Marine Biological Laboratory library

Woods Hole, Massachusetts

Gift of F. R. Lillie estate - 1977

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DARWIN AND MODERN SCIENCE

CAMBRIDGE UNIVERSITY PRESS

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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

EDITED, FOR THE CAMBRIDGE PHILOSOPHICAL SOCIETY
AND THE SYNDICS OF THE UNIVERSITY PRESS,

BY

A. C. SEWARD

PROFESSOR OF BOTANY IN THE UNIVERSITY
HONORARY FELLOW OF EMMANUEL COLLEGE

Cambridge :

at the University Press

1909

"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 impor-
tant 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. I. p. 107.

PREFACE

/4T 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 pre-
liminary 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 illus-
trating 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 on page 71, 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.

vi Preface

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. Weismaun and
Prof. Schwalbe ; Mrs James Ward was good enough to assist me by
translating Prof. Bougie'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
Vortrdge iiber 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 funda-

Preface vii

mental 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 employ-
ing 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

a 5

viii Preface

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

PAGE

I. Introductory Letter to the Editor from SIR

JOSEPH DALTON HOOKER, O.M. . . . 1

II. Darwin's Predecessors :

J. ARTHUR THOMSON, Professor of Natural History

in the University of Aberdeen .... 3

III. The Selection Theory:

AUGUST WEISMANN, Professor of Zoology in the

University of Freiburg (Baden) . . . 18

IV. Variation :

HUGO DE VRIES, Professor of Botany in the Uni-
versity of Amsterdam 66

V. Heredity and Variation in Modern Lights:

W. BATESON, Professor of Biology in the University

of Cambridge 85

VI. The Minute Structure of Cells in Relation to

Heredity :

EDUARD STRASBURGER, Professor of Botany in the

University of Bonn 102

VII. " The Descent of Man " :

G. SCHWALBE, Professor of Anatomy in the Uni-
versity of Strassburg 112

VIII. Charles Darwin as an Anthropologist:

ERNST HAECKEL, Professor of Zoology in the

University of Jena . . . . . .137

IX. Some Primitive Theories of the Origin of Man :

J. G. FRAZER, Fellow of Trinity College, Cambridge 152

x Contents

PAGE

X. The Influence of Darwin on the Study of
Animal Embryology:

A. SEDGWICK, Professor of Zoology and Compara-
tive Anatomy in the University of Cambridge 171

XL The Palaeontological Record. I. Animals:

W. B. SCOTT, Professor of Geology in the Uni-
versity of Princeton 185

XII. The Palaeontological Record. II. Plants:

D. H. SCOTT, President of the Linnean Society of

London 200

XIII. The Influence of Environment on the Forms

of Plants :

GEORG KLEBS, Professor of Botany in the Uni-
versity of Heidelberg 223

XIV. Experimental Study of the Influence of

Environment on Animals :

JACQUES LOEB, Professor of Physiology in the

University of California .... 247

XV. The Value of Colour in the Struggle for Life :

E. B. POULTON, Hope Professor of Zoology in

the University of Oxford . . . .271

XVI. Geographical Distribution of Plants :

Sir WILLIAM THISELTON-DYER .... 298

XVII. Geographical Distribution of Animals :

HANS GADOW, Strickland Curator and Lecturer

on Zoology in the University of Cambridge. 319

XVIII. Darwin and Geology :

J. W. JUDD 337

XIX. Darwin's work on the Movements of Plants :

FRANCIS DARWIN 385

XX. The Biology of Flowers :

K. GOEBEL, Professor of Botany in the Uni-
versity of Munich 401

XXI. Mental Factors in Evolution :

C. LLOYD MORGAN, Professor of Psychology at

University College, Bristol .... 424

Contents xi

PAGE

XXII. The Influence of the Conception of Evolu-
tion on Modern Philosophy :

H. HOFFDING, Professor of Philosophy in the

University of Copenhagen .... 446

XXIII. Darwinism and Sociology :

C. BOUGLE\ Professor of Social Philosophy in the
University of Toulouse, and Deputy-Professor
at the Sorbonne, Paris 465

XXIV. The Influence of Darwin upon Religious

Thought:
Rev. P. K WAGGETT 477

XXV. The Influence of Darwinism on the Study of

Religions :

JANE ELLEN HARRISON, Staft-Lecturer and some-
time Fellow of Newnham College, Cambridge 494

XXVI. Evolution and the Science of Language :

P. GILES, Reader in Comparative Philology in

the University of Cambridge . . . 512

XXVII. Darwinism and History :

J. B. BURY, Regius Professor of Modern History

in the University of Cambridge . . . 529

XXVIII. The Genesis of Double Stars :

Sir GEORGE DARWIN, Plumian Professor of As-
tronomy and Experimental Philosophy in
the University of Cambridge . . . 543

XXIX. The Evolution of Matter :

W. C. D. WHETHAM, Fellow of Trinity College,

Cambridge 565

INDEX .... 583

LIST OF ILLUSTRATIONS

FRONTISPIECE. Portrait of Charles Darwin ( ? 1854) from a photograph
by Messrs Maull & Fox, previously reproduced in More Letters
of Charles Darwin and in the Annals of Botany, xni. 1899,
as the frontispiece of an article " The Botanical Work of Darwin,"
by Francis Darwin.

Plate illustrating Anaea dimna . . . Facing page 53

Plate from Professor Weismann's Vortrage uber Descendenztheorie,
illustrating Mimicry in Butterflies . . Facing page 57

The study at Down, from an etching by Mr Axel Haig

Facing page 379

Portrait of Charles Darwin (? 1880) from a photograph by Messrs
Elliott & Fry Facing page 493

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 8J 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 unpre-
tending 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 01 n-oXXoi or crowd of men who do not go in

for honours."
"I am very busy,... and see a great deal of Heuslow, 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. Fitziloy.
" There is indeed a tide in the affairs of men."

xiv Epitome of Charles Danvin's Life

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 18.36 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 Maryborough 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 ' Mai thus on Population,' and
being well prepared to appreciate the struggle for existence which every-
where 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. in. 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 n., Mam-
malia, by G. R. Waterhouse, with a Notice of their liabits 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.

Epitome of Charles Darwin's Life xv

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] possess1."

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 (he 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.

" 1 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 uiy 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 Liuneau
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 1 thought Mr Wallace might consider my doing so unjustifi-
able, for I did not then know how generous and noble was his disposition."

"July 20 to Aug. 12 at Saudovvu [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."

1 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.

xvi Epitome of Charles Damviris Life

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 Plan ts 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 1 did on the many adaptations for self-fertilisation."
Publication of the second edition of Observations on Volcanic Islands.

Epitome of Charles Darwin's Life xvii

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....! 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 sou, 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.

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
D. 1

2 Introductory Letter

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 back-
wards 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 intelli-
gence 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, fore-
seeing 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 know-
ledge of the factors in the evolution-process, especially by his analysis

1—2

4 Darwin's Predecessors

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 .^Etiology
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 naturalists 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 Darwin1, 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
imperfect2." But the fundamental idea of one stage giving origin to
another was absent. As the blue vEgean 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.

1 Columbia University Biological Series, Vol. i. New York and London, 1894. We
must acknowledge our great indebtedness to this fine piece of work.
- op. cit. p. 41.

Evolutionist Philosophers 5

Aristotle's views of Nature1 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 con-
tained 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 out2, 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 seven-
teenth centuries who had at least got beyond static formulae, but, as
Professor Osborn points out3, " 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

1 See G. J. Romanes, "Aristotle as a Naturalist," Contemporary Review, Vol. LIX.
p. 275, 1891 ; G. Pouchet, La Biologic Aristotelique, Paris, 1885 ; E. Zeller, A History
of Greek Philosophy, London, 1881, and " Ueber die griecbischen Vorganger Darwin's,"
Abhandl. Berlin Akad. 1878, pp. 111—124.

2 op. cit. p. 81. 3 op. cit. p. 87.

6 Darwin's Predecessors

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 Kant1 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 agree-
ment of so many kinds of animals in a certain common plan of
structure "...an "analogy of forms" which "strengthens the sup-
position 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 con-
tinuous 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 comprehen-
sible, according to natural laws ordained by no intention." As Prof.
Haeckel finely observes, Darwin rose up as Kant's Newton2.

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

1 See Brock, "Die Stellung Kant's zur Deszendenztheorie," Biol. Centralbl. vm.
1889, pp. 641—648. Fritz Schultze, Kant und Darwin, Jena, 1875.

2 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 preserva-
tion 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 " (Dannnism, London, 1889, p. 9). See also Prof. Karl
Pearson'8 Grammar of Science (2nd edit. ), London, 1900, p. 32. See Osborn, op. cit. p. 100.

Erasmus Darwin 7

(1609) Dr Henry de Varigny1 gives us a glimpse, to Lorenz Oken
(1779 — 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 Pro-
fessor 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 dubious2.

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 species8,
went the length of admitting (in 1762) that new species might
arise by intercrossing. Buflbn'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 " 1'euchaine-
ment des etres."

Erasmus Darwin (1731 — 1802), probably influenced by Buffon,
was another firm evolutionist, and the outline of his argument in the
Zoonomia* 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 pro-
duced 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 commence-

1 Experimental Evolution. London,* 1892. Chap. i. p. 14.

2 See J. Arthur Thomson, The Science of Life. London, 1899. Chap. xvi. "Evolution
of Evolution Theory."

3 See Carus Sterne (Ernst Krause), Die allgemeine Weltanschauung in ihrer historischen
Entwickelung. Stuttgart, 1889. Chapter entitled " Bestandigkeit oder Veranderlichkeit
der Naturwesen."

4 Zoonomia, or the Laws of Organic Life, 2 vols. London, 1794 ; Osborn, op. cit. p. 145.

8 Darwin's Predecessors

ment of the history of mankind, that all warm-blooded animals have
arisen from one living filament ?".... "This idea of the gradual genera-
tion 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 Trpwrov MOV, or first great egg,
produced by night, that is, whose origin is involved in obscurity, and
animated by "Ep<»9, that is, by Divine Love ; from whence proceeded
all things which exist."

Lamarck (1744 — 1829) seems to have become an evolutionist inde-
pendently of Erasmus Darwin's influence, though the parallelism
between them is striking. He probably owed something to Buftbn,
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 Philo-
sophic Zoologique as "the first connected and thoroughly logical
exposition of the theory of descent1."

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
Geoffrey 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 Geoffrey 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 18552.

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 t\vo fallacies. It may suggest that Darwin simply entered into

1 See Alpheus S. Packard, Lamarck, the. Founder of Evolution, His Life and Work,
with Translations of his writings on Organic Evolution. London, 1901.

2 See Edward Clodd, Pioneers of Evolution, London, p. 161, 1897.

Pre-Danvinian Evolutionists 9

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 system1 ; 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 depart-
ments 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 bio-
logical 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 —
" pense'es de la jeunesse, executes par 1'age mftr " — 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

1 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.

10 Darwin's Predecessors

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 refer1.

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 varia-
bility.

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 Darwinism2.

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

1 See Prof. W. A. Locy's Biology and its Makers. New York, 1908. Part n. "The
Doctrine of Organic Evolution."

2 Presidential Address to the British Association meeting at Dublin in 1908.

Pre-Darwinian Theories of Evolution 11

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-organisnial competition, this might be included
under the rubric of the animate environment.

In many passages Buffon1 definitely suggested that environ-
mental 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 these2 :

" Le cours ordinaire de la nature vivante, est en ge'ne'ral toujours
constant, toujours le meme ; son mouvement, toujours re"gulier, roule
sur deux points in^branlables : 1'un, la fe"condite sans bornes donne"e
a toutes les especes ; 1'autre, les obstacles sans nombre qui re"duisent
cette fe"condit£ & une mesure d^termin^e et ne laissent en tout temps
qu'k peu pres la meme quantite d'individus de chaque espece"..."Les
especes les moins parfaites, les plus dedicates, les plus pesantes, les
moins agissantes, les moins armies, etc., ont deja disparu ou dis-
paraitront."

Erasmus Darwin3 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

1 See in particular Samuel Butler, Evolution Old and New, London, 1879; J. L. de
Lanessan, "Buffon et Darwin," Revue Scientifique, XLIII. pp. 385—391, 425—432, 1889.

2 op. cit. p. 136.

3 See Ernst Krausc and Charles Darwin, Erasmus Darwin, London, 1879.

12 Darwin's Predecessors

misses the connection between this struggle and the Survival of the
Fittest1."

Lamarck2 (1744 — 1829) 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.

Treviranus3 (1776 — 1837), 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."

Goethe4 (1749 — 1832), 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

1 Osborn, op. cit. p. 142.

'J See: E. Perrier, La Philosophic Zoologique avant Darwin, Paris, 1884; A. de
Quatrefages, Darwin et ses Precurseurs Fran$aist Paris, 1870; Packard, op. cit.; also
Claus, Lamarck als Begriinder der Descendenzlehre, Wien, 1888 ; Haeckel, Natural History
of Creation, Eng. transl. London, 1879; Lang, Zur Chttrakteristik der Forschungswege
von Lamarck und Darwin, Jena, 1889.

3 See Huxley's article "Evolution in Biolopy," Encyclopaedia Britannica (9th edit.),
1878, pp. 744—751, and Sully's article, "Evolution in Philosophy," ibid. pp. 751—772.

4 See Haeckel, Die Naturantehmtung von Darwin, Goethe und Lamarck, Jena, 1882.

Goethe and other Pioneers of Evolution 1 3

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 Geoflroy 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 in-
fluences. The complete history of evolution-theories will include
many instances of guesses at truth which were afterwards sub-
stantiated, 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 views1." 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 observa-
tion 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'2."

Although Malthus gives no adumbration of the idea of Natural

1 Origin of Species (6th edit.), p. xvii.

2 The Life and Letters of Charles Darwin, Vol. i. p. 83. London, 1887.

14 Darwin's Predecessors

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 species1." 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*" 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."

1 A. B. Wallace, My Life, A Record of Events and Opinions, London, 1905, Vol. i. p. 232.

2 Ibid. Vol. i. p. 361.

Influence of Malthus 15

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 theo-
logical 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 progress1." 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 inhabit2.' "
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

1 P. Geddes, article "Biology," Chambers's Encyclopaedia.

2 Origin of Species (6th edit.) p. xv.

16 Darwin's Predecessors

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 Timber1."

De Quatrefages and De Yarigny 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 Geoffrey 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 modifi-
cations 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 (& la convenance) the new environment."

Prof. E. B. Poulton2 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

1 Life and Letter*, n. p. 301.

2 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.

Pre-Dartvinian Hints of Natural Selection 17

finds in Prichard's work a recognition of the operation of Natural
Selection. "After inquiring how it is that 'these varieties are de-
veloped and preserved in connexion 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 dis-
appear in climates for which they are, by peculiarity of constitution,
not adapted. Of this fact proofs have been already mentioned."1 Mr
Francis Darwin and Prof. A. C. Seward discuss Prichard's " anticipa-
tions " in More Letters of Charles Darwin, Vol. I. p. 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 else-
where. James Watt1, 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, favour-
able 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 verifi-
cation, 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 interpre-
tation it has advanced to the rank of a causal theory, the most
convincing part of which men will never cease to call Darwinism.

1 See Prof. Patrick Geddes's article "Variation and Selection," Encyclopaedia
Britannica (9th edit.) 1888.

D. 2

Ill

THE SELECTION THEORY
BY AUGUST WEISMANN.

Professor of Zoology in the University of Freibury (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 purposivenees 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

Selection 19

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 under-
gone 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 observa-
tions, 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

9 o

4— -i

20 The Selection Theory

«

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 at-
tention 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 re-
garded 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 re-
mained 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 re-
produce.

Thus the principle of natural selection is the selection of the
best for reproduction, whether the " best " refers to the whole con-
stitution, 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 genera-
tions 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

The Lamarckian Principle 21

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 inter-
vention 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 homo-
geneity 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
Leibnitziau 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 evolu-
tion 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

22 The Selection Theory

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 ajso regarded this Lamarckian principle, as it is now
generally called, as a factor in evolution, but he was not fully con-
vinced 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 Kamnierer 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. Kblliker, 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

Saltatory Evolution 23

medusoid from a free-swimming animal to a mere brood-sac (gono-
phore) 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 repre-
sent 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

24 The Selection Theory

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. Kor-
schinksky attributes to them weaknesses of organisation in general ;
" they bloom late, ripen few of their seeds, and show great sensitive-
ness 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 trans-
formation 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 weak-
nesses of this theory1, and I am the less inclined to return to it here
that it now appears2 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 Darwin3 was right in regard-
ing transformations as taking place by minute steps, which, if useful,

1 Vortrage ilber Descendenztheorie, Jena, 1904, n. 269. Eng. Transl. London, 1904, n.
p. 317.

2 See Poulton, Essays on Evolution, Oxford, 1908, pp. xix — xxii.

3 Origin of Species (6th edit.), pp. 176 et seq.

Importance of small differences 25

are augmented in the course of innumerable generations, because
their possessors more frequently survive in the struggle for existence.

($) 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 in-
significant 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 be-
ginnings 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 thick-
ness 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 Radiolariaus 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 signifi-
cance (Hacker). The same thing has been shown by Schiitt 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

26 The Selection Theory

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 long1 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 elimina-
tion ? 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 raindrops. 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.

1 Chun, Eeise der Valdivia, Leipzig, 1904.

Useful Variations 27

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 use/id 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
formulated1 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 can-
not 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 them-
selves 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

1 Plate, Selektionsprinzip u. Probleme der Artbildung (3rd edit.), Leipzig, 1908.

28 The Selection Theonj

.
prospect of its being preserved, notwithstanding its utility. Darwin

. at first believed, that even single variations might lead to trans-
formation 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 colour1.

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 longi-
tudinal 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, evolu-
tion 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 require-
ments 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

1 Studien zur Descendenz-Theorie n.,"Die Enatebung der Zeichnung bei den Schmetter-
lings-raupen," Leipzig, 1876.

Initial Stages of Variation 29

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 8. ocellata rust-red spots appear
in individual caterpillars, but more rarely than in 8. 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 8. tiliae, in which species the coloured
stripes are a normal specific character. In the other species, £ populi
and 8. 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 sum-
mation. 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 (Figs. A, B). 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

30

The Selection Theory

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

a

Fig. A.

Anchor (a) and basal-plate (b) of Synapta lappa. Length of anchor = 0'35 rnrn.
(After Oestergren, Zool. Anzeiger, xx. 1897.)

a

Fig. B.
Anchor (a) and basal-plate (b) in side-view (after Oestergren).

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° 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

Anchors of Holothurians 31

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 improve-
ments, 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

32 The Selection Theory

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 ?

(7) 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

Coadaptation 33

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 un-
tenable, because it assumes the transmissibility of functional modi-
fications (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 corre-
lative variations, occur also in cases in which the animals concerned
are sterile and therefore cannot transmit anything to their de-
scendants. 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

D. 3

34 The Selection Theory

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 ivay 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 insur-
mountable 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

Harmonious Adaptation 35

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 high1."

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 (co-
adaptation) 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 selection2." He explains his
view by a simple but interesting illustration. Gardeners have pro-
duced, by means of long continued artificial selection, a variety of
Stock, which bears entirely double, and therefore infertile flowers3.
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 trans-
formations that have taken place parallel with the sterility of the
ants are useful, since they procure for the colony an advantage in

1 Origin of Species (6th edit.), p. 232.

3 Origin of Species, p. 233 ; see also edit. 1, p. 242. 3 Ibid. p. 230.

3—2

36 The Selection Theory

the struggle for existence, and they are therefore preserved by
natural selection. Even the sterility itself in this case is not dis-
advantageous, 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 pro-
cesses, 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 con-
stituents 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

Germinal Selection 37

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 deter-
minant now actively nourishes itself more abundantly, — that is to say, x
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 ad- •
vantageous, 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

38 The Selection Theory

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, ivhen 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 uninter-
ruptedly 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 equili-
brium again, but that, when the movement has attained to a certain
strength, it continues in the same direction. We have entire certainty

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 mathemati-
cally, since we cannot actually see the play of forces of the passive
fluctuations and their causes. We cannot say how great these fluctua-
tions are, and how quickly or slowly, how regularly or irregularly they

Degeneration of disused parts 39

change. Nor do AVC 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 varia-
tions 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 : j
adaptations. The importance for the theory of the process of degenera- «
tion 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 Lamarekian 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

40 The Selection Theory

the wings? These parts have therefore degenerated because they
were of no furtlier 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 butter-
flies, flies, and locusts, but in the larvae the imaginal discs of the
wings are still laid down. With regard to the ovaries, degenera-
tion 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 them-
selves 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 interven-
tion 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

Organic Selection 41

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 them-
selves 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 tJierefore 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 in-
creasing 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 bones1.

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 adap-
tations. 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

1 The Effect of External Influences upon Development, Romanes Lecture, Oxford,
1894.

42 The Selection Theory

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 rudi-
mentary, 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 ex-
tremely 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 ami Se&ual Selection,

Sexual Selection 43

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

44 The Selection Theory

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 pre-
liminary 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 re-
production.

In many cases the organ of smell shows a similar improvement.

Sexual Selection 45

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 main-
tenance 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 en-
ticing, 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

46 The Selection Theory

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 Miiller 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 recog-
nisable 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 insects1. 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 oft' 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

1 See Poulton, Essays on Evolution, 1908, pp. 316, 317.

Decorative Colours 47

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 con-
nection, 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

48 The Selection Theory

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 carni-
vores, 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 dis-
played before the female during courtship. I have elsewhere l 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 deco-
rative 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

1 The Evolution Theory, London, 1904, i. p. 219.

Natural Selection 49

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 ot
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 explain-
ing 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.

(/3) 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 posses-
sion 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 excite-
ment 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
D. 4

50 The Selection Theory

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 Pqulton and Sanders1 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 % °f the pupae at Oxford were killed,
chiefly by small birds, while at St Helens 68 % perished. The experi-
ments 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 °/0 ; on bark, 66 % ; on
walls, 54 °/0; and among nettles, 57 %• These interesting experi-
ments 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, be-
cause 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 inter-
pretative value of the theory. Let us consider this point in greater
detail.

In the first place, it is necessary to emphasise what is often over-
looked, 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.

1 Report of the British Association (Bristol, 1898), London, 1899, pp. 900—909.

Sympathetic Coloration 51

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
Lamarcldan 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 un-
necessary 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.

4—2

52 The Selection Theory

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 indica-
tion 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 aftect 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

DARWIN AND MODERN SCIENCE

Fig. C.
Anaea divina (under side).

Leaf-like Butterflies 53

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 semi-
circular piece is of a clear, pale yellow colour, while the rest of the
wing is of a strongly contrasted dark brown (Fig. C).

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 observations1 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 s
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 under-
stand 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.

1 Proc. Ent. Soc., London, May 6, 1903.

54 The Selection Theory

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 Poulton1,
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 ob-
servations 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 fre-
quently 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* 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 con-
sequences— the existence of mimetic palatable forms — confirm it in
the most convincing manner. Of the many cases now known I select

1 Essays on Evolution, 1889—1907, Oxford, 1908, passim, e.g. p. 269.

2 The expression does not refer to all the enemies of this butterfly ; against ichneumon-
flies, for instance, their unpleasant smell usually gives no protection.

Mimicry 55

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- L& "
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 poly-
morphism 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 (pp. 373 — 375 *). 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 explana-
tion 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 mimeti-
cally 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

1 Professor Poulton has corrected some wrong descriptions which I had unfortunately
overlooked in the Plates of my book Vortrage ilber Descendenztheorie, and which refer
to Papilio dardanus (merope). These mistakes are of no importance as far as an under-
standing of the mimicry-theory is concerned, but I hope shortly to be able to correct
thum in a later edition.

56 The Selection Theory

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 we could
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 sur-
rounds 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

DARWIN A.\'I> MODERN SCIENCE.

MIMICRY ix BUTTERFLIES.

. ,lcnn.

Mimicry 57

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 com-
paratively 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.

EXPLANATION OF FIGS. 1—12.
Figs. 1 — 4 represent a Mimicry-ring from Eastern Brazil composed of four immune

species belonging to three different sub-families and four different genera.
Fig. 1. Lycorea halia (Danainae).
Fig. 2. Heliconius narcaea (eucrate) (Heliconinae).
Fig. 3. Melinaea ethra (Ithomiinae).
Fig. 4. Mechanitis lysimnia (Ithomiinae).
Figs. 5, 6. Perrhybris pyrrha, male and female, S. American " Whites " (Pierinae).

The female mimics immune Ithomiines, while the male shows only an indication

of the mimetic colouring on the under surface.
Figs. 7, 8. Dismorphia astynome, male and female, also belonging to the family of

S. American " whites," and mimicking immune Ithomiines ; a white patch on

the posterior wing of the male and another on the corresponding surface of the

under side of the upper wing, remain as traces of the original "white" coloration.
Fig. 9. Elymnias phegea, W. Africa, of the sub-family of Satyrines, mimics the

succeeding species (Fig. 10).
Fig. 10. Planema epaea (gea\ an immune West African species belonging to the

Acraeinae.

Fig. 11. Danaida genutia, an immune Danaid from India, Burmah, etc.
Fig. 12. Elymnias undularis, female, one of the mimics of Fig. 11.

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 chri/sippus 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 (Fig. 12) with its
model Danaida genutia (Fig. 11) ; there is a general resemblance, but
the marking of the Danaida is very roughly imitated in Elymuias.

58 The Selection Theory

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 entomo-
logical 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 means1. Thus the glass-like trans-
parency 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 colour-
lessness and transparency, and to the fact that they stand upright.
In another moth mimic (Anthomyza) the arrangement of the trans-
parent 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 favour-
able variations that present themselves. The great faithfulness of
the copy is astonishing in these cases, for it is not tJie 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 other-
wise 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 irreconcileable 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 Heli-
conidae). 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

1 Journ. Linn. Soc. London (Zool), Vol. xxvi. 1898, pp. 598—602.

Mimicry 59

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 (Figs. 1 — 4). 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 Miiller1,
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. The four Brazilian species are figured
on the accompanying plate (Figs. 1 — 4) : Lycorea halia (Danainae),
Heliconius narcaea (eucrate) (Heliconinae), Melinaea ethra, and
Mechanitis lysimnia (Ithomiinae).

These interesting mimicry-rings (trusts), which have much signi-
ficance for the theory, have been the subject of numerous and careful
investigations, and at least their essential features are now fully
established. Miiller took for granted, without making any investi-
gations, that young birds only learn by experience to distinguish
between different kinds of victims. But Lloyd Morgan's2 experiments
with young birds proved that this is really the case, and at the same
time furnished an additional argument against the LamarcMan
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 !

1 In Kosmos, 1879, p. 100. 2 Habit and Instinct, London, 1896.

60 The Selection Theory

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 incon-
spicuous 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 trans-
formed 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,

Importance of Selection 61

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 them1.

Many people are willing to admit that selection explains adapta-
tions, 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 what-
ever, 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 can-
not 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, tempe-
rature, nutrition, climate and the like ? Undoubtedly these can give
rise to variations, but they too must pass through the door of selec-
tion, 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

1 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.

62 The Selection Theory

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 estab-
lishing 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 colour-
ing 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
F. urticae than in V. polychloros. In this case, as in most leaf-butter-
flies, the holding of the wing was probably the primary character ;
only after that was thoroughly established did the protective mark-
ing 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

Adaptation 63

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 remark-
able 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 correct1.

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 laud. I cited a number of these transformations — the
fish-like form of the body, the hairlessness of the skin, the trans-
formation 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

1 The Evolution Theory, London, 1904, p. 144.

64 The Selection Theory

under water. I might have added many more, for the list of adapta-
tions in the whale to aquatic life is by no means exhausted; they
are found in the histological structure and in the minutest combina-
tions 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 com-
pared 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

Adaptation 65

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 par-
ticular 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 result1. 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 anc|f i
other low forms of life, or only a germ-substance, as in unicellular •
and multicellular organisms2.

1 Variation under Domestication, 1875, n. pp. 426, 427.

2 The Author and Editor are indebted to Professor Poulton for kindly assisting in the
revision of the proof of this Essay.

D.

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 monstro-
sities. 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

Tendency to Vary 67

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 varia-
tions. 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 varia-
bility 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 distri-
bution 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

5—2

68 Variation

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 develop-
ment. 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 differentia-
tion 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 sudden-
ness. On the contrary, Darwin shows very convincingly that a modi-
fication 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.

Polymorphic Species 69

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 adapta-
tions 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 varia-
tions, 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 pre-
vailing 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 vernci) 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

70 Variation

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 differ-
ence 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 varia-
tions 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.

Two Types of Variation 71

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
diiferences of a beneficial nature happen to arise, these will be
preserved1." 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
hypothesis2.

A distinction is indicated between ordinary fluctuations which are
always present, and such variations as " happen to arise " from time
to time3. 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

1 Origin of Species (6th edit.), p. 169, 1882.

2 Cf. de Vries, Intracellulare Pangenesis, p. 73, Jena, 1889, and Die Mutatiomtheorie,
i. p. 63. Leipzig, 1901.

3 [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 tban 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.]

\\

72 Variation

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 selection1; for as these morpho-
logical characters do not affect the welfare of the species, any slight
deviation in them could not have been governed or accumulated
through this latter agency2." 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 measure-
ments 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 beforehand, 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 pro-

1 The italics are mine (H. de V.). a Origin of Species (6th edit.), p. 176.

Fluctuations and Mutations 73

duced 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 point1. 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 recog-
nised to be the main source of varieties of horticultural plants.

As already stated, I do not pretend that the production of horti-
cultural 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 con-""
stancy which is the mark of specific characters, and on this basis every I jj
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,

1 S. Korschinsky, " Heterogenesis und Evolution," Flora, Vol. LXXXIX. pp. 240 — 363, 1901.

74 Variation

it is in fullest harmony with the great principle laid down by
Darwin. In order to be acted upon by that complex of environ-
mental forces, which Darwin has called natural selection, the changes
must obviously first be there. The manner in which they are pro-
duced is of secondary importance and has hardly any bearing on the
theory of descent with modification1.

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 muta-
tions— 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.

1 Life and Letters, n. 125.

Mutability 75

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 fluctua-
tions 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 pro-
duced 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

76 Variation

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 disappear-
ance or reappearance of some character. With progressive mutations
the case is not so simple, since the new character must first be pro-
duced 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 Theory1.

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 accumu-
lative 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 equi-
librium 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 genera-
tions. 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, aflbrd 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.

1 Die Mutationstheorie, 2 vols., Leipzig, 1901.

Variability in Cereals 77

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, intro-
duced 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. innricata 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 system-
atically 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 neighbour-
ing 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

78 Variation

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 ex-
ternal 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
i 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 de-
scribing 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 ob-
servation shows the existence of different forms; how these have
originated is a question which it does not deal with. In his M'ell-
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.

Breeding of Cereals 79

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 Couteur1 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 con-
sidered 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, dis-
covered 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 " Belle vuede 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 de-
stroyed its capacity for further improvement by selection.

The principle of single-ear sowing, with a view to obtain pure and

1 On the Varieties, Properties, and Classification of Wheat, Jersey, 1837.

80 Variation

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'1 in Scotland and
Willet M. Hays2 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 in-
cluding 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 Svalbf 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,

1 Die Verbesserung der Getreide-Arten, translated by R. Hesse, Halle, 1880.

2 Wheat, varieties, breeding, cultivation, Univ. Minnesota, Agricultural Experiment
Station, Bull. no. 62, 1899.

Breeding of Cereals 81

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 that 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 con-
stituting 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 demon-
strated 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
D. 6

82 Variation

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, there-
fore, 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 uni-
formity 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 every-
where ; 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 Shirreft', 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 exception-

Breeding of Cereals 83

ably 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 acci-
dental 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 pro-
duced, 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 Svalb'f new and un-
expected 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 o f

6—2

84 Variation

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 sub-
ordinate 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.

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 know-
ledge 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 accomplish-
ment, 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 : Varia-

86 Heredity and Variation in Modern Lights

tion ; 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. Mau-
pertuis, for example, wrote : " Ce qui nous reste k 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 1'art les mettent en oeuvre. C'est ainsi que ceux
dont 1'industrie s'applique & satisfaire le gofit des curieux, sont, pour
ainsi dire, cre"ateurs d'especes nouvelles V

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 Buffon2, developed
by Erasmus Darwin, and independently proclaimed above all by
Lamarck, gave to the doctrine of descent a wide renown. The uni-
formitarian teaching which Lyell deduced from geological observation
had gained acceptance. The facts of geographical distribution3 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 con-
temptuous 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

1 Vfnus Physique, contenant deux Dissertations, Vune sur Vorigine des Homines et des
Animaux: Et Vautre sur Vorigine des Noirs, La Haye, 1746, pp. 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.

2 For the fullest account of the views of these pioneers of Evolution, see the works of
Samuel Butler, especially Evolution, Old and New (2nd edit.) 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 ideet tres-elevees sur la generation" contained in the Letters of
Maupertuis.

8 See especially W. Lawrence, Lectures on Physiology, London, 1823, pp. 213 f.

Why Darwin succeeded 87

such views had been promulgated ; and many must, as Huxley says,
have taken up his own position of "critical expectancy1."

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 Origin2 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.' '

1 See the chapter contributed to the Life and Letters of Charles Dane in, n. p. 195. I do
not clearly understand the sense in which Darwin wrote (Autobiography, ibid. i. p. 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, p. 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."

2 Origin, 6th edit. (1882), p. 421.

88 Heredity and Variation in Modern Lights

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 remem-
bered 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 solution1. The moment of in-
spiration did not come with the reading of Malthus, but with the
opening of the " first note-book on Transmutation of Species2." Evolu-
tion 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 be-
ginning 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 com-
pression 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.

1 Whatever be our estimate of the importance of Natural Selection, in this we all agree.
Samuel Butler, the most brilliant, arid 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."

2 Life and Letters, i. pp. 276 and 83.

Weismanris Challenge 89

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 systematists1, 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

1 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 edit. (1882), p. 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 ?

90 Heredity and Variation in Modern Lights

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 com-
paring passages from the Origin1 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 degenera-
tion 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 charac-
teristics had seemed to most naturalists so obvious as not to call for
demonstration2. 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 inter-
pretation 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 en-
courage 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,

1 6th edit. pp. 109 and 401. See Butler, Essays on Life, Art, and Science, p. 265,
reprinted 1908, and Evolution, Old and New, chap. zxn. (2nd edit.), 1882.

2 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, pp. 436 — 437, 447
Prichard, Edin. Inaug. Disp. 1808 [not seen by me], quoted ibid, and Nat. Hist. Man,
1843, pp. 34 f.

Cytology and Heredity 91

but these mostly resolve themselves into improbable attempts to
expand or magnify the powers of Natural Selection.

Weismaun'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 cell-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 Weis-
mann'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 illu-
minating1. 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 organisa-
tion. 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 chromo-
somes seems in my opinion quite incompatible with the belief that
they alone govern form, and are the sole agents responsible in
heredity2.

1 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, p. 86.

• 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,
p. 233), and from the recent observations of Godlewski it has received distinct experi-
mental support.

92 Heredity and Variation in Modern Lights

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 un-
expected 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 revela-
tion. 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 pro-
cesses 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 there-
fore in variation. This order cannot by the nature of the case be
dependent on Natural Selection for its existence, but must be a con-
sequence 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

Mendel's Discovery 93

species contains. The further investigation of the species-problem
must thus proceed by the analytical method which breeding experi-
ments 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 trans-
mitted 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 redis-
tributed 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 element1. It is not a little remarkable that on this
point — which is the only one where observations of the nuclear pro-
cesses 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

1 In other words, the ova are each either female, or male (i.e. non-female), but the
sperms are all non-female.

94 Heredity and Variation in Modern Isights

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. Morgan1,
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 degene-
rating. 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 grossu-
lariata). The accessory chromosome has been now observed in most
of the great divisions of insects2, 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

1 Morgan, Proc. Soc. Exp. Biol. Med. v. 1908, and von Baehr, Zool. Anz. sxxn. p. 507,
1908.

2 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.

What is a Variation? 95

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 possi-
bilities 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 genera-
tion 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 experi-
menter 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

96 Heredity and Variation in Modern Lights

dominant, and at some moment since Gattus banJciva 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 insur-
mountable, 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 regular1 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 fart les
mettent en ceuvre," 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 wrote2 : "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

1 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.

a Vortrage iiber Viehzucht und Rassenerkenntniss, p. 120, Berlin, 1872.

Sterility of Hybrids 97

rechten Weg zur Ergriindung der Gravitationsgesetze fiihrte." 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 dis-
tinction, 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
D. 7

98 Heredity and Variation in Modern Lights

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 acquisi-
tion 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 ex-
perimental 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 pro-
ducing the slightest sterility ; others have totally sterile offspring, and
so on. The hybrids between several genera of Orchids are perfectly

Definite Variation 99

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 sterile1. 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'"2, 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

1 See Button, A. W., Journ. Linn. Soc. xxxvm. p. 341, 1908.

2 Life and Habit, London, p. 263, 1878.

7—2

100 Heredity and Variation in Modern Lights

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 BO.
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 wi«
meet with definite structures or patterns. Such things are, as often

Definite Variation 101

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 + ri
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 funda-
mental 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 investigators1 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 con-
necting 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-

1 As for example the illustrious Wilhelm Hofmeister in his Lehre von der Pflanzenzelle
(1867).

Niiclear Division 103

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. Biitschli, O. Hertwig, W. Flemming,
H. Fol and of the author of this article1, 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 Chromosomes2,
there may usually be recognised a separation into thicker and thinner
discs ; the former are often termed Chromomeres3. 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 bodies4, which it is customary to speak of as Centro-
somes. 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 pole5.

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 pro-

1 For further reference to literature, see my article on " Die Ontogenie der Zelle seit
1875," in the Progressus Rei Botanicae, Vol. i. p. 1, Jena, 1907.

2 By W. Waldeyer in 1888.

3 Discovered by W. Pfitzner in 1880.

4 Their existence and their multiplication by fission were demonstrated by E. van
Beneden and Th. Boveri in 1887.

6 These important facts, suspected by W. Flemming in 1882, were demonstrated by
E. Heuser, L. Guignard, E. van Beneden, M. Nussbaum, and C. Eabl.

104 Cell Structure in Relation to Heredity

gressive 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 importance1. 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 phe-
nomena immediately followed researches into the nucleus. The
fundamental discovery of the union of two nuclei in the sexual
act was then made2 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 characters3 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 trans-
ference 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 know-
ledge 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-
kinesis, 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

1 First shown by W. Boux in 1883.

2 By 0. Hertwig iu 1875.

8 This was done by 0. Hertwig and the author of this essay simultaneously in
1884.

Homotypic Nuclear Division 105

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
gonotokonts1 (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 gono-
tokonts, 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 longi-
tudinal 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 gemini2. 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 division3. This stage in division deter-
mines 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 longi-
tudinal halves of the chromosomes are present ready for the next

1 At the suggestion of J. P. Lotsy in 1904.

2 J. E. S. Moore and A. L. Embleton, Proc. Roy. Soc. London, Vol. LXXVII. p. 555, 1906;
V. Gregoire, 1907.

3 In 1887 W. Flemming termed this the heterotypic form of nuclear division.

106 Cell Structure in Relation to Heredity

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 division1.

Reduction division and homotypic nuclear division are included
together under the term allotypic nuclear division and are dis-
tinguished from the ordinary or typical nuclear division. The
name Meiosis2 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 diiferentiated 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 main-
tained 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 develop-
ment, was followed by fertilisation and therefore by the creation of a
diploid or double-chromosome product. So long as the germina-
tion 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

1 The name was proposed by W. Flemming in 1887 ; the nature of this type of
division was, however, not, explained until later.

2 By J. Bretland Farmer and J. E. S. Moore in 1905.

Nuclei as Carriers of Hereditary Characters 107

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 genera-
tion 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 in-
dependent organisms with diploid nuclei only. The haploid genera-
tion 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 investigations1 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 chromo-
somes 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 chromo-
somes, 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 chromo-
somes carry must be also constant. The ultimate hereditary units

1 Particularly those of V. Gr^goire and his pupils.

108 Cell Structure in Relation to Heredity

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 insure the transmission of all hereditary units in the pro-
ducts 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 sub-
ject 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 considera-
tions give an affirmative answer to this question. The differentia-
tion 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 organisms1, characterised by
the same reactions as nuclear material, provided also with a nuclear
network, but without a limiting membrane2. Thus the carriers
of hereditary characters may originally have been distributed in
the common protoplasm, afterwards coining 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,

1 Bacteria, Cyanophyceae, Protozoa.

2 This is the result of the work of R. Hertwig and of the most recently published
investigations.

Chromosome Pairs 109

the carriers of the same hereditary unit were represented in consider-
able quantity ; they became gradually differentiated to an extent
commensurate with newly acquired characters. It was also neces-
sary that, in proportion as this happened, the mechanism of nuclear
division must be refined. At first processes resembling a simple con-
striction 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 quali-
tative 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 multipli-
cation of the nuclei. They serve chiefly to nourish the plant, but,
unlike the other cells, they are iYicapable 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 chromo-
somes are homologous, and that one comes from the father, the other
from the mother1. 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 chro-
mosomes, 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 pro-
portion between the daughter-nuclei; and it is not impossible that
one daughter-nucleus might occasionally contain paternal chromo-
somes only and its sister-nucleus exclusively maternal chromosomes.

1 First stated by T. H. Montgomery in 1901 and by W. S. Sutton in 1902.

110 Cell Structure in Relation to Heredity

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 experi-
ments 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 development1.

The recently discovered fact that in diploid nuclei the chromo-
somes 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 kingdoms2. Probably for the
purpose of entering into most intimate relation, the pairs are
stretched to long threads in which the chroniomeres come to lie
opposite one another3. It seems probable that these are homo-
logous chroniomeres, and that the pairs afterwards unite for a short
time, so that an exchange of hereditary units is rendered possible4.
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

1 Demonstrated by Th. Boveri in 1902.

2 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. Gr6goire and his
pupil C. A. Allen, by the researches conducted in the Bonn Botanical Institute, and by
A. and K. E. Schreiner.

3 C. A. Allen, A. and K. E. Schreiner, and Strasburger.

4 H. de Vries and Strasburger.

Pangenesis 111

which in fertilization again produces the most varied combinations1.
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 Pangenesis2, 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 con-
clusion 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 pangens3 :
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 repro-
ductive cells. When Darwin foresaw this possibility, the continuity
of the germinal substance was still unknown4, 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 histo-
logical 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.

1 A. Weismann gave the impulse to these ideas in his theory on Amphimixis.
- Animals and Plants under Domestication, London, 1868, Chapter xxvii.

3 So called by H. de Vries in 1889.

4 Demonstrated by Nussbaum in 1880, by Sachs in 1882, and by Weismann in 1885.

VII

T "

"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

it

The Origin of Species" 113

on the descent of man made its appearance so late. Huxley, always
generous, never thought of claiming priority for himself. In enthu-
siastic 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 agent1." Huxley says of
himself " I am Darwin's bulldog2."

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 inten-
tionally 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 views3, 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 origin4."

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 opinion5."

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

1 Life and Letters of Thomas Henry Huxley, Vol. i. p. 171, London, 1900.

2 Ibid. p. 363.

3 No italics in original.

4 Life and Letters of Charles Dancin, Vol. i. p. 93.

5 Ibid. Vol. n. p. 263.

D. 8

114 " The Descent of Man"

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 book1: the
first edition, which appeared in 1871, was followed in 1874 by a much
improved second edition, the preparation of which he very reluctantly
undertook2.

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, 18573, 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. Never-
theless he did not escape reproaches for having been so reticent.
This is unmistakably apparent from a letter to Fritz Miiller dated
Feb. 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 con-
cealing my opinions4."

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
Francis5. 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

1 Life and Letters, Vol. I. p. 94. 2 Ibid. Vol. in. p. 175.

3 Ibid. Vol. n. p. 109. * Ibid. Vol. m. p. 112.

5 Ibid. Vol. i. pp. 304—317.

Sexual Selection 115

Books of the Hindoos; the miracles by which Christianity is sup-
ported, the discrepancies between the accounts in the different
Gospels, gradually led him to disbelieve in Christianity as a divine
revelation. "Thus," he writes1, "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 Agnostic2."

Darwin was always very unwilling to give publicity to his views in
regard to religion. In a letter to Asa Gray on May 22, I8603, 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. Ridley4 (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

1 Life and Letters, Vol. i. p. 309. 2 Loc. cit. p. 313. 3 Ibid. Vol. n. p. 310.

4 Ibid. Vol. in. p. 236. ["C. Ridley," Mr Francis Darwin points out to me, should be
H. N. Ridley. A.C.S.]

8—2

116 " The Descent of Man"

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 every-
thing 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 un-
pleasant 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 as-
tonishing 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 tin's latter
problem the whole of Part I is devoted, Avhile Part III contains a

Man and the Lower Animals 117

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, em-
bryonic forms, and he illustrates this by two figures placed one
above the other, one representing a human embryo, after Ecker, the
other a dog embryo, after Bischoff1.

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 develop-
ment 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 Woollier. 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 ear2. 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

1 Descent of Man (Popular Edit., 1901), fig. 1, p. 14.

2 G. Schwalbe, "Das Darwin'sche Spitzohr beim rnenschlichen Embryo," Anatom.
Anzeiger, 1889, pp. 176—189, and other papers.

118 " The Descent of Man"

corrected. A large ear with a point is shown in the photograph1,
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 uritt 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 ivas the work of a separate
act of creation1."

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 Queclma-
Indians of the high plateaus of Peru show a striking development

1 Descent of Man, fig. 3, p. 24. * Ibid. p. 36.

Man's Erect Position 119

of lungs and thorax, as a result of living constantly at high al-
titudes.

Such special forms of variation as arrests of development (micro-
cephalism) and reversion to lower forms are next discussed. Darwin
himself felt1 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 ab-
normal 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 develop-
ment 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

1 Descent of Man, p. 54.

120 "The Descent of Man"

show that some of the most distinctive human characters are in all
probability directly or indirectly due to natural selection. With
characteristic modesty he adds1: "Hence, if I have erred in giving
to natural selection great power, which I am very far from ad-
mitting, 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 man2."

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 charac-
teristics 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 some-
thing 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

1 Descent of Man, p. 92.

Intellectual and Moral Faculties 121

implements will be read with interest; these are similar to the
observations on modern eoliths, and their bearing on the develop-
ment of the stone-industry. It is interesting to learn from a letter
to Hooker1, 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
glaciers2."

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
Miiller3 : " 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 point4: "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 idea5."

The result of the investigations recorded in this chapter is to
show that, great as the difference in mental powers between man and

1 Life and Letters, Vol. n. p. 161, June 22, 1859.

2 Ibid. Vol. in. p. 15, March 17, 1863.

3 Descent of Man, p. 132. 4 Ibid. pp. 136, 137.
5 Ibid. p. 143.

122 " The Descent of Man"

the higher animals may be, it is undoubtedly only a difference " of
degree and not of kind1."

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 quanti-

1 Descent of Man, p. 193.

Genealogy of Man 123

tative, 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 Darwin1: "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 arrange-
ment 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 (Platyrrhiue)
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

1 Descent of Man, p. 231.

124 " The Descent of Man"

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 popula-
tion 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 environ-
ment.

i

The Descent of Man" 125

The final section of this chapter deals with the formation of the
races of mankind. Darwin discusses the question how far the direct
eifect of different conditions of life, or the inherited effects of in-
creased 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 races1."

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 "nonsense2," and of Lamarck's "absurd,
though clever work3" and expressly declaring, "I attribute very
little to the direct action of climate, etc.4" yet in later life he
became more and more convinced of the influence of external con-
ditions. 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 selection5." 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 in-
fluence 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

1 Descent of Man, p. 308. 2 Life and Letters, Vol. n. p. 23.

3 Loc. cit. p. 39. 4 Loc. cit. (1856), p. 82. 5 Ibid. Vol. in. p. 159.

126 " The Descent of Man '

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 environ-
ment. 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
precision1." 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 me2, 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 origin3."

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

1 Descent of Man, p. 924.

2 " Die Hautfarbe des Menschen," Mitteilungen der Anthropologischen Gesellschaft in
Wien, Vol. xxxiv. pp. 331—352.

3 Ibid. p. 947.

Fossil Monkeys 1*27

apes. Let us consider for a little the more essential additions to our
knowledge since the publication of The Descent of Mem.

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 avail-
able 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 fills 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 Europe1, 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 (Pliopi-
thecus), 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,

1 Descent of Man, p. 240.

128 "The Descent of Man"

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 inter-
mediate position of Pithecanthropus, still holds good. Volz says with
justice1, that even if Pithe&mfkropu& 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 never-
theless 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 oldest 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 Diisseldorf, 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 them2 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 discoverer3,
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 Croatia4. 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 I5 have referred to Homo primigenius, and
which has lately been examined in detail by Sollas6, has made us

1 "Das geologische Alter der Pithecanthropus- Schichten bei Trinil, Ost-Java." Neues
Jahrb. f. Mineralogie. Festband, 1907.

2 Descent of Man, p. 82.

3 " La race humaine de Neanderthal ou de Canstatt en Belgique." Arch, de Biologic,
vn. 1887.

4 Gorjanovic-Kramberger. Der diluviale Meiisch von Krapina in Kroatien, 1906.

5 Stiidicn zur Vorgeschichte des Menschcn, 1906, pp. 151 ff.

8 "On the cranial and facial characters of the Neandertal Race." Trans. B. Soc.
London, vol. 199, 1908, p. 281.

Post-Darwinian Discoveries 129

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 estab-
lishing 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 day1.

In quite a different domain from that of morphological relation-
ship, 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.

1 [Since this essay was written Sehoetensack 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. (Sehoetensack, Der Unterkiefer des Homo heidelbergensis. Leipzig,
1908.) G. S.]

D. 9

130 " The Descent of Man"

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 dis-
posal 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 de-
fence and diffusion of Darwin's doctrines, and how in Mans 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

Genealogical Trees 131

over the new conception of the universe. As far back as 1866, in his
Generelle Morphologic, 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 structural relationships of
the different animal groups ; the last of these illustrated the relation-
ships 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 con-
ception 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 sketch1. 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

1 Life and Letters of Thomas Henry Huxley, Vol. n. p. 394.

9—2

132 " The Descent of Man"

life ; he even believes that in his 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 con-
siderations, 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 words1 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 re-
semblance 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 classification2." It has also to be
remembered that numerous separate points of agreement are of
much greater importance than the amount of similarity or dis-
similarity 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

1 Descent of Man, p. 229. 8 Loc. cit.

Man and Monkeys 133

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 (Klaatsch1, Giuffrida-Riiggeri). 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 anthro-
poid 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 re-
semblance between them, without regarding man as derived directly
from the anthropoids. Their many striking points of agreement

1 Klaatsch in his last publications speaks in the main only of an ancestral form
common to men and anthropoid apes.

134 " The Descent of Man'

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 relation-
ship 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 resem-
blances 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 Inverte-
brates, 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 classifica-
tion, 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 par-
ticular. 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 hypo-
thesis 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 per-
verted ; 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.

Man and Monkeys 135

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 in-
dicated 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 Morphologic in 1866, but its general
basis remains the same1. 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. Sergi2 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 Pithecan-
thropus. Kollmann regards existing human races as derived from
small primitive races (pigmies), and considers that Homo primi-
genius must have arisen in a secondary and degenerative manner.

1 Haeckel's latest genealogical tree is to be found in his most recent work, Unsere
Ahnenreihe. Jena, 1908.

2 Sergi, G. Europa, 1908.

136 " The Descent of Man"

But this is not the place, nor have I the space to criticise the
various special theories of descent. One, however, must receive par-
ticular notice. According to Ameghino, the South American monkeys
(Pithecvlite8)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 pampaeus1.
The fossil forms discovered by Ameghino deserve the most minute
investigation, as does also the fossil man from South America of
which Lehmann-Nitsche2 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 investiga-
tion of the question of all questions, the descent of the human race.

1 See Ameghino's latest paper, "Notas preliminares sobre el Tetraprotliomo aryentinus,"
etc. Anales del Museo national de Buenos Aires, xvi. pp. 107 — 242, 1907.

2 " Nouvelles recherches sur la formation patnpeenne et 1'houime fossile de la Kepublique
Argentine." Rivista del Museo de la Plata, T. xiv. pp. 193—488.

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 im-
possible until the theory of descent had been established.

It is now a hundred years since the great French biologist
Jean Lamarck published his Philosophic Zoologique. By a re-
markable 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 trans-
formation 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 found-
ing of comparative embryology by Baer (1828) and of the cell-theory
by Schleiden and Schwann (1838), the advance of physiology under
Johannes Miiller (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

138 Darwin as an Anthropologist

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 Morphologic (1866)1
which was followed by a more popular treatment of the subject in
my Naturliche Schopfungsgeschichte (1868)2, a compilation from the
earlier work. In the first volume of the Generelle Morpkologie
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 palae-
ontological or genealogical series) conditioned by laws of heredity
and adaptation." The " Systematic introduction to general evo-
lution," with which the second volume of the Generelle Morpho-
logie 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 Morphologic — 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 pro-
gressive : 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 oft" dysteleology

1 Generelle Morphologic tier Organismen, 2 vols., Berlin, 18G6.

2 Eng. transl. ; The History of Creation, London, 1876.

Heredity 139

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 con-
servative 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 morpho-
logical 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 off-
spring 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 modi-
fications (degeneration, retrograde metamorphosis, etc.) come under
the same head.

Transformative heredity — or the transmission of acquired charac-
ters— 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

140 Darwin as an Anthropologist

through a series of generations, and is not affected by environ-
mental 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 ex-
pounded 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}1, 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 mor-
phology 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

1 London, Hies.

Darwin's Successors 141

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
Meclianisch-Physiologische Theorie der Abstammungslehre1, 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 Vries2, 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
Roux3 of "the struggle of parts within the organism, a supple-
mentation 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

1 Munich, 1884. 2 Die Mutationstheorie, Leipzig, 1903.

1 Der Kampf der Theile im Organismus, Leipzig, 1881.

142 Darwin as an Anthropologist

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 cumu-
lative 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 "me-
chanical 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 selec-
tion is, in my opinion, the work of Richard Semon: Die Mneme
als erhaltendes Prinzip im Wechsel ties organischen Geschehens1.
He offers a psychological explanation of the facts of heredity by
reducing them to a process of (unconscious) memory. The physio-
logist 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 Plastidwle* I elabo-
rated 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 triuitarian
conception of substance in the nineteenth chapter of my Die
Lebenswunder (1904)3, 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.

1 Leipzig, 1904. • Berlin, 1876.

3 Wonders of Life, London, 1904.

Embryology 143

I had endeavoured to show in 1874, in the first chapter of my
Anthropogenic1, 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 period2."

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 Miiller made a closer
study of these important phenomena in the instructive instance of
the Crustacean larva, as given in his able work Fiir Darwin3 (1864).
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, main-
tained 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*. 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

1 Eng. transl. ; The Evolution of Man, 2 vols., London, 1879 and 1905.

2 Origin of Species (6th edit.), p. 396.

s Eng. transl. ; Facts and Arguments for Darwin, London, 1869.
4 3 vols., Berlin, 1894—96.

144 Damvin as an Anthropologist

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 adaption 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 (187 1)1. In the "General summary and con-
clusion" (chap, 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 struc-
tures, 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 anthro-
pologist, nor does the school of modern anthropologists regard him

1 Descent of Man (Popular Edit.), p. 927.

Virchoiv's opposition to Darwin 145

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 Wiirzburg (1848 —
1856), he had been a consistent free-thinker, and had in a number of
able articles (collected in his Gesammelte Abhandlungen)1 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

1 Gesammelte Abhandlungen zur wissenschaftlichen Medizin, Berlin, 1856.
D. 10

146 Darwin as an Anthropologist

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 Anthro-
pological 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-
Gedanken1.

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, proceeded2."

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

1 Eng. transl. ; Last Words on Evolution, London, 1906.

2 Descent of Man (Popular Edit.), p. 255.

" The Descent of Man" 147

in geology which Darwin maintained throughout his life and his
complete knowledge- of palaeontology enabled him to grasp the funda-
mental 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 con-
vinced of it as was his great precursor Jean Lamarck in 1809.
Moreover, Darwin adds, with particular explicitness, in the "general
summary and conclusion" (chap, xxi.) of that standard work1:

" By considering the embryological structure of man — the homo-
logies 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 pro-
genitors ; 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 Catar-
rhinae, 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, psy-
chology, 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 Monotre-
mata. The essential identity of all the Mammals in point of ana-
tomical 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.

1 Descent of Man, p. 930.

10—2

148 Darwin as an Anthropologist

The fundamental importance of this comparative morphology of
the Mammals, as a sound basis of scientific anthropology, was re-
cognised 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 ( 1 784),
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 Morphologic (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 Natiirliche Schopfungs-
geschichte (1868 — 1902) \ 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 Phylogenie2 (1894 Protists and Plants,
1895 Vertebrates, 1896 Invertebrates). In my Anthropogenic* 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 develop-
ment of each organ of the body, beginning with the most elemen-
tary 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.

1 Eng. transl.; The History of Creation, London, 1876. 2 Berlin, 1894—96.

8 Leipzig, 1874, 5th edit. 1905. Eng. transl. ; The Evolution of Man, London,
1905.

Man's Place in Nature 149

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
Man1. 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) Ce-
nozoic Primates (Lemuridae 24 — 25, Tailed Apes 26 — 27, Anthropo-
morpha 28 — 30). An improved and enlarged edition of this hypothetic
" Progonotaxis hominis" was published in 1908, in my essay Unsere
AhnenreiJie2.

If I have succeeded in furthering, in some degree, by these an-
thropological 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 them-
selves 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 in-
ductive law was firmly established was it possible to vindicate the
special conclusion, the descent of man from a series of other Verte-
brates. By his illuminating discovery Darwin did more for anthro-
pology 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

1 London, 1898.

2 Festschrift zur 350-jahrigen Jubelfeier der Thilringer Universitat Jena. Jena,
1908.

150 Darwin as an Anthropologist

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 un-
cultivated 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 Man1.

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 sup-
plementary work, TheExpression of the Emotion* in Man and A n imals.
To understand the historical development of Darwin's anthropology one

1 London, 1885; 1888.

Darwin's vietvs on the Descent of Man 151

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)1 and in the supplementary volume Die Lebens-
wunder (1904)2, 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-em-
bracing " 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 " mo-
nistic 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.

1 The Riddle of the Universe, London, 1900.

2 The Wonders of Life, London, 1904.

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 Aveather 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 Procue and
Philomela, which Greek tradition associated with the spot. North-
wards, 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

Creation of Man out of Clay 153

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 battle-
field 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 clay1. 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
soul2." 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

1 Pausanias, x. 4. 4. Compare Apollodorus, Bibliotheca, i. 7. 1 ; Ovid, Mrtamorph.
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 Lycaouia. 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.
'Iriviov, pp. 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,
n. 27. The creation of man by Prometheus is figured on ancient works of art. See
J. Toutain, Etudes de Mytltoloyie et d'Histoire des Religions Antiques (Paris, 1909), p. 190.
According to Hesiod (Works find Days, 60 sqq.) it was Hephaestus who at the bidding
of Zeus moulded the first woman out of moist earth.

8 Genesis ii. 7.

154 Primitive Theories of the Origin of Man

(adani)1. From various allusions in Babylonian literature it would
seem that the Babylonians also conceived man to have been moulded
out of clay2. 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 blood3. In Egyptian mythology Khnoumou,
the Father of the gods, is said to have moulded men out of clay4.
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 men5. 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 like-
ness6. A very generally received tradition in Tahiti was that the
first human pair was made by Taaroa, the chief god. They say that

1 S. B. Driver and W. H. Bennett, in their commentaries on Genesis ii. 7.

2 H. Zimmern, in E. Schrader's Die Keilinschriften und das Alte Testament3 (Berlin,
1902), p. 506.

3 Eusebius, Chronicon, ed. A. Schoene, Vol. i. (Berlin, 1875), col. 16.

4 G. Maspero, Histoire Ancienne des Peuples de V Orient Classique, i. (Paris, 1895),
p. 128.

6 E. 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. pp. 220 sq.~\.

B B. Taylor, Te Ika A Maui, or New Zealand and its Inhabitants, Second Edition
(London, 1870), p. 117. Compare E. Shortland, Maori Religion and Mythology (London,
1882), pp. 21 sq.

Creation of Man out of Clay 155

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 race1." However, the same tradi-
tion 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 pair2. The Maoris also are
reported to believe that the first woman was made out of the first
man's ribs3. 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 Tetata4.

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

1 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), p. 109.

2 G. Turner, Samoa (London, 1884), pp. 267 sq.

3 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."

4 G. Turner, Samoa, pp. 300 sq.

156 Primitive Theories of the Origin of Man

in them are sneaks, and men who have cock's blood in them are
brave1. 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 woman2. 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 death3.

The inhabitants of Noo-hoo-roa, in the Kei Islands say that their
ancestors were fashioned out of clay by the supreme god, Dooad-
lera, who breathed life into the clay figures4. 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

1 J. Kubary, "Die Religion der Pelauer," in A. Bastian's Allerlti aus Volka- u»d
Menscht-nkunde (Berlin, 1888), i. 3, 56.

2 R. H. Codringtou, Th- Mslnm'tinns (Oxford, 1891), p. 158.

3 R. H. Codrington, op. cit., pp. 157 sq.

4 C. M. Pleyte, "Ethnographische Beschrijving der Kei-Eilnnden," Tijdschrift van het
Nederlandsch Aardrijkskundig Genootschap, Tweede Serie, x. (1893), p. 564.

Creation of Man out of Clay 157

Adam and the woman Ewa1." 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
kum pang- tree. After that they called to him and he answered ; they
cut him and blood flowed from his wounds2.

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 com-
pletion 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 same3." The Khasis of Assam
tell a similar tale4.

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

1 N. Graafland, De Minahassa (Rotterdam, 1869), i. pp. 96 sq.

2 Horsburgh, quoted by H. Ling Roth, The Natives of Sarawak and of British North
Borneo (London, 1896), i. pp. 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, n. (1863), p. 27.

3 Capt. T. H. Lewin, Wild Races of South-Eastern India (London, 1870), pp. 224 — 26.

4 A. Bastian, Vdlkerstcimme am Brahmaputra und verwandtschaftliche Nachbarn (Berlin,
1883), p. 8; Major P. R. T. Gurdon, The Khasis (London, 1907), p. 106.

158 Primitive Theories of the Origin of Man

other and began to laugh, whereupon God sent them into the world1.
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 d 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 life2. 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 woman3. 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 descendants4. 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
Scripture5. 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 mankind6.

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

1 J. Spieth, Die Ewe-Stamme, Material zur Kunde des Eive-Volkes in Deutsch-Togo
(Berlin, 1906), pp. 828, 840.

2 Report of the International Expedition to Point Barrow (Washington, 1885), p. 47.

3 E. W. Nelson, "The Eskimo about Bering Strait," Eighteenth Annual Report of
the Bureau of American Ethnology, Part i. (Washington, 1899), p. 454.

4 Friar Geronimo Boscana, "Chinigchinich," appended to [A. Eobinson's] Life in
California (New York, 1846), p. 247.

5 M. Le Page Du Pratz, The History of Louisiana (London, 1774), p. 330.

6 A. de Herrera, General History of the vast Continent and Islands of America, trans-
lated into English by Capt. J. Stevens (London, 1725, 1726), in. 254 ; Brasseur de Bour-
bourg, Histoire des Nations Civilisees du Mexique et de VAmerique-Centrale (Paris, 1857—
1859), in. 80 sq. ; compare id. i. 54 sq.

Kinship of Man witli Animals 159

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 go1."

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 a man, if it had them2." 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 clothes3."
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 beings4.
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 die5.

1 E. J. Payne, History of the New World called America, i. (Oxford, 1892), p. 462.
- Bev. John Campbell, Travels in South Africa (London, 1822), n. p. 34.

3 I. Petroff, Report on the Population, Industries, and Resources of Alaska, p. 145.

4 L. Sternberg, "Die Eeligion der Giljaken," Archiv fur Religionswissenschaft, vin.
(1905), p. 248.

5 K. von den Steinen, Unter den Naturvolkern Zentral-Brasiliens (Berlin, 1894),
pp. 352 sq., 512.

160 Primitive Theories of the Origin of Man

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 mem-
bers 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
violence1. 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 cranes2. 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?3" 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 our-
selves, 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

1 A. 0. Haddon, "The Ethnography of the Western Tribe of Torres Straits," Journal
of the Anthropological Institute, xix. (1890), p. 393 ; Reports of the Cambridge Anthropolo-
gical Expedition to Torres Straits, v. (Cambridge, 1904), pp. 166, 1S4.

2 W. W. Warren, "History of the Ojibways," Collections of the Minnesota Historical
Society, v. (Saint Paul, Minn. 1885), pp. 47, 49.

3 E. Palmer, "Notes on some Australian Tribes," Journal of the Anthropological
Institute, xm. (1884), p. 300.

Kinship of Man with Animals 161

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 \ A Mandingo porter has been known
to offer the Avhole of his month's pay to save the life of a python, be-
cause 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 venge-
ance to be taken by the reptile kinsfolk of the murdered serpent2.

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 death3. 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*."
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 pretext5. Once when Mr Partridge's canoe-

1 T. Arbousset et F. Daumas, Relation d'un Voyage d! Exploration an Nord-Est de la
Colonie du Cap de Bonne-Esperance (Paris, 1842), pp. 349 s<?., 422 — 24.

a M. le Docteur Tautain, "Notes sur les Croyances et Pratiques Eeligieuses des
Banmanas," Revue d' Ethnographic, in. (1885), pp. 396 sq. ; A. Rancon, Dans la Haute-
Gambie, Voyage d'Exploration Scientijique (Paris, 1894), p. 445.

1 J. Keller, "Ueber das Land und Volk der Balong," Deutsches Kolonialblatt,
1 Oktober, 1895, p. 484.

4 Father Trilles, "Chez les Fang, leurs Moeurs, leur Langue, leur Religion," Les
Missions Catholiques, xxx. (1898), p. 322.

6 Miss Mary H. Kingsley, Travels in West Africa (London, 1897), pp. 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. pp. 459 — 461 ; R. Hen-
shaw, "Notes on the Efik belief in 'bush soul,'" Han, vi. (1906), pp. 121 sq.; J. Parkinson,
"Notes on the Asaba people (Ibos) of the Niger," Journal of the Anthropological Institute,
xxxvi. (1906), pp. 314 sq.

D. 11

162 Primitive Theories of the Origin of Man

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 die1." 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 compensa-
tion for the murder of the woman, whose soul or second self had been
in that hippopotamus2. 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 animal3.

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 upright4.
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 position5." The Turtle
clan 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 eifort he heaved it off
altogether. After that he gradually developed into a man and
became the progenitor of the Turtle clan6. The Crawfish band of the

1 Charles Partridge, Cross River Natives (London, 1905), pp. 225 s^.
1 C. H. Robinson, Hausaland (London, 1896), pp. 36 sq.

3 Notes Analytiques sur les Collections Ethnographiques du Musee du Congo, i.
(Brussels, 1902—06), p. 150.

4 H. B. Schoolcraft, Indian Tribes of the United States, iv. (Philadelphia, 1856),
pp. 224 nq. ; compare id. v. p. 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), p. 299.

6 Charles Darwin, The Descent of Man, Second Edition (London, 1879), p. 60.
8 E. A. Smith, "Myths of the Iroquois," Second Annual Report of the Bureau of
Ethnology (Washington, 1883), p. 77.

Descent of Man from Animals 163

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 oft* 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 day1. 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 brethren2. 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 sun3. 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 woman4. 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 walking5." 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 produced6. The Delaware Indians
called the rattle-snake their grandfather and would on no account

1 Geo. Catlin, North American Indians* (London, 1844), n. p. 128.
3 Lewis and Clarke, Travels to the Source of the Missouri River (London, 1815), i. 12
(Vol. i. pp. 44 sq. of the London reprint, 1905).

3 Lettres Edifiantes et Curieuses, Nouvelle Edition, vi. (Paris, 1781), p. 171.

4 L. H. Morgan, Ancient Society (London, 1877), p. 180.

5 J. Owen Dorsey, "Omaha Sociology," Third Annual Report of the Bureau of
Ethnology (Washington, 1884), pp. 229, 233.

6 G. M. Dawson, Report on the Queen Charlotte Islands (Montreal, 1880), pp. 149 B sq.
(Geological Survey of Canada) ; F. Poole, Queen Charlotte Islands, p. 136.

11—2

164 Primitive Theories of the Origin of Man

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 grand-
father 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
themselves1."

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 bird2. 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 hyaena3. Some Malagasy families
claim to be descended from the babacoote (Lichanotus brevi-
caudatus), 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 him4. Many of the

1 Rev. John Heckewelder, "An Account of the History, Manners, and Customs, of the
Indian Nations, who once inhabited Pennsylvania and the Neighbouring States," Trans-
actions of the Historical and Literary Committee of the American Philosophical Society, i.
(Philadelphia, 1819), pp. 245, 247, 248.

2 Garcilasso de la Vega, First Part of the Royal Commentaries of the Yncas, Vol. i.
p. 323, Vol. n. p. 156 (Markham's translation).

3 Charles New, Life, Wanderings, and Labours in Eastern Africa (London, 1H73), p. 122.
* Father Abiiial, "Croyances fabuleuses des Malgaches," Les Missions Cutholiques, xii.

(1880), p. 526; G. H. Smith, "Some Betsimisaraka superstitions," The Antananarivo
Annual and Madagascar Magazine, No. 10 (Antananarivo, 1886), p. 239 ; H. W. Little,
Madagascar, its History and People (London, 1884), pp. 321 sq. ; A. van Gennep, 1'abou et
Totemisme a Madagascar (Paris, 1904), pp. 214 sqq.

Descent of Man from Animals 165

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 consequence1." 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
head2.

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 sort3. 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. Con-
ceiving the idea she would make, what he had long wished for, a

1 G. A. Shaw, "The Aye-aye," Antananarivo Annual and Madagascar Magazine,
Vol. n. (Antananarivo, 1896), pp. 201, 203 (Reprint of the Second four Numbers). Com-
pare A. van Gennep, Tabou et Totemisme a Madagascar, pp. 223 sq.

2 Father Abinal, "Croyances fabuleuses des Malgaches," Les Missions Catholiques, xn.
(1880), p. 527 ; A. van Genuep, Tabou et Totemisme a Madagascar, pp. 281 sq.

3 A. B. Ellis, The Tshi-speaking Peoples of the Gold Coast of West Africa (London,
1887), pp. 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. pp. 211 sq.).

166 Primitive Theories of the Origin of Man

charming wife for his son, he took her home and educated her untL
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 race1."

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 clan2. 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
animals3. 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 Panrlion
Haliaetus. Others claim to be sprung from pigs, octopuses, croco-
diles, 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 taboos4. Similarly in
Ceram persons who think they are descended from crocodiles,
serpents, iguanas, and sharks will not eat the flesh of these animals5.

1 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, n. (London,
1863), pp. 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.

2 H. Ris, "De Onderafdeeling Klein Mandailing Oeloe en Pahantan en hare Bevolking
met uitzondering van de Oeloes," Bijdragen tot de Taal- Land- en Volkenkunde run Neder-
landsch-Indifl, XLVI. (1896), p. 473.

3 J. B. Neumann, "Het Pane en Bila-stroomgebied op het eiland Sumatra," Tijdsclirift
van het Nederlandsch Aardrijkskundig Genootschap, Tweede Serie, in. Afdeeliug, Meer
uitgebreide Artikelen, No. 2 (Amsterdam, 1886), pp. 311 sq. ; id. ib. Tweede Serie, iv.
Afdeeling, Meer uitgebreide Artikelen, No. 1 (Amsterdam, 1887), pp. 8 sq.

4 J. G. F. Biedel, De sluik- en kroeshariae rassen tusschfii Selebes en Papua (The Hague,
1886), pp. 32, 61 ; G. W. W. C. Baron van Hoevell, Ambon en meer bepualdelijk de Oeliasen
(Dordrecht, 1875), p. 152.

8 J. G. F. Biedel, op. cit. p. 122.

Descent of Man from, Animals 167

Many other peoples of the Molucca Islands entertain similar beliefs
and observe similar taboos1. 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 sacrilege2.

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 men3. 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
niadas) 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 ago4. 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 everywhere5. 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

1 J. G. F. Eiedel, De sltiik- en kroesharige rassen tmschen Selebes en Papua (The
Hague, 1886), pp. 253, 334, 341, 348, 412, 414, 432.

2 Dr Habl, "Mittheilungeu iiber Sitteu und rechtliche Verhaltnisse auf Ponape,"
Ethnologisches Notizblatt, Vol. n. Heft 2 (Berlin, 1901), p. 10.

8 Captain G. Grey, A Vocabulary of the Dialects of South Western Australia, Second
Edition (London, 1840), pp. 29, 37, 61, 63, 66, 71.

* A. W. Howitt, Native Tribes of South-East Australia (London, 1904), pp. 476, 779 sq.
e A. W. Howitt, op. cit., pp. 476, 780 sq.

168 Primitive Theories of the Origin of Man

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 mankind1.

The Arunta tribe of Central Australia similarly tell how in the be-
ginning mankind was developed out of various rudimentary forms of
animal life. They say that in those days two beings called UngamM-
&M/et, 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 Ungam-
bikula 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 com-
pleted 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 par-
ticular 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

1 S. Gasou, "The Manners and Customs of the Dieyerie tribe of Australian
Aborigines," Native Tribes of South Australia (Adelaide, 1879), p. 260. This \rriter
fell into the mistake of regarding the Mura-Mura (Moor a moor a) 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- Kast Australia, pp. ilosqq.

Arunta Theory of Evolution 169

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 flies1."

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 totem2." 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
evolved3. 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

1 Baldwin Spencer and F. J. Gillen, Native Tribes of Central Australia (London, 1899),
pp. 388 sq.; compare id., Northern Tribes of Central Australia (London, 1904), p. 150.

2 Baldwin Spencer and F. J. Gillen, Native Tribes of Central Australia, pp. 391 sq.

3 E. Zeller, Die Philosophic der Griechen, i.4 (Leipsic, 1876), pp. 718 sq. ; H. Bitter et
L. fie[l(iT,HistoriaPhilosophiae Graecae etRomanae exfontium locis contexta5, pp. 102 sq. ;
H. Diels, Die Fragmente der Vorsokratiker2, i. (Berlin, 1906), pp. 190 sqq. Compare
Lucretius, De rerum natura, v. 837 sqq.

170 Primitive Theories of the Origin of Man

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 DAKWIN 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 pre-
ceding generation, to Cuvier, L. Agassiz, J. Miiller, 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 view1 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 class2." 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 classifi-
cation. 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 develop-
mental processes, so greatly excited by the promulgation of the
Darwinian theory, has to a considerable extent been satisfied.

1 First clearly enunciated by Fritz Miiller in his well-known work, Fur Darwin,
Leipzig, 1864 ; (English Edition, Facts for Darwin, 1869).

2 Origin (6th edit.), p. 396.

172 Darwin and Embryology

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 philo-
sophers, 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 l :

" 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-forin ;
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 Miiller, 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 under-
stand 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

1 Origin (6th edit.), P- 395.

Embryology and Phytogeny 173

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 develop-
ment 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 develop-
mental or (if we include larvae with embryos) embryonic period, for
the developmental changes are more numerous and take place with

174 Darwin and Embryology

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 deter-
mining 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 im-
portance 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 Huxley1 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

1 See Huxley's Scientific Memoirs, London, 1898, Vol. i. p. 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. n. p. 512.

Theory of Recapitulation 175

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 "recapitu-
lation" 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 generalisa-
tion 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 stated1, 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

1 The Evolution Theory, by A. Weismann, English Translation, Vol. n. p. 176,
London, 1904.

176 Darwin and Embryology

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 accom-
panied 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

Reaction and Environment 177

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 necessi-
tate, 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 impair-
ment 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

D. 12

178 Darwin and Embryology

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 pro-
ceeded 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 repeti-
tion, 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

Growth Variations 179

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 differ^
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 modifica-
tion 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 zygotes1,
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 environ-
ment. 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

1 A zygote is a fertilised ovum, i.e. a new organism resulting from the fusion of an
ovum and a spermatozoon.

12—2

180 Darwin and Embryology

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 causa-
tion. 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 con-
stitution and which are caused solely by differences in the environ-
ment 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 con-
ditions 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 ap-
plying 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 Avhat we call in-
heritance 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

Sexual Maturity 181

organism. This brings us back to the question with which we started
this discussion, viz. what is the relation of these variations in struc-
ture, 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 appear-
ance 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

182 Darwin and Embryology

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 en-
vironments 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 develop-
ment 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.

Embryonic Vestiges 183

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 develop-
ment 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.

184 Darwin and Embryology

In writing this essay I have purposely refrained from taking a
definite position with regard to the problems touched. My desire
has been to write a chapter showing the influence of Darwin's work
so far as Embryology is concerned, and the various points which come
up for consideration in discussing his views. Darwin was the last
man who would have claimed finality for any of his doctrines, but he
might fairly have claimed to have set going a process of intellectual
fermentation which is still very far from completion.

XI

THE PALAEONTOLOGICAL RECORD

I. ANIMALS

BY W. B. SCOTT.

Professor of Geology in the University of Princeton, U.S.A.

To no branch of science did the publication of TJte 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 re-
garding 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 life1." The geo-
logical 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 suc-
cession 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 funda-
mentally 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

1 Zittel, History of Geology and Palaeontology, p. 363, London, 1901.

186 Tlic Palaeontological Record. I. Animals

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 re-
peatedly devastated by great cataclysms, which destroyed every
living thing, necessitating an entirely new creation, thus regarding
the geological periods as sharply demarcated and strictly contem-
poraneous 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 "Cata-
strophism" was attacked by several geologists, most effectively by
Sir Charles Lyell, who greatly amplified the principles enunciated
by Button and Play fair 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," "syn-

"The Origin of Species " 187

thetic," "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 theory1."
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 pro-
ceeding 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 group2." 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 lines3."
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
selection4."

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 simul-
taneous origin of certain species and their gradual decay, would
perhaps teach us as much about the mysteries of organisation as

1 Origin of Species (6th edit.), p. 310.

2 Life and Letters of Charles Darwin, i. p. 82.

3 Origin of Species, p. 289. 4 Ibid. p. 313.

188 The Palaeontological Record. I. Animals

we can possibly learn through experiments with living organisms1."
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 phylo-
genetic 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 un-
solved 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

1 Zittel, op. cit. p. 140.

Fossil Mammals 189

wished, different observers will put different interpretations upon
it, as in the notorious case of the Steinheim shells1. The ludicrous
discrepancies 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 un-
worthy 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
diagrammatic2."

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 con-
tinental 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 preserva-
tion. 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 develop-
ment 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.

1 In the Miocene beds of Steinheim, Wiirtemberg, occur countless fresh-water shells,
which show numerous lines of modification, but these have been very differently inter-
preted by different writers.

2 D. H. Scott, Studies in Fossil Botany, p. 524. London, 1900.

190 The Palaeontological Record. I. Animals

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 fore-
arm 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 Mesohippm, 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

Evolution of the Horses 191

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 oif 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 Kowalevsky1, the Palaeotheres were placed in the
direct line, because the number of adequately known Eocene niain-

1 " Sur VAnchitherium aurelianense Cuv. et sur 1'histoire paleontologique des Chevaux,"
Mem. de I'Acad. Imp. des Sc. de St Petersbourg, xx. no. 5, 1873.

192 The Palaeontological Record. I. Animals

mals 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 well 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 pro-
portions, 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

Rhinoceroses, Camels, and Llamas 193

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

D. 13

194 The Palaeontological Record. I. Animals

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 wrhich 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 elephants1. 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

1 C W. Andrews, "On the Evolution of the Proboscidea," Phil. Tram. Roy. Soc.
London, Vol. 196, 1904, p. 99.

The Origin of Whales and Carnivores 195

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 oif, 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.

13—2

196 The Palaeontological Record. I. Animals

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 like-
nesses 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 extra-
ordinary genus Archaeopteryoc 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 preserva-
tion 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 ;

The Descent of the Ammonites 197

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 con-
cealed 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

198 The Palaeontological Record. I. Animals

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 genera 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 com-
paratively 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 suc-
cession 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

Trilobites ami Echinoderms 199

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 Echino-
derms 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 Echino-
derms, 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 incom-
plete as Darwin believed it to be. Since The Origin of Species was
written, our knowledge of that record has been enormously extended
and we now possess, no complete volumes, it is true, but some
remarkably full and illuminating chapters. The main significance of
the whole lies in the fact, that just in proportion to the completeness
of the record is the unequivocal character of its testimony to the
truth of the evolutionary theory.

The test of a true, as distinguished from a false, theory is the
manner in which newly discovered and unanticipated facts arrange
themselves under it. No more striking illustration of this can be
found than in the contrasted fates of Cuvier's theory and of that of
Darwin. Even before Cuvier's death his views had been undermined
and the progress of discovery soon laid them in irreparable ruin,
while the activity of half-a-century in many different lines of inquiry
has established the theory of evolution upon a foundation of ever
growing solidity. It is Darwin's imperishable glory that he prescribed
the lines along which all the biological sciences were to advance to
conquests not dreamed of when he wrote.

XII

THE PALAEONTOLOGICAL RECORD
II. PLANTS

BY D. H. SCOTT, F.R.S.

President of the Linnean Society.

THERE are several points of view from which the subject of the
present essay may be regarded. We may consider the fossil record
of plants in its bearing : I. on the truth of the doctrine of Evolution ;
II. on Phylogeny, or the course of Evolution; III. on the theory of
Natural Selection. The remarks which follow, illustrating certain
aspects only of an extensive subject, may conveniently be grouped
under these three headings.

I. THE TRUTH OF EVOLUTION.

When The Origin of Species was written, it was necessary to
show that the Geological Record was favourable to, or at least
consistent with, the Theory of Descent. The point is argued, closely
and fully, in Chapter x. "On the Imperfection of the Geological
Record," and Chapter XL " 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 science1. 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

1 J. Reinke, " Kritische Abstammungslehre," Wiesncr-Fegtschrift, p. 11, Vienna, 1908.

The Truth of Evolution 201

the last section of this essay) or must still rely on Darwin's explana-
tion 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 l. 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 still2.

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 gener-
ally 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
stress3 and which has more recently been elaborated by Poulton4.
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 over-
looked, which has lately been revived by Reinke5. As all admit,

1 Trans. Royal Soc. Edinburgh, Vol. 45, Pt. in. 1907, Vol. 46, Pt. 11. 1908, Vol. 46,
Pt. in. 1909.

2 See Seward and Gowan, "The Maidenhair Tree (Ginkgo biloba)," Annals of Botany,
Vol. xiv. 1900, p. 109; also A. Sprecher, Le Ginkgo biloba L., Geneva, 1907.

3 Origin of Species (6th edit.), p. 286.

4 Essays on Evolution, pp. 46 et seq., Oxford, 1908.

5 Reinke, loc. cit. p. 13.

202 The Palaeontological Record. II. Plants

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 tin's 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 King-
dom. 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 : " Xo 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 descendants1." 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 pro-
gression 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

1 Origin of Speciea, p. 425.

From the Complex to the Simple 203

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 Angio-
sperms came from a type with a flower resembling in its complexity
that of Mesozoic " Cvcads," 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 conside-
ration) 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 counter-
vailing 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 pro-
portion 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 advanced1."
Further on2 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 Meso-
zoic Cycads. There is a general advance in the succession of classes,
but not within each class.

1 Origin of Species, p. 308. 2 Ibid. p. 309.

204 The Palaeontological Record. II. Plants

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 scale1" is unanswerable,
but we must remember that "higher in the scale" only means "better
adapted to the existing conditions." Darwin points out2 that species
have remained unchanged for long periods, probably longer than the
periods of modification, and only underwent change when the con-
ditions 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 in-
coming 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 palaeonto-
logical 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

1 Origin of Species, p. 315. a Ibid. p. 279.

Origin of Angiosperms 205

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 inter-
vention of a stigma, the strange phenomenon of double fertilisation1,
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 mystery2." 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 appa-
rently 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 Pole3." 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

1 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.

2 More Letters of Charles Darwin, Vol. n. p. 20, letter to J. D. Hooker, 1879.

3 Ibid. p. 26, letter to Hooker, 1881.

206 The Pdlaeontological Record. II. Plants

leaves give the Cycads a superficial resemblance in habit to Palms.
Recent Cycads are dioecious ; throughout the family the male fructifi-
cation 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 crypto-
gamic 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 repro-
ductive 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 fructifi-
cations, 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
Wyoming1. 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

1 G. K. Wieland, American Fossil Cycads, Carnegie Institution, Washington, 1906.

Origin of Angiosperms 207

bracts, forming collectively a kind of perianth and completely en-
closing 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 com-
partments 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 sur-
rounding whorl of stamens and an enveloping perianth ; there is,
as we have seen, some approach to the closed ovary of an Angio-
sperm ; 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,

208 The Palaeontological Record. II. Plants

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 Angiospenns, 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 times1.

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
Angiospenns 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 elabora-
tion of floral structure attained among the Mesozoic Cycadophyta,
which preceded the Angiosperms in evolution.

If, as now seems probable, the Augiosperms 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 grounds2. So far,
however, as the palaeoutological 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 gyrn-
nospermoiis level as regards their pollination, for the exposed

1 On this subject see, in addition to Wieland's great work above cited, F. W. Oliver,
" Pteridosperms and Augiosperms," 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 Angio-
sperms," Journal Linn. Soc. (Bot.) Vol. xxxvm. p. 29, 1907.

2 See especially Ethel Sargant, " The Reconstruction of a Race of Primitive Angio-
sperms," Annals of Botany, Vol. xxn. p. 121, 1908.

Origin of Seed-plants 209

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 promi-
nent 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 century1. 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 light2." 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

1 W. Hofmeister, 0/t the Germination, Development and Fructification of the Higher
Cryptogamia, Kay Society, London, 1862. The original German treatise appeared in
1851.

2 Ibid. p. 438.

D. 14

210 The Palaeontological Record. II. Plants

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 sperma-
tozoids 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 charac-
ters of Ferns and Cycads1. 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 Lygiuodendron, 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

1 See especially his "Organisation of the Fossil Plants of the Coal-Measures," Part xm.
Phil. Trans. Royal Soc. 1887, B. p. 299.

Pteridospermeae 211

association between the seed and the plant1. 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 Lygino-
dendron, 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
Cycadaceae2. 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 Ferns3.

The general conclusion which follows from the various obser-
vations 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, re-
taining 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,

1 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.

2 A summary of the evidence will be found in the writer's article "On the present
position of Palaeozoic Botany," Progressus Rei Botanicae, 1907, p. 139, and Studies in
Fossil Botany, Vol. n. (2nd edit.) London, 1909.

3 Kidston, " On the Microsporangia of the Pteridospermeae, etc." Phil. Trans. Royal
Soc. Vol. 198, B. 1906.

14—2

212 The Palaeontological Record. II. Plants

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 unmis-
takable 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 Cycado-
phyta 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 \

It may be mentioned here that the small gymnospennous
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

1 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, Eecent
and Extinct," Phil. Trans. Royal Soc. Vol. 198, B. 1906.

Early History of Ferns 213

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 Pteri-
dophyta 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 Palaeo-
zoic, 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 diffi-
culty ; 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

214 The Palaeontological Record. II. Plants

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 Botryopte-
rideae) 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 repre-
sented 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 proba-
bility, 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

Early History of Lycopods 215

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 Pseudo-
bornia, consisting of large plants, remarkable for their highly com-
pound 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 Pseudoborniales1.

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 Pseudo-
borniales 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 remark-
able 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 genera2 (Selaginella and Isoetes) have spores
of two kinds, while the other two (Lycopodium and Phylloglossum)
are homosporous. Curiously enough, no certain instance of a homo-
sporous 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 Carboni-
ferous, 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

1 A. G. Nathorst, " Zur Oberdevonischen Flora der Baren-Insel," Kotigl. Svenska
Vetenskaps-Akademiem Handlingar, Bd. 36, No. 3, Stockholm, 1902.

2 Excluding Psilotaceae.

216 The Palaeontological Record. II. Plants

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 repre-
sentatives show no special simplicity. If the indications of affinity
with Sphenophylls are of any value the Lycopods are open to sus-
picion 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 hypo-
thetical, 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

Natural Selection 217

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 maintain-
ing 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 descend-
ants 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

218 The Palaeontological Record. II. Plants

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 morpho-
logical and adaptive characters, on which Nageli, in particular, laid
so much stress. The question is a difficult one ; it was discussed by
Darwin1, 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 agency2."

This is a sufficiently liberal concession ; Nageli, however, went
much further when he said: "I do not know among plants a morpho-
logical modification which can be explained on utilitarian principles3."
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

1 Origin of Species (6th edit.), pp. 170—176. - Ibid. p. 176.

8 See More Letters, Vol. n. p. 375 (footnote).

Morphological C/iaracters 219

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 recognised1.
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 spermato-
zoids 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 indistinguish-
able 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 Selaginella2. 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

1 F. W. Oliver, "On Physostoma elegans, an archaic type of seed from the Palaeozoic
Bocks," Annals of Botany, January, 1909. See also the earlier papers there cited.

2 See Margaret Benson, "Miadesmia membranacea, a new Palaeozoic Lycopod with a
seed-like structure," Phil. Tram. Royal Soc. Vol. 199, B. 1908.

220 The Palaeontological Record. II. Plants

sprang into being in obedience to a Law of Advance (" Vervollkom-
mungsprincip"), from which other contemporary Lycopods were ex-
empt, 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 crytogamic 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 (p. 208), 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 differen-
tiation of the seed was a process of adaptation, and consequently

Mutations 221

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 ap-
parently 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 *and Zeiller2,
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 suc-
cessive terms of which we yet recognise bonds of filiation3.

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 earth4."

It must 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 com-
paratively small changes, of sub-specific value, described by De Vries
in the type-case of Oenothera Lamarckiana. The results of palaeo-
botanical research have undoubtedly tended to fill up gaps in the
Natural System of plants — that many such gaps still persist is not

1 C. Grand'Eury, "Sur les mutations de quelques Plantes fossiles du Terrain houiller."
Comptes Rendus, CXLII. p. 25, 1906.

2 B. Zeiller, "Les Ve'ge'taux fossiles et leurs Enchainements," Revue du Mois, in.
February, 1907.

3 loc. cit. p. 23. * Origin of Species, p. 424.

222 The Palaeontological Record. //. Plants

surprising ; their presence may well serve as an incentive to further
research but does not, as it seems to the writer, justify the assump-
tion of changes in the past, wholly without analogy among living
organisms.

As regards the succession of species, there are no greater au-
thorities 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 Darwin1; 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 selection2."

1 Origin of Species, pp. 275—282, and p. 312. " Ibid. p. 313.

XIII

THE INFLUENCE OF ENVIRONMENT ON THE

FORMS OF PLANTS

BY GEORG KLEBS, Pn.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 investi-
gated 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 com-
parative morphology and the study of phases of development reached
their highest point.

The forms of plants appeared to be the expression of their in-
scrutable 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 im-
portance of such a causal morphology emerged from the researches
of the physiologists of that time, more especially from those of
Hoftneister1, and afterwards from the work of Sachs2. 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 deter-
mining its form." This advance was the outcome of the influence of

1 Hofmeister, Allyemeine Morphologie, Leipzig, 1868, p. 579.

2 Sachs, Staff und Form der Pflanzenorgane, Vol. r. 1880 ; Vol. n. 1882. Gesammelte
Abhandlungen ilber PJlanzen-Physiologie, n. Leipzig, 1893.

224 Influence of Environment on Plants

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.
Lamarck1 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 it2."

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 book3. 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 variability4." Darwin
did not draw further conclusions from this general principle.

Variations produced in organisms by the environment are dis-
tinguished by Darwin as "the definite" and "the indefinite6." 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

1 Lamarck, Philosophic zoologique, pp. 223 — 227. Paris, 1809.

2 Life and Letters, Vol. n. p. 215.

3 Darwin, The variation of Animals and Plants under domestication, 2 vols., edit. 1,
1868; edit. 2, 1875; popular edit. 1905.

4 The variation of Animals and Plants (2nd edit.), Vol. n. p. 242.

5 Ibid. n. p. 260. See also Origin of Species ^6th edit.), p. 6.

Variability 225

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 spon-
taneously1." 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 varia-
bility. 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 vary2": 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, Nageli3 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

1 Origin of Species (6th edit.), p. 421.

2 Life and Letters, Vol. in. p. 342.

3 Nageli, Theorie der Abstammungslehre, Munich, 1884; cf. Chapter in.

D. 15

226 Influence of Environment on Plants

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 re-
cognisable 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 Vries1, 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 Johannsen2 says,
on a pure "line." What has long been recognised as necessary in
the investigation of fungi, bacteria and algae must also be in-
sisted on in the case of flowering plants; we must start with a
single individual which is reproduced vegetatively or by strict self-

1 de Vries, Die Mutationstheorie, Leipzig, 1901, Vol. i. p. 33.

2 Johannsen, Ueber Erblichkeit in Populationen und reinen Linien, Jena, 1903.

Specific Structure 227

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 environ-
ment 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 after-
wards 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 conditions1, are to be included as such potentialities in cells;
the conception of specific structure includes the whole of the poten-
tialities 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 systems2; 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

1 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 Bliiten," Pringsheim's Jahrb. Wiss. Bot.
1905, p. 298; also Detto, Biol. Centralbl. 1907, p. 81, "Die Erklarbarkeit der Ontogenese
durch materielle Anlagen."

2 Compare Kohl's work on Anatomisch-phys. Untersuchungen ilber Kalktahe, etc.
Marburg, 1889.

15—2

228 Influence of Environment on Plants

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 solu-
tions, 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 gene-
rations 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

Relation between External Influences and Development 229

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 inde-
pendently 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 con-
venience 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 charac-
teristic of each species, and these consist in a regular sequence of
definite forms. It is impossible to form an opinion from mere obser-
vation 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 treat-
ment. 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

230 Influence of Environment on Plants

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
Algae1, as in the case of Fungi, we may classify the stages of develop-
ment 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 modify-
ing 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 repro-
duction. 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 differ-
ences 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 un-
doubtedly detect a certain unity in the multiplicity of the individual
phenomena.

If we compare the factors essential for the different stages in de-
velopment, 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 con-
ditions of nutrition remain at a certain optimum for growth. In
order to bring about asexual reproduction, e.g. the formation of zoo-
spores, 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 vari-
ations which induce sexual reproduction in algae. The controlling

1 See Klebs, Die Bedingung der Fortpjianzung..., Jena, 1896 ; also Jahrb.fiir TTi'ss. Bot.
1898 and 1900; "Problems der Entwickelung, in." Liol. Centralbl. 1904, p. 452.

Quantitative alteration of External Conditions 231

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 distri-
bution 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 pro-
duced 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 repro-
ductive purposes, or buds on tubers, runners, rhizomes, etc. A grow-
ing 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, de-
pendent simply on the specific structure, which compels a plant to
produce its flowers after a definite period of vegetative growth \

1 Klebs, Willkurliche Entwickelungsanderunoen, Jena 1903 ; see also " Probleme der
Entwickelung, i. n." Biol. Centralbl. 1904.

232 Influence of Environment on Plants

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 germination1.
This shortening of the period of development is exhibited in the
most striking form in trees, as in the oak2, 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 flower3. Theoretically, however, experi-
ments are of greater importance in which the production of flowers is
inhibited by very favourable conditions of nutrition4 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, how-
ever, 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 case of 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.

1 Cf. numerous records of this kind by Diels, Jutjendformen itnd Blilten, Berlin, 1906.

2 Mobiua, Beitrage zur Lehre von der Fortpjlanzujic/, Jena, 1897, p. 89.
'•'• Klebs, Willkiirliche Aenderungen, etc. Jena, 1903, p. 130.

4 Klebs, Ueber Idinstliche Metamorphoses, Stuttgart, 190G, p. 115 (Abh. Nattirf. Ges.
Halle, xxv.).

Influence of Environment on Plant-organs 233

ii. Influence of the environment on the form of single organs1.

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 pro-
duce 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 Knight2 that tubers may be developed
on the aerial stem in place of foliage shoots. These observations
were considerably extended by Vochting3. 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 sub-
stitution 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 import-
ance as regards the problem of the development and place of origin
of organs4. 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 comple-
mentary 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.

1 A considerable number of observations bearing on this question are given by Goebel
in his Experimented Morphologic der Pflanzen, Leipzig, 1908. It is not possible to deal
here with the alteration in anatomical structure ; of. Kiister, Pathologische Pflanzen-
anatomie, Jena, 1903.

2 Knight, Selection from the Physiological and Horticultural Papers, London, 1841.

3 Vochting, Veber die Bildung der Knollen, Cassel, 1887 ; see also Bot. Zeit. 1902, 87.

4 Reference may be made to the full summary of results given by Goebel in his Experi~
mentelle Morphologie, Leipzig and Berlin, 1908, Section iv.

234 Influence of Environment on Plants

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 con-
sists 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 pro-
duction of new roots or buds may be induced without previous
injury and simply by a change in external conditions assumes an
importance1.

A specially striking phenomenon of regeneration, exhibited also
by uninjured plants, is afforded by polarity, which was discovered by
Vbchting2. 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 ex-
pression of previous development. Vbchting 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

1 Klebs, Willkilrliche Entieickelung, p. 100; also, " Probleme der Entwickelung," Biol.
Centralbl. 1904, p. 610.

8 See the classic work of Vochting, Ueber Organbildung im Pflantenreich, i. Bonn,
1888 ; also Bot. Zeit. 1906, p. 101 ; cf. Goebel, Experimentelle Morphologic, Leipzig and
Berlin, 1908, Section v, Polaritat.

Influence of Environment on Plant-organs 235

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. Sempervivum1,
rosettes or flower-shoots are formed in response to external con-
ditions 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 experi-
ments of Stahl, Winkler, Kniep, and others indicate the right method
of attacking the problem.

The relation of leaf-form to environment has often been investi-
gated and is well known. The leaves of bog and water plants2 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 modi-
fied. 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 mountains3 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 essenti-
ally 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 de-
pend 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,

1 Klebs, " Variationen der Bliiten," Jahrb. Wiss. Bot. 1905, p. 260.

2 Cf. Goebel, loc. cit. chap. n. ; also Gliick, Untersuchungen iiber Wasser-'und Sumpf-
gewdchse, Jena, Vols. i. — n. 1905 — 06.

3 Bonnier, Recherches sur V Anatomic experimentale des Vegttaux, Corbeil, 1895.

236 Influence of Environment on Plants

Gallon, and others the statistical examination of individual differ-
ences 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 variability1.
But there is no such law which compels a plant to vary in a par-
ticular 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 conditions2.
As each of these conditions includes within certain limits all possible
values and exhibits all possible combinations, it follows that, accord-
ing to the rules of probability, there must be a mean value, about
which the larger and smaller deviations are distributed. Any cha-
racter 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 experi-
mental investigation3. 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 Serf urn
spectabile, in special circumstances (red light) this is replaced by the
number 5. The more accurately we know the conditions for a par-

1 de Vries, Mutatiomtheorie, Vol. i. p. 35, Leipzig, 1901.

'- Klebs, WillkUrl. Ent. Jena, 1903, p. 141.

3 Klebs, " Studien iiber Variation," Arch, fiir Entw. 1907.

Monstrosities 237

ticular 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 pro-
nounced fluctuations occur relatively rarely and sporadically which
are spoken of as "single variations," or if specially striking as ab-
normalities 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 Masters1 and Penzig2. 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 environ-
ment

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 Blaringhem3 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 Semper vivum* ; indi-
viduals, 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
obtained5. Abnormalities in the greatest variety are produced in

1 Masters, Vegetable Teratology, London, 1869.

2 Penzig, Pflanzen-Teratologie, Vols. i. and u. Genua, 1890 — 94.

3 Blaringhem, Mutation et traumatismes, Paris, 1907.

4 Klebs, Kilnstliche Metamorphosen, Stuttgart, 1906.

8 Of. Lotsy, Vorlesungen ilber Deszendenztheorien, Vol. n. pi. 3, Jena, 1908.

238 Influence of Environment on Plants

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 con-
ditions 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 con-
nection 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; Bateson1
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 environ-
ment 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

1 Bateson, Materials for the study of Variation, London, 1894, p. 5.

The Control of Plant-form 239

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 environ-
ment 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 pro-
duced 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
part 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 Livingstone1
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 sphere2. 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

1 Livingstone, " On the nature of the stimulus which causes the change of form, etc."
Botanical Gazette, xxx. 1900; also xxxir. 1901.

2 Bitter, " Ueber Kugelhefe, etc.," Ber. bot. Gesell. Berlin, xxv. p. 255, 1907.

240 Influence of Environment on Plants

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 repro-
duction ?

The facts, which are as clearly established for the lower as for the
higher plants, teach us that quantitative alteration in the environ-
ment 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, par-
ticularly 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 phy-
siology 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 physio-
logically 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 palaeontology1. A
glance at the controversy which is going on to-day in regard to
different hypotheses shows that the same material may lead different

1 See Lotsy, Vorlesungen (Jena, i. 1900, n. 1908), for summary of the facts.

Transformation of Species 241

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 justi-
fied 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 hybrid1, 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 con-
nection 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-floAvering forms, that a transformation of stamens into
petals may be caused by fungi or by the influence of changed con-
ditions 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 con-
ditions 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

1 Bateson, Reports to the Evolution Committee of the Royal Society, London, 1902 ; cf.
also Lotsy, Vorlesungen, Vol. i. p. 234.

D. 16

242 Influence of Environment on Plants

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 quanti-
tative 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
radicals1. Much more important, however, would be an answer to the
question, whether an individual variation can be converted experi-
mentally 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 trans-
formation 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 essen-
tially 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 Yeasts2 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

1 For instance ethylchloride (C2H3C1) is a gas at 21° C. , ethylenechloride (C.,H4Cla) a
fluid boiling at 84° C., /3 trichlorethane (C.2H3C13) a fluid boiling at 113° C., percblorethane
(CaCl6) a crystalline substance. Klebs, Willkttrliche Entivickehingsanderungen, p. 158.

2 Cf. Detto, Die Theorie der direkten Anpassung..., pp. 98 et s?q., Jena, 1904; see also
Lotsy, Vorlesungen, n. pp. G36 et seq., where other similar cases are described.

Production of Constant Races 243

found in some races which under certain definite conditions lose
their colour or their virulence. Among the phanerogams the in-
vestigations of Schiibler 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 experi-
ments ; 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 gene-
ration. 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 chamaedrys1. During the cultivation of
an artificially modified inflorescence I obtained a race showing modi-
fications in different directions, among which twisting was especially
conspicuous. This plant, however, does not behave as the twisted
race of Dipsacus isolated by de Vries2, which produced each year a
definite percentage of twisted individuals. In the vegetative repro-
duction 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 in-
florescences 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 (^) of the plants obtained from the transformed shoots,
the modification appeared in the following year without any inter-
ference. Of the three plants which were under observation several
years the first lost the character in a short time, while the two others

1 Klebs, Kumtliche Metamorphosen, Stuttgart, 1906, p. 132.

2 de Vries, Mutatio-nstheorie, Vol. 11. Leipzig, 1903, p. 573.

16—2

244 Influence of Environment on Plants

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 bj
Blaringhem1. 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. Tri/olium 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 MacDougal2 who injected
strong (10%) 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 ele-
mentary 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 ob-
tained 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, how-
ever, 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

1 Blaringhem, Mutation et Traumatisme, Paris, 1907.

2 MacDougal, " Heredity and Origin of species," Monist, 1906; " Keport of department nf
botanical research," Fifth Year-book of the Carnegie Institution of Washington, p. 119, 1907.

Effect of Cultivation 245

others, de Vries1 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 Korschinsky2
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 Vilmorin3, 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*
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 pro-
duce 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.

1 Mutationstheorie, Vol. i. pp. 412 et seq.

2 Korschinsky, " Heterogenesis und Evolution," Flora, 1901.

3 L. de Vilmorin, Notices sur I 'amelioration des plantes, Paris, 1886, p. 36.

4 Klebs, Kiinstliche Metamorphosen, Stuttgart, 1906, p. 152.

246 Influence of Environment on Plants

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 circum-
stances favourable to growth differ from those which promote repro-
duction ; 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 sub-
stances, 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 depends1. 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 in-
tensity, 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.

1 Klebs, Kilnstliche Metamorphosen, p. 117.

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, re-
sults must be obtainable which do not appear in the natural environ-
ment. 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 in-
complete, 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.

248 Influence of environment on animals

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 sper-
matozoa are carried to the eggs by chance and are not attracted
by the latter. This statement is the result of numerous experi-
ments 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 of 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
heterogeneous hybridisations, which in normal sea-water are im-
possible. This assumption proved correct. Sea- water has a faintly
alkaline reaction (in terms of the physical chemist its concentration

Heterogeneous hybridisation 249

of hydroxyl ions is about 10~6JV at Pacific Grove, California, and
about 10~5 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 diiferent 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/W 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 % or more of the sea-urchin eggs, while the
sperm of Pycnopodia and Asterina fertilised only 2 °/0 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). Kupel-
wieser 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 franciscamis 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 en-
vironment 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 in-
crease 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 hybridi-
sations in the ocean which in the present state of alkalinity are
practically excluded.

250 Influence of environment on animals

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 experi-
ments on heterogeneous hybridisation of the egg of the sea-urchin
with the sperm of starfish, brittle-stars, criuoids 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 corre-
sponding 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 hybridisa-
tion 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.

(fc) 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

Artificial Parthenogenesis 251

as in the domain of fertilisation. The reader knows that the eggs of
the overAvhelming 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 Avith which such
experiments have been tried long enough. In each form the method
of procedure is someAvhat different and a long series of experiments
is often required before the successful method is found.

The facts of Artificial Parthenogenesis, as the chemical fertilisa-
tion 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 Avith 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 partheno-
genesis 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 AVC 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
A\ray 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

252 Influence of environment on animals

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 develop-
ment soon ceases and the eggs perish in the early stages of segmen-
tation, or after the first nuclear division. But if we treat the same
eggs, after membrane-formation, for from 35 to 55 minutes (at 15° 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

Action of blood on eggs 253

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 essen-
tially 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 (pre-
sumably 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 meta-
morphosis 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.

254 Influence of environment on animals

(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 pro-
duced 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, how-
ever, a second condition, namely, that the solution used for the produc-
tion 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% of the
eggs of Strongylocentrotm jmrpuratns 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 solu-
tion 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.

Origin of twins 255

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 forma-
tion 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 heteroditus) 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 centi-
metres of sea-water and placed the fertilised eggs in the mixture,
about 50% 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 nature1."

We have confined ourselves to a discussion of rather simple
effects of the change in the constitution of the sea-water upon de-
velopment. 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 abnor-
malities 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.

1 Stockard, Archivf. Entwickelunysmechanik, Vol. 23, p. 249, 1907.

256 Influence of environment on animals

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 Yaldivia expedition,
Chun1 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° 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-pheno-
mena 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° 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 develop-
ment holds for the egg of the frog, as Cohen and Peter calculated
from the experiments of 0. Hertwig. The writer found the same
temperature-coefficient for the rate of maturation of the egg of a
mollusc (Lottia).

1 Chun, Aus den Tiefen des Weltmeeres, p. 225, Jena, 1903.

Duration of life 257

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° C. and from
four to nine times smaller than in seas the temperature of which
is about 20° 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 tempera-
ture 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 tempera-
ture by 1° C. the duration of life was about doubled. Lowering the
temperature by 10 degrees therefore prolongs the life of the organism
210, i.e. over a thousand times, and a lowering by 20 degrees pro-
longs 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 develop-
ment 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 tempera-
ture 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° C. the duration
of life is altered five hundred times as much as the rate of develop-
ment ; and, for a change of 20° 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

D. 17

258

Influence of environment on animals

determine natural death are certainly not identical with the pro-
cesses 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 tempera-
ture of from 0° to 1° 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 :

0° to - 20° C.

0° to + 10° C.

A.

(Normal
Forms)

+ 35° to
+ 37° C.

+ 36° to

+ 4PC.

+ 42° to
+ 4fi° C.

ichnusoides
(nigrita)

polaris

urticae

ichnusa

polaris

ichnusoides
(nigrita)

antigone
(ioka&te)

fischeri

io

—

fischeri

antigone
(iokaste)

testudo

dixeyi

polychloros

erythromelas

dixeyi

testudo

Itygiaea

artemis

antiopa

epione

artemis

hygiaea

elymi

wiskotti

cardui

—

wiskotti

elyini

klymene

merrifieldi

atalanta

—

merrifieldi

kli/mene

weismanni

porima

prorsa

porima

weismanni

Effect of temperature on development 259

The reader will notice that the aberrations produced at a very
low temperature (from 0° to — 20° C.) are absolutely identical with
the aberrations produced by exposing the pupae to extremely high
temperatures (42° to 46° C.). Moreover the aberrations produced by
a moderately low temperature (from 0° to 10° C.) are identical with
the aberrations produced by a moderately high temperature (36° to
41° 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. hydro-
lyses) 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°.
But we know also that the temperature coefficients do not vary
equally for 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 tempera-
tures ; 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

17—2

260 Influence of environment on animals

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, Endendrium 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 experi-
ments, 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 rami-
fications 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
flcxuosa appears transparent and colourless or grey on sandy ground.
On a dark ground their colour becomes darker. These animals have

Effect of colour 261

two pigments in their chroinatophores, 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. Poulton1 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 awrare, 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

1 Poulton, E. B., Colours of Animals (The International Scientific Series), London,
1890, p. 121.

262 Influence of environment on animals

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, how-
ever, 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,
Antennnlaria 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

Instinct-reactions of animals 263

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 hori-
zontal 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.

•264 Influence of environment on animals

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 locornotor 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
heliotropic, are attracted by the light, since it can be shown that
they go towards the source of 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 pro-
cesses 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

Heliotropism of animals 265

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.

(6) The production of positive heliotropism by acids and otJier
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 centi-
metres 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.

266 Influence of environment on animals

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 down-
wards, 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 heliotropic 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 cater-
pillars of Porthesia chrysorrhoea are very strongly positively helio-
tropic 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.

Tropic reactions of tissue-cells 267

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 syn-
thesis 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 stereo-
tropism.

(c) The tropic reactions of certain tissue-cells and the morpho-
genetic 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 antici-
pate that the tiger-like colouration of the yolk-sac in the later stages
of 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

268 Influence of environment on animals

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 mesen-
chyme 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.

Conditions governing deposition of eggs 269

Kammerer lias investigated the conditions for the laying of eggs in
two forms of salamanders, e.g. Salamandra atra and S. maeulosa.
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 experi-
ments, 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 un-
known, 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 muta-
tion 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 experi-
mental biologist the definite task of producing mutations by physico-
chemical means. It is true that certain authors claim to have

270 Influence of environment on animals

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 develop-
ment 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 sug-
gested 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 Miillerian. 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 appeared1.
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

1 Poulton, Essays on Evolution, Oxford, 1908, pp. 293—382.

272 Colour and the Struggle for Life

dioecious floAvers ; 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 gems1."

Incidental colours remain as available assets of the organism ready
to be turned to account by natural selection. It is a probable specu-
lation 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
concealment2.

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 main-
taining 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

1 More Letters of Charles Darwin, Vol. i. pp. 354, 355. See also the admirable
account of incidental colours in Descent of Man ('2nd edit.), 1874, pp. 261, 202.

2 See pp. 273, 276.

Teleology ami Adaptation 273

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 science1."

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 wrote2: " 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 "Gryttm" (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 color, 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

1 From History and Arrangement of the Ashmolean Museum, by P. B. Duncan : see
pp. vi, vii of A Catalogue of the Ashmolean Museum, Oxford, 1836.

2 Travels in the Interior of Southern Africa, London, Vol. i. 1822, p. 505. The
references to Burchell's observations iu the present essay are adapted from the author's
article in Report of the British and South African Associations, 1905, Vol. in. pp. 57 — 110.

D. 18

274 Colour and the Struggle for Life

wild animals1." 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 p. 226 of his Vol. I. We
here find that 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 crushed2."

Adaptation and Natural Selection.

1 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

1 Loc. cit. pp. 310, 311. See Sir William Thiselton-Dyer "Morphological Notes," xi.;
''Protective Adaptations," i. ; Annals of Botany, Vol. xx. p. 124. In plates vn. viu. 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 110 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. p. 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."

- More Letters, I. p. 308.

Natural Selection and Adaptation 275

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 Selection1. 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 Auto-
biography 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 argumentation2."

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 possessor3."

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 history4."

Protective and Aggressive Resemblance: Procri/ptic and

A nticryptic colouring.

Colouring for the purpose of concealment is sometimes included
under the head Mimicry, a classification adopted by H. W. Bates in

1 "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. p. 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), p. 3.

2 Life and Letters, i. p. 47. s Origin of Species (1st edit.) 1859, p. 201.
4 More Letters, n. p. 428.

18—2

276 Colour and the Struggle for Life

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 (PhyUotettix) from Jamaica. Of this insect he says
"the thorax is like a leaf that is raised perpendicularly from the
body1."

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 them-
selves either to avoid danger, or to spring upon their prey2."

Protective Resemblance of a very marked and beautiful kind is
found in certain plants, inhabitants of desert areas. Examples ob-
served by Burchell almost exactly a hundred years ago have already
been mentioned on p. 2/3. 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 birds3. 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 Makkwurin 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. 1 have often had occasion to remark that in stony
place[sj there grow many small succulent plants and abound insects
(chiefly Grylli) which have exactly the same color as the ground and
must for ever escape observation unless a person sit on the ground
and observe very attentively."

1 Phil. Trans. Ray. Hoc. Vol. LIV. Tab. vi. p. 55.

- Zoonomia, Vol. i. p. 509, London, 1794.

3 Sir William Thiseltou-Dyer has suggested the same method of concealment (Annuls oj
Botany, Vol. xx. p. 123). Referring to Aiiacampseros pupynicea, 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. p. 1'26). The student of insects, who is so familiar with this very form of
protective resemblance in larvav, and even perfect insects, will not be inclined to
consider the suggestion far-fetched.

Protective Resemblance 277

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 Autobiography1. 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 p. 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 longest2."

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 con-
tention that Natural Selection was incompetent to produce it3, 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 death4." It is clear
from the account given in The Descent of Man5, that the divergence
was due to the fact that Darwin ascribed more importance to Sexual
Selection than did Wallace, and Wallace more importance to Pro-
tective 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 tiger6."
Here too Darwin was preferring the explanation offered by Sexual
Selection7, 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 on p. 289 that Darwin con-
templated the possibility of cryptic colours such as those of Patagonian
animals being due to sexual selection influenced by the aspect of
surrounding nature.

1 Life and Letters, Vol. i. p. 94.

2 Journ. Proc. Linn. Soc. Vol. in. 1859, p. 61. The italics are Wallace's.

3 Origin (6th edit.) London, 1872, pp. 181, 182; see also p. 66.

4 More Letters, i. p. 304.

5 London, 1874, pp. 452—458. See also Life and Letters, in. pp. 123—125, and More
Letters, n. pp. 59—63, 72—74, 76—78, 84—90, 92, 93.

r> More Letters, i. p. 283. 7 Descent of Man (2nd edit.) 1874, pp. 545, 546.

278 Colour and the Struggle for Life

Nearly a year later Darwin in his letter of May 5, 1868?, expressed
his agreement with Wallace's views : " Except that I should put
sexual selection as an equal, or perhaps as even a more important
agent in giving colour than Natural Selection for protection1." 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 :
" Hackel 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 protection2."
Darwin also admitted the justice of Professor E. S. Morse's con-
tention that the shells of molluscs are often adaptively coloured3.
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 9f/<,
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 pro-
tective resemblance, has only recently been shown to me by my friend
Professor E. B. Wilson, the great American Cytologist. With his kind

1 More Letters, u. pp. 77, 78.

- More Letters, n. p. 62. See also Descent of Man, p. 261.

3 More Letters, n. p. 95.

Protective Resemblance 279

consent and that of Mr Francis Darwin, this letter, written four months
before Darwin's death on April 19, 1882, is reproduced here1 :

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 Giinther in Proc.
Zoolog. 8oc.y) 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 w.d 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 color. The concealment of the animal may be judged from the
fact that we found the animal quite by accident on a piece of
Sargas&um 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 ' !

1 The letter is addressed :

"Edmund B. Wilson, Esq., Assistant in Biology, John Hopkins University, Baltimore

Md., U. States."

280 Colour and the Struggle for Life

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 V

Darwin was well aware of the power of individual colour ad-
justment, now known to be possessed by large numbers of Lepi-
dopterous pupae and larvae. An excellent example was brought
to his notice by C. V. Riley2, 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 London3.

It is also necessary to direct attention to C. W. Beebe's4 recent
discovery that the pigmentation of the plumage of certain birds is
increased by confinement in a superhumid atmosphere. In Scarda-
fella 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 corre-
sponding increase in the choroidal pigment of the eye. At a certain

1 Life and Letters, i. pp. 235, 236. See also Darwin's Jour mil of Researches, 1876,
pp. 0—8, where a far more detailed account is given together with a reference to Encycl. of
Anat. and Physiol.

- More Letters, n. pp. 385, 386.

; Trans. Ent. Soc. Land. 1874, p. 519. See also More Letter*, u. p. 403.

4 Zoolvgica : N.Y. Zool. Soc. Vol. i. No. 1, Sept. 25, 1907: Geographic variation in
bir<>,< with especial reference to the effects of humidity.

Warning Colours 281

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.

Wanting 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
orange1." In the Journal of Researches'2 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
duck3.

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
difficulties4." Darwin's original letter exists5, 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 reply0 is extremely interesting both for its

1 More Letters, i. p. 12. 2 1876, p. 97.

3 The Naturalist in Nicaragua (2nd edit.) London, 1888, p. 321.

4 Descent of Man, p. 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,
pp. 117-122.

5 Life and Letters, in. pp. 93, 94.
fi Lift and Letters, in. pp. 94, 95.

282 Colour and the Struggle for Life

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 moths1; 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 observa-
tions 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 2."

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
episemes. 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 male3." The most familiar of all recognition
characters was carefully explained by him, although here too ex-
plained 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 tail4."

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 Origin5.

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.

1 A single white moth which was rejected by young turkeys, while other moths were
greedily devoured : Natural Selection, 1875, p. 78.

2 More Letters, n. p. 71 (footnote). 3 Descent of Man, p. 544.
4 Descent of Man, p. 542.

8 Ed. 1872, p. 1(51. For a good example of Darwin's caution in dealing with exceptions
see the allusion to brightly coloured fruit in More Letters, n. p. 348.

Mimicry 283

Mimicry, — Batesian or Pseudaposematie, Mullcrian 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 vetch1.

This is an interesting recent example from South Africa, and
large numbers of others might be added — the observations of many

1 Trans. Ent. Soc, Land. 1902, p. 535, plate xix. figs. 53—59.

284 Colour and the Struggle for Life

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. \V. Bates and Fritz Miiller. 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 Alydns) 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 (I/uteva
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 JSphex, both in colour and the rapid palpitating and movement of
the antennae " (November 15, 1820)- At the same time it is im-
possible 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

Mimicry 285

concealment (see pp. 275, 276, 278). Such an interpretation of
mimicry was perfectly consistent with the theological doctrines of
his day1.

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 Miiller. 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 pro-
tected 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 Miiller's hypothesis we should expect that the rnimickers
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 Miiller ? Figures 1 to 52 of Mr Marshall's
coloured plate2 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 (Bracon-
idae, a group much mimicked and shown by some experiments to
be distasteful) ; five bugs (Hemiptera, a largely unpalatable group) ;
three moths (Arctiidac and Zygaenidae, distasteful families) ; one fly.

1 See Kirby and Spence, An Introduction to Entomology (1st edit.), London, Vol. n. 1817,
p. 223.

- Trans. Ent. Soc. Land. 1902, plate xvui. See also p. 517, where the group is analysed.

286 Colour and the Struggle for Life

In fact the whole combination, except perhaps one Phytophagous, one
Coprid and the Longicorn beetles, and the fly, fall under the hypothesis
of Miiller 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 re-
semblance 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 afiinity,
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 super-
ficial 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 seen1."

Many years later, in 1867, he wrote to Fritz Miiller suggesting
that the resemblance of a soberly coloured British Planarian to a
slug might be due to mimicry2.

The most interesting copy of Bates's classical memoir on Mimicry3,
read before the Linnean Society in 1861, is that given by him to the

1 More Letters, i. p. (J. - Life urul Letters, in. p. 71.

3 "Contributions to an Insect Fauna of the Amazon Valley." Trans. Linn. Soc. Vol.
xxin. 1862, p. 4U5.

Mimicry 287

man who has done most to support and extend the theory. My kind
friend has given that copy to me ; it bears the inscription :

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 in-
habiting the same country1."

The next letter, written about six months later, reveals the re-
markable fact that the illustrious naturalist who had anticipated
Edward Forbes in the explanation of arctic forms on alpine heights2,
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 other3."

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 solve4." The memoir

1 The letter is dated April 4, 1861. More Letters, i. p. 183.

2 «i 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. p. 88.

3 The letter is dated Sept. 25, 1861 : More Letters, i. p. 197.
* Life and Letters, n. p. 378.

288 Colour and the Struggle for Life

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 it1." 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
observations2."

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 subject3. If Bates's
opinion were well founded, sexual selection would bear a most im-
portant part in the establishment of such species4. 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 con-
tributed by Darwin to the Natural History Revieiv5 and an account
of it is to be found in the Origin^ and in The Descent of Man7.

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 valuable8." 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

1 Life and Letters, n. pp. 391—393.
* More Letters, i. p. 214.

3 More Letters, i. p. 215. See also parts of Darwin's letter to Bates in Life uinl
Letters, n. p. 3<J2.

4 See Poulton, Essays on Evolution, 1908, pp. 65, 85 — 88.

5 New Ser. Vol. in. 1863, p. 219. " Ed. 1872, pp. 375—378.
7 Ed. 1874, pp. 323—325. 8 More Letters, i. p. 176.

Mimicry 289

to the theory of mimicry, the other to the influence of local con-
ditions,— could not be sustained.

Fritz Miiller'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 1 contain abundant proofs of his interest in Miiller's
work upon Mimicry. One deeply interesting letter2 dated Jan. 23,
1872, proves that Fritz Miiller before he originated the theory of
Common Warning Colours (Synaposematic Resemblance or Miillerian
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 Miiller even goes so far as to
believe that the sight of gaudy butterflies might influence the taste
of distinct species3."

This remarkable suggestion affords interesting evidence that
F. Miiller 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 Miiller'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 Miiller'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

1 Poulton, Charles Darwin and the theory of Natural Selection, London, 1896, pp.
199—218.

- Loc. cit. pp. 201, 202. s Life and Letters, in. p. 157.

D. 19

290 Colour and the Struggle for Life

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 Mailer's well-
known theory, published in 18791, and immediately translated by
Meldola and brought before the Entomological Society2. Darwin's
letter to Meldola dated June 6, 1K79, shows "that the first intro-
duction 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
naturalists3." Of the hypothesis itself Darwin wrote "F. Miiller's
view of the mutual protection was quite new to me4." The hypo-
thesis of Miillerian 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 >vhose 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 mind5."

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 ofJ&rebia 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 Acraca joknstoni of S.E. Rhodesia and of Kiliman-
jaro. A naturalist who is interested by the Ercbia should be equally
interested by the Acraca ; and so he would be if the student of

v

1 Kosmos, May 1879, p. 100. 2 Proc. Ent. Soc. Lond. 1879, p. xx.

3 Charles Duricin and fhf Theory of \titural Selection, p. '214. 4 Ibid. p. 213.

* To Sir J. Hooker, July 28, lst>8, More Letters, i. p. 305. See also the letter to
A. K. Wallace, April 30, 1868, in More Letters, n. p. 77, lines 6 — 8 from top.

Mimicry 291

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 informa-
tion 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
Miiller. 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
mind1."

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 entity2."

Mimicry was not only one of the first great departments of zoo-
logical 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.

1 More Letters, i. p. 175. * Life and Letters, n. p. 245.

19—2

292 Colour and the Struggle for Life

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 pro-
tection. 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 explana-
tion. 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 dis-
advantage, 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

Mimicry and Sex 293

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 principle1."

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 female2."

Comparing these conflicting arguments we are led to believe that
the first is the stronger. Mimicry in the male would be no dis-
advantage 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 impressed3 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 (Dismoiphia), 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 interest-
ing 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 More Letters, n. pp. 73, 74. On the same subject — "the gay-coloured females of
Pieris" [Perrhybris (Mylotliris) pyrrha of Brazil], Darwin wrote to Wallace, May 5, 1868, as
follows: "I believe I quite follow yon 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, n. p. 78.

2 Letter from Darwin to Wallace, May 5, 1867, More Letters, n. p. 61.

3 Descent of Man, p. 325.

294 Colour and the Struggle for Life

(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. Cethosid) 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 Cosmodesmns presenting us with
a later stage of the history begun in Papilio ; for in Africa Cosmo-
desmus 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 di-
morphic 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

Sexual Selection 295

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 Society1. 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 pro-
duced 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."

1 Journ. Proc. Linn. Soc. Vol. in. 1859, p. 50.

296 Colour and the Struggle for Life

A full exposition of Sexual Selection appeared in 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 man1."

Darwin, as we know from his Autobiography'2, 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 interpre-
tation 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 ; there-
fore, though I am fully convinced that it is largely true, you may
imagine how pleased I am at what you say on your belief3."

The existence of sound-producing organs in the males of insects
Avas, Darwin considered, the strongest evidence in favour of the
operation of sexual selection in this group4. Such a conclusion has
received strong support in recent years by the numerous careful
observations of Dr F. A. Dixey5 and Dr G. B. Longstaff6 on the
scents of male butterflies. The experience of these naturalists
abundantly confirms and extends the account given by Fritz Midler7
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.

1 More Letters, ir. p. 33. 2 Life and Letters, i. p. 94.

:* More Letters, i. p. 183. 4 Life and Letters, in. pp. 94, 138.

5 Proc. Ent. Soc. Lond. 1904, p. Ivi; 1905, pp. xxxvii, liv; 1906, p. ii.
K Proc. Ent. Soc. Lond. 1905, p. xxxv; Trans. Ent. Soc. Lond. 1905, p. 136; 1908,
].. 007.

7 Jen. Zeit. Vol. xi. 1877, p. 99 ; Trans. Ent. Soc. Lond. 1878, p. 211.

Sexual Selection 297

Entirely new light upon the seasonal appearance of epigamic
characters is shed by the recent researches of C. W. Beebe1, 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 colors 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."

1 The American Naturalist, Vol. XLII. No. 493, Jan. 1908, p. 34.

XVI

GEOGRAPHICAL DISTRIBUTION OF PLANTS
BY SIR WILLIAM THISELTON-DYEB, 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 Gfographie Botanique raisonnte 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 etudi^ sagement les modifications possibles des
etres organises....

" Et si Ton s'e" carte des exage"rations de Lamarck, si Ton suppose
un premier type de chaque genre, de chaque famille tout au moins,
on se trouve encore a regard de 1'origine de ces types en presence de
la grande question de la creation.

" Le seul parti k prendre est done d'envisager les etres organises
comme existant depuis certaines ^poques, avec leurs qualit^s par-
ticulieres1."

Reviewing the position fourteen years afterwards, Bentham re-
marked:— "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 distribution2."

Writing to Asa Gray in 1856, Darwin gave a brief preliminary
account of his ideas as to the origin of species, and said that

! Vol. n. p. 1107. - Pres. Addr. (1869) Proc. Linn. Soc. 1868—69, p. Ixviii.

Permanence of Continents 299

geographical distribution must be one of the tests of their validity1.
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,...! 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 descent2."
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 Distribution3."

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 e*chappe, par sa nature et par son anciennete1, h nos moyens
d'observation4," 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
Gmeliu 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
change5.

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"
this6, 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 separa-
tion 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

1 Life and Letters, n. p. 78.

2 The Variatioji of Animals and Plants (2nd edit.), 1890, i. pp. 9, 10.

3 Life and Letters, i. p. 336. 4 Loc. cit. p. 1106. 5 Loc. cit. p. 1116.
6 Life and Letters, in. p. 247. Dana says : — " The continents and oceans had their

general outline or form defined in earliest time," Manual of Geology, revised edition.
Philadelphia, 1869, p. 732. I have no access to an earlier edition.

300 Geographical Distribution of Plants

figure1." 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 degree2,'' 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 eccentric3."
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 continents4."

It would be trespassing on the province of the geologist to pursue
the subject at any length. But as Wallace5, who has admirably
vindicated Darwin's position, points out, the "question of the per-
manence 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 detail5" 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 ancient7." 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 ages8."

Evidence, however, steadily accumulates in Darwin's support.

1 Report of the llth Meeting of the British Association (Leicester, 1907), London, 1908,
p. 431.

2 Ibid. p. 436. a Ibid. p. 431.

4 Encycl. Jirit. (9tb edit.), Vol. xxm. "Tides," p. 379.

5 Island Life (2nd edit.), 1895, p. 103. « Loc. cit. p. 101.

7 Mure Letters, n. p. 135.

8 Lyell's Principles of Geology (llth edit.), London, 1*72, i. p. 2">8.

Permanence of Continents 301

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 shores1." The following year Sir Archibald Geikie2
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 oceans3."

Dr Guppy, who devoted several years to geological and botanical
investigations in the Pacific, found himself forced to similar con-
clusions. " 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 organ-
isms is ever sufficiently precise to justify a recourse to hypothetical
alterations in the present relations of land and sea4." 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 waves5."

Writing to Wallace (1876), Darwin warmly approves the former's
"protest against sinking imaginary continents in a quite reckless

1 More Letters, n. p. 146.

2 "Geographical Evolution," Proc. E. Geogr. Soc. 1879, p. 427.

3 More Letters, n. p. 146.

* Observation* of a Naturalist in the Pacific between 1896 and 1899, London, 1903,
i. p. 380.

8 Island Life, p. 105.

302 Geographical Distribution of Plants

manner, as was stated by Forbes, followed, alas, by Hooker, and
caricatured by Wollaston and [Andrew] Murray1." 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' 'Atlantis' was an ill-service to science,
as checking a close study of means of dissemination2," 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 de-
voured 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 Atlantic3."

It has always been the fashion to minimise Darwin's conclusions,
and these have not escaped objection. The advocatns 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 birds4." 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 wrere greater, and he tells us that
in the craws of six specimens of Lagopus hyperborciis shot in Spitz-
bergen 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, &c "

" The result of Ekstam's observations in Spitzbergen was to lead
him to attach a very considerable importance in plant dispersal to

1 Life and Letters, in. p. 230. 2 Ibid. n. p. 78. 3 More Letters, i. p. 483.

4 B. F. Scbarff, European Animals, p. 64, London, 1907.

Multiple Origins 303

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 bird1."

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 islands2," 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 extensions3/' and that he
regarded as a mere counsel of despair: — "to make continents, as
easily as a cook does pancakes4."

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 aifords
...a simple explanation of the facts5."

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 regret6."

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

1 Guppy, op. cit. n. pp. 511, 512. 2 Life and Letters, 11. p. 77.

3 Ibid. ii. p. 82. 4 Ibid. 11. p. 74.

B Origin of Species (6th ed.) p. 330. 6 Life and Letters, i. p. 88.

304 Geographical Distribution of Plants

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 northward1." 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's2." Assuming that local races have derived from a
common ancestor, Hooker's great paper placed the fact of the migra-
tion 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 inde-
pendent evidence : this was simply to attempt to explain ignotwm
per ignotius. He found a real and, as it has turned out, a far-
reaching solution in climatic change due to cosniical causes which
compelled the migration of species as a condition of their existence.
The logical force of the argument consists in dispensing with any

1 Life and Letters, n. p. 136.

2 Linn. Trans, xxm. p. 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,
p. 128). I find no suggestion of his having hit upon it in his correspondence with Darwiu
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.

Plant Migration 305

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 con-
clusions 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 small1." 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 subject2." 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 hemisphere3. The divergence how-
ever 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 stations4." 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 process5.

It is interesting to remark that Darwin drew from the facts of
plant distribution one of his most ingenious arguments in support
of this theory6. 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 genera7." 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 action8." 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 hemisphere9/' besides voluminous works such as De Can-
dolle'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 work10."

1 More Letters, i. p. 177. 2 Loc. cit.

3 More Letters, n. p. 25 (footnote 1). 4 Island Life (2nd edit.), London, 1895, p. 512.

5 Loc. cit. p. 518. 6 See More Letters, i. p. 424.

7 Origin, p. 44. 8 Ibid. p. 45.

9 More Letters, i. p. 107. 10 Ibid. n. p. 235.

a 20

306 Geographical Distribution of Plants

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 forms1." In this single
sentence Darwin has stated a theory which, as his son F. Darwin
has said with justice, has "revolutionized botanical geography2." 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 intellect3" 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 me4." 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 distribu-
tion, 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

1 Origin, p. 360.

2 "The Botanical Work of Darwin," Ann. Bot. 1899, p. xi.

3 More Letters, i. p. 134. * Life and Letters, n. p. 294.

Hooker's Contributions to Geographical Botany 307

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
subject1." 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 acknowledge-
ment 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 show2." Fourteen years before he had written
to Hooker : " I know I shall live to see you the first authority in
Europe on... Geographical Distribution3." 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
views4." 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 Botany5." But
this was only part of his constant half-humourous self-deprecia-
tion. 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

1 More Letters, n. p. 7. '2 Life and Letters, n. p. 148 (footnote). 3 Ibid. i. p. 336.
4 Pres. Addr. (1869), Proc. Linn. Soc. 1868—69, p. Ixxiv. 8 Mare Letters, i. p. 400.

20—2

308 Geographical Distribution of Plants

thought singular that he should have been elected a "correspondant"
of the Academic 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
beings1." And he declares that he finds " any proposition more easily
tested in botanical works2 than in zoological."

In the Introductory Essay Hooker dwelt on the "continuous
current of vegetation from Scandinavia to Tasmania3," 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 Mexico4." Hooker con-
sidered that this negatived "the idea that the Southern and Northern
Floras have had common origin within comparatively modern geo-
logical epochs5." 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 power6." 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

1 Life and Letters, i. p. 98. 2 Ibid. n. p. 99.

3 Introductory Essay to the Flora of Taniiiania, London, 1859. Reprinted from the
Botany of the Antarctic Expedition, Part in., Flora of Tasmania, Vol. i. p. ciii.

4 p. civ. 6 Loc. cit.

6 Origin of Species (6th edit.), p. 340; cf. also Life and Letters, n. p. 142.

Plant Migration 309

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 rooted1."

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 pre-
valence 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
Hooker2 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 out-
side 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

1 Pres. Addr. (1869), Proc. Linn. Soc. 1868—69, pp. Ixvi, Ixvii.

2 Royal Institution Lecture, April 12, 1878.

310 Geographical Distribution of Plants

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 says1: "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 connections2." "Their utility in these respects is
an accident in the plant's life3." 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 seeds4. 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 bird5."

1 Guppy, op. cit. ii. p. 99. - Loc. cit. p. 102. 3 Loc. cit. p. 100.

* Loc. cit. p. 102. 5 Loc. cit. n. p. 221.

Plant Migration 311

Darwin was clearly prepared to go further than Hooker in ac-
counting 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 Japan1." 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 Abyssinia2, 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
south3." Eventually he conjectured " that there must have been a
Tertiary Antarctic continent, from which various forms radiated to
the southern extremities of our present continents4." But character-
istically he could not admit any land connections and trusted to
" floating ice for transporting seed5." 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 south6." 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 south-
wards. 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 adapta-
tion to new conditions point to long-continued isolation. " An island
...will prevent free immigration and competition, hence a greater
number of ancient forms will survive7." But variability is itself
subject to variation. The nemesis of a high degree of protected

1 More Letters, n. p. 9. 2 Ibid. i. p. 447. 3 Ibid. i. p. 380.

4 Life and Letters, in. p. 231. 5 More Letters, i. p. 116.

6 Ibid. i. p. 453. 7 ibid. i. p. 481.

312 Geographical Distribution of Plants

specialisation is the loss of adaptability1. 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 dis-
appearing 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 associa-
tion with Dipteris conjugata and Dipteris lobbiana, represent a
phase of Mesozoic life which survives

'Like a dim picture of the drowned past2.'"

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 views3." 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 domain4."

It will be noticed that in the summary I have attempted to give
of the history of the subject, efforts have been concentrated on bring-
ing 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 re-
membered on the one hand that our detailed knowledge of the
floras of the tropics is still very incomplete and far inferior to that

1 See Lyell, The Geological Evidences of the Antiquity of Man, London, 1803, p. 446.

2 Report of the 73rd Meeting of the British Assoc. (Southport, 1903), London, 1904,
p. 844.

3 More Letters, n. p. 12. •» Wallace, Island Life, pp. 527, 528.

Ancestry of Angiosperms 313

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 regions1."

As early as 1848 Debey had described from the Upper Cre-
taceous rocks of Aix-la-Chapelle Flowering plants of as high a
degree of development as those now existing. The fact was com-
mented upon by Hooker2, 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° of latitude. The con-
clusion 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 intercross-
ing3." Writing to him in 1877 he says: "Your idea that dicoty-
ledonous 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
phenomenon4."

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

1 More Letters, n. p. 240. 2 Iiitrod. Essay to the Flora of Tasmania, p. xx.

3 More Letters, n. p. 21.

4 Life and Letters, in. p. 285. Substantially the same idea had occurred earlier to
F. W. A. Miquel. Bemarking 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 out 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 pre-
ponderance in the vegetable kingdom." Archives Neerlandaises, in. (1868). English
translation in Journ. of Bot. 1869, p. 101.

314 Geographical Distribution of Plants

abrupt development of the higher plants. I have sometimes specu-
lated whether there did not exist somewhere during long ages an
extremely isolated continent, perhaps near the South Pole1."

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
birth2." 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 con-
tinental condition during the Palaeozoic and Mesozoic periods, and
that their submergence and subsequent emergence took place in
Tertiary times3."

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 hemi-
sphere is precisely paralleled by that of Protcaccae and Rcstiaceae in

1 Life and Letters, in. p. 248.

2 Encycl. Brit. (10th edit. 1902), Vol. xxxi. (" Palaeobotany ; Mesozoio"), p. 422.

3 Guppy, op. cit. u. p. 304.

Ancestry of Angiosperms 315

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 floras1." 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 Europe2." He snowed 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 Nearctic regions ought to be separated3." 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 Holarctic. 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 America4." 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 America5." The
recent discoveries of a Tulip tree and a Sassafras in China afford

1 Life and Letters, m. p. 247. 2 pp. 333, 334.

3 Life and Letters, in. p. 230.

4 Clement Reid, Encycl. Brit. (10th edit.), Vol. xxxi. ("Palaeobotany; Tertiary"),
p. 435.

6 More Letters, i. p. 434.

316 Geographical Distribution of Plants

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 Atlas1. 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 Gesne-
raceae 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 determined et marcher du nord
au sud, k la recherche de regions et de stations plus favorables, mieux
appropri^es aux adaptations acquises, & m£me que la temperature
terrestre perd ses conditions premieres2." If, as is so often the case,
the theory now seems to be ct 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

1 John Ball iu Appendix G, p. 438, in Journal of a Tour in Morocco and the Great Atlas,
3. D. Hooker and J. Ball, London, 1878.

2 Origine Paleontologique des arbres, Paris, 1888, p. 28.

The New Flora of Krakatau 317

POSTSCRIPTUM.

Since this essay was put in type Dr Ernst's striking account of
the New Flora of the Volcanic Island of Krakatau^ 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 vegetation2." 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 tropics3." 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 coloni-
sation 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 plants4." 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 gales5?" 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

1 Cambridge, 1909. 2 Op. cit. p. 4. 3 Op. cit. p. 72.

* Op. cit. p. 56. 5 More Letters, i. p. 483.

318 Geographical Distribution of Plants

must continually be happening1." 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 Distri-
bution 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 in 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'* : — " 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."

1 Life and Letters, n. pp. 56, 57. 2 Origin of S})ecies (6th edit.), p 429.

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 maybe 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
Quadrupedwn..., deals in a statistical way with the mammals ; im-
portant 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 Gr. R. Treviranus1 devoted a long chapter of his
great work on Biologic to a philosophical and coherent treatment of
the distribution of the whole animal kingdom. Remarkable progress
was made in 1810 by F. Tiedemann2 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 distribu-
tion 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, distribu-
tion, and migration, upon the structure of the Birds ! In short,

1 Biologie oder Philosophic der lebenden Natur, Vol. n. Gottingen, 1803.

2 Anatomic und Naturgeschichte der Vogel. Heidelberg, 1810.

320 Geographical Distribution of Animals

this anatomist dealt with some of the fundamental causes of distri-
bution.

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 distri-
bution. 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. Swainson1 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.

I/yell'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.

1 "A Treatise on the Geography and Classification of Animals," Lardner's Cabinet
Cyclopaedia. London, 1835.

Geographical Regions 321

In 1853 appeared L. K. Schmarda's1 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 charac-
terises, 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. Sclater2. 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 onto-
logical 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 continua-
tions 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 18683, 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 Nearctic
regions ; and Notogaea, the Southern world, which he divided into

1 Die geographische Verbreitung der Thiere. Wien, 1853.

2 " On the general Geographical Distribution of the members of the class Aves," Proc.
Linn. Soc. (Zoology), n. 1858, pp. 130—145.

3 "On the classification and distribution of the Alectoromorphae and Heteromorphae,"
Proc. Zool. Soc. 1868, p. 294.

D. 21

322 Geographical Distribution of Animals

(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 18741, 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. Blanford2,
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, m. p. 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, experi-
ment 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 uni-
versally, 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.

1 " The geographical distribution of Mammals," Manchester Science Lectures, 1874.

2 Anniversary address (Geological Society, 1889), Proc. Geol. Soc. 1889—90, p. 67;
Quart. Jonrn. XLVI. 1890.

"The Origin of Species" 323

For the so-called multiple, independently repeated creation of
species as an explanation of their very wide and often quite dis-
continuous 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 in-
dividual, 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 re-
mains1") 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 south-
ern lands than vice versti, 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 forms2. "..."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 funda-
mental 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

1 The Origin of Species (1st edit.), p. 396. 2 Ibid. p. 380.

21—2

324 Geographical Distribution of Animals

their new surroundings. The usual standpoint was also that of
Pucheran1 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 harmonic post-e"tablie " ; 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 con-
temporaneous 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 accept-
ance 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 modifica-
tion and the multiplication of new forms." We can thus under-
stand 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 iden-
tical species... and of distinct but representative species2."

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

1 " Note sur 1'^quateur zoologique," Rev. et Mag. de Zoologie, 1855 ; also several
other papers, ibid. 1865, 1866, and 1867.

2 The Origin of Species (1st edit.), pp. 408, 409.

Murray's Work on Distribution 325

are now quite separate, have been continuously, or almost con-
tinuously, united with each other, and with the many existing oceanic
islands1." Again, "believing... that our continents have long remained
in nearly the same relative position, though subjected to large, but par-
tial oscillations of level," that means to say within the period of existing
species, or "within the recent period2." 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 intro-
ductory 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 by 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

1 Ibid. p. 357. 2 Ibid. p. 370.

326 Geographical Distribution of Animals

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 centre1." 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 publica-
tion of Haeckel's Natiirliche ScJwepfnngsgeschichte, 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 Getter die Morphologie in 1866. The
fourteenth chapter of the History of Creation is devoted to the
distribution of organisms, their chorology, with the emphatic asser-
tion 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 draw-
backs of the theory. Therefore every help to ease and shorten this
process should have been welcomed. In 1868 M. Wagner2 came to

1 Murray, The Geographical Distribution of Mammals, p. 14. London, 1866.

2 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 con-
tinents 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
epecies 6, 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.

Wagner, Huxley, and Wallace 327

the rescue with his Darivirische Theorie und das Migrations-Gesetz
der Organismen1. 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 re-
stricted 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 subse-
quent 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 work2. 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

1 Leipzig, 1868.

2 The Geographical Distribution of Animals, 2 vols. London, 1876.

328 Geographical Distribution of Animals

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 corroboratiou, 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 ;

The Past the Key to the Present 329

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 discon-
tinuous 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 literal 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 there-
fore 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 dis-
tribution 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

330 Geographical Distribution of Animals

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 com-
paratively 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
inquiries into climatic changes, culminating [in irreconcilable astro-
nomical 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 import-
ance 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 Value of Fossils 331

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 trust-
worthiness 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 Den-
drobatidae, 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 arti-
ficiality 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 lament-
able instance is that of certain flightless Rails, recently extinct or
sub-fossil, on the islands 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 morpho-
logical grounds, to justify their separation into Aphanapteryx in
Mauritius, Erythromachus in Rodriguez and Diaphorapteryx on

332 Geographical Distribution of Animals

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.

Tlte 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's1 exhaus-
tive 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 autoch-
thonous, others as immigrants, and the directions followed by them
will be inquired into ; the search may lead far and in various direc-
tions, 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 past2.
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 com-
plexes while elsewhere they subsided again : like pontoon-bridges

1 " The geographical distribution of Freshwater Decapods and its bearing upon ancient
geography," Proc. Amer. Phil. Soc. Vol. 41, 1902.

2 A fair sample of this method is C. H. Eigenmanu's "The Freshwater Fishes of
South and Middle America," Popular Science Monthly, Vol. G8, 1906.

Mesozoic Geography 333

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 con-
siderable 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 connections1 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.

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-South 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, some-

1 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 been submerged
at some time or other.

334 Geographical Distribution of Animals

where 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 Antarctica 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 atten-
tion, 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

Distribution of Peripatus 335

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 Aus-
tralia, 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 respec-

336 Geographical Distribution of Animals

tive 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 tem-
perature, 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 con-
vergences 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 out-
come 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.RS.

IN one of the very interesting conversations which I had^with
Charles Darwin during the last seven years of his life1, he asked
me in a very pointed manner if I were able to recall the circum-
stances, 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 ?

1 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."

D. 22

338 Darwin and Geology

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 para-
mount 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 evolution1 ; and Alfred Russel
Wallace is scarcely less emphatic concerning the part played by
Lyell's teaching in his scientific education2. Huxley wrote in 1887
" I owe more than I can tell to the careful study of the Principles of
Geology in my young days3." 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 Geology4," and
"Lyell, for others, as for myself, was the chief agent in smoothing
the road for Darwin5."

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

1 Herbert Spencer's Autobiography, London, 1904, Vol. i. pp. 175 — 177.

2 See My Life ; a record of Events and Opinions, London, 1905, Vol. i. p. 355, etc.
Also his review of Lyell's Principles in Quarterly Review (Vol. 126), 1869, pp. 359 — 394.
See also The Darwin-Wallace Celebration by the Linnean Society (1909), p. 118.

8 " Science and Pseudo Science;" Collected Essays, London, 1902, Vol. v. p. 101.

4 Proc. Roy. Soc. Vol. XLIV. (1888), p. viii. ; Collected Essays, n. p. 268, 1902.

5 Life and Letters of Charles Darwin, n. p. 190.

In Childhood and School Life 339

in Darwin's mind, and are able to record the story almost entirely in
his own words1.

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 2." He further states that while at Mr Case's
school "I do not remember any mental pursuits except those of
collecting stones," etc.... "I was born a naturalist3."

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 neighbour-
ing gravel-pit, being derived from the glacial drift, exhibit very

1 The first of these works is indicated in the following pages by the letters L. L. ; the
second by M. L.

2 M. L. i. p. 3. 8 M. L. i. p. 4.

99 9

- -i — _

o

40 Darwin and Geology

striking differences in colour and form. It was probably this circum-
stance 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-warned mineral, and I hardly attempted
to classify them1."

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 stone2."

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 Marker 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 Border3. 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 Geology4. When at

1 L. L. i. p. 34. •- L. L. i. p. 41.

3 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 !

4 L. L. i. p. 41.

At Edinburgh University 341

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 school-
fellows, while undergoing solemn and public reprimand from Dr Butler
at Shrewsbury School for thus wasting his time \ 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
experienced2 ! " 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 science3!"

The misfortune was that Edinburgh at that time had become the
cockpit in which the barren conflict between " Neptunism " and "Plu-
tonism " was being waged with blind fury and theological bitterness.
Jameson and his pupils, on the one hand, and the friends and disciples
of Button, 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 condition4." "When I think of this lecture," added Darwin,
"I do not wonder that I determined never to attend to Geology5."
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, Coldstreani, 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

1 L. L. i. p. 35. 2 L. L. i. p. 340.

3 L. L. i. p. 41. 4 L. L. i. pp. 41—42.

6 This was written in 1876 and Darwin had in the summer of 1839 revisited and
carefully studied the locality (L. L. i. p. 290).

342 Darwin and Geology

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 crystallisa-
tion 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
forgotten1." 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 Beche2. Darwin
himself possessed a copy of Playfair's Illustrations oftlie 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 stared3."

As a consequence of the influences brought to bear on his mind

1 Quarterly Review, Vol. cxxvi. (1869), p. 363.

2 Of the strength and persistencs 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"!

:i M. L. n. p. 149.

At Cambridge University 343

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, how-
ever, " I was so sickened with lectures at Edinburgh that I did not
even attend Sedgwick's eloquent and interesting lectures1."

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 Intro-
duction to the Study of Natural Philosophy, and of Humboldt's Per-
sonal 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 geology2."
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 expected3." 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 started4." 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

1 L. L. i. p. 48. 2 L. L. i. p. 56.

3 L. L. i. p. 189. * L. L. i. p. 189.

344 Darwin and Geology

during the geological tour1. We find Darwin looking forward to this
privilege with the keenest interest2.

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, Con way,
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 map3."
On his return to Shrewsbury, Darwin wrote to Henslow, "My trip
with Sedgwick answered most perfectly4," 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 mountains5."

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 science6 ! "

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 end7."

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

1 L. L. i. p. 56. 2 L. L. i. p. 189. s L. L. i. p. 57.

4 L. L. i. p. 195. 5 L. L. i. pp. 237—8. 6 L. L. i. p. 58.

7 L. L. i. p. 18'J.

On board the " Beagle " 345

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 Shrews-
bury, nor the professoriate of Edinburgh, nor the tutors of Cambridge
had managed to give him1." 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
life2"; 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;...! 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 developed3."

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 intelligible4."

The famous voyage began amid doubts, discouragements and dis-
appointments. Fearful of heart-disease, sad at parting from home
and friends, depressed by sea-sickness, the young explorer, after
being twice driven back by bafHing 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
Ly ell's Principles of Geology, then just published — but cautioned
him (as nearly all the leaders in geological science at that day would

1 Proc. Roy. Soc. Vol. XLIV. (1888), p. ix. 2 L. L. i. p. 214.

3 L. L. i. p. 61. 4 L. L. i. p. 62.

346 Darwin and Geology

certainly have done) "on no account to accept the views therein
advocated1." 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 read2."

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 vou into most beautiful

V

and retired spots3." 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 LyellV After more than forty years the memory
of this, his first geological work, seems as fresh as ever, and he wrote
in 18/6, "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 lava5."

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, pp. 1 and 9). His first im-
portant 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 Mrith delight. That was a memorable hour to me,
and how distinctly I can call to mind the low cliif of lava beneath
which I rested, with the sun glaring hot, a few strange desert

1 L. L. i. p. 73. 3 L. L. i. p. 62. 3 L. L. i. p. 228.

4 /.. L. i. p. 235. 6 L. L. i. p. 65.

Geological Journeys in South America 347

plants growing near, and with living corals in the tidal pools at
my feet1."

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 granite2." In the
passage quoted on page 345 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 bets3."

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,

1 L. L. i. p. 66. 2 L. L. i. p. 249. 3 L. L. i. p. 233.

348 Darwin and Geolof/i/

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 wrork was entirely thrown away, " a great pile of MS. which
I made during the vovage has proved almost useless1." Huxley
confirmed this judgment on his biological work, declaring that " all
his zeal and industry resulted, for the most part, in a vast accumu-
lation of useless manuscript2." 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 wrrote to Henslow, " My notes
are becoming bulky. I have about 600 small quarto pages full ; about
half of this is Geology3." The last, and certainly not the least import-
ant 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 boxes4."

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

1 L. L. i. p. 62. 2 Proc, Roy SoCi Vol. XLIV. (1888), p. ix.

3 M. L. i. p. 14.

4 Life of Henslow, by L. Jenyns (Blomefield), London, 18(52, p. 53.

Geological Study on board the "Beagle" 349

they were packed up for despatcli to Henslow. Besides hand-
magnifiers and a microscope, Darwin had an equipment for blow-
pipe-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 Cambridge1) 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 : also 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 Classi-
fication of Rocks. How diligently and well he employed his instru-
ments 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 later2.

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 " astonishment3."

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 com-
parative anatomists. And this seemed to be confirmed by Darwin's
own entry in his pocket-book for 1837, " In July opened first note-

1 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.

2 I am greatly indebted to my friend Mr A. Barker, 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.

3 L. L. i. p. 38.

350 Darwin and Geology

book on Transmutation of Species. Had been greatly struck from
about the month of previous March on character of South American
fossils...1."

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 catastrophies, 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 globe2."

1 L. L. i. p. 276.

2 Principles of Geology, Vol. n. (1st edit. 1832), p. 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 Hantell, "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. p. 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. p. 467).
He expressed the same views to Whewell in 1837 (Ibid. Vol. n. p. 5), and to Sedgwick
(Ibid. Vol. n. p. 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. 11.
pp. 190—195).

First Germ of the "Species Work" 351

After pointing out how impossible it would be for a naturalist to
prove that a newly discovered species was really newly created1, Lyell
argued that no satisfactory evidence of the way in which these new
forms were created, had as yet been discovered, but that he enter-
tained 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 does2."

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 Panipean 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....! 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 Edentata3."

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 longer4." 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 armadillo5."

3 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. n. chap. 1).

2 L. L. i. p. 263.

s M. L. i. pp. 11, 12. See Extracts of Letters addressed to Prof. Henslow by G. Darwin
(1835), p. 7.

4 L. L. i. p. 276 (footnote).

6 Haeckel, History of Creation, Vol. i. p. 134, London, 1876.

352 Darwin and Geology

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 mine1."

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 preserved2." 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.3."

Darwin's own recollections entirely bear out the conclusion that
he fully recognised, while in South America, the wonderful signi-
ficance 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 armadillos4."

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 animals5.

1 M. L. i. p. 15.

2 Extracts from Letters etc., pp. 13 — 14.

s Proc. Geol. Soc. Vol. n. pp. 211—212. « L. L. i. p. 82.

* 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 hippo-
potamus, 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],

Importance of discovery of Fossil Mammals 353

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, 18.32, 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 discovered1/' 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 mind2.

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 servant3. 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

pp. 394—6, and Lyell's Principles [3rd edit.], Vol. in. p. 421). Darwin referred to this
discovery in 1839 (see his Journal, p. 210).

1 M. L. i. p. 38.

2 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.

3 L. L. i. p. 63.

D. 23

354 Darwin and Geology

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....! 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 years1."

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 pie2."

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 crater3."
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

1 L. L. i. pp. 257—58. 2 L. L. I. pp. 259—60.

3 M. L. i. p. 26.

Concentration on Geological Work 355

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 sediment1."

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 Geology2." 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 hammer3 ! "

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 Presi-
dent, 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 Ms 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 atid
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,

1 L. L. i. p. 70. a L. L. i. p. 265. * L. L. i. p. 66.

23—2

356 Darwin mul Geology

1835, stated that "they were extracted from a series of letters
(addressed to Professor Henslow), containing a great mass of informa-
tion 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 Pro-
ceedings of the Geological Society1, 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 Cam-
bridge, 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 cele-
brated 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,

1 Vol. n. pp. 210—12.

At the Geological Society 357

after a stormy and troublous career, he retired from the society
in 1832. In all the writings of the great pioneers in English geology,
Button 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 for-
gotten 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 "im-
piety"— 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 recep-
tion 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 Huxley1. Among Lyell's
fellow-geologists, two only — G. Poulett Scrope and John Herschel2 —
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 un-
able 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

1 L. L. n. pp. 179—204.

2 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. p. 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 waa
John Herschel ! "

358 Darwin and Geology

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 con-
vinced 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, 1 explained to him my views
on coral-reefs. This encouraged me greatly, and his advice and
example had much influence on me1." 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 Society2.

"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

1 L. L. i. p. 68. J L. L. i. p. 67.

Welcome from Geologists 359

than the heart-and-soul manner in whicli he put himself in my place
and thought what would be best to do1."

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 Broderip2." 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 paper3 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 earth-
quakes 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

1 L. L. i. p. 275. - The Life of Richard Owen, London, 1894, Vol. i. p. 102.

3 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.

360 Darwin and Geology

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 in-
teresting 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, pp. 505 — 510.

During this session, Darwin attended nearly all the Council meet-
ings, 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 con-
sented to accept the appointment1.

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 Umformitarianism 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 discussions2."

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 hear 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 -

1 L. L. i. p. 285.

2 The Life and Letters of the Reverend Adam Sedgwick, Vol. i. p. 484, Cambridge, 1890.

The Fight for Uniformitarianism 361

law, Leonard Horner, wrote a very lively account of the pro-
ceedings 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 ac-
companied by movements of the land on either side of the fracture.
In conclusion he boldly advanced the view " that continental eleva-
tions, 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
volcanoes1."

Ly ell's account2 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 volcanos 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, &c., 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 over-
flowed, and the strata would have been blown up and annihilated3.
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 rock4.
When he had done his description of the reiterated strokes of his
volcanic pump, De la Beche gave us a long oration about the impossi-
bility of strata of the Alps, &c., remaining flexible for such a time as

1 Proc. Geol. Soc. Vol. n. pp. 654—60.

2 Life, Letters and Journals of Sir Charles Lyell, Bart., edited by his sister-in-law, Mrs
Lyell, Vol. n. pp. 40, 41 (Letter to Leonard Horner, 1838), 2 vola. London, 1881.

3 It is interesting to compare this with what Darwin wrote to Heuslow seven years
earlier, see p. 344.

4 Ideas somewhat similar to this suggestion have recently been revived by Dr See
(Proc. Am. Phil. Soc. Vol. XLVH. 1908, p. 262).

362 Darwin and Geology

they must have done, if they were to be tilted, convoluted, or over-
turned by gradual small shoves. He never, however, explained his
theory of original flexibility, and therefore I am as unable as ever to
comprehend why flexibility 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 calcu-
lations, 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 Button'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 witli 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."

Activity in the Geological Society 363

This important paper was, in spite of its theoretical character,
published in full in the Transactions of the Geological Society
(Ser. 2, Vol. v. pp. 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 suc-
ceeded 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 8,
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 stout1."

1 Memoirs of Leonard Horner (privately printed), Vol. n. pp. 39 and 195.

364 Darwin and Geology

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 up1."

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 society2."
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
illness3."

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 ex-
amining the Salisbury Craigs, in a very different spirit to that excited
by Jameson's discourse4. 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 years5, altogether wrong. The alternative lake-theory he
found himself unable to accept at the time, for he could not under-
stand 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 difficult} 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

1 L. L. ii. pp. 42, 43. 2 L. L. i. pp. 67, 68. 3 L. L. i. p. 69.

4 L. L. i. p. 290. 6 M. L. n. p. 188.

Work on Glacial Questions 365

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
exclusion1."

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 Contem-
poraneous 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
features2. 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 Geology3." To the Geographical Journal
he had sent in 1839 a note "On a Rock seen on an Iceberg in
16° S. Latitude." For the subject of ice-action, indeed, Darwin
retained the greatest interest to the end of his life4.

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.

1 M. L. n. pp. 171—93. 2 L. L. i. p. 58.

3 L. L. i. p. 41. « M. L. ii. pp. 148—71.

366 Darwin and Geology

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 views1/' 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 arrange-
ments for the publication of the five volumes of the Zoology of the
Beagle and in getting the necessary financial aid from the govern-
ment for the preparation of the plates. He was at the same time

1 L. L. i. p. 276.

" The Geology of the Voyage of the Beagle " 367

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 Maryborough
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 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-reef1." 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

1 L.L. i. p. 70.

368 Danvin and Geology

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^. 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 generally2.

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*, 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
Expedition4, 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 geolo-
gists 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 Huxley6.

1 Vol. n. pp. 552—554 (May 31, 1837). 2 Journal (1st edit.), pp. 439—69.

3 1st edit. Vol. ii. p. 296. * M. L. n. pp. 226—8.

* Essays upon some Controverted Questions, London, 1892, pp. 314 — 328 and 623 — 625.

Tlie Coral-Reef Theory 369

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, sub-
sidence 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 feet1."

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 selec-
tion, the splendid atoll of Funafuti, was not a most judicious one.

By the pluck and perseverence of Professor Sollas in the pre-
liminary 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

1 L. L. in. p. 184.
D. 24

370 Darwin and Geology

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 10l£ 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 zoologists1.

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 pro-
longed 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, flourish-
ing 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

1 The Atoll of Funafuti; Report of the Coral Reef Committee of the Royal Society,
London, 1904.

Geology of Volcanic Islands 371

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 regu-
larly1." 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
geologists2."

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 denuda-
tion 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 Challenger3, he says :

" Je dus, en me livraut k ces recherches, suivre ligne par ligne les
divers chapitres des Observations gtfologiques consacrees aux iles de

1 L. L. i. p. 321. 2 Loc. cit.

3 Kenard'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.

24—2

372 Darwin and Geology

1'Atlantique, oblig^ que j'^tais de comparer (Time maniere suivie les
re^ultats auxquels j'^tais conduit avec ceux de Darwin, qui servaient
de controle k mes constatations. Je ne tardai pas k ^prouver 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 & discerner la nature des
agr^gats mineValogiques les plus complexes et les plus varies. Ce
coup d'oeil qui savait embrasser de si vastes horizons, p^netre ici
profond^ment tous les details lithologiques. Avec quelle suret^ et
quelle exactitude la structure et la composition des roches ne sont-
elles pas determiners, 1'origine de ces masses mineVales d^duite et
confirmee par 1'^tude compared des manifestations volcaniques
d'autres regions ; avec quelle science les relations entre les faits
qu'il d^couvre et ceux signals ailleurs par ses devanciers ne sont-
elles pas e^ablies, et comme voici ^branlees les hypotheses r^gnantes,
admises sans preuves, celles, par exemple, des crateres de souleve-
ment et de la differentiation radicale des ph&iomenes plutoniques et
volcaniques ! Ce qui acheve de donner k ce livre un incomparable
meVite, ce sont les id^es nouvelles qui s'y trouvent en germe et
jet^es Ik comme au hasard ainsi qu'un superflu d'abondance in-
tellectuelle in^puisable1."

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 Edinburgh2.

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 informa-
tion collected by the author under great difficulties and not un-
frequently at considerable risk to life and health. No sooner had

1 Observations Geologiques sur les ties Volcaniques..., Paris, 1902, pp. vi., vii.
3 Vol. ii. (1844-5), pp. 17, 18.

Geology of South America 373

Darwin landed in South America than two sets of phenomena power-
fully 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 meta-
morphic and plutonic rocks, and in them Darwin announced his
important conclusions concerning the relations of cleavage and folia-
tion, 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

374 Darwin and Geology

he wrote to Leonard Horner " I am astonished that you should have
had the courage to go right through my book1."

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 books2" — 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 con-
trast 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 absorb-
ing 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 remem-
bered only as a very able geologist of most advanced views, and
a traveller who had written a scientific narrative of more than or-
dinary excellence !

The completion of the Geology of tJie Beagle and the preparation
of a revised narrative of the voyage mark the termination of that

1 M. L. n. p. 221. 2 L. L. i. p. 80.

Combination of Geological and Biological Work 375

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 im-
portant 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 indeed1.

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 Palaeozoic 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 die2."

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 Enquiry 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

1 L. L. n. pp. 247—48. 2 M. L. I. pp. 63, 64.

376 Darwin and Geology

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 pages1 ; 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 ex-
perience 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 naturalist2."

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 illus-
trations. 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.

1 [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.]

2 L. L. n. pp. 16, 17.

Geological Chapters in the " Origin " 377

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 better1." Since this was written, the im-
portant 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

1 M. L. ii. p. 147.

378 Darwin and Geology

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 inquiries 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 Avith
intermissions during his whole life, and he extended his inquiries
from time to time to the neighbouring parks of Knole and Holwood.
In 1844 we find him making a communication to the Gardeners
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 con-
cerning 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 dis-
covered 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 inquiries at
Chideock and Silchester ; while Francis Galton contributed facts
noticed in his walks in Hyde Park. By correspondence with Fritz
Miiller 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 in-
formation 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

•

^

i

-^
5

Geological Work in Old Age 379

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 humourous smile, he would murmur some-
thing 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
Species1 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 Evolution2; 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 successfully eliminated from sober geological
speculation3."

Huxley's admiration for the Principles of Geology, and his con-
viction of the greatness of the revolution of thought brought about
by Lyell, was almost as marked as in the case of Darwin himself4. 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

1 L. L. ii. pp. 179—204.

2 Huxley's Address to the Geological Society, 1869. Collected Essays, Vol. vin. p. 305,
London, 1896.

3 L. L. n. p. 190.

4 See his Essay on "Science and Pseudo Science." Collected Essays, Vol. v. p. 90,
London, 1902.

380 Darwin and Geology

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 editions1." 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 him2.

Darwin's generous nature seems often to have made him ex-
perience 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 geo-
logically 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 ascent3."
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

1 M. L. ii. p. 222.

2 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. Hia 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 Koyal 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 rue, shortly afterwards,
how Huxley had sat by his bedside and "repeated the whole lecture to him."

3 L. L. i. pp. 337—8.

Influence of the "Principles of Geology" 381

acknowledge this sufficiently1." 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 " Ly ell'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 occasion2.

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 England3. 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 remark-
able. 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 lived4."

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

1 M. L. n. p. 117. 2 L. L. i. p. 342.

:l L. L. i. p. 62. * L. L. i. pp. 71 — 2 (the italics are mine).

382 Darwin and Geology

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 corre-
spondence. 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 dis-
coveries1." 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-."

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 re-
mained the "doubting Thomas."

Many must have felt like H. C. Watson when he wrote: "How

1 Lyell's Life, Letters and Journals, Vol. H. p. 44. - L. L. i. p. 296.

The Friendships of Damvin 383

could Sir C. Ly ell... for thirty years read, write, and think, on the
subject of species and their succession, and yet constantly look down
the wrong road1 ! " Huxley attributed this hesitation of Lyell to his
"profound antipathy" to the doctrine of the "pithecoid origin of
man2." 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... awe? 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 communi-
cation 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 con-
fidence 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

1 L. L. ii. p. 227. 2 L. L. n. p. 193.

384 Darwin and Geology

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
succeed1; 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 book2; it was Lyell who, in 1856, induced
Darwin to lay the foundations of a treatise3 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 Ly ell'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 parallel4."

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 meet-
ing, 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.

1 L. L. i. p. 83. 2 L. L. ii. pp. 17—18.

3 L. L. i. p. 84. * L. L. n. pp. 229—30.

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 evolu-
tionary work, and despised himself for belonging to the "blessed
gang " of compilers. And he correspondingly rejoiced in the employ-
ment 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 led1/' 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 import-
ance in reference to the meaning and origin of sexual reproduction2.

1 Life and Letters, i. p. 90.

2 See Professor Goebel's article in the present volume, p. 401.

D.

386 The Movements of Plants

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 knowledge1."

His doctrine of natural selection gave, as is well known, an im-
pulse 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 Orchids2, " It will perhaps serve to illustrate
how Natural History may be worked under the belief of the modifica-
tion of species" (1861). And in 1862 he speaks3 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*, 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.

1 Huxley in Darwin's Life and Letters, H. p. 204.

2 Life and Letters, in. p. 254. s Loc. cit.
4 Now being prepared for publication.

Climbing Plants 387

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 me1." He goes on to remark with some-
thing 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 com-
pelled 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 Phaseohis 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 reached2."

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 twiners3. 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 remark-
able 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 revolving4, on which most

1 Life and Letters, in. p. 315. He had, however, made a beginning on the movements
of Drosera.

2 Climbing Plants (2nd edit. 1875), p. 193.

3 Loc. cit. p. 195.

4 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.

25—2

388 The Movements of Plants

climbers depend, is inherent, though undeveloped, in almost every
plant in the vegetable kingdom1."

In the Origin* 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 Fumariaceae3.
"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 clavicu-
lata (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 move-
ment (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 physiologists4 differ from
Darwin.

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 instru-
ment 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

1 Climbing Plants, p. 205.

2 Ed. i. p. 427, Ed. vi. p. 374. 3 Climbing Plant*, p. 195.

4 See the discussion in Pfeffer's The Physiology of Plant*, Eng. Tr. (Oxford, 1906),
in. p. 34, where the literature is given. Also Jost, Vorlesungen iiber PJlanzenphysiologie,
p. 562, Jena, 1904.

Theories of Twining 389

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 move-
ment 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... unknown1."

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 " niggling2 " 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 curvature3, as did a loop of cotton
weighing 2 mg. Pfeffer4, 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 cotton-

1 The Physiology of Plants, Eng. Tr. (Oxford, 1906), m. p. 37.

2 Life and Letters, in. p. 312. 3 Climbing Plants, p. 171.
4 Untersuchungen a. d. Bot. Inst. z. Tubingen, Bd. i. 1881 — 85, p. 506.

390 The Movements of Plants

wool 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 contain-
ing 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. Pfeffer1 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 Gray2
describing the tendrils of Bignonia caprcolata, 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 productions3."

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 Hooker4: "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
y8ooo of one grain in weight placed on gland, will cause one of the
gland -bearing hairs of Drosera to curve inwards." Here again
Pfeffer5 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

1 Physiology, Eng. Tr. HI. p. 52. Pl'effer 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. p. 504).

2 Life and Letters, in. p. 314.

3 Climbing Plants, p. 102.

4 Life and Letters, in. p. 319.

5 Pfeffer in Untersuchungen a. d. Hot. Inst. z. Tubingen, i. p. 491.

Sense of Touch 391

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 Pfeffer1
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.
Haberlandt2 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,
p. 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 Nemec3 published independently and simul-
taneously 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 be-
lieve that special loose and freely movable starch-grains play the
part of the otoliths or statoliths of the Crustacea, while the proto-
plasm 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 theory4 the sense of vertically 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
records5 that a Passion-Flower tendril moved distinctly within 25

1 Tubingen Untersuchungen, i. p. 524.

2 Physiologische Pflanzenanatomie, Ed. in. Leipzig, 1904. Sinnesorgane im Pflanzen-
reich, Leipzig, 1901, and other publications.

3 Ber. d. Deutschen bot. Gesellscliaft, xvni. 1900. See F. Darwin, Presidential Address
to Section K, British Association, 1904.

4 The original conception was due to Noll (Heterogene Induction, Leipzig, 1892), but
his view differed in essential points from those here given.

5 Climbing Plants, p. 155. Others have observed movement after about 6".

392 The Movements of Plants

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 Fitting1 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*. "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 adjoin-
ing parts, acts like the brain of one of the lower animals ; the brain
being seated within the anterior end of the body, receiving impres-
sions 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? the projecting organs or antennae are sensitive to a
touch, and transmit an influence "for more than one inch instan-
taneously" 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 Hooker4 : " I cannot avoid the conclusion, that
Drosera possesses matter at least in some degree analogous in con-
stitution 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

1 Pringsheim's Jahrb. xxxviu. 1903, p. 545.

2 The Power of Movement in Plants, 1880, pp. 571—3.

3 Life and Letters, in. p. 268.

4 Life and Letters, in. p. 321.

Root-tip 393

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 l 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 gravita-
tional 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 longitudinally2,
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 Rothert3
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

1 Rothert, Cohn's Beitrage, vn. 1894.

2 See F. Darwin, Linnean Soc. Journal (Bot.) xix. 1882, p. 218.

3 See his excellent summary of the subject in Flora, 1894 (Erganzungsband),
p. 199.

394 The Movements of Plants

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
laboratory1. 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 down-
wards, 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.

Czapek2 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 stimu-
lated, can be distinguished by a chemical test from vertical, i.e. un-
stimulated 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 method3 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 coty-
ledon 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 hori-
zontal, 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 Massart4 and myself5 with a similar though

1 See Pfeffer, Annals of Botany, vin. 1894, p. 317, and Czapek, Priugsheiin's Jahrb.
xxvii. 1895, p. 243.

2 Berichte d. Deutsch. bot. Ges. xv. 1897, p. 516, and numerous subsequent papers.
English readers should consult Czapek iu the Annals of Botany, xix. 11J05, p. 75.

3 F. Darwin, Annals of Botany, xm. 1899, p. 567.

4 Massart, Mtm. Conronnes Acad. R. Belg. LXII. 1902.

5 F. Darwin, Linnean Soc. Journ. xxxv. 1902, p. 266.

Root-tip 395

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 Piccard1.

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. The root is oblique to the axis of rotation,
and the extreme tip projects beyond that axis as shown in the sketch.
The dotted line A A represents the axis of rotation, T is the tip of
the root, B is the region 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 away from the axis of
rotation, as shown by the arrow 6, 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 the curvature in the direction t. We may think of
the line A A 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

1 Pringsheim's Jahrb. XL. 1904, p. 94.

396 The Movements of Plants

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 tip1.

Haberlandt2 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 ap-
parently 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 truth3.

Another observation of Darwin's has given rise to much con-
troversy4. 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

1 Czapek (Pringsheim's Jahrb. xxxv. 1900, p. 362) had previously given reasons for
believing that, in the root, there is uo sharp line of separation between the regions of
perception and movement.

2 Pringsheim's Jahrb. XLV. 1908, p. 575.

3 By using Piccard's method I have succeeded in showing that the gravitational sensi-
tiveness 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.

4 Power of Movement, p. 133.

Sleeping Plants 397

applied to the root ; gold-beaters skin being by itself almost with-
out 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
with 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 experi-
ments 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. Stahl1 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 radia-
tion.

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 Move-
ment* 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.

1 Bot. Zeitimg, 1897, p. 81.

2 In 1881 Professor Wiesner published his Das Bewegungsvermogen der Pftanzen, a
book devoted to the criticism of The Power of Movement in Plants. A letter to Wiesner,
published in Life and Letters, in. p. 336, shows Darwin's warm appreciation of his critic's
work, and of the spirit iii which it is written.

398 The Movements of Plants

Darwin's view is plainly stated on pp. 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 acquire-
ment, 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 be-
lieving 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. Accord-
ing to Jennings1 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 how-
ever 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 Paramcecium distributed regularly about its
course by means of rotation2. 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 Paramcecium 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

1 H. S. Jennings, The Behavior of the Lower Animals. Columbia U. Press, N.Y.
1906.

2 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.

Circumnutation 399

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 appro-
priate movement without going through the tentative series of
actions.

I am tempted to recognise in circumnutation a similar ground-
work 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. Pfeffer1, 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 ex-
planation 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

1 The Physiology of Plants, Eng. Tr. in. p. 11.

400 The Movements of Plants

are dissimilar in the two cases. We must come back, in fact, to
Darwin's comparison of plants to animals. In both there is per-
ceptive 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 fertili-
sation of such plants as Primula and Lythrum, or again Anacamptis
or Listera1."

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 under-
taken 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 ivhich
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

1 More Letters of Charles Darwin, Vol. n. p. 419.
D. 26

402 The Biology of Floivers

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 com-
press 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 light1."

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 con-
clusions 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 service2!"

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 selection3." 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 life4."
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

1 More Letters, Vol. n. p. 324. 2 Ibid. Vol. i. p. 195.

u Fertilisation of Orchids (1st edit.), p. 351 ; (2nd edit. 1904), p. 286.
4 Ibid. p. 351.

Sprengel; Camerarius; Kolreuter 403

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 plant1."

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 aiford 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 constant2." 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 — 18063), the same observer to whom we owe the earliest experi-
ments 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,

1 Cross and Self fertilisation (1st edit.), p. 6.

a The Life and Letters of Charles Darwin, Vol. i. p. 90, London, 1888.

3 Kolreuter, Vorlaujiye Nachricht von einigen das Geschlecht der Pfianzen betreffenden
Versuchen und Beobachtungen, Leipzig, 1761 ; with three supplements, 1763 — 66. Also,
Mtm. de Vacad. St Petersbourg, Vol. xv. 1809.

26—2

404 The Biology of Flowers

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 Ban mid 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 demon-
strating a number of beautiful adaptations in flowers for ensuring
pollination ; but his work exercised but little influence on his con-
temporaries and indeed for a long time after his death. It was
through Darwin that Sprengel's wrork 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 wrork Versuche und
Beobaehtungen uber die Befruchtungsorgane der vollkommeneren
Geicdchse und iiber die natiirliche und Mnstliche 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 show7 " that
a very small proportion of the plants included in this category
require this assistance in their native habitat1." 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

1 Gartner, Versuche und Beobachtungen..., p. 335, Stuttgart, 1844.

Fertilisation of Orchids 405

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
flower1." 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 fertilisation2 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 condi-
tions, occurs only exceptionally. On the other hand these plants
present a series of extraordinarily beautiful and remarkable adapta-
tions 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 obser-
vations and of the perspicuity employed in interpretating the facts.

1 Fertilisation of Orchids, p. 1.

2 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 tt is so used here.

406 The Biology of Flowers

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, under-
goes 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 con&psea, 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 investi-
gations, 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 adaptation1!"

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

1 Fertilisation of Orchids (1st edit.), p. 53.

Floral Structure of Orchids 407

had shown that it is only a touch on the antennae that causes the ex-
plosion, 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 Monachan-
thus 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 Mycmthm barbatus, was regarded by Darwin
as a third form: this was afterwards recognised by Rolfe1 as the
male flower of another species, Catasetum barbatum Link, an identi-
fication in accordance with the discovery made by Criiger 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 Criiger — 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 existence2."

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 parts3. Although the interpretation of the orchid flower
given by Darwin has not proved satisfactory in one particular point

1 Kolfe, E. A. " On the sexual forms of Catasetum with special reference to the
researches of Darwin and others," Journ. Linn. Soc. Vol. xxvu. (Botany), 1891, pp. 206 —
225.

2 Fertilisation of Orchids, p. 289.

3 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. n. p. 275).

408 The Biology of Flowers

— 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 whorls1." 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 leading2. 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 another3."

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 generations4 ? "

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

1 Fertilisation of Orchids (1st edit.), p. 307.

2 Life and Letters, Vol. in. p. 276 (footnote).

3 Fertilisation of Orchids, p. 71. * Ibid., p. 359.

Heterostyled Flowers 409

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 in-
creasing 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 con-
clusions 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 animals1." 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

1 Forms of Flowers (1st edit.), p. 2.

410 The Biology of 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 qfficinalis (P. veris) (Cowslip) ... 69

Primula elatior (Oxlip) 27

Primula acaidis (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 genera-
tions, sterile pollen and in the open a feebler growth1. 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 dis-
tinctness'2": 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

1 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 question?,
deserves further investigation.

2 Forms of Flowers, p. 242.

Heterostyled Flowers 411

hybrids1, with which their behaviour iu 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 ojficinalis, 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 offspring2." 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 plants3."

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.

1 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, p. 466), he adopted the term species in a comprehensive sense.
The recent researches of Bateson and Gregory ("On the inheritance of Heterostylistn
in Primula"; Proc. Roy. Soc. Ser. B, Vol. LXXVI. 1905, p. 581) appear to me also to
support the view that the results of illegitimate crossing of heterostyled Primulas corre-
spond 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.

2 Forms of Flowers, p. 258. 3 Life and Letters, Vol. i. p. 91.

412 The Biology of Flowers

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 chas-
mogamous 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 con-
cerned 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 chasmo-
gamous flowers of the same species are usually cross-fertilised and
"their offspring will thus be invigorated, as we may infer from a
wide-spread analogy1." 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 experi-
ment 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

1 Forms of Flowers (1st edit.), p. 341.

Cross and Self-fertilisation 413

experiments, as we have pointed out1, 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 experi-
ments on the effect of cross and self-fertilisation. Plants of Linaria
vidgaris 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
wrere 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-ferti-
lisation, 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 me2."

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

1 Ante, p. 408. 2 More Letters, Vol. n. p. 373.

414

The Biology of Flowers

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 jmrpurea may be quoted as an example. If we express
the result of cross-fertilisation by 100, we obtain the following
numbers for the self-fertilised plants.

Height.

Number of

seeds.

1 Generation

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

1 "•

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 sterile1.

The superiority of crossed individuals is not exhibited in the
same way in all plants. For example in Eschschohia call for nica
the crossed seedlings do not exceed the self-fertilised in height and

1 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 Zttchtung der Landunrtschaftlichen Kulturpflanzen,
Berlin, 1904, n. p. 6.)

Autogamy and Geitonogamy 415

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, Pelar-
gonium, Origanum) were not in complete agreement; but on the
whole they pointed to the conclusion that Geitonogamy shows no
superiority over self-fertilisation (Autogamy)1. 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 constitution2."

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
O'OOO 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 con-
ditions 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

1 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.
• Cross and Self fertilisation (1st edit.), p. 444.

416

The Biology of Flowers

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
conditions1."

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
with a fresh
stock

On crossing
plants of the
same stock

On self-
fertilisation

Mimulus 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
formerly2. We know that most of Linnaeus'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 in-

1 More Letters, Vol. n. p. 406.

2 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.

Cross-fertilisation 417

fluenced 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 con-
ditions. 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 genera-
tion 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.

Janczewski1 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 sub-
jected, is securely fortified on all sides2."

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 beneficial3, crossing between organisms which
have been exposed to different conditions becomes still more ad-
vantageous. 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

1 Janczewski, "Sur les autheres ste'riles des Groseilliers," Bull, de Vacad. des sciences
de Cracovie, June, 1008.

- Cross and Self fertilisation (1st edit.), p. 444.

3 Beasons for this are given by Darwin in Variation under Domestication (2nd edit.),
Vol. ir. p. 127.

D. 27

418 The Biology of Flowers

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-fertilisation1." 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 Nicotiana2, 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 plant3." 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 differentia-
tion 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-fertilisa-
tion ; 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

1 Cross and Self fertilisation (1st edit.), p. 371.

2 In Pisuni 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 kiinstliche Kreuzung an Pisum satirum ") 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.

u Cross and Self fertilisation, p. 350.

Self-fertilisation 419

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 pollen1. This has been demonstrated in the case of Mimulus
lute us (for the fixed white-flowering variety) and Iberis uinbellata
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 seedlings2." 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 ex-
pressed 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 im-
portance 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-fertilisation3." 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-fertilisation4 " is, however, a pregnant

1 Cross and Self fertilisation, p. 391. * Ibid. p. 397. 3 Ibid. p. 437.

4 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 (p. 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."

27—2

420 The Biology of Flowers

expression of the fact that cross-fertilisation is exceedingly wide-
spread 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 Bliitenbiologie (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 genera-
tions, and grow the seedlings under the same conditions1."

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.

1 Cross and Self fertilisation (1st edit.), p. 460.

Self-fertilisation 421

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 counter arguments, 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 wide-
spread 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-fertilisation1." 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.

Loew2 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 im-
portance 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. Bateson3 found that cross-fertilisation gave a beneficial result,

1 It is impossible (as has been attempted) to express Darwin's point of view in a single
sentence, such as H. Miiller'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.

2 E. Loew, "Bemerkungen zu Burck...," Biolog. Centralbl. xxvi. (1906).

3 Anna Bateson, " The effects of cross-fertilisation on inconspicuous flowers," Annals of
Botany, Vol. i. 1888, p. 255.

422 The Biology of Flowers

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. Burck1 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 origin2. 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 cross3." 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 characterised 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
generations4. As yet it is impossible to lay dowrn rules of general
application for the self-fertility of hybrids. That the beneficial in-
fluence 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,

1 Burck, "Darwin's Kreuzungsgesetz...," Biol. Centralbl. xxvm. 1908, p. 177.

2 It is questionable if this was always the case.

3 Cross and Self fertilisation (1st edit.), p. 55.

4 K. F. Gartner, Verauche ttber die Bastarderseugung, Stuttgart, 1849, p. 149.

Cleistogamous Flowers 423

wealth of flowers, etc. corresponds entirely with Darwin's con-
clusions. 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 ex-
clusively 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 evi-
dence, 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. The
facts mentioned on page 415 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 investi-
gations 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.RS.

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 class1." When he passed to the detailed con-
sideration 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 faculties2." " 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 developed3." 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 mind4." 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
males5." 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 develop-
ment of various bodily structures and of certain mental qualities6."

Throughout his treatment, mental evolution was for Darwin in-
cidental 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

1 Origin of Species (6th edit.), p. 205.

* Descent of Man (2nd edit. 1888), Vol. i. p. 99; Popular edit. p. 99. 3 Ibid. p. 99.

1 The Expression of the Emotion* (2nd edit.), p. 32.

5 Descent of Man, Vol. n. p. 435. 6 Ibid. pp. 437, 438.

Mental Evolution 425

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 pro-
cesses 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 evolu-
tionary 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 said1, "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 : conscious-
ness 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

1 Origin of Species (6th edit.), p. 205.

426 Mental Factors in Evolution

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. Sub-
ordinate 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 ex-
perience 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 distinguish-
able : 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
says1, "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

1 Origin of Species (6th edit.), p. 205.

Racial Preparation 427

action, which we ourselves require experience to enable us to per-
form, 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 says1, "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 nature2." 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 per-
formance) is the outcome of heredity and due to the direct trans-
mission 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 develop-
ment 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

1 Origin of Species (6th edit.), p. 233. 2 Ibid. p. 205.

428 Mental Factors in Evolution

but also, to some extent, the modifications are inherited. He there-
fore 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 says1, " 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 says2, " 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 selection3, 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 inter-
pretation. 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) Varia-

1 Origin of Species (6th edit.), p. 233. - Ibid. pp. 210, 211.

* Independently suggested, on somewhat different lines, hy Profs. J. Murk Baldwin,
Henry F. Osboru and the writer.

Organic Selection 429

tions (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) + Vwith+M,

(b) +Vwith-M,

(c) - V with + M,

(d) -Vwith-M.

Of these (cl) 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 aifords a satisfactory basis for genetic
treatment. To carry out the spirit of Darwin's teaching it is neces-
sary 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 be-
haviour. 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

430 Mental Factors in Evolution

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 prepara-
tion. 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 evolu-
tion 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 appro-
priate 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

Instinctive Behaviour 431

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 out1, 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 inter-
pretation, 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 regarded 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 distin-
guish 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

1 Origin of Species (6th edit.), p. 206.

432 Mental Factors in Evolution

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 said1, "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 com-
munity 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
degree2." 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 desire3."

" Our second principle is that of antithesis. The habit of volun-

1 Expression of the Emotions, p. 13. The passage is here somewhat condensed.
- Ibid. p. 368. 3 Ibid. pp. 373, 374.

Expression of the Emotions 433

tarily 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 mind1." This principle of anti-
thesis has not been widely accepted. Nor is Darwin's own position
easy to grasp.

"Our third principle," he says2, "is the direct action of the excited
nervous system on the body, independently of the will, and inde-
pendently, 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 master-
piece 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 dis-
tinguished 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 bio-
logical means of expression are full of subtle suggestiveness. Many
modes of expression, otherwise useless, are signs of behaviour that

1 Expression of the Emotions, p. 368. 2 Ibid. p. 369.

D. 28

434 Mental Factors in Evolution

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 stress1 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 emo-
tional 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 expres-
sion 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 ac-
quired 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 psycho-
logists 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 James2; 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, affec-
tions 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

1 Expression of the Emotions, pp. 65 ff .

2 Cf. William James, Principles of Psychology, Vol. n. Chap, xxv, London, 1890.

Genesis of the Emotions 435

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 emo-
tional 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 ex-
perience 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 accompani-
ments, 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 effective-
ness and persistency of behaviour, it must on Darwin's principles be
subject to natural selection.

28—2

436 Mental Factors in Evolution

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 phe-
nomena 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 alert-
ness and skill which are the outcome of the psychological develop-
ment 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 Wallace1 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 Wallace2, "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

1 Darwinism, pp. 2iS2, 283, London, 1889. " Ibid. p. 283.

Sexual Selection 437

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 ex-
tension 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 con-
stant. 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 says1: "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 jttdice 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

1 Darwinism, pp. 283, 284.

438 Mental Factors in Evolution

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 de-
veloped 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 emo-
tional. 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, — cor-
relative 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 states1 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."

1 Descent of Man (2nd edit.), Vol. n. pp. 136, 137 ; (Popular edit.), pp. 642, 643.

Sexual Selection 439

The view here put forward, which has been developed by Prof. Groos1,
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 height-
ened 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 coy-
ness of females as " a most efficient means of preventing the too early
and too frequent yielding to the sexual impulse2." 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 implica-
tions, is raised to a level otherwise perhaps unattainable by natural
means, while in the female it affords opportunities for the develop-
ment 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 con-
sidered, 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 says3, " is
more common than for animals to take pleasure in practising what-
ever 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 says4,
" 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 urges5 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

1 The Play of Animals, p. 244, London. 1898. 2 Ibid. p. 283.

3 Descent of Man, Vol. n. p. 60; (Popular edit.), p. 566.

4 The Play of Animals, p. 76. 5 Ibid. p. 75.

440 Mental Factors in Evolution

no doubt they are closely related and have some common factors.
It is probable that play, as preparatory behaviour, differs in bio-
logical 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-pro-
pensity 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 foundations1. 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 psycho-
logical activities which are included under the comprehensive term
"intelligent."

In TJie Descent of Man Darwin dealt at some length with intelli-
gence and the higher mental faculties2. 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 fore-
shadowed in the mental life of animals. Still he contends that these
may be explained on the doctrine of evolution. He urges3 "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 brain4. "As the
various mental faculties gradually developed themselves, the brain

1 The Play of Animals, p. 24.

2 Descent of Man (1st edit.), Chaps, n, in, v; (2nd edit.), Chaps, in, iv, v.
* Ibid. Vol. i. pp. 70, 71 ; (Popular edit.), pp. 70, 71. * Ibid. p. 81.

" The Descent of Man" 441

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 says1, "M. E. Lartet2, 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 trans-
mitted, 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 ac-
quired 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 defective3."

In this statement we have a good example of the further develop-
ment 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.

1 Descent of Man (Popular edit.), p. 82. 2 Comptes Eendus des Sciences, June 1, 1868.

3 Nature, Vol. LXI. pp. 624, 625 (1900).

442 Mental Factors in Evolution

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 said1 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
says2 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 con-
sideration 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 em-
phasise 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 informa-
tion from reliable sources, he presented the whole subject in a new
light and showed that a natural history of mind might be written

1 Descent of Man, Vol. I. p. 100. a Principles of Ptycholoyy, Vol. n. p. 280.

Instinct and Educability 443

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 re-
fashions 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 con-
structions 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

444 Mental Factors in Evolution

man from those of the lower animals has been brought about — a '
differentiation the existence of which he again and again acknow-
ledges. 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 founda-
tions on which man's systems of ethics are built. He definitely
stated that he approached the subject " exclusively from the side of
natural history1." 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 says2, "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 notes3 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 senti-
ments 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

1 Descent of Man, Vol. i. p. 149. • Ibid. p. 185.

3 Ibid. p. 150 (footnote).

Biological Foundations of Ethics 445

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 intelli-
gently 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. Further-
more, 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 super-
structure. 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 opera-
tions 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 to 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 the way of experience, and then
not to turn dizzy when a summit is gained. Darwinians have some-
times 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

" The Origin of Species " 447

finally because of the influence it would exert on the whole con-
ception 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] metaphysics1."

We can distinguish four main points in which Darwin's investiga-
tions 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 (1/86). 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

1 Life and Letters of Charles Darwin, Vol. I. p. 8.

448 Evolution and Modern Philosophy

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 character-
istically 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

Darwin and Contemporary Philosophy 449

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 production1."

The only one of the philosophers of Romanticism who believed in
a real, historical evolution, a real production of new species, was
Oken2. 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 succession3 !

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

1 Encyclopadie der philosophischen Wissenschaften (4th edit.), Berlin, 1845, §249.

2 Lehrbuch der Naturphilosophie, Jena, 1809.

3 Ueber den Willen in der Natur (2nd edit.), Frankfurt a. M., 1854, pp. 41 — 43.

D. 29

450 Evolution and Modern Philosophy

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 con-
tinuity 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 d, priori.

Herbert Spencer 451

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

29—2

452 Evolution and Modern Philosophy

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 function-
ally-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 up1."
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 preserves2." 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, differentia-
tion 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

1 Spencer, Autobiography, Vol. n. p. 50, London, 1904. a Ibid. p. 100.

German, Italian and French Philosophers 453

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
consistently1 — 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, re-
pudiated the ascription of materialism. He is no more a materialist
than Spinoza. In his Principles of Psychology (§ 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 differentia-
tion ; 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 cosmo-
logical, psychical evolution being conceived as in analogy with physical,
a group of eminent thinkers — in Germany Wundt, in France Fouill^e,
in Italy Ardigb — 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 Fouill^e 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

1 Cf. my letter to him, 1876, now printed in Duncan's Life and Letters of Herbert Spencer,
p. 178, London, 1908.

454 Evolution and Modern Philosophy

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 Ardig6 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 Ardigb 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 Fouill^e 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
Ardig5, 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 Fouille'e
Ardig5 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/ Evolu-
tion Crtfatrice, evolution consists in an (flan 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 ex-
pressed : in the domain of internal conditions spontaneous develop-
ment of qualitative forms — in the domain of external conditions
discontinuity and mechanical combination.

We see, then, that the theory of evolution has influenced philosophy

The Evolution hypothesis 455

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 repre-
sentative 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 hypo-
thesis 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

456 Evolution and Modern Philosophy

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 con-
sidered 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
d priori, original, basis (or Anlage) for all mental life ; but in the
species all powers have developed in reciprocity with external con-
ditions. 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 suc-
cessively 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
given1.

But there is another side of the problem which is, perhaps, of

! The present writer, many years ago, iu his Psychology (Copenhagen, 1882 ; Eng.
transl. London, 1891), criticised the evolutiouistic treatment of the problem of knowledge
from the Kantian point of view.

Evolutionism and Systematism 457

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 con-
sequence 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 Cirri-
pedia. 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 systematist1." 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 varia-
tion2?" 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 im-
possible, 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.

1 Life and Letters, Vol. n. p. 37. 2 Ibid. p. 232.

458 Evolution and Modern Philosophy

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 develop-
ment of the single individual1. As Leibniz said long ago, individuality
consists in the law of the changes of a being: "La loi du change-
ment fait I'lndividualite* 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

1 The new science of Ecology occupies an intermediate position between the biography
of species and the biography of individuals. Compare Conr/ress of Arts ami Science,
St Louis, Vol. v. 1900 (the Reports of Drude and Robinson) and the work of my colleague,
E. Warming.

Ethical Development 459

regarded these as one of the strongest objections against it ; so
Diihring and Kropotkiu (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 helium 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 alla3Ted 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)1. 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 2. 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.

1 Cf. my History of Modern Philosophy (Eng. transl. London, 1900), i. pp. 76 — 79.

2 " Herrschaft und Kriechtschaft," Phanomenologie des Geistes, iv. A., Leiden,
1907.

460 Evolution and Modern Philosophy

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
chapter1 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 repre-
sented by Hutchesou, 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
unexplained2 ; 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 demonstra-
tion 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 evolu-

1 The Descent of Man, Vol. i. Ch. iii.

a The works of Westerrnarck and Hobhouse throw new light on many of these features.

The Importance of Individual Variations 461

tionism. I may, however, here refer to the book of C. M. Williams,
A Review of the Systems of Ethics founded on the Theory of
Evolution1, in which, besides Darwin, the following authors are
reviewed : Wallace, Haeckel, Spencer, Fiske, Rolph, Barratt, Stephen,
Carneri, Hb'ffding, Gizycki, Alexander, Re"e. As works which criticise
evolutionistic ethics from an intuitive point of view and in an
instructive way, may be cited : Guyau, La morale anglaise contem-
poraine*, 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 reached3." 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 here4. 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

i New York and London, 1893. 2 Paris, 1879.

3 English literature and society in the eighteenth century, London, 1904, p. 187.

4 Cf. my paper, "The law of relativity in Ethics," International Journal of Ethics, Vol. i.
1891, pp. 37—62.

462 Evolution and Modern Philosophy

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 genera-
tions, 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

Darwin's attitude towards ultimate questions 463

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 Cause1.

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 degraded2." 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 conse-
quence, 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 them-
selves 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 evolu-
tion 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 con-
dition 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

1 Life and Letters, Vol. r. p. 310. a Ibid. Vol. n. p. 177.

464 Evolution and Modern Philosophy

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 arose1." He saw, as Kant had seen before him and
expressed in his Kritik der Urtheilskrqft, 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 con-
structing 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 duty2."

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 evolu-
tion. Moreover there are lines of evolution which have their end in
ethical idealism, in a kingdom of values, wrhich must struggle for
life as all things in the world must do, but a kingdom which has its
firm foundation in reality.

1 Life and Letters, Vol. i. p. 306. a Ibid. p. 307.

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 " re'inte'grer 1'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

D. 30

466 Darwinism and Sociology

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, "Who-
soever 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-con-
ception 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 determinism. 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 grdce : 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

The Philosophy of Becoming 467

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 : Trdvra pel. 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 re-
search 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
personifications1." 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 ;

1 P. Floureris, Examen du Livre de M. Darwin sur VOrigine des Especes, p. 53,
Paris, 1864. See also Huxley, " Criticisms on the Origin of Species," Collected Essays,
Vol. ii, p. 102, London, 1902.

30—2

468 Darwinism and Sociology

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 en-
lightened 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 im-
provements. 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 socio-
logical 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,

Selection in Mankind 469

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 others' 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 Development1, 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 Polities'2 reminds us of Darwin's remark that the insti-
tution 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 ranks3." 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 impor-
tance 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 under-
taking 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

1 Inquiries into Human Faculty, pp. 1, 2, 3sq., London, 1883.

2 Darwinism and Politics, pp. 9, 22, London, 1889.

3 Life and Letters of Charles Darwin, n. p. 385.

470 Darwinism and Sociology

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 eighteenth1." 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 Bases2, 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 in-
spired 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 insufficiency 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

1 V. de Lapouge, Les Selections societies, p. 259, Paris, 1896.

2 Die nalilrliche Auslese beim Menschen, Jena, 1893; Die Gesellschaftsordnuny und ihre
natiirlichen Grundlagen. Entwurf einer Sozialanthropologie, Jena, 1896.

Struggle for Existence 471

Man1, 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 Hansen2 (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 rhas
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 dispro-
portion 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 gladiators3.

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

1 Etudes sur la Selection dans ses rapports avec Vhereditt chez Vhomme, Paris, p. 481,
1881.

2 Die drei Bevolkerungsstufen, Munich, 1889.

2 Evolution and Ethics, p. 200 ; Collected Essays, vol. ix, London, 1894.

472 Darwinism and Sociology

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 rein-
forcements 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 pro-
tests 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 Jwar partisans of the " struggle for existence " can be
found : there are disciples of Darwin in the peace party. Novicow,
for example, admits the " combat universe!" of Avhich Le Dantec1
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

1 Les Luttes entre Societes humaines et leurs phases successives, Paris, 1893.

Struggle for Existence 473

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 Laveleye1, 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, in-
capable, 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 main-
tain 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 association2." Experience shows, according to Geddes,

1 Le socialisme contemporain, p. 384 (6th edit.), Paris, 1891.

2 Geddes and Thomson, The Evolution of Sex, p. 311, London, 1889.

474 Darwinism and Sociology

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 observa-
tions 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 prefer-
ences, 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 Diihring.

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

Social Evolution 475

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 produc-
tion 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 : — 7roXe/i09 frar^p Travrcov. 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 Labour1.
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,

1 De la Division du Travail social, Paris, 1893.

476 Darwinism and Sociology

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 de-
clared ; 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 Universette he has directly combatted all forms of
sociological Darwinism. According to him the idea that the evolu-
tion 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 varia-
tions upon which Darwin builds. Thus, accepting Tarde's own repre-
sentations, 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. K 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 bene-
ficial 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.

478 Darwinism and Religious Thought

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 out-
stepped it did so only with the most scrupulously careful acknowledg-
ment— 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 advan-
tages 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 begin-
nings 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 de-
scription 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

Three Gains: I, A Juster Method 479

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. Accord-
ingly 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 recogni-
tion 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 signifi-
cance 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

480 Darwinism and Religious Thought

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 reinforce-
ment 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 inquiry1, 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 Berthelot2 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 con-
sider 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

1 F. E. Tennant : "The Being of God in the light of Physical Science," in Essays on
some theological questions of the day. London, 1905.

2 Evolutionisme et Platonisme, pp. 45, 46, 47. Paris, 1908.

//. A More Scientific Temper 481

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 labora-
tory 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 diffi-
culties 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 reading1?" 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 reflexion 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 examples2, it is truly scientific in
its determination to know the very truth, to tell what we think, not

1 Essays of Ella, "New Year's Eve," p. 41 ; Ainger's edition. London, 1899.

2 Such an example is given in Baron F. von Hiigel's recently finished book, the result
of thirty years' research : The Mystical Element of Religion, an studied in Saint Catherine
of Genoa and her Friends. London, 1908.

D. 31

482 Darwinism and Religious Thought

what we think we ought to think1, 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 rudi-
ment, 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 discovery2." With what
miraculous mental energy and divine good fortune — as Romans said
of their soldiers — did our men of curiosity face the apparently im-
penetrable 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

1 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, p. 182, London, 1908.

2 Queen of the Air, Preface, p. vii. London, 1906.

///. A Solder Language 483

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 science1.

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.

1 The scientific rank of its writer justifies the insertion of the following letter from
the late Sir John Burdon-Sanderson to rne. 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 SIB,

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 Keligion, 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

484 Darwinism and Religious Thought

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 ex-
planation 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 Miiller 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 tra-
ditional opinion, yet evolution and natural selection must be separated
in theological no less than in biological estimation. Evolution seemed

Creation and Evolution 485

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
Liddon1 was supposed by many biologists to be the necessary
foundation of an honest Christianity. It was really more character-
istic of devout naturalists like Philip Henry Gosse, than of religious
believers as such2. 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 "Hie 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 re-
spiciunt adpauca, de facili prommciant*."

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 con-
servative 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.

1 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).

2 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 observa-
tions gained for him a deserved approbation and confidence."

3 Aristotle, in Bacon, quoted by Newman in his Idea of a University, p. 78. London,
1873.

486 Darwinism and Religious Thought

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 Darwin1 and to the story of Huxley's impassioned
championship, all that they can learn of George Romanes2. 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, incredible3. 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 con-
troversialists 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.

1 Life and Letters and More Letters of Charles Darwin.

2 Life and Letters, London, 1896. Thoughts on Religion, London, 1895. Candid
Examination of Theism, London, 1878.

3 " 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 Darwiu)
behold advancing as a deluge, black with destruction, resistless in might, uprooting our
most cherished hopes, engulphiug our most precious creed, and burying our highest life in
mindless destruction."—^ Candid Examination of Theism, p. 51.

The Narrower Tradition 487

Huxley1 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 seven-
teenth 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 preciseuess 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, Goethe2 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 philosophic reTormatrice du XVIIP
siecle3 ramenait la nature et la societ^ k des m^canismes que la
pens^e re'fle'chie peut concevoir et r^composer." 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

1 Science and Christian Tradition. London, 1904.

2 "No productiveness of the highest kind is in the power of anyone." — Conversa-
tions of Goethe with Eckermann ond Soret. London, 1850.

3 Berthelot, Evolutionisme et Platonisme, Paris, 1908, p. 45.

488 Darwinism and Religious Thought

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 18921 — 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 pro-
cess. 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

1 Times, 1892, passim.

A Bolder Theism Needed 489

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 par-
ticular 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 evolution1.

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

1 See Von Hartmann's Wahrheit und Irrthum in Darwinismus. Berlin, 1875.

490 Darwinism and Religious Thought

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 source1."

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 contempla-
tion 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 evolu-
tion 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.

1 Hymn of the Church —

Rerum Deus tenax vigor,

Immotus in te permanens.

Design and Natural Selection 491

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 com-
plex 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 dis-
appear 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 sur-
vive," 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 heredi-
tary equilibrium, and in "the unstable state of species"; equally
present on both sides of every strain, in all pressures and in all

492 Darwinism and Religious Thought

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 con-
templation 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 import-
ance 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

A Bolder Teleology 493

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 know-
ledge. 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 good1" 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 improve-
ments in the preaching of the Christian faith.

1 Life and Letters, Vol. HI. p. 359.

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-day1. From this second inquiry it will, I hope, be abund-
antly 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 con-
sidered, it was held to be a form in which beliefs, already defined
and fixed as dogma, found a natural mode of expression. This, it

1 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.

Pre-Darwinian Attitude towards Religion 495

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 busi-
ness 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 Creation1 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 mission-
aries 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."

1 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.

496 Darwinism and the Study of Religions

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 \ve 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 dog-
matic 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 Chap. vni. of the Life and Letters1. 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.

1 Vol. i. p. 304. For Darwin's religious views see also Detcent of Nan, 1871, Vol. i..
p. 65 ; 2nd edit. Vol. i. p. 142.

" The Origin of Species " 497

The acts of religion which may result from such convictions, i.e.
devotion in all its forms, prayer, praise, sacraments, are left un-
mentioned. 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 Review1, 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*, "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 associa-
tion, 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, in-
augurated. Writing in 1871 to Dr Tylor, on the publication of his
Primitive Culture, he says3, "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 acquire-
ment 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

1 1871. 2 6th edition, p. 428. 3 Life and Letters, Vol. in. p. 151.

D. 32

498 Darwinism and the Study of Religions

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 com-
parative 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 investi-
gations of such masters as Drs Wundt, Lehmann, Preuss, Bergsen,
Beck and in our own country Drs Tylor and Frazer1.

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 Mysteries2 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 practi-
cally 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,

1 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 Dcnkens" in Zeitschrift f. Philos. mid
Philos. Kritik, 1903, p. 172, and 1904, p. 9. Henri Bergson, L'Evolution Creatrice and
MatiZre et M6moire, 1908. K. Th. Preuss, various articles published in the Globus (see
p. 507, note 1), and in the Archiv f. Religionswissemchaft, and for the subject of magic,
MM. Hubert et Mauss, " The'orie generate de la Magie," in UAnnte Sociologique, vn.

* See my Prolegomena to the Study of Greek Religion, p. 155, Cambridge, 1903.

Content of Primitive Supersensuous World 499

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 sub-
jective ; 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 sub-
jective 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 Ideas1, 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

1 I owe this psychological analysis of the elements of the primitive supersensuous world
mainly to Dr Beck, "Erkenntnisstheorie des primitiven Denkens," see p. 498, note 1.

32—2

500 Darwinism and the Study of Religions

mind of the thinker, they have in some shadowy way spatial exten-
sion. 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 de-
lusion," 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 con-
fusion fraught with disaster. He passes naturally enough, being eco-
nomical 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 super-
sensuous 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 in-
visible 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

Content of Primitive Supersensuous World 501

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 it1." 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 per-
ception, 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 — what-
ever 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; per-
haps 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)2.

1 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.

2 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 Kiirper-
scele and Psyche have been very fully discussed in Wundt's Volkerpsychologie, n.
pp. 1—142, Leipzig, 1900.

502 Darwinism and the Study of Religions

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, geo-
metrical 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 Tylor1 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 naming2. 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 seven-
ness, 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 rarefied, 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

1 Primitive Culture, Vol. n. p. 245 (4th edit.), 1903.

z For a full discussion of this point see Beck, Nachahmung, p. 41, Die Sprache.

Magical Element in Primitive Ritual 503

" soul " without lapsing into a sensuous mythology. The Cartesians'
sharp distinction between res extensa non cogitans and res cogitans
non extensa 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-Gbtter), 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, pro-
jected 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 occu-

504 Darwinism and the Study of Religions

pation 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 Tarahumares1 in Mexico the word for dancing, noldvoa, 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 work2. 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

1 Carl Lumholtz, Unknown Mexico, p. 330, London, 1903.

a Karl Backer, Arbeit und Rhythmus, Leipzig (3rd edit.), 1902, passim.

The Psychology of Magic 505

magician, a god; he does not pray, he wills. Moreover he wills
collectively1, reinforced by the will and action of his whole tribe.
Truly of him it may be said, "La vie d^borde I'intelligence, 1'intelligence
c'est un retr^cissement2."

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 repro-
duce the characteristic movements and habits of the animals imper-
sonated. So characteristic is this impersonation in magical dancing
that among the Mexicans the word for magic, navali, means "dis-
guise3." 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 V.

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 a 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 under-
standing 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.

1 The subject of collective hallucination as an element in magic has been fully worked
out by MM. Hubert and Mauss. "The'orie gen6rale de la Magie," in L'Annee Sociologique,
1902—3, p. 140.

2 Henri Bergson, L'Evolution Crgatrice, p. 50.

3 K. Th. Preuss, Archiv f. Beligionswissenschaft, 1906, p. 97.

4 Bergson, L'Evolution Creatrice, p. 205.

506 Darwinism and the Study of Religions

The Iroquois1 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 0u/xo'?, 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 Melanesians2 is somewThat 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 benefit3."

Specially instructive is a word in use among the Omaka4, 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-spatial5.

1 Hewitt, American Anthropologist, iv. i. p. 32, 1902, N.S.

2 Codriugton, The Melanesians, pp. 118, 119, 192, Oxford, 1891.

3 Codrington, The Melanesians, p. 120, Oxford, 1891.

4 See Prof. Haddoii, Magic and Fetishism, p. GO, London, 1906. Dr Vierkaudt (Glvbus,
July, 1907, p. 41) thinks that Fernzauber is a later development from Nahzauber.

8 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 SiW/m
and <f>vffis. See MM. Hubert et Mauss, " Theorie ge"ne"rale de la Magie," p. 117, in L'Annfe
Sociologique, vn.

The Psychology of Magic 507

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 action1,
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, brdhman 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 inquire2.

1 I owe this observation to Dr K. Th. Preuss. He writes (Archiv /. Eelig. 1006, p. 98),
"Die Betonung des Willens in den Zauberakten 1st der richtige Kern. In der Tat muss
der Mensch den Willen haben, sich selbst und seiner Umgebung besondere Fabigkeiten
zuzuschreiben, und den Willen hat er, sobald sein Verstand ihn befahigt, eine ubcr
den Instinkt hinausgehende Filrsorge fur sich zu zeigen. So lange ihn der Instinkt
allein leitet, konrifti Zauberhandlunf/en nicht enstehen." For more detailed analysis of
the origin of magic, see Dr Preuss "Ursprung der Religion und Kunst," Globus,
LXXXVI. and LXXXVII.

2 If external stimuli leave on organisms a trace or record such as is known as an
Engrain, 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, p. 8, and again Bergson places memory
at the very root of conscious existence, see L' Evolution Creatrice, p. 18, le fond meme
de notre existence consciente est memoire, cVst a dire prolongation du passee dans le present,
and again, la duree mord dans le temps et y laisse Vempreint de son dent, and again,
I'Evolution implique une continuation rielle du passee par le present.

508 Darwinism and the Study of Religions

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, therio-
morphism), 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 dis-
tinction, 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

Relation of Magic to Religion 509

to another, though they ultimately blend, they are at the outset
diametrically opposed, magic being a sort of rudimentary and mis-
taken science1, 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 my2 view 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 in-
formed by the life-impulse, more and more externalised. Dr Beck3
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*.

Dr Beck's remarks on ritual are I think profoundly true and

1 This view held by Dr Frazer is fully set forth in his Golden Bough (2nd edit.),
pp. 73 — 79, London, 1900. It is criticised by Mr B. E. Marett in From Spell to Prayer,
Folk-Lore, xi. 1900, p. 132, also very fully by MM. Hubert and Mauss, " Theorie generate
de la Magie," in L'Armee Sociologique, vn. p. 1, with Mr Marett's view and with that of
MM. Hubert and Mauss I am in substantial agreement.

2 This view as explained on p. 508 is, I believe, my own most serious contribution to the
subject. In thinking it out I was much helped by Prof. Gilbert Murray.

3 Die Nachahmung und ihre Bedeutung filr Psychologie und Volkerkunde, Leipzig,
1904.

4 Bergson, op. cit. p. 143.

510 Darwinism and the Study of Religions

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 rfeultat d'une science et d'une habitude qui
exaltent la volonte" humaine au-dessus de ses limites habituelles1."
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-con-
fident will. Is religion then entirely a delusion? I think not2.
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 medi-
aevalisms such as Body and Soul, and by the perhaps scarcely less

1 feliphas Le"vi, Dogme et Ritttel de la haute Mtujie, n. p. 32, Paris, 1861, and "A
defence of Magic," by Evelyn Underbill, Fortnightly Review, 1907.

2 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.

The Relation of Magic to Religion 511

mythological segregations of Intellect, Emotion, Will. But new facts1
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 evolu-
tion 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 r6aliU 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 anthropo-
morphic 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 out-
grown 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.

1 See the Proceedings of the Society for Psychical Research, London, passim, and
especially Vols. vn. — xv. For a valuable collection of the phenomena of mysticism, see
William James, Varieties of Religious Experience, Edinburgh, 1901 — 2.

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 in-
fluence 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 country-
men 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 forward1. In

1 For an account of the Cratylus with references to other literature see Sandys' History
of Classical Scholarship, i. p. 92 ff., Cambridge, 1903.

The earlier treatment of Language 513

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 many stages further
removed from the parent language than Greek is ; 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 develop-
ment 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 com-
parison 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 had 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 Tongue1 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 utter-
ance 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

1 Dante, de Vulgari Eloquio, i. 4.
D. 33

514 Evolution and Language

some authorities, to be written in excellent Hebrew. The study
of them has been the fascination and the despair of many a philo-
logist. 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 attempts1 to
establish connection between the Indo-Germanic and the Semitic
families of languages, there is no satisfactory evidence of such re-
lation 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 relation-
ship, 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

1 Most recently in H. Holler's Semitisch timl Indogermanisch, Erster Teil, Kopenhagen,
1907.

Sir William Jones and his successors 515

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
Grreek, 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 dis-
cussing any question concerning the antiquities of Persia1."

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 re-
search, 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. Need-
less to say much remained to be done, much still remains to be

1 Asiatic Researches, i. p. 422, Works of Sir W. Jones, i. p. 26, London, 1799.

33—2

516 Evolution and Language

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 vocabu-
lary, 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. Un-
fortunately, 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 Home Tooke remarked a century ago, Locke
had found a whole philosophy in language. What have the philoso-
phers 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 Volkerp8ychologiel,and Mauthner's brilliantly

1 Erster Band : Die Sprache, Leipzig, 1900. New edition, 1904. This work has been
fertile iu producing both opponents and supporters. Delbriick, Grundfragen tier .$/ iacli-

The Origin of Language 517

written Beitrage zu einer Kritik der Sprache1 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 develop-
ment 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 Philo-
logy 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 languages2. 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 con-

forsehung, Strassburg, 1901, with a rejoinder by Wundt, Sprachgeschichte and Sprach-
psychologie, Leipzig, 1901 ; L. Siitterlin, Das Wesen der Sprachgebilde, Heidelberg, 1902 ;
von Kozwadowski, Wortbildung und Wortbedeutung, Heidelberg, 1904; 0. Dittrich,
Grundzuge der Sprachpsychologie, Halle, 1904 ; Ch. A. Sechehaye, Programme et methodes
de la linguistique thtorique, Paris, 1908.

1 In three parts : (i) Sprache und Psychologie, (ii) Zur Sprachwissenschaft, both
Stuttgart 1901, (iii) Zur Grammatik und Logik (with index to all three volumes), Stutt-
gart and Berlin, 1902.

- 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.

518 Evolution and Language

tains 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 Secret or <f>vcrei, 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 says1, "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 <f>v<rei. 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 sup-
porters 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 Miiller who, how-
ever, when questioned, repudiated it as his own belief2. It was taken
by him fi-om Heyse's lectures on language which were published
posthumously by Steinthal. Put shortly the theory is that "every-
thing which is struck, rings. Each substance has its peculiar ring.
We can tell the more and less perfect structure of metals by their

1 Volkerpsycholoyie, i. 2, p. 585.

2 Science of Thought, London, 1887, p. 211.

Theories of the Origin of Language 519

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 work1."
Max Miiller'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 forgotten2."

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

1 Max Mtiller as above, translating from Heyse. 2 Science of Thought, p. 212.

520 Evolution and Language

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 Miiller, not without energetic protest
from their supporters, the bow-wow and pooh-pooh theories of lan-
guage. 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 inter] ectional 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 Miiller, 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 under-
stand 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 Noird
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 reason1." As illustrations of such common effort he cites

1 Noire, Der Ursprung der Sprache, p. 331, Maiuz, 1877.

Darwin's views on Language 521

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 Miiller 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 connexion 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 also1." In so far
as this theory recognises language as a social institution it is un-
doubtedly correct. Darwin some years before Noir£ 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 intercommuni-
cation, 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 degree2."

Darwin's own views on language which are set forth most fully in
The Descent of Man3 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 Miiller's denial of
thought without words, "what a strange definition must here be given
to the word thought 4 ! " 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 gestures5.... 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 6." On man's own instinctive cries, he has
more to say in The Expression of the Emotions7. 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 singing8.

1 op. cit. p. 339. - The Expression of the Emotions, p. 84 (Popular Edition, 1904).
3 p. 131 ff. (Popular Edition, 1906). < op. cit. p. 135, footnote 63.

5 op. cit. p. 132. 6 op. cit. p. 133.

7 p. 93 (Popular Edition, 1904) and elsewhere.

8 Progress in Language, p. 361, London, 1894.

522 Evolution and Language

For many years and in many books Max Miiller argued against
Darwin's views on evolution on the one ground that thought is im-
possible without speech ; consequently as speech is confined to the
human race, there is a gulf which cannot be bridged between man
and all other creatures1. On the title-page of his Science of Thought
he put the two sentences No Reason imthout Language: No
Language ivithout 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'2,'' 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,

1 Some interesting comments on the theory will be found in a lecture on Thought and
Language in Samuel Butler's Essays on Lift, Art and Sciencf, London, 1908.
a Macnamara, Human Speech, p. 197, London, 1908.

Language and Thought 523

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 Griinbaum have still more precisely defined the rela-
tions between brain areas and certain groups of muscles. One form of
aphasia is the result of injury to or disease in the third frontal convolu-
tion 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 developed1. 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
speech2."

While Max Miiller's theory is Shelley's

" He gave man speech, and speech created thought,
Which is the measure of the universe3,"

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 than 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

1 op. cit. p. 226. 2 op. cit. p. 223.

3 Prometheus Unbound, n. 4.

524 Evolution and 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 etymo-
logically 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 tobacco, French (abac, 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 plant1 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

1 According to William Barclay, Nepenthes, or the Virtue of Tobacco, Edinburgh, 1C14,
"the countrey which God hath honoured and blessed with this happie and holy herbe
doth call it in their native language Petum."

The growth of Language 525

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 satl, " 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-appef), while dialectically in German a form Grumbire appears,
which is a corruption of Grwnd-birne, ' ground pear1." 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 dlnde was abbreviated to
(KInde 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 gatto

1 Kluge, Etymologisches Worterbuch der deutschen Sprache (Strassburg), s.v. Kartoffel.

526 Evolution and Language

d' India still 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 classifica-
tion of languages the same features as in the evolution and classifica-
tion 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 de-
velopment 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 both1." 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." Un-
fortunately Schleicher's views went a good deal farther than is

1 Haeckel, The Evolution of Man, p. 485, London, 1905. This represents Schleicher's
own words: Was die Naturforscher als Gattung bezeichnen warden, heisst bei den
Glottikern Sprachstamm, auch Sprachsippe; niiher verwandte Gattungen bezeichnen sie
wohl auch als Spraehfamilien 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 Varietateu und Spielarten entsprechen die
Untermundarten oder Nebenmundarten und endlich den einzelnen Individueu die
Sprechweise der einzelnen die Sprachen redendeu Menschen. Die Darwinsche Theorie
und die Sprachwissenschaft, Weimar, 1863, p. 12 f. Darwin makes a more cautious
statement about the classification of languages in The Origin of Species, p. 578 (Popular
Edition, 1900).

The Darwinians aiul Language 527

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, de-
veloped 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 sciences1." In accordance with this view he declared2
that the root in language might be compared with the simple cell in
physiology, the linguistic simple cell or root being as yet not diffe-
rentiated 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 Leskien3, and by Leskien's colleagues and friends, Brugmanu
and Osthoff. This was the principle that phonetic laws have no ex-
ceptions. 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 repre-
sentation 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

1 Die Darwinsche Tlicorie, p. 6 f. 2 op. cit. p. 23.

3 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.

528 Evolution and Language

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
belong1."

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 com-
munity it is of the nature of an institution2. 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 feminine3. 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, corrected and modified
by his disciples, had upon the science. In spite of the difference
which the psychological element represented by analogy makes be-
tween 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 evolu-
tion 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.

1 P. Giles, Short Manual of Comparative Philology, 2nd edit., p. 57, London, 1901.

2 This view of language is worked out at some length by Prof. W. D. Whitney in an
article in the Contemporary Review for 1875, p. 713 ff. This article forms part of a con-
troversy with Max Miiller, which is partly concerned with Darwin's views on language.
He criticises Schleicher's views severely in his Oriental and Linguistic Studies, p. 298 ff. ,
New York, 1873. In this volume will be found criticisms of various other views mentioned
in this essay.

3 Bluntschli, Theory of the State, p. 24, Second English Edition, Oxford, 1892.

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 concep-
tion 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

D. 34

530 Darwinism and History

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 cen-
turies 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 Au/ktiirung, 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 tra-
ditions of pragmatical historiography had by no means disappeared.

The Genetic conception of History 531

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 con-
dition 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
Aufklcirung, 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 nation 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 investiga-
tion 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.

34—2

532 Darwinism and History

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 (1/50), 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 concep-
tion which Turgot's friend Condorcet elaborated in the famous work,
published in 1795, Esquisse d'un tableau historique des progres de
I'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 Democratic en Amtfrique, where the theory is main-
tained 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")1, that social evolution is
a progressive change from militarism to industrialism.

1 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

Condorcet; Hegel; Comte 533

•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 induc-
tion— 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 philosophic 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 con-
dition 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.

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.

534 Darwinism and History

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 Civilization 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 I'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. Tn 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

History related to other Sciences 535

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 history1.
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 develop-
ment

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

1 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, &c. — 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.)

536 Darwinism and History

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. Philo-
sophically 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 investiga-
tions 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 develop-
ment of civilisation in terms of "adaptation to environment," "struggle
for existence," "natural selection," "survival of the fittest," etc.1

1 Recently 0. Seeck has applied these principles to the decline of Graeco-Boman
civilisation in his Untergang der antiken Welt, 2 vols., Berlin, 1895, 1901.

Darwinian principles applied to History 537

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 mani-
festations 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. Hitter'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 signifi-
cant 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 character1.

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

1 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.

538 Darwinism and History

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 assimi-
lated 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 con-
sequences. 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 elimi-
nation 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 individuals1, 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 six-
teenth century, introduced into France the fashion of imitating Italian

1 We can ignore here the metaphysical question of freewill arid determinism. For the
character of the individual's brain depends in any case on ante-natal accidents and coin-
cidences, and so it may be said that the role of individuals ultimately depends on chance,—
the accidental coincidence of independent sequences.

Sociological theories of History 539

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 years1." 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 Cidtwgeschichte which have come to the front in modern times
that generalisation is most fruitful, but even in these it may be con-
tended 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 develop-
ment. 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.

1 I have taken this example from G. Tarde's La logique sociale- (p. 403), Paris, 1904,
where it is used for quite a different purpose.

540 Darwinism and 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 (Geistesivissenschaften)
the same place (that of a Grmidwissenschaft} 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 (seeliseher Gesamtzustand)" controlling the period, "a
diapason which penetrates all psychical phenomena and thereby all
historical events of the time1." 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 in-
creasing 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 events2."
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.

1 Die kultnrlii.ttorinche Methode, Berlin, I'JOO. p. 26. - Ibid. pp. 28, 29.

Lamprecht's Method 541

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 indi-
vidual 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 con-
trolled. 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 environ-
ment (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

542 Darwinism and History

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 ; com-
paratively 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 historio-
graphy cannot permanently evade the questions raised by these
theories. One may venture to say that no historical change or trans-
formation 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.RS.

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 homo-
logous conceptions are applicable in the consideration of the trans-
mutations 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
Avhat 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

544 The Genesis of Double Stars

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 orbit1.

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. 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 deter-
minate.

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

1 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.

Classification of modes of motion in "families" 545

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 simpli-
city I will suppose that only two types are possible, so that there will

Fig. 1.
A "family" of elliptic orbits with constant rotational momentum.

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
D. 35

546 The Genesis of Double Stars

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 short-
hand this second family may be described as A + b,. . . A,. . . A — b.

In each family there is one single member which is indistinguish-
able 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 types1."

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

1 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.

Illustrations of exchanges of stability 547

homologous considerations in other fields of thought *, 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 circum-
stances, 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 govern-
ment. 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 6. 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.

1 I considered this subject in my Presidential address to the British Association in
1905, Eeport of the 15th Meeting of the British Assoc. (S. Africa, 1905), London, 1906, p. 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.

35—2

548 The Genesis of Double Stars

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 universe1.

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 approach-
ing 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

1 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 p. 213.

The shape of a mass of rotating liquid 549

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 con-
clusions 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 rota-
tion 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.

550 The Genesis of Double Stars

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 ; farther let the liquid always remain at
any instant incompressible and homogeneous. All that we are con-
cerned 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 homogeneity1.

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 com-
posed 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 flatten-
ing 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 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 corre-
sponds 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.

1 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 planetary figure becomes unstable

551

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 increases1,
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

Fig. 2.
Planetary spheroid just becoming unstable.

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 de-
clines. 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.

1 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.

552

The Genesis of Double Stars

At length when the longest axis of the three has become about
three times as long as the shortest1, 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 Fig. 3 ; 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 Poincar^ 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

B

Axis

o

A

: o c

Fig. 3.
The " pear-shaped figure " and the Jacobian figure from which it is derived.

snout forms a sort of stalk, and between the stalk and the axis of
rotation the surface is somewhat flattened These are the character-
istics of a pear, and the figure has therefore been called the " pear-
shaped figure of equilibrium." The firm line in Fig. 3 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 difibrences. 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 stable2,

1 The three axes of the ellipsoid are then proportional to 1000, 432, 343.

2 M. Liapounoff contends that for constant density the new series of figures, which
M. Poincar6 discovered, has less rotational momentum than that of the figure of bifurca-
tion. If he is correct, the figure of bifurcation is a limit of stable figures, and none can

The pear-shaped figure 553

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.

Fig. 4.
Section of a rotating cylinder of liquid.

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 con-
sequence 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 Fig. 4, but

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.

554 The Genesis of Double Stars

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 undeter-
mined 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 /3 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
waned1, and devoted himself to observing it on every fine night from
the 28th December 1782 to the 12th May 1783. He communicated

1 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), p. 203.

Variable Stars 555

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 fi Lyrae and of B 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 Society1.

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 brightness2 ; the curve which represents the
variation in the light is shown in Fig. 7 below.

The spectroscope has enabled astronomers to prove that many
stars, although apparently single, really consist of two stars circling
around one another3; they are known as spectroscopic binaries.
Campbell of the Lick Observatory believes that about one star in six
is a binary4; 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 com-
ponents must move very close to one another.

1 Diet, of National Biography; article Goodricke (John). The article is by Miss Agnes
Clerke. It is strange that she did not then seem to he aware that he was a deaf-mute,
but she notes the fact in her Problems of Astrophysics, p. 337, London, 1903.

2 Clerke, Problems of Astrophysics, p. 302 and ch. xvm.

3 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.

4 Aatrophysical Journ. Vol. xin. p. 89, 1901. See also A. Koberts, Nature, Sept. 12,
1901, p. 468.

556 The Genesis of Double Stars

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 the 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 evolution1." 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 " magni-
tude." 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 2J times as much light is of the fifth magnitude, and
successive multiplications or divisions by 2i define the lower or higher
magnitudes. Negative magnitudes have clearly to be contemplated ;
thus Sirius is of magnitude — 1*4, and the sun is of magnitude — 26.

The definition of magnitude is also extended to fractions ; for
example, the lights given by two candles which are placed at 100 ft.
and 100 ft. 6 in. 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 bright-
ness 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

1 Proc. Roy. Soc. Edinburgh, xxiv. Pt. n. (1902), p. 73.

The light-curve of a variable star

557

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.
Examples of light curves will be found in Figs. 5 and 7 below.

Jan. 1, 1900

Scale of hours

J 1 234 6 6 7 8 9 1O 11 12 IS 14 15 10

>g =

733

' t

7 33

30

.-"-• .-*•-*

•36

39

•59

43

•45

: / \ / \

•42
•45

<D

"3

a

•46
51

1 S \ / \

•48
•51

• — «

i . i "

1

•54
•67

/ \ / \

•54

•67

S

•60

/ \ ^

•eo

"o

1

X

•33
66
•69
•72

/ \ F '»

: / \ / \
\ / \ / \

•€3

•ee

•69
•72

75

\ / \/ V ••

•75

78

•78

•81

*•-• x*.^'

•81

784

i i i i i i i i i i i ,.,, i

7 Rj

Fig. 5.
Light curve of RR Centauri.

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 essay1. This star has a mean magnitude of about 7%, and it is
therefore invisible to the naked eye. Its period of variability is
14h 32m 10B76, 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

1 See Monthly Notices R.A.S. Vol. 63, 1903, p. 527.

558 The Genesis of Double Stars

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 inter-
pret 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

Fig. G.
The shape of the star BB Centauri.

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 now reproduced as Fig. 6. The dotted curve

Determination of the shape of a double star 559

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 gravita-
tion 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 confirma-
tion 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 ld 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 Centauri1. 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
p. 177 of Vol. xxvin. 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 ld'454 (i.e. ld 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

1 Astrophysical Journ. Vol. xni. (1901), p. 177.

560

The Genesis of Double Stars

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 ft Lyrae which was observed by Goodricke,

Argelanc/er's Curve
Computed Cur re.

Fig- 7.
The light-curve and system of /3 Lyrae.

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. 71.

1 Astrophysical Journ. Vol. vii. (1898), p. 1.

The density of double-star systems 561

The period of fi Lyrae is relatively long', being 12'1 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 fi-om 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 liquid1.

Although, as already explained, a good deal is known about the
shapes and the stability of figures consisting of homogeneous incom-
pressible 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 more-
over proved more recently that such a figure of homogeneous liquid
is unstable. Notwithstanding this instability it does not necessarily

1 See J. H. Jeans, " On the density of Algol variables," Astrophysical Journ. Vol. xxn.
(1905), p. 97.

D. 36

562 The Genesis of Double Stars

follow that the analogous figure for compressible fluid is also un-
stable, as will be pointed out more fully hereafter.

Professor Jeans has discussed in a paper of great ability the
difficult problems oifered by the conditions of equilibrium and of
stability of a spherical nebula1. In a later paper2, 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 separa-
tion. ...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 pro-
ceeded 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

1 Phil. Trans. E.S. Vol. cxcix. A (1902), p. 1. See also A. Roberts, S. African Astoc.
Adv. Sci. Vol. i. (11)03), p. 6.

2 Astrophysical Journ. Vol. xxii. (1905), p. 97.

Sketch of the process of evolution 563

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 rotation1. 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.

1 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 sym-
metrical arrangement.

36—2

564 The Genesis of Double Stars

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 astrono-
mers ; 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 unalter-
able, has modified our view of the physical universe, even as Darwin's
scheme of the mode of evolution changed the trend of thought con-
cerning 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 — Tldvra pet.

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 dia-
metrically 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

566 The Evolution of Matter

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 denied1."

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 Mendele"efF developed Newland's hypothesis in a form
that attracted at once general attention. Placing the elements in

1 Report of the IWi Meeting of the British Association (Presidential Address, Cambridge
1904), p. 9, London, 1905.

The Theory of Electrons 567

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 dis-
covered, 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 Mendele'eff'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 electro-
magnetic 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 inertia1. The movement of
electric charges would be affected by a magnetic field, and hence the

1 Larmor, Aether and Matter, Cambridge, 1900.

568 The Evolution of Matter

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 matter1. 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 elec-
tricity 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

1 Thomson, Conduction of Electricity through Gases (2nd edit.), Cambridge,
1906.

Radio-activity 569

are led therefore to regard the corpuscle from one aspect as a dis-
embodied 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 place1." 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

1 Larmor, loc. cit.

570 The Evolution of Matter

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 com-
pounds of a new and intensely radio-active substance which they
named radium.

Radium resembles barium in its chemical properties, and is pre-
cipitated 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 there-
fore 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 complex1. Three
types of rays \vere soon distinguished. The first, named by Rutherford
a -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 a-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 /3 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 /3-rays much more than a-rays, indicating that, although the

1 Rutherford, Radio-activity (2nd edit.), Cambridge, 1905.

Radio-activity 571

speed is greater, approaching in some cases within five per cent, that
of light, the mass is very much less. The /5-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 7 type of radiation was also detected.
More penetrating even than £-rays, the 7-rays have never been
deflected by any magnetic or electric force yet applied. Like
Rb'ntgen rays, it is probable that 7-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
measureably 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 pre-
viously 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 tem-
perature, 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

572 The Evolution of Matter

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, how-
ever, 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 accom-
panied 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 pro-

The Theory of Transmutation 573

gression, 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 in-
destructible 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
Rutherford1 and Soddy in 1903. By its light, all recent work on the
subject has been guided ; it has stood the supreme test of a hypo-
thesis, 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 a-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

1 Rutherford, Radio-activity (2nd edit.), Cambridge, 1905, p. 307.

574

The Evolution of Matter

emanation decayed. By isolating a very narrow pencil of a-rays, and
watching through a microscope their impact on a fluorescent screen,
Rutherford has lately counted the individual a-prqjectiles, and con-
firmed his original conclusion that their mass corresponded to that of
helium atoms and their charge to double that on a univalent atom1.
Still more recently, he has collected the a-particles shot through an
extremely thin wall of glass, and demonstrated by direct spectroscopic
evidence the presence of helium2.

But the most thorough investigation of a radio-active pedigree is
found in Rutherford's classical researches on the successive disinte-
gration products of radium. In order to follow the evidence on

100

80 100

Time in Day s

Fi». 1.

160

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
the falling curve of 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

1 Proc. Roy. Soc. A, p. 141, 1908.

2 Phil. Mag. Feb. 1909.

Decay of Radio-activity

575

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

ioor

80

o

•o*

t-»

^ 60

1*40

a

20

60 80 100

Time in Minutes

Fig. 2.

120 140

p Ray Curve of Radium
Short Exposure, i Min.

15 30 45 60 75

Time in Mimitfx.

Fig. 3.

90

105

120

576 The Evolution of Matter

curve. Thus the activity of a rod exposed to radium emanation for
1 minute decays in accordance with the curve of Fig. 2, which
represents the activity as measured by the a-rays. If the electro-
scope be screened from the a-rays, it is found that the activity of the
rod in /3- and 7-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 another1. 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 a-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 dis-
integration 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 them-
selves 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 & and 7
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 a-rays
only, one yS- and 7-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 re-
quired for a given quantity to be half transformed into its next
derivative.

1 Rutherford, Radio-activity (2nd edit.), Cambridge, 1905, p. 379.

Descendants of Uranium

577

Time of
half decay

Radio-activity

Properties

Radium

about

a rays

Element chemically analogous

1

2600 years

to barium.

Emanation

3 '8 days

a rays

Chemically inert gas ; con-

1

denses at - 150° C.

1
Radium-A

3 mins.

a rays

Behaves as a solid deposited

1

on surfaces ; concentrated

J

on a negative electrode.

Radium- B

21 mins.

no rays

Soluble in strong acids ; vola-

1

tile at a white heat; more

1

volatile than A or C.

Radium-C

28 mins.

a, ft y rays

Soluble in strong acids; less

1

volatile than B.

Radium-D

about

no rays

Soluble in strong acids ; vola-

I

40 years

tile below 1000 C.

Radium-E

6 days

ft y rays

Non-volatile at 1000 C.

Radium-F

143 days

a rays

Volatile at 1000 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 dis-
appears 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 im-
possible 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 a-rays. Uranium-X decays to half value in
22 days, giving out /3- and 7-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.

D. 37

578 The Evolution of Matter

With this idea in mind we see at once the significance of the con-
stitution 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
uranium1. In Bolt wood'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 genea-
logist. 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 ex-
periment 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
Mine Curie for the preparation of radium, Debierne discovered and

1 Strutt, I'roc. Roy. Soc. A, Feb. 1905; Boltwood, Phil. Mag. April, 1905.

Filial Products 579

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 3P9 seconds.
The emanation deposits two successive disintegration products ac-
tinium-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 10~9 gramme of radium in
193 days, agreeing with that indicated by theory within the limits
of experimental error1. 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 a-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 a-ray particles given out by succes-
sive radio-active changes.

In considering the nature of the residue left after the expulsion
of the five a-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 a-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 years2.

1 American Journal of Science, December, 1906.

2 American Journal of Science, October, 1905, and February, 1907.

37—2

580

The Evolution of Matter

We can now exhibit in tabular form the amazing pedigree of
radio-active change shown by this one family of elements. An im-
mediate 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
decay

Radio-
activity

Uranium

1
Uranium-X

238-5

22 days

a

ft y

Actinium

I
Actinium-X

1

10'2 days

no rays

a (ft y)

Actinium Emanation

?

3'9 seconds

a

Actinium-A

1
Actinium-B

,

35 '7 minutes
2'15 minutes

no rays
«, ft y

Radium

225

about 2600 years

a

Radium Emanation

1

3-8 days

a

Radium-A

1
Radium-B

?

3 minutes
21 minutes

a

no rays

Radium-C

I
Radium-D

I
Radium-E

I
Radium-F

'

28 minutes
about 40 years
6 days
143 days

a, ft y
no rays

a

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

General Radio-activity 581

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. Thomson1. Thomson
regards the atom as composed of a number of mutually repelling
negative corpuscles or electrons held together by some central attrac-
tive 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 un-
stable, 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 spon-
taneous redistribution of the constituents, taking place with an
explosive violence, and accompanied by the ejection of a corpuscle
as a /3-ray, or of a large fragment of the atom as an a-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 disintegra-
tion. The detection of ray-less changes by Rutherford, when those

1 Phil. Mag. March, 1904.

582 The Evolution of Matter

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 occur-
rence 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 disintegra-
tion 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 disintegra-
tion ? 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, 94

Acquired characters, transmission of, 16,
22, 33, 90, 118, 139, 179, 180, 428, 429

Acraea johnstoni, 290

Adaptation, 19, 21, 26, 33-35, 45, 61-65,
99, 100, 272-275

Adloff, 133

Adlumia cirrhosa, 388

Agassiz, A., 369, 370

Agassiz, L., 171, 174

Alexander, 461

Allen, C. A., HO2

Alternation of generations, 106, 107, 217

Ameghino, 131, 132, 136

Ammon, 0., Works of, 470

Ammonites, Descent of, 197, 198

Amphidesmus analis, 286

Anaea divina, 53

Andrews, C. W., 1941

Angiosperms, evolution of, 205-212, 313-
316

Anglicus, Bartholomaeus, 487

Ankyroderma, 31

Anomma, 35

Antedon rosacea, 249

Antennularia antennina, 262, 263

Anthropops, 127

Ants, modifications of, 34-36, 39

Arber, E. A. N., 213, 214

— and J. Parkin, on the origin of Angio-
sperms, 221

Archaeopteryx, 196

Arctic regions, velocity of development of
life in, 257

Ardigo, 453, 454

Argelander, 556, 560

Argyll, Huxley and the Duke of, 488

Aristotle, 5, 487, 490

Arrhenius, 249

Asterias, Loeb on hybridisation of, 249

Autogamy, 415

Avena fatua, 78

Avenarius, 456

Bacon, on mutability of species, 5, 6
Baehr, von, on Cytology, 94
Baer, law of von, 175

Bain, 444

Baldwin, J. M., 41, 4283
Balfour, A. J., 490, 566
Ball, J., 3161

Barber, Mrs M. E., on Papilio nireus, 280
Barclay, W., 5241
Barratt, 461
Bary, de, 226

Bates, H. W., on Mimicry, 54, 58, 275,
276, 286, 287, 290

— Letters from Darwin to, 287, 288, 296

- 484
Bateson, A., 421

BATESON, W., on Heredity and Variation
in Modern lights, 85-101

- on discontinuous evolution, 23, 238

— on hybridisation, 242

Bateson, W. and R. P. Gregory, 41 11
Bathmism, 13
Beche, de la, 361, 362
Beck, P., 498, 501, 509, 510
Becquerel, H., 569

Beebe, C. W., on the plumage of birds, 280,
281

— on sexual selection, 297
Beguyer de Chancourtois, 566

Bell's (Sir Charles) Anatomy of Expression,

432

Belopolsky, 560
Belt, T., on Mimicry, 293
Beneden, E. van, 103s
Benson, M., 2192, 220
Bentham, G., on Darwin's species-theory,

307

— on geographical distribution, 298, 309
Bentham, Jeremy, 461

Bergson, H., 454, 498, 5052, 507*

Berkeley, 448

Berthelot, 480

Betham, Sir W., 514

Bickford, E., experiments on degeneration

by, 40

Bignonia capreolata, 390
Biophores, 36, 37
Birds, geological history of, 196
Blanford, W. T., 322, 377
Blaringhem, on wounding, 237, 244

584

Index

Blumenbach, 86

Bodin, 536

Boltwood, B. B., 578, 579

Bonald, on war, 471

Bonnet, 7

Bonney, T. G., 368

Bonnier, G., 2353

Bopp, F., on language, 515, 516

BOUGLE, C., on Darwinism and Sociology,

465-476
Bourdeau, 534
Bourget, P., 470
Boutroux, 454
Boveri, T., HO1, 103*
Brachiopods, history of, 198
Brassica, hybrids of, 99
Brassica Napus, 415
Broca, 131, 470, 522
Brock, on Kant, 61
Brown, Kobert, 404, 407
Brugmann and Osthoff, 5273
Brugmann, 527s
Brunetiere, 472
Bruno, on Evolution, 5
Buch, von, 13
Biicher, K., 5042
Buckland, 273, 361, 365
Buckle, 534, 536, 538
Buffon, 7-13, 17, 86, 319
Burchell, W. J., 270, 273, 274, 276, 283-

286

Burck, W., 422

Burdon-Sanderson, J., letter from, 4831
BURY, J. B., on Darwinism and History,

529-542

Butler, A. G., 282

Butler, Samuel, 9, 11, 862, 881, 90, 911, 99
Butschli, 0., 103
Butterflies, mimicry in, 50-63
— sexual characters in, 46-48

Gabanis, 449

Campbell, 555

Camels, geological history of, 193

Camerarius, B. J., 403

Candolle, A. de, 297, 298

Candolle, de, 469

Cannon and Davenport, experiments on

Daphniae by, 26C
Capsella bursapastoris, 421
Carneri, 461
Castnia linus, 58
Catasetum barbatum, 407
C. tridentatum, 406
Caterpillars, variation in, 28, 29

Celosia, variability of, 74

Cereals, variability in, 77-84

Cesnola, experiments on Mantis by, 50

Chaerocampa, colouring of, 52

Chambers, R., The Vestiges of Creation by,

13
Chromosomes and Chromomerea, 36,91-94,

103-110
Chun, 261, 256
Cieslar, experiments by, 243
Circumnutation, Darwin on, 397-399
Claus, 122

Cleistogamy, 412, 423
Clerke, Miss A., 5551-2
Clodd, E., 82
Cluer, 4141
Clytus arietis, 283
Coadaptation, 32-42
Codringtou, 506
Cohen and Peter, 256
Collingwood, 287
Colobopsis truncata, 34
Colour, E. B. Poulton on The Value in

the Struggle for life of, 271-297

— influence and temperature on changes
in, 258, 259

— in relation to Sexual Selection, 47-50
Colours, incidental, 271, 272

- warning, 281, 282
Comte, A., 448-450, 466, 533-535, 540
Condorcet, 463, 532, 533, 538
Cope, 131

Coral reefs, Darwin's work on, 367-370
Correlation of organisms, Darwin's idea

of the, 4

Correlation of parts, 67
Corydalis claviculata, 388
Cournot, 465
Couteur, Col. Le, 79, 82
Crookes, Sir William, 567
Criiger, on Orchids, 407
Cunningham and Marchand, on the brain,

523

Curie, M. and Mme, 570, 571, 578
Cuvier, 8, 9, 171, 185-188, 199, 466, 468
Cycadeoidea dacotensis, 207
Cycads, geological history of, 203-209
Cystidea, an ancient group, 199
Cytology and heredity, 91, 93, 94, 102-111
Cytolysis and fertilisation, 252, 253
Czapek, 394, 3961

Dalton's atomic theory, 565, 566
Dana, J. D., on marine faunas, 320
Danaida chrysippus, 57

Index

585

Danaida genittia, 57
I), plexippus, 57
Dante, 513
Dantec, Le, 472

Darwin, Charles, as an Anthropologist,
137-151

- on ants, 34, 35

- and the Beagle Voyage, 299, 345-356

- on the Biology of Flowers, 401-423

- as a Botanist, 307, 308, 315

- his influence on Botany, 306, 307

- and S. Butler, 881, 90

- at Cambridge, 343, 366

- on Cirripedia, 375, 457

- on climbing plants, 387-392

- on colour, 277, 278, 280, 281

- on coral reefs, 367-370

- on the Descent of Man, 112-136

- his work on Drosera, 390, 392

- at Edinburgh, 341, 343

- his influence on Animal Embryology,
171-184

- on Geographical Distribution, 299-303,
322, 323

— his work on Earthworms, 377-379

— evolutionist authors referred to in the
Origin by, 8

- and E. Forbes, 303, 304

- on the geological record, 187

- and Geology, 337-384

- his early love for geology, 340

- his connection with the Geological
Society of London, 359-364

- and Haeckel, 130, 131

- and Heoslow, 280, 343, 344, 351, 352

- and History, 529-542

— and Hooker, 1, 2

- and Huxley, 112, 113, 130

— on ice-action, 365

— on igneous rocks, 373

- on Lamarck, 22, 125, 224

- on Language, 121, 521, 522

- his Scientific Library, 349

- and the Linnean Society, 355

- and Lyell, 338, 358, 359, 379-384

- and Malthus, 16, 19, 88

- on Patrick Matthew, 16

- on mental evolution, 424-445

- on Mimicry, 286-290

— a "Monistic Philosopher," 15

— on the movements of plants, 385-400

— on Natural Selection, 17, 32, 42, 43,
120

— a "Naturalist for Naturalists," 85

— on Paley, 275

Darwin, Charles, his Pangenesis hypothesis,
102, 111

- on the permanence of continents, 300,
301

- his personality, 446

- his influence on Philosophy, 446-464

- predecessors of, 3-17

— his views on religion, etc., 114, 115,
462-464, 496

- his influence on religious thought,
477-493

— his influence on the study of religions,
494-511

— his methods of research, 375, 402, 403

- and Sedgwick, 343, 344

- on Sexual Selection, 277, 295

— the first germ of his species theory, 88,
350, 351, 366

— on H. Spencer, 305

— causes of his success, 9, 87

- on Variation, 66-73, 83, 235

- on the Vestiges of Creation, 13

- on volcanic islands, 371, 372

- and Wallace, 18, 436

— letter to Wallace from, 278

- letter to E. B. Wilson from, 279
Darwin, E., ou the colour of animals,

276-278

— Charles Darwin's reference to, 349

- on evolution, 7-13, 86

DAEWIN, F., on Darwin's work on the Move-
ments of Plants, 385-400

— on Darwin as a botanist, 306'2

— observations on Earthworms by, 378

- on Lamarckism, 10

— on Memory, 5072

- on Prichard's "Anticipations," 17

— 713, 8371, 349, 351, 353

DAKWIN, Sir G., on The Genesis of Double
Stars, 543-564

— on the earth's mass, 300
Darwin, H., 378

Darwin, W., 378

Darwinism, Sociology, Evolution and, 15

Davenport and Cannon, experiments on

Daphniae by, 266
David, T. E., his work on Funafuti, 369,

370

Death, cause of natural, 257
Debey, on Cretaceous plants, 313
Debierne, 578
Degeneration, 38-40, 89
Delage, experiments on parthenogenesis

by, 253
Delbrtick, 5161

37—5

586

Index

Democritus, 565
Deniker, 131
Descartes, 5

Descent, history of doctrine of, 3
Descent of Man, G. Schwalbe on The,
112-136

— Darwin on Sexual Selection in The, 277,
296

— rejection in Germany of The, 145
Desinatippus, 191

Desmoulins, A., on Geographical Distri-
bution, 320
Detto, 2271, 2422

Embryology, as a clue to Phylogeny, 173-
176

— the Origin of Species and, 143, 144
Empedocles, 4, 21, 141, 169

Engles, 474, 475

Environment, action of, 10, 11, 13, 125,
177, 240-246

— Klebs on the influence on plants of,
223-246

— Loeb on experimental study in relation
to, 247-270

Eohippus, 190, 191

Epicurus, a poet of Evolution, 5

Development, effect of environment on, Eristalis, 57

229-233

Dianthus caryophyllus, 409, 416
Diderot, 7, 447
Digitalis purpurca, 415
Dimorphism, seasonal, 23
Dismorphia astynome, 57
D. orise, 58
Distribution, H. Gadow on Geographical,

319-336

— Sir W. Thiselton-Dyer on, 298-318
Dittrick, 0., 5161

Ernst, 378

Ernst, A., on the Flora of Krakatau, 317,

318

Eschscholzia californica, 414-417
Espinas, 473

Eudendrium racemosum, 260
Evolution, in relation to Astronomy, 543-

564

- and creation, 485

- conception of, 4-6, 9, 139, 141, 447
— discontinuous, 23, 67

Dixey, F. A., on the scent of Butterflies, 296 - experimental, 6, 7

Dolichonyx oryzivorus, 297

Dorfmeister, 258

Down, Darwin at, 378, 379

Draba verna, 69

Dragomirov, 471

Driesch, experiments by, 254, 268

— 91*

Drosera, Darwin's work on, 390, 392

Dryopithecus, 127

- factors of, 10-13

— fossil plants as evidence of, 200

— and language, 512

- of matter, W. C. D. Whetham on, 565,
582

— mental, 445

- Lloyd Morgan on mental factors in,
424-445

— Darwinism and Social, 15

Dubois, E., on Pithecanthropus, 127, 131 — Saltatory, 22-25

Diihring, 459, 474

Duhamel, 223

Duncan, J. S., 272, 273

Duncan, P. B., 272, 273'

Duns Scotus, 448

Duret, C., 6

Durkheira, on division of labour, 475

Dutrochet, 386

— Herbert Spencer on, 451-453
- Uniformitarian, 379

— Philosophers and modern methods of
studying, 5

Expression of the Emotions, 432-436

Fabricius, J. C., on geographical distribu-
tion, 319

Farmer, J. B., 1062, HO2
Farrer, Lord, 378
Fearnsides, W. G., 340
Felton, S., on protective resemblance,
Ferri, 474

Echinoderms, ancestry of, 199

Ecology, 326, 336, 420, 4581

Eimer, 101

Ekstam, 302

Elephants, geological history of, 194, 195 Ferrier, his work on the brain, 523

PJlymnias phegea, 57 Fertilisation, experimental work on animal-,

E. undularis, 55, 57 248-255

Embleton, A. L., 1052 Fertilisation of Flowers, 401-424

Embryology, A. Sedgwick on the influence Fichte, 464

of Darwin on, 171-184 Field, Admiral A. W., 369

Index

587

Fischer, experiments on Butterflies by,

258, 259
Fitting, 392

Flemming, W., 103, 105:i, 1061
Flourens, 467

Flowering plants, ancestry of, 313-316
Flowers, K. Goebel on the Biology of, 401-

423

Flowers and Insects, 47, 60, 282, 405
Flowers, relation of external influences to

the production of, 232
Fol, H., 103
Forbes, E., 287, 303, 320

- and C. Darwin, 303, 304

Ford, S. 0. and A. C. Seward, on the
Araucarieae, 2121

Fossil Animals, W. B. Scott on their bear-
ing on evolution, 185-199

Fossil Plants, D. H. Scott on their bear-
ing on evolution, 200-222

Fouillee, 453, 454

Fraipont, on skulls from Spy, 128

FRAZEB, J. G., on Some Primitive Theories
of the Origin of Man, 152-170

- 498, 5091
Frmvirth, 4141
Fumaria qfficinalis, 388
Funafuti, coral atoll of, 369, 370
Fundulus, 267

F. heteroclitus, 255

GADOW, H., on Geographical Distribution
of Animals, 319-336

- 149

Gartner, K. F., 404, 422

Gallus bankiva, 96

Galton, F., 122, 140, 225, 236, 378, 469

Gamble, F. W. and F. W. Keeble, 260,

261

Gasca, La, 79
Geddes, P., 14, 171
Geddes, P. and A. W. Thomson, 473
Gegenbauer, 140, 149
Geikie, Sir A., 301
Geitonogamy, 415
Genetics, 89, 92
Geographical Distribution of Animals, 319-

336

- of Plants, 298-318

- influence of The Origin of Species on,
323, 324

— Wallace's contribution to, 328
Geography of former periods, reconstruction

of, 332-336
Geology, Darwin and, 337-384

Geranium spinosum, 274

Germ-plasm, continuity of, 91

• — Weismann on, 36-40

Germinal Selection, 27, 28, 36-40, 49

Gibbon, 530

Gilbert, 309

GILES, P., on Evolution and the Science of

Language, 512-528
Giuffrida-Ruggeri, 131, 133
Giotto, 538, 539
Gizycki, 461

Glossopteris Flora, 314, 315
Gmelin, 303

Godlewski, on hybridisation, 249, 250
GOEBEL, K., on The Biology of Floivers,

401-423

- his work on Morphology, 912, 233, 2352
Goethe and Evolution, 8, 12, 13, 449

— on the relation between Man and Mam-
mals, 148, 149

— 463

Goldfarb, 260
Gondwana Land, 334
Goodricke, J., 554, 555, 560
Gore, Dr, 479

Gorjanovic-Kramberger, 128
Gosse, P. H., 485

Grabau, A. W., on Fusus, 332
Grand'Eury, F. C., on fossil plants, 200,

221, 222

Grapta C. album, 53
Gravitation, effect on life-phenomena of,

261-263

Gray, Asa, 298, 303, 304
Gr^goire, V., 1052, 1071, HO2
Groom, T. T., on heliotropism, 265
Groos, 439, 440
Grunbaum, on the brain, 523
Guiguard, L., 1035, HO2
Gulick, 13, 41
Guppy, on plant-distribution, 301, 302,

314, 318
Guyau, 461
Gwynne-Vaughan, D. T., on Osmundaceae,

201
Oymnadenia conopsea, 406

Haberlandt, G., 26, 391, 396
Haddon, A. C., 5064

HAECKEL, E., on Charles Darwin as an
Anthropologist, 137-151

- on Colour, 278

- and Darwin, 61, 130, 135-151

- on the Descent of Man, 131, 135

— contributions to Evolution by, 326

588

Index

Haeckel, E., on Lamarck, 8, 122

- on Language, 526

- a leader in the Darwinian controversy,
130, 131

— on Lyell's influence on Darwin, 379

- 125, 351, 461
Hacker, 25

Hagedoorn, on hybridisation, 250

Hales, S., 223

Hansen, 471

Barker, A., 340, 3492

HARRISON, J. E., on The Influence of Dar-
winism on the Study of Religions, 494-511

Hartmann, von, 489

Harvey, 5

Haupt, P., on Language, 517

Haycraft, 473

Hays, W. M., 80, 82

Hegel, 449, 450, 459, 533, 535

Heliconius narcaea, 57

Heliotropism in animals, 265-267

Henslow, Kev. J. S. and Darwin, 2, 281,
286, 343, 348, 355

Hensen, Van, 378

Herbst, his experiments ou sea urchins, 255

Heracleitus, 475, 565

Herder, 5, 6, 16

Heredity and Cytology, 91, 102-111

- Haeckel on, 138, 139, 142

— and Variation, 85-101

— 462, 477

Hering, E., on Memory, 142

Herschel, J., 357, 375

Hertwig, E., 1082

Hertwig, 0., 103, 1042-3, 140, 256

Hertz, 567

Heteromorphosis, 263

Heterostylism, 409-413

Heuser, E., 1035

Hewitt, 5061

Heyse's theory of language, 519

Hinde, G. J., his work on Funafuti, 369

Hipparion, 191

Hippolyte cranchii, 261

Hirase, 210

History, Darwin and, 529-542

Hobbes, T., 448, 459

Hobhouse, 491

HOFFDINO, H., on The Influence of the Con-
ception of Evolution on Modern Philo-
sophy, 446-464

Hofmeister, W., 1021, 209, 223

Holmes, S. J., on Arthropods, 264, 265

Holothurians, calcareous bodies in skin of,
29-32

Homo hcidelbergeiuis, 1291
H. neandertalensis, 131
H. pampaeus, 136

H. primigenius, 128, 129, 131, 132, 135
Homunculus, 127

Hooker, Sir J. D., and Darwin, 18, 116, 277,
288

- on Distribution of Plants, 304, 307-
311

- on Ferns, 69, 70

- Letter to the Editor from, 1, 2
Horner, L., 361-363, 374

Horse, Geological history of the, 190-

192

Huber, 427

Hubert and Mauss, 4981, 5051, 5091
Hubrecht, A. B. W., 5481
Hiigel, F. von, 4812
Humboldt, A. von, 4, 324
Humboldt, W. von, 516
Hume, 448, 495, 496
Hutcheson, 460
Hutton, 342
Huxley, T. H., and Darwin, 113, 116,

468

- aud the Duke of Argyll, 488

— on Embryology, 174, 175, 176

— on Geographical Distribution, 321, 322,
327

- on Lamarck, 86, 87

- Letter to J. W. Judd from, 3802

— on Lyell, 338, 379, 380

- on Man, 112, 113, 130, 137, 145, 147,
149

— on The Origin of Species, 113, 497

— on Selection, 18, 88

- on Teleology, 2741

— on transmission of acquired characters,
139

- 12, 18, 97 471, 472, 482-487
Hybridisation, 242, 248-250, 416, 422
Hybrids, Sterility of, 97, 98
Hyracodon, 192

Iberis umbellata, 419

Ikeno, 210

Imperfection of the Geological Record, 187,

188

Ingenhousz, on plant physiology, 223
Inheritance of acquired characters, 89
Insects and Flowers, 47, 60, 282
Instinct, 120, 429-431
Instincts, experimental control of animal,

263-269
Ipomaea piirpurt'a, 414, 415

Index

589

Irish Elk, an example of co-adaptation, 32,
33, 35

Jacobian figures, 551, 552

Jacoby, Studies in Selection by, 470, 471

James, W., 434, 442, 456, 5111

Janczewski, 417

Jeans, J. H., 553, 554, 5611, 562, 563

Jennings, H. S., on Paramoecium, 398,

399

Jentsch, 473

Jespersen, Prof., Theory of, 5*21
Johannsen, on Species, 226
Jones, Sir William, on Language, 514-517
Jordan, 226
J0DD, J. W., on Darwin and Geology, 337-

384

Kallima, protective colouring of, 27, 52,
53

K. inachis, 52

Kainmerer's experiments on Salamanders,
22, 269

Kant, I., 5, 6, 21, 447, 457, 461, 464

Keane, on the Primates, 131

Keeble, F. W. and F. W. Gamble, on
Colour-change, 260, 261

Keith, on Anthropoid Apes, 131

Kellogg, V., on heliotropism, 266

Kepler, 447, 561

Kerguelen Island, 256

Kidd, 273

Kidston, B., on fossil plants, 201, 211

Killmann, on origin of human races, 135

King, Sir George, 378

Klaatsch, on Ancestry of Man, 133

Klaatsch and Hauser, 129

KLEBS, G., on The influence of Environ-
ment on the forms of plants, 223-246

Kniep, 235

Knies, 467

Knight, A. , experiments on plants by, 233

— on Geotropism, 395

Knight-Darwin law, 4211

Knuth, 420

Kolliker, his views on Evolution, 22, 140

Kolreuter, J. G., 403-405, 420

Kohl, 2272

Korschinsky, 24, 73, 245

Kowalevsky, on fossil horses, 191, 192

Krakatau, Ernst on the Flora of, 317, 318

Krause, E., 73, 11, 12

Kreft, Dr, 378

Kropotkin, 459, 473

Kupelwieser, on hybridisation, 249, 250

Lagopus hyperboreus, 302
Lamarck, his division of the Animal King-
dom, 148

— Darwin's opinion of, 125

- on Evolution, 8-12, 17, 21, 22, 179, 180,
224, 428, 429, 433, 434, 449, 450, 534

— on Man, 137, 138, 147, 149

- 86, 101, 449, 450, 484
Lamarckian principle, 21, 22, 32-34, 39-

42, 51, 64, 65
Lamb, C., 481
Lamettrie, 447
Lamprecht, 540, 541
Lanessan, J. L. de, II1, 473
Lang, 122
Lange, 434
Language, Darwin on, 121

— Evolution and the Science of, 512-528

— 433, 440

Lankester, Sir E. Ray, on degeneration, 468

- on educability, 427, 441

— on the germ-plasm theory, 140

- 378

Lapouge, Vacher de, 471

Larmor, J., 567, 569

Lartet, M. E., 441

Lassalle, 467

Lathyrus odoratus, 418

Lavelaye, de, 473

Lawrence, W., 86, 902

Lehmann, 498

Lehmann-Nitsche, 132, 136

Leibnitz, 5, 6, 458

Lepidium Draba, 309

Lepidoptera, variation in, 28, 46-48

Leskien, A., on language, 527

Lessing, 5, 463

Leucippus, 565

Levi, E., 5101

Lewes, G. H., 274

Lewin, Capt. , 157

Liapounoff, 5522

Liddon, H. P., 485

Light, effect on organisms of, 25U-261

Limenitis archippus, 57, 294

— arthemis, 294
Linnaeus, 7, 405
Livingstone, on plant-forms, 239
Llamas, geological history of, 193
Lockyer, Sir N., 567

Locy, W. A., 101

LOEB, J., on The Experimental Study of

the influence of Environment on Animals,

247-270
Loew, E., 421

590

Index

Longstaff, G. B., on the Scents of Butter-
flies, 296

Lorentz, 567

Lotsy, J. P., 1051, 2401, 2411

Love, A. E. W., 299, 300

Lovejoy, 861

Lubbock, 122

Lucas, K , 256

Lucretius, a poet of Evolution, 5

Lumholtz, C., 5041

Luteva macrophthalma, 284

Lycorea halia, 57

Lyell, Sir Charles, and Darwin, 18, 116,
358, 359, 380-384

— the influence of, 186, 338, 342, 346,
350, 351

- on geographical distribution, 320, 323

— on The Origin of Species, 324, 325, 350

— on the permanence of Ocean-basins,
300

— publication of the Principles by, 357,
358

— the uniformitarian teaching of, 86
Lythrum salicaria, 411

Macacus, ear of, 117, 118

MacDougal, on wounding, 244

Mach, E., 142, 456

Macromytis flexuosa, colour-change in, 260,

261

Magic and religion, 505, 505, 511
Mahoudeau, 131
Maillet, de, 7
Majewski, 5331, 5351
Malthus, his influence on Darwin, 13-15,

17, 19, 88

- 448, 471

Mammalia, history of, 189-193, 196
Man, Descent of, 123, 124, 127-136, 144-
151, 441, 466, 535

- J. G. Frazer on some primitive theories
of the origin of, 152-170

— mental and moral qualities of animals
and, 120-123, 150, 440-442

— pre-Darwinian views on the Descent of,
3

- religious views of primitive, 499-501,
504-506

— Tertiary flints worked by, 130

Man, G. Schwalbe on Darwin's Descent of,

112-136

Manouvrier, 131
Mantis religiosa, colour experiments on,

50, 52
Marett, R. R., 5091

Markwick, 560

Marshall, G. A. K., 283, 285

Marx, 474, 475, 541

Massart, 394

Masters, M., 237

Matonia pectinata, 312

Matthew, P., and Natural Selection, 15, 16,

342

Maupertnis, 7, 86, 96
Maurandia semperftorens, 387
Mauss and Herbert, 4981, 5051, 5091
Mauthner, 516
Maxwell, 256
Maxwell, Clerk, 566, 567
Mayer, R., 446
Mechanitis tysimnia, 57, 59
Meehan, T., 271
Meldola, R., Letters from Darwin to, 289,

290

Melinaea ethra, 57, 59
Mendel, 92, 93, 225, 247, 269, 437, 481
Mendel6eff, 566, 567
Merrifield, 258
Merz, J. T., 91

Mesembryanthemum truncatum, 273
Mesohippus, 190, 191
Mesopithecus, 127
Metschnikoff, 181
Mill, J. S., 444, 448, 450, 461
Mimicry, 54-62, 275-295

- H. W. Bates on, 286, 287, 290, 291

- F. Miiller on, 289-291
Mimulus hiteus, 415, 416, 418, 419
Miquel, F. W. A., 3134

Mobius, 2322
Mohl, H. von, 386, 412
Moltke, on war, 471
Monachanthus viridis, 407
Monkeys, fossil, 127
Montesquieu, 530
Montgomery, T. H., 1091
Monstrosities, 66, 68, 237, 238, 244
Monticelli, 143
Moore, J. E. S., 105-, 1062
MORGAN, C. LLOYD, on Mental Factors in
Evolution, 424-445

- on Organic Selection, 41
Morgan, T. H., 94, 262
Morse, E. S., on colour, 278
Morselli, 131

Mortillet, 130

Moseley, 4831

Mottier, M., HO2

Miiller, Fritz, Fiir Darwin by, 143, 1711

— on Mimicry, 284, 285, 289-291, 484

Index

591

Miiller, Fritz, 46, 59, 172, 296
Miiller, J., 137, 171

Miiller, Max, on language, 121, 518-523
Murray, A., on geographical distribution,

302, 325, 326
Murray, G., 5092
Mutability, 75, 76
Mutation, 13, 24, 67-75, 84, 179-181, 200,

201, 221, 222, 225, 242, 269, 270, 437,

447, 455

Myanthus barbatus, 409
Myers, G. W., on Eclipses, 560

Niigeli, 101, 141, 142, 218, 225
Nathorst, A. G., 215
Nathusius, 96, 97

Natural Selection, and adaptation, 272,
274

— Darwin's views on, 66, 87, 120, 140, 336

- Darwin and Wallace on, 4, 150, 436

- and design, 490, 491

— and educability, 445

- Fossil plants in relation to, 217-221

— and human development, 122, 536, 537

— and Mimicry, 291

— and Mutability, 77, 84

— 13-16, 19, 20, 32, 42-45, 49-65, 70,
85-91, 274, 275, 386, 447, 484

Naudin, 6

Neandertal skulls, 128

Nemec, 391

Neoclytus curvatus, 283 ,

Neodarwinistn, 140

Neumayr, M., 333

Newton, A., 871

Newton, I., 446, 447

Niebuhr, 531, 541

Nietzsche, 458, 470

Nilsson, on cereals, 80-83

Nitsche, 117, 118

Noire1, 519-521

Noll, 391"

Novicow, 472

Nuclear division, 102-111

Nussbaum, M., 1035, 1114

Nuttall, G. H. F., 129

Occam, 448

Odin, 469

Oecology, see Ecology

Oenothera biennis, 77, 244

O. gigas, 68

0. Lamarckiana, 24, 68, 76, 77, 221, 241

O. muricata, 77

0. nanella, 76

Oestergren, on Holothurians, 29-31

Oken, L., 7, 449

Oliver, F. W., on Palaeozoic Seeds, 210,

211, 2191

Ononis minutissima, 423
Ophyrs apifera, 408
Orchids, Darwin's work on the fertilisation

of, 405-408

Organic Selection, 41, 428, 429
Origin of Species, first draft of the, 376,

386

— geological chapter in the, 376, 377
Orthogenesis, 101

Ortmann, A. E., 332
Osborn, H. F., 41, 4283

— From the Greeks to Darwin by, 4-6,
11, 12, 16

Osthoff and Brugmann, 5273

Ostwald, W., 259

Ovibos moschatus, 51

Owen, Sir Kichard, 112, 171, 187

Oxford, Ashmolean Museum at, 272

Packard, A. S., 81, 122

Palaeoutological Eecord, D. H. Scott on

the, 200-222

- W. B. Scott on the, 185-199
Palaeopithecus, 127

Paley, 15, 272, 273, 275, 491, 492, 496
Palitzch, G., 5541
Palm, 386

Pangenesis, 71, 84, 102, 111
Panmixia, Weismann's principle of, 41, 42
Papilio dardanus, 55, 56, 292
P. meriones, 55
P. merope, 55, 292
P. nireus, 280

Paramoecium, Jennings on, 398
Parker, G. H., on Butterflies, 264
Parkin, J. and E. A. N. Arber, on the

origin of Angiosperms, 221
Parthenogenesis, artificial, 250-253
Paul, H. and Wundt, 5273
Pearson, K., 61

Peckham, Dr and Mrs, on the Attidae, 284
Penck, 130
Penzig, 237

Peripatus, distribution of, 335
Peridineae, 25, 26

Permanence of continents, 299, 300, 377
Perrier, E., 122, 16, 378
Perrhybris pyrrha, 57
Perthes, B. de, 121
Peter, on sea urchin's eggs, 256
Petunia violacea, 416

592

Index

Pfeffer, W., 22, 389-391, 394

Pfitzner, W., 103

Pflueger, 262

Phillips, 361, 362

Philosophy, influence of the conception of

evolution on modern, 446-464
Phryniscus nigricans, 281
Phylogeny, embryology as a clue to, 173-

176

— Palaeontological evidence on, 188, 189,
204-217

Physiology of plants, development of,

223

Piccard, on Geotropism, 395, 396
Pickering, spectroscopic observations by,

559

Piranga erythromelas, 297
Pisum sativum, 418
Pithecanthropus, 127-129, 131, 135
Pitheculites, 136
Planema epaea, 57
Plants, Darwin's work on the movements

of, 385-400

— geographical distribution of, 298-318

— Palaeontological record of fossil, 200-
222

Platanthera bifolia, 406
Plate, 271
Plato, 512, 513
Playfair, 342, 362
Pliopithecus, 127
Pocock, B. I., 284
Poincare", 543, 551, 552
Polarity, Vochting on, 234, 235
Polymorphic species, 69, 70

— variability in cereals, 77-84
Polypodium incanum, 390
Porthesia chrysorrhoea, 263, 266
Potoni6, R., 210

Pouchet, G., 51, 260

POULTON, E. B., on The Value of Colour
in the Struggle for Life, 271-297

- experiments on Butterflies by, 50, 261

- on J. C. Prichard, 16

— on Mimicry, 53, 54, 58, 59

- 242, 46, 55\ 651, 201, 261
Pratt, 299

Pratz, du, 158

Premutation, 76

Preuss, K. Th., 498, 505s

Prichard, J. C., 16, 17, 86, 902

Primula, heterostylism in, 409-411

P. acaulis, 410

P. elatior, 410

P. officinalis, 410, 411

Promeces viridis, 283

Pronuba yuccaseUa, 60

Protective resemblance, 50-53, 275-281

Protocetus, 195

Protohippus, 191

Psychology, 497-499

Pteridophytes, history of, 213-217

Pteridospermeae, 211-213, 220

Pucheran, 324

Pusey, 115

Quatrefages, A. de, 122, 16
Quetelet, statistical investigations by, 72,
225, 235, 534

Kabl, C., 1035

Radio-activity, 569-582

Eadiolarians, 25

Raimannia odorata, 244

Eamsay, Sir W. and Soddy, 573

Eanke, 531, 533, 536, 541

Eau, A., 142

Ray, J., 5

Reade, Mellard, 307, 377

Eecapitulation, the theory of, 174-176, 182

Seduction, 182, 183, 202, 203

Eegeneratiou, 961, 233, 234

Eeid, C., 3154

Eeinke, 200, 201

Eeligion, Darwin's attitude towards, 496

— Darwin's influence on the study of,

494-511

- and Magic, 504-511
Eeligious thought, Darwin's influence on,

477-493
Eenard, on Darwin's work on Tolcanic

islands, 371, 372
Eeproduction, effect of environment on,

230-232

Reptiles, history of, 196, 197
Eeversion, 68, 119

Ehinoceros, the history of the, 192, 193
Eidley, H. N., 1154
Eiley, C. V., 280
Eitchie, 469
Ritual, 503

Roberts, A., 556-560, 5621
Eobertson, T. B., 256, 258
Robinet, 7
Eolfe, R. A., 4071
Rolph, 461

Romanes, G. J., o1, 13, 25, 42, 150, 486
Rothert, 393, 394
Roux, 1041, 141, 142, 262
Rozwadowski, von, 516'

Index

593

Buskin, 482

Butherford, E., 570-576, 581

Butot, 130

Sachs, J., Ill4, 210, 223

St Hilaire, E. G. de, 8, 13, 16

Salamandra atra, 269

S. maculosa, 269

Saltatory Evolution, 22-25 (see also Muta-
tions)

Sanders, experiments on Vanessa by, 50

Saporta, on the Evolution of Angiosperms,
313, 316

Sargant, Ethel, on the Evolution of Angio-
sperms, 208s

Savigny, 531, 532

Scardafella inca, 280, 281

Scent, in relation to Sexual Selection, 296

Scharff, B. F., 302*

Schelling, 5, 6, 448, 449

Schlegel, 515

Schleicher, A., on language, 526-528

Schleiden and Schwann, Cell-theory of,
137

Schmarda, L. K., on geographical distri-
bution, 321

Schoetensack, on Homo heidelbergensis,
1291

Schreiner, K. E., HO2

Schubler, on cereals, 243

Schultze, 0., experiments on Frogs, 262

Schur, 560

Schutt, 25, 26

SCHWALBE, G., on The Descent of Man,
112-136

Sclater, P. L., on geographical distri-
bution, 321-324, 327

SCOTT, D. H., on The Palaeontological
Eecord (Plants), 200-222

— 1892

SCOTT, W. B., on The Palaeontological
Record (Animals), 185-199

Scrope, 357, 373

Scyllaea, 279

Sechehaye, C. A., 5161

SEDGWICK, A. , on The Influence of Darwin

on Animal Embryology, 171-184
Sedgwick, A., Darwin's Geological Expedi-
tion with, 343, 344
Seeck, 0., 5361

Seed-plants, origin of, 209-213
Segregation, 92, 93
Selection, artificial, 19, 20, 32, 35, 67, 118,

469-471
_ germinal, 27, 28, 36-40, 49

Selection, natural (see Natural Selection)

- organic, 41, 428, 429

- sexual, 43-49, 116, 117, 277, 292-297,
417

— social and natural, 470

— 18-65, 96, 125, 126
Selenka, 127
Semnopithecus, 127
Semon, B., 22, 142
Semper, 368
Senebier, 223
Senecio vulgaris, 421
Sergi, 131, 135

Seward, A. C., 1, 713, 312, 314, 317

- and S. O. Ford, 2121

— and J. Gowan, 2012

Sex, recent investigations on, 93, 94

Sharpe, D., 373

Sherrington, C. S., 523

Shirreff, P., 80, 82

Shrewsbury, Darwin's recollections of, 340,

341

Sibbern, 449
Sinapis alba, 415
Smerinthus ocellata, 29
S. populi, 29
S. tiliae, 29
Smith, A., 448
Smith, W., 185
Snyder, 256
Sociology, Darwinism and, 465-476

— History and, 535
Soddy, 573

Sollas, W. J., 128, 129, 369
Sorley, W. B., 461

Species, Darwin's early work on trans-
mutation of, 350-353

— geographical distribution and origin of,
322, 323

— immutability of, 323

— influence of environment on, 240-246

— Lamarck on, 244

— multiple origin of, 323, 324

— the nature of a, 226, 227

— polymorphic, 69, 70

— production by physico-chemical means
of, 270

— and varieties, 69, 94, 95

— de Vries's work on, 241, 242
Spencer, H., on evolution, 451-456

— on Lyell's Principles, 338

— on the nature of the living cell, 227

— on primitive man, 501

— on the theory of Selection, 32

— on Sociology, 468

594

Index

Spencer, H., on the transmission of ac-
quired characters, 139

— on Weismanu, 33, 140

— 3, 14, 305, 461, 467, 482, 497
Sphingidae, variation in, 28
Spinoza, 142, 453

Sports, 6'J, 73, 181

Sprengel, C. K., 4, 403-405, 409, 420

Stability, principle of, 543-554

Stahl, 397

Standfuss, 62, 258

Stars, evolution of double, 543-546

Stellaria media, 421

Stephen, L., 461

Sterility in hybrids, 97-99

Sterne, C., 71

Stockard, his experiments on fish embryos,

255
STBASBURGEB, E., on The Minute Structure

of Cells in relation to Heredity, 102-111
Strongylocentrotus franciscanus, 249
S. purpuratus, 249, 252, 254
Struggle for existence, 19, 20, 77, 78, 471-

473

Strutt, B. J., 578
Stuart, A., 369
Sturdee, F. C. D., 370
Siitterlin, L., 5161
Sully, 123
Sutton, A. W., 991
Sutton, W. S., 1091
Svalof, agricultural station of, 80-83
Swainson, W., 320, 324
Synapta, calcareous bodies in skin of,

29-32

S. lappa, 30
Syrphus, 57

Tarde, G., 476

Teleology and adaptation, 272-274
Tennant, F. K., 4801
Teratology, 66
Tetraprothomo, 132, 136
THISELTON-DYER, Sir WILLIAM, on Geo-
graphical distribution of Plants, 298-318

- on Burchell, 2741

— on protective resemblance, 2762

- 275

THOMSON, J. A., on Darwin's Predecessors,
3-17

- 140

- and P. Geddes, 473

Thomson, Sir J. J., 568, 571, 581, 582
Theology, Darwin and, 477
Tiedemann, F., 319

Tooke, Horne, 516

Totemism, 160-169

Treschow, 449

Treviranus, 8, 12, 13, 319, 320

Trifolium pratense quinquefolium, 244

Trigonias, 193

Trilobites, phylogeny of, 199

Tschermack, 242, 4182

Turgot, 532

Turner, Sir W., 140

Twins, artificial production of, 254, 255

Tylor, 467, 497, 498, 502

Tyndall, W., 482

Tyrrell, G., 4821

Uhlenhuth, on blood reactions, 129
Underbill, E., 5101

Use and disuse, 22, 32-34, 37-42, 89, 90,
118, 139

Vanessa, 48
V. antiope, 264
V. levana, 23, 24, 258
V. polychloros, 62
V. urticae, 50, 62
Van 't Hoff, 256
Varartus Salvator, 317
Variability, Darwin's attention directed to,
19

— W. Bateson on, 85-101

— and cultivation, 245, 246

— causes of, 74-77, 225, 448

— polymorphic, 77-84

Variation, continuous and discontinuous,
238, 239

— Darwin's views as an evolutionist, and
as a systematist, on, 457

— definite and indefinite, 224, 225

- environment and, 224, 235-237

— and heredity, 84-101, 242

— as seen in the life-history of an or-
ganism, 179-182

- minute, 21-25

- mutability and, 179-182

- in relation to species, 69, 94, 95

— H. de Vries on, 66-84
Varigny, H. de, 7, 16
Varro, on language, 513
Veronica chamaedrys, 243, 245
Verworn, 130

Vestiges of Creation, Darwin on The, 13
Vierkaudt, 506*
Vilmorin, L. de, 245
Virchow, his opposition to Darwin, 145,
146

Index

595

Virohow, on the transmission of acquired

characters, 139
Vochting, 233, 234
Vogt, C., 130
Voltaire, 530
Volvox, 267
VBIES, H. de, on Variation, 66-84

— the Mutation theory of, 24, 95, HO4,
1113, 141, 226, 241-245, 269, 270, 458,
5481

WAGGETT, Kev. P. N., on The Influence of
Darwin upon religious thought, 477-493

Wagner, 13, 141, 326, 327

Waldeyer, W., 1032

Wallace, A. E., on Malayan Butterflies,
292

— on Colour, 48, 49, 54, 62, 277

— and Darwin, 61, 18, 277, 278, 282, 292,
293, 301, 342, 436

— on the Descent of Man, 116

- on distribution, 305, 312, 327

— on Malthus, 14

— on Natural Selection, 4, 14, 150,
484

— on the permanence of continents, 300,
301

— on social reforms, 473, 474

— on Sexual Selection, 436, 437
Waller, A. D., 266

Walton, 487
Watson, H. C., 382
Watson, S., 514

Watt, J., and Natural Selection, 17
Watts, W. W., 340
Wedgwood, L., 378
Weir, J. J., 282

WEISMANN, A., on The Selection Theory,
18-65

— on Amphimixis, 1111

Weismann, A., his germ-plasm theory, 36-
40, 139, 140

— on ontogeny, 175

— and Prichard, 16

— and Spencer, 33

- on the transmission of acquired charac-
ters, 89-91

- 141, 258

Wells, W. C., and Natural Selection, 15,
342

Weston, S., on language, 514

WHETHAM, W. C. D., on The Evolution of
Matter, 565-582

Whewell, 360, 362

White, G., 4

Wichmann, 314

Wieland, G. B., on fossil Cycads, 206-208

Wiesner, on Darwin's work on plant move-
ments, 397

Williams, C. M., 461

Williamson, W. C., 210

Wilson, E. B., on cytology, 93, 94, HO2

— letter from Darwin to, 278, 279
Wolf, 531, 532

Wollaston's, T. V., Variation of Species,

871

Woltmann, 474
Woolner, 117
Wundt, on language, 453, 454, 498, 516-

518

Xylina vetusta, 62, 63
Yucca, fertilisation of, 60

Zeiller, R., on Fossil Plants, 200, 221, 222

Zeller, E., 51

Zimmermann, E. A. W., 319

Zittel, on palaeontological research, 185

Zoonomia, Erasmus Darwin's, 7, 349

CAMBRIDGE I PRINTED BY JOHN CLAY, M.A. AT THE UNIVERSITY PRESS.