ones. It may be objected +that the danger from cold is very slight in warm countries where sleeping +plants abound. But it is quite possible that a lowering of the temperature +which produces no visible injury may nevertheless be hurtful by checking +the nutritive processes (e.g. translocation of carbohydrates), which go on +at night. Stahl ("Bot. Zeitung", 1897, page 81.) however has ingeniously +suggested that the exposure of the leaves to radiation is not DIRECTLY +hurtful because it lowers the temperature of the leaf, but INDIRECTLY +because it leads to the deposition of dew on the leaf-surface. He gives +reasons for believing that dew-covered leaves are unable to transpire +efficiently, and that the absorption of mineral food-material is +correspondingly checked. Stahl's theory is in no way destructive of +Darwin's, and it is possible that nyctitropic leaves are adapted to avoid +the indirect as well as the direct results of cooling by radiation. + +In what has been said I have attempted to give an idea of some of the +discoveries brought before the world in the "Power of Movement" (In 1881 +Professor Wiesner published his "Das Bewegungsvermogen der Pflanzen", a +book devoted to the criticism of "The Power of Movement in Plants". A +letter to Wiesner, published in "Life and Letters", III. page 336, shows +Darwin's warm appreciation of his critic's work, and of the spirit in which +it is written.) and of the subsequent history of the problems. We must now +pass on to a consideration of the central thesis of the book,--the relation +of circumnutation to the adaptive curvatures of plants. + +Darwin's view is plainly stated on pages 3-4 of the "Power of Movement". +Speaking of circumnutation he says, "In this universally present movement +we have the basis or groundwork for the acquirement, according to the +requirements of the plant, of the most diversified movements." He then +points out that curvatures such as those towards the light or towards the +centre of the earth can be shown to be exaggerations of circumnutation in +the given directions. He finally points out that the difficulty of +conceiving how the capacities of bending in definite directions were +acquired is diminished by his conception. "We know that there is always +movement in progress, and its amplitude, or direction, or both, have only +to be modified for the good of the plant in relation with internal or +external stimuli." + +It may at once be allowed that the view here given has not been accepted by +physiologists. The bare fact that circumnutation is a general property of +plants (other than climbing species) is not generally rejected. But the +botanical world is no nearer to believing in the theory of reaction built +on it. + +If we compare the movements of plants with those of the lower animals we +find a certain resemblance between the two. According to Jennings (H.S. +Jennings, "The Behavior of the Lower Animals". Columbia U. Press, N.Y. +1906.) a Paramoecium constantly tends to swerve towards the aboral side of +its body owing to certain peculiarities in the set and power of its cilia. +But the tendency to swim in a circle, thus produced, is neutralised by the +rotation of the creature about its longitudinal axis. Thus the direction +of the swerves IN RELATION TO THE PATH of the organism is always changing, +with the result that the creature moves in what approximates to a straight +line, being however actually a spiral about the general line of progress. +This method of motion is strikingly like the circumnutation of a plant, the +apex of which also describes a spiral about the general line of growth. A +rooted plant obviously cannot rotate on its axis, but the regular series of +curvatures of which its growth consists correspond to the aberrations of +Paramoecium distributed regularly about its course by means of rotation. +(In my address to the Biological Section of the British Association at +Cardiff (1891) I have attempted to show the connection between +circumnutation and RECTIPETALITY, i.e. the innate capacity of growing in a +straight line.) Just as a plant changes its direction of growth by an +exaggeration of one of the curvature-elements of which circumnutation +consists, so does a Paramoecium change its course by the accentuation of +one of the deviations of which its path is built. Jennings has shown that +the infusoria, etc., react to stimuli by what is known as the "method of +trial." If an organism swims into a region where the temperature is too +high or where an injurious substance is present, it changes its course. It +then moves forward again, and if it is fortunate enough to escape the +influence, it continues to swim in the given direction. If however its +change of direction leads it further into the heated or poisonous region it +repeats the movement until it emerges from its difficulties. Jennings +finds in the movements of the lower organisms an analogue with what is +known as pain in conscious organisms. There is certainly this much +resemblance that a number of quite different sub-injurious agencies produce +in the lower organisms a form of reaction by the help of which they, in a +partly fortuitous way, escape from the threatening element in their +environment. The higher animals are stimulated in a parallel manner to +vague and originally purposeless movements, one of which removes the +discomfort under which they suffer, and the organism finally learns to +perform the appropriate movement without going through the tentative series +of actions. + +I am tempted to recognise in circumnutation a similar groundwork of +tentative movements out of which the adaptive ones were originally selected +by a process rudely representative of learning by experience. + +It is, however, simpler to confine ourselves to the assumption that those +plants have survived which have acquired through unknown causes the power +of reacting in appropriate ways to the external stimuli of light, gravity, +etc. It is quite possible to conceive this occurring in plants which have +no power of circumnutating--and, as already pointed out, physiologists do +as a fact neglect circumnutation as a factor in the evolution of movements. +Whatever may be the fate of Darwin's theory of circumnutation there is no +doubt that the research he carried out in support of, and by the light of, +this hypothesis has had a powerful influence in guiding the modern theories +of the behaviour of plants. Pfeffer ("The Physiology of Plants", Eng. Tr. +III. page 11.), who more than any one man has impressed on the world a +rational view of the reactions of plants, has acknowledged in generous +words the great value of Darwin's work in the same direction. The older +view was that, for instance, curvature towards the light is the direct +mechanical result of the difference of illumination on the lighted and +shaded surfaces of the plant. This has been proved to be an incorrect +explanation of the fact, and Darwin by his work on the transmission of +stimuli has greatly contributed to the current belief that stimuli act +indirectly. Thus we now believe that in a root and a stem the mechanism +for the perception of gravitation is identical, but the resulting movements +are different because the motor-irritabilities are dissimilar in the two +cases. We must come back, in fact, to Darwin's comparison of plants to +animals. In both there is perceptive machinery by which they are made +delicately alive to their environment, in both the existing survivors are +those whose internal constitution has enabled them to respond in a +beneficial way to the disturbance originating in their sense-organs. + + +XX. THE BIOLOGY OF FLOWERS. + +By K. GOEBEL, Ph.D. +Professor of Botany in the University of Munich. + +There is scarcely any subject to which Darwin devoted so much time and work +as to his researches into the biology of flowers, or, in other words, to +the consideration of the question to what extent the structural and +physiological characters of flowers are correlated with their function of +producing fruits and seeds. We know from his own words what fascination +these studies possessed for him. We repeatedly find, for example, in his +letters expressions such as this:--"Nothing in my life has ever interested +me more than the fertilisation of such plants as Primula and Lythrum, or +again Anacamptis or Listera." ("More Letters of Charles Darwin", Vol. II. +page 419.) + +Expressions of this kind coming from a man whose theories exerted an epoch- +making influence, would be unintelligible if his researches into the +biology of flowers had been concerned only with records of isolated facts, +however interesting these might be. We may at once take it for granted +that the investigations were undertaken with the view of following up +important problems of general interest, problems which are briefly dealt +with in this essay. + +Darwin published the results of his researches in several papers and in +three larger works, (i) "On the various contrivances by which British and +Foreign Orchids are fertilised by insects" (First edition, London, 1862; +second edition, 1877; popular edition, 1904.) (ii) "The effects of Cross +and Self fertilisation in the vegetable kingdom" (First edition, 1876; +second edition, 1878). (iii) "The different forms of Flowers on plants of +the same species" (First edition, 1877; second edition, 1880). + +Although the influence of his work is considered later, we may here point +out that it was almost without a parallel; not only does it include a mass +of purely scientific observations, but it awakened interest in very wide +circles, as is shown by the fact that we find the results of Darwin's +investigations in floral biology universally quoted in school books; they +are even willingly accepted by those who, as regards other questions, are +opposed to Darwin's views. + +The works which we have mentioned are, however, not only of special +interest because of the facts they contribute, but because of the MANNER in +which the facts are expressed. A superficial reader seeking merely for +catch-words will, for instance, probably find the book on cross and self- +fertilisation rather dry because of the numerous details which it contains: +it is, indeed, not easy to compress into a few words the general +conclusions of this volume. But on closer examination, we cannot be +sufficiently grateful to the author for the exactness and objectivity with +which he enables us to participate in the scheme of his researches. He +never tries to persuade us, but only to convince us that his conclusions +are based on facts; he always gives prominence to such facts as appear to +be in opposition to his opinions,--a feature of his work in accordance with +a maxim which he laid down:--"It is a golden rule, which I try to follow, +to put every fact which is opposed to one's preconceived opinion in the +strongest light." ("More Letters", Vol. II. page 324.) + +The result of this method of presentation is that the works mentioned above +represent a collection of most valuable documents even for those who feel +impelled to draw from the data other conclusions than those of the author. +Each investigation is the outcome of a definite question, a "preconceived +opinion," which is either supported by the facts or must be abandoned. +"How odd it is that anyone should not see that all observation must be for +or against some view if it is to be of any service!" (Ibid. Vol. I. page +195.) + +The points of view which Darwin had before him were principally the +following. In the first place the proof that a large number of the +peculiarities in the structure of flowers are not useless, but of the +greatest significance in pollination must be of considerable importance for +the interpretation of adaptations; "The use of each trifling detail of +structure is far from a barren search to those who believe in natural +selection." ("Fertilisation of Orchids" (1st edition), page 351; (2nd +edition 1904) page 286.) Further, if these structural relations are shown +to be useful, they may have been acquired because from the many variations +which have occurred along different lines, those have been preserved by +natural selection "which are beneficial to the organism under the complex +and ever-varying conditions of life." (Ibid. page 351.) But in the case +of flowers there is not only the question of adaptation to fertilisation to +be considered. Darwin, indeed, soon formed the opinion which he has +expressed in the following sentence,--"From my own observations on plants, +guided to a certain extent by the experience of the breeders of animals, I +became convinced many years ago that it is a general law of nature that +flowers are adapted to be crossed, at least occasionally, by pollen from a +distinct plant." ("Cross and Self fertilisation" (1st edition), page 6.) + +The experience of animal breeders pointed to the conclusion that continual +in-breeding is injurious. If this is correct, it raises the question +whether the same conclusion holds for plants. As most flowers are +hermaphrodite, plants afford much more favourable material than animals for +an experimental solution of the question, what results follow from the +union of nearly related sexual cells as compared with those obtained by the +introduction of new blood. The answer to this question must, moreover, +possess the greatest significance for the correct understanding of sexual +reproduction in general. + +We see, therefore, that the problems which Darwin had before him in his +researches into the biology of flowers were of the greatest importance, and +at the same time that the point of view from which he attacked the problems +was essentially a teleological one. + +We may next inquire in what condition he found the biology of flowers at +the time of his first researches, which were undertaken about the year +1838. In his autobiography he writes,--"During the summer of 1839, and, I +believe, during the previous summer, I was led to attend to the cross- +fertilisation of flowers by the aid of insects, from having come to the +conclusion in my speculations on the origin of species, that crossing +played an important part in keeping specific forms constant." ("The Life +and Letters of Charles Darwin", Vol. I. page 90, London, 1888.) In 1841 he +became acquainted with Sprengel's work: his researches into the biology of +flowers were thus continued for about forty years. + +It is obvious that there could only be a biology of flowers after it had +been demonstrated that the formation of seeds and fruit in the flower is +dependent on pollination and subsequent fertilisation. This proof was +supplied at the end of the seventeenth century by R.J. Camerarius (1665- +1721). He showed that normally seeds and fruits are developed only when +the pollen reaches the stigma. The manner in which this happens was first +thoroughly investigated by J.G. Kolreuter (1733-1806 (Kolreuter, +"Vorlaufige Nachricht von einigen das Geschlecht der Planzen betreffenden +Versuchen und Beobachtungen", Leipzig, 1761; with three supplements, 1763- +66. Also, "Mem. de l'acad. St Petersbourg", Vol. XV. 1809.)), the same +observer to whom we owe the earliest experiments in hybridisation of real +scientific interest. Kolreuter mentioned that pollen may be carried from +one flower to another partly by wind and partly by insects. But he held +the view, and that was, indeed, the natural assumption, that self- +fertilisation usually occurs in a flower, in other words that the pollen of +a flower reaches the stigma of the same flower. He demonstrated, however, +certain cases in which cross-pollination occurs, that is in which the +pollen of another flower of the same species is conveyed to the stigma. He +was familiar with the phenomenon, exhibited by numerous flowers, to which +Sprengel afterwards applied the term Dichogamy, expressing the fact that +the anthers and stigmas of a flower often ripen at different times, a +peculiarity which is now recognised as one of the commonest means of +ensuring cross-pollination. + +With far greater thoroughness and with astonishing power of observation +C.K. Sprengel (1750-1816) investigated the conditions of pollination of +flowers. Darwin was introduced by that eminent botanist Robert Brown to +Sprengel's then but little appreciated work,--"Das entdeckte Geheimniss der +Natur im Bau und in der Befruchtung der Blumen" (Berlin, 1793); this is by +no means the least service to Botany rendered by Robert Brown. + +Sprengel proceeded from a naive teleological point of view. He firmly +believed "that the wise Author of nature had not created a single hair +without a definite purpose." He succeeded in demonstrating a number of +beautiful adaptations in flowers for ensuring pollination; but his work +exercised but little influence on his contemporaries and indeed for a long +time after his death. It was through Darwin that Sprengel's work first +achieved a well deserved though belated fame. Even such botanists as +concerned themselves with researches into the biology of flowers appear to +have formerly attached much less value to Sprengel's work than it has +received since Darwin's time. In illustration of this we may quote C.F. +Gartner whose name is rightly held in the highest esteem as that of one of +the most eminent hybridologists. In his work "Versuche und Beobachtungen +uder die Befruchtungsorgane der vollkommeneren Gewachse und uber die +naturliche und kunstliche Befruchtung durch den eigenen Pollen" he also +deals with flower-pollination. He recognised the action of the wind, but +he believed, in spite of the fact that he both knew and quoted Kolreuter +and Sprengel, that while insects assist pollination, they do so only +occasionally, and he held that insects are responsible for the conveyance +of pollen; thorough investigations would show "that a very small proportion +of the plants included in this category require this assistance in their +native habitat." (Gartner, "Versucher und Beobachtungen...", page 335, +Stuttgart, 1844.) In the majority of plants self-pollination occurs. + +Seeing that even investigators who had worked for several decades at +fertilisation-phenomena had not advanced the biology of flowers beyond the +initial stage, we cannot be surprised that other botanists followed to even +a less extent the lines laid down by Kolreuter and Sprengel. This was in +part the result of Sprengel's supernatural teleology and in part due to the +fact that his book appeared at a time when other lines of inquiry exerted a +dominating influence. + +At the hands of Linnaeus systematic botany reached a vigorous development, +and at the beginning of the nineteenth century the anatomy and physiology +of plants grew from small beginnings to a flourishing branch of science. +Those who concerned themselves with flowers endeavoured to investigate +their development and structure or the most minute phenomena connected with +fertilisation and the formation of the embryo. No room was left for the +extension of the biology of flowers on the lines marked out by Kolreuter +and Sprengel. Darwin was the first to give new life and a deeper +significance to this subject, chiefly because he took as his starting-point +the above-mentioned problems, the importance of which is at once admitted +by all naturalists. + +The further development of floral biology by Darwin is in the first place +closely connected with the book on the fertilisation of Orchids. It is +noteworthy that the title includes the sentence,--"and on the good effects +of intercrossing." + +The purpose of the book is clearly stated in the introduction:--"The object +of the following work is to show that the contrivances by which Orchids are +fertilised, are as varied and almost as perfect as any of the most +beautiful adaptations in the animal kingdom; and, secondly, to show that +these contrivances have for their main object the fertilisation of each +flower by the pollen of another flower." ("Fertilisation of Orchids", page +1.) Orchids constituted a particularly suitable family for such +researches. Their flowers exhibit a striking wealth of forms; the +question, therefore, whether the great variety in floral structure bears +any relation to fertilisation (In the older botanical literature the word +fertilisation is usually employed in cases where POLLINATION is really in +question: as Darwin used it in this sense it is so used here.) must in +this case possess special interest. + +Darwin succeeded in showing that in most of the orchids examined self- +fertilisation is either an impossibility, or, under natural conditions, +occurs only exceptionally. On the other hand these plants present a series +of extraordinarily beautiful and remarkable adaptations which ensure the +transference of pollen by insects from one flower to another. It is +impossible to describe adequately in a few words the wealth of facts +contained in the Orchid book. A few examples may, however, be quoted in +illustration of the delicacy of the observations and of the perspicuity +employed in interpreting the facts. + +The majority of orchids differ from other seed plants (with the exception +of the Asclepiads) in having no dust-like pollen. The pollen, or more +correctly, the pollen-tetrads, remain fastened together as club-shaped +pollinia usually borne on a slender pedicel. At the base of the pedicel is +a small viscid disc by which the pollinium is attached to the head or +proboscis of one of the insects which visit the flower. Darwin +demonstrated that in Orchis and other flowers the pedicel of the pollinium, +after its removal from the anther, undergoes a curving movement. If the +pollinium was originally vertical, after a time it assumed a horizontal +position. In the latter position, if the insect visited another flower, +the pollinium would exactly hit the sticky stigmatic surface and thus +effect fertilisation. The relation between the behaviour of the viscid +disc and the secretion of nectar by the flower is especially remarkable. +The flowers possess a spur which in some species (e.g. Gymnadenia conopsea, +Platanthera bifolia, etc.) contains honey (nectar), which serves as an +attractive bait for insects, but in others (e.g. our native species of +Orchis) the spur is empty. Darwin held the opinion, confirmed by later +investigations, that in the case of flowers without honey the insects must +penetrate the wall of the nectarless spurs in order to obtain a nectar-like +substance. The glands behave differently in the nectar-bearing and in the +nectarless flowers. In the former they are so sticky that they at once +adhere to the body of the insect; in the nectarless flowers firm adherence +only occurs after the viscid disc has hardened. It is, therefore, +adaptively of value that the insects should be detained longer in the +nectarless flowers (by having to bore into the spur),--than in flowers in +which the nectar is freely exposed. "If this relation, on the one hand, +between the viscid matter requiring some little time to set hard, and the +nectar being so lodged that moths are delayed in getting it; and, on the +other hand, between the viscid matter being at first as viscid as ever it +will become, and the nectar lying all ready for rapid suction, be +accidental, it is a fortunate accident for the plant. If not accidental, +and I cannot believe it to be accidental, what a singular case of +adaptation!" ("Fertilisation of Orchids" (1st edition), page 53.) + +Among exotic orchids Catasetum is particularly remarkable. One and the +same species bears different forms of flowers. The species known as +Catasetum tridentatum has pollinia with very large viscid discs; on +touching one of the two filaments (antennae) which occur on the gynostemium +of the flower the pollinia are shot out to a fairly long distance (as far +as 1 metre) and in such manner that they alight on the back of the insect, +where they are held. The antennae have, moreover, acquired an importance, +from the point of view of the physiology of stimulation, as stimulus- +perceiving organs. Darwin had shown that it is only a touch on the +antennae that causes the explosion, while contact, blows, wounding, etc. on +other places produce no effect. This form of flower proved to be the male. +The second form, formerly regarded as a distinct species and named +Monachanthus viridis, is shown to be the female flower. The anthers have +only rudimentary pollinia and do not open; there are no antennae, but on +the other hand numerous seeds are produced. Another type of flower, known +as Myanthus barbatus, was regarded by Darwin as a third form: this was +afterwards recognised by Rolfe (Rolfe, R.A. "On the sexual forms of +Catasetum with special reference to the researches of Darwin and others," +"Journ. Linn. Soc." Vol. XXVII. (Botany), 1891, pages 206-225.) as the male +flower of another species, Catasetum barbatum Link, an identification in +accordance with the discovery made by Cruger in Trinidad that it always +remains sterile. + +Darwin had noticed that the flowers of Catasetum do not secrete nectar, and +he conjectured that in place of it the insects gnaw a tissue in the cavity +of the labellum which has a "slightly sweet, pleasant and nutritious +taste." This conjecture as well as other conclusions drawn by Darwin from +Catasetum have been confirmed by Cruger--assuredly the best proof of the +acumen with which the wonderful floral structure of this "most remarkable +of the Orchids" was interpretated far from its native habitat. + +As is shown by what we have said about Catasetum, other problems in +addition to those concerned with fertilisation are dealt with in the Orchid +book. This is especially the case in regard to flower morphology. The +scope of flower morphology cannot be more clearly and better expressed than +by these words: "He will see how curiously a flower may be moulded out of +many separate organs--how perfect the cohesion of primordially distinct +parts may become,--how organs may be used for purposes widely different +from their proper function,--how other organs may be entirely suppressed, +or leave mere useless emblems of their former existence." ("Fertilisation +of Orchids", page 289.) + +In attempting, from this point of view, to refer the floral structure of +orchids to their original form, Darwin employed a much more thorough method +than that of Robert Brown and others. The result of this was the +production of a considerable literature, especially in France, along the +lines suggested by Darwin's work. This is the so-called anatomical method, +which seeks to draw conclusions as to the morphology of the flower from the +course of the vascular bundles in the several parts. (He wrote in one of +his letters, "...the destiny of the whole human race is as nothing to the +course of vessels of orchids" ("More Letters", Vol. II. page 275.) +Although the interpretation of the orchid flower given by Darwin has not +proved satisfactory in one particular point--the composition of the +labellum--the general results have received universal assent, namely "that +all Orchids owe what they have in common to descent from some +monocotyledonous plant, which, like so many other plants of the same +division, possessed fifteen organs arranged alternately three within three +in five whorls." ("Fertilisation of Orchids" (1st edition), page 307.) +The alterations which their original form has undergone have persisted so +far as they were found to be of use. + +We see also that the remarkable adaptations of which we have given some +examples are directed towards cross-fertilisation. In only a few of the +orchids investigated by Darwin--other similar cases have since been +described--was self-fertilisation found to occur regularly or usually. The +former is the case in the Bee Ophrys (Ophrys apifera), the mechanism of +which greatly surprised Darwin. He once remarked to a friend that one of +the things that made him wish to live a few thousand years was his desire +to see the extinction of the Bee Ophrys, an end to which he believed its +self-fertilising habit was leading. ("Life and Letters", Vol. III. page +276 (footnote).) But, he wrote, "the safest conclusion, as it seems to me, +is, that under certain unknown circumstances, and perhaps at very long +intervals of time, one individual of the Bee Ophrys is crossed by another." +("Fertilisation of Orchids" page 71.) + +If, on the one hand, we remember how much more sure self-fertilisation +would be than cross-fertilisation, and, on the other hand, if we call to +mind the numerous contrivances for cross-fertilisation, the conclusion is +naturally reached that "it is an astonishing fact that self-fertilisation +should not have been an habitual occurrence. It apparently demonstrates to +us that there must be something injurious in the process. Nature thus +tells us, in the most emphatic manner, that she abhors perpetual self- +fertilisation...For may we not further infer as probable, in accordance +with the belief of the vast majority of the breeders of our domestic +productions, that marriage between near relations is likewise in some way +injurious, that some unknown great good is derived from the union of +individuals which have been kept distinct for many generations?" (Ibid., +page 359.) + +This view was supported by observations on plants of other families, e.g. +Papilionaceae; it could, however, in the absence of experimental proof, be +regarded only as a "working hypothesis." + +All adaptations to cross-pollination might also be of use simply because +they made pollination possible when for any reason self-pollination had +become difficult or impossible. Cross-pollination would, therefore, be of +use, not as such, but merely as a means of pollination in general; it would +to some extent serve as a remedy for a method unsuitable in itself, such as +a modification standing in the way of self-pollination, and on the other +hand as a means of increasing the chance of pollination in the case of +flowers in which self-pollination was possible, but which might, in +accidental circumstances, be prevented. It was, therefore, very important +to obtain experimental proof of the conclusion to which Darwin was led by +the belief of the majority of breeders and by the evidence of the +widespread occurrence of cross-pollination and of the remarkable +adaptations thereto. + +This was supplied by the researches which are described in the two other +works named above. The researches on which the conclusions rest had, in +part at least, been previously published in separate papers: this is the +case as regards the heterostyled plants. The discoveries which Darwin made +in the course of his investigations of these plants belong to the most +brilliant in biological science. + +The case of Primula is now well known. C.K. Sprengel and others were +familiar with the remarkable fact that different individuals of the +European species of Primula bear differently constructed flowers; some +plants possess flowers in which the styles project beyond the stamens +attached to the corolla-tube (long-styled form), while in others the +stamens are inserted above the stigma which is borne on a short style +(short-styled form). It has been shown by Breitenbach that both forms of +flower may occur on the same plant, though this happens very rarely. An +analogous case is occasionally met with in hybrids, which bear flowers of +different colour on the same plant (e.g. Dianthus caryophyllus). Darwin +showed that the external differences are correlated with others in the +structure of the stigma and in the nature of the pollen. The long-styled +flowers have a spherical stigma provided with large stigmatic papillae; the +pollen grains are oblong and smaller than those of the short-styled +flowers. The number of the seeds produced is smaller and the ovules +larger, probably also fewer in number. The short-styled flowers have a +smooth compressed stigma and a corolla of somewhat different form; they +produce a greater number of seeds. + +These different forms of flowers were regarded as merely a case of +variation, until Darwin showed "that these heterostyled plants are adapted +for reciprocal fertilisation; so that the two or three forms, though all +are hermaphrodites, are related to one another almost like the males and +females of ordinary unisexual animals." ("Forms of Flowers" (1st edition), +page 2.) We have here an example of hermaphrodite flowers which are +sexually different. There are essential differences in the manner in which +fertilisation occurs. This may be effected in four different ways; there +are two legitimate and two illegitimate types of fertilisation. The +fertilisation is legitimate if pollen from the long-styled flowers reaches +the stigma of the short-styled form or if pollen of the short-styled +flowers is brought to the stigma of the long-styled flower, that is the +organs of the same length of the two different kinds of flower react on one +another. Illegitimate fertilisation is represented by the two kinds of +self-fertilisation, also by cross-fertilisation, in which the pollen of the +long-styled form reaches the stigma of the same type of flower and, +similarly, by cross-pollination in the case of the short-styled flowers. + +The applicability of the terms legitimate and illegitimate depends, on the +one hand, upon the fact that insects which visit the different forms of +flowers pollinate them in the manner suggested; the pollen of the short- +styled flowers adhere to that part of the insect's body which touches the +stigma of the long-styled flower and vice versa. On the other hand, it is +based also on the fact that experiment shows that artificial pollination +produces a very different result according as this is legitimate or +illegitimate; only the legitimate union ensures complete fertility, the +plants thus produced being stronger than those which are produced +illegitimately. + +If we take 100 as the number of flowers which produce seeds as the result +of legitimate fertilisation, we obtain the following numbers from +illegitimate fertilisation: + +Primula officinalis (P. veris) (Cowslip) ... 69 +Primula elatior (Oxlip) .................... 27 +Primula acaulis (P. vulgaris) (Primrose) ... 60 + +Further, the plants produced by the illegitimate method of fertilisation +showed, e.g. in P. officinalis, a decrease in fertility in later +generations, sterile pollen and in the open a feebler growth. (Under very +favourable conditions (in a greenhouse) the fertility of the plants of the +fourth generation increases--a point, which in view of various theoretical +questions, deserves further investigation.) They behave in fact precisely +in the same way as hybrids between species of different genera. This +result is important, "for we thus learn that the difficulty in sexually +uniting two organic forms and the sterility of their offspring, afford no +sure criterion of so-called specific distinctness" ("Forms of Flowers", +page 242): the relative or absolute sterility of the illegitimate unions +and that of their illegitimate descendants depend exclusively on the nature +of the sexual elements and on their inability to combine in a particular +manner. This functional difference of sexual cells is characteristic of +the behaviour of hybrids as of the illegitimate unions of heterostyled +plants. The agreement becomes even closer if we regard the Primula plants +bearing different forms of flowers not as belonging to a systematic entity +or "species," but as including several elementary species. The +legitimately produced plants are thus true hybrids (When Darwin wrote in +reference to the different forms of heterostyled plants, "which all belong +to the same species as certainly as do the two sexes of the same species" +("Cross and Self fertilisation", page 466), he adopted the term species in +a comprehensive sense. The recent researches of Bateson and Gregory ("On +the inheritance of Heterostylism in Primula"; "Proc. Roy. Soc." Ser. B, +Vol. LXXVI. 1905, page 581) appear to me also to support the view that the +results of illegitimate crossing of heterostyled Primulas correspond with +those of hybridisation. The fact that legitimate pollen effects +fertilisation, even if illegitimate pollen reaches the stigma a short time +previously, also points to this conclusion. Self-pollination in the case +of the short-styled form, for example, is not excluded. In spite of this, +the numerical proportion of the two forms obtained in the open remains +approximately the same as when the pollination was exclusively legitimate, +presumably because legitimate pollen is prepotent.), with which their +behaviour in other respects, as Darwin showed, presents so close an +agreement. This view receives support also from the fact that descendants +of a flower fertilised illegitimately by pollen from another plant with the +same form of flower belong, with few exceptions, to the same type as that +of their parents. The two forms of flower, however, behave differently in +this respect. Among 162 seedlings of the long-styled illegitimately +pollinated plants of Primula officinalis, including five generations, there +were 156 long-styled and only six short-styled forms, while as the result +of legitimate fertilisation nearly half of the offspring were long-styled +and half short-styled. The short-styled illegitimately pollinated form +gave five long-styled and nine short-styled; the cause of this difference +requires further explanation. The significance of heterostyly, whether or +not we now regard it as an arrangement for the normal production of +hybrids, is comprehensively expressed by Darwin: "We may feel sure that +plants have been rendered heterostyled to ensure cross-fertilisation, for +we now know that a cross between the distinct individuals of the same +species is highly important for the vigour and fertility of the offspring." +("Forms of Flowers", page 258.) If we remember how important the +interpretation of heterostyly has become in all general problems as, for +example, those connected with the conditions of the formation of hybrids, a +fact which was formerly overlooked, we can appreciate how Darwin was able +to say in his autobiography: "I do not think anything in my scientific +life has given me so much satisfaction as making out the meaning of the +structure of these plants." ("Life and Letters", Vol. I. page 91.) + +The remarkable conditions represented in plants with three kinds of +flowers, such as Lythrum and Oxalis, agree in essentials with those in +Primula. These cannot be considered in detail here; it need only be noted +that the investigation of these cases was still more laborious. In order +to establish the relative fertility of the different unions in Lythrum +salicaria 223 different fertilisations were made, each flower being +deprived of its male organs and then dusted with the appropriate pollen. + +In the book containing the account of heterostyled plants other species are +dealt with which, in addition to flowers opening normally (chasmogamous), +also possess flowers which remain closed but are capable of producing +fruit. These cleistogamous flowers afford a striking example of habitual +self-pollination, and H. von Mohl drew special attention to them as such +shortly after the appearance of Darwin's Orchid book. If it were only a +question of producing seed in the simplest way, cleistogamous flowers would +be the most conveniently constructed. The corolla and frequently other +parts of the flower are reduced; the development of the seed may, +therefore, be accomplished with a smaller expenditure of building material +than in chasmogamous flowers; there is also no loss of pollen, and thus a +smaller amount suffices for fertilisation. + +Almost all these plants, as Darwin pointed out, have also chasmogamous +flowers which render cross-fertilisation possible. His view that +cleistogamous flowers are derived from originally chasmogamous flowers has +been confirmed by more recent researches. Conditions of nutrition in the +broader sense are the factors which determine whether chasmogamous or +cleistogamous flowers are produced, assuming, of course, that the plants in +question have the power of developing both forms of flower. The former may +fail to appear for some time, but are eventually developed under favourable +conditions of nourishment. The belief of many authors that there are +plants with only cleistogamous flowers cannot therefore be accepted as +authoritative without thorough experimental proof, as we are concerned with +extra-european plants for which it is often difficult to provide +appropriate conditions in cultivation. + +Darwin sees in cleistogamous flowers an adaptation to a good supply of +seeds with a small expenditure of material, while chasmogamous flowers of +the same species are usually cross-fertilised and "their offspring will +thus be invigorated, as we may infer from a wide-spread analogy." ("Forms +of Flowers" (1st edition), page 341.) Direct proof in support of this has +hitherto been supplied in a few cases only; we shall often find that the +example set by Darwin in solving such problems as these by laborious +experiment has unfortunately been little imitated. + +Another chapter of this book treats of the distribution of the sexes in +polygamous, dioecious, and gyno-dioecious plants (the last term, now in +common use, we owe to Darwin). It contains a number of important facts and +discussions and has inspired the experimental researches of Correns and +others. + +The most important of Darwin's work on floral biology is, however, that on +cross and self-fertilisation, chiefly because it states the results of +experimental investigations extending over many years. Only such +experiments, as we have pointed out, could determine whether cross- +fertilisation is in itself beneficial, and self-fertilisation on the other +hand injurious; a conclusion which a merely comparative examination of +pollination-mechanisms renders in the highest degree probable. Later +floral biologists have unfortunately almost entirely confined themselves to +observations on floral mechanisms. But there is little more to be gained +by this kind of work than an assumption long ago made by C.K. Sprengel that +"very many flowers have the sexes separate and probably at least as many +hermaphrodite flowers are dichogamous; it would thus appear that Nature was +unwilling that any flower should be fertilised by its own pollen." + +It was an accidental observation which inspired Darwin's experiments on the +effect of cross and self-fertilisation. Plants of Linaria vulgaris were +grown in two adjacent beds; in the one were plants produced by cross- +fertilisation, that is, from seeds obtained after fertilisation by pollen +of another plant of the same species; in the other grew plants produced by +self-fertilisation, that is from seed produced as the result of pollination +of the same flower. The first were obviously superior to the latter. + +Darwin was surprised by this observation, as he had expected a prejudicial +influence of self-fertilisation to manifest itself after a series of +generations: "I always supposed until lately that no evil effects would be +visible until after several generations of self-fertilisation, but now I +see that one generation sometimes suffices and the existence of dimorphic +plants and all the wonderful contrivances of orchids are quite intelligible +to me." ("More Letters", Vol. II. page 373.) + +The observations on Linaria and the investigations of the results of +legitimate and illegitimate fertilisation in heterostyled plants were +apparently the beginning of a long series of experiments. These were +concerned with plants of different families and led to results which are of +fundamental importance for a true explanation of sexual reproduction. + +The experiments were so arranged that plants were shielded from insect- +visits by a net. Some flowers were then pollinated with their own pollen, +others with pollen from another plant of the same species. The seeds were +germinated on moist sand; two seedlings of the same age, one from a cross +and the other from a self-fertilised flower, were selected and planted on +opposite sides of the same pot. They grew therefore under identical +external conditions; it was thus possible to compare their peculiarities +such as height, weight, fruiting capacity, etc. In other cases the +seedlings were placed near to one another in the open and in this way their +capacity of resisting unfavourable external conditions was tested. The +experiments were in some cases continued to the tenth generation and the +flowers were crossed in different ways. We see, therefore, that this book +also represents an enormous amount of most careful and patient original +work. + +The general result obtained is that plants produced as the result of cross- +fertilisation are superior, in the majority of cases, to those produced as +the result of self-fertilisation, in height, resistance to external +injurious influences, and in seed-production. + +Ipomoea purpurea may be quoted as an example. If we express the result of +cross-fertilisation by 100, we obtain the following numbers for the +fertilised plants. + +Generation. Height. Number of seeds. + +1 100 : 76 100 : 64 +2 100 : 79 - +3 100 : 68 100 : 94 +4 100 : 86 100 : 94 +5 100 : 75 100 : 89 +6 100 : 72 - +7 100 : 81 - +8 100 : 85 - +9 100 : 79 100 : 26 (Number of capsules) +10 100 : 54 - + +Taking the average, the ratio as regards growth is 100:77. The +considerable superiority of the crossed plants is apparent in the first +generation and is not increased in the following generations; but there is +some fluctuation about the average ratio. The numbers representing the +fertility of crossed and self-fertilised plants are more difficult to +compare with accuracy; the superiority of the crossed plants is chiefly +explained by the fact that they produce a much larger number of capsules, +not because there are on the average more seeds in each capsule. The ratio +of the capsules was, e.g. in the third generation, 100:38, that of the +seeds in the capsules 100:94. It is also especially noteworthy that in the +self-fertilised plants the anthers were smaller and contained a smaller +amount of pollen, and in the eighth generation the reduced fertility showed +itself in a form which is often found in hybrids, that is the first flowers +were sterile. (Complete sterility was not found in any of the plants +investigated by Darwin. Others appear to be more sensitive; Cluer found +Zea Mais "almost sterile" after three generations of self-fertilisation. +(Cf. Fruwirth, "Die Zuchtung der Landwirtschaftlichen Kulturpflanzen", +Berlin, 1904, II. page 6.) + +The superiority of crossed individuals is not exhibited in the same way in +all plants. For example in Eschscholzia californica the crossed seedlings +do not exceed the self-fertilised in height and vigour, but the crossing +considerably increases the plant's capacity for flower-production, and the +seedlings from such a mother-plant are more fertile. + +The conception implied by the term crossing requires a closer analysis. As +in the majority of plants, a large number of flowers are in bloom at the +same time on one and the same plant, it follows that insects visiting the +flowers often carry pollen from one flower to another of the same stock. +Has this method, which is spoken of as Geitonogamy, the same influence as +crossing with pollen from another plant? The results of Darwin's +experiments with different plants (Ipomoea purpurea, Digitalis purpurea, +Mimulus luteus, Pelargonium, Origanum) were not in complete agreement; but +on the whole they pointed to the conclusion that Geitonogamy shows no +superiority over self-fertilisation (Autogamy). (Similarly crossing in the +case of flowers of Pelargonium zonale, which belong to plants raised from +cuttings from the same parent, shows no superiority over self- +fertilisation.) Darwin, however, considered it possible that this may +sometimes be the case. "The sexual elements in the flowers on the same +plant can rarely have been differentiated, though this is possible, as +flower-buds are in one sense distinct individuals, sometimes varying and +differing from one another in structure or constitution." ("Cross and Self +fertilisation" (1st edition), page 444.) + +As regards the importance of this question from the point of view of the +significance of cross-fertilisation in general, it may be noted that later +observers have definitely discovered a difference between the results of +autogamy and geitonogamy. Gilley and Fruwirth found that in Brassica +Napus, the length and weight of the fruits as also the total weight of the +seeds in a single fruit were less in the case of autogamy than in +geitonogamy. With Sinapis alba a better crop of seeds was obtained after +geitonogamy, and in the Sugar Beet the average weight of a fruit in the +case of a self-fertilised plant was 0.009 gr., from geitonogamy 0.012 gr., +and on cross-fertilisation 0.013 gr. + +On the whole, however, the results of geitonogamy show that the favourable +effects of cross-fertilisation do not depend simply on the fact that the +pollen of one flower is conveyed to the stigma of another. But the plants +which are crossed must in some way be different. If plants of Ipomoea +purpurea (and Mimulus luteus) which have been self-fertilised for seven +generations and grown under the same conditions of cultivation are crossed +together, the plants so crossed would not be superior to the self- +fertilised; on the other hand crossing with a fresh stock at once proves +very advantageous. The favourable effect of crossing is only apparent, +therefore, if the parent plants are grown under different conditions or if +they belong to different varieties. "It is really wonderful what an effect +pollen from a distinct seedling plant, which has been exposed to different +conditions of life, has on the offspring in comparison with pollen from the +same flower or from a distinct individual, but which has been long +subjected to the same conditions. The subject bears on the very principle +of life, which seems almost to require changes in the conditions." ("More +Letters", Vol. II. page 406.) + +The fertility--measured by the number or weight of the seeds produced by an +equal number of plants--noticed under different conditions of fertilisation +may be quoted in illustration. + + On crossing On crossing On self- + with a fresh plants of the fertilisation + stock same stock +Mimuleus luteus + (First and ninth generation) 100 4 3 + +Eschscholzia californica + (second generation) 100 45 40 + +Dianthus caryophyllus + (third and fourth generation) 100 45 33 + +Petunia violacea 100 54 46 + +Crossing under very similar conditions shows, therefore, that the +difference between the sexual cells is smaller and thus the result of +crossing is only slightly superior to that given by self-fertilisation. +Is, then, the favourable result of crossing with a foreign stock to be +attributed to the fact that this belongs to another systematic entity or to +the fact that the plants, though belonging to the same entity were exposed +to different conditions? This is a point on which further researches must +be taken into account, especially since the analysis of the systematic +entities has been much more thorough than formerly. (In the case of garden +plants, as Darwin to a large extent claimed, it is not easy to say whether +two individuals really belong to the same variety, as they are usually of +hybrid origin. In some instances (Petunia, Iberis) the fresh stock +employed by Darwin possessed flowers differing in colour from those of the +plant crossed with it.) We know that most of Linneaus's species are +compound species, frequently consisting of a very large number of smaller +or elementary species formerly included under the comprehensive term +varieties. Hybridisation has in most cases affected our garden and +cultivated plants so that they do not represent pure species but a mixture +of species. + +But this consideration has no essential bearing on Darwin's point of view, +according to which the nature of the sexual cells is influenced by external +conditions. Even individuals growing close to one another are only +apparently exposed to identical conditions. Their sexual cells may +therefore be differently influenced and thus give favourable results on +crossing, as "the benefits which so generally follow from a cross between +two plants apparently depend on the two differing somewhat in constitution +or character." As a matter of fact we are familiar with a large number of +cases in which the condition of the reproductive organs is influenced by +external conditions. Darwin has himself demonstrated this for self-sterile +plants, that is plants in which self-fertilisation produces no result. +This self-sterility is affected by climatic conditions: thus in Brazil +Eschscholzia californica is absolutely sterile to the pollen of its own +flowers; the descendants of Brazilian plants in Darwin's cultures were +partially self-fertile in one generation and in a second generation still +more so. If one has any doubt in this case whether it is a question of the +condition of the style and stigma, which possibly prevents the entrance of +the pollen-tube or even its development, rather than that of the actual +sexual cells, in other cases there is no doubt that an influence is exerted +on the latter. + +Janczewski (Janczewski, "Sur les antheres steriles des Groseilliers", +"Bull. de l'acad. des sciences de Cracovie", June, 1908.) has recently +shown that species of Ribes cultivated under unnatural conditions +frequently produce a mixed (i.e. partly useless) or completely sterile +pollen, precisely as happens with hybrids. There are, therefore, +substantial reasons for the conclusion that conditions of life exert an +influence on the sexual cells. "Thus the proposition that the benefit from +cross-fertilisation depends on the plants which are crossed having been +subjected during previous generations to somewhat different conditions, or +to their having varied from some unknown cause as if they had been thus +subjected, is securely fortified on all sides." ("Cross and Self +fertilisation" (1st edition), page 444.) + +We thus obtain an insight into the significance of sexuality. If an +occasional and slight alteration in the conditions under which plants and +animals live is beneficial (Reasons for this are given by Darwin in +"Variation under Domestication" (2nd edition), Vol. II. page 127.), +crossing between organisms which have been exposed to different conditions +becomes still more advantageous. The entire constitution is in this way +influenced from the beginning, at a time when the whole organisation is in +a highly plastic state. The total life-energy, so to speak, is increased, +a gain which is not produced by asexual reproduction or by the union of +sexual cells of plants which have lived under the same or only slightly +different conditions. All the wonderful arrangements for cross- +fertilisation now appear to be useful adaptations. Darwin was, however, +far from giving undue prominence to this point of view, though this has +been to some extent done by others. He particularly emphasised the +following consideration:--"But we should always keep in mind that two +somewhat opposed ends have to be gained; the first and more important one +being the production of seeds by any means, and the second, cross- +fertilisation." ("Cross and Self fertilisation" (1st edition), page 371.) +Just as in some orchids and cleistogamic flowers self-pollination regularly +occurs, so it may also occur in other cases. Darwin showed that Pisum +sativum and Lathyrus odoratus belong to plants in which self-pollination is +regularly effected, and that this accounts for the constancy of certain +sorts of these plants, while a variety of form is produced by crossing. +Indeed among his culture plants were some which derived no benefit from +crossing. Thus in the sixth self-fertilised generation of his Ipomoea +cultures the "Hero" made its appearance, a form slightly exceeding its +crossed companion in height; this was in the highest degree self-fertile +and handed on its characteristics to both children and grandchildren. +Similar forms were found in Mimulus luteus and Nicotiana (In Pisum sativum +also the crossing of two individuals of the same variety produced no +advantage; Darwin attributed this to the fact that the plants had for +several generations been self-fertilised and in each generation cultivated +under almost the same conditions. Tschermak ("Ueber kunstliche Kreuzung an +Pisum sativum") afterwards recorded the same result; but he found on +crossing different varieties that usually there was no superiority as +regards height over the products of self-fertilisation, while Darwin found +a greater height represented by the ratios 100:75 and 100:60.), types +which, after self-fertilisation, have an enhanced power of seed-production +and of attaining a greater height than the plants of the corresponding +generation which are crossed together and self-fertilised and grown under +the same conditions. "Some observations made on other plants lead me to +suspect that self-fertilisation is in some respects beneficial; although +the benefit thus derived is as a rule very small compared with that from a +cross with a distinct plant." ("Cross and Self fertilisation", page 350.) +We are as ignorant of the reason why plants behave differently when crossed +and self-fertilised as we are in regard to the nature of the +differentiation of the sexual cells, which determines whether a union of +the sexual cells will prove favourable or unfavourable. + +It is impossible to discuss the different results of cross-fertilisation; +one point must, however, be emphasised, because Darwin attached +considerable importance to it. It is inevitable that pollen of different +kinds must reach the stigma. It was known that pollen of the same +"species" is dominant over the pollen of another species, that, in other +words, it is prepotent. Even if the pollen of the same species reaches the +stigma rather later than that of another species, the latter does not +effect fertilisation. + +Darwin showed that the fertilising power of the pollen of another variety +or of another individual is greater than that of the plant's own pollen. +("Cross and Self fertilisation", page 391.) This has been demonstrated in +the case of Mimulus luteus (for the fixed white-flowering variety) and +Iberis umbellata with pollen of another variety, and observations on +cultivated plants, such as cabbage, horseradish, etc. gave similar results. +It is, however, especially remarkable that pollen of another individual of +the same variety may be prepotent over the plant's own pollen. This +results from the superiority of plants crossed in this manner over self- +fertilised plants. "Scarcely any result from my experiments has surprised +me so much as this of the prepotency of pollen from a distinct individual +over each plant's own pollen, as proved by the greater constitutional +vigour of the crossed seedlings." (Ibid. page 397.) Similarly, in self- +fertile plants the flowers of which have not been deprived of the male +organs, pollen brought to the stigma by the wind or by insects from another +plant effects fertilisation, even if the plant's own pollen has reached the +stigma somewhat earlier. + +Have the results of his experimental investigations modified the point of +view from which Darwin entered on his researches, or not? In the first +place the question is, whether or not the opinion expressed in the Orchid +book that there is "Something injurious" connected with self-fertilisation, +has been confirmed. We can, at all events, affirm that Darwin adhered in +essentials to his original position; but self-fertilisation afterwards +assumed a greater importance than it formerly possessed. Darwin emphasised +the fact that "the difference between the self-fertilised and crossed +plants raised by me cannot be attributed to the superiority of the crossed, +but to the inferiority of the self-fertilised seedlings, due to the +injurious effects of self-fertilisation." (Ibid. page 437.) But he had no +doubt that in favourable circumstances self-fertilised plants were able to +persist for several generations without crossing. An occasional crossing +appears to be useful but not indispensable in all cases; its sporadic +occurrence in plants in which self-pollination habitually occurs is not +excluded. Self-fertilisation is for the most part relatively and not +absolutely injurious and always better than no fertilisation. "Nature +abhors perpetual self-fertilisation" (It is incorrect to say, as a writer +has lately said, that the aphorism expressed by Darwin in 1859 and 1862, +"Nature abhors perpetual self-fertilisation," is not repeated in his later +works. The sentence is repeated in "Cross and Self fertilisation" (page +8), with the addition, "If the word perpetual had been omitted, the +aphorism would have been false. As it stands, I believe that it is true, +though perhaps rather too strongly expressed.") is, however, a pregnant +expression of the fact that cross-fertilisation is exceedingly widespread +and has been shown in the majority of cases to be beneficial, and that in +those plants in which we find self-pollination regularly occurring cross- +pollination may occasionally take place. + +An attempt has been made to express in brief the main results of Darwin's +work on the biology of flowers. We have seen that his object was to +elucidate important general questions, particularly the question of the +significance of sexual reproduction. + +It remains to consider what influence his work has had on botanical +science. That this influence has been very considerable, is shown by a +glance at the literature on the biology of flowers published since Darwin +wrote. Before the book on orchids was published there was nothing but the +old and almost forgotten works of Kolreuter and Sprengel with the exception +of a few scattered references. Darwin's investigations gave the first +stimulus to the development of an extensive literature on floral biology. +In Knuth's "Handbuch der Blutenbiologie" ("Handbook of Flower Pollination", +Oxford, 1906) as many as 3792 papers on this subject are enumerated as +having been published before January 1, 1904. These describe not only the +different mechanisms of flowers, but deal also with a series of remarkable +adaptations in the pollinating insects. As a fertilising rain quickly +calls into existence the most varied assortment of plants on a barren +steppe, so activity now reigns in a field which men formerly left deserted. +This development of the biology of flowers is of importance not only on +theoretical grounds but also from a practical point of view. The rational +breeding of plants is possible only if the flower-biology of the plants in +question (i.e. the question of the possibility of self-pollination, self- +sterility, etc.) is accurately known. And it is also essential for plant- +breeders that they should have "the power of fixing each fleeting variety +of colour, if they will fertilise the flowers of the desired kind with +their own pollen for half-a-dozen generations, and grow the seedlings under +the same conditions." ("Cross and Self fertilisation" (1st edition), page +460.) + +But the influence of Darwin on floral biology was not confined to the +development of this branch of Botany. Darwin's activity in this domain has +brought about (as Asa Gray correctly pointed out) the revival of teleology +in Botany and Zoology. Attempts were now made to determine, not only in +the case of flowers but also in vegetative organs, in what relation the +form and function of organs stand to one another and to what extent their +morphological characters exhibit adaptation to environment. A branch of +Botany, which has since been called Ecology (not a very happy term) has +been stimulated to vigorous growth by floral biology. + +While the influence of the work on the biology of flowers was +extraordinarily great, it could not fail to elicit opinions at variance +with Darwin's conclusions. The opposition was based partly on reasons +valueless as counterarguments, partly on problems which have still to be +solved; to some extent also on that tendency against teleological +conceptions which has recently become current. This opposing trend of +thought is due to the fact that many biologists are content with +teleological explanations, unsupported by proof; it is also closely +connected with the fact that many authors estimate the importance of +natural selection less highly than Darwin did. We may describe the +objections which are based on the widespread occurrence of self- +fertilisation and geitonogamy as of little importance. Darwin did not deny +the occurrence of self-fertilisation, even for a long series of +generations; his law states only that "Nature abhors PERPETUAL self- +fertilisation." (It is impossible (as has been attempted) to express +Darwin's point of view in a single sentence, such as H. Muller's statement +of the "Knight-Darwin law." The conditions of life in organisms are so +various and complex that laws, such as are formulated in physics and +chemistry, can hardly be conceived.) An exception to this rule would +therefore occur only in the case of plants in which the possibility of +cross-pollination is excluded. Some of the plants with cleistogamous +flowers might afford examples of such cases. We have already seen, +however, that such a case has not as yet been shown to occur. Burck +believed that he had found an instance in certain tropical plants +(Anonaceae, Myrmecodia) of the complete exclusion of cross-fertilisation. +The flowers of these plants, in which, however,--in contrast to the +cleistogamous flowers--the corolla is well developed, remain closed and +fruit is produced. + +Loew (E. Loew, "Bemerkungen zu Burck...", "Biolog. Centralbl." XXVI. +(1906).) has shown that cases occur in which cross-fertilisation may be +effected even in these "cleistopetalous" flowers: humming birds visit the +permanently closed flowers of certain species of Nidularium and transport +the pollen. The fact that the formation of hybrids may occur as the result +of this shows that pollination may be accomplished. + +The existence of plants for which self-pollination is of greater importance +than it is for others is by no means contradictory to Darwin's view. Self- +fertilisation is, for example, of greater importance for annuals than for +perennials as without it seeds might fail to be produced. Even in the case +of annual plants with small inconspicuous flowers in which self- +fertilisation usually occurs, such as Senecio vulgaris, Capsella bursa- +pastoris and Stellaria media, A. Bateson (Anna Bateson, "The effects of +cross-fertilisation on inconspicuous flowers", "Annals of Botany", Vol. I. +1888, page 255.) found that cross-fertilisation gave a beneficial result, +although only in a slight degree. If the favourable effects of sexual +reproduction, according to Darwin's view, are correlated with change of +environment, it is quite possible that this is of less importance in plants +which die after ripening their seeds ("hapaxanthic") and which in any case +constantly change their situation. Objections which are based on the proof +of the prevalence of self-fertilisation are not, therefore, pertinent. At +first sight another point of view, which has been more recently urged, +appears to have more weight. + +W. Burck (Burck, "Darwin's Kreuzeungsgesetz...", "Biol. Centralbl". XXVIII. +1908, page 177.) has expressed the opinion that the beneficial results of +cross-fertilisation demonstrated by Darwin concern only hybrid plants. +These alone become weaker by self-pollination; while pure species derive no +advantage from crossing and no disadvantage from self-fertilisation. It is +certain that some of the plants used by Darwin were of hybrid origin. (It +is questionable if this was always the case.) This is evident from his +statements, which are models of clearness and precision; he says that his +Ipomoea plants "were probably the offspring of a cross." ("Cross and Self +fertilisation" (1st edition), page 55.) The fixed forms of this plant, +such as Hero, which was produced by self-fertilisation, and a form of +Mimulus with white flowers spotted with red probably resulted from +splitting of the hybrids. It is true that the phenomena observed in self- +pollination, e.g. in Ipomoea, agree with those which are often noticed in +hybrids; Darwin himself drew attention to this. + +Let us next call to mind some of the peculiarities connected with +hybridisation. We know that hybrids are often characterized by their large +size, rapidity of growth, earlier production of flowers, wealth of flower- +production and a longer life; hybrids, if crossed with one of the two +parent forms, are usually more fertile than when they are crossed together +or with another hybrid. But the characters which hybrids exhibit on self- +fertilisation are rather variable. The following instance may be quoted +from Gartner: "There are many hybrids which retain the self-fertility of +the first generation during the second and later generations, but very +often in a less degree; a considerable number, however, become sterile." +But the hybrid varieties may be more fertile in the second generation than +in the first, and in some hybrids the fertility with their own pollen +increases in the second, third, and following generations. (K.F. Gartner, +"Versuche uber die Bastarderzeugung", Stuttgart, 1849, page 149.) As yet +it is impossible to lay down rules of general application for the self- +fertility of hybrids. That the beneficial influence of crossing with a +fresh stock rests on the same ground--a union of sexual cells possessing +somewhat different characters--as the fact that many hybrids are +distinguished by greater luxuriance, wealth of flowers, etc. corresponds +entirely with Darwin's conclusions. It seems to me to follow clearly from +his investigations that there is no essential difference between cross- +fertilisation and hybridisation. The heterostyled plants are normally +dependent on a process corresponding to hybridisation. The view that +specifically distinct species could at best produce sterile hybrids was +always opposed by Darwin. But if the good results of crossing were +EXCLUSIVELY dependent on the fact that we are concerned with hybrids, there +must then be a demonstration of two distinct things. First, that crossing +with a fresh stock belonging to the same systematic entity or to the same +hybrid, but cultivated for a considerable time under different conditions, +shows no superiority over self-fertilisation, and that in pure species +crossing gives no better results than self-pollination. If this were the +case, we should be better able to understand why in one plant crossing is +advantageous while in others, such as Darwin's Hero and the forms of +Mimulus and Nicotiana no advantage is gained; these would then be pure +species. But such a proof has not been supplied; the inference drawn from +cleistogamous and cleistopetalous plants is not supported by evidence, and +the experiments on geitonogamy and on the advantage of cross-fertilisation +in species which are usually self-fertilised are opposed to this view. +There are still but few researches on this point; Darwin found that in +Ononis minutissima, which produces cleistogamous as well as self-fertile +chasmogamous flowers, the crossed and self-fertilised capsules produced +seed in the proportion of 100:65 and that the average bore the proportion +100:86. Facts previously mentioned are also applicable to this case. +Further, it is certain that the self-sterility exhibited by many plants has +nothing to do with hybridisation. Between self-sterility and reduced +fertility as the result of self-fertilisation there is probably no +fundamental difference. + +It is certain that so difficult a problem as that of the significance of +sexual reproduction requires much more investigation. Darwin was anything +but dogmatic and always ready to alter an opinion when it was not based on +definite proof: he wrote, "But the veil of secrecy is as yet far from +lifted; nor will it be, until we can say why it is beneficial that the +sexual elements should be differentiated to a certain extent, and why, if +the differentiation be carried still further, injury follows." He has also +shown us the way along which to follow up this problem; it is that of +carefully planned and exact experimental research. It may be that +eventually many things will be viewed in a different light, but Darwin's +investigations will always form the foundation of Floral Biology on which +the future may continue to build. + + +XXI. MENTAL FACTORS IN EVOLUTION. + +By C. LLOYD MORGAN, LL.D., F.R.S. + +In developing his conception of organic evolution Charles Darwin was of +necessity brought into contact with some of the problems of mental +evolution. In "The Origin of Species" he devoted a chapter to "the +diversities of instinct and of the other mental faculties in animals of the +same class." ("Origin of Species" (6th edition), page 205.) When he +passed to the detailed consideration of "The Descent of Man", it was part +of his object to show "that there is no fundamental difference between man +and the higher mammals in their mental faculties." ("Descent of Man" (2nd +edition 1888), Vol. I. page 99; Popular edition page 99.) "If no organic +being excepting man," he said, "had possessed any mental power, or if his +powers had been of a wholly different nature from those of the lower +animals, then we should never have been able to convince ourselves that our +high faculties had been gradually developed." (Ibid. page 99.) In his +discussion of "The Expression of the Emotions" it was important for his +purpose "fully to recognise that actions readily become associated with +other actions and with various states of the mind." ("The Expression of +the Emotions" (2nd edition), page 32.) His hypothesis of sexual selection +is largely dependent upon the exercise of choice on the part of the female +and her preference for "not only the more attractive but at the same time +the more vigorous and victorious males." ("Descent of Man", Vol. II. page +435.) Mental processes and physiological processes were for Darwin closely +correlated; and he accepted the conclusion "that the nervous system not +only regulates most of the existing functions of the body, but has +indirectly influenced the progressive development of various bodily +structures and of certain mental qualities." (Ibid. pages 437, 438.) + +Throughout his treatment, mental evolution was for Darwin incidental to and +contributory to organic evolution. For specialised research in comparative +and genetic psychology, as an independent field of investigation, he had +neither the time nor the requisite training. None the less his writings +and the spirit of his work have exercised a profound influence on this +department of evolutionary thought. And, for those who follow Darwin's +lead, mental evolution is still in a measure subservient to organic +evolution. Mental processes are the accompaniments or concomitants of the +functional activity of specially differentiated parts of the organism. +They are in some way dependent on physiological and physical conditions. +But though they are not physical in their nature, and though it is +difficult or impossible to conceive that they are physical in their origin, +they are, for Darwin and his followers, factors in the evolutionary process +in its physical or organic aspect. By the physiologist within his special +and well-defined universe of discourse they may be properly regarded as +epiphenomena; but by the naturalist in his more catholic survey of nature +they cannot be so regarded, and were not so regarded by Darwin. +Intelligence has contributed to evolution of which it is in a sense a +product. + +The facts of observation or of inference which Darwin accepted are these: +Conscious experience accompanies some of the modes of animal behaviour; it +is concomitant with certain physiological processes; these processes are +the outcome of development in the individual and evolution in the race; the +accompanying mental processes undergo a like development. Into the subtle +philosophical questions which arise out of the naive acceptance of such a +creed it was not Darwin's province to enter; "I have nothing to do," he +said ("Origin of Species" (6th edition), page 205.), "with the origin of +the mental powers, any more than I have with that of life itself." He +dealt with the natural history of organisms, including not only their +structure but their modes of behaviour; with the natural history of the +states of consciousness which accompany some of their actions; and with the +relation of behaviour to experience. We will endeavour to follow Darwin in +his modesty and candour in making no pretence to give ultimate +explanations. But we must note one of the implications of this self- +denying ordinance of science. Development and evolution imply continuity. +For Darwin and his followers the continuity is organic through physical +heredity. Apart from speculative hypothesis, legitimate enough in its +proper place but here out of court, we know nothing of continuity of mental +evolution as such: consciousness appears afresh in each succeeding +generation. Hence it is that for those who follow Darwin's lead, mental +evolution is and must ever be, within his universe of discourse, +subservient to organic evolution. Only in so far as conscious experience, +or its neural correlate, effects some changes in organic structure can it +influence the course of heredity; and conversely only in so far as changes +in organic structure are transmitted through heredity, is mental evolution +rendered possible. Such is the logical outcome of Darwin's teaching. + +Those who abide by the cardinal results of this teaching are bound to +regard all behaviour as the expression of the functional activities of the +living tissues of the organism, and all conscious experience as correlated +with such activities. For the purposes of scientific treatment, mental +processes are one mode of expression of the same changes of which the +physiological processes accompanying behaviour are another mode of +expression. This is simply accepted as a fact which others may seek to +explain. The behaviour itself is the adaptive application of the energies +of the organism; it is called forth by some form of presentation or +stimulation brought to bear on the organism by the environment. This +presentation is always an individual or personal matter. But in order that +the organism may be fitted to respond to the presentation of the +environment it must have undergone in some way a suitable preparation. +According to the theory of evolution this preparation is primarily racial +and is transmitted through heredity. Darwin's main thesis was that the +method of preparation is predominantly by natural selection. Subordinate +to racial preparation, and always dependent thereon, is individual or +personal preparation through some kind of acquisition; of which the +guidance of behaviour through individually won experience is a typical +example. We here introduce the mental factor because the facts seem to +justify the inference. Thus there are some modes of behaviour which are +wholly and solely dependent upon inherited racial preparation; there are +other modes of behaviour which are also dependent, in part at least, on +individual preparation. In the former case the behaviour is adaptive on +the first occurrence of the appropriate presentation; in the latter case +accommodation to circumstances is only reached after a greater or less +amount of acquired organic modification of structure, often accompanied (as +we assume) in the higher animals by acquired experience. Logically and +biologically the two classes of behaviour are clearly distinguishable: but +the analysis of complex cases of behaviour where the two factors cooperate, +is difficult and requires careful and critical study of life-history. + +The foundations of the mental life are laid in the conscious experience +that accompanies those modes of behaviour, dependent entirely on racial +preparation, which may broadly be described as instinctive. In the eighth +chapter of "The Origin of Species" Darwin says ("Origin of Species" (6th +edition), page 205.), "I will not attempt any definition of +instinct...Every one understands what is meant, when it is said that +instinct impels the cuckoo to migrate and to lay her eggs in other birds' +nests. An action, which we ourselves require experience to enable us to +perform, when performed by an animal, more especially by a very young one, +without experience, and when performed by many individuals in the same way, +without their knowing for what purpose it is performed, is usually said to +be instinctive." And in the summary at the close of the chapter he says +("Origin of Species" (6th edition), page 233.), "I have endeavoured briefly +to show that the mental qualities of our domestic animals vary, and that +the variations are inherited. Still more briefly I have attempted to show +that instincts vary slightly in a state of nature. No one will dispute +that instincts are of the highest importance to each animal. Therefore +there is no real difficulty, under changing conditions of life, in natural +selection accumulating to any extent slight modifications of instinct which +are in any way useful. In many cases habit or use and disuse have probably +come into play." + +Into the details of Darwin's treatment there is neither space nor need to +enter. There are some ambiguous passages; but it may be said that for him, +as for his followers to-day, instinctive behaviour is wholly the result of +racial preparation transmitted through organic heredity. For the +performance of the instinctive act no individual preparation under the +guidance of personal experience is necessary. It is true that Darwin +quotes with approval Huber's saying that "a little dose of judgment or +reason often comes into play, even with animals low in the scale of +nature." (Ibid. page 205.) But we may fairly interpret his meaning to be +that in behaviour, which is commonly called instinctive, some element of +intelligent guidance is often combined. If this be conceded the strictly +instinctive performance (or part of the performance) is the outcome of +heredity and due to the direct transmission of parental or ancestral +aptitudes. Hence the instinctive response as such depends entirely on how +the nervous mechanism has been built up through heredity; while intelligent +behaviour, or the intelligent factor in behaviour, depends also on how the +nervous mechanism has been modified and moulded by use during its +development and concurrently with the growth of individual experience in +the customary situations of daily life. Of course it is essential to the +Darwinian thesis that what Sir E. Ray Lankester has termed "educability," +not less than instinct, is hereditary. But it is also essential to the +understanding of this thesis that the differentiae of the hereditary +factors should be clearly grasped. + +For Darwin there were two modes of racial preparation, (1) natural +selection, and (2) the establishment of individually acquired habit. He +showed that instincts are subject to hereditary variation; he saw that +instincts are also subject to modification through acquisition in the +course of individual life. He believed that not only the variations but +also, to some extent, the modifications are inherited. He therefore held +that some instincts (the greater number) are due to natural selection but +that others (less numerous) are due, or partly due, to the inheritance of +acquired habits. The latter involve Lamarckian inheritance, which of late +years has been the centre of so much controversy. It is noteworthy however +that Darwin laid especial emphasis on the fact that many of the most +typical and also the most complex instincts--those of neuter insects--do +not admit of such an interpretation. "I am surprised," he says ("Origin of +Species" (6th edition), page 233.), "that no one has hitherto advanced this +demonstrative case of neuter insects, against the well-known doctrine of +inherited habit, as advanced by Lamarck." None the less Darwin admitted +this doctrine as supplementary to that which was more distinctively his +own--for example in the case of the instincts of domesticated animals. +Still, even in such cases, "it may be doubted," he says (Ibid. pages 210, +211.), "whether any one would have thought of training a dog to point, had +not some one dog naturally shown a tendency in this line...so that habit +and some degree of selection have probably concurred in civilising by +inheritance our dogs." But in the interpretation of the instincts of +domesticated animals, a more recently suggested hypothesis, that of organic +selection (Independently suggested, on somewhat different lines, by Profs. +J. Mark Baldwin, Henry F. Osborn and the writer.), may be helpful. +According to this hypothesis any intelligent modification of behaviour +which is subject to selection is probably coincident in direction with an +inherited tendency to behave in this fashion. Hence in such behaviour +there are two factors: (1) an incipient variation in the line of such +behaviour, and (2) an acquired modification by which the behaviour is +carried further along the same line. Under natural selection those +organisms in which the two factors cooperate are likely to survive. Under +artificial selection they are deliberately chosen out from among the rest. + +Organic selection has been termed a compromise between the more strictly +Darwinian and the Lamarckian principles of interpretation. But it is not +in any sense a compromise. The principle of interpretation of that which +is instinctive and hereditary is wholly Darwinian. It is true that some of +the facts of observation relied upon by Lamarckians are introduced. For +Lamarckians however the modifications which are admittedly factors in +survival, are regarded as the parents of inherited variations; for +believers in organic selection they are only the foster parents or nurses. +It is because organic selection is the direct outcome of and a natural +extension of Darwin's cardinal thesis that some reference to it here is +justifiable. The matter may be put with the utmost brevity as follows. +(1) Variations (V) occur, some of which are in the direction of increased +adaptation (+), others in the direction of decreased adaptation (-). (2) +Acquired modifications (M) also occur. Some of these are in the direction +of increased accommodation to circumstances (+), while others are in the +direction of diminished accommodation (-). Four major combinations are + +(a) + V with + M, +(b) + V with - M, +(c) - V with + M, +(d) - V with - M. + +Of these (d) must inevitably be eliminated while (a) are selected. The +predominant survival of (a) entails the survival of the adaptive variations +which are inherited. The contributory acquisitions (+M) are not inherited; +but they are none the less factors in determining the survival of the +coincident variations. It is surely abundantly clear that this is +Darwinism and has no tincture of Lamarck's essential principle, the +inheritance of acquired characters. + +Whether Darwin himself would have accepted this interpretation of some at +least of the evidence put forward by Lamarckians is unfortunately a matter +of conjecture. The fact remains that in his interpretation of instinct and +in allied questions he accepted the inheritance of individually acquired +modifications of behaviour and structure. + +Darwin was chiefly concerned with instinct from the biological rather than +from the psychological point of view. Indeed it must be confessed that, +from the latter standpoint, his conception of instinct as a "mental +faculty" which "impels" an animal to the performance of certain actions, +scarcely affords a satisfactory basis for genetic treatment. To carry out +the spirit of Darwin's teaching it is necessary to link more closely +biological and psychological evolution. The first step towards this is to +interpret the phenomena of instinctive behaviour in terms of stimulation +and response. It may be well to take a particular case. Swimming on the +part of a duckling is, from the biological point of view, a typical example +of instinctive behaviour. Gently lower a recently hatched bird into water: +coordinated movements of the limbs follow in rhythmical sequence. The +behaviour is new to the individual though it is no doubt closely related to +that of walking, which is no less instinctive. There is a group of stimuli +afforded by the "presentation" which results from partial immersion: upon +this there follows as a complex response an application of the functional +activities in swimming; the sequence of adaptive application on the +appropriate presentation is determined by racial preparation. We know, it +is true, but little of the physiological details of what takes place in the +central nervous system; but in broad outline the nature of the organic +mechanism and the manner of its functioning may at least be provisionally +conjectured in the present state of physiological knowledge. Similarly in +the case of the pecking of newly-hatched chicks; there is a visual +presentation, there is probably a cooperating group of stimuli from the +alimentary tract in need of food, there is an adaptive application of the +activities in a definite mode of behaviour. Like data are afforded in a +great number of cases of instinctive procedure, sometimes occurring very +early in life, not infrequently deferred until the organism is more fully +developed, but all of them dependent upon racial preparation. No doubt +there is some range of variation in the behaviour, just such variation as +the theory of natural selection demands. But there can be no question that +the higher animals inherit a bodily organisation and a nervous system, the +functional working of which gives rise to those inherited modes of +behaviour which are termed instinctive. + +It is to be noted that the term "instinctive" is here employed in the +adjectival form as a descriptive heading under which may be grouped many +and various modes of behaviour due to racial preparation. We speak of +these as inherited; but in strictness what is transmitted through heredity +is the complex of anatomical and physiological conditions under which, in +appropriate circumstances, the organism so behaves. So far the term +"instinctive" has a restricted biological connotation in terms of +behaviour. But the connecting link between biological evolution and +psychological evolution is to be sought,--as Darwin fully realised,--in the +phenomena of instinct, broadly considered. The term "instinctive" has also +a psychological connotation. What is that connotation? + +Let us take the case of the swimming duckling or the pecking chick, and fix +our attention on the first instinctive performance. Grant that just as +there is, strictly speaking, no inherited behaviour, but only the +conditions which render such behaviour under appropriate circumstances +possible; so too there is no inherited experience, but only the conditions +which render such experience possible; then the cerebral conditions in both +cases are the same. The biological behaviour-complex, including the total +stimulation and the total response with the intervening or resultant +processes in the sensorium, is accompanied by an experience-complex +including the initial stimulation-consciousness and resulting response- +consciousness. In the experience-complex are comprised data which in +psychological analysis are grouped under the headings of cognition, +affective tone and conation. But the complex is probably experienced as an +unanalysed whole. If then we use the term "instinctive" so as to comprise +all congenital modes of behaviour which contribute to experience, we are in +a position to grasp the view that the net result in consciousness +constitutes what we may term the primary tissue of experience. To the +development of this experience each instinctive act contributes. The +nature and manner of organisation of this primary tissue of experience are +dependent on inherited biological aptitudes; but they are from the outset +onwards subject to secondary development dependent on acquired aptitudes. +Biological values are supplemented by psychological values in terms of +satisfaction or the reverse. + +In our study of instinct we have to select some particular phase of animal +behaviour and isolate it so far as is possible from the life of which it is +a part. But the animal is a going concern, restlessly active in many ways. +Many instinctive performances, as Darwin pointed out ("Origin of Species" +(6th edition), page 206.), are serial in their nature. But the whole of +active life is a serial and coordinated business. The particular +instinctive performance is only an episode in a life-history, and every +mode of behaviour is more or less closely correlated with other modes. +This coordination of behaviour is accompanied by a correlation of the modes +of primary experience. We may classify the instinctive modes of behaviour +and their accompanying modes of instinctive experience under as many heads +as may be convenient for our purposes of interpretation, and label them +instincts of self-preservation, of pugnacity, of acquisition, the +reproductive instincts, the parental instincts, and so forth. An instinct, +in this sense of the term (for example the parental instinct), may be +described as a specialised part of the primary tissue of experience +differentiated in relation to some definite biological end. Under such an +instinct will fall a large number of particular and often well-defined +modes of behaviour, each with its own peculiar mode of experience. + +It is no doubt exceedingly difficult as a matter of observation and of +inference securely based thereon to distinguish what is primary from what +is in part due to secondary acquisition--a fact which Darwin fully +appreciated. Animals are educable in different degrees; but where they are +educable they begin to profit by experience from the first. Only, +therefore, on the occasion of the first instinctive act of a given type can +the experience gained be weighed as WHOLLY primary; all subsequent +performance is liable to be in some degree, sometimes more, sometimes less, +modified by the acquired disposition which the initial behaviour engenders. +But the early stages of acquisition are always along the lines +predetermined by instinctive differentiation. It is the task of +comparative psychology to distinguish the primary tissue of experience from +its secondary and acquired modifications. We cannot follow up the matter +in further detail. It must here suffice to suggest that this conception of +instinct as a primary form of experience lends itself better to natural +history treatment than Darwin's conception of an impelling force, and that +it is in line with the main trend of Darwin's thought. + +In a characteristic work,--characteristic in wealth of detail, in closeness +and fidelity of observation, in breadth of outlook, in candour and +modesty,--Darwin dealt with "The Expression of the Emotions in Man and +Animals". Sir Charles Bell in his "Anatomy of Expression" had contended +that many of man's facial muscles had been specially created for the sole +purpose of being instrumental in the expression of his emotions. Darwin +claimed that a natural explanation, consistent with the doctrine of +evolution, could in many cases be given and would in other cases be +afforded by an extension of the principles he advocated. "No doubt," he +said ("Expression of the Emotions", page 13. The passage is here somewhat +condensed.), "as long as man and all other animals are viewed as +independent creations, an effectual stop is put to our natural desire to +investigate as far as possible the causes of Expression. By this doctrine, +anything and everything can be equally well explained...With mankind, some +expressions...can hardly be understood, except on the belief that man once +existed in a much lower and animal-like condition. The community of +certain expressions in distinct though allied species...is rendered +somewhat more intelligible, if we believe in their descent from a common +progenitor. He who admits on general grounds that the structure and habits +of all animals have been gradually evolved, will look at the whole subject +of Expression in a new and interesting light." + +Darwin relied on three principles of explanation. "The first of these +principles is, that movements which are serviceable in gratifying some +desire, or in relieving some sensation, if often repeated, become so +habitual that they are performed, whether or not of any service, whenever +the same desire or sensation is felt, even in a very weak degree." (Ibid. +page 368.) The modes of expression which fall under this head have become +instinctive through the hereditary transmission of acquired habit. "As far +as we can judge, only a few expressive movements are learnt by each +individual; that is, were consciously and voluntarily performed during the +early years of life for some definite object, or in imitation of others, +and then became habitual. The far greater number of the movements of +expression, and all the more important ones, are innate or inherited; and +such cannot be said to depend on the will of the individual. Nevertheless, +all those included under our first principle were at first voluntarily +performed for a definite object,--namely, to escape some danger, to relieve +some distress, or to gratify some desire." (Ibid. pages 373, 374.) + +"Our second principle is that of antithesis. The habit of voluntarily +performing opposite movements under opposite impulses has become firmly +established in us by the practice of our whole lives. Hence, if certain +actions have been regularly performed, in accordance with our first +principle, under a certain frame of mind, there will be a strong and +involuntary tendency to the performance of directly opposite actions, +whether or not these are of any use, under the excitement of an opposite +frame of mind." ("Expression of the Emotions", page 368.) This principle +of antithesis has not been widely accepted. Nor is Darwin's own position +easy to grasp. + +"Our third principle," he says (Ibid. page 369.), "is the direct action of +the excited nervous system on the body, independently of the will, and +independently, in large part, of habit. Experience shows that nerve-force +is generated and set free whenever the cerebro-spinal system is excited. +The direction which this nerve-force follows is necessarily determined by +the lines of connection between the nerve-cells, with each other and with +various parts of the body." + +Lack of space prevents our following up the details of Darwin's treatment +of expression. Whether we accept or do not accept his three principles of +explanation we must regard his work as a masterpiece of descriptive +analysis, packed full of observations possessing lasting value. For a +further development of the subject it is essential that the instinctive +factors in expression should be more fully distinguished from those which +are individually acquired--a difficult task--and that the instinctive +factors should be rediscussed in the light of modern doctrines of heredity, +with a view to determining whether Lamarckian inheritance, on which Darwin +so largely relied, is necessary for an interpretation of the facts. + +The whole subject as Darwin realised is very complex. Even the term +"expression" has a certain amount of ambiguity. When the emotion is in +full flood the animal fights, flees, or faints. Is this full-tide effect +to be regarded as expression; or are we to restrict the term to the +premonitory or residual effects--the bared canine when the fighting mood is +being roused, the ruffled fur when reminiscent representations of the +object inducing anger cross the mind? Broadly considered both should be +included. The activity of premonitory expression as a means of +communication was recognised by Darwin; he might, perhaps, have emphasised +it more strongly in dealing with the lower animals. Man so largely relies +on a special means of communication, that of language, that he sometimes +fails to realise that for animals with their keen powers of perception, and +dependent as they are on such means of communication, the more strictly +biological means of expression are full of subtle suggestiveness. Many +modes of expression, otherwise useless, are signs of behaviour that may be +anticipated,--signs which stimulate the appropriate attitude of response. +This would not, however, serve to account for the utility of the organic +accompaniments--heart-affection, respiratory changes, vaso-motor effects +and so forth, together with heightened muscular tone,--on all of which +Darwin lays stress ("Expression of the Emotions", pages 65 ff.) under his +third principle. The biological value of all this is, however, of great +importance, though Darwin was hardly in a position to take it fully into +account. + +Having regard to the instinctive and hereditary factors of emotional +expression we may ask whether Darwin's third principle does not alone +suffice as an explanation. Whether we admit or reject Lamarckian +inheritance it would appear that all hereditary expression must be due to +pre-established connections within the central nervous system and to a +transmitted provision for coordinated response under the appropriate +stimulation. If this be so, Darwin's first and second principles are +subordinate and ancillary to the third, an expression, so far as it is +instinctive or hereditary, being "the direct result of the constitution of +the nervous system." + +Darwin accepted the emotions themselves as hereditary or acquired states of +mind and devoted his attention to their expression. But these emotions +themselves are genetic products and as such dependent on organic +conditions. It remained, therefore, for psychologists who accepted +evolution and sought to build on biological foundations to trace the +genesis of these modes of animal and human experience. The subject has +been independently developed by Professors Lange and James (Cf. William +James, "Principles of Psychology", Vol. II. Chap. XXV, London, 1890.); and +some modification of their view is regarded by many evolutionists as +affording the best explanation of the facts. We must fix our attention on +the lower emotions, such as anger or fear, and on their first occurrence in +the life of the individual organism. It is a matter of observation that if +a group of young birds which have been hatched in an incubator are +frightened by an appropriate presentation, auditory or visual, they +instinctively respond in special ways. If we speak of this response as the +expression, we find that there are many factors. There are certain visible +modes of behaviour, crouching at once, scattering and then crouching, +remaining motionless, the braced muscles sustaining an attitude of arrest, +and so forth. There are also certain visceral or organic effects, such as +affections of the heart and respiration. These can be readily observed by +taking the young bird in the hand. Other effects cannot be readily +observed; vaso-motor changes, affections of the alimentary canal, the skin +and so forth. Now the essence of the James-Lange view, as applied to these +congenital effects, is that though we are justified in speaking of them as +effects of the stimulation, we are not justified, without further evidence, +in speaking of them as effects of the emotional state. May it not rather +be that the emotion as a primary mode of experience is the concomitant of +the net result of the organic situation--the initial presentation, the +instinctive mode of behaviour, the visceral disturbances? According to +this interpretation the primary tissue of experience of the emotional +order, felt as an unanalysed complex, is generated by the stimulation of +the sensorium by afferent or incoming physiological impulses from the +special senses, from the organs concerned in the responsive behaviour, from +the viscera and vaso-motor system. + +Some psychologists, however, contend that the emotional experience is +generated in the sensorium prior to, and not subsequent to, the behaviour- +response and the visceral disturbances. It is a direct and not an indirect +outcome of the presentation to the special senses. Be this as it may, +there is a growing tendency to bring into the closest possible relation, or +even to identify, instinct and emotion in their primary genesis. The +central core of all such interpretations is that instinctive behaviour and +experience, its emotional accompaniments, and its expression, are but +different aspects of the outcome of the same organic occurrences. Such +emotions are, therefore, only a distinguishable aspect of the primary +tissue of experience and exhibit a like differentiation. Here again a +biological foundation is laid for a psychological doctrine of the mental +development of the individual. + +The intimate relation between emotion as a psychological mode of experience +and expression as a group of organic conditions has an important bearing on +biological interpretation. The emotion, as the psychological accompaniment +of orderly disturbances in the central nervous system profoundly influences +behaviour and often renders it more vigorous and more effective. The +utility of the emotions in the struggle for existence can, therefore, +scarcely be over-estimated. Just as keenness of perception has survival- +value; just as it is obviously subject to variation; just as it must be +enhanced under natural selection, whether individually acquired increments +are inherited or not; and just as its value lies not only in this or that +special perceptive act but in its importance for life as a whole; so the +vigorous effectiveness of activity has survival-value; it is subject to +variation; it must be enhanced under natural selection; and its importance +lies not only in particular modes of behaviour but in its value for life as +a whole. If emotion and its expression as a congenital endowment are but +different aspects of the same biological occurrence; and if this is a +powerful supplement to vigour effectiveness and persistency of behaviour, +it must on Darwin's principles be subject to natural selection. + +If we include under the expression of the emotions not only the premonitory +symptoms of the initial phases of the organic and mental state, not only +the signs or conditions of half-tide emotion, but the full-tide +manifestation of an emotion which dominates the situation, we are naturally +led on to the consideration of many of the phenomena which are discussed +under the head of sexual selection. The subject is difficult and complex, +and it was treated by Darwin with all the strength he could summon to the +task. It can only be dealt with here from a special point of view--that +which may serve to illustrate the influence of certain mental factors on +the course of evolution. From this point of view too much stress can +scarcely be laid on the dominance of emotion during the period of courtship +and pairing in the more highly organised animals. It is a period of +maximum vigour, maximum activity, and, correlated with special modes of +behaviour and special organic and visceral accompaniments, a period also of +maximum emotional excitement. The combats of males, their dances and +aerial evolutions, their elaborate behaviour and display, or the flood of +song in birds, are emotional expressions which are at any rate coincident +in time with sexual periodicity. From the combat of the males there +follows on Darwin's principles the elimination of those which are deficient +in bodily vigour, deficient in special structures, offensive or protective, +which contribute to success, deficient in the emotional supplement of which +persistent and whole-hearted fighting is the expression, and deficient in +alertness and skill which are the outcome of the psychological development +of the powers of perception. Few biologists question that we have here a +mode of selection of much importance, though its influence on psychological +evolution often fails to receive its due emphasis. Mr Wallace +("Darwinism", pages 282, 283, London, 1889.) regards it as "a form of +natural selection"; "to it," he says, "we must impute the development of +the exceptional strength, size, and activity of the male, together with the +possession of special offensive and defensive weapons, and of all other +characters which arise from the development of these or are correlated with +them." So far there is little disagreement among the followers of Darwin-- +for Mr Wallace, with fine magnanimity, has always preferred to be ranked as +such, notwithstanding his right, on which a smaller man would have +constantly insisted, to the claim of independent originator of the doctrine +of natural selection. So far with regard to sexual selection Darwin and Mr +Wallace are agreed; so far and no farther. For Darwin, says Mr Wallace +(Ibid. page 283.), "has extended the principle into a totally different +field of action, which has none of that character of constancy and of +inevitable result that attaches to natural selection, including male +rivalry; for by far the larger portion of the phenomena, which he +endeavours to explain by the direct action of sexual selection, can only be +so explained on the hypothesis that the immediate agency is female choice +or preference. It is to this that he imputes the origin of all secondary +sexual characters other than weapons of offence and defence...In this +extension of sexual selection to include the action of female choice or +preference, and in the attempt to give to that choice such wide-reaching +effects, I am unable to follow him more than a very little way." + +Into the details of Mr Wallace's criticisms it is impossible to enter here. +We cannot discuss either the mode of origin of the variations in structure +which have rendered secondary sexual characters possible or the modes of +selection other than sexual which have rendered them, within narrow limits, +specifically constant. Mendelism and mutation theories may have something +to say on the subject when these theories have been more fully correlated +with the basal principles of selection. It is noteworthy that Mr Wallace +says ("Darwinism", pages 283, 284.): "Besides the acquisition of weapons +by the male for the purpose of fighting with other males, there are some +other sexual characters which may have been produced by natural selection. +Such are the various sounds and odours which are peculiar to the male, and +which serve as a call to the female or as an indication of his presence. +These are evidently a valuable addition to the means of recognition of the +two sexes, and are a further indication that the pairing season has +arrived; and the production, intensification, and differentiation of these +sounds and odours are clearly within the power of natural selection. The +same remark will apply to the peculiar calls of birds, and even to the +singing of the males." Why the same remark should not apply to their +colours and adornments is not obvious. What is obvious is that "means of +recognition" and "indication that the pairing season has arrived" are +dependent on the perceptive powers of the female who recognises and for +whom the indication has meaning. The hypothesis of female preference, +stripped of the aesthetic surplusage which is psychologically both +unnecessary and unproven, is really only different in degree from that +which Mr Wallace admits in principle when he says that it is probable that +the female is pleased or excited by the display. + +Let us for our present purpose leave on one side and regard as sub judice +the question whether the specific details of secondary sexual characters +are the outcome of female choice. For us the question is whether certain +psychological accompaniments of the pairing situation have influenced the +course of evolution and whether these psychological accompaniments are +themselves the outcome of evolution. As a matter of observation, specially +differentiated modes of behaviour, often very elaborate, frequently +requiring highly developed skill, and apparently highly charged with +emotional tone, are the precursors of pairing. They are generally confined +to the males, whose fierce combats during the period of sexual activity are +part of the emotional manifestation. It is inconceivable that they have no +biological meaning; and it is difficult to conceive that they have any +other biological end than to evoke in the generally more passive female the +pairing impulse. They are based on instinctive foundations ingrained in +the nervous constitution through natural (or may we not say sexual?) +selection in virtue of their profound utility. They are called into play +by a specialised presentation such as the sight or the scent of the female +at, or a little in advance of, a critical period of the physiological +rhythm. There is no necessity that the male should have any knowledge of +the end to which his strenuous activity leads up. In presence of the +female there is an elaborate application of all the energies of behaviour, +just because ages of racial preparation have made him biologically and +emotionally what he is--a functionally sexual male that must dance or sing +or go through hereditary movements of display, when the appropriate +stimulation comes. Of course after the first successful courtship his +future behaviour will be in some degree modified by his previous +experience. No doubt during his first courtship he is gaining the primary +data of a peculiarly rich experience, instinctive and emotional. But the +biological foundations of the behaviour of courtship are laid in the +hereditary coordinations. It would seem that in some cases, not indeed in +all, but perhaps especially in those cases in which secondary sexual +behaviour is most highly evolved,--correlative with the ardour of the male +is a certain amount of reluctance in the female. The pairing act on her +part only takes place after prolonged stimulation, for affording which the +behaviour of male courtship is the requisite presentation. The most +vigorous, defiant and mettlesome male is preferred just because he alone +affords a contributory stimulation adequate to evoke the pairing impulse +with its attendant emotional tone. + +It is true that this places female preference or choice on a much lower +psychological plane than Darwin in some passages seems to contemplate +where, for example, he says that the female appreciates the display of the +male and places to her credit a taste for the beautiful. But Darwin +himself distinctly states ("Descent of Man" (2nd edition), Vol. II. pages +136, 137; (Popular edition), pages 642, 643.) that "it is not probable that +she consciously deliberates; but she is most excited or attracted by the +most beautiful, or melodious, or gallant males." The view here put +forward, which has been developed by Prof. Groos ("The Play of Animals", +page 244, London, 1898.), therefore seems to have Darwin's own sanction. +The phenomena are not only biological; there are psychological elements as +well. One can hardly suppose that the female is unconscious of the male's +presence; the final yielding must surely be accompanied by heightened +emotional tone. Whether we call it choice or not is merely a matter of +definition of terms. The behaviour is in part determined by supplementary +psychological values. Prof. Groos regards the coyness of females as "a +most efficient means of preventing the too early and too frequent yielding +to the sexual impulse." (Ibid. page 283.) Be that as it may, it is, in +any case, if we grant the facts, a means through which male sexual +behaviour with all its biological and psychological implications, is raised +to a level otherwise perhaps unattainable by natural means, while in the +female it affords opportunities for the development in the individual and +evolution in the race of what we may follow Darwin in calling appreciation, +if we empty this word of the aesthetic implications which have gathered +round it in the mental life of man. + +Regarded from this standpoint sexual selection, broadly considered, has +probably been of great importance. The psychological accompaniments of the +pairing situation have profoundly influenced the course of biological +evolution and are themselves the outcome of that evolution. + +Darwin makes only passing reference to those modes of behaviour in animals +which go by the name of play. "Nothing," he says ("Descent of Man", Vol. +II. page 60; (Popular edition), page 566.), "is more common than for +animals to take pleasure in practising whatever instinct they follow at +other times for some real good." This is one of the very numerous cases in +which a hint of the master has served to stimulate research in his +disciples. It was left to Prof. Groos to develop this subject on +evolutionary lines and to elaborate in a masterly manner Darwin's +suggestion. "The utility of play," he says ("The Play of Animals", page +76.), "is incalculable. This utility consists in the practice and exercise +it affords for some of the more important duties of life,"--that is to say, +for the performance of activities which will in adult life be essential to +survival. He urges (Ibid. page 75.) that "the play of young animals has +its origin in the fact that certain very important instincts appear at a +time when the animal does not seriously need them." It is, however, +questionable whether any instincts appear at a time when they are not +needed. And it is questionable whether the instinctive and emotional +attitude of the play-fight, to take one example, can be identified with +those which accompany fighting in earnest, though no doubt they are closely +related and have some common factors. It is probable that play, as +preparatory behaviour, differs in biological detail (as it almost certainly +does in emotional attributes) from the earnest of after-life and that it +has been evolved through differentiation and integration of the primary +tissue of experience, as a preparation through which certain essential +modes of skill may be acquired--those animals in which the preparatory +play-propensity was not inherited in due force and requisite amount being +subsequently eliminated in the struggle for existence. In any case there +is little question that Prof. Groos is right in basing the play-propensity +on instinctive foundations. ("The Play of Animals" page 24.) None the +less, as he contends, the essential biological value of play is that it is +a means of training the educable nerve-tissue, of developing that part of +the brain which is modified by experience and which thus acquires new +characters, of elaborating the secondary tissue of experience on the +predetermined lines of instinctive differentiation and thus furthering the +psychological activities which are included under the comprehensive term +"intelligent." + +In "The Descent of Man" Darwin dealt at some length with intelligence and +the higher mental faculties. ("Descent of Man" (1st edition), Chapters II, +III, V; (2nd edition), Chapters III, IV, V.) His object, he says, is to +show that there is no fundamental difference between man and the higher +mammals in their mental faculties; that these faculties are variable and +the variations tend to be inherited; and that under natural selection +beneficial variations of all kinds will have been preserved and injurious +ones eliminated. + +Darwin was too good an observer and too honest a man to minimise the +"enormous difference" between the level of mental attainment of civilised +man and that reached by any animal. His contention was that the +difference, great as it is, is one of degree and not of kind. He realised +that, in the development of the mental faculties of man, new factors in +evolution have supervened--factors which play but a subordinate and +subsidiary part in animal intelligence. Intercommunication by means of +language, approbation and blame, and all that arises out of reflective +thought, are but foreshadowed in the mental life of animals. Still he +contends that these may be explained on the doctrine of evolution. He +urges (Ibid. Vol. I. pages 70, 71; (Popular edition), pages 70, 71.)" that +man is variable in body and mind; and that the variations are induced, +either directly or indirectly, by the same general causes, and obey the +same general laws, as with the lower animals." He correlates mental +development with the evolution of the brain. (Ibid. page 81.) "As the +various mental faculties gradually developed themselves, the brain would +almost certainly become larger. No one, I presume, doubts that the large +proportion which the size of man's brain bears to his body, compared to the +same proportion in the gorilla or orang, is closely connected with his +higher mental powers." "With respect to the lower animals," he says +("Descent of Man" (Popular edition), page 82.), "M.E. Lartet ("Comptes +Rendus des Sciences", June 1, 1868.), by comparing the crania of tertiary +and recent mammals belonging to the same groups, has come to the remarkable +conclusion that the brain is generally larger and the convolutions are more +complex in the more recent form." + +Sir E. Ray Lankester has sought to express in the simplest terms the +implications of the increase in size of the cerebrum. "In what," he asks, +"does the advantage of a larger cerebral mass consist?" "Man," he replies +"is born with fewer ready-made tricks of the nerve-centres--these +performances of an inherited nervous mechanism so often called by the ill- +defined term 'instincts'--than are the monkeys or any other animal. +Correlated with the absence of inherited ready-made mechanism, man has a +greater capacity of developing in the course of his individual growth +similar nervous mechanisms (similar to but not identical with those of +'instinct') than any other animal...The power of being educated-- +'educability' as we may term it--is what man possesses in excess as +compared with the apes. I think we are justified in forming the hypothesis +that it is this 'educability' which is the correlative of the increased +size of the cerebrum." There has been natural selection of the more +educable animals, for "the character which we describe as 'educability' can +be transmitted, it is a congenital character. But the RESULTS of education +can NOT be transmitted. In each generation they have to be acquired +afresh, and with increased 'educability' they are more readily acquired and +a larger variety of them...The fact is that there is no community between +the mechanisms of instinct and the mechanisms of intelligence, and that the +latter are later in the history of the evolution of the brain than the +former and can only develop in proportion as the former become feeble and +defective." ("Nature", Vol. LXI. pages 624, 625 (1900).) + +In this statement we have a good example of the further development of +views which Darwin foreshadowed but did not thoroughly work out. It states +the biological case clearly and tersely. Plasticity of behaviour in +special accommodation to special circumstances is of survival value; it +depends upon acquired characters; it is correlated with increase in size +and complexity of the cerebrum; under natural selection therefore the +larger and more complex cerebrum as the organ of plastic behaviour has been +the outcome of natural selection. We have thus the biological foundations +for a further development of genetic psychology. + +There are diversities of opinion, as Darwin showed, with regard to the +range of instinct in man and the higher animals as contrasted with lower +types. Darwin himself said ("Descent of Man", Vol. I. page 100.) that +"Man, perhaps, has somewhat fewer instincts than those possessed by the +animals which come next to him in the series." On the other hand, Prof. +Wm. James says ("Principles of Psychology," Vol. II. page 289.) that man is +probably the animal with most instincts. The true position is that man and +the higher animals have fewer complete and self-sufficing instincts than +those which stand lower in the scale of mental evolution, but that they +have an equally large or perhaps larger mass of instinctive raw material +which may furnish the stuff to be elaborated by intelligent processes. +There is, perhaps, a greater abundance of the primary tissue of experience +to be refashioned and integrated by secondary modification; there is +probably the same differentiation in relation to the determining biological +ends, but there is at the outset less differentiation of the particular and +specific modes of behaviour. The specialised instinctive performances and +their concomitant experience-complexes are at the outset more indefinite. +Only through acquired connections, correlated with experience, do they +become definitely organised. + +The full working-out of the delicate and subtle relationship of instinct +and educability--that is, of the hereditary and the acquired factors in the +mental life--is the task which lies before genetic and comparative +psychology. They interact throughout the whole of life, and their +interactions are very complex. No one can read the chapters of "The +Descent of Man" which Darwin devotes to a consideration of the mental +characters of man and animals without noticing, on the one hand, how +sedulous he is in his search for hereditary foundations, and, on the other +hand, how fully he realises the importance of acquired habits of mind. The +fact that educability itself has innate tendencies--is in fact a partially +differentiated educability--renders the unravelling of the factors of +mental progress all the more difficult. + +In his comparison of the mental powers of men and animals it was essential +that Darwin should lay stress on points of similarity rather than on points +of difference. Seeking to establish a doctrine of evolution, with its +basal concept of continuity of process and community of character, he was +bound to render clear and to emphasise the contention that the difference +in mind between man and the higher animals, great as it is, is one of +degree and not of kind. To this end Darwin not only recorded a large +number of valuable observations of his own, and collected a considerable +body of information from reliable sources, he presented the whole subject +in a new light and showed that a natural history of mind might be written +and that this method of study offered a wide and rich field for +investigation. Of course those who regarded the study of mind only as a +branch of metaphysics smiled at the philosophical ineptitude of the mere +man of science. But the investigation, on natural history lines, has been +prosecuted with a large measure of success. Much indeed still remains to +be done; for special training is required, and the workers are still few. +Promise for the future is however afforded by the fact that investigation +is prosecuted on experimental lines and that something like organised +methods of research are taking form. There is now but little reliance on +casual observations recorded by those who have not undergone the necessary +discipline in these methods. There is also some change of emphasis in +formulating conclusions. Now that the general evolutionary thesis is fully +and freely accepted by those who carry on such researches, more stress is +laid on the differentiation of the stages of evolutionary advance than on +the fact of their underlying community of nature. The conceptual +intelligence which is especially characteristic of the higher mental +procedure of man is more firmly distinguished from the perceptual +intelligence which he shares with the lower animals--distinguished now as a +higher product of evolution, no longer as differing in origin or different +in kind. Some progress has been made, on the one hand in rendering an +account of intelligent profiting by experience under the guidance of +pleasure and pain in the perceptual field, on lines predetermined by +instinctive differentiation for biological ends, and on the other hand in +elucidating the method of conceptual thought employed, for example, by the +investigator himself in interpreting the perceptual experience of the lower +animals. + +Thus there is a growing tendency to realise more fully that there are two +orders of educability--first an educability of the perceptual intelligence +based on the biological foundation of instinct, and secondly an educability +of the conceptual intelligence which refashions and rearranges the data +afforded by previous inheritance and acquisition. It is in relation to +this second and higher order of educability that the cerebrum of man shows +so large an increase of mass and a yet larger increase of effective surface +through its rich convolutions. It is through educability of this order +that the human child is brought intellectually and affectively into touch +with the ideal constructions by means of which man has endeavoured, with +more or less success, to reach an interpretation of nature, and to guide +the course of the further evolution of his race--ideal constructions which +form part of man's environment. + +It formed no part of Darwin's purpose to consider, save in broad outline, +the methods, or to discuss in any fulness of detail the results of the +process by which a differentiation of the mental faculties of man from +those of the lower animals has been brought about--a differentiation the +existence of which he again and again acknowledges. His purpose was rather +to show that, notwithstanding this differentiation, there is basal +community in kind. This must be remembered in considering his treatment of +the biological foundations on which man's systems of ethics are built. He +definitely stated that he approached the subject "exclusively from the side +of natural history." ("Descent of Man", Vol. I. page 149.) His general +conclusion is that the moral sense is fundamentally identical with the +social instincts, which have been developed for the good of the community; +and he suggests that the concept which thus enables us to interpret the +biological ground-plan of morals also enables us to frame a rational ideal +of the moral end. "As the social instincts," he says (Ibid. page 185.), +"both of man and the lower animals have no doubt been developed by nearly +the same steps, it would be advisable, if found practicable, to use the +same definition in both cases, and to take as the standard of morality, the +general good or welfare of the community, rather than the general +happiness." But the kind of community for the good of which the social +instincts of animals and primitive men were biologically developed may be +different from that which is the product of civilisation, as Darwin no +doubt realised. Darwin's contention was that conscience is a social +instinct and has been evolved because it is useful to the tribe in the +struggle for existence against other tribes. On the other hand, J.S. Mill +urged that the moral feelings are not innate but acquired, and Bain held +the same view, believing that the moral sense is acquired by each +individual during his life-time. Darwin, who notes (Ibid. page 150 +(footnote).) their opinion with his usual candour, adds that "on the +general theory of evolution this is at least extremely improbable. It is +impossible to enter into the question here: much turns on the exact +connotation of the terms "conscience" and "moral sense," and on the meaning +we attach to the statement that the moral sense is fundamentally identical +with the social instincts. + +Presumably the majority of those who approach the subjects discussed in the +third, fourth and fifth chapters of "The Descent of Man" in the full +conviction that mental phenomena, not less than organic phenomena, have a +natural genesis, would, without hesitation, admit that the intellectual and +moral systems of civilised man are ideal constructions, the products of +conceptual thought, and that as such they are, in their developed form, +acquired. The moral sentiments are the emotional analogues of highly +developed concepts. This does not however imply that they are outside the +range of natural history treatment. Even though it may be desirable to +differentiate the moral conduct of men from the social behaviour of animals +(to which some such term as "pre-moral" or "quasi-moral" may be applied), +still the fact remains that, as Darwin showed, there is abundant evidence +of the occurrence of such social behaviour--social behaviour which, even +granted that it is in large part intelligently acquired, and is itself so +far a product of educability, is of survival value. It makes for that +integration without which no social group could hold together and escape +elimination. Furthermore, even if we grant that such behaviour is +intelligently acquired, that is to say arises through the modification of +hereditary instincts and emotions, the fact remains that only through these +instinctive and emotional data is afforded the primary tissue of the +experience which is susceptible of such modification. + +Darwin sought to show, and succeeded in showing, that for the intellectual +and moral life there are instinctive foundations which a biological +treatment alone can disclose. It is true that he did not in all cases +analytically distinguish the foundations from the superstructure. Even to- +day we are scarcely in a position to do so adequately. But his treatment +was of great value in giving an impetus to further research. This value +indeed can scarcely be overestimated. And when the natural history of the +mental operations shall have been written, the cardinal fact will stand +forth, that the instinctive and emotional foundations are the outcome of +biological evolution and have been ingrained in the race through natural +selection. We shall more clearly realise that educability itself is a +product of natural selection, though the specific results acquired through +cerebral modifications are not transmitted through heredity. It will, +perhaps, also be realised that the instinctive foundations of social +behaviour are, for us, somewhat out of date and have undergone but little +change throughout the progress of civilisation, because natural selection +has long since ceased to be the dominant factor in human progress. The +history of human progress has been mainly the history of man's higher +educability, the products of which he has projected on to his environment. +This educability remains on the average what it was a dozen generations +ago; but the thought-woven tapestry of his surroundings is refashioned and +improved by each succeeding generation. Few men have in greater measure +enriched the thought-environment with which it is the aim of education to +bring educable human beings into vital contact, than has Charles Darwin. +His special field of work was the wide province of biology; but he did much +to help us realise that mental factors have contributed to organic +evolution and that in man, the highest product of Evolution, they have +reached a position of unquestioned supremacy. + + +XXII. THE INFLUENCE OF THE CONCEPTION OF EVOLUTION ON MODERN PHILOSOPHY. + +By H. HOFFDING. +Professor of Philosophy in the University of Copenhagen. + +I. + +It is difficult to draw a sharp line between philosophy and natural +science. The naturalist who introduces a new principle, or demonstrates a +fact which throws a new light on existence, not only renders an important +service to philosophy but is himself a philosopher in the broader sense of +the word. The aim of philosophy in the stricter sense is to attain points +of view from which the fundamental phenomena and the principles of the +special sciences can be seen in their relative importance and connection. +But philosophy in this stricter sense has always been influenced by +philosophy in the broader sense. Greek philosophy came under the influence +of logic and mathematics, modern philosophy under the influence of natural +science. The name of Charles Darwin stands with those of Galileo, Newton, +and Robert Mayer--names which denote new problems and great alterations in +our conception of the universe. + +First of all we must lay stress on Darwin's own personality. His deep love +of truth, his indefatigable inquiry, his wide horizon, and his steady self- +criticism make him a scientific model, even if his results and theories +should eventually come to possess mainly an historical interest. In the +intellectual domain the primary object is to reach high summits from which +wide surveys are possible, to reach them toiling honestly upwards by way of +experience, and then not to turn dizzy when a summit is gained. Darwinians +have sometimes turned dizzy, but Darwin never. He saw from the first the +great importance of his hypothesis, not only because of its solution of the +old problem as to the value of the concept of species, not only because of +the grand picture of natural evolution which it unrolls, but also because +of the life and inspiration its method would impart to the study of +comparative anatomy, of instinct and of heredity, and finally because of +the influence it would exert on the whole conception of existence. He +wrote in his note-book in the year 1837: "My theory would give zest to +recent and fossil comparative anatomy; it would lead to the study of +instinct, heredity, and mind-heredity, whole (of) metaphysics." ("Life and +Letters of Charles Darwin", Vol. I. page 8.) + +We can distinguish four main points in which Darwin's investigations +possess philosophical importance. + +The evolution hypothesis is much older than Darwin; it is, indeed, one of +the oldest guessings of human thought. In the eighteenth century it was +put forward by Diderot and Lamettrie and suggested by Kant (1786). As we +shall see later, it was held also by several philosophers in the first half +of the nineteenth century. In his preface to "The Origin of Species", +Darwin mentions the naturalists who were his forerunners. But he has set +forth the hypothesis of evolution in so energetic and thorough a manner +that it perforce attracts the attention of all thoughtful men in a much +higher degree than it did before the publication of the "Origin". + +And further, the importance of his teaching rests on the fact that he, much +more than his predecessors, even than Lamarck, sought a foundation for his +hypothesis in definite facts. Modern science began by demanding--with +Kepler and Newton--evidence of verae causae; this demand Darwin +industriously set himself to satisfy--hence the wealth of material which he +collected by his observations and his experiments. He not only revived an +old hypothesis, but he saw the necessity of verifying it by facts. Whether +the special cause on which he founded the explanation of the origin of +species--Natural Selection--is sufficient, is now a subject of discussion. +He himself had some doubt in regard to this question, and the criticisms +which are directed against his hypothesis hit Darwinism rather than Darwin. +In his indefatigable search for empirical evidence he is a model even for +his antagonists: he has compelled them to approach the problems of life +along other lines than those which were formerly followed. + +Whether the special cause to which Darwin appealed is sufficient or not, at +least to it is probably due the greater part of the influence which he has +exerted on the general trend of thought. "Struggle for existence" and +"natural selection" are principles which have been applied, more or less, +in every department of thought. Recent research, it is true, has +discovered greater empirical discontinuity--leaps, "mutations"--whereas +Darwin believed in the importance of small variations slowly accumulated. +It has also been shown by the experimental method, which in recent +biological work has succeeded Darwin's more historical method, that types +once constituted possess great permanence, the fluctuations being +restricted within clearly defined boundaries. The problem has become more +precise, both as to variation and as to heredity. The inner conditions of +life have in both respects shown a greater independence than Darwin had +supposed in his theory, though he always admitted that the cause of +variation was to him a great enigma, "a most perplexing problem," and that +the struggle for life could only occur where variation existed. But, at +any rate, it was of the greatest importance that Darwin gave a living +impression of the struggle for life which is everywhere going on, and to +which even the highest forms of existence must be amenable. The +philosophical importance of these ideas does not stand or fall with the +answer to the question, whether natural selection is a sufficient +explanation of the origin of species or not: it has an independent, +positive value for everyone who will observe life and reality with an +unbiassed mind. + +In accentuating the struggle for life Darwin stands as a characteristically +English thinker: he continues a train of ideas which Hobbes and Malthus +had already begun. Moreover in his critical views as to the conception of +species he had English forerunners; in the middle ages Occam and Duns +Scotus, in the eighteenth century Berkeley and Hume. In his moral +philosophy, as we shall see later, he is an adherent of the school which is +represented by Hutcheson, Hume and Adam Smith. Because he is no +philosopher in the stricter sense of the term, it is of great interest to +see that his attitude of mind is that of the great thinkers of his nation. + +In considering Darwin's influence on philosophy we will begin with an +examination of the attitude of philosophy to the conception of evolution at +the time when "The Origin of Species" appeared. We will then examine the +effects which the theory of evolution, and especially the idea of the +struggle for life, has had, and naturally must have, on the discussion of +philosophical problems. + +II. + +When "The Origin of Species" appeared fifty years ago Romantic speculation, +Schelling's and Hegel's philosophy, still reigned on the continent, while +in England Positivism, the philosophy of Comte and Stuart Mill, represented +the most important trend of thought. German speculation had much to say on +evolution, it even pretended to be a philosophy of evolution. But then the +word "evolution" was to be taken in an ideal, not in a real, sense. To +speculative thought the forms and types of nature formed a system of ideas, +within which any form could lead us by continuous transitions to any other. +It was a classificatory system which was regarded as a divine world of +thought or images, within which metamorphoses could go on--a condition +comparable with that in the mind of the poet when one image follows another +with imperceptible changes. Goethe's ideas of evolution, as expressed in +his "Metamorphosen der Pflanzen und der Thiere", belong to this category; +it is, therefore, incorrect to call him a forerunner of Darwin. Schelling +and Hegel held the same idea; Hegel expressly rejected the conception of a +real evolution in time as coarse and materialistic. "Nature," he says, "is +to be considered as a SYSTEM OF STAGES, the one necessarily arising from +the other, and being the nearest truth of that from which it proceeds; but +not in such a way that the one is NATURALLY generated by the other; on the +contrary (their connection lies) in the inner idea which is the ground of +nature. The METAMORPHOSIS can be ascribed only to the notion as such, +because it alone is evolution...It has been a clumsy idea in the older as +well as in the newer philosophy of nature, to regard the transformation and +the transition from one natural form and sphere to a higher as an outward +and actual production." ("Encyclopaedie der philosophischen +Wissenschaften" (4th edition), Berlin, 1845, paragraph 249.) + +The only one of the philosophers of Romanticism who believed in a real, +historical evolution, a real production of new species, was Oken. +("Lehrbuch der Naturphilosophie", Jena, 1809.) Danish philosophers, such +as Treschow (1812) and Sibbern (1846), have also broached the idea of an +historical evolution of all living beings from the lowest to the highest. +Schopenhauer's philosophy has a more realistic character than that of +Schelling's and Hegel's, his diametrical opposites, though he also belongs +to the romantic school of thought. His philosophical and psychological +views were greatly influenced by French naturalists and philosophers, +especially by Cabanis and Lamarck. He praises the "ever memorable +Lamarck," because he laid so much stress on the "will to live." But he +repudiates as a "wonderful error" the idea that the organs of animals +should have reached their present perfection through a development in time, +during the course of innumerable generations. It was, he said, a +consequence of the low standard of contemporary French philosophy, that +Lamarck came to the idea of the construction of living beings in time +through succession! ("Ueber den Willen in der Natur" (2nd edition), +Frankfurt a. M., 1854, pages 41-43.) + +The positivistic stream of thought was not more in favour of a real +evolution than was the Romantic school. Its aim was to adhere to positive +facts: it looked with suspicion on far-reaching speculation. Comte laid +great stress on the discontinuity found between the different kingdoms of +nature, as well as within each single kingdom. As he regarded as +unscientific every attempt to reduce the number of physical forces, so he +rejected entirely the hypothesis of Lamarck concerning the evolution of +species; the idea of species would in his eyes absolutely lose its +importance if a transition from species to species under the influence of +conditions of life were admitted. His disciples (Littre, Robin) continued +to direct against Darwin the polemics which their master had employed +against Lamarck. Stuart Mill, who, in the theory of knowledge, represented +the empirical or positivistic movement in philosophy--like his English +forerunners from Locke to Hume--founded his theory of knowledge and morals +on the experience of the single individual. He sympathised with the theory +of the original likeness of all individuals and derived their differences, +on which he practically and theoretically laid much stress, from the +influence both of experience and education, and, generally, of physical and +social causes. He admitted an individual evolution, and, in the human +species, an evolution based on social progress; but no physiological +evolution of species. He was afraid that the hypothesis of heredity would +carry us back to the old theory of "innate" ideas. + +Darwin was more empirical than Comte and Mill; experience disclosed to him +a deeper continuity than they could find; closer than before the nature and +fate of the single individual were shown to be interwoven in the great web +binding the life of the species with nature as a whole. And the continuity +which so many idealistic philosophers could find only in the world of +thought, he showed to be present in the world of reality. + +III. + +Darwin's energetic renewal of the old idea of evolution had its chief +importance in strengthening the conviction of this real continuity in the +world, of continuity in the series of form and events. It was a great +support for all those who were prepared to base their conception of life on +scientific grounds. Together with the recently discovered law of the +conservation of energy, it helped to produce the great realistic movement +which characterises the last third of the nineteenth century. After the +decline of the Romantic movement people wished to have firmer ground under +their feet and reality now asserted itself in a more emphatic manner than +in the period of Romanticism. It was easy for Hegel to proclaim that "the +real" was "the rational," and that "the rational" was "the real": reality +itself existed for him only in the interpretation of ideal reason, and if +there was anything which could not be merged in the higher unity of +thought, then it was only an example of the "impotence of nature to hold to +the idea." But now concepts are to be founded on nature and not on any +system of categories too confidently deduced a priori. The new devotion to +nature had its recompense in itself, because the new points of view made us +see that nature could indeed "hold to ideas," though perhaps not to those +which we had cogitated beforehand. + +A most important question for philosophers to answer was whether the new +views were compatible with an idealistic conception of life and existence. +Some proclaimed that we have now no need of any philosophy beyond the +principles of the conservation of matter and energy and the principle of +natural evolution: existence should and could be definitely and completely +explained by the laws of material nature. But abler thinkers saw that the +thing was not so simple. They were prepared to give the new views their +just place and to examine what alterations the old views must undergo in +order to be brought into harmony with the new data. + +The realistic character of Darwin's theory was shown not only in the idea +of natural continuity, but also, and not least, in the idea of the cause +whereby organic life advances step by step. This idea--the idea of the +struggle for life--implied that nothing could persist, if it had no power +to maintain itself under the given conditions. Inner value alone does not +decide. Idealism was here put to its hardest trial. In continuous +evolution it could perhaps still find an analogy to the inner evolution of +ideas in the mind; but in the demand for power in order to struggle with +outward conditions Realism seemed to announce itself in its most brutal +form. Every form of Idealism had to ask itself seriously how it was going +to "struggle for life" with this new Realism. + +We will now give a short account of the position which leading thinkers in +different countries have taken up in regard to this question. + +I. Herbert Spencer was the philosopher whose mind was best prepared by his +own previous thinking to admit the theory of Darwin to a place in his +conception of the world. His criticism of the arguments which had been put +forward against the hypothesis of Lamarck, showed that Spencer, as a young +man, was an adherent to the evolution idea. In his "Social Statics" (1850) +he applied this idea to human life and moral civilisation. In 1852 he +wrote an essay on "The Development Hypothesis", in which he definitely +stated his belief that the differentiation of species, like the +differentiation within a single organism, was the result of development. +In the first edition of his "Psychology" (1855) he took a step which put +him in opposition to the older English school (from Locke to Mill): he +acknowledged "innate ideas" so far as to admit the tendency of acquired +habits to be inherited in the course of generations, so that the nature and +functions of the individual are only to be understood through its +connection with the life of the species. In 1857, in his essay on +"Progress", he propounded the law of differentiation as a general law of +evolution, verified by examples from all regions of experience, the +evolution of species being only one of these examples. On the effect which +the appearance of "The Origin of Species" had on his mind he writes in his +"Autobiography": "Up to that time...I held that the sole cause of organic +evolution is the inheritance of functionally-produced modifications. The +"Origin of Species" made it clear to me that I was wrong, and that the +larger part of the facts cannot be due to any such cause...To have the +theory of organic evolution justified was of course to get further support +for that theory of evolution at large with which...all my conceptions were +bound up." (Spencer, "Autobiography", Vol. II. page 50, London, 1904.) +Instead of the metaphorical expression "natural selection," Spencer +introduced the term "survival of the fittest," which found favour with +Darwin as well as with Wallace. + +In working out his ideas of evolution, Spencer found that differentiation +was not the only form of evolution. In its simplest form evolution is +mainly a concentration, previously scattered elements being integrated and +losing independent movement. Differentiation is only forthcoming when +minor wholes arise within a greater whole. And the highest form of +evolution is reached when there is a harmony between concentration and +differentiation, a harmony which Spencer calls equilibration and which he +defines as a moving equilibrium. At the same time this definition enables +him to illustrate the expression "survival of the fittest." "Every living +organism exhibits such a moving equilibrium--a balanced set of functions +constituting its life; and the overthrow of this balanced set of functions +or moving equilibrium is what we call death. Some individuals in a species +are so constituted that their moving equilibria are less easily overthrown +than those of other individuals; and these are the fittest which survive, +or, in Mr Darwin's language, they are the select which nature preserves." +(Ibid. page 100.) Not only in the domain of organic life, but in all +domains, the summit of evolution is, according to Spencer, characterised by +such a harmony--by a moving equilibrium. + +Spencer's analysis of the concept of evolution, based on a great variety of +examples, has made this concept clearer and more definite than before. It +contains the three elements; integration, differentiation and +equilibration. It is true that a concept which is to be valid for all +domains of experience must have an abstract character, and between the +several domains there is, strictly speaking, only a relation of analogy. +So there is only analogy between psychical and physical evolution. But +this is no serious objection, because general concepts do not express more +than analogies between the phenomena which they represent. Spencer takes +his leading terms from the material world in defining evolution (in the +simplest form) as integration of matter and dissipation of movement; but as +he--not always quite consistently (Cf. my letter to him, 1876, now printed +in Duncan's "Life and Letters of Herbert Spencer", page 178, London, +1908.)--assumed a correspondence of mind and matter, he could very well +give these terms an indirect importance for psychical evolution. Spencer +has always, in my opinion with full right, repudiated the ascription of +materialism. He is no more a materialist than Spinoza. In his "Principles +of Psychology" (paragraph 63) he expressed himself very clearly: "Though +it seems easier to translate so-called matter into so-called spirit, than +to translate so-called spirit into so-called matter--which latter is indeed +wholly impossible--yet no translation can carry us beyond our symbols." +These words lead us naturally to a group of thinkers whose starting-point +was psychical evolution. But we have still one aspect of Spencer's +philosophy to mention. + +Spencer founded his "laws of evolution" on an inductive basis, but he was +convinced that they could be deduced from the law of the conservation of +energy. Such a deduction is, perhaps, possible for the more elementary +forms of evolution, integration and differentiation; but it is not possible +for the highest form, the equilibration, which is a harmony of integration +and differentiation. Spencer can no more deduce the necessity for the +eventual appearance of "moving equilibria" of harmonious totalities than +Hegel could guarantee the "higher unities" in which all contradictions +should be reconciled. In Spencer's hands the theory of evolution acquired +a more decidedly optimistic character than in Darwin's; but I shall deal +later with the relation of Darwin's hypothesis to the opposition of +optimism and pessimism. + +II. While the starting-point of Spencer was biological or cosmological, +psychical evolution being conceived as in analogy with physical, a group of +eminent thinkers--in Germany Wundt, in France Fouillee, in Italy Ardigo-- +took, each in his own manner, their starting-point in psychical evolution +as an original fact and as a type of all evolution, the hypothesis of +Darwin coming in as a corroboration and as a special example. They +maintain the continuity of evolution; they find this character most +prominent in psychical evolution, and this is for them a motive to demand a +corresponding continuity in the material, especially in the organic domain. + +To Wundt and Fouillee the concept of will is prominent. They see the type +of all evolution in the transformation of the life of will from blind +impulse to conscious choice; the theories of Lamarck and Darwin are used to +support the view that there is in nature a tendency to evolution in steady +reciprocity with external conditions. The struggle for life is here only a +secondary fact. Its apparent prominence is explained by the circumstance +that the influence of external conditions is easily made out, while inner +conditions can be verified only through their effects. For Ardigo the +evolution of thought was the starting-point and the type: in the evolution +of a scientific hypothesis we see a progress from the indefinite +(indistinto) to the definite (distinto), and this is a characteristic of +all evolution, as Ardigo has pointed out in a series of works. The +opposition between indistinto and distinto corresponds to Spencer's +opposition between homogeneity and heterogeneity. The hypothesis of the +origin of differences of species from more simple forms is a special +example of the general law of evolution. + +In the views of Wundt and Fouillee we find the fundamental idea of +idealism: psychical phenomena as expressions of the innermost nature of +existence. They differ from the older Idealism in the great stress which +they lay on evolution as a real, historical process which is going on +through steady conflict with external conditions. The Romantic dread of +reality is broken. It is beyond doubt that Darwin's emphasis on the +struggle for life as a necessary condition of evolution has been a very +important factor in carrying philosophy back to reality from the heaven of +pure ideas. The philosophy of Ardigo, on the other side, appears more as a +continuation and deepening of positivism, though the Italian thinker +arrived at his point of view independently of French-English positivism. +The idea of continuous evolution is here maintained in opposition to +Comte's and Mill's philosophy of discontinuity. From Wundt and Fouillee +Ardigo differs in conceiving psychical evolution not as an immediate +revelation of the innermost nature of existence, but only as a single, +though the most accessible example, of evolution. + +III. To the French philosophers Boutroux and Bergson, evolution proper is +continuous and qualitative, while outer experience and physical science +give us fragments only, sporadic processes and mechanical combinations. To +Bergson, in his recent work "L'Evolution Creatrice", evolution consists in +an elan de vie which to our fragmentary observation and analytic reflexion +appears as broken into a manifold of elements and processes. The concept +of matter in its scientific form is the result of this breaking asunder, +essential for all scientific reflexion. In these conceptions the strongest +opposition between inner and outer conditions of evolution is expressed: +in the domain of internal conditions spontaneous development of qualitative +forms--in the domain of external conditions discontinuity and mechanical +combination. + +We see, then, that the theory of evolution has influenced philosophy in a +variety of forms. It has made idealistic thinkers revise their relation to +the real world; it has led positivistic thinkers to find a closer +connection between the facts on which they based their views; it has made +us all open our eyes for new possibilities to arise through the prima facie +inexplicable "spontaneous" variations which are the condition of all +evolution. This last point is one of peculiar interest. Deeper than +speculative philosophy and mechanical science saw in the days of their +triumph, we catch sight of new streams, whose sources and laws we have +still to discover. Most sharply does this appear in the theory of +mutation, which is only a stronger accentuation of a main point in +Darwinism. It is interesting to see that an analogous problem comes into +the foreground in physics through the discovery of radioactive phenomena, +and in psychology through the assumption of psychical new formations (as +held by Boutroux, William James and Bergson). From this side, Darwin's +ideas, as well as the analogous ideas in other domains, incite us to +renewed examination of our first principles, their rationality and their +value. On the other hand, his theory of the struggle for existence +challenges us to examine the conditions and discuss the outlook as to the +persistence of human life and society and of the values that belong to +them. It is not enough to hope (or fear?) the rising of new forms; we have +also to investigate the possibility of upholding the forms and ideals which +have hitherto been the bases of human life. Darwin has here given his age +the most earnest and most impressive lesson. This side of Darwin's theory +is of peculiar interest to some special philosophical problems to which I +now pass. + +IV. + +Among philosophical problems the problem of knowledge has in the last +century occupied a foremost place. It is natural, then, to ask how Darwin +and the hypothesis whose most eminent representative he is, stand to this +problem. + +Darwin started an hypothesis. But every hypothesis is won by inference +from certain presuppositions, and every inference is based on the general +principles of human thought. The evolution hypothesis presupposes, then, +human thought and its principles. And not only the abstract logical +principles are thus presupposed. The evolution hypothesis purports to be +not only a formal arrangement of phenomena, but to express also the law of +a real process. It supposes, then, that the real data--all that in our +knowledge which we do not produce ourselves, but which we in the main +simply receive--are subjected to laws which are at least analogous to the +logical relations of our thoughts; in other words, it assumes the validity +of the principle of causality. If organic species could arise without +cause there would be no use in framing hypotheses. Only if we assume the +principle of causality, is there a problem to solve. + +Though Darwinism has had a great influence on philosophy considered as a +striving after a scientific view of the world, yet here is a point of view +--the epistemological--where philosophy is not only independent but reaches +beyond any result of natural science. Perhaps it will be said: the powers +and functions of organic beings only persist (perhaps also only arise) when +they correspond sufficiently to the conditions under which the struggle of +life is to go on. Human thought itself is, then, a variation (or a +mutation) which has been able to persist and to survive. Is not, then, the +problem of knowledge solved by the evolution hypothesis? Spencer had given +an affirmative answer to this question before the appearance of "The Origin +of Species". For the individual, he said, there is an a priori, original, +basis (or Anlage) for all mental life; but in the species all powers have +developed in reciprocity with external conditions. Knowledge is here +considered from the practical point of view, as a weapon in the struggle +for life, as an "organon" which has been continuously in use for +generations. In recent years the economic or pragmatic epistemology, as +developed by Avenarius and Mach in Germany, and by James in America, points +in the same direction. Science, it is said, only maintains those +principles and presuppositions which are necessary to the simplest and +clearest orientation in the world of experience. All assumptions which +cannot be applied to experience and to practical work, will successively be +eliminated. + +In these views a striking and important application is made of the idea of +struggle for life to the development of human thought. Thought must, as +all other things in the world, struggle for life. But this whole +consideration belongs to psychology, not to the theory of knowledge +(epistemology), which is concerned only with the validity of knowledge, not +with its historical origin. Every hypothesis to explain the origin of +knowledge must submit to cross-examination by the theory of knowledge, +because it works with the fundamental forms and principles of human +thought. We cannot go further back than these forms and principles, which +it is the aim of epistemology to ascertain and for which no further reason +can be given. (The present writer, many years ago, in his "Psychology" +(Copenhagen, 1882; English translation London, 1891), criticised the +evolutionistic treatment of the problem of knowledge from the Kantian point +of view.) + +But there is another side of the problem which is, perhaps, of more +importance and which epistemology generally overlooks. If new variations +can arise, not only in organic but perhaps also in inorganic nature, new +tasks are placed before the human mind. The question is, then, if it has +forms in which there is room for the new matter? We are here touching a +possibility which the great master of epistemology did not bring to light. +Kant supposed confidently that no other matter of knowledge could stream +forth from the dark source which he called "the thing-in-itself," than such +as could be synthesised in our existing forms of knowledge. He mentions +the possibility of other forms than the human, and warns us against the +dogmatic assumption that the human conception of existence should be +absolutely adequate. But he seems to be quite sure that the thing-in- +itself works constantly, and consequently always gives us only what our +powers can master. This assumption was a consequence of Kant's +rationalistic tendency, but one for which no warrant can be given. +Evolutionism and systematism are opposing tendencies which can never be +absolutely harmonised one with the other. Evolution may at any time break +some form which the system-monger regards as finally established. Darwin +himself felt a great difference in looking at variation as an evolutionist +and as a systematist. When he was working at his evolution theory, he was +very glad to find variations; but they were a hindrance to him when he +worked as a systematist, in preparing his work on Cirripedia. He says in a +letter: "I had thought the same parts of the same species more resemble +(than they do anyhow in Cirripedia) objects cast in the same mould. +Systematic work would be easy were it not for this confounded variation, +which, however, is pleasant to me as a speculatist, though odious to me as +a systematist." ("Life and Letters", Vol. II. page 37.) He could indeed +be angry with variations even as an evolutionist; but then only because he +could not explain them, not because he could not classify them. "If, as I +must think, external conditions produce little DIRECT effect, what the +devil determines each particular variation?" (Ibid. page 232.) What +Darwin experienced in his particular domain holds good of all knowledge. +All knowledge is systematic, in so far as it strives to put phenomena in +quite definite relations, one to another. But the systematisation can +never be complete. And here Darwin has contributed much to widen the world +for us. He has shown us forces and tendencies in nature which make +absolute systems impossible, at the same time that they give us new objects +and problems. There is still a place for what Lessing called "the +unceasing striving after truth," while "absolute truth" (in the sense of a +closed system) is unattainable so long as life and experience are going on. + +There is here a special remark to be made. As we have seen above, recent +research has shown that natural selection or struggle for life is no +explanation of variations. Hugo de Vries distinguishes between partial and +embryonal variations, or between variations and mutations, only the last- +named being heritable, and therefore of importance for the origin of new +species. But the existence of variations is not only of interest for the +problem of the origin of species; it has also a more general interest. An +individual does not lose its importance for knowledge, because its +qualities are not heritable. On the contrary, in higher beings at least, +individual peculiarities will become more and more independent objects of +interest. Knowledge takes account of the biographies not only of species, +but also of individuals: it seeks to find the law of development of the +single individual. (The new science of Ecology occupies an intermediate +position between the biography of species and the biography of individuals. +Compare "Congress of Arts and Science", St Louis, Vol. V. 1906 (the Reports +of Drude and Robinson) and the work of my colleague E. Warming.) As +Leibniz said long ago, individuality consists in the law of the changes of +a being. "La loi du changement fait l'individualite de chaque substance." +Here is a world which is almost new for science, which till now has mainly +occupied itself with general laws and forms. But these are ultimately only +means to understand the individual phenomena, in whose nature and history a +manifold of laws and forms always cooperate. The importance of this remark +will appear in the sequel. + +V. + +To many people the Darwinian theory of natural selection or struggle for +existence seemed to change the whole conception of life, and particularly +all the conditions on which the validity of ethical ideas depends. If only +that has persistence which can be adapted to a given condition, what will +then be the fate of our ideals, of our standards of good and evil? Blind +force seems to reign, and the only thing that counts seems to be the most +heedless use of power. Darwinism, it was said, has proclaimed brutality. +No other difference seems permanent save that between the sound, powerful +and happy on the one side, the sick, feeble and unhappy on the other; and +every attempt to alleviate this difference seems to lead to general +enervation. Some of those who interpreted Darwinism in this manner felt an +aesthetic delight in contemplating the heedlessness and energy of the great +struggle for existence and anticipated the realisation of a higher human +type as the outcome of it: so Nietzsche and his followers. Others +recognising the same consequences in Darwinism regarded these as one of the +strongest objections against it; so Duhring and Kropotkin (in his earlier +works). + +This interpretation of Darwinism was frequent in the interval between the +two main works of Darwin--"The Origin of Species" and "The Descent of Man". +But even during this interval it was evident to an attentive reader that +Darwin himself did not found his standard of good and evil on the features +of the life of nature he had emphasised so strongly. He did not justify +the ways along which nature reached its ends; he only pointed them out. +The "real" was not to him, as to Hegel, one with the "rational." Darwin +has, indeed, by his whole conception of nature, rendered a great service to +ethics in making the difference between the life of nature and the ethical +life appear in so strong a light. The ethical problem could now be stated +in a sharper form than before. But this was not the first time that the +idea of the struggle for life was put in relation to the ethical problem. +In the seventeenth century Thomas Hobbes gave the first impulse to the +whole modern discussion of ethical principles in his theory of bellum +omnium contra omnes. Men, he taught, are in the state of nature enemies +one of another, and they live either in fright or in the glory of power. +But it was not the opinion of Hobbes that this made ethics impossible. On +the contrary, he found a standard for virtue and vice in the fact that some +qualities and actions have a tendency to bring us out of the state of war +and to secure peace, while other qualities have a contrary tendency. In +the eighteenth century even Immanuel Kant's ideal ethics had--so far as can +be seen--a similar origin. Shortly before the foundation of his definitive +ethics, Kant wrote his "Idee zu einer allgemeinen Weltgeschichte" (1784), +where--in a way which reminds us of Hobbes, and is prophetic of Darwin--he +describes the forward-driving power of struggle in the human world. It is +here as with the struggle of the trees for light and air, through which +they compete with one another in height. Anxiety about war can only be +allayed by an ordinance which gives everyone his full liberty under +acknowledgment of the equal liberty of others. And such ordinance and +acknowledgment are also attributes of the content of the moral law, as Kant +proclaimed it in the year after the publication of his essay (1785) (Cf. +my "History of Modern Philosophy" (English translation London, 1900), I. +pages 76-79.) Kant really came to his ethics by the way of evolution, +though he afterwards disavowed it. Similarly the same line of thought may +be traced in Hegel though it has been disguised in the form of speculative +dialectics. ("Herrschaft und Knechtschaft", "Phanomenologie des Geistes", +IV. A., Leiden, 1907.) And in Schopenhauer's theory of the blind will to +live and its abrogation by the ethical feeling, which is founded on +universal sympathy, we have a more individualistic form of the same idea. + +It was, then, not entirely a foreign point of view which Darwin introduced +into ethical thought, even if we take no account of the poetical character +of the word "struggle" and of the more direct adaptation, through the use +and non-use of power, which Darwin also emphasised. In "The Descent of +Man" he has devoted a special chapter ("The Descent of Man", Vol. I. Ch. +iii.) to a discussion of the origin of the ethical consciousness. The +characteristic expression of this consciousness he found, just as Kant did, +in the idea of "ought"; it was the origin of this new idea which should be +explained. His hypothesis was that the ethical "ought" has its origin in +the social and parental instincts, which, as well as other instincts (e.g. +the instinct of self-preservation), lie deeper than pleasure and pain. In +many species, not least in the human species, these instincts are fostered +by natural selection; and when the powers of memory and comparison are +developed, so that single acts can be valued according to the claims of the +deep social instinct, then consciousness of duty and remorse are possible. +Blind instinct has developed to conscious ethical will. + +As already stated, Darwin, as a moral philosopher belongs to the school +that was founded by Shaftesbury, and was afterwards represented by +Hutcheson, Hume, Adam Smith, Comte and Spencer. His merit is, first, that +he has given this tendency of thought a biological foundation, and that he +has stamped on it a doughty character in showing that ethical ideas and +sentiments, rightly conceived, are forces which are at work in the struggle +for life. + +There are still many questions to solve. Not only does the ethical +development within the human species contain features still unexplained +(The works of Westermarck and Hobhouse throw new light on many of these +features.); but we are confronted by the great problem whether after all a +genetic historical theory can be of decisive importance here. To every +consequent ethical consciousness there is a standard of value, a primordial +value which determines the single ethical judgments as their last +presupposition, and the "rightness" of this basis, the "value" of this +value can as little be discussed as the "rationality" of our logical +principles. There is here revealed a possibility of ethical scepticism +which evolutionistic ethics (as well as intuitive or rationalistic ethics) +has overlooked. No demonstration can show that the results of the ethical +development are definitive and universal. We meet here again with the +important opposition of systematisation and evolution. There will, I +think, always be an open question here, though comparative ethics, of which +we have so far only the first attempts, can do much to throw light on it. + +It would carry us too far to discuss all the philosophical works on ethics, +which have been influenced directly or indirectly by evolutionism. I may, +however, here refer to the book of C.M. Williams, "A Review of the Systems +of Ethics founded on the Theory of Evolution" (New York and London, 1893.), +in which, besides Darwin, the following authors are reviewed: Wallace, +Haeckel, Spencer, Fiske, Rolph, Barratt, Stephen, Carneri, Hoffding, +Gizycki, Alexander, Ree. As works which criticise evolutionistic ethics +from an intuitive point of view and in an instructive way, may be cited: +Guyau "La morale anglaise contemporaine" (Paris, 1879.), and Sorley, +"Ethics of Naturalism". I will only mention some interesting contributions +to ethical discussion which can be found in Darwinism besides the idea of +struggle for life. + +The attention which Darwin has directed to variations has opened our eyes +to the differences in human nature as well as in nature generally. There +is here a fact of great importance for ethical thought, no matter from what +ultimate premiss it starts. Only from a very abstract point of view can +different individuals be treated in the same manner. The most eminent +ethical thinkers, men such as Jeremy Bentham and Immanuel Kant, who +discussed ethical questions from very opposite standpoints, agreed in +regarding all men as equal in respect of ethical endowment. In regard to +Bentham, Leslie Stephen remarks: "He is determined to be thoroughly +empirical, to take men as he found them. But his utilitarianism supposed +that men's views of happiness and utility were uniform and clear, and that +all that was wanted was to show them the means by which their ends could be +reached." ("English literature and society in the eighteenth century", +London, 1904, page 187.) And Kant supposed that every man would find the +"categorical imperative" in his consciousness, when he came to sober +reflexion, and that all would have the same qualifications to follow it. +But if continual variations, great or small, are going on in human nature, +it is the duty of ethics to make allowance for them, both in making claims, +and in valuing what is done. A new set of ethical problems have their +origin here. (Cf. my paper, "The law of relativity in Ethics," +"International Journal of Ethics", Vol. I. 1891, pages 37-62.) It is an +interesting fact that Stuart Mill's book "On Liberty" appeared in the same +year as "The Origin of Species". Though Mill agreed with Bentham about the +original equality of all men's endowments, he regarded individual +differences as a necessary result of physical and social influences, and he +claimed that free play shall be allowed to differences of character so far +as is possible without injury to other men. It is a condition of +individual and social progress that a man's mode of action should be +determined by his own character and not by tradition and custom, nor by +abstract rules. This view was to be corroborated by the theory of Darwin. + +But here we have reached a point of view from which the criticism, which in +recent years has often been directed against Darwin--that small variations +are of no importance in the struggle for life--is of no weight. From an +ethical standpoint, and particularly from the ethical standpoint of Darwin +himself, it is a duty to foster individual differences that can be +valuable, even though they can neither be of service for physical +preservation nor be physically inherited. The distinction between +variation and mutation is here without importance. It is quite natural +that biologists should be particularly interested in such variations as can +be inherited and produce new species. But in the human world there is not +only a physical, but also a mental and social heredity. When an ideal +human character has taken form, then there is shaped a type, which through +imitation and influence can become an important factor in subsequent +development, even if it cannot form a species in the biological sense of +the word. Spiritually strong men often succumb in the physical struggle +for life; but they can nevertheless be victorious through the typical +influence they exert, perhaps on very distant generations, if the +remembrance of them is kept alive, be it in legendary or in historical +form. Their very failure can show that a type has taken form which is +maintained at all risks, a standard of life which is adhered to in spite of +the strongest opposition. The question "to be or not to be" can be put +from very different levels of being: it has too often been considered a +consequence of Darwinism that this question is only to be put from the +lowest level. When a stage is reached, where ideal (ethical, intellectual, +aesthetic) interests are concerned, the struggle for life is a struggle for +the preservation of this stage. The giving up of a higher standard of life +is a sort of death; for there is not only a physical, there is also a +spiritual, death. + +VI. + +The Socratic character of Darwin's mind appears in his wariness in drawing +the last consequences of his doctrine, in contrast both with the audacious +theories of so many of his followers and with the consequences which his +antagonists were busy in drawing. Though he, as we have seen, saw from the +beginning that his hypothesis would occasion "a whole of metaphysics," he +was himself very reserved as to the ultimate questions, and his answers to +such questions were extorted from him. + +As to the question of optimism and pessimism, Darwin held that though pain +and suffering were very often the ways by which animals were led to pursue +that course of action which is most beneficial to the species, yet +pleasurable feelings were the most habitual guides. "We see this in the +pleasure from exertion, even occasionally from great exertion of the body +or mind, in the pleasure of our daily meals, and especially in the pleasure +derived from sociability, and from loving our families." But there was to +him so much suffering in the world that it was a strong argument against +the existence of an intelligent First Cause. ("Life and Letters" Vol. I. +page 310.) + +It seems to me that Darwin was not so clear on another question, that of +the relation between improvement and adaptation. He wrote to Lyell: "When +you contrast natural selection and 'improvement,' you seem always to +overlook...that every step in the natural selection of each species implies +improvement in that species IN RELATION TO ITS CONDITION OF +LIFE...Improvement implies, I suppose, EACH FORM OBTAINING MANY PARTS OR +ORGANS, all excellently adapted for their functions." "All this," he adds, +"seems to me quite compatible with certain forms fitted for simple +conditions, remaining unaltered, or being degraded." (Ibid. Vol. II. page +177.) But the great question is, if the conditions of life will in the +long run favour "improvement" in the sense of differentiation (or harmony +of differentiation and integration). Many beings are best adapted to their +conditions of life if they have few organs and few necessities. Pessimism +would not only be the consequence, if suffering outweighed happiness, but +also if the most elementary forms of happiness were predominant, or if +there were a tendency to reduce the standard of life to the simplest +possible, the contentment of inertia or stable equilibrium. There are +animals which are very highly differentiated and active in their young +state, but later lose their complex organisation and concentrate themselves +on the one function of nutrition. In the human world analogies to this +sort of adaptation are not wanting. Young "idealists" very often end as +old "Philistines." Adaptation and progress are not the same. + +Another question of great importance in respect to human evolution is, +whether there will be always a possibility for the existence of an impulse +to progress, an impulse to make great claims on life, to be active and to +alter the conditions of life instead of adapting to them in a passive +manner. Many people do not develop because they have too few necessities, +and because they have no power to imagine other conditions of life than +those under which they live. In his remarks on "the pleasure from +exertion" Darwin has a point of contact with the practical idealism of +former times--with the ideas of Lessing and Goethe, of Condorcet and +Fichte. The continual striving which was the condition of salvation to +Faust's soul, is also the condition of salvation to mankind. There is a +holy fire which we ought to keep burning, if adaptation is really to be +improvement. If, as I have tried to show in my "Philosophy of Religion", +the innermost core of all religion is faith in the persistence of value in +the world, and if the highest values express themselves in the cry +"Excelsior!" then the capital point is, that this cry should always be +heard and followed. We have here a corollary of the theory of evolution in +its application to human life. + +Darwin declared himself an agnostic, not only because he could not +harmonise the large amount of suffering in the world with the idea of a God +as its first cause, but also because he "was aware that if we admit a first +cause, the mind still craves to know whence it came and how it arose." +("Life and Letters", Vol. I. page 306.) He saw, as Kant had seen before +him and expressed in his "Kritik der Urtheilskraft", that we cannot accept +either of the only two possibilities which we are able to conceive: chance +(or brute force) and design. Neither mechanism nor teleology can give an +absolute answer to ultimate questions. The universe, and especially the +organic life in it, can neither be explained as a mere combination of +absolute elements nor as the effect of a constructing thought. Darwin +concluded, as Kant, and before him Spinoza, that the oppositions and +distinctions which our experience presents, cannot safely be regarded as +valid for existence in itself. And, with Kant and Fichte, he found his +stronghold in the conviction that man has something to do, even if he +cannot solve all enigmas. "The safest conclusion seems to me that the +whole subject is beyond the scope of man's intellect; but man can do his +duty." (Ibid. page 307.) + +Is this the last word of human thought? Does not the possibility, that man +can do his duty, suppose that the conditions of life allow of continuous +ethical striving, so that there is a certain harmony between cosmic order +and human ideals? Darwin himself has shown how the consciousness of duty +can arise as a natural result of evolution. Moreover there are lines of +evolution which have their end in ethical idealism, in a kingdom of values, +which must struggle for life as all things in the world must do, but a +kingdom which has its firm foundation in reality. + + +XXIII. DARWINISM AND SOCIOLOGY. + +By C. BOUGLE. +Professor of Social Philosophy in the University of Toulouse and Deputy- +Professor at the Sorbonne, Paris. + +How has our conception of social phenomena, and of their history, been +affected by Darwin's conception of Nature and the laws of its +transformations? To what extent and in what particular respects have the +discoveries and hypotheses of the author of "The Origin of Species" aided +the efforts of those who have sought to construct a science of society? + +To such a question it is certainly not easy to give any brief or precise +answer. We find traces of Darwinism almost everywhere. Sociological +systems differing widely from each other have laid claim to its authority; +while, on the other hand, its influence has often made itself felt only in +combination with other influences. The Darwinian thread is worked into a +hundred patterns along with other threads. + +To deal with the problem, we must, it seems, first of all distinguish the +more general conclusions in regard to the evolution of living beings, which +are the outcome of Darwinism, from the particular explanations it offers of +the ways and means by which that evolution is effected. That is to say, we +must, as far as possible, estimate separately the influence of Darwin as an +evolutionist and Darwin as a selectionist. + +The nineteenth century, said Cournot, has witnessed a mighty effort to +"reintegrer l'homme dans la nature." From divers quarters there has been a +methodical reaction against the persistent dualism of the Cartesian +tradition, which was itself the unconscious heir of the Christian +tradition. Even the philosophy of the eighteenth century, materialistic as +were for the most part the tendencies of its leaders, seemed to revere man +as a being apart, concerning whom laws might be formulated a priori. To +bring him down from his pedestal there was needed the marked predominance +of positive researches wherein no account was taken of the "pride of man." +There can be no doubt that Darwin has done much to familiarise us with this +attitude. Take for instance the first part of "The Descent of Man": it is +an accumulation of typical facts, all tending to diminish the distance +between us and our brothers, the lower animals. One might say that the +naturalist had here taken as his motto, "Whosoever shall exalt himself +shall be abased; and he that shall humble himself shall be exalted." +Homologous structures, the survival in man of certain organs of animals, +the rudiments in the animal of certain human faculties, a multitude of +facts of this sort, led Darwin to the conclusion that there is no ground +for supposing that the "king of the universe" is exempt from universal +laws. Thus belief in the imperium in imperio has been, as it were, +whittled away by the progress of the naturalistic spirit, itself +continually strengthened by the conquests of the natural sciences. The +tendency may, indeed, drag the social sciences into overstrained analogies, +such, for instance, as the assimilation of societies to organisms. But it +will, at least, have had the merit of helping sociology to shake off the +pre-conception that the groups formed by men are artificial, and that +history is completely at the mercy of chance. Some years before the +appearance of "The Origin of Species", Auguste Comte had pointed out the +importance, as regards the unification of positive knowledge, of the +conviction that the social world, the last refuge of spiritualism, is +itself subject to determininism. It cannot be doubted that the movement of +thought which Darwin's discoveries promoted contributed to the spread of +this conviction, by breaking down the traditional barrier which cut man off +from Nature. + +But Nature, according to modern naturalists, is no immutable thing: it is +rather perpetual movement, continual progression. Their discoveries batter +a breach directly into the Aristotelian notion of species; they refuse to +see in the animal world a collection of immutable types, distinct from all +eternity, and corresponding, as Cuvier said, to so many particular thoughts +of the Creator. Darwin especially congratulated himself upon having been +able to deal this doctrine the coup de grace: immutability is, he says, +his chief enemy; and he is concerned to show--therein following up Lyell's +work--that everything in the organic world, as in the inorganic, is +explained by insensible but incessant transformations. "Nature makes no +leaps"--"Nature knows no gaps": these two dicta form, as it were, the two +landmarks between which Darwin's idea of transformation is worked out. +That is to say, the development of Darwinism is calculated to further the +application of the philosophy of Becoming to the study of human +institutions. + +The progress of the natural sciences thus brings unexpected reinforcements +to the revolution which the progress of historical discipline had begun. +The first attempt to constitute an actual science of social phenomena-- +that, namely, of the economists--had resulted in laws which were called +natural, and which were believed to be eternal and universal, valid for all +times and all places. But this perpetuality, brother, as Knies said, of +the immutability of the old zoology, did not long hold out against the ever +swelling tide of the historical movement. Knowledge of the transformations +that had taken place in language, of the early phases of the family, of +religion, of property, had all favoured the revival of the Heraclitean +view: panta rei. As to the categories of political economy, it was soon +to be recognised, as by Lassalle, that they too are only historical. The +philosophy of history, moreover, gave expression under various forms to the +same tendency. Hegel declares that "all that is real is rational," but at +the same time he shows that all that is real is ephemeral, and that for +history there is nothing fixed beneath the sun. It is this sense of +universal evolution that Darwin came with fresh authority to enlarge. It +was in the name of biological facts themselves that he taught us to see +only slow metamorphoses in the history of institutions, and to be always on +the outlook for survivals side by side with rudimentary forms. Anyone who +reads "Primitive Culture", by Tylor,--a writer closely connected with +Darwin--will be able to estimate the services which these cardinal ideas +were to render to the social sciences when the age of comparative research +had succeeded to that of a priori construction. + +Let us note, moreover, that the philosophy of Becoming in passing through +the Darwinian biology became, as it were, filtered: it got rid of those +traces of finalism, which, under different forms, it had preserved through +all the systems of German Romanticism. Even in Herbert Spencer, it has +been plausibly argued, one can detect something of that sort of mystic +confidence in forces spontaneously directing life, which forms the very +essence of those systems. But Darwin's observations were precisely +calculated to render such an hypothesis futile. At first people may have +failed to see this; and we call to mind the ponderous sarcasms of Flourens +when he objected to the theory of Natural Selection that it attributed to +nature a power of free choice. "Nature endowed with will! That was the +final error of last century; but the nineteenth no longer deals in +personifications." (P. Flourens, "Examen du Livre de M. Darwin sur +l'Origine des Especes", page 53, Paris, 1864. See also Huxley, "Criticisms +on the 'Origin of Species'", "Collected Essays", Vol. II, page 102, London, +1902.) In fact Darwin himself put his readers on their guard against the +metaphors he was obliged to use. The processes by which he explains the +survival of the fittest are far from affording any indication of the design +of some transcendent breeder. Nor, if we look closely, do they even imply +immanent effort in the animal; the sorting out can be brought about +mechanically, simply by the action of the environment. In this connection +Huxley could with good reason maintain that Darwin's originality consisted +in showing how harmonies which hitherto had been taken to imply the agency +of intelligence and will could be explained without any such intervention. +So, when later on, objective sociology declares that, even when social +phenomena are in question, all finalist preconceptions must be distrusted +if a science is to be constituted, it is to Darwin that its thanks are due; +he had long been clearing paths for it which lay well away from the old +familiar road trodden by so many theories of evolution. + +This anti-finalist doctrine, when fully worked out, was, moreover, +calculated to aid in the needful dissociation of two notions: that of +evolution and that of progress. In application to society these had long +been confounded; and, as a consequence, the general idea seemed to be that +only one type of evolution was here possible. Do we not detect such a view +in Comte's sociology, and perhaps even in Herbert Spencer's? Whoever, +indeed, assumes an end for evolution is naturally inclined to think that +only one road leads to that end. But those whose minds the Darwinian +theory has enlightened are aware that the transformations of living beings +depend primarily upon their conditions, and that it is these conditions +which are the agents of selection from among individual variations. Hence, +it immediately follows that transformations are not necessarily +improvements. Here, Darwin's thought hesitated. Logically his theory +proves, as Ray Lankester pointed out, that the struggle for existence may +have as its outcome degeneration as well as amelioration: evolution may be +regressive as well as progressive. Then, too--and this is especially to be +borne in mind--each species takes its good where it finds it, seeks its own +path and survives as best it can. Apply this notion to society and you +arrive at the theory of multilinear evolution. Divergencies will no longer +surprise you. You will be forewarned not to apply to all civilisations the +same measure of progress, and you will recognise that types of evolution +may differ just as social species themselves differ. Have we not here one +of the conceptions which mark off sociology proper from the old philosophy +of history? + +But if we are to estimate the influence of Darwinism upon sociological +conceptions, we must not dwell only upon the way in which Darwin impressed +the general notion of evolution upon the minds of thinkers. We must go +into details. We must consider the influence of the particular theories by +which he explained the mechanism of this evolution. The name of the author +of "The Origin of Species" has been especially attached, as everyone knows, +to the doctrines of "natural selection" and of "struggle for existence," +completed by the notion of "individual variation." These doctrines were +turned to account by very different schools of social philosophy. +Pessimistic and optimistic, aristocratic and democratic, individualistic +and socialistic systems were to war with each other for years by casting +scraps of Darwinism at each other's heads. + +It was the spectacle of human contrivance that suggested to Darwin his +conception of natural selection. It was in studying the methods of pigeon +breeders that he divined the processes by which nature, in the absence of +design, obtains analogous results in the differentiation of types. As soon +as the importance of artificial selection in the transformation of species +of animals was understood, reflection naturally turned to the human +species, and the question arose, How far do men observe, in connection with +themselves, those laws of which they make practical application in the case +of animals? Here we come upon one of the ideas which guided the researches +of Galton, Darwin's cousin. The author of "Inquiries into Human Faculty +and its Development" ("Inquiries into Human Faculty", pages 1, 2, 3 sq., +London, 1883.), has often expressed his surprise that, considering all the +precautions taken, for example, in the breeding of horses, none whatever +are taken in the breeding of the human species. It seems to be forgotten +that the species suffers when the "fittest" are not able to perpetuate +their type. Ritchie, in his "Darwinism and Politics" ("Darwinism and +Politics" pages 9, 22, London, 1889.) reminds us of Darwin's remark that +the institution of the peerage might be defended on the ground that peers, +owing to the prestige they enjoy, are enabled to select as wives "the most +beautiful and charming women out of the lower ranks." ("Life and Letters +of Charles Darwin", II. page 385.) But, says Galton, it is as often as not +"heiresses" that they pick out, and birth statistics seem to show that +these are either less robust or less fecund than others. The truth is that +considerations continue to preside over marriage which are entirely foreign +to the improvement of type, much as this is a condition of general +progress. Hence the importance of completing Odin's and De Candolle's +statistics which are designed to show how characters are incorporated in +organisms, how they are transmitted, how lost, and according to what law +eugenic elements depart from the mean or return to it. + +But thinkers do not always content themselves with undertaking merely the +minute researches which the idea of Selection suggests. They are eager to +defend this or that thesis. In the name of this idea certain social +anthropologists have recast the conception of the process of civilisation, +and have affirmed that Social Selection generally works against the trend +of Natural Selection. Vacher de Lapouge--following up an observation by +Broca on the point--enumerates the various institutions, or customs, such +as the celibacy of priests and military conscription, which cause +elimination or sterilisation of the bearers of certain superior qualities, +intellectual or physical. In a more general way he attacks the democratic +movement, a movement, as P. Bourget says, which is "anti-physical" and +contrary to the natural laws of progress; though it has been inspired "by +the dreams of that most visionary of all centuries, the eighteenth." (V. +de Lapouge, "Les Selections sociales", page 259, Paris, 1896.) The +"Equality" which levels down and mixes (justly condemned, he holds, by the +Comte de Gobineau), prevents the aristocracy of the blond dolichocephales +from holding the position and playing the part which, in the interests of +all, should belong to them. Otto Ammon, in his "Natural Selection in Man", +and in "The Social Order and its Natural Bases" ("Die naturliche Auslese +beim Menschen", Jena, 1893; "Die Gesellschaftsordnung und ihre naturlichen +Grundlagen". "Entwurf einer Sozialanthropologie", Jena, 1896.), defended +analogous doctrines in Germany; setting the curve representing frequency of +talent over against that of income, he attempted to show that all +democratic measures which aim at promoting the rise in the social scale of +the talented are useless, if not dangerous; that they only increase the +panmixia, to the great detriment of the species and of society. + +Among the aristocratic theories which Darwinism has thus inspired we must +reckon that of Nietzsche. It is well known that in order to complete his +philosophy he added biological studies to his philological; and more than +once in his remarks upon the "Wille zur Macht" he definitely alludes to +Darwin; though it must be confessed that it is generally in order to +proclaim the in sufficiency of the processes by which Darwin seeks to +explain the genesis of species. Nevertheless, Nietzsche's mind is +completely possessed by an ideal of Selection. He, too, has a horror of +panmixia. The naturalists' conception of "the fittest" is joined by him to +that of the "hero" of romance to furnish a basis for his doctrine of the +Superman. Let us hasten to add, moreover, that at the very moment when +support was being sought in the theory of Selection for the various forms +of the aristocratic doctrine, those same forms were being battered down on +another side by means of that very theory. Attention was drawn to the fact +that by virtue of the laws which Darwin himself had discovered isolation +leads to etiolation. There is a risk that the privilege which withdraws +the privileged elements of Society from competition will cause them to +degenerate. In fact, Jacoby in his "Studies in Selection, in connexion +with Heredity in Man", ("Etudes sur la Selection dans ses rapports avec +l'heredite chez l'homme", Paris, page 481, 1881.), concludes that +"sterility, mental debility, premature death and, finally, the extinction +of the stock were not specially and exclusively the fate of sovereign +dynasties; all privileged classes, all families in exclusively elevated +positions share the fate of reigning families, although in a minor degree +and in direct proportion to the loftiness of their social standing. From +the mass of human beings spring individuals, families, races, which tend to +raise themselves above the common level; painfully they climb the rugged +heights, attain the summits of power, of wealth, of intelligence, of +talent, and then, no sooner are they there than they topple down and +disappear in gulfs of mental and physical degeneracy." The demographical +researches of Hansen ("Die drei Bevolkerungsstufen", Munich, 1889.) +(following up and completing Dumont's) tended, indeed, to show that urban +as well as feudal aristocracies, burgher classes as well as noble castes, +were liable to become effete. Hence it might well be concluded that the +democratic movement, operating as it does to break down class barriers, was +promoting instead of impeding human selection. + +So we see that, according to the point of view, very different conclusions +have been drawn from the application of the Darwinian idea of Selection to +human society. Darwin's other central idea, closely bound up with this, +that, namely, of the "struggle for existence" also has been diversely +utilised. But discussion has chiefly centered upon its signification. And +while some endeavour to extend its application to everything, we find +others trying to limit its range. The conception of a "struggle for +existence" has in the present day been taken up into the social sciences +from natural science, and adopted. But originally it descended from social +science to natural. Darwin's law is, as he himself said, only Malthus' law +generalised and extended to the animal world: a growing disproportion +between the supply of food and the number of the living is the fatal order +whence arises the necessity of universal struggle, a struggle which, to the +great advantage of the species, allows only the best equipped individuals +to survive. Nature is regarded by Huxley as an immense arena where all +living beings are gladiators. ("Evolution and Ethics", page 200; +"Collected Essays", Vol. IX, London, 1894.) + +Such a generalisation was well adapted to feed the stream of pessimistic +thought; and it furnished to the apologists of war, in particular, new +arguments, weighted with all the authority which in these days attaches to +scientific deliverances. If people no longer say, as Bonald did, and +Moltke after him, that war is a providential fact, they yet lay stress on +the point that it is a natural fact. To the peace party Dragomirov's +objection is urged that its attempts are contrary to the fundamental laws +of nature, and that no sea wall can hold against breakers that come with +such gathered force. + +But in yet another quarter Darwinism was represented as opposed to +philanthropic intervention. The defenders of the orthodox political +economy found in it support for their tenets. Since in the organic world +universal struggle is the condition of progress, it seemed obvious that +free competition must be allowed to reign unchecked in the economic world. +Attempts to curb it were in the highest degree imprudent. The spirit of +Liberalism here seemed in conformity with the trend of nature: in this +respect, at least, contemporary naturalism, offspring of the discoveries of +the nineteenth century, brought reinforcements to the individualist +doctrine, begotten of the speculations of the eighteenth: but only, it +appeared, to turn mankind away for ever from humanitarian dreams. Would +those whom such conclusions repelled be content to oppose to nature's +imperatives only the protests of the heart? There were some who declared, +like Brunetiere, that the laws in question, valid though they might be for +the animal kingdom, were not applicable to the human. And so a return was +made to the classic dualism. This indeed seems to be the line that Huxley +took, when, for instance, he opposed to the cosmic process an ethical +process which was its reverse. + +But the number of thinkers whom this antithesis does not satisfy grows +daily. Although the pessimism which claims authorisation from Darwin's +doctrines is repugnant to them, they still are unable to accept the dualism +which leaves a gulf between man and nature. And their endeavour is to link +the two by showing that while Darwin's laws obtain in both kingdoms, the +conditions of their application are not the same: their forms, and, +consequently, their results, vary with the varying mediums in which the +struggle of living beings takes place, with the means these beings have at +disposal, with the ends even which they propose to themselves. + +Here we have the explanation of the fact that among determined opponents of +war partisans of the "struggle for existence" can be found: there are +disciples of Darwin in the peace party. Novicow, for example, admits the +"combat universel" of which Le Dantec ("Les Luttes entre Societies humaines +et leurs phases successives", Paris, 1893,) speaks; but he remarks that at +different stages of evolution, at different stages of life the same weapons +are not necessarily employed. Struggles of brute force, armed hand to hand +conflicts, may have been a necessity in the early phases of human +societies. Nowadays, although competition may remain inevitable and +indispensable, it can assume milder forms. Economic rivalries, struggles +between intellectual influences, suffice to stimulate progress: the +processes which these admit are, in the actual state of civilisation, the +only ones which attain their end without waste, the only ones logical. +From one end to the other of the ladder of life, struggle is the order of +the day; but more and more as the higher rungs are reached, it takes on +characters which are proportionately more "humane." + +Reflections of this kind permit the introduction into the economic order of +limitations to the doctrine of "laisser faire, laisser passer." This +appeals, it is said, to the example of nature where creatures, left to +themselves, struggle without truce and without mercy; but the fact is +forgotten that upon industrial battlefields the conditions are different. +The competitors here are not left simply to their natural energies: they +are variously handicapped. A rich store of artificial resources exists in +which some participate and others do not. The sides then are unequal; and +as a consequence the result of the struggle is falsified. "In the animal +world," said De Laveleye ("Le socialisme contemporain", page 384 (6th +edition), Paris, 1891.), criticising Spencer, "the fate of each creature is +determined by its individual qualities; whereas in civilised societies a +man may obtain the highest position and the most beautiful wife because he +is rich and well-born, although he may be ugly, idle or improvident; and +then it is he who will perpetuate the species. The wealthy man, ill +constituted, incapable, sickly, enjoys his riches and establishes his stock +under the protection of the laws." Haycraft in England and Jentsch in +Germany have strongly emphasised these "anomalies," which nevertheless are +the rule. That is to say that even from a Darwinian point of view all +social reforms can readily be justified which aim at diminishing, as +Wallace said, inequalities at the start. + +But we can go further still. Whence comes the idea that all measures +inspired by the sentiment of solidarity are contrary to Nature's trend? +Observe her carefully, and she will not give lessons only in individualism. +Side by side with the struggle for existence do we not find in operation +what Lanessan calls "association for existence." Long ago, Espinas had +drawn attention to "societies of animals," temporary or permanent, and to +the kind of morality that arose in them. Since then, naturalists have +often insisted upon the importance of various forms of symbiosis. +Kropotkin in "Mutual Aid" has chosen to enumerate many examples of altruism +furnished by animals to mankind. Geddes and Thomson went so far as to +maintain that "Each of the greater steps of progress is in fact associated +with an increased measure of subordination of individual competition to +reproductive or social ends, and of interspecific competition to co- +operative association." (Geddes and Thomson, "The Evolution of Sex", page +311, London, 1889.) Experience shows, according to Geddes, that the types +which are fittest to surmount great obstacles are not so much those who +engage in the fiercest competitive struggle for existence, as those who +contrive to temper it. From all these observations there resulted, along +with a limitation of Darwinian pessimism, some encouragement for the +aspirations of the collectivists. + +And Darwin himself would, doubtless, have subscribed to these +rectifications. He never insisted, like his rival, Wallace, upon the +necessity of the solitary struggle of creatures in a state of nature, each +for himself and against all. On the contrary, in "The Descent of Man", he +pointed out the serviceableness of the social instincts, and corroborated +Bagehot's statements when the latter, applying laws of physics to politics, +showed the great advantage societies derived from intercourse and +communion. Again, the theory of sexual evolution which makes the evolution +of types depend increasingly upon preferences, judgments, mental factors, +surely offers something to qualify what seems hard and brutal in the theory +of natural selection. + +But, as often happens with disciples, the Darwinians had out-Darwined +Darwin. The extravagancies of social Darwinism provoked a useful reaction; +and thus people were led to seek, even in the animal kingdom, for facts of +solidarity which would serve to justify humane effort. + +On quite another line, however, an attempt has been made to connect +socialist tendencies with Darwinian principles. Marx and Darwin have been +confronted; and writers have undertaken to show that the work of the German +philosopher fell readily into line with that of the English naturalist and +was a development of it. Such has been the endeavour of Ferri in Italy and +of Woltmann in Germany, not to mention others. The founders of "scientific +socialism" had, moreover, themselves thought of this reconciliation. They +make more than one allusion to Darwin in works which appeared after 1859. +And sometimes they use his theory to define by contrast their own ideal. +They remark that the capitalist system, by giving free course to individual +competition, ends indeed in a bellum omnium contra omnes; and they make it +clear that Darwinism, thus understood, is as repugnant to them as to +Duhring. + +But it is at the scientific and not at the moral point of view that they +place themselves when they connect their economic history with Darwin's +work. Thanks to this unifying hypothesis, they claim to have constructed-- +as Marx does in his preface to "Das Kapital"--a veritable natural history +of social evolution. Engels speaks in praise of his friend Marx as having +discovered the true mainspring of history hidden under the veil of idealism +and sentimentalism, and as having proclaimed in the primum vivere the +inevitableness of the struggle for existence. Marx himself, in "Das +Kapital", indicated another analogy when he dwelt upon the importance of a +general technology for the explanation of this psychology:--a history of +tools which would be to social organs what Darwinism is to the organs of +animal species. And the very importance they attach to tools, to +apparatus, to machines, abundantly proves that neither Marx nor Engels were +likely to forget the special characters which mark off the human world from +the animal. The former always remains to a great extent an artificial +world. Inventions change the face of its institutions. New modes of +production revolutionise not only modes of government, but modes even of +collective thought. Therefore it is that the evolution of society is +controlled by laws special to it, of which the spectacle of nature offers +no suggestion. + +If, however, even in this special sphere, it can still be urged that the +evolution of the material conditions of society is in accord with Darwin's +theory, it is because the influence of the methods of production is itself +to be explained by the incessant strife of the various classes with each +other. So that in the end Marx, like Darwin, finds the source of all +progress in struggle. Both are grandsons of Heraclitus:--polemos pater +panton. It sometimes happens, in these days, that the doctrine of +revolutionary socialism is contrasted as rude and healthy with what may +seem to be the enervating tendency of "solidarist" philanthropy: the +apologists of the doctrine then pride themselves above all upon their +faithfulness to Darwinian principles. + +So far we have been mainly concerned to show the use that social +philosophies have made of the Darwinian laws for practical purposes: in +order to orientate society towards their ideals each school tries to show +that the authority of natural science is on its side. But even in the most +objective of theories, those which systematically make abstraction of all +political tendencies in order to study the social reality in itself, traces +of Darwinism are readily to be found. + +Let us take for example Durkheim's theory of Division of Labour ("De la +Division du Travail social", Paris, 1893.) The conclusions he derives from +it are that whenever professional specialisation causes multiplication of +distinct branches of activity, we get organic solidarity--implying +differences--substituted for mechanical solidarity, based upon likenesses. +The umbilical cord, as Marx said, which connects the individual +consciousness with the collective consciousness is cut. The personality +becomes more and more emancipated. But on what does this phenomenon, so +big with consequences, itself depend? The author goes to social morphology +for the answer: it is, he says, the growing density of population which +brings with it this increasing differentiation of activities. But, again, +why? Because the greater density, in thrusting men up against each other, +augments the intensity of their competition for the means of existence; and +for the problems which society thus has to face differentiation of +functions presents itself as the gentlest solution. + +Here one sees that the writer borrows directly from Darwin. Competition is +at its maximum between similars, Darwin had declared; different species, +not laying claim to the same food, could more easily coexist. Here lay the +explanation of the fact that upon the same oak hundreds of different +insects might be found. Other things being equal, the same applies to +society. He who finds some unadopted speciality possesses a means of his +own for getting a living. It is by this division of their manifold tasks +that men contrive not to crush each other. Here we obviously have a +Darwinian law serving as intermediary in the explanation of that progress +of division of labour which itself explains so much in the social +evolution. + +And we might take another example, at the other end of the series of +sociological systems. G. Tarde is a sociologist with the most pronounced +anti-naturalistic views. He has attempted to show that all application of +the laws of natural science to society is misleading. In his "Opposition +Universelle" he has directly combatted all forms of sociological Darwinism. +According to him the idea that the evolution of society can be traced on +the same plan as the evolution of species is chimerical. Social evolution +is at the mercy of all kinds of inventions, which by virtue of the laws of +imitation modify, through individual to individual, through neighbourhood +to neighbourhood, the general state of those beliefs and desires which are +the only "quantities" whose variation matters to the sociologist. But, it +may be rejoined, that however psychical the forces may be, they are none +the less subject to Darwinian laws. They compete with each other; they +struggle for the mastery of minds. Between types of ideas, as between +organic forms, selection operates. And though it may be that these types +are ushered into the arena by unexpected discoveries, we yet recognise in +the psychological accidents, which Tarde places at the base of everything, +near relatives of those small accidental variations upon which Darwin +builds. Thus, accepting Tarde's own representations, it is quite possible +to express in Darwinian terms, with the necessary transpositions, one of +the most idealistic sociologies that have ever been constructed. + +These few examples suffice. They enable us to estimate the extent of the +field of influence of Darwinism. It affects sociology not only through the +agency of its advocates but through that of its opponents. The +questionings to which it has given rise have proved no less fruitful than +the solutions it has suggested. In short, few doctrines, in the history of +social philosophy, will have produced on their passage a finer outcrop of +ideas. + + +XXIV. THE INFLUENCE OF DARWIN UPON RELIGIOUS THOUGHT. + +By P.N. WAGGETT, M.A., S.S.J.E. + +I. + +The object of this paper is first to point out certain elements of the +Darwinian influence upon Religious thought, and then to show reason for the +conclusion that it has been, from a Christian point of view, satisfactory. +I shall not proceed further to urge that the Christian apologetic in +relation to biology has been successful. A variety of opinions may be held +on this question, without disturbing the conclusion that the movements of +readjustment have been beneficial to those who remain Christians, and this +by making them more Christian and not only more liberal. The theologians +may sometimes have retreated, but there has been an advance of theology. I +know that this account incurs the charge of optimism. It is not the worst +that could be made. The influence has been limited in personal range, +unequal, even divergent, in operation, and accompanied by the appearance of +waste and mischievous products. The estimate which follows requires for +due balance a full development of many qualifying considerations. For this +I lack space, but I must at least distinguish my view from the popular one +that our difficulties about religion and natural science have come to an +end. + +Concerning the older questions about origins--the origin of the world, of +species, of man, of reason, conscience, religion--a large measure of +understanding has been reached by some thoughtful men. But meanwhile new +questions have arisen, questions about conduct, regarding both the reality +of morals and the rule of right action for individuals and societies. And +these problems, still far from solution, may also be traced to the +influence of Darwin. For they arise from the renewed attention to +heredity, brought about by the search for the causes of variation, without +which the study of the selection of variations has no sufficient basis. + +Even the existing understanding about origins is very far from universal. +On these points there were always thoughtful men who denied the necessity +of conflict, and there are still thoughtful men who deny the possibility of +a truce. + +It must further be remembered that the earlier discussion now, as I hope to +show, producing favourable results, created also for a time grave damage, +not only in the disturbance of faith and the loss of men--a loss not +repaired by a change in the currents of debate--but in what I believe to be +a still more serious respect. I mean the introduction of a habit of facile +and untested hypothesis in religious as in other departments of thought. + +Darwin is not responsible for this, but he is in part the cause of it. +Great ideas are dangerous guests in narrow minds; and thus it has happened +that Darwin--the most patient of scientific workers, in whom hypothesis +waited upon research, or if it provisionally outstepped it did so only with +the most scrupulously careful acknowledgment--has led smaller and less +conscientious men in natural science, in history, and in theology to an +over-eager confidence in probable conjecture and a loose grip upon the +facts of experience. It is not too much to say that in many quarters the +age of materialism was the least matter-of-fact age conceivable, and the +age of science the age which showed least of the patient temper of inquiry. + +I have indicated, as shortly as I could, some losses and dangers which in a +balanced account of Darwin's influence would be discussed at length. + +One other loss must be mentioned. It is a defect in our thought which, in +some quarters, has by itself almost cancelled all the advantages secured. +I mean the exaggerated emphasis on uniformity or continuity; the +unwillingness to rest any part of faith or of our practical expectation +upon anything that from any point of view can be called exceptional. The +high degree of success reached by naturalists in tracing, or reasonably +conjecturing, the small beginnings of great differences, has led the +inconsiderate to believe that anything may in time become anything else. + +It is true that this exaggeration of the belief in uniformity has produced +in turn its own perilous reaction. From refusing to believe whatever can +be called exceptional, some have come to believe whatever can be called +wonderful. + +But, on the whole, the discontinuous or highly various character of +experience received for many years too little deliberate attention. The +conception of uniformity which is a necessity of scientific description has +been taken for the substance of history. We have accepted a postulate of +scientific method as if it were a conclusion of scientific demonstration. +In the name of a generalisation which, however just on the lines of a +particular method, is the prize of a difficult exploit of reflexion, we +have discarded the direct impressions of experience; or, perhaps it is more +true to say, we have used for the criticism of alleged experiences a +doctrine of uniformity which is only valid in the region of abstract +science. For every science depends for its advance upon limitation of +attention, upon the selection out of the whole content of consciousness of +that part or aspect which is measurable by the method of the science. +Accordingly there is a science of life which rightly displays the unity +underlying all its manifestations. But there is another view of life, +equally valid, and practically sometimes more important, which recognises +the immediate and lasting effect of crisis, difference, and revolution. +Our ardour for the demonstration of uniformity of process and of minute +continuous change needs to be balanced by a recognition of the catastrophic +element in experience, and also by a recognition of the exceptional +significance for us of events which may be perfectly regular from an +impersonal point of view. + +An exorbitant jealousy of miracle, revelation, and ultimate moral +distinctions has been imported from evolutionary science into religious +thought. And it has been a damaging influence, because it has taken men's +attention from facts, and fixed them upon theories. + +II. + +With this acknowledgment of important drawbacks, requiring many words for +their proper description, I proceed to indicate certain results of Darwin's +doctrine which I believe to be in the long run wholly beneficial to +Christian thought. These are: + +The encouragement in theology of that evolutionary method of observation +and study, which has shaped all modern research: + +The recoil of Christian apologetics towards the ground of religious +experience, a recoil produced by the pressure of scientific criticism upon +other supports of faith: + +The restatement, or the recovery of ancient forms of statement, of the +doctrines of Creation and of divine Design in Nature, consequent upon the +discussion of evolution and of natural selection as its guiding factor. + +(1) The first of these is quite possibly the most important of all. It +was well defined in a notable paper read by Dr Gore, now Bishop of +Birmingham, to the Church Congress at Shrewsbury in 1896. We have learnt a +new caution both in ascribing and in denying significance to items of +evidence, in utterance or in event. There has been, as in art, a study of +values, which secures perspective and solidity in our representation of +facts. On the one hand, a given utterance or event cannot be drawn into +evidence as if all items were of equal consequence, like sovereigns in a +bag. The question whence and whither must be asked, and the particular +thing measured as part of a series. Thus measured it is not less truly +important, but it may be important in a lower degree. On the other hand, +and for exactly the same reason, nothing that is real is unimportant. The +"failures" are not mere mistakes. We see them, in St Augustine's words, as +"scholar's faults which men praise in hope of fruit." + +We cannot safely trace the origin of the evolutionistic method to the +influence of natural science. The view is tenable that theology led the +way. Probably this is a case of alternate and reciprocal debt. Quite +certainly the evolutionist method in theology, in Christian history, and in +the estimate of scripture, has received vast reinforcement from biology, in +which evolution has been the ever present and ever victorious conception. + +(2) The second effect named is the new willingness of Christian thinkers +to take definite account of religious experience. This is related to +Darwin through the general pressure upon religious faith of scientific +criticism. The great advance of our knowledge of organisms has been an +important element in the general advance of science. It has acted, by the +varied requirements of the theory of organisms, upon all other branches of +natural inquiry, and it held for a long time that leading place in public +attention which is now occupied by speculative physics. Consequently it +contributed largely to our present estimation of science as the supreme +judge in all matters of inquiry (F.R. Tennant: "The Being of God in the +light of Physical Science", in "Essays on some theological questions of the +day". London, 1905.), to the supposed destruction of mystery and the +disparagement of metaphysic which marked the last age, as well as to the +just recommendation of scientific method in branches of learning where the +direct acquisitions of natural science had no place. + +Besides this, the new application of the idea of law and mechanical +regularity to the organic world seemed to rob faith of a kind of refuge. +The romantics had, as Berthelot ("Evolutionisme et Platonisme", pages 45, +46, 47. Paris, 1908.) shows, appealed to life to redress the judgments +drawn from mechanism. Now, in Spencer, evolution gave us a vitalist +mechanic or mechanical vitalism, and the appeal seemed cut off. We may +return to this point later when we consider evolution; at present I only +endeavour to indicate that general pressure of scientific criticism which +drove men of faith to seek the grounds of reassurance in a science of their +own; in a method of experiment, of observation, of hypothesis checked by +known facts. It is impossible for me to do more than glance across the +threshold of this subject. But it is necessary to say that the method is +in an elementary stage of revival. The imposing success that belongs to +natural science is absent: we fall short of the unchallengeable unanimity +of the Biologists on fundamentals. The experimental method with its sure +repetitions cannot be applied to our subject-matter. But we have something +like the observational method of palaeontology and geographical +distribution; and in biology there are still men who think that the large +examination of varieties by way of geography and the search of strata is as +truly scientific, uses as genuinely the logical method of difference, and +is as fruitful in sure conclusions as the quasi-chemical analysis of +Mendelian laboratory work, of which last I desire to express my humble +admiration. Religion also has its observational work in the larger and +possibly more arduous manner. + +But the scientific work in religion makes its way through difficulties and +dangers. We are far from having found the formula of its combination with +the historical elements of our apologetic. It is exposed, therefore, to a +damaging fire not only from unspiritualist psychology and pathology but +also from the side of scholastic dogma. It is hard to admit on equal terms +a partner to the old undivided rule of books and learning. With Charles +Lamb, we cry in some distress, "must knowledge come to me, if it come at +all, by some awkward experiment of intuition, and no longer by this +familiar process of reading?" ("Essays of Elia", "New Year's Eve", page +41; Ainger's edition. London, 1899.) and we are answered that the old +process has an imperishable value, only we have not yet made clear its +connection with other contributions. And all the work is young, liable to +be drawn into unprofitable excursions, side-tracked by self-deceit and +pretence; and it fatally attracts, like the older mysticism, the curiosity +and the expository powers of those least in sympathy with it, ready writers +who, with all the air of extended research, have been content with narrow +grounds for induction. There is a danger, besides, which accompanies even +the most genuine work of this science and must be provided against by all +its serious students. I mean the danger of unbalanced introspection both +for individuals and for societies; of a preoccupation comparable to our +modern social preoccupation with bodily health; of reflection upon mental +states not accompanied by exercise and growth of the mental powers; the +danger of contemplating will and neglecting work, of analysing conviction +and not criticising evidence. + +Still, in spite of dangers and mistakes, the work remains full of hopeful +indications, and, in the best examples (Such an example is given in Baron +F. von Hugel's recently finished book, the result of thirty years' +research: "The Mystical Element of Religion, as studied in Saint Catherine +of Genoa and her Friends". London, 1908.), it is truly scientific in its +determination to know the very truth, to tell what we think, not what we +think we ought to think. (G. Tyrrell, in "Mediaevalism", has a chapter +which is full of the important MORAL element in a scientific attitude. +"The only infallible guardian of truth is the spirit of truthfulness." +"Mediaevalism" page 182, London, 1908.), truly scientific in its employment +of hypothesis and verification, and in growing conviction of the reality of +its subject-matter through the repeated victories of a mastery which +advances, like science, in the Baconian road of obedience. It is +reasonable to hope that progress in this respect will be more rapid and +sure when religious study enlists more men affected by scientific desire +and endowed with scientific capacity. + +The class of investigating minds is a small one, possibly even smaller than +that of reflecting minds. Very few persons at any period are able to find +out anything whatever. There are few observers, few discoverers, few who +even wish to discover truth. In how many societies the problems of +philology which face every person who speaks English are left unattempted! +And if the inquiring or the successfully inquiring class of minds is small, +much smaller, of course, is the class of those possessing the scientific +aptitude in an eminent degree. During the last age this most distinguished +class was to a very great extent absorbed in the study of phenomena, a +study which had fallen into arrears. For we stood possessed, in rudiment, +of means of observation, means for travelling and acquisition, qualifying +men for a larger knowledge than had yet been attempted. These were now to +be directed with new accuracy and ardour upon the fabric and behaviour of +the world of sense. Our debt to the great masters in physical science who +overtook and almost out-stripped the task cannot be measured; and, under +the honourable leadership of Ruskin, we may all well do penance if we have +failed "in the respect due to their great powers of thought, or in the +admiration due to the far scope of their discovery." ("Queen of the Air", +Preface, page vii. London, 1906.) With what miraculous mental energy and +divine good fortune--as Romans said of their soldiers--did our men of +curiosity face the apparently impenetrable mysteries of nature! And how +natural it was that immense accessions of knowledge, unrelated to the +spiritual facts of life, should discredit Christian faith, by the apparent +superiority of the new work to the feeble and unprogressive knowledge of +Christian believers! The day is coming when men of this mental character +and rank, of this curiosity, this energy and this good fortune in +investigation, will be employed in opening mysteries of a spiritual nature. +They will silence with masterful witness the over-confident denials of +naturalism. They will be in danger of the widespread recognition which +thirty years ago accompanied every utterance of Huxley, Tyndall, Spencer. +They will contribute, in spite of adulation, to the advance of sober +religious and moral science. + +And this result will be due to Darwin, first because by raising the dignity +of natural science, he encouraged the development of the scientific mind; +secondly because he gave to religious students the example of patient and +ardent investigation; and thirdly because by the pressure of naturalistic +criticism the religious have been driven to ascertain the causes of their +own convictions, a work in which they were not without the sympathy of men +of science. (The scientific rank of its writer justifies the insertion of +the following letter from the late Sir John Burdon-Sanderson to me. In the +lecture referred to I had described the methods of Professor Moseley in +teaching Biology as affording a suggestion of the scientific treatment of +religion. + +Oxford, April 30, 1902. + +Dear Sir, + +I feel that I must express to you my thanks for the discourse which I had +the pleasure of listening to yesterday afternoon. + +I do not mean to say that I was able to follow all that you said as to the +identity of Method in the two fields of Science and Religion, but I +recognise that the "mysticism" of which you spoke gives us the only way by +which the two fields can be brought into relation. + +Among much that was memorable, nothing interested me more than what you +said of Moseley. + +No one, I am sure, knew better than you the value of his teaching and in +what that value consisted. + +Yours faithfully + +J. Burdon-Sanderson. +31-2.) + +In leaving the subject of scientific religious inquiry, I will only add +that I do not believe it receives any important help--and certainly it +suffers incidentally much damaging interruption--from the study of abnormal +manifestations or abnormal conditions of personality. + +(3) Both of the above effects seem to me of high, perhaps the very +highest, importance to faith and to thought. But, under the third head, I +name two which are more directly traceable to the personal work of Darwin, +and more definitely characteristic of the age in which his influence was +paramount: viz. the influence of the two conceptions of evolution and +natural selection upon the doctrine of creation and of design respectively. + +It is impossible here, though it is necessary for a complete sketch of the +matter, to distinguish the different elements and channels of this +Darwinian influence; in Darwin's own writings, in the vigorous polemic of +Huxley, and strangely enough, but very actually for popular thought, in the +teaching of the definitely anti-Darwinian evolutionist Spencer. + +Under the head of the directly and purely Darwinian elements I should class +as preeminent the work of Wallace and of Bates; for no two sets of facts +have done more to fix in ordinary intelligent minds a belief in organic +evolution and in natural selection as its guiding factor than the facts of +geographical distribution and of protective colour and mimicry. The facts +of geology were difficult to grasp and the public and theologians heard +more often of the imperfection than of the extent of the geological record. +The witness of embryology, depending to a great extent upon microscopic +work, was and is beyond the appreciation of persons occupied in fields of +work other than biology. + +III. + +From the influence in religion of scientific modes of thought we pass to +the influence of particular biological conceptions. The former effect +comes by way of analogy, example, encouragement and challenge; inspiring or +provoking kindred or similar modes of thought in the field of theology; the +latter by a collision of opinions upon matters of fact or conjecture which +seem to concern both science and religion. + +In the case of Darwinism the story of this collision is familiar, and falls +under the heads of evolution and natural selection, the doctrine of descent +with modification, and the doctrine of its guidance or determination by the +struggle for existence between related varieties. These doctrines, though +associated and interdependent, and in popular thought not only combined but +confused, must be considered separately. It is true that the ancient +doctrine of Evolution, in spite of the ingenuity and ardour of Lamarck, +remained a dream tantalising the intellectual ambition of naturalists, +until the day when Darwin made it conceivable by suggesting the machinery +of its guidance. And, further, the idea of natural selection has so +effectively opened the door of research and stimulated observation in a +score of principal directions that, even if the Darwinian explanation +became one day much less convincing than, in spite of recent criticism, it +now is, yet its passing, supposing it to pass, would leave the doctrine of +Evolution immeasurably and permanently strengthened. For in the interests +of the theory of selection, "Fur Darwin," as Muller wrote, facts have been +collected which remain in any case evidence of the reality of descent with +modification. + +But still, though thus united in the modern history of convictions, though +united and confused in the collision of biological and traditional opinion, +yet evolution and natural selection must be separated in theological no +less than in biological estimation. Evolution seemed inconsistent with +Creation; natural selection with Providence and Divine design. + +Discussion was maintained about these points for many years and with much +dark heat. It ranged over many particular topics and engaged minds +different in tone, in quality, and in accomplishment. There was at most +times a degree of misconception. Some naturalists attributed to +theologians in general a poverty of thought which belonged really to men of +a particular temper or training. The "timid theism" discerned in Darwin by +so cautious a theologian as Liddon (H.P. Liddon, "The Recovery of S. +Thomas"; a sermon preached in St Paul's, London, on April 23rd, 1882 (the +Sunday after Darwin's death).) was supposed by many biologists to be the +necessary foundation of an honest Christianity. It was really more +characteristic of devout NATURALISTS like Philip Henry Gosse, than of +religious believers as such. (Dr Pusey ("Unscience not Science adverse to +Faith" 1878) writes: "The questions as to 'species,' of what variations +the animal world is capable, whether the species be more or fewer, whether +accidental variations may become hereditary...and the like, naturally fall +under the province of science. In all these questions Mr Darwin's careful +observations gained for him a deserved approbation and confidence.") The +study of theologians more considerable and even more typically conservative +than Liddon does not confirm the description of religious intolerance given +in good faith, but in serious ignorance, by a disputant so acute, so +observant and so candid as Huxley. Something hid from each other's +knowledge the devoted pilgrims in two great ways of thought. The truth may +be, that naturalists took their view of what creation was from Christian +men of science who naturally looked in their own special studies for the +supports and illustrations of their religious belief. Of almost every +laborious student it may be said "Hic ab arte sua non recessit." And both +the believing and the denying naturalists, confining habitual attention to +a part of experience, are apt to affirm and deny with trenchant vigour and +something of a narrow clearness "Qui respiciunt ad pauca, de facili +pronunciant." (Aristotle, in Bacon, quoted by Newman in his "Idea of a +University", page 78. London, 1873.) + +Newman says of some secular teachers that "they persuade the world of what +is false by urging upon it what is true." Of some early opponents of +Darwin it might be said by a candid friend that, in all sincerity of +devotion to truth, they tried to persuade the world of what is true by +urging upon it what is false. If naturalists took their version of +orthodoxy from amateurs in theology, some conservative Christians, instead +of learning what evolution meant to its regular exponents, took their view +of it from celebrated persons, not of the front rank in theology or in +thought, but eager to take account of public movements and able to arrest +public attention. + +Cleverness and eloquence on both sides certainly had their share in +producing the very great and general disturbance of men's minds in the +early days of Darwinian teaching. But by far the greater part of that +disturbance was due to the practical novelty and the profound importance of +the teaching itself, and to the fact that the controversy about evolution +quickly became much more public than any controversy of equal seriousness +had been for many generations. + +We must not think lightly of that great disturbance because it has, in some +real sense, done its work, and because it is impossible in days of more +coolness and light, to recover a full sense of its very real difficulties. + +Those who would know them better should add to the calm records of Darwin +("Life and Letters" and "More Letters of Charles Darwin".) and to the story +of Huxley's impassioned championship, all that they can learn of George +Romanes. ("Life and Letters", London, 1896. "Thoughts on Religion", +London, 1895. "Candid Examination of Theism", London, 1878.) For his life +was absorbed in this very struggle and reproduced its stages. It began in +a certain assured simplicity of biblical interpretation; it went on, +through the glories and adventures of a paladin in Darwin's train, to the +darkness and dismay of a man who saw all his most cherished beliefs +rendered, as he thought, incredible. ("Never in the history of man has so +terrific a calamity befallen the race as that which all who look may now +(viz. in consequence of the scientific victory of Darwin) behold advancing +as a deluge, black with destruction, resistless in might, uprooting our +most cherished hopes, engulphing our most precious creed, and burying our +highest life in mindless destruction."--"A Candid Examination of Theism", +page 51.) He lived to find the freer faith for which process and purpose +are not irreconcilable, but necessary to one another. His development, +scientific, intellectual and moral, was itself of high significance; and +its record is of unique value to our own generation, so near the age of +that doubt and yet so far from it; certainly still much in need of the +caution and courage by which past endurance prepares men for new +emergencies. We have little enough reason to be sure that in the +discussions awaiting us we shall do as well as our predecessors in theirs. +Remembering their endurance of mental pain, their ardour in mental labour, +the heroic temper and the high sincerity of controversialists on either +side, we may well speak of our fathers in such words of modesty and self- +judgment as Drayton used when he sang the victors of Agincourt. The +progress of biblical study, in the departments of Introduction and +Exegesis, resulting in the recovery of a point of view anciently tolerated +if not prevalent, has altered some of the conditions of that discussion. +In the years near 1858, the witness of Scripture was adduced both by +Christian advocates and their critics as if unmistakeably irreconcilable +with Evolution. + +Huxley ("Science and Christian Tradition". London, 1904.) found the path +of the blameless naturalist everywhere blocked by "Moses": the believer in +revelation was generally held to be forced to a choice between revealed +cosmogony and the scientific account of origins. It is not clear how far +the change in Biblical interpretation is due to natural science, and how +far to the vital movements of theological study which have been quite +independent of the controversy about species. It belongs to a general +renewal of Christian movement, the recovery of a heritage. "Special +Creation"--really a biological rather than a theological conception,--seems +in its rigid form to have been a recent element even in English biblical +orthodoxy. + +The Middle Ages had no suspicion that religious faith forbad inquiry into +the natural origination of the different forms of life. Bartholomaeus +Anglicus, an English Franciscan of the thirteenth century, was a +mutationist in his way, as Aristotle, "the Philosopher" of the Christian +Schoolmen, had been in his. So late as the seventeenth century, as we +learn not only from early proceedings of the Royal Society, but from a +writer so homely and so regularly pious as Walton, the variation of species +and "spontaneous" generations had no theological bearing, except as +instances of that various wonder of the world which in devout minds is food +for devotion. + +It was in the eighteenth century that the harder statement took shape. +Something in the preciseness of that age, its exaltation of law, its cold +passion for a stable and measured universe, its cold denial, its cold +affirmation of the power of God, a God of ice, is the occasion of that +rigidity of religious thought about the living world which Darwin by +accident challenged, or rather by one of those movements of genius which, +Goethe ("No productiveness of the highest kind...is in the power of +anyone."--"Conversations of Goethe with Eckermann and Soret". London, +1850.) declares, are "elevated above all earthly control." + +If religious thought in the eighteenth century was aimed at a fixed and +nearly finite world of spirit, it followed in all these respects the +secular and critical lead. ("La philosophie reformatrice du XVIIIe siecle +(Berthelot, "Evolutionisme et Platonisme", Paris, 1908, page 45.) ramenait +la nature et la societe a des mecanismes que la pensee reflechie peut +concevoir et recomposer." In fact, religion in a mechanical age is +condemned if it takes any but a mechanical tone. Butler's thought was too +moving, too vital, too evolutionary, for the sceptics of his time. In a +rationalist, encyclopaedic period, religion also must give hard outline to +its facts, it must be able to display its secret to any sensible man in the +language used by all sensible men. Milton's prophetic genius furnished the +eighteenth century, out of the depth of the passionate age before it, with +the theological tone it was to need. In spite of the austere magnificence +of his devotion, he gives to smaller souls a dangerous lead. The rigidity +of Scripture exegesis belonged to this stately but imperfectly sensitive +mode of thought. It passed away with the influence of the older +rationalists whose precise denials matched the precise and limited +affirmations of the static orthodoxy. + +I shall, then, leave the specially biblical aspect of the debate-- +interesting as it is and even useful, as in Huxley's correspondence with +the Duke of Argyll and others in 1892 ("Times", 1892, passim.)--in order to +consider without complication the permanent elements of Christian thought +brought into question by the teaching of evolution. + +Such permanent elements are the doctrine of God as Creator of the universe, +and the doctrine of man as spiritual and unique. Upon both the doctrine of +evolution seemed to fall with crushing force. + +With regard to Man I leave out, acknowledging a grave omission, the +doctrine of the Fall and of Sin. And I do so because these have not yet, +as I believe, been adequately treated: here the fruitful reaction to the +stimulus of evolution is yet to come. The doctrine of sin, indeed, falls +principally within the scope of that discussion which has followed or +displaced the Darwinian; and without it the Fall cannot be usefully +considered. For the question about the Fall is a question not merely of +origins, but of the interpretation of moral facts whose moral reality must +first be established. + +I confine myself therefore to Creation and the dignity of man. + +The meaning of evolution, in the most general terms, is that the +differentiation of forms is not essentially separate from their behaviour +and use; that if these are within the scope of study, that is also; that +the world has taken the form we see by movements not unlike those we now +see in progress; that what may be called proximate origins are continuous +in the way of force and matter, continuous in the way of life, with actual +occurrences and actual characteristics. All this has no revolutionary +bearing upon the question of ultimate origins. The whole is a statement +about process. It says nothing to metaphysicians about cause. It simply +brings within the scope of observation or conjecture that series of changes +which has given their special characters to the different parts of the +world we see. In particular, evolutionary science aspires to the discovery +of the process or order of the appearance of life itself: if it were to +achieve its aim it could say nothing of the cause of this or indeed of the +most familiar occurrences. We should have become spectators or convinced +historians of an event which, in respect of its cause and ultimate meaning, +would be still impenetrable. + +With regard to the origin of species, supposing life already established, +biological science has the well founded hopes and the measure of success +with which we are all familiar. All this has, it would seem, little chance +of collision with a consistent theism, a doctrine which has its own +difficulties unconnected with any particular view of order or process. But +when it was stated that species had arisen by processes through which new +species were still being made, evolutionism came into collision with a +statement, traditionally religious, that species were formed and fixed once +for all and long ago. + +What is the theological import of such a statement when it is regarded as +essential to belief in God? Simply that God's activity, with respect to +the formation of living creatures, ceased at some point in past time. + +"God rested" is made the touchstone of orthodoxy. And when, under the +pressure of the evidences, we found ourselves obliged to acknowledge and +assert the present and persistent power of God, in the maintenance and in +the continued formation of "types," what happened was the abolition of a +time-limit. We were forced only to a bolder claim, to a theistic language +less halting, more consistent, more thorough in its own line, as well as +better qualified to assimilate and modify such schemes as Von Hartmann's +philosophy of the unconscious--a philosophy, by the way, quite intolerant +of a merely mechanical evolution. (See Von Hartmann's "Wahrheit und +Irrthum in Darwinismus". Berlin, 1875.) + +Here was not the retrenchment of an extravagant assertion, but the +expansion of one which was faltering and inadequate. The traditional +statement did not need paring down so as to pass the meshes of a new and +exacting criticism. It was itself a net meant to surround and enclose +experience; and we must increase its size and close its mesh to hold newly +disclosed facts of life. The world, which had seemed a fixed picture or +model, gained first perspective and then solidity and movement. We had a +glimpse of organic HISTORY; and Christian thought became more living and +more assured as it met the larger view of life. + +However unsatisfactory the new attitude might be to our critics, to +Christians the reform was positive. What was discarded was a limitation, a +negation. The movement was essentially conservative, even actually +reconstructive. For the language disused was a language inconsistent with +the definitions of orthodoxy; it set bounds to the infinite, and by +implication withdrew from the creative rule all such processes as could be +brought within the descriptions of research. It ascribed fixity and +finality to that "creature" in which an apostle taught us to recognise the +birth-struggles of an unexhausted progress. It tended to banish mystery +from the world we see, and to confine it to a remote first age. + +In the reformed, the restored, language of religion, Creation became again +not a link in a rational series to complete a circle of the sciences, but +the mysterious and permanent relation between the infinite and the finite, +between the moving changes we know in part, and the Power, after the +fashion of that observation, unknown, which is itself "unmoved all motion's +source." (Hymn of the Church-- + Rerum Deus tenax vigor, + Immotus in te permanens.) + +With regard to man it is hardly necessary, even were it possible, to +illustrate the application of this bolder faith. When the record of his +high extraction fell under dispute, we were driven to a contemplation of +the whole of his life, rather than of a part and that part out of sight. +We remembered again, out of Aristotle, that the result of a process +interprets its beginnings. We were obliged to read the title of such +dignity as we may claim, in results and still more in aspirations. + +Some men still measure the value of great present facts in life--reason and +virtue and sacrifice--by what a self-disparaged reason can collect of the +meaner rudiments of these noble gifts. Mr Balfour has admirably displayed +the discrepancy, in this view, between the alleged origin and the alleged +authority of reason. Such an argument ought to be used not to discredit +the confident reason, but to illuminate and dignify its dark beginnings, +and to show that at every step in the long course of growth a Power was at +work which is not included in any term or in all the terms of the series. + +I submit that the more men know of actual Christian teaching, its fidelity +to the past, and its sincerity in face of discovery, the more certainly +they will judge that the stimulus of the doctrine of evolution has produced +in the long run vigour as well as flexibility in the doctrine of Creation +and of man. + +I pass from Evolution in general to Natural Selection. + +The character in religious language which I have for short called +mechanical was not absent in the argument from design as stated before +Darwin. It seemed to have reference to a world conceived as fixed. It +pointed, not to the plastic capacity and energy of living matter, but to +the fixed adaptation of this and that organ to an unchanging place or +function. + +Mr Hobhouse has given us the valuable phrase "a niche of organic +opportunity." Such a phrase would have borne a different sense in non- +evolutionary thought. In that thought, the opportunity was an opportunity +for the Creative Power, and Design appeared in the preparation of the +organism to fit the niche. The idea of the niche and its occupant growing +together from simpler to more complex mutual adjustment was unwelcome to +this teleology. If the adaptation was traced to the influence, through +competition, of the environment, the old teleology lost an illustration and +a proof. For the cogency of the proof in every instance depended upon the +absence of explanation. Where the process of adaptation was discerned, the +evidence of Purpose or Design was weak. It was strong only when the +natural antecedents were not discovered, strongest when they could be +declared undiscoverable. + +Paley's favourite word is "Contrivance"; and for him contrivance is most +certain where production is most obscure. He points out the physiological +advantage of the valvulae conniventes to man, and the advantage for +teleology of the fact that they cannot have been formed by "action and +pressure." What is not due to pressure may be attributed to design, and +when a "mechanical" process more subtle than pressure was suggested, the +case for design was so far weakened. The cumulative proof from the +multitude of instances began to disappear when, in selection, a natural +sequence was suggested in which all the adaptations might be reached by the +motive power of life, and especially when, as in Darwin's teaching, there +was full recognition of the reactions of life to the stimulus of +circumstance. "The organism fits the niche," said the teleologist, +"because the Creator formed it so as to fit." "The organism fits the +niche," said the naturalist, "because unless it fitted it could not exist." +"It was fitted to survive," said the theologian. "It survives because it +fits," said the selectionist. The two forms of statement are not +incompatible; but the new statement, by provision of an ideally universal +explanation of process, was hostile to a doctrine of purpose which relied +upon evidences always exceptional however numerous. Science persistently +presses on to find the universal machinery of adaptation in this planet; +and whether this be found in selection, or in direct-effect, or in vital +reactions resulting in large changes, or in a combination of these and +other factors, it must always be opposed to the conception of a Divine +Power here and there but not everywhere active. + +For science, the Divine must be constant, operative everywhere and in every +quality and power, in environment and in organism, in stimulus and in +reaction, in variation and in struggle, in hereditary equilibrium, and in +"the unstable state of species"; equally present on both sides of every +strain, in all pressures and in all resistances, in short in the general +wonder of life and the world. And this is exactly what the Divine Power +must be for religious faith. + +The point I wish once more to make is that the necessary readjustment of +teleology, so as to make it depend upon the contemplation of the whole +instead of a part, is advantageous quite as much to theology as to science. +For the older view failed in courage. Here again our theism was not +sufficiently theistic. + +Where results seemed inevitable, it dared not claim them as God-given. In +the argument from Design it spoke not of God in the sense of theology, but +of a Contriver, immensely, not infinitely wise and good, working within a +world, the scene, rather than the ever dependent outcome, of His Wisdom; +working in such emergencies and opportunities as occurred, by forces not +altogether within His control, towards an end beyond Himself. It gave us, +instead of the awful reverence due to the Cause of all substance and form, +all love and wisdom, a dangerously detached appreciation of an ingenuity +and benevolence meritorious in aim and often surprisingly successful in +contrivance. + +The old teleology was more useful to science than to religion, and the +design-naturalists ought to be gratefully remembered by Biologists. Their +search for evidences led them to an eager study of adaptations and of +minute forms, a study such as we have now an incentive to in the theory of +Natural Selection. One hardly meets with the same ardour in microscopical +research until we come to modern workers. But the argument from Design was +never of great importance to faith. Still, to rid it of this character was +worth all the stress and anxiety of the gallant old war. If Darwin had +done nothing else for us, we are to-day deeply in his debt for this. The +world is not less venerable to us now, not less eloquent of the causing +mind, rather much more eloquent and sacred. But our wonder is not that +"the underjaw of the swine works under the ground" or in any or all of +those particular adaptations which Paley collected with so much skill, but +that a purpose transcending, though resembling, our own purposes, is +everywhere manifest; that what we live in is a whole, mutually sustaining, +eventful and beautiful, where the "dead" forces feed the energies of life, +and life sustains a stranger existence, able in some real measure to +contemplate the whole, of which, mechanically considered, it is a minor +product and a rare ingredient. Here, again, the change was altogether +positive. It was not the escape of a vessel in a storm with loss of spars +and rigging, not a shortening of sail to save the masts and make a port of +refuge. It was rather the emergence from narrow channels to an open sea. +We had propelled the great ship, finding purchase here and there for slow +and uncertain movement. Now, in deep water, we spread large canvas to a +favouring breeze. + +The scattered traces of design might be forgotten or obliterated. But the +broad impression of Order became plainer when seen at due distance and in +sufficient range of effect, and the evidence of love and wisdom in the +universe could be trusted more securely for the loss of the particular +calculation of their machinery. + +Many other topics of faith are affected by modern biology. In some of +these we have learnt at present only a wise caution, a wise uncertainty. +We stand before the newly unfolded spectacle of suffering, silenced; with +faith not scientifically reassured but still holding fast certain other +clues of conviction. In many important topics we are at a loss. But in +others, and among them those I have mentioned, we have passed beyond this +negative state and find faith positively strengthened and more fully +expressed. + +We have gained also a language and a habit of thought more fit for the +great and dark problems that remain, less liable to damaging conflicts, +equipped for more rapid assimilation of knowledge. And by this change +biology itself is a gainer. For, relieved of fruitless encounters with +popular religion, it may advance with surer aim along the path of really +scientific life-study which was reopened for modern men by the publication +of "The Origin of Species". + +Charles Darwin regretted that, in following science, he had not done "more +direct good" ("Life and Letters", Vol. III. page 359.) to his fellow- +creatures. He has, in fact, rendered substantial service to interests +bound up with the daily conduct and hopes of common men; for his work has +led to improvements in the preaching of the Christian faith. + + +XXV. THE INFLUENCE OF DARWINISM ON THE STUDY OF RELIGIONS. + +By JANE ELLEN HARRISON. +Hon. D.Litt. (Durham), Hon. LL.D. (Aberdeen), Staff Lecturer and sometime +Fellow of Newnham College, Cambridge. Corresponding member of the German +Archaeological Institute. + +The title of my paper might well have been "the creation by Darwinism of +the scientific study of Religions," but that I feared to mar my tribute to +a great name by any shadow of exaggeration. Before the publication of "The +Origin of Species" and "The Descent of Man", even in the eighteenth +century, isolated thinkers, notably Hume and Herder, had conjectured that +the orthodox beliefs of their own day were developments from the cruder +superstitions of the past. These were however only particular speculations +of individual sceptics. Religion was not yet generally regarded as a +proper subject for scientific study, with facts to be collected and +theories to be deduced. A Congress of Religions such as that recently held +at Oxford would have savoured of impiety. + +In the brief space allotted me I can attempt only two things; first, and +very briefly, I shall try to indicate the normal attitude towards religion +in the early part of the last century; second, and in more detail, I shall +try to make clear what is the outlook of advanced thinkers to-day. (To be +accurate I ought to add "in Europe." I advisedly omit from consideration +the whole immense field of Oriental mysticism, because it has remained +practically untouched by the influence of Darwinism.) From this second +inquiry it will, I hope, be abundantly manifest that it is the doctrine of +evolution that has made this outlook possible and even necessary. + +The ultimate and unchallenged presupposition of the old view was that +religion was a DOCTRINE, a body of supposed truths. It was in fact what we +should now call Theology, and what the ancients called Mythology. Ritual +was scarcely considered at all, and, when considered, it was held to be a +form in which beliefs, already defined and fixed as dogma, found a natural +mode of expression. This, it will be later shown, is a profound error or +rather a most misleading half-truth. Creeds, doctrines, theology and the +like are only a part, and at first the least important part, of religion. + +Further, and the fact is important, this DOGMA, thus supposed to be the +essential content of the "true" religion, was a teleological scheme +complete and unalterable, which had been revealed to man once and for all +by a highly anthropomorphic God, whose existence was assumed. The duty of +man towards this revelation was to accept its doctrines and obey its +precepts. The notion that this revelation had grown bit by bit out of +man's consciousness and that his business was to better it would have +seemed rank blasphemy. Religion, so conceived, left no place for +development. "The Truth" might be learnt, but never critically examined; +being thus avowedly complete and final, it was doomed to stagnation. + +The details of this supposed revelation seem almost too naive for +enumeration. As Hume observed, "popular theology has a positive appetite +for absurdity." It is sufficient to recall that "revelation" included such +items as the Creation (It is interesting to note that the very word +"Creator" has nowadays almost passed into the region of mythology. Instead +we have "L'Evolution Creatrice".) of the world out of nothing in six days; +the making of Eve from one of Adam's ribs; the Temptation by a talking +snake; the confusion of tongues at the tower of Babel; the doctrine of +Original Sin; a scheme of salvation which demanded the Virgin Birth, +Vicarious Atonement, and the Resurrection of the material body. The scheme +was unfolded in an infallible Book, or, for one section of Christians, +guarded by the tradition of an infallible Church, and on the acceptance or +refusal of this scheme depended an eternity of weal or woe. There is not +one of these doctrines that has not now been recast, softened down, +mysticised, allegorised into something more conformable with modern +thinking. It is hard for the present generation, unless their breeding has +been singularly archaic, to realise that these amazing doctrines were +literally held and believed to constitute the very essence of religion; to +doubt them was a moral delinquency. + +It had not, however, escaped the notice of travellers and missionaries that +savages carried on some sort of practices that seemed to be religious, and +believed in some sort of spirits or demons. Hence, beyond the confines +illuminated by revealed truth, a vague region was assigned to NATURAL +Religion. The original revelation had been kept intact only by one chosen +people, the Jews, by them to be handed on to Christianity. Outside the +borders of this Goshen the world had sunk into the darkness of Egypt. +Where analogies between savage cults and the Christian religions were +observed, they were explained as degradations; the heathen had somehow +wilfully "lost the light." Our business was not to study but, exclusively, +to convert them, to root out superstition and carry the torch of revelation +to "Souls in heathen darkness lying." To us nowadays it is a commonplace +of anthropological research that we must seek for the beginnings of +religion in the religions of primitive peoples, but in the last century the +orthodox mind was convinced that it possessed a complete and luminous +ready-made revelation; the study of what was held to be a mere degradation +seemed idle and superfluous. + +But, it may be asked, if, to the orthodox, revealed religion was sacrosanct +and savage religion a thing beneath consideration, why did not the sceptics +show a more liberal spirit, and pursue to their logical issue the +conjectures they had individually hazarded? The reason is simple and +significant. The sceptics too had not worked free from the presupposition +that the essence of religion is dogma. Their intellectualism, expressive +of the whole eighteenth century, was probably in England strengthened by +the Protestant doctrine of an infallible Book. Hume undoubtedly confused +religion with dogmatic theology. The attention of orthodox and sceptics +alike was focussed on the truth or falsity of certain propositions. Only a +few minds of rare quality were able dimly to conceive that religion might +be a necessary step in the evolution of human thought. + +It is not a little interesting to note that Darwin, who was leader and +intellectual king of his generation, was also in this matter to some extent +its child. His attitude towards religion is stated clearly, in Chapter +VIII. of the "Life and Letters". (Vol. I. page 304. For Darwin's +religious views see also "Descent of Man", 1871, Vol. I. page 65; 2nd +edition. Vol. I. page 142.) On board the "Beagle" he was simply orthodox +and was laughed at by several of the officers for quoting the Bible as an +unanswerable authority on some point of morality. By 1839 he had come to +see that the Old Testament was no more to be trusted than the sacred books +of the Hindoos. Next went the belief in miracles, and next Paley's +"argument from design" broke down before the law of natural selection; the +suffering so manifest in nature is seen to be compatible rather with +Natural Selection than with the goodness and omnipotence of God. Darwin +felt to the full all the ignorance that lay hidden under specious phrases +like "the plan of creation" and "Unity of design." Finally, he tells us +"the mystery of the beginning of all things is insoluble by us; and I for +one must be content to remain an Agnostic." + +The word Agnostic is significant not only of the humility of the man +himself but also of the attitude of his age. Religion, it is clear, is +still conceived as something to be KNOWN, a matter of true or false +OPINION. Orthodox religion was to Darwin a series of erroneous hypotheses +to be bit by bit discarded when shown to be untenable. The ACTS of +religion which may result from such convictions, i.e. devotion in all its +forms, prayer, praise, sacraments, are left unmentioned. It is clear that +they are not, as now to us, sociological survivals of great interest and +importance, but rather matters too private, too personal, for discussion. + +Huxley, writing in the "Contemporary Review" (1871.), says, "In a dozen +years "The Origin of Species" has worked as complete a revolution in +biological science as the "Principia" did in astronomy." It has done so +because, in the words of Helmholtz, it contained "an essentially new +creative thought," that of the continuity of life, the absence of breaks. +In the two most conservative subjects, Religion and Classics, this creative +ferment was slow indeed to work. Darwin himself felt strongly "that a man +should not publish on a subject to which he has not given special and +continuous thought," and hence wrote little on religion and with manifest +reluctance, though, as already seen, in answer to pertinacious inquiry he +gave an outline of his own views. But none the less he foresaw that his +doctrine must have, for the history of man's mental evolution, issues wider +than those with which he was prepared personally to deal. He writes, in +"The Origin of Species" (6th edition, page 428.), "In the future I see open +fields for far more important researches. Psychology will be securely +based on the foundation already well laid by Mr Herbert Spencer, that of +the necessary acquirement of each mental power and capacity by gradation." + +Nowhere, it is true, does Darwin definitely say that he regarded religion +as a set of phenomena, the development of which may be studied from the +psychological standpoint. Rather we infer from his PIETY--in the beautiful +Roman sense--towards tradition and association, that religion was to him in +some way sacrosanct. But it is delightful to see how his heart went out +towards the new method in religious study which he had himself, if half- +unconsciously, inaugurated. Writing in 1871 to Dr Tylor, on the +publication of his "Primitive Culture", he says ("Life and Letters", Vol. +III. page 151.), "It is wonderful how you trace animism from the lower +races up the religious belief of the highest races. It will make me for +the future look at religion--a belief in the soul, etc.--from a new point +of view." + +Psychology was henceforth to be based on "the necessary acquirement of each +mental capacity by gradation." With these memorable words the door closes +on the old and opens on the new horizon. The mental focus henceforth is +not on the maintaining or refuting of an orthodoxy but on the genesis and +evolution of a capacity, not on perfection but on process. Continuous +evolution leaves no gap for revelation sudden and complete. We have +henceforth to ask, not when was religion revealed or what was the +revelation, but how did religious phenomena arise and develop. For an +answer to this we turn with new and reverent eyes to study "the heathen in +his blindness" and the child "born in sin." We still indeed send out +missionaries to convert the heathen, but here at least in Cambridge before +they start they attend lectures on anthropology and comparative religion. +The "decadence" theory is dead and should be buried. + +The study of primitive religions then has been made possible and even +inevitable by the theory of Evolution. We have now to ask what new facts +and theories have resulted from that study. This brings us to our second +point, the advanced outlook on religion to-day. + +The view I am about to state is no mere personal opinion of my own. To my +present standpoint I have been led by the investigations of such masters as +Drs Wundt, Lehmann, Preuss, Bergson, Beck and in our own country Drs Tylor +and Frazer. (I can only name here the books that have specially influenced +my own views. They are W. Wundt, "Volkerpsychologie", Leipzig, 1900, P. +Beck, "Die Nachahmung", Leipzig, 1904, and "Erkenntnisstheorie des +primitiven Denkens" in "Zeitschrift f. Philos. und Philos. Kritik", 1903, +page 172, and 1904, page 9. Henri Bergson, "L'Evolution Creatrice" and +"Matiere et Memoire", 1908, K. Th. Preuss, various articles published in +the "Globus" (see page 507, note 1), and in the "Archiv. f. +Religionswissenschaft", and for the subject of magic, MM. Hubert et Mauss, +"Theorie generale de la Magie", in "L'Annee Sociologique", VII.) + +Religion always contains two factors. First, a theoretical factor, what a +man THINKS about the unseen--his theology, or, if we prefer so to call it, +his mythology. Second, what he DOES in relation to this unseen--his +ritual. These factors rarely if ever occur in complete separation; they +are blended in very varying proportions. Religion we have seen was in the +last century regarded mainly in its theoretical aspect as a doctrine. +Greek religion for example meant to most educated persons Greek mythology. +Yet even a cursory examination shows that neither Greek nor Roman had any +creed or dogma, any hard and fast formulation of belief. In the Greek +Mysteries (See my "Prolegomena to the Study of Greek Religion", page 155, +Cambridge, 1903.) only we find what we should call a Confiteor; and this is +not a confession of faith, but an avowal of rites performed. When the +religion of primitive peoples came to be examined it was speedily seen that +though vague beliefs necessarily abound, definite creeds are practically +non-existent. Ritual is dominant and imperative. + +This predominance and priority of ritual over definite creed was first +forced upon our notice by the study of savages, but it promptly and happily +joined hands with modern psychology. Popular belief says, I think, +therefore I act; modern scientific psychology says, I act (or rather, REact +to outside stimulus), and so I come to think. Thus there is set going a +recurrent series: act and thought become in their turn stimuli to fresh +acts and thoughts. In examining religion as envisaged to-day it would +therefore be more correct to begin with the practice of religion, i.e. +ritual, and then pass to its theory, theology or mythology. But it will be +more convenient to adopt the reverse method. The theoretical content of +religion is to those of us who are Protestants far more familiar and we +shall thus proceed from the known to the comparatively unknown. + +I shall avoid all attempt at rigid definition. The problem before the +modern investigator is, not to determine the essence and definition of +religion but to inquire how religious phenomena, religious ideas and +practices arose. Now the theoretical content of religion, the domain of +theology or mythology, is broadly familiar to all. It is the world of the +unseen, the supersensuous; it is the world of what we call the soul and the +supposed objects of the soul's perception, sprites, demons, ghosts and +gods. How did this world grow up? + +We turn to our savages. Intelligent missionaries of bygone days used to +ply savages with questions such as these: Had they any belief in God? Did +they believe in the immortality of the soul? Taking their own clear-cut +conceptions, discriminated by a developed terminology, these missionaries +tried to translate them into languages that had neither the words nor the +thoughts, only a vague, inchoate, tangled substratum, out of which these +thoughts and words later differentiated themselves. Let us examine this +substratum. + +Nowadays we popularly distinguish between objective and subjective; and +further, we regard the two worlds as in some sense opposed. To the +objective world we commonly attribute some reality independent of +consciousness, while we think of the subjective as dependent for its +existence on the mind. The objective world consists of perceptible things, +or of the ultimate constituents to which matter is reduced by physical +speculation. The subjective world is the world of beliefs, hallucinations, +dreams, abstract ideas, imaginations and the like. Psychology of course +knows that the objective and subjective worlds are interdependent, +inextricably intertwined, but for practical purposes the distinction is +convenient. + +But primitive man has not yet drawn the distinction between objective and +subjective. Nay, more, it is foreign to almost the whole of ancient +philosophy. Plato's Ideas (I owe this psychological analysis of the +elements of the primitive supersensuous world mainly to Dr Beck, +"Erkenntnisstheorie des primitiven Denkens", see page 498, note 1.), his +Goodness, Truth, Beauty, his class-names, horse, table, are it is true +dematerialised as far as possible, but they have outside existence, apart +from the mind of the thinker, they have in some shadowy way spatial +extension. Yet ancient philosophies and primitive man alike needed and +possessed for practical purposes a distinction which served as well as our +subjective and objective. To the primitive savage all his thoughts, every +object of which he was conscious, whether by perception or conception, had +reality, that is, it had existence outside himself, but it might have +reality of various kinds or different degrees. + +It is not hard to see how this would happen. A man's senses may mislead +him. He sees the reflection of a bird in a pond. To his eyes it is a real +bird. He touches it, HE PUTS IT TO THE TOUCH, and to his touch it is not a +bird at all. It is real then, but surely not quite so real as a bird that +you can touch. Again, he sees smoke. It is real to his eyes. He tries to +grasp it, it vanishes. The wind touches him, but he cannot see it, which +makes him feel uncanny. The most real thing is that which affects most +senses and especially what affects the sense of touch. Apparently touch is +the deepest down, most primitive, of senses. The rest are specialisations +and complications. Primitive man has no formal rubric "optical delusion," +but he learns practically to distinguish between things that affect only +one sense and things that affect two or more--if he did not he would not +survive. But both classes of things are real to him. Percipi est esse. + +So far, primitive man has made a real observation; there are things that +appeal to one sense only. But very soon creeps in confusion fraught with +disaster. He passes naturally enough, being economical of any mental +effort, from what he really sees but cannot feel to what he thinks he sees, +and gives to it the same secondary reality. He has dreams, visions, +hallucinations, nightmares. He dreams that an enemy is beating him, and he +wakes rubbing his head. Then further he remembers things; that is, for +him, he sees them. A great chief died the other day and they buried him, +but he sees him still in his mind, sees him in his war-paint, splendid, +victorious. So the image of the past goes together with his dreams and +visions to the making of this other less real, but still real world, his +other-world of the supersensuous, the supernatural, a world, the outside +existence of which, independent of himself, he never questions. + +And, naturally enough, the future joins the past in this supersensuous +world. He can hope, he can imagine, he can prophesy. And again the images +of his hope are real; he sees them with that mind's eye which as yet he has +not distinguished from his bodily eye. And so the supersensuous world +grows and grows big with the invisible present, and big also with the past +and the future, crowded with the ghosts of the dead and shadowed with +oracles and portents. It is this supersensuous, supernatural world which +is the eternity, the other-world, of primitive religion, not an endlessness +of time, but a state removed from full sensuous reality, a world in which +anything and everything may happen, a world peopled by demonic ancestors +and liable to a splendid vagueness, to a "once upon a time-ness" denied to +the present. It not unfrequently happens that people who know that the +world nowadays obeys fixed laws have no difficulty in believing that six +thousand years ago man was made direct from a lump of clay, and woman was +made from one of man's superfluous ribs. + +The fashioning of the supersensuous world comes out very clearly in +primitive man's views about the soul and life after death. Herbert Spencer +noted long ago the influence of dreams in forming a belief in immortality, +but being very rational himself, he extended to primitive man a quite alien +quality of rationality. Herbert Spencer argued that when a savage has a +dream he seeks to account for it, and in so doing invents a spirit world. +The mistake here lies in the "seeks to account for it." (Primitive man, as +Dr Beck observes, is not impelled by an Erkenntnisstrieb. Dr Beck says he +has counted upwards of 30 of these mythological Triebe (tendencies) with +which primitive man has been endowed.) Man is at first too busy LIVING to +have any time for disinterested THINKING. He dreams a dream and it is real +for him. He does not seek to account for it any more than for his hands +and feet. He cannot distinguish between a CONception and a PERception, +that is all. He remembers his ancestors or they appear to him in a dream; +therefore they are alive still, but only as a rule to about the third +generation. Then he remembers them no more and they cease to be. + +Next as regards his own soul. He feels something within him, his life- +power, his will to live, his power to act, his personality--whatever we +like to call it. He cannot touch this thing that is himself, but it is +real. His friend too is alive and one day he is dead; he cannot move, he +cannot act. Well, something has gone that was his friend's self. He has +stopped breathing. Was it his breath? or he is bleeding; is it his blood? +This life-power IS something; does it live in his heart or his lungs or his +midriff? He did not see it go; perhaps it is like wind, an anima, a Geist, +a ghost. But again it comes back in a dream, only looking shadowy; it is +not the man's life, it is a thin copy of the man; it is an "image" +(eidolon). It is like that shifting distorted thing that dogs the living +man's footsteps in the sunshine; it is a "shade" (skia). (The two +conceptions of the soul, as a life-essence, inseparable from the body, and +as a separable phantom seem to occur in most primitive systems. They are +distinct conceptions but are inextricably blended in savage thought. The +two notions Korperseele and Psyche have been very fully discussed in +Wundt's "Volkerpsychologie" II. pages 1-142, Leipzig, 1900.) + +Ghosts and sprites, ancestor worship, the soul, oracles, prophecy; all +these elements of the primitive supersensuous world we willingly admit to +be the proper material of religion; but other elements are more surprising; +such are class-names, abstract ideas, numbers, geometrical figures. We do +not nowadays think of these as of religious content, but to primitive men +they were all part of the furniture of his supernatural world. + +With respect to class-names, Dr Tylor ("Primitive Culture", Vol. II. page +245 (4th edition), 1903.) has shown how instructive are the first attempts +of the savage to get at the idea of a class. Things in which similarity is +observed, things indeed which can be related at all are to the savage +KINDRED. A species is a family or a number of individuals with a common +god to look after them. Such for example is the Finn doctrine of the +haltia. Every object has its haltia, but the haltiat were not tied to the +individual, they interested themselves in every member of the species. +Each stone had its haltia, but that haltia was interested in other stones; +the individuals disappeared, the haltia remained. + +Nor was it only class-names that belonged to the supersensuous world. A +man's own proper-name is a sort of spiritual essence of him, a kind of soul +to be carefully concealed. By pronouncing a name you bring the thing +itself into being. When Elohim would create Day "he called out to the +Light 'Day,' and to the Darkness he called out 'Night'"; the great magician +pronounced the magic Names and the Things came into being. "In the +beginning was the Word" is literally true, and this reflects the fact that +our CONCEPTUAL world comes into being by the mental process of naming. (For +a full discussion of this point see Beck, "Nachahmung" page 41, "Die +Sprache".) In old times people went further; they thought that by naming +events they could bring them to be, and custom even to-day keeps up the +inveterate magical habit of wishing people "Good Morning" and a "Happy +Christmas." + +Number, too, is part of the supersensuous world that is thoroughly +religious. We can see and touch seven apples, but seven itself, that +wonderful thing that shifts from object to object, giving it its SEVENness, +that living thing, for it begets itself anew in multiplication--surely +seven is a fit denizen of the upper-world. Originally all numbers dwelt +there, and a certain supersensuous sanctity still clings to seven and +three. We still say "Holy, Holy, Holy," and in some mystic way feel the +holier. + +The soul and the supersensuous world get thinner and thinner, rarer and +more rarified, but they always trail behind them clouds of smoke and vapour +from the world of sense and space whence they have come. It is difficult +for us even nowadays to use the word "soul" without lapsing into a sensuous +mythology. The Cartesians' sharp distinction between res extensa non +cogitans and res cogitans non extansa is remote. + +So far then man, through the processes of his thinking, has provided +himself with a supersensuous world, the world of sense-delusion, of smoke +and cloud, of dream and phantom, of imagination, of name and number and +image. The natural course would now seem to be that this supersensuous +world should develop into the religious world as we know it, that out of a +vague animism with ghosts of ancestors, demons, and the like, there should +develop in due order momentary gods (Augenblicks-Gotter), tribal gods, +polytheism, and finally a pure monotheism. + +This course of development is usually assumed, but it is not I think quite +what really happens. The supersensuous world as we have got it so far is +too theoretic to be complete material of religion. It is indeed only one +factor, or rather it is as it were a lifeless body that waits for a living +spirit to possess and inform it. Had the theoretic factor remained +uninformed it would eventually have separated off into its constituent +elements of error and truth, the error dying down as a belated metaphysic, +the truth developing into a correct and scientific psychology of the +subjective. But man has ritual as well as mythology; that is, he feels and +acts as well as thinks; nay more he probably feels and acts long before he +definitely thinks. This contradicts all our preconceived notions of +theology. Man, we imagine, believes in a god or gods and then worships. +The real order seems to be that, in a sense presently to be explained, he +worships, he feels and acts, and out of his feeling and action, projected +into his confused thinking, he develops a god. We pass therefore to our +second factor in religion:--ritual. + +The word "ritual" brings to our modern minds the notion of a church with a +priesthood and organised services. Instinctively we think of a +congregation meeting to confess sins, to receive absolution, to pray, to +praise, to listen to sermons, and possibly to partake of sacraments. Were +we to examine these fully developed phenomena we should hardly get further +in the analysis of our religious conceptions than the notion of a highly +anthropomorphic god approached by purely human methods of personal entreaty +and adulation. + +Further, when we first come to the study of primitive religions we expect a +priori to find the same elements, though in a ruder form. We expect to see +"The heathen in his blindness bow down to wood and stone," but the facts +that actually confront us are startlingly dissimilar. Bowing down to wood +and stone is an occupation that exists mainly in the minds of hymn-writers. +The real savage is more actively engaged. Instead of asking a god to do +what he wants done, he does it or tries to do it himself; instead of +prayers he utters spells. In a word he is busy practising magic, and above +all he is strenuously engaged in dancing magical dances. When the savage +wants rain or wind or sunshine, he does not go to church; he summons his +tribe and they dance a rain-dance or wind-dance or sun-dance. When a +savage goes to war we must not picture his wife on her knees at home +praying for the absent; instead we must picture her dancing the whole night +long; not for mere joy of heart or to pass the weary hours; she is dancing +his war-dance to bring him victory. + +Magic is nowadays condemned alike by science and by religion; it is both +useless and impious. It is obsolete, and only practised by malign +sorcerers in obscure holes and corners. Undoubtedly magic is neither +religion nor science, but in all probability it is the spiritual protoplasm +from which religion and science ultimately differentiated. As such the +doctrine of evolution bids us scan it closely. Magic may be malign and +private; nowadays it is apt to be both. But in early days magic was as +much for good as for evil; it was publicly practised for the common weal. + +The gist of magic comes out most clearly in magical dances. We think of +dancing as a light form of recreation, practised by the young from sheer +joie de vivre and unsuitable for the mature. But among the Tarahumares +(Carl Lumholtz, "Unknown Mexico", page 330, London, 1903.) in Mexico the +word for dancing, nolavoa, means "to work." Old men will reproach young +men saying "Why do you not go to work?" meaning why do you not dance +instead of only looking on. The chief religious sin of which the +Tarahumare is conscious is that he has not danced enough and not made +enough tesvino, his cereal intoxicant. + +Dancing then is to the savage WORKING, DOING, and the dance is in its +origin an imitation or perhaps rather an intensification of processes of +work. (Karl Bucher, "Arbeit und Rhythmus", Leipzig (3rd edition), 1902, +passim.) Repetition, regular and frequent, constitutes rhythm and rhythm +heightens the sense of will power in action. Rhythmical action may even, +as seen in the dances of Dervishes, produce a condition of ecstasy. +Ecstasy among primitive peoples is a condition much valued; it is often, +though not always, enhanced by the use of intoxicants. Psychologically the +savage starts from the sense of his own will power, he stimulates it by +every means at his command. Feeling his will strongly and knowing nothing +of natural law he recognises no limits to his own power; he feels himself a +magician, a god; he does not pray, he WILLS. Moreover he wills +collectively (The subject of collective hallucination as an element in +magic has been fully worked out by MM. Hubert and Mauss. "Theorie generale +de la Magie", In "L'Annee Sociologique", 1902--3, page 140.), reinforced by +the will and action of his whole tribe. Truly of him it may be said "La +vie deborde l'intelligence, l'intelligence c'est un retrecissement." +(Henri Bergson, "L'Evolution Creatrice", page 50.) + +The magical extension and heightening of personality come out very clearly +in what are rather unfortunately known as MIMETIC dances. Animal dances +occur very frequently among primitive peoples. The dancers dress up as +birds, beasts, or fishes, and reproduce the characteristic movements and +habits of the animals impersonated. So characteristic is this +impersonation in magical dancing that among the Mexicans the word for +magic, navali, means "disguise." K. Th. Preuss, "Archiv f. +Religionswissenschaft", 1906, page 97.) A very common animal dance is the +frog-dance. When it rains the frogs croak. If you desire rain you dress +up like a frog and croak and jump. We think of such a performance as a +conscious imitation. The man, we think, is more or less LIKE a frog. That +is not how primitive man thinks; indeed, he scarcely thinks at all; what HE +wants done the frog can do by croaking and jumping, so he croaks and jumps +and, for all he can, BECOMES a frog. "L'intelligence animale JOUE sans +doute les representations plutot qu'elle ne les pense." (Bergson, +"L'Evolution Creatrice", page 205.) + +We shall best understand this primitive state of mind if we study the child +"born in sin." If a child is "playing at lions" he does not IMITATE a +lion, i.e. he does not consciously try to be a thing more or less like a +lion, he BECOMES one. His reaction, his terror, is the same as if the real +lion were there. It is this childlike power of utter impersonation, of +BEING the thing we act or even see acted, this extension and +intensification of our own personality that lives deep down in all of us +and is the very seat and secret of our joy in the drama. + +A child's mind is indeed throughout the best clue to the understanding of +savage magic. A young and vital child knows no limit to his own will, and +it is the only reality to him. It is not that he wants at the outset to +fight other wills, but that they simply do not exist for him. Like the +artist he goes forth to the work of creation, gloriously alone. His +attitude towards other recalcitrant wills is "they simply must." Let even +a grown man be intoxicated, be in love, or subject to an intense +excitement, the limitations of personality again fall away. Like the +omnipotent child he is again a god, and to him all things are possible. +Only when he is old and weary does he cease to command fate. + +The Iroquois (Hewitt, "American Anthropologist", IV. I. page 32, 1902, +N.S.) of North America have a word, orenda, the meaning of which is easier +to describe than to define, but it seems to express the very soul of magic. +This orenda is your power to do things, your force, sometimes almost your +personality. A man who hunts well has much and good orenda; the shy bird +who escapes his snares has a fine orenda. The orenda of the rabbit +controls the snow and fixes the depth to which it will fall. When a storm +is brewing the magician is said to be making its orenda. When you yourself +are in a rage, great is your orenda. The notes of birds are utterances of +their orenda. When the maize is ripening, the Iroquois know it is the +sun's heat that ripens it, but they know more; it is the cigala makes the +sun to shine and he does it by chirping, by uttering his orenda. This +orenda is sometimes very like the Greek thumos, your bodily life, your +vigour, your passion, your power, the virtue that is in you to feel and do. +This notion of orenda, a sort of pan-vitalism, is more fluid than animism, +and probably precedes it. It is the projection of man's inner experience, +vague and unanalysed, into the outer world. + +The mana of the Melanesians (Codrington, "The Melanesians", pages 118, 119, +192, Oxford, 1891.) is somewhat more specialised--all men do not possess +mana--but substantially it is the same idea. Mana is not only a force, it +is also an action, a quality, a state, at once a substantive, an adjective, +and a verb. It is very closely neighboured by the idea of sanctity. +Things that have mana are tabu. Like orenda it manifests itself in noises, +but specially mysterious ones, it is mana that is rustling in the trees. +Mana is highly contagious, it can pass from a holy stone to a man or even +to his shadow if it cross the stone. "All Melanesian religion," Dr +Codrington says, "consists in getting mana for oneself or getting it used +for one's benefit." (Codrington, "The Melanesians", page 120, Oxford, +1891.) + +Specially instructive is a word in use among the Omaka (See Prof. Haddon, +"Magic and Fetishism", page 60, London, 1906. Dr Vierkandt ("Globus", +July, 1907, page 41) thinks that "Fernzauber" is a later development from +Nahzauber.), wazhin-dhedhe, "directive energy, to send." This word means +roughly what we should call telepathy, sending out your thought or will- +power to influence another and affect his action. Here we seem to get +light on what has always been a puzzle, the belief in magic exercised at a +distance. For the savage will, distance is practically non-existent, his +intense desire feels itself as non-spatial. (This notion of mana, orenda, +wazhin-dhedhe and the like lives on among civilised peoples in such words +as the Vedic brahman in the neuter, familiar to us in its masculine form +Brahman. The neuter, brahman, means magic power of a rite, a rite itself, +formula, charm, also first principle, essence of the universe. It is own +cousin to the Greek dunamis and phusis. See MM. Hubert et Mauss, "Theorie +generale de la Magie", page 117, in "L'Annee Sociologique", VII.) + +Through the examination of primitive ritual we have at last got at one +tangible, substantial factor in religion, a real live experience, the +sense, that is, of will, desire, power actually experienced in person by +the individual, and by him projected, extended into the rest of the world. + +At this stage it may fairly be asked, though the question cannot with any +certainty be answered, "at what point in the evolution of man does this +religious experience come in?" + +So long as an organism reacts immediately to outside stimulus, with a +certainty and conformity that is almost chemical, there is, it would seem, +no place, no possibility for magical experience. But when the germ appears +of an intellect that can foresee an end not immediately realised, or rather +when a desire arises that we feel and recognise as not satisfied, then +comes in the sense of will and the impulse magically to intensify that +will. The animal it would seem is preserved by instinct from drawing into +his horizon things which do not immediately subserve the conservation of +his species. But the moment man's life-power began to make on the outside +world demands not immediately and inevitably realised in action (I owe this +observation to Dr K. Th. Preuss. He writes ("Archiv f. Relig." 1906, page +98), "Die Betonung des Willens in den Zauberakten ist der richtige Kern. +In der Tat muss der Mensch den Willen haben, sich selbst und seiner +Umgebung besondere Fahigkeiten zuzuschreiben, und den Willen hat er, sobald +sein Verstand ihn befahigt, EINE UBER DEN INSTINKT HINAUSGEHEN DER FURSORGE +fur sich zu zeigen. SO LANGE IHN DER INSTINKT ALLEIN LEITET, KONNEN +ZAUBERHANDLUNGEN NICHT ENSTEHEN." For more detailed analysis of the origin +of magic, see Dr Preuss "Ursprung der Religion und Kunst", "Globus", +LXXXVI. and LXXXVII.), then a door was opened to magic, and in the train of +magic followed errors innumerable, but also religion, philosophy, science +and art. + +The world of mana, orenda, brahman is a world of feeling, desiring, +willing, acting. What element of thinking there may be in it is not yet +differentiated out. But we have already seen that a supersensuous world of +thought grew up very early in answer to other needs, a world of sense- +illusions, shadows, dreams, souls, ghosts, ancestors, names, numbers, +images, a world only wanting as it were the impulse of mana to live as a +religion. Which of the two worlds, the world of thinking or the world of +doing, developed first it is probably idle to inquire. (If external +stimuli leave on organisms a trace or record such as is known as an Engram, +this physical basis of memory and hence of thought is almost coincident +with reaction of the most elementary kind. See Mr Francis Darwin's +Presidential Address to the British Association, Dublin, 1908, page 8, and +again Bergson places memory at the very root of conscious existence, see +"L'Evolution Creatrice", page 18, "le fond meme de notre existence +consciente est memoire, c'est a dire prolongation du passee dans le +present," and again "la duree mord dans le temps et y laisse l'enpreint de +son dent," and again, "l'Evolution implique une continuation reelle du +passee par le present.") + +It is more important to ask, Why do these two worlds join? Because, it +would seem, mana, the egomaniac or megalomaniac element, cannot get +satisfied with real things, and therefore goes eagerly out to a false +world, the supersensuous other-world whose growth we have sketched. This +junction of the two is fact, not fancy. Among all primitive peoples dead +men, ghosts, spirits of all kinds, become the chosen vehicle of mana. Even +to this day it is sometimes urged that religion, i.e. belief in the +immortality of the soul, is true "because it satisfies the deepest craving +of human nature." The two worlds, of mana and magic on the one hand, of +ghosts and other-world on the other, combine so easily because they have +the same laws, or rather the same comparative absence of law. As in the +world of dreams and ghosts, so in the world of mana, space and time offer +no obstacles; with magic all things are possible. In the one world what +you imagine is real; in the other what you desire is ipso facto +accomplished. Both worlds are egocentric, megalomaniac, filled to the full +with unbridled human will and desire. + +We are all of us born in sin, in that sin which is to science "the seventh +and deadliest," anthropomorphism, we are egocentric, ego-projective. Hence +necessarily we make our gods in our own image. Anthropomorphism is often +spoken of in books on religion and mythology as if it were a last climax, a +splendid final achievement in religious thought. First, we are told, we +have the lifeless object as god (fetichism), then the plant or animal +(phytomorphism, theriomorphism), and last God is incarnate in the human +form divine. This way of putting things is misleading. Anthropomorphism +lies at the very beginning of our consciousness. Man's first achievement +in thought is to realise that there is anything at all not himself, any +object to his subject. When he has achieved however dimly this +distinction, still for long, for very long he can only think of those other +things in terms of himself; plants and animals are people with ways of +their own, stronger or weaker than himself but to all intents and purposes +human. + +Again the child helps us to understand our own primitive selves. To +children animals are always people. You promise to take a child for a +drive. The child comes up beaming with a furry bear in her arms. You say +the bear cannot go. The child bursts into tears. You think it is because +the child cannot endure to be separated from a toy. It is no such thing. +It is the intolerable hurt done to the bear's human heart--a hurt not to be +healed by any proffer of buns. He wanted to go, but he was a shy, proud +bear, and he would not say so. + +The relation of magic to religion has been much disputed. According to one +school religion develops out of magic, according to another, though they +ultimately blend, they are at the outset diametrically opposed, magic being +a sort of rudimentary and mistaken science (This view held by Dr Frazer is +fully set forth in his "Golden Bough" (2nd edition), pages 73-79, London, +1900. It is criticised by Mr R.R. Marett in "From Spell to Prayer", "Folk- +Lore" XI. 1900, page 132, also very fully by MM. Hubert and Mauss, "Theorie +generale de la Magie", in "L'Annee Sociologique", VII. page 1, with Mr +Marett's view and with that of MM. Hubert and Mauss I am in substantial +agreement.), religion having to do from the outset with spirits. + +But, setting controversy aside, at the present stage of our inquiry their +relation becomes, I think, fairly clear. Magic is, if my view (This view +as explained above is, I believe, my own most serious contribution to the +subject. In thinking it out I was much helped by Prof. Gilbert Murray.) be +correct, the active element which informs a supersensuous world fashioned +to meet other needs. This blend of theory and practice it is convenient to +call religion. In practice the transition from magic to religion, from +Spell to Prayer, has always been found easy. So long as mana remains +impersonal you order it about; when it is personified and bulks to the +shape of an overgrown man, you drop the imperative and cringe before it. +"My will be done" is magic, "Thy Will be done" is the last word in +religion. The moral discipline involved in the second is momentous, the +intellectual advance not striking. + +I have spoken of magical ritual as though it were the informing life-spirit +without which religion was left as an empty shell. Yet the word ritual +does not, as normally used, convey to our minds this notion of intense +vitalism. Rather we associate ritual with something cut and dried, a +matter of prescribed form and monotonous repetition. The association is +correct; ritual tends to become less and less informed by the life-impulse, +more and more externalised. Dr Beck ("Die Nachahmung und ihre Bedeutung +fur Psychologie und Volkerkunde", Leipzig, 1904.) in his brilliant +monograph on "Imitation" has laid stress on the almost boundless influence +of the imitation of one man by another in the evolution of civilisation. +Imitation is one of the chief spurs to action. Imitation begets custom, +custom begets sanctity. At first all custom is sacred. To the savage it +is as much a religious duty to tattoo himself as to sacrifice to his gods. +But certain customs naturally survive, because they are really useful; they +actually have good effects, and so need no social sanction. Others are +really useless; but man is too conservative and imitative to abandon them. +These become ritual. Custom is cautious, but la vie est aleatoire. +(Bergson, op. cit. page 143.) + +Dr Beck's remarks on ritual are I think profoundly true and suggestive, but +with this reservation--they are true of ritual only when uninformed by +personal experience. The very elements in ritual on which Dr Beck lays +such stress, imitation, repetition, uniformity and social collectivity, +have been found by the experience of all time to have a twofold influence-- +they inhibit the intellect, they stimulate and suggest emotion, ecstasy, +trance. The Church of Rome knows what she is about when she prescribes the +telling of the rosary. Mystery-cults and sacraments, the lineal +descendants of magic, all contain rites charged with suggestion, with +symbols, with gestures, with half-understood formularies, with all the +apparatus of appeal to emotion and will--the more unintelligible they are +the better they serve their purpose of inhibiting thought. Thus ritual +deadens the intellect and stimulates will, desire, emotion. "Les +operations magiques...sont le resultat d'une science et d'une habitude qui +exaltent la volonte humaine au-dessus de ses limites habituelles." +(Eliphas Levi, "Dogme et Rituel de la haute Magie", II. page 32, Paris, +1861, and "A defence of Magic", by Evelyn Underhill, "Fortnightly Review", +1907.) It is this personal EXPERIENCE, this exaltation, this sense of +immediate, non-intellectual revelation, of mystical oneness with all +things, that again and again rehabilitates a ritual otherwise moribund. + +To resume. The outcome of our examination of ORIGINES seems to be that +religious phenomena result from two delusive processes--a delusion of the +non-critical intellect, a delusion of the over-confident will. Is religion +then entirely a delusion? I think not. (I am deeply conscious that what I +say here is a merely personal opinion or sentiment, unsupported and perhaps +unsupportable by reason, and very possibly quite worthless, but for fear of +misunderstanding I prefer to state it.) Every dogma religion has hitherto +produced is probably false, but for all that the religious or mystical +spirit may be the only way of apprehending some things and these of +enormous importance. It may also be that the contents of this mystical +apprehension cannot be put into language without being falsified and +misstated, that they have rather to be felt and lived than uttered and +intellectually analysed, and thus do not properly fall under the category +of true or false, in the sense in which these words are applied to +propositions; yet they may be something for which "true" is our nearest +existing word and are often, if not necessary at least highly advantageous +to life. That is why man through a series of more or less grossly +anthropomorphic mythologies and theologies with their concomitant rituals +tries to restate them. Meantime we need not despair. Serious psychology +is yet young and has only just joined hands with physiology. Religious +students are still hampered by mediaevalisms such as Body and Soul, and by +the perhaps scarcely less mythological segregations of Intellect, Emotion, +Will. But new facts (See the "Proceedings" of the Society for Psychical +Research, London, passim, and especially Vols. VII.-XV. For a valuable +collection of the phenomena of mysticism, see William James, "Varieties of +Religious Experience", Edinburgh, 1901-2.) are accumulating, facts about +the formation and flux of personality, and the relations between the +conscious and the sub-conscious. Any moment some great imagination may +leap out into the dark, touch the secret places of life, lay bare the +cardinal mystery of the marriage of the spatial with the non-spatial. It +is, I venture to think, towards the apprehension of such mysteries, not by +reason only, but by man's whole personality, that the religious spirit in +the course of its evolution through ancient magic and modern mysticism is +ever blindly yet persistently moving. + +Be this as it may, it is by thinking of religion in the light of evolution, +not as a revelation given, not as a realite faite but as a process, and it +is so only, I think, that we attain to a spirit of real patience and +tolerance. We have ourselves perhaps learnt laboriously something of the +working of natural law, something of the limitations of our human will, and +we have therefore renounced the practice of magic. Yet we are bidden by +those in high places to pray "Sanctify this water to the mystical washing +away of sin." Mystical in this connection spells magical, and we have no +place for a god-magician: the prayer is to us unmeaning, irreverent. Or +again, after much toil we have ceased, or hope we have ceased, to think +anthropomorphically. Yet we are invited to offer formal thanks to God for +a meal of flesh whose sanctity is the last survival of that sacrifice of +bulls and goats he has renounced. Such a ritual confuses our intellect and +fails to stir our emotion. But to others this ritual, magical or +anthropomorphic as it is, is charged with emotional impulse, and others, a +still larger number, think that they act by reason when really they are +hypnotised by suggestion and tradition; their fathers did this or that and +at all costs they must do it. It was good that primitive man in his youth +should bear the yoke of conservative custom; from each man's neck that yoke +will fall, when and because he has outgrown it. Science teaches us to +await that moment with her own inward and abiding patience. Such a +patience, such a gentleness we may well seek to practise in the spirit and +in the memory of Darwin. + + +XXVI. EVOLUTION AND THE SCIENCE OF LANGUAGE. + +By P. GILES, M.A., LL.D. (Aberdeen), +Reader in Comparative Philology in the University of Cambridge. + +In no study has the historical method had a more salutary influence than in +the Science of Language. Even the earliest records show that the meaning +of the names of persons, places, and common objects was then, as it has +always been since, a matter of interest to mankind. And in every age the +common man has regarded himself as competent without special training to +explain by inspection (if one may use a mathematical phrase) the meaning of +any words that attracted his attention. Out of this amateur etymologising +has sprung a great amount of false history, a kind of historical mythology +invented to explain familiar names. A single example will illustrate the +tendency. According to the local legend the ancestor of the Earl of +Erroll--a husbandman who stayed the flight of his countrymen in the battle +of Luncarty and won the victory over the Danes by the help of the yoke of +his oxen--exhausted with the fray uttered the exclamation "Hoch heigh!" +The grateful king about to ennoble the victorious ploughman at once +replied: + +"Hoch heigh! said ye +And Hay shall ye be." + +The Norman origin of the name Hay is well-known, and the battle of Luncarty +long preceded the appearance of Normans in Scotland, but the legend +nevertheless persists. + +Though the earliest European treatise on philological questions which is +now extant--the "Cratylus" of Plato,--as might be expected from its +authorship, contains some acute thinking and some shrewd guesses, yet the +work as a whole is infantine in its handling of language, and it has been +doubted whether Plato was more than half serious in some of the suggestions +which he puts forward. (For an account of the "Cratylus" with references +to other literature see Sandys' "History of Classical Scholarship", I. page +92 ff., Cambridge, 1903.) In the hands of the Romans things were worse +even than they had been in the hands of Plato and his Greek successors. +The lack of success on the part of Varro and later Roman writers may have +been partly due to the fact that, from the etymological point of view, +Latin is a much more difficult language than Greek; it is by no means so +closely connected with Greek as the ancients imagined, and they had no +knowledge of the Celtic languages from which, on some sides at least, much +greater light on the history of the Latin language might have been +obtained. Roman civilisation was a late development compared with Greek, +and its records dating earlier than 300 B.C.--a period when the best of +Greek literature was already in existence--are very few and scanty. Varro +it is true was much more of an antiquary than Plato, but his extant works +seem to show that he was rather a "dungeon of learning" than an original +thinker. + +A scientific knowledge of language can be obtained only by comparison of +different languages of the same family and the contrasting of their +characteristics with those of another family or other families. It never +occurred to the Greeks that any foreign language was worthy of serious +study. Herodotus and other travellers and antiquaries indeed picked up +individual words from various languages, either as being necessary in +communication with the inhabitants of the countries where they sojourned, +or because of some point which interested them personally. Plato and +others noticed the similarity of some Phrygian words to Greek, but no +systematic comparison seems ever to have been instituted. + +In the Middle Ages the treatment of language was in a sense more +historical. The Middle Ages started with the hypothesis, derived from the +book of Genesis, that in the early world all men were of one language and +of one speech. Though on the same authority they believed that the plain +of Shinar has seen that confusion of tongues whence sprang all the +languages upon earth, they seem to have considered that the words of each +separate language were nevertheless derived from this original tongue. And +as Hebrew was the language of the Chosen People, it was naturally assumed +that this original tongue was Hebrew. Hence we find Dante declaring in his +treatise on the Vulgar Tongue (Dante "de Vulgari Eloquio", I. 4.) that the +first word man uttered in Paradise must have been "El," the Hebrew name of +his Maker, while as a result of the fall of Adam, the first utterance of +every child now born into this world of sin and misery is "heu," Alas! +After the splendidly engraved bronze plates containing, as we now know, +ritual regulations for certain cults, were discovered in 1444 at the town +of Gubbio, in Umbria, they were declared, by some authorities, to be +written in excellent Hebrew. The study of them has been the fascination +and the despair of many a philologist. Thanks to the devoted labours of +numerous scholars, mainly in the last sixty years, the general drift of +these inscriptions is now known. They are the only important records of +the ancient Umbrian language, which was related closely to that of the +Samnites and, though not so closely, to that of the Romans on the other +side of the Apennines. Yet less than twenty years ago a book was published +in Germany, which boasts itself the home of Comparative Philology, wherein +the German origin of the Umbrian language was no less solemnly demonstrated +than had been its Celtic origin by Sir William Betham in 1842. + +It is good that the study of language should be historical, but the first +requisite is that the history should be sound. How little had been learnt +of the true history of language a century ago may be seen from a little +book by Stephen Weston first published in 1802 and several times reprinted, +where accidental assonance is considered sufficient to establish +connection. Is there not a word "bad" in English and a word "bad" in +Persian which mean the same thing? Clearly therefore Persian and English +must be connected. The conclusion is true, but it is drawn from erroneous +premises. As stated, this identity has no more value than the similar +assonance between the English "cover" and the Hebrew "kophar", where the +history of "cover" as coming through French from a Latin "co-operire" was +even in 1802 well-known to many. To this day, in spite of recent elaborate +attempts (Most recently in H. Moller's "Semitisch und Indogermanisch", +Erster Teil, Kopenhagen, 1907.) to establish connection between the Indo- +Germanic and the Semitic families of languages, there is no satisfactory +evidence of such relation between these families. This is not to deny the +possibility of such a connection at a very early period; it is merely to +say that through the lapse of long ages all trustworthy record of such +relationship, if it ever existed, has been, so far as present knowledge +extends, obliterated. + +But while Stephen Weston was publishing, with much public approval, his +collection of amusing similarities between languages--similarities which +proved nothing--the key to the historical study of at least one family of +languages had already been found by a learned Englishman in a distant land. +In 1783 Sir William Jones had been sent out as a judge in the supreme court +of judicature in Bengal. While still a young man at Oxford he was noted as +a linguist; his reputation as a Persian scholar had preceded him to the +East. In the intervals of his professional duties he made a careful study +of the language which was held sacred by the natives of the country in +which he was living. He was mainly instrumental in establishing a society +for the investigation of language and related subjects. He was himself the +first president of the society, and in the "third anniversary discourse" +delivered on February 2, 1786, he made the following observations: "The +Sanscrit language, whatever be its antiquity, is of a wonderful structure; +more perfect than the GREEK, more copious than the LATIN, and more +exquisitely refined than either, yet bearing to both of them a stronger +affinity, both in the roots of verbs and in the forms of grammar, than +could possibly have been produced by accident; so strong indeed, that no +philologer could examine them all three, without believing them to have +sprung from some common source, which, perhaps, no longer exists: there is +a similar reason, though not quite so forcible, for supposing that both the +Gothick and the Celtick, though blended with a very different idiom, had +the same origin with the Sanscrit; and the old Persian might be added to +the same family, if this was the place for discussing any question +concerning the antiquities of Persia." ("Asiatic Researches", I. page 422, +"Works of Sir W. Jones", I. page 26, London, 1799.) + +No such epoch-making discovery was probably ever announced with less +flourish of trumpets. Though Sir William Jones lived for eight years more +and delivered other anniversary discourses, he added nothing of importance +to this utterance. He had neither the time nor the health that was needed +for the prosecution of so arduous an undertaking. + +But the good seed did not fall upon stony ground. The news was speedily +conveyed to Europe. By a happy chance, the sudden renewal of war between +France and England in 1803 gave Friedrich Schlegel the opportunity of +learning Sanscrit from Alexander Hamilton, an Englishman who, like many +others, was confined in Paris during the long struggle with Napoleon. The +influence of Schlegel was not altogether for good in the history of this +research, but he was inspiring. Not upon him but upon Franz Bopp, a +struggling German student who spent some time in Paris and London a dozen +years later, fell the mantle of Sir William Jones. In Bopp's Comparative +Grammar of the Indo-Germanic languages which appeared in 1833, three- +quarters of a century ago, the foundations of Comparative Philology were +laid. Since that day the literature of the subject has grown till it is +almost, if not altogether, beyond the power of any single man to cope with +it. But long as the discourse may be, it is but the elaboration of the +text that Sir William Jones supplied. + +With the publication of Bopp's Comparative Grammar the historical study of +language was put upon a stable footing. Needless to say much remained to +be done, much still remains to be done. More than once there has been +danger of the study following erroneous paths. Its terminology and its +point of view have in some degree changed. But nothing can shake the truth +of the statement that the Indo-Germanic languages constitute in themselves +a family sprung from the same source, marked by the same characteristics, +and differentiated from all other languages by formation, by vocabulary, +and by syntax. The historical method was applied to language long before +it reached biology. Nearly a quarter of a century before Charles Darwin +was born, Sir William Jones had made the first suggestion of a comparative +study of languages. Bopp's Comparative Grammar began to be published nine +years before the first draft of Darwin's treatise on the Origin of Species +was put on paper in 1842. + +It is not therefore on the history of Comparative Philology in general that +the ideas of Darwin have had most influence. Unfortunately, as Jowett has +said in the introduction to his translation of Plato's "Republic", most men +live in a corner. The specialisation of knowledge has many advantages, but +it has also disadvantages, none worse perhaps than that it tends to narrow +the specialist's horizon and to make it more difficult for one worker to +follow the advances that are being made by workers in other departments. +No longer is it possible as in earlier days for an intellectual prophet to +survey from a Pisgah height all the Promised Land. And the case of +linguistic research has been specially hard. This study has, if the +metaphor may be allowed, a very extended frontier. On one side it touches +the domain of literature, on other sides it is conterminous with history, +with ethnology and anthropology, with physiology in so far as language is +the production of the brain and tissues of a living being, with physics in +questions of pitch and stress accent, with mental science in so far as the +principles of similarity, contrast, and contiguity affect the forms and the +meanings of words through association of ideas. The territory of +linguistic study is immense, and it has much to supply which might be +useful to the neighbours who border on that territory. But they have not +regarded her even with that interest which is called benevolent because it +is not actively maleficent. As Horne Tooke remarked a century ago, Locke +had found a whole philosophy in language. What have the philosophers done +for language since? The disciples of Kant and of Wilhelm von Humboldt +supplied her plentifully with the sour grapes of metaphysics; otherwise her +neighbours have left her severely alone save for an occasional "Ausflug," +on which it was clear they had sadly lost their bearings. Some articles in +Psychological Journals, Wundt's great work on "Volkerpsychologie" (Erster +Band: "Die Sprache", Leipzig, 1900. New edition, 1904. This work has +been fertile in producing both opponents and supporters. Delbruck, +"Grundfragen der Sprachforschung", Strassburg, 1901, with a rejoinder by +Wundt, "Sprachgeschichte" and "Sprachpsychologie", Leipzig, 1901; L. +Sutterlin, "Das Wesen der Sprachgebilde", Heidelberg, 1902; von +Rozwadowski, "Wortbildung und Wortbedeutung", Heidelberg, 1904; O. +Dittrich, "Grundzuge der Sprachpsychologie", Halle, 1904, Ch. A. Sechehaye, +"Programme et methodes de la linguistique theorique", Paris, 1908.), and +Mauthner's brilliantly written "Beitrage zu einer Kritik der Sprache" (In +three parts: (i) "Sprache und Psychologie, (ii) "Zur Sprachwissenschaft", +both Stuttgart 1901, (iii) "Zur Grammatic und Logik" (with index to all +three volumes), Stuttgart and Berlin, 1902.) give some reason to hope that, +on one side at least, the future may be better than the past. + +Where Charles Darwin's special studies came in contact with the Science of +Language was over the problem of the origin and development of language. +It is curious to observe that, where so many fields of linguistic research +have still to be reclaimed--many as yet can hardly be said to be mapped +out,--the least accessible field of all--that of the Origin of Language-- +has never wanted assiduous tillers. Unfortunately it is a field beyond +most others where it may be said that + +"Wilding oats and luckless darnel grow." + +If Comparative Philology is to work to purpose here, it must be on results +derived from careful study of individual languages and groups of languages. +But as yet the group which Sir William Jones first mapped out and which +Bopp organised is the only one where much has been achieved. Investigation +of the Semitic group, in some respects of no less moment in the history of +civilisation and religion, where perhaps the labour of comparison is not so +difficult, as the languages differ less among themselves, has for some +reason strangely lagged behind. Some years ago in the "American Journal of +Philology" Paul Haupt pointed out that if advance was to be made, it must +be made according to the principles which had guided the investigation of +the Indo-Germanic languages to success, and at last a Comparative Grammar +of an elaborate kind is in progress also for the Semitic languages. +(Brockelmann, "Vergleichende Grammatik der semitischen Sprachen", Berlin, +1907 ff. Brockelmann and Zimmern had earlier produced two small hand- +books. The only large work was William Wright's "Lectures on the +Comparative Grammar of the Semitic Languages", Cambridge, 1890.) For the +great group which includes Finnish, Hungarian, Turkish and many languages +of northern Asia, a beginning, but only a beginning has been made. It may +be presumed from the great discoveries which are in progress in Turkestan +that presently much more will be achieved in this field. But for a certain +utterance to be given by Comparative Philology on the question of the +origin of language it is necessary that not merely for these languages but +also for those in other quarters of the globe, the facts should be +collected, sifted and tabulated. England rules an empire which contains a +greater variety of languages by far than were ever held under one sway +before. The Government of India is engaged in producing, under the +editorship of Dr Grierson, a linguistic survey of India, a remarkable +undertaking and, so far as it has gone, a remarkable achievement. Is it +too much to ask that, with the support of the self-governing colonies, a +similar survey should be undertaken for the whole of the British Empire? + +Notwithstanding the great number of books that have been written on the +origin of language in the last three and twenty centuries, the results of +the investigation which can be described as certain are very meagre. The +question originally raised was whether language came into being thesei or +phusei, by convention or by nature. The first alternative, in its baldest +form at least, has passed from out the field of controversy. No one now +claims that names were given to living things or objects or activities by +formal agreement among the members of an early community, or that the first +father of mankind passed in review every living thing and gave it its name. +Even if the record of Adam's action were to be taken literally there would +still remain the question, whence had he this power? Did he develop it +himself or was it a miraculous gift with which he was endowed at his +creation? If the latter, then as Wundt says ("Volkerpsychologie", I. 2, +page 585.), "the miracle of language is subsumed in the miracle of +creation." If Adam developed language of himself, we are carried over to +the alternative origin of phusei. On this hypothesis we must assume that +the natural growth which modern theories of development regard as the +painful progress of multitudinous generations was contracted into the +experience of a single individual. + +But even if the origin of language is admitted to be NATURAL there may +still be much variety of signification attached to the word: NATURE, like +most words which are used by philosophers, has accumulated many meanings, +and as research into the natural world proceeds, is accumulating more. + +Forty years ago an animated controversy raged among the supporters of the +theories which were named for short the bow-wow, the pooh-pooh and the +ding-dong theories of the origin of language. The third, which was the +least tenacious of life, was made known to the English-speaking world by +the late Professor Max Muller who, however, when questioned, repudiated it +as his own belief. ("Science of Thought", London, 1887, page 211.) It was +taken by him from Heyse's lectures on language which were published +posthumously by Steinthal. Put shortly the theory is that "everything +which is struck, rings. Each substance has its peculiar ring. We can tell +the more or less perfect structure of metals by their vibrations, by the +answer which they give. Gold rings differently from tin, wood rings +differently from stone; and different sounds are produced according to the +nature of each percussion. It may be the same with man, the most highly +organised of nature's work." (Max Muller as above, translating from +Heyse.) Max Muller's repudiation of this theory was, however, not very +whole-hearted for he proceeds later in the same argument: "Heyse's theory, +which I neither adopted nor rejected, but which, as will be seen, is by no +means incompatible with that which for many years has been gaining on me, +and which of late has been so clearly formulated by Professor Noire, has +been assailed with ridicule and torn to pieces, often by persons who did +not even suspect how much truth was hidden behind its paradoxical +appearance. We are still very far from being able to identify roots with +nervous vibrations, but if it should appear hereafter that sensuous +vibrations supply at least the raw material of roots, it is quite possible +that the theory, proposed by Oken and Heyse, will retain its place in the +history of the various attempts at solving the problem of the origin of +language, when other theories, which in our own days were received with +popular applause, will be completely forgotten." ("Science of Thought", +page 212.) + +Like a good deal else that has been written on the origin of language, this +statement perhaps is not likely to be altogether clear to the plain man, +who may feel that even the "raw material of roots" is some distance removed +from nervous vibrations, though obviously without the existence of afferent +and efferent nerves articulate speech would be impossible. But Heyse's +theory undoubtedly was that every thought or idea which occurred to the +mind of man for the first time had its own special phonetic expression, and +that this responsive faculty, when its object was thus fulfilled, became +extinct. Apart from the philosophical question whether the mind acts +without external stimulus, into which it is not necessary to enter here, it +is clear that this theory can neither be proved nor disproved, because it +postulates that this faculty existed only when language first began, and +later altogether disappeared. As we have already seen, it is impossible +for us to know what happened at the first beginnings of language, because +we have no information from any period even approximately so remote; nor +are we likely to attain it. Even in their earliest stages the great +families of language which possess a history extending over many centuries +--the Indo-Germanic and the Semitic--have very little in common. With the +exception of Chinese, the languages which are apparently of a simpler or +more primitive formation have either a history which, compared with that of +the families mentioned, is very short, or, as in the case of the vast +majority, have no history beyond the time extending only over a few years +or, at most, a few centuries when they have been observed by competent +scholars of European origin. But, if we may judge by the history of +geology and other studies, it is well to be cautious in assuming for the +first stages of development forces which do not operate in the later, +unless we have direct evidence of their existence. + +It is unnecessary here to enter into a prolonged discussion of the other +views christened by Max Muller, not without energetic protest from their +supporters, the bow-wow and pooh-pooh theories of language. Suffice it to +say that the former recognises as a source of language the imitation of the +sounds made by animals, the fall of bodies into water or on to solid +substances and the like, while the latter, also called the interjectional +theory, looks to the natural ejaculations produced by particular forms of +effort for the first beginnings of speech. It would be futile to deny that +some words in most languages come from imitation, and that others, probably +fewer in number, can be traced to ejaculations. But if either of these +sources alone or both in combination gave rise to primitive speech, it +clearly must have been a simple form of language and very limited in +amount. There is no reason to think that it was otherwise. Presumably in +its earliest stages language only indicated the most elementary ideas, +demands for food or the gratification of other appetites, indications of +danger, useful animals and plants. Some of these, such as animals or +indications of danger, could often be easily represented by imitative +sounds: the need for food and the like could be indicated by gesture and +natural cries. Both sources are verae causae; to them Noire, supported by +Max Muller, has added another which has sometimes been called the Yo-heave- +ho theory. Noire contends that the real crux in the early stages of +language is for primitive man to make other primitive men understand what +he means. The vocal signs which commend themselves to one may not have +occurred to another, and may therefore be unintelligible. It may be +admitted that this difficulty exists, but it is not insuperable. The old +story of the European in China who, sitting down to a meal and being +doubtful what the meat in the dish might be, addressed an interrogative +Quack-quack? to the waiter and was promptly answered by Bow-wow, +illustrates a simple situation where mutual understanding was easy. But +obviously many situations would be more complex than this, and to grapple +with them Noire has introduced his theory of communal action. "It was +common effort directed to a common object, it was the most primitive +(uralteste) labour of our ancestors, from which sprang language and the +life of reason." (Noire "Der Ursprung der Sprache", page 331, Mainz, +1877.) As illustrations of such common effort he cites battle cries, the +rescue of a ship running on shore (a situation not likely to occur very +early in the history of man), and others. Like Max Muller he holds that +language is the utterance and the organ of thought for mankind, the one +characteristic which separates man from the brute. "In common action the +word was first produced; for long it was inseparably connected with action; +through long-continued connection it gradually became the firm, +intelligible symbol of action, and then in its development indicated also +things of the external world in so far as the action affected them and +finally the sound began to enter into a connexion with them also." (Op. +cit. page 339.) In so far as this theory recognises language as a social +institution it is undoubtedly correct. Darwin some years before Noire had +pointed to the same social origin of language in the fourth chapter of his +work on "The Expression of the Emotions in Man and Animals". "Naturalists +have remarked, I believe with truth, that social animals, from habitually +using their vocal organs as a means of intercommunication, use them on +other occasions much more freely than other animals...The principle, also, +of association, which is so widely extended in its power, has likewise +played its part. Hence it allows that the voice, from having been employed +as a serviceable aid under certain conditions, inducing pleasure, pain, +rage, etc., is commonly used whenever the same sensations or emotions are +excited, under quite different conditions, or in a lesser degree." ("The +Expression of the Emotions", page 84 (Popular Edition, 1904). + +Darwin's own views on language which are set forth most fully in "The +Descent of Man" (page 131 ff. (Popular Edition, 1906).) are characterised +by great modesty and caution. He did not profess to be a philologist and +the facts are naturally taken from the best known works of the day (1871). +In the notes added to the second edition he remarks on Max Muller's denial +of thought without words, "what a strange definition must here be given to +the word thought!" (Op. cit. page 135, footnote 63.) He naturally finds +the origin of language in "the imitation and modification of various +natural sounds, the voices of other animals, and man's own instinctive +cries aided by signs and gestures (op. cit. page 132.)...As the voice was +used more and more, the vocal organs would have been strengthened and +perfected through the principle of the inherited effects of use; and this +would have reacted on the power of speech." (Op. cit. page 133.) On man's +own instinctive cries, he has more to say in "The Expression of the +Emotions". (Page 93 (Popular Edition, 1904) and elsewhere.) These remarks +have been utilised by Prof. Jespersen of Copenhagen in propounding an +ingenious theory of his own to the effect that speech develops out of +singing. ("Progress in Language", page 361, London, 1894.) + +For many years and in many books Max Muller argued against Darwin's views +on evolution on the one ground that thought is impossible without speech; +consequently as speech is confined to the human race, there is a gulf which +cannot be bridged between man and all other creatures. (Some interesting +comments on the theory will be found in a lecture on "Thought and Language" +in Samuel Butler's "Essays on Life, Art and Science", London, 1908.) On +the title-page of his "Science of Thought" he put the two sentences "No +Reason without Language: No Language without Reason." It may be readily +admitted that the second dictum is true, that no language properly so- +called can exist without reason. Various birds can learn to repeat words +or sentences used by their masters or mistresses. In most cases probably +the birds do not attach their proper meaning to the words they have learnt; +they repeat them in season and out of season, sometimes apparently for +their own amusement, generally in the expectation, raised by past +experience, of being rewarded for their proficiency. But even here it is +difficult to prove a universal negative, and most possessors of such pets +would repudiate indignantly the statement that the bird did not understand +what was said to it, and would also contend that in many cases the words +which it used were employed in their ordinary meaning. The first dictum +seems to be inconsistent with fact. The case of deaf mutes, such as Laura +Bridgeman, who became well educated, or the still more extraordinary case +of Helen Keller, deaf, dumb, and blind, who in spite of these disadvantages +has learnt not only to reason but to reason better than the average of +persons possessed of all their senses, goes to show that language and +reason are not necessarily always in combination. Reason is but the +conscious adaptation of means to ends, and so defined is a faculty which +cannot be denied to many of the lower animals. In these days when so many +books on Animal Intelligence are issued from the press, it seems +unnecessary to labour the point. Yet none of these animals, except by +parrot-imitation, makes use of speech, because man alone possesses in a +sufficient degree of development the centres of nervous energy which are +required for the working of articulation in speech. On this subject much +investigation was carried on during the last years of Darwin's life and +much more in the period since his death. As early as 1861 Broca, following +up observations made by earlier French writers, located the centre of +articulate speech in the third left frontal convolution of the brain. In +1876 he more definitely fixed the organ of speech in "the posterior two- +fifths of the third frontal convolution" (Macnamara, "Human Speech", page +197, London, 1908.), both sides and not merely the left being concerned in +speech production. Owing however to the greater use by most human beings +of the right side of the body, the left side of the brain, which is the +motor centre for the right side of the body, is more highly developed than +its right side, which moves the left side of the body. The investigations +of Professors Ferrier, Sherrington and Grunbaum have still more precisely +defined the relations between brain areas and certain groups of muscles. +One form of aphasia is the result of injury to or disease in the third +frontal convolution because the motor centre is no longer equal to the task +of setting the necessary muscles in motion. In the brain of idiots who are +unable to speak, the centre for speech is not developed. (Op. cit. page +226.) In the anthropoid apes the brain is similarly defective, though it +has been demonstrated by Professors Cunningham and Marchand "that there is +a tendency, especially in the gorilla's brain, for the third frontal +convolution to assume the human form...But if they possessed a centre for +speech, those parts of the hemispheres of their brains which form the +mechanism by which intelligence is elaborated are so ill-developed, as +compared with the rest of their bodies, that we can not conceive, even with +more perfect frontal convolutions, that these animals could formulate ideas +expressible in intelligent speech." (Op. cit. page 223.) + +While Max Muller's theory is Shelley's + +"He gave man speech, and speech created thought, +Which is the measure of the universe" ("Prometheus Unbound" II. 4.), + +it seems more probable that the development was just the opposite--that the +development of new activities originated new thoughts which required new +symbols to express them, symbols which may at first have been, even to a +greater extent than with some of the lower races at present, sign language +as much as articulation. When once the faculty of articulation was +developed, which, though we cannot trace the process, was probably a very +gradual growth, there is no reason to suppose that words developed in any +other way then they do at present. An erroneous notion of the development +of language has become widely spread through the adoption of the +metaphorical term "roots" for the irreducible elements of human speech. +Men never talked in roots; they talked in words. Many words of kindred +meaning have a part in common, and a root is nothing but that common part +stripped of all additions. In some cases it is obvious that one word is +derived from another by the addition of a fresh element; in other cases it +is impossible to say which of two kindred words is the more primitive. A +root is merely a convenient term for an abstraction. The simplest word may +be called a root, but it is nevertheless a word. How are new words added +to a language in the present day? Some communities, like the Germans, +prefer to construct new words for new ideas out of the old material +existing in the language; others, like the English, prefer to go to the +ancient languages of Greece and Rome for terms to express new ideas. The +same chemical element is described in the two languages as sour stuff +(Sauerstoff) and as oxygen. Both terms mean the same thing etymologically +as well as in fact. On behalf of the German method, it may be contended +that the new idea is more closely attached to already existing ideas, by +being expressed in elements of the language which are intelligible even to +the meanest capacity. For the English practice it may be argued that, if +we coin a new word which means one thing, and one thing only, the idea +which it expresses is more clearly defined than if it were expressed in +popularly intelligible elements like "sour stuff." If the etymological +value of words were always present in the minds of their users, "oxygen" +would undoubtedly have an advantage over "sour stuff" as a technical term. +But the tendency in language is to put two words of this kind which express +but one idea under a single accent, and when this has taken place, no one +but the student of language any longer observes what the elements really +mean. When the ordinary man talks of a "blackbird" it is certainly not +present to his consciousness that he is talking of a black bird, unless for +some reason conversation has been dwelling upon the colour rather than +other characteristics of the species. + +But, it may be said, words like "oxygen" are introduced by learned men, and +do not represent the action of the man in the street, who, after all, is +the author of most additions to the stock of human language. We may go +back therefore some four centuries to a period, when scientific study was +only in its infancy, and see what process was followed. With the discovery +of America new products never seen before reached Europe, and these +required names. Three of the most characteristic were tobacco, the potato, +and the turkey. How did these come to be so named? The first people to +import these products into Europe were naturally the Spanish discoverers. +The first of these words--tobacco--appears in forms which differ only +slightly in the languages of all civilised countries: Spanish tabaco, +Italian tabacco, French tabac, Dutch and German tabak, Swedish tobak, etc. +The word in the native dialect of Hayti is said to have been tabaco, but to +have meant not the plant (According to William Barclay, "Nepenthes, or the +Virtue of Tobacco", Edinburgh, 1614, "the countrey which God hath honoured +and blessed with this happie and holy herbe doth call it in their native +language 'Petum'.") but the pipe in which it was smoked. It thus +illustrates a frequent feature of borrowing--that the word is not borrowed +in its proper signification, but in some sense closely allied thereto, +which a foreigner, understanding the language with difficulty, might +readily mistake for the real meaning. Thus the Hindu practice of burning a +wife upon the funeral pyre of her husband is called in English "suttee", +this word being in fact but the phonetic spelling of the Sanskrit "sati", +"a virtuous woman," and passing into its English meaning because formerly +the practice of self-immolation by a wife was regarded as the highest +virtue. + +The name of the potato exhibits greater variety. The English name was +borrowed from the Spanish "patata", which was itself borrowed from a native +word for the "yam" in the dialect of Hayti. The potato appeared early in +Italy, for the mariners of Genoa actively followed the footsteps of their +countryman Columbus in exploring America. In Italian generally the form +"patata" has survived. The tubers, however, also suggested a resemblance +to truffles, so that the Italian word "tartufolo", a diminutive of the +Italian modification of the Latin "terrae tuber" was applied to them. In +the language of the Rhaetian Alps this word appears as "tartufel". From +there it seems to have passed into Germany where potatoes were not +cultivated extensively till the eighteenth century, and "tartufel" has in +later times through some popular etymology been metamorphosed into +"Kartoffel". In France the shape of the tubers suggested the name of +earth-apple (pomme de terre), a name also adopted in Dutch (aard-appel), +while dialectically in German a form "Grumbire" appears, which is a +corruption of "Grund-birne", "ground pear". (Kluge "Etymologisches +Worterbuch der deutschen Sprache" (Strassburg), s.v. "Kartoffel".) Here +half the languages have adopted the original American word for an allied +plant, while others have adopted a name originating in some more or less +fanciful resemblance discovered in the tubers; the Germans alone in Western +Europe, failing to see any meaning in their borrowed name, have modified it +almost beyond recognition. To this English supplies an exact parallel in +"parsnep" which, though representing the Latin "pastinaca" through the Old +French "pastenaque", was first assimilated in the last syllable to the +"nep" of "turnep" ("pasneppe" in Elizabethan English), and later had an "r" +introduced into the first syllable, apparently on the analogy of "parsley". + +The turkey on the other hand seems never to be found with its original +American name. In England, as the name implies, the turkey cock was +regarded as having come from the land of the Turks. The bird no doubt +spread over Europe from the Italian seaports. The mistake, therefore, was +not unnatural, seeing that these towns conducted a great trade with the +Levant, while the fact that America when first discovered was identified +with India helped to increase the confusion. Thus in French the "coq +d'Inde" was abbreviated to "d'Inde" much as "turkey cock" was to "turkey"; +the next stage was to identify "dinde" as a feminine word and create a new +"dindon" on the analogy of "chapon" as the masculine. In Italian the name +"gallo d'India" besides survives, while in German the name "Truthahn" seems +to be derived onomatopoetically from the bird's cry, though a dialectic +"Calecutischer Hahn" specifies erroneously an origin for the bird from the +Indian Calicut. In the Spanish "pavo", on the other hand, there is a +curious confusion with the peacock. Thus in these names for objects of +common knowledge, the introduction of which into Europe can be dated with +tolerable definiteness, we see evinced the methods by which in remoter ages +objects were named. The words were borrowed from the community whence came +the new object, or the real or fancied resemblance to some known object +gave the name, or again popular etymology might convert the unknown term +into something that at least approached in sound a well-known word. + +"The Origin of Species" had not long been published when the parallelism of +development in natural species and in languages struck investigators. At +the time, one of the foremost German philologists was August Schleicher, +Professor at Jena. He was himself keenly interested in the natural +sciences, and amongst his colleagues was Ernst Haeckel, the protagonist in +Germany of the Darwinian theory. How the new ideas struck Schleicher may +be seen from the following sentences by his colleague Haeckel. "Speech is +a physiological function of the human organism, and has been developed +simultaneously with its organs, the larynx and tongue, and with the +functions of the brain. Hence it will be quite natural to find in the +evolution and classification of languages the same features as in the +evolution and classification of organic species. The various groups of +languages that are distinguished in philology as primitive, fundamental, +parent, and daughter languages, dialects, etc., correspond entirely in +their development to the different categories which we classify in zoology +and botany as stems, classes, orders, families, genera, species and +varieties. The relation of these groups, partly coordinate and partly +subordinate, in the general scheme is just the same in both cases; and the +evolution follows the same lines in both." (Haeckel, "The Evolution of +Man", page 485, London, 1905. This represents Schleicher's own words: Was +die Naturforscher als Gattung bezeichnen wurden, heisst bei den Glottikern +Sprachstamm, auch Sprachsippe; naher verwandte Gattungen bezeichnen sie +wohl auch als Sprachfamilien einer Sippe oder eines Sprachstammes...Die +Arten einer Gattung nennen wir Sprachen eines Stammes; die Unterarten einer +Art sind bei uns die Dialekte oder Mundarten einer Sprache; den Varietaten +und Spielarten entsprechen die Untermundarten oder Nebenmundarten und +endlich den einzelnen Individuen die Sprechweise der einzelnen die Sprachen +redenden Menschen. "Die Darwinische Theorie und die Sprachwissenschaft", +Weimar, 1863, page 12 f. Darwin makes a more cautious statement about the +classification of languages in "The Origin of Species", page 578, (Popular +Edition, 1900).) These views were set forth in an open letter addressed to +Haeckel in 1863 by Schleicher entitled, "The Darwinian theory and the +science of language". Unfortunately Schleicher's views went a good deal +farther than is indicated in the extract given above. He appended to the +pamphlet a genealogical tree of the Indo-Germanic languages which, though +to a large extent confirmed by later research, by the dichotomy of each +branch into two other branches, led the unwary reader to suppose their +phylogeny (to use Professor Haeckel's term) was more regular than our +evidence warrants. + +Without qualification Schleicher declared languages to be "natural +organisms which originated unconditioned by the human will, developed +according to definite laws, grow old and die; they also are characterised +by that series of phenomena which we designate by the term 'Life.' +Consequently Glottic, the science of language, is a natural science; its +method is in general the same as that of the other natural sciences." +("Die Darwinische Theorie", page 6 f.) In accordance with this view he +declared (op. cit. page 23.) that the root in language might be compared +with the simple cell in physiology, the linguistic simple cell or root +being as yet not differentiated into special organs for the function of +noun, verb, etc. + +In this probably all recent philologists admit that Schleicher went too +far. One of the most fertile theories in the modern science of language +originated with him, and was further developed by his pupil, August Leskien +("Die Declination im Slavisch-litanischen und Germanischen", Leipzig, 1876; +Osthoff and Brugmann, "Morphologische Untersuchungen", I. (Introduction), +1878. The general principles of this school were formulated (1880) in a +fuller form in H. Paul's "Prinzipien der Sprachgeschichte", Halle (3rd +edition, 1898). Paul and Wundt (in his "Volkerpsychologie") deal largely +with the same matter, but begin their investigations from different points +of view, Paul being a philologist with leanings to philosophy and Wundt a +philosopher interested in language.), and by Leskien's colleagues and +friends, Brugmann and Osthoff. This was the principle that phonetic laws +have no exceptions. Under the influence of this generalisation much +greater precision in etymology was insisted upon, and a new and remarkably +active period in the study of language began. Stated broadly in the +fashion given above the principle is not true. A more accurate statement +would be that an original sound is represented in a given dialect at a +given time and in a given environment only in one way; provided that the +development of the original sound into its representation in the given +dialect has not been influenced by the working of analogy. + +It is this proviso that is most important for the characterisation of the +science of language. As I have said elsewhere, it is at this point that +this science parts company with the natural sciences. "If the chemist +compounds two pure simple elements, there can be but one result, and no +power of the chemist can prevent it. But the minds of men do act upon the +sounds which they produce. The result is that, when this happens, the +phonetic law which would have acted in the case is stopped, and this +particular form enters on the same course of development as other forms to +which it does not belong." (P. Giles, "Short Manual of Comparative +Philology", 2nd edition, page 57, London, 1901.) + +Schleicher was wrong in defining a language to be an organism in the sense +in which a living being is an organism. Regarded physiologically, language +is a function or potentiality of certain human organs; regarded from the +point of view of the community it is of the nature of an institution. +(This view of language is worked out at some length by Prof. W.D. Whitney +in an article in the "Contemporary Review" for 1875, page 713 ff. This +article forms part of a controversy with Max Muller, which is partly +concerned with Darwin's views on language. He criticises Schleicher's +views severely in his "Oriental and Linguistic Studies", page 298 ff., New +York, 1873. In this volume will be found criticisms of various other views +mentioned in this essay.) More than most influences it conduces to the +binding together of the elements that form a state. That geographical or +other causes may effectively counteract the influence of identity of +language is obvious. One need only read the history of ancient Greece, or +observe the existing political separation of Germany and Austria, of Great +Britain and the United States of America. But however analogous to an +organism, language is not an organism. In a less degree Schleicher, by +defining languages as such, committed the same mistake which Bluntschli +made regarding the State, and which led him to declare that the State is by +nature masculine and the Church feminine. (Bluntschli, "Theory of the +State", page 24, Second English Edition, Oxford, 1892.) The views of +Schleicher were to some extent injurious to the proper methods of +linguistic study. But this misfortune was much more than fully compensated +by the inspiration which his ideas, collected and modified by his +disciples, had upon the science. In spite of the difference which the +psychological element represented by analogy makes between the science of +language and the natural sciences, we are entitled to say of it as +Schleicher said of Darwin's theory of the origin of species, "it depends +upon observation, and is essentially an attempt at a history of +development." + +Other questions there are in connection with language and evolution which +require investigation--the survival of one amongst several competing words +(e.g. why German keeps only as a high poetic word "ross", which is +identical in origin with the English work-a-day "horse", and replaces it by +"pferd", whose congener the English "palfrey" is almost confined to poetry +and romance), the persistence of evolution till it becomes revolution in +languages like English or Persian which have practically ceased to be +inflectional languages, and many other problems. Into these Darwin did not +enter, and they require a fuller investigation than is possible within the +limits of the present paper. + + +XXVII. DARWINISM AND HISTORY. + +By J.B. BURY, Litt.D., LL.D. +Regius Professor of Modern History in the University of Cambridge. + +1. Evolution, and the principles associated with the Darwinian theory, +could not fail to exert a considerable influence on the studies connected +with the history of civilised man. The speculations which are known as +"philosophy of history," as well as the sciences of anthropology, +ethnography, and sociology (sciences which though they stand on their own +feet are for the historian auxiliary), have been deeply affected by these +principles. Historiographers, indeed, have with few exceptions made little +attempt to apply them; but the growth of historical study in the nineteenth +century has been determined and characterised by the same general principle +which has underlain the simultaneous developments of the study of nature, +namely the GENETIC idea. The "historical" conception of nature, which has +produced the history of the solar system, the story of the earth, the +genealogies of telluric organisms, and has revolutionised natural science, +belongs to the same order of thought as the conception of human history as +a continuous, genetic, causal process--a conception which has +revolutionised historical research and made it scientific. Before +proceeding to consider the application of evolutional principles, it will +be pertinent to notice the rise of this new view. + +2. With the Greeks and Romans history had been either a descriptive record +or had been written in practical interests. The most eminent of the +ancient historians were pragmatical; that is, they regarded history as an +instructress in statesmanship, or in the art of war, or in morals. Their +records reached back such a short way, their experience was so brief, that +they never attained to the conception of continuous process, or realised +the significance of time; and they never viewed the history of human +societies as a phenomenon to be investigated for its own sake. In the +middle ages there was still less chance of the emergence of the ideas of +progress and development. Such notions were excluded by the fundamental +doctrines of the dominant religion which bounded and bound men's minds. As +the course of history was held to be determined from hour to hour by the +arbitrary will of an extra-cosmic person, there could be no self-contained +causal development, only a dispensation imposed from without. And as it +was believed that the world was within no great distance from the end of +this dispensation, there was no motive to take much interest in +understanding the temporal, which was to be only temporary. + +The intellectual movements of the fifteenth and sixteenth centuries +prepared the way for a new conception, but it did not emerge immediately. +The historians of the Renaissance period simply reverted to the ancient +pragmatical view. For Machiavelli, exactly as for Thucydides and Polybius, +the use of studying history was instruction in the art of politics. The +Renaissance itself was the appearance of a new culture, different from +anything that had gone before; but at the time men were not conscious of +this; they saw clearly that the traditions of classical antiquity had been +lost for a long period, and they were seeking to revive them, but otherwise +they did not perceive that the world had moved, and that their own spirit, +culture, and conditions were entirely unlike those of the thirteenth +century. It was hardly till the seventeenth century that the presence of a +new age, as different from the middle ages as from the ages of Greece and +Rome, was fully realised. It was then that the triple division of ancient, +medieval, and modern was first applied to the history of western +civilisation. Whatever objections may be urged against this division, +which has now become almost a category of thought, it marks a most +significant advance in man's view of his own past. He has become conscious +of the immense changes in civilisation which have come about slowly in the +course of time, and history confronts him with a new aspect. He has to +explain how those changes have been produced, how the transformations were +effected. The appearance of this problem was almost simultaneous with the +rise of rationalism, and the great historians and thinkers of the +eighteenth century, such as Montesquieu, Voltaire, Gibbon, attempted to +explain the movement of civilisation by purely natural causes. These +brilliant writers prepared the way for the genetic history of the following +century. But in the spirit of the Aufklarung, that eighteenth-century +Enlightenment to which they belonged, they were concerned to judge all +phenomena before the tribunal of reason; and the apotheosis of "reason" +tended to foster a certain superior a priori attitude, which was not +favourable to objective treatment and was incompatible with a "historical +sense." Moreover the traditions of pragmatical historiography had by no +means disappeared. + +3. In the first quarter of the nineteenth century the meaning of genetic +history was fully realised. "Genetic" perhaps is as good a word as can be +found for the conception which in this century was applied to so many +branches of knowledge in the spheres both of nature and of mind. It does +not commit us to the doctrine proper of evolution, nor yet to any +teleological hypothesis such as is implied in "progress." For history it +meant that the present condition of the human race is simply and strictly +the result of a causal series (or set of causal series)--a continuous +succession of changes, where each state arises causally out of the +preceding; and that the business of historians is to trace this genetic +process, to explain each change, and ultimately to grasp the complete +development of the life of humanity. Three influential writers, who +appeared at this stage and helped to initiate a new period of research, may +specially be mentioned. Ranke in 1824 definitely repudiated the +pragmatical view which ascribes to history the duties of an instructress, +and with no less decision renounced the function, assumed by the historians +of the Aufklarung, to judge the past; it was his business, he said, merely +to show how things really happened. Niebuhr was already working in the +same spirit and did more than any other writer to establish the principle +that historical transactions must be related to the ideas and conditions of +their age. Savigny about the same time founded the "historical school" of +law. He sought to show that law was not the creation of an enlightened +will, but grew out of custom and was developed by a series of adaptations +and rejections, thus applying the conception of evolution. He helped to +diffuse the notion that all the institutions of a society or a notion are +as closely interconnected as the parts of a living organism. + +4. The conception of the history of man as a causal development meant the +elevation of historical inquiry to the dignity of a science. Just as the +study of bees cannot become scientific so long as the student's interest in +them is only to procure honey or to derive moral lessons from the labours +of "the little busy bee," so the history of human societies cannot become +the object of pure scientific investigation so long as man estimates its +value in pragmatical scales. Nor can it become a science until it is +conceived as lying entirely within a sphere in which the law of cause and +effect has unreserved and unrestricted dominion. On the other hand, once +history is envisaged as a causal process, which contains within itself the +explanation of the development of man from his primitive state to the point +which he has reached, such a process necessarily becomes the object of +scientific investigation and the interest in it is scientific curiosity. + +At the same time, the instruments were sharpened and refined. Here Wolf, a +philologist with historical instinct, was a pioneer. His "Prolegomena" to +Homer (1795) announced new modes of attack. Historical investigation was +soon transformed by the elaboration of new methods. + +5. "Progress" involves a judgment of value, which is not involved in the +conception of history as a genetic process. It is also an idea distinct +from that of evolution. Nevertheless it is closely related to the ideas +which revolutionised history at the beginning of the last century; it swam +into men's ken simultaneously; and it helped effectively to establish the +notion of history as a continuous process and to emphasise the significance +of time. Passing over earlier anticipations, I may point to a "Discours" +of Turgot (1750), where history is presented as a process in which "the +total mass of the human race" "marches continually though sometimes slowly +to an ever increasing perfection." That is a clear statement of the +conception which Turgot's friend Condorcet elaborated in the famous work, +published in 1795, "Esquisse d'un tableau historique des progres de +l'esprit humain". This work first treated with explicit fulness the idea +to which a leading role was to fall in the ideology of the nineteenth +century. Condorcet's book reflects the triumphs of the Tiers etat, whose +growing importance had also inspired Turgot; it was the political changes +in the eighteenth century which led to the doctrine, emphatically +formulated by Condorcet, that the masses are the most important element in +the historical process. I dwell on this because, though Condorcet had no +idea of evolution, the pre-dominant importance of the masses was the +assumption which made it possible to apply evolutional principles to +history. And it enabled Condorcet himself to maintain that the history of +civilisation, a progress still far from being complete, was a development +conditioned by general laws. + +6. The assimilation of society to an organism, which was a governing +notion in the school of Savigny, and the conception of progress, combined +to produce the idea of an organic development, in which the historian has +to determine the central principle or leading character. This is +illustrated by the apotheosis of democracy in Tocqueville's "Democratie en +Amerique", where the theory is maintained that "the gradual and progressive +development of equality is at once the past and the future of the history +of men." The same two principles are combined in the doctrine of Spencer +(who held that society is an organism, though he also contemplated its +being what he calls a "super-organic aggregate") (A society presents +suggestive analogies with an organism, but it certainly is not an organism, +and sociologists who draw inferences from the assumption of its organic +nature must fall into error. A vital organism and a society are radically +distinguished by the fact that the individual components of the former, +namely the cells, are morphologically as well as functionally +differentiated, whereas the individuals which compose a society are +morphologically homogeneous and only functionally differentiated. The +resemblances and the differences are worked out in E. de Majewski's +striking book "La Science de la Civilisation", Paris, 1908.), that social +evolution is a progressive change from militarism to industrialism. + +7. the idea of development assumed another form in the speculations of +German idealism. Hegel conceived the successive periods of history as +corresponding to the ascending phases or ideas in the self-evolution of his +Absolute Being. His "Lectures on the Philosophy of History" were published +in 1837 after his death. His philosophy had a considerable effect, direct +and indirect, on the treatment of history by historians, and although he +was superficial and unscientific himself in dealing with historical +phenomena, he contributed much towards making the idea of historical +development familiar. Ranke was influenced, if not by Hegel himself, at +least by the Idealistic philosophies of which Hegel's was the greatest. He +was inclined to conceive the stages in the process of history as marked by +incarnations, as it were, of ideas, and sometimes speaks as if the ideas +were independent forces, with hands and feet. But while Hegel determined +his ideas by a priori logic, Ranke obtained his by induction--by a strict +investigation of the phenomena; so that he was scientific in his method and +work, and was influenced by Hegelian prepossessions only in the kind of +significance which he was disposed to ascribe to his results. It is to be +noted that the theory of Hegel implied a judgment of value; the movement +was a progress towards perfection. + +8. In France, Comte approached the subject from a different side, and +exercised, outside Germany, a far wider influence than Hegel. The 4th +volume of his "Cours de philosophie positive", which appeared in 1839, +created sociology and treated history as a part of this new science, namely +as "social dynamics." Comte sought the key for unfolding historical +development, in what he called the social-psychological point of view, and +he worked out the two ideas which had been enunciated by Condorcet: that +the historian's attention should be directed not, as hitherto, principally +to eminent individuals, but to the collective behaviour of the masses, as +being the most important element in the process; and that, as in nature, so +in history, there are general laws, necessary and constant, which condition +the development. The two points are intimately connected, for it is only +when the masses are moved into the foreground that regularity, uniformity, +and law can be conceived as applicable. To determine the social- +psychological laws which have controlled the development is, according to +Comte, the task of sociologists and historians. + +9. The hypothesis of general laws operative in history was carried further +in a book which appeared in England twenty years later and exercised an +influence in Europe far beyond its intrinsic merit, Buckle's "History of +Civilisation in England" (1857-61). Buckle owed much to Comte, and +followed him, or rather outdid him, in regarding intellect as the most +important factor conditioning the upward development of man, so that +progress, according to him, consisted in the victory of the intellectual +over the moral laws. + +10. The tendency of Comte and Buckle to assimilate history to the sciences +of nature by reducing it to general "laws," derived stimulus and +plausibility from the vista offered by the study of statistics, in which +the Belgian Quetelet, whose book "Sur l'homme" appeared in 1835, discerned +endless possibilities. The astonishing uniformities which statistical +inquiry disclosed led to the belief that it was only a question of +collecting a sufficient amount of statistical material, to enable us to +predict how a given social group will act in a particular case. Bourdeau, +a disciple of this school, looks forward to the time when historical +science will become entirely quantitative. The actions of prominent +individuals, which are generally considered to have altered or determined +the course of things, are obviously not amenable to statistical computation +or explicable by general laws. Thinkers like Buckle sought to minimise +their importance or explain them away. + +11. These indications may suffice to show that the new efforts to +interpret history which marked the first half of the nineteenth century +were governed by conceptions closely related to those which were current in +the field of natural science and which resulted in the doctrine of +evolution. The genetic principle, progressive development, general laws, +the significance of time, the conception of society as an organic +aggregate, the metaphysical theory of history as the self-evolution of +spirit,--all these ideas show that historical inquiry had been advancing +independently on somewhat parallel lines to the sciences of nature. It was +necessary to bring this out in order to appreciate the influence of +Darwinism. + +12. In the course of the dozen years which elapsed between the appearances +of "The Origin of Species" (observe that the first volume of Buckle's work +was published just two years before) and of "The Descent of Man" (1871), +the hypothesis of Lamarck that man is the co-descendant with other species +of some lower extinct form was admitted to have been raised to the rank of +an established fact by most thinkers whose brains were not working under +the constraint of theological authority. + +One important effect of the discovery of this fact (I am not speaking now +of the Darwinian explanation) was to assign to history a definite place in +the coordinated whole of knowledge, and relate it more closely to other +sciences. It had indeed a defined logical place in systems such as Hegel's +and Comte's; but Darwinism certified its standing convincingly and without +more ado. The prevailing doctrine that man was created ex abrupto had +placed history in an isolated position, disconnected with the sciences of +nature. Anthropology, which deals with the animal anthropos, now comes +into line with zoology, and brings it into relation with history. (It is +to be observed that history is (not only different in scope but) not +coextensive with anthropology IN TIME. For it deals only with the +development of man in societies, whereas anthropology includes in its +definition the proto-anthropic period when anthropos was still non-social, +whether he lived in herds like the chimpanzee, or alone like the male +ourang-outang. (It has been well shown by Majewski that congregations-- +herds, flocks, packs, etc.--of animals are not SOCIETIES; the +characteristic of a society is differentiation of function. Bee hives, ant +hills, may be called quasi-societies; but in their case the classes which +perform distinct functions are morphologically different.) Man's condition +at the present day is the result of a series of transformations, going back +to the most primitive phase of society, which is the ideal (unattainable) +beginning of history. But that beginning had emerged without any breach of +continuity from a development which carries us back to a quadrimane +ancestor, still further back (according to Darwin's conjecture) to a marine +animal of the ascidian type, and then through remoter periods to the lowest +form of organism. It is essential in this theory that though links have +been lost there was no break in the gradual development; and this +conception of a continuous progress in the evolution of life, resulting in +the appearance of uncivilised Anthropos, helped to reinforce, and increase +a belief in, the conception of the history of civilised Anthropos as itself +also a continuous progressive development. + +13. Thus the diffusion of the Darwinian theory of the origin of man, by +emphasising the idea of continuity and breaking down the barriers between +the human and animal kingdoms, has had an important effect in establishing +the position of history among the sciences which deal with telluric +development. The perspective of history is merged in a larger perspective +of development. As one of the objects of biology is to find the exact +steps in the genealogy of man from the lowest organic form, so the scope of +history is to determine the stages in the unique causal series from the +most rudimentary to the present state of human civilisation. + +It is to be observed that the interest in historical research implied by +this conception need not be that of Comte. In the Positive Philosophy +history is part of sociology; the interest in it is to discover the +sociological laws. In the view of which I have just spoken, history is +permitted to be an end in itself; the reconstruction of the genetic process +is an independent interest. For the purpose of the reconstruction, +sociology, as well as physical geography, biology, psychology, is +necessary; the sociologist and the historian play into each other's hands; +but the object of the former is to establish generalisations; the aim of +the latter is to trace in detail a singular causal sequence. + +14. The success of the evolutional theory helped to discredit the +assumption or at least the invocation of transcendent causes. +Philosophically of course it is compatible with theism, but historians have +for the most part desisted from invoking the naive conception of a "god in +history" to explain historical movements. A historian may be a theist; +but, so far as his work is concerned, this particular belief is otiose. +Otherwise indeed (as was remarked above) history could not be a science; +for with a deus ex machina who can be brought on the stage to solve +difficulties scientific treatment is a farce. The transcendent element had +appeared in a more subtle form through the influence of German philosophy. +I noticed how Ranke is prone to refer to ideas as if they were transcendent +existences manifesting themselves in the successive movements of history. +It is intelligible to speak of certain ideas as controlling, in a given +period,--for instance, the idea of nationality; but from the scientific +point of view, such ideas have no existence outside the minds of +individuals and are purely psychical forces; and a historical "idea," if it +does not exist in this form, is merely a way of expressing a synthesis of +the historian himself. + +15. From the more general influence of Darwinism on the place of history +in the system of human knowledge, we may turn to the influence of the +principles and methods by which Darwin explained development. It had been +recognised even by ancient writers (such as Aristotle and Polybius) that +physical circumstances (geography, climate) were factors conditioning the +character and history of a race or society. In the sixteenth century Bodin +emphasised these factors, and many subsequent writers took them into +account. The investigations of Darwin, which brought them into the +foreground, naturally promoted attempts to discover in them the chief key +to the growth of civilisation. Comte had expressly denounced the notion +that the biological methods of Lamarck could be applied to social man. +Buckle had taken account of natural influences, but had relegated them to a +secondary plane, compared with psychological factors. But the Darwinian +theory made it tempting to explain the development of civilisation in terms +of "adaptation to environment," "struggle for existence," "natural +selection," "survival of the fittest," etc. (Recently O. Seeck has applied +these principles to the decline of Graeco-Roman civilisation in his +"Untergang der antiken Welt", 2 volumes, Berlin, 1895, 1901.) + +The operation of these principles cannot be denied. Man is still an +animal, subject to zoological as well as mechanical laws. The dark +influence of heredity continues to be effective; and psychical development +had begun in lower organic forms,--perhaps with life itself. The organic +and the social struggles for existence are manifestations of the same +principle. Environment and climatic influence must be called in to explain +not only the differentiation of the great racial sections of humanity, but +also the varieties within these sub-species and, it may be, the +assimilation of distinct varieties. Ritter's "Anthropogeography" has +opened a useful line of research. But on the other hand, it is urged that, +in explaining the course of history, these principles do not take us very +far, and that it is chiefly for the primitive ultra-prehistoric period that +they can account for human development. It may be said that, so far as +concerns the actions and movements of men which are the subject of recorded +history, physical environment has ceased to act mechanically, and in order +to affect their actions must affect their wills first; and that this +psychical character of the causal relations substantially alters the +problem. The development of human societies, it may be argued, derives a +completely new character from the dominance of the conscious psychical +element, creating as it does new conditions (inventions, social +institutions, etc.) which limit and counteract the operation of natural +selection, and control and modify the influence of physical environment. +Most thinkers agree now that the chief clews to the growth of civilisation +must be sought in the psychological sphere. Imitation, for instance, is a +principle which is probably more significant for the explanation of human +development than natural selection. Darwin himself was conscious that his +principles had only a very restricted application in this sphere, as is +evident from his cautious and tentative remarks in the 5th chapter of his +"Descent of Man". He applied natural selection to the growth of the +intellectual faculties and of the fundamental social instincts, and also to +the differentiation of the great races or "sub-species" (Caucasian, +African, etc.) which differ in anthropological character. (Darwinian +formulae may be suggestive by way of analogy. For instance, it is +characteristic of social advance that a multitude of inventions, schemes +and plans are framed which are never carried out, similar to, or designed +for the same end as, an invention or plan which is actually adopted because +it has chanced to suit better the particular conditions of the hour (just +as the works accomplished by an individual statesman, artist or savant are +usually only a residue of the numerous projects conceived by his brain). +This process in which so much abortive production occurs is analogous to +elimination by natural selection.) + +16. But if it is admitted that the governing factors which concern the +student of social development are of the psychical order, the preliminary +success of natural science in explaining organic evolution by general +principles encouraged sociologists to hope that social evolution could be +explained on general principles also. The idea of Condorcet, Buckle, and +others, that history could be assimilated to the natural sciences was +powerfully reinforced, and the notion that the actual historical process, +and every social movement involved in it, can be accounted for by +sociological generalisations, so-called "laws," is still entertained by +many, in one form or another. Dissentients from this view do not deny that +the generalisations at which the sociologist arrives by the comparative +method, by the analysis of social factors, and by psychological deduction +may be an aid to the historian; but they deny that such uniformities are +laws or contain an explanation of the phenomena. They can point to the +element of chance coincidence. This element must have played a part in the +events of organic evolution, but it has probably in a larger measure helped +to determine events in social evolution. The collision of two unconnected +sequences may be fraught with great results. The sudden death of a leader +or a marriage without issue, to take simple cases, has again and again led +to permanent political consequences. More emphasis is laid on the decisive +actions of individuals, which cannot be reduced under generalisations and +which deflect the course of events. If the significance of the individual +will had been exaggerated to the neglect of the collective activity of the +social aggregate before Condorcet, his doctrine tended to eliminate as +unimportant the roles of prominent men, and by means of this elimination it +was possible to found sociology. But it may be urged that it is patent on +the face of history that its course has constantly been shaped and modified +by the wills of individuals (We can ignore here the metaphysical question +of freewill and determinism. For the character of the individual's brain +depends in any case on ante-natal accidents and coincidences, and so it may +be said that the role of individuals ultimately depends on chance,--the +accidental coincidence of independent sequences.), which are by no means +always the expression of the collective will; and that the appearance of +such personalities at the given moments is not a necessary outcome of the +conditions and cannot be deduced. Nor is there any proof that, if such and +such an individual had not been born, some one else would have arisen to do +what he did. In some cases there is no reason to think that what happened +need ever have come to pass. In other cases, it seems evident that the +actual change was inevitable, but in default of the man who initiated and +guided it, it might have been postponed, and, postponed or not, might have +borne a different cachet. I may illustrate by an instance which has just +come under my notice. Modern painting was founded by Giotto, and the +Italian expedition of Charles VIII, near the close of the sixteenth +century, introduced into France the fashion of imitating Italian painters. +But for Giotto and Charles VIII, French painting might have been very +different. It may be said that "if Giotto had not appeared, some other +great initiator would have played a role analogous to his, and that without +Charles VIII there would have been the commerce with Italy, which in the +long run would have sufficed to place France in relation with Italian +artists. But the equivalent of Giotto might have been deferred for a +century and probably would have been different; and commercial relations +would have required ages to produce the rayonnement imitatif of Italian art +in France, which the expedition of the royal adventurer provoked in a few +years." (I have taken this example from G. Tarde's "La logique sociale" 2 +(page 403), Paris, 1904, where it is used for quite a different purpose.) +Instances furnished by political history are simply endless. Can we +conjecture how events would have moved if the son of Philip of Macedon had +been an incompetent? The aggressive action of Prussia which astonished +Europe in 1740 determined the subsequent history of Germany; but that +action was anything but inevitable; it depended entirely on the personality +of Frederick the Great. + +Hence it may be argued that the action of individual wills is a determining +and disturbing factor, too significant and effective to allow history to be +grasped by sociological formulae. The types and general forms of +development which the sociologist attempts to disengage can only assist the +historian in understanding the actual course of events. It is in the +special domains of economic history and Culturgeschichte which have come to +the front in modern times that generalisation is most fruitful, but even in +these it may be contended that it furnishes only partial explanations. + +17. The truth is that Darwinism itself offers the best illustration of the +insufficiency of general laws to account for historical development. The +part played by coincidence, and the part played by individuals--limited by, +and related to, general social conditions--render it impossible to deduce +the course of the past history of man or to predict the future. But it is +just the same with organic development. Darwin (or any other zoologist) +could not deduce the actual course of evolution from general principles. +Given an organism and its environment, he could not show that it must +evolve into a more complex organism of a definite pre-determined type; +knowing what it has evolved into, he could attempt to discover and assign +the determining causes. General principles do not account for a particular +sequence; they embody necessary conditions; but there is a chapter of +accidents too. It is the same in the case of history. + +18. Among the evolutional attempts to subsume the course of history under +general syntheses, perhaps the most important is that of Lamprecht, whose +"kulturhistorische Methode," which he has deduced from and applied to +German history, exhibits the (indirect) influence of the Comtist school. +It is based upon psychology, which, in his view, holds among the sciences +of mind (Geisteswissenschaften) the same place (that of a +Grundwissenschaft) which mechanics holds among the sciences of nature. +History, by the same comparison, corresponds to biology, and, according to +him, it can only become scientific if it is reduced to general concepts +(Begriffe). Historical movements and events are of a psychical character, +and Lamprecht conceives a given phase of civilisation as "a collective +psychical condition (seelischer Gesamtzustand)" controlling the period, "a +diapason which penetrates all psychical phenomena and thereby all +historical events of the time." ("Die kulturhistorische Methode", Berlin, +1900, page 26.) He has worked out a series of such phases, "ages of +changing psychical diapason," in his "Deutsche Geschichte" with the aim of +showing that all the feelings and actions of each age can be explained by +the diapason; and has attempted to prove that these diapasons are exhibited +in other social developments, and are consequently not singular but +typical. He maintains further that these ages succeed each other in a +definite order; the principle being that the collective psychical +development begins with the homogeneity of all the individual members of a +society and, through heightened psychical activity, advances in the form of +a continually increasing differentiation of the individuals (this is akin +to the Spencerian formula). This process, evolving psychical freedom from +psychical constraint, exhibits a series of psychical phenomena which define +successive periods of civilisation. The process depends on two simple +principles, that no idea can disappear without leaving behind it an effect +or influence, and that all psychical life, whether in a person or a +society, means change, the acquisition of new mental contents. It follows +that the new have to come to terms with the old, and this leads to a +synthesis which determines the character of a new age. Hence the ages of +civilisation are defined as the "highest concepts for subsuming without +exception all psychical phenomena of the development of human societies, +that is, of all historical events." (Ibid. pages 28, 29.) Lamprecht +deduces the idea of a special historical science, which might be called +"historical ethnology," dealing with the ages of civilisation, and bearing +the same relation to (descriptive or narrative) history as ethnology to +ethnography. Such a science obviously corresponds to Comte's social +dynamics, and the comparative method, on which Comte laid so much emphasis, +is the principal instrument of Lamprecht. + +19. I have dwelt on the fundamental ideas of Lamprecht, because they are +not yet widely known in England, and because his system is the ablest +product of the sociological school of historians. It carries the more +weight as its author himself is a historical specialist, and his historical +syntheses deserve the most careful consideration. But there is much in the +process of development which on such assumptions is not explained, +especially the initiative of individuals. Historical development does not +proceed in a right line, without the choice of diverging. Again and again, +several roads are open to it, of which it chooses one--why? On Lamprecht's +method, we may be able to assign the conditions which limit the psychical +activity of men at a particular stage of evolution, but within those limits +the individual has so many options, such a wide room for moving, that the +definition of those conditions, the "psychical diapasons," is only part of +the explanation of the particular development. The heel of Achilles in all +historical speculations of this class has been the role of the individual. + +The increasing prominence of economic history has tended to encourage the +view that history can be explained in terms of general concepts or types. +Marx and his school based their theory of human development on the +conditions of production, by which, according to them, all social movements +and historical changes are entirely controlled. The leading part which +economic factors play in Lamprecht's system is significant, illustrating +the fact that economic changes admit most readily this kind of treatment, +because they have been less subject to direction or interference by +individual pioneers. + +Perhaps it may be thought that the conception of SOCIAL ENVIRONMENT +(essentially psychical), on which Lamprecht's "psychical diapasons" depend, +is the most valuable and fertile conception that the historian owes to the +suggestion of the science of biology--the conception of all particular +historical actions and movements as (1) related to and conditioned by the +social environment, and (2) gradually bringing about a transformation of +that environment. But no given transformation can be proved to be +necessary (pre-determined). And types of development do not represent +laws; their meaning and value lie in the help they may give to the +historian, in investigating a certain period of civilisation, to enable him +to discover the interrelations among the diverse features which it +presents. They are, as some one has said, an instrument of heuretic +method. + +20. The men engaged in special historical researches--which have been +pursued unremittingly for a century past, according to scientific methods +of investigating evidence (initiated by Wolf, Niebuhr, Ranke)--have for the +most part worked on the assumptions of genetic history or at least followed +in the footsteps of those who fully grasped the genetic point of view. But +their aim has been to collect and sift evidence, and determine particular +facts; comparatively few have given serious thought to the lines of +research and the speculations which have been considered in this paper. +They have been reasonably shy of compromising their work by applying +theories which are still much debated and immature. But historiography +cannot permanently evade the questions raised by these theories. One may +venture to say that no historical change or transformation will be fully +understood until it is explained how social environment acted on the +individual components of the society (both immediately and by heredity), +and how the individuals reacted upon their environment. The problem is +psychical, but it is analogous to the main problem of the biologist. + + +XXVIII. THE GENESIS OF DOUBLE STARS. + +By SIR GEORGE DARWIN, K.C.B., F.R.S. +Plumian Professor of Astronomy and Experimental Philosophy in the +University of Cambridge. + +In ordinary speech a system of any sort is said to be stable when it cannot +be upset easily, but the meaning attached to the word is usually somewhat +vague. It is hardly surprising that this should be the case, when it is +only within the last thirty years, and principally through the +investigations of M. Poincare, that the conception of stability has, even +for physicists, assumed a definiteness and clearness in which it was +previously lacking. The laws which govern stability hold good in regions +of the greatest diversity; they apply to the motion of planets round the +sun, to the internal arrangement of those minute corpuscles of which each +chemical atom is constructed, and to the forms of celestial bodies. In the +present essay I shall attempt to consider the laws of stability as relating +to the last case, and shall discuss the succession of shapes which may be +assumed by celestial bodies in the course of their evolution. I believe +further that homologous conceptions are applicable in the consideration of +the transmutations of the various forms of animal and of vegetable life and +in other regions of thought. Even if some of my readers should think that +what I shall say on this head is fanciful, yet at least the exposition will +serve to illustrate the meaning to be attached to the laws of stability in +the physical universe. + +I propose, therefore, to begin this essay by a sketch of the principles of +stability as they are now formulated by physicists. + +I. + +If a slight impulse be imparted to a system in equilibrium one of two +consequences must ensue; either small oscillations of the system will be +started, or the disturbance will increase without limit and the arrangement +of the system will be completely changed. Thus a stick may be in +equilibrium either when it hangs from a peg or when it is balanced on its +point. If in the first case the stick is touched it will swing to and fro, +but in the second case it will topple over. The first position is a stable +one, the second is unstable. But this case is too simple to illustrate all +that is implied by stability, and we must consider cases of stable and of +unstable motion. Imagine a satellite and its planet, and consider each of +them to be of indefinitely small size, in fact particles; then the +satellite revolves round its planet in an ellipse. A small disturbance +imparted to the satellite will only change the ellipse to a small amount, +and so the motion is said to be stable. If, on the other hand, the +disturbance were to make the satellite depart from its initial elliptic +orbit in ever widening circuits, the motion would be unstable. This case +affords an example of stable motion, but I have adduced it principally with +the object of illustrating another point not immediately connected with +stability, but important to a proper comprehension of the theory of +stability. + +The motion of a satellite about its planet is one of revolution or +rotation. When the satellite moves in an ellipse of any given degree of +eccentricity, there is a certain amount of rotation in the system, +technically called rotational momentum, and it is always the same at every +part of the orbit. (Moment of momentum or rotational momentum is measured +by the momentum of the satellite multiplied by the perpendicular from the +planet on to the direction of the path of the satellite at any instant.) + +Now if we consider all the possible elliptic orbits of a satellite about +its planet which have the same amount of "rotational momentum," we find +that the major axis of the ellipse described will be different according to +the amount of flattening (or the eccentricity) of the ellipse described. A +figure titled "A 'family' of elliptic orbits with constant rotational +momentum" (Fig. 1) illustrates for a given planet and satellite all such +orbits with constant rotational momentum, and with all the major axes in +the same direction. It will be observed that there is a continuous +transformation from one orbit to the next, and that the whole forms a +consecutive group, called by mathematicians "a family" of orbits. In this +case the rotational momentum is constant and the position of any orbit in +the family is determined by the length of the major axis of the ellipse; +the classification is according to the major axis, but it might have been +made according to anything else which would cause the orbit to be exactly +determinate. + +I shall come later to the classification of all possible forms of ideal +liquid stars, which have the same amount of rotational momentum, and the +classification will then be made according to their densities, but the idea +of orderly arrangement in a "family" is just the same. + +We thus arrive at the conception of a definite type of motion, with a +constant amount of rotational momentum, and a classification of all members +of the family, formed by all possible motions of that type, according to +the value of some measurable quantity (this will hereafter be density) +which determines the motion exactly. In the particular case of the +elliptic motion used for illustration the motion was stable, but other +cases of motion might be adduced in which the motion would be unstable, and +it would be found that classification in a family and specification by some +measurable quantity would be equally applicable. + +A complex mechanical system may be capable of motion in several distinct +modes or types, and the motions corresponding to each such type may be +arranged as before in families. For the sake of simplicity I will suppose +that only two types are possible, so that there will only be two families; +and the rotational momentum is to be constant. The two types of motion +will have certain features in common which we denote in a sort of shorthand +by the letter A. Similarly the two types may be described as A + a and A + +b, so that a and b denote the specific differences which discriminate the +families from one another. Now following in imagination the family of the +type A + a, let us begin with the case where the specific difference a is +well marked. As we cast our eyes along the series forming the family, we +find the difference a becoming less conspicuous. It gradually dwindles +until it disappears; beyond this point it either becomes reversed, or else +the type has ceased to be a possible one. In our shorthand we have started +with A + a, and have watched the characteristic a dwindling to zero. When +it vanishes we have reached a type which may be specified as A; beyond this +point the type would be A - a or would be impossible. + +Following the A + b type in the same way, b is at first well marked, it +dwindles to zero, and finally may become negative. Hence in shorthand this +second family may be described as A + b,...A,...A - b. + +In each family there is one single member which is indistinguishable from a +member of the other family; it is called by Poincare a form of bifurcation. +It is this conception of a form of bifurcation which forms the important +consideration in problems dealing with the forms of liquid or gaseous +bodies in rotation. + +But to return to the general question,--thus far the stability of these +families has not been considered, and it is the stability which renders +this way of looking at the matter so valuable. It may be proved that if +before the point of bifurcation the type A + a was stable, then A + b must +have been unstable. Further as a and b each diminish A + a becomes less +pronouncedly stable, and A + b less unstable. On reaching the point of +bifurcation A + a has just ceased to be stable, or what amounts to the same +thing is just becoming unstable, and the converse is true of the A + b +family. After passing the point of bifurcation A + a has become definitely +unstable and A + b has become stable. Hence the point of bifurcation is +also a point of "exchange of stabilities between the two types." (In order +not to complicate unnecessarily this explanation of a general principle I +have not stated fully all the cases that may occur. Thus: firstly, after +bifurcation A + a may be an impossible type and A + a will then stop at +this point; or secondly, A + b may have been an impossible type before +bifurcation, and will only begin to be a real one after it; or thirdly, +both A + a and A + b may be impossible after the point of bifurcation, in +which case they coalesce and disappear. This last case shows that types +arise and disappear in pairs, and that on appearance or before +disappearance one must be stable and the other unstable.) + +In nature it is of course only the stable types of motion which can persist +for more than a short time. Thus the task of the physical evolutionist is +to determine the forms of bifurcation, at which he must, as it were, change +carriages in the evolutionary journey so as always to follow the stable +route. He must besides be able to indicate some natural process which +shall correspond in effect to the ideal arrangement of the several types of +motion in families with gradually changing specific differences. Although, +as we shall see hereafter, it may frequently or even generally be +impossible to specify with exactness the forms of bifurcation in the +process of evolution, yet the conception is one of fundamental importance. + +The ideas involved in this sketch are no doubt somewhat recondite, but I +hope to render them clearer to the non-mathematical reader by homologous +considerations in other fields of thought (I considered this subject in my +Presidential address to the British Association in 1905, "Report of the +75th Meeting of the British Assoc." (S. Africa, 1905), London, 1906, page +3. Some reviewers treated my speculations as fanciful, but as I believe +that this was due generally to misapprehension, and as I hold that +homologous considerations as to stability and instability are really +applicable to evolution of all sorts, I have thought it well to return to +the subject in the present paper.), and I shall pass on thence to +illustrations which will teach us something of the evolution of stellar +systems. + +States or governments are organised schemes of action amongst groups of +men, and they belong to various types to which generic names, such as +autocracy, aristocracy or democracy, are somewhat loosely applied. A +definite type of government corresponds to one of our types of motion, and +while retaining its type it undergoes a slow change as the civilisation and +character of the people change, and as the relationship of the nation to +other nations changes. In the language used before, the government belongs +to a family, and as time advances we proceed through the successive members +of the family. A government possesses a certain degree of stability-- +hardly measurable in numbers however--to resist disintegrating influences +such as may arise from wars, famines, and internal dissensions. This +stability gradually rises to a maximum and gradually declines. The degree +of stability at any epoch will depend on the fitness of some leading +feature of the government to suit the slowly altering circumstances, and +that feature corresponds to the characteristic denoted by a in the physical +problem. A time at length arrives when the stability vanishes, and the +slightest shock will overturn the government. At this stage we have +reached the crisis of a point of bifurcation, and there will then be some +circumstance, apparently quite insignificant and almost unnoticed, which is +such as to prevent the occurrence of anarchy. This circumstance or +condition is what we typified as b. Insignificant although it may seem, it +has started the government on a new career of stability by imparting to it +a new type. It grows in importance, the form of government becomes +obviously different, and its stability increases. Then in its turn this +newly acquired stability declines, and we pass on to a new crisis or +revolution. There is thus a series of "points of bifurcation" in history +at which the continuity of political history is maintained by means of +changes in the type of government. These ideas seem, to me at least, to +give a true account of the history of states, and I contend that it is no +mere fanciful analogy but a true homology, when in both realms of thought-- +the physical and the political--we perceive the existence of forms of +bifurcation and of exchanges of stability. + +Further than this, I would ask whether the same train of ideas does not +also apply to the evolution of animals? A species is well adapted to its +environment when the individual can withstand the shocks of famine or the +attacks and competition of other animals; it then possesses a high degree +of stability. Most of the casual variations of individuals are +indifferent, for they do not tell much either for or against success in +life; they are small oscillations which leave the type unchanged. As +circumstances change, the stability of the species may gradually dwindle +through the insufficiency of some definite quality, on which in earlier +times no such insistent demands were made. The individual animals will +then tend to fail in the struggle for life, the numbers will dwindle and +extinction may ensue. But it may be that some new variation, at first of +insignificant importance, may just serve to turn the scale. A new type may +be formed in which the variation in question is preserved and augmented; +its stability may increase and in time a new species may be produced. + +At the risk of condemnation as a wanderer beyond my province into the +region of biological evolution, I would say that this view accords with +what I understand to be the views of some naturalists, who recognise the +existence of critical periods in biological history at which extinction +occurs or which form the starting-point for the formation of new species. +Ought we not then to expect that long periods will elapse during which a +type of animal will remain almost constant, followed by other periods, +enormously long no doubt as measured in the life of man, of acute struggle +for existence when the type will change more rapidly? This at least is the +view suggested by the theory of stability in the physical universe. (I +make no claim to extensive reading on this subject, but refer the reader +for example to a paper by Professor A.A.W. Hubrecht on "De Vries's theory +of Mutations", "Popular Science Monthly", July 1904, especially to page +213.) + +And now I propose to apply these ideas of stability to the theory of +stellar evolution, and finally to illustrate them by certain recent +observations of a very remarkable character. + +Stars and planets are formed of materials which yield to the enormous +forces called into play by gravity and rotation. This is obviously true if +they are gaseous or fluid, and even solid matter becomes plastic under +sufficiently great stresses. Nothing approaching a complete study of the +equilibrium of a heterogeneous star has yet been found possible, and we are +driven to consider only bodies of simpler construction. I shall begin +therefore by explaining what is known about the shapes which may be assumed +by a mass of incompressible liquid of uniform density under the influences +of gravity and of rotation. Such a liquid mass may be regarded as an ideal +star, which resembles a real star in the fact that it is formed of +gravitating and rotating matter, and because its shape results from the +forces to which it is subject. It is unlike a star in that it possesses +the attributes of incompressibility and of uniform density. The difference +between the real and the ideal is doubtless great, yet the similarity is +great enough to allow us to extend many of the conclusions as to ideal +liquid stars to the conditions which must hold good in reality. Thus with +the object of obtaining some insight into actuality, it is justifiable to +discuss an avowedly ideal problem at some length. + +The attraction of gravity alone tends to make a mass of liquid assume the +shape of a sphere, and the effects of rotation, summarised under the name +of centrifugal force, are such that the liquid seeks to spread itself +outwards from the axis of rotation. It is a singular fact that it is +unnecessary to take any account of the size of the mass of liquid under +consideration, because the shape assumed is exactly the same whether the +mass be small or large, and this renders the statement of results much +easier than would otherwise be the case. + +A mass of liquid at rest will obviously assume the shape of a sphere, under +the influence of gravitation, and it is a stable form, because any +oscillation of the liquid which might be started would gradually die away +under the influence of friction, however small. If now we impart to the +whole mass of liquid a small speed of rotation about some axis, which may +be called the polar axis, in such a way that there are no internal currents +and so that it spins in the same way as if it were solid, the shape will +become slightly flattened like an orange. Although the earth and the other +planets are not homogeneous they behave in the same way, and are flattened +at the poles and protuberant at the equator. This shape may therefore +conveniently be described as planetary. + +If the planetary body be slightly deformed the forces of restitution are +slightly less than they were for the sphere; the shape is stable but +somewhat less so than the sphere. We have then a planetary spheroid, +rotating slowly, slightly flattened at the poles, with a high degree of +stability, and possessing a certain amount of rotational momentum. Let us +suppose this ideal liquid star to be somewhere in stellar space far removed +from all other bodies; then it is subject to no external forces, and any +change which ensues must come from inside. Now the amount of rotational +momentum existing in a system in motion can neither be created nor +destroyed by any internal causes, and therefore, whatever happens, the +amount of rotational momentum possessed by the star must remain absolutely +constant. + +A real star radiates heat, and as it cools it shrinks. Let us suppose then +that our ideal star also radiates and shrinks, but let the process proceed +so slowly that any internal currents generated in the liquid by the cooling +are annulled so quickly by fluid friction as to be insignificant; further +let the liquid always remain at any instant incompressible and homogeneous. +All that we are concerned with is that, as time passes, the liquid star +shrinks, rotates in one piece as if it were solid, and remains +incompressible and homogeneous. The condition is of course artificial, but +it represents the actual processes of nature as well as may be, +consistently with the postulated incompressibility and homogeneity. +(Mathematicians are accustomed to regard the density as constant and the +rotational momentum as increasing. But the way of looking at the matter, +which I have adopted, is easier of comprehension, and it comes to the same +in the end.) + +The shrinkage of a constant mass of matter involves an increase of its +density, and we have therefore to trace the changes which supervene as the +star shrinks, and as the liquid of which it is composed increases in +density. The shrinkage will, in ordinary parlance, bring the weights +nearer to the axis of rotation. Hence in order to keep up the rotational +momentum, which as we have seen must remain constant, the mass must rotate +quicker. The greater speed of rotation augments the importance of +centrifugal force compared with that of gravity, and as the flattening of +the planetary spheroid was due to centrifugal force, that flattening is +increased; in other words the ellipticity of the planetary spheroid +increases. + +As the shrinkage and corresponding increase of density proceed, the +planetary spheroid becomes more and more elliptic, and the succession of +forms constitutes a family classified according to the density of the +liquid. The specific mark of this family is the flattening or ellipticity. + +Now consider the stability of the system, we have seen that the spheroid +with a slow rotation, which forms our starting-point, was slightly less +stable than the sphere, and as we proceed through the family of ever +flatter ellipsoids the stability continues to diminish. At length when it +has assumed the shape shown in a figure titled "Planetary spheroid just +becoming unstable" (Fig. 2.) where the equatorial and polar axes are +proportional to the numbers 1000 and 583, the stability has just +disappeared. According to the general principle explained above this is a +form of bifurcation, and corresponds to the form denoted A. The specific +difference a of this family must be regarded as the excess of the +ellipticity of this figure above that of all the earlier ones, beginning +with the slightly flattened planetary spheroid. Accordingly the specific +difference a of the family has gradually diminished from the beginning and +vanishes at this stage. + +According to Poincare's principle the vanishing of the stability serves us +with notice that we have reached a figure of bifurcation, and it becomes +necessary to inquire what is the nature of the specific difference of the +new family of figures which must be coalescent with the old one at this +stage. This difference is found to reside in the fact that the equator, +which in the planetary family has hitherto been circular in section, tends +to become elliptic. Hitherto the rotational momentum has been kept up to +its constant value partly by greater speed of rotation and partly by a +symmetrical bulging of the equator. But now while the speed of rotation +still increases (The mathematician familiar with Jacobi's ellipsoid will +find that this is correct, although in the usual mode of exposition, +alluded to above in a footnote, the speed diminishes.), the equator tends +to bulge outwards at two diametrically opposite points and to be flattened +midway between these protuberances. The specific difference in the new +family, denoted in the general sketch by b, is this ellipticity of the +equator. If we had traced the planetary figures with circular equators +beyond this stage A, we should have found them to have become unstable, and +the stability has been shunted off along the A + b family of forms with +elliptic equators. + +This new series of figures, generally named after the great mathematician +Jacobi, is at first only just stable, but as the density increases the +stability increases, reaches a maximum and then declines. As this goes on +the equator of these Jacobian figures becomes more and more elliptic, so +that the shape is considerably elongated in a direction at right angles to +the axis of rotation. + +At length when the longest axis of the three has become about three times +as long as the shortest (The three axes of the ellipsoid are then +proportional to 1000, 432, 343.), the stability of this family of figures +vanishes, and we have reached a new form of bifurcation and must look for a +new type of figure along which the stable development will presumably +extend. Two sections of this critical Jacobian figure, which is a figure +of bifurcation, are shown by the dotted lines in a figure titled "The +'pear-shaped figure' and the Jocobian figure from which it is derived" +(Fig. 3.) comprising two figures, one above the other: the upper figure is +the equatorial section at right angles to the axis of rotation, the lower +figure is a section through the axis. + +Now Poincare has proved that the new type of figure is to be derived from +the figure of bifurcation by causing one of the ends to be prolonged into a +snout and by bluntening the other end. The snout forms a sort of stalk, +and between the stalk and the axis of rotation the surface is somewhat +flattened. These are the characteristics of a pear, and the figure has +therefore been called the "pear-shaped figure of equilibrium." The firm +line shows this new type of figure, whilst, as already explained, the +dotted line shows the form of bifurcation from which it is derived. The +specific mark of this new family is the protrusion of the stalk together +with the other corresponding smaller differences. If we denote this +difference by c, while A + b denotes the Jacobian figure of bifurcation +from which it is derived, the new family may be called A + b + c, and c is +zero initially. According to my calculations this series of figures is +stable (M. Liapounoff contends that for constant density the new series of +figures, which M. Poincare discovered, has less rotational momentum than +that of the figure of bifurcation. If he is correct, the figure of +bifurcation is a limit of stable figures, and none can exist with stability +for greater rotational momentum. My own work seems to indicate that the +opposite is true, and, notwithstanding M. Liapounoff's deservedly great +authority, I venture to state the conclusions in accordance with my own +work.), but I do not know at what stage of its development it becomes +unstable. + +Professor Jeans has solved a problem which is of interest as throwing light +on the future development of the pear-shaped figure, although it is of a +still more ideal character than the one which has been discussed. He +imagines an INFINITELY long circular cylinder of liquid to be in rotation +about its central axis. The existence is virtually postulated of a demon +who is always occupied in keeping the axis of the cylinder straight, so +that Jeans has only to concern himself with the stability of the form of +the section of the cylinder, which as I have said is a circle with the axis +of rotation at the centre. He then supposes the liquid forming the +cylinder to shrink in diameter, just as we have done, and finds that the +speed of rotation must increase so as to keep up the constancy of the +rotational momentum. The circularity of section is at first stable, but as +the shrinkage proceeds the stability diminishes and at length vanishes. +This stage in the process is a form of bifurcation, and the stability +passes over to a new series consisting of cylinders which are elliptic in +section. The circular cylinders are exactly analogous with our planetary +spheroids, and the elliptic ones with the Jacobian ellipsoids. + +With further shrinkage the elliptic cylinders become unstable, a new form +of bifurcation is reached, and the stability passes over to a series of +cylinders whose section is pear-shaped. Thus far the analogy is complete +between our problem and Jeans's, and in consequence of the greater +simplicity of the conditions, he is able to carry his investigation +further. He finds that the stalk end of the pear-like section continues to +protrude more and more, and the flattening between it and the axis of +rotation becomes a constriction. Finally the neck breaks and a satellite +cylinder is born. Jeans's figure for an advanced stage of development is +shown in a figure titled "Section of a rotating cylinder of liquid" (Fig. +4.), but his calculations do not enable him actually to draw the state of +affairs after the rupture of the neck. + +There are certain difficulties in admitting the exact parallelism between +this problem and ours, and thus the final development of our pear-shaped +figure and the end of its stability in a form of bifurcation remain hidden +from our view, but the successive changes as far as they have been +definitely traced are very suggestive in the study of stellar evolution. + +Attempts have been made to attack this problem from the other end. If we +begin with a liquid satellite revolving about a liquid planet and proceed +backwards in time, we must make the two masses expand so that their density +will be diminished. Various figures have been drawn exhibiting the shapes +of two masses until their surfaces approach close to one another and even +until they just coalesce, but the discussion of their stability is not +easy. At present it would seem to be impossible to reach coalescence by +any series of stable transformations, and if this is so Professor Jeans's +investigation has ceased to be truly analogous to our problem at some +undetermined stage. However this may be this line of research throws an +instructive light on what we may expect to find in the evolution of real +stellar systems. + +In the second part of this paper I shall point out the bearing which this +investigation of the evolution of an ideal liquid star may have on the +genesis of double stars. + +II. + +There are in the heavens many stars which shine with a variable brilliancy. +Amongst these there is a class which exhibits special peculiarities; the +members of this class are generally known as Algol Variables, because the +variability of the star Beta Persei or Algol was the first of such cases to +attract the attention of astronomers, and because it is perhaps still the +most remarkable of the whole class. But the circumstances which led to +this discovery were so extraordinary that it seems worth while to pause a +moment before entering on the subject. + +John Goodricke, a deaf-mute, was born in 1764; he was grandson and heir of +Sir John Goodricke of Ribston Hall, Yorkshire. In November 1782, he noted +that the brilliancy of Algol waxed and waned (It is said that Georg +Palitzch, a farmer of Prohlis near Dresden, had about 1758 already noted +the variability of Algol with the naked eye. "Journ. Brit. Astron. Assoc." +Vol. XV. (1904-5), page 203.), and devoted himself to observing it on every +fine night from the 28th December 1782 to the 12th May 1783. He +communicated his observations to the Royal Society, and suggested that the +variation in brilliancy was due to periodic eclipses by a dark companion +star, a theory now universally accepted as correct. The Royal Society +recognised the importance of the discovery by awarding to Goodricke, then +only 19 years of age, their highest honour, the Copley medal. His later +observations of Beta Lyrae and of Delta Cephei were almost as remarkable as +those of Algol, but unfortunately a career of such extraordinary promise +was cut short by death, only a fortnight after his election to the Royal +Society. ("Dict. of National Biography"; article Goodricke (John). The +article is by Miss Agnes Clerke. It is strange that she did not then seem +to be aware that he was a deaf-mute, but she notes the fact in her +"Problems of Astrophysics", page 337, London, 1903.) + +It was not until 1889 that Goodricke's theory was verified, when it was +proved by Vogel that the star was moving in an orbit, and in such a manner +that it was only possible to explain the rise and fall in the luminosity by +the partial eclipse of a bright star by a dark companion. + +The whole mass of the system of Algol is found to be half as great again as +that of our sun, yet the two bodies complete their orbit in the short +period of 2d 20h 48m 55s. The light remains constant during each period, +except for 9h 20m when it exhibits a considerable fall in brightness +(Clerke, "Problems of Astrophysics" page 302 and chapter XVIII.); the curve +which represents the variation in the light is shown in a figure titled +"The light-curve and system of Beta Lyrae" (Fig. 7.). + +The spectroscope has enabled astronomers to prove that many stars, although +apparently single, really consist of two stars circling around one another +(If a source of light is approaching with a great velocity the waves of +light are crowded together, and conversely they are spaced out when the +source is receding. Thus motion in the line of sight virtually produces an +infinitesimal change of colour. The position of certain dark lines in the +spectrum affords an exceedingly accurate measurement of colour. Thus +displacements of these spectral lines enables us to measure the velocity of +the source of light towards or away from the observer.); they are known as +spectroscopic binaries. Campbell of the Lick Observatory believes that +about one star in six is a binary ("Astrophysical Journ." Vol. XIII. page +89, 1901. See also A. Roberts, "Nature", Sept. 12, 1901, page 468.); thus +there must be many thousand such stars within the reach of our +spectroscopes. + +The orientation of the planes of the orbits of binary stars appears to be +quite arbitrary, and in general the star does not vary in brightness. +Amongst all such orbits there must be some whose planes pass nearly through +the sun, and in these cases the eclipse of one of the stars by the other +becomes inevitable, and in each circuit there will occur two eclipses of +unequal intensities. + +It is easy to see that in the majority of such cases the two components +must move very close to one another. + +The coincidence between the spectroscopic and the photometric evidence +permits us to feel complete confidence in the theory of eclipses. When +then we find a star with a light-curve of perfect regularity and with a +characteristics of that of Algol, we are justified in extending the theory +of eclipses to it, although it may be too faint to permit of adequate +spectroscopic examination. This extension of the theory secures a +considerable multiplication of the examples available for observation, and +some 30 have already been discovered. + +Dr Alexander Roberts, of Lovedale in Cape Colony, truly remarks that the +study of Algol variables "brings us to the very threshold of the question +of stellar evolution." ("Proc. Roy. Soc. Edinburgh", XXIV. Part II. +(1902), page 73.) It is on this account that I propose to explain in some +detail the conclusion to which he and some other observers have been led. + +Although these variable stars are mere points of light, it has been proved +by means of the spectroscope that the law of gravitation holds good in the +remotest regions of stellar space, and further it seems now to have become +possible even to examine the shapes of stars by indirect methods, and thus +to begin the study of their evolution. The chain of reasoning which I +shall explain must of necessity be open to criticism, yet the explanation +of the facts by the theory is so perfect that it is not easy to resist the +conviction that we are travelling along the path of truth. + +The brightness of a star is specified by what is called its "magnitude." +The average brightness of all the stars which can just be seen with the +naked eye defines the sixth magnitude. A star which only gives two-fifths +as much light is said to be of the seventh magnitude; while one which gives +2 1/2 times as much light is of the fifth magnitude, and successive +multiplications or divisions by 2 1/2 define the lower or higher +magnitudes. Negative magnitudes have clearly to be contemplated; thus +Sirius is of magnitude minus 1.4, and the sun is of magnitude minus 26. + +The definition of magnitude is also extended to fractions; for example, the +lights given by two candles which are placed at 100 feet and 100 feet 6 +inches from the observer differ in brightness by one-hundredth of a +magnitude. + +A great deal of thought has been devoted to the measurement of the +brightness of stars, but I will only describe one of the methods used, that +of the great astronomer Argelander. In the neighbourhood of the star under +observation some half dozen standard stars are selected of known invariable +magnitudes, some being brighter and some fainter than the star to be +measured; so that these stars afford a visible scale of brightness. +Suppose we number them in order of increasing brightness from 1 to 6; then +the observer estimates that on a given night his star falls between stars 2 +and 3, on the next night, say between 3 and 4, and then again perhaps it +may return to between 2 and 3, and so forth. With practice he learns to +evaluate the brightness down to small fractions of a magnitude, even a +hundredth part of a magnitude is not quite negligible. + +For example, in observing the star RR Centauri five stars were in general +used for comparison by Dr Roberts, and in course of three months he secured +thereby 300 complete observations. When the period of the cycle had been +ascertained exactly, these 300 values were reduced to mean values which +appertained to certain mean places in the cycle, and a mean light-curve was +obtained in this way. Figures titled "Light curve of RR Centauri" (Fig. 5) +and "The light-curve and system of Beta Lyrae" (Fig. 7) show examples of +light curves. + +I shall now follow out the results of the observation of RR Centauri not +only because it affords the easiest way of explaining these investigations, +but also because it is one of the stars which furnishes the most striking +results in connection with the object of this essay. (See "Monthly notices +R.A.S." Vol. 63, 1903, page 527.) This star has a mean magnitude of about +7 1/2, and it is therefore invisible to the naked eye. Its period of +variability is 14h 32m 10s.76, the last refinement of precision being of +course only attained in the final stages of reduction. Twenty-nine mean +values of the magnitude were determined, and they were nearly equally +spaced over the whole cycle of changes. The black dots in Fig. 5 exhibit +the mean values determined by Dr Roberts. The last three dots on the +extreme right are merely the same as the first three on the extreme left, +and are repeated to show how the next cycle would begin. The smooth dotted +curve will be explained hereafter, but, by reference to the scale of +magnitudes on the margins of the figure, it may be used to note that the +dots might be brought into a perfectly smooth curve by shifting some few of +the dots by about a hundredth of a magnitude. + +This light-curve presents those characteristics which are due to successive +eclipses, but the exact form of the curve must depend on the nature of the +two mutually eclipsing stars. If we are to interpret the curve with all +possible completeness, it is necessary to make certain assumptions as to +the stars. It is assumed then that the stars are equally bright all over +their disks, and secondly that they are not surrounded by an extensive +absorptive atmosphere. This last appears to me to be the most dangerous +assumption involved in the whole theory. + +Making these assumptions, however, it is found that if each of the +eclipsing stars were spherical it would not be possible to generate such a +curve with the closest accuracy. The two stars are certainly close +together, and it is obvious that in such a case the tidal forces exercised +by each on the other must be such as to elongate the figure of each towards +the other. Accordingly it is reasonable to adopt the hypothesis that the +system consists of a pair of elongated ellipsoids, with their longest axes +pointed towards one another. No supposition is adopted a priori as to the +ratio of the two masses, or as to their relative size or brightness, and +the orbit may have any degree of eccentricity. These last are all to be +determined from the nature of the light-curve. + +In the case of RR Centauri, however, Dr Roberts finds the conditions are +best satisfied by supposing the orbit to be circular, and the sizes and +masses of the components to be equal, while their luminosities are to one +another in the ratio of 4 to 3. As to their shapes he finds them to be so +much elongated that they overlap, as exhibited in his figure titled "The +shape of the star RR Centauri" (Fig. 6.). The dotted curve shows a form of +equilibrium of rotating liquid as computed by me some years before, and it +was added for the sake of comparison. + +On turning back to Fig. 5 the reader will see in the smooth dotted curve +the light variation which would be exhibited by such a binary system as +this. The curve is the result of computation and it is impossible not to +be struck by the closeness of the coincidence with the series of black dots +which denote the observations. + +It is virtually certain that RR Centauri is a case of an eclipsing binary +system, and that the two stars are close together. It is not of course +proved that the figures of the stars are ellipsoids, but gravitation must +deform them into a pair of elongated bodies, and, on the assumptions that +they are not enveloped in an absorptive atmosphere and that they are +ellipsoidal, their shapes must be as shown in the figure. + +This light-curve gives an excellent illustration of what we have reason to +believe to be a stage in the evolution of stars, when a single star is +proceeding to separate into a binary one. + +As the star is faint, there is as yet no direct spectroscopic evidence of +orbital motion. Let us turn therefore to the case of another star, namely +V Puppis, in which such evidence does already exist. I give an account of +it, because it presents a peculiarly interesting confirmation of the +correctness of the theory. + +In 1895 Pickering announced in the "Harvard Circular" No. 14 that the +spectroscopic observations at Arequipa proved V Puppis to be a double star +with a period of 3d 2h 46m. Now when Roberts discussed its light-curve he +found that the period was 1d 10h 54m 27s, and on account of this serious +discrepancy he effected the reduction only on the simple assumption that +the two stars were spherical, and thus obtained a fairly good +representation of the light-curve. It appeared that the orbit was circular +and that the two spheres were not quite in contact. Obviously if the stars +had been assumed to be ellipsoids they would have been found to overlap, as +was the case for RR Centauri. ("Astrophysical Journ." Vol. XIII. (1901), +page 177.) The matter rested thus for some months until the spectroscopic +evidence was re-examined by Miss Cannon on behalf of Professor Pickering, +and we find in the notes on page 177 of Vol. XXVIII. of the "Annals of the +Harvard Observatory" the following: "A.G.C. 10534. This star, which is +the Algol variable V Puppis, has been found to be a spectroscopic binary. +The period 1d.454 (i.e. 1d 10h 54m) satisfies the observations of the +changes in light, and of the varying separation of the lines of the +spectrum. The spectrum has been examined on 61 plates, on 23 of which the +lines are double." Thus we have valuable evidence in confirmation of the +correctness of the conclusions drawn from the light-curve. In the +circumstances, however, I have not thought it worth while to reproduce Dr +Roberts's provisional figure. + +I now turn to the conclusions drawn a few years previously by another +observer, where we shall find the component stars not quite in contact. +This is the star Beta Lyrae which was observed by Goodricke, Argelander, +Belopolsky, Schur, Markwick and by many others. The spectroscopic method +has been successfully applied in this case, and the component stars are +proved to move in an orbit about one another. In 1897, Mr. G.W. Myers +applied the theory of eclipses to the light-curve, on the hypothesis that +the stars are elongated ellipsoids, and he obtained the interesting results +exhibited in Fig. 7. ("Astrophysical Journ." Vol. VII. (1898), page 1.) + +The period of Beta Lyrae is relatively long, being 12d 21h 47m, the orbit +is sensibly eccentric, and the two spheroids are not so much elongated as +was the case with RR Centauri. The mass of the system is enormous, one of +the two stars being 10 times and the other 21 times as heavy as our sun. + +Further illustrations of this subject might be given, but enough has been +said to explain the nature of the conclusions which have been drawn from +this class of observation. + +In my account of these remarkable systems the consideration of one very +important conclusion has been purposely deferred. Since the light-curve is +explicable by eclipses, it follows that the sizes of the two stars are +determinable relatively to the distance between them. The period of their +orbital motion is known, being identical with the complete period of the +variability of their light, and an easy application of Kepler's law of +periodic times enables us to compute the sum of the masses of the two stars +divided by the cube of the distance between their centres. Now the sizes +of the bodies being known, the mean density of the whole system may be +calculated. In every case that density has been found to be much less than +the sun's, and indeed the average of a number of mean densities which have +been determined only amounts to one-eighth of that of the sun. In some +cases the density is extremely small, and in no case is it quite so great +as half the solar density. + +It would be absurd to suppose that these stars can be uniform in density +throughout, and from all that is known of celestial bodies it is probable +that they are gaseous in their external parts with great condensation +towards their centres. This conclusion is confirmed by arguments drawn +from the theory of rotating masses of liquid. (See J.H. Jeans, "On the +density of Algol variables", "Astrophysical Journ." Vol. XXII. (1905), page +97.) + +Although, as already explained, a good deal is known about the shapes and +the stability of figures consisting of homogeneous incompressible liquid in +rotation, yet comparatively little has hitherto been discovered about the +equilibrium of rotating gaseous stars. The figures calculated for +homogeneous liquid can obviously only be taken to afford a general +indication of the kind of figure which we might expect to find in the +stellar universe. Thus the dotted curve in Fig. 5, which exhibits one of +the figures which I calculated, has some interest when placed alongside the +figures of the stars in RR Centauri, as computed from the observations, but +it must not be accepted as the calculated form of such a system. I have +moreover proved more recently that such a figure of homogeneous liquid is +unstable. Notwithstanding this instability it does not necessarily follow +that the analogous figure for compressible fluid is also unstable, as will +be pointed out more fully hereafter. + +Professor Jeans has discussed in a paper of great ability the difficult +problems offered by the conditions of equilibrium and of stability of a +spherical nebula. ("Phil. Trans. R.S." Vol. CXCIX. A (1902), page 1. See +also A. Roberts, "S. African Assoc. Adv. Sci." Vol. I. (1903), page 6.) In +a later paper ("Astrophysical Journ." Vol. XXII. (1905), page 97.), in +contrasting the conditions which must govern the fission of a star into two +parts when the star is gaseous and compressible with the corresponding +conditions in the case of incompressible liquid, he points out that for a +gaseous star (the agency which effects the separation will no longer be +rotation alone; gravitation also will tend towards separation...From +numerical results obtained in the various papers of my own,...I have been +led to the conclusion that a gravitational instability of the kind +described must be regarded as the primary agent at work in the actual +evolution of the universe, Laplace's rotation playing only the secondary +part of separating the primary and satellite after the birth of the +satellite." + +It is desirable to add a word in explanation of the expression +"gravitational instability" in this passage. It means that when the +concentration of a gaseous nebula (without rotation) has proceeded to a +certain stage, the arrangement in spherical layers of equal density becomes +unstable, and a form of bifurcation has been reached. For further +concentration concentric spherical layers become unstable, and the new +stable form involves a concentration about two centres. The first sign of +this change is that the spherical layers cease to be quite concentric and +then the layers of equal density begin to assume a somewhat pear-shaped +form analogous to that which we found to occur under rotation for an +incompressible liquid. Accordingly it appears that while a sphere of +liquid is stable a sphere of gas may become unstable. Thus the conditions +of stability are different in these two simple cases, and it is likely that +while certain forms of rotating liquid are unstable the analogous forms for +gas may be stable. This furnishes a reason why it is worth while to +consider the unstable forms of rotating liquid. + +There can I think be little doubt but that Jeans is right in looking to +gravitational instability as the primary cause of fission, but when we +consider that a binary system, with a mass larger than the sun's, is found +to rotate in a few hours, there seems reason to look to rotation as a +contributory cause scarcely less important than the primary one. + +With the present extent of our knowledge it is only possible to reconstruct +the processes of the evolution of stars by means of inferences drawn from +several sources. We have first to rely on the general principles of +stability, according to which we are to look for a series of families of +forms, each terminating in an unstable form, which itself becomes the +starting-point of the next family of stable forms. Secondly we have as a +guide the analogy of the successive changes in the evolution of ideal +liquid stars; and thirdly we already possess some slender knowledge as to +the equilibrium of gaseous stars. + +From these data it is possible to build up in outline the probable history +of binary stars. Originally the star must have been single, it must have +been widely diffused, and must have been endowed with a slow rotation. In +this condition the strata of equal density must have been of the planetary +form. As it cooled and contracted the symmetry round the axis of rotation +must have become unstable, through the effects of gravitation, assisted +perhaps by the increasing speed of rotation. (I learn from Professor Jeans +that he now (December 1908) believes that he can prove that some small +amount of rotation is necessary to induce instability in the symmetrical +arrangement.) The strata of equal density must then become somewhat pear- +shaped, and afterwards like an hour-glass, with the constriction more +pronounced in the internal than in the external strata. The constrictions +of the successive strata then begin to rupture from the inside +progressively outwards, and when at length all are ruptured we have the +twin stars portrayed by Roberts and by others. + +As we have seen, the study of the forms of equilibrium of rotating liquid +is almost complete, and Jeans has made a good beginning in the +investigation of the equilibrium of gaseous stars, but much more remains to +be discovered. The field for the mathematician is a wide one, and in +proportion as the very arduous exploration of that field is attained so +will our knowledge of the processes of cosmical evolution increase. + +From the point of view of observation, improved methods in the use of the +spectroscope and increase of accuracy in photometry will certainly lead to +a great increase in our knowledge within the next few years. Probably the +observational advance will be more rapid than that of theory, for we know +how extraordinary has been the success attained within the last few years, +and the theory is one of extreme difficulty; but the two ought to proceed +together hand in hand. Human life is too short to permit us to watch the +leisurely procedure of cosmical evolution, but the celestial museum +contains so many exhibits that it may become possible, by the aid of +theory, to piece together bit by bit the processes through which stars pass +in the course of their evolution. + +In the sketch which I have endeavoured to give of this fascinating subject, +I have led my reader to the very confines of our present knowledge. It is +not much more than a quarter of a century since this class of observation +has claimed the close attention of astronomers; something considerable has +been discovered already and there seems scarcely a discernible limit to +what will be known in this field a century from now. Some of the results +which I have set forth may then be shown to be false, but it seems +profoundly improbable that we are being led astray by a Will-of-the-Wisp. + + +XXIX. THE EVOLUTION OF MATTER. + +By W.C.D. WHETHAM, M.A., F.R.S. +Trinity College, Cambridge. + +The idea of evolution in the organic world, made intelligible by the work +of Charles Darwin, has little in common with the recent conception of +change in certain types of matter. The discovery that a process of +disintegration may take place in some at least of the chemical atoms, +previously believed to be indestructible and unalterable, has modified our +view of the physical universe, even as Darwin's scheme of the mode of +evolution changed the trend of thought concerning the organic world. Both +conceptions have in common the idea of change throughout extended realms of +space and time, and, therefore, it is perhaps not unfitting that some +account of the most recent physical discoveries should be included in the +present volume. + +The earliest conception of the evolution of matter is found in the +speculation of the Greeks. Leucippus and Democritus imagined unchanging +eternal atoms, Heracleitus held that all things were in a continual state +of flux--Panta rei. + +But no one in the Ancient World--no one till quite modern times--could +appreciate the strength of the position which the theory of the evolution +of matter must carry before it wins the day. Vague speculation, even by +the acute minds of philosophers, is of little use in physical science +before experimental facts are available. The true problems at issue cannot +even be formulated, much less solved, till the humble task of the observer +and experimenter has given us a knowledge of the phenomena to be explained. + +It was only through the atomic theory, at first apparently diametrically +opposed to it, that the conception of evolution in the physical world was +to gain an established place. For a century the atomic theory, when put +into a modern form by Dalton, led farther and farther away from the idea of +change in matter. The chemical elements seemed quite unalterable, and the +atoms, of which each element in modern view is composed, bore to Clerk +Maxwell, writing about 1870, "the stamp of manufactured articles" exactly +similar in kind, unchanging, eternal. + +Nevertheless throughout these years, on the whole so unfavourable to its +existence, there persisted the idea of a common origin of the distinct +kinds of matter known to chemists. Indeed, this idea of unity in substance +in nature seems to accord with some innate desire or intimate structure of +the human mind. As Mr Arthur Balfour well puts it, "There is no a priori +reason that I know of for expecting that the material world should be a +modification of a single medium, rather than a composite structure built +out of sixty or seventy elementary substances, eternal and eternally +different. Why then should we feel content with the first hypothesis and +not with the second? Yet so it is. Men of science have always been +restive under the multiplication of entities. They have eagerly watched +for any sign that the different chemical elements own a common origin, and +are all compounded out of some primordial substance. Nor, for my part, do +I think that such instincts should be ignored...that they exist is certain; +that they modify the indifferent impartiality of pure empiricism can hardly +be denied." ("Report of the 74th Meeting of the British Association" +(Presidential Address, Cambridge 1904), page 9, London, 1905.) + +When Dalton's atomic theory had been in existence some half century, it was +noted that certain numerical relations held good between the atomic weights +of elements chemically similar to one another. Thus the weight (88) of an +atom of strontium compared with that of hydrogen as unity, is about the +mean of those of calcium (40) and barium (137). Such relations, in this +and other chemical groups, were illustrated by Beguyer de Chancourtois in +1862 by the construction of a spiral diagram in which the atomic weights +are placed in order round a cylinder and elements chemically similar are +found to fall on vertical lines. + +Newlands seems to have been the first to see the significance of such a +diagram. In his "law of octaves," formulated in 1864, he advanced the +hypothesis that, if arranged in order of rising atomic weight, the elements +fell into groups, so that each eighth element was chemically similar. +Stated thus, the law was too definite; no room was left for newly- +discovered elements, and some dissimilar elements were perforce grouped +together. + +But in 1869 Mendeleeff developed Newland's hypothesis in a form that +attracted at once general attention. Placing the elements in order of +rising atomic weight, but leaving a gap where necessary to bring similar +elements into vertical columns, he obtained a periodic table with natural +vacancies to be filled as new elements were discovered, and with a certain +amount of flexibility at the ends of the horizontal lines. From the +position of the vacancies, the general chemical and physical properties of +undiscovered elements could be predicted, and the success of such +predictions gave a striking proof of the usefulness of Mendeleeff's +generalisation. + +When the chemical and physical properties of the elements were known to be +periodic functions of their atomic weights, the idea of a common origin and +common substance became much more credible. Differences in atomic weight +and differences in properties alike might reasonably be explained by the +differences in the amount of the primordial substance present in the +various atoms; an atom of oxygen being supposed to be composed of sixteen +times as much stuff as the atom of hydrogen, but to be made of the same +ultimate material. Speculations about the mode of origin of the elements +now began to appear, and put on a certain air of reality. Of these +speculations perhaps the most detailed was that of Crookes, who imagined an +initial chaos of a primordial medium he named protyle, and a process of +periodic change in which the chemical elements successively were +precipitated. + +From another side too, suggestions were put forward by Sir Norman Lockyer +and others that the differences in spectra observed in different classes of +stars, and produced by different conditions in the laboratory, were to be +explained by changes in the structure of the vibrating atoms. + +The next step in advance gave a theoretical basis for the idea of a common +structure of matter, and was taken in an unexpected direction. Clerk +Maxwell's electromagnetic theory of light, accepted in England, was driven +home to continental minds by the confirmatory experiments of Hertz, who in +1888 detected and measured the electromagnetic waves that Maxwell had +described twenty years earlier. But, if light be an electromagnetic +phenomenon, the light waves radiated by hot bodies must take their origin +in the vibrations of electric systems. Hence within the atoms must exist +electric charges capable of vibration. On these lines Lorentz and Larmor +have developed an electronic theory of matter, which is imagined in its +essence to be a conglomerate of electric charges, with electro-magnetic +inertia to explain mechanical inertia. (Larmor, "Aether and Matter", +Cambridge, 1900.) The movement of electric charges would be affected by a +magnetic field, and hence the discovery by Zeeman that the spectral lines +of sodium were doubled by a strong magnetic force gave confirmatory +evidence to the theory of electrons. + +Then came J.J. Thomson's great discovery of minute particles, much smaller +than any chemical atom, forming a common constituent of many different +kinds of matter. (Thomson, "Conduction of Electricity through Gases" (2nd +edition), Cambridge, 1906.) If an electric discharge be passed between +metallic terminals through a glass vessel containing air at very low +pressure, it is found that rectilinear rays, known as cathode rays, proceed +from the surface of the cathode or negative terminal. Where these rays +strike solid objects, they give rise to the Rontgen rays now so well known; +but it is with the cathode rays themselves that we are concerned. When +they strike an insulated conductor, they impart to it a negative charge, +and Thomson found that they were deflected from their path both by magnetic +and electric forces in the direction in which negatively electrified +particles would be deflected. Cathode rays then were accepted as flights +of negatively charged particles, moving with high velocities. The electric +and magnetic deflections give two independent measurements which may be +made on a cathode ray, and both the deflections involve theoretically three +unknown quantities, the mass of the particles, their electric charge and +their velocity. There is strong cumulative evidence that all such +particles possess the same charge, which is identical with that associated +with a univalent atom in electrolytic liquids. The number of unknown +quantities was thus reduced to two--the mass and the velocity. The +measurement of the magnetic and electric deflections gave two independent +relations between the unknowns, which could therefore be determined. The +velocities of the cathode ray particles were found to vary round a value +about one-tenth that of light, but the mass was found always to be the same +within the limits of error, whatever the nature of the terminals, of the +residual gas in the vessel, and of the conditions of the experiment. The +mass of a cathode ray particle, or corpuscle, as Thomson, adopting Newton's +name, called it, is about the eight-hundredth part of the mass of a +hydrogen atom. + +These corpuscles, found in so many different kinds of substance, are +inevitably regarded as a common constituent of matter. They are associated +each with a unit of negative electricity. Now electricity in motion +possesses electromagnetic energy, and produces effects like those of +mechanical inertia. In other words, an electric charge possesses mass, and +there is evidence to show that the effective mass of a corpuscle increases +as its velocity approaches that of light in the way it would do if all its +mass were electromagnetic. We are led therefore to regard the corpuscle +from one aspect as a disembodied charge of electricity, and to identify it +with the electron of Lorentz and Larmor. + +Thus, on this theory, matter and electricity are identified; and a great +simplification of our conception of the physical structure of Nature is +reached. Moreover, from our present point of view, a common basis for +matter suggests or implies a common origin, and a process of development +possibly intelligible to our minds. The idea of the evolution of matter +becomes much more probable. + +The question of the nature and physical meaning of a corpuscle or electron +remains for consideration. On the hypothesis of a universal luminiferous +aether, Larmor has suggested a centre of aethereal strain "a place where +the continuity of the medium has been broken and cemented together again +(to use a crude but effective image) without accurately fitting the parts, +so that there is a residual strain all round the place." (Larmor, loc. +cit.) Thus he explains in quasi-mechanical terms the properties of an +electron. But whether we remain content for the time with our +identification of matter and electricity, or attempt to express both of +them in terms of hypothetical aether, we have made a great step in advance +on the view that matter is made up of chemical atoms fundamentally distinct +and eternally isolated. + +Such was the position when the phenomena of radio-activity threw a new +light on the problem, and, for the first time in the history of science, +gave definite experimental evidence of the transmutation of matter from one +chemical element to another. + +In 1896 H. Becquerel discovered that compounds of the metal uranium +continually emitted rays capable of penetrating opaque screens and +affecting photographic plates. Like cathode and Rontgen rays, the rays +from uranium make the air through which they pass a conductor of +electricity, and this property gives the most convenient method of +detecting the rays and of measuring their intensity. An electroscope may +be made of a strip of gold-leaf attached to an insulated brass plate and +confined in a brass vessel with glass windows. When the gold-leaf is +electrified, it is repelled from the similarly electrified brass plate, and +the angle at which it stands out measures the electrification. Such a +system, if well insulated, holds its charge for hours, the leakage of +electricity through the air being very slow. But, if radio-active +radiation reach the air within, the gold-leaf falls, and the rate of its +fall, as watched through a microscope with a scale in the eye-piece, +measures the intensity of the radiation. With some form of this simple +instrument, or with the more complicated quadrant electrometer, most radio- +active measurements have been made. + +It was soon discovered that the activity of uranium compounds was +proportional to the amount of uranium present in them. Thus radio-activity +is an atomic property dependent on the amount of an element and independent +of its state of chemical combination. + +In a search for radio-activity in different minerals, M. and Mme Curie +found a greater effect in pitch-blende than its contents of uranium +warranted, and, led by the radio-active property alone, they succeeded, by +a long series of chemical separations, in isolating compounds of a new and +intensely radio-active substance which they named radium. + +Radium resembles barium in its chemical properties, and is precipitated +with barium in the ordinary course of chemical analysis. It is separated +by a prolonged course of successive crystallisation, the chloride of radium +being less soluble than that of barium, and therefore sooner separated from +an evaporating solution. When isolated, radium chloride has a composition, +which, on the assumption that one atom of metal combines with two of +chlorine as in barium chloride, indicates that the relative weight of the +atom of radium is about 225. As thus prepared, radium is a well-marked +chemical element, forming a series of compounds analogous to those of +barium and showing a characteristic line spectrum. But, unlike most other +chemical elements, it is intensely radio-active, and produces effects some +two million times greater than those of uranium. + +In 1899 E. Rutherford, then of Montreal, discovered that the radiation from +uranium, thorium and radium was complex. (Rutherford, "Radio-activity" +(2nd edition), Cambridge, 1905.) Three types of rays were soon +distinguished. The first, named by Rutherford alpha-rays, are absorbed by +thin metal foil or a few centimetres of air. When examined by measurements +of the deflections caused by magnetic and electric fields, the alpha-rays +are found to behave as would positively electrified particles of the +magnitude of helium atoms possessing a double ionic charge and travelling +with a velocity about one-tenth that of light. The second or beta type of +radiation is much more penetrating. It will pass through a considerable +thickness of metallic foil, or many centimetres of air, and still affect +photographic plates or discharge electroscopes. Magnetic and electric +forces deflect beta-rays much more than alpha-rays, indicating that, +although the speed is greater, approaching in some cases within five per +cent. that of light, the mass is very much less. The beta-rays must be +streams of particles, identical with those of cathode rays, possessing the +minute mass of J.J. Thomson's corpuscle, some eight-hundredth part of that +of a hydrogen atom. A third or gamma type of radiation was also detected. +More penetrating even than beta-rays, the gamma-rays have never been +deflected by any magnetic or electric force yet applied. Like Rontgen +rays, it is probable that gamma-rays are wave-pulses in the luminiferous +aether, though the possibility of explaining them as flights of non- +electrified particles is before the minds of some physicists. + +Still another kind of radiation has been discovered more recently by +Thomson, who has found that in high vacua, rays become apparent which are +absorbed at once by air at any ordinary pressure. + +The emission of all these different types of radiation involves a continual +drain of energy from the radio-active body. When M. and Mme Curie had +prepared as much as a gramme of radium chloride, the energy of the +radiation became apparent as an evolution of heat. The radium salt itself, +and the case containing it, absorbed the major part of the radiation, and +were thus maintained at a temperature measurably higher than that of the +surroundings. The rate of thermal evolution was such that it appeared that +one gramme of pure radium must emit about 100 gramme-calories of heat in an +hour. This observation, naturally as it follows from the phenomena +previously discovered, first called attention to the question of the source +of the energy which maintains indefinitely and without apparent diminution +the wonderful stream of radiation proceeding from a radio-active substance. +In the solution of this problem lies the point of the present essay. + +In order to appreciate the evidence which bears on the question we must now +describe two other series of phenomena. + +It is a remarkable fact that the intensity of the radiation from a radio- +active body is independent of the external conditions of temperature, +pressure, etc. which modify so profoundly almost all other physical and +chemical processes. Exposure to the extreme cold of liquid air, or to the +great heat of a furnace, leaves the radio-activity of a substance +unchanged, apparent exceptions to this statement having been traced to +secondary causes. + +Then, it is found that radio-activity is always accompanied by some +chemical change; a new substance always appears as the parent substance +emits these radiations. Thus by chemical reactions it is possible to +separate from uranium and thorium minute quantities of radio-active +materials to which the names of uranium-X and thorium-X have been given. +These bodies behave differently from their parents uranium and thorium, and +show all the signs of distinct chemical individuality. They are strongly +radio-active, while, after the separation, the parents uranium and thorium +are found to have lost some of their radio-activity. If the X-substances +be kept, their radio-activity decays, while that of the uranium or thorium +from which they were obtained gradually rises to the initial value it had +before the separation. At any moment, the sum of the radio-activity is +constant, the activity lost by the product being equal to that gained by +the parent substance. These phenomena are explained if we suppose that the +X-product is slowly produced in the substance of the parent, and decays at +a constant rate. Uranium, as usually seen, contains a certain amount of +uranium-X, and its radio-activity consists of two parts--that of the +uranium itself, and that of the X product. When the latter is separated by +means of its chemical reactions, its radio-activity is separated also, and +the rates of decay and recovery may be examined. + +Radium and thorium, but not uranium, give rise to radio-active gases which +have been called emanations. Rutherford has shown that their radio- +activity, like that of the X products, suffers decay, while the walls of +the vessel in which the emanation is confined, become themselves radio- +active. If washed with certain acids, however, the walls lose their +activity, which is transferred to the acid, and can be deposited by +evaporation from it on to a solid surface. Here again it is clear that the +emanation gives rise to a radio-active substance which clings to the walls +of the vessel, and is soluble in certain liquids, but not in others. + +We shall return to this point, and trace farther the history of the radio- +active matter. At present we wish to emphasise the fact that, as in other +cases, the radio-activity of the emanation is accompanied by the appearance +of a new kind of substance with distinct chemical properties. + +We are now in a position to consider as a whole the evidence on the +question of the source of radio-active energy. + +(1) Radio-activity is accompanied by the appearance of new chemical +substances. The energy liberated is therefore probably due to the +associated chemical change. (2) The activity of a series of compounds is +found to accompany the presence of a radio-active element, the activity of +each compound depends only on the contents of the element, and is +independent of the nature of its combination. Thus radio-activity is a +property of the element, and is not affected by its state of isolation or +chemical combination. (3) The radio-activity of a simple transient product +decays in a geometrical progression, the loss per second being proportional +to the mass of substance still left at the moment, and independent of its +state of concentration or dilution. This type of reaction is well known in +chemistry to mark a mono-molecular change, where each molecule is +dissociated or altered in structure independently. If two or more +molecules were concerned simultaneously, the rate of reaction would depend +on the nearness of the molecules to each other, that is, to the +concentration of the material. (4) The amount of energy liberated by the +change of a given mass of material far transcends the amount set free by +any known ordinary chemical action. The activity of radium decays so +slowly that it would not sink to half its initial value in less than some +two thousand years, and yet one gramme of radium emits about 100 calories +of heat during each hour of its existence. + +The energy of radio-activity is due to chemical change, but clearly to no +chemical change hitherto familiar to science. It is an atomic property, +characteristic of a given element, and the atoms undergo the change +individually, not by means of interaction among each other. The conclusion +is irresistible that we are dealing with a fundamental change in the +structure of the individual atoms, which, one by one, are dissociating into +simpler parts. We are watching the disintegration of the "atoms" of the +chemist, hitherto believed indestructible and eternal, and measuring the +liberation of some of the long-suspected store of internal atomic energy. +We have stumbled on the transmutation dreamed by the alchemist, and +discovered the process of a veritable evolution of matter. + +The transmutation theory of radio-activity was formulated by Rutherford +(Rutherford, "Radio-activity" (2nd edition), Cambridge, 1905, page 307.) +and Soddy in 1903. By its light, all recent work on the subject has been +guided; it has stood the supreme test of a hypothesis, and shown power to +suggest new investigations and to co-ordinate and explain them, when +carried out. We have summarised the evidence which led to the conception +of the theory; we have now to consider the progress which has been made in +tracing the successive disintegration of radio-active atoms. + +Soon after the statement of the transmutation theory, a striking +verification of one of its consequences appeared. The measurement of the +magnetic and electric deflection of the alpha-rays suggested to Rutherford +the idea that the stream of projectiles of which they consisted was a +flight of helium atoms. Ramsay and Soddy, confining a minute bubble of +radium emanation in a fine glass tube, were able to watch the development +of the helium spectrum as, day by day, the emanation decayed. By isolating +a very narrow pencil of alpha-rays, and watching through a microscope their +impact on a fluorescent screen, Rutherford has lately counted the +individual alpha-projectiles, and confirmed his original conclusion that +their mass corresponded to that of helium atoms and their charge to double +that on a univalent atom. ("Proc. Roy. Soc." A, page 141, 1908.) Still +more recently, he has collected the alpha-particles shot through an +extremely thin wall of glass, and demonstrated by direct spectroscopic +evidence the presence of helium. ("Phil. Mag." February 1909.) + +But the most thorough investigation of a radio-active pedigree is found in +Rutherford's classical researches on the successive disintegration products +of radium, in order to follow the evidence on which his results are +founded, we must describe more fully the process of decay of the activity +of a simple radio-active substance. The decay of activity of the body +known as uranium-X is shown in a falling curve (Fig. 1.). It will be seen +that, in each successive 22 days, the activity falls to half the value it +possessed at the beginning. + +This change in a geometrical progression is characteristic of simple radio- +active processes, and can be expressed mathematically by a simple +exponential formula. + +As we have said above, solid bodies exposed to the emanations of radium or +thorium become coated with a radio-active deposit. The rate of decay of +this activity depends on the time of exposure to the emanation, and does +not always show the usual simple type of curve. Thus the activity of a rod +exposed to radium emanation for 1 minute decays in accordance with a curve +(Fig. 2) which represents the activity as measured by the alpha-rays. If +the electroscope be screened from the alpha-rays, it is found that the +activity of the rod in beta- an gamma-rays increases for some 35 minutes +and then diminishes (Fig. 3.). + +These complicated relations have been explained satisfactorily and +completely by Rutherford on the hypothesis of successive changes of the +radio-active matter into one new body after another. (Rutherford, "Radio- +activity" (2nd edition), Cambridge, 1905, page 379.) The experimental +curve represents the resultant activity of all the matter present at a +given moment, and the process of disentangling the component effects +consists in finding a number of curves, which express the rise and fall of +activity of each kind of matter as it is produced and decays, and, fitted +together, give the curve of the experiments. + +Other methods of investigation also are open. They have enabled Rutherford +to complete the life-history of radium and its products, and to clear up +doubtful points left by the analysis of the curves. By the removal of the +emanation, the activity of radium itself has been shown to consist solely +of alpha-rays. This removal can be effected by passing air through the +solution of a radium salt. The emanation comes away, and the activity of +the deposit which it leaves behind decays rapidly to a small fraction of +its initial value. Again, some of the active deposits of the emanation are +more volatile than others, and can be separated from them by the agency of +heat. + +From such evidence Rutherford has traced a long series of disintegration +products of radium, all but the first of which exist in much too minute +quantities to be detected otherwise than by their radio-activities. +Moreover, two of these products are not themselves appreciably radio- +active, though they are born from radio-active parents, and give rise to a +series of radio-active descendants. Their presence is inferred from such +evidence as the rise of beta and gamma radio-activity in the solid newly +deposited by the emanation; this rise measuring the growth of the first +radio-active offspring of one of the non-active bodies. Some of the radium +products give out alpha-rays only, one beta- and gamma-rays, while one +yields all three types of radiation. The pedigree of the radium family may +be expressed in the following table, the time noted in the second column +being the time required for a given quantity to be half transformed into +its next derivative. + + Time of half Radio- Properties + decay activity + +Radium About 2600 years alpha rays Element chemically analogous + to barium. +> +Emanation 3.8 days alpha rays Chemically inert gas; + condenses at -150 deg C. +> +Radium-A 3 minutes alpha rays Behaves as a solid deposited on + surfaces; concentrated on a + negative electrode. +> +Radium-B 21 minutes no rays Soluble in strong acids; + volatile at a white heat; more + volatile than A or C. +> +Radium-C 28 minutes alpha, beta, Soluble in strong acids; less + gamma rays volatile than B. +> +Radium-D about 40 years no rays Soluble in strong acids; volatile + below 1000 deg C. +> +Radium-E 6 days beta, gamma Non-volatile at 1000 deg C. + rays +> +Radium-F 143 days alpha rays Volatile at 1000 deg C. + Deposited from solution on a + bismuth plate. + +Of these products, A, B, and C constitute that part of the active deposit +of the emanation which suffers rapid decay and nearly disappears in a few +hours. Radium-D, continually producing its short-lived descendants E and +F, remains for years on surfaces once exposed to the emanation, and makes +delicate radio-active researches impossible in laboratories which have been +contaminated by an escape of radium emanation. + +A somewhat similar pedigree has been made out in the case of thorium. Here +thorium-X is interposed between thorium and its short-lived emanation, +which decays to half its initial quantity in 54 seconds. Two active +deposits, thorium A and B, arise successively from the emanation. In +uranium, we have the one obvious derivative uranium-X, and the question +remains whether this one descent can be connected with any other individual +or family. Uranium is long-lived, and emits only alpha-rays. Uranium-X +decays to half value in 22 days, giving out beta- and gamma-rays. Since +our evidence goes to show that radio-activity is generally accompanied by +the production of new elements, it is natural to search for the substance +of uranium-X in other forms, and perhaps under other names, rather than to +surrender immediately our belief in the conservation of matter. + +With this idea in mind we see at once the significance of the constitution +of uranium minerals. Formed in the remote antiquity of past geological +ages, these minerals must become store-houses of all the products of +uranium except those which may have escaped as gases or possibly liquids. +Even gases may be expected to some extent to be retained by occlusion. +Among the contents of uranium minerals, then, we may look for the +descendants of the parent uranium. If the descendants are permanent or +more long-lived than uranium, they will accumulate continually. If they +are short-lived, they will accumulate at a steady rate till enough is +formed for the quantity disintegrating to be equal to the quantity +developed. A state of mobile equilibrium will then be reached, and the +amount of the product will remain constant. This constant amount of +substance will depend only on the amount of uranium which is its source, +and, for different minerals, if all the product is retained, the quantity +of the product will be proportional to the quantity of uranium. In a +series of analyses of uranium minerals, therefore, we ought to be able to +pick out its more short-lived descendants by seeking for instances of such +proportionality. + +Now radium itself is a constituent of uranium minerals, and two series of +experiments by R.J. Strutt and B.B. Boltwood have shown that the content of +radium, as measured by the radio-activity of the emanation, is directly +proportional to the content of uranium. (Strutt, "Proc. Roy. Soc." A, +February 1905; Boltwood, "Phil. Mag." April, 1905.) In Boltwood's +investigation, some twenty minerals, with amounts of uranium varying from +that in a specimen of uraninite with 74.65 per cent., to that in a monazite +with 0.30 per cent., gave a ratio of uranium to radium, constant within +about one part in ten. + +The conclusion is irresistible that radium is a descendant of uranium, +though whether uranium is its parent or a more remote ancestor requires +further investigation by the radio-active genealogist. On the hypothesis +of direct parentage, it is easy to calculate that the amount of radium +produced in a month by a kilogramme of a uranium salt would be enough to be +detected easily by the radio-activity of its emanation. The investigation +has been attempted by several observers, and the results, especially those +of a careful experiment of Boltwood, show that from purified uranium salts +the growth of radium, if appreciable at all, is much less than would be +found if the radium was the first product of change of the uranium. It is +necessary, therefore, to look for one or more intermediate substances. + +While working in 1899 with the uranium residues used by M. and Mme Curie +for the preparation of radium, Debierne discovered and partially separated +another radio-active element which he called actinium. It gives rise to an +intermediate product actinium-X, which yields an emanation with the short +half-life of 3.9 seconds. The emanation deposits two successive +disintegration products actinium-A and actinium-B. + +Evidence gradually accumulated that the amounts of actinium in radio-active +minerals were, roughly at any rate, proportional to the amounts of uranium. +This result pointed to a lineal connection between them, and led Boltwood +to undertake a direct attack on the problem. Separating a quantity of +actinium from a kilogramme of ore, Boltwood observed a growth of 8.5 x (10 +to the power -9) gramme of radium in 193 days, agreeing with that indicated +by theory within the limits of experimental error. ("American Journal of +Science", December, 1906.) We may therefore insert provisionally actinium +and its series of derivatives between uranium and radium in the radio- +active pedigree. + +Turning to the other end of the radium series we are led to ask what +becomes of radium-F when in turn it disintegrates? What is the final non- +active product of the series of changes we have traced from uranium through +actinium and radium? + +One such product has been indicated above. The alpha-ray particles appear +to possess the mass of helium atoms, and the growth of helium has been +detected by its spectrum in a tube of radium emanation. Moreover, helium +is found occluded in most if not all radio-active minerals in amount which +approaches, but never exceeds, the quantity suggested by theory. We may +safely regard such helium as formed by the accumulation of alpha-ray +particles given out by successive radio-active changes. + +In considering the nature of the residue left after the expulsion of the +five alpha-particles, and the consequent passage of radium to radium-F we +are faced by the fact that lead is a general constituent of uranium +minerals. Five alpha-particles, each of atomic weight 4, taken from the +atomic weight (about 225) of radium gives 205--a number agreeing fairly +well with the 207 of lead. Since lead is more permanent than uranium, it +must steadily accumulate, no radio-active equilibrium will be reached, and +the amount of lead will depend on the age of the mineral as well as on the +quantity of uranium present in it. In primary minerals from the same +locality, Boltwood has shown that the contents of lead are proportional to +the amounts of uranium, while, accepting this theory, the age of minerals +with a given content of uranium may be calculated from the amount of lead +they contain. The results vary from 400 to 2000 million years. ("American +Journal of Science", October, 1905, and February, 1907.) + +We can now exhibit in tabular form the amazing pedigree of radio-active +change shown by this one family of elements. An immediate descent is +indicated by >, while one which may either be immediate or involve an +intermediate step is shown by .... No place is found in this pedigree for +thorium and its derivatives. They seem to form a separate and independent +radio-active family. + + Atomic Weight Time of half Radio-Activity + decay + +Uranium 238.5 alpha +> +Uranium-X ? 22 days beta, gamma +... +Actinium ? ? no rays +> +Actinium-X ? 10.2 days alpha (beta, gamma) +> +Actinium Emanation ? 3.9 seconds alpha +> +Actinium-A ? 35.7 minutes no rays +> +Actinium-B ? 2.15 minutes alpha, beta, gamma +... +Radium 225 about 2600 years alpha +> +Radium Emanation ? 3.8 days alpha +> +Radium-A ? 3 minutes alpha +> +Radium-B ? 21 minutes no rays +> +Radium-C ? 28 minutes alpha, beta, gamma +> +Radium-D ? about 40 years no rays +> +Radium-E ? 6 days beta (gamma) +> +Radium-F ? 143 days alpha +... +Lead 207 ? no rays + +As soon as the transmutation theory of radio-activity was accepted, it +became natural to speculate about the intimate structure of the radio- +active atoms, and the mode in which they broke up with the liberation of +some of their store of internal energy. How could we imagine an atomic +structure which would persist unchanged for long periods of time, and yet +eventually spontaneously explode, as here an atom and there an atom reached +a condition of instability? + +The atomic theory of corpuscles or electrons fortunately was ready to be +applied to this new problem. Of the resulting speculations the most +detailed and suggestive is that of J.J. Thomson. ("Phil. Mag." March, +1904.) Thomson regards the atom as composed of a number of mutually +repelling negative corpuscles or electrons held together by some central +attractive force which he represents by supposing them immersed in a +uniform sphere of positive electricity. Under the action of the two +forces, the electrons space themselves in symmetrical patterns, which +depend on the number of electrons. Three place themselves at the corner of +an equilateral triangle, four at those of a square, and five form a +pentagon. With six, however, the single ring becomes unstable, one +corpuscle moves to the middle and five lie round it. But if we imagine the +system rapidly to rotate, the centrifugal force would enable the six +corpuscles to remain in a single ring. Thus internal kinetic energy would +maintain a configuration which would become unstable as the energy drained +away. Now in a system of electrons, electromagnetic radiation would result +in a loss of energy, and at one point of instability we might well have a +sudden spontaneous redistribution of the constituents, taking place with an +explosive violence, and accompanied by the ejection of a corpuscle as a +beta-ray, or of a large fragment of the atom as an alpha-ray. + +The discovery of the new property of radio-activity in a small number of +chemical elements led physicists to ask whether the property might not be +found in other elements, though in a much less striking form. Are ordinary +materials slightly radio-active? Does the feeble electric conductivity +always observed in the air contained within the walls of an electroscope +depend on ionizing radiations from the material of the walls themselves? +The question is very difficult, owing to the wide distribution of slight +traces of radium. Contact with radium emanation results in a deposit of +the fatal radium-D, which in 40 years is but half removed. Is the +"natural" leak of a brass electroscope due to an intrinsic radio-activity +of brass, or to traces of a radio-active impurity on its surface? Long and +laborious researches have succeeded in establishing the existence of slight +intrinsic radio-activity in a few metals such as potassium, and have left +the wider problem still unsolved. + +It should be noted, however, that, even if ordinary elements are not radio- +active, they may still be undergoing spontaneous disintegration. The +detection of ray-less changes by Rutherford, when those changes are +interposed between two radio-active transformations which can be followed, +show that spontaneous transmutation is possible without measureable radio- +activity. And, indeed, any theory of disintegration, such as Thomson's +corpuscular hypothesis, would suggest that atomic rearrangements are of +much more general occurrence than would be apparent to one who could +observe them only by the effect of the projectiles, which, in special +cases, owing to some peculiarity of atomic configuration, happened to be +shot out with the enormous velocity needed to ionize the surrounding gas. +No evidence for such ray-less changes in ordinary elements is yet known, +perhaps none may ever be obtained; but the possibility should not be +forgotten. + +In the strict sense of the word, the process of atomic disintegration +revealed to us by the new science of radio-activity can hardly be called +evolution. In each case radio-active change involves the breaking up of a +heavier, more complex atom into lighter and simpler fragments. Are we to +regard this process as characteristic of the tendencies in accord with +which the universe has reached its present state, and is passing to its +unknown future? Or have we chanced upon an eddy in a backwater, opposed to +the main stream of advance? In the chaos from which the present universe +developed, was matter composed of large highly complex atoms, which have +formed the simpler elements by radio-active or ray-less disintegration? Or +did the primaeval substance consist of isolated electrons, which have +slowly come together to form the elements, and yet have left here and there +an anomaly such as that illustrated by the unstable family of uranium and +radium, or by some such course are returning to their state of primaeval +simplicity? + + +INDEX. + +Abraxas grossulariata. + +Acquired characters, transmission of. + +Acraea johnstoni. + +Adaptation. + +Adloff. + +Adlumia cirrhosa. + +Agassiz, A. + +Agassiz, L. + +Alexander. + +Allen, C.A. + +Alternation of generations. + +Ameghino. + +Ammon, O., Works of. + +Ammonites, Descent of. + +Amphidesmus analis. + +Anaea divina. + +Andrews, C.W. + +Angiosperms, evolution of. + +Anglicus, Bartholomaeus. + +Ankyroderma. + +Anomma. + +Antedon rosacea. + +Antennularia antennina. + +Anthropops. + +Ants, modifications of. + +Arber, E.A.N., +--and J. Parkin, on the origin of Angiosperms. + +Archaeopteryx. + +Arctic regions, velocity of development of life in. + +Ardigo. + +Argelander. + +Argyll, Huxley and the Duke of. + +Aristotle. + +Arrhenius. + +Asterias, Loeb on hybridisation of. + +Autogamy. + +Avena fatua. + +Avenarius. + +Bacon, on mutability of species. + +Baehr, von, on Cytology. + +Baer, law of von. + +Bain. + +Baldwin, J.M. + +Balfour, A.J. + +Ball, J. + +Barber, Mrs M.E., on Papilio nireus. + +Barclay, W. + +Barratt. + +Bary, de. + +Bates, H.W., on Mimicry. +--Letters from Darwin to. +--elsewhere. + +Bateson, A. + +BATESON, W., on "Heredity and Variation in Modern lights". +--on discontinuous evolution. +--on hybridisation. + +Bateson, W. and R.P. Gregory. + +Bathmism. + +Beche, de la. + +Beck, P. + +Becquerel, H. + +Beebe, C.W., on the plumage of birds. +--on sexual selection. + +Beguyer de Chancourtois. + +Bell's (Sir Charles) "Anatomy of Expression". + +Belopolsky. + +Belt, T., on Mimicry. + +Beneden, E. van. + +Benson, M. + +Bentham, G., on Darwin's species-theory. +--on geographical distribution. + +Bentham, Jeremy. + +Bergson, H. + +Berkeley. + +Berthelot. + +Betham, Sir W. + +Bickford, E., experiments on degeneration by. + +Bignonia capreolata. + +Biophores. + +Birds, geological history of. + +Blanford, W.T. + +Blaringhem, on wounding. + +Blumenbach. + +Bodin. + +Boltwood, B.B. + +Bonald, on war. + +Bonnet. + +Bonney, T.G. + +Bonnier, G. + +Bopp, F., on language. + +BOUGLE C., on "Darwinism and Sociology". + +Bourdeau. + +Bourget, P. + +Boutroux. + +Boveri, T. + +Brachiopods, history of. + +Brassica, hybrids of. + +Brassica Napus. + +Broca. + +Brock, on Kant. + +Brown, Robert. + +Brugmann and Osthoff. + +Brugmann. + +Brunetiere. + +Bruno, on Evolution. + +Buch, von. + +Bucher, K. + +Buckland. + +Buckle. + +Buffon. + +Burchell, W.J. + +Burck, W. + +Burdon-Sanderson, J., letter from. + +BURY, J.B., on "Darwinism and History". + +Butler, A.G. + +Butler, Samuel. + +Butschli, O. + +Butterflies, mimicry in. +--sexual characters in. + +Cabanis. + +Campbell. + +Camels, geological history of. + +Camerarius, R.J. + +Candolle, A. de. + +Cannon and Davenport, experiments on Daphniae by. + +Capsella bursapastoris. + +Carneri. + +Castnia linus. + +Catasetum barbatum. + +Catasetum tridentatum. + +Caterpillars, variation in. + +Celosia, variability of. + +Cereals, variability in. + +Cesnola, experiments on Mantis by. + +Chaerocampa, colouring of. + +Chambers, R., "The Vestiges of Creation" by. + +Chromosomes and Chromomeres. + +Chun. + +Cieslar, experiments by. + +Circumnutation, Darwin on. + +Claus. + +Cleistogamy. + +Clerke, Miss A. + +Clodd, E. + +Cluer. + +Clytus arietis. + +Coadaptation. + +Codrington. + +Cohen and Peter. + +Collingwood. + +Colobopsis truncata. + +Colour, E.B. Poulton on The Value in the Struggle for life of. +--influence and temperature on changes in. +--in relation to Sexual Selection. + +Colours, incidental. +--warning. + +Comte, A. + +Condorcet. + +Cope. + +Coral reefs, Darwin's work on. + +Correlation of organisms, Darwin's idea of the. + +Correlation of parts. + +Corydalis claviculata. + +Cournot. + +Couteur, Col. Le. + +Crooks, Sir William. + +Cruger, on Orchids. + +Cunningham and Marchand, on the brain. + +Curie, M. and Mme. + +Cuvier. + +Cycadeoidea dacotensis. + +Cycads, geological history of. + +Cystidea, an ancient group. + +Cytology and heredity. + +Cytolysis and fertilisation. + +Czapek. + +Dalton's atomic theory. + +Dana, J.D., on marine faunas. + +Danaida chrysippus. + +Danaida genutia. + +Danaida plexippus. + +Dante. + +Dantec, Le, + +Darwin, Charles, as an Anthropologist. +--on ants. +--and the "Beagle" Voyage. +--on the Biology of Flowers. +--as a Botanist. +--his influence on Botany. +--and S. Butler. +--at Cambridge. +--on Cirripedia. +--on climbing plants. +--on colour. +--on coral reefs. +--on the Descent of Man. +--his work on Drosera. +--at Edinburgh. +--his influence on Animal Embryology. +--on Geographical Distribution. +--his work on Earthworms. +--evolutionist authors referred to in the "Origin" by. +--and E. Forbes. +--on the geological record. +--and Geology. +--his early love for geology. +--his connection with the Geological Society of London. +--and Haeckel. +--and Henslow. +--and History. +--and Hooker. +--and Huxley. +--on ice-action. +--on igneous rocks. +--on Lamarck. +--on Language. +--his Scientific Library. +--and the Linnean Society. +--and Lyell. +--and Malthus. +--on Patrick Matthew. +--on mental evolution. +--on Mimicry. +--a "Monistic Philosopher." +--on the movements of plants. +--on Natural Selection. +--a "Naturalist for Naturalists." +--on Paley. + +Darwin, Charles, his Pangenesis hypothesis. +--on the permanence of continents. +--his personality. +--his influence on Philosophy. +--predecessors of. +--his views on religion, etc. +--his influence on religious thought. +--his influence on the study of religions. +--his methods of research. +--and Sedgwick. +--on Sexual Selection. +--the first germ of his species theory. +--on H. Spencer. +--causes of his success. +--on Variation. +--on the "Vestiges of Creation". +--on volcanic islands. +--and Wallace. +--letter to Wallace from. +--letter to E.B. Wilson from. + +Darwin, E., on the colour of animals. +--Charles Darwin's reference to. +--on evolution. + +DARWIN, F., on "Darwin's work on the Movements of Plants". +--on Darwin as a botanist. +--observations on Earthworms by. +--on Lamarckism. +--on Memory. +--on Prichard's "Anticipations". +--various. + +DARWIN, SIR G., on "The Genesis of Double Stars". +--on the earth's mass. + +Darwin, H. + +Darwin, W. + +Darwinism, Sociology, Evolution and. + +Davenport and Cannon, experiments on Daphniae by. + +David, T.E., his work on Funafuti. + +Death, cause of natural. + +Debey, on Cretaceous plants. + +Debierne. + +Degeneration. + +Delage, experiments on parthenogenesis by. + +Delbruck. + +Democritus. + +Deniker. + +Descartes. + +Descent, history of doctrine of. + +"Descent of Man", G. Schwalbe on "The". +--Darwin on Sexual Selection in "The". +--rejection in Germany of "The". + +Desmatippus. + +Desmoulins, A., on Geographical Distribution. + +Detto. + +Development, effect of environment on. + +Dianthus caryophyllus. + +Diderot. + +Digitalis purpurea. + +Dimorphism, seasonal. + +Dismorphia astynome. + +Dismorphia orise. + +Distribution, H. Gadow on Geographical. +--Sir W. Thiselton-Dyer on. + +Dittrick, O. + +Dixey, F.A., on the scent of Butterflies. + +Dolichonyx oryzivorus. + +Dorfmeister. + +Down, Darwin at. + +Draba verna. + +Dragomirov. + +Driesch, experiments by. +--elsewhere. + +Drosera, Darwin's work on. + +Dryopithecus. + +Dubois, E., on Pithecanthropus. + +Duhring. + +Duhamel. + +Duncan, J.S. + +Duncan, P.B. + +Duns Scotus. + +Duret, C. + +Durkheim, on division of labour. + +Dutrochet. + +Echinoderms, ancestry of. + +Ecology. + +Eimer. + +Ekstam. + +Elephants, geological history of. + +Elymnias phegea. + +E. undularis. + +Embleton, A.L. + +Embryology, A. Sedgwick on the influence of Darwin on. + +Embryology, as a clue to Phylogeny. +--the Origin of Species and. + +Empedocles. + +Engles. + +Environment, action of. +--Klebs on the influence on plants of. +--Loeb on experimental study in relation to. + +Eohippus. + +Epicurus, a poet of Evolution. + +Eristalis. + +Ernst. + +Ernst, A., on the Flora of Krakatau. + +Eschscholzia californica. + +Espinas. + +Eudendrium racemosum. + +Evolution, in relation to Astronomy. +--and creation. +--conception of. +--discontinuous. +--experimental. +--factors of. +--fossil plants as evidence of. +--and language. +--of matter, W.C.D. Whetham on. +--mental. +--Lloyd Morgan on mental factors in. +--Darwinism and Social. +--Saltatory. +--Herbert Spencer on. +--Uniformitarian. +--Philosophers and modern methods of studying. + +Expression of the Emotions. + +Fabricius, J.C., on geographical distribution. + +Farmer, J.B. + +Farrer, Lord. + +Fearnsides, W.G. + +Felton, S., on protective resemblance. + +Ferri. + +Ferrier, his work on the brain. + +Fertilisation, experimental work on animal-. + +Fertilisation of Flowers. + +Fichte. + +Field, Admiral A.M. + +Fischer, experiments on Butterflies by. + +Fitting. + +Flemming, W. + +Flourens. + +Flowering plants, ancestry of. + +Flowers, K. Goebel on the Biology of. + +Flowers and Insects. + +Flowers, relation of external influences to the production of. + +Fol, H. + +Forbes, E. +--and C. Darwin. + +Ford, S.O. and A.C. Seward, on the Araucarieae. + +Fossil Animals, W.B. Scott on their bearing on evolution. + +Fossil Plants, D.H. Scott on their bearing on evolution. + +Fouillee. + +Fraipont, on skulls from Spy. + +FRAZER, J.G., on "Some Primitive Theories of the Origin of Man". +--various. + +Fruwirth. + +Fumaria officinalis. + +Funafuti, coral atoll of. + +Fundulus. + +F. heteroclitus. + +GADOW, H., on "Geographical Distribution of Animals". +--elsewhere. + +Gartner, K.F. + +Gallus bankiva. + +Galton, F. + +Gamble, F.W. and F.W. Keeble. + +Gasca, La. + +Geddes, P. + +Geddes, P. and A.W. Thomson. + +Gegenbauer. + +Geikie, Sir A. + +Geitonogamy. + +Genetics. + +Geographical Distribution of Animals. +--of Plants. +--influence of "The Origin of Species" on. +--Wallace's contribution to. + +Geography of former periods, reconstruction of. + +Geology, Darwin and. + +Geranium spinosum. + +Germ-plasm, continuity of. +--Weismann on. + +Germinal Selection. + +Gibbon. + +Gilbert. + +GILES, P., on "Evolution and the Science of Language". + +Giuffrida-Ruggeri. + +Giotto. + +Gizycki. + +Glossopteris Flora. + +Gmelin. + +Godlewski, on hybridisation. + +GOEBEL, K., on "The Biology of Flowers". +--his work on Morphology. + +Goethe and Evolution. +--on the relation between Man and Mammals. +--elsewhere. + +Goldfarb. + +Gondwana Land. + +Goodricke, J. + +Gore, Dr. + +Gorjanovic-Kramberger. + +Gosse, P.H. + +Grabau, A.W., on Fusus. + +Grand'Eury, F.C., on fossil plants. + +Grapta C. album. + +Gravitation, effect on life-phenomena of. + +Gray, Asa. + +Gregoire, V. + +Groom, T.T., on heliotropism. + +Groos. + +Grunbaum, on the brain. + +Guignard, L. + +Gulick. + +Guppy, on plant-distribution. + +Guyau. + +Gwynne-Vaughan, D.T., on Osmundaceae. + +Gymnadenia conopsea. + +Haberlandt, G. + +Haddon, A.C. + +HAECKEL, E., on "Charles Darwin as an Anthropologist". +--on Colour. +--and Darwin. +--on the Descent of Man. +--contributions to Evolution by. + +Haeckel, E., on Lamarck. +--on Language. +--a leader in the Darwinian controversy. +--on Lyell's influence on Darwin. +--various. + +Hacker. + +Hagedoorn, on hybridisation. + +Hales, S. + +Hansen. + +Harker, A. + +HARRISON, J.E., on "The Influence of Darwinism on the Study of Religions". + +Hartmann, von. + +Harvey. + +Haupt, P., on Language. + +Haycraft. + +Hays, W.M. + +Hegel. + +Heliconius narcaea. + +Heliotropism in animals. + +Henslow, Rev. J.S. and Darwin. + +Hensen, Van. + +Herbst, his experiments on sea urchins. + +Heracleitus. + +Herder. + +Heredity and Cytology. +--Haeckel on. +--and Variation. +--various. + +Hering, E., on Memory. + +Herschel, J. + +Hertwig, R. + +Hertwig, O. + +Hertz. + +Heteromorphosis. + +Heterostylism. + +Heuser, E. + +Hewitt. + +Heyse's theory of language. + +Hinde, G.J., his work on Funafuti. + +Hipparion. + +Hippolyte cranchii. + +Hirase. + +History, Darwin and. + +Hobbes, T. + +Hobhouse. + +HOFFDING, H., on "The Influence of the Conception of Evolution on Modern +Philosophy". + +Hofmeister, W. + +Holmes, S.J., on Arthropods. + +Holothurians, calcareous bodies in skin of. + +Homo heidelbergensis. + +Homo neandertalensis. + +Homo pampaeus. + +Homo primigenius. + +Homunculus. + +Hooker, Sir J.D., and Darwin. +--on Distribution of Plants. +--on Ferns. +--Letter to the Editor from. + +Horner, L. + +Horse, Geological history of the. + +Huber. + +Hubert and Mauss. + +Hubrecht, A.R.W. + +Hugel, F. von. + +Humboldt, A. von. + +Humboldt, W. von. + +Hume. + +Hutcheson. + +Hutton. + +Huxley, T.H., and Darwin. +--and the Duke of Argyll. +--on Embryology. +--on Geographical Distribution. +--on Lamarck. +--Letter to J.W. Judd from. +--on Lyell. +--on Man. +--on "The Origin of Species". +--on Selection. +--on Teleology. +--on transmission of acquired characters. +--various. + +Hybridisation. + +Hybrids, Sterility of. + +Hyracodon. + +Iberis umbellata. + +Ikeno. + +Imperfection of the Geological Record. + +Ingenhousz, on plant physiology. + +Inheritance of acquired characters. + +Insects and Flowers. + +Instinct. + +Instincts, experimental control of animal. + +Ipomaea purpurea. + +Irish Elk, an example of co-adaptation. + +Jacobian figures. + +Jacoby, "Studies in Selection" by. + +James, W. + +Janczewski. + +Jeans, J.H. + +Jennings, H.S., on Paramoecium. + +Jentsch. + +Jespersen, Prof., Theory of. + +Johannsen, on Species. + +Jones, Sir William, on Language. + +Jordan. + +JUDD, J.W., on "Darwin and Geology". + +Kallima, protective colouring of. + +Kallima inachis. + +Kammerer's experiments on Salamanders. + +Kant, I. + +Keane, on the Primates. + +Keeble, F.W. and F.W. Gamble, on Colour-change. + +Keith, on Anthropoid Apes. + +Kellogg, V., on heliotropism. + +Kepler. + +Kerguelen Island. + +Kidd. + +Kidston, R., on fossil plants. + +Killmann, on origin of human races. + +King, Sir George. + +Klaatsch, on Ancestry of Man. + +Klaatsch and Hauser. + +KLEBS, G., on "The influence of Environment on the forms of plants". + +Kniep. + +Knies. + +Knight, A., experiments on plants by. +--on Geotropism. + +Knight-Darwin law. + +Knuth. + +Kolliker, his views on Evolution. + +Kolreuter, J.G. + +Kohl. + +Korschinsky. + +Kowalevsky, on fossil horses. + +Krakatau, Ernst on the Flora of. + +Krause, E. + +Kreft, Dr. + +Kropotkin. + +Kupelwieser, on hybridisation. + +Lagopus hyperboreus. + +Lamarck, his division of the Animal Kingdom. +--Darwin's opinion of. +--on Evolution. +--on Man. +--various. + +Lamarckian principle. + +Lamb, C. + +Lamettrie. + +Lamprecht. + +Lanessan, J.L. de. + +Lang. + +Lange. + +Language, Darwin on. +--Evolution and the Science of. +--various. + +Lankester, Sir E. Ray, on degeneration. +--on educability. +--on the germ-plasm theory. +--elsewhere. + +Lapouge, Vacher de. + +Larmor, J. + +Lartet, M.E. + +Lassalle. + +Lathyrus odoratus. + +Lavelaye, de. + +Lawrence, W. + +Lehmann. + +Lehmann-Nitsche. + +Leibnitz. + +Lepidium Draba. + +Lepidoptera, variation in. + +Leskien, A., on language. + +Lessing. + +Leucippus. + +Levi, E. + +Lewes, G.H. + +Lewin, Capt. + +Liapounoff. + +Liddon, H.P. + +Light, effect on organisms of. + +Limenitis archippus. +--arthemis. + +Linnaeus. + +Livingstone, on plant-forms. + +Llamas, geological history of. + +Lockyer, Sir N. + +Locy, W.A. + +LOEB, J., on "The Experimental Study of the influence of environment on +Animals. + +Loew, E. + +Longstaff, G.B., on the Scents of Butterflies. + +Lorentz. + +Lotsy, J.P. + +Love, A.E.W. + +Lovejoy. + +Lubbock. + +Lucas, K. + +Lucretius, a poet of Evolution. + +Lumholtz, C. + +Luteva macrophthalma. + +Lycorea halia. + +Lyell, Sir Charles, and Darwin. +--the influence of. +--on geographical distribution. +--on "The Origin of Species". +--on the permanence of Ocean-basins. +--publication of the "Principles" by. +--the uniformitarian teaching of. + +Lythrum salicaria. + +Macacus, ear of. + +MacDougal, on wounding. + +Mach, E. + +Macromytis flexuosa, colour-change in. + +Magic and religion. + +Mahoudeau. + +Maillet, de. + +Majewski. + +Malthus, his influence on Darwin. +--various. + +Mammalia, history of. + +Man, Descent of. +--J.G. Frazer on some primitive theories of the origin of. +--mental and moral qualities of animals and. +--pre-Darwinian views on the Descent of. +--religious views of primitive. +--Tertiary flints worked by. + +"Man", G. Schwalbe on Darwin's "Descent of". + +Manouvrier. + +Mantis religiosa, colour experiments on. + +Marett, R.R. + +Markwick. + +Marshall, G.A.K. + +Marx. + +Massart. + +Masters, M. + +Matonia pectinata. + +Matthew, P., and Natural Selection. + +Maupertuis. + +Maurandia semperflorens. + +Mauss and Herbert. + +Mauthner. + +Maxwell. + +Maxwell, Clerk. + +Mayer, R. + +Mechanitis lysimnia. + +Meehan, T. + +Meldola, R., Letters from Darwin to. + +Melinaea ethra. + +Mendel. + +Mendeleeff. + +Merrifield. + +Merz, J.T. + +Mesembryanthemum truncatum. + +Mesohippus. + +Mesopithecus. + +Metschnikoff. + +Mill, J.S. + +Mimicry. +--H.W. Bates on. +--F. Muller on. + +Mimulus luteus. + +Miquel, F.W.A. + +Mobius. + +Mohl, H. von. + +Moltke, on war. + +Monachanthus viridis. + +Monkeys, fossil. + +Montesquieu. + +Montgomery, T.H. + +Monstrosoties. + +Monticelli. + +Moore, J.E.S. + +MORGAN, C. LLOYD, on "Mental Factors in Evolution". +--on Organic Selection. + +Morgan, T.H. + +Morse, E.S., on colour. + +Morselli. + +Mortillet. + +Moseley. + +Mottier, M. + +Muller, Fritz, "Fur Darwin" by. +--on Mimicry. + +Muller, Fritz. + +Muller, J. + +Muller, Max, on language. + +Murray, A., on geographical distribution. + +Murray, G. + +Mutability. + +Mutation. + +Myanthus barbatus. + +Myers, G.W., on Eclipses. + +Nageli. + +Nathorst, A.G. + +Nathusius. + +Natural Selection, and adaptation. +--Darwin's views on. +--Darwin and Wallace on. +--and design. +--and educability. +--Fossil plants in relation to. +--and human development. +--and Mimicry. +--and Mutability. +--various. + +Naudin. + +Neandertal skulls. + +Nemec. + +Neoclytus curvatus. + +Neodarwinism. + +Neumayr, M. + +Newton, A. + +Newton, I. + +Niebuhr. + +Nietzsche. + +Nilsson, on cereals. + +Nitsche. + +Noire. + +Noll. + +Novicow. + +Nuclear division. + +Nussbaum, M. + +Nuttall, G.H.F. + +Occam. + +Odin. + +Oecology, see Ecology. + +Oenothera biennis. + +Oenothera gigas. + +Oenothera Lamarckiana. + +Oenothera muricata. + +Oenothera nanella. + +Oestergren, on Holothurians. + +Oken, L. + +Oliver, F.W., on Palaeozoic Seeds. + +Ononis minutissima. + +Ophyrs apifera. + +Orchids, Darwin's work on the fertilisation of. + +Organic Selection. + +"Origin of Species", first draft of the. +--geological chapter in the. + +Orthogenesis. + +Ortmann, A.E. + +Osborn, H.F. +--"From the Greeks to Darwin" by. + +Osthoff and Brugmann. + +Ostwald, W. + +Ovibos moschatus. + +Owen, Sir Richard. + +Oxford, Ashmolean Museum at. + +Packard, A.S. + +Palaeontological Record, D.H. Scott on the. +--W.B. Scott on the. + +Palaeopithecus. + +Paley. + +Palitzch, G. + +Palm. + +Pangenesis. + +Panmixia, Weismann's principle of. + +Papilio dardanus. + +Papilio meriones. + +Papilio merope. + +Papilio nireus. + +Paramoecium, Jennings on. + +Parker, G.H., on Butterflies. + +Parkin, J. and E.A.N. Arber, on the origin of Angiosperms. + +Parthenogenesis, artificial. + +Paul, H. and Wundt. + +Pearson, K. + +Peckham, Dr and Mrs, on the Attidae. + +Penck. + +Penzig. + +Peripatus, distribution of. + +Peridineae. + +Permanence of continents. + +Perrier, E. + +Perrhybris pyrrha. + +Perthes, B. de. + +Peter, on sea urchin's eggs. + +Petunia violacea. + +Pfeffer, W. + +Pfitzner, W. + +Pflueger. + +Phillips. + +Philosophy, influence of the conception of evolution on modern. + +Phryniscus nigricans. + +Phylogeny, embryology as a clue to. +--Palaeontological evidence on. + +Physiology of plants, development of. + +Piccard, on Geotropism. + +Pickering, spectroscopic observations by. + +Piranga erythromelas. + +Pisum sativum. + +Pithecanthropus. + +Pitheculites. + +Planema epaea. + +Plants, Darwin's work on the movements of. +--geographical distribution of. +--Palaeontological record of fossil. + +Platanthera bifolia. + +Plate. + +Plato. + +Playfair. + +Pliopithecus. + +Pocock, R.I. + +Poincare. + +Polarity, Vochting on. + +Polymorphic species. +--variability in cereals. + +Polypodium incanum. + +Porthesia chrysorrhoea. + +Potonie, R. + +Pouchet, G. + +POULTON, E.B., on "The Value of Colour in the Struggle for Life". +--experiments on Butterflies by. +--on J.C. Prichard. +--on Mimicry. +--various. + +Pratt. + +Pratz, du. + +Premutation. + +Preuss, K. Th. + +Prichard, J.C. + +Primula, heterostylism in. + +Primula acaulis. + +Primula elatior. + +Primula officinalis. + +Promeces viridis. + +Pronuba yuccasella. + +Protective resemblance. + +Protocetus. + +Protohippus. + +Psychology. + +Pteridophytes, history of. + +Pteridospermeae. + +Pucheran. + +Pusey. + +Quatrefages, A. de. + +Quetelet, statistical investigations by. + +Rabl, C. + +Radio-activity. + +Radiolarians. + +Raimannia odorata. + +Ramsay, Sir W. and Soddy. + +Ranke. + +Rau, A. + +Ray, J. + +Reade, Mellard. + +Recapitulation, the theory of. + +Reduction. + +Regeneration. + +Reid, C. + +Reinke. + +Religion, Darwin's attitude towards. +--Darwin's influence on the study of. +--and Magic. + +Religious thought, Darwin's influence on. + +Renard, on Darwin's work on volcanic islands. + +Reproduction, effect of environment on. + +Reptiles, history of. + +Reversion. + +Rhinoceros, the history of the. + +Ridley, H.N. + +Riley, C.V. + +Ritchie. + +Ritual. + +Roberts, A. + +Robertson, T.B. + +Robinet. + +Rolfe, R.A. + +Rolph. + +Romanes, G.J. + +Rothert. + +Roux. + +Rozwadowski, von. + +Ruskin. + +Rutherford, E. + +Rutot. + +Sachs, J. + +St Hilaire, E.G. de. + +Salamandra atra. + +Salamandra maculosa. + +Saltatory Evolution, (see also Mutations). + +Sanders, experiments on Vanessa by. + +Saporta, on the Evolution of Angiosperms. + +Sargant, Ethel, on the Evolution of Angiosperms. + +Savigny. + +Scardafella inca. + +Scent, in relation to Sexual Selection. + +Scharff, R.F. + +Schelling. + +Schlegel. + +Schleicher, A., on language. + +Schleiden and Schwann, Cell-theory of. + +Schmarda, L.K., on geographical distribution. + +Schoetensack, on Homo heidelbergensis. + +Schreiner, K.E. + +Schubler, on cereals. + +Schultze, O., experiments on Frogs. + +Schur. + +Schutt. + +SCHWALBE, G., on "The Descent of Man". + +Sclater, P.L., on geographical distribution. + +SCOTT, D.H., on "The Palaeontological Record (Plants)". +--elsewhere. + +SCOTT, W.B., on "The Palaeontological Record (Animals)". + +Scrope. + +Scyllaea. + +Sechehaye, C.A. + +SEDGWICK, A., on "The Influence of Darwin on Animal Embryology". + +Sedgwick, A., Darwin's Geological Expedition with. + +Seeck, O. + +Seed-plants, origin of. + +Segregation. + +Selection, artificial. +--germinal. + +Selection, natural (see Natural Selection). +--organic. +--sexual. +--social and natural. +--various. + +Selenka. + +Semnopithecus. + +Semon, R. + +Semper. + +Senebier. + +Senecio vulgaris. + +Sergi. + +Seward, A.C. +--and S.O. Ford. +--and J. Gowan. + +Sex, recent investigations on. + +Sharpe, D. + +Sherrington, C.S. + +Shirreff, P. + +Shrewsbury, Darwin's recollections of. + +Sibbern. + +Sinapis alba. + +Smerinthus ocellata. + +Smerinthus populi. + +Smerinthus tiliae. + +Smith, A. + +Smith, W. + +Snyder. + +Sociology, Darwinism and. +--History and. + +Soddy. + +Sollas, W.J. + +Sorley, W.R. + +Species, Darwin's early work on transmutation of. +--geographical distribution and origin of. +--immutability of. +--influence on environment on. +--Lamarck on. +--multiple origin of. +--the nature of a. +--polymorphic. +--production by physico-chemical means of. +--and varieties. +--de Vries's work on. + +Spencer, H., on evolution. +--on Lyell's "Principles". +--on the nature of the living cell. +--on primitive man. +--on the theory of Selection. +--on Sociology. + +Spencer, H., on the transmission of acquired characters. +--on Weismann. +--various. + +Sphingidae, variation in. + +Spinoza. + +Sports. + +Sprengel, C.K. + +Stability, principle of. + +Stahl. + +Standfuss. + +Stars, evolution of double. + +Stellaria media. + +Stephen, L. + +Sterility in hybrids. + +Sterne, C. + +Stockard, his experiments on fish embryos. + +STRASBURBER, E., on "The Minute Structure of Cells in relation to +Heredity". + +Strongylocentrotus franciscanus. + +Strongylocentrotus purpuratus. + +Struggle for existence. + +Strutt, R.J. + +Stuart, A. + +Sturdee, F.C.D. + +Sutterlin, L. + +Sully. + +Sutton, A.W. + +Sutton, W.S. + +Svalof, agricultural station of. + +Swainson, W. + +Synapta, calcareous bodies in skin of. + +S. lappa. + +Syrphus. + +Tarde, G. + +Teleology and adaptation. + +Tennant, F.R. + +Teratology. + +Tetraprothomo. + +THISELTON-DYER, SIR WILLIAM, on "Geographical distribution of Plants". +--on Burchell. +--on protective resemblance. +--elsewhere. + +THOMSON, J.A., on "Darwin's Predecessors. +--elsewhere. +--and P. Geddes. + +Thomson, Sir J.J. + +Theology, Darwin and. + +Tiedemann, F. + +Tooke, Horne. + +Totemism. + +Treschow. + +Treviranus. + +Trifolium pratense quinquefolium. + +Trigonias. + +Trilobites, phylogeny of. + +Tschermack. + +Turgot. + +Turner, Sir W. + +Twins, artificial production of. + +Tylor. + +Tyndall, W. + +Tyrrell, G. + +Uhlenhuth, on blood reactions. + +Underhill, E. + +Use and disuse. + +Vanessa. + +Vanessa antiope. + +Vanessa levana. + +Vanessa polychloros. + +Vanessa urticae. + +Van 't Hoff. + +Varanus Salvator. + +Variability, Darwin's attention directed to. +--W. Bateson on. +--and cultivation. +--causes of. +--polymorphic. + +Variation, continuous and discontinuous. +--Darwin's views as an evolutionist, and as a systematist, on. +--definite and indefinite. +--environment and. +--and heredity. +--as seen in the life-history of an organism. +--minute. +--mutability and. +--in relation to species. +--H. de Vries on. + +Varigny, H. de. + +Varro, on language. + +Veronica chamaedrys. + +Verworn. + +"Vestiges of Creation", Darwin on "The". + +Vierkandt. + +Vilmorin, L. de. + +Virchow, his opposition to Darwin. + +Virchow, on the transmission of acquired characters. + +Vochting. + +Vogt, C. + +Voltaire. + +Volvox. + +VRIES, H. de, on "Variation" +--the Mutation theory of. + +WAGGETT, REV. P.N., on "The Influence of Darwin upon religious thought". + +Wagner. + +Waldeyer, W. + +Wallace, A.R., on Malayan Butterflies. +--on Colour. +--and Darwin. +--on the Descent of Man. +--on distribution. +--on Malthus. +--on Natural Selection. +--on the permanence of continents. +--on social reforms. +--on Sexual Selection. + +Waller, A.D. + +Walton. + +Watson, H.C. + +Watson, S. + +Watt, J., and Natural Selection. + +Watts, W.W. + +Wedgwood, L. + +Weir, J.J. + +WEISMANN, A., on "The Selection Theory". +--on Amphimixis. + +Weismann, A., his germ-plasm theory. +--on ontogeny. +--and Prichard. +--and Spencer. +--on the transmission of acquired characters. +--various. + +Wells, W.C., and Natural Selection. + +Weston, S., on language. + +WHETHAM, W.C.D., on "The Evolution of Matter". + +Whewell. + +White, G. + +Wichmann. + +Wieland, G.R., on fossil Cycads. + +Wiesner, on Darwin's work on plant movements. + +Williams, C.M. + +Williamson, W.C. + +Wilson, E.B., on cytology. +--letter from Darwin to. + +Wolf. + +Wollaston's, T.V. "Variation of Species". + +Woltmann. + +Woolner. + +Wundt, on language. + +Xylina vetusta. + +Yucca, fertilisation of. + +Zeiller, R., on Fossil Plants. + +Zeller, E. + +Zimmermann, E.A.W. + +Zittel, on palaeontological research. + +"Zoonomia", Erasmus Darwin's. + + + + + +End of Project Gutenberg Etext Darwin and Modern Science, by A C Seward + diff --git a/old/drwnm10.zip b/old/drwnm10.zip Binary files differnew file mode 100644 index 0000000..39867a9 --- /dev/null +++ b/old/drwnm10.zip |