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+Project Gutenberg's Darwin and Modern Science, by A.C. Seward and Others
+
+This eBook is for the use of anyone anywhere at no cost and with
+almost no restrictions whatsoever.  You may copy it, give it away or
+re-use it under the terms of the Project Gutenberg License included
+with this eBook or online at www.gutenberg.org
+
+
+Title: Darwin and Modern Science
+
+Author: A.C. Seward and Others
+
+Release Date: September, 1999  [Etext #1909]
+Posting Date: November 20, 2009
+
+Language: English
+
+Character set encoding: ASCII
+
+*** START OF THIS PROJECT GUTENBERG EBOOK DARWIN AND MODERN SCIENCE ***
+
+
+
+
+Produced by Sue Asscher
+
+
+
+
+
+DARWIN AND MODERN SCIENCE
+
+ESSAYS IN COMMEMORATION OF THE CENTENARY OF THE BIRTH OF CHARLES DARWIN
+AND OF THE FIFTIETH ANNIVERSARY OF THE PUBLICATION OF "THE ORIGIN OF
+SPECIES"
+
+
+By A.C. Seward
+
+
+
+"My success as a man of science, whatever this may have amounted to,
+has been determined, as far as I can judge, by complex and diversified
+mental qualities and conditions. Of these, the most important have
+been--the love of science--unbounded patience in long reflecting over
+any subject--industry in observing and collecting facts--and a fair
+share of invention as well as of common sense. With such moderate
+abilities as I possess, it is truly surprising that I should have
+influenced to a considerable extent the belief of scientific men on some
+important points."
+
+Autobiography (1881); "The Life and Letters of Charles Darwin", Vol. 1.
+page 107.
+
+
+
+
+PREFACE
+
+At the suggestion of the Cambridge Philosophical Society, the Syndics
+of the University Press decided in March, 1908, to arrange for the
+publication of a series of Essays in commemoration of the Centenary
+of the birth of Charles Darwin and of the Fiftieth anniversary of the
+publication of "The Origin of Species". The preliminary arrangements
+were made by a committee consisting of the following representatives of
+the Council of the Philosophical Society and of the Press Syndicate:
+Dr H.K. Anderson, Prof. Bateson, Mr Francis Darwin, Dr Hobson, Dr Marr,
+Prof. Sedgwick, Mr David Sharp, Mr Shipley, Prof. Sorley, Prof. Seward.
+In the course of the preparation of the volume, the original scheme and
+list of authors have been modified: a few of those invited to contribute
+essays were, for various reasons, unable to do so, and some alterations
+have been made in the titles of articles. For the selection of authors
+and for the choice of subjects, the committee are mainly responsible,
+but for such share of the work in the preparation of the volume as
+usually falls to the lot of an editor I accept full responsibility.
+
+Authors were asked to address themselves primarily to the educated
+layman rather than to the expert. It was hoped that the publication
+of the essays would serve the double purpose of illustrating the
+far-reaching influence of Darwin's work on the progress of knowledge and
+the present attitude of original investigators and thinkers towards the
+views embodied in Darwin's works.
+
+In regard to the interpretation of a passage in "The Origin of Species"
+quoted by Hugo de Vries, it seemed advisable to add an editorial
+footnote; but, with this exception, I have not felt it necessary to
+record any opinion on views stated in the essays.
+
+In reading the essays in proof I have availed myself freely of the
+willing assistance of several Cambridge friends, among whom I wish more
+especially to thank Mr Francis Darwin for the active interest he
+has taken in the preparation of the volume. Mrs J.A. Thomson kindly
+undertook the translation of the essays by Prof. Weismann and Prof.
+Schwalbe; Mrs James Ward was good enough to assist me by translating
+Prof. Bougle's article on Sociology, and to Mr McCabe I am indebted for
+the translation of the essay by Prof. Haeckel. For the translation
+of the botanical articles by Prof. Goebel, Prof. Klebs and Prof.
+Strasburger, I am responsible; in the revision of the translation of
+Prof. Strasburger's essay Madame Errera of Brussels rendered valuable
+help. Mr Wright, the Secretary of the Press Syndicate, and Mr Waller,
+the Assistant Secretary, have cordially cooperated with me in my
+editorial work; nor can I omit to thank the readers of the University
+Press for keeping watchful eyes on my shortcomings in the correction of
+proofs.
+
+The two portraits of Darwin are reproduced by permission of Messrs Maull
+and Fox and Messrs Elliott and Fry. The photogravure of the study at
+Down is reproduced from an etching by Mr Axel Haig, lent by Mr Francis
+Darwin; the coloured plate illustrating Prof. Weismann's essay was
+originally published by him in his "Vortrage uber Descendenztheorie"
+which afterwards appeared (1904) in English under the title "The
+Evolution Theory". Copies of this plate were supplied by Messrs Fischer
+of Jena.
+
+The Syndics of the University Press have agreed, in the event of
+this volume being a financial success, to hand over the profits to a
+University fund for the endowment of biological research.
+
+It is clearly impossible to express adequately in a single volume of
+Essays the influence of Darwin's contributions to knowledge on the
+subsequent progress of scientific inquiry. As Huxley said in 1885:
+"Whatever be the ultimate verdict of posterity upon this or that opinion
+which Mr Darwin has propounded; whatever adumbrations or anticipations
+of his doctrines may be found in the writings of his predecessors; the
+broad fact remains that, since the publication and by reason of the
+publication of "The Origin of Species" the fundamental conceptions
+and the aims of the students of living Nature have been completely
+changed... But the impulse thus given to scientific thought rapidly
+spread beyond the ordinarily recognised limits of Biology. Psychology,
+Ethics, Cosmology were stirred to their foundations, and 'The Origin of
+Species' proved itself to be the fixed point which the general doctrine
+needed in order to move the world."
+
+In the contributions to this Memorial Volume, some of the authors
+have more especially concerned themselves with the results achieved by
+Darwin's own work, while others pass in review the progress of research
+on lines which, though unknown or but little followed in his day, are
+the direct outcome of his work.
+
+The divergence of views among biologists in regard to the origin of
+species and as to the most promising directions in which to seek for
+truth is illustrated by the different opinions of contributors. Whether
+Darwin's views on the modus operandi of evolutionary forces receive
+further confirmation in the future, or whether they are materially
+modified, in no way affects the truth of the statement that, by
+employing his life "in adding a little to Natural Science," he
+revolutionised the world of thought. Darwin wrote in 1872 to Alfred
+Russel Wallace: "How grand is the onward rush of science: it is enough
+to console us for the many errors which we have committed, and for our
+efforts being overlaid and forgotten in the mass of new facts and new
+views which are daily turning up." In the onward rush, it is easy for
+students convinced of the correctness of their own views and equally
+convinced of the falsity of those of their fellow-workers to forget the
+lessons of Darwin's life. In his autobiographical sketch, he tells us,
+"I have steadily endeavoured to keep my mind free so as to give up any
+hypothesis, however much beloved...as soon as facts are shown to be
+opposed to it." Writing to Mr J. Scott, he says, "It is a golden rule,
+which I try to follow, to put every fact which is opposed to one's
+preconceived opinion in the strongest light. Absolute accuracy is the
+hardest merit to attain, and the highest merit. Any deviation is ruin."
+
+He acted strictly in accordance with his determination expressed in a
+letter to Lyell in 1844, "I shall keep out of controversy, and just
+give my own facts." As was said of another son of Cambridge, Sir George
+Stokes, "He would no more have thought of disputing about priority,
+or the authorship of an idea, than of writing a report for a company
+promoter." Darwin's life affords a striking confirmation of the truth
+of Hazlitt's aphorism, "Where the pursuit of truth has been the habitual
+study of any man's life, the love of truth will be his ruling passion."
+Great as was the intellect of Darwin, his character, as Huxley wrote,
+was even nobler than his intellect.
+
+A.C. SEWARD.
+
+Botany School, Cambridge, March 20, 1909.
+
+
+
+CONTENTS
+I. INTRODUCTORY LETTER TO THE EDITOR from SIR JOSEPH DALTON HOOKER, O.M.
+
+II. DARWIN'S PREDECESSORS:  J. ARTHUR THOMSON, Professor of Natural
+History in the University of Aberdeen.
+
+III. THE SELECTION THEORY:  AUGUST WEISMANN, Professor of Zoology in the
+University of Freiburg (Baden).
+
+IV. VARIATION:  HUGO DE VRIES, Professor of Botany in the University of
+Amsterdam.
+
+V. HEREDITY AND VARIATION IN MODERN LIGHTS:  W. BATESON, Professor of
+Biology in the University of Cambridge.
+
+VI. THE MINUTE STRUCTURE OF CELLS IN RELATION TO HEREDITY:  EDUARD
+STRASBURGER, Professor of Botany in the University of Bonn.
+
+VII. "THE DESCENT OF MAN":  G. SCHWALBE, Professor of Anatomy in the
+University of Strassburg.
+
+VIII. CHARLES DARWIN AS AN ANTHROPOLOGIST:  ERNST HAECKEL, Professor of
+Zoology in the University of Jena.
+
+IX. SOME PRIMITIVE THEORIES OF THE ORIGIN OF MAN:  J.G. FRAZER, Fellow
+of Trinity College, Cambridge.
+
+X. THE INFLUENCE OF DARWIN ON THE STUDY OF ANIMAL EMBRYOLOGY:  A.
+SEDGWICK, Professor of Zoology and Comparative Anatomy in the University
+of Cambridge.
+
+XI. THE PALAEONTOLOGICAL RECORD. I. ANIMALS:  W.B. SCOTT, Professor of
+Geology in the University of Princeton.
+
+XII. THE PALAEONTOLOGICAL RECORD. II. PLANTS:  D.H. SCOTT, President of
+the Linnean Society of London.
+
+XIII. THE INFLUENCE OF ENVIRONMENT ON THE FORMS OF PLANTS:  GEORG KLEBS,
+Professor of Botany in the University of Heidelberg.
+
+XIV. EXPERIMENTAL STUDY OF THE INFLUENCE OF ENVIRONMENT ON ANIMALS:
+JACQUES LOEB, Professor of Physiology in the University of California.
+
+XV. THE VALUE OF COLOUR IN THE STRUGGLE FOR LIFE:  E.B. POULTON, Hope
+Professor of Zoology in the University of Oxford.
+
+XVI. GEOGRAPHICAL DISTRIBUTION OF PLANTS:  SIR WILLIAM THISELTON-DYER.
+
+XVII. GEOGRAPHICAL DISTRIBUTION OF ANIMALS:  HANS GADOW, Strickland
+Curator and Lecturer on Zoology in the University of Cambridge.
+
+XVIII. DARWIN AND GEOLOGY:  J.W. JUDD.
+
+XIX. DARWIN'S WORK ON THE MOVEMENTS OF PLANTS:  FRANCIS DARWIN.
+
+XX. THE BIOLOGY OF FLOWERS:  K. GOEBEL, Professor of Botany in the
+University of Munich.
+
+XXI. MENTAL FACTORS IN EVOLUTION:  C. LLOYD MORGAN, Professor of
+Psychology at University College, Bristol.
+
+XXII. THE INFLUENCE OF THE CONCEPTION OF EVOLUTION ON MODERN PHILOSOPHY:
+H. HOFFDING, Professor of Philosophy in the University of Copenhagen.
+
+XXIII. DARWINISM AND SOCIOLOGY:  C. BOUGLE, Professor of Social
+Philosophy in the University of Toulouse, and Deputy-Professor at the
+Sorbonne, Paris.
+
+XXIV. THE INFLUENCE OF DARWIN UPON RELIGIOUS THOUGHT:  REV. P.N.
+WAGGETT.
+
+XXV. THE INFLUENCE OF DARWINISM ON THE STUDY OF RELIGIONS:  JANE ELLEN
+HARRISON, Staff-Lecturer and sometime Fellow of Newnham College,
+Cambridge.
+
+XXVI. EVOLUTION AND THE SCIENCE OF LANGUAGE:  P. GILES, Reader in
+Comparative Philology in the University of Cambridge.
+
+XXVII. DARWINISM AND HISTORY:  J.B. BURY, Regius Professor of Modern
+History in the University of Cambridge.
+
+XXVIII. THE GENESIS OF DOUBLE STARS:  SIR GEORGE DARWIN, Plumian
+Professor of Astronomy and Experimental Philosophy in the University of
+Cambridge.
+
+XXIX. THE EVOLUTION OF MATTER:  W.C.D. WHETHAM, Fellow of Trinity
+College, Cambridge.
+
+INDEX.
+
+
+
+
+DATES OF THE PUBLICATION Of CHARLES DARWIN'S BOOKS AND OF THE PRINCIPAL
+EVENTS IN HIS LIFE
+
+1809:
+
+Charles Darwin born at Shrewsbury, February 12.
+
+1817:
+
+"At 8 1/2 years old I went to Mr Case's school." (A day-school at
+Shrewsbury kept by the Rev G. Case, Minister of the Unitarian Chapel.)
+
+1818:
+
+"I was at school at Shrewsbury under a great scholar, Dr Butler; I
+learnt absolutely nothing, except by amusing myself by reading and
+experimenting in Chemistry."
+
+1825:
+
+"As I was doing no good at school, my father wisely took me away at
+a rather earlier age than usual, and sent me (Oct. 1825) to Edinburgh
+University with my brother, where I stayed for two years."
+
+1828:
+
+Began residence at Christ's College, Cambridge.
+
+"I went to Cambridge early in the year 1828, and soon became acquainted
+with Professor Henslow...Nothing could be more simple, cordial and
+unpretending than the encouragement which he afforded to all young
+naturalists."
+
+"During the three years which I spent at Cambridge my time was wasted,
+as far as the academical studies were concerned, as completely as at
+Edinburgh and at school."
+
+"In order to pass the B.A. Examination, it was...necessary to get up
+Paley's 'Evidences of Christianity,' and his 'Moral Philosophy'... The
+careful study of these works, without attempting to learn any part by
+rote, was the only part of the academical course which...was of the
+least use to me in the education of my mind."
+
+1831:
+
+Passed the examination for the B.A. degree in January and kept the
+following terms.
+
+"I gained a good place among the oi polloi or crowd of men who do not go
+in for honours."
+
+"I am very busy,...and see a great deal of Henslow, whom I do not know
+whether I love or respect most."
+
+Dec. 27. "Sailed from England on our circumnavigation," in H.M.S.
+"Beagle", a barque of 235 tons carrying 6 guns, under Capt. FitzRoy.
+
+"There is indeed a tide in the affairs of men."
+
+1836:
+
+Oct. 4. "Reached Shrewsbury after absence of 5 years and 2 days."
+
+"You cannot imagine how gloriously delightful my first visit was at
+home; it was worth the banishment."
+
+Dec. 13. Went to live at Cambridge (Fitzwilliam Street).
+
+"The only evil I found in Cambridge was its being too pleasant."
+
+1837:
+
+"On my return home (in the 'Beagle') in the autumn of 1836 I immediately
+began to prepare my journal for publication, and then saw how many facts
+indicated the common descent of species... In July (1837) I opened my
+first note-book for facts in relation to the Origin of Species, about
+which I had long reflected, and never ceased working for the next twenty
+years... Had been greatly struck from about the month of previous
+March on character of South American fossils, and species on Galapagos
+Archipelago. These facts (especially latter), origin of all my views."
+
+"On March 7, 1837 I took lodgings in (36) Great Marlborough Street in
+London, and remained there for nearly two years, until I was married."
+
+1838:
+
+"In October, that is fifteen months after I had begun my systematic
+enquiry, I happened to read for amusement 'Malthus on Population,'
+and being well prepared to appreciate the struggle for existence which
+everywhere goes on from long-continued observation of the habits of
+animals and plants, it at once struck me that under these circumstances
+favourable variations would tend to be preserved, and unfavourable
+ones to be destroyed. The result of this would be the formation of new
+species. Here then I had at last got a theory by which to work; but I
+was so anxious to avoid prejudice, that I determined not for some time
+to write even the briefest sketch of it."
+
+1839:
+
+Married at Maer (Staffordshire) to his first cousin Emma Wedgwood,
+daughter of Josiah Wedgwood.
+
+"I marvel at my good fortune that she, so infinitely my superior in
+every single moral quality, consented to be my wife. She has been my
+wise adviser and cheerful comforter throughout life, which without
+her would have been during a very long period a miserable one
+from ill-health. She has earned the love of every soul near her"
+(Autobiography).
+
+Dec. 31. "Entered 12 Upper Gower street" (now 110 Gower street, London).
+"There never was so good a house for me, and I devoutly trust you (his
+future wife) will approve of it equally. The little garden is worth its
+weight in gold."
+
+Published "Journal and Researches", being Vol. III. of the "Narrative of
+the Surveying Voyage of H.M.S. 'Adventure' and 'Beagle'"...
+
+Publication of the "Zoology of the Voyage of H.M.S. 'Beagle'", Part
+II., "Mammalia", by G.R. Waterhouse, with a "Notice of their habits and
+ranges", by Charles Darwin.
+
+1840:
+
+Contributed Geological Introduction to Part I. ("Fossil Mammalia") of
+the "Zoology of the Voyage of H.M.S. 'Beagle'" by Richard Owen.
+
+1842:
+
+"In June 1842 I first allowed myself the satisfaction of writing a very
+brief abstract of my (species) theory in pencil in 35 pages; and this
+was enlarged during the summer of 1844 into one of 230 pages, which I
+had fairly copied out and still (1876) possess." (The first draft of
+"The Origin of Species", edited by Mr Francis Darwin, will be published
+this year (1909) by the Syndics of the Cambridge University Press.)
+
+Sept. 14. Settled at the village of Down in Kent.
+
+"I think I was never in a more perfectly quiet country."
+
+Publication of "The Structure and Distribution of Coral Reefs"; being
+Part I. of the "Geology of the Voyage of the Beagle".
+
+1844:
+
+Publication of "Geological Observations on the Volcanic Islands visited
+during the Voyage of H.M.S. 'Beagle'"; being Part II. of the "Geology of
+the Voyage of the 'Beagle'".
+
+"I think much more highly of my book on Volcanic Islands since Mr Judd,
+by far the best judge on the subject in England, has, as I hear, learnt
+much from it." (Autobiography, 1876.)
+
+1845:
+
+Publication of the "Journal of Researches" as a separate book.
+
+1846:
+
+Publication of "Geological Observations on South America"; being Part
+III. of the "Geology of the Voyage of the 'Beagle'".
+
+1851:
+
+Publication of a "Monograph of the Fossil Lepadidae" and of a "Monograph
+of the sub-class Cirripedia".
+
+"I fear the study of the Cirripedia will ever remain 'wholly unapplied,'
+and yet I feel that such study is better than castle-building."
+
+1854:
+
+Publication of Monographs of the Balanidae and Verrucidae.
+
+"I worked steadily on this subject for...eight years, and ultimately
+published two thick volumes, describing all the known living
+species, and two thin quartos on the extinct species... My work was of
+considerable use to me, when I had to discuss in the "Origin of Species"
+the principles of a natural classification. Nevertheless, I doubt
+whether the work was worth the consumption of so much time."
+
+"From September 1854 I devoted my whole time to arranging my huge
+pile of notes, to observing, and to experimenting in relation to the
+transmutation of species."
+
+1856:
+
+"Early in 1856 Lyell advised me to write out my views pretty fully, and
+I began at once to do so on a scale three or four times as extensive as
+that which was afterwards followed in my 'Origin of Species'."
+
+1858:
+
+Joint paper by Charles Darwin and Alfred Russel Wallace "On the Tendency
+of Species to form Varieties; and on the perpetuation of Varieties and
+Species by Natural Means of Selection," communicated to the Linnean
+Society by Sir Charles Lyell and Sir Joseph Hooker.
+
+"I was at first very unwilling to consent (to the communication of his
+MS. to the Society) as I thought Mr Wallace might consider my doing so
+unjustifiable, for I did not then know how generous and noble was his
+disposition."
+
+"July 20 to Aug. 12 at Sandown (Isle of Wight) began abstract of Species
+book."
+
+1859:
+
+Nov. 24. Publication of "The Origin of Species" (1250 copies).
+
+"Oh, good heavens, the relief to my head and body to banish the whole
+subject from my mind!... But, alas, how frequent, how almost universal it
+is in an author to persuade himself of the truth of his own dogmas.
+My only hope is that I certainly see many difficulties of gigantic
+stature."
+
+1860:
+
+Publication of the second edition of the "Origin" (3000 copies).
+
+Publication of a "Naturalist's Voyage".
+
+1861:
+
+Publication of the third edition of the "Origin" (2000 copies).
+
+"I am going to write a little book... on Orchids, and to-day I hate them
+worse than everything."
+
+1862:
+
+Publication of the book "On the various contrivances by which Orchids
+are fertilised by Insects".
+
+1865:
+
+Read paper before the Linnean Society "On the Movements and Habits of
+Climbing plants". (Published as a book in 1875.)
+
+1866:
+
+Publication of the fourth edition of the "Origin" (1250 copies).
+
+1868:
+
+"I have sent the MS. of my big book, and horridly, disgustingly big it
+will be, to the printers."
+
+Publication of the "Variation of Animals and Plants under
+Domestication".
+
+"About my book, I will give you (Sir Joseph Hooker) a bit of advice.
+Skip the whole of Vol. I, except the last chapter, (and that need only
+be skimmed), and skip largely in the 2nd volume; and then you will say
+it is a very good book."
+
+"Towards the end of the work I give my well-abused hypothesis of
+Pangenesis. An unverified hypothesis is of little or no value; but if
+anyone should hereafter be led to make observations by which some such
+hypothesis could be established, I shall have done good service, as an
+astonishing number of isolated facts can be thus connected together and
+rendered intelligible."
+
+1869:
+
+Publication of the fifth edition of the "Origin".
+
+1871:
+
+Publication of "The Descent of Man".
+
+"Although in the 'Origin of Species' the derivation of any particular
+species is never discussed, yet I thought it best, in order that no
+honourable man should accuse me of concealing my views, to add that by
+the work 'light would be thrown on the origin of man and his history'."
+
+1872:
+
+Publication of the sixth edition of the "Origin".
+
+Publication of "The Expression of the Emotions in Man and Animals".
+
+1874:
+
+Publication of the second edition of "The Descent of Man".
+
+"The new edition of the "Descent" has turned out an awful job. It took
+me ten days merely to glance over letters and reviews with criticisms
+and new facts. It is a devil of a job."
+
+Publication of the second edition of "The Structure and Distribution of
+Coral Reefs".
+
+1875:
+
+Publication of "Insectivorous Plants".
+
+"I begin to think that every one who publishes a book is a fool."
+
+Publication of the second edition of "Variation in Animals and Plants".
+
+Publication of "The Movements and Habits of Climbing Plants" as a
+separate book.
+
+1876:
+
+Wrote Autobiographical Sketch ("Life and Letters", Vol. I., Chap II.).
+
+Publication of "The Effects of Cross and Self fertilisation".
+
+"I now (1881) believe, however,...that I ought to have insisted more
+strongly than I did on the many adaptations for self-fertilisation."
+
+Publication of the second edition of "Observations on Volcanic Islands".
+
+1877:
+
+Publication of "The Different Forms of Flowers on Plants of the same
+species".
+
+"I do not suppose that I shall publish any more books... I cannot endure
+being idle, but heaven knows whether I am capable of any more good
+work."
+
+Publication of the second edition of the Orchid book.
+
+1878:
+
+Publication of the second edition of "The Effects of Cross and Self
+fertilisation".
+
+1879:
+
+Publication of an English translation of Ernst Krause's "Erasmus
+Darwin", with a notice by Charles Darwin. "I am EXTREMELY glad that
+you approve of the little 'Life' of our Grandfather, for I have been
+repenting that I ever undertook it, as the work was quite beyond my
+tether." (To Mr Francis Galton, Nov. 14, 1879.)
+
+1880:
+
+Publication of "The Power of Movement in Plants".
+
+"It has always pleased me to exalt plants in the scale of organised
+beings."
+
+Publication of the second edition of "The Different Forms of Flowers".
+
+1881:
+
+Wrote a continuation of the Autobiography.
+
+Publication of "The Formation of Vegetable Mould, through the Action of
+Worms".
+
+"It is the completion of a short paper read before the Geological
+Society more than forty years ago, and has revived old geological
+thoughts... As far as I can judge it will be a curious little book."
+
+1882:
+
+Charles Darwin died at Down, April 19, and was buried in Westminster
+Abbey, April 26, in the north aisle of the Nave a few feet from the
+grave of Sir Isaac Newton.
+
+"As for myself, I believe that I have acted rightly in steadily
+following and devoting my life to Science. I feel no remorse from having
+committed any great sin, but have often and often regretted that I have
+not done more direct good to my fellow creatures."
+
+The quotations in the above Epitome are taken from the Autobiography and
+published Letters:--
+
+"The Life and Letters of Charles Darwin", including an Autobiographical
+Chapter. Edited by his son, Francis Darwin, 3 Vols., London, 1887.
+
+"Charles Darwin": His life told in an Autobiographical Chapter, and in
+a selected series of his published Letters. Edited by his son, Francis
+Darwin, London, 1902.
+
+"More Letters of Charles Darwin". A record of his work in a series of
+hitherto unpublished Letters. Edited by Francis Darwin and A.C. Seward,
+2 Vols., London, 1903.
+
+
+
+
+I. INTRODUCTORY LETTER From Sir Joseph Dalton Hooker, O.M., G.C.S.I.,
+C.B., M.D., D.C.L., LL.D., F.R.S., ETC.
+
+
+The Camp,
+
+near Sunningdale,
+
+January 15, 1909.
+
+Dear Professor Seward,
+
+The publication of a Series of Essays in Commemoration of the century
+of the birth of Charles Darwin and of the fiftieth anniversary of the
+publication of "The Origin of Species" is assuredly welcome and is a
+subject of congratulation to all students of Science.
+
+These Essays on the progress of Science and Philosophy as affected by
+Darwin's labours have been written by men known for their ability to
+discuss the problems which he so successfully worked to solve. They
+cannot but prove to be of enduring value, whether for the information of
+the general reader or as guides to investigators occupied with problems
+similar to those which engaged the attention of Darwin.
+
+The essayists have been fortunate in having for reference the five
+published volumes of Charles Darwin's Life and Correspondence. For there
+is set forth in his own words the inception in his mind of the problems,
+geological, zoological and botanical, hypothetical and theoretical,
+which he set himself to solve and the steps by which he proceeded to
+investigate them with the view of correlating the phenomena of life with
+the evolution of living things. In his letters he expressed himself in
+language so lucid and so little burthened with technical terms that they
+may be regarded as models for those who were asked to address themselves
+primarily to the educated reader rather than to the expert.
+
+I may add that by no one can the perusal of the Essays be more vividly
+appreciated than by the writer of these lines. It was my privilege for
+forty years to possess the intimate friendship of Charles Darwin and to
+be his companion during many of his working hours in Study, Laboratory,
+and Garden. I was the recipient of letters from him, relating mainly to
+the progress of his researches, the copies of which (the originals are
+now in the possession of his family) cover upwards of a thousand pages
+of foolscap, each page containing, on an average, three hundred words.
+
+That the editorship of these Essays has been entrusted to a Cambridge
+Professor of Botany must be gratifying to all concerned in their
+production and in their perusal, recalling as it does the fact that
+Charles Darwin's instructor in scientific methods was his lifelong
+friend the late Rev. J.S. Henslow at that time Professor of Botany in
+the University. It was owing to his recommendation that his pupil was
+appointed Naturalist to H.M.S. "Beagle", a service which Darwin himself
+regarded as marking the dawn of his scientific career.
+
+Very sincerely yours,
+
+J.D. HOOKER.
+
+
+
+
+II. DARWIN'S PREDECESSORS. By J. Arthur Thomson.
+
+Professor of Natural History in the University of Aberdeen.
+
+
+In seeking to discover Darwin's relation to his predecessors it is
+useful to distinguish the various services which he rendered to the
+theory of organic evolution.
+
+(I) As everyone knows, the general idea of the Doctrine of Descent
+is that the plants and animals of the present-day are the lineal
+descendants of ancestors on the whole somewhat simpler, that these again
+are descended from yet simpler forms, and so on backwards towards the
+literal "Protozoa" and "Protophyta" about which we unfortunately know
+nothing. Now no one supposes that Darwin originated this idea, which in
+rudiment at least is as old as Aristotle. What Darwin did was to make
+it current intellectual coin. He gave it a form that commended itself
+to the scientific and public intelligence of the day, and he won
+wide-spread conviction by showing with consummate skill that it was
+an effective formula to work with, a key which no lock refused. In
+a scholarly, critical, and pre-eminently fair-minded way, admitting
+difficulties and removing them, foreseeing objections and forestalling
+them, he showed that the doctrine of descent supplied a modal
+interpretation of how our present-day fauna and flora have come to be.
+
+(II) In the second place, Darwin applied the evolution-idea to
+particular problems, such as the descent of man, and showed what a
+powerful organon it is, introducing order into masses of uncorrelated
+facts, interpreting enigmas both of structure and function, both
+bodily and mental, and, best of all, stimulating and guiding further
+investigation. But here again it cannot be claimed that Darwin was
+original. The problem of the descent or ascent of man, and other
+particular cases of evolution, had attracted not a few naturalists
+before Darwin's day, though no one (except Herbert Spencer in the
+psychological domain (1855)) had come near him in precision and
+thoroughness of inquiry.
+
+(III) In the third place, Darwin contributed largely to a knowledge of
+the factors in the evolution-process, especially by his analysis of what
+occurs in the case of domestic animals and cultivated plants, and by
+his elaboration of the theory of Natural Selection, which Alfred Russel
+Wallace independently stated at the same time, and of which there had
+been a few previous suggestions of a more or less vague description.
+It was here that Darwin's originality was greatest, for he revealed to
+naturalists the many different forms--often very subtle--which natural
+selection takes, and with the insight of a disciplined scientific
+imagination he realised what a mighty engine of progress it has been and
+is.
+
+(IV) As an epoch-marking contribution, not only to Aetiology but to
+Natural History in the widest sense, we rank the picture which
+Darwin gave to the world of the web of life, that is to say, of
+the inter-relations and linkages in Nature. For the Biology of the
+individual--if that be not a contradiction in terms--no idea is more
+fundamental than that of the correlation of organs, but Darwin's most
+characteristic contribution was not less fundamental,--it was the idea
+of the correlation of organisms. This, again, was not novel; we find
+it in the works of naturalist like Christian Conrad Sprengel, Gilbert
+White, and Alexander von Humboldt, but the realisation of its full
+import was distinctively Darwinian.
+
+AS REGARDS THE GENERAL IDEA OF ORGANIC EVOLUTION.
+
+While it is true, as Prof. H.F. Osborn puts it, that "'Before and after
+Darwin' will always be the ante et post urbem conditam of biological
+history," it is also true that the general idea of organic evolution
+is very ancient. In his admirable sketch "From the Greeks to Darwin"
+("Columbia University Biological Series", Vol. I. New York and London,
+1894. We must acknowledge our great indebtness to this fine piece of
+work.), Prof. Osborn has shown that several of the ancient philosophers
+looked upon Nature as a gradual development and as still in process of
+change. In the suggestions of Empedocles, to take the best instance,
+there were "four sparks of truth,--first, that the development of life
+was a gradual process; second, that plants were evolved before animals;
+third, that imperfect forms were gradually replaced (not succeeded)
+by perfect forms; fourth, that the natural cause of the production of
+perfect forms was the extinction of the imperfect." (Op. cit. page
+41.) But the fundamental idea of one stage giving origin to another was
+absent. As the blue Aegean teemed with treasures of beauty and threw
+many upon its shores, so did Nature produce like a fertile artist what
+had to be rejected as well as what was able to survive, but the idea of
+one species emerging out of another was not yet conceived.
+
+Aristotle's views of Nature (See G.J. Romanes, "Aristotle as a
+Naturalist", "Contemporary Review", Vol. LIX. page 275, 1891; G. Pouchet
+"La Biologie Aristotelique", Paris, 1885; E. Zeller, "A History of
+Greek Philosophy", London, 1881, and "Ueber die griechischen Vorganger
+Darwin's", "Abhandl. Berlin Akad." 1878, pages 111-124.) seem to have
+been more definitely evolutionist than those of his predecessors, in
+this sense, at least, that he recognised not only an ascending scale,
+but a genetic series from polyp to man and an age-long movement towards
+perfection. "It is due to the resistance of matter to form that Nature
+can only rise by degrees from lower to higher types." "Nature produces
+those things which, being continually moved by a certain principle
+contained in themselves, arrive at a certain end."
+
+To discern the outcrop of evolution-doctrine in the long interval
+between Aristotle and Bacon seems to be very difficult, and some of
+the instances that have been cited strike one as forced. Epicurus and
+Lucretius, often called poets of evolution, both pictured animals as
+arising directly out of the earth, very much as Milton's lion long
+afterwards pawed its way out. Even when we come to Bruno who wrote that
+"to the sound of the harp of the Universal Apollo (the World Spirit),
+the lower organisms are called by stages to higher, and the lower stages
+are connected by intermediate forms with the higher," there is great
+room, as Prof. Osborn points out (op. cit. page 81.), for difference of
+opinion as to how far he was an evolutionist in our sense of the term.
+
+The awakening of natural science in the sixteenth century brought the
+possibility of a concrete evolution theory nearer, and in the early
+seventeenth century we find evidences of a new spirit--in the embryology
+of Harvey and the classifications of Ray. Besides sober naturalists
+there were speculative dreamers in the sixteenth and seventeenth
+centuries who had at least got beyond static formulae, but, as Professor
+Osborn points out (op. cit. page 87.), "it is a very striking fact, that
+the basis of our modern methods of studying the Evolution problem was
+established not by the early naturalists nor by the speculative writers,
+but by the Philosophers." He refers to Bacon, Descartes, Leibnitz, Hume,
+Kant, Lessing, Herder, and Schelling. "They alone were upon the main
+track of modern thought. It is evident that they were groping in the
+dark for a working theory of the Evolution of life, and it is remarkable
+that they clearly perceived from the outset that the point to which
+observation should be directed was not the past but the present
+mutability of species, and further, that this mutability was simply the
+variation of individuals on an extended scale."
+
+Bacon seems to have been one of the first to think definitely about the
+mutability of species, and he was far ahead of his age in his suggestion
+of what we now call a Station of Experimental Evolution. Leibnitz
+discusses in so many words how the species of animals may be changed
+and how intermediate species may once have linked those that now seem
+discontinuous. "All natural orders of beings present but a single
+chain"... "All advances by degrees in Nature, and nothing by leaps."
+Similar evolutionist statements are to be found in the works of the
+other "philosophers," to whom Prof. Osborn refers, who were, indeed,
+more scientific than the naturalists of their day. It must be borne in
+mind that the general idea of organic evolution--that the present is
+the child of the past--is in great part just the idea of human history
+projected upon the natural world, differentiated by the qualification
+that the continuous "Becoming" has been wrought out by forces inherent
+in the organisms themselves and in their environment.
+
+A reference to Kant (See Brock, "Die Stellung Kant's zur
+Deszendenztheorie," "Biol. Centralbl." VIII. 1889, pages 641-648. Fritz
+Schultze, "Kant und Darwin", Jena, 1875.) should come in historical
+order after Buffon, with whose writings he was acquainted, but he seems,
+along with Herder and Schelling, to be best regarded as the culmination
+of the evolutionist philosophers--of those at least who interested
+themselves in scientific problems. In a famous passage he speaks of
+"the agreement of so many kinds of animals in a certain common plan of
+structure"... an "analogy of forms" which "strengthens the supposition
+that they have an actual blood-relationship, due to derivation from a
+common parent." He speaks of "the great Family of creatures, for as
+a Family we must conceive it, if the above-mentioned continuous and
+connected relationship has a real foundation." Prof. Osborn alludes to
+the scientific caution which led Kant, biology being what it was, to
+refuse to entertain the hope "that a Newton may one day arise even to
+make the production of a blade of grass comprehensible, according
+to natural laws ordained by no intention." As Prof. Haeckel finely
+observes, Darwin rose up as Kant's Newton. (Mr Alfred Russel Wallace
+writes: "We claim for Darwin that he is the Newton of natural history,
+and that, just so surely as that the discovery and demonstration by
+Newton of the law of gravitation established order in place of chaos and
+laid a sure foundation for all future study of the starry heavens, so
+surely has Darwin, by his discovery of the law of natural selection and
+his demonstration of the great principle of the preservation of useful
+variations in the struggle for life, not only thrown a flood of light
+on the process of development of the whole organic world, but
+also established a firm foundation for all future study of nature."
+("Darwinism", London, 1889, page 9). See also Prof. Karl Pearson's
+"Grammar of Science" (2nd edition), London, 1900, page 32. See Osborn,
+op. cit. Page 100.))
+
+The scientific renaissance brought a wealth of fresh impressions and
+some freedom from the tyranny of tradition, and the twofold stimulus
+stirred the speculative activity of a great variety of men from old
+Claude Duret of Moulins, of whose weird transformism (1609) Dr Henry
+de Varigny ("Experimental Evolution". London, 1892. Chap. 1. page 14.)
+gives us a glimpse, to Lorenz Oken (1799-1851) whose writings are such
+mixtures of sense and nonsense that some regard him as a
+far-seeing prophet and others as a fatuous follower of intellectual
+will-o'-the-wisps. Similarly, for De Maillet, Maupertuis, Diderot,
+Bonnet, and others, we must agree with Professor Osborn that they were
+not actually in the main Evolution movement. Some have been included in
+the roll of honour on very slender evidence, Robinet for instance, whose
+evolutionism seems to us extremely dubious. (See J. Arthur Thomson,
+"The Science of Life". London, 1899. Chap. XVI. "Evolution of Evolution
+Theory".)
+
+The first naturalist to give a broad and concrete expression to the
+evolutionist doctrine of descent was Buffon (1707-1788), but it
+is interesting to recall the fact that his contemporary Linnaeus
+(1707-1778), protagonist of the counter-doctrine of the fixity
+of species (See Carus Sterne (Ernest Krause), "Die allgemeine
+Weltanschauung in ihrer historischen Entwickelung". Stuttgart, 1889.
+Chapter entitled "Bestandigkeit oder Veranderlichkeit der Naturwesen".),
+went the length of admitting (in 1762) that new species might arise
+by intercrossing. Buffon's position among the pioneers of the
+evolution-doctrine is weakened by his habit of vacillating between his
+own conclusions and the orthodoxy of the Sorbonne, but there is no doubt
+that he had a firm grasp of the general idea of "l'enchainement des
+etres."
+
+Erasmus Darwin (1731-1802), probably influenced by Buffon, was another
+firm evolutionist, and the outline of his argument in the "Zoonomia"
+("Zoonomia, or the Laws of Organic Life", 2 vols. London, 1794; Osborn
+op. cit. page 145.) might serve in part at least to-day. "When we
+revolve in our minds the metamorphoses of animals, as from the tadpole
+to the frog; secondly, the changes produced by artificial cultivation,
+as in the breeds of horses, dogs, and sheep; thirdly, the changes
+produced by conditions of climate and of season, as in the sheep of
+warm climates being covered with hair instead of wool, and the hares and
+partridges of northern climates becoming white in winter: when,
+further, we observe the changes of structure produced by habit, as seen
+especially in men of different occupations; or the changes produced by
+artificial mutilation and prenatal influences, as in the crossing
+of species and production of monsters; fourth, when we observe the
+essential unity of plan in all warm-blooded animals,--we are led to
+conclude that they have been alike produced from a similar living
+filament"... "From thus meditating upon the minute portion of time in
+which many of the above changes have been produced, would it be too bold
+to imagine, in the great length of time since the earth began to exist,
+perhaps millions of years before the commencement of the history of
+mankind, that all warm-blooded animals have arisen from one living
+filament?"... "This idea of the gradual generation of all things seems to
+have been as familiar to the ancient philosophers as to the modern
+ones, and to have given rise to the beautiful hieroglyphic figure of the
+proton oon, or first great egg, produced by night, that is, whose origin
+is involved in obscurity, and animated by Eros, that is, by Divine Love;
+from whence proceeded all things which exist."
+
+Lamarck (1744-1829) seems to have become an evolutionist independently
+of Erasmus Darwin's influence, though the parallelism between them is
+striking. He probably owed something to Buffon, but he developed his
+theory along a different line. Whatever view be held in regard to that
+theory there is no doubt that Lamarck was a thorough-going evolutionist.
+Professor Haeckel speaks of the "Philosophie Zoologique" as "the first
+connected and thoroughly logical exposition of the theory of descent."
+(See Alpheus S. Packard, "Lamarck, the Founder of Evolution, His Life
+and Work, with Translations of his writings on Organic Evolution".
+London, 1901.)
+
+Besides the three old masters, as we may call them, Buffon, Erasmus
+Darwin, and Lamarck, there were other quite convinced pre-Darwinian
+evolutionists. The historian of the theory of descent must take account
+of Treviranus whose "Biology or Philosophy of Animate Nature" is full of
+evolutionary suggestions; of Etienne Geoffroy St Hilaire, who in
+1830, before the French Academy of Sciences, fought with Cuvier, the
+fellow-worker of his youth, an intellectual duel on the question of
+descent; of Goethe, one of the founders of morphology and the greatest
+poet of Evolution--who, in his eighty-first year, heard the tidings
+of Geoffroy St Hilaire's defeat with an interest which transcended the
+political anxieties of the time; and of many others who had gained with
+more or less confidence and clearness a new outlook on Nature. It
+will be remembered that Darwin refers to thirty-four more or less
+evolutionist authors in his Historical Sketch, and the list might be
+added to. Especially when we come near to 1858 do the numbers increase,
+and one of the most remarkable, as also most independent champions of
+the evolution-idea before that date was Herbert Spencer, who not only
+marshalled the arguments in a very forcible way in 1852, but applied the
+formula in detail in his "Principles of Psychology" in 1855. (See Edward
+Clodd, "Pioneers of Evolution", London, page 161, 1897.)
+
+It is right and proper that we should shake ourselves free from all
+creationist appreciations of Darwin, and that we should recognise the
+services of pre-Darwinian evolutionists who helped to make the time
+ripe, yet one cannot help feeling that the citation of them is apt to
+suggest two fallacies. It may suggest that Darwin simply entered into
+the labours of his predecessors, whereas, as a matter of fact, he knew
+very little about them till after he had been for years at work. To
+write, as Samuel Butler did, "Buffon planted, Erasmus Darwin and Lamarck
+watered, but it was Mr Darwin who said 'That fruit is ripe,' and shook
+it into his lap"... seems to us a quite misleading version of the facts
+of the case. The second fallacy which the historical citation is
+a little apt to suggest is that the filiation of ideas is a simple
+problem. On the contrary, the history of an idea, like the pedigree
+of an organism, is often very intricate, and the evolution of the
+evolution-idea is bound up with the whole progress of the world. Thus
+in order to interpret Darwin's clear formulation of the idea of organic
+evolution and his convincing presentation of it, we have to do more than
+go back to his immediate predecessors, such as Buffon, Erasmus Darwin,
+and Lamarck; we have to inquire into the acceptance of evolutionary
+conceptions in regard to other orders of facts, such as the earth and
+the solar system (See Chapter IX. "The Genetic View of Nature" in J.T.
+Merz's "History of European Thought in the Nineteenth Century", Vol. 2,
+Edinburgh and London, 1903.); we have to realise how the growing success
+of scientific interpretation along other lines gave confidence to those
+who refused to admit that there was any domain from which science could
+be excluded as a trespasser; we have to take account of the development
+of philosophical thought, and even of theological and religious
+movements; we should also, if we are wise enough, consider social
+changes. In short, we must abandon the idea that we can understand
+the history of any science as such, without reference to contemporary
+evolution in other departments of activity.
+
+While there were many evolutionists before Darwin, few of them were
+expert naturalists and few were known outside a small circle; what
+was of much more importance was that the genetic view of nature was
+insinuating itself in regard to other than biological orders of facts,
+here a little and there a little, and that the scientific spirit had
+ripened since the days when Cuvier laughed Lamarck out of court. How was
+it that Darwin succeeded where others had failed? Because, in the first
+place, he had clear visions--"pensees de la jeunesse, executees par
+l'age mur"--which a University curriculum had not made impossible, which
+the "Beagle" voyage made vivid, which an unrivalled British doggedness
+made real--visions of the web of life, of the fountain of change within
+the organism, of the struggle for existence and its winnowing, and of
+the spreading genealogical tree. Because, in the second place, he put
+so much grit into the verification of his visions, putting them to the
+proof in an argument which is of its kind--direct demonstration being
+out of the question--quite unequalled. Because, in the third place,
+he broke down the opposition which the most scientific had felt to
+the seductive modal formula of evolution by bringing forward a more
+plausible theory of the process than had been previously suggested.
+Nor can one forget, since questions of this magnitude are human and not
+merely academic, that he wrote so that all men could understand.
+
+AS REGARDS THE FACTORS OF EVOLUTION.
+
+It is admitted by all who are acquainted with the history of biology
+that the general idea of organic evolution as expressed in the Doctrine
+of Descent was quite familiar to Darwin's grandfather, and to others
+before and after him, as we have briefly indicated. It must also be
+admitted that some of these pioneers of evolutionism did more than apply
+the evolution-idea as a modal formula of becoming, they began to inquire
+into the factors in the process. Thus there were pre-Darwinian theories
+of evolution, and to these we must now briefly refer. (See Prof. W.A.
+Locy's "Biology and its Makers". New York, 1908. Part II. "The Doctrine
+of Organic Evolution".)
+
+In all biological thinking we have to work with the categories
+Organism--Function--Environment, and theories of evolution may be
+classified in relation to these. To some it has always seemed that the
+fundamental fact is the living organism,--a creative agent, a striving
+will, a changeful Proteus, selecting its environment, adjusting
+itself to it, self-differentiating and self-adaptive. The necessity of
+recognising the importance of the organism is admitted by all Darwinians
+who start with inborn variations, but it is open to question whether the
+whole truth of what we might call the Goethian position is exhausted in
+the postulate of inherent variability.
+
+To others it has always seemed that the emphasis should be laid on
+Function,--on use and disuse, on doing and not doing. Practice makes
+perfect; c'est a force de forger qu'on devient forgeron. This is one of
+the fundamental ideas of Lamarckism; to some extent it met with Darwin's
+approval; and it finds many supporters to-day. One of the ablest
+of these--Mr Francis Darwin--has recently given strong reasons for
+combining a modernised Lamarckism with what we usually regard as sound
+Darwinism. (Presidential Address to the British Association meeting at
+Dublin in 1908.)
+
+To others it has always seemed that the emphasis should be laid on the
+Environment, which wakes the organism to action, prompts it to change,
+makes dints upon it, moulds it, prunes it, and finally, perhaps, kills
+it. It is again impossible to doubt that there is truth in this
+view, for even if environmentally induced "modifications" be not
+transmissible, environmentally induced "variations" are; and even if
+the direct influence of the environment be less important than
+many enthusiastic supporters of this view--may we call them
+Buffonians--think, there remains the indirect influence which Darwinians
+in part rely on,--the eliminative process. Even if the extreme view
+be held that the only form of discriminate elimination that counts is
+inter-organismal competition, this might be included under the rubric of
+the animate environment.
+
+In many passages Buffon (See in particular Samuel Butler, "Evolution
+Old and New", London, 1879; J.L. de Lanessan, "Buffon et Darwin",
+"Revue Scientifique", XLIII. pages 385-391, 425-432, 1889.) definitely
+suggested that environmental influences--especially of climate and
+food--were directly productive of changes in organisms, but he did not
+discuss the question of the transmissibility of the modifications so
+induced, and it is difficult to gather from his inconsistent writings
+what extent of transformation he really believed in. Prof. Osborn
+says of Buffon: "The struggle for existence, the elimination of the
+least-perfected species, the contest between the fecundity of certain
+species and their constant destruction, are all clearly expressed in
+various passages." He quotes two of these (op. cit. page 136.):
+
+"Le cours ordinaire de la nature vivante, est en general toujours
+constant, toujours le meme; son mouvement, toujours regulier, roule
+sur deux points inebranlables: l'un, la fecondite sans bornes donnee
+a toutes les especes; l'autre, les obstacles sans nombre qui reduisent
+cette fecondite a une mesure determinee et ne laissent en tout temps
+qu'a peu pres la meme quantite d'individus de chaque espece"... "Les
+especes les moins parfaites, les plus delicates, les plus pesantes,
+les moins agissantes, les moins armees, etc., ont deja disparu ou
+disparaitront."
+
+Erasmus Darwin (See Ernst Krause and Charles Darwin, "Erasmus Darwin",
+London, 1879.) had a firm grip of the "idea of the gradual formation and
+improvement of the Animal world," and he had his theory of the process.
+No sentence is more characteristic than this: "All animals undergo
+transformations which are in part produced by their own exertions, in
+response to pleasures and pains, and many of these acquired forms or
+propensities are transmitted to their posterity." This is Lamarckism
+before Lamarck, as his grandson pointed out. His central idea is that
+wants stimulate efforts and that these result in improvements, which
+subsequent generations make better still. He realised something of the
+struggle for existence and even pointed out that this advantageously
+checks the rapid multiplication. "As Dr Krause points out, Darwin just
+misses the connection between this struggle and the Survival of the
+Fittest." (Osborn op. cit. page 142.)
+
+Lamarck (1744-1829) (See E. Perrier "La Philosophie Zoologique avant
+Darwin", Paris, 1884; A. de Quatrefages, "Darwin et ses Precurseurs
+Francais", Paris, 1870; Packard op. cit.; also Claus, "Lamarck als
+Begrunder der Descendenzlehre", Wien, 1888; Haeckel, "Natural History
+of Creation", English translation London, 1879; Lang "Zur Charakteristik
+der Forschungswege von Lamarck und Darwin", Jena, 1889.) seems to have
+thought out his theory of evolution without any knowledge of Erasmus
+Darwin's which it closely resembled. The central idea of his theory
+was the cumulative inheritance of functional modifications. "Changes
+in environment bring about changes in the habits of animals. Changes in
+their wants necessarily bring about parallel changes in their habits. If
+new wants become constant or very lasting, they form new habits, the new
+habits involve the use of new parts, or a different use of old
+parts, which results finally in the production of new organs and the
+modification of old ones." He differed from Buffon in not attaching
+importance, as far as animals are concerned, to the direct influence of
+the environment, "for environment can effect no direct change whatever
+upon the organisation of animals," but in regard to plants he agreed
+with Buffon that external conditions directly moulded them.
+
+Treviranus (1776-1837) (See Huxley's article "Evolution in Biology",
+"Encyclopaedia Britannica" (9th edit.), 1878, pages 744-751, and Sully's
+article, "Evolution in Philosophy", ibid. pages 751-772.), whom Huxley
+ranked beside Lamarck, was on the whole Buffonian, attaching chief
+importance to the influence of a changeful environment both in modifying
+and in eliminating, but he was also Goethian, for instance in his idea
+that species like individuals pass through periods of growth, full
+bloom, and decline. "Thus, it is not only the great catastrophes of
+Nature which have caused extinction, but the completion of cycles
+of existence, out of which new cycles have begun." A characteristic
+sentence is quoted by Prof. Osborn: "In every living being there exists
+a capability of an endless variety of form-assumption; each possesses
+the power to adapt its organisation to the changes of the outer world,
+and it is this power, put into action by the change of the universe,
+that has raised the simple zoophytes of the primitive world to
+continually higher stages of organisation, and has introduced a
+countless variety of species into animate Nature."
+
+Goethe (1749-1832) (See Haeckel, "Die Naturanschauung von Darwin, Goethe
+und Lamarck", Jena, 1882.), who knew Buffon's work but not Lamarck's, is
+peculiarly interesting as one of the first to use the evolution-idea as
+a guiding hypothesis, e.g. in the interpretation of vestigial structures
+in man, and to realise that organisms express an attempt to make a
+compromise between specific inertia and individual change. He gave the
+finest expression that science has yet known--if it has known it--of
+the kernel-idea of what is called "bathmism," the idea of an "inherent
+growth-force"--and at the same time he held that "the way of life
+powerfully reacts upon all form" and that the orderly growth of form
+"yields to change from externally acting causes."
+
+Besides Buffon, Erasmus Darwin, Lamarck, Treviranus, and Goethe,
+there were other "pioneers of evolution," whose views have been often
+discussed and appraised. Etienne Geoffroy Saint-Hilaire (1772-1844),
+whose work Goethe so much admired, was on the whole Buffonian,
+emphasising the direct action of the changeful milieu. "Species
+vary with their environment, and existing species have descended by
+modification from earlier and somewhat simpler species." He had a
+glimpse of the selection idea, and believed in mutations or sudden
+leaps--induced in the embryonic condition by external influences. The
+complete history of evolution-theories will include many instances
+of guesses at truth which were afterwards substantiated, thus the
+geographer von Buch (1773-1853) detected the importance of the Isolation
+factor on which Wagner, Romanes, Gulick and others have laid great
+stress, but we must content ourselves with recalling one other pioneer,
+the author of the "Vestiges of Creation" (1844), a work which passed
+through ten editions in nine years and certainly helped to harrow the
+soil for Darwin's sowing. As Darwin said, "it did excellent service in
+this country in calling attention to the subject, in removing prejudice,
+and in thus preparing the ground for the reception of analogous views."
+("Origin of Species" (6th edition), page xvii.) Its author, Robert
+Chambers (1802-1871) was in part a Buffonian--maintaining
+that environment moulded organisms adaptively, and in part a
+Goethian--believing in an inherent progressive impulse which lifted
+organisms from one grade of organisation to another.
+
+AS REGARDS NATURAL SELECTION.
+
+The only thinker to whom Darwin was directly indebted, so far as the
+theory of Natural Selection is concerned, was Malthus, and we may once
+more quote the well-known passage in the Autobiography: "In October,
+1838, that is, fifteen months after I had begun my systematic enquiry,
+I happened to read for amusement 'Malthus on Population', and being well
+prepared to appreciate the struggle for existence which everywhere goes
+on from long-continued observation of the habits of animals and
+plants, it at once struck me that under these circumstances favourable
+variations would tend to be preserved, and unfavourable ones to be
+destroyed. The result of this would be the formation of new species."
+("The Life and Letters of Charles Darwin", Vol. 1. page 83. London,
+1887.)
+
+Although Malthus gives no adumbration of the idea of Natural Selection
+in his exposition of the eliminative processes which go on in mankind,
+the suggestive value of his essay is undeniable, as is strikingly
+borne out by the fact that it gave to Alfred Russel Wallace also "the
+long-sought clue to the effective agent in the evolution of organic
+species." (A.R. Wallace, "My Life, A Record of Events and Opinions",
+London, 1905, Vol. 1. page 232.) One day in Ternate when he was resting
+between fits of fever, something brought to his recollection the work of
+Malthus which he had read twelve years before. "I thought of his clear
+exposition of 'the positive checks to increase'--disease, accidents,
+war, and famine--which keep down the population of savage races to
+so much lower an average than that of more civilized peoples. It then
+occurred to me that these causes or their equivalents are continually
+acting in the case of animals also; and as animals usually breed much
+more rapidly than does mankind, the destruction every year from these
+causes must be enormous in order to keep down the numbers of each
+species, since they evidently do not increase regularly from year to
+year, as otherwise the world would long ago have been densely crowded
+with those that breed most quickly. Vaguely thinking over the enormous
+and constant destruction which this implied, it occurred to me to ask
+the question, Why do some die and some live? And the answer was clearly,
+that on the whole the best fitted live. From the effects of disease the
+most healthy escaped; from enemies the strongest, the swiftest, or
+the most cunning; from famine the best hunters or those with the
+best digestion; and so on. Then it suddenly flashed upon me that this
+self-acting process would necessarily IMPROVE THE RACE, because in every
+generation the inferior would inevitably be killed off and the superior
+would remain--that is, THE FITTEST WOULD SURVIVE." (Ibid. Vol. 1. page
+361.) We need not apologise for this long quotation, it is a tribute
+to Darwin's magnanimous colleague, the Nestor of the evolutionist
+camp,--and it probably indicates the line of thought which Darwin
+himself followed. It is interesting also to recall the fact that in
+1852, when Herbert Spencer wrote his famous "Leader" article on "The
+Development Hypothesis" in which he argued powerfully for the thesis
+that the whole animate world is the result of an age-long process of
+natural transformation, he wrote for "The Westminster Review" another
+important essay, "A Theory of Population deduced from the General Law of
+Animal Fertility", towards the close of which he came within an ace
+of recognising that the struggle for existence was a factor in organic
+evolution. At a time when pressure of population was practically
+interesting men's minds, Darwin, Wallace, and Spencer were being
+independently led from a social problem to a biological theory. There
+could be no better illustration, as Prof. Patrick Geddes has pointed
+out, of the Comtian thesis that science is a "social phenomenon."
+
+Therefore, as far more important than any further ferreting out of vague
+hints of Natural Selection in books which Darwin never read, we would
+indicate by a quotation the view that the central idea in Darwinism
+is correlated with contemporary social evolution. "The substitution
+of Darwin for Paley as the chief interpreter of the order of nature is
+currently regarded as the displacement of an anthropomorphic view by a
+purely scientific one: a little reflection, however, will show that
+what has actually happened has been merely the replacement of the
+anthropomorphism of the eighteenth century by that of the nineteenth.
+For the place vacated by Paley's theological and metaphysical
+explanation has simply been occupied by that suggested to Darwin and
+Wallace by Malthus in terms of the prevalent severity of industrial
+competition, and those phenomena of the struggle for existence which the
+light of contemporary economic theory has enabled us to discern, have
+thus come to be temporarily exalted into a complete explanation
+of organic progress." (P. Geddes, article "Biology", "Chambers's
+Encyclopaedia".) It goes without saying that the idea suggested by
+Malthus was developed by Darwin into a biological theory which was then
+painstakingly verified by being used as an interpretative formula, and
+that the validity of a theory so established is not affected by what
+suggested it, but the practical question which this line of thought
+raises in the mind is this: if Biology did thus borrow with such
+splendid results from social theory, why should we not more deliberately
+repeat the experiment?
+
+Darwin was characteristically frank and generous in admitting that the
+principle of Natural Selection had been independently recognised by
+Dr W.C. Wells in 1813 and by Mr Patrick Matthew in 1831, but he had no
+knowledge of these anticipations when he published the first edition
+of "The Origin of Species". Wells, whose "Essay on Dew" is still
+remembered, read in 1813 before the Royal Society a short paper entitled
+"An account of a White Female, part of whose skin resembles that of a
+Negro" (published in 1818). In this communication, as Darwin said, "he
+observes, firstly, that all animals tend to vary in some degree, and,
+secondly, that agriculturists improve their domesticated animals by
+selection; and then, he adds, but what is done in this latter case
+'by art, seems to be done with equal efficacy, though more slowly, by
+nature, in the formation of varieties of mankind, fitted for the country
+which they inhabit.'" ("Origin of Species" (6th edition) page xv.)
+Thus Wells had the clear idea of survival dependent upon a favourable
+variation, but he makes no more use of the idea and applies it only
+to man. There is not in the paper the least hint that the author ever
+thought of generalising the remarkable sentence quoted above.
+
+Of Mr Patrick Matthew, who buried his treasure in an appendix to a work
+on "Naval Timber and Arboriculture", Darwin said that "he clearly saw
+the full force of the principle of natural selection." In 1860 Darwin
+wrote--very characteristically--about this to Lyell: "Mr Patrick
+Matthew publishes a long extract from his work on "Naval Timber and
+Arboriculture", published in 1831, in which he briefly but completely
+anticipates the theory of Natural Selection. I have ordered the book,
+as some passages are rather obscure, but it is certainly, I think, a
+complete but not developed anticipation. Erasmus always said that surely
+this would be shown to be the case some day. Anyhow, one may be excused
+in not having discovered the fact in a work on Naval Timber." ("Life and
+Letters" II. page 301.)
+
+De Quatrefages and De Varigny have maintained that the botanist Naudin
+stated the theory of evolution by natural selection in 1852. He explains
+very clearly the process of artificial selection, and says that in the
+garden we are following Nature's method. "We do not think that Nature
+has made her species in a different fashion from that in which we
+proceed ourselves in order to make our variations." But, as Darwin said,
+"he does not show how selection acts under nature." Similarly it must
+be noted in regard to several pre-Darwinian pictures of the struggle
+for existence (such as Herder's, who wrote in 1790 "All is in
+struggle... each one for himself" and so on), that a recognition of this
+is only the first step in Darwinism.
+
+Profs. E. Perrier and H.F. Osborn have called attention to a remarkable
+anticipation of the selection-idea which is to be found in the
+speculations of Etienne Geoffroy St Hilaire (1825-1828) on the evolution
+of modern Crocodilians from the ancient Teleosaurs. Changing environment
+induced changes in the respiratory system and far-reaching consequences
+followed. The atmosphere, acting upon the pulmonary cells, brings about
+"modifications which are favourable or destructive ('funestes'); these
+are inherited, and they influence all the rest of the organisation of
+the animal because if these modifications lead to injurious effects,
+the animals which exhibit them perish and are replaced by others of a
+somewhat different form, a form changed so as to be adapted to (a la
+convenance) the new environment."
+
+Prof. E.B. Poulton ("Science Progress", New Series, Vol. I. 1897. "A
+Remarkable Anticipation of Modern Views on Evolution". See also
+Chap. VI. in "Essays on Evolution", Oxford, 1908.) has shown that the
+anthropologist James Cowles Prichard (1786-1848) must be included, even
+in spite of himself, among the precursors of Darwin. In some passages
+of the second edition of his "Researches into the Physical History of
+Mankind" (1826), he certainly talks evolution and anticipates Prof.
+Weismann in denying the transmission of acquired characters. He is,
+however, sadly self-contradictory and his evolutionism weakens in
+subsequent editions--the only ones that Darwin saw. Prof. Poulton finds
+in Prichard's work a recognition of the operation of Natural Selection.
+"After enquiring how it is that 'these varieties are developed and
+preserved in connection with particular climates and differences of
+local situation,' he gives the following very significant answer: 'One
+cause which tends to maintain this relation is obvious. Individuals and
+families, and even whole colonies, perish and disappear in climates for
+which they are, by peculiarity of constitution, not adapted. Of this
+fact proofs have been already mentioned.'" Mr Francis Darwin and Prof.
+A.C. Seward discuss Prichard's "anticipations" in "More Letters of
+Charles Darwin", Vol. I. page 43, and come to the conclusion that the
+evolutionary passages are entirely neutralised by others of an opposite
+trend. There is the same difficulty with Buffon.
+
+Hints of the idea of Natural Selection have been detected elsewhere.
+James Watt (See Prof. Patrick Geddes's article "Variation and
+Selection", "Encyclopaedia Britannica (9th edition) 1888.), for
+instance, has been reported as one of the anticipators (1851). But we
+need not prolong the inquiry further, since Darwin did not know of any
+anticipations until after he had published the immortal work of 1859,
+and since none of those who got hold of the idea made any use of it.
+What Darwin did was to follow the clue which Malthus gave him, to
+realise, first by genius and afterwards by patience, how the complex
+and subtle struggle for existence works out a natural selection of
+those organisms which vary in the direction of fitter adaptation to the
+conditions of their life. So much success attended his application of
+the Selection-formula that for a time he regarded Natural Selection
+as almost the sole factor in evolution, variations being pre-supposed;
+gradually, however, he came to recognise that there was some validity in
+the factors which had been emphasized by Lamarck and by Buffon, and in
+his well-known summing up in the sixth edition of the "Origin" he
+says of the transformation of species: "This has been effected chiefly
+through the natural selection of numerous successive, slight, favourable
+variations; aided in an important manner by the inherited effects of
+the use and disuse of parts; and in an unimportant manner, that is, in
+relation to adaptive structures, whether past or present, by the direct
+action of external conditions, and by variations which seem to us in our
+ignorance to arise spontaneously."
+
+To sum up: the idea of organic evolution, older than Aristotle, slowly
+developed from the stage of suggestion to the stage of verification, and
+the first convincing verification was Darwin's; from being an a priori
+anticipation it has become an interpretation of nature, and Darwin is
+still the chief interpreter; from being a modal interpretation it has
+advanced to the rank of a causal theory, the most convincing part of
+which men will never cease to call Darwinism.
+
+
+
+
+III. THE SELECTION THEORY, By August Weismann.
+
+Professor of Zoology in the University of Freiburg (Baden).
+
+
+I. THE IDEA OF SELECTION.
+
+Many and diverse were the discoveries made by Charles Darwin in the
+course of a long and strenuous life, but none of them has had so
+far-reaching an influence on the science and thought of his time as the
+theory of selection. I do not believe that the theory of evolution would
+have made its way so easily and so quickly after Darwin took up the
+cudgels in favour of it, if he had not been able to support it by a
+principle which was capable of solving, in a simple manner, the greatest
+riddle that living nature presents to us,--I mean the purposiveness
+of every living form relative to the conditions of its life and its
+marvellously exact adaptation to these.
+
+Everyone knows that Darwin was not alone in discovering the principle
+of selection, and that the same idea occurred simultaneously and
+independently to Alfred Russel Wallace. At the memorable meeting of the
+Linnean Society on 1st July, 1858, two papers were read (communicated by
+Lyell and Hooker) both setting forth the same idea of selection. One
+was written by Charles Darwin in Kent, the other by Alfred Wallace
+in Ternate, in the Malay Archipelago. It was a splendid proof of
+the magnanimity of these two investigators, that they thus, in all
+friendliness and without envy, united in laying their ideas before a
+scientific tribunal: their names will always shine side by side as two
+of the brightest stars in the scientific sky.
+
+But it is with Charles Darwin that I am here chiefly concerned, since
+this paper is intended to aid in the commemoration of the hundredth
+anniversary of his birth.
+
+The idea of selection set forth by the two naturalists was at the time
+absolutely new, but it was also so simple that Huxley could say of it
+later, "How extremely stupid not to have thought of that." As Darwin was
+led to the general doctrine of descent, not through the labours of
+his predecessors in the early years of the century, but by his own
+observations, so it was in regard to the principle of selection. He was
+struck by the innumerable cases of adaptation, as, for instance, that
+of the woodpeckers and tree-frogs to climbing, or the hooks and
+feather-like appendages of seeds, which aid in the distribution of
+plants, and he said to himself that an explanation of adaptations was
+the first thing to be sought for in attempting to formulate a theory of
+evolution.
+
+But since adaptations point to CHANGES which have been undergone by the
+ancestral forms of existing species, it is necessary, first of all, to
+inquire how far species in general are VARIABLE. Thus Darwin's attention
+was directed in the first place to the phenomenon of variability, and
+the use man has made of this, from very early times, in the breeding of
+his domesticated animals and cultivated plants. He inquired carefully
+how breeders set to work, when they wished to modify the structure and
+appearance of a species to their own ends, and it was soon clear to him
+that SELECTION FOR BREEDING PURPOSES played the chief part.
+
+But how was it possible that such processes should occur in free
+nature? Who is here the breeder, making the selection, choosing out one
+individual to bring forth offspring and rejecting others? That was the
+problem that for a long time remained a riddle to him.
+
+Darwin himself relates how illumination suddenly came to him. He had
+been reading, for his own pleasure, Malthus' book on Population, and, as
+he had long known from numerous observations, that every species gives
+rise to many more descendants than ever attain to maturity, and that,
+therefore, the greater number of the descendants of a species perish
+without reproducing, the idea came to him that the decision as to which
+member of a species was to perish, and which was to attain to maturity
+and reproduction might not be a matter of chance, but might be
+determined by the constitution of the individuals themselves, according
+as they were more or less fitted for survival. With this idea the
+foundation of the theory of selection was laid.
+
+In ARTIFICIAL SELECTION the breeder chooses out for pairing only such
+individuals as possess the character desired by him in a somewhat higher
+degree than the rest of the race. Some of the descendants inherit this
+character, often in a still higher degree, and if this method be pursued
+throughout several generations, the race is transformed in respect of
+that particular character.
+
+NATURAL SELECTION depends on the same three factors as ARTIFICIAL
+SELECTION: on VARIABILITY, INHERITANCE, and SELECTION FOR BREEDING, but
+this last is here carried out not by a breeder but by what Darwin called
+the "struggle for existence." This last factor is one of the special
+features of the Darwinian conception of nature. That there are
+carnivorous animals which take heavy toll in every generation of the
+progeny of the animals on which they prey, and that there are herbivores
+which decimate the plants in every generation had long been known, but
+it is only since Darwin's time that sufficient attention has been paid
+to the facts that, in addition to this regular destruction, there exists
+between the members of a species a keen competition for space and food,
+which limits multiplication, and that numerous individuals of each
+species perish because of unfavourable climatic conditions. The
+"struggle for existence," which Darwin regarded as taking the place
+of the human breeder in free nature, is not a direct struggle between
+carnivores and their prey, but is the assumed competition for survival
+between individuals OF THE SAME species, of which, on an average, only
+those survive to reproduce which have the greatest power of resistance,
+while the others, less favourably constituted, perish early. This
+struggle is so keen, that, within a limited area, where the conditions
+of life have long remained unchanged, of every species, whatever be the
+degree of fertility, only two, ON AN AVERAGE, of the descendants of each
+pair survive; the others succumb either to enemies, or to disadvantages
+of climate, or to accident. A high degree of fertility is thus not an
+indication of the special success of a species, but of the numerous
+dangers that have attended its evolution. Of the six young brought forth
+by a pair of elephants in the course of their lives only two survive in
+a given area; similarly, of the millions of eggs which two thread-worms
+leave behind them only two survive. It is thus possible to estimate the
+dangers which threaten a species by its ratio of elimination, or, since
+this cannot be done directly, by its fertility.
+
+Although a great number of the descendants of each generation fall
+victims to accident, among those that remain it is still the greater
+or lesser fitness of the organism that determines the "selection
+for breeding purposes," and it would be incomprehensible if, in this
+competition, it were not ultimately, that is, on an average, the best
+equipped which survive, in the sense of living long enough to reproduce.
+
+Thus the principle of natural selection is THE SELECTION OF THE BEST FOR
+REPRODUCTION, whether the "best" refers to the whole constitution,
+to one or more parts of the organism, or to one or more stages of
+development. Every organ, every part, every character of an animal,
+fertility and intelligence included, must be improved in this manner,
+and be gradually brought up in the course of generations to its highest
+attainable state of perfection. And not only may improvement of parts
+be brought about in this way, but new parts and organs may arise,
+since, through the slow and minute steps of individual or "fluctuating"
+variations, a part may be added here or dropped out there, and thus
+something new is produced.
+
+The principle of selection solved the riddle as to how what was
+purposive could conceivably be brought about without the intervention
+of a directing power, the riddle which animate nature presents to our
+intelligence at every turn, and in face of which the mind of a Kant
+could find no way out, for he regarded a solution of it as not to be
+hoped for. For, even if we were to assume an evolutionary force that is
+continually transforming the most primitive and the simplest forms of
+life into ever higher forms, and the homogeneity of primitive times into
+the infinite variety of the present, we should still be unable to infer
+from this alone how each of the numberless forms adapted to particular
+conditions of life should have appeared PRECISELY AT THE RIGHT MOMENT
+IN THE HISTORY OF THE EARTH to which their adaptations were appropriate,
+and precisely at the proper place in which all the conditions of life to
+which they were adapted occurred: the humming-birds at the same time as
+the flowers; the trichina at the same time as the pig; the bark-coloured
+moth at the same time as the oak, and the wasp-like moth at the same
+time as the wasp which protects it. Without processes of selection we
+should be obliged to assume a "pre-established harmony" after the famous
+Leibnitzian model, by means of which the clock of the evolution of
+organisms is so regulated as to strike in exact synchronism with that of
+the history of the earth! All forms of life are strictly adapted to the
+conditions of their life, and can persist under these conditions alone.
+
+There must therefore be an intrinsic connection between the conditions
+and the structural adaptations of the organism, and, SINCE THE
+CONDITIONS OF LIFE CANNOT BE DETERMINED BY THE ANIMAL ITSELF, THE
+ADAPTATIONS MUST BE CALLED FORTH BY THE CONDITIONS.
+
+The selection theory teaches us how this is conceivable, since it
+enables us to understand that there is a continual production of what is
+non-purposive as well as of what is purposive, but the purposive alone
+survives, while the non-purposive perishes in the very act of arising.
+This is the old wisdom taught long ago by Empedocles.
+
+II. THE LAMARCKIAN PRINCIPLE.
+
+Lamarck, as is well known, formulated a definite theory of evolution at
+the beginning of the nineteenth century, exactly fifty years before
+the Darwin-Wallace principle of selection was given to the world.
+This brilliant investigator also endeavoured to support his theory by
+demonstrating forces which might have brought about the transformations
+of the organic world in the course of the ages. In addition to other
+factors, he laid special emphasis on the increased or diminished use
+of the parts of the body, assuming that the strengthening or weakening
+which takes place from this cause during the individual life, could be
+handed on to the offspring, and thus intensified and raised to the rank
+of a specific character. Darwin also regarded this LAMARCKIAN PRINCIPLE,
+as it is now generally called, as a factor in evolution, but he was not
+fully convinced of the transmissibility of acquired characters.
+
+As I have here to deal only with the theory of selection, I need not
+discuss the Lamarckian hypothesis, but I must express my opinion that
+there is room for much doubt as to the cooperation of this principle in
+evolution. Not only is it difficult to imagine how the transmission of
+functional modifications could take place, but, up to the present time,
+notwithstanding the endeavours of many excellent investigators, not
+a single actual proof of such inheritance has been brought forward.
+Semon's experiments on plants are, according to the botanist Pfeffer,
+not to be relied on, and even the recent, beautiful experiments made
+by Dr Kammerer on salamanders, cannot, as I hope to show elsewhere,
+be regarded as proof, if only because they do not deal at all with
+functional modifications, that is, with modifications brought about by
+use, and it is to these ALONE that the Lamarckian principle refers.
+
+III. OBJECTIONS TO THE THEORY OF SELECTION.
+
+(a) Saltatory evolution.
+
+The Darwinian doctrine of evolution depends essentially on THE
+CUMULATIVE AUGMENTATION of minute variations in the direction of
+utility. But can such minute variations, which are undoubtedly
+continually appearing among the individuals of the same species,
+possess any selection-value; can they determine which individuals are
+to survive, and which are to succumb; can they be increased by natural
+selection till they attain to the highest development of a purposive
+variation?
+
+To many this seems so improbable that they have urged a theory of
+evolution by leaps from species to species. Kolliker, in 1872, compared
+the evolution of species with the processes which we can observe in the
+individual life in cases of alternation of generations. But a polyp only
+gives rise to a medusa because it has itself arisen from one, and there
+can be no question of a medusa ever having arisen suddenly and de
+novo from a polyp-bud, if only because both forms are adapted in their
+structure as a whole, and in every detail to the conditions of their
+life. A sudden origin, in a natural way, of numerous adaptations is
+inconceivable. Even the degeneration of a medusoid from a free-swimming
+animal to a mere brood-sac (gonophore) is not sudden and saltatory, but
+occurs by imperceptible modifications throughout hundreds of years, as
+we can learn from the numerous stages of the process of degeneration
+persisting at the same time in different species.
+
+If, then, the degeneration to a simple brood-sac takes place only by
+very slow transitions, each stage of which may last for centuries, how
+could the much more complex ASCENDING evolution possibly have taken
+place by sudden leaps? I regard this argument as capable of further
+extension, for wherever in nature we come upon degeneration, it is
+taking place by minute steps and with a slowness that makes it not
+directly perceptible, and I believe that this in itself justifies us in
+concluding that THE SAME MUST BE TRUE OF ASCENDING evolution. But in the
+latter case the goal can seldom be distinctly recognised while in cases
+of degeneration the starting-point of the process can often be inferred,
+because several nearly related species may represent different stages.
+
+In recent years Bateson in particular has championed the idea of
+saltatory, or so-called discontinuous evolution, and has collected a
+number of cases in which more or less marked variations have suddenly
+appeared. These are taken for the most part from among domesticated
+animals which have been bred and crossed for a long time, and it is
+hardly to be wondered at that their much mixed and much influenced
+germ-plasm should, under certain conditions, give rise to remarkable
+phenomena, often indeed producing forms which are strongly suggestive of
+monstrosities, and which would undoubtedly not survive in free nature,
+unprotected by man. I should regard such cases as due to an intensified
+germinal selection--though this is to anticipate a little--and from this
+point of view it cannot be denied that they have a special interest. But
+they seem to me to have no significance as far as the transformation
+of species is concerned, if only because of the extreme rarity of their
+occurrence.
+
+There are, however, many variations which have appeared in a sudden and
+saltatory manner, and some of these Darwin pointed out and discussed
+in detail: the copper beech, the weeping trees, the oak with "fern-like
+leaves," certain garden-flowers, etc. But none of them have persisted in
+free nature, or evolved into permanent types.
+
+On the other hand, wherever enduring types have arisen, we find traces
+of a gradual origin by successive stages, even if, at first sight, their
+origin may appear to have been sudden. This is the case with SEASONAL
+DIMORPHISM, the first known cases of which exhibited marked differences
+between the two generations, the winter and the summer brood. Take
+for instance the much discussed and studied form Vanessa (Araschnia)
+levana-prorsa. Here the differences between the two forms are so great
+and so apparently disconnected, that one might almost believe it to be
+a sudden mutation, were it not that old transition-stages can be called
+forth by particular temperatures, and we know other butterflies, as for
+instance our Garden Whites, in which the differences between the
+two generations are not nearly so marked; indeed, they are so little
+apparent that they are scarcely likely to be noticed except by experts.
+Thus here again there are small initial steps, some of which, indeed,
+must be regarded as adaptations, such as the green-sprinkled or lightly
+tinted under-surface which gives them a deceptive resemblance to parsley
+or to Cardamine leaves.
+
+Even if saltatory variations do occur, we cannot assume that these HAVE
+EVER LED TO FORMS WHICH ARE CAPABLE OF SURVIVAL UNDER THE CONDITIONS
+OF WILD LIFE. Experience has shown that in plants which have suddenly
+varied the power of persistence is diminished. Korschinksky attributes
+to them weaknesses of organisation in general; "they bloom late, ripen
+few of their seeds, and show great sensitiveness to cold." These are not
+the characters which make for success in the struggle for existence.
+
+We must briefly refer here to the views--much discussed in the last
+decade--of H. de Vries, who believes that the roots of transformation
+must be sought for in SALTATORY VARIATIONS ARISING FROM INTERNAL CAUSES,
+and distinguishes such MUTATIONS, as he has called them, from ordinary
+individual variations, in that they breed true, that is, with strict
+inbreeding they are handed on pure to the next generation. I have
+elsewhere endeavoured to point out the weaknesses of this theory
+("Vortrage uber Descendenztheorie", Jena, 1904, II. 269. English
+Translation London, 1904, II. page 317.), and I am the less inclined
+to return to it here that it now appears (See Poulton, "Essays on
+Evolution", Oxford, 1908, pages xix-xxii.) that the far-reaching
+conclusions drawn by de Vries from his observations on the Evening
+Primrose, Oenothera lamarckiana, rest upon a very insecure
+foundation. The plant from which de Vries saw numerous "species"--his
+"mutations"--arise was not, as he assumed, a WILD SPECIES that had been
+introduced to Europe from America, but was probably a hybrid form which
+was first discovered in the Jardin des Plantes in Paris, and which does
+not appear to exist anywhere in America as a wild species.
+
+This gives a severe shock to the "Mutation theory," for the other
+ACTUALLY WILD species with which de Vries experimented showed no
+"mutations" but yielded only negative results.
+
+Thus we come to the conclusion that Darwin ("Origin of Species" (6th
+edition), pages 176 et seq.) was right in regarding transformations as
+taking place by minute steps, which, if useful, are augmented in
+the course of innumerable generations, because their possessors more
+frequently survive in the struggle for existence.
+
+(b) SELECTION-VALUE OF THE INITIAL STEPS.
+
+Is it possible that the significant deviations which we know as
+"individual variations" can form the beginning of a process of
+selection? Can they decide which is to perish and which to survive? To
+use a phrase of Romanes, can they have SELECTION-VALUE?
+
+Darwin himself answered this question, and brought together many
+excellent examples to show that differences, apparently insignificant
+because very small, might be of decisive importance for the life of the
+possessor. But it is by no means enough to bring forward cases of this
+kind, for the question is not merely whether finished adaptations have
+selection-value, but whether the first beginnings of these, and whether
+the small, I might almost say minimal increments, which have led up
+from these beginnings to the perfect adaptation, have also had
+selection-value. To this question even one who, like myself, has been
+for many years a convinced adherent of the theory of selection, can only
+reply: WE MUST ASSUME SO, BUT WE CANNOT PROVE IT IN ANY CASE. It is not
+upon demonstrative evidence that we rely when we champion the doctrine
+of selection as a scientific truth; we base our argument on quite other
+grounds. Undoubtedly there are many apparently insignificant features,
+which can nevertheless be shown to be adaptations--for instance, the
+thickness of the basin-shaped shell of the limpets that live among the
+breakers on the shore. There can be no doubt that the thickness of these
+shells, combined with their flat form, protects the animals from the
+force of the waves breaking upon them,--but how have they become so
+thick? What proportion of thickness was sufficient to decide that of two
+variants of a limpet one should survive, the other be eliminated? We can
+say nothing more than that we infer from the present state of the shell,
+that it must have varied in regard to differences in shell-thickness,
+and that these differences must have had selection-value,--no proof
+therefore, but an assumption which we must show to be convincing.
+
+For a long time the marvellously complex RADIATE and LATTICE-WORK
+skeletons of Radiolarians were regarded as a mere outflow of "Nature's
+infinite wealth of form," as an instance of a purely morphological
+character with no biological significance. But recent investigations
+have shown that these, too, have an adaptive significance (Hacker). The
+same thing has been shown by Schutt in regard to the lowly unicellular
+plants, the Peridineae, which abound alike on the surface of the ocean
+and in its depths. It has been shown that the long skeletal processes
+which grow out from these organisms have significance not merely as a
+supporting skeleton, but also as an extension of the superficial area,
+which increases the contact with the water-particles, and prevents
+the floating organisms from sinking. It has been established that the
+processes are considerably shorter in the colder layers of the ocean,
+and that they may be twelve times as long (Chun, "Reise der Valdivia",
+Leipzig, 1904.) in the warmer layers, thus corresponding to the greater
+or smaller amount of friction which takes place in the denser and less
+dense layers of the water.
+
+The Peridineae of the warmer ocean layers have thus become long-rayed,
+those of the colder layers short-rayed, not through the direct effect
+of friction on the protoplasm, but through processes of selection, which
+favoured the longer rays in warm water, since they kept the organism
+afloat, while those with short rays sank and were eliminated. If we put
+the question as to selection-value in this case, and ask how great
+the variations in the length of processes must be in order to possess
+selection-value; what can we answer except that these variations must
+have been minimal, and yet sufficient to prevent too rapid sinking
+and consequent elimination? Yet this very case would give the
+ideal opportunity for a mathematical calculation of the minimal
+selection-value, although of course it is not feasible from lack of data
+to carry out the actual calculation.
+
+But even in organisms of more than microscopic size there must
+frequently be minute, even microscopic differences which set going the
+process of selection, and regulate its progress to the highest possible
+perfection.
+
+Many tropical trees possess thick, leathery leaves, as a protection
+against the force of the tropical rain drops. The DIRECT influence
+of the rain cannot be the cause of this power of resistance, for the
+leaves, while they were still thin, would simply have been torn to
+pieces. Their toughness must therefore be referred to selection, which
+would favour the trees with slightly thicker leaves, though we cannot
+calculate with any exactness how great the first stages of increase in
+thickness must have been. Our hypothesis receives further support from
+the fact that, in many such trees, the leaves are drawn out into a
+beak-like prolongation (Stahl and Haberlandt) which facilitates the
+rapid falling off of the rain water, and also from the fact that the
+leaves, while they are still young, hang limply down in bunches which
+offer the least possible resistance to the rain. Thus there are here
+three adaptations which can only be interpreted as due to selection.
+The initial stages of these adaptations must undoubtedly have had
+selection-value.
+
+But even in regard to this case we are reasoning in a circle, not giving
+"proofs," and no one who does not wish to believe in the selection-value
+of the initial stages can be forced to do so. Among the many pieces of
+presumptive evidence a particularly weighty one seems to me to be THE
+SMALLNESS OF THE STEPS OF PROGRESS which we can observe in certain
+cases, as for instance in leaf-imitation among butterflies, and
+in mimicry generally. The resemblance to a leaf, for instance of a
+particular Kallima, seems to us so close as to be deceptive, and yet we
+find in another individual, or it may be in many others, a spot added
+which increases the resemblance, and which could not have become fixed
+unless the increased deceptiveness so produced had frequently led to
+the overlooking of its much persecuted possessor. But if we take the
+selection-value of the initial stages for granted, we are confronted
+with the further question which I myself formulated many years ago: How
+does it happen THAT THE NECESSARY BEGINNINGS OF A USEFUL VARIATION ARE
+ALWAYS PRESENT? How could insects which live upon or among green leaves
+become all green, while those that live on bark become brown? How have
+the desert animals become yellow and the Arctic animals white? Why were
+the necessary variations always present? How could the green locust lay
+brown eggs, or the privet caterpillar develop white and lilac-coloured
+lines on its green skin?
+
+It is of no use answering to this that the question is wrongly
+formulated (Plate, "Selektionsprinzip u. Probleme der Artbildung" (3rd
+edition), Leipzig, 1908.) and that it is the converse that is true; that
+the process of selection takes place in accordance with the variations
+that present themselves. This proposition is undeniably true, but so
+also is another, which apparently negatives it: the variation required
+has in the majority of cases actually presented itself. Selection cannot
+solve this contradiction; it does not call forth the useful variation,
+but simply works upon it. The ultimate reason why one and the same
+insect should occur in green and in brown, as often happens in
+caterpillars and locusts, lies in the fact that variations towards brown
+presented themselves, and so also did variations towards green: THE
+KERNEL OF THE RIDDLE LIES IN THE VARYING, and for the present we
+can only say, that small variations in different directions present
+themselves in every species. Otherwise so many different kinds of
+variations could not have arisen. I have endeavoured to explain this
+remarkable fact by means of the intimate processes that must take place
+within the germ-plasm, and I shall return to the problem when dealing
+with "germinal selection."
+
+We have, however, to make still greater demands on variation, for it
+is not enough that the necessary variation should occur in isolated
+individuals, because in that case there would be small prospect of its
+being preserved, notwithstanding its utility. Darwin at first believed,
+that even single variations might lead to transformation of the species,
+but later he became convinced that this was impossible, at least
+without the cooperation of other factors, such as isolation and sexual
+selection.
+
+In the case of the GREEN CATERPILLARS WITH BRIGHT LONGITUDINAL STRIPES,
+numerous individuals exhibiting this useful variation must have been
+produced to start with. In all higher, that is, multicellular organisms,
+the germ-substance is the source of all transmissible variations, and
+this germ-plasm is not a simple substance but is made up of many primary
+constituents. The question can therefore be more precisely stated thus:
+How does it come about that in so many cases the useful variations
+present themselves in numbers just where they are required, the white
+oblique lines in the leaf-caterpillar on the under surface of the body,
+the accompanying coloured stripes just above them? And, further, how has
+it come about that in grass caterpillars, not oblique but longitudinal
+stripes, which are more effective for concealment among grass and
+plants, have been evolved? And finally, how is it that the same
+Hawk-moth caterpillars, which to-day show oblique stripes, possessed
+longitudinal stripes in Tertiary times? We can read this fact from the
+history of their development, and I have before attempted to show
+the biological significance of this change of colour. ("Studien
+zur Descendenz-Theorie" II., "Die Enstehung der Zeichnung bei den
+Schmetterlings-raupen," Leipzig, 1876.)
+
+For the present I need only draw the conclusion that one and the same
+caterpillar may exhibit the initial stages of both, and that it depends
+on the manner in which these marking elements are INTENSIFIED and
+COMBINED by natural selection whether whitish longitudinal or oblique
+stripes should result. In this case then the "useful variations"
+were actually "always there," and we see that in the same group of
+Lepidoptera, e.g. species of Sphingidae, evolution has occurred in both
+directions according to whether the form lived among grass or on broad
+leaves with oblique lateral veins, and we can observe even now that the
+species with oblique stripes have longitudinal stripes when young, that
+is to say, while the stripes have no biological significance. The white
+places in the skin which gave rise, probably first as small spots,
+to this protective marking could be combined in one way or another
+according to the requirements of the species. They must therefore either
+have possessed selection-value from the first, or, if this was not
+the case at their earliest occurrence, there must have been SOME OTHER
+FACTORS which raised them to the point of selection-value. I shall
+return to this in discussing germinal selection. But the case may be
+followed still farther, and leads us to the same alternative on a still
+more secure basis.
+
+Many years ago I observed in caterpillars of Smerinthus populi (the
+poplar hawk-moth), which also possess white oblique stripes, that
+certain individuals showed RED SPOTS above these stripes; these spots
+occurred only on certain segments, and never flowed together to form
+continuous stripes. In another species (Smerinthus tiliae) similar
+blood-red spots unite to form a line-like coloured seam in the last
+stage of larval life, while in S. ocellata rust-red spots appear in
+individual caterpillars, but more rarely than in S. Populi, and they
+show no tendency to flow together.
+
+Thus we have here the origin of a new character, arising from small
+beginnings, at least in S. tiliae, in which species the coloured stripes
+are a normal specific character. In the other species, S. populi and
+S. ocellata, we find the beginnings of the same variation, in one more
+rarely than in the other, and we can imagine that, in the course of
+time, in these two species, coloured lines over the oblique stripes will
+arise. In any case these spots are the elements of variation, out
+of which coloured lines MAY be evolved, if they are combined in this
+direction through the agency of natural selection. In S. populi the
+spots are often small, but sometimes it seems as though several had
+united to form large spots. Whether a process of selection in this
+direction will arise in S. populi and S. ocellata, or whether it is
+now going on cannot be determined, since we cannot tell in advance what
+biological value the marking might have for these two species. It is
+conceivable that the spots may have no selection-value as far as these
+species are concerned, and may therefore disappear again in the course
+of phylogeny, or, on the other hand, that they may be changed in another
+direction, for instance towards imitation of the rust-red fungoid
+patches on poplar and willow leaves. In any case we may regard the
+smallest spots as the initial stages of variation, the larger as a
+cumulative summation of these. Therefore either these initial stages
+must already possess selection-value, or, as I said before: THERE MUST
+BE SOME OTHER REASON FOR THEIR CUMULATIVE SUMMATION. I should like to
+give one more example, in which we can infer, though we cannot directly
+observe, the initial stages.
+
+All the Holothurians or sea-cucumbers have in the skin calcareous bodies
+of different forms, usually thick and irregular, which make the
+skin tough and resistant. In a small group of them--the species of
+Synapta--the calcareous bodies occur in the form of delicate anchors of
+microscopic size. Up till 1897 these anchors, like many other delicate
+microscopic structures, were regarded as curiosities, as natural
+marvels. But a Swedish observer, Oestergren, has recently shown that
+they have a biological significance: they serve the footless Synapta as
+auxiliary organs of locomotion, since, when the body swells up in the
+act of creeping, they press firmly with their tips, which are embedded
+in the skin, against the substratum on which the animal creeps, and thus
+prevent slipping backwards. In other Holothurians this slipping is
+made impossible by the fixing of the tube-feet. The anchors act
+automatically, sinking their tips towards the ground when the
+corresponding part of the body thickens, and returning to the original
+position at an angle of 45 degrees to the upper surface when the part
+becomes thin again. The arms of the anchor do not lie in the same plane
+as the shaft, and thus the curve of the arms forms the outermost part
+of the anchor, and offers no further resistance to the gliding of the
+animal. Every detail of the anchor, the curved portion, the little teeth
+at the head, the arms, etc., can be interpreted in the most beautiful
+way, above all the form of the anchor itself, for the two arms prevent
+it from swaying round to the side. The position of the anchors, too, is
+definite and significant; they lie obliquely to the longitudinal axis of
+the animal, and therefore they act alike whether the animal is creeping
+backwards or forwards. Moreover, the tips would pierce through the skin
+if the anchors lay in the longitudinal direction. Synapta burrows in the
+sand; it first pushes in the thin anterior end, and thickens this again,
+thus enlarging the hole, then the anterior tentacles displace more sand,
+the body is worked in a little farther, and the process begins anew. In
+the first act the anchors are passive, but they begin to take an
+active share in the forward movement when the body is contracted again.
+Frequently the animal retains only the posterior end buried in the sand,
+and then the anchors keep it in position, and make rapid withdrawal
+possible.
+
+Thus we have in these apparently random forms of the calcareous bodies,
+complex adaptations in which every little detail as to direction, curve,
+and pointing is exactly determined. That they have selection-value in
+their present perfected form is beyond all doubt, since the animals
+are enabled by means of them to bore rapidly into the ground and so to
+escape from enemies. We do not know what the initial stages were, but we
+cannot doubt that the little improvements, which occurred as variations
+of the originally simple slimy bodies of the Holothurians, were
+preserved because they already possessed selection-value for the
+Synaptidae. For such minute microscopic structures whose form is so
+delicately adapted to the role they have to play in the life of the
+animal, cannot have arisen suddenly and as a whole, and every new
+variation of the anchor, that is, in the direction of the development
+of the two arms, and every curving of the shaft which prevented the tips
+from projecting at the wrong time, in short, every little adaptation
+in the modelling of the anchor must have possessed selection-value. And
+that such minute changes of form fall within the sphere of fluctuating
+variations, that is to say, THAT THEY OCCUR is beyond all doubt.
+
+In many of the Synaptidae the anchors are replaced by calcareous rods
+bent in the form of an S, which are said to act in the same way. Others,
+such as those of the genus Ankyroderma, have anchors which project
+considerably beyond the skin, and, according to Oestergren, serve "to
+catch plant-particles and other substances" and so mask the animal. Thus
+we see that in the Synaptidae the thick and irregular calcareous bodies
+of the Holothurians have been modified and transformed in various ways
+in adaptation to the footlessness of these animals, and to the peculiar
+conditions of their life, and we must conclude that the earlier stages
+of these changes presented themselves to the processes of selection in
+the form of microscopic variations. For it is as impossible to think of
+any origin other than through selection in this case as in the case of
+the toughness, and the "drip-tips" of tropical leaves. And as these
+last could not have been produced directly by the beating of the heavy
+rain-drops upon them, so the calcareous anchors of Synapta cannot have
+been produced directly by the friction of the sand and mud at the bottom
+of the sea, and, since they are parts whose function is PASSIVE the
+Lamarckian factor of use and disuse does not come into question. The
+conclusion is unavoidable, that the microscopically small variations of
+the calcareous bodies in the ancestral forms have been intensified
+and accumulated in a particular direction, till they have led to the
+formation of the anchor. Whether this has taken place by the action
+of natural selection alone, or whether the laws of variation and the
+intimate processes within the germ-plasm have cooperated will become
+clear in the discussion of germinal selection. This whole process of
+adaptation has obviously taken place within the time that has
+elapsed since this group of sea-cucumbers lost their tube-feet, those
+characteristic organs of locomotion which occur in no group except the
+Echinoderms, and yet have totally disappeared in the Synaptidae.
+And after all what would animals that live in sand and mud do with
+tube-feet?
+
+(c) COADAPTATION.
+
+Darwin pointed out that one of the essential differences between
+artificial and natural selection lies in the fact that the former can
+modify only a few characters, usually only one at a time, while Nature
+preserves in the struggle for existence all the variations of a species,
+at the same time and in a purely mechanical way, if they possess
+selection-value.
+
+Herbert Spencer, though himself an adherent of the theory of selection,
+declared in the beginning of the nineties that in his opinion the range
+of this principle was greatly over-estimated, if the great changes which
+have taken place in so many organisms in the course of ages are to
+be interpreted as due to this process of selection alone, since no
+transformation of any importance can be evolved by itself; it is always
+accompanied by a host of secondary changes. He gives the familiar
+example of the Giant Stag of the Irish peat, the enormous antlers of
+which required not only a much stronger skull cap, but also greater
+strength of the sinews, muscles, nerves and bones of the whole anterior
+half of the animal, if their mass was not to weigh down the animal
+altogether. It is inconceivable, he says, that so many processes of
+selection should take place SIMULTANEOUSLY, and we are therefore
+forced to fall back on the Lamarckian factor of the use and disuse of
+functional parts. And how, he asks, could natural selection follow two
+opposite directions of evolution in different parts of the body at the
+same time, as for instance in the case of the kangaroo, in which the
+forelegs must have become shorter, while the hind legs and the tail were
+becoming longer and stronger?
+
+Spencer's main object was to substantiate the validity of the Lamarckian
+principle, the cooperation of which with selection had been doubted
+by many. And it does seem as though this principle, if it operates
+in nature at all, offers a ready and simple explanation of all such
+secondary variations. Not only muscles, but nerves, bones, sinews,
+in short all tissues which function actively, increase in strength
+in proportion as they are used, and conversely they decrease when the
+claims on them diminish. All the parts, therefore, which depend on the
+part that varied first, as for instance the enlarged antlers of the
+Irish Elk, must have been increased or decreased in strength, in exact
+proportion to the claims made upon them,--just as is actually the case.
+
+But beautiful as this explanation would be, I regard it as untenable,
+because it assumes the TRANSMISSIBILITY OF FUNCTIONAL MODIFICATIONS
+(so-called "acquired" characters), and this is not only undemonstrable,
+but is scarcely theoretically conceivable, for the secondary variations
+which accompany or follow the first as correlative variations, occur
+also in cases in which the animals concerned are sterile and THEREFORE
+CANNOT TRANSMIT ANYTHING TO THEIR DESCENDANTS. This is true of WORKER
+BEES, and particularly of ANTS, and I shall here give a brief survey of
+the present state of the problem as it appears to me.
+
+Much has been written on both sides of this question since the published
+controversy on the subject in the nineties between Herbert Spencer and
+myself. I should like to return to the matter in detail, if the space
+at my disposal permitted, because it seems to me that the arguments I
+advanced at that time are equally cogent to-day, notwithstanding all the
+objections that have since been urged against them. Moreover, the matter
+is by no means one of subordinate interest; it is the very kernel of the
+whole question of the reality and value of the principle of selection.
+For if selection alone does not suffice to explain "HARMONIOUS
+ADAPTATION" as I have called Spencer's COADAPTATION, and if we require
+to call in the aid of the Lamarckian factor it would be questionable
+whether selection could explain any adaptations whatever. In this
+particular case--of worker bees--the Lamarckian factor may be excluded
+altogether, for it can be demonstrated that here at any rate the effects
+of use and disuse cannot be transmitted.
+
+But if it be asked why we are unwilling to admit the cooperation of
+the Darwinian factor of selection and the Lamarckian factor, since this
+would afford us an easy and satisfactory explanation of the phenomena,
+I answer: BECAUSE THE LAMARCKIAN PRINCIPLE IS FALLACIOUS, AND BECAUSE BY
+ACCEPTING IT WE CLOSE THE WAY TOWARDS DEEPER INSIGHT. It is not a spirit
+of combativeness or a desire for self-vindication that induces me to
+take the field once more against the Lamarckian principle, it is the
+conviction that the progress of our knowledge is being obstructed by the
+acceptance of this fallacious principle, since the facile explanation it
+apparently affords prevents our seeking after a truer explanation and a
+deeper analysis.
+
+The workers in the various species of ants are sterile, that is to say,
+they take no regular part in the reproduction of the species, although
+individuals among them may occasionally lay eggs. In addition to this
+they have lost the wings, and the receptaculum seminis, and their
+compound eyes have degenerated to a few facets. How could this last
+change have come about through disuse, since the eyes of workers are
+exposed to light in the same way as are those of the sexual insects and
+thus in this particular case are not liable to "disuse" at all? The same
+is true of the receptaculum seminis, which can only have been disused
+as far as its glandular portion and its stalk are concerned, and also
+of the wings, the nerves tracheae and epidermal cells of which could
+not cease to function until the whole wing had degenerated, for the
+chitinous skeleton of the wing does not function at all in the active
+sense.
+
+But, on the other hand, the workers in all species have undergone
+modifications in a positive direction, as, for instance, the greater
+development of brain. In many species large workers have evolved,--the
+so-called SOLDIERS, with enormous jaws and teeth, which defend the
+colony,--and in others there are SMALL workers which have taken over
+other special functions, such as the rearing of the young Aphides. This
+kind of division of the workers into two castes occurs among several
+tropical species of ants, but it is also present in the Italian species,
+Colobopsis truncata. Beautifully as the size of the jaws could be
+explained as due to the increased use made of them by the "soldiers," or
+the enlarged brain as due to the mental activities of the workers, the
+fact of the infertility of these forms is an insurmountable obstacle
+to accepting such an explanation. Neither jaws nor brain can have been
+evolved on the Lamarckian principle.
+
+The problem of coadaptation is no easier in the case of the ant than in
+the case of the Giant Stag. Darwin himself gave a pretty illustration to
+show how imposing the difference between the two kinds of workers in one
+species would seem if we translated it into human terms. In regard to
+the Driver ants (Anomma) we must picture to ourselves a piece of work,
+"for instance the building of a house, being carried on by two kinds of
+workers, of which one group was five feet four inches high, the other
+sixteen feet high." ("Origin of Species" (6th edition), page 232.)
+
+Although the ant is a small animal as compared with man or with the
+Irish Elk, the "soldier" with its relatively enormous jaws is hardly
+less heavily burdened than the Elk with its antlers, and in the ant's
+case, too, a strengthening of the skeleton, of the muscles, the nerves
+of the head, and of the legs must have taken place parallel with the
+enlargement of the jaws. HARMONIOUS ADAPTATION (coadaptation) has here
+been active in a high degree, and yet these "soldiers" are sterile!
+There thus remains nothing for it but to refer all their adaptations,
+positive and negative alike, to processes of selection which have taken
+place in the rudiments of the workers within the egg and sperm-cells
+of their parents. There is no way out of the difficulty except the one
+Darwin pointed out. He himself did not find the solution of the riddle
+at once. At first he believed that the case of the workers among social
+insects presented "the most serious special difficulty" in the way of
+his theory of natural selection; and it was only after it had become
+clear to him, that it was not the sterile insects themselves but their
+parents that were selected, according as they produced more or less
+well adapted workers, that he was able to refer to this very case of the
+conditions among ants "IN ORDER TO SHOW THE POWER OF NATURAL SELECTION"
+("Origin of Species", page 233; see also edition 1, page 242.). He
+explains his view by a simple but interesting illustration. Gardeners
+have produced, by means of long continued artificial selection, a
+variety of Stock, which bears entirely double, and therefore infertile
+flowers (Ibid. page 230.). Nevertheless the variety continues to be
+reproduced from seed, because in addition to the double and infertile
+flowers, the seeds always produce a certain number of single, fertile
+blossoms, and these are used to reproduce the double variety. These
+single and fertile plants correspond "to the males and females of an
+ant-colony, the infertile plants, which are regularly produced in large
+numbers, to the neuter workers of the colony."
+
+This illustration is entirely apt, the only difference between the two
+cases consisting in the fact that the variation in the flower is not
+a useful, but a disadvantageous one, which can only be preserved
+by artificial selection on the part of the gardener, while the
+transformations that have taken place parallel with the sterility of the
+ants are useful, since they procure for the colony an advantage in the
+struggle for existence, and they are therefore preserved by
+natural selection. Even the sterility itself in this case is not
+disadvantageous, since the fertility of the true females has at the same
+time considerably increased. We may therefore regard the sterile forms
+of ants, which have gradually been adapted in several directions to
+varying functions, AS A CERTAIN PROOF that selection really takes place
+in the germ-cells of the fathers and mothers of the workers, and that
+SPECIAL COMPLEXES OF PRIMORDIA (IDS) are present in the workers and in
+the males and females, and these complexes contain the primordia of the
+individual parts (DETERMINANTS). But since all living entities vary, the
+determinants must also vary, now in a favourable, now in an unfavourable
+direction. If a female produces eggs, which contain favourably varying
+determinants in the worker-ids, then these eggs will give rise to
+workers modified in the favourable direction, and if this happens with
+many females, the colony concerned will contain a better kind of worker
+than other colonies.
+
+I digress here in order to give an account of the intimate processes,
+which, according to my view, take place within the germ-plasm, and which
+I have called "GERMINAL SELECTION." These processes are of importance
+since they form the roots of variation, which in its turn is the root
+of natural selection. I cannot here do more than give a brief outline of
+the theory in order to show how the Darwin-Wallace theory of selection
+has gained support from it.
+
+With others, I regard the minimal amount of substance which is contained
+within the nucleus of the germ-cells, in the form of rods, bands, or
+granules, as the GERM-SUBSTANCE or GERM-PLASM, and I call the individual
+granules IDS. There is always a multiplicity of such ids present in the
+nucleus, either occurring individually, or united in the form of rods
+or bands (chromosomes). Each id contains the primary constituents of a
+WHOLE individual, so that several ids are concerned in the development
+of a new individual.
+
+In every being of complex structure thousands of primary constituents
+must go to make up a single id; these I call DETERMINANTS, and I mean
+by this name very small individual particles, far below the limits of
+microscopic visibility, vital units which feed, grow, and multiply
+by division. These determinants control the parts of the developing
+embryo,--in what manner need not here concern us. The determinants
+differ among themselves, those of a muscle are differently constituted
+from those of a nerve-cell or a glandular cell, etc., and every
+determinant is in its turn made up of minute vital units, which I
+call BIOPHORS, or the bearers of life. According to my view, these
+determinants not only assimilate, like every other living unit, but they
+VARY in the course of their growth, as every living unit does; they may
+vary qualitatively if the elements of which they are composed vary, they
+may grow and divide more or less rapidly, and their variations give rise
+to CORRESPONDING variations of the organ, cell, or cell-group which they
+determine. That they are undergoing ceaseless fluctuations in regard to
+size and quality seems to me the inevitable consequence of their unequal
+nutrition; for although the germ-cell as a whole usually receives
+sufficient nutriment, minute fluctuations in the amount carried to
+different parts within the germ-plasm cannot fail to occur.
+
+Now, if a determinant, for instance of a sensory cell, receives for a
+considerable time more abundant nutriment than before, it will grow more
+rapidly--become bigger, and divide more quickly, and, later, when the
+id concerned develops into an embryo, this sensory cell will become
+stronger than in the parents, possibly even twice as strong. This is an
+instance of a HEREDITARY INDIVIDUAL VARIATION, arising from the germ.
+
+The nutritive stream which, according to our hypothesis, favours the
+determinant N by chance, that is, for reasons unknown to us, may remain
+strong for a considerable time, or may decrease again; but even in
+the latter case it is conceivable that the ascending movement of the
+determinant may continue, because the strengthened determinant now
+ACTIVELY nourishes itself more abundantly,--that is to say, it attracts
+the nutriment to itself, and to a certain extent withdraws it from its
+fellow-determinants. In this way, it may--as it seems to me--get into
+PERMANENT UPWARD MOVEMENT, AND ATTAIN A DEGREE OF STRENGTH FROM WHICH
+THERE IS NO FALLING BACK. Then positive or negative selection sets in,
+favouring the variations which are advantageous, setting aside those
+which are disadvantageous.
+
+In a similar manner a DOWNWARD variation of the determinants may take
+place, if its progress be started by a diminished flow of nutriment. The
+determinants which are weakened by this diminished flow will have less
+affinity for attracting nutriment because of their diminished strength,
+and they will assimilate more feebly and grow more slowly, unless chance
+streams of nutriment help them to recover themselves. But, as will
+presently be shown, a change of direction cannot take place at EVERY
+stage of the degenerative process. If a certain critical stage of
+downward progress be passed, even favourable conditions of food-supply
+will no longer suffice permanently to change the direction of
+the variation. Only two cases are conceivable; if the determinant
+corresponds to a USEFUL organ, only its removal can bring back the
+germ-plasm to its former level; therefore personal selection removes the
+id in question, with its determinants, from the germ-plasm, by causing
+the elimination of the individual in the struggle for existence. But
+there is another conceivable case; the determinants concerned may be
+those of an organ which has become USELESS, and they will then continue
+unobstructed, but with exceeding slowness, along the downward path,
+until the organ becomes vestigial, and finally disappears altogether.
+
+The fluctuations of the determinants hither and thither may thus be
+transformed into a lasting ascending or descending movement; and THIS IS
+THE CRUCIAL POINT OF THESE GERMINAL PROCESSES.
+
+This is not a fantastic assumption; we can read it in the fact of the
+degeneration of disused parts. USELESS ORGANS ARE THE ONLY ONES WHICH
+ARE NOT HELPED TO ASCEND AGAIN BY PERSONAL SELECTION, AND THEREFORE IN
+THEIR CASE ALONE CAN WE FORM ANY IDEA OF HOW THE PRIMARY CONSTITUENTS
+BEHAVE, WHEN THEY ARE SUBJECT SOLELY TO INTRA-GERMINAL FORCES.
+
+The whole determinant system of an id, as I conceive it, is in a state
+of continual fluctuation upwards and downwards. In most cases the
+fluctuations will counteract one another, because the passive streams of
+nutriment soon change, but in many cases the limit from which a return
+is possible will be passed, and then the determinants concerned will
+continue to vary in the same direction, till they attain positive or
+negative selection-value. At this stage personal selection intervenes
+and sets aside the variation if it is disadvantageous, or favours--that
+is to say, preserves--it if it is advantageous. Only THE DETERMINANT
+OF A USELESS ORGAN IS UNINFLUENCED BY PERSONAL SELECTION, and,
+as experience shows, it sinks downwards; that is, the organ that
+corresponds to it degenerates very slowly but uninterruptedly till,
+after what must obviously be an immense stretch of time, it disappears
+from the germ-plasm altogether.
+
+Thus we find in the fact of the degeneration of disused parts the proof
+that not all the fluctuations of a determinant return to equilibrium
+again, but that, when the movement has attained to a certain strength,
+it continues IN THE SAME DIRECTION. We have entire certainty in regard
+to this as far as the downward progress is concerned, and we must
+assume it also in regard to ascending variations, as the phenomena of
+artificial selection certainly justify us in doing. If the Japanese
+breeders were able to lengthen the tail feathers of the cock to
+six feet, it can only have been because the determinants of the
+tail-feathers in the germ-plasm had already struck out a path of
+ascending variation, and this movement was taken advantage of by the
+breeder, who continually selected for reproduction the individuals in
+which the ascending variation was most marked. For all breeding depends
+upon the unconscious selection of germinal variations.
+
+Of course these germinal processes cannot be proved mathematically,
+since we cannot actually see the play of forces of the passive
+fluctuations and their causes. We cannot say how great these
+fluctuations are, and how quickly or slowly, how regularly or
+irregularly they change. Nor do we know how far a determinant must be
+strengthened by the passive flow of the nutritive stream if it is to
+be beyond the danger of unfavourable variations, or how far it must be
+weakened passively before it loses the power of recovering itself by its
+own strength. It is no more possible to bring forward actual proofs in
+this case than it was in regard to the selection-value of the initial
+stages of an adaptation. But if we consider that all heritable
+variations must have their roots in the germ-plasm, and further, that
+when personal selection does not intervene, that is to say, in the case
+of parts which have become useless, a degeneration of the part, and
+therefore also of its determinant must inevitably take place; then we
+must conclude that processes such as I have assumed are running their
+course within the germ-plasm, and we can do this with as much certainty
+as we were able to infer, from the phenomena of adaptation, the
+selection-value of their initial stages. The fact of the degeneration
+of disused parts seems to me to afford irrefutable proof that the
+fluctuations within the germ-plasm ARE THE REAL ROOT OF ALL HEREDITARY
+VARIATION, and the preliminary condition for the occurrence of the
+Darwin-Wallace factor of selection. Germinal selection supplies the
+stones out of which personal selection builds her temples and
+palaces: ADAPTATIONS. The importance for the theory of the process of
+degeneration of disused parts cannot be over-estimated, especially when
+it occurs in sterile animal forms, where we are free from the doubt as
+to the alleged LAMARCKIAN FACTOR which is apt to confuse our ideas in
+regard to other cases.
+
+If we regard the variation of the many determinants concerned in the
+transformation of the female into the sterile worker as having come
+about through the gradual transformation of the ids into worker-ids,
+we shall see that the germ-plasm of the sexual ants must contain three
+kinds of ids, male, female, and worker ids, or if the workers have
+diverged into soldiers and nest-builders, then four kinds. We understand
+that the worker-ids arose because their determinants struck out a useful
+path of variation, whether upward or downward, and that they continued
+in this path until the highest attainable degree of utility of the parts
+determined was reached. But in addition to the organs of positive or
+negative selection-value, there were some which were indifferent as far
+as the success and especially the functional capacity of the workers was
+concerned: wings, ovarian tubes, receptaculum seminis, a number of the
+facets of the eye, perhaps even the whole eye. As to the ovarian tubes
+it is possible that their degeneration was an advantage for the workers,
+in saving energy, and if so selection would favour the degeneration; but
+how could the presence of eyes diminish the usefulness of the workers to
+the colony? or the minute receptaculum seminis, or even the wings? These
+parts have therefore degenerated BECAUSE THEY WERE OF NO FURTHER VALUE
+TO THE INSECT. But if selection did not influence the setting aside of
+these parts because they were neither of advantage nor of disadvantage
+to the species, then the Darwinian factor of selection is here
+confronted with a puzzle which it cannot solve alone, but which at once
+becomes clear when germinal selection is added. For the determinants
+of organs that have no further value for the organism, must, as we have
+already explained, embark on a gradual course of retrograde development.
+
+In ants the degeneration has gone so far that there are no
+wing-rudiments present in ANY species, as is the case with so many
+butterflies, flies, and locusts, but in the larvae the imaginal discs of
+the wings are still laid down. With regard to the ovaries, degeneration
+has reached different levels in different species of ants, as has been
+shown by the researches of my former pupil, Elizabeth Bickford. In many
+species there are twelve ovarian tubes, and they decrease from that
+number to one; indeed, in one species no ovarian tube at all is present.
+So much at least is certain from what has been said, that in this
+case EVERYTHING depends on the fluctuations of the elements of the
+germ-plasm. Germinal selection, here as elsewhere, presents the
+variations of the determinants, and personal selection favours or
+rejects these, or,--if it be a question of organs which have become
+useless,--it does not come into play at all, and allows the descending
+variation free course.
+
+It is obvious that even the problem of COADAPTATION IN STERILE
+ANIMALS can thus be satisfactorily explained. If the determinants are
+oscillating upwards and downwards in continual fluctuation, and
+varying more pronouncedly now in one direction now in the other, useful
+variations of every determinant will continually present themselves
+anew, and may, in the course of generations, be combined with one
+another in various ways. But there is one character of the determinants
+that greatly facilitates this complex process of selection, that,
+after a certain limit has been reached, they go on varying in the same
+direction. From this it follows that development along a path once
+struck out may proceed without the continual intervention of personal
+selection. This factor only operates, so to speak, at the beginning,
+when it selects the determinants which are varying in the right
+direction, and again at the end, when it is necessary to put a check
+upon further variation. In addition to this, enormously long periods
+have been available for all these adaptations, as the very gradual
+transition stages between females and workers in many species plainly
+show, and thus this process of transformation loses the marvellous and
+mysterious character that seemed at the first glance to invest it,
+and takes rank, without any straining, among the other processes of
+selection. It seems to me that, from the facts that sterile animal forms
+can adapt themselves to new vital functions, their superfluous parts
+degenerate, and the parts more used adapt themselves in an ascending
+direction, those less used in a descending direction, we must draw
+the conclusion that harmonious adaptation here comes about WITHOUT
+THE COOPERATION OF THE LAMARCKIAN PRINCIPLE. This conclusion once
+established, however, we have no reason to refer the thousands of cases
+of harmonious adaptation, which occur in exactly the same way among
+other animals or plants, to a principle, the ACTIVE INTERVENTION OF
+WHICH IN THE TRANSFORMATION OF SPECIES IS NOWHERE PROVED. WE DO NOT
+REQUIRE IT TO EXPLAIN THE FACTS, AND THEREFORE WE MUST NOT ASSUME IT.
+
+The fact of coadaptation, which was supposed to furnish the strongest
+argument against the principle of selection, in reality yields the
+clearest evidence in favour of it. We MUST assume it, BECAUSE NO OTHER
+POSSIBILITY OF EXPLANATION IS OPEN TO US, AND BECAUSE THESE ADAPTATIONS
+ACTUALLY EXIST, THAT IS TO SAY, HAVE REALLY TAKEN PLACE. With this
+conviction I attempted, as far back as 1894, when the idea of germinal
+selection had not yet occurred to me, to make "harmonious adaptation"
+(coadaptation) more easily intelligible in some way or other, and so
+I was led to the idea, which was subsequently expounded in detail by
+Baldwin, and Lloyd Morgan, and also by Osborn, and Gulick as ORGANIC
+SELECTION. It seemed to me that it was not necessary that all the
+germinal variations required for secondary variations should have
+occurred SIMULTANEOUSLY, since, for instance, in the case of the
+stag, the bones, muscles, sinews, and nerves would be incited by
+the increasing heaviness of the antlers to greater activity in THE
+INDIVIDUAL LIFE, and so would be strengthened. The antlers can only have
+increased in size by very slow degrees, so that the muscles and bones
+may have been able to keep pace with their growth in the individual
+life, until the requisite germinal variations presented themselves. In
+this way a disharmony between the increasing weight of the antlers and
+the parts which support and move them would be avoided, since time would
+be given for the appropriate germinal variations to occur, and so to set
+agoing the HEREDITARY variation of the muscles, sinews, and bones.
+("The Effect of External Influences upon Development", Romanes Lecture,
+Oxford, 1894.)
+
+I still regard this idea as correct, but I attribute less importance
+to "organic selection" than I did at that time, in so far that I do
+not believe that it ALONE could effect complex harmonious adaptations.
+Germinal selection now seems to me to play the chief part in bringing
+about such adaptations. Something the same is true of the principle
+I have called "Panmixia". As I became more and more convinced, in the
+course of years, that the LAMARCKIAN PRINCIPLE ought not to be called in
+to explain the dwindling of disused parts, I believed that this process
+might be simply explained as due to the cessation of the conservative
+effect of natural selection. I said to myself that, from the moment in
+which a part ceases to be of use, natural selection withdraws its
+hand from it, and then it must inevitably fall from the height of its
+adaptiveness, because inferior variants would have as good a chance of
+persisting as better ones, since all grades of fitness of the part in
+question would be mingled with one another indiscriminately. This is
+undoubtedly true, as Romanes pointed out ten years before I did, and
+this mingling of the bad with the good probably does bring about a
+deterioration of the part concerned. But it cannot account for the
+steady diminution, which always occurs when a part is in process of
+becoming rudimentary, and which goes on until it ultimately disappears
+altogether. The process of dwindling cannot therefore be explained as
+due to panmixia alone; we can only find a sufficient explanation in
+germinal selection.
+
+IV. DERIVATIVES OF THE THEORY OF SELECTION.
+
+The impetus in all directions given by Darwin through his theory of
+selection has been an immeasurable one, and its influence is still felt.
+It falls within the province of the historian of science to enumerate
+all the ideas which, in the last quarter of the nineteenth century, grew
+out of Darwin's theories, in the endeavour to penetrate more deeply into
+the problem of the evolution of the organic world. Within the narrow
+limits to which this paper is restricted, I cannot attempt to discuss
+any of these.
+
+V. ARGUMENTS FOR THE REALITY OF THE PROCESSES OF SELECTION.
+
+(a) SEXUAL SELECTION.
+
+Sexual selection goes hand in hand with natural selection. From the
+very first I have regarded sexual selection as affording an extremely
+important and interesting corroboration of natural selection, but,
+singularly enough, it is precisely against this theory that an adverse
+judgment has been pronounced in so many quarters, and it is only quite
+recently, and probably in proportion as the wealth of facts in proof of
+it penetrates into a wider circle, that we seem to be approaching a
+more general recognition of this side of the problem of adaptation. Thus
+Darwin's words in his preface to the second edition (1874) of his book,
+"The Descent of Man and Sexual Selection", are being justified: "My
+conviction as to the operation of natural selection remains unshaken,"
+and further, "If naturalists were to become more familiar with the idea
+of sexual selection, it would, I think, be accepted to a much greater
+extent, and already it is fully and favourably accepted by many
+competent judges." Darwin was able to speak thus because he was already
+acquainted with an immense mass of facts, which, taken together,
+yield overwhelming evidence of the validity of the principle of sexual
+selection.
+
+NATURAL SELECTION chooses out for reproduction the individuals that are
+best equipped for the struggle for existence, and it does so at every
+stage of development; it thus improves the species in all its stages and
+forms. SEXUAL SELECTION operates only on individuals that are already
+capable of reproduction, and does so only in relation to the attainment
+of reproduction. It arises from the rivalry of one sex, usually the
+male, for the possession of the other, usually the female. Its influence
+can therefore only DIRECTLY affect one sex, in that it equips it
+better for attaining possession of the other. But the effect may
+extend indirectly to the female sex, and thus the whole species may be
+modified, without, however, becoming any more capable of resistance
+in the struggle for existence, for sexual selection only gives rise to
+adaptations which are likely to give their possessor the victory over
+rivals in the struggle for possession of the female, and which are
+therefore peculiar to the wooing sex: the manifold "secondary sexual
+characters." The diversity of these characters is so great that I cannot
+here attempt to give anything approaching a complete treatment of them,
+but I should like to give a sufficient number of examples to make the
+principle itself, in its various modes of expression, quite clear.
+
+One of the chief preliminary postulates of sexual selection is the
+unequal number of individuals in the two sexes, for if every male
+immediately finds his mate there can be no competition for the
+possession of the female. Darwin has shown that, for the most part, the
+inequality between the sexes is due simply to the fact that there are
+more males than females, and therefore the males must take some pains
+to secure a mate. But the inequality does not always depend on the
+numerical preponderance of the males, it is often due to polygamy; for,
+if one male claims several females, the number of females in proportion
+to the rest of the males will be reduced. Since it is almost always
+the males that are the wooers, we must expect to find the occurrence
+of secondary sexual characters chiefly among them, and to find it
+especially frequent in polygamous species. And this is actually the
+case.
+
+If we were to try to guess--without knowing the facts--what means the
+male animals make use of to overcome their rivals in the struggle for
+the possession of the female, we might name many kinds of means, but it
+would be difficult to suggest any which is not actually employed in some
+animal group or other. I begin with the mere difference in strength,
+through which the male of many animals is so sharply distinguished from
+the female, as, for instance, the lion, walrus, "sea-elephant," and
+others. Among these the males fight violently for the possession of the
+female, who falls to the victor in the combat. In this simple case no
+one can doubt the operation of selection, and there is just as little
+room for doubt as to the selection-value of the initial stages of the
+variation. Differences in bodily strength are apparent even among human
+beings, although in their case the struggle for the possession of the
+female is no longer decided by bodily strength alone.
+
+Combats between male animals are often violent and obstinate, and the
+employment of the natural weapons of the species in this way has led
+to perfecting of these, e.g. the tusks of the boar, the antlers of the
+stag, and the enormous, antler-like jaws of the stag-beetle. Here again
+it is impossible to doubt that variations in these organs presented
+themselves, and that these were considerable enough to be decisive in
+combat, and so to lead to the improvement of the weapon.
+
+Among many animals, however, the females at first withdraw from the
+males; they are coy, and have to be sought out, and sometimes held by
+force. This tracking and grasping of the females by the males has given
+rise to many different characters in the latter, as, for instance,
+the larger eyes of the male bee, and especially of the males of the
+Ephemerids (May-flies), some species of which show, in addition to the
+usual compound eyes, large, so-called turban-eyes, so that the whole
+head is covered with seeing surfaces. In these species the females are
+very greatly in the minority (1-100), and it is easy to understand that
+a keen competition for them must take place, and that, when the insects
+of both sexes are floating freely in the air, an unusually wide range
+of vision will carry with it a decided advantage. Here again the actual
+adaptations are in accordance with the preliminary postulates of the
+theory. We do not know the stages through which the eye has passed
+to its present perfected state, but, since the number of simple eyes
+(facets) has become very much greater in the male than in the female,
+we may assume that their increase is due to a gradual duplication of
+the determinants of the ommatidium in the germ-plasm, as I have already
+indicated in regard to sense-organs in general. In this case, again,
+the selection-value of the initial stages hardly admits of doubt; better
+vision DIRECTLY secures reproduction.
+
+In many cases THE ORGAN OF SMELL shows a similar improvement. Many lower
+Crustaceans (Daphnidae) have better developed organs of smell in the
+male sex. The difference is often slight and amounts only to one or two
+olfactory filaments, but certain species show a difference of nearly
+a hundred of these filaments (Leptodora). The same thing occurs among
+insects.
+
+We must briefly consider the clasping or grasping organs which have
+developed in the males among many lower Crustaceans, but here natural
+selection plays its part along with sexual selection, for the union
+of the sexes is an indispensable condition for the maintenance of the
+species, and as Darwin himself pointed out, in many cases the two forms
+of selection merge into each other. This fact has always seemed to me to
+be a proof of natural selection, for, in regard to sexual selection,
+it is quite obvious that the victory of the best-equipped could have
+brought about the improvement only of the organs concerned, the factors
+in the struggle, such as the eye and the olfactory organ.
+
+We come now to the EXCITANTS; that is, to the group of sexual characters
+whose origin through processes of selection has been most frequently
+called in question. We may cite the LOVE-CALLS produced by many male
+insects, such as crickets and cicadas. These could only have arisen in
+animal groups in which the female did not rapidly flee from the male,
+but was inclined to accept his wooing from the first. Thus, notes like
+the chirping of the male cricket serve to entice the females. At first
+they were merely the signal which showed the presence of a male in the
+neighbourhood, and the female was gradually enticed nearer and nearer
+by the continued chirping. The male that could make himself heard to the
+greatest distance would obtain the largest following, and would transmit
+the beginnings, and, later, the improvement of his voice to the greatest
+number of descendants. But sexual excitement in the female
+became associated with the hearing of the love-call, and then the
+sound-producing organ of the male began to improve, until it attained to
+the emission of the long-drawn-out soft notes of the mole-cricket or
+the maenad-like cry of the cicadas. I cannot here follow the process
+of development in detail, but will call attention to the fact that the
+original purpose of the voice, the announcing of the male's presence,
+became subsidiary, and the exciting of the female became the chief goal
+to be aimed at. The loudest singers awakened the strongest excitement,
+and the improvement resulted as a matter of course. I conceive of the
+origin of bird-song in a somewhat similar manner, first as a means of
+enticing, then of exciting the female.
+
+One more kind of secondary sexual character must here be mentioned: the
+odour which emanates from so many animals at the breeding season. It is
+possible that this odour also served at first merely to give notice
+of the presence of individuals of the other sex, but it soon became an
+excitant, and as the individuals which caused the greatest degree of
+excitement were preferred, it reached as high a pitch of perfection as
+was possible to it. I shall confine myself here to the comparatively
+recently discovered fragrance of butterflies. Since Fritz Muller found
+out that certain Brazilian butterflies gave off fragrance "like a
+flower," we have become acquainted with many such cases, and we now know
+that in all lands, not only many diurnal Lepidoptera but nocturnal ones
+also give off a delicate odour, which is agreeable even to man.
+The ethereal oil to which this fragrance is due is secreted by the
+skin-cells, usually of the wing, as I showed soon after the discovery
+of the SCENT-SCALES. This is the case in the males; the females have no
+SPECIAL scent-scales recognisable as such by their form, but they must,
+nevertheless, give off an extremely delicate fragrance, although our
+imperfect organ of smell cannot perceive it, for the males become aware
+of the presence of a female, even at night, from a long distance off,
+and gather round her. We may therefore conclude, that both sexes have
+long given forth a very delicate perfume, which announced their presence
+to others of the same species, and that in many species (NOT IN ALL)
+these small beginnings became, in the males, particularly strong
+scent-scales of characteristic form (lute, brush, or lyre-shaped). At
+first these scales were scattered over the surface of the wing, but
+gradually they concentrated themselves, and formed broad, velvety bands,
+or strong, prominent brushes, and they attained their highest pitch of
+evolution when they became enclosed within pits or folds of the skin,
+which could be opened to let the delicious fragrance stream forth
+suddenly towards the female. Thus in this case also we see that
+characters, the original use of which was to bring the sexes together,
+and so to maintain the species, have been evolved in the males into
+means for exciting the female. And we can hardly doubt, that the females
+are most readily enticed to yield to the butterfly that sends out the
+strongest fragrance,--that is to say, that excites them to the highest
+degree. It is a pity that our organs of smell are not fine enough to
+examine the fragrance of male Lepidoptera in general, and to compare it
+with other perfumes which attract these insects. (See Poulton, "Essays
+on Evolution", 1908, pages 316, 317.) As far as we can perceive them
+they resemble the fragrance of flowers, but there are Lepidoptera
+whose scent suggests musk. A smell of musk is also given off by several
+plants: it is a sexual excitant in the musk-deer, the musk-sheep, and
+the crocodile.
+
+As far as we know, then, it is perfumes similar to those of flowers that
+the male Lepidoptera give off in order to entice their mates, and this
+is a further indication that animals, like plants, can to a large extent
+meet the claims made upon them by life, and produce the adaptations
+which are most purposive,--a further proof, too, of my proposition
+that the useful variations, so to speak, are ALWAYS THERE. The flowers
+developed the perfumes which entice their visitors, and the male
+Lepidoptera developed the perfumes which entice and excite their mates.
+
+There are many pretty little problems to be solved in this connection,
+for there are insects, such as some flies, that are attracted by smells
+which are unpleasant to us, like those from decaying flesh and carrion.
+But there are also certain flowers, some orchids for instance, which
+give forth no very agreeable odour, but one which is to us repulsive
+and disgusting; and we should therefore expect that the males of such
+insects would give off a smell unpleasant to us, but there is no case
+known to me in which this has been demonstrated.
+
+In cases such as we have discussed, it is obvious that there is no
+possible explanation except through selection. This brings us to the
+last kind of secondary sexual characters, and the one in regard to
+which doubt has been most frequently expressed,--decorative colours
+and decorative forms, the brilliant plumage of the male pheasant, the
+humming-birds, and the bird of Paradise, as well as the bright colours
+of many species of butterfly, from the beautiful blue of our little
+Lycaenidae to the magnificent azure of the large Morphinae of Brazil. In
+a great many cases, though not by any means in all, the male butterflies
+are "more beautiful" than the females, and in the Tropics in particular
+they shine and glow in the most superb colours. I really see no reason
+why we should doubt the power of sexual selection, and I myself stand
+wholly on Darwin's side. Even though we certainly cannot assume that
+the females exercise a conscious choice of the "handsomest" mate, and
+deliberate like the judges in a court of justice over the perfections
+of their wooers, we have no reason to doubt that distinctive forms
+(decorative feathers) and colours have a particularly exciting effect
+upon the female, just as certain odours have among animals of so many
+different groups, including the butterflies. The doubts which existed
+for a considerable time, as a result of fallacious experiments, as to
+whether the colours of flowers really had any influence in attracting
+butterflies have now been set at rest through a series of more careful
+investigations; we now know that the colours of flowers are there on
+account of the butterflies, as Sprengel first showed, and that the
+blossoms of Phanerogams are selected in relation to them, as Darwin
+pointed out.
+
+Certainly it is not possible to bring forward any convincing proof of
+the origin of decorative colours through sexual selection, but there
+are many weighty arguments in favour of it, and these form a body of
+presumptive evidence so strong that it almost amounts to certainty.
+
+In the first place, there is the analogy with other secondary sexual
+characters. If the song of birds and the chirping of the cricket have
+been evolved through sexual selection, if the penetrating odours of male
+animals,--the crocodile, the musk-deer, the beaver, the carnivores, and,
+finally, the flower-like fragrances of the butterflies have been evolved
+to their present pitch in this way, why should decorative colours
+have arisen in some other way? Why should the eye be less sensitive
+to SPECIFICALLY MALE colours and other VISIBLE signs ENTICING TO THE
+FEMALE, than the olfactory sense to specifically male odours, or the
+sense of hearing to specifically male sounds? Moreover, the decorative
+feathers of birds are almost always spread out and displayed before
+the female during courtship. I have elsewhere ("The Evolution Theory",
+London, 1904, I. page 219.) pointed out that decorative colouring and
+sweet-scentedness may replace one another in Lepidoptera as well as
+in flowers, for just as some modestly coloured flowers (mignonette and
+violet) have often a strong perfume, while strikingly coloured ones are
+sometimes quite devoid of fragrance, so we find that the most beautiful
+and gaily-coloured of our native Lepidoptera, the species of Vanessa,
+have no scent-scales, while these are often markedly developed in grey
+nocturnal Lepidoptera. Both attractions may, however, be combined in
+butterflies, just as in flowers. Of course, we cannot explain why both
+means of attraction should exist in one genus, and only one of them in
+another, since we do not know the minutest details of the conditions
+of life of the genera concerned. But from the sporadic distribution of
+scent-scales in Lepidoptera, and from their occurrence or absence in
+nearly related species, we may conclude that fragrance is a relatively
+MODERN acquirement, more recent than brilliant colouring.
+
+One thing in particular that stamps decorative colouring as a product of
+selection is ITS GRADUAL INTENSIFICATION by the addition of new spots,
+which we can quite well observe, because in many cases the colours have
+been first acquired by the males, and later transmitted to the females
+by inheritance. The scent-scales are never thus transmitted, probably
+for the same reason that the decorative colours of many birds are often
+not transmitted to the females: because with these they would be exposed
+to too great elimination by enemies. Wallace was the first to point out
+that in species with concealed nests the beautiful feathers of the male
+occurred in the female also, as in the parrots, for instance, but
+this is not the case in species which brood on an exposed nest. In the
+parrots one can often observe that the general brilliant colouring of
+the male is found in the female, but that certain spots of colour are
+absent, and these have probably been acquired comparatively recently by
+the male and have not yet been transmitted to the female.
+
+Isolation of the group of individuals which is in process of varying
+is undoubtedly of great value in sexual selection, for even a solitary
+conspicuous variation will become dominant much sooner in a small
+isolated colony, than among a large number of members of a species.
+
+Anyone who agrees with me in deriving variations from germinal selection
+will regard that process as an essential aid towards explaining the
+selection of distinctive courtship-characters, such as coloured spots,
+decorative feathers, horny outgrowths in birds and reptiles, combs,
+feather-tufts, and the like, since the beginnings of these would
+be presented with relative frequency in the struggle between the
+determinants within the germ-plasm. The process of transmission of
+decorative feathers to the female results, as Darwin pointed out and
+illustrated by interesting examples, in the COLOUR-TRANSFORMATION OF A
+WHOLE SPECIES, and this process, as the phyletically older colouring
+of young birds shows, must, in the course of thousands of years, have
+repeated itself several times in a line of descent.
+
+If we survey the wealth of phenomena presented to us by secondary sexual
+characters, we can hardly fail to be convinced of the truth of the
+principle of sexual selection. And certainly no one who has accepted
+natural selection should reject sexual selection, for, not only do the
+two processes rest upon the same basis, but they merge into one another,
+so that it is often impossible to say how much of a particular character
+depends on one and how much on the other form of selection.
+
+(b) NATURAL SELECTION.
+
+An actual proof of the theory of sexual selection is out of the
+question, if only because we cannot tell when a variation attains to
+selection-value. It is certain that a delicate sense of smell is of
+value to the male moth in his search for the female, but whether the
+possession of one additional olfactory hair, or of ten, or of twenty
+additional hairs leads to the success of its possessor we are unable
+to tell. And we are groping even more in the dark when we discuss the
+excitement caused in the female by agreeable perfumes, or by striking
+and beautiful colours. That these do make an impression is beyond doubt;
+but we can only assume that slight intensifications of them give any
+advantage, and we MUST assume this SINCE OTHERWISE SECONDARY SEXUAL
+CHARACTERS REMAIN INEXPLICABLE.
+
+The same thing is true in regard to natural selection. It is not
+possible to bring forward any actual proof of the selection-value of
+the initial stages, and the stages in the increase of variations, as has
+been already shown. But the selection-value of a finished adaptation can
+in many cases be statistically determined. Cesnola and Poulton have made
+valuable experiments in this direction. The former attached forty-five
+individuals of the green, and sixty-five of the brown variety of the
+praying mantis (Mantis religiosa), by a silk thread to plants, and
+watched them for seventeen days. The insects which were on a surface of
+a colour similar to their own remained uneaten, while twenty-five green
+insects on brown parts of plants had all disappeared in eleven days.
+
+The experiments of Poulton and Sanders ("Report of the British
+Association" (Bristol, 1898), London, 1899, pages 906-909.) were made
+with 600 pupae of Vanessa urticae, the "tortoise-shell butterfly." The
+pupae were artificially attached to nettles, tree-trunks, fences, walls,
+and to the ground, some at Oxford, some at St Helens in the Isle of
+Wight. In the course of a month 93 per cent of the pupae at Oxford were
+killed, chiefly by small birds, while at St Helens 68 per cent perished.
+The experiments showed very clearly that the colour and character of the
+surface on which the pupa rests--and thus its own conspicuousness--are
+of the greatest importance. At Oxford only the four pupae which were
+fastened to nettles emerged; all the rest--on bark, stones and the
+like--perished. At St Helens the elimination was as follows: on fences
+where the pupae were conspicuous, 92 per cent; on bark, 66 per cent; on
+walls, 54 per cent; and among nettles, 57 per cent. These interesting
+experiments confirm our views as to protective coloration, and show
+further, THAT THE RATIO OF ELIMINATION IN THE SPECIES IS A VERY HIGH
+ONE, AND THAT THEREFORE SELECTION MUST BE VERY KEEN.
+
+We may say that the process of selection follows as a logical necessity
+from the fulfilment of the three preliminary postulates of the theory:
+variability, heredity, and the struggle for existence, with its enormous
+ratio of elimination in all species. To this we must add a fourth
+factor, the INTENSIFICATION of variations which Darwin established as
+a fact, and which we are now able to account for theoretically on
+the basis of germinal selection. It may be objected that there is
+considerable uncertainty about this LOGICAL proof, because of our
+inability to demonstrate the selection-value of the initial stages and
+the individual stages of increase. We have therefore to fall back on
+PRESUMPTIVE EVIDENCE. This is to be found in THE INTERPRETATIVE VALUE OF
+THE THEORY. Let us consider this point in greater detail.
+
+In the first place, it is necessary to emphasise what is often
+overlooked, namely, that the theory not only explains the
+TRANSFORMATIONS of species, it also explains THEIR REMAINING THE SAME;
+in addition to the principle of varying, it contains within itself that
+of PERSISTING. It is part of the essence of selection, that it not
+only causes a part to VARY till it has reached its highest pitch of
+adaptation, but that it MAINTAINS IT AT THIS PITCH. THIS CONSERVING
+INFLUENCE OF NATURAL SELECTION is of great importance, and was early
+recognised by Darwin; it follows naturally from the principle of the
+survival of the fittest.
+
+We understand from this how it is that a species which has become
+fully adapted to certain conditions of life ceases to vary, but remains
+"constant," as long as the conditions of life FOR IT remain unchanged,
+whether this be for thousands of years, or for whole geological epochs.
+But the most convincing proof of the power of the principle of selection
+lies in the innumerable multitude of phenomena which cannot be explained
+in any other way. To this category belong all structures which are only
+PASSIVELY of advantage to the organism, because none of these can have
+arisen by the alleged LAMARCKIAN PRINCIPLE. These have been so often
+discussed that we need do no more than indicate them here. Until quite
+recently the sympathetic coloration of animals--for instance, the
+whiteness of Arctic animals--was referred, at least in part, to
+the DIRECT influence of external factors, but the facts can best be
+explained by referring them to the processes of selection, for then it
+is unnecessary to make the gratuitous assumption that many species are
+sensitive to the stimulus of cold and that others are not. The great
+majority of Arctic land-animals, mammals and birds, are white, and this
+proves that they were all able to present the variation which was most
+useful for them. The sable is brown, but it lives in trees, where
+the brown colouring protects and conceals it more effectively. The
+musk-sheep (Ovibos moschatus) is also brown, and contrasts sharply
+with the ice and snow, but it is protected from beasts of prey by its
+gregarious habit, and therefore it is of advantage to be visible from
+as great a distance as possible. That so many species have been able to
+give rise to white varieties does not depend on a special sensitiveness
+of the skin to the influence of cold, but to the fact that Mammals and
+Birds have a general tendency to vary towards white. Even with us, many
+birds--starlings, blackbirds, swallows, etc.--occasionally produce white
+individuals, but the white variety does not persist, because it readily
+falls a victim to the carnivores. This is true of white fawns, foxes,
+deer, etc. The whiteness, therefore, arises from internal causes, and
+only persists when it is useful. A great many animals living in a
+GREEN ENVIRONMENT have become clothed in green, especially insects,
+caterpillars, and Mantidae, both persecuted and persecutors.
+
+That it is not the direct effect of the environment which calls forth
+the green colour is shown by the many kinds of caterpillar which rest on
+leaves and feed on them, but are nevertheless brown. These feed by night
+and betake themselves through the day to the trunk of the tree, and hide
+in the furrows of the bark. We cannot, however, conclude from this that
+they were UNABLE to vary towards green, for there are Arctic animals
+which are white only in winter and brown in summer (Alpine hare, and
+the ptarmigan of the Alps), and there are also green leaf-insects which
+remain green only while they are young and difficult to see on the leaf,
+but which become brown again in the last stage of larval life, when they
+have outgrown the leaf. They then conceal themselves by day, sometimes
+only among withered leaves on the ground, sometimes in the earth itself.
+It is interesting that in one genus, Chaerocampa, one species is brown
+in the last stage of larval life, another becomes brown earlier, and in
+many species the last stage is not wholly brown, a part remaining green.
+Whether this is a case of a double adaptation, or whether the green is
+being gradually crowded out by the brown, the fact remains that the same
+species, even the same individual, can exhibit both variations. The case
+is the same with many of the leaf-like Orthoptera, as, for instance, the
+praying mantis (Mantis religiosa) which we have already mentioned.
+
+But the best proofs are furnished by those often-cited cases in which
+the insect bears a deceptive resemblance to another object. We now know
+many such cases, such as the numerous imitations of green or withered
+leaves, which are brought about in the most diverse ways, sometimes by
+mere variations in the form of the insect and in its colour, sometimes
+by an elaborate marking, like that which occurs in the Indian
+leaf-butterflies, Kallima inachis. In the single butterfly-genus Anaea,
+in the woods of South America, there are about a hundred species which
+are all gaily coloured on the upper surface, and on the reverse side
+exhibit the most delicate imitation of the colouring and pattern of a
+leaf, generally without any indication of the leaf-ribs, but extremely
+deceptive nevertheless. Anyone who has seen only one such butterfly
+may doubt whether many of the insignificant details of the marking can
+really be of advantage to the insect. Such details are for instance the
+apparent holes and splits in the apparently dry or half-rotten leaf,
+which are usually due to the fact that the scales are absent on a
+circular or oval patch so that the colourless wing-membrane lies bare,
+and one can look through the spot as through a window. Whether the
+bird which is seeking or pursuing the butterflies takes these holes for
+dewdrops, or for the work of a devouring insect, does not affect
+the question; the mirror-like spot undoubtedly increases the general
+deceptiveness, for the same thing occurs in many leaf-butterflies,
+though not in all, and in some cases it is replaced in quite a peculiar
+manner. In one species of Anaea (A. divina), the resting butterfly looks
+exactly like a leaf out of the outer edge of which a large semicircular
+piece has been eaten, possibly by a caterpillar; but if we look more
+closely it is obvious that there is no part of the wing absent, and that
+the semicircular piece is of a clear, pale yellow colour, while the rest
+of the wing is of a strongly contrasted dark brown.
+
+But the deceptive resemblance may be caused in quite a different manner.
+I have often speculated as to what advantage the brilliant white C
+could give to the otherwise dusky-coloured "Comma butterfly" (Grapta C.
+album). Poulton's recent observations ("Proc. Ent. Soc"., London, May 6,
+1903.) have shown that this represents the imitation of a crack such as
+is often seen in dry leaves, and is very conspicuous because the light
+shines through it.
+
+The utility obviously lies in presenting to the bird the very familiar
+picture of a broken leaf with a clear shining slit, and we may conclude,
+from the imitation of such small details, that the birds are very sharp
+observers and that the smallest deviation from the usual arrests their
+attention and incites them to closer investigation. It is obvious that
+such detailed--we might almost say such subtle--deceptive resemblances
+could only have come about in the course of long ages through the
+acquirement from time to time of something new which heightened the
+already existing resemblance.
+
+In face of facts like these there can be no question of chance, and no
+one has succeeded so far in finding any other explanation to replace
+that by selection. For the rest, the apparent leaves are by no means
+perfect copies of a leaf; many of them only represent the torn or
+broken piece, or the half or two-thirds of a leaf, but then the leaves
+themselves frequently do not present themselves to the eye as a whole,
+but partially concealed among other leaves. Even those butterflies
+which, like the species of Kallima and Anaea, represent the whole of
+a leaf with stalk, ribs, apex, and the whole breadth, are not actual
+copies which would satisfy a botanist; there is often much wanting.
+In Kallima the lateral ribs of the leaf are never all included in the
+markings; there are only two or three on the left side and at most four
+or five on the right, and in many individuals these are rather obscure,
+while in others they are comparatively distinct. This furnishes us with
+fresh evidence in favour of their origin through processes of selection,
+for a botanically perfect picture could not arise in this way; there
+could only be a fixing of such details as heightened the deceptive
+resemblance.
+
+Our postulate of origin through selection also enables us to understand
+why the leaf-imitation is on the lower surface of the wing in the
+diurnal Lepidoptera, and on the upper surface in the nocturnal forms,
+corresponding to the attitude of the wings in the resting position of
+the two groups.
+
+The strongest of all proofs of the theory, however, is afforded by
+cases of true "mimicry," those adaptations discovered by Bates in 1861,
+consisting in the imitation of one species by another, which becomes
+more and more like its model. The model is always a species that enjoys
+some special protection from enemies, whether because it is unpleasant
+to taste, or because it is in some way dangerous.
+
+It is chiefly among insects and especially among butterflies that we
+find the greatest number of such cases. Several of these have been
+minutely studied, and every detail has been investigated, so that it is
+difficult to understand how there can still be disbelief in regard
+to them. If the many and exact observations which have been carefully
+collected and critically discussed, for instance by Poulton ("Essays
+on Evolution", 1889-1907, Oxford, 1908, passim, e.g. page 269.) were
+thoroughly studied, the arguments which are still frequently urged
+against mimicry would be found untenable; we can hardly hope to find
+more convincing proof of the actuality of the processes of selection
+than these cases put into our hands. The preliminary postulates of
+the theory of mimicry have been disputed, for instance, that diurnal
+butterflies are persecuted and eaten by birds, but observations
+specially directed towards this point in India, Africa, America and
+Europe have placed it beyond all doubt. If it were necessary I could
+myself furnish an account of my own observations on this point.
+
+In the same way it has been established by experiment and observation
+in the field that in all the great regions of distribution there
+are butterflies which are rejected by birds and lizards, their
+chief enemies, on account of their unpleasant smell or taste. These
+butterflies are usually gaily and conspicuously coloured and thus--as
+Wallace first interpreted it--are furnished with an easily recognisable
+sign: a sign of unpalatableness or WARNING COLOURS. If they were not
+thus recognisable easily and from a distance, they would frequently be
+pecked at by birds, and then rejected because of their unpleasant taste;
+but as it is, the insect-eaters recognise them at once as unpalatable
+booty and ignore them. Such IMMUNE (The expression does not refer to all
+the enemies of this butterfly; against ichneumon-flies, for instance,
+their unpleasant smell usually gives no protection.) species, wherever
+they occur, are imitated by other palatable species, which thus acquire
+a certain degree of protection.
+
+It is true that this explanation of the bright, conspicuous colours
+is only a hypothesis, but its foundations,--unpalatableness, and the
+liability of other butterflies to be eaten,--are certain, and its
+consequences--the existence of mimetic palatable forms--confirm it in
+the most convincing manner. Of the many cases now known I select
+one, which is especially remarkable, and which has been thoroughly
+investigated, Papilio dardanus (merope), a large, beautiful, diurnal
+butterfly which ranges from Abyssinia throughout the whole of Africa to
+the south coast of Cape Colony.
+
+The males of this form are everywhere ALMOST the same in colour and in
+form of wings, save for a few variations in the sparse black markings on
+the pale yellow ground. But the females occur in several quite different
+forms and colourings, and one of these only, the Abyssinian form, is
+like the male, while the other three or four are MIMETIC, that is to
+say, they copy a butterfly of quite a different family the Danaids,
+which are among the IMMUNE forms. In each region the females have thus
+copied two or three different immune species. There is much that is
+interesting to be said in regard to these species, but it would be out
+of keeping with the general tenor of this paper to give details of this
+very complicated case of polymorphism in P. dardanus. Anyone who is
+interested in the matter will find a full and exact statement of the
+case in as far as we know it, in Poulton's "Essays on Evolution" (pages
+373-375). (Professor Poulton has corrected some wrong descriptions which
+I had unfortunately overlooked in the Plates of my book "Vortrage uber
+Descendenztheorie", and which refer to Papilio dardanus (merope).
+These mistakes are of no importance as far as and understanding of the
+mimicry-theory is concerned, but I hope shortly to be able to correct
+them in a later edition.) I need only add that three different mimetic
+female forms have been reared from the eggs of a single female in South
+Africa. The resemblance of these forms to their immune models goes so
+far that even the details of the LOCAL forms of the models are copied by
+the mimetic species.
+
+It remains to be said that in Madagascar a butterfly, Papilio meriones,
+occurs, of which both sexes are very similar in form and markings to
+the non-mimetic male of P. dardanus, so that it probably represents the
+ancestor of this latter species.
+
+In face of such facts as these every attempt at another explanation must
+fail. Similarly all the other details of the case fulfil the preliminary
+postulates of selection, and leave no room for any other interpretation.
+That the males do not take on the protective colouring is easily
+explained, because they are in general more numerous, and the females
+are more important for the preservation of the species, and must also
+live longer in order to deposit their eggs. We find the same state of
+things in many other species, and in one case (Elymnias undularis)
+in which the male is also mimetically coloured, it copies quite a
+differently coloured immune species from the model followed by the
+female. This is quite intelligible when we consider that if there were
+TOO MANY false immune types, the birds would soon discover that there
+were palatable individuals among those with unpalatable warning colours.
+Hence the imitation of different immune species by Papilio dardanus!
+
+I regret that lack of space prevents my bringing forward more examples
+of mimicry and discussing them fully. But from the case of Papilio
+dardanus alone there is much to be learnt which is of the highest
+importance for our understanding of transformations. It shows us chiefly
+what I once called, somewhat strongly perhaps, THE OMNIPOTENCE OF
+NATURAL SELECTION in answer to an opponent who had spoken of its
+"inadequacy." We here see that one and the same species is capable of
+producing four or five different patterns of colouring and marking;
+thus the colouring and marking are not, as has often been supposed,
+a necessary outcome of the specific nature of the species, but a
+true adaptation, which cannot arise as a direct effect of climatic
+conditions, but solely through what I may call the sorting out of the
+variations produced by the species, according to their utility. That
+caterpillars may be either green or brown is already something more than
+could have been expected according to the old conception of species, but
+that one and the same butterfly should be now pale yellow, with black;
+now red with black and pure white; now deep black with large, pure white
+spots; and again black with a large ochreous-yellow spot, and many small
+white and yellow spots; that in one sub-species it may be tailed like
+the ancestral form, and in another tailless like its Danaid model,--all
+this shows a far-reaching capacity for variation and adaptation that
+wide never have expected if we did not see the facts before us. How
+it is possible that the primary colour-variations should thus be
+intensified and combined remains a puzzle even now; we are reminded of
+the modern three-colour printing,--perhaps similar combinations of the
+primary colours take place in this case; in any case the direction of
+these primary variations is determined by the artist whom we know as
+natural selection, for there is no other conceivable way in which the
+model could affect the butterfly that is becoming more and more like it.
+The same climate surrounds all four forms of female; they are subject
+to the same conditions of nutrition. Moreover, Papilio dardanus is by
+no means the only species of butterfly which exhibits different kinds of
+colour-pattern on its wings. Many species of the Asiatic genus Elymnias
+have on the upper surface a very good imitation of an immune Euploeine
+(Danainae), often with a steel-blue ground-colour, while the under
+surface is well concealed when the butterfly is at rest,--thus there are
+two kinds of protective coloration each with a different meaning! The
+same thing may be observed in many non-mimetic butterflies, for
+instance in all our species of Vanessa, in which the under side shows
+a grey-brown or brownish-black protective coloration, but we do not yet
+know with certainty what may be the biological significance of the gaily
+coloured upper surface.
+
+In general it may be said that mimetic butterflies are comparatively
+rare species, but there are exceptions, for instance Limenitis archippus
+in North America, of which the immune model (Danaida plexippus) also
+occurs in enormous numbers.
+
+In another mimicry-category the imitators are often more numerous than
+the models, namely in the case of the imitation of DANGEROUS INSECTS by
+harmless species. Bees and wasps are dreaded for their sting, and they
+are copied by harmless flies of the genera Eristalis and Syrphus, and
+these mimics often occur in swarms about flowering plants without damage
+to themselves or to their models; they are feared and are therefore left
+unmolested.
+
+In regard also to the FAITHFULNESS OF THE COPY the facts are quite in
+harmony with the theory, according to which the resemblance must have
+arisen and increased BY DEGREES. We can recognise this in many
+cases, for even now the mimetic species show very VARYING DEGREES OF
+RESEMBLANCE to their immune model. If we compare, for instance, the
+many different imitators of Danaida chrysippus we find that, with their
+brownish-yellow ground-colour, and the position and size, and more or
+less sharp limitation of their clear marginal spots, they have reached
+very different degrees of nearness to their model. Or compare the female
+of Elymnias undularis with its model Danaida genutia; there is a general
+resemblance, but the marking of the Danaida is very roughly imitated in
+Elymnias.
+
+Another fact that bears out the theory of mimicry is, that even when the
+resemblance in colour-pattern is very great, the WING-VENATION, which is
+so constant, and so important in determining the systematic position
+of butterflies, is never affected by the variation. The pursuers of the
+butterfly have no time to trouble about entomological intricacies.
+
+I must not pass over a discovery of Poulton's which is of great
+theoretical importance--that mimetic butterflies may reach the same
+effect by very different means. ("Journ. Linn. Soc. London (Zool.)",
+Vol. XXVI. 1898, pages 598-602.) Thus the glass-like transparency of the
+wing of a certain Ithomiine (Methona) and its Pierine mimic (Dismorphia
+orise) depends on a diminution in the size of the scales; in the Danaine
+genus Ituna it is due to the fewness of the scales, and in a third
+imitator, a moth (Castnia linus var. heliconoides) the glass-like
+appearance of the wing is due neither to diminution nor to absence of
+scales, but to their absolute colourlessness and transparency, and to
+the fact that they stand upright. In another moth mimic (Anthomyza) the
+arrangement of the transparent scales is normal. Thus it is not some
+unknown external influence that has brought about the transparency of
+the wing in these five forms, as has sometimes been supposed. Nor is it
+a hypothetical INTERNAL evolutionary tendency, for all three vary in a
+different manner. The cause of this agreement can only lie in selection,
+which preserves and intensifies in each species the favourable
+variations that present themselves. The great faithfulness of the copy
+is astonishing in these cases, for it is not THE WHOLE wing which is
+transparent; certain markings are black in colour, and these contrast
+sharply with the glass-like ground. It is obvious that the pursuers
+of these butterflies must be very sharp-sighted, for otherwise the
+agreement between the species could never have been pushed so far. The
+less the enemies see and observe, the more defective must the imitation
+be, and if they had been blind, no visible resemblance between the
+species which required protection could ever have arisen.
+
+A seemingly irreconcilable contradiction to the mimicry theory is
+presented in the following cases, which were known to Bates, who,
+however, never succeeded in bringing them into line with the principle
+of mimicry.
+
+In South America there are, as we have already said, many mimics of the
+immune Ithomiinae (or as Bates called them Heliconidae). Among these
+there occur not merely species which are edible, and thus require the
+protection of a disguise, but others which are rejected on account of
+their unpalatableness. How could the Ithomiine dress have developed in
+their case, and of what use is it, since the species would in any case
+be immune? In Eastern Brazil, for instance, there are four butterflies,
+which bear a most confusing resemblance to one another in colour,
+marking, and form of wing, and all four are unpalatable to birds. They
+belong to four different genera and three sub-families, and we have to
+inquire: Whence came this resemblance and what end does it serve? For
+a long time no satisfactory answer could be found, but Fritz Muller
+(In "Kosmos", 1879, page 100.), seventeen years after Bates, offered a
+solution to the riddle, when he pointed out that young birds could not
+have an instinctive knowledge of the unpalatableness of the Ithomiines,
+but must learn by experience which species were edible and which
+inedible. Thus each young bird must have tasted at least one individual
+of each inedible species and discovered its unpalatability, before it
+learnt to avoid, and thus to spare the species. But if the four species
+resemble each other very closely the bird will regard them all as of
+the same kind, and avoid them all. Thus there developed a process
+of selection which resulted in the survival of the Ithomiine-like
+individuals, and in so great an increase of resemblance between the four
+species, that they are difficult to distinguish one from another even in
+a collection. The advantage for the four species, living side by side
+as they do e.g. in Bahia, lies in the fact that only one individual
+from the MIMICRY-RING ("inedible association") need be tasted by a young
+bird, instead of at least four individuals, as would otherwise be the
+case. As the number of young birds is great, this makes a considerable
+difference in the ratio of elimination.
+
+These interesting mimicry-rings (trusts), which have much significance
+for the theory, have been the subject of numerous and careful
+investigations, and at least their essential features are now fully
+established. Muller took for granted, without making any investigations,
+that young birds only learn by experience to distinguish between
+different kinds of victims. But Lloyd Morgan's ("Habit and Instinct",
+London, 1896.) experiments with young birds proved that this is really
+the case, and at the same time furnished an additional argument against
+the LAMARCKIAN PRINCIPLE.
+
+In addition to the mimicry-rings first observed in South America, others
+have been described from Tropical India by Moore, and by Poulton and
+Dixey from Africa, and we may expect to learn many more interesting
+facts in this connection. Here again the preliminary postulates of the
+theory are satisfied. And how much more that would lead to the same
+conclusion might be added!
+
+As in the case of mimicry many species have come to resemble one another
+through processes of selection, so we know whole classes of phenomena
+in which plants and animals have become adapted to one another, and have
+thus been modified to a considerable degree. I refer particularly to the
+relation between flowers and insects; but as there is an article on "The
+Biology of Flowers" in this volume, I need not discuss the subject, but
+will confine myself to pointing out the significance of these remarkable
+cases for the theory of selection. Darwin has shown that the originally
+inconspicuous blossoms of the phanerogams were transformed into flowers
+through the visits of insects, and that, conversely, several large
+orders of insects have been gradually modified by their association
+with flowers, especially as regards the parts of their body actively
+concerned. Bees and butterflies in particular have become what they
+are through their relation to flowers. In this case again all that is
+apparently contradictory to the theory can, on closer investigation, be
+beautifully interpreted in corroboration of it. Selection can give rise
+only to what is of use to the organism actually concerned, never to what
+is of use to some other organism, and we must therefore expect to find
+that in flowers only characters of use to THEMSELVES have arisen, never
+characters which are of use to insects only, and conversely that in the
+insects characters useful to them and not merely to the plants would
+have originated. For a long time it seemed as if an exception to this
+rule existed in the case of the fertilisation of the yucca blossoms by
+a little moth, Pronuba yuccasella. This little moth has a sickle-shaped
+appendage to its mouth-parts which occurs in no other Lepidopteron,
+and which is used for pushing the yellow pollen into the opening of
+the pistil, thus fertilising the flower. Thus it appears as if a new
+structure, which is useful only to the plant, has arisen in the insect.
+But the difficulty is solved as soon as we learn that the moth lays
+its eggs in the fruit-buds of the Yucca, and that the larvae, when they
+emerge, feed on the developing seeds. In effecting the fertilisation
+of the flower the moth is at the same time making provision for its own
+offspring, since it is only after fertilisation that the seeds begin to
+develop. There is thus nothing to prevent our referring this structural
+adaptation in Pronuba yuccasella to processes of selection, which
+have gradually transformed the maxillary palps of the female into the
+sickle-shaped instrument for collecting the pollen, and which have at
+the same time developed in the insect the instinct to press the pollen
+into the pistil.
+
+In this domain, then, the theory of selection finds nothing but
+corroboration, and it would be impossible to substitute for it any
+other explanation, which, now that the facts are so well known, could
+be regarded as a serious rival to it. That selection is a factor, and
+a very powerful factor in the evolution of organisms, can no longer be
+doubted. Even although we cannot bring forward formal proofs of it IN
+DETAIL, cannot calculate definitely the size of the variations which
+present themselves, and their selection-value, cannot, in short,
+reduce the whole process to a mathematical formula, yet we must assume
+selection, because it is the only possible explanation applicable to
+whole classes of phenomena, and because, on the other hand, it is made
+up of factors which we know can be proved actually to exist, and
+which, IF they exist, must of logical necessity cooperate in the manner
+required by the theory. WE MUST ACCEPT IT BECAUSE THE PHENOMENA OF
+EVOLUTION AND ADAPTATION MUST HAVE A NATURAL BASIS, AND BECAUSE IT IS
+THE ONLY POSSIBLE EXPLANATION OF THEM. (This has been discussed in many
+of my earlier works. See for instance "The All-Sufficiency of Natural
+Selection, a reply to Herbert Spencer", London, 1893.)
+
+Many people are willing to admit that selection explains adaptations,
+but they maintain that only a part of the phenomena are thus explained,
+because everything does not depend upon adaptation. They regard
+adaptation as, so to speak, a special effort on the part of Nature,
+which she keeps in readiness to meet particularly difficult claims
+of the external world on organisms. But if we look at the matter more
+carefully we shall find that adaptations are by no means exceptional,
+but that they are present everywhere in such enormous numbers, that it
+would be difficult in regard to any structure whatever, to prove that
+adaptation had NOT played a part in its evolution.
+
+How often has the senseless objection been urged against selection that
+it can create nothing, it can only reject. It is true that it cannot
+create either the living substance or the variations of it; both must be
+given. But in rejecting one thing it preserves another, intensifies
+it, combines it, and in this way CREATES what is new. EVERYTHING in
+organisms depends on adaptation; that is to say, everything must be
+admitted through the narrow door of selection, otherwise it can take
+no part in the building up of the whole. But, it is asked, what of the
+direct effect of external conditions, temperature, nutrition, climate
+and the like? Undoubtedly these can give rise to variations, but they
+too must pass through the door of selection, and if they cannot do this
+they are rejected, eliminated from the constitution of the species.
+
+It may, perhaps, be objected that such external influences are often of
+a compelling power, and that every animal MUST submit to them, and that
+thus selection has no choice and can neither select nor reject. There
+may be such cases; let us assume for instance that the effect of the
+cold of the Arctic regions was to make all the mammals become black; the
+result would be that they would all be eliminated by selection, and
+that no mammals would be able to live there at all. But in most cases a
+certain percentage of animals resists these strong influences, and
+thus selection secures a foothold on which to work, eliminating the
+unfavourable variation, and establishing a useful colouring, consistent
+with what is required for the maintenance of the species.
+
+Everything depends upon adaptation! We have spoken much of adaptation
+in colouring, in connection with the examples brought into prominence by
+Darwin, because these are conspicuous, easily verified, and at the same
+time convincing for the theory of selection. But is it only desert and
+polar animals whose colouring is determined through adaptation? Or the
+leaf-butterflies, and the mimetic species, or the terrifying markings,
+and "warning-colours" and a thousand other kinds of sympathetic
+colouring? It is, indeed, never the colouring alone which makes up
+the adaptation; the structure of the animal plays a part, often a very
+essential part, in the protective disguise, and thus MANY variations may
+cooperate towards ONE common end. And it is to be noted that it is by
+no means only external parts that are changed; internal parts are ALWAYS
+modified at the same time--for instance, the delicate elements of the
+nervous system on which depend the INSTINCT of the insect to hold its
+wings, when at rest, in a perfectly definite position, which, in the
+leaf-butterfly, has the effect of bringing the two pieces on which
+the marking occurs on the anterior and posterior wing into the same
+direction, and thus displaying as a whole the fine curve of the midrib
+on the seeming leaf. But the wing-holding instinct is not regulated in
+the same way in all leaf-butterflies; even our indigenous species
+of Vanessa, with their protective ground-colouring, have quite a
+distinctive way of holding their wings so that the greater part of the
+anterior wing is covered by the posterior when the butterfly is at rest.
+But the protective colouring appears on the posterior wing and on the
+tip of the anterior, TO PRECISELY THE DISTANCE TO WHICH IT IS LEFT
+UNCOVERED. This occurs, as Standfuss has shown, in different degree in
+our two most nearly allied species, the uncovered portion being
+smaller in V. urticae than in V. polychloros. In this case, as in most
+leaf-butterflies, the holding of the wing was probably the primary
+character; only after that was thoroughly established did the protective
+marking develop. In any case, the instinctive manner of holding the
+wings is associated with the protective colouring, and must remain as it
+is if the latter is to be effective. How greatly instincts may change,
+that is to say, may be adapted, is shown by the case of the Noctuid
+"shark" moth, Xylina vetusta. This form bears a most deceptive
+resemblance to a piece of rotten wood, and the appearance is greatly
+increased by the modification of the innate impulse to flight common to
+so many animals, which has here been transformed into an almost contrary
+instinct. This moth does not fly away from danger, but "feigns death,"
+that is, it draws antennae, legs and wings close to the body, and
+remains perfectly motionless. It may be touched, picked up, and thrown
+down again, and still it does not move. This remarkable instinct must
+surely have developed simultaneously with the wood-colouring; at all
+events, both cooperating variations are now present, and prove that both
+the external and the most minute internal structure have undergone a
+process of adaptation.
+
+The case is the same with all structural variations of animal parts,
+which are not absolutely insignificant. When the insects acquired wings
+they must also have acquired the mechanism with which to move them--the
+musculature, and the nervous apparatus necessary for its automatic
+regulation. All instincts depend upon compound reflex mechanisms and are
+just as indispensable as the parts they have to set in motion, and all
+may have arisen through processes of selection if the reasons which I
+have elsewhere given for this view are correct. ("The Evolution Theory",
+London, 1904, page 144.)
+
+Thus there is no lack of adaptations within the organism, and
+particularly in its most important and complicated parts, so that we may
+say that there is no actively functional organ that has not undergone a
+process of adaptation relative to its function and the requirements of
+the organism. Not only is every gland structurally adapted, down to the
+very minutest histological details, to its function, but the function
+is equally minutely adapted to the needs of the body. Every cell in the
+mucous lining of the intestine is exactly regulated in its relation to
+the different nutritive substances, and behaves in quite a different way
+towards the fats, and towards nitrogenous substances, or peptones.
+
+I have elsewhere called attention to the many adaptations of the whale
+to the surrounding medium, and have pointed out--what has long been
+known, but is not universally admitted, even now--that in it a great
+number of important organs have been transformed in adaptation to the
+peculiar conditions of aquatic life, although the ancestors of the whale
+must have lived, like other hair-covered mammals, on land. I cited a
+number of these transformations--the fish-like form of the body, the
+hairlessness of the skin, the transformation of the fore-limbs to fins,
+the disappearance of the hind-limbs and the development of a tail fin,
+the layer of blubber under the skin, which affords the protection
+from cold necessary to a warm-blooded animal, the disappearance of the
+ear-muscles and the auditory passages, the displacement of the external
+nares to the forehead for the greater security of the breathing-hole
+during the brief appearance at the surface, and certain remarkable
+changes in the respiratory and circulatory organs which enable the
+animal to remain for a long time under water. I might have added many
+more, for the list of adaptations in the whale to aquatic life is by no
+means exhausted; they are found in the histological structure and in the
+minutest combinations in the nervous system. For it is obvious that a
+tail-fin must be used in quite a different way from a tail, which serves
+as a fly-brush in hoofed animals, or as an aid to springing in the
+kangaroo or as a climbing organ; it will require quite different
+reflex-mechanisms and nerve-combinations in the motor centres.
+
+I used this example in order to show how unnecessary it is to assume a
+special internal evolutionary power for the phylogenesis of species, for
+this whole order of whales is, so to speak, MADE UP OF ADAPTATIONS; it
+deviates in many essential respects from the usual mammalian type, and
+all the deviations are adaptations to aquatic life. But if precisely the
+most essential features of the organisation thus depend upon adaptation,
+what is left for a phyletic force to do, since it is these essential
+features of the structure it would have to determine? There are few
+people now who believe in a phyletic evolutionary power, which is not
+made up of the forces known to us--adaptation and heredity--but the
+conviction that EVERY part of an organism depends upon adaptation has
+not yet gained a firm footing. Nevertheless, I must continue to regard
+this conception as the correct one, as I have long done.
+
+I may be permitted one more example. The feather of a bird is a
+marvellous structure, and no one will deny that as a whole it depends
+upon adaptation. But what part of it DOES NOT depend upon adaptation?
+The hollow quill, the shaft with its hard, thin, light cortex, and the
+spongy substance within it, its square section compared with the round
+section of the quill, the flat barbs, their short, hooked barbules
+which, in the flight-feathers, hook into one another with just
+sufficient firmness to resist the pressure of the air at each wing-beat,
+the lightness and firmness of the whole apparatus, the elasticity of
+the vane, and so on. And yet all this belongs to an organ which is only
+passively functional, and therefore can have nothing to do with the
+LAMARCKIAN PRINCIPLE. Nor can the feather have arisen through some
+magical effect of temperature, moisture, electricity, or specific
+nutrition, and thus selection is again our only anchor of safety.
+
+But--it will be objected--the substance of which the feather consists,
+this peculiar kind of horny substance, did not first arise through
+selection in the course of the evolution of the birds, for it formed the
+covering of the scales of their reptilian ancestors. It is quite true
+that a similar substance covered the scales of the Reptiles, but why
+should it not have arisen among them through selection? Or in what other
+way could it have arisen, since scales are also passively useful parts?
+It is true that if we are only to call adaptation what has been acquired
+by the species we happen to be considering, there would remain a great
+deal that could not be referred to selection; but we are postulating an
+evolution which has stretched back through aeons, and in the course of
+which innumerable adaptations took place, which had not merely ephemeral
+persistence in a genus, a family or a class, but which was continued
+into whole Phyla of animals, with continual fresh adaptations to
+the special conditions of each species, family, or class, yet with
+persistence of the fundamental elements. Thus the feather, once
+acquired, persisted in all birds, and the vertebral column, once gained
+by adaptation in the lowest forms, has persisted in all the Vertebrates,
+from Amphioxus upwards, although with constant readaptation to the
+conditions of each particular group. Thus everything we can see in
+animals is adaptation, whether of to-day, or of yesterday, or of ages
+long gone by; every kind of cell, whether glandular, muscular, nervous,
+epidermic, or skeletal, is adapted to absolutely definite and specific
+functions, and every organ which is composed of these different kinds
+of cells contains them in the proper proportions, and in the particular
+arrangement which best serves the function of the organ; it is thus
+adapted to its function.
+
+All parts of the organism are tuned to one another, that is, THEY ARE
+ADAPTED TO ONE ANOTHER, and in the same way THE ORGANISM AS A WHOLE IS
+ADAPTED TO THE CONDITIONS OF ITS LIFE, AND IT IS SO AT EVERY STAGE OF
+ITS EVOLUTION.
+
+But all adaptations CAN be referred to selection; the only point that
+remains doubtful is whether they all MUST be referred to it.
+
+However that may be, whether the LAMARCKIAN PRINCIPLE is a factor that
+has cooperated with selection in evolution, or whether it is altogether
+fallacious, the fact remains, that selection is the cause of a great
+part of the phyletic evolution of organisms on our earth. Those
+who agree with me in rejecting the LAMARCKIAN PRINCIPLE will regard
+selection as the only GUIDING factor in evolution, which creates what
+is new out of the transmissible variations, by ordering and arranging
+these, selecting them in relation to their number and size, as the
+architect does his building-stones so that a particular style must
+result. ("Variation under Domestication", 1875 II. pages 426, 427.) But
+the building-stones themselves, the variations, have their basis in the
+influences which cause variation in those vital units which are handed
+on from one generation to another, whether, taken together they form the
+WHOLE organism, as in Bacteria and other low forms of life, or only
+a germ-substance, as in unicellular and multicellular organisms. (The
+Author and Editor are indebted to Professor Poulton for kindly assisting
+in the revision of the proof of this Essay.)
+
+
+
+
+IV. VARIATION. By HUGO DE VRIES.
+
+Professor of Botany in the University of Amsterdam.
+
+
+I. DIFFERENT KINDS OF VARIABILITY.
+
+Before Darwin, little was known concerning the phenomena of variability.
+The fact, that hardly two leaves on a tree were exactly the same, could
+not escape observation: small deviations of the same kind were met with
+everywhere, among individuals as well as among the organs of the same
+plant. Larger aberrations, spoken of as monstrosities, were for a
+long time regarded as lying outside the range of ordinary phenomena. A
+special branch of inquiry, that of Teratology, was devoted to them, but
+it constituted a science by itself, sometimes connected with morphology,
+but having scarcely any bearing on the processes of evolution and
+heredity.
+
+Darwin was the first to take a broad survey of the whole range of
+variations in the animal and vegetable kingdoms. His theory of Natural
+Selection is based on the fact of variability. In order that this
+foundation should be as strong as possible he collected all the facts,
+scattered in the literature of his time, and tried to arrange them in a
+scientific way. He succeeded in showing that variations may be grouped
+along a line of almost continuous gradations, beginning with simple
+differences in size and ending with monstrosities. He was struck by the
+fact that, as a rule, the smaller the deviations, the more frequently
+they appear, very abrupt breaks in characters being of rare occurrence.
+
+Among these numerous degrees of variability Darwin was always on the
+look out for those which might, with the greatest probability, be
+considered as affording material for natural selection to act upon in
+the development of new species. Neither of the extremes complied with
+his conceptions. He often pointed out, that there are a good many small
+fluctuations, which in this respect must be absolutely useless. On the
+other hand, he strongly combated the belief, that great changes would be
+necessary to explain the origin of species. Some authors had propounded
+the idea that highly adapted organs, e.g. the wings of a bird, could
+not have been developed in any other way than by a comparatively sudden
+modification of a well defined and important kind. Such a conception
+would allow of great breaks or discontinuity in the evolution of highly
+differentiated animals and plants, shortening the time for the evolution
+of the whole organic kingdom and getting over numerous difficulties
+inherent in the theory of slow and gradual progress. It would, moreover,
+account for the genetic relation of the larger groups of both animals
+and plants. It would, in a word, undoubtedly afford an easy means of
+simplifying the problem of descent with modification.
+
+Darwin, however, considered such hypotheses as hardly belonging to the
+domain of science; they belong, he said, to the realm of miracles. That
+species have a capacity for change is admitted by all evolutionists; but
+there is no need to invoke modifications other than those represented by
+ordinary variability. It is well known that in artificial selection this
+tendency to vary has given rise to numerous distinct races, and there is
+no reason for denying that it can do the same in nature, by the aid of
+natural selection. On both lines an advance may be expected with equal
+probability.
+
+His main argument, however, is that the most striking and most highly
+adapted modifications may be acquired by successive variations. Each
+of these may be slight, and they may affect different organs, gradually
+adapting them to the same purpose. The direction of the adaptations
+will be determined by the needs in the struggle for life, and natural
+selection will simply exclude all such changes as occur on opposite
+or deviating lines. In this way, it is not variability itself which is
+called upon to explain beautiful adaptations, but it is quite sufficient
+to suppose that natural selection has operated during long periods in
+the same way. Eventually, all the acquired characters, being transmitted
+together, would appear to us, as if they had all been simultaneously
+developed.
+
+Correlations must play a large part in such special evolutions: when
+one part is modified, so will be other parts. The distribution of
+nourishment will come in as one of the causes, the reactions of
+different organs to the same external influences as another. But no
+doubt the more effective cause is that of the internal correlations,
+which, however, are still but dimly understood. Darwin repeatedly laid
+great stress on this view, although a definite proof of its correctness
+could not be given in his time. Such proof requires the direct
+observation of a mutation, and it should be stated here that even
+the first observations made in this direction have clearly confirmed
+Darwin's ideas. The new evening primroses which have sprung in my garden
+from the old form of Oenothera Lamarckiana, and which have evidently
+been derived from it, in each case, by a single mutation, do not differ
+from their parent species in one character only, but in almost all their
+organs and qualities. Oenothera gigas, for example, has stouter stems
+and denser foliage; the leaves are larger and broader; its thick
+flower-buds produce gigantic flowers, but only small fruits with large
+seeds. Correlative changes of this kind are seen in all my new forms,
+and they lend support to the view that in the gradual development of
+highly adapted structures, analogous correlations may have played a
+large part. They easily explain large deviations from an original type,
+without requiring the assumption of too many steps.
+
+Monstrosities, as their name implies, are widely different in character
+from natural species; they cannot, therefore, be adduced as evidence in
+the investigation of the origin of species. There is no doubt that they
+may have much in common as regards their manner of origin, and that the
+origin of species, once understood, may lead to a better understanding
+of the monstrosities. But the reverse is not true, at least not as
+regards the main lines of development. Here, it is clear, monstrosities
+cannot have played a part of any significance.
+
+Reversions, or atavistic changes, would seem to give a better support
+to the theory of descent through modifications. These have been of
+paramount importance on many lines of evolution of the animal as well
+as of the vegetable kingdom. It is often assumed that monocotyledons are
+descended from some lower group of dicotyledons, probably allied to that
+which includes the buttercup family. On this view the monocotyledons
+must be assumed to have lost the cambium and all its influence on
+secondary growth, the differentiation of the flower into calyx and
+corolla, the second cotyledon or seed-leaf and several other characters.
+Losses of characters such as these may have been the result of abrupt
+changes, but this does not prove that the characters themselves have
+been produced with equal suddenness. On the contrary, Darwin shows very
+convincingly that a modification may well be developed by a series of
+steps, and afterwards suddenly disappear. Many monstrosities, such as
+those represented by twisted stems, furnish direct proofs in support of
+this view, since they are produced by the loss of one character and this
+loss implies secondary changes in a large number of other organs and
+qualities.
+
+Darwin criticises in detail the hypothesis of great and abrupt changes
+and comes to the conclusion that it does not give even a shadow of
+an explanation of the origin of species. It is as improbable as it is
+unnecessary.
+
+Sports and spontaneous variations must now be considered. It is well
+known that they have produced a large number of fine horticultural
+varieties. The cut-leaved maple and many other trees and shrubs with
+split leaves are known to have been produced at a single step; this
+is true in the case of the single-leaf strawberry plant and of the
+laciniate variety of the greater celandine: many white flowers, white
+or yellow berries and numerous other forms had a similar origin. But
+changes such as these do not come under the head of adaptations, as they
+consist for the most part in the loss of some quality or organ belonging
+to the species from which they were derived. Darwin thinks it impossible
+to attribute to this cause the innumerable structures, which are so well
+adapted to the habits of life of each species. At the present time we
+should say that such adaptations require progressive modifications,
+which are additions to the stock of qualities already possessed by
+the ancestors, and cannot, therefore, be explained on the ground of
+a supposed analogy with sports, which are for the most part of a
+retrogressive nature.
+
+Excluding all these more or less sudden changes, there remains a long
+series of gradations of variability, but all of these are not assumed by
+Darwin to be equally fit for the production of new species. In the
+first place, he disregards all mere temporary variations, such as size,
+albinism, etc.; further, he points out that very many species have
+almost certainly been produced by steps, not greater, and probably not
+very much smaller, than those separating closely related varieties. For
+varieties are only small species. Next comes the question of polymorphic
+species: their occurrence seems to have been a source of much doubt and
+difficulty in Darwin's mind, although at present it forms one of
+the main supports of the prevailing explanation of the origin of new
+species. Darwin simply states that this kind of variability seems to
+be of a peculiar nature; since polymorphic species are now in a stable
+condition their occurrence gives no clue as to the mode of origin of
+new species. Polymorphic species are the expression of the result
+of previous variability acting on a large scale; but they now simply
+consist of more or less numerous elementary species, which, as far as we
+know, do not at present exhibit a larger degree of variability than any
+other more uniform species. The vernal whitlow-grass (Draba verna) and
+the wild pansy are the best known examples; both have spread over almost
+the whole of Europe and are split up into hundreds of elementary
+forms. These sub-species show no signs of any extraordinary degree
+of variability, when cultivated under conditions necessary for the
+exclusion of inter-crossing. Hooker has shown, in the case of some ferns
+distributed over still wider areas, that the extinction of some of the
+intermediate forms in such groups would suffice to justify the elevation
+of the remaining types to the rank of distinct species. Polymorphic
+species may now be regarded as the link which unites ordinary
+variability with the historical production of species. But it does not
+appear that they had this significance for Darwin; and, in fact, they
+exhibit no phenomena which could explain the processes by which one
+species has been derived from another. By thus narrowing the limits
+of the species-producing variability Darwin was led to regard small
+deviations as the source from which natural selection derives material
+upon which to act. But even these are not all of the same type, and
+Darwin was well aware of the fact.
+
+It should here be pointed out that in order to be selected, a change
+must first have been produced. This proposition, which now seems
+self-evident, has, however, been a source of much difference of opinion
+among Darwin's followers. The opinion that natural selection produces
+changes in useful directions has prevailed for a long time. In other
+words, it was assumed that natural selection, by the simple means of
+singling out, could induce small and useful changes to increase and
+to reach any desired degree of deviation from the original type. In
+my opinion this view was never actually held by Darwin. It is
+in contradiction with the acknowledged aim of all his work,--the
+explanation of the origin of species by means of natural forces and
+phenomena only. Natural selection acts as a sieve; it does not single
+out the best variations, but it simply destroys the larger number of
+those which are, from some cause or another, unfit for their present
+environment. In this way it keeps the strains up to the required
+standard, and, in special circumstances, may even improve them.
+
+Returning to the variations which afford the material for the
+sieving-action of natural selection, we may distinguish two main kinds.
+It is true that the distinction between these was not clear at the time
+of Darwin, and that he was unable to draw a sharp line between them.
+Nevertheless, in many cases, he was able to separate them, and he often
+discussed the question which of the two would be the real source of
+the differentiation of species. Certain variations constantly occur,
+especially such as are connected with size, weight, colour, etc. They
+are usually too small for natural selection to act upon, having hardly
+any influence in the struggle for life: others are more rare, occurring
+only from time to time, perhaps once or twice in a century, perhaps even
+only once in a thousand years. Moreover, these are of another type, not
+simply affecting size, number or weight, but bringing about something
+new, which may be useful or not. Whenever the variation is useful
+natural selection will take hold of it and preserve it; in other cases
+the variation may either persist or disappear.
+
+In his criticism of miscellaneous objections brought forward against the
+theory of natural selection after the publication of the first edition
+of "The Origin of Species", Darwin stated his view on this point very
+clearly:--"The doctrine of natural selection or the survival of the
+fittest, which implies that when variations or individual differences of
+a beneficial nature happen to arise, these will be preserved." ("Origin
+of Species" (6th edition), page 169, 1882.) In this sentence the words
+"HAPPEN TO ARISE" appear to me of prominent significance. They are
+evidently due to the same general conception which prevailed in Darwin's
+Pangenesis hypothesis. (Cf. de Vries, "Intracellulare Pangenesis", page
+73, Jena, 1889, and "Die Mutationstheorie", I. page 63. Leipzig, 1901.)
+
+A distinction is indicated between ordinary fluctuations which are
+always present, and such variations as "happen to arise" from time to
+time. ((I think it right to point out that the interpretation of this
+passage from the "Origin" by Professor de Vries is not accepted as
+correct either by Mr Francis Darwin or by myself. We do not believe that
+Darwin intended to draw any distinction between TWO TYPES of variation;
+the words "when variations or individual differences of a beneficial
+nature happen to arise" are not in our opinion meant to imply a
+distinction between ordinary fluctuations and variations which "happen
+to arise," but we believe that "or" is here used in the sense of ALIAS.
+With the permission of Professor de Vries, the following extract is
+quoted from a letter in which he replied to the objection raised to his
+reading of the passage in question:
+
+"As to your remarks on the passage on page 6, I agree that it is now
+impossible to see clearly how far Darwin went in his distinction of the
+different kinds of variability. Distinctions were only dimly guessed at
+by him. But in our endeavour to arrive at a true conception of his view
+I think that the chapter on Pangenesis should be our leading guide,
+and that we should try to interpret the more difficult passages by that
+chapter. A careful and often repeated study of the Pangenesis hypothesis
+has convinced me that Darwin, when he wrote that chapter, was well aware
+that ordinary variability has nothing to do with evolution, but that
+other kinds of variation were necessary. In some chapters he comes
+nearer to a clear distinction than in others. To my mind the expression
+'happen to arise' is the sharpest indication of his inclining in this
+direction. I am quite convinced that numerous expressions in his book
+become much clearer when looked at in this way."
+
+The statement in this passage that "Darwin was well aware that ordinary
+variability has nothing to do with evolution, but that other kinds
+of variation were necessary" is contradicted by many passages in the
+"Origin". A.C.S.)) The latter afford the material for natural selection
+to act upon on the broad lines of organic development, but the first
+do not. Fortuitous variations are the species-producing kind, which the
+theory requires; continuous fluctuations constitute, in this respect, a
+useless type.
+
+Of late, the study of variability has returned to the recognition of
+this distinction. Darwin's variations, which from time to time happen
+to arise, are MUTATIONS, the opposite type being commonly designed
+fluctuations. A large mass of facts, collected during the last few
+decades, has confirmed this view, which in Darwin's time could only be
+expressed with much reserve, and everyone knows that Darwin was always
+very careful in statements of this kind.
+
+From the same chapter I may here cite the following paragraph: "Thus
+as I am inclined to believe, morphological differences,... such as
+the arrangement of the leaves, the divisions of the flower or of the
+ovarium, the position of the ovules, etc.--first appeared in many cases
+as fluctuating variations, which sooner or later became constant through
+the nature of the organism and of the surrounding conditions... but NOT
+THROUGH NATURAL SELECTION (The italics are mine (H. de V.).); for as
+these morphological characters do not affect the welfare of the species,
+any slight deviation in them could not have been governed or accumulated
+through this latter agency." ("Origin of Species" (6th edition), page
+176.) We thus see that in Darwin's opinion, all small variations had
+not the same importance. In favourable circumstances some could become
+constant, but others could not.
+
+Since the appearance of the first edition of "The Origin of Species"
+fluctuating variability has been thoroughly studied by Quetelet. He
+discovered the law, which governs all phenomena of organic life falling
+under this head. It is a very simple law, and states that individual
+variations follow the laws of probability. He proved it, in the first
+place, for the size of the human body, using the measurements published
+for Belgian recruits; he then extended it to various other measurements
+of parts of the body, and finally concluded that it must be of universal
+validity for all organic beings. It must hold true for all characters in
+man, physical as well as intellectual and moral qualities; it must hold
+true for the plant kingdom as well as for the animal kingdom; in short,
+it must include the whole living world.
+
+Quetelet's law may be most easily studied in those cases where the
+variability relates to measure, number and weight, and a vast number of
+facts have since confirmed its exactness and its validity for all kinds
+of organisms, organs and qualities. But if we examine it more closely,
+we find that it includes just those minute variations, which, as Darwin
+repeatedly pointed out, have often no significance for the origin of
+species. In the phenomena, described by Quetelet's law nothing "happens
+to arise"; all is governed by the common law, which states that small
+deviations from the mean type are frequent, but that larger aberrations
+are rare, the rarer as they are larger. Any degree of variation will
+be found to occur, if only the number of individuals studied is large
+enough: it is even possible to calculate before hand, how many
+specimens must be compared in order to find a previously fixed degree of
+deviation.
+
+The variations, which from time to time happen to appear, are evidently
+not governed by this law. They cannot, as yet, be produced at will: no
+sowings of thousands or even of millions of plants will induce them,
+although by such means the chance of their occurring will obviously
+be increased. But they are known to occur, and to occur suddenly and
+abruptly. They have been observed especially in horticulture, where they
+are ranged in the large and ill-defined group called sports. Korschinsky
+has collected all the evidence which horticultural literature affords
+on this point. (S. Korschinsky, "Heterogenesis und Evolution", "Flora",
+Vol. LXXXIX. pages 240-363, 1901.) Several cases of the first appearance
+of a horticultural novelty have been recorded: this has always happened
+in the same way; it appeared suddenly and unexpectedly without any
+definite relation to previously existing variability. Dwarf types are
+one of the commonest and most favourite varieties of flowering plants;
+they are not originated by a repeated selection of the smallest
+specimens, but appear at once, without intermediates and without any
+previous indication. In many instances they are only about half the
+height of the original type, thus constituting obvious novelties. So it
+is in other cases described by Korschinsky: these sports or mutations
+are now recognised to be the main source of varieties of horticultural
+plants.
+
+As already stated, I do not pretend that the production of horticultural
+novelties is the prototype of the origin of new species in nature. I
+assume that they are, as a rule, derived from the parent species by the
+loss of some organ or quality, whereas the main lines of the evolution
+of the animal and vegetable kingdom are of course determined by
+progressive changes. Darwin himself has often pointed out this
+difference. But the saltatory origin of horticultural novelties is as
+yet the simplest parallel for natural mutations, since it relates to
+forms and phenomena, best known to the general student of evolution.
+
+The point which I wish to insist upon is this. The difference between
+small and ever present fluctuations and rare and more sudden variations
+was clear to Darwin, although the facts known at his time were too
+meagre to enable a sharp line to be drawn between these two great
+classes of variability. Since Darwin's time evidence, which proves
+the correctness of his view, has accumulated with increasing rapidity.
+Fluctuations constitute one type; they are never absent and follow the
+law of chance, but they do not afford the material from which to build
+new species. Mutations, on the other hand, only happen to occur from
+time to time. They do not necessarily produce greater changes than
+fluctuations, but such as may become, or rather are from their very
+nature, constant. It is this constancy which is the mark of specific
+characters, and on this basis every new specific character may be
+assumed to have arisen by mutation.
+
+Some authors have tried to show that the theory of mutation is opposed
+to Darwin's views. But this is erroneous. On the contrary, it is in
+fullest harmony with the great principle laid down by Darwin. In order
+to be acted upon by that complex of environmental forces, which Darwin
+has called natural selection, the changes must obviously first be there.
+The manner in which they are produced is of secondary importance and has
+hardly any bearing on the theory of descent with modification. ("Life
+and Letters" II. 125.)
+
+A critical survey of all the facts of variability of plants in nature as
+well as under cultivation has led me to the conviction, that Darwin was
+right in stating that those rare beneficial variations, which from time
+to time happen to arise,--the now so-called mutations--are the real
+source of progress in the whole realm of the organic world.
+
+II. EXTERNAL AND INTERNAL CAUSES OF VARIABILITY.
+
+All phenomena of animal and plant life are governed by two sets of
+causes; one of these is external, the other internal. As a rule the
+internal causes determine the nature of a phenomenon--what an organism
+can do and what it cannot do. The external causes, on the other hand,
+decide when a certain variation will occur, and to what extent its
+features may be developed.
+
+As a very clear and wholly typical instance I cite the cocks-combs
+(Celosia). This race is distinguished from allied forms by its faculty
+of producing the well-known broad and much twisted combs. Every single
+individual possesses this power, but all individuals do not exhibit
+it in its most complete form. In some cases this faculty may not be
+exhibited at the top of the main stem, although developed in lateral
+branches: in others it begins too late for full development. Much
+depends upon nourishment and cultivation, but almost always the
+horticulturist has to single out the best individuals and to reject
+those which do not come up to the standard.
+
+The internal causes are of a historical nature. The external ones may be
+defined as nourishment and environment. In some cases nutrition is
+the main factor, as, for instance, in fluctuating variability, but in
+natural selection environment usually plays the larger part.
+
+The internal or historical causes are constant during the life-time of
+a species, using the term species in its most limited sense, as
+designating the so-called elementary species or the units out of which
+the ordinary species are built up. These historical causes are simply
+the specific characters, since in the origin of a species one or more of
+these must have been changed, thus producing the characters of the new
+type. These changes must, of course, also be due partly to internal and
+partly to external causes.
+
+In contrast to these changes of the internal causes, the ordinary
+variability which is exhibited during the life-time of a species
+is called fluctuating variability. The name mutations or mutating
+variability is then given to the changes in the specific characters.
+It is desirable to consider these two main divisions of variability
+separately.
+
+In the case of fluctuations the internal causes, as well as the external
+ones, are often apparent. The specific characters may be designated as
+the mean about which the observed forms vary. Almost every character may
+be developed to a greater or a less degree, but the variations of the
+single characters producing a small deviation from the mean are usually
+the commonest. The limits of these fluctuations may be called wide or
+narrow, according to the way we look at them, but in numerous cases the
+extreme on the favoured side hardly surpasses double the value of that
+on the other side. The degree of this development, for every individual
+and for every organ, is dependent mainly on nutrition. Better
+nourishment or an increased supply of food produces a higher
+development; only it is not always easy to determine which direction
+is the fuller and which is the poorer one. The differences among
+individuals grown from different seeds are described as examples of
+individual variability, but those which may be observed on the same
+plant, or on cuttings, bulbs or roots derived from one individual
+are referred to as cases of partial variability. Partial variability,
+therefore, determines the differences among the flowers, fruits, leaves
+or branches of one individual: in the main, it follows the same laws
+as individual variability, but the position of a branch on a plant also
+determines its strength, and the part it may take in the nourishment of
+the whole. Composite flowers and umbels therefore have, as a rule,
+fewer rays on weak branches than on the strong main ones. The number of
+carpels in the fruits of poppies becomes very small on the weak lateral
+branches, which are produced towards the autumn, as well as on crowded,
+and therefore on weakened individuals. Double flowers follow the same
+rule, and numerous other instances could easily be adduced.
+
+Mutating variability occurs along three main lines. Either a character
+may disappear, or, as we now say, become latent; or a latent character
+may reappear, reproducing thereby a character which was once prominent
+in more or less remote ancestors. The third and most interesting case
+is that of the production of quite new characters which never existed in
+the ancestors. Upon this progressive mutability the main development of
+the animal and vegetable kingdom evidently depends. In contrast to this,
+the two other cases are called retrogressive and degressive mutability.
+In nature retrogressive mutability plays a large part; in agriculture
+and in horticulture it gives rise to numerous varieties, which have
+in the past been preserved, either on account of their usefulness or
+beauty, or simply as fancy-types. In fact the possession of numbers
+of varieties may be considered as the main character of domesticated
+animals and cultivated plants.
+
+In the case of retrogressive and degressive mutability the internal
+cause is at once apparent, for it is this which causes the disappearance
+or reappearance of some character. With progressive mutations the case
+is not so simple, since the new character must first be produced and
+then displayed. These two processes are theoretically different, but
+they may occur together or after long intervals. The production of the
+new character I call premutation, and the displaying mutation. Both of
+course must have their external as well as their internal causes, as
+I have repeatedly pointed out in my work on the Mutation Theory. ("Die
+Mutationstheorie", 2 vols., Leipzig, 1901.)
+
+It is probable that nutrition plays as important a part among the
+external causes of mutability as it does among those of fluctuating
+variability. Observations in support of this view, however, are too
+scanty to allow of a definite judgment. Darwin assumed an accumulative
+influence of external causes in the case of the production of new
+varieties or species. The accumulation might be limited to the life-time
+of a single individual, or embrace that of two or more generations.
+In the end a degree of instability in the equilibrium of one or more
+characters might be attained, great enough for a character to give
+way under a small shock produced by changed conditions of life. The
+character would then be thrown over from the old state of equilibrium
+into a new one.
+
+Characters which happen to be in this state of unstable equilibrium are
+called mutable. They may be either latent or active, being in the
+former case derived from old active ones or produced as new ones (by the
+process, designated premutation). They may be inherited in this mutable
+condition during a long series of generations. I have shown that in the
+case of the evening primrose of Lamarck this state of mutability
+must have existed for at least half a century, for this species was
+introduced from Texas into England about the year 1860, and since then
+all the strains derived from its first distribution over the several
+countries of Europe show the same phenomena in producing new forms.
+The production of the dwarf evening primrose, or Oenothera nanella,
+is assumed to be due to one of the factors, which determines the tall
+stature of the parent form, becoming latent; this would, therefore,
+afford an example of retrogressive mutation. Most of the other types
+of my new mutants, on the other hand, seem to be due to progressive
+mutability.
+
+The external causes of this curious period of mutability are as yet
+wholly unknown and can hardly be guessed at, since the origin of the
+Oenothera Lamarckiana is veiled in mystery. The seeds, introduced into
+England about 1860, were said to have come from Texas, but whether from
+wild or from cultivated plants we do not know. Nor has the species been
+recorded as having been observed in the wild condition. This, however,
+is nothing peculiar. The European types of Oenothera biennis and O.
+muricata are in the same condition. The first is said to have been
+introduced from Virginia, and the second from Canada, but both probably
+from plants cultivated in the gardens of these countries. Whether the
+same elementary species are still growing on those spots is unknown,
+mainly because the different sub-species of the species mentioned have
+not been systematically studied and distinguished.
+
+The origin of new species, which is in part the effect of mutability,
+is, however, due mainly to natural selection. Mutability provides the
+new characters and new elementary species. Natural selection, on the
+other hand, decides what is to live and what to die. Mutability seems to
+be free, and not restricted to previously determined lines. Selection,
+however, may take place along the same main lines in the course of long
+geological epochs, thus directing the development of large branches of
+the animal and vegetable kingdom. In natural selection it is evident
+that nutrition and environment are the main factors. But it is probable
+that, while nutrition may be one of the main causes of mutability,
+environment may play the chief part in the decisions ascribed to natural
+selection. Relations to neighbouring plants and to injurious or useful
+animals, have been considered the most important determining factors
+ever since the time when Darwin pointed out their prevailing influence.
+
+From this discussion of the main causes of variability we may derive the
+proposition that the study of every phenomenon in the field of heredity,
+of variability, and of the origin of new species will have to be
+considered from two standpoints; on one hand we have the internal
+causes, on the other the external ones. Sometimes the first are more
+easily detected, in other cases the latter are more accessible to
+investigation. But the complete elucidation of any phenomenon of life
+must always combine the study of the influence of internal with that of
+external causes.
+
+III. POLYMORPHIC VARIABILITY IN CEREALS.
+
+One of the propositions of Darwin's theory of the struggle for life
+maintains that the largest amount of life can be supported on any area,
+by great diversification or divergence in the structure and constitution
+of its inhabitants. Every meadow and every forest affords a proof of
+this thesis. The numerical proportion of the different species of the
+flora is always changing according to external influences. Thus, in a
+given meadow, some species will flower abundantly in one year and then
+almost disappear, until, after a series of years, circumstances allow
+them again to multiply rapidly. Other species, which have taken their
+places, will then become rare. It follows from this principle, that
+notwithstanding the constantly changing conditions, a suitable
+selection from the constituents of a meadow will ensure a continued
+high production. But, although the principle is quite clear, artificial
+selection has, as yet, done very little towards reaching a really high
+standard.
+
+The same holds good for cereals. In ordinary circumstances a field
+will give a greater yield, if the crop grown consists of a number of
+sufficiently differing types. Hence it happens that almost all older
+varieties of wheat are mixtures of more or less diverging forms. In the
+same variety the numerical composition will vary from year to year, and
+in oats this may, in bad years, go so far as to destroy more than half
+of the harvest, the wind-oats (Avena fatua), which scatter their grain
+to the winds as soon as it ripens, increasing so rapidly that they
+assume the dominant place. A severe winter, a cold spring and other
+extreme conditions of life will destroy one form more completely
+than another, and it is evident that great changes in the numerical
+composition of the mixture may thus be brought about.
+
+This mixed condition of the common varieties of cereals was well known
+to Darwin. For him it constituted one of the many types of variability.
+It is of that peculiar nature to which, in describing other groups,
+he applies the term polymorphy. It does not imply that the single
+constituents of the varieties are at present really changing their
+characters. On the other hand, it does not exclude the possibility of
+such changes. It simply states that observation shows the existence of
+different forms; how these have originated is a question which it
+does not deal with. In his well-known discussion of the variability of
+cereals, Darwin is mainly concerned with the question, whether under
+cultivation they have undergone great changes or only small ones.
+The decision ultimately depends on the question, how many forms have
+originally been taken into cultivation. Assuming five or six initial
+species, the variability must be assumed to have been very large, but
+on the assumption that there were between ten and fifteen types, the
+necessary range of variability is obviously much smaller. But in regard
+to this point, we are of course entirely without historical data.
+
+Few of the varieties of wheat show conspicuous differences, although
+their number is great. If we compare the differentiating characters of
+the smaller types of cereals with those of ordinary wild species, even
+within the same genus or family, they are obviously much less marked.
+All these small characters, however, are strictly inherited, and this
+fact makes it very probable that the less obvious constituents of the
+mixtures in ordinary fields must be constant and pure as long as they do
+not intercross. Natural crossing is in most cereals a phenomenon of rare
+occurrence, common enough to admit of the production of all possible
+hybrid combinations, but requiring the lapse of a long series of years
+to reach its full effect.
+
+Darwin laid great stress on this high amount of variability in the
+plants of the same variety, and illustrated it by the experience of
+Colonel Le Couteur ("On the Varieties, Properties, and Classification of
+Wheat", Jersey, 1837.) on his farm on the isle of Jersey, who cultivated
+upwards of 150 varieties of wheat, which he claimed were as pure as
+those of any other agriculturalist. But Professor La Gasca of Madrid,
+who visited him, drew attention to aberrant ears, and pointed out, that
+some of them might be better yielders than the majority of plants in the
+crop, whilst others might be poor types. Thence he concluded that the
+isolation of the better ones might be a means of increasing his crops.
+Le Couteur seems to have considered the constancy of such smaller types
+after isolation as absolutely probable, since he did not even discuss
+the possibility of their being variable or of their yielding a
+changeable or mixed progeny. This curious fact proves that he considered
+the types, discovered in his fields by La Gasca to be of the same kind
+as his other varieties, which until that time he had relied upon as
+being pure and uniform. Thus we see, that for him, the variability of
+cereals was what we now call polymorphy. He looked through his fields
+for useful aberrations, and collected twenty-three new types of wheat.
+He was, moreover, clear about one point, which, on being rediscovered
+after half a century, has become the starting-point for the new Swedish
+principle of selecting agricultural plants. It was the principle of
+single-ear sowing, instead of mixing the grains of all the selected ears
+together. By sowing each ear on a separate plot he intended not only
+to multiply them, but also to compare their value. This comparison
+ultimately led him to the choice of some few valuable sorts, one of
+which, the "Bellevue de Talavera," still holds its place among the
+prominent sorts of wheat cultivated in France. This variety seems to be
+really a uniform type, a quality very useful under favourable conditions
+of cultivation, but which seems to have destroyed its capacity for
+further improvement by selection.
+
+The principle of single-ear sowing, with a view to obtain pure and
+uniform strains without further selection, has, until a few years ago,
+been almost entirely lost sight of. Only a very few agriculturists have
+applied it: among these are Patrick Shirreff ("Die Verbesserung der
+Getreide-Arten", translated by R. Hesse, Halle, 1880.) in Scotland
+and Willet M. Hays ("Wheat, varieties, breeding, cultivation", Univ.
+Minnesota, Agricultural Experimental Station, Bull. no. 62, 1899.) in
+Minnesota. Patrick Shirreff observed the fact, that in large fields of
+cereals, single plants may from time to time be found with larger ears,
+which justify the expectation of a far greater yield. In the course of
+about twenty-five years he isolated in this way two varieties of wheat
+and two of oats. He simply multiplied them as fast as possible, without
+any selection, and put them on the market.
+
+Hays was struck by the fact that the yield of wheat in Minnesota was far
+beneath that in the neighbouring States. The local varieties were Fife
+and Blue Stem. They gave him, on inspection, some better specimens,
+"phenomenal yielders" as he called them. These were simply isolated and
+propagated, and, after comparison with the parent-variety and with some
+other selected strains of less value, were judged to be of sufficient
+importance to be tested by cultivation all over the State of Minnesota.
+They have since almost supplanted the original types, at least in most
+parts of the State, with the result that the total yield of wheat in
+Minnesota is said to have been increased by about a million dollars
+yearly.
+
+Definite progress in the method of single-ear sowing has, however, been
+made only recently. It had been foreshadowed by Patrick Shirreff, who
+after the production of the four varieties already mentioned, tried
+to carry out his work on a larger scale, by including numerous minor
+deviations from the main type. He found by doing so that the chances
+of obtaining a better form were sufficiently increased to justify
+the trial. But it was Nilsson who discovered the almost inexhaustible
+polymorphy of cereals and other agricultural crops and made it the
+starting-point for a new and entirely trustworthy method of the highest
+utility. By this means he has produced during the last fifteen years a
+number of new and valuable races, which have already supplanted the old
+types on numerous farms in Sweden and which are now being introduced on
+a large scale into Germany and other European countries.
+
+It is now twenty years since the station at Svalof was founded. During
+the first period of its work, embracing about five years, selection was
+practised on the principle which was then generally used in Germany. In
+order to improve a race a sample of the best ears was carefully selected
+from the best fields of the variety. These ears were considered as
+representatives of the type under cultivation, and it was assumed that
+by sowing their grains on a small plot a family could be obtained, which
+could afterwards be improved by a continuous selection. Differences
+between the collected ears were either not observed or disregarded. At
+Svalof this method of selection was practised on a far larger scale than
+on any German farm, and the result was, broadly speaking, the same.
+This may be stated in the following words: improvement in a few cases,
+failure in all the others. Some few varieties could be improved and
+yielded excellent new types, some of which have since been introduced
+into Swedish agriculture and are now prominent races in the southern
+and middle parts of the country. But the station had definite aims, and
+among them was the improvement of the Chevalier barley. This, in
+Middle Sweden, is a fine brewer's barley, but liable to failure during
+unfavourable summers on account of its slender stems. It was selected
+with a view of giving it stiffer stems, but in spite of all the care and
+work bestowed upon it no satisfactory result was obtained.
+
+This experience, combined with a number of analogous failures, could
+not fail to throw doubt upon the whole method. It was evident that good
+results were only exceptions, and that in most cases the principle
+was not one that could be relied upon. The exceptions might be due
+to unknown causes, and not to the validity of the method; it became
+therefore of much more interest to search for the causes than to
+continue the work along these lines.
+
+In the year 1892 a number of different varieties of cereals were
+cultivated on a large scale and a selection was again made from
+them. About two hundred samples of ears were chosen, each apparently
+constituting a different type. Their seeds were sown on separate plots
+and manured and treated as much as possible in the same manner. The
+plots were small and arranged in rows so as to facilitate the comparison
+of allied types. During the whole period of growth and during the
+ripening of the ears the plots were carefully studied and compared: they
+were harvested separately; ears and kernels were counted and weighed,
+and notes were made concerning layering, rust and other cereal pests.
+
+The result of this experiment was, in the main, no distinct improvement.
+Nilsson was especially struck by the fact that the plots, which should
+represent distinct types, were far from uniform. Many of them were as
+multiform as the fields from which the parent-ears were taken. Others
+showed variability in a less degree, but in almost all of them it was
+clear that a pure race had not been obtained. The experiment was a fair
+one, inasmuch as it demonstrated the polymorphic variability of cereals
+beyond all doubt and in a degree hitherto unsuspected; but from the
+standpoint of the selectionist it was a failure. Fortunately there were,
+however, one or two exceptions. A few lots showed a perfect uniformity
+in regard to all the stalks and ears: these were small families. This
+fact suggested the idea that each might have been derived from a single
+ear. During the selection in the previous summer, Nilsson had tried to
+find as many ears as possible of each new type which he recognised in
+his fields. But the variability of his crops was so great, that he was
+rarely able to include more than two or three ears in the same group,
+and, in a few cases, he found only one representative of the supposed
+type. It might, therefore, be possible that those small uniform plots
+were the direct progeny of ears, the grains of which had not been mixed
+with those from other ears before sowing. Exact records had, of course,
+been kept of the chosen samples, and the number of ears had been noted
+in each case. It was, therefore, possible to answer the question and it
+was found that those plots alone were uniform on which the kernels of
+one single ear only had been sown. Nilsson concluded that the mixture
+of two or more ears in a single sowing might be the cause of the lack of
+uniformity in the progeny. Apparently similar ears might be different in
+their progeny.
+
+Once discovered, this fact was elevated to the rank of a leading
+principle and tested on as large a scale as possible. The fields were
+again carefully investigated and every single ear, which showed a
+distinct divergence from the main type in one character or another,
+was selected. A thousand samples were chosen, but this time each sample
+consisted of one ear only. Next year, the result corresponded to the
+expectation. Uniformity prevailed almost everywhere; only a few
+lots showed a discrepancy, which might be ascribed to the accidental
+selection of hybrid ears. It was now clear that the progeny of single
+ears was, as a rule, pure, whereas that of mixed ears was impure.
+The single-ear selection or single-ear sowing, which had fallen into
+discredit in Germany and elsewhere in Europe, was rediscovered. It
+proved to be the only trustworthy principle of selection. Once isolated,
+such single-parent races are constant from seed and remain true to their
+type. No further selection is needed; they have simply to be multiplied
+and their real value tested.
+
+Patrick Shirreff, in his early experiments, Le Couteur, Hays and others
+had observed the rare occurrence of exceptionally good yielders and the
+value of their isolation to the agriculturist. The possibility of error
+in the choice of such striking specimens and the necessity of judging
+their value by their progeny were also known to these investigators, but
+they had not the slightest idea of all the possibilities suggested by
+their principle. Nilsson, who is a botanist as well as an agriculturist,
+discovered that, besides these exceptionably good yielders, every
+variety of a cereal consists of hundreds of different types, which find
+the best conditions for success when grown together, but which, after
+isolation, prove to be constant. Their preference for mixed growth is so
+definite, that once isolated, their claims on manure and treatment
+are found to be much higher than those of the original mixed variety.
+Moreover, the greatest care is necessary to enable them to retain
+their purity, and as soon as they are left to themselves they begin to
+deteriorate through accidental crosses and admixtures and rapidly return
+to the mixed condition.
+
+Reverting now to Darwin's discussion of the variability of cereals, we
+may conclude that subsequent investigation has proved it to be exactly
+of the kind which he describes. The only difference is that in reality
+it reaches a degree, quite unexpected by Darwin and his contemporaries.
+But it is polymorphic variability in the strictest sense of the word.
+How the single constituents of a variety originate we do not see. We
+may assume, and there can hardly be a doubt about the truth of the
+assumption, that a new character, once produced, will slowly but surely
+be combined through accidental crosses with a large number of
+previously existing types, and so will tend to double the number of the
+constituents of the variety. But whether it first appears suddenly or
+whether it is only slowly evolved we cannot determine. It would, of
+course, be impossible to observe either process in such a mixture. Only
+cultures of pure races, of single-parent races as we have called them,
+can afford an opportunity for this kind of observation. In the fields of
+Svalof new and unexpected qualities have recently been seen, from time
+to time, to appear suddenly. These characters are as distinct as the
+older ones and appear to be constant from the moment of their origin.
+
+Darwin has repeatedly insisted that man does not cause variability. He
+simply selects the variations given to him by the hand of nature. He may
+repeat this process in order to accumulate different new characters
+in the same family, thus producing varieties of a higher order. This
+process of accumulation would, if continued for a longer time, lead to
+the augmentation of the slight differences characteristic of varieties
+into the greater differences characteristic of species and genera. It is
+in this way that horticultural and agricultural experience contribute
+to the problem of the conversion of varieties into species, and to the
+explanation of the admirable adaptations of each organism to its complex
+conditions of life. In the long run new forms, distinguished from their
+allies by quite a number of new characters, would, by the extermination
+of the older intermediates, become distinct species.
+
+Thus we see that the theory of the origin of species by means of natural
+selection is quite independent of the question, how the variations to
+be selected arise. They may arise slowly, from simple fluctuations, or
+suddenly, by mutations; in both cases natural selection will take hold
+of them, will multiply them if they are beneficial, and in the course of
+time accumulate them, so as to produce that great diversity of organic
+life, which we so highly admire.
+
+Darwin has left the decision of this difficult and obviously subordinate
+point to his followers. But in his Pangenesis hypothesis he has given us
+the clue for a close study and ultimate elucidation of the subject under
+discussion.
+
+
+
+
+V. HEREDITY AND VARIATION IN MODERN LIGHTS. By W. Bateson, M.A., F.R.S.
+
+Professor of Biology in the University of Cambridge.
+
+
+Darwin's work has the property of greatness in that it may be admired
+from more aspects than one. For some the perception of the principle of
+Natural Selection stands out as his most wonderful achievement to which
+all the rest is subordinate. Others, among whom I would range myself,
+look up to him rather as the first who plainly distinguished, collected,
+and comprehensively studied that new class of evidence from which
+hereafter a true understanding of the process of Evolution may be
+developed. We each prefer our own standpoint of admiration; but I think
+that it will be in their wider aspect that his labours will most command
+the veneration of posterity.
+
+A treatise written to advance knowledge may be read in two moods. The
+reader may keep his mind passive, willing merely to receive the impress
+of the writer's thought; or he may read with his attention strained and
+alert, asking at every instant how the new knowledge can be used in a
+further advance, watching continually for fresh footholds by which to
+climb higher still. Of Shelley it has been said that he was a poet
+for poets: so Darwin was a naturalist for naturalists. It is when his
+writings are used in the critical and more exacting spirit with which
+we test the outfit for our own enterprise that we learn their full value
+and strength. Whether we glance back and compare his performance with
+the efforts of his predecessors, or look forward along the course which
+modern research is disclosing, we shall honour most in him not the
+rounded merit of finite accomplishment, but the creative power by which
+he inaugurated a line of discovery endless in variety and extension.
+Let us attempt thus to see his work in true perspective between the past
+from which it grew, and the present which is its consequence. Darwin
+attacked the problem of Evolution by reference to facts of three
+classes: Variation; Heredity; Natural Selection. His work was not as the
+laity suppose, a sudden and unheralded revelation, but the first fruit
+of a long and hitherto barren controversy. The occurrence of variation
+from type, and the hereditary transmission of such variation had of
+course been long familiar to practical men, and inferences as to the
+possible bearing of those phenomena on the nature of specific difference
+had been from time to time drawn by naturalists. Maupertuis, for
+example, wrote "Ce qui nous reste a examiner, c'est comment d'un seul
+individu, il a pu naitre tant d'especes si differentes." And again "La
+Nature contient le fonds de toutes ces varietes: mais le hasard ou l'art
+les mettent en oeuvre. C'est ainsi que ceux dont l'industrie s'applique
+a satisfaire le gout des curieux, sont, pour ainsi dire, creatures
+d'especes nouvelles." ("Venus Physique, contenant deux Dissertations,
+l'une sur l'origine des Hommes et des Animaux: Et l'autre sur l'origine
+des Noirs" La Haye, 1746, pages 124 and 129. For an introduction to the
+writings of Maupertuis I am indebted to an article by Professor Lovejoy
+in "Popular Sci. Monthly", 1902.)
+
+Such passages, of which many (though few so emphatic) can be found in
+eighteenth century writers, indicate a true perception of the mode of
+Evolution. The speculations hinted at by Buffon (For the fullest account
+of the views of these pioneers of Evolution, see the works of Samuel
+Butler, especially "Evolution, Old and New" (2nd edition) 1882. Butler's
+claims on behalf of Buffon have met with some acceptance; but after
+reading what Butler has said, and a considerable part of Buffon's own
+works, the word "hinted" seems to me a sufficiently correct description
+of the part he played. It is interesting to note that in the chapter on
+the Ass, which contains some of his evolutionary passages, there is a
+reference to "plusieurs idees tres-elevees sur la generation" contained
+in the Letters of Maupertuis.), developed by Erasmus Darwin, and
+independently proclaimed above all by Lamarck, gave to the doctrine of
+descent a wide renown. The uniformitarian teaching which Lyell deduced
+from geological observation had gained acceptance. The facts of
+geographical distribution (See especially W. Lawrence, "Lectures on
+Physiology", London, 1823, pages 213 f.) had been shown to be obviously
+inconsistent with the Mosaic legend. Prichard, and Lawrence, following
+the example of Blumenbach, had successfully demonstrated that the races
+of Man could be regarded as different forms of one species, contrary
+to the opinion up till then received. These treatises all begin, it is
+true, with a profound obeisance to the sons of Noah, but that performed,
+they continue on strictly modern lines. The question of the mutability
+of species was thus prominently raised.
+
+Those who rate Lamarck no higher than did Huxley in his contemptuous
+phrase "buccinator tantum," will scarcely deny that the sound of the
+trumpet had carried far, or that its note was clear. If then there were
+few who had already turned to evolution with positive conviction,
+all scientific men must at least have known that such views had been
+promulgated; and many must, as Huxley says, have taken up his own
+position of "critical expectancy." (See the chapter contributed to the
+"Life and Letters of Charles Darwin" II. page 195. I do not clearly
+understand the sense in which Darwin wrote (Autobiography, ibid. I. page
+87): "It has sometimes been said that the success of the "Origin" proved
+'that the subject was in the air,' or 'that men's minds were prepared
+for it.' I do not think that this is strictly true, for I occasionally
+sounded not a few naturalists, and never happened to come across a
+single one who seemed to doubt about the permanence of species." This
+experience may perhaps have been an accident due to Darwin's isolation.
+The literature of the period abounds with indications of "critical
+expectancy." A most interesting expression of that feeling is given in
+the charming account of the "Early Days of Darwinism" by Alfred Newton,
+"Macmillan's Magazine", LVII. 1888, page 241. He tells how in 1858
+when spending a dreary summer in Iceland, he and his friend, the
+ornithologist John Wolley, in default of active occupation, spent
+their days in discussion. "Both of us taking a keen interest in Natural
+History, it was but reasonable that a question, which in those days
+was always coming up wherever two or more naturalists were gathered
+together, should be continually recurring. That question was, 'What is
+a species?' and connected therewith was the other question, 'How did a
+species begin?'... Now we were of course fairly well acquainted with what
+had been published on these subjects." He then enumerates some of these
+publications, mentioning among others T. Vernon Wollaston's "Variation
+of Species"--a work which has in my opinion never been adequately
+appreciated. He proceeds: "Of course we never arrived at anything like
+a solution of these problems, general or special, but we felt very
+strongly that a solution ought to be found, and that quickly, if the
+study of Botany and Zoology was to make any great advance." He then
+describes how on his return home he received the famous number of the
+"Linnean Journal" on a certain evening. "I sat up late that night to
+read it; and never shall I forget the impression it made upon me. Herein
+was contained a perfectly simple solution of all the difficulties which
+had been troubling me for months past... I went to bed satisfied that a
+solution had been found.")
+
+Why, then, was it, that Darwin succeeded where the rest had failed?
+The cause of that success was two-fold. First, and obviously, in the
+principle of Natural Selection he had a suggestion which would work. It
+might not go the whole way, but it was true as far as it went. Evolution
+could thus in great measure be fairly represented as a consequence of
+demonstrable processes. Darwin seldom endangers the mechanism he devised
+by putting on it strains much greater than it can bear. He at least was
+under no illusion as to the omnipotence of Selection; and he introduces
+none of the forced pleading which in recent years has threatened to
+discredit that principle.
+
+For example, in the latest text of the "Origin" ("Origin", (6th edition
+(1882), page 421.)) we find him saying:
+
+"But as my conclusions have lately been much misrepresented, and it has
+been stated that I attribute the modification of species exclusively
+to natural selection, I may be permitted to remark that in the first
+edition of this work, and subsequently, I placed in a most conspicuous
+position--namely, at the close of the Introduction--the following words:
+'I am convinced that natural selection has been the main but not the
+exclusive means of modification.'"
+
+But apart from the invention of this reasonable hypothesis, which may
+well, as Huxley estimated, "be the guide of biological and psychological
+speculation for the next three or four generations," Darwin made a more
+significant and imperishable contribution. Not for a few generations,
+but through all ages he should be remembered as the first who showed
+clearly that the problems of Heredity and Variation are soluble by
+observation, and laid down the course by which we must proceed to
+their solution. (Whatever be our estimate of the importance of Natural
+Selection, in this we all agree. Samuel Butler, the most brilliant, and
+by far the most interesting of Darwin's opponents--whose works are at
+length emerging from oblivion--in his Preface (1882) to the 2nd edition
+of "Evolution, Old and New", repeats his earlier expression of homage to
+one whom he had come to regard as an enemy: "To the end of time, if
+the question be asked, 'Who taught people to believe in Evolution?' the
+answer must be that it was Mr. Darwin. This is true, and it is hard to
+see what palm of higher praise can be awarded to any philosopher.") The
+moment of inspiration did not come with the reading of Malthus, but with
+the opening of the "first note-book on Transmutation of Species." ("Life
+and Letters", I. pages 276 and 83.) Evolution is a process of Variation
+and Heredity. The older writers, though they had some vague idea that
+it must be so, did not study Variation and Heredity. Darwin did, and so
+begat not a theory, but a science.
+
+The extent to which this is true, the scientific world is only beginning
+to realise. So little was the fact appreciated in Darwin's own time that
+the success of his writings was followed by an almost total cessation of
+work in that special field. Of the causes which led to this remarkable
+consequence I have spoken elsewhere. They proceeded from circumstances
+peculiar to the time; but whatever the causes there is no doubt that
+this statement of the result is historically exact, and those who
+make it their business to collect facts elucidating the physiology of
+Heredity and Variation are well aware that they will find little to
+reward their quest in the leading scientific Journals of the Darwinian
+epoch.
+
+In those thirty years the original stock of evidence current and in
+circulation even underwent a process of attrition. As in the story of
+the Eastern sage who first wrote the collected learning of the universe
+for his sons in a thousand volumes, and by successive compression and
+burning reduced them to one, and from this by further burning distilled
+the single ejaculation of the Faith, "There is no god but God and
+Mohamed is the Prophet of God," which was all his maturer wisdom deemed
+essential:--so in the books of that period do we find the corpus of
+genetic knowledge dwindle to a few prerogative instances, and these at
+last to the brief formula of an unquestioned creed.
+
+And yet in all else that concerns biological science this period was,
+in very truth, our Golden Age, when the natural history of the earth was
+explored as never before; morphology and embryology were exhaustively
+ransacked; the physiology of plants and animals began to rival chemistry
+and physics in precision of method and in the rapidity of its advances;
+and the foundations of pathology were laid.
+
+In contrast with this immense activity elsewhere the neglect which befel
+the special physiology of Descent, or Genetics as we now call it, is
+astonishing. This may of course be interpreted as meaning that the
+favoured studies seemed to promise a quicker return for effort, but it
+would be more true to say that those who chose these other pursuits did
+so without making any such comparison; for the idea that the physiology
+of Heredity and Variation was a coherent science, offering possibilities
+of extraordinary discovery, was not present to their minds at all. In
+a word, the existence of such a science was well nigh forgotten. It is
+true that in ancillary periodicals, as for example those that treat of
+entomology or horticulture, or in the writings of the already isolated
+systematists (This isolation of the systematists is the one most
+melancholy sequela of Darwinism. It seems an irony that we should
+read in the peroration to the "Origin" that when the Darwinian view
+is accepted "Systematists will be able to pursue their labours as at
+present; but they will not be incessantly haunted by the shadowy doubt
+whether this or that form be a true species. This, I feel sure, and I
+speak after experience, will be no slight relief. The endless disputes
+whether or not some fifty species of British brambles are good species
+will cease." "Origin", 6th edition (1882), page 425. True they have
+ceased to attract the attention of those who lead opinion, but anyone
+who will turn to the literature of systematics will find that they have
+not ceased in any other sense. Should there not be something disquieting
+in the fact that among the workers who come most into contact with
+specific differences, are to be found the only men who have failed to
+be persuaded of the unreality of those differences?), observations with
+this special bearing were from time to time related, but the class of
+fact on which Darwin built his conceptions of Heredity and Variation was
+not seen in the highways of biology. It formed no part of the official
+curriculum of biological students, and found no place among the subjects
+which their teachers were investigating.
+
+During this period nevertheless one distinct advance was made, that
+with which Weismann's name is prominently connected. In Darwin's genetic
+scheme the hereditary transmission of parental experience and its
+consequences played a considerable role. Exactly how great that role was
+supposed to be, he with his habitual caution refrained from specifying,
+for the sufficient reason that he did not know. Nevertheless much of
+the process of Evolution, especially that by which organs have become
+degenerate and rudimentary, was certainly attributed by Darwin to
+such inheritance, though since belief in the inheritance of acquired
+characters fell into disrepute, the fact has been a good deal
+overlooked. The "Origin" without "use and disuse" would be a materially
+different book. A certain vacillation is discernible in Darwin's
+utterances on this question, and the fact gave to the astute Butler
+an opportunity for his most telling attack. The discussion which best
+illustrates the genetic views of the period arose in regard to the
+production of the rudimentary condition of the wings of many beetles
+in the Madeira group of islands, and by comparing passages from the
+"Origin" (6th edition pages 109 and 401. See Butler, "Essays on Life,
+Art, and Science", page 265, reprinted 1908, and "Evolution, Old and
+New", chapter XXII. (2nd edition), 1882.) Butler convicts Darwin
+of saying first that this condition was in the main the result of
+Selection, with disuse aiding, and in another place that the main cause
+of degeneration was disuse, but that Selection had aided. To Darwin
+however I think the point would have seemed one of dialectics merely. To
+him the one paramount purpose was to show that somehow an Evolution
+by means of Variation and Heredity might have brought about the facts
+observed, and whether they had come to pass in the one way or the other
+was a matter of subordinate concern.
+
+
+To us moderns the question at issue has a diminished significance. For
+over all such debates a change has been brought by Weismann's challenge
+for evidence that use and disuse have any transmitted effects at all.
+Hitherto the transmission of many acquired characteristics had seemed
+to most naturalists so obvious as not to call for demonstration. (W.
+Lawrence was one of the few who consistently maintained the contrary
+opinion. Prichard, who previously had expressed himself in the same
+sense, does not, I believe repeat these views in his later writings, and
+there are signs that he came to believe in the transmission of acquired
+habits. See Lawrence, "Lect. Physiol." 1823, pages 436-437, 447
+Prichard, Edin. Inaug. Disp. 1808 (not seen by me), quoted ibid. and
+"Nat. Hist. Man", 1843, pages 34 f.) Weismann's demand for facts in
+support of the main proposition revealed at once that none having real
+cogency could be produced. The time-honoured examples were easily shown
+to be capable of different explanations. A few certainly remain
+which cannot be so summarily dismissed, but--though it is manifestly
+impossible here to do justice to such a subject--I think no one will
+dispute that these residual and doubtful phenomena, whatever be their
+true nature, are not of a kind to help us much in the interpretation
+of any of those complex cases of adaptation which on the hypothesis of
+unguided Natural Selection are especially difficult to understand. Use
+and disuse were invoked expressly to help us over these hard places; but
+whatever changes can be induced in offspring by direct treatment of the
+parents, they are not of a kind to encourage hope of real assistance
+from that quarter. It is not to be denied that through the collapse of
+this second line of argument the Selection hypothesis has had to take
+an increased and perilous burden. Various ways of meeting the difficulty
+have been proposed, but these mostly resolve themselves into improbable
+attempts to expand or magnify the powers of Natural Selection.
+
+Weismann's interpellation, though negative in purpose, has had a lasting
+and beneficial effect, for through his thorough demolition of the old
+loose and distracting notions of inherited experience, the ground has
+been cleared for the construction of a true knowledge of heredity based
+on experimental fact.
+
+In another way he made a contribution of a more positive character,
+for his elaborate speculations as to the genetic meaning of cytological
+appearances have led to a minute investigation of the visible phenomena
+occurring in those divisions by which germ-cells arise. Though the
+particular views he advocated have very largely proved incompatible
+with the observed facts of heredity, yet we must acknowledge that it was
+chiefly through the stimulus of Weismann's ideas that those advances
+in cytology were made; and though the doctrine of the continuity of
+germ-plasm cannot be maintained in the form originally propounded, it is
+in the main true and illuminating. (It is interesting to see how nearly
+Butler was led by natural penetration, and from absolutely opposite
+conclusions, back to this underlying truth: "So that each ovum when
+impregnate should be considered not as descended from its ancestors, but
+as being a continuation of the personality of every ovum in the chain
+of its ancestry, which every ovum IT ACTUALLY IS quite as truly as the
+octogenarian IS the same identity with the ovum from which he has been
+developed. This process cannot stop short of the primordial cell,
+which again will probably turn out to be but a brief resting-place. We
+therefore prove each one of us to BE ACTUALLY the primordial cell which
+never died nor dies, but has differentiated itself into the life of the
+world, all living beings whatever, being one with it and members one of
+another," "Life and Habit", 1878, page 86.) Nevertheless in the present
+state of knowledge we are still as a rule quite unable to connect
+cytological appearances with any genetic consequence and save in one
+respect (obviously of extreme importance--to be spoken of later) the two
+sets of phenomena might, for all we can see, be entirely distinct.
+
+I cannot avoid attaching importance to this want of connection between
+the nuclear phenomena and the features of bodily organisation. All
+attempts to investigate Heredity by cytological means lie under
+the disadvantage that it is the nuclear changes which can alone be
+effectively observed. Important as they must surely be, I have never
+been persuaded that the rest of the cell counts for nothing. What we
+know of the behaviour and variability of chromosomes seems in my opinion
+quite incompatible with the belief that they alone govern form, and are
+the sole agents responsible in heredity. (This view is no doubt contrary
+to the received opinion. I am however interested to see it lately
+maintained by Driesch ("Science and Philosophy of the Organism", London,
+1907, page 233), and from the recent observations of Godlewski it has
+received distinct experimental support.)
+
+If, then, progress was to be made in Genetics, work of a different kind
+was required. To learn the laws of Heredity and Variation there is
+no other way than that which Darwin himself followed, the direct
+examination of the phenomena. A beginning could be made by collecting
+fortuitous observations of this class, which have often thrown a
+suggestive light, but such evidence can be at best but superficial and
+some more penetrating instrument of research is required. This can only
+be provided by actual experiments in breeding.
+
+The truth of these general considerations was becoming gradually clear
+to many of us when in 1900 Mendel's work was rediscovered. Segregation,
+a phenomenon of the utmost novelty, was thus revealed. From that moment
+not only in the problem of the origin of species, but in all the great
+problems of biology a new era began. So unexpected was the discovery
+that many naturalists were convinced it was untrue, and at once
+proclaimed Mendel's conclusions as either altogether mistaken, or if
+true, of very limited application. Many fantastic notions about the
+workings of Heredity had been asserted as general principles before:
+this was probably only another fancy of the same class.
+
+Nevertheless those who had a preliminary acquaintance with the facts
+of Variation were not wholly unprepared for some such revelation. The
+essential deduction from the discovery of segregation was that the
+characters of living things are dependent on the presence of definite
+elements or factors, which are treated as units in the processes of
+Heredity. These factors can thus be recombined in various ways. They act
+sometimes separately, and sometimes they interact in conjunction with
+each other, producing their various effects. All this indicates a
+definiteness and specific order in heredity, and therefore in variation.
+This order cannot by the nature of the case be dependent on Natural
+Selection for its existence, but must be a consequence of the
+fundamental chemical and physical nature of living things. The study of
+Variation had from the first shown that an orderliness of this kind was
+present. The bodies and the properties of living things are cosmic,
+not chaotic. No matter how low in the scale we go, never do we find the
+slightest hint of a diminution in that all-pervading orderliness, nor
+can we conceive an organism existing for a moment in any other state.
+Moreover not only does this order prevail in normal forms, but again
+and again it is to be seen in newly-sprung varieties, which by general
+consent cannot have been subjected to a prolonged Selection. The
+discovery of Mendelian elements admirably coincided with and at once
+gave a rationale of these facts. Genetic Variation is then primarily the
+consequence of additions to, or omissions from, the stock of
+elements which the species contains. The further investigation of
+the species-problem must thus proceed by the analytical method which
+breeding experiments provide.
+
+In the nine years which have elapsed since Mendel's clue became
+generally known, progress has been rapid. We now understand the process
+by which a polymorphic race maintains its polymorphism. When a family
+consists of dissimilar members, given the numerical proportions in
+which these members are occurring, we can represent their composition
+symbolically and state what types can be transmitted by the various
+members. The difficulty of the "swamping effects of intercrossing" is
+practically at an end. Even the famous puzzle of sex-limited inheritance
+is solved, at all events in its more regular manifestations, and we know
+now how it is brought about that the normal sisters of a colour-blind
+man can transmit the colour-blindness while his normal brothers cannot
+transmit it.
+
+We are still only on the fringe of the inquiry. It can be seen extending
+and ramifying in many directions. To enumerate these here would be
+impossible. A whole new range of possibilities is being brought into
+view by study of the interrelations between the simple factors. By
+following up the evidence as to segregation, indications have been
+obtained which can only be interpreted as meaning that when many factors
+are being simultaneously redistributed among the germ-cells, certain of
+them exert what must be described as a repulsion upon other factors. We
+cannot surmise whither this discovery may lead.
+
+In the new light all the old problems wear a fresh aspect. Upon the
+question of the nature of Sex, for example, the bearing of Mendelian
+evidence is close. Elsewhere I have shown that from several sets of
+parallel experiments the conclusion is almost forced upon us that, in
+the types investigated, of the two sexes the female is to be regarded as
+heterozygous in sex, containing one unpaired dominant element, while the
+male is similarly homozygous in the absence of that element. (In other
+words, the ova are each EITHER female, OR male (i.e. non-female), but
+the sperms are all non-female.) It is not a little remarkable that on
+this point--which is the only one where observations of the nuclear
+processes of gameto-genesis have yet been brought into relation with
+the visible characteristics of the organisms themselves--there should be
+diametrical opposition between the results of breeding experiments and
+those derived from cytology.
+
+Those who have followed the researches of the American school will
+be aware that, after it had been found in certain insects that the
+spermatozoa were of two kinds according as they contained or did not
+contain the accessory chromosome, E.B. Wilson succeeded in proving that
+the sperms possessing this accessory body were destined to form FEMALES
+on fertilisation, while sperms without it form males, the eggs being
+apparently indifferent. Perhaps the most striking of all this series
+of observations is that lately made by T.H. Morgan (Morgan, "Proc. Soc.
+Exp. Biol. Med." V. 1908, and von Baehr, "Zool. Anz." XXXII. page 507,
+1908.), since confirmed by von Baehr, that in a Phylloxeran two kinds
+of spermatids are formed, respectively with and without an accessory
+(in this case, DOUBLE) chromosome. Of these, only those possessing the
+accessory body become functional spermatozoa, the others degenerating.
+We have thus an elucidation of the puzzling fact that in these forms
+fertilisation results in the formation of FEMALES only. How the
+males are formed--for of course males are eventually produced by the
+parthenogenetic females--we do not know.
+
+If the accessory body is really to be regarded as bearing the factor
+for femaleness, then in Mendelian terms female is DD and male is DR. The
+eggs are indifferent and the spermatozoa are each male, OR female.
+But according to the evidence derived from a study of the sex-limited
+descent of certain features in other animals the conclusion seems
+equally clear that in them female must be regarded as DR and male as
+RR. The eggs are thus each either male or female and the spermatozoa are
+indifferent. How this contradictory evidence is to be reconciled we
+do not yet know. The breeding work concerns fowls, canaries, and the
+Currant moth (Abraxas grossulariata). The accessory chromosome has been
+now observed in most of the great divisions of insects (As Wilson has
+proved, the unpaired body is not a universal feature even in those
+orders in which it has been observed. Nearly allied types may differ.
+In some it is altogether unpaired. In others it is paired with a body of
+much smaller size, and by selection of various types all gradations can
+be demonstrated ranging to the condition in which the members of the
+pair are indistinguishable from each other.), except, as it happens,
+Lepidoptera. At first sight it seems difficult to suppose that a feature
+apparently so fundamental as sex should be differently constituted
+in different animals, but that seems at present the least improbable
+inference. I mention these two groups of facts as illustrating the
+nature and methods of modern genetic work. We must proceed by minute and
+specific analytical investigation. Wherever we look we find traces of
+the operation of precise and specific rules.
+
+In the light of present knowledge it is evident that before we can
+attack the Species-problem with any hope of success there are vast
+arrears to be made up. He would be a bold man who would now assert that
+there was no sense in which the term Species might not have a strict and
+concrete meaning in contradistinction to the term Variety. We have been
+taught to regard the difference between species and variety as one of
+degree. I think it unlikely that this conclusion will bear the test of
+further research. To Darwin the question, What is a variation? presented
+no difficulties. Any difference between parent and offspring was a
+variation. Now we have to be more precise. First we must, as de Vries
+has shown, distinguish real, genetic, variation from FLUCTUATIONAL
+variations, due to environmental and other accidents, which cannot
+be transmitted. Having excluded these sources of error the variations
+observed must be expressed in terms of the factors to which they are due
+before their significance can be understood. For example, numbers of the
+variations seen under domestication, and not a few witnessed in nature,
+are simply the consequence of some ingredient being in an unknown way
+omitted from the composition of the varying individual. The variation
+may on the contrary be due to the addition of some new element, but to
+prove that it is so is by no means an easy matter. Casual observation
+is useless, for though these latter variations will always be dominants,
+yet many dominant characteristics may arise from another cause, namely
+the meeting of complementary factors, and special study of each case
+in two generations at least is needed before these two phenomena can be
+distinguished.
+
+When such considerations are fully appreciated it will be realised that
+medleys of most dissimilar occurrences are all confused together under
+the term Variation. One of the first objects of genetic analysis is to
+disentangle this mass of confusion.
+
+To those who have made no study of heredity it sometimes appears that
+the question of the effect of conditions in causing variation is one
+which we should immediately investigate, but a little thought will
+show that before any critical inquiry into such possibilities can be
+attempted, a knowledge of the working of heredity under conditions as
+far as possible uniform must be obtained. At the time when Darwin was
+writing, if a plant brought into cultivation gave off an albino variety,
+such an event was without hesitation ascribed to the change of life. Now
+we see that albino GAMETES, germs, that is to say, which are destitute
+of the pigment-forming factor, may have been originally produced by
+individuals standing an indefinite number of generations back in the
+ancestry of the actual albino, and it is indeed almost certain that the
+variation to which the appearance of the albino is due cannot have taken
+place in a generation later than that of the grandparents. It is true
+that when a new DOMINANT appears we should feel greater confidence
+that we were witnessing the original variation, but such events are
+of extreme rarity, and no such case has come under the notice of an
+experimenter in modern times, as far as I am aware. That they must have
+appeared is clear enough. Nothing corresponding to the Brown-breasted
+Game fowl is known wild, yet that colour is a most definite dominant,
+and at some moment since Gallus bankiva was domesticated, the element on
+which that special colour depends must have at least once been formed in
+the germ-cell of a fowl; but we need harder evidence than any which has
+yet been produced before we can declare that this novelty came through
+over-feeding, or change of climate, or any other disturbance consequent
+on domestication. When we reflect on the intricacies of genetic problems
+as we must now conceive them there come moments when we feel almost
+thankful that the Mendelian principles were unknown to Darwin. The time
+called for a bold pronouncement, and he made it, to our lasting profit
+and delight. With fuller knowledge we pass once more into a period of
+cautious expectation and reserve.
+
+In every arduous enterprise it is pleasanter to look back at
+difficulties overcome than forward to those which still seem
+insurmountable, but in the next stage there is nothing to be gained by
+disguising the fact that the attributes of living things are not what
+we used to suppose. If they are more complex in the sense that the
+properties they display are throughout so regular (I have in view, for
+example, the marvellous and specific phenomena of regeneration,
+and those discovered by the students of "Entwicklungsmechanik". The
+circumstances of its occurrence here preclude any suggestion that this
+regularity has been brought about by the workings of Selection. The
+attempts thus to represent the phenomena have resulted in mere parodies
+of scientific reasoning.) that the Selection of minute random variations
+is an unacceptable account of the origin of their diversity, yet by
+virtue of that very regularity the problem is limited in scope and thus
+simplified.
+
+To begin with, we must relegate Selection to its proper place. Selection
+permits the viable to continue and decides that the non-viable shall
+perish; just as the temperature of our atmosphere decides that no liquid
+carbon shall be found on the face of the earth: but we do not suppose
+that the form of the diamond has been gradually achieved by a process of
+Selection. So again, as the course of descent branches in the successive
+generations, Selection determines along which branch Evolution shall
+proceed, but it does not decide what novelties that branch shall bring
+forth. "La Nature contient le fonds de toutes ces varietes, mais le
+hazard ou l'art les mettent en oeuvre," as Maupertuis most truly said.
+
+Not till knowledge of the genetic properties of organisms has attained
+to far greater completeness can evolutionary speculations have more than
+a suggestive value. By genetic experiment, cytology and physiological
+chemistry aiding, we may hope to acquire such knowledge. In 1872
+Nathusius wrote ("Vortrage uber Viehzucht und Rassenerkenntniss", page
+120, Berlin, 1872.): "Das Gesetz der Vererbung ist noch nicht erkannt;
+der Apfel ist noch nicht vom Baum der Erkenntniss gefallen, welcher,
+der Sage nach, Newton auf den rechten Weg zur Ergrundung der
+Gravitationsgesetze fuhrte." We cannot pretend that the words are not
+still true, but in Mendelian analysis the seeds of that apple-tree at
+last are sown.
+
+If we were asked what discovery would do most to forward our inquiry,
+what one bit of knowledge would more than any other illuminate the
+problem, I think we may give the answer without hesitation. The greatest
+advance that we can foresee will be made when it is found possible to
+connect the geometrical phenomena of development with the chemical. The
+geometrical symmetry of living things is the key to a knowledge of
+their regularity, and the forces which cause it. In the symmetry of
+the dividing cell the basis of that resemblance we call Heredity is
+contained. To imitate the morphological phenomena of life we have to
+devise a system which can divide. It must be able to divide, and to
+segment as--grossly--a vibrating plate or rod does, or as an icicle can
+do as it becomes ribbed in a continuous stream of water; but with
+this distinction, that the distribution of chemical differences and
+properties must simultaneously be decided and disposed in orderly
+relation to the pattern of the segmentation. Even if a model which would
+do this could be constructed it might prove to be a useful beginning.
+
+This may be looking too far ahead. If we had to choose some one piece of
+more proximate knowledge which we would more especially like to acquire,
+I suppose we should ask for the secret of interracial sterility. Nothing
+has yet been discovered to remove the grave difficulty, by which Huxley
+in particular was so much oppressed, that among the many varieties
+produced under domestication--which we all regard as analogous to the
+species seen in nature--no clear case of interracial sterility has
+been demonstrated. The phenomenon is probably the only one to which the
+domesticated products seem to afford no parallel. No solution of the
+difficulty can be offered which has positive value, but it is perhaps
+worth considering the facts in the light of modern ideas. It should be
+observed that we are not discussing incompatibility of two species to
+produce offspring (a totally distinct phenomenon), but the sterility of
+the offspring which many of them do produce.
+
+When two species, both perfectly fertile severally, produce on crossing
+a sterile progeny, there is a presumption that the sterility is due to
+the development in the hybrid of some substance which can only be formed
+by the meeting of two complementary factors. That some such account is
+correct in essence may be inferred from the well-known observation that
+if the hybrid is not totally sterile but only partially so, and thus is
+able to form some good germ-cells which develop into new individuals,
+the sterility of these daughter-individuals is sensibly reduced or may
+be entirely absent. The fertility once re-established, the sterility
+does not return in the later progeny, a fact strongly suggestive of
+segregation. Now if the sterility of the cross-bred be really the
+consequence of the meeting of two complementary factors, we see that the
+phenomenon could only be produced among the divergent offspring of
+one species by the acquisition of at least TWO new factors; for if the
+acquisition of a single factor caused sterility the line would then
+end. Moreover each factor must be separately acquired by distinct
+individuals, for if both were present together, the possessors would by
+hypothesis be sterile. And in order to imitate the case of species each
+of these factors must be acquired by distinct breeds. The factors need
+not, and probably would not, produce any other perceptible effects;
+they might, like the colour-factors present in white flowers, make
+no difference in the form or other characters. Not till the cross was
+actually made between the two complementary individuals would either
+factor come into play, and the effects even then might be unobserved
+until an attempt was made to breed from the cross-bred.
+
+Next, if the factors responsible for sterility were acquired, they would
+in all probability be peculiar to certain individuals and would not
+readily be distributed to the whole breed. Any member of the breed
+also into which BOTH the factors were introduced would drop out of the
+pedigree by virtue of its sterility. Hence the evidence that the various
+domesticated breeds say of dogs or fowls can when mated together produce
+fertile offspring, is beside the mark. The real question is, Do they
+ever produce sterile offspring? I think the evidence is clearly that
+sometimes they do, oftener perhaps than is commonly supposed. These
+suggestions are quite amenable to experimental tests. The most obvious
+way to begin is to get a pair of parents which are known to have had any
+sterile offspring, and to find the proportions in which these steriles
+were produced. If, as I anticipate, these proportions are found to be
+definite, the rest is simple.
+
+In passing, certain other considerations may be referred to. First, that
+there are observations favouring the view that the production of totally
+sterile cross-breds is seldom a universal property of two species, and
+that it may be a matter of individuals, which is just what on the view
+here proposed would be expected. Moreover, as we all know now, though
+incompatibility may be dependent to some extent on the degree to which
+the species are dissimilar, no such principle can be demonstrated to
+determine sterility or fertility in general. For example, though all our
+Finches can breed together, the hybrids are all sterile. Of Ducks some
+species can breed together without producing the slightest sterility;
+others have totally sterile offspring, and so on. The hybrids between
+several genera of Orchids are perfectly fertile on the female side, and
+some on the male side also, but the hybrids produced between the Turnip
+(Brassica napus) and the Swede (Brassica campestris), which, according
+to our estimates of affinity should be nearly allied forms, are totally
+sterile. (See Sutton, A.W., "Journ. Linn. Soc." XXXVIII. page 341,
+1908.) Lastly, it may be recalled that in sterility we are almost
+certainly considering a meristic phenomenon. FAILURE TO DIVIDE is,
+we may feel fairly sure, the immediate "cause" of the sterility. Now,
+though we know very little about the heredity of meristic differences,
+all that we do know points to the conclusion that the less-divided is
+dominant to the more-divided, and we are thus justified in supposing
+that there are factors which can arrest or prevent cell-division. My
+conjecture therefore is that in the case of sterility of cross-breds we
+see the effect produced by a complementary pair of such factors. This
+and many similar problems are now open to our analysis.
+
+The question is sometimes asked, Do the new lights on Variation and
+Heredity make the process of Evolution easier to understand? On the
+whole the answer may be given that they do. There is some appearance of
+loss of simplicity, but the gain is real. As was said above, the time
+is not ripe for the discussion of the origin of species. With faith in
+Evolution unshaken--if indeed the word faith can be used in application
+to that which is certain--we look on the manner and causation of adapted
+differentiation as still wholly mysterious. As Samuel Butler so truly
+said: "To me it seems that the 'Origin of Variation,' whatever it is, is
+the only true 'Origin of Species'" ("Life and Habit", London, page
+263, 1878.), and of that Origin not one of us knows anything. But given
+Variation--and it is given: assuming further that the variations are not
+guided into paths of adaptation--and both to the Darwinian and to
+the modern school this hypothesis appears to be sound if unproven--an
+evolution of species proceeding by definite steps is more, rather than
+less, easy to imagine than an evolution proceeding by the accumulation
+of indefinite and insensible steps. Those who have lost themselves in
+contemplating the miracles of Adaptation (whether real or spurious) have
+not unnaturally fixed their hopes rather on the indefinite than on the
+definite changes. The reasons are obvious. By suggesting that the
+steps through which an adaptative mechanism arose were indefinite and
+insensible, all further trouble is spared. While it could be said that
+species arise by an insensible and imperceptible process of variation,
+there was clearly no use in tiring ourselves by trying to perceive that
+process. This labour-saving counsel found great favour. All that had
+to be done to develop evolution-theory was to discover the good in
+everything, a task which, in the complete absence of any control or test
+whereby to check the truth of the discovery, is not very onerous. The
+doctrine "que tout est au mieux" was therefore preached with fresh
+vigour, and examples of that illuminating principle were discovered with
+a facility that Pangloss himself might have envied, till at last even
+the spectators wearied of such dazzling performances.
+
+But in all seriousness, why should indefinite and unlimited variation
+have been regarded as a more probable account of the origin of
+Adaptation? Only, I think, because the obstacle was shifted one plane
+back, and so looked rather less prominent. The abundance of Adaptation,
+we all grant, is an immense, almost an unsurpassable difficulty in
+all non-Lamarckian views of Evolution; but if the steps by which
+that adaptation arose were fortuitous, to imagine them insensible is
+assuredly no help. In one most important respect indeed, as has often
+been observed, it is a multiplication of troubles. For the smaller
+the steps, the less could Natural Selection act upon them. Definite
+variations--and of the occurrence of definite variations in abundance we
+have now the most convincing proof--have at least the obvious merit
+that they can make and often do make a real difference in the chances of
+life.
+
+There is another aspect of the Adaptation problem to which I can only
+allude very briefly. May not our present ideas of the universality and
+precision of Adaptation be greatly exaggerated? The fit of organism to
+its environment is not after all so very close--a proposition unwelcome
+perhaps, but one which could be illustrated by very copious evidence.
+Natural Selection is stern, but she has her tolerant moods.
+
+We have now most certain and irrefragable proof that much definiteness
+exists in living things apart from Selection, and also much that
+may very well have been preserved and so in a sense constituted by
+Selection. Here the matter is likely to rest. There is a passage in the
+sixth edition of the "Origin" which has I think been overlooked. On page
+70 Darwin says "The tuft of hair on the breast of the wild turkey-cock
+cannot be of any use, and it is doubtful whether it can be ornamental in
+the eyes of the female bird." This tuft of hair is a most definite and
+unusual structure, and I am afraid that the remark that it "cannot be
+of any use" may have been made inadvertently; but it may have been
+intended, for in the first edition the usual qualification was given and
+must therefore have been deliberately excised. Anyhow I should like to
+think that Darwin did throw over that tuft of hair, and that he felt
+relief when he had done so. Whether however we have his great authority
+for such a course or not, I feel quite sure that we shall be rightly
+interpreting the facts of nature if we cease to expect to find
+purposefulness wherever we meet with definite structures or patterns.
+Such things are, as often as not, I suspect rather of the nature of
+tool-marks, mere incidents of manufacture, benefiting their possessor
+not more than the wire-marks in a sheet of paper, or the ribbing on the
+bottom of an oriental plate renders those objects more attractive in our
+eyes.
+
+If Variation may be in any way definite, the question once more arises,
+may it not be definite in direction? The belief that it is has had many
+supporters, from Lamarck onwards, who held that it was guided by need,
+and others who, like Nageli, while laying no emphasis on need, yet were
+convinced that there was guidance of some kind. The latter view under
+the name of "Orthogenesis," devised I believe by Eimer, at the present
+day commends itself to some naturalists. The objection to such a
+suggestion is of course that no fragment of real evidence can be
+produced in its support. On the other hand, with the experimental proof
+that variation consists largely in the unpacking and repacking of an
+original complexity, it is not so certain as we might like to think
+that the order of these events is not pre-determined. For instance
+the original "pack" may have been made in such a way that at the nth
+division of the germ-cells of a Sweet Pea a colour-factor might be
+dropped, and that at the n plus n prime division the hooded variety be
+given off, and so on. I see no ground whatever for holding such a view,
+but in fairness the possibility should not be forgotten, and in the
+light of modern research it scarcely looks so absurdly improbable as
+before.
+
+No one can survey the work of recent years without perceiving that
+evolutionary orthodoxy developed too fast, and that a great deal has
+got to come down; but this satisfaction at least remains, that in the
+experimental methods which Mendel inaugurated, we have means of reaching
+certainty in regard to the physiology of Heredity and Variation upon
+which a more lasting structure may be built.
+
+
+
+
+VI. THE MINUTE STRUCTURE OF CELLS IN RELATION TO HEREDITY. By Eduard
+Strasburger.
+
+Professor of Botany in the University of Bonn.
+
+Since 1875 an unexpected insight has been gained into the internal
+structure of cells. Those who are familiar with the results of
+investigations in this branch of Science are convinced that any modern
+theory of heredity must rest on a basis of cytology and cannot be at
+variance with cytological facts. Many histological discoveries, both
+such as have been proved correct and others which may be accepted as
+probably well founded, have acquired a fundamental importance from the
+point of view of the problems of heredity.
+
+My aim is to describe the present position of our knowledge of Cytology.
+The account must be confined to essentials and cannot deal with
+far-reaching and controversial questions. In cases where difference of
+opinion exists, I adopt my own view for which I hold myself responsible.
+I hope to succeed in making myself intelligible even without the aid of
+illustrations: in order to convey to the uninitiated an adequate idea
+of the phenomena connected with the life of a cell, a greater number
+of figures would be required than could be included within the scope of
+this article.
+
+So long as the most eminent investigators (As for example the
+illustrious Wilhelm Hofmeister in his "Lehre von der Pflanzenzelle"
+(1867).) believed that the nucleus of a cell was destroyed in the course
+of each division and that the nuclei of the daughter-cells were produced
+de novo, theories of heredity were able to dispense with the nucleus.
+If they sought, as did Charles Darwin, who showed a correct grasp of
+the problem in the enunciation of his Pangenesis hypothesis, for
+histological connecting links, their hypotheses, or at least the best of
+them, had reference to the cell as a whole. It was known to Darwin
+that the cell multiplied by division and was derived from a similar
+pre-existing cell. Towards 1870 it was first demonstrated that
+cell-nuclei do not arise de novo, but are invariably the result of
+division of pre-existing nuclei. Better methods of investigation
+rendered possible a deeper insight into the phenomena accompanying cell
+and nuclear divisions and at the same time disclosed the existence of
+remarkable structures. The work of O. Butschli, O. Hertwig, W. Flemming
+H. Fol and of the author of this article (For further reference to
+literature, see my article on "Die Ontogenie der Zelle seit 1875",
+in the "Progressus Rei Botanicae", Vol. I. page 1, Jena, 1907.), have
+furnished conclusive evidence in favour of these facts. It was found
+that when the reticular framework of a nucleus prepares to divide, it
+separates into single segments. These then become thicker and denser,
+taking up with avidity certain stains, which are used as aids to
+investigation, and finally form longer or shorter, variously bent,
+rodlets of uniform thickness. In these organs which, on account of their
+special property of absorbing certain stains, were styled Chromosomes
+(By W. Waldeyer in 1888.), there may usually be recognised a separation
+into thicker and thinner discs; the former are often termed Chromomeres.
+(Discovered by W. Pfitzner in 1880.) In the course of division of the
+nucleus, the single rows of chromomeres in the chromosomes are doubled
+and this produces a band-like flattening and leads to the longitudinal
+splitting by which each chromosome is divided into two exactly equal
+halves. The nuclear membrane then disappears and fibrillar cell-plasma
+or cytoplasm invades the nuclear area. In animal cells these fibrillae
+in the cytoplasm centre on definite bodies (Their existence and their
+multiplication by fission were demonstrated by E. van Beneden and Th.
+Boveri in 1887.), which it is customary to speak of as Centrosomes.
+Radiating lines in the adjacent cell-plasma suggest that these bodies
+constitute centres of force. The cells of the higher plants do not
+possess such individualised centres; they have probably disappeared in
+the course of phylogenetic development: in spite of this, however, in
+the nuclear division-figures the fibrillae of the cell-plasma are seen
+to radiate from two opposite poles. In both animal and plant cells a
+fibrillar bipolar spindle is formed, the fibrillae of which grasp the
+longitudinally divided chromosomes from two opposite sides and arrange
+them on the equatorial plane of the spindle as the so-called nuclear
+or equatorial plate. Each half-chromosome is connected with one of the
+spindle poles only and is then drawn towards that pole. (These important
+facts, suspected by W. Flemming in 1882, were demonstrated by E. Heuser,
+L. Guignard, E. van Beneden, M. Nussbaum, and C. Rabl.)
+
+The formation of the daughter-nuclei is then effected. The changes
+which the daughter-chromosomes undergo in the process of producing the
+daughter-nuclei repeat in the reverse order the changes which they went
+through in the course of their progressive differentiation from the
+mother-nucleus. The division of the cell-body is completed midway
+between the two daughter-nuclei. In animal cells, which possess no
+chemically differentiated membrane, separation is effected by simple
+constriction, while in the case of plant cells provided with a definite
+wall, the process begins with the formation of a cytoplasmic separating
+layer.
+
+The phenomena observed in the course of the division of the nucleus show
+beyond doubt that an exact halving of its substance is of the greatest
+importance. (First shown by W. Roux in 1883.) Compared with the method
+of division of the nucleus, that of the cytoplasm appears to be very
+simple. This led to the conception that the cell-nucleus must be the
+chief if not the sole carrier of hereditary characters in the organism.
+It is for this reason that the detailed investigation of fertilisation
+phenomena immediately followed researches into the nucleus. The
+fundamental discovery of the union of two nuclei in the sexual act was
+then made (By O. Hertwig in 1875.) and this afforded a new support for
+the correct conception of the nuclear functions. The minute study of the
+behaviour of the other constituents of sexual cells during fertilisation
+led to the result, that the nucleus alone is concerned with handing on
+hereditary characters (This was done by O. Hertwig and the author of
+this essay simultaneously in 1884.) from one generation to another.
+Especially important, from the point of view of this conclusion, is
+the study of fertilisation in Angiosperms (Flowering plants); in these
+plants the male sexual cells lose their cell-body in the pollen-tube and
+the nucleus only--the sperm-nucleus--reaches the egg. The cytoplasm of
+the male sexual cell is therefore not necessary to ensure a transference
+of hereditary characters from parents to offspring. I lay stress on the
+case of the Angiosperms because researches recently repeated with
+the help of the latest methods failed to obtain different results.
+As regards the descendants of angiospermous plants, the same laws of
+heredity hold good as for other sexually differentiated organisms; we
+may, therefore, extend to the latter what the Angiosperms so clearly
+teach us.
+
+The next advance in the hitherto rapid progress in our knowledge of
+nuclear division was delayed, because it was not at once recognised that
+there are two absolutely different methods of nuclear division. All
+such nuclear divisions were united under the head of indirect or
+mitotic divisions; these were also spoken of as karyo-kineses, and
+were distinguished from the direct or amitotic divisions which are
+characterised by a simple constriction of the nuclear body. So long
+as the two kinds of indirect nuclear division were not clearly
+distinguished, their correct interpretation was impossible. This was
+accomplished after long and laborious research, which has recently
+been carried out and with results which should, perhaps, be regarded as
+provisional.
+
+Soon after the new study of the nucleus began, investigators were struck
+by the fact that the course of nuclear division in the mother-cells, or
+more correctly in the grandmother-cells, of spores, pollen-grains, and
+embryo-sacs of the more highly organised plants and in the spermatozoids
+and eggs of the higher animals, exhibits similar phenomena, distinct
+from those which occur in the somatic cells.
+
+In the nuclei of all those cells which we may group together as
+gonotokonts (At the suggestion of J.P. Lotsy in 1904.) (i.e. cells
+concerned in reproduction) there are fewer chromosomes than in the
+adjacent body-cells (somatic cells). It was noticed also that there is a
+peculiarity characteristic of the gonotokonts, namely the occurrence of
+two nuclear divisions rapidly succeeding one another. It was afterwards
+recognised that in the first stage of nuclear division in
+the gonotokonts the chromosomes unite in pairs: it is these
+chromosome-pairs, and not the two longitudinal halves of single
+chromosomes, which form the nuclear plate in the equatorial plane of
+the nuclear spindle. It has been proposed to call these pairs gemini.
+(J.E.S. Moore and A.L. Embleton, "Proc. Roy. Soc." London, Vol. LXXVII.
+page 555, 1906; V. Gregoire, 1907.) In the course of this division
+the spindle-fibrillae attach themselves to the gemini, i.e. to entire
+chromosomes and direct them to the points where the new daughter-nuclei
+are formed, that is to those positions towards which the longitudinal
+halves of the chromosomes travel in ordinary nuclear divisions. It
+is clear that in this way the number of chromosomes which the
+daughter-nuclei contain, as the result of the first stage in division
+in the gonotokonts, will be reduced by one half, while in ordinary
+divisions the number of chromosomes always remains the same. The first
+stage in the division of the nucleus in the gonotokonts has therefore
+been termed the reduction division. (In 1887 W. Flemming termed this the
+heterotypic form of nuclear division.) This stage in division determines
+the conditions for the second division which rapidly ensues. Each of the
+paired chromosomes of the mother-nucleus has already, as in an ordinary
+nuclear division, completed the longitudinal fission, but in this case
+it is not succeeded by the immediate separation of the longitudinal
+halves and their allotment to different nuclei. Each chromosome,
+therefore, takes its two longitudinal halves into the same
+daughter-nucleus. Thus, in each daughter-nucleus the longitudinal halves
+of the chromosomes are present ready for the next stage in the
+division; they only require to be arranged in the nuclear plate and then
+distributed among the granddaughter-nuclei. This method of division,
+which takes place with chromosomes already split, and which have only
+to provide for the distribution of their longitudinal halves to the next
+nuclear generation, has been called homotypic nuclear division. (The
+name was proposed by W. Flemming in 1887; the nature of this type of
+division was, however, not explained until later.)
+
+Reduction division and homotypic nuclear division are included together
+under the term allotypic nuclear division and are distinguished from the
+ordinary or typical nuclear division. The name Meiosis (By J. Bretland
+Farmer and J.E.S. Moore in 1905.) has also been proposed for these two
+allotypic nuclear divisions. The typical divisions are often spoken of
+as somatic.
+
+Observers who were actively engaged in this branch of recent
+histological research soon noticed that the chromosomes of a given
+organism are differentiated in definite numbers from the nuclear
+network in the course of division. This is especially striking in the
+gonotokonts, but it applies also to the somatic tissues. In the latter,
+one usually finds twice as many chromosomes as in the gonotokonts. Thus
+the conclusion was gradually reached that the doubling of chromosomes,
+which necessarily accompanies fertilisation, is maintained in the
+product of fertilisation, to be again reduced to one half in the
+gonotokonts at the stage of reduction-division. This enabled us to form
+a conception as to the essence of true alternation of generations, in
+which generations containing single and double chromosomes alternate
+with one another.
+
+The single-chromosome generation, which I will call the HAPLOID, must
+have been the primitive generation in all organisms; it might also
+persist as the only generation. Every sexual differentiation in
+organisms, which occurred in the course of phylogenetic development, was
+followed by fertilisation and therefore by the creation of a diploid or
+double-chromosome product. So long as the germination of the product
+of fertilisation, the zygote, began with a reducing process, a special
+DIPLOID generation was not represented. This, however, appeared later
+as a product of the further evolution of the zygote, and the reduction
+division was correspondingly postponed. In animals, as in plants, the
+diploid generation attained the higher development and gradually assumed
+the dominant position. The haploid generation suffered a proportional
+reduction, until it finally ceased to have an independent existence and
+became restricted to the role of producing the sexual products within
+the body of the diploid generation. Those who do not possess the
+necessary special knowledge are unable to realise what remains of the
+first haploid generation in a phanerogamic plant or in a vertebrate
+animal. In Angiosperms this is actually represented only by the short
+developmental stages which extend from the pollen mother-cells to the
+sperm-nucleus of the pollen-tube, and from the embryo-sac mother-cell to
+the egg and the endosperm tissue. The embryo-sac remains enclosed in
+the diploid ovule, and within this from the fertilised egg is formed
+the embryo which introduces the new diploid generation. On the full
+development of the diploid embryo of the next generation, the diploid
+ovule of the preceding diploid generation is separated from the latter
+as a ripe seed. The uninitiated sees in the more highly organised plants
+only a succession of diploid generations. Similarly all the higher
+animals appear to us as independent organisms with diploid nuclei only.
+The haploid generation is confined in them to the cells produced as the
+result of the reduction division of the gonotokonts; the development of
+these is completed with the homotypic stage of division which succeeds
+the reduction division and produces the sexual products.
+
+The constancy of the numbers in which the chromosomes separate
+themselves from the nuclear network during division gave rise to the
+conception that, in a certain degree, chromosomes possess individuality.
+Indeed the most careful investigations (Particularly those of V.
+Gregoire and his pupils.) have shown that the segments of the nuclear
+network, which separate from one another and condense so as to produce
+chromosomes for a new division, correspond to the segments produced from
+the chromosomes of the preceding division. The behaviour of such nuclei
+as possess chromosomes of unequal size affords confirmatory evidence of
+the permanence of individual chromosomes in corresponding sections of an
+apparently uniform nuclear network. Moreover at each stage in division
+chromosomes with the same differences in size reappear. Other cases are
+known in which thicker portions occur in the substance of the resting
+nucleus, and these agree in number with the chromosomes. In this
+network, therefore, the individual chromosomes must have retained
+their original position. But the chromosomes cannot be regarded as the
+ultimate hereditary units in the nuclei, as their number is too small.
+Moreover, related species not infrequently show a difference in the
+number of their chromosomes, whereas the number of hereditary units
+must approximately agree. We thus picture to ourselves the carriers of
+hereditary characters as enclosed in the chromosomes; the transmitted
+fixed number of chromosomes is for us only the visible expression of
+the conception that the number of hereditary units which the chromosomes
+carry must be also constant. The ultimate hereditary units may, like
+the chromosomes themselves, retain a definite position in the resting
+nucleus. Further, it may be assumed that during the separation of the
+chromosomes from one another and during their assumption of the rod-like
+form, the hereditary units become aggregated in the chromomeres and
+that these are characterised by a constant order of succession.
+The hereditary units then grow, divide into two and are uniformly
+distributed by the fission of the chromosomes between their longitudinal
+halves.
+
+As the contraction and rod-like separation of the chromosomes serve
+to isnure the transmission of all hereditary units in the products of
+division of a nucleus, so, on the other hand, the reticular distension
+of each chromosome in the so-called resting nucleus may effect a
+separation of the carriers of hereditary units from each other and
+facilitate the specific activity of each of them.
+
+In the stages preliminary to their division, the chromosomes become
+denser and take up a substance which increases their staining capacity;
+this is called chromatin. This substance collects in the chromomeres
+and may form the nutritive material for the carriers of hereditary units
+which we now believe to be enclosed in them. The chromatin cannot itself
+be the hereditary substance, as it afterwards leaves the chromosomes,
+and the amount of it is subject to considerable variation in the
+nucleus, according to its stage of development. Conjointly with the
+materials which take part in the formation of the nuclear spindle and
+other processes in the cell, the chromatin accumulates in the resting
+nucleus to form the nucleoli.
+
+Naturally connected with the conclusion that the nuclei are the carriers
+of hereditary characters in the organism, is the question whether
+enucleate organisms can also exist. Phylogenetic considerations give an
+affirmative answer to this question. The differentiation into nucleus
+and cytoplasm represents a division of labour in the protoplast. A
+study of organisms which belong to the lowest class of the organic world
+teaches us how this was accomplished. Instead of well-defined nuclei,
+scattered granules have been described in the protoplasm of several of
+these organisms (Bacteria, Cyanophyceae, Protozoa.), characterised by
+the same reactions as nuclear material, provided also with a nuclear
+network, but without a limiting membrane. (This is the result of the
+work of R. Hertwig and of the most recently published investigations.)
+Thus the carriers of hereditary characters may originally have been
+distributed in the common protoplasm, afterwards coming together and
+eventually assuming a definite form as special organs of the cell. It
+may be also assumed that in the protoplasm and in the primitive types
+of nucleus, the carriers of the same hereditary unit were represented in
+considerable quantity; they became gradually differentiated to an extent
+commensurate with newly acquired characters. It was also necessary that,
+in proportion as this happened, the mechanism of nuclear division must
+be refined. At first processes resembling a simple constriction would
+suffice to provide for the distribution of all hereditary units to each
+of the products of division, but eventually in both organic kingdoms
+nuclear division, which alone insured the qualitative identity of the
+products of division, became a more marked feature in the course of
+cell-multiplication.
+
+Where direct nuclear division occurs by constriction in the higher
+organisms, it does not result in the halving of hereditary units. So far
+as my observations go, direct nuclear division occurs in the more highly
+organised plants only in cells which have lost their specific
+functions. Such cells are no longer capable of specific reproduction. An
+interesting case in this connection is afforded by the internodal cells
+of the Characeae, which possess only vegetative functions. These cells
+grow vigorously and their cytoplasm increases, their growth being
+accompanied by a correspondingly direct multiplication of the nuclei.
+They serve chiefly to nourish the plant, but, unlike the other
+cells, they are incapable of producing any offspring. This is a very
+instructive case, because it clearly shows that the nuclei are not only
+carriers of hereditary characters, but that they also play a definite
+part in the metabolism of the protoplasts.
+
+Attention was drawn to the fact that during the reducing division of
+nuclei which contain chromosomes of unequal size, gemini are constantly
+produced by the pairing of chromosomes of the same size. This led to
+the conclusion that the pairing chromosomes are homologous, and that one
+comes from the father, the other from the mother. (First stated by T.H.
+Montgomery in 1901 and by W.S. Sutton in 1902.) This evidently applies
+also to the pairing of chromosomes in those reduction-divisions in
+which differences in size do not enable us to distinguish the individual
+chromosomes. In this case also each pair would be formed by two
+homologous chromosomes, the one of paternal, the other of maternal
+origin. When the separation of these chromosomes and their distribution
+to both daughter-nuclei occur a chromosome of each kind is provided for
+each of these nuclei. It would seem that the components of each pair
+might pass to either pole of the nuclear spindle, so that the paternal
+and maternal chromosomes would be distributed in varying proportion
+between the daughter-nuclei; and it is not impossible that one
+daughter-nucleus might occasionally contain paternal chromosomes only
+and its sister-nucleus exclusively maternal chromosomes.
+
+The fact that in nuclei containing chromosomes of various sizes, the
+chromosomes which pair together in reduction-division are always of
+equal size, constitutes a further and more important proof of their
+qualitative difference. This is supported also by ingenious experiments
+which led to an unequal distribution of chromosomes in the products of
+division of a sea-urchin's egg, with the result that a difference was
+induced in their further development. (Demonstrated by Th. Boveri in
+1902.)
+
+The recently discovered fact that in diploid nuclei the chromosomes are
+arranged in pairs affords additional evidence in favour of the unequal
+value of the chromosomes. This is still more striking in the case of
+chromosomes of different sizes. It has been shown that in the first
+division-figure in the nucleus of the fertilised egg the chromosomes of
+corresponding size form pairs. They appear with this arrangement in all
+subsequent nuclear divisions in the diploid generation. The longitudinal
+fissions of the chromosomes provide for the unaltered preservation
+of this condition. In the reduction nucleus of the gonotokonts the
+homologous chromosomes being near together need not seek out one
+another; they are ready to form gemini. The next stage is their
+separation to the haploid daughter-nuclei, which have resulted from the
+reduction process.
+
+Peculiar phenomena in the reduction nucleus accompany the formation of
+gemini in both organic kingdoms. (This has been shown more particularly
+by the work of L. Guignard, M. Mottier, J.B. Farmer, C.B. Wilson, V.
+Hacker and more recently by V. Gregoire and his pupil C.A. Allen, by the
+researches conducted in the Bonn Botanical Institute, and by A. and
+K.E. Schreiner.) Probably for the purpose of entering into most
+intimate relation, the pairs are stretched to long threads in which the
+chromomeres come to lie opposite one another. (C.A. Allen, A. and K.E.
+Schreiner, and Strasburger.) It seems probable that these are homologous
+chromomeres, and that the pairs afterwards unite for a short time, so
+that an exchange of hereditary units is rendered possible. (H. de Vries
+and Strasburger.) This cannot be actually seen, but certain facts of
+heredity point to the conclusion that this occurs. It follows from
+these phenomena that any exchange which may be effected must be one of
+homologous carriers of hereditary units only. These units continue to
+form exchangeable segments after they have undergone unequal changes;
+they then constitute allelotropic pairs. We may thus calculate what sum
+of possible combinations the exchange of homologous hereditary units
+between the pairing chromosomes provides for before the reduction
+division and the subsequent distribution of paternal and maternal
+chromosomes in the haploid daughter-nuclei. These nuclei then transmit
+their characters to the sexual cells, the conjugation of which in
+fertilization again produces the most varied combinations. (A. Weismann
+gave the impulse to these ideas in his theory on "Amphimixis".) In this
+way all the cooperations which the carriers of hereditary characters are
+capable of in a species are produced; this must give it an appreciable
+advantage in the struggle for life.
+
+The admirers of Charles Darwin must deeply regret that he did not live
+to see the results achieved by the new Cytology. What service would they
+have been to him in the presentation of his hypothesis of Pangenesis;
+what an outlook into the future would they have given to his active
+mind!
+
+The Darwinian hypothesis of Pangenesis rests on the conception that all
+inheritable properties are represented in the cells by small invisible
+particles or gemmules and that these gemmules increase by division.
+Cytology began to develop on new lines some years after the publication
+in 1868 of Charles Darwin's "Provisional hypothesis of Pangenesis"
+("Animals and Plants under Domestication", London, 1868, Chapter
+XXVII.), and when he died in 1882 it was still in its infancy. Darwin
+would have soon suggested the substitution of the nuclei for his
+gemmules. At least the great majority of present-day investigators in
+the domain of cytology have been led to the conclusion that the nucleus
+is the carrier of hereditary characters, and they also believe that
+hereditary characters are represented in the nucleus as distinct units.
+Such would be Darwin's gemmules, which in conformity with the name
+of his hypothesis may be called pangens (So called by H. de Vries in
+1889.): these pangens multiply by division. All recently adopted
+views may be thus linked on to this part of Darwin's hypothesis. It is
+otherwise with Darwin's conception to which Pangenesis owes its name,
+namely the view that all cells continually give off gemmules, which
+migrate to other places in the organism, where they unite to form
+reproductive cells. When Darwin foresaw this possibility, the continuity
+of the germinal substance was still unknown (Demonstrated by Nussbaum in
+1880, by Sachs in 1882, and by Weismann in 1885.), a fact which excludes
+a transference of gemmules.
+
+But even Charles Darwin's genius was confined within finite boundaries
+by the state of science in his day.
+
+It is not my province to deal with other theories of development which
+followed from Darwin's Pangenesis, or to discuss their histological
+probabilities. We can, however, affirm that Charles Darwin's idea that
+invisible gemmules are the carriers of hereditary characters and that
+they multiply by division has been removed from the position of a
+provisional hypothesis to that of a well-founded theory. It is supported
+by histology, and the results of experimental work in heredity, which
+are now assuming extraordinary prominence, are in close agreement with
+it.
+
+
+
+
+VII. "THE DESCENT OF MAN". By G. Schwalbe.
+
+Professor of Anatomy in the University of Strassburg.
+
+The problem of the origin of the human race, of the descent of man, is
+ranked by Huxley in his epoch-making book "Man's Place in Nature", as
+the deepest with which biology has to concern itself, "the question
+of questions,"--the problem which underlies all others. In the same
+brilliant and lucid exposition, which appeared in 1863, soon after the
+publication of Darwin's "Origin of Species", Huxley stated his own views
+in regard to this great problem. He tells us how the idea of a natural
+descent of man gradually grew up in his mind, it was especially the
+assertions of Owen in regard to the total difference between the human
+and the simian brain that called forth strong dissent from the great
+anatomist Huxley, and he easily succeeded in showing that Owen's
+supposed differences had no real existence; he even established, on the
+basis of his own anatomical investigations, the proposition that the
+anatomical differences between the Marmoset and the Chimpanzee are much
+greater than those between the Chimpanzee and Man.
+
+But why do we thus introduce the study of Darwin's "Descent of Man",
+which is to occupy us here, by insisting on the fact that Huxley had
+taken the field in defence of the descent of man in 1863, while Darwin's
+book on the subject did not appear till 1871? It is in order that we may
+clearly understand how it happened that from this time onwards Darwin
+and Huxley followed the same great aim in the most intimate association.
+
+Huxley and Darwin working at the same Problema maximum! Huxley fiery,
+impetuous, eager for battle, contemptuous of the resistance of a dull
+world, or energetically triumphing over it. Darwin calm, weighing every
+problem slowly, letting it mature thoroughly,--not a fighter, yet having
+the greater and more lasting influence by virtue of his immense mass of
+critically sifted proofs. Darwin's friend, Huxley, was the first to do
+him justice, to understand his nature, and to find in it the reason why
+the detailed and carefully considered book on the descent of man made
+its appearance so late. Huxley, always generous, never thought of
+claiming priority for himself. In enthusiastic language he tells how
+Darwin's immortal work, "The Origin of Species", first shed light for
+him on the problem of the descent of man; the recognition of a vera
+causa in the transformation of species illuminated his thoughts as with
+a flash. He was now content to leave what perplexed him, what he could
+not yet solve, as he says himself, "in the mighty hands of Darwin."
+Happy in the bustle of strife against old and deep-rooted prejudices,
+against intolerance and superstition, he wielded his sharp weapons on
+Darwin's behalf; wearing Darwin's armour he joyously overthrew adversary
+after adversary. Darwin spoke of Huxley as his "general agent." ("Life
+and Letters of Thomas Henry Huxley", Vol. I. page 171, London, 1900.)
+Huxley says of himself "I am Darwin's bulldog." (Ibid. page 363.)
+
+Thus Huxley openly acknowledged that it was Darwin's "Origin of Species"
+that first set the problem of the descent of man in its true light, that
+made the question of the origin of the human race a pressing one. That
+this was the logical consequence of his book Darwin himself had long
+felt. He had been reproached with intentionally shirking the application
+of his theory to Man. Let us hear what he says on this point in his
+autobiography: "As soon as I had become, in the year 1837 or 1838,
+convinced that species were mutable productions, I could not avoid the
+belief that man must come under the same law. Accordingly I collected
+notes on the subject for my own satisfaction, and not for a long time
+with any intention of publishing. Although in the 'Origin of Species'
+the derivation of any particular species is never discussed, yet I
+thought it best, in order THAT NO HONOURABLE MAN SHOULD ACCUSE ME OF
+CONCEALING MY VIEWS (No italics in original.), to add that by the work
+'light would be thrown on the origin of man and his history.' It would
+have been useless and injurious to the success of the book to have
+paraded, without giving any evidence, my conviction with respect to his
+origin." ("Life and Letters of Charles Darwin", Vol. 1. page 93.)
+
+In a letter written in January, 1860, to the Rev. L. Blomefield, Darwin
+expresses himself in similar terms. "With respect to man, I am very far
+from wishing to obtrude my belief; but I thought it dishonest to quite
+conceal my opinion." (Ibid. Vol. II. page 263.)
+
+The brief allusion in the "Origin of Species" is so far from prominent
+and so incidental that it was excusable to assume that Darwin had not
+touched upon the descent of man in this work. It was solely the desire
+to have his mass of evidence sufficiently complete, solely Darwin's
+great characteristic of never publishing till he had carefully weighed
+all aspects of his subject for years, solely, in short, his most
+fastidious scientific conscience that restrained him from challenging
+the world in 1859 with a book in which the theory of the descent of man
+was fully set forth. Three years, frequently interrupted by ill-health,
+were needed for the actual writing of the book ("Life and Letters", Vol.
+I. page 94.): the first edition, which appeared in 1871, was followed in
+1874 by a much improved second edition, the preparation of which he very
+reluctantly undertook. (Ibid. Vol. III. page 175.)
+
+This, briefly, is the history of the work, which, with the "Origin of
+Species", marks an epoch in the history of biological sciences--the work
+with which the cautious, peace-loving investigator ventured forth from
+his contemplative life into the arena of strife and unrest, and
+laid himself open to all the annoyances that deep-rooted belief and
+prejudice, and the prevailing tendency of scientific thought at the time
+could devise.
+
+Darwin did not take this step lightly. Of great interest in this
+connection is a letter written to Wallace on Dec. 22, 1857 (Ibid. Vol.
+II. page 109.), in which he says "You ask whether I shall discuss
+'man.' I think I shall avoid the whole subject, as so surrounded
+with prejudices; though I fully admit that it is the highest and most
+interesting problem for the naturalist." But his conscientiousness
+compelled him to state briefly his opinion on the subject in the "Origin
+of Species" in 1859. Nevertheless he did not escape reproaches for
+having been so reticent. This is unmistakably apparent from a letter to
+Fritz Muller dated February 22 (1869?), in which he says: "I am thinking
+of writing a little essay on the Origin of Mankind, as I have been
+taunted with concealing my opinions." (Ibid. Vol. III. page 112.)
+
+It might be thought that Darwin behaved thus hesitatingly, and was so
+slow in deciding on the full publication of his collected material in
+regard to the descent of man, because he had religious difficulties to
+overcome.
+
+But this was not the case, as we can see from his admirable confession
+of faith, the publication of which we owe to his son Francis. (Ibid.
+Vol. I. pages 304-317.) Whoever wishes really to understand the lofty
+character of this great man should read these immortal lines in which he
+unfolds to us in simple and straightforward words the development of his
+conception of the universe. He describes how, though he was still quite
+orthodox during his voyage round the world on board the "Beagle", he
+came gradually to see, shortly afterwards (1836-1839) that the Old
+Testament was no more to be trusted than the Sacred Books of the
+Hindoos; the miracles by which Christianity is supported, the
+discrepancies between the accounts in the different Gospels, gradually
+led him to disbelieve in Christianity as a divine revelation. "Thus," he
+writes ("Life and Letters", Vol. 1. page 309.), "disbelief crept over me
+at a very slow rate, but was at last complete. The rate was so slow that
+I felt no distress." But Darwin was too modest to presume to go beyond
+the limits laid down by science. He wanted nothing more than to be able
+to go, freely and unhampered by belief in authority or in the Bible, as
+far as human knowledge could lead him. We learn this from the concluding
+words of his chapter on religion: "The mystery of the beginning of all
+things is insoluble by us; and I for one must be content to remain an
+Agnostic." (Loc. cit. page 313.)
+
+Darwin was always very unwilling to give publicity to his views in
+regard to religion. In a letter to Asa Gray on May 22, 1860 (Ibid. Vol.
+II. page 310.), he declares that it is always painful to him to have
+to enter into discussion of religious problems. He had, he said, no
+intention of writing atheistically.
+
+Finally, let us cite one characteristic sentence from a letter from
+Darwin to C. Ridley (Ibid. Vol. III. page. 236. ("C. Ridley," Mr Francis
+Darwin points out to me, should be H.N. Ridley. A.C.S.)) (Nov. 28,
+1878.) A clergyman, Dr Pusey, had asserted that Darwin had written
+the "Origin of Species" with some relation to theology. Darwin writes
+emphatically, "Many years ago, when I was collecting facts for the
+'Origin', my belief in what is called a personal God was as firm as that
+of Dr Pusey himself, and as to the eternity of matter I never troubled
+myself about such insoluble questions." The expression "many years ago"
+refers to the time of his voyage round the world, as has already been
+pointed out. Darwin means by this utterance that the views which had
+gradually developed in his mind in regard to the origin of species were
+quite compatible with the faith of the Church.
+
+If we consider all these utterances of Darwin in regard to religion and
+to his outlook on life (Weltanschauung), we shall see at least so much,
+that religious reflection could in no way have influenced him in regard
+to the writing and publishing of his book on "The Descent of Man".
+Darwin had early won for himself freedom of thought, and to this freedom
+he remained true to the end of his life, uninfluenced by the customs and
+opinions of the world around him.
+
+Darwin was thus inwardly fortified and armed against the host of
+calumnies, accusations, and attacks called forth by the publication of
+the "Origin of Species", and to an even greater extent by the appearance
+of the "Descent of Man". But in his defence he could rely on the aid of
+a band of distinguished auxiliaries of the rarest ability. His faithful
+confederate, Huxley, was joined by the botanist Hooker, and, after
+longer resistance, by the famous geologist Lyell, whose "conversion"
+afforded Darwin peculiar satisfaction. All three took the field with
+enthusiasm in defence of the natural descent of man. From Wallace, on
+the other hand, though he shared with him the idea of natural selection,
+Darwin got no support in this matter. Wallace expressed himself in a
+strange manner. He admitted everything in regard to the morphological
+descent of man, but maintained, in a mystic way, that something else,
+something of a spiritual nature must have been added to what man
+inherited from his animal ancestors. Darwin, whose esteem for Wallace
+was extraordinarily high, could not understand how he could give
+utterance to such a mystical view in regard to man; the idea seemed
+to him so "incredibly strange" that he thought some one else must have
+added these sentences to Wallace's paper.
+
+Even now there are thinkers who, like Wallace, shrink from applying to
+man the ultimate consequences of the theory of descent. The idea
+that man is derived from ape-like forms is to them unpleasant and
+humiliating.
+
+So far I have been depicting the development of Darwin's work on the
+descent of man. In what follows I shall endeavour to give a condensed
+survey of the contents of the book.
+
+It must at once be said that the contents of Darwin's work fall into two
+parts, dealing with entirely different subjects. "The Descent of Man"
+includes a very detailed investigation in regard to secondary sexual
+characters in the animal series, and on this investigation Darwin
+founded a new theory, that of sexual selection. With astonishing
+patience he gathered together an immense mass of material, and showed,
+in regard to Arthropods and Vertebrates, the wide distribution of
+secondary characters, which develop almost exclusively in the male, and
+which enable him, on the one hand, to get the better of his rivals in
+the struggle for the female by the greater perfection of his weapons,
+and on the other hand, to offer greater allurements to the female
+through the higher development of decorative characters, of song, or of
+scent-producing glands. The best equipped males will thus crowd out the
+less well-equipped in the matter of reproduction, and thus the relevant
+characters will be increased and perfected through sexual selection.
+It is, of course, a necessary assumption that these secondary sexual
+characters may be transmitted to the female, although perhaps in
+rudimentary form.
+
+As we have said, this theory of sexual selection takes up a great deal
+of space in Darwin's book, and it need only be considered here in so far
+as Darwin applied it to the descent of man. To this latter problem the
+whole of Part I is devoted, while Part III contains a discussion of
+sexual selection in relation to man, and a general summary. Part II
+treats of sexual selection in general, and may be disregarded in our
+present study. Moreover, many interesting details must necessarily be
+passed over in what follows, for want of space.
+
+The first part of the "Descent of Man" begins with an enumeration of
+the proofs of the animal descent of man taken from the structure of
+the human body. Darwin chiefly emphasises the fact that the human body
+consists of the same organs and of the same tissues as those of the
+other mammals; he shows also that man is subject to the same diseases
+and tormented by the same parasites as the apes. He further dwells
+on the general agreement exhibited by young, embryonic forms, and
+he illustrates this by two figures placed one above the other, one
+representing a human embryo, after Eaker, the other a dog embryo, after
+Bischoff. ("Descent of Man" (Popular Edition, 1901), fig. 1, page 14.)
+
+Darwin finds further proofs of the animal origin of man in the
+reduced structures, in themselves extremely variable, which are either
+absolutely useless to their possessors, or of so little use that they
+could never have developed under existing conditions. Of such vestiges
+he enumerates: the defective development of the panniculus carnosus
+(muscle of the skin) so widely distributed among mammals, the
+ear-muscles, the occasional persistence of the animal ear-point in man,
+the rudimentary nictitating membrane (plica semilunaris) in the human
+eye, the slight development of the organ of smell, the general hairiness
+of the human body, the frequently defective development or entire
+absence of the third molar (the wisdom tooth), the vermiform appendix,
+the occasional reappearance of a bony canal (foramen supracondyloideum)
+at the lower end of the humerus, the rudimentary tail of man (the
+so-called taillessness), and so on. Of these rudimentary structures
+the occasional occurrence of the animal ear-point in man is most fully
+discussed. Darwin's attention was called to this interesting structure
+by the sculptor Woolner. He figures such a case observed in man, and
+also the head of an alleged orang-foetus, the photograph of which he
+received from Nitsche.
+
+Darwin's interpretation of Woolner's case as having arisen through a
+folding over of the free edge of a pointed ear has been fully borne out
+by my investigations on the external ear. (G. Schwalbe, "Das Darwin'sche
+Spitzohr beim menschlichen Embryo", "Anatom. Anzeiger", 1889, pages
+176-189, and other papers.) In particular, it was established by these
+investigations that the human foetus, about the middle of its embryonic
+life, possesses a pointed ear somewhat similar to that of the monkey
+genus Macacus. One of Darwin's statements in regard to the head of the
+orang-foetus must be corrected. A LARGE ear with a point is shown in
+the photograph ("Descent of Man", fig.3, page 24.), but it can easily be
+demonstrated--and Deniker has already pointed this out--that the figure
+is not that of an orang-foetus at all, for that form has much smaller
+ears with no point; nor can it be a gibbon-foetus, as Deniker supposes,
+for the gibbon ear is also without a point. I myself regard it as that
+of a Macacus-embryo. But this mistake, which is due to Nitsche, in no
+way affects the fact recognised by Darwin, that ear-forms showing the
+point characteristic of the animal ear occur in man with extraordinary
+frequency.
+
+Finally, there is a discussion of those rudimentary structures which
+occur only in ONE sex, such as the rudimentary mammary glands in the
+male, the vesicula prostatica, which corresponds to the uterus of the
+female, and others. All these facts tell in favour of the common descent
+of man and all other vertebrates. The conclusion of this section is
+characteristic: "IT IS ONLY OUR NATURAL PREJUDICE, AND THAT ARROGANCE
+WHICH MADE OUR FOREFATHERS DECLARE THAT THEY WERE DESCENDED FROM
+DEMI-GODS, WHICH LEADS US TO DEMUR TO THIS CONCLUSION. BUT THE TIME WILL
+BEFORE LONG COME, WHEN IT WILL BE THOUGHT WONDERFUL THAT NATURALISTS,
+WHO WERE WELL ACQUAINTED WITH THE COMPARATIVE STRUCTURE AND DEVELOPMENT
+OF MAN, AND OTHER MAMMALS, SHOULD HAVE BELIEVED THAT EACH WAS THE WORK
+OF A SEPARATE ACT OF CREATION." (Ibid. page 36.)
+
+In the second chapter there is a more detailed discussion, again based
+upon an extraordinary wealth of facts, of the problem as to the manner
+in which, and the causes through which, man evolved from a lower form.
+Precisely the same causes are here suggested for the origin of man, as
+for the origin of species in general. Variability, which is a necessary
+assumption in regard to all transformations, occurs in man to a high
+degree. Moreover, the rapid multiplication of the human race creates
+conditions which necessitate an energetic struggle for existence, and
+thus afford scope for the intervention of natural selection. Of the
+exercise of ARTIFICIAL selection in the human race, there is nothing
+to be said, unless we cite such cases as the grenadiers of Frederick
+William I, or the population of ancient Sparta. In the passages already
+referred to and in those which follow, the transmission of acquired
+characters, upon which Darwin does not dwell, is taken for granted.
+In man, direct effects of changed conditions can be demonstrated (for
+instance in regard to bodily size), and there are also proofs of the
+influence exerted on his physical constitution by increased use or
+disuse. Reference is here made to the fact, established by Forbes,
+that the Quechua-Indians of the high plateaus of Peru show a striking
+development of lungs and thorax, as a result of living constantly at
+high altitudes.
+
+Such special forms of variation as arrests of development
+(microcephalism) and reversion to lower forms are next discussed. Darwin
+himself felt ("Descent of Man", page 54.) that these subjects are so
+nearly related to the cases mentioned in the first chapter, that many
+of them might as well have been dealt with there. It seems to me that it
+would have been better so, for the citation of additional instances
+of reversion at this place rather disturbs the logical sequence of his
+ideas as to the conditions which have brought about the evolution of
+man from lower forms. The instances of reversion here discussed
+are microcephalism, which Darwin wrongly interpreted as atavistic,
+supernumerary mammae, supernumerary digits, bicornuate uterus, the
+development of abnormal muscles, and so on. Brief mention is also made
+of correlative variations observed in man.
+
+Darwin next discusses the question as to the manner in which man
+attained to the erect position from the state of a climbing quadruped.
+Here again he puts the influence of Natural Selection in the first
+rank. The immediate progenitors of man had to maintain a struggle for
+existence in which success was to the more intelligent, and to those
+with social instincts. The hand of these climbing ancestors, which
+had little skill and served mainly for locomotion, could only undergo
+further development when some early member of the Primate series came to
+live more on the ground and less among trees.
+
+A bipedal existence thus became possible, and with it the liberation
+of the hand from locomotion, and the one-sided development of the human
+foot. The upright position brought about correlated variations in the
+bodily structure; with the free use of the hand it became possible
+to manufacture weapons and to use them; and this again resulted in a
+degeneration of the powerful canine teeth and the jaws, which were then
+no longer necessary for defence. Above all, however, the intelligence
+immediately increased, and with it skull and brain. The nakedness of
+man, and the absence of a tail (rudimentariness of the tail vertebrae)
+are next discussed. Darwin is inclined to attribute the nakedness of
+man, not to the action of natural selection on ancestors who originally
+inhabited a tropical land, but to sexual selection, which, for aesthetic
+reasons, brought about the loss of the hairy covering in man, or
+primarily in woman. An interesting discussion of the loss of the tail,
+which, however, man shares with the anthropoid apes, some other monkeys
+and lemurs, forms the conclusion of the almost superabundant material
+which Darwin worked up in the second chapter. His object was to
+show that some of the most distinctive human characters are in all
+probability directly or indirectly due to natural selection. With
+characteristic modesty he adds ("Descent of Man", page 92.): "Hence, if
+I have erred in giving to natural selection great power, which I am
+very far from admitting, or in having exaggerated its power, which is in
+itself probable, I have at least, as I hope, done good service in aiding
+to overthrow the dogma of separate creations." At the end of the chapter
+he touches upon the objection as to man's helpless and defenceless
+condition. Against this he urges his intelligence and social instincts.
+
+The two following chapters contain a detailed discussion of the
+objections drawn from the supposed great differences between the mental
+powers of men and animals. Darwin at once admits that the differences
+are enormous, but not that any fundamental difference between the two
+can be found. Very characteristic of him is the following passage:
+"In what manner the mental powers were first developed in the
+lowest organisms, is as hopeless an enquiry as how life itself first
+originated. These are problems for the distant future, if they are ever
+to be solved by man." (Ibid. page 100.)
+
+After some brief observations on instinct and intelligence, Darwin
+brings forward evidence to show that the greater number of the emotional
+states, such as pleasure and pain, happiness and misery, love and hate
+are common to man and the higher animals. He goes on to give various
+examples showing that wonder and curiosity, imitation, attention, memory
+and imagination (dreams of animals), can also be observed in the higher
+mammals, especially in apes. In regard even to reason there are
+no sharply defined limits. A certain faculty of deliberation is
+characteristic of some animals, and the more thoroughly we know an
+animal the more intelligence we are inclined to credit it with. Examples
+are brought forward of the intelligent and deliberate actions of apes,
+dogs and elephants. But although no sharply defined differences exist
+between man and animals, there is, nevertheless, a series of other
+mental powers which are characteristics usually regarded as absolutely
+peculiar to man. Some of these characteristics are examined in detail,
+and it is shown that the arguments drawn from them are not conclusive.
+Man alone is said to be capable of progressive improvement; but against
+this must be placed as something analogous in animals, the fact that
+they learn cunning and caution through long continued persecution. Even
+the use of tools is not in itself peculiar to man (monkeys use sticks,
+stones and twigs), but man alone fashions and uses implements DESIGNED
+FOR A SPECIAL PURPOSE. In this connection the remarks taken from Lubbock
+in regard to the origin and gradual development of the earliest
+flint implements will be read with interest; these are similar to the
+observations on modern eoliths, and their bearing on the development of
+the stone-industry. It is interesting to learn from a letter to Hooker
+("Life and Letters", Vol. II. page 161, June 22, 1859.), that Darwin
+himself at first doubted whether the stone implements discovered
+by Boucher de Perthes were really of the nature of tools. With the
+relentless candour as to himself which characterised him, he writes four
+years later in a letter to Lyell in regard to this view of Boucher de
+Perthes' discoveries: "I know something about his errors, and looked at
+his book many years ago, and am ashamed to think that I concluded the
+whole was rubbish! Yet he has done for man something like what Agassiz
+did for glaciers." (Ibid. Vol. III. page 15, March 17, 1863.)
+
+To return to Darwin's further comparisons between the higher mental
+powers of man and animals. He takes much of the force from the argument
+that man alone is capable of abstraction and self-consciousness by his
+own observations on dogs. One of the main differences between man and
+animals, speech, receives detailed treatment. He points out that various
+animals (birds, monkeys, dogs) have a large number of different sounds
+for different emotions, that, further, man produces in common with
+animals a whole series of inarticulate cries combined with gestures, and
+that dogs learn to understand whole sentences of human speech. In regard
+to human language, Darwin expresses a view contrary to that held by Max
+Muller ("Descent of Man", page 132.): "I cannot doubt that language owes
+its origin to the imitation and modification of various natural sounds,
+the voices of other animals, and man's own instinctive cries, aided by
+signs and gestures." The development of actual language presupposes a
+higher degree of intelligence than is found in any kind of ape. Darwin
+remarks on this point (Ibid. pages 136, 137.): "The fact of the higher
+apes not using their vocal organs for speech no doubt depends on their
+intelligence not having been sufficiently advanced."
+
+The sense of beauty, too, has been alleged to be peculiar to man. In
+refutation of this assertion Darwin points to the decorative colours of
+birds, which are used for display. And to the last objection, that man
+alone has religion, that he alone has a belief in God, it is answered
+"that numerous races have existed, and still exist, who have no idea of
+one or more gods, and who have no words in their languages to express
+such an idea." (Ibid. page 143.)
+
+The result of the investigations recorded in this chapter is to show
+that, great as the difference in mental powers between man and the
+higher animals may be, it is undoubtedly only a difference "of degree
+and not of kind." ("Descent of Man", page 193.)
+
+In the fourth chapter Darwin deals with the MORAL SENSE or CONSCIENCE,
+which is the most important of all differences between man and animals.
+It is a result of social instincts, which lead to sympathy for other
+members of the same society, to non-egoistic actions for the good
+of others. Darwin shows that social tendencies are found among many
+animals, and that among these love and kin-sympathy exist, and he gives
+examples of animals (especially dogs) which may exhibit characters that
+we should call moral in man (e.g. disinterested self-sacrifice for the
+sake of others). The early ape-like progenitors of the human race were
+undoubtedly social. With the increase of intelligence the moral sense
+develops farther; with the acquisition of speech public opinion arises,
+and finally, moral sense becomes habit. The rest of Darwin's detailed
+discussions on moral philosophy may be passed over.
+
+The fifth chapter may be very briefly summarised. In it Darwin shows
+that the intellectual and moral faculties are perfected through natural
+selection. He inquires how it can come about that a tribe at a low level
+of evolution attains to a higher, although the best and bravest among
+them often pay for their fidelity and courage with their lives without
+leaving any descendants. In this case it is the sentiment of glory,
+praise and blame, the admiration of others, which bring about the
+increase of the better members of the tribe. Property, fixed dwellings,
+and the association of families into a community are also indispensable
+requirements for civilisation. In the longer second section of the
+fifth chapter Darwin acts mainly as recorder. On the basis of numerous
+investigations, especially those of Greg, Wallace, and Galton, he
+inquires how far the influence of natural selection can be demonstrated
+in regard to civilised nations. In the final section, which deals with
+the proofs that all civilised nations were once barbarians, Darwin again
+uses the results gained by other investigators, such as Lubbock and
+Tylor. There are two sets of facts which prove the proposition in
+question. In the first place, we find traces of a former lower state
+in the customs and beliefs of all civilised nations, and in the second
+place, there are proofs to show that savage races are independently able
+to raise themselves a few steps in the scale of civilisation, and that
+they have thus raised themselves.
+
+In the sixth chapter of the work, Morphology comes into the foreground
+once more. Darwin first goes back, however, to the argument based on the
+great difference between the mental powers of the highest animals and
+those of man. That this is only quantitative, not qualitative, he has
+already shown. Very instructive in this connection is the reference to
+the enormous difference in mental powers in another class. No one
+would draw from the fact that the cochineal insect (Coccus) and the ant
+exhibit enormous differences in their mental powers, the conclusion that
+the ant should therefore be regarded as something quite distinct, and
+withdrawn from the class of insects altogether.
+
+Darwin next attempts to establish the SPECIFIC genealogical tree of
+man, and carefully weighs the differences and resemblances between the
+different families of the Primates. The erect position of man is an
+adaptive character, just as are the various characters referable to
+aquatic life in the seals, which, notwithstanding these, are ranked as
+a mere family of the Carnivores. The following utterance is very
+characteristic of Darwin ("Descent of Man", page 231.): "If man had
+not been his own classifier, he would never have thought of founding
+a separate order for his own reception." In numerous characters not
+mentioned in systematic works, in the features of the face, in the form
+of the nose, in the structure of the external ear, man resembles the
+apes. The arrangement of the hair in man has also much in common with
+the apes; as also the occurrence of hair on the forehead of the human
+embryo, the beard, the convergence of the hair of the upper and under
+arm towards the elbow, which occurs not only in the anthropoid apes, but
+also in some American monkeys. Darwin here adopts Wallace's explanation
+of the origin of the ascending direction of the hair in the forearm of
+the orang,--that it has arisen through the habit of holding the hands
+over the head in rain. But this explanation cannot be maintained when we
+consider that this disposition of the hair is widely distributed among
+the most different mammals, being found in the dog, in the sloth, and in
+many of the lower monkeys.
+
+After further careful analysis of the anatomical characters Darwin
+reaches the conclusion that the New World monkeys (Platyrrhine) may
+be excluded from the genealogical tree altogether, but that man is
+an offshoot from the Old World monkeys (Catarrhine) whose progenitors
+existed as far back as the Miocene period. Among these Old World monkeys
+the forms to which man shows the greatest resemblance are the anthropoid
+apes, which, like him, possess neither tail nor ischial callosities. The
+platyrrhine and catarrhine monkeys have their primitive ancestor among
+extinct forms of the Lemuridae. Darwin also touches on the question of
+the original home of the human race and supposes that it may have been
+in Africa, because it is there that man's nearest relatives, the gorilla
+and the chimpanzee, are found. But he regards speculation on this point
+as useless. It is remarkable that, in this connection, Darwin regards
+the loss of the hair-covering in man as having some relation to a
+warm climate, while elsewhere he is inclined to make sexual selection
+responsible for it. Darwin recognises the great gap between man and
+his nearest relatives, but similar gaps exist at other parts of the
+mammalian genealogical tree: the allied forms have become extinct. After
+the extermination of the lower races of mankind, on the one hand, and of
+the anthropoid apes on the other, which will undoubtedly take place, the
+gulf will be greater than ever, since the baboons will then bound it on
+the one side, and the white races on the other. Little weight need be
+attached to the lack of fossil remains to fill up this gap, since the
+discovery of these depends upon chance. The last part of the chapter is
+devoted to a discussion of the earlier stages in the genealogy of
+man. Here Darwin accepts in the main the genealogical tree, which had
+meantime been published by Haeckel, who traces the pedigree back through
+Monotremes, Reptiles, Amphibians, and Fishes, to Amphioxus.
+
+Then follows an attempt to reconstruct, from the atavistic characters,
+a picture of our primitive ancestor who was undoubtedly an arboreal
+animal. The occurrence of rudiments of parts in one sex which only come
+to full development in the other is next discussed. This state of things
+Darwin regards as derived from an original hermaphroditism. In regard to
+the mammary glands of the male he does not accept the theory that they
+are vestigial, but considers them rather as not fully developed.
+
+The last chapter of Part I deals with the question whether the different
+races of man are to be regarded as different species, or as sub-species
+of a race of monophyletic origin. The striking differences between
+the races are first emphasised, and the question of the fertility or
+infertility of hybrids is discussed. That fertility is the more usual
+is shown by the excessive fertility of the hybrid population of Brazil.
+This, and the great variability of the distinguishing characters of
+the different races, as well as the fact that all grades of transition
+stages are found between these, while considerable general agreement
+exists, tell in favour of the unity of the races and lead to the
+conclusion that they all had a common primitive ancestor.
+
+Darwin therefore classifies all the different races as sub-species of
+ONE AND THE SAME SPECIES. Then follows an interesting inquiry into the
+reasons for the extinction of human races. He recognises as the ultimate
+reason the injurious effects of a change of the conditions of life,
+which may bring about an increase in infantile mortality, and a
+diminished fertility. It is precisely the reproductive system, among
+animals also, which is most susceptible to changes in the environment.
+
+The final section of this chapter deals with the formation of the races
+of mankind. Darwin discusses the question how far the direct effect of
+different conditions of life, or the inherited effects of increased use
+or disuse may have brought about the characteristic differences between
+the different races. Even in regard to the origin of the colour of the
+skin he rejects the transmitted effects of an original difference of
+climate as an explanation. In so doing he is following his tendency to
+exclude Lamarckian explanations as far as possible. But here he makes
+gratuitous difficulties from which, since natural selection fails, there
+is no escape except by bringing in the principle of sexual selection, to
+which, he regarded it as possible, skin-colouring, arrangement of
+hair, and form of features might be traced. But with his characteristic
+conscientiousness he guards himself thus: "I do not intend to assert
+that sexual selection will account for all the differences between the
+races." ("Descent of Man", page 308.)
+
+I may be permitted a remark as to Darwin's attitude towards Lamarck.
+While, at an earlier stage, when he was engaged in the preliminary
+labours for his immortal work, "The Origin of Species", Darwin expresses
+himself very forcibly against the views of Lamarck, speaking of
+Lamarckian "nonsense," ("Life and Letters", Vol. II. page 23.), and
+of Lamarck's "absurd, though clever work" (Loc. cit. page 39.) and
+expressly declaring, "I attribute very little to the direct action of
+climate, etc." (Loc. cit. (1856), page 82.) yet in later life he became
+more and more convinced of the influence of external conditions. In
+1876, that is, two years after the appearance of the second edition of
+"The Descent of Man", he writes with his usual candid honesty: "In my
+opinion the greatest error which I have committed, has been not allowing
+sufficient weight to the direct action of the environment, i.e. food,
+climate, etc. independently of natural selection." (Ibid. Vol. III. page
+159.) It is certain from this change of opinion that, if he had been
+able to make up his mind to issue a third edition of "The Descent of
+Man", he would have ascribed a much greater influence to the effect of
+external conditions in explaining the different characters of the races
+of man than he did in the second edition. He would also undoubtedly have
+attributed less influence to sexual selection as a factor in the origin
+of the different bodily characteristics, if indeed he would not have
+excluded it altogether.
+
+In Part III of the "Descent" two additional chapters are devoted to the
+discussion of sexual selection in relation to man. These may be very
+briefly referred to. Darwin here seeks to show that sexual selection has
+been operative on man and his primitive progenitor. Space fails me to
+follow out his interesting arguments. I can only mention that he is
+inclined to trace back hairlessness, the development of the beard in
+man, and the characteristic colour of the different human races to
+sexual selection. Since bareness of the skin could be no advantage, but
+rather a disadvantage, this character cannot have been brought about by
+natural selection. Darwin also rejected a direct influence of climate as
+a cause of the origin of the skin-colour. I have already expressed the
+opinion, based on the development of his views as shown in his letters,
+that in a third edition Darwin would probably have laid more stress on
+the influence of external environment. He himself feels that there are
+gaps in his proofs here, and says in self-criticism: "The views here
+advanced, on the part which sexual selection has played in the history
+of man, want scientific precision." ("Descent of Man", page 924.) I
+need here only point out that it is impossible to explain the graduated
+stages of skin-colour by sexual selection, since it would have produced
+races sharply defined by their colour and not united to other races
+by transition stages, and this, it is well known, is not the case.
+Moreover, the fact established by me ("Die Hautfarbe des Menschen",
+"Mitteilungen der Anthropologischen Gesellschaft in Wien", Vol. XXXIV.
+pages 331-352.), that in all races the ventral side of the trunk is
+paler than the dorsal side, and the inner surface of the extremities
+paler than the outer side, cannot be explained by sexual selection in
+the Darwinian sense.
+
+With this I conclude my brief survey of the rich contents of Darwin's
+book. I may be permitted to conclude by quoting the magnificent final
+words of "The Descent of Man": "We must, however, acknowledge, as it
+seems to me, that man, with all his noble qualities, with sympathy which
+feels for the most debased, with benevolence which extends not only
+to other men but to the humblest living creature, with his god-like
+intellect which has penetrated into the movements and constitution of
+the solar system--with all these exalted powers--Man still bears in his
+bodily frame the indelible stamp of his lowly origin." (Ibid. page 947.)
+
+What has been the fate of Darwin's doctrines since his great
+achievement? How have they been received and followed up by the
+scientific and lay world? And what do the successors of the mighty hero
+and genius think now in regard to the origin of the human race?
+
+At the present time we are incomparably more favourably placed than
+Darwin was for answering this question of all questions. We have at our
+command an incomparably greater wealth of material than he had at his
+disposal. And we are more fortunate than he in this respect, that we
+now know transition-forms which help to fill up the gap, still great,
+between the lowest human races and the highest apes. Let us consider
+for a little the more essential additions to our knowledge since the
+publication of "The Descent of Man".
+
+Since that time our knowledge of animal embryos has increased
+enormously. While Darwin was obliged to content himself with comparing
+a human embryo with that of a dog, there are now available the youngest
+embryos of monkeys of all possible groups (Orang, Gibbon, Semnopithecus,
+Macacus), thanks to Selenka's most successful tour in the East Indies in
+search of such material. We can now compare corresponding stages of
+the lower monkeys and of the Anthropoid apes with human embryos, and
+convince ourselves of their great resemblance to one another, thus
+strengthening enormously the armour prepared by Darwin in defence of his
+view on man's nearest relatives. It may be said that Selenka's material
+fils up the blanks in Darwin's array of proofs in the most satisfactory
+manner.
+
+The deepening of our knowledge of comparative anatomy also gives us much
+surer foundations than those on which Darwin was obliged to build. Just
+of late there have been many workers in the domain of the anatomy of
+apes and lemurs, and their investigations extend to the most different
+organs. Our knowledge of fossil apes and lemurs has also become much
+wider and more exact since Darwin's time: the fossil lemurs have been
+especially worked up by Cope, Forsyth Major, Ameghino, and others.
+Darwin knew very little about fossil monkeys. He mentions two or three
+anthropoid apes as occurring in the Miocene of Europe ("Descent of
+Man", page 240.), but only names Dryopithecus, the largest form from
+the Miocene of France. It was erroneously supposed that this form was
+related to Hylobates. We now know not only a form that actually stands
+near to the gibbon (Pliopithecus), and remains of other anthropoids
+(Pliohylobates and the fossil chimpanzee, Palaeopithecus), but also
+several lower catarrhine monkeys, of which Mesopithecus, a form nearly
+related to the modern Sacred Monkeys (a species of Semnopithecus) and
+found in strata of the Miocene period in Greece, is the most important.
+Quite recently, too, Ameghino's investigations have made us acquainted
+with fossil monkeys from South America (Anthropops, Homunculus), which,
+according to their discoverer, are to be regarded as in the line of
+human descent.
+
+What Darwin missed most of all--intermediate forms between apes
+and man--has been recently furnished. (E. Dubois, as is well known,
+discovered in 1893, near Trinil in Java, in the alluvial deposits of
+the river Bengawan, an important form represented by a skull-cap, some
+molars, and a femur. His opinion--much disputed as it has been--that in
+this form, which he named Pithecanthropus, he has found a long-desired
+transition-form is shared by the present writer. And although the
+geological age of these fossils, which, according to Dubois, belong to
+the uppermost Tertiary series, the Pliocene, has recently been fixed
+at a later date (the older Diluvium)), the MORPHOLOGICAL VALUE of
+these interesting remains, that is, the intermediate position of
+Pithecanthropus, still holds good. Volz says with justice ("Das
+geologische Alter der Pithecanthropus-Schichten bei Trinil, Ost-Java".
+"Neues Jahrb. f.Mineralogie". Festband, 1907.), that even if
+Pithecanthropus is not THE missing link, it is undoubtedly _A_ missing
+link.
+
+As on the one hand there has been found in Pithecanthropus a form which,
+though intermediate between apes and man, is nevertheless more closely
+allied to the apes, so on the other hand, much progress has been made
+since Darwin's day in the discovery and description of the older
+human remains. Since the famous roof of a skull and the bones of the
+extremities belonging to it were found in 1856 in the Neandertal near
+Dusseldorf, the most varied judgments have been expressed in regard
+to the significance of the remains and of the skull in particular.
+In Darwin's "Descent of Man" there is only a passing allusion to them
+("Descent of Man", page 82.) in connection with the discussion of the
+skull-capacity, although the investigations of Schaaffhausen, King, and
+Huxley were then known. I believe I have shown, in a series of papers,
+that the skull in question belongs to a form different from any of the
+races of man now living, and, with King and Cope, I regard it as at
+least a different species from living man, and have therefore designated
+it Homo primigenius. The form unquestionably belongs to the older
+Diluvium, and in the later Diluvium human forms already appear, which
+agree in all essential points with existing human races.
+
+As far back as 1886 the value of the Neandertal skull was greatly
+enhanced by Fraipont's discovery of two skulls and skeletons from Spy in
+Belgium. These are excellently described by their discoverer ("La race
+humaine de Neanderthal ou de Canstatt en Belgique". "Arch. de Biologie",
+VII. 1887.), and are regarded as belonging to the same group of forms
+as the Neandertal remains. In 1899 and the following years came the
+discovery by Gorjanovic-Kramberger of different skeletal parts of
+at least ten individuals in a cave near Krapina in Croatia.
+(Gorjanovic-Kramberger "Der diluviale Mensch von Krapina in Kroatien",
+1906.) It is in particular the form of the lower jaw which is different
+from that of all recent races of man, and which clearly indicates
+the lowly position of Homo primigenius, while, on the other hand, the
+long-known skull from Gibraltar, which I ("Studien zur Vorgeschichte des
+Menschen", 1906, pages 154 ff.) have referred to Homo primigenius, and
+which has lately been examined in detail by Sollas ("On the cranial and
+facial characters of the Neandertal Race". "Trans. R. Soc." London, vol.
+199, 1908, page 281.), has made us acquainted with the surprising shape
+of the eye-orbit, of the nose, and of the whole upper part of the face.
+Isolated lower jaws found at La Naulette in Belgium, and at Malarnaud
+in France, increase our material which is now as abundant as could be
+desired. The most recent discovery of all is that of a skull dug up in
+August of this year (1908) by Klaatsch and Hauser in the lower grotto
+of the Le Moustier in Southern France, but this skull has not yet
+been fully described. Thus Homo primigenius must also be regarded as
+occupying a position in the gap existing between the highest apes and
+the lowest human races, Pithecanthropus, standing in the lower part of
+it, and Homo primigenius in the higher, near man. In order to prevent
+misunderstanding, I should like here to emphasise that in arranging this
+structural series--anthropoid apes, Pithecanthropus, Homo primigenius,
+Homo sapiens--I have no intention of establishing it as a direct
+genealogical series. I shall have something to say in regard to the
+genetic relations of these forms, one to another, when discussing the
+different theories of descent current at the present day. ((Since
+this essay was written Schoetensack has discovered near Heidelberg
+and briefly described an exceedingly interesting lower jaw from rocks
+between the Pliocene and Diluvial beds. This exhibits interesting
+differences from the forms of lower jaw of Homo primigenius.
+(Schoetensack "Der Unterkiefer des Homo heidelbergensis". Leipzig,
+1908.) G.S.))
+
+In quite a different domain from that of morphological relationship,
+namely in the physiological study of the blood, results have recently
+been gained which are of the highest importance to the doctrine of
+descent. Uhlenhuth, Nuttall, and others have established the fact
+that the blood-serum of a rabbit which has previously had human blood
+injected into it, forms a precipitate with human blood. This biological
+reaction was tried with a great variety of mammalian species, and it was
+found that those far removed from man gave no precipitate under these
+conditions. But as in other cases among mammals all nearly related forms
+yield an almost equally marked precipitate, so the serum of a rabbit
+treated with human blood and then added to the blood of an anthropoid
+ape gives ALMOST as marked a precipitate as in human blood; the reaction
+to the blood of the lower Eastern monkeys is weaker, that to the Western
+monkeys weaker still; indeed in this last case there is only a slight
+clouding after a considerable time and no actual precipitate. The blood
+of the Lemuridae (Nuttall) gives no reaction or an extremely weak one,
+that of the other mammals none whatever. We have in this not only a
+proof of the literal blood-relationship between man and apes, but the
+degree of relationship with the different main groups of apes can be
+determined beyond possibility of mistake.
+
+Finally, it must be briefly mentioned that in regard to remains of human
+handicraft also, the material at our disposal has greatly increased of
+late years, that, as a result of this, the opinions of archaeologists
+have undergone many changes, and that, in particular, their views in
+regard to the age of the human race have been greatly influenced. There
+is a tendency at the present time to refer the origin of man back to
+Tertiary times. It is true that no remains of Tertiary man have been
+found, but flints have been discovered which, according to the opinion
+of most investigators, bear traces either of use, or of very primitive
+workmanship. Since Rutot's time, following Mortillet's example,
+investigators have called these "eoliths," and they have been traced
+back by Verworn to the Miocene of the Auvergne, and by Rutot even to the
+upper Oligocene. Although these eoliths are even nowadays the subject of
+many different views, the preoccupation with them has kept the problem
+of the age of the human race continually before us.
+
+Geology, too, has made great progress since the days of Darwin and
+Lyell, and has endeavoured with satisfactory results to arrange the
+human remains of the Diluvial period in chronological order (Penck). I
+do not intend to enter upon the question of the primitive home of the
+human race; since the space at my disposal will not allow of my
+touching even very briefly upon all the departments of science which are
+concerned in the problem of the descent of man. How Darwin would have
+rejoiced over each of the discoveries here briefly outlined! What use
+he would have made of the new and precious material, which would have
+prevented the discouragement from which he suffered when preparing the
+second edition of "The Descent of Man"! But it was not granted to him to
+see this progress towards filling up the gaps in his edifice of which he
+was so painfully conscious.
+
+He did, however, have the satisfaction of seeing his ideas steadily
+gaining ground, notwithstanding much hostility and deep-rooted
+prejudice. Even in the years between the appearance of "The Origin
+of Species" and of the first edition of the "Descent", the idea of a
+natural descent of man, which was only briefly indicated in the work of
+1859, had been eagerly welcomed in some quarters. It has been already
+pointed out how brilliantly Huxley contributed to the defence and
+diffusion of Darwin's doctrines, and how in "Man's Place in Nature"
+he has given us a classic work as a foundation for the doctrine of
+the descent of man. As Huxley was Darwin's champion in England, so in
+Germany Carl Vogt, in particular, made himself master of the Darwinian
+ideas. But above all it was Haeckel who, in energy, eagerness for
+battle, and knowledge may be placed side by side with Huxley, who took
+over the leadership in the controversy over the new conception of the
+universe. As far back as 1866, in his "Generelle Morphologie", he had
+inquired minutely into the question of the descent of man, and not
+content with urging merely the general theory of descent from lower
+animal forms, he drew up for the first time genealogical trees showing
+the close relationships of the different animal groups; the last of
+these illustrated the relationships of Mammals, and among them of all
+groups of the Primates, including man. It was Haeckel's genealogical
+trees that formed the basis of the special discussion of the
+relationships of man, in the sixth chapter of Darwin's "Descent of Man".
+
+In the last section of this essay I shall return to Haeckel's conception
+of the special descent of man, the main features of which he still
+upholds, and rightly so. Haeckel has contributed more than any one else
+to the spread of the Darwinian doctrine.
+
+I can only allow myself a few words as to the spread of the theory
+of the natural descent of man in other countries. The Parisian
+anthropological school, founded and guided by the genius of Broca, took
+up the idea of the descent of man, and made many notable contributions
+to it (Broca, Manouvrier, Mahoudeau, Deniker and others). In England
+itself Darwin's work did not die. Huxley took care of that, for he, with
+his lofty and unprejudiced mind, dominated and inspired English biology
+until his death on June 29, 1895. He had the satisfaction shortly before
+his death of learning of Dubois' discovery, which he illustrated by a
+humorous sketch. ("Life and Letters of Thomas Henry Huxley", Vol. II.
+page 394.) But there are still many followers in Darwin's footsteps
+in England. Keane has worked at the special genealogical tree of the
+Primates; Keith has inquired which of the anthropoid apes has the
+greatest number of characters in common with man; Morris concerns
+himself with the evolution of man in general, especially with
+his acquisition of the erect position. The recent discoveries of
+Pithecanthropus and Homo primigenius are being vigorously discussed; but
+the present writer is not in a position to form an opinion of the
+extent to which the idea of descent has penetrated throughout England
+generally.
+
+In Italy independent work in the domain of the descent of man is being
+produced, especially by Morselli; with him are associated, in the
+investigation of related problems, Sergi and Giuffrida-Ruggeri. From
+the ranks of American investigators we may single out in particular the
+eminent geologist Cope, who championed with much decision the idea
+of the specific difference of Homo neandertalensis (primigenius) and
+maintained a more direct descent of man from the fossil Lemuridae. In
+South America too, in Argentina, new life is stirring in this department
+of science. Ameghino in Buenos Ayres has awakened the fossil primates
+of the Pampas formation to new life; he even believes that in
+Tetraprothomo, represented by a femur, he has discovered a direct
+ancestor of man. Lehmann-Nitsche is working at the other side of the
+gulf between apes and men, and he describes a remarkable first cervical
+vertebra (atlas) from Monte Hermoso as belonging to a form which
+may bear the same relation to Homo sapiens in South America as Homo
+primigenius does in the Old World. After a minute investigation he
+establishes a human species Homo neogaeus, while Ameghino ascribes this
+atlas vertebra to his Tetraprothomo.
+
+Thus throughout the whole scientific world there is arising a new
+life, an eager endeavour to get nearer to Huxley's problema maximum,
+to penetrate more deeply into the origin of the human race. There are
+to-day very few experts in anatomy and zoology who deny the animal
+descent of man in general. Religious considerations, old prejudices,
+the reluctance to accept man, who so far surpasses mentally all
+other creatures, as descended from "soulless" animals, prevent a few
+investigators from giving full adherence to the doctrine. But there are
+very few of these who still postulate a special act of creation for
+man. Although the majority of experts in anatomy and zoology accept
+unconditionally the descent of man from lower forms, there is much
+diversity of opinion among them in regard to the special line of
+descent.
+
+In trying to establish any special hypothesis of descent, whether by
+the graphic method of drawing up genealogical trees or otherwise, let us
+always bear in mind Darwin's words ("Descent of Man", page 229.) and use
+them as a critical guiding line: "As we have no record of the lines of
+descent, the pedigree can be discovered only by observing the degrees of
+resemblance between the beings which are to be classed." Darwin carries
+this further by stating "that resemblances in several unimportant
+structures, in useless and rudimentary organs, or not now functionally
+active, or in an embryological condition, are by far the most
+serviceable for classification." (Loc. cit.) It has also to be
+remembered that NUMEROUS separate points of agreement are of much
+greater importance than the amount of similarity or dissimilarity in a
+few points.
+
+The hypotheses as to descent current at the present day may be divided
+into two main groups. The first group seeks for the roots of the human
+race not among any of the families of the apes--the anatomically nearest
+forms--nor among their very similar but less specialised ancestral
+forms, the fossil representatives of which we can know only in part,
+but, setting the monkeys on one side, it seeks for them lower down among
+the fossil Eocene Pseudo-lemuridae or Lemuridae (Cope), or even among
+the primitive pentadactylous Eocene forms, which may either have led
+directly to the evolution of man (Adloff), or have given rise to an
+ancestral form common to apes and men (Klaatsch (Klaatsch in his last
+publications speaks in the main only of an ancestral form common to men
+and anthropoid apes.), Giuffrida-Ruggeri). The common ancestral form,
+from which man and apes are thus supposed to have arisen independently,
+may explain the numerous resemblances which actually exist between
+them. That is to say, all the characters upon which the great structural
+resemblance between apes and man depends must have been present in their
+common ancestor. Let us take an example of such a common character. The
+bony external ear-passage is in general as highly developed in the lower
+Eastern monkeys and the anthropoid apes as in man. This character must,
+therefore, have already been present in the common primitive form. In
+that case it is not easy to understand why the Western monkeys have
+not also inherited the character, instead of possessing only a tympanic
+ring. But it becomes more intelligible if we assume that forms with a
+primitive tympanic ring were the original type, and that from these were
+evolved, on the one hand, the existing New World monkeys with persistent
+tympanic ring, and on the other an ancestral form common to the lower
+Old World monkeys, the anthropoid apes and man. For man shares with
+these the character in question, and it is also one of the "unimportant"
+characters required by Darwin. Thus we have two divergent lines arising
+from the ancestral form, the Western monkeys (Platyrrhine) on the one
+hand, and an ancestral form common to the lower Eastern monkeys, the
+anthropoid apes, and man, on the other. But considerations similar to
+those which showed it to be impossible that man should have developed
+from an ancestor common to him and the monkeys, yet outside of and
+parallel with these, may be urged also against the likelihood of a
+parallel evolution of the lower Eastern monkeys, the anthropoid apes,
+and man. The anthropoid apes have in common with man many characters
+which are not present in the lower Old World monkeys. These characters
+must therefore have been present in the ancestral form common to the
+three groups. But here, again, it is difficult to understand why the
+lower Eastern monkeys should not also have inherited these characters.
+As this is not the case, there remains no alternative but to assume
+divergent evolution from an indifferent form. The lower Eastern monkeys
+are carrying on the evolution in one direction--I might almost say
+towards a blind alley--while anthropoids and men have struck out a
+progressive path, at first in common, which explains the many points of
+resemblance between them, without regarding man as derived directly
+from the anthropoids. Their many striking points of agreement indicate a
+common descent, and cannot be explained as phenomena of convergence.
+
+I believe I have shown in the above sketch that a theory which derives
+man directly from lower forms without regarding apes as transition-types
+leads ad absurdum. The close structural relationship between man and
+monkeys can only be understood if both are brought into the same line
+of evolution. To trace man's line of descent directly back to the old
+Eocene mammals, alongside of, but with no relation to these very similar
+forms, is to abandon the method of exact comparison, which, as Darwin
+rightly recognised, alone justifies us in drawing up genealogical trees
+on the basis of resemblances and differences. The farther down we go the
+more does the ground slip from beneath our feet. Even the Lemuridae
+show very numerous divergent conditions, much more so the Eocene
+mammals (Creodonta, Condylarthra), the chief resemblance of which to man
+consists in the possession of pentadactylous hands and feet! Thus the
+farther course of the line of descent disappears in the darkness of the
+ancestry of the mammals. With just as much reason we might pass by the
+Vertebrates altogether, and go back to the lower Invertebrates, but
+in that case it would be much easier to say that man has arisen
+independently, and has evolved, without relation to any animals, from
+the lowest primitive form to his present isolated and dominant position.
+But this would be to deny all value to classification, which must after
+all be the ultimate basis of a genealogical tree. We can, as Darwin
+rightly observed, only infer the line of descent from the degree of
+resemblance between single forms. If we regard man as directly derived
+from primitive forms very far back, we have no way of explaining the
+many points of agreement between him and the monkeys in general, and the
+anthropoid apes in particular. These must remain an inexplicable marvel.
+
+I have thus, I trust, shown that the first class of special theories
+of descent, which assumes that man has developed, parallel with the
+monkeys, but without relation to them, from very low primitive forms
+cannot be upheld, because it fails to take into account the close
+structural affinity of man and monkeys. I cannot but regard this
+hypothesis as lamentably retrograde, for it makes impossible any
+application of the facts that have been discovered in the course of
+the anatomical and embryological study of man and monkeys, and indeed
+prejudges investigations of that class as pointless. The whole method is
+perverted; an unjustifiable theory of descent is first formulated with
+the aid of the imagination, and then we are asked to declare that all
+structural relations between man and monkeys, and between the different
+groups of the latter, are valueless,--the fact being that they are the
+only true basis on which a genealogical tree can be constructed.
+
+So much for this most modern method of classification, which has
+probably found adherents because it would deliver us from the
+relationship to apes which many people so much dislike. In contrast
+to it we have the second class of special hypotheses of descent, which
+keeps strictly to the nearest structural relationships. This is the only
+basis that justifies the drawing up of a special hypothesis of descent.
+If this fundamental proposition be recognised, it will be admitted that
+the doctrine of special descent upheld by Haeckel, and set forth in
+Darwin's "Descent of Man", is still valid to-day. In the genealogical
+tree, man's place is quite close to the anthropoid apes; these again
+have as their nearest relatives the lower Old World monkeys, and their
+progenitors must be sought among the less differentiated Platyrrhine
+monkeys, whose most important characters have been handed on to the
+present day New World monkeys. How the different genera are to be
+arranged within the general scheme indicated depends in the main on
+the classificatory value attributed to individual characters. This is
+particularly true in regard to Pithecanthropus, which I consider as the
+root of a branch which has sprung from the anthropoid ape root and has
+led up to man; the latter I have designated the family of the Hominidae.
+
+For the rest, there are, as we have said, various possible ways of
+constructing the narrower genealogy within the limits of this branch
+including men and apes, and these methods will probably continue to
+change with the accumulation of new facts. Haeckel himself has modified
+his genealogical tree of the Primates in certain details since the
+publication of his "Generelle Morphologie" in 1866, but its general
+basis remains the same. (Haeckel's latest genealogical tree is to be
+found in his most recent work, "Unsere Ahnenreihe". Jena, 1908.) All the
+special genealogical trees drawn up on the lines laid down by Haeckel
+and Darwin--and that of Dubois may be specially mentioned--are based, in
+general, on the close relationship of monkeys and men, although they may
+vary in detail. Various hypotheses have been formulated on these lines,
+with special reference to the evolution of man. "Pithecanthropus" is
+regarded by some authorities as the direct ancestor of man, by others as
+a side-track failure in the attempt at the evolution of man. The problem
+of the monophyletic or polyphyletic origin of the human race has also
+been much discussed. Sergi (Sergi G. "Europa", 1908.) inclines towards
+the assumption of a polyphyletic origin of the three main races of man,
+the African primitive form of which has given rise also to the
+gorilla and chimpanzee, the Asiatic to the Orang, the Gibbon, and
+Pithecanthropus. Kollmann regards existing human races as derived from
+small primitive races (pigmies), and considers that Homo primigenius
+must have arisen in a secondary and degenerative manner.
+
+But this is not the place, nor have I the space to criticise the various
+special theories of descent. One, however, must receive particular
+notice. According to Ameghino, the South American monkeys (Pitheculites)
+from the oldest Tertiary of the Pampas are the forms from which have
+arisen the existing American monkeys on the one hand, and on the other,
+the extinct South American Homunculidae, which are also small forms.
+From these last, anthropoid apes and man have, he believes, been
+evolved. Among the progenitors of man, Ameghino reckons the form
+discovered by him (Tetraprothomo), from which a South American primitive
+man, Homo pampaeus, might be directly evolved, while on the other hand
+all the lower Old World monkeys may have arisen from older fossil
+South American forms (Clenialitidae), the distribution of which may
+be explained by the bridge formerly existing between South America and
+Africa, as may be the derivation of all existing human races from Homo
+pampaeus. (See Ameghino's latest paper, "Notas preliminares sobre el
+Tetraprothomo argentinus", etc. "Anales del Museo nacional de Buenos
+Aires", XVI. pages 107-242, 1907.) The fossil forms discovered by
+Ameghino deserve the most minute investigation, as does also the fossil
+man from South America of which Lehmann-Nitsche ("Nouvelles recherches
+sur la formation pampeenne et l'homme fossile de la Republique
+Argentine". "Rivista del Museo de la Plata", T. XIV. pages 193-488.) has
+made a thorough study.
+
+It is obvious that, notwithstanding the necessity for fitting man's line
+of descent into the genealogical tree of the Primates, especially the
+apes, opinions in regard to it differ greatly in detail. This could not
+be otherwise, since the different Primate forms, especially the fossil
+forms, are still far from being exhaustively known. But one thing
+remains certain,--the idea of the close relationship between man and
+monkeys set forth in Darwin's "Descent of Man". Only those who deny the
+many points of agreement, the sole basis of classification, and thus of
+a natural genealogical tree, can look upon the position of Darwin and
+Haeckel as antiquated, or as standing on an insufficient foundation.
+For such a genealogical tree is nothing more than a summarised
+representation of what is known in regard to the degree of resemblance
+between the different forms.
+
+Darwin's work in regard to the descent of man has not been surpassed;
+the more we immerse ourselves in the study of the structural
+relationships between apes and man, the more is our path illumined by
+the clear light radiating from him, and through his calm and deliberate
+investigation, based on a mass of material in the accumulation of which
+he has never had an equal. Darwin's fame will be bound up for all time
+with the unprejudiced investigation of the question of all questions,
+the descent of the human race.
+
+
+
+
+VIII. CHARLES DARWIN AS AN ANTHROPOLOGIST. By Ernst Haeckel.
+
+Professor of Zoology in the University of Jena.
+
+The great advance that anthropology has made in the second half of the
+nineteenth century is due in the first place, to Darwin's discovery of
+the origin of man. No other problem in the whole field of research is so
+momentous as that of "Man's place in nature," which was justly described
+by Huxley (1863) as the most fundamental of all questions. Yet the
+scientific solution of this problem was impossible until the theory of
+descent had been established.
+
+It is now a hundred years since the great French biologist Jean Lamarck
+published his "Philosophie Zoologique". By a remarkable coincidence the
+year in which that work was issued, 1809, was the year of the birth of
+his most distinguished successor, Charles Darwin. Lamarck had
+already recognised that the descent of man from a series of other
+Vertebrates--that is, from a series of Ape-like Primates--was
+essentially involved in the general theory of transformation which
+he had erected on a broad inductive basis; and he had sufficient
+penetration to detect the agencies that had been at work in the
+evolution of the erect bimanous man from the arboreal and quadrumanous
+ape. He had, however, few empirical arguments to advance in support
+of his hypothesis, and it could not be established until the further
+development of the biological sciences--the founding of comparative
+embryology by Baer (1828) and of the cell-theory by Schleiden and
+Schwann (1838), the advance of physiology under Johannes Muller (1833),
+and the enormous progress of palaeontology and comparative anatomy
+between 1820 and 1860--provided this necessary foundation. Darwin was
+the first to coordinate the ample results of these lines of research.
+With no less comprehensiveness than discrimination he consolidated them
+as a basis of a modified theory of descent, and associated with them
+his own theory of natural selection, which we take to be distinctive
+of "Darwinism" in the stricter sense. The illuminating truth of these
+cumulative arguments was so great in every branch of biology that,
+in spite of the most vehement opposition, the battle was won within a
+single decade, and Darwin secured the general admiration and recognition
+that had been denied to his forerunner, Lamarck, up to the hour of his
+death (1829).
+
+Before, however, we consider the momentous influence that Darwinism has
+had in anthropology, we shall find it useful to glance at its history
+in the course of the last half century, and notice the various theories
+that have contributed to its advance. The first attempt to give
+extensive expression to the reform of biology by Darwin's work will be
+found in my "Generelle Morphologie" (1866) ("Generelle Morphologie
+der Organismen", 2 vols., Berlin, 1866.) which was followed by a more
+popular treatment of the subject in my "Naturliche Schopfungsgeschichte"
+(1868) (English translation; "The History of Creation", London,
+1876.), a compilation from the earlier work. In the first volume of the
+"Generelle Morphologie" I endeavoured to show the great importance
+of evolution in settling the fundamental questions of biological
+philosophy, especially in regard to comparative anatomy. In the second
+volume I dealt broadly with the principle of evolution, distinguishing
+ontogeny and phylogeny as its two coordinate main branches, and
+associating the two in the Biogenetic Law. The Law may be formulated
+thus: "Ontogeny (embryology or the development of the individual) is a
+concise and compressed recapitulation of phylogeny (the palaeontological
+or genealogical series) conditioned by laws of heredity and adaptation."
+The "Systematic introduction to general evolution," with which the
+second volume of the "Generelle Morphologie" opens, was the first
+attempt to draw up a natural system of organisms (in harmony with
+the principles of Lamarck and Darwin) in the form of a hypothetical
+pedigree, and was provisionally set forth in eight genealogical tables.
+
+In the nineteenth chapter of the "Generelle Morphologie"--a part of
+which has been republished, without any alteration, after a lapse of
+forty years--I made a critical study of Lamarck's theory of descent and
+of Darwin's theory of selection, and endeavoured to bring the complex
+phenomena of heredity and adaptation under definite laws for the first
+time. Heredity I divided into conservative and progressive: adaptation
+into indirect (or potential) and direct (or actual). I then found
+it possible to give some explanation of the correlation of the two
+physiological functions in the struggle for life (selection), and to
+indicate the important laws of divergence (or differentiation) and
+complexity (or division of labour), which are the direct and inevitable
+outcome of selection. Finally, I marked off dysteleology as the science
+of the aimless (vestigial, abortive, atrophied, and useless) organs
+and parts of the body. In all this I worked from a strictly monistic
+standpoint, and sought to explain all biological phenomena on the
+mechanical and naturalistic lines that had long been recognised in the
+study of inorganic nature. Then (1866), as now, being convinced of the
+unity of nature, the fundamental identity of the agencies at work in the
+inorganic and the organic worlds, I discarded vitalism, teleology, and
+all hypotheses of a mystic character.
+
+It was clear from the first that it was essential, in the monistic
+conception of evolution, to distinguish between the laws of conservative
+and progressive heredity. Conservative heredity maintains from
+generation to generation the enduring characters of the species. Each
+organism transmits to its descendants a part of the morphological
+and physiological qualities that it has received from its parents and
+ancestors. On the other hand, progressive heredity brings new characters
+to the species--characters that were not found in preceding generations.
+Each organism may transmit to its offspring a part of the morphological
+and physiological features that it has itself acquired, by adaptation,
+in the course of its individual career, through the use or disuse of
+particular organs, the influence of environment, climate, nutrition,
+etc. At that time I gave the name of "progressive heredity" to
+this inheritance of acquired characters, as a short and convenient
+expression, but have since changed the term to "transformative heredity"
+(as distinguished from conservative). This term is preferable,
+as inherited regressive modifications (degeneration, retrograde
+metamorphisis, etc.) come under the same head.
+
+Transformative heredity--or the transmission of acquired characters--is
+one of the most important principles in evolutionary science. Unless
+we admit it most of the facts of comparative anatomy and physiology are
+inexplicable. That was the conviction of Darwin no less than of Lamarck,
+of Spencer as well as Virchow, of Huxley as well as Gegenbaur, indeed of
+the great majority of speculative biologists. This fundamental principle
+was for the first time called in question and assailed in 1885 by
+August Weismann of Freiburg, the eminent zoologist to whom the theory
+of evolution owes a great deal of valuable support, and who has attained
+distinction by his extension of the theory of selection. In explanation
+of the phenomena of heredity he introduced a new theory, the "theory of
+the continuity of the germ-plasm." According to him the living substance
+in all organisms consists of two quite distinct kinds of plasm, somatic
+and germinal. The permanent germ-plasm, or the active substance of the
+two germ-cells (egg-cell and sperm-cell), passes unchanged through a
+series of generations, and is not affected by environmental influences.
+The environment modifies only the soma-plasm, the organs and tissues
+of the body. The modifications that these parts undergo through the
+influence of the environment or their own activity (use and habit), do
+not affect the germ-plasm, and cannot therefore be transmitted.
+
+This theory of the continuity of the germ-plasm has been expounded by
+Weismann during the last twenty-four years in a number of able volumes,
+and is regarded by many biologists, such as Mr Francis Galton, Sir E.
+Ray Lankester, and Professor J. Arthur Thomson (who has recently made
+a thoroughgoing defence of it in his important work "Heredity" (London,
+1908.)), as the most striking advance in evolutionary science. On the
+other hand, the theory has been rejected by Herbert Spencer, Sir W.
+Turner, Gegenbaur, Kolliker, Hertwig, and many others. For my part I
+have, with all respect for the distinguished Darwinian, contested
+the theory from the first, because its whole foundation seems to me
+erroneous, and its deductions do not seem to be in accord with the main
+facts of comparative morphology and physiology. Weismann's theory in its
+entirety is a finely conceived molecular hypothesis, but it is devoid of
+empirical basis. The notion of the absolute and permanent independence
+of the germ-plasm, as distinguished from the soma-plasm, is purely
+speculative; as is also the theory of germinal selection. The
+determinants, ids, and idants, are purely hypothetical elements. The
+experiments that have been devised to demonstrate their existence really
+prove nothing.
+
+It seems to me quite improper to describe this hypothetical structure
+as "Neodarwinism." Darwin was just as convinced as Lamarck of the
+transmission of acquired characters and its great importance in the
+scheme of evolution. I had the good fortune to visit Darwin at Down
+three times and discuss with him the main principles of his system, and
+on each occasion we were fully agreed as to the incalculable importance
+of what I call transformative inheritance. It is only proper to point
+out that Weismann's theory of the germ-plasm is in express contradiction
+to the fundamental principles of Darwin and Lamarck. Nor is it more
+acceptable in what one may call its "ultradarwinism"--the idea that the
+theory of selection explains everything in the evolution of the organic
+world. This belief in the "omnipotence of natural selection" was not
+shared by Darwin himself. Assuredly, I regard it as of the utmost
+value, as the process of natural selection through the struggle for
+life affords an explanation of the mechanical origin of the adapted
+organisation. It solves the great problem: how could the finely adapted
+structure of the animal or plant body be formed unless it was built on a
+preconceived plan? It thus enables us to dispense with the teleology of
+the metaphysician and the dualist, and to set aside the old mythological
+and poetic legends of creation. The idea had occurred in vague form to
+the great Empedocles 2000 years before the time of Darwin, but it was
+reserved for modern research to give it ample expression. Nevertheless,
+natural selection does not of itself give the solution of all our
+evolutionary problems. It has to be taken in conjunction with the
+transformism of Lamarck, with which it is in complete harmony.
+
+The monumental greatness of Charles Darwin, who surpasses every other
+student of science in the nineteenth century by the loftiness of his
+monistic conception of nature and the progressive influence of his
+ideas, is perhaps best seen in the fact that not one of his many
+successors has succeeded in modifying his theory of descent in any
+essential point or in discovering an entirely new standpoint in the
+interpretation of the organic world. Neither Nageli nor Weismann,
+neither De Vries nor Roux, has done this. Nageli, in his
+"Mechanisch-Physiologische Theorie der Abstammungslehre" (Munich,
+1884.), which is to a great extent in agreement with Weismann,
+constructed a theory of the idioplasm, that represents it (like the
+germ-plasm) as developing continuously in a definite direction from
+internal causes. But his internal "principle of progress" is at the
+bottom just as teleological as the vital force of the Vitalists, and
+the micellar structure of the idioplasm is just as hypothetical as the
+"dominant" structure of the germ-plasm. In 1889 Moritz Wagner sought to
+explain the origin of species by migration and isolation, and on that
+basis constructed a special "migration-theory." This, however, is not
+out of harmony with the theory of selection. It merely elevates one
+single factor in the theory to a predominant position. Isolation is
+only a special case of selection, as I had pointed out in the fifteenth
+chapter of my "Natural history of creation". The "mutation-theory" of De
+Vries ("Die Mutationstheorie", Leipzig, 1903.), that would explain the
+origin of species by sudden and saltatory variations rather than by
+gradual modification, is regarded by many botanists as a great step
+in advance, but it is generally rejected by zoologists. It affords no
+explanation of the facts of adaptation, and has no causal value.
+
+Much more important than these theories is that of Wilhelm Roux ("Der
+Kampf der Theile im Organismus", Leipzig, 1881.) of "the struggle of
+parts within the organism, a supplementation of the theory of mechanical
+adaptation." He explains the functional autoformation of the purposive
+structure by a combination of Darwin's principle of selection with
+Lamarck's idea of transformative heredity, and applies the two
+in conjunction to the facts of histology. He lays stress on the
+significance of functional adaptation, which I had described in 1866,
+under the head of cumulative adaptation, as the most important factor in
+evolution. Pointing out its influence in the cell-life of the tissues,
+he puts "cellular selection" above "personal selection," and shows how
+the finest conceivable adaptations in the structure of the tissue may
+be brought about quite mechanically, without preconceived plan. This
+"mechanical teleology" is a valuable extension of Darwin's monistic
+principle of selection to the whole field of cellular physiology and
+histology, and is wholly destructive of dualistic vitalism.
+
+The most important advance that evolution has made since Darwin and
+the most valuable amplification of his theory of selection is, in my
+opinion, the work of Richard Semon: "Die Mneme als erhaltendes Prinzip
+im Wechsel des organischen Geschehens" (Leipzig, 1904.). He offers a
+psychological explanation of the facts of heredity by reducing them to a
+process of (unconscious) memory. The physiologist Ewald Hering had shown
+in 1870 that memory must be regarded as a general function of organic
+matter, and that we are quite unable to explain the chief vital
+phenomena, especially those of reproduction and inheritance, unless
+we admit this unconscious memory. In my essay "Die Perigenesis der
+Plastidule" (Berlin, 1876.) I elaborated this far-reaching idea, and
+applied the physical principle of transmitted motion to the plastidules,
+or active molecules of plasm. I concluded that "heredity is the memory
+of the plastidules, and variability their power of comprehension." This
+"provisional attempt to give a mechanical explanation of the elementary
+processes of evolution" I afterwards extended by showing that
+sensitiveness is (as Carl Nageli, Ernst Mach, and Albrecht Rau express
+it) a general quality of matter. This form of panpsychism finds its
+simplest expression in the "trinity of substance."
+
+To the two fundamental attributes that Spinoza ascribed to
+substance--Extension (matter as occupying space) and Cogitation
+(energy, force)--we now add the third fundamental quality of Psychoma
+(sensitiveness, soul). I further elaborated this trinitarian conception
+of substance in the nineteenth chapter of my "Die Lebenswunder" (1904)
+("Wonders of Life", London, 1904.), and it seems to me well calculated
+to afford a monistic solution of many of the antitheses of philosophy.
+
+This important Mneme-theory of Semon and the luminous physiological
+experiments and observations associated with it not only throw
+considerable light on transformative inheritance, but provide a sound
+physiological foundation for the biogenetic law. I had endeavoured
+to show in 1874, in the first chapter of my "Anthropogenie" (English
+translation; "The Evolution of Man", 2 volumes, London, 1879 and 1905.),
+that this fundamental law of organic evolution holds good generally, and
+that there is everywhere a direct causal connection between ontogeny
+and phylogeny. "Phylogenesis is the mechanical cause of ontogenesis"; in
+other words, "The evolution of the stem or race is--in accordance with
+the laws of heredity and adaptation--the real cause of all the changes
+that appear, in a condensed form, in the development of the individual
+organism from the ovum, in either the embryo or the larva."
+
+It is now fifty years since Charles Darwin pointed out, in the
+thirteenth chapter of his epoch-making "Origin of Species", the
+fundamental importance of embryology in connection with his theory of
+descent:
+
+"The leading facts in embryology, which are second to none in
+importance, are explained on the principle of variations in the many
+descendants from some one ancient progenitor, having appeared at a not
+very early period of life, and having been inherited at a corresponding
+period." ("Origin of Species" (6th edition), page 396.)
+
+He then shows that the striking resemblance of the embryos and larvae
+of closely related animals, which in the mature stage belong to widely
+different species and genera, can only be explained by their descent
+from a common progenitor. Fritz Muller made a closer study of these
+important phenomena in the instructive instance of the Crustacean larva,
+as given in his able work "Fur Darwin" (1864). (English translation;
+"Facts and Arguments for Darwin", London, 1869.) I then, in 1872,
+extended the range so as to include all animals (with the exception
+of the unicellular Protozoa) and showed, by means of the theory of
+the Gastraea, that all multicellular, tissue-forming animals--all
+the Metazoa--develop in essentially the same way from the primary
+germ-layers. I conceived the embryonic form, in which the whole
+structure consists of only two layers of cells, and is known as the
+gastrula, to be the ontogenetic recapitulation, maintained by tenacious
+heredity, of a primitive common progenitor of all the Metazoa, the
+Gastraea. At a later date (1895) Monticelli discovered that this
+conjectural ancestral form is still preserved in certain primitive
+Coelenterata--Pemmatodiscus, Kunstleria, and the nearly-related
+Orthonectida.
+
+The general application of the biogenetic law to all classes of animals
+and plants has been proved in my "Systematische Phylogenie". (3 volumes,
+Berlin, 1894-96.) It has, however, been frequently challenged, both
+by botanists and zoologists, chiefly owing to the fact that many have
+failed to distinguish its two essential elements, palingenesis and
+cenogenesis. As early as 1874 I had emphasised, in the first chapter
+of my "Evolution of Man", the importance of discriminating carefully
+between these two sets of phenomena:
+
+"In the evolutionary appreciation of the facts of embryology we must
+take particular care to distinguish sharply and clearly between
+the primary, palingenetic evolutionary processes and the secondary,
+cenogenetic processes. The palingenetic phenomena, or embryonic
+RECAPITULATIONS, are due to heredity, to the transmission of characters
+from one generation to another. They enable us to draw direct inferences
+in regard to corresponding structures in the development of the species
+(e.g. the chorda or the branchial arches in all vertebrate embryos). The
+cenogenetic phenomena, on the other hand, or the embryonic VARIATIONS,
+cannot be traced to inheritance from a mature ancestor, but are due to
+the adaptation of the embryo or the larva to certain conditions of
+its individual development (e.g. the amnion, the allantois, and the
+vitelline arteries in the embryos of the higher vertebrates). These
+cenogenetic phenomena are later additions; we must not infer from them
+that there were corresponding processes in the ancestral history, and
+hence they are apt to mislead."
+
+The fundamental importance of these facts of comparative anatomy,
+atavism, and the rudimentary organs, was pointed out by Darwin in the
+first part of his classic work, "The Descent of Man and Selection in
+Relation to Sex" (1871). ("Descent of Man" (Popular Edition), page 927.)
+In the "General summary and conclusion" (chapter XXI.) he was able
+to say, with perfect justice: "He who is not content to look, like a
+savage, at the phenomena of nature as disconnected, cannot any longer
+believe that man is the work of a separate act of creation. He will be
+forced to admit that the close resemblance of the embryo of man to that,
+for instance, of a dog--the construction of his skull, limbs, and whole
+frame on the same plan with that of other mammals, independently of
+the uses to which the parts may be put--the occasional reappearance of
+various structures, for instance of several muscles, which man does not
+normally possess, but which are common to the Quadrumana--and a crowd of
+analogous facts--all point in the plainest manner to the conclusion that
+man is the co-descendant with other mammals of a common progenitor."
+
+These few lines of Darwin's have a greater scientific value than
+hundreds of those so-called "anthropological treatises," which give
+detailed descriptions of single organs, or mathematical tables with
+series of numbers and what are claimed to be "exact analyses," but are
+devoid of synoptic conclusions and a philosophical spirit.
+
+Charles Darwin is not generally recognised as a great anthropologist,
+nor does the school of modern anthropologists regard him as a leading
+authority. In Germany, especially, the great majority of the members of
+the anthropological societies took up an attitude of hostility to him
+from the very beginning of the controversy in 1860. "The Descent of Man"
+was not merely rejected, but even the discussion of it was forbidden on
+the ground that it was "unscientific."
+
+The centre of this inveterate hostility for thirty years--especially
+after 1877--was Rudolph Virchow of Berlin, the leading investigator in
+pathological anatomy, who did so much for the reform of medicine by
+his establishment of cellular pathology in 1858. As a prominent
+representative of "exact" or "descriptive" anthropology, and lacking a
+broad equipment in comparative anatomy and ontogeny, he was unable to
+accept the theory of descent. In earlier years, and especially during
+his splendid period of activity at Wurzburg (1848-1856), he had been a
+consistent free-thinker, and had in a number of able articles (collected
+in his "Gesammelte Abhandlungen") ("Gesammelte Abhandlungen zur
+wissenschaftlichen Medizin", Berlin, 1856.) upheld the unity of human
+nature, the inseparability of body and spirit. In later years at Berlin,
+where he was more occupied with political work and sociology (especially
+after 1866), he abandoned the positive monistic position for one of
+agnosticism and scepticism, and made concessions to the dualistic dogma
+of a spiritual world apart from the material frame.
+
+In the course of a Scientific Congress at Munich in 1877 the conflict
+of these antithetic views of nature came into sharp relief. At this
+memorable Congress I had undertaken to deliver the first address
+(September 18th) on the subject of "Modern evolution in relation to the
+whole of science." I maintained that Darwin's theory not only solved
+the great problem of the origin of species, but that its implications,
+especially in regard to the nature of man, threw considerable light on
+the whole of science, and on anthropology in particular. The discovery
+of the real origin of man by evolution from a long series of mammal
+ancestors threw light on his place in nature in every aspect, as Huxley
+had already shown in his excellent lectures of 1863. Just as all the
+organs and tissues of the human body had originated from those of the
+nearest related mammals, certain ape-like forms, so we were bound to
+conclude that his mental qualities also had been derived from those of
+his extinct primate ancestor.
+
+This monistic view of the origin and nature of man, which is now
+admitted by nearly all who have the requisite acquaintance with
+biology, and approach the subject without prejudice, encountered a sharp
+opposition at that time. The opposition found its strongest expression
+in an address that Virchow delivered at Munich four days afterwards
+(September 22nd), on "The freedom of science in the modern State." He
+spoke of the theory of evolution as an unproved hypothesis, and declared
+that it ought not to be taught in the schools, because it was dangerous
+to the State. "We must not," he said, "teach that man has descended from
+the ape or any other animal." When Darwin, usually so lenient in his
+judgment, read the English translation of Virchow's speech, he expressed
+his disapproval in strong terms. But the great authority that Virchow
+had--an authority well founded in pathology and sociology--and his
+prestige as President of the German Anthropological Society, had the
+effect of preventing any member of the Society from raising serious
+opposition to him for thirty years. Numbers of journals and treatises
+repeated his dogmatic statement: "It is quite certain that man has
+descended neither from the ape nor from any other animal." In this he
+persisted till his death in 1902. Since that time the whole position of
+German anthropology has changed. The question is no longer whether
+man was created by a distinct supernatural act or evolved from other
+mammals, but to which line of the animal hierarchy we must look for the
+actual series of ancestors. The interested reader will find an account
+of this "battle of Munich" (1877) in my three Berlin lectures (April,
+1905) ("Der Kampf um die Entwickelungs-Gedanken". (English translation;
+"Last Words on Evolution", London, 1906.))
+
+The main points in our genealogical tree were clearly recognised by
+Darwin in the sixth chapter of the "Descent of Man". Lowly organised
+fishes, like the lancelet (Amphioxus), are descended from lower
+invertebrates resembling the larvae of an existing Tunicate
+(Appendicularia). From these primitive fishes were evolved higher fishes
+of the ganoid type and others of the type of Lepidosiren (Dipneusta). It
+is a very small step from these to the Amphibia:
+
+"In the class of mammals the steps are not difficult to conceive which
+led from the ancient Monotremata to the ancient Marsupials; and from
+these to the early progenitors of the placental mammals. We may thus
+ascend to the Lemuridae; and the interval is not very wide from these to
+the Simiadae. The Simiadae then branched off into two great stems,
+the New World and Old World monkeys; and from the latter, at a remote
+period, Man, the wonder and glory of the Universe, proceeded." ("Descent
+of Man" (Popular Edition), page 255.)
+
+In these few lines Darwin clearly indicated the way in which we were
+to conceive our ancestral series within the vertebrates. It is fully
+confirmed by all the arguments of comparative anatomy and embryology,
+of palaeontology and physiology; and all the research of the subsequent
+forty years has gone to establish it. The deep interest in geology which
+Darwin maintained throughout his life and his complete knowledge of
+palaeontology enabled him to grasp the fundamental importance of the
+palaeontological record more clearly than anthropologists and zoologists
+usually do.
+
+There has been much debate in subsequent decades whether Darwin himself
+maintained that man was descended from the ape, and many writers
+have sought to deny it. But the lines I have quoted verbatim from the
+conclusion of the sixth chapter of the "Descent of Man" (1871) leave no
+doubt that he was as firmly convinced of it as was his great
+precursor Jean Lamarck in 1809. Moreover, Darwin adds, with particular
+explicitness, in the "general summary and conclusion" (chapter XXI.) of
+that standard work ("Descent of Man", page 930.):
+
+"By considering the embryological structure of man--the homologies
+which he presents with the lower animals,--the rudiments which he
+retains,--and the reversions to which he is liable, we can partly recall
+in imagination the former condition of our early progenitors; and can
+approximately place them in their proper place in the zoological series.
+We thus learn that man is descended from a hairy, tailed quadruped,
+probably arboreal in its habits, and an inhabitant of the Old World.
+This creature, if its whole structure had been examined by a naturalist,
+would have been classed amongst the Quadrumana, as surely as the still
+more ancient progenitor of the Old and New World monkeys."
+
+These clear and definite lines leave no doubt that Darwin--so critical
+and cautious in regard to important conclusions--was quite as firmly
+convinced of the descent of man from the apes (the Catarrhinae, in
+particular) as Lamarck was in 1809 and Huxley in 1863.
+
+It is to be noted particularly that, in these and other observations
+on the subject, Darwin decidedly assumes the monophyletic origin of
+the mammals, including man. It is my own conviction that this is of the
+greatest importance. A number of difficult questions in regard to the
+development of man, in respect of anatomy, physiology, psychology,
+and embryology, are easily settled if we do not merely extend our
+progonotaxis to our nearest relatives, the anthropoid apes and the
+tailed monkeys from which these have descended, but go further back and
+find an ancestor in the group of the Lemuridae, and still further back
+to the Marsupials and Monotremata. The essential identity of all the
+Mammals in point of anatomical structure and embryonic development--in
+spite of their astonishing differences in external appearance and habits
+of life--is so palpably significant that modern zoologists are agreed
+in the hypothesis that they have all sprung from a common root, and that
+this root may be sought in the earlier Palaeozoic Amphibia.
+
+The fundamental importance of this comparative morphology of the
+Mammals, as a sound basis of scientific anthropology, was recognised
+just before the beginning of the nineteenth century, when Lamarck first
+emphasised (1794) the division of the animal kingdom into Vertebrates
+and Invertebrates. Even thirteen years earlier (1781), when Goethe made
+a close study of the mammal skeleton in the Anatomical Institute at
+Jena, he was intensely interested to find that the composition of the
+skull was the same in man as in the other mammals. His discovery of the
+os intermaxillare in man (1784), which was contradicted by most of
+the anatomists of the time, and his ingenious "vertebral theory of
+the skull," were the splendid fruit of his morphological studies. They
+remind us how Germany's greatest philosopher and poet was for many years
+ardently absorbed in the comparative anatomy of man and the mammals, and
+how he divined that their wonderful identity in structure was no mere
+superficial resemblance, but pointed to a deep internal connection.
+In my "Generelle Morphologie" (1866), in which I published the first
+attempts to construct phylogenetic trees, I have given a number of
+remarkable theses of Goethe, which may be called "phyletic prophecies."
+They justify us in regarding him as a precursor of Darwin.
+
+In the ensuing forty years I have made many conscientious efforts to
+penetrate further along that line of anthropological research that was
+opened up by Goethe, Lamarck, and Darwin. I have brought together the
+many valuable results that have constantly been reached in comparative
+anatomy, physiology, ontogeny, and palaeontology, and maintained
+the effort to reform the classification of animals and plants in an
+evolutionary sense. The first rough drafts of pedigrees that were
+published in the "Generelle Morphologie" have been improved time after
+time in the ten editions of my "Naturaliche Schopfungsgeschichte"
+(1868-1902). (English translation; "The History of Creation", London,
+1876.) A sounder basis for my phyletic hypotheses, derived from a
+discriminating combination of the three great records--morphology,
+ontogeny, and palaeontology--was provided in the three volumes of my
+"Systematische Phylogenie" (Berlin, 1894-96.) (1894 Protists and Plants,
+1895 Vertebrates, 1896 Invertebrates). In my "Anthropogenie" (Leipzig,
+1874, 5th edition 1905. English translation; "The Evolution of
+Man", London, 1905.) I endeavoured to employ all the known facts of
+comparative ontogeny (embryology) for the purpose of completing my
+scheme of human phylogeny (evolution). I attempted to sketch the
+historical development of each organ of the body, beginning with the
+most elementary structures in the germ-layers of the Gastraea. At the
+same time I drew up a corrected statement of the most important steps in
+the line of our ancestral series.
+
+At the fourth International Congress of Zoology at Cambridge (August
+26th, 1898) I delivered an address on "Our present knowledge of the
+Descent of Man." It was translated into English, enriched with many
+valuable notes and additions, by my friend and pupil in earlier days Dr
+Hans Gadow (Cambridge), and published under the title: "The Last Link;
+our present knowledge of the Descent of Man". (London, 1898.) The
+determination of the chief animal forms that occur in the line of our
+ancestry is there restricted to thirty types, and these are distributed
+in six main groups.
+
+The first half of this "Progonotaxis hominis," which has no support
+from fossil evidence, comprises three groups: (i) Protista (unicellular
+organisms, 1-5: (ii) Invertebrate Metazoa (Coelenteria 6-8, Vermalia
+9-11): (iii) Monorrhine Vertebrates (Acrania 12-13, Cyclostoma 14-15).
+The second half, which is based on fossil records, also comprises three
+groups: (iv) Palaeozoic cold-blooded Craniota (Fishes 16-18, Amphibia
+19, Reptiles 20: (v) Mesozoic Mammals (Monotrema 21, Marsupialia 22,
+Mallotheria 23): (vi) Cenozoic Primates (Lemuridae 24-25, Tailed Apes
+26-27, Anthropomorpha 28-30). An improved and enlarged edition of this
+hypothetic "Progonotaxis hominis" was published in 1908, in my essay
+"Unsere Ahnenreihe". ("Festschrift zur 350-jahrigen Jubelfeier der
+Thuringer Universitat Jena". Jena, 1908.)
+
+If I have succeeded in furthering, in some degree, by these
+anthropological works, the solution of the great problem of Man's place
+in nature, and particularly in helping to trace the definite stages in
+our ancestral series, I owe the success, not merely to the vast progress
+that biology has made in the last half century, but largely to the
+luminous example of the great investigators who have applied themselves
+to the problem, with so much assiduity and genius, for a century and
+a quarter--I mean Goethe and Lamarck, Gegenbaur and Huxley, but, above
+all, Charles Darwin. It was the great genius of Darwin that first
+brought together the scattered material of biology and shaped it into
+that symmetrical temple of scientific knowledge, the theory of descent.
+It was Darwin who put the crown on the edifice by his theory of natural
+selection. Not until this broad inductive law was firmly established was
+it possible to vindicate the special conclusion, the descent of man from
+a series of other Vertebrates. By his illuminating discovery Darwin
+did more for anthropology than thousands of those writers, who are
+more specifically titled anthropologists, have done by their technical
+treatises. We may, indeed, say that it is not merely as an exact
+observer and ingenious experimenter, but as a distinguished
+anthropologist and far-seeing thinker, that Darwin takes his place among
+the greatest men of science of the nineteenth century.
+
+To appreciate fully the immortal merit of Darwin in connection with
+anthropology, we must remember that not only did his chief work, "The
+Origin of Species", which opened up a new era in natural history in
+1859, sustain the most virulent and widespread opposition for a lengthy
+period, but even thirty years later, when its principles were generally
+recognised and adopted, the application of them to man was energetically
+contested by many high scientific authorities. Even Alfred Russel
+Wallace, who discovered the principle of natural selection independently
+in 1858, did not concede that it was applicable to the higher mental
+and moral qualities of man. Dr Wallace still holds a spiritualist and
+dualist view of the nature of man, contending that he is composed of a
+material frame (descended from the apes) and an immortal immaterial soul
+(infused by a higher power). This dual conception, moreover, is still
+predominant in the wide circles of modern theology and metaphysics,
+and has the general and influential adherence of the more conservative
+classes of society.
+
+In strict contradiction to this mystical dualism, which is generally
+connected with teleology and vitalism, Darwin always maintained the
+complete unity of human nature, and showed convincingly that the
+psychological side of man was developed, in the same way as the body,
+from the less advanced soul of the anthropoid ape, and, at a still more
+remote period, from the cerebral functions of the older vertebrates. The
+eighth chapter of the "Origin of Species", which is devoted to instinct,
+contains weighty evidence that the instincts of animals are subject,
+like all other vital processes, to the general laws of historic
+development. The special instincts of particular species were formed
+by adaptation, and the modifications thus acquired were handed on to
+posterity by heredity; in their formation and preservation natural
+selection plays the same part as in the transformation of every other
+physiological function. The higher moral qualities of civilised man
+have been derived from the lower mental functions of the uncultivated
+barbarians and savages, and these in turn from the social instincts
+of the mammals. This natural and monistic psychology of Darwin's was
+afterwards more fully developed by his friend George Romanes in his
+excellent works "Mental Evolution in Animals" and "Mental Evolution in
+Man". (London, 1885; 1888.)
+
+Many valuable and most interesting contributions to this monistic
+psychology of man were made by Darwin in his fine work on "The Descent
+of Man and Selection in Relation to Sex", and again in his supplementary
+work, "The Expression of the Emotions in Man and Animals". To understand
+the historical development of Darwin's anthropology one must read his
+life and the introduction to "The Descent of Man". From the moment that
+he was convinced of the truth of the principle of descent--that is to
+say, from his thirtieth year, in 1838--he recognised clearly that
+man could not be excluded from its range. He recognised as a logical
+necessity the important conclusion that "man is the co-descendant with
+other species of some ancient, lower, and extinct form." For many years
+he gathered notes and arguments in support of this thesis, and for the
+purpose of showing the probable line of man's ancestry. But in the first
+edition of "The Origin of Species" (1859) he restricted himself to the
+single line, that by this work "light would be thrown on the origin of
+man and his history." In the fifty years that have elapsed since that
+time the science of the origin and nature of man has made astonishing
+progress, and we are now fairly agreed in a monistic conception of
+nature that regards the whole universe, including man, as a wonderful
+unity, governed by unalterable and eternal laws. In my philosophical
+book "Die Weltratsel" (1899) ("The Riddle of the Universe", London,
+1900.) and in the supplementary volume "Die Lebenswunder" (1904) "The
+Wonders of Life", London, (1904.), I have endeavoured to show that this
+pure monism is securely established, and that the admission of the
+all-powerful rule of the same principle of evolution throughout the
+universe compels us to formulate a single supreme law--the all-embracing
+"Law of Substance," or the united laws of the constancy of matter and
+the conservation of energy. We should never have reached this supreme
+general conception if Charles Darwin--a "monistic philosopher" in
+the true sense of the word--had not prepared the way by his theory of
+descent by natural selection, and crowned the great work of his life by
+the association of this theory with a naturalistic anthropology.
+
+
+IX. SOME PRIMITIVE THEORIES OF THE ORIGIN OF MAN.
+
+By J.G. FRAZER. Fellow of Trinity College, Cambridge.
+
+On a bright day in late autumn a good many years ago I had ascended the
+hill of Panopeus in Phocis to examine the ancient Greek fortifications
+which crest its brow. It was the first of November, but the weather was
+very hot; and when my work among the ruins was done, I was glad to
+rest under the shade of a clump of fine holly-oaks, to inhale the sweet
+refreshing perfume of the wild thyme which scented all the air, and
+to enjoy the distant prospects, rich in natural beauty, rich too in
+memories of the legendary and historic past. To the south the finely-cut
+peak of Helicon peered over the low intervening hills. In the west
+loomed the mighty mass of Parnassus, its middle slopes darkened by
+pine-woods like shadows of clouds brooding on the mountain-side; while
+at its skirts nestled the ivy-mantled walls of Daulis overhanging the
+deep glen, whose romantic beauty accords so well with the loves and
+sorrows of Procne and Philomela, which Greek tradition associated
+with the spot. Northwards, across the broad plain to which the hill
+of Panopeus descends, steep and bare, the eye rested on the gap in the
+hills through which the Cephissus winds his tortuous way to flow under
+grey willows, at the foot of barren stony hills, till his turbid waters
+lose themselves, no longer in the vast reedy swamps of the now vanished
+Copaic Lake, but in the darkness of a cavern in the limestone rock.
+Eastward, clinging to the slopes of the bleak range of which the hill
+of Panopeus forms part, were the ruins of Chaeronea, the birthplace of
+Plutarch; and out there in the plain was fought the disastrous battle
+which laid Greece at the feet of Macedonia. There, too, in a later age
+East and West met in deadly conflict, when the Roman armies under Sulla
+defeated the Asiatic hosts of Mithridates. Such was the landscape spread
+out before me on one of those farewell autumn days of almost pathetic
+splendour, when the departing summer seems to linger fondly, as if loth
+to resign to winter the enchanted mountains of Greece. Next day the
+scene had changed: summer was gone. A grey November mist hung low on the
+hills which only yesterday had shone resplendent in the sun, and under
+its melancholy curtain the dead flat of the Chaeronean plain, a wide
+treeless expanse shut in by desolate slopes, wore an aspect of chilly
+sadness befitting the battlefield where a nation's freedom was lost.
+
+But crowded as the prospect from Panopeus is with memories of the past,
+the place itself, now so still and deserted, was once the scene of an
+event even more ancient and memorable, if Greek story-tellers can be
+trusted. For here, they say, the sage Prometheus created our first
+parents by fashioning them, like a potter, out of clay. (Pausanias X.
+4.4. Compare Apollodorus, "Bibliotheca", I. 7. 1; Ovid, "Metamorph."
+I. 82 sq.; Juvenal, "Sat". XIV. 35. According to another version of
+the tale, this creation of mankind took place not at Panopeus, but
+at Iconium in Lycaonia. After the original race of mankind had been
+destroyed in the great flood of Deucalion, the Greek Noah, Zeus
+commanded Prometheus and Athena to create men afresh by moulding images
+out of clay, breathing the winds into them, and making them live. See
+"Etymologicum Magnum", s.v. "'Ikonion", pages 470 sq. It is said that
+Prometheus fashioned the animals as well as men, giving to each kind of
+beast its proper nature. See Philemon, quoted by Stobaeus, "Florilegium"
+II. 27. The creation of man by Prometheus is figured on ancient works of
+art. See J. Toutain, "Etudes de Mythologie et d'Histoire des Religions
+Antiques" (Paris, 1909), page 190. According to Hesiod ("Works and
+Days", 60 sqq.) it was Hephaestus who at the bidding of Zeus moulded the
+first woman out of moist earth.) The very spot where he did so can still
+be seen. It is a forlorn little glen or rather hollow behind the hill
+of Panopeus, below the ruined but still stately walls and towers which
+crown the grey rocks of the summit. The glen, when I visited it that hot
+day after the long drought of summer, was quite dry; no water trickled
+down its bushy sides, but in the bottom I found a reddish crumbling
+earth, a relic perhaps of the clay out of which the potter Prometheus
+moulded the Greek Adam and Eve. In a volume dedicated to the honour of
+one who has done more than any other in modern times to shape the ideas
+of mankind as to their origin it may not be out of place to recall this
+crude Greek notion of the creation of the human race, and to compare or
+contrast it with other rudimentary speculations of primitive peoples
+on the same subject, if only for the sake of marking the interval which
+divides the childhood from the maturity of science.
+
+The simple notion that the first man and woman were modelled out of clay
+by a god or other superhuman being is found in the traditions of many
+peoples. This is the Hebrew belief recorded in Genesis: "The Lord God
+formed man of the dust of the ground, and breathed into his nostrils the
+breath of life; and man became a living soul." (Genesis ii.7.) To the
+Hebrews this derivation of our species suggested itself all the more
+naturally because in their language the word for "ground" (adamah) is
+in form the feminine of the word for man (adam). (S.R. Driver and
+W.H.Bennett, in their commentaries on Genesis ii. 7.) From various
+allusions in Babylonian literature it would seem that the Babylonians
+also conceived man to have been moulded out of clay. (H. Zimmern, in E.
+Schrader's "Die Keilinschriften und das Alte Testament" 3 (Berlin, 1902),
+page 506.) According to Berosus, the Babylonian priest whose account of
+creation has been preserved in a Greek version, the god Bel cut off his
+own head, and the other gods caught the flowing blood, mixed it with
+earth, and fashioned men out of the bloody paste; and that, they said,
+is why men are so wise, because their mortal clay is tempered with
+divine blood. (Eusebius, "Chronicon", ed. A. Schoene, Vol. I. (Berlin,
+1875), col. 16.) In Egyptian mythology Khnoumou, the Father of the gods,
+is said to have moulded men out of clay. (G. Maspero, "Histoire Ancienne
+des Peuples de l'Orient Classique", I. (Paris, 1895), page 128.) We
+cannot doubt that such crude conceptions of the origin of our race were
+handed down to the civilised peoples of antiquity by their savage or
+barbarous forefathers. Certainly stories of the same sort are known to
+be current among savages and barbarians.
+
+Thus the Australian blacks in the neighbourhood of Melbourne said that
+Pund-jel, the creator, cut three large sheets of bark with his big
+knife. On one of these he placed some clay and worked it up with his
+knife into a proper consistence. He then laid a portion of the clay on
+one of the other pieces of bark and shaped it into a human form; first
+he made the feet, then the legs, then the trunk, the arms, and the head.
+Thus he made a clay man on each of the two pieces of bark; and being
+well pleased with them he danced round them for joy. Next he took
+stringy bark from the Eucalyptus tree, made hair of it, and stuck it
+on the heads of his clay men. Then he looked at them again, was pleased
+with his work, and again danced round them for joy. He then lay down
+on them, blew his breath hard into their mouths, their noses, and their
+navels; and presently they stirred, spoke, and rose up as full-grown
+men. (R. Brough Smyth, "The Aborigines of Victoria" (Melbourne, 1878),
+I. 424. This and many of the following legends of creation have been
+already cited by me in a note on Pausanias X. 4. 4 ("Pausanias's
+Description of Greece, translated with a Commentary" (London, 1898),
+Vol V. pages 220 sq.).) The Maoris of New Zealand say that Tiki made man
+after his own image. He took red clay, kneaded it, like the Babylonian
+Bel, with his own blood, fashioned it in human form, and gave the image
+breath. As he had made man in his own likeness he called him Tiki-ahua
+or Tiki's likeness. (R. Taylor "Te Ika A Maui, or New Zealand and
+its Inhabitants", Second Edition (London, 1870), page 117. Compare E.
+Shortland, "Maori Religion and Mythology" (London, 1882), pages 21 sq.)
+A very generally received tradition in Tahiti was that the first human
+pair was made by Taaroa, the chief god. They say that after he had
+formed the world he created man out of red earth, which was also the
+food of mankind until bread-fruit was produced. Further, some say that
+one day Taaroa called for the man by name, and when he came he made him
+fall asleep. As he slept, the creator took out one of his bones (ivi)
+and made a woman of it, whom he gave to the man to be his wife, and the
+pair became the progenitors of mankind. This narrative was taken down
+from the lips of the natives in the early years of the mission to
+Tahiti. The missionary who records it observes: "This always appeared
+to me a mere recital of the Mosaic account of creation, which they
+had heard from some European, and I never placed any reliance on it,
+although they have repeatedly told me it was a tradition among them
+before any foreigner arrived. Some have also stated that the woman's
+name was Ivi, which would be by them pronounced as if written "Eve".
+"Ivi" is an aboriginal word, and not only signifies a bone, but also a
+widow, and a victim slain in war. Notwithstanding the assertion of
+the natives, I am disposed to think that "Ivi", or Eve, is the only
+aboriginal part of the story, as far as it respects the mother of the
+human race. (W. Ellis, "Polynesian Researches", Second Edition (London,
+1832), I. 110 sq. "Ivi" or "iwi" is the regular word for "bone" in the
+various Polynesian languages. See E. Tregear, "The Maori-Polynesian
+Comparative Dictionary" (Wellington, New Zealand, 1891), page 109.)
+However, the same tradition has been recorded in other parts of
+Polynesia besides Tahiti. Thus the natives of Fakaofo or Bowditch Island
+say that the first man was produced out of a stone. After a time he
+bethought him of making a woman. So he gathered earth and moulded the
+figure of a woman out of it, and having done so he took a rib out of his
+left side and thrust it into the earthen figure, which thereupon started
+up a live woman. He called her Ivi (Eevee) or "rib" and took her to
+wife, and the whole human race sprang from this pair. (G. Turner,
+"Samoa" (London, 1884), pages 267 sq.) The Maoris also are reported to
+believe that the first woman was made out of the first man's ribs. (J.L.
+Nicholas, "Narrative of a Voyage to New Zealand" (London, 1817), I.
+59, who writes "and to add still more to this strange coincidence, the
+general term for bone is 'Hevee'.") This wide diffusion of the story
+in Polynesia raises a doubt whether it is merely, as Ellis thought, a
+repetition of the Biblical narrative learned from Europeans. In Nui, or
+Netherland Island, it was the god Aulialia who made earthen models of
+a man and woman, raised them up, and made them live. He called the man
+Tepapa and the woman Tetata. (G. Turner, "Samoa", pages 300 sq.)
+
+In the Pelew Islands they say that a brother and sister made men out of
+clay kneaded with the blood of various animals, and that the characters
+of these first men and of their descendants were determined by the
+characters of the animals whose blood had been kneaded with the
+primordial clay; for instance, men who have rat's blood in them are
+thieves, men who have serpent's blood in them are sneaks, and men who
+have cock's blood in them are brave. (J. Kubary, "Die Religion der
+Pelauer", in A. Bastian's "Allerlei aus Volks- und Menschenkunde"
+(Berlin, 1888), I. 3, 56.) According to a Melanesian legend, told in
+Mota, one of the Banks Islands, the hero Qat moulded men of clay, the
+red clay from the marshy river-side at Vanua Lava. At first he made men
+and pigs just alike, but his brothers remonstrated with him, so he
+beat down the pigs to go on all fours and made men walk upright. Qat
+fashioned the first woman out of supple twigs, and when she smiled
+he knew she was a living woman. (R.H. Codrington, "The Melanesians"
+(Oxford, 1891), page 158.) A somewhat different version of the
+Melanesian story is told at Lakona, in Santa Maria. There they say that
+Qat and another spirit ("vui") called Marawa both made men. Qat made
+them out of the wood of dracaena-trees. Six days he worked at them,
+carving their limbs and fitting them together. Then he allowed them six
+days to come to life. Three days he hid them away, and three days more
+he worked to make them live. He set them up and danced to them and beat
+his drum, and little by little they stirred, till at last they could
+stand all by themselves. Then Qat divided them into pairs and called
+each pair husband and wife. Marawa also made men out of a tree, but it
+was a different tree, the tavisoviso. He likewise worked at them six
+days, beat his drum, and made them live, just as Qat did. But when he
+saw them move, he dug a pit and buried them in it for six days, and
+then, when he scraped away the earth to see what they were doing, he
+found them all rotten and stinking. That was the origin of death. (R.H.
+Codrington op. cit., pages 157 sq.)
+
+The inhabitants of Noo-Hoo-roa, in the Kei Islands say that their
+ancestors were fashioned out of clay by the supreme god, Dooadlera,
+who breathed life into the clay figures. (C.M. Pleyte, "Ethnographische
+Beschrijving der Kei-Eilanden", "Tijdschrift van het Nederlandsch
+Aardrijkskundig Genootschap", Tweede Serie X. (1893), page 564.) The
+aborigines of Minahassa, in the north of Celebes, say that two beings
+called Wailan Wangko and Wangi were alone on an island, on which grew
+a cocoa-nut tree. Said Wailan Wangko to Wangi, "Remain on earth while
+I climb up the tree." Said Wangi to Wailan Wangko, "Good." But then
+a thought occurred to Wangi and he climbed up the tree to ask Wailan
+Wangko why he, Wangi, should remain down there all alone. Said Wailan
+Wangko to Wangi, "Return and take earth and make two images, a man and a
+woman." Wangi did so, and both images were men who could move but could
+not speak. So Wangi climbed up the tree to ask Wailan Wangko, "How now?
+The two images are made, but they cannot speak." Said Wailan Wangko to
+Wangi, "Take this ginger and go and blow it on the skulls and the ears
+of these two images, that they may be able to speak; call the man Adam
+and the woman Ewa." (N. Graafland "De Minahassa" (Rotterdam, 1869), I.
+pages 96 sq.) In this narrative the names of the man and woman betray
+European influence, but the rest of the story may be aboriginal. The
+Dyaks of Sakarran in British Borneo say that the first man was made by
+two large birds. At first they tried to make men out of trees, but
+in vain. Then they hewed them out of rocks, but the figures could not
+speak. Then they moulded a man out of damp earth and infused into his
+veins the red gum of the kumpang-tree. After that they called to him and
+he answered; they cut him and blood flowed from his wounds. (Horsburgh,
+quoted by H. Ling Roth, "The Natives of Sarawak and of British North
+Borneo" (London, 1896), I. pages 299 sq. Compare The Lord Bishop
+of Labuan, "On the Wild Tribes of the North-West Coast of Borneo,"
+"Transactions of the Ethnological Society of London", New Series, II.
+(1863), page 27.)
+
+The Kumis of South-Eastern India related to Captain Lewin, the Deputy
+Commissioner of Hill Tracts, the following tradition of the creation of
+man. "God made the world and the trees and the creeping things first,
+and after that he set to work to make one man and one woman, forming
+their bodies of clay; but each night, on the completion of his work,
+there came a great snake, which, while God was sleeping, devoured the
+two images. This happened twice or thrice, and God was at his wit's end,
+for he had to work all day, and could not finish the pair in less than
+twelve hours; besides, if he did not sleep, he would be no good," said
+Captain Lewin's informant. "If he were not obliged to sleep, there would
+be no death, nor would mankind be afflicted with illness. It is when
+he rests that the snake carries us off to this day. Well, he was at his
+wit's end, so at last he got up early one morning and first made a dog
+and put life into it, and that night, when he had finished the images,
+he set the dog to watch them, and when the snake came, the dog barked
+and frightened it away. This is the reason at this day that when a
+man is dying the dogs begin to howl; but I suppose God sleeps heavily
+now-a-days, or the snake is bolder, for men die all the same." (Capt.
+T.H. Lewin, "Wild Races of South-Eastern India" (London, 1870),
+pages 224-26.) The Khasis of Assam tell a similar tale. (A. Bastian,
+"Volkerstamme am Brahmaputra und verwandtschaftliche Nachbarn" (Berlin,
+1883), page 8; Major P.R.T. Gurdon, "The Khasis" (London, 1907), page
+106.)
+
+The Ewe-speaking tribes of Togo-land, in West Africa, think that God
+still makes men out of clay. When a little of the water with which he
+moistens the clay remains over, he pours it on the ground and out of
+that he makes the bad and disobedient people. When he wishes to make a
+good man he makes him out of good clay; but when he wishes to make a
+bad man, he employs only bad clay for the purpose. In the beginning
+God fashioned a man and set him on the earth; after that he fashioned
+a woman. The two looked at each other and began to laugh, whereupon
+God sent them into the world. (J. Spieth, "Die Ewe-Stamme, Material zur
+Kunde des Ewe-Volkes in Deutsch-Togo" (Berlin, 1906), pages 828, 840.)
+The Innuit or Esquimaux of Point Barrow, in Alaska, tell of a time when
+there was no man in the land, till a spirit named "a se lu", who resided
+at Point Barrow, made a clay man, set him up on the shore to dry,
+breathed into him and gave him life. ("Report of the International
+Expedition to Point Barrow" (Washington, 1885), page 47.) Other
+Esquimaux of Alaska relate how the Raven made the first woman out of
+clay to be a companion to the first man; he fastened water-grass to the
+back of the head to be hair, flapped his wings over the clay figure,
+and it arose, a beautiful young woman. (E.W. Nelson, "The Eskimo about
+Bering Strait", "Eighteenth Annual Report of the Bureau of American
+Ethnology", Part I. (Washington, 1899), page 454.) The Acagchemem
+Indians of California said that a powerful being called Chinigchinich
+created man out of clay which he found on the banks of a lake; male and
+female created he them, and the Indians of the present day are their
+descendants. (Friar Geronimo Boscana, "Chinigchinich", appended to (A.
+Robinson's) "Life in California" (New York, 1846), page 247.) A priest
+of the Natchez Indians in Louisiana told Du Pratz "that God had kneaded
+some clay, such as that which potters use and had made it into a little
+man; and that after examining it, and finding it well formed, he blew up
+his work, and forthwith that little man had life, grew, acted, walked,
+and found himself a man perfectly well shaped." As to the mode in which
+the first woman was created, the priest had no information, but thought
+she was probably made in the same way as the first man; so Du Pratz
+corrected his imperfect notions by reference to Scripture. (M. Le Page
+Du Pratz, "The History of Louisiana" (London, 1774), page 330.) The
+Michoacans of Mexico said that the great god Tucapacha first made man
+and woman out of clay, but that when the couple went to bathe in a river
+they absorbed so much water that the clay of which they were composed
+all fell to pieces. Then the creator went to work again and moulded them
+afresh out of ashes, and after that he essayed a third time and made
+them of metal. This last attempt succeeded. The metal man and woman
+bathed in the river without falling to pieces, and by their union they
+became the progenitors of mankind. (A. de Herrera, "General History of
+the vast Continent and Islands of America", translated into English by
+Capt. J. Stevens (London, 1725, 1726), III. 254; Brasseur de Bourbourg,
+"Histoire des Nations Civilisees du Mexique et de l'Amerique-Centrale"
+(Paris, 1857--1859), III. 80 sq; compare id. I. 54 sq.)
+
+According to a legend of the Peruvian Indians, which was told to a
+Spanish priest in Cuzco about half a century after the conquest, it was
+in Tiahuanaco that man was first created, or at least was created afresh
+after the deluge. "There (in Tiahuanaco)," so runs the legend, "the
+Creator began to raise up the people and nations that are in that
+region, making one of each nation of clay, and painting the dresses that
+each one was to wear; those that were to wear their hair, with hair, and
+those that were to be shorn, with hair cut. And to each nation was given
+the language, that was to be spoken, and the songs to be sung, and the
+seeds and food that they were to sow. When the Creator had finished
+painting and making the said nations and figures of clay, he gave life
+and soul to each one, as well men as women, and ordered that they should
+pass under the earth. Thence each nation came up in the places to which
+he ordered them to go." (E.J. Payne, "History of the New World called
+America", I. (Oxford, 1892), page 462.)
+
+These examples suffice to prove that the theory of the creation of man
+out of dust or clay has been current among savages in many parts of
+the world. But it is by no means the only explanation which the savage
+philosopher has given of the beginnings of human life on earth. Struck
+by the resemblances which may be traced between himself and the beasts,
+he has often supposed, like Darwin himself, that mankind has been
+developed out of lower forms of animal life. For the simple savage has
+none of that high notion of the transcendant dignity of man which makes
+so many superior persons shrink with horror from the suggestion that
+they are distant cousins of the brutes. He on the contrary is not too
+proud to own his humble relations; indeed his difficulty often is
+to perceive the distinction between him and them. Questioned by a
+missionary, a Bushman of more than average intelligence "could not state
+any difference between a man and a brute--he did not know but a buffalo
+might shoot with bows and arrows as well as man, if it had them."
+(Reverend John Campbell, "Travels in South Africa" (London, 1822, II.
+page 34.) When the Russians first landed on one of the Alaskan islands,
+the natives took them for cuttle-fish "on account of the buttons on
+their clothes." (I. Petroff, "Report on the Population, Industries, and
+Resources of Alaska", page 145.) The Giliaks of the Amoor think that the
+outward form and size of an animal are only apparent; in substance every
+beast is a real man, just like a Giliak himself, only endowed with an
+intelligence and strength, which often surpass those of mere ordinary
+human beings. (L. Sternberg, "Die Religion der Giljaken", "Archiv fur
+Religionswissenschaft", VIII. (1905), page 248.) The Borororos, an
+Indian tribe of Brazil, will have it that they are parrots of a gorgeous
+red plumage which live in their native forests. Accordingly they treat
+the birds as their fellow-tribesmen, keeping them in captivity, refusing
+to eat their flesh, and mourning for them when they die. (K. von den
+Steinen, "Unter den Naturvolkern Zentral-Brasiliens" (Berlin, 1894),
+pages 352 sq., 512.))
+
+This sense of the close relationship of man to the lower creation is the
+essence of totemism, that curious system of superstition which unites
+by a mystic bond a group of human kinsfolk to a species of animals or
+plants. Where that system exists in full force, the members of a totem
+clan identify themselves with their totem animals in a way and to an
+extent which we find it hard even to imagine. For example, men of the
+Cassowary clan in Mabuiag think that cassowaries are men or nearly so.
+"Cassowary, he all same as relation, he belong same family," is the
+account they give of their relationship with the long-legged bird.
+Conversely they hold that they themselves are cassowaries for all
+practical purposes. They pride themselves on having long thin legs like
+a cassowary. This reflection affords them peculiar satisfaction when
+they go out to fight, or to run away, as the case may be; for at such
+times a Cassowary man will say to himself, "My leg is long and thin, I
+can run and not feel tired; my legs will go quickly and the grass will
+not entangle them." Members of the Cassowary clan are reputed to be
+pugnacious, because the cassowary is a bird of very uncertain temper and
+can kick with extreme violence. (A.C. Haddon, "The Ethnography of
+the Western Tribe of Torres Straits", "Journal of the Anthropological
+Institute", XIX. (1890), page 393; "Reports of the Cambridge
+Anthropological Expedition to Torres Straits", V. (Cambridge, 1904),
+pages 166, 184.) So among the Ojibways men of the Bear clan are reputed
+to be surly and pugnacious like bears, and men of the Crane clan to
+have clear ringing voices like cranes. (W.W. Warren, "History of the
+Ojibways", "Collections of the Minnesota Historical Society", V. (Saint
+Paul, Minn. 1885), pages 47, 49.) Hence the savage will often speak of
+his totem animal as his father or his brother, and will neither kill it
+himself nor allow others to do so, if he can help it. For example, if
+somebody were to kill a bird in the presence of a native Australian who
+had the bird for his totem, the black might say, "What for you kill
+that fellow? that my father!" or "That brother belonging to me you
+have killed; why did you do it?" (E. Palmer, "Notes on some Australian
+Tribes", "Journal of the Anthropological Institute", XIII. (1884), page
+300.) Bechuanas of the Porcupine clan are greatly afflicted if anybody
+hurts or kills a porcupine in their presence. They say, "They have
+killed our brother, our master, one of ourselves, him whom we sing of";
+and so saying they piously gather the quills of their murdered brother,
+spit on them, and rub their eyebrows with them. They think they would
+die if they touched its flesh. In like manner Bechuanas of the Crocodile
+clan call the crocodile one of themselves, their master, their
+brother; and they mark the ears of their cattle with a long slit like a
+crocodile's mouth by way of a family crest. Similarly Bechuanas of the
+Lion clan would not, like the members of other clans, partake of lion's
+flesh; for how, say they, could they eat their grandfather? If they are
+forced in self-defence to kill a lion, they do so with great regret and
+rub their eyes carefully with its skin, fearing to lose their sight if
+they neglected this precaution. (T. Arbousset et F. Daumas, "Relation
+d'un Voyage d'Exploration au Nord-Est de la Colonie du Cap de
+Bonne-Esperance" (Paris, 1842), pages 349 sq., 422-24.) A Mandingo
+porter has been known to offer the whole of his month's pay to save
+the life of a python, because the python was his totem and he therefore
+regarded the reptile as his relation; he thought that if he allowed
+the creature to be killed, the whole of his own family would perish,
+probably through the vengeance to be taken by the reptile kinsfolk of
+the murdered serpent. (M. le Docteur Tautain, "Notes sur les Croyances
+et Pratiques Religieuses des Banmanas", "Revue d'Ethnographie",
+III. (1885), pages 396 sq.; A. Rancon, "Dans la Haute-Gambie, Voyage
+d'Exploration Scientifique" (Paris, 1894), page 445.)
+
+Sometimes, indeed, the savage goes further and identifies the revered
+animal not merely with a kinsman but with himself; he imagines that one
+of his own more or less numerous souls, or at all events that a vital
+part of himself, is in the beast, so that if it is killed he must die.
+Thus, the Balong tribe of the Cameroons, in West Africa, think that
+every man has several souls, of which one is lodged in an elephant, a
+wild boar, a leopard, or what not. When any one comes home, feels ill,
+and says, "I shall soon die," and is as good as his word, his friends
+are of opinion that one of his souls has been shot by a hunter in a wild
+boar or a leopard, for example, and that that is the real cause of his
+death. (J. Keller, "Ueber das Land und Volk der Balong", "Deutsches
+Kolonialblatt", 1 October, 1895, page 484.) A Catholic missionary,
+sleeping in the hut of a chief of the Fan negroes, awoke in the middle
+of the night to see a huge black serpent of the most dangerous sort
+in the act of darting at him. He was about to shoot it when the chief
+stopped him, saying, "In killing that serpent, it is me that you would
+have killed. Fear nothing, the serpent is my elangela." (Father Trilles,
+"Chez les Fang, leurs Moeurs, leur Langue, leur Religion", "Les Missions
+Catholiques", XXX. (1898), page 322.) At Calabar there used to be some
+years ago a huge old crocodile which was well known to contain the
+spirit of a chief who resided in the flesh at Duke Town. Sporting
+Vice-Consuls, with a reckless disregard of human life, from time to time
+made determined attempts to injure the animal, and once a peculiarly
+active officer succeeded in hitting it. The chief was immediately laid
+up with a wound in his leg. He SAID that a dog had bitten him, but
+few people perhaps were deceived by so flimsy a pretext. (Miss Mary H.
+Kingsley, "Travels in West Africa" (London, 1897), pages 538 sq. As to
+the external or bush souls of human beings, which in this part of Africa
+are supposed to be lodged in the bodies of animals, see Miss Mary H.
+Kingsley op. cit. pages 459-461; R. Henshaw, "Notes on the Efik belief
+in 'bush soul'", "Man", VI.(1906), pages 121 sq.; J. Parkinson,
+"Notes on the Asaba people (Ibos) of the Niger", "Journal of the
+Anthropological Institute", XXXVI. (1906), pages 314 sq.) Once when Mr
+Partridge's canoe-men were about to catch fish near an Assiga town in
+Southern Nigeria, the natives of the town objected, saying, "Our
+souls live in those fish, and if you kill them we shall die." (Charles
+Partridge, "Cross River Natives" (London, 1905), pages 225 sq.) On
+another occasion, in the same region, an Englishman shot a hippopotamus
+near a native village. The same night a woman died in the village,
+and her friends demanded and obtained from the marksman five pounds as
+compensation for the murder of the woman, whose soul or second self had
+been in that hippopotamus. (C.H. Robinson, "Hausaland" (London, 1896),
+pages 36 sq.) Similarly at Ndolo, in the Congo region, we hear of a
+chief whose life was bound up with a hippopotamus, but he prudently
+suffered no one to fire at the animal. ("Notes Analytiques sur les
+Collections Ethnographiques du Musee du Congo", I. (Brussels, 1902-06),
+page 150.)
+
+Amongst people who thus fail to perceive any sharp line of distinction
+between beasts and men it is not surprising to meet with the belief that
+human beings are directly descended from animals. Such a belief is often
+found among totemic tribes who imagine that their ancestors sprang from
+their totemic animals or plants; but it is by no means confined to
+them. Thus, to take instances, some of the Californian Indians, in whose
+mythology the coyote or prairie-wolf is a leading personage, think that
+they are descended from coyotes. At first they walked on all fours; then
+they began to have some members of the human body, one finger, one toe,
+one eye, one ear, and so on; then they got two fingers, two toes, two
+eyes, two ears, and so forth; till at last, progressing from period to
+period, they became perfect human beings. The loss of their tails, which
+they still deplore, was produced by the habit of sitting upright. (H.R.
+Schoolcraft, "Indian Tribes of the United States", IV. (Philadelphia,
+1856), pages 224 sq.; compare id. V. page 217. The descent of some, not
+all, Indians from coyotes is mentioned also by Friar Boscana, in (A.
+Robinson's) "Life in California" (New York, 1846), page 299.)
+Similarly Darwin thought that "the tail has disappeared in man and the
+anthropomorphous apes, owing to the terminal portion having been injured
+by friction during a long lapse of time; the basal and embedded portion
+having been reduced and modified, so as to become suitable to the erect
+or semi-erect position." (Charles Darwin, "The Descent of Man", Second
+Edition (London, 1879), page 60.) The Turtle clam of the Iroquois think
+that they are descended from real mud turtles which used to live in a
+pool. One hot summer the pool dried up, and the mud turtles set out to
+find another. A very fat turtle, waddling after the rest in the heat,
+was much incommoded by the weight of his shell, till by a great effort
+he heaved it off altogether. After that he gradually developed into a
+man and became the progenitor of the Turtle clan. (E.A. Smith, "Myths
+of the Iroquois", "Second Annual Report of the Bureau of Ethnology"
+(Washington, 1883), page 77.) The Crawfish band of the Choctaws are
+in like manner descended from real crawfish, which used to live under
+ground, only coming up occasionally through the mud to the surface. Once
+a party of Choctaws smoked them out, taught them the Choctaw language,
+taught them to walk on two legs, made them cut off their toe nails and
+pluck the hair from their bodies, after which they adopted them into the
+tribe. But the rest of their kindred, the crawfish, are crawfish under
+ground to this day. (Geo. Catlin, "North American Indians" 4 (London,
+1844), II. page 128.) The Osage Indians universally believed that they
+were descended from a male snail and a female beaver. A flood swept the
+snail down to the Missouri and left him high and dry on the bank, where
+the sun ripened him into a man. He met and married a beaver maid, and
+from the pair the tribe of the Osages is descended. For a long time
+these Indians retained a pious reverence for their animal ancestors and
+refrained from hunting beavers, because in killing a beaver they killed
+a brother of the Osages. But when white men came among them and offered
+high prices for beaver skins, the Osages yielded to the temptation and
+took the lives of their furry brethren. (Lewis and Clarke, "Travels to
+the Source of the Missouri River" (London, 1815), I. 12 (Vol. I. pages
+44 sq. of the London reprint, 1905).) The Carp clan of the Ootawak
+Indians are descended from the eggs of a carp which had been deposited
+by the fish on the banks of a stream and warmed by the sun. ("Lettres
+Edifiantes et Curieuses", Nouvelle Edition, VI. (Paris, 1781), page
+171.) The Crane clan of the Ojibways are sprung originally from a pair
+of cranes, which after long wanderings settled on the rapids at the
+outlet of Lake Superior, where they were changed by the Great Spirit
+into a man and woman. (L.H. Morgan, "Ancient Society" (London, 1877),
+page 180.) The members of two Omaha clans were originally buffaloes and
+lived, oddly enough, under water, which they splashed about, making it
+muddy. And at death all the members of these clans went back to their
+ancestors the buffaloes. So when one of them lay adying, his friends
+used to wrap him up in a buffalo skin with the hair outside and say to
+him, "You came hither from the animals and you are going back thither.
+Do not face this way again. When you go, continue walking. (J. Owen
+Dorsey, "Omaha Sociology", "Third Annual Report of the Bureau of
+Ethnology" (Washington, 1884), pages 229, 233.) The Haida Indians of
+Queen Charlotte Islands believe that long ago the raven, who is the
+chief figure in the mythology of North-West America, took a cockle from
+the beach and married it; the cockle gave birth to a female child, whom
+the raven took to wife, and from their union the Indians were produced.
+(G.M. Dawson, "Report on the Queen Charlotte Islands" (Montreal,
+1880), pages 149B sq. ("Geological Survey of Canada"); F. Poole,
+"Queen Charlotte Islands", page 136.) The Delaware Indians called the
+rattle-snake their grandfather and would on no account destroy one of
+these reptiles, believing that were they to do so the whole race of
+rattle-snakes would rise up and bite them. Under the influence of the
+white man, however, their respect for their grandfather the rattle-snake
+gradually died away, till at last they killed him without compunction
+or ceremony whenever they met him. The writer who records the old custom
+observes that he had often reflected on the curious connection which
+appears to subsist in the mind of an Indian between man and the brute
+creation; "all animated nature," says he, "in whatever degree, is in
+their eyes a great whole, from which they have not yet ventured to
+separate themselves." (Rev. John Heckewelder, "An Account of the
+History, Manners, and Customs, of the Indian Nations, who once inhabited
+Pennsylvania and the Neighbouring States", "Transactions of the
+Historical and Literary Committee of the American Philosophical
+Society", I. (Philadelphia, 1819), pages 245, 247, 248.)
+
+Some of the Indians of Peru boasted of being descended from the puma
+or American lion; hence they adored the lion as a god and appeared at
+festivals like Hercules dressed in the skins of lions with the heads
+of the beasts fixed over their own. Others claimed to be sprung from
+condors and attired themselves in great black and white wings, like
+that enormous bird. (Garcilasso de la Vega, "First Part of the Royal
+Commentaries of the Yncas", Vol. I. page 323, Vol. II. page 156
+(Markham's translation).) The Wanika of East Africa look upon the hyaena
+as one of their ancestors or as associated in some way with their origin
+and destiny. The death of a hyaena is mourned by the whole people, and
+the greatest funeral ceremonies which they perform are performed for
+this brute. The wake held over a chief is as nothing compared to the
+wake held over a hyaena; one tribe only mourns the death of its chief,
+but all the tribes unite to celebrate the obsequies of a hyaena.
+(Charles New, "Life, Wanderings, and Labours in Eastern Africa" (London,
+1873) page 122.) Some Malagasy families claim to be descended from the
+babacoote (Lichanotus brevicaudatus), a large lemur of grave appearance
+and staid demeanour, which lives in the depth of the forest. When
+they find one of these creatures dead, his human descendants bury it
+solemnly, digging a grave for it, wrapping it in a shroud, and weeping
+and lamenting over its carcase. A doctor who had shot a babacoote was
+accused by the inhabitants of a Betsimisaraka village of having
+killed "one of their grandfathers in the forest," and to appease their
+indignation he had to promise not to skin the animal in the village
+but in a solitary place where nobody could see him. (Father Abinal,
+"Croyances fabuleuses des Malgaches", "Les Missions Catholiques", XII.
+(1880), page 526; G.H. Smith, "Some Betsimisaraka superstitions", "The
+Antananarivo Annual and Madagascar Magazine", No. 10 (Antananarivo,
+1886), page 239; H.W. Little, "Madagascar, its History and People"
+(London, 1884), pages 321 sq; A. van Gennep, "Tabou et Totemisme a
+Madagascar" (Paris, 1904), pages 214 sqq.) Many of the Betsimisaraka
+believe that the curious nocturnal animal called the aye-aye (Cheiromys
+madagascariensis) "is the embodiment of their forefathers, and hence
+will not touch it, much less do it an injury. It is said that when one
+is discovered dead in the forest, these people make a tomb for it and
+bury it with all the forms of a funeral. They think that if they attempt
+to entrap it, they will surely die in consequence." (G.A. Shaw, "The
+Aye-aye", "Antananarivo Annual and Madagascar Magazine", Vol. II.
+(Antananarivo, 1896), pages 201, 203 (Reprint of the Second four
+Numbers). Compare A. van Gennep, "Tabou et Totemisme a Madagascar",
+pages 223 sq.) Some Malagasy tribes believe themselves descended from
+crocodiles and accordingly they deem the formidable reptiles their
+brothers. If one of these scaly brothers so far forgets the ties of
+kinship as to devour a man, the chief of the tribe, or in his absence
+an old man familiar with the tribal customs, repairs at the head of the
+people to the edge of the water, and summons the family of the culprit
+to deliver him up to the arm of justice. A hook is then baited and cast
+into the river or lake. Next day the guilty brother or one of his family
+is dragged ashore, formally tried, sentenced to death, and executed. The
+claims of justice being thus satisfied, the dead animal is lamented
+and buried like a kinsman; a mound is raised over his grave and a stone
+marks the place of his head. (Father Abinal, "Croyances fabuleuses des
+Malgaches", "Les Missions Catholiques", XII. (1880), page 527; A. van
+Gennep, "Tabou et Totemisme a Madagascar", pages 281 sq.)
+
+Amongst the Tshi-speaking tribes of the Gold Coast in West Africa the
+Horse-mackerel family traces its descent from a real horse-mackerel whom
+an ancestor of theirs once took to wife. She lived with him happily
+in human shape on shore till one day a second wife, whom the man had
+married, cruelly taunted her with being nothing but a fish. That hurt
+her so much that bidding her husband farewell she returned to her old
+home in the sea, with her youngest child in her arms, and never came
+back again. But ever since the Horse-mackerel people have refrained from
+eating horse-mackerels, because the lost wife and mother was a fish of
+that sort. (A.B. Ellis, "The Tshi-speaking Peoples of the Gold Coast
+of West Africa" (London, 1887), pages 208-11. A similar tale is told by
+another fish family who abstain from eating the fish (appei) from which
+they take their name (A.B. Ellis op. cit. pages 211 sq.).) Some of the
+Land Dyaks of Borneo tell a similar tale to explain a similar custom.
+"There is a fish which is taken in their rivers called a puttin, which
+they would on no account touch, under the idea that if they did they
+would be eating their relations. The tradition respecting it is, that a
+solitary old man went out fishing and caught a puttin, which he dragged
+out of the water and laid down in his boat. On turning round, he found
+it had changed into a very pretty little girl. Conceiving the idea she
+would make, what he had long wished for, a charming wife for his son,
+he took her home and educated her until she was fit to be married. She
+consented to be the son's wife cautioning her husband to use her well.
+Some time after their marriage, however, being out of temper, he struck
+her, when she screamed, and rushed away into the water; but not without
+leaving behind her a beautiful daughter, who became afterwards the
+mother of the race." (The Lord Bishop of Labuan, "On the Wild Tribes
+of the North-West Coast of Borneo", "Transactions of the Ethnological
+Society of London", New Series II. (London, 1863), pages 26 sq. Such
+stories conform to a well-known type which may be called the Swan-Maiden
+type of story, or Beauty and the Beast, or Cupid and Psyche. The
+occurrence of stories of this type among totemic peoples, such as the
+Tshi-speaking negroes of the Gold Coast, who tell them to explain their
+totemic taboos, suggests that all such tales may have originated in
+totemism. I shall deal with this question elsewhere.)
+
+Members of a clan in Mandailing, on the west coast of Sumatra, assert
+that they are descended from a tiger, and at the present day, when a
+tiger is shot, the women of the clan are bound to offer betel to the
+dead beast. When members of this clan come upon the tracks of a tiger,
+they must, as a mark of homage, enclose them with three little sticks.
+Further, it is believed that the tiger will not attack or lacerate his
+kinsmen, the members of the clan. (H. Ris, "De Onderafdeeling Klein
+Mandailing Oeloe en Pahantan en hare Bevolking met uitzondering van
+de Oeloes", "Bijdragen tot de Tall- Land- en Volkenkunde van
+Nederlansch-Indie, XLVI." (1896), page 473.) The Battas of Central
+Sumatra are divided into a number of clans which have for their totems
+white buffaloes, goats, wild turtle-doves, dogs, cats, apes, tigers, and
+so forth; and one of the explanations which they give of their totems
+is that these creatures were their ancestors, and that their own souls
+after death can transmigrate into the animals. (J.B. Neumann, "Het
+Pane en Bila-stroomgebied op het eiland Sumatra", "Tijdschrift van het
+Nederlandsch Aardrijkskundig Genootschap", Tweede Serie, III. Afdeeling,
+Meer uitgebreide Artikelen, No. 2 (Amsterdam, 1886), pages 311 sq.;
+id. ib. Tweede Serie, IV. Afdeeling, Meer uitgebreide Artikelen, No. 1
+(Amsterdam, 1887), pages 8 sq.) In Amboyna and the neighbouring islands
+the inhabitants of some villages aver that they are descended from
+trees, such as the Capellenia moluccana, which had been fertilised by
+the Pandion Haliaetus. Others claim to be sprung from pigs, octopuses,
+crocodiles, sharks, and eels. People will not burn the wood of the trees
+from which they trace their descent, nor eat the flesh of the animals
+which they regard as their ancestors. Sicknesses of all sorts are
+believed to result from disregarding these taboos. (J.G.F. Riedel, "De
+sluik- en kroesharige rassen tusschen Selebes en Papua" (The Hague,
+1886), pages 32, 61; G.W.W.C. Baron van Hoevell, "Ambon en meer
+bepaaldelijk de Oeliasers" (Dordrecht, 1875), page 152.) Similarly in
+Ceram persons who think they are descended from crocodiles, serpents,
+iguanas, and sharks will not eat the flesh of these animals. (J.G.F.
+Riedel op. cit. page 122.) Many other peoples of the Molucca Islands
+entertain similar beliefs and observe similar taboos. (J.G.F. Riedel
+"De sluik- en kroesharige rassen tusschen Selebes en Papua" (The Hague,
+1886), pages 253, 334, 341, 348, 412, 414, 432.) Again, in Ponape, one
+of the Caroline Islands, "The different families suppose themselves to
+stand in a certain relation to animals, and especially to fishes, and
+believe in their descent from them. They actually name these animals
+'mothers'; the creatures are sacred to the family and may not be
+injured. Great dances, accompanied with the offering of prayers, are
+performed in their honour. Any person who killed such an animal would
+expose himself to contempt and punishment, certainly also to the
+vengeance of the insulted deity." Blindness is commonly supposed to
+be the consequence of such a sacrilege. (Dr Hahl, "Mittheilungen
+uber Sitten und rechtliche Verhaltnisse auf Ponape", "Ethnologisches
+Notizblatt", Vol. II. Heft 2 (Berlin, 1901), page 10.)
+
+Some of the aborigines of Western Australia believe that their ancestors
+were swans, ducks, or various other species of water-fowl before they
+were transformed into men. (Captain G. Grey, "A Vocabulary of the
+Dialects of South Western Australia", Second Edition (London, 1840),
+pages 29, 37, 61, 63, 66, 71.) The Dieri tribe of Central Australia, who
+are divided into totemic clans, explain their origin by the following
+legend. They say that in the beginning the earth opened in the midst of
+Perigundi Lake, and the totems (murdus or madas) came trooping out one
+after the other. Out came the crow, and the shell parakeet, and the emu,
+and all the rest. Being as yet imperfectly formed and without members
+or organs of sense, they laid themselves down on the sandhills which
+surrounded the lake then just as they do now. It was a bright day and
+the totems lay basking in the sunshine, till at last, refreshed and
+invigorated by it, they stood up as human beings and dispersed in all
+directions. That is why people of the same totem are now scattered all
+over the country. You may still see the island in the lake out of which
+the totems came trooping long ago. (A.W. Howitt, "Native Tribes of
+South-East Australia" (London, 1904), pages 476, 779 sq.) Another
+Dieri legend relates how Paralina, one of the Mura-Muras or mythical
+predecessors of the Dieri, perfected mankind. He was out hunting
+kangaroos, when he saw four incomplete beings cowering together. So he
+went up to them, smoothed their bodies, stretched out their limbs, slit
+up their fingers and toes, formed their mouths, noses, and eyes, stuck
+ears on them, and blew into their ears in order that they might hear.
+Having perfected their organs and so produced mankind out of these
+rudimentary beings, he went about making men everywhere. (A.W. Howitt
+op. cit., pages 476, 780 sq.) Yet another Dieri tradition sets forth how
+the Mura-Mura produced the race of man out of a species of small black
+lizards, which may still be met with under dry bark. To do this he
+divided the feet of the lizards into fingers and toes, and, applying
+his forefinger to the middle of their faces, created a nose; likewise he
+gave them human eyes, mouths and ears. He next set one of them upright,
+but it fell down again because of its tail; so he cut off its tail and
+the lizard then walked on its hind legs. That is the origin of mankind.
+(S. Gason, "The Manners and Customs of the Dieyerie tribe of Australian
+Aborigines", "Native Tribes of South Australia" (Adelaide, 1879),
+page 260. This writer fell into the mistake of regarding the Mura-Mura
+(Mooramoora) as a Good-Spirit instead of as one of the mythical but more
+or less human predecessors of the Dieri in the country. See A.W. Howitt,
+"Native Tribes of South-East Australia", pages 475 sqq.)
+
+The Arunta tribe of Central Australia similarly tell how in the
+beginning mankind was developed out of various rudimentary forms of
+animal life. They say that in those days two beings called Ungambikula,
+that is, "out of nothing," or "self-existing," dwelt in the western sky.
+From their lofty abode they could see, far away to the east, a number
+of inapertwa creatures, that is, rudimentary human beings or incomplete
+men, whom it was their mission to make into real men and women. For at
+that time there were no real men and women; the rudimentary creatures
+(inapertwa) were of various shapes and dwelt in groups along the shore
+of the salt water which covered the country. These embryos, as we may
+call them, had no distinct limbs or organs of sight, hearing, and smell;
+they did not eat food, and they presented the appearance of human beings
+all doubled up into a rounded mass, in which only the outline of the
+different parts of the body could be vaguely perceived. Coming down
+from their home in the western sky, armed with great stone knives, the
+Ungambikula took hold of the embryos, one after the other. First of all
+they released the arms from the bodies, then making four clefts at the
+end of each arm they fashioned hands and fingers; afterwards legs, feet,
+and toes were added in the same way. The figure could now stand; a nose
+was then moulded and the nostrils bored with the fingers. A cut with the
+knife made the mouth, which was pulled open several times to render it
+flexible. A slit on each side of the face separated the upper and lower
+eye-lids, disclosing the eyes, which already existed behind them; and
+a few strokes more completed the body. Thus out of the rudimentary
+creatures were formed men and women. These rudimentary creatures or
+embryos, we are told, "were in reality stages in the transformation
+of various animals and plants into human beings, and thus they were
+naturally, when made into human beings, intimately associated with the
+particular animal or plant, as the case may be, of which they were the
+transformations--in other words, each individual of necessity belonged
+to a totem, the name of which was of course that of the animal or plant
+of which he or she was a transformation." However, it is not said
+that all the totemic clans of the Arunta were thus developed; no such
+tradition, for example, is told to explain the origin of the important
+Witchetty Grub clan. The clans which are positively known, or at least
+said, to have originated out of embryos in the way described are the
+Plum Tree, the Grass Seed, the Large Lizard, the Small Lizard, the
+Alexandra Parakeet, and the Small Rat clans. When the Ungambikula had
+thus fashioned people of these totems, they circumcised them all, except
+the Plum Tree men, by means of a fire-stick. After that, having done the
+work of creation or evolution, the Ungambikula turned themselves
+into little lizards which bear a name meaning "snappers-up of flies."
+(Baldwin Spencer and F.J. Gillen, "Native Tribes of Central Australia"
+(London, 1899), pages 388 sq.; compare id., "Northern Tribes of Central
+Australia" (London, 1904), page 150.)
+
+This Arunta tradition of the origin of man, as Messrs Spencer and
+Gillen, who have recorded it, justly observe, "is of considerable
+interest; it is in the first place evidently a crude attempt to describe
+the origin of human beings out of non-human creatures who were of
+various forms; some of them were representatives of animals, others of
+plants, but in all cases they are to be regarded as intermediate stages
+in the transition of an animal or plant ancestor into a human individual
+who bore its name as that of his or her totem." (Baldwin Spencer and
+F.J. Gillen, "Native Tribes of Central Australia", pages 391 sq.) In a
+sense these speculations of the Arunta on their own origin may be said
+to combine the theory of creation with the theory of evolution; for
+while they represent men as developed out of much simpler forms of life,
+they at the same time assume that this development was effected by the
+agency of two powerful beings, whom so far we may call creators. It is
+well known that at a far higher stage of culture a crude form of
+the evolutionary hypothesis was propounded by the Greek philosopher
+Empedocles. He imagined that shapeless lumps of earth and water, thrown
+up by the subterranean fires, developed into monstrous animals, bulls
+with the heads of men, men with the heads of bulls, and so forth; till
+at last, these hybrid forms being gradually eliminated, the various
+existing species of animals and men were evolved. (E. Zeller, "Die
+Philosophie der Griechen", I.4 (Leipsic, 1876), pages 718 sq.; H. Ritter
+et L. Preller, "Historia Philosophiae Graecae et Romanae ex fontium
+locis contexta" 5, pages 102 sq. H. Diels, "Die Fragmente der
+Vorsokratiker" 2, I. (Berlin, 1906), pages 190 sqq. Compare Lucretius "De
+rerum natura", V. 837 sqq.) The theory of the civilised Greek of Sicily
+may be set beside the similar theory of the savage Arunta of Central
+Australia. Both represent gropings of the human mind in the dark abyss
+of the past; both were in a measure grotesque anticipations of the
+modern theory of evolution.
+
+In this essay I have made no attempt to illustrate all the many various
+and divergent views which primitive man has taken of his own origin. I
+have confined myself to collecting examples of two radically different
+views, which may be distinguished as the theory of creation and the
+theory of evolution. According to the one, man was fashioned in his
+existing shape by a god or other powerful being; according to the other
+he was evolved by a natural process out of lower forms of animal life.
+Roughly speaking, these two theories still divide the civilised world
+between them. The partisans of each can appeal in support of their view
+to a large consensus of opinion; and if truth were to be decided by
+weighing the one consensus against the other, with "Genesis" in the
+one scale and "The Origin of Species" in the other, it might perhaps be
+found, when the scales were finally trimmed, that the balance hung very
+even between creation and evolution.
+
+
+
+
+X. THE INFLUENCE OF DARWIN ON THE STUDY OF ANIMAL EMBRYOLOGY. By A.
+Sedgwick, M.A., F.R.S.
+
+Professor of Zoology and Comparative Anatomy in the University of
+Cambridge.
+
+The publication of "The Origin of Species" ushered in a new era in the
+study of Embryology. Whereas, before the year 1859 the facts of anatomy
+and development were loosely held together by the theory of types, which
+owed its origin to the great anatomists of the preceding generation,
+to Cuvier, L. Agassiz, J. Muller, and R. Owen, they were now combined
+together into one organic whole by the theory of descent and by the
+hypothesis of recapitulation which was deduced from that theory. The
+view (First clearly enunciated by Fritz Muller in his well-known work,
+"Fur Darwin", Leipzig, 1864; (English Edition, "Facts for Darwin",
+1869).) that a knowledge of embryonic and larval histories would lay
+bare the secrets of race-history and enable the course of evolution
+to be traced, and so lead to the discovery of the natural system of
+classification, gave a powerful stimulus to morphological study in
+general and to embryological investigation in particular. In Darwin's
+words: "Embryology rises greatly in interest, when we look at the embryo
+as a picture, more or less obscured, of the progenitor, either in its
+adult or larval state, of all the members of the same great class."
+("Origin" (6th edition), page 396.) In the period under consideration
+the output of embryological work has been enormous. No group of the
+animal kingdom has escaped exhaustive examination and no effort has been
+spared to obtain the embryos of isolated and out of the way forms, the
+development of which might have an important bearing upon questions
+of phylogeny and classification. Marine zoological stations have been
+established, expeditions have been sent to distant countries, and the
+methods of investigation have been greatly improved. The result of this
+activity has been that the main features of the developmental history
+of all the most important animals are now known and the curiosity as to
+developmental processes, so greatly excited by the promulgation of the
+Darwinian theory, has to a considerable extent been satisfied.
+
+To what extent have the results of this vast activity fulfilled the
+expectations of the workers who have achieved them? The Darwin centenary
+is a fitting moment at which to take stock of our position. In this
+inquiry we shall leave out of consideration the immense and intensely
+interesting additions to our knowledge of Natural History. These may be
+said to constitute a capital fund upon which philosophers, poets and
+men of science will draw for many generations. The interest of Natural
+History existed long before Darwinian evolution was thought of and
+will endure without any reference to philosophic speculations. She is
+a mistress in whose face are beauties and in whose arms are delights
+elsewhere unattainable. She is and always has been pursued for her own
+sake without any reference to philosophy, science, or utility.
+
+Darwin's own views of the bearing of the facts of embryology upon
+questions of wide scientific interest are perfectly clear. He writes
+("Origin" (6th edition), page 395.):
+
+"On the other hand it is highly probable that with many animals the
+embryonic or larval stages show us, more or less completely, the
+condition of the progenitor of the whole group in its adult state. In
+the great class of the Crustacea, forms wonderfully distinct from each
+other, namely, suctorial parasites, cirripedes, entomostraca, and even
+the malacostraca, appear at first as larvae under the nauplius-form; and
+as these larvae live and feed in the open sea, and are not adapted for
+any peculiar habits of life, and from other reasons assigned by Fritz
+Muller, it is probable that at some very remote period an independent
+adult animal, resembling the Nauplius, existed, and subsequently
+produced, along several divergent lines of descent, the above-named
+great Crustacean groups. So again it is probable, from what we know of
+the embryos of mammals, birds, fishes, and reptiles, that these animals
+are the modified descendants of some ancient progenitor, which was
+furnished in its adult state with branchiae, a swim-bladder, four
+fin-like limbs, and a long tail, all fitted for an aquatic life.
+
+"As all the organic beings, extinct and recent, which have ever lived,
+can be arranged within a few great classes; and as all within each
+class have, according to our theory, been connected together by fine
+gradations, the best, and, if our collections were nearly perfect, the
+only possible arrangement, would be genealogical; descent being the
+hidden bond of connexion which naturalists have been seeking under the
+term of the Natural System. On this view we can understand how it is
+that, in the eyes of most naturalists, the structure of the embryo is
+even more important for classification than that of the adult. In two or
+more groups of animals, however much they may differ from each other
+in structure and habits in their adult condition, if they pass through
+closely similar embryonic stages, we may feel assured that they all are
+descended from one parent-form, and are therefore closely related.
+Thus, community in embryonic structure reveals community of descent; but
+dissimilarity in embryonic development does not prove discommunity of
+descent, for in one of two groups the developmental stages may have been
+suppressed, or may have been so greatly modified through adaptation to
+new habits of life, as to be no longer recognisable. Even in groups, in
+which the adults have been modified to an extreme degree, community of
+origin is often revealed by the structure of the larvae; we have seen,
+for instance, that cirripedes, though externally so like shell-fish,
+are at once known by their larvae to belong to the great class of
+crustaceans. As the embryo often shows us more or less plainly the
+structure of the less modified and ancient progenitor of the group, we
+can see why ancient and extinct forms so often resemble in their
+adult state the embryos of existing species of the same class. Agassiz
+believes this to be a universal law of nature; and we may hope hereafter
+to see the law proved true. It can, however, be proved true only in
+those cases in which the ancient state of the progenitor of the group
+has not been wholly obliterated, either by successive variations having
+supervened at a very early period of growth, or by such variations
+having been inherited at an earlier stage than that at which they first
+appeared. It should also be borne in mind, that the law may be true,
+but yet, owing to the geological record not extending far enough back
+in time, may remain for a long period, or for ever, incapable of
+demonstration. The law will not strictly hold good in those cases in
+which an ancient form became adapted in its larval state to some special
+line of life, and transmitted the same larval state to a whole group of
+descendants; for such larvae will not resemble any still more ancient
+form in its adult state."
+
+As this passage shows, Darwin held that embryology was of interest
+because of the light it seems to throw upon ancestral history
+(phylogeny) and because of the help it would give in enabling us to
+arrive at a natural system of classification. With regard to the latter
+point, he quotes with approval the opinion that "the structure of
+the embryo is even more important for classification than that of the
+adult." What justification is there for this view? The phase of life
+chosen for the ordinary anatomical and physiological studies, namely,
+the adult phase, is merely one of the large number of stages of
+structure through which the organism passes. By far the greater number
+of these are included in what is specially called the developmental
+or (if we include larvae with embryos) embryonic period, for the
+developmental changes are more numerous and take place with greater
+rapidity at the beginning of life than in its later periods. As each of
+these stages is equal in value, for our present purpose, to the adult
+phase, it clearly follows that if there is anything in the view that
+the anatomical study of organisms is of importance in determining their
+mutual relations, the study of the organism in its various embryonic
+(and larval) stages must have a greater importance than the study of the
+single and arbitrarily selected stage of life called the adult.
+
+But a deeper reason than this has been assigned for the importance of
+embryology in classification. It has been asserted, and is implied by
+Darwin in the passage quoted, that the ancestral history is repeated
+in a condensed form in the embryonic, and that a study of the latter
+enables us to form a picture of the stages of structure through which
+the organism has passed in its evolution. It enables us on this view to
+reconstruct the pedigrees of animals and so to form a genealogical tree
+which shall be the true expression of their natural relations.
+
+The real question which we have to consider is to what extent the
+embryological studies of the last 50 years have confirmed or rendered
+probable this "theory of recapitulation." In the first place it must
+be noted that the recapitulation theory is itself a deduction from the
+theory of evolution. The facts of embryology, particularly of vertebrate
+embryology, and of larval history receive, it is argued, an explanation
+on the view that the successive stages of development are, on the
+whole, records of adult stages of structure which the species has passed
+through in its evolution. Whether this statement will bear a critical
+verbal examination I will not now pause to inquire, for it is more
+important to determine whether any independent facts can be alleged in
+favour of the theory. If it could be shown, as was stated to be the case
+by L. Agassiz, that ancient and extinct forms of life present features
+of structure now only found in embryos, we should have a body of facts
+of the greatest importance in the present discussion. But as Huxley (See
+Huxley's "Scientific Memoirs", London, 1898, Vol. I. page 303: "There is
+no real parallel between the successive forms assumed in the development
+of the life of the individual at present, and those which have appeared
+at different epochs in the past." See also his Address to the
+Geological Society of London (1862) 'On the Palaeontological Evidence of
+Evolution', ibid. Vol. II. page 512.) has shown and as the whole course
+of palaeontological and embryological investigation has demonstrated, no
+such statement can be made. The extinct forms of life are very similar
+to those now existing and there is nothing specially embryonic about
+them. So that the facts, as we know them, lend no support to theory.
+
+But there is another class of facts which have been alleged in favour
+of the theory, viz. the facts which have been included in the
+generalisation known as the Law of v. Baer. The law asserts that embryos
+of different species of animals of the same group are more alike
+than the adults and that, the younger the embryo, the greater are the
+resemblances. If this law could be established it would undoubtedly be
+a strong argument in favour of the "recapitulation" explanation of the
+facts of embryology. But its truth has been seriously disputed. If it
+were true we should expect to find that the embryos of closely similar
+species would be indistinguishable from one another, but this is
+notoriously not the case. It is more difficult to meet the assertion
+when it is made in the form given above, for here we are dealing with
+matters of opinion. For instance, no one would deny that the embryo of a
+dogfish is different from the embryo of a rabbit, but there is room for
+difference of opinion when it is asserted that the difference is less
+than the difference between an adult dogfish and an adult rabbit. It
+would be perfectly true to say that the differences between the embryos
+concern other organs more than do the differences between the adults,
+but who is prepared to affirm that the presence of a cephalic coelom and
+of cranial segments, of external gills, of six gill slits, of the kidney
+tubes opening into the muscle-plate coelom, of an enormous yolk-sac, of
+a neurenteric canal, and the absence of any trace of an amnion, of an
+allantois and of a primitive streak are not morphological facts of as
+high an import as those implied by the differences between the adults?
+The generalisation undoubtedly had its origin in the fact that there is
+what may be called a family resemblance between embryos and larvae, but
+this resemblance, which is by no means exact, is largely superficial and
+does not extend to anatomical detail.
+
+It is useless to say, as Weismann has stated ("The Evolution Theory",
+by A. Weismann, English Translation, Vol. II. page 176, London, 1904.),
+that "it cannot be disputed that the rudiments [vestiges his translator
+means] of gill-arches and gill-clefts, which are peculiar to one stage
+of human ontogeny, give us every ground for concluding that we possessed
+fish-like ancestors." The question at issue is: did the pharyngeal
+arches and clefts of mammalian embryos ever discharge a branchial
+function in an adult ancestor of the mammalia? We cannot therefore,
+without begging the question at issue in the grossest manner, apply to
+them the terms "gill-arches" and "gill-clefts". That they are homologous
+with the "gill-arches" and "gill-clefts" of fishes is true; but there
+is no evidence to show that they ever discharged a branchial function.
+Until such evidence is forthcoming, it is beside the point to say that
+it "cannot be disputed" that they are evidence of a piscine ancestry.
+
+It must, therefore, be admitted that one outcome of the progress of
+embryological and palaeontological research for the last 50 years is
+negative. The recapitulation theory originated as a deduction from the
+evolution theory and as a deduction it still remains.
+
+Let us before leaving the subject apply another test. If the evolution
+theory and the recapitulation theory are both true, how is it that
+living birds are not only without teeth but have no rudiments of teeth
+at any stage of their existence? How is it that the missing digits in
+birds and mammals, the missing or reduced limb of snakes and whales, the
+reduced mandibulo-hyoid cleft of elasmobranch fishes are not present or
+relatively more highly developed in the embryo than in the adult? How
+is it that when a marked variation, such as an extra digit, or a reduced
+limb, or an extra segment, makes its appearance, it is not confined to
+the adult but can be seen all through the development? All the clear
+evidence we can get tends to show that marked variations, whether of
+reduction or increase, of organs are manifest during the whole of the
+development of the organ and do not merely affect the adult. And on
+reflection we see that it could hardly be otherwise. All such evidence
+is distinctly at variance with the theory of recapitulation, at least
+as applied to embryos. In the case of larvae of course the case will be
+different, for in them the organs are functional, and reduction in the
+adult will not be accompanied by reduction in the larva unless a change
+in the conditions of life of the larva enables it to occur.
+
+If after 50 years of research and close examination of the facts of
+embryology the recapitulation theory is still without satisfactory
+proof, it seems desirable to take a wider sweep and to inquire whether
+the facts of embryology cannot be included in a larger category.
+
+As has been pointed out by Huxley, development and life are
+co-extensive, and it is impossible to point to any period in the life of
+an organism when the developmental changes cease. It is true that these
+changes take place more rapidly at the commencement of life, but they
+are never wholly absent, and those which occur in the later or so-called
+adult stages of life do not differ in their essence, however much they
+may differ in their degree, from those which occur during the embryonic
+and larval periods. This consideration at once brings the changes of
+the embryonic period into the same category as those of the adult and
+suggests that an explanation which will account for the one will account
+for the other. What then is the problem we are dealing with? Surely
+it is this: Why does an organism as soon as it is established at the
+fertilisation of the ovum enter upon a cycle of transformations which
+never cease until death puts an end to them? In other words what is
+the meaning of that cycle of changes which all organisms present in a
+greater or less degree and which constitute the very essence of life?
+It is impossible to give an answer to this question so long as we remain
+within the precincts of Biology--and it is not my present purpose to
+penetrate beyond those precincts into the realms of philosophy. We have
+to do with an ultimate biological fact, with a fundamental property of
+living matter, which governs and includes all its other properties. How
+may this property be stated? Thus: it is a property of living matter
+to react in a remarkable way to external forces without undergoing
+destruction. The life-cycle, of which the embryonic and larval periods
+are a part, consists of the orderly interaction between the organism
+and its environment. The action of the environment produces certain
+morphological changes in the organism. These changes enable the organism
+to come into relation with new external forces, to move into what
+is practically a new environment, which in its turn produces further
+structural changes in the organism. These in their turn enable, indeed
+necessitate, the organism to move again into a new environment, and so
+the process continues until the structural changes are of such a nature
+that the organism is unable to adapt itself to the environment in which
+it finds itself. The essential condition of success in this process is
+that the organism should always shift into the environment to which its
+new structure is suited--any failure in this leading to the impairment
+of the organism. In most cases the shifting of the environment is a
+very gradual process (whether consisting in the very slight and gradual
+alteration in the relation of the embryo as a whole to the egg-shell or
+uterine wall, or in the relations of its parts to each other, or in
+the successive phases of adult life), and the morphological changes in
+connection with each step of it are but slight. But in some cases jumps
+are made such as we find in the phenomena known as hatching, birth, and
+metamorphosis.
+
+This property of reacting to the environment without undergoing
+destruction is, as has been stated, a fundamental property of organisms.
+It is impossible to conceive of any matter, to which the term living
+could be applied, being without it. And with this property of reacting
+to the environment goes the further property of undergoing a change
+which alters the relation of the organism to the old environment
+and places it in a new environment. If this reasoning is correct, it
+necessarily follows that this property must have been possessed by
+living matter at its first appearance on the earth. In other words
+living matter must always have presented a life-cycle, and the question
+arises what kind of modification has that cycle undergone? Has it
+increased or diminished in duration and complexity since organisms first
+appeared on the earth? The current view is that the cycle was at first
+very short and that it has increased in length by the evolutionary
+creation of new adult phases, that these new phases are in addition to
+those already existing and that each of them as it appears takes
+over from the preceding adult phase the functional condition of the
+reproductive organs. According to the same view the old adult phases are
+not obliterated but persist in a more or less modified form as larval
+stages. It is further supposed that as the life-history lengthens at one
+end by the addition of new adult phases, it is shortened at the other by
+the abbreviation of embryonic development and by the absorption of some
+of the early larval stages into the embryonic period; but on the whole
+the lengthening process has exceeded that of shortening, so that the
+whole life-history has, with the progress of evolution, become longer
+and more complicated.
+
+Now there can be no doubt that the life-history of organisms has been
+shortened in the way above suggested, for cases are known in which this
+can practically be seen to occur at the present day. But the process
+of lengthening by the creation of new stages at the other end of the
+life-cycle is more difficult to conceive and moreover there is no
+evidence for its having occurred. This, indeed, may have occurred, as
+is suggested below, but the evidence we have seems to indicate
+that evolutionary modification has proceeded by ALTERING and not by
+SUPERSEDING: that is to say that each stage in the life-history, as we
+see it to-day, has proceeded from a corresponding stage in a former era
+by the modification of that stage and not by the creation of a new one.
+Let me, at the risk of repetition, explain my meaning more fully by
+taking a concrete illustration. The mandibulo-hyoid cleft (spiracle)
+of the elasmobranch fishes, the lateral digits of the pig's foot, the
+hind-limbs of whales, the enlarged digit of the ostrich's foot
+are supposed to be organs which have been recently modified.
+This modification is not confined to the final adult stage of the
+life-history but characterises them throughout the whole of their
+development. A stage with a reduced spiracle does not proceed in
+development from a preceding stage in which the spiracle shows no
+reduction: it is reduced at its first appearance. The same statement may
+be made of organs which have entirely disappeared in the adult, such as
+bird's teeth and snake's fore-limbs: the adult stage in which they have
+disappeared is not preceded by embryonic stages in which the teeth and
+limbs or rudiments of them are present. In fact the evidence indicates
+that adult variations of any part are accompanied by precedent
+variations in the same direction in the embryo. The evidence seems to
+show, not that a stage is added on at the end of the life-history, but
+only that some of the stages in the life-history are modified. Indeed,
+on the wider view of development taken in this essay, a view which makes
+it coincident with life, one would not expect often to find, even if new
+stages are added in the course of evolution, that they are added at the
+end of the series when the organism has passed through its reproductive
+period. It is possible of course that new stages have been intercalated
+in the course of the life-history, though it is difficult to see
+how this has occurred. It is much more likely, if we may judge from
+available evidence, that every stage has had its counterpart in
+the ancestral form from which it has been derived by descent with
+modification. Just as the adult phase of the living form differs, owing
+to evolutionary modification, from the adult phase of the ancestor from
+which it has proceeded, so each larval phase will differ for the same
+reason from the corresponding larval phase in the life-history of the
+ancestor. Inasmuch as the organism is variable at every stage of its
+independent existence and is exposed to the action of natural selection
+there is no reason why it should escape modification at any stage.
+
+If there is any truth in these considerations it would seem to follow
+that at the dawn of life the life-cycle must have been, either in posse
+or in esse, at least as long as it is at the present time, and that
+the peculiarity of passing through a series of stages in which new
+characters are successively evolved is a primordial quality of living
+matter.
+
+Before leaving this part of the subject, it is necessary to touch upon
+another aspect of it. What are these variations in structure which
+succeed one another in the life-history of an organism? I am conscious
+that I am here on the threshold of a chamber which contains the clue to
+some of our difficulties, and that I cannot enter it. Looked at from
+one point of view they belong to the class of genetic variations, which
+depend upon the structure or constitution of the protoplasm; but instead
+of appearing in different zygotes (A zygote is a fertilised ovum, i.e. a
+new organism resulting from the fusion of an ovum and a spermatozoon.),
+they are present in the same zygote though at different times in its
+life-history. They are of the same order as the mutational variations
+of the modern biologist upon which the appearance of a new character
+depends. What is a genetic or mutational variation? It is a genetic
+character which was not present in either of the parents. But these
+"growth variations" were present in the parents, and in this they differ
+from mutational variations. But what are genetic characters? They are
+characters which must appear if any development occurs. They are usually
+contrasted with "acquired characters," using the expression "acquired
+character" in the Lamarckian sense. But strictly speaking they ARE
+acquired characters, for the zygote at first has none of the characters
+which it subsequently acquires, but only the power of acquiring them
+in response to the action of the environment. But the characters so
+acquired are not what we technically understand and what Lamarck meant
+by "acquired characters." They are genetic characters, as defined above.
+What then are Lamarck's "acquired characters"? They are variations in
+genetic characters caused in a particular way. There are, in fact,
+two kinds of variation in genetic characters depending on the mode
+of causation. Firstly, there are those variations consequent upon a
+variation in the constitution of the protoplasm of a particular zygote,
+and independent of the environment in which the organism develops,
+save in so far as this simply calls them forth: these are the so-called
+genetic or mutational variations. Secondly, there are those variations
+which occur in zygotes of similar germinal constitution and which are
+caused solely by differences in the environment to which the individuals
+are respectively exposed: these are the "acquired characters" of Lamarck
+and of authors generally. In consequence of this double sense in which
+the term "acquired characters" may be used, great confusion may and
+does occur. If the protoplasm be compared to a machine, and the external
+conditions to the hand that works the machine, then it may be said that,
+as the machine can only work in one way, it can only produce one kind
+of result (genetic character), but the particular form or quality
+(Lamarckian "acquired character") of the result will depend upon the
+hand that works the machine (environment), just as the quality of the
+sound produced by a fiddle depends entirely upon the hand which plays
+upon it. It would be improper to apply the term "mutation" to those
+genetic characters which are not new characters or new variants of old
+characters, but such genetic characters are of the same nature as
+those characters to which the term mutation has been applied. It may be
+noticed in passing that it is very questionable if the modern biologist
+has acted in the real interests of science in applying the term mutation
+in the sense in which he has applied it. The genetic characters of
+organisms come from one of two sources: either they are old characters
+and are due to the action of what we call inheritance or they are new
+and are due to what we call variation. If the term mutation is applied
+to the actual alteration of the machinery of the protoplasm, no
+objection can be felt to its use; but if it be applied, as it is, to the
+product of the action of the altered machine, viz. to the new genetic
+character, it leads to confusion. Inheritance is the persistence of the
+structure of the machine; characters are the products of the working of
+the machine; variation in genetic characters is due to the alteration
+(mutation) in the arrangement of the machinery, while variation in
+acquired characters (Lamarckian) is due to differences in the mode of
+working the machinery. The machinery when it starts (in the new zygote)
+has the power of grinding out certain results, which we call the
+characters of the organism. These appear at successive intervals
+of time, and the orderly manifestation of them is what we call the
+life-history of the organism. This brings us back to the question with
+which we started this discussion, viz. what is the relation of these
+variations in structure, which successively appear in an organism and
+constitute its life-history, to the mutational variations which appear
+in different organisms of the same brood or species. The question is
+brought home to us when we ask what is a bud-sport, such as a nectarine
+appearing on a peach-tree? From one point of view, it is simply a
+mutation appearing in asexual reproduction; from another it is one of
+these successional characters ("growth variations") which constitute
+the life-history of the zygote, for it appears in the same zygote which
+first produces a peach. Here our analogy of a machine which only works
+in one way seems to fail us, for these bud-sports do not appear in all
+parts of the organism, only in certain buds or parts of it, so that one
+part of the zygotic machine would appear to work differently to another.
+To discuss this question further would take us too far from our subject.
+Suffice it to say that we cannot answer it, any more than we can this
+further question of burning interest at the present day, viz. to
+what extent and in what manner is the machine itself altered by the
+particular way in which it is worked. In connection with this question
+we can only submit one consideration: the zygotic machine can, by
+its nature, only work once, so that any alteration in it can only be
+ascertained by studying the replicas of it which are produced in the
+reproductive organs.
+
+It is a peculiarity that the result which we call the ripening of the
+generative organs nearly always appears among the final products of the
+action of the zygotic machine. It is remarkable that this should be
+the case. What is the reason of it? The late appearance of functional
+reproductive organs is almost a universal law, and the explanation of it
+is suggested by expressing the law in another way, viz. that the machine
+is almost always so constituted that it ceases to work efficiently
+soon after the reproductive organs have sufficiently discharged their
+function. Why this should occur we cannot explain: it is an ultimate
+fact of nature, and cannot be included in any wider category. The
+period during which the reproductive organs can act may be short as
+in ephemerids or long as in man and trees, and there is no reason to
+suppose that their action damages the vital machinery, though sometimes,
+as in the case of annual plants (Metschnikoff), it may incidentally
+do so; but, long or short, the cessation of their actions is always
+a prelude to the end. When they and their action are impaired, the
+organism ceases to react with precision to the environment, and the
+organism as a whole undergoes retrogressive changes.
+
+It has been pointed out above that there is reason to believe that at
+the dawn of life the life-cycle was, EITHER IN ESSE OR IN POSSE, at
+least as long as it is at the present time. The qualification implied by
+the words in italics is necessary, for it is clearly possible that the
+external conditions then existing were not suitable for the production
+of all the stages of the potential life-history, and that what we
+call organic evolution has consisted in a gradual evolution of new
+environments to which the organism's innate capacity of change has
+enabled it to adapt itself. We have warrant for this possibility in the
+case of the Axolotl and in other similar cases of neoteny. And these
+cases further bring home to us the fact, to which I have already
+referred, that the full development of the functional reproductive
+organs is nearly always associated with the final stages of the
+life-history.
+
+On this view of the succession of characters in the life-history of
+organisms, how shall we explain the undoubted fact that the development
+of buds hardly ever presents any phenomena corresponding to the
+embryonic and larval changes? The reason is clearly this, that budding
+usually occurs after the embryonic stage is past; when the characters of
+embryonic life have been worked out by the machine. When it takes place
+at an early stage in embryonic life, as it does in cases of so-called
+embryonic fission, the product shows, either partly or entirely,
+phenomena similar to those of embryonic development. The only case known
+to me in which budding by the adult is accompanied by morphological
+features similar to those displayed by embryos is furnished by the
+budding of the medusiform spore-sacs of hydrozoon polyps. But this case
+is exceptional, for here we have to do with an attempt, which fails, to
+form a free-swimming organism, the medusa; and the vestiges which appear
+in the buds are the umbrella-cavity, marginal tentacles, circular canal,
+etc., of the medusa arrested in development.
+
+But the question still remains, are there no cases in which, as implied
+by the recapitulation theory, variations in any organ are confined to
+the period in which the organ is functional and do not affect it in the
+embryonic stages? The teeth of the whalebone whales may be cited as
+a case in which this is said to occur; but here the teeth are only
+imperfectly developed in the embryo and are soon absorbed. They have
+been affected by the change which has produced their disappearance in
+the adult, but not to complete extinction. Nor are they now likely to be
+extinguished, for having become exclusively embryonic they are largely
+protected from the action of natural selection. This consideration
+brings up a most important aspect of the question, so far as
+disappearing organs are concerned. Every organ is laid down at a certain
+period in the embryo and undergoes a certain course of growth until
+it obtains full functional development. When for any cause reduction
+begins, it is affected at all stages of its growth, unless it has
+functional importance in the larva, and in some cases its life is
+shortened at one or both ends. In cases, as in that of the whale's
+teeth, in which it entirely disappears in the adult, the latter part
+of its life is cut off; in others, the beginning of its life may
+be deferred. This happens, for instance, with the spiracle of many
+Elasmobranchs, which makes its appearance after the hyobranchial cleft,
+not before it as it should do, being anterior to it in position, and
+as it does in the Amniota in which it shows no reduction in size as
+compared with the other pharyngeal clefts. In those Elasmobranchs
+in which it is absent in the adult but present in the embryo (e.g.
+Carcharias) its life is shortened at both ends. Many more instances
+of organs, of which the beginning and end have been cut off, might be
+mentioned; e.g. the muscle-plate coelom of Aves, the primitive streak
+and the neurenteric canal of amniote blastoderms. In yet other cases in
+which the reduced organ is almost on the verge of disappearance, it
+may appear for a moment and disappear more than once in the course of
+development. As an instance of this striking phenomenon I may mention
+the neurenteric canal of avine embryos, and the anterior neuropore of
+Ascidians. Lastly the reduced organ may disappear in the developing
+stages before it does so in the adult. As an instance of this may be
+mentioned the mandibular palp of those Crustacea with zoaea larvae. This
+structure disappears in the larva only to reappear in a reduced form in
+later stages. In all these cases we are dealing with an organ which, we
+imagine, attained a fuller functional development at some previous stage
+in race-history, but in most of them we have no proof that it did so. It
+may be, and the possibility must not be lost sight of, that these organs
+never were anything else than functionless and that though they have
+been got rid of in the adult by elimination in the course of time, they
+have been able to persist in embryonic stages which are protected from
+the full action of natural selection. There is no reason to suppose that
+living matter at its first appearance differed from non-living matter
+in possessing only properties conducive to its well-being and prolonged
+existence. No one thinks that the properties of the various forms of
+inorganic matter are all strictly related to external conditions.
+Of what use to the diamond is its high specific gravity and high
+refrangibility, and to gold of its yellow colour and great weight? These
+substances continue to exist in virtue of other properties than these.
+It is impossible to suppose that the properties of living matter at
+its first appearance were all useful to it, for even now after aeons of
+elimination we find that it possesses many useless organs and that
+many of its relations to the external world are capable of considerable
+improvement.
+
+In writing this essay I have purposely refrained from taking a definite
+position with regard to the problems touched. My desire has been
+to write a chapter showing the influence of Darwin's work so far as
+Embryology is concerned, and the various points which come up for
+consideration in discussing his views. Darwin was the last man who would
+have claimed finality for any of his doctrines, but he might fairly have
+claimed to have set going a process of intellectual fermentation which
+is still very far from completion.
+
+
+
+
+XI. THE PALAEONTOLOGICAL RECORD. By W.B. Scott.
+
+Professor of Geology in the University of Princeton, U.S.A.
+
+
+I. ANIMALS.
+
+To no branch of science did the publication of "The Origin of Species"
+prove to be a more vivifying and transforming influence than to
+Palaeontology. This science had suffered, and to some extent, still
+suffers from its rather anomalous position between geology and biology,
+each of which makes claim to its territory, and it was held in strict
+bondage to the Linnean and Cuvierian dogma that species were immutable
+entities. There is, however, reason to maintain that this strict bondage
+to a dogma now abandoned, was not without its good side, and served the
+purpose of keeping the infant science in leading-strings until it was
+able to walk alone, and preventing a flood of premature generalisations
+and speculations.
+
+As Zittel has said: "Two directions were from the first apparent
+in palaeontological research--a stratigraphical and a biological.
+Stratigraphers wished from palaeontology mainly confirmation regarding
+the true order or relative age of zones of rock-deposits in the field.
+Biologists had, theoretically at least, the more genuine interest in
+fossil organisms as individual forms of life." (Zittel, "History of
+Geology and Palaeontology", page 363, London, 1901.) The geological
+or stratigraphical direction of the science was given by the work of
+William Smith, "the father of historical geology," in the closing decade
+of the eighteenth century. Smith was the first to make a systematic use
+of fossils in determining the order of succession of the rocks which
+make up the accessible crust of the earth, and this use has continued,
+without essential change, to the present day. It is true that the
+theory of evolution has greatly modified our conceptions concerning the
+introduction of new species and the manner in which palaeontological
+data are to be interpreted in terms of stratigraphy, but, broadly
+speaking, the method remains fundamentally the same as that introduced
+by Smith.
+
+The biological direction of palaeontology was due to Cuvier and his
+associates, who first showed that fossils were not merely varieties
+of existing organisms, but belonged to extinct species and genera,
+an altogether revolutionary conception, which startled the scientific
+world. Cuvier made careful studies, especially of fossil vertebrates,
+from the standpoint of zoology and was thus the founder of palaeontology
+as a biological science. His great work on "Ossements Fossiles" (Paris,
+1821) has never been surpassed as a masterpiece of the comparative
+method of anatomical investigation, and has furnished to the
+palaeontologist the indispensable implements of research.
+
+On the other hand, Cuvier's theoretical views regarding the history
+of the earth and its successive faunas and floras are such as no one
+believes to-day. He held that the earth had been repeatedly devastated
+by great cataclysms, which destroyed every living thing, necessitating
+an entirely new creation, thus regarding the geological periods as
+sharply demarcated and strictly contemporaneous for the whole earth,
+and each species of animal and plant as confined to a single period.
+Cuvier's immense authority and his commanding personality dominated
+scientific thought for more than a generation and marked out the line
+which the development of palaeontology was to follow. The work was
+enthusiastically taken up by many very able men in the various European
+countries and in the United States, but, controlled as it was by the
+belief in the fixity of species, it remained almost entirely descriptive
+and consisted in the description and classification of the different
+groups of fossil organisms. As already intimated, this narrowness of
+view had its compensations, for it deferred generalisations until some
+adequate foundations for these had been laid.
+
+Dominant as it was, Cuvier's authority was slowly undermined by the
+progress of knowledge and the way was prepared for the introduction of
+more rational conceptions. The theory of "Catastrophism" was attacked by
+several geologists, most effectively by Sir Charles Lyell, who greatly
+amplified the principles enunciated by Hutton and Playfair in the
+preceding century, and inaugurated a new era in geology. Lyell's
+uniformitarian views of the earth's history and of the agencies which
+had wrought its changes, had undoubted effect in educating men's minds
+for the acceptance of essentially similar views regarding the organic
+world. In palaeontology too the doctrine of the immutability of species,
+though vehemently maintained and reasserted, was gradually weakening. In
+reviewing long series of fossils, relations were observed which pointed
+to genetic connections and yet were interpreted as purely ideal.
+Agassiz, for example, who never accepted the evolutionary theory, drew
+attention to facts which could be satisfactorily interpreted only in
+terms of that theory. Among the fossils he indicated "progressive,"
+"synthetic," "prophetic," and "embryonic" types, and pointed out the
+parallelism which obtains between the geological succession of ancient
+animals and the ontogenetic development of recent forms. In Darwin's
+words: "This view accords admirably well with our theory." ("Origin of
+Species" (6th edition), page 310.) Of similar import were Owen's views
+on "generalised types" and "archetypes."
+
+The appearance of "The Origin of Species" in 1859 revolutionised all
+the biological sciences. From the very nature of the case, Darwin
+was compelled to give careful consideration to the palaeontological
+evidence; indeed, it was the palaeontology and modern distribution of
+animals in South America which first led him to reflect upon the great
+problem. In his own words: "I had been deeply impressed by discovering
+in the Pampean formation great fossil animals covered with armour
+like that on the existing armadillos; secondly, by the manner in which
+closely allied animals replace one another in proceeding southward over
+the Continent; and thirdly, by the South American character of most of
+the productions of the Galapagos archipelago, and more especially by
+the manner in which they differ slightly on each island of the group."
+("Life and Letters of Charles Darwin", I. page 82.) In the famous tenth
+and eleventh chapters of the "Origin", the palaeontological evidence
+is examined at length and the imperfection of the geological record is
+strongly emphasised. The conclusion is reached, that, in view of this
+extreme imperfection, palaeontology could not reasonably be expected to
+yield complete and convincing proof of the evolutionary theory. "I look
+at the geological record as a history of the world imperfectly kept,
+and written in a changing dialect; of this history we possess the last
+volume alone, relating only to two or three countries. Of this volume,
+only here and there a short chapter has been preserved; and of each
+page, only here and there a few lines." ("Origin of Species", page 289.)
+Yet, aside from these inevitable difficulties, he concludes, that "the
+other great leading facts in palaeontology agree admirably with the
+theory of descent with modification through variation and natural
+selection." (Ibid. page 313.)
+
+Darwin's theory gave an entirely new significance and importance to
+palaeontology. Cuvier's conception of the science had been a limited,
+though a lofty one. "How glorious it would be if we could arrange the
+organised products of the universe in their chronological order!... The
+chronological succession of organised forms, the exact determination
+of those types which appeared first, the simultaneous origin of certain
+species and their gradual decay, would perhaps teach us as much
+about the mysteries of organisation as we can possibly learn through
+experiments with living organisms." (Zittel op. cit. page 140.) This,
+however, was rather the expression of a hope for the distant future than
+an account of what was attainable, and in practice the science remained
+almost purely descriptive, until Darwin gave it a new standpoint, new
+problems and an altogether fresh interest and charm. The revolution
+thus accomplished is comparable only to that produced by the Copernican
+astronomy.
+
+From the first it was obvious that one of the most searching tests
+of the evolutionary theory would be given by the advance of
+palaeontological discovery. However imperfect the geological record
+might be, its ascertained facts would necessarily be consistent, under
+any reasonable interpretation, with the demands of a true theory;
+otherwise the theory would eventually be overwhelmed by the mass of
+irreconcilable data. A very great stimulus was thus given to geological
+investigation and to the exploration of new lands. In the last forty
+years, the examination of North and South America, of Africa and Asia
+has brought to light many chapters in the history of life, which are
+astonishingly full and complete. The flood of new material continues to
+accumulate at such a rate that it is impossible to keep abreast of it,
+and the very wealth of the collections is a source of difficulty and
+embarrassment. In modern palaeontology phylogenetic questions and
+problems occupy a foremost place and, as a result of the labours of many
+eminent investigators in many lands, it may be said that this science
+has proved to be one of the most solid supports of Darwin's theory.
+True, there are very many unsolved problems, and the discouraged worker
+is often tempted to believe that the fossils raise more questions than
+they answer. Yet, on the other hand, the whole trend of the evidence
+is so strongly in favour of the evolutionary doctrine, that no other
+interpretation seems at all rational.
+
+To present any adequate account of the palaeontological record from the
+evolutionary standpoint, would require a large volume and a singularly
+unequal, broken and disjointed history it would be. Here the record is
+scanty, interrupted, even unintelligible, while there it is crowded with
+embarrassing wealth of material, but too often these full chapters are
+separated by such stretches of unrecorded time, that it is difficult to
+connect them. It will be more profitable to present a few illustrative
+examples than to attempt an outline of the whole history.
+
+At the outset, the reader should be cautioned not to expect too
+much, for the task of determining phylogenies fairly bristles with
+difficulties and encounters many unanswered questions. Even when the
+evidence seems to be as copious and as complete as could be wished,
+different observers will put different interpretations upon it, as in
+the notorious case of the Steinheim shells. (In the Miocene beds of
+Steinheim, Wurtemberg, occur countless fresh-water shells, which show
+numerous lines of modification, but these have been very differently
+interpreted by different writers.) The ludicrous discrepances which
+often appear between the phylogenetic "trees" of various writers have
+cast an undue discredit upon the science and have led many zoologists
+to ignore palaeontology altogether as unworthy of serious attention. One
+principal cause of these discrepant and often contradictory results is
+our ignorance concerning the exact modes of developmental change.
+What one writer postulates as almost axiomatic, another will reject as
+impossible and absurd. Few will be found to agree as to how far a given
+resemblance is offset by a given unlikeness, and so long as the question
+is one of weighing evidence and balancing probabilities, complete
+harmony is not to be looked for. These formidable difficulties confront
+us even in attempting to work out from abundant material a brief chapter
+in the phylogenetic history of some small and clearly limited group,
+and they become disproportionately greater, when we extend our view over
+vast periods of time and undertake to determine the mutual relationships
+of classes and types. If the evidence were complete and available, we
+should hardly be able to unravel its infinite complexity, or to find
+a clue through the mazes of the labyrinth. "Our ideas of the course of
+descent must of necessity be diagrammatic." (D.H. Scott, "Studies in
+Fossil Botany", page 524. London, 1900.)
+
+Some of the most complete and convincing examples of descent with
+modification are to be found among the mammals, and nowhere more
+abundantly than in North America, where the series of continental
+formations, running through the whole Tertiary period, is remarkably
+full. Most of these formations contain a marvellous wealth of mammalian
+remains and in an unusual state of preservation. The oldest Eocene
+(Paleocene) has yielded a mammalian fauna which is still of prevailingly
+Mesozoic character, and contains but few forms which can be regarded
+as ancestral to those of later times. The succeeding fauna of the lower
+Eocene proper (Wasatch stage) is radically different and, while a few
+forms continue over from the Paleocene, the majority are evidently
+recent immigrants from some region not yet identified. From the Wasatch
+onward, the development of many phyla may be traced in almost unbroken
+continuity, though from time to time the record is somewhat obscured by
+migrations from the Old World and South America. As a rule, however, it
+is easy to distinguish between the immigrant and the indigenous elements
+of the fauna.
+
+From their gregarious habits and individual abundance, the history of
+many hoofed animals is preserved with especial clearness. So well known
+as to have become a commonplace, is the phylogeny of the horses, which,
+contrary to all that would have been expected, ran the greater part of
+its course in North America. So far as it has yet been traced, the line
+begins in the lower Eocene with the genus Eohippus, a little creature
+not much larger than a cat, which has a short neck, relatively short
+limbs, and in particular, short feet, with four functional digits and
+a splint-like rudiment in the fore-foot, three functional digits and
+a rudiment in the hind-foot. The forearm bones (ulna and radius) are
+complete and separate, as are also the bones of the lower leg (fibula
+and tibia). The skull has a short face, with the orbit, or eye-socket,
+incompletely enclosed with bone, and the brain-case is slender and
+of small capacity. The teeth are short-crowned, the incisors without
+"mark," or enamel pit, on the cutting edge; the premolars are all
+smaller and simpler than the molars. The pattern of the upper molars is
+so entirely different from that seen in the modern horses that, without
+the intermediate connecting steps, no one would have ventured to derive
+the later from the earlier plan. This pattern is quadritubercular, with
+four principal, conical cusps arranged in two transverse pairs, forming
+a square, and two minute cuspules between each transverse pair, a tooth
+which is much more pig-like than horse-like. In the lower molars the
+cusps have already united to form two crescents, one behind the other,
+forming a pattern which is extremely common in the early representatives
+of many different families, both of the Perissodactyla and the
+Artiodactyla. In spite of the manifold differences in all parts of the
+skeleton between Eohippus and the recent horses, the former has stamped
+upon it an equine character which is unmistakable, though it can hardly
+be expressed in words.
+
+Each one of the different Eocene and Oligocene horizons has its
+characteristic genus of horses, showing a slow, steady progress in a
+definite direction, all parts of the structure participating in the
+advance. It is not necessary to follow each of these successive steps
+of change, but it should be emphasised that the changes are gradual and
+uninterrupted. The genus Mesohippus, of the middle Oligocene, may be
+selected as a kind of half-way stage in the long progression. Comparing
+Mesohippus with Eohippus, we observe that the former is much larger,
+some species attaining the size of a sheep, and has a relatively longer
+neck, longer limbs and much more elongate feet, which are tridactyl, and
+the middle toe is so enlarged that it bears most of the weight, while
+the lateral digits are very much more slender. The fore-arm bones have
+begun to co-ossify and the ulna is greatly reduced, while the fibula,
+though still complete, is hardly more than a thread of bone. The skull
+has a longer face and a nearly enclosed orbit, and the brain-case is
+fuller and more capacious, the internal cast of which shows that the
+brain was richly convoluted. The teeth are still very short-crowned,
+but the upper incisors plainly show the beginning of the "mark"; the
+premolars have assumed the molar form, and the upper molars, though
+plainly derived from those of Eohippus, have made a long stride toward
+the horse pattern, in that the separate cusps have united to form a
+continuous outer wall and two transverse crests.
+
+In the lower Miocene the interesting genus Desmatippus shows a further
+advance in the development of the teeth, which are beginning to assume
+the long-crowned shape, delaying the formation of roots; a thin layer
+of cement covers the crowns, and the transverse crests of the upper
+grinding teeth display an incipient degree of their modern complexity.
+This tooth-pattern is strictly intermediate between the recent type
+and the ancient type seen in Mesohippus and its predecessors. The
+upper Miocene genera, Protohippus and Hipparion are, to all intents and
+purposes, modern in character, but their smaller size, tridactyl feet
+and somewhat shorter-crowned teeth are reminiscences of their ancestry.
+
+From time to time, when a land-connection between North America and
+Eurasia was established, some of the successive equine genera migrated
+to the Old World, but they do not seem to have gained a permanent
+footing there until the end of the Miocene or beginning of the Pliocene,
+eventually diversifying into the horses, asses, and zebras of Africa,
+Asia and Europe. At about the same period, the family extended its range
+to South America and there gave rise to a number of species and genera,
+some of them extremely peculiar. For some unknown reason, all the horse
+tribe had become extinct in the western hemisphere before the European
+discovery, but not until after the native race of man had peopled the
+continents.
+
+In addition to the main stem of equine descent, briefly considered
+in the foregoing paragraphs, several side-branches were given off at
+successive levels of the stem. Most of these branches were short-lived,
+but some of them flourished for a considerable period and ramified into
+many species.
+
+Apparently related to the horses and derived from the same root-stock is
+the family of the Palaeotheres, confined to the Eocene and Oligocene of
+Europe, dying out without descendants. In the earlier attempts to work
+out the history of the horses, as in the famous essay of Kowalevsky
+("Sur l'Anchitherium aurelianense Cuv. et sur l'histoire paleontologique
+des Chevaux", "Mem. de l'Acad. Imp. des Sc. de St Petersbourg", XX. no.
+5, 1873.), the Palaeotheres were placed in the direct line, because
+the number of adequately known Eocene mammals was then so small, that
+Cuvier's types were forced into various incongruous positions, to serve
+as ancestors for unrelated series.
+
+The American family of the Titanotheres may also be distantly related
+to the horses, but passed through an entirely different course of
+development. From the lower Eocene to the lower sub-stage of the middle
+Oligocene the series is complete, beginning with small and rather
+lightly built animals. Gradually the stature and massiveness increase,
+a transverse pair of nasal horns make their appearance and, as
+these increase in size, the canine tusks and incisors diminish
+correspondingly. Already in the oldest known genus the number of digits
+had been reduced to four in the fore-foot and three in the hind, but
+there the reduction stops, for the increasing body-weight made necessary
+the development of broad and heavy feet. The final members of the
+series comprise only large, almost elephantine animals, with immensely
+developed and very various nasal horns, huge and massive heads, and
+altogether a grotesque appearance. The growth of the brain did not
+at all keep pace with the increase of the head and body, and the
+ludicrously small brain may will have been one of the factors which
+determined the startlingly sudden disappearance and extinction of the
+group.
+
+Less completely known, but of unusual interest, is the genealogy of the
+rhinoceros family, which probably, though not certainly, was likewise
+of American origin. The group in North America at least, comprised three
+divisions, or sub-families, of very different proportions, appearance
+and habits, representing three divergent lines from the same stem.
+Though the relationship between the three lines seems hardly open
+to question, yet the form ancestral to all of them has not yet been
+identified. This is because of our still very incomplete knowledge
+of several perissodactyl genera of the Eocene, any one of which may
+eventually prove to be the ancestor sought for.
+
+The first sub-family is the entirely extinct group of Hyracodonts, which
+may be traced in successive modifications through the upper Eocene,
+lower and middle Oligocene, then disappearing altogether. As yet, the
+hyracodonts have been found only in North America, and the last genus of
+the series, Hyracodon, was a cursorial animal. Very briefly stated,
+the modifications consist in a gradual increase in size, with greater
+slenderness of proportions, accompanied by elongation of the neck,
+limbs, and feet, which become tridactyl and very narrow. The grinding
+teeth have assumed the rhinoceros-like pattern and the premolars
+resemble the molars in form; on the other hand, the front teeth,
+incisors and canines, have become very small and are useless as weapons.
+As the animal had no horns, it was quite defenceless and must have found
+its safety in its swift running, for Hyracodon displays many superficial
+resemblances to the contemporary Oligocene horses, and was evidently
+adapted for speed. It may well have been the competition of the horses
+which led to the extinction of these cursorial rhinoceroses.
+
+The second sub-family, that of the Amynodonts, followed a totally
+different course of development, becoming short-legged and short-footed,
+massive animals, the proportions of which suggest aquatic habits; they
+retained four digits in the front foot. The animal was well provided
+with weapons in the large canine tusks, but was without horns. Some
+members of this group extended their range to the Old World, but they
+all died out in the middle Oligocene, leaving no successors.
+
+The sub-family of the true rhinoceroses cannot yet be certainly traced
+farther back than to the base of the middle Oligocene, though some
+fragmentary remains found in the lower Oligocene are probably also
+referable to it. The most ancient and most primitive member of
+this series yet discovered, the genus Trigonias, is unmistakably a
+rhinoceros, yet much less massive, having more the proportions of a
+tapir; it had four toes in the front foot, three in the hind, and had a
+full complement of teeth, except for the lower canines, though the upper
+canines are about to disappear, and the peculiar modification of the
+incisors, characteristic of the true rhinoceroses, is already apparent;
+the skull is hornless. Representatives of this sub-family continue
+through the Oligocene and Miocene of North America, becoming rare and
+localised in the Pliocene and then disappearing altogether. In the Old
+World, on the other hand, where the line appeared almost as early as it
+did in America, this group underwent a great expansion and ramification,
+giving rise not only to the Asiatic and African forms, but also to
+several extinct series.
+
+Turning now to the Artiodactyla, we find still another group of mammals,
+that of the camels and llamas, which has long vanished from North
+America, yet took its rise and ran the greater part of its course in
+that continent. From the lower Eocene onward the history of this series
+is substantially complete, though much remains to be learned concerning
+the earlier members of the family. The story is very like that of the
+horses, to which in many respects it runs curiously parallel. Beginning
+with very small, five-toed animals, we observe in the successive genera
+a gradual transformation in all parts of the skeleton, an elongation of
+the neck, limbs and feet, a reduction of the digits from five to two,
+and eventually the coalescence of the remaining two digits into a
+"cannon-bone." The grinding teeth, by equally gradual steps, take on
+the ruminant pattern. In the upper Miocene the line divides into the two
+branches of the camels and llamas, the former migrating to Eurasia
+and the latter to South America, though representatives of both lines
+persisted in North America until a very late period. Interesting
+side-branches of this line have also been found, one of which ended in
+the upper Miocene in animals which had almost the proportions of the
+giraffes and must have resembled them in appearance.
+
+The American Tertiary has yielded several other groups of ruminant-like
+animals, some of which form beautifully complete evolutionary series,
+but space forbids more than this passing mention of them.
+
+It was in Europe that the Artiodactyla had their principal development,
+and the upper Eocene, Oligocene and Miocene are crowded with such an
+overwhelming number and variety of forms that it is hardly possible to
+marshal them in orderly array and determine their mutual relationships.
+Yet in this chaotic exuberance of life, certain important facts stand
+out clearly, among these none is of greater interest and importance than
+the genealogy of the true Ruminants, or Pecora, which may be traced from
+the upper Eocene onward. The steps of modification and change are very
+similar to those through which the camel phylum passed in North America,
+but it is instructive to note that, despite their many resemblances, the
+two series can be connected only in their far distant beginnings. The
+pecoran stock became vastly more expanded and diversified than did
+the camel line and was evidently more plastic and adaptable, spreading
+eventually over all the continents except Australia, and forming to-day
+one of the dominant types of mammals, while the camels are on the
+decline and not far from extinction. The Pecora successively ramified
+into the deer, antelopes, sheep, goats and oxen, and did not reach
+North America till the Miocene, when they were already far advanced in
+specialisation. To this invasion of the Pecora, or true ruminants, it
+seems probable that the decline and eventual disappearance of the camels
+is to be ascribed.
+
+Recent discoveries in Egypt have thrown much light upon a problem which
+long baffled the palaeontologist, namely, the origin of the elephants.
+(C.W. Andrews, "On the Evolution of the Proboscidea", "Phil. Trans. Roy.
+Soc." London, Vol. 196, 1904, page 99.) Early representatives of this
+order, Mastodons, had appeared almost simultaneously (in the geological
+sense of that word) in the upper Miocene of Europe and North America,
+but in neither continent was any more ancient type known which
+could plausibly be regarded as ancestral to them. Evidently, these
+problematical animals had reached the northern continents by migrating
+from some other region, but no one could say where that region lay. The
+Eocene and Oligocene beds of the Fayoum show us that the region sought
+for is Africa, and that the elephants form just such a series of gradual
+modifications as we have found among other hoofed animals. The later
+steps of the transformation, by which the mastodons lost their lower
+tusks, and their relatively small and simple grinding teeth acquired the
+great size and highly complex structure of the true elephants, may be
+followed in the uppermost Miocene and Pliocene fossils of India and
+southern Europe.
+
+Egypt has also of late furnished some very welcome material which
+contributes to the solution of another unsolved problem which had quite
+eluded research, the origin of the whales. The toothed-whales may be
+traced back in several more or less parallel lines as far as the
+lower Miocene, but their predecessors in the Oligocene are still so
+incompletely known that safe conclusions can hardly be drawn from
+them. In the middle Eocene of Egypt, however, has been found a
+small, whale-like animal (Protocetus), which shows what the ancestral
+toothed-whale was like, and at the same time seems to connect these
+thoroughly marine mammals with land-animals. Though already entirely
+adapted to an aquatic mode of life, the teeth, skull and backbone of
+Protocetus display so many differences from those of the later
+whales and so many approximations to those of primitive, carnivorous
+land-mammals, as, in a large degree, to bridge over the gap between the
+two groups. Thus one of the most puzzling of palaeontological questions
+is in a fair way to receive a satisfactory answer. The origin of the
+whalebone-whales and their relations to the toothed-whales cannot yet be
+determined, since the necessary fossils have not been discovered.
+
+Among the carnivorous mammals, phylogenetic series are not so clear and
+distinct as among the hoofed animals, chiefly because the carnivores are
+individually much less abundant, and well-preserved skeletons are among
+the prizes of the collector. Nevertheless, much has already been learned
+concerning the mutual relations of the carnivorous families, and several
+phylogenetic series, notably that of the dogs, are quite complete. It
+has been made extremely probable that the primitive dogs of the Eocene
+represent the central stock, from which nearly or quite all the other
+families branched off, though the origin and descent of the cats have
+not yet been determined.
+
+It should be clearly understood that the foregoing account of mammalian
+descent is merely a selection of a few representative cases and might be
+almost indefinitely extended. Nothing has been said, for example, of
+the wonderful museum of ancient mammalian life which is entombed in the
+rocks of South America, especially of Patagonia, and which opens a
+world so entirely different from that of the northern continents,
+yet exemplifying the same laws of "descent with modification." Very
+beautiful phylogenetic series have already been established among these
+most interesting and marvellously preserved fossils, but lack of space
+forbids a consideration of them.
+
+The origin of the mammalia, as a class, offers a problem of which
+palaeontology can as yet present no definitive solution. Many
+morphologists regard the early amphibia as the ancestral group from
+which the mammals were derived, while most palaeontologists believe
+that the mammals are descended from the reptiles. The most ancient known
+mammals, those from the upper Triassic of Europe and North America, are
+so extremely rare and so very imperfectly known, that they give little
+help in determining the descent of the class, but, on the other
+hand, certain reptilian orders of the Permian period, especially
+well represented in South Africa, display so many and such close
+approximations to mammalian structure, as strongly to suggest a genetic
+relationship. It is difficult to believe that all those likenesses
+should have been independently acquired and are without phylogenetic
+significance.
+
+Birds are comparatively rare as fossils and we should therefore look in
+vain among them for any such long and closely knit series as the
+mammals display in abundance. Nevertheless, a few extremely fortunate
+discoveries have made it practically certain that birds are descended
+from reptiles, of which they represent a highly specialised branch. The
+most ancient representative of this class is the extraordinary genus
+Archaeopteryx from the upper Jurassic of Bavaria, which, though
+an unmistakable bird, retains so many reptilian structures and
+characteristics as to make its derivation plain. Not to linger over
+anatomical minutiae, it may suffice to mention the absence of a horny
+beak, which is replaced by numerous true teeth, and the long lizard-like
+tail, which is made up of numerous distinct vertebrae, each with a pair
+of quill-like feathers attached to it. Birds with teeth are also found
+in the Cretaceous, though in most other respects the birds of that
+period had attained a substantially modern structure. Concerning
+the interrelations of the various orders and families of birds,
+palaeontology has as yet little to tell us.
+
+The life of the Mesozoic era was characterised by an astonishing number
+and variety of reptiles, which were adapted to every mode of life,
+and dominated the air, the sea and the land, and many of which were
+of colossal proportions. Owing to the conditions of preservation which
+obtained during the Mesozoic period, the history of the reptiles is a
+broken and interrupted one, so that we can make out many short series,
+rather than any one of considerable length. While the relations of
+several reptilian orders can be satisfactorily determined, others still
+baffle us entirely, making their first known appearance in a fully
+differentiated state. We can trace the descent of the sea-dragons, the
+Ichthyosaurs and Plesiosaurs, from terrestrial ancestors, but the most
+ancient turtles yet discovered show us no closer approximation to any
+other order than do the recent turtles; and the oldest known Pterosaurs,
+the flying dragons of the Jurassic, are already fully differentiated.
+There is, however, no ground for discouragement in this, for the
+progress of discovery has been so rapid of late years, and our knowledge
+of Mesozoic life has increased with such leaps and bounds, that there is
+every reason to expect a solution of many of the outstanding problems in
+the near future.
+
+Passing over the lower vertebrates, for lack of space to give them
+any adequate consideration, we may briefly take up the record of
+invertebrate life. From the overwhelming mass of material it is
+difficult to make a representative selection and even more difficult
+to state the facts intelligibly without the use of unduly technical
+language and without the aid of illustrations.
+
+Several groups of the Mollusca, or shell-fish, yield very full and
+convincing evidence of their descent from earlier and simpler forms,
+and of these none is of greater interest than the Ammonites, an extinct
+order of the cephalopoda. The nearest living ally of the ammonites is
+the pearly nautilus, the other existing cephalopods, such as the squids,
+cuttle-fish, octopus, etc., are much more distantly related. Like the
+nautilus, the ammonites all possess a coiled and chambered shell, but
+their especial characteristic is the complexity of the "sutures." By
+sutures is meant the edges of the transverse partitions, or septa, where
+these join the shell-wall, and their complexity in the fully developed
+genera is extraordinary, forming patterns like the most elaborate
+oak-leaf embroidery, while in the nautiloids the sutures form simple
+curves. In the rocks of the Mesozoic era, wherever conditions of
+preservation are favourable, these beautiful shells are stored in
+countless multitudes, of an incredible variety of form, size and
+ornamentation, as is shown by the fact that nearly 5000 species have
+already been described. The ammonites are particularly well adapted for
+phylogenetic studies, because, by removing the successive whorls of the
+coiled shell, the individual development may be followed back in inverse
+order, to the microscopic "protoconch," or embryonic shell, which lies
+concealed in the middle of the coil. Thus the valuable aid of embryology
+is obtained in determining relationships.
+
+The descent of the ammonites, taken as a group, is simple and clear;
+they arose as a branch of the nautiloids in the lower Devonian, the
+shells known as goniatites having zigzag, angulated sutures. Late in
+the succeeding Carboniferous period appear shells with a truly ammonoid
+complexity of sutures, and in the Permian their number and variety
+cause them to form a striking element of the marine faunas. It is in the
+Mesozoic era, however, that these shells attain their full development;
+increasing enormously in the Triassic, they culminate in the Jurassic
+in the number of families, genera and species, in the complexity of
+the sutures, and in the variety of shell-ornamentation. A slow decline
+begins in the Cretaceous, ending in the complete extinction of the whole
+group at the end of that period. As a final phase in the history of the
+ammonites, there appear many so-called "abnormal" genera, in which the
+shell is irregularly coiled, or more or less uncoiled, in some forms
+becoming actually straight. It is interesting to observe that some of
+these genera are not natural groups, but are "polyphyletic," i.e.
+are each derived from several distinct ancestral genera, which have
+undergone a similar kind of degeneration.
+
+In the huge assembly of ammonites it is not yet possible to arrange all
+the forms in a truly natural classification, which shall express the
+various interrelations of the genera, yet several beautiful series have
+already been determined. In these series the individual development
+of the later general shows transitory stages which are permanent in
+antecedent genera. To give a mere catalogue of names without figures
+would not make these series more intelligible.
+
+The Brachiopoda, or "lamp-shells," are a phylum of which comparatively
+few survive to the present day; their shells have a superficial likeness
+to those of the bivalved Mollusca, but are not homologous with the
+latter, and the phylum is really very distinct from the molluscs. While
+greatly reduced now, these animals were incredibly abundant throughout
+the Palaeozoic era, great masses of limestone being often composed
+almost exclusively of their shells, and their variety is in keeping with
+their individual abundance. As in the case of the ammonites, the problem
+is to arrange this great multitude of forms in an orderly array that
+shall express the ramifications of the group according to a genetic
+system. For many brachiopods, both recent and fossil, the individual
+development, or ontogeny, has been worked out and has proved to be
+of great assistance in the problems of classification and phylogeny.
+Already very encouraging progress has been made in the solution of these
+problems. All brachiopods form first a tiny, embryonic shell, called
+the protegulum, which is believed to represent the ancestral form of the
+whole group, and in the more advanced genera the developmental stages
+clearly indicate the ancestral genera of the series, the succession
+of adult forms in time corresponding to the order of the ontogenetic
+stages. The transformation of the delicate calcareous supports of the
+arms, often exquisitely preserved, are extremely interesting. Many of
+the Palaeozoic genera had these supports coiled like a pair of spiral
+springs, and it has been shown that these genera were derived from types
+in which the supports were simply shelly loops.
+
+The long extinct class of crustacea known as the Trilobites are likewise
+very favourable subjects for phylogenetic studies. So far as the known
+record can inform us, the trilobites are exclusively Palaeozoic in
+distribution, but their course must have begun long before that era, as
+is shown by the number of distinct types among the genera of the
+lower Cambrian. The group reached the acme of abundance and relative
+importance in the Cambrian and Ordovician; then followed a long, slow
+decline, ending in complete and final disappearance before the end of
+the Permian. The newly-hatched and tiny trilobite larva, known as
+the protaspis, is very near to the primitive larval form of all the
+crustacea. By the aid of the correlated ontogenetic stages and the
+succession of the adult forms in the rocks, many phylogenetic series
+have been established and a basis for the natural arrangement of the
+whole class has been laid.
+
+Very instructive series may also be observed among the Echinoderms and,
+what is very rare, we are able in this sub-kingdom to demonstrate the
+derivation of one class from another. Indeed, there is much reason to
+believe that the extinct class Cystidea of the Cambrian is the ancestral
+group, from which all the other Echinoderms, star-fishes, brittle-stars,
+sea-urchins, feather-stars, etc., are descended.
+
+The foregoing sketch of the palaeontological record is, of necessity,
+extremely meagre, and does not represent even an outline of the
+evidence, but merely a few illustrative examples, selected almost
+at random from an immense body of material. However, it will perhaps
+suffice to show that the geological record is not so hopelessly
+incomplete as Darwin believed it to be. Since "The Origin of Species"
+was written, our knowledge of that record has been enormously extended
+and we now possess, no complete volumes, it is true, but some remarkably
+full and illuminating chapters. The main significance of the whole lies
+in the fact, that JUST IN PROPORTION TO THE COMPLETENESS OF THE RECORD
+IS THE UNEQUIVOCAL CHARACTER OF ITS TESTIMONY TO THE TRUTH OF THE
+EVOLUTIONARY THEORY.
+
+The test of a true, as distinguished from a false, theory is the manner
+in which newly discovered and unanticipated facts arrange themselves
+under it. No more striking illustration of this can be found than in the
+contrasted fates of Cuvier's theory and of that of Darwin. Even before
+Cuvier's death his views had been undermined and the progress of
+discovery soon laid them in irreparable ruin, while the activity of
+half-a-century in many different lines of inquiry has established the
+theory of evolution upon a foundation of ever growing solidity. It is
+Darwin's imperishable glory that he prescribed the lines along which all
+the biological sciences were to advance to conquests not dreamed of when
+he wrote.
+
+
+
+
+XII. THE PALAEONTOLOGICAL RECORD. By D.H. Scott, F.R.S.
+
+President of the Linnean Society.
+
+
+II. PLANTS.
+
+There are several points of view from which the subject of the present
+essay may be regarded. We may consider the fossil record of plants
+in its bearing: I. on the truth of the doctrine of Evolution; II. on
+Phylogeny, or the course of Evolution; III. on the theory of Natural
+Selection. The remarks which follow, illustrating certain aspects only
+of an extensive subject, may conveniently be grouped under these three
+headings.
+
+I. THE TRUTH OF EVOLUTION.
+
+When "The Origin of Species" was written, it was necessary to show that
+the Geological Record was favourable to, or at least consistent with,
+the Theory of Descent. The point is argued, closely and fully, in
+Chapter X. "On the Imperfection of the Geological Record," and Chapter
+XI. "On the Geological Succession of Organic Beings"; there is, however,
+little about plants in these chapters. At the present time the truth
+of Evolution is no longer seriously disputed, though there are writers,
+like Reinke, who insist, and rightly so, that the doctrine is still
+only a belief, rather than an established fact of science. (J. Reinke,
+"Kritische Abstammungslehre", "Wiesner-Festschrift", page 11, Vienna,
+1908.) Evidently, then, however little the Theory of Descent may be
+questioned in our own day, it is desirable to assure ourselves how the
+case stands, and in particular how far the evidence from fossil plants
+has grown stronger with time.
+
+As regards direct evidence for the derivation of one species from
+another, there has probably been little advance since Darwin wrote, at
+least so we must infer from the emphasis laid on the discontinuity
+of successive fossil species by great systematic authorities like
+Grand'Eury and Zeiller in their most recent writings. We must either
+adopt the mutationist views of those authors (referred to in the last
+section of this essay) or must still rely on Darwin's explanation of the
+absence of numerous intermediate varieties. The attempts which have been
+made to trace, in the Tertiary rocks, the evolution of recent species,
+cannot, owing to the imperfect character of the evidence, be regarded as
+wholly satisfactory.
+
+When we come to groups of a somewhat higher order we have an interesting
+history of the evolution of a recent family in the work, not yet
+completed, of Kidston and Gwynne-Vaughan on the fossil Osmundaceae.
+("Trans. Royal Soc. Edinburgh", Vol. 45, Part III. 1907, Vol. 46, Part
+II. 1908, Vol. 46, Part III. 1909.) The authors are able, mainly on
+anatomical evidence, to trace back this now limited group of Ferns,
+through the Tertiary and Mesozoic to the Permian, and to show, with
+great probability, how their structure has been derived from that of
+early Palaeozoic types.
+
+The history of the Ginkgoaceae, now represented only by the isolated
+maidenhair tree, scarcely known in a wild state, offers another striking
+example of a family which can be traced with certainty to the older
+Mesozoic and perhaps further back still. (See Seward and Gowan, "The
+Maidenhair Tree (Gingko biloba)", "Annals of Botany", Vol. XIV. 1900,
+page 109; also A. Sprecher "Le Ginkgo biloba", L., Geneva, 1907.)
+
+On the wider question of the derivation of the great groups of plants,
+a very considerable advance has been made, and, so far as the higher
+plants are concerned, we are now able to form a far better conception
+than before of the probable course of evolution. This is a matter
+of phylogeny, and the facts will be considered under that head; our
+immediate point is that the new knowledge of the relations between the
+classes of plants in question materially strengthens the case for the
+theory of descent. The discoveries of the last few years throw light
+especially on the relation of the Angiosperms to the Gymnosperms,
+on that of the Seed-plants generally to the Ferns, and on the
+interrelations between the various classes of the higher Cryptogams.
+
+That the fossil record has not done still more for Evolution is due to
+the fact that it begins too late--a point on which Darwin laid stress
+("Origin of Species" (6th edition), page 286.) and which has more
+recently been elaborated by Poulton. ("Essays on Evolution", pages 46
+et seq., Oxford, 1908.) An immense proportion of the whole evolutionary
+history lies behind the lowest fossiliferous rocks, and the case is
+worse for plants than for animals, as the record for the former begins,
+for all practical purposes, much higher up in the rocks.
+
+It may be well here to call attention to a question, often overlooked,
+which has lately been revived by Reinke. (Reinke, loc. cit. page 13.) As
+all admit, we know nothing of the origin of life; consequently, for all
+we can tell, it is as probable that life began, on this planet, with
+many living things, as with one. If the first organic beings were many,
+they may have been heterogeneous, or at least exposed to different
+conditions, from their origin; in either case there would have been a
+number of distinct series from the beginning, and if so we should not
+be justified in assuming that all organisms are related to one another.
+There may conceivably be several of the original lines of descent still
+surviving, or represented among extinct forms--to reverse the remark
+of a distinguished botanist, there may be several Vegetable Kingdoms!
+However improbable this may sound, the possibility is one to be borne in
+mind.
+
+That all VASCULAR plants really belong to one stock seems certain, and
+here the palaeontological record has materially strengthened the
+case for a monophyletic history. The Bryophyta are not likely to be
+absolutely distinct, for their sexual organs, and the stomata of the
+Mosses strongly suggest community of descent with the higher plants; if
+this be so it no doubt establishes a certain presumption in favour of
+a common origin for plants generally, for the gap between "Mosses and
+Ferns" has been regarded as the widest in the Vegetable Kingdom. The
+direct evidence of consanguinity is however much weaker when we come to
+the Algae, and it is conceivable (even if improbable) that the higher
+plants may have had a distinct ancestry (now wholly lost) from the
+beginning. The question had been raised in Darwin's time, and he
+referred to it in these words: "No doubt it is possible, as Mr G.H.
+Lewes has urged, that at the first commencement of life many different
+forms were evolved; but if so, we may conclude that only a very few
+have left modified descendants." ("Origin of Species", page 425.) This
+question, though it deserves attention, does not immediately affect the
+subject of the palaeontological record of plants, for there can be no
+reasonable doubt as to the interrelationship of those groups on which
+the record at present throws light.
+
+The past history of plants by no means shows a regular progression from
+the simple to the complex, but often the contrary. This apparent anomaly
+is due to two causes.
+
+1. The palaeobotanical record is essentially the story of the successive
+ascendancy of a series of dominant families, each of which attained
+its maximum, in organisation as well as in extent, and then sank into
+comparative obscurity, giving place to other families, which under new
+conditions were better able to take a leading place. As each family ran
+its downward course, either its members underwent an actual reduction in
+structure as they became relegated to herbaceous or perhaps aquatic life
+(this may have happened with the Horsetails and with Isoetes if derived
+from Lepidodendreae), or the higher branches of the family were crowded
+out altogether and only the "poor relations" were able to maintain their
+position by evading the competition of the ascendant races; this is also
+illustrated by the history of the Lycopod phylum. In either case there
+would result a lowering of the type of organisation within the group.
+
+2. The course of real progress is often from the complex to the simple.
+If, as we shall find some grounds for believing, the Angiosperms came
+from a type with a flower resembling in its complexity that of Mesozoic
+"Cycads," almost the whole evolution of the flower in the highest
+plants has been a process of reduction. The stamen, in particular, has
+undoubtedly become extremely simplified during evolution; in the most
+primitive known seed-plants it was a highly compound leaf or pinna; its
+reduction has gone on in the Conifers and modern Cycads, as well as in
+the Angiosperms, though in different ways and to a varying extent.
+
+The seed offers another striking example; the Palaeozoic seeds (if we
+leave the seed-like organs of certain Lycopods out of consideration)
+were always, so far as we know, highly complex structures, with
+an elaborate vascular system, a pollen-chamber, and often a
+much-differentiated testa. In the present day such seeds exist only in a
+few Gymnosperms which retain their ancient characters--in all the higher
+Spermophytes the structure is very much simplified, and this holds good
+even in the Coniferae, where there is no countervailing complication of
+ovary and stigma.
+
+Reduction, in fact, is not always, or even generally, the same thing as
+degeneration. Simplification of parts is one of the most usual means of
+advance for the organism as a whole. A large proportion of the higher
+plants are microphyllous in comparison with the highly megaphyllous
+fern-like forms from which they appear to have been derived.
+
+Darwin treated the general question of advance in organisation with much
+caution, saying: "The geological record... does not extend far enough
+back, to show with unmistakeable clearness that within the known history
+of the world organisation has largely advanced." ("Origin of Species",
+page 308.) Further on (Ibid. page 309.) he gives two standards by which
+advance may be measured: "We ought not solely to compare the highest
+members of a class at any two periods... but we ought to compare all the
+members, high and low, at the two periods." Judged by either standard
+the Horsetails and Club Mosses of the Carboniferous were higher than
+those of our own day, and the same is true of the Mesozoic Cycads. There
+is a general advance in the succession of classes, but not within each
+class.
+
+Darwin's argument that "the inhabitants of the world at each successive
+period in its history have beaten their predecessors in the race for
+life, and are, in so far, higher in the scale" ("Origin of Species",
+page 315.) is unanswerable, but we must remember that "higher in the
+scale" only means "better adapted to the existing conditions." Darwin
+points out (Ibid. page 279.) that species have remained unchanged for
+long periods, probably longer than the periods of modification, and only
+underwent change when the conditions of their life were altered. Higher
+organisation, judged by the test of success, is thus purely relative to
+the changing conditions, a fact of which we have a striking illustration
+in the sudden incoming of the Angiosperms with all their wonderful
+floral adaptations to fertilisation by the higher families of Insects.
+
+II. PHYLOGENY.
+
+The question of phylogeny is really inseparable from that of the truth
+of the doctrine of evolution, for we cannot have historical evidence
+that evolution has actually taken place without at the same time having
+evidence of the course it has followed.
+
+As already pointed out, the progress hitherto made has been rather in
+the way of joining up the great classes of plants than in tracing the
+descent of particular species or genera of the recent flora. There
+appears to be a difference in this respect from the Animal record,
+which tells us so much about the descent of living species, such as the
+elephant or the horse. The reason for this difference is no doubt to be
+found in the fact that the later part of the palaeontological record
+is the most satisfactory in the case of animals and the least so in the
+case of plants. The Tertiary plant-remains, in the great majority of
+instances, are impressions of leaves, the conclusions to be drawn from
+which are highly precarious; until the whole subject of Angiospermous
+palaeobotany has been reinvestigated, it would be rash to venture on
+any statements as to the descent of the families of Dicotyledons or
+Monocotyledons.
+
+Our attention will be concentrated on the following questions, all
+relating to the phylogeny of main groups of plants: i. The Origin of the
+Angiosperms. ii. The Origin of the Seed-plants. iii. The Origin of the
+different classes of the Higher Cryptogamia.
+
+i. THE ORIGIN OF THE ANGIOSPERMS.
+
+The first of these questions has long been the great crux of botanical
+phylogeny, and until quite recently no light had been thrown upon the
+difficulty. The Angiosperms are the Flowering Plants, par excellence,
+and form, beyond comparison, the dominant sub-kingdom in the flora of
+our own age, including, apart from a few Conifers and Ferns, all the
+most familiar plants of our fields and gardens, and practically all
+plants of service to man. All recent work has tended to separate the
+Angiosperms more widely from the other seed-plants now living, the
+Gymnosperms. Vast as is the range of organisation presented by the great
+modern sub-kingdom, embracing forms adapted to every environment, there
+is yet a marked uniformity in certain points of structure, as in the
+development of the embryo-sac and its contents, the pollination
+through the intervention of a stigma, the strange phenomenon of double
+fertilisation (One sperm fertilising the egg, while the other unites
+with the embryo-sac nucleus, itself the product of a nuclear fusion, to
+give rise to a nutritive tissue, the endosperm.), the structure of
+the stamens, and the arrangement of the parts of the flower. All these
+points are common to Monocotyledons and Dicotyledons, and separate the
+Angiosperms collectively from all other plants.
+
+In geological history the Angiosperms first appear in the Lower
+Cretaceous, and by Upper Cretaceous times had already swamped all other
+vegetation and seized the dominant position which they still hold. Thus
+they are isolated structurally from the rest of the Vegetable Kingdom,
+while historically they suddenly appear, almost in full force, and
+apparently without intermediaries with other groups. To quote Darwin's
+vigorous words: "The rapid development, as far as we can judge, of
+all the higher plants within recent geological times is an abominable
+mystery." ("More Letters of Charles Darwin", Vol. II. page 20, letter
+to J.D. Hooker, 1879.) A couple of years later he made a bold suggestion
+(which he only called an "idle thought") to meet this difficulty. He
+says: "I have been so astonished at the apparently sudden coming in of
+the higher phanerogams, that I have sometimes fancied that development
+might have slowly gone on for an immense period in some isolated
+continent or large island, perhaps near the South Pole." (Ibid, page
+26, letter to Hooker, 1881.) This idea of an Angiospermous invasion from
+some lost southern land has sometimes been revived since, but has not,
+so far as the writer is aware, been supported by evidence. Light on the
+problem has come from a different direction.
+
+The immense development of plants with the habit of Cycads, during the
+Mesozoic Period up to the Lower Cretaceous, has long been known. The
+existing Order Cycadaceae is a small family, with 9 genera and perhaps
+100 species, occurring in the tropical and sub-tropical zones of both
+the Old and New World, but nowhere forming a dominant feature in the
+vegetation. Some few attain the stature of small trees, while in the
+majority the stem is short, though often living to a great age. The
+large pinnate or rarely bipinnate leaves give the Cycads a superficial
+resemblance in habit to Palms. Recent Cycads are dioecious; throughout
+the family the male fructification is in the form of a cone, each scale
+of the cone representing a stamen, and bearing on its lower surface
+numerous pollen-sacs, grouped in sori like the sporangia of Ferns. In
+all the genera, except Cycas itself, the female fructifications are
+likewise cones, each carpel bearing two ovules on its margin. In Cycas,
+however, no female cone is produced, but the leaf-like carpels, bearing
+from two to six ovules each, are borne directly on the main stem of the
+plant in rosettes alternating with those of the ordinary leaves--the
+most primitive arrangement known in any living seed-plant. The
+whole Order is relatively primitive, as shown most strikingly in its
+cryptogamic mode of fertilisation, by means of spermatozoids, which it
+shares with the maidenhair tree alone, among recent seed-plants.
+
+In all the older Mesozoic rocks, from the Trias to the Lower Cretaceous,
+plants of the Cycad class (Cycadophyta, to use Nathorst's comprehensive
+name) are extraordinarily abundant in all parts of the world; in
+fact they were almost as prominent in the flora of those ages as the
+Dicotyledons are in that of our own day. In habit and to a great extent
+in anatomy, the Mesozoic Cycadophyta for the most part much resemble the
+recent Cycadaceae. But, strange to say, it is only in the rarest
+cases that the fructification has proved to be of the simple type
+characteristic of the recent family; the vast majority of the abundant
+fertile specimens yielded by the Mesozoic rocks possess a type of
+reproductive apparatus far more elaborate than anything known in
+Cycadaceae or other Gymnosperms. The predominant Mesozoic family,
+characterised by this advanced reproductive organisation, is known
+as the Bennettiteae; in habit these plants resembled the more stunted
+Cycads of the recent flora, but differed from them in the presence of
+numerous lateral fructifications, like large buds, borne on the stem
+among the crowded bases of the leaves. The organisation of these
+fructifications was first worked out on European specimens by
+Carruthers, Solms-Laubach, Lignier and others, but these observers had
+only more or less ripe fruits to deal with; the complete structure of
+the flower has only been elucidated within the last few years by the
+researches of Wieland on the magnificent American material, derived from
+the Upper Jurassic and Lower Cretaceous beds of Maryland, Dakota and
+Wyoming. (G.R. Wieland, "American Fossil Cycads", Carnegie Institution,
+Washington, 1906.) The word "flower" is used deliberately, for reasons
+which will be apparent from the following brief description, based on
+Wieland's observations.
+
+The fructification is attached to the stem by a thick stalk, which,
+in its upper part, bears a large number of spirally arranged bracts,
+forming collectively a kind of perianth and completely enclosing the
+essential organs of reproduction. The latter consist of a whorl of
+stamens, of extremely elaborate structure, surrounding a central cone
+or receptacle bearing numerous ovules. The stamens resemble the fertile
+fronds of a fern; they are of a compound, pinnate form, and bear
+very large numbers of pollen-sacs, each of which is itself a compound
+structure consisting of a number of compartments in which the pollen
+was formed. In their lower part the stamens are fused together by their
+stalks, like the "monadelphous" stamens of a mallow. The numerous ovules
+borne on the central receptacle are stalked, and are intermixed with
+sterile scales; the latter are expanded at their outer ends, which are
+united to form a kind of pericarp or ovary-wall, only interrupted by the
+protruding micropyles of the ovules. There is thus an approach to
+the closed pistil of an Angiosperm, but it is evident that the ovules
+received the pollen directly. The whole fructification is of large size;
+in the case of Cycadeoidea dacotensis, one of the species investigated
+by Wieland, the total length, in the bud condition, is about 12 cm.,
+half of which belongs to the peduncle.
+
+The general arrangement of the organs is manifestly the same as in a
+typical Angiospermous flower, with a central pistil, a surrounding whorl
+of stamens and an enveloping perianth; there is, as we have seen, some
+approach to the closed ovary of an Angiosperm; another point, first
+discovered nearly 20 years ago by Solms-Laubach in his investigation of
+a British species, is that the seed was practically "exalbuminous," its
+cavity being filled by the large, dicotyledonous embryo, whereas in all
+known Gymnosperms a large part of the sac is occupied by a nutritive
+tissue, the prothallus or endosperm; here also we have a condition only
+met with elsewhere among the higher Flowering Plants.
+
+Taking all the characters into account, the indications of affinity
+between the Mesozoic Cycadophyta and the Angiosperms appear extremely
+significant, as was recognised by Wieland when he first discovered the
+hermaphrodite nature of the Bennettitean flower. The Angiosperm
+with which he specially compared the fossil type was the Tulip tree
+(Liriodendron) and certainly there is a remarkable analogy with
+the Magnoliaceous flowers, and with those of related orders such as
+Ranunculaceae and the Water-lilies. It cannot, of course, be maintained
+that the Bennettiteae, or any other Mesozoic Cycadophyta at present
+known, were on the direct line of descent of the Angiosperms, for there
+are some important points of difference, as, for example, in the great
+complexity of the stamens, and in the fact that the ovary-wall
+or pericarp was not formed by the carpels themselves, but by the
+accompanying sterile scale-leaves. Botanists, since the discovery of the
+bisexual flowers of the Bennettiteae, have expressed different views as
+to the nearness of their relation to the higher Flowering Plants, but
+the points of agreement are so many that it is difficult to resist the
+conviction that a real relation exists, and that the ancestry of the
+Angiosperms, so long shrouded in complete obscurity, is to be sought
+among the great plexus of Cycad-like plants which dominated the flora
+of the world in Mesozoic times. (On this subject see, in addition
+to Wieland's great work above cited, F.W. Oliver, "Pteridosperms
+and Angiosperms", "New Phytologist", Vol. V. 1906; D.H. Scott,
+"The Flowering Plants of the Mesozoic Age in the Light of Recent
+Discoveries", "Journal R. Microscop. Soc." 1907, and especially E.A.N.
+Arber and J. Parkin, "On the Origin of Angiosperms", "Journal Linn.
+Soc." (Bot.) Vol. XXXVIII. page 29, 1907.)
+
+The great complexity of the Bennettitean flower, the earliest known
+fructification to which the word "flower" can be applied without forcing
+the sense, renders it probable, as Wieland and others have pointed
+out, that the evolution of the flower in Angiosperms has consisted
+essentially in a process of reduction, and that the simplest forms
+of flower are not to be regarded as the most primitive. The older
+morphologists generally took the view that such simple flowers were to
+be explained as reductions from a more perfect type, and this opinion,
+though abandoned by many later writers, appears likely to be true when
+we consider the elaboration of floral structure attained among the
+Mesozoic Cycadophyta, which preceded the Angiosperms in evolution.
+
+If, as now seems probable, the Angiosperms were derived from ancestors
+allied to the Cycads, it would naturally follow that the Dicotyledons
+were first evolved, for their structure has most in common with that of
+the Cycadophyta. We should then have to regard the Monocotyledons as
+a side-line, diverging probably at a very early stage from the main
+dicotyledonous stock, a view which many botanists have maintained,
+of late, on other grounds. (See especially Ethel Sargant, "The
+Reconstruction of a Race of Primitive Angiosperms", "Annals of Botany",
+Vol. XXII. page 121, 1908.) So far, however, as the palaeontological
+record shows, the Monocotyledons were little if at all later in their
+appearance than the Dicotyledons, though always subordinate in numbers.
+The typical and beautifully preserved Palm-wood from Cretaceous rocks
+is striking evidence of the early evolution of a characteristic
+monocotyledonous family. It must be admitted that the whole question of
+the evolution of Monocotyledons remains to be solved.
+
+Accepting, provisionally, the theory of the cycadophytic origin of
+Angiosperms, it is interesting to see to what further conclusions we
+are led. The Bennettiteae, at any rate, were still at the gymnospermous
+level as regards their pollination, for the exposed micropyles of the
+ovules were in a position to receive the pollen directly, without the
+intervention of a stigma. It is thus indicated that the Angiosperms
+sprang from a gymnospermous source, and that the two great phyla of
+Seed-plants have not been distinct from the first, though no doubt the
+great majority of known Gymnosperms, especially the Coniferae, represent
+branch-lines of their own.
+
+The stamens of the Bennettiteae are arranged precisely as in an
+angiospermous flower, but in form and structure they are like the
+fertile fronds of a Fern, in fact the compound pollen-sacs, or synangia
+as they are technically called, almost exactly agree with the spore-sacs
+of a particular family of Ferns--the Marattiaceae, a limited group,
+now mainly tropical, which was probably more prominent in the later
+Palaeozoic times than at present. The scaly hairs, or ramenta, which
+clothe every part of the plant, are also like those of Ferns.
+
+It is not likely that the characters in which the Bennettiteae resemble
+the Ferns came to them directly from ancestors belonging to that class;
+an extensive group of Seed-plants, the Pteridospermeae, existed in
+Palaeozoic times and bear evident marks of affinity with the Fern
+phylum. The fern-like characters so remarkably persistent in the highly
+organised Cycadophyta of the Mesozoic were in all likelihood derived
+through the Pteridosperms, plants which show an unmistakable approach to
+the cycadophytic type.
+
+The family Bennettiteae thus presents an extraordinary association
+of characters, exhibiting, side by side, features which belong to the
+Angiosperms, the Gymnosperms and the Ferns.
+
+ii. ORIGIN OF SEED-PLANTS.
+
+The general relation of the gymnospermous Seed-plants to the Higher
+Cryptogamia was cleared up, independently of fossil evidence, by the
+brilliant researches of Hofmeister, dating from the middle of the
+past century. (W. Hofmeister, "On the Germination, Development and
+Fructification of the Higher Cryptogamia", Ray Society, London, 1862.
+The original German treatise appeared in 1851.) He showed that "the
+embryo-sac of the Coniferae may be looked upon as a spore remaining
+enclosed in its sporangium; the prothallium which it forms does not come
+to the light." (Ibid. page 438.) He thus determined the homologies on
+the female side. Recognising, as some previous observers had already
+done, that the microspores of those Cryptogams in which two kinds of
+spore are developed, are equivalent to the pollen-grains of the higher
+plants, he further pointed out that fertilisation "in the Rhizocarpeae
+and Selaginellae takes place by free spermatozoa, and in the Coniferae
+by a pollen-tube, in the interior of which spermatozoa are probably
+formed"--a remarkable instance of prescience, for though spermatozoids
+have not been found in the Conifers proper, they were demonstrated
+in the allied groups Cycadaceae and Ginkgo, in 1896, by the Japanese
+botanists Ikeno and Hirase. A new link was thus established between the
+Gymnosperms and the Cryptogams.
+
+It remained uncertain, however, from which line of Cryptogams the
+gymnospermous Seed-plants had sprung. The great point of morphological
+comparison was the presence of two kinds of spore, and this was known to
+occur in the recent Lycopods and Water-ferns (Rhizocarpeae) and was
+also found in fossil representatives of the third phylum, that of the
+Horsetails. As a matter of fact all the three great Cryptogamic classes
+have found champions to maintain their claim to the ancestry of the
+Seed-plants, and in every case fossil evidence was called in. For a long
+time the Lycopods were the favourites, while the Ferns found the least
+support. The writer remembers, however, in the year 1881, hearing the
+late Prof. Sachs maintain, in a lecture to his class, that the descent
+of the Cycads could be traced, not merely from Ferns, but from a
+definite family of Ferns, the Marattiaceae, a view which, though in a
+somewhat crude form, anticipated more modern ideas.
+
+Williamson appears to have been the first to recognise the presence, in
+the Carboniferous flora, of plants combining the characters of Ferns and
+Cycads. (See especially his "Organisation of the Fossil Plants of the
+Coal-Measures", Part XIII. "Phil. Trans. Royal Soc." 1887 B. page 299.)
+This conclusion was first reached in the case of the genera Heterangium
+and Lyginodendron, plants, which with a wholly fern-like habit, were
+found to unite an anatomical structure holding the balance between
+that of Ferns and Cycads, Heterangium inclining more to the former
+and Lyginodendron to the latter. Later researches placed Williamson's
+original suggestion on a firmer basis, and clearly proved the
+intermediate nature of these genera, and of a number of others, so far
+as their vegetative organs were concerned. This stage in our knowledge
+was marked by the institution of the class Cycadofilices by Potonie in
+1897.
+
+Nothing, however, was known of the organs of reproduction of the
+Cycadofilices, until F.W. Oliver, in 1903, identified a fossil seed,
+Lagenostoma Lomaxi, as belonging to Lyginodendron, the identification
+depending, in the first instance, on the recognition of an identical
+form of gland, of very characteristic structure, on the vegetative
+organs of Lyginodendron and on the cupule enveloping the seed. This
+evidence was supported by the discovery of a close anatomical agreement
+in other respects, as well as by constant association between the seed
+and the plant. (F.W. Oliver and D.H. Scott, "On the Structure of the
+Palaeozoic Seed, Lagenostoma Lomaxi, etc." "Phil. Trans. Royal Soc."
+Vol. 197 B. 1904.) The structure of the seed of Lyginodendron, proved to
+be of the same general type as that of the Cycads, as shown especially
+by the presence of a pollen-chamber or special cavity for the reception
+of the pollen-grains, an organ only known in the Cycads and Ginkgo among
+recent plants.
+
+Within a few months after the discovery of the seed of Lyginodendron,
+Kidston found the large, nut-like seed of a Neuropteris, another
+fern-like Carboniferous plant, in actual connection with the pinnules
+of the frond, and since then seeds have been observed on the frond in
+species of Aneimites and Pecopteris, and a vast body of evidence, direct
+or indirect, has accumulated, showing that a large proportion of the
+Palaeozoic plants formerly classed as Ferns were in reality reproduced
+by seeds of the same type as those of recent Cycadaceae. (A summary
+of the evidence will be found in the writer's article "On the present
+position of Palaeozoic Botany", "Progressus Rei Botanicae", 1907, page
+139, and "Studies in Fossil Botany", Vol. II. (2nd edition) London,
+1909.) At the same time, the anatomical structure, where it is open to
+investigation, confirms the suggestion given by the habit, and shows
+that these early seed-bearing plants had a real affinity with Ferns.
+This conclusion received strong corroboration when Kidston, in 1905,
+discovered the male organs of Lyginodendron, and showed that they were
+identical with a fructification of the genus Crossotheca, hitherto
+regarded as belonging to Marattiaceous Ferns. (Kidston, "On the
+Microsporangia of the Pteridospermeae, etc." "Phil. Trans. Royal Soc."
+Vol. 198, B. 1906.)
+
+The general conclusion which follows from the various observations
+alluded to, is that in Palaeozoic times there was a great body of plants
+(including, as it appears, a large majority of the fossils previously
+regarded as Ferns) which had attained the rank of Spermophyta,
+bearing seeds of a Cycadean type on fronds scarcely differing from the
+vegetative foliage, and in other respects, namely anatomy, habit and the
+structure of the pollen-bearing organs, retaining many of the characters
+of Ferns. From this extensive class of plants, to which the name
+Pteridospermeae has been given, it can scarcely be doubted that the
+abundant Cycadophyta, of the succeeding Mesozoic period, were derived.
+This conclusion is of far-reaching significance, for we have already
+found reason to think that the Angiosperms themselves sprang, in
+later times, from the Cycadophytic stock; it thus appears that the
+Fern-phylum, taken in a broad sense, ultimately represents the source
+from which the main line of descent of the Phanerogams took its rise.
+
+It must further be borne in mind that in the Palaeozoic period there
+existed another group of seed-bearing plants, the Cordaiteae, far more
+advanced than the Pteridospermeae, and in many respects approaching the
+Coniferae, which themselves begin to appear in the latest Palaeozoic
+rocks. The Cordaiteae, while wholly different in habit from the
+contemporary fern-like Seed-plants, show unmistakable signs of a common
+origin with them. Not only is there a whole series of forms
+connecting the anatomical structure of the Cordaiteae with that of the
+Lyginodendreae among Pteridosperms, but a still more important point is
+that the seeds of the Cordaiteae, which have long been known, are of
+the same Cycadean type as those of the Pteridosperms, so that it is not
+always possible, as yet, to discriminate between the seeds of the two
+groups. These facts indicate that the same fern-like stock which gave
+rise to the Cycadophyta and through them, as appears probable, to the
+Angiosperms, was also the source of the Cordaiteae, which in their turn
+show manifest affinity with some at least of the Coniferae. Unless the
+latter are an artificial group, a view which does not commend itself to
+the writer, it would appear probable that the Gymnosperms generally,
+as well as the Angiosperms, were derived from an ancient race of
+Cryptogams, most nearly related to the Ferns. (Some botanists, however,
+believe that the Coniferae, or some of them, are probably more nearly
+related to the Lycopods. See Seward and Ford, "The Araucarieae, Recent
+and Extinct", "Phil. Trans. Royal Soc." Vol. 198 B. 1906.)
+
+It may be mentioned here that the small gymnospermous group Gnetales
+(including the extraordinary West African plant Welwitschia) which were
+formerly regarded by some authorities as akin to the Equisetales, have
+recently been referred, on better grounds, to a common origin with the
+Angiosperms, from the Mesozoic Cycadophyta.
+
+The tendency, therefore, of modern work on the palaeontological record
+of the Seed-plants has been to exalt the importance of the Fern-phylum,
+which, on present evidence, appears to be that from which the great
+majority, possibly the whole, of the Spermophyta have been derived.
+
+One word of caution, however, is necessary. The Seed-plants are of
+enormous antiquity; both the Pteridosperms and the more highly organised
+family Cordaiteae, go back as far in geological history (namely to the
+Devonian) as the Ferns themselves or any other Vascular Cryptogams. It
+must therefore be understood that in speaking of the derivation of the
+Spermophyta from the Fern-phylum, we refer to that phylum at a very
+early stage, probably earlier than the most ancient period to which
+our record of land-plants extends. The affinity between the oldest
+Seed-plants and the Ferns, in the widest sense, seems established, but
+the common stock from which they actually arose is still unknown; though
+no doubt nearer to the Ferns than to any other group, it must have
+differed widely from the Ferns as we now know them, or perhaps even from
+any which the fossil record has yet revealed to us.
+
+iii. THE ORIGIN OF THE HIGHER CRYPTOGAMIA.
+
+The Sub-kingdom of the higher Spore-plants, the Cryptogamia possessing a
+vascular system, was more prominent in early geological periods than at
+present. It is true that the dominance of the Pteridophyta in Palaeozoic
+times has been much exaggerated owing to the assumption that everything
+which looked like a Fern really was a Fern. But, allowing for the fact,
+now established, that most of the Palaeozoic fern-like plants were
+already Spermophyta, there remains a vast mass of Cryptogamic forms
+of that period, and the familiar statement that they formed the main
+constituent of the Coal-forests still holds good. The three
+classes, Ferns (Filicales), Horsetails (Equisetales) and Club-mosses
+(Lycopodiales), under which we now group the Vascular Cryptogams, all
+extend back in geological history as far as we have any record of the
+flora of the land; in the Palaeozoic, however, a fourth class, the
+Sphenophyllales, was present.
+
+As regards the early history of the Ferns, which are of special interest
+from their relation to the Seed-plants, it is impossible to speak quite
+positively, owing to the difficulty of discriminating between true
+fossil Ferns and the Pteridosperms which so closely simulated them.
+The difficulty especially affects the question of the position of
+Marattiaceous Ferns in the Palaeozoic Floras. This family, now so
+restricted, was until recently believed to have been one of the
+most important groups of Palaeozoic plants, especially during later
+Carboniferous and Permian times. Evidence both from anatomy and from
+sporangial characters appeared to establish this conclusion. Of late,
+however, doubts have arisen, owing to the discovery that some
+supposed members of the Marattiaceae bore seeds, and that a form of
+fructification previously referred to that family (Crossotheca) was
+really the pollen-bearing apparatus of a Pteridosperm (Lyginodendron).
+The question presents much difficulty; though it seems certain that our
+ideas of the extent of the family in Palaeozoic times will have to be
+restricted, there is still a decided balance of evidence in favour
+of the view that a considerable body of Marattiaceous Ferns actually
+existed. The plants in question were of large size (often arborescent)
+and highly organised--they represent, in fact, one of the highest
+developments of the Fern-stock, rather than a primitive type of the
+class.
+
+There was, however, in the Palaeozoic period, a considerable group of
+comparatively simple Ferns (for which Arber has proposed the collective
+name Primofilices); the best known of these are referred to the family
+Botryopterideae, consisting of plants of small or moderate dimensions,
+with, on the whole, a simple anatomical structure, in certain cases
+actually simpler than that of any recent Ferns. On the other hand the
+sporangia of these plants were usually borne on special fertile fronds,
+a mark of rather high differentiation. This group goes back to the
+Devonian and includes some of the earliest types of Fern with which we
+are acquainted. It is probable that the Primofilices (though not the
+particular family Botryopterideae) represent the stock from which the
+various families of modern Ferns, already developed in the Mesozoic
+period, may have sprung.
+
+None of the early Ferns show any clear approach to other classes of
+Vascular Cryptogams; so far as the fossil record affords any evidence,
+Ferns have always been plants with relatively large and usually compound
+leaves. There is no indication of their derivation from a microphyllous
+ancestry, though, as we shall see, there is some slight evidence for the
+converse hypothesis. Whatever the origin of the Ferns may have been it
+is hidden in the older rocks.
+
+It has, however, been held that certain other Cryptogamic phyla had
+a common origin with the Ferns. The Equisetales are at present a
+well-defined group; even in the rich Palaeozoic floras the habit,
+anatomy and reproductive characters usually render the members of this
+class unmistakable, in spite of the great development and stature which
+they then attained. It is interesting, however, to find that in the
+oldest known representatives of the Equisetales the leaves were highly
+developed and dichotomously divided, thus differing greatly from the
+mere scale-leaves of the recent Horsetails, or even from the simple
+linear leaves of the later Calamites. The early members of the class, in
+their forked leaves, and in anatomical characters, show an approximation
+to the Sphenophyllales, which are chiefly represented by the large genus
+Sphenophyllum, ranging through the Palaeozoic from the Middle Devonian
+onwards. These were plants with rather slender, ribbed stems, bearing
+whorls of wedge-shaped or deeply forked leaves, six being the typical
+number in each whorl. From their weak habit it has been conjectured,
+with much probability, that they may have been climbing plants, like the
+scrambling Bedstraws of our hedgerows. The anatomy of the stem is simple
+and root-like; the cones are remarkable for the fact that each scale or
+sporophyll is a double structure, consisting of a lower, usually sterile
+lobe and one or more upper lobes bearing the sporangia; in one species
+both parts of the sporophyll were fertile. Sphenophyllum was evidently
+much specialised; the only other known genus is based on an isolated
+cone, Cheirostrobus, of Lower Carboniferous age, with an extraordinarily
+complex structure. In this genus especially, but also in the entire
+group, there is an evident relation to the Equisetales; hence it is of
+great interest that Nathorst has described, from the Devonian of Bear
+Island in the Arctic regions, a new genus Pseudobornia, consisting of
+large plants, remarkable for their highly compound leaves which,
+when found detached, were taken for the fronds of a Fern. The whorled
+arrangement of the leaves, and the habit of the plant, suggest
+affinities either with the Equisetales or the Sphenophyllales; Nathorst
+makes the genus the type of a new class, the Pseudoborniales. (A.G.
+Nathorst, "Zur Oberdevonischen Flora der Baren-Insel", "Kongl. Svenska
+Vetenskaps-Akademiens Handlingar" Bd. 36, No. 3, Stockholm, 1902.)
+
+The available data, though still very fragmentary, certainly suggest
+that both Equisetales and Sphenophyllales may have sprung from a
+common stock having certain fern-like characters. On the other hand the
+Sphenophylls, and especially the peculiar genus Cheirostrobus, have in
+their anatomy a good deal in common with the Lycopods, and of late years
+they have been regarded as the derivatives of a stock common to
+that class and the Equisetales. At any rate the characters of the
+Sphenophyllales and of the new group Pseudoborniales suggest the
+existence, at a very early period, of a synthetic race of plants,
+combining the characters of various phyla of the Vascular Cryptogams.
+It may further be mentioned that the Psilotaceae, an isolated epiphytic
+family hitherto referred to the Lycopods, have been regarded by several
+recent authors as the last survivors of the Sphenophyllales, which they
+resemble both in their anatomy and in the position of their sporangia.
+
+The Lycopods, so far as their early history is known, are remarkable
+rather for their high development in Palaeozoic times than for any
+indications of a more primitive ancestry. In the recent Flora, two
+of the four living genera (Excluding Psilotaceae.) (Selaginella and
+Isoetes) have spores of two kinds, while the other two (Lycopodium and
+Phylloglossum) are homosporous. Curiously enough, no certain instance
+of a homosporous Palaeozoic Lycopod has yet been discovered, though
+well-preserved fructifications are numerous. Wherever the facts have
+been definitely ascertained, we find two kinds of spore, differentiated
+quite as sharply as in any living members of the group. Some of the
+Palaeozoic Lycopods, in fact, went further, and produced bodies of the
+nature of seeds, some of which were actually regarded, for many
+years, as the seeds of Gymnosperms. This specially advanced form of
+fructification goes back at least as far as the Lower Carboniferous,
+while the oldest known genus of Lycopods, Bothrodendron, which is found
+in the Devonian, though not seed-bearing, was typically heterosporous,
+if we may judge from the Coal-measure species. No doubt homosporous
+Lycopods existed, but the great prevalence of the higher mode of
+reproduction in days which to us appear ancient, shows how long a course
+of evolution must have already been passed through before the oldest
+known members of the group came into being. The other characters of
+the Palaeozoic Lycopods tell the same tale; most of them attained
+the stature of trees, with a corresponding elaboration of anatomical
+structure, and even the herbaceous forms show no special simplicity.
+It appears from recent work that herbaceous Lycopods, indistinguishable
+from our recent Selaginellas, already existed in the time of the
+Coal-measures, while one herbaceous form (Miadesmia) is known to have
+borne seeds.
+
+The utmost that can be said for primitiveness of character in Palaeozoic
+Lycopods is that the anatomy of the stem, in its primary ground-plan, as
+distinguished from its secondary growth, was simpler than that of most
+Lycopodiums and Selaginellas at the present day. There are also some
+peculiarities in the underground organs (Stigmaria) which suggest the
+possibility of a somewhat imperfect differentiation between root and
+stem, but precisely parallel difficulties are met with in the case of
+the living Selaginellas, and in some degree in species of Lycopodium.
+
+In spite of their high development in past ages the Lycopods, recent
+and fossil, constitute, on the whole, a homogeneous group, and there is
+little at present to connect them with other phyla. Anatomically some
+relation to the Sphenophylls is indicated, and perhaps the recent
+Psilotaceae give some support to this connection, for while their
+nearest alliance appears to be with the Sphenophylls, they approach the
+Lycopods in anatomy, habit, and mode of branching.
+
+The typically microphyllous character of the Lycopods, and the simple
+relation between sporangium and sporophyll which obtains throughout the
+class, have led various botanists to regard them as the most primitive
+phylum of the Vascular Cryptogams. There is nothing in the fossil record
+to disprove this view, but neither is there anything to support it, for
+this class so far as we know is no more ancient than the megaphyllous
+Cryptogams, and its earliest representatives show no special simplicity.
+If the indications of affinity with Sphenophylls are of any value
+the Lycopods are open to suspicion of reduction from a megaphyllous
+ancestry, but there is no direct palaeontological evidence for such a
+history.
+
+The general conclusions to which we are led by a consideration of the
+fossil record of the Vascular Cryptogams are still very hypothetical,
+but may be provisionally stated as follows:
+
+The Ferns go back to the earliest known period. In Mesozoic times
+practically all the existing families had appeared; in the Palaeozoic
+the class was less extensive than formerly believed, a majority of the
+supposed Ferns of that age having proved to be seed-bearing plants. The
+oldest authentic representatives of the Ferns were megaphyllous plants,
+broadly speaking, of the same type as those of later epochs, though
+differing much in detail. As far back as the record extends they show no
+sign of becoming merged with other phyla in any synthetic group.
+
+The Equisetales likewise have a long history, and manifestly attained
+their greatest development in Palaeozoic times. Their oldest forms show
+an approach to the extinct class Sphenophyllales, which connects them
+to some extent, by anatomical characters, with the Lycopods. At the
+same time the oldest Equisetales show a somewhat megaphyllous character,
+which was more marked in the Devonian Pseudoborniales. Some remote
+affinity with the Ferns (which has also been upheld on other grounds)
+may thus be indicated. It is possible that in the Sphenophyllales we
+may have the much-modified representatives of a very ancient synthetic
+group.
+
+The Lycopods likewise attained their maximum in the Palaeozoic, and
+show, on the whole, a greater elaboration of structure in their early
+forms than at any later period, while at the same time maintaining a
+considerable degree of uniformity in morphological characters throughout
+their history. The Sphenophyllales are the only other class with which
+they show any relation; if such a connection existed, the common point
+of origin must lie exceedingly far back.
+
+The fossil record, as at present known, cannot, in the nature of things,
+throw any direct light on what is perhaps the most disputed question in
+the morphology of plants--the origin of the alternating generations of
+the higher Cryptogams and the Spermophyta. At the earliest period
+to which terrestrial plants have been traced back all the groups of
+Vascular Cryptogams were in a highly advanced stage of evolution, while
+innumerable Seed-plants--presumably the descendants of Cryptogamic
+ancestors--were already flourishing. On the other hand we know
+practically nothing of Palaeozoic Bryophyta, and the evidence even for
+their existence at that period cannot be termed conclusive. While
+there are thus no palaeontological grounds for the hypothesis that the
+Vascular plants came of a Bryophytic stock, the question of their actual
+origin remains unsolved.
+
+III. NATURAL SELECTION.
+
+Hitherto we have considered the palaeontological record of plants in
+relation to Evolution. The question remains, whether the record
+throws any light on the theory of which Darwin and Wallace were the
+authors--that of Natural Selection. The subject is clearly one which
+must be investigated by other methods than those of the palaeontologist;
+still there are certain important points involved, on which the
+palaeontological record appears to bear.
+
+One of these points is the supposed distinction between morphological
+and adaptive characters, on which Nageli, in particular, laid so much
+stress. The question is a difficult one; it was discussed by Darwin
+("Origin of Species" (6th edition), pages 170-176.), who, while
+showing that the apparent distinction is in part to be explained by our
+imperfect knowledge of function, recognised the existence of important
+morphological characters which are not adaptations. The following
+passage expresses his conclusion. "Thus, as I am inclined to believe,
+morphological differences, which we consider as important--such as
+the arrangement of the leaves, the divisions of the flower or of the
+ovarium, the position of the ovules, etc.--first appeared in many cases
+as fluctuating variations, which sooner or later became constant through
+the nature of the organism and of the surrounding conditions, as well
+as through the inter-crossing of distinct individuals, but not through
+natural selection; for as these morphological characters do not affect
+the welfare of the species, any slight deviations in them could not have
+been governed or accumulated through this latter agency." (Ibid. page
+176.)
+
+This is a sufficiently liberal concession; Nageli, however, went much
+further when he said: "I do not know among plants a morphological
+modification which can be explained on utilitarian principles." (See
+"More Letters", Vol. II. page 375 (footnote).) If this were true the
+field of Natural Selection would be so seriously restricted, as to leave
+the theory only a very limited importance.
+
+It can be shown, as the writer believes, that many typical
+"morphological characters," on which the distinction between great
+classes of plants is based, were adaptive in origin, and even that their
+constancy is due to their functional importance. Only one or two cases
+will be mentioned, where the fossil evidence affects the question.
+
+The pollen-tube is one of the most important morphological characters of
+the Spermophyta as now existing--in fact the name Siphonogama is used
+by Engler in his classification, as expressing a peculiarly constant
+character of the Seed-plants. Yet the pollen-tube is a manifest
+adaptation, following on the adoption of the seed-habit, and serving
+first to bring the spermatozoids with greater precision to their
+goal, and ultimately to relieve them of the necessity for independent
+movement. The pollen-tube is constant because it has proved to be
+indispensable.
+
+In the Palaeozoic Seed-plants there are a number of instances in which
+the pollen-grains, contained in the pollen-chamber of a seed, are so
+beautifully preserved that the presence of a group of cells within the
+grain can be demonstrated; sometimes we can even see how the cell-walls
+broke down to emit the sperms, and quite lately it is said that the
+sperms themselves have been recognised. (F.W. Oliver, "On Physostoma
+elegans, an archaic type of seed from the Palaeozoic Rocks", "Annals of
+Botany", January, 1909. See also the earlier papers there cited.) In
+no case, however, is there as yet any satisfactory evidence for
+the formation of a pollen-tube; it is probable that in these early
+Seed-plants the pollen-grains remained at about the evolutionary level
+of the microspores in Pilularia or Selaginella, and discharged their
+spermatozoids directly, leaving them to find their own way to the
+female cells. It thus appears that there were once Spermophyta without
+pollen-tubes. The pollen-tube method ultimately prevailed, becoming a
+constant "morphological character," for no other reason than because,
+under the new conditions, it provided a more perfect mechanism for the
+accomplishment of the act of fertilisation. We have still, in the Cycads
+and Ginkgo, the transitional case, where the tube remains short, serves
+mainly as an anchor and water-reservoir, but yet is able, by its slight
+growth, to give the spermatozoids a "lift" in the right direction. In
+other Seed-plants the sperms are mere passengers, carried all the way by
+the pollen-tube; this fact has alone rendered the Angiospermous method
+of fertilisation through a stigma possible.
+
+We may next take the seed itself--the very type of a morphological
+character. Our fossil record does not go far enough back to tell us the
+origin of the seed in the Cycadophyta and Pteridosperms (the main line
+of its development) but some interesting sidelights may be obtained from
+the Lycopod phylum. In two Palaeozoic genera, as we have seen, seed-like
+organs are known to have been developed, resembling true seeds in the
+presence of an integument and of a single functional embryo-sac, as well
+as in some other points. We will call these organs "seeds" for the sake
+of shortness. In one genus (Lepidocarpon) the seeds were borne on a cone
+indistinguishable from that of the ordinary cryptogamic Lepidodendreae,
+the typical Lycopods of the period, while the seed itself retained
+much of the detailed structure of the sporangium of that family. In the
+second genus, Miadesmia, the seed-bearing plant was herbaceous, and much
+like a recent Selaginella. (See Margaret Benson, "Miadesmia membranacea,
+a new Palaeozoic Lycopod with a seed-like structure", "Phil. Trans.
+Royal Soc. Vol." 199, B. 1908.) The seeds of the two genera are
+differently constructed, and evidently had an independent origin. Here,
+then, we have seeds arising casually, as it were, at different points
+among plants which otherwise retain all the characters of their
+cryptogamic fellows; the seed is not yet a morphological character of
+importance. To suppose that in these isolated cases the seed sprang into
+being in obedience to a Law of Advance ("Vervollkommungsprincip"),
+from which other contemporary Lycopods were exempt, involves us in
+unnecessary mysticism. On the other hand it is not difficult to see how
+these seeds may have arisen, as adaptive structures, under the influence
+of Natural Selection. The seed-like structure afforded protection to the
+prothallus, and may have enabled the embryo to be launched on the world
+in greater security. There was further, as we may suppose, a gain in
+certainty of fertilisation. As the writer has pointed out elsewhere,
+the chances against the necessary association of the small male with the
+large female spores must have been enormously great when the cones were
+borne high up on tall trees. The same difficulty may have existed in the
+case of the herbaceous Miadesmia, if, as Miss Benson conjectures, it was
+an epiphyte. One way of solving the problem was for pollination to take
+place while the megaspore was still on the parent plant, and this is
+just what the formation of an ovule or seed was likely to secure.
+
+The seeds of the Pteridosperms, unlike those of the Lycopod stock,
+have not yet been found in statu nascendi--in all known cases they were
+already highly developed organs and far removed from the cryptogamic
+sporangium. But in two respects we find that these seeds, or some
+of them, had not yet realised their possibilities. In the seed
+of Lyginodendron and other cases the micropyle, or orifice of the
+integument, was not the passage through which the pollen entered; the
+open neck of the pollen-chamber protruded through the micropyle and
+itself received the pollen. We have met with an analogous case, at a
+more advanced stage of evolution, in the Bennettiteae, where the wall
+of the gynaecium, though otherwise closed, did not provide a stigma to
+catch the pollen, but allowed the micropyles of the ovules to protrude
+and receive the pollen in the old gymnospermous fashion. The integument
+in the one case and the pistil in the other had not yet assumed all
+the functions to which the organ ultimately became adapted. Again, no
+Palaeozoic seed has yet been found to contain an embryo, though the
+preservation is often good enough for it to have been recognised if
+present. It is probable that the nursing of the embryo had not yet come
+to be one of the functions of the seed, and that the whole embryonic
+development was relegated to the germination stage.
+
+In these two points, the reception of the pollen by the micropyle and
+the nursing of the embryo, it appears that many Palaeozoic seeds
+were imperfect, as compared with the typical seeds of later times.
+As evolution went on, one function was superadded on another, and
+it appears impossible to resist the conclusion that the whole
+differentiation of the seed was a process of adaptation, and
+consequently governed by Natural Selection, just as much as the
+specialisation of the rostellum in an Orchid, or of the pappus in a
+Composite.
+
+Did space allow, other examples might be added. We may venture to
+maintain that the glimpses which the fossil record allows us into early
+stages in the evolution of organs now of high systematic importance,
+by no means justify the belief in any essential distinction between
+morphological and adaptive characters.
+
+Another point, closely connected with Darwin's theory, on which the
+fossil history of plants has been supposed to have some bearing, is
+the question of Mutation, as opposed to indefinite variation. Arber and
+Parkin, in their interesting memoir on the Origin of Angiosperms,
+have suggested calling in Mutation to explain the apparently sudden
+transition from the cycadean to the angiospermous type of foliage, in
+late Mesozoic times, though they express themselves with much caution,
+and point out "a distinct danger that Mutation may become the last
+resort of the phylogenetically destitute"!
+
+The distinguished French palaeobotanists, Grand'Eury (C. Grand'Eury,
+"Sur les mutations de quelques Plantes fossiles du Terrain houiller".
+"Comptes Rendus", CXLII. page 25, 1906.) and Zeiller (R. Zeiller
+"Les Vegetaux fossiles et leurs Enchainements", "Revue du Mois", III.
+February, 1907.), are of opinion, to quote the words of the latter
+writer, that the facts of fossil Botany are in agreement with the sudden
+appearance of new forms, differing by marked characters from those that
+have given them birth; he adds that these results give more amplitude
+to this idea of Mutation, extending it to groups of a higher order,
+and even revealing the existence of discontinuous series between the
+successive terms of which we yet recognise bonds of filiation. (Loc.
+cit. page 23.)
+
+If Zeiller's opinion should be confirmed, it would no doubt be a serious
+blow to the Darwinian theory. As Darwin said: "Under a scientific point
+of view, and as leading to further investigation, but little advantage
+is gained by believing that new forms are suddenly developed in an
+inexplicable manner from old and widely different forms, over the old
+belief in the creation of species from the dust of the earth." ("Origin
+of Species", page 424.)
+
+It most however be pointed out, that such mutations as Zeiller, and to
+some extent Arber and Parkin, appear to have in view, bridging the gulf
+between different Orders and Classes, bear no relation to any mutations
+which have been actually observed, such as the comparatively small
+changes, of sub-specific value, described by De Vries in the type-case
+of Oenothera Lamarckiana. The results of palaeobotanical research have
+undoubtedly tended to fill up gaps in the Natural System of plants--that
+many such gaps still persist is not surprising; their presence may well
+serve as an incentive to further research but does not, as it seems
+to the writer, justify the assumption of changes in the past, wholly
+without analogy among living organisms.
+
+As regards the succession of species, there are no greater authorities
+than Grand'Eury and Zeiller, and great weight must be attached to their
+opinion that the evidence from continuous deposits favours a somewhat
+sudden change from one specific form to another. At the same time
+it will be well to bear in mind that the subject of the "absence of
+numerous intermediate varieties in any single formation" was fully
+discussed by Darwin. ("Origin of Species", pages 275-282, and page
+312.); the explanation which he gave may go a long way to account for
+the facts which recent writers have regarded as favouring the theory of
+saltatory mutation.
+
+The rapid sketch given in the present essay can do no more than call
+attention to a few salient points, in which the palaeontological records
+of plants has an evident bearing on the Darwinian theory. At the present
+day the whole subject of palaeobotany is a study in evolution, and
+derives its chief inspiration from the ideas of Darwin and Wallace. In
+return it contributes something to the verification of their teaching;
+the recent progress of the subject, in spite of the immense difficulties
+which still remain, has added fresh force to Darwin's statement that
+"the great leading facts in palaeontology agree admirably with the
+theory of descent with modification through variation and natural
+selection." (Ibid. page 313.)
+
+
+
+
+XIII. THE INFLUENCE OF ENVIRONMENT ON THE FORMS OF PLANTS. By Georg
+Klebs, PH.D.
+
+Professor of Botany in the University of Heidelberg.
+
+
+The dependence of plants on their environment became the object of
+scientific research when the phenomena of life were first investigated
+and physiology took its place as a special branch of science. This
+occurred in the course of the eighteenth century as the result of the
+pioneer work of Hales, Duhamel, Ingenhousz, Senebier and others. In
+the nineteenth century, particularly in the second half, physiology
+experienced an unprecedented development in that it began to concern
+itself with the experimental study of nutrition and growth, and with
+the phenomena associated with stimulus and movement; on the other hand,
+physiology neglected phenomena connected with the production of form, a
+department of knowledge which was the province of morphology, a purely
+descriptive science. It was in the middle of the last century that the
+growth of comparative morphology and the study of phases of development
+reached their highest point.
+
+The forms of plants appeared to be the expression of their inscrutable
+inner nature; the stages passed through in the development of the
+individual were regarded as the outcome of purely internal and hidden
+laws. The feasibility of experimental inquiry seemed therefore remote.
+Meanwhile, the recognition of the great importance of such a causal
+morphology emerged from the researches of the physiologists of that
+time, more especially from those of Hofmeister (Hofmeister, "Allgemeine
+Morphologie", Leipzig, 1868, page 579.), and afterwards from the work of
+Sachs. (Sachs, "Stoff und Form der Pflanzenorgane", Vol. I. 1880; Vol.
+II. 1882. "Gesammelte Abhandlungen uber Pflanzen-Physiologie", II.
+Leipzig, 1893.) Hofmeister, in speaking of this line of inquiry,
+described it as "the most pressing and immediate aim of the investigator
+to discover to what extent external forces acting on the organism are of
+importance in determining its form." This advance was the outcome of the
+influence of that potent force in biology which was created by Darwin's
+"Origin of Species" (1859).
+
+The significance of the splendid conception of the transformation of
+species was first recognised and discussed by Lamarck (1809); as an
+explanation of transformation he at once seized upon the idea--an
+intelligible view--that the external world is the determining factor.
+Lamarck (Lamarck, "Philosophie zoologique", pages 223-227. Paris, 1809.)
+endeavoured, more especially, to demonstrate from the behaviour
+of plants that changes in environment induce change in form which
+eventually leads to the production of new species. In the case of
+animals, Lamarck adopted the teleological view that alterations in the
+environment first lead to alterations in the needs of the organisms,
+which, as the result of a kind of conscious effort of will, induce
+useful modifications and even the development of new organs. His work
+has not exercised any influence on the progress of science: Darwin
+himself confessed in regard to Lamarck's work--"I got not a fact or idea
+from it." ("Life and Letters", Vol. II. page 215.)
+
+On a mass of incomparably richer and more essential data Darwin
+based his view of the descent of organisms and gained for it general
+acceptance; as an explanation of modification he elaborated the
+ingeniously conceived selection theory. The question of special interest
+in this connection, namely what is the importance of the influence
+of the environment, Darwin always answered with some hesitation and
+caution, indeed with a certain amount of indecision.
+
+The fundamental principle underlying his theory is that of general
+variability as a whole, the nature and extent of which, especially
+in cultivated organisms, are fully dealt with in his well-known book.
+(Darwin, "The variation of Animals and Plants under domestication",
+2 vols., edition 1, 1868; edition 2, 1875; popular edition 1905.) In
+regard to the question as to the cause of variability Darwin adopts a
+consistently mechanical view. He says: "These several considerations
+alone render it probable that variability of every kind is directly or
+indirectly caused by changed conditions of life. Or, to put the case
+under another point of view, if it were possible to expose all the
+individuals of a species during many generations to absolutely uniform
+conditions of life, there would be no variability." ("The variation of
+Animals and Plants" (2nd edition), Vol. II. page 242.) Darwin did not
+draw further conclusions from this general principle.
+
+Variations produced in organisms by the environment are distinguished by
+Darwin as "the definite" and "the indefinite." (Ibid. II. page 260. See
+also "Origin of Species" (6th edition), page 6.) The first occur "when
+all or nearly all the offspring of an individual exposed to certain
+conditions during several generations are modified in the same manner."
+Indefinite variation is much more general and a more important factor in
+the production of new species; as a result of this, single individuals
+are distinguished from one another by "slight" differences, first in
+one then in another character. There may also occur, though this is very
+rare, more marked modifications, "variations which seem to us in our
+ignorance to arise spontaneously." ("Origin of Species" (6th edition),
+page 421.) The selection theory demands the further postulate that such
+changes, "whether extremely slight or strongly marked," are inherited.
+Darwin was no nearer to an experimental proof of this assumption than to
+the discovery of the actual cause of variability. It was not until the
+later years of his life that Darwin was occupied with the "perplexing
+problem... what causes almost every cultivated plant to vary" ("Life
+and Letters", Vol. III. page 342.): he began to make experiments on the
+influence of the soil, but these were soon given up.
+
+In the course of the violent controversy which was the outcome of
+Darwin's work the fundamental principles of his teaching were not
+advanced by any decisive observations. Among the supporters and
+opponents, Nageli (Nageli, "Theorie der Abstammungslehre", Munich, 1884;
+cf. Chapter III.) was one of the few who sought to obtain proofs by
+experimental methods. His extensive cultural experiments with alpine
+Hieracia led him to form the opinion that the changes which are induced
+by an alteration in the food-supply, in climate or in habitat, are not
+inherited and are therefore of no importance from the point of view of
+the production of species. And yet Nageli did attribute an important
+influence to the external world; he believed that adaptations of plants
+arise as reactions to continuous stimuli, which supply a need and are
+therefore useful. These opinions, which recall the teleological
+aspect of Lamarckism, are entirely unsupported by proof. While other
+far-reaching attempts at an explanation of the theory of descent were
+formulated both in Nageli's time and afterwards, some in support of,
+others in opposition to Darwin, the necessity of investigating, from
+different standpoints, the underlying causes, variability and heredity,
+was more and more realised. To this category belong the statistical
+investigations undertaken by Quetelet and Galton, the researches into
+hybridisation, to which an impetus was given by the re-discovery of
+the Mendelian law of segregation, as also by the culture experiments
+on mutating species following the work of de Vries, and lastly the
+consideration of the question how far variation and heredity are
+governed by external influences. These latter problems, which
+are concerned in general with the causes of form-production and
+form-modification, may be treated in a short summary which falls under
+two heads, one having reference to the conditions of form-production in
+single species, the other being concerned with the conditions governing
+the transformation of species.
+
+I. THE INFLUENCE OF EXTERNAL CONDITIONS ON FORM-PRODUCTION IN SINGLE
+SPECIES.
+
+The members of plants, which we express by the terms stem, leaf, flower,
+etc. are capable of modification within certain limits; since Lamarck's
+time this power of modification has been brought more or less into
+relation with the environment. We are concerned not only with the
+question of experimental demonstration of this relationship, but, more
+generally, with an examination of the origin of forms, the sequences of
+stages in development that are governed by recognisable causes. We have
+to consider the general problem; to study the conditions of all typical
+as well as of atypic forms, in other words, to found a physiology of
+form.
+
+If we survey the endless variety of plant-forms and consider the highly
+complex and still little known processes in the interior of cells, and
+if we remember that the whole of this branch of investigation came into
+existence only a few decades ago, we are able to grasp the fact that
+a satisfactory explanation of the factors determining form cannot be
+discovered all at once. The goal is still far away. We are not concerned
+now with the controversial question, whether, on the whole, the
+fundamental processes in the development of form can be recognised by
+physiological means. A belief in the possibility of this can in any case
+do no harm. What we may and must attempt is this--to discover points
+of attack on one side or another, which may enable us by means of
+experimental methods to come into closer touch with these elusive
+and difficult problems. While we are forced to admit that there is at
+present much that is insoluble there remains an inexhaustible supply of
+problems capable of solution.
+
+The object of our investigations is the species; but as regards the
+question, what is a species, science of to-day takes up a position
+different from that of Darwin. For him it was the Linnean species which
+illustrates variation: we now know, thanks to the work of Jordan,
+de Bary, and particularly to that of de Vries (de Vries, "Die
+Mutationstheorie", Leipzig, 1901, Vol. I. page 33.), that the Linnean
+species consists of a large or small number of entities, elementary
+species. In experimental investigation it is essential that observations
+be made on a pure species, or, as Johannsen (Johannsen, "Ueber
+Erblichkeit in Populationen und reinen Linien", Jena, 1903.) says, on
+a pure "line." What has long been recognised as necessary in the
+investigation of fungi, bacteria and algae must also be insisted on in
+the case of flowering plants; we must start with a single individual
+which is reproduced vegetatively or by strict self-fertilisation.
+In dioecious plants we must aim at the reproduction of brothers and
+sisters.
+
+We may at the outset take it for granted that a pure species remains the
+same under similar external conditions; it varies as these vary. IT IS
+CHARACTERISTIC OF A SPECIES THAT IT ALWAYS EXHIBITS A CONSTANT RELATION
+TO A PARTICULAR ENVIRONMENT. In the case of two different species, e.g.
+the hay and anthrax bacilli or two varieties of Campanula with blue and
+white flowers respectively, a similar environment produces a constant
+difference. The cause of this is a mystery.
+
+According to the modern standpoint, the living cell is a complex
+chemico-physical system which is regarded as a dynamical system of
+equilibrium, a conception suggested by Herbert Spencer and which has
+acquired a constantly increasing importance in the light of modern
+developments in physical chemistry. The various chemical compounds,
+proteids, carbohydrates, fats, the whole series of different ferments,
+etc. occur in the cell in a definite physical arrangement. The two
+systems of two species must as a matter of fact possess a constant
+difference, which it is necessary to define by a special term. We say,
+therefore, that the SPECIFIC STRUCTURE is different.
+
+By way of illustrating this provisionally, we may assume that the
+proteids of the two species possess a constant chemical difference. This
+conception of specific structure is specially important in its bearing
+on a further treatment of the subject. In the original cell, eventually
+also in every cell of a plant, the characters which afterwards
+become apparent must exist somewhere; they are integral parts of the
+capabilities or potentialities of specific structure. Thus not only the
+characters which are exhibited under ordinary conditions in nature, but
+also many others which become apparent only under special conditions (In
+this connection I leave out of account, as before, the idea of material
+carriers of heredity which since the publication of Darwin's Pangenesis
+hypothesis has been frequently suggested. See my remarks in "Variationen
+der Bluten", "Pringsheim's Jahrb. Wiss. Bot." 1905, page 298; also
+Detto, "Biol. Centralbl." 1907, page 81, "Die Erklarbarkeit der
+Ontogenese durch materielle Anlagen".), are to be included as such
+potentialities in cells; the conception of specific structure includes
+the WHOLE OF THE POTENTIALITIES OF A SPECIES; specific structure
+comprises that which we must always assume without being able to explain
+it.
+
+A relatively simple substance, such as oxalate of lime, is known under
+a great number of different crystalline forms belonging to different
+systems (Compare Kohl's work on "Anatomisch-phys. Untersuchungen uber
+Kalksalze", etc. Marburg, 1889.); these may occur as single crystals,
+concretions or as concentric sphaerites. The power to assume this
+variety of form is in some way inherent in the molecular structure,
+though we cannot, even in this case, explain the necessary connection
+between structure and crystalline form. These potentialities can only
+become operative under the influence of external conditions; their
+stimulation into activity depends on the degree of concentration of the
+various solutions, on the nature of the particular calcium salt, on the
+acid or alkaline reactions. Broadly speaking, the plant cell behaves in
+a similar way. The manifestation of each form, which is inherent as a
+potentiality in the specific structure, is ultimately to be referred to
+external conditions.
+
+An insight into this connection is, however, rendered exceedingly
+difficult, often quite impossible, because the environment never
+directly calls into action the potentialities. Its influence is exerted
+on what we may call the inner world of the organism, the importance of
+which increases with the degree of differentiation. The production of
+form in every plant depends upon processes in the interior of the cells,
+and the nature of these determines which among the possible characters
+is to be brought to light. In no single case are we acquainted with the
+internal process responsible for the production of a particular
+form. All possible factors may play a part, such as osmotic pressure,
+permeability of the protoplasm, the degree of concentration of the
+various chemical substances, etc.; all these factors should be included
+in the category of INTERNAL CONDITIONS. This inner world appears the
+more hidden from our ken because it is always represented by a certain
+definite state, whether we are dealing with a single cell or with a
+small group of cells. These have been produced from pre-existing cells
+and they in turn from others; the problem is constantly pushed back
+through a succession of generations until it becomes identified with
+that of the origin of species.
+
+A way, however, is opened for investigation; experience teaches us that
+this inner world is not a constant factor: on the contrary, it appears
+to be very variable. The dependence of VARIABLE INTERNAL on VARIABLE
+EXTERNAL conditions gives us the key with which research may open the
+door. In the lower plants this dependence is at once apparent, each cell
+is directly subject to external influences. In the higher plants with
+their different organs, these influences were transmitted to cells in
+course of development along exceedingly complex lines. In the case of
+the growing-point of a bud, which is capable of producing a complete
+plant, direct influences play a much less important part than those
+exerted through other organs, particularly through the roots and leaves,
+which are essential in nutrition. These correlations, as we may call
+them, are of the greatest importance as aids to an understanding of
+form-production. When a bud is produced on a particular part of a plant,
+it undergoes definite internal modifications induced by the influence of
+other organs, the activity of which is governed by the environment, and
+as the result of this it develops along a certain direction; it may,
+for example, become a flower. The particular direction of development
+is determined before the rudiment is differentiated and is exerted so
+strongly that further development ensues without interruption, even
+though the external conditions vary considerably and exert a positively
+inimical influence: this produces the impression that development
+proceeds entirely independently of the outer world. The widespread
+belief that such independence exists is very premature and at all events
+unproven.
+
+The state of the young rudiment is the outcome of previous influences of
+the external world communicated through other organs. Experiments show
+that in certain cases, if the efficiency of roots and leaves as organs
+concerned with nutrition is interfered with, the production of flowers
+is affected, and their characters, which are normally very constant,
+undergo far-reaching modifications. To find the right moment at which to
+make the necessary alteration in the environment is indeed difficult
+and in many cases not yet possible. This is especially the case with
+fertilised eggs, which in a higher degree than buds have acquired,
+through parental influences, an apparently fixed internal organisation,
+and this seems to have pre-determined their development. It is, however,
+highly probable that it will be possible, by influencing the parents,
+to alter the internal organisation and to switch off development on to
+other lines.
+
+Having made these general observations I will now cite a few of the many
+facts at our disposal, in order to illustrate the methods and aim of the
+experimental methods of research. As a matter of convenience I will deal
+separately with modification of development and with modification of
+single organs.
+
+I. EFFECT OF ENVIRONMENT UPON THE COURSE OF DEVELOPMENT.
+
+Every plant, whether an alga or a flowering plant passes, under natural
+conditions, through a series of developmental stages characteristic of
+each species, and these consist in a regular sequence of definite
+forms. It is impossible to form an opinion from mere observation and
+description as to what inner changes are essential for the production of
+the several forms. We must endeavour to influence the inner factors by
+known external conditions in such a way that the individual stages in
+development are separately controlled and the order of their sequence
+determined at will by experimental treatment. Such control over the
+course of development may be gained with special certainty in the case
+of the lower organisms.
+
+With these it is practicable to control the principal conditions of
+cultivation and to vary them in various ways. By this means it has been
+demonstrated that each developmental stage depends upon special external
+conditions, and in cases where our knowledge is sufficient, a particular
+stage may be obtained at will. In the Green Algae (See Klebs, "Die
+Bedingung der Fortpflanzung... ", Jena, 1896; also "Jahrb. fur
+Wiss. Bot." 1898 and 1900; "Probleme der Entwickelung, III." "Biol.
+Centralbl." 1904, page 452.), as in the case of Fungi, we may classify
+the stages of development into purely vegetative growth (growth,
+cell-division, branching), asexual reproduction (formation of zoospores,
+conidia) and sexual processes (formation of male and female sexual
+organs). By modifying the external conditions it is possible to induce
+algae or fungi (Vaucheria, Saprolegnia) to grow continuously for
+several years or, in the course of a few days, to die after an enormous
+production of asexual or sexual cells. In some instances even an almost
+complete stoppage of growth may be caused, reproductive cells being
+scarcely formed before the organism is again compelled to resort to
+reproduction. Thus the sequence of the different stages in development
+can be modified as we may desire.
+
+The result of a more thorough investigation of the determining
+conditions appears to produce at first sight a confused impression
+of all sorts of possibilities. Even closely allied species exhibit
+differences in regard to the connection between their development and
+external conditions. It is especially noteworthy that the same form in
+development may be produced as the result of very different alterations
+in the environment. At the same time we can undoubtedly detect a certain
+unity in the multiplicity of the individual phenomena.
+
+If we compare the factors essential for the different stages in
+development, we see that the question always resolves itself into one
+of modification of similar conditions common to all life-processes. We
+should rather have inferred that there exist specific external stimuli
+for each developmental stage, for instance, certain chemical agencies.
+Experiments hitherto made support the conclusion that QUANTITATIVE
+alterations in the general conditions of life produce different types of
+development. An alga or a fungus grows so long as all the conditions
+of nutrition remain at a certain optimum for growth. In order to bring
+about asexual reproduction, e.g. the formation of zoospores, it is
+sometimes necessary to increase the degree of intensity of external
+factors; sometimes, on the other hand, these must be reduced in
+intensity. In the case of many algae a decrease in light-intensity or
+in the amount of salts in the culture solution, or in the temperature,
+induces asexual reproduction, while in others, on the contrary, an
+increase in regard to each of these factors is required to produce
+the same result. This holds good for the quantitative variations which
+induce sexual reproduction in algae. The controlling factor is found to
+be a reduction in the supply of nutritive salts and the exposure of the
+plants to prolonged illumination or, better still, an increase in the
+intensity of the light, the efficiency of illumination depending on the
+consequent formation of organic substances such as carbohydrates.
+
+The quantitative alterations of external conditions may be spoken of as
+releasing stimuli. They produce, in the complex equilibrium of the cell,
+quantitative modifications in the arrangement and distribution of mass,
+by means of which other chemical processes are at once set in motion,
+and finally a new condition of equilibrium is attained. But the
+commonly expressed view that the environment can as a rule act only as
+a releasing agent is incorrect, because it overlooks an essential point.
+The power of a cell to receive stimuli is only acquired as the result
+of previous nutrition, which has produced a definite condition of
+concentration of different substances. Quantities are in this case
+the determining factors. The distribution of quantities is especially
+important in the sexual reproduction of algae, for which a vigorous
+production of the materials formed during carbon-assimilation appears to
+be essential.
+
+In the Flowering plants, on the other hand, for reasons already
+mentioned, the whole problem is more complicated. Investigations on
+changes in the course of development of fertilised eggs have hitherto
+been unsuccessful; the difficulty of influencing egg-cells deeply
+immersed in tissue constitutes a serious obstacle. Other parts of plants
+are, however, convenient objects of experiment; e.g. the growing apices
+of buds which serve as cuttings for reproductive purposes, or buds on
+tubers, runners, rhizomes, etc. A growing apex consists of cells capable
+of division in which, as in egg-cells, a complete series of latent
+possibilities of development is embodied. Which of these possibilities
+becomes effective depends upon the action of the outer world transmitted
+by organs concerned with nutrition.
+
+Of the different stages which a flowering plant passes through in the
+course of its development we will deal only with one in order to show
+that, in spite of its great complexity, the problem is, in essentials,
+equally open to attack in the higher plants and in the simplest
+organisms. The most important stage in the life of a flowering plant
+is the transition from purely vegetative growth to sexual
+reproduction--that is, the production of flowers. In certain cases it
+can be demonstrated that there is no internal cause, dependent simply
+on the specific structure, which compels a plant to produce its flowers
+after a definite period of vegetative growth. (Klebs, "Willkurliche
+Entwickelungsanderungen", Jena 1903; see also "Probleme der
+Entwickelung", I. II. "Centralbl." 1904.)
+
+One extreme case, that of exceptionally early flowering, has been
+observed in nature and more often in cultivation. A number of plants
+under certain conditions are able to flower soon after germination.
+(Cf. numerous records of this kind by Diels, "Jugendformen und Bluten",
+Berlin, 1906.) This shortening of the period of development is exhibited
+in the most striking form in trees, as in the oak (Mobius, "Beitrage zur
+Lehre von der Fortpflanzung", Jena, 1897, page 89.), flowering seedlings
+of which have been observed from one to three years old, whereas
+normally the tree does not flower until it is sixty or eighty years old.
+
+Another extreme case is represented by prolonged vegetative growth
+leading to the complete suppression of flower-production. This result
+may be obtained with several plants, such as Glechoma, the sugar beet,
+Digitalis, and others, if they are kept during the winter in a warm,
+damp atmosphere, and in rich soil; in the following spring or summer
+they fail to flower. (Klebs, "Willkurliche Aenderungen", etc. Jena,
+1903, page 130.) Theoretically, however, experiments are of greater
+importance in which the production of flowers is inhibited by
+very favourable conditions of nutrition (Klebs, "Ueber kunstliche
+Metamorphosen", Stuttgart, 1906, page 115) ("Abh. Naturf. Ges. Halle",
+XXV.) occurring at the normal flowering period. Even in the case of
+plants of Sempervivum several years old, which, as is shown by control
+experiments on precisely similar plants, are on the point of flowering,
+flowering is rendered impossible if they are forced to very vigorous
+growth by an abundant supply of water and salts in the spring.
+Flowering, however, occurs, if such plants are cultivated in relatively
+dry sandy soil and in the presence of strong light. Careful researches
+into the conditions of growth have led, in the cases Sempervivum, to
+the following results: (1) With a strong light and vigorous
+carbon-assimilation a considerably increased supply of water and
+nutritive salts produces active vegetative growth. (2) With a vigorous
+carbon-assimilation in strong light, and a decrease in the supply of
+water and salts active flower-production is induced. (3) If an average
+supply of water and salts is given both processes are possible;
+the intensity of carbon-assimilation determines which of the two is
+manifested. A diminution in the production of organic substances,
+particularly of carbohydrates, induces vegetative growth. This can
+be effected by culture in feeble light or in light deprived of the
+yellow-red rays: on the other hand, flower-production follows an
+increase in light-intensity. These results are essentially in agreement
+with well-known observations on cultivated plants, according to which,
+the application of much moisture, after a plentiful supply of manure
+composed of inorganic salts, hinders the flower-production of many
+vegetables, while a decrease in the supply of water and salts favours
+flowering.
+
+ii. INFLUENCE OF THE ENVIRONMENT ON THE FORM OF SINGLE ORGANS. (A
+considerable number of observations bearing on this question are given
+by Goebel in his "Experimentelle Morphologie der Pflanzen", Leipzig,
+1908. It is not possible to deal here with the alteration in anatomical
+structure; cf. Kuster, "Pathologische Pflanzenanatomie", Jena, 1903.)
+
+If we look closely into the development of a flowering plant, we notice
+that in a given species differently formed organs occur in definite
+positions. In a potato plant colourless runners are formed from the
+base of the main stem which grow underground and produce tubers at their
+tips: from a higher level foliage shoots arise nearer the apex. External
+appearances suggest that both the place of origin and the form of these
+organs were predetermined in the egg-cell or in the tuber. But it was
+shown experimentally by the well-known investigator Knight (Knight,
+"Selection from the Physiological and Horticultural Papers", London,
+1841.) that tubers may be developed on the aerial stem in place of
+foliage shoots. These observations were considerably extended by
+Vochting. (Vochting, "Ueber die Bildung der Knollen", Cassel, 1887; see
+also "Bot. Zeit." 1902, 87.) In one kind of potato, germinating tubers
+were induced to form foliage shoots under the influence of a higher
+temperature; at a lower temperature they formed tuber-bearing shoots.
+Many other examples of the conversion of foliage-shoots into runners and
+rhizomes, or vice versa, have been described by Goebel and others. As in
+the asexual reproduction of algae quantitative alteration in the amount
+of moisture, light, temperature, etc. determines whether this or that
+form of shoot is produced. If the primordia of these organs are exposed
+to altered conditions of nutrition at a sufficiently early stage a
+complete substitution of one organ for another is effected. If the
+rudiment has reached a certain stage in development before it is exposed
+to these influences, extraordinary intermediate forms are obtained,
+bearing the characters of both organs.
+
+The study of regeneration following injury is of greater importance as
+regards the problem of the development and place of origin of organs.
+(Reference may be made to the full summary of results given by Goebel in
+his "Experimentelle Morphologie", Leipzig and Berlin, 1908, Section IV.)
+Only in relatively very rare cases is there a complete re-formation
+of the injured organ itself, as e.g. in the growing-apex. Much more
+commonly injury leads to the development of complementary formations, it
+may be the rejuvenescence of a hitherto dormant rudiment, or it may be
+the formation of such ab initio. In all organs, stems, roots, leaves,
+as well as inflorescences, this kind of regeneration, which occurs in
+a great variety of ways according to the species, may be observed on
+detached pieces of the plant. Cases are also known, such, for example,
+as the leaves of many plants which readily form roots but not shoots,
+where a complete regeneration does not occur.
+
+The widely spread power of reacting to wounding affords a very valuable
+means of inducing a fresh development of buds and roots on places
+where they do not occur in normal circumstances. Injury creates special
+conditions, but little is known as yet in regard to alterations directly
+produced in this way. Where the injury consists in the separation of
+an organ from its normal connections, the factors concerned are more
+comprehensible. A detached leaf, e.g., is at once cut off from a supply
+of water and salts, and is deprived of the means of getting rid of
+organic substances which it produces; the result is a considerable
+alteration in the degree of concentration. No experimental investigation
+on these lines has yet been made. Our ignorance has often led to the
+view that we are dealing with a force whose specific quality is the
+restitution of the parts lost by operation; the proof, therefore,
+that in certain cases a similar production of new roots or buds may
+be induced without previous injury and simply by a change in external
+conditions assumes an importance. (Klebs, "Willkurliche Entwickelung",
+page 100; also, "Probleme der Entwickelung", "Biol. Centralbl." 1904,
+page 610.)
+
+A specially striking phenomenon of regeneration, exhibited also by
+uninjured plants, is afforded by polarity, which was discovered by
+Vochting. (See the classic work of Vochting, "Ueber Organbildung im
+Pflanzenreich", I. Bonn, 1888; also "Bot. Zeit." 1906, page 101; cf.
+Goebel, "Experimentelle Morphologie", Leipzig and Berlin, 1908, Section
+V, Polaritat.) It is found, for example, that roots are formed from the
+base of a detached piece of stem and shoots from the apex. Within
+the limits of this essay it is impossible to go into this difficult
+question; it is, however, important from the point of view of our
+general survey to emphasise the fact that the physiological distinctions
+between base and apex of pieces of stem are only of a quantitative
+kind, that is, they consist in the inhibition of certain phenomena or
+in favouring them. As a matter of fact roots may be produced from the
+apices of willows and cuttings of other plants; the distinction is thus
+obliterated under the influence of environment. The fixed polarity of
+cuttings from full grown stems cannot be destroyed; it is the expression
+of previous development. Vochting speaks of polarity as a fixed
+inherited character. This is an unconvincing conclusion, as nothing can
+be deduced from our present knowledge as to the causes which led up to
+polarity. We know that the fertilised egg, like the embryo, is fixed at
+one end by which it hangs freely in the embryo-sac and afterwards in
+the endosperm. From the first, therefore, the two ends have different
+natures, and these are revealed in the differentiation into root-apex
+and stem-apex. A definite direction in the flow of food-substances
+is correlated with this arrangement, and this eventually leads to a
+polarity in the tissues. This view requires experimental proof, which in
+the case of the egg-cells of flowering plants hardly appears possible;
+but it derives considerable support from the fact that in herbaceous
+plants, e.g. Sempervivum (Klebs, "Variationen der Bluten", "Jahrb. Wiss.
+Bot." 1905, page 260.), rosettes or flower-shoots are formed in response
+to external conditions at the base, in the middle, or at the apex of the
+stem, so that polarity as it occurs under normal conditions cannot be
+the result of unalterable hereditary factors. On the other hand, the
+lower plants should furnish decisive evidence on this question, and
+the experiments of Stahl, Winkler, Kniep, and others indicate the right
+method of attacking the problem.
+
+The relation of leaf-form to environment has often been investigated and
+is well known. The leaves of bog and water plants (Cf.Goebel, loc.
+cit. chapter II.; also Gluck, "Untersuchungen uber Wasser- und
+Sumpfgewachse", Jena, Vols. I.-II. 1905-06.) afford the most striking
+examples of modifications: according as they are grown in water, moist
+or dry air, the form of the species characteristic of the particular
+habitat is produced, since the stems are also modified. To the same
+group of phenomena belongs the modification of the forms of leaves and
+stems in plants on transplantation from the plains to the mountains
+(Bonnier, "Recherches sur l'Anatomie experimentale des Vegetaux",
+Corbeil, 1895.) or vice versa. Such variations are by no means isolated
+examples. All plants exhibit a definite alteration in form as the result
+of prolonged cultivation in moist or dry air, in strong or feeble
+light, or in darkness, or in salt solutions of different composition and
+strength.
+
+Every individual which is exposed to definite combinations of external
+factors exhibits eventually the same type of modification. This is the
+type of variation which Darwin termed "definite." It is easy to realise
+that indefinite or fluctuating variations belong essentially to the same
+class of phenomena; both are reactions to changes in environment. In the
+production of individual variations two different influences undoubtedly
+cooperate. One set of variations is caused by different external
+conditions, during the production, either of sexual cells or of
+vegetative primordia; another set is the result of varying external
+conditions during the development of the embryo into an adult plant. The
+two sets of influences cannot as yet be sharply differentiated. If,
+for purposes of vegetative reproduction, we select pieces of the
+same parent-plant of a pure species, the second type of variation
+predominates. Individual fluctuations depend essentially in such cases
+on small variations in environment during development.
+
+These relations must be borne in mind if we wish to understand the
+results of statistical methods. Since the work of Quetelet, Galton, and
+others the statistical examination of individual differences in animals
+and plants has become a special science, which is primarily based on the
+consideration that the application of the theory of probability renders
+possible mathematical statement and control of the results. The facts
+show that any character, size of leaf, length of stem, the number of
+members in a flower, etc. do not vary haphazard but in a very regular
+manner. In most cases it is found that there is a value which occurs
+most commonly, the average or medium value, from which the larger and
+smaller deviations, the so-called plus and minus variations fall away in
+a continuous series and end in a limiting value. In the simpler cases
+a falling off occurs equally on both sides of the curve; the curve
+constructed from such data agrees very closely with the Gaussian curve
+of error. In more complicated cases irregular curves of different kinds
+are obtained which may be calculated on certain suppositions.
+
+The regular fluctuations about a mean according to the rule of
+probability is often attributed to some law underlying variability. (de
+Vries, "Mutationstheorie", Vol. I. page 35, Leipzig, 1901.) But there is
+no such law which compels a plant to vary in a particular manner. Every
+experimental investigation shows, as we have already remarked, that
+the fluctuation of characters depends on fluctuation in the external
+factors. The applicability of the method of probability follows from
+the fact that the numerous individuals of a species are influenced by
+a limited number of variable conditions. (Klebs, "Willkurl. Ent." Jena,
+1903, page 141.) As each of these conditions includes within certain
+limits all possible values and exhibits all possible combinations, it
+follows that, according to the rules of probability, there must be
+a mean value, about which the larger and smaller deviations are
+distributed. Any character will be found to have the mean value which
+corresponds with that combination of determining factors which occurs
+most frequently. Deviations towards plus and minus values will be
+correspondingly produced by rarer conditions.
+
+A conclusion of fundamental importance may be drawn from this
+conception, which is, to a certain extent, supported by experimental
+investigation. (Klebs, "Studien uber Variation", "Arch. fur Entw."
+1907.) There is no normal curve for a particular CHARACTER, there is
+only a curve for the varying combinations of conditions occurring in
+nature or under cultivation. Under other conditions entirely different
+curves may be obtained with other variants as a mean value. If, for
+example, under ordinary conditions the number 10 is the most frequent
+variant for the stamens of Sedum spectabile, in special circumstances
+(red light) this is replaced by the number 5. The more accurately we
+know the conditions for a particular form or number, and are able to
+reproduce it by experiment, the nearer we are to achieving our aim of
+rendering a particular variation impossible or of making it dominant.
+
+In addition to the individual variations of a species, more pronounced
+fluctuations occur relatively rarely and sporadically which are spoken
+of as "single variations," or if specially striking as abnormalities
+or monstrosities. These forms have long attracted the attention of
+morphologists; a large number of observations of this kind are given
+in the handbooks of Masters (Masters, "Vegetable Teratology", London,
+1869.) and Penzig (Penzig, "Pflanzen-Teratologie", Vols I. and II. Genua,
+1890-94.) These variations, which used to be regarded as curiosities,
+have now assumed considerable importance in connection with the causes
+of form-development. They also possess special interest in relation to
+the question of heredity, a subject which does not at present concern
+us, as such deviations from normal development undoubtedly arise as
+individual variations induced by the influence of environment.
+
+Abnormal developments of all kinds in stems, leaves, and flowers, may
+be produced by parasites, insects, or fungi. They may also be induced
+by injury, as Blaringhem (Blaringhem, "Mutation et traumatismes", Paris,
+1907.) has more particularly demonstrated, which, by cutting away the
+leading shoots of branches in an early stage of development, caused
+fasciation, torsion, anomalous flowers, etc. The experiments of
+Blaringhem point to the probability that disturbances in the conditions
+of food-supply consequent on injury are the cause of the production of
+monstrosities. This is certainly the case in my experiments with species
+of Sempervivum (Klebs, "Kunstliche Metamorphosen", Stuttgart, 1906.);
+individuals, which at first formed normal flowers, produced a great
+variety of abnormalities as the result of changes in nutrition, we
+may call to mind the fact that the formation of inflorescences occurs
+normally when a vigorous production of organic compounds, such as
+starch, sugar, etc. follows a diminution in the supply of mineral
+salts. On the other hand, the development of inflorescences is entirely
+suppressed if, at a suitable moment before the actual foundations have
+been laid, water and mineral salts are supplied to the roots. If, during
+the week when the inflorescence has just been laid down and is growing
+very slowly, the supply of water and salts is increased, the internal
+conditions of the cells are essentially changed. At a later stage, after
+the elongation of the inflorescence, rosettes of leaves are produced
+instead of flowers, and structures intermediate between the two kinds of
+organs; a number of peculiar plant-forms are thus obtained (Cf. Lotsy,
+"Vorlesungen uber Deszendenztheorien", Vol. II. pl. 3, Jena, 1908.)
+Abnormalities in the greatest variety are produced in flowers by varying
+the time at which the stimulus is applied, and by the cooperation
+of other factors such as temperature, darkness, etc. In number and
+arrangement the several floral members vary within wide limits;
+sepals, petals, stamens, and carpels are altered in form and colour, a
+transformation of stamens to carpels and from carpels to stamens occurs
+in varying degrees. The majority of the deviations observed had not
+previously been seen either under natural conditions or in cultivation;
+they were first brought to light through the influence of external
+factors.
+
+Such transformations of flowers become apparent at a time, which is
+separated by about two months from the period at which the particular
+cause began to act. There is, therefore, no close connection between
+the appearance of the modifications and the external conditions which
+prevail at the moment. When we are ignorant of the causes which are
+operative so long before the results are seen, we gain the impression
+that such variations as occur are spontaneous or autonomous expressions
+of the inner nature of the plant. It is much more likely that, as in
+Sempervivum, they were originally produced by an external stimulus which
+had previously reached the sexual cells or the young embryo. In any case
+abnormalities of this kind appear to be of a special type as compared
+with ordinary fluctuating variations. Darwin pointed out this
+difference; Bateson (Bateson, "Materials for the study of Variation",
+London, 1894, page 5.) has attempted to make the distinction sharper, at
+the same time emphasising its importance in heredity.
+
+Bateson applies the term CONTINUOUS to small variations connected with
+one another by transitional stages, while those which are more striking
+and characterised from the first by a certain completeness, he names
+DISCONTINUOUS. He drew attention to a great difficulty which stands in
+the way of Lamarck's hypothesis, as also of Darwin's view. "According to
+both theories, specific diversity of form is consequent upon diversity
+of environment, and diversity of environment is thus the ultimate
+measure of diversity of specific form. Here then we meet the difficulty
+that diverse environments often shade into each other insensibly and
+form a continuous series, whereas the Specific Forms of life which
+are subject to them on the whole form a Discontinuous Series."
+This difficulty is, however, not of fundamental importance as well
+authenticated facts have been adduced showing that by alteration of the
+environment discontinuous variations, such as alterations in the number
+and form of members of a flower, may be produced. We can as yet no more
+explain how this happens than we can explain the existence of continuous
+variations. We can only assert that both kinds of variation arise
+in response to quantitative alterations in external conditions. The
+question as to which kind of variation is produced depends on the
+greater or less degree of alteration; it is correlated with the state of
+the particular cells at the moment.
+
+In this short sketch it is only possible to deal superficially with a
+small part of the subject. It has been clearly shown that in view of the
+general dependence of development on the factors of the environment
+a number of problems are ready for experimental treatment. One must,
+however, not forget that the science of the physiology of form has not
+progressed beyond its initial stages. Just now our first duty is to
+demonstrate the dependence on external factors in as many forms of
+plants as possible, in order to obtain a more thorough control of all
+the different plant-forms. The problem is not only to produce at will
+(and independently of their normal mode of life) forms which occur
+in nature, but also to stimulate into operation potentialities which
+necessarily lie dormant under the conditions which prevail in nature.
+The constitution of a species is much richer in possibilities of
+development than would appear to be the case under normal conditions. It
+remains for man to stimulate into activity all the potentialities.
+
+But the control of plant-form is only a preliminary step--the foundation
+stones on which to erect a coherent scientific structure. We must
+discover what are the internal processes in the cell produced by
+external factors, which as a necessary consequence result in the
+appearance of a definite form. We are here brought into contact with the
+most obscure problem of life. Progress can only be made pari passu with
+progress in physics and chemistry, and with the growth of our knowledge
+of nutrition, growth, etc.
+
+Let us take one of the simplest cases--an alteration in form. A
+cylindrical cell of the alga Stigeoclonium assumes, as Livingstone
+(Livingstone, "On the nature of the stimulus which causes the change
+of form, etc." "Botanical Gazette", XXX. 1900; also XXXII. 1901.) has
+shown, a spherical form when the osmotic pressure of the culture fluid
+is increased; or a spore of Mucor, which, in a sugar solution grows
+into a branched filament, in the presence of a small quantity of acid
+(hydrogen ions) becomes a comparatively large sphere. (Ritter, "Ueber
+Kugelhefe, etc." "Ber. bot. Gesell." Berlin, XXV. page 255, 1907.)
+In both cases there has undoubtedly been an alteration in the osmotic
+pressure of the cell-sap, but this does not suffice to explain the
+alteration in form, since the unknown alterations, which are induced in
+the protoplasm, must in their turn influence the cell-membrane. In
+the case of the very much more complex alterations in form, such as we
+encounter in the course of development of plants, there do not appear
+to be any clues which lead us to a deeper insight into the phenomena.
+Nevertheless we continue the attempt, seeking with the help of any
+available hypothesis for points of attack, which may enable us to
+acquire a more complete mastery of physiological methods. To quote a
+single example; I may put the question, what internal changes produce a
+transition from vegetative growth to sexual reproduction?
+
+The facts, which are as clearly established from the lower as for the
+higher plants, teach us that quantitative alteration in the environment
+produces such a transition. This suggests the conclusion that
+quantitative internal changes in the cells, and with them disturbances
+in the degree of concentration, are induced, through which the chemical
+reactions are led in the direction of sexual reproduction. An increase
+in the production of organic substances in the presence of light,
+chiefly of the carbohydrates, with a simultaneous decrease in the amount
+of inorganic salts and water, are the cause of the disturbance and
+at the same time of the alteration in the direction of development.
+Possibly indeed mineral salts as such are not in question, but only in
+the form of other organic combinations, particularly proteid material,
+so that we are concerned with an alteration in the relation of the
+carbohydrates and proteids. The difficulties of such researches are very
+great because the methods are not yet sufficiently exact to demonstrate
+the frequently small quantitative differences in chemical composition.
+Questions relating to the enzymes, which are of the greatest importance
+in all these life-processes, are especially complicated. In any case
+it is the necessary result of such an hypothesis that we must employ
+chemical methods of investigation in dealing with problems connected
+with the physiology of form.
+
+II. INFLUENCE OF ENVIRONMENT ON THE TRANSFORMATION OF SPECIES.
+
+The study of the physiology of form-development in a pure species has
+already yielded results and makes slow but sure progress. The physiology
+of the possibility of the transformation of one species into another is
+based, as yet, rather on pious hope than on accomplished fact. From
+the first it appeared to be hopeless to investigate physiologically
+the origin of Linnean species and at the same time that of the natural
+system, an aim which Darwin had before him in his enduring work. The
+historical sequence of events, of which an organism is the expression,
+can only be treated hypothetically with the help of facts supplied
+by comparative morphology, the history of development, geographical
+distribution, and palaeontology. (See Lotsy, "Vorlesungen" (Jena, I.
+1906, II. 1908), for summary of the facts.) A glance at the controversy
+which is going on today in regard to different hypotheses shows that
+the same material may lead different investigators to form entirely
+different opinions. Our ultimate aim is to find a solution of the
+problem as to the cause of the origin of species. Indeed such
+attempts are now being made: they are justified by the fact that under
+cultivation new and permanent strains are produced; the fundamental
+importance of this was first grasped by Darwin. New points of view in
+regard to these lines of inquiry have been adopted by H. de Vries
+who has succeeded in obtaining from Oenothera Lamarckiana a number of
+constant "elementary" species. Even if it is demonstrated that he was
+simply dealing with the complex splitting up of a hybrid (Bateson,
+"Reports to the Evolution Committee of the Royal Society", London, 1902;
+cf. also Lotsy, "Vorlesungen", Vol. I. page 234.), the facts adduced in
+no sense lose their very great value.
+
+We must look at the problem in its simplest form; we find it in every
+case where a new race differs essentially from the original type in a
+single character only; for example, in the colour of the flowers or in
+the petalody of the stamens (doubling of flowers). In this connection
+we must keep in view the fact that every visible character in a plant is
+the resultant of the cooperation of specific structure, with its various
+potentialities, and the influence of the environment. We know, that in
+a pure species all characters vary, that a blue-flowering Campanula or
+a red Sempervivum can be converted by experiment into white-flowering
+forms, that a transformation of stamens into petals may be caused by
+fungi or by the influence of changed conditions of nutrition, or
+that plants in dry and poor soil become dwarfed. But so far as the
+experiments justify a conclusion, it would appear that such alterations
+are not inherited by the offspring. Like all other variations they
+appear only so long as special conditions prevail in the surroundings.
+
+It has been shown that the case is quite different as regards the
+white-flowering, double or dwarf races, because these retain their
+characters when cultivated under practically identical conditions, and
+side by side with the blue, single-flowering or tall races. The problem
+may therefore be stated thus: how can a character, which appears in the
+one case only under the strictly limited conditions of the experiment,
+in other cases become apparent under the very much wider conditions of
+ordinary cultivation? If a character appears, in these circumstances,
+in the case of all individuals, we then speak of constant races. In such
+simple cases the essential point is not the creation of a new character
+but rather an ALTERATION OF THIS CHARACTER IN ACCORDANCE WITH THE
+ENVIRONMENT. In the examples mentioned the modified character in the
+simple varieties (or a number of characters in elementary species)
+appears more or less suddenly and is constant in the above sense. The
+result is what de Vries has termed a Mutation. In this connection we
+must bear in mind the fact that no difference, recognisable externally,
+need exist between individual variation and mutation. Even the most
+minute quantitative difference between two plants may be of specific
+value if it is preserved under similar external conditions during many
+successive generations. We do not know how this happens. We may state
+the problem in other terms; by saying that the specific structure must
+be altered. It is possible, to some extent, to explain this sudden
+alteration, if we regard it as a chemical alteration of structure either
+in the specific qualities of the proteids or of the unknown carriers
+of life. In the case of many organic compounds their morphological
+characters (the physical condition, crystalline form, etc.) are at once
+changed by alteration of atomic relations or by incorporation of new
+radicals. (For instance ethylchloride (C2H5Cl) is a gas at 21 deg
+C., ethylenechloride (C2H4Cl2) a fluid boiling at 84 deg C., beta
+trichlorethane (C2H3Cl3) a fluid boiling at 113 deg C.,
+perchlorethane (C2Cl6) a crystalline substance. Klebs, ("Willkurliche
+Entwickelungsanderungen" page 158.) Much more important, however, would
+be an answer to the question, whether an individual variation can be
+converted experimentally into an inherited character--a mutation in de
+Vries's sense.
+
+In all circumstances we may recognise as a guiding principle the
+assumption adopted by Lamarck, Darwin, and many others, that the
+inheritance of any one character, or in more general terms, the
+transformation of one species into another, is, in the last instance,
+to be referred to a change in the environment. From a causal-mechanical
+point of view it is not a priori conceivable that one species can
+ever become changed into another so long as external conditions remain
+constant. The inner structure of a species must be essentially altered
+by external influences. Two methods of experimental research may be
+adopted, the effect of crossing distinct species and, secondly, the
+effect of definite factors of the environment.
+
+The subject of hybridisation is dealt with in another part of this
+essay. It is enough to refer here to the most important fact, that as
+the result of combinations of characters of different species new and
+constant forms are produced. Further, Tschermack, Bateson and others
+have demonstrated the possibility that hitherto unknown inheritable
+characters may be produced by hybridisation.
+
+The other method of producing constant races by the influence of special
+external conditions has often been employed. The sporeless races of
+Bacteria and Yeasts (Cf. Detto, "Die Theorie der direkten Anpassung... ",
+pages 98 et seq., Jena, 1904; see also Lotsy, "Vorlesungen", II. pages
+636 et seq., where other similar cases are described.) are well known,
+in which an internal alteration of the cells is induced by the influence
+of poison or higher temperature, so that the power of producing spores
+even under normal conditions appears to be lost. A similar state of
+things is found in some races which under certain definite conditions
+lose their colour or their virulence. Among the phanerogams the
+investigations of Schubler on cereals afford parallel cases, in which
+the influence of a northern climate produces individuals which ripen
+their seeds early; these seeds produce plants which seed early in
+southern countries. Analogous results were obtained by Cieslar in his
+experiments; seeds of conifers from the Alps when planted in the plains
+produced plants of slow growth and small diameter.
+
+All these observations are of considerable interest theoretically; they
+show that the action of environment certainly induces such internal
+changes, and that these are transmitted to the next generation. But as
+regards the main question, whether constant races may be obtained by
+this means, the experiments cannot as yet supply a definite answer. In
+phanerogams, the influence very soon dies out in succeeding generations;
+in the case of bacteria, in which it is only a question of the loss of
+a character it is relatively easy for this to reappear. It is not
+impossible, that in all such cases there is a material hanging-on of
+certain internal conditions, in consequence of which the modification
+of the character persists for a time in the descendants, although the
+original external conditions are no longer present.
+
+Thus a slow dying-out of the effect of a stimulus was seen in my
+experiments on Veronica chamaedrys. (Klebs, "Kunstliche Metamorphosen",
+Stuttgart, 1906, page 132.) During the cultivation of an artificially
+modified inflorescence I obtained a race showing modifications in
+different directions, among which twisting was especially conspicuous.
+This plant, however, does not behave as the twisted race of Dipsacus
+isolated by de Vries (de Vries, "Mutationstheorie", Vol. II. Leipzig,
+1903, page 573.), which produced each year a definite percentage of
+twisted individuals. In the vegetative reproduction of this Veronica the
+torsion appeared in the first, also in the second and third year, but
+with diminishing intensity. In spite of good cultivation this character
+has apparently now disappeared; it disappeared still more quickly in
+seedlings. In another character of the same Veronica chamaedrys the
+influence of the environment was stronger. The transformation of the
+inflorescences to foliage-shoots formed the starting-point; it occurred
+only under narrowly defined conditions, namely on cultivation as a
+cutting in moist air and on removal of all other leaf-buds. In the
+majority (7/10) of the plants obtained from the transformed shoots, the
+modification appeared in the following year without any interference.
+Of the three plants which were under observation several years the first
+lost the character in a short time, while the two others still retain
+it, after vegetative propagation, in varying degrees. The same character
+occurs also in some of the seedlings; but anything approaching a
+constant race has not been produced.
+
+Another means of producing new races has been attempted by Blaringhem.
+(Blaringhem, "Mutation et Traumatisme", Paris, 1907.) On removing at
+an early stage the main shoots of different plants he observed various
+abnormalities in the newly formed basal shoots. From the seeds of such
+plants he obtained races, a large percentage of which exhibited these
+abnormalities. Starting from a male Maize plant with a fasciated
+inflorescence, on which a proportion of the flowers had become male,
+a new race was bred in which hermaphrodite flowers were frequently
+produced. In the same way Blaringhem obtained, among other similar
+results, a race of barley with branched ears. These races, however,
+behaved in essentials like those which have been demonstrated by de
+Vries to be inconstant, e.g. Trifolium pratense quinquefolium and
+others. The abnormality appears in a proportion of the individuals
+and only under very special conditions. It must be remembered too that
+Blaringhem worked with old cultivated plants, which from the first had
+been disposed to split into a great variety of races. It is possible,
+but difficult to prove, that injury contributed to this result.
+
+A third method has been adopted by MacDougal (MacDougal, "Heredity and
+Origin of species", "Monist", 1906; "Report of department of botanical
+research", "Fifth Year-book of the Carnegie Institution of Washington",
+page 119, 1907.) who injected strong (10 percent) sugar solution or weak
+solutions of calcium nitrate and zinc sulphate into young carpels of
+different plants. From the seeds of a plant of Raimannia odorata the
+carpels of which had been thus treated he obtained several plants
+distinguished from the parent-forms by the absence of hairs and by
+distinct forms of leaves. Further examination showed that he had here to
+do with a new elementary species. MacDougal also obtained a more or less
+distinct mutant of Oenothera biennis. We cannot as yet form an opinion
+as to how far the effect is due to the wound or to the injection of
+fluid as such, or to its chemical properties. This, however, is not so
+essential as to decide whether the mutant stands in any relation to the
+influence of external factors. It is at any rate very important that
+this kind of investigation should be carried further.
+
+If it could be shown that new and inherited races were obtained by
+MacDougal's method, it would be safe to conclude that the same end might
+be gained by altering the conditions of the food-stuff conducted to the
+sexual cells. New races or elementary species, however, arise without
+wounding or injection. This at once raises the much discussed question,
+how far garden-cultivation has led to the creation of new races?
+Contrary to the opinion expressed by Darwin and others, de Vries
+("Mutationstheorie", Vol. I. pages 412 et seq.) tried to show that
+garden-races have been produced only from spontaneous types which occur
+in a wild state or from sub-races, which the breeder has accidentally
+discovered but not originated. In a small number of cases only has de
+Vries adduced definite proof. On the other side we have the work of
+Korschinsky (Korschinsky, "Heterogenesis und Evolution", "Flora", 1901.)
+which shows that whole series of garden-races have made their appearance
+only after years of cultivation. In the majority of races we are
+entirely ignorant of their origin.
+
+It is, however, a fact that if a plant is removed from natural
+conditions into cultivation, a well-marked variation occurs. The
+well-known plant-breeder L. de Vilmorin (L. de Vilmorin, "Notices sur
+l'amelioration des plantes", Paris, 1886, page 36.), speaking from his
+own experience, states that a plant is induced to "affoler," that is
+to exhibit all possible variations from which the breeder may make a
+further selection only after cultivation for several generations. The
+effect of cultivation was particularly striking in Veronica chamaedrys
+(Klebs, "Kunstliche Metamorphosen", Stuttgart, 1906, page 152.) which,
+in spite of its wide distribution in nature, varies very little. After a
+few years of cultivation this "good" and constant species becomes highly
+variable. The specimens on which the experiments were made were three
+modified inflorescence cuttings, the parent-plants of which certainly
+exhibited no striking abnormalities. In a short time many hitherto
+latent potentialities became apparent, so that characters, never
+previously observed, or at least very rarely, were exhibited, such
+as scattered leaf-arrangement, torsion, terminal or branched
+inflorescences, the conversion of the inflorescence into foliage-shoots,
+every conceivable alteration in the colour of flowers, the assumption of
+a green colour by parts of the flowers, the proliferation of flowers.
+
+All this points to some disturbance in the species resulting from
+methods of cultivation. It has, however, not yet been possible to
+produce constant races with any one of these modified characters. But
+variations appeared among the seedlings, some of which, e.g. yellow
+variegation, were not inheritable, while others have proved constant.
+This holds good, so far as we know at present, for a small rose-coloured
+form which is to be reckoned as a mutation. Thus the prospect of
+producing new races by cultivation appears to be full of promise.
+
+So long as the view is held that good nourishment, i.e. a plentiful
+supply of water and salts, constitutes the essential characteristic of
+garden-cultivation, we can hardly conceive that new mutations can be
+thus produced. But perhaps the view here put forward in regard to the
+production of form throws new light on this puzzling problem.
+
+Good manuring is in the highest degree favourable to vegetative growth,
+but is in no way equally favourable to the formation of flowers. The
+constantly repeated expression, good or favourable nourishment, is not
+only vague but misleading, because circumstances favourable to growth
+differ from those which promote reproduction; for the production of
+every form there are certain favourable conditions of nourishment, which
+may be defined for each species. Experience shows that, within definite
+and often very wide limits, it does not depend upon the ABSOLUTE AMOUNT
+of the various food substances, but upon their respective degrees of
+concentration. As we have already stated, the production of flowers
+follows a relative increase in the amount of carbohydrates formed in
+the presence of light, as compared with the inorganic salts on which
+the formation of albuminous substances depends. (Klebs, "Kunstliche
+Metamorphosen", page 117.) The various modifications of flowers are due
+to the fact that a relatively too strong solution of salts is supplied
+to the rudiments of these organs. As a general rule every plant
+form depends upon a certain relation between the different chemical
+substances in the cells and is modified by an alteration of that
+relation.
+
+During long cultivation under conditions which vary in very different
+degrees, such as moisture, the amount of salts, light intensity,
+temperature, oxygen, it is possible that sudden and special disturbances
+in the relations of the cell substances have a directive influence on
+the inner organisation of the sexual cells, so that not only inconstant
+but also constant varieties will be formed.
+
+Definite proof in support of this view has not yet been furnished, and
+we must admit that the question as to the cause of heredity remains,
+fundamentally, as far from solution as it was in Darwin's time. As the
+result of the work of many investigators, particularly de Vries,
+the problem is constantly becoming clearer and more definite. The
+penetration into this most difficult and therefore most interesting
+problem of life and the creation by experiment of new races or
+elementary species are no longer beyond the region of possibility.
+
+
+
+
+XIV. EXPERIMENTAL STUDY OF THE INFLUENCE OF ENVIRONMENT ON ANIMALS.
+By Jacques Loeb, M.D. Professor of Physiology in the University of
+California.
+
+
+I. INTRODUCTORY REMARKS.
+
+What the biologist calls the natural environment of an animal is from a
+physical point of view a rather rigid combination of definite forces. It
+is obvious that by a purposeful and systematic variation of these and
+by the application of other forces in the laboratory, results must be
+obtainable which do not appear in the natural environment. This is the
+reasoning underlying the modern development of the study of the effects
+of environment upon animal life. It was perhaps not the least important
+of Darwin's services to science that the boldness of his conceptions
+gave to the experimental biologist courage to enter upon the attempt of
+controlling at will the life-phenomena of animals, and of bringing about
+effects which cannot be expected in Nature.
+
+The systematic physico-chemical analysis of the effect of outside
+forces upon the form and reactions of animals is also our only means of
+unravelling the mechanism of heredity beyond the scope of the Mendelian
+law. The manner in which a germ-cell can force upon the adult certain
+characters will not be understood until we succeed in varying
+and controlling hereditary characteristics; and this can only be
+accomplished on the basis of a systematic study of the effects of
+chemical and physical forces upon living matter.
+
+Owing to limitation of space this sketch is necessarily very incomplete,
+and it must not be inferred that studies which are not mentioned here
+were considered to be of minor importance. All the writer could hope to
+do was to bring together a few instances of the experimental analysis of
+the effect of environment, which indicate the nature and extent of our
+control over life-phenomena and which also have some relation to the
+work of Darwin. In the selection of these instances preference is given
+to those problems which are not too technical for the general reader.
+
+The forces, the influence of which we shall discuss, are in succession
+chemical agencies, temperature, light, and gravitation. We shall also
+treat separately the effect of these forces upon form and instinctive
+reactions.
+
+
+II. THE EFFECTS OF CHEMICAL AGENCIES.
+
+(a) HETEROGENEOUS HYBRIDISATION.
+
+It was held until recently that hybridisation is not possible except
+between closely related species and that even among these a successful
+hybridisation cannot always be counted upon. This view was well
+supported by experience. It is, for instance, well known that the
+majority of marine animals lay their unfertilised eggs in the ocean and
+that the males shed their sperm also into the sea-water. The numerical
+excess of the spermatozoa over the ova in the sea-water is the only
+guarantee that the eggs are fertilised, for the spermatozoa are
+carried to the eggs by chance and are not attracted by the latter. This
+statement is the result of numerous experiments by various authors,
+and is contrary to common belief. As a rule all or the majority of
+individuals of a species in a given region spawn on the same day, and
+when this occurs the sea-water constitutes a veritable suspension of
+sperm. It has been shown by experiment that in fresh sea-water the sperm
+may live and retain its fertilising power for several days. It is thus
+unavoidable that at certain periods more than one kind of spermatozoon
+is suspended in the sea-water and it is a matter of surprise that the
+most heterogeneous hybridisations do not constantly occur. The reason
+for this becomes obvious if we bring together mature eggs and equally
+mature and active sperm of a different family. When this is done no egg
+is, as a rule, fertilised. The eggs of a sea-urchin can be fertilised by
+sperm of their own species, or, though in smaller numbers, by the sperm
+of other species of sea-urchins, but not by the sperm of other groups of
+echinoderms, e.g. starfish, brittle-stars, holothurians or crinoids, and
+still less by the sperm of more distant groups of animals. The consensus
+of opinion seemed to be that the spermatozoon must enter the egg
+through a narrow opening or canal, the so-called micropyle, and that
+the micropyle allowed only the spermatozoa of the same or of a closely
+related species to enter the egg.
+
+It seemed to the writer that the cause of this limitation of
+hybridisation might be of another kind and that by a change in the
+constitution of the sea-water it might be possible to bring about
+heterogenous hybridisations, which in normal sea-water are impossible.
+This assumption proved correct. Sea-water has a faintly alkaline
+reaction (in terms of the physical chemist its concentration of hydroxyl
+ions is about (10 to the power minus six)N at Pacific Grove, California,
+and about (10 to the power minus 5)N at Woods Hole, Massachusetts).
+If we slightly raise the alkalinity of the sea-water by adding to it a
+small but definite quantity of sodium hydroxide or some other alkali,
+the eggs of the sea-urchin can be fertilised with the sperm of widely
+different groups of animals, possibly with the sperm of any marine
+animal which sheds it into the ocean. In 1903 it was shown that if we
+add from about 0.5 to 0.8 cubic centimetre N/10 sodium hydroxide to
+50 cubic centimetres of sea-water, the eggs of Strongylocentrotus
+purpuratus (a sea-urchin which is found on the coast of California)
+can be fertilised in large quantities by the sperm of various kinds of
+starfish, brittle-stars and holothurians; while in normal sea-water or
+with less sodium hydroxide not a single egg of the same female could
+be fertilised with the starfish sperm which proved effective in the
+hyper-alkaline sea-water. The sperm of the various forms of starfish was
+not equally effective for these hybridisations; the sperm of Asterias
+ochracea and A. capitata gave the best results, since it was possible to
+fertilise 50 per cent or more of the sea-urchin eggs, while the sperm of
+Pycnopodia and Asterina fertilised only 2 per cent of the same eggs.
+
+Godlewski used the same method for the hybridisation of the sea-urchin
+eggs with the sperm of a crinoid (Antedon rosacea). Kupelwieser
+afterwards obtained results which seemed to indicate the possibility of
+fertilising the eggs of Strongylocentrotus with the sperm of a mollusc
+(Mytilus.) Recently, the writer succeeded in fertilising the
+eggs of Strongylocentrotus franciscanus with the sperm of a
+mollusc--Chlorostoma. This result could only be obtained in sea-water
+the alkalinity of which had been increased (through the addition of
+0.8 cubic centimetre N/10 sodium hydroxide to 50 cubic centimetres
+of sea-water). We thus see that by increasing the alkalinity of the
+sea-water it is possible to effect heterogeneous hybridisations which
+are at present impossible in the natural environment of these animals.
+
+It is, however, conceivable that in former periods of the earth's
+history such heterogeneous hybridisations were possible. It is known
+that in solutions like sea-water the degree of alkalinity must increase
+when the amount of carbon-dioxide in the atmosphere is diminished. If it
+be true, as Arrhenius assumes, that the Ice age was caused or preceded
+by a diminution in the amount of carbon-dioxide in the air, such a
+diminution must also have resulted in an increase of the alkalinity
+of the sea-water, and one result of such an increase must have been to
+render possible heterogeneous hybridisations in the ocean which in the
+present state of alkalinity are practically excluded.
+
+But granted that such hybridisations were possible, would they have
+influenced the character of the fauna? In other words, are the hybrids
+between sea-urchin and starfish, or better still, between sea-urchin and
+mollusc, capable of development, and if so, what is their character?
+The first experiment made it appear doubtful whether these heterogeneous
+hybrids could live. The sea-urchin eggs which were fertilised in the
+laboratory by the spermatozoa of the starfish, as a rule, died earlier
+than those of the pure breeds. But more recent results indicate that
+this was due merely to deficiencies in the technique of the earlier
+experiments. The writer has recently obtained hybrid larvae between the
+sea-urchin egg and the sperm of a mollusc (Chlorostoma) which, in the
+laboratory, developed as well and lived as long as the pure breeds of
+the sea-urchin, and there was nothing to indicate any difference in the
+vitality of the two breeds.
+
+So far as the question of heredity is concerned, all the experiments on
+heterogeneous hybridisation of the egg of the sea-urchin with the sperm
+of starfish, brittle-stars, crinoids and molluscs, have led to the same
+result, namely, that the larvae have purely maternal characteristics and
+differ in no way from the pure breed of the form from which the egg
+is taken. By way of illustration it may be said that the larvae of the
+sea-urchin reach on the third day or earlier (according to species
+and temperature) the so-called pluteus stage, in which they possess a
+typical skeleton; while neither the larvae of the starfish nor those
+of the mollusc form a skeleton at the corresponding stage. It was,
+therefore, a matter of some interest to find out whether or not the
+larvae produced by the fertilisation of the sea-urchin egg with the
+sperm of starfish or mollusc would form the normal and typical pluteus
+skeleton. This was invariably the case in the experiments of Godlewski,
+Kupelwieser, Hagedoorn, and the writer. These hybrid larvae were
+exclusively maternal in character.
+
+It might be argued that in the case of heterogeneous hybridisation the
+sperm-nucleus does not fuse with the egg-nucleus, and that, therefore,
+the spermatozoon cannot transmit its hereditary substances to the
+larvae. But these objections are refuted by Godlewski's experiments,
+in which he showed definitely that if the egg of the sea-urchin is
+fertilised with the sperm of a crinoid the fusion of the egg-nucleus
+and sperm-nucleus takes place in the normal way. It remains for further
+experiments to decide what the character of the adult hybrids would be.
+
+(b). ARTIFICIAL PARTHENOGENESIS.
+
+Possibly in no other field of Biology has our ability to control
+life-phenomena by outside conditions been proved to such an extent as
+in the domain of fertilisation. The reader knows that the eggs of the
+overwhelming majority of animals cannot develop unless a spermatozoon
+enters them. In this case a living agency is the cause of development
+and the problem arises whether it is possible to accomplish the same
+result through the application of well-known physico-chemical agencies.
+This is, indeed, true, and during the last ten years living larvae
+have been produced by chemical agencies from the unfertilised eggs
+of sea-urchins, starfish, holothurians and a number of annelids and
+molluscs; in fact this holds true in regard to the eggs of practically
+all forms of animals with which such experiments have been tried long
+enough. In each form the method of procedure is somewhat different and
+a long series of experiments is often required before the successful
+method is found.
+
+The facts of Artificial Parthenogenesis, as the chemical fertilisation
+of the egg is called, have, perhaps, some bearing on the problem of
+evolution. If we wish to form a mental image of the process of evolution
+we have to reckon with the possibility that parthenogenetic propagation
+may have preceded sexual reproduction. This suggests also the
+possibility that at that period outside forces may have supplied
+the conditions for the development of the egg which at present the
+spermatozoon has to supply. For this, if for no other reason, a brief
+consideration of the means of artificial parthenogenesis may be of
+interest to the student of evolution.
+
+It seemed necessary in these experiments to imitate as completely as
+possible by chemical agencies the effects of the spermatozoon upon
+the egg. When a spermatozoon enters the egg of a sea-urchin or certain
+starfish or annelids, the immediate effect is a characteristic change of
+the surface of the egg, namely the formation of the so-called membrane
+of fertilisation. The writer found that we can produce this membrane in
+the unfertilised egg by certain acids, especially the monobasic acids
+of the fatty series, e.g. formic, acetic, propionic, butyric, etc.
+Carbon-dioxide is also very efficient in this direction. It was also
+found that the higher acids are more efficient than the lower ones,
+and it is possible that the spermatozoon induces membrane-formation by
+carrying into the egg a higher fatty acid, namely oleic acid or one of
+its salts or esters.
+
+The physico-chemical process which underlies the formation of the
+membrane seems to be the cause of the development of the egg. In all
+cases in which the unfertilised egg has been treated in such a way as
+to cause it to form a membrane it begins to develop. For the eggs of
+certain animals membrane-formation is all that is required to induce a
+complete development of the unfertilised egg, e.g. in the starfish and
+certain annelids. For the eggs of other animals a second treatment is
+necessary, presumably to overcome some of the injurious effects of
+acid treatment. Thus the unfertilised eggs of the sea-urchin
+Strongylocentrotus purpuratus of the Californian coast begin to develop
+when membrane-formation has been induced by treatment with a fatty acid,
+e.g. butyric acid; but the development soon ceases and the eggs
+perish in the early stages of segmentation, or after the first nuclear
+division. But if we treat the same eggs, after membrane-formation, for
+from 35 to 55 minutes (at 15 deg C.) with sea-water the concentration
+(osmotic pressure) of which has been raised through the addition of a
+definite amount of some salt or sugar, the eggs will segment and develop
+normally, when transferred back to normal sea-water. If care is taken,
+practically all the eggs can be caused to develop into plutei, the
+majority of which may be perfectly normal and may live as long as larvae
+produced from eggs fertilised with sperm.
+
+It is obvious that the sea-urchin egg is injured in the process of
+membrane-formation and that the subsequent treatment with a hypertonic
+solution only acts as a remedy. The nature of this injury became clear
+when it was discovered that all the agencies which cause haemolysis,
+i.e. the destruction of the red blood corpuscles, also cause
+membrane-formation in unfertilised eggs, e.g. fatty acids or ether,
+alcohols or chloroform, etc., or saponin, solanin, digitalin, bile
+salts and alkali. It thus happens that the phenomena of artificial
+parthenogenesis are linked together with the phenomena of haemolysis
+which at present play so important a role in the study of immunity. The
+difference between cytolysis (or haemolysis) and fertilisation seems to
+be this, that the latter is caused by a superficial or slight cytolysis
+of the egg, while if the cytolytic agencies have time to act on the
+whole egg the latter is completely destroyed. If we put unfertilised
+eggs of a sea-urchin into sea-water which contains a trace of saponin we
+notice that, after a few minutes, all the eggs form the typical
+membrane of fertilisation. If the eggs are then taken out of the saponin
+solution, freed from all traces of saponin by repeated washing in normal
+sea-water, and transferred to the hypertonic sea-water for from 35 to
+55 minutes, they develop into larvae. If, however, they are left in
+the sea-water containing the saponin they undergo, a few minutes after
+membrane-formation, the disintegration known in pathology as CYTOLYSIS.
+Membrane-formation is, therefore, caused by a superficial or incomplete
+cytolysis. The writer believes that the subsequent treatment of the egg
+with hypertonic sea-water is needed only to overcome the destructive
+effects of this partial cytolysis. The full reasons for this belief
+cannot be given in a short essay.
+
+Many pathologists assume that haemolysis or cytolysis is due to a
+liquefaction of certain fatty or fat-like compounds, the so-called
+lipoids, in the cell. If this view is correct, it would be necessary to
+ascribe the fertilisation of the egg to the same process.
+
+The analogy between haemolysis and fertilisation throws, possibly,
+some light on a curious observation. It is well known that the blood
+corpuscles, as a rule, undergo cytolysis if injected into the blood of
+an animal which belongs to a different family. The writer found last
+year that the blood of mammals, e.g. the rabbit, pig, and cattle, causes
+the egg of Strongylocentrotus to form a typical fertilisation-membrane.
+If such eggs are afterwards treated for a short period with hypertonic
+sea-water they develop into normal larvae (plutei). Some substance
+contained in the blood causes, presumably, a superficial cytolysis of
+the egg and thus starts its development.
+
+We can also cause the development of the sea-urchin egg without
+membrane-formation. The early experiments of the writer were done in
+this way and many experimenters still use such methods. It is probable
+that in this case the mechanism of fertilisation is essentially the same
+as in the case where the membrane-formation is brought about, with
+this difference only, that the cytolytic effect is less when no
+fertilisation-membrane is formed. This inference is corroborated by
+observations on the fertilisation of the sea-urchin egg with ox blood.
+It very frequently happens that not all of the eggs form membranes in
+this process. Those eggs which form membranes begin to develop, but
+perish if they are not treated with hypertonic sea-water. Some of the
+other eggs, however, which do not form membranes, develop directly into
+normal larvae without any treatment with hypertonic sea-water, provided
+they are exposed to the blood for only a few minutes. Presumably some
+blood enters the eggs and causes the cytolytic effects in a less degree
+than is necessary for membrane-formation, but in a sufficient degree to
+cause their development. The slightness of the cytolytic effect allows
+the egg to develop without treatment with hypertonic sea-water.
+
+Since the entrance of the spermatozoon causes that degree of cytolysis
+which leads to membrane-formation, it is probable that, in addition to
+the cytolytic or membrane-forming substance (presumably a higher fatty
+acid), it carries another substance into the egg which counteracts the
+deleterious cytolytic effects underlying membrane-formation.
+
+The question may be raised whether the larvae produced by artificial
+parthenogenesis can reach the mature stage. This question may be
+answered in the affirmative, since Delage has succeeded in raising
+several parthenogenetic sea-urchin larvae beyond the metamorphosis into
+the adult stage and since in all the experiments made by the writer
+the parthenogenetic plutei lived as long as the plutei produced from
+fertilised eggs.
+
+(c). ON THE PRODUCTION OF TWINS FROM ONE EGG THROUGH A CHANGE IN THE
+CHEMICAL CONSTITUTION OF THE SEA-WATER.
+
+The reader is probably familiar with the fact that there exist two
+different types of human twins. In the one type the twins differ as much
+as two children of the same parents born at different periods; they
+may or may not have the same sex. In the second type the twins have
+invariably the same sex and resemble each other most closely. Twins
+of the latter type are produced from the same egg, while twins of the
+former type are produced from two different eggs.
+
+The experiments of Driesch and others have taught us that twins
+originate from one egg in this manner, namely, that the first two cells
+into which the egg divides after fertilisation become separated from
+each other. This separation can be brought about by a change in the
+chemical constitution of the sea-water. Herbst observed that if the
+fertilised eggs of the sea-urchin are put into sea-water which is freed
+from calcium, the cells into which the egg divides have a tendency
+to fall apart. Driesch afterwards noticed that eggs of the sea-urchin
+treated with sea-water which is free from lime have a tendency to give
+rise to twins. The writer has recently found that twins can be produced
+not only by the absence of lime, but also through the absence of sodium
+or of potassium; in other words, through the absence of one or two of
+the three important metals in the sea-water. There is, however, a second
+condition, namely, that the solution used for the production of twins
+must have a neutral or at least not an alkaline reaction.
+
+The procedure for the production of twins in the sea-urchin egg consists
+simply in this:--the eggs are fertilised as usual in normal sea-water
+and then, after repeated washing in a neutral solution of sodium
+chloride (of the concentration of the sea-water), are placed in a
+neutral mixture of potassium chloride and calcium chloride, or of sodium
+chloride and potassium chloride, or of sodium chloride and calcium
+chloride, or of sodium chloride and magnesium chloride. The eggs must
+remain in this solution until half an hour or an hour after they have
+reached the two-cell stage. They are then transferred into normal
+sea-water and allowed to develop. From 50 to 90 per cent of the eggs of
+Strongylocentrotus purpuratus treated in this manner may develop into
+twins. These twins may remain separate or grow partially together and
+form double monsters, or heal together so completely that only slight or
+even no imperfections indicate that the individual started its career
+as a pair of twins. It is also possible to control the tendency of such
+twins to grow together by a change in the constitution of the sea-water.
+If we use as a twin-producing solution a mixture of sodium, magnesium
+and potassium chlorides (in the proportion in which these salts exist in
+the sea-water) the tendency of the twins to grow together is much
+more pronounced than if we use simply a mixture of sodium chloride and
+magnesium chloride.
+
+The mechanism of the origin of twins, as the result of altering the
+composition of the sea-water, is revealed by observation of the first
+segmentation of the egg in these solutions. This cell-division is
+modified in a way which leads to a separation of the first two cells.
+If the egg is afterwards transferred back into normal sea-water, each
+of these two cells develops into an independent embryo. Since normal
+sea-water contains all three metals, sodium, calcium, and potassium, and
+since it has besides an alkaline reaction, we perceive the reason why
+twins are not normally produced from one egg. These experiments suggest
+the possibility of a chemical cause for the origin of twins from one egg
+or of double monstrosities in mammals. If, for some reason, the liquids
+which surround the human egg a short time before and after the first
+cell-division are slightly acid, and at the same time lacking in one
+of the three important metals, the conditions for the separation of the
+first two cells and the formation of identical twins are provided.
+
+In conclusion it may be pointed out that the reverse result, namely,
+the fusion of normally double organs, can also be brought about
+experimentally through a change in the chemical constitution of the
+sea-water. Stockard succeeded in causing the eyes of fish embryos
+(Fundulus heteroclitus) to fuse into a single cyclopean eye through the
+addition of magnesium chloride to the sea-water. When he added about 6
+grams of magnesium chloride to 100 cubic centimetres of sea-water and
+placed the fertilised eggs in the mixture, about 50 per cent of the
+eggs gave rise to one-eyed embryos. "When the embryos were studied the
+one-eyed condition was found to result from the union or fusion of the
+'anlagen' of the two eyes. Cases were observed which showed various
+degrees in this fusion; it appeared as though the optic vessels were
+formed too far forward and ventral, so that their antero-ventro-median
+surfaces fused. This produces one large optic cup, which in all cases
+gives more or less evidence of its double nature." (Stockard, "Archiv f.
+Entwickelungsmechanik", Vol. 23, page 249, 1907.)
+
+We have confined ourselves to a discussion of rather simple effects of
+the change in the constitution of the sea-water upon development. It
+is a priori obvious, however, that an unlimited number of pathological
+variations might be produced by a variation in the concentration and
+constitution of the sea-water, and experience confirms this statement.
+As an example we may mention the abnormalities observed by Herbst in the
+development of sea-urchins through the addition of lithium to sea-water.
+It is, however, as yet impossible to connect in a rational way the
+effects produced in this and similar cases with the cause which produced
+them; and it is also impossible to define in a simple way the character
+of the change produced.
+
+III. THE INFLUENCE OF TEMPERATURE.
+
+(a) THE INFLUENCE OF TEMPERATURE UPON THE DENSITY OF PELAGIC ORGANISMS
+AND THE DURATION OF LIFE.
+
+It has often been noticed by explorers who have had a chance to compare
+the faunas in different climates that in polar seas such species as
+thrive at all in those regions occur, as a rule, in much greater density
+than they do in the moderate or warmer regions of the ocean. This refers
+to those members of the fauna which live at or near the surface, since
+they alone lend themselves to a statistical comparison. In his account
+of the Valdivia expedition, Chun (Chun, "Aus den Tiefen des Weltmeeres",
+page 225, Jena, 1903.) calls especial attention to this quantitative
+difference in the surface fauna and flora of different regions. "In the
+icy water of the Antarctic, the temperature of which is below 0 deg C.,
+we find an astonishingly rich animal and plant life. The same condition
+with which we are familiar in the Arctic seas is repeated here, namely,
+that the quantity of plankton material exceeds that of the temperate and
+warm seas." And again, in regard to the pelagic fauna in the region of
+the Kerguelen Islands, he states: "The ocean is alive with transparent
+jelly fish, Ctenophores (Bolina and Callianira) and of Siphonophore
+colonies of the genus Agalma."
+
+The paradoxical character of this general observation lies in the fact
+that a low temperature retards development, and hence should be
+expected to have the opposite effect from that mentioned by Chun. Recent
+investigations have led to the result that life-phenomena are affected
+by temperature in the same sense as the velocity of chemical reactions.
+In the case of the latter van't Hoff had shown that a decrease in
+temperature by 10 degrees reduces their velocity to one half or less,
+and the same has been found for the influence of temperature on the
+velocity of physiological processes. Thus Snyder and T.B. Robertson
+found that the rate of heartbeat in the tortoise and in Daphnia is
+reduced to about one-half if the temperature is lowered 10 deg C., and
+Maxwell, Keith Lucas, and Snyder found the same influence of temperature
+for the rate with which an impulse travels in the nerve. Peter observed
+that the rate of development in a sea-urchin's egg is reduced to less
+than one-half if the temperature (within certain limits) is reduced by
+10 degrees. The same effect of temperature upon the rate of development
+holds for the egg of the frog, as Cohen and Peter calculated from
+the experiments of O. Hertwig. The writer found the same
+temperature-coefficient for the rate of maturation of the egg of a
+mollusc (Lottia).
+
+All these facts prove that the velocity of development of animal life
+in Arctic regions, where the temperature is near the freezing point of
+water, must be from two to three times smaller than in regions where the
+temperature of the ocean is about 10 deg C. and from four to nine times
+smaller than in seas the temperature of which is about 20 deg C. It is,
+therefore, exactly the reverse of what we should expect when authors
+state that the density of organisms at or near the surface of the ocean
+in polar regions is greater than in more temperate regions.
+
+The writer believes that this paradox finds its explanation in
+experiments which he has recently made on the influence of temperature
+on the duration of life of cold-blooded marine animals. The experiments
+were made on the fertilised and unfertilised eggs of the sea-urchin, and
+yielded the result that for the lowering of temperature by 1 deg C.
+the duration of life was about doubled. Lowering the temperature by 10
+degrees therefore prolongs the life of the organism 2 to the power 10,
+i.e. over a thousand times, and a lowering by 20 degrees prolongs it
+about one million times. Since this prolongation of life is far
+in excess of the retardation of development through a lowering of
+temperature, it is obvious that, in spite of the retardation of
+development in Arctic seas, animal life must be denser there than in
+temperate or tropical seas. The excessive increase of the duration of
+life at the poles will necessitate the simultaneous existence of more
+successive generations of the same species in these regions than in the
+temperate or tropical regions.
+
+The writer is inclined to believe that these results have some bearing
+upon a problem which plays an important role in theories of evolution,
+namely, the cause of natural death. It has been stated that the
+processes of differentiation and development lead also to the natural
+death of the individual. If we express this in chemical terms it means
+that the chemical processes which underlie development also determine
+natural death. Physical chemistry has taught us to identify two chemical
+processes even if only certain of their features are known. One of
+these means of identification is the temperature coefficient. When two
+chemical processes are identical, their velocity must be reduced by
+the same amount if the temperature is lowered to the same extent.
+The temperature coefficient for the duration of life of cold-blooded
+organisms seems, however, to differ enormously from the temperature
+coefficient for their rate of development. For a difference in
+temperature of 10 deg C. the duration of life is altered five hundred
+times as much as the rate of development; and, for a change of 20 deg
+C., it is altered more than a hundred thousand times as much. From this
+we may conclude that, at least for the sea-urchin eggs and embryo,
+the chemical processes which determine natural death are certainly not
+identical with the processes which underlie their development. T.B.
+Robertson has also arrived at the conclusion, for quite different
+reasons, that the process of senile decay is essentially different from
+that of growth and development.
+
+(b) CHANGES IN THE COLOUR OF BUTTERFLIES PRODUCED THROUGH THE INFLUENCE
+OF TEMPERATURE.
+
+The experiments of Dorfmeister, Weismann, Merrifield, Standfuss,
+and Fischer, on seasonal dimorphism and the aberration of colour in
+butterflies have so often been discussed in biological literature that
+a short reference to them will suffice. By seasonal dimorphism is meant
+the fact that species may appear at different seasons of the year in a
+somewhat different form or colour. Vanessa prorsa is the summer form,
+Vanessa levana the winter form of the same species. By keeping the pupae
+of Vanessa prorsa several weeks at a temperature of from 0 deg to 1 deg
+Weismann succeeded in obtaining from the summer chrysalids specimens
+which resembled the winter variety, Vanessa levana.
+
+If we wish to get a clear understanding of the causes of variation in
+the colour and pattern of butterflies, we must direct our attention to
+the experiments of Fischer, who worked with more extreme temperatures
+than his predecessors, and found that almost identical aberrations
+of colour could be produced by both extremely high and extremely low
+temperatures. This can be clearly seen from the following tabulated
+results of his observations. At the head of each column the reader
+finds the temperature to which Fischer submitted the pupae, and in the
+vertical column below are found the varieties that were produced. In the
+vertical column A are given the normal forms:
+
+(Temperatures in deg C.)
+
+  0 to -20     0 to +10    A.           +35 to +37    +36 to +41  +42 to +46
+                          (Normal forms)
+
+  ichnusoides  polaris     urticae      ichnusa       polaris     ichnusoides
+    (nigrita)                                                       (nigrita)
+
+  antigone     fischeri    io             -           fischeri    antigone
+    (iokaste)                                                       (iokaste)
+
+  testudo      dixeyi      polychloros  erythromelas  dixeyi      testudo
+
+  hygiaea      artemis     antiopa      epione        artemis     hygiaea
+
+  elymi        wiskotti    cardui         -           wiskotti    elymi
+
+  klymene      merrifieldi atalanta       -           merrifieldi klymene
+
+  weismanni    porima      prorsa         -           porima      weismanni
+
+The reader will notice that the aberrations produced at a very low
+temperature (from 0 to -20 deg C.) are absolutely identical with
+the aberrations produced by exposing the pupae to extremely high
+temperatures (42 to 46 deg C.). Moreover the aberrations produced by a
+moderately low temperature (from 0 to 10 deg C.) are identical with the
+aberrations produced by a moderately high temperature (36 to 41 deg C.)
+
+From these observations Fischer concludes that it is erroneous to speak
+of a specific effect of high and of low temperatures, but that there
+must be a common cause for the aberration found at the high as well
+as at the low temperature limits. This cause he seems to find in the
+inhibiting effects of extreme temperatures upon development.
+
+If we try to analyse such results as Fischer's from a physico-chemical
+point of view, we must realise that what we call life consists of a
+series of chemical reactions, which are connected in a catenary way;
+inasmuch as one reaction or group of reactions (a) (e.g. hydrolyses)
+causes or furnishes the material for a second reaction or group
+of reactions (b) (e.g. oxydations). We know that the temperature
+coefficient for physiological processes varies slightly at various parts
+of the scale; as a rule it is higher near 0 and lower near 30 deg. But
+we know also that the temperature coefficients do not vary equally from
+the various physiological processes. It is, therefore, to be expected
+that the temperature coefficients for the group of reactions of the type
+(a) will not be identical through the whole scale with the temperature
+coefficients for the reactions of the type (b). If therefore a certain
+substance is formed at the normal temperature of the animal in such
+quantities as are needed for the catenary reaction (b), it is not to be
+expected that this same perfect balance will be maintained for extremely
+high or extremely low temperatures; it is more probable that one group
+of reactions will exceed the other and thus produce aberrant chemical
+effects, which may underlie the colour aberrations observed by Fischer
+and other experimenters.
+
+It is important to notice that Fischer was also able to produce
+aberrations through the application of narcotics. Wolfgang Ostwald has
+produced experimentally, through variation of temperature, dimorphism of
+form in Daphnia. Lack of space precludes an account of these important
+experiments, as of so many others.
+
+IV. THE EFFECTS OF LIGHT.
+
+At the present day nobody seriously questions the statement that the
+action of light upon organisms is primarily one of a chemical character.
+While this chemical action is of the utmost importance for organisms,
+the nutrition of which depends upon the action of chlorophyll, it
+becomes of less importance for organisms devoid of chlorophyll.
+Nevertheless, we find animals in which the formation of organs by
+regeneration is not possible unless they are exposed to light. An
+observation made by the writer on the regeneration of polyps in a
+hydroid, Eudendrium racemosum, at Woods Hole, may be mentioned as an
+instance of this. If the stem of this hydroid, which is usually covered
+with polyps, is put into an aquarium the polyps soon fall off. If the
+stems are kept in an aquarium where light strikes them during the day, a
+regeneration of numerous polyps takes place in a few days. If, however,
+the stems of Eudendrium are kept permanently in the dark, no polyps are
+formed even after an interval of some weeks; but they are formed in a
+few days after the same stems have been transferred from the dark to
+the light. Diffused daylight suffices for this effect. Goldfarb, who
+repeated these experiments, states that an exposure of comparatively
+short duration is sufficient for this effect, it is possible that the
+light favours the formation of substances which are a prerequisite for
+the origin of polyps and their growth.
+
+Of much greater significance than this observation are the facts which
+show that a large number of animals assume, to some extent, the
+colour of the ground on which they are placed. Pouchet found through
+experiments upon crustaceans and fish that this influence of the ground
+on the colour of animals is produced through the medium of the eyes.
+If the eyes are removed or the animals made blind in another way these
+phenomena cease. The second general fact found by Pouchet was that the
+variation in the colour of the animal is brought about through an action
+of the nerves on the pigment-cells of the skin; the nerve-action being
+induced through the agency of the eye.
+
+The mechanism and the conditions for the change in colouration were made
+clear through the beautiful investigations of Keeble and Gamble, on
+the colour-change in crustaceans. According to these authors the
+pigment-cells can, as a rule, be considered as consisting of a central
+body from which a system of more or less complicated ramifications or
+processes spreads out in all directions. As a rule, the centre of the
+cell contains one or more different pigments which under the influence
+of nerves can spread out separately or together into the ramifications.
+These phenomena of spreading and retraction of the pigments into or from
+the ramifications of the pigment-cells form on the whole the basis for
+the colour changes under the influence of environment. Thus Keeble
+and Gamble observed that Macromysis flexuosa appears transparent and
+colourless or grey on sandy ground. On a dark ground their colour
+becomes darker. These animals have two pigments in their chromatophores,
+a brown pigment and a whitish or yellow pigment; the former is much more
+plentiful than the latter. When the animal appears transparent all the
+pigment is contained in the centre of the cells, while the ramifications
+are free from pigment. When the animal appears brown both pigments are
+spread out into the ramifications. In the condition of maximal spreading
+the animals appear black.
+
+This is a comparatively simple case. Much more complicated conditions
+were found by Keeble and Gamble in other crustaceans, e.g. in Hippolyte
+cranchii, but the influence of the surroundings upon the colouration of
+this form was also satisfactorily analysed by these authors.
+
+While many animals show transitory changes in colour under the influence
+of their surroundings, in a few cases permanent changes can be produced.
+The best examples of this are those which were observed by Poulton
+in the chrysalids of various butterflies, especially the small
+tortoise-shell. These experiments are so well known that a short
+reference to them will suffice. Poulton (Poulton, E.B., "Colours of
+Animals" (The International Scientific Series), London, 1890, page 121.)
+found that in gilt or white surroundings the pupae became light coloured
+and there was often an immense development of the golden spots, "so that
+in many cases the whole surface of the pupae glittered with an apparent
+metallic lustre. So remarkable was the appearance that a physicist to
+whom I showed the chrysalids, suggested that I had played a trick and
+had covered them with goldleaf." When black surroundings were used "the
+pupae were as a rule extremely dark, with only the smallest trace, and
+often no trace at all, of the golden spots which are so conspicuous in
+the lighter form." The susceptibility of the animal to this influence of
+its surroundings was found to be greatest during a definite period when
+the caterpillar undergoes the metamorphosis into the chrysalis stage.
+As far as the writer is aware, no physico-chemical explanation, except
+possibly Wiener's suggestion of colour-photography by mechanical colour
+adaptation, has ever been offered for the results of the type of those
+observed by Poulton.
+
+
+V. EFFECTS OF GRAVITATION.
+
+(a) EXPERIMENTS ON THE EGG OF THE FROG.
+
+Gravitation can only indirectly affect life-phenomena; namely, when we
+have in a cell two different non-miscible liquids (or a liquid and a
+solid) of different specific gravity, so that a change in the position
+of the cell or the organ may give results which can be traced to a
+change in the position of the two substances. This is very nicely
+illustrated by the frog's egg, which has two layers of very viscous
+protoplasm one of which is black and one white. The dark one occupies
+normally the upper position in the egg and may therefore be assumed to
+possess a smaller specific gravity than the white substance. When
+the egg is turned with the white pole upwards a tendency of the white
+protoplasm to flow down again manifests itself. It is, however, possible
+to prevent or retard this rotation of the highly viscous protoplasm, by
+compressing the eggs between horizontal glass plates. Such compression
+experiments may lead to rather interesting results, as O. Schultze first
+pointed out. Pflueger had already shown that the first plane of division
+in a fertilised frog's egg is vertical and Roux established the fact
+that the first plane of division is identical with the plane of symmetry
+of the later embryo. Schultze found that if the frog's egg is turned
+upside down at the time of its first division and kept in this abnormal
+position, through compression between two glass plates for about 20
+hours, a small number of eggs may give rise to twins. It is possible,
+in this case, that the tendency of the black part of the egg to rotate
+upwards along the surface of the egg leads to a separation of its first
+cells, such a separation leading to the formation of twins.
+
+T.H. Morgan made an interesting additional observation. He destroyed
+one half of the egg after the first segmentation and found that the
+half which remained alive gave rise to only one half of an embryo, thus
+confirming an older observation of Roux. When, however, Morgan put the
+egg upside down after the destruction of one of the first two cells, and
+compressed the eggs between two glass plates, the surviving half of the
+egg gave rise to a perfect embryo of half size (and not to a half embryo
+of normal size as before.) Obviously in this case the tendency of the
+protoplasm to flow back to its normal position was partially successful
+and led to a partial or complete separation of the living from the dead
+half; whereby the former was enabled to form a whole embryo, which, of
+course, possessed only half the size of an embryo originating from a
+whole egg.
+
+(b) EXPERIMENTS ON HYDROIDS.
+
+A striking influence of gravitation can be observed in a hydroid,
+Antennularia antennina, from the bay of Naples. This hydroid consists of
+a long straight main stem which grows vertically upwards and which has
+at regular intervals very fine and short bristle-like lateral branches,
+on the upper side of which the polyps grow. The main stem is negatively
+geotropic, i.e. its apex continues to grow vertically upwards when we
+put it obliquely into the aquarium, while the roots grow vertically
+downwards. The writer observed that when the stem is put horizontally
+into the water the short lateral branches on the lower side give rise to
+an altogether different kind of organ, namely, to roots, and these roots
+grow indefinitely in length and attach themselves to solid bodies; while
+if the stem had remained in its normal position no further growth
+would have occurred in the lateral branches. From the upper side of the
+horizontal stem new stems grow out, mostly directly from the original
+stem, occasionally also from the short lateral branches. It is thus
+possible to force upon this hydroid an arrangement of organs which is
+altogether different from the hereditary arrangement. The writer
+had called the change in the hereditary arrangement of organs or the
+transformation of organs by external forces HETEROMORPHOSIS. We cannot
+now go any further into this subject, which should, however, prove of
+interest in relation to the problem of heredity.
+
+If it is correct to apply inferences drawn from the observation on the
+frog's egg to the behaviour of Antennularia, one might conclude that the
+cells of Antennularia also contain non-miscible substances of different
+specific gravity, and that wherever the specifically lighter substance
+comes in contact with the sea-water (or gets near the surface of the
+cell) the growth of a stem is favoured; while contact with the sea-water
+of the specifically heavier of the substances, will favour the formation
+of roots.
+
+VI. THE EXPERIMENTAL CONTROL OF ANIMAL INSTINCTS.
+
+(a) EXPERIMENTS ON THE MECHANISM OF HELIOTROPIC REACTIONS IN ANIMALS.
+
+Since the instinctive reactions of animals are as hereditary as
+their morphological character, a discussion of experiments on the
+physico-chemical character of the instinctive reactions of animals
+should not be entirely omitted from this sketch. It is obvious that such
+experiments must begin with the simplest type of instincts, if they are
+expected to lead to any results; and it is also obvious that only such
+animals must be selected for this purpose, the reactions of which are
+not complicated by associative memory, or, as it may preferably be
+termed, associative hysteresis.
+
+The simplest type of instincts is represented by the purposeful motions
+of animals to or from a source of energy, e.g. light; and it is with
+some of these that we intend to deal here. When we expose winged aphides
+(after they have flown away from the plant), or young caterpillars of
+Porthesia chrysorrhoea (when they are aroused from their winter sleep)
+or marine or freshwater copepods and many other animals, to diffused
+daylight falling in from a window, we notice a tendency among these
+animals to move towards the source of light. If the animals are
+naturally sensitive, or if they are rendered sensitive through the
+agencies which we shall mention later, and if the light is strong
+enough, they move towards the source of light in as straight a line as
+the imperfections and peculiarities of their locomotor apparatus will
+permit. It is also obvious that we are here dealing with a forced
+reaction in which the animals have no more choice in the direction
+of their motion than have the iron filings in their arrangement in a
+magnetic field. This can be proved very nicely in the case of starving
+caterpillars of Porthesia. The writer put such caterpillars into a glass
+tube the axis of which was at right angles to the plane of the window:
+the caterpillars went to the window side of the tube and remained there,
+even if leaves of their food-plant were put into the tube directly
+behind them. Under such conditions the animals actually died from
+starvation, the light preventing them from turning to the food, which
+they eagerly ate when the light allowed them to do so. One cannot say
+that these animals, which we call positively helioptropic, are attracted
+by the light, since it can be shown that they go towards the source
+of the light even if in so doing they move from places of a higher to
+places of a lower degree of illumination.
+
+The writer has advanced the following theory of these instinctive
+reactions. Animals of the type of those mentioned are automatically
+orientated by the light in such a way that symmetrical elements of their
+retina (or skin) are struck by the rays of light at the same angle.
+In this case the intensity of light is the same for both retinae or
+symmetrical parts of the skin.
+
+This automatic orientation is determined by two factors, first a
+peculiar photo-sensitiveness of the retina (or skin), and second
+a peculiar nervous connection between the retina and the muscular
+apparatus. In symmetrically built heliotropic animals in which the
+symmetrical muscles participate equally in locomotion, the symmetrical
+muscles work with equal energy as long as the photo-chemical processes
+in both eyes are identical. If, however, one eye is struck by stronger
+light than the other, the symmetrical muscles will work unequally and
+in positively heliotropic animals those muscles will work with greater
+energy which bring the plane of symmetry back into the direction of the
+rays of light and the head towards the source of light. As soon as both
+eyes are struck by the rays of light at the same angle, there is no more
+reason for the animal to deviate from this direction and it will move in
+a straight line. All this holds good on the supposition that the animals
+are exposed to only one source of light and are very sensitive to light.
+
+Additional proof for the correctness of this theory was furnished
+through the experiments of G.H. Parker and S.J. Holmes. The former
+worked on a butterfly, Vanessa antiope, the latter on other arthropods.
+All the animals were in a marked degree positively heliotropic. These
+authors found that if one cornea is blackened in such an animal, it
+moves continually in a circle when it is exposed to a source of light,
+and in these motions the eye which is not covered with paint is directed
+towards the centre of the circle. The animal behaves, therefore, as if
+the darkened eye were in the shade.
+
+(b) THE PRODUCTION OF POSITIVE HELIOTROPISM BY ACIDS AND OTHER MEANS AND
+THE PERIODIC DEPTH-MIGRATIONS OF PELAGIC ANIMALS.
+
+When we observe a dense mass of copepods collected from a freshwater
+pond, we notice that some have a tendency to go to the light while
+others go in the opposite direction and many, if not the majority,
+are indifferent to light. It is an easy matter to make the negatively
+heliotropic or the indifferent copepods almost instantly positively
+heliotropic by adding a small but definite amount of carbon-dioxide
+in the form of carbonated water to the water in which the animals are
+contained. If the animals are contained in 50 cubic centimetres of water
+it suffices to add from three to six cubic centimetres of carbonated
+water to make all the copepods energetically positively heliotropic.
+This heliotropism lasts about half an hour (probably until all the
+carbon-dioxide has again diffused into the air.) Similar results may be
+obtained with any other acid.
+
+The same experiments may be made with another freshwater crustacean,
+namely Daphnia, with this difference, however, that it is as a rule
+necessary to lower the temperature of the water also. If the water
+containing the Daphniae is cooled and at the same time carbon-dioxide
+added, the animals which were before indifferent to light now become
+most strikingly positively heliotropic. Marine copepods can be made
+positively heliotropic by the lowering of the temperature alone, or by a
+sudden increase in the concentration of the sea-water.
+
+These data have a bearing upon the depth-migrations of pelagic animals,
+as was pointed out years ago by Theo. T. Groom and the writer. It is
+well known that many animals living near the surface of the ocean or
+freshwater lakes, have a tendency to migrate upwards towards evening and
+downwards in the morning and during the day. These periodic motions are
+determined to a large extent, if not exclusively, by the heliotropism
+of these animals. Since the consumption of carbon-dioxide by the green
+plants ceases towards evening, the tension of this gas in the water must
+rise and this must have the effect of inducing positive heliotropism or
+increasing its intensity. At the same time the temperature of the
+water near the surface is lowered and this also increases the positive
+heliotropism in the organisms.
+
+The faint light from the sky is sufficient to cause animals which are in
+a high degree positively heliotropic to move vertically upwards towards
+the light, as experiments with such pelagic animals, e.g. copepods, have
+shown. When, in the morning, the absorption of carbon-dioxide by the
+green algae begins again and the temperature of the water rises, the
+animals lose their positive heliotropism, and slowly sink down or become
+negatively heliotropic and migrate actively downwards.
+
+These experiments have also a bearing upon the problem of the
+inheritance of instincts. The character which is transmitted in this
+case is not the tendency to migrate periodically upwards and downwards,
+but the positive heliotropism. The tendency to migrate is the outcome of
+the fact that periodically varying external conditions induce a periodic
+change in the sense and intensity of the heliotropism of these animals.
+It is of course immaterial for the result, whether the carbon-dioxide or
+any other acid diffuse into the animal from the outside or whether they
+are produced inside in the tissue cells of the animals. Davenport and
+Cannon found that Daphniae, which at the beginning of the experiment,
+react sluggishly to light react much more quickly after they have been
+made to go to the light a few times. The writer is inclined to attribute
+this result to the effect of acids, e.g. carbon-dioxide, produced in the
+animals themselves in consequence of their motion. A similar effect of
+the acids was shown by A.D. Waller in the case of the response of nerve
+to stimuli.
+
+The writer observed many years ago that winged male and female ants
+are positively helioptropic and that their heliotropic sensitiveness
+increases and reaches its maximum towards the period of nuptial flight.
+Since the workers show no heliotropism it looks as if an internal
+secretion from the sexual glands were the cause of their heliotropic
+sensitiveness. V. Kellogg has observed that bees also become intensely
+positively heliotropic at the period of their wedding flight, in fact so
+much so that by letting light fall into the observation hive from above,
+the bees are prevented from leaving the hive through the exit at the
+lower end.
+
+We notice also the reverse phenomenon, namely, that chemical changes
+produced in the animal destroy its heliotropism. The caterpillars of
+Porthesia chrysorrhoea are very strongly positively heliotropic when
+they are first aroused from their winter sleep. This heliotropic
+sensitiveness lasts only as long as they are not fed. If they are kept
+permanently without food they remain permanently positively heliotropic
+until they die from starvation. It is to be inferred that as soon as
+these animals take up food, a substance or substances are formed
+in their bodies which diminish or annihilate their heliotropic
+sensitiveness.
+
+The heliotropism of animals is identical with the heliotropism of
+plants. The writer has shown that the experiments on the effect of acids
+on the heliotropism of copepods can be repeated with the same result in
+Volvox. It is therefore erroneous to try to explain these heliotropic
+reactions of animals on the basis of peculiarities (e.g. vision) which
+are not found in plants.
+
+We may briefly discuss the question of the transmission through the sex
+cells of such instincts as are based upon heliotropism. This problem
+reduces itself simply to that of the method whereby the gametes transmit
+heliotropism to the larvae or to the adult. The writer has expressed the
+idea that all that is necessary for this transmission is the presence in
+the eyes (or in the skin) of the animal of a photo-sensitive substance.
+For the transmission of this the gametes need not contain anything more
+than a catalyser or ferment for the synthesis of the photo-sensitive
+substance in the body of the animal. What has been said in regard to
+animal heliotropism might, if space permitted, be extended, mutatis
+mutandis, to geotropism and stereotropism.
+
+(c) THE TROPIC REACTIONS OF CERTAIN TISSUE-CELLS AND THE MORPHOGENETIC
+EFFECTS OF THESE REACTIONS.
+
+Since plant-cells show heliotropic reactions identical with those
+of animals, it is not surprising that certain tissue-cells also show
+reactions which belong to the class of tropisms. These reactions of
+tissue-cells are of special interest by reason of their bearing upon the
+inheritance of morphological characters. An example of this is found in
+the tiger-like marking of the yolk-sac of the embryo of Fundulus and in
+the marking of the young fish itself. The writer found that the former
+is entirely, and the latter at least in part, due to the creeping of the
+chromatophores upon the blood-vessels. The chromatophores are at first
+scattered irregularly over the yolk-sac and show their characteristic
+ramifications. There is at that time no definite relation between
+blood-vessels and chromatophores. As soon as a ramification of a
+chromatophore comes in contact with a blood-vessel the whole mass of the
+chromatophore creeps gradually on the blood-vessel and forms a complete
+sheath around the vessel, until finally all the chromatophores form a
+sheath around the vessels and no more pigment cells are found in the
+meshes between the vessels. Nobody who has not actually watched the
+process of the creeping of the chromatophores upon the blood-vessels
+would anticipate that the tiger-like colouration of the yolk-sac in the
+later stages of the development was brought about in this way. Similar
+facts can be observed in regard to the first marking of the embryo
+itself. The writer is inclined to believe that we are here dealing with
+a case of chemotropism, and that the oxygen of the blood may be the
+cause of the spreading of the chromatophores around the blood-vessels.
+Certain observations seem to indicate the possibility that in the adult
+the chromatophores have, in some forms at least, a more rigid structure
+and are prevented from acting in the way indicated. It seems to the
+writer that such observations as those made on Fundulus might simplify
+the problem of the hereditary transmission of certain markings.
+
+Driesch has found that a tropism underlies the arrangement of the
+skeleton in the pluteus larvae of the sea-urchin. The position of this
+skeleton is predetermined by the arrangement of the mesenchyme cells,
+and Driesch has shown that these cells migrate actively to the place
+of their destination, possibly led there under the influence of certain
+chemical substances. When Driesch scattered these cells mechanically
+before their migration, they nevertheless reached their destination.
+
+In the developing eggs of insects the nuclei, together with some
+cytoplasm, migrate to the periphery of the egg. Herbst pointed out that
+this might be a case of chemotropism, caused by the oxygen surrounding
+the egg. The writer has expressed the opinion that the formation of
+the blastula may be caused generally by a tropic reaction of the
+blastomeres, the latter being forced by an outside influence to creep to
+the surface of the egg.
+
+These examples may suffice to indicate that the arrangement of definite
+groups of cells and the morphological effects resulting therefrom may
+be determined by forces lying outside the cells. Since these forces are
+ubiquitous and constant it appears as if we were dealing exclusively
+with the influence of a gamete; while in reality all that it is
+necessary for the gamete to transmit is a certain form of irritability.
+
+(d) FACTORS WHICH DETERMINE PLACE AND TIME FOR THE DEPOSITION OF EGGS.
+
+For the preservation of species the instinct of animals to lay their
+eggs in places in which the young larvae find their food and can develop
+is of paramount importance. A simple example of this instinct is the
+fact that the common fly lays its eggs on putrid material which serves
+as food for the young larvae. When a piece of meat and of fat of the
+same animal are placed side by side, the fly will deposit its eggs upon
+the meat on which the larvae can grow, and not upon the fat, on which
+they would starve. Here we are dealing with the effect of a volatile
+nitrogenous substance which reflexly causes the peristaltic motions for
+the laying of the egg in the female fly.
+
+Kammerer has investigated the conditions for the laying of eggs in two
+forms of salamanders, e.g. Salamandra atra and S. maculosa. In both
+forms the eggs are fertilised in the body and begin to develop in the
+uterus. Since there is room only for a few larvae in the uterus, a large
+number of eggs perish and this number is the greater the longer the
+period of gestation. It thus happens that when the animals retain their
+eggs a long time, very few young ones are born; and these are in a
+rather advanced stage of development, owing to the long time which
+elapsed since they were fertilised. When the animal lays its eggs
+comparatively soon after copulation, many eggs (from 12 to 72) are
+produced and the larvae are of course in an early stage of development.
+In the early stage the larvae possess gills and can therefore live in
+water, while in later stages they have no gills and breathe through
+their lungs. Kammerer showed that both forms of Salamandra can be
+induced to lay their eggs early or late, according to the physical
+conditions surrounding them. If they are kept in water or in proximity
+to water and in a moist atmosphere they have a tendency to lay their
+eggs earlier and a comparatively high temperature enhances the tendency
+to shorten the period of gestation. If the salamanders are kept in
+comparative dryness they show a tendency to lay their eggs rather late
+and a low temperature enhances this tendency.
+
+Since Salamandra atra is found in rather dry alpine regions with a
+relatively low temperature and Salamandra maculosa in lower regions with
+plenty of water and a higher temperature, the fact that S. atra bears
+young which are already developed and beyond the stage of aquatic life,
+while S. maculosa bears young ones in an earlier stage, has been termed
+adaptation. Kammerer's experiments, however, show that we are dealing
+with the direct effects of definite outside forces. While we may speak
+of adaptation when all or some of the variables which determine a
+reaction are unknown, it is obviously in the interest of further
+scientific progress to connect cause and effect directly whenever our
+knowledge allows us to do so.
+
+VII. CONCLUDING REMARKS.
+
+The discovery of De Vries, that new species may arise by mutation and
+the wide if not universal applicability of Mendel's Law to phenomena of
+heredity, as shown especially by Bateson and his pupils, must, for
+the time being, if not permanently, serve as a basis for theories of
+evolution. These discoveries place before the experimental biologist the
+definite task of producing mutations by physico-chemical means. It
+is true that certain authors claim to have succeeded in this, but
+the writer wishes to apologise to these authors for his inability to
+convince himself of the validity of their claims at the present moment.
+He thinks that only continued breeding of these apparent mutants through
+several generations can afford convincing evidence that we are here
+dealing with mutants rather than with merely pathological variations.
+
+What was said in regard to the production of new species by
+physico-chemical means may be repeated with still more justification
+in regard to the second problem of transformation, namely the making
+of living from inanimate matter. The purely morphological imitations
+of bacteria or cells which physicists have now and then proclaimed as
+artificially produced living beings; or the plays on words by which,
+e.g. the regeneration of broken crystals and the regeneration of lost
+limbs by a crustacean were declared identical, will not appeal to the
+biologist. We know that growth and development in animals and plants are
+determined by definite although complicated series of catenary chemical
+reactions, which result in the synthesis of a DEFINITE compound or group
+of compounds, namely, NUCLEINS.
+
+The nucleins have the peculiarity of acting as ferments or enzymes
+for their own synthesis. Thus a given type of nucleus will continue to
+synthesise other nuclein of its own kind. This determines the continuity
+of a species; since each species has, probably, its own specific nuclein
+or nuclear material. But it also shows us that whoever claims to have
+succeeded in making living matter from inanimate will have to prove that
+he has succeeded in producing nuclein material which acts as a ferment
+for its own synthesis and thus reproduces itself. Nobody has thus far
+succeeded in this, although nothing warrants us in taking it for granted
+that this task is beyond the power of science.
+
+
+
+
+XV. THE VALUE OF COLOUR IN THE STRUGGLE FOR LIFE. By E.B. Poulton.
+
+Hope Professor of Zoology in the University of Oxford.
+
+
+INTRODUCTION.
+
+The following pages have been written almost entirely from the
+historical stand-point. Their principal object has been to give some
+account of the impressions produced on the mind of Darwin and his great
+compeer Wallace by various difficult problems suggested by the colours
+of living nature. In order to render the brief summary of Darwin's
+thoughts and opinions on the subject in any way complete, it was found
+necessary to say again much that has often been said before. No attempt
+has been made to display as a whole the vast contribution of Wallace;
+but certain of its features are incidentally revealed in passages quoted
+from Darwin's letters. It is assumed that the reader is familiar with
+the well-known theories of Protective Resemblance, Warning Colours, and
+Mimicry both Batesian and Mullerian. It would have been superfluous to
+explain these on the present occasion; for a far more detailed account
+than could have been attempted in these pages has recently appeared.
+(Poulton, "Essays on Evolution" Oxford, 1908, pages 293-382.) Among the
+older records I have made a point of bringing together the principal
+observations scattered through the note-books and collections of W.J.
+Burchell. These have never hitherto found a place in any memoir dealing
+with the significance of the colours of animals.
+
+INCIDENTAL COLOURS.
+
+Darwin fully recognised that the colours of living beings are not
+necessarily of value as colours, but that they may be an incidental
+result of chemical or physical structure. Thus he wrote to T. Meehan,
+Oct. 9, 1874: "I am glad that you are attending to the colours of
+dioecious flowers; but it is well to remember that their colours may be
+as unimportant to them as those of a gall, or, indeed, as the colour
+of an amethyst or ruby is to these gems." ("More Letters of Charles
+Darwin", Vol. I. pages 354, 355. See also the admirable account of
+incidental colours in "Descent of Man" (2nd edition), 1874, pages 261,
+262.)
+
+Incidental colours remain as available assets of the organism ready to
+be turned to account by natural selection. It is a probable speculation
+that all pigmentary colours were originally incidental; but now and for
+immense periods of time the visible tints of animals have been modified
+and arranged so as to assist in the struggle with other organisms or in
+courtship. The dominant colouring of plants, on the other hand, is
+an essential element in the paramount physiological activity of
+chlorophyll. In exceptional instances, however, the shapes and visible
+colours of plants may be modified in order to promote concealment.
+
+TELEOLOGY AND ADAPTATION.
+
+In the department of Biology which forms the subject of this essay,
+the adaptation of means to an end is probably more evident than in
+any other; and it is therefore of interest to compare, in a brief
+introductory section, the older with the newer teleological views.
+
+The distinctive feature of Natural Selection as contrasted with other
+attempts to explain the process of Evolution is the part played by the
+struggle for existence. All naturalists in all ages must have known
+something of the operations of "Nature red in tooth and claw"; but it
+was left for this great theory to suggest that vast extermination is
+a necessary condition of progress, and even of maintaining the ground
+already gained.
+
+Realising that fitness is the outcome of this fierce struggle, thus
+turned to account for the first time, we are sometimes led to associate
+the recognition of adaptation itself too exclusively with Natural
+Selection. Adaptation had been studied with the warmest enthusiasm
+nearly forty years before this great theory was given to the scientific
+world, and it is difficult now to realise the impetus which the works
+of Paley gave to the study of Natural History. That they did inspire the
+naturalists of the early part of the last century is clearly shown in
+the following passages.
+
+In the year 1824 the Ashmolean Museum at Oxford was intrusted to the
+care of J.S. Duncan of New College. He was succeeded in this office by
+his brother, P.B. Duncan, of the same College, author of a History of
+the Museum, which shows very clearly the influence of Paley upon the
+study of nature, and the dominant position given to his teachings:
+"Happily at this time (1824) a taste for the study of natural history
+had been excited in the University by Dr Paley's very interesting
+work on Natural Theology, and the very popular lectures of Dr Kidd on
+Comparative Anatomy, and Dr Buckland on Geology." In the arrangement of
+the contents of the Museum the illustration of Paley's work was given
+the foremost place by J.S. Duncan: "The first division proposes to
+familiarize the eye to those relations of all natural objects which form
+the basis of argument in Dr Paley's Natural Theology; to induce a mental
+habit of associating the view of natural phenomena with the conviction
+that they are the media of Divine manifestation; and by such association
+to give proper dignity to every branch of natural science." (From
+"History and Arrangement of the Ashmolean Museum" by P.B. Duncan: see
+pages vi, vii of "A Catalogue of the Ashmolean Museum", Oxford, 1836.)
+
+The great naturalist, W.J. Burchell, in his classical work shows the
+same recognition of adaptation in nature at a still earlier date.
+Upon the subject of collections he wrote ("Travels in the Interior of
+Southern Africa", London, Vol. I. 1822, page 505. The references to
+Burchell's observations in the present essay are adapted from
+the author's article in "Report of the British and South African
+Associations", 1905, Vol. III. pages 57-110.): "It must not be supposed
+that these charms (the pleasures of Nature) are produced by the mere
+discovery of new objects: it is the harmony with which they have been
+adapted by the Creator to each other, and to the situations in which
+they are found, which delights the observer in countries where Art has
+not yet introduced her discords." The remainder of the passage is so
+admirable that I venture to quote it: "To him who is satisfied with
+amassing collections of curious objects, simply for the pleasure of
+possessing them, such objects can afford, at best, but a childish
+gratification, faint and fleeting; while he who extends his view beyond
+the narrow field of nomenclature, beholds a boundless expanse, the
+exploring of which is worthy of the philosopher, and of the best talents
+of a reasonable being."
+
+On September 14, 1811, Burchell was at Zand Valley (Vlei), or Sand Pool,
+a few miles south-west of the site of Prieska, on the Orange River. Here
+he found a Mesembryanthemum (M. turbiniforme, now M. truncatum) and also
+a "Gryllus" (Acridian), closely resembling the pebbles with which their
+locality was strewn. He says of both of these, "The intention of Nature,
+in these instances, seems to have been the same as when she gave to the
+Chameleon the power of accommodating its color, in a certain degree,
+to that of the object nearest to it, in order to compensate for the
+deficiency of its locomotive powers. By their form and colour, this
+insect may pass unobserved by those birds, which otherwise would soon
+extirpate a species so little able to elude its pursuers, and this juicy
+little Mesembryanthemum may generally escape the notice of cattle and
+wild animals." (Loc. cit. pages 310, 311. See Sir William Thiselton-Dyer
+"Morphological Notes", XI.; "Protective Adaptations", I.; "Annals of
+Botany", Vol. XX. page 124. In plates VII., VIII. and IX. accompanying
+this article the author represents the species observed by Burchell,
+together with others in which analogous adaptations exist. He writes:
+"Burchell was clearly on the track on which Darwin reached the goal.
+But the time had not come for emancipation from the old teleology. This,
+however, in no respect detracts from the merit or value of his work.
+For, as Huxley has pointed out ("Life and Letters of Thomas Henry
+Huxley", London, 1900, I. page 457), the facts of the old teleology are
+immediately transferable to Darwinism, which simply supplies them with a
+natural in place of a supernatural explanation.") Burchell here seems
+to miss, at least in part, the meaning of the relationship between the
+quiescence of the Acridian and its cryptic colouring. Quiescence is an
+essential element in the protective resemblance to a stone--probably
+even more indispensable than the details of the form and colouring.
+Although Burchell appears to overlook this point he fully recognised the
+community between protection by concealment and more aggressive modes
+of defence; for, in the passage of which a part is quoted above, he
+specially refers to some earlier remarks on page 226 of his Vol. I. We
+here find that even when the oxen were resting by the Juk rivier (Yoke
+river), on July 19, 1811, Burchell observed "Geranium spinosum, with
+a fleshy stem and large white flowers...; and a succulent species of
+Pelargonium... so defended by the old panicles, grown to hard woody
+thorns, that no cattle could browze upon it." He goes on to say, "In
+this arid country, where every juicy vegetable would soon be eaten up by
+the wild animals, the Great Creating Power, with all-provident wisdom,
+has given to such plants either an acrid or poisonous juice, or sharp
+thorns, to preserve the species from annihilation... " All these modes
+of defence, especially adapted to a desert environment, have since
+been generally recognised, and it is very interesting to place beside
+Burchell's statement the following passage from a letter written by
+Darwin, Aug. 7, 1868, to G.H. Lewes; "That Natural Selection would tend
+to produce the most formidable thorns will be admitted by every one
+who has observed the distribution in South America and Africa (vide
+Livingstone) of thorn-bearing plants, for they always appear where the
+bushes grow isolated and are exposed to the attacks of mammals. Even
+in England it has been noticed that all spine-bearing and sting-bearing
+plants are palatable to quadrupeds, when the thorns are crushed." ("More
+Letters", I. page 308.)
+
+ADAPTATION AND NATURAL SELECTION.
+
+I have preferred to show the influence of the older teleology upon
+Natural History by quotations from a single great and insufficiently
+appreciated naturalist. It might have been seen equally well in the
+pages of Kirby and Spence and those of many other writers. If the older
+naturalists who thought and spoke with Burchell of "the intention
+of Nature" and the adaptation of beings "to each other, and to
+the situations in which they are found," could have conceived the
+possibility of evolution, they must have been led, as Darwin was, by the
+same considerations to Natural Selection. This was impossible for them,
+because the philosophy which they followed contemplated the phenomena of
+adaptation as part of a static immutable system. Darwin, convinced that
+the system is dynamic and mutable, was prevented by these very phenomena
+from accepting anything short of the crowning interpretation offered by
+Natural Selection. ("I had always been much struck by such adaptations
+(e.g. woodpecker and tree-frog for climbing, seeds for dispersal),
+and until these could be explained it seemed to me almost useless
+to endeavour to prove by indirect evidence that species have been
+modified." "Autobiography" in "Life and Letters of Charles Darwin", Vol.
+I. page 82. The same thought is repeated again and again in Darwin's
+letters to his friends. It is forcibly urged in the Introduction to
+the "Origin" (1859), page 3.) And the birth of Darwin's unalterable
+conviction that adaptation is of dominant importance in the organic
+world,--a conviction confirmed and ever again confirmed by his
+experience as a naturalist--may probably be traced to the influence of
+the great theologian. Thus Darwin, speaking of his Undergraduate days,
+tells us in his "Autobiography" that the logic of Paley's "Evidences
+of Christianity" and "Moral Philosophy" gave him as much delight as did
+Euclid.
+
+"The careful study of these works, without attempting to learn any part
+by rote, was the only part of the academical course which, as I then
+felt and as I still believe, was of the least use to me in the education
+of my mind. I did not at that time trouble myself about Paley's
+premises; and taking these on trust, I was charmed and convinced by the
+long line of argumentation." ("Life and Letters", I. page 47.)
+
+When Darwin came to write the "Origin" he quoted in relation to Natural
+Selection one of Paley's conclusions. "No organ will be formed, as Paley
+has remarked, for the purpose of causing pain or for doing an injury to
+its possessor." ("Origin of Species" (1st edition) 1859, page 201.)
+
+The study of adaptation always had for Darwin, as it has for many,
+a peculiar charm. His words, written Nov. 28, 1880, to Sir W.
+Thiselton-Dyer, are by no means inapplicable to-day: "Many of the
+Germans are very contemptuous about making out use of organs; but they
+may sneer the souls out of their bodies, and I for one shall think it
+the most interesting part of natural history." ("More Letters" II. page
+428.)
+
+PROTECTIVE AND AGGRESSIVE RESEMBLANCE: PROCRYPTIC AND ANTICRYPTIC
+COLOURING.
+
+Colouring for the purpose of concealment is sometimes included under the
+head Mimicry, a classification adopted by H.W. Bates in his classical
+paper. Such an arrangement is inconvenient, and I have followed Wallace
+in keeping the two categories distinct.
+
+The visible colours of animals are far more commonly adapted for
+Protective Resemblance than for any other purpose. The concealment of
+animals by their colours, shapes and attitudes, must have been well
+known from the period at which human beings first began to take an
+intelligent interest in Nature. An interesting early record is that of
+Samuel Felton, who (Dec. 2, 1763) figured and gave some account of an
+Acridian (Phyllotettix) from Jamaica. Of this insect he says "THE THORAX
+is like a leaf that is raised perpendicularly from the body." ("Phil.
+Trans. Roy. Soc." Vol. LIV. Tab. VI. page 55.)
+
+Both Protective and Aggressive Resemblances were appreciated and clearly
+explained by Erasmus Darwin in 1794: "The colours of many animals seem
+adapted to their purposes of concealing themselves either to avoid
+danger, or to spring upon their prey." ("Zoonomia", Vol. I. page 509,
+London, 1794.)
+
+Protective Resemblance of a very marked and beautiful kind is found
+in certain plants, inhabitants of desert areas. Examples observed by
+Burchell almost exactly a hundred years ago have already been mentioned.
+In addition to the resemblance to stones Burchell observed, although
+he did not publish the fact, a South African plant concealed by its
+likeness to the dung of birds. (Sir William Thiselton-Dyer has suggested
+the same method of concealment ("Annals of Botany", Vol. XX. page 123).
+Referring to Anacampseros papyracea, figured on plate IX., the author
+says of its adaptive resemblance: "At the risk of suggesting one perhaps
+somewhat far-fetched, I must confess that the aspect of the plant always
+calls to my mind the dejecta of some bird, and the more so owing to the
+whitening of the branches towards the tips" (loc. cit. page 126). The
+student of insects, who is so familiar with this very form of protective
+resemblance in larvae, and even perfect insects, will not be inclined to
+consider the suggestion far-fetched.) The observation is recorded in
+one of the manuscript journals kept by the great explorer during his
+journey. I owe the opportunity of studying it to the kindness of Mr
+Francis A. Burchell of the Rhodes University College, Grahamstown. The
+following account is given under the date July 5, 1812, when Burchell
+was at the Makkwarin River, about half-way between the Kuruman River and
+Litakun the old capital of the Bachapins (Bechuanas): "I found a curious
+little Crassula (not in flower) so snow white, that I should never has
+(have) distinguished it from the white limestones... It was an inch high
+and a little branchy,... and was at first mistaken for the dung of birds
+of the passerine order. I have often had occasion to remark that in
+stony place(s) there grow many small succulent plants and abound insects
+(chiefly Grylli) which have exactly the same colour as the ground and
+must for ever escape observation unless a person sit on the ground and
+observe very attentively."
+
+The cryptic resemblances of animals impressed Darwin and Wallace in
+very different degrees, probably in part due to the fact that Wallace's
+tropical experiences were so largely derived from the insect world, in
+part to the importance assigned by Darwin to Sexual Selection "a
+subject which had always greatly interested me," as he says in his
+"Autobiography", ("Life and Letters", Vol. I. page 94.) There is no
+reference to Cryptic Resemblance in Darwin's section of the Joint Essay,
+although he gives an excellent short account of Sexual Selection (see
+page 295). Wallace's section on the other hand contains the following
+statement: "Even the peculiar colours of many animals, especially
+insects, so closely resembling the soil or the leaves or the trunks on
+which they habitually reside, are explained on the same principle; for
+though in the course of ages varieties of many tints may have occurred,
+YET THOSE RACES HAVING COLOURS BEST ADAPTED TO CONCEALMENT FROM THEIR
+ENEMIES WOULD INEVITABLY SURVIVE THE LONGEST." ("Journ. Proc. Linn.
+Soc." Vol. III. 1859, page 61. The italics are Wallace's.)
+
+It would occupy too much space to attempt any discussion of the
+difference between the views of these two naturalists, but it is clear
+that Darwin, although fully believing in the efficiency of protective
+resemblance and replying to St George Mivart's contention that Natural
+Selection was incompetent to produce it ("Origin" (6th edition) London,
+1872, pages 181, 182; see also page 66.), never entirely agreed with
+Wallace's estimate of its importance. Thus the following extract from a
+letter to Sir Joseph Hooker, May 21, 1868, refers to Wallace: "I find
+I must (and I always distrust myself when I differ from him) separate
+rather widely from him all about birds' nests and protection; he is
+riding that hobby to death." ("More Letters", I. page 304.) It is clear
+from the account given in "The Descent of Man", (London, 1874, pages
+452-458. See also "Life and Letters", III. pages 123-125, and "More
+Letters", II. pages 59-63, 72-74, 76-78, 84-90, 92, 93.), that the
+divergence was due to the fact that Darwin ascribed more importance
+to Sexual Selection than did Wallace, and Wallace more importance to
+Protective Resemblance than Darwin. Thus Darwin wrote to Wallace,
+Oct. 12 and 13, 1867: "By the way, I cannot but think that you push
+protection too far in some cases, as with the stripes on the tiger."
+("More Letters", I. page 283.) Here too Darwin was preferring the
+explanation offered by Sexual Selection ("Descent of Man" (2nd edition)
+1874, pages 545, 546.), a preference which, considering the relation of
+the colouring of the lion and tiger to their respective environments,
+few naturalists will be found to share. It is also shown that Darwin
+contemplated the possibility of cryptic colours such as those of
+Patagonian animals being due to sexual selection influenced by the
+aspect of surrounding nature.
+
+Nearly a year later Darwin in his letter of May 5, 1868?, expressed
+his agreement with Wallace's views: "Expect that I should put sexual
+selection as an equal, or perhaps as even a more important agent in
+giving colour than Natural Selection for protection." ("More Letters",
+II. pages 77, 78.) The conclusion expressed in the above quoted passage
+is opposed by the extraordinary development of Protective Resemblance in
+the immature stages of animals, especially insects.
+
+It must not be supposed, however, that Darwin ascribed an unimportant
+role to Cryptic Resemblances, and as observations accumulated he came to
+recognise their efficiency in fresh groups of the animal kingdom. Thus
+he wrote to Wallace, May 5, 1867: "Haeckel has recently well shown that
+the transparency and absence of colour in the lower oceanic animals,
+belonging to the most different classes, may be well accounted for on
+the principle of protection." ("More Letters", II. page 62. See also
+"Descent of Man", page 261.) Darwin also admitted the justice of
+Professor E.S. Morse's contention that the shells of molluscs are often
+adaptively coloured. ("More Letters", II. page 95.) But he looked
+upon cryptic colouring and also mimicry as more especially Wallace's
+departments, and sent to him and to Professor Meldola observations and
+notes bearing upon these subjects. Thus the following letter given to me
+by Dr A.R. Wallace and now, by kind permission, published for the first
+time, accompanied a photograph of the chrysalis of Papilio sarpedon
+choredon, Feld., suspended from a leaf of its food-plant:
+
+July 9th, Down, Beckenham, Kent.
+
+My Dear Wallace,
+
+Dr G. Krefft has sent me the enclosed from Sydney. A nurseryman saw a
+caterpillar feeding on a plant and covered the whole up, but when he
+searched for the cocoon (pupa), was long before he could find it, so
+good was its imitation in colour and form to the leaf to which it was
+attached. I hope that the world goes well with you. Do not trouble
+yourself by acknowledging this.
+
+Ever yours
+
+Ch. Darwin.
+
+Another deeply interesting letter of Darwin's bearing upon protective
+resemblance, has only recently been shown to me by my friend Professor
+E.B. Wilson, the great American Cytologist. With his kind consent and
+that of Mr Francis Darwin, this letter, written four months before
+Darwin's death on April 19, 1882, is reproduced here (The letter is
+addressed: "Edmund B. Wilson, Esq., Assistant in Biology, John Hopkins
+University, Baltimore Md, U. States."):
+
+December 21, 1881.
+
+Dear Sir,
+
+I thank you much for having taken so much trouble in describing fully
+your interesting and curious case of mimickry.
+
+I am in the habit of looking through many scientific Journals, and
+though my memory is now not nearly so good as it was, I feel pretty sure
+that no such case as yours has been described (amongst the nudibranch)
+molluscs. You perhaps know the case of a fish allied to Hippocampus,
+(described some years ago by Dr Gunther in "Proc. Zoolog. Socy.") which
+clings by its tail to sea-weeds, and is covered with waving filaments
+so as itself to look like a piece of the same sea-weed. The parallelism
+between your and Dr Gunther's case makes both of them the more
+interesting; considering how far a fish and a mollusc stand apart. It
+would be difficult for anyone to explain such cases by the direct
+action of the environment.--I am glad that you intend to make further
+observations on this mollusc, and I hope that you will give a figure and
+if possible a coloured figure.
+
+With all good wishes from an old brother naturalist,
+
+I remain, Dear Sir,
+
+Yours faithfully,
+
+Charles Darwin.
+
+Professor E.B. Wilson has kindly given the following account of the
+circumstances under which he had written to Darwin: "The case to which
+Darwin's letter refers is that of the nudibranch mollusc Scyllaea,
+which lives on the floating Sargassum and shows a really astonishing
+resemblance to the plant, having leaf-shaped processes very closely
+similar to the fronds of the sea-weed both in shape and in colour. The
+concealment of the animal may be judged from the fact that we found
+the animal quite by accident on a piece of Sargassum that had been in a
+glass jar in the laboratory for some time and had been closely examined
+in the search for hydroids and the like without disclosing the presence
+upon it of two large specimens of the Scyllaea (the animal, as I recall
+it, is about two inches long). It was first detected by its movements
+alone, by someone (I think a casual visitor to the laboratory) who was
+looking closely at the Sargassum and exclaimed 'Why, the sea-weed is
+moving its leaves'! We found the example in the summer of 1880 or 1881
+at Beaufort, N.C., where the Johns Hopkins laboratory was located for
+the time being. It must have been seen by many others, before or since.
+
+"I wrote and sent to Darwin a short description of the case at the
+suggestion of Brooks, with whom I was at the time a student. I was, of
+course, entirely unknown to Darwin (or to anyone else) and to me the
+principal interest of Darwin's letter is the evidence that it gives of
+his extraordinary kindness and friendliness towards an obscure youngster
+who had of course absolutely no claim upon his time or attention. The
+little incident made an indelible impression upon my memory and taught
+me a lesson that was worth learning."
+
+VARIABLE PROTECTIVE RESEMBLANCE.
+
+The wonderful power of rapid colour adjustment possessed by the
+cuttle-fish was observed by Darwin in 1832 at St Jago, Cape de Verd
+Islands, the first place visited during the voyage of the "Beagle".
+From Rio he wrote to Henslow, giving the following account of his
+observations, May 18, 1832: "I took several specimens of an Octopus
+which possessed a most marvellous power of changing its colours,
+equalling any chameleon, and evidently accommodating the changes to the
+colour of the ground which it passed over. Yellowish green, dark brown,
+and red, were the prevailing colours; this fact appears to be new, as
+far as I can find out." ("Life and Letters", I. pages 235, 236. See
+also Darwin's "Journal of Researches", 1876, pages 6-8, where a far more
+detailed account is given together with a reference to "Encycl. of Anat.
+and Physiol.")
+
+Darwin was well aware of the power of individual colour adjustment,
+now known to be possessed by large numbers of lepidopterous pupae and
+larvae. An excellent example was brought to his notice by C.V. Riley
+("More Letters" II, pages 385, 386.), while the most striking of the
+early results obtained with the pupae of butterflies--those of Mrs M.E.
+Barber upon Papilio nireus--was communicated by him to the Entomological
+Society of London. ("Trans. Ent. Soc. Lond." 1874, page 519. See also
+"More Letters", II. page 403.)
+
+It is also necessary to direct attention to C.W. Beebe's ("Zoologica:
+N.Y. Zool. Soc." Vol. I. No. 1, Sept. 25, 1907: "Geographic variation
+in birds with especial reference to the effects of humidity".) recent
+discovery that the pigmentation of the plumage of certain birds is
+increased by confinement in a superhumid atmosphere. In Scardafella
+inca, on which the most complete series of experiments was made, the
+changes took place only at the moults, whether normal and annual or
+artificially induced at shorter periods. There was a corresponding
+increase in the choroidal pigment of the eye. At a certain advanced
+stage of feather pigmentation a brilliant iridescent bronze or green
+tint made its appearance on those areas where iridescence most often
+occurs in allied genera. Thus in birds no less than in insects,
+characters previously regarded as of taxonomic value, can be evoked or
+withheld by the forces of the environment.
+
+WARNING OR APOSEMATIC COLOURS.
+
+From Darwin's description of the colours and habits it is evident that
+he observed, in 1833, an excellent example of warning colouring in a
+little South American toad (Phryniscus nigricans). He described it in a
+letter to Henslow, written from Monte Video, Nov. 24, 1832: "As for
+one little toad, I hope it may be new, that it may be christened
+'diabolicus.' Milton must allude to this very individual when he talks
+of 'squat like a toad'; its colours are by Werner ("Nomenclature of
+Colours", 1821) ink black, vermilion red and buff orange." ("More
+Letters", I. page 12.) In the "Journal of Researches" (1876, page 97.)
+its colours are described as follows: "If we imagine, first, that it had
+been steeped in the blackest ink, and then, when dry, allowed to crawl
+over a board, freshly painted with the brightest vermilion, so as to
+colour the soles of its feet and parts of its stomach, a good idea
+of its appearance will be gained." "Instead of being nocturnal in its
+habits, as other toads are, and living in damp obscure recesses, it
+crawls during the heat of the day about the dry sand-hillocks and
+arid plains,... " The appearance and habits recall T. Belt's well-known
+description of the conspicuous little Nicaraguan frog which he found to
+be distasteful to a duck. ("The Naturalist in Nicaragua" (2nd edition)
+London, 1888, page 321.)
+
+The recognition of the Warning Colours of caterpillars is due in the
+first instance to Darwin, who, reflecting on Sexual Selection, was
+puzzled by the splendid colours of sexually immature organisms. He
+applied to Wallace "who has an innate genius for solving difficulties."
+("Descent of Man", page 325. On this and the following page an excellent
+account of the discovery will be found, as well as in Wallace's "Natural
+Selection", London, 1875, pages 117-122.) Darwin's original letter
+exists ("Life and Letters", III. pages 93, 94.), and in it we are
+told that he had taken the advice given by Bates: "You had better ask
+Wallace." After some consideration Wallace replied that he believed the
+colours of conspicuous caterpillars and perfect insects were a warning
+of distastefulness and that such forms would be refused by birds.
+Darwin's reply ("Life and Letters", III. pages 94, 95.) is extremely
+interesting both for its enthusiasm at the brilliancy of the hypothesis
+and its caution in acceptance without full confirmation:
+
+"Bates was quite right; you are the man to apply to in a difficulty. I
+never heard anything more ingenious than your suggestion, and I hope you
+may be able to prove it true. That is a splendid fact about the white
+moths (A single white moth which was rejected by young turkeys, while
+other moths were greedily devoured: "Natural Selection", 1875, page
+78.); it warms one's very blood to see a theory thus almost proved to be
+true."
+
+Two years later the hypothesis was proved to hold for caterpillars of
+many kinds by J. Jenner Weir and A.G. Butler, whose observations have
+since been abundantly confirmed by many naturalists. Darwin wrote to
+Weir, May 13, 1869: "Your verification of Wallace's suggestion seems
+to me to amount to quite a discovery." ("More Letters", II. page 71
+(footnote).)
+
+RECOGNITION OR EPISEMATIC CHARACTERS.
+
+This principle does not appear to have been in any way foreseen by
+Darwin, although he draws special attention to several elements of
+pattern which would now be interpreted by many naturalists as epismes.
+He believed that the markings in question interfered with the cryptic
+effect, and came to the conclusion that, even when common to both sexes,
+they "are the result of sexual selection primarily applied to the male."
+("Descent of Man", page 544.) The most familiar of all recognition
+characters was carefully explained by him, although here too explained
+as an ornamental feature now equally transmitted to both sexes: "The
+hare on her form is a familiar instance of concealment through colour;
+yet this principle partly fails in a closely-allied species, the rabbit,
+for when running to its burrow, it is made conspicuous to the sportsman,
+and no doubt to all beasts of prey, by its upturned white tail."
+("Descent of Man", page 542.)
+
+The analogous episematic use of the bright colours of flowers to attract
+insects for effecting cross-fertilisation and of fruits to attract
+vertebrates for effecting dispersal is very clearly explained in the
+"Origin". (Edition 1872, page 161. For a good example of Darwin's
+caution in dealing with exceptions see the allusion to brightly coloured
+fruit in "More Letters", II. page 348.)
+
+It is not, at this point, necessary to treat sematic characters at
+any greater length. They will form the subject of a large part of
+the following section, where the models of Batesian (Pseudaposematic)
+mimicry are considered as well as the Mullerian (Synaposematic)
+combinations of Warning Colours.
+
+MIMICRY,--BATESIAN OR PSEUDAPOSEMATIC, MULLERIAN OR SYNAPOSEMATIC.
+
+The existence of superficial resemblances between animals of various
+degrees of affinity must have been observed for hundreds of years.
+Among the early examples, the best known to me have been found in
+the manuscript note-books and collections of W.J. Burchell, the great
+traveller in Africa (1810-15) and Brazil (1825-30). The most interesting
+of his records on this subject are brought together in the following
+paragraphs.
+
+Conspicuous among well-defended insects are the dark steely or
+iridescent greenish blue fossorial wasps or sand-wasps, Sphex and the
+allied genera. Many Longicorn beetles mimic these in colour, slender
+shape of body and limbs, rapid movements, and the readiness with which
+they take to flight. On Dec. 21, 1812, Burchell captured one such beetle
+(Promeces viridis) at Kosi Fountain on the journey from the source
+of the Kuruman River to Klaarwater. It is correctly placed among the
+Longicorns in his catalogue, but opposite to its number is the comment
+"Sphex! totus purpureus."
+
+In our own country the black-and-yellow colouring of many stinging
+insects, especially the ordinary wasps, affords perhaps the commonest
+model for mimicry. It is reproduced with more or less accuracy on moths,
+flies and beetles. Among the latter it is again a Longicorn which offers
+one of the best-known, although by no means one of the most perfect,
+examples. The appearance of the well-known "wasp-beetle" (Clytus
+arietis) in the living state is sufficiently suggestive to prevent
+the great majority of people from touching it. In Burchell's Brazilian
+collection there is a nearly allied species (Neoclytus curvatus) which
+appears to be somewhat less wasp-like than the British beetle. The
+specimen bears the number "1188," and the date March 27, 1827, when
+Burchell was collecting in the neighbourhood of San Paulo. Turning to
+the corresponding number in the Brazilian note-book we find this
+record: "It runs rapidly like an ichneumon or wasp, of which it has the
+appearance."
+
+The formidable, well-defended ants are as freely mimicked by other
+insects as the sand-wasps, ordinary wasps and bees. Thus on February
+17, 1901, Guy A.K. Marshall captured, near Salisbury, Mashonaland,
+three similar species of ants (Hymenoptera) with a bug (Hemiptera) and
+a Locustid (Orthoptera), the two latter mimicking the former. All the
+insects, seven in number, were caught on a single plant, a small bushy
+vetch. ("Trans. Ent. Soc. Lond." 1902, page 535, plate XIX. figs.
+53-59.)
+
+This is an interesting recent example from South Africa, and large
+numbers of others might be added--the observations of many naturalists
+in many lands; but nearly all of them known since that general awakening
+of interest in the subject which was inspired by the great hypotheses
+of H.W. Bates and Fritz Muller. We find, however, that Burchell had
+more than once recorded the mimetic resemblance to ants. An extremely
+ant-like bug (the larva of a species of Alydus) in his Brazilian
+collection is labelled "1141," with the date December 8, 1826, when
+Burchell was at the Rio das Pedras, Cubatao, near Santos. In the
+note-book the record is as follows: "1141 Cimex. I collected this for a
+Formica."
+
+Some of the chief mimics of ants are the active little hunting spiders
+belonging to the family Attidae. Examples have been brought forward
+during many recent years, especially by my friends Dr and Mrs Peckham,
+of Milwaukee, the great authorities on this group of Araneae. Here too
+we find an observation of the mimetic resemblance recorded by Burchell,
+and one which adds in the most interesting manner to our knowledge
+of the subject. A fragment, all that is now left, of an Attid spider,
+captured on June 30, 1828, at Goyaz, Brazil, bears the following note,
+in this case on the specimen and not in the note-book: "Black... runs and
+seems like an ant with large extended jaws." My friend Mr R.I. Pocock,
+to whom I have submitted the specimen, tells me that it is not one of
+the group of species hitherto regarded as ant-like, and he adds, "It is
+most interesting that Burchell should have noticed the resemblance to an
+ant in its movements. This suggests that the perfect imitation in shape,
+as well as in movement, seen in many species was started in forms of an
+appropriate size and colour by the mimicry of movement alone." Up to the
+present time Burchell is the only naturalist who has observed an example
+which still exhibits this ancestral stage in the evolution of mimetic
+likeness.
+
+Following the teachings of his day, Burchell was driven to believe that
+it was part of the fixed and inexorable scheme of things that these
+strange superficial resemblances existed. Thus, when he found other
+examples of Hemipterous mimics, including one (Luteva macrophthalma)
+with "exactly the manners of a Mantis," he added the sentence, "In the
+genus Cimex (Linn.) are to be found the outward resemblances of insects
+of many other genera and orders" (February 15, 1829). Of another
+Brazilian bug, which is not to be found in his collection, and cannot
+therefore be precisely identified, he wrote: "Cimex... Nature seems
+to have intended it to imitate a Sphex, both in colour and the rapid
+palpitating and movement of the antennae" (November 15, 1826). At the
+same time it is impossible not to feel the conviction that Burchell felt
+the advantage of a likeness to stinging insects and to aggressive ants,
+just as he recognised the benefits conferred on desert plants by spines
+and by concealment. Such an interpretation of mimicry was perfectly
+consistent with the theological doctrines of his day. (See Kirby and
+Spence, "An Introduction to Entomology" (1st edition), London, Vol. II.
+1817, page 223.)
+
+The last note I have selected from Burchell's manuscript refers to one
+of the chief mimics of the highly protected Lycid beetles. The whole
+assemblage of African insects with a Lycoid colouring forms a most
+important combination and one which has an interesting bearing upon the
+theories of Bates and Fritz Muller. This most wonderful set of
+mimetic forms, described in 1902 by Guy A.K. Marshall, is composed
+of flower-haunting beetles belonging to the family Lycidae, and the
+heterogeneous group of varied insects which mimic their conspicuous and
+simple scheme of colouring. The Lycid beetles, forming the centre or
+"models" of the whole company, are orange-brown in front for about
+two-thirds of the exposed surface, black behind for the remaining third.
+They are undoubtedly protected by qualities which make them excessively
+unpalatable to the bulk of insect-eating animals. Some experimental
+proof of this has been obtained by Mr Guy Marshall. What are the forms
+which surround them? According to the hypothesis of Bates they would be,
+at any rate mainly, palatable hard-pressed insects which only hold their
+own in the struggle for life by a fraudulent imitation of the trade-mark
+of the successful and powerful Lycidae. According to Fritz Muller's
+hypothesis we should expect that the mimickers would be highly
+protected, successful and abundant species, which (metaphorically
+speaking) have found it to their advantage to possess an advertisement,
+a danger-signal, in common with each other, and in common with the
+beetles in the centre of the group.
+
+How far does the constitution of this wonderful combination--the largest
+and most complicated as yet known in all the world--convey to us the
+idea of mimicry working along the lines supposed by Bates or those
+suggested by Muller? Figures 1 to 52 of Mr Marshall's coloured plate
+("Trans. Ent. Soc. Lond." 1902, plate XVIII. See also page 517, where
+the group is analysed.) represent a set of forty-two or forty-three
+species or forms of insects captured in Mashonaland, and all except two
+in the neighbourhood of Salisbury. The combination includes six species
+of Lycidae; nine beetles of five groups all specially protected by
+nauseous qualities, Telephoridae, Melyridae, Phytophaga, Lagriidae,
+Cantharidae; six Longicorn beetles; one Coprid beetle; eight stinging
+Hymenoptera; three or four parasitic Hymenoptera (Braconidae, a group
+much mimicked and shown by some experiments to be distasteful); five
+bugs (Hemiptera, a largely unpalatable group); three moths (Arctiidae
+and Zygaenidae, distasteful families); one fly. In fact the whole
+combination, except perhaps one Phytophagous, one Coprid and the
+Longicorn beetles, and the fly, fall under the hypothesis of Muller
+and not under that of Bates. And it is very doubtful whether these
+exceptions will be sustained: indeed the suspicion of unpalatability
+already besets the Longicorns and is always on the heels,--I should say
+the hind tarsi--of a Phytophagous beetle.
+
+This most remarkable group which illustrates so well the problem of
+mimicry and the alternative hypotheses proposed for its solution, was,
+as I have said, first described in 1902. Among the most perfect of
+the mimetic resemblances in it is that between the Longicorn beetle,
+Amphidesmus analis, and the Lycidae. It was with the utmost astonishment
+and pleasure that I found this very resemblance had almost certainly
+been observed by Burchell. A specimen of the Amphidesmus exists in his
+collection and it bears "651." Turning to the same number in the
+African Catalogue we find that the beetle is correctly placed among the
+Longicorns, that it was captured at Uitenhage on Nov. 18, 1813, and that
+it was found associated with Lycid beetles in flowers ("consocians cum
+Lycis 78-87 in floribus"). Looking up Nos. 78-87 in the collection and
+catalogue, three species of Lycidae are found, all captured on Nov. 18,
+1813, at Uitenhage. Burchell recognised the wide difference in affinity,
+shown by the distance between the respective numbers; for his catalogue
+is arranged to represent relationships. He observed, what students of
+mimicry are only just beginning to note and record, the coincidence
+between model and mimic in time and space and in habits. We are
+justified in concluding that he observed the close superficial likeness
+although he does not in this case expressly allude to it.
+
+One of the most interesting among the early observations of superficial
+resemblance between forms remote in the scale of classification was made
+by Darwin himself, as described in the following passage from his letter
+to Henslow, written from Monte Video, Aug. 15, 1832: "Amongst the lower
+animals nothing has so much interested me as finding two species of
+elegantly coloured true Planaria inhabiting the dewy forest! The false
+relation they bear to snails is the most extraordinary thing of the kind
+I have ever seen." ("More Letters", I. page 9.)
+
+Many years later, in 1867, he wrote to Fritz Muller suggesting that the
+resemblance of a soberly coloured British Planarian to a slug might be
+due to mimicry. ("Life and Letters", III. page 71.)
+
+The most interesting copy of Bates's classical memoir on Mimicry
+("Contributions to an Insect Fauna of the Amazon Valley". "Trans. Linn.
+Soc." Vol. XXIII. 1862, page 495.), read before the Linnean Society in
+1861, is that given by him to the man who has done most to support and
+extend the theory. My kind friend has given that copy to me; it bears
+the inscription:
+
+"Mr A.R. Wallace from his old travelling companion the Author."
+
+Only a year and a half after the publication of the "Origin", we find
+that Darwin wrote to Bates on the subject which was to provide such
+striking evidence of the truth of Natural Selection: "I am glad to hear
+that you have specially attended to 'mimetic' analogies--a most curious
+subject; I hope you publish on it. I have for a long time wished to
+know whether what Dr Collingwood asserts is true--that the most striking
+cases generally occur between insects inhabiting the same country." (The
+letter is dated April 4, 1861. "More Letters", I. page 183.)
+
+The next letter, written about six months later, reveals the remarkable
+fact that the illustrious naturalist who had anticipated Edward Forbes
+in the explanation of arctic forms on alpine heights ("I was forestalled
+in only one important point, which my vanity has always made me regret,
+namely, the explanation by means of the Glacial period of the presence
+of the same species of plants and of some few animals on distant
+mountain summits and in the arctic regions. This view pleased me so much
+that I wrote it out in extenso, and I believe that it was read by Hooker
+some years before E. Forbes published his celebrated memoir on the
+subject. In the very few points in which we differed, I still think
+that I was in the right. I have never, of course, alluded in print to
+my having independently worked out this view." "Autobiography, Life and
+Letters", I. page 88.), had also anticipated H.W. Bates in the theory
+of Mimicry: "What a capital paper yours will be on mimetic resemblances!
+You will make quite a new subject of it. I had thought of such cases
+as a difficulty; and once, when corresponding with Dr Collingwood, I
+thought of your explanation; but I drove it from my mind, for I felt
+that I had not knowledge to judge one way or the other." (The letter is
+dated Sept. 25, 1861: "More Letters", I. page 197.)
+
+Bates read his paper before the Linnean Society, Nov. 21, 1861, and
+Darwin's impressions on hearing it were conveyed in a letter to
+the author dated Dec. 3: "Under a general point of view, I am quite
+convinced (Hooker and Huxley took the same view some months ago) that
+a philosophic view of nature can solely be driven into naturalists by
+treating special subjects as you have done. Under a special point of
+view, I think you have solved one of the most perplexing problems which
+could be given to solve." ("Life and Letters", II. page 378.) The memoir
+appeared in the following year, and after reading it Darwin wrote
+as follows, Nov. 20, 1862: "... In my opinion it is one of the most
+remarkable and admirable papers I ever read in my life... I am rejoiced
+that I passed over the whole subject in the "Origin", for I should have
+made a precious mess of it. You have most clearly stated and solved a
+wonderful problem... Your paper is too good to be largely appreciated by
+the mob of naturalists without souls; but, rely on it, that it will
+have LASTING value, and I cordially congratulate you on your first great
+work. You will find, I should think, that Wallace will fully appreciate
+it." ("Life and Letters", II. pages 391-393.) Four days later, Nov. 24,
+Darwin wrote to Hooker on the same subject: "I have now finished his
+paper...' it seems to me admirable. To my mind the act of segregation of
+varieties into species was never so plainly brought forward, and there
+are heaps of capital miscellaneous observations." ("More Letters", I.
+page 214.)
+
+Darwin was here referring to the tendency of similar varieties of the
+same species to pair together, and on Nov. 25 he wrote to Bates asking
+for fuller information on this subject. ("More Letters", I. page 215.
+See also parts of Darwin's letter to Bates in "Life and Letters", II.
+page 392.) If Bates's opinion were well founded, sexual selection would
+bear a most important part in the establishment of such species. (See
+Poulton, "Essays on Evolution", 1908, pages 65, 85-88.) It must be
+admitted, however, that the evidence is as yet quite insufficient to
+establish this conclusion. It is interesting to observe how Darwin
+at once fixed on the part of Bates's memoir which seemed to bear upon
+sexual selection. A review of Bates's theory of Mimicry was contributed
+by Darwin to the "Natural History Review" (New Ser. Vol. III. 1863, page
+219.) and an account of it is to be found in the "Origin" (Edition
+1872, pages 375-378.) and in "The Descent of Man". (Edition 1874, pages
+323-325.)
+
+Darwin continually writes of the value of hypothesis as the inspiration
+of inquiry. We find an example in his letter to Bates, Nov. 22, 1860:
+"I have an old belief that a good observer really means a good theorist,
+and I fully expect to find your observations most valuable." ("More
+Letters", I. page 176.) Darwin's letter refers to many problems upon
+which Bates had theorised and observed, but as regards Mimicry itself
+the hypothesis was thought out after the return of the letter from the
+Amazons, when he no longer had the opportunity of testing it by the
+observation of living Nature. It is by no means improbable that, had
+he been able to apply this test, Bates would have recognised that his
+division of butterfly resemblances into two classes,--one due to
+the theory of mimicry, the other to the influence of local
+conditions,--could not be sustained.
+
+Fritz Muller's contributions to the problem of Mimicry were all made
+in S.E. Brazil, and numbers of them were communicated, with other
+observations on natural history, to Darwin, and by him sent to Professor
+R. Meldola who published many of the facts. Darwin's letters to Meldola
+(Poulton, "Charles Darwin and the theory of Natural Selection", London,
+1896, pages 199-218.) contain abundant proofs of his interest in
+Muller's work upon Mimicry. One deeply interesting letter (Loc. cit.
+pages 201, 202.) dated Jan. 23, 1872, proves that Fritz Muller before
+he originated the theory of Common Warning Colours (Synaposematic
+Resemblance or Mullerian Mimicry), which will ever be associated with
+his name, had conceived the idea of the production of mimetic likeness
+by sexual selection.
+
+Darwin's letter to Meldola shows that he was by no means inclined to
+dismiss the suggestion as worthless, although he considered it daring.
+"You will also see in this letter a strange speculation, which I should
+not dare to publish, about the appreciation of certain colours being
+developed in those species which frequently behold other forms similarly
+ornamented. I do not feel at all sure that this view is as incredible as
+it may at first appear. Similar ideas have passed through my mind
+when considering the dull colours of all the organisms which inhabit
+dull-coloured regions, such as Patagonia and the Galapagos Is." A little
+later, on April 5, he wrote to Professor August Weismann on the same
+subject: "It may be suspected that even the habit of viewing differently
+coloured surrounding objects would influence their taste, and
+Fritz Muller even goes so far as to believe that the sight of gaudy
+butterflies might influence the taste of distinct species." ("Life and
+Letters", III. page 157.)
+
+This remarkable suggestion affords interesting evidence that F. Muller
+was not satisfied with the sufficiency of Bates's theory. Nor is
+this surprising when we think of the numbers of abundant conspicuous
+butterflies which he saw exhibiting mimetic likenesses. The common
+instances in his locality, and indeed everywhere in tropical America,
+were anything but the hard-pressed struggling forms assumed by the
+theory of Bates. They belonged to the groups which were themselves
+mimicked by other butterflies. Fritz Muller's suggestion also shows
+that he did not accept Bates's alternative explanation of a superficial
+likeness between models themselves, based on some unknown influence of
+local physico-chemical forces. At the same time Muller's own suggestion
+was subject to this apparently fatal objection, that the sexual
+selection he invoked would tend to produce resemblances in the males
+rather than the females, while it is well known that when the sexes
+differ the females are almost invariably more perfectly mimetic than the
+males and in a high proportion of cases are mimetic while the males are
+non-mimetic.
+
+The difficulty was met several years later by Fritz Muller's well-known
+theory, published in 1879 ("Kosmos", May 1879, page 100.), and
+immediately translated by Meldola and brought before the Entomological
+Society. ("Proc. Ent. Soc. Lond." 1879, page xx.) Darwin's letter to
+Meldola dated June 6, 1879, shows "that the first introduction of this
+new and most suggestive hypothesis into this country was due to the
+direct influence of Darwin himself, who brought it before the notice
+of the one man who was likely to appreciate it at its true value and to
+find the means for its presentation to English naturalists." ("Charles
+Darwin and the Theory of Natural Selection", page 214.) Of the
+hypothesis itself Darwin wrote "F. Muller's view of the mutual
+protection was quite new to me." (Ibid. page 213.) The hypothesis of
+Mullerian mimicry was at first strongly opposed. Bates himself could
+never make up his mind to accept it. As the Fellows were walking out
+of the meeting at which Professor Meldola explained the hypothesis, an
+eminent entomologist, now deceased, was heard to say to Bates: "It's a
+case of save me from my friends!" The new ideas encountered and still
+encounter to a great extent the difficulty that the theory of Bates had
+so completely penetrated the literature of natural history. The present
+writer has observed that naturalists who have not thoroughly absorbed
+the older hypothesis are usually far more impressed by the newer
+one than are those whose allegiance has already been rendered. The
+acceptance of Natural Selection itself was at first hindered by
+similar causes, as Darwin clearly recognised: "If you argue about the
+non-acceptance of Natural Selection, it seems to me a very striking fact
+that the Newtonian theory of gravitation, which seems to every one now
+so certain and plain, was rejected by a man so extraordinarily able as
+Leibnitz. The truth will not penetrate a preoccupied mind." (To Sir J.
+Hooker, July 28, 1868, "More Letters", I. page 305. See also the letter
+to A.R. Wallace, April 30, 1868, in "More Letters" II. page 77, lines
+6-8 from top.)
+
+There are many naturalists, especially students of insects, who appear
+to entertain an inveterate hostility to any theory of mimicry. Some of
+them are eager investigators in the fascinating field of geographical
+distribution, so essential for the study of Mimicry itself. The changes
+of pattern undergone by a species of Erebia as we follow it over
+different parts of the mountain ranges of Europe is indeed a most
+interesting inquiry, but not more so than the differences between e.g.
+the Acraea johnstoni of S.E. Rhodesia and of Kilimanjaro. A naturalist
+who is interested by the Erebia should be equally interested by the
+Acraea; and so he would be if the student of mimicry did not also
+record that the characteristics which distinguish the northern from
+the southern individuals of the African species correspond with the
+presence, in the north but not in the south, of certain entirely
+different butterflies. That this additional information should so
+greatly weaken, in certain minds, the appeal of a favourite study, is a
+psychological problem of no little interest. This curious antagonism is
+I believe confined to a few students of insects. Those naturalists who,
+standing rather farther off, are able to see the bearings of the subject
+more clearly, will usually admit the general support yielded by an
+ever-growing mass of observations to the theories of Mimicry propounded
+by H.W. Bates and Fritz Muller. In like manner natural selection itself
+was in the early days often best understood and most readily accepted by
+those who were not naturalists. Thus Darwin wrote to D.T. Ansted, Oct.
+27, 1860: "I am often in despair in making the generality of NATURALISTS
+even comprehend me. Intelligent men who are not naturalists and have not
+a bigoted idea of the term species, show more clearness of mind." ("More
+Letters", I. page 175.)
+
+Even before the "Origin" appeared Darwin anticipated the first results
+upon the mind of naturalists. He wrote to Asa Gray, Dec. 21, 1859: "I
+have made up my mind to be well abused; but I think it of importance
+that my notions should be read by intelligent men, accustomed to
+scientific argument, though NOT naturalists. It may seem absurd, but
+I think such men will drag after them those naturalists who have too
+firmly fixed in their heads that a species is an entity." ("Life and
+Letters" II. page 245.)
+
+Mimicry was not only one of the first great departments of zoological
+knowledge to be studied under the inspiration of natural Selection,
+it is still and will always remain one of the most interesting
+and important of subjects in relation to this theory as well as to
+evolution. In mimicry we investigate the effect of environment in its
+simplest form: we trace the effects of the pattern of a single species
+upon that of another far removed from it in the scale of classification.
+When there is reason to believe that the model is an invader from
+another region and has only recently become an element in the
+environment of the species native to its second home, the problem gains
+a special interest and fascination. Although we are chiefly dealing with
+the fleeting and changeable element of colour we expect to find and we
+do find evidence of a comparatively rapid evolution. The invasion of
+a fresh model is for certain species an unusually sudden change in the
+forces of the environment and in some instances we have grounds for the
+belief that the mimetic response has not been long delayed.
+
+MIMICRY AND SEX.
+
+Ever since Wallace's classical memoir on mimicry in the Malayan
+Swallowtail butterflies, those naturalists who have written on the
+subject have followed his interpretation of the marked prevalence of
+mimetic resemblance in the female sex as compared with the male. They
+have believed with Wallace that the greater dangers of the female, with
+slower flight and often alighting for oviposition, have been in part
+met by the high development of this special mode of protection. The fact
+cannot be doubted. It is extremely common for a non-mimetic male to be
+accompanied by a beautifully mimetic female and often by two or three
+different forms of female, each mimicking a different model. The male
+of a polymorphic mimetic female is, in fact, usually non-mimetic (e.g.
+Papilio dardanus = merope), or if a mimic (e.g. the Nymphaline genus
+Euripus), resembles a very different model. On the other hand a
+non-mimetic female accompanied by a mimetic male is excessively rare. An
+example is afforded by the Oriental Nymphaline, Cethosia, in which the
+males of some species are rough mimics of the brown Danaines. In some
+of the orb-weaving spiders the males mimic ants, while the much larger
+females are non-mimetic. When both sexes mimic, it is very common in
+butterflies and is also known in moths, for the females to be better and
+often far better mimics than the males.
+
+Although still believing that Wallace's hypothesis in large part
+accounts for the facts briefly summarised above, the present writer has
+recently been led to doubt whether it offers a complete explanation.
+Mimicry in the male, even though less beneficial to the species than
+mimicry in the female, would still surely be advantageous. Why then is
+it so often entirely restricted to the female? While the attempt to find
+an answer to this question was haunting me, I re-read a letter
+written by Darwin to Wallace, April 15, 1868, containing the following
+sentences: "When female butterflies are more brilliant than their males
+you believe that they have in most cases, or in all cases, been rendered
+brilliant so as to mimic some other species, and thus escape danger. But
+can you account for the males not having been rendered equally brilliant
+and equally protected? Although it may be most for the welfare of
+the species that the female should be protected, yet it would be some
+advantage, certainly no disadvantage, for the unfortunate male to enjoy
+an equal immunity from danger. For my part, I should say that the female
+alone had happened to vary in the right manner, and that the beneficial
+variations had been transmitted to the same sex alone. Believing in
+this, I can see no improbability (but from analogy of domestic animals
+a strong probability) that variations leading to beauty must often have
+occurred in the males alone, and been transmitted to that sex alone.
+Thus I should account in many cases for the greater beauty of the male
+over the female, without the need of the protective principle." ("More
+Letters", II. pages 73, 74. On the same subject--"the gay-coloured
+females of Pieris" (Perrhybris (Mylothris) pyrrha of Brazil), Darwin
+wrote to Wallace, May 5, 1868, as follows: "I believe I quite follow you
+in believing that the colours are wholly due to mimicry; and I further
+believe that the male is not brilliant from not having received through
+inheritance colour from the female, and from not himself having varied;
+in short, that he has not been influenced by selection." It should be
+noted that the male of this species does exhibit a mimetic pattern on
+the under surface. "More Letters" II. page 78.)
+
+The consideration of the facts of mimicry thus led Darwin to the
+conclusion that the female happens to vary in the right manner more
+commonly than the male, while the secondary sexual characters of males
+supported the conviction "that from some unknown cause such characters
+(viz. new characters arising in one sex and transmitted to it alone)
+apparently appear oftener in the male than in the female." (Letter from
+Darwin to Wallace, May 5, 1867, "More Letters", II. Page 61.)
+
+Comparing these conflicting arguments we are led to believe that the
+first is the stronger. Mimicry in the male would be no disadvantage but
+an advantage, and when it appears would be and is taken advantage of
+by selection. The secondary sexual characters of males would be no
+advantage but a disadvantage to females, and, as Wallace thinks, are
+withheld from this sex by selection. It is indeed possible that mimicry
+has been hindered and often prevented from passing to the males by
+sexual selection. We know that Darwin was much impressed ("Descent of
+Man", page 325.) by Thomas Belt's daring and brilliant suggestion that
+the white patches which exist, although ordinarily concealed, on the
+wings of mimetic males of certain Pierinae (Dismorphia), have been
+preserved by preferential mating. He supposed this result to have been
+brought about by the females exhibiting a deep-seated preference for
+males that displayed the chief ancestral colour, inherited from periods
+before any mimetic pattern had been evolved in the species. But it has
+always appeared to me that Belt's deeply interesting suggestion requires
+much solid evidence and repeated confirmation before it can be accepted
+as a valid interpretation of the facts. In the present state of our
+knowledge, at any rate of insects and especially of Lepidoptera, it is
+probable that the female is more apt to vary than the male and that an
+important element in the interpretation of prevalent female mimicry is
+provided by this fact.
+
+In order adequately to discuss the question of mimicry and sex it would
+be necessary to analyse the whole of the facts, so far as they are known
+in butterflies. On the present occasion it is only possible to state the
+inferences which have been drawn from general impressions,--inferences
+which it is believed will be sustained by future inquiry.
+
+(1) Mimicry may occasionally arise in one sex because the differences
+which distinguish it from the other sex happen to be such as to afford a
+starting-point for the resemblance. Here the male is at no disadvantage
+as compared with the female, and the rarity of mimicry in the male
+alone (e.g. Cethosia) is evidence that the great predominance of female
+mimicry is not to be thus explained.
+
+(2) The tendency of the female to dimorphism and polymorphism has been
+of great importance in determining this predominance. Thus if the female
+appear in two different forms and the male in only one it will be twice
+as probable that she will happen to possess a sufficient foundation for
+the evolution of mimicry.
+
+(3) The appearance of melanic or partially melanic forms in the female
+has been of very great service, providing as it does a change of
+ground-colour. Thus the mimicry of the black generally red-marked
+American "Aristolochia swallowtails" (Pharmacophagus) by the females of
+Papilio swallowtails was probably begun in this way.
+
+(4) It is probably incorrect to assume with Haase that mimicry always
+arose in the female and was later acquired by the male. Both sexes of
+the third section of swallowtails (Cosmodesmus) mimic Pharmacophagus in
+America, far more perfectly than do the females of Papilio. But this is
+not due to Cosmodesmus presenting us with a later stage of history begun
+in Papilio; for in Africa Cosmodesmus is still mimetic (of Danainae) in
+both sexes although the resemblances attained are imperfect, while
+many African species of Papilio have non-mimetic males with beautifully
+mimetic females. The explanation is probably to be sought in the fact
+that the females of Papilio are more variable and more often tend to
+become dimorphic than those of Cosmodesmus, while the latter group has
+more often happened to possess a sufficient foundation for the origin of
+the resemblance in patterns which, from the start, were common to male
+and female.
+
+(5) In very variable species with sexes alike, mimicry can be rapidly
+evolved in both sexes out of very small beginnings. Thus the reddish
+marks which are common in many individuals of Limenitis arthemis were
+almost certainly the starting-point for the evolution of the beautifully
+mimetic L. archippus. Nevertheless in such cases, although there is
+no reason to suspect any greater variability, the female is commonly a
+somewhat better mimic than the male and often a very much better mimic.
+Wallace's principle seems here to supply the obvious interpretation.
+
+(6) When the difference between the patterns of the model and presumed
+ancestor of the mimic is very great, the female is often alone mimetic;
+when the difference is comparatively small, both sexes are commonly
+mimetic. The Nymphaline genus Hypolimnas is a good example. In
+Hypolimnas itself the females mimic Danainae with patterns very
+different from those preserved by the non-mimetic males: in the
+sub-genus Euralia, both sexes resemble the black and white Ethiopian
+Danaines with patterns not very dissimilar from that which we infer to
+have existed in the non-mimetic ancestor.
+
+(7) Although a melanic form or other large variation may be of the
+utmost importance in facilitating the start of a mimetic likeness, it is
+impossible to explain the evolution of any detailed resemblance in
+this manner. And even the large colour variation itself may well be
+the expression of a minute and "continuous" change in the chemical and
+physical constitution of pigments.
+
+SEXUAL SELECTION (EPIGAMIC CHARACTERS).
+
+We do not know the date at which the idea of Sexual Selection arose in
+Darwin's mind, but it was probably not many years after the sudden flash
+of insight which, in October 1838, gave to him the theory of Natural
+Selection. An excellent account of Sexual Selection occupies the
+concluding paragraph of Part I. of Darwin's Section of the Joint Essay
+on Natural Selection, read July 1st, 1858, before the Linnean Society.
+("Journ. Proc. Linn. Soc." Vol. III. 1859, page 50.) The principles are
+so clearly and sufficiently stated in these brief sentences that it
+is appropriate to quote the whole: "Besides this natural means of
+selection, by which those individuals are preserved, whether in their
+egg, or larval, or mature state, which are best adapted to the place
+they fill in nature, there is a second agency at work in most unisexual
+animals, tending to produce the same effect, namely, the struggle of the
+males for the females. These struggles are generally decided by the law
+of battle, but in the case of birds, apparently, by the charms of their
+song, by their beauty or their power of courtship, as in the dancing
+rock-thrush of Guiana. The most vigorous and healthy males, implying
+perfect adaptation, must generally gain the victory in their contests.
+This kind of selection, however, is less rigorous than the other; it
+does not require the death of the less successful, but gives to them
+fewer descendants. The struggle falls, moreover, at a time of year when
+food is generally abundant, and perhaps the effect chiefly produced
+would be the modification of the secondary sexual characters, which are
+not related to the power of obtaining food, or to defence from enemies,
+but to fighting with or rivalling other males. The result of this
+struggle amongst the males may be compared in some respects to that
+produced by those agriculturists who pay less attention to the careful
+selection of all their young animals, and more to the occasional use of
+a choice mate."
+
+A full exposition of Sexual Selection appeared in the "The Descent of
+Man" in 1871, and in the greatly augmented second edition, in 1874.
+It has been remarked that the two subjects, "The Descent of Man and
+Selection in Relation to Sex", seem to fuse somewhat imperfectly into
+the single work of which they form the title. The reason for their
+association is clearly shown in a letter to Wallace, dated May 28, 1864:
+"... I suspect that a sort of sexual selection has been the most powerful
+means of changing the races of man." ("More Letters", II. page 33.)
+
+Darwin, as we know from his Autobiography ("Life and Letters", I. page
+94.), was always greatly interested in this hypothesis, and it has been
+shown in the preceding pages that he was inclined to look favourably
+upon it as an interpretation of many appearances usually explained by
+Natural Selection. Hence Sexual Selection, incidentally discussed in
+other sections of the present essay, need not be considered at any
+length, in the section specially allotted to it.
+
+Although so interested in the subject and notwithstanding his conviction
+that the hypothesis was sound, Darwin was quite aware that it was
+probably the most vulnerable part of the "Origin". Thus he wrote to H.W.
+Bates, April 4, 1861: "If I had to cut up myself in a review I would
+have (worried?) and quizzed sexual selection; therefore, though I am
+fully convinced that it is largely true, you may imagine how pleased I
+am at what you say on your belief." ("More Letters", I. page 183.)
+
+The existence of sound-producing organs in the males of insects was,
+Darwin considered, the strongest evidence in favour of the operation
+of sexual selection in this group. ("Life and Letters", III. pages 94,
+138.) Such a conclusion has received strong support in recent years by
+the numerous careful observations of Dr F.A. Dixey ("Proc. Ent. Soc.
+Lond." 1904, page lvi; 1905, pages xxxvii, liv; 1906, page ii.) and Dr
+G.B. Longstaff ("Proc. Ent. Soc. Lond." 1905, page xxxv; "Trans. Ent.
+Soc. Lond." 1905, page 136; 1908, page 607.) on the scents of male
+butterflies. The experience of these naturalists abundantly confirms and
+extends the account given by Fritz Muller ("Jen. Zeit." Vol. XI. 1877,
+page 99; "Trans. Ent. Soc. Lond." 1878, page 211.) of the scents
+of certain Brazilian butterflies. It is a remarkable fact that the
+apparently epigamic scents of male butterflies should be pleasing to
+man while the apparently aposematic scents in both sexes of species with
+warning colours should be displeasing to him. But the former is far more
+surprising than the latter. It is not perhaps astonishing that a scent
+which is ex hypothesi unpleasant to an insect-eating Vertebrate should
+be displeasing to the human sense; but it is certainly wonderful that an
+odour which is ex hypothesi agreeable to a female butterfly should also
+be agreeable to man.
+
+Entirely new light upon the seasonal appearance of epigamic characters
+is shed by the recent researches of C.W. Beebe ("The American
+Naturalist", Vol. XLII. No. 493, Jan. 1908, page 34.), who caused the
+scarlet tanager (Piranga erythromelas) and the bobolink (Dolichonyx
+oryzivorus) to retain their breeding plumage through the whole year by
+means of fattening food, dim illumination, and reduced activity. Gradual
+restoration to the light and the addition of meal-worms to the diet
+invariably brought back the spring song, even in the middle of winter.
+A sudden alteration of temperature, either higher or lower, caused the
+birds nearly to stop feeding, and one tanager lost weight rapidly and in
+two weeks moulted into the olive-green winter plumage. After a year, and
+at the beginning of the normal breeding season, "individual tanagers
+and bobolinks were gradually brought under normal conditions and
+activities," and in every case moulted from nuptial plumage to nuptial
+plumage. "The dull colours of the winter season had been skipped." The
+author justly claims to have established "that the sequence of plumage
+in these birds is not in any way predestined through inheritance...,
+but that it may be interrupted by certain factors in the environmental
+complex."
+
+
+
+
+XVI. GEOGRAPHICAL DISTRIBUTION OF PLANTS. By Sir William Thiselton-Dyer,
+K.C.M.G., C.I.E. Sc.D., F.R.S.
+
+The publication of "The Origin of Species" placed the study of Botanical
+Geography on an entirely new basis. It is only necessary to study the
+monumental "Geographie Botanique raisonnee" of Alphonse De Candolle,
+published four years earlier (1855), to realise how profound and
+far-reaching was the change. After a masterly and exhaustive discussion
+of all available data De Candolle in his final conclusions could only
+arrive at a deadlock. It is sufficient to quote a few sentences:--
+
+"L'opinion de Lamarck est aujourd'hui abandonee par tous les
+naturalistes qui ont etudie sagement les modifications possibles des
+etres organises...
+
+"Et si l'on s'ecarte des exagerations de Lamarck, si l'on suppose un
+premier type de chaque genre, de chaque famille tout au moins, on se
+trouve encore a l'egard de l'origine de ces types en presence de la
+grande question de la creation.
+
+"Le seul parti a prendre est donc d'envisager les etres organises comme
+existant depuis certaines epoques, avec leurs qualites particulieres."
+(Vol. II. page 1107.)
+
+Reviewing the position fourteen years afterwards, Bentham
+remarked:--"These views, generally received by the great majority of
+naturalists at the time De Candolle wrote, and still maintained by a
+few, must, if adhered to, check all further enquiry into any connection
+of facts with causes," and he added, "there is little doubt but that if
+De Candolle were to revise his work, he would follow the example of
+so many other eminent naturalists, and... insist that the present
+geographical distribution of plants was in most instances a derivative
+one, altered from a very different former distribution." ("Pres. Addr."
+(1869) "Proc. Linn. Soc." 1868-69, page lxviii.)
+
+Writing to Asa Gray in 1856, Darwin gave a brief preliminary account
+of his ideas as to the origin of species, and said that geographical
+distribution must be one of the tests of their validity. ("Life and
+Letters", II. page 78.) What is of supreme interest is that it was also
+their starting-point. He tells us:--"When I visited, during the voyage
+of H.M.S. "Beagle", the Galapagos Archipelago,... I fancied myself
+brought near to the very act of creation. I often asked myself how these
+many peculiar animals and plants had been produced: the simplest answer
+seemed to be that the inhabitants of the several islands had descended
+from each other, undergoing modification in the course of their
+descent." ("The Variation of Animals and Plants" (2nd edition), 1890, I.
+pages 9, 10.) We need not be surprised then, that in writing in 1845
+to Sir Joseph Hooker, he speaks of "that grand subject, that almost
+keystone of the laws of creation, Geographical Distribution." ("Life and
+Letters", I. page 336.)
+
+Yet De Candolle was, as Bentham saw, unconsciously feeling his way,
+like Lyell, towards evolution, without being able to grasp it. They both
+strove to explain phenomena by means of agencies which they saw actually
+at work. If De Candolle gave up the ultimate problem as insoluble:--"La
+creation ou premiere formation des etres organises echappe, par sa
+nature et par son anciennete, a nos moyens d'observation" (Loc. cit.
+page 1106.), he steadily endeavoured to minimise its scope. At least
+half of his great work is devoted to the researches by which he
+extricated himself from a belief in species having had a multiple
+origin, the view which had been held by successive naturalists from
+Gmelin to Agassiz. To account for the obvious fact that species
+constantly occupy dissevered areas, De Candolle made a minute study of
+their means of transport. This was found to dispose of the vast majority
+of cases, and the remainder he accounted for by geographical change.
+(Loc. cit. page 1116.)
+
+But Darwin strenuously objected to invoking geographical change as a
+solution of every difficulty. He had apparently long satisfied himself
+as to the "permanence of continents and great oceans." Dana, he tells us
+"was, I believe, the first man who maintained" this ("Life and Letters",
+III. page 247. Dana says:--"The continents and oceans had their general
+outline or form defined in earliest time," "Manual of Geology", revised
+edition. Philadelphia, 1869, page 732. I have no access to an earlier
+edition.), but he had himself probably arrived at it independently.
+Modern physical research tends to confirm it. The earth's centre of
+gravity, as pointed out by Pratt from the existence of the Pacific
+Ocean, does not coincide with its centre of figure, and it has been
+conjectured that the Pacific Ocean dates its origin from the separation
+of the moon from the earth.
+
+The conjecture appears to be unnecessary. Love shows that "the force
+that keeps the Pacific Ocean on one side of the earth is gravity,
+directed more towards the centre of gravity than the centre of the
+figure." ("Report of the 77th Meeting of the British Association"
+(Leicester, 1907), London, 1908, page 431.) I can only summarise the
+conclusions of a technical but masterly discussion. "The broad general
+features of the distribution of continent and ocean can be regarded
+as the consequences of simple causes of a dynamical character," and
+finally, "As regards the contour of the great ocean basins, we seem
+to be justified in saying that the earth is approximately an oblate
+spheroid, but more nearly an ellipsoid with three unequal axes, having
+its surface furrowed according to the formula for a certain spherical
+harmonic of the third degree" (Ibid. page 436.), and he shows that this
+furrowed surface must be produced "if the density is greater in one
+hemispheroid than in the other, so that the position of the centre of
+gravity is eccentric." (Ibid. page 431.) Such a modelling of the earth's
+surface can only be referred to a primitive period of plasticity. If
+the furrows account for the great ocean basins, the disposition of the
+continents seems equally to follow. Sir George Darwin has pointed out
+that they necessarily "arise from a supposed primitive viscosity or
+plasticity of the earth's mass. For during this course of evolution the
+earth's mass must have suffered a screwing motion, so that the polar
+regions have travelled a little from west to east relatively to the
+equator. This affords a possible explanation of the north and south
+trend of our great continents." ("Encycl. Brit." (9th edition), Vol.
+XXIII. "Tides", page 379.)
+
+It would be trespassing on the province of the geologist to pursue the
+subject at any length. But as Wallace ("Island Life" (2nd edition),
+1895, page 103.), who has admirably vindicated Darwin's position, points
+out, the "question of the permanence of our continents... lies at the
+root of all our inquiries into the great changes of the earth and its
+inhabitants." But he proceeds: "The very same evidence which has been
+adduced to prove the GENERAL stability and permanence of our continental
+areas also goes to prove that they have been subjected to wonderful
+and repeated changes in DETAIL." (Loc. cit. page 101.) Darwin of course
+would have admitted this, for with a happy expression he insisted
+to Lyell (1856) that "the skeletons, at least, of our continents are
+ancient." ("More Letters", II. page 135.) It is impossible not to
+admire the courage and tenacity with which he carried on the conflict
+single-handed. But he failed to convince Lyell. For we still find
+him maintaining in the last edition of the "Principles": "Continents
+therefore, although permanent for whole geological epochs, shift their
+positions entirely in the course of ages." (Lyell's "Principles of
+Geology" (11th edition), London, 1872, I. page 258.)
+
+Evidence, however, steadily accumulates in Darwin's support. His
+position still remains inexpugnable that it is not permissible to invoke
+geographical change to explain difficulties in distribution without
+valid geological and physical support. Writing to Mellard Reade, who in
+1878 had said, "While believing that the ocean-depths are of enormous
+age, it is impossible to reject other evidences that they have once
+been land," he pointed out "the statement from the 'Challenger' that all
+sediment is deposited within one or two hundred miles from the shores."
+("More Letters", II. page 146.) The following year Sir Archibald Geikie
+("Geographical Evolution", "Proc. R. Geogr. Soc." 1879, page 427.)
+informed the Royal Geographical Society that "No part of the results
+obtained by the 'Challenger' expedition has a profounder interest for
+geologists and geographers than the proof which they furnish that the
+floor of the ocean basins has no real analogy among the sedimentary
+formations which form most of the framework of the land."
+
+Nor has Darwin's earlier argument ever been upset. "The fact which
+I pointed out many years ago, that all oceanic islands are volcanic
+(except St Paul's, and now that is viewed by some as the nucleus of an
+ancient volcano), seem to me a strong argument that no continent ever
+occupied the great oceans." ("More Letters", II. page 146.)
+
+Dr Guppy, who devoted several years to geological and botanical
+investigations in the Pacific, found himself forced to similar
+conclusions. "It may be at once observed," he says, "that my belief in
+the general principle that islands have always been islands has not
+been shaken," and he entirely rejects "the hypothesis of a Pacific
+continent." He comes back, in full view of the problems on the spot,
+to the position from which, as has been seen, Darwin started: "If the
+distribution of a particular group of plants or animals does not seem to
+accord with the present arrangement of the land, it is by far the safest
+plan, even after exhausting all likely modes of explanation, not to
+invoke the intervention of geographical changes; and I scarcely think
+that our knowledge of any one group of organisms is ever sufficiently
+precise to justify a recourse to hypothetical alterations in the present
+relations of land and sea." ("Observations of a Naturalist in the
+Pacific between 1896 and 1899", London, 1903, I. page 380.) Wallace
+clinches the matter when he finds "almost the whole of the vast areas of
+the Atlantic, Pacific, Indian, and Southern Oceans, without a solitary
+relic of the great islands or continents supposed to have sunk beneath
+their waves." ("Island Life", page 105.)
+
+Writing to Wallace (1876), Darwin warmly approves the former's "protest
+against sinking imaginary continents in a quite reckless manner, as
+was stated by Forbes, followed, alas, by Hooker, and caricatured by
+Wollaston and (Andrew) Murray." ("Life and Letters", III. page 230.)
+The transport question thus became of enormously enhanced importance. We
+need not be surprised then at his writing to Lyell in 1856:--"I cannot
+avoid thinking that Forbes's 'Atlantis' was an ill-service to science,
+as checking a close study of means of dissemination" (Ibid. II. page
+78.), and Darwin spared no pains to extend our knowledge of them. He
+implores Hooker, ten years later, to "admit how little is known on the
+subject," and summarises with some satisfaction what he had himself
+achieved:--"Remember how recently you and others thought that salt
+water would soon kill seeds... Remember that no one knew that seeds would
+remain for many hours in the crops of birds and retain their vitality;
+that fish eat seeds, and that when the fish are devoured by birds the
+seeds can germinate, etc. Remember that every year many birds are blown
+to Madeira and to the Bermudas. Remember that dust is blown 1000 miles
+across the Atlantic." ("More Letters", I. page 483.)
+
+It has always been the fashion to minimise Darwin's conclusions, and
+these have not escaped objection. The advocatus diaboli has a useful
+function in science. But in attacking Darwin his brief is generally
+found to be founded on a slender basis of facts. Thus Winge and Knud
+Andersen have examined many thousands of migratory birds and found "that
+their crops and stomachs were always empty. They never observed any
+seeds adhering to the feathers, beaks or feet of the birds." (R.F.
+Scharff, "European Animals", page 64, London, 1907.) The most
+considerable investigation of the problem of Plant Dispersal since
+Darwin is that of Guppy. He gives a striking illustration of how easily
+an observer may be led into error by relying on negative evidence.
+
+"When Ekstam published, in 1895, the results of his observations on the
+plants of Nova Zembla, he observed that he possessed no data to show
+whether swimming and wading birds fed on berries; and he attached all
+importance to dispersal by winds. On subsequently visiting Spitzbergen
+he must have been at first inclined, therefore, to the opinion
+of Nathorst, who, having found only a solitary species of bird (a
+snow-sparrow) in that region, naturally concluded that birds had been
+of no importance as agents in the plant-stocking. However, Ekstam's
+opportunities were greater, and he tells us that in the craws of six
+specimens of Lagopus hyperboreus shot in Spitzbergen in August he found
+represented almost 25 per cent. of the usual phanerogamic flora of that
+region in the form of fruits, seeds, bulbils, flower-buds, leaf-buds,
+etc... "
+
+"The result of Ekstam's observations in Spitzbergen was to lead him to
+attach a very considerable importance in plant dispersal to the agency
+of birds; and when in explanation of the Scandinavian elements in the
+Spitzbergen flora he had to choose between a former land connection and
+the agency of birds, he preferred the bird." (Guppy, op. cit. II. pages
+511, 512.)
+
+Darwin objected to "continental extensions" on geological grounds,
+but he also objected to Lyell that they do not "account for all the
+phenomena of distribution on islands" ("Life and Letters", II. page
+77.), such for example as the absence of Acacias and Banksias in New
+Zealand. He agreed with De Candolle that "it is poor work putting
+together the merely POSSIBLE means of distribution." But he also
+agreed with him that they were the only practicable door of escape from
+multiple origins. If they would not work then "every one who believes
+in single centres will have to admit continental extensions" (Ibid. II.
+page 82.), and that he regarded as a mere counsel of despair:--"to make
+continents, as easily as a cook does pancakes." (Ibid. II. page 74.)
+
+The question of multiple origins however presented itself in another
+shape where the solution was much more difficult. The problem, as
+stated by Darwin, is this:--"The identity of many plants and animals,
+on mountain-summits, separated from each other by hundreds of miles of
+lowlands... without the apparent possibility of their having migrated
+from one point to the other." He continues, "even as long ago as 1747,
+such facts led Gmelin to conclude that the same species must have been
+independently created at several distinct points; and we might have
+remained in this same belief, had not Agassiz and others called vivid
+attention to the Glacial period, which affords... a simple explanation of
+the facts." ("Origin of Species" (6th edition) page 330.)
+
+The "simple explanation" was substantially given by E. Forbes in 1846.
+It is scarcely too much to say that it belongs to the same class of
+fertile and far-reaching ideas as "natural selection" itself. It is
+an extraordinary instance, if one were wanted at all, of Darwin's
+magnanimity and intense modesty that though he had arrived at the theory
+himself, he acquiesced in Forbes receiving the well-merited credit.
+"I have never," he says, "of course alluded in print to my having
+independently worked out this view." But he would have been more than
+human if he had not added:--"I was forestalled in... one important point,
+which my vanity has always made me regret." ("Life and Letters", I. page
+88.)
+
+Darwin, however, by applying the theory to trans-tropical migration,
+went far beyond Forbes. The first enunciation to this is apparently
+contained in a letter to Asa Gray in 1858. The whole is too long
+to quote, but the pith is contained in one paragraph. "There is a
+considerable body of geological evidence that during the Glacial epoch
+the whole world was colder; I inferred that,... from erratic boulder
+phenomena carefully observed by me on both the east and west coast of
+South America. Now I am so bold as to believe that at the height of
+the Glacial epoch, AND WHEN ALL TROPICAL PRODUCTIONS MUST HAVE BEEN
+CONSIDERABLY DISTRESSED, several temperate forms slowly travelled into
+the heart of the Tropics, and even reached the southern hemisphere; and
+some few southern forms penetrated in a reverse direction northward."
+("Life and Letters", II. page 136.) Here again it is clear that though
+he credits Agassiz with having called vivid attention to the Glacial
+period, he had himself much earlier grasped the idea of periods of
+refrigeration.
+
+Putting aside the fact, which has only been made known to us since
+Darwin's death, that he had anticipated Forbes, it is clear that he gave
+the theory a generality of which the latter had no conception. This is
+pointed out by Hooker in his classical paper "On the Distribution of
+Arctic Plants" (1860). "The theory of a southern migration of northern
+types being due to the cold epochs preceding and during the glacial,
+originated, I believe, with the late Edward Forbes; the extended one,
+of the trans-tropical migration, is Mr Darwin's." ("Linn. Trans."
+XXIII. page 253. The attempt appears to have been made to claim for Heer
+priority in what I may term for short the arctic-alpine theory (Scharff,
+"European Animals", page 128). I find no suggestion of his having hit
+upon it in his correspondence with Darwin or Hooker. Nor am I aware
+of any reference to his having done so in his later publications. I
+am indebted to his biographer, Professor Schroter, of Zurich, for an
+examination of his earlier papers with an equally negative result.)
+Assuming that local races have derived from a common ancestor, Hooker's
+great paper placed the fact of the migration on an impregnable basis.
+And, as he pointed out, Darwin has shown that "such an explanation meets
+the difficulty of accounting for the restriction of so many American and
+Asiatic arctic types to their own peculiar longitudinal zones, and for
+what is a far greater difficulty, the representation of the same arctic
+genera by most closely allied species in different longitudes."
+
+The facts of botanical geography were vital to Darwin's argument. He
+had to show that they admitted of explanation without assuming multiple
+origins for species, which would be fatal to the theory of Descent. He
+had therefore to strengthen and extend De Candolle's work as to means
+of transport. He refused to supplement them by hypothetical geographical
+changes for which there was no independent evidence: this was simply to
+attempt to explain ignotum per ignotius. He found a real and, as it has
+turned out, a far-reaching solution in climatic change due to cosmical
+causes which compelled the migration of species as a condition of their
+existence. The logical force of the argument consists in dispensing with
+any violent assumption, and in showing that the principle of descent is
+adequate to explain the ascertained facts.
+
+It does not, I think, detract from the merit of Darwin's conclusions
+that the tendency of modern research has been to show that the effects
+of the Glacial period were less simple, more localised and less
+general than he perhaps supposed. He admitted that "equatorial
+refrigeration... must have been small." ("More Letters", I. page 177.) It
+may prove possible to dispense with it altogether. One cannot but regret
+that as he wrote to Bates:--"the sketch in the 'Origin' gives a very
+meagre account of my fuller MS. essay on this subject." (Loc. cit.)
+Wallace fully accepted "the effect of the Glacial epoch in bringing
+about the present distribution of Alpine and Arctic plants in the
+NORTHERN HEMISPHERE," but rejected "the lowering of the temperature of
+the tropical regions during the Glacial period" in order to account for
+their presence in the SOUTHERN hemisphere. ("More Letters", II. page 25
+(footnote 1).) The divergence however does not lie very deep. Wallace
+attaches more importance to ordinary means of transport. "If plants can
+pass in considerable numbers and variety over wide seas and oceans, it
+must be yet more easy for them to traverse continuous areas of land,
+wherever mountain-chains offer suitable stations." ("Island Life" (2nd
+edition), London, 1895, page 512.) And he argues that such periodical
+changes of climate, of which the Glacial period may be taken as a type,
+would facilitate if not stimulate the process. (Loc. cit. page 518.)
+
+It is interesting to remark that Darwin drew from the facts of plant
+distribution one of his most ingenious arguments in support of this
+theory. (See "More Letters", I. page 424.) He tells us, "I was led to
+anticipate that the species of the larger genera in each country would
+oftener present varieties, than the species of the smaller genera."
+("Origin", page 44.) He argues "where, if we may use the expression, the
+manufactory of species has been active, we ought generally to find the
+manufactory still in action." (Ibid. page 45.) This proved to be the
+case. But the labour imposed upon him in the study was immense. He
+tabulated local floras "belting the whole northern hemisphere" ("More
+Letters", I. page 107.), besides voluminous works such as De Candolle's
+"Prodromus". The results scarcely fill a couple of pages. This is a good
+illustration of the enormous pains which he took to base any statement
+on a secure foundation of evidence, and for this the world, till the
+publication of his letters, could not do him justice. He was a great
+admirer of Herbert Spencer, whose "prodigality of original thought"
+astonished him. "But," he says, "the reflection constantly recurred to
+me that each suggestion, to be of real value to service, would require
+years of work." (Ibid. II. page 235.)
+
+At last the ground was cleared and we are led to the final conclusion.
+"If the difficulties be not insuperable in admitting that in the long
+course of time all the individuals of the same species belonging to
+the same genus, have proceeded from some one source; then all the grand
+leading facts of geographical distribution are explicable on the
+theory of migration, together with subsequent modification and the
+multiplication of new forms." ("Origin", page 360.) In this single
+sentence Darwin has stated a theory which, as his son F. Darwin has said
+with justice, has "revolutionized botanical geography." ("The Botanical
+Work of Darwin", "Ann. Bot." 1899, page xi.) It explains how physical
+barriers separate and form botanical regions; how allied species become
+concentrated in the same areas; how, under similar physical conditions,
+plants may be essentially dissimilar, showing that descent and not the
+surroundings is the controlling factor; how insular floras have acquired
+their peculiarities; in short how the most various and apparently
+uncorrelated problems fall easily and inevitably into line.
+
+The argument from plant distribution was in fact irresistible. A proof,
+if one were wanted, was the immediate conversion of what Hooker called
+"the stern keen intellect" ("More Letters", I. page 134.) of Bentham, by
+general consent the leading botanical systematist at the time. It is a
+striking historical fact that a paper of his own had been set down for
+reading at the Linnean Society on the same day as Darwin's, but had to
+give way. In this he advocated the fixity of species. He withdrew it
+after hearing Darwin's. We can hardly realise now the momentous effect
+on the scientific thought of the day of the announcement of the new
+theory. Years afterwards (1882) Bentham, notwithstanding his habitual
+restraint, could not write of it without emotion. "I was forced, however
+reluctantly, to give up my long-cherished convictions, the results of
+much labour and study." The revelation came without preparation. Darwin,
+he wrote, "never made any communications to me in relation to his
+views and labours." But, he adds, "I... fully adopted his theories and
+conclusions, notwithstanding the severe pain and disappointment they
+at first occasioned me." ("Life and Letters", II. page 294.) Scientific
+history can have few incidents more worthy. I do not know what is most
+striking in the story, the pathos or the moral dignity of Bentham's
+attitude.
+
+Darwin necessarily restricted himself in the "Origin" to establishing
+the general principles which would account for the facts of
+distribution, as a part of his larger argument, without attempting
+to illustrate them in particular cases. This he appears to have
+contemplated doing in a separate work. But writing to Hooker in 1868
+he said:--"I shall to the day of my death keep up my full interest
+in Geographical Distribution, but I doubt whether I shall ever have
+strength to come in any fuller detail than in the "Origin" to this grand
+subject." ("More Letters", II. page 7.) This must be always a matter for
+regret. But we may gather some indication of his later speculations from
+the letters, the careful publication of which by F. Darwin has rendered
+a service to science, the value of which it is difficult to exaggerate.
+They admit us to the workshop, where we see a great theory, as it were,
+in the making. The later ideas that they contain were not it is true
+public property at the time. But they were communicated to the leading
+biologists of the day and indirectly have had a large influence.
+
+If Darwin laid the foundation, the present fabric of Botanical Geography
+must be credited to Hooker. It was a happy partnership. The far-seeing,
+generalising power of the one was supplied with data and checked in
+conclusions by the vast detailed knowledge of the other. It may be
+permitted to quote Darwin's generous acknowledgment when writing the
+"Origin":--"I never did pick any one's pocket, but whilst writing my
+present chapter I keep on feeling (even when differing most from you)
+just as if I were stealing from you, so much do I owe to your writings
+and conversation, so much more than mere acknowledgements show." ("Life
+and Letters", II. page 148 (footnote).) Fourteen years before he had
+written to Hooker: "I know I shall live to see you the first authority
+in Europe on... Geographical Distribution." (Ibid. I. page 336.) We owe
+it to Hooker that no one now undertakes the flora of a country without
+indicating the range of the species it contains. Bentham tells us:
+"After De Candolle, independently of the great works of Darwin... the
+first important addition to the science of geographical botany was that
+made by Hooker in his "Introductory Essay to the Flora of Tasmania",
+which, though contemporaneous only with the "Origin of Species", was
+drawn up with a general knowledge of his friend's observations and
+views." (Pres. Addr. (1869), "Proc. Linn. Soc." 1868-69, page lxxiv.) It
+cannot be doubted that this and the great memoir on the "Distribution of
+Arctic Plants" were only less epoch-making than the "Origin" itself, and
+must have supplied a powerful support to the general theory of organic
+evolution.
+
+Darwin always asserted his "entire ignorance of Botany." ("More
+Letters", I. page 400.) But this was only part of his constant
+half-humorous self-depreciation. He had been a pupil of Henslow, and it
+is evident that he had a good working knowledge of systematic botany. He
+could find his way about in the literature and always cites the names of
+plants with scrupulous accuracy. It was because he felt the want of
+such a work for his own researches that he urged the preparation of
+the "Index Kewensis", and undertook to defray the expense. It has been
+thought singular that he should have been elected a "correspondant"
+of the Academie des Sciences in the section of Botany, but it is not
+surprising that his work in Geographical Botany made the botanists
+anxious to claim him. His heart went with them. "It has always pleased
+me," he tells us, "to exalt plants in the scale of organised beings."
+("Life and Letters", I. page 98.) And he declares that he finds "any
+proposition more easily tested in botanical works (Ibid. II. page 99.)
+than in zoological."
+
+In the "Introductory Essay" Hooker dwelt on the "continuous current of
+vegetation from Scandinavia to Tasmania" ("Introductory Essay to the
+Flora of Tasmania", London, 1859. Reprinted from the "Botany of the
+Antarctic Expedition", Part III., "Flora of Tasmania", Vol I. page
+ciii.), but finds little evidence of one in the reverse direction.
+"In the New World, Arctic, Scandinavian, and North American genera and
+species are continuously extended from the north to the south temperate
+and even Antarctic zones; but scarcely one Antarctic species, or even
+genus advances north beyond the Gulf of Mexico" (page civ.). Hooker
+considered that this negatived "the idea that the Southern and Northern
+Floras have had common origin within comparatively modern geological
+epochs." (Loc. cit.) This is no doubt a correct conclusion. But it is
+difficult to explain on Darwin's view alone, of alternating cold in the
+two hemispheres, the preponderant migration from the north to the south.
+He suggests, therefore, that it "is due to the greater extent of land
+in the north and to the northern forms... having... been advanced through
+natural selection and competition to a higher stage of perfection or
+dominating power." ("Origin of Species" (6th edition), page 340; cf.
+also "Life and Letters", II. page 142.) The present state of the Flora
+of New Zealand affords a striking illustration of the correctness of
+this view. It is poor in species, numbering only some 1400, of which
+three-fourths are endemic. They seem however quite unable to resist the
+invasion of new comers and already 600 species of foreign origin have
+succeeded in establishing themselves.
+
+If we accept the general configuration of the earth's surface as
+permanent a continuous and progressive dispersal of species from the
+centre to the circumference, i.e. southwards, seems inevitable. If an
+observer were placed above a point in St George's Channel from which
+one half of the globe was visible he would see the greatest possible
+quantity of land spread out in a sort of stellate figure. The maritime
+supremacy of the English race has perhaps flowed from the central
+position of its home. That such a disposition would facilitate a
+centrifugal migration of land organisms is at any rate obvious, and
+fluctuating conditions of climate operating from the pole would supply
+an effective means of propulsion. As these became more rigorous animals
+at any rate would move southwards to escape them. It would be equally
+the case with plants if no insuperable obstacle interposed. This implies
+a mobility in plants, notwithstanding what we know of means of transport
+which is at first sight paradoxical. Bentham has stated this in a
+striking way: "Fixed and immovable as is the individual plant, there is
+no class in which the race is endowed with greater facilities for the
+widest dispersion... Plants cast away their offspring in a dormant state,
+ready to be carried to any distance by those external agencies which we
+may deem fortuitous, but without which many a race might perish from the
+exhaustion of the limited spot of soil in which it is rooted." (Pres.
+Addr.(1869), "Proc. Linn. Soc." 1868-69, pages lxvi, lxvii.)
+
+I have quoted this passage from Bentham because it emphasises a point
+which Darwin for his purpose did not find it necessary to dwell upon,
+though he no doubt assumed it. Dispersal to a distance is, so to speak,
+an accidental incident in the life of a species. Lepidium Draba, a
+native of South-eastern Europe, owes its prevalence in the Isle of
+Thanet to the disastrous Walcheren expedition; the straw-stuffing of the
+mattresses of the fever-stricken soldiers who were landed there was used
+by a farmer for manure. Sir Joseph Hooker ("Royal Institution Lecture",
+April 12, 1878.) tells us that landing on Lord Auckland's Island, which
+was uninhabited, "the first evidence I met with of its having been
+previously visited by man was the English chickweed; and this I traced
+to a mound that marked the grave of a British sailor, and that was
+covered with the plant, doubtless the offspring of seed that had adhered
+to the spade or mattock with which the grave had been dug."
+
+Some migration from the spot where the individuals of a species
+have germinated is an essential provision against extinction. Their
+descendants otherwise would be liable to suppression by more vigorous
+competitors. But they would eventually be extinguished inevitably,
+as pointed out by Bentham, by the exhaustion of at any rate some one
+necessary constituent of the soil. Gilbert showed by actual analysis
+that the production of a "fairy ring" is simply due to the using up
+by the fungi of the available nitrogen in the enclosed area which
+continually enlarges as they seek a fresh supply on the outside margin.
+Anyone who cultivates a garden can easily verify the fact that every
+plant has some adaptation for varying degrees of seed-dispersal. It
+cannot be doubted that slow but persistent terrestrial migration has
+played an enormous part in bringing about existing plant-distribution,
+or that climatic changes would intensify the effect because they would
+force the abandonment of a former area and the occupation of a new one.
+We are compelled to admit that as an incident of the Glacial period a
+whole flora may have moved down and up a mountain side, while only some
+of its constituent species would be able to take advantage of means of
+long-distance transport.
+
+I have dwelt on the importance of what I may call short-distance
+dispersal as a necessary condition of plant life, because I think it
+suggests the solution of a difficulty which leads Guppy to a conclusion
+with which I am unable to agree. But the work which he has done taken as
+a whole appears to me so admirable that I do so with the utmost respect.
+He points out, as Bentham had already done, that long-distance dispersal
+is fortuitous. And being so it cannot have been provided for by
+previous adaptation. He says (Guppy, op. cit. II. page 99.): "It is not
+conceivable that an organism can be adapted to conditions outside
+its environment." To this we must agree; but, it may be asked, do the
+general means of plant dispersal violate so obvious a principle? He
+proceeds: "The great variety of the modes of dispersal of seeds is in
+itself an indication that the dispersing agencies avail themselves in a
+hap-hazard fashion of characters and capacities that have been developed
+in other connections." (Loc. cit. page 102.) "Their utility in these
+respects is an accident in the plant's life." (Loc. cit. page 100.) He
+attributes this utility to a "determining agency," an influence which
+constantly reappears in various shapes in the literature of Evolution
+and is ultra-scientific in the sense that it bars the way to the search
+for material causes. He goes so far as to doubt whether fleshy fruits
+are an adaptation for the dispersal of their contained seeds. (Loc. cit.
+page 102.) Writing as I am from a hillside which is covered by hawthorn
+bushes sown by birds, I confess I can feel little doubt on the subject
+myself. The essential fact which Guppy brings out is that long-distance
+unlike short-distance dispersal is not universal and purposeful, but
+selective and in that sense accidental. But it is not difficult to see
+how under favouring conditions one must merge into the other.
+
+Guppy has raised one novel point which can only be briefly referred to
+but which is of extreme interest. There are grounds for thinking that
+flowers and insects have mutually reacted upon one another in their
+evolution. Guppy suggests that something of the same kind may be true
+of birds. I must content myself with the quotation of a single sentence.
+"With the secular drying of the globe and the consequent differentiation
+of climate is to be connected the suspension to a great extent of the
+agency of birds as plant dispersers in later ages, not only in the
+Pacific Islands but all over the tropics. The changes of climate, birds
+and plants have gone on together, the range of the bird being controlled
+by the climate, and the distribution of the plant being largely
+dependent on the bird." (Loc.cit. II. page 221.)
+
+Darwin was clearly prepared to go further than Hooker in accounting for
+the southern flora by dispersion from the north. Thus he says: "We must,
+I suppose, admit that every yard of land has been successively covered
+with a beech-forest between the Caucasus and Japan." ("More Letters",
+II. page 9.) Hooker accounted for the dissevered condition of the
+southern flora by geographical change, but this Darwin could not admit.
+He suggested to Hooker that the Australian and Cape floras might have
+had a point of connection through Abyssinia (Ibid. I. page 447.), an
+idea which was promptly snuffed out. Similarly he remarked to Bentham
+(1869): "I suppose you think that the Restiaceae, Proteaceae, etc., etc.
+once extended over the whole world, leaving fragments in the south."
+(Ibid. I. page 380.) Eventually he conjectured "that there must have
+been a Tertiary Antarctic continent, from which various forms radiated
+to the southern extremities of our present continents." ("Life and
+Letters", III. page 231.) But characteristically he could not admit any
+land connections and trusted to "floating ice for transporting seed."
+("More Letters", I. page 116.) I am far from saying that this theory is
+not deserving of serious attention, though there seems to be no positive
+evidence to support it, and it immediately raises the difficulty how did
+such a continent come to be stocked?
+
+We must, however, agree with Hooker that the common origin of the
+northern and southern floras must be referred to a remote past. That
+Darwin had this in his mind at the time of the publication of the
+"Origin" is clear from a letter to Hooker. "The view which I should have
+looked at as perhaps most probable (though it hardly differs from yours)
+is that the whole world during the Secondary ages was inhabited by
+marsupials, araucarias (Mem.--Fossil wood of this nature in South
+America), Banksia, etc.; and that these were supplanted and exterminated
+in the greater area of the north, but were left alive in the south."
+(Ibid. I. page 453.) Remembering that Araucaria, unlike Banksia, belongs
+to the earlier Jurassic not to the angiospermous flora, this view is a
+germinal idea of the widest generality.
+
+The extraordinary congestion in species of the peninsulas of the Old
+World points to the long-continued action of a migration southwards.
+Each is in fact a cul-de-sac into which they have poured and from which
+there is no escape. On the other hand the high degree of specialisation
+in the southern floras and the little power the species possess of
+holding their own in competition or in adaptation to new conditions
+point to long-continued isolation. "An island... will prevent free
+immigration and competition, hence a greater number of ancient forms
+will survive." (Ibid. I. page 481.) But variability is itself subject to
+variation. The nemesis of a high degree of protected specialisation is
+the loss of adaptability. (See Lyell, "The Geological Evidences of the
+Antiquity of Man", London, 1863, page 446.) It is probable that many
+elements of the southern flora are doomed: there is, for example, reason
+to think that the singular Stapelieae of S. Africa are a disappearing
+group. The tree Lobelias which linger in the mountains of Central
+Africa, in Tropical America and in the Sandwich Islands have the aspect
+of extreme antiquity. I may add a further striking illustration from
+Professor Seward: "The tall, graceful fronds of Matonia pectinata,
+forming miniature forests on the slopes of Mount Ophir and other
+districts in the Malay Peninsula in association with Dipteris conjugata
+and Dipteris lobbiana, represent a phase of Mesozoic life which survives
+'Like a dim picture of the drowned past.'" ("Report of the 73rd Meeting
+of the British Assoc." (Southport, 1903), London, 1904, page 844.)
+
+The Matonineae are ferns with an unusually complex vascular system and
+were abundant "in the northern hemisphere during the earlier part of the
+Mesozoic era."
+
+It was fortunate for science that Wallace took up the task which his
+colleague had abandoned. Writing to him on the publication of his
+"Geographical Distribution of Animals" Darwin said: "I feel sure
+that you have laid a broad and safe foundation for all future work on
+Distribution. How interesting it will be to see hereafter plants treated
+in strict relation to your views." ("More Letters", II. page 12.) This
+hope was fulfilled in "Island Life". I may quote a passage from it which
+admirably summarises the contrast between the northern and the southern
+floras.
+
+"Instead of the enormous northern area, in which highly organised
+and dominant groups of plants have been developed gifted with
+great colonising and aggressive powers, we have in the south three
+comparatively small and detached areas, in which rich floras have
+been developed with SPECIAL adaptations to soil, climate, and organic
+environment, but comparatively impotent and inferior beyond their own
+domain." (Wallace, "Island Life", pages 527, 528.)
+
+It will be noticed that in the summary I have attempted to give of the
+history of the subject, efforts have been concentrated on bringing into
+relation the temperate floras of the northern and southern hemispheres,
+but no account has been taken of the rich tropical vegetation which
+belts the world and little to account for the original starting-point
+of existing vegetation generally. It must be remembered on the one hand
+that our detailed knowledge of the floras of the tropics is still very
+incomplete and far inferior to that of temperate regions; on the other
+hand palaeontological discoveries have put the problem in an entirely
+new light. Well might Darwin, writing to Heer in 1875, say: "Many
+as have been the wonderful discoveries in Geology during the last
+half-century, I think none have exceeded in interest your results with
+respect to the plants which formerly existed in the arctic regions."
+("More Letters", II. page 240.)
+
+As early as 1848 Debey had described from the Upper Cretaceous rocks of
+Aix-la-Chapelle Flowering plants of as high a degree of development
+as those now existing. The fact was commented upon by Hooker ("Introd.
+Essay to the Flora of Tasmania", page xx.), but its full significance
+seems to have been scarcely appreciated. For it implied not merely that
+their evolution must have taken place but the foundations of existing
+distribution must have been laid in a preceding age. We now know
+from the discoveries of the last fifty years that the remains of the
+Neocomian flora occur over an area extending through 30 deg of latitude.
+The conclusion is irresistible that within this was its centre of
+distribution and probably of origin.
+
+Darwin was immensely impressed with the outburst on the world of a
+fully fledged angiospermous vegetation. He warmly approved the brilliant
+theory of Saporta that this happened "as soon (as) flower-frequenting
+insects were developed and favoured intercrossing." ("More Letters", II.
+page 21.) Writing to him in 1877 he says: "Your idea that dicotyledonous
+plants were not developed in force until sucking insects had been
+evolved seems to me a splendid one. I am surprised that the idea never
+occurred to me, but this is always the case when one first hears a
+new and simple explanation of some mysterious phenomenon." ("Life
+and Letters", III. page 285. Substantially the same idea had
+occurred earlier to F.W.A. Miquel. Remarking that "sucking insects
+(Haustellata)... perform in nature the important duty of maintaining the
+existence of the vegetable kingdom, at least as far as the higher orders
+are concerned," he points our that "the appearance in great numbers of
+haustellate insects occurs at and after the Cretaceous epoch, when
+the plants with pollen and closed carpels (Angiosperms) are found, and
+acquire little by little the preponderance in the vegetable kingdom."
+"Archives Neerlandaises", III. (1868). English translation in "Journ. of
+Bot." 1869, page 101.)
+
+Even with this help the abruptness still remains an almost insoluble
+problem, though a forecast of floral structure is now recognised in some
+Jurassic and Lower Cretaceous plants. But the gap between this and the
+structural complexity and diversity of angiosperms is enormous. Darwin
+thought that the evolution might have been accomplished during a period
+of prolonged isolation. Writing to Hooker (1881) he says: "Nothing is
+more extraordinary in the history of the Vegetable Kingdom, as it seems
+to me, than the APPARENTLY very sudden or abrupt development of the
+higher plants. I have sometimes speculated whether there did not exist
+somewhere during long ages an extremely isolated continent, perhaps near
+the South Pole." ("Life and Letters", III. page 248.)
+
+The present trend of evidence is, however, all in favour of a northern
+origin for flowering plants, and we can only appeal to the imperfection
+of the geological record as a last resource to extricate us from the
+difficulty of tracing the process. But Darwin's instinct that at some
+time or other the southern hemisphere had played an important part in
+the evolution of the vegetable kingdom did not mislead him. Nothing
+probably would have given him greater satisfaction than the masterly
+summary in which Seward has brought together the evidence for the origin
+of the Glossopteris flora in Gondwana land.
+
+"A vast continental area, of which remnants are preserved in Australia,
+South Africa and South America... A tract of enormous extent occupying
+an area, part of which has since given place to a southern ocean, while
+detached masses persist as portions of more modern continents, which
+have enabled us to read in their fossil plants and ice-scratched
+boulders the records of a lost continent, in which the Mesozoic
+vegetation of the northern continent had its birth." ("Encycl. Brit."
+(10th edition 1902), Vol. XXXI. ("Palaeobotany; Mesozoic"), page 422.)
+Darwin would probably have demurred on physical grounds to the extent
+of the continent, and preferred to account for the transoceanic
+distribution of its flora by the same means which must have accomplished
+it on land.
+
+It must in fairness be added that Guppy's later views give some support
+to the conjectural existence of the "lost continent." "The distribution
+of the genus Dammara" (Agathis) led him to modify his earlier
+conclusions. He tells us:--"In my volume on the geology of Vanua Levu
+it was shown that the Tertiary period was an age of submergence in the
+Western Pacific, and a disbelief in any previous continental condition
+was expressed. My later view is more in accordance with that of
+Wichmann, who, on geological grounds, contended that the islands of the
+Western Pacific were in a continental condition during the Palaeozoic
+and Mesozoic periods, and that their submergence and subsequent
+emergence took place in Tertiary times." (Guppy, op. cit. II. page 304.)
+
+The weight of the geological evidence I am unable to scrutinise. But
+though I must admit the possibility of some unconscious bias in my
+own mind on the subject, I am impressed with the fact that the known
+distribution of the Glossopteris flora in the southern hemisphere is
+precisely paralleled by that of Proteaceae and Restiaceae in it at the
+present time. It is not unreasonable to suppose that both phenomena,
+so similar, may admit of the same explanation. I confess it would not
+surprise me if fresh discoveries in the distribution of the Glossopteris
+flora were to point to the possibility of its also having migrated
+southwards from a centre of origin in the northern hemisphere.
+
+Darwin, however, remained sceptical "about the travelling of plants
+from the north EXCEPT DURING THE TERTIARY PERIOD." But he added, "such
+speculations seem to me hardly scientific, seeing how little we know
+of the old floras." ("Life and Letters", III. page 247.) That in later
+geological times the south has been the grave of the weakened offspring
+of the aggressive north can hardly be doubted. But if we look to the
+Glossopteris flora for the ancestry of Angiosperms during the Secondary
+period, Darwin's prevision might be justified, though he has given us no
+clue as to how he arrived at it.
+
+It may be true that technically Darwin was not a botanist. But in two
+pages of the "Origin" he has given us a masterly explanation of "the
+relationship, with very little identity, between the productions of
+North America and Europe." (Pages 333, 334.) He showed that this could
+be accounted for by their migration southwards from a common area, and
+he told Wallace that he "doubted much whether the now called Palaearctic
+and Neartic regions ought to be separated." ("Life and Letters", III.
+page 230.) Catkin-bearing deciduous trees had long been seen to justify
+Darwin's doubt: oaks, chestnuts, beeches, hazels, hornbeams, birches,
+alders, willows and poplars are common both to the Old and New World.
+Newton found that the separate regions could not be sustained for birds,
+and he is now usually followed in uniting them as the Holartic. One
+feels inclined to say in reading the two pages, as Lord Kelvin did to
+a correspondent who asked for some further development of one of his
+papers, It is all there. We have only to apply the principle to previous
+geological ages to understand why the flora of the Southern United
+States preserves a Cretaceous facies. Applying it still further we can
+understand why, when the northern hemisphere gradually cooled through
+the Tertiary period, the plants of the Eocene "suggest a comparison of
+the climate and forests with those of the Malay Archipelago and Tropical
+America." (Clement Reid, "Encycl. Brit." (10th edition), Vol. XXXI.
+("Palaeobotany; Tertiary"), page 435.) Writing to Asa Gray in 1856
+with respect to the United States flora, Darwin said that "nothing has
+surprised me more than the greater generic and specific affinity with
+East Asia than with West America." ("More Letters", I. page 434.) The
+recent discoveries of a Tulip tree and a Sassafras in China afford fresh
+illustrations. A few years later Asa Gray found the explanation in
+both areas being centres of preservation of the Cretaceous flora from
+a common origin. It is interesting to note that the paper in which this
+was enunciated at once established his reputation.
+
+In Europe the latitudinal range of the great mountain chains gave the
+Miocene flora no chance of escape during the Glacial period, and the
+Mediterranean appears to have equally intercepted the flow of alpine
+plants to the Atlas. (John Ball in Appendix G, page 438, in "Journal of
+a Tour in Morocco and the Great Atlas", J.D. Hooker and J. Ball, London,
+1878.) In Southern Europe the myrtle, the laurel, the fig and the
+dwarf-palm are the sole representatives of as many great tropical
+families. Another great tropical family, the Gesneraceae has left single
+representatives from the Pyrenees to the Balkans; and in the former
+a diminutive yam still lingers. These are only illustrations of the
+evidence which constantly accumulates and which finds no rational
+explanation except that which Darwin has given to it.
+
+The theory of southward migration is the key to the interpretation of
+the geographical distribution of plants. It derived enormous support
+from the researches of Heer and has now become an accepted commonplace.
+Saporta in 1888 described the vegetable kingdom as "emigrant pour suivre
+une direction determinee et marcher du nord au sud, a la recherche
+de regions et de stations plus favorables, mieux appropriees aux
+adaptations acquises, a meme que la temperature terrestre perd ses
+conditions premieres." ("Origine Paleontologique des arbres", Paris,
+1888, page 28.) If, as is so often the case, the theory now seems to be
+a priori inevitable, the historian of science will not omit to record
+that the first germ sprang from the brain of Darwin.
+
+In attempting this sketch of Darwin's influence on Geographical
+Distribution, I have found it impossible to treat it from an external
+point of view. His interest in it was unflagging; all I could say became
+necessarily a record of that interest and could not be detached from it.
+He was in more or less intimate touch with everyone who was working
+at it. In reading the letters we move amongst great names. With an
+extraordinary charm of persuasive correspondence he was constantly
+suggesting, criticising and stimulating. It is hardly an exaggeration
+to say that from the quiet of his study at Down he was founding and
+directing a wide-world school.
+
+POSTSCRIPTUM.
+
+Since this essay was put in type Dr Ernst's striking account of the "New
+Flora of the Volcanic Island of Krakatau" (Cambridge, 1909.) has reached
+me. All botanists must feel a debt of gratitude to Prof. Seward for
+his admirable translation of a memoir which in its original form
+is practically unprocurable and to the liberality of the Cambridge
+University Press for its publication. In the preceding pages I have
+traced the laborious research by which the methods of Plant Dispersal
+were established by Darwin. In the island of Krakatau nature has
+supplied a crucial experiment which, if it had occurred earlier, would
+have at once secured conviction of their efficiency. A quarter of a
+century ago every trace of organic life in the island was "destroyed
+and buried under a thick covering of glowing stones." Now, it is "again
+covered with a mantle of green, the growth being in places so
+luxuriant that it is necessary to cut one's way laboriously through the
+vegetation." (Op. cit. page 4.) Ernst traces minutely how this has been
+brought about by the combined action of wind, birds and sea currents,
+as means of transport. The process will continue, and he concludes:--"At
+last after a long interval the vegetation on the desolated island will
+again acquire that wealth of variety and luxuriance which we see in the
+fullest development which Nature has reached in the primaeval forest
+in the tropics." (Op. cit. page 72.) The possibility of such a result
+revealed itself to the insight of Darwin with little encouragement or
+support from contemporary opinion.
+
+One of the most remarkable facts established by Ernst is that this has
+not been accomplished by the transport of seeds alone. "Tree stems and
+branches played an important part in the colonisation of Krakatau by
+plants and animals. Large piles of floating trees, stems, branches and
+bamboos are met with everywhere on the beach above high-water mark and
+often carried a considerable distance inland. Some of the animals on the
+island, such as the fat Iguana (Varanus salvator) which suns itself in
+the beds of streams, may have travelled on floating wood, possibly also
+the ancestors of the numerous ants, but certainly plants." (Op. cit.
+page 56.) Darwin actually had a prevision of this. Writing to Hooker he
+says:--"Would it not be a prodigy if an unstocked island did not in the
+course of ages receive colonists from coasts whence the currents flow,
+trees are drifted and birds are driven by gales?" ("More Letters", I.
+page 483.) And ten years earlier:--"I must believe in the... whole
+plant or branch being washed into the sea; with floods and slips and
+earthquakes; this must continually be happening." ("Life and Letters",
+II. pages 56, 57.) If we give to "continually" a cosmic measure, can the
+fact be doubted? All this, in the light of our present knowledge, is too
+obvious to us to admit of discussion. But it seems to me nothing less
+than pathetic to see how in the teeth of the obsession as to continental
+extension, Darwin fought single-handed for what we now know to be the
+truth.
+
+Guppy's heart failed him when he had to deal with the isolated case of
+Agathis which alone seemed inexplicable by known means of transport. But
+when we remember that it is a relic of the pre-Angiospermous flora, and
+is of Araucarian ancestry, it cannot be said that the impossibility,
+in so prolonged a history, of the bodily transference of cone-bearing
+branches or even of trees, compels us as a last resort to fall back on
+continental extension to account for its existing distribution.
+
+When Darwin was in the Galapagos Archipelago, he tells us that he
+fancied himself "brought near to the very act of creation." He saw
+how new species might arise from a common stock. Krakatau shows us an
+earlier stage and how by simple agencies, continually at work, that
+stock might be supplied. It also shows us how the mixed and casual
+elements of a new colony enter into competition for the ground and
+become mutually adjusted. The study of Plant Distribution from a
+Darwinian standpoint has opened up a new field of research in Ecology.
+The means of transport supply the materials for a flora, but their
+ultimate fate depends on their equipment for the "struggle for
+existence." The whole subject can no longer be regarded as a mere
+statistical inquiry which has seemed doubtless to many of somewhat arid
+interest. The fate of every element of the earth's vegetation has sooner
+or later depended on its ability to travel and to hold its own under
+new conditions. And the means by which it has secured success is an
+each case a biological problem which demands and will reward the most
+attentive study. This is the lesson which Darwin has bequeathed to us.
+It is summed up in the concluding paragraph of the "Origin" ("Origin of
+Species" (6th edition), page 429.):--"It is interesting to contemplate a
+tangled bank, clothed with many plants of many kinds, with birds singing
+on the bushes, with various insects flitting about, and with worms
+crawling through the damp earth, and to reflect that these elaborately
+constructed forms, so different from each other, and dependent upon
+each other in so complex a manner, have all been produced by laws acting
+around us."
+
+
+
+
+XVII. GEOGRAPHICAL DISTRIBUTION OF ANIMALS. By Hans Gadow, M.A., Ph.D.,
+F.R.S.
+
+Strickland Curator and Lecturer on Zoology in the University of
+Cambridge.
+
+
+The first general ideas about geographical distribution may be found
+in some of the brilliant speculations contained in Buffon's "Histoire
+Naturelle". The first special treatise on the subject was however
+written in 1777 by E.A.W. Zimmermann, Professor of Natural Science
+at Brunswick, whose large volume, "Specimen Zoologiae Geographicae
+Quadrupedum"..., deals in a statistical way with the mammals; important
+features of the large accompanying map of the world are the ranges
+of mountains and the names of hundreds of genera indicating their
+geographical range. In a second work he laid special stress on
+domesticated animals with reference to the spreading of the various
+races of Mankind.
+
+In the following year appeared the "Philosophia Entomologica" by J.C.
+Fabricius, who was the first to divide the world into eight regions. In
+1803 G.R. Treviranus ("Biologie oder Philosophie der lebenden Natur",
+Vol. II. Gottingen, 1803.) devoted a long chapter of his great work on
+"Biologie" to a philosophical and coherent treatment of the distribution
+of the whole animal kingdom. Remarkable progress was made in 1810 by F.
+Tiedemann ("Anatomie und Naturgeschichte der Vogel". Heidelberg, 1810.)
+of Heidelberg. Few, if any, of the many subsequent Ornithologists seem
+to have appreciated, or known of, the ingenious way in which Tiedemann
+marshalled his statistics in order to arrive at general conclusions.
+There are, for instance, long lists of birds arranged in accordance
+with their occurrence in one or more continents: by correlating the
+distribution of the birds with their food he concludes "that the
+countries of the East Indian flora have no vegetable feeders in common
+with America," and "that it is probably due to the great peculiarity of
+the African flora that Africa has few phytophagous kinds in common with
+other countries, whilst zoophagous birds have a far more independent,
+often cosmopolitan, distribution." There are also remarkable chapters
+on the influence of environment, distribution, and migration, upon the
+structure of the Birds! In short, this anatomist dealt with some of the
+fundamental causes of distribution.
+
+Whilst Tiedemann restricted himself to Birds, A. Desmoulins in 1822
+wrote a short but most suggestive paper on the Vertebrata, omitting
+the birds; he combated the view recently proposed by the entomologist
+Latreille that temperature was the main factor in distribution. Some of
+his ten main conclusions show a peculiar mixture of evolutionary ideas
+coupled with the conception of the stability of species: whilst each
+species must have started from but one creative centre, there may be
+several "analogous centres of creation" so far as genera and families
+are concerned. Countries with different faunas, but lying within the
+same climatic zones, are proof of the effective and permanent existence
+of barriers preventing an exchange between the original creative
+centres.
+
+The first book dealing with the "geography and classification" of the
+whole animal kingdom was written by W. Swainson ("A Treatise on
+the Geography and Classification of Animals", Lardner's "Cabinet
+Cyclopaedia" London, 1835.) in 1835. He saw in the five races of Man
+the clue to the mapping of the world into as many "true zoological
+divisions," and he reconciled the five continents with his mystical
+quinary circles.
+
+Lyell's "Principles of Geology" should have marked a new epoch, since
+in his "Elements" he treats of the past history of the globe and the
+distribution of animals in time, and in his "Principles" of their
+distribution in space in connection with the actual changes undergone by
+the surface of the world. But as the sub-title of his great work "Modern
+changes of the Earth and its inhabitants" indicates, he restricted
+himself to comparatively minor changes, and, emphatically believing
+in the permanency of the great oceans, his numerous and careful
+interpretations of the effect of the geological changes upon the
+dispersal of animals did after all advance the problem but little.
+
+Hitherto the marine faunas had been neglected. This was remedied by E.
+Forbes, who established nine homozoic zones, based mainly on the study
+of the mollusca, the determining factors being to a great extent
+the isotherms of the sea, whilst the 25 provinces were given by the
+configuration of the land. He was followed by J.D. Dana, who, taking
+principally the Crustacea as a basis, and as leading factors the mean
+temperatures of the coldest and of the warmest months, established
+five latitudinal zones. By using these as divisors into an American,
+Afro-European, Oriental, Arctic and Antarctic realm, most of which were
+limited by an eastern and western land-boundary, he arrived at about
+threescore provinces.
+
+In 1853 appeared L.K. Schmarda's ("Die geographische Verbreitung der
+Thiere", Wien, 1853.) two volumes, embracing the whole subject. Various
+centres of creation being, according to him, still traceable, he formed
+the hypothesis that these centres were originally islands, which later
+became enlarged and joined together to form the great continents, so
+that the original faunas could overlap and mix whilst still remaining
+pure at their respective centres. After devoting many chapters to the
+possible physical causes and modes of dispersal, he divided the land
+into 21 realms which he shortly characterises, e.g. Australia as the
+only country inhabited by marsupials, monotremes and meliphagous birds.
+Ten main marine divisions were diagnosed in a similar way. Although some
+of these realms were not badly selected from the point of view of being
+applicable to more than one class of animals, they were obviously too
+numerous for general purposes, and this drawback was overcome, in 1857,
+by P.L. Sclater. ("On the general Geographical Distribution of the
+members of the class Aves", "Proc. Linn. Soc." (Zoology II. 1858, pages
+130-145.)) Starting with the idea, that "each species must have been
+created within and over the geographical area, which it now occupies,"
+he concluded "that the most natural primary ontological divisions of the
+Earth's surface" were those six regions, which since their adoption
+by Wallace in his epoch-making work, have become classical. Broadly
+speaking, these six regions are equivalent to the great masses of land;
+they are convenient terms for geographical facts, especially since the
+Palaearctic region expresses the unity of Europe with the bulk of Asia.
+Sclater further brigaded the regions of the Old World as Palaeogaea and
+the two Americas as Neogaea, a fundamental mistake, justifiable to a
+certain extent only since he based his regions mainly upon the present
+distribution of the Passerine birds.
+
+Unfortunately these six regions are not of equal value. The Indian
+countries and the Ethiopian region (Africa south of the Sahara) are
+obviously nothing but the tropical, southern continuations or appendages
+of one greater complex. Further, the great eastern mass of land is so
+intimately connected with North America that this continent has much
+more in common with Europe and Asia than with South America. Therefore,
+instead of dividing the world longitudinally as Sclater had done,
+Huxley, in 1868 ("On the classification and distribution of the
+Alectoromorphae and Heteromorphae", "Proc. Zool. Soc." 1868, page
+294.), gave weighty reasons for dividing it transversely. Accordingly
+he established two primary divisions, Arctogaea or the North world in
+a wider sense, comprising Sclater's Indian, African, Palaearctic and
+Neartic regions; and Notogaea, the Southern world, which he divided
+into (1) Austro-Columbia (an unfortunate substitute for the neotropical
+region), (2) Australasia, and (3) New Zealand, the number of big regions
+thus being reduced to three but for the separation of New Zealand upon
+rather negative characters. Sclater was the first to accept these four
+great regions and showed, in 1874 ("The geographical distribution of
+Mammals", "Manchester Science Lectures", 1874.), that they were well
+borne out by the present distribution of the Mammals.
+
+Although applicable to various other groups of animals, for instance to
+the tailless Amphibia and to Birds (Huxley himself had been led to found
+his two fundamental divisions on the distribution of the Gallinaceous
+birds), the combination of South America with Australia was gradually
+found to be too sweeping a measure. The obvious and satisfactory
+solution was provided by W.T. Blanford (Anniversary address (Geological
+Society, 1889), "Proc. Geol. Soc." 1889-90, page 67; "Quart. Journ."
+XLVI 1890.), who in 1890 recognised three main divisions, namely
+Australian, South American, and the rest, for which the already existing
+terms (although used partly in a new sense, as proposed by an anonymous
+writer in "Natural Science", III. page 289) "Notogaea," "Neogaea" and
+"Arctogaea" have been gladly accepted by a number of English writers.
+
+After this historical survey of the search for larger and largest or
+fundamental centres of animal creation, which resulted in the mapping
+of the world into zoological regions and realms of after all doubtful
+value, we have to return to the year 1858. The eleventh and twelfth
+chapters of "The Origin of Species" (1859), dealing with "Geographical
+Distribution," are based upon a great amount of observation, experiment
+and reading. As Darwin's main problem was the origin of species,
+nature's way of making species by gradual changes from others previously
+existing, he had to dispose of the view, held universally, of the
+independent creation of each species and at the same time to insist upon
+a single centre of creation for each species; and in order to emphasise
+his main point, the theory of descent, he had to disallow convergent, or
+as they were then called, analogous forms. To appreciate the difficulty
+of his position we have to take the standpoint of fifty years ago, when
+the immutability of the species was an axiom and each was supposed to
+have been created within or over the geographical area which it now
+occupies. If he once admitted that a species could arise from many
+individuals instead of from one pair, there was no way of shutting the
+door against the possibility that these individuals may have been so
+numerous that they occupied a very large district, even so large that
+it had become as discontinuous as the distribution of many a species
+actually is. Such a concession would at once be taken as an admission of
+multiple, independent, origin instead of descent in Darwin's sense.
+
+For the so-called multiple, independently repeated creation of species
+as an explanation of their very wide and often quite discontinuous
+distribution, he substituted colonisation from the nearest and readiest
+source together with subsequent modification and better adaptation to
+their new home.
+
+He was the first seriously to call attention to the many accidental
+means, "which more properly should be called occasional means of
+distribution," especially to oceanic islands. His specific, even
+individual, centres of creation made migrations all the more necessary,
+but their extent was sadly baulked by the prevailing dogma of the
+permanency of the oceans. Any number of small changes ("many islands
+having existed as halting places, of which not a wreck now remains"
+("The Origin of Species" (1st edition), page 396.).) were conceded
+freely, but few, if any, great enough to permit migration of truly
+terrestrial creatures. The only means of getting across the gaps was by
+the principle of the "flotsam and jetsam," a theory which Darwin took
+over from Lyell and further elaborated so as to make it applicable to
+many kinds of plants and animals, but sadly deficient, often grotesque,
+in the case of most terrestrial creatures.
+
+Another very fertile source was Darwin's strong insistence upon the
+great influence which the last glacial epoch must have had upon the
+distribution of animals and plants. Why was the migration of northern
+creatures southwards of far-reaching and most significant importance?
+More northerners have established themselves in southern lands than
+vice versa, because there is such a great mass of land in the north
+and greater continents imply greater intensity of selection. "The
+productions of real islands have everywhere largely yielded to
+continental forms." (Ibid. page 380.)... "The Alpine forms have almost
+everywhere largely yielded to the more dominant forms generated in the
+larger areas and more efficient workshops of the North."
+
+Let us now pass in rapid survey the influence of the publication of "The
+Origin of Species" upon the study of Geographical Distribution in its
+wider sense.
+
+Hitherto the following thought ran through the minds of most writers:
+Wherever we examine two or more widely separated countries their
+respective faunas are very different, but where two faunas can come into
+contact with each other, they intermingle. Consequently these faunas
+represent centres of creation, whence the component creatures have
+spread peripherally so far as existing boundaries allowed them to do so.
+This is of course the fundamental idea of "regions." There is not one
+of the numerous writers who considered the possibility that these
+intermediate belts might represent not a mixture of species but
+transitional forms, the result of changes undergone by the most
+peripheral migrants in adaptation to their new surroundings. The usual
+standpoint was also that of Pucheran ("Note sur l'equateur zoologique",
+"Rev. et Mag. de Zoologie", 1855; also several other papers, ibid. 1865,
+1866, and 1867.) in 1855. But what a change within the next ten years!
+Pucheran explains the agreement in coloration between the desert and
+its fauna as "une harmonie post-etablie"; the Sahara, formerly a marine
+basin, was peopled by immigrants from the neighbouring countries, and
+these new animals adapted themselves to the new environment. He also
+discusses, among other similar questions, the Isthmus of Panama with
+regard to its having once been a strait. From the same author may be
+quoted the following passage as a strong proof of the new influence:
+"By the radiation of the contemporaneous faunas, each from one centre,
+whence as the various parts of the world successively were formed and
+became habitable, they spread and became modified according to the local
+physical conditions."
+
+The "multiple" origin of each species as advocated by Sclater and
+Murray, although giving the species a broader basis, suffered from the
+same difficulties. There was only one alternative to the old
+orthodox view of independent creation, namely the bold acceptance of
+land-connections to an extent for which geological and palaeontological
+science was not yet ripe. Those who shrank from either view, gave up
+the problem as mysterious and beyond the human intellect. This was the
+expressed opinion of men like Swainson, Lyell and Humboldt. Only Darwin
+had the courage to say that the problem was not insoluble. If we admit
+"that in the long course of time the individuals of the same species,
+and likewise of allied species, have proceeded from some one source;
+then I think all the grand leading facts of geographical distribution
+are explicable on the theory of migration... together with subsequent
+modification and the multiplication of new forms." We can thus
+understand how it is that in some countries the inhabitants "are linked
+to the extinct beings which formerly inhabited the same continent."
+We can see why two areas, having nearly the same physical conditions,
+should often be inhabited by very different forms of life,... and "we can
+see why in two areas, however distant from each other, there should be a
+correlation, in the presence of identical species... and of distinct but
+representative species." ("The Origin of Species" (1st edition), pages
+408, 409.)
+
+Darwin's reluctance to assume great geological changes, such as a
+land-connection of Europe with North America, is easily explained by the
+fact that he restricted himself to the distribution of the present and
+comparatively recent species. "I do not believe that it will ever be
+proved that within the recent period continents which are now quite
+separate, have been continuously, or almost continuously, united with
+each other, and with the many existing oceanic islands." (Ibid. page
+357.) Again, "believing... that our continents have long remained in
+nearly the same relative position, though subjected to large, but
+partial oscillations of level," that means to say within the period of
+existing species, or "within the recent period." (Ibid. page. 370.) The
+difficulty was to a great extent one of his own making. Whilst almost
+everybody else believed in the immutability of the species, which
+implies an enormous age, logically since the dawn of creation, to him
+the actually existing species as the latest results of evolution, were
+necessarily something very new, so young that only the very latest of
+the geological epochs could have affected them. It has since come to
+our knowledge that a great number of terrestrial "recent" species, even
+those of the higher classes of Vertebrates, date much farther back than
+had been thought possible. Many of them reach well into the Miocene, a
+time since which the world seems to have assumed the main outlines of
+the present continents.
+
+In the year 1866 appeared A. Murray's work on the "Geographical
+Distribution of Mammals", a book which has perhaps received less
+recognition than it deserves. His treatment of the general introductory
+questions marks a considerable advance of our problem, although, and
+partly because, he did not entirely agree with Darwin's views as laid
+down in the first edition of "The Origin of Species", which after all
+was the great impulse given to Murray's work. Like Forbes he did not
+shrink from assuming enormous changes in the configuration of the
+continents and oceans because the theory of descent, with its necessary
+postulate of great migrations, required them. He stated, for instance,
+"that a Miocene Atlantis sufficiently explains the common distribution
+of animals and plants in Europe and America up to the glacial epoch."
+And next he considers how, and by what changes, the rehabilitation and
+distribution of these lands themselves were effected subsequent to
+that period. Further, he deserves credit for having cleared up a
+misunderstanding of the idea of specific centres of creation. Whilst for
+instance Schmarda assumed without hesitation that the same species,
+if occurring at places separated by great distances, or apparently
+insurmountable barriers, had been there created independently (multiple
+centres), Lyell and Darwin held that each species had only one single
+centre, and with this view most of us agree, but their starting point
+was to them represented by one individual, or rather one single pair.
+According to Murray, on the other hand, this centre of a species is
+formed by all the individuals of a species, all of which equally undergo
+those changes which new conditions may impose upon them. In this respect
+a new species has a multiple origin, but this in a sense very different
+from that which was upheld by L. Agassiz. As Murray himself puts it: "To
+my multiple origin, communication and direct derivation is essential.
+The species is compounded of many influences brought together through
+many individuals, and distilled by Nature into one species; and, being
+once established it may roam and spread wherever it finds the conditions
+of life not materially different from those of its original centre."
+(Murray, "The Geographical Distribution of Mammals", page 14. London,
+1866.) This declaration fairly agrees with more modern views, and
+it must be borne in mind that the application of the single-centre
+principle to the genera, families and larger groups in the search for
+descent inevitably leads to one creative centre for the whole animal
+kingdom, a condition as unwarrantable as the myth of Adam and Eve being
+the first representatives of Mankind.
+
+It looks as if it had required almost ten years for "The Origin
+of Species" to show its full effect, since the year 1868 marks the
+publication of Haeckel's "Naturliche Schoepfungsgeschichte" in addition
+to other great works. The terms "Oecology" (the relation of organisms
+to their environment) and "Chorology" (their distribution in space) had
+been given us in his "Generelle Morphologie" in 1866. The fourteenth
+chapter of the "History of Creation" is devoted to the distribution of
+organisms, their chorology, with the emphatic assertion that "not
+until Darwin can chorology be spoken of as a separate science, since
+he supplied the acting causes for the elucidation of the hitherto
+accumulated mass of facts." A map (a "hypothetical sketch") shows the
+monophyletic origin and the routes of distribution of Man.
+
+Natural Selection may be all-mighty, all-sufficient, but it requires
+time, so much that the countless aeons required for the evolution of the
+present fauna were soon felt to be one of the most serious drawbacks of
+the theory. Therefore every help to ease and shorten this process should
+have been welcomed. In 1868 M. Wagner (The first to formulate clearly
+the fundamental idea of a theory of migration and its importance in
+the origin of new species was L. von Buch, who in his "Physikalische
+Beschreibung der Canarischen Inseln", written in 1825, wrote as follows:
+"Upon the continents the individuals of the genera by spreading far,
+form, through differences of the locality, food and soil, varieties
+which finally become constant as new species, since owing to the
+distances they could never be crossed with other varieties and thus
+be brought back to the main type. Next they may again, perhaps upon
+different roads, return to the old home where they find the old
+type likewise changed, both having become so different that they can
+interbreed no longer. Not so upon islands, where the individuals shut
+up in narrow valleys or within narrow districts, can always meet one
+another and thereby destroy every new attempt towards the fixing of a
+new variety." Clearly von Buch explains here why island types remain
+fixed, and why these types themselves have become so different from
+their continental congeners.--Actually von Buch is aware of a most
+important point, the difference in the process of development which
+exists between a new species b, which is the result of an ancestral
+species a having itself changed into b and thereby vanished itself, and
+a new species c which arose through separation out of the same ancestral
+a, which itself persists as such unaltered. Von Buch's prophetic view
+seems to have escaped Lyell's and even Wagner's notice.) came to the
+rescue with his "Darwin'sche Theorie und das Migrations-Gesetz der
+Organismen". (Leipzig, 1868.) He shows that migration, i.e. change of
+locality, implies new environmental conditions (never mind whether
+these be new stimuli to variation, or only acting as their selectors or
+censors), and moreover secures separation from the original stock and
+thus eliminates or lessens the reactionary dangers of panmixia. Darwin
+accepted Wagner's theory as "advantageous." Through the heated polemics
+of the more ardent selectionists Wagner's theory came to grow into an
+alternative instead of a help to the theory of selectional evolution.
+Separation is now rightly considered a most important factor by modern
+students of geographical distribution.
+
+For the same year, 1868, we have to mention Huxley, whose Arctogaea and
+Notogaea are nothing less than the reconstructed main masses of land
+of the Mesozoic period. Beyond doubt the configuration of land at that
+remote period has left recognisable traces in the present continents,
+but whether they can account for the distribution of such a much later
+group as the Gallinaceous birds is more than questionable. In any case
+he took for his text a large natural group of birds, cosmopolitan as
+a whole, but with a striking distribution. The Peristeropodes, or
+pigeon-footed division, are restricted to the Australian and Neotropical
+regions, in distinction to the Alectoropodes (with the hallux inserted
+at a level above the front toes) which inhabit the whole of the
+Arctogaea, only a few members having spread into the South World.
+Further, as Asia alone has its Pheasants and allies, so is Africa
+characterised by its Guinea-fowls and relations, America has the Turkey
+as an endemic genus, and the Grouse tribe in a wider sense has its
+centre in the holarctic region: a splendid object lesson of descent,
+world-wide spreading and subsequent differentiation. Huxley, by the way,
+was the first--at least in private talk--to state that it will be for
+the morphologist, the well-trained anatomist, to give the casting vote
+in questions of geographical distribution, since he alone can determine
+whether we have to deal with homologous, or analogous, convergent,
+representative forms.
+
+It seems late to introduce Wallace's name in 1876, the year of the
+publication of his standard work. ("The Geographical Distribution of
+Animals", 2 vols. London, 1876.) We cannot do better than quote the
+author's own words, expressing the hope that his "book should bear a
+similar relation to the eleventh and twelfth chapters of the "Origin of
+Species" as Darwin's "Animals and Plants under Domestication" does to
+the first chapter of that work," and to add that he has amply succeeded.
+Pleading for a few primary centres he accepts Sclater's six regions and
+does not follow Huxley's courageous changes which Sclater himself had
+accepted in 1874. Holding the view of the permanence of the oceans he
+accounts for the colonisation of outlying islands by further elaborating
+the views of Lyell and Darwin, especially in his fascinating "Island
+Life", with remarkable chapters on the Ice Age, Climate and Time and
+other fundamental factors. His method of arriving at the degree
+of relationship of the faunas of the various regions is eminently
+statistical. Long lists of genera determine by their numbers the
+affinity and hence the source of colonisation. In order to make sure
+of his material he performed the laborious task of evolving a new
+classification of the host of Passerine birds. This statistical method
+has been followed by many authors, who, relying more upon quantity than
+quality, have obscured the fact that the key to the present distribution
+lies in the past changes of the earth's surface. However, with Wallace
+begins the modern study of the geographical distribution of animals and
+the sudden interest taken in this subject by an ever widening circle of
+enthusiasts far beyond the professional brotherhood.
+
+A considerable literature has since grown up, almost bewildering in its
+range, diversity of aims and style of procedure. It is a chaos, with
+many paths leading into the maze, but as yet very few take us to a
+position commanding a view of the whole intricate terrain with its
+impenetrable tangle and pitfalls.
+
+One line of research, not initiated but greatly influenced by Wallace's
+works, became so prominent as to almost constitute a period which may
+be characterised as that of the search by specialists for either the
+justification or the amending of his regions. As class after class of
+animals was brought up to reveal the secret of the true regions, some
+authors saw in their different results nothing but the faultiness of
+previously established regions; others looked upon eventual agreements
+as their final corroboration, especially when for instance such diverse
+groups as mammals and scorpions could, with some ingenuity, be made to
+harmonise. But the obvious result of all these efforts was the growing
+knowledge that almost every class seemed to follow principles of its
+own. The regions tallied neither in extent nor in numbers, although
+most of them gravitated more and more towards three centres, namely
+Australia, South America and the rest of the world. Still zoologists
+persisted in the search, and the various modes and capabilities of
+dispersal of the respective groups were thought sufficient explanation
+of the divergent results in trying to bring the mapping of the world
+under one scheme.
+
+Contemporary literature is full of devices for the mechanical dispersal
+of animals. Marine currents, warm and cold, were favoured all the
+more since they showed the probable original homes of the creatures in
+question. If these could not stand sea-water, they floated upon logs or
+icebergs, or they were blown across by storms; fishes were lifted over
+barriers by waterspouts, and there is on record even an hypothetical
+land tortoise, full of eggs, which colonised an oceanic island after a
+perilous sea voyage upon a tree trunk. Accidents will happen, and beyond
+doubt many freaks of discontinuous distribution have to be accounted
+for by some such means. But whilst sufficient for the scanty settlers of
+true oceanic islands, they cannot be held seriously to account for the
+rich fauna of a large continent, over which palaeontology shows us that
+the immigrants have passed like waves. It should also be borne in mind
+that there is a great difference between flotsam and jetsam. A current
+is an extension of the same medium and the animals in it may suffer no
+change during even a long voyage, since they may be brought from one
+litoral to another where they will still be in the same or but slightly
+altered environment. But the jetsam is in the position of a passenger
+who has been carried off by the wrong train. Almost every year some
+American land birds arrive at our western coasts and none of them have
+gained a permanent footing although such visits must have taken place
+since prehistoric times. It was therefore argued that only those groups
+of animals should be used for locating and defining regions which were
+absolutely bound to the soil. This method likewise gave results not
+reconcilable with each other, even when the distribution of fossils
+was taken into account, but it pointed to the absolute necessity of
+searching for former land-connections regardless of their extent and the
+present depths to which they may have sunk.
+
+That the key to the present distribution lies in the past had been felt
+long ago, but at last it was appreciated that the various classes of
+animals and plants have appeared in successive geological epochs and
+also at many places remote from each other. The key to the distribution
+of any group lies in the configuration of land and water of that epoch
+in which it made its first appearance. Although this sounds like a
+platitude, it has frequently been ignored. If, for argument's sake,
+Amphibia were evolved somewhere upon the great southern land-mass of
+Carboniferous times (supposed by some to have stretched from South
+America across Africa to Australia), the distribution of this developing
+class must have proceeded upon lines altogether different from that of
+the mammals which dated perhaps from lower Triassic times, when the old
+south continental belt was already broken up. The broad lines of this
+distribution could never coincide with that of the other, older class,
+no matter whether the original mammalian centre was in the Afro-Indian,
+Australian, or Brazilian portion. If all the various groups of animals
+had come into existence at the same time and at the same place, then it
+would be possible, with sufficient geological data, to construct a map
+showing the generalised results applicable to the whole animal kingdom.
+But the premises are wrong. Whatever regions we may seek to establish
+applicable to all classes, we are necessarily mixing up several
+principles, namely geological, historical, i.e. evolutionary, with
+present day statistical facts. We might as well attempt one compound
+picture representing a chick's growth into an adult bird and a child's
+growth into manhood.
+
+In short there are no general regions, not even for each class
+separately, unless this class be one which is confined to a
+comparatively short geological period. Most of the great classes have
+far too long a history and have evolved many successive main groups.
+Let us take the mammals. Marsupials live now in Australia and in both
+Americas, because they already existed in Mesozoic times; Ungulata
+existed at one time or other all over the world except in Australia,
+because they are post-Cretaceous; Insectivores, although as old as any
+Placentalia, are cosmopolitan excepting South America and Australia;
+Stags and Bears, as examples of comparatively recent Arctogaeans, are
+found everywhere with the exception of Ethiopia and Australia. Each of
+these groups teaches a valuable historical lesson, but when these are
+combined into the establishment of a few mammalian "realms," they mean
+nothing but statistical majorities. If there is one at all, Australia is
+such a realm backed against the rest of the world, but as certainly it
+is not a mammalian creative centre!
+
+Well then, if the idea of generally applicable regions is a mare's nest,
+as was the search for the Holy Grail, what is the object of the study
+of geographical distribution? It is nothing less than the history of the
+evolution of life in space and time in the widest sense. The attempt to
+account for the present distribution of any group of organisms involves
+the aid of every branch of science. It bids fair to become a history of
+the world. It started in a mild, statistical way, restricting itself to
+the present fauna and flora and to the present configuration of land
+and water. Next came Oceanography concerned with the depths of the seas,
+their currents and temperatures; then enquiries into climatic changes,
+culminating in irreconcilable astronomical hypotheses as to glacial
+epochs; theories about changes of the level of the seas, mainly from the
+point of view of the physicist and astronomer. Then came more and more
+to the front the importance of the geological record, hand in hand with
+the palaeontological data and the search for the natural affinities, the
+genetic system of the organisms. Now and then it almost seems as if the
+biologists had done their share by supplying the problems and that the
+physicists and geologists would settle them, but in reality it is not
+so. The biologists not only set the problems, they alone can check the
+offered solutions. The mere fact of palms having flourished in Miocene
+Spitzbergen led to an hypothetical shifting of the axis of the world
+rather than to the assumption, by way of explanation, that the palms
+themselves might have changed their nature. One of the most valuable
+aids in geological research, often the only means for reconstructing the
+face of the earth in by-gone periods, is afforded by fossils, but only
+the morphologist can pronounce as to their trustworthiness as witnesses,
+because of the danger of mistaking analogous for homologous forms. This
+difficulty applies equally to living groups, and it is so important that
+a few instances may not be amiss.
+
+There is undeniable similarity between the faunas of Madagascar and
+South America. This was supported by the Centetidae and Dendrobatidae,
+two entire "families," as also by other facts. The value of the
+Insectivores, Solenodon in Cuba, Centetes in Madagascar, has been much
+lessened by their recognition as an extremely ancient group and as a
+case of convergence, but if they are no longer put into the same
+family, this amendment is really to a great extent due to their widely
+discontinuous distribution. The only systematic difference of the
+Dendrobatidae from the Ranidae is the absence of teeth, morphologically
+a very unimportant character, and it is now agreed, on the strength of
+their distribution, that these little arboreal, conspicuously coloured
+frogs, Dendrobates in South America, Mantella in Madagascar, do not form
+a natural group, although a third genus, Cardioglossa in West Africa,
+seems also to belong to them. If these creatures lived all on the
+same continent, we should unhesitatingly look upon them as forming a
+well-defined, natural little group. On the other hand the Aglossa, with
+their three very divergent genera, namely Pipa in South America, Xenopus
+and Hymenochirus in Africa, are so well characterised as one ancient
+group that we use their distribution unhesitatingly as a hint of a
+former connection between the two continents. We are indeed arguing in
+vicious circles. The Ratitae as such are absolutely worthless since they
+are a most heterogeneous assembly, and there are untold groups, of
+the artificiality of which many a zoo-geographer had not the slightest
+suspicion when he took his statistical material, the genera and
+families, from some systematic catalogues or similar lists. A lamentable
+instance is that of certain flightless Rails, recently extinct or
+sub-fossil, on the isalnds of Mauritius, Rodriguez and Chatham. Being
+flightless they have been used in support of a former huge Antarctic
+continent, instead of ruling them out of court as Rails which, each in
+its island, have lost the power of flight, a process which must have
+taken place so recently that it is difficult, upon morphological
+grounds, to justify their separation into Aphanapteryx in Mauritius,
+Erythromachus in Rodriguez and Diaphorapteryx on Chatham Island.
+Morphologically they may well form but one genus, since they have sprung
+from the same stock and have developed upon the same lines; they are
+therefore monogenetic: but since we know that they have become what they
+are independently of each other (now unlike any other Rails), they are
+polygenetic and therefore could not form one genus in the old Darwinian
+sense. Further, they are not a case of convergence, since their ancestry
+is not divergent but leads into the same stratum.
+
+THE RECONSTRUCTION OF THE GEOGRAPHY OF SUCCESSIVE EPOCHS.
+
+A promising method is the study by the specialist of a large, widely
+distributed group of animals from an evolutionary point of view.
+Good examples of this method are afforded by A.E. Ortmann's ("The
+geographical distribution of Freshwater Decapods and its bearing upon
+ancient geography", "Proc. Amer. Phil. Soc." Vol. 41, 1902.) exhaustive
+paper and by A.W. Grabau's "Phylogeny of Fusus and its Allies"
+("Smithsonian Misc. Coll." 44, 1904.) After many important groups of
+animals have been treated in this way--as yet sparingly attempted--the
+results as to hypothetical land-connections etc. are sure to be
+corrective and supplementary, and their problems will be solved, since
+they are not imaginary.
+
+The same problems are attacked, in the reverse way, by starting with the
+whole fauna of a country and thence, so to speak, letting the research
+radiate. Some groups will be considered as autochthonous, others as
+immigrants, and the directions followed by them will be inquired into;
+the search may lead far and in various directions, and by comparison of
+results, by making compound maps, certain routes will assume definite
+shape, and if they lead across straits and seas they are warrants to
+search for land-connections in the past. (A fair sample of this method
+is C.H. Eigenmann's "The Freshwater Fishes of South and Middle America",
+"Popular Science Monthly", Vol. 68, 1906.) There are now not a few maps
+purporting to show the outlines of land and water at various epochs.
+Many of these attempts do not tally with each other, owing to the
+lamentable deficiencies of geological and fossil data, but the bolder
+the hypothetical outlines are drawn, the better, and this is preferable
+to the insertion of bays and similar detail which give such maps a
+fallacious look of certainty where none exists. Moreover it must be
+borne in mind that, when we draw a broad continental belt across an
+ocean, this belt need never have existed in its entirety at any one
+time. The features of dispersal, intended to be explained by it, would
+be accomplished just as well by an unknown number of islands which have
+joined into larger complexes while elsewhere they subsided again:
+like pontoon-bridges which may be opened anywhere, or like a series
+of superimposed dissolving views of land and sea-scapes. Hence the
+reconstructed maps of Europe, the only continent tolerably known, show
+a considerable number of islands in puzzling changes, while elsewhere,
+e.g. in Asia, we have to be satisfied with sweeping generalisations.
+
+At present about half-a-dozen big connections are engaging our
+attention, leaving as comparatively settled the extent and the duration
+of such minor "bridges" as that between Africa and Madagascar, Tasmania
+and Australia, the Antilles and Central America, Europe and North
+Africa. (Not a few of those who are fascinated by, and satisfied with,
+the statistical aspect of distribution still have a strong dislike to
+the use of "bridges" if these lead over deep seas, and they get
+over present discontinuous occurrences by a former "universal or
+sub-universal distribution" of their groups.) This is indeed an easy
+method of cutting the knot, but in reality they shunt the question only
+a stage or two back, never troubling to explain how their groups managed
+to attain to that sub-universal range; or do they still suppose that the
+whole world was originally one paradise where everything lived side by
+side, until sin and strife and glacial epochs left nothing but scattered
+survivors?
+
+The permanence of the great ocean-basins had become a dogma since it
+was found that a universal elevation of the land to the extent of 100
+fathoms would produce but little changes, and when it was shown that
+even the 1000 fathom-line followed the great masses of land rather
+closely, and still leaving the great basins (although transgression
+of the sea to the same extent would change the map of the world beyond
+recognition), by general consent one mile was allowed as the utmost
+speculative limit of subsidence. Naturally two or three miles, the
+average depth of the oceans, seems enormous, and yet such a difference
+in level is as nothing in comparison with the size of the Earth. On
+a clay model globe ten feet in diameter an ocean bed three miles deep
+would scarcely be detected, and the highest mountains would be smaller
+than the unavoidable grains in the glazed surface of our model. There
+are but few countries which have not be submerged at some time or
+other.
+
+CONNECTION OF SOUTH EASTERN ASIA WITH AUSTRALIA. Neumayr's
+Sino-Australian continent during mid-Mesozoic times was probably a
+much changing Archipelago, with final separations subsequent to the
+Cretaceous period. Henceforth Australasia was left to its own fate, but
+for a possible connection with the antarctic continent.
+
+AFRICA, MADAGASCAR, INDIA. The "Lemuria" of Sclater and Haeckel cannot
+have been more than a broad bridge in Jurassic times; whether it was
+ever available for the Lemurs themselves must depend upon the time of
+its duration, the more recent the better, but it is difficult to show
+that it lasted into the Miocene.
+
+AFRICA AND SOUTH AMERICA. Since the opposite coasts show an entire
+absence of marine fossils and deposits during the Mesozoic period,
+whilst further north and south such are known to exist and are mostly
+identical on either side, Neumayr suggested the existence of a great
+Afro-Son American mass of land during the Jurassic epoch. Such land
+is almost a necessity and is supported by many facts; it would easily
+explain the distribution of numerous groups of terrestrial creatures.
+Moreover to the north of this hypothetical land, somewhere across
+from the Antilles and Guiana to North Africa and South Western Europe,
+existed an almost identical fauna of Corals and Molluscs, indicating
+either a coast-line or a series of islands interrupted by shallow seas,
+just as one would expect if, and when, a Brazil-Ethiopian mass of land
+were breaking up. Lastly from Central America to the Mediterranean
+stretches one of the Tertiary tectonic lines of the geologists. Here
+also the great question is how long this continent lasted. Apparently
+the South Atlantic began to encroach from the south so that by the
+later Cretaceous epoch the land was reduced to a comparatively narrow
+Brazil-West Africa, remnants of which persisted certainly into the early
+Tertiary, until the South Atlantic joined across the equator with the
+Atlantic portion of the "Thetys," leaving what remained of South America
+isolated from the rest of the world.
+
+ANTARCTIC CONNECTIONS. Patagonia and Argentina seem to have joined
+Antartica during the Cretaceous epoch, and this South Georgian bridge
+had broken down again by mid-Tertiary times when South America became
+consolidated. The Antarctic continent, presuming that it existed, seems
+also to have been joined, by way of Tasmania, with Australia,
+also during the Cretaceous epoch, and it is assumed that the great
+Australia-Antarctic-Patagonian land was severed first to the south of
+Tasmania and then at the South Georgian bridge. No connection, and
+this is important, is indicated between Antarctica and either Africa or
+Madagascar.
+
+So far we have followed what may be called the vicissitudes of the great
+Permo-Carboniferous Gondwana land in its fullest imaginary extent,
+an enormous equatorial and south temperate belt from South America to
+Africa, South India and Australia, which seems to have provided the
+foundation of the present Southern continents, two of which temporarily
+joined Antarctica, of which however we know nothing except that it
+exists now.
+
+Let us next consider the Arctic and periarctic lands. Unfortunately very
+little is known about the region within the arctic circle. If it was all
+land, or more likely great changing archipelagoes, faunistic exchange
+between North America, Europe and Siberia would present no difficulties,
+but there is one connection which engages much attention, namely a land
+where now lies the North temperate and Northern part of the Atlantic
+ocean. How far south did it ever extend and what is the latest date of
+a direct practicable communication, say from North Western Europe
+to Greenland? Connections, perhaps often interrupted, e.g. between
+Greenland and Labrador, at another time between Greenland and
+Scandinavia, seem to have existed at least since the Permo-Carboniferous
+epoch. If they existed also in late Cretaceous and in Tertiary times,
+they would of course easily explain exchanges which we know to have
+repeatedly taken place between America and Europe, but they are not
+proved thereby, since most of these exchanges can almost as easily
+have occurred across the polar regions, and others still more easily by
+repeated junction of Siberia with Alaska.
+
+Let us now describe a hypothetical case based on the supposition of
+connecting bridges. Not to work in a circle, we select an important
+group which has not served as a basis for the reconstruction of bridges;
+and it must be a group which we feel justified in assuming to be old
+enough to have availed itself of ancient land-connections.
+
+The occurrence of one species of Peripatus in the whole of Australia,
+Tasmania and New Zealand (the latter being joined to Australia by way of
+New Britain in Cretaceous times but not later) puts the genus back
+into this epoch, no unsatisfactory assumption to the morphologist. The
+apparent absence of Peripatus in Madagascar indicates that it did not
+come from the east into Africa, that it was neither Afro-Indian, nor
+Afro-Australian; nor can it have started in South America. We therefore
+assume as its creative centre Australia or Malaya in the Cretaceous
+epoch, whence its occurrence in Sumatra, Malay Peninsula, New Britain,
+New Zealand and Australia is easily explained. Then extension across
+Antarctica to Patagonia and Chile, whence it could spread into the rest
+of South America as this became consolidated in early Tertiary times.
+For getting to the Antilles and into Mexico it would have to wait until
+the Miocene, but long before that time it could arrive in Africa, there
+surviving as a Congolese and a Cape species. This story is unsupported
+by a single fossil. Peripatus may have been "sub-universal" all over
+greater Gondwana land in Carboniferous times, and then its absence from
+Madagascar would be difficult to explain, but the migrations suggested
+above amount to little considering that the distance from Tasmania to
+South America could be covered in far less time than that represented by
+the whole of the Eocene epoch alone.
+
+There is yet another field, essentially the domain of geographical
+distribution, the cultivation of which promises fair to throw much light
+upon Nature's way of making species. This is the study of the organisms
+with regard to their environment. Instead of revealing pedigrees or
+of showing how and when the creatures got to a certain locality, it
+investigates how they behaved to meet the ever changing conditions of
+their habitats. There is a facies, characteristic of, and often peculiar
+to, the fauna of tropical moist forests, another of deserts, of high
+mountains, of underground life and so forth; these same facies are
+stamped upon whole associations of animals and plants, although these
+may be--and in widely separated countries generally are--drawn from
+totally different families of their respective orders. It does not go to
+the root of the matter to say that these facies have been brought about
+by the extermination of all the others which did not happen to fit into
+their particular environment. One might almost say that tropical moist
+forests must have arboreal frogs and that these are made out of whatever
+suitable material happened to be available; in Australia and South
+America Hylidae, in Africa Ranidae, since there Hylas are absent. The
+deserts must have lizards capable of standing the glare, the great
+changes of temperature, of running over or burrowing into the loose
+sand. When as in America Iguanids are available, some of these are thus
+modified, while in Africa and Asia the Agamids are drawn upon. Both in
+the Damara and in the Transcaspian deserts, a Gecko has been turned into
+a runner upon sand!
+
+We cannot assume that at various epochs deserts, and at others moist
+forests were continuous all over the world. The different facies and
+associations were developed at various times and places. Are we to
+suppose that, wherever tropical forests came into existence, amongst
+the stock of humivagous lizards were always some which presented those
+nascent variations which made them keep step with the similarly nascent
+forests, the overwhelming rest being eliminated? This principle would
+imply that the same stratum of lizards always had variations ready to
+fit any changed environment, forests and deserts, rocks and swamps.
+The study of Ecology indicates a different procedure, a great, almost
+boundless plasticity of the organism, not in the sense of an exuberant
+moulding force, but of a readiness to be moulded, and of this the
+"variations" are the visible outcome. In most cases identical facies
+are produced by heterogeneous convergences and these may seem to be but
+superficial, affecting only what some authors are pleased to call the
+physiological characters; but environment presumably affects first those
+parts by which the organism comes into contact with it most directly,
+and if the internal structures remain unchanged, it is not because these
+are less easily modified but because they are not directly affected.
+When they are affected, they too change deeply enough.
+
+That the plasticity should react so quickly--indeed this very quickness
+seems to have initiated our mistaking the variations called forth for
+something performed--and to the point, is itself the outcome of the long
+training which protoplasm has undergone since its creation.
+
+In Nature's workshop he does not succeed who has ready an arsenal of
+tools for every conceivable emergency, but he who can make a tool at the
+spur of the moment. The ordeal of the practical test is Charles Darwin's
+glorious conception of Natural Selection.
+
+
+
+
+XVIII. DARWIN AND GEOLOGY. By J.W. Judd, C.B., LL.D., F.R.S.
+
+
+(Mr Francis Darwin has related how his father occasionally came up from
+Down to spend a few days with his brother Erasmus in London, and,
+after his brother's death, with his daughter, Mrs Litchfield. On these
+occasions, it was his habit to arrange meetings with Huxley, to talk
+over zoological questions, with Hooker, to discuss botanical problems,
+and with Lyell to hold conversations on geology. After the death of
+Lyell, Darwin, knowing my close intimacy with his friend during his
+later years, used to ask me to meet him when he came to town, and "talk
+geology." The "talks" took place sometimes at Jermyn Street Museum, at
+other times in the Royal College of Science, South Kensington; but
+more frequently, after having lunch with him, at his brother's or his
+daughter's house. On several occasions, however, I had the pleasure of
+visiting him at Down. In the postscript of a letter (of April 15, 1880)
+arranging one of these visits, he writes: "Since poor, dear Lyell's
+death, I rarely have the pleasure of geological talk with anyone.")
+
+In one of the very interesting conversations which I had with Charles
+Darwin during the last seven years of his life, he asked me in a very
+pointed manner if I were able to recall the circumstances, accidental or
+otherwise, which had led me to devote myself to geological studies. He
+informed me that he was making similar inquiries of other friends, and I
+gathered from what he said that he contemplated at that time a study
+of the causes producing SCIENTIFIC BIAS in individual minds. I have
+no means of knowing how far this project ever assumed anything like
+concrete form, but certain it is that Darwin himself often indulged
+in the processes of mental introspection and analysis; and he has
+thus fortunately left us--in his fragments of autobiography and in his
+correspondence--the materials from which may be reconstructed a fairly
+complete history of his own mental development.
+
+There are two perfectly distinct inquiries which we have to undertake
+in connection with the development of Darwin's ideas on the subject of
+evolution:
+
+FIRST. How, when, and under what conditions was Darwin led to a
+conviction that species were not immutable, but were derived from
+pre-existing forms?
+
+SECONDLY. By what lines of reasoning and research was he brought to
+regard "natural selection" as a vera causa in the process of evolution?
+
+It is the first of these inquiries which specially interests the
+geologist; though geology undoubtedly played a part--and by no means an
+insignificant part--in respect to the second inquiry.
+
+When, indeed, the history comes to be written of that great revolution
+of thought in the nineteenth century, by which the doctrine of
+evolution, from being the dream of poets and visionaries, gradually grew
+to be the accepted creed of naturalists, the paramount influence exerted
+by the infant science of geology--and especially that resulting from
+the publication of Lyell's epoch-making work, the "Principles of
+Geology"--cannot fail to be regarded as one of the leading factors.
+Herbert Spencer in his "Autobiography" bears testimony to the effect
+produced on his mind by the recently published "Principles", when, at
+the age of twenty, he had already begun to speculate on the subject
+of evolution (Herbert Spencer's "Autobiography", London, 1904, Vol. I.
+pages 175-177.); and Alfred Russel Wallace is scarcely less emphatic
+concerning the part played by Lyell's teaching in his scientific
+education. (See "My Life; a record of Events and Opinions", London,
+1905, Vol. I. page 355, etc. Also his review of Lyell's "Principles"
+in "Quarterly Review" (Vol. 126), 1869, pages 359-394. See also "The
+Darwin-Wallace Celebration by the Linnean Society" (1909), page 118.)
+Huxley wrote in 1887 "I owe more than I can tell to the careful study
+of the "Principles of Geology" in my young days." ("Science and Pseudo
+Science"; "Collected Essays", London, 1902, Vol. V. page 101.) As for
+Charles Darwin, he never tired--either in his published writings, his
+private correspondence or his most intimate conversations--of ascribing
+the awakening of his enthusiasm and the direction of his energies
+towards the elucidation of the problem of development to the "Principles
+of Geology" and the personal influence of its author. Huxley has well
+expressed what the author of the "Origin of Species" so constantly
+insisted upon, in the statements "Darwin's greatest work is the outcome
+of the unflinching application to Biology of the leading idea and the
+method applied in the "Principles" to Geology ("Proc. Roy. Soc." Vol.
+XLIV. (1888), page viii.; "Collected Essays" II. page 268, 1902.), and
+"Lyell, for others, as for myself, was the chief agent in smoothing the
+road for Darwin." ("Life and Letters of Charles Darwin" II. page 190.)
+
+We propose therefore to consider, first, what Darwin owed to geology and
+its cultivators, and in the second place how he was able in the end so
+fully to pay a great debt which he never failed to acknowledge. Thanks
+to the invaluable materials contained in the "Life and Letters of
+Charles Darwin" (3 vols.) published by Mr Francis Darwin in 1887; and to
+"More Letters of Charles Darwin" (2 vols.) issued by the same author,
+in conjunction with Professor A.C. Seward, in 1903, we are permitted to
+follow the various movements in Darwin's mind, and are able to record
+the story almost entirely in his own words. (The first of these works
+is indicated in the following pages by the letters "L.L."; the second by
+"M.L.")
+
+From the point of view of the geologist, Darwin's life naturally divides
+itself into four periods. In the first, covering twenty-two years,
+various influences were at work militating, now for and now against,
+his adoption of a geological career; in the second period--the five
+memorable years of the voyage of the "Beagle"--the ardent sportsman with
+some natural-history tastes, gradually became the most enthusiastic and
+enlightened of geologists; in the third period, lasting ten years, the
+valuable geological recruit devoted nearly all his energies and time
+to geological study and discussion and to preparing for publication the
+numerous observations made by him during the voyage; the fourth period,
+which covers the latter half of his life, found Darwin gradually drawn
+more and more from geological to biological studies, though always
+retaining the deepest interest in the progress and fortunes of his "old
+love." But geologists gladly recognise the fact that Darwin immeasurably
+better served their science by this biological work, than he could
+possibly have done by confining himself to purely geological questions.
+
+From his earliest childhood, Darwin was a collector, though up to the
+time when, at eight years of age, he went to a preparatory school,
+seals, franks and similar trifles appear to have been the only objects
+of his quest. But a stone, which one of his schoolfellows at that time
+gave to him, seems to have attracted his attention and set him seeking
+for pebbles and minerals; as the result of this newly acquired taste, he
+says (writing in 1838) "I distinctly recollect the desire I had of being
+able to know something about every pebble in front of the hall door--it
+was my earliest and only geological aspiration at that time." ("M.L."
+I. page 3.) He further suspects that while at Mr Case's school "I do
+not remember any mental pursuits except those of collecting stones,"
+etc... "I was born a naturalist." ("M.L." I. page 4.)
+
+The court-yard in front of the hall door at the Mount House, Darwin's
+birthplace and the home of his childhood, is surrounded by beds or
+rockeries on which lie a number of pebbles. Some of these pebbles (in
+quite recent times as I am informed) have been collected to form a
+"cobbled" space in front of the gate in the outer wall, which fronts the
+hall door; and a similar "cobbled area," there is reason to believe, may
+have existed in Darwin's childhood before the door itself. The pebbles,
+which were obtained from a neighbouring gravel-pit, being derived from
+the glacial drift, exhibit very striking differences in colour and form.
+It was probably this circumstance which awakened in the child his
+love of observation and speculation. It is certainly remarkable that
+"aspirations" of the kind should have arisen in the mind of a child of 9
+or 10!
+
+When he went to Shrewsbury School, he relates "I continued collecting
+minerals with much zeal, but quite unscientifically,--all that I cared
+about was a new-NAMED mineral, and I hardly attempted to classify them."
+("L.L." I. page 34.)
+
+There has stood from very early times in Darwin's native town of
+Shrewsbury, a very notable boulder which has probably marked a boundary
+and is known as the "Bell-stone"--giving its name to a house and street.
+Darwin tells us in his "Autobiography" that while he was at Shrewsbury
+School at the age of 13 or 14 "an old Mr Cotton in Shropshire, who knew
+a good deal about rocks" pointed out to me "... the 'bell-stone'; he told
+me that there was no rock of the same kind nearer than Cumberland or
+Scotland, and he solemnly assured me that the world would come to an end
+before anyone would be able to explain how this stone came where it
+now lay"! Darwin adds "This produced a deep impression on me, and I
+meditated over this wonderful stone." ("L.L." I. page 41.)
+
+The "bell-stone" has now, owing to the necessities of building, been
+removed a short distance from its original site, and is carefully
+preserved within the walls of a bank. It is a block of irregular shape 3
+feet long and 2 feet wide, and about 1 foot thick, weighing probably not
+less than one-third of a ton. By the courtesy of the directors of the
+National Provincial Bank of England, I have been able to make a minute
+examination of it, and Professors Bonney and Watts, with Mr Harker and
+Mr Fearnsides have given me their valuable assistance. The rock is a
+much altered andesite and was probably derived from the Arenig district
+in North Wales, or possibly from a point nearer the Welsh Border. (I
+am greatly indebted to the Managers of the Bank at Shrewsbury for kind
+assistance in the examination of this interesting memorial: and Mr
+H.T. Beddoes, the Curator of the Shrewsbury Museum, has given me some
+archaeological information concerning the stone. Mr Richard Cotton was
+a good local naturalist, a Fellow both of the Geological and Linnean
+Societies; and to the officers of these societies I am indebted for
+information concerning him. He died in 1839, and although he does not
+appear to have published any scientific papers, he did far more for
+science by influencing the career of the school boy!) It was of course
+brought to where Shrewsbury now stands by the agency of a glacier--as
+Darwin afterwards learnt.
+
+We can well believe from the perusal of these reminiscences that,
+at this time, Darwin's mind was, as he himself says, "prepared for a
+philosophical treatment of the subject" of Geology. ("L.L." I. page 41.)
+When at the age of 16, however, he was entered as a medical student at
+Edinburgh University, he not only did not get any encouragement of
+his scientific tastes, but was positively repelled by the ordinary
+instruction given there. Dr Hope's lectures on Chemistry, it is true,
+interested the boy, who with his brother Erasmus had made a laboratory
+in the toolhouse, and was nicknamed "Gas" by his schoolfellows, while
+undergoing solemn and public reprimand from Dr Butler at Shrewsbury
+School for thus wasting his time. ("L.L." I. page 35.) But most of
+the other Edinburgh lectures were "intolerably dull," "as dull as the
+professors" themselves, "something fearful to remember." In after life
+the memory of these lectures was like a nightmare to him. He speaks in
+1840 of Jameson's lectures as something "I... for my sins experienced!"
+("L.L." I. page 340.) Darwin especially signalises these lectures on
+Geology and Zoology, which he attended in his second year, as being
+worst of all "incredibly dull. The sole effect they produced on me was
+the determination never so long as I lived to read a book on Geology, or
+in any way to study the science!" ("L.L." I. page 41.)
+
+The misfortune was that Edinburgh at that time had become the cockpit in
+which the barren conflict between "Neptunism" and "Plutonism" was being
+waged with blind fury and theological bitterness. Jameson and his
+pupils, on the one hand, and the friends and disciples of Hutton, on the
+other, went to the wildest extremes in opposing each other's peculiar
+tenets. Darwin tells us that he actually heard Jameson "in a field
+lecture at Salisbury Craigs, discoursing on a trap-dyke, with
+amygdaloidal margins and the strata indurated on each side, with
+volcanic rocks all around us, say that it was a fissure filled with
+sediment from above, adding with a sneer that there were men who
+maintained that it had been injected from beneath in a molten
+condition." ("L.L." I. pages 41-42.) "When I think of this lecture,"
+added Darwin, "I do not wonder that I determined never to attend to
+Geology." (This was written in 1876 and Darwin had in the summer of 1839
+revisited and carefully studied the locality ("L.L." I. page 290.) It is
+probable that most of Jameson's teaching was of the same controversial
+and unilluminating character as this field-lecture at Salisbury Craigs.
+
+There can be no doubt that, while at Edinburgh, Darwin must have become
+acquainted with the doctrines of the Huttonian School. Though so young,
+he mixed freely with the scientific society of the city, Macgillivray,
+Grant, Leonard Horner, Coldstream, Ainsworth and others being among
+his acquaintances, while he attended and even read papers at the local
+scientific societies. It is to be feared, however, that what Darwin
+would hear most of, as characteristic of the Huttonian teaching, would
+be assertions that chalk-flints were intrusions of molten silica, that
+fossil wood and other petrifactions had been impregnated with fused
+materials, that heat--but never water--was always the agent by which
+the induration and crystallisation of rock-materials (even siliceous
+conglomerate, limestone and rock-salt) had been effected! These
+extravagant "anti-Wernerian" views the young student might well regard
+as not one whit less absurd and repellant than the doctrine of the
+"aqueous precipitation" of basalt. There is no evidence that Darwin,
+even if he ever heard of them, was in any way impressed, in his early
+career, by the suggestive passages in Hutton and Playfair, to which
+Lyell afterwards called attention, and which foreshadowed the main
+principles of Uniformitarianism.
+
+As a matter of fact, I believe that the influence of Hutton and Playfair
+in the development of a philosophical theory of geology has been very
+greatly exaggerated by later writers on the subject. Just as Wells
+and Matthew anticipated the views of Darwin on Natural Selection,
+but without producing any real influence on the course of biological
+thought, so Hutton and Playfair adumbrated doctrines which only became
+the basis of vivifying theory in the hands of Lyell. Alfred Russel
+Wallace has very justly remarked that when Lyell wrote the "Principles
+of Geology", "the doctrines of Hutton and Playfair, so much in advance
+of their age, seemed to be utterly forgotten." ("Quarterly Review", Vol.
+CXXVI. (1869), page 363.) In proof of this it is only necessary to
+point to the works of the great masters of English geology, who preceded
+Lyell, in which the works of Hutton and his followers are scarcely ever
+mentioned. This is true even of the "Researches in Theoretical Geology"
+and the other works of the sagacious De la Beche. (Of the strength
+and persistence of the prejudice felt against Lyell's views by his
+contemporaries, I had a striking illustration some little time after
+Lyell's death. One of the old geologists who in the early years of the
+century had done really good work in connection with the Geological
+Society expressed a hope that I was not "one of those who had been
+carried away by poor Lyell's fads." My surprise was indeed great when
+further conversation showed me that the whole of the "Principles" were
+included in the "fads"!) Darwin himself possessed a copy of Playfair's
+"Illustrations of the Huttonian Theory", and occasionally quotes it;
+but I have met with only one reference to Hutton, and that a somewhat
+enigmatical one, in all Darwin's writings. In a letter to Lyell in 1841,
+when his mind was much exercised concerning glacial questions, he says
+"What a grand new feature all this ice work is in Geology! How old
+Hutton would have stared!" ("M.L." II. page 149.)
+
+As a consequence of the influences brought to bear on his mind during
+his two years' residence in Edinburgh, Darwin, who had entered that
+University with strong geological aspirations, left it and proceeded to
+Cambridge with a pronounced distaste for the whole subject. The result
+of this was that, during his career as an under-graduate, he neglected
+all the opportunities for geological study. During that important period
+of life, when he was between eighteen and twenty years of age, Darwin
+spent his time in riding, shooting and beetle-hunting, pursuits which
+were undoubtedly an admirable preparation for his future work as an
+explorer; but in none of his letters of this period does he even mention
+geology. He says, however, "I was so sickened with lectures at
+Edinburgh that I did not even attend Sedgwick's eloquent and interesting
+lectures." ("L.L." I. page 48.)
+
+It was only after passing his examination, and when he went up to spend
+two extra terms at Cambridge, that geology again began to attract his
+attention. The reading of Sir John Herschel's "Introduction to the Study
+of Natural Philosophy", and of Humboldt's "Personal Narrative", a
+copy of which last had been given to him by his good friend and mentor
+Henslow, roused his dormant enthusiasm for science, and awakened in his
+mind a passionate desire for travel. And it was from Henslow, whom
+he had accompanied in his excursions, but without imbibing any marked
+taste, at that time, for botany, that the advice came to think of and to
+"begin the study of geology." ("L.L." I. page 56.) This was in 1831, and
+in the summer vacation of that year we find him back again at Shrewsbury
+"working like a tiger" at geology and endeavouring to make a map
+and section of Shropshire--work which he says was not "as easy as I
+expected." ("L.L." I. page 189.) No better field for geological studies
+could possibly be found than Darwin's native county.
+
+Writing to Henslow at this time, and referring to a form of the
+instrument devised by his friend, Darwin says: "I am very glad to say I
+think the clinometer will answer admirably. I put all the tables in my
+bedroom at every conceivable angle and direction. I will venture to say
+that I have measured them as accurately as any geologist going could
+do." But he adds: "I have been working at so many things that I have
+not got on much with geology. I suspect the first expedition I take,
+clinometer and hammer in hand, will send me back very little wiser and
+a good deal more puzzled than when I started." ("L.L." I. page 189.)
+Valuable aid was, however, at hand, for at this time Sedgwick, to whom
+Darwin had been introduced by the ever-helpful Henslow, was making one
+of his expeditions into Wales, and consented to accept the young student
+as his companion during the geological tour. ("L.L." I. page 56.) We
+find Darwin looking forward to this privilege with the keenest interest.
+("L.L." I. page 189.)
+
+When at the beginning of August (1831), Sedgwick arrived at his father's
+house in Shrewsbury, where he spent a night, Darwin began to receive his
+first and only instruction as a field-geologist. The journey they took
+together led them through Llangollen, Conway, Bangor, and Capel Curig,
+at which latter place they parted after spending many hours in examining
+the rocks at Cwm Idwal with extreme care, seeking for fossils but
+without success. Sedgwick's mode of instruction was admirable--he from
+time to time sent the pupil off on a line parallel to his own, "telling
+me to bring back specimens of the rocks and to mark the stratification
+on a map." ("L.L." I. page 57.) On his return to Shrewsbury, Darwin
+wrote to Henslow, "My trip with Sedgwick answered most perfectly,"
+("L.L." I. page 195.), and in the following year he wrote again from
+South America to the same friend, "Tell Professor Sedgwick he does not
+know how much I am indebted to him for the Welsh expedition; it has
+given me an interest in Geology which I would not give up for any
+consideration. I do not think I ever spent a more delightful three weeks
+than pounding the north-west mountains." ("L.L." I. pages 237-8.)
+
+It would be a mistake, however, to suppose that at this time Darwin
+had acquired anything like the affection for geological study, which
+he afterwards developed. After parting with Sedgwick, he walked in a
+straight line by compass and map across the mountains to Barmouth to
+visit a reading party there, but taking care to return to Shropshire
+before September 1st, in order to be ready for the shooting. For as
+he candidly tells us, "I should have thought myself mad to give up the
+first days of partridge-shooting for geology or any other science!"
+("L.L." I. page 58.)
+
+Any regret we may be disposed to feel that Darwin did not use his
+opportunities at Edinburgh and Cambridge to obtain systematic and
+practical instruction in mineralogy and geology, will be mitigated,
+however, when we reflect on the danger which he would run of being
+indoctrinated with the crude "catastrophic" views of geology, which were
+at that time prevalent in all the centres of learning.
+
+Writing to Henslow in the summer of 1831, Darwin says "As yet I have
+only indulged in hypotheses, but they are such powerful ones that I
+suppose, if they were put into action but for one day, the world would
+come to an end." ("L.L." I. page 189.)
+
+May we not read in this passage an indication that the self-taught
+geologist had, even at this early stage, begun to feel a distrust for
+the prevalent catastrophism, and that his mind was becoming a field in
+which the seeds which Lyell was afterwards to sow would "fall on good
+ground"?
+
+The second period of Darwin's geological career--the five years spent
+by him on board the "Beagle"--was the one in which by far the most
+important stage in his mental development was accomplished. He left
+England a healthy, vigorous and enthusiastic collector; he returned five
+years later with unique experiences, the germs of great ideas, and
+a knowledge which placed him at once in the foremost ranks of the
+geologists of that day. Huxley has well said that "Darwin found on board
+the "Beagle" that which neither the pedagogues of Shrewsbury, nor the
+professoriate of Edinburgh, nor the tutors of Cambridge had managed
+to give him." ("Proc. Roy. Soc." Vol. XLIV. (1888), page IX.) Darwin
+himself wrote, referring to the date at which the voyage was expected to
+begin: "My second life will then commence, and it shall be as a birthday
+for the rest of my life." ("L.L." I. page 214.); and looking back on the
+voyage after forty years, he wrote; "The voyage of the 'Beagle' has been
+by far the most important event in my life, and has determined my whole
+career;... I have always felt that I owe to the voyage the first real
+training or education of my mind; I was led to attend closely to several
+branches of natural history, and thus my powers of observation were
+improved, though they were always fairly developed." ("L.L." I. page
+61.)
+
+Referring to these general studies in natural history, however, Darwin
+adds a very significant remark: "The investigation of the geology of
+the places visited was far more important, as reasoning here comes into
+play. On first examining a new district nothing can appear more hopeless
+than the chaos of rocks; but by recording the stratification and nature
+of the rocks and fossils at many points, always reasoning and predicting
+what will be found elsewhere, light soon begins to dawn on the district,
+and the structure of the whole becomes more or less intelligible."
+("L.L." I. page 62.)
+
+The famous voyage began amid doubts, discouragements and
+disappointments. Fearful of heart-disease, sad at parting from home
+and friends, depressed by sea-sickness, the young explorer, after being
+twice driven back by baffling winds, reached the great object of
+his ambition, the island of Teneriffe, only to find that, owing to
+quarantine regulations, landing was out of the question.
+
+But soon this inauspicious opening of the voyage was forgotten. Henslow
+had advised his pupil to take with him the first volume of Lyell's
+"Principles of Geology", then just published--but cautioned him (as
+nearly all the leaders in geological science at that day would certainly
+have done) "on no account to accept the views therein advocated."
+("L.L." I. page 73.) It is probable that the days of waiting, discomfort
+and sea-sickness at the beginning of the voyage were relieved by the
+reading of this volume. For he says that when he landed, three weeks
+after setting sail from Plymouth, in St Jago, the largest of the Cape de
+Verde Islands, the volume had already been "studied attentively; and
+the book was of the highest service to me in many ways... " His first
+original geological work, he declares, "showed me clearly the wonderful
+superiority of Lyell's manner of treating geology, compared with that
+of any other author, whose works I had with me or ever afterwards read."
+("L.L." I. page 62.)
+
+At St Jago Darwin first experienced the joy of making new discoveries,
+and his delight was unbounded. Writing to his father he says,
+"Geologising in a volcanic country is most delightful; besides the
+interest attached to itself, it leads you into most beautiful and
+retired spots." ("L.L." I. page 228.) To Henslow he wrote of St Jago:
+"Here we spent three most delightful weeks... St Jago is singularly
+barren, and produces few plants or insects, so that my hammer was my
+usual companion, and in its company most delightful hours I spent." "The
+geology was pre-eminently interesting, and I believe quite new; there
+are some facts on a large scale of upraised coast (which is an excellent
+epoch for all the volcanic rocks to date from), that would interest Mr
+Lyell." ("L.L." I. page 235.) After more than forty years the memory of
+this, his first geological work, seems as fresh as ever, and he wrote in
+1876, "The geology of St Jago is very striking, yet simple: a stream
+of lava formerly flowed over the bed of the sea, formed of triturated
+recent shells and corals, which it has baked into a hard white rock.
+Since then the whole island has been upheaved. But the line of white
+rock revealed to me a new and important fact, namely, that there had
+been afterwards subsidence round the craters, which had since been in
+action, and had poured forth lava." ("L.L." I. page 65.)
+
+It was at this time, probably, that Darwin made his first attempt at
+drawing a sketch-map and section to illustrate the observations he had
+made (see his "Volcanic Islands", pages 1 and 9). His first important
+geological discovery, that of the subsidence of strata around volcanic
+vents (which has since been confirmed by Mr Heaphy in New Zealand and
+other authors) awakened an intense enthusiasm, and he writes: "It then
+first dawned on me that I might perhaps write a book on the geology of
+the various countries visited, and this made me thrill with delight.
+That was a memorable hour to me, and how distinctly I can call to mind
+the low cliff of lava beneath which I rested, with the sun glaring hot,
+a few strange desert plants growing near, and with living corals in the
+tidal pools at my feet." ("L.L." I. page 66.)
+
+But it was when the "Beagle", after touching at St Paul's rock and
+Tristan d'Acunha (for a sufficient time only to collect specimens),
+reached the shores of South America, that Darwin's real work began; and
+he was able, while the marine surveys were in progress, to make many
+extensive journeys on land. His letters at this time show that geology
+had become his chief delight, and such exclamations as "Geology carries
+the day," "I find in Geology a never failing interest," etc. abound in
+his correspondence.
+
+Darwin's time was divided between the study of the great deposits of red
+mud--the Pampean formation--with its interesting fossil bones and shells
+affording proofs of slow and constant movements of the land, and the
+underlying masses of metamorphic and plutonic rocks. Writing to Henslow
+in March, 1834, he says: "I am quite charmed with Geology, but, like
+the wise animal between two bundles of hay, I do not know which to
+like best; the old crystalline groups of rocks, or the softer and
+fossiliferous beds. When puzzling about stratification, etc., I
+feel inclined to cry 'a fig for your big oysters, and your bigger
+megatheriums.' But then when digging out some fine bones, I wonder how
+any man can tire his arms with hammering granite." ("L.L." I. page
+249.) We are told by Darwin that he loved to reason about and attempt to
+predict the nature of the rocks in each new district before he arrived
+at it.
+
+This love of guessing as to the geology of a district he was about to
+visit is amusingly expressed by him in a letter (of May, 1832) to his
+cousin and old college-friend, Fox. After alluding to the beetles he
+had been collecting--a taste his friend had in common with himself--he
+writes of geology that "It is like the pleasure of gambling. Speculating
+on first arriving, what the rocks may be, I often mentally cry out 3 to
+1 tertiary against primitive; but the latter have hitherto won all the
+bets." ("L.L." I. page 233.)
+
+Not the least important of the educational results of the voyage to
+Darwin was the acquirement by him of those habits of industry and method
+which enabled him in after life to accomplish so much--in spite of
+constant failures of health. From the outset, he daily undertook
+and resolutely accomplished, in spite of sea-sickness and other
+distractions, four important tasks. In the first place he regularly
+wrote up the pages of his Journal, in which, paying great attention to
+literary style and composition, he recorded only matters that would be
+of general interest, such as remarks on scenery and vegetation, on the
+peculiarities and habits of animals, and on the characters, avocations
+and political institutions of the various races of men with whom he was
+brought in contact. It was the freshness of these observations that gave
+his "Narrative" so much charm. Only in those cases in which his ideas
+had become fully crystallised, did he attempt to deal with scientific
+matters in this journal. His second task was to write in voluminous
+note-books facts concerning animals and plants, collected on sea or
+land, which could not be well made out from specimens preserved in
+spirit; but he tells us that, owing to want of skill in dissecting and
+drawing, much of the time spent in this work was entirely thrown away,
+"a great pile of MS. which I made during the voyage has proved almost
+useless." ("L.L." I. page 62.) Huxley confirmed this judgment on his
+biological work, declaring that "all his zeal and industry resulted, for
+the most part, in a vast accumulation of useless manuscript." ("Proc.
+Roy. Soc." Vol. XLIV. (1888), page IX.) Darwin's third task was of a
+very different character and of infinitely greater value. It consisted
+in writing notes of his journeys on land--the notes being devoted to
+the geology of the districts visited by him. These formed the basis, not
+only of a number of geological papers published on his return, but also
+of the three important volumes forming "The Geology of the voyage of the
+'Beagle'". On July 24th, 1834, when little more than half of the voyage
+had been completed, Darwin wrote to Henslow, "My notes are becoming
+bulky. I have about 600 small quarto pages full; about half of this is
+Geology." ("M.L." I. page 14.) The last, and certainly not the least
+important of all his duties, consisted in numbering, cataloguing, and
+packing his specimens for despatch to Henslow, who had undertaken the
+care of them. In his letters he often expresses the greatest solicitude
+lest the value of these specimens should be impaired by the removal of
+the numbers corresponding to his manuscript lists. Science owes much
+to Henslow's patient care of the collections sent to him by Darwin. The
+latter wrote in Henslow's biography, "During the five years' voyage,
+he regularly corresponded with me and guided my efforts; he received,
+opened, and took care of all the specimens sent home in many large
+boxes." ("Life of Henslow", by L. Jenyns (Blomefield), London, 1862,
+page 53.)
+
+Darwin's geological specimens are now very appropriately lodged for the
+most part in the Sedgwick Museum, Cambridge, his original Catalogue with
+subsequent annotations being preserved with them. From an examination of
+these catalogues and specimens we are able to form a fair notion of
+the work done by Darwin in his little cabin in the "Beagle", in the
+intervals between his land journeys.
+
+Besides writing up his notes, it is evident that he was able to
+accomplish a considerable amount of study of his specimens, before they
+were packed up for despatch to Henslow. Besides hand-magnifiers and
+a microscope, Darwin had an equipment for blowpipe-analysis, a
+contact-goniometer and magnet; and these were in constant use by him.
+His small library of reference (now included in the Collection of books
+placed by Mr F. Darwin in the Botany School at Cambridge ("Catalogue
+of the Library of Charles Darwin now in the Botany School, Cambridge".
+Compiled by H.W. Rutherford; with an introduction by Francis Darwin.
+Cambridge, 1908.)) appears to have been admirably selected, and in all
+probability contained (in addition to a good many works relating to
+South America) a fair number of excellent books of reference. Among
+those relating to mineralogy, he possessed the manuals of Phillips,
+Alexander Brongniart, Beudant, von Kobell and Jameson: all the
+"Cristallographie" of Brochant de Villers and, for blowpipe work, Dr
+Children's translation of the book of Berzelius on the subject. In
+addition to these, he had Henry's "Experimental Chemistry" and Ure's
+"Dictionary" (of Chemistry). A work, he evidently often employed, was P.
+Syme's book on "Werner's Nomenclature of Colours"; while, for Petrology,
+he used Macculloch's "Geological Classification of Rocks". How
+diligently and well he employed his instruments and books is shown by
+the valuable observations recorded in the annotated Catalogues drawn up
+on board ship.
+
+These catalogues have on the right-hand pages numbers and descriptions
+of the specimens, and on the opposite pages notes on the specimens--the
+result of experiments made at the time and written in a very small hand.
+Of the subsequently made pencil notes, I shall have to speak later.
+(I am greatly indebted to my friend Mr A. Harker, F.R.S., for his
+assistance in examining these specimens and catalogues. He has also
+arranged the specimens in the Sedgwick Museum, so as to make reference
+to them easy. The specimens from Ascension and a few others are however
+in the Museum at Jermyn Street.)
+
+It is a question of great interest to determine the period and the
+occasion of Darwin's first awakening to the great problem of the
+transmutation of species. He tells us himself that his grandfather's
+"Zoonomia" had been read by him "but without producing any effect," and
+that his friend Grant's rhapsodies on Lamarck and his views on evolution
+only gave rise to "astonishment." ("L.L." I. page 38.)
+
+Huxley, who had probably never seen the privately printed volume of
+letters to Henslow, expressed the opinion that Darwin could not have
+perceived the important bearing of his discovery of bones in the Pampean
+Formation, until they had been studied in England, and their analogies
+pronounced upon by competent comparative anatomists. And this seemed to
+be confirmed by Darwin's own entry in his pocket-book for 1837, "In
+July opened first notebook on Transmutation of Species. Had been greatly
+struck from about the month of previous March on character of South
+American fossils... " ("L.L." I. page 276.)
+
+The second volume of Lyell's "Principles of Geology" was published in
+January, 1832, and Darwin's copy (like that of the other two volumes,
+in a sadly dilapidated condition from constant use) has in it the
+inscription, "Charles Darwin, Monte Video. Nov. 1832." As everyone
+knows, Darwin in dedicating the second edition of his Journal of the
+Voyage to Lyell declared, "the chief part of whatever scientific merit
+this journal and the other works of the author may possess, has been
+derived from studying the well-known and admirable 'Principles of
+Geology'".
+
+In the first chapter of this second volume of the "Principles", Lyell
+insists on the importance of the species question to the geologist,
+but goes on to point out the difficulty of accepting the only
+serious attempt at a transmutation theory which had up to that time
+appeared--that of Lamarck. In subsequent chapters he discusses the
+questions of the modification and variability of species, of hybridity,
+and of the geographical distribution of plants and animals. He then
+gives vivid pictures of the struggle for existence, ever going
+on between various species, and of the causes which lead to their
+extinction--not by overwhelming catastrophes, but by the silent and
+almost unobserved action of natural causes. This leads him to consider
+theories with regard to the introduction of new species, and, rejecting
+the fanciful notions of "centres or foci of creation," he argues
+strongly in favour of the view, as most reconcileable with observed
+facts, that "each species may have had its origin in a single pair, or
+individual, where an individual was sufficient, and species may have
+been created in succession at such times and in such places as to enable
+them to multiply and endure for an appointed period, and occupy an
+appointed space on the globe." ("Principles of Geology", Vol. II. (1st
+edition 1832), page 124. We now know, as has been so well pointed out
+by Huxley, that Lyell, as early as 1827, was prepared to accept the
+doctrine of the transmutation of species. In that year he wrote to
+Mantell, "What changes species may really undergo! How impossible will
+it be to distinguish and lay down a line, beyond which some of the
+so-called extinct species may have never passed into recent ones"
+(Lyell's "Life and Letters" Vol. I. page 168). To Sir John Herschel in
+1836, he wrote, "In regard to the origination of new species, I am
+very glad to find that you think it probable that it may be carried on
+through the intervention of intermediate causes. I left this rather to
+be inferred, not thinking it worth while to offend a certain class of
+persons by embodying in words what would only be a speculation" (Ibid.
+page 467). He expressed the same views to Whewell in 1837 (Ibid. Vol.
+II. page 5.), and to Sedgwick (Ibid. Vol. II. page 36) to whom he says,
+of "the theory, that the creation of new species is going on at the
+present day"--"I really entertain it," but "I have studiously avoided
+laying the doctrine down dogmatically as capable of proof" (see Huxley
+in "L.L." II. pages 190-195.))
+
+After pointing out how impossible it would be for a naturalist to prove
+that a newly DISCOVERED species was really newly CREATED (Mr F. Darwin
+has pointed out that his father (like Lyell) often used the term
+"Creation" in speaking of the origin of new species ("L.L." II. chapter
+1.)), Lyell argued that no satisfactory evidence OF THE WAY in which
+these new forms were created, had as yet been discovered, but that he
+entertained the hope of a possible solution of the problem being found
+in the study of the geological record.
+
+It is not difficult, in reading these chapters of Lyell's great work,
+to realise what an effect they would have on the mind of Darwin, as
+new facts were collected and fresh observations concerning extinct and
+recent forms were made in his travels. We are not surprised to find him
+writing home, "I am become a zealous disciple of Mr Lyell's views, as
+known in his admirable book. Geologising in South America, I am tempted
+to carry parts to a greater extent even than he does." ("L.L." I. page
+263.)
+
+Lyell's anticipation that the study of the geological record might
+afford a clue to the discovery of how new species originate was
+remarkably fulfilled, within a few months, by Darwin's discovery of
+fossil bones in the red Pampean mud.
+
+It is very true that, as Huxley remarked, Darwin's knowledge of
+comparative anatomy must have been, at that time, slight; but that he
+recognised the remarkable resemblances between the extinct and existing
+mammals of South America is proved beyond all question by a passage in
+his letter to Henslow, written November 24th, 1832: "I have been very
+lucky with fossil bones; I have fragments of at least six
+distinct animals... I found a large surface of osseous polygonal
+plates... Immediately I saw them I thought they must belong to an
+enormous armadillo, living species of which genus are so abundant here,"
+and he goes on to say that he has "the lower jaw of some large animal
+which, from the molar teeth, I should think belonged to the Edentata."
+("M.L." I. pages 11, 12. See "Extracts of Letters addressed to Prof.
+Henslow by C. Darwin" (1835), page 7.)
+
+Having found this important clue, Darwin followed it up with
+characteristic perseverance. In his quest for more fossil bones he was
+indefatigable. Mr Francis Darwin tells us, "I have often heard him speak
+of the despair with which he had to break off the projecting extremity
+of a huge, partly excavated bone, when the boat waiting for him would
+wait no longer." ("L.L." I. page 276 (footnote).) Writing to Haeckel in
+1864, Darwin says: "I shall never forget my astonishment when I dug
+out a gigantic piece of armour, like that of the living armadillo."
+(Haeckel, "History of Creation", Vol. I. page 134, London, 1876.)
+
+In a letter to Henslow in 1834 Darwin says: "I have just got scent
+of some fossil bones... what they may be I do not know, but if gold or
+galloping will get them they shall be mine." ("M.L." I. page 15.)
+
+Darwin also showed his sense of the importance of the discovery of these
+bones by his solicitude about their safe arrival and custody. From the
+Falkland Isles (March, 1834), he writes to Henslow: "I have been alarmed
+by your expression 'cleaning all the bones' as I am afraid the printed
+numbers will be lost: the reason I am so anxious they should not be, is,
+that a part were found in a gravel with recent shells, but others in a
+very different bed. Now with these latter there were bones of an Agouti,
+a genus of animals, I believe, peculiar to America, and it would
+be curious to prove that some one of the genus co-existed with the
+Megatherium: such and many other points depend on the numbers being
+carefully preserved." ("Extracts from Letters etc.", pages 13-14.) In
+the abstract of the notes read to the Geological Society in 1835, we
+read: "In the gravel of Patagonia he (Darwin) also found many bones of
+the Megatherium and of five or six other species of quadrupeds, among
+which he has detected the bones of a species of Agouti. He also met with
+several examples of the polygonal plates, etc." ("Proc. Geol. Soc." Vol.
+II. pages 211-212.)
+
+Darwin's own recollections entirely bear out the conclusion that he
+fully recognised, WHILE IN SOUTH AMERICA, the wonderful significance
+of the resemblances between the extinct and recent mammalian faunas. He
+wrote in his "Autobiography": "During the voyage of the 'Beagle' I had
+been deeply impressed by discovering in the Pampean formation
+great fossil animals covered with armour like that on the existing
+armadillos." ("L.L." I. page 82.)
+
+The impression made on Darwin's mind by the discovery of these fossil
+bones, was doubtless deepened as, in his progress southward from Brazil
+to Patagonia, he found similar species of Edentate animals everywhere
+replacing one another among the living forms, while, whenever fossils
+occurred, they also were seen to belong to the same remarkable group of
+animals. (While Darwin was making these observations in South America,
+a similar generalisation to that at which he arrived was being reached,
+quite independently and almost simultaneously, with respect to the
+fossil and recent mammals of Australia. In the year 1831, Clift gave
+to Jameson a list of bones occurring in the caves and breccias of
+Australia, and in publishing this list the latter referred to the fact
+that the forms belonged to marsupials, similar to those of the
+existing Australian fauna. But he also stated that, as a skull had been
+identified (doubtless erroneously) as having belonged to a hippopotamus,
+other mammals than marsupials must have spread over the island in late
+Tertiary times. It is not necessary to point out that this paper was
+quite unknown to Darwin while in South America. Lyell first noticed it
+in the third edition of his "Principles", which was published in May,
+1834 (see "Edinb. New Phil. Journ." Vol. X. (1831), pages 394-6, and
+Lyell's "Principles" (3rd edition), Vol. III. page 421). Darwin referred
+to this discovery in 1839 (see his "Journal", page 210.))
+
+That the passage in Darwin's pocket-book for 1837 can only refer to an
+AWAKENING of Darwin's interest in the subject--probably resulting from
+a sight of the bones when they were being unpacked--I think there
+cannot be the smallest doubt; AND WE MAY THEREFORE CONFIDENTLY FIX UPON
+NOVEMBER, 1832, AS THE DATE AT WHICH DARWIN COMMENCED THAT LONG SERIES
+OF OBSERVATIONS AND REASONINGS WHICH EVENTUALLY CULMINATED IN THE
+PREPARATION OF THE "ORIGIN OF SPECIES". Equally certain is it, that it
+was his geological work that led Darwin into those paths of research
+which in the end conducted him to his great discoveries. I quite agree
+with the view expressed by Mr F. Darwin and Professor Seward, that
+Darwin, like Lyell, "thought it 'almost useless' to try to prove the
+truth of evolution until the cause of change was discovered" ("M.L."
+I. page 38.), and that possibly he may at times have vacillated in his
+opinions, but I believe there is evidence that, from the date mentioned,
+the "species question" was always more or less present in Darwin's mind.
+(Although we admit with Huxley that Darwin's training in comparative
+anatomy was very small, yet it may be remembered that he was a medical
+student for two years, and, if he hated the lectures, he enjoyed the
+society of naturalists. He had with him in the little "Beagle" library a
+fair number of zoological books, including works on Osteology by Cuvier,
+Desmarest and Lesson, as well as two French Encyclopaedias of Natural
+History. As a sportsman, he would obtain specimens of recent mammals in
+South America, and would thus have opportunities of studying their teeth
+and general anatomy. Keen observer, as he undoubtedly was, we need not
+then be surprised that he was able to make out the resemblances between
+the recent and fossil forms.)
+
+It is clear that, as time went on, Darwin became more and more absorbed
+in his geological work. One very significant fact was that the once
+ardent sportsman, when he found that shooting the necessary game and
+zoological specimens interfered with his work with the hammer, gave up
+his gun to his servant. ("L.L." I. page 63.) There is clear evidence
+that Darwin gradually became aware how futile were his attempts to add
+to zoological knowledge by dissection and drawing, while he felt ever
+increasing satisfaction with his geological work.
+
+The voyage fortunately extended to a much longer period (five years)
+than the two originally intended, but after being absent nearly three
+years, Darwin wrote to his sister in November, 1834, "Hurrah! hurrah!
+it is fixed that the 'Beagle' shall not go one mile south of Cape
+Tres Montes (about 200 miles south of Chiloe), and from that point to
+Valparaiso will be finished in about five months. We shall examine the
+Chonos Archipelago, entirely unknown, and the curious inland sea behind
+Chiloe. For me it is glorious. Cape Tres Montes is the most southern
+point where there is much geological interest, as there the modern beds
+end. The Captain then talks of crossing the Pacific; but I think we
+shall persuade him to finish the coast of Peru, where the climate
+is delightful, the country hideously sterile, but abounding with the
+highest interest to the geologist... I have long been grieved and most
+sorry at the interminable length of the voyage (though I never would
+have quitted it)... I could not make up my mind to return. I could not
+give up all the geological castles in the air I had been building up for
+the last two years." ("L.L." I. pages 257-58.)
+
+In April, 1835, he wrote to another sister: "I returned a week ago from
+my excursion across the Andes to Mendoza. Since leaving England I have
+never made so successful a journey... how deeply I have enjoyed it; it
+was something more than enjoyment; I cannot express the delight which I
+felt at such a famous winding-up of all my geology in South America. I
+literally could hardly sleep at nights for thinking over my day's work.
+The scenery was so new, and so majestic; everything at an elevation
+of 12,000 feet bears so different an aspect from that in the lower
+country... To a geologist, also, there are such manifest proofs of
+excessive violence; the strata of the highest pinnacles are tossed about
+like the crust of a broken pie." ("L.L." I. pages 259-60.)
+
+Darwin anticipated with intense pleasure his visit to the Galapagos
+Islands. On July 12th, 1835, he wrote to Henslow: "In a few days' time
+the "Beagle" will sail for the Galapagos Islands. I look forward with
+joy and interest to this, both as being somewhat nearer to England and
+for the sake of having a good look at an active volcano. Although
+we have seen lava in abundance, I have never yet beheld the crater."
+("M.L." I. page 26.) He could little anticipate, as he wrote these
+lines, the important aid in the solution of the "species question" that
+would ever after make his visit to the Galapagos Islands so memorable.
+In 1832, as we have seen, the great discovery of the relations of living
+to extinct mammals in the same area had dawned upon his mind; in 1835
+he was to find a second key for opening up the great mystery, by
+recognising the variations of similar types in adjoining islands among
+the Galapagos.
+
+The final chapter in the second volume of the "Principles" had aroused
+in Darwin's mind a desire to study coral-reefs, which was gratified
+during his voyage across the Pacific and Indian Oceans. His theory on
+the subject was suggested about the end of 1834 or the beginning of
+1835, as he himself tells us, before he had seen a coral-reef,
+and resulted from his work during two years in which he had "been
+incessantly attending to the effects on the shores of South America of
+the intermittent elevation of the land, together with denudation and the
+deposition of sediment." ("L.L." I. page 70.)
+
+On arriving at the Cape of Good Hope in July, 1836, Darwin was greatly
+gratified by hearing that Sedgwick had spoken to his father in high
+terms of praise concerning the work done by him in South America.
+Referring to the news from home, when he reached Bahia once more, on the
+return voyage (August, 1836), he says: "The desert, volcanic rocks, and
+wild sea of Ascension... suddenly wore a pleasing aspect, and I set to
+work with a good-will at my old work of Geology." ("L.L." I. page 265.)
+Writing fifty years later, he says: "I clambered over the mountains of
+Ascension with a bounding step and made the volcanic rocks resound under
+my geological hammer!" ("L.L." I. page 66.)
+
+That his determination was now fixed to devote his own labours to the
+task of working out the geological results of the voyage, and that
+he was prepared to leave to more practised hands the study of his
+biological collections, is clear from the letters he sent home at this
+time. From St Helena he wrote to Henslow asking that he would propose
+him as a Fellow of the Geological Society; and his Certificate, in
+Henslow's handwriting, is dated September 8th, 1836, being signed from
+personal knowledge by Henslow and Sedgwick. He was proposed on November
+2nd and elected November 30th, being formally admitted to the Society
+by Lyell, who was then President, on January 4th, 1837, on which date he
+also read his first paper. Darwin did not become a Fellow of the Linnean
+Society till eighteen years later (in 1854).
+
+An estimate of the value and importance of Darwin's geological
+discoveries during the voyage of the "Beagle" can best be made when
+considering the various memoirs and books in which the author
+described them. He was too cautious to allow himself to write his first
+impressions in his Journal, and wisely waited till he could study his
+specimens under better conditions and with help from others on his
+return. The extracts published from his correspondence with Henslow and
+others, while he was still abroad, showed, nevertheless, how great was
+the mass of observation, how suggestive and pregnant with results were
+the reasonings of the young geologist.
+
+Two sets of these extracts from Darwin's letters to Henslow were
+printed while he was still abroad. The first of these was the series of
+"Geological Notes made during a survey of the East and West Coasts of
+South America, in the years 1832, 1833, 1834 and 1835, with an account
+of a transverse section of the Cordilleras of the Andes between
+Valparaiso and Mendoza". Professor Sedgwick, who read these notes to
+the Geological Society on November 18th, 1835, stated that "they were
+extracted from a series of letters (addressed to Professor Henslow),
+containing a great mass of information connected with almost every
+branch of natural history," and that he (Sedgwick) had made a selection
+of the remarks which he thought would be more especially interesting to
+the Geological Society. An abstract of three pages was published in the
+"Proceedings of the Geological Society" (Vol. II. pages 210-12.), but so
+unknown was the author at this time that he was described as F. Darwin,
+Esq., of St John's College, Cambridge! Almost simultaneously (on
+November 16th, 1835) a second set of extracts from these letters--this
+time of a general character--were read to the Philosophical Society at
+Cambridge, and these excited so much interest that they were privately
+printed in pamphlet form for circulation among the members.
+
+Many expeditions and "scientific missions" have been despatched to
+various parts of the world since the return of the "Beagle" in 1836, but
+it is doubtful whether any, even the most richly endowed of them, has
+brought back such stores of new information and fresh discoveries as
+did that little "ten-gun brig"--certainly no cabin or laboratory was the
+birth-place of ideas of such fruitful character as was that narrow end
+of a chart-room, where the solitary naturalist could climb into his
+hammock and indulge in meditation.
+
+The third and most active portion of Darwin's career as a geologist was
+the period which followed his return to England at the end of 1836. His
+immediate admission to the Geological Society, at the beginning of 1837,
+coincided with an important crisis in the history of geological science.
+
+The band of enthusiasts who nearly thirty years before had inaugurated
+the Geological Society--weary of the fruitless conflicts between
+"Neptunists" and "Plutonists"--had determined to eschew theory and
+confine their labours to the collection of facts, their publications to
+the careful record of observations. Greenough, the actual founder of the
+Society, was an ardent Wernerian, and nearly all his fellow-workers had
+come, more or less directly, under the Wernerian teaching. Macculloch
+alone gave valuable support to the Huttonian doctrines, so far as they
+related to the influence of igneous activity--but the most important
+portion of the now celebrated "Theory of the Earth"--that dealing with
+the competency of existing agencies to account for changes in past
+geological times--was ignored by all alike. Macculloch's influence on
+the development of geology, which might have had far-reaching effects,
+was to a great extent neutralised by his peculiarities of mind and
+temper; and, after a stormy and troublous career, he retired from the
+society in 1832. In all the writings of the great pioneers in English
+geology, Hutton and his splendid generalisation are scarcely ever
+referred to. The great doctrines of Uniformitarianism, which he had
+foreshadowed, were completely ignored, and only his extravagances of
+"anti-Wernerianism" seem to have been remembered.
+
+When between 1830 and 1832, Lyell, taking up the almost forgotten ideas
+of Hutton, von Hoff and Prevost, published that bold challenge to
+the Catastrophists--the "Principles of Geology"--he was met with the
+strongest opposition, not only from the outside world, which was amused
+by his "absurdities" and shocked by his "impiety"--but not less from
+his fellow-workers and friends in the Geological Society. For Lyell's
+numerous original observations, and his diligent collection of facts his
+contemporaries had nothing but admiration, and they cheerfully admitted
+him to the highest offices in the society, but they met his reasonings
+on geological theory with vehement opposition and his conclusions with
+coldness and contempt.
+
+There is, indeed, a very striking parallelism between the reception of
+the "Principles of Geology" by Lyell's contemporaries and the manner in
+which the "Origin of Species" was met a quarter of a century later, as
+is so vividly described by Huxley. ("L.L." II. pages 179-204.) Among
+Lyell's fellow-geologists, two only--G. Poulett Scrope and John Herschel
+(Both Lyell and Darwin fully realised the value of the support of these
+two friends. Scrope in his appreciative reviews of the "Principles"
+justly pointed out what was the weakest point, the inadequate
+recognition of sub-aerial as compared with marine denudation. Darwin
+also admitted that Scrope had to a great extent forestalled him in his
+theory of Foliation. Herschel from the first insisted that the leading
+idea of the "Principles" must be applied to organic as well as to
+inorganic nature and must explain the appearance of new species (see
+Lyell's "Life and Letters", Vol. I. page 467). Darwin tells us that
+Herschel's "Introduction to the Study of Natural Philosophy" with
+Humboldt's "Personal Narrative" "stirred up in me a burning zeal" in
+his undergraduate days. I once heard Lyell exclaim with fervour "If
+ever there was a heaven-born genius it was John Herschel!")--declared
+themselves from the first his strong supporters. Scrope in two
+luminous articles in the "Quarterly Review" did for Lyell what Huxley
+accomplished for Darwin in his famous review in the "Times"; but Scrope
+unfortunately was at that time immersed in the stormy sea of politics,
+and devoted his great powers of exposition to the preparation of
+fugitive pamphlets. Herschel, like Scrope, was unable to support
+Lyell at the Geological Society, owing to his absence on the important
+astronomical mission to the Cape.
+
+It thus came about that, in the frequent conflicts of opinion within the
+walls of the Geological Society, Lyell had to bear the brunt of battle
+for Uniformitarianism quite alone, and it is to be feared that he found
+himself sadly overmatched when opposed by the eloquence of Sedgwick, the
+sarcasm of Buckland, and the dead weight of incredulity on the part of
+Greenough, Conybeare, Murchison and other members of the band of pioneer
+workers. As time went on there is evidence that the opposition of De la
+Beche and Whewell somewhat relaxed; the brilliant "Paddy" Fitton (as his
+friends called him) was sometimes found in alliance with Lyell, but was
+characteristically apt to turn his weapon, as occasion served, on friend
+or foe alike; the amiable John Phillips "sat upon the fence." Only when
+a new generation arose--including Jukes, Ramsay, Forbes and Hooker--did
+Lyell find his teachings received with anything like favour.
+
+We can well understand, then, how Lyell would welcome such a recruit as
+young Darwin--a man who had declared himself more Lyellian than Lyell,
+and who brought to his support facts and observations gleaned from so
+wide a field.
+
+The first meeting of Lyell and Darwin was characteristic of the two men.
+Darwin at once explained to Lyell that, with respect to the origin of
+coral-reefs, he had arrived at views directly opposed to those published
+by "his master." To give up his own theory, cost Lyell, as he told
+Herschel, a "pang at first," but he was at once convinced of the
+immeasurable superiority of Darwin's theory. I have heard members
+of Lyell's family tell of the state of wild excitement and sustained
+enthusiasm, which lasted for days with Lyell after this interview, and
+his letters to Herschel, Whewell and others show his pleasure at the new
+light thrown upon the subject and his impatience to have the matter laid
+before the Geological Society.
+
+Writing forty years afterwards, Darwin, speaking of the time of the
+return of the "Beagle", says: "I saw a great deal of Lyell. One of his
+chief characteristics was his sympathy with the work of others, and
+I was as much astonished as delighted at the interest which he
+showed when, on my return to England, I explained to him my views on
+coral-reefs. This encouraged me greatly, and his advice and example had
+much influence on me." ("L.L." I. page 68.) Darwin further states that
+he saw more of Lyell at this time than of any other scientific man, and
+at his request sent his first communication to the Geological Society.
+("L.L." I. page 67.)
+
+"Mr Lonsdale" (the able curator of the Geological Society), Darwin wrote
+to Henslow, "with whom I had much interesting conversation," "gave me a
+most cordial reception," and he adds, "If I was not much more inclined
+for geology than the other branches of Natural History, I am sure Mr
+Lyell's and Lonsdale's kindness ought to fix me. You cannot conceive
+anything more thoroughly good-natured than the heart-and-soul manner in
+which he put himself in my place and thought what would be best to do."
+("L.L." I. page 275.)
+
+Within a few days of Darwin's arrival in London we find Lyell writing to
+Owen as follows:
+
+"Mrs Lyell and I expect a few friends here on Saturday next, 29th
+(October), to an early tea party at eight o'clock, and it will give us
+great pleasure if you can join it. Among others you will meet Mr Charles
+Darwin, whom I believe you have seen, just returned from South America,
+where he has laboured for zoologists as well as for hammer-bearers.
+I have also asked your friend Broderip." ("The Life of Richard Owen",
+London, 1894, Vol. I. page 102.) It would probably be on this occasion
+that the services of Owen were secured for the work on the fossil bones
+sent home by Darwin.
+
+On November 2nd, we find Lyell introducing Darwin as his guest at the
+Geological Society Club; on December 14th, Lyell and Stokes proposed
+Darwin as a member of the Club; between that date and May 3rd of the
+following year, when his election to the Club took place, he was several
+times dining as a guest.
+
+On January 4th, 1837, as we have already seen, Darwin was formally
+admitted to the Geological Society, and on the same evening he read
+his first paper (I have already pointed out that the notes read at the
+Geological Society on Nov. 18, 1835 were extracts made by Sedgwick from
+letters sent to Henslow, and not a paper sent home for publication by
+Darwin.) before the Society, "Observations of proofs of recent elevation
+on the coast of Chili, made during the Survey of H.M.S. "Beagle",
+commanded by Captain FitzRoy, R.N." By C. Darwin, F.G.S. This paper was
+preceded by one on the same subject by Mr A. Caldcleugh, and the reading
+of a letter and other communications from the Foreign Office also
+relating to the earthquakes in Chili.
+
+At the meeting of the Council of the Geological Society on February 1st,
+Darwin was nominated as a member of the new Council, and he was elected
+on February 17th.
+
+The meeting of the Geological Society on April 19th was devoted to the
+reading by Owen of his paper on Toxodon, perhaps the most remarkable
+of the fossil mammals found by Darwin in South America; and at the
+next meeting, on May 3rd, Darwin himself read "A Sketch of the Deposits
+containing extinct Mammalia in the neighbourhood of the Plata". The
+next following meeting, on May 17th, was devoted to Darwin's Coral-reef
+paper, entitled "On certain areas of elevation and subsidence in
+the Pacific and Indian Oceans, as deduced from the study of Coral
+Formations". Neither of these three early papers of Darwin were
+published in the Transactions of the Geological Society, but the
+minutes of the Council show that they were "withdrawn by the author by
+permission of the Council."
+
+Darwin's activity during this session led to some rather alarming
+effects upon his health, and he was induced to take a holiday in
+Staffordshire and the Isle of Wight. He was not idle, however, for a
+remark of his uncle, Mr Wedgwood, led him to make those interesting
+observations on the work done by earthworms, that resulted in his
+preparing a short memoir on the subject, and this paper, "On the
+Formation of Mould", was read at the Society on November 1st, 1837,
+being the first of Darwin's papers published in full; it appeared in
+Vol. V. of the "Geological Transactions", pages 505-510.
+
+During this session, Darwin attended nearly all the Council meetings,
+and took such an active part in the work of the Society that it is not
+surprising to find that he was now requested to accept the position of
+Secretary. After some hesitation, in which he urged his inexperience
+and want of knowledge of foreign languages, he consented to accept the
+appointment. ("L.L." I. page 285.)
+
+At the anniversary meeting on February 16th, 1838, the Wollaston Medal
+was given to Owen in recognition of his services in describing the
+fossil mammals sent home by Darwin. In his address, the President,
+Professor Whewell, dwelt at length on the great value of the papers
+which Darwin had laid before the Society during the preceding session.
+
+On March 7th, Darwin read before the Society the most important perhaps
+of all his geological papers, "On the Connexion of certain Volcanic
+Phenomena in South America, and on the Formation of Mountain-Chains and
+Volcanoes as the effect of Continental Elevations". In this paper he
+boldly attacked the tenets of the Catastrophists. It is evident that
+Darwin at this time, taking advantage of the temporary improvement in
+his health, was throwing himself into the breach of Uniformitarianism
+with the greatest ardour. Lyell wrote to Sedgwick on April 21st, 1837,
+"Darwin is a glorious addition to any society of geologists, and is
+working hard and making way, both in his book and in our discussions."
+("The Life and Letters of the Reverend Adam Sedgwick", Vol. I. page 484,
+Cambridge, 1890.)
+
+We have unfortunately few records of the animated debates which took
+place at this time between the old and new schools of geologists. I have
+often heard Lyell tell how Lockhart would bring down a party of friends
+from the Athenaeum Club to Somerset House on Geological nights, not, as
+he carefully explained, that "he cared for geology, but because he liked
+to while the fellows fight." But it fortunately happens that a few days
+after this last of Darwin's great field-days, at the Geological Society,
+Lyell, in a friendly letter to his father-in-law, Leonard Horner, wrote
+a very lively account of the proceedings while his impressions were
+still fresh; and this gives us an excellent idea of the character of
+these discussions.
+
+Neither Sedgwick nor Buckland were present on this occasion, but we can
+imagine how they would have chastised their two "erring pupils"--more
+in sorrow than in anger--had they been there. Greenough, too, was
+absent--possibly unwilling to countenance even by his presence such
+outrageous doctrines.
+
+Darwin, after describing the great earthquakes which he had experienced
+in South America, and the evidence of their connection with volcanic
+outbursts, proceeded to show that earthquakes originated in fractures,
+gradually formed in the earth's crust, and were accompanied by movements
+of the land on either side of the fracture. In conclusion he boldly
+advanced the view "that continental elevations, and the action of
+volcanoes, are phenomena now in progress, caused by some great but slow
+change in the interior of the earth; and, therefore, that it might
+be anticipated, that the formation of mountain chains is likewise in
+progress: and at a rate which may be judged of by either actions, but
+most clearly by the growth of volcanoes." ("Proc. Geol. Soc." Vol. II.
+pages 654-60.)
+
+Lyell's account ("Life, Letters and Journals of Sir Charles Lyell,
+Bart.", edited by his sister-in-law, Mrs Lyell, Vol. II. pages 40,
+41 (Letter to Leonard Horner, 1838), 2 vols. London, 1881.) of the
+discussion was as follows: "In support of my heretical notions," Darwin
+"opened upon De la Beche, Phillips and others his whole battery of the
+earthquakes and volcanoes of the Andes, and argued that spaces at least
+a thousand miles long were simultaneously subject to earthquakes and
+volcanic eruptions, and that the elevation of the Pampas, Patagonia,
+etc., all depended on a common cause; also that the greater the
+contortions of strata in a mountain chain, the smaller must have been
+each separate and individual movement of that long series which was
+necessary to upheave the chain. Had they been more violent, he
+contended that the subterraneous fluid matter would have gushed out and
+overflowed, and the strata would have been blown up and annihilated. (It
+is interesting to compare this with what Darwin wrote to Henslow
+seven years earlier.) He therefore introduces a cooling of one small
+underground injection, and then the pumping in of other lava, or
+porphyry, or granite, into the previously consolidated and first-formed
+mass of igneous rock. (Ideas somewhat similar to this suggestion have
+recently been revived by Dr See ("Proc. Am. Phil. Soc." Vol. XLVII.
+1908, page 262.).) When he had done his description of the reiterated
+strokes of his volcanic pump, De la Beche gave us a long oration about
+the impossibility of strata of the Alps, etc., remaining flexible
+for such a time as they must have done, if they were to be tilted,
+convoluted, or overturned by gradual small shoves. He never, however,
+explained his theory of original flexibility, and therefore I am as
+unable as ever to comprehend why flexiblility is a quality so limited in
+time.
+
+"Phillips then got up and pronounced a panegyric upon the "Principles
+of Geology", and although he still differed, thought the actual cause
+doctrine had been so well put, that it had advanced the science and
+formed a date or era, and that for centuries the two opposite doctrines
+would divide geologists, some contending for greater pristine forces,
+others satisfied, like Lyell and Darwin, with the same intensity as
+nature now employs.
+
+"Fitton quizzed Phillips a little for the warmth of his eulogy, saying
+that he (Fitton) and others, who had Mr Lyell always with them, were in
+the habit of admiring and quarrelling with him every day, as one
+might do with a sister or cousin, whom one would only kiss and embrace
+fervently after a long absence. This seemed to be Mr Phillips' case,
+coming up occasionally from the provinces. Fitton then finished this
+drollery by charging me with not having done justice to Hutton, who he
+said was for gradual elevation.
+
+"I replied, that most of the critics had attacked me for overrating
+Hutton, and that Playfair understood him as I did.
+
+"Whewell concluded by considering Hopkins' mathematical calculations, to
+which Darwin had often referred. He also said that we ought not to try
+and make out what Hutton would have taught and thought, if he had known
+the facts which we now know."
+
+It may be necessary to point out, in explanation of the above narrative,
+that while it was perfectly clear from Hutton's rather obscure and
+involved writings that he advocated slow and gradual change on
+the earth's surface, his frequent references to violent action and
+earthquakes led many--including Playfair, Lyell and Whewell--to believe
+that he held the changes going on in the earth's interior to be of
+a catastrophic nature. Fitton, however, maintained that Hutton was
+consistently uniformitarian. Before the idea of the actual "flowing" of
+solid bodies under intense pressure had been grasped by geologists,
+De la Beche, like Playfair before him, maintained that the bending
+and folding of rocks must have been effected before their complete
+consolidation.
+
+In concluding his account of this memorable discussion, Lyell adds: "I
+was much struck with the different tone in which my gradual causes
+was treated by all, even including De la Beche, from that which they
+experienced in the same room four years ago, when Buckland, De la
+Beche(?), Sedgwick, Whewell, and some others treated them with as much
+ridicule as was consistent with politeness in my presence."
+
+This important paper was, in spite of its theoretical character,
+published in full in the "Transactions of the Geological Society" (Ser.
+2, Vol. V. pages 601-630). It did not however appear till 1840, and
+possibly some changes may have been made in it during the long interval
+between reading and printing. During the year 1839, Darwin continued his
+regular attendance at the Council meetings, but there is no record of
+any discussions in which he may have taken part, and he contributed
+no papers himself to the Society. At the beginning of 1840, he was
+re-elected for the third time as Secretary, but the results of failing
+health are indicated by the circumstance that, only at one meeting early
+in the session, was he able to attend the Council. At the beginning of
+the next session (Feb. 1841) Bunbury succeeded him as Secretary,
+Darwin still remaining on the Council. It may be regarded as a striking
+indication of the esteem in which he was held by his fellow geologists,
+that Darwin remained on the Council for 14 consecutive years down to
+1849, though his attendances were in some years very few. In 1843 and
+1844 he was a Vice-president, but after his retirement at the beginning
+of 1850, he never again accepted re-nomination. He continued, however,
+to contribute papers to the Society, as we shall see, down to the end of
+1862.
+
+Although Darwin early became a member of the Geological Dining Club, it
+is to be feared that he scarcely found himself in a congenial atmosphere
+at those somewhat hilarious gatherings, where the hardy wielders of the
+hammer not only drank port--and plenty of it--but wound up their
+meal with a mixture of Scotch ale and soda water, a drink which, as
+reminiscent of the "field," was regarded as especially appropriate to
+geologists. Even after the meetings, which followed the dinners,
+they reassembled for suppers, at which geological dainties, like
+"pterodactyle pie" figured in the bill of fare, and fines of bumpers
+were inflicted on those who talked the "ologies."
+
+After being present at a fair number of meetings in 1837 and 1838,
+Darwin's attendances at the Club fell off to two in 1839, and by 1841
+he had ceased to be a member. In a letter to Lyell on Dec. 2nd, 1841,
+Leonard Horner wrote that the day before "At the Council, I had the
+satisfaction of seeing Darwin again in his place and looking well. He
+tried the last evening meeting, but found it too much, but I hope before
+the end of the season he will find himself equal to that also. I hail
+Darwin's recovery as a vast gain to science." Darwin's probably last
+attendance, this time as a guest, was in 1851, when Horner again
+wrote to Lyell, "Charles Darwin was at the Geological Society's Club
+yesterday, where he had not been for ten years--remarkably well, and
+grown quite stout." ("Memoirs of Leonard Horner" (privately printed),
+Vol. II. pages 39 and 195.)
+
+It may be interesting to note that at the somewhat less lively dining
+Club--the Philosophical--in the founding of which his friends Lyell and
+Hooker had taken so active a part, Darwin found himself more at home,
+and he was a frequent attendant--in spite of his residence being at
+Down--from 1853 to 1864. He even made contributions on scientific
+questions after these dinners. In a letter to Hooker he states that he
+was deeply interested in the reforms of the Royal Society, which the
+Club was founded to promote. He says also that he had arranged to come
+to town every Club day "and then my head, I think, will allow me on an
+average to go to every other meeting. But it is grievous how often any
+change knocks me up." ("L.L." II. pages 42, 43.)
+
+Of the years 1837 and 1838 Darwin himself says they were "the most
+active ones which I ever spent, though I was occasionally unwell, and
+so lost some time... I also went a little into society." ("L.L." I. pages
+67, 68.) But of the four years from 1839 to 1842 he has to confess sadly
+"I did less scientific work, though I worked as hard as I could, than
+during any other equal length of time in my life. This was owing to
+frequently recurring unwellness, and to one long and serious illness."
+("L.L." I. page 69.)
+
+Darwin's work at the Geological Society did not by any means engage the
+whole of his energies, during the active years 1837 and 1838. In June of
+the latter year, leaving town in somewhat bad health, he found himself
+at Edinburgh again, and engaged in examining the Salisbury Craigs, in a
+very different spirit to that excited by Jameson's discourse. ("L.L."
+I. page 290.) Proceeding to the Highlands he then had eight days of hard
+work at the famous "Parallel Roads of Glen Roy", being favoured with
+glorious weather.
+
+He says of the writing of the paper on the subject--the only memoir
+contributed by Darwin to the Royal Society, to which he had been
+recently elected--that it was "one of the most difficult and instructive
+tasks I was ever engaged on." The paper extends to 40 quarto pages
+and is illustrated by two plates. Though it is full of the records
+of careful observation and acute reasoning, yet the theory of marine
+beaches which he propounded was, as he candidly admitted in after years
+("M.L." II page 188.), altogether wrong. The alternative lake-theory he
+found himself unable to accept at the time, for he could not understand
+how barriers could be formed at successive levels across the valleys;
+and until the following year, when the existence of great glaciers
+in the district was proved by the researches of Agassiz, Buckland and
+others, the difficulty appeared to him an insuperable one. Although
+Darwin said of this paper in after years that it "was a great failure
+and I am ashamed of it"--yet he retained his interest in the question
+ever afterwards, and he says "my error has been a good lesson to me
+never to trust in science to the principle of exclusion." ("M.L." II.
+pages 171-93.)
+
+Although Darwin had not realised in 1838 that large parts of the British
+Islands had been occupied by great glaciers, he had by no means failed
+while in South America to recognise the importance of ice-action. His
+observations, as recorded in his Journal, on glaciers coming down to
+the sea-level, on the west coast of South America, in a latitude
+corresponding to a much lower one than that of the British Islands,
+profoundly interested geologists; and the same work contains many
+valuable notes on the boulders and unstratified beds in South America in
+which they were included.
+
+But in 1840 Agassiz read his startling paper on the evidence of the
+former existence of glaciers in the British Islands, and this was
+followed by Buckland's memoir on the same subject. On April 14, 1841,
+Darwin contributed to the Geological Society his important paper "On the
+Distribution of Erratic Boulders and the Contemporaneous Unstratified
+Deposits of South America", a paper full of suggestiveness for those
+studying the glacial deposits of this country. It was published in the
+"Transactions" in 1842.
+
+The description of traces of glacial action in North Wales, by Buckland,
+appears to have greatly excited the interest of Darwin. With Sedgwick he
+had, in 1831, worked at the stratigraphy of that district, but neither
+of them had noticed the very interesting surface features. ("L.L." I.
+page 58.) Darwin was able to make a journey to North Wales in June,
+1842 (alas! it was his last effort in field-geology) and as a result
+he published his most able and convincing paper on the subject in the
+September number of the "Philosophical Magazine" for 1842. Thus the
+mystery of the bell-stone was at last solved and Darwin, writing many
+years afterwards, said "I felt the keenest delight when I first read of
+the action of icebergs in transporting boulders, and I gloried in the
+progress of Geology." ("L.L." I. page 41.) To the "Geographical Journal"
+he had sent in 1839 a note "On a Rock seen on an Iceberg in 16 deg S.
+Latitude." For the subject of ice-action, indeed, Darwin retained the
+greatest interest to the end of his life. ("M.L." II. pages 148-71.)
+
+In 1846, Darwin read two papers to the Geological Society "On the
+dust which falls on vessels in the Atlantic, and On the Geology of the
+Falkland Islands"; in 1848 he contributed a note on the transport of
+boulders from lower to higher levels; and in 1862 another note on the
+thickness of the Pampean formation, as shown by recent borings at Buenos
+Ayres. An account of the "British Fossil Lepadidae" read in 1850, was
+withdrawn by him.
+
+At the end of 1836 Darwin had settled himself in lodgings in Fitzwilliam
+Street, Cambridge, and devoted three months to the work of unpacking his
+specimens and studying his collection of rocks. The pencilled notes on
+the Manuscript Catalogue in the Sedgwick Museum enable us to realise
+his mode of work, and the diligence with which it was carried on. The
+letters M and H, indicate the assistance he received from time to
+time from Professor Miller, the crystallographer, and from his friend
+Henslow. Miller not only measured many of the crystals submitted to him,
+but evidently taught Darwin to use the reflecting goniometer himself
+with considerable success. The "book of measurements" in which the
+records were kept, appears to have been lost, but the pencilled notes
+in the catalogue show how thoroughly the work was done. The letter R
+attached to some of the numbers in the catalogue evidently refers to the
+fact that they were submitted to Mr Trenham Reeks (who analysed some of
+his specimens) at the Geological Survey quarters in Craig's Court. This
+was at a later date when Darwin was writing the "Volcanic Islands" and
+"South America".
+
+It was about the month of March, 1837, that Darwin completed this work
+upon his rocks, and also the unpacking and distribution of his fossil
+bones and other specimens. We have seen that November, 1832, must
+certainly be regarded as the date when he FIRST realised the important
+fact that the fossil mammals of the Pampean formation were all closely
+related to the existing forms in South America; while October, 1835,
+was, as undoubtedly, the date when the study of the birds and other
+forms of life in the several islands of the Galapagos Islands gave
+him his SECOND impulse towards abandoning the prevalent view of the
+immutability of species. When then in his pocket-book for 1837 Darwin
+wrote the often quoted passage: "In July opened first note-book on
+Transmutation of Species. Had been greatly struck from about the month
+of previous March on character of South American fossils, and species on
+Galapagos Archipelago. These facts (especially latter), origin of all my
+views" ("L.L." I. page 276.), it is clear that he must refer, not to
+his first inception of the idea of evolution, but to the flood of
+recollections, the reawakening of his interest in the subject, which
+could not fail to result from the sight of his specimens and the
+reference to his notes.
+
+Except during the summer vacation, when he was visiting his father and
+uncle, and with the latter making his first observations upon the work
+of earthworms, Darwin was busy with his arrangements for the publication
+of the five volumes of the "Zoology of the 'Beagle'" and in getting the
+necessary financial aid from the government for the preparation of the
+plates. He was at the same time preparing his "Journal" for publication.
+During the years 1837 to 1843, Darwin worked intermittently on the
+volumes of Zoology, all of which he edited, while he wrote introductions
+to those by Owen and Waterhouse and supplied notes to the others.
+
+Although Darwin says of his Journal that the preparation of the book
+"was not hard work, as my MS. Journal had been written with care." Yet
+from the time that he settled at 36, Great Marlborough Street in March,
+1837, to the following November he was occupied with this book. He tells
+us that the account of his scientific observations was added at this
+time. The work was not published till March, 1839, when it appeared
+as the third volume of the "Narrative of the Surveying Voyages of H.M.
+Ships 'Adventure' and 'Beagle' between the years 1826 and 1836". The
+book was probably a long time in the press, for there are no less than
+20 pages of addenda in small print. Even in this, its first form, the
+work is remarkable for its freshness and charm, and excited a great
+amount of attention and interest. In addition to matters treated of in
+greater detail in his other works, there are many geological notes of
+extreme value in this volume, such as his account of lightning tubes, of
+the organisms found in dust, and of the obsidian bombs of Australia.
+
+Having thus got out of hand a number of preliminary duties, Darwin was
+ready to set to work upon the three volumes which were designed by him
+to constitute "The Geology of the Voyage of the 'Beagle'". The first of
+these was to be on "The Structure and Distribution of Coral-reefs". He
+commenced the writing of the book on October 5, 1838, and the last proof
+was corrected on May 6, 1842. Allowing for the frequent interruptions
+through illness, Darwin estimated that it cost him twenty months of hard
+work.
+
+Darwin has related how his theory of Coral-reefs which was begun in a
+more "deductive spirit" than any of his other work, for in 1834 or 1835
+it "was thought out on the west coast of South America, before I had
+seen a true coral-reef." ("L.L." I. page 70.) The final chapter in
+Lyell's second volume of the "Principles" was devoted to the subject
+of Coral-reefs, and a theory was suggested to account for the peculiar
+phenomena of "atolls." Darwin at once saw the difficulty of accepting
+the view that the numerous and diverse atolls all represent submerged
+volcanic craters. His own work had for two years been devoted to the
+evidence of land movements over great areas in South America, and thus
+he was led to announce his theory of subsidence to account for barrier
+and encircling reefs as well as atolls.
+
+Fortunately, during his voyage across the Pacific and Indian Oceans, in
+his visit to Australia and his twelve days' hard work at Keeling Island,
+he had opportunities for putting his theory to the test of observation.
+
+On his return to England, Darwin appears to have been greatly surprised
+at the amount of interest that his new theory excited. Urged by Lyell,
+he read to the Geological Society a paper on the subject, as we have
+seen, with as little delay as possible, but this paper was "withdrawn by
+permission of the Council." An abstract of three pages however appeared
+in the "Proceedings of the Geological Society". (Vol. II. pages 552-554
+(May 31, 1837).) A full account of the observations and the theory was
+given in the "Journal" (1839) in the 40 pages devoted to Keeling
+Island in particular and to Coral formations generally. ("Journal" (1st
+edition), pages 439-69.)
+
+It will be readily understood what an amount of labour the book on
+Coral reefs cost Darwin when we reflect on the number of charts, sailing
+directions, narratives of voyages and other works which, with the
+friendly assistance of the authorities at the Admiralty, he had
+to consult before he could draw up his sketch of the nature and
+distribution of the reefs, and this was necessary before the theory, in
+all its important bearings, could be clearly enunciated. Very pleasing
+is it to read how Darwin, although arriving at a different conclusion to
+Lyell, shows, by quoting a very suggestive passage in the "Principles"
+(1st edition Vol. II. page 296.), how the latter only just missed the
+true solution. This passage is cited, both in the "Journal" and the
+volume on Coral-reefs. Lyell, as we have seen, received the new theory
+not merely ungrudgingly, but with the utmost enthusiasm.
+
+In 1849 Darwin was gratified by receiving the support of Dana, after his
+prolonged investigation in connection with the U.S. Exploring Expedition
+("M.L." II. pages 226-8.), and in 1874 he prepared a second edition of
+his book, in which some objections which had been raised to the theory
+were answered. A third edition, edited by Professor Bonney, appeared in
+1880, and a fourth (a reprint of the first edition, with introduction by
+myself) in 1890.
+
+Although Professor Semper, in his account of the Pelew Islands, had
+suggested difficulties in the acceptance of Darwin's theory, it was
+not till after the return of the "Challenger" expedition in 1875 that a
+rival theory was propounded, and somewhat heated discussions were raised
+as to the respective merits of the two theories. While geologists have,
+nearly without exception, strongly supported Darwin's views, the notes
+of dissent have come almost entirely from zoologists. At the height
+of the controversy unfounded charges of unfairness were made against
+Darwin's supporters and the authorities of the Geological Society, but
+this unpleasant subject has been disposed of, once for all, by Huxley.
+("Essays upon some Controverted Questions", London, 1892, pages 314-328
+and 623-625.)
+
+Darwin's final and very characteristic utterance on the coral-reef
+controversy is found in a letter which he wrote to Professor Alexander
+Agassiz, May 5th, 1881: less than a year before his death: "If I am
+wrong, the sooner I am knocked on the head and annihilated so much the
+better. It still seems to me a marvellous thing that there should not
+have been much, and long-continued, subsidence in the beds of the great
+oceans. I wish that some doubly rich millionaire would take it into his
+head to have borings made in some of the Pacific and Indian atolls, and
+bring home cores for slicing from a depth of 500 or 600 feet." ("L.L."
+III. page 184.)
+
+Though the "doubly rich millionaire" has not been forthcoming, the
+energy, in England, of Professor Sollas, and in New South Wales of
+Professor Anderson Stuart served to set on foot a project, which, aided
+at first by the British Association for the Advancement of Science, and
+afterwards taken up jointly by the Royal Society, the New South
+Wales Government, and the Admiralty, has led to the most definite and
+conclusive results.
+
+The Committee appointed by the Royal Society to carry out the
+undertaking included representatives of all the views that had been
+put forward on the subject. The place for the experiment was, with the
+consent of every member of the Committee, selected by the late Admiral
+Sir W.J. Wharton--who was not himself an adherent of Darwin's views--and
+no one has ventured to suggest that his selection, the splendid atoll of
+Funafuti, was not a most judicious one.
+
+By the pluck and perseverance of Professor Sollas in the preliminary
+expedition, and of Professor T. Edgeworth David and his pupils, in
+subsequent investigations of the island, the rather difficult piece
+of work was brought to a highly satisfactory conclusion. The New South
+Wales Government lent boring apparatus and workmen, and the Admiralty
+carried the expedition to its destination in a surveying ship which,
+under Captain (now Admiral) A. Mostyn Field, made the most complete
+survey of the atoll and its surrounding seas that has ever been
+undertaken in the case of a coral formation.
+
+After some failures and many interruptions, the boring was carried to
+the depth of 1114 feet, and the cores obtained were sent to England.
+Here the examination of the materials was fortunately undertaken by
+a zoologist of the highest repute, Dr G.J. Hinde--who has a wide
+experience in the study of organisms by sections--and he was aided at
+all points by specialists in the British Museum of Natural History
+and by other naturalists. Nor were the chemical and other problems
+neglected.
+
+The verdict arrived at, after this most exhaustive study of a series of
+cores obtained from depths twice as great as that thought necessary by
+Darwin, was as follows:--"The whole of the cores are found to be built
+up of those organisms which are seen forming coral-reefs near the
+surface of the ocean--many of them evidently in situ; and not the
+slightest indication could be detected, by chemical or microscopic
+means, which suggested the proximity of non-calcareous rocks, even in
+the lowest portions brought up."
+
+But this was not all. Professor David succeeded in obtaining the aid
+of a very skilful engineer from Australia, while the Admiralty allowed
+Commander F.C.D. Sturdee to take a surveying ship into the lagoon
+for further investigations. By very ingenious methods, and with great
+perseverance, two borings were put down in the midst of the lagoon to
+the depth of nearly 200 feet. The bottom of the lagoon, at the depth of
+101 1/2 feet from sea-level, was found to be covered with remains of the
+calcareous, green sea-weed Halimeda, mingled with many foraminifera; but
+at a depth of 163 feet from the surface of the lagoon the boring tools
+encountered great masses of coral, which were proved from the fragments
+brought up to belong to species that live within AT MOST 120 feet from
+the surface of the ocean, as admitted by all zoologists. ("The Atoll
+of Funafuti; Report of the Coral Reef Committee of the Royal Society",
+London, 1904.)
+
+Darwin's theory, as is well known, is based on the fact that the
+temperature of the ocean at any considerable depth does not permit of
+the existence and luxuriant growth of the organisms that form the reefs.
+He himself estimated this limit of depth to be from 120 to 130 feet;
+Dana, as an extreme, 150 feet; while the recent very prolonged and
+successful investigations of Professor Alexander Agassiz in the Pacific
+and Indian Oceans lead him also to assign a limiting depth of 150 feet;
+the EFFECTIVE, REEF-FORMING CORALS, however, flourishing at a much
+smaller depth. Mr Stanley Gardiner gives for the most important
+reef-forming corals depths between 30 and 90 feet, while a few are found
+as low as 120 feet or even 180 feet.
+
+It will thus be seen that the verdict of Funafuti is clearly and
+unmistakeably in favour of Darwin's theory. It is true that some
+zoologists find a difficulty in realising a slow sinking of parts of the
+ocean floor, and have suggested new and alternative explanations: but
+geologists generally, accepting the proofs of slow upheaval in
+some areas--as shown by the admirable researches of Alexander
+Agassiz--consider that it is absolutely necessary to admit that this
+elevation is balanced by subsidence in other areas. If atolls and
+barrier-reefs did not exist we should indeed be at a great loss to frame
+a theory to account for their absence.
+
+After finishing his book on Coral-reefs, Darwin made his summer
+excursion to North Wales, and prepared his important memoir on the
+glaciers of that district: but by October (1842) we find him fairly
+settled at work upon the second volume of his "Geology of the
+'Beagle'--Geological Observations on the Volcanic Islands, visited
+during the Voyage of H.M.S. 'Beagle'". The whole of the year 1843 was
+devoted to this work, but he tells his friend Fox that he could "manage
+only a couple of hours per day, and that not very regularly." ("L.L." I.
+page 321.) Darwin's work on the various volcanic islands examined by
+him had given him the most intense pleasure, but the work of writing
+the book by the aid of his notes and specimens he found "uphill
+work," especially as he feared the book would not be read, "even by
+geologists." (Loc. cit.)
+
+As a matter of fact the work is full of the most interesting
+observations and valuable suggestions, and the three editions (or
+reprints) which have appeared have proved a most valuable addition to
+geological literature. It is not necessary to refer to the novel and
+often very striking discoveries described in this well-known work. The
+subsidence beneath volcanic vents, the enormous denudation of volcanic
+cones reducing them to "basal wrecks," the effects of solfatarric action
+and the formation of various minerals in the cavities of rocks--all
+of these subjects find admirable illustration from his graphic
+descriptions. One of the most important discussions in this volume is
+that dealing with the "lamination" of lavas as especially well seen in
+the rocks of Ascension. Like Scrope, Darwin recognised the close analogy
+between the structure of these rocks and those of metamorphic origin--a
+subject which he followed out in the volume "Geological Observations on
+South America".
+
+Of course in these days, since the application of the microscope to the
+study of rocks in thin sections, Darwin's nomenclature and descriptions
+of the petrological characters of the lavas appear to us somewhat crude.
+But it happened that the "Challenger" visited most of the volcanic
+islands described by Darwin, and the specimens brought home were
+examined by the eminent petrologist Professor Renard. Renard was so
+struck with the work done by Darwin, under disadvantageous conditions,
+that he undertook a translation of Darwin's work into French, and I
+cannot better indicate the manner in which the book is regarded by
+geologists than by quoting a passage from Renard's preface. Referring
+to his own work in studying the rocks brought home by the "Challenger"
+(Renard's descriptions of these rocks are contained in the "Challenger
+Reports". Mr Harker is supplementing these descriptions by a series of
+petrological memoirs on Darwin's specimens, the first of which appeared
+in the "Geological Magazine" for March, 1907.), he says:
+
+"Je dus, en me livrant a ces recherches, suivre ligne par ligne les
+divers chapitres des "Observations geologiques" consacrees aux iles de
+l'Atlantique, oblige que j'etais de comparer d'une maniere suivie les
+resultats auxquels j'etais conduit avec ceux de Darwin, qui servaient
+de controle a mes constatations. Je ne tardai pas a eprouver une vive
+admiration pour ce chercheur qui, sans autre appareil que la loupe,
+sans autre reaction que quelques essais pyrognostiques, plus rarement
+quelques mesures au goniometre, parvenait a discerner la nature des
+agregats mineralogiques les plue complexes et les plus varies. Ce
+coup d'oeil qui savait embrasser de si vastes horizons, penetre ici
+profondement tous les details lithologiques. Avec quelle surete
+et quelle exactitude la structure et la composition des roches ne
+sont'elles pas determinees, l'origne de ces masses minerales deduite et
+confirmee par l'etude comparee des manifestations volcaniques d'autres
+regions; avec quelle science les relations entre les faits qu'il
+decouvre et ceux signales ailleurs par ses devanciers ne sont'elles pas
+etablies, et comme voici ebranlees les hypotheses regnantes, admises
+sans preuves, celles, par exemple, des crateres de soulevement et de la
+differenciation radicale des phenomenes plutoniques et volcaniques!
+Ce qui acheve de donner a ce livre un incomparable merite, ce sont les
+idees nouvelles qui s'y trouvent en germe et jetees la comme au
+hasard ainsi qu'un superflu d'abondance intellectuelle inepuisable."
+("Observations Geologiques sur les Iles Volcaniques... ", Paris, 1902,
+pages vi., vii.)
+
+While engaged in his study of banded lavas, Darwin was struck with the
+analogy of their structure with that of glacier ice, and a note on the
+subject, in the form of a letter addressed to Professor J.D. Forbes, was
+published in the "Proceedings of the Royal Society of Edinburgh". (Vol.
+II. (1844-5), pages 17, 18.)
+
+From April, 1832, to September, 1835, Darwin had been occupied in
+examining the coast or making inland journeys in the interior of the
+South American continent. Thus while eighteen months were devoted, at
+the beginning and end of the voyage to the study of volcanic islands
+and coral-reefs, no less than three and a half years were given to South
+American geology. The heavy task of dealing with the notes and specimens
+accumulated during that long period was left by Darwin to the last.
+Finishing the "Volcanic Islands" on February 14th, 1844, he, in July of
+the same year, commenced the preparation of two important works which
+engaged him till near the end of the year 1846. The first was his
+"Geological Observations on South America", the second a recast of his
+"Journal", published under the short title of "A Naturalist's Voyage
+round the World".
+
+The first of these works contains an immense amount of information
+collected by the author under great difficulties and not unfrequently
+at considerable risk to life and health. No sooner had Darwin landed
+in South America than two sets of phenomena powerfully arrested his
+attention. The first of these was the occurrence of great masses of red
+mud containing bones and shells, which afforded striking evidence that
+the whole continent had shared in a series of slow and gradual but
+often interrupted movements. The second related to the great masses of
+crystalline rocks which, underlying the muds, cover so great a part of
+the continent. Darwin, almost as soon as he landed, was struck by
+the circumstance that the direction, as shown by his compass, of
+the prominent features of these great crystalline rock-masses--their
+cleavage, master-joints, foliation and pegmatite veins--was the same as
+the orientation described by Humboldt (whose works he had so carefully
+studied) on the west of the same great continent.
+
+The first five chapters of the book on South America were devoted to
+formations of recent date and to the evidence collected on the east and
+west coasts of the continent in regard to those grand earth-movements,
+some of which could be shown to have been accompanied by
+earthquake-shocks. The fossil bones, which had given him the first hint
+concerning the mutability of species, had by this time been studied and
+described by comparative anatomists, and Darwin was able to elaborate
+much more fully the important conclusion that the existing fauna of
+South America has a close analogy with that of the period immediately
+preceding our own.
+
+The remaining three chapters of the book dealt with the metamorphic and
+plutonic rocks, and in them Darwin announced his important conclusions
+concerning the relations of cleavage and foliation, and on the close
+analogy of the latter structure with the banding found in rock-masses
+of igneous origin. With respect to the first of these conclusions, he
+received the powerful support of Daniel Sharpe, who in the years
+1852 and 1854 published two papers on the structure of the Scottish
+Highlands, supplying striking confirmation of the correctness of
+Darwin's views. Although Darwin's and Sharpe's conclusions were
+contested by Murchison and other geologists, they are now universally
+accepted. In his theory concerning the origin of foliation, Darwin had
+been to some extent anticipated by Scrope, but he supplied many facts
+and illustrations leading to the gradual acceptance of a doctrine which,
+when first enunciated, was treated with neglect, if not with contempt.
+
+The whole of this volume on South American geology is crowded with the
+records of patient observations and suggestions of the greatest value;
+but, as Darwin himself saw, it was a book for the working geologist and
+"caviare to the general." Its author, indeed, frequently expressed
+his sense of the "dryness" of the book; he even says "I long hesitated
+whether I would publish it or not," and he wrote to Leonard Horner "I am
+astonished that you should have had the courage to go right through my
+book." ("M.L." II. page 221.)
+
+Fortunately the second book, on which Darwin was engaged at this time,
+was of a very different character. His "Journal", almost as he had
+written it on board ship, with facts and observations fresh in his mind,
+had been published in 1839 and attracted much attention. In 1845, he
+says, "I took much pains in correcting a new edition," and the work
+which was commenced in April, 1845, was not finished till August of
+that year. The volume contains a history of the voyage with "a sketch
+of those observations in Natural History and Geology, which I think will
+possess some interest for the general reader." It is not necessary
+to speak of the merits of this scientific classic. It became a
+great favourite with the general public--having passed through many
+editions--it was, moreover, translated into a number of different
+languages. Darwin was much gratified by these evidences of popularity,
+and naively remarks in his "Autobiography", "The success of this my
+first literary child tickles my vanity more than that of any of my other
+books" ("L.L." I. page 80.)--and this was written after the "Origin of
+Species" had become famous!
+
+In Darwin's letters there are many evidences that his labours during
+these ten years devoted to the working out of the geological results
+of the voyage often made many demands on his patience and indomitable
+courage. Most geologists have experience of the contrast between the
+pleasures felt when wielding the hammer in the field, and the duller
+labour of plying the pen in the study. But in Darwin's case, innumerable
+interruptions from sickness and other causes, and the oft-deferred hope
+of reaching the end of his task were not the only causes operating to
+make the work irksome. The great project, which was destined to become
+the crowning achievement of his life, was now gradually assuming more
+definite shape, and absorbing more of his time and energies.
+
+Nevertheless, during all this period, Darwin so far regarded his
+geological pursuits as his PROPER "work," that attention to other
+matters was always spoken of by him as "indulging in idleness." If at
+the end of this period the world had sustained the great misfortune of
+losing Darwin by death before the age of forty--and several times that
+event seemed only too probable--he might have been remembered only as
+a very able geologist of most advanced views, and a traveller who had
+written a scientific narrative of more than ordinary excellence!
+
+The completion of the "Geology of the 'Beagle'" and the preparation of
+a revised narrative of the voyage mark the termination of that period of
+fifteen years of Darwin's life during which geological studies were
+his principal occupation. Henceforth, though his interest in geological
+questions remained ever keen, biological problems engaged more and more
+of his attention to the partial exclusion of geology.
+
+The eight years from October, 1846, to October, 1854, were mainly
+devoted to the preparation of his two important monographs on the recent
+and fossil Cirripedia. Apart from the value of his description of the
+fossil forms, this work of Darwin's had an important influence on the
+progress of geological science. Up to that time a practice had prevailed
+for the student of a particular geological formation to take up the
+description of the plant and animal remains in it--often without
+having anything more than a rudimentary knowledge of the living forms
+corresponding to them. Darwin in his monograph gave a very admirable
+illustration of the enormous advantage to be gained--alike for biology
+and geology--by undertaking the study of the living and fossil forms
+of a natural group of organisms in connection with one another. Of the
+advantage of these eight years of work to Darwin himself, in preparing
+for the great task lying before him, Huxley has expressed a very strong
+opinion indeed. ("L.L." II. pages 247-48.)
+
+But during these eight years of "species work," Darwin found
+opportunities for not a few excursions into the field of geology. He
+occasionally attended the Geological Society, and, as we have already
+seen, read several papers there during this period. His friend, Dr
+Hooker, then acting as botanist to the Geological Survey, was engaged
+in studying the Carboniferous flora, and many discussions on Palaezoic
+plants and on the origin of coal took place at this period. On this last
+subject he felt the deepest interest and told Hooker, "I shall never
+rest easy in Down churchyard without the problem be solved by some one
+before I die." ("M.L." I. pages 63, 64.)
+
+As at all times, conversations and letters with Lyell on every branch of
+geological science continued with unabated vigour, and in spite of the
+absorbing character of the work on the Cirripedes, time was found for
+all. In 1849 his friend Herschel induced him to supply a chapter of
+forty pages on Geology to the Admiralty "Manual of Scientific Inquiry"
+which he was editing. This is Darwin's single contribution to books of
+an "educational" kind. It is remarkable for its clearness and simplicity
+and attention to minute details. It may be read by the student of
+Darwin's life with much interest, for the directions he gives to an
+explorer are without doubt those which he, as a self-taught geologist,
+proved to be serviceable during his life on the "Beagle".
+
+On the completion of the Cirripede volumes, in 1854, Darwin was able to
+grapple with the immense pile of MS. notes which he had accumulated
+on the species question. The first sketch of 35 pages (1842), had been
+enlarged in 1844 into one of 230 pages ([The first draft of the "Origin"
+is being prepared for Press by Mr Francis Darwin and will be published
+by the Cambridge University Press this year (1909). A.C.S.]); but in
+1856 was commenced the work (never to be completed) which was designed
+on a scale three or four times more extensive than that on which the
+"Origin of Species" was in the end written.
+
+In drawing up those two masterly chapters of the "Origin", "On
+the Imperfection of the Geological Record," and "On the Geological
+Succession of Organic Beings", Darwin had need of all the experience and
+knowledge he had been gathering during thirty years, the first half
+of which had been almost wholly devoted to geological study. The most
+enlightened geologists of the day found much that was new, and still
+more that was startling from the manner of its presentation, in these
+wonderful essays. Of Darwin's own sense of the importance of the
+geological evidence in any presentation of his theory a striking proof
+will be found in a passage of the touching letter to his wife, enjoining
+the publication of his sketch of 1844. "In case of my sudden death,"
+he wrote, "... the editor must be a geologist as well as a naturalist."
+("L.L." II. pages 16, 17.)
+
+In spite of the numerous and valuable palaeontological discoveries made
+since the publication of "The Origin of Species", the importance of the
+first of these two geological chapters is as great as ever. It still
+remains true that "Those who believe that the geological record is in
+any degree perfect, will at once reject the theory"--as indeed they must
+reject any theory of evolution. The striking passage with which Darwin
+concludes this chapter--in which he compares the record of the rocks
+to the much mutilated volumes of a human history--remains as apt an
+illustration as it did when first written.
+
+And the second geological chapter, on the Succession of Organic
+Beings--though it has been strengthened in a thousand ways, by the
+discoveries concerning the pedigrees of the horse, the elephant and
+many other aberrant types, though new light has been thrown even on the
+origin of great groups like the mammals, and the gymnosperms, though
+not a few fresh links have been discovered in the chains of evidence,
+concerning the order of appearance of new forms of life--we would
+not wish to have re-written. Only the same line of argument could be
+adopted, though with innumerable fresh illustrations. Those who reject
+the reasonings of this chapter, neither would they be persuaded if a
+long and complete succession of "ancestral forms" could rise from the
+dead and pass in procession before them.
+
+Among the geological discussions, which so frequently occupied Darwin's
+attention during the later years of his life, there was one concerning
+which his attitude seemed somewhat remarkable--I allude to his views
+on "the permanence of Continents and Ocean-basins." In a letter to Mr
+Mellard Reade, written at the end of 1880, he wrote: "On the whole, I
+lean to the side that the continents have since Cambrian times occupied
+approximately their present positions. But, as I have said, the question
+seems a difficult one, and the more it is discussed the better." ("M.L."
+II. page 147.) Since this was written, the important contribution to the
+subject by the late Dr W.T. Blanford (himself, like Darwin, a naturalist
+and geologist) has appeared in an address to the Geological Society in
+1890; and many discoveries, like that of Dr Woolnough in Fiji, have
+led to considerable qualifications of the generalisation that all the
+islands in the great ocean are wholly of volcanic or coral origin.
+
+I remember once expressing surprise to Darwin that, after the views
+which he had originated concerning the existence of areas of elevation
+and others of subsidence in the Pacific Ocean, and in face of the
+admitted difficulty of accounting for the distribution of certain
+terrestrial animals and plants, if the land and sea areas had been
+permanent in position, he still maintained that theory. Looking at me
+with a whimsical smile, he said: "I have seen many of my old friends
+make fools of themselves, by putting forward new theoretical views or
+revising old ones, AFTER THEY WERE SIXTY YEARS OF AGE; so, long ago,
+I determined that on reaching that age I would write nothing more of a
+speculative character."
+
+Though Darwin's letters and conversations on geology during these later
+years were the chief manifestations of the interest he preserved in his
+"old love," as he continued to call it, yet in the sunset of that active
+life a gleam of the old enthusiasm for geology broke forth once more.
+There can be no doubt that Darwin's inability to occupy himself with
+field-work proved an insuperable difficulty to any attempt on his part
+to resume active geological research. But, as is shown by the series of
+charming volumes on plant-life, Darwin had found compensation in making
+patient and persevering experiment take the place of enterprising and
+exact observation; and there was one direction in which he could indulge
+the "old love" by employment of the new faculty.
+
+We have seen that the earliest memoir written by Darwin, which was
+published in full, was a paper "On the Formation of Mould" which was
+read at the Geological Society on November 1st, 1837, but did not appear
+in the "Transactions" of the Society till 1840, where it occupied four
+and a half quarto pages, including some supplementary matter, obtained
+later, and a woodcut. This little paper was confined to observations
+made in his uncle's fields in Staffordshire, where burnt clay, cinders,
+and sand were found to be buried under a layer of black earth, evidently
+brought from below by earthworms, and to a recital of similar facts from
+Scotland obtained through the agency of Lyell. The subsequent history
+of Darwin's work on this question affords a striking example of the
+tenacity of purpose with which he continued his enquiries on any subject
+that interested him.
+
+In 1842, as soon as he was settled at Down, he began a series of
+observations on a foot-path and in his fields, that continued with
+intermissions during his whole life, and he extended his enquiries from
+time to time to the neighbouring parks of Knole and Holwood. In 1844
+we find him making a communication to the "Gardener's Chronicle" on the
+subject. About 1870, his attention to the question was stimulated by the
+circumstance that his niece (Miss L. Wedgwood) undertook to collect and
+weigh the worm-casts thrown up, during a whole year, on measured
+squares selected for the purpose, at Leith Hill Place. He also obtained
+information from Professor Ramsay concerning observations made by him on
+a pavement near his house in 1871. Darwin at this time began to realise
+the great importance of the action of worms to the archaeologist. At
+an earlier date he appears to have obtained some information concerning
+articles found buried on the battle-field of Shrewsbury, and the old
+Roman town of Uriconium, near his early home; between 1871 and 1878 Mr
+(afterwards Lord) Farrer carried on a series of investigations at the
+Roman Villa discovered on his land at Abinger; Darwin's son William
+examined for his father the evidence at Beaulieu Abbey, Brading,
+Stonehenge and other localities in the neighbourhood of his home; his
+sons Francis and Horace were enlisted to make similar enquiries at
+Chideock and Silchester; while Francis Galton contributed facts noticed
+in his walks in Hyde Park. By correspondence with Fritz Muller and Dr
+Ernst, Darwin obtained information concerning the worm-casts found in
+South America; from Dr Kreft those of Australia; and from Mr Scott
+and Dr (afterwards Sir George) King, those of India; the last-named
+correspondent also supplied him with much valuable information obtained
+in the South of Europe. Help too was obtained from the memoirs on
+Earthworms published by Perrier in 1874 and van Hensen in 1877, while
+Professor Ray Lankester supplied important facts with regard to their
+anatomy.
+
+When therefore the series of interesting monographs on plant-life had
+been completed, Darwin set to work in bringing the information that he
+had gradually accumulated during forty-four years to bear on the subject
+of his early paper. He also utilised the skill and ingenuity he had
+acquired in botanical work to aid in the elucidation of many of the
+difficulties that presented themselves. I well remember a visit which
+I paid to Down at this period. At the side of the little study stood
+flower-pots containing earth with worms, and, without interrupting
+our conversation, Darwin would from time to time lift the glass plate
+covering a pot to watch what was going on. Occasionally, with a humorous
+smile, he would murmur something about a book in another room, and slip
+away; returning shortly, without the book but with unmistakeable signs
+of having visited the snuff-jar outside. After working about a year at
+the worms, he was able at the end of 1881 to publish the charming little
+book--"The Formation of Vegetable Mould through the Action of Worms,
+with Observations on their Habits". This was the last of his books, and
+its reception by reviewers and the public alike afforded the patient old
+worker no little gratification. Darwin's scientific career, which had
+begun with geological research, most appropriately ended with a return
+to it.
+
+It has been impossible to sketch the origin and influence of Darwin's
+geological work without, at almost every step, referring to the part
+played by Lyell and the "Principles of Geology". Haeckel, in the
+chapters on Lyell and Darwin in his "History of Creation", and Huxley in
+his striking essay "On the Reception of the Origin of Species" ("L.L."
+II. pages 179-204.) have both strongly insisted on the fact that the
+"Origin" of Darwin was a necessary corollary to the "Principles" of
+Lyell.
+
+It is true that, in an earlier essay, Huxley had spoken of the doctrine
+of Uniformitarianism as being, in a certain sense, opposed to that of
+Evolution (Huxley's Address to the Geological Society, 1869. "Collected
+Essays", Vol. VIII. page 305, London, 1896.); but in his later years he
+took up a very different and more logical position, and maintained
+that "Consistent uniformitarianism postulates evolution as much in the
+organic as in the inorganic world. The origin of a new species by other
+than ordinary agencies would be a vastly greater 'catastrophe' than
+any of those which Lyell success fully eliminated from sober geological
+speculation." ("L.L." II. page 190.)
+
+Huxley's admiration for the "Principles of Geology", and his conviction
+of the greatness of the revolution of thought brought about by Lyell,
+was almost as marked as in the case of Darwin himself. (See his Essay
+on "Science and Pseudo Science". "Collected Essays", Vol. V. page 90,
+London, 1902.) He felt, however, as many others have done, that in one
+respect the very success of Lyell's masterpiece has been the reason why
+its originality and influence have not been so fully recognised as they
+deserved to be. Written as the book was before its author had arrived at
+the age of thirty, no less than eleven editions of the "Principles"
+were called for in his lifetime. With the most scrupulous care, Lyell,
+devoting all his time and energies to the task of collecting and sifting
+all evidence bearing on the subjects of his work, revised and re-revised
+it; and as in each edition, eliminations, modifications, corrections,
+and additions were made, the book, while it increased in value as a
+storehouse of facts, lost much of its freshness, vigour and charm as a
+piece of connected reasoning.
+
+Darwin undoubtedly realised this when he wrote concerning the
+"Principles", "the first edition, my old true love, which I never
+deserted for the later editions." ("M.L." II. page 222.) Huxley once
+told me that when, in later life, he read the first edition, he was both
+surprised and delighted, feeling as if it were a new book to him. (I
+have before me a letter which illustrates this feeling on Huxley's
+part. He had lamented to me that he did not possess a copy of the first
+edition of the "Principles", when, shortly afterwards, I picked up a
+dilapidated copy on a bookstall; this I had bound and sent to my old
+teacher and colleague. His reply is characteristic:
+
+October 8, 1884.
+
+My Dear Judd,
+
+You could not have made me a more agreeable present than the copy of the
+first edition of Lyell, which I find on my table. I have never been able
+to meet with the book, and your copy is, as the old woman said of her
+Bible, "the best of books in the best of bindings."
+
+Ever yours sincerely,
+
+T.H. Huxley.
+
+(I cannot refrain from relating an incident which very strikingly
+exemplifies the affection for one another felt by Lyell and Huxley. In
+his last illness, when confined to his bed, Lyell heard that Huxley was
+to lecture at the Royal Institution on the "Results of the 'Challenger'
+expedition": he begged me to attend the lecture and bring him an account
+of it. Happening to mention this to Huxley, he at once undertook to
+go to Lyell in my place, and he did so on the morning following his
+lecture. I shall never forget the look of gratitude on the face of the
+invalid when he told me, shortly afterwards, how Huxley had sat by his
+bedside and "repeated the whole lecture to him.")
+
+Darwin's generous nature seems often to have made him experience a fear
+lest he should do less than justice to his "dear old master," and to the
+influence that the "Principles of Geology" had in moulding his mind. In
+1845 he wrote to Lyell, "I have long wished, not so much for your sake,
+as for my own feelings of honesty, to acknowledge more plainly than by
+mere reference, how much I geologically owe you. Those authors, however,
+who like you, educate people's minds as well as teach them special
+facts, can never, I should think, have full justice done them except by
+posterity, for the mind thus insensibly improved can hardly perceive
+its own upward ascent." ("L.L." I. pages 337-8.) In another letter, to
+Leonard Horner, he says: "I always feel as if my books came half out of
+Lyell's brain, and that I never acknowledge this sufficiently." ("M.L."
+II. page 117.) Darwin's own most favourite book, the "Narrative of the
+Voyage", was dedicated to Lyell in glowing terms; and in the "Origin of
+Species" he wrote of "Lyell's grand work on the "Principles of
+Geology", which the future historian will recognise as having produced a
+revolution in Natural Science." "What glorious good that work has done"
+he fervently exclaims on another occasion. ("L.L." I. page 342.)
+
+To the very end of his life, as all who were in the habit of talking
+with Darwin can testify, this sense of his indebtedness to Lyell
+remained with him. In his "Autobiography", written in 1876, the year
+after Lyell's death, he spoke in the warmest terms of the value to him
+of the "Principles" while on the voyage and of the aid afforded to him
+by Lyell on his return to England. ("L.L." I. page 62.) But the year
+before his own death, Darwin felt constrained to return to the subject
+and to place on record a final appreciation--one as honourable to the
+writer as it is to his lost friend:
+
+"I saw more of Lyell than of any other man, both before and after
+my marriage. His mind was characterised, as it appeared to me, by
+clearness, caution, sound judgment, and a good deal of originality. When
+I made any remark to him on Geology, he never rested until he saw the
+whole case clearly, and often made me see it more clearly than I had
+done before. He would advance all possible objections to my suggestion,
+and even after these were exhausted would remain long dubious. A second
+characteristic was his hearty sympathy with the work of other scientific
+men... His delight in science was ardent, and he felt the
+keenest interest in the future progress of mankind. He was very
+kind-hearted... His candour was highly remarkable. He exhibited this by
+becoming a convert to the Descent theory, though he had gained much fame
+by opposing Lamarck's views, and this after he had grown old."
+
+"THE SCIENCE OF GEOLOGY IS ENORMOUSLY INDEBTED TO LYELL--MORE SO, AS I
+BELIEVE, THAN TO ANY OTHER MAN WHO EVER LIVED." ("L.L." I. pages 71-2
+(the italics are mine.))
+
+Those who knew Lyell intimately will recognise the truth of the portrait
+drawn by his dearest friend, and I believe that posterity will endorse
+Darwin's deliberate verdict concerning the value of his labours.
+
+It was my own good fortune, to be brought into close contact with these
+two great men during the later years of their life, and I may perhaps be
+permitted to put on record the impressions made upon me during friendly
+intercourse with both.
+
+In some respects, there was an extraordinary resemblance in their modes
+and habits of thought, between Lyell and Darwin; and this likeness was
+also seen in their modesty, their deference to the opinion of younger
+men, their enthusiasm for science, their freedom from petty jealousies
+and their righteous indignation for what was mean and unworthy in
+others. But yet there was a difference. Both Lyell and Darwin were
+cautious, but perhaps Lyell carried his caution to the verge of
+timidity. I think Darwin possessed, and Lyell lacked, what I can only
+describe by the theological term, "faith--the substance of things hoped
+for, the evidence of things not seen." Both had been constrained to feel
+that the immutability of species could not be maintained. Both,
+too, recognised the fact that it would be useless to proclaim this
+conviction, unless prepared with a satisfactory alternative to what
+Huxley called "the Miltonic hypothesis." But Darwin's conviction was so
+far vital and operative that it sustained him while working unceasingly
+for twenty-two years in collecting evidence bearing on the question,
+till at last he was in the position of being able to justify that
+conviction to others.
+
+And yet Lyell's attitude--and that of Hooker, which was very
+similar--proved of inestimable service to science, as Darwin often
+acknowledged. One of the greatest merits of the "Origin of Species" is
+that so many difficulties and objections are anticipated and fairly met;
+and this was to a great extent the result of the persistent and very
+candid--if always friendly--criticism of Lyell and Hooker.
+
+I think the divergence of mental attitude in Lyell and Darwin must
+be attributed to a difference in temperament, the evidence of which
+sometimes appears in a very striking manner in their correspondence.
+Thus in 1838, while they were in the thick of the fight with
+the Catastrophists of the Geological Society, Lyell wrote
+characteristically: "I really find, when bringing up my Preliminary
+Essays in "Principles" to the science of the present day, so far as I
+know it, that the great outline, and even most of the details, stand
+so uninjured, and in many cases they are so much strengthened by new
+discoveries, especially by yours, that we may begin to hope that
+the great principles there insisted on will stand the test of new
+discoveries." (Lyell's "Life, Letters and Journals", Vol. II. page 44.)
+To which the more youthful and impetuous Darwin replies: "BEGIN TO HOPE:
+why the POSSIBILITY of a doubt has never crossed my mind for many a day.
+This may be very unphilosophical, but my geological salvation is staked
+on it... it makes me quite indignant that you should talk of HOPING."
+("L.L." I. page 296.)
+
+It was not only Darwin's "geological salvation" that was at stake, when
+he surrendered himself to his enthusiasm for an idea. To his firm faith
+in the doctrine of continuity we owe the "Origin of Species"; and while
+Darwin became the "Paul" of evolution, Lyell long remained the "doubting
+Thomas."
+
+Many must have felt like H.C. Watson when he wrote: "How could Sir
+C. Lyell... for thirty years read, write, and think, on the subject of
+species AND THEIR SUCCESSION, and yet constantly look down the wrong
+road!" ("L.L." II. page 227.) Huxley attributed this hesitation of Lyell
+to his "profound antipathy" to the doctrine of the "pithecoid origin of
+man." ("L.L." II. page 193.) Without denying that this had considerable
+influence (and those who knew Lyell and his great devotion to his wife
+and her memory, are aware that he and she felt much stronger convictions
+concerning such subjects as the immortality of the soul than Darwin
+was able to confess to) yet I think Darwin had divined the real
+characteristics of his friend's mind, when he wrote: "He would advance
+all possible objections... AND EVEN AFTER THESE WERE EXHAUSTED, WOULD
+REMAIN LONG DUBIOUS."
+
+Very touching indeed was the friendship maintained to the end between
+these two leaders of thought--free as their intercourse was from any
+smallest trace of self-seeking or jealousy. When in 1874 I spent some
+time with Lyell in his Forfarshire home, a communication from Darwin was
+always an event which made a "red-letter day," as Lyell used to say;
+and he gave me many indications in his conversation of how strongly he
+relied upon the opinion of Darwin--more indeed than on the judgment
+of any other man--this confidence not being confined to questions of
+science, but extending to those of morals, politics, and religion.
+
+I have heard those who knew Lyell only slightly, speak of his manners
+as cold and reserved. His complete absorption in his scientific work,
+coupled with extreme short-sightedness, almost in the end amounting to
+blindness, may have permitted those having but a casual acquaintance
+with him to accept such a view. But those privileged to know him
+intimately recognised the nobleness of his character and can realise
+the justice and force of Hooker's words when he heard of his death: "My
+loved, my best friend, for well nigh forty years of my life. The most
+generous sharer of my own and my family's hopes, joys and sorrows, whose
+affection for me was truly that of a father and brother combined."
+
+But the strongest of all testimonies to the grandeur of Lyell's
+character is the lifelong devotion to him of such a man as Darwin.
+Before the two met, we find Darwin constantly writing of facts and
+observations that he thinks "will interest Mr Lyell"; and when they came
+together the mutual esteem rapidly ripened into the warmest affection.
+Both having the advantage of a moderate independence, permitting of an
+entire devotion of their lives to scientific research, they had much in
+common, and the elder man--who had already achieved both scientific and
+literary distinction--was able to give good advice and friendly help
+to the younger one. The warmth of their friendship comes out very
+strikingly in their correspondence. When Darwin first conceived the idea
+of writing a book on the "species question," soon after his return from
+the voyage, it was "by following the example of Lyell in Geology" that
+he hoped to succeed ("L.L." I. page 83.); when in 1844, Darwin had
+finished his first sketch of the work, and, fearing that his life might
+not be spared to complete his great undertaking, committed the care of
+it in a touching letter to his wife, it was his friend Lyell whom he
+named as her adviser and the possible editor of the book ("L.L." II.
+pages 17-18.); it was Lyell who, in 1856, induced Darwin to lay the
+foundations of a treatise ("L.L." I. page 84.) for which the author
+himself selected the "Principles" as his model; and when the dilemma
+arose from the receipt of Wallace's essay, it was to Lyell jointly with
+Hooker that Darwin turned, not in vain, for advice and help.
+
+During the later years of his life, I never heard Darwin allude to his
+lost friend--and he did so very often--without coupling his name
+with some term of affection. For a brief period, it is true, Lyell's
+excessive caution when the "Origin" was published, seemed to try even
+the patience of Darwin; but when "the master" was at last able to
+declare himself fully convinced, he was the occasion of more rejoicing
+on the part of Darwin, than any other convert to his views. The latter
+was never tired of talking of Lyell's "magnanimity" and asserted that,
+"To have maintained in the position of a master, one side of a question
+for thirty years, and then deliberately give it up, is a fact to which I
+much doubt whether the records of science offer a parallel." ("L.L." II.
+pages 229-30.)
+
+Of Darwin himself, I can safely affirm that I never knew anyone who
+had met him, even for the briefest period, who was not charmed by his
+personality. Who could forget the hearty hand-grip at meeting, the
+gentle and lingering pressure of the palm at parting, and above all
+that winning smile which transformed his countenance--so as to make
+portraits, and even photographs, seem ever afterwards unsatisfying!
+Looking back, one is indeed tempted to forget the profoundness of the
+philosopher, in recollection of the loveableness of the man.
+
+
+
+
+XIX. DARWIN'S WORK ON THE MOVEMENTS OF PLANTS. By Francis Darwin,
+
+Honorary Fellow of Christ's College, Cambridge.
+
+
+My father's interest in plants was of two kinds, which may be roughly
+distinguished as EVOLUTIONARY and PHYSIOLOGICAL. Thus in his purely
+evolutionary work, for instance in "The Origin of Species" and in his
+book on "Variation under Domestication", plants as well as animals
+served as material for his generalisations. He was largely dependent
+on the work of others for the facts used in the evolutionary work, and
+despised himself for belonging to the "blessed gang" of compilers. And
+he correspondingly rejoiced in the employment of his wonderful power of
+observation in the physiological problems which occupied so much of his
+later life. But inasmuch as he felt evolution to be his life's work, he
+regarded himself as something of an idler in observing climbing plants,
+insectivorous plants, orchids, etc. In this physiological work he was
+to a large extent urged on by his passionate desire to understand the
+machinery of all living things. But though it is true that he worked
+at physiological problems in the naturalist's spirit of curiosity, yet
+there was always present to him the bearing of his facts on the problem
+of evolution. His interests, physiological and evolutionary, were indeed
+so interwoven that they cannot be sharply separated. Thus his original
+interest in the fertilisation of flowers was evolutionary. "I was
+led" ("Life and Letters", I. page 90.), he says, "to attend to the
+cross-fertilisation of flowers by the aid of insects, from having come
+to the conclusion in my speculations on the origin of species, that
+crossing played an important part in keeping specific forms constant."
+In the same way the value of his experimental work on heterostyled
+plants crystalised out in his mind into the conclusion that the product
+of illegitimate unions are equivalent to hybrids--a conclusion of the
+greatest interest from an evolutionary point of view. And again his work
+"Cross and Self Fertilisation" may be condensed to a point of view
+of great importance in reference to the meaning and origin of sexual
+reproduction. (See Professor Goebel's article in the present volume.)
+
+The whole of his physiological work may be looked at as an illustration
+of the potency of his theory as an "instrument for the extension of the
+realm of natural knowledge." (Huxley in Darwin's "Life and Letters." II.
+page 204.)
+
+His doctrine of natural selection gave, as is well known, an impulse
+to the investigation of the use of organs--and thus created the great
+school of what is known in Germany as Biology--a department of science
+for which no English word exists except the rather vague term Natural
+History. This was especially the case in floral biology, and it is
+interesting to see with what hesitation he at first expressed the value
+of his book on Orchids ("Life and Letters", III. page 254.), "It will
+perhaps serve to illustrate how Natural History may be worked under the
+belief of the modification of species" (1861). And in 1862 he speaks
+(Loc. cit.) more definitely of the relation of his work to natural
+selection: "I can show the meaning of some of the apparently meaningless
+ridges (and) horns; who will now venture to say that this or that
+structure is useless?" It is the fashion now to minimise the value of
+this class of work, and we even find it said by a modern writer that to
+inquire into the ends subserved by organs is not a scientific problem.
+Those who take this view surely forget that the structure of all living
+things is, as a whole, adaptive, and that a knowledge of how the
+present forms come to be what they are includes a knowledge of why
+they survived. They forget that the SUMMATION of variations on which
+divergence depends is under the rule of the environment considered as
+a selective force. They forget that the scientific study of the
+interdependence of organisms is only possible through a knowledge of the
+machinery of the units. And that, therefore, the investigation of such
+widely interesting subjects as extinction and distribution must include
+a knowledge of function. It is only those who follow this line of
+work who get to see the importance of minute points of structure and
+understand as my father did even in 1842, as shown in his sketch of the
+"Origin" (Now being prepared for publication.), that every grain of sand
+counts for something in the balance. Much that is confidently stated
+about the uselessness of different organs would never have been
+written if the naturalist spirit were commoner nowadays. This spirit
+is strikingly shown in my father's work on the movements of plants. The
+circumstance that botanists had not, as a class, realised the interest
+of the subject accounts for the fact that he was able to gather such a
+rich harvest of results from such a familiar object as a twining plant.
+The subject had been investigated by H. von Mohl, Palm, and Dutrochet,
+but they failed not only to master the problem but (which here concerns
+us) to give the absorbing interest of Darwin's book to what they
+discovered.
+
+His work on climbing plants was his first sustained piece of work on the
+physiology of movement, and he remarks in 1864: "This has been new sort
+of work for me." ("Life and Letters", III. page 315. He had, however,
+made a beginning on the movements of Drosera.) He goes on to remark with
+something of surprise, "I have been pleased to find what a capital guide
+for observations a full conviction of the change of species is."
+
+It was this point of view that enabled him to develop a broad conception
+of the power of climbing as an adaptation by means of which plants are
+enabled to reach the light. Instead of being compelled to construct a
+stem of sufficient strength to stand alone, they succeed in the struggle
+by making use of other plants as supports. He showed that the great
+class of tendril- and root-climbers which do not depend on twining round
+a pole, like a scarlet-runner, but on attaching themselves as they grow
+upwards, effect an economy. Thus a Phaseolus has to manufacture a stem
+three feet in length to reach a height of two feet above the ground,
+whereas a pea "which had ascended to the same height by the aid of its
+tendrils, was but little longer than the height reached." ("Climbing
+Plants" (2nd edition 1875), page 193.)
+
+Thus he was led on to the belief that TWINING is the more ancient form
+of climbing, and that tendril-climbers have been developed from twiners.
+In accordance with this view we find LEAF-CLIMBERS, which may be looked
+on as incipient tendril-bearers, occurring in the same genera with
+simple twiners. (Loc. cit. page 195.) He called attention to the case
+of Maurandia semperflorens in which the young flower-stalks revolve
+spontaneously and are sensitive to a touch, but neither of these
+qualities is of any perceptible value to the species. This forced him to
+believe that in other young plants the rudiments of the faculty needed
+for twining would be found--a prophecy which he made good in his "Power
+of Movement" many years later.
+
+In "Climbing Plants" he did little more than point out the remarkable
+fact that the habit of climbing is widely scattered through the
+vegetable kingdom. Thus climbers are to be found in 35 out of the 59
+Phanerogamic Alliances of Lindley, so that "the conclusion is forced
+on our minds that the capacity of revolving (If a twining plant, e.g.
+a hop, is observed before it has begun to ascend a pole, it will
+be noticed that, owing to the curvature of the stem, the tip is not
+vertical but hangs over in a roughly horizontal position. If such a
+shoot is watched it will be found that if, for instance, it points
+to the north at a given hour, it will be found after a short interval
+pointing north-east, then east, and after about two hours it will once
+more be looking northward. The curvature of the stem depends on one side
+growing quicker than the opposite side, and the revolving movement,
+i.e. circumnutation, depends on the region of quickest growth creeping
+gradually round the stem from south through west to south again. Other
+plants, e.g. Phaseolus, revolve in the opposite direction.), on which
+most climbers depend, is inherent, though undeveloped, in almost every
+plant in the vegetable kingdom." ("Climbing Plants", page 205.)
+
+In the "Origin" (Edition I. page 427, Edition VI. page 374.) Darwin
+speaks of the "apparent paradox, that the very same characters are
+analogical when one class or order is compared with another, but give
+true affinities when the members of the same class or order are compared
+one with another." In this way we might perhaps say that the climbing
+of an ivy and a hop are analogical; the resemblance depending on the
+adaptive result rather than on community of blood; whereas the relation
+between a leaf-climber and a true tendril-bearer reveals descent. This
+particular resemblance was one in which my father took especial delight.
+He has described an interesting case occurring in the Fumariaceae.
+("Climbing Plants", page 195.) "The terminal leaflets of the
+leaf-climbing Fumaria officinalis are not smaller than the other
+leaflets; those of the leaf-climbing Adlumia cirrhosa are greatly
+reduced; those of Corydalis claviculata (a plant which may be
+indifferently called a leaf-climber or a tendril-bearer) are either
+reduced to microscopical dimensions or have their blades wholly aborted,
+so that this plant is actually in a state of transition; and finally in
+the Dicentra the tendrils are perfectly characterized."
+
+It is a remarkable fact that the quality which, broadly speaking, forms
+the basis of the climbing habit (namely revolving nutation, otherwise
+known as circumnutation) subserves two distinct ends. One of these is
+the finding of a support, and this is common to twiners and tendrils.
+Here the value ends as far as tendril-climbers are concerned, but in
+twiners Darwin believed that the act of climbing round a support is a
+continuation of the revolving movement (circumnutation). If we imagine a
+man swinging a rope round his head and if we suppose the rope to strike
+a vertical post, the free end will twine round it. This may serve as
+a rough model of twining as explained in the "Movements and Habits
+of Climbing Plants". It is on these points--the nature of revolving
+nutation and the mechanism of twining--that modern physiologists differ
+from Darwin. (See the discussion in Pfeffer's "The Physiology of Plants"
+Eng. Tr. (Oxford, 1906), III. page 34, where the literature is given.
+Also Jost, "Vorlesungen uber Pflanzenphysiologie", page 562, Jena,
+1904.)
+
+Their criticism originated in observations made on a revolving shoot
+which is removed from the action of gravity by keeping the plant slowly
+rotating about a horizontal axis by means of the instrument known as a
+klinostat. Under these conditions circumnutation becomes irregular or
+ceases altogether. When the same experiment is made with a plant which
+has twined spirally up a stick, the process of climbing is checked and
+the last few turns become loosened or actually untwisted. From this
+it has been argued that Darwin was wrong in his description of
+circumnutation as an automatic change in the region of quickest growth.
+When the free end of a revolving shoot points towards the north there
+is no doubt that the south side has been elongating more than the north;
+after a time it is plain from the shoot hanging over to the east that
+the west side of the plant has grown most, and so on. This rhythmic
+change of the position of the region of greatest growth Darwin ascribes
+to an unknown internal regulating power. Some modern physiologists,
+however, attempt to explain the revolving movement as due to a
+particular form of sensitiveness to gravitation which it is not
+necessary to discuss in detail in this place. It is sufficient for my
+purpose to point out that Darwin's explanation of circumnutation is
+not universally accepted. Personally I believe that circumnutation is
+automatic--is primarily due to internal stimuli. It is however in some
+way connected with gravitational sensitiveness, since the movement
+normally occurs round a vertical line. It is not unnatural that,
+when the plant has no external stimulus by which the vertical can be
+recognised, the revolving movement should be upset.
+
+Very much the same may be said of the act of twining, namely that most
+physiologists refuse to accept Darwin's view (above referred to) that
+twining is the direct result of circumnutation. Everyone must allow
+that the two phenomena are in some way connected, since a plant
+which circumnutates clockwise, i.e. with the sun, twines in the same
+direction, and vice versa. It must also be granted that geotropism has a
+bearing on the problem, since all plants twine upwards, and cannot twine
+along a horizontal support. But how these two factors are combined, and
+whether any (and if so what) other factors contribute, we cannot say.
+If we give up Darwin's explanation, we must at the same time say with
+Pfeffer that "the causes of twining are... unknown." ("The Physiology of
+Plants", Eng. Tr. (Oxford, 1906), III. page 37.)
+
+Let us leave this difficult question and consider some other points made
+out in the progress of the work on climbing plants. One result of what
+he called his "niggling" ("Life and Letters", III. page 312.) work on
+tendrils was the discovery of the delicacy of their sense of touch, and
+the rapidity of their movement. Thus in a passion-flower tendril, a bit
+of platinum wire weighing 1.2 mg. produced curvature ("Climbing
+Plants", page 171.), as did a loop of cotton weighing 2 mg. Pfeffer
+("Untersuchungen a.d. Bot. Inst. z. Tubingen", Bd. I. 1881-85, page
+506.), however, subsequently found much greater sensitiveness: thus
+the tendril of Sicyos angulatus reacted to 0.00025 mg., but this only
+occurred when the delicate rider of cottonwool fibre was disturbed by
+the wind. The same author expanded and explained in a most interesting
+way the meaning of Darwin's observation that tendrils are not stimulated
+to movement by drops of water resting on them. Pfeffer showed that
+DIRTY water containing minute particles of clay in suspension acts as a
+stimulus. He also showed that gelatine acts like pure water; if a smooth
+glass rod is coated with a 10 per cent solution of gelatine and is then
+applied to a tendril, no movement occurs in spite of the fact that the
+gelatine is solid when cold. Pfeffer ("Physiology", Eng. Tr. III.
+page 52. Pfeffer has pointed out the resemblance between the contact
+irritability of plants and the human sense of touch. Our skin is not
+sensitive to uniform pressure such as is produced when the finger
+is dipped into mercury (Tubingen "Untersuchungen", I. page 504.)
+generalises the result in the statement that the tendril has a special
+form of irritability and only reacts to "differences of pressure or
+variations of pressure in contiguous... regions." Darwin was especially
+interested in such cases of specialised irritability. For instance in
+May, 1864, he wrote to Asa Gray ("Life and Letters", III. page 314.)
+describing the tendrils of Bignonia capreolata, which "abhor a simple
+stick, do not much relish rough bark, but delight in wool or moss."
+He received, from Gray, information as to the natural habitat of the
+species, and finally concluded that the tendrils "are specially adapted
+to climb trees clothed with lichens, mosses, or other such productions."
+("Climbing Plants", page 102.)
+
+Tendrils were not the only instance discovered by Darwin of delicacy
+of touch in plants. In 1860 he had already begun to observe Sundew
+(Drosera), and was full of astonishment at its behaviour. He wrote to
+Sir Joseph Hooker ("Life and Letters", III. page 319.): "I have been
+working like a madman at Drosera. Here is a fact for you which is
+certain as you stand where you are, though you won't believe it, that a
+bit of hair 1/78000 of one grain in weight placed on gland, will cause
+ONE of the gland-bearing hairs of Drosera to curve inwards." Here again
+Pfeffer (Pfeffer in "Untersuchungen a. d. Bot. Inst. z. Tubingen",
+I. page 491.) has, as in so many cases, added important facts to my
+father's observations. He showed that if the leaf of Drosera is entirely
+freed from such vibrations as would reach it if observed on an ordinary
+table, it does not react to small weights, so that in fact it was the
+vibration of the minute fragment of hair on the gland that produced
+movement. We may fancifully see an adaptation to the capture of
+insects--to the dancing of a gnat's foot on the sensitive surface.
+
+Darwin was fond of telling how when he demonstrated the sensitiveness
+of Drosera to Mr Huxley and (I think) to Sir John Burdon Sanderson, he
+could perceive (in spite of their courtesy) that they thought the whole
+thing a delusion. And the story ended with his triumph when Mr Huxley
+cried out, "It IS moving."
+
+Darwin's work on tendrils has led to some interesting investigations on
+the mechanisms by which plants perceive stimuli. Thus Pfeffer (Tubingen
+"Untersuchungen" I. page 524.) showed that certain epidermic cells
+occurring in tendrils are probably organs of touch. In these cells the
+protoplasm burrows as it were into cavities in the thickness of the
+external cell-walls and thus comes close to the surface, being separated
+from an object touching the tendril merely by a very thin layer of
+cell-wall substance. Haberlandt ("Physiologische Pflanzenanatomie",
+Edition III. Leipzig, 1904. "Sinnesorgane im Pflanzenreich", Leipzig,
+1901, and other publications.) has greatly extended our knowledge of
+vegetable structure in relation to mechanical stimulation. He defines a
+sense-organ as a contrivance by which the DEFORMATION or forcible change
+of form in the protoplasm--on which mechanical stimulation depends--is
+rendered rapid and considerable in amplitude ("Sinnesorgane", page 10).
+He has shown that in certain papillose and bristle-like contrivances,
+plants possess such sense-organs; and moreover that these contrivances
+show a remarkable similarity to corresponding sense-organs in animals.
+
+Haberlandt and Nemec ("Ber. d. Deutschen bot. Gesellschaft", XVIII.
+1900. See F. Darwin, Presidential Address to Section K, British
+Association, 1904.) published independently and simultaneously a
+theory of the mechanism by which plants are orientated in relation
+to gravitation. And here again we find an arrangement identical in
+principle with that by which certain animals recognise the vertical,
+namely the pressure of free particles on the irritable wall of a cavity.
+In the higher plants, Nemec and Haberlandt believe that special loose
+and freely movable starch-grains play the part of the otoliths or
+statoliths of the crustacea, while the protoplasm lining the cells in
+which they are contained corresponds to the sensitive membrane lining
+the otocyst of the animal. What is of special interest in our present
+connection is that according to this ingenious theory (The original
+conception was due to Noll ("Heterogene Induction", Leipzig, 1892), but
+his view differed in essential points from those here given.) the
+sense of verticality in a plant is a form of contact-irritability. The
+vertical position is distinguished from the horizontal by the fact that,
+in the latter case, the loose starch-grains rest on the lateral walls
+of the cells instead of on the terminal walls as occurs in the normal
+upright position. It should be added that the statolith theory is
+still sub judice; personally I cannot doubt that it is in the main a
+satisfactory explanation of the facts.
+
+With regard to the RAPIDITY of the reaction of tendrils, Darwin records
+("Climbing Plants", page 155. Others have observed movement after about
+6".) that a Passion-Flower tendril moved distinctly within 25 seconds of
+stimulation. It was this fact, more than any other, that made him doubt
+the current explanation, viz. that the movement is due to unequal
+growth on the two sides of the tendril. The interesting work of Fitting
+(Pringsheim's "Jahrb." XXXVIII. 1903, page 545.) has shown, however,
+that the primary cause is not (as Darwin supposed) contraction on the
+concave, but an astonishingly rapid increase in growth-rate on the
+convex side.
+
+On the last page of "Climbing Plants" Darwin wrote: "It has often been
+vaguely asserted that plants are distinguished from animals by not
+having the power of movement. It should rather be said that plants
+acquire and display this power only when it is of some advantage to
+them."
+
+He gradually came to realise the vividness and variety of vegetable
+life, and that a plant like an animal has capacities of behaving in
+different ways under different circumstances, in a manner that may be
+compared to the instinctive movements of animals. This point of view is
+expressed in well-known passages in the "Power of Movement". ("The Power
+of Movement in Plants", 1880, pages 571-3.) "It is impossible not to be
+struck with the resemblance between the... movements of plants and many
+of the actions performed unconsciously by the lower animals." And
+again, "It is hardly an exaggeration to say that the tip of the
+radicle... having the power of directing the movements of the adjoining
+parts, acts like the brain of one of the lower animals; the brain being
+seated within the anterior end of the body, receiving impressions from
+the sense-organs, and directing the several movements."
+
+The conception of a region of perception distinct from a region of
+movement is perhaps the most fruitful outcome of his work on the
+movements of plants. But many years before its publication, viz. in
+1861, he had made out the wonderful fact that in the Orchid Catasetum
+("Life and Letters", III. page 268.) the projecting organs or antennae
+are sensitive to a touch, and transmit an influence "for more than one
+inch INSTANTANEOUSLY," which leads to the explosion or violent ejection
+of the pollinia. And as we have already seen a similar transmission of
+a stimulus was discovered by him in Sundew in 1860, so that in 1862 he
+could write to Hooker ("Life and Letters", III. page 321.): "I cannot
+avoid the conclusion, that Drosera possesses matter at least in some
+degree analogous in constitution and function to nervous matter." I
+propose in what follows to give some account of the observations on
+the transmission of stimuli given in the "Power of Movement". It is
+impossible within the space at my command to give anything like a
+complete account of the matter, and I must necessarily omit all mention
+of much interesting work. One well-known experiment consisted in putting
+opaque caps on the tips of seedling grasses (e.g. oat and canary-grass)
+and then exposing them to light from one side. The difference, in the
+amount of curvature towards the light, between the blinded and
+unblinded specimens, was so great that it was concluded that the
+light-sensitiveness resided exclusively in the tip. The experiment
+undoubtedly proves that the sensitiveness is much greater in the tip
+than elsewhere, and that there is a transmission of stimulus from the
+tip to the region of curvature. But Rothert (Rothert, Cohn's "Beitrage",
+VII. 1894.) has conclusively proved that the basal part where the
+curvature occurs is also DIRECTLY sensitive to light. He has shown,
+however, that in other grasses (Setaria, Panicum) the cotyledon is the
+only part which is sensitive, while the hypocotyl, where the movement
+occurs, is not directly sensitive.
+
+It was however the question of the localisation of the gravitational
+sense in the tip of the seedling root or radicle that aroused most
+attention, and it was on this question that a controversy arose which
+has continued to the present day.
+
+The experiment on which Darwin's conclusion was based consisted simply
+in cutting off the tip, and then comparing the behaviour of roots so
+treated with that of normal specimens. An uninjured root when placed
+horizontally regains the vertical by means of a sharp downward
+curve; not so a decapitated root which continues to grow more or less
+horizontally. It was argued that this depends on the loss of an organ
+specialised for the perception of gravity, and residing in the tip of
+the root; and the experiment (together with certain important variants)
+was claimed as evidence of the existence of such an organ.
+
+It was at once objected that the amputation of the tip might check
+curvature by interfering with longitudinal growth, on the distribution
+of which curvature depends. This objection was met by showing that an
+injury, e.g. splitting the root longitudinally (See F. Darwin, "Linnean
+Soc. Journal (Bot)." XIX. 1882, page 218.), which does not remove the
+tip, but seriously checks growth, does not prevent geotropism. This
+was of some interest in another and more general way, in showing that
+curvature and longitudinal growth must be placed in different categories
+as regards the conditions on which they depend.
+
+Another objection of a much more serious kind was that the amputation
+of the tip acts as a shock. It was shown by Rothert (See his excellent
+summary of the subject in "Flora" 1894 (Erganzungsband), page 199.) that
+the removal of a small part of the cotyledon of Setaria prevents the
+plant curving towards the light, and here there is no question of
+removing the sense-organ since the greater part of the sensitive
+cotyledon is intact. In view of this result it was impossible to rely on
+the amputations performed on roots as above described.
+
+At this juncture a new and brilliant method originated in Pfeffer's
+laboratory. (See Pfeffer, "Annals of Botany", VIII. 1894, page 317, and
+Czapek, Pringsheim's "Jahrb." XXVII. 1895, page 243.) Pfeffer and Czapek
+showed that it is possible to bend the root of a lupine so that, for
+instance, the supposed sense-organ at the tip is vertical while the
+motile region is horizontal. If the motile region is directly sensitive
+to gravity the root ought to curve downwards, but this did not occur: on
+the contrary it continued to grow horizontally. This is precisely what
+should happen if Darwin's theory is the right one: for if the tip is
+kept vertical, the sense-organ is in its normal position and receives no
+stimulus from gravitation, and therefore can obviously transmit none to
+the region of curvature. Unfortunately this method did not convince the
+botanical world because some of those who repeated Czapek's experiment
+failed to get his results.
+
+Czapek ("Berichte d. Deutsch. bot. Ges." XV. 1897, page 516, and
+numerous subsequent papers. English readers should consult Czapek in the
+"Annals of Botany", XIX. 1905, page 75.) has devised another interesting
+method which throws light on the problem. He shows that roots, which
+have been placed in a horizontal position and have therefore been
+geotropically stimulated, can be distinguished by a chemical test from
+vertical, i.e. unstimulated roots. The chemical change in the root can
+be detected before any curvature has occurred and must therefore be a
+symptom of stimulation, not of movement. It is particularly interesting
+to find that the change in the root, on which Czapek's test depends,
+takes place in the tip, i.e. in the region which Darwin held to be the
+centre for gravitational sensitiveness.
+
+In 1899 I devised a method (F. Darwin, "Annals of Botany", XIII. 1899,
+page 567.) by which I sought to prove that the cotyledon of Setaria is
+not only the organ for light-perception, but also for gravitation. If
+a seedling is supported horizontally by pushing the apical part
+(cotyledon) into a horizontal tube, the cotyledon will, according to
+my supposition, be stimulated gravitationally and a stimulus will be
+transmitted to the basal part of the stem (hypocotyl) causing it to
+bend. But this curvature merely raises the basal end of the seedling,
+the sensitive cotyledon remains horizontal, imprisoned in its tube; it
+will therefore be continually stimulated and will continue to transmit
+influences to the bending region, which should therefore curl up into a
+helix or corkscrew-like form,--and this is precisely what occurred.
+
+I have referred to this work principally because the same method was
+applied to roots by Massart (Massart, "Mem. Couronnes Acad. R. Belg."
+LXII. 1902.) and myself (F. Darwin, "Linnean Soc. Journ." XXXV. 1902,
+page 266.) with a similar though less striking result. Although these
+researches confirmed Darwin's work on roots, much stress cannot be laid
+on them as there are several objections to them, and they are not easily
+repeated.
+
+The method which--as far as we can judge at present--seems likely
+to solve the problem of the root-tip is most ingenious and is due to
+Piccard. (Pringsheim's "Jahrb." XL. 1904, page 94.)
+
+Andrew Knight's celebrated experiment showed that roots react to
+centrifugal force precisely as they do to gravity. So that if a bean
+root is fixed to a wheel revolving rapidly on a horizontal axis, it
+tends to curve away from the centre in the line of a radius of the
+wheel. In ordinary demonstrations of Knight's experiment the seed is
+generally fixed so that the root is at right angles to a radius, and as
+far as convenient from the centre of rotation. Piccard's experiment is
+arranged differently. (A seed is depicted below a horizontal dotted
+line AA, projecting a root upwards.) The root is oblique to the axis
+of rotation, and the extreme tip projects beyond that axis. Line AA
+represents the axis of rotation, T is the tip of the root just above the
+line AA, and B is the region just below line AA in which curvature takes
+place. If the motile region B is directly sensitive to gravitation (and
+is the only part which is sensitive) the root will curve (down and away
+from the vertical) away from the axis of rotation, just as in Knight's
+experiment. But if the tip T is alone sensitive to gravitation the
+result will be exactly reversed, the stimulus originating in T and
+conveyed to B will produce curvature (up towards the vertical). We may
+think of the line AA as a plane dividing two worlds. In the lower one
+gravity is of the earthly type and is shown by bodies falling and roots
+curving downwards: in the upper world bodies fall upwards and roots
+curve in the same direction. The seedling is in the lower world, but its
+tip containing the supposed sense-organ is in the strange world where
+roots curve upwards. By observing whether the root bends up or down we
+can decide whether the impulse to bend originates in the tip or in the
+motile region.
+
+Piccard's results showed that both curvatures occurred and he
+concluded that the sensitive region is not confined to the tip. (Czapek
+(Pringsheim's "Jahrb." XXXV. 1900, page 362) had previously given
+reasons for believing that, in the root, there is no sharp line of
+separation between the regions of perception and movement.)
+
+Haberlandt (Pringsheim's "Jahrb." XLV. 1908, page 575.) has recently
+repeated the experiment with the advantage of better apparatus and more
+experience in dealing with plants, and has found as Piccard did that
+both the tip and the curving region are sensitive to gravity, but with
+the important addition that the sensitiveness of the tip is much greater
+than that of the motile region. The case is in fact similar to that of
+the oat and canary-grass. In both instances my father and I were wrong
+in assuming that the sensitiveness is confined to the tip, yet there
+is a concentration of irritability in that region and transmission of
+stimulus is as true for geotropism as it is for heliotropism. Thus after
+nearly thirty years the controversy of the root-tip has apparently ended
+somewhat after the fashion of the quarrels at the "Rainbow" in
+"Silas Marner"--"you're both right and you're both wrong." But the
+"brain-function" of the root-tip at which eminent people laughed in
+early days turns out to be an important part of the truth. (By using
+Piccard's method I have succeeded in showing that the gravitational
+sensitiveness of the cotyledon of Sorghum is certainly much greater than
+the sensitiveness of the hypocotyl--if indeed any such sensitiveness
+exists. See Wiesner's "Festschrift", Vienna, 1908.)
+
+Another observation of Darwin's has given rise to much controversy.
+("Power of Movement", page 133.) If a minute piece of card is fixed
+obliquely to the tip of a root some influence is transmitted to the
+region of curvature and the root bends away from the side to which
+the card was attached. It was thought at the time that this proved the
+root-tip to be sensitive to contact, but this is not necessarily the
+case. It seems possible that the curvature is a reaction to the injury
+caused by the alcoholic solution of shellac with which the cards were
+cemented to the tip. This agrees with the fact given in the "Power of
+Movement" that injuring the root-tip on one side, by cutting or burning
+it, induced a similar curvature. On the other hand it was shown that
+curvature could be produced in roots by cementing cards, not to the
+naked surface of the root-tip, but to pieces of gold-beaters skin
+applied to the root; gold-beaters skin being by itself almost without
+effect. But it must be allowed that, as regards touch, it is not clear
+how the addition of shellac and card can increase the degree of contact.
+There is however some evidence that very close contact from a solid
+body, such as a curved fragment of glass, produces curvature: and this
+may conceivably be the explanation of the effect of gold-beaters skin
+covered with shellac. But on the whole it is perhaps safer to classify
+the shellac experiments with the results of undoubted injury rather than
+with those of contact.
+
+Another subject on which a good deal of labour was expended is the sleep
+of leaves, or as Darwin called it their NYCTITROPIC movement. He showed
+for the first time how widely spread this phenomenon is, and attempted
+to give an explanation of the use to the plant of the power of sleeping.
+His theory was that by becoming more or less vertical at night the
+leaves escape the chilling effect of radiation. Our method of testing
+this view was to fix some of the leaves of a sleeping plant so that they
+remained horizontal at night and therefore fully exposed to radiation,
+while their fellows were partly protected by assuming the nocturnal
+position. The experiments showed clearly that the horizontal leaves were
+more injured than the sleeping, i.e. more or less vertical, ones. It may
+be objected that the danger from cold is very slight in warm countries
+where sleeping plants abound. But it is quite possible that a lowering
+of the temperature which produces no visible injury may nevertheless
+be hurtful by checking the nutritive processes (e.g. translocation of
+carbohydrates), which go on at night. Stahl ("Bot. Zeitung", 1897, page
+81.) however has ingeniously suggested that the exposure of the leaves
+to radiation is not DIRECTLY hurtful because it lowers the temperature
+of the leaf, but INDIRECTLY because it leads to the deposition of dew on
+the leaf-surface. He gives reasons for believing that dew-covered leaves
+are unable to transpire efficiently, and that the absorption of mineral
+food-material is correspondingly checked. Stahl's theory is in no way
+destructive of Darwin's, and it is possible that nyctitropic leaves are
+adapted to avoid the indirect as well as the direct results of cooling
+by radiation.
+
+In what has been said I have attempted to give an idea of some of the
+discoveries brought before the world in the "Power of Movement" (In 1881
+Professor Wiesner published his "Das Bewegungsvermogen der Pflanzen",
+a book devoted to the criticism of "The Power of Movement in Plants". A
+letter to Wiesner, published in "Life and Letters", III. page 336, shows
+Darwin's warm appreciation of his critic's work, and of the spirit in
+which it is written.) and of the subsequent history of the problems.
+We must now pass on to a consideration of the central thesis of the
+book,--the relation of circumnutation to the adaptive curvatures of
+plants.
+
+Darwin's view is plainly stated on pages 3-4 of the "Power of Movement".
+Speaking of circumnutation he says, "In this universally present
+movement we have the basis or groundwork for the acquirement, according
+to the requirements of the plant, of the most diversified movements."
+He then points out that curvatures such as those towards the light or
+towards the centre of the earth can be shown to be exaggerations of
+circumnutation in the given directions. He finally points out that
+the difficulty of conceiving how the capacities of bending in definite
+directions were acquired is diminished by his conception. "We know that
+there is always movement in progress, and its amplitude, or direction,
+or both, have only to be modified for the good of the plant in relation
+with internal or external stimuli."
+
+It may at once be allowed that the view here given has not been accepted
+by physiologists. The bare fact that circumnutation is a general
+property of plants (other than climbing species) is not generally
+rejected. But the botanical world is no nearer to believing in the
+theory of reaction built on it.
+
+If we compare the movements of plants with those of the lower animals we
+find a certain resemblance between the two. According to Jennings (H.S.
+Jennings, "The Behavior of the Lower Animals". Columbia U. Press, N.Y.
+1906.) a Paramoecium constantly tends to swerve towards the aboral side
+of its body owing to certain peculiarities in the set and power of
+its cilia. But the tendency to swim in a circle, thus produced, is
+neutralised by the rotation of the creature about its longitudinal
+axis. Thus the direction of the swerves IN RELATION TO THE PATH of the
+organism is always changing, with the result that the creature moves in
+what approximates to a straight line, being however actually a spiral
+about the general line of progress. This method of motion is strikingly
+like the circumnutation of a plant, the apex of which also describes a
+spiral about the general line of growth. A rooted plant obviously cannot
+rotate on its axis, but the regular series of curvatures of which its
+growth consists correspond to the aberrations of Paramoecium distributed
+regularly about its course by means of rotation. (In my address to the
+Biological Section of the British Association at Cardiff (1891) I
+have attempted to show the connection between circumnutation and
+RECTIPETALITY, i.e. the innate capacity of growing in a straight line.)
+Just as a plant changes its direction of growth by an exaggeration of
+one of the curvature-elements of which circumnutation consists, so
+does a Paramoecium change its course by the accentuation of one of
+the deviations of which its path is built. Jennings has shown that the
+infusoria, etc., react to stimuli by what is known as the "method of
+trial." If an organism swims into a region where the temperature is too
+high or where an injurious substance is present, it changes its course.
+It then moves forward again, and if it is fortunate enough to escape the
+influence, it continues to swim in the given direction. If however its
+change of direction leads it further into the heated or poisonous region
+it repeats the movement until it emerges from its difficulties. Jennings
+finds in the movements of the lower organisms an analogue with what
+is known as pain in conscious organisms. There is certainly this much
+resemblance that a number of quite different sub-injurious agencies
+produce in the lower organisms a form of reaction by the help of which
+they, in a partly fortuitous way, escape from the threatening element
+in their environment. The higher animals are stimulated in a parallel
+manner to vague and originally purposeless movements, one of which
+removes the discomfort under which they suffer, and the organism finally
+learns to perform the appropriate movement without going through the
+tentative series of actions.
+
+I am tempted to recognise in circumnutation a similar groundwork of
+tentative movements out of which the adaptive ones were originally
+selected by a process rudely representative of learning by experience.
+
+It is, however, simpler to confine ourselves to the assumption that
+those plants have survived which have acquired through unknown causes
+the power of reacting in appropriate ways to the external stimuli of
+light, gravity, etc. It is quite possible to conceive this occurring in
+plants which have no power of circumnutating--and, as already pointed
+out, physiologists do as a fact neglect circumnutation as a factor in
+the evolution of movements. Whatever may be the fate of Darwin's theory
+of circumnutation there is no doubt that the research he carried out
+in support of, and by the light of, this hypothesis has had a powerful
+influence in guiding the modern theories of the behaviour of plants.
+Pfeffer ("The Physiology of Plants", Eng. Tr. III. page 11.), who more
+than any one man has impressed on the world a rational view of the
+reactions of plants, has acknowledged in generous words the great value
+of Darwin's work in the same direction. The older view was that, for
+instance, curvature towards the light is the direct mechanical result of
+the difference of illumination on the lighted and shaded surfaces of the
+plant. This has been proved to be an incorrect explanation of the
+fact, and Darwin by his work on the transmission of stimuli has greatly
+contributed to the current belief that stimuli act indirectly. Thus we
+now believe that in a root and a stem the mechanism for the perception
+of gravitation is identical, but the resulting movements are different
+because the motor-irritabilities are dissimilar in the two cases. We
+must come back, in fact, to Darwin's comparison of plants to animals.
+In both there is perceptive machinery by which they are made delicately
+alive to their environment, in both the existing survivors are those
+whose internal constitution has enabled them to respond in a beneficial
+way to the disturbance originating in their sense-organs.
+
+
+
+
+XX. THE BIOLOGY OF FLOWERS. By K. Goebel, Ph.D.
+
+Professor of Botany in the University of Munich.
+
+
+There is scarcely any subject to which Darwin devoted so much time and
+work as to his researches into the biology of flowers, or, in other
+words, to the consideration of the question to what extent the
+structural and physiological characters of flowers are correlated with
+their function of producing fruits and seeds. We know from his own words
+what fascination these studies possessed for him. We repeatedly find,
+for example, in his letters expressions such as this:--"Nothing in my
+life has ever interested me more than the fertilisation of such plants
+as Primula and Lythrum, or again Anacamptis or Listera." ("More Letters
+of Charles Darwin", Vol. II. page 419.)
+
+Expressions of this kind coming from a man whose theories exerted an
+epoch-making influence, would be unintelligible if his researches into
+the biology of flowers had been concerned only with records of isolated
+facts, however interesting these might be. We may at once take it
+for granted that the investigations were undertaken with the view of
+following up important problems of general interest, problems which are
+briefly dealt with in this essay.
+
+Darwin published the results of his researches in several papers and in
+three larger works, (i) "On the various contrivances by which British
+and Foreign Orchids are fertilised by insects" (First edition, London,
+1862; second edition, 1877; popular edition, 1904.) (ii) "The effects of
+Cross and Self fertilisation in the vegetable kingdom" (First edition,
+1876; second edition, 1878). (iii) "The different forms of Flowers on
+plants of the same species" (First edition, 1877; second edition, 1880).
+
+Although the influence of his work is considered later, we may here
+point out that it was almost without a parallel; not only does it
+include a mass of purely scientific observations, but it awakened
+interest in very wide circles, as is shown by the fact that we find the
+results of Darwin's investigations in floral biology universally quoted
+in school books; they are even willingly accepted by those who, as
+regards other questions, are opposed to Darwin's views.
+
+The works which we have mentioned are, however, not only of special
+interest because of the facts they contribute, but because of the MANNER
+in which the facts are expressed. A superficial reader seeking merely
+for catch-words will, for instance, probably find the book on cross and
+self-fertilisation rather dry because of the numerous details which
+it contains: it is, indeed, not easy to compress into a few words the
+general conclusions of this volume. But on closer examination, we cannot
+be sufficiently grateful to the author for the exactness and objectivity
+with which he enables us to participate in the scheme of his researches.
+He never tries to persuade us, but only to convince us that his
+conclusions are based on facts; he always gives prominence to such facts
+as appear to be in opposition to his opinions,--a feature of his work in
+accordance with a maxim which he laid down:--"It is a golden rule,
+which I try to follow, to put every fact which is opposed to one's
+preconceived opinion in the strongest light." ("More Letters", Vol. II.
+page 324.)
+
+The result of this method of presentation is that the works mentioned
+above represent a collection of most valuable documents even for those
+who feel impelled to draw from the data other conclusions than those of
+the author. Each investigation is the outcome of a definite question, a
+"preconceived opinion," which is either supported by the facts or
+must be abandoned. "How odd it is that anyone should not see that all
+observation must be for or against some view if it is to be of any
+service!" (Ibid. Vol. I. page 195.)
+
+The points of view which Darwin had before him were principally the
+following. In the first place the proof that a large number of the
+peculiarities in the structure of flowers are not useless, but of the
+greatest significance in pollination must be of considerable importance
+for the interpretation of adaptations; "The use of each trifling detail
+of structure is far from a barren search to those who believe in natural
+selection." ("Fertilisation of Orchids" (1st edition), page 351; (2nd
+edition 1904) page 286.) Further, if these structural relations are
+shown to be useful, they may have been acquired because from the many
+variations which have occurred along different lines, those have been
+preserved by natural selection "which are beneficial to the organism
+under the complex and ever-varying conditions of life." (Ibid. page
+351.) But in the case of flowers there is not only the question of
+adaptation to fertilisation to be considered. Darwin, indeed,
+soon formed the opinion which he has expressed in the following
+sentence,--"From my own observations on plants, guided to a certain
+extent by the experience of the breeders of animals, I became convinced
+many years ago that it is a general law of nature that flowers are
+adapted to be crossed, at least occasionally, by pollen from a distinct
+plant." ("Cross and Self fertilisation" (1st edition), page 6.)
+
+The experience of animal breeders pointed to the conclusion that
+continual in-breeding is injurious. If this is correct, it raises the
+question whether the same conclusion holds for plants. As most flowers
+are hermaphrodite, plants afford much more favourable material than
+animals for an experimental solution of the question, what results
+follow from the union of nearly related sexual cells as compared with
+those obtained by the introduction of new blood. The answer to this
+question must, moreover, possess the greatest significance for the
+correct understanding of sexual reproduction in general.
+
+We see, therefore, that the problems which Darwin had before him in his
+researches into the biology of flowers were of the greatest importance,
+and at the same time that the point of view from which he attacked the
+problems was essentially a teleological one.
+
+We may next inquire in what condition he found the biology of flowers at
+the time of his first researches, which were undertaken about the year
+1838. In his autobiography he writes,--"During the summer of 1839,
+and, I believe, during the previous summer, I was led to attend to the
+cross-fertilisation of flowers by the aid of insects, from having come
+to the conclusion in my speculations on the origin of species, that
+crossing played an important part in keeping specific forms constant."
+("The Life and Letters of Charles Darwin", Vol. I. page 90, London,
+1888.) In 1841 he became acquainted with Sprengel's work: his researches
+into the biology of flowers were thus continued for about forty years.
+
+It is obvious that there could only be a biology of flowers after it had
+been demonstrated that the formation of seeds and fruit in the flower
+is dependent on pollination and subsequent fertilisation. This proof
+was supplied at the end of the seventeenth century by R.J. Camerarius
+(1665-1721). He showed that normally seeds and fruits are developed only
+when the pollen reaches the stigma. The manner in which this happens was
+first thoroughly investigated by J.G. Kolreuter (1733-1806 (Kolreuter,
+"Vorlaufige Nachricht von einigen das Geschlecht der Planzen
+betreffenden Versuchen und Beobachtungen", Leipzig, 1761; with three
+supplements, 1763-66. Also, "Mem. de l'acad. St Petersbourg", Vol. XV.
+1809.)), the same observer to whom we owe the earliest experiments in
+hybridisation of real scientific interest. Kolreuter mentioned that
+pollen may be carried from one flower to another partly by wind and
+partly by insects. But he held the view, and that was, indeed, the
+natural assumption, that self-fertilisation usually occurs in a flower,
+in other words that the pollen of a flower reaches the stigma of
+the same flower. He demonstrated, however, certain cases in which
+cross-pollination occurs, that is in which the pollen of another flower
+of the same species is conveyed to the stigma. He was familiar with the
+phenomenon, exhibited by numerous flowers, to which Sprengel afterwards
+applied the term Dichogamy, expressing the fact that the anthers and
+stigmas of a flower often ripen at different times, a peculiarity
+which is now recognised as one of the commonest means of ensuring
+cross-pollination.
+
+With far greater thoroughness and with astonishing power of observation
+C.K. Sprengel (1750-1816) investigated the conditions of pollination of
+flowers. Darwin was introduced by that eminent botanist Robert Brown to
+Sprengel's then but little appreciated work,--"Das entdeckte Geheimniss
+der Natur im Bau und in der Befruchtung der Blumen" (Berlin, 1793); this
+is by no means the least service to Botany rendered by Robert Brown.
+
+Sprengel proceeded from a naive teleological point of view. He firmly
+believed "that the wise Author of nature had not created a single hair
+without a definite purpose." He succeeded in demonstrating a number of
+beautiful adaptations in flowers for ensuring pollination; but his work
+exercised but little influence on his contemporaries and indeed for a
+long time after his death. It was through Darwin that Sprengel's work
+first achieved a well deserved though belated fame. Even such botanists
+as concerned themselves with researches into the biology of flowers
+appear to have formerly attached much less value to Sprengel's work
+than it has received since Darwin's time. In illustration of this we may
+quote C.F. Gartner whose name is rightly held in the highest esteem as
+that of one of the most eminent hybridologists. In his work "Versuche
+und Beobachtungen uder die Befruchtungsorgane der vollkommeneren
+Gewachse und uber die naturliche und kunstliche Befruchtung durch den
+eigenen Pollen" he also deals with flower-pollination. He recognised the
+action of the wind, but he believed, in spite of the fact that he
+both knew and quoted Kolreuter and Sprengel, that while insects assist
+pollination, they do so only occasionally, and he held that insects are
+responsible for the conveyance of pollen; thorough investigations
+would show "that a very small proportion of the plants included in this
+category require this assistance in their native habitat." (Gartner,
+"Versucher und Beobachtungen... ", page 335, Stuttgart, 1844.) In the
+majority of plants self-pollination occurs.
+
+Seeing that even investigators who had worked for several decades at
+fertilisation-phenomena had not advanced the biology of flowers beyond
+the initial stage, we cannot be surprised that other botanists followed
+to even a less extent the lines laid down by Kolreuter and Sprengel.
+This was in part the result of Sprengel's supernatural teleology and in
+part due to the fact that his book appeared at a time when other lines
+of inquiry exerted a dominating influence.
+
+At the hands of Linnaeus systematic botany reached a vigorous
+development, and at the beginning of the nineteenth century the anatomy
+and physiology of plants grew from small beginnings to a flourishing
+branch of science. Those who concerned themselves with flowers
+endeavoured to investigate their development and structure or the most
+minute phenomena connected with fertilisation and the formation of the
+embryo. No room was left for the extension of the biology of flowers on
+the lines marked out by Kolreuter and Sprengel. Darwin was the first to
+give new life and a deeper significance to this subject, chiefly
+because he took as his starting-point the above-mentioned problems, the
+importance of which is at once admitted by all naturalists.
+
+The further development of floral biology by Darwin is in the first
+place closely connected with the book on the fertilisation of Orchids.
+It is noteworthy that the title includes the sentence,--"and on the good
+effects of intercrossing."
+
+The purpose of the book is clearly stated in the introduction:--"The
+object of the following work is to show that the contrivances by which
+Orchids are fertilised, are as varied and almost as perfect as any of
+the most beautiful adaptations in the animal kingdom; and, secondly,
+to show that these contrivances have for their main object the
+fertilisation of each flower by the pollen of another flower."
+("Fertilisation of Orchids", page 1.) Orchids constituted a particularly
+suitable family for such researches. Their flowers exhibit a striking
+wealth of forms; the question, therefore, whether the great variety
+in floral structure bears any relation to fertilisation (In the older
+botanical literature the word fertilisation is usually employed in cases
+where POLLINATION is really in question: as Darwin used it in this sense
+it is so used here.) must in this case possess special interest.
+
+Darwin succeeded in showing that in most of the orchids examined
+self-fertilisation is either an impossibility, or, under natural
+conditions, occurs only exceptionally. On the other hand these plants
+present a series of extraordinarily beautiful and remarkable adaptations
+which ensure the transference of pollen by insects from one flower to
+another. It is impossible to describe adequately in a few words the
+wealth of facts contained in the Orchid book. A few examples may,
+however, be quoted in illustration of the delicacy of the observations
+and of the perspicuity employed in interpreting the facts.
+
+The majority of orchids differ from other seed plants (with the
+exception of the Asclepiads) in having no dust-like pollen. The pollen,
+or more correctly, the pollen-tetrads, remain fastened together as
+club-shaped pollinia usually borne on a slender pedicel. At the base of
+the pedicel is a small viscid disc by which the pollinium is attached
+to the head or proboscis of one of the insects which visit the flower.
+Darwin demonstrated that in Orchis and other flowers the pedicel of
+the pollinium, after its removal from the anther, undergoes a curving
+movement. If the pollinium was originally vertical, after a time it
+assumed a horizontal position. In the latter position, if the insect
+visited another flower, the pollinium would exactly hit the sticky
+stigmatic surface and thus effect fertilisation. The relation between
+the behaviour of the viscid disc and the secretion of nectar by the
+flower is especially remarkable. The flowers possess a spur which in
+some species (e.g. Gymnadenia conopsea, Platanthera bifolia, etc.)
+contains honey (nectar), which serves as an attractive bait for insects,
+but in others (e.g. our native species of Orchis) the spur is empty.
+Darwin held the opinion, confirmed by later investigations, that in the
+case of flowers without honey the insects must penetrate the wall of the
+nectarless spurs in order to obtain a nectar-like substance. The glands
+behave differently in the nectar-bearing and in the nectarless flowers.
+In the former they are so sticky that they at once adhere to the body of
+the insect; in the nectarless flowers firm adherence only occurs after
+the viscid disc has hardened. It is, therefore, adaptively of value
+that the insects should be detained longer in the nectarless flowers (by
+having to bore into the spur),--than in flowers in which the nectar is
+freely exposed. "If this relation, on the one hand, between the viscid
+matter requiring some little time to set hard, and the nectar being so
+lodged that moths are delayed in getting it; and, on the other hand,
+between the viscid matter being at first as viscid as ever it will
+become, and the nectar lying all ready for rapid suction, be accidental,
+it is a fortunate accident for the plant. If not accidental, and I
+cannot believe it to be accidental, what a singular case of adaptation!"
+("Fertilisation of Orchids" (1st edition), page 53.)
+
+Among exotic orchids Catasetum is particularly remarkable. One and the
+same species bears different forms of flowers. The species known as
+Catasetum tridentatum has pollinia with very large viscid discs;
+on touching one of the two filaments (antennae) which occur on the
+gynostemium of the flower the pollinia are shot out to a fairly long
+distance (as far as 1 metre) and in such manner that they alight on the
+back of the insect, where they are held. The antennae have, moreover,
+acquired an importance, from the point of view of the physiology of
+stimulation, as stimulus-perceiving organs. Darwin had shown that it is
+only a touch on the antennae that causes the explosion, while contact,
+blows, wounding, etc. on other places produce no effect. This form of
+flower proved to be the male. The second form, formerly regarded as
+a distinct species and named Monachanthus viridis, is shown to be the
+female flower. The anthers have only rudimentary pollinia and do not
+open; there are no antennae, but on the other hand numerous seeds
+are produced. Another type of flower, known as Myanthus barbatus, was
+regarded by Darwin as a third form: this was afterwards recognised
+by Rolfe (Rolfe, R.A. "On the sexual forms of Catasetum with special
+reference to the researches of Darwin and others," "Journ. Linn. Soc."
+Vol. XXVII. (Botany), 1891, pages 206-225.) as the male flower
+of another species, Catasetum barbatum Link, an identification in
+accordance with the discovery made by Cruger in Trinidad that it always
+remains sterile.
+
+Darwin had noticed that the flowers of Catasetum do not secrete nectar,
+and he conjectured that in place of it the insects gnaw a tissue in
+the cavity of the labellum which has a "slightly sweet, pleasant and
+nutritious taste." This conjecture as well as other conclusions drawn by
+Darwin from Catasetum have been confirmed by Cruger--assuredly the best
+proof of the acumen with which the wonderful floral structure of this
+"most remarkable of the Orchids" was interpretated far from its native
+habitat.
+
+As is shown by what we have said about Catasetum, other problems in
+addition to those concerned with fertilisation are dealt with in the
+Orchid book. This is especially the case in regard to flower morphology.
+The scope of flower morphology cannot be more clearly and better
+expressed than by these words: "He will see how curiously a flower may
+be moulded out of many separate organs--how perfect the cohesion of
+primordially distinct parts may become,--how organs may be used for
+purposes widely different from their proper function,--how other organs
+may be entirely suppressed, or leave mere useless emblems of their
+former existence." ("Fertilisation of Orchids", page 289.)
+
+In attempting, from this point of view, to refer the floral structure
+of orchids to their original form, Darwin employed a much more thorough
+method than that of Robert Brown and others. The result of this was the
+production of a considerable literature, especially in France, along
+the lines suggested by Darwin's work. This is the so-called anatomical
+method, which seeks to draw conclusions as to the morphology of the
+flower from the course of the vascular bundles in the several parts. (He
+wrote in one of his letters, "... the destiny of the whole human race is
+as nothing to the course of vessels of orchids" ("More Letters", Vol.
+II. page 275.) Although the interpretation of the orchid flower given
+by Darwin has not proved satisfactory in one particular point--the
+composition of the labellum--the general results have received universal
+assent, namely "that all Orchids owe what they have in common to descent
+from some monocotyledonous plant, which, like so many other plants of
+the same division, possessed fifteen organs arranged alternately three
+within three in five whorls." ("Fertilisation of Orchids" (1st edition),
+page 307.) The alterations which their original form has undergone have
+persisted so far as they were found to be of use.
+
+We see also that the remarkable adaptations of which we have given some
+examples are directed towards cross-fertilisation. In only a few of
+the orchids investigated by Darwin--other similar cases have since been
+described--was self-fertilisation found to occur regularly or usually.
+The former is the case in the Bee Ophrys (Ophrys apifera), the mechanism
+of which greatly surprised Darwin. He once remarked to a friend that one
+of the things that made him wish to live a few thousand years was his
+desire to see the extinction of the Bee Ophrys, an end to which he
+believed its self-fertilising habit was leading. ("Life and Letters",
+Vol. III. page 276 (footnote).) But, he wrote, "the safest conclusion,
+as it seems to me, is, that under certain unknown circumstances, and
+perhaps at very long intervals of time, one individual of the Bee Ophrys
+is crossed by another." ("Fertilisation of Orchids" page 71.)
+
+If, on the one hand, we remember how much more sure self-fertilisation
+would be than cross-fertilisation, and, on the other hand, if we call to
+mind the numerous contrivances for cross-fertilisation, the
+conclusion is naturally reached that "it is an astonishing fact that
+self-fertilisation should not have been an habitual occurrence. It
+apparently demonstrates to us that there must be something injurious in
+the process. Nature thus tells us, in the most emphatic manner, that she
+abhors perpetual self-fertilisation... For may we not further infer as
+probable, in accordance with the belief of the vast majority of the
+breeders of our domestic productions, that marriage between near
+relations is likewise in some way injurious, that some unknown great
+good is derived from the union of individuals which have been kept
+distinct for many generations?" (Ibid., page 359.)
+
+This view was supported by observations on plants of other families,
+e.g. Papilionaceae; it could, however, in the absence of experimental
+proof, be regarded only as a "working hypothesis."
+
+All adaptations to cross-pollination might also be of use simply because
+they made pollination possible when for any reason self-pollination had
+become difficult or impossible. Cross-pollination would, therefore, be
+of use, not as such, but merely as a means of pollination in general;
+it would to some extent serve as a remedy for a method unsuitable in
+itself, such as a modification standing in the way of self-pollination,
+and on the other hand as a means of increasing the chance of pollination
+in the case of flowers in which self-pollination was possible, but which
+might, in accidental circumstances, be prevented. It was, therefore,
+very important to obtain experimental proof of the conclusion to which
+Darwin was led by the belief of the majority of breeders and by the
+evidence of the widespread occurrence of cross-pollination and of the
+remarkable adaptations thereto.
+
+This was supplied by the researches which are described in the two other
+works named above. The researches on which the conclusions rest had, in
+part at least, been previously published in separate papers: this is the
+case as regards the heterostyled plants. The discoveries which Darwin
+made in the course of his investigations of these plants belong to the
+most brilliant in biological science.
+
+The case of Primula is now well known. C.K. Sprengel and others were
+familiar with the remarkable fact that different individuals of the
+European species of Primula bear differently constructed flowers; some
+plants possess flowers in which the styles project beyond the stamens
+attached to the corolla-tube (long-styled form), while in others the
+stamens are inserted above the stigma which is borne on a short style
+(short-styled form). It has been shown by Breitenbach that both forms of
+flower may occur on the same plant, though this happens very rarely. An
+analogous case is occasionally met with in hybrids, which bear flowers
+of different colour on the same plant (e.g. Dianthus caryophyllus).
+Darwin showed that the external differences are correlated with others
+in the structure of the stigma and in the nature of the pollen.
+The long-styled flowers have a spherical stigma provided with large
+stigmatic papillae; the pollen grains are oblong and smaller than those
+of the short-styled flowers. The number of the seeds produced is smaller
+and the ovules larger, probably also fewer in number. The short-styled
+flowers have a smooth compressed stigma and a corolla of somewhat
+different form; they produce a greater number of seeds.
+
+These different forms of flowers were regarded as merely a case of
+variation, until Darwin showed "that these heterostyled plants are
+adapted for reciprocal fertilisation; so that the two or three forms,
+though all are hermaphrodites, are related to one another almost
+like the males and females of ordinary unisexual animals." ("Forms
+of Flowers" (1st edition), page 2.) We have here an example of
+hermaphrodite flowers which are sexually different. There are essential
+differences in the manner in which fertilisation occurs. This may
+be effected in four different ways; there are two legitimate and two
+illegitimate types of fertilisation. The fertilisation is legitimate
+if pollen from the long-styled flowers reaches the stigma of the
+short-styled form or if pollen of the short-styled flowers is brought
+to the stigma of the long-styled flower, that is the organs of the
+same length of the two different kinds of flower react on one
+another. Illegitimate fertilisation is represented by the two kinds of
+self-fertilisation, also by cross-fertilisation, in which the pollen of
+the long-styled form reaches the stigma of the same type of flower and,
+similarly, by cross-pollination in the case of the short-styled flowers.
+
+The applicability of the terms legitimate and illegitimate depends, on
+the one hand, upon the fact that insects which visit the different forms
+of flowers pollinate them in the manner suggested; the pollen of the
+short-styled flowers adhere to that part of the insect's body which
+touches the stigma of the long-styled flower and vice versa. On the
+other hand, it is based also on the fact that experiment shows that
+artificial pollination produces a very different result according as
+this is legitimate or illegitimate; only the legitimate union ensures
+complete fertility, the plants thus produced being stronger than those
+which are produced illegitimately.
+
+If we take 100 as the number of flowers which produce seeds as the
+result of legitimate fertilisation, we obtain the following numbers from
+illegitimate fertilisation:
+
+Primula officinalis (P. veris) (Cowslip)... 69 Primula elatior
+(Oxlip).................... 27 Primula acaulis (P. vulgaris)
+(Primrose)... 60
+
+Further, the plants produced by the illegitimate method of fertilisation
+showed, e.g. in P. officinalis, a decrease in fertility in later
+generations, sterile pollen and in the open a feebler growth. (Under
+very favourable conditions (in a greenhouse) the fertility of the plants
+of the fourth generation increases--a point, which in view of various
+theoretical questions, deserves further investigation.) They behave in
+fact precisely in the same way as hybrids between species of different
+genera. This result is important, "for we thus learn that the difficulty
+in sexually uniting two organic forms and the sterility of their
+offspring, afford no sure criterion of so-called specific distinctness"
+("Forms of Flowers", page 242): the relative or absolute sterility
+of the illegitimate unions and that of their illegitimate descendants
+depend exclusively on the nature of the sexual elements and on their
+inability to combine in a particular manner. This functional difference
+of sexual cells is characteristic of the behaviour of hybrids as of the
+illegitimate unions of heterostyled plants. The agreement becomes
+even closer if we regard the Primula plants bearing different forms of
+flowers not as belonging to a systematic entity or "species," but as
+including several elementary species. The legitimately produced plants
+are thus true hybrids (When Darwin wrote in reference to the different
+forms of heterostyled plants, "which all belong to the same species
+as certainly as do the two sexes of the same species" ("Cross and
+Self fertilisation", page 466), he adopted the term species in a
+comprehensive sense. The recent researches of Bateson and Gregory ("On
+the inheritance of Heterostylism in Primula"; "Proc. Roy. Soc." Ser. B,
+Vol. LXXVI. 1905, page 581) appear to me also to support the view that
+the results of illegitimate crossing of heterostyled Primulas correspond
+with those of hybridisation. The fact that legitimate pollen effects
+fertilisation, even if illegitimate pollen reaches the stigma a short
+time previously, also points to this conclusion. Self-pollination in the
+case of the short-styled form, for example, is not excluded. In spite
+of this, the numerical proportion of the two forms obtained in the open
+remains approximately the same as when the pollination was exclusively
+legitimate, presumably because legitimate pollen is prepotent.), with
+which their behaviour in other respects, as Darwin showed, presents so
+close an agreement. This view receives support also from the fact that
+descendants of a flower fertilised illegitimately by pollen from another
+plant with the same form of flower belong, with few exceptions, to the
+same type as that of their parents. The two forms of flower, however,
+behave differently in this respect. Among 162 seedlings of the
+long-styled illegitimately pollinated plants of Primula officinalis,
+including five generations, there were 156 long-styled and only six
+short-styled forms, while as the result of legitimate fertilisation
+nearly half of the offspring were long-styled and half short-styled. The
+short-styled illegitimately pollinated form gave five long-styled
+and nine short-styled; the cause of this difference requires further
+explanation. The significance of heterostyly, whether or not we now
+regard it as an arrangement for the normal production of hybrids, is
+comprehensively expressed by Darwin: "We may feel sure that plants have
+been rendered heterostyled to ensure cross-fertilisation, for we now
+know that a cross between the distinct individuals of the same species
+is highly important for the vigour and fertility of the offspring."
+("Forms of Flowers", page 258.) If we remember how important the
+interpretation of heterostyly has become in all general problems as,
+for example, those connected with the conditions of the formation of
+hybrids, a fact which was formerly overlooked, we can appreciate how
+Darwin was able to say in his autobiography: "I do not think anything in
+my scientific life has given me so much satisfaction as making out the
+meaning of the structure of these plants." ("Life and Letters", Vol. I.
+page 91.)
+
+The remarkable conditions represented in plants with three kinds of
+flowers, such as Lythrum and Oxalis, agree in essentials with those
+in Primula. These cannot be considered in detail here; it need only be
+noted that the investigation of these cases was still more laborious.
+In order to establish the relative fertility of the different unions in
+Lythrum salicaria 223 different fertilisations were made, each flower
+being deprived of its male organs and then dusted with the appropriate
+pollen.
+
+In the book containing the account of heterostyled plants other
+species are dealt with which, in addition to flowers opening normally
+(chasmogamous), also possess flowers which remain closed but are capable
+of producing fruit. These cleistogamous flowers afford a striking
+example of habitual self-pollination, and H. von Mohl drew special
+attention to them as such shortly after the appearance of Darwin's
+Orchid book. If it were only a question of producing seed in the
+simplest way, cleistogamous flowers would be the most conveniently
+constructed. The corolla and frequently other parts of the flower are
+reduced; the development of the seed may, therefore, be accomplished
+with a smaller expenditure of building material than in chasmogamous
+flowers; there is also no loss of pollen, and thus a smaller amount
+suffices for fertilisation.
+
+Almost all these plants, as Darwin pointed out, have also chasmogamous
+flowers which render cross-fertilisation possible. His view that
+cleistogamous flowers are derived from originally chasmogamous flowers
+has been confirmed by more recent researches. Conditions of nutrition in
+the broader sense are the factors which determine whether chasmogamous
+or cleistogamous flowers are produced, assuming, of course, that the
+plants in question have the power of developing both forms of flower.
+The former may fail to appear for some time, but are eventually
+developed under favourable conditions of nourishment. The belief of many
+authors that there are plants with only cleistogamous flowers cannot
+therefore be accepted as authoritative without thorough experimental
+proof, as we are concerned with extra-european plants for which it is
+often difficult to provide appropriate conditions in cultivation.
+
+Darwin sees in cleistogamous flowers an adaptation to a good supply of
+seeds with a small expenditure of material, while chasmogamous flowers
+of the same species are usually cross-fertilised and "their offspring
+will thus be invigorated, as we may infer from a wide-spread analogy."
+("Forms of Flowers" (1st edition), page 341.) Direct proof in support of
+this has hitherto been supplied in a few cases only; we shall often
+find that the example set by Darwin in solving such problems as these by
+laborious experiment has unfortunately been little imitated.
+
+Another chapter of this book treats of the distribution of the sexes in
+polygamous, dioecious, and gyno-dioecious plants (the last term, now in
+common use, we owe to Darwin). It contains a number of important facts
+and discussions and has inspired the experimental researches of Correns
+and others.
+
+The most important of Darwin's work on floral biology is, however, that
+on cross and self-fertilisation, chiefly because it states the results
+of experimental investigations extending over many years. Only
+such experiments, as we have pointed out, could determine whether
+cross-fertilisation is in itself beneficial, and self-fertilisation
+on the other hand injurious; a conclusion which a merely comparative
+examination of pollination-mechanisms renders in the highest degree
+probable. Later floral biologists have unfortunately almost entirely
+confined themselves to observations on floral mechanisms. But there is
+little more to be gained by this kind of work than an assumption
+long ago made by C.K. Sprengel that "very many flowers have the sexes
+separate and probably at least as many hermaphrodite flowers are
+dichogamous; it would thus appear that Nature was unwilling that any
+flower should be fertilised by its own pollen."
+
+It was an accidental observation which inspired Darwin's experiments on
+the effect of cross and self-fertilisation. Plants of Linaria vulgaris
+were grown in two adjacent beds; in the one were plants produced by
+cross-fertilisation, that is, from seeds obtained after fertilisation
+by pollen of another plant of the same species; in the other grew plants
+produced by self-fertilisation, that is from seed produced as the result
+of pollination of the same flower. The first were obviously superior to
+the latter.
+
+Darwin was surprised by this observation, as he had expected a
+prejudicial influence of self-fertilisation to manifest itself after
+a series of generations: "I always supposed until lately that no
+evil effects would be visible until after several generations of
+self-fertilisation, but now I see that one generation sometimes suffices
+and the existence of dimorphic plants and all the wonderful contrivances
+of orchids are quite intelligible to me." ("More Letters", Vol. II. page
+373.)
+
+The observations on Linaria and the investigations of the results of
+legitimate and illegitimate fertilisation in heterostyled plants were
+apparently the beginning of a long series of experiments. These were
+concerned with plants of different families and led to results which are
+of fundamental importance for a true explanation of sexual reproduction.
+
+The experiments were so arranged that plants were shielded from
+insect-visits by a net. Some flowers were then pollinated with their own
+pollen, others with pollen from another plant of the same species. The
+seeds were germinated on moist sand; two seedlings of the same age, one
+from a cross and the other from a self-fertilised flower, were selected
+and planted on opposite sides of the same pot. They grew therefore under
+identical external conditions; it was thus possible to compare their
+peculiarities such as height, weight, fruiting capacity, etc. In other
+cases the seedlings were placed near to one another in the open and in
+this way their capacity of resisting unfavourable external conditions
+was tested. The experiments were in some cases continued to the tenth
+generation and the flowers were crossed in different ways. We see,
+therefore, that this book also represents an enormous amount of most
+careful and patient original work.
+
+The general result obtained is that plants produced as the result of
+cross-fertilisation are superior, in the majority of cases, to those
+produced as the result of self-fertilisation, in height, resistance to
+external injurious influences, and in seed-production.
+
+Ipomoea purpurea may be quoted as an example. If we express the result
+of cross-fertilisation by 100, we obtain the following numbers for the
+fertilised plants.
+
+     Generation.   Height.    Number of seeds.
+
+     1             100: 76   100: 64
+     2             100: 79   -
+     3             100: 68   100: 94
+     4             100: 86   100: 94
+     5             100: 75   100: 89
+     6             100: 72   -
+     7             100: 81   -
+     8             100: 85   -
+     9             100: 79   100: 26 (Number of capsules)
+     10            100: 54   -
+
+
+Taking the average, the ratio as regards growth is 100:77. The
+considerable superiority of the crossed plants is apparent in the first
+generation and is not increased in the following generations; but there
+is some fluctuation about the average ratio. The numbers representing
+the fertility of crossed and self-fertilised plants are more difficult
+to compare with accuracy; the superiority of the crossed plants is
+chiefly explained by the fact that they produce a much larger number
+of capsules, not because there are on the average more seeds in each
+capsule. The ratio of the capsules was, e.g. in the third generation,
+100:38, that of the seeds in the capsules 100:94. It is also especially
+noteworthy that in the self-fertilised plants the anthers were smaller
+and contained a smaller amount of pollen, and in the eighth generation
+the reduced fertility showed itself in a form which is often found in
+hybrids, that is the first flowers were sterile. (Complete sterility was
+not found in any of the plants investigated by Darwin. Others appear
+to be more sensitive; Cluer found Zea Mais "almost sterile" after three
+generations of self-fertilisation. (Cf. Fruwirth, "Die Zuchtung der
+Landwirtschaftlichen Kulturpflanzen", Berlin, 1904, II. page 6.))
+
+The superiority of crossed individuals is not exhibited in the same
+way in all plants. For example in Eschscholzia californica the crossed
+seedlings do not exceed the self-fertilised in height and vigour,
+but the crossing considerably increases the plant's capacity for
+flower-production, and the seedlings from such a mother-plant are more
+fertile.
+
+The conception implied by the term crossing requires a closer analysis.
+As in the majority of plants, a large number of flowers are in bloom
+at the same time on one and the same plant, it follows that insects
+visiting the flowers often carry pollen from one flower to another of
+the same stock. Has this method, which is spoken of as Geitonogamy, the
+same influence as crossing with pollen from another plant? The results
+of Darwin's experiments with different plants (Ipomoea purpurea,
+Digitalis purpurea, Mimulus luteus, Pelargonium, Origanum) were not in
+complete agreement; but on the whole they pointed to the conclusion that
+Geitonogamy shows no superiority over self-fertilisation (Autogamy).
+(Similarly crossing in the case of flowers of Pelargonium zonale, which
+belong to plants raised from cuttings from the same parent, shows no
+superiority over self-fertilisation.) Darwin, however, considered it
+possible that this may sometimes be the case. "The sexual elements
+in the flowers on the same plant can rarely have been differentiated,
+though this is possible, as flower-buds are in one sense distinct
+individuals, sometimes varying and differing from one another in
+structure or constitution." ("Cross and Self fertilisation" (1st
+edition), page 444.)
+
+As regards the importance of this question from the point of view of
+the significance of cross-fertilisation in general, it may be noted
+that later observers have definitely discovered a difference between the
+results of autogamy and geitonogamy. Gilley and Fruwirth found that in
+Brassica Napus, the length and weight of the fruits as also the total
+weight of the seeds in a single fruit were less in the case of autogamy
+than in geitonogamy. With Sinapis alba a better crop of seeds was
+obtained after geitonogamy, and in the Sugar Beet the average weight
+of a fruit in the case of a self-fertilised plant was 0.009 gr., from
+geitonogamy 0.012 gr., and on cross-fertilisation 0.013 gr.
+
+On the whole, however, the results of geitonogamy show that the
+favourable effects of cross-fertilisation do not depend simply on the
+fact that the pollen of one flower is conveyed to the stigma of another.
+But the plants which are crossed must in some way be different.
+If plants of Ipomoea purpurea (and Mimulus luteus) which have been
+self-fertilised for seven generations and grown under the same
+conditions of cultivation are crossed together, the plants so crossed
+would not be superior to the self-fertilised; on the other hand crossing
+with a fresh stock at once proves very advantageous. The favourable
+effect of crossing is only apparent, therefore, if the parent plants
+are grown under different conditions or if they belong to different
+varieties. "It is really wonderful what an effect pollen from a distinct
+seedling plant, which has been exposed to different conditions of life,
+has on the offspring in comparison with pollen from the same flower or
+from a distinct individual, but which has been long subjected to the
+same conditions. The subject bears on the very principle of life, which
+seems almost to require changes in the conditions." ("More Letters",
+Vol. II. page 406.)
+
+The fertility--measured by the number or weight of the seeds produced
+by an equal number of plants--noticed under different conditions of
+fertilisation may be quoted in illustration.
+
+
+                                  On crossing   On crossing    On self-
+                                  with a fresh  plants of the  fertilisation
+                                  stock         same stock
+  Mimuleus luteus
+   (First and ninth generation)       100             4              3
+
+  Eschscholzia californica
+   (second generation)                100            45             40
+
+  Dianthus caryophyllus
+   (third and fourth generation)      100            45             33
+
+  Petunia violacea                    100            54             46
+
+
+Crossing under very similar conditions shows, therefore, that the
+difference between the sexual cells is smaller and thus the result of
+crossing is only slightly superior to that given by self-fertilisation.
+Is, then, the favourable result of crossing with a foreign stock to be
+attributed to the fact that this belongs to another systematic entity
+or to the fact that the plants, though belonging to the same entity
+were exposed to different conditions? This is a point on which further
+researches must be taken into account, especially since the analysis of
+the systematic entities has been much more thorough than formerly. (In
+the case of garden plants, as Darwin to a large extent claimed, it
+is not easy to say whether two individuals really belong to the same
+variety, as they are usually of hybrid origin. In some instances
+(Petunia, Iberis) the fresh stock employed by Darwin possessed flowers
+differing in colour from those of the plant crossed with it.) We
+know that most of Linneaus's species are compound species, frequently
+consisting of a very large number of smaller or elementary species
+formerly included under the comprehensive term varieties. Hybridisation
+has in most cases affected our garden and cultivated plants so that they
+do not represent pure species but a mixture of species.
+
+But this consideration has no essential bearing on Darwin's point of
+view, according to which the nature of the sexual cells is influenced by
+external conditions. Even individuals growing close to one another are
+only apparently exposed to identical conditions. Their sexual cells may
+therefore be differently influenced and thus give favourable results
+on crossing, as "the benefits which so generally follow from a cross
+between two plants apparently depend on the two differing somewhat in
+constitution or character." As a matter of fact we are familiar with a
+large number of cases in which the condition of the reproductive organs
+is influenced by external conditions. Darwin has himself demonstrated
+this for self-sterile plants, that is plants in which self-fertilisation
+produces no result. This self-sterility is affected by climatic
+conditions: thus in Brazil Eschscholzia californica is absolutely
+sterile to the pollen of its own flowers; the descendants of Brazilian
+plants in Darwin's cultures were partially self-fertile in one
+generation and in a second generation still more so. If one has any
+doubt in this case whether it is a question of the condition of
+the style and stigma, which possibly prevents the entrance of the
+pollen-tube or even its development, rather than that of the actual
+sexual cells, in other cases there is no doubt that an influence is
+exerted on the latter.
+
+Janczewski (Janczewski, "Sur les antheres steriles des Groseilliers",
+"Bull. de l'acad. des sciences de Cracovie", June, 1908.) has recently
+shown that species of Ribes cultivated under unnatural conditions
+frequently produce a mixed (i.e. partly useless) or completely sterile
+pollen, precisely as happens with hybrids. There are, therefore,
+substantial reasons for the conclusion that conditions of life exert an
+influence on the sexual cells. "Thus the proposition that the benefit
+from cross-fertilisation depends on the plants which are crossed
+having been subjected during previous generations to somewhat different
+conditions, or to their having varied from some unknown cause as if they
+had been thus subjected, is securely fortified on all sides." ("Cross
+and Self fertilisation" (1st edition), page 444.)
+
+We thus obtain an insight into the significance of sexuality. If an
+occasional and slight alteration in the conditions under which plants
+and animals live is beneficial (Reasons for this are given by Darwin
+in "Variation under Domestication" (2nd edition), Vol. II. page
+127.), crossing between organisms which have been exposed to different
+conditions becomes still more advantageous. The entire constitution
+is in this way influenced from the beginning, at a time when the whole
+organisation is in a highly plastic state. The total life-energy, so
+to speak, is increased, a gain which is not produced by asexual
+reproduction or by the union of sexual cells of plants which have lived
+under the same or only slightly different conditions. All the
+wonderful arrangements for cross-fertilisation now appear to be useful
+adaptations. Darwin was, however, far from giving undue prominence to
+this point of view, though this has been to some extent done by others.
+He particularly emphasised the following consideration:--"But we should
+always keep in mind that two somewhat opposed ends have to be gained;
+the first and more important one being the production of seeds by
+any means, and the second, cross-fertilisation." ("Cross and Self
+fertilisation" (1st edition), page 371.) Just as in some orchids and
+cleistogamic flowers self-pollination regularly occurs, so it may also
+occur in other cases. Darwin showed that Pisum sativum and Lathyrus
+odoratus belong to plants in which self-pollination is regularly
+effected, and that this accounts for the constancy of certain sorts of
+these plants, while a variety of form is produced by crossing. Indeed
+among his culture plants were some which derived no benefit from
+crossing. Thus in the sixth self-fertilised generation of his Ipomoea
+cultures the "Hero" made its appearance, a form slightly exceeding its
+crossed companion in height; this was in the highest degree self-fertile
+and handed on its characteristics to both children and grandchildren.
+Similar forms were found in Mimulus luteus and Nicotiana (In Pisum
+sativum also the crossing of two individuals of the same variety
+produced no advantage; Darwin attributed this to the fact that the
+plants had for several generations been self-fertilised and in each
+generation cultivated under almost the same conditions. Tschermak
+("Ueber kunstliche Kreuzung an Pisum sativum") afterwards recorded the
+same result; but he found on crossing different varieties that usually
+there was no superiority as regards height over the products of
+self-fertilisation, while Darwin found a greater height represented by
+the ratios 100:75 and 100:60.), types which, after self-fertilisation,
+have an enhanced power of seed-production and of attaining a greater
+height than the plants of the corresponding generation which are crossed
+together and self-fertilised and grown under the same conditions.
+"Some observations made on other plants lead me to suspect that
+self-fertilisation is in some respects beneficial; although the benefit
+thus derived is as a rule very small compared with that from a cross
+with a distinct plant." ("Cross and Self fertilisation", page 350.) We
+are as ignorant of the reason why plants behave differently when
+crossed and self-fertilised as we are in regard to the nature of the
+differentiation of the sexual cells, which determines whether a union of
+the sexual cells will prove favourable or unfavourable.
+
+It is impossible to discuss the different results of
+cross-fertilisation; one point must, however, be emphasised, because
+Darwin attached considerable importance to it. It is inevitable that
+pollen of different kinds must reach the stigma. It was known that
+pollen of the same "species" is dominant over the pollen of another
+species, that, in other words, it is prepotent. Even if the pollen of
+the same species reaches the stigma rather later than that of another
+species, the latter does not effect fertilisation.
+
+Darwin showed that the fertilising power of the pollen of another
+variety or of another individual is greater than that of the plant's
+own pollen. ("Cross and Self fertilisation", page 391.) This has
+been demonstrated in the case of Mimulus luteus (for the fixed
+white-flowering variety) and Iberis umbellata with pollen of another
+variety, and observations on cultivated plants, such as cabbage,
+horseradish, etc. gave similar results. It is, however, especially
+remarkable that pollen of another individual of the same variety may be
+prepotent over the plant's own pollen. This results from the superiority
+of plants crossed in this manner over self-fertilised plants. "Scarcely
+any result from my experiments has surprised me so much as this of the
+prepotency of pollen from a distinct individual over each plant's own
+pollen, as proved by the greater constitutional vigour of the crossed
+seedlings." (Ibid. page 397.) Similarly, in self-fertile plants the
+flowers of which have not been deprived of the male organs, pollen
+brought to the stigma by the wind or by insects from another plant
+effects fertilisation, even if the plant's own pollen has reached the
+stigma somewhat earlier.
+
+Have the results of his experimental investigations modified the point
+of view from which Darwin entered on his researches, or not? In the
+first place the question is, whether or not the opinion expressed in
+the Orchid book that there is "Something injurious" connected with
+self-fertilisation, has been confirmed. We can, at all events, affirm
+that Darwin adhered in essentials to his original position; but
+self-fertilisation afterwards assumed a greater importance than it
+formerly possessed. Darwin emphasised the fact that "the difference
+between the self-fertilised and crossed plants raised by me cannot be
+attributed to the superiority of the crossed, but to the inferiority
+of the self-fertilised seedlings, due to the injurious effects of
+self-fertilisation." (Ibid. page 437.) But he had no doubt that in
+favourable circumstances self-fertilised plants were able to persist for
+several generations without crossing. An occasional crossing appears to
+be useful but not indispensable in all cases; its sporadic occurrence
+in plants in which self-pollination habitually occurs is not excluded.
+Self-fertilisation is for the most part relatively and not absolutely
+injurious and always better than no fertilisation. "Nature abhors
+perpetual self-fertilisation" (It is incorrect to say, as a writer has
+lately said, that the aphorism expressed by Darwin in 1859 and 1862,
+"Nature abhors perpetual self-fertilisation," is not repeated in his
+later works. The sentence is repeated in "Cross and Self fertilisation"
+(page 8), with the addition, "If the word perpetual had been omitted,
+the aphorism would have been false. As it stands, I believe that it is
+true, though perhaps rather too strongly expressed.") is, however, a
+pregnant expression of the fact that cross-fertilisation is exceedingly
+widespread and has been shown in the majority of cases to be beneficial,
+and that in those plants in which we find self-pollination regularly
+occurring cross-pollination may occasionally take place.
+
+An attempt has been made to express in brief the main results of
+Darwin's work on the biology of flowers. We have seen that his object
+was to elucidate important general questions, particularly the question
+of the significance of sexual reproduction.
+
+It remains to consider what influence his work has had on botanical
+science. That this influence has been very considerable, is shown by
+a glance at the literature on the biology of flowers published since
+Darwin wrote. Before the book on orchids was published there was nothing
+but the old and almost forgotten works of Kolreuter and Sprengel with
+the exception of a few scattered references. Darwin's investigations
+gave the first stimulus to the development of an extensive literature on
+floral biology. In Knuth's "Handbuch der Blutenbiologie" ("Handbook
+of Flower Pollination", Oxford, 1906) as many as 3792 papers on this
+subject are enumerated as having been published before January 1, 1904.
+These describe not only the different mechanisms of flowers, but deal
+also with a series of remarkable adaptations in the pollinating insects.
+As a fertilising rain quickly calls into existence the most varied
+assortment of plants on a barren steppe, so activity now reigns in a
+field which men formerly left deserted. This development of the biology
+of flowers is of importance not only on theoretical grounds but also
+from a practical point of view. The rational breeding of plants is
+possible only if the flower-biology of the plants in question (i.e. the
+question of the possibility of self-pollination, self-sterility, etc.)
+is accurately known. And it is also essential for plant-breeders that
+they should have "the power of fixing each fleeting variety of colour,
+if they will fertilise the flowers of the desired kind with their own
+pollen for half-a-dozen generations, and grow the seedlings under the
+same conditions." ("Cross and Self fertilisation" (1st edition), page
+460.)
+
+But the influence of Darwin on floral biology was not confined to the
+development of this branch of Botany. Darwin's activity in this domain
+has brought about (as Asa Gray correctly pointed out) the revival of
+teleology in Botany and Zoology. Attempts were now made to determine,
+not only in the case of flowers but also in vegetative organs, in what
+relation the form and function of organs stand to one another and
+to what extent their morphological characters exhibit adaptation to
+environment. A branch of Botany, which has since been called Ecology
+(not a very happy term) has been stimulated to vigorous growth by floral
+biology.
+
+While the influence of the work on the biology of flowers was
+extraordinarily great, it could not fail to elicit opinions at variance
+with Darwin's conclusions. The opposition was based partly on reasons
+valueless as counterarguments, partly on problems which have still to
+be solved; to some extent also on that tendency against teleological
+conceptions which has recently become current. This opposing trend
+of thought is due to the fact that many biologists are content with
+teleological explanations, unsupported by proof; it is also closely
+connected with the fact that many authors estimate the importance of
+natural selection less highly than Darwin did. We may describe
+the objections which are based on the widespread occurrence of
+self-fertilisation and geitonogamy as of little importance. Darwin did
+not deny the occurrence of self-fertilisation, even for a long series
+of generations; his law states only that "Nature abhors PERPETUAL
+self-fertilisation." (It is impossible (as has been attempted) to
+express Darwin's point of view in a single sentence, such as H.
+Muller's statement of the "Knight-Darwin law." The conditions of life in
+organisms are so various and complex that laws, such as are formulated
+in physics and chemistry, can hardly be conceived.) An exception to
+this rule would therefore occur only in the case of plants in which the
+possibility of cross-pollination is excluded. Some of the plants with
+cleistogamous flowers might afford examples of such cases. We have
+already seen, however, that such a case has not as yet been shown to
+occur. Burck believed that he had found an instance in certain
+tropical plants (Anonaceae, Myrmecodia) of the complete exclusion of
+cross-fertilisation. The flowers of these plants, in which, however,--in
+contrast to the cleistogamous flowers--the corolla is well developed,
+remain closed and fruit is produced.
+
+Loew (E. Loew, "Bemerkungen zu Burck... ", "Biolog. Centralbl." XXVI.
+(1906).) has shown that cases occur in which cross-fertilisation may be
+effected even in these "cleistopetalous" flowers: humming birds visit
+the permanently closed flowers of certain species of Nidularium and
+transport the pollen. The fact that the formation of hybrids may occur
+as the result of this shows that pollination may be accomplished.
+
+The existence of plants for which self-pollination is of greater
+importance than it is for others is by no means contradictory to
+Darwin's view. Self-fertilisation is, for example, of greater importance
+for annuals than for perennials as without it seeds might fail to be
+produced. Even in the case of annual plants with small inconspicuous
+flowers in which self-fertilisation usually occurs, such as Senecio
+vulgaris, Capsella bursa-pastoris and Stellaria media, A. Bateson (Anna
+Bateson, "The effects of cross-fertilisation on inconspicuous
+flowers", "Annals of Botany", Vol. I. 1888, page 255.) found that
+cross-fertilisation gave a beneficial result, although only in a slight
+degree. If the favourable effects of sexual reproduction, according to
+Darwin's view, are correlated with change of environment, it is quite
+possible that this is of less importance in plants which die after
+ripening their seeds ("hapaxanthic") and which in any case constantly
+change their situation. Objections which are based on the proof of the
+prevalence of self-fertilisation are not, therefore, pertinent. At first
+sight another point of view, which has been more recently urged, appears
+to have more weight.
+
+W. Burck (Burck, "Darwin's Kreuzeungsgesetz... ", "Biol. Centralbl".
+XXVIII. 1908, page 177.) has expressed the opinion that the beneficial
+results of cross-fertilisation demonstrated by Darwin concern only
+hybrid plants. These alone become weaker by self-pollination; while
+pure species derive no advantage from crossing and no disadvantage from
+self-fertilisation. It is certain that some of the plants used by Darwin
+were of hybrid origin. (It is questionable if this was always the case.)
+This is evident from his statements, which are models of clearness and
+precision; he says that his Ipomoea plants "were probably the offspring
+of a cross." ("Cross and Self fertilisation" (1st edition), page 55.)
+The fixed forms of this plant, such as Hero, which was produced by
+self-fertilisation, and a form of Mimulus with white flowers spotted
+with red probably resulted from splitting of the hybrids. It is true
+that the phenomena observed in self-pollination, e.g. in Ipomoea, agree
+with those which are often noticed in hybrids; Darwin himself drew
+attention to this.
+
+Let us next call to mind some of the peculiarities connected with
+hybridisation. We know that hybrids are often characterized by their
+large size, rapidity of growth, earlier production of flowers, wealth of
+flower-production and a longer life; hybrids, if crossed with one of the
+two parent forms, are usually more fertile than when they are crossed
+together or with another hybrid. But the characters which hybrids
+exhibit on self-fertilisation are rather variable. The following
+instance may be quoted from Gartner: "There are many hybrids which
+retain the self-fertility of the first generation during the second
+and later generations, but very often in a less degree; a considerable
+number, however, become sterile." But the hybrid varieties may be more
+fertile in the second generation than in the first, and in some hybrids
+the fertility with their own pollen increases in the second, third,
+and following generations. (K.F. Gartner, "Versuche uber die
+Bastarderzeugung", Stuttgart, 1849, page 149.) As yet it is impossible
+to lay down rules of general application for the self-fertility of
+hybrids. That the beneficial influence of crossing with a fresh stock
+rests on the same ground--a union of sexual cells possessing somewhat
+different characters--as the fact that many hybrids are distinguished
+by greater luxuriance, wealth of flowers, etc. corresponds entirely
+with Darwin's conclusions. It seems to me to follow clearly from
+his investigations that there is no essential difference between
+cross-fertilisation and hybridisation. The heterostyled plants are
+normally dependent on a process corresponding to hybridisation. The view
+that specifically distinct species could at best produce sterile hybrids
+was always opposed by Darwin. But if the good results of crossing were
+EXCLUSIVELY dependent on the fact that we are concerned with hybrids,
+there must then be a demonstration of two distinct things. First, that
+crossing with a fresh stock belonging to the same systematic entity
+or to the same hybrid, but cultivated for a considerable time under
+different conditions, shows no superiority over self-fertilisation,
+and that in pure species crossing gives no better results than
+self-pollination. If this were the case, we should be better able to
+understand why in one plant crossing is advantageous while in others,
+such as Darwin's Hero and the forms of Mimulus and Nicotiana no
+advantage is gained; these would then be pure species. But such a
+proof has not been supplied; the inference drawn from cleistogamous and
+cleistopetalous plants is not supported by evidence, and the experiments
+on geitonogamy and on the advantage of cross-fertilisation in species
+which are usually self-fertilised are opposed to this view. There are
+still but few researches on this point; Darwin found that in Ononis
+minutissima, which produces cleistogamous as well as self-fertile
+chasmogamous flowers, the crossed and self-fertilised capsules
+produced seed in the proportion of 100:65 and that the average bore the
+proportion 100:86. Facts previously mentioned are also applicable to
+this case. Further, it is certain that the self-sterility exhibited by
+many plants has nothing to do with hybridisation. Between self-sterility
+and reduced fertility as the result of self-fertilisation there is
+probably no fundamental difference.
+
+It is certain that so difficult a problem as that of the significance
+of sexual reproduction requires much more investigation. Darwin was
+anything but dogmatic and always ready to alter an opinion when it was
+not based on definite proof: he wrote, "But the veil of secrecy is
+as yet far from lifted; nor will it be, until we can say why it is
+beneficial that the sexual elements should be differentiated to a
+certain extent, and why, if the differentiation be carried still
+further, injury follows." He has also shown us the way along which
+to follow up this problem; it is that of carefully planned and exact
+experimental research. It may be that eventually many things will be
+viewed in a different light, but Darwin's investigations will always
+form the foundation of Floral Biology on which the future may continue
+to build.
+
+
+
+
+XXI. MENTAL FACTORS IN EVOLUTION. By C. Lloyd Morgan, LL.D., F.R.S.
+
+In developing his conception of organic evolution Charles Darwin was
+of necessity brought into contact with some of the problems of mental
+evolution. In "The Origin of Species" he devoted a chapter to "the
+diversities of instinct and of the other mental faculties in animals of
+the same class." ("Origin of Species" (6th edition), page 205.) When
+he passed to the detailed consideration of "The Descent of Man", it
+was part of his object to show "that there is no fundamental difference
+between man and the higher mammals in their mental faculties." ("Descent
+of Man" (2nd edition 1888), Vol. I. page 99; Popular edition page 99.)
+"If no organic being excepting man," he said, "had possessed any mental
+power, or if his powers had been of a wholly different nature from those
+of the lower animals, then we should never have been able to convince
+ourselves that our high faculties had been gradually developed." (Ibid.
+page 99.) In his discussion of "The Expression of the Emotions" it
+was important for his purpose "fully to recognise that actions readily
+become associated with other actions and with various states of the
+mind." ("The Expression of the Emotions" (2nd edition), page 32.) His
+hypothesis of sexual selection is largely dependent upon the exercise
+of choice on the part of the female and her preference for "not only the
+more attractive but at the same time the more vigorous and victorious
+males." ("Descent of Man", Vol. II. page 435.) Mental processes and
+physiological processes were for Darwin closely correlated; and he
+accepted the conclusion "that the nervous system not only regulates most
+of the existing functions of the body, but has indirectly influenced
+the progressive development of various bodily structures and of certain
+mental qualities." (Ibid. pages 437, 438.)
+
+Throughout his treatment, mental evolution was for Darwin incidental
+to and contributory to organic evolution. For specialised research
+in comparative and genetic psychology, as an independent field of
+investigation, he had neither the time nor the requisite training.
+None the less his writings and the spirit of his work have exercised a
+profound influence on this department of evolutionary thought. And, for
+those who follow Darwin's lead, mental evolution is still in a
+measure subservient to organic evolution. Mental processes are the
+accompaniments or concomitants of the functional activity of specially
+differentiated parts of the organism. They are in some way dependent on
+physiological and physical conditions. But though they are not physical
+in their nature, and though it is difficult or impossible to conceive
+that they are physical in their origin, they are, for Darwin and his
+followers, factors in the evolutionary process in its physical or
+organic aspect. By the physiologist within his special and well-defined
+universe of discourse they may be properly regarded as epiphenomena; but
+by the naturalist in his more catholic survey of nature they cannot
+be so regarded, and were not so regarded by Darwin. Intelligence has
+contributed to evolution of which it is in a sense a product.
+
+The facts of observation or of inference which Darwin accepted are
+these: Conscious experience accompanies some of the modes of animal
+behaviour; it is concomitant with certain physiological processes; these
+processes are the outcome of development in the individual and
+evolution in the race; the accompanying mental processes undergo a like
+development. Into the subtle philosophical questions which arise out
+of the naive acceptance of such a creed it was not Darwin's province
+to enter; "I have nothing to do," he said ("Origin of Species" (6th
+edition), page 205.), "with the origin of the mental powers, any more
+than I have with that of life itself." He dealt with the natural history
+of organisms, including not only their structure but their modes of
+behaviour; with the natural history of the states of consciousness which
+accompany some of their actions; and with the relation of behaviour
+to experience. We will endeavour to follow Darwin in his modesty and
+candour in making no pretence to give ultimate explanations. But we must
+note one of the implications of this self-denying ordinance of science.
+Development and evolution imply continuity. For Darwin and his followers
+the continuity is organic through physical heredity. Apart from
+speculative hypothesis, legitimate enough in its proper place but here
+out of court, we know nothing of continuity of mental evolution as such:
+consciousness appears afresh in each succeeding generation. Hence it is
+that for those who follow Darwin's lead, mental evolution is and must
+ever be, within his universe of discourse, subservient to organic
+evolution. Only in so far as conscious experience, or its neural
+correlate, effects some changes in organic structure can it influence
+the course of heredity; and conversely only in so far as changes in
+organic structure are transmitted through heredity, is mental evolution
+rendered possible. Such is the logical outcome of Darwin's teaching.
+
+Those who abide by the cardinal results of this teaching are bound to
+regard all behaviour as the expression of the functional activities
+of the living tissues of the organism, and all conscious experience
+as correlated with such activities. For the purposes of scientific
+treatment, mental processes are one mode of expression of the same
+changes of which the physiological processes accompanying behaviour
+are another mode of expression. This is simply accepted as a fact
+which others may seek to explain. The behaviour itself is the adaptive
+application of the energies of the organism; it is called forth by some
+form of presentation or stimulation brought to bear on the organism by
+the environment. This presentation is always an individual or personal
+matter. But in order that the organism may be fitted to respond to the
+presentation of the environment it must have undergone in some way
+a suitable preparation. According to the theory of evolution this
+preparation is primarily racial and is transmitted through heredity.
+Darwin's main thesis was that the method of preparation is predominantly
+by natural selection. Subordinate to racial preparation, and always
+dependent thereon, is individual or personal preparation through
+some kind of acquisition; of which the guidance of behaviour through
+individually won experience is a typical example. We here introduce
+the mental factor because the facts seem to justify the inference. Thus
+there are some modes of behaviour which are wholly and solely dependent
+upon inherited racial preparation; there are other modes of behaviour
+which are also dependent, in part at least, on individual preparation.
+In the former case the behaviour is adaptive on the first occurrence
+of the appropriate presentation; in the latter case accommodation to
+circumstances is only reached after a greater or less amount of acquired
+organic modification of structure, often accompanied (as we assume) in
+the higher animals by acquired experience. Logically and biologically
+the two classes of behaviour are clearly distinguishable: but the
+analysis of complex cases of behaviour where the two factors cooperate,
+is difficult and requires careful and critical study of life-history.
+
+The foundations of the mental life are laid in the conscious experience
+that accompanies those modes of behaviour, dependent entirely on racial
+preparation, which may broadly be described as instinctive. In the
+eighth chapter of "The Origin of Species" Darwin says ("Origin of
+Species" (6th edition), page 205.), "I will not attempt any definition
+of instinct... Every one understands what is meant, when it is said
+that instinct impels the cuckoo to migrate and to lay her eggs in other
+birds' nests. An action, which we ourselves require experience to enable
+us to perform, when performed by an animal, more especially by a very
+young one, without experience, and when performed by many individuals in
+the same way, without their knowing for what purpose it is performed, is
+usually said to be instinctive." And in the summary at the close of the
+chapter he says ("Origin of Species" (6th edition), page 233.), "I have
+endeavoured briefly to show that the mental qualities of our domestic
+animals vary, and that the variations are inherited. Still more briefly
+I have attempted to show that instincts vary slightly in a state of
+nature. No one will dispute that instincts are of the highest importance
+to each animal. Therefore there is no real difficulty, under changing
+conditions of life, in natural selection accumulating to any extent
+slight modifications of instinct which are in any way useful. In many
+cases habit or use and disuse have probably come into play."
+
+Into the details of Darwin's treatment there is neither space nor need
+to enter. There are some ambiguous passages; but it may be said that for
+him, as for his followers to-day, instinctive behaviour is wholly the
+result of racial preparation transmitted through organic heredity. For
+the performance of the instinctive act no individual preparation under
+the guidance of personal experience is necessary. It is true that Darwin
+quotes with approval Huber's saying that "a little dose of judgment
+or reason often comes into play, even with animals low in the scale of
+nature." (Ibid. page 205.) But we may fairly interpret his meaning to be
+that in behaviour, which is commonly called instinctive, some element of
+intelligent guidance is often combined. If this be conceded the strictly
+instinctive performance (or part of the performance) is the outcome of
+heredity and due to the direct transmission of parental or ancestral
+aptitudes. Hence the instinctive response as such depends entirely on
+how the nervous mechanism has been built up through heredity; while
+intelligent behaviour, or the intelligent factor in behaviour, depends
+also on how the nervous mechanism has been modified and moulded by use
+during its development and concurrently with the growth of individual
+experience in the customary situations of daily life. Of course it is
+essential to the Darwinian thesis that what Sir E. Ray Lankester has
+termed "educability," not less than instinct, is hereditary. But it is
+also essential to the understanding of this thesis that the differentiae
+of the hereditary factors should be clearly grasped.
+
+For Darwin there were two modes of racial preparation, (1) natural
+selection, and (2) the establishment of individually acquired habit. He
+showed that instincts are subject to hereditary variation; he saw that
+instincts are also subject to modification through acquisition in the
+course of individual life. He believed that not only the variations but
+also, to some extent, the modifications are inherited. He therefore held
+that some instincts (the greater number) are due to natural selection
+but that others (less numerous) are due, or partly due, to the
+inheritance of acquired habits. The latter involve Lamarckian
+inheritance, which of late years has been the centre of so much
+controversy. It is noteworthy however that Darwin laid especial emphasis
+on the fact that many of the most typical and also the most
+complex instincts--those of neuter insects--do not admit of such an
+interpretation. "I am surprised," he says ("Origin of Species"
+(6th edition), page 233.), "that no one has hitherto advanced this
+demonstrative case of neuter insects, against the well-known doctrine of
+inherited habit, as advanced by Lamarck." None the less Darwin admitted
+this doctrine as supplementary to that which was more distinctively his
+own--for example in the case of the instincts of domesticated animals.
+Still, even in such cases, "it may be doubted," he says (Ibid. pages
+210, 211.), "whether any one would have thought of training a dog to
+point, had not some one dog naturally shown a tendency in this line... so
+that habit and some degree of selection have probably concurred in
+civilising by inheritance our dogs." But in the interpretation of the
+instincts of domesticated animals, a more recently suggested hypothesis,
+that of organic selection (Independently suggested, on somewhat
+different lines, by Profs. J. Mark Baldwin, Henry F. Osborn and the
+writer.), may be helpful. According to this hypothesis any intelligent
+modification of behaviour which is subject to selection is probably
+coincident in direction with an inherited tendency to behave in this
+fashion. Hence in such behaviour there are two factors: (1) an
+incipient variation in the line of such behaviour, and (2) an acquired
+modification by which the behaviour is carried further along the same
+line. Under natural selection those organisms in which the two factors
+cooperate are likely to survive. Under artificial selection they are
+deliberately chosen out from among the rest.
+
+Organic selection has been termed a compromise between the more strictly
+Darwinian and the Lamarckian principles of interpretation. But it is not
+in any sense a compromise. The principle of interpretation of that which
+is instinctive and hereditary is wholly Darwinian. It is true that some
+of the facts of observation relied upon by Lamarckians are introduced.
+For Lamarckians however the modifications which are admittedly factors
+in survival, are regarded as the parents of inherited variations; for
+believers in organic selection they are only the foster parents or
+nurses. It is because organic selection is the direct outcome of and a
+natural extension of Darwin's cardinal thesis that some reference to it
+here is justifiable. The matter may be put with the utmost brevity as
+follows. (1) Variations (V) occur, some of which are in the direction
+of increased adaptation (+), others in the direction of decreased
+adaptation (-). (2) Acquired modifications (M) also occur. Some of these
+are in the direction of increased accommodation to circumstances (+),
+while others are in the direction of diminished accommodation (-). Four
+major combinations are
+
+     (a)  + V with + M,
+     (b)  + V with - M,
+     (c)  - V with + M,
+     (d)  - V with - M.
+
+Of these (d) must inevitably be eliminated while (a) are selected.
+The predominant survival of (a) entails the survival of the adaptive
+variations which are inherited. The contributory acquisitions (+M) are
+not inherited; but they are none the less factors in determining the
+survival of the coincident variations. It is surely abundantly clear
+that this is Darwinism and has no tincture of Lamarck's essential
+principle, the inheritance of acquired characters.
+
+Whether Darwin himself would have accepted this interpretation of some
+at least of the evidence put forward by Lamarckians is unfortunately
+a matter of conjecture. The fact remains that in his interpretation
+of instinct and in allied questions he accepted the inheritance of
+individually acquired modifications of behaviour and structure.
+
+Darwin was chiefly concerned with instinct from the biological rather
+than from the psychological point of view. Indeed it must be confessed
+that, from the latter standpoint, his conception of instinct as a
+"mental faculty" which "impels" an animal to the performance of certain
+actions, scarcely affords a satisfactory basis for genetic treatment. To
+carry out the spirit of Darwin's teaching it is necessary to link more
+closely biological and psychological evolution. The first step towards
+this is to interpret the phenomena of instinctive behaviour in terms
+of stimulation and response. It may be well to take a particular case.
+Swimming on the part of a duckling is, from the biological point
+of view, a typical example of instinctive behaviour. Gently lower a
+recently hatched bird into water: coordinated movements of the limbs
+follow in rhythmical sequence. The behaviour is new to the individual
+though it is no doubt closely related to that of walking, which is
+no less instinctive. There is a group of stimuli afforded by the
+"presentation" which results from partial immersion: upon this
+there follows as a complex response an application of the functional
+activities in swimming; the sequence of adaptive application on the
+appropriate presentation is determined by racial preparation. We know,
+it is true, but little of the physiological details of what takes place
+in the central nervous system; but in broad outline the nature of the
+organic mechanism and the manner of its functioning may at least
+be provisionally conjectured in the present state of physiological
+knowledge. Similarly in the case of the pecking of newly-hatched chicks;
+there is a visual presentation, there is probably a cooperating group of
+stimuli from the alimentary tract in need of food, there is an adaptive
+application of the activities in a definite mode of behaviour. Like
+data are afforded in a great number of cases of instinctive procedure,
+sometimes occurring very early in life, not infrequently deferred until
+the organism is more fully developed, but all of them dependent upon
+racial preparation. No doubt there is some range of variation in the
+behaviour, just such variation as the theory of natural selection
+demands. But there can be no question that the higher animals inherit
+a bodily organisation and a nervous system, the functional working of
+which gives rise to those inherited modes of behaviour which are termed
+instinctive.
+
+It is to be noted that the term "instinctive" is here employed in the
+adjectival form as a descriptive heading under which may be grouped many
+and various modes of behaviour due to racial preparation. We speak
+of these as inherited; but in strictness what is transmitted through
+heredity is the complex of anatomical and physiological conditions under
+which, in appropriate circumstances, the organism so behaves. So far the
+term "instinctive" has a restricted biological connotation in terms
+of behaviour. But the connecting link between biological evolution and
+psychological evolution is to be sought,--as Darwin fully realised,--in
+the phenomena of instinct, broadly considered. The term "instinctive"
+has also a psychological connotation. What is that connotation?
+
+Let us take the case of the swimming duckling or the pecking chick, and
+fix our attention on the first instinctive performance. Grant that just
+as there is, strictly speaking, no inherited behaviour, but only the
+conditions which render such behaviour under appropriate circumstances
+possible; so too there is no inherited experience, but only the
+conditions which render such experience possible; then the cerebral
+conditions in both cases are the same. The biological behaviour-complex,
+including the total stimulation and the total response with the
+intervening or resultant processes in the sensorium, is accompanied by
+an experience-complex including the initial stimulation-consciousness
+and resulting response-consciousness. In the experience-complex are
+comprised data which in psychological analysis are grouped under the
+headings of cognition, affective tone and conation. But the complex is
+probably experienced as an unanalysed whole. If then we use the term
+"instinctive" so as to comprise all congenital modes of behaviour which
+contribute to experience, we are in a position to grasp the view that
+the net result in consciousness constitutes what we may term the
+primary tissue of experience. To the development of this experience each
+instinctive act contributes. The nature and manner of organisation of
+this primary tissue of experience are dependent on inherited biological
+aptitudes; but they are from the outset onwards subject to secondary
+development dependent on acquired aptitudes. Biological values are
+supplemented by psychological values in terms of satisfaction or the
+reverse.
+
+In our study of instinct we have to select some particular phase of
+animal behaviour and isolate it so far as is possible from the life of
+which it is a part. But the animal is a going concern, restlessly active
+in many ways. Many instinctive performances, as Darwin pointed out
+("Origin of Species" (6th edition), page 206.), are serial in their
+nature. But the whole of active life is a serial and coordinated
+business. The particular instinctive performance is only an episode in
+a life-history, and every mode of behaviour is more or less closely
+correlated with other modes. This coordination of behaviour is
+accompanied by a correlation of the modes of primary experience. We may
+classify the instinctive modes of behaviour and their accompanying modes
+of instinctive experience under as many heads as may be convenient
+for our purposes of interpretation, and label them instincts of
+self-preservation, of pugnacity, of acquisition, the reproductive
+instincts, the parental instincts, and so forth. An instinct, in this
+sense of the term (for example the parental instinct), may be described
+as a specialised part of the primary tissue of experience differentiated
+in relation to some definite biological end. Under such an instinct
+will fall a large number of particular and often well-defined modes of
+behaviour, each with its own peculiar mode of experience.
+
+It is no doubt exceedingly difficult as a matter of observation and of
+inference securely based thereon to distinguish what is primary from
+what is in part due to secondary acquisition--a fact which Darwin fully
+appreciated. Animals are educable in different degrees; but where they
+are educable they begin to profit by experience from the first. Only,
+therefore, on the occasion of the first instinctive act of a given type
+can the experience gained be weighed as WHOLLY primary; all subsequent
+performance is liable to be in some degree, sometimes more, sometimes
+less, modified by the acquired disposition which the initial behaviour
+engenders. But the early stages of acquisition are always along the
+lines predetermined by instinctive differentiation. It is the task of
+comparative psychology to distinguish the primary tissue of experience
+from its secondary and acquired modifications. We cannot follow up the
+matter in further detail. It must here suffice to suggest that this
+conception of instinct as a primary form of experience lends itself
+better to natural history treatment than Darwin's conception of an
+impelling force, and that it is in line with the main trend of Darwin's
+thought.
+
+In a characteristic work,--characteristic in wealth of detail, in
+closeness and fidelity of observation, in breadth of outlook, in candour
+and modesty,--Darwin dealt with "The Expression of the Emotions in
+Man and Animals". Sir Charles Bell in his "Anatomy of Expression" had
+contended that many of man's facial muscles had been specially created
+for the sole purpose of being instrumental in the expression of his
+emotions. Darwin claimed that a natural explanation, consistent with the
+doctrine of evolution, could in many cases be given and would in other
+cases be afforded by an extension of the principles he advocated. "No
+doubt," he said ("Expression of the Emotions", page 13. The passage is
+here somewhat condensed.), "as long as man and all other animals are
+viewed as independent creations, an effectual stop is put to our natural
+desire to investigate as far as possible the causes of Expression.
+By this doctrine, anything and everything can be equally well
+explained... With mankind, some expressions... can hardly be understood,
+except on the belief that man once existed in a much lower and
+animal-like condition. The community of certain expressions in distinct
+though allied species... is rendered somewhat more intelligible, if we
+believe in their descent from a common progenitor. He who admits on
+general grounds that the structure and habits of all animals have been
+gradually evolved, will look at the whole subject of Expression in a new
+and interesting light."
+
+Darwin relied on three principles of explanation. "The first of these
+principles is, that movements which are serviceable in gratifying some
+desire, or in relieving some sensation, if often repeated, become
+so habitual that they are performed, whether or not of any service,
+whenever the same desire or sensation is felt, even in a very weak
+degree." (Ibid. page 368.) The modes of expression which fall under
+this head have become instinctive through the hereditary transmission of
+acquired habit. "As far as we can judge, only a few expressive movements
+are learnt by each individual; that is, were consciously and voluntarily
+performed during the early years of life for some definite object, or in
+imitation of others, and then became habitual. The far greater number of
+the movements of expression, and all the more important ones, are innate
+or inherited; and such cannot be said to depend on the will of the
+individual. Nevertheless, all those included under our first principle
+were at first voluntarily performed for a definite object,--namely,
+to escape some danger, to relieve some distress, or to gratify some
+desire." (Ibid. pages 373, 374.)
+
+"Our second principle is that of antithesis. The habit of voluntarily
+performing opposite movements under opposite impulses has become firmly
+established in us by the practice of our whole lives. Hence, if certain
+actions have been regularly performed, in accordance with our first
+principle, under a certain frame of mind, there will be a strong and
+involuntary tendency to the performance of directly opposite actions,
+whether or not these are of any use, under the excitement of an opposite
+frame of mind." ("Expression of the Emotions", page 368.) This principle
+of antithesis has not been widely accepted. Nor is Darwin's own position
+easy to grasp.
+
+"Our third principle," he says (Ibid. page 369.), "is the direct action
+of the excited nervous system on the body, independently of the will,
+and independently, in large part, of habit. Experience shows that
+nerve-force is generated and set free whenever the cerebro-spinal system
+is excited. The direction which this nerve-force follows is necessarily
+determined by the lines of connection between the nerve-cells, with each
+other and with various parts of the body."
+
+Lack of space prevents our following up the details of Darwin's
+treatment of expression. Whether we accept or do not accept his three
+principles of explanation we must regard his work as a masterpiece of
+descriptive analysis, packed full of observations possessing lasting
+value. For a further development of the subject it is essential that
+the instinctive factors in expression should be more fully distinguished
+from those which are individually acquired--a difficult task--and that
+the instinctive factors should be rediscussed in the light of modern
+doctrines of heredity, with a view to determining whether Lamarckian
+inheritance, on which Darwin so largely relied, is necessary for an
+interpretation of the facts.
+
+The whole subject as Darwin realised is very complex. Even the term
+"expression" has a certain amount of ambiguity. When the emotion is in
+full flood the animal fights, flees, or faints. Is this full-tide effect
+to be regarded as expression; or are we to restrict the term to the
+premonitory or residual effects--the bared canine when the fighting mood
+is being roused, the ruffled fur when reminiscent representations of the
+object inducing anger cross the mind? Broadly considered both should
+be included. The activity of premonitory expression as a means of
+communication was recognised by Darwin; he might, perhaps, have
+emphasised it more strongly in dealing with the lower animals. Man so
+largely relies on a special means of communication, that of language,
+that he sometimes fails to realise that for animals with their keen
+powers of perception, and dependent as they are on such means of
+communication, the more strictly biological means of expression are full
+of subtle suggestiveness. Many modes of expression, otherwise useless,
+are signs of behaviour that may be anticipated,--signs which stimulate
+the appropriate attitude of response. This would not, however, serve to
+account for the utility of the organic accompaniments--heart-affection,
+respiratory changes, vaso-motor effects and so forth, together
+with heightened muscular tone,--on all of which Darwin lays stress
+("Expression of the Emotions", pages 65 ff.) under his third principle.
+The biological value of all this is, however, of great importance,
+though Darwin was hardly in a position to take it fully into account.
+
+Having regard to the instinctive and hereditary factors of emotional
+expression we may ask whether Darwin's third principle does not alone
+suffice as an explanation. Whether we admit or reject Lamarckian
+inheritance it would appear that all hereditary expression must be due
+to pre-established connections within the central nervous system and to
+a transmitted provision for coordinated response under the appropriate
+stimulation. If this be so, Darwin's first and second principles are
+subordinate and ancillary to the third, an expression, so far as it is
+instinctive or hereditary, being "the direct result of the constitution
+of the nervous system."
+
+Darwin accepted the emotions themselves as hereditary or acquired
+states of mind and devoted his attention to their expression. But
+these emotions themselves are genetic products and as such dependent
+on organic conditions. It remained, therefore, for psychologists who
+accepted evolution and sought to build on biological foundations to
+trace the genesis of these modes of animal and human experience. The
+subject has been independently developed by Professors Lange and James
+(Cf. William James, "Principles of Psychology", Vol. II. Chap. XXV,
+London, 1890.); and some modification of their view is regarded by many
+evolutionists as affording the best explanation of the facts. We must
+fix our attention on the lower emotions, such as anger or fear, and on
+their first occurrence in the life of the individual organism. It is
+a matter of observation that if a group of young birds which have been
+hatched in an incubator are frightened by an appropriate presentation,
+auditory or visual, they instinctively respond in special ways. If we
+speak of this response as the expression, we find that there are many
+factors. There are certain visible modes of behaviour, crouching at
+once, scattering and then crouching, remaining motionless, the braced
+muscles sustaining an attitude of arrest, and so forth. There are also
+certain visceral or organic effects, such as affections of the heart and
+respiration. These can be readily observed by taking the young bird in
+the hand. Other effects cannot be readily observed; vaso-motor changes,
+affections of the alimentary canal, the skin and so forth. Now the
+essence of the James-Lange view, as applied to these congenital effects,
+is that though we are justified in speaking of them as effects of the
+stimulation, we are not justified, without further evidence, in speaking
+of them as effects of the emotional state. May it not rather be that the
+emotion as a primary mode of experience is the concomitant of the
+net result of the organic situation--the initial presentation, the
+instinctive mode of behaviour, the visceral disturbances? According to
+this interpretation the primary tissue of experience of the emotional
+order, felt as an unanalysed complex, is generated by the stimulation
+of the sensorium by afferent or incoming physiological impulses from the
+special senses, from the organs concerned in the responsive behaviour,
+from the viscera and vaso-motor system.
+
+Some psychologists, however, contend that the emotional experience
+is generated in the sensorium prior to, and not subsequent to, the
+behaviour-response and the visceral disturbances. It is a direct and not
+an indirect outcome of the presentation to the special senses. Be
+this as it may, there is a growing tendency to bring into the closest
+possible relation, or even to identify, instinct and emotion in their
+primary genesis. The central core of all such interpretations is that
+instinctive behaviour and experience, its emotional accompaniments, and
+its expression, are but different aspects of the outcome of the
+same organic occurrences. Such emotions are, therefore, only a
+distinguishable aspect of the primary tissue of experience and exhibit
+a like differentiation. Here again a biological foundation is laid for a
+psychological doctrine of the mental development of the individual.
+
+The intimate relation between emotion as a psychological mode of
+experience and expression as a group of organic conditions has an
+important bearing on biological interpretation. The emotion, as the
+psychological accompaniment of orderly disturbances in the central
+nervous system profoundly influences behaviour and often renders it more
+vigorous and more effective. The utility of the emotions in the struggle
+for existence can, therefore, scarcely be over-estimated. Just as
+keenness of perception has survival-value; just as it is obviously
+subject to variation; just as it must be enhanced under natural
+selection, whether individually acquired increments are inherited
+or not; and just as its value lies not only in this or that special
+perceptive act but in its importance for life as a whole; so the
+vigorous effectiveness of activity has survival-value; it is subject
+to variation; it must be enhanced under natural selection; and its
+importance lies not only in particular modes of behaviour but in its
+value for life as a whole. If emotion and its expression as a congenital
+endowment are but different aspects of the same biological occurrence;
+and if this is a powerful supplement to vigour effectiveness and
+persistency of behaviour, it must on Darwin's principles be subject to
+natural selection.
+
+If we include under the expression of the emotions not only the
+premonitory symptoms of the initial phases of the organic and mental
+state, not only the signs or conditions of half-tide emotion, but the
+full-tide manifestation of an emotion which dominates the situation, we
+are naturally led on to the consideration of many of the phenomena
+which are discussed under the head of sexual selection. The subject
+is difficult and complex, and it was treated by Darwin with all the
+strength he could summon to the task. It can only be dealt with here
+from a special point of view--that which may serve to illustrate the
+influence of certain mental factors on the course of evolution. From
+this point of view too much stress can scarcely be laid on the dominance
+of emotion during the period of courtship and pairing in the more highly
+organised animals. It is a period of maximum vigour, maximum activity,
+and, correlated with special modes of behaviour and special organic and
+visceral accompaniments, a period also of maximum emotional excitement.
+The combats of males, their dances and aerial evolutions, their
+elaborate behaviour and display, or the flood of song in birds, are
+emotional expressions which are at any rate coincident in time with
+sexual periodicity. From the combat of the males there follows on
+Darwin's principles the elimination of those which are deficient in
+bodily vigour, deficient in special structures, offensive or protective,
+which contribute to success, deficient in the emotional supplement
+of which persistent and whole-hearted fighting is the expression,
+and deficient in alertness and skill which are the outcome of the
+psychological development of the powers of perception. Few biologists
+question that we have here a mode of selection of much importance,
+though its influence on psychological evolution often fails to receive
+its due emphasis. Mr Wallace ("Darwinism", pages 282, 283, London,
+1889.) regards it as "a form of natural selection"; "to it," he says,
+"we must impute the development of the exceptional strength, size, and
+activity of the male, together with the possession of special offensive
+and defensive weapons, and of all other characters which arise from
+the development of these or are correlated with them." So far there is
+little disagreement among the followers of Darwin--for Mr Wallace,
+with fine magnanimity, has always preferred to be ranked as such,
+notwithstanding his right, on which a smaller man would have constantly
+insisted, to the claim of independent originator of the doctrine of
+natural selection. So far with regard to sexual selection Darwin and Mr
+Wallace are agreed; so far and no farther. For Darwin, says Mr Wallace
+(Ibid. page 283.), "has extended the principle into a totally different
+field of action, which has none of that character of constancy and of
+inevitable result that attaches to natural selection, including male
+rivalry; for by far the larger portion of the phenomena, which he
+endeavours to explain by the direct action of sexual selection, can only
+be so explained on the hypothesis that the immediate agency is female
+choice or preference. It is to this that he imputes the origin of
+all secondary sexual characters other than weapons of offence and
+defence... In this extension of sexual selection to include the action of
+female choice or preference, and in the attempt to give to that choice
+such wide-reaching effects, I am unable to follow him more than a very
+little way."
+
+Into the details of Mr Wallace's criticisms it is impossible to enter
+here. We cannot discuss either the mode of origin of the variations in
+structure which have rendered secondary sexual characters possible
+or the modes of selection other than sexual which have rendered them,
+within narrow limits, specifically constant. Mendelism and mutation
+theories may have something to say on the subject when these theories
+have been more fully correlated with the basal principles of selection.
+It is noteworthy that Mr Wallace says ("Darwinism", pages 283, 284.):
+"Besides the acquisition of weapons by the male for the purpose of
+fighting with other males, there are some other sexual characters which
+may have been produced by natural selection. Such are the various sounds
+and odours which are peculiar to the male, and which serve as a call to
+the female or as an indication of his presence. These are evidently a
+valuable addition to the means of recognition of the two sexes, and
+are a further indication that the pairing season has arrived; and the
+production, intensification, and differentiation of these sounds and
+odours are clearly within the power of natural selection. The same
+remark will apply to the peculiar calls of birds, and even to the
+singing of the males." Why the same remark should not apply to their
+colours and adornments is not obvious. What is obvious is that "means
+of recognition" and "indication that the pairing season has arrived" are
+dependent on the perceptive powers of the female who recognises and for
+whom the indication has meaning. The hypothesis of female preference,
+stripped of the aesthetic surplusage which is psychologically both
+unnecessary and unproven, is really only different in degree from that
+which Mr Wallace admits in principle when he says that it is probable
+that the female is pleased or excited by the display.
+
+Let us for our present purpose leave on one side and regard as sub
+judice the question whether the specific details of secondary sexual
+characters are the outcome of female choice. For us the question is
+whether certain psychological accompaniments of the pairing situation
+have influenced the course of evolution and whether these psychological
+accompaniments are themselves the outcome of evolution. As a matter of
+observation, specially differentiated modes of behaviour, often very
+elaborate, frequently requiring highly developed skill, and apparently
+highly charged with emotional tone, are the precursors of pairing. They
+are generally confined to the males, whose fierce combats during the
+period of sexual activity are part of the emotional manifestation. It is
+inconceivable that they have no biological meaning; and it is difficult
+to conceive that they have any other biological end than to evoke in
+the generally more passive female the pairing impulse. They are based
+on instinctive foundations ingrained in the nervous constitution
+through natural (or may we not say sexual?) selection in virtue of
+their profound utility. They are called into play by a specialised
+presentation such as the sight or the scent of the female at, or a
+little in advance of, a critical period of the physiological rhythm.
+There is no necessity that the male should have any knowledge of the
+end to which his strenuous activity leads up. In presence of the female
+there is an elaborate application of all the energies of behaviour,
+just because ages of racial preparation have made him biologically and
+emotionally what he is--a functionally sexual male that must dance or
+sing or go through hereditary movements of display, when the appropriate
+stimulation comes. Of course after the first successful courtship
+his future behaviour will be in some degree modified by his previous
+experience. No doubt during his first courtship he is gaining the
+primary data of a peculiarly rich experience, instinctive and emotional.
+But the biological foundations of the behaviour of courtship are laid
+in the hereditary coordinations. It would seem that in some cases, not
+indeed in all, but perhaps especially in those cases in which secondary
+sexual behaviour is most highly evolved,--correlative with the ardour
+of the male is a certain amount of reluctance in the female. The pairing
+act on her part only takes place after prolonged stimulation, for
+affording which the behaviour of male courtship is the requisite
+presentation. The most vigorous, defiant and mettlesome male is
+preferred just because he alone affords a contributory stimulation
+adequate to evoke the pairing impulse with its attendant emotional tone.
+
+It is true that this places female preference or choice on a much lower
+psychological plane than Darwin in some passages seems to contemplate
+where, for example, he says that the female appreciates the display of
+the male and places to her credit a taste for the beautiful. But Darwin
+himself distinctly states ("Descent of Man" (2nd edition), Vol. II.
+pages 136, 137; (Popular edition), pages 642, 643.) that "it is not
+probable that she consciously deliberates; but she is most excited or
+attracted by the most beautiful, or melodious, or gallant males." The
+view here put forward, which has been developed by Prof. Groos ("The
+Play of Animals", page 244, London, 1898.), therefore seems to have
+Darwin's own sanction. The phenomena are not only biological; there are
+psychological elements as well. One can hardly suppose that the female
+is unconscious of the male's presence; the final yielding must surely be
+accompanied by heightened emotional tone. Whether we call it choice or
+not is merely a matter of definition of terms. The behaviour is in part
+determined by supplementary psychological values. Prof. Groos regards
+the coyness of females as "a most efficient means of preventing the
+too early and too frequent yielding to the sexual impulse." (Ibid. page
+283.) Be that as it may, it is, in any case, if we grant the facts, a
+means through which male sexual behaviour with all its biological and
+psychological implications, is raised to a level otherwise perhaps
+unattainable by natural means, while in the female it affords
+opportunities for the development in the individual and evolution in the
+race of what we may follow Darwin in calling appreciation, if we empty
+this word of the aesthetic implications which have gathered round it in
+the mental life of man.
+
+Regarded from this standpoint sexual selection, broadly considered, has
+probably been of great importance. The psychological accompaniments
+of the pairing situation have profoundly influenced the course of
+biological evolution and are themselves the outcome of that evolution.
+
+Darwin makes only passing reference to those modes of behaviour in
+animals which go by the name of play. "Nothing," he says ("Descent of
+Man", Vol. II. page 60; (Popular edition), page 566.), "is more common
+than for animals to take pleasure in practising whatever instinct they
+follow at other times for some real good." This is one of the very
+numerous cases in which a hint of the master has served to stimulate
+research in his disciples. It was left to Prof. Groos to develop this
+subject on evolutionary lines and to elaborate in a masterly manner
+Darwin's suggestion. "The utility of play," he says ("The Play of
+Animals", page 76.), "is incalculable. This utility consists in the
+practice and exercise it affords for some of the more important duties
+of life,"--that is to say, for the performance of activities which will
+in adult life be essential to survival. He urges (Ibid. page 75.) that
+"the play of young animals has its origin in the fact that certain very
+important instincts appear at a time when the animal does not seriously
+need them." It is, however, questionable whether any instincts appear
+at a time when they are not needed. And it is questionable whether
+the instinctive and emotional attitude of the play-fight, to take
+one example, can be identified with those which accompany fighting in
+earnest, though no doubt they are closely related and have some common
+factors. It is probable that play, as preparatory behaviour, differs in
+biological detail (as it almost certainly does in emotional attributes)
+from the earnest of after-life and that it has been evolved through
+differentiation and integration of the primary tissue of experience,
+as a preparation through which certain essential modes of skill may be
+acquired--those animals in which the preparatory play-propensity was
+not inherited in due force and requisite amount being subsequently
+eliminated in the struggle for existence. In any case there is little
+question that Prof. Groos is right in basing the play-propensity on
+instinctive foundations. ("The Play of Animals" page 24.) None the less,
+as he contends, the essential biological value of play is that it is a
+means of training the educable nerve-tissue, of developing that part of
+the brain which is modified by experience and which thus acquires new
+characters, of elaborating the secondary tissue of experience on the
+predetermined lines of instinctive differentiation and thus furthering
+the psychological activities which are included under the comprehensive
+term "intelligent."
+
+In "The Descent of Man" Darwin dealt at some length with intelligence
+and the higher mental faculties. ("Descent of Man" (1st edition),
+Chapters II, III, V; (2nd edition), Chapters III, IV, V.) His object, he
+says, is to show that there is no fundamental difference between man and
+the higher mammals in their mental faculties; that these faculties are
+variable and the variations tend to be inherited; and that under natural
+selection beneficial variations of all kinds will have been preserved
+and injurious ones eliminated.
+
+Darwin was too good an observer and too honest a man to minimise
+the "enormous difference" between the level of mental attainment of
+civilised man and that reached by any animal. His contention was that
+the difference, great as it is, is one of degree and not of kind. He
+realised that, in the development of the mental faculties of man,
+new factors in evolution have supervened--factors which play but
+a subordinate and subsidiary part in animal intelligence.
+Intercommunication by means of language, approbation and blame, and
+all that arises out of reflective thought, are but foreshadowed in the
+mental life of animals. Still he contends that these may be explained
+on the doctrine of evolution. He urges (Ibid. Vol. I. pages 70, 71;
+(Popular edition), pages 70, 71.)" that man is variable in body
+and mind; and that the variations are induced, either directly or
+indirectly, by the same general causes, and obey the same general laws,
+as with the lower animals." He correlates mental development with
+the evolution of the brain. (Ibid. page 81.) "As the various mental
+faculties gradually developed themselves, the brain would almost
+certainly become larger. No one, I presume, doubts that the large
+proportion which the size of man's brain bears to his body, compared to
+the same proportion in the gorilla or orang, is closely connected with
+his higher mental powers." "With respect to the lower animals," he says
+("Descent of Man" (Popular edition), page 82.), "M.E. Lartet ("Comptes
+Rendus des Sciences", June 1, 1868.), by comparing the crania of
+tertiary and recent mammals belonging to the same groups, has come to
+the remarkable conclusion that the brain is generally larger and the
+convolutions are more complex in the more recent form."
+
+Sir E. Ray Lankester has sought to express in the simplest terms the
+implications of the increase in size of the cerebrum. "In what," he
+asks, "does the advantage of a larger cerebral mass consist?" "Man,"
+he replies "is born with fewer ready-made tricks of the
+nerve-centres--these performances of an inherited nervous mechanism so
+often called by the ill-defined term 'instincts'--than are the monkeys
+or any other animal. Correlated with the absence of inherited ready-made
+mechanism, man has a greater capacity of developing in the course of
+his individual growth similar nervous mechanisms (similar to but not
+identical with those of 'instinct') than any other animal... The power of
+being educated--'educability' as we may term it--is what man possesses
+in excess as compared with the apes. I think we are justified in forming
+the hypothesis that it is this 'educability' which is the correlative of
+the increased size of the cerebrum." There has been natural selection
+of the more educable animals, for "the character which we describe as
+'educability' can be transmitted, it is a congenital character. But the
+RESULTS of education can NOT be transmitted. In each generation they
+have to be acquired afresh, and with increased 'educability' they are
+more readily acquired and a larger variety of them... The fact is
+that there is no community between the mechanisms of instinct and the
+mechanisms of intelligence, and that the latter are later in the history
+of the evolution of the brain than the former and can only develop in
+proportion as the former become feeble and defective." ("Nature", Vol.
+LXI. pages 624, 625 (1900).)
+
+In this statement we have a good example of the further development
+of views which Darwin foreshadowed but did not thoroughly work out. It
+states the biological case clearly and tersely. Plasticity of behaviour
+in special accommodation to special circumstances is of survival value;
+it depends upon acquired characters; it is correlated with increase in
+size and complexity of the cerebrum; under natural selection therefore
+the larger and more complex cerebrum as the organ of plastic behaviour
+has been the outcome of natural selection. We have thus the biological
+foundations for a further development of genetic psychology.
+
+There are diversities of opinion, as Darwin showed, with regard to the
+range of instinct in man and the higher animals as contrasted with lower
+types. Darwin himself said ("Descent of Man", Vol. I. page 100.) that
+"Man, perhaps, has somewhat fewer instincts than those possessed by the
+animals which come next to him in the series." On the other hand, Prof.
+Wm. James says ("Principles of Psychology," Vol. II. page 289.) that man
+is probably the animal with most instincts. The true position is that
+man and the higher animals have fewer complete and self-sufficing
+instincts than those which stand lower in the scale of mental
+evolution, but that they have an equally large or perhaps larger mass of
+instinctive raw material which may furnish the stuff to be elaborated
+by intelligent processes. There is, perhaps, a greater abundance of
+the primary tissue of experience to be refashioned and integrated by
+secondary modification; there is probably the same differentiation in
+relation to the determining biological ends, but there is at the outset
+less differentiation of the particular and specific modes of behaviour.
+The specialised instinctive performances and their concomitant
+experience-complexes are at the outset more indefinite. Only through
+acquired connections, correlated with experience, do they become
+definitely organised.
+
+The full working-out of the delicate and subtle relationship of instinct
+and educability--that is, of the hereditary and the acquired factors in
+the mental life--is the task which lies before genetic and comparative
+psychology. They interact throughout the whole of life, and their
+interactions are very complex. No one can read the chapters of "The
+Descent of Man" which Darwin devotes to a consideration of the mental
+characters of man and animals without noticing, on the one hand, how
+sedulous he is in his search for hereditary foundations, and, on the
+other hand, how fully he realises the importance of acquired habits of
+mind. The fact that educability itself has innate tendencies--is in fact
+a partially differentiated educability--renders the unravelling of the
+factors of mental progress all the more difficult.
+
+In his comparison of the mental powers of men and animals it was
+essential that Darwin should lay stress on points of similarity rather
+than on points of difference. Seeking to establish a doctrine of
+evolution, with its basal concept of continuity of process and community
+of character, he was bound to render clear and to emphasise the
+contention that the difference in mind between man and the higher
+animals, great as it is, is one of degree and not of kind. To this end
+Darwin not only recorded a large number of valuable observations of
+his own, and collected a considerable body of information from reliable
+sources, he presented the whole subject in a new light and showed that
+a natural history of mind might be written and that this method of study
+offered a wide and rich field for investigation. Of course those who
+regarded the study of mind only as a branch of metaphysics smiled at
+the philosophical ineptitude of the mere man of science. But the
+investigation, on natural history lines, has been prosecuted with a
+large measure of success. Much indeed still remains to be done; for
+special training is required, and the workers are still few. Promise
+for the future is however afforded by the fact that investigation is
+prosecuted on experimental lines and that something like organised
+methods of research are taking form. There is now but little reliance
+on casual observations recorded by those who have not undergone the
+necessary discipline in these methods. There is also some change of
+emphasis in formulating conclusions. Now that the general evolutionary
+thesis is fully and freely accepted by those who carry on such
+researches, more stress is laid on the differentiation of the stages of
+evolutionary advance than on the fact of their underlying community of
+nature. The conceptual intelligence which is especially characteristic
+of the higher mental procedure of man is more firmly distinguished
+from the perceptual intelligence which he shares with the lower
+animals--distinguished now as a higher product of evolution, no longer
+as differing in origin or different in kind. Some progress has been
+made, on the one hand in rendering an account of intelligent profiting
+by experience under the guidance of pleasure and pain in the perceptual
+field, on lines predetermined by instinctive differentiation for
+biological ends, and on the other hand in elucidating the method of
+conceptual thought employed, for example, by the investigator himself in
+interpreting the perceptual experience of the lower animals.
+
+Thus there is a growing tendency to realise more fully that there
+are two orders of educability--first an educability of the perceptual
+intelligence based on the biological foundation of instinct, and
+secondly an educability of the conceptual intelligence which
+refashions and rearranges the data afforded by previous inheritance
+and acquisition. It is in relation to this second and higher order of
+educability that the cerebrum of man shows so large an increase of
+mass and a yet larger increase of effective surface through its rich
+convolutions. It is through educability of this order that the human
+child is brought intellectually and affectively into touch with the
+ideal constructions by means of which man has endeavoured, with more
+or less success, to reach an interpretation of nature, and to guide the
+course of the further evolution of his race--ideal constructions which
+form part of man's environment.
+
+It formed no part of Darwin's purpose to consider, save in broad
+outline, the methods, or to discuss in any fulness of detail the results
+of the process by which a differentiation of the mental faculties of
+man from those of the lower animals has been brought about--a
+differentiation the existence of which he again and again
+acknowledges. His purpose was rather to show that, notwithstanding
+this differentiation, there is basal community in kind. This must be
+remembered in considering his treatment of the biological foundations
+on which man's systems of ethics are built. He definitely stated that he
+approached the subject "exclusively from the side of natural history."
+("Descent of Man", Vol. I. page 149.) His general conclusion is that the
+moral sense is fundamentally identical with the social instincts, which
+have been developed for the good of the community; and he suggests
+that the concept which thus enables us to interpret the biological
+ground-plan of morals also enables us to frame a rational ideal of the
+moral end. "As the social instincts," he says (Ibid. page 185.), "both
+of man and the lower animals have no doubt been developed by nearly the
+same steps, it would be advisable, if found practicable, to use the same
+definition in both cases, and to take as the standard of morality,
+the general good or welfare of the community, rather than the general
+happiness." But the kind of community for the good of which the social
+instincts of animals and primitive men were biologically developed may
+be different from that which is the product of civilisation, as Darwin
+no doubt realised. Darwin's contention was that conscience is a social
+instinct and has been evolved because it is useful to the tribe in the
+struggle for existence against other tribes. On the other hand, J.S.
+Mill urged that the moral feelings are not innate but acquired, and Bain
+held the same view, believing that the moral sense is acquired by each
+individual during his life-time. Darwin, who notes (Ibid. page 150
+(footnote).) their opinion with his usual candour, adds that "on the
+general theory of evolution this is at least extremely improbable. It
+is impossible to enter into the question here: much turns on the exact
+connotation of the terms "conscience" and "moral sense," and on the
+meaning we attach to the statement that the moral sense is fundamentally
+identical with the social instincts."
+
+Presumably the majority of those who approach the subjects discussed in
+the third, fourth and fifth chapters of "The Descent of Man" in the full
+conviction that mental phenomena, not less than organic phenomena,
+have a natural genesis, would, without hesitation, admit that the
+intellectual and moral systems of civilised man are ideal constructions,
+the products of conceptual thought, and that as such they are, in
+their developed form, acquired. The moral sentiments are the emotional
+analogues of highly developed concepts. This does not however imply that
+they are outside the range of natural history treatment. Even though
+it may be desirable to differentiate the moral conduct of men from the
+social behaviour of animals (to which some such term as "pre-moral" or
+"quasi-moral" may be applied), still the fact remains that, as Darwin
+showed, there is abundant evidence of the occurrence of such social
+behaviour--social behaviour which, even granted that it is in large part
+intelligently acquired, and is itself so far a product of educability,
+is of survival value. It makes for that integration without which no
+social group could hold together and escape elimination. Furthermore,
+even if we grant that such behaviour is intelligently acquired, that
+is to say arises through the modification of hereditary instincts and
+emotions, the fact remains that only through these instinctive and
+emotional data is afforded the primary tissue of the experience which is
+susceptible of such modification.
+
+Darwin sought to show, and succeeded in showing, that for the
+intellectual and moral life there are instinctive foundations which a
+biological treatment alone can disclose. It is true that he did not
+in all cases analytically distinguish the foundations from the
+superstructure. Even to-day we are scarcely in a position to do so
+adequately. But his treatment was of great value in giving an impetus to
+further research. This value indeed can scarcely be overestimated.
+And when the natural history of the mental operations shall have been
+written, the cardinal fact will stand forth, that the instinctive and
+emotional foundations are the outcome of biological evolution and have
+been ingrained in the race through natural selection. We shall more
+clearly realise that educability itself is a product of natural
+selection, though the specific results acquired through cerebral
+modifications are not transmitted through heredity. It will, perhaps,
+also be realised that the instinctive foundations of social behaviour
+are, for us, somewhat out of date and have undergone but little change
+throughout the progress of civilisation, because natural selection
+has long since ceased to be the dominant factor in human progress. The
+history of human progress has been mainly the history of man's
+higher educability, the products of which he has projected on to his
+environment. This educability remains on the average what it was a dozen
+generations ago; but the thought-woven tapestry of his surroundings is
+refashioned and improved by each succeeding generation. Few men have in
+greater measure enriched the thought-environment with which it is the
+aim of education to bring educable human beings into vital contact, than
+has Charles Darwin. His special field of work was the wide province of
+biology; but he did much to help us realise that mental factors have
+contributed to organic evolution and that in man, the highest product of
+Evolution, they have reached a position of unquestioned supremacy.
+
+
+
+
+XXII. THE INFLUENCE OF THE CONCEPTION OF EVOLUTION ON MODERN PHILOSOPHY.
+By H. Hoffding.
+
+Professor of Philosophy in the University of Copenhagen.
+
+
+I.
+
+It is difficult to draw a sharp line between philosophy and natural
+science. The naturalist who introduces a new principle, or demonstrates
+a fact which throws a new light on existence, not only renders an
+important service to philosophy but is himself a philosopher in the
+broader sense of the word. The aim of philosophy in the stricter sense
+is to attain points of view from which the fundamental phenomena and
+the principles of the special sciences can be seen in their relative
+importance and connection. But philosophy in this stricter sense
+has always been influenced by philosophy in the broader sense. Greek
+philosophy came under the influence of logic and mathematics, modern
+philosophy under the influence of natural science. The name of Charles
+Darwin stands with those of Galileo, Newton, and Robert Mayer--names
+which denote new problems and great alterations in our conception of the
+universe.
+
+First of all we must lay stress on Darwin's own personality. His deep
+love of truth, his indefatigable inquiry, his wide horizon, and his
+steady self-criticism make him a scientific model, even if his results
+and theories should eventually come to possess mainly an historical
+interest. In the intellectual domain the primary object is to reach
+high summits from which wide surveys are possible, to reach them toiling
+honestly upwards by way of experience, and then not to turn dizzy when
+a summit is gained. Darwinians have sometimes turned dizzy, but Darwin
+never. He saw from the first the great importance of his hypothesis, not
+only because of its solution of the old problem as to the value of the
+concept of species, not only because of the grand picture of natural
+evolution which it unrolls, but also because of the life and inspiration
+its method would impart to the study of comparative anatomy, of instinct
+and of heredity, and finally because of the influence it would exert on
+the whole conception of existence. He wrote in his note-book in the
+year 1837: "My theory would give zest to recent and fossil comparative
+anatomy; it would lead to the study of instinct, heredity, and
+mind-heredity, whole (of) metaphysics." ("Life and Letters of Charles
+Darwin", Vol. I. page 8.)
+
+We can distinguish four main points in which Darwin's investigations
+possess philosophical importance.
+
+The evolution hypothesis is much older than Darwin; it is, indeed, one
+of the oldest guessings of human thought. In the eighteenth century it
+was put forward by Diderot and Lamettrie and suggested by Kant (1786).
+As we shall see later, it was held also by several philosophers in the
+first half of the nineteenth century. In his preface to "The Origin of
+Species", Darwin mentions the naturalists who were his forerunners.
+But he has set forth the hypothesis of evolution in so energetic
+and thorough a manner that it perforce attracts the attention of
+all thoughtful men in a much higher degree than it did before the
+publication of the "Origin".
+
+And further, the importance of his teaching rests on the fact that he,
+much more than his predecessors, even than Lamarck, sought a foundation
+for his hypothesis in definite facts. Modern science began by
+demanding--with Kepler and Newton--evidence of verae causae; this
+demand Darwin industriously set himself to satisfy--hence the wealth of
+material which he collected by his observations and his experiments.
+He not only revived an old hypothesis, but he saw the necessity of
+verifying it by facts. Whether the special cause on which he founded the
+explanation of the origin of species--Natural Selection--is sufficient,
+is now a subject of discussion. He himself had some doubt in regard
+to this question, and the criticisms which are directed against his
+hypothesis hit Darwinism rather than Darwin. In his indefatigable search
+for empirical evidence he is a model even for his antagonists: he has
+compelled them to approach the problems of life along other lines than
+those which were formerly followed.
+
+Whether the special cause to which Darwin appealed is sufficient or not,
+at least to it is probably due the greater part of the influence which
+he has exerted on the general trend of thought. "Struggle for existence"
+and "natural selection" are principles which have been applied, more or
+less, in every department of thought. Recent research, it is true, has
+discovered greater empirical discontinuity--leaps, "mutations"--whereas
+Darwin believed in the importance of small variations slowly
+accumulated. It has also been shown by the experimental method, which
+in recent biological work has succeeded Darwin's more historical method,
+that types once constituted possess great permanence, the fluctuations
+being restricted within clearly defined boundaries. The problem has
+become more precise, both as to variation and as to heredity. The inner
+conditions of life have in both respects shown a greater independence
+than Darwin had supposed in his theory, though he always admitted that
+the cause of variation was to him a great enigma, "a most perplexing
+problem," and that the struggle for life could only occur where
+variation existed. But, at any rate, it was of the greatest importance
+that Darwin gave a living impression of the struggle for life which is
+everywhere going on, and to which even the highest forms of existence
+must be amenable. The philosophical importance of these ideas does not
+stand or fall with the answer to the question, whether natural selection
+is a sufficient explanation of the origin of species or not: it has
+an independent, positive value for everyone who will observe life and
+reality with an unbiassed mind.
+
+In accentuating the struggle for life Darwin stands as a
+characteristically English thinker: he continues a train of ideas which
+Hobbes and Malthus had already begun. Moreover in his critical views as
+to the conception of species he had English forerunners; in the middle
+ages Occam and Duns Scotus, in the eighteenth century Berkeley and Hume.
+In his moral philosophy, as we shall see later, he is an adherent of the
+school which is represented by Hutcheson, Hume and Adam Smith. Because
+he is no philosopher in the stricter sense of the term, it is of great
+interest to see that his attitude of mind is that of the great thinkers
+of his nation.
+
+In considering Darwin's influence on philosophy we will begin with an
+examination of the attitude of philosophy to the conception of evolution
+at the time when "The Origin of Species" appeared. We will then examine
+the effects which the theory of evolution, and especially the idea
+of the struggle for life, has had, and naturally must have, on the
+discussion of philosophical problems.
+
+II.
+
+When "The Origin of Species" appeared fifty years ago Romantic
+speculation, Schelling's and Hegel's philosophy, still reigned on the
+continent, while in England Positivism, the philosophy of Comte and
+Stuart Mill, represented the most important trend of thought. German
+speculation had much to say on evolution, it even pretended to be a
+philosophy of evolution. But then the word "evolution" was to be taken
+in an ideal, not in a real, sense. To speculative thought the forms and
+types of nature formed a system of ideas, within which any form could
+lead us by continuous transitions to any other. It was a classificatory
+system which was regarded as a divine world of thought or images, within
+which metamorphoses could go on--a condition comparable with that in
+the mind of the poet when one image follows another with imperceptible
+changes. Goethe's ideas of evolution, as expressed in his "Metamorphosen
+der Pflanzen und der Thiere", belong to this category; it is, therefore,
+incorrect to call him a forerunner of Darwin. Schelling and Hegel
+held the same idea; Hegel expressly rejected the conception of a real
+evolution in time as coarse and materialistic. "Nature," he says, "is
+to be considered as a SYSTEM OF STAGES, the one necessarily arising from
+the other, and being the nearest truth of that from which it proceeds;
+but not in such a way that the one is NATURALLY generated by the other;
+on the contrary (their connection lies) in the inner idea which is the
+ground of nature. The METAMORPHOSIS can be ascribed only to the notion
+as such, because it alone is evolution... It has been a clumsy idea in
+the older as well as in the newer philosophy of nature, to regard the
+transformation and the transition from one natural form and sphere to
+a higher as an outward and actual production." ("Encyclopaedie der
+philosophischen Wissenschaften" (4th edition), Berlin, 1845, paragraph
+249.)
+
+The only one of the philosophers of Romanticism who believed in a
+real, historical evolution, a real production of new species, was Oken.
+("Lehrbuch der Naturphilosophie", Jena, 1809.) Danish philosophers, such
+as Treschow (1812) and Sibbern (1846), have also broached the idea of
+an historical evolution of all living beings from the lowest to the
+highest. Schopenhauer's philosophy has a more realistic character than
+that of Schelling's and Hegel's, his diametrical opposites, though he
+also belongs to the romantic school of thought. His philosophical and
+psychological views were greatly influenced by French naturalists and
+philosophers, especially by Cabanis and Lamarck. He praises the "ever
+memorable Lamarck," because he laid so much stress on the "will to
+live." But he repudiates as a "wonderful error" the idea that the
+organs of animals should have reached their present perfection through
+a development in time, during the course of innumerable generations. It
+was, he said, a consequence of the low standard of contemporary French
+philosophy, that Lamarck came to the idea of the construction of living
+beings in time through succession! ("Ueber den Willen in der Natur" (2nd
+edition), Frankfurt a. M., 1854, pages 41-43.)
+
+The positivistic stream of thought was not more in favour of a real
+evolution than was the Romantic school. Its aim was to adhere to
+positive facts: it looked with suspicion on far-reaching speculation.
+Comte laid great stress on the discontinuity found between the different
+kingdoms of nature, as well as within each single kingdom. As he
+regarded as unscientific every attempt to reduce the number of physical
+forces, so he rejected entirely the hypothesis of Lamarck concerning the
+evolution of species; the idea of species would in his eyes absolutely
+lose its importance if a transition from species to species under the
+influence of conditions of life were admitted. His disciples (Littre,
+Robin) continued to direct against Darwin the polemics which their
+master had employed against Lamarck. Stuart Mill, who, in the theory
+of knowledge, represented the empirical or positivistic movement in
+philosophy--like his English forerunners from Locke to Hume--founded
+his theory of knowledge and morals on the experience of the single
+individual. He sympathised with the theory of the original likeness of
+all individuals and derived their differences, on which he practically
+and theoretically laid much stress, from the influence both of
+experience and education, and, generally, of physical and social causes.
+He admitted an individual evolution, and, in the human species, an
+evolution based on social progress; but no physiological evolution of
+species. He was afraid that the hypothesis of heredity would carry us
+back to the old theory of "innate" ideas.
+
+Darwin was more empirical than Comte and Mill; experience disclosed to
+him a deeper continuity than they could find; closer than before the
+nature and fate of the single individual were shown to be interwoven in
+the great web binding the life of the species with nature as a whole.
+And the continuity which so many idealistic philosophers could find
+only in the world of thought, he showed to be present in the world of
+reality.
+
+III.
+
+Darwin's energetic renewal of the old idea of evolution had its chief
+importance in strengthening the conviction of this real continuity in
+the world, of continuity in the series of form and events. It was a
+great support for all those who were prepared to base their conception
+of life on scientific grounds. Together with the recently discovered law
+of the conservation of energy, it helped to produce the great realistic
+movement which characterises the last third of the nineteenth century.
+After the decline of the Romantic movement people wished to have firmer
+ground under their feet and reality now asserted itself in a more
+emphatic manner than in the period of Romanticism. It was easy for Hegel
+to proclaim that "the real" was "the rational," and that "the
+rational" was "the real": reality itself existed for him only in the
+interpretation of ideal reason, and if there was anything which could
+not be merged in the higher unity of thought, then it was only an
+example of the "impotence of nature to hold to the idea." But now
+concepts are to be founded on nature and not on any system of categories
+too confidently deduced a priori. The new devotion to nature had its
+recompense in itself, because the new points of view made us see that
+nature could indeed "hold to ideas," though perhaps not to those which
+we had cogitated beforehand.
+
+A most important question for philosophers to answer was whether the
+new views were compatible with an idealistic conception of life and
+existence. Some proclaimed that we have now no need of any philosophy
+beyond the principles of the conservation of matter and energy and the
+principle of natural evolution: existence should and could be definitely
+and completely explained by the laws of material nature. But abler
+thinkers saw that the thing was not so simple. They were prepared to
+give the new views their just place and to examine what alterations the
+old views must undergo in order to be brought into harmony with the new
+data.
+
+The realistic character of Darwin's theory was shown not only in the
+idea of natural continuity, but also, and not least, in the idea of the
+cause whereby organic life advances step by step. This idea--the idea of
+the struggle for life--implied that nothing could persist, if it had no
+power to maintain itself under the given conditions. Inner value
+alone does not decide. Idealism was here put to its hardest trial. In
+continuous evolution it could perhaps still find an analogy to the inner
+evolution of ideas in the mind; but in the demand for power in order to
+struggle with outward conditions Realism seemed to announce itself in
+its most brutal form. Every form of Idealism had to ask itself seriously
+how it was going to "struggle for life" with this new Realism.
+
+We will now give a short account of the position which leading thinkers
+in different countries have taken up in regard to this question.
+
+I. Herbert Spencer was the philosopher whose mind was best prepared by
+his own previous thinking to admit the theory of Darwin to a place in
+his conception of the world. His criticism of the arguments which had
+been put forward against the hypothesis of Lamarck, showed that Spencer,
+as a young man, was an adherent to the evolution idea. In his
+"Social Statics" (1850) he applied this idea to human life and moral
+civilisation. In 1852 he wrote an essay on "The Development Hypothesis",
+in which he definitely stated his belief that the differentiation of
+species, like the differentiation within a single organism, was the
+result of development. In the first edition of his "Psychology" (1855)
+he took a step which put him in opposition to the older English school
+(from Locke to Mill): he acknowledged "innate ideas" so far as to
+admit the tendency of acquired habits to be inherited in the course of
+generations, so that the nature and functions of the individual are only
+to be understood through its connection with the life of the species.
+In 1857, in his essay on "Progress", he propounded the law of
+differentiation as a general law of evolution, verified by examples from
+all regions of experience, the evolution of species being only one of
+these examples. On the effect which the appearance of "The Origin of
+Species" had on his mind he writes in his "Autobiography": "Up to
+that time... I held that the sole cause of organic evolution is the
+inheritance of functionally-produced modifications. The "Origin of
+Species" made it clear to me that I was wrong, and that the larger part
+of the facts cannot be due to any such cause... To have the theory of
+organic evolution justified was of course to get further support for
+that theory of evolution at large with which... all my conceptions were
+bound up." (Spencer, "Autobiography", Vol. II. page 50, London, 1904.)
+Instead of the metaphorical expression "natural selection," Spencer
+introduced the term "survival of the fittest," which found favour with
+Darwin as well as with Wallace.
+
+In working out his ideas of evolution, Spencer found that
+differentiation was not the only form of evolution. In its simplest form
+evolution is mainly a concentration, previously scattered elements being
+integrated and losing independent movement. Differentiation is only
+forthcoming when minor wholes arise within a greater whole. And the
+highest form of evolution is reached when there is a harmony between
+concentration and differentiation, a harmony which Spencer calls
+equilibration and which he defines as a moving equilibrium. At the same
+time this definition enables him to illustrate the expression "survival
+of the fittest." "Every living organism exhibits such a moving
+equilibrium--a balanced set of functions constituting its life; and the
+overthrow of this balanced set of functions or moving equilibrium is
+what we call death. Some individuals in a species are so constituted
+that their moving equilibria are less easily overthrown than those of
+other individuals; and these are the fittest which survive, or, in Mr
+Darwin's language, they are the select which nature preserves." (Ibid.
+page 100.) Not only in the domain of organic life, but in all domains,
+the summit of evolution is, according to Spencer, characterised by such
+a harmony--by a moving equilibrium.
+
+Spencer's analysis of the concept of evolution, based on a great variety
+of examples, has made this concept clearer and more definite than
+before. It contains the three elements; integration, differentiation and
+equilibration. It is true that a concept which is to be valid for all
+domains of experience must have an abstract character, and between the
+several domains there is, strictly speaking, only a relation of analogy.
+So there is only analogy between psychical and physical evolution. But
+this is no serious objection, because general concepts do not express
+more than analogies between the phenomena which they represent. Spencer
+takes his leading terms from the material world in defining evolution
+(in the simplest form) as integration of matter and dissipation of
+movement; but as he--not always quite consistently (Cf. my letter
+to him, 1876, now printed in Duncan's "Life and Letters of Herbert
+Spencer", page 178, London, 1908.)--assumed a correspondence of mind and
+matter, he could very well give these terms an indirect importance for
+psychical evolution. Spencer has always, in my opinion with full right,
+repudiated the ascription of materialism. He is no more a materialist
+than Spinoza. In his "Principles of Psychology" (paragraph 63) he
+expressed himself very clearly: "Though it seems easier to translate
+so-called matter into so-called spirit, than to translate so-called
+spirit into so-called matter--which latter is indeed wholly
+impossible--yet no translation can carry us beyond our symbols." These
+words lead us naturally to a group of thinkers whose starting-point
+was psychical evolution. But we have still one aspect of Spencer's
+philosophy to mention.
+
+Spencer founded his "laws of evolution" on an inductive basis, but
+he was convinced that they could be deduced from the law of the
+conservation of energy. Such a deduction is, perhaps, possible for the
+more elementary forms of evolution, integration and differentiation; but
+it is not possible for the highest form, the equilibration, which is a
+harmony of integration and differentiation. Spencer can no more deduce
+the necessity for the eventual appearance of "moving equilibria" of
+harmonious totalities than Hegel could guarantee the "higher unities"
+in which all contradictions should be reconciled. In Spencer's hands the
+theory of evolution acquired a more decidedly optimistic character
+than in Darwin's; but I shall deal later with the relation of Darwin's
+hypothesis to the opposition of optimism and pessimism.
+
+II. While the starting-point of Spencer was biological or cosmological,
+psychical evolution being conceived as in analogy with physical, a group
+of eminent thinkers--in Germany Wundt, in France Fouillee, in Italy
+Ardigo--took, each in his own manner, their starting-point in psychical
+evolution as an original fact and as a type of all evolution, the
+hypothesis of Darwin coming in as a corroboration and as a special
+example. They maintain the continuity of evolution; they find this
+character most prominent in psychical evolution, and this is for them a
+motive to demand a corresponding continuity in the material, especially
+in the organic domain.
+
+To Wundt and Fouillee the concept of will is prominent. They see the
+type of all evolution in the transformation of the life of will from
+blind impulse to conscious choice; the theories of Lamarck and Darwin
+are used to support the view that there is in nature a tendency to
+evolution in steady reciprocity with external conditions. The struggle
+for life is here only a secondary fact. Its apparent prominence is
+explained by the circumstance that the influence of external conditions
+is easily made out, while inner conditions can be verified only
+through their effects. For Ardigo the evolution of thought was the
+starting-point and the type: in the evolution of a scientific hypothesis
+we see a progress from the indefinite (indistinto) to the definite
+(distinto), and this is a characteristic of all evolution, as Ardigo has
+pointed out in a series of works. The opposition between indistinto and
+distinto corresponds to Spencer's opposition between homogeneity and
+heterogeneity. The hypothesis of the origin of differences of species
+from more simple forms is a special example of the general law of
+evolution.
+
+In the views of Wundt and Fouillee we find the fundamental idea of
+idealism: psychical phenomena as expressions of the innermost nature of
+existence. They differ from the older Idealism in the great stress which
+they lay on evolution as a real, historical process which is going on
+through steady conflict with external conditions. The Romantic dread
+of reality is broken. It is beyond doubt that Darwin's emphasis on the
+struggle for life as a necessary condition of evolution has been a very
+important factor in carrying philosophy back to reality from the heaven
+of pure ideas. The philosophy of Ardigo, on the other side, appears
+more as a continuation and deepening of positivism, though the Italian
+thinker arrived at his point of view independently of French-English
+positivism. The idea of continuous evolution is here maintained in
+opposition to Comte's and Mill's philosophy of discontinuity. From Wundt
+and Fouillee Ardigo differs in conceiving psychical evolution not as an
+immediate revelation of the innermost nature of existence, but only as a
+single, though the most accessible example, of evolution.
+
+III. To the French philosophers Boutroux and Bergson, evolution proper
+is continuous and qualitative, while outer experience and physical
+science give us fragments only, sporadic processes and mechanical
+combinations. To Bergson, in his recent work "L'Evolution Creatrice",
+evolution consists in an elan de vie which to our fragmentary
+observation and analytic reflexion appears as broken into a manifold of
+elements and processes. The concept of matter in its scientific form
+is the result of this breaking asunder, essential for all scientific
+reflexion. In these conceptions the strongest opposition between
+inner and outer conditions of evolution is expressed: in the domain of
+internal conditions spontaneous development of qualitative forms--in the
+domain of external conditions discontinuity and mechanical combination.
+
+We see, then, that the theory of evolution has influenced philosophy
+in a variety of forms. It has made idealistic thinkers revise their
+relation to the real world; it has led positivistic thinkers to find a
+closer connection between the facts on which they based their views; it
+has made us all open our eyes for new possibilities to arise through
+the prima facie inexplicable "spontaneous" variations which are the
+condition of all evolution. This last point is one of peculiar interest.
+Deeper than speculative philosophy and mechanical science saw in the
+days of their triumph, we catch sight of new streams, whose sources and
+laws we have still to discover. Most sharply does this appear in the
+theory of mutation, which is only a stronger accentuation of a main
+point in Darwinism. It is interesting to see that an analogous
+problem comes into the foreground in physics through the discovery
+of radioactive phenomena, and in psychology through the assumption
+of psychical new formations (as held by Boutroux, William James and
+Bergson). From this side, Darwin's ideas, as well as the analogous
+ideas in other domains, incite us to renewed examination of our first
+principles, their rationality and their value. On the other hand,
+his theory of the struggle for existence challenges us to examine the
+conditions and discuss the outlook as to the persistence of human life
+and society and of the values that belong to them. It is not enough to
+hope (or fear?) the rising of new forms; we have also to investigate the
+possibility of upholding the forms and ideals which have hitherto been
+the bases of human life. Darwin has here given his age the most earnest
+and most impressive lesson. This side of Darwin's theory is of peculiar
+interest to some special philosophical problems to which I now pass.
+
+IV.
+
+Among philosophical problems the problem of knowledge has in the last
+century occupied a foremost place. It is natural, then, to ask how
+Darwin and the hypothesis whose most eminent representative he is, stand
+to this problem.
+
+Darwin started an hypothesis. But every hypothesis is won by inference
+from certain presuppositions, and every inference is based on
+the general principles of human thought. The evolution hypothesis
+presupposes, then, human thought and its principles. And not only
+the abstract logical principles are thus presupposed. The evolution
+hypothesis purports to be not only a formal arrangement of phenomena,
+but to express also the law of a real process. It supposes, then,
+that the real data--all that in our knowledge which we do not produce
+ourselves, but which we in the main simply receive--are subjected
+to laws which are at least analogous to the logical relations of our
+thoughts; in other words, it assumes the validity of the principle of
+causality. If organic species could arise without cause there would
+be no use in framing hypotheses. Only if we assume the principle of
+causality, is there a problem to solve.
+
+Though Darwinism has had a great influence on philosophy considered as
+a striving after a scientific view of the world, yet here is a point of
+view--the epistemological--where philosophy is not only independent but
+reaches beyond any result of natural science. Perhaps it will be said:
+the powers and functions of organic beings only persist (perhaps also
+only arise) when they correspond sufficiently to the conditions under
+which the struggle of life is to go on. Human thought itself is, then, a
+variation (or a mutation) which has been able to persist and to
+survive. Is not, then, the problem of knowledge solved by the evolution
+hypothesis? Spencer had given an affirmative answer to this question
+before the appearance of "The Origin of Species". For the individual, he
+said, there is an a priori, original, basis (or Anlage) for all mental
+life; but in the species all powers have developed in reciprocity with
+external conditions. Knowledge is here considered from the practical
+point of view, as a weapon in the struggle for life, as an "organon"
+which has been continuously in use for generations. In recent years the
+economic or pragmatic epistemology, as developed by Avenarius and Mach
+in Germany, and by James in America, points in the same direction.
+Science, it is said, only maintains those principles and presuppositions
+which are necessary to the simplest and clearest orientation in
+the world of experience. All assumptions which cannot be applied to
+experience and to practical work, will successively be eliminated.
+
+In these views a striking and important application is made of the idea
+of struggle for life to the development of human thought. Thought must,
+as all other things in the world, struggle for life. But this whole
+consideration belongs to psychology, not to the theory of knowledge
+(epistemology), which is concerned only with the validity of knowledge,
+not with its historical origin. Every hypothesis to explain the
+origin of knowledge must submit to cross-examination by the theory of
+knowledge, because it works with the fundamental forms and principles
+of human thought. We cannot go further back than these forms and
+principles, which it is the aim of epistemology to ascertain and for
+which no further reason can be given. (The present writer, many years
+ago, in his "Psychology" (Copenhagen, 1882; English translation London,
+1891), criticised the evolutionistic treatment of the problem of
+knowledge from the Kantian point of view.)
+
+But there is another side of the problem which is, perhaps, of more
+importance and which epistemology generally overlooks. If new variations
+can arise, not only in organic but perhaps also in inorganic nature, new
+tasks are placed before the human mind. The question is, then, if it has
+forms in which there is room for the new matter? We are here touching
+a possibility which the great master of epistemology did not bring to
+light. Kant supposed confidently that no other matter of knowledge could
+stream forth from the dark source which he called "the thing-in-itself,"
+than such as could be synthesised in our existing forms of knowledge.
+He mentions the possibility of other forms than the human, and warns us
+against the dogmatic assumption that the human conception of existence
+should be absolutely adequate. But he seems to be quite sure that the
+thing-in-itself works constantly, and consequently always gives us only
+what our powers can master. This assumption was a consequence of Kant's
+rationalistic tendency, but one for which no warrant can be given.
+Evolutionism and systematism are opposing tendencies which can never
+be absolutely harmonised one with the other. Evolution may at any time
+break some form which the system-monger regards as finally established.
+Darwin himself felt a great difference in looking at variation as an
+evolutionist and as a systematist. When he was working at his evolution
+theory, he was very glad to find variations; but they were a hindrance
+to him when he worked as a systematist, in preparing his work on
+Cirripedia. He says in a letter: "I had thought the same parts of the
+same species more resemble (than they do anyhow in Cirripedia) objects
+cast in the same mould. Systematic work would be easy were it not
+for this confounded variation, which, however, is pleasant to me as a
+speculatist, though odious to me as a systematist." ("Life and Letters",
+Vol. II. page 37.) He could indeed be angry with variations even as
+an evolutionist; but then only because he could not explain them, not
+because he could not classify them. "If, as I must think, external
+conditions produce little DIRECT effect, what the devil determines each
+particular variation?" (Ibid. page 232.) What Darwin experienced in
+his particular domain holds good of all knowledge. All knowledge is
+systematic, in so far as it strives to put phenomena in quite definite
+relations, one to another. But the systematisation can never be
+complete. And here Darwin has contributed much to widen the world for
+us. He has shown us forces and tendencies in nature which make absolute
+systems impossible, at the same time that they give us new objects and
+problems. There is still a place for what Lessing called "the unceasing
+striving after truth," while "absolute truth" (in the sense of a closed
+system) is unattainable so long as life and experience are going on.
+
+There is here a special remark to be made. As we have seen above, recent
+research has shown that natural selection or struggle for life is no
+explanation of variations. Hugo de Vries distinguishes between partial
+and embryonal variations, or between variations and mutations, only the
+last-named being heritable, and therefore of importance for the origin
+of new species. But the existence of variations is not only of interest
+for the problem of the origin of species; it has also a more general
+interest. An individual does not lose its importance for knowledge,
+because its qualities are not heritable. On the contrary, in higher
+beings at least, individual peculiarities will become more and more
+independent objects of interest. Knowledge takes account of the
+biographies not only of species, but also of individuals: it seeks to
+find the law of development of the single individual. (The new science
+of Ecology occupies an intermediate position between the biography of
+species and the biography of individuals. Compare "Congress of Arts and
+Science", St Louis, Vol. V. 1906 (the Reports of Drude and Robinson)
+and the work of my colleague E. Warming.) As Leibniz said long ago,
+individuality consists in the law of the changes of a being. "La loi du
+changement fait l'individualite de chaque substance." Here is a world
+which is almost new for science, which till now has mainly occupied
+itself with general laws and forms. But these are ultimately only means
+to understand the individual phenomena, in whose nature and history
+a manifold of laws and forms always cooperate. The importance of this
+remark will appear in the sequel.
+
+V.
+
+To many people the Darwinian theory of natural selection or struggle
+for existence seemed to change the whole conception of life, and
+particularly all the conditions on which the validity of ethical ideas
+depends. If only that has persistence which can be adapted to a given
+condition, what will then be the fate of our ideals, of our standards
+of good and evil? Blind force seems to reign, and the only thing that
+counts seems to be the most heedless use of power. Darwinism, it was
+said, has proclaimed brutality. No other difference seems permanent save
+that between the sound, powerful and happy on the one side, the sick,
+feeble and unhappy on the other; and every attempt to alleviate this
+difference seems to lead to general enervation. Some of those who
+interpreted Darwinism in this manner felt an aesthetic delight in
+contemplating the heedlessness and energy of the great struggle for
+existence and anticipated the realisation of a higher human type as the
+outcome of it: so Nietzsche and his followers. Others recognising the
+same consequences in Darwinism regarded these as one of the strongest
+objections against it; so Duhring and Kropotkin (in his earlier works).
+
+This interpretation of Darwinism was frequent in the interval between
+the two main works of Darwin--"The Origin of Species" and "The Descent
+of Man". But even during this interval it was evident to an attentive
+reader that Darwin himself did not found his standard of good and evil
+on the features of the life of nature he had emphasised so strongly. He
+did not justify the ways along which nature reached its ends; he only
+pointed them out. The "real" was not to him, as to Hegel, one with
+the "rational." Darwin has, indeed, by his whole conception of nature,
+rendered a great service to ethics in making the difference between the
+life of nature and the ethical life appear in so strong a light. The
+ethical problem could now be stated in a sharper form than before. But
+this was not the first time that the idea of the struggle for life
+was put in relation to the ethical problem. In the seventeenth century
+Thomas Hobbes gave the first impulse to the whole modern discussion of
+ethical principles in his theory of bellum omnium contra omnes. Men, he
+taught, are in the state of nature enemies one of another, and they live
+either in fright or in the glory of power. But it was not the opinion
+of Hobbes that this made ethics impossible. On the contrary, he found a
+standard for virtue and vice in the fact that some qualities and actions
+have a tendency to bring us out of the state of war and to secure
+peace, while other qualities have a contrary tendency. In the eighteenth
+century even Immanuel Kant's ideal ethics had--so far as can be seen--a
+similar origin. Shortly before the foundation of his definitive ethics,
+Kant wrote his "Idee zu einer allgemeinen Weltgeschichte" (1784),
+where--in a way which reminds us of Hobbes, and is prophetic of
+Darwin--he describes the forward-driving power of struggle in the human
+world. It is here as with the struggle of the trees for light and air,
+through which they compete with one another in height. Anxiety about
+war can only be allayed by an ordinance which gives everyone his full
+liberty under acknowledgment of the equal liberty of others. And such
+ordinance and acknowledgment are also attributes of the content of the
+moral law, as Kant proclaimed it in the year after the publication
+of his essay (1785) (Cf. my "History of Modern Philosophy" (English
+translation London, 1900), I. pages 76-79.) Kant really came to his
+ethics by the way of evolution, though he afterwards disavowed it.
+Similarly the same line of thought may be traced in Hegel though it has
+been disguised in the form of speculative dialectics. ("Herrschaft und
+Knechtschaft", "Phanomenologie des Geistes", IV. A., Leiden, 1907.) And
+in Schopenhauer's theory of the blind will to live and its abrogation by
+the ethical feeling, which is founded on universal sympathy, we have a
+more individualistic form of the same idea.
+
+It was, then, not entirely a foreign point of view which Darwin
+introduced into ethical thought, even if we take no account of the
+poetical character of the word "struggle" and of the more direct
+adaptation, through the use and non-use of power, which Darwin also
+emphasised. In "The Descent of Man" he has devoted a special chapter
+("The Descent of Man", Vol. I. Ch. iii.) to a discussion of the origin
+of the ethical consciousness. The characteristic expression of this
+consciousness he found, just as Kant did, in the idea of "ought"; it was
+the origin of this new idea which should be explained. His hypothesis
+was that the ethical "ought" has its origin in the social and parental
+instincts, which, as well as other instincts (e.g. the instinct of
+self-preservation), lie deeper than pleasure and pain. In many species,
+not least in the human species, these instincts are fostered by natural
+selection; and when the powers of memory and comparison are developed,
+so that single acts can be valued according to the claims of the deep
+social instinct, then consciousness of duty and remorse are possible.
+Blind instinct has developed to conscious ethical will.
+
+As already stated, Darwin, as a moral philosopher belongs to the school
+that was founded by Shaftesbury, and was afterwards represented by
+Hutcheson, Hume, Adam Smith, Comte and Spencer. His merit is, first,
+that he has given this tendency of thought a biological foundation, and
+that he has stamped on it a doughty character in showing that ethical
+ideas and sentiments, rightly conceived, are forces which are at work in
+the struggle for life.
+
+There are still many questions to solve. Not only does the ethical
+development within the human species contain features still unexplained
+(The works of Westermarck and Hobhouse throw new light on many of these
+features.); but we are confronted by the great problem whether after all
+a genetic historical theory can be of decisive importance here. To
+every consequent ethical consciousness there is a standard of value, a
+primordial value which determines the single ethical judgments as their
+last presupposition, and the "rightness" of this basis, the "value"
+of this value can as little be discussed as the "rationality" of our
+logical principles. There is here revealed a possibility of ethical
+scepticism which evolutionistic ethics (as well as intuitive or
+rationalistic ethics) has overlooked. No demonstration can show that the
+results of the ethical development are definitive and universal. We
+meet here again with the important opposition of systematisation and
+evolution. There will, I think, always be an open question here, though
+comparative ethics, of which we have so far only the first attempts, can
+do much to throw light on it.
+
+It would carry us too far to discuss all the philosophical works
+on ethics, which have been influenced directly or indirectly by
+evolutionism. I may, however, here refer to the book of C.M. Williams,
+"A Review of the Systems of Ethics founded on the Theory of Evolution"
+(New York and London, 1893.), in which, besides Darwin, the following
+authors are reviewed: Wallace, Haeckel, Spencer, Fiske, Rolph, Barratt,
+Stephen, Carneri, Hoffding, Gizycki, Alexander, Ree. As works which
+criticise evolutionistic ethics from an intuitive point of view and
+in an instructive way, may be cited: Guyau "La morale anglaise
+contemporaine" (Paris, 1879.), and Sorley, "Ethics of Naturalism". I
+will only mention some interesting contributions to ethical discussion
+which can be found in Darwinism besides the idea of struggle for life.
+
+The attention which Darwin has directed to variations has opened our
+eyes to the differences in human nature as well as in nature generally.
+There is here a fact of great importance for ethical thought, no matter
+from what ultimate premiss it starts. Only from a very abstract point of
+view can different individuals be treated in the same manner. The most
+eminent ethical thinkers, men such as Jeremy Bentham and Immanuel Kant,
+who discussed ethical questions from very opposite standpoints, agreed
+in regarding all men as equal in respect of ethical endowment. In regard
+to Bentham, Leslie Stephen remarks: "He is determined to be thoroughly
+empirical, to take men as he found them. But his utilitarianism supposed
+that men's views of happiness and utility were uniform and clear, and
+that all that was wanted was to show them the means by which their ends
+could be reached." ("English literature and society in the eighteenth
+century", London, 1904, page 187.) And Kant supposed that every man
+would find the "categorical imperative" in his consciousness, when he
+came to sober reflexion, and that all would have the same qualifications
+to follow it. But if continual variations, great or small, are going on
+in human nature, it is the duty of ethics to make allowance for them,
+both in making claims, and in valuing what is done. A new set of ethical
+problems have their origin here. (Cf. my paper, "The law of relativity
+in Ethics," "International Journal of Ethics", Vol. I. 1891, pages
+37-62.) It is an interesting fact that Stuart Mill's book "On Liberty"
+appeared in the same year as "The Origin of Species". Though Mill agreed
+with Bentham about the original equality of all men's endowments, he
+regarded individual differences as a necessary result of physical and
+social influences, and he claimed that free play shall be allowed to
+differences of character so far as is possible without injury to other
+men. It is a condition of individual and social progress that a man's
+mode of action should be determined by his own character and not
+by tradition and custom, nor by abstract rules. This view was to be
+corroborated by the theory of Darwin.
+
+But here we have reached a point of view from which the criticism,
+which in recent years has often been directed against Darwin--that
+small variations are of no importance in the struggle for life--is of
+no weight. From an ethical standpoint, and particularly from the
+ethical standpoint of Darwin himself, it is a duty to foster individual
+differences that can be valuable, even though they can neither be of
+service for physical preservation nor be physically inherited. The
+distinction between variation and mutation is here without importance.
+It is quite natural that biologists should be particularly interested in
+such variations as can be inherited and produce new species. But in the
+human world there is not only a physical, but also a mental and social
+heredity. When an ideal human character has taken form, then there
+is shaped a type, which through imitation and influence can become an
+important factor in subsequent development, even if it cannot form a
+species in the biological sense of the word. Spiritually strong
+men often succumb in the physical struggle for life; but they can
+nevertheless be victorious through the typical influence they exert,
+perhaps on very distant generations, if the remembrance of them is kept
+alive, be it in legendary or in historical form. Their very failure
+can show that a type has taken form which is maintained at all risks,
+a standard of life which is adhered to in spite of the strongest
+opposition. The question "to be or not to be" can be put from
+very different levels of being: it has too often been considered a
+consequence of Darwinism that this question is only to be put from
+the lowest level. When a stage is reached, where ideal (ethical,
+intellectual, aesthetic) interests are concerned, the struggle for life
+is a struggle for the preservation of this stage. The giving up of a
+higher standard of life is a sort of death; for there is not only a
+physical, there is also a spiritual, death.
+
+VI.
+
+The Socratic character of Darwin's mind appears in his wariness in
+drawing the last consequences of his doctrine, in contrast both with the
+audacious theories of so many of his followers and with the consequences
+which his antagonists were busy in drawing. Though he, as we have seen,
+saw from the beginning that his hypothesis would occasion "a whole of
+metaphysics," he was himself very reserved as to the ultimate questions,
+and his answers to such questions were extorted from him.
+
+As to the question of optimism and pessimism, Darwin held that though
+pain and suffering were very often the ways by which animals were led
+to pursue that course of action which is most beneficial to the species,
+yet pleasurable feelings were the most habitual guides. "We see this in
+the pleasure from exertion, even occasionally from great exertion of the
+body or mind, in the pleasure of our daily meals, and especially in the
+pleasure derived from sociability, and from loving our families." But
+there was to him so much suffering in the world that it was a strong
+argument against the existence of an intelligent First Cause. ("Life and
+Letters" Vol. I. page 310.)
+
+It seems to me that Darwin was not so clear on another question, that
+of the relation between improvement and adaptation. He wrote to Lyell:
+"When you contrast natural selection and 'improvement,' you seem always
+to overlook... that every step in the natural selection of each species
+implies improvement in that species IN RELATION TO ITS CONDITION OF
+LIFE... Improvement implies, I suppose, EACH FORM OBTAINING MANY PARTS
+OR ORGANS, all excellently adapted for their functions." "All this," he
+adds, "seems to me quite compatible with certain forms fitted for simple
+conditions, remaining unaltered, or being degraded." (Ibid. Vol. II.
+page 177.) But the great question is, if the conditions of life will in
+the long run favour "improvement" in the sense of differentiation
+(or harmony of differentiation and integration). Many beings are best
+adapted to their conditions of life if they have few organs and few
+necessities. Pessimism would not only be the consequence, if suffering
+outweighed happiness, but also if the most elementary forms of happiness
+were predominant, or if there were a tendency to reduce the standard
+of life to the simplest possible, the contentment of inertia or stable
+equilibrium. There are animals which are very highly differentiated and
+active in their young state, but later lose their complex organisation
+and concentrate themselves on the one function of nutrition. In the
+human world analogies to this sort of adaptation are not wanting. Young
+"idealists" very often end as old "Philistines." Adaptation and progress
+are not the same.
+
+Another question of great importance in respect to human evolution
+is, whether there will be always a possibility for the existence of
+an impulse to progress, an impulse to make great claims on life, to be
+active and to alter the conditions of life instead of adapting to them
+in a passive manner. Many people do not develop because they have
+too few necessities, and because they have no power to imagine other
+conditions of life than those under which they live. In his remarks
+on "the pleasure from exertion" Darwin has a point of contact with
+the practical idealism of former times--with the ideas of Lessing and
+Goethe, of Condorcet and Fichte. The continual striving which was
+the condition of salvation to Faust's soul, is also the condition
+of salvation to mankind. There is a holy fire which we ought to keep
+burning, if adaptation is really to be improvement. If, as I have
+tried to show in my "Philosophy of Religion", the innermost core of all
+religion is faith in the persistence of value in the world, and if
+the highest values express themselves in the cry "Excelsior!" then the
+capital point is, that this cry should always be heard and followed. We
+have here a corollary of the theory of evolution in its application to
+human life.
+
+Darwin declared himself an agnostic, not only because he could not
+harmonise the large amount of suffering in the world with the idea of a
+God as its first cause, but also because he "was aware that if we admit
+a first cause, the mind still craves to know whence it came and how it
+arose." ("Life and Letters", Vol. I. page 306.) He saw, as Kant had
+seen before him and expressed in his "Kritik der Urtheilskraft", that we
+cannot accept either of the only two possibilities which we are able
+to conceive: chance (or brute force) and design. Neither mechanism
+nor teleology can give an absolute answer to ultimate questions.
+The universe, and especially the organic life in it, can neither be
+explained as a mere combination of absolute elements nor as the effect
+of a constructing thought. Darwin concluded, as Kant, and before him
+Spinoza, that the oppositions and distinctions which our experience
+presents, cannot safely be regarded as valid for existence in itself.
+And, with Kant and Fichte, he found his stronghold in the conviction
+that man has something to do, even if he cannot solve all enigmas. "The
+safest conclusion seems to me that the whole subject is beyond the scope
+of man's intellect; but man can do his duty." (Ibid. page 307.)
+
+Is this the last word of human thought? Does not the possibility,
+that man can do his duty, suppose that the conditions of life allow of
+continuous ethical striving, so that there is a certain harmony
+between cosmic order and human ideals? Darwin himself has shown how
+the consciousness of duty can arise as a natural result of evolution.
+Moreover there are lines of evolution which have their end in ethical
+idealism, in a kingdom of values, which must struggle for life as all
+things in the world must do, but a kingdom which has its firm foundation
+in reality.
+
+
+
+
+XXIII. DARWINISM AND SOCIOLOGY. By C. Bougle.
+
+Professor of Social Philosophy in the University of Toulouse and
+Deputy-Professor at the Sorbonne, Paris.
+
+
+How has our conception of social phenomena, and of their history,
+been affected by Darwin's conception of Nature and the laws of its
+transformations? To what extent and in what particular respects have
+the discoveries and hypotheses of the author of "The Origin of Species"
+aided the efforts of those who have sought to construct a science of
+society?
+
+To such a question it is certainly not easy to give any brief or precise
+answer. We find traces of Darwinism almost everywhere. Sociological
+systems differing widely from each other have laid claim to its
+authority; while, on the other hand, its influence has often made itself
+felt only in combination with other influences. The Darwinian thread is
+worked into a hundred patterns along with other threads.
+
+To deal with the problem, we must, it seems, first of all distinguish
+the more general conclusions in regard to the evolution of living
+beings, which are the outcome of Darwinism, from the particular
+explanations it offers of the ways and means by which that evolution
+is effected. That is to say, we must, as far as possible, estimate
+separately the influence of Darwin as an evolutionist and Darwin as a
+selectionist.
+
+The nineteenth century, said Cournot, has witnessed a mighty effort to
+"reintegrer l'homme dans la nature." From divers quarters there has been
+a methodical reaction against the persistent dualism of the Cartesian
+tradition, which was itself the unconscious heir of the Christian
+tradition. Even the philosophy of the eighteenth century, materialistic
+as were for the most part the tendencies of its leaders, seemed to
+revere man as a being apart, concerning whom laws might be formulated a
+priori. To bring him down from his pedestal there was needed the marked
+predominance of positive researches wherein no account was taken of
+the "pride of man." There can be no doubt that Darwin has done much to
+familiarise us with this attitude. Take for instance the first part
+of "The Descent of Man": it is an accumulation of typical facts, all
+tending to diminish the distance between us and our brothers, the lower
+animals. One might say that the naturalist had here taken as his motto,
+"Whosoever shall exalt himself shall be abased; and he that shall humble
+himself shall be exalted." Homologous structures, the survival in man of
+certain organs of animals, the rudiments in the animal of certain
+human faculties, a multitude of facts of this sort, led Darwin to the
+conclusion that there is no ground for supposing that the "king of the
+universe" is exempt from universal laws. Thus belief in the imperium
+in imperio has been, as it were, whittled away by the progress of the
+naturalistic spirit, itself continually strengthened by the conquests of
+the natural sciences. The tendency may, indeed, drag the social sciences
+into overstrained analogies, such, for instance, as the assimilation
+of societies to organisms. But it will, at least, have had the merit of
+helping sociology to shake off the pre-conception that the groups formed
+by men are artificial, and that history is completely at the mercy of
+chance. Some years before the appearance of "The Origin of Species",
+Auguste Comte had pointed out the importance, as regards the unification
+of positive knowledge, of the conviction that the social world, the last
+refuge of spiritualism, is itself subject to determininism. It cannot be
+doubted that the movement of thought which Darwin's discoveries promoted
+contributed to the spread of this conviction, by breaking down the
+traditional barrier which cut man off from Nature.
+
+But Nature, according to modern naturalists, is no immutable thing: it
+is rather perpetual movement, continual progression. Their discoveries
+batter a breach directly into the Aristotelian notion of species; they
+refuse to see in the animal world a collection of immutable types,
+distinct from all eternity, and corresponding, as Cuvier said, to so
+many particular thoughts of the Creator. Darwin especially congratulated
+himself upon having been able to deal this doctrine the coup de grace:
+immutability is, he says, his chief enemy; and he is concerned to
+show--therein following up Lyell's work--that everything in the organic
+world, as in the inorganic, is explained by insensible but incessant
+transformations. "Nature makes no leaps"--"Nature knows no gaps": these
+two dicta form, as it were, the two landmarks between which Darwin's
+idea of transformation is worked out. That is to say, the development of
+Darwinism is calculated to further the application of the philosophy of
+Becoming to the study of human institutions.
+
+The progress of the natural sciences thus brings unexpected
+reinforcements to the revolution which the progress of historical
+discipline had begun. The first attempt to constitute an actual science
+of social phenomena--that, namely, of the economists--had resulted in
+laws which were called natural, and which were believed to be
+eternal and universal, valid for all times and all places. But this
+perpetuality, brother, as Knies said, of the immutability of the old
+zoology, did not long hold out against the ever swelling tide of the
+historical movement. Knowledge of the transformations that had taken
+place in language, of the early phases of the family, of religion, of
+property, had all favoured the revival of the Heraclitean view: panta
+rei. As to the categories of political economy, it was soon to be
+recognised, as by Lassalle, that they too are only historical. The
+philosophy of history, moreover, gave expression under various forms to
+the same tendency. Hegel declares that "all that is real is rational,"
+but at the same time he shows that all that is real is ephemeral, and
+that for history there is nothing fixed beneath the sun. It is this
+sense of universal evolution that Darwin came with fresh authority
+to enlarge. It was in the name of biological facts themselves that he
+taught us to see only slow metamorphoses in the history of institutions,
+and to be always on the outlook for survivals side by side with
+rudimentary forms. Anyone who reads "Primitive Culture", by Tylor,--a
+writer closely connected with Darwin--will be able to estimate the
+services which these cardinal ideas were to render to the social
+sciences when the age of comparative research had succeeded to that of a
+priori construction.
+
+Let us note, moreover, that the philosophy of Becoming in passing
+through the Darwinian biology became, as it were, filtered: it got
+rid of those traces of finalism, which, under different forms, it had
+preserved through all the systems of German Romanticism. Even in Herbert
+Spencer, it has been plausibly argued, one can detect something of that
+sort of mystic confidence in forces spontaneously directing life, which
+forms the very essence of those systems. But Darwin's observations
+were precisely calculated to render such an hypothesis futile. At first
+people may have failed to see this; and we call to mind the ponderous
+sarcasms of Flourens when he objected to the theory of Natural Selection
+that it attributed to nature a power of free choice. "Nature endowed
+with will! That was the final error of last century; but the nineteenth
+no longer deals in personifications." (P. Flourens, "Examen du Livre
+de M. Darwin sur l'Origine des Especes", page 53, Paris, 1864. See also
+Huxley, "Criticisms on the 'Origin of Species'", "Collected Essays",
+Vol. II, page 102, London, 1902.) In fact Darwin himself put his
+readers on their guard against the metaphors he was obliged to use. The
+processes by which he explains the survival of the fittest are far from
+affording any indication of the design of some transcendent breeder.
+Nor, if we look closely, do they even imply immanent effort in the
+animal; the sorting out can be brought about mechanically, simply by
+the action of the environment. In this connection Huxley could with
+good reason maintain that Darwin's originality consisted in showing
+how harmonies which hitherto had been taken to imply the agency of
+intelligence and will could be explained without any such intervention.
+So, when later on, objective sociology declares that, even when
+social phenomena are in question, all finalist preconceptions must be
+distrusted if a science is to be constituted, it is to Darwin that its
+thanks are due; he had long been clearing paths for it which lay
+well away from the old familiar road trodden by so many theories of
+evolution.
+
+This anti-finalist doctrine, when fully worked out, was, moreover,
+calculated to aid in the needful dissociation of two notions: that of
+evolution and that of progress. In application to society these had long
+been confounded; and, as a consequence, the general idea seemed to be
+that only one type of evolution was here possible. Do we not detect
+such a view in Comte's sociology, and perhaps even in Herbert Spencer's?
+Whoever, indeed, assumes an end for evolution is naturally inclined to
+think that only one road leads to that end. But those whose minds the
+Darwinian theory has enlightened are aware that the transformations of
+living beings depend primarily upon their conditions, and that it is
+these conditions which are the agents of selection from among individual
+variations. Hence, it immediately follows that transformations are not
+necessarily improvements. Here, Darwin's thought hesitated. Logically
+his theory proves, as Ray Lankester pointed out, that the struggle for
+existence may have as its outcome degeneration as well as amelioration:
+evolution may be regressive as well as progressive. Then, too--and this
+is especially to be borne in mind--each species takes its good where
+it finds it, seeks its own path and survives as best it can. Apply this
+notion to society and you arrive at the theory of multilinear evolution.
+Divergencies will no longer surprise you. You will be forewarned not to
+apply to all civilisations the same measure of progress, and you will
+recognise that types of evolution may differ just as social species
+themselves differ. Have we not here one of the conceptions which mark
+off sociology proper from the old philosophy of history?
+
+But if we are to estimate the influence of Darwinism upon sociological
+conceptions, we must not dwell only upon the way in which Darwin
+impressed the general notion of evolution upon the minds of thinkers. We
+must go into details. We must consider the influence of the particular
+theories by which he explained the mechanism of this evolution. The name
+of the author of "The Origin of Species" has been especially attached,
+as everyone knows, to the doctrines of "natural selection" and of
+"struggle for existence," completed by the notion of "individual
+variation." These doctrines were turned to account by very different
+schools of social philosophy. Pessimistic and optimistic, aristocratic
+and democratic, individualistic and socialistic systems were to war
+with each other for years by casting scraps of Darwinism at each other's
+heads.
+
+It was the spectacle of human contrivance that suggested to Darwin
+his conception of natural selection. It was in studying the methods of
+pigeon breeders that he divined the processes by which nature, in the
+absence of design, obtains analogous results in the differentiation
+of types. As soon as the importance of artificial selection in the
+transformation of species of animals was understood, reflection
+naturally turned to the human species, and the question arose, How far
+do men observe, in connection with themselves, those laws of which they
+make practical application in the case of animals? Here we come upon one
+of the ideas which guided the researches of Galton, Darwin's cousin. The
+author of "Inquiries into Human Faculty and its Development" ("Inquiries
+into Human Faculty", pages 1, 2, 3 sq., London, 1883.), has often
+expressed his surprise that, considering all the precautions taken,
+for example, in the breeding of horses, none whatever are taken in the
+breeding of the human species. It seems to be forgotten that the species
+suffers when the "fittest" are not able to perpetuate their type.
+Ritchie, in his "Darwinism and Politics" ("Darwinism and Politics" pages
+9, 22, London, 1889.) reminds us of Darwin's remark that the institution
+of the peerage might be defended on the ground that peers, owing to the
+prestige they enjoy, are enabled to select as wives "the most beautiful
+and charming women out of the lower ranks." ("Life and Letters of
+Charles Darwin", II. page 385.) But, says Galton, it is as often as not
+"heiresses" that they pick out, and birth statistics seem to show that
+these are either less robust or less fecund than others. The truth is
+that considerations continue to preside over marriage which are entirely
+foreign to the improvement of type, much as this is a condition of
+general progress. Hence the importance of completing Odin's and De
+Candolle's statistics which are designed to show how characters are
+incorporated in organisms, how they are transmitted, how lost, and
+according to what law eugenic elements depart from the mean or return to
+it.
+
+But thinkers do not always content themselves with undertaking merely
+the minute researches which the idea of Selection suggests. They are
+eager to defend this or that thesis. In the name of this idea certain
+social anthropologists have recast the conception of the process of
+civilisation, and have affirmed that Social Selection generally works
+against the trend of Natural Selection. Vacher de Lapouge--following
+up an observation by Broca on the point--enumerates the various
+institutions, or customs, such as the celibacy of priests and military
+conscription, which cause elimination or sterilisation of the bearers of
+certain superior qualities, intellectual or physical. In a more general
+way he attacks the democratic movement, a movement, as P. Bourget says,
+which is "anti-physical" and contrary to the natural laws of progress;
+though it has been inspired "by the dreams of that most visionary of all
+centuries, the eighteenth." (V. de Lapouge, "Les Selections sociales",
+page 259, Paris, 1896.) The "Equality" which levels down and mixes
+(justly condemned, he holds, by the Comte de Gobineau), prevents the
+aristocracy of the blond dolichocephales from holding the position and
+playing the part which, in the interests of all, should belong to them.
+Otto Ammon, in his "Natural Selection in Man", and in "The Social Order
+and its Natural Bases" ("Die naturliche Auslese beim Menschen", Jena,
+1893; "Die Gesellschaftsordnung und ihre naturlichen Grundlagen".
+"Entwurf einer Sozialanthropologie", Jena, 1896.), defended analogous
+doctrines in Germany; setting the curve representing frequency of talent
+over against that of income, he attempted to show that all democratic
+measures which aim at promoting the rise in the social scale of the
+talented are useless, if not dangerous; that they only increase the
+panmixia, to the great detriment of the species and of society.
+
+Among the aristocratic theories which Darwinism has thus inspired
+we must reckon that of Nietzsche. It is well known that in order to
+complete his philosophy he added biological studies to his philological;
+and more than once in his remarks upon the "Wille zur Macht" he
+definitely alludes to Darwin; though it must be confessed that it is
+generally in order to proclaim the in sufficiency of the processes by
+which Darwin seeks to explain the genesis of species. Nevertheless,
+Nietzsche's mind is completely possessed by an ideal of Selection.
+He, too, has a horror of panmixia. The naturalists' conception of "the
+fittest" is joined by him to that of the "hero" of romance to furnish a
+basis for his doctrine of the Superman. Let us hasten to add, moreover,
+that at the very moment when support was being sought in the theory of
+Selection for the various forms of the aristocratic doctrine, those same
+forms were being battered down on another side by means of that very
+theory. Attention was drawn to the fact that by virtue of the laws which
+Darwin himself had discovered isolation leads to etiolation. There is
+a risk that the privilege which withdraws the privileged elements of
+Society from competition will cause them to degenerate. In fact, Jacoby
+in his "Studies in Selection, in connexion with Heredity in Man",
+("Etudes sur la Selection dans ses rapports avec l'heredite chez
+l'homme", Paris, page 481, 1881.), concludes that "sterility, mental
+debility, premature death and, finally, the extinction of the stock
+were not specially and exclusively the fate of sovereign dynasties; all
+privileged classes, all families in exclusively elevated positions share
+the fate of reigning families, although in a minor degree and in direct
+proportion to the loftiness of their social standing. From the mass of
+human beings spring individuals, families, races, which tend to raise
+themselves above the common level; painfully they climb the rugged
+heights, attain the summits of power, of wealth, of intelligence, of
+talent, and then, no sooner are they there than they topple down and
+disappear in gulfs of mental and physical degeneracy." The demographical
+researches of Hansen ("Die drei Bevolkerungsstufen", Munich, 1889.)
+(following up and completing Dumont's) tended, indeed, to show that
+urban as well as feudal aristocracies, burgher classes as well as noble
+castes, were liable to become effete. Hence it might well be concluded
+that the democratic movement, operating as it does to break down class
+barriers, was promoting instead of impeding human selection.
+
+So we see that, according to the point of view, very different
+conclusions have been drawn from the application of the Darwinian idea
+of Selection to human society. Darwin's other central idea, closely
+bound up with this, that, namely, of the "struggle for existence" also
+has been diversely utilised. But discussion has chiefly centered upon
+its signification. And while some endeavour to extend its application to
+everything, we find others trying to limit its range. The conception of
+a "struggle for existence" has in the present day been taken up into
+the social sciences from natural science, and adopted. But originally it
+descended from social science to natural. Darwin's law is, as he himself
+said, only Malthus' law generalised and extended to the animal world: a
+growing disproportion between the supply of food and the number of
+the living is the fatal order whence arises the necessity of universal
+struggle, a struggle which, to the great advantage of the species,
+allows only the best equipped individuals to survive. Nature is regarded
+by Huxley as an immense arena where all living beings are gladiators.
+("Evolution and Ethics", page 200; "Collected Essays", Vol. IX, London,
+1894.)
+
+Such a generalisation was well adapted to feed the stream of pessimistic
+thought; and it furnished to the apologists of war, in particular, new
+arguments, weighted with all the authority which in these days attaches
+to scientific deliverances. If people no longer say, as Bonald did, and
+Moltke after him, that war is a providential fact, they yet lay stress
+on the point that it is a natural fact. To the peace party Dragomirov's
+objection is urged that its attempts are contrary to the fundamental
+laws of nature, and that no sea wall can hold against breakers that come
+with such gathered force.
+
+But in yet another quarter Darwinism was represented as opposed to
+philanthropic intervention. The defenders of the orthodox political
+economy found in it support for their tenets. Since in the organic world
+universal struggle is the condition of progress, it seemed obvious that
+free competition must be allowed to reign unchecked in the economic
+world. Attempts to curb it were in the highest degree imprudent. The
+spirit of Liberalism here seemed in conformity with the trend of nature:
+in this respect, at least, contemporary naturalism, offspring of the
+discoveries of the nineteenth century, brought reinforcements to the
+individualist doctrine, begotten of the speculations of the eighteenth:
+but only, it appeared, to turn mankind away for ever from humanitarian
+dreams. Would those whom such conclusions repelled be content to oppose
+to nature's imperatives only the protests of the heart? There were some
+who declared, like Brunetiere, that the laws in question, valid though
+they might be for the animal kingdom, were not applicable to the human.
+And so a return was made to the classic dualism. This indeed seems to be
+the line that Huxley took, when, for instance, he opposed to the cosmic
+process an ethical process which was its reverse.
+
+But the number of thinkers whom this antithesis does not satisfy grows
+daily. Although the pessimism which claims authorisation from Darwin's
+doctrines is repugnant to them, they still are unable to accept the
+dualism which leaves a gulf between man and nature. And their endeavour
+is to link the two by showing that while Darwin's laws obtain in both
+kingdoms, the conditions of their application are not the same: their
+forms, and, consequently, their results, vary with the varying mediums
+in which the struggle of living beings takes place, with the means
+these beings have at disposal, with the ends even which they propose to
+themselves.
+
+Here we have the explanation of the fact that among determined opponents
+of war partisans of the "struggle for existence" can be found: there are
+disciples of Darwin in the peace party. Novicow, for example, admits
+the "combat universel" of which Le Dantec ("Les Luttes entre Societies
+humaines et leurs phases successives", Paris, 1893,) speaks; but he
+remarks that at different stages of evolution, at different stages of
+life the same weapons are not necessarily employed. Struggles of brute
+force, armed hand to hand conflicts, may have been a necessity in the
+early phases of human societies. Nowadays, although competition may
+remain inevitable and indispensable, it can assume milder forms.
+Economic rivalries, struggles between intellectual influences, suffice
+to stimulate progress: the processes which these admit are, in the
+actual state of civilisation, the only ones which attain their end
+without waste, the only ones logical. From one end to the other of the
+ladder of life, struggle is the order of the day; but more and more
+as the higher rungs are reached, it takes on characters which are
+proportionately more "humane."
+
+Reflections of this kind permit the introduction into the economic order
+of limitations to the doctrine of "laisser faire, laisser passer." This
+appeals, it is said, to the example of nature where creatures, left to
+themselves, struggle without truce and without mercy; but the fact
+is forgotten that upon industrial battlefields the conditions are
+different. The competitors here are not left simply to their natural
+energies: they are variously handicapped. A rich store of artificial
+resources exists in which some participate and others do not. The sides
+then are unequal; and as a consequence the result of the struggle is
+falsified. "In the animal world," said De Laveleye ("Le socialisme
+contemporain", page 384 (6th edition), Paris, 1891.), criticising
+Spencer, "the fate of each creature is determined by its individual
+qualities; whereas in civilised societies a man may obtain the highest
+position and the most beautiful wife because he is rich and well-born,
+although he may be ugly, idle or improvident; and then it is he who will
+perpetuate the species. The wealthy man, ill constituted, incapable,
+sickly, enjoys his riches and establishes his stock under the protection
+of the laws." Haycraft in England and Jentsch in Germany have strongly
+emphasised these "anomalies," which nevertheless are the rule. That is
+to say that even from a Darwinian point of view all social reforms
+can readily be justified which aim at diminishing, as Wallace said,
+inequalities at the start.
+
+But we can go further still. Whence comes the idea that all measures
+inspired by the sentiment of solidarity are contrary to Nature's
+trend? Observe her carefully, and she will not give lessons only in
+individualism. Side by side with the struggle for existence do we not
+find in operation what Lanessan calls "association for existence." Long
+ago, Espinas had drawn attention to "societies of animals," temporary or
+permanent, and to the kind of morality that arose in them. Since then,
+naturalists have often insisted upon the importance of various forms
+of symbiosis. Kropotkin in "Mutual Aid" has chosen to enumerate many
+examples of altruism furnished by animals to mankind. Geddes and Thomson
+went so far as to maintain that "Each of the greater steps of progress
+is in fact associated with an increased measure of subordination
+of individual competition to reproductive or social ends, and of
+interspecific competition to co-operative association." (Geddes and
+Thomson, "The Evolution of Sex", page 311, London, 1889.) Experience
+shows, according to Geddes, that the types which are fittest to surmount
+great obstacles are not so much those who engage in the fiercest
+competitive struggle for existence, as those who contrive to temper it.
+From all these observations there resulted, along with a limitation
+of Darwinian pessimism, some encouragement for the aspirations of the
+collectivists.
+
+And Darwin himself would, doubtless, have subscribed to these
+rectifications. He never insisted, like his rival, Wallace, upon the
+necessity of the solitary struggle of creatures in a state of nature,
+each for himself and against all. On the contrary, in "The Descent of
+Man", he pointed out the serviceableness of the social instincts, and
+corroborated Bagehot's statements when the latter, applying laws of
+physics to politics, showed the great advantage societies derived from
+intercourse and communion. Again, the theory of sexual evolution which
+makes the evolution of types depend increasingly upon preferences,
+judgments, mental factors, surely offers something to qualify what seems
+hard and brutal in the theory of natural selection.
+
+But, as often happens with disciples, the Darwinians had out-Darwined
+Darwin. The extravagancies of social Darwinism provoked a useful
+reaction; and thus people were led to seek, even in the animal kingdom,
+for facts of solidarity which would serve to justify humane effort.
+
+On quite another line, however, an attempt has been made to connect
+socialist tendencies with Darwinian principles. Marx and Darwin have
+been confronted; and writers have undertaken to show that the work of
+the German philosopher fell readily into line with that of the English
+naturalist and was a development of it. Such has been the endeavour of
+Ferri in Italy and of Woltmann in Germany, not to mention others. The
+founders of "scientific socialism" had, moreover, themselves thought of
+this reconciliation. They make more than one allusion to Darwin in works
+which appeared after 1859. And sometimes they use his theory to define
+by contrast their own ideal. They remark that the capitalist system, by
+giving free course to individual competition, ends indeed in a bellum
+omnium contra omnes; and they make it clear that Darwinism, thus
+understood, is as repugnant to them as to Duhring.
+
+But it is at the scientific and not at the moral point of view that they
+place themselves when they connect their economic history with
+Darwin's work. Thanks to this unifying hypothesis, they claim to have
+constructed--as Marx does in his preface to "Das Kapital"--a veritable
+natural history of social evolution. Engels speaks in praise of his
+friend Marx as having discovered the true mainspring of history hidden
+under the veil of idealism and sentimentalism, and as having proclaimed
+in the primum vivere the inevitableness of the struggle for existence.
+Marx himself, in "Das Kapital", indicated another analogy when he dwelt
+upon the importance of a general technology for the explanation of this
+psychology:--a history of tools which would be to social organs what
+Darwinism is to the organs of animal species. And the very importance
+they attach to tools, to apparatus, to machines, abundantly proves that
+neither Marx nor Engels were likely to forget the special characters
+which mark off the human world from the animal. The former always
+remains to a great extent an artificial world. Inventions change the
+face of its institutions. New modes of production revolutionise not only
+modes of government, but modes even of collective thought. Therefore it
+is that the evolution of society is controlled by laws special to it, of
+which the spectacle of nature offers no suggestion.
+
+If, however, even in this special sphere, it can still be urged that
+the evolution of the material conditions of society is in accord
+with Darwin's theory, it is because the influence of the methods of
+production is itself to be explained by the incessant strife of the
+various classes with each other. So that in the end Marx, like Darwin,
+finds the source of all progress in struggle. Both are grandsons of
+Heraclitus:--polemos pater panton. It sometimes happens, in these days,
+that the doctrine of revolutionary socialism is contrasted as rude and
+healthy with what may seem to be the enervating tendency of "solidarist"
+philanthropy: the apologists of the doctrine then pride themselves above
+all upon their faithfulness to Darwinian principles.
+
+So far we have been mainly concerned to show the use that social
+philosophies have made of the Darwinian laws for practical purposes:
+in order to orientate society towards their ideals each school tries to
+show that the authority of natural science is on its side. But even
+in the most objective of theories, those which systematically make
+abstraction of all political tendencies in order to study the social
+reality in itself, traces of Darwinism are readily to be found.
+
+Let us take for example Durkheim's theory of Division of Labour ("De la
+Division du Travail social", Paris, 1893.) The conclusions he
+derives from it are that whenever professional specialisation causes
+multiplication of distinct branches of activity, we get organic
+solidarity--implying differences--substituted for mechanical solidarity,
+based upon likenesses. The umbilical cord, as Marx said, which connects
+the individual consciousness with the collective consciousness is cut.
+The personality becomes more and more emancipated. But on what does this
+phenomenon, so big with consequences, itself depend? The author goes to
+social morphology for the answer: it is, he says, the growing density
+of population which brings with it this increasing differentiation of
+activities. But, again, why? Because the greater density, in thrusting
+men up against each other, augments the intensity of their competition
+for the means of existence; and for the problems which society thus has
+to face differentiation of functions presents itself as the gentlest
+solution.
+
+Here one sees that the writer borrows directly from Darwin. Competition
+is at its maximum between similars, Darwin had declared; different
+species, not laying claim to the same food, could more easily coexist.
+Here lay the explanation of the fact that upon the same oak hundreds
+of different insects might be found. Other things being equal, the same
+applies to society. He who finds some unadopted speciality possesses a
+means of his own for getting a living. It is by this division of their
+manifold tasks that men contrive not to crush each other. Here
+we obviously have a Darwinian law serving as intermediary in the
+explanation of that progress of division of labour which itself explains
+so much in the social evolution.
+
+And we might take another example, at the other end of the series of
+sociological systems. G. Tarde is a sociologist with the most pronounced
+anti-naturalistic views. He has attempted to show that all application
+of the laws of natural science to society is misleading. In his
+"Opposition Universelle" he has directly combatted all forms of
+sociological Darwinism. According to him the idea that the evolution of
+society can be traced on the same plan as the evolution of species is
+chimerical. Social evolution is at the mercy of all kinds of inventions,
+which by virtue of the laws of imitation modify, through individual to
+individual, through neighbourhood to neighbourhood, the general state
+of those beliefs and desires which are the only "quantities" whose
+variation matters to the sociologist. But, it may be rejoined, that
+however psychical the forces may be, they are none the less subject
+to Darwinian laws. They compete with each other; they struggle for the
+mastery of minds. Between types of ideas, as between organic forms,
+selection operates. And though it may be that these types are ushered
+into the arena by unexpected discoveries, we yet recognise in the
+psychological accidents, which Tarde places at the base of everything,
+near relatives of those small accidental variations upon which Darwin
+builds. Thus, accepting Tarde's own representations, it is
+quite possible to express in Darwinian terms, with the necessary
+transpositions, one of the most idealistic sociologies that have ever
+been constructed.
+
+These few examples suffice. They enable us to estimate the extent of the
+field of influence of Darwinism. It affects sociology not only through
+the agency of its advocates but through that of its opponents. The
+questionings to which it has given rise have proved no less fruitful
+than the solutions it has suggested. In short, few doctrines, in the
+history of social philosophy, will have produced on their passage a
+finer outcrop of ideas.
+
+
+
+
+XXIV. THE INFLUENCE OF DARWIN UPON RELIGIOUS THOUGHT. By P.N. Waggett,
+M.A., S.S.J.E.
+
+
+I.
+
+The object of this paper is first to point out certain elements of the
+Darwinian influence upon Religious thought, and then to show reason
+for the conclusion that it has been, from a Christian point of view,
+satisfactory. I shall not proceed further to urge that the Christian
+apologetic in relation to biology has been successful. A variety of
+opinions may be held on this question, without disturbing the conclusion
+that the movements of readjustment have been beneficial to those who
+remain Christians, and this by making them more Christian and not only
+more liberal. The theologians may sometimes have retreated, but there
+has been an advance of theology. I know that this account incurs
+the charge of optimism. It is not the worst that could be made. The
+influence has been limited in personal range, unequal, even divergent,
+in operation, and accompanied by the appearance of waste and mischievous
+products. The estimate which follows requires for due balance a full
+development of many qualifying considerations. For this I lack space,
+but I must at least distinguish my view from the popular one that our
+difficulties about religion and natural science have come to an end.
+
+Concerning the older questions about origins--the origin of the world,
+of species, of man, of reason, conscience, religion--a large measure of
+understanding has been reached by some thoughtful men. But meanwhile
+new questions have arisen, questions about conduct, regarding both
+the reality of morals and the rule of right action for individuals and
+societies. And these problems, still far from solution, may also be
+traced to the influence of Darwin. For they arise from the renewed
+attention to heredity, brought about by the search for the causes of
+variation, without which the study of the selection of variations has no
+sufficient basis.
+
+Even the existing understanding about origins is very far from
+universal. On these points there were always thoughtful men who denied
+the necessity of conflict, and there are still thoughtful men who deny
+the possibility of a truce.
+
+It must further be remembered that the earlier discussion now, as I hope
+to show, producing favourable results, created also for a time grave
+damage, not only in the disturbance of faith and the loss of men--a
+loss not repaired by a change in the currents of debate--but in what I
+believe to be a still more serious respect. I mean the introduction of
+a habit of facile and untested hypothesis in religious as in other
+departments of thought.
+
+Darwin is not responsible for this, but he is in part the cause of
+it. Great ideas are dangerous guests in narrow minds; and thus it has
+happened that Darwin--the most patient of scientific workers, in whom
+hypothesis waited upon research, or if it provisionally outstepped it
+did so only with the most scrupulously careful acknowledgment--has led
+smaller and less conscientious men in natural science, in history, and
+in theology to an over-eager confidence in probable conjecture and a
+loose grip upon the facts of experience. It is not too much to say that
+in many quarters the age of materialism was the least matter-of-fact age
+conceivable, and the age of science the age which showed least of the
+patient temper of inquiry.
+
+I have indicated, as shortly as I could, some losses and dangers which
+in a balanced account of Darwin's influence would be discussed at
+length.
+
+One other loss must be mentioned. It is a defect in our thought which,
+in some quarters, has by itself almost cancelled all the advantages
+secured. I mean the exaggerated emphasis on uniformity or continuity;
+the unwillingness to rest any part of faith or of our practical
+expectation upon anything that from any point of view can be called
+exceptional. The high degree of success reached by naturalists in
+tracing, or reasonably conjecturing, the small beginnings of great
+differences, has led the inconsiderate to believe that anything may in
+time become anything else.
+
+It is true that this exaggeration of the belief in uniformity has
+produced in turn its own perilous reaction. From refusing to believe
+whatever can be called exceptional, some have come to believe whatever
+can be called wonderful.
+
+But, on the whole, the discontinuous or highly various character of
+experience received for many years too little deliberate attention. The
+conception of uniformity which is a necessity of scientific description
+has been taken for the substance of history. We have accepted a
+postulate of scientific method as if it were a conclusion of scientific
+demonstration. In the name of a generalisation which, however just on
+the lines of a particular method, is the prize of a difficult exploit of
+reflexion, we have discarded the direct impressions of experience;
+or, perhaps it is more true to say, we have used for the criticism of
+alleged experiences a doctrine of uniformity which is only valid in the
+region of abstract science. For every science depends for its advance
+upon limitation of attention, upon the selection out of the whole
+content of consciousness of that part or aspect which is measurable by
+the method of the science. Accordingly there is a science of life which
+rightly displays the unity underlying all its manifestations. But there
+is another view of life, equally valid, and practically sometimes more
+important, which recognises the immediate and lasting effect of
+crisis, difference, and revolution. Our ardour for the demonstration
+of uniformity of process and of minute continuous change needs to be
+balanced by a recognition of the catastrophic element in experience, and
+also by a recognition of the exceptional significance for us of events
+which may be perfectly regular from an impersonal point of view.
+
+An exorbitant jealousy of miracle, revelation, and ultimate moral
+distinctions has been imported from evolutionary science into religious
+thought. And it has been a damaging influence, because it has taken
+men's attention from facts, and fixed them upon theories.
+
+II.
+
+With this acknowledgment of important drawbacks, requiring many words
+for their proper description, I proceed to indicate certain results
+of Darwin's doctrine which I believe to be in the long run wholly
+beneficial to Christian thought. These are:
+
+The encouragement in theology of that evolutionary method of observation
+and study, which has shaped all modern research:
+
+The recoil of Christian apologetics towards the ground of religious
+experience, a recoil produced by the pressure of scientific criticism
+upon other supports of faith:
+
+The restatement, or the recovery of ancient forms of statement, of the
+doctrines of Creation and of divine Design in Nature, consequent upon
+the discussion of evolution and of natural selection as its guiding
+factor.
+
+(1) The first of these is quite possibly the most important of all.
+It was well defined in a notable paper read by Dr Gore, now Bishop of
+Birmingham, to the Church Congress at Shrewsbury in 1896. We have learnt
+a new caution both in ascribing and in denying significance to items of
+evidence, in utterance or in event. There has been, as in art, a study
+of values, which secures perspective and solidity in our representation
+of facts. On the one hand, a given utterance or event cannot be drawn
+into evidence as if all items were of equal consequence, like sovereigns
+in a bag. The question whence and whither must be asked, and the
+particular thing measured as part of a series. Thus measured it is not
+less truly important, but it may be important in a lower degree. On the
+other hand, and for exactly the same reason, nothing that is real is
+unimportant. The "failures" are not mere mistakes. We see them, in St
+Augustine's words, as "scholar's faults which men praise in hope of
+fruit."
+
+We cannot safely trace the origin of the evolutionistic method to the
+influence of natural science. The view is tenable that theology led the
+way. Probably this is a case of alternate and reciprocal debt. Quite
+certainly the evolutionist method in theology, in Christian history,
+and in the estimate of scripture, has received vast reinforcement
+from biology, in which evolution has been the ever present and ever
+victorious conception.
+
+(2) The second effect named is the new willingness of Christian thinkers
+to take definite account of religious experience. This is related to
+Darwin through the general pressure upon religious faith of scientific
+criticism. The great advance of our knowledge of organisms has been an
+important element in the general advance of science. It has acted,
+by the varied requirements of the theory of organisms, upon all other
+branches of natural inquiry, and it held for a long time that leading
+place in public attention which is now occupied by speculative physics.
+Consequently it contributed largely to our present estimation of science
+as the supreme judge in all matters of inquiry (F.R. Tennant: "The Being
+of God in the light of Physical Science", in "Essays on some theological
+questions of the day". London, 1905.), to the supposed destruction of
+mystery and the disparagement of metaphysic which marked the last age,
+as well as to the just recommendation of scientific method in branches
+of learning where the direct acquisitions of natural science had no
+place.
+
+Besides this, the new application of the idea of law and mechanical
+regularity to the organic world seemed to rob faith of a kind of refuge.
+The romantics had, as Berthelot ("Evolutionisme et Platonisme", pages
+45, 46, 47. Paris, 1908.) shows, appealed to life to redress the
+judgments drawn from mechanism. Now, in Spencer, evolution gave us a
+vitalist mechanic or mechanical vitalism, and the appeal seemed cut off.
+We may return to this point later when we consider evolution; at
+present I only endeavour to indicate that general pressure of scientific
+criticism which drove men of faith to seek the grounds of reassurance
+in a science of their own; in a method of experiment, of observation,
+of hypothesis checked by known facts. It is impossible for me to do more
+than glance across the threshold of this subject. But it is necessary to
+say that the method is in an elementary stage of revival. The imposing
+success that belongs to natural science is absent: we fall short of
+the unchallengeable unanimity of the Biologists on fundamentals. The
+experimental method with its sure repetitions cannot be applied to our
+subject-matter. But we have something like the observational method of
+palaeontology and geographical distribution; and in biology there are
+still men who think that the large examination of varieties by way
+of geography and the search of strata is as truly scientific, uses as
+genuinely the logical method of difference, and is as fruitful in sure
+conclusions as the quasi-chemical analysis of Mendelian laboratory work,
+of which last I desire to express my humble admiration. Religion also
+has its observational work in the larger and possibly more arduous
+manner.
+
+But the scientific work in religion makes its way through difficulties
+and dangers. We are far from having found the formula of its combination
+with the historical elements of our apologetic. It is exposed,
+therefore, to a damaging fire not only from unspiritualist psychology
+and pathology but also from the side of scholastic dogma. It is hard to
+admit on equal terms a partner to the old undivided rule of books and
+learning. With Charles Lamb, we cry in some distress, "must knowledge
+come to me, if it come at all, by some awkward experiment of intuition,
+and no longer by this familiar process of reading?" ("Essays of Elia",
+"New Year's Eve", page 41; Ainger's edition. London, 1899.) and we are
+answered that the old process has an imperishable value, only we have
+not yet made clear its connection with other contributions. And all
+the work is young, liable to be drawn into unprofitable excursions,
+side-tracked by self-deceit and pretence; and it fatally attracts, like
+the older mysticism, the curiosity and the expository powers of those
+least in sympathy with it, ready writers who, with all the air of
+extended research, have been content with narrow grounds for induction.
+There is a danger, besides, which accompanies even the most genuine
+work of this science and must be provided against by all its serious
+students. I mean the danger of unbalanced introspection both for
+individuals and for societies; of a preoccupation comparable to our
+modern social preoccupation with bodily health; of reflection upon
+mental states not accompanied by exercise and growth of the mental
+powers; the danger of contemplating will and neglecting work, of
+analysing conviction and not criticising evidence.
+
+Still, in spite of dangers and mistakes, the work remains full of
+hopeful indications, and, in the best examples (Such an example is given
+in Baron F. von Hugel's recently finished book, the result of thirty
+years' research: "The Mystical Element of Religion, as studied in
+Saint Catherine of Genoa and her Friends". London, 1908.), it is truly
+scientific in its determination to know the very truth, to tell what
+we think, not what we think we ought to think. (G. Tyrrell, in
+"Mediaevalism", has a chapter which is full of the important MORAL
+element in a scientific attitude. "The only infallible guardian of truth
+is the spirit of truthfulness." "Mediaevalism" page 182, London, 1908.),
+truly scientific in its employment of hypothesis and verification, and
+in growing conviction of the reality of its subject-matter through the
+repeated victories of a mastery which advances, like science, in the
+Baconian road of obedience. It is reasonable to hope that progress in
+this respect will be more rapid and sure when religious study enlists
+more men affected by scientific desire and endowed with scientific
+capacity.
+
+The class of investigating minds is a small one, possibly even smaller
+than that of reflecting minds. Very few persons at any period are able
+to find out anything whatever. There are few observers, few discoverers,
+few who even wish to discover truth. In how many societies the problems
+of philology which face every person who speaks English are left
+unattempted! And if the inquiring or the successfully inquiring class
+of minds is small, much smaller, of course, is the class of those
+possessing the scientific aptitude in an eminent degree. During the last
+age this most distinguished class was to a very great extent absorbed
+in the study of phenomena, a study which had fallen into arrears. For
+we stood possessed, in rudiment, of means of observation, means for
+travelling and acquisition, qualifying men for a larger knowledge than
+had yet been attempted. These were now to be directed with new accuracy
+and ardour upon the fabric and behaviour of the world of sense. Our
+debt to the great masters in physical science who overtook and almost
+out-stripped the task cannot be measured; and, under the honourable
+leadership of Ruskin, we may all well do penance if we have failed "in
+the respect due to their great powers of thought, or in the admiration
+due to the far scope of their discovery." ("Queen of the Air", Preface,
+page vii. London, 1906.) With what miraculous mental energy and divine
+good fortune--as Romans said of their soldiers--did our men of curiosity
+face the apparently impenetrable mysteries of nature! And how natural
+it was that immense accessions of knowledge, unrelated to the spiritual
+facts of life, should discredit Christian faith, by the apparent
+superiority of the new work to the feeble and unprogressive knowledge of
+Christian believers! The day is coming when men of this mental character
+and rank, of this curiosity, this energy and this good fortune in
+investigation, will be employed in opening mysteries of a spiritual
+nature. They will silence with masterful witness the over-confident
+denials of naturalism. They will be in danger of the widespread
+recognition which thirty years ago accompanied every utterance of
+Huxley, Tyndall, Spencer. They will contribute, in spite of adulation,
+to the advance of sober religious and moral science.
+
+And this result will be due to Darwin, first because by raising the
+dignity of natural science, he encouraged the development of the
+scientific mind; secondly because he gave to religious students the
+example of patient and ardent investigation; and thirdly because by the
+pressure of naturalistic criticism the religious have been driven to
+ascertain the causes of their own convictions, a work in which they were
+not without the sympathy of men of science. (The scientific rank of its
+writer justifies the insertion of the following letter from the late Sir
+John Burdon-Sanderson to me. In the lecture referred to I had described
+the methods of Professor Moseley in teaching Biology as affording a
+suggestion of the scientific treatment of religion.)
+
+Oxford, April 30, 1902.
+
+Dear Sir,
+
+I feel that I must express to you my thanks for the discourse which I
+had the pleasure of listening to yesterday afternoon.
+
+I do not mean to say that I was able to follow all that you said as to
+the identity of Method in the two fields of Science and Religion, but I
+recognise that the "mysticism" of which you spoke gives us the only way
+by which the two fields can be brought into relation.
+
+Among much that was memorable, nothing interested me more than what you
+said of Moseley.
+
+No one, I am sure, knew better than you the value of his teaching and in
+what that value consisted.
+
+Yours faithfully
+
+J. Burdon-Sanderson. 31-2.)
+
+In leaving the subject of scientific religious inquiry, I will only add
+that I do not believe it receives any important help--and certainly
+it suffers incidentally much damaging interruption--from the study of
+abnormal manifestations or abnormal conditions of personality.
+
+(3) Both of the above effects seem to me of high, perhaps the very
+highest, importance to faith and to thought. But, under the third head,
+I name two which are more directly traceable to the personal work of
+Darwin, and more definitely characteristic of the age in which his
+influence was paramount: viz. the influence of the two conceptions of
+evolution and natural selection upon the doctrine of creation and of
+design respectively.
+
+It is impossible here, though it is necessary for a complete sketch of
+the matter, to distinguish the different elements and channels of this
+Darwinian influence; in Darwin's own writings, in the vigorous polemic
+of Huxley, and strangely enough, but very actually for popular thought,
+in the teaching of the definitely anti-Darwinian evolutionist Spencer.
+
+Under the head of the directly and purely Darwinian elements I should
+class as preeminent the work of Wallace and of Bates; for no two sets
+of facts have done more to fix in ordinary intelligent minds a belief
+in organic evolution and in natural selection as its guiding factor
+than the facts of geographical distribution and of protective colour and
+mimicry. The facts of geology were difficult to grasp and the public and
+theologians heard more often of the imperfection than of the extent of
+the geological record. The witness of embryology, depending to a great
+extent upon microscopic work, was and is beyond the appreciation of
+persons occupied in fields of work other than biology.
+
+III.
+
+From the influence in religion of scientific modes of thought we pass
+to the influence of particular biological conceptions. The former effect
+comes by way of analogy, example, encouragement and challenge; inspiring
+or provoking kindred or similar modes of thought in the field of
+theology; the latter by a collision of opinions upon matters of fact or
+conjecture which seem to concern both science and religion.
+
+In the case of Darwinism the story of this collision is familiar, and
+falls under the heads of evolution and natural selection, the doctrine
+of descent with modification, and the doctrine of its guidance or
+determination by the struggle for existence between related varieties.
+These doctrines, though associated and interdependent, and in popular
+thought not only combined but confused, must be considered separately.
+It is true that the ancient doctrine of Evolution, in spite of the
+ingenuity and ardour of Lamarck, remained a dream tantalising the
+intellectual ambition of naturalists, until the day when Darwin made it
+conceivable by suggesting the machinery of its guidance. And, further,
+the idea of natural selection has so effectively opened the door of
+research and stimulated observation in a score of principal directions
+that, even if the Darwinian explanation became one day much less
+convincing than, in spite of recent criticism, it now is, yet its
+passing, supposing it to pass, would leave the doctrine of Evolution
+immeasurably and permanently strengthened. For in the interests of the
+theory of selection, "Fur Darwin," as Muller wrote, facts have been
+collected which remain in any case evidence of the reality of descent
+with modification.
+
+But still, though thus united in the modern history of convictions,
+though united and confused in the collision of biological and
+traditional opinion, yet evolution and natural selection must be
+separated in theological no less than in biological estimation.
+Evolution seemed inconsistent with Creation; natural selection with
+Providence and Divine design.
+
+Discussion was maintained about these points for many years and with
+much dark heat. It ranged over many particular topics and engaged minds
+different in tone, in quality, and in accomplishment. There was at
+most times a degree of misconception. Some naturalists attributed to
+theologians in general a poverty of thought which belonged really to
+men of a particular temper or training. The "timid theism" discerned in
+Darwin by so cautious a theologian as Liddon (H.P. Liddon, "The Recovery
+of S. Thomas"; a sermon preached in St Paul's, London, on April 23rd,
+1882 (the Sunday after Darwin's death).) was supposed by many biologists
+to be the necessary foundation of an honest Christianity. It was really
+more characteristic of devout NATURALISTS like Philip Henry Gosse,
+than of religious believers as such. (Dr Pusey ("Unscience not Science
+adverse to Faith" 1878) writes: "The questions as to 'species,' of what
+variations the animal world is capable, whether the species be more or
+fewer, whether accidental variations may become hereditary... and
+the like, naturally fall under the province of science. In all these
+questions Mr Darwin's careful observations gained for him a deserved
+approbation and confidence.") The study of theologians more considerable
+and even more typically conservative than Liddon does not confirm the
+description of religious intolerance given in good faith, but in serious
+ignorance, by a disputant so acute, so observant and so candid as
+Huxley. Something hid from each other's knowledge the devoted pilgrims
+in two great ways of thought. The truth may be, that naturalists took
+their view of what creation was from Christian men of science who
+naturally looked in their own special studies for the supports and
+illustrations of their religious belief. Of almost every laborious
+student it may be said "Hic ab arte sua non recessit." And both the
+believing and the denying naturalists, confining habitual attention to a
+part of experience, are apt to affirm and deny with trenchant vigour
+and something of a narrow clearness "Qui respiciunt ad pauca, de facili
+pronunciant." (Aristotle, in Bacon, quoted by Newman in his "Idea of a
+University", page 78. London, 1873.)
+
+Newman says of some secular teachers that "they persuade the world of
+what is false by urging upon it what is true." Of some early opponents
+of Darwin it might be said by a candid friend that, in all sincerity of
+devotion to truth, they tried to persuade the world of what is true
+by urging upon it what is false. If naturalists took their version
+of orthodoxy from amateurs in theology, some conservative Christians,
+instead of learning what evolution meant to its regular exponents,
+took their view of it from celebrated persons, not of the front rank in
+theology or in thought, but eager to take account of public movements
+and able to arrest public attention.
+
+Cleverness and eloquence on both sides certainly had their share in
+producing the very great and general disturbance of men's minds in the
+early days of Darwinian teaching. But by far the greater part of that
+disturbance was due to the practical novelty and the profound importance
+of the teaching itself, and to the fact that the controversy about
+evolution quickly became much more public than any controversy of equal
+seriousness had been for many generations.
+
+We must not think lightly of that great disturbance because it has, in
+some real sense, done its work, and because it is impossible in days
+of more coolness and light, to recover a full sense of its very real
+difficulties.
+
+Those who would know them better should add to the calm records of
+Darwin ("Life and Letters" and "More Letters of Charles Darwin".) and to
+the story of Huxley's impassioned championship, all that they can learn
+of George Romanes. ("Life and Letters", London, 1896. "Thoughts on
+Religion", London, 1895. "Candid Examination of Theism", London, 1878.)
+For his life was absorbed in this very struggle and reproduced
+its stages. It began in a certain assured simplicity of biblical
+interpretation; it went on, through the glories and adventures of a
+paladin in Darwin's train, to the darkness and dismay of a man who saw
+all his most cherished beliefs rendered, as he thought, incredible.
+("Never in the history of man has so terrific a calamity befallen the
+race as that which all who look may now (viz. in consequence of the
+scientific victory of Darwin) behold advancing as a deluge, black with
+destruction, resistless in might, uprooting our most cherished hopes,
+engulphing our most precious creed, and burying our highest life in
+mindless destruction."--"A Candid Examination of Theism", page 51.)
+He lived to find the freer faith for which process and purpose are
+not irreconcilable, but necessary to one another. His development,
+scientific, intellectual and moral, was itself of high significance; and
+its record is of unique value to our own generation, so near the age of
+that doubt and yet so far from it; certainly still much in need of
+the caution and courage by which past endurance prepares men for
+new emergencies. We have little enough reason to be sure that in the
+discussions awaiting us we shall do as well as our predecessors in
+theirs. Remembering their endurance of mental pain, their ardour
+in mental labour, the heroic temper and the high sincerity of
+controversialists on either side, we may well speak of our fathers in
+such words of modesty and self-judgment as Drayton used when he sang the
+victors of Agincourt. The progress of biblical study, in the departments
+of Introduction and Exegesis, resulting in the recovery of a point
+of view anciently tolerated if not prevalent, has altered some of the
+conditions of that discussion. In the years near 1858, the witness of
+Scripture was adduced both by Christian advocates and their critics as
+if unmistakeably irreconcilable with Evolution.
+
+Huxley ("Science and Christian Tradition". London, 1904.) found the path
+of the blameless naturalist everywhere blocked by "Moses": the believer
+in revelation was generally held to be forced to a choice between
+revealed cosmogony and the scientific account of origins. It is not
+clear how far the change in Biblical interpretation is due to natural
+science, and how far to the vital movements of theological study which
+have been quite independent of the controversy about species. It belongs
+to a general renewal of Christian movement, the recovery of a heritage.
+"Special Creation"--really a biological rather than a theological
+conception,--seems in its rigid form to have been a recent element even
+in English biblical orthodoxy.
+
+The Middle Ages had no suspicion that religious faith forbad
+inquiry into the natural origination of the different forms of life.
+Bartholomaeus Anglicus, an English Franciscan of the thirteenth century,
+was a mutationist in his way, as Aristotle, "the Philosopher" of
+the Christian Schoolmen, had been in his. So late as the seventeenth
+century, as we learn not only from early proceedings of the Royal
+Society, but from a writer so homely and so regularly pious as
+Walton, the variation of species and "spontaneous" generations had no
+theological bearing, except as instances of that various wonder of the
+world which in devout minds is food for devotion.
+
+It was in the eighteenth century that the harder statement took shape.
+Something in the preciseness of that age, its exaltation of law, its
+cold passion for a stable and measured universe, its cold denial, its
+cold affirmation of the power of God, a God of ice, is the occasion of
+that rigidity of religious thought about the living world which Darwin
+by accident challenged, or rather by one of those movements of genius
+which, Goethe ("No productiveness of the highest kind... is in the power
+of anyone."--"Conversations of Goethe with Eckermann and Soret". London,
+1850.) declares, are "elevated above all earthly control."
+
+If religious thought in the eighteenth century was aimed at a fixed and
+nearly finite world of spirit, it followed in all these respects the
+secular and critical lead. ("La philosophie reformatrice du XVIIIe
+siecle" (Berthelot, "Evolutionisme et Platonisme", Paris, 1908, page
+45.) ramenait la nature et la societe a des mecanismes que la pensee
+reflechie peut concevoir et recomposer." In fact, religion in a
+mechanical age is condemned if it takes any but a mechanical tone.
+Butler's thought was too moving, too vital, too evolutionary, for the
+sceptics of his time. In a rationalist, encyclopaedic period, religion
+also must give hard outline to its facts, it must be able to display
+its secret to any sensible man in the language used by all sensible men.
+Milton's prophetic genius furnished the eighteenth century, out of the
+depth of the passionate age before it, with the theological tone it was
+to need. In spite of the austere magnificence of his devotion, he gives
+to smaller souls a dangerous lead. The rigidity of Scripture exegesis
+belonged to this stately but imperfectly sensitive mode of thought. It
+passed away with the influence of the older rationalists whose precise
+denials matched the precise and limited affirmations of the static
+orthodoxy.
+
+I shall, then, leave the specially biblical aspect of the
+debate--interesting as it is and even useful, as in Huxley's
+correspondence with the Duke of Argyll and others in 1892 ("Times",
+1892, passim.)--in order to consider without complication the permanent
+elements of Christian thought brought into question by the teaching of
+evolution.
+
+Such permanent elements are the doctrine of God as Creator of the
+universe, and the doctrine of man as spiritual and unique. Upon both the
+doctrine of evolution seemed to fall with crushing force.
+
+With regard to Man I leave out, acknowledging a grave omission, the
+doctrine of the Fall and of Sin. And I do so because these have not yet,
+as I believe, been adequately treated: here the fruitful reaction to the
+stimulus of evolution is yet to come. The doctrine of sin, indeed, falls
+principally within the scope of that discussion which has followed or
+displaced the Darwinian; and without it the Fall cannot be usefully
+considered. For the question about the Fall is a question not merely of
+origins, but of the interpretation of moral facts whose moral reality
+must first be established.
+
+I confine myself therefore to Creation and the dignity of man.
+
+The meaning of evolution, in the most general terms, is that the
+differentiation of forms is not essentially separate from their
+behaviour and use; that if these are within the scope of study, that is
+also; that the world has taken the form we see by movements not unlike
+those we now see in progress; that what may be called proximate origins
+are continuous in the way of force and matter, continuous in the way of
+life, with actual occurrences and actual characteristics. All this has
+no revolutionary bearing upon the question of ultimate origins. The
+whole is a statement about process. It says nothing to metaphysicians
+about cause. It simply brings within the scope of observation or
+conjecture that series of changes which has given their special
+characters to the different parts of the world we see. In particular,
+evolutionary science aspires to the discovery of the process or order
+of the appearance of life itself: if it were to achieve its aim it
+could say nothing of the cause of this or indeed of the most familiar
+occurrences. We should have become spectators or convinced historians of
+an event which, in respect of its cause and ultimate meaning, would be
+still impenetrable.
+
+With regard to the origin of species, supposing life already
+established, biological science has the well founded hopes and the
+measure of success with which we are all familiar. All this has, it
+would seem, little chance of collision with a consistent theism, a
+doctrine which has its own difficulties unconnected with any particular
+view of order or process. But when it was stated that species had
+arisen by processes through which new species were still being made,
+evolutionism came into collision with a statement, traditionally
+religious, that species were formed and fixed once for all and long ago.
+
+What is the theological import of such a statement when it is regarded
+as essential to belief in God? Simply that God's activity, with respect
+to the formation of living creatures, ceased at some point in past time.
+
+"God rested" is made the touchstone of orthodoxy. And when, under the
+pressure of the evidences, we found ourselves obliged to acknowledge and
+assert the present and persistent power of God, in the maintenance and
+in the continued formation of "types," what happened was the abolition
+of a time-limit. We were forced only to a bolder claim, to a theistic
+language less halting, more consistent, more thorough in its own line,
+as well as better qualified to assimilate and modify such schemes as
+Von Hartmann's philosophy of the unconscious--a philosophy, by the way,
+quite intolerant of a merely mechanical evolution. (See Von Hartmann's
+"Wahrheit und Irrthum in Darwinismus". Berlin, 1875.)
+
+Here was not the retrenchment of an extravagant assertion, but the
+expansion of one which was faltering and inadequate. The traditional
+statement did not need paring down so as to pass the meshes of a new and
+exacting criticism. It was itself a net meant to surround and enclose
+experience; and we must increase its size and close its mesh to hold
+newly disclosed facts of life. The world, which had seemed a fixed
+picture or model, gained first perspective and then solidity and
+movement. We had a glimpse of organic HISTORY; and Christian thought
+became more living and more assured as it met the larger view of life.
+
+However unsatisfactory the new attitude might be to our critics, to
+Christians the reform was positive. What was discarded was a limitation,
+a negation. The movement was essentially conservative, even actually
+reconstructive. For the language disused was a language inconsistent
+with the definitions of orthodoxy; it set bounds to the infinite, and by
+implication withdrew from the creative rule all such processes as could
+be brought within the descriptions of research. It ascribed fixity and
+finality to that "creature" in which an apostle taught us to recognise
+the birth-struggles of an unexhausted progress. It tended to banish
+mystery from the world we see, and to confine it to a remote first age.
+
+In the reformed, the restored, language of religion, Creation became
+again not a link in a rational series to complete a circle of the
+sciences, but the mysterious and permanent relation between the infinite
+and the finite, between the moving changes we know in part, and the
+Power, after the fashion of that observation, unknown, which is itself
+"unmoved all motion's source." (Hymn of the Church-- Rerum Deus tenax
+vigor,  Immotus in te permanens.)
+
+With regard to man it is hardly necessary, even were it possible, to
+illustrate the application of this bolder faith. When the record of his
+high extraction fell under dispute, we were driven to a contemplation of
+the whole of his life, rather than of a part and that part out of sight.
+We remembered again, out of Aristotle, that the result of a process
+interprets its beginnings. We were obliged to read the title of such
+dignity as we may claim, in results and still more in aspirations.
+
+Some men still measure the value of great present facts in life--reason
+and virtue and sacrifice--by what a self-disparaged reason can collect
+of the meaner rudiments of these noble gifts. Mr Balfour has admirably
+displayed the discrepancy, in this view, between the alleged origin and
+the alleged authority of reason. Such an argument ought to be used not
+to discredit the confident reason, but to illuminate and dignify its
+dark beginnings, and to show that at every step in the long course of
+growth a Power was at work which is not included in any term or in all
+the terms of the series.
+
+I submit that the more men know of actual Christian teaching, its
+fidelity to the past, and its sincerity in face of discovery, the more
+certainly they will judge that the stimulus of the doctrine of evolution
+has produced in the long run vigour as well as flexibility in the
+doctrine of Creation and of man.
+
+I pass from Evolution in general to Natural Selection.
+
+The character in religious language which I have for short called
+mechanical was not absent in the argument from design as stated before
+Darwin. It seemed to have reference to a world conceived as fixed. It
+pointed, not to the plastic capacity and energy of living matter, but
+to the fixed adaptation of this and that organ to an unchanging place or
+function.
+
+Mr Hobhouse has given us the valuable phrase "a niche of organic
+opportunity." Such a phrase would have borne a different sense in
+non-evolutionary thought. In that thought, the opportunity was
+an opportunity for the Creative Power, and Design appeared in the
+preparation of the organism to fit the niche. The idea of the niche
+and its occupant growing together from simpler to more complex mutual
+adjustment was unwelcome to this teleology. If the adaptation was traced
+to the influence, through competition, of the environment, the old
+teleology lost an illustration and a proof. For the cogency of the proof
+in every instance depended upon the absence of explanation. Where the
+process of adaptation was discerned, the evidence of Purpose or Design
+was weak. It was strong only when the natural antecedents were not
+discovered, strongest when they could be declared undiscoverable.
+
+Paley's favourite word is "Contrivance"; and for him contrivance is
+most certain where production is most obscure. He points out the
+physiological advantage of the valvulae conniventes to man, and the
+advantage for teleology of the fact that they cannot have been formed by
+"action and pressure." What is not due to pressure may be attributed to
+design, and when a "mechanical" process more subtle than pressure was
+suggested, the case for design was so far weakened. The cumulative proof
+from the multitude of instances began to disappear when, in selection,
+a natural sequence was suggested in which all the adaptations might be
+reached by the motive power of life, and especially when, as in Darwin's
+teaching, there was full recognition of the reactions of life to the
+stimulus of circumstance. "The organism fits the niche," said the
+teleologist, "because the Creator formed it so as to fit." "The organism
+fits the niche," said the naturalist, "because unless it fitted it
+could not exist." "It was fitted to survive," said the theologian.
+"It survives because it fits," said the selectionist. The two forms of
+statement are not incompatible; but the new statement, by provision of
+an ideally universal explanation of process, was hostile to a doctrine
+of purpose which relied upon evidences always exceptional however
+numerous. Science persistently presses on to find the universal
+machinery of adaptation in this planet; and whether this be found in
+selection, or in direct-effect, or in vital reactions resulting in large
+changes, or in a combination of these and other factors, it must always
+be opposed to the conception of a Divine Power here and there but not
+everywhere active.
+
+For science, the Divine must be constant, operative everywhere and in
+every quality and power, in environment and in organism, in stimulus and
+in reaction, in variation and in struggle, in hereditary equilibrium,
+and in "the unstable state of species"; equally present on both sides of
+every strain, in all pressures and in all resistances, in short in
+the general wonder of life and the world. And this is exactly what the
+Divine Power must be for religious faith.
+
+The point I wish once more to make is that the necessary readjustment of
+teleology, so as to make it depend upon the contemplation of the whole
+instead of a part, is advantageous quite as much to theology as to
+science. For the older view failed in courage. Here again our theism was
+not sufficiently theistic.
+
+Where results seemed inevitable, it dared not claim them as God-given.
+In the argument from Design it spoke not of God in the sense of
+theology, but of a Contriver, immensely, not infinitely wise and good,
+working within a world, the scene, rather than the ever dependent
+outcome, of His Wisdom; working in such emergencies and opportunities
+as occurred, by forces not altogether within His control, towards an end
+beyond Himself. It gave us, instead of the awful reverence due to the
+Cause of all substance and form, all love and wisdom, a dangerously
+detached appreciation of an ingenuity and benevolence meritorious in aim
+and often surprisingly successful in contrivance.
+
+The old teleology was more useful to science than to religion, and the
+design-naturalists ought to be gratefully remembered by Biologists.
+Their search for evidences led them to an eager study of adaptations
+and of minute forms, a study such as we have now an incentive to in the
+theory of Natural Selection. One hardly meets with the same ardour in
+microscopical research until we come to modern workers. But the argument
+from Design was never of great importance to faith. Still, to rid it of
+this character was worth all the stress and anxiety of the gallant old
+war. If Darwin had done nothing else for us, we are to-day deeply in
+his debt for this. The world is not less venerable to us now, not less
+eloquent of the causing mind, rather much more eloquent and sacred.
+But our wonder is not that "the underjaw of the swine works under the
+ground" or in any or all of those particular adaptations which Paley
+collected with so much skill, but that a purpose transcending, though
+resembling, our own purposes, is everywhere manifest; that what we live
+in is a whole, mutually sustaining, eventful and beautiful, where the
+"dead" forces feed the energies of life, and life sustains a stranger
+existence, able in some real measure to contemplate the whole, of which,
+mechanically considered, it is a minor product and a rare ingredient.
+Here, again, the change was altogether positive. It was not the escape
+of a vessel in a storm with loss of spars and rigging, not a shortening
+of sail to save the masts and make a port of refuge. It was rather the
+emergence from narrow channels to an open sea. We had propelled the
+great ship, finding purchase here and there for slow and uncertain
+movement. Now, in deep water, we spread large canvas to a favouring
+breeze.
+
+The scattered traces of design might be forgotten or obliterated. But
+the broad impression of Order became plainer when seen at due distance
+and in sufficient range of effect, and the evidence of love and wisdom
+in the universe could be trusted more securely for the loss of the
+particular calculation of their machinery.
+
+Many other topics of faith are affected by modern biology. In some of
+these we have learnt at present only a wise caution, a wise uncertainty.
+We stand before the newly unfolded spectacle of suffering, silenced;
+with faith not scientifically reassured but still holding fast certain
+other clues of conviction. In many important topics we are at a loss.
+But in others, and among them those I have mentioned, we have passed
+beyond this negative state and find faith positively strengthened and
+more fully expressed.
+
+We have gained also a language and a habit of thought more fit for the
+great and dark problems that remain, less liable to damaging conflicts,
+equipped for more rapid assimilation of knowledge. And by this change
+biology itself is a gainer. For, relieved of fruitless encounters with
+popular religion, it may advance with surer aim along the path of
+really scientific life-study which was reopened for modern men by the
+publication of "The Origin of Species".
+
+Charles Darwin regretted that, in following science, he had not done
+"more direct good" ("Life and Letters", Vol. III. page 359.) to his
+fellow-creatures. He has, in fact, rendered substantial service to
+interests bound up with the daily conduct and hopes of common men;
+for his work has led to improvements in the preaching of the Christian
+faith.
+
+
+
+
+XXV. THE INFLUENCE OF DARWINISM ON THE STUDY OF RELIGIONS. By Jane Ellen
+Harrison.
+
+Hon. D.Litt. (Durham), Hon. LL.D. (Aberdeen), Staff Lecturer and
+sometime Fellow of Newnham College, Cambridge.
+
+Corresponding member of the German Archaeological Institute.
+
+The title of my paper might well have been "the creation by Darwinism of
+the scientific study of Religions," but that I feared to mar my tribute
+to a great name by any shadow of exaggeration. Before the publication of
+"The Origin of Species" and "The Descent of Man", even in the eighteenth
+century, isolated thinkers, notably Hume and Herder, had conjectured
+that the orthodox beliefs of their own day were developments from the
+cruder superstitions of the past. These were however only particular
+speculations of individual sceptics. Religion was not yet generally
+regarded as a proper subject for scientific study, with facts to be
+collected and theories to be deduced. A Congress of Religions such as
+that recently held at Oxford would have savoured of impiety.
+
+In the brief space allotted me I can attempt only two things; first,
+and very briefly, I shall try to indicate the normal attitude towards
+religion in the early part of the last century; second, and in more
+detail, I shall try to make clear what is the outlook of advanced
+thinkers to-day. (To be accurate I ought to add "in Europe." I advisedly
+omit from consideration the whole immense field of Oriental mysticism,
+because it has remained practically untouched by the influence of
+Darwinism.) From this second inquiry it will, I hope, be abundantly
+manifest that it is the doctrine of evolution that has made this outlook
+possible and even necessary.
+
+The ultimate and unchallenged presupposition of the old view was that
+religion was a DOCTRINE, a body of supposed truths. It was in fact what
+we should now call Theology, and what the ancients called Mythology.
+Ritual was scarcely considered at all, and, when considered, it was held
+to be a form in which beliefs, already defined and fixed as dogma,
+found a natural mode of expression. This, it will be later shown, is
+a profound error or rather a most misleading half-truth. Creeds,
+doctrines, theology and the like are only a part, and at first the least
+important part, of religion.
+
+Further, and the fact is important, this DOGMA, thus supposed to be
+the essential content of the "true" religion, was a teleological scheme
+complete and unalterable, which had been revealed to man once and for
+all by a highly anthropomorphic God, whose existence was assumed. The
+duty of man towards this revelation was to accept its doctrines and obey
+its precepts. The notion that this revelation had grown bit by bit out
+of man's consciousness and that his business was to better it would
+have seemed rank blasphemy. Religion, so conceived, left no place for
+development. "The Truth" might be learnt, but never critically examined;
+being thus avowedly complete and final, it was doomed to stagnation.
+
+The details of this supposed revelation seem almost too naive for
+enumeration. As Hume observed, "popular theology has a positive appetite
+for absurdity." It is sufficient to recall that "revelation" included
+such items as the Creation (It is interesting to note that the very
+word "Creator" has nowadays almost passed into the region of mythology.
+Instead we have "L'Evolution Creatrice".) of the world out of nothing in
+six days; the making of Eve from one of Adam's ribs; the Temptation by
+a talking snake; the confusion of tongues at the tower of Babel; the
+doctrine of Original Sin; a scheme of salvation which demanded the
+Virgin Birth, Vicarious Atonement, and the Resurrection of the material
+body. The scheme was unfolded in an infallible Book, or, for one section
+of Christians, guarded by the tradition of an infallible Church, and on
+the acceptance or refusal of this scheme depended an eternity of weal or
+woe. There is not one of these doctrines that has not now been recast,
+softened down, mysticised, allegorised into something more conformable
+with modern thinking. It is hard for the present generation, unless
+their breeding has been singularly archaic, to realise that these
+amazing doctrines were literally held and believed to constitute the
+very essence of religion; to doubt them was a moral delinquency.
+
+It had not, however, escaped the notice of travellers and missionaries
+that savages carried on some sort of practices that seemed to be
+religious, and believed in some sort of spirits or demons. Hence, beyond
+the confines illuminated by revealed truth, a vague region was assigned
+to NATURAL Religion. The original revelation had been kept intact only
+by one chosen people, the Jews, by them to be handed on to Christianity.
+Outside the borders of this Goshen the world had sunk into the darkness
+of Egypt. Where analogies between savage cults and the Christian
+religions were observed, they were explained as degradations; the
+heathen had somehow wilfully "lost the light." Our business was not to
+study but, exclusively, to convert them, to root out superstition and
+carry the torch of revelation to "Souls in heathen darkness lying." To
+us nowadays it is a commonplace of anthropological research that we
+must seek for the beginnings of religion in the religions of primitive
+peoples, but in the last century the orthodox mind was convinced that
+it possessed a complete and luminous ready-made revelation; the study of
+what was held to be a mere degradation seemed idle and superfluous.
+
+But, it may be asked, if, to the orthodox, revealed religion was
+sacrosanct and savage religion a thing beneath consideration, why did
+not the sceptics show a more liberal spirit, and pursue to their logical
+issue the conjectures they had individually hazarded? The reason is
+simple and significant. The sceptics too had not worked free from
+the presupposition that the essence of religion is dogma. Their
+intellectualism, expressive of the whole eighteenth century, was
+probably in England strengthened by the Protestant doctrine of an
+infallible Book. Hume undoubtedly confused religion with dogmatic
+theology. The attention of orthodox and sceptics alike was focussed on
+the truth or falsity of certain propositions. Only a few minds of rare
+quality were able dimly to conceive that religion might be a necessary
+step in the evolution of human thought.
+
+It is not a little interesting to note that Darwin, who was leader and
+intellectual king of his generation, was also in this matter to some
+extent its child. His attitude towards religion is stated clearly, in
+Chapter VIII. of the "Life and Letters". (Vol. I. page 304. For Darwin's
+religious views see also "Descent of Man", 1871, Vol. I. page 65; 2nd
+edition. Vol. I. page 142.) On board the "Beagle" he was simply orthodox
+and was laughed at by several of the officers for quoting the Bible as
+an unanswerable authority on some point of morality. By 1839 he had come
+to see that the Old Testament was no more to be trusted than the sacred
+books of the Hindoos. Next went the belief in miracles, and next Paley's
+"argument from design" broke down before the law of natural selection;
+the suffering so manifest in nature is seen to be compatible rather with
+Natural Selection than with the goodness and omnipotence of God. Darwin
+felt to the full all the ignorance that lay hidden under specious
+phrases like "the plan of creation" and "Unity of design." Finally, he
+tells us "the mystery of the beginning of all things is insoluble by us;
+and I for one must be content to remain an Agnostic."
+
+The word Agnostic is significant not only of the humility of the man
+himself but also of the attitude of his age. Religion, it is clear,
+is still conceived as something to be KNOWN, a matter of true or
+false OPINION. Orthodox religion was to Darwin a series of erroneous
+hypotheses to be bit by bit discarded when shown to be untenable. The
+ACTS of religion which may result from such convictions, i.e. devotion
+in all its forms, prayer, praise, sacraments, are left unmentioned.
+It is clear that they are not, as now to us, sociological survivals
+of great interest and importance, but rather matters too private, too
+personal, for discussion.
+
+Huxley, writing in the "Contemporary Review" (1871.), says, "In a dozen
+years "The Origin of Species" has worked as complete a revolution in
+biological science as the "Principia" did in astronomy." It has done
+so because, in the words of Helmholtz, it contained "an essentially
+new creative thought," that of the continuity of life, the absence of
+breaks. In the two most conservative subjects, Religion and Classics,
+this creative ferment was slow indeed to work. Darwin himself felt
+strongly "that a man should not publish on a subject to which he has
+not given special and continuous thought," and hence wrote little on
+religion and with manifest reluctance, though, as already seen, in
+answer to pertinacious inquiry he gave an outline of his own views. But
+none the less he foresaw that his doctrine must have, for the history
+of man's mental evolution, issues wider than those with which he was
+prepared personally to deal. He writes, in "The Origin of Species"
+(6th edition, page 428.), "In the future I see open fields for far
+more important researches. Psychology will be securely based on
+the foundation already well laid by Mr Herbert Spencer, that of the
+necessary acquirement of each mental power and capacity by gradation."
+
+Nowhere, it is true, does Darwin definitely say that he regarded
+religion as a set of phenomena, the development of which may be studied
+from the psychological standpoint. Rather we infer from his PIETY--in
+the beautiful Roman sense--towards tradition and association, that
+religion was to him in some way sacrosanct. But it is delightful to see
+how his heart went out towards the new method in religious study which
+he had himself, if half-unconsciously, inaugurated. Writing in 1871 to
+Dr Tylor, on the publication of his "Primitive Culture", he says ("Life
+and Letters", Vol. III. page 151.), "It is wonderful how you trace
+animism from the lower races up the religious belief of the highest
+races. It will make me for the future look at religion--a belief in the
+soul, etc.--from a new point of view."
+
+Psychology was henceforth to be based on "the necessary acquirement of
+each mental capacity by gradation." With these memorable words the
+door closes on the old and opens on the new horizon. The mental focus
+henceforth is not on the maintaining or refuting of an orthodoxy but
+on the genesis and evolution of a capacity, not on perfection but on
+process. Continuous evolution leaves no gap for revelation sudden and
+complete. We have henceforth to ask, not when was religion revealed
+or what was the revelation, but how did religious phenomena arise and
+develop. For an answer to this we turn with new and reverent eyes to
+study "the heathen in his blindness" and the child "born in sin." We
+still indeed send out missionaries to convert the heathen, but here
+at least in Cambridge before they start they attend lectures on
+anthropology and comparative religion. The "decadence" theory is dead
+and should be buried.
+
+The study of primitive religions then has been made possible and even
+inevitable by the theory of Evolution. We have now to ask what new facts
+and theories have resulted from that study. This brings us to our second
+point, the advanced outlook on religion to-day.
+
+The view I am about to state is no mere personal opinion of my own.
+To my present standpoint I have been led by the investigations of such
+masters as Drs Wundt, Lehmann, Preuss, Bergson, Beck and in our own
+country Drs Tylor and Frazer. (I can only name here the books that
+have specially influenced my own views. They are W. Wundt,
+"Volkerpsychologie", Leipzig, 1900, P. Beck, "Die Nachahmung", Leipzig,
+1904, and "Erkenntnisstheorie des primitiven Denkens" in "Zeitschrift
+f. Philos. und Philos. Kritik", 1903, page 172, and 1904, page 9. Henri
+Bergson, "L'Evolution Creatrice" and "Matiere et Memoire", 1908, K. Th.
+Preuss, various articles published in the "Globus" (see page 507, note
+1), and in the "Archiv. f. Religionswissenschaft", and for the subject
+of magic, MM. Hubert et Mauss, "Theorie generale de la Magie", in
+"L'Annee Sociologique", VII.)
+
+Religion always contains two factors. First, a theoretical factor, what
+a man THINKS about the unseen--his theology, or, if we prefer so to call
+it, his mythology. Second, what he DOES in relation to this unseen--his
+ritual. These factors rarely if ever occur in complete separation; they
+are blended in very varying proportions. Religion we have seen was
+in the last century regarded mainly in its theoretical aspect as a
+doctrine. Greek religion for example meant to most educated persons
+Greek mythology. Yet even a cursory examination shows that neither
+Greek nor Roman had any creed or dogma, any hard and fast formulation
+of belief. In the Greek Mysteries (See my "Prolegomena to the Study of
+Greek Religion", page 155, Cambridge, 1903.) only we find what we should
+call a Confiteor; and this is not a confession of faith, but an avowal
+of rites performed. When the religion of primitive peoples came to be
+examined it was speedily seen that though vague beliefs necessarily
+abound, definite creeds are practically non-existent. Ritual is dominant
+and imperative.
+
+This predominance and priority of ritual over definite creed was first
+forced upon our notice by the study of savages, but it promptly and
+happily joined hands with modern psychology. Popular belief says, I
+think, therefore I act; modern scientific psychology says, I act (or
+rather, REact to outside stimulus), and so I come to think. Thus there
+is set going a recurrent series: act and thought become in their turn
+stimuli to fresh acts and thoughts. In examining religion as envisaged
+to-day it would therefore be more correct to begin with the practice
+of religion, i.e. ritual, and then pass to its theory, theology or
+mythology. But it will be more convenient to adopt the reverse
+method. The theoretical content of religion is to those of us who are
+Protestants far more familiar and we shall thus proceed from the known
+to the comparatively unknown.
+
+I shall avoid all attempt at rigid definition. The problem before the
+modern investigator is, not to determine the essence and definition of
+religion but to inquire how religious phenomena, religious ideas and
+practices arose. Now the theoretical content of religion, the domain of
+theology or mythology, is broadly familiar to all. It is the world of
+the unseen, the supersensuous; it is the world of what we call the soul
+and the supposed objects of the soul's perception, sprites, demons,
+ghosts and gods. How did this world grow up?
+
+We turn to our savages. Intelligent missionaries of bygone days used to
+ply savages with questions such as these: Had they any belief in God?
+Did they believe in the immortality of the soul? Taking their own
+clear-cut conceptions, discriminated by a developed terminology, these
+missionaries tried to translate them into languages that had neither the
+words nor the thoughts, only a vague, inchoate, tangled substratum, out
+of which these thoughts and words later differentiated themselves. Let
+us examine this substratum.
+
+Nowadays we popularly distinguish between objective and subjective;
+and further, we regard the two worlds as in some sense opposed. To
+the objective world we commonly attribute some reality independent of
+consciousness, while we think of the subjective as dependent for its
+existence on the mind. The objective world consists of perceptible
+things, or of the ultimate constituents to which matter is reduced by
+physical speculation. The subjective world is the world of beliefs,
+hallucinations, dreams, abstract ideas, imaginations and the like.
+Psychology of course knows that the objective and subjective worlds are
+interdependent, inextricably intertwined, but for practical purposes the
+distinction is convenient.
+
+But primitive man has not yet drawn the distinction between objective
+and subjective. Nay, more, it is foreign to almost the whole of ancient
+philosophy. Plato's Ideas (I owe this psychological analysis of the
+elements of the primitive supersensuous world mainly to Dr Beck,
+"Erkenntnisstheorie des primitiven Denkens", see page 498, note 1.), his
+Goodness, Truth, Beauty, his class-names, horse, table, are it is true
+dematerialised as far as possible, but they have outside existence,
+apart from the mind of the thinker, they have in some shadowy way
+spatial extension. Yet ancient philosophies and primitive man alike
+needed and possessed for practical purposes a distinction which served
+as well as our subjective and objective. To the primitive savage all his
+thoughts, every object of which he was conscious, whether by perception
+or conception, had reality, that is, it had existence outside himself,
+but it might have reality of various kinds or different degrees.
+
+It is not hard to see how this would happen. A man's senses may mislead
+him. He sees the reflection of a bird in a pond. To his eyes it is a
+real bird. He touches it, HE PUTS IT TO THE TOUCH, and to his touch it
+is not a bird at all. It is real then, but surely not quite so real as
+a bird that you can touch. Again, he sees smoke. It is real to his eyes.
+He tries to grasp it, it vanishes. The wind touches him, but he cannot
+see it, which makes him feel uncanny. The most real thing is that which
+affects most senses and especially what affects the sense of touch.
+Apparently touch is the deepest down, most primitive, of senses. The
+rest are specialisations and complications. Primitive man has no formal
+rubric "optical delusion," but he learns practically to distinguish
+between things that affect only one sense and things that affect two or
+more--if he did not he would not survive. But both classes of things are
+real to him. Percipi est esse.
+
+So far, primitive man has made a real observation; there are things that
+appeal to one sense only. But very soon creeps in confusion fraught with
+disaster. He passes naturally enough, being economical of any mental
+effort, from what he really sees but cannot feel to what he thinks
+he sees, and gives to it the same secondary reality. He has dreams,
+visions, hallucinations, nightmares. He dreams that an enemy is beating
+him, and he wakes rubbing his head. Then further he remembers things;
+that is, for him, he sees them. A great chief died the other day and
+they buried him, but he sees him still in his mind, sees him in his
+war-paint, splendid, victorious. So the image of the past goes together
+with his dreams and visions to the making of this other less real,
+but still real world, his other-world of the supersensuous, the
+supernatural, a world, the outside existence of which, independent of
+himself, he never questions.
+
+And, naturally enough, the future joins the past in this supersensuous
+world. He can hope, he can imagine, he can prophesy. And again the
+images of his hope are real; he sees them with that mind's eye which
+as yet he has not distinguished from his bodily eye. And so the
+supersensuous world grows and grows big with the invisible present, and
+big also with the past and the future, crowded with the ghosts of the
+dead and shadowed with oracles and portents. It is this supersensuous,
+supernatural world which is the eternity, the other-world, of primitive
+religion, not an endlessness of time, but a state removed from full
+sensuous reality, a world in which anything and everything may happen,
+a world peopled by demonic ancestors and liable to a splendid vagueness,
+to a "once upon a time-ness" denied to the present. It not unfrequently
+happens that people who know that the world nowadays obeys fixed laws
+have no difficulty in believing that six thousand years ago man was
+made direct from a lump of clay, and woman was made from one of man's
+superfluous ribs.
+
+The fashioning of the supersensuous world comes out very clearly in
+primitive man's views about the soul and life after death. Herbert
+Spencer noted long ago the influence of dreams in forming a belief in
+immortality, but being very rational himself, he extended to primitive
+man a quite alien quality of rationality. Herbert Spencer argued that
+when a savage has a dream he seeks to account for it, and in so doing
+invents a spirit world. The mistake here lies in the "seeks to account
+for it." (Primitive man, as Dr Beck observes, is not impelled by an
+Erkenntnisstrieb. Dr Beck says he has counted upwards of 30 of these
+mythological Triebe (tendencies) with which primitive man has been
+endowed.) Man is at first too busy LIVING to have any time for
+disinterested THINKING. He dreams a dream and it is real for him. He
+does not seek to account for it any more than for his hands and feet. He
+cannot distinguish between a CONception and a PERception, that is all.
+He remembers his ancestors or they appear to him in a dream; therefore
+they are alive still, but only as a rule to about the third generation.
+Then he remembers them no more and they cease to be.
+
+Next as regards his own soul. He feels something within him,
+his life-power, his will to live, his power to act, his
+personality--whatever we like to call it. He cannot touch this thing
+that is himself, but it is real. His friend too is alive and one day he
+is dead; he cannot move, he cannot act. Well, something has gone that
+was his friend's self. He has stopped breathing. Was it his breath? or
+he is bleeding; is it his blood? This life-power IS something; does it
+live in his heart or his lungs or his midriff? He did not see it go;
+perhaps it is like wind, an anima, a Geist, a ghost. But again it comes
+back in a dream, only looking shadowy; it is not the man's life, it is
+a thin copy of the man; it is an "image" (eidolon). It is like that
+shifting distorted thing that dogs the living man's footsteps in the
+sunshine; it is a "shade" (skia). (The two conceptions of the soul, as a
+life-essence, inseparable from the body, and as a separable phantom seem
+to occur in most primitive systems. They are distinct conceptions but
+are inextricably blended in savage thought. The two notions Korperseele
+and Psyche have been very fully discussed in Wundt's "Volkerpsychologie"
+II. pages 1-142, Leipzig, 1900.)
+
+Ghosts and sprites, ancestor worship, the soul, oracles, prophecy; all
+these elements of the primitive supersensuous world we willingly admit
+to be the proper material of religion; but other elements are more
+surprising; such are class-names, abstract ideas, numbers, geometrical
+figures. We do not nowadays think of these as of religious content, but
+to primitive men they were all part of the furniture of his supernatural
+world.
+
+With respect to class-names, Dr Tylor ("Primitive Culture", Vol. II.
+page 245 (4th edition), 1903.) has shown how instructive are the first
+attempts of the savage to get at the idea of a class. Things in which
+similarity is observed, things indeed which can be related at all are
+to the savage KINDRED. A species is a family or a number of individuals
+with a common god to look after them. Such for example is the Finn
+doctrine of the haltia. Every object has its haltia, but the haltiat
+were not tied to the individual, they interested themselves in every
+member of the species. Each stone had its haltia, but that haltia was
+interested in other stones; the individuals disappeared, the haltia
+remained.
+
+Nor was it only class-names that belonged to the supersensuous world. A
+man's own proper-name is a sort of spiritual essence of him, a kind
+of soul to be carefully concealed. By pronouncing a name you bring the
+thing itself into being. When Elohim would create Day "he called out to
+the Light 'Day,' and to the Darkness he called out 'Night'"; the great
+magician pronounced the magic Names and the Things came into being. "In
+the beginning was the Word" is literally true, and this reflects the
+fact that our CONCEPTUAL world comes into being by the mental process of
+naming. (For a full discussion of this point see Beck, "Nachahmung" page
+41, "Die Sprache".) In old times people went further; they thought that
+by naming events they could bring them to be, and custom even to-day
+keeps up the inveterate magical habit of wishing people "Good Morning"
+and a "Happy Christmas."
+
+Number, too, is part of the supersensuous world that is thoroughly
+religious. We can see and touch seven apples, but seven itself, that
+wonderful thing that shifts from object to object, giving it
+its SEVENness, that living thing, for it begets itself anew in
+multiplication--surely seven is a fit denizen of the upper-world.
+Originally all numbers dwelt there, and a certain supersensuous sanctity
+still clings to seven and three. We still say "Holy, Holy, Holy," and in
+some mystic way feel the holier.
+
+The soul and the supersensuous world get thinner and thinner, rarer and
+more rarified, but they always trail behind them clouds of smoke and
+vapour from the world of sense and space whence they have come. It is
+difficult for us even nowadays to use the word "soul" without lapsing
+into a sensuous mythology. The Cartesians' sharp distinction between res
+extensa non cogitans and res cogitans non extansa is remote.
+
+So far then man, through the processes of his thinking, has provided
+himself with a supersensuous world, the world of sense-delusion, of
+smoke and cloud, of dream and phantom, of imagination, of name and
+number and image. The natural course would now seem to be that this
+supersensuous world should develop into the religious world as we know
+it, that out of a vague animism with ghosts of ancestors, demons,
+and the like, there should develop in due order momentary gods
+(Augenblicks-Gotter), tribal gods, polytheism, and finally a pure
+monotheism.
+
+This course of development is usually assumed, but it is not I think
+quite what really happens. The supersensuous world as we have got it so
+far is too theoretic to be complete material of religion. It is indeed
+only one factor, or rather it is as it were a lifeless body that waits
+for a living spirit to possess and inform it. Had the theoretic factor
+remained uninformed it would eventually have separated off into its
+constituent elements of error and truth, the error dying down as a
+belated metaphysic, the truth developing into a correct and scientific
+psychology of the subjective. But man has ritual as well as mythology;
+that is, he feels and acts as well as thinks; nay more he probably feels
+and acts long before he definitely thinks. This contradicts all our
+preconceived notions of theology. Man, we imagine, believes in a god
+or gods and then worships. The real order seems to be that, in a sense
+presently to be explained, he worships, he feels and acts, and out
+of his feeling and action, projected into his confused thinking,
+he develops a god. We pass therefore to our second factor in
+religion:--ritual.
+
+The word "ritual" brings to our modern minds the notion of a church
+with a priesthood and organised services. Instinctively we think of a
+congregation meeting to confess sins, to receive absolution, to pray,
+to praise, to listen to sermons, and possibly to partake of sacraments.
+Were we to examine these fully developed phenomena we should hardly get
+further in the analysis of our religious conceptions than the notion
+of a highly anthropomorphic god approached by purely human methods of
+personal entreaty and adulation.
+
+Further, when we first come to the study of primitive religions we
+expect a priori to find the same elements, though in a ruder form. We
+expect to see "The heathen in his blindness bow down to wood and stone,"
+but the facts that actually confront us are startlingly dissimilar.
+Bowing down to wood and stone is an occupation that exists mainly in the
+minds of hymn-writers. The real savage is more actively engaged. Instead
+of asking a god to do what he wants done, he does it or tries to do
+it himself; instead of prayers he utters spells. In a word he is busy
+practising magic, and above all he is strenuously engaged in dancing
+magical dances. When the savage wants rain or wind or sunshine, he does
+not go to church; he summons his tribe and they dance a rain-dance or
+wind-dance or sun-dance. When a savage goes to war we must not picture
+his wife on her knees at home praying for the absent; instead we must
+picture her dancing the whole night long; not for mere joy of heart
+or to pass the weary hours; she is dancing his war-dance to bring him
+victory.
+
+Magic is nowadays condemned alike by science and by religion; it is
+both useless and impious. It is obsolete, and only practised by malign
+sorcerers in obscure holes and corners. Undoubtedly magic is neither
+religion nor science, but in all probability it is the spiritual
+protoplasm from which religion and science ultimately differentiated.
+As such the doctrine of evolution bids us scan it closely. Magic may
+be malign and private; nowadays it is apt to be both. But in early days
+magic was as much for good as for evil; it was publicly practised for
+the common weal.
+
+The gist of magic comes out most clearly in magical dances. We think of
+dancing as a light form of recreation, practised by the young from sheer
+joie de vivre and unsuitable for the mature. But among the Tarahumares
+(Carl Lumholtz, "Unknown Mexico", page 330, London, 1903.) in Mexico the
+word for dancing, nolavoa, means "to work." Old men will reproach young
+men saying "Why do you not go to work?" meaning why do you not dance
+instead of only looking on. The chief religious sin of which the
+Tarahumare is conscious is that he has not danced enough and not made
+enough tesvino, his cereal intoxicant.
+
+Dancing then is to the savage WORKING, DOING, and the dance is in its
+origin an imitation or perhaps rather an intensification of processes of
+work. (Karl Bucher, "Arbeit und Rhythmus", Leipzig (3rd edition), 1902,
+passim.) Repetition, regular and frequent, constitutes rhythm and rhythm
+heightens the sense of will power in action. Rhythmical action may even,
+as seen in the dances of Dervishes, produce a condition of ecstasy.
+Ecstasy among primitive peoples is a condition much valued; it is often,
+though not always, enhanced by the use of intoxicants. Psychologically
+the savage starts from the sense of his own will power, he stimulates
+it by every means at his command. Feeling his will strongly and knowing
+nothing of natural law he recognises no limits to his own power; he
+feels himself a magician, a god; he does not pray, he WILLS. Moreover
+he wills collectively (The subject of collective hallucination as an
+element in magic has been fully worked out by MM. Hubert and Mauss.
+"Theorie generale de la Magie", In "L'Annee Sociologique", 1902--3, page
+140.), reinforced by the will and action of his whole tribe. Truly of
+him it may be said "La vie deborde l'intelligence, l'intelligence c'est
+un retrecissement." (Henri Bergson, "L'Evolution Creatrice", page 50.)
+
+The magical extension and heightening of personality come out very
+clearly in what are rather unfortunately known as MIMETIC dances. Animal
+dances occur very frequently among primitive peoples. The dancers
+dress up as birds, beasts, or fishes, and reproduce the characteristic
+movements and habits of the animals impersonated. (So characteristic is
+this impersonation in magical dancing that among the Mexicans the
+word for magic, navali, means "disguise." K. Th. Preuss, "Archiv f.
+Religionswissenschaft", 1906, page 97.) A very common animal dance is
+the frog-dance. When it rains the frogs croak. If you desire rain you
+dress up like a frog and croak and jump. We think of such a performance
+as a conscious imitation. The man, we think, is more or less LIKE a
+frog. That is not how primitive man thinks; indeed, he scarcely thinks
+at all; what HE wants done the frog can do by croaking and jumping, so
+he croaks and jumps and, for all he can, BECOMES a frog. "L'intelligence
+animale JOUE sans doute les representations plutot qu'elle ne les
+pense." (Bergson, "L'Evolution Creatrice", page 205.)
+
+We shall best understand this primitive state of mind if we study
+the child "born in sin." If a child is "playing at lions" he does not
+IMITATE a lion, i.e. he does not consciously try to be a thing more or
+less like a lion, he BECOMES one. His reaction, his terror, is the same
+as if the real lion were there. It is this childlike power of utter
+impersonation, of BEING the thing we act or even see acted, this
+extension and intensification of our own personality that lives deep
+down in all of us and is the very seat and secret of our joy in the
+drama.
+
+A child's mind is indeed throughout the best clue to the understanding
+of savage magic. A young and vital child knows no limit to his own will,
+and it is the only reality to him. It is not that he wants at the outset
+to fight other wills, but that they simply do not exist for him. Like
+the artist he goes forth to the work of creation, gloriously alone. His
+attitude towards other recalcitrant wills is "they simply must." Let
+even a grown man be intoxicated, be in love, or subject to an intense
+excitement, the limitations of personality again fall away. Like the
+omnipotent child he is again a god, and to him all things are possible.
+Only when he is old and weary does he cease to command fate.
+
+The Iroquois (Hewitt, "American Anthropologist", IV. I. page 32, 1902,
+N.S.) of North America have a word, orenda, the meaning of which is
+easier to describe than to define, but it seems to express the very soul
+of magic. This orenda is your power to do things, your force, sometimes
+almost your personality. A man who hunts well has much and good orenda;
+the shy bird who escapes his snares has a fine orenda. The orenda of the
+rabbit controls the snow and fixes the depth to which it will fall. When
+a storm is brewing the magician is said to be making its orenda. When
+you yourself are in a rage, great is your orenda. The notes of birds
+are utterances of their orenda. When the maize is ripening, the Iroquois
+know it is the sun's heat that ripens it, but they know more; it is the
+cigala makes the sun to shine and he does it by chirping, by uttering
+his orenda. This orenda is sometimes very like the Greek thumos, your
+bodily life, your vigour, your passion, your power, the virtue that is
+in you to feel and do. This notion of orenda, a sort of pan-vitalism, is
+more fluid than animism, and probably precedes it. It is the projection
+of man's inner experience, vague and unanalysed, into the outer world.
+
+The mana of the Melanesians (Codrington, "The Melanesians", pages 118,
+119, 192, Oxford, 1891.) is somewhat more specialised--all men do not
+possess mana--but substantially it is the same idea. Mana is not only a
+force, it is also an action, a quality, a state, at once a substantive,
+an adjective, and a verb. It is very closely neighboured by the idea
+of sanctity. Things that have mana are tabu. Like orenda it manifests
+itself in noises, but specially mysterious ones, it is mana that is
+rustling in the trees. Mana is highly contagious, it can pass from a
+holy stone to a man or even to his shadow if it cross the stone. "All
+Melanesian religion," Dr Codrington says, "consists in getting mana
+for oneself or getting it used for one's benefit." (Codrington, "The
+Melanesians", page 120, Oxford, 1891.)
+
+Specially instructive is a word in use among the Omaka (See Prof.
+Haddon, "Magic and Fetishism", page 60, London, 1906. Dr Vierkandt
+("Globus", July, 1907, page 41) thinks that "Fernzauber" is a later
+development from Nahzauber.), wazhin-dhedhe, "directive energy, to
+send." This word means roughly what we should call telepathy, sending
+out your thought or will-power to influence another and affect his
+action. Here we seem to get light on what has always been a puzzle, the
+belief in magic exercised at a distance. For the savage will, distance
+is practically non-existent, his intense desire feels itself as
+non-spatial. (This notion of mana, orenda, wazhin-dhedhe and the like
+lives on among civilised peoples in such words as the Vedic brahman in
+the neuter, familiar to us in its masculine form Brahman. The neuter,
+brahman, means magic power of a rite, a rite itself, formula, charm,
+also first principle, essence of the universe. It is own cousin to the
+Greek dunamis and phusis. See MM. Hubert et Mauss, "Theorie generale de
+la Magie", page 117, in "L'Annee Sociologique", VII.)
+
+Through the examination of primitive ritual we have at last got at one
+tangible, substantial factor in religion, a real live experience, the
+sense, that is, of will, desire, power actually experienced in person
+by the individual, and by him projected, extended into the rest of the
+world.
+
+At this stage it may fairly be asked, though the question cannot with
+any certainty be answered, "at what point in the evolution of man does
+this religious experience come in?"
+
+So long as an organism reacts immediately to outside stimulus, with a
+certainty and conformity that is almost chemical, there is, it would
+seem, no place, no possibility for magical experience. But when the
+germ appears of an intellect that can foresee an end not immediately
+realised, or rather when a desire arises that we feel and recognise as
+not satisfied, then comes in the sense of will and the impulse magically
+to intensify that will. The animal it would seem is preserved by
+instinct from drawing into his horizon things which do not immediately
+subserve the conservation of his species. But the moment man's
+life-power began to make on the outside world demands not immediately
+and inevitably realised in action (I owe this observation to Dr K. Th.
+Preuss. He writes ("Archiv f. Relig." 1906, page 98), "Die Betonung des
+Willens in den Zauberakten ist der richtige Kern. In der Tat muss der
+Mensch den Willen haben, sich selbst und seiner Umgebung besondere
+Fahigkeiten zuzuschreiben, und den Willen hat er, sobald sein Verstand
+ihn befahigt, EINE UBER DEN INSTINKT HINAUSGEHEN DER FURSORGE fur
+sich zu zeigen. SO LANGE IHN DER INSTINKT ALLEIN LEITET, KONNEN
+ZAUBERHANDLUNGEN NICHT ENSTEHEN." For more detailed analysis of the
+origin of magic, see Dr Preuss "Ursprung der Religion und Kunst",
+"Globus", LXXXVI. and LXXXVII.), then a door was opened to magic, and
+in the train of magic followed errors innumerable, but also religion,
+philosophy, science and art.
+
+The world of mana, orenda, brahman is a world of feeling, desiring,
+willing, acting. What element of thinking there may be in it is not yet
+differentiated out. But we have already seen that a supersensuous world
+of thought grew up very early in answer to other needs, a world of
+sense-illusions, shadows, dreams, souls, ghosts, ancestors, names,
+numbers, images, a world only wanting as it were the impulse of mana to
+live as a religion. Which of the two worlds, the world of thinking or
+the world of doing, developed first it is probably idle to inquire. (If
+external stimuli leave on organisms a trace or record such as is known
+as an Engram, this physical basis of memory and hence of thought is
+almost coincident with reaction of the most elementary kind. See Mr
+Francis Darwin's Presidential Address to the British Association,
+Dublin, 1908, page 8, and again Bergson places memory at the very root
+of conscious existence, see "L'Evolution Creatrice", page 18, "le
+fond meme de notre existence consciente est memoire, c'est a dire
+prolongation du passee dans le present," and again "la duree mord dans
+le temps et y laisse l'enpreint de son dent," and again, "l'Evolution
+implique une continuation reelle du passee par le present.")
+
+It is more important to ask, Why do these two worlds join? Because,
+it would seem, mana, the egomaniac or megalomaniac element, cannot get
+satisfied with real things, and therefore goes eagerly out to a false
+world, the supersensuous other-world whose growth we have sketched. This
+junction of the two is fact, not fancy. Among all primitive peoples dead
+men, ghosts, spirits of all kinds, become the chosen vehicle of mana.
+Even to this day it is sometimes urged that religion, i.e. belief in
+the immortality of the soul, is true "because it satisfies the deepest
+craving of human nature." The two worlds, of mana and magic on the one
+hand, of ghosts and other-world on the other, combine so easily because
+they have the same laws, or rather the same comparative absence of law.
+As in the world of dreams and ghosts, so in the world of mana, space and
+time offer no obstacles; with magic all things are possible. In the one
+world what you imagine is real; in the other what you desire is ipso
+facto accomplished. Both worlds are egocentric, megalomaniac, filled to
+the full with unbridled human will and desire.
+
+We are all of us born in sin, in that sin which is to science
+"the seventh and deadliest," anthropomorphism, we are egocentric,
+ego-projective. Hence necessarily we make our gods in our own image.
+Anthropomorphism is often spoken of in books on religion and mythology
+as if it were a last climax, a splendid final achievement in religious
+thought. First, we are told, we have the lifeless object as god
+(fetichism), then the plant or animal (phytomorphism, theriomorphism),
+and last God is incarnate in the human form divine. This way of putting
+things is misleading. Anthropomorphism lies at the very beginning of
+our consciousness. Man's first achievement in thought is to realise that
+there is anything at all not himself, any object to his subject. When
+he has achieved however dimly this distinction, still for long, for very
+long he can only think of those other things in terms of himself; plants
+and animals are people with ways of their own, stronger or weaker than
+himself but to all intents and purposes human.
+
+Again the child helps us to understand our own primitive selves. To
+children animals are always people. You promise to take a child for a
+drive. The child comes up beaming with a furry bear in her arms. You say
+the bear cannot go. The child bursts into tears. You think it is because
+the child cannot endure to be separated from a toy. It is no such thing.
+It is the intolerable hurt done to the bear's human heart--a hurt not
+to be healed by any proffer of buns. He wanted to go, but he was a shy,
+proud bear, and he would not say so.
+
+The relation of magic to religion has been much disputed. According to
+one school religion develops out of magic, according to another, though
+they ultimately blend, they are at the outset diametrically opposed,
+magic being a sort of rudimentary and mistaken science (This view held
+by Dr Frazer is fully set forth in his "Golden Bough" (2nd edition),
+pages 73-79, London, 1900. It is criticised by Mr R.R. Marett in "From
+Spell to Prayer", "Folk-Lore" XI. 1900, page 132, also very fully by
+MM. Hubert and Mauss, "Theorie generale de la Magie", in "L'Annee
+Sociologique", VII. page 1, with Mr Marett's view and with that of MM.
+Hubert and Mauss I am in substantial agreement.), religion having to do
+from the outset with spirits.
+
+But, setting controversy aside, at the present stage of our inquiry
+their relation becomes, I think, fairly clear. Magic is, if my view
+(This view as explained above is, I believe, my own most serious
+contribution to the subject. In thinking it out I was much helped by
+Prof. Gilbert Murray.) be correct, the active element which informs a
+supersensuous world fashioned to meet other needs. This blend of
+theory and practice it is convenient to call religion. In practice the
+transition from magic to religion, from Spell to Prayer, has always been
+found easy. So long as mana remains impersonal you order it about; when
+it is personified and bulks to the shape of an overgrown man, you drop
+the imperative and cringe before it. "My will be done" is magic,
+"Thy Will be done" is the last word in religion. The moral discipline
+involved in the second is momentous, the intellectual advance not
+striking.
+
+I have spoken of magical ritual as though it were the informing
+life-spirit without which religion was left as an empty shell. Yet the
+word ritual does not, as normally used, convey to our minds this notion
+of intense vitalism. Rather we associate ritual with something cut
+and dried, a matter of prescribed form and monotonous repetition. The
+association is correct; ritual tends to become less and less informed by
+the life-impulse, more and more externalised. Dr Beck ("Die Nachahmung
+und ihre Bedeutung fur Psychologie und Volkerkunde", Leipzig, 1904.)
+in his brilliant monograph on "Imitation" has laid stress on the almost
+boundless influence of the imitation of one man by another in the
+evolution of civilisation. Imitation is one of the chief spurs to
+action. Imitation begets custom, custom begets sanctity. At first all
+custom is sacred. To the savage it is as much a religious duty to tattoo
+himself as to sacrifice to his gods. But certain customs naturally
+survive, because they are really useful; they actually have good
+effects, and so need no social sanction. Others are really useless;
+but man is too conservative and imitative to abandon them. These become
+ritual. Custom is cautious, but la vie est aleatoire. (Bergson, op. cit.
+page 143.)
+
+Dr Beck's remarks on ritual are I think profoundly true and suggestive,
+but with this reservation--they are true of ritual only when uninformed
+by personal experience. The very elements in ritual on which Dr
+Beck lays such stress, imitation, repetition, uniformity and social
+collectivity, have been found by the experience of all time to have
+a twofold influence--they inhibit the intellect, they stimulate and
+suggest emotion, ecstasy, trance. The Church of Rome knows what she is
+about when she prescribes the telling of the rosary. Mystery-cults and
+sacraments, the lineal descendants of magic, all contain rites charged
+with suggestion, with symbols, with gestures, with half-understood
+formularies, with all the apparatus of appeal to emotion and will--the
+more unintelligible they are the better they serve their purpose of
+inhibiting thought. Thus ritual deadens the intellect and stimulates
+will, desire, emotion. "Les operations magiques... sont le resultat d'une
+science et d'une habitude qui exaltent la volonte humaine au-dessus de
+ses limites habituelles." (Eliphas Levi, "Dogme et Rituel de la haute
+Magie", II. page 32, Paris, 1861, and "A defence of Magic", by Evelyn
+Underhill, "Fortnightly Review", 1907.) It is this personal EXPERIENCE,
+this exaltation, this sense of immediate, non-intellectual revelation,
+of mystical oneness with all things, that again and again rehabilitates
+a ritual otherwise moribund.
+
+To resume. The outcome of our examination of ORIGINES seems to be that
+religious phenomena result from two delusive processes--a delusion of
+the non-critical intellect, a delusion of the over-confident will. Is
+religion then entirely a delusion? I think not. (I am deeply conscious
+that what I say here is a merely personal opinion or sentiment,
+unsupported and perhaps unsupportable by reason, and very possibly quite
+worthless, but for fear of misunderstanding I prefer to state it.) Every
+dogma religion has hitherto produced is probably false, but for all that
+the religious or mystical spirit may be the only way of apprehending
+some things and these of enormous importance. It may also be that the
+contents of this mystical apprehension cannot be put into language
+without being falsified and misstated, that they have rather to be felt
+and lived than uttered and intellectually analysed, and thus do not
+properly fall under the category of true or false, in the sense in which
+these words are applied to propositions; yet they may be something
+for which "true" is our nearest existing word and are often, if not
+necessary at least highly advantageous to life. That is why man through
+a series of more or less grossly anthropomorphic mythologies and
+theologies with their concomitant rituals tries to restate them.
+Meantime we need not despair. Serious psychology is yet young and has
+only just joined hands with physiology. Religious students are still
+hampered by mediaevalisms such as Body and Soul, and by the perhaps
+scarcely less mythological segregations of Intellect, Emotion, Will. But
+new facts (See the "Proceedings" of the Society for Psychical Research,
+London, passim, and especially Vols. VII.-XV. For a valuable collection
+of the phenomena of mysticism, see William James, "Varieties of
+Religious Experience", Edinburgh, 1901-2.) are accumulating, facts about
+the formation and flux of personality, and the relations between the
+conscious and the sub-conscious. Any moment some great imagination may
+leap out into the dark, touch the secret places of life, lay bare the
+cardinal mystery of the marriage of the spatial with the non-spatial. It
+is, I venture to think, towards the apprehension of such mysteries,
+not by reason only, but by man's whole personality, that the religious
+spirit in the course of its evolution through ancient magic and modern
+mysticism is ever blindly yet persistently moving.
+
+Be this as it may, it is by thinking of religion in the light of
+evolution, not as a revelation given, not as a realite faite but as a
+process, and it is so only, I think, that we attain to a spirit of real
+patience and tolerance. We have ourselves perhaps learnt laboriously
+something of the working of natural law, something of the limitations of
+our human will, and we have therefore renounced the practice of magic.
+Yet we are bidden by those in high places to pray "Sanctify this water
+to the mystical washing away of sin." Mystical in this connection spells
+magical, and we have no place for a god-magician: the prayer is to us
+unmeaning, irreverent. Or again, after much toil we have ceased, or
+hope we have ceased, to think anthropomorphically. Yet we are invited
+to offer formal thanks to God for a meal of flesh whose sanctity is the
+last survival of that sacrifice of bulls and goats he has renounced.
+Such a ritual confuses our intellect and fails to stir our emotion. But
+to others this ritual, magical or anthropomorphic as it is, is charged
+with emotional impulse, and others, a still larger number, think that
+they act by reason when really they are hypnotised by suggestion and
+tradition; their fathers did this or that and at all costs they must do
+it. It was good that primitive man in his youth should bear the yoke of
+conservative custom; from each man's neck that yoke will fall, when and
+because he has outgrown it. Science teaches us to await that moment with
+her own inward and abiding patience. Such a patience, such a gentleness
+we may well seek to practise in the spirit and in the memory of Darwin.
+
+
+
+
+XXVI. EVOLUTION AND THE SCIENCE OF LANGUAGE. By P. Giles, M.A., LL.D.
+(Aberdeen),
+
+Reader in Comparative Philology in the University of Cambridge.
+
+
+In no study has the historical method had a more salutary influence
+than in the Science of Language. Even the earliest records show that the
+meaning of the names of persons, places, and common objects was then, as
+it has always been since, a matter of interest to mankind. And in every
+age the common man has regarded himself as competent without special
+training to explain by inspection (if one may use a mathematical phrase)
+the meaning of any words that attracted his attention. Out of this
+amateur etymologising has sprung a great amount of false history, a kind
+of historical mythology invented to explain familiar names. A single
+example will illustrate the tendency. According to the local legend the
+ancestor of the Earl of Erroll--a husbandman who stayed the flight of
+his countrymen in the battle of Luncarty and won the victory over the
+Danes by the help of the yoke of his oxen--exhausted with the fray
+uttered the exclamation "Hoch heigh!" The grateful king about to ennoble
+the victorious ploughman at once replied:
+
+     "Hoch heigh! said ye
+     And Hay shall ye be."
+
+The Norman origin of the name Hay is well-known, and the battle of
+Luncarty long preceded the appearance of Normans in Scotland, but the
+legend nevertheless persists.
+
+Though the earliest European treatise on philological questions which
+is now extant--the "Cratylus" of Plato,--as might be expected from its
+authorship, contains some acute thinking and some shrewd guesses, yet
+the work as a whole is infantine in its handling of language, and it
+has been doubted whether Plato was more than half serious in some of
+the suggestions which he puts forward. (For an account of the "Cratylus"
+with references to other literature see Sandys' "History of Classical
+Scholarship", I. page 92 ff., Cambridge, 1903.) In the hands of the
+Romans things were worse even than they had been in the hands of Plato
+and his Greek successors. The lack of success on the part of Varro and
+later Roman writers may have been partly due to the fact that, from the
+etymological point of view, Latin is a much more difficult language than
+Greek; it is by no means so closely connected with Greek as the ancients
+imagined, and they had no knowledge of the Celtic languages from which,
+on some sides at least, much greater light on the history of the
+Latin language might have been obtained. Roman civilisation was a late
+development compared with Greek, and its records dating earlier than
+300 B.C.--a period when the best of Greek literature was already in
+existence--are very few and scanty. Varro it is true was much more of
+an antiquary than Plato, but his extant works seem to show that he was
+rather a "dungeon of learning" than an original thinker.
+
+A scientific knowledge of language can be obtained only by comparison
+of different languages of the same family and the contrasting of their
+characteristics with those of another family or other families. It never
+occurred to the Greeks that any foreign language was worthy of serious
+study. Herodotus and other travellers and antiquaries indeed picked up
+individual words from various languages, either as being necessary
+in communication with the inhabitants of the countries where they
+sojourned, or because of some point which interested them personally.
+Plato and others noticed the similarity of some Phrygian words to Greek,
+but no systematic comparison seems ever to have been instituted.
+
+In the Middle Ages the treatment of language was in a sense more
+historical. The Middle Ages started with the hypothesis, derived
+from the book of Genesis, that in the early world all men were of one
+language and of one speech. Though on the same authority they believed
+that the plain of Shinar has seen that confusion of tongues whence
+sprang all the languages upon earth, they seem to have considered that
+the words of each separate language were nevertheless derived from this
+original tongue. And as Hebrew was the language of the Chosen People,
+it was naturally assumed that this original tongue was Hebrew. Hence
+we find Dante declaring in his treatise on the Vulgar Tongue (Dante "de
+Vulgari Eloquio", I. 4.) that the first word man uttered in Paradise
+must have been "El," the Hebrew name of his Maker, while as a result of
+the fall of Adam, the first utterance of every child now born into this
+world of sin and misery is "heu," Alas! After the splendidly engraved
+bronze plates containing, as we now know, ritual regulations for certain
+cults, were discovered in 1444 at the town of Gubbio, in Umbria, they
+were declared, by some authorities, to be written in excellent Hebrew.
+The study of them has been the fascination and the despair of many a
+philologist. Thanks to the devoted labours of numerous scholars, mainly
+in the last sixty years, the general drift of these inscriptions is
+now known. They are the only important records of the ancient Umbrian
+language, which was related closely to that of the Samnites and,
+though not so closely, to that of the Romans on the other side of
+the Apennines. Yet less than twenty years ago a book was published in
+Germany, which boasts itself the home of Comparative Philology,
+wherein the German origin of the Umbrian language was no less solemnly
+demonstrated than had been its Celtic origin by Sir William Betham in
+1842.
+
+It is good that the study of language should be historical, but the
+first requisite is that the history should be sound. How little had been
+learnt of the true history of language a century ago may be seen from a
+little book by Stephen Weston first published in 1802 and several
+times reprinted, where accidental assonance is considered sufficient to
+establish connection. Is there not a word "bad" in English and a word
+"bad" in Persian which mean the same thing? Clearly therefore Persian
+and English must be connected. The conclusion is true, but it is drawn
+from erroneous premises. As stated, this identity has no more value
+than the similar assonance between the English "cover" and the Hebrew
+"kophar", where the history of "cover" as coming through French from a
+Latin "co-operire" was even in 1802 well-known to many. To this day,
+in spite of recent elaborate attempts (Most recently in H. Moller's
+"Semitisch und Indogermanisch", Erster Teil, Kopenhagen, 1907.) to
+establish connection between the Indo-Germanic and the Semitic families
+of languages, there is no satisfactory evidence of such relation between
+these families. This is not to deny the possibility of such a connection
+at a very early period; it is merely to say that through the lapse
+of long ages all trustworthy record of such relationship, if it ever
+existed, has been, so far as present knowledge extends, obliterated.
+
+But while Stephen Weston was publishing, with much public approval, his
+collection of amusing similarities between languages--similarities which
+proved nothing--the key to the historical study of at least one family
+of languages had already been found by a learned Englishman in a distant
+land. In 1783 Sir William Jones had been sent out as a judge in the
+supreme court of judicature in Bengal. While still a young man at Oxford
+he was noted as a linguist; his reputation as a Persian scholar had
+preceded him to the East. In the intervals of his professional duties
+he made a careful study of the language which was held sacred by
+the natives of the country in which he was living. He was mainly
+instrumental in establishing a society for the investigation of language
+and related subjects. He was himself the first president of the society,
+and in the "third anniversary discourse" delivered on February 2, 1786,
+he made the following observations: "The Sanscrit language, whatever be
+its antiquity, is of a wonderful structure; more perfect than the GREEK,
+more copious than the LATIN, and more exquisitely refined than either,
+yet bearing to both of them a stronger affinity, both in the roots
+of verbs and in the forms of grammar, than could possibly have been
+produced by accident; so strong indeed, that no philologer could examine
+them all three, without believing them to have sprung from some common
+source, which, perhaps, no longer exists: there is a similar reason,
+though not quite so forcible, for supposing that both the Gothick and
+the Celtick, though blended with a very different idiom, had the same
+origin with the Sanscrit; and the old Persian might be added to the same
+family, if this was the place for discussing any question concerning the
+antiquities of Persia." ("Asiatic Researches", I. page 422, "Works of
+Sir W. Jones", I. page 26, London, 1799.)
+
+No such epoch-making discovery was probably ever announced with less
+flourish of trumpets. Though Sir William Jones lived for eight years
+more and delivered other anniversary discourses, he added nothing of
+importance to this utterance. He had neither the time nor the health
+that was needed for the prosecution of so arduous an undertaking.
+
+But the good seed did not fall upon stony ground. The news was speedily
+conveyed to Europe. By a happy chance, the sudden renewal of war between
+France and England in 1803 gave Friedrich Schlegel the opportunity of
+learning Sanscrit from Alexander Hamilton, an Englishman who, like many
+others, was confined in Paris during the long struggle with Napoleon.
+The influence of Schlegel was not altogether for good in the history of
+this research, but he was inspiring. Not upon him but upon Franz Bopp,
+a struggling German student who spent some time in Paris and London
+a dozen years later, fell the mantle of Sir William Jones. In Bopp's
+Comparative Grammar of the Indo-Germanic languages which appeared in
+1833, three-quarters of a century ago, the foundations of Comparative
+Philology were laid. Since that day the literature of the subject has
+grown till it is almost, if not altogether, beyond the power of any
+single man to cope with it. But long as the discourse may be, it is but
+the elaboration of the text that Sir William Jones supplied.
+
+With the publication of Bopp's Comparative Grammar the historical study
+of language was put upon a stable footing. Needless to say much remained
+to be done, much still remains to be done. More than once there has been
+danger of the study following erroneous paths. Its terminology and its
+point of view have in some degree changed. But nothing can shake the
+truth of the statement that the Indo-Germanic languages constitute in
+themselves a family sprung from the same source, marked by the same
+characteristics, and differentiated from all other languages by
+formation, by vocabulary, and by syntax. The historical method was
+applied to language long before it reached biology. Nearly a quarter of
+a century before Charles Darwin was born, Sir William Jones had made the
+first suggestion of a comparative study of languages. Bopp's Comparative
+Grammar began to be published nine years before the first draft of
+Darwin's treatise on the Origin of Species was put on paper in 1842.
+
+It is not therefore on the history of Comparative Philology in general
+that the ideas of Darwin have had most influence. Unfortunately, as
+Jowett has said in the introduction to his translation of Plato's
+"Republic", most men live in a corner. The specialisation of knowledge
+has many advantages, but it has also disadvantages, none worse perhaps
+than that it tends to narrow the specialist's horizon and to make it
+more difficult for one worker to follow the advances that are being made
+by workers in other departments. No longer is it possible as in earlier
+days for an intellectual prophet to survey from a Pisgah height all the
+Promised Land. And the case of linguistic research has been specially
+hard. This study has, if the metaphor may be allowed, a very extended
+frontier. On one side it touches the domain of literature, on other
+sides it is conterminous with history, with ethnology and anthropology,
+with physiology in so far as language is the production of the brain and
+tissues of a living being, with physics in questions of pitch and stress
+accent, with mental science in so far as the principles of similarity,
+contrast, and contiguity affect the forms and the meanings of words
+through association of ideas. The territory of linguistic study
+is immense, and it has much to supply which might be useful to the
+neighbours who border on that territory. But they have not regarded her
+even with that interest which is called benevolent because it is not
+actively maleficent. As Horne Tooke remarked a century ago, Locke had
+found a whole philosophy in language. What have the philosophers done
+for language since? The disciples of Kant and of Wilhelm von Humboldt
+supplied her plentifully with the sour grapes of metaphysics; otherwise
+her neighbours have left her severely alone save for an occasional
+"Ausflug," on which it was clear they had sadly lost their bearings.
+Some articles in Psychological Journals, Wundt's great work on
+"Volkerpsychologie" (Erster Band: "Die Sprache", Leipzig, 1900. New
+edition, 1904. This work has been fertile in producing both opponents
+and supporters. Delbruck, "Grundfragen der Sprachforschung",
+Strassburg, 1901, with a rejoinder by Wundt, "Sprachgeschichte" and
+"Sprachpsychologie", Leipzig, 1901; L. Sutterlin, "Das Wesen der
+Sprachgebilde", Heidelberg, 1902; von Rozwadowski, "Wortbildung
+und Wortbedeutung", Heidelberg, 1904; O. Dittrich, "Grundzuge der
+Sprachpsychologie", Halle, 1904, Ch. A. Sechehaye, "Programme et
+methodes de la linguistique theorique", Paris, 1908.), and Mauthner's
+brilliantly written "Beitrage zu einer Kritik der Sprache" (In three
+parts: (i) "Sprache und Psychologie, (ii) "Zur Sprachwissenschaft", both
+Stuttgart 1901, (iii) "Zur Grammatic und Logik" (with index to all three
+volumes), Stuttgart and Berlin, 1902.) give some reason to hope that, on
+one side at least, the future may be better than the past.
+
+Where Charles Darwin's special studies came in contact with the Science
+of Language was over the problem of the origin and development of
+language. It is curious to observe that, where so many fields of
+linguistic research have still to be reclaimed--many as yet can hardly
+be said to be mapped out,--the least accessible field of all--that
+of the Origin of Language--has never wanted assiduous tillers.
+Unfortunately it is a field beyond most others where it may be said that
+
+"Wilding oats and luckless darnel grow."
+
+If Comparative Philology is to work to purpose here, it must be on
+results derived from careful study of individual languages and groups of
+languages. But as yet the group which Sir William Jones first mapped out
+and which Bopp organised is the only one where much has been achieved.
+Investigation of the Semitic group, in some respects of no less moment
+in the history of civilisation and religion, where perhaps the labour
+of comparison is not so difficult, as the languages differ less among
+themselves, has for some reason strangely lagged behind. Some years ago
+in the "American Journal of Philology" Paul Haupt pointed out that if
+advance was to be made, it must be made according to the principles
+which had guided the investigation of the Indo-Germanic languages to
+success, and at last a Comparative Grammar of an elaborate kind is in
+progress also for the Semitic languages. (Brockelmann, "Vergleichende
+Grammatik der semitischen Sprachen", Berlin, 1907 ff. Brockelmann and
+Zimmern had earlier produced two small hand-books. The only large work
+was William Wright's "Lectures on the Comparative Grammar of the
+Semitic Languages", Cambridge, 1890.) For the great group which includes
+Finnish, Hungarian, Turkish and many languages of northern Asia, a
+beginning, but only a beginning has been made. It may be presumed from
+the great discoveries which are in progress in Turkestan that presently
+much more will be achieved in this field. But for a certain utterance
+to be given by Comparative Philology on the question of the origin of
+language it is necessary that not merely for these languages but also
+for those in other quarters of the globe, the facts should be collected,
+sifted and tabulated. England rules an empire which contains a greater
+variety of languages by far than were ever held under one sway before.
+The Government of India is engaged in producing, under the editorship of
+Dr Grierson, a linguistic survey of India, a remarkable undertaking and,
+so far as it has gone, a remarkable achievement. Is it too much to ask
+that, with the support of the self-governing colonies, a similar survey
+should be undertaken for the whole of the British Empire?
+
+Notwithstanding the great number of books that have been written on the
+origin of language in the last three and twenty centuries, the results
+of the investigation which can be described as certain are very meagre.
+The question originally raised was whether language came into being
+thesei or phusei, by convention or by nature. The first alternative, in
+its baldest form at least, has passed from out the field of controversy.
+No one now claims that names were given to living things or objects or
+activities by formal agreement among the members of an early community,
+or that the first father of mankind passed in review every living thing
+and gave it its name. Even if the record of Adam's action were to be
+taken literally there would still remain the question, whence had he
+this power? Did he develop it himself or was it a miraculous gift with
+which he was endowed at his creation? If the latter, then as Wundt says
+("Volkerpsychologie", I. 2, page 585.), "the miracle of language is
+subsumed in the miracle of creation." If Adam developed language of
+himself, we are carried over to the alternative origin of phusei. On
+this hypothesis we must assume that the natural growth which modern
+theories of development regard as the painful progress of multitudinous
+generations was contracted into the experience of a single individual.
+
+But even if the origin of language is admitted to be NATURAL there may
+still be much variety of signification attached to the word: NATURE,
+like most words which are used by philosophers, has accumulated
+many meanings, and as research into the natural world proceeds, is
+accumulating more.
+
+Forty years ago an animated controversy raged among the supporters of
+the theories which were named for short the bow-wow, the pooh-pooh and
+the ding-dong theories of the origin of language. The third, which was
+the least tenacious of life, was made known to the English-speaking
+world by the late Professor Max Muller who, however, when questioned,
+repudiated it as his own belief. ("Science of Thought", London, 1887,
+page 211.) It was taken by him from Heyse's lectures on language which
+were published posthumously by Steinthal. Put shortly the theory is
+that "everything which is struck, rings. Each substance has its peculiar
+ring. We can tell the more or less perfect structure of metals by their
+vibrations, by the answer which they give. Gold rings differently
+from tin, wood rings differently from stone; and different sounds are
+produced according to the nature of each percussion. It may be the same
+with man, the most highly organised of nature's work." (Max Muller as
+above, translating from Heyse.) Max Muller's repudiation of this theory
+was, however, not very whole-hearted for he proceeds later in the same
+argument: "Heyse's theory, which I neither adopted nor rejected, but
+which, as will be seen, is by no means incompatible with that which for
+many years has been gaining on me, and which of late has been so clearly
+formulated by Professor Noire, has been assailed with ridicule and torn
+to pieces, often by persons who did not even suspect how much truth was
+hidden behind its paradoxical appearance. We are still very far from
+being able to identify roots with nervous vibrations, but if it should
+appear hereafter that sensuous vibrations supply at least the raw
+material of roots, it is quite possible that the theory, proposed by
+Oken and Heyse, will retain its place in the history of the various
+attempts at solving the problem of the origin of language, when other
+theories, which in our own days were received with popular applause,
+will be completely forgotten." ("Science of Thought", page 212.)
+
+Like a good deal else that has been written on the origin of language,
+this statement perhaps is not likely to be altogether clear to the plain
+man, who may feel that even the "raw material of roots" is some distance
+removed from nervous vibrations, though obviously without the existence
+of afferent and efferent nerves articulate speech would be impossible.
+But Heyse's theory undoubtedly was that every thought or idea which
+occurred to the mind of man for the first time had its own special
+phonetic expression, and that this responsive faculty, when its object
+was thus fulfilled, became extinct. Apart from the philosophical
+question whether the mind acts without external stimulus, into which it
+is not necessary to enter here, it is clear that this theory can neither
+be proved nor disproved, because it postulates that this faculty existed
+only when language first began, and later altogether disappeared. As we
+have already seen, it is impossible for us to know what happened at the
+first beginnings of language, because we have no information from any
+period even approximately so remote; nor are we likely to attain it.
+Even in their earliest stages the great families of language which
+possess a history extending over many centuries--the Indo-Germanic and
+the Semitic--have very little in common. With the exception of Chinese,
+the languages which are apparently of a simpler or more primitive
+formation have either a history which, compared with that of the
+families mentioned, is very short, or, as in the case of the vast
+majority, have no history beyond the time extending only over a few
+years or, at most, a few centuries when they have been observed by
+competent scholars of European origin. But, if we may judge by the
+history of geology and other studies, it is well to be cautious in
+assuming for the first stages of development forces which do not operate
+in the later, unless we have direct evidence of their existence.
+
+It is unnecessary here to enter into a prolonged discussion of the other
+views christened by Max Muller, not without energetic protest from their
+supporters, the bow-wow and pooh-pooh theories of language. Suffice it
+to say that the former recognises as a source of language the imitation
+of the sounds made by animals, the fall of bodies into water or on
+to solid substances and the like, while the latter, also called the
+interjectional theory, looks to the natural ejaculations produced by
+particular forms of effort for the first beginnings of speech. It would
+be futile to deny that some words in most languages come from
+imitation, and that others, probably fewer in number, can be traced
+to ejaculations. But if either of these sources alone or both in
+combination gave rise to primitive speech, it clearly must have been a
+simple form of language and very limited in amount. There is no reason
+to think that it was otherwise. Presumably in its earliest stages
+language only indicated the most elementary ideas, demands for food
+or the gratification of other appetites, indications of danger, useful
+animals and plants. Some of these, such as animals or indications of
+danger, could often be easily represented by imitative sounds: the need
+for food and the like could be indicated by gesture and natural cries.
+Both sources are verae causae; to them Noire, supported by Max Muller,
+has added another which has sometimes been called the Yo-heave-ho
+theory. Noire contends that the real crux in the early stages of
+language is for primitive man to make other primitive men understand
+what he means. The vocal signs which commend themselves to one may not
+have occurred to another, and may therefore be unintelligible. It may be
+admitted that this difficulty exists, but it is not insuperable. The
+old story of the European in China who, sitting down to a meal and being
+doubtful what the meat in the dish might be, addressed an interrogative
+Quack-quack? to the waiter and was promptly answered by Bow-wow,
+illustrates a simple situation where mutual understanding was easy.
+But obviously many situations would be more complex than this, and to
+grapple with them Noire has introduced his theory of communal action.
+"It was common effort directed to a common object, it was the most
+primitive (uralteste) labour of our ancestors, from which sprang
+language and the life of reason." (Noire "Der Ursprung der Sprache",
+page 331, Mainz, 1877.) As illustrations of such common effort he cites
+battle cries, the rescue of a ship running on shore (a situation not
+likely to occur very early in the history of man), and others. Like Max
+Muller he holds that language is the utterance and the organ of thought
+for mankind, the one characteristic which separates man from the
+brute. "In common action the word was first produced; for long it was
+inseparably connected with action; through long-continued connection it
+gradually became the firm, intelligible symbol of action, and then in
+its development indicated also things of the external world in so far
+as the action affected them and finally the sound began to enter into a
+connexion with them also." (Op. cit. page 339.) In so far as this theory
+recognises language as a social institution it is undoubtedly correct.
+Darwin some years before Noire had pointed to the same social origin
+of language in the fourth chapter of his work on "The Expression of the
+Emotions in Man and Animals". "Naturalists have remarked, I believe with
+truth, that social animals, from habitually using their vocal organs
+as a means of intercommunication, use them on other occasions much more
+freely than other animals... The principle, also, of association, which
+is so widely extended in its power, has likewise played its part. Hence
+it allows that the voice, from having been employed as a serviceable
+aid under certain conditions, inducing pleasure, pain, rage, etc., is
+commonly used whenever the same sensations or emotions are excited,
+under quite different conditions, or in a lesser degree." ("The
+Expression of the Emotions", page 84 (Popular Edition, 1904).
+
+Darwin's own views on language which are set forth most fully in
+"The Descent of Man" (page 131 ff. (Popular Edition, 1906).) are
+characterised by great modesty and caution. He did not profess to be a
+philologist and the facts are naturally taken from the best known works
+of the day (1871). In the notes added to the second edition he remarks
+on Max Muller's denial of thought without words, "what a strange
+definition must here be given to the word thought!" (Op. cit. page
+135, footnote 63.) He naturally finds the origin of language in "the
+imitation and modification of various natural sounds, the voices of
+other animals, and man's own instinctive cries aided by signs and
+gestures (op. cit. page 132.)... As the voice was used more and more,
+the vocal organs would have been strengthened and perfected through the
+principle of the inherited effects of use; and this would have reacted
+on the power of speech." (Op. cit. page 133.) On man's own instinctive
+cries, he has more to say in "The Expression of the Emotions". (Page 93
+(Popular Edition, 1904) and elsewhere.) These remarks have been utilised
+by Prof. Jespersen of Copenhagen in propounding an ingenious theory of
+his own to the effect that speech develops out of singing. ("Progress in
+Language", page 361, London, 1894.)
+
+For many years and in many books Max Muller argued against Darwin's
+views on evolution on the one ground that thought is impossible without
+speech; consequently as speech is confined to the human race, there is a
+gulf which cannot be bridged between man and all other creatures.
+(Some interesting comments on the theory will be found in a lecture
+on "Thought and Language" in Samuel Butler's "Essays on Life, Art and
+Science", London, 1908.) On the title-page of his "Science of Thought"
+he put the two sentences "No Reason without Language: No Language
+without Reason." It may be readily admitted that the second dictum is
+true, that no language properly so-called can exist without reason.
+Various birds can learn to repeat words or sentences used by their
+masters or mistresses. In most cases probably the birds do not attach
+their proper meaning to the words they have learnt; they repeat them in
+season and out of season, sometimes apparently for their own amusement,
+generally in the expectation, raised by past experience, of being
+rewarded for their proficiency. But even here it is difficult to prove
+a universal negative, and most possessors of such pets would repudiate
+indignantly the statement that the bird did not understand what was said
+to it, and would also contend that in many cases the words which it used
+were employed in their ordinary meaning. The first dictum seems to be
+inconsistent with fact. The case of deaf mutes, such as Laura Bridgeman,
+who became well educated, or the still more extraordinary case of Helen
+Keller, deaf, dumb, and blind, who in spite of these disadvantages
+has learnt not only to reason but to reason better than the average of
+persons possessed of all their senses, goes to show that language and
+reason are not necessarily always in combination. Reason is but the
+conscious adaptation of means to ends, and so defined is a faculty which
+cannot be denied to many of the lower animals. In these days when so
+many books on Animal Intelligence are issued from the press, it seems
+unnecessary to labour the point. Yet none of these animals, except by
+parrot-imitation, makes use of speech, because man alone possesses in a
+sufficient degree of development the centres of nervous energy which are
+required for the working of articulation in speech. On this subject much
+investigation was carried on during the last years of Darwin's life
+and much more in the period since his death. As early as 1861 Broca,
+following up observations made by earlier French writers, located the
+centre of articulate speech in the third left frontal convolution of
+the brain. In 1876 he more definitely fixed the organ of speech in
+"the posterior two-fifths of the third frontal convolution" (Macnamara,
+"Human Speech", page 197, London, 1908.), both sides and not merely the
+left being concerned in speech production. Owing however to the greater
+use by most human beings of the right side of the body, the left side of
+the brain, which is the motor centre for the right side of the body, is
+more highly developed than its right side, which moves the left side
+of the body. The investigations of Professors Ferrier, Sherrington and
+Grunbaum have still more precisely defined the relations between brain
+areas and certain groups of muscles. One form of aphasia is the result
+of injury to or disease in the third frontal convolution because the
+motor centre is no longer equal to the task of setting the necessary
+muscles in motion. In the brain of idiots who are unable to speak,
+the centre for speech is not developed. (Op. cit. page 226.) In the
+anthropoid apes the brain is similarly defective, though it has been
+demonstrated by Professors Cunningham and Marchand "that there is a
+tendency, especially in the gorilla's brain, for the third frontal
+convolution to assume the human form... But if they possessed a centre
+for speech, those parts of the hemispheres of their brains which form
+the mechanism by which intelligence is elaborated are so ill-developed,
+as compared with the rest of their bodies, that we can not conceive,
+even with more perfect frontal convolutions, that these animals could
+formulate ideas expressible in intelligent speech." (Op. cit. page 223.)
+
+While Max Muller's theory is Shelley's
+
+"He gave man speech, and speech created thought, Which is the measure of
+the universe" ("Prometheus Unbound" II. 4.),
+
+it seems more probable that the development was just the opposite--that
+the development of new activities originated new thoughts which required
+new symbols to express them, symbols which may at first have been, even
+to a greater extent than with some of the lower races at present, sign
+language as much as articulation. When once the faculty of articulation
+was developed, which, though we cannot trace the process, was probably a
+very gradual growth, there is no reason to suppose that words developed
+in any other way then they do at present. An erroneous notion of the
+development of language has become widely spread through the adoption
+of the metaphorical term "roots" for the irreducible elements of human
+speech. Men never talked in roots; they talked in words. Many words of
+kindred meaning have a part in common, and a root is nothing but that
+common part stripped of all additions. In some cases it is obvious that
+one word is derived from another by the addition of a fresh element; in
+other cases it is impossible to say which of two kindred words is the
+more primitive. A root is merely a convenient term for an abstraction.
+The simplest word may be called a root, but it is nevertheless a
+word. How are new words added to a language in the present day? Some
+communities, like the Germans, prefer to construct new words for new
+ideas out of the old material existing in the language; others, like the
+English, prefer to go to the ancient languages of Greece and Rome for
+terms to express new ideas. The same chemical element is described in
+the two languages as sour stuff (Sauerstoff) and as oxygen. Both terms
+mean the same thing etymologically as well as in fact. On behalf of the
+German method, it may be contended that the new idea is more closely
+attached to already existing ideas, by being expressed in elements of
+the language which are intelligible even to the meanest capacity. For
+the English practice it may be argued that, if we coin a new word which
+means one thing, and one thing only, the idea which it expresses is
+more clearly defined than if it were expressed in popularly intelligible
+elements like "sour stuff." If the etymological value of words were
+always present in the minds of their users, "oxygen" would undoubtedly
+have an advantage over "sour stuff" as a technical term. But the
+tendency in language is to put two words of this kind which express but
+one idea under a single accent, and when this has taken place, no one
+but the student of language any longer observes what the elements really
+mean. When the ordinary man talks of a "blackbird" it is certainly not
+present to his consciousness that he is talking of a black bird, unless
+for some reason conversation has been dwelling upon the colour rather
+than other characteristics of the species.
+
+But, it may be said, words like "oxygen" are introduced by learned men,
+and do not represent the action of the man in the street, who, after
+all, is the author of most additions to the stock of human language. We
+may go back therefore some four centuries to a period, when scientific
+study was only in its infancy, and see what process was followed. With
+the discovery of America new products never seen before reached Europe,
+and these required names. Three of the most characteristic were tobacco,
+the potato, and the turkey. How did these come to be so named? The first
+people to import these products into Europe were naturally the Spanish
+discoverers. The first of these words--tobacco--appears in forms which
+differ only slightly in the languages of all civilised countries:
+Spanish tabaco, Italian tabacco, French tabac, Dutch and German tabak,
+Swedish tobak, etc. The word in the native dialect of Hayti is said to
+have been tabaco, but to have meant not the plant (According to William
+Barclay, "Nepenthes, or the Virtue of Tobacco", Edinburgh, 1614, "the
+countrey which God hath honoured and blessed with this happie and holy
+herbe doth call it in their native language 'Petum'.") but the pipe
+in which it was smoked. It thus illustrates a frequent feature of
+borrowing--that the word is not borrowed in its proper signification,
+but in some sense closely allied thereto, which a foreigner,
+understanding the language with difficulty, might readily mistake for
+the real meaning. Thus the Hindu practice of burning a wife upon the
+funeral pyre of her husband is called in English "suttee", this word
+being in fact but the phonetic spelling of the Sanskrit "sati", "a
+virtuous woman," and passing into its English meaning because formerly
+the practice of self-immolation by a wife was regarded as the highest
+virtue.
+
+The name of the potato exhibits greater variety. The English name was
+borrowed from the Spanish "patata", which was itself borrowed from a
+native word for the "yam" in the dialect of Hayti. The potato appeared
+early in Italy, for the mariners of Genoa actively followed the
+footsteps of their countryman Columbus in exploring America. In Italian
+generally the form "patata" has survived. The tubers, however,
+also suggested a resemblance to truffles, so that the Italian word
+"tartufolo", a diminutive of the Italian modification of the Latin
+"terrae tuber" was applied to them. In the language of the Rhaetian Alps
+this word appears as "tartufel". From there it seems to have passed
+into Germany where potatoes were not cultivated extensively till the
+eighteenth century, and "tartufel" has in later times through some
+popular etymology been metamorphosed into "Kartoffel". In France the
+shape of the tubers suggested the name of earth-apple (pomme de terre),
+a name also adopted in Dutch (aard-appel), while dialectically in German
+a form "Grumbire" appears, which is a corruption of "Grund-birne",
+"ground pear". (Kluge "Etymologisches Worterbuch der deutschen Sprache"
+(Strassburg), s.v. "Kartoffel".) Here half the languages have adopted
+the original American word for an allied plant, while others have
+adopted a name originating in some more or less fanciful resemblance
+discovered in the tubers; the Germans alone in Western Europe, failing
+to see any meaning in their borrowed name, have modified it almost
+beyond recognition. To this English supplies an exact parallel in
+"parsnep" which, though representing the Latin "pastinaca" through the
+Old French "pastenaque", was first assimilated in the last syllable to
+the "nep" of "turnep" ("pasneppe" in Elizabethan English), and later had
+an "r" introduced into the first syllable, apparently on the analogy of
+"parsley".
+
+The turkey on the other hand seems never to be found with its original
+American name. In England, as the name implies, the turkey cock was
+regarded as having come from the land of the Turks. The bird no doubt
+spread over Europe from the Italian seaports. The mistake, therefore,
+was not unnatural, seeing that these towns conducted a great trade
+with the Levant, while the fact that America when first discovered was
+identified with India helped to increase the confusion. Thus in French
+the "coq d'Inde" was abbreviated to "d'Inde" much as "turkey cock" was
+to "turkey"; the next stage was to identify "dinde" as a feminine word
+and create a new "dindon" on the analogy of "chapon" as the masculine.
+In Italian the name "gallo d'India" besides survives, while in German
+the name "Truthahn" seems to be derived onomatopoetically from
+the bird's cry, though a dialectic "Calecutischer Hahn" specifies
+erroneously an origin for the bird from the Indian Calicut. In the
+Spanish "pavo", on the other hand, there is a curious confusion with
+the peacock. Thus in these names for objects of common knowledge,
+the introduction of which into Europe can be dated with tolerable
+definiteness, we see evinced the methods by which in remoter ages
+objects were named. The words were borrowed from the community whence
+came the new object, or the real or fancied resemblance to some known
+object gave the name, or again popular etymology might convert the
+unknown term into something that at least approached in sound a
+well-known word.
+
+"The Origin of Species" had not long been published when the parallelism
+of development in natural species and in languages struck investigators.
+At the time, one of the foremost German philologists was August
+Schleicher, Professor at Jena. He was himself keenly interested in the
+natural sciences, and amongst his colleagues was Ernst Haeckel, the
+protagonist in Germany of the Darwinian theory. How the new ideas struck
+Schleicher may be seen from the following sentences by his colleague
+Haeckel. "Speech is a physiological function of the human organism,
+and has been developed simultaneously with its organs, the larynx and
+tongue, and with the functions of the brain. Hence it will be quite
+natural to find in the evolution and classification of languages the
+same features as in the evolution and classification of organic species.
+The various groups of languages that are distinguished in philology as
+primitive, fundamental, parent, and daughter languages, dialects, etc.,
+correspond entirely in their development to the different categories
+which we classify in zoology and botany as stems, classes, orders,
+families, genera, species and varieties. The relation of these groups,
+partly coordinate and partly subordinate, in the general scheme is just
+the same in both cases; and the evolution follows the same lines in
+both." (Haeckel, "The Evolution of Man", page 485, London, 1905. This
+represents Schleicher's own words: Was die Naturforscher als Gattung
+bezeichnen wurden, heisst bei den Glottikern Sprachstamm, auch
+Sprachsippe; naher verwandte Gattungen bezeichnen sie wohl auch als
+Sprachfamilien einer Sippe oder eines Sprachstammes... Die Arten einer
+Gattung nennen wir Sprachen eines Stammes; die Unterarten einer Art sind
+bei uns die Dialekte oder Mundarten einer Sprache; den Varietaten
+und Spielarten entsprechen die Untermundarten oder Nebenmundarten und
+endlich den einzelnen Individuen die Sprechweise der einzelnen
+die Sprachen redenden Menschen. "Die Darwinische Theorie und die
+Sprachwissenschaft", Weimar, 1863, page 12 f. Darwin makes a more
+cautious statement about the classification of languages in "The Origin
+of Species", page 578, (Popular Edition, 1900).) These views were set
+forth in an open letter addressed to Haeckel in 1863 by Schleicher
+entitled, "The Darwinian theory and the science of language".
+Unfortunately Schleicher's views went a good deal farther than is
+indicated in the extract given above. He appended to the pamphlet a
+genealogical tree of the Indo-Germanic languages which, though to a
+large extent confirmed by later research, by the dichotomy of each
+branch into two other branches, led the unwary reader to suppose their
+phylogeny (to use Professor Haeckel's term) was more regular than our
+evidence warrants.
+
+Without qualification Schleicher declared languages to be "natural
+organisms which originated unconditioned by the human will,
+developed according to definite laws, grow old and die; they also are
+characterised by that series of phenomena which we designate by the
+term 'Life.' Consequently Glottic, the science of language, is a natural
+science; its method is in general the same as that of the other natural
+sciences." ("Die Darwinische Theorie", page 6 f.) In accordance with
+this view he declared (op. cit. page 23.) that the root in language
+might be compared with the simple cell in physiology, the linguistic
+simple cell or root being as yet not differentiated into special organs
+for the function of noun, verb, etc.
+
+In this probably all recent philologists admit that Schleicher went too
+far. One of the most fertile theories in the modern science of language
+originated with him, and was further developed by his pupil, August
+Leskien ("Die Declination im Slavisch-litanischen und Germanischen",
+Leipzig, 1876; Osthoff and Brugmann, "Morphologische Untersuchungen",
+I. (Introduction), 1878. The general principles of this school were
+formulated (1880) in a fuller form in H. Paul's "Prinzipien der
+Sprachgeschichte", Halle (3rd edition, 1898). Paul and Wundt (in his
+"Volkerpsychologie") deal largely with the same matter, but begin their
+investigations from different points of view, Paul being a philologist
+with leanings to philosophy and Wundt a philosopher interested in
+language.), and by Leskien's colleagues and friends, Brugmann and
+Osthoff. This was the principle that phonetic laws have no exceptions.
+Under the influence of this generalisation much greater precision in
+etymology was insisted upon, and a new and remarkably active period in
+the study of language began. Stated broadly in the fashion given above
+the principle is not true. A more accurate statement would be that an
+original sound is represented in a given dialect at a given time and in
+a given environment only in one way; provided that the development of
+the original sound into its representation in the given dialect has not
+been influenced by the working of analogy.
+
+It is this proviso that is most important for the characterisation of
+the science of language. As I have said elsewhere, it is at this point
+that this science parts company with the natural sciences. "If the
+chemist compounds two pure simple elements, there can be but one result,
+and no power of the chemist can prevent it. But the minds of men do
+act upon the sounds which they produce. The result is that, when this
+happens, the phonetic law which would have acted in the case is stopped,
+and this particular form enters on the same course of development as
+other forms to which it does not belong." (P. Giles, "Short Manual of
+Comparative Philology", 2nd edition, page 57, London, 1901.)
+
+Schleicher was wrong in defining a language to be an organism in the
+sense in which a living being is an organism. Regarded physiologically,
+language is a function or potentiality of certain human organs; regarded
+from the point of view of the community it is of the nature of an
+institution. (This view of language is worked out at some length by
+Prof. W.D. Whitney in an article in the "Contemporary Review" for 1875,
+page 713 ff. This article forms part of a controversy with Max Muller,
+which is partly concerned with Darwin's views on language. He criticises
+Schleicher's views severely in his "Oriental and Linguistic Studies",
+page 298 ff., New York, 1873. In this volume will be found criticisms of
+various other views mentioned in this essay.) More than most influences
+it conduces to the binding together of the elements that form a state.
+That geographical or other causes may effectively counteract the
+influence of identity of language is obvious. One need only read the
+history of ancient Greece, or observe the existing political separation
+of Germany and Austria, of Great Britain and the United States of
+America. But however analogous to an organism, language is not an
+organism. In a less degree Schleicher, by defining languages as such,
+committed the same mistake which Bluntschli made regarding the State,
+and which led him to declare that the State is by nature masculine and
+the Church feminine. (Bluntschli, "Theory of the State", page 24, Second
+English Edition, Oxford, 1892.) The views of Schleicher were to some
+extent injurious to the proper methods of linguistic study. But this
+misfortune was much more than fully compensated by the inspiration
+which his ideas, collected and modified by his disciples, had upon the
+science. In spite of the difference which the psychological element
+represented by analogy makes between the science of language and the
+natural sciences, we are entitled to say of it as Schleicher said of
+Darwin's theory of the origin of species, "it depends upon observation,
+and is essentially an attempt at a history of development."
+
+Other questions there are in connection with language and evolution
+which require investigation--the survival of one amongst several
+competing words (e.g. why German keeps only as a high poetic word
+"ross", which is identical in origin with the English work-a-day
+"horse", and replaces it by "pferd", whose congener the English
+"palfrey" is almost confined to poetry and romance), the persistence
+of evolution till it becomes revolution in languages like English or
+Persian which have practically ceased to be inflectional languages, and
+many other problems. Into these Darwin did not enter, and they require
+a fuller investigation than is possible within the limits of the present
+paper.
+
+
+
+
+XXVII. DARWINISM AND HISTORY. By J.B. Bury, Litt.D., LL.D.
+
+Regius Professor of Modern History in the University of Cambridge.
+
+
+1. Evolution, and the principles associated with the Darwinian theory,
+could not fail to exert a considerable influence on the studies
+connected with the history of civilised man. The speculations which
+are known as "philosophy of history," as well as the sciences of
+anthropology, ethnography, and sociology (sciences which though they
+stand on their own feet are for the historian auxiliary), have been
+deeply affected by these principles. Historiographers, indeed, have
+with few exceptions made little attempt to apply them; but the growth
+of historical study in the nineteenth century has been determined and
+characterised by the same general principle which has underlain the
+simultaneous developments of the study of nature, namely the GENETIC
+idea. The "historical" conception of nature, which has produced the
+history of the solar system, the story of the earth, the genealogies of
+telluric organisms, and has revolutionised natural science, belongs
+to the same order of thought as the conception of human history as
+a continuous, genetic, causal process--a conception which has
+revolutionised historical research and made it scientific. Before
+proceeding to consider the application of evolutional principles, it
+will be pertinent to notice the rise of this new view.
+
+2. With the Greeks and Romans history had been either a descriptive
+record or had been written in practical interests. The most eminent of
+the ancient historians were pragmatical; that is, they regarded history
+as an instructress in statesmanship, or in the art of war, or in morals.
+Their records reached back such a short way, their experience was so
+brief, that they never attained to the conception of continuous process,
+or realised the significance of time; and they never viewed the history
+of human societies as a phenomenon to be investigated for its own sake.
+In the middle ages there was still less chance of the emergence of the
+ideas of progress and development. Such notions were excluded by the
+fundamental doctrines of the dominant religion which bounded and bound
+men's minds. As the course of history was held to be determined from
+hour to hour by the arbitrary will of an extra-cosmic person, there
+could be no self-contained causal development, only a dispensation
+imposed from without. And as it was believed that the world was within
+no great distance from the end of this dispensation, there was no motive
+to take much interest in understanding the temporal, which was to be
+only temporary.
+
+The intellectual movements of the fifteenth and sixteenth centuries
+prepared the way for a new conception, but it did not emerge
+immediately. The historians of the Renaissance period simply reverted to
+the ancient pragmatical view. For Machiavelli, exactly as for Thucydides
+and Polybius, the use of studying history was instruction in the art of
+politics. The Renaissance itself was the appearance of a new culture,
+different from anything that had gone before; but at the time men were
+not conscious of this; they saw clearly that the traditions of classical
+antiquity had been lost for a long period, and they were seeking to
+revive them, but otherwise they did not perceive that the world had
+moved, and that their own spirit, culture, and conditions were
+entirely unlike those of the thirteenth century. It was hardly till the
+seventeenth century that the presence of a new age, as different from
+the middle ages as from the ages of Greece and Rome, was fully realised.
+It was then that the triple division of ancient, medieval, and modern
+was first applied to the history of western civilisation. Whatever
+objections may be urged against this division, which has now become
+almost a category of thought, it marks a most significant advance in
+man's view of his own past. He has become conscious of the immense
+changes in civilisation which have come about slowly in the course of
+time, and history confronts him with a new aspect. He has to explain how
+those changes have been produced, how the transformations were effected.
+The appearance of this problem was almost simultaneous with the rise
+of rationalism, and the great historians and thinkers of the eighteenth
+century, such as Montesquieu, Voltaire, Gibbon, attempted to explain
+the movement of civilisation by purely natural causes. These brilliant
+writers prepared the way for the genetic history of the following
+century. But in the spirit of the Aufklarung, that eighteenth-century
+Enlightenment to which they belonged, they were concerned to judge all
+phenomena before the tribunal of reason; and the apotheosis of "reason"
+tended to foster a certain superior a priori attitude, which was
+not favourable to objective treatment and was incompatible with
+a "historical sense." Moreover the traditions of pragmatical
+historiography had by no means disappeared.
+
+3. In the first quarter of the nineteenth century the meaning of genetic
+history was fully realised. "Genetic" perhaps is as good a word as can
+be found for the conception which in this century was applied to so many
+branches of knowledge in the spheres both of nature and of mind. It
+does not commit us to the doctrine proper of evolution, nor yet to any
+teleological hypothesis such as is implied in "progress." For history
+it meant that the present condition of the human race is simply and
+strictly the result of a causal series (or set of causal series)--a
+continuous succession of changes, where each state arises causally out
+of the preceding; and that the business of historians is to trace this
+genetic process, to explain each change, and ultimately to grasp the
+complete development of the life of humanity. Three influential writers,
+who appeared at this stage and helped to initiate a new period
+of research, may specially be mentioned. Ranke in 1824 definitely
+repudiated the pragmatical view which ascribes to history the duties
+of an instructress, and with no less decision renounced the function,
+assumed by the historians of the Aufklarung, to judge the past; it
+was his business, he said, merely to show how things really happened.
+Niebuhr was already working in the same spirit and did more than any
+other writer to establish the principle that historical transactions
+must be related to the ideas and conditions of their age. Savigny about
+the same time founded the "historical school" of law. He sought to show
+that law was not the creation of an enlightened will, but grew out of
+custom and was developed by a series of adaptations and rejections, thus
+applying the conception of evolution. He helped to diffuse the notion
+that all the institutions of a society or a notion are as closely
+interconnected as the parts of a living organism.
+
+4. The conception of the history of man as a causal development meant
+the elevation of historical inquiry to the dignity of a science. Just
+as the study of bees cannot become scientific so long as the student's
+interest in them is only to procure honey or to derive moral lessons
+from the labours of "the little busy bee," so the history of human
+societies cannot become the object of pure scientific investigation so
+long as man estimates its value in pragmatical scales. Nor can it become
+a science until it is conceived as lying entirely within a sphere
+in which the law of cause and effect has unreserved and unrestricted
+dominion. On the other hand, once history is envisaged as a causal
+process, which contains within itself the explanation of the development
+of man from his primitive state to the point which he has reached, such
+a process necessarily becomes the object of scientific investigation and
+the interest in it is scientific curiosity.
+
+At the same time, the instruments were sharpened and refined. Here Wolf,
+a philologist with historical instinct, was a pioneer. His "Prolegomena"
+to Homer (1795) announced new modes of attack. Historical investigation
+was soon transformed by the elaboration of new methods.
+
+5. "Progress" involves a judgment of value, which is not involved in the
+conception of history as a genetic process. It is also an idea distinct
+from that of evolution. Nevertheless it is closely related to the ideas
+which revolutionised history at the beginning of the last century;
+it swam into men's ken simultaneously; and it helped effectively to
+establish the notion of history as a continuous process and to emphasise
+the significance of time. Passing over earlier anticipations, I may
+point to a "Discours" of Turgot (1750), where history is presented as a
+process in which "the total mass of the human race" "marches continually
+though sometimes slowly to an ever increasing perfection." That is
+a clear statement of the conception which Turgot's friend Condorcet
+elaborated in the famous work, published in 1795, "Esquisse d'un tableau
+historique des progres de l'esprit humain". This work first treated with
+explicit fulness the idea to which a leading role was to fall in the
+ideology of the nineteenth century. Condorcet's book reflects the
+triumphs of the Tiers etat, whose growing importance had also inspired
+Turgot; it was the political changes in the eighteenth century which led
+to the doctrine, emphatically formulated by Condorcet, that the masses
+are the most important element in the historical process. I dwell
+on this because, though Condorcet had no idea of evolution, the
+pre-dominant importance of the masses was the assumption which made
+it possible to apply evolutional principles to history. And it enabled
+Condorcet himself to maintain that the history of civilisation, a
+progress still far from being complete, was a development conditioned by
+general laws.
+
+6. The assimilation of society to an organism, which was a governing
+notion in the school of Savigny, and the conception of progress,
+combined to produce the idea of an organic development, in which the
+historian has to determine the central principle or leading character.
+This is illustrated by the apotheosis of democracy in Tocqueville's
+"Democratie en Amerique", where the theory is maintained that "the
+gradual and progressive development of equality is at once the past and
+the future of the history of men." The same two principles are combined
+in the doctrine of Spencer (who held that society is an organism,
+though he also contemplated its being what he calls a "super-organic
+aggregate") (A society presents suggestive analogies with an organism,
+but it certainly is not an organism, and sociologists who draw
+inferences from the assumption of its organic nature must fall into
+error. A vital organism and a society are radically distinguished by the
+fact that the individual components of the former, namely the cells,
+are morphologically as well as functionally differentiated, whereas the
+individuals which compose a society are morphologically homogeneous and
+only functionally differentiated. The resemblances and the differences
+are worked out in E. de Majewski's striking book "La Science de la
+Civilisation", Paris, 1908.), that social evolution is a progressive
+change from militarism to industrialism.
+
+7. the idea of development assumed another form in the speculations of
+German idealism. Hegel conceived the successive periods of history as
+corresponding to the ascending phases or ideas in the self-evolution
+of his Absolute Being. His "Lectures on the Philosophy of History" were
+published in 1837 after his death. His philosophy had a considerable
+effect, direct and indirect, on the treatment of history by historians,
+and although he was superficial and unscientific himself in dealing with
+historical phenomena, he contributed much towards making the idea of
+historical development familiar. Ranke was influenced, if not by Hegel
+himself, at least by the Idealistic philosophies of which Hegel's was
+the greatest. He was inclined to conceive the stages in the process of
+history as marked by incarnations, as it were, of ideas, and sometimes
+speaks as if the ideas were independent forces, with hands and feet. But
+while Hegel determined his ideas by a priori logic, Ranke obtained his
+by induction--by a strict investigation of the phenomena; so that he
+was scientific in his method and work, and was influenced by Hegelian
+prepossessions only in the kind of significance which he was disposed
+to ascribe to his results. It is to be noted that the theory of Hegel
+implied a judgment of value; the movement was a progress towards
+perfection.
+
+8. In France, Comte approached the subject from a different side, and
+exercised, outside Germany, a far wider influence than Hegel. The 4th
+volume of his "Cours de philosophie positive", which appeared in 1839,
+created sociology and treated history as a part of this new science,
+namely as "social dynamics." Comte sought the key for unfolding
+historical development, in what he called the social-psychological point
+of view, and he worked out the two ideas which had been enunciated by
+Condorcet: that the historian's attention should be directed not, as
+hitherto, principally to eminent individuals, but to the collective
+behaviour of the masses, as being the most important element in the
+process; and that, as in nature, so in history, there are general laws,
+necessary and constant, which condition the development. The two points
+are intimately connected, for it is only when the masses are moved into
+the foreground that regularity, uniformity, and law can be conceived
+as applicable. To determine the social-psychological laws which
+have controlled the development is, according to Comte, the task of
+sociologists and historians.
+
+9. The hypothesis of general laws operative in history was carried
+further in a book which appeared in England twenty years later and
+exercised an influence in Europe far beyond its intrinsic merit,
+Buckle's "History of Civilisation in England" (1857-61). Buckle owed
+much to Comte, and followed him, or rather outdid him, in regarding
+intellect as the most important factor conditioning the upward
+development of man, so that progress, according to him, consisted in the
+victory of the intellectual over the moral laws.
+
+10. The tendency of Comte and Buckle to assimilate history to the
+sciences of nature by reducing it to general "laws," derived stimulus
+and plausibility from the vista offered by the study of statistics, in
+which the Belgian Quetelet, whose book "Sur l'homme" appeared in 1835,
+discerned endless possibilities. The astonishing uniformities which
+statistical inquiry disclosed led to the belief that it was only a
+question of collecting a sufficient amount of statistical material, to
+enable us to predict how a given social group will act in a particular
+case. Bourdeau, a disciple of this school, looks forward to the time
+when historical science will become entirely quantitative. The actions
+of prominent individuals, which are generally considered to have altered
+or determined the course of things, are obviously not amenable to
+statistical computation or explicable by general laws. Thinkers like
+Buckle sought to minimise their importance or explain them away.
+
+11. These indications may suffice to show that the new efforts to
+interpret history which marked the first half of the nineteenth century
+were governed by conceptions closely related to those which were current
+in the field of natural science and which resulted in the doctrine of
+evolution. The genetic principle, progressive development, general
+laws, the significance of time, the conception of society as an organic
+aggregate, the metaphysical theory of history as the self-evolution of
+spirit,--all these ideas show that historical inquiry had been advancing
+independently on somewhat parallel lines to the sciences of nature. It
+was necessary to bring this out in order to appreciate the influence of
+Darwinism.
+
+12. In the course of the dozen years which elapsed between the
+appearances of "The Origin of Species" (observe that the first volume of
+Buckle's work was published just two years before) and of "The Descent
+of Man" (1871), the hypothesis of Lamarck that man is the co-descendant
+with other species of some lower extinct form was admitted to have been
+raised to the rank of an established fact by most thinkers whose brains
+were not working under the constraint of theological authority.
+
+One important effect of the discovery of this fact (I am not speaking
+now of the Darwinian explanation) was to assign to history a definite
+place in the coordinated whole of knowledge, and relate it more closely
+to other sciences. It had indeed a defined logical place in systems
+such as Hegel's and Comte's; but Darwinism certified its standing
+convincingly and without more ado. The prevailing doctrine that man
+was created ex abrupto had placed history in an isolated position,
+disconnected with the sciences of nature. Anthropology, which deals with
+the animal anthropos, now comes into line with zoology, and brings it
+into relation with history. (It is to be observed that history is not
+only different in scope but) not coextensive with anthropology IN TIME.
+For it deals only with the development of man in societies, whereas
+anthropology includes in its definition the proto-anthropic period
+when anthropos was still non-social, whether he lived in herds like
+the chimpanzee, or alone like the male ourang-outang. (It has been well
+shown by Majewski that congregations--herds, flocks, packs, etc.--of
+animals are not SOCIETIES; the characteristic of a society is
+differentiation of function. Bee hives, ant hills, may be called
+quasi-societies; but in their case the classes which perform distinct
+functions are morphologically different.) Man's condition at the present
+day is the result of a series of transformations, going back to the most
+primitive phase of society, which is the ideal (unattainable) beginning
+of history. But that beginning had emerged without any breach of
+continuity from a development which carries us back to a quadrimane
+ancestor, still further back (according to Darwin's conjecture) to a
+marine animal of the ascidian type, and then through remoter periods to
+the lowest form of organism. It is essential in this theory that though
+links have been lost there was no break in the gradual development;
+and this conception of a continuous progress in the evolution of
+life, resulting in the appearance of uncivilised Anthropos, helped to
+reinforce, and increase a belief in, the conception of the history of
+civilised Anthropos as itself also a continuous progressive development.
+
+13. Thus the diffusion of the Darwinian theory of the origin of man,
+by emphasising the idea of continuity and breaking down the barriers
+between the human and animal kingdoms, has had an important effect in
+establishing the position of history among the sciences which deal with
+telluric development. The perspective of history is merged in a larger
+perspective of development. As one of the objects of biology is to find
+the exact steps in the genealogy of man from the lowest organic form,
+so the scope of history is to determine the stages in the unique
+causal series from the most rudimentary to the present state of human
+civilisation.
+
+It is to be observed that the interest in historical research implied
+by this conception need not be that of Comte. In the Positive Philosophy
+history is part of sociology; the interest in it is to discover the
+sociological laws. In the view of which I have just spoken, history
+is permitted to be an end in itself; the reconstruction of the
+genetic process is an independent interest. For the purpose of the
+reconstruction, sociology, as well as physical geography, biology,
+psychology, is necessary; the sociologist and the historian play
+into each other's hands; but the object of the former is to establish
+generalisations; the aim of the latter is to trace in detail a singular
+causal sequence.
+
+14. The success of the evolutional theory helped to discredit
+the assumption or at least the invocation of transcendent causes.
+Philosophically of course it is compatible with theism, but historians
+have for the most part desisted from invoking the naive conception of a
+"god in history" to explain historical movements. A historian may be a
+theist; but, so far as his work is concerned, this particular belief is
+otiose. Otherwise indeed (as was remarked above) history could not be a
+science; for with a deus ex machina who can be brought on the stage to
+solve difficulties scientific treatment is a farce. The transcendent
+element had appeared in a more subtle form through the influence of
+German philosophy. I noticed how Ranke is prone to refer to ideas as
+if they were transcendent existences manifesting themselves in the
+successive movements of history. It is intelligible to speak of certain
+ideas as controlling, in a given period,--for instance, the idea of
+nationality; but from the scientific point of view, such ideas have
+no existence outside the minds of individuals and are purely psychical
+forces; and a historical "idea," if it does not exist in this form, is
+merely a way of expressing a synthesis of the historian himself.
+
+15. From the more general influence of Darwinism on the place of history
+in the system of human knowledge, we may turn to the influence of the
+principles and methods by which Darwin explained development. It had
+been recognised even by ancient writers (such as Aristotle and
+Polybius) that physical circumstances (geography, climate) were factors
+conditioning the character and history of a race or society. In the
+sixteenth century Bodin emphasised these factors, and many subsequent
+writers took them into account. The investigations of Darwin, which
+brought them into the foreground, naturally promoted attempts to
+discover in them the chief key to the growth of civilisation. Comte had
+expressly denounced the notion that the biological methods of Lamarck
+could be applied to social man. Buckle had taken account of natural
+influences, but had relegated them to a secondary plane, compared with
+psychological factors. But the Darwinian theory made it tempting to
+explain the development of civilisation in terms of "adaptation to
+environment," "struggle for existence," "natural selection," "survival
+of the fittest," etc. (Recently O. Seeck has applied these principles to
+the decline of Graeco-Roman civilisation in his "Untergang der antiken
+Welt", 2 volumes, Berlin, 1895, 1901.)
+
+The operation of these principles cannot be denied. Man is still an
+animal, subject to zoological as well as mechanical laws. The dark
+influence of heredity continues to be effective; and psychical
+development had begun in lower organic forms,--perhaps with life itself.
+The organic and the social struggles for existence are manifestations of
+the same principle. Environment and climatic influence must be called in
+to explain not only the differentiation of the great racial sections of
+humanity, but also the varieties within these sub-species and, it may
+be, the assimilation of distinct varieties. Ritter's "Anthropogeography"
+has opened a useful line of research. But on the other hand, it is urged
+that, in explaining the course of history, these principles do not take
+us very far, and that it is chiefly for the primitive ultra-prehistoric
+period that they can account for human development. It may be said
+that, so far as concerns the actions and movements of men which are
+the subject of recorded history, physical environment has ceased to act
+mechanically, and in order to affect their actions must affect their
+wills first; and that this psychical character of the causal relations
+substantially alters the problem. The development of human societies, it
+may be argued, derives a completely new character from the dominance
+of the conscious psychical element, creating as it does new conditions
+(inventions, social institutions, etc.) which limit and counteract the
+operation of natural selection, and control and modify the influence of
+physical environment. Most thinkers agree now that the chief clews to
+the growth of civilisation must be sought in the psychological
+sphere. Imitation, for instance, is a principle which is probably
+more significant for the explanation of human development than natural
+selection. Darwin himself was conscious that his principles had only
+a very restricted application in this sphere, as is evident from his
+cautious and tentative remarks in the 5th chapter of his "Descent of
+Man". He applied natural selection to the growth of the intellectual
+faculties and of the fundamental social instincts, and also to the
+differentiation of the great races or "sub-species" (Caucasian, African,
+etc.) which differ in anthropological character. (Darwinian formulae may
+be suggestive by way of analogy. For instance, it is characteristic of
+social advance that a multitude of inventions, schemes and plans are
+framed which are never carried out, similar to, or designed for the same
+end as, an invention or plan which is actually adopted because it has
+chanced to suit better the particular conditions of the hour (just as
+the works accomplished by an individual statesman, artist or savant are
+usually only a residue of the numerous projects conceived by his brain).
+This process in which so much abortive production occurs is analogous to
+elimination by natural selection.)
+
+16. But if it is admitted that the governing factors which concern
+the student of social development are of the psychical order, the
+preliminary success of natural science in explaining organic evolution
+by general principles encouraged sociologists to hope that social
+evolution could be explained on general principles also. The idea of
+Condorcet, Buckle, and others, that history could be assimilated to
+the natural sciences was powerfully reinforced, and the notion that the
+actual historical process, and every social movement involved in it, can
+be accounted for by sociological generalisations, so-called "laws," is
+still entertained by many, in one form or another. Dissentients from
+this view do not deny that the generalisations at which the sociologist
+arrives by the comparative method, by the analysis of social factors,
+and by psychological deduction may be an aid to the historian; but they
+deny that such uniformities are laws or contain an explanation of the
+phenomena. They can point to the element of chance coincidence. This
+element must have played a part in the events of organic evolution, but
+it has probably in a larger measure helped to determine events in social
+evolution. The collision of two unconnected sequences may be fraught
+with great results. The sudden death of a leader or a marriage without
+issue, to take simple cases, has again and again led to permanent
+political consequences. More emphasis is laid on the decisive actions
+of individuals, which cannot be reduced under generalisations and which
+deflect the course of events. If the significance of the individual will
+had been exaggerated to the neglect of the collective activity of the
+social aggregate before Condorcet, his doctrine tended to eliminate as
+unimportant the roles of prominent men, and by means of this elimination
+it was possible to found sociology. But it may be urged that it is
+patent on the face of history that its course has constantly been
+shaped and modified by the wills of individuals (We can ignore here the
+metaphysical question of freewill and determinism. For the character of
+the individual's brain depends in any case on ante-natal accidents
+and coincidences, and so it may be said that the role of individuals
+ultimately depends on chance,--the accidental coincidence of independent
+sequences.), which are by no means always the expression of the
+collective will; and that the appearance of such personalities at the
+given moments is not a necessary outcome of the conditions and cannot be
+deduced. Nor is there any proof that, if such and such an individual
+had not been born, some one else would have arisen to do what he did. In
+some cases there is no reason to think that what happened need ever have
+come to pass. In other cases, it seems evident that the actual change
+was inevitable, but in default of the man who initiated and guided it,
+it might have been postponed, and, postponed or not, might have borne
+a different cachet. I may illustrate by an instance which has just come
+under my notice. Modern painting was founded by Giotto, and the Italian
+expedition of Charles VIII, near the close of the sixteenth century,
+introduced into France the fashion of imitating Italian painters.
+But for Giotto and Charles VIII, French painting might have been very
+different. It may be said that "if Giotto had not appeared, some other
+great initiator would have played a role analogous to his, and that
+without Charles VIII there would have been the commerce with Italy,
+which in the long run would have sufficed to place France in relation
+with Italian artists. But the equivalent of Giotto might have been
+deferred for a century and probably would have been different; and
+commercial relations would have required ages to produce the rayonnement
+imitatif of Italian art in France, which the expedition of the royal
+adventurer provoked in a few years." (I have taken this example from G.
+Tarde's "La logique sociale" 2 (page 403), Paris, 1904, where it is used
+for quite a different purpose.) Instances furnished by political history
+are simply endless. Can we conjecture how events would have moved if the
+son of Philip of Macedon had been an incompetent? The aggressive action
+of Prussia which astonished Europe in 1740 determined the subsequent
+history of Germany; but that action was anything but inevitable; it
+depended entirely on the personality of Frederick the Great.
+
+Hence it may be argued that the action of individual wills is a
+determining and disturbing factor, too significant and effective to
+allow history to be grasped by sociological formulae. The types and
+general forms of development which the sociologist attempts to disengage
+can only assist the historian in understanding the actual course
+of events. It is in the special domains of economic history and
+Culturgeschichte which have come to the front in modern times that
+generalisation is most fruitful, but even in these it may be contended
+that it furnishes only partial explanations.
+
+17. The truth is that Darwinism itself offers the best illustration of
+the insufficiency of general laws to account for historical
+development. The part played by coincidence, and the part played
+by individuals--limited by, and related to, general social
+conditions--render it impossible to deduce the course of the past
+history of man or to predict the future. But it is just the same with
+organic development. Darwin (or any other zoologist) could not deduce
+the actual course of evolution from general principles. Given an
+organism and its environment, he could not show that it must evolve into
+a more complex organism of a definite pre-determined type; knowing
+what it has evolved into, he could attempt to discover and assign the
+determining causes. General principles do not account for a particular
+sequence; they embody necessary conditions; but there is a chapter of
+accidents too. It is the same in the case of history.
+
+18. Among the evolutional attempts to subsume the course of history
+under general syntheses, perhaps the most important is that of
+Lamprecht, whose "kulturhistorische Methode," which he has deduced from
+and applied to German history, exhibits the (indirect) influence of the
+Comtist school. It is based upon psychology, which, in his view, holds
+among the sciences of mind (Geisteswissenschaften) the same place (that
+of a Grundwissenschaft) which mechanics holds among the sciences of
+nature. History, by the same comparison, corresponds to biology, and,
+according to him, it can only become scientific if it is reduced to
+general concepts (Begriffe). Historical movements and events are of
+a psychical character, and Lamprecht conceives a given phase of
+civilisation as "a collective psychical condition (seelischer
+Gesamtzustand)" controlling the period, "a diapason which penetrates
+all psychical phenomena and thereby all historical events of the time."
+("Die kulturhistorische Methode", Berlin, 1900, page 26.) He has worked
+out a series of such phases, "ages of changing psychical diapason," in
+his "Deutsche Geschichte" with the aim of showing that all the feelings
+and actions of each age can be explained by the diapason; and has
+attempted to prove that these diapasons are exhibited in other social
+developments, and are consequently not singular but typical. He
+maintains further that these ages succeed each other in a definite
+order; the principle being that the collective psychical development
+begins with the homogeneity of all the individual members of a society
+and, through heightened psychical activity, advances in the form of a
+continually increasing differentiation of the individuals (this is akin
+to the Spencerian formula). This process, evolving psychical freedom
+from psychical constraint, exhibits a series of psychical phenomena
+which define successive periods of civilisation. The process depends on
+two simple principles, that no idea can disappear without leaving behind
+it an effect or influence, and that all psychical life, whether in
+a person or a society, means change, the acquisition of new mental
+contents. It follows that the new have to come to terms with the old,
+and this leads to a synthesis which determines the character of a new
+age. Hence the ages of civilisation are defined as the "highest
+concepts for subsuming without exception all psychical phenomena of
+the development of human societies, that is, of all historical events."
+(Ibid. pages 28, 29.) Lamprecht deduces the idea of a special historical
+science, which might be called "historical ethnology," dealing with the
+ages of civilisation, and bearing the same relation to (descriptive or
+narrative) history as ethnology to ethnography. Such a science obviously
+corresponds to Comte's social dynamics, and the comparative method,
+on which Comte laid so much emphasis, is the principal instrument of
+Lamprecht.
+
+19. I have dwelt on the fundamental ideas of Lamprecht, because they are
+not yet widely known in England, and because his system is the ablest
+product of the sociological school of historians. It carries the
+more weight as its author himself is a historical specialist, and his
+historical syntheses deserve the most careful consideration. But there
+is much in the process of development which on such assumptions is
+not explained, especially the initiative of individuals. Historical
+development does not proceed in a right line, without the choice of
+diverging. Again and again, several roads are open to it, of which it
+chooses one--why? On Lamprecht's method, we may be able to assign the
+conditions which limit the psychical activity of men at a particular
+stage of evolution, but within those limits the individual has so many
+options, such a wide room for moving, that the definition of those
+conditions, the "psychical diapasons," is only part of the explanation
+of the particular development. The heel of Achilles in all historical
+speculations of this class has been the role of the individual.
+
+The increasing prominence of economic history has tended to encourage
+the view that history can be explained in terms of general concepts or
+types. Marx and his school based their theory of human development on
+the conditions of production, by which, according to them, all social
+movements and historical changes are entirely controlled. The leading
+part which economic factors play in Lamprecht's system is significant,
+illustrating the fact that economic changes admit most readily this
+kind of treatment, because they have been less subject to direction or
+interference by individual pioneers.
+
+Perhaps it may be thought that the conception of SOCIAL ENVIRONMENT
+(essentially psychical), on which Lamprecht's "psychical diapasons"
+depend, is the most valuable and fertile conception that the historian
+owes to the suggestion of the science of biology--the conception of
+all particular historical actions and movements as (1) related to and
+conditioned by the social environment, and (2) gradually bringing about
+a transformation of that environment. But no given transformation can be
+proved to be necessary (pre-determined). And types of development do not
+represent laws; their meaning and value lie in the help they may give
+to the historian, in investigating a certain period of civilisation,
+to enable him to discover the interrelations among the diverse features
+which it presents. They are, as some one has said, an instrument of
+heuretic method.
+
+20. The men engaged in special historical researches--which have been
+pursued unremittingly for a century past, according to scientific
+methods of investigating evidence (initiated by Wolf, Niebuhr,
+Ranke)--have for the most part worked on the assumptions of genetic
+history or at least followed in the footsteps of those who fully grasped
+the genetic point of view. But their aim has been to collect and sift
+evidence, and determine particular facts; comparatively few have given
+serious thought to the lines of research and the speculations which
+have been considered in this paper. They have been reasonably shy
+of compromising their work by applying theories which are still much
+debated and immature. But historiography cannot permanently evade the
+questions raised by these theories. One may venture to say that no
+historical change or transformation will be fully understood until it is
+explained how social environment acted on the individual components of
+the society (both immediately and by heredity), and how the individuals
+reacted upon their environment. The problem is psychical, but it is
+analogous to the main problem of the biologist.
+
+
+
+
+XXVIII. THE GENESIS OF DOUBLE STARS. By Sir George Darwin, K.C.B.,
+F.R.S.
+
+Plumian Professor of Astronomy and Experimental Philosophy in the
+University of Cambridge.
+
+In ordinary speech a system of any sort is said to be stable when it
+cannot be upset easily, but the meaning attached to the word is usually
+somewhat vague. It is hardly surprising that this should be the case,
+when it is only within the last thirty years, and principally through
+the investigations of M. Poincare, that the conception of stability has,
+even for physicists, assumed a definiteness and clearness in which it
+was previously lacking. The laws which govern stability hold good in
+regions of the greatest diversity; they apply to the motion of planets
+round the sun, to the internal arrangement of those minute corpuscles of
+which each chemical atom is constructed, and to the forms of celestial
+bodies. In the present essay I shall attempt to consider the laws of
+stability as relating to the last case, and shall discuss the succession
+of shapes which may be assumed by celestial bodies in the course of
+their evolution. I believe further that homologous conceptions are
+applicable in the consideration of the transmutations of the various
+forms of animal and of vegetable life and in other regions of thought.
+Even if some of my readers should think that what I shall say on this
+head is fanciful, yet at least the exposition will serve to illustrate
+the meaning to be attached to the laws of stability in the physical
+universe.
+
+I propose, therefore, to begin this essay by a sketch of the principles
+of stability as they are now formulated by physicists.
+
+I.
+
+If a slight impulse be imparted to a system in equilibrium one of two
+consequences must ensue; either small oscillations of the system will
+be started, or the disturbance will increase without limit and the
+arrangement of the system will be completely changed. Thus a stick may
+be in equilibrium either when it hangs from a peg or when it is balanced
+on its point. If in the first case the stick is touched it will swing to
+and fro, but in the second case it will topple over. The first position
+is a stable one, the second is unstable. But this case is too simple to
+illustrate all that is implied by stability, and we must consider cases
+of stable and of unstable motion. Imagine a satellite and its planet,
+and consider each of them to be of indefinitely small size, in fact
+particles; then the satellite revolves round its planet in an ellipse. A
+small disturbance imparted to the satellite will only change the ellipse
+to a small amount, and so the motion is said to be stable. If, on the
+other hand, the disturbance were to make the satellite depart from its
+initial elliptic orbit in ever widening circuits, the motion would be
+unstable. This case affords an example of stable motion, but I have
+adduced it principally with the object of illustrating another point
+not immediately connected with stability, but important to a proper
+comprehension of the theory of stability.
+
+The motion of a satellite about its planet is one of revolution or
+rotation. When the satellite moves in an ellipse of any given degree
+of eccentricity, there is a certain amount of rotation in the system,
+technically called rotational momentum, and it is always the same at
+every part of the orbit. (Moment of momentum or rotational momentum
+is measured by the momentum of the satellite multiplied by the
+perpendicular from the planet on to the direction of the path of the
+satellite at any instant.)
+
+Now if we consider all the possible elliptic orbits of a satellite about
+its planet which have the same amount of "rotational momentum," we find
+that the major axis of the ellipse described will be different according
+to the amount of flattening (or the eccentricity) of the ellipse
+described. A figure titled "A 'family' of elliptic orbits with constant
+rotational momentum" (Fig. 1) illustrates for a given planet and
+satellite all such orbits with constant rotational momentum, and with
+all the major axes in the same direction. It will be observed that there
+is a continuous transformation from one orbit to the next, and that the
+whole forms a consecutive group, called by mathematicians "a family"
+of orbits. In this case the rotational momentum is constant and the
+position of any orbit in the family is determined by the length of the
+major axis of the ellipse; the classification is according to the major
+axis, but it might have been made according to anything else which would
+cause the orbit to be exactly determinate.
+
+I shall come later to the classification of all possible forms of ideal
+liquid stars, which have the same amount of rotational momentum, and the
+classification will then be made according to their densities, but the
+idea of orderly arrangement in a "family" is just the same.
+
+We thus arrive at the conception of a definite type of motion, with
+a constant amount of rotational momentum, and a classification of all
+members of the family, formed by all possible motions of that type,
+according to the value of some measurable quantity (this will hereafter
+be density) which determines the motion exactly. In the particular case
+of the elliptic motion used for illustration the motion was stable,
+but other cases of motion might be adduced in which the motion would
+be unstable, and it would be found that classification in a family and
+specification by some measurable quantity would be equally applicable.
+
+A complex mechanical system may be capable of motion in several distinct
+modes or types, and the motions corresponding to each such type may
+be arranged as before in families. For the sake of simplicity I will
+suppose that only two types are possible, so that there will only be two
+families; and the rotational momentum is to be constant. The two types
+of motion will have certain features in common which we denote in a sort
+of shorthand by the letter A. Similarly the two types may be described
+as A + a and A + b, so that a and b denote the specific differences
+which discriminate the families from one another. Now following in
+imagination the family of the type A + a, let us begin with the case
+where the specific difference a is well marked. As we cast our eyes
+along the series forming the family, we find the difference a becoming
+less conspicuous. It gradually dwindles until it disappears; beyond this
+point it either becomes reversed, or else the type has ceased to be
+a possible one. In our shorthand we have started with A + a, and have
+watched the characteristic a dwindling to zero. When it vanishes we have
+reached a type which may be specified as A; beyond this point the type
+would be A - a or would be impossible.
+
+Following the A + b type in the same way, b is at first well marked, it
+dwindles to zero, and finally may become negative. Hence in shorthand
+this second family may be described as A + b,... A,... A - b.
+
+In each family there is one single member which is indistinguishable
+from a member of the other family; it is called by Poincare a form of
+bifurcation. It is this conception of a form of bifurcation which forms
+the important consideration in problems dealing with the forms of liquid
+or gaseous bodies in rotation.
+
+But to return to the general question,--thus far the stability of these
+families has not been considered, and it is the stability which renders
+this way of looking at the matter so valuable. It may be proved that if
+before the point of bifurcation the type A + a was stable, then A + b
+must have been unstable. Further as a and b each diminish A + a becomes
+less pronouncedly stable, and A + b less unstable. On reaching the point
+of bifurcation A + a has just ceased to be stable, or what amounts to
+the same thing is just becoming unstable, and the converse is true
+of the A + b family. After passing the point of bifurcation A + a has
+become definitely unstable and A + b has become stable. Hence the point
+of bifurcation is also a point of "exchange of stabilities between the
+two types." (In order not to complicate unnecessarily this explanation
+of a general principle I have not stated fully all the cases that may
+occur. Thus: firstly, after bifurcation A + a may be an impossible type
+and A + a will then stop at this point; or secondly, A + b may have been
+an impossible type before bifurcation, and will only begin to be a real
+one after it; or thirdly, both A + a and A + b may be impossible after
+the point of bifurcation, in which case they coalesce and disappear.
+This last case shows that types arise and disappear in pairs, and that
+on appearance or before disappearance one must be stable and the other
+unstable.)
+
+In nature it is of course only the stable types of motion which can
+persist for more than a short time. Thus the task of the physical
+evolutionist is to determine the forms of bifurcation, at which he must,
+as it were, change carriages in the evolutionary journey so as always
+to follow the stable route. He must besides be able to indicate
+some natural process which shall correspond in effect to the ideal
+arrangement of the several types of motion in families with gradually
+changing specific differences. Although, as we shall see hereafter, it
+may frequently or even generally be impossible to specify with exactness
+the forms of bifurcation in the process of evolution, yet the conception
+is one of fundamental importance.
+
+The ideas involved in this sketch are no doubt somewhat recondite, but I
+hope to render them clearer to the non-mathematical reader by homologous
+considerations in other fields of thought (I considered this subject in
+my Presidential address to the British Association in 1905, "Report of
+the 75th Meeting of the British Assoc." (S. Africa, 1905), London, 1906,
+page 3. Some reviewers treated my speculations as fanciful, but as I
+believe that this was due generally to misapprehension, and as I hold
+that homologous considerations as to stability and instability are
+really applicable to evolution of all sorts, I have thought it well to
+return to the subject in the present paper.), and I shall pass on thence
+to illustrations which will teach us something of the evolution of
+stellar systems.
+
+States or governments are organised schemes of action amongst groups of
+men, and they belong to various types to which generic names, such as
+autocracy, aristocracy or democracy, are somewhat loosely applied. A
+definite type of government corresponds to one of our types of
+motion, and while retaining its type it undergoes a slow change as the
+civilisation and character of the people change, and as the relationship
+of the nation to other nations changes. In the language used before, the
+government belongs to a family, and as time advances we proceed through
+the successive members of the family. A government possesses a certain
+degree of stability--hardly measurable in numbers however--to resist
+disintegrating influences such as may arise from wars, famines, and
+internal dissensions. This stability gradually rises to a maximum and
+gradually declines. The degree of stability at any epoch will depend on
+the fitness of some leading feature of the government to suit the
+slowly altering circumstances, and that feature corresponds to the
+characteristic denoted by a in the physical problem. A time at length
+arrives when the stability vanishes, and the slightest shock will
+overturn the government. At this stage we have reached the crisis of
+a point of bifurcation, and there will then be some circumstance,
+apparently quite insignificant and almost unnoticed, which is such as
+to prevent the occurrence of anarchy. This circumstance or condition
+is what we typified as b. Insignificant although it may seem, it has
+started the government on a new career of stability by imparting to it
+a new type. It grows in importance, the form of government becomes
+obviously different, and its stability increases. Then in its turn this
+newly acquired stability declines, and we pass on to a new crisis or
+revolution. There is thus a series of "points of bifurcation" in history
+at which the continuity of political history is maintained by means of
+changes in the type of government. These ideas seem, to me at least, to
+give a true account of the history of states, and I contend that it is
+no mere fanciful analogy but a true homology, when in both realms of
+thought--the physical and the political--we perceive the existence of
+forms of bifurcation and of exchanges of stability.
+
+Further than this, I would ask whether the same train of ideas does not
+also apply to the evolution of animals? A species is well adapted to its
+environment when the individual can withstand the shocks of famine or
+the attacks and competition of other animals; it then possesses a high
+degree of stability. Most of the casual variations of individuals are
+indifferent, for they do not tell much either for or against success
+in life; they are small oscillations which leave the type unchanged. As
+circumstances change, the stability of the species may gradually dwindle
+through the insufficiency of some definite quality, on which in earlier
+times no such insistent demands were made. The individual animals will
+then tend to fail in the struggle for life, the numbers will dwindle and
+extinction may ensue. But it may be that some new variation, at first of
+insignificant importance, may just serve to turn the scale. A new
+type may be formed in which the variation in question is preserved and
+augmented; its stability may increase and in time a new species may be
+produced.
+
+At the risk of condemnation as a wanderer beyond my province into the
+region of biological evolution, I would say that this view accords with
+what I understand to be the views of some naturalists, who recognise the
+existence of critical periods in biological history at which extinction
+occurs or which form the starting-point for the formation of new
+species. Ought we not then to expect that long periods will elapse
+during which a type of animal will remain almost constant, followed by
+other periods, enormously long no doubt as measured in the life of man,
+of acute struggle for existence when the type will change more rapidly?
+This at least is the view suggested by the theory of stability in
+the physical universe. (I make no claim to extensive reading on this
+subject, but refer the reader for example to a paper by Professor A.A.W.
+Hubrecht on "De Vries's theory of Mutations", "Popular Science Monthly",
+July 1904, especially to page 213.)
+
+And now I propose to apply these ideas of stability to the theory of
+stellar evolution, and finally to illustrate them by certain recent
+observations of a very remarkable character.
+
+Stars and planets are formed of materials which yield to the enormous
+forces called into play by gravity and rotation. This is obviously true
+if they are gaseous or fluid, and even solid matter becomes plastic
+under sufficiently great stresses. Nothing approaching a complete study
+of the equilibrium of a heterogeneous star has yet been found possible,
+and we are driven to consider only bodies of simpler construction. I
+shall begin therefore by explaining what is known about the shapes which
+may be assumed by a mass of incompressible liquid of uniform density
+under the influences of gravity and of rotation. Such a liquid mass may
+be regarded as an ideal star, which resembles a real star in the fact
+that it is formed of gravitating and rotating matter, and because its
+shape results from the forces to which it is subject. It is unlike a
+star in that it possesses the attributes of incompressibility and
+of uniform density. The difference between the real and the ideal is
+doubtless great, yet the similarity is great enough to allow us
+to extend many of the conclusions as to ideal liquid stars to the
+conditions which must hold good in reality. Thus with the object of
+obtaining some insight into actuality, it is justifiable to discuss an
+avowedly ideal problem at some length.
+
+The attraction of gravity alone tends to make a mass of liquid assume
+the shape of a sphere, and the effects of rotation, summarised under
+the name of centrifugal force, are such that the liquid seeks to spread
+itself outwards from the axis of rotation. It is a singular fact that
+it is unnecessary to take any account of the size of the mass of liquid
+under consideration, because the shape assumed is exactly the same
+whether the mass be small or large, and this renders the statement of
+results much easier than would otherwise be the case.
+
+A mass of liquid at rest will obviously assume the shape of a sphere,
+under the influence of gravitation, and it is a stable form, because
+any oscillation of the liquid which might be started would gradually die
+away under the influence of friction, however small. If now we impart
+to the whole mass of liquid a small speed of rotation about some axis,
+which may be called the polar axis, in such a way that there are no
+internal currents and so that it spins in the same way as if it were
+solid, the shape will become slightly flattened like an orange. Although
+the earth and the other planets are not homogeneous they behave in the
+same way, and are flattened at the poles and protuberant at the equator.
+This shape may therefore conveniently be described as planetary.
+
+If the planetary body be slightly deformed the forces of restitution
+are slightly less than they were for the sphere; the shape is stable
+but somewhat less so than the sphere. We have then a planetary spheroid,
+rotating slowly, slightly flattened at the poles, with a high degree of
+stability, and possessing a certain amount of rotational momentum. Let
+us suppose this ideal liquid star to be somewhere in stellar space far
+removed from all other bodies; then it is subject to no external forces,
+and any change which ensues must come from inside. Now the amount
+of rotational momentum existing in a system in motion can neither be
+created nor destroyed by any internal causes, and therefore, whatever
+happens, the amount of rotational momentum possessed by the star must
+remain absolutely constant.
+
+A real star radiates heat, and as it cools it shrinks. Let us suppose
+then that our ideal star also radiates and shrinks, but let the process
+proceed so slowly that any internal currents generated in the liquid
+by the cooling are annulled so quickly by fluid friction as to be
+insignificant; further let the liquid always remain at any instant
+incompressible and homogeneous. All that we are concerned with is that,
+as time passes, the liquid star shrinks, rotates in one piece as if it
+were solid, and remains incompressible and homogeneous. The condition is
+of course artificial, but it represents the actual processes of nature
+as well as may be, consistently with the postulated incompressibility
+and homogeneity. (Mathematicians are accustomed to regard the density
+as constant and the rotational momentum as increasing. But the way of
+looking at the matter, which I have adopted, is easier of comprehension,
+and it comes to the same in the end.)
+
+The shrinkage of a constant mass of matter involves an increase of its
+density, and we have therefore to trace the changes which supervene as
+the star shrinks, and as the liquid of which it is composed increases
+in density. The shrinkage will, in ordinary parlance, bring the weights
+nearer to the axis of rotation. Hence in order to keep up the rotational
+momentum, which as we have seen must remain constant, the mass must
+rotate quicker. The greater speed of rotation augments the importance of
+centrifugal force compared with that of gravity, and as the flattening
+of the planetary spheroid was due to centrifugal force, that flattening
+is increased; in other words the ellipticity of the planetary spheroid
+increases.
+
+As the shrinkage and corresponding increase of density proceed, the
+planetary spheroid becomes more and more elliptic, and the succession
+of forms constitutes a family classified according to the density of
+the liquid. The specific mark of this family is the flattening or
+ellipticity.
+
+Now consider the stability of the system, we have seen that the spheroid
+with a slow rotation, which forms our starting-point, was slightly less
+stable than the sphere, and as we proceed through the family of ever
+flatter ellipsoids the stability continues to diminish. At length when
+it has assumed the shape shown in a figure titled "Planetary spheroid
+just becoming unstable" (Fig. 2.) where the equatorial and polar axes
+are proportional to the numbers 1000 and 583, the stability has just
+disappeared. According to the general principle explained above this
+is a form of bifurcation, and corresponds to the form denoted A. The
+specific difference a of this family must be regarded as the excess
+of the ellipticity of this figure above that of all the earlier ones,
+beginning with the slightly flattened planetary spheroid. Accordingly
+the specific difference a of the family has gradually diminished from
+the beginning and vanishes at this stage.
+
+According to Poincare's principle the vanishing of the stability serves
+us with notice that we have reached a figure of bifurcation, and
+it becomes necessary to inquire what is the nature of the specific
+difference of the new family of figures which must be coalescent with
+the old one at this stage. This difference is found to reside in the
+fact that the equator, which in the planetary family has hitherto been
+circular in section, tends to become elliptic. Hitherto the rotational
+momentum has been kept up to its constant value partly by greater speed
+of rotation and partly by a symmetrical bulging of the equator. But now
+while the speed of rotation still increases (The mathematician familiar
+with Jacobi's ellipsoid will find that this is correct, although in
+the usual mode of exposition, alluded to above in a footnote, the speed
+diminishes.), the equator tends to bulge outwards at two diametrically
+opposite points and to be flattened midway between these protuberances.
+The specific difference in the new family, denoted in the general sketch
+by b, is this ellipticity of the equator. If we had traced the planetary
+figures with circular equators beyond this stage A, we should have found
+them to have become unstable, and the stability has been shunted off
+along the A + b family of forms with elliptic equators.
+
+This new series of figures, generally named after the great
+mathematician Jacobi, is at first only just stable, but as the density
+increases the stability increases, reaches a maximum and then declines.
+As this goes on the equator of these Jacobian figures becomes more
+and more elliptic, so that the shape is considerably elongated in a
+direction at right angles to the axis of rotation.
+
+At length when the longest axis of the three has become about three
+times as long as the shortest (The three axes of the ellipsoid are
+then proportional to 1000, 432, 343.), the stability of this family of
+figures vanishes, and we have reached a new form of bifurcation and must
+look for a new type of figure along which the stable development will
+presumably extend. Two sections of this critical Jacobian figure, which
+is a figure of bifurcation, are shown by the dotted lines in a figure
+titled "The 'pear-shaped figure' and the Jocobian figure from which it
+is derived" (Fig. 3.) comprising two figures, one above the other: the
+upper figure is the equatorial section at right angles to the axis of
+rotation, the lower figure is a section through the axis.
+
+Now Poincare has proved that the new type of figure is to be derived
+from the figure of bifurcation by causing one of the ends to be
+prolonged into a snout and by bluntening the other end. The snout forms
+a sort of stalk, and between the stalk and the axis of rotation the
+surface is somewhat flattened. These are the characteristics of a pear,
+and the figure has therefore been called the "pear-shaped figure of
+equilibrium." The firm line shows this new type of figure, whilst, as
+already explained, the dotted line shows the form of bifurcation
+from which it is derived. The specific mark of this new family is the
+protrusion of the stalk together with the other corresponding smaller
+differences. If we denote this difference by c, while A + b denotes the
+Jacobian figure of bifurcation from which it is derived, the new family
+may be called A + b + c, and c is zero initially. According to my
+calculations this series of figures is stable (M. Liapounoff contends
+that for constant density the new series of figures, which M. Poincare
+discovered, has less rotational momentum than that of the figure of
+bifurcation. If he is correct, the figure of bifurcation is a limit of
+stable figures, and none can exist with stability for greater rotational
+momentum. My own work seems to indicate that the opposite is true, and,
+notwithstanding M. Liapounoff's deservedly great authority, I venture
+to state the conclusions in accordance with my own work.), but I do not
+know at what stage of its development it becomes unstable.
+
+Professor Jeans has solved a problem which is of interest as throwing
+light on the future development of the pear-shaped figure, although
+it is of a still more ideal character than the one which has been
+discussed. He imagines an INFINITELY long circular cylinder of liquid
+to be in rotation about its central axis. The existence is virtually
+postulated of a demon who is always occupied in keeping the axis of the
+cylinder straight, so that Jeans has only to concern himself with the
+stability of the form of the section of the cylinder, which as I have
+said is a circle with the axis of rotation at the centre. He then
+supposes the liquid forming the cylinder to shrink in diameter, just as
+we have done, and finds that the speed of rotation must increase so as
+to keep up the constancy of the rotational momentum. The circularity of
+section is at first stable, but as the shrinkage proceeds the stability
+diminishes and at length vanishes. This stage in the process is a form
+of bifurcation, and the stability passes over to a new series consisting
+of cylinders which are elliptic in section. The circular cylinders are
+exactly analogous with our planetary spheroids, and the elliptic ones
+with the Jacobian ellipsoids.
+
+With further shrinkage the elliptic cylinders become unstable, a new
+form of bifurcation is reached, and the stability passes over to a
+series of cylinders whose section is pear-shaped. Thus far the analogy
+is complete between our problem and Jeans's, and in consequence of
+the greater simplicity of the conditions, he is able to carry his
+investigation further. He finds that the stalk end of the pear-like
+section continues to protrude more and more, and the flattening between
+it and the axis of rotation becomes a constriction. Finally the neck
+breaks and a satellite cylinder is born. Jeans's figure for an advanced
+stage of development is shown in a figure titled "Section of a rotating
+cylinder of liquid" (Fig. 4.), but his calculations do not enable him
+actually to draw the state of affairs after the rupture of the neck.
+
+There are certain difficulties in admitting the exact parallelism
+between this problem and ours, and thus the final development of our
+pear-shaped figure and the end of its stability in a form of bifurcation
+remain hidden from our view, but the successive changes as far as they
+have been definitely traced are very suggestive in the study of stellar
+evolution.
+
+Attempts have been made to attack this problem from the other end. If
+we begin with a liquid satellite revolving about a liquid planet and
+proceed backwards in time, we must make the two masses expand so that
+their density will be diminished. Various figures have been drawn
+exhibiting the shapes of two masses until their surfaces approach close
+to one another and even until they just coalesce, but the discussion of
+their stability is not easy. At present it would seem to be impossible
+to reach coalescence by any series of stable transformations, and
+if this is so Professor Jeans's investigation has ceased to be truly
+analogous to our problem at some undetermined stage. However this may be
+this line of research throws an instructive light on what we may expect
+to find in the evolution of real stellar systems.
+
+In the second part of this paper I shall point out the bearing which
+this investigation of the evolution of an ideal liquid star may have on
+the genesis of double stars.
+
+II.
+
+There are in the heavens many stars which shine with a variable
+brilliancy. Amongst these there is a class which exhibits special
+peculiarities; the members of this class are generally known as Algol
+Variables, because the variability of the star Beta Persei or Algol was
+the first of such cases to attract the attention of astronomers, and
+because it is perhaps still the most remarkable of the whole class. But
+the circumstances which led to this discovery were so extraordinary that
+it seems worth while to pause a moment before entering on the subject.
+
+John Goodricke, a deaf-mute, was born in 1764; he was grandson and heir
+of Sir John Goodricke of Ribston Hall, Yorkshire. In November 1782,
+he noted that the brilliancy of Algol waxed and waned (It is said that
+Georg Palitzch, a farmer of Prohlis near Dresden, had about 1758 already
+noted the variability of Algol with the naked eye. "Journ. Brit. Astron.
+Assoc." Vol. XV. (1904-5), page 203.), and devoted himself to observing
+it on every fine night from the 28th December 1782 to the 12th May 1783.
+He communicated his observations to the Royal Society, and suggested
+that the variation in brilliancy was due to periodic eclipses by a dark
+companion star, a theory now universally accepted as correct. The
+Royal Society recognised the importance of the discovery by awarding to
+Goodricke, then only 19 years of age, their highest honour, the Copley
+medal. His later observations of Beta Lyrae and of Delta Cephei were
+almost as remarkable as those of Algol, but unfortunately a career of
+such extraordinary promise was cut short by death, only a fortnight
+after his election to the Royal Society. ("Dict. of National Biography";
+article Goodricke (John). The article is by Miss Agnes Clerke. It is
+strange that she did not then seem to be aware that he was a deaf-mute,
+but she notes the fact in her "Problems of Astrophysics", page 337,
+London, 1903.)
+
+It was not until 1889 that Goodricke's theory was verified, when it
+was proved by Vogel that the star was moving in an orbit, and in such
+a manner that it was only possible to explain the rise and fall in the
+luminosity by the partial eclipse of a bright star by a dark companion.
+
+The whole mass of the system of Algol is found to be half as great again
+as that of our sun, yet the two bodies complete their orbit in the short
+period of 2d 20h 48m 55s. The light remains constant during each period,
+except for 9h 20m when it exhibits a considerable fall in brightness
+(Clerke, "Problems of Astrophysics" page 302 and chapter XVIII.); the
+curve which represents the variation in the light is shown in a figure
+titled "The light-curve and system of Beta Lyrae" (Fig. 7.).
+
+The spectroscope has enabled astronomers to prove that many stars,
+although apparently single, really consist of two stars circling around
+one another (If a source of light is approaching with a great velocity
+the waves of light are crowded together, and conversely they are spaced
+out when the source is receding. Thus motion in the line of sight
+virtually produces an infinitesimal change of colour. The position
+of certain dark lines in the spectrum affords an exceedingly accurate
+measurement of colour. Thus displacements of these spectral lines
+enables us to measure the velocity of the source of light towards or
+away from the observer.); they are known as spectroscopic binaries.
+Campbell of the Lick Observatory believes that about one star in six is
+a binary ("Astrophysical Journ." Vol. XIII. page 89, 1901. See also A.
+Roberts, "Nature", Sept. 12, 1901, page 468.); thus there must be many
+thousand such stars within the reach of our spectroscopes.
+
+The orientation of the planes of the orbits of binary stars appears to
+be quite arbitrary, and in general the star does not vary in brightness.
+Amongst all such orbits there must be some whose planes pass nearly
+through the sun, and in these cases the eclipse of one of the stars by
+the other becomes inevitable, and in each circuit there will occur two
+eclipses of unequal intensities.
+
+It is easy to see that in the majority of such cases the two components
+must move very close to one another.
+
+The coincidence between the spectroscopic and the photometric evidence
+permits us to feel complete confidence in the theory of eclipses. When
+then we find a star with a light-curve of perfect regularity and with
+a characteristics of that of Algol, we are justified in extending the
+theory of eclipses to it, although it may be too faint to permit of
+adequate spectroscopic examination. This extension of the theory secures
+a considerable multiplication of the examples available for observation,
+and some 30 have already been discovered.
+
+Dr Alexander Roberts, of Lovedale in Cape Colony, truly remarks that
+the study of Algol variables "brings us to the very threshold of the
+question of stellar evolution." ("Proc. Roy. Soc. Edinburgh", XXIV. Part
+II. (1902), page 73.) It is on this account that I propose to explain
+in some detail the conclusion to which he and some other observers have
+been led.
+
+Although these variable stars are mere points of light, it has been
+proved by means of the spectroscope that the law of gravitation holds
+good in the remotest regions of stellar space, and further it seems now
+to have become possible even to examine the shapes of stars by indirect
+methods, and thus to begin the study of their evolution. The chain of
+reasoning which I shall explain must of necessity be open to criticism,
+yet the explanation of the facts by the theory is so perfect that it is
+not easy to resist the conviction that we are travelling along the path
+of truth.
+
+The brightness of a star is specified by what is called its "magnitude."
+The average brightness of all the stars which can just be seen with
+the naked eye defines the sixth magnitude. A star which only gives
+two-fifths as much light is said to be of the seventh magnitude; while
+one which gives 2 1/2 times as much light is of the fifth magnitude,
+and successive multiplications or divisions by 2 1/2 define the lower or
+higher magnitudes. Negative magnitudes have clearly to be contemplated;
+thus Sirius is of magnitude minus 1.4, and the sun is of magnitude minus
+26.
+
+The definition of magnitude is also extended to fractions; for example,
+the lights given by two candles which are placed at 100 feet and 100
+feet 6 inches from the observer differ in brightness by one-hundredth of
+a magnitude.
+
+A great deal of thought has been devoted to the measurement of the
+brightness of stars, but I will only describe one of the methods used,
+that of the great astronomer Argelander. In the neighbourhood of the
+star under observation some half dozen standard stars are selected of
+known invariable magnitudes, some being brighter and some fainter than
+the star to be measured; so that these stars afford a visible scale of
+brightness. Suppose we number them in order of increasing brightness
+from 1 to 6; then the observer estimates that on a given night his star
+falls between stars 2 and 3, on the next night, say between 3 and 4, and
+then again perhaps it may return to between 2 and 3, and so forth. With
+practice he learns to evaluate the brightness down to small fractions
+of a magnitude, even a hundredth part of a magnitude is not quite
+negligible.
+
+For example, in observing the star RR Centauri five stars were in
+general used for comparison by Dr Roberts, and in course of three months
+he secured thereby 300 complete observations. When the period of the
+cycle had been ascertained exactly, these 300 values were reduced to
+mean values which appertained to certain mean places in the cycle, and
+a mean light-curve was obtained in this way. Figures titled "Light curve
+of RR Centauri" (Fig. 5) and "The light-curve and system of Beta Lyrae"
+(Fig. 7) show examples of light curves.
+
+I shall now follow out the results of the observation of RR Centauri
+not only because it affords the easiest way of explaining these
+investigations, but also because it is one of the stars which furnishes
+the most striking results in connection with the object of this essay.
+(See "Monthly notices R.A.S." Vol. 63, 1903, page 527.) This star has
+a mean magnitude of about 7 1/2, and it is therefore invisible to
+the naked eye. Its period of variability is 14h 32m 10s.76, the last
+refinement of precision being of course only attained in the final
+stages of reduction. Twenty-nine mean values of the magnitude were
+determined, and they were nearly equally spaced over the whole cycle of
+changes. The black dots in Fig. 5 exhibit the mean values determined by
+Dr Roberts. The last three dots on the extreme right are merely the same
+as the first three on the extreme left, and are repeated to show how
+the next cycle would begin. The smooth dotted curve will be explained
+hereafter, but, by reference to the scale of magnitudes on the margins
+of the figure, it may be used to note that the dots might be brought
+into a perfectly smooth curve by shifting some few of the dots by about
+a hundredth of a magnitude.
+
+This light-curve presents those characteristics which are due to
+successive eclipses, but the exact form of the curve must depend on the
+nature of the two mutually eclipsing stars. If we are to interpret the
+curve with all possible completeness, it is necessary to make certain
+assumptions as to the stars. It is assumed then that the stars are
+equally bright all over their disks, and secondly that they are not
+surrounded by an extensive absorptive atmosphere. This last appears to
+me to be the most dangerous assumption involved in the whole theory.
+
+Making these assumptions, however, it is found that if each of the
+eclipsing stars were spherical it would not be possible to generate such
+a curve with the closest accuracy. The two stars are certainly close
+together, and it is obvious that in such a case the tidal forces
+exercised by each on the other must be such as to elongate the figure
+of each towards the other. Accordingly it is reasonable to adopt the
+hypothesis that the system consists of a pair of elongated ellipsoids,
+with their longest axes pointed towards one another. No supposition
+is adopted a priori as to the ratio of the two masses, or as to their
+relative size or brightness, and the orbit may have any degree of
+eccentricity. These last are all to be determined from the nature of the
+light-curve.
+
+In the case of RR Centauri, however, Dr Roberts finds the conditions are
+best satisfied by supposing the orbit to be circular, and the sizes and
+masses of the components to be equal, while their luminosities are to
+one another in the ratio of 4 to 3. As to their shapes he finds them
+to be so much elongated that they overlap, as exhibited in his figure
+titled "The shape of the star RR Centauri" (Fig. 6.). The dotted curve
+shows a form of equilibrium of rotating liquid as computed by me some
+years before, and it was added for the sake of comparison.
+
+On turning back to Fig. 5 the reader will see in the smooth dotted curve
+the light variation which would be exhibited by such a binary system as
+this. The curve is the result of computation and it is impossible not to
+be struck by the closeness of the coincidence with the series of black
+dots which denote the observations.
+
+It is virtually certain that RR Centauri is a case of an eclipsing
+binary system, and that the two stars are close together. It is not
+of course proved that the figures of the stars are ellipsoids, but
+gravitation must deform them into a pair of elongated bodies, and, on
+the assumptions that they are not enveloped in an absorptive atmosphere
+and that they are ellipsoidal, their shapes must be as shown in the
+figure.
+
+This light-curve gives an excellent illustration of what we have reason
+to believe to be a stage in the evolution of stars, when a single star
+is proceeding to separate into a binary one.
+
+As the star is faint, there is as yet no direct spectroscopic evidence
+of orbital motion. Let us turn therefore to the case of another star,
+namely V Puppis, in which such evidence does already exist. I give an
+account of it, because it presents a peculiarly interesting confirmation
+of the correctness of the theory.
+
+In 1895 Pickering announced in the "Harvard Circular" No. 14 that the
+spectroscopic observations at Arequipa proved V Puppis to be a double
+star with a period of 3d 2h 46m. Now when Roberts discussed its
+light-curve he found that the period was 1d 10h 54m 27s, and on account
+of this serious discrepancy he effected the reduction only on the simple
+assumption that the two stars were spherical, and thus obtained a fairly
+good representation of the light-curve. It appeared that the orbit was
+circular and that the two spheres were not quite in contact. Obviously
+if the stars had been assumed to be ellipsoids they would have been
+found to overlap, as was the case for RR Centauri. ("Astrophysical
+Journ." Vol. XIII. (1901), page 177.) The matter rested thus for some
+months until the spectroscopic evidence was re-examined by Miss Cannon
+on behalf of Professor Pickering, and we find in the notes on page
+177 of Vol. XXVIII. of the "Annals of the Harvard Observatory" the
+following: "A.G.C. 10534. This star, which is the Algol variable V
+Puppis, has been found to be a spectroscopic binary. The period 1d.454
+(i.e. 1d 10h 54m) satisfies the observations of the changes in light,
+and of the varying separation of the lines of the spectrum. The spectrum
+has been examined on 61 plates, on 23 of which the lines are double."
+Thus we have valuable evidence in confirmation of the correctness of the
+conclusions drawn from the light-curve. In the circumstances, however,
+I have not thought it worth while to reproduce Dr Roberts's provisional
+figure.
+
+I now turn to the conclusions drawn a few years previously by another
+observer, where we shall find the component stars not quite in contact.
+This is the star Beta Lyrae which was observed by Goodricke, Argelander,
+Belopolsky, Schur, Markwick and by many others. The spectroscopic method
+has been successfully applied in this case, and the component stars are
+proved to move in an orbit about one another. In 1897, Mr. G.W. Myers
+applied the theory of eclipses to the light-curve, on the hypothesis
+that the stars are elongated ellipsoids, and he obtained the interesting
+results exhibited in Fig. 7. ("Astrophysical Journ." Vol. VII. (1898),
+page 1.)
+
+The period of Beta Lyrae is relatively long, being 12d 21h 47m, the
+orbit is sensibly eccentric, and the two spheroids are not so much
+elongated as was the case with RR Centauri. The mass of the system is
+enormous, one of the two stars being 10 times and the other 21 times as
+heavy as our sun.
+
+Further illustrations of this subject might be given, but enough has
+been said to explain the nature of the conclusions which have been drawn
+from this class of observation.
+
+In my account of these remarkable systems the consideration of one very
+important conclusion has been purposely deferred. Since the light-curve
+is explicable by eclipses, it follows that the sizes of the two stars
+are determinable relatively to the distance between them. The period of
+their orbital motion is known, being identical with the complete period
+of the variability of their light, and an easy application of Kepler's
+law of periodic times enables us to compute the sum of the masses of the
+two stars divided by the cube of the distance between their centres.
+Now the sizes of the bodies being known, the mean density of the whole
+system may be calculated. In every case that density has been found to
+be much less than the sun's, and indeed the average of a number of mean
+densities which have been determined only amounts to one-eighth of that
+of the sun. In some cases the density is extremely small, and in no case
+is it quite so great as half the solar density.
+
+It would be absurd to suppose that these stars can be uniform in
+density throughout, and from all that is known of celestial bodies it
+is probable that they are gaseous in their external parts with great
+condensation towards their centres. This conclusion is confirmed by
+arguments drawn from the theory of rotating masses of liquid. (See J.H.
+Jeans, "On the density of Algol variables", "Astrophysical Journ." Vol.
+XXII. (1905), page 97.)
+
+Although, as already explained, a good deal is known about the shapes
+and the stability of figures consisting of homogeneous incompressible
+liquid in rotation, yet comparatively little has hitherto been
+discovered about the equilibrium of rotating gaseous stars. The figures
+calculated for homogeneous liquid can obviously only be taken to afford
+a general indication of the kind of figure which we might expect to find
+in the stellar universe. Thus the dotted curve in Fig. 5, which exhibits
+one of the figures which I calculated, has some interest when placed
+alongside the figures of the stars in RR Centauri, as computed from the
+observations, but it must not be accepted as the calculated form of such
+a system. I have moreover proved more recently that such a figure of
+homogeneous liquid is unstable. Notwithstanding this instability it does
+not necessarily follow that the analogous figure for compressible fluid
+is also unstable, as will be pointed out more fully hereafter.
+
+Professor Jeans has discussed in a paper of great ability the difficult
+problems offered by the conditions of equilibrium and of stability of a
+spherical nebula. ("Phil. Trans. R.S." Vol. CXCIX. A (1902), page 1. See
+also A. Roberts, "S. African Assoc. Adv. Sci." Vol. I. (1903), page 6.)
+In a later paper ("Astrophysical Journ." Vol. XXII. (1905), page 97.),
+in contrasting the conditions which must govern the fission of a star
+into two parts when the star is gaseous and compressible with the
+corresponding conditions in the case of incompressible liquid, he points
+out that for a gaseous star (the agency which effects the separation
+will no longer be rotation alone; gravitation also will tend towards
+separation... From numerical results obtained in the various papers of
+my own,... I have been led to the conclusion that a gravitational
+instability of the kind described must be regarded as the primary agent
+at work in the actual evolution of the universe, Laplace's rotation
+playing only the secondary part of separating the primary and satellite
+after the birth of the satellite.)
+
+It is desirable to add a word in explanation of the expression
+"gravitational instability" in this passage. It means that when the
+concentration of a gaseous nebula (without rotation) has proceeded to
+a certain stage, the arrangement in spherical layers of equal density
+becomes unstable, and a form of bifurcation has been reached. For
+further concentration concentric spherical layers become unstable, and
+the new stable form involves a concentration about two centres. The
+first sign of this change is that the spherical layers cease to be
+quite concentric and then the layers of equal density begin to assume
+a somewhat pear-shaped form analogous to that which we found to occur
+under rotation for an incompressible liquid. Accordingly it appears that
+while a sphere of liquid is stable a sphere of gas may become unstable.
+Thus the conditions of stability are different in these two simple
+cases, and it is likely that while certain forms of rotating liquid are
+unstable the analogous forms for gas may be stable. This furnishes a
+reason why it is worth while to consider the unstable forms of rotating
+liquid.
+
+There can I think be little doubt but that Jeans is right in looking to
+gravitational instability as the primary cause of fission, but when we
+consider that a binary system, with a mass larger than the sun's, is
+found to rotate in a few hours, there seems reason to look to rotation
+as a contributory cause scarcely less important than the primary one.
+
+With the present extent of our knowledge it is only possible to
+reconstruct the processes of the evolution of stars by means of
+inferences drawn from several sources. We have first to rely on the
+general principles of stability, according to which we are to look for a
+series of families of forms, each terminating in an unstable form, which
+itself becomes the starting-point of the next family of stable forms.
+Secondly we have as a guide the analogy of the successive changes in
+the evolution of ideal liquid stars; and thirdly we already possess some
+slender knowledge as to the equilibrium of gaseous stars.
+
+From these data it is possible to build up in outline the probable
+history of binary stars. Originally the star must have been single, it
+must have been widely diffused, and must have been endowed with a slow
+rotation. In this condition the strata of equal density must have been
+of the planetary form. As it cooled and contracted the symmetry round
+the axis of rotation must have become unstable, through the effects of
+gravitation, assisted perhaps by the increasing speed of rotation. (I
+learn from Professor Jeans that he now (December 1908) believes that
+he can prove that some small amount of rotation is necessary to induce
+instability in the symmetrical arrangement.) The strata of equal
+density must then become somewhat pear-shaped, and afterwards like an
+hour-glass, with the constriction more pronounced in the internal than
+in the external strata. The constrictions of the successive strata then
+begin to rupture from the inside progressively outwards, and when at
+length all are ruptured we have the twin stars portrayed by Roberts and
+by others.
+
+As we have seen, the study of the forms of equilibrium of rotating
+liquid is almost complete, and Jeans has made a good beginning in the
+investigation of the equilibrium of gaseous stars, but much more remains
+to be discovered. The field for the mathematician is a wide one, and in
+proportion as the very arduous exploration of that field is attained so
+will our knowledge of the processes of cosmical evolution increase.
+
+From the point of view of observation, improved methods in the use of
+the spectroscope and increase of accuracy in photometry will certainly
+lead to a great increase in our knowledge within the next few years.
+Probably the observational advance will be more rapid than that of
+theory, for we know how extraordinary has been the success attained
+within the last few years, and the theory is one of extreme difficulty;
+but the two ought to proceed together hand in hand. Human life is
+too short to permit us to watch the leisurely procedure of cosmical
+evolution, but the celestial museum contains so many exhibits that it
+may become possible, by the aid of theory, to piece together bit by bit
+the processes through which stars pass in the course of their evolution.
+
+In the sketch which I have endeavoured to give of this fascinating
+subject, I have led my reader to the very confines of our present
+knowledge. It is not much more than a quarter of a century since this
+class of observation has claimed the close attention of astronomers;
+something considerable has been discovered already and there seems
+scarcely a discernible limit to what will be known in this field a
+century from now. Some of the results which I have set forth may then be
+shown to be false, but it seems profoundly improbable that we are being
+led astray by a Will-of-the-Wisp.
+
+
+
+
+XXIX. THE EVOLUTION OF MATTER. By W.C.D. Whetham, M.A., F.R.S.
+
+Trinity College, Cambridge.
+
+
+The idea of evolution in the organic world, made intelligible by the
+work of Charles Darwin, has little in common with the recent conception
+of change in certain types of matter. The discovery that a process of
+disintegration may take place in some at least of the chemical atoms,
+previously believed to be indestructible and unalterable, has modified
+our view of the physical universe, even as Darwin's scheme of the mode
+of evolution changed the trend of thought concerning the organic world.
+Both conceptions have in common the idea of change throughout extended
+realms of space and time, and, therefore, it is perhaps not unfitting
+that some account of the most recent physical discoveries should be
+included in the present volume.
+
+The earliest conception of the evolution of matter is found in the
+speculation of the Greeks. Leucippus and Democritus imagined unchanging
+eternal atoms, Heracleitus held that all things were in a continual
+state of flux--Panta rei.
+
+But no one in the Ancient World--no one till quite modern times--could
+appreciate the strength of the position which the theory of the
+evolution of matter must carry before it wins the day. Vague
+speculation, even by the acute minds of philosophers, is of little use
+in physical science before experimental facts are available. The true
+problems at issue cannot even be formulated, much less solved, till the
+humble task of the observer and experimenter has given us a knowledge of
+the phenomena to be explained.
+
+It was only through the atomic theory, at first apparently diametrically
+opposed to it, that the conception of evolution in the physical world
+was to gain an established place. For a century the atomic theory, when
+put into a modern form by Dalton, led farther and farther away from
+the idea of change in matter. The chemical elements seemed quite
+unalterable, and the atoms, of which each element in modern view is
+composed, bore to Clerk Maxwell, writing about 1870, "the stamp of
+manufactured articles" exactly similar in kind, unchanging, eternal.
+
+Nevertheless throughout these years, on the whole so unfavourable to its
+existence, there persisted the idea of a common origin of the distinct
+kinds of matter known to chemists. Indeed, this idea of unity in
+substance in nature seems to accord with some innate desire or intimate
+structure of the human mind. As Mr Arthur Balfour well puts it, "There
+is no a priori reason that I know of for expecting that the material
+world should be a modification of a single medium, rather than a
+composite structure built out of sixty or seventy elementary substances,
+eternal and eternally different. Why then should we feel content with
+the first hypothesis and not with the second? Yet so it is. Men of
+science have always been restive under the multiplication of entities.
+They have eagerly watched for any sign that the different chemical
+elements own a common origin, and are all compounded out of some
+primordial substance. Nor, for my part, do I think that such instincts
+should be ignored... that they exist is certain; that they modify the
+indifferent impartiality of pure empiricism can hardly be denied."
+("Report of the 74th Meeting of the British Association" (Presidential
+Address, Cambridge 1904), page 9, London, 1905.)
+
+When Dalton's atomic theory had been in existence some half century, it
+was noted that certain numerical relations held good between the atomic
+weights of elements chemically similar to one another. Thus the weight
+(88) of an atom of strontium compared with that of hydrogen as unity,
+is about the mean of those of calcium (40) and barium (137). Such
+relations, in this and other chemical groups, were illustrated by
+Beguyer de Chancourtois in 1862 by the construction of a spiral diagram
+in which the atomic weights are placed in order round a cylinder and
+elements chemically similar are found to fall on vertical lines.
+
+Newlands seems to have been the first to see the significance of such
+a diagram. In his "law of octaves," formulated in 1864, he advanced
+the hypothesis that, if arranged in order of rising atomic weight, the
+elements fell into groups, so that each eighth element was chemically
+similar. Stated thus, the law was too definite; no room was left for
+newly-discovered elements, and some dissimilar elements were perforce
+grouped together.
+
+But in 1869 Mendeleeff developed Newland's hypothesis in a form that
+attracted at once general attention. Placing the elements in order of
+rising atomic weight, but leaving a gap where necessary to bring similar
+elements into vertical columns, he obtained a periodic table with
+natural vacancies to be filled as new elements were discovered, and with
+a certain amount of flexibility at the ends of the horizontal lines.
+From the position of the vacancies, the general chemical and physical
+properties of undiscovered elements could be predicted, and the
+success of such predictions gave a striking proof of the usefulness of
+Mendeleeff's generalisation.
+
+When the chemical and physical properties of the elements were known
+to be periodic functions of their atomic weights, the idea of a common
+origin and common substance became much more credible. Differences in
+atomic weight and differences in properties alike might reasonably be
+explained by the differences in the amount of the primordial substance
+present in the various atoms; an atom of oxygen being supposed to be
+composed of sixteen times as much stuff as the atom of hydrogen, but to
+be made of the same ultimate material. Speculations about the mode of
+origin of the elements now began to appear, and put on a certain air
+of reality. Of these speculations perhaps the most detailed was that of
+Crookes, who imagined an initial chaos of a primordial medium he named
+protyle, and a process of periodic change in which the chemical elements
+successively were precipitated.
+
+From another side too, suggestions were put forward by Sir Norman
+Lockyer and others that the differences in spectra observed in
+different classes of stars, and produced by different conditions in
+the laboratory, were to be explained by changes in the structure of the
+vibrating atoms.
+
+The next step in advance gave a theoretical basis for the idea of a
+common structure of matter, and was taken in an unexpected direction.
+Clerk Maxwell's electromagnetic theory of light, accepted in England,
+was driven home to continental minds by the confirmatory experiments of
+Hertz, who in 1888 detected and measured the electromagnetic waves
+that Maxwell had described twenty years earlier. But, if light be an
+electromagnetic phenomenon, the light waves radiated by hot bodies must
+take their origin in the vibrations of electric systems. Hence within
+the atoms must exist electric charges capable of vibration. On these
+lines Lorentz and Larmor have developed an electronic theory of matter,
+which is imagined in its essence to be a conglomerate of electric
+charges, with electro-magnetic inertia to explain mechanical inertia.
+(Larmor, "Aether and Matter", Cambridge, 1900.) The movement of electric
+charges would be affected by a magnetic field, and hence the discovery
+by Zeeman that the spectral lines of sodium were doubled by a strong
+magnetic force gave confirmatory evidence to the theory of electrons.
+
+Then came J.J. Thomson's great discovery of minute particles, much
+smaller than any chemical atom, forming a common constituent of many
+different kinds of matter. (Thomson, "Conduction of Electricity through
+Gases" (2nd edition), Cambridge, 1906.) If an electric discharge be
+passed between metallic terminals through a glass vessel containing
+air at very low pressure, it is found that rectilinear rays, known
+as cathode rays, proceed from the surface of the cathode or negative
+terminal. Where these rays strike solid objects, they give rise to
+the Rontgen rays now so well known; but it is with the cathode rays
+themselves that we are concerned. When they strike an insulated
+conductor, they impart to it a negative charge, and Thomson found that
+they were deflected from their path both by magnetic and electric forces
+in the direction in which negatively electrified particles would be
+deflected. Cathode rays then were accepted as flights of negatively
+charged particles, moving with high velocities. The electric and
+magnetic deflections give two independent measurements which may be made
+on a cathode ray, and both the deflections involve theoretically three
+unknown quantities, the mass of the particles, their electric charge
+and their velocity. There is strong cumulative evidence that all
+such particles possess the same charge, which is identical with that
+associated with a univalent atom in electrolytic liquids. The number of
+unknown quantities was thus reduced to two--the mass and the velocity.
+The measurement of the magnetic and electric deflections gave two
+independent relations between the unknowns, which could therefore be
+determined. The velocities of the cathode ray particles were found to
+vary round a value about one-tenth that of light, but the mass was found
+always to be the same within the limits of error, whatever the nature of
+the terminals, of the residual gas in the vessel, and of the conditions
+of the experiment. The mass of a cathode ray particle, or corpuscle, as
+Thomson, adopting Newton's name, called it, is about the eight-hundredth
+part of the mass of a hydrogen atom.
+
+These corpuscles, found in so many different kinds of substance,
+are inevitably regarded as a common constituent of matter. They are
+associated each with a unit of negative electricity. Now electricity in
+motion possesses electromagnetic energy, and produces effects like those
+of mechanical inertia. In other words, an electric charge possesses
+mass, and there is evidence to show that the effective mass of a
+corpuscle increases as its velocity approaches that of light in the way
+it would do if all its mass were electromagnetic. We are led therefore
+to regard the corpuscle from one aspect as a disembodied charge of
+electricity, and to identify it with the electron of Lorentz and Larmor.
+
+Thus, on this theory, matter and electricity are identified; and a great
+simplification of our conception of the physical structure of Nature is
+reached. Moreover, from our present point of view, a common basis for
+matter suggests or implies a common origin, and a process of development
+possibly intelligible to our minds. The idea of the evolution of matter
+becomes much more probable.
+
+The question of the nature and physical meaning of a corpuscle or
+electron remains for consideration. On the hypothesis of a universal
+luminiferous aether, Larmor has suggested a centre of aethereal strain
+"a place where the continuity of the medium has been broken and cemented
+together again (to use a crude but effective image) without accurately
+fitting the parts, so that there is a residual strain all round the
+place." (Larmor, loc. cit.) Thus he explains in quasi-mechanical terms
+the properties of an electron. But whether we remain content for the
+time with our identification of matter and electricity, or attempt to
+express both of them in terms of hypothetical aether, we have made a
+great step in advance on the view that matter is made up of chemical
+atoms fundamentally distinct and eternally isolated.
+
+Such was the position when the phenomena of radio-activity threw a new
+light on the problem, and, for the first time in the history of science,
+gave definite experimental evidence of the transmutation of matter from
+one chemical element to another.
+
+In 1896 H. Becquerel discovered that compounds of the metal uranium
+continually emitted rays capable of penetrating opaque screens and
+affecting photographic plates. Like cathode and Rontgen rays, the
+rays from uranium make the air through which they pass a conductor
+of electricity, and this property gives the most convenient method of
+detecting the rays and of measuring their intensity. An electroscope may
+be made of a strip of gold-leaf attached to an insulated brass plate
+and confined in a brass vessel with glass windows. When the gold-leaf is
+electrified, it is repelled from the similarly electrified brass plate,
+and the angle at which it stands out measures the electrification. Such
+a system, if well insulated, holds its charge for hours, the leakage
+of electricity through the air being very slow. But, if radio-active
+radiation reach the air within, the gold-leaf falls, and the rate of
+its fall, as watched through a microscope with a scale in the eye-piece,
+measures the intensity of the radiation. With some form of this simple
+instrument, or with the more complicated quadrant electrometer, most
+radio-active measurements have been made.
+
+It was soon discovered that the activity of uranium compounds
+was proportional to the amount of uranium present in them. Thus
+radio-activity is an atomic property dependent on the amount of an
+element and independent of its state of chemical combination.
+
+In a search for radio-activity in different minerals, M. and Mme Curie
+found a greater effect in pitch-blende than its contents of uranium
+warranted, and, led by the radio-active property alone, they succeeded,
+by a long series of chemical separations, in isolating compounds of a
+new and intensely radio-active substance which they named radium.
+
+Radium resembles barium in its chemical properties, and is precipitated
+with barium in the ordinary course of chemical analysis. It is separated
+by a prolonged course of successive crystallisation, the chloride of
+radium being less soluble than that of barium, and therefore sooner
+separated from an evaporating solution. When isolated, radium chloride
+has a composition, which, on the assumption that one atom of metal
+combines with two of chlorine as in barium chloride, indicates that the
+relative weight of the atom of radium is about 225. As thus prepared,
+radium is a well-marked chemical element, forming a series of compounds
+analogous to those of barium and showing a characteristic line spectrum.
+But, unlike most other chemical elements, it is intensely radio-active,
+and produces effects some two million times greater than those of
+uranium.
+
+In 1899 E. Rutherford, then of Montreal, discovered that the
+radiation from uranium, thorium and radium was complex. (Rutherford,
+"Radio-activity" (2nd edition), Cambridge, 1905.) Three types of rays
+were soon distinguished. The first, named by Rutherford alpha-rays, are
+absorbed by thin metal foil or a few centimetres of air. When examined
+by measurements of the deflections caused by magnetic and electric
+fields, the alpha-rays are found to behave as would positively
+electrified particles of the magnitude of helium atoms possessing a
+double ionic charge and travelling with a velocity about one-tenth that
+of light. The second or beta type of radiation is much more penetrating.
+It will pass through a considerable thickness of metallic foil, or many
+centimetres of air, and still affect photographic plates or discharge
+electroscopes. Magnetic and electric forces deflect beta-rays much
+more than alpha-rays, indicating that, although the speed is greater,
+approaching in some cases within five per cent. that of light, the mass
+is very much less. The beta-rays must be streams of particles, identical
+with those of cathode rays, possessing the minute mass of J.J. Thomson's
+corpuscle, some eight-hundredth part of that of a hydrogen atom. A third
+or gamma type of radiation was also detected. More penetrating even than
+beta-rays, the gamma-rays have never been deflected by any magnetic
+or electric force yet applied. Like Rontgen rays, it is probable that
+gamma-rays are wave-pulses in the luminiferous aether, though the
+possibility of explaining them as flights of non-electrified particles
+is before the minds of some physicists.
+
+Still another kind of radiation has been discovered more recently by
+Thomson, who has found that in high vacua, rays become apparent which
+are absorbed at once by air at any ordinary pressure.
+
+The emission of all these different types of radiation involves a
+continual drain of energy from the radio-active body. When M. and Mme
+Curie had prepared as much as a gramme of radium chloride, the energy of
+the radiation became apparent as an evolution of heat. The radium salt
+itself, and the case containing it, absorbed the major part of the
+radiation, and were thus maintained at a temperature measurably higher
+than that of the surroundings. The rate of thermal evolution was such
+that it appeared that one gramme of pure radium must emit about 100
+gramme-calories of heat in an hour. This observation, naturally as it
+follows from the phenomena previously discovered, first called attention
+to the question of the source of the energy which maintains indefinitely
+and without apparent diminution the wonderful stream of radiation
+proceeding from a radio-active substance. In the solution of this
+problem lies the point of the present essay.
+
+In order to appreciate the evidence which bears on the question we must
+now describe two other series of phenomena.
+
+It is a remarkable fact that the intensity of the radiation from
+a radio-active body is independent of the external conditions of
+temperature, pressure, etc. which modify so profoundly almost all other
+physical and chemical processes. Exposure to the extreme cold of liquid
+air, or to the great heat of a furnace, leaves the radio-activity of a
+substance unchanged, apparent exceptions to this statement having been
+traced to secondary causes.
+
+Then, it is found that radio-activity is always accompanied by some
+chemical change; a new substance always appears as the parent substance
+emits these radiations. Thus by chemical reactions it is possible to
+separate from uranium and thorium minute quantities of radio-active
+materials to which the names of uranium-X and thorium-X have been given.
+These bodies behave differently from their parents uranium and thorium,
+and show all the signs of distinct chemical individuality. They are
+strongly radio-active, while, after the separation, the parents uranium
+and thorium are found to have lost some of their radio-activity. If the
+X-substances be kept, their radio-activity decays, while that of the
+uranium or thorium from which they were obtained gradually rises to the
+initial value it had before the separation. At any moment, the sum of
+the radio-activity is constant, the activity lost by the product being
+equal to that gained by the parent substance. These phenomena are
+explained if we suppose that the X-product is slowly produced in the
+substance of the parent, and decays at a constant rate. Uranium,
+as usually seen, contains a certain amount of uranium-X, and its
+radio-activity consists of two parts--that of the uranium itself, and
+that of the X product. When the latter is separated by means of its
+chemical reactions, its radio-activity is separated also, and the rates
+of decay and recovery may be examined.
+
+Radium and thorium, but not uranium, give rise to radio-active gases
+which have been called emanations. Rutherford has shown that their
+radio-activity, like that of the X products, suffers decay, while
+the walls of the vessel in which the emanation is confined, become
+themselves radio-active. If washed with certain acids, however, the
+walls lose their activity, which is transferred to the acid, and can be
+deposited by evaporation from it on to a solid surface. Here again it
+is clear that the emanation gives rise to a radio-active substance which
+clings to the walls of the vessel, and is soluble in certain liquids,
+but not in others.
+
+We shall return to this point, and trace farther the history of the
+radio-active matter. At present we wish to emphasise the fact that, as
+in other cases, the radio-activity of the emanation is accompanied
+by the appearance of a new kind of substance with distinct chemical
+properties.
+
+We are now in a position to consider as a whole the evidence on the
+question of the source of radio-active energy.
+
+(1) Radio-activity is accompanied by the appearance of new chemical
+substances. The energy liberated is therefore probably due to the
+associated chemical change. (2) The activity of a series of compounds is
+found to accompany the presence of a radio-active element, the activity
+of each compound depends only on the contents of the element, and is
+independent of the nature of its combination. Thus radio-activity is a
+property of the element, and is not affected by its state of isolation
+or chemical combination. (3) The radio-activity of a simple transient
+product decays in a geometrical progression, the loss per second being
+proportional to the mass of substance still left at the moment, and
+independent of its state of concentration or dilution. This type of
+reaction is well known in chemistry to mark a mono-molecular
+change, where each molecule is dissociated or altered in structure
+independently. If two or more molecules were concerned simultaneously,
+the rate of reaction would depend on the nearness of the molecules
+to each other, that is, to the concentration of the material. (4) The
+amount of energy liberated by the change of a given mass of material far
+transcends the amount set free by any known ordinary chemical action.
+The activity of radium decays so slowly that it would not sink to half
+its initial value in less than some two thousand years, and yet one
+gramme of radium emits about 100 calories of heat during each hour of
+its existence.
+
+The energy of radio-activity is due to chemical change, but clearly
+to no chemical change hitherto familiar to science. It is an atomic
+property, characteristic of a given element, and the atoms undergo the
+change individually, not by means of interaction among each other. The
+conclusion is irresistible that we are dealing with a fundamental
+change in the structure of the individual atoms, which, one by one, are
+dissociating into simpler parts. We are watching the disintegration
+of the "atoms" of the chemist, hitherto believed indestructible and
+eternal, and measuring the liberation of some of the long-suspected
+store of internal atomic energy. We have stumbled on the transmutation
+dreamed by the alchemist, and discovered the process of a veritable
+evolution of matter.
+
+The transmutation theory of radio-activity was formulated by Rutherford
+(Rutherford, "Radio-activity" (2nd edition), Cambridge, 1905, page 307.)
+and Soddy in 1903. By its light, all recent work on the subject has been
+guided; it has stood the supreme test of a hypothesis, and shown power
+to suggest new investigations and to co-ordinate and explain them, when
+carried out. We have summarised the evidence which led to the conception
+of the theory; we have now to consider the progress which has been made
+in tracing the successive disintegration of radio-active atoms.
+
+Soon after the statement of the transmutation theory, a striking
+verification of one of its consequences appeared. The measurement of
+the magnetic and electric deflection of the alpha-rays suggested
+to Rutherford the idea that the stream of projectiles of which they
+consisted was a flight of helium atoms. Ramsay and Soddy, confining a
+minute bubble of radium emanation in a fine glass tube, were able
+to watch the development of the helium spectrum as, day by day, the
+emanation decayed. By isolating a very narrow pencil of alpha-rays,
+and watching through a microscope their impact on a fluorescent screen,
+Rutherford has lately counted the individual alpha-projectiles, and
+confirmed his original conclusion that their mass corresponded to that
+of helium atoms and their charge to double that on a univalent atom.
+("Proc. Roy. Soc." A, page 141, 1908.) Still more recently, he has
+collected the alpha-particles shot through an extremely thin wall of
+glass, and demonstrated by direct spectroscopic evidence the presence of
+helium. ("Phil. Mag." February 1909.)
+
+But the most thorough investigation of a radio-active pedigree is found
+in Rutherford's classical researches on the successive disintegration
+products of radium, in order to follow the evidence on which his results
+are founded, we must describe more fully the process of decay of the
+activity of a simple radio-active substance. The decay of activity of
+the body known as uranium-X is shown in a falling curve (Fig. 1.). It
+will be seen that, in each successive 22 days, the activity falls to
+half the value it possessed at the beginning.
+
+This change in a geometrical progression is characteristic of simple
+radio-active processes, and can be expressed mathematically by a simple
+exponential formula.
+
+As we have said above, solid bodies exposed to the emanations of radium
+or thorium become coated with a radio-active deposit. The rate of decay
+of this activity depends on the time of exposure to the emanation, and
+does not always show the usual simple type of curve. Thus the activity
+of a rod exposed to radium emanation for 1 minute decays in accordance
+with a curve (Fig. 2) which represents the activity as measured by the
+alpha-rays. If the electroscope be screened from the alpha-rays, it is
+found that the activity of the rod in beta- an gamma-rays increases for
+some 35 minutes and then diminishes (Fig. 3.).
+
+These complicated relations have been explained satisfactorily and
+completely by Rutherford on the hypothesis of successive changes of
+the radio-active matter into one new body after another. (Rutherford,
+"Radio-activity" (2nd edition), Cambridge, 1905, page 379.) The
+experimental curve represents the resultant activity of all the
+matter present at a given moment, and the process of disentangling the
+component effects consists in finding a number of curves, which express
+the rise and fall of activity of each kind of matter as it is produced
+and decays, and, fitted together, give the curve of the experiments.
+
+Other methods of investigation also are open. They have enabled
+Rutherford to complete the life-history of radium and its products, and
+to clear up doubtful points left by the analysis of the curves. By the
+removal of the emanation, the activity of radium itself has been shown
+to consist solely of alpha-rays. This removal can be effected by passing
+air through the solution of a radium salt. The emanation comes away, and
+the activity of the deposit which it leaves behind decays rapidly to a
+small fraction of its initial value. Again, some of the active deposits
+of the emanation are more volatile than others, and can be separated
+from them by the agency of heat.
+
+From such evidence Rutherford has traced a long series of disintegration
+products of radium, all but the first of which exist in much too minute
+quantities to be detected otherwise than by their radio-activities.
+Moreover, two of these products are not themselves appreciably
+radio-active, though they are born from radio-active parents, and give
+rise to a series of radio-active descendants. Their presence is inferred
+from such evidence as the rise of beta and gamma radio-activity in the
+solid newly deposited by the emanation; this rise measuring the growth
+of the first radio-active offspring of one of the non-active bodies.
+Some of the radium products give out alpha-rays only, one beta- and
+gamma-rays, while one yields all three types of radiation. The pedigree
+of the radium family may be expressed in the following table, the time
+noted in the second column being the time required for a given quantity
+to be half transformed into its next derivative.
+
+
+             Time of half      Radio-       Properties
+             decay             activity
+
+  Radium     About 2600 years  alpha rays   Element chemically analogous
+                                            to barium.
+
+  Emanation  3.8 days          alpha rays   Chemically inert gas;
+                                             condenses at -150 deg C.
+
+  Radium-A   3 minutes         alpha rays   Behaves as a solid deposited on
+                                             surfaces; concentrated on a
+                                             negative electrode.
+
+  Radium-B   21 minutes        no rays      Soluble in strong acids;
+                                             volatile at a white heat; more
+                                             volatile than A or C.
+
+  Radium-C   28 minutes        alpha, beta, Soluble in strong acids; less
+                               gamma rays    volatile than B.
+
+  Radium-D   about 40 years    no rays      Soluble in strong acids; volatile
+                                             below 1000 deg C.
+
+  Radium-E   6 days            beta, gamma  Non-volatile at 1000 deg C.
+                               rays
+
+  Radium-F   143 days          alpha rays   Volatile at 1000 deg C.
+                                             Deposited from solution on a
+                                             bismuth plate.
+
+
+Of these products, A, B, and C constitute that part of the active
+deposit of the emanation which suffers rapid decay and nearly disappears
+in a few hours. Radium-D, continually producing its short-lived
+descendants E and F, remains for years on surfaces once exposed to the
+emanation, and makes delicate radio-active researches impossible
+in laboratories which have been contaminated by an escape of radium
+emanation.
+
+A somewhat similar pedigree has been made out in the case of thorium.
+Here thorium-X is interposed between thorium and its short-lived
+emanation, which decays to half its initial quantity in 54 seconds. Two
+active deposits, thorium A and B, arise successively from the emanation.
+In uranium, we have the one obvious derivative uranium-X, and the
+question remains whether this one descent can be connected with any
+other individual or family. Uranium is long-lived, and emits only
+alpha-rays. Uranium-X decays to half value in 22 days, giving out beta-
+and gamma-rays. Since our evidence goes to show that radio-activity is
+generally accompanied by the production of new elements, it is natural
+to search for the substance of uranium-X in other forms, and perhaps
+under other names, rather than to surrender immediately our belief in
+the conservation of matter.
+
+With this idea in mind we see at once the significance of the
+constitution of uranium minerals. Formed in the remote antiquity of
+past geological ages, these minerals must become store-houses of all
+the products of uranium except those which may have escaped as gases
+or possibly liquids. Even gases may be expected to some extent to be
+retained by occlusion. Among the contents of uranium minerals, then, we
+may look for the descendants of the parent uranium. If the descendants
+are permanent or more long-lived than uranium, they will accumulate
+continually. If they are short-lived, they will accumulate at a steady
+rate till enough is formed for the quantity disintegrating to be equal
+to the quantity developed. A state of mobile equilibrium will then
+be reached, and the amount of the product will remain constant. This
+constant amount of substance will depend only on the amount of uranium
+which is its source, and, for different minerals, if all the product
+is retained, the quantity of the product will be proportional to the
+quantity of uranium. In a series of analyses of uranium minerals,
+therefore, we ought to be able to pick out its more short-lived
+descendants by seeking for instances of such proportionality.
+
+Now radium itself is a constituent of uranium minerals, and two series
+of experiments by R.J. Strutt and B.B. Boltwood have shown that the
+content of radium, as measured by the radio-activity of the emanation,
+is directly proportional to the content of uranium. (Strutt, "Proc.
+Roy. Soc." A, February 1905; Boltwood, "Phil. Mag." April, 1905.) In
+Boltwood's investigation, some twenty minerals, with amounts of uranium
+varying from that in a specimen of uraninite with 74.65 per cent.,
+to that in a monazite with 0.30 per cent., gave a ratio of uranium to
+radium, constant within about one part in ten.
+
+The conclusion is irresistible that radium is a descendant of uranium,
+though whether uranium is its parent or a more remote ancestor requires
+further investigation by the radio-active genealogist. On the hypothesis
+of direct parentage, it is easy to calculate that the amount of radium
+produced in a month by a kilogramme of a uranium salt would be enough
+to be detected easily by the radio-activity of its emanation. The
+investigation has been attempted by several observers, and the results,
+especially those of a careful experiment of Boltwood, show that from
+purified uranium salts the growth of radium, if appreciable at all, is
+much less than would be found if the radium was the first product of
+change of the uranium. It is necessary, therefore, to look for one or
+more intermediate substances.
+
+While working in 1899 with the uranium residues used by M. and Mme
+Curie for the preparation of radium, Debierne discovered and partially
+separated another radio-active element which he called actinium. It
+gives rise to an intermediate product actinium-X, which yields an
+emanation with the short half-life of 3.9 seconds. The emanation
+deposits two successive disintegration products actinium-A and
+actinium-B.
+
+Evidence gradually accumulated that the amounts of actinium in
+radio-active minerals were, roughly at any rate, proportional to the
+amounts of uranium. This result pointed to a lineal connection between
+them, and led Boltwood to undertake a direct attack on the problem.
+Separating a quantity of actinium from a kilogramme of ore, Boltwood
+observed a growth of 8.5 x (10 to the power -9) gramme of radium in
+193 days, agreeing with that indicated by theory within the limits of
+experimental error. ("American Journal of Science", December, 1906.)
+We may therefore insert provisionally actinium and its series of
+derivatives between uranium and radium in the radio-active pedigree.
+
+Turning to the other end of the radium series we are led to ask what
+becomes of radium-F when in turn it disintegrates? What is the final
+non-active product of the series of changes we have traced from uranium
+through actinium and radium?
+
+One such product has been indicated above. The alpha-ray particles
+appear to possess the mass of helium atoms, and the growth of helium has
+been detected by its spectrum in a tube of radium emanation. Moreover,
+helium is found occluded in most if not all radio-active minerals in
+amount which approaches, but never exceeds, the quantity suggested by
+theory. We may safely regard such helium as formed by the accumulation
+of alpha-ray particles given out by successive radio-active changes.
+
+In considering the nature of the residue left after the expulsion of the
+five alpha-particles, and the consequent passage of radium to radium-F
+we are faced by the fact that lead is a general constituent of uranium
+minerals. Five alpha-particles, each of atomic weight 4, taken from the
+atomic weight (about 225) of radium gives 205--a number agreeing fairly
+well with the 207 of lead. Since lead is more permanent than uranium, it
+must steadily accumulate, no radio-active equilibrium will be reached,
+and the amount of lead will depend on the age of the mineral as well as
+on the quantity of uranium present in it. In primary minerals from
+the same locality, Boltwood has shown that the contents of lead are
+proportional to the amounts of uranium, while, accepting this theory,
+the age of minerals with a given content of uranium may be calculated
+from the amount of lead they contain. The results vary from 400 to
+2000 million years. ("American Journal of Science", October, 1905, and
+February, 1907.)
+
+We can now exhibit in tabular form the amazing pedigree of radio-active
+change shown by this one family of elements. An immediate descent is
+indicated by >, while one which may either be immediate or involve an
+intermediate step is shown by.... No place is found in this pedigree
+for thorium and its derivatives. They seem to form a separate and
+independent radio-active family.
+
+
+                       Atomic Weight  Time of half     Radio-Activity
+                                         decay
+
+   Uranium               238.5                         alpha
+
+   Uranium-X             ?            22 days          beta, gamma
+   ...
+   Actinium              ?            ?                no rays
+
+   Actinium-X            ?            10.2 days        alpha (beta, gamma)
+
+   Actinium Emanation    ?            3.9 seconds      alpha
+
+   Actinium-A            ?            35.7 minutes     no rays
+
+   Actinium-B            ?            2.15 minutes      alpha, beta, gamma
+   ...
+   Radium                225          about 2600 years  alpha
+
+   Radium Emanation      ?            3.8 days          alpha
+
+   Radium-A              ?            3 minutes         alpha
+
+   Radium-B              ?            21 minutes        no rays
+
+   Radium-C              ?            28 minutes        alpha, beta, gamma
+
+   Radium-D              ?            about 40 years    no rays
+
+   Radium-E              ?            6 days            beta (gamma)
+
+   Radium-F              ?            143 days          alpha
+   ...
+   Lead                  207          ?                 no rays
+
+
+As soon as the transmutation theory of radio-activity was accepted,
+it became natural to speculate about the intimate structure of the
+radio-active atoms, and the mode in which they broke up with the
+liberation of some of their store of internal energy. How could we
+imagine an atomic structure which would persist unchanged for long
+periods of time, and yet eventually spontaneously explode, as here an
+atom and there an atom reached a condition of instability?
+
+The atomic theory of corpuscles or electrons fortunately was ready to
+be applied to this new problem. Of the resulting speculations the most
+detailed and suggestive is that of J.J. Thomson. ("Phil. Mag." March,
+1904.) Thomson regards the atom as composed of a number of mutually
+repelling negative corpuscles or electrons held together by some central
+attractive force which he represents by supposing them immersed in a
+uniform sphere of positive electricity. Under the action of the two
+forces, the electrons space themselves in symmetrical patterns, which
+depend on the number of electrons. Three place themselves at the corner
+of an equilateral triangle, four at those of a square, and five form
+a pentagon. With six, however, the single ring becomes unstable, one
+corpuscle moves to the middle and five lie round it. But if we imagine
+the system rapidly to rotate, the centrifugal force would enable the
+six corpuscles to remain in a single ring. Thus internal kinetic energy
+would maintain a configuration which would become unstable as the energy
+drained away. Now in a system of electrons, electromagnetic radiation
+would result in a loss of energy, and at one point of instability we
+might well have a sudden spontaneous redistribution of the constituents,
+taking place with an explosive violence, and accompanied by the ejection
+of a corpuscle as a beta-ray, or of a large fragment of the atom as an
+alpha-ray.
+
+The discovery of the new property of radio-activity in a small number of
+chemical elements led physicists to ask whether the property might not
+be found in other elements, though in a much less striking form. Are
+ordinary materials slightly radio-active? Does the feeble electric
+conductivity always observed in the air contained within the walls of
+an electroscope depend on ionizing radiations from the material of the
+walls themselves? The question is very difficult, owing to the wide
+distribution of slight traces of radium. Contact with radium emanation
+results in a deposit of the fatal radium-D, which in 40 years is but
+half removed. Is the "natural" leak of a brass electroscope due to
+an intrinsic radio-activity of brass, or to traces of a radio-active
+impurity on its surface? Long and laborious researches have succeeded in
+establishing the existence of slight intrinsic radio-activity in a
+few metals such as potassium, and have left the wider problem still
+unsolved.
+
+It should be noted, however, that, even if ordinary elements are not
+radio-active, they may still be undergoing spontaneous disintegration.
+The detection of ray-less changes by Rutherford, when those changes
+are interposed between two radio-active transformations which can
+be followed, show that spontaneous transmutation is possible without
+measureable radio-activity. And, indeed, any theory of disintegration,
+such as Thomson's corpuscular hypothesis, would suggest that atomic
+rearrangements are of much more general occurrence than would be
+apparent to one who could observe them only by the effect of the
+projectiles, which, in special cases, owing to some peculiarity of
+atomic configuration, happened to be shot out with the enormous velocity
+needed to ionize the surrounding gas. No evidence for such ray-less
+changes in ordinary elements is yet known, perhaps none may ever be
+obtained; but the possibility should not be forgotten.
+
+In the strict sense of the word, the process of atomic disintegration
+revealed to us by the new science of radio-activity can hardly be called
+evolution. In each case radio-active change involves the breaking up of
+a heavier, more complex atom into lighter and simpler fragments. Are
+we to regard this process as characteristic of the tendencies in accord
+with which the universe has reached its present state, and is passing
+to its unknown future? Or have we chanced upon an eddy in a backwater,
+opposed to the main stream of advance? In the chaos from which the
+present universe developed, was matter composed of large highly complex
+atoms, which have formed the simpler elements by radio-active or
+ray-less disintegration? Or did the primaeval substance consist
+of isolated electrons, which have slowly come together to form the
+elements, and yet have left here and there an anomaly such as that
+illustrated by the unstable family of uranium and radium, or by some
+such course are returning to their state of primaeval simplicity?
+
+
+
+
+INDEX.
+
+Abraxas grossulariata.
+
+Acquired characters, transmission of.
+
+Acraea johnstoni.
+
+Adaptation.
+
+Adloff.
+
+Adlumia cirrhosa.
+
+Agassiz, A.
+
+Agassiz, L.
+
+Alexander.
+
+Allen, C.A.
+
+Alternation of generations.
+
+Ameghino.
+
+Ammon, O., Works of.
+
+Ammonites, Descent of.
+
+Amphidesmus analis.
+
+Anaea divina.
+
+Andrews, C.W.
+
+Angiosperms, evolution of.
+
+Anglicus, Bartholomaeus.
+
+Ankyroderma.
+
+Anomma.
+
+Antedon rosacea.
+
+Antennularia antennina.
+
+Anthropops.
+
+Ants, modifications of.
+
+Arber, E.A.N.,--and J. Parkin, on the origin of Angiosperms.
+
+Archaeopteryx.
+
+Arctic regions, velocity of development of life in.
+
+Ardigo.
+
+Argelander.
+
+Argyll, Huxley and the Duke of.
+
+Aristotle.
+
+Arrhenius.
+
+Asterias, Loeb on hybridisation of.
+
+Autogamy.
+
+Avena fatua.
+
+Avenarius.
+
+Bacon, on mutability of species.
+
+Baehr, von, on Cytology.
+
+Baer, law of von.
+
+Bain.
+
+Baldwin, J.M.
+
+Balfour, A.J.
+
+Ball, J.
+
+Barber, Mrs M.E., on Papilio nireus.
+
+Barclay, W.
+
+Barratt.
+
+Bary, de.
+
+Bates, H.W., on Mimicry.--Letters from Darwin to.--elsewhere.
+
+Bateson, A.
+
+BATESON, W., on "Heredity and Variation in Modern lights".--on
+discontinuous evolution.--on hybridisation.
+
+Bateson, W. and R.P. Gregory.
+
+Bathmism.
+
+Beche, de la.
+
+Beck, P.
+
+Becquerel, H.
+
+Beebe, C.W., on the plumage of birds.--on sexual selection.
+
+Beguyer de Chancourtois.
+
+Bell's (Sir Charles) "Anatomy of Expression".
+
+Belopolsky.
+
+Belt, T., on Mimicry.
+
+Beneden, E. van.
+
+Benson, M.
+
+Bentham, G., on Darwin's species-theory.--on geographical distribution.
+
+Bentham, Jeremy.
+
+Bergson, H.
+
+Berkeley.
+
+Berthelot.
+
+Betham, Sir W.
+
+Bickford, E., experiments on degeneration by.
+
+Bignonia capreolata.
+
+Biophores.
+
+Birds, geological history of.
+
+Blanford, W.T.
+
+Blaringhem, on wounding.
+
+Blumenbach.
+
+Bodin.
+
+Boltwood, B.B.
+
+Bonald, on war.
+
+Bonnet.
+
+Bonney, T.G.
+
+Bonnier, G.
+
+Bopp, F., on language.
+
+BOUGLE C., on "Darwinism and Sociology".
+
+Bourdeau.
+
+Bourget, P.
+
+Boutroux.
+
+Boveri, T.
+
+Brachiopods, history of.
+
+Brassica, hybrids of.
+
+Brassica Napus.
+
+Broca.
+
+Brock, on Kant.
+
+Brown, Robert.
+
+Brugmann and Osthoff.
+
+Brugmann.
+
+Brunetiere.
+
+Bruno, on Evolution.
+
+Buch, von.
+
+Bucher, K.
+
+Buckland.
+
+Buckle.
+
+Buffon.
+
+Burchell, W.J.
+
+Burck, W.
+
+Burdon-Sanderson, J., letter from.
+
+BURY, J.B., on "Darwinism and History".
+
+Butler, A.G.
+
+Butler, Samuel.
+
+Butschli, O.
+
+Butterflies, mimicry in.--sexual characters in.
+
+Cabanis.
+
+Campbell.
+
+Camels, geological history of.
+
+Camerarius, R.J.
+
+Candolle, A. de.
+
+Cannon and Davenport, experiments on Daphniae by.
+
+Capsella bursapastoris.
+
+Carneri.
+
+Castnia linus.
+
+Catasetum barbatum.
+
+Catasetum tridentatum.
+
+Caterpillars, variation in.
+
+Celosia, variability of.
+
+Cereals, variability in.
+
+Cesnola, experiments on Mantis by.
+
+Chaerocampa, colouring of.
+
+Chambers, R., "The Vestiges of Creation" by.
+
+Chromosomes and Chromomeres.
+
+Chun.
+
+Cieslar, experiments by.
+
+Circumnutation, Darwin on.
+
+Claus.
+
+Cleistogamy.
+
+Clerke, Miss A.
+
+Clodd, E.
+
+Cluer.
+
+Clytus arietis.
+
+Coadaptation.
+
+Codrington.
+
+Cohen and Peter.
+
+Collingwood.
+
+Colobopsis truncata.
+
+Colour, E.B. Poulton on The Value in the Struggle for life
+of.--influence and temperature on changes in.--in relation to Sexual
+Selection.
+
+Colours, incidental.--warning.
+
+Comte, A.
+
+Condorcet.
+
+Cope.
+
+Coral reefs, Darwin's work on.
+
+Correlation of organisms, Darwin's idea of the.
+
+Correlation of parts.
+
+Corydalis claviculata.
+
+Cournot.
+
+Couteur, Col. Le.
+
+Crooks, Sir William.
+
+Cruger, on Orchids.
+
+Cunningham and Marchand, on the brain.
+
+Curie, M. and Mme.
+
+Cuvier.
+
+Cycadeoidea dacotensis.
+
+Cycads, geological history of.
+
+Cystidea, an ancient group.
+
+Cytology and heredity.
+
+Cytolysis and fertilisation.
+
+Czapek.
+
+Dalton's atomic theory.
+
+Dana, J.D., on marine faunas.
+
+Danaida chrysippus.
+
+Danaida genutia.
+
+Danaida plexippus.
+
+Dante.
+
+Dantec, Le,
+
+Darwin, Charles, as an Anthropologist.--on ants.--and the "Beagle"
+Voyage.--on the Biology of Flowers.--as a Botanist.--his influence on
+Botany.--and S. Butler.--at Cambridge.--on Cirripedia.--on climbing
+plants.--on colour.--on coral reefs.--on the Descent of Man.--his work
+on Drosera.--at Edinburgh.--his influence on Animal Embryology.--on
+Geographical Distribution.--his work on Earthworms.--evolutionist
+authors referred to in the "Origin" by.--and E. Forbes.--on the
+geological record.--and Geology.--his early love for geology.--his
+connection with the Geological Society of London.--and Haeckel.--and
+Henslow.--and History.--and Hooker.--and Huxley.--on ice-action.--on
+igneous rocks.--on Lamarck.--on Language.--his Scientific Library.--and
+the Linnean Society.--and Lyell.--and Malthus.--on Patrick Matthew.--on
+mental evolution.--on Mimicry.--a "Monistic Philosopher."--on the
+movements of plants.--on Natural Selection.--a "Naturalist for
+Naturalists."--on Paley.
+
+Darwin, Charles, his Pangenesis hypothesis.--on the permanence
+of continents.--his personality.--his influence on
+Philosophy.--predecessors of.--his views on religion, etc.--his
+influence on religious thought.--his influence on the study of
+religions.--his methods of research.--and Sedgwick.--on Sexual
+Selection.--the first germ of his species theory.--on H.
+Spencer.--causes of his success.--on Variation.--on the "Vestiges
+of Creation".--on volcanic islands.--and Wallace.--letter to Wallace
+from.--letter to E.B. Wilson from.
+
+Darwin, E., on the colour of animals.--Charles Darwin's reference
+to.--on evolution.
+
+DARWIN, F., on "Darwin's work on the Movements of Plants".--on Darwin
+as a botanist.--observations on Earthworms by.--on Lamarckism.--on
+Memory.--on Prichard's "Anticipations".--various.
+
+DARWIN, SIR G., on "The Genesis of Double Stars".--on the earth's mass.
+
+Darwin, H.
+
+Darwin, W.
+
+Darwinism, Sociology, Evolution and.
+
+Davenport and Cannon, experiments on Daphniae by.
+
+David, T.E., his work on Funafuti.
+
+Death, cause of natural.
+
+Debey, on Cretaceous plants.
+
+Debierne.
+
+Degeneration.
+
+Delage, experiments on parthenogenesis by.
+
+Delbruck.
+
+Democritus.
+
+Deniker.
+
+Descartes.
+
+Descent, history of doctrine of.
+
+"Descent of Man", G. Schwalbe on "The".--Darwin on Sexual Selection in
+"The".--rejection in Germany of "The".
+
+Desmatippus.
+
+Desmoulins, A., on Geographical Distribution.
+
+Detto.
+
+Development, effect of environment on.
+
+Dianthus caryophyllus.
+
+Diderot.
+
+Digitalis purpurea.
+
+Dimorphism, seasonal.
+
+Dismorphia astynome.
+
+Dismorphia orise.
+
+Distribution, H. Gadow on Geographical.--Sir W. Thiselton-Dyer on.
+
+Dittrick, O.
+
+Dixey, F.A., on the scent of Butterflies.
+
+Dolichonyx oryzivorus.
+
+Dorfmeister.
+
+Down, Darwin at.
+
+Draba verna.
+
+Dragomirov.
+
+Driesch, experiments by.--elsewhere.
+
+Drosera, Darwin's work on.
+
+Dryopithecus.
+
+Dubois, E., on Pithecanthropus.
+
+Duhring.
+
+Duhamel.
+
+Duncan, J.S.
+
+Duncan, P.B.
+
+Duns Scotus.
+
+Duret, C.
+
+Durkheim, on division of labour.
+
+Dutrochet.
+
+Echinoderms, ancestry of.
+
+Ecology.
+
+Eimer.
+
+Ekstam.
+
+Elephants, geological history of.
+
+Elymnias phegea.
+
+E. undularis.
+
+Embleton, A.L.
+
+Embryology, A. Sedgwick on the influence of Darwin on.
+
+Embryology, as a clue to Phylogeny.--the Origin of Species and.
+
+Empedocles.
+
+Engles.
+
+Environment, action of.--Klebs on the influence on plants of.--Loeb on
+experimental study in relation to.
+
+Eohippus.
+
+Epicurus, a poet of Evolution.
+
+Eristalis.
+
+Ernst.
+
+Ernst, A., on the Flora of Krakatau.
+
+Eschscholzia californica.
+
+Espinas.
+
+Eudendrium racemosum.
+
+Evolution, in relation to Astronomy.--and creation.--conception
+of.--discontinuous.--experimental.--factors of.--fossil plants
+as evidence of.--and language.--of matter, W.C.D. Whetham
+on.--mental.--Lloyd Morgan on mental factors in.--Darwinism and
+Social.--Saltatory.--Herbert Spencer on.--Uniformitarian.--Philosophers
+and modern methods of studying.
+
+Expression of the Emotions.
+
+Fabricius, J.C., on geographical distribution.
+
+Farmer, J.B.
+
+Farrer, Lord.
+
+Fearnsides, W.G.
+
+Felton, S., on protective resemblance.
+
+Ferri.
+
+Ferrier, his work on the brain.
+
+Fertilisation, experimental work on animal-.
+
+Fertilisation of Flowers.
+
+Fichte.
+
+Field, Admiral A.M.
+
+Fischer, experiments on Butterflies by.
+
+Fitting.
+
+Flemming, W.
+
+Flourens.
+
+Flowering plants, ancestry of.
+
+Flowers, K. Goebel on the Biology of.
+
+Flowers and Insects.
+
+Flowers, relation of external influences to the production of.
+
+Fol, H.
+
+Forbes, E.--and C. Darwin.
+
+Ford, S.O. and A.C. Seward, on the Araucarieae.
+
+Fossil Animals, W.B. Scott on their bearing on evolution.
+
+Fossil Plants, D.H. Scott on their bearing on evolution.
+
+Fouillee.
+
+Fraipont, on skulls from Spy.
+
+FRAZER, J.G., on "Some Primitive Theories of the Origin of
+Man".--various.
+
+Fruwirth.
+
+Fumaria officinalis.
+
+Funafuti, coral atoll of.
+
+Fundulus.
+
+F. heteroclitus.
+
+GADOW, H., on "Geographical Distribution of Animals".--elsewhere.
+
+Gartner, K.F.
+
+Gallus bankiva.
+
+Galton, F.
+
+Gamble, F.W. and F.W. Keeble.
+
+Gasca, La.
+
+Geddes, P.
+
+Geddes, P. and A.W. Thomson.
+
+Gegenbauer.
+
+Geikie, Sir A.
+
+Geitonogamy.
+
+Genetics.
+
+Geographical Distribution of Animals.--of Plants.--influence of "The
+Origin of Species" on.--Wallace's contribution to.
+
+Geography of former periods, reconstruction of.
+
+Geology, Darwin and.
+
+Geranium spinosum.
+
+Germ-plasm, continuity of.--Weismann on.
+
+Germinal Selection.
+
+Gibbon.
+
+Gilbert.
+
+GILES, P., on "Evolution and the Science of Language".
+
+Giuffrida-Ruggeri.
+
+Giotto.
+
+Gizycki.
+
+Glossopteris Flora.
+
+Gmelin.
+
+Godlewski, on hybridisation.
+
+GOEBEL, K., on "The Biology of Flowers".--his work on Morphology.
+
+Goethe and Evolution.--on the relation between Man and
+Mammals.--elsewhere.
+
+Goldfarb.
+
+Gondwana Land.
+
+Goodricke, J.
+
+Gore, Dr.
+
+Gorjanovic-Kramberger.
+
+Gosse, P.H.
+
+Grabau, A.W., on Fusus.
+
+Grand'Eury, F.C., on fossil plants.
+
+Grapta C. album.
+
+Gravitation, effect on life-phenomena of.
+
+Gray, Asa.
+
+Gregoire, V.
+
+Groom, T.T., on heliotropism.
+
+Groos.
+
+Grunbaum, on the brain.
+
+Guignard, L.
+
+Gulick.
+
+Guppy, on plant-distribution.
+
+Guyau.
+
+Gwynne-Vaughan, D.T., on Osmundaceae.
+
+Gymnadenia conopsea.
+
+Haberlandt, G.
+
+Haddon, A.C.
+
+HAECKEL, E., on "Charles Darwin as an Anthropologist".--on Colour.--and
+Darwin.--on the Descent of Man.--contributions to Evolution by.
+
+Haeckel, E., on Lamarck.--on Language.--a leader in the Darwinian
+controversy.--on Lyell's influence on Darwin.--various.
+
+Hacker.
+
+Hagedoorn, on hybridisation.
+
+Hales, S.
+
+Hansen.
+
+Harker, A.
+
+HARRISON, J.E., on "The Influence of Darwinism on the Study of
+Religions".
+
+Hartmann, von.
+
+Harvey.
+
+Haupt, P., on Language.
+
+Haycraft.
+
+Hays, W.M.
+
+Hegel.
+
+Heliconius narcaea.
+
+Heliotropism in animals.
+
+Henslow, Rev. J.S. and Darwin.
+
+Hensen, Van.
+
+Herbst, his experiments on sea urchins.
+
+Heracleitus.
+
+Herder.
+
+Heredity and Cytology.--Haeckel on.--and Variation.--various.
+
+Hering, E., on Memory.
+
+Herschel, J.
+
+Hertwig, R.
+
+Hertwig, O.
+
+Hertz.
+
+Heteromorphosis.
+
+Heterostylism.
+
+Heuser, E.
+
+Hewitt.
+
+Heyse's theory of language.
+
+Hinde, G.J., his work on Funafuti.
+
+Hipparion.
+
+Hippolyte cranchii.
+
+Hirase.
+
+History, Darwin and.
+
+Hobbes, T.
+
+Hobhouse.
+
+HOFFDING, H., on "The Influence of the Conception of Evolution on Modern
+Philosophy".
+
+Hofmeister, W.
+
+Holmes, S.J., on Arthropods.
+
+Holothurians, calcareous bodies in skin of.
+
+Homo heidelbergensis.
+
+Homo neandertalensis.
+
+Homo pampaeus.
+
+Homo primigenius.
+
+Homunculus.
+
+Hooker, Sir J.D., and Darwin.--on Distribution of Plants.--on
+Ferns.--Letter to the Editor from.
+
+Horner, L.
+
+Horse, Geological history of the.
+
+Huber.
+
+Hubert and Mauss.
+
+Hubrecht, A.R.W.
+
+Hugel, F. von.
+
+Humboldt, A. von.
+
+Humboldt, W. von.
+
+Hume.
+
+Hutcheson.
+
+Hutton.
+
+Huxley, T.H., and Darwin.--and the Duke of Argyll.--on Embryology.--on
+Geographical Distribution.--on Lamarck.--Letter to J.W. Judd from.--on
+Lyell.--on Man.--on "The Origin of Species".--on Selection.--on
+Teleology.--on transmission of acquired characters.--various.
+
+Hybridisation.
+
+Hybrids, Sterility of.
+
+Hyracodon.
+
+Iberis umbellata.
+
+Ikeno.
+
+Imperfection of the Geological Record.
+
+Ingenhousz, on plant physiology.
+
+Inheritance of acquired characters.
+
+Insects and Flowers.
+
+Instinct.
+
+Instincts, experimental control of animal.
+
+Ipomaea purpurea.
+
+Irish Elk, an example of co-adaptation.
+
+Jacobian figures.
+
+Jacoby, "Studies in Selection" by.
+
+James, W.
+
+Janczewski.
+
+Jeans, J.H.
+
+Jennings, H.S., on Paramoecium.
+
+Jentsch.
+
+Jespersen, Prof., Theory of.
+
+Johannsen, on Species.
+
+Jones, Sir William, on Language.
+
+Jordan.
+
+JUDD, J.W., on "Darwin and Geology".
+
+Kallima, protective colouring of.
+
+Kallima inachis.
+
+Kammerer's experiments on Salamanders.
+
+Kant, I.
+
+Keane, on the Primates.
+
+Keeble, F.W. and F.W. Gamble, on Colour-change.
+
+Keith, on Anthropoid Apes.
+
+Kellogg, V., on heliotropism.
+
+Kepler.
+
+Kerguelen Island.
+
+Kidd.
+
+Kidston, R., on fossil plants.
+
+Killmann, on origin of human races.
+
+King, Sir George.
+
+Klaatsch, on Ancestry of Man.
+
+Klaatsch and Hauser.
+
+KLEBS, G., on "The influence of Environment on the forms of plants".
+
+Kniep.
+
+Knies.
+
+Knight, A., experiments on plants by.--on Geotropism.
+
+Knight-Darwin law.
+
+Knuth.
+
+Kolliker, his views on Evolution.
+
+Kolreuter, J.G.
+
+Kohl.
+
+Korschinsky.
+
+Kowalevsky, on fossil horses.
+
+Krakatau, Ernst on the Flora of.
+
+Krause, E.
+
+Kreft, Dr.
+
+Kropotkin.
+
+Kupelwieser, on hybridisation.
+
+Lagopus hyperboreus.
+
+Lamarck, his division of the Animal Kingdom.--Darwin's opinion of.--on
+Evolution.--on Man.--various.
+
+Lamarckian principle.
+
+Lamb, C.
+
+Lamettrie.
+
+Lamprecht.
+
+Lanessan, J.L. de.
+
+Lang.
+
+Lange.
+
+Language, Darwin on.--Evolution and the Science of.--various.
+
+Lankester, Sir E. Ray, on degeneration.--on educability.--on the
+germ-plasm theory.--elsewhere.
+
+Lapouge, Vacher de.
+
+Larmor, J.
+
+Lartet, M.E.
+
+Lassalle.
+
+Lathyrus odoratus.
+
+Lavelaye, de.
+
+Lawrence, W.
+
+Lehmann.
+
+Lehmann-Nitsche.
+
+Leibnitz.
+
+Lepidium Draba.
+
+Lepidoptera, variation in.
+
+Leskien, A., on language.
+
+Lessing.
+
+Leucippus.
+
+Levi, E.
+
+Lewes, G.H.
+
+Lewin, Capt.
+
+Liapounoff.
+
+Liddon, H.P.
+
+Light, effect on organisms of.
+
+Limenitis archippus.--arthemis.
+
+Linnaeus.
+
+Livingstone, on plant-forms.
+
+Llamas, geological history of.
+
+Lockyer, Sir N.
+
+Locy, W.A.
+
+LOEB, J., on "The Experimental Study of the influence of environment on
+Animals.
+
+Loew, E.
+
+Longstaff, G.B., on the Scents of Butterflies.
+
+Lorentz.
+
+Lotsy, J.P.
+
+Love, A.E.W.
+
+Lovejoy.
+
+Lubbock.
+
+Lucas, K.
+
+Lucretius, a poet of Evolution.
+
+Lumholtz, C.
+
+Luteva macrophthalma.
+
+Lycorea halia.
+
+Lyell, Sir Charles, and Darwin.--the influence of.--on geographical
+distribution.--on "The Origin of Species".--on the permanence of
+Ocean-basins.--publication of the "Principles" by.--the uniformitarian
+teaching of.
+
+Lythrum salicaria.
+
+Macacus, ear of.
+
+MacDougal, on wounding.
+
+Mach, E.
+
+Macromytis flexuosa, colour-change in.
+
+Magic and religion.
+
+Mahoudeau.
+
+Maillet, de.
+
+Majewski.
+
+Malthus, his influence on Darwin.--various.
+
+Mammalia, history of.
+
+Man, Descent of.--J.G. Frazer on some primitive theories of the origin
+of.--mental and moral qualities of animals and.--pre-Darwinian views on
+the Descent of.--religious views of primitive.--Tertiary flints worked
+by.
+
+"Man", G. Schwalbe on Darwin's "Descent of".
+
+Manouvrier.
+
+Mantis religiosa, colour experiments on.
+
+Marett, R.R.
+
+Markwick.
+
+Marshall, G.A.K.
+
+Marx.
+
+Massart.
+
+Masters, M.
+
+Matonia pectinata.
+
+Matthew, P., and Natural Selection.
+
+Maupertuis.
+
+Maurandia semperflorens.
+
+Mauss and Herbert.
+
+Mauthner.
+
+Maxwell.
+
+Maxwell, Clerk.
+
+Mayer, R.
+
+Mechanitis lysimnia.
+
+Meehan, T.
+
+Meldola, R., Letters from Darwin to.
+
+Melinaea ethra.
+
+Mendel.
+
+Mendeleeff.
+
+Merrifield.
+
+Merz, J.T.
+
+Mesembryanthemum truncatum.
+
+Mesohippus.
+
+Mesopithecus.
+
+Metschnikoff.
+
+Mill, J.S.
+
+Mimicry.--H.W. Bates on.--F. Muller on.
+
+Mimulus luteus.
+
+Miquel, F.W.A.
+
+Mobius.
+
+Mohl, H. von.
+
+Moltke, on war.
+
+Monachanthus viridis.
+
+Monkeys, fossil.
+
+Montesquieu.
+
+Montgomery, T.H.
+
+Monstrosoties.
+
+Monticelli.
+
+Moore, J.E.S.
+
+MORGAN, C. LLOYD, on "Mental Factors in Evolution".--on Organic
+Selection.
+
+Morgan, T.H.
+
+Morse, E.S., on colour.
+
+Morselli.
+
+Mortillet.
+
+Moseley.
+
+Mottier, M.
+
+Muller, Fritz, "Fur Darwin" by.--on Mimicry.
+
+Muller, Fritz.
+
+Muller, J.
+
+Muller, Max, on language.
+
+Murray, A., on geographical distribution.
+
+Murray, G.
+
+Mutability.
+
+Mutation.
+
+Myanthus barbatus.
+
+Myers, G.W., on Eclipses.
+
+Nageli.
+
+Nathorst, A.G.
+
+Nathusius.
+
+Natural Selection, and adaptation.--Darwin's views on.--Darwin and
+Wallace on.--and design.--and educability.--Fossil plants in relation
+to.--and human development.--and Mimicry.--and Mutability.--various.
+
+Naudin.
+
+Neandertal skulls.
+
+Nemec.
+
+Neoclytus curvatus.
+
+Neodarwinism.
+
+Neumayr, M.
+
+Newton, A.
+
+Newton, I.
+
+Niebuhr.
+
+Nietzsche.
+
+Nilsson, on cereals.
+
+Nitsche.
+
+Noire.
+
+Noll.
+
+Novicow.
+
+Nuclear division.
+
+Nussbaum, M.
+
+Nuttall, G.H.F.
+
+Occam.
+
+Odin.
+
+Oecology, see Ecology.
+
+Oenothera biennis.
+
+Oenothera gigas.
+
+Oenothera Lamarckiana.
+
+Oenothera muricata.
+
+Oenothera nanella.
+
+Oestergren, on Holothurians.
+
+Oken, L.
+
+Oliver, F.W., on Palaeozoic Seeds.
+
+Ononis minutissima.
+
+Ophyrs apifera.
+
+Orchids, Darwin's work on the fertilisation of.
+
+Organic Selection.
+
+"Origin of Species", first draft of the.--geological chapter in the.
+
+Orthogenesis.
+
+Ortmann, A.E.
+
+Osborn, H.F.--"From the Greeks to Darwin" by.
+
+Osthoff and Brugmann.
+
+Ostwald, W.
+
+Ovibos moschatus.
+
+Owen, Sir Richard.
+
+Oxford, Ashmolean Museum at.
+
+Packard, A.S.
+
+Palaeontological Record, D.H. Scott on the.--W.B. Scott on the.
+
+Palaeopithecus.
+
+Paley.
+
+Palitzch, G.
+
+Palm.
+
+Pangenesis.
+
+Panmixia, Weismann's principle of.
+
+Papilio dardanus.
+
+Papilio meriones.
+
+Papilio merope.
+
+Papilio nireus.
+
+Paramoecium, Jennings on.
+
+Parker, G.H., on Butterflies.
+
+Parkin, J. and E.A.N. Arber, on the origin of Angiosperms.
+
+Parthenogenesis, artificial.
+
+Paul, H. and Wundt.
+
+Pearson, K.
+
+Peckham, Dr and Mrs, on the Attidae.
+
+Penck.
+
+Penzig.
+
+Peripatus, distribution of.
+
+Peridineae.
+
+Permanence of continents.
+
+Perrier, E.
+
+Perrhybris pyrrha.
+
+Perthes, B. de.
+
+Peter, on sea urchin's eggs.
+
+Petunia violacea.
+
+Pfeffer, W.
+
+Pfitzner, W.
+
+Pflueger.
+
+Phillips.
+
+Philosophy, influence of the conception of evolution on modern.
+
+Phryniscus nigricans.
+
+Phylogeny, embryology as a clue to.--Palaeontological evidence on.
+
+Physiology of plants, development of.
+
+Piccard, on Geotropism.
+
+Pickering, spectroscopic observations by.
+
+Piranga erythromelas.
+
+Pisum sativum.
+
+Pithecanthropus.
+
+Pitheculites.
+
+Planema epaea.
+
+Plants, Darwin's work on the movements of.--geographical distribution
+of.--Palaeontological record of fossil.
+
+Platanthera bifolia.
+
+Plate.
+
+Plato.
+
+Playfair.
+
+Pliopithecus.
+
+Pocock, R.I.
+
+Poincare.
+
+Polarity, Vochting on.
+
+Polymorphic species.--variability in cereals.
+
+Polypodium incanum.
+
+Porthesia chrysorrhoea.
+
+Potonie, R.
+
+Pouchet, G.
+
+POULTON, E.B., on "The Value of Colour in the Struggle for
+Life".--experiments on Butterflies by.--on J.C. Prichard.--on
+Mimicry.--various.
+
+Pratt.
+
+Pratz, du.
+
+Premutation.
+
+Preuss, K. Th.
+
+Prichard, J.C.
+
+Primula, heterostylism in.
+
+Primula acaulis.
+
+Primula elatior.
+
+Primula officinalis.
+
+Promeces viridis.
+
+Pronuba yuccasella.
+
+Protective resemblance.
+
+Protocetus.
+
+Protohippus.
+
+Psychology.
+
+Pteridophytes, history of.
+
+Pteridospermeae.
+
+Pucheran.
+
+Pusey.
+
+Quatrefages, A. de.
+
+Quetelet, statistical investigations by.
+
+Rabl, C.
+
+Radio-activity.
+
+Radiolarians.
+
+Raimannia odorata.
+
+Ramsay, Sir W. and Soddy.
+
+Ranke.
+
+Rau, A.
+
+Ray, J.
+
+Reade, Mellard.
+
+Recapitulation, the theory of.
+
+Reduction.
+
+Regeneration.
+
+Reid, C.
+
+Reinke.
+
+Religion, Darwin's attitude towards.--Darwin's influence on the study
+of.--and Magic.
+
+Religious thought, Darwin's influence on.
+
+Renard, on Darwin's work on volcanic islands.
+
+Reproduction, effect of environment on.
+
+Reptiles, history of.
+
+Reversion.
+
+Rhinoceros, the history of the.
+
+Ridley, H.N.
+
+Riley, C.V.
+
+Ritchie.
+
+Ritual.
+
+Roberts, A.
+
+Robertson, T.B.
+
+Robinet.
+
+Rolfe, R.A.
+
+Rolph.
+
+Romanes, G.J.
+
+Rothert.
+
+Roux.
+
+Rozwadowski, von.
+
+Ruskin.
+
+Rutherford, E.
+
+Rutot.
+
+Sachs, J.
+
+St Hilaire, E.G. de.
+
+Salamandra atra.
+
+Salamandra maculosa.
+
+Saltatory Evolution, (see also Mutations).
+
+Sanders, experiments on Vanessa by.
+
+Saporta, on the Evolution of Angiosperms.
+
+Sargant, Ethel, on the Evolution of Angiosperms.
+
+Savigny.
+
+Scardafella inca.
+
+Scent, in relation to Sexual Selection.
+
+Scharff, R.F.
+
+Schelling.
+
+Schlegel.
+
+Schleicher, A., on language.
+
+Schleiden and Schwann, Cell-theory of.
+
+Schmarda, L.K., on geographical distribution.
+
+Schoetensack, on Homo heidelbergensis.
+
+Schreiner, K.E.
+
+Schubler, on cereals.
+
+Schultze, O., experiments on Frogs.
+
+Schur.
+
+Schutt.
+
+SCHWALBE, G., on "The Descent of Man".
+
+Sclater, P.L., on geographical distribution.
+
+SCOTT, D.H., on "The Palaeontological Record (Plants)".--elsewhere.
+
+SCOTT, W.B., on "The Palaeontological Record (Animals)".
+
+Scrope.
+
+Scyllaea.
+
+Sechehaye, C.A.
+
+SEDGWICK, A., on "The Influence of Darwin on Animal Embryology".
+
+Sedgwick, A., Darwin's Geological Expedition with.
+
+Seeck, O.
+
+Seed-plants, origin of.
+
+Segregation.
+
+Selection, artificial.--germinal.
+
+Selection, natural (see Natural Selection).--organic.--sexual.--social
+and natural.--various.
+
+Selenka.
+
+Semnopithecus.
+
+Semon, R.
+
+Semper.
+
+Senebier.
+
+Senecio vulgaris.
+
+Sergi.
+
+Seward, A.C.--and S.O. Ford.--and J. Gowan.
+
+Sex, recent investigations on.
+
+Sharpe, D.
+
+Sherrington, C.S.
+
+Shirreff, P.
+
+Shrewsbury, Darwin's recollections of.
+
+Sibbern.
+
+Sinapis alba.
+
+Smerinthus ocellata.
+
+Smerinthus populi.
+
+Smerinthus tiliae.
+
+Smith, A.
+
+Smith, W.
+
+Snyder.
+
+Sociology, Darwinism and.--History and.
+
+Soddy.
+
+Sollas, W.J.
+
+Sorley, W.R.
+
+Species, Darwin's early work on transmutation of.--geographical
+distribution and origin of.--immutability of.--influence on
+environment on.--Lamarck on.--multiple origin of.--the nature of
+a.--polymorphic.--production by physico-chemical means of.--and
+varieties.--de Vries's work on.
+
+Spencer, H., on evolution.--on Lyell's "Principles".--on the nature of
+the living cell.--on primitive man.--on the theory of Selection.--on
+Sociology.
+
+Spencer, H., on the transmission of acquired characters.--on
+Weismann.--various.
+
+Sphingidae, variation in.
+
+Spinoza.
+
+Sports.
+
+Sprengel, C.K.
+
+Stability, principle of.
+
+Stahl.
+
+Standfuss.
+
+Stars, evolution of double.
+
+Stellaria media.
+
+Stephen, L.
+
+Sterility in hybrids.
+
+Sterne, C.
+
+Stockard, his experiments on fish embryos.
+
+STRASBURBER, E., on "The Minute Structure of Cells in relation to
+Heredity".
+
+Strongylocentrotus franciscanus.
+
+Strongylocentrotus purpuratus.
+
+Struggle for existence.
+
+Strutt, R.J.
+
+Stuart, A.
+
+Sturdee, F.C.D.
+
+Sutterlin, L.
+
+Sully.
+
+Sutton, A.W.
+
+Sutton, W.S.
+
+Svalof, agricultural station of.
+
+Swainson, W.
+
+Synapta, calcareous bodies in skin of.
+
+S. lappa.
+
+Syrphus.
+
+Tarde, G.
+
+Teleology and adaptation.
+
+Tennant, F.R.
+
+Teratology.
+
+Tetraprothomo.
+
+THISELTON-DYER, SIR WILLIAM, on "Geographical distribution of
+Plants".--on Burchell.--on protective resemblance.--elsewhere.
+
+THOMSON, J.A., on "Darwin's Predecessors.--elsewhere.--and P. Geddes.
+
+Thomson, Sir J.J.
+
+Theology, Darwin and.
+
+Tiedemann, F.
+
+Tooke, Horne.
+
+Totemism.
+
+Treschow.
+
+Treviranus.
+
+Trifolium pratense quinquefolium.
+
+Trigonias.
+
+Trilobites, phylogeny of.
+
+Tschermack.
+
+Turgot.
+
+Turner, Sir W.
+
+Twins, artificial production of.
+
+Tylor.
+
+Tyndall, W.
+
+Tyrrell, G.
+
+Uhlenhuth, on blood reactions.
+
+Underhill, E.
+
+Use and disuse.
+
+Vanessa.
+
+Vanessa antiope.
+
+Vanessa levana.
+
+Vanessa polychloros.
+
+Vanessa urticae.
+
+Van 't Hoff.
+
+Varanus Salvator.
+
+Variability, Darwin's attention directed to.--W. Bateson on.--and
+cultivation.--causes of.--polymorphic.
+
+Variation, continuous and discontinuous.--Darwin's views as
+an evolutionist, and as a systematist, on.--definite and
+indefinite.--environment and.--and heredity.--as seen in the
+life-history of an organism.--minute.--mutability and.--in relation to
+species.--H. de Vries on.
+
+Varigny, H. de.
+
+Varro, on language.
+
+Veronica chamaedrys.
+
+Verworn.
+
+"Vestiges of Creation", Darwin on "The".
+
+Vierkandt.
+
+Vilmorin, L. de.
+
+Virchow, his opposition to Darwin.
+
+Virchow, on the transmission of acquired characters.
+
+Vochting.
+
+Vogt, C.
+
+Voltaire.
+
+Volvox.
+
+VRIES, H. de, on "Variation"--the Mutation theory of.
+
+WAGGETT, REV. P.N., on "The Influence of Darwin upon religious thought".
+
+Wagner.
+
+Waldeyer, W.
+
+Wallace, A.R., on Malayan Butterflies.--on Colour.--and Darwin.--on
+the Descent of Man.--on distribution.--on Malthus.--on Natural
+Selection.--on the permanence of continents.--on social reforms.--on
+Sexual Selection.
+
+Waller, A.D.
+
+Walton.
+
+Watson, H.C.
+
+Watson, S.
+
+Watt, J., and Natural Selection.
+
+Watts, W.W.
+
+Wedgwood, L.
+
+Weir, J.J.
+
+WEISMANN, A., on "The Selection Theory".--on Amphimixis.
+
+Weismann, A., his germ-plasm theory.--on ontogeny.--and Prichard.--and
+Spencer.--on the transmission of acquired characters.--various.
+
+Wells, W.C., and Natural Selection.
+
+Weston, S., on language.
+
+WHETHAM, W.C.D., on "The Evolution of Matter".
+
+Whewell.
+
+White, G.
+
+Wichmann.
+
+Wieland, G.R., on fossil Cycads.
+
+Wiesner, on Darwin's work on plant movements.
+
+Williams, C.M.
+
+Williamson, W.C.
+
+Wilson, E.B., on cytology.--letter from Darwin to.
+
+Wolf.
+
+Wollaston's, T.V. "Variation of Species".
+
+Woltmann.
+
+Woolner.
+
+Wundt, on language.
+
+Xylina vetusta.
+
+Yucca, fertilisation of.
+
+Zeiller, R., on Fossil Plants.
+
+Zeller, E.
+
+Zimmermann, E.A.W.
+
+Zittel, on palaeontological research.
+
+"Zoonomia", Erasmus Darwin's.
+
+
+
+
+
+
+End of the Project Gutenberg EBook of Darwin and Modern Science, by 
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