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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. 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