f —

Ciltnmt af

mrUiicitb from

ESSAYS ON EVOLUTION

EDWARD BAGNALL POULTON, D.Sc, M.A.

Hon. LL.D. Princeton, F.R.S., V-P.L.S., F.Z.S., F.G.S., F.E.S.

HOPE PROFESSOR OF ZOOLOGY IN THE UNIVERSITY OF OXFORD
FELLOW OF JESUS COLLEGE, OXFORD
MEMBRE HONORAIRE DE LA SOCIETE ENTOMOLOGIOUE DE BELGIOUE
CORRESPONDING MEMBER OF THE ACADEMY OF SCIENCE, NEW YORK
AND THE SOCIETY OF NATURAL HISTORY, BOSTON

BY

OXFORD

AT THE CLARENDON PRESS

1908

HENRY FROWDE, M.A.

PUBLISHER TO THE UNIVERSITY OF OXFORD
LONDON, EDINBURGH
NEW YORK AND TORONTO

SCIENCE

QH
92

TO

RAPHAEL MELDOLA, F.R.S.

WHOSE EARLIER WRITINGS, UNDER THE INSPIRING
INFLUENCE OF CHARLES DARWIN AND
ALFRED RUSSEL WALLACE, WERE THE
FOUNDATION OF A FRIENDSHIP
AND A LIFE-WORK

PREFACE

The essays on evolution included in this book have
not been placed in the order of their original publication,
but are grouped according to the relationship of the
subjects with which they deal. The first is concerned
with the time in which evolution took place, and is a reply
to the late Lord Salisbury's contention that the age of the
habitable globe is not sufficient for the process as con-
ceived by Darwin and Wallace. The second attempts
to define the material which has been subject to organic
evolution — species. The third contrasts the Darwin-
Wallace with the Lamarck-Spencer theory of evolution.
Heredity, the arbiter between the two rival theories,
forms the subject of the fourth and fifth essays. The
sixth deals with a neglected episode in the history of
modern views on heredity and evolution, and shows how
they were born out of due time but afterwards died in
the mind of James Cowles Prichard, the great anthropo-
logist. The seventh, discussing Huxley's attitude
towards Natural Selection, maintains that above all it is
the experience of the student of living nature which
inspires confidence in the theory. The eighth and ninth
essays form the natural continuation of the argument of
the seventh, and show that the immense number of facts
grouped under Mimicry are consistent with an interpreta-
tion based on Natural Selection, and inconsistent with
other attempted explanations. The argument of the

vi

PREFACE

seventh, eighth, and ninth essays being concerned with
the value of the visible surface of animals in the struggle
for life, it was considered appropriate to include under
the tenth head, and to illustrate by many examples, a
comprehensive classification of the various uses which
external colouring and appearance may subserve.

It will, I think, be realized that, although the separate
essays were delivered as addresses or published on various
occasions and at very different dates, they are the expres-
sion of a continuous line of thought, and therefore fall
together as naturally as if they had been written at one
time, for the purposes of the present volume.

A certain amount of overlap is necessary in essays
dealing with closely related subjects. Any inconvenience
from this cause and the scattered use of examples, in-
evitable in an essay, will be removed by consulting the
Appendix and the analytical index, to the preparation of
which much time and labour have been devoted.

Wherever the progress of knowledge has led to modifi-
cation of statement or conclusion the necessary alterations
have been made. These are in the form of footnotes
whenever the importance and interest of the advance is
such as to call for prominence. In other cases I have not
hesitated to alter the text. Whether right or wrong, the
arguments and conclusions in this volume of essays
represent my views at the present moment.

It will be observed that the style of the third essay
differs from that of all the others. This is because it is
the revised shorthand record of an address, spoken not
read. The seventh (hitherto unpublished) and ninth
addresses were also spoken, but the corresponding essays
were written subsequently from the notes. They there-

PREFACE

vii

fore contain much that was omitted from want of time and
the interruption caused by the exhibition of numerous
illustrations. The last and longest essay has been written
for the present volume. Its title, The Place of Mimicry
in a Scheme of Defensive Coloration, formed the subject
of a lecture delivered seventeen years ago. I have now
attempted to discuss the same question, replacing the
standpoint of 1890 by that of 1907, and directing special
attention to the advance which has been made in the
interval between these two dates.

Mendelism and Mutation, which occupy so large a share
of public attention at the present moment, are not directly
discussed in any of the essays. The relation of these
interesting modern researches and speculations to older
theories of evolution is briefly considered in an intro-
ductory chapter, in which it is maintained that the
conclusions supported in the present volume are incon-
sistent with a theory of evolution by Mutation, inconsistent
with the views often expressed by Mendelians, but not
inconsistent with the discoveries of Mendel himself.

A full reference to the original source of publication will
be found in the introductory note to those essays which
have already appeared. I desire to thank the administra-
tive bodies of scientific societies and the proprietors of
journals for permission to reprint from the publications
under their control.

Much invaluable assistance has been rendered by kind
friends in the preparation of this volume or of the original
addresses. A large part of the first essay on the age of
the earth could never have been written without the help
of Professor Perry, F.R.S., who has now kindly contri-
buted a note (p. 15) on the bearing of the discovery of

viii PREFACE

Radium upon the argument founded on the life of the
sun. The hiatus in my argument caused by the want of
any reference to the evolution of land-plants has now
been to some extent filled by a brief summary of the main
conclusions, prepared forme by my kind friend Dr. D. H.
Scott, F.R.S. ; also by a quotation from an address by
Professor A. C. Seward, F.R.S. I well remember how
much I owed to the kind help of my friend Sir Ray
Lankester, F.R.S., in the difficult task of summing up
in a few words the chief conclusions as to the origin and
history of each of the main branches of the animal
kingdom. And essential parts of the second and fifth
essays are due to his published writings, or have sprung
from the memory of discussions with him.

In rewriting large parts of the fourth essay I owe a
great debt to Dr. J. W. Jenkinson for valuable sugges-
tions and criticism. Without the help of one who is
devoting his life to the subject, I should have shrunk
from the attempt to display in a few pages the main con-
clusions of the modern embryologist as to the potentiali-
ties latent in the germ, and their gradual emergence
into actuality during the developmental history of the
individual.

It is unnecessary to speak here individually of all the
numerous friends who have rendered the kindest assist-
ance in the preparation of this volume, and especially of
essays VII-X, dealing with Protective Resemblance and
Mimicry. All such help is fully acknowledged in the
pages of the work. I wish, however, especially to thank
my friends Dr. F. A. Dixey and Mr. Guy A. K. Marshall.
Not only do their researches contribute a most important
element to this volume, but I also owe them a deep debt

PREFACE

ix

of gratitude for continual advice and criticism, and for
most efficient assistance in correcting proofs and verifying
references.

I have attempted to express my indebtedness to Pro-
fessor Meldola, F.R.S., by dedicating this volume to him.
His writings were the original stimulus to which I owe
the work of my life, and during nearly a quarter of a
century devoted to that work I have relied probably even
more than I am myself aware upon his sympathy and
help. The great names of Darwin and Wallace are
associated with Meldola's in the dedication, thus express-
ing, although very insufficiently, my sense of an im-
measurable debt of gratitude. The life and immortal
work of Darwin are a heritage of inspiration to every
naturalist. To Alfred Russel Wallace I owe not only the
stimulus of epoch-making thoughts, but the incalculable
influence of long years of friendship and encouragement.

EDWARD B. POULTON.

Oxford,
J ] larch 31, 1908.

CONTENTS

PAGE

Introduction: Mutation, Mendelism, and Natural
Selection xiii

t A Naturalist's contribution to the Dis-
cussion upon the Age of the Earth
(Liverpool, 1896) 1

II. ' What is a Species?' (London, 1904) . . 46

III. Theories of Evolution (Boston, 1894) . . 95

IV. Theories of Heredity (Oxford, 1889) • • I2>°

V. The Bearing of the Study of Insects upon
the Question 'Are Acquired Charac-
ters Hereditary?' (London, 1905) . . 139

VI. A Remarkable anticipation of Modern

Views on Evolution (1897) . . . .173

VII. Thomas Henry Huxley and the Theory

of Natural Selection (Birmingham, 1905) . 193

VIII. Natural Selection the Cause of Mimetic
Resemblance and Common Warning
Colours (London, 1898) 220

IX. Mimicry and Natural Selection (Berlin, 1901) 271

X. The Place of Mimicry in a Scheme of

Defensive Coloration (Leeds, 1890) . . 293

Appendix : A Classification and Index of the
Examples of Mimicry quoted in the Text . 383

Analytical Index 395

ERRATA

p. 3, 1. 15. For ' Jenkins's' read 'Jenkin's'.

p. 199,1. 13. For 'road' read 'roads'.

p. 240, L 2. For ' Dismorphina ' read ' Dismorphia \

p. 272, 1. 4 from bottom. Place "Heliconine' between 'Danaine' and
1 Nymphaline '.

p. 274. Further consideration has led to the conclusion that Anosia
plexippus originally invaded North America from the tropics of the
Old World and not from tropical America. The argument on
p. 274 is not affected.

p. 277, lines 8, 9 from bottom. For 1 and Heliconinae ' read ' (Danaoid
Hcliconidae) \

p. 288. lines 18, 19. For ' thyodamtts' read ' thyodamas \

INTRODUCTION

MUTATION, MENDELISM, AND NATURAL
SELECTION

The essays in this volume do not deal with the
questions of Mutation and Mendelism which are so much
discussed at the present time. It did not come in my way
to examine them carefully until quite recently. When,
however, I did look into the English publications on these
subjects and the earlier work of Bateson on Variation, I
was almost startled at the narrowness and prejudice which
were continually apparent. Bateson's writings appear to
me to have introduced a new and most regrettable
element into scientific controversy. I cannot therefore
let this book go to press without the following pages.
The writings to which I have alluded are injurious to
Biological Science, and a hindrance in the attempt
to solve the problem of Evolution, for the following
reasons : —

1. The amount of dogmatism concerning work with

which the writer is evidently imperfectly ac-
quainted.

2. The assumptions made by Mutationists on the

slenderest evidence.

3. The appropriation under the name of Mendel of

results which the present generation owes to
Weismann.

4. The exaggerated estimate of the importance for

MUTATION, MENDELISM, ETC.

Evolution of, first, Bateson's work on Variation,
secondly Mendel's interesting discovery.

5. The contemptuous depreciation of other lines of

investigation directly inspired by the work and
teaching of Darwin and Wallace.

6. The natural consequence of this last : — a wide-

spread belief among the ill-informed that the
teachings of the founders of modern biology are
abandoned.

1 should wish to add that, although solely responsible
for the contents of this Introductory chapter, I did not
venture to publish it without consulting a number of
the leading zoologists and botanists in this country.
Without a single exception my friends agreed with the
general line of argument, and felt with me that the protest
was called for.

1. Evolution, Continuous or Discontinuous.

Although the word 1 Mutation ' is so much in evidence
in the opening years of this century — as if it implied
some new and illuminating idea — the conception of the
origin of species by sudden steps is in reality very old.

The terms Continuous and Discontinuous are of course
merely relative, as Bateson has clearly expressed it :—
' In proportion as the transition from term to term is
minimal and imperceptible we may speak of the Series
as being Continuous, while in proportion as there appear
in it lacunae, filled by no transitional form, we may
describe it as Discontinuous! 1 Judged by this statement,
parts of the series of species in the Organic World are
discontinuous, parts continuous. It is the discontinuity

1 Materials for the Study of Variation, London, 1894, p. 15. Here-
after quoted as On Variation.

A TOO-ASSERTIVE CONTINUITY xv

which strikes Bateson 1 and those who follow him ; 2 but
it is the continuity which rather aggressively impresses
the great majority of those whose lives are devoted to the
study of species. The work of the systematist would
be immensely facilitated by that very discontinuity which
is always eluding him, but obtrudes itself upon Bateson.
The letters of Darwin quoted on pp. 59, 60 and 67 of
the present work are almost pathetic in their statement
of difficulties due to continuity in Cirrhipedes.

How are we to account for the discontinuous parts
of the series ? Is discontinuity a result of gradual
growth, or did it spring into existence ready made ?
Ever since the appearance of the Origin of Species, the
great majority of naturalists have believed the former ; the
latter is maintained by a small group of active workers
who, sometimes called ' Mutationists sometimes g Men-
delians would in this country be more correctly termed
' Batesonians '. It would be absurd to attempt to
account for the sharp discontinuity in the series of
mature individuals by supposing that each member of
it suddenly came into existence full grown. Similarly,
in attempting to account for the discontinuity of species
it is surely unreasonable to neglect all study of the birth
and growth of species which are going on all over the
world. Blinded by the assurance of the dogmatic state-
ment that the problem can only be attacked in one

1 ' We see all organized nature arranged in a discontinuous series of
groups differing from each other by differences which are Specific.'
1. c, p. 16.

Variation may teach us ' the origin of that Discontinuity of which
Species is the objective expression '. 1. c, p. 1 7.

2 ' The species riddle presents itself definitely as the problem of the
existence of a series of discontinuous groups of creatures, sharply marked
off the one from the other . . .' R. H. Lock, in Variation, Heredity and
Evolution, London, 1906, p. 11.

xvi MUTATION, MENDELISM, ETC.

way,1 Batesonians are heedless of all investigation into
the geographical distribution of species and the changes
on the borders of their range. The Zoological Museum
at Tring is pre-eminent for exact and thorough re-
searches of this kind, and the conclusions to which they
lead are well expressed by Rothschild and Jordan : —
' Geographical varieties . . . represent various steps in
the evolution of daughter-species.' And again, with
special reference to the believer in discontinuity : — ' Who-
ever studies the distinctions of geographical varieties
closely and extensively, will smile at the conception of
the origin of species per saltum! 2

Nor is there any reason to wonder at the confidence
felt by these naturalists. It is explained on pp. 50-4 of
this work how it is that the evolution which has occurred
in time is preserved in the distribution of certain species
in space. Bateson's observations lead him to certain con-
jectures as to what has happened in the past. The
student of geographical distribution is recording history ;
and it is in the geographical distribution of varieties
rather than in 1 V ariation ' that we do indeed see, and
that without the chance of failure, ' Evolution rolling
out before our eyes/ 3

1 'I am convinced that the investigation of heredity by experimental
methods offers the sole chance of progress with the fundamental problems
of evolution.' Bateson, in Report British Association, 1904, p. 579, It
must be the same restriction to a point of view which, with all its vast
importance, is limited, that led Bateson to maintain, on p. 575 of the
same Report, ' that the survey of terrestrial types by existing methods
is happily approaching completion.' These words will sound somewhat
ironical to any naturalist who has had to do with museums, and knows
something of the difficulty in getting material worked out. There are
unfortunately very few animal groups concerning which Bateson's
statement is correct.

2 Nov. Zoo!., 1903, vol. x, p. 492.

3 Bateson, On Variation, p. 17.

DISCONTINUITY AND COLOUR

xvii

2. The Subjective Element in Judging of Discontinuity.

The amount of discontinuity in a series of living forms
cannot be inferred with safety from superficial appear-
ances. Notwithstanding the statement of R. H. Lock,1
especial caution is necessary when the differences are
those of colour. Discontinuous colour impressions are of
course due to different rates of vibration in the different
parts of a continuous series. The discontinuity is in our-
selves, and not in the object. It is in everyway probable
that the chemical changes by which a pigment is trans-
formed are excessively minute, although the impression
produced on our senses is so great. A change in the
colours of a butterfly's wing would doubtless appear as an
important discontinuity, while a slight modification of
venation in the same wing might well appear as an
example of continuous evolution. And yet it is well
known that a very small change in venation more truly
represents specific difference than does the largest change
in colour.

3. De Vriess Evidence in Favour of Mutation.

Although the term Mutation might just as well have
been applied to evolution of any kind, even the slowest
and most imperceptible, it is employed to designate a
theory of modification by large and sudden steps.2 Unin-
structed statements — commonly encountered just now in
the press — inform the world that Natural Selection is
entirely dispensed with by modern writers on Mutation

1 ' Definite alterations in the colour of offspring as compared with their
parents seem almost necessarily to be of this nature ' : viz. discontinuous.
I.e., p. 124.

2 ' Species arise by mutation, by a sudden step in which either a single
character or a whole set of characters together become changed.'
Variation, Heredity and Evolution, R. H. Lock, London, 1906, p. 144.

POULTON K

xviii MUTATION, MENDELISM, ETC.

and Mendelism. This is of course an error : Mutation
without Selection may be left to those who desire to revive
Special Creation under another name. But the error is
a not unnatural outcome of the depreciatory and con-
temptuous tone adopted by the leader of Mendelism in
this country. Passing onwards from one to another,
contempt is easily translated into an open expression of
disbelief, and for a little day we hear on all sides that
the central thoughts of Darwin and Wallace were in vain.
But even while these random assertions are being made,
De Vries in Holland and Bateson in England are main-
taining that Natural Selection is necessary to the theories
of evolution they support — necessary indeed, but, as
Bateson teaches, so commonplace as to be unworthy of
investigation.1

Mutation was of course well known to Darwin. It
came before him in a rather extreme but unmistakable
form in that clever but discredited work, the Vestiges,
and what he thought of it is clearly expressed in the
Introduction to the Origin : — 1 The author of the
" Vestiges of Creation " would, I presume, say that, after

1 * To prove the reality of Selection as a factor in evolution is, as I
have said, a work of supererogation.' Report British Association, 1904,
p. 578.

' That the dread test of Natural Selection must be passed by every
aspirant to existence, however brief, is a truism which needs no special
proof. Those who find satisfaction in demonstrations of the obvious
may amply indulge themselves by starting various sorts of some annual,
say French poppy, in a garden, letting them run to seed, and noticing
in a few years how many of the finer sorts are represented.' 1. c, p. 577.

It is by no means obvious why, in any particular case, the finer sorts
are supplanted. If our object is to ascertain how living things have
become what they are (the problem as put by Bateson), a solution can
never be attained unless the details of the selective process are studied
at least as fully and thoroughly as the material which is subjected to
selection.

THE VESTIGES' REVIVED

xix

a certain unknown number of generations, some bird
had given birth to a woodpecker, and some plant to
the misseltoe, and that these had been produced perfect
as we now see them ; but this assumption seems to me
to be no explanation, for it leaves the case of the co-
adaptations of organic beings to each other and to their
physical conditions of life, untouched and unexplained.' 1
The modern mutationist also admits 2 that adaptation is
not explained by his hypothesis, but his way of dealing
with this deficiency is at one time to pour contempt upon
adaptation as a subject for investigation ; 3 at another to
assume that it is so difficult that the attempt is hardly
worth a trial.4

The only important evidence adduced in favour of
Mutation in Nature is to be found in the behaviour of
certain Oenotheras (Evening Primroses), first studied by
De Vries and subsequently by many other naturalists.5
Oenothera lamarckianct, supposed to be an American plant
introduced into Europe but unknown in the wild state in
America, is the form which De Vries found to be throwing
off species, as he believes them to be, in all directions.
The Dutch botanist also tested about a hundred native
species of varied genera, every one of which gave, as

1 Origin of Species, 1859, PP- 3> 4-

2 ' Nor have we any definite light on the problem of adaptation. . . .'
Bateson, 1. c, p. 587.

3 See p. xviii n. 1.

4 On Variation, W. Bateson, London, 1894, pp. 10-13.

5 The latest memoirs are (1) Mutations, Variations, and Relationships
of the Oenotheras by D. T. Macdougal, A. M. Vail and G. H. Shull,
Carnegie Institution of Washington, 1907. A full list of publications is
appended: pp. 91-2 ; (2) On the Variations of the Evening Primrose by
G. A. Boulenger, F.R.S., fournal of Botany, October, 1907. A good
general account will be found in R. H. Lock's Variation, Heredity and
Evolution, London, 1906, chapter v.

b 2

MUTATION, MENDELISM, ETC.

regards ' real mutability ', a negative result.1 The lethargy
of the Dutch plants, contrasted with the volcanic energy
of the American, appears to have wounded De Vries's
national pride so sharply that he felt bound to meet the
situation with a hypothesis which gave promise of equal
powers to his compatriots. He found comfort in the
startling speculation * that species are subject to com-
paratively short periods of mutability which recur at
relatively long intervals, and that all the species he
examined except the CEnothera were in this intermediate
stable period of their existence \2

It would be interesting and probably amusing to hear
the words with which a speculative edifice equally vast,
on a foundation equally insecure, if such were possible,
would be assailed by the leader of Mutation in England,
had it been erected in relation to continuous evolution.

The comparison between the other plants and the
Oenothera did not apparently lead De Vries to conjecture
that there might be something wrong with the latter,
even though the original wild plant was unknown. ' It
is unfortunate,' as R. H. Lock remarks, ' from the point
of view of de Vries' interpretation of this case that the
behaviour of O. Lamarckiana should suggest in some
respects, as Bateson has pointed out, the phenomena of
hybridization.' 3 The supposed fact 1 that the species
appears to exhibit the same phenomenon in other locali-
ties ' 4 is, however, brought forward by Lock in support
of De Vries's hypothesis. Well, the form O. lamarckiana

1 Hugo De Vries, Species and Varieties, London, 1905, p. 520.

2 R. H. Lock, 1. c, p. 140. Lock adds somewhat laconically, 'Direct
proof of this suggestion is naturally out of the question.' By a printer's
error the word ' stable ' in the above-quoted passage appears as ' staple '
in the original.

8 1. c, p. 278.
4 Ibid.

DE VRIES'S EVIDENCE

xxi

has been studied at La Garde St. Cast, on the coast
of Brittany, in 1899, 1904, and 1907 by G. A. Boulenger,
F.R.S., and also by Mr. Charles Bailey at St. Anne's-on-
the-Sea, North Lancashire, and neither of these naturalists
finds the same phenomenon exhibited, although the
latter observer appears to have discovered about two of
De Vries's 'species '. Boulengers conclusions are quoted
in full in the following paragraph : —

' To sum up, I would suggest the possibility of the
Mutations-theorie being based on false premisses.
De Vries has assumed, without any justification, that
Oenothera Lamarckiana is a natural species. The fact
that it was originally described from a garden flower,
grown in the Paris Jardin des Plantes, and that, in spite
of diligent search, it has not been discovered wild any-
where in America, favours the probability that it was
produced by crossing various forms of the polymorphic
CE. biennis, which had previously been introduced in
Europe. If it be so, and the onus probandi of the
contrary rests with the mutationists, we have no evidence
of mutations in the phenomenon observed by De Vries,
but simply one of those cases of Mendelian disjunction of
hybrids to which he was the first to call the attention
of the naturalists of the present generation. The
characters of several parent forms, which may, for all we
know, have originated through fluctuating variation, have
remained latent in some individuals of CE. Lamarckiana
and reappear in different combinations, thus producing
the appearance of distinct " species," each definable by
several characters, springing up under our eyes.' 1

In the recent work of Macdougal, Vail and Shull we
are told that ' fixed hybrids constituting species were
secured in combinations of O. lamarckiana and O. cru-
1 Journal of Botany, October, 1907.

xxii MUTATION, MENDELISM, ETC.

data V Such forms (it is, I submit, extremely unsafe to
speak of them as species) may, in the future, either
spontaneously or under some external stimulus break
up into their components, repeating the history which
Boulenger believes to have occurred in O. lamarckiana
itself.

As this chapter was passing through the press an
interesting letter on Specific Stability and Mutation, by
Sir W. T. Thiselton-Dyer, appeared in Nature} The
author, after describing a number of Mutations which
have occurred in cultivated plants, comes to the following
conclusion : — ' In all these cases I think we may safely
infer from the persistent specific stability at the com-
mencement of cultivation that the changes which sub-
sequently occur would not have occurred in nature. . . .
The evidence, on the other hand, that such changes
follow cultural conditions as a result is simply over-
whelming. . . .'

4. Mutation and the Facts of Mimicry \ &c.

The very same ideas of Discontinuity and Mutation, the
same revolt of the clay against the power of the potter,
arose again and again in the interval between the appear-
ance of the Origin and this modern revival. The formula
* before a thing can be selected it must be ' had been
repeated by Cope, Semper, Eimer, and many another
naturalist, long before it assumed the more picturesque
form given to it by Bateson : — ' The creature is beheld
to be very good after, not before its creation.' !

1 Carnegie Institution of Washington, 1907, I.e., p. 89.

2 Nov. 28, 1907, pp. 77-9.

s Report British Association, 1904, p. 578: also on p. 577: —
t Selection is a true phenomenon ; but its function is to select, not to
create.'

NATURAL SELECTION CREATIVE xxiii

Mutation is the importunate hypothesis, at length
admitted on account of its importunity.

Darwin's view, that Selection is the paramount power
in the production of species, is made very clear by his
metaphor of an architect constructing a beautiful building
out of the fragments of broken stone at the foot of a
precipice.1 For the purposes of the controversy of the
hour, a more appropriate metaphor is that of the artist.
Pictorial effects could no doubt be obtained from time
to time by the simple method of throwing colours at a
screen : occasionally, perhaps, such 1 Mutations ' would
be superior to anything which an artist could achieve by
adding here a little and there a little to the developing
picture. It would hardly be reasonable to infer from a
few such successes that the proper function of the artist
is merely to wait for the appropriate Mutation, and to
cease producing effects by the accumulation of minute
increments — in fact 1 to select not to create \ The
essential difficulty about the chance method is that it
could never yield representations of particular objects.
Now there is an important section of the organic world
where the metaphor passes into reality. I refer to the
countless thousands of cases in which there has been
evolved on the surface of an animal a picture of some
portion of its environment — the unending instances of
Protective Resemblance and the still more striking
examples of Mimicry.

It is as unlikely that a key could be made to fit a com-
plicated lock by a number of chance blows upon a blank
piece of metal, as that the elaborate pattern on the wings
of a butterfly should have been reproduced on those
of its mimic by Mutation.

It is necessary to state very prominently that the

1 Variation under Domestication, London, 1875, vol. ii, pp. 426-7.

xxiv MUTATION, MENDELISM, ETC.

question of a Mlillerian as against a Batesian interpretation
of the facts of Mimicry (so fully discussed in the present
volume) is of no importance to the present argument.
The metaphor in the preceding paragraph sufficiently
indicates why it is that the facts of Mimicry are them-
selves inconsistent with an evolution based on discon-
tinuous variation.

I should be the last to maintain that the followers
of any other subject are bound to go into the details
of Cryptic Resemblance and Mimicry, and I should have
been well pleased if Mendelian workers had confined
themselves to the interesting and indeed exciting lines
of inquiry started by Mendel. But they have by no
means been content with this. R. H. Lock, in his
recent work, Variation, Heredity and Evolution? refers
to Mimicry, &c, apparently without making himself in any
way acquainted with the work that has been done in these
subjects. His suggestion of alternative interpretations
had been made long ago, and met long ago, as may be
seen in the eighth essay in the present volume, originally
published in 1898. It is well known that in the Hope
Department of the Oxford University Museum a special
study of Mimicry has been made and special illustrative
sets of specimens brought together. I should have been
only too pleased to show the material to this author, or
to any other naturalist. It is not fair controversy, after
utterly neglecting what has been done, to profess to sum
up the evidence for Mimicry in these words : 1 Several
supposed examples of this phenomenon have been
described in the case of different genera of tropical
butterflies/ 2

1 London, 1906.

2 R. H. Lock, 1. c, p. 51. The following statement on the subject of
Protective Resemblance is also very misleading : — ' Examples of this

MUTATION AND MIMICRY xxv

If, instead of attempting to criticize without knowledge,
R. H. Lock were to make a careful study of the
subject, he would find much that bears upon his own
opinions and beliefs. The influence of the organism
itself upon the direction taken by Natural Selection can
be clearly proved in numbers of cases. For in Mimicry
the changes have often been so rapid, that we may
see the finished product and the stages of its preparation
living side by side, and we can safely conclude that the
type of the original non-mimetic pattern determined the
evolution of one mimetic likeness rather than any other.

In order to facilitate this study, I had intended to add
an eleventh essay, which might serve as a guide to the
most striking examples of Mimicry to be found in any
large collection of butterflies. But I found that anything
like an adequate introduction to the subject in butterflies
alone would require a book to itself. In the meantime,
until that volume appears, as it will, I hope, at no distant
date, the instances mentioned in the last three essays will,
if examined in any collection, give some conception of
the subject. A study of the examples described in the
various memoirs referred to will convey full information
of the state of existing knowledge, but such a task would
be an arduous one.

If believers in Mutation will do me the honour not
to accept my statements of mimetic resemblance, but will
merely use them as a guide to the species themselves,
I have no doubt that they will recognize some of the
difficulties in the way of an interpretation based on a
hypothesis of discontinuous evolution. Reversing the
order of discovery, the study should begin with the

kind in which the shape of an animal leads to its concealment are com-
paratively infrequent, although a considerable number might be collected 9
(1. c, pp. 50-1).

xxvi MUTATION, MENDELISM, ETC.

Ethiopian Region, and, proceeding through the Oriental
and Australian, reach its final culmination in the astonish-
ingly complex associations and the wonderful resem-
blances, perfect in the minutest details, of the Neotropical
Region.

Confidence in the theory of Gravitation is, I believe,
founded on indirect evidence. A continually widening
knowledge of the systems and movements of the Cosmos
remains ever consistent with the theory. The knowledge
itself will always be of the deepest interest, even if
Gravitation should ultimately be refuted or extended out
of recognition. So, to compare small things with great, is
it with the theory of Natural Selection and the evidence of
Mimicry. The great mimetic combinations of the various
degrees — grouped like planets and satellites round centres
of primary and secondary importance — sweep along the
path of Evolution, just as the gravitational systems drift
through space, without disturbing their internal relation-
ships. A rapidly-increasing knowledge of the mimetic
systems still remains consistent with Natural Selection,
and, whatever be the fate of this great theory, the facts
must always be interesting in a high degree. And as to
the ultimate fate of the theory we may use with far
greater confidence than in 1859 the words with which
Darwin sent the Origin of Species to Asa Gray : — ' I
cannot possibly believe that a false theory would explain
so many classes of facts as I think it certainly does
explain. On these grounds I drop my anchor, and
believe that the difficulties will slowly disappear.' 1

5. Mendelism and Natural Selection.

The relationship of Natural Selection to this recently-
known discovery will, I think, appear most clearly by the

1 Life and Letters of Charles Darwin^ London, 1887, vol. ii, p. 217.

DARWIN ON THE PRIMROSE xxvii

discussion of a single case. Its consideration will also
serve to show the wide divergence between the true
bearing of the discovery itself and the claims of Men-
delians.

' The thrum-eyed condition of the primrose has been
shown by Bateson and Gregory to be a Mendelian domi-
nant to the pin-eyed condition, so that we have here the
solution, so far as solution is possible, of a biological
problem to which Darwin devoted the greater part of a
volume.' 1

Let us inquire what Darwin did achieve in the pages
referred to ; for Lock only leads his readers to infer that
the great naturalist failed to find a solution.

1. In the first place, Darwin examined not only the
primrose, but all the heterostyled plants of which he
could obtain specimens, paying special attention to such
points as the diameter of the pollen-grains, the structure
of the stigma, &c. For he would by no means accept
differences in length of stamen and pistil alone as suffi-
cient evidence of the heterostyled condition.

2. After proving that the plants were truly hetero-
styled, he showed in all available species, by numbers of
laborious experiments, that one form of a heterostyled
plant is only fully fertilized by pollen from an individual
of the other form (or one of the other forms in the case
of trimorphic heterostyled plants).

3. He proved that when the stigma receives pollen
from a form the same as its own, together with pollen
from the other form, the latter is prepotent.

4. As regards some of the species, he proved, by
covering with a net, that the visits of insects are necessary

1 R. H. Lock, Variation^ Heredity and Evolution, London, 1906,
p. 201. Darwin's volume referred to is Different Forms of Flowers
(London, 1877).

xxviii MUTATION, MENDELISM, ETC.

for fertilization. As regards some he showed the pro-
portion in which the different forms exist in the wild
state in various localities.

5. He proved in many species that when a plant was
artificially fertilized by pollen from the same form, that
form immensely preponderated in the offspring.

6. Such a union as that last described, which he called
' illegitimate \ never yielded the full number of offspring.
From these facts he reached the following conclusion
given in his own words : 1 The results of crossing such
flowers in an illegitimate manner, I believe to be very
important, as bearing on the sterility of hybrids ; although
these results have been noticed by only a few persons/1

7. Incidentally he produced much evidence that the
primrose, cowslip, and Bardfield oxlip are true species,
and that the common oxlip is a hybrid between the cow-
slip and the primrose, the latter investigation involving
many crossing experiments.

8. Finally, he concluded with an extraordinarily inter-
esting and illuminating discussion on the distribution of
heterostyled species throughout the families of plants, on
the advantages of the heterostyled condition as compared
with other methods of securing cross-fertilization, and on
the steps by which plants may have become hetero-
styled.

This last part of Darwin's great memoir is a conspi-
cuous example of the reasoning so severely condemned
by W. Bateson in his work on Variation.2 I have now
summed up, far too briefly, the main results to the exposi-

1 Life and Letters of Charles Darwin, London, 1887, vol. i, p. 97.
Certain aspects of this question are discussed on pp. 90-4 of the present
volume.

2 Materials for the Study of Variation, London, 1894, pp. 10-13. See
also parts of the Preface to that book.

BATESON ON THE PRIMROSE xxix

tion of which ' Darwin devoted the greater part of
a volume' — in fact the whole volume up to p. 277, the
last page being 345. Of the great central discovery he
says in his Autobiography : 4 I do not think anything in
my scientific life has given me so much satisfaction as
making out the meaning of the structure of these
plants';1 and again, a few pages later: ' No little dis-
covery of mine ever gave me so much pleasure as the
making out the meaning of heterostyled flowers.' -

And now what have Bateson and Gregory done that
makes their work the only possible solution of the
problem upon which Darwin made all these fruitful
investigations ?

Mendel published his discovery in 1866, but it was
' entirely lost sight of until the same facts were inde-
pendently rediscovered in 1899 by de Vries working
in Holland, by Correns in Germany, and by Tschermak
in Austria '.3 Bateson and Gregory in England then
applied the rediscovery to the characters upon which
depend the heterostyled condition of the primrose. In
Lock's triumphant statement quoted on p. xxvii we are told
that in the result the thrum-eyed condition (stamens high
up, pistil short) was a Mendelian dominant to the pin-
eyed condition (stamens low down, pistil long).4 Accept-
ing this account, what does it amount to ? Beginning
with two parents, one thrum-eyed and one pin-eyed, the
next or second generation would have the appearance of
thrum-eyed. Breeding these together, a quarter of the

1 Life and Letters, vol. i, p. 91.

* Ibid., vol. i, p. 97.

a R. H. Lock, I.e., pp. 178-9.

4 This, however, is not Bateson's own account of his result ; for he
says : — ' It is doubtful if " thrum " ever breeds true, as both the other
types can do . . . .' The third type here referred to is the mid-styled or
intermediate condition. See Report British Association, 1904, p. 586 n.

xxx MUTATION, MENDELISM, ETC.

third generation would be pure thrum-eyed, and bred
together for any number of generations would yield no
other form ; another quarter would similarly be pure pin-
eyed, while the remaining half would have the appear-
ance of thrum-eyed, but when tested by breeding would
behave in the same manner as the second generation.
Pursuing this process to infinity, if it were possible to do
so,1 we should be confronted by two sets of individuals
equal in number, one thrum-eyed, the other pin-eyed. The
word ' dominant ', then, only means that the individuals
which in each generation contain both conditions, the indi-
viduals whose offspring will in the course of future genera-
tions divide themselves equally between the two camps
— that these have the superficial appearance of one
condition alone, and that the thrum-eyed. The pin-
eyed condition, equally present, as is proved by breeding,
but not superficially evident, is called 1 recessive \

' Dominant,' then, implies no permanent superiority, but
describes a superficial appearance which analysis proves
to be misleading.

It has been necessary to say all this, although often
said before, because it is important to explain as clearly
as possible what is the nature of the * solution ' at which,
accepting Locks account, Bateson and Gregory have
arrived. And it is desirable that this knowledge should
be available for those who have not studied the elements
of Mendelism as well as for those who have.

What does the 1 solution ' amount to ? Merely this,
— the knowledge that the two conditions 1 thrum-eye '
and ' pin-eye ', so far as they follow Mendelian laws, do

1 In this particular example there is little doubt that the experiment
would soon come to an end. Darwin's results, as stated in 6 on p. xxviii,
indicate that it would be impossible to produce many generations by
' illegitimate ' unions.

MENDEL'S DISCOVERY

xxxi

not combine in successive generations, but may be shown
by an appropriately arranged experiment gradually to
become divided between two groups of individuals.
Existing information as to the occurrence of these two
forms in Nature is given an arithmetical precision we
did not possess before ; furthermore we are led back to
a fascinating picture of the distribution of the antecedents
of 1 thrum-eye ' and ' pin-eye ' among the germ-cells, and
of their unions in fertilization.

In order to do justice to Mendel and because of the
value and interest of the inference, it is necessary to
explain in few words and as simply as possible what is
the nature of this picture of events we can never hope to
see with the microscope. The fertilized germ or zygote
from which all the higher animals develop is a single cell
of which the essential or nuclear elements are contributed
equally by the two parents. It has been proved by
observation that these essential parts of germ-cells (or
gametes) are reduced by half as a preparation for the
reception of a fresh half in fertilization or zygosis. Thus
it is that the starting-point of the individual is a single
cell and not a double cell. What Van Beneden and
others have seen with the microscope in the gamete and
the fertilized germ, Mendel's discovery enables the mind
to see in the material germinal basis of certain single
hereditary characters. Here, too, the material precursor
of a character at the starting-point of the individual is
made up of two parts, the allelomorphs, one from each
parental gamete. In the case of yellow and green
cotyledoned peas originally investigated by Mendel, we
may call the allelomorphs of the yellow character and the
green character respectively Y and G. In the first cross
between a pure yellow and a pure green pea it is obvious
that all the gametes of the one parent would carry Y and

xxxii MUTATION, MENDELISM, ETC.

all those of the other G. In fertilization therefore G
must unite with Y and the fertilized ovum must contain
YG. The germ, containing the two different allelo-
morphs of such a pair of Mendelian characters, is called
a heterozygote. All the peas produced by these hetero-
zygotes were superficially indistinguishable from the pure
yellow parent. Yellowness of the cotyledon is therefore
dominant over greenness. In the development of the
germ-cells (gametes) from which the next generation will
arise it is obvious that the precursors of the Mendelian
characters in question can only be represented by half of
what they will become after fertilization. This might
be effected by each gamete coming to possess in the course
of its development both Y and G of half the normal size ;
or it might be brought about by each gamete possessing
either Y or G, but never both. Mendel proved that the
facts (in characters that follow his principle) are invariably
consistent with the latter alternative. For, assuming that
the allelomorphs Y and G are thus scattered singly
among the gametes produced by each individual, it follows
that half the gametes will contain each a single Y, and
half each a single G. Hence in the event of self-ferti-
lization, a gamete containing Y will on the average meet
and unite with one containing Y as often as one with G ;
and G similarly will unite with G as often as with Y.
A quarter of the individuals of the following generation
will therefore be developed from a fertilized germ con-
taining YY, hence called a homozygote ; another quarter
from the other homozygote GG, while half will arise from
the heterozygote YG. But yellowness being dominant,
the latter individuals will superficially resemble those
developed from YY, and the generation will produce
approximately three yellow peas to one green. And this
is precisely what Mendel obtained by experiment. He

MENDEL'S DISCOVERY xxxiii

then proved by breeding further generations (i) that these
green peas contain the character in a pure state and yield
no other colour ; (2) that one third of the yellow peas
are similarly pure ; (3) that the remainder or half the
generation are heterozygotes, which when interbred
behave in precisely the same manner as the second
generation exclusively composed of heterozygotes. Con-
tinuing the process to infinity the yellows and greens
would sort themselves out into two equal bodies of pure
yellow and pure green respectively.

I should be the last to undervalue these results, but
their true worth is not enhanced by such astonishing
exaggeration as that which appears in the passage I have
quoted from R. H. Lock on p. xxvii. The human mind
is so constituted that a touch of megalomania is to be
expected, is even to be regarded with sympathy, in the
first flush of a new victory over the unknown ; and I have
always felt that the revelation of ' the underworld of
gametes ' 1 by Mendel's discovery is a fascinating and
arresting addition to knowledge. But to suppose that
the problem of Evolution is thereby solved, or likely to
be solved, is unreasonable. Lock's statement not only
reveals a grotesque exaggeration of the importance of
the results achieved, but also conveys the impression
that the Mendelian is to some extent paralysed by the
contemplation of his own work. He seems to say, —
* We have solved the mystery so far as it can be solved,
and all that is now expected of us is to apply and apply
again the Mendelian principle to one strain after another.'
Such an outlook does not offer much hope of progress
in solving the problem of Evolution.

' How have living things become what they are, and
what are the laws which govern their forms?' These
1 Bateson, Report British Association, 1904, p. 583.

POULTON P

xxxiv MUTATION, MENDELISM, ETC.

are the words in which Bateson at the outset of his
work 1 truly states the problem to be solved. Hardly
any assistance in this solution is afforded by the
Mendelian discovery. In the case of heterostyled plants,
Darwin had already proved that both forms exist in
Nature, and that in fact the offspring do arrange
themselves in two groups of approximately equal
numbers. The gametic explanation of this, although
intensely interesting, carries us no step further on the
road of Evolution. Furthermore, Darwin showed what
is the meaning of the heterostyled condition in the life
of the plant, and thus explained how it was that the
character has been selected, and incorporated into the
structure of the species. To look on this record and
on that, and maintain that Darwin failed to solve the
problem which the Mendelian has now solved, is, to
put it as mildly as possible, unreasonable and absurd.

It is probable that the part played by Mendel's prin-
ciple in evolution is limited to the prevention, in certain
cases, of the supposed ' swamping effect of intercrossing \
Interbreeding between a species and its variety could not
obliterate or weaken the latter when the relationship of
the two forms is Mendelian. As explained on pp. xxix,
xxx, a Mendelian variety would never really fuse with
the parent form, but would sooner or later emerge pure
in some future generation. On the other hand, the
characters of the variety, unless favoured by selection,
are prevented by the same principle from penetrating the
mass of the species. The average numbers of adults in
successive generations remaining constant, the number of
adult descendants of a new variety (with fertility equal
to that of the parent species) would, unless subject to
discriminative selection, remain constant also.

1 On Variation, p. i.

THE VALUE OF MENDELISM xxxv

A good example of the contact between a species and
subspecies is described on pp. 68, 69. Such cases require
investigation on Mendelian lines. If it be found that the
intermediates between the two butterflies {Amatiris),
which are believed to interbreed on the eastern shore of
the Victoria Nyanza, split up according to the Mendelian
principle, it will be obvious that this principle is helpful
in keeping the species and subspecies apart. It is much
to be hoped that work of this kind will be undertaken in
a large number of cases, selecting forms from points along
the line where different geographical varieties of a species
come into contact.

In the meantime the existence of abundant hybrids 1
which do not immediately resolve themselves into their
components throws doubt upon the extent of the appli-
cation of Mendel's principle. It is probable, however,
as R. H. Lock clearly explains, that the discovery will
have a most important bearing upon the art of the
breeder of both plants and animals. In this domain it is
difficult to see how the results can fail to be as far-reach-
ing as they will be beneficent. It must be remembered,
however, that results can only be obtained when the
characters obey the law of Mendel 2. Beyond this
the only chance of disappointment appears to lie in the
possibility of the Mendelian characters proving, in the
long run, to be less fixed than they are in the early
series of generations.

1 Such as that arising from Oenothera lamarckiana and Ot cruciata ;
probably also 0. lamarckiana itself (see p. xxi). Mendel concluded
from his experiments that the hybrids of Hieracium reproduce themselves
like true species, and Wichura obtained the same result in Salix.

2 Correns concludes that while crosses between varieties of plants do,
hybrids between species do not, follow the Mendelian principle. See
Variation in Animals and Plants, H. M. Vernon, London, 1903, pp. 159,
1 60. This work supplies an excellent introduction to the whole subject.

xxxvi MUTATION, MENDELISM, ETC.

6. No Essential Divergence between Mendelism and
Natu ral Selection .

The divergence between the Darwinian and the
Mendelian has been exaggerated. Differences have been
assumed that do not exist. Thus Bateson, after explain-
ing that the blue Andalusian fowl is the heterozygote pro-
duct of mating a black parent with a parent of a peculiar
white, and that it splits up into the parental strains on the
Mendelian principle (see pp. xxix, xxx), continues '.'Selection
will never make the blues breed true ; nor can this ever
come to pass unless a blue be found whose germ-cells are
bearers of the blue character — which may or may not be
possible. If the selectionist reflect on this experience
he will be led straight to the centre of our problem.
There will fall, as it were, scales from his eyes, and in a
flash he will see the true meaning of fixation of type,
variability, and mutation, vaporous mysteries no more.' 1
This is really no novelty, no falling of scales from the
eyes, for we have been aware, ever since Weismann's
researches and illuminating thoughts on the germ-cells.,
that no characters except those predetermined in the
germ are available for evolution. The same calm
appropriation by Bateson of Weismann's conclusions
is seen in the following passage : — ' We can answer
one of the oldest questions in philosophy. In terms
of the ancient riddle, we may reply that the Owl's
egg existed before the Owl. . . .' 2 But the same answer
was given, as the outcome of Weismann's investigations,
long before the re-discovery of Mendel's work. The
following statement was first made by Weismann in 1883 :
1 Natural Selection, while it apparently decides between

1 Report British Association, 1904, p. 579.

2 Ibid., 1904, pp. 587-8. Quoted by R. H. Lock, I c, p. 277.

A DEBT TO WEISMANN xxxvii

individuals of various degrees of strength, is in truth
operating upon the stronger and weaker germs.' 1 I
fully admit the importance of Mendel's discovery in
increasing our knowledge of the constitution and relation-
ships of germ-cells, but this by no means justifies the
appropriation under his name of results which the present
generation owes to Weismann.2

1 Essays upon Heredity, Oxford, 2nd ed., 1891, vol. i, p. 85. The
same thought is expressed in Weismann' s term ' blastogenic '. It also
appears in the following sentence (1. c, p. 84) : — 'The perfection of form of
an organ does not however depend upon the amount of exercise under-
gone by it during the life of the organism, but primarily and principally
upon the fact that the germ from which the individual arose was predis-
posed to produce a perfect organ/ The very same idea was published by
J. C. Prichard in 1826, as may be seen on p. 183 of the present work,
where these words occur: — ' . . . whatever varieties are produced in the
race, have their beginning in the original structure of some particular
ovum or germ, . . /

2 An example of the respect with which Bateson treats this great dis-
coverer is to be found on p. 573 of his work, On Variation. Without in
any way meeting the difficulty which Weismann attempted to face,
without any discussion of Weismann's hypothesis, Bateson simply waves
the solution aside, concluding in these words : — ' We may doubt indeed
whether the ideas associated with that flower of speech, " Panmixia," are
not as false to the laws of life as the word to the laws of language.' It
would be interesting to know something of the height of linguistic attain-
ment from which Bateson pours his scorn on a far greater and much older
man than himself. The unscholarly use of the 1 behold ' of Genesis in
the passage I have quoted on p. xxii throws some light on Bateson's
capacity as a critic ; but however necessary it may be for him to borrow
the information, he can always supply the scorn.

The absorption of the results of other workers in part explains, and
is in part the outcome of, the extraordinarily exaggerated importance
which is attached to the extremely interesting and valuable work of
Mendel. The following statement was made by Bateson in 1904 : — 4 It will
aid appreciation of the change coming over evolutionary science if it be
realised that the new knowledge of heredity and variation rather replaces
than extends current ideas on those subjects ' {Report British Association,
I9°4i P- 574). R. H. Lock (I.e., p. 265) also uses these words: —
1 There can be no sort of doubt that Mendel's brief paper is the most

xxxviii MUTATION, MENDELISM, ETC.

There is no dispute between Darwinians and Muta-
tionists as to the germinal origin of variation and
hereditary individual difference of every kind and degree.
Darwinians hold that evolution has proceeded by small
steps : Mutationists hold that it has advanced by large
ones. That I believe to be the sole essential difference,
and the reconciliation will come when, joining hands
with the student of geographical distribution, and un-
deterred by cheap sneers about ' ingenious persons ' and
'demonstrating the obvious', Darwinians shall have proved
that the relations of an organism to its environment are so
accurately and elaborately adjusted that any advance by
large variation is only possible as a very rare coincidence.
In that day the Mutationist will discover that 'something
mistakably like continuous evolution ' has occurred.1

There are indications that Mutation would still be
claimed as the method of evolution, even if advance by
large variations were to be abandoned. Any such con-
tention has been effectively dealt with by F. A. Dixey :
— ' If it be replied that a well-adapted type must have
arisen, not by one or more large mutations, but by a series

important contribution of its size which has ever been made to biological
science.' A subject is injured rather than advanced by such language.
Excessive inflation naturally tends to undue depression. Mendel's principle
has not yet been applied to a large number of species, and important
exceptions have been already revealed. (Bateson, Report British
Association^ 1904, p. 581.) — Complications have appeared which are as
yet imperfectly understood and have immensely increased the complexity
of an explanation which appeared at first to be of singularly beautiful
simplicity. The hypothetical germinal mechanism which a few years ago
seemed to accommodate the facts so comfortably is already beginning to
creak and groan. I am not aware that such an assertion as Lock's
has ever been made for the Darwin-Wallace essay of 1858, with nearly
half a century of prolific work as the firstfruits of its harvest.

1 1 When the unit of segregation is small, something mistakably like
continuous evolution must surely exist.' Bateson, in Report British
Association, 1904, p. 577 n.

MUTATION AND SMALL VARIATION xxxix

of mutations both numerous and minute, we should wish
to know how such mutations are to be distinguished from
continuous variations. To say, with de Vries, that
selection of individual differences is powerless to raise
permanently the mean of a species, seems perilously like
begging the question. As soon as the mean had been
permanently raised, the result would be claimed as a
mutation.' 1 The position is as follows. Darwin assumed
that selection of minute differences would permanently
raise the mean of the species. De Vries and others
believe they have proved that selection of certain
minute differences cannot thus raise the mean. Should
this conclusion be hereafter established it is obvious that
the variational material for evolution would be reinforced
by no new category. The only effect would be to reduce
the old category. The power which Darwin and others
believed to reside in minute variations generally would
be shown to exist in a part and not the whole of these.
Our knowledge would be widened by the revelation of
weakness in the part taken away, not by the strength of
the part left behind ; and there would be no justification
for speaking of the variations included in the latter as
Mutations.

I should have thought that Bateson, instead of urging
upon us the facts we had learnt so long ago, would have
had his own eyes opened by the blue Andalusian, and that
he would have been driven to realize the uselessness for
evolution of many a result which the breeder can attain.
He might even have been led to include in the category
of things valueless for the study of evolution not only
composite forms which cannot be depended upon to
reproduce themselves by heredity, but also the great mass
of teratological phenomena — supernumerary toes and
1 Nature, vol. lxxv, 1907, April 18, p. 579.

xl MUTATION, MENDELISM, ETC.

fingers, double hands and feet, abnormal horns, displaced
appendages, etc. — which form so large a part of a
work1 whose object is to assist in solving the problem of
Species. I am very far from undervaluing the study
of such material, but its high importance and interest
consist in the light thrown upon the development of the
individual, and not upon the question as put by Bateson
himself : 1 How have living things become what they are,
and what are the laws which govern their forms ? '

Not only does the leader of Mendelism in this country
appropriate the discoveries and illuminating thoughts of
Weismann, but he also erroneously claims the protecting
aegis of Darwin. Thus in 1904 he said : ' Darwin gave
us sound teaching when he compared man's selective
operations with those of Nature.' 2 But this statement
gives an entirely wrong impression of Darwin's views.
Darwin even tells us that he was ' deceived by single
variations offering such simple illustrations, as when man
selects '. And from the first he had always thought the
minute differences between individuals of more importance
for Natural Selection and Evolution than the large, simple
variations on which man relies. After reading Fleeming
Jenkin's article in the North British Review for June
1867, he concluded that the individual differences are
paramount.3 I am here referring to Darwin's views, not

1 On Variation.

2 Report British Association, 1904, p. 577. The error of his leader
has been repeated by R. H. Lock only so recently as Nov. 14, 1907.
In a letter to Nature of that date he writes : —

• If Dr. Archdall Reid discards Darwin's opinion, based as it was
upon an unequalled experience, that domestic and natural varieties have
arisen by essentially the same process, he may find himself landed among
a crowd of unsuspected difficulties.'

3 Darwin wrote in a letter to Wallace, dated January 22, 1869: —
* I always thought individual differences more important than single
variations, but now I have come to the conclusion that they are of para-

THE WORDS OF DARWIN

xli

to the Fleeming Jenkin argument of the ' swamping effect
of intercrossing'. There is no doubt that this argument
is affected by the Mendelian discovery (see p. xxxiv). Nor
is there any dispute about the vast importance of the
study of Artificial Selection. The point at issue is
whether Darwin considered the selection of man and
that of Nature to be essentially the same process.

7. Antagonism Promoted between Studies, all of which
are Needed for Attacking the Problem of Evolution.
Long before the rediscovery of the Mendelian principle,
Bateson, in his work, On Variation, did his best to dis-
parage other lines of inquiry, again and again asserting
that his own study was the only one in which lay
any hope of solving the problem of evolution. 1 Codlin's
the friend, not Short,' was the dogma rather than the
advice which he issued to the world. Little effect was

mount importance, and in this I believe I agree with you. Fleeming
Jenkin's arguments have convinced me.' The sentence is ambiguous and
was misunderstood by Wallace. Darwin wrote again on February 2 : —
' I must have expressed myself atrociously ; I meant to say exactly the
reverse of what you have understood. F. Jenkin argued in the " North
British Review " against single variations ever being perpetuated, and has
convinced me, though not in quite so broad a manner as here put,
I always thought individual differences more important ; but I was blind
and thought that single variations might be preserved much oftener than
I now see is possible or probable. I mentioned this in my former note
merely because I believed that you had come to a similar conclusion, and
I like much to be in accord with you. I believe I was mainly deceived
by single variations offering such simple illustrations, as when man
selects.' He also wrote on May 2, 1869, to Victor Carus : — 1 1 have
been led , . . to infer that single variations are even of less importance,
in comparison with individual differences, than I formerly thought.'
Francis Darwin remarks concerning Fleeming Jenkin's article, 1 It is
not a little remarkable that the criticisms, which my father, as I believe,
felt to be the most valuable ever made on his views should have come,
not from a professed naturalist but from a Professor of Engineering.'

The above quotations are to be found in Life and Letters, Lond., 1887,
vol. iii, pp. 107 and 109. See also pp. 2-4 of the present work.

xlii MUTATION, MENDELISM, ETC.

produced until Mendel's extremely interesting discovery
became known, and was in its turn proclaimed by Bate-
son as the only hope of evolutionary salvation. Mendel
himself was evidently a modest as well as a great man,
and by no means inclined to enthrone his important
principle as the Juggernaut of Biological Science. It is
due to the followers of Mendel that the new deity
threatens to exercise a malignant influence on the study
of Nature. No man is likely to continue the labours of
investigation with enthusiasm and persistence when he
is convinced, or even half convinced, by the overween-
ing assurance of another that his subject is barren and
useless. If such converts were likely to be added to the
number of Mendelian investigators there would be some
compensating gain; but men cannot always turn to entirely
new lines of work, nor is the result usually satisfactory
when they attempt to do so after long years at very different
inquiries, pursued with very different methods. The
spirit of investigation is as the wind that bloweth where it
listeth. It may be possible to arrest the current of inquiry,
without the power of diverting it into a fresh direction.

I should be sorry if the above remarks were considered
to imply any want of sympathy with the efforts of the
energetic and enthusiastic workers on Mendelian problems
at Cambridge. The subject and the work itself are de-
serving of the warmest appreciation. I am only taking
exception to the quite unnecessary depreciation of other
subjects and other workers.

By a curious irony, the very department of biology that
more than any other has produced classical work at Cam-
bridge, the splendid subject of Embryology, is one of
those specially selected for depreciation. And here, too,
most harm is likely to be done ; for a great tradition is
one of the noblest and most fruitful incentives to research.

UNNECESSARY ANTAGONISMS xliii

In order, if possible, to diminish any such injurious
effect, however transient, I propose to direct attention to
the reason given by Bateson for dissatisfaction with
Embryology as an aid in studying the problem of Species
— the reason which he places in the forefront, very clearly
stating it in the preface to his work, On Variation. He
tells us that after working at the anatomy and develop-
ment of Balanoglossus, he attempted to show the bearing
of the facts upon questions of relationship and descent —
involving in this case the ancestry of the Vertebrates.
He was dissatisfied with the uncertainty which must, in
the present state of our knowledge, attend an attempt to
solve about the most obscure and difficult problem in the
whole realm of zoology. A few of the main facts con-
cerning the past history of the Vertebrates are given on
pp. 26, 30 and 31 of the present volume. It will there be
seen that the stupendous problem to which the Embryo-
logy of a living organism could not give a decisive answer,
was nothing less than the reconstruction of a particular
episode in the course of evolutionary history at the period
when the oldest fossiliferous rocks were laid down, or
probably very much earlier. For this reason the study
of Embryology was to be discouraged, and Variation
proclaimed as our only hope, although not one particle
of evidence was brought forward to show that Varia-
tion could tell us even as much as Embryology about
the ancestry of the Vertebrates in Cambrian or pre-
Cambrian times.

Bateson does not hesitate to compare his opponents to
Procrustes.1 But there is a method beside which the
Procrustean is commonplace. Instead of making the
observations fit the hypothesis, a more original method
is to discourage the study by which awkward facts are
1 Report British Association, 1904, p. 578.

xliv MUTATION, MENDELISM, ETC.

likely to be yielded. That, in few words, is the treatment
accorded by Bateson to adaptation.

8. The Study of Adaptation Stimulates and does not
Bar the Way of Inquiry.

Professor J. B. Farmer, F.R.S., has recently main-
tained that the explanation which Natural Selection
offers of the origin and growth of certain adaptive
features in plants, not only fails to explain the pheno-
mena, but actually stands in the way of an inquiry into
the sequence of events by which they are developed in
the individual.1 Such a conclusion seems to me at
variance with the constitution of the human mind, and
the psychology of curiosity. Any point of view which
makes a set of scientific facts more interesting to man
increases the probability of their forming the material of
investigation. A few days ago I was passing some cases

1 Presidential Address to Botanical Section of British Association,
1907. I refer to the following passages : —

"... I would venture to express the opinion that much real harm is done
by the toleration of an uncritical habit of mind, all too common, as to the
significance of structures which are regarded as adaptive responses to
stimuli of various sorts. It is not enough to explain the appearance of a
structure on the ground of its utility ; properly speaking, such attempts,
so far from providing any explanation, actually tend to bar the way of
enquiry just where scientific investigation ought to commence.'

< That many of the responses to such stimuli are of a kind to render
the organism " adapted " to its environment no one, of course, will
dispute ; but to put forward the adapledness as an explanation of the
process is both unscientific and superficial. The size and the spherical
shape of duckshot are admirably adapted to the purposes for which duck-
shot is used; but this affords no insight into the necessary sequence
of cause and effect, which makes the melted lead assume the characters
in question as it falls down the shot-tower.'

1 But many people still find consolation and satisfaction in an anthropo-
morphic and somewhat slipshod application of a kind of doctrine of
free-will to matters that really call for rigorous examination into the causes
which, under given conditions, must inevitably and of necessity bring
about their definite result.' Report, pp. 675-6.

THE STIMULUS OF INTEREST xlv

of Oriental butterflies and moths which had been exposed
to light for a long period of years. I noticed that the pig-
ments of the moths had as a whole faded far more than
those of the butterflies.1 It at once occurred to me that
stable pigments are far more necessary for the butterfly
exposed to the light of a tropical sun, than for the moth
flying in the evening or at night. Hence a much higher
level of stability would be selected in the pigments of
butterflies than in those of moths. Professor Farmer
would of course maintain that this is one of the ' teleo-
logical explanations that really explain nothing, but
rather bar the way of scientific inquiry ' (see p. 74 n. 2 of
the present work). I, on the contrary, believe that it ex-
plains a great deal. It explains the reason why pigments
with particular qualities were selected, and have now
come to be characters of certain species. It does not
pretend to explain how it was that pigments with these
qualities were there to be selected ; but, so far from bar-
ring the way, this suggestion actually points the road to
scientific inquiry. As a matter of fact, a further investi-
gation into the chemical nature of these pigments, and
the steps by which they arise in the individual, is now
more probable than it was before the suggestion was made.
It is precisely the same with regard to the example
brought forward by Professor Farmer in his Address
(p. 676) : — 1 One of the commonest responses to the sti-
mulus of wounding, in the higher plants, is the formation
of a layer of cork over the injured and exposed tissue.
No one can deny that this is a reaction of great utility,
checking as it does the undue evaporation of water, and
the entrance of other parasitic organisms. And yet
I suppose that no one would go so far as to seriously

1 Confirmatory evidence was afforded by the condition of the day-
flying moths and the shade-loving and crepuscular butterflies.

xlvi MUTATION, MENDELISM, ETC.

maintain that the obviousness of these advantages
satisfactorily explains why the cork layer is produced.'
On the contrary, these advantages, if scientifically proved
to be conferred, probably do explain why it is that the
power of forming cork was selected, and has come to
be a character of the higher plants. They do not
explain how the layer is formed ; but, so far from barring
the way, it is quite clear that the proof of important
advantages conferred adds immensely to the interest
of the cork, and greatly increases the probability of the
student undertaking an investigation into the sequence
of events by which it is produced in the individual plant.1
The attempts to answer the questions ' Why ' and
1 How ' — ' To what end ? ' and ' In what way ? ' — by no
means interfere with each other. These two sides of
investigation, on the contrary, provide mutual assistance
and encouragement. There are always these two
questions to be answered with reference to any natural
phenomenon, and both must be answered if the facts are
to be fully understood. Any one who is foolish enough
to maintain that the answer to one of these questions

1 My friend Professor S. H. Vines, F.R.S., has kindly drawn my attention
to the following interesting and relevant passages from Whewell's History
of the Inductive Sciences (vol. iii, 3rd edition, p. 390) : — 1 Cuvier's merit
consisted, not in seeing that an animal cannot exist without combining
all the conditions of its existence ; but in perceiving that this truth may
be taken as a guide in our researches concerning animals : — that the
mode of their existence may be collected from one part of their structure,
and then applied to interpret or detect another part/ This bears out the
argument that knowledge of the use or purpose of a structure or a pro-
perty acts as a stimulus to investigation.

Furthermore, in his Philosophy of the Inductive Sciences, Whewell
says (vol. ii, p. 78), * The idea of a Final Cause is an essential condition
in order to the pursuing our researches respecting organized bodies.'
Again (p. 90), ' The doctrine of a purpose in organization has been some-
times called the doctrine of the Conditions of Existence.1

TWO ANSWERS ESSENTIAL xlvii

provides also the answer to the other, deserves criticism ;
but it is irrelevant to criticize the aim of an inquiry
because of the mistaken views of the inquirer.

Every scientific man will agree that careless and
slipshod work must be discouraged ; and it will probably
be admitted that the study of adaptation, unless under-
taken in a spirit of rigid self-criticism, is especially likely
to produce an unsatisfactory result. But who is so much
interested as the serious student of adaptation in keeping
the subject at a high scientific level ? The most notable
protest 1 against facile speculation based on Natural
Selection that has ever appeared in this country was
written by so thorough a Darwinian as Sir William
Thiselton-Dyer, and it is hardly necessary to state that
it was the work and not the subject that he criticized.
The younger men who have devoted themselves to the
problems of adaptation under my guidance would be the
last to say that they have found the road of investigation
a broad and easy one. And, when the necessary pre-
cautions are taken, there is no more fruitful study in
Biological Science than the one which we owe to the
central discovery of Darwin and Wallace.

9. The Motive Force of Investigation.

These attempts to disparage one subject and exalt
another naturally raise the question, ' Why do we investi-
gate at all ?' It was by curiosity, as I have heard Sir
Michael Foster say, that our first parents lost the Garden
of Eden ; but, in transmitting this same curiosity to
their descendants, they gave us a golden bridge by which
we may re-enter Paradise. The ultimate justification of
all scientific research is, ' 1 do it because it interests me :
I want to find out.' Any further motive — the well-being

1 The article Deductive Biology in Nature, vol. xxvii, 1883, pp. 554-5.

xlviii MUTATION, MENDELISM, ETC.

of humanity, the pursuit of gain, the gratification of
ambition — only tends to bias and mar the inquiry. We
want to know why. That is all. Whither the know-
ledge we accumulate is tending no one can tell. One of
the greatest men of all time said that we are like children
picking up shells on the shore of the ocean. A realiza-
tion of the truth of the saying might save us from
carrying the likeness still further, by quarrelling over
our little collections.

For myself and my own work I should greatly prefer
to have said nothing, or only to have used words
suggested by the old-world reply to the fears of the
timid and the inexperienced : — ' The sun-darkening cloud
of arrows is much less deadly than it looks : no great
harm will be done : in the meantime we can fight all the
better in the shade/ But this comfortable course is shut
out, and that for two reasons — because of an immeasur-
able debt due to the past, because of heavy responsibilities
incurred for the future.

Naturalists who are striving to carry on, however
imperfectly, a great tradition, can neglect the attempt to
depreciate their own work, but they cannot be indifferent
to an attack which falls on those who created the tradition
— on the founders of modern Biological Science. As
for the future, the thoughts of Darwin and Wallace are
potent as ever to inspire and direct the labours of the
young biologist. I do not speak without knowledge ;
for many a student of nature has come to me for
guidance, and I have not directed them in vain to this
source. Not without the strongest protest shall the
work which has meant, and still means, so much to them
be assailed by the unscientific and, I must add, the
unworthy weapon of contempt.

I

A NATURALIST'S CONTRIBUTION

TO THE DISCUSSION UPON

THE AGE OF THE EARTH

The Presidential Address read to the Zoological Section of the British
Association, September 17, 1896. Reprinted from the Report of the
Meeting of the Association held at Liverpool, 1896, p. 808.

Revised: additional /oolnotes and terminal note.

A very brief study of the proceedings of this Section
in bygone years will show that Presidents have exercised
a wide choice in the selection of subjects. At the last
Meeting of the Association in this City in 1870 the
Biological Section had as its President the late Professor
George Rolleston, a man whose remarkable personality
made a deep impression upon all who came under his
influence, as I have the strongest reason for remember-
ing, inasmuch as he was my first teacher in zoology, and
I attended his lectures when but little over seventeen.
His address was most characteristic, glancing over a great
variety of subjects, literary as well as scientific, and
abounding in quotations from several languages, living
and dead. A very different style of address was that
delivered by the distinguished zoologist who presided
over the Meeting. Professor Huxley took as his subject
The History of the Rise arid Progress of a Single Bio-
logical Doctrine.

Of these two types I selected the latter as my example,
and especially desired to attempt the discussion, however
inadequate, of some difficulty which confronts the zoolo-
gist at the very outset, when he begins to reason from
the facts around him, a difficulty which is equally obvious
and of equal moment to the highly trained investigator and
the man who is keenly interested in the results obtained
by others, but cannot himself lay claim to the position and

POVLTON B

2 THE AGE OF THE EARTH

authority of a skilled observer — to the naturalist and to
one who follows some other branch of knowledge, but
is interested in the progress of a sister science.

Two such difficulties were alluded to by Lord Salisbury
in his interesting Presidential Address to the British
Association at Oxford in 1894, when he spoke of 'two
of the strongest objections to the Darwinian explanation 9
of evolution — viz. the theory of Natural Selection — as
appearing 'still to retain all their force \ The first of
these objections was the insufficiency of the time during
which the earth has been in a habitable state, as cal-
culated by Lord Kelvin and Professor Tait, one hundred
million years being conceded by the former, but only
ten million by the latter. Lord Salisbury quite rightly
stated that, for the evolution of the organic world as we
know it, by the slow process of Natural Selection, at least
many hundred million years are required ; whereas, ' if
the mathematicians are right, the biologists cannot have
what they demand. . . . The jelly-fish would have been
dissipated in steam long before he had had a chance of
displaying the advantageous variation which was to make
him the ancestor of the human race/

The second objection was that ' we cannot demonstrate
the process of Natural Selection in detail ; we cannot
even, with more or less ease, imagine it ' In Natural
Selection who is to supply the breeder's place ? 9 ' There
would be nothing but mere chance to secure that the
advantageously varied bridegroom at one end of the
wood should meet the bride, who by a happy contingency
had been advantageously varied in the same direction
at the same time at the other end of the wood. It would
be a mere chance if they ever knew of each other's exis-
tence— a still more unlikely chance that they should resist
on both sides all temptations to a less advantageous
alliance. But unless they did so the new breed would
never even begin, let alone the question of its perpetua-
tion after it had begun.'

Professor Huxley, in seconding the vote of thanks to
the President, said he could imagine that certain parts
of the address might raise a very good discussion

LORD SALISBURY'S 1894 ADDRESS 3

in one of the Sections, and I have little doubt that he
referred to these criticisms and to this Section. When
I had to face the duty of preparing this address, I could
find no subjects better than those provided by Lord Salis-
bury.

At first the second objection seemed to offer the more
attractive subject. It was clear that the theory of
Natural Selection as held by Darwin was misconceived
by the speaker, and that the criticism was ill-aimed.
Darwin and Wallace, from the very first, considered that
the minute differences which separate individuals were
of far more importance than the large single variations
which occasionally arise — Lord Salisbury's advanta-
geously varied bride and bridegroom at opposite ends
of the wood. In fact, after Fleeming Jenkins's criticisms
in the North British Review for June, 1867, Darwin
abandoned these large single variations altogether. Thus
he wrote in a letter to Wallace (February 2, 1869) :
' 1 always thought individual differences more important ;
but I was blind, and thought single variations might
be preserved much oftener than I now see is possible
or probable. I mentioned this in my former note
merely because I believed that you had come to a
similar conclusion, and I like much to be in accord
with you.' 1 Hence we may infer that the other great
discoverer of Natural Selection had come to the same
conclusion at an even earlier date. But this fact
removes the whole point from the criticism I have just
quoted. According to the Darwin-Wallace theory of
Natural Selection, individuals sufficiently advantageously
varied to become the material for a fresh advance
when an advance became necessary, and at other times
competent to maintain the ground previously gained —
such individuals existed not only at the opposite ends
of the wood, but were common enough in every colony
within its confines. The mere fact that an individual
had been able to reach the condition of a possible
bride or bridegroom would count for much. Few will
dispute that such individuals 'have already successfully

1 Life and Letters, vol. iii.
B 2

THE AGE OF THE EARTH

run the gauntlet of by far the greatest dangers which
beset the higher animals [and, it may be added, the
lower animals also] — the dangers of youth. Natural
Selection has already pronounced a satisfactory verdict
upon the vast majority of animals which have reached
maturity.' 1

But the criticism retains much force when applied to
another theory of evolution by the selection of large
and conspicuous variations, a theory which certain
writers have all along sought to add to or substitute
for that of Darwin. Thus Huxley from the very first
considered that Darwin had burdened himself unneces-
sarily in rejecting per saltum evolution so unreservedly.2
And recently this view has been revived by Bateson's
work on variation and by DeVries' researches on Oenothera
lamarckiana. I had at first intended to attempt a discus-
sion of this theory, together with Lord Salisbury's and
other objections which may be urged against it ; but the
more fully the two were considered, the more pressing
became the claims of the criticism alluded to at first — the
argument that the history of our planet does not allow
sufficient time for a process which all its advocates admit
to be extremely slow in its operation. I select this subject
because of its transcendent importance in relation to
organic evolution, and because I hope to show that the
naturalist has something of weight to contribute to
the controversy which has been waged intermittently
ever since Lord Kelvin's paper On Geological Time'2,
appeared in 1868. It has been urged by the great
worker and teacher who occupied the Presidential Chair
of this Association when it last met in Liverpool that
biologists have no right to take part in this discussion.
In his Anniversary Address to the Geological Society in
1869 Huxley said: ' Biology takes her time from geology.

1 Poulton, Colours of Animals, p. 308.

2 See his letter to Darwin, November 23, 1859 : Life and Letter s, vol. ii.

3 Trans. Geol. Soc, Glasgow, vol. iii. See also On the Age of the Sun's
Heat, Macmillan, March, 1862 : reprinted as Appendix to Thomson and
Tait, Natural Philosophy, vol. i. part 2, second edition; and On the
Secular Cooling of the Earth, Royal Society of Edinburgh, 1862.

THE EVIDENCE OF THE NATURALIST 5

. . . If the geological clock is wrong, all the naturalist
will have to do is to modify his notions of the rapidity
of change accordingly.' This contention is obviously
true as regards the time which has elapsed since the
earliest fossiliferous rocks were laid down. For the
duration of the three great periods we must look to the
geologist ; but the question as to whether the whole of
organic evolution is comprised within these limits, or, if
not, what proportion of it is so contained, is a question
for the naturalist. The naturalist alone can tell the
geologist whether his estimate is sufficient, or whether it
must be multiplied by a small or by some unknown but
certainly high figure, in order to account for the evolu-
tion of the earliest forms of life known in the rocks.
This, I submit, is a most important contribution to the
discussion.

Before proceeding further it is right to point out that
obviously these arguments will have no weight with
those who do not believe that evolution is a reality. But
although the causes of evolution are greatly debated, it
may be assumed that there is no perceptible difference of
opinion as to evolution itself, and this common ground
will bear the weight of all the zoological arguments
I shall advance to-day.

It will be of interest to consider first how the matter
presented itself to naturalists before the beginning of this
controversy on the age of the habitable earth. I will
content myself with quotations from three great writers
on biological problems — men of extremely different types
of mind, who yet agreed in their conclusions on this
subject.

In the original edition of the Origin of Species (1859),
Darwin, arguing from the presence of trilobites, Nautilus,
Lingula, &c, in the earliest fossiliferous rocks, came to
the following conclusion (pp. 306, 307) : ' Consequently,
if my theory be true, it is indisputable that before the
lowest Silurian stratum was deposited long periods
elapsed, as long as, or probably far longer than, the
whole interval from the Silurian age to the present day ;

6 THE AGE OF THE EARTH

and that during these vast yet quite unknown periods of
time the world swarmed with living creatures.'

The depth of his conviction in the validity of this con-
clusion is seen in the fact that the passage remains sub-
stantially the same in later editions, in which, however,
Cambrian is substituted for Silurian, while the words
1 yet quite unknown ' are omitted, as a concession, no
doubt, to Lord Kelvin's calculations, which he then pro-
ceeds to discuss, admitting as possible a more rapid
change in organic life, induced by more violent physical
changes.1

We know, however, that such concessions troubled
Darwin much, and that he was really giving up what his
judgement still approved. Thus he wrote to Wallace on
April 14, 1869 : ' Thomson's views of the recent age of
the world have been for some time one of my sorest
troubles. . . .' And again, on July 12, 1871, alluding to
Mivart's criticisms, he says : ' I can say nothing more
about missing links than what I have said. I should
rely much on pre-Silurian times ; but then comes Sir W.
Thomson, like an odious spectre.'

Huxley's demands for time in order to account for
pre-Cambrian evolution, as he conceived it, were far
more extensive. Although in 1869 he bade the naturalist
stand aside and take no part in the controversy, he had
nevertheless spoken as a naturalist in 1862, when, at the
close of another Anniversary Address to the same
Society, he argued from the prevalence of persistent
types 1 that any admissible hypothesis of progressive
modification must be compatible with persistence without
progression through indefinite periods ' ; and then main-
tained that ' should such an hypothesis eventually be
proved to be true . . . the conclusion will inevitably
present itself that the Palaeozoic, Mesozoic, and Cainozoic
faunae and florae, taken together, bear somewhat the same
proportion to the whole series of living beings which
have occupied this globe as the existing fauna and flora
do to them \

Herbert Spencer, in his article on Illogical Geology
1 Sixth ed. 1872, p. 286.

PRE-CAMBRIAN EVOLUTION 7

in the Universal Review for July, 1859,1 uses these
words : ' Only the last chapter of the earths history has
come down to us. The many previous chapters, stretch-
ing back to a time immeasurably remote, have been
burnt, and with them all the records of life we may
presume they contained.' Indeed, so brief and unim-
portant does Herbert Spencer consider this last chapter
to have been that he is puzzled to account for * such
evidences of progression as exist'; and finally concludes
that they are of no significance in relation to the doctrine
of evolution, but probably represent the succession of
forms by which a newly upheaved land would be peopled.
He argues that the earliest immigrants would be the
lower forms of animal and vegetable life, and that these
would be followed by an irregular succession of higher
and higher forms, which ' would thus simulate the succes-
sion presented by our own sedimentary series '.

We see, then, what these three great writers on evolu-
tion thought on the subject : they were all convinced
that the time during which the geologists concluded that
the fossiliferous rocks had been formed was utterly
insufficient to account for organic evolution.

Our object to-day is first to consider the objections
raised by physicists against the time demanded by the
geologist, and still more against its multiplication by the
student of organic evolution ; secondly, to inquire whether
the present state of palaeontological and zoological know-
ledge increases or diminishes the weight of the threefold
opinion quoted above — an opinion formed on far more
slender evidence than that which is now available.
And if we find the conclusion sustained, it must be con-
sidered to have a very important bearing upon the
controversy.

The arguments of the physicists are three : —
First, the argument from the calculated secular change
in the length of the day the most important element of
which is due to tidal retardation. It has been known for
a very long time that the tides are slowly increasing the

1 Reprinted in his Essays , 1868, vol. i. pp. 324-76.

8 THE AGE OF THE EARTH

length of our day. Huxley explains the reason with his
usual lucidity : ' That this must be so is obvious, if one
considers, roughly, that the tides result from the pull
which the sun and the moon exert upon the sea, causing
it to act as a sort of break upon the solid earth.' 1

A liquid earth takes a shape which follows from its
rate of revolution, and from which, therefore, its rate of
revolution can be calculated.

The liquid earth consolidated in the form it last
assumed, and this shape has persisted until now, and
informs us of the rate of revolution at the time of con-
solidation. Comparing this with the present rate, and
knowing the amount of lengthening in a given time due
to tidal friction, we can calculate the date of consolidation
as certainly less than 1,000 million years ago.

The argument is fallacious, as many mathematicians
have shown. The present shape tells us nothing of the
length of the day at the date of consolidation ; for the
earth, even when solid, will alter its form when exposed
for a long time to the action of great forces. As
Professor Perry said in a letter to Professor Tait : 2 ' I
know that solid rock is not like cobbler's wax, but 1,000
million years is a very long time, and the forces are
great.' Furthermore, we know that the earth is always
altering its shape, and that whole coast-lines are slowly
rising or falling, and that this has been true, at any rate,
during the formation of the stratified rocks.

This first argument is dead and gone.3 We are, indeed,
tempted to wonder that the physicist, who was looking
about for reasoning by which to revise what he con-
ceived to be the hasty conclusions of the geologist as to
the age of the earth, should have exposed himself to
such an obvious retort in basing his own conclusions
as to its age on the assumption that the earth, which
we know to be always changing in shape, has been

1 Anniversary Address to Geol. Soc. 1869.

2 Nature, January 3, 1895.

3 It must not be forgotten, however, that this argument and those
which follow it have done good work in modifying the unreasonable
demands of geologists a quarter of a century ago.

ROTATION AND SHAPE OF THE EARTH 9

unable to alter its equatorial radius by a few miles
under the action of tremendous forces constantly tending
to alter it, and having 1,000 million years in which to do
the work.

With this flaw in the case it is hardly necessary to
insist on our great uncertainty as to the rate at which
the tides are lengthening the day.

The spectacle presented by the geologist and biologist,
deeply shocked at Lord Kelvin's extreme uniformitarian-
ism in the domain of astronomy and cosmic physics, is
altogether too comforting to be passed by without remark ;
but in thus indulging in a friendly tu quoqite, I am quite
sure that I am speaking for every member of this Section
in saying that we are in no way behind the members of
Section A in our pride and admiration at the noble work
which he has done for science, and we are glad to take
this opportunity of congratulating him on the half-century
of work and teaching — both equally fruitful — which has
reached its completion in the present year [1896].

The second argument is based upon the cooling of
the earth, and this is the one brought forward and
explained by Lord Salisbury in his Presidential Address.
It has been the argument on which perhaps the chief
reliance has been placed, and of which the data — so it
was believed — were the least open to doubt.

On the Sunday during the meeting of the British
Association at Leeds (1890), I went for a walk with
Professor Perry, and asked him to explain the physical
reasons for limiting the age of the earth to a period
which the students of other sciences considered to be
very inadequate. He gave me an account of the data
on which Lord Kelvin relied in constructing this second
argument, and expressed the strong opinion that they
were perfectly sound, while, as for the mathematics,
it might be taken for granted, he said, that they were
entirely correct. He did not attach much weight to the
other arguments, which he regarded as merely offering
support to the second.

This little piece of personal history is of interest,

io THE AGE OF THE EARTH

inasmuch as Professor Perry has now provided us with
a satisfactory answer to the line of reasoning which so
fully satisfied him in 1890. And he was led to a critical
examination of the subject by the attitude taken up
by Lord Salisbury in 1894. Professor Perry was not
present at the meeting, but when he read the Presidents
address, and saw how other conclusions were ruled out
of court, how the only theory of evolution which com-
mands anything approaching universal assent was set
on one side because of certain assumptions as to the
way in which the earth was believed to have cooled,
he was seized with a desire to sift these assumptions,
and to inquire whether they would bear the weight of
such far-reaching conclusions. Before stating the results
of his examination, it is necessary to give a brief account
of the argument on which so much has been built.

Lord Kelvin assumed that the earth is a homogeneous
mass of rock similar to that with which we are familiar
on the surface. Assuming, further, that the temperature
increases, on the average, i° F. for every fifty feet of
depth near the surface everywhere, he concluded that
the earth would have occupied not less than twenty,
nor more than four hundred, million years in reaching
its present condition from the time when it first began
to consolidate and possessed a uniform temperature of
7,000° F.

If, in the statement of the argument, we substitute
for the assumption of a homogeneous earth an earth
which conducts heat better internally than it does
towards the surface, Professor Perry, whose calculations
have been verified by Mr. O. Heaviside, finds that the
time of cooling has to be lengthened to an extent which
depends upon the value assigned to the internal con-
ducting power. If, for instance, we assume that the
deeper part of the earth conducts ten times as well
as the outer part, Lord Kelvin's age would require to
be multiplied by fifty-six. Even if the conductivity be
the same throughout, the increase of density in the
deeper part, by augmenting the capacity for heat of
unit volume, implies a longer age than that conceded

THE COOLING OF THE EARTH n

by Lord Kelvin. If the interior of the earth be fluid
or contain fluid in a honeycomb structure, the rate at
which heat can travel would be immensely increased
by convection currents, and the age would have to be
correspondingly lengthened. If, furthermore, such con-
ditions, although not obtaining now, did obtain in past
times, they will have operated in the same direction.

Professor Tait, in his letter to Professor Perry
(published in Nature of January 3, 1895), takes the
entirely indefensible position that the latter is bound
to prove the higher internal conductivity. The obliga-
tion is all on the other side, and rests with those who
have pressed their conclusions hard and carried them
far. These conclusions have been, as Darwin found
them, one of our 'sorest troubles'; but when it is
admitted that there is just as much to be said for
another set of assumptions leading to entirely different
conclusions, our troubles are at an end, and we cease to
be terrified by an array of symbols, however unintelli-
gible to us. It would seem that Professor Tait, without,
as far as I can learn, publishing any independent calcula-
tion of the age of the earth, has lent the weight of his
authority to a period of ten million years, or half of
Lord Kelvin's minimum. But in making this suggestion
he apparently feels neither interest nor responsibility in
establishing the data of the calculations which he
borrowed to infer therefrom a very different result
from that obtained by their author.

Professor Perry's object was not to substitute a more
correct age for that obtained by Lord Kelvin, but rather
to show that the data from which the true age could be
calculated are not really available. We obtain different
results by making different assumptions, and there is
no sufficient evidence for accepting one assumption
rather than another. Nevertheless, there is some
evidence which indicates that the interior of the earth
in all probability conducts better than the surface.
Its far higher density is consistent with the belief
that it is rich in metals, free or combined. Professor
Schuster concludes that the internal electric conductivity

12 THE ACxE OF THE EARTH

must be considerably greater than the external. Geo-
logists have argued from the amount of folding to which
the crust has been subjected that cooling must have
taken place to a greater depth than 1 20 miles, as assumed
in Lord Kelvin's argument. Professor Perry's assump-
tion would involve cooling to a much greater depth.

Professor Perry's conclusion that the age of the
habitable earth is lengthened by increased conductivity
is the very reverse of that to which we should be led
by a superficial examination of the case. Professor Tait,
indeed, in the letter to which I have already alluded,
has said : ' Why, then, drag in mathematics at all,
since it is absolutely obvious that the better conductor
the interior in comparison with the skin, the longer
ago must it have been when the whole was at 7,000° F. :
the state of the skin being as at present ? ' Professor
Perry, in reply, pointed out that one mathematician
who had refuted the tidal retardation argument1 had
assumed that the conditions described by Professor Tait
would have involved a shorter period of time. And
it is probable that Lord Kelvin thought the same ; for
he had assumed conditions which would give the result
— so he believed at the time — most acceptable to the
geologist and biologist. Professor Perry's conclusion
is very far from obvious, and without the mathematical
reasoning would not be arrived at by the vast majority
of thinking men.

The ' natural man ' without mathematics would say,
so far from this being ' absolutely obvious ', it is quite
clear that increased conductivity, favouring escape of
heat, would lead to more rapid cooling, and would make
Lord Kelvin's age even shorter.

The argument can, however, be put clearly without
mathematics, and, with Professor Perry's help, I am
able to state it in a few words. Lord Kelvin's assump-
tion of an earth resembling the surface rock in its
relations to heat leads to the present condition of things,
namely, a surface gradient of i° F. for every fifty feet,
in 100,000,000 years, more or less. Deeper than
1 Rev. M. H. Close in R. Dublin Soc, February, 1878.

THE LIFE OF THE SUN

13

1 50 miles he imagines that there has been almost no
cooling. If, however, we take one of the cases put
by Professor Perry, and assume that below a depth of
four miles there is ten times the conductivity, we find
that after a period of 10,000,000,000 years the gradient
at the surface is still i° F. for every fifty feet; but that
we have to descend to a depth of 1,500 miles before we
find the initial temperature of 7,000° F. undiminished
by cooling. In fact the earth, as a whole, has cooled
far more quickly than under Lord Kelvin's conditions,
the greater conductivity enabling a far larger amount
of the internal heat to escape ; but in escaping it has
kept up the temperature gradient at the surface.

Lord Kelvin, replying to Professor Perry's criticisms,
quite admits that the age at which he had arrived by
the use of this argument may be insufficient. Thus, he
says, in his letter : 1 'I thought my range from 20
millions to 400 millions was probably wide enough, but
it is quite possible that I should have put the superior
limit a good deal higher, perhaps 4,000 instead of 400/

The third argument was suggested by Helmholtz, and
depends on the life of the sun. If the energy of the sun
is due only to the mutual gravitation of its parts, and if
the sun is now of uniform density, ' the amount of heat
generated by his contraction to his present volume would
have been sufficient to last eighteen million years at his
present rate of radiation.' 3 Lord Kelvin rejects the
assumption of uniform density, and is, in consequence of
this change, able to offer a much higher upward limit
of 500 million years.

This argument also implies the strictest uniformitarian-
ism as regards the sun. We know that other suns may
suddenly gain a great accession of energy, so that their
radiation is immensely increased. We only detect such
changes when they are large and sudden, but they prepare
us to believe that smaller accessions may be much more
frequent, and perhaps a normal occurrence in the evolution

1 Nature, January 3, 1895.

2 Newcomb's Popular Astronomy, p. 523.

i4 THE AGE OF THE EARTH

of a sun. Such accessions may have followed from the
convergence of a stream of meteors. Again, it is possible
that the radiation of the sun may have been diminished
and his energy conserved by a solar atmosphere.

Newcomb has objected to these two possible modes by
which the life of the sun may have been greatly lengthened,
that a lessening of the sun's heat by under a quarter
would cause all the water on the earth to freeze, while
an increase of much over half would probably boil it all
into steam. But such changes in the amount of radiation
received would follow from a greater distance from the
sun of 15I per cent., and a greater proximity to him of
1 8*4 per cent., respectively. Venus is inside the latter
limit, and Mars outside the former, and yet it would be
a very large assumption to conclude that all the water in
the former is steam, and all in the latter ice. Indeed, the
existence of water and the melting of snow on Mars are
considered to be thoroughly well authenticated. It is
further possible that in a time of lessened solar radiation
the earth may have possessed an atmosphere which
would retain a larger proportion of the sun's heat ; and
the internal heat of the earth itself, great lakes of lava
under a canopy of cloud for example, may have played
an important part in supplying warmth.

Again we have a greater age if there was more energy
available than in Helmholtz's hypothesis. Lord Kelvin
maintains that this is improbable because of the slow
rotation of the sun, but Perry has given reasons for an
opposite conclusion.

The collapse of the first argument based on tidal
retardation, and of the second based on the cooling of
the earth, warn us to beware of a conclusion founded on
the assumption that the sun's energy depends, and has
ever depended, on a single source of which we know the
beginning and the end. It may be safely maintained
that such a conclusion has not that degree of certainty
which justifies the followers of one science in assuming
that the conclusions of other sciences must be wrong,
and in disregarding the evidence brought forward by
workers in other lines of research,

THE LIFE OF THE SUN

15

We must freely admit that this third argument has
not yet fully shared the fate of the two other lines of
reasoning. Indeed, Professor Sir George Darwin,
although not feeling the force of these latter, agrees
with Lord Kelvin in regarding 500 million years as
the maximum life of the sun.1

We may observe, too, that 500 million years is by no
means to be despised : a great deal may happen in such
a period of time. Although I should be sorry to say
that it is sufficient, it is a very different offer from
Professor Tait's ten million.2

In drawing up this account of the physical arguments,
I owe almost everything to Professor Perry for his
articles in Nature (January 3 and April 18, 1895), and
his kindness in explaining any difficulties that arose.
I have thought it right to enter into these arguments in
some detail, and to consume a considerable proportion
of our time in their discussion. This was imperatively
necessary, because they claimed to stand as barriers across
our path, and, so long as they were admitted to be
impassable, any further progress was out of the question.
What I hope has been an unbiased examination has
shown that, as barriers, they are more imposing than

1 British Association Reports, 1886, pp. 514-18.

2 Professor Perry has kindly sent me a few lines on the bearing of
the discovery of Radium upon the problem. 1 At the time when your
address was delivered/ he writes, 'I thought that the sun's heat argument
was the one that was most difficult to meet. But now, the discovery of
Radium has disposed of it as well as the conclusions founded on
conductivity. The duration of Radium itself is known to be only a few
thousand years, but quantity of Radium indicates quantity of that substance,
probably Uranium, whose exceedingly slow change is constantly producing
Radium.

1 1. The heat conductivity argument. This is completely disposed of
even if Mr. Strutt has overestimated the amount of Radium in rock.
Suppose only -^th of what he has assumed from his measurements and we
have the possibility of multiplying Lord Kelvin's age by 1,000 or more.

1 2. The suns heat argument. Assume that there is Radium in the sun
and this gives us almost any multiple we please to imagine of the total
energy assumed by Helmholtz. We are now in a position to say that
the physicist can make no calculation either as to the probable or possible
age of life on the earth.' Nov. 8, 1906.

16 THE AGE OF THE EARTH

effective ; and we are free to proceed, and to look for
the conclusions warranted by our own evidence. In this
matter we are at one with the geologists ; for, as has been
already pointed out, we rely on them for an estimate of
the time occupied by the deposition of the stratified
rocks, while they rely on us for a conclusion as to how far
this period is sufficient for the whole of organic evolution.

First, then, we must briefly consider the geological
argument, and I cannot do better than take the case as
put by Sir Archibald Geikie in his Presidential Address
to this Association at Edinburgh in 1892.

Arguing from the amount of material removed from the
land by denuding agencies, and carried down to the sea
by rivers, he showed that the time required to reduce
the height of the land by one foot varies, according to
the activity of the agencies at work, from 730 years to
6,800 years. But this also supplies a measure of the rate
of deposition of rock ; for the same material is laid down
elsewhere, and would of course add the same height of
one foot to some other area equal in size to that from
which it was removed.

The next datum to be obtained is the total thickness
of the stratified rocks from the Cambrian system to the
present day. ' On a reasonable computation these stratified
masses, where most fully developed, attain a united
thickness of not less than 100,000 feet. If they were all
laid down at the most rapid recorded rate of denudation,
they would require a period of seventy-three millions of
years for their completion. If they were laid down at
the slowest rate, they would demand a period of not less
than 680 millions.'

The argument that geological agencies acted much
more vigorously in past times he entirely refuted by
pointing to the character of the deposits of which the
stratified series is composed. 1 We can see no proof
whatever, nor even any evidence which suggests that on
the whole the rate of waste and sedimentation was more
rapid during Mesozoic and Palaeozoic time than it is
to-day. Had there been any marked difference in this

AGE OF THE STRATIFIED ROCKS 17

rate from ancient to modern times, it would be incredible
that no clear proof of it should have been recorded in the
crust of the earth.'

It may therefore be inferred that the rate of deposition
was no nearer the more rapid than the slower of the rates
recorded above, and, if so, the stratified rocks would have
been laid down in about 400 million years.

There are other arguments favouring the uniformity
of conditions throughout the time during which the
stratified rocks were laid down, in addition to those
which are purely geological and depend upon the cha-
racter of the rocks themselves. Although more biological
than geological, these arguments are best considered
here.

The geological agency to which attention is chiefly
directed by those who desire to hurry up the phenomena
of rock formation is that of the tides. But it seems
certain that the tides were not sufficiently higher in
Silurian times to prevent the deposition of certain beds
of great thickness under conditions as tranquil as any
of which we have evidence in the case of a formation
extending over a large area. From the character of the
organic remains it is known that these beds were laid
down in the sea, and there are the strongest grounds for
believing that they were accumulated along shores and
in fairly shallow water. The remains of extremely
delicate organisms are found in immense numbers, and
over a very large area. The recent discovery, in the
Silurian system of America, of trilobites, with their long
delicate antennae perfectly preserved, proves that in one
locality (Rome, New York State) the tranquillity of
deposition was quite as profound as in any locality yet
discovered on this side of the Atlantic.

There are, then, among the older Palaeozoic rocks
a set of deposits than which we can imagine none better
calculated to test the force of the tides ; and we find
that they supply evidence for exceptional tranquillity of
conditions over a long period of time.

There is other evidence of the permanence, through-
out the time during which the stratified rocks were

POL'LION Q

i§ THE AGE OF THE EARTH

deposited, of conditions not very dissimilar from those
which obtain to-day. Thus the attachments of marine
organisms, which are permanently rooted to the bottom
or on the shores, did not differ in strength from those
which we now find — an indication that the strains due to
the movements of the sea did not greatly differ in the
past.

We have evidence of a somewhat similar kind to prove
uniformity in the movements of the air. The expanse
of the wings of flying organisms certainly does not differ
in a direction which indicates any greater violence in the
atmospheric conditions. Before the birds had become
dominant among the larger flying organisms, their place
was taken by the flying reptiles, the pterodactyls, and
before the appearance of these we know that, in Palaeozoic
times, the insects were of immense size, a dragon-fly from
the Carboniferous rocks of France being upwards of
two feet in the expanse of its wings. As one group after
another of widely dissimilar organisms gained control of
the air, each was in turn enabled to increase to the size
which was best suited to such an environment, but we
find that the limits which obtain to-day were not widely
different in the past. And this is evidence for the
uniformity in the strains due to wind and storm no less
than to those due to gravity. Furthermore, the con-
dition of the earth's surface at present shows us how
extremely sensitive the flying organism is to an increase
in the former of these strains, when it occurs in proximity
to the sea. Thus it is well known that an unusually
large proportion of the Madeiran beetles are wingless,
while those which require the power of flight possess it
in a stronger degree than on continental areas. This
evolution in two directions is readily explained by the
destruction by drowning of the winged individuals of the
species which can manage to live without the power of
flight, and of the less strongly winged individuals of
those which need it. In the far more stormy, treeless
Kerguelen Land, the whole of the known insect fauna,
except two Diptera and probably a moth, is wingless.

The size and strength of the trunks of fossil trees afford,

UNIFORMITY OF CONDITIONS 19

as Professor George Darwin has pointed out, evidence
of uniformity in the strains due to the condition of the
atmosphere.

We can trace the prints of raindrops at various geo-
logical horizons, and in some cases found in this country
it is even said that the eastern side of the depressions is
the more deeply pitted, proving that the rain drove from
the west, as the great majority of our storms do to-day.

When, therefore, we -are accused of uniformitarianism,
as if it were an entirely unproved assumption, we can at
any rate point to a large body of positive evidence which
supports our contention, and the absence of any evidence
against it. Furthermore, the data on which we rely are
likely to increase largely, as the result of future work.

After this interpolation, chiefly of biological argument
in support of the geologist, I cannot do better than bring
the geological evidence to a close in the words which
conclude Sir Archibald Geikie's address : ' After careful
reflection on the subject, I affirm that the geological
record furnishes a mass of evidence which no arguments
drawn from other departments of Nature can explain
away, and which, it seems to me, cannot be satisfactorily
interpreted save with an allowance of time much beyond
the narrow limits which recent physical speculation would
concede.'

In his letter to Professor Perry,1 Lord Kelvin says: —
1 So far as underground heat alone is concerned, you
are quite right that my estimate was 100 million, and
please remark 2 that that is all Geikie wants ; but I should
be exceedingly frightened to meet him now with only
20 million in my mouth.'

We have seen, however, that Geikie considered the
rate of sedimentation to be, on the whole, uniform with
that which now obtains, and this would demand a period
of nearly 400 million years. He points out furthermore
that the time must be greatly increased on account of the
breaks and interruptions which occur in the series, so
that we shall probably get as near an estimate as is
possible from the data which are available by taking 450
1 Nature, Jan. 3, 1895. 2 P. L. and A., vol. ii. p. 87.

C 2

THE AGE OF THE EARTH

million years as the time during which the stratified rocks
were formed.

Before leaving this part of the subject, I cannot refrain
from suggesting a line of inquiry which may very possibly
furnish important data for checking the estimates at
present formed by geologists, and which, if the mechanical
difficulties can be overcome, is certain to lead to results
of the greatest interest and importance. Ever since the
epoch-making voyage of the Challenger, it has been known
that the floor of the deep oceans outside the shallow shelf
which fringes the continental areas is covered by a peculiar
deposit formed entirely of meteoric and volcanic dust,
the waste of floating pumice, and the hard parts of
animals living in the ocean. Of these latter only the
most resistant can escape the powerful solvent agencies.
Many observations prove that the accumulation of this
deposit is extremely slow. One indication of this is
especially convincing : the teeth of sharks and the most
resistant part of the skeleton — the ear-bones — of whales
are so thickly spread over the surface that they are con-
tinually brought up in the dredge, while sometimes a
single haul will yield a large number of them. Imagine
the countless generations of sharks and whales which
must have succeeded each other in order that these in-
significant portions of them should be so thickly spread
over that vast area which forms the ocean floor. We
have no reason to suppose that sharks and whales die
more frequently in the deep ocean than in the shallow
fringing seas ; in fact, many observations point in the
opposite direction, for wounded and dying whales often
enter shallow creeks and inlets, and not uncommonly
become stranded. And yet these remains of sharks and
whales, although well known in the stratified rocks which
were laid down in comparatively shallow water and near
coasts, are only found in certain beds, and then in far less
abundance than in the oceanic deposit. We can only
explain this difference by supposing that the latter ac-
cumulate with such almost infinite slowness as compared
with the continental deposits that these remains form an

THE FLOOR OF THE OCEAN

important and conspicuous constituent of the one, while
they are merely found here and there when looked for
embedded in the other. The rate of accumulation of all
other constituents is so slow as to leave a layer of teeth
and ear-bones uncovered, or covered by so thin a deposit
that the dredge can collect them freely. Sir John
Murray calculates that only a few inches of this deposit
have accumulated since the Tertiary Period. These
most interesting facts prove furthermore that the great
ocean basins and continental areas have occupied the
same relative positions since the formation of the first
stratified rocks ; for no oceanic deposits are found any-
where in the latter. We know the sources of the oceanic
deposit, and it might be possible to form an estimate,
within wide limits, of its rate of accumulation. If it were
possible to ascertain its thickness by means of a boring,
some conclusions as to the time which has elapsed during
the lifetime of certain species — perhaps even the lifetime
of the oceans themselves — might be arrived at. Lower
down the remains of earlier species would probably be
found. The depth of this deposit and its character at
deeper levels are questions of overwhelming interest ;
and perhaps even more so is the question as to what lies
beneath. Long before the Challenger had proved the
persistence of oceanic and continental areas, Darwin,
with extraordinary foresight, and opposed by all other
naturalists and geologists, including his revered teacher,
Lyell, had come to the same conclusion. His reasoning
on the subject is so convincing that it is remarkable that
he made so few converts, and this is all the more sur-
prising since the arguments were published in the Origin
of Species, which in other respects produced so profound
an effect. In speculating as to the rocks in which the
remains of the ancestors of the earliest known fossils may
still exist, he suggested that, although the existing relation-
ship between the positions of our present oceans and
continental areas is of immense antiquity, there is no
reason for the belief that it has persisted for an indefinite
period, but that at some time long antecedent to the
earliest known fossiliferous rocks 'continents may have

THE AGE OF THE EARTH

existed where oceans are now spread out ; and clear and
open oceans may have existed where our continents now
stand.' Not the least interesting result would be the
test of this hypothesis, which would probably be forth-
coming as the result of boring into the floor of a deep
ocean ; for although, as Darwin pointed out, it is likely
enough that such rocks would be highly metamorphosed,
yet it might still be possible to ascertain whether they
had at any time formed part of a continental deposit, and
perhaps to discover much more than this. Such an
undertaking might be carried out in conjunction with
other investigations of the highest interest, such as the
attempt to obtain a record of the swing of a pendulum
at the bottom of the ocean.

We now come to the strictly biological part of our
subject — to the inquiry as to how much of the whole
scheme of organic evolution has been worked out in the
time during which the fossiliferous rocks were formed,
and how far, therefore, the time required by the geologist
is sufficient.

It is first necessary to consider Lord Kelvin's sugges-
tion that life may have reached the earth on a meteorite —
a suggestion which might be made the basis of an attempt
to rescue us from the dilemma in which we were placed
by the insufficiency of time for evolution. It might be
argued that the evolution which took place elsewhere
may have been merely completed, in a comparatively
brief space of time, on our earth.

We know nothing of the origin of life here or elsewhere,
and our only attitude towards this or any other hypo-
thesis on the subject is that of the anxious inquirer for
some particle of evidence. But a few brief considerations
will show that no escape from the demands for time can
be gained in this way.

Our argument does not deal with the time required for
the origin of life, or for the development of the lowest
beings with which we are acquainted from the first formed
beings, of which we know nothing. Both these processes
may have required an immensity of time ; but as we know

THE METEORIC HYPOTHESIS

nothing whatever about them, and have as yet no pro-
spect of acquiring any information, we are compelled to
confine ourselves to as much of the process of evolution
as we can infer from the structure of living and fossil
forms — that is, as regards animals, to the development
ot the simplest into the most complex Protozoa, the
evolution of the Metazoa from the Protozoa, and the
branching of the former into its numerous Phyla, with
all their Classes, Orders, Families, Genera, and Species.
But we shall find that this is quite enough to necessitate a
very large increase in the time estimated by the geologist.

The Protozoa, simple and complex, still exist upon the
earth in countless species, together with the Metazoan
Phyla. Descendants of forms which in their day consti-
tuted the beginning of that scheme of evolution which
I have defined above, descendants, furthermore, of a large
proportion of those forms which, age after age, constituted
the shifting phases of its onward progress, still exist, and
in a sufficiently unmodified condition to enable us to recon-
struct, at any rate in mere outline, the history of the past.
Innumerable details and many phases of supreme impor-
tance are still hidden from us, some of them perhaps
never to be recovered. But this frank admission, and
the eager and premature attempts to expound too much,
to go further than the evidence permits, must not be
allowed to throw an undeserved suspicion upon conclusions
which are sound and well supported, upon the firm
conviction of every zoologist that the general trend of
evolution has been, as I have stated it, that each of the
Metazoan Phyla originated, directly or indirectly, in the
Protozoa.

The argument founded on the meteorite hypothesis
would, however, require that the process of evolution
went backward on a scale as vast as that on which it went
forward, that certain descendants of some central type,
coming to the earth on a meteorite, gradually lost their
Metazoan complexity and developed backward into the
Protozoa, throwing off the lower Metazoan Phyla on the
way, while certain other descendants evolved all the
higher Metazoan groups. Such a process would shorten

24 THE AGE OF THE EARTH

the period of evolution by half, but it need hardly be said
that all available evidence is entirely against it.

The only other assumption by means of which the
meteorite hypothesis might be used to shorten the time
is even more wild and improbable. Thus it might be
supposed that the evolution which we believe to have
taken place on this earth, really took place elsewhere — at
any rate as regards all its main lines — and that samples
of all the various phases, including the earliest and
simplest, reached us by a regular meteoric service, which
could only have attained to its culminating delivery at
some time after the completion of the scheme of organic
evolution. Hence the evidences which we study would
point to an evolution which occurred in some unknown
world with an age which even Professor Tait has no
desire to limit.

If these wild assumptions be rejected, there remains
the supposition that, if life was brought by a meteorite,
it was life no higher than that of the simplest Protozoon —
a supposition which leaves our argument intact. The
alternative supposition, that one or more of the Metazoan
Phyla were introduced in this way while the others were
evolved from the terrestrial Protozoa, is hardly worth
consideration. In the first place, some evidence of a part
in a common scheme of evolution is to be found in every
Phylum. In the second place, the gain would be small ;
the arbitrary assumption would only affect the evidence
of the time required for evolution derived from the
particular Phylum or Phyla of supposed meteoric origin.

The meteoric hypothesis, then, can only affect our
argument by making the most improbable assumptions,
for which, moreover, not a particle of evidence can be
brought forward.1

We are therefore free to follow the biological evidence
fearlessly. It is necessary, in the first place, to expand

1 The arguments here set forth are only intended to oppose certain
rash deductions which might be drawn from Lord Kelvin's meteoric
hypothesis. They are in no way opposed to the hypothesis itself; still
less do they imply that any such conclusions were ever reached by Lord
Kelvin.

ANIMAL CLASSIFICATION

somewhat the brief outline of the past history of the
animal kingdom, which has already been given. Since
the appearance of the Origin of Species, the zoologist, in
making his classifications, has attempted as far as possible
to set forth a genealogical arrangement. Our purpose
will be served by an account of the main outlines of
a recent classification, which has been framed with a due
consideration for all sides of zoological research, new
and old, and has met with general approval. Professor
Lankester divides the animal kingdom into two grades,
the higher of which, the Enterozoa (Metazoa), were
derived from the lower, the Plastidozoa (Protozoa). Each
of these grades is again divided into two sub-grades, and
each of these is again divided into Phyla, corresponding
more or less to the older Sub-Kingdoms. Beginning
from below, the most primitive animals in existence are
found in the seven Phyla of the lower Protozoan sub-
grade, the Gymnomyxa. Of these unfortunately only
two, the Reticulata (Foraminifera) and Radiolaria,
possess a structure which renders possible their preserva-
tion in the rocks. The lowest and simplest of these
Gymnomyxa represent the starting-point of that scheme
of organic evolution which we are considering to-day.
The higher order of Protozoan life, the sub-grade Corti-
cata, contains three Phyla, no one of which is available in
the fossil state. They are, however, of great interest
and importance to us as showing that the Protozoan type
assumes a far higher organization on its way to evolve
the more advanced grade of animal life. The first-formed
of these latter are contained in the two Phyla of the sub-
grade Coelentera, the Porifera or Sponges, and the
Nematophora or Corals, Sea-Anemones, Hydrozoa and
allied groups. Both of these Phyla are plentifully repre-
sented in the fossil state. It is considered certain that
the latter of these, the Nematophora, gave rise to the
higher sub-grade, the Coelomata, or animals with a coelom
or body-cavity surrounding the digestive tract. This
latter includes all the remaining species of animals in nine
Phyla, five of which are found fossil — the Echinoderma,
Gephyrea, Mollusca, Appendiculata, and Vertebrata.

26

THE AGE OF THE EARTH

Before proceeding further, I wish to lay emphasis on
the immense evolutionary history which must have been
passed through before the ancestor of one of the higher
of these nine Phyla came into being. Let us consider
one or two examples, since the establishment of this
position is of the utmost importance for our argument.
First, consider the past history of the Vertebrata, — of
the common ancestor of our Balanoglossus, Tunicates,
Amphioxus, Lampreys, Fishes, Dipnoi, Amphibia, Rep-
tiles, Birds, and Mammals. Although zoologists differ
very widely in their opinions as to the affinities of this
ancestral form, they all agree in maintaining that it did
not arise direct from the Nematophora in the lower sub-
grade of Metazoa, but that it was the product of a long-
history within the Coelomate sub-grade. The question
as to which of the other Coelomate Phyla it was associated
with will form the subject of one of our discussions at
this meeting, and I will, therefore, say no more upon this
period of its evolution, except to point out that the very
question itself, 1 the ancestry of Vertebrates,' only means
a relatively small part of the evolutionary history of the
Vertebrate ancestor within the Coelomate group. For
when we have decided the question of the other Coelo-
mate Phylum or Phyla to which the Vertebrate ancestor
belonged, there remains of course the history of that
Phylum or those Phyla earlier than the point at which
the Vertebrates diverged, right back to the origin of the
Coelomata ; while, beyond and below, the wide gulf
between this and the Coelentera had to be crossed, and
then, probably after a long history as a Coelenterate, the
widest and most significant of all the morphological
intervals — that between the lowest Metazoon and the
highest Protozoon — was traversed. But this was by no
means all. There remains the history within the higher
Protozoan sub-grade, in the interval from this to the
lower, and within the lower sub-grade itself, until we
finally retrace our steps to the lowest and simplest forms.
It is impossible to suppose that all this history of change
can have been otherwise than immensely prolonged ; for
it will be shown below that all the available evidence

EVOLUTION OF ANCESTRAL FORMS 27

warrants the belief that the changes during these earlier
phases were at least as slow as those which occurred
later.

If we take the history of another of the higher Phyla,
the Appendiculata, we find that the evidence points in
the same direction. The common ancestor of our Roti-
fera, earthworms, leeches, Peripatus, centipedes, insects,
Crustacea, spiders and scorpions, and forms allied to all
these, is generally admitted to have been Chaetopod-
like, and probably arose in relation to the beginnings
of certain other Coelomate Phyla, such as the Gephyrea
and perhaps Mollusca. At the origin of the Coelomate
sub-grade the common ancestor of all Coelomate Phyla
is reached, and its evolution has been already traced in
the case of the Vertebrata.

What is likely to be the relation between the time
required for the evolution of the ancestor of a Coelomate
Phylum and that required for the evolution, which sub-
sequently occurred, within the Phylum itself ? The only
indication of an answer to this question is to be found
in a study of the rate of evolution in the lower parts of
the animal kingdom as compared with that in the higher.
Contrary, perhaps, to anticipation, we find that all the
evidences of rapid evolution are confined to the most
advanced of the smaller groups within the highest Phyla,
and especially to the higher Classes of the Vertebrata.
Such evidence as we have strongly indicates the most
remarkable persistence of the lower animal types. Thus
in the Class Imperforata of the Reticulata (Foramini-
fera) one of our existing genera (Saccamina) occurs in
the Carboniferous strata, another (Trochammina) in the
Permian, while a single new genus (Receptaculites) occurs
in the Silurian and Devonian. The evidence from the
Class Perforata is much stronger, the existing genera
Nodosaria, Dentalina, Textularia, Grammostomum, Val-
vulina, and Nummulina all occurring in the Carboni-
ferous, together with the new genera Archaediscus (?) and
Fusilina.

I omit reference to the much-disputed Eozoon from
the Laurentian rocks, far below the horizon which for

28

THE AGE OF THE EARTH

the purpose of this address I am considering as the
lowest fossiliferous stratum. We are looking forward
to the new light which will be thrown upon this form in
the communication of its veteran defender, Sir William
Dawson, whom we are all glad to welcome.

Passing by the Radiolaria, with delicate skeletons less
suited for fossilization, and largely pelagic and therefore
less likely to reach the strata laid down along the fringes
of the continental areas, the next Phylum which is found
in a fossil state is that of the Porifera, including the
sponges, and divided into two Classes, the Calcispongiae
and Silicospongiae. Although the fossilization of sponges
is in many cases very incomplete, distinctly recognizable
traces can be made out in a large number of strata.
From these we know that representatives of all the
groups of both Classes (except the Halisarcidae, which
have no hard parts) occurred in the Silurian, Devonian,
and Carboniferous systems. The whole Phylum is an
example of long persistence with extremely little change.
And the same is true of the Nematophora : new groups
indeed come in, sometimes extremely rich in species, such
as the Palaeozoic Rugose corals and Graptolites ; but
they existed side by side with representatives of existing
groups, and they are not in themselves primitive or an-
cestral. A study of the immensely numerous fossil corals
reveals no advance in 'organization, while researches into
the structure of existing Alcyonaria and Hydrocorallina
have led to the interpretation of certain Palaeozoic forms
which were previously obscure, and the conclusion that
they find their place close beside the living species.

All available evidence points to the extreme slowness
of progressive evolutionary changes in the Coelenterate
Phyla, although the Protozoa, if we may judge by the
Reticularia (Foraminifera), are even more conservative.

When we consider later on the five Coelomate Phyla
which occur fossil, we shall find that the progressive
changes were slower and indeed hardly appreciable in
the two lower and less complex Phyla, viz., the Echino-
derma, and Gephyrea, as compared with the Mollusca,
Appendiculata, and Vertebrata.

SLOW EVOLUTION IN LOWER PHYLA 29

Within these latter Phyla we have evidence for the
evolution of higher groups presenting a more or less
marked advance in organization. And not only is the
rate of development more rapid in the highest Phyla of
the animal kingdom, but it appears to be most rapid
when dealing with the highest animal tissue, the central
nervous system. The chief, and doubtless the most sig-
nificant, difference between the early Tertiary mammals
and those which succeeded them, between the Secondary
and Tertiary reptiles, between man and the mammals
most nearly allied to him, is a difference in the size of
the brain. In all these cases an enormous increase in
this, the dominant tissue of the body, has taken place
in a time which, geologically speaking, is very brief.

When glancing later on over the evolution which has
taken place within the Phyla, further details upon this
subject will be given, although in this as in other cases
the time at our disposal demands that the exposition of
evidence must largely yield to an exposition of the con-
clusions which follow from its study. And undoubtedly
a study of all the available evidence points to the con-
clusion that in the lower grade, sub-grades, and Phyla of
the animal kingdom evolution has been extremely slow
as compared with that in the higher. We do not know
the reason. It may be that this remarkable persistence
through the stratified series of deposits is due to an in-
nate fixity of constitution which has rigidly limited the
power of variation ; or, more probably perhaps, that the
lower members of the animal kingdom were, as they are
now, more closely confined to particular environments,
with particular sets of conditions, with which they had to
cope, and, this being successfully accomplished, Natural
Selection has done little more than keep up a standard of
organization which was sufficient for their needs ; while
the higher and more aggressive forms ranging over many
environments, and always prone to encounter new sets of
conditions, were compelled to undergo responsive changes
or to succumb. But whatever be the cause, the fact
remains, and is of importance for our argument. When
the ancestor of one of the higher Phyla was associated

30

THE AGE OF THE EARTH

with the lower Phyla of the Coelomate sub-grade, when
further back it passed through a Coelenterate, a higher
Protozoan, and finally a lower Protozoan phase, we are
led to believe that its evolution was probably very slow
as compared with the rate which it subsequently attained.
But this conclusion is of the utmost importance ; for the
history contained in the stratified rocks nowhere reveals
to us the origin of a Phylum. And this is not mere
negative evidence, but positive evidence of the most
unmistakable character. All the five Coelomate Phyla
which occur fossil appear low down in the Palaeozoic
rocks, in the Silurian or Cambrian strata, and they are
represented by forms which are very far from being
primitive, or, if primitive, are persistent types, such as
Chiton, which are now living. Thus Vertebrata are
represented by fishes, both sharks and ganoids ; the
Appendiculata by cockroaches, scorpions, Limulids, Tri-
lobites, and many Crustacea; the Mollusca by Nautilus and
numerous allied genera, by Dentalium, Chiton, Pteropods,
and many Gastropods and Lamellibranchs; the Gephyrea
by very numerous Brachiopods, and many Polyzoa ; the
Echinoderma by Crinoids, Cystoids, Blastoids, Asteroids,
Ophiuroids, and Echinoids. It is just conceivable, al-
though, as I believe, most improbable, that the Vertebrate
Phylum originated at the time when the earliest known
fossiliferous rocks were laid down. It must be remem-
bered, however, that an enormous morphological interval
separates the fishes which appear in the Silurian strata
from the lower branches, grades, and classes of the Phylum
in which Balanoglossus, the Ascidians, Amphioxus, and
the Lampreys are placed. The earliest Vertebrates to
appear are, in fact, very advanced members of the Phylum,
and, from the point of view of anatomy, much nearer to
man than to Amphioxus. If, however, we grant the im-
probable contention that so highly organized an animal
as a shark could be evolved from the ancestral vertebrate
in the period which intervened between the earliest Cam-
brian strata and the Upper Silurian, it is quite impossible
to urge the same with regard to the other Phyla. It has
been shown above that when these appear in the Cam-

EARLIEST FORMS OF HIGHER PHYLA 31

brian and Silurian, they are flourishing in full force, while
their numerous specialized forms are a positive proof of
a long antecedent history within the limits of the Phylum.

If, however, we assume for the moment that the
Phyla began in the Cambrian, the geologist's estimate
must still be increased considerably, and perhaps
doubled, in order to account for the evolution of
the higher Phyla from forms as low as many which
are now known upon the earth ; unless, indeed, it is
supposed, against the weight of all such evidence as
is available, that the evolutionary history in these early
times was comparatively rapid.

To recapitulate, if we represent the history of animal
evolution by the form of a tree, we find that the follow-
ing growth took place in some age antecedent to the
earliest fossil records, before the establishment of the
higher Phyla of the Animal Kingdom. The main
trunk representing the lower Protozoa divided, originating
the higher Protozoa ; the latter portion again divided,
probably in a threefold manner, originating the two
lowest Metazoan Phyla, constituting the Coelentera.
The branch representing the higher of these Phyla,
the Nematophora, divided, originating the lower Coelo-
mate Phyla, which again branched and originated the
higher Phyla. And, as has been shown above, the
relatively ancestral line, at every stage of this complex
history, after originating some higher line, itself con-
tinued down to the present day, throughout the whole
series of fossiliferous rocks, with but little change in
its general characters, and practically nothing in the
way of progressive evolution. Evidences of marked
advance are to be found alone in the most advanced
groups of the latest highest products — the Phyla formed
by the last of these divisions.

It may be asked how is it possible for the zoologist
to feel so confident as to the past history of the various
animal groups. I have already explained that he does
not feel this confidence as regards the details of the
history, but as to its general lines. The evidence which

32 THE AGE OF THE EARTH

leads to this conviction is based upon the fact that animal
structure and mode of development can be, and have
been, handed down from generation to generation from
a period far more remote than that which is represented
by the earliest fossils ; that fundamental facts in structure
and development may remain changeless amid endless
changes of a more general character; that especially
favourable conditions have preserved ancestral forms
comparatively unchanged. Working upon this material,
comparative anatomy and embryology can reconstruct
for us the general aspects of a history which took place
long before the Cambrian rocks were deposited. This
line of reasoning may appear very speculative and un-
sound, and it may easily become so when pressed too
far. But applied with due caution and reserve, it may
be trusted to supply us with an immense amount of
valuable information which cannot be obtained in any
other way. Furthermore, it is capable of standing the
very true and searching test supplied by the verification
of predictions made on its authority. Many facts taken
together lead the zoologist to believe that A was
descended from C through B ; but if this be true, B
should possess certain characters which are not known
to belong to it. Under the inspiration of hypothesis
a more searching investigation is made, and the charac-
ters are found. Again, that relatively small amount
of the whole scheme of animal evolution which is con-
tained in the fossiliferous rocks has furnished abundant
confirmation of the validity of the zoologists method.
The comparative anatomy of the higher Vertebrate
Classes leads the zoologist to believe that the toothless
beak and the fused caudal vertebrae of a bird were not
ancestral characters, but were at some time derived from
a condition more conformable to the general plan of
vertebrate construction, and especially to that of reptiles.
Numerous secondary fossils prove to us that the birds
of that time possessed teeth and separate caudal vertebrae,
culminating in the long lizard-like tail of Archaeopteryx.

Prediction and confirmation of this kind, both zoo-
logical and palaeontological, have been going on ever

EVOLUTION WITHIN HIGHER PHYLA 33

since the historic point of view was adopted by the
naturalist as the outcome of Darwin's teaching, and
the zoologist may safely claim that his method, confirmed
by palaeontology so far as evidence is available, may
be extended beyond the period in which such evidence
is to be found.

And now our last endeavour must be to obtain some
conception of the amount of evolution which has taken
place within the higher Phyla of the Animal Kingdom
during the period in which the fossiliferous rocks were
deposited. The evidence must necessarily be considered
very briefly, and we shall be compelled to omit the
Vertebrata altogether.

The Phylum Appendiculata is divided by Lankester
into three branches, the first containing the Rotifera,
the second the Chaetopoda, the third the Arthropoda.
Of these the second is the oldest, and gave rise to the
other two, or at any rate to the Arthropoda, with which
we are alone concerned, inasmuch as the fossil records
of the others are insufficient. The Arthropoda contain
seven Classes, divided into two grades, according to the
presence or absence of antennae1 — the Ceratophora, con-
taining the Peripatoidea, the Myriapoda, and the Hexa-
poda (or insects) ; the Acerata, containing the Crustacea,
Arachnida, and two other classes (the Pantopoda and
Tardigrada) which we need not consider. The first
Class of the antenna-bearing group contains the single
genus Peripatus — one of the most interesting and ancestral
of animals, as proved by its structure and development,
and by its immense geographical range. Ever since the
researches of Moseley and Balfour, extended more re-
cently by those of Sedgwick, it has been recognized
as one of the most beautiful of the connecting links
to be found amongst animals, uniting the antenna-bearing
Arthropods, of which it is the oldest member, with the
Chaetopods. Peripatus is a magnificent example of the
far-reaching conclusions of zoology, and of its superiority

1 The so-called antennae of Crustacea are developed very differently
from true antennae.

POLLTON D

34 THE AGE OF THE EARTH

to palaeontology as a guide in unravelling the tangled
history of animal evolution. Peripatus is alive to-day,
and can be studied in all the details of its structure
and development ; it is infinitely more ancestral, and
tells of a far more remote past than any fossil Arthropod,
although such fossils are well known in all the older
of the Palaeozoic rocks. And yet Peripatus is not
known as a fossil. Peripatus has come down, with
but little change, from a time, on a moderate estimate,
at least twice as remote, and probably many times as
remote, as the earliest known Cambrian fossil. The
agencies which, it is believed, have crushed and heated
the Archaean rocks so as to obliterate the traces of
life which they contained were powerless to efface this
ancient type, for, although the passing generations may
have escaped record, the likeness of each was stamped
on that which succeeded it, and has continued down
to the present day. It is, of course, a perfectly trite
and obvious conclusion but not the less one to be
wondered at, that the force of heredity should thus far
outlast the ebb and flow of terrestrial change throughout
the vast period over which the geologist is our guide.

If, however, the older Palaeozoic rocks tell us nothing
of the origin of the antenna-bearing Arthropods, what do
they tell us of the history of the Myriapod and Hexapod
Classes ?

The Myriapods are well represented in Palaeozoic
strata, two species being found in the Devonian and no
less than thirty-two in the Carboniferous. Although
placed in an Order (Archipolypoda) separate from those
of living Myriapods, these species are by no means
primitive, and do not supply any information as to the
steps by which the Class arose. The imperfection of
the record is well seen in the traces of this Class ; for
between the Carboniferous rocks and the Oligocene
there are no remains of undoubted Myriapods.

We now come to the consideration of insects, of which
an adequate discussion would occupy a great deal too
much of your time. An immense number of species
are found in the Palaeozoic rocks, and these are con-

THE INSECTS OF THE COAL

sidered by Scudder, the great authority on fossil insects,
to form an Order, the Palaeodictyoptera, distinct from
any of the existing Orders. The latter, he believes,
were evolved from the former in Mesozoic times. These
views do not appear to derive support from the wonder-
ful discoveries of M. Brongniart1 in the Upper Carboni-
ferous of Commentry in the Department of Allier in
Central France. Concerning this marvellous assemblage
of species, arranged by their discoverer into 46 genera
and 10 1 species, Scudder truly says : —

' Our knowledge of Palaeozoic insects will have been
increased three or four fold at a single stroke. . . . No
former contribution in this field can in any way compare
with it, nor even all former contributions taken together \2

When we remember that the group of fossil insects, of
which so much can be affirmed by so great an authority
as Scudder, lived at one time and in a single locality, we
cannot escape the conclusion that the insect fauna of the
habitable earth during the whole Palaeozoic period was
of immense importance and variety. Our knowledge of
this single group of species is largely due to the accident
that coal-mining in Commentry is carried on in the open air.

Now, these abundant remains of insects, so far from
upholding the view that the existing orders had not been
developed in Palaeozoic times, are all arranged by
Brongniart in four out of the nine Orders into which
insects are usually divided, viz. the Orthoptera, Neuro-
ptera, Thysanoptera, and Homoptera. The importance
of the discovery is well seen in the Neuroptera, the
whole known Palaeozoic fauna of this Order being
divided into 45 genera and 99 species, of which 33 and
72 respectively have been found at Commentry.

Although the Carboniferous insects of Commentry
are placed in new families, some of them come wonder-
fully near those into which existing insects are classified,
and obviously form the precursors of these. This is true

1 Charles Brongniart. — Recherches ponrf servir a Thistoire des insectes
fossiles des temps primaires, pre'cede'es d'une Etude sur la nervation des ailes

des insectes. 1894.

2 S. H. Scudder, Am. Jour n. Sci.t vol. xlvii, February, 1894. Art. viii.

D 2

36 THE AGE OF THE EARTH

of the Blattidae, Phasmidae, Acridiidae, and Locustidae
among the Orthoptera, the Perlidae among the Neuro-
ptera, and the Fulgoridae among the Homoptera.
The differences which separate these existing families
from their Carboniferous ancestors are most interesting
and instructive. Thus the Carboniferous cockroaches
possessed ovipositors, and probably laid their eggs one
at a time, while ours are either viviparous or lay their
eggs in a capsule. The Protophasmidae resemble living
species in the form of the head, antennae, legs, and
body ; but while our species are either wingless or, with
the exception of the female Phyllidae, have the anterior
pair reduced to tegmina, useless for flight, those of
Palaeozoic times possessed four well-developed wings.
The forms representing locusts and grasshoppers (Palae-
acridiidae) possessed long slender antennae like the green
grasshoppers (Locustidae), from which the Acridiidae
are now distinguished by their short antennae. The
divergence and specialization which is thus shown is
amazingly small in amount. In the vast period between
the Upper Carboniferous rocks and the present day the
cockroaches have gained a rather different wing venation,
and have succeeded in laying their eggs in a manner
rather more specialized than that of insects in general ;
the stick insects and leaf insects have lost or reduced
their wings, the grasshoppers have shortened their
antennae. These, however, are the insects which most
closely resemble the existing species ; let us turn to the
forms which exhibit the greatest differences. Many
species have retained in the adult state characters which
are now confined to the larval stage of existence, such as
the presence of tracheal gills on the sides of the abdomen.
In some, the two membranes of the wing were not
firmly fixed together, so that the blood could circulate
freely between them. On the other hand, they are not
very firmly fixed together in existing insects. Another
important point was the condition of the three thoracic
segments, which were quite distinct and separate, instead
of being fused as they are now in the imago stage.
This external difference probably also extended to the

THE INSECTS OF THE COAL

37

nervous system, so that the thoracic ganglia were
separate instead of concentrated. The most interesting
distinction, however, was the possession by many species
of a pair of prothoracic appendages much resembling
miniature wings, and which especially suggest the appear-
ance assumed by the anterior pair (tegmina) in existing
Phasmidae. There is some evidence in favour of the view
that they were articulated, and they exhibit what appears
to be a trace of venation. Brongniart concludes that
in still earlier strata, insects with six wings will be
discovered, or rather insects with six of the tracheal
gills sufficiently developed to serve as parachutes. Of
these, the two posterior pair developed into the wings
as we know them, while the anterior pair degenerated,
some of the Carboniferous insects presenting us with
a stage in which degeneration had taken place but was
not complete.

One very important character was, as I have already
pointed out, the enormous size reached by insects in
this distant period. This was true of the whole known
fauna as compared with existing species, but it was
especially the case with the Protodonata, some of these
giant dragon-flies measuring over two feet in the expanse
of the wings.

As regards the habits of life and metamorphoses,
Brongniart concludes that some species of Protoephe-
meridae, Protoperlidae, &c, obtained their food in an
aquatic larval stage, and did not require it when mature.
He concludes that the Protodonata fed on other animals,
like our dragon-flies ; that the Palaeacridiidae were
herbivorous like our locusts and grasshoppers, the
Protolocustidae herbivorous and animal feeders like our
green grasshoppers, the Palaeoblattidae omnivorous
like our cockroaches. The Homoptera, too, had elon-
gated sucking mouth-parts like the existing species. It
is known that in Carboniferous times there was a lake
with rivers entering it, at Commentry. From their great
resemblance to living forms of known habits, it is
probable that the majority of these insects lived near
the water and their larvae in it.

38 THE AGE OF THE EARTH

When we look at this most important piece of research
as a whole, we cannot fail to be struck with the small
advance in insect structure which has taken place since
Carboniferous times. All the great questions of meta-
morphosis, and of the structures peculiar to insects,
appear to have been very much in the position in which
they are to-day. It is indeed probable enough that the
Orders which zoologists have always recognized as com-
paratively modern and specialized, such as the Lepido-
ptera, Coleoptera, and Hymenoptera, had not come into
existence. But as regards the emergence of the Class
from a single primitive group, as regards its approxima-
tion towards the Myriapods, which lived at the same
time, and of both towards their ancestor Peripatus, we
learn absolutely nothing. All we can say is that there
is evidence for the evolution of the most modern and
specialized members of the Class, and some slight pro-
gressive evolution in the rest. Such evolution is of
importance as giving us some vague conception of the
rate at which the process travels in this division of the
Arthropoda. If we look upon development as a series
of paths which, by successively uniting, at length meet
in a common point, then some conception of the position
of that distant centre may be gained by measuring the
angle of divergence and finding the number of unions
which occur in a given length. In this case, the amount
of approximation and union shown in the interval between
the Carboniferous Period and the present day is relatively
so small that it would require to be multiplied many
times before we could expect the lines to meet in the
common point, the ancestor of insects, to say nothing
of the far more distant past, in which the Tracheate
Arthropods met in an ancestor presenting many resem-
blances to Peripatus. But it must not be forgotten that
all this vast undefined period is required for the history
of one of the two grades of one of the three branches of
the whole Phylum.

Turning now to the brief consideration of the second
grade of Arthropods, distinguished from the first grade
by the absence of antennae, the Trilobites are probably

THE EARLIEST CRUSTACEA 39

the nearest approach to an ancestral form met with in
the fossil state. Now that the possession of true
antennae is certain, it is reasonable to suppose that
the Trilobites represent an early Class of the Aceratous
branch which had not yet become Aceratous. They
are thus of the deepest interest in helping us to under-
stand the origin of the antennaless branch, not by the
ancestral absence, but by the loss of true antennae which
formerly existed in the group. But the Trilobites did
not themselves originate the other Classes, at any rate
during Palaeozoic times. They represent a large and
dominant Class, presenting more of the characters of
the common ancestor than the other Classes ; but the
latter had diverged and had become distinct long before
the earliest fossiliferous rocks ; for we find well-marked
representatives of the Crustacea in Cambrian, and of
the Arachnida in Silurian strata. The Trilobites, more-
over, appear in the Cambrian with many distinct and
very different forms, contained in upwards of forty genera,
so that we are clearly very far from the origin of the
group.

Of the lower group of Crustacea, the Entomostraca,
the Cirripedes are represented by two genera in the
Silurian, the Ostracodes by four genera in the Cambrian
and over twenty in the Silurian ; of these latter, two
genera (Cythere and Bairdia) continue right through
the fossiliferous series and exist at the present day.
Remains of Phyllopods are more scanty, but can be
traced in the Devonian and Carboniferous rocks. The
early appearance of the Cirripedes is of especial interest,
inasmuch as the fixed condition of these forms in the
mature state is certainly not primitive, and yet, never-
theless, appears in the earliest representatives.

The higher group, the Malacostraca, are represented
by many genera of Phyllocarida in the Silurian and
Devonian, and two in the Cambrian. These also afford
a good example of the imperfection of the record, inas-
much as no traces of the group are to be found between
the Carboniferous and our existing fauna in which it
is represented by the genus Nebalia. The Phyllocarida

4Q

THE AGE OF THE EARTH

are recognized as the ancestors of the higher Malaco-
straca, and yet these latter already existed — in small
numbers, it is true — side by side with the Phyllocarida
in the Devonian. The evolution of the one into the
other must have been much earlier. Here, as in the
Arthropoda, we have evidence of progressive evolution
among the highest groups of the Class, as we see in
the comparatively late development of the Brachyura
as compared with the Macrura. We find no trace of
the origin of the Class, or of the larger groups into
which it is divided, or, indeed, of the older among the
small groupings into families and genera.1

Of the Arachnida, although some of the most won-
derful examples of persistent types are to be found in
this class, but little can be said. Merely to state the
bare fact that three kinds of scorpion are found in the
Silurian, two Pedipalpi, eight scorpions, and two spiders
in the Carboniferous, is sufficient to show that the period
computed by geologists must be immensely extended
to account for the development of this Class alone,
inasmuch as it existed in a highly specialized condition
almost at the beginning of the fossiliferous series ; while,
as regards so extraordinarily complex an animal as a
scorpion, nothing apparent in the way of progressive
development has happened since. Professor Lankester
has, however, pointed out to me that the Silurian scorpion
Palaeophonus possessed heavier limbs than those of
existing species, and this is a point in favour of an
aquatic life like that of its near relation, Limulus. If
so, it is probable that it possessed external gills, not
yet introverted to form the lung-book. The Merostomata
are of course a Palaeozoic group, and reach their highest
known development at their first appearance in the
Silurian ; since then they have done nothing but dis-
appear gradually, leaving the single genus Limulus,
unmodified since its first appearance in the Trias, to
represent them. It is impossible to find clearer evidence

1 For an account of the evolution of the Crustacea see the Presidential
Addresses to the Geological Society in 1895 and 1896 by Dr. Henry
Woodward.

THE EARLIEST ARACHNIDA 41

of the decline rather than the rise of a group. No
progressive development, but a gradual or rapid ex-
tinction, and consequent reduction in the number of
genera and species, is a summary of the record of the
fossiliferous rocks as regards this group and many others,
such as the Trilobites, the Brachiopods, and the Nautili-
dae. All these groups begin with many forms in the
oldest fossiliferous rocks, and three of them have left
genera practically unchanged from their first appearance
to the present day. What must have been the time
required to carry through the vast amount of structural
change implied in the origin of these persistent types
and the groups to which they belong — a period so ex-
tended that the interval between the oldest Palaeozoic
rocks and the present day supplies no measurable
unit ?

But I am digressing from the Appendiculate Phylum.
We have seen that the fossil record is unusually com-
plete as regards two Classes in each grade of the
Arthropod branch, but that these Classes were well
developed and flourishing in Palaeozoic times. The
only evidence of progressive evolution is in the develop-
ment of the highest orders and families of the Classes.
Of the origin of the Classes nothing is told, and we
can hardly escape the conclusion that for the development
of the Arthropod branches from a common Chaetopod-
like ancestor, and for the further development of the
Classes of each branch, a period many times the length
of the fossiliferous series is required, judging from the
insignificant amount of development which has taken
place during the formation of this series.

It is impossible to consider the other Coelomate Phyla
as I have done the Appendiculata. I can only briefly
state the conclusions to which we are led.

As regards the Molluscan Phylum, the evidence is
perhaps even stronger than in the Appendiculata. Re-
presentatives of the whole of the Classes are, it is
believed, found in the Cambrian or Lower Silurian.
The Pteropods are generally admitted to be a recent
modification of the Gastropods, and yet, if the fossils

42 THE AGE OF THE EARTH

described in the genera Conularia, Hyolithes, Pterotheca,
&c., are true Pteropods, as they are supposed to be,
they occur in the Cambrian and Silurian strata, while
the group of Gastropods from which they almost certainly
arose, the Bullidae, are not known before the Trias.
Furthermore, the forms which are clearly the oldest
of the Pteropods — Limacina and Spinalis — are not
known before the beginning of the Tertiary Period.
Either there is a mistake in the identification of the
Palaeozoic fossils at Pteropods, or the record is even
more incomplete than usual, and the most specialized
of all Molluscan groups had been formed before the
date of the earliest fossiliferous rocks. Even if this
should hereafter be disproved, there can be no doubt
about the early appearance of the Molluscan Classes,
and that it is the irony of an incomplete record which
places the Cephalopods and Gastropods in the Cambrian
and the far more ancestral Chiton no lower than the
Silurian. Throughout the fossiliferous series the older
families of Gastropods and Lamellibranchs are followed
by numerous other families, which were doubtless derived
from them ; new and higher groups of Cephalopods were
developed, and, with the older groups, either persisted
until the present time or became extinct. But in all
this splitting up of the Classes into groups of not widely
different morphological value, there is very little pro-
gressive modification, and, taking such changes in such
a period as our unit for the determination of the time
which was necessary for the origin of the Classes from
a form like Chiton, we are led to the same conclusion
as that which followed from the consideration of the
Appendiculata, viz. that the fossiliferous series would
have to be multiplied several times in order to pro-
vide it.

Of the Phylum Gephyrea, I will only mention the
Brachiopods, which are found in immense profusion in
the early Palaeozoic rocks and have occupied the sub-
sequent time in becoming less dominant and important.
So far from helping us to clear up the mystery which
surrounds the origin of the Class, the earliest forms are

MOLLUSCA AND ECHINODERMA 43

quite as specialized as those living now, and, some of
them (Lingula, Discina), even generically identical. The
demand for time to originate the group is quite as grasp-
ing as that of the others we have been considering.

All the Classes of Echinoderma, except the Holo-
thurians, which do not possess a structure favourable for
fossilization, are found early in the Palaeozoic rocks, and
many of them in the Cambrian. Although these early
forms are very different from those which succeeded them
in the later geological periods, they do not possess a
structure which can be recognized as in any way primitive
or ancestral. The Echinoderma are the most distinct
and separate of all the Coelomate Phyla, and they were
apparently equally distinct and separate at the beginning
of the fossiliferous series.

In concluding this imperfect attempt to deal with a
very vast subject in a very short time, I will remind you
that we were led to conclude that the evolution of the
ancestor of each of the higher animal Phyla probably
occupied a very long period, perhaps as long as that
required for the evolution which subsequently occurred
within the Phylum. But the consideration of the higher
Phyla which occur fossil, except the Vertebrata, leads to
the irresistible conclusion that the whole period in which
the fossiliferous rocks were laid clown must be multiplied
several times for this later history alone. The period
thus obtained requires to be again increased, and perhaps
doubled, for the earlier history.

In the preparation of the latter part of this address
I have largely consulted Zittel's great work. I wish also
to express my thanks to my friend Professor Lankester,
whom I have consulted on many of the details, as well as
the general plan which has been adopted.

If the facts and arguments set forth in the address to
which you have done me the honour of listening be
sound, the naturalist need not fear for the result of this
attack upon the great theory which has been a light to
his path for nearly half a century. Natural Selection will
never be stifled in the Procrustean bed of insufficient
geological time.

THE AGE OF THE EARTH

Note. — At the time when this address was delivered
I felt keenly the gap left in the argument by the absence
of any statement concerning the evolution of land-plants.
Since 1896 an immense amount of labour has been ex-
pended upon fossil floras, and startling conclusions as to
the affinities of certain groups have been placed on a
solid foundation. Now, after the lapse of ten years, it is
far more possible than it was in 1896 to compare safely
the evidence yielded by fossil plants with that of fossil
animals. Allowing for the important difference in the
length of the records — animals appearing in full force in
the Cambrian, plants only in the Devonian — the two lines
of evidence support precisely the same conclusion.

Professor A. C. Seward, F.R.S., in his Presidential
Address to Section K (Botany) of the meeting of the
British Association at South port, in 1903, took as his
subject Floras of the Past : their Composition and
Distribution. He speaks of the Devonian and Lower
Carboniferous plants as 1 practically the oldest records of
plant-life and states that they ' lead us away from the
present along converging lines of evolution to a remote
stage in the history of life': the distribution of their fossil
remains over the globe ' shows how widely some of the
plants had migrated from an unknown centre far back in
a still more remote age. We are, as yet, unable to
follow these Devonian plants to an earlier stage in their
evolution. We are left in amazement at their specialized
structure and extended geographical distribution, without
the means of perusing the opening chapters of their
history \ 1

During the present year my friend Dr. D. H. Scott,
F.R.S., has published a valuable and comprehensive
memoir on The Present Position of Palaeozoic Botany?
setting forth the results of modern researches upon the
structure and evolution of fossil plants.

Dr. Scott has most kindly provided me with the fol-
lowing concise summary of the history of plant evolution
as set forth in the fossil record at present known to us: —

1 Report, 1903, p. 831.

2 Progressus Rei Botanicae, Jena, 1906, pp. 139-217.

THE EARLIEST LAND-PLANTS 45

1 Of the main divisions of the Vegetable Kingdom the
Angiosperms alone appear to originate within the periods
of which we have any adequate fossil record. They do
not appear, as at present known, until late in the Mesozoic.
Some affinity between them and the much more ancient
Cycadophyta is indicated by the latest work.

1 The other seed-plants go back certainly to the
Devonian — we do not know how much further. During
Palaeozoic times there was a great group of seed-plants —
the Pteridospermeae — of a relatively primitive type,
showing affinity with Ferns. Most of the so-called
Palaeozoic " Ferns " were really seed-bearing plants of
this kind.

1 But, side by side with them, and going back equally
far according to present records, there were the Cor-
daiteae, a well characterized family of Gymnosperms com-
parable in many respects to the Coniferae.

' Hence the evolution of seed-plants had already reached
a very advanced stage at the period to which our earliest
satisfactory records of land-plants belong.

* It is thus only a very small fraction of the whole
course of plant-evolution which is revealed in the fossil
record.'

II

'WHAT IS A SPECIES?'

The Presidential Address read at the Annual Meeiing of the Entomo-
logical Society of London, January 20, 1904. Reprinted from the
Proceedings of the Society, 1903, p. lxxvii.

Revised and modified: several paragraphs added and several rewritten :
additional footnotes.

The late Professor Max Muller, in an eloquent speech
delivered at Reading in 1891, spoke of the necessity
of examining, and, as time passes by, re-examining the
meaning of words. He referred as an illustration to the
man at the railway station who taps the wheels with his
hammer, testing whether each still rings true or has
undergone some change that may mean disaster. In
almost the same way, the speaker maintained, a word
may slowly and unobtrusively change its meaning, be-
coming, unless critically tested to ascertain whether it
still rings true, a danger instead of an aid to clear think-
ing, a pitfall on the field of controversy. He then went
on to say, that Darwin had written a great work upon
the Origin of Species, and had never once explained
what he meant by the word Species. So decided an
utterance — the statement was made emphatically — ought
to have involved a careful and critical search through the
pages of the work that was attacked. However this
may be, it is quite certain that the search was unsuccess-
ful ; and yet a few minutes' investigation brought me
to a passage in which the meaning attached by the author
to the term Species is set down in the clear, calm, and
simple language which did so much to convince an
unwilling world.

Darwin is speaking of the revolution which the accept-
ance of his views will bring about. ' 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 in essence a species. This
I feel sure, and I speak after experience, will be no slight

DARWIN'S ACCOUNT OF SPECIES: 1859 47

relief. The endless disputes whether or not some fifty
species of British brambles are true species will cease.
Systematists will have only to decide {not that this will be
easy) whether any form be sufficiently constant and dis-
tinct from other forms, to be capable of definition ; and
if definable, whether the differences be sufficiently important
to deserve a specific name. This latter point will become
a far more essential consideration than it is at present ;
for differences, however slight, between any two forms,
if not blended by intermediate gradations, are looked
at by most naturalists as sufficient to raise both forms to
the rank of species. Hereafter zve shall be compelled
to acknowledge that the only distinction between species and
well-marked varieties is, that the latter are known, or
believed, to be connected at the present day by intermediate
gradations, whereas species were formerly thus connected.
Hence, without quite rejecting the consideration of the
present existence of intermediate gradations between
any two forms, we shall be led to weigh more carefully
and to value higher the actual amount of difference
between them. It is quite possible that forms now
generally acknowledged to be merely varieties may here-
after be thought worthy of specific names, as with the
primrose and cowslip ; and in this case scientific and
common language will come into accordance. In short,
we shall have to treat species in the same manner as
those naturalists treat genera, who admit that genera are
merely artificial combinations made for convenience.
This may not be a cheering prospect; but we shall at
least be freed from the vain search for the undiscovered
and undiscoverable essence of the term species.' I have
quoted from pages 484, 485 of the original edition (1859),
and have italicized the sentences in which Darwin defines
a species and distinguishes it from a variety.

Max Miiller's special criticism falls to the ground, but
his general exhortation remains, and I think we shall do
well to be guided by it, and attempt to apply it to this
difficult and elusive word species.

The passage I have quoted was Darwin's prediction of
the meaning which would be attached to the word ' species '

48

'WHAT IS A SPECIES ?'

by the naturalist of the future. Nearly half a century
has passed since those words were written. For more
than a generation the central ideas of the Origin have
been an essential part of the intellectual equipment, not
only of every naturalist, but of every moderately intelligent
man. What then is the meaning of the word ' species '
to-day, and how does it differ from that of the years
before July i, 1858, when the Darwin- Wallace conception
of Natural Selection was first launched upon the world ?

The present occasion is specially favourable for this
inquiry, because we have just been given two additional
volumes of the letters of Charles Darwin. After the
three volumes published in 1887, naturalists were cer-
tainly unprepared for the welcome revelation of such
a mine of wealth. The work is all the more valuable
because it contains many letters from Alfred Russel
Wallace and Sir Joseph Hooker, thus giving both sides
of a part of their correspondence with Darwin. Then in
1900 the Life and Letters of Thomas Henry Huxley
appeared, so that we are now admitted 1 behind the veil
and can read, as never before, the central thoughts of the
great makers of biological history. On the publication of
the last-named work, I took occasion to combat the view
that the thousand closely-printed pages might have been
reduced by omitting and condensing many of the letters.
The serious student of those stirring years requires the
opportunity of thinking over and comparing all the avail-
able thoughts and opinions of the chief actors in the
memorable scene ; and the very repetition of certain
ideas, which proves their persistence and dominance in
the writer's mind, is a matter of deep importance and
interest. However it may be to the general reader, the
student would deprecate the omission or condensation
of any of the writings of Darwin or Huxley. The
special interest and value in the letters of these men
depend on the fact that their inmost convictions on subjects
of the deepest scientific importance are to be read, often
in the compass of a brief sentence. There we find, as we
cannot find in any other way, the real core of the matter,
with all accessory and surrounding considerations stripped

DARWIN'S LETTERS TO HIS FRIENDS 49

away from it.1 A careful study of the two recent
volumes of Darwin's letters, and a re-study of the three
earlier volumes, with a view to this Address, have shown
how the writer's thoughts were again and again occupied
upon subjects bound up with the problem I have ventured
to bring before you this evening. The interest reaches
its height when we find that strongly marked differences
of opinion on fundamental questions are threshed out in
the correspondence, when we see, as I shall have occasion
to point out in greater detail in the later pages of this
Address, Darwin differing sharply from Huxley on the
one hand, and with Wallace on the other, as to the
significance and history of sterility between species.

In such episodes we are permitted to become the
witnesses of a supremely interesting struggle, where
the central figure of modern biological inquiry is contend-
ing with his chief comrades in the great fight, — with the
co-discoverer of Natural Selection, with the warrior hero
who stood in the forefront of the battle.

The correspondence of Charles Darwin has a further
deep interest for us. We see the means by which
a gentle, sympathetic, intensely human nature overpassed
the stern limits imposed by health, and was able to impart
and to receive fresh ideas, and a stimulus ever renewed —
the impulse to varied and unceasing research. I have
lately been studying with keen interest the life of another
great Englishman, William John Burchell,2 than whom
no better equipped or more learned traveller ever explored
large areas in two continents. When I state that search-
ing inquiry has only brought to light a dozen of his
letters,3 and that he was known to few of the great
naturalists of his day, we see the reason for the sad,
unproductive, brooding close of a career which opened

1 Quarterly Review, January 1901, p. 258.

2 Ann. and Mag. Nat. Hist., January 1904, p. 45.

8 Since these words were written I have through the courtesy of
Mr. Francis A. Burchell of the Rhodes University College, Grahamstown,
been permitted to see a large number of letters written by the great
explorer to members of his family. A number of Burchell's letters to
Swainson, of which I was unaware when this Address was written, are
preserved in the library of the Linnean Society.

POULTON E

'WHAT IS A SPECIES?'

with almost unexampled brilliancy and promise. The
time which we give to Societies such as this — time we
are sometimes apt to grudge — is well spent. Here, and
in kindred communities, a 4 man sharpeneth the counten-
ance of his friend,' and there is born of the influence
of mind upon mind, thought, — not a mere resultant of
diverse forces, but a new creation.

The scientific man who shuts himself away from his
fellow men, in the belief that he is thereby obtaining
conditions the most favourable for research, is grievously
mistaken. Man, scientific man perhaps more inevitably
than others, is a social animal, and the contrast between
the lives of Darwin and Burchell shows us that friendly
sympathy with our brother naturalists is an essential
element in successful and continued investigation.

Insects, and especially Lepidoptera, pre-eminently fitted to
supply examples for a Discussion on Species.

I do not suppose that it is necessary to justify a dis-
cussion of the term ' species ' as the subject of the
Anniversary Address to the Entomological Society of
London. The students of insect form and function hold
an exalted place among naturalists. The material of
their researches enables them, almost compels them, to
take the keenest and most active interest in broad ques-
tions affecting the history and course of life on our planet.
Naturalists engaged upon other groups may reasonably
inquire why insects, above all other animals, should be
so especially valuable for the elucidation of the larger
problems which deal, not only with the species of a single
group, but with every one of the innumerable and infinitely
varied forms, vegetable no less than animal, in which life
manifests itself. The answer is to be found in the large
number of offspring produced by each pair of insects,
and the rapidity with which the generations succeed each
other, many cycles being completed in a single year in
warm countries ; in the severity of the struggle for life
which prevents this remarkable rate of multiplication
from becoming the cause of any progressive increase

INSECTS AS EXAMPLES OF EVOLUTION 51

in the number of individuals ; and finally, in the character
of the struggle itself, which is precisely of that highly
specialized kind between the keen senses and activities of
enemies, and the means of concealment or other modes
of defence of their insect prey, which leads, by action and
answering reaction, to a progressive raising of the standard
in both pursuer and pursued. This is why it is that
insects mean so much to the naturalist or to the philo-
sopher who desires to look beneath the surface for the
forces which have moulded existing forms of life out of
earlier and very different forms. The wings of butterflies,
it has been said, ' serve as a tablet on which Nature writes
the story of the modifications of species.' 1 But the careful
study of insects tells us even more than this ; for it gives
us the clearest insight we as yet possess into the forces
by which these changes have been brought about. Light
is thrown upon the causes to which organic evolution
is due no less than upon the course which organic evolu-
tion has pursued.2

And I think we shall find that a consideration of the
numerous distinct categories of forms presented by the
insect world is especially advantageous in an attack
upon the difficult question — ' What is a species ? while
properly directed observation of insects, and experiments
upon insects afford the most hopeful prospect of a final
answer.

And here I am compelled to say a word in defence of
the Lepidoptera from this point of view. Undoubtedly
it is most unfortunate that the obvious attractions of the
group have led entomologists to neglect other Orders ;
for this can be the only explanation why naturalists have
so often preferred to do over again what others have
done already, apparently oblivious of fields comparatively
empty and unexplored. It must further be admitted,
that the greater visibility of structure, and the more

1 H. W. Bates, quoted by A. R. Wallace in Natural Selection, London,
1875, p. 132. The original passage may be found in The Naturalist on
the Amazons (London, pp. 347, 348 of the 1879 edition).

55 This justification for the study of insects was urged by the present
writer in the Hope Reports, vol. iii, 1903, preface, pp. 4, 5.

E 2

52

'WHAT IS A SPECIES?'

urgent necessity for the study of structure in other groups,
render them better instruments of zoological education.
But although the Lepidoptera are inferior in this respect,
although they lack the unique interest of the Hymenoptera
and the social Neuroptera, and cannot claim any of the
respect due to venerable age like the Aptera, Orthoptera
and Neuroptera — in spite of their many demerits they
stand at the head, not only of all insects, but of the whole
organic world, as the registers of subtle and elusive
change — ever going on, yet never seen, — by means of
which forms are slowly becoming different from what
they have been in the past. It is the existence of a com-
plex pattern composed of several colours, which renders
butterflies and to a less extent moths such a remarkably
delicate record of change. As we trace the representative
individuals of a community of butterflies over any wide
range, the trained eye, and often the inexperienced eye,
can detect differences which are not seen to anything like
the same extent in the individuals of other Orders with
corresponding ranges. If the wings of Hymenoptera,
Diptera, or Orthoptera possessed the same elaborate
patterns as the Lepidoptera, we cannot doubt that they
too would exhibit the same differences in various parts of
their areas. The continual change which we find as
we study the distribution of Lepidopterous forms in space,
is undoubtedly a measure of the speed with which evolu-
tion has occurred in time. Rapidity of change is essential
if it is to keep its adjustment with nicety to the fleeting
details of distribution.1 Hence we may confidently

1 It is to be observed that I speak of the details as fleeting. The
general area of distribution is doubtless extremely ancient in most cases.
Thus, although a species of Heliconius, &c, may have originated within
the South American tropics, and never have wandered beyond them, the
complex shape of its actual area of distribution at any one time cannot be
regarded as fixed or ancient. Yet in many a species the variation of the
constituent individuals is adjusted with precision to the geographical details
of the existing range.

Mr. Roland Trimen, on reading the above footnote, writes to me
January 24, 1904 : — 1 Your note reminds me of the recent appearance on
the Natal coast of several conspicuous East-African butterflies, vid. : Pieris
spilleri, Crenis rosa, and Godartia wakefieldii, all of which are shown to
have not only extended their range to a point where they were previously

BUTTERFLIES AS REGISTERS OF CHANGE 53

believe, that if we could wake up in say a thousand
years, we should be able to detect changes in the pat-
terns of some butterflies. Although I am afraid the
advance of science is not likely to be sufficiently rapid in
our time for me to hold out any prospect of such an
experience for any of you, there is every reason why we
should afford this opportunity to posterity. A critical
examination of the fragments of many species of butter-
flies captured over ninety years ago by Burchell in South
Africa, and gnawed to pieces during his Brazilian travels
from 1825 to 1830, renders it probable, nay, almost cer-
tain, that with moderate care, insect pigments will endure
for an indefinite period in our museums. One important
justification for the great and permanent outlay required
to bring together and maintain large collections of insects
is, that we are allowing our successors the chance of
detecting and measuring the rate of specific change.1
And, as I have already said, for this purpose the Lepi-
doptera stand pre-eminent.

For the purpose of the inquiry this evening, our

quite unknown, but to have also established themselves in the fresh area.
This is a good case, as Durban has had, for the last twenty- five years
at least, a number of keen collectors of Lepidoptera, whom such con-
spicuous forms could not possibly have escaped had they inhabited the
neighbourhood. Besides these species, the last butterfly that my friend
and collaborator, the late Colonel Bowker, sent to me (1898) was the
large and extremely conspicuous black-and-white Acraea satis ', which he
took at Malvern, near Durban. This is the only example known to me
to have occurred in Natal ; but Bowker, who noted the resemblance on
the wing to Papilio morania, wrote that he had seen one other for certain,
and thought that he might very possibly have passed over more examples
for the common Papilio named. This last case is of special interest
(should it prove one of extended range like the three mentioned), because
the Acraeae are so exceptionally slow-flying and gregarious, that they must
spread very slowly indeed into fresh areas.'

1 Karl Jordan argues wiih great force in favour of specialization in this
direction by our museums. (See Novitates Zoologicae, vol. iii, December
1896, pp. 431-3.) The Burchell collection from Brazil was made between
1825 and 1830, and is therefore only seventy-fix to eighty-one years old.
but the species are numerous, and often represented by long series. Miss
Cora B. Sanders' account of the Iihomiine, Danaine and Satyrine butterflies
contains evidence that certain species have undergone change of form or
of distribution. See Antials and Magazine of Natural History, 1904,
PP- 305-23, 356-71.

54

'WHAT IS A SPECIES?'

instances will be drawn from the Lepidoptera rather
than other Orders of insects, because of the numberless
examples of subtle distinction between forms which but
yesterday, so to speak, became separate ; because of our
knowledge, insufficient but considerable, of their geo-
graphical range ; because of our experience, excessively
imperfect and scanty, but still much larger than in other
Orders, of interbreeding and of descent from parent to
offspring.

The Linnaean Conception of Species as Separately Created,
and Fixed for all time at their Creation.

First among the attempts to define species must be
placed that which we rightly associate with the name of
Linnaeus : — ' Species tot sunt, quot diversas formas ab
initio produxit Infinitum Ens, quae formae, secundum
generationis inditas leges produxere plures, at sibi semper
similes/

It is necessary at the outset to point out that the
Linnaean definition contains two widely different ideas.

First, species are diversae formae, distinguished from
one another by characters which can be studied and de-
fined. Secondly, these specific differences were originally
created as we see them, and are for ever permanent and
fixed.

I propose to discuss the second idea before the first.

It has been admirably pointed out by the late Rev.
Aubrey L. Moore,1 that the dogma of the fixity of
species is entitled to none of the respect which is due to
age. 4 It is hardly credible to us/ he wrote, ' that Lord
Bacon, " the father of modern science " as he is called,
though he was only a schoolman touched with empiricism,
believed not only that one species might pass into
another, but that it was a matter of chance what the
transmutation would be. Sometimes the mediaeval
notion of vivification from putrefaction is appealed to, as
where he explains the reason why oak boughs put into
the earth send forth wild vines, " which, if it be true (no

1 Science and the Faith, London, 1889, pp. 174 et seq.

OLDER BELIEFS IN TRANSMUTATION 55

doubt)," he says l, " it is not the oak that turneth into
a vine, but the oak bough, putrefying, qualifieth the
earth to put forth a vine of itself." Sometimes he
suggests a reason which implies a kind of law, as when
he thinks that the stump of a beech tree when cut down
will " put forth birch " because it is a " tree of a smaller
kind which needeth less nourishment ". 2 Elsewhere he
suggests the experiment of polling a willow to see what
it will turn into, he himself having seen one which had
a bracken fern growing out of it ! 3 And he takes it as
probable, though it is inter magnalia naturae, that " what-
ever creature having life is generated without seed, that
creature will change out of one species into another".
Bacon looks upon the seed as a restraining power,
limiting a variation which, in spontaneous generations,
is practically infinite, " for it is the seed, and the nature
of it, which locketh and boundeth in the creature that it
doth not expatiate." ' And the author also shows that
much earlier than the date at which Bacon wrote,
theologians were by no means unanimous in accepting
1 special creation ' ; that St. Augustine even distinctly
rejected it, and propounded an idea which was evidently
considered tenable by the greatest of the schoolmen,
St. Thomas Aquinas. St. Thomas's words, quoted by
Mr. Aubrey Moore, are as follows : — ' As to the pro-
duction of plants, Augustine holds a different view.
For some expositors say that, on this third day (of
creation), plants were actually produced each in his kind —
a view which is favoured by a superficial reading of the
letter of Scripture. But Augustine says that the earth
is then said to have brought forth grass and trees
causaliter — i. e. it then received the power to produce
them.' 4

How then did the fixity of species become an article of
belief in later years ? Aubrey Moore traces it to the in-
fluence of Milton's account of creation in the seventh book

1 Nat. Hist., Cent, vi, 522, fol. ed.

2 loc. cit. p. 523. 3 loc. cit. p. 112.

4 St. Thomas Aquinas, Summa TheoL, Prima Pars, Quaest. lxix.
Art. 2.

56

< WHAT IS A SPECIES?'

of Paradise Lost (1. 414 et seq.), and Professor Huxley
had still earlier suggested the same cause in his American
Addresses. I cannot help thinking that the belief had
even more to do with the spirit of the age which spoke,
and spoke for all time, with Milton for its interpreter —
the spirit of the Puritan movement, with its insistence
on literal interpretation and verbal inspiration.

John Ray was Milton's younger contemporary, and
many writers, including Aubrey Moore, have thought
that with him began the idea of the fixity of species.
Sir William Thiselton-Dyer has, however, recently
pointed out, that a conception similar to Ray's may be
traced to Kaspar Bauhin (1 550-1624), and to Jung
(1587-1657).'

From Ray we pass to Linnaeus with his celebrated
definition. Of the Ray-Linnaeus-Cuvier conception of
species which found its most precise and authoritative
expression in the Latin sentence quoted on p. 54, Dr.
F. A. Dixey has well said that it ' left order where it had
found confusion, but in substituting exactness of definition
for the vague conceptions of a former age, it did much to
obscure the rudimentary notions of organic evolution
which had influenced naturalists and philosophers from
Aristotle downwards'.2 At the same time it is by no
means improbable, as Dixey has suggested, that the
Linnaean conception 1 of the reality and fixity of species
perhaps marks a necessary stage in the progress of
scientific inquiry '.3

The Linnaean idea of special creation has no place in
the realm of science; it is a theological dogma. The
formation of species, said Darwin in a letter to Lyell,
1 has hitherto been viewed as beyond law ; in fact, this
branch of science is still with most people under its
theological phase of development.' 4 And this explains

1 The Edinburgh Review, October, 1902, p. 370.

2 Nature, June 19, 1902, p. 169. For the history of these early ideas
upon evolution see From the Greeks to Darwin, by H. F. Osborn, New
York, 1894.

3 Church Quarterly Review, October, 1902, Art. II, p. 28.

4 Letter 132 to C. Lyell, August 21, 1861. More Letters of Charles
Darwin, London, 1903, i, p. 194.

THEOLOGICAL ASPECTS OF SPECIES 57

the intense opposition at first encountered by the
principles of the Origin. The naturalist whose genius
sympathized most fully with the Linnaean conception
would feel that he was admitted, like a seer of old,
into the thoughts of the Maker of the Universe. His
convictions as to species were to him more than the
conclusions of the naturalist ; they were a revelation,
stirring him to 1 break forth and prophesy '. Do we
not sometimes recognize a lingering trace of this phase
of thought in the serious shake of the head and tone
of profound inner conviction with which we are some-
times told that the speaker is decidedly of the opinion
that so-and-so is a perfectly good species ?

We recognize the same sharp antagonism between
two irreconcilable sets of ideas when the late W. C.
Hewitson expressed such horror at Roland Trimen's
remarkable discovery of the polymorphic mimetic females
of the Papilio dardamcs (inerope) group. The wonderfully
acute detection of minute but significant resemblance
hidden under the widest possible superficial difference,
which enabled the great South African naturalist to un-
ravel the tangled relationships, was to Hewitson but one
of ' the childish guesses of the . . . Darwinian School '.
To meet the carefully-thought-out argument, the only
objections that could be urged were, that the conclusion
stretched too severely the imagination of the writer, and
that it shocked his notion of propriety ! 1

1 See an account of the controversy in Trans. Ent. Soc. Lond., 1874,
p. 137. The passages I have alluded to are as follows : — 'P. merope, of
Madagascar, has a female the exact image of itself; and it would require
a stretch of the imagination, of which I am incapable, to believe that the
P. merope of the mainland, having no specific difference, indulges in
a whole harem of females, differing as widely from it as any other species
in the genus. ... In the two species of Papilio which have lately been
united, Torqnatus and Caudius, and Argentus and Torqnaiinus, though
much unlike each other, there is quite sufficient resemblance not to shock
one's notions of propriety.' A little later Mr. Hewitson himself received
evidence of the truth of the conclusion he so disliked ; for he told how his
collector Rogers had sent ' Papilio merope and P. hippocoon, taken by him
in copulation, another illustration of the saying that " truth is stranger
than fiction". I find it very difficult (even with this evidence) to believe

WHAT IS A SPECIES?'

In leaving the dogma of ' special creation and the
assumption of ' fixity of species ' with which it is bound
up, it is only right to point out how completely the
logical foundations of both were undermined by the
great thinker who has just passed away. Years before
the appearance of the Darwin- Wallace essay, and of the
Origin, Herbert Spencer wrote on The Development
Hypothesis} Although of course wanting the great mo-
tive power to evolution supplied by Natural Selection,
this essay is a powerful and convincing argument for
evolution as against special creation. It is astonishing
that it did not produce more effect. I may appropriately
conclude this section of the Address by quoting the
results of Herbert Spencer's critical examination, from
every point of view, of the Linnaean conception of the
origin of species. 1 Thus, however regarded, the hypo-
thesis of special creations turns out to be worthless —
worthless by its derivation ; worthless in its intrinsic
incoherence ; worthless as absolutely without evidence ;
worthless as not supplying an intellectual need ; worthless
as not satisfying a moral want.' 2

I now pass to the first idea contained in the Linnaean
conception : — that species are different from one another.
Stripped of the assumption that the differences were
determined by separate creation and of the assumption
that they are fixed for all time, this idea is no less than
the recognition of specific characters definable by the
method of Diagnosis. And it is only fair to remember
that if the theology of Linnaeus demanded the acceptance
of these assumptions, his life was really devoted to the
ceaseless study of animal and vegetable forms as a
foundation for the definition and grouping of species.
A discussion of the method of Diagnosis, its implications

that a butterfly, which, when a resident in Madagascar, has a female the
image of itself, should, in West Africa, have one without any re-
semblance to it at all' (Entomologist's Monthly Magazine, October, 1874,
P. "3)-

1 In the Leader, between January, 1852, and May, 1854, reprinted
in Essays Scientific, Political, and Speculative, London, 1868, vol. i,
P- 377-

2 The Principles of Biology, London, 1864, vol. i, p. 345.

DIFFERENT IDEAS ABOUT SPECIES 59

and limitations, will be attempted in the later pages of
this Address.

Various conceptions of Species.

In a letter to Hooker, Dec. 24, 1856, Darwin gave
a short account of the various definitions he had met
with. ' I have just been comparing definitions of species,
and stating briefly how systematic naturalists work out
their subjects. ... It is really laughable to see what
different ideas are prominent in various naturalists
minds, when they speak of " species " ; in some, re-
semblance is everything, and descent of little weight —
in some, resemblance seems to go for nothing, and
Creation the reigning idea — in some, descent is the
key, — in some, sterility an unfailing test, with others it
is not worth a farthing. It all comes, I believe, from
trying to define the indefinable.'1

As regards the work done by the systematist, we find
that Darwin did not agree with those of his friends who
thought that a belief in evolution would entirely alter its
character. Thus he wrote to Hooker, Sept. 25, 1853 : —
* In my own work I have not felt conscious that dis-
believing in the mere permanence of species has made
much difference one way or the other ; in some few cases
(if publishing avowedly on the doctrine of non-per-
manence), I should not have affixed names, and in some
few cases should have affixed names to remarkable
varieties. Certainly I have felt it humiliating, discussing
and doubting, and examining over and over again, when
in my own mind the only doubt has been whether the
form varied to-day or yesterday (not to put too fine a point
on it, as Snagsby would say). After describing a set of
forms as distinct species, tearing up my MS., and making
them one species, tearing that up and making them
separate, and then making them one again (which has
happened to me), I have gnashed my teeth, cursed
species, and asked what sin I had committed to be so
punished. But I must confess that perhaps nearly the

1 Life a?td Letters of Charles Darwin, London, 1887, vol. ii, p. 88.

6o 'WHAT IS A SPECIES?'

same thing would have happened to me on any scheme
of work.' 1

The essentially subjective character of the results
reached by the systematist stands out with remarkable
force in this as in other passages of Darwin's letters.

A few years later, on July 30, 1856, he wrote to the
same friend : — 'I differ from him [Lyell] greatly in
thinking that those who believe that species are not
fixed will multiply specific names : I know in my own
case my most frequent source of doubt was whether
others would not think this or that was a God-created
Barnacle, and surely deserved a name. Otherwise I
should only have thought whether the amount of differ-
ence and permanence was sufficient to justify a name.' 2

Disregarding for the moment the term species, it is
convenient to consider the various groupings of individual
animals and plants.

1. Forms having certain structural characters in
common distinguishing them from the forms of other
groups. Groups thus defined by the Linnaean method
of Diagnosis may be conveniently called Syndiagnostic
(vvv, together ; Sidyvaxris, distinction).

2. Forms which freely interbreed together. These
may be conveniently called Syngamic (aw, together ;
ya/xo?, marriage). Free interbreeding under natural
conditions may be termed Syngamy ; its cessation or
absence, A syngamy (equivalent to the Amixia of Weis-
mann).3

1 Life and Let1ers> vol. ii, p. 40.

2 Ibid. vol. ii, p. 81.

3 The history of the term Syngamy, although brief, has been re-
markable. By a curious coincidence this very word was independently
proposed by my friend, Professor Marcus Hartog, of Queen's College,
Cork, in order to express that fusion of the essential reproductive elements,
or gametes, which has been generally known by the inconvenient and
in many ways misleading term fertilization. Prof. Hartog suggested
the word (Sept. 14, 1903) in introducing a discussion on fertilization irt
Section D (Zoology) at the meeting of the British Association at Southport.
The Report of the meeting (p. 693) only prints the names of the speakers.
I was not at the Southport meeting, and never heard the word until it
was suggested as suitable for my purpose by Mr. Arthur Sidgwick.

VARIOUS GROUPINGS OF INDIVIDUALS 61

3. Forms which have been shown by human observa-
tion to be descended from common ancestors or from
a common parthenogenetic or self-fertilizing ancestor.
Such groups may be called Synepigomc (a-vy, together ;
kirtyovos, descendant). Breeding from common parents
or from a common parthenogenetic or self-fertilizing
parent may be spoken of as Epigony or the production
of Epigonic evidence.1

I first made use of it in the Presidential Address to the Entomological
Society, delivered Jan. 20, 1904, but it was not published until the six-
teenth of the following March, the date of issue, printed upon the cover of
Part V of the Transactions for 1903. Professor Hartog first published
Syngamy in the number of the Quarterly Journal of Microscopical Science
for March, 1904. The precise date of publication is not given, but the
publishers, Messrs. J. and A. Churchill, have courteously informed me that
copies did not leave their office until April 12. Professor Hartog's
article is entitled Some Problems of Reproduction. — 77, and is to be
found in New Ser. vol. xlvii, 1903-4, p. 583, of the Quarterly Journal.
The second part B. An Essay on Fertilization (pp. 590-605) begins
with an allusion to the discussion at Southport which was opened by
the author, on very short notice, by the invitation of Professor Hickson,
President of Section D. ' The following pages/ Professor Hartog con-
tinues, 1 represent far more closely what I would have wished to say than
what I actually said.' On p. 595 the word is introduced as follows : —
' . . . I venture to propose the term " Syngamy " to replace " fertilisation,"
in its modern restricted sense . . . ' I have now given the history of this
strange and unfortunate coincidence, and desire to express my regret that
Professor Hartog, who made use of the word at the earlier date, should
lose priority because of the later publication. But if such technical rules
exist and if they are applicable to scientific terms of this class, I do not
see how it is possible to avoid enforcing them. It would be extremely
inconvenient to use the same term for ideas so closely related and yet
so utterly different as Professor Hartog's and mine. Furthermore, there
is a word as was suggested to me by Professor Lankester, which seems
almost to coin itself for Professor Hartog's purpose. When the two
gametes have united in 1 fertilization ' their product is known as the
' zygote '. Thus Professor Hartog in his summary on p. 605 speaks
of 1 the cell freshly produced by syngamy (the zygote) '. It is obvious
that Zygosis ((vyaxns) is in every way a most convenient term for the fusion
of gametes. There is also the term Amphimixis introduced by Professor
Weismann in 1891, but this term really expresses a theory as to the
significance of gametic fusion rather than the fact of the fusion itself.
(Weismann, Essays upon Heredity, vol. ii, p. 101, Oxford, 1892).

1 My friend, Mr. Arthur Sidgwick, has kindly helped me by suggesting
the appropriate Greek words. The use of cVi'yovos I owe to my friends
Dr. Arthur Evans, F.R.S., and Dr. R. W. Macan. The adjectival ter-

62

4 WHAT IS A SPECIES ?'

4. Finally there is geographical distribution, of the
utmost importance in the modification and origin of
species and sub-species. Forms found together in cer-
tain geographical areas may be called Sympatric (aw,
together ; irdrpa, native country). The occurrence of
forms together may be termed Sympairy, and the dis-
continuous distribution of forms A sympatry.

My friend, Professor E. Ray Lankester, to whom I owe
so much, in this as in many other subjects, is inclined to
think that we should discard the word species not merely
momentarily but altogether. Modern zoology having
abandoned Linnaeus's conception of ' species ' should,
he considers, abandon the use of the word. In his
opinion the ' origin ' of species was really the abolition
of species, and zoologists should now be content to
describe, name, draw, and catalogue forms. Further-
more, the various groups of forms briefly defined above
should be separately and distinctly treated by the zoolo-
gist, without confusion or inference from one to the
other. The systematist should say, ' I describe and name
certain forms a, b, &c. ' ; and then he or another may
write a separate chapter, as it were : — ' I now show that
the forms ad, ac, ad (form names) are syngamic ' : at
another time he may give reason for regarding any
of them as related by Epigony.

I fear that this suggestion is a ' counsel of perfection
impossible of attainment, although there would be many
and great advantages in thus making a fresh start and
in the abandonment of 'species', or rather the re-
striction of the word to the only meaning it originally
possessed before it was borrowed from logic to become
a technical term in zoology.1 If the main contention of
this Address be accepted, that a species is a syngamic and
synepigonic group of individuals, — an objective reality
however difficult to establish in practice, — we have an
additional powerful reason for the permanent use of the
word.

mination is made -ic throughout for the sake of convenience, although
Sympatriote or Sympatrid would have been more correct.
1 See F. A. Dixey in Nature, June 19, 1902, p. 169.

THE IMPORTANCE OF PERSISTENCE 63

Professor Lankester in former years 1 published the
suggestion that the term species should be limited to
a group which includes all the forms derived from
common ancestors within human experience, or inferred
to be so derived within the possible period of human
observation. Thus if the common ancestry of two
forms has to be traced back to a period beyond the
late prehistoric times (or beyond any other arbitrary
line which is agreed upon), then they are not members
of the same species. Professor Lankester is the first
to admit that the practical application of this as of
every other conception of species would very often
mean a great deal more than we can prove, in fact,
hypothesis.

It is evident that Darwin regarded constancy of
form as an important criterion of a species. We re-
cognize this in the definition I have quoted from the
Origin (see p. 47), and it is stated with even greater
force in the following passage, where persistence is placed
beside other distinguishing marks of a species and given
the pre-eminence. In a letter to Hooker (October 22,
1864) Darwin says : — ' I will fight you to the death that
as primrose and cowslip are different in appearance (not
to mention odour, habitat and range), and as I can now
show that, when they cross, the intermediate offspring are
sterile like ordinary hybrids, they must be called as good
species as a man and a gorilla. . . . The power of re-
maining for a good long period constant I look at as
the essence of a species, combined with an appreciable
amount of difference.' 2

Introdtcction to the Discussion 1 What is a Species ? 1

The preceding pages have been occupied with pre-
liminary considerations necessary for a discussion of
the problem stated in the title of this Address. It is now
proposed to preface that discussion with a few words

1 Neither Professor Lankester nor I have been able at present to lay
our hands upon the communication.

2 More Letters^ vol. i, p. 252, Letter 179.

64

'WHAT IS A SPECIES?'

of introduction, setting forth the main conclusions which
will be defended.

Diagnosis, it will be maintained, is founded upon the
conception that there is unbroken transition in the
characters of the component individuals of a species.
Underlying this idea are the more fundamental con-
ceptions of species as groups of individuals related by
Syngamy and Epigony.

In immense numbers of cases it will be shown that
the component individuals of a species do not form
an unbroken series, but one that is sharply broken at one
or more points. At each of these breaks the older syste-
matist made a new species, which the modern systematist
has rejected, because in his day the more fundamental
criteria have been actually established or by strong
indirect evidence have been inferred. When the test
of Diagnosis necessarily fails — as it will be shown to
do in many large groups of examples — the appeal is made
to Syngamy and Epigony.

Syngamy and Epigony are but two sides of the same
phenomenon — Reproduction. Although occasional union
between individuals of distinct species may occur in nature,
sometimes leading to the production of hybrid offspring,
this is not the ' free interbreeding under natural con-
ditions ' which I have called Syngamy. Syngamy, thus de-
fined, implies the production of normal offspring capable of
continuing the species — implies Epigony. As a practical
criterion, the evidences of Syngamy are generally much
easier to collect than those of Epigony. Both Syngamy
and Epigony can be established by indirect evidence
based on a sufficient number of accurate observations
upon the habits and modes of occurrence of individuals.
The criterion of Syngamy of course fails in the case
of parthenogenetic and self-fertilizing species. In such
cases, like that of the Bee Orchis referred to below on
p. 92, we are compelled to fall back on Epigony. This
latter criterion may lead, although only in rare and
exceptional instances, to an erroneous inference, when
hybrid are mistaken for normal offspring.

There is a great advantage in the admission that

INTRODUCTION TO DISCUSSION 65

Diagnosis is only a provisional criterion, inasmuch as the
systematist would then continually seek and continually
suggest the search for the more fundamental tests.

It will be argued that the true interspecific barrier
is not sterility but Asyngamy — the cessation of inter-
breeding— but that the first will inevitably follow, sooner
or later, as the incidental consequence of the second.

Various causes of the origin of species by Asyngamy
will be discussed. One of these, preferential interbreed-
ing, may hereafter appear of the utmost significance
in species maintenance and species formation in the
higher animal sub-kingdoms. This, of course, would
imply that the instincts leading to preference are of
dominant importance. We can imagine hardly any
operation of Natural Selection more obvious or more
effective than that by which these instincts are led to
promote a maximum fertility. Any variation of instinct
causing an individual to attempt to pair outside the
syngamic community to which it belongs could only
result in a diminished representation in future genera-
tions.

The consideration of a special form of Asyngamy
at the close of the Address leads to an unexpected result :
suspicion as to the validity of the generally accepted
interpretation of the manifold adaptations for cross-
fertilization.

The conclusions set forth above, if hereafter established,
lead to a belief in the reality of species. Unlike and
apart from genera, families and other groups employed
in our ' little systems ' of classification which 1 have their
day and cease to be ', not only do individuals stand out
as objective realities, but equally real, though far less
evident, are the societies into which individuals are
bound together in space and time by Syngamy and
E pigony.

The Definition of Species by Diagnosis,

It is now necessary to examine in some detail the most
usual conception of a species, a conception based upon
distinguishing structural characters, or Diagnosis.

POULTON F

66

'WHAT IS A SPECIES?*

This idea of a species is clearly expressed by Sir
William Thiselton-Dyer, when he speaks of the older
writers who employed i the word species as a designation
for the totality of individuals differing from all others by
marks or characters which experience showed to be
reasonably constant and trustworthy, as is the practice
of modern naturalists'.1

This conception of a species is founded upon transi-
tion. Whenever a set of individuals can be arranged,
according to the characters fixed upon by the systematise
in a series without marked breaks, that set is regarded as
a species. The two ends of the series may differ im-
mensely, may diverge far more widely than the series
itself does from other series ; but the gradual transition
proclaims it a single species. If transitions were all
equally perfect, of course there would be no difficulty.
But transitions are infinite in their variety ; while the
subjective element is obviously dominant in the selection
of gaps just wide enough to constitute interspecific breaks,
just narrow enough to fuse the species separated by some
other writer, — dominant also in the choice of the specific
characters themselves.2 Looking back upon the interval
between Linnaeus and Darwin, it seems remarkable that
the mutability of species was not forced upon systematists
as the result of their own labours. It is astonishing that
many a naturalist was not driven by his descriptive work
to the conclusion which Darwin stated to Asa Gray on
July 20, 1856: ' — as an honest man, I must tell you
that I have come to the heterodox conclusion, that there
are no such things as independently created species —
that species are only strongly defined varieties.' 3

For, as I have said above, every describer of species
made continuity and transition in characters the test of
a variety, discontinuity the test of a separate species.

1 loc. cit. p. 370.

2 How important this choice may be is well shown by Karl Jordan in
Noviiates Zoologicae, vol. iii, Dec. 1896, pp. 428-30. Characters are
subject to independefit variation as well as correlated variation. Hence
there will often be the widest discrepancy between the transitions con-
structed by naturalists making use of different characters.

3 Life and Letter s, vol. ii, p. 79.

TRANSITION UNDERLIES DIAGNOSIS 67

And in difficult cases no two of them agreed in their
conclusions. Many passages in Darwin's correspondence
convincingly prove how essential an element is this con-
tinuity, and how inevitable is the dominance of the
subjective element. Thus he writes about his descriptive
work on Cirrhipedes to Hooker, October 12, 1849 : —
* I have of late been at work at mere species describing,
which is much more difficult than I expected, and has
much the same sort of interest as a puzzle has ; but
I confess I often feel wearied with the work, and cannot
help sometimes asking myself what is the good of spend-
ing a week or fortnight in ascertaining that certain just
perceptible differences blend together and constitute
varieties and not species. As long as I am on anatomy
I never feel myself in that disgusting, horrid, cut bono,
inquiring, humour.' 1

On another occasion, when Darwin was anxious to
ascertain the 1 close species ' in the North American
Flora, and wrote for information to Asa Gray, he frankly
adopted the subjective criterion in order to explain exactly
what he meant. He wrote, June 8 [1855]: — 'The
definition I should give of a " close species " was one that
yotc thought specifically distinct, but which you could
conceive some other good botanist might think only
a race or variety ; or, again, a species that you had
trouble, though having opportunities of knowing it well,
in discriminating from some other species/ 2

Asa Gray's reply is also very interesting from the
same point of view. He wrote, June 30, 1855 : — ' Those
thus connected ' [he had bracketed the 1 close species ' in
a list of the Flora], * some of them, I should in revision
unite under one, many more Dr. Hooker would unite,
and for the rest it would not be extraordinary if, in any
case, the discovery of intermediate forms compelled their
union.' 3

Darwin was evidently in high spirits when he wrote
the following passage which bears on the same subject.
The Origin had been published on November 24, 1859,

1 Life and Letters, vol. i, p. 379. 2 Ibid., vol. ii, p. 64.

3 More Letters, vol. i, p. 421, Letter 324.

F 2

68

'WHAT IS A SPECIES?'

and the whole edition of 1,250 copies sold on the day
of issue. On November 29 he wrote to Asa Gray: —
k You speak of species not having any material base
to rest on, but is this any greater hardship than deciding
what deserves to be called a variety, and be designated
by a Greek letter ? When I was at systematic work
I know I longed to have no other difficulty (great enough)
than deciding whether the form was distinct enough
to deserve a name, and not to be haunted with undefined
and unanswerable questions whether it was a true species.
What a jump it is from a well-marked variety, produced
by natural cause, to a species produced by the separate
act of the hand of God ! But I am running on foolishly.
By the way, I met the other day Phillips, the palaeonto-
logist, and he asked me, " How do you define a species ? "
I answered, " I cannot." Whereupon he said, " At last
I have found out the only true definition, — any form
which has ever had a specific name ! " ' 1

The idea of Syngamy underlies the gradual transitions
as ivell as the more uniform resemblances charac-
teristic of Diagnostic Species.

The idea of a species as an interbreeding community,
as syngamic, is, I believe, the more or less acknowledged
foundation of the importance given to transition. This
will become clearer from the consideration of a concrete
example. The common black-and-white Danaine butter-
fly, Amauris niavius of West Africa, is represented on
the East and South-East Coasts by a very similar butter-
fly, distinguished by the greater size of the largest white
patch, and of the white spot in the cell of the fore-wing.
Both forms are very constant in the areas over which they
were known, and on these constant easily recognizable
characters the eastern butterfly was described as a dis-
tinct species under the name of A. dominicamis. Auri-
villius, however, in his valuable Catalogue refuses to
recognize this latter as a distinct species, and considers it
as the dominicanus variety of niavius. Through the

1 More Letters, vol. i, p. 127, Letter 79.

SYNGAMY UNDERLIES TRANSITION 69

kindness of Mr. C. A. Wiggins and Mr. A. H. Harrison,
the Hope Department has recently been presented with
an exceedingly fine series of butterflies from both east
and west of the northern shores of the Victoria Nyanza.
These have been carefully studied by Mr. S. A. Neave,
M.A., B.Sc, of Magdalen College, Oxford, who finds that
the typical niavius occurs in great abundance to the west
of the lake, while on the east he meets, in both collections,
with varieties beautifully intermediate between it and
dominie arms- These varieties, occurring precisely in the
zone where the eastern form meets the western, complete
for the systematist the transition which renders domini-
canus a variety of niavitis and not a distinct species.
But it is clear that they do more than this ; they make it
almost certain that the two forms freely interbreed, and
constitute but a single syngamic community.

This is one of the remarkably clear examples. In
many cases we know the transition, but the extremes are
not sorted out in different parts of the total area of
distribution. Nevertheless, if complete enough, the transi-
tion of forms on the same area always raises the strong
presumption that we are dealing with a syngamic com-
munity.

Probably the most remarkable series of transitional
varieties ever depicted is that shown in the eleven
quarto plates of the last part of Monsieur Charles
Oberthur's great £ hides d ' Eutomologie, entitled 'Varia-
tion des Heliconia thelxiope et vesta ' (Rennes, February,
1902).

The failure of Diagnosis as the sole test of Species-

The method of Diagnosis, at its clearest and simplest,
is always consistent with, and often strongly suggests, an
underlying Syngamy. There are, however, numberless
examples belonging to various categories in which a rigid
adherence to Diagnosis cannot avail. In these cases the
systematist frankly appeals to Syngamy or Epigony as
decisive ; and if he has not direct proof of the existence of
either of these, indirect evidence is, at any rate provision-

7o

'WHAT IS A SPECIES?

ally, regarded as sufficient. Some of the chief of these
categories are briefly set forth under the five heads a-e.

a. Dimorphism, Polymorphism : — In an ever increasing
number of examples an assemblage of individuals is re-
garded as a single species, although split up into two or
more widely different and sharply separated groups,
between which transitional varieties are excessively rare
or even unknown. For instance, the extremely abundant,
widely distributed butterfly Limnas chrysippus includes
among other forms one in which the black-and-white tip
is wanting from the fore-wing, the dorippus ( = klugii)
form. This variety is sharply cut off from the type form.
Although faint traces of a former white bar can be made
out in doiHppus, I have never seen, among thousands of
individuals, the material out of which a good transitional
series between it and chrysippus could be constructed.
In this case the evidence of Syngamy is strong and com-
plete ; for Col. Yerbury has recorded the fact that the
two forms certainly occur in copula K But even if this
record were wanting there would still be strong presump-
tive evidence that the forms are associated by Syngamy
and Epigony. Thus, so far as our knowledge extends,
dorippus occurs as the only form in certain parts of
NE. Africa alone. From this, its metropolis, dorippus
spreads on all sides, its individuals existing intermingled
with those o( chrysippus, becoming less and less numerous
until they finally die out. Thus if we trace the two
forms eastward we find them both abundant at Aden ;
further east, at Karachi, dorippus is well known, but very
scarce as compared with chrysippus ; in Southern India
it is a great rarity, if indeed it is known at all on
the mainland ; in Ceylon a single specimen was cap-
tured by Col. Yerbury in 1891, and since then others
have been taken.2 Further east I have never heard

1 Speaking of his experience at Aden, Col. Yerbury says: 'I have
taken them [the forms of chrysippus^ " in coitu " in every possible combina-
tion' {Journ. Bomb. Nat. Hist. Soc, vii (1892), p. 209).

2 See Major N. Manders, F.Z.S., in Journ. Bomb. Nat. Hist. Soc, xiv
(1902), p. 716 : —

* The first specimen of this insect [dorippus =.klugii] in Ceylon was
captured by Lieut.- Colonel Yerbury at Trincomalie, April 15, 189 1 . . .'

POLYMORPHISM AND DIAGNOSIS 71

of a specimen. Similarly when it is traced southward
in Africa, doripptts is dominant in the coast strip of
British East Africa, where it constitutes about three-
quarters of the total number of individuals. Further to
the south it becomes rarer and rarer, until in Natal and
the Cape, if it occurs at all, it is even rarer than in Ceylon.1
Such a distribution is consistent with the interpretation
that dorippus and chrysipptis are two forms in one syn-
gamic community. It is difficult on any other hypothesis
to account for the facts which we observe on the out-
skirts of the range of dorippics — the occasional appearance
of single individuals in the swarms of the type form.
And if the two are syngamic on the outskirts, the gradual
transition in proportions towards the metropolis of dorippics
suggests that they are syngamic throughout. Common
as the species is — probably the commonest butterfly in
the world — the evidence from Epigony has never been
obtained, although from the point of view of heredity the
investigation promises to be of the deepest interest.

The remarkable forms of the females of the Papilio
dardanus (inerope) group already alluded to afford another

Of five or six more recent examples Major Manders writes, ' These speci-
mens were captured by Mr. Pole at Puttalam on the east coast and
Hambantotte on the south coast in the dryest and perhaps most arid
portion of the island. It is evidently widely distributed in the desert
portion of the island and is possibly not uncommon.'

1 The distribution of this insect in India cannot yet be fully known ;
it is rare in Canara, but is not yet reported from the plains of the Deccan,
or Southern India so far as I am aware though it probably exists.' The
occurrence of dorippus at Bombay, Khandalla, Poona, and Karachi had
been previously published by Col. C. Swinhoe (P. Z. S. 1884, p. 504; 1885,
p. 1 26) ; and at Campbellpore (Col. Yerbury) by Dr. A. G. Butler (P. Z. S.
1886, p. 356).

1 Mr. Roland Trimen tells me that he knows of only three South
African dorippus : — two from Durban and one from Pretoria. The latter
and one of the former were taken by Mr. W. L. Distant (A?in. Mag. Nat.
Hist. (7), vol. i, 1898, pp. 48, 49). Mr. Geo. F. Leigh, of Durban,
Natal, writes March 3, 1904: — 'I have myself captured two or three
specimens during the past three years, and one was taken only last
September by Mr. Burn who was out collecting with me.' Two speci-
mens captured in 1905 at Salisbury, Rhodesia, have been presented to
the Oxford University Collection by Mr. Guy A. K. Marshall. They
are, so far as I am aware, the only examples of dorippus hitherto recorded
from Rhodesia.

' WHAT IS A SPECIES?'

excellent example, although in this case good transitional
series can be constructed. The evidence of Syngamy was
first obtained by Hewitson (see p. 57, footnote 1), but is
now well known. The evidence of Epigony has fortu-
nately been obtained in 1902 and again within the last
few weeks by one of our Fellows at Durban, Mr. G. F.
Leigh. Eggs laid in 1902 by a female of the commonest
South African form, cenea, yielded a synepigonic group,
including a large majority of forms like the parent, but
also examples of the very different hippocoon form. In
the more recent example seven eggs from the rarest of
the South African forms, trophonius, produced, in addition
to males, two females of the cenea variety, and not one
resembling the parent.1

These differences, although only of colour and pattern,
greatly exceed those between ordinary close species.
When we deal with other kinds of dimorphism or poly-
morphism involving important structural differences, such
as those of the social Hymenoptera and Neuroptera, the
discriminating characters between nearly related genera
are commonly equalled or exceeded.

5. Seasonal Dimorphism : — In certain exceedingly in-
teresting examples of dimorphism the relation between
the forms is epigonic and not syngamic ; for rare and
occasional interbreeding is not Syngamy. I refer to the
most strongly-marked cases of seasonal dimorphism in
butterflies, especially the wonderful examples proved
to be epigonic by Guy A. K. Marshall.2 In some of the
forms the two seasonal phases were not even regarded as
closely related species. In these extraordinary cases,

1 Trans. Ent. Soc. Lond., 1904, pp. 677-88, Plate XXXI. Still later,
in 1904, Mr. G. F. Leigh bred from the eggs laid by a trophonius female,
six males, four females of the cenea form, and one female of the trophonius
form {Trans. Ent. Soc. Lond., 1906, pp. 281-3, Plate XVII). Finally,
within the last few weeks I have received from the same keen naturalist
a splendid synepigonic group of twenty-eight specimens bred from a hippo-
coon parent — the first time that offspring have been reared from this form
of female. Of the twenty-eight, fourteen are males, eight are cenea females,
three are hippocoon females, and three are trophonius females [December 2,
1906].

3 Trans. Ent. Soc. Lond., 1902, pp. 414-60.

SEASONAL FORMS AND DIAGNOSIS 73

where the widest difference in colour and pattern exists,
in combination with others which are far more deep-
seated, I urged upon Mr. Marshall that the few recorded
examples of capture or observation in coitu were insuf-
ficient evidence of specific identity, and that nothing
short of Epigony would suffice.

In seasonal dimorphism, in the dimorphism of social
insects, and doubtless in a large proportion of other
examples, it is probable, indeed often certain, that the
different forms are produced in response to some stimulus
which acts at a specially susceptible period of the life-
history ; but from the point of view of the systematist
the mature individuals can only be known as forms
which, structurally widely different, must nevertheless
be placed within the limits of a single species. The
investigation of the probable physiological causes of
difference is, however, of the utmost importance from
other points of view. Altogether apart from its bearing
upon dimorphism, the effect of individual susceptibility to
stimulus requires treatment in a separate category.

c. Individual Modification : — One of the most striking-
developments of recent years has been the growth in the
number of these very cases in which an individual animal
or plant has been rendered by Natural Selection sus-
ceptible to some stimulus associated with each one of its
possible normal environments. Every individual of such
species comes into the world with two or more very
distinct and very different possibilities before it, each
of which will be realized only in the appropriate environ-
ment— realized as the response to some stimulus provided
by the environment itself. We can see clearly that this

idea was in Darwin's mind, although there were then but
. ......

few observations which pointed in its direction. Thus in

Schmankewitsch's experiments Crustacea of the species

Artemia salina were described as gradually changing in

the course of generations, as the result of a progressive

1 'A structural change wrought during the individual's lifetime (or
acquired), in contradistinction from variation, which is of germinal origin
(or congenital).' Diet, of Phil, and Psych., ed. by J. Mark Baldwin. New
York and London, vol. ii. 1902. p. 94.

74

'WHAT IS A SPECIES?'

freshening of the water in which they were kept, until
they took on the characters of the genus Branchipus.
On this subject Darwin wrote to Karl Semper, February 6,
1 88 1 : — 'When I read imperfectly some years ago the
original paper I could not avoid thinking that some special
explanation would hereafter be found for so curious
a case. I speculated whether a species, very liable to
repeated and great changes of conditions, might not
acquire a fluctuating condition ready to be adapted to
either conditions/ 1

I venture to express the prediction that this class of
cases, already very numerous, will hereafter be im-
mensely enlarged, and will become especially important
in the vegetable kingdom.2 Although Hooker at one
time took the opposite side, and thought that plants
were never ' changed materially by external conditions . . .
except in such a coarse way as stunting or enlarging,' 3

1 More Letters, vol. i, p. 391, Letter 303.

- See Stimulus and Mechanism as Factors in Organization^ by J. Bretland
Farmer, F.R.S. (the New Phytologist, vol. ii, Nos. 9 and 10, November and
December, 1903). Professor Farmer speaks of the probable prevalence
in the plant-world of ' a constant specific mechanism that is able to be
actuated in different ways by different kinds of stimuli Although for
the purpose of his paper Professor Farmer is concerned with the train of
physico-chemical sequences which is set going, utility or no utility, when-
ever the mechanism of an individual is stimulated, he fully admits that the
mechanism itself has come to be a character of the species by the operation
of Natural Selection. ' Naturally/ he says. ' only those species whose inner
character expressed itself in making these " suitable " adjustments to the
environment were able to survive.'

Toward the close of his paper Prof. Farmer seems to bring the con-
siderations that have regard to the species into somewhat unnecessary
conflict with those that have regard to the individual. Thus he says that
' current literature still teems with teleological explanations that really
explain nothing, but rather bar the way of scientific inquiry \

A properly loaded, well-constructed modern gun goes off, for disad-
vantage no less than for advantage, when its trigger is pulled ; but the
very existence of the gun depends upon a long succession of past stages,
each of which was more advantageous than its predecessor. The recogni-
tion of this history does not bar the way of inquiry, but rather stimulates
and suggests a searching and intelligent study of the latest mechanism
with all its intricacy.

3 See the letter from Hooker to Darwin, March 17, 1862, in More
Letters, vol. i, p. 197, footnote 2.

MODIFICATION AND DIAGNOSIS 75

Darwin considered that ' physical conditions have a more
direct effect on plants than on animals'.1 Undoubtedly
the view at the time was that of Buffon, the idea of an
operation of the environing forces almost as direct as
those which produce the weathering of rocks or the
whitening of an exposed flint. But it is probable that
the more intimately we know the conditions of plant-
life, the more fully it will be recognized that all such
changes are adaptive. I will mention merely by way of
illustration that my attention has been called in recent
years to the dwarfing effect of the prevalent south-
western winds on the vegetation of the exposed chalk
downs of the Isle of Wight. It has occurred to me
as a mere suggestion, but one worth investigating, that
the effect of wind upon a tall flower-head might be such
as to render less easy and less frequent the visits of
insects. If this were so, it would perhaps explain why
certain species of entomophilous plants liable to grow in
such situations have gained a special susceptibility to
the stimulus provided by constant winds during some
particular period of growth. The absence of this stimulus
would also correspond to a condition in which the plants
would gain in the conspicuousness brought about by
increased height.

The further growth of a class already proved to be
large would play havoc with a definition of species rigidly
based upon discriminating structural characters alone.

d. Geographical Races or Sub-Species : — If we depend
upon unaided Diagnosis there is no means of discriminat-
ing between species and those sub-species of which the
whole mass of individuals are distinguished by recogniz-
able characters. Here again the mere beginning of the
difficulty is in sight ; for as museums recognize more and
more the necessity for long series of specimens with exact
geographical data, so will the comparatively simple con-
ception of the single species be replaced again and again
by the far more complex but much truer idea of sub-
specific groups still fused by Syngamy into a single

1 See the letter from Darwin to Lyell [June 14, i860]. Life and Letters,
vol. ii, p. 319.

76

'WHAT IS A SPECIES?

species, but, as it were, trembling on the edge of dis-
ruption, ever ready, by the development of pronounced
preferential mating or by the accumulated incidental
effects of isolation prolonged beyond a certain point,
to break up into distinct and separate species.

e. Results of Artificial Selection : — These obvious
difficulties encountered by a mechanical adherence to
definition by Diagnosis naturally lead to the consideration
of the further difficulties presented by domestic races
of animals and plants. The wide structural differences
between the forms accumulated by human selection
greatly impressed Darwin. Thus he wrote to Hooker,
September 8, [1856]: — ' By the way, I have been aston-
ished at the differences in the skeletons of domestic
rabbits. I showed some of the points to Waterhouse,
and asked him whether he could pretend that they were
not as great as between species, and he answered, " They
are a great deal more." How very odd that no zoologist
should ever have thought it worth while to look to the
real structure of varieties. . . 1 But if the differences
between many of our domestic breeds, and between
them and the nearest wild species, are, as is well known,
generic rather than specific, why do we not consider
such races to be of different species and genera ? Be-
cause of the criterion suggested by Lankester ; because
we have reason to believe in their descent from common
parents within the historic period ; because, in spite of
their wide differences, they are still syngamic.

What is the practical bearing of these criticisms upon
the definition of species by Diagnosis and Diagnosis alone ?
The systematist, confronted by his series of specimens in
a museum cannot do otherwise than arrange them in
groups which he will describe and name as species. But
much would be gained if he admitted at the outset that
his conclusions are provisional, if he said with Dr. Karl

'es of the admission that conclusions based on
Diagnosis are provisional.

1 More Letters, vol. ii, p. 210, Letter 543.

DIAGNOSIS REQUIRES CONFIRMATION 77

Jordan, ' The actual proof of specific distinctness the
systematist as such cannot bring ; ... we work, or we
ought to work, with the mental reservation that the
specific distinctness of our species novae deduced from
morphological differences will be corroborated by bio-

The advantage of this attitude is obvious. Work
would go on as at present. Powers of acute observation
and good judgement would still furnish descriptions of
species to be hereafter confirmed or confirmed at the
time by observation and experiment upon the living
material. But the systematist would not only receive
our gratitude for the performance of these important and
necessary duties : he would also be seeking in every
direction for the evidence of Syngamy and of Epigony.
The museum would become a centre for the inspiration
of researches of the highest interest to the investigator
himself, of the greatest importance to the whole body
of naturalists.

Interspecific Sterility as a test of Species.

We now turn to the consideration of interspecific
sterility, which many have supposed to be an infallible
criterion. Huxley himself felt this so strongly that he
was, in consequence, never able to give his full assent
to Natural Selection. The grounds of his objection were
the subject of prolonged correspondence with Darwin.
In order to prove that Natural Selection has produced
natural species separated rigidly, as he believed, by the
barrier of sterility, Huxley maintained that we ought to be
able to produce the same sterility between our artificially
selected breeds ; and until this had been done he could
not thoroughly accept the theory of Natural Selection.
This objection he expressed, or implied, in many speeches
and writings up to within a few months of his death. One
of the simplest statements is contained in a letter to the
late Charles Kingsley. Huxley wrote, April 30, 1863 : —

1 Novitates Zoologicae, vol. iii, December, 1896, pp. 450, 451. I here
desire to express my indebtedness to the author of this learned and valuable
paper.

78 'WHAT IS A SPECIES?'

' Their produce [viz. that of Horse and Ass] is usually
a sterile hybrid.

'So if Carrier and Tumbler, e.g., were physiological
species equivalent to Horse and Ass, their progeny ought
to be sterile or semi-sterile. So far as experience has
gone, on the contrary, it is perfectly fertile — as fertile
as the progeny of Carrier and Carrier or Tumbler and
Tumbler.

' From the first time that I wrote about Darwin's book
in the Times and in the Westminster until now, it has
been obvious to me that this is the weak point of Darwin's
doctrine. He has shown that selective breeding is a vera
causa for morphological species ; he has not yet shown it
a vera causa for physiological species.

' But I entertain little doubt that a carefully devised
system of experimentation would produce physiological
species by selection — only the feat has not been per-
formed yet.' 1

It was against this same view, as expressed in Huxley's
Lectures to Working Men in 1863, that Darwin argued
with convincing force in many letters. The main facts
with which he confronted Huxley again and again were
the artificially selected races of certain plants which are
sterile inter se. The position is clearly expressed in the
following amusing, vehement passages from two letters : —

'Dec. 18, [1862.]

' Do you mean to say that Gartner lied, after experi-
ments by the hundred (and he a hostile witness), when he
showed that this was the case with Verbascum and with
maize (and here you have selected races) : does Kolreuter
lie when he speaks about the varieties of tobacco ? My
God, is not the case difficult enough, without its being, as
I must think, falsely made more difficult ? I believe it is

my own fault — my d d candour: I ought to have

made ten times more fuss about these most careful
experiments.' 2

1 Life and Letters of Thomas He?iry Huxley, vol. i, p. 239.

2 More Letters, vol. i, p. 230, Letter 156.

INTERSPECIFIC STERILITY

«[>».} io, [1863.]
1 In plants the test of first cross seems as fair as test of
sterility of hybrids. And this latter test applies, I will
maintain to the death, to the crossing of varieties of
Verbascum, and varieties, selected varieties, of Zea. You
will say Go to the Devil and hold your tongue. No,
I will not hold my tongue ; for I must add that after
going, for my present book [ Variation under Domestica-
tion^, all through domestic animals, I have come to the
conclusion that there are almost certainly several cases of
two or three or more species blended together and now
perfectly fertile together. Hence I conclude that there
must be something in domestication, — perhaps the less
stable conditions, the very cause which induces so much
variability, — which eliminates the natural sterility of
species when crossed. If so, we can see how unlikely
that sterility should arise between domestic races. Now
I will hold my tongue.'1

Darwin made attempts to ' produce physiological
species by selection ', and thus meet his friend's criticism.
He thought out and suggested a plan of experiment
to W. B. Tegetmeier,2 and gave a brief account of the
scheme to Huxley, December 28, [1862] : — 1 I have . . .
given him [Tegetmeier] the result of my crosses of the
birds which he proposes to try, and have told him how
alone I think the experiment could be tried with the
faintest hope of success — namely, to get, if possible,
a case of two birds which when paired were unproductive,
yet neither impotent. For instance, I had this morning
a letter with a case of a Hereford heifer, which seemed
to be, after repeated trials, sterile with one particular and
far from impotent bull, but not with another bull. But it
is too long a story — it is to attempt to make two strains,
both fertile, and yet sterile when one of one strain is
crossed with one of the other strain. But the difficulty
. . . would be beyond calculation.' 3

The experiment was evidently unsuccessful, — perhaps

1 More Letters, vol. i, pp. 231, 232, Letter 157.

2 Ibid. vol. i, pp. 223, 224, Letter 153, [1862, December] 27.

3 Ibid. vol. i, pp. 225, 226, Letter 154.

8o

'WHAT IS A SPECIES?'

was never seriously undertaken, — and a few years later
Darwin added the following postscript to a letter to
Huxley, January 7, [1867].

' P.S. — Nature never made species mutually sterile by
selection, nor will men/ 1

This was probably only an off-hand expression of
opinion, not intended to be taken* seriously. An alto-
gether hopeless attitude would not be reasonable until
the suggested scheme had been applied many times,
and In several parts of the animal and vegetable king-
doms.

But the positive results demanded by Huxley, even if
obtained, would by no means justify his far-reaching con-
clusions. If the barrier of sterility were thus artificially
produced, we should be very far from the proof that its
existence in nature is due to the same kind of cause,
viz. selection. If Darwin was right in his controversy
with Wallace, if ' Nature never made species mutually
sterile by selection', the suggested experiment would
merely do by Artificial Selection what is not done by
Natural Selection.

Interspecific Sterility an incidental consequence of
Asyngamy,

It is by no means difficult to understand the mutual
sterility which is usual between natural species as an inci-
dental result of their separation by Asyngamy for a long-
period of time. In the process of fertilization a portion
of a single cell nucleus from one individual fuses with
a portion from another individual, the two combining
to form the complete nucleus of the first cell of the
offspring, from which all the countless cells of the future
individual will arise by division. Each part-nucleus con-
tains the whole of the hereditary qualities received from
and through its respective parent, and must therefore be
of inconceivable complexity. We can only speak in
generalities about processes of which so little is known,
but we cannot be wrong in assuming that sterility is
sometimes due to the fact that the complex architecture
1 More Letters, vol. i, p. 277, Letter 197.

ASYNGAMY LEADS TO STERILITY 81

of one part- nucleus fails in some way to suit the equally
Gomplex structure of the other. The individuals of an
interbreeding community form a biological whole, in which
selection inevitably keeps up a high standard of mutual
compatibility between the sexual nuclei. Individuals
whose sexual nuclei possess a structure which leads to
sterile combinations with those of other individuals are
excluded ' from contributing to the generations of the
future. As soon, however, as a group of individuals
ceases, from any reason, to breed with the rest of the
species, there is no reason why the compatibility of the
sexual nuclei of the two sets should be retained. Within
each set, selection would work as before and keep up
a high standard of compatibility ; between the sets, com-
patibility would only persist as a heritage of past selection,
gradually diminishing as slight changes of structure in
either or both of the sets rendered them less and less
fitted to produce fertile combinations.1

It is probable that of all the nice adjustments required in
the living organism, the mutual adjustment of these incon-
ceivably complex part-nuclei is the most delicate and
precise. Now, delicately adjusted organs, such as those
of sight, rapidly become incapable of performing their
functions when in any species they have been withdrawn
from the operation of Natural Selection ; similarly it is
suggested, that the adjustment of sexual nuclei to each
other would sooner or later give way when no longer
sustained by selection. If, then, mutual fertility be the
result of unceasing selection, and mutual sterility the

1 I must guard against the inference that the only explanation of
sterility is here set forth. It is indeed maintained that incompatibility of
the sexual part-nuclei is the inevitable outcome of enduring Asyngamy,
and is the probable cause of the sterility of hybrids. Thus it may be
suggested that sterility is a result of the combination of two incompatible
germ-plasms in the sexual cells of the hybrid. When the incompatibility
is not strongly marked we can understand how such sexual cells may be
capable of fertile fusion with the cells of either parent, but not with those
of another hybrid.

But short of these ultimate effects it must not be forgotten that there
are many obscure factors of Asyngamy — causes of various kinds which
interfere with the fusion under normal conditions or entirely prevent the
meeting of the sexual cells.

POtLTON

G

82

'WHAT IS A SPECIES?

inevitable, even if long-postponed, consequence of its
cessation, it is obvious that Huxley's difficulty is solved,
while his suggested experimental creation of sterility by
selection would not reproduce any natural operation:
it would afford a picture of a natural result but would be
produced in an unnatural way. This criticism of Huxley's
contention was advanced by the present writer three
years ago,1 the final conclusion being stated in the para-
graph printed below : —

' If, then, we cannot as yet reproduce by artificial
selection all the characteristics of natural species-forma-
tion, but can only imitate natural race-formation, we can,
nevertheless, appreciate the reasons for this want of
success, and are no more compelled to relinquish our full
confidence in natural selection than we are compelled to
adopt a guarded attitude towards evolution because our
historical records are not long enough to register the
change of one species into another.' 2

It was, therefore, with intense interest and pleasure
that I read the following sentences in a letter written
by Darwin to Huxley, December 28, [1862] — sentences
which show that criticism practically identical had been
made by the illustrious naturalist nearly forty years
earlier.

' We differ so much that it is no use arguing. To get
the degree of sterility you expect in recently formed
varieties seems to me simply hopeless. It seems to me
almost like those naturalists who declare they will never
believe that one species turns into another till they see
every stage in process.' 3

After reading, in the first volume of More Letters, the
often-repeated refutation of Huxley's objection so clearly
and strongly expressed in letters received by the objector
himself, it is surprising that no effect was produced, and
that reference should have been nearly always made
to this supposed flaw in the theory of Natural Selection,
whenever the great comparative anatomist had occasion

1 The Quarterly Review, No. 385, January, 1901, pp. 368-71.

2 loc. cit. p. 371.

3 More Letters, vol. i, p. 225, Letter 154.

FERTILITY BETWEEN DOMESTIC RACES 83

to speak or write on the broader aspects of biological
inquiry.1

Darwin also considered that there was something in
the very conditions of domestication which tended to
promote fertility between races and even between distinct
species. Thus he followed Pallas in believing that the
domestic dog has been derived from more than one wild
species, although he did not trace existing differences to
this cause but to Artificial Selection.2 However, as re-
gards the origin of the dog, ' the evidence is, and must
be, very doubtful,' as he wrote to Lyell, August ir,
[i860]. The fact which Darwin 'considered the most
remarkable as yet recorded with respect to the fertility
of hybrids ' was the fertility of the offspring of the
Common and Chinese Goose, originally described by
Eyton, and confirmed by Goodacre and by Darwin
himself. 1 The two species of goose now shown to
be fertile inter se are so distinct that they have
been placed by some authorities in distinct genera or
sub-genera.' 3

Another interesting and exceedingly difficult experi-
ment in hybridization has been carried through by the
Rev. P. St. M. Podmore, F.Z.S., who in September,
1899, after numerous failures, succeeded in rearing a
healthy male hybrid between the Ring Dove (Columba
palumbus) and the domestic pigeon. On May 27, 1903,

1 For several instances see Poulton's Charles Darwin and the Theory
of Natural Selection, Lond. 1896, pp. 124-41.

2 1 Though I believe that our domestic dogs have descended from
several wild forms, and though I must think that the sterility, which they
would probably have evinced, if crossed before being domesticated, has
been eliminated, yet I go but a very little way with Pallas & Co. in
their belief in the importance of the crossing and blending of the
aboriginal stocks. . . . Although the hound, greyhound, and bull-dog may
possibly have descended from three distinct stocks, I am convinced that
their present great amount of difference is mainly due to the same causes
[Artificial Selection] which have made the breeds of pigeons so different
from each other, though these breeds of pigeons have all descended from
one wild stock ; so that the Pallasian doctrine I look at as but of quite
secondary importance.' More Letters, vol. i, pp. 127, 128, Letter 80,
to Lyell, October 31, [1859].

3 Life and Letters^ vol. iii, p. 240.

G 2

84

'WHAT IS A SPECIES?'

this male was mated with a Blue Homer hen, which
produced healthy offspring.1

A comparison between the difficulty of producing such
a cross and that of obtaining hybrids between the Ring
Dove and the Rock Pigeon, the ancestor of the domestic
breeds, would probably throw much light on the Pallasian
hypothesis.

If the view here proposed be sound — that Syngamy
lies behind, and is at least provisionally implied in the
transition which means so much to the systematise and is
his only real evidence when the structural test breaks
down, the conclusion is suggested that the real inter-
specific barrier is not sterility but Asyngamy. Neverthe-
less, as argued on pp. 80, 81, Asyngamy will infallibly
lead to sterility, although the result may be long delayed.
This latter view, which was that of Darwin, is the exact
opposite of the ' physiological selection ' of Romanes,
in which sterility is supposed to arise spontaneously,
Asyngamy being not the cause, but the consequence.

Asyngamy as a consequence of Asympatry.

Asyngamy may be brought about in various ways,
of which the most obvious is geographical separation.
But Asyngamy is by no means the necessary result of
geographical discontinuity or Asympatry. Thus Darwin
considered that there is regular interbreeding between
Madeiran and continental birds of the same species. He
wrote to Hooker, August 8, [1866]. ' I do not think
it a mystery that birds have not been modified in Madeira.
Pray look at p. 422 of Origin [ed. iiij You would not
think it a mystery if you had seen the long lists which
I have (somewhere) of the birds annually blown, even in
flocks, to Madeira. The crossed stock would be the
more vigorous.' 2 An even more striking case is that

1 The Zoologist, November, 1903, p. 401.

8 More Letters, vol. i, pp. 487, 488, Letter 370. Dr. Karl Jordan has
maintained (' Der Gegensatz zwischen geographischer und nichtgeo-
graphischer Variation', Zeitschr. /. Wissenschaft. Zool. Bd. lxxxiii) that
this argument is valueless, inasmuch as more critical study of extensive

VARIOUS CAUSES OF ASYNGAMY 85

of Pyrameis cardui (the ' Painted Lady ' butterfly), which
ranges over nearly the whole world. The singular rarity
of local geographical races1 in this abundant species
is almost certainly due to the astonishing powers of dis-
persal which enable intermittent Syngamy to prevail over
the nearly whole vast area of its distribution.

A syngamy as a consequence of Mechanical Incompati-
bility.

An interesting and curious cause of persistent Asyngamy
is the ' Mechanical Selection ' so thoroughly explained
and abundantly illustrated by Karl Jordan.2 The com-
plex genital armature of Lepidoptera is during Syngamy
kept constant by unceasing selection. Comparatively
brief isolation of a group of individuals may lead to
a departure from the specific type of apparatus prevalent
in other areas, and may thus mechanically prevent Syn-
gamy if from any cause members of the group became
again sympatric with those of the parent species.

Asyngamy as a consequence of Preferential Mating.

A very different but exceedingly interesting origin of
Asyngamy is suggested by observations which support the
conclusion that varietal forms may show a tendency
towards preferential interbreeding.

H. W. Bates believed that he had strong evidence for
the existence of this tendency in the races of certain
tropical American butterflies. He stated this in his
epoch-making paper on the butterflies of the Amazon
valley,3 and it is interesting to observe in the published

material in recent years has revealed peculiarities in the Madeiran birds
which were unknown when Darwin wrote. But the general argument
still holds good, even though our knowledge has been increased and
modified. Madeiran birds have changed but slightly as compared with
those of the Galapagos Islands, where interbreeding with the related
mainland species has been almost or entirely prevented by local con-
ditions contrasting sharply with those by which Madeira is surrounded.

1 There is only the small, slightly modified form, kershawi, from the
Australian Region.

2 Novitaies Zoologicae, vol. iii, Dec. 1896. pp. 518-22.

3 Tra?ts. Linn. Soc, vol. xxiii (1862), p. 495.

86

WHAT IS A SPECIES V

letters how Darwin instantly fixed upon the point and
tried to elicit the data upon which the conclusion was
formed. Thus he wrote to Bates, November 20, [1862]: —
' No doubt with most people this [viz. the interpretation
of Mimicry] will be the cream of the paper ; but I am not
sure that all your facts and reasonings on variation, and
on the segregation of complete and semi-complete species,
is not really more, or at least as valuable, a part. I never
conceived the process nearly so clearly before ; one feels
present at the creation of new forms. I wish, however,
you had enlarged a little more on the pairing of similar
varieties ; a rather more numerous body of facts seems
here wanted.' 1

Then a few days later we find Darwin still thinking of
the subject, and writing to Hooker [1862, November^ : —
1 I have now finished his [Bates'] paper . . . ; it seems to
me admirable. To my mind the act of segregation of
varieties into species was never so plainly brought for-
ward, and there are heaps of capital miscellaneous obser-
vations.' 2

He also again wrote to Bates, probably on the following-
day, November 25, [1862 ?], asking for the solid facts
which are so greatly wanted : —

' Could you find me some place, even a footnote (though
these are in nine cases out of ten objectionable), where
you could state, as fully as your materials permit, all the
facts about similar varieties pairing, — at a guess how
many you caught, and how many now in your collection ?
I look at this fact as very important ; if not in your book,
put it somewhere else, or let me have cases.' 3

Remembering that Mr. Roland Trimen, F.R.S., had
expressed the same opinion as the result of his wide and
long experience of South African butterflies, I asked him
if he would kindly furnish me with a statement. His
reply, dated December 28, 1903, is as follows : — ' I have
noticed the tendency of the sexes of a variety to pair
together rather than with other varieties in the numerous

1 Life and Letters, vol. ii, p. 392.

2 More Letters, vol. i, p. 214, Letter 147.
s Ibid. vol. i, p. 215, Letter 148.

PREFERENTIAL MATING OF VARIETIES 87

cases of captured pairs sent to me by correspondents
in South Africa, and sometimes in cases of the same kind
which occurred to myself when collecting. The species
which particularly attracted my notice in this way during
my visit to Natal was Hypanis acheloia (= Gotzius> Herbst,
part), which is curiously variable on the underside, from
pale creamy to deep chocolate. I did not know of its
seasonal variation at the time, but I was in Natal just at
the change of season from wet to dry, when the inter-
mediate gradations were about, and I was struck with
the close resemblance of the sexes in pairs that I caught.
I am sorry to have nothing more definite to give on this
head ; it is a point much requiring exact and prolonged
observation.'

Mr. Trimen furthermore entertains no doubt that much,
if not all, of the material upon which he based the con-
clusion that the individuals of the same race tend to inter-
breed, exists, distinctively labelled, in the South African
Museum, at Cape Town. It is greatly to be hoped that
collectors will in future carefully label all specimens cap-
tured in coitu, and that the fact will be recorded on the
labels in museums and in private collections. It is
tantalizing to reflect upon the number of interesting and
important questions which could be now decided if this
practice had prevailed during the past fifty years. The
question of the possible origin of species from races by
preferential Syngamy is of such high importance that we
may confidently hope that the attention here directed
to the question, and especially the quotation of Darwin's
letters to Bates, may lead to that ' exact and prolonged
observation ', accompanied by careful records, without
which a safe decision cannot be reached. In the mean-
time the decided impressions of two such naturalists
as H. W. Bates in South America and Roland Trimen in
South Africa render it in every way probable that the
conclusion will be established on a firm foundation.1 It

1 Dr. T. A. Chapman sends me the following interesting and suggestive
note : —

' I met lately with a curious instance that deserves following up, of some
bearing on the question of selective mating of varieties.

88

WHAT IS A SPECIES?'

has been already pointed out on p. 65 that, should
preferential Syngamy be established on a large scale, the
instincts concerned would assume fundamental significance
in the origin of species.

Asyngct7ny as a consequence of the breaking of
a Syngamic Chain.

It is also possible that Asyngamy may be brought about
by the breaking of what we may call ' a Syngamic Chain'.
In the case of large and widely-distributed interbreed-
ing communities it is an open question whether Syngamy
would freely take place between the most distant of the
outlying sections if directly brought into contact, and
whether, even if Syngamy prevailed, there would be any
diminution in fertility.

Limnas chrysippus, perhaps the commonest butterfly
in the world, forms a probably continuous syngamic chain
stretching from the Cape of Good Hope at least as far as
Southern China. It is even reported from Japan. The
far Eastern forms are readily distinguishable by the
greater size of a single white spot, giving quite a different
appearance to the fore-wing. If pupae or eggs were
transferred from Hong-Kong or Macao to South Africa,
would the perfect butterflies freely interbreed with the
indigenous forms of chrysippus ? We do not know ; but
it is an experiment well worth trying, and one which

1 1 saw some broods of P. phlaeas lately that differed from each other,
but each brood was remarkably uniform. There were three broods, all bred
in the same conditions, in a greenhouse (by Mr. Carpenter of Leatherhead).
It seems difficult to explain this, unless both parents of each brood were
very nearly identical.

4 Mr. Frohawk, who has bred the species largely, tells me he has noticed
similar facts.

'When I bred Acronycta tridens and psi largely, some fifteen or more
years ago, I noticed that each brood had its own facies, and suggested
that tridens was now trying to break up into separate species just as some
ancestor split into psi, tridens, and cuspis.

'Another fact I observed in Acronycta rather bears on the other side
of the question. Of A. strigosa I reared a large brood, which paired
readily and frequently together, but no eggs were laid. I then got some
captured males, which paired with equal readiness with the bred females,
and as a result obtained plenty of fertile eggs/

THE BREAKING OF A SYNGAMIC CHAIN 89

would yield results valuable in many ways. If inter-
breeding did not take place, or if the unions were sterile,
then we should have the interesting case of a single
species which would instantly become two if through any
circumstance a central link dropped out of the chain.
Even if chrysippus yielded negative evidence in this
respect, it is highly probable that other widely-distributed
species would, under these circumstances, fall into two
or more groups, each held together by interbreeding, and
divided from others by Asyngamy.

Sterility, if present in any degree, would have been
brought about quite independently of selection ; for
in such cases each link of the chain would be freely
syngamic with the links on either side, and Asyngamy
or sterility would only be revealed by artificially bringing
together the widely-separated ends of the chain.

I cannot but think, therefore, that such experiments
made upon many carefully-selected species would probably
bring important additional evidence to bear upon the
controversy as to whether sterility between species is,
as Wallace believes, a selected quality, or, as Darwin
held, an incidental one. The deep interest of this
question is realized when we thus remember that the two
discoverers of Natural Selection held widely different
opinions about it. We cannot read the letters on both
sides, printed in the first volume of More Letters,
without realizing how deeply this divergence — one of the
principal differences between them — was felt by the two
great naturalists.

This is one of the many reasons for which I plead
with Mr. Roland Trimen 1 for the establishment of
tropical biological stations where work of the kind could
be carried on. Such establishments should be associated
with and be under the control of museums at home,
where the experiments could be directed and the results
studied and made available for all time for the researches

1 In his two Presidential Addresses to the Entomological Society oi
London. Proc. Ent. Soc. Lond., 1897, pp. xcvi, xcvii ; 1898, pp. lxxvii,
Ixxviii. See also his remarks from the Chair in the discussion on May 5.
1897, loc. cit. pp. xxxi, xxxii.

9o 1 WHAT IS A SPECIES?'

of the naturalist. Just as Harvard has her main Obser-
vatory at the University, but also maintains an outlying
institution in the Peruvian Andes, where certain kinds of
research, unsuited to New England, can be carried on
under the most favourable conditions, so our chief
museums should be provided with the means of es-
tablishing temporary stations in the most favourable
parts of the tropics. When I say temporary, I do not
refer to the means, but to the position of the station,
which should be freely movable in response to the call
of important problems as they present themselves for
solution in other localities.

Another urgent reason for the establishment of bio-
logical stations is forced upon us by the inadequacy
of Diagnosis for the separation of very variable species,
such as many of the African Acraeinae. I cordially
agree with the view often expressed to me by my friend
Mr. F. A. Heron, of the British Museum of Natural
History, that we shall never reach a secure foundation
until epigonic series have been obtained on a large
scale. To achieve this end a temporary station would
be required. In this way our museums could receive,
and should keep for permanent study, the whole of the
offspring reared from the eggs of a single parent. If
several species were thus represented by one or more
large epigonic series, we should know what to expect
and what to allow for ; and Diagnosis in general would
gain the most helpful guidance.

Asyngamy as a consequence of certain Adaptations for
Cross-Fertilization.

Asyngamy, as regards particular lines of union, has
also been incidentally brought about by certain adapta-
tions for cross-fertilization in plants, and such Asyngamy
has in some cases persisted long enough to have led to
sterility in greater or less degree. Of all Darwin's work,
that upon the fertilization of heterostyled plants threw
most light, he considered, upon sterility between species.
As Francis Darwin has stated, ' He found that a wonder-

CROSS-FERTILIZATION AND ASYNGAMY 91

fully close parallelism exists between hybridisation and
certain forms of fertilisation among heterostyled plants.
So that it is hardly an exaggeration to say that the
" illegitimately " reared seedlings are hybrids, although
both their parents belong to identically the same species.
In a letter to Professor Huxley, given in the second
volume [of Life and Letter s~\ (p. 384), my father writes
as if his researches on heterostyled plants tended to make
him believe that sterility is a selected or acquired quality.
But in his later publications, e. g. in the sixth edition
of the "Origin", he adheres to the belief that sterility
is an incidental rather than a selected quality. The
result of his work on heterostyled plants is of importance
as showing that sterility is no test of specific distinctness,
and that it depends on differentiation of the sexual
elements which is independent of any racial difference.' 1

The different forms of a heterostyled plant are adapted
for cross-fertilization by insects, and each individual of
each form is by the same means excluded more or less
completely from fertilization by another of the same form.
In the former case the sexual cells and the accessory
apparatus have been kept by selection during long genera-
tions of Syngamy in a high state of mutual compatibility ;
in the latter Asyngamy, partial or complete, has produced
a large measure of the sterility which is its inevitable
even if long-delayed result.

A re the injuriotts effects of Self- Fertilization the conse-
quence and not the cause of the Adaptations
for Cross- Fertilization t

The argument based upon heterostyled plants has,
I admit, carried me much further than I originally in-
tended, and it will be a pleasure to me if the following
criticism can be overthrown.

If the special adaptation of heterostyled plants for
particular lines of Syngamy has incidentally resulted
in lessened fertility, when the unions discouraged by
these adaptations are artificially secured, and in this case

1 Life and Letters, vol. iii, p. 296.

92

'WHAT IS A SPECIES?'

without appeal to the physiologically injurious effects
of self-fertilization, why should we not similarly explain
these effects whenever manifest in the self-bred 1 offspring
of any plant especially adapted for cross-fertilization ?

Darwin tells us in the Autobiography that as soon as
his 'attention was thoroughly aroused to the remarkable
fact that seedlings of self-fertilised parentage are inferior,
even in the first generation, in height and vigour to
seedlings of cross-fertilised parentage ',2 he entered upon
a series of experiments which lasted eleven years, ap-
pearing in 1876 as Effects of Cross and Self- Fertilisa-
tion in the Vegetable Kingdom. Of this work he wrote
in 1 88 1, ' the results there arrived at explain, as I believe,
the endless and wonderful contrivances for the transportal
of pollen from one plant to another of the same species.' 3
It is here suggested that these injurious results have
been not the cause but the consequence of specialization
for cross-fertilization. In such plants fertilization is
mainly brought about along the line for which special
adaptation is made : self-fertilization is relatively infre-
quent, often very rare, sometimes perhaps absent alto-
gether. May not the less successful results have followed
from a condition in which self-fertilization is but little
tried by the fires of selection ? 4 It would be of much
interest to compare a long series of experiments on
the cross-fertilization of plants which are habitually
self-fertilized and on the self-fertilization of plants in
which the adaptations for cross-fertilization are made
use of in widely different degrees.

This criticism, should it be sustained, would of course
throw much light upon the case of the Bee Orchis and the
numbers of tropical Orchidaceae, &c, which are now
known to be regularly self-fertilizing without apparent
physiological injury. It would also bear powerfully upon
an intrusive set of facts which must often have weighed
upon the minds of naturalists as they reflected upon the

1 See The Knight-Darwin Law, by Francis Darwin in Nature, Octo-
ber 27, 1898, p. 630.

2 Life and Letters, vol. i, p. 96. 3 Ibid. vol. i, p. 97.

4 See also A. R. Wallace in Darwinism, London, 1889, pp. 321-6.

EFFECTS OF SELF-FERTILIZATION 93

commonly received hypothesis that assumes the dangers
of continued breeding between near of kin. A. R. Wal-
lace speaks of these facts in Darwinism,1 and I have
drawn attention to them in discussing the meaning of
insect migration, although, as will be seen in the follow-
ing passage, without any serious doubt as to the physio-
logical significance of cross-fertilization.2

4 We may well inquire why it should be necessary for
such emigration, with a possible successful issue in coloni-
zation, to require the services of countless individuals
when the importation of half a dozen rabbits or a few
specimens of Pieris rapae will, for the naturalist, change
the face of a continent. The results of these unin-
tentional, or intentional but ill-considered, experiments
do indeed shake the belief in the paramount necessity
for crosses and the dangers of in-and-in breeding ; but
the end is not yet, and the teeming colonies which have
arisen from such small beginnings may in time vanish
from the operation of deep-seated causes. The varied
adaptations for cross-fertilization and the prevention
of in-and-in breeding are so evident in nature, that we
are compelled to believe that they meet and counteract
serious dangers which sooner or later would menace
the very existence of the species.'3 But now the considera-
tions set forth in this and the preceding Section throw
doubt upon the existence of such serious dangers and the
reality of any such compulsion.

It is impossible to do more than mention certain advan-
tages which may have favoured cross-fertilization, if here-
after the generally accepted physiological necessity turn out
to be a delusion. Brief reference may, however, be made
to the special advantages of community which are possible
through Syngamy alone. By interbreeding the favourable
variations arising in one direction are combined with
others arising in different directions ; by the kaleidoscopic
changes produced by interbreeding more varied results
are presented for selection, and the beneficial qualities
arising in one part of the mass may quickly become

1 p. 326. 2 Trans. Eni. Soc, Lond., 1902, pp. 460-65.

3 loc. cit. p. 464.

94

'WHAT IS A SPECIES?'

the heritage of the whole ; by interbreeding excessive
spontaneous variation is checked, and the whole com-
munity of the species advances surely and with stability
into adjustment with the progressive changes of the
environment.

We all remember Darwin's beautifully elaborated
metaphor1 by which the past history of evolution is
shown forth in the form and branching of a great tree.
Darwin represented species by the ' green and budding
twigs', and we may suppose that the leaves stand for
individuals, and that Syngamy is represented by the
contact of leaf with leaf when the branches sway in the
wind. And just as contact may run through large and
small, irregular and compact masses of leaves, so Syngamy
binds together groups of varying size and distribution.
So too a mass of foliage breached by a sudden storm
pictures for us the splitting of a syngamic chain into two
species by the disappearance of an intermediate link.

It has been a pleasure to me that the central idea
which I have endeavoured to bring before you should
be represented, I trust without violence to the imagery,
by means of ' the great Tree of Life, which fills with its
dead and broken branches the crust of the earth, and
covers the surface with its ever branching and beautiful
ramifications '.2

1 Origin of Species, 1859, p. 129.

2 loc. cit. p. 130.

Ill

THEORIES OF EVOLUTION

An Address delivered to the Boston Society of Natural History, as
an Introduction to the Discussion, held on February 7, 1894. Reprinted
from the Proceedings of the Society, vol. xxvi, p. 327.

Revised: additional footnotes.

In dealing with theories of evolution, I think that we
shall all be agreed that we may leave out of consideration
the question of the origin of life, and deal only with
what has happened to life after its appearance, however
that may have taken place. On this subject we shall
probably most of us still agree with the opinion of
Darwin \ that we are not in a position to even speculate
or think upon that question, — that any speculation about
it is almost a waste of time. And this, I think, remains
true in spite of the magnificent results of the organic
chemists in producing chemical bodies by synthesis,
which before had been regarded as capable of being
made only in the laboratory of the living body. Many
of these can now certainly be produced, but that is very
different indeed from creating protoplasm endowed with
life ; and so far are we from achieving this by any
chemical means that I think we may venture to dismiss
all consideration of the ultimate origin of life.

But granting the origin of living matter, these theories
of evolution which we are considering and hope to discuss
to-night can deal with it, and with their help we believe
that we can account for what has subsequently happened ;
namely, the evolution of all forms of life, animal and
vegetable, upon the surface of the earth.

The first of these theories which I propose to discuss
is the well-known Darwin-Wallace theory of Natural
Selection, with its three factors.

First, Individual Variation, — the fact that individuals
differ, and that the differences are essential or inherent

1 In Life and Letters.

96 THEORIES OF EVOLUTION

in the organism, so that even if animals were brought up
alike, we know they would still be unlike, and so that,
however much the offspring may resemble their parents,
they are never exactly like their parents or exactly like
each other. There is, then, first, individual difference,
one of the most essential facts in the organism.

Secondly, the fact of Heredity, — the fact that these
inherent differences may be and are inherited. Although
the hereditary transmission of acquired differences is
disputed, the transmission of those that are inherent
is certain. This stands before us as one of the most
obvious and certain of conclusions, equally proved by
the observation and experience of every one of us.

Thirdly, the fact that there must be a Struggle for
Existence ; that there are far more individuals born into
the world in every species, even the most slowly increasing,
than can possibly survive and reproduce.

These three factors must by logical necessity lead to
a survival of the fittest among individual variations. It
does not require a scientific mind to comprehend that, —
to infer that some amount of evolution must ensue from
the co-operation of those three factors, every one of which
stands firm and undisputed. Among all the advocates
of rival theories which have been brought forward to
explain evolution, no one has ever ventured to attempt
to disprove any one of these three factors. They stand
unchallenged.

The politician, Henry Fawcett, saw, long before scien-
tific people themselves understood what Darwin meant
by Natural Selection, that logically some result must
ensue from such co-operation. Fawcett said that Natural
Selection must produce evolution as surely as a round
stone will roll further than a square one. Some measure
of evolution is simply the logical result of the co-opera-
tion of these three undisputed, abundantly proved factors.

Now, certain writers have thought to undermine the
theory of Natural Selection by arguing that the important
and essential factor of individual variation is not explained
by the theory which rests upon it. True, it is not ; but
for the theory of Natural Selection, the explanation does

FACTORS OF NATURAL SELECTION 97

not signify. So long as individual variation is present,
so long as it is hereditary, it does not signify how it is
produced. There are, indeed, many theories professing
to account for it ; but biologists are not generally agreed
as to the manner in which it is produced. But so long
as it is there, it is available, and Natural Selection can
make use of it.

It is interesting to note that, when Newton discovered
the principle of Universal Gravitation, some people main-
tained that he had discovered nothing because he had
not explained what gravity itself was. Now, after over
two hundred years, we can safely assert that Universal
Gravitation stands out as one of the most triumphant
discoveries of the human intellect; and yet we, even
now, are just as much in the dark as to what gravitation
itself is as when Newton wrote. Exactly so it is with
regard to individual variation. So long as it is a fact
essential to organic nature, that one individual must be
different from another, and so long as these differences
are hereditary, so long may Natural Selection have abun-
dant material for its work, even though it does not itself
explain how that individual difference is produced. I am
very far from undervaluing the interest of such an explana-
tion ; on the contrary, I maintain that it forms one of
the most interesting of biological problems now before the
scientific world, or likely to be before it for many a day.

In fact, every successful attempt at scientific explana-
tion only interprets down to a certain level of causation ;
and this is just as true of Universal Gravitation and
Natural Selection as it is of smaller efforts. Down to
a certain level of causation, Natural Selection explains at
any rate some part of organic evolution. A more funda-
mental level would be to explain the factors upon which
Natural Selection itself depends ; but because we have not
yet reached that lower level, we have no reason for doubt-
ing, as some would believe, the complete efficiency, at
its own level, of the explanation we do happily possess.

The theory which stands in contrast with Natural
Selection, and has been supported in the United States
more fully than in any other civilized country, with the

POULTON J-J

98 THEORIES OF EVOLUTION

exception of France, is the theory we usually attribute
to Lamarck. Erasmus Darwin in England, however,
has the priority, in that he first brought forward the
principles which Lamarck more effectively supported.
But to Herbert Spencer belongs the chief credit, because
he has taken that part of the earlier theory which is
acceptable to modern biological thought, and upon this
basis has formed his great theory of evolution.

Lamarck believed in an innate tendency toward
perfection in animals. Now, that is a view which very
few zoologists at the present time, if any, would dare
to sustain. In fact, an evolution due to an innate
principle of perfection is not very far removed from
special creation, — a doctrine which opposes any theory
of evolution. Herbert Spencer, therefore, rejecting all
those elements of Lamarck, which the scientific world
could not possibly accept, has taken that which was
likely to commend itself to science, and upon it has formed
his great theory of evolution ; so that the Lamarckian
Theory, as presented to the world to-day, comes before
it in Spencerian language, and in the closest relation
to Spencerian thought. In saying this, however, I do
not by any means intend to be understood as supporting
Spencer's theories or the views upon which he bases them.

The Lamarckian Theory, then, upon which Spencer
has based his philosophy, is a theory of evolution de-
pendent, not like Natural Selection upon three factors,
but upon two. It depends first of all upon the effect
wrought on the individual by that which happens during
its lifetime. Instead of depending on those innate and
essential differences upon which Natural Selection rests,
this theory depends on those changes which are caused
during the life of the individual, — the action of some
external force upon it, the effect of its own will, the
changes produced by the use and disuse of its own parts.
The Lamarckian Theory depends in fact on all those
changes in an individual which we now call its Acquired
Characters ; that is, characters which the individual has
come to possess but which were not potentially present
at the very beginning of its development.

FACTORS OF LAMARCK'S THEORY 99

The first factor, therefore, is made up by changes that
are wrought in this way. The second factor is Heredity,
by which it is supposed that these changes are trans-
mitted ; and it is certainly true that if such transmission
is possible, some amount of evolution must result. You
will all be prepared to admit that if these two factors
represent facts, their co-operation must produce some
amount of evolution.

It is important to remember, however, that both factors
are not undisputed, as are the three factors of Dar-
winian Evolution. Although we all admit the existence
of acquired characters as the effect of external causes
upon the individual during its life, yet biologists are by
no means agreed that these effects are hereditary, and,
if not, the acquired character ends with the individual
in which it arose, and, not being handed on, can never
become a character of the species. It is impossible for
those who hold the Lamarckian or Spencerian view to
escape from this. If it is true that such characters are
transmitted, then the foundation of the theory is secure ;
but the transmission of acquired characters is by no
means proved. Herbert Spencer has preferred to occupy
himself in building a magnificent edifice upon this founda-
tion, rather than employ his acute intellect in testing its
firmness and security in every possible way.

So far as observation goes, all those characters
which are believed by many to owe their origin to
the Lamarckian principle are present, actually or poten-
tially, in the individual before the beginning of its active
life, before the operation of those causes which were
believed originally to account for the characters. Accord-
ing to the Lamarckian Theory such characters have
already become hereditary ; and therefore it is of essential
importance to the Lamarckian to prove that acquired
modifications can be and are transmitted. Only in this
way can he give good grounds for the opinion that such
characters, when they occur ready-made in the individual,
are to be explained by the action of external causes
during the lives of ancestors.

These are the two main theories of evolution. There

11 2

THEORIES OF EVOLUTION

are several others, upon which I will dwell only for a
moment because these two alone command any very
large amount of attention at the present time.

In the first place, Lamarck's theory of the innate
tendency towards progressive perfection in animals is
not held in exactly that form, but some zoologists in the
United States and other countries believe that they see
evidence in the rise and fall of certain groups of fossil
animals for the existence of a tendency towards extinc-
tion, or a tendency towards sudden growth, which lies
within the animal itself and is not determined by any
external cause. That is a very close approach to
Lamarck's original principle of an innate tendency in
one direction or another. I will not discuss it at any
length, because I think that this evening if we can get
a clear idea and attempt some discussion of the merits
of the two main theories of evolution, that will be as
much as we can expect. I will only say with regard
to the subject that arguments based upon fossil remains
are apt to be somewhat dangerous, because we have,
at least so far as the conditions of life are concerned,
so small an amount of evidence. In certain parts of
Africa, for instance, the presence of the tse-tse fly
absolutely limits the existence of some of the larger
quadrupeds. Wherever that fly is, the animal cannot
exist. It is very possible that in future times skeletons
will be found in specially large numbers on the borders
of districts where the fly abounded, and any attempt
to argue, from the appearance of the skeletons them-
selves, as to the causes of this great extinction will
obviously be entirely false and misleading. We have
in the skeleton of an animal so small an indication of
the events of its life and the conditions of its death,
that it is, except in very rare cases, most unsafe to argue
as to the causes of its extinction.

Another theory of evolution is one which has been
brought forward by Professor Geddes of Edinburgh. He
believes that there is an innate tendency towards growth
and towards that dissipation of matter which constitutes
its reverse, — the anabolic and katabolic tendencies, as he

OTHER THEORIES OF EVOLUTION 101

calls them. But that view, although he argues it with
much eloquence, has not been widely accepted, and
I think it will be generally admitted that it does not
yet rest on sufficient proof.

In addition to these, there are some who maintain the
position that there is an unknown cause of evolution.
They believe that these theories, although one or more
of them may be of value, are yet insufficient to account
for organic evolution. Those who take this line are of
course logically bound to bring forward the classes of
facts with which no existing theory is, as they maintain,
competent to deal.

All we shall have time for to-night is briefly to compare
Natural Selection, the Darwinian interpretation of evolu-
tion, with the Lamarckian Theory. It is interesting to
note that, although they are so essentially distinct one
from another, in earlier times these two theories appear
to have been entirely confused. Lamarckian Evolution,
Spencerian Evolution, appeals to the mind of man far
more strongly than Darwinian Evolution. Any one of
us, were he to have created the organic world, would
certainly have created it according to Lamarck. We
should have made evolution by use and disuse of parts,
and not by Natural Selection. However, we are not
concerned with the sort of world that we should have
created. The question before us as scientific men is
not what might have happened, but what has happened.
Nature, as I have heard Prof. Michael Foster say, has
a very queer way of going by roundabout paths and
refusing to take the roads we should lay out for her
ourselves, — roads which we look upon as the most direct
and obvious. The fact that the general aspect of the
Lamarckian Theory commends itself to the human mind
affords no reason for looking upon it as the correct one,
as opposed to the Darwinian Theory.

The Duke of Argyll, who is still strongly antagonistic
to Natural Selection, a few years ago wrote an article
in The Nineteenth Century called The Power of Loose
Analogy. By this title he intended to imply that those
who believe in Natural Selection have been led away

io2 THEORIES OF EVOLUTION

by the specious character of the words themselves.
I suppose that the Duke feels himself bound to account
in some way or other for the fact that people believe in
Natural Selection, while he does not, and accordingly he
suggests that the seductive power of the title employed
by Darwin has misled the scientific mind into a belief
in the process itself, — only rare and subtle intellects like
his own being proof against such an allurement. Natural:
a word expressive of familiar objects and processes always
around us. Selection : a process with which we are all
familiar. In this way it seems reasonable to the Duke
of Argyll to suppose that men have been misled by the
seductive nature of the terms employed by Darwin.
The terms apply to processes familiar to every one,
and therefore every one accepted them at once, without
inquiring what they really meant. This is, of course,
an explanation eminently satisfactory to the single writer
who was not to be overcome by 1 the power of loose
analogy'. But when we proceed to test this ingenious
suggestion, and look into the history of the times to
which it applies, when we read Darwin's letters, we find
that he continually complains that people do not under-
stand what he means by Natural Selection, and he almost
regrets having used the words. He says more than once
that he wishes he had employed Herbert Spencer's term,
the Survival of the Fittest, because his own title, Natural
Selection, is comprehended with such difficulty.

When we look to another class of evidence we find
equally sure ground for the conviction that Natural
Selection was driven into men's minds with the very
greatest difficulty, and by no means with the ease which
the Duke of Argyll assumes. It is very interesting to
consult the various skits written between twenty and
thirty-five years ago,1 in which the writers supposed that
they were making fun of Darwin's theory. If you will
read them, you will be struck by one very remarkable
fact : their authors are all making fun of Lamarck when
they believe they are making fun of Darwin.

1 The discussion at which these words were used took place Feb. 7,
1894.

EARLY PARODIES OF DARWINISM 103

I remember once seeing a picture in Punch, repre-
senting the evolution of the power of flight by the
human species. It represented a man standing upon
the roof of a house and waving his hands, which, in
consequence of the use to which they were put during
his individual life, grew somewhat in size. Passing
down to the next generation, his son was found waving
rather larger hands, and the waving made them still
larger. In the course of generations the descendants
acquired large wings and flew down from the roof of
the house. That was supposed to be a parody on
evolution according to Darwin. I have called it a skit,
but you will see at once that you cannot get a better
illustration of Lamarckism. It is Lamarckism. It is
not making fun of it ; it is a description of the process
itself.

Then Lord Neaves wrote a song [May, 1861] in which he
attempted to make great fun of Darwin's theory. It was
a very long song, many verses of which were skits upon
Lamarck, while supposed to be skits upon Darwin.

A deer with a neck that was longer by half
Than the rest of its family's (try not to laugh),
By stretching and stretching, became a Giraffe,
Which nobody can deny.

This is pure Lamarckism. The evolution was supposed
to be caused by stretching without any selection at all.

The best example of all, however, is given by Mr. Court-
hope, in his Paradise of Birds [1870]. I commend his
account of the evolution of birds and mammals to those who
believe the Lamarckian Theory. He tells us there about
the Ornithorhynchus, which he praises as a very prudent
beast : —

For he saw in the distance the strife for existence,

That must his grandchildren betide,
And resolved, as he could, for their ultimate good,

A remedy sure to provide.
With that, to prepare each descendant and heir

For a different diet and clime,
He laid, as a test, four eggs in his nest —

But he only laid two at a time.

THEORIES OF EVOLUTION

On the first he sat still, and kept using his bill,

That the head in his chicks might prevail:
Ere he hatched the next young, head downwards he slung

From the branches, to lengthen his tail.
Conceive how he watched till his chickens were hatched,

With what joy he observed that each brood
Were unlike at the start, had their dwellings apart,

And distinct adaptations for food.

From the bill, in brief words, were developed the Birds,

Unless our tame pigeons and ducks lie;
From the tail and hind legs, in the second-laid eggs,

The Apes and — Professor Huxley.

If we now turn to the skits on evolution written at the
present day we find they are very different. Miss May
Kendall, in writing her Ballad of the Ichthyosaurus, only
a few years ago [1887], says : —

E'er Man was developed, our brother,
We swam and we ducked and we dived,

And we dined, as a rule, on each other —
What matter, the toughest survived.

This is true Natural Selection. The authoress under-
stood what she was talking about. But, strangely enough,
what might well be looked upon as the most incisive
parody of Natural Selection was published more than ten
years too early ! The first part of James Russell Lowell's
Biglow Papers appeared between 1846 and 1848. One
of the earlier poems contains the following lines : —

Some flossifers think thet a fakkilty's granted

The minnit it's proved to be thoroughly wanted,
Thet a change o' demand makes a change o' condition,

An' thet everythin' 's nothin' except by position ;
Ez, fer instance, thet rubber-trees fust begun bearin'

Wen p'litikle conshunces come into wearin, —
Thet the fears of a monkey, whose holt chanced to fail,

Drawed the vertibry out to a prehensile tail.

If these amusing verses had been written later they
would certainly have been accepted as a satire upon the
origin as opposed to the survival of the fittest. As it is,
we must believe that they were indirectly inspired by the
Lamarckian idea of change wrought by the desires of
animals. The publication in 1844 of the Vestiges of the

ELIMINATION VERSUS SELECTION 105

Natural History of Creation was probably the immediate
occasion of the parody.

Another interesting question has been raised by
Professor Lloyd Morgan as to whether the phrase
' Natural Elimination ' would not be a more correct one
than ' Natural Selection \ The process is, of course,
selection by and through elimination. The survival of
the fittest means the elimination of the unfittest.

The relation between selection and elimination has
been put in a very striking way by Mr. Samuel Butler,
who says that according to Natural Selection we are
what we are, not by the successes of our fathers and
mothers, but by the failures of our uncles and aunts.
The question is, shall we dignify with the title of this
important cause of evolution those who have failed in the
struggle, and do not happen to be the ancestors of any
living species, or those who have succeeded in the
struggle and are now abundantly represented by descen-
dants ? I think that ' Natural Selection * forms on the
whole the best term for the process. It has the advantage,
also, of being the historic term proposed by Darwin.

Another important point in favour of ' Natural Selec-
tion ' as a term is that it suggests a parallelism or
comparison with the process of Artificial Selection. Yet
another point is the fact that you may find in the words
themselves all the three factors obviously suggested ; for
selection would be impossible without individual differ-
ence, and it would be useless unless these differences
were hereditary ; and, furthermore, selection implies
something which selects ; that is to say, the conditions of
nature. The rate of increase makes a struggle for
existence inevitable : natural conditions at the time deter-
mine the relationship between the qualities of survivors
and the qualities of those that fail. The three factors
of Natural Selection are implied by the very words
themselves.

Now I want very briefly to bring forward the chief
objections that have been urged against Natural Selection.
In the first place, if Natural Selection be true, all the
varied characters of animals and plants must prove to be

io6 THEORIES OF EVOLUTION

useful to the possessor in the struggle, or to have been
useful at some time in its history.

We are only required, however, to prove utility as
regards undoubted characters of the species, — and these
are hereditary, — and we must put on one side certain
characters which are confined to the individual in which
they appear. For instance, if it were proved that the
Mollusca of any one river differed from those of the same
species in another river, but that the differences were
confined to the individuals in which they occurred, so
that if these Mollusca were placed when young in the
second river, they would come to resemble those which
were proper to it, then we should not be concerned with
characters of the species at all. The language spoken
by a nation similarly is not a character of the human
species, for we know that a child of another nation would
acquire it perfectly, together with the particular modes
of thought and expression, tortuous or direct, which are
associated with it. These results of environment are not
characters of the human species. The individuals of the
human species come into the world with a certain
elasticity, a certain power of being developed in various
directions. But although the elasticity itself is a character
of the species, and is inherent, the particular quality in
which it may result when developed by environment is
certainly not a specific character.

The more we study the characters of animals in
general, even though we at first can see no utility, the
more we come to admit this principle, and to believe that
either now or in some past time, the characters have been
useful. I can certainly say of many characters which
I have studied in some of my investigations, that at first
they seemed to be meaningless, but afterwards appeared
to be of much importance in the struggle for existence.
I think we may safely assume with regard to many
characters of which we can now see no explanation that
ultimately the explanation will be forthcoming.

Being unable to prove utility does not invalidate
Natural Selection. If inutility could be proved for any
large class of characters, the theory would certainly be

OBJECTIONS TO DARWIN'S THEORY 107

destroyed as a wide-reaching and significant process.
I do not think, however, that any such evidence has been
forthcoming. I shall be interested in the discussion
which follows this paper to hear whether those who
believe in the Lamarckian Theory have such evidence to
produce, whether they can prove that any one great class
of characters has been useless in the past and remains
useless in the present.

Another kind of objection has been urged long ago,
and is still urged to-day. Why do we not find in the
palaeontological series the records of individual failures ?
Now, as regards the individuals of a species we cannot
expect to find any such evidence. What is failure ?
Failure means, according to Natural Selection, the failure
to produce offspring. The individual which comes into
the world and dies without offspring has failed. The
individual which is represented in the generations of the
future has succeeded. Natural Selection has set its stamp
upon that individual. But it is impossible to decide from
the fossil record whether any particular individual of
sufficient maturity had failed or succeeded. We have
not got the facts before us by which we can form any
conclusions.

Furthermore, we know the struggle for existence is
excessively complicated. The skeleton alone, though
of the highest value in association with the rest of the
organism, has been the sole turning-point in the struggle
in a comparatively small number of cases. When it has
been the turning-point in association with other parts, these
latter are absent. We have only a very small part of the
problem before us, and never can expect any more.

But while we cannot expect to find evidence of the
survival of the fittest among the individuals of a species,
we may expect to find it in the supplanting of classes by
classes, of groups of species by groups of species. Some
of the facts which have been brought forward as evidence
in this direction do, to my mind, very strongly support
the theory of Natural Selection by palaeontological
evidence. Consider especially the case of the large
mammals preceding those which gave rise to the quad-

io8 THEORIES OF EVOLUTION

rupeds now upon the earth. So far as we can judge
of these huge forms by their skeletons, they appear to
have possessed a bodily structure as well fitted to survive
as that of many now living in the world ; but they differed
from these latter in that they had extremely small brains.
We can easily understand that inferiority of intellect
would cause them to be worsted by animals which were
in other respects no better endowed.

Exactly parallel is the relation of man and the apes.
In bodily structure the difference is insignificant. In the
brain, however, we meet an important and essential
distinction. It would appear here that Natural Selection
has taken one particular part of the organism of paramount
importance in the struggle, and has developed that rather
than made a change along the whole line.

We see the same relationship in the gigantic reptiles
of the Secondary Period as compared with the mammals
of the Tertiary. The latter with their larger brains and
higher intelligence were able to supplant the former, just
as they have in turn been supplanted by the still larger
brained animals whose descendants now people the earth.
All this seems to me to afford very strong support to the
theory of Natural Selection.

Passing now to another class of objections : Natural
Selection, it is said, can never account for the beginnings
of things. Until an organ is raised to a useful level,
selection can have nothing to do with it. At first sight
that is a serious objection, but it suggests its own answer,
viz. that an organ so rarely develops ab initio. Organs
are not formed anew in an animal, but they are formed
by the modification of pre-existing organs ; so that, instead
of having one beginning for each organ, we have to push
the beginning further and further back, and find that
a single origin accounts for several successive organs, or
at any rate several functions instead of one.

The typical vertebrate has four limbs. These in
fishes are used for swimming, while in terrestrial forms
the same limbs are modified and used for walking. New
organs are not introduced, but the old are modified for
a new purpose. When the terrestrial form again becomes

THE ORIGIN OF ORGANS 109

aquatic, the limb that was used for terrestrial progression
is modified back into a functional fin ; and again, when
flight becomes necessary, the same organ is used for the
new function. So that whatever the changes in the mode
of progression, we need no new organ at all ; for the old
organ is used for the new purpose. It is very much
easier to understand how a useful level can be attained
in that way than by organs starting ad initio. But of
course we must come down to a true beginning if we
push our inquiries far enough. In attempting this, we
are carried to those remote times in which the ancestors
of vertebrates arose. Upon these forms we can do no
more than speculate, but it is at any rate impossible to
prove that bud-like projections from the body, probably
later reduced to four, may not have been useful, from
their very beginning, to a slender worm-like animal for
pushing its way through mud or thick weeds, or for the
purpose of respiration. Professor E. B. Tylor has told
me that he believes that the same thing holds with regard
to human weapons. He said that, in examining ancient
weapons, he was often struck with the fact that a weapon
or implement had ultimately turned out to be so very
much more useful for a new purpose rather than that for
which it was originally formed. Here, then, one origin
apparently accounts for several forms of implement.

Another objection raised against Natural Selection is
that a selective cause is never a true cause. Professor
Cope means to imply that when he speaks of the 1 Origin
of the fittest'. But Darwin's argument on this point is
perfectly sufficient. He says that when a man drops
iron into sulphuric acid, he does not originate the chemical
force that operates, but he may be fairly said to make
sulphate of iron. So Natural Selection does not itself
originate the factors upon which it depends, but it is so
essential to the result that it may be fairly looked upon
as the true cause (at that level of causation). In Galton's
work we have a most complete inquiry into human
variation and its inheritance, and he shows us that such
variation by itself, unguided by selection, can never
advance to anything. Even if you start with ancestors

I IO

THEORIES OF EVOLUTION

who are remarkable for any intellectual or structural
feature, their descendants, although some of them may
partake of their parents' peculiarities, sometimes even to
an increased extent, will ultimately return to the pattern
of the race. There is always a ' recession towards
mediocrity'. Hence, unguided variation can never
explain the ' origin of the fittest \ [Since these last words
were written De Vries and others have brought forward
many facts which, as they believe, support the hypothesis
that sudden large variations lead to a fresh position of
organic stability and the origin of a new species by
' Mutation'. Natural Selection is, however, still invoked
in order to arbitrate between different mutations, as well
as between these and the parent species. A final decision
as to whether the course of evolutionary history has been
interrupted or continuous will probably be reached by the
study of Palaeontology.]

I have briefly touched on some of the chief difficulties
which are advanced against Natural Selection. I now
propose to devote the remaining part of my time to the
difficulties which seem to me to apply to the Lamarckian
Theory.

Lamarckian Evolution, as I have mentioned before,
depends upon acquired characters. A good deal of mis-
conception has arisen from this use of the word ' acquired'.
An acquired character has sometimes been interpreted to
mean any character that an animal has come to possess ;
hence, inherent and acquired characters have been con-
fused. The word ' acquired ', as used by biologists, must
be understood to have a limited and special application,
meaning only those characters which have been produced
in the organism by the incidence of external forces, or by
the action of its own forces, use and disuse of parts, and
so on, during its life. Weismann has suggested the term
4 Blastogenic ' for characters potentially present in the
germ at the very beginning of life, and ' Somatogenic '
for those which appear afterwards and are not potentially
present in the germ. Here blastogenic is the equivalent
of inherent, and somatogenic of acquired.

Some years ago I suggested that the terms ' Centri-

OBJECTIONS TO LAMARCK'S THEORY in

petal ' and 1 Centrifugal ' might be employed to express
this acquired difference.1 Acquired characters are centri-
petal, because they are impressed upon the body or one
of its parts from without ; inherent characters are centri-
fugal, because, arising from within due to the essential
nature of the organism itself, in the course of development
they come to appear, as it were, on the surface as visible
features.

When we now consider the transmission of acquired
characters, upon which the Lamarckian Theory certainly
depends, we are led first of all to inquire whether it is
possible to frame a theory of heredity within which such
transmission can be included. If, for instance, there is
a change in the brain of an animal, owing to the exercise
of some part of it, how can such a change in the brain-
cell be transferred to the germ-cells of the animal, so as
to be transmitted to its offspring ? It may be objected, if
you can prove that such transmission does take place, it is
no matter how it takes place. Quite true, if the evidence
is sufficient and indisputable. But we must remember
that the amount of evidence required, in order that there
may be sufficient, depends upon the probability or impro-
bability of the thing to be proved. This view is extremely
well put by Professor Huxley in his memoir of Hume,
where he says that if any one came to him and stated
that he had seen a piebald horse in Piccadilly he would
be prepared to believe it ; that he might require con-
firmatory evidence if the statement were that a zebra had
been seen ; but that if even the friend in whom he trusted
told him he had seen a centaur trotting down that eminent
thoroughfare, he should emphatically disbelieve it, and
that nothing short of a monograph on the anatomy of the
centaur by a comparative anatomist of the stamp of
Johannes Muller would convince him that the observation
was correct. We are compelled to admit that the amount
of evidence we require does to a great extent depend
upon the inherent probability or improbability of the
conclusion to be sustained. If it appears to us to be
almost impossible to conceive of a mechanism whereby

1 See page 123.

ii2 THEORIES OF EVOLUTION

an acquired character can be transmitted from the outlying
parts of the organism to its germ-cells, then we have
every reason for scrutinizing most carefully any evidence
that is alleged to prove such transmission.

Let me first of all give you a concrete example which
is frequently brought forward by those in this country 1
who believe in the Lamarckian Theory, and have chiefly
studied the skeletons of Mammalia. They say the joint
of an animal possesses just the sort of shape that would
be produced by the motion of the joint itself, and they
urge that the joint as we see it has arisen from the
hereditary effects of that motion. They look upon this
as a very satisfactory explanation, because they consider
it to be so obvious and fundamental. You do not require
anything further, selection is unnecessary, and even the
individual variation — so mysterious a factor of the
Darwinian Theory — is here entirely explained.

But is the interpretation valid ? In the first place, it
is clear that such an hypothesis can never afford a wide
or general explanation. There are a great many parts
of the animal body which are not modified by their use.
You cannot thus explain the growth of hair, or the colour
upon the surface of the organism. For these and other
useful but passive structures the Lamarckian interpre-
tation will not hold at all. Hence we may divide the
organism into two sections, to one of which the Lamarckian
Theory might be held to apply, and to the other the
Darwinian alone.

But upholders of the Darwinian Theory consider that
it applies to the other section as well. They point out,
that while the form of the joint is the sort of form that
would be produced by the motion, it is also necessarily
one which admits of convenient motion, that motion has
been essential to the life of the organism, that alert and
rapid movements have been a necessity in the struggle
for existence, and that any form which would prevent or
clog the movements would be at once destroyed by the
operation of Natural Selection. Natural Selection they
hold to be competent to explain those parts which the
1 The United States.

PASSIVE AND ACTIVE STRUCTURES 113

Lamarckians also claim to explain, while it offers the
only explanation of the other parts.

If we suppose that Lamarckian Evolution in part
explains the actively used organs, and Darwinian Evolu-
tion in part, we should expect that modification would
take place more quickly in that section of the organism
where the two principles were at work than in the other
section where only one principle — the Darwinian — can
play a part. But there is no evidence of such especially
rapid evolution. It seems to me that we are in a position
to use the old principle of cutting off superfluous causes.
No unnecessary cause should ever be introduced into an
explanation, and if Lamarckism, untenable in the one
section, is superfluous in the other, it should be removed,
unless there is very clear evidence proving that it has
been at work.

Furthermore, in certain cases, such as the protective
attitudes and appearances assumed by many animals, we
meet with clear evidence that the two kinds of parts —
those that are affected by their use and those that are
not affected — have undergone development together,
suggesting strongly that their evolution has been under
the direction of one set of forces, and not of two sets
which have little in common.

Having now brought forward certain general objections
to the Lamarckian position, let me take exception to one
or two special cases.

Certain animals, such as lobsters and crabs, have the
power of very readily parting with some of the most
important of their members. The large claws are easily
thrown off, and this may be of great advantage in the
struggle for life, because when an individual is attacked,
and has seized the enemy with its claw, it has a chance of
escaping. In the case of the lobster, the dismembered
claw may not let go of the enemy although the enemy
may wish to let go of the claw. The claw may take
charge of the enemy while the lobster escapes.

Now that is a very interesting adaptation. We find
the claw so constituted that it can be thrown off, but even
when thrown off it continues to be of much use to the

pocuon l

U4

THEORIES OF EVOLUTION

organism. Its nervous and muscular mechanism is so
arranged that mutilation actually stimulates it to contract,
and it continues to hold the enemy. In the case of
certain crabs, the dismembered claws keep snapping and
jumping about. The same is true of the tails of many
lizards, which, when thrown off, will jump about in the most
active way, distracting the attention of the enemy, while the
lizard makes its escape. Here, too, mutilation stimulates
the nervous and muscular mechanism in claw and tail.

In these cases of actively used parts of the organism
the Lamarckian interpretation is absolutely at fault.
You cannot apply it. It is impossible to explain upon
the theory of the transmitted effects of use and disuse.
No activity manifested by the tail after it has ceased to
be part of the lizard can ever be transmitted. Not only
that, but it is difficult to see how the development under-
gone by the tail from the effects of use and disuse, &c,
up to the time of its severance, can be hereditary. And
so with the claw. The large claws are the most im-
portant appendages of the lobster, and yet it is certain
that many a lobster loses one of these organs and grows
a new one, several times in the course of its life. We
have here a very specialized organ with definite functions
which continue in even an increased degree after severance
from the animal : all this is readily explained by the
Darwinian Theory, but cannot be explained by the
Lamarckian.

The same inadequacy of the Lamarckian Theory is
forced upon us when we examine a little more deeply
into the nature of the process which is supposed to occur.
The Lamarckians attempt to explain joints and some
other structures by the effects of stress and pressure, but
when we look into the matter we find that the explanation
is not so complete as it is supposed to be.

For instance, it has been believed in the United States
by many distinguished biologists that the complex shape
of mammalian teeth is due to pressure produced by
mastication. As the pressure has been applied to the
tooth, so has the tooth grown. But would pressure
produce such an effect upon a tooth ? That is certainly

FORMS OF JOINTS AND TEETH 115

not our experience. Pressure and friction have an
unfortunate way of wearing a hole in the tooth, rather
than causing it to grow an elevation. As a matter of fact
we know that the shape of teeth is predetermined, long
before they are cut, in the soft dental matrix beneath the
gum. It is not a question of the transmission of acquired
characters, but the supposed transmission of a character
which the parent cannot by any means acquire. Teeth,
so far as they react to pressure or friction, can only react
by wearing away.

With regard to the joint, we are told by some La-
marckian writers that pressure and friction produce the
reverse effect and wear away cavities rather than stimulate
growth. I was reading the other day a most interesting
paper by Dr. Wortman of New York, in which the
author attempted to explain the occurrence of a furrow
in a joint owing to the pressure of a corresponding ridge.
The pressure of the ridge, he said, produces a furrow in
the opposite side of the joint. It seems to me that in this
we are going a little beyond what physiology and histology
teach us and making a blind appeal to mechanical forces
unsupported by any adequate investigation of the tissues
concerned. Is it likely that a bone would react to
intermittent pressure by producing a furrow? It is far
more probable that the reverse effect would tend to be
caused.

I will only ask one more question with regard to this
subject of use and disuse, and that is, why, if you are
going to explain any of these parts by pressure and
friction, should the process be stopped when a useful
level is reached ? If the pressure does cause such effects
and they are hereditary, how are they prevented from
increasing beyond all bounds in the course of generations ?
Why should pressure on teeth cease to produce further
growth, when the tubercle has reached its proper height ?
The fact that all these shapes of bones and teeth just
reach and stay at an adaptive level is the strongest
evidence that they are not produced by the operation of
mechanical forces, but by Natural Selection.

We now pass to the consideration of indirect evidence:

I 2

u6 THEORIES OF EVOLUTION

that it would be impossible to explain evolution without
the Lamarckian Theory.

Time will permit me to deal with only one class of
characters, a class associated with the nervous system
and manifested as instinct. These instinctive actions
are generally thought to be the strongest evidence in
favour of Lamarckian Evolution. It has been argued
that we cannot explain the instinctive action of animals —
the wonderful instincts which are due, as we know, to
modifications of the nervous system, — except by supposing
that animals have intelligently modified their actions in
consequence of experience and observation, and that the
result has then been transmitted and has become the
non-intelligent instinct of their offspring. If we had no
other explanation of instinctive action, such an interpreta-
tion would constitute a strong support to the Lamarckian
Theory.

I do not, however, believe that this is the only, or,
indeed, the correct explanation of instinct. In consider-
ing this question, we must distinguish between the
instinct manifested by many of the higher invertebrate
animals and much that we are apt to call the instinct
of the vertebrates. A great many actions which are put
down to instinct in the higher vertebrates, such as birds
and mammals, are not instinctive at all, but the result of
intelligence. We see an example of this in the altered
behaviour of the seal which, as Nansen tells us, took up
a position on the outer ice-floes to escape the dangers of
the polar bear, and afterwards incurred this very danger
on the inner floes to avoid the greater peril from the
hunter. This is a clear case of intelligent association,
and no instinctive avoidance of danger. So also with
a bird which flies away if you have a gun in your hand,
but allows you to come near when you have a walking-
stick. This is the result of intelligence and not merely
instinct ; and we must carefully distinguish between
a lesson learned by the individual, however well learned
and easily repeated it may be, and a true instinctive action
which is never learned at all but springs fully formed
into existence. Such true instincts certainly occur in the

THE ORIGIN OF INSTINCT 117

higher vertebrates, such as the act of sucking performed
so perfectly without any education or practice by the
newly-born mammal. But in the lower animals true
instincts are relatively far more numerous and play
a most prominent part in the life of the individual. In
these cases of true instinct I would suggest that we are
dealing with actions which have never been intelligent at
any time in the past history of the species, but have
arisen through the operation of Natural Selection upon
the nervous system. Certain activities which are most
strongly held to be the outcome of the transmission of
experience and the acquired results of practice obviously
cannot be explained in this way.

For instance, how upon any such hypothesis can you
explain the wonderful structure of the cocoon spun by the
larva of an insect ? The view would be, I suppose, that
the ancestral larva spun a cocoon which was not much of
a success and was in consequence attacked by enemies ;
that the larva observed these attacks, and accordingly
improved its cocoon. But that is not the way in which
the struggle for existence is waged with insects. If the
larva failed, it failed, and that would be the end of the
matter. It has no chance of improvement ; it has no
opportunity of learning by experience. Its only chance
of survival is to avoid experience of foes altogether ;
experience is the most dangerous thing in the world to
an edible insect. This becomes still more obvious when
we remember that failure or success is almost always
determined long after the cocoon is made. The cater-
pillar perhaps spins the cocoon in autumn, but the real
stress of competition will come in winter, when insect-
eating animals are pressed hard with hunger and search
high and low for food. But the caterpillar by this time
is a chrysalis and of course has no opportunity of im-
proving the cocoon. The selective test is applied long
after the operation has been performed, and when there
is no possibility of gaining by experience. We are thrown
back, then, solely upon Natural Selection, which acts on
the nervous system of the caterpillar, and thus compels
it to make the cocoon in a certain way. In other words,

n8 THEORIES OF EVOLUTION

those caterpillars which are impelled by their nervous
system to make ill-formed, conspicuous cocoons have no
chance of living, and, in the perfect stage, of producing
offspring. Hence, the selection caused by the keen sight
of foes first raises and then maintains at a high level the
standard of cocoon-making.

This contention as to the uselessness and danger of
experience applies to the whole of those smaller defenceless
animals which, when once they have been detected, have
no chance of fighting with their enemies and but little of
escaping.

Another special kind of instinct has been greatly relied
on by Romanes as evidence for the Lamarckian Theory
of transmitted experience. Certain Hymenoptera allied
to wasps, the Fossores or sand-wasps, possess an instinct
which leads them to sting larvae and store them up in
their nests as food for their young. It is generally be-
lieved that the larva is stung in the central part of the
nervous system so that it can no longer struggle. I say
' generally believed ' because it has been pointed out to
me by so distinguished an observer as Dr. G. W. Peck-
ham of Milwaukee, that certain facts are opposed to the
generally received account.1 It is to be hoped that the
observations, which are chiefly due to Fabre, will be
repeated and tested as minutely as possible. The prey
is stored up in the mud-tube or burrow of the Hymeno-
pteron, and keeps perfectly fresh because it is alive,
although completely paralysed. Larvae stored up in this
way appear to live much longer than those which, in the
full possession of their faculties, are deprived of food.

Now this is a very wonderful instinct, which, it has been
argued, cannot be explained except on Lamarckian lines.
I maintain, on the contrary, that it is a case which cannot
by any possibility be explained by the Lamarckian Theory.

1 My friends Mr. and Mrs. Peckham have now published their
valuable researches upon the habits of the Fossorial Hymenoptera in
two works, which are a mine of information on this fascinating subject.
George W. Peckham and Elizabeth G. Peckham, On the Instincts and
Habits of the Solitary Wasps; Wisconsin Geological and Natural History
Survey: Madison, Wis., U.S.A., 1898. Wasps Social and Solitary.
Boston and New York, 1905.

PROPHETIC INSTINCT OF FOSSOR 119

The wasp-like insect has no opportunity of learning by
experience, because it can never know whether the larva
stored up is a failure or a success. If the larva had not
been stung, or, accepting the received accounts, had been
stung in the wrong place, it would struggle and perhaps
kill the young grub; or, dying of starvation, it might dry
up and be useless as food. But the Hymenopteron never
goes back to inquire. It makes all the difference to the
young grubs whether the food provided for them is in an
appropriate condition or not, but it makes no difference
whatever to the parent insect. The latter seals up the
chamber in which its eggs have been laid and never
opens it again ; it has no chance of noting the failure or
success of the food it has provided. It is clearly a case,
like that of the cocoon, which cannot be explained on the
Lamarckian Theory and must be explained on the Dar-
winian. And this latter interpretation is easy : those
insects which possessed the nervous mechanism impelling
them to provide food in an appropriate condition gave to
their offspring the opportunity of surviving and inheriting
the same instinct ; while others, impelled to perform less
efficient actions, were thereby cut off from any representa-
tion in the next generation.

If the origin of wonderful and complex examples of
instinct such as these cannot be explained by the La-
marckian Theory but readily by the Darwinian, why
should not Natural Selection also offer an adequate
explanation of all other cases ?

I have already taken up a great deal too much of your
time. I hope to have the opportunity to-night of hearing
stronger arguments in favour of the Lamarckian Theory
than it has been my opportunity to meet hitherto.

Note. — In revising the shorthand transcript for publication, I have
not made any changes which alter the character of the address. It
remains the record of a spoken address, the sequence and continuity
of which were maintained by the use of brief notes. I have not verified
the quoted opinions and words of others, and there are probably verbal
errors. I believe, however, that in every case the true meaning of the
author has been preserved.

Oxford, May 21, 1894.

IV

THEORIES OF HEREDITY

The Presidential Address read at the Annual Meeting of the Midland
Union of Natural History Societies, held at Oxford, September 23, 1889.
Reprinted from the Midland Naturalist, November, 1889.

Revised and greatly modified: in large part rewritten.

In order to understand the problem of heredity, it is
necessary to have some general idea of the manner in
which the higher organisms are built up. The lowest
organisms, both animal and vegetable (Protozoa and
Protophyta), consist of single cells, while all higher
animals and plants (Metazoa and Metaphyta) are com-
posed of cell aggregates. A single Protozoon does not
represent a single Metazoon, but one of the innumerable
units of which all except the minutest Metazoa are com-
posed.

The higher animals are, however, something more
than aggregates of cells ; they are cell-republics, in which,
at any rate in health, the structure and function of the
units are subordinated to the good of the whole. Certain
diseases are due to the literal tnsttbordination of some
of these units, which grow and multiply in defiance of
that relationship in proportion, in position, and in the
consumption of nutriment, which is necessary for the
well-being of the whole. The surest hope of successful
treatment lies in an early extirpation of the centre of
insurrection. Later on, the centre will not only grow,
but will dispatch agents along the channels of communi-
cation, setting up other centres of mischief in distant
parts of the body. Such a republic is not only liable to
destruction from within by the revolt of its own members,
but also by the successful attack of enemies from without.
Numerous other forms of life are ever seeking to obtain a

Diagram /.

Pangenesis.

Stage i.
Diagram III.

Development of
Identical Twins.

Stage 4.

©0©3

Stage 3.

Stage 1.
Diagram //.

Continuity of
Germ-Plasm.

face p. 120

BODY-CELLS AND GERM-CELLS

121

lodgement within it,»and, if successful, discomfort, disease,
or death, is almost invariably caused.1 The larger
enemies, or parasites, have been known for ages ; while
the smaller, but far more dangerous foes, the germs of
disease, have only been appreciated in comparatively
recent times. Now, however, they attract a very large
amount of attention, and the germ theory of disease has
led to the most fruitful advance ever made in the history
of medicine and surgery.

The cells, or units, which compose the body of one of
the higher animals differ greatly in structure according
to the part they play in the economy of the organism.
Thus, in man, the upper skin, or epidermis, is composed
of layers of cells, becoming horny scales on the surface.
The epidermic cells are continuous with those lining the
digestive tract and passing up the ducts into the various
glandular organs. The connective tissues which bind
the various structures together and make up many parts,
such as tendons and the lower skin or dermis, are also
composed of cells and fibrous elements derived from
cells. The supporting tissues, bone and cartilage, are
composed of cells and structures derived from cells ; and
the same is true of the great contractile tissues, striped
and unstriped muscular fibre, and of the elements of the
nervous system — nerve-cells and nerve-fibres. Out of
many of these elements the complex organs are built
up, with the addition of peculiar or specific cells of their
own.

All the varied units which compose the Metazoan body
may be classified under two chief heads. There are the
cells which are concerned with maintaining the life of the
individual — the body-cells or somatic cells ; and there are
those concerned with maintaining the life of the species
— the reproductive cells or germ-cells.

In the higher animals, the latter are aggregated in

1 An example of benefit rather than injury may be found in the lactic
acid bacillus which, according to MetschnikofT, plays a valuable part in
digestion. MetschnikofT believes that the custom of drinking sour milk,
common to many races, is founded on an empirical knowledge of the
beneficial effects wrought by this bacillus.

122 THEORIES OF HEREDITY

a comparatively limited area, the reproductive organs
(ovaries or testes). These primary sexual organs can be
removed in the operation of castration without essentially
affecting any somatic cells except the components of
characters indicative of sex. When the influence of the
germ-cells is withdrawn such secondary sexual characters,
as they are called, tend to be transformed into those
indicative of the opposite sex. Although the succession
of individuals is of course prevented by the removal of
the primary organs, the life of the individual may continue
to its normal length.

The problem of heredity may be stated as follows : —
How is it that a single germ-cell can produce, by repeated
division, an organism in which the peculiarities of the
somatic units of the parent are reproduced ? A single
cell separates from a small area in the body of the parent,
but it controls the development of the offspring, so that
the characters of every part of the parent are repeated
with more or less accuracy.

It seems that there are only two possible ways in which
this marvellous fact can be explained. First, the whole
of the somatic cells may be so intimately connected with
the germ-cells that each of the latter bears within itself
the influence of the whole of the former — an influence,
too, of such a nature as to lead to the reappearance of
the corresponding somatic cell in the course of develop-
ment ; clearly, therefore, an influence of a material nature.
Secondly, we may look upon the germ-cells as directly
developed from the germ-cell from which the parent
arose. Parent and offspring would then resemble each
other, because they are developed from the same thing,
although at different times.

There is an essential difference between these two
theories of heredity. In the first, the germ-cells may
bear the impress of every event which happens to the
somatic cells during the life of the parent, and such
characters may therefore be looked for in the offspring ;
in the second, offspring and parent can only resemble
each other in characters which were predetermined in
the germ-cell from which the parent arose. These latter

ACQUIRED CHARACTERS DEFINED 123

characters — peculiarities of any somatic cell which follow
from the structure of the original germ-cell — have there-
fore been called blastogenic by Weismann. They have
also been called spontaneous, because they spring up in
the individual without reference to the causes which
operate during its lifetime ; also inherent or centri-
fugal, because they belong to the essential nature of the
individual, and because they may be looked upon as
developing from within rather than as impressed from
without. Conversely, the characters which appear in
the somatic cells as the result of external influences, or
as the outcome of their own special or unusual activities,
— in fact, any characters appearing in the body which
were not predetermined in the original germ-cell, have
been called somatogefiic , because their origin cannot be
traced to the structure of the original germ-cell, but is
entirely due to events brought about in somatic cells ;
they are also called acquired, because the individual comes
to possess them, although they do not belong to its
essential nature ; and centripetal, because they are im-
pressed upon the individual from without, and are not
the outcome of internal causes.

It is my object to give a more detailed account of
these two theories of heredity, and then to allude very
briefly to some of the evidence which has been believed
to establish the hereditary transmission of acquired or
somatogenic characters.

The first theory, maintaining that a close relationship
of a material kind exists throughout life between somatic
and germ-cells, was suggested by Darwin, under the
name of Pangenesis.

This theory is illustrated by Diagram /, in which the
large circles, indicated by the capital letters P to \Y,
represent the body-cells of a Metazoon, which, for the
sake of simplicity, is supposed to be composed of only
sixteen somatic and four germ-cells, the latter beiiiL;
placed in the centre. The somatic cells are arranged in
pairs, P P, Q O, &c, in order to indicate the fact that
similar cells are generally found on opposite sides of the
body in the higher Metazoa (bilateral symmetry).

i24 THEORIES OF HEREDITY

The fact that each germ-cell, placed under appropriate
conditions, will develop somatic cells like those of the
parent, is explained by the supposition that all the latter
cells give off gemmules, which are stored up in the germ-
cells. The gemmules are represented in Diagram / by
the small circles marked with the small letters p to w.
The gemmules are seen to be traversing the space which
separates them from the germ-cells, and also stored up
in the latter. This double representation is explained
on p. 125.

The space between the circle of somatic cells and the
central germ-cells in Diagram / has been introduced
for the sake of clearness. In higher animals the distance
which the gemmules would be compelled to travel in
order that the change in a brain-cell may be registered
in a germ-cell, would be relatively greater than that
represented in the diagram.

With this hypothesis every somatic cell is a germ-cell,
while the germ-cells proper are merely the meeting-place
for the germs of somatic cells. Because every part of
the body is thus supposed to reproduce itself, Darwin
called his hypothesis Pangenesis. Each germ-cell is sup-
posed to be, as it were, an extract of the whole body ;
a microcosm, in which every cell that takes part in the
composition of the organism is represented.

The first difficulty which this hypothesis encounters
is the almost infinite complexity of a germ-cell which
contains a material particle, a representative or gemmule,
from every somatic cell of one of the higher animals.
The countless number of cells in the human body may
be imagined from the fact that it would require over ten
million red blood corpuscles, lying flat, one deep, to
cover an area one inch square. And yet every single
blood corpuscle, although not exactly a cell itself, is the
product of a single cell.

But this is not all ; for we must also suppose that each
cell of every stage of development, and of the cell-
generations which succeed each other during maturity,
is also represented in each germ-cell, and is the material
cause of the reappearance of such stages and such genera-

THE HYPOTHESIS OF PANGENESIS 125

tions when the germ-cell itself undergoes development
and becomes a mature individual.

Thus the gemmules stored up in the germ-cells of
Diagram / represent a previous generation of body-
cells, while those crossing the space separating body-
from germ-cells represent the existing generation.

Nor is this all ; for we are also compelled to believe
that gemmules from the cells of large numbers of genera-
tions of ancestors are present in many germ-cells,
accounting for the facts of atavism or 1 throwing back \
When an animal 4 throws back 9 to some remote ancestor,
the gemmules must have been handed down in a dormant
condition through all intermediate generations.

Furthermore, there are grave practical difficulties in
the way of the acceptance of Darwin's hypothesis. If it
were true, we should expect that mutilations, especially
such as are inflicted early in life, would be transmitted
to offspring; for all the cell-generations later than the
date of the injury would be absent, and therefore unrepre-
sented by gemmules. But there is no evidence in favour
of the transmission of mutilations, however early they
may be inflicted. All the evidence, when carefully
examined, points in the opposite direction.

Again, in the process of transfusion, when the blood
of one individual is replaced by that of another, it seems
reasonable to suppose that, if the gemmules exist, many
of them would be carried over, and would collect in the
germ-cells of the individual which received the blood,
and that thus some characters of one individual would
afterwards appear in the offspring of another. Careful
experiments, conducted by Galton and later by Romanes,
prove that such transference of hereditary characters does
not accompany the transfusion of blood.

Not only may blood be transfused, but various tissues
may be grafted and will thrive on another individual of
the same species \ In these cases, too, we should expect
that such transferred tissues would produce effects upon

1 Grafted tissues will also thrive on an individual of a very different
species ; but such an experiment, however interesting from other points
of view, would obviously be unsuitable as a test of Pangenesis.

126 THEORIES OF HEREDITY

the offspring, for, according to the hypothesis, they
would continue to give off gemmules. No such here-
ditary influence has ever been traced or even rendered
probable.

When we inquire why Darwin was led to frame such
a hypothesis, which, in spite of its great merit in con-
necting together a number of apparently isolated facts,
has so much to be said against it, we find the answer in
a reply to one of Huxley's letters, in which Pangenesis
had evidently been adversely criticized. Thus Darwin
says : * I do not doubt your judgment is perfectly just,
and I will try to persuade myself not to publish. The
whole affair is much too speculative ; yet I think some
such view will have to be adopted, when I call to mind
such facts as the inherited effects of use and disuse, &c.' 1

This opinion of Darwin's is as true to-day as when it
was written at some uncertain date about the year 1865.
If the effects of use and disuse are transmitted, the
explanation must be sought in a hypothesis constructed
on the lines of Pangenesis. But if we are mistaken in
believing that such transmission occurs, a very different
hypothesis will account for the facts.

The manner in which the transmission of such effects
can be explained by the hypothesis of Pangenesis is
shown in Diagram /. Two of the somatic cells, Q on
the right side and V on the left, are dark coloured.
This is to represent some change wrought in their
structure by the influence of an external force, or by
some unusual exercise or practice of a part. Thus the
darkened Q might represent the change which occurs in
a bone-cell when a bony growth has been caused by
intermittent pressure long-continued ; V on the left side
might represent the change which occurs in a nerve-cell
when some new habit is acquired by long practice. Such
altered cells would produce correspondingly altered gem-
mules, indicated by the same dark appearance : these
ex hypothesi would be stored up in the germ-cells, and
would reproduce similarly altered cells in the offspring.

I have given a very brief account of the main features
1 Life and Letters) first edition, 1887, vol. iii, p. 44.

CONTINUITY OF THE GERM-PLASM 127

of Pangenesis. It is a hypothesis which would explain
the hereditary transmission of acquired characters. At
the same time it is beset by difficulties which appear
well-nigh insuperable.

We will now proceed to examine another theory of
heredity, that of Professor Weismann. The hypothesis
is called 'The Continuity of the Germ-plasm', the name
germ-plasm being applied to the essential part of the
germ-cell which determines its development into an
individual. The word 1 continuity ' is employed to
express the theory that heredity depends upon the fact
that a minute quantity of this germ-plasm is reserved
unchanged during the development of the individual,
and subsequently grows and gives rise to the germ-cells.
Hence the germ-plasm is continuous from one generation
to another in unending succession, and from it the germ-
cells of each generation are produced.

The germ- plasm in a germ-cell possesses such a con-
stitution that, placed under appropriate conditions, an
individual of a certain species will be produced ; but the
germ-cells of this individual will also contain the same
germ-plasm, and will therefore develop into offspring
which resemble the parent. Parent and offspring resemble
each other because both arise from the same substance,
although it develops later in the case of the offspring.
Hence everything which is predetermined in the germ-
cell, every blastogenic character, may be transmitted,
while somatogenic characters cannot be transmitted.

The hypothesis will be rendered more intelligible if
we refer to Diagram II, in which the development of a
Metazoon, like that shown in Diagram /, is represented,
according to the theory of the continuity of the germ-
plasm. Development is complete in five stages, the
number of the somatic cells being doubled in every stage,
after their first appearance in the second. The first
Stage (Fig. 1) is the fertilized ovum, A, the single cell out
of which all others are produced. It contains germ-
plasm from two individuals, the combination being the
process of fertilization. In the preparation for fertili-
zation and the twofold nature of the fertilized ovum

128 THEORIES OF HEREDITY

Weismann sees the causes of individual difference and
the divergence of offspring from parent. Weismann
believes that the germ-plasm is in reality only found in
the nucleus, but the distinction between this and the cell
has been omitted from the diagram for the sake of sim-
plicity. The germ-plasm is supposed to be represented
by the dots in the circle A.

The second Stage (2) is produced by division of the
ovum into two cells (B and C), in one of which (C) a
small part of the original germ-plasm, represented by the
small circle a, is carried on, unchanged.

Roux has demonstrated that, if one of the products
of the first division of the egg of a frog (B or C in
Diagram II) be destroyed with a hot needle, develop-
ment is not necessarily arrested, but, when it proceeds,
leads to the formation of an embryo from which either
the right or the left side is absent. When the first
division takes place in another direction, either the
hind or front half was absent from the embryo which
was afterwards produced. After the next division,
when four cells were present, destruction of one pro-
duced an embryo from which one-fourth was absent.1

The preceding paragraph was written in 1889 before
Roux's experiments had been repeated and , tested by
other workers ; but their arresting interest was such
that they soon became the foundation of a prolific school
of experimental embryology. The ultimate result of
numerous researches is to leave no doubt that Roux
was mistaken in some of his conclusions. An excel-
lent discussion of the whole question will be found in
Professor T. H. Morgan's work.2 The general con-
clusion that there is a necessary correspondence in
position between the early embryonic precursors and
the organs or parts to which they give rise has been
abandoned. On the other hand, the still broader and
more fundamental conclusion that definite organ-forming

1 My attention was first directed to these interesting experiments by
Professor Windle's paper in the Journal of A?iato7iiy and Physiology,
vol. xxiii, p. 393.

3 Regeneration^ chapter xi, New York, 1901.

ROUX'S EXPERIMENTS ON THE EGG 129

material is present at the beginning of development has
been proved at any rate for embryonic organs of many
species. Thus pre-formation (in the above sense) in the
earliest stages, at least of embryonic organs, is confirmed,
although it is not necessarily accompanied by pre-
localization.

Turning to the details of Roux's researches upon the
frog, briefly mentioned on p. 128, the results he claimed
to produce by destroying one or both of the anterior or
posterior pair of the first four cells (blastomeres) formed
by the second cleavage are not now accepted. As
regards the injury to one of the first two cells (blasto-
meres) and the development of a half-embryo from the
other, Roux stated that after a time the material
of the injured cell is ' reorganized and the missing-
half of the embryo restored by ' post-generation \
The reorganization is, according to Roux, of complex
origin, in part due to formation of cells from the injured
part itself, but chiefly to the influence of the uninjured
part. When converted into cells by reorganization, post-
generation begins. 'A few hours or a night is sometimes
sufficient to change a hemi-embryo into a whole embryo/
' The pieces of the old nucleus . . . may take a part in
the formation of the new cells ; wandering cells migrate
from the yolk mass of the old half into the new, and the
cells of the formed germ-layers may be pushed over to
the other side.' This brief recapitulation of Roux's
account is quoted from T. H. Morgan, who has himself
shown that a half-embryo is formed by the uninjured
cell when it and the injured cell retain their original
position, but that the missing part is regenerated from
the uninjured half or from the still living material of the
injured cell. Morgan also proved that if the two first
cells do not retain their original position — e.g. if the egg
be turned upside down — the uninjured cell forms not
a half but a whole embryo, as in Hertwig's experiments.
Furthermore, Schulze and Wetzel have proved that the
uninjured egg, if kept upside down in the two-celled
stage, develops into a double monster, one from each
cell (blastomere). We are thus driven to the conclusion

POULTON K

i3o THEORIES OF HEREDITY

that the pre-localization in normal development of each
half of the frog in one of the two first cells does not
warrant the conclusion that such pre-localization is
a fundamental or essential phenomenon. For, as shown
above, mere change of position will compel each of
these two cells to manifest a far wider potentiality —
the potentiality of the whole body instead of one of its
halves. The most crucial test which could be applied
to Roux's conclusion would be not to injure but to
remove altogether one of the first two cells of the egg.
This is unfortunately impossible in the case of the frog ;
for the single remaining cell collapses. The experiment
has, however, been successfully performed upon the egg
of the newt (Triton),1 by Herlitzka, who ' found that each
blastomere gives rise to a perfect, whole embryo of half-
size \ ' Thus we see \ Morgan concludes, ' that whatever
the factors may be that determine the development of
a single embryo from the egg, still each half, and perhaps
each fourth also, has the power of producing a whole
embryo.' 2 When we consider the development of widely
different animals we are led to widely different con-
clusions. Thus, according to Driesch, of the egg
of an Echinoderm (Sea-urchin) can undergo at least
the preparatory stages of complete development.

It has been shown that the planes of division by
which the egg is cut up into cells may bear no relation-
ship whatever to the position of the future embryo.
Dr. Jenkinson has even proved that the position of the
embryo frog, although predetermined in the egg itself,
is nevertheless without relationship to the direction of
the furrow which divides the egg into the two first cells.3

Returning to Diagram //, the second division pro-
duces the four cells of Stage 3, indicated by the letters

1 Dr. J. W. Jenkinson points out that by a clerical error Professor
T. H. Morgan (I.e. p. 226) has spoken of the salamander (Salamandra)
instead of the newt {Triton). Herlitzka's two papers {Arch./. Entwick.-
Mech. d. Organis?n.,\\. 1896, p. 352 ; iv. 1897, p. 624 : Leipzig) describe
experiments upon Triton {Molge) cristatus.

2 1. c. p. 226.

8 Biometrika, vol. v, pts. i and ii, Oct. 1906, On the Relation between
the Symmetry of the Egg and the Symmetry of the Embryo in the Frog.

DEVELOPMENT OF THE GERM-CELLS 131

D to G. In one of these, F, the unaltered germ-plasm
is supposed to be carried on. The third division leads
to Stage 4, with eight cells marked H to O, L being the
carrier of the germ-plasm. Finally, the fourth and last
division leads to the ultimate Stage 5, with sixteen
body-cells indicated by P to W, the two cells of each
pair being marked by the same letter. We must also
suppose that the minute mass of germ-plasm, a, grows
and separates as a germ-cell or germ-cells from either L
or one or more of the somatic cells into which the latter
divides. The four germ-cells of the adult Metazoon
are then produced by division. These germ-cells are,
therefore, similar to that which started development ;
they are, in fact, a piece of it, which has grown without
undergoing any essential alteration. The four germ-
cells will, therefore, tend to produce offspring resembling
their parents. It must be borne in mind, however, that
in actual development the precursors of future germ-cells
become recognizable as a definite group at a far earlier
stage than that shown in the diagram. In certain species,
e. g. Cyclops and Ascaris, the germ-antecedent has been
traced at almost the very beginning of development. In
Ascaris megalocephala, Boveri has shown that one of the
two cells formed by the first division of the egg con-
tains the germ-antecedents together with many other
potentialities. These latter are gradually told off in the
succeeding divisions, until, at the sixth, a single cell out of
the sixty-four into which the egg is then divided is the
precursor of the future germ-cells and germ-duct, but
bears no other potentiality.1

If, however, some of the somatic cells become modified
from that nature which was predetermined in the germ-
plasm of the ovum, there is no way in which the heredi-
tary transmission of such modifications can be explained by
the hypothesis of the continuity of the germ-plasm ; for
it does not include any means by which the effects could
be conveyed to the germ-cells, or, if conveyed, could
produce in them changes such as would predetermine

1 Kupffer's Festschrift, Jena, 1899, p. 383, Die Enhmckehtng von
Ascaris megalocephala.

K 2

THEORIES OF HEREDITY

similar effects in the corresponding somatic cells of the
offspring. The acquired changes in O on the right side
and V on the left, indicated by their dark colour, would
be confined to the organism in which they arose, and
would not affect its offspring, at any rate in a corre-
sponding manner.

If the transmission of acquired characters were proved
to be an undoubted fact, Weismann's hypothesis of
heredity would inevitably collapse. It cannot, however,
be maintained that such proof is forthcoming.

The question largely turns upon an exact knowledge
of the proportion borne by blastogenic or inherent to
somatogenic or acquired characters. We know how
dominant a share of our physical and mental qualities
is hereditary — so dominant indeed that it would follow,
if Weismann's hypothesis be correct, that blastogenic
characters are far more important than somatogenic.

There is some evidence that this is the case, and
I will here bring forward one line of proof, which also
supports the conclusion that the whole organism is pre-
determined in the ovum.

If this last conclusion be valid, it follows that the
differences which characterize individuals are predeter-
mined in the ova from which they arise, and that ova
are not in their essential nature alike any more than
individuals. We do, however, occasionally meet with
individuals so much alike that we (incorrectly) speak of
them as ' identical '. The resemblance between certain
twins is far closer than that between other members of
the same family. If, therefore, we can prove that such
1 identical ' individuals are derived from ' identical ' ova,
the above-mentioned arguments and conclusions will
receive strong support.

' Identical ' twins are invariably of the same sex.
When twins are of different sex, the degree of resem-
blance is no greater than that between brothers and
sisters generally. This is also true of many twins of
the same sex, and Galton has brought forward evidence
to show that they may even differ more widely than is
usual with brothers or sisters.

DEVELOPMENT OF IDENTICAL' TWINS 133

It has been long known that twins of the same sex
are often enclosed in the same embryonic membranes,
while twins of opposite sex are always enclosed in
separate membranes. The latter would be the product
of distinct ova, which had been separately fertilized, as
in the ordinary multiple births of animals (cats, dogs,
rabbits, &c). The former would be the product of
a single ovum, which has divided into two ova, in all
probability after fertilization. But it is clear that the
ova arising from the two halves of a single ovum, at
a time when the individual characteristics were already
determined, would be very nearly identical : their resem-
blance would be of a very different order from that of
separate ova. We also find that some twins of the
same sex present resemblances of a very different order
from that of brothers or sisters who are developed from
separate ova. It must be admitted, therefore, that there is
a very high degree of probability that the ' identical ' ova
are those which develop into the ' identical ' individuals.
The interesting conclusion that sex is predetermined in
the fertilized ovum also follows from the same facts.

The probable beginning of the development of 1 iden-
tical ' twins is shown in Diagram III A* is a fertilized
ovum with the individual characteristics predetermined.
At its first division A* does not, like A in Diagram //,
form the cells of Stage 2, indicated by the letters B
and C ; but it divides without differentiation into two
equivalent cells, like each other and like the ovum.
Hence the first division of A* does not produce Stage 2,
but Stage ia, consisting of two similar ova. Each of
these then divides, as shown in Diagram III, forming
a true Stage 2, comparable to that of Diagram //.
After this the other stages succeed as in the latter,
and finally two individuals will be formed, which must
resemble each other if it be true that individual charac-
teristics are predetermined in the fertilized ovum. And,
as a matter of fact, such resemblances are seen in indi-
viduals whose development may be considered, with a
very high degree of probability, to have followed the
lines indicated in Diagram III.

134 THEORIES OF HEREDITY

The germ-plasm A* is carried on in C and ex hypothesi
would, in the mature offspring, develop into germ-cells
with a tendency to divide like those of the parent and
to produce 'identical' twins. It is, however, necessary
to bear in mind the effects of union in fertilization with
a germ bearing different tendencies, as well as the changes
introduced by the preparation for fertilization.

The amount of resemblance between ' identical ' twins
has been shown by Galton,1 who traced the after-life of
about eighty as far and as completely as possible, obtain-
ing instructive details in thirty-five cases. Of the latter
there were no less than seven examples ' in which both
twins suffered from some special ailment or had some
exceptional peculiarity ' ; in nine cases it appeared ' that
both twins are apt to sicken at the same time ' ; in eleven
cases there was evidence for a remarkable association of
ideas ; in sixteen cases the tastes and dispositions were
described as closely similar. These points of identity
are given in addition to the more superficial indications
presented by the failure of strangers or even parents to
distinguish between the twins.

When the lives of twins were followed in after years
' in some cases the resemblance of body and mind con-
tinued up to old age, notwithstanding very different
conditions of life'. In other cases 'the parents ascribed
such dissimilarity as there was wholly, or almost wholly,
to some form of illness '.

The conclusions of the author are as follows : — ' Twins
who closely resembled each other in childhood and early
youth, and were reared under not very dissimilar con-
ditions, either grow unlike through the development of
natural characteristics which had lain dormant at first,
or else they continue their lives, keeping time like two
watches, hardly to be thrown out of accord except by
some physical jar. Nature is far stronger than nurture
within the limited range that I have been careful to
assign to the latter.' And again, ' where the maladies
of twins are continually alike, the clocks of their two
lives move regularly on, and at the same rate, governed

1 Journal of the Anthropological Institute, 1875, pp. 324 and 391.

THE AFTER-LIVES OF TWINS 135

by their internal mechanism. Necessitarians may derive
new arguments from the life histories of twins.'

Mr. Galton furthermore met with twenty cases of twins
(also of the same sex) in whom the differences were
greater than those which usually distinguish children of
the same family. In such twins the conditions of training,
&c, had been as similar as possible, so that the evidence
of the. power of nature over nurture is strongly confirmed.
Mr. Galton writes, ' I have not a single case in which my
correspondents speak of originally dissimilar characters
having become assimilated through identity of nurture.
The impression that all this evidence leaves on the
mind is one of wonder whether nurture can do any-
thing at all beyond giving instruction and professional
training.'

The argument thus leads to the conclusion that nearly
everything which is characteristic of an individual is
blastogenic, and therefore can be transmitted by the
continuity of the germ-plasm. We can thus appreciate
Weismann's contention that Natural Selection, while
seeming to decide between successful and unsuccessful
individuals, is in reality deciding between successful and
unsuccessful germs.

Monstrosities (except such as are produced by external
agencies) can be satisfactorily explained, in the same
manner as ' identical ' twins, by the occurrence, at some
stage of development, of an equivalent division instead of
a differentiating division of a cell or a substance which
is the precursor of the doubled part. During the vast
succession of differentiating divisions which take place
in the development of one of the higher animals, the
cells which represent parts of less and less importance
are gradually told off. Thus the divisions which lead
to the doubling of a small part of the body would occur
far later in development than those which would lead
to the doubling of a large and important part. But
early or late the occurrence of an equivalent instead
of a differentiating division at the critical stage was
predetermined in the structure of the fertilized egg.
We know that supernumerary digits are in a high

136

THEORIES OF HEREDITY

degree hereditary, as they would be if the germ -plasm
were continuous.1

Repair, and the renewal of lost parts in certain animals,
is also explained by the persistence of substances or cells
of the same kind as those which were the precursors
of the injured tissue or lost part ; — substances or cells
which would be ready to initiate development under
the stimulus provided by an injury.

The simplicity and beauty of Professor Weismann's
hypothesis of heredity commends it to our favourable
attention, and demands a searching inquiry into the
evidence for the supposed transmission of acquired or
somatogenic characters.

Into this inquiry it is impossible to enter on the
present occasion. I will only mention the various lines
of evidence which require investigation. The evidence
may be either Direct or Indirect. Direct proof would
be afforded if an undoubtedly somatogenic character
could be shown to have reappeared in the offspring
sufficiently often to prevent its explanation as a coin-
cidence. Thus, if mutilations, or the results of training,
exercise, or education (as apart from predisposition), or
acquired diseases (some diseases are certainly blastogenic)
reappeared in the offspring as the result of the operation
of heredity, the required proof would be afforded and
the hypothesis of the continuity of the germ-plasm would
collapse. Many diseases are due to living organisms
(' germs and when these reappear in the offspring the
result is clearly due to inoculation of the embryo or even
the germ-cell (as in the silkworm disease), and is not
therefore due to the operation of heredity.

The present [in 1889] adverse position of the medical
faculty is in part due to want of discrimination between
blastogenic and somatogenic characters ; in part to the
fact that the evidence on which they rely was collected
when the transmission of somatogenic characters was

1 See Professor Windle's interesting papers on Teratology, published
during the last few years [previous to the date at which this address was
read] in the Journal of Anatomy and Physiology, and the Proceedings of
the Birmingham Philosophical Society.

ACQUIRED CHANGES AND HEREDITY 137

assumed by every one ; and in part to real difficulties
which, however, require the most careful re-examination
before they can be accepted as proofs of the transmission
of acquired characters and as the death-blow to Weis-
mann's hypothesis.

If the direct evidence for the transmission of acquired
characters fails to stand the ordeal of a thorough investi-
gation, the indirect evidence still remains. If it could
be shown that certain phases of evolution would have
been impossible without such transmission, we should be
compelled to maintain that the latter had taken place.

The chief lines of indirect evidence are : — The fact of
individual variation, the effects of use and disuse of parts,
the facts presented by the phenomena of instinct.

Individual variation was believed to be due to the
hereditary effect of the direct action of environment. It
is known that in some cases (e. g. certain plants) variation
has been caused by the direct action of environment on
the germ-cells while still contained in the body of the
parent. Such a change is, of course, blastogenic, and
would be transmitted. There is less evidence for the
operation of such causes in the case of animals. The
consideration of twins and monstrosities pointed to the
conclusion that individual variation is predetermined in
the fertilized ovum. If it be asked why the germ-cells
of an individual should differ among themselves, Weis-
mann has pointed out that there is reason to believe that
the changes which ova and spermatozoa undergo, as
a preparation for their fusion in fertilization, must lead
to individual differences. He, therefore, considers that
variation is produced by sexual reproduction, and is, in
fact, its raison d'etre. The meaning of this form of
reproduction is to supply variations upon which Natural
Selection can operate.

The apparently hereditary effects of increased use are
more probably due to the operation of Natural Selection
upon a part which is, ex hypothesi, of especial importance,
combined with the admitted strengthening and growth
which follow increased use during the life of the indi-
vidual. The apparently hereditary effects of disuse arc

138 THEORIES OF HEREDITY

more probably due to the cessation of Natural Selection,
which can no longer maintain the efficiency of a useless
part. All functional parts of an organism are kept up
to a high standard by the operation of Natural Selection ;
withdraw selection and sooner or later degeneration will
begin. It is very interesting to find that both Galton
and Weismann independently arrived at the conclusion
that the cessation of Natural Selection offered a better
explanation of the gradual dwindling of useless parts,
than that afforded by the supposed transmission of the
admitted dwindling which follows from disuse during
an individual life.

Finally, the phenomena of instinct seem capable of
explanation by the operation of Natural Selection upon
blastogenic variations of the nervous system, rather than
by the supposed transmission of acquired habit. In
many cases we are compelled to adopt the former theory,
and it is open to us in all.

The time at our disposal has made it impossible to
attempt any real discussion of the transmission of acquired
characters. I have only indicated the lines along which
it is likely that discussion will be directed.

Note. — Mr. Francis Galton kindly writes to me (Feb. 12, 1907) on
the subject of the first paragraph on p. 134 : — 'There is plenty of evidence
that twin-bearing runs in families, but I know of no inquiry as to whether
the tendency to produce identical twins does so. It would be a hard task
to collect and to sift adequate evidence on this point.'

V

THE BEARING OF THE STUDY OF
INSECTS UPON THE QUESTION
'ARE ACQUIRED CHARACTERS
HEREDITARY?'

The Presidential Address read at the Annual Meeting of the Entomo-
logical Society of London, January i8, 1905. Reprinted from the
Proceedings of the Society, 1904, p. civ.

Revised: addition io footnote 2 011 pp. 167-8.

To those who incline to criticize the subject of this
Address as a raking of the embers of a dead and almost
forgotten fire, I would reply that the controversy which
sprang into sudden flame — in this country in the year
1887 — is still a great memory. I trust that it will ever
remain as a great memory. Of August Weismann it has
been well said that ' he awoke us from our dogmatic
sleep'. He made us realize that cherished convictions
upon fundamental questions were based on nothing more
solid than assumptions, and thus administered the most
stimulating shock that has been received by the biological
world since the appearance of the Origin of Species.

It was impossible that a controversy of this magnitude
could be conducted without frequent appeals to the
Insecta. Their structures, functions, and instincts offered
evidence so striking in character, and upon a scale so vast,
that discussion was inevitably attracted again and again
towards this centre. Indeed, the controversy would have
been but one-sided, the conclusion unconvincing, had it
been otherwise. At the same time discussion is and must
be free and, being free, is almost necessarily scattered.
To attempt therefore to disentangle from the mass and
to present as a whole the evidence offered by the study

140 INSECTS AND HEREDITY

of insects is of value in two ways. First, we are made to
realize the importance of our study : by the contemplation
of its relation to one majestic example we are prepared for
the belief that our subject is essential for the solution of
all the widest and deepest problems concerned with organic
nature as a whole. Secondly, the attempt for the first
time to marshal the whole of the evidence supplied by the
study of insects will make it possible to strengthen and
amplify certain parts, and thus render the whole fabric
better balanced and more stable.

I should wish at the outset to express my indebtedness
to the columns of Nature by means of which nearly the
whole of the controversy has been followed. We are
happy in the possession of a single journal in which dis-
cussions on general scientific questions are, by common
consent, carried on.

'Acquired Characters' defined.

Before beginning a discussion it is important to remove
any possibility of doubt or uncertainty as to the precise
meaning of the terms which are employed. The word
' acquired ' as used in this controversy has been the source
of as much confusion as the word 'mimicry'. Just as
almost every one who hears of 1 mimicry ' for the first
time assumes that the word means a power of intentional
imitation, so the inexperienced think that an acquired
character is any new structure which a species has gained
in the course of its history. 'Why should we not consider
every character acquired as an " acquired character" ?' they
not unnaturally ask. And the answer is the same in both
cases. Because these ordinary and untechnical words
were given a special and technical meaning by the writers
of memoirs which have become classical. In spite of
all inconvenience both words are, in their scientific use,
historic, and we must reckon with the fact that they
have a special meaning which differs from their ordinary
meaning.

Erasmus Darwin was, I believe, the first to use
'acquired' in this restricted sense. 'Fifthly,' he says,
• all animals undergo transformations which are in part

THE LAWS OF LAMARCK

produced by their own exertions, in response to pleasures
and pains, and many of these acquired forms or propensities
are transmitted to their posterity.'1 Although Lamarck
made a preliminary statement of his views on evolution
in 1802, the celebrated Philosophie Zoologique was not
published until 1809, fifteen years after the appearance of
Darwin's Zoonomia, and it is uncertain whether the author
of the later work had ever seen the earlier treatise.
Professor Osborn concludes upon the whole that he had
not (1. c, pp. 152-5). However this may be, the technical
use of the words ' acquired characters ' is chiefly due to
his memoir. The essential passages are the two following
Laws of Lamarck : —

1 Premiere Lot. — Dans tout animal qui n'a point depasse
le terme de ses developpemens, l'emploi plus frequent
et soutenu d'un organe quelconque, fortifie peu a peu
cet organe, le developpe, l'agrandit, et lui donne une
puissance proportionnee a la duree de cet emploi ; tandis
que le defaut constant d'usage de tel organe, l'affoiblit
insensiblement, le deteriore, diminue progressivement
ses faculte^s, et finit par le faire disparoitre.'

1 Deuxieme Loi. — Tout ce que la nature a fait acque'rir
ou perdre aux individus par l'tnfluenoe des circonstances
ou leur race se trouve depuis long-temps exposed, et, par
consequent, par l'influence de l'emploi predominant de tel
organe, ou par celle d'un defaut constant d'usage de telle
partie ; elle le conserve par la generation aux nouveaux
individus qui en proviennent, pourvu que les changcmens
acquis soient communs aux deux sexes, ou a ceux qui ont
produit ces nouveaux individus.' 2

Opposite to the characters which Lamarck spoke of as
' acquired ' are the characters which may be called con-
stitutional, congenital, genetic, inborn, innate or inherent.

1 Zoonomia, 1794. Quoted by Professor H. F. Osborn, From the
Greeks to Darwin. New York, 1894, p. 145.

2 Philosophie Zoologique, tome i. p. 235, Nouv. £d., 1830 : quoted by
Professor E. R. Lankester in Nature, vol. xli. 1890, p. 415. There
had been a tendency in the discussion on this subject to protest against
the restricted application of the word ' acquired \ and it was assumed that
the use was quite recent, and in fact due to Professor Weismann himself.
Professor Lankester shows the error of this assumption.

142 INSECTS AND HEREDITY

Other names have been specially proposed in order to
render apparent the distinction between these two classes
of characters. Weismann employed terms which set forth
their different origin. The inherent characters he called
blastogenic, expressing an origin that lay far back in the
germ-cell from which the individual arose. Acquired
characters he called somatogenic, to express a later origin
due to circumstances which had affected the body-cells.
The word centrifugal suggests characters developing from
within rather than as impressed from without : centripetal
conversely suggests characters impressed upon the in-
dividual from without, characters which are not the out-
come of internal causes.1 Acquired structural changes
have also been spoken of as modifications, the term
variation being restricted to characters of germinal origin.2
All the terms suggested for these two classes of cha-
racters convey something of a definition. Thus the brief
convenient definition of acquired characters as 1 those
modifications of bodily structure or habit which are im-
pressed on the organism in the course of individual life'3
is obviously suggested more or less completely by one
set of terms, and ' those characters or properties with
which the organism is originally endowed ' 4 by the other
set. Another attempted definition of an acquired cha-
racter is as follows : — 1 Whenever an organism reacts
under an external force, that part of the reaction which is
directly due to the force is an acquired character.' 5 And
although it may be impossible entirely to unravel the one
part from the other, certain elements may easily be dis-
criminated. For instance, the starting of the reaction as
contrasted with the sequence of events which make
up the reaction itself is obviously an acquired element,
and those who -maintain the hereditary transmission of

1 Theories of Heredity, in the Midland Naturalist, Nov. 1889. Re-
printed in the present volume, see p. 120.

2 Prof. J. Mark Baldwin, A New Factor in Evolution, in the American
Naturalist for June and July, 1896.

3 Prof. C. Lloyd Morgan in Baldwin's Dictionary of Philosophy and
Psychology, New York, 1901, vol. i, p. 10.

4 E. S. Goodrich, 1. c., p. 10.

5 Nature, vol. li, 1894, p. 55.

ACQUIRED CHARACTERS DEFINED 143

acquired characters are required to prove that a reaction,
which can only be started by an external force in the
parent, starts without this stimulus in the offspring.

We owe another definition to Mr. Francis Galton :
' Characters are said to be acquired, when they are
regularly found in those individuals only, who have been
subjected to certain special and abnormal conditions/1

Professor Lloyd Morgan's definition conveys nearly the
same idea: — ' When the complex of stimuli, which con-
stitute the normal environment, are sufficiently altered (to
upset that balance established between environment and
innate qualities resulting in the production of a normal
individual) to produce an appreciable change, such a
modification or * difference ' may be called an acquired
character/ 2

Such results of abnormal conditions undoubtedly supply
extremely striking examples of acquired characters, but it
is, I submit, a mistake to make too much of abnormality,
or to import it into a definition. Some of the most
marked and certainly the most easily studied and tested
of acquired characters are the differences between the
effects of alternative environments, all of which are
normal, upon the individuals of a single species. The
green colour of a larva of Amphidasys betnlaria, if fed
upon broom, is an acquired character, as is the dark
colour it would assume upon oak, &c. I think therefore
that a more satisfactory definition of, at any rate, a large
class of acquired characters may be framed as follows : —
• Whenever change in the environment regularly produces
appreciable change in an organism, such difference may
be called an acquired character.'

Sir Edward Fry has objected to Mr. Galton's definition
— and his objection would equally apply to that which
I have suggested above — that 'the possibility of inheri-
tance is excluded by the definition, and the inquiry
whether acquired characters are inherited is impossible V'

1 Nature, vol. li, 1894, p. 56.

- Baldwins Dictionary of Philosophy a?id Psychology, vol. i, p. 10.
3 Nature, vol. li, 1894, p. 198. See also Professor Lankester's reply
to the criticism, on p. 245.

INSECTS AND HEREDITY

This appears to me to be only a verbal difficulty,
Before attempting to prove whether a certain class of
characters can be inherited, it is essential to be able to
decide whether a given character which it is proposed to
test belongs to the class. If a satisfactory criterion can
be reached we can proceed with the test even though the
name ' acquired ' be by our definition denied to the cha-
racter after transmission by inheritance. The interest of
the result would remain all the same. If the character
were there — appreciable, measurable, — the effects would
be incalculable in their importance, and would not be
diminished one iota by the consideration that the name
would no longer apply. Sir Edward Fry's criticism does
indeed suggest a change — and I think a desirable change —
in the statement of the problem. For the question ' Are
acquired characters hereditary?' it would be more accurate
to substitute ' Can the acquired characters of the parent
be handed down as inherent characters in the offspring?'

It is in no way necessary that the acquired elements of
a character should be disentangled from the inherent
elements, if only we can prove that the character as a
whole is dependent upon a controllable external cause,
and is therefore itself controllable. In fact we speak of
a character as * acquired ' just as we speak of an article
as ' manufactured ', although the result itself is a complex
of the properties of natural substances and of changes
introduced by art.1

LamarcKs Second Law a contradiction of his First Law.

Before leaving these general introductory considerations
and proceeding to weigh the evidence offered by the
insect world, it is of importance to demonstrate that there
is an inconsistency in the teaching of Lamarck and his
followers which, startling as it is, was never noticed until
pointed out by Professor E. R. Lankester in 1894.2

' Normal conditions of environment have for many

1 For an interesting discussion on the relation between ' acquired '
and 1 genetic ' characters see Adam Sedgwick's Presidential Address to
Section D of the British Association at Dover {Report 1899, pp. 759-66).

2 Nature^ vol. li, 1894, P- I02-

LAMARCK'S LAWS INCONSISTENT 145

thousands of generations moulded the individuals of
a given species of organism, and determined as each
individual developed and grew " responsive " quantities
in its parts (characters) ; yet, as Lamarck tells us, and
as we know, there is in every individual born a potentiality
which has not been extinguished. Change the normal
conditions of the species in the case of a young individual
taken to-day from the site where for thousands of genera-
tions its ancestors have responded in a perfectly defined
way to the normal and defined conditions of environment;
reduce the daily or the seasonal amount of solar radiation
to which the individual is exposed ; or remove the aqueous
vapour from the atmosphere ; or alter the chemical com-
position of the pabulum accessible; or force the individual
to previously unaccustomed muscular effort or to new
pressures and strains ; and (as Lamarck bids us observe),
in spite of all the long-continued response to the earlier
normal specific conditions, the innate congenital poten-
tiality shows itself. The individual under the new
quantities of environing agencies shows new responsive
quantities in those parts of its structure concerned, new
or acquired characters.

1 So far, so good. What Lamarck next asks us to
accept, as his " second law ", seems not only to lack the
support of experimental proof, but to be inconsistent with
what has just preceded it. The new character, which is
ex hypothesi, as was the old character (length, breadth,
weight of a part) which it has replaced — a response to
environment, a particular moulding or manipulation by
incident forces of the potential congenital quality of the
race — is, according to Lamarck, all of a sudden raised
to extraordinary powers. The new or freshly acquired
character is declared by Lamarck and his adherents to
be capable of transmission by generation ; that is to say,
it alters the potential character of the species. It is no
longer a merely responsive or reactive character, deter-
mined quantitatively by quantitative conditions of the
environment, but becomes fixed and incorporated in the
potential of the race, so as to persist when other quanti-
tative external conditions are substituted for those which

1*01X1 ON L

146 INSECTS AND HEREDITY

originally determined it. In opposition to Lamarck, one
must urge, in the first place, that this thing has never
been shown experimentally to occur ; and in the second
place, there is no ground for holding its occurrence to be
probable, but, on the contrary, strong reason for holding
it to be improbable. Since the old character (length,
breadth, weight) had not become fixed and congenital
after many thousands of successive generations of in-
dividuals had developed it in response to environment,
but gave place to a new character when new conditions
operated on an individual (Lamarck's first law), why
should we suppose that the new character is likely to
become fixed after a much shorter time of responsive
existence, or to escape the operation of the first law ?
Clearly there is no reason (so far as Lamarck's statement
goes) for any such supposition, and the two so-called laws
of Lamarck are at variance with one another/

These passages have been quoted at length because
they apply not only to the thoughts of Lamarck but to
those of many modern naturalists as well, and because,
so far as I am aware, no attempt has been made to meet
the objection. In its most condensed form the argument
may be stated thus : — Lamarck's ' first law assumes that
a past history of indefinite duration is powerless to create
a bias by which the present can be controlled ; while the
second assumes that the brief history of the present can
readily raise a bias to control the future V

I now pass to the discussion of evidence derived from
the study of the insect world.

I do not propose to multiply examples, but shall be
content with a few of those which seem sufficiently well
adapted to illustrate the main lines of evidence. They
have been chiefly, but by no means invariably, selected
from the Lepidoptera. This is merely due to the accident
that my experience has been chiefly gained in this Order,
and not because the examples are in any way more
suitable or convincing than those of other Orders. As
regards the most interesting part of the discussion, that

1 Nature, vol. li, 1894, p. 127.

ORIGIN OF APPARENT MUTILATION 147

relating to instinct, the most striking examples have of
course been chosen from the Hymenoptera.

The Origin of the Pupal Groove which receives
the Silken Loop in Pierinae, &c.

If we examine the dorsal surface of such a Pierinc
butterfly as Pieris brassicae (the ' Large Garden White ')
or P. rapae (the 4 Small Garden White ') it is at once seen
that the first abdominal segment is traversed by a strongly
marked line parallel with its posterior boundary. This
character is so well marked that it presents all the
appearance of a morphological feature.

A study of the living suspended pupa shows that the
line is formed by the approximated lips of a groove which
receives the silken loop or 1 girdle ' as it is often called.
Longitudinal vertical sections of the dorsal cuticle are of
course transverse to the line, and reveal the fact that the
bottom of the groove is specially thickened. Here was
a feature at first sight strongly suggestive of the mechani-
cal effects of linear pressure, pointing to an origin in
a kind of mutilation performed by the silken cord upon
the soft freshly-exposed surface of the pupa. When
I found that removal of the loop before pupation, but
after the period at which the larva could spin another,
did not alter the normal appearance of line and groove
in the resulting pupa, I was for the moment convinced
that acquired characters are hereditary. But fortunately
the inquiry did not come to an end at this point. It was
observed that the Pierine pupae which furnished the
material for experiment (P. brassicae or P. rapae) invari-
ably suspended themselves either horizontally or verti-
cally with the head upward, — never vertically with the
head downward. Several larvae of P. brassicae had fixed
themselves in the normal vertical position preparatory to
pupation, upon a sheet of glass. Before pupation, but
after the period at which the larvae could fix themselves
afresh or indeed make any attempt to spin, the glass
sheet was rotated through half a circle, so that all the
larvae came to be suspended head downward. In this

L 2

i48 INSECTS AND HEREDITY

position they were compelled to pupate. The condition
of the resulting pupae clearly refuted the hypothesis of
a mechanically-created groove and thickening, caused by
the cutting into and pressure upon the soft yielding
cuticle. For in the vertical position with head down-
ward the pupa slips through the silken loop beyond the
position of the groove, so that the pressure has to be
borne by an unprepared part of the cuticular surface.
Upon the mechanical hypothesis, we should expect that
the fresh surface would gain some measure of resistance
from the strain ; but on the contrary the pupae were all
hopelessly deformed and the imagines — if indeed they
could have emerged at all — would have been incapable
of flight.1 It is evident that from the very beginning
the loop has been accompanied by a sufficient strengthen-
ing of the part of the surface exposed to its pressure as
soon as the larval skin is thrown off.

The silken loop together with the attachment of the
posterior extremity of the pupa is in all probability the
persistent trace of a vanished cocoon, and we may imagine
the selective process which made good each step on the
road of gradual transformation. A cocoon is one form
of passive defence, cryptic colouring is another, although
the two are commonly combined, especially in cocoons
built to endure for comparatively long periods, including
the times of special stress — the winter of the northern
belt, the dry season of more southern latitudes. The
original decline of the cocoon was probably favoured by
a short pupal period falling wholly within the time of
least stress — summer or the wet season. When the
cryptic colouring of the bare pupal surface is as effective
for concealment as that of the cocoon, it presents certain
advantages over the latter. The secretion of a large
quantity of material is unnecessary and tell-tale move-
ments in the period before pupation are greatly reduced.
These benefits are conferred when the concealment

1 This experiment has not been published hitherto. It was, however,
described and the pupae exhibited in the discussion in Section D of the
British Association at Manchester, on Monday, Sept. 5, 1887. See
Report, p. 755.

ORIGIN OF SILKEN LOOP 149

afforded is equal ; but the pupal cuticle lends itself to
certain forms of cryptic defence much more freely and
completely than the walls of the cocoon : — to the pro-
duction of angular shapes and of smooth or polished
surfaces, to the attainment of varied colours and the
perfect gradation of tints, above all to the power of
individual colour-adjustment. This latter culminating
effort of adaptation — so commonly possessed by larvae
and exposed pupae — is apparently extremely rare in the
cocoon. Indeed the only positive evidence of its existence
is supplied by Hylophila (Halias) prasinana,1 and even
in this case it would be satisfactory to repeat the experi-
ments on a far larger scale than has been as yet attempted.
The transition is easy from a loose and open cocoon with
apertures through which the cryptic colours of the enclosed
pupa could play their part in defence, through stages in
which the latter element becomes more and more im-
portant as the cocoon progressively diminishes, to the
climax when the almost invisible remnants of the silken
covering are retained as supporting structures merely.
In all except small and light pupae a point would be
reached, at a greater or less distance from the climax,
when some special strengthening of the cuticle exposed
to the strain became the indispensable condition of further
advance. Thenceforth further reduction and further
strengthening would proceed together, the existing groove
and thickening being but the concentration of the broader
band of pupal tissue specially prepared to meet the
pressure when it first became a danger.

Comparison with the pupae of some of our common
British Geometrae supports the hypothesis set forth above ;
for it is seen that very similar changes have independently
occurred, and occurred so recently that the essential stages
are still preserved. Furthermore, they are invariably met
with in species which have a short pupal period passed
in the warmer months of the northern year. Eugonia
quercinaria (the 1 August Thorn Moth ') spins a loose
and open cocoon, within which the chrysalis, as well as
the larva before pupation, develops an effective cryptic
1 Trans. Ent. Soc. Zona7., 1892, pp. 448-51.

i5o INSECTS AND HEREDITY

colouring.1 Both larva and pupa are freely exposed to
view through chinks in the scanty network and between
the imperfectly united leaves. Uropteryx sambncaria (the
1 Swallow-tailed Moth') constructs a slight hanging cocoon,
affording very little concealment. The enclosed pupa
bears a marked cryptic appearance, while the only experi-
ment which has been made indicates the possibility of a
well-developed power of individual colour adjustment.2
Both these species, and especially the last, have long since
reached the stage at which the reduction of the cocoon
became advantageous. In the genus Zonosoma (Ephyra)
we independently arrive at the same climax of reduction
attained in the Pierinae, &c, the cocoon being repre-
sented by a supporting loop and the means of fixation of
the posterior extremity.3 No search has been made, so
far as I am aware, for a special strengthening of the
cuticle upon which the loop presses, but it is probable
that nothing of the kind is required by these small light
pupae. The exposed Ephyrid chrysalis is fully as cryptic
as that of the average butterfly, but it lacks the power of
colour adjustment. When the Ephyrid larva is dimorphic,
green or brown, the colour of the pupa corresponds
to that of the larva from which it developed.4 Such
correspondence has not been observed in any other
Lepidopterous insect.

If we take into account the fact ti\2X Zonosoma {Ep/iyra)
is a characteristic Geometrid genus, although its method of
pupal suspension is unique in a family whose species make
cocoons or bury, we may feel confident that it has been
descended from cocoon-making ancestors, and that Eugo-
nia quercinaria and Uropteryx sambucaria give us a clear
idea of the steps by which the reduction was effected.

1 Traits. Ent. Soc. Lond., 1885, p. 319.

2 See Colours of Animals, London, 1890, pp. in, 112. Only one
example was placed on white paper before pupation. Although the
resulting chrysalis was very pale and strikingly different from the ordinary
appearance, the evidence is quite insufficient, and it is much to be hoped
that the experiment will be repeated upon a large scale.

3 Trans. Ent. Soc. Lond.. 1884, p. 57.

4 Trans. Ent. Soc. Lond., 1884, p. 51 ; Phil. Trans. Roy. Soc, vol. 178
(1887), B, pp. 437.438-

SHAPE AFFECTED BY GRAVITY 151

The effect of Gravity upon the shape of Suspended Pupae
such as those of the Nymphalinae.

Every naturalist who has watched the pupation of a
Vanessid must have observed the extraordinary mobility
of the abdominal region of the freshly-exposed chrysalis.
Movements of remarkable amplitude take place in every
direction, and especially in the dorso-ventral plane, these
latter being essential for the withdrawal of the posterior
segments from the larval skin and the remarkable feat of
attachment to the silken boss close to the point from
which the skin itself is hanging. Success is only rendered
possible by the remarkable contractile power of the inter-
segmental muscles along the median ventral area. These,
by their contraction, keep the rigid hook-armed apex of
the abdomen firmly pressed to the outside of the larval
skin up which it is being forced, and enable it to press
down or push aside any of the stiff spines which oppose
the movement : these finally bring it to the small silken
boss which alone provides a secure basis of attachment
for the terminal hooks. For this purpose the ventral
muscles require to be far stronger than those of any-
other region, and we invariably find that they entirely
overbalance the dorsal intersegmental muscles in pupae
which have been produced on the floor of the breeding-
cage. In such pupae the abdominal segments are curved
round towards the ventral side, so that the long axis of
the apical part forms at least a right angle with that
of the thoracic region, and this attitude becomes stereo-
typed with the hardening of the pupal cuticle and the
consequent loss of all power of dorso-ventral move-
ment. These free pupae form a striking contrast with
the normal attached individuals in which the long axis
of the abdominal segments is nearly in the same line
with that of the thoracic. Suspension by the posterior
apical hooks and the assumption of a form in which
the long axis of the body is nearly in one line, is very
ancient, dating back to the common ancestor of a number
of closely-related species. For a countless number of
generations the soft and yielding Vanessid pupa has

INSECTS AND HEREDITY

been subjected to the strain of gravity and has responded
by the production of a definite shape, viz. one in which
the long axis is parallel with the line of force. And yet
not a trace of any hereditary effect is manifest. Remove
the strain and the individual is free, unbiased by the
forces exerted upon unnumbered ancestors, to assume
an entirely different shape.

Vanessid pupae alone, so far as I am aware, have
been studied from this point of view. Figures of other
suspended Nymphaline pupae, however, indicate that all
do not yield equally to the strain, although I believe
that all are to some extent affected. The pupae of
the Argynnidae (the 1 Fritillaries ') contrast in an interest-
ing manner with those of the Vanessidae in this respect.
The strongly-curved pupa of Argynnis aglaia figured by
W. Buckler1 was probably supported wholly or in part
by a leaf, as is suggested not only by the shape but the
plane of the surface of attachment, as shown in the figure,
and to some extent by the description.

Variable Protective Resemblance in Insects.

The power which it is now known that many larvae
and pupae possess of changing their colour into corre-
spondence with the tints of each one of several possible
environments has been thought to favour the Lamarckian
interpretation of the origin of variation. Thus the late
George J. Romanes said of the evidence which had been
brought forward to prove the power in question : 'It
has always appeared to me that the experiments them-
selves are among the most valuable which have hitherto
been made regarding the causes of variation ' ; 2 an
opinion due, as the writer states, to his acceptance of
the ' Lamarckian conception '.

On the other hand, I have never doubted that the
results are in the nature of a climax rather than a founda-
tion, that they represent the highest achievement of
Natural Selection in the protective colours of insects.

1 Ray Society, Larvae of British Butterflies and Moths, vol. i, Plate X,
fig. 3^, 1886.

2 Nature, vol. xxxviii, 1888, p. 364.

OBJECTIONS TO 'SELF-ADAPTATION' 153

If these variable colours represented the beginnings
of ordinary fixed colour variations the species would
lose and not gain by the change. The essence of the
protective value is the power of being concealed in each
of several different environments, and hereditary trans-
mission of the results would only injure the individuals
of the next generation. The intricacy of the processes
by which the stimulus gives rise to each appropriate
colour-effect is no difficulty to the interpretation based
on Natural Selection — 'an agency capable of dealing
with complex physiological relationships in precisely
the same way that it deals with all other kinds of
variations \J

The barren conception of ' self-adaptation ' — the hypo-
thesis that organisms possess a constitution which compels
them to react adaptively, breaks down when we find the
adaptation is only possible by means of a specialized
and complex train of physiological sequences.

We must remember that the species we investigate
are 'heirs of all the ages', thoroughly inured to experi-
mental research, past masters in the art of meeting
by adaptive response the infinite variety of stimulus
provided by the environment. If we remember this
we shall always be on our guard against a too hasty
interpretation based on the fundamental properties of
protoplasm.2

The hypothesis that organisms are so built that
they must produce useful variations seems to be little
more than the old £ internal developmental force \ or
' innate tendency towards perfection', in a modern dress.
Furthermore, a consideration of the essential meaning
of adaptation proves the futility of any such attempt at
explanation. The ultimate object of adaptation is to
obtain food, to escape enemies, or to subserve reproduc-
tion. The most conspicuous adaptations manifested by

1 Professor Meldola in Nature, vol. xxxviii, 1888, p. 389. See also
Professor Meldola's Presidential Address in Proc. Ent. Soc. Lend., 1896,
pp. lxx, lxxi ; and the first scientific paper published by him, viz. Proc.
Zool. Soc, 1873, p. 153.

2 Nature, vol. lxxi, 1905, p. 244.

154 INSECTS AND HEREDITY

an individual are relative to the condition of the organic
environment with which its contact is in many respects
irregular, uncertain, or even wanting. Caterpillars are
provided with beautiful protective adaptations, but the
successful individual never comes into contact with an
enemy. But there is an environment which the organism
cannot avoid — the physico-chemical stimuli of climate
and food ; and it is presumably here, in the inorganic
conditions of life, that the influences which bear a pre-
eminent part in evoking useful variations are supposed
to reside. So that stimuli provided by one form of
environment are looked upon as the direct causes of
adaptations which are essentially related to another and
very different environment.1

The Instincts of Insects.

Those who advocate the hereditary transmission of
acquired characters have made great use of the argu-
ment that the wonderfully complex and precise adaptive
instincts of insects require for their production the
accumulation of experience and of effort through many
generations. Only by such transmission, they maintain,
is it possible to understand such development.

It is safest to begin with a definition, and I accept
the brief, convenient, and in my opinion entirely accurate,
statement of Lloyd Morgan : * Instinct depends on how
the nervous system is built through heredity ; while
intelligence depends upon how the nervous system is
developed through use.' 2

We observe in the first place that the Lamarckian
interpretation places the more difficult phases of the
evolution of instinct — the phases when it was not
instinct at all but something much higher — in some
remote epoch of the past, and at a lower level of pro-
gress. In such times, ex hypothesis the less developed
and presumably less efficient brains of insects did by
the intelligent use of experience what they now do

1 The substance of the argument set forth in this paragraph was
published by the writer in Nature, vol. 1, 1894, p. 445.
Animal Behaviour, London, 1900, p. 120.

THE DANGERS OF EXPERIENCE 155

mechanically by instinct. This is an inversion of the
probable course of evolution : the less efficient instru-
ment has assigned to it by far the more difficult task.

Apart from this prima facie objection there are solid
grounds for the belief that the exquisitely perfect opera-
tions of insects with which we are familiar arose as
instincts, as instincts were gradually perfected, and that
intelligence never came into the history at all.

It is not from the insects which have had the most
varied experience of enemies, most opportunity of learning
by contact with danger how to avoid them, and thus of
developing their nervous systems through use — it is not
from these that existing forms have been descended, but
from precisely those which have had the least experience.
Even for ourselves experience is spoken of as ' the stern
guide \ To an insect she is apt to be so stern as to lose
all her educational value. The less an insect sees of her
the better the chance of existence and of representation
in the generations of the future. The prime necessity
for an insect, as for all animals which cannot in any real
sense contend with their foes, is to avoid experience of
them altogether.1

This is an argument with the broadest possible appli-
cation to all Orders of insects. To the adaptive move-
ments of a beetle which when disturbed falls to the
ground, draws in its limbs and antennae, and looks
exactly like a little lump of earth ; to the alertness of a
fly to take wing before an enemy is within striking
distance ; to the perfection of all such means of defence
in insects, and they are numberless, we may apply the
words of Browning : —

Oh, the little more, and how much it is !
And the little less, and what worlds away !

1 This argument was brought forward by the present writer in the
discussion on Are Acquired Characters Hereditary ? at the meeting of
Section D of the British Association, at Manchester, Sept. 5, 1887
{Report, p. 755). No part of the discussion is published. The argument
is, however, briefly stated in Proc. Boston Society of Nat. History, vol. xwi,
I^95, p. 391 (reprinted in the present volume: see pp. 117. 118). and
also quoted in The Zoologist, Dec. 1900, pp. 551, 552.

t56 INSECTS AND HEREDITY

It is all the difference in fact between success and failure,
between life and death. Comparatively rarely are the
conditions of the struggle such as to admit of partial
failure or of improvement by experience.

One special reason for the passive means of defence
adopted by the vast majority of insects is to be found in
the peculiar dangers of their structure. Especially is this
true of larvae, with their haemolymph contained in freely
communicating cavities, and subject to the pressure of
muscular body-walls. Hence an insignificant injury may
often cause death or imperfect development from the
quantity of fluid which is lost. 'It is, I believe, in con-
sequence of these facts that the various means of pro-
tection in larvae are almost always of a passive kind. . . .
Nearly all the means of defence against . . . enemies
[other than ichneumons, &c.] are such as tend to prevent
the larva from being seen or touched, rarely such as to
be of any avail when actually attacked. There may be
various changes in the mode of defence, but the object
is always the same, — to leave the larva untouched, a
touch being practically fatal.' 1

Let us consider for a moment the mental operations
involved in the act of profiting by experience. Consider,
for instance, Mr. A. H. Hamm's interesting observation
— since abundantly confirmed by the testimony of many
naturalists — that the vast majority of the individuals of
Hybemia leucophaearia (one of the common ' Winter
Moths ') rest with the body horizontal, thus bringing the
lines of the wings into parallelism with the dark shadows
in the vertical cracks of the oak-bark.2 An individual
which adopted a different attitude and rested so as to
cause the main lines of its pattern to cut the main lines
of its environment might indeed escape by flight ; but
can any one really believe that a moth, or any of the
ancestors of moths, could associate the special disturbance
and danger to which it had been exposed with the special
attitude it had assumed, and would as a result of that
association begin to make changes in its attitude ? It is

1 Trafis. Ent. Soc. Lo?id., 1885, pp. 321-3.

2 Proc. Ent. Soc. Land, for March 19, 1902. p. xv.

INSTINCT VERSUS EXPERIENCE 157

easy to speak of improvement by experience, perhaps
easy to think of the progress of an insects education
under the sternest of teachers : — easy so long as we confine
ourselves to generalities. Attempt to picture the process
in a definite case, and apply it, as I have done, to account
for the growth of some special protective adaptation,
and it is instantly borne in upon us that we are placing
on insect psychology a load it is altogether unable to
bear.

The Cocoon-making Instinct.

There are, however, numberless examples in which it
is impossible that improvement could be thus effected,
even if insects did possess the requisite brains, that is
unless we also accord to them the gift of prophecy.
These are the cases in which instinct prepares for the
dangers of a struggle at some future time, when the
organism which manifested the instinct will have changed
its form, and become incapable of making further changes
in the means of protection, and indeed as a rule entirely
incapable of making any defence.

Consider, for example, another observation made by
Mr. Hamm in July, 1900, upon the cocoons of Malaco-
soma neustria (the common ' Lackey Moth ') spun within
the leaves of black-currant and apple in his garden at
Oxford. These he found to be opened by birds, probably
sparrows, which had pecked a hole in the leaf, thus
breaking through the cocoon at its thinnest point,1 and
abstracted the chrysalis.

1 The cocoons were exhibited to the Entomological Society on
March 19, 1902. See Proc. Ent. Soc. Lond., 1902, p. xv.

Mr. W. Holland many years ago showed that birds attack in this
particular way, but his observation was upon larvae spun between leaves,
and not pupae ; and the latter are specially suited for enforcing the present
argument. Mr. Holland's observation is as follows : —

'On the 6th of this month [June, 1890, near Reading] Capt.
Robertson and I went to get some larvae of populeii from some low-
trees of Popidus tremula which were covered with that species. Capt.
Robertson had picked off about 100 larvae the night before ; but this
morning when we arrived at the trees, we found some starlings had also
discovered the caterpillars, and had gone over the trees systematically
from branch to branch, pecking a hole in one side of the spun together
leaves, and drawing out the caterpillar, and so nearly had they cleared

158 INSECTS AND HEREDITY

A still more convincing example is to be found in the
origin and maintenance of the instincts involved in the
construction of a freely exposed yet admirably concealed
cocoon on bark. Think of the natural cracks just filled
up, of tunnels closed flush with the surfaces around, of
the resemblance to excrescences or ridges which appear
perfectly natural upon bark. Considering not only the
forms but the colours and texture of the external surface,
we recognize at once that such structures are the product
of a highly perfected group of instincts. At first sight
indeed the case seems to prove too much ; for it may
be thought that such cocoons are so completely hidden
as to defy the sharpness of any enemy however acute,
and believers in Natural Selection may properly be asked
to bring evidence of the existence of a struggle in which
the high elaboration of the instincts in question is a
defence. There is no difficulty in meeting the challenge,
for specially directed observation at once reveals the
existence of a keen struggle in which the concealment
of the cocoon is the criterion of life or death.

My attention was first directed to this particular aspect
of the struggle for existence in insects, on April 12, 1893,
when I found on the bark of Populus nigra near Yoxford,
Suffolk, a cocoon of Dicranura bifida (the ' Poplar Kitten
Moth ') which had been opened by some enemy, and the
pupa removed. The observation is, I believe, a common
one, in fact Commander Walker and Mr. Holland inform
me that it is usually difficult to find cocoons of this
species which have not been thus attacked. Never-
theless, for the sake of those who have not had the
experience, I think it is worth while to re-describe the
evidence which certainly justifies us in inferring that 4 an
enemy hath done this'.

' The edges of the opening were still brown and fresh,
as was the interior of the cocoon ; and the larval skin
remained fresh and untouched inside. The opening was

them all off, that we had much trouble to find a dozen. We caught the
birds in the act, and although they had so nearly finished their feast they
were very unwilling to go, and loudly objected to our disturbing them/ —
Entomologist's Monthly Magazine. 1890, p. 216.

CONCEALMENT IN COCOONS 159

in the middle of the exposed surface and not at one end,
as it is when the moth emerges. Besides, the cocoon
had been opened and cracked by a blow from some hard
object such as a bird's beak, and the sharp irregular
margins were quite different from those of the natural
opening made by the moth, doubtless by means of a
corrosive fluid, as in the allied species, Dicranura vinula
(the " Puss Moth % which Mr. O. H. Latter has recently
shown to secrete caustic potash for this purpose. Further-
more, the moth emerges far later in the year, and, had
it emerged at an exceptional time, the empty pupal skin
would have been left behind in the cocoon. We may
therefore safely assume that the opening was the work
of an enemy, and, as the cocoon was five feet from the
ground, it was probably due to some tree-creeping, bark-
exploring species of bird. ... It is probable that the
attention of the enemy is directed to any cocoon-like
object by the sense of sight and that the object is then
tapped, and, if found to be hollow, opened and the pupa
devoured.' 1

The cocoons of bifida are spun in the autumn, but the
attack did not take place for several months. The
example is probably typical in this respect. The pro-
cryptic preparation of the autumn is the adaptation by
which the average numbers of the species are kept up in
spite of ceaseless bark-hunting during the months when
the trees are leafless and food is scarce. The Lamarckian
interpretation fails to account for the cocoon-making
instinct for two very sufficient reasons : first, a chrysalis
is incapable of learning by experience how to improve
anything, — even more obviously incapable of learning
concerning a structure which it never makes. Secondly,
however intelligent a chrysalis may be, the experience
itself is of such a nature that its stores of learning cannot
be handed down to posterity.2

1 The enemies of Lepidopterous pupae enclosed in bark-formed cocoons.
— Science, xxiii, 1894, p. 62. The date of the observation is erroneously
given as the year of issue instead of 1893. Some of the later sentences
of the same communication are also quoted with slight modification on
the present occasion.

2 This argument also is briefly stated in the Free, Bos/on Soc. Nat,

i6o INSECTS AND HEREDITY

If the Lamarckian interpretation of the cocoon-making
instinct must inevitably fail, as I think we shall agree it
must, what is there to put in its place ? Those who
believe in the efficiency of Natural Selection in evolution
will probably regard the instinct of building these beauti-
fully-adapted structures as the outcome of countless
generations during which the attacks of enemies have
been, on the whole, more successful against the products
of less perfected instincts and less so against those of
the more perfected. They will further suppose that the
increasing perfection in instinct has acted selectively on
enemies, sharpening their faculties, until, by action and
reaction, the present high level of constructive skill has
been reached, and is maintained.

The Instincts of the Hymenoptera.

No discussion of instinct would be in any way complete
without a consideration of the most wonderful examples
of all, viz. those manifested by the Hymenoptera. The
instincts of the Fossorial Aculeates in providing for their
larvae — studied with all the sympathy of a born natura-
list and described by a master of style — have formed
the foundation of a gigantic speculative edifice. The
controversy has in reality been a three-sided one.

I. First, we have Fabre disbelieving in evolution alto-
gether, and adducing evidence that his favourite insects
have not gained their wonderful instincts by progressive
change, pointing out that they perform their duties under
some stimulus which to them is imperative, whether the
object of their pains be achieved or not : arguing, for
example, that in those that feed their larvae from time to
time, the stimulus to enter and deposit the insect food is
not the young larva itself but the door of the tunnel.

II. Secondly, Lord Avebury and the late George J.
Romanes have argued in favour of evolution by a gradual
education, finally inherited as instinct. There is reason
to believe that Darwin accepted the same view. He
certainly never opposed it. Lord Avebury alludes to the

Hist.y vol. xxvi, 1895, p. 391 (reprinted on pp. 117, 118 of this volume),
and quoted in The' Zoologist, Dec. 1900, pp. 551, 552.

THE ORIGIN OF INSTINCTS 161

letter written to Fabre, in which Darwin ' refers to the
great skill of the Gauchos in killing cattle, and suggests
that each young Gaucho sees how the others do it, and
with a very little practice learns the art'.1

Lord Avebury identifies himself with this view, which,
indeed, he had himself set forth in the Contemporary
Review^ in 1885. Concerning the instinct of the Ammo-
phila to sting the ganglionic centres of its caterpillar prey,
he suggests that 1 during these long ages they may have
gradually learnt the spots where their sting would be
most effective, and ... so have gradually acquired their
present habits \2 He finally concludes that ' these remark-
able instincts ' are ' the result of innumerable repetitions
of similar actions carried on by a long series of ancestors \3

George J. Romanes, in reviewing Lord Avebury's book,
goes much further: — 'Here, by the way, we have an
excellent instance of the difficulty which we so often
encounter in the domain of instinct, when we relinquish
the so-called Lamarckian principle of the inheritance of
acquired characters. The hypothesis in question goes
upon the supposition that some of the ancestors of the
Sphex were intelligent enough to notice the peculiar
effects which followed upon stinging insects or caterpillars
in the particular regions occupied by nerve-centres, and
that, in consequence of being habitually guided by their
intelligence to sting in these particular regions, their
action became hereditary, i.e. instinctive. But if, in
accordance with post-Darwinian theory, we relinquish
this possible guidance by intelligence, and suppose that
the whole of this wonderful instinct was built up by
natural selection waiting for congenital (i.e. fortuitous)
variations in the direction of a propensity to sting, say,
the nine nerve-centres of a caterpillar — then it surely
becomes inconceivable that such an instinct should ever
have been developed at all.' 4

1 Sir J. Lubbock, On the Senses, Instincts, and Intelligence of Animals,
with Special Reference to Insects. London, 1888. Internal. Sci. Ser.f
p. 248.

2 lb. p. 248. 8 lb. p. 252.
4 Nature, vol. xxxix, 1888, p. 77.

POULTQN M

162 INSECTS AND HEREDITY

Eimer is even more rash in his statements : — ' This is
one of the most marvellous instincts that exist ; since
the wasp operates on various larvae with nervous systems
of various forms, she must effect the paralysis in various
ways, and even apart from this, she makes a physiological
experiment which is far in advance of the knowledge
of man. ... It may be suggested that the wasp only
paralysed the larvae in order to carry them more easily ;
but even if this were the case, she must, since she now
invariably acts in this way, have drawn a conclusion by
deductive reasoning. In this case it is absolutely impos-
sible that the animal has arrived at its habit otherwise
than by reflection upon the facts of experience.'

Mr. and Mrs. Peckham make the following comment
upon this wild passage from Eimer : — 1 One can hardly
be expected to take such statements seriously, since it is
certain that the writer has no knowledge of the life
histories of these insects.' 1

III. Thirdly, there are those who believe that the
instincts in question are to be explained by the operation
of Natural Selection upon hereditary nervous mechanisms,
who believe that the Lamarckian principle of the heredi-
tary transmission of education has never come into the
history at any stage. Fabre's observations are quite
consistent with this view ; in fact it would almost appear
that Darwinian evolution as apart from Lamarckian
evolution is really unknown to this great naturalist. He
seems invariably to strike Lamarck when he aims at
Darwin. In this, however, he is only acting in the same
manner as the majority of the early critics of the Origin.2

In attempting to decide upon the past history of these
insects the first necessity is to be sure of the facts.
Fortunately the ground has been re-traversed by Mr.
and Mrs. Peckham, so that we can compare the observa-
tions of great and keen naturalists in two hemispheres.

1 The Instincts and Habits of the Solitary Wasps, by George W. and
Elizabeth G. Peckham, Madison, Wis., 1898, p. 221.

2 Proc. Boston Soc. Nat. Jfist.,xo\. xxvi, 1895, pp. 377-9 (pp. 102-4
of this volume). See also Poulton, Charles Darwin and the Theory of
Natural Selection. London, 1896, chapters xix; xx, pp. 144-60,

INSTINCTS ARISE BY SELECTION 163

We find that by the study of nine wasps of an American
species, A. tirnaria, of the very genus Ammophila, which,
as previously described, chiefly furnished the basis of
speculation, the American naturalists have shown that
the immense superstructure is in large part due to a fertile
imagination. So far from the assumed perfection and
accuracy with which every detail is supposed to be
repeated, the instinct is shown to be excessively variable.
The frequently-quoted conclusions that the object of the
sting is to reduce the larvae to helplessness and yet keep
it in a fresh condition, that a dead larva would be unsuit-
able food and an active one a danger to the offspring of
the wasp — all these conclusions are entirely disposed
of by a few careful specially directed observations. These
show that the larva rapidly dies in a large proportion
of cases and yet affords excellent food, and that it may
remain sufficiently uninjured to wriggle continuously
without stimulation, and to move violently when bitten
by the larva of the wasp.1

The following activities or performances are regarded
as truly instinctive, viz. as due to the compulsion of heredi-
tary nervous mechanism : — Stinging, the methods of attack,
capture and carriage of prey peculiar to each species, the
kind of prey selected, the general style and situation
of the nest, the form of cocoon.2

The American naturalists finally conclude their volume
with these words : — 1 The general impression that remains
with us as a result of our study of these activities is that
their complexity and perfection have been greatly over-
estimated. We have found them in all stages of develop-
ment and are convinced that they have passed through
many degrees, from the simple to the complex, by the
action of natural selection. Indeed, we find in them
beautiful examples of the survival of the fittest.' 3

As long ago as 1889 the present writer had argued
that the Lamarckian interpretation of the instincts of
Ammophila or Sphex introduced the same difficulty as

1 Instincts and Habits of Solitary Wasps, pp. 30, 31. 1 I.e. p. 234.
3 See the review of Dr. and Mrs. Peckham's work in Nature, vol. lix,
1899, pp. 466-8.

M 2

1 64 INSECTS AND HEREDITY

that alluded to in the discussion of the cocoon-making
instinct. It implied a gift of prophecy, a knowledge of
what would happen to offspring after the burrow had
been sealed and the inmate left to its fate.1

Another powerful argument is derived from the com-
parison between the instincts which are performed but
once and those which are performed many times in a
single life. Various elaborate performances are under-
taken but once in an insect's lifetime, and thus are always
' prior to individual experience \2 The behaviour which
leads to the production of an elaborate cocoon or the
burial of a larva in its earthen cell is clearly instinctive,
and the most convincing evidence would be required —
evidence which it is needless to say is entirely lacking —
in order to prove that certain insects which perform an
act no more elaborate many times in their lives are guided
by anything except the compulsion of a 1 nervous system
built through heredity \3 If the cocoon-making instinct
has evolved through selection, the comb-making instinct
of the social Hymenoptera has surely arisen in the same
way and not through the operation of an entirely different
set of causes.

As a matter of fact, I have witnessed the perfection of
comb-building ' prior to individual experience ' and under
conditions which prevented the worker from profiting by
the experience of others. I have seen ' the worker of
a species of Vespa freshly emerged from the pupa, and

1 The argument was used in the Discussion on Acquired Characters in
Section D of the British Association at Newcastle, Friday, September 13,
1889. See Report, p. 620, where, however, only the title of the paper is
printed. The following sentences are quoted from the abstract in Nature,
vol. xl, 1889, p. 610 : —

' With regard to instinct, Dr. Romanes had suggested a difficulty — that
was, the instinct of certain wasps to sting and paralyze the nerve centres
of their prey. But it must be remembered that the benefits arising from
this instinct were felt not by the wasps themselves, but by their progeny.'

In Proc. Boston Soc. Nat. Hist., vol. xxvi, 1895, p. 392 (pp. 118, 119
of the present volume), the argument is stated in greater detail.

2 For instance, the cocoon-making instinct, already alluded to (see
pp. 157-60). Weismann has directed particular attention to this
argument against a Lamarckian interpretation (The Evolution Theory,
London, 1904, vol. i, pp. 155 et sqq.).

3 Nature, vol. lxv, 1 901, p. 51. The passage has been slightly modified.

INSTINCTS PRIOR TO EXPERIENCE 165

the sole perfect insect upon the young comb (the queen-
mother having been previously killed) immediately seize
upon the broken material of the comb and begin accurately
and with exact precision to build up the thin and delicate
sides of injured cells containing the living larvae V

The strongest of all arguments against Lamarckian
evolution was advanced nearly fifty years ago by Darwin
in the first edition of the Origin of Species ; and here too
we see that demonstrative evidence was supplied to the
greatest of all naturalists by reflection upon the insect
world, and of the part of it which we are now considering.
1 No amount of exercise, or habit, or volition/ he says,
speaking of ants, ' in the utterly sterile members of a
community could possibly have affected the structure
or instincts of the fertile members, which alone leave
descendants. I am surprised that no one has advanced
this demonstrative case of neuter insects against the well-
known doctrine of Lamarck.'2

It is indeed surprising that Darwin himself, after his
own crushing argument against the hypothesis of evolution
by inherited experience, should have been willing to admit
some tincture of the same principle in other parts of the
wide field. If we are perforce thrown upon unaided
Natural Selection for the origin and growth of the most
complex and specialized societies of the Hymenoptera,
what need have we for co-operating causes of evolution
elsewhere ?

I conclude this section of my Address dealing with the
most remarkable of all nerve-mechanisms of instinct known
to us, with the following impressive comparison, made by
Professor Lankester, after contemplating the higher forms
in which instincts have been replaced by the power of
educability : — 'The character which we describe as "educa-
bility " can be transmitted ; it is a congenital character.
But the results of education can not be transmitted. In
each generation they have to be acquired afresh. With
increased " educability " they are more readily acquired
and a larger variety of them. On the other hand, the

1 Nature, vol. Ixv, 1901, p. 50.

2 The Origin of Species, London, 1859, p. 242.

1 66 INSECTS AND HEREDITY

nerve-mechanisms of instinct are transmitted, and owe
their inferiority as compared with the results of education
to the very fact that they are not acquired by the indi-
vidual in relation to his particular needs, but have arisen
by selection of congenital variation in a long series of
preceding generations.

' To a large extent the two series of brain-mechanisms,
the " instinctive " and the 4< individually acquired", are in
opposition to one another. Congenital brain-mechanisms
may prevent the education of the brain and the develop-
ment of new mechanisms specially fitted to the special
conditions of life. To the educable animal — the less there
is of specialised mechanism transmitted by heredity,
the better. The loss of instinct is what permits and
necessitates the education of the receptive brain.

' We are thus led to [the] view that it is hardly possible
for a theory to be further from the truth than that
espoused by George H. Lewes and adopted by George
Romanes, namely that instincts are due to " lapsed "
intelligence. 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 development of the brain than the former, and can
only develop in proportion as the former become feeble
and defective/ 1

The bearing of Insect Warning and Mimetic Colours
upon the supposed Hereditary Transmission of Experience
by their Vertebrate Enemies.

Adaptations which facilitate the education of entomo-
phagous vertebrates are so perfect and so wide-spread
in insects that they constitute a large body of indirect
evidence in favour of the non-transmission by heredity of
the results of experience. Fritz Mtiller, in his celebrated
theory of mimicry, suggested that the object of the likeness
between the warning colours of specially-protected species
was to reduce the danger from the attacks of young and
inexperienced enemies. This is all the more interesting

1 From the Jubilee Volume of the Soc. de Biol., Paris, 1899.
Reprinted in Nature, vol. lxi, 1900, pp. 624-5.

EXPERIENCE NOT HEREDITARY 167

because, as Professor Meldola has pointed out, 'in 1879
the question of the non-transmission of acquired characters
had not been brought into prominence. It was tacitly
assumed in the theory of Bates that a knowledge of
edible and inedible types could be transmitted by heredity.
It is remarkable that Muller, by virtue of his hypothesis,
should have unconsciously challenged this tacit assumption
by suggesting that young birds had to learn by experience,
and did not derive their knowledge of eatable and dis-
tasteful forms by heredity. The whole tendency of Pro-
fessor Lloyd Morgan's work of late years has been to
confirm this suggestion by actual observation and experi-
ment ; and Mr. Finn, also, in summing up his results,
states that " each bird has to separately acquire its ex-
perience, and well remembers what it has learned." Thus
the Mullerian theory of 1879 has now been placed on
a psychological basis of well-ascertained facts.'1

The problem has been attacked from both sides with
concordant results. In contemplating the vast scale upon
which these aids to memory and education are developed,
it is necessary to take into account the pressure of the
struggle for existence upon the enemies themselves.
1 This pressure is chiefly felt by the young, and it is so
excessive that comparatively few individuals in the fresh
wave sent forth at each breeding season, survive to
become mature and experienced. It follows from this
fact that the amount of selective pressure exerted by
inexperienced enemies of insects is many times as great
as that which is due to the educational period of the
mature enemies existing at any moment.' 2 We also realize

1 Nature, vol. Ix, 1899, P- 57-

2 Proc. Ent. Soc, Lond., 1903, p. Ixv. The form of the passage has
been slightly modified.

My kind friend Dr. A. R. Wallace, D.C.L., F.R.S., wrote (April 3,
1905) concerning these quoted sentences — 'There is one short passage
. . . which I had to read two or three times to see the point, which is
quite sound but too condensed. ... It wants much amplifying to make it
clear. . . .'

The argument may be stated in another and I hope clearer form, as
follows : —

The numbers of the species keeping approximately constant over
a long period of time, we are compelled to suppose that each pair of

168 INSECTS AND HEREDITY

the fact that insects as food are of far greater importance
than might be at first sight supposed ; for they supply
not only the insectivorous species but those other forms
which in turn prey upon them.

Thus, when we bring together the evidence supplied
by the study of insects it is seen that it nowhere sup-
ports the assumption upon which Lamarckian evolution is
founded, the assumption that acquired characters are
transmissible by heredity.

Before leaving the Chair at the conclusion of my second
year of office I desire warmly to thank the Officers,
Members of Council, and Fellows of the Society, who by
their kindness have made my task so easy and altogether
pleasurable. You will, I know full well, accord the
same generous sympathy to my successor, and under
his guidance I feel confident that the prosperity of
recent years will be continued, I hope in even larger
measure.

Before taking leave of the Fellows in my official
capacity I desire to direct their attention to two thoughts,

insect-eating birds of one generation is on the average replaced in the
next generation by a pair and only a pair of its offspring. Consequently,
each pair produces relatively enormous numbers of young which are
destined to destruction. If, merely as an illustration, we suppose that the
duration of the natural individual life in a given species of small bird is
ten years, and that five young are produced each year, then the pressure "
upon insect life of a single family during one generation is that exerted
by two adult birds, the parents, by the two offspring which will survive
and take their place, and by forty-eight offspring which will themselves
succumb in the struggle for existence at various ages. Special attention
is here directed to the pressure of these forty-eight, of which a large
proportion will not survive for more than a very small fraction of the
natural term of life. Every season will bring forth its fresh supply of
five young uneducated enemies of insects. Any of these which live long
enough to feed themselves will enter upon an educational career during
which they will exert that very kind of selection which tends towards
Miillerian (Synaposematic) mimicry. After exerting this pressure for
a variable time they will themselves succumb ; and there is no doubt that
only a very small proportion will survive until their education is complete.

Extending these considerations to the whole community of insect-eating
birds in any country, we realize at once that the selective pressure of the
inexperienced enemies is, as has been maintained above, many times as
great as that exerted by the experienced and educated.

SCIENCE AND THE EMPIRE 169

both of which I have endeavoured to keep prominently
before the Society, thoughts which I trust will always
inspire our meetings.

First, ever to remember the high significance of the
material we study; to realize its priceless value for the
elucidation and the solution of problems the most intricate,
difficult and important ; to feel that this unrivalled
opportunity is a serious personal responsibility.

Secondly, always to bear in mind that London is a
great deal more than the capital of England, and that
the Entomological Society of London can do much to
help the work of naturalists all over the world — men in
some conditions better off than we are, in other condi-
tions less well provided ; — with new and inspiring problems
at hand calling for study, but without the stimulus and
the continual aid of our vast stores of literature and our
easy intercourse with kindred minds. We can do much
to help such men, not only by means of our publications
but even more by establishing contact with them, by
showing them that their work is of value and interest
to the naturalists of a distant land. And although I
know full well that such encouragement will be offered
freely to every naturalist who may approach us, what-
ever be his nationality, yet the wide extent of the British
Empire and the roving spirit of her sons, ensure that it
will be our own people in many lands whom we shall
chiefly benefit, who will benefit us in turn. And thus
we may hope to aid in no small measure the forces that
make for sympathy and friendship and true union between
men whose communication is thwarted by both time and
space. And this happy result will be achieved by and
will itself promote the advancement of that branch of
learning for which this great Society came into being,
grew into strength and beneficence, and awaits I doubt
not a yet more glorious future.

170 INSECTS AND HEREDITY

Note. — The following statement formed part of the general introduc-
tion to the Anniversary Address. The importance of the subject, and
the very insufficient attention as yet directed to it, are my excuse for
reproducing it in the present volume.

Before I proceed to the subject of my address there is
one important point upon which I feel bound to warn not
only this Society, but other Scientific Societies as well.
I refer to the enduring qualities of the paper on which
scientific publications are often printed, and still more
emphatically the 1 paper ' on which they are often illus-
trated. I allude especially to the so-called ' art papers',
assuredly named on the principle ' ut lucus a non lucendo'.
The opaque, white, polished surface, which yields the
most successful ' half-tone ' and ' three-colour ' printings,
is at present only possible by means of a veneer of china-
clay. Dust it is, and we are assured by experts that not
many years will pass by before it succumbs to the fate
which the highest authority tells us is in store for dust.
For the purposes of advertisement, this is no disadvan-
tage : the cynic may even maintain that the writings of the
present day are, to the great benefit of the human race,
recorded upon a fitting medium. But cynicism has no part
in science, and every Fellow of this Society will agree that
an age producing scientific records which cannot be made
to endure, is an age to be rightly scorned by the genera-
tions of the future, — scorned as one that sunk to the
lowest level of production, that, intellectually, owing its
very existence to the noble standard reached by days yet
earlier, took the benefits, and deliberately or carelessly
neglected in like manner to assist its successors.

We have only to reflect upon the paramount importance
of tradition in order to realize the weight of our responsi-
bilities. Lloyd Morgan, discussing the trend of human
development, speaks of a 1 transference of evolution from
the individual to the environment', which ' may leave the
faculty of the race at a standstill, while the achievements
of the race are progressing by leaps and bounds/1 Or,
again, he contrasts the progressive evolution of the
intellectual and moral edifice of society with the cessation

1 Habit and Instinct, London, 1896, p. 340.

MATERIAL BASIS OF TRADITION 171

of evolution, perhaps even the declining level of 1 the
human builders that contribute in each generation a few
more stones to take a permanent place in its fabric'.1

This great edifice was founded on oral tradition. Later
on written tradition, and still later printed tradition took
its place. When Society comes to depend upon the one
it in large part ceases to depend upon the others, and in
changing its methods it is itself changed. Contrast, for
instance, the period in the life of each one of us when we
ceased to remember the affairs of daily life and gave our
memory into the keeping of ink and paper. Although
much was gained in the inevitable change, something was
lost. Until recently there have been many people in this
country, there are probably a few now, who, unable to
read or write, can remember the details of complicated
accounts in a manner astonishing and impossible to those
who possess these accomplishments. We see that when
society in any age has come to depend upon printing it
will be through printing and not in other ways that it will
contribute its chief share to the social edifice ; and this is
not a mere truism, for that age will have lost in large
measure other powers which would have developed in
earlier times, powers which would still develop if printing
did not exist.

Our American friends, who enter so thoroughly into
the essentials of a subject whenever they direct their
attention to it, have not, so far as I am aware, made
any determined attack upon this problem. Indeed, the
majority of the scientific works, which they so freely and
generously place at the disposal of students in other lands,
are printed upon material — I cannot call it paper — con-
structed of the felted fragments of wood, or of a thin
paper backing overlaid and loaded with china-clay. The
latter class are abnormally heavy, the former abnormally
light.

This is a matter so important that it ought not to be
left to the President of your Society to sound the warning.
It is a matter which it would have been well if the Royal
Society or the British Association had taken up years

1 I.e. p. 345.

172 INSECTS AND HEREDITY

ago. It is not creditable to have left to our artist brethren
a subject of such paramount importance to ourselves; for
to them belongs the honour of having made the only
serious attempts to improve our practice and to call
attention to the evil.

To the trades concerned I would say that it is strange
want of enterprise to continue methods and use materials
which only require to be thoroughly understood to ensure
a swift and sudden collapse for all but the most ephemeral
purposes. I know no producer, scientific or other, whose
self-respect would suffer the employment of materials,
however good the effect, however low the cost, which
would not last over so brief a period as five-and-twenty
years.

I desire to thank Mr. Horace Hart, Controller of the
Oxford University Press, and Mr. J. W. North, A.R.A.,
for the kind manner in which they have freely given
information on this most important matter.

VI

A REMARKABLE ANTICIPATION OF
MODERN VIEWS ON EVOLUTION

Reprinted from Science Progress, New Series, vol. i, no. 3, April,
1897.

Revised: additional footnotes.

The great pioneer of modern anthropological and
ethnological research — James Cowles Prichard, was born
at Ross, in Herefordshire, February 11, 1786. The
following brief account of his life is taken from an article
by Professor E. B. Tylor, F.R.S.1 Prichard was brought
up as a member of the Society of Friends, to which body
his parents belonged. He joined the medical profession,
taking his Doctor s degree at Edinburgh, ' afterwards
reading for a year at Trinity College, Cambridge, whence,
joining the Church of England, he migrated to St. John's
College, Oxford, afterwards entering as a gentleman
commoner at Trinity College, Oxford, but seeking no
degree in either university. In 18 10 he settled at Bristol
as a physician.' Among his many great achievements in
anthropology was the proof * that the Celtic nations are
allied by language with the Slavonian, German, and
Pelasgian (Greek and Latin), thus forming a fourth
European branch of the Asiatic stock (which would now
be called Indo-European or Aryan)'. His treatise on
the subject, entitled Eastern Origin of the Celtic Nations,
appeared in 183 1. 4 It is remarkable that the essay by
Adolphe Pictet, De V A finite1 des Langues Celtiqnes avec
le Sanscrit, which was crowned by the French Academy
and made its author's reputation, should have been pub-
lished in 1837 m evident ignorance of the earlier and in
some respects stricter investigations of Prichard.'

1 Encyclopaedia Britannica, 1885, vol. xix, pp. 722, 723.

174 A REMARKABLE ANTICIPATION OF

Although Pochard's memory is much honoured, it
appears that in one important respect he has not hitherto
received his due. My friend Professor Meldola, F.R.S.,
lately drew my attention to a section of the second
volume of Prichard's Researches into the Physical History
of Mankind1 which, as he pointed out, anticipated in
the clearest manner the arguments which have been
recently advanced by Professor Weismann in favour of
the non-transmission of acquired characters. The deep
significance of the passages in question had been observed
by Dr. Maurice Davis, J. P., who brought them under the
notice of his son-in-law, Professor Meldola.

In response to Professor Meldola' s invitation to pre-
pare an account of this most interesting contribution
to the history of evolution, I read the work carefully
and soon found that other important ideas are anticipated
in it.

Thus, Prichard apprehended with perfect clearness
that domesticated races of animals and plants have been
produced by the selection of man and not by favourable
surroundings, careful training or cultivation. He believed
in the possibility of organic evolution and supported it
by excellent arguments which still have the strongest
weight to-day. He even recognized the operation of
Natural Selection, although he assigned to it a subordinate
role.2 The most important anticipation is, however, the
masterly discussion on the transmission of acquired

1 2nd edition, 1826.

2 Mr. Francis Darwin, F.R.S., and Professor A. C. Seward, F.R.S.,
consider that the present essay exaggerates ' the degree to which Prichard
believed in evolution' [More Letters 0/ Charles Darwin, vol. i, p. 43,
London, 1903), and, while admitting the tendency of passages here
brought forward, believe that they are entirely neutralized by other
passages. I had endeavoured to make it evident that this antagonism
exists in Prichard's writings, not only as regards the evolutionary
passages, but also in those dealing with the non-transmission of acquired
characters. My object was and is to show that certain of Prichard's
thoughts, as expressed in his published works, were a remarkable
anticipation of modern views on evolution. The historic and human
interest of these thoughts remain, notwithstanding the fact that they were
abandoned by their author in later years, and were even inconsistent with
other thoughts to be fcund in the same work.

MODERN VIEWS ON EVOLUTION 175

characters, a discussion in which the distinction between
acquired and inherent or congenital characters is clearly
drawn, and many of the most difficult cases are fully
argued out, the conclusions reached being those inde-
pendently arrived at by Professor Weismann over half
a century later.

It is very remarkable that all this should have passed,
as I believe, unnoticed. The neglect can only be ex-
plained by supposing that this particular edition was
never consulted, but that Darwin and others always went
to later editions of the same work. I shall be able to
show that Prichard was not very confident in the strength
of his own conclusions and, so far as I have consulted
his later editions and works, I find reason for the belief
that his convictions weakened still further. Indeed, strong
indications of uncertainty are to be found in the second
edition itself, although they are confined to the later
sections, and do not appear in close proximity to the
important conclusions which they nevertheless affect.

It is certain that if Darwin had read this second edition
he would have given Prichard a high place in the account
of the history of evolution which appears in the intro-
duction to all later editions of the Origin} So too would
my friend Professor Osborn have given high honour
to Prichard in his interesting work, From the Greeks to
Darwin. It is an anomaly that such works as the Vestiges
should attract attention, while Prichard's keen insight,
sound judgement, and balanced reasoning on many aspects
of organic evolution, and especially on the scope of
heredity, should remain unknown.

I am very far from maintaining that these most
interesting anticipations in any way diminish the credit
of those recent writers who have treated the same sub-
jects in greater detail and of course independently. The
interest evoked by Dr. Davis's discovery in the literature
of evolution is mainly due to the work of those recent

1 F. Darwin and Seward state that Charles Darwin only possessed the
third and fourth editions (I.e. p. 44) ; they also agree that 1 in the historical
sketch prefixed to the Origin of Species writers are named as precursors
whose claims are less strong than Prichard's' (I.e. p. 45).

176 A REMARKABLE ANTICIPATION OF

authors by whom the whole subject has been brought
into the light of day, and the attention of every intel-
lectual man and woman has been compelled.

The limits of space oblige me immediately to proceed,
after this too brief introduction, with a detailed statement
of Prichard's arguments and conclusions, which will be
found to justify, in the fullest manner, all that I have
said in his praise.

It has already been said that the arguments referred
to are found in the Researches into the Physical History
of Mankind} They are included in the seven sections
of the first chapter of Book ix (p. 525), which is entitled
a General Survey of the Causes which have Produced
Varieties in the Human Species, with Remarks on the
Origin of Nations and on the Diversity of Languages.
The first chapter treats Of the Causes which have given
rise to Varieties in the Human Species. In the first
Section of the first chapter the author admits that it is
fruitless to seek for a complete explanation of the causes
which have produced the varieties which are witnessed
in the human species. ' The origin of the varieties in
the breed is enveloped in the same obscurity which
still hangs over every question relating to the theory
of propagation.'

The opinion that the different shades of colour met
with in various races are caused by climatic changes and
by varying intensity in the rays of the sun, is then con-
sidered, and a great many ancient and modern exponents
of this view are quoted. After reproducing a long
passage from Buffon, the hypotheses of the Rev. Dr. S. S.
Smith of New Jersey are described. These deal not
only with the 'gradation in the complexion, nearly in
proportion to the latitude. , . / but also with the influence
which heat exerts upon the secretion of bile. In con-
sequence of heat ' the bile ... is augmented. . . . This
liquor tinges the complexion. . . 1 Bile, exposed to the
sun and air, is known to change its colour to black —
black is, therefore, the tropical hue.' This latter and
the very similar views of Blumenbach are, however,
1 Vol. ii, London, 2nd edition, 1826.

MODERN VIEWS ON EVOLUTION 177

dismissed by Prichard as 1 without foundation 1 ; while
as to the suggestion of Dr. Smith, together with that
of Bufifon and the older writers upon the effect of
latitude, he observes that the principal observations on
which it is based are correct. ' It is certain that the
majority of black races of men are inhabitants of the
intertropical regions, and that most of the light-coloured
nations, . . . are to be found in cold or temperate climates.'
But although he admits the fact, he maintains that it
is capable of * a different interpretation from that which
modern writers have in general adopted '. He similarly
admits that the skin of a European is darkened by
the sun, and continues : 'It seems, at first, not very
improbable, that individuals, darkened by exposure to
heat in southern climates, may have an offspring of
deeper colour in consequence, and if this effect increases
in every generation, it may be thought sufficient, in a
long course of ages, to produce a black colour of the
deepest tint.' But this view does not by any means
commend itself to him ; for he continues, 1 that this
notion, however, is altogether incorrect I venture to
conclude from the following considerations.

' I. The progeny of individuals, embrowned by ex-
posure to the sun, is born with the original complexion,
and not with the acquired hue of the parents.' Further-
more, he points out that white and black races moved
respectively to tropical and temperate climates have
retained their original colour for ages. The second
consideration which leads him to reject the above-
mentioned conclusion is very significant, and I give it
in his own words (p. 532) : —

1 2. The supposition is contrary to a general law
of the animal economy, according to which, acquired
varieties are not transmitted from parents to their
offspring, but terminate in the generation in which
they have taken their rise.'

The succeeding two Sections are allotted to the con-
siderations contained in paragraphs 1 and 2.

Section ii (p. 532) is headed, Instances showing the
Permanency of Complexion in different Races. The

POULTON N

178 A REMARKABLE ANTICIPATION OF

cases in which races have completely changed in colour
after removal to a different climate he explains by
a mixture of breed ; and points out that ' it is easy to
find examples of an opposite tendency, and to show
that the original hue has been preserved. . . .* Thus
he brings forward the instances of the descendants of
English colonists in the West Indies and Spanish in
South America who 'remain as fair as their European
ancestors', when there has been no intermarriage with
other races. ' That this assertion is correct, I am con-
vinced,' he says, 'by the result of repeated inquiries.'
In the East the same results are found, although the
migration of white races into hot climates took place
at far earlier dates. Thus amongst other examples he
mentions that of the 'white or Jerusalem Jews' who
are believed to have migrated to the Malabar coast in
the year 490 a.d., and whose living descendants are
'said to resemble the European Jews in features and
in complexion '.

The converse ' experiment of transplanting black races
into northern climates ' has not been carried on for so
long a period, but Dr. Prichard points out that ' several
generations have produced little or no alteration in the
complexion of Negroes in the United States and in
other temperate climates'. It is indeed stated that
1 the domestic Negroes who are protected from the heat
of the sun by more clothing, and who pass their time in
sheltered houses, are of a darker complexion than the
slaves who labour half naked in the fields '.

Section iii. This most significant and remarkable part
of the work is headed (p. 536), Laws of the Animal
Economy in regard to the Hereditary Transmission of
peculiarities of Structtire : the brief title at the head of
the pages runs, Laws of Nature in Hereditary Trans-
mission. This discussion, which forestalls by more than
half a century the considerations and conclusions of
recent writers and especially of Professor Weismann,
is opened by the statement that physiological writers
have often inquired 'what peculiarities of structure are
liable to be transmitted by parents to their offspring,

MODERN VIEWS ON EVOLUTION 179

and what terminate with the individual without affecting
the race. Perhaps the following remark,' the author
goes on to say, 1 may afford the solution of this inquiry.'

I must now quote without any omission the suc-
ceeding two paragraphs in which the two classes of
characters — inherent and acquired — are defined, as fully
and clearly as they have ever been, and where the opinion
is strongly expressed that the former are transmissible,
the latter non-transmissible by heredity : —

' It appears to be a general fact, that all connate
varieties of structure, or peculiarities which are con-
genital, or which form a part of the natural constitution
impressed on an individual from his birth, or rather from
the commencement of his organization, whether they
happen to descend to him from a long inheritance, or
to spring up for the first time in his own person — for
this is perhaps altogether indifferent — are apt to re-appear
in his offspring. It may be said in other words, that
the organization of the offspring is always modelled
according to the type of the original structure of the
parent.

* On the other hand, changes produced by external
causes in the appearance or constitution of the individual
are temporary, and, in general, acquired characters are
transient ; they terminate with the individual, and have
no influence on the progeny/

At this point the author adds a most interesting foot-
note, in which he tells us (p. 537) that 'this distinction,
which has not been pointed out by any former writer on
physiological subjects, was first suggested to me in con-
versation many years ago by Mr. Benjamin Grainger,
of Derby'. It would be of high interest to ascertain
something more about Mr. Grainger and to find out
whether he ever published on his own account. It is
however probable, from the other pregnant ideas con-
tained in Dr. Prichard's work, that the clear expression,
apt illustration, and admirable discussion of these prin-
ciples are entirely original.

He then proceeds to illustrate the first proposition
1 that all original or connate peculiarities of body are

N 2

180 A REMARKABLE ANTICIPATION OF

hereditary ' ; first instancing the well-known ' porcupine
family, in which a remarkable peculiarity of the [human]
skin was transmitted through three successive genera-
tions/ and the facts which prove the hereditary nature
of complexion, as shown in Section ii. Supernumerary
and abnormally thickened digits are then brought forward
and proved by many examples to be markedly hereditary ;
as also 'a singular thickness of the upper lip, in the
Imperial house of Austria', introduced it is believed
' many centuries ago, ... by an intermarriage with the
ancient house of Jagellon\

The last examples of such connate characters are
especially significant. ' The same observation equally
applies to those minute varieties of organization, which
give rise to peculiarities of habit or temperament, and
predispose to a variety of morbid affections, as deafness,
scrofulous complaints, and the whole catalogue of dis-
orders in the nervous system. Even those singular
peculiarities termed idiosyncrasies are often hereditary,
as in the instance of a remarkable susceptibility of the
action of particular medicines, such as mercury.'

With regard to the second proposition ' that acquired
peculiarities, or characters impressed by adventitious
circumstances, and not arising in the spontaneous deve-
lopement of the bodily structure, are never transmitted . . /
he remarks, as it has often been insisted upon since,
that the conclusion ■ is more difficult to establish than
the foregoing . . ., since the proofs must needs be of
a negative kind. But,' he continues, 1 there is no want
of evidence of this description/ And he again insists,
as if he could not put it too clearly and emphatically :
' It seems to be the law of the animal economy, that
the organization of the offspring, which as we have seen
follows the type given by the natural and original struc-
ture of the parent, is unaffected by any change the latter
may have undergone, and uninfluenced by any new state
it may have acquired.'

He then discusses the examples which are supposed
to support the opposite conclusion, first mentioning the
statement ' that dogs and cats, the tails of which had

MODERN VIEWS ON EVOLUTION 181

been cut oft* sometimes produce young ones which have
a natural defect of the same part. It is taken for granted
that these appearances are connected together in the
relation of cause and effect, and therefore afford a proof
that acquired peculiarities are hereditary.' The author
argues that cases of this kind are accidental, and he
points out that such defect of parts is apt to occur in
every species ; — in man as well as in animals. He
points to the vast experiment due to ' our caprice ' in
mutilating the ears and tails of domestic animals, and
to the effects of surgical operations upon man. What
remarkable results would be witnessed if such changes
were hereditary !

Professor Weismann was first led to the same con-
clusion as Dr. Prichard by constructing a theory of
heredity which seemed to him to explain the facts and
observations better than any which had been previously
proposed. But the theory did not include any mechanism
by which the transmission of acquired characters could
take place. Professor Weismann, believing that his
theory was in the main right, began to inquire for the
evidence on which the belief in such transmission is
based, and as soon as he commenced his inquiries the
evidence broke down in every direction.

With Prichard it was otherwise, for the existing
theories seem to have been against him. Thus he
argues that his opponents 1 seem to have derived their
opinion rather from some conjectural theory of genera-
tion, than from any facts which have appeared well
established ' ; and he goes on to contend that we know
so little 1 that we are not authorized to reason from any
hypothesis on this subject

He next deals with the statement 'that after any mutila-
tion or other artificial change has been repeated through
many generations, a sort of habit may be acquired, by
which the new state becomes as it were natural, and may
thus modify the race '. To this he replies that the evidence
of such habit could only be obtained by diminishing the
mutilation in progressive generations and comparing the
result ; whereas in all such cases the violence committed

182 A REMARKABLE ANTICIPATION OF

and the resulting injuries are continued unabated. ' If,
however, an experiment be wanting to prove that repeti-
tion effects no difference in the results,' he points to the
practice of circumcision which has gone on for some
thousands of years without producing any hereditary
change.

Prichard argues that such non-transmission is beneficial,
in fact he contends ' that all the laws of nature, or the
general plans which we trace through the organized
world, tend uniformly to produce beneficial effects, though
particular evils are sometimes contingent upon their
operation'. With regard to this instance he points out
that, if such transmission took place, both man and
animals would practically become more and more ' muti-
lated and defective '.

The author next proceeds to consider the effects of
disease, introducing the subject in the following paragraph :
1 We cannot discern any essential circumstance, in which
changes produced by art, or by casual injury, differ from
those which are effected by other external causes. We
should therefore suppose from analogy that the latter are
not more communicable to posterity than the former, and
this presumption is confirmed when we inquire into facts.'

He points out that the constitutional effects of many
diseases ('small-pox, measles, scarlatina, hooping-cough'),
rendering those who have suffered from them more or
less immune, are never hereditary. Without attempting to
explain in what the change consists, he rightly claims it
as a 1 permanent state of the constitution, which lasts as
long as the individual. . . . Those imperceptible modifi-
cations in the bodily structure which render the constitution
incapable of being acted upon by certain morbid poisons
are governed by the same law, as far as regards heredi-
tary descent, as the observable changes of form which
are induced by art or accident '.

At this point the writer intercalates another clear
statement of the essential distinction between inherent
hereditary and acquired non-hereditary characters. The
statement is so admirable that I quote it in full.

' We may remark in general that each individual being,

MODERN VIEWS ON EVOLUTION 183

through the animal and vegetable worlds, has certain laws
of organization impressed upon its original germ ; accord-
ing to which the future developement of its structure is
destined to take place. These inbred or spontaneous
tendencies, governing the future evolution of the bodily
fabric, cause it to assume certain qualities of form and
texture at different periods of growth. From these pre-
dispositions are derived the characteristic differences, and
the peculiarities of individual beings. Now it appears
that such spontaneous tendencies are alone hereditary,
and that whatever changes of organization are superin-
duced by external circumstances, and are foreign to the
character of structure impressed upon the original stamina,
cease with the individual, and have no influence on the
race.

1 Yet this law of hereditary conformation exists with
a certain latitude or sphere of variety, but whatever
varieties are produced in the race, have their beginning
in the original structure of some particular ovum or germ,
and not in any qualities superinduced by external causes
in the progress of its developement.'

These sentences might well have been written to-day,
to sum up the results of all our observations on such
subjects. They have been summed up at greater length
and in more technical language, but I venture to think
that Dr. Prichard's statement contains everything that
is valuable and essential in every later attempt. It will
be observed that Weismann's conception of inherent
characters as blastogenic, acquired as somatogenic, stands
out clear and distinct ; furthermore, that the source of
individual difference is traced to the germ.

After these general statements he returns to the ques-
tion of disease, and discusses predisposition. He points
out that medical writers have generally believed that any
predisposition to disease may arise in any constitution if
subjected to the appropriate causes ; 1 that . . . the gouty
diathesis, for example, may be acquired by long habits of
intemperance, and transmitted to posterity/ and so also
with other ill effects witnessed in the children of dissolute
parents. If this be so, Prichard admits that 'we have

184 A REMARKABLE ANTICIPATION OF

a clear proof of the hereditary nature of acquired states
of the constitution \

Against such a view he contends that any particular
disease can only follow when there exists ' a preparation,
laid in the first place by nature, in the original stamina
and habit of the body' ; and he points out that the same
hurtful cause may produce quite distinct diseases. Thus
' intemperate living ... is commonly said to bring on, in
one person, a predisposition to gout, in another to diseases
of the liver, or of the stomach, or of the brain. Now,
since the difference is not in the external causes, it must
be in the natural peculiarities of the constitutions on
which they act. These, therefore, are previously fitted by
original organization to take on them one form of morbid
affection rather than another. It is then clear that the
predisposition is laid by natural or congenital structure,
in the first instance'. Individuals differ in particular
organs ; the exciting causes of disease bring out the
weaknesses which previously existed and might other-
wise have remained unknown. Such defects ' being a part
of the original bodily structure ' are hereditary. 4 The
first individual who exposes himself to the morbid causes,
first betrays the peculiar defect of the race, and is thus
erroneously supposed to lay the foundation for it.'

Syphilis, which appears to be an exception, he explains
by ' a peculiar mode of infection. . . . This is evidently
a phenomenon of a very different kind from the simi-
larity of structure which the laws of nature have ordained
between parents and their offspring'.

Hence he infers f that the phenomena of predisposition
to diseases rather confirms than invalidates the general
observations before laid down, and we may be allowed to
conclude, that no acquired varieties of constitution become
hereditary, or in any manner affect the race '.

The preservation of complexion after a race has
migrated to a very different climate conforms to the
general law. Although the parents may alter greatly,
* the adventitious colour has no influence on the offspring \

Hence in looking for the causes of varieties of mankind
we must not 1 direct our attention to the class of external

MODERN VIEWS ON EVOLUTION 185

powers which produce changes on individuals in their own
persons, but to those more important causes, which, acting
on the parents, so influence them that they produce an
offspring endowed with certain peculiar characters, which
characters, according to the law of nature, become heredi-
tary, and thus modify the race

The sentence I have last quoted concludes the Section
and very naturally introduces Section iv, entitled, Theory
of the Origin of Varieties (p. 548).

This Section opens with a sentence which might well
have been written by Darwin : 1 Varieties of form or
colour, as they spring up in any race, are commonly called
accidental, a term only expressive of our ignorance as to
the causes which give rise to them.' On the other hand —
1 how, by what influence, and in what manner ' they are
produced, 'we shall perhaps never be able to ascertain.'

Examples of new varieties which have sprung up within
the experience of man are then given: the 'porcupine'
and six-fingered man, albinos, and variations in colour.
He next describes the sudden origin of the ancon or otter
breed of sheep, quoting from Colonel Humphries in the
Philosophical Transactions for 1 8 1 3 (part i).

Prichard favours the view that when the offspring does
not exhibit a new variety but follows the main lines of its
race or breed it is apt to be influenced by the father rather
than the mother ; and he quotes a number of statements
and opinions believed to favour this view ; and finally
alludes to the celebrated cross between the mare and the
male quagga, in which it was confidently believed that so
great an effect was produced on the former that her later
offspring, although begotten by a stallion, were influenced
in the direction of the quagga (telegony).

The mother, on the other hand, was believed to be in
the main responsible for the new varieties which arise
from time to time. This opinion Prichard considered to
be probably well grounded ; and the conclusion that size
and stature chiefly depend on the mother he also thought
to be well established. Hence we see that his judgement
and penetration were not always proof against popular
convictions insufficiently sustained by evidence. These

186 A REMARKABLE ANTICIPATION OF

strange views about the relative importance of the two
parents seem to have disappeared, and only traces of
them are to be found in the popular beliefs of the day.

The author dismisses the extreme cases of the supposed
effect of the mother's imagination upon the unborn child
as manifestly absurd ; but looks with some favour upon
the opinion, also held by Erasmus Darwin, whom he
quotes, that the future offspring may be affected by the
imagination of the parent at the moment of conception.
In proof of the ancient origin of this belief he alludes to
Jacob's experiments upon the flocks of Laban.

When, however, Prichard comes to reconsider all his
suggested causes of variation he is dissatisfied with them
and admits that ' the circumstances . . . are of a more per-
manent nature ', and that it is often ' impossible to discover
any peculiar circumstance in the condition of the mother '.
This leads him to consider the similar instances among
domestic animals and among plants, and at this point he
anticipates in a truly remarkable manner Darwin's general
conclusions as to the origin of our domestic breeds.

' It is generally supposed/ he says on page 557, 'that
cultivation is the most productive cause of varieties in
the kind, both in the animal and vegetable kingdom.
But it may be questioned, does cultivation actually give
rise to entirely new varieties, or does it only foster and
propagate those which have sprung up naturally, or as
it is termed accidentally ?

1 In this latter way the influence of art is very important
in constituting breeds, as of cattle, dogs, horses. The
artificial process consists in a careful selection of those
individual animals which happen to be possessed, in
a greater degree than the generality, of any particular
characters which it is desirable to perpetuate. These are
kept for the propagation of the stock, and a repeated
attention is paid to the same circumstances, till, the effect
continually increasing, a particular figure, colour, propor-
tion of limbs, or any other attainable quality, is established
in the race, and the uniformity of the breed is afterwards
maintained by removing from it any new variety which
may casually spring up in it'

MODERN VIEWS ON EVOLUTION 187

The main result of Darwin's indefatigable labours
on the formation of domestic races could not be more
accurately summarized than in these words published
in 1826.

Prichard expresses himself as uncertain whether
domestic animals are more prone to vary than others,
but considers that the artificial conditions may in all
probability 1 occasion deviations in their progeny \

The influence of climate seemed to him the most impor-
tant of all causes of race-formation — so important in fact
that he discusses its examples under a separate Section,
while the adaptation of races, animal and human, to their
climates form the subjects of the concluding Sections vi
and vii.

The examples of the effect of climate are brought
forward in Section v (p. 558), entitled, Instances of
variety in the Breed, arising from the operation
of external, chiefly of local causes. The first instance
is that of the swine of Cuba, which are said to be twice
the size of the parent breed. He then instances the
peculiar and uniform colour of the cattle and horses
' descended from the variegated domestic breeds ' which
have become wild in South America, and the common
bear, which differs in colour in various European localities.

When the races of several distinct species resemble
each other in a single locality it is fairly maintained that
some special local influence may be strongly inferred.
Thus it is stated that the Angora breeds of rabbits, goats,
and cats are remarkable for their long, fine, silky hair, and
white colour. 1 These characters . . . indicate a common
cause, which must be some peculiarity in the circumstances
under which these animals exist in the climate and
situation occupied by them.'

Then follow many other examples — the blackness which
characterizes both men and animals in Malabar and
Guinea, the whiteness of Polar animals, the height of
Patagonian man, the differences which separate the
English race in America and the West Indian Islands
from that in the parent country, and the negroes of
America from those of Africa.

188 A REMARKABLE ANTICIPATION OF

The Section concludes in a significant paragraph in
which the author suggests that perhaps some of these
local varieties may be specially adapted to ' the circum-
stances of the countries in which the deviation has taken
rise and he finally concludes by introducing the succeed-
ing Section in these words : ' It may indeed be inquired,
whether the deviations in general, which appear to follow
a change of climate, are not founded on a law of the
animal economy, which gives rise to an alteration in the
breed calculated to fit the race for its new abode* (page
566).

The sixth Section (p. 567) is headed Adaptation of
certain Breeds to particular local circumstances. In
this Section we are provided with numerous instances
of the adaptation of races to their environments. Blumen-
bach's opinion in favour of the multiple origin of the dog
is quoted at some length. Considering the undoubted
adaptation of many breeds for certain ends, this naturalist
concludes : 1 1 can scarcely persuade myself to look upon
this as a mere accidental consequence of degeneration,
and not rather as an intentional contrivance of the
wise Creator.' To this Prichard replies that such a
remark ' suggests the inquiry whether the degeneration
or variation of animals is in fact a mere accidental phe-
nomenon . . . We should note that degeneration is
here used in the sense of departure from ancestral type,
and not implying, as it does in our time, any degradation
or simplification of structure.

Then follows a paragraph most significant of modern
views of organic evolution and the kind of evidence on
which the modern naturalist relies. The remarkable
* double relation ' which individual species bear on the
one hand to their special localities, and on the other to
the group to which they belong, is first pointed out, and
maintained to be characteristic of the vegetable kingdom
as well as the animal. Thus the species of a family or
genus are often distributed round a centre 1 which seems
to be the principal focus or favourite seat of the tribe
from which the branches diverge in various directions.
The particular species, when compared, can be referred

MODERN VIEWS ON EVOLUTION 189

to 1 one type of organization '. The slighter differences
between them 1 seem to lose themselves in the sameness
of form belonging to the genus, and even suggest a sus-
picion that they all proceeded from one original. The
phaenomena of resemblance must have had their sufficient
reason as well as those of diversity'. He then inquires
whether the explanation is to be found in the action
of 'some slight modification in the productive causes'
which stamped the genus at its first appearance ' with
all these specific diversities ' ; or whether, on the other
hand, a uniform genus was first created which 'after-
wards became diversified by the influence of external
agents'. He concludes that the former of these alterna-
tives is more strongly indicated by the knowledge of
his time.

' Whichever of these suppositions may be true in point
of fact, the separation of families and genera into parti-
cular species, and the distribution of these species to
particular habitations, according to their physical proper-
ties, is evidently a part of the provision of nature for
replenishing the earth with organized inhabitants, placed
everywhere according to the congruity of soils and tem-
peratures, with their structure and habitudes.

1 But why is it to be supposed that the influence of this
law of adaptation has stopped here ? Is it not probable
that the varieties which spring up within the limits of
particular species, are further adaptations of structure to
the circumstances under which the tribe is destined
to exist [?] Varieties branch out from the common form
of a species, just as the forms of species deviate from the
common type of a genus. Why should the one class
of phaenomena be without end or utility, a mere effect
of contingency or chance, more than the other ?

1 There are indeed many instances in which we can
perceive an advantage in the varieties of form, and an
adaptation of particular breeds to external circumstances.'
He then gives numerous examples — the small, active cattle
and horses which are found in mountainous countries,
the larger forms which flourish on fertile plains ; the
various breeds of the hog which are believed to hold

i9o A REMARKABLE ANTICIPATION OF

i a particular relation to the localities in which they are
placed ' ; the change of a thick fleece into a thin coat
when certain breeds of sheep are transported to the
tropics. 6 On considering these and analogous pheno-
mena, we can scarcely avoid concluding that the variation
of animals proceeds according to certain laws, by which
the structure is adapted to the necessity of local circum-
stances.'

This statement looks at first sight very much like
Natural Selection. It is clear, however, that the writer
held a view similar to that which has been termed ' self-
adaptation ' by some modern writers, viz., that external
influences act on the organism in such a manner as to
evoke directly a favourable response.

Examples of similar adaptation are then found among
the races of man. The skin of black races is considered
to be a protection against the effect of heat ; the native
African races can multiply in localities where a white
population cannot maintain its numbers, while negroes
are unable to establish themselves in northern latitudes.
From these and many other instances, it appears that 1 in
mankind, as in some other races, particular varieties are
adapted by constitution and physical peculiarities to
particular local situations \

The Section finally concludes with the following para-
graph : ' These remarks, if they are well founded, serve
to illustrate the doctrine of variation, or deviation, in
the races of animals in general, and they seem to lead
us to the conclusion, that this is not merely an accidental
phenomenon, but a part of the provision of nature for
furnishing to each region an appropriate stock of inhabi-
tants, or for modifying the structure and constitution of
species, in such a way as to produce races fitted for each
mode and condition of existence. A great part of this
plan of local adaptation appears to have been accom-
plished by the original modification of a genus into a
variety of species. It has been further continued, and
the same end promoted, by the ramification of a species
into several varieties.*

The seventh and last Section (p. 575) of this part of

MODERN VIEWS ON EVOLUTION 191

the work treats Of the Relation of particular Varieties
of the Human Species to Climates.

Prichard evidently thought that adaptation of races to
climate is especially characteristic of the human species,
and must be admitted to hold in certain instances, what-
ever be thought of his hypothesis that * the varieties in
the species of animals proceed from a principle in nature,
modifying the structure and constitution of races, and
adapting them to the physical circumstances under which
these races may be destined to exist . . . '. He con-
siders that the distribution of the races of men bears
i a certain relation to climates \ and gives a broad sketch
of the geographical arrangement of races in support of
this opinion. At the conclusion, after inquiring how it
is that ' these varieties are developed 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 disappear in climates for which they
are, by peculiarity of constitution, not adapted. Of this
fact proofs have been already mentioned.' We have here
the undoubted recognition of Natural Selection, and it is
remarkable that a man of such penetration who recognized
fully that domestic breeds are due to man's selection,
should not have seen in this principle a larger importance
and have extended it to the relations of species to each
other as well as to their physical environment. Great as
Prichard was, he did not appreciate the most pressing
part of the 1 struggle for existence \

Prichard furthermore considers it probable that there
are local influences which ' promote the appearance of
those varieties which are best suited to them, or tend to
give rise to their production in the breed'. He freely
admits that this conclusion conflicts with his contention in
Section ii, that the colour of a race is not permanently
affected by a change of climate, and, he might have added,
conflicts equally strongly with his argument in Section iii,
that acquired characters are not transmitted. However,
he is so fascinated by the view of a local influence directly

192 A REMARKABLE ANTICIPATION, ETC.

producing adaptation that he throws over much that he
had previously argued for in a most convincing manner.
Thus he suggests that races of men when removed into
another climate may not change because they are defended
from the local influences by living in houses, adhering to
their old foods, &c, also that the facts about the black
and white Jews of Cochin, from which he argued in
Section ii that climate produces no permanent effect on
the race, may be insufficiently known.

It is strange that one who reasoned so acutely in Section
iii did not seem to see that the following view, if proved
to be true, would undermine the whole of the argument :
' It may however be true, that particular varieties, once
established in the stock, and transmitted for many genera-
tions, though originally resulting in a certain degree from
the influence of local causes, will nevertheless continue
permanent, even long after the race has been removed
from the climate in which they originated/

In spite of this logical flaw, which is in itself of much
interest, inasmuch as it probably explains the suppression
of Prichard's original views in later works, sufficient has
been said to prove that the author was one of the most
remarkable and clear-sighted of the predecessors of
Darwin and Wallace.

VII

THOMAS HENRY HUXLEY AND THE
THEORY OF NATURAL SELECTION

The Huxley Lecture for 1905, delivered before the University of
Birmingham, March 23.
Hitherto unpublished.

The relation of a great man to a great theory which
arose in his time is always a deeply interesting subject
of contemplation. A great theory, like Gravitation or
Natural Selection, is an all-powerful weapon of inquiry —
strong enough to effect a reclassification of workers —
inexorable sometimes in making the first last and the last
first, according to the prejudice or the sympathy with
which the new instrument is received. A theory of the
highest rank compels attention and can be no more
passed by with indifference than the discovery of iron
or of gunpowder.

The attitude of Huxley towards Natural Selection was,
I shall endeavour to show, remarkable and unusual.
Although no one strove so nobly and against such odds
in its defence from unfair attack, although no one ever
fought the battle of science with more complete success,
Huxley was at no time a convinced believer in the theory
he protected.

The origin and growth of the theory and the circum-
stances under which it was made public have often been
told, but no lecture of this kind would be complete with-
out a brief recapitulation of the main points.

Darwin, convinced of evolution by reflection upon his
observations in South America, during the voyage of the
Beagle (183 1-6) began in July, 1837, systematically to
collect facts bearing upon the modification of species

POULTON O

194 HUXLEY AND NATURAL SELECTION

and its causes. In October of the following year, when a
few months under thirty, he read Mai thus On Population,
and the idea of Natural Selection at once dawned on his
mind. In June, 1842, he wrote a brief account of the
theory in thirty-five pages, expanded two years later into
an essay of 231 pages, folio ; but he could not bring him-
self to publish until, on June 18, 1858, almost exactly
twenty years after the conception first came to him, he
received a manuscript essay written by Alfred Russel
Wallace at Ternate, in the Moluccas, On the Tendency of
Varieties to depart indefinitely from the Original Type. In
the accompanying letter Wallace asked him if he thought
well of the essay to send it to Sir Charles Lyell. In the
paper which had reached him from the other side of the
world Darwin was astounded to find a clear, concise
statement of his own theory of Natural Selection. He
sent it on to Lyell that very day and shortly afterwards
asked him to forward it to Sir Joseph Hooker. Thus
appealed to, Lyell and Hooker requested Darwin to give
them an abstract of his own work, and presented this,
together with Wallace's paper, as a joint communication
to the Linnean Society. They explained the circum-
stances of the case in an introductory note to the Darwin-
Wallace memoir, which was read at the meeting held on
July 1, 1858.1

That, of two naturalists on opposite sides of the globe,
one should seek the other for advice upon the theory at
which they had independently arrived, is a sufficiently
remarkable fact in the history of discovery ; but now that
we know the circumstances under which Wallace wrote
his essay, the coincidence is far more striking. He also
was convinced of Evolution before he thought of a motive
cause, and had in 1855 defended it in a powerful paper,
written in Borneo, On the Law which has regulated the
hitrodtution of New Species. In February, 1858, lying
ill of intermittent fever in Ternate, he, too, began to think
of Malthus On Population, which he had read some

1 In addition to the specially prepared abstract, Darwin's section of
the joint memoir includes a copy of a letter he had written Sept. 5, 1857,
explaining his theory to Asa Gray, the great American botanist.

THE DARWIN-WALLACE ESSAY 195

years before, and the idea of Natural Selection instantly
flashed across his mind. But he did not wait for twenty
years of thought for repeated observation and experi-
mental test. In two hours of ague he had thought out
almost the whole of the theory, in three evenings he
had completed his account, and it was posted to Darwin
by the next mail.

Thus on July 1st, 1858, when Darwin was nearly fifty,
and Huxley just over thirty-three, the great theory was
before the world ; and the striking thing about the relation
of the younger man to this crisis in the history of science,
is that he knew really nothing about it. Darwin and
Huxley had corresponded for some years prior to 1858 ;
but even had this not been so, Darwin was a great
central power in biological science, and his writings would
naturally be received with the widest interest. Huxley
did not become a Fellow of the Linnean Society until
December, 1858, but the publications of scientific societies
are readily accessible to all. Huxley certainly knew that
Wallace had in some way acted as a stimulus to Darwin ;
for he wrote to Hooker on September 5, 1858, 1 Wallace's
impetus seems to have set Darwin going in earnest,
and I am rejoiced to hear we shall learn his views in
full, at last. I look forward to a great revolution being
effected.'1 But Huxley clearly knew nothing of the
contents of the joint memoir; for on June 25, 1859,
almost exactly a year after it had appeared, he wrote to
Lyell2 in favour of transmutation of species but against
the idea of transition between species. The letter contains
no reference to Natural Selection, but only to the direct
action of external conditions and to laws analogous to
those of chemical change, where one substance passes
into another without intermediate stages, e. g. by the
substitution of one element for another. ' I have a sort
of notion that similar laws of definite combination rule
over the modifications of organic bodies, and that in
passing from species to species " Natura fecit saltum'7
And yet, in October, 1859,3 Canon H. B. Tristram, writing

1 Life a?id Letters of Thomas Henry Huxley, London, 1 900, vol. i, p. 159.

2 Ibid. p. 173. 3 In The Ibis, vol. i.

O 2

iq6 HUXLEY AND NATURAL SELECTION

upon the larks of the Sahara, made use of the Darwin-
Wallace theory in the interpretation of the colours of
desert animals.

The Origin of Species was published, and the whole
of the 1,250 copies sold, on November 24, 1859. An
advance copy had been sent by Darwin to the
friend whose opinion he was so extremely anxious to
learn. * I shall be intensely curious to hear what effect
the book produces on you,' he wrote on October 15.1
Huxley replied on November 23 that he had finished the
Origin on the previous day. He wrote of 'the great
store of new views you have given me ' ; 2 and in his
chapter On the Reception of the Origin of Species, he
says, ' my reflection, when I first made myself master of
the central idea of the " Origin" was, " How extremely
stupid not to have thought of that !" '3 — further evidence
that he knew nothing of the subject of the Linnean Society
memoir, where this central idea is admirably, although of
course briefly, set forth and illustrated by its two great
discoverers.

Huxley's ignorance of Natural Selection between July
1, 1858, and the end of November, 1859, suggests certain
interesting conclusions. Great and original workers rarely
have the time for wide reading in their subject away
from the lines of their special investigations. But want
of time is not the only cause. They are, perhaps
unconsciously, led by an instinct which warns them that
the attempt to be encyclopaedic, though within the limits
of but a single science, is itself destructive of originality.
And yet there is nothing so inspiring to a young worker
as the fact that his attempts have interested a great leader
in his own subject. To a Darwin at the age of fifty, it
may be a small thing that his younger friend is too
engrossed to read his paper, and yet many years before
we know that even Darwin keenly felt the neglect, as it
appeared to be, of his early geological work. Thus he
wrote in 1844 or 1845: 'I have long discovered that
geologists never read each other's works, and that the

1 Life and Letters of Charles Darwin, London, 1887, vol. ii, pp. 172, 3.

2 Ibid. p. 23 j, 3 Ibid, p. 197.

MEMORY VERSUS IMAGINATION 197

only object in writing a book is a proof of earnestness,
and that you do not form your opinions without under-
going labour of some kind.' 1

The first research which has tempted a young man
over the Rubicon of his life is and ought to be every-
thing to him. It is a crisis in his life when, in spite of
all the inspiration of the work itself, he needs every
encouragement, and yet is apt to find disappointment
and neglect as an incidental result of the devotion of
other workers to other work. The position looks like a
dilemma, but fortunately for scientific students the escape
is easy. The conditions of science are daily becoming
more favourable at our Universities. Here the older
worker has a parental interest in the younger, and will
by no means quench the smoking flax by unintended
neglect. Science is also rich in numerous societies where
old and young can meet, and where through personal
contact, far better than by endless hours of reading,
the deepest inspiration and the highest encouragement
can be given and received.

If however the antagonism between the excessive
cultivation of the memory and the development of
originality is seen in the lives of older men whose capacity
for the highest work is proved and certain, surely con-
clusions of value may be learned by those whose duty it
is to watch over and direct the developing mind of the
young. A little knowledge, we are told, is a dangerous
thing, but as regards the awakening and the growth of
the most indispensable part of our intellectual equipment
— the imagination — it may be more truly said that
excessive knowledge is a dangerous thing. Owing to the
deadly grip of the examination system upon our country,
we develop the memory far too exclusively, and a poor
sort of memory at that, valuable for the purposes of thr:
barrister but of little use for any other career. The
imagination is not only neglected but actually stunted
and atrophied by forcing into disproportionate growth an
antagonistic intellectual faculty of a rather low order.
Not unintentionally, Kingsley chose the turnip, beet, and
1 Life and Letters of Charles Darwin, vol. i, pp. 334-5.

198 HUXLEY AND NATURAL SELECTION

radish as symbols of the unfortunate victims of the
' Examiner of all Examiners \ With the very best
intentions, but with the very worst effects, the idea has
taken root in this country that the imagination must not
be allowed free play until some arbitrary amount of
knowledge has been absorbed, with the result that too
often all original faculty is water-logged and drowned in
a sea of facts. We lose sight of the educational value
of research, and the fact that the imagination needs exer-
cise and grows by performance. We frequently hear of
the danger of encouraging crude work. The real danger
is the other way : it is only too easy to discourage and
dishearten, forgetting the great truth that a first research,
poor and immature though it be, means a rich intellectual
growth — forgetting that to chill the divine spark is often
to quench it for ever.

The home of information is in this country too often
the grave of the imagination. The mind of man appeals
to the known for instruction, to the unknown for inspira-
tion ; and the teacher who understands education, which
means development, will continually bring his pupils,
however young, with a stimulating shock right up against
the boundaries of knowledge.

Huxley, in his essay on A Liberal Education, spoke of
one ' whose mind is stored with a knowledge of the great
and fundamental truths of Nature and of the laws of her
operations ' ; 1 but the emphasis is here laid on quality
rather than quantity. He knew full well that no training
of any man worth calling a man is complete without
research. Thus we find that on December 31, 1856, at
the age of thirty-one, he made this entry in his journal,2
1 1856-7-8 must still be " Lehrjahre " to complete train-
ing in principles of Histology, Morphology, Physiology,
Zoology, and Geology by Monographic Work in each
Department' It must not be concluded that Huxley
waited until he was thirty-one before beginning original
work. In 1845, when he was twenty, he published an
account of what has since been known as ' Huxley's layer '

1 Lay Sermons, &c, London, 1877, pp. 34-5.

2 Life and Letters of T. H. Huxley, vol. i, p. 151.

TRAINING OF THE IMAGINATION 199

in the * root-sheath ' of the hair,1 and at the end of the
following year his four years' voyage in the Rattlesnake
began — a record of a ceaseless energy in research.

The commonly received British doctrine teaches that
research may only be attempted after the most heroic
preparation. Existing knowledge of any important educa-
tional subject may be likened to avast plain dipping beyond
the horizon in every direction, and the student is supposed
to explore it all in a superficial kind of way before pro-
ceeding to climb the height which he would fain make
his own. In a true system of education, developing the
higher as well as the lower faculties, he would be shown
the main road traversing the plain, but his search for
unconquered peaks would be aided from the first, in the
full knowledge that a wide extent of country round
the mountain base would be gladly explored and learnt
with a zest and a thoroughness attainable in no other way.
And if the appetite for discovery be not acquired early
in life it is hardly ever acquired at all. For, as regards
research, it is not so much in the old age of which Matthew
Arnold wrote, as in the tantalizing consciousness of
strength unfit for highest exercise that —

— long the way appears, which seem'd so short
To the less practised eye of sanguine youth ;

And high the mountain-tops, in cloudy air,
The mountain-tops where is the throne of Truth,

Tops in life's morning-sun so bright and bare !

Once reached in youth they will be seen ever more
clearly in after life, and if the pathos of its close should
be deepened by a time of failing power, it will be
illumined by the bright and unquenchable memory of
the heights.

To return to Huxley's views on Evolution. Before
November, 1859, these were what we should expect of
a great student of animal structure rather than of animal
life, who was at the same time a profound and cautious
thinker. Huxley states that before the appearance of the
Origin he took his stand upon two grounds, ' firstly, that
1 Life and Letters of 7. H. Huxley \ vol. i, p. 21.

200 HUXLEY AND NATURAL SELECTION

up to that time, the evidence in favour of transmutation
was wholly insufficient ; and, secondly, that no suggestion
respecting the causes of the transmutation assumed, which
had been made, was in any way adequate to explain the
phenomena.'1 'So/ he tells us, ' I usually defended the
tenability of the received doctrines, when I had to do with
the transmutationists ; and stood up for the possibility of
transmutation among the orthodox — thereby, no doubt,
increasing an already current, but quite undeserved, re-
putation for needless combativeness.'2 And yet all along
there was alive in him 'a sort of pious conviction that
Evolution, after all, would turn out true '.3 And the kind
of evolution he imagined was, so far as we are able to
judge, a conception which would arise in the mind of
one who studied and compared animal structures with
the eye and brain of the artist or engineer rather than
of the naturalist. At the age of twenty-six, only seven
years before the appearance of the Darwin- Wallace essay,
we find him writing to W. S. Macleay, 1 1 am every day
becoming more and more certain that you were on the
right track thirty years ago in your views of the order
and symmetry to be traced in the true natural system.'4
Macleay's views of the grouping of the animal kingdom
are about as regular and symmetrical as the figures
seen in a kaleidoscope. Such a conception of sharply
separated mathematically grouped forms would naturally
lead to the idea of evolution by abrupt steps, whereby
a new form would appear from the sudden transformation
of the old, just as a chemical compound changes when
one element in it is replaced by another — the metaphor
employed by Huxley in his letter to Lyell, already
referred to on p. 195.

The evidence at our disposal leads to the belief that
this was the state of Huxley's opinion when, towards the
end of November, 1859, he read the Origin. The book
is planned so as precisely to meet his two-fold difficulty.
In place of insufficient evidence in favour of evolution, he
here met with convincing and weighty proofs ; and these

1 Life and Letters of C. Darwin, vol. ii, p. 188. 2 Lbid. p. 196.

3 Ibid. p. 190. 4 Life and Letters of T. H. Huxley, vol. i, p. 92.

CONVICTIONS AND DOUBTS 201

he accepted at once, unreservedly, and permanently. He
furthermore encountered what was to him the entirely
new idea of Natural Selection, and he instantly recognized
that it disposed of his second objection that no suggestion
in any way adequate to explain the phenomena had been
made. But to the end of his life he never went beyond
this. He never committed himself to a full belief in
Natural Selection, and even contemplated the possibility
of its ultimate disappearance.

But Natural Selection appeared to him so reasonable,
so well worth consideration, that he could no longer feel
any force in an adverse argument depending on the want
of a cause. If we were so dense as not to think of such
a reasonable idea founded upon the most familiar of facts,
what right have we to make use of any such argument ?
To the Transmutationists and the non-Transmutationists
he had said, with Mercutio, 'a plague on both your houses,'
and he might have expressed his opinion of Natural
Selection by another quotation from the same character.
It may not be 1 so deep as a well, nor so wide as a church-
door, but 'tis enough, 'twill serve \

But while Natural Selection thus enabled Huxley freely
to accept evolution, it is evident, as I have said, that he
was by no means fully satisfied with it. The difficulty
which he felt early and late, and about which he had
a prolonged discussion with Darwin, was the fact that
the breeds created by the artificial selection of man are
mutually fertile, wrhile the species created ex hypothesi by
Natural Selection are mutually sterile. Without going
into the controversy,1 it may be said briefly, that, accord-
ing to Darwin, Huxley's objection merely meant that the
results of an experiment prolonged for an immense period
were not in every respect the same as those attained when
it endured for a time comparatively short.

The reason why other students have felt a confidence
in Natural Selection not shared by this great leader is to
be found in his own words. Speaking of 1 every great
advance in natural knowledge', Huxley says: 'The

1 A fairly complete account of the controversy will be found on pp.
77-83 of the present volume.

202 HUXLEY AND NATURAL SELECTION

most ardent votary of science holds his firmest convictions
. . . because his experience teaches him that whenever he
chooses to bring these convictions into contact with their
primary source, Nature — whenever he thinks fit to test
them by appealing to experiment and to observation —
Nature will confirm them.' But with respect to Natural
Selection, as it required the student of living nature to
discover the principle itself, so the experience which brings
confidence in it is that mainly of the naturalist. The
strongest confidence in the abiding truth of a theory is
gained by those whose imagination has been inspired by
it. Every verified prediction made in the light of Natural
Selection places the theory upon a more secure foundation.
That foundation has been growing firmer for nearly half
a century ; but, as I hope to show by illustration in the
remaining section of this address, the increasing confidence
is not so much due to the facts which are the province
of the anatomist as those which form the everyday
experience of the naturalist, of the man who studies
animal form and change and instinct, not in relation to
the single individual or the single species, but in rela-
tion to the whole environment, and especially the world
of living organisms. Huxley's researches, determined
by the bent of his mind, were not of this kind, they were
physiological, anatomical, and palaeontological. To use
his son's words, 1 It was the engineering side of nature,
the unity of plan of animal construction, worked out in
infinitely varying detail which engrossed him.' 1 Again,
'walking once with Hooker in the Rhone valley, where
the grass was alive with red and green grasshoppers, he
said, u I would give anything to be as interested in them
as you are." ' 2

It is no wonder, therefore, that, as Huxley's experience
was not that of the naturalist, the confidence in Natural
Selection of which I have spoken was not for him.

I now propose to draw your attention to a few examples
of that adaptation which more than anything else kept
Darwin orthodox, but in the end furnished him with the

1 Life and Letters of T. H. Huxley \ vol. ii, p. 443.

2 Ibid. p. 443.

THE STUDY OF LIVING NATURE 203

strongest evidence in favour of his theory. The illustra-
tions will be chiefly selected from old subjects in which
something new may still be found. The examples must
be limited, and therefore I propose to select them from
a single Order of insects — the Lepidoptera, or butterflies
and moths.

Some points in the Resemblance of Butterflies to Dead

Leaves,

One of the finest and best-known examples of conceal-
ment for the purposes of defence is found in the under-
side coloration of butterflies of the genus Kallima, so
graphically described by Wallace.1 Among the most
interesting details of the resemblance is an oval transparent
patch on each fore-wing, which allows the light to pass
through and produces the effect of a hole in the apparent
dead leaf. In another part of the fore-wing of Kallima
the appearance of a hole is produced as an artist would
paint it, by the use of white body-colour. Of these two
methods found on the same wing, the former is undoubtedly
the more recent and more highly-specialized method ; for
when the transparent 'window' is examined under the
microscope, scattered opaque white scales can still be
seen in abundance over its surface, not thickly placed so
as to prevent the passage of light, but witnesses to an
earlier and less perfect representation of light shining
-through a hole.

In many species a hole is suggested by means of the
more primitive method alone. One of the most remark-
able markings possessed by any British insect is the white
4 C ' or 1 comma ' on the under surface of the hind-wing
of the 1 Comma ' butterfly, Polygonia (Graptd) C-albnm.
Many years ago I came to the conclusion that it repre-
sents, in bright, strongly-reflecting ' body-colour the
light shining through a semi-circular rent in a fragment
of dead leaf — the rent produced when a little segment of
leaf has broken away along a curved line, but still remains
connected with the rest across the chord of the arc.
Unless such a segment remains precisely in the plane

1 Essays on Natural Selection, London, 1875, pp. 59-62.

204 HUXLEY AND NATURAL SELECTION

of the leaf, light may pass through a curved and often
a semi-circular slit-like window. Such curved cracks are
extremely common in old weather-beaten dead leaves.
They are probably produced by drying and shrinkage
after much wetting and some decay.

On April 23, 1903, I had the opportunity of testing
how far the whole attitude of Polygonia C-album, during
profound repose, is consistent with the interpretation
suggested above. By a curious coincidence, I had been
speaking of the differences between temporary and pro-
longed resting attitudes in butterflies, at the meeting of
the Entomological Society of France on the evening
of April 22, and the very next morning saw for the first
time in my life the position of this species during complete
repose. The day was excessively cold for this time of the
year, and the butterfly was hanging perfectly torpid from
the horizontal rail of a wood fence in a street at Passy.
Several excellent but very small photographs were taken
with my daughter's camera : enlargements have been
made, and from these the actual specimen has been set
and photographs taken of the natural size.1 These show
that the two anterior wings are held so far forward that
a deep wedge-shaped notch appears between them and
the hind-wings. On each side of this notch the well-
known ragged outline of the wings is extremely distinct.
The two posterior pairs of legs by which the butterfly
clings to the supporting surface are light-brown in colour
and unexpectedly conspicuous. The antennae are con-
cealed, and the contour of the head does not break that
of the costal margin of the anterior wings so as to interfere
in any way with the general effect. The whole appearance
is consistent with a single interpretation — concealment
effected by resemblance to a weather-beaten fragment
of dead leaf, deeply notched and ragged, and hanging by
two denuded fibro-vascular ' veins ' standing out far beyond
one of the edges. The kind of injury suggested by the
' comma ' only adds another convincing detail to a perfectly
harmonious cryptic effect.

It is interesting to compare this mode of concealment
1 Exhibited upon the screen.

DEAD-LEAF-LIKE BUTTERFLIES 205

with that which is common in other Nymphaline butter-
flies (Kallima, Dolcschallia, Anaea, Precis, &c), viz. the
resemblance not to a fragment but an entire dead leaf,
with midrib and suggestion of lateral oblique venation.

Holes may not only be suggested by opaque 1 body-
colour ' and by transparent windows, but also by actual
discontinuity, as is probably the case in certain species
of Anaea in which the deeply-cut bay in the inner margin
of the fore-wing may be converted into the likeness of
a hole by closure along its open side by the costal margin
of the hind-wing. The holes represented in these apparent
entire dead leaves seem to have been produced by gnaw-
ing, e.g. of insect larvae.1 They are surrounded very
conspicuously with a marginal zone of modified colour
varying greatly in different individuals as regards both
tint and breadth. This border of altered colour may
represent the effect of the attacks of fungi entering along
the freshly exposed tissues of the edge. On the other
hand, in the leaf-fragment suggested by C-album the forces
of the inorganic environment, which by their prolonged
action have produced the wear and tear of the margin,
have also been responsible for the more centrally-placed
discontinuity. Comparing various species of the genus
Polygonia (Grapta), it is seen that the curved C-like
window occurs in several ; in some the suggested rent is
V-like, while occasionally the mark appears to represent
a hole of a reniform shape.2

Another interesting point in the likeness to a dead leaf
is the appearance of fungus-growth, finely described by

1 Mr. W. B. Grove, of Handsworth, Birmingham, who was present at
the Huxley Lecture, afterwards sent me leaves of several plants attacked
by minute fungi, species of Phyllosticia and Cercospora. The attack was
local and followed by the death and disappearance of the central portion
of the leaf-tissue of each patch, leaving a roundish or oval window out-
lined with brown, sometimes in the form of a narrow line, sometimes
spreading centrifugally into the leaf for a greater or less distance. I have
no doubt that Mr. Grove is right in believing that the ' windows ' of
Kallima resemble perforations made in this way, and not, as I supposed,
by the gnawing of larvae followed by fungus attack along the raw edge
of the aperture. See Proc. En/. Soc, Lond., June 7, 1905.

2 See Ibid. May 6, 1903, for the account from which the foregoing
description has been adapted.

2o6 HUXLEY AND NATURAL SELECTION

Wallace, on the wings of a large proportion of the indi-
viduals of Kallima. Here, too, further investigation has
shown greater detail in the resemblance. The markings
which represent the largest patches of cryptogamic growth
bear a black central column composed of tall, upstanding
scales. When the patch is photographed slightly magnified,
under oblique illumination, the character of the scales is
well shown, together with the pronounced shadow cast
by the column.1 These tall, black scales doubtless repre-
sent, in form as well as in colour, the fructification in the
centre of a patch of leaf-attacking fungus, perhaps the
very kind which at a later stage of development produces
the holes suggested by the ' windows ' on another part
of the wing surface.2

Hence it is seen that recent research into this long-
known resemblance to dead leaves has brought out many
new details, but only such as add to and strengthen the
old descriptions and support the old interpretation. The
likeness to leaves is shown to be even more remarkable
and more detailed than was at first supposed, but not
a single new fact suggests that the appearance serves any
purpose except protection from enemies in the struggle for
life, or hints at any cause of evolution except accumulation
by the survival of the best-concealed individuals through
innumerable generations.

Some Seasonal Changes in Btitterflies and their
Significance.

The fact that there are well-marked differences between
the wet season and the dry season broods of certain butter-
flies has been known for many years. Among the most
characteristic of these is the tendency of the apex of the
fore-wing to be much elongated and bent, or some-
times even hooked, in the dry season. Almost equally
marked is the greatly produced anal angle of the hind-
wing at the same season of the year. These characters
have been recently observed to be conspicuous in the
Indian Kallimas of the dry season, which are also larger

1 Exhibited upon the screen.

2 Proc. Ent. Soc, Lond., June 7, 1905.

SEASONAL FORMS OF BUTTERFLIES 207

than those of the wet, and possess paler tints.1 In
attempting to understand the difference in outline which
is characteristic of so many butterflies in the dry season,
it must be borne in mind that the apex of the fore-wing
represents the tip and the anal angle of the hind-wing the
base of a leaf, and that the two are commonly joined by
a streak representing the mid-rib, with more or less distinct
lateral marks suggesting traces of the oblique veins. All
are peculiarly well marked in Kallima. Now the dry
season outline certainly cannot be explained by affinity
between the butterflies possessing it, inasmuch as it is
found independently in Salyrmae, Nymphalinae, and
Pierinae. Its explanation is rather to be sought for in
the independent protective resemblance to some feature
which is characteristic of the surroundings in the dry
season, as contrasted with the wet. Such a feature may
probably be found in the forms assumed by dead leaves :
curled and warped in the dry season, flat — like damp
blotting-paper — in the wet.2

The differences here described are not invariably cha-
racteristic of the season. Thus in Kallima paralekta,
of the Malay archipelago, the species rendered classical
by Wallace's description, the dry season appearance is
borne by the females, the wet by the males. The inter-
pretation may perhaps be found in the different habits
of the two sexes, or it maybe an advantage to the species
that one set of individuals should resemble leaves of one
form, another set those of another form, thus increasing
the categories of objects in the surroundings for which
they might be mistaken by their enemies.

Both seasonal forms of the Indian Kallimas tend
strongly towards concealment, although the individuals of
the dry season are probably more perfectly hidden than
the others. In Africa the two seasons are more sharply
contrasted than in India, and the differences between the
forms of butterflies with seasonal phases may also be far
greater. Some of the African species of the genus

1 See Observations on Indian Butterflies, by T. R. Bell ; Ent. Month.
Mag., 1906, pp. 1 2 1-8.

2 Proc. Ent. Soc, Lond., Oct. 21, 1903 ; see also Ent. Month. Mag.,
1906, p. 126.

208 HUXLEY AND NATURAL SELECTION

Precis, allied to Kallima, possess seasonal forms closely
resembling those of the latter. In other species, however,
the phases are more distinct than those of any known
butterfly. Naturalists were fairly astounded when, in
1898, Mr. Guy A. K. Marshall first bred the black and
blue dry season Precis sesamus from the black and red
wet season P. natalensis} The two butterflies differ in
size, form, pattern, colours, relation of upper to under
surface, and habits. But for the fact that very rare inter-
mediate examples were known, they would not have been
looked upon as closely allied. The under side of the dry
form is very dark and well-adapted to hide the insect in
the sheltered places it frequents ; the under side of the
wet form resembles the upper side, save that it is even
more conspicuous, and the individuals of this phase
furthermore seek exposed and open ground. The same
alternation between a dry form with under side strongly
adapted for concealment, and a wet form in which it is
highly conspicuous, has been established in other species
by Mr. Marshall, by the same incontrovertible evi-
dence. Of these Precis antilope and P. actia are almost,
if not quite, as remarkable as P. sesamus. In Precis
archesia, which he has not yet succeeded in breeding from
one form to the other, the difference is particularly instruc-
tive. A mid-rib-like stripe is, perhaps, the most effective
detail in the dead-leaf-like appearance of the dry phase
under side, and this very feature is emphasized — broadened,
lightened in tint, and with sharp outlines — into the most
conspicuous character of the wet form. The very cha-
racter which chiefly promotes the concealment of one
phase is the principal element in the conspicuousness
of the other. In attempting to understand these astonish-
ing alternations it is necessary to study the relationship
between the seasons and the struggle for existence which
goes on in them. The dry season is a time of far greater
pressure than the wet ; for although enemies of insects are
fewer, the insects themselves are proportionately even more
reduced. Large groups of insects bury themselves in the
ground, and so disappear altogether. Hence the struggle
1 Ann. Mag. Nat. Hist.} ser. 7, vol. ii, July 1898, p. 30.

DANGERS OF THE DRY SEASON 209

falls with especial severity on those still to be seen. Further-
more, the dry season forms are much less upon the wing
than the wet forms of the same species, and are apt to pass
long periods in a state of hybernation. Although drought
rather than cold is the probable cause of these periods of
torpor, the term hybernation is not inappropriate ; for
almost everywhere in southern Africa the dry season corre-
sponds with the winter, the wet with summer. Although less
upon the wing, the dry forms are commonly more alert and
active, and thus more difficult to catch than the wet. The
succession of broods is also nearly or quite at a standstill
in the dry season, so that the individual insects must endure
the repeated risks of a much longer life than those of
the other season, when the numbers are suddenly multi-
plied again and again by a series of brief generations.
Hence each individual of the dry phase is worth far
more to the species, and its loss is a much greater loss
than that of a short-lived individual of the other phase.
The risks during the periods of repose form a much larger
proportion of the total risks in the dry season than in the
wet. During these periods the insects are sought by
enemies different from those which pursue them upon the
wing and in the brief rests between short flights. It is
probable that the former enemies — insectivorous mam-
mals, reptiles, and birds which explore crevices for their
food — are less scrupulous in their tastes than those which
hunt alert and active butterflies. In the wet season, on
the other hand, butterflies are upon the wing in every
gleam of sunshine throughout their comparatively short
life ; and the enemies which they chiefly have to encounter
are those which pursue them on the wing or stalk them
in the brief intervals of rest. It has already been pointed
out that insectivorous forms generally are living in a time
of comparative plenty in the wet season. From these con-
siderations we can understand how it may be an advantage
to a somewhat distasteful species to be represented by
individuals with conspicuous warning (aposematic) colours
at a time when there is abundance of more palatable food,
and by well-concealed individuals at a time when food is
scarce and the struggle for life severe.
pouLTON p

210 HUXLEY AND NATURAL SELECTION

Similar considerations encourage the hope that we may
understand another feature which has been long known
to be characteristic of wet season forms, especially in
the Satyrinae, the group which includes our well-known
'Meadow-brown', 'Heath,' and ' Ringlet' butterflies.
I refer to the development of eye-spots on the under side
of the wings in wet season broods and their disappearance
in those of the dry. An observation made in 1887 by
Professor Meldola and the present writer throws light
upon the problem. I had introduced a ' Small Heath
Butterfly* {Coenonympha pamphihts) into the cage of
a lizard. It was at once obvious that the reptile was
greatly interested in the large eye-spot on the under side
of the fore wing; it examined the mark intently, and
several times attempted to bite it.1 Mr. Marshall has
also observed that a South African kestrel pecked out
the eye-spots from the hind-wing of a ' Swallow-tail '
butterfly before eating any other part.2 Furthermore,
captured butterflies are especially liable to exhibit injuries
in the vicinity of such marks. Some of these tears or
snips out of the wing afford very strong indirect evidence
that they were made by an enemy.3 It is probable,
therefore, that such eye-spots as those of the Satyrinae,
which are placed on parts of the wing surface remote
from the body, are adapted to divert the attention of an
enemy from the vital parts, thus giving the insect another
chance of escape. Such directive marks will render the
butterflies more conspicuous during the periods of com-
plete repose, and we can readily understand that they
would be a great danger, and why they should be withheld
in the dry season. The fact that these markings are of
value in a period of activity and a danger in complete
repose, is also rendered probable by movements of the
fore wing which have been observed in many Satyrines,
changes in the attitude such as to reveal the eye-spot
during a brief rest when the insect is alert, but to conceal
it when the rest becomes prolonged.4 It is probable,

1 Colours oj 'Animals , London, 1890, pp. 206. 207.

2 Trans. Enl. Soc, Lond., 1902, p. 341.

3 I.e. pp. 366-75. 4 I.e. pp. 372, 440.

EYE-SPOTS OF THE WET SEASON 211

therefore, that the eye-spots tend to be developed in the
active wet season individuals of many Satyr inae and a few
Nymphalinae as a special adaptation to meet the attacks
that are made upon them in the alert condition ; and
that eye-spots are withheld in the dry season brood
because they would be a danger in the periods of repose,
which are far more pronounced in this as compared with
the wet phase.1

The light thrown by recent investigations leads us confi-
dently to believe that the differences between the seasonal
forms — hitherto devoid of interpretation — have a meaning
and a value in the struggle for existence, and came into
being under the sway of Natural Selection.

A new Interpretation of an old example of Mimicry in

Butter flies.

In the short time that remains I can only say a few
words about the recent growth of the theory of mimicry
which we owe to Fritz Mtiller, and its gradual encroach-
ment upon the area formerly held by the theory of
H. W. Bates. This latter was not, as has been generally
supposed, originated by Bates during his years of obser-
vation in the valley of the Amazon. It arose in his mind
after his return home, when he came to examine his
collection and to reflect upon his experiences. His theory,
published in 1862,2 is so well known that it is unnecessary
to do more than direct attention to the essential point,
that the mimics are supposed to be hard-pressed and
palatable insects which gain advantage from their close
resemblance to abundant, distasteful, conspicuous species.
Bates did not fail to see that these common, unpalatable
models certainly mimic each other, but the fact could
not be explained on his hypothesis ; and although he
mentioned the fact, no example finds a place in the
beautiful coloured figures of his historic memoir. Had
they been thus illustrated, I venture to think that his theory
would never have received the general support which has
been accorded to it ; for it would have been at once

1 See Ann. Soc. Ent. France, vol. lxxii, 1903, p. 407.

2 Trans. Linn. Soc, Loud., vol. xxiii, p. 495.

P 2

2i2 HUXLEY AND NATURAL SELECTION

recognized that the resemblance between his mimic and
his model was a very poor thing as compared with the
astonishing likeness of one model to another. And there
is no question of affinity in the resemblance of models any
more than in that of mimic and model. In 1879, when
Fritz Mliller offered an explanation of these mysterious
resemblances,1 the Batesian theory had been before the
world for seventeen years, and had attracted a great deal
of attention. Furthermore, the examples selected by
Miiller were not very striking, and were illustrated
without the use of colour. He made the illuminating
suggestion that the resemblance between the dominant
models was mutually advantageous, inasmuch as it facili-
tated the education of their inexperienced foes, reducing
the amount of destruction which must be wrought during
the time in which young birds and other insect-eating
animals are learning what to eat and what to avoid. If
A and B be two distasteful species closely resembling
each other, and if they be equally common, an individual
of A will be seized before B by an inexperienced enemy
as often as an individual of B before A. In the first
case B benefits from the unpleasant effects produced by
A, in the second A benefits from the effects of B.
Professor Lloyd Morgan's observations upon the activities
and instincts of young birds of many species 2 prove that
their education is actually of the kind presupposed by the
Mullerian theory. He shows that they have no instinctive
knowledge of things which are good for food, but examine
and test everything. On the other hand, they have very
good memories, and retain a firm impression of the appear-
ance of objects which have given them an unpleasant
experience. Furthermore, there is evidence that they
are influenced in their behaviour towards objects resem-
bling the one which has proved objectionable to them.

Fritz Mullers paper was translated by Professor R. Mel-
dola,and published in this country almost immediately after
its appearance,3 with the result that the theory has been

1 In Jfosmos, for May, 1879, P* I0°-

2 Habit and Instinct, London, 1896.

1 Proc. Ent, Soc, Lond., 1879, p. xx.

RIVAL THEORIES OF MIMICRY 213

more widely understood and has gained a larger number of
supporters in this country than in any other. Nevertheless,
in spite of the powerful defence always accorded to it by
Professor Meldola, the progress of opinion in the direction
of Miiller's hypothesis has been until quite lately slow
and gradual ; and this is probably due to the fact that
the minds of naturalists were already occupied by the
older and, in many respects, antagonistic theory. It is
impossible on this occasion to give any general account
of the evidence which has been gradually accumulating
in support of the Muilerian theory ; but the name of
Dr. F. A. Dixey will always stand out as one of its chief
defenders, and one who, more than any other, is respon-
sible for the recent rapid growth of opinion in its favour.1

Ever since the appearance of Bates's original paper
textbooks have copied from it and from one another
the wonderful examples of palatable Pierine butterflies
(belonging to the group which contains our own ' Garden
Whites ') living upon the evil reputation of their models
belonging to the tropical American ' Heliconidae' (a com-
posite group in Bates's memoir). But Dr. Dixey has
even dared to lay his hand, so to speak, upon the Ark of
Batesian Mimicry itself, when, in 1894, he argued that
the Heliconid models in certain respects mimic their
Pierine imitators : that the resemblance has been attained
by means of reciprocal approach.

It has been shown on page 103 that the columns of Punch
afforded an excellent reflection of the state of contemporary
thought and criticism on Darwinian and Lamarckian Evolu-
tion. It is precisely the same with Batesian and Muilerian
Mimicry, as is clearly shown in the following passages : 2 —

1 The same [museum] case contains an object-lesson illus-
trating what is described as " Reciprocal Advantage \ So
far as I can follow it, the situation is something like this :

1 See especially the following memoirs by Dr. Dixey : Rep. Brit. Ass.,
1894, p. 692 (abstract); Trans. Ent. Soc, Lo?id., 1894, p. 249; ibid.,
1896, p. 65 ; ibid., 1897, p. 317 ; see also the discussion which followed
this latter paper, in Proceedings, 1897, pp. xx-xxxii and xxxiv-xlvii.

- Punch, May 2, 1906, pp. 312, 313, Moral Reflections at the
Natural History Museum, I.

2i4 HUXLEY AND NATURAL SELECTION

1 There is a Nice Butterfly (whom we will call A.) who is
uncomfortably conscious of being regarded as a delicious tit-
bit by every bird or lizard with any pretensions to a palate.

' There is also a Nasty Butterfly (hereinafter referred
to as B.) whom even the least particular lizard or bird
will, after a single experience of his peculiar flavour, take
uncommonly good care never to touch again.

' So says A. to himself (or else Nature says it for him —
I am too unscientific to know which) : "If I could only
make myself look as nasty as B. is, all the birds and
lizards would let me alone ! " Which, by patience and
perseverance, A. gradually contrives to do.

' Well, I will admit that this idea of A.'s is not without
a showy ingenuity, even if it is wanting in true reciprocity
and consideration for B.'s interests. What I fail to see is
that, from A.'s point of view, it is really such a very
masterly stratagem.'

The writer then goes on to point out that when the
enemy comes across A before B all the advantages as
he conceives them would be lost, while B itself would be
endangered in spite of its nauseous qualities.

Omitting the allusions to conscious imitation, which,
although expressing a common popular error, are clearly
not intended to be taken seriously, the whole argument
is a fair presentation and criticism of Batesian mimicry.
It only fails to do justice to this hypothesis in one respect,
— the mimics are represented as relatively common, so
common indeed that it is assumed to be a matter of
indifference whether A or B be met with first. But
Bates assumed that the nauseous models are hundreds
or even thousands of times as abundant as their palatable
mimics. It is true, however, that the mimics are often
extremely abundant, but then it is probable that such cases
are to be explained by the alternative theory of Fritz
Muller. As a matter of fact, the title of the exhibit,
1 Reciprocal Advantage is conclusive evidence that it
was this theory, and not that of Bates, which was being
illustrated. In fact both A and B are supposed to be
nauseous : then if an enemy eats B first it will be warned
against the appearance of A as well as B ; if it eats A

BATES VERSUS FRITZ MULLER 215

first, against B as well as A. A certain number of lives
must be sacrificed in the period during which inexperienced
enemies are being educated to avoid the appearance which
A and B bear in common. If we assume that the in-
dividuals of the two species are equally abundant and
occur intermixed, it follows that these necessary losses will
be shared between them, instead of being contributed
by each independently, as would be the case if their
colours and patterns were different. Each loses only
fifty per cent, of what it would lose but for the
resemblance — surely an ample measure of 1 Reciprocal
Advantage \

The writer in Punch criticized an illustration of the
Mullerian theory, believing it to be an illustration of
Batesian mimicry.

I propose, in conclusion, to draw your attention to one
of the oldest and best-known, as well as one of the most
beautiful, examples of mimicry — one upon which new
light has been thrown by increase of knowledge. The
example will serve as an illustration of the reasons which
have led to the gradual transference of confidence from
the Batesian to the Mullerian theory.

The Danaine butterfly Limnas chrysippus is, perhaps,
the commonest species on the earth, ranging over nearly
the whole of the Old World tropics. Its conspicuous
colouring and simple pattern are everywhere mimicked ;
but especially in Africa. In fact, we may confidently
conclude that Africa is the ancestral home of the species,
because of the intensity of the effect which has been
wrought by it upon the butterfly and moth fauna of this
part of the world.1 One of its mimics accompanies
chrysippus in all parts of the range : — Hypolimnas misippus,
a Nymphaline butterfly of powerful flight. The mimetic
likeness is, as in so many other species, borne by the
female alone, but in this sex it is singularly perfect, and
in earlier years it has always been regarded as one
of the best-known and commonest illustrations of Bates's
theory. But it is far more likely that H. misippus belongs
to a genus which is in some way unpalatable, and that it
1 Proc. Amer. Ass. Ad:'. Sci., 1897, vol. xlvi, p. 244.

216 HUXLEY AND NATURAL SELECTION

enters into Mullerian association with a Danaine butterfly
even more distasteful to insect-eating animals. Bates
supposed that his mimics were hard-pressed forms which
managed to survive by their deceptive likeness to some
well-known, specially-protected, conspicuous, abundant
model. But misippus is an extraordinarily dominant
species : it may often be met with more abundantly than
its model.1 Furthermore, the mimic has now succeeded
in establishing itself and lives without its model in several
places in the New World — Florida, certain West Indian
islands, Demerara, Brazil. This remarkable extension
of range is mainly due to its wonderful power of flight,2
but also to the possession of qualities the very reverse
of those commonly supposed to be characteristic of
a Batesian mimic. The tropics of the New World are
inhabited by a community in which a feeble intruder is
by no means likely to hold its own.

Furthermore, Hypolimnas misippus belongs to a genus
of which nearly all the species mimic Danaine butterflies
and yet none appear to be hard pressed in the struggle
for life. This is readily explicable if the whole genus
possesses distasteful qualities. The males when non-
mimetic, as in many of the forms, bear a marked likeness
to one another, whereas the mimetic females have been
modified in all kinds of directions by the mimicry of diverse
models. The remarkable species from Madagascar,
Hypolimnas dexithea, mimetic in neither sex, possesses
a pattern of the same general type as that of the non-
mimetic males of other species. There can be little doubt
that this is the ancestral appearance of the genus, and
that the females at one time possessed the pattern of their
non-mimetic males, to which indeed in many species they
commonly tend to revert in a greater or less degree.
Now this ancestral non-mimetic pattern is about as con-
spicuous as that of any known butterfly, — a black ground-
colour, with a large white patch in the centre of each wing,

1 See Mr. C. A. Wiggins's and Mr. H. A. Byatt's observations in
Africa, Proc. Ent. Soc, Lond., May 6, 1903, p. xxix.

2 See E?it. Record, xii, Dec. 1900, p. 315, for the account of a swarm
encountered on the Atlantic 580 miles from the nearest South American
land, and 960 from the nearest African.

A MIMETIC SPECIES MIMICKED 217

and an additional smaller patch at the apex of the fore-wing.
The under side, although different from the upper, is
also conspicuous, and evidently belongs to a very different
category from, e.g., the leaf-like under sides of Kallima.

If the remarkable cryptic coloration and attitude of this
latter is held to be indirect evidence that the species is
palatable to insect-eating animals, it follows that such an
under side as that of the male H. misippus constitutes
indirect evidence of unpalatability, in other words that it
is a warning (aposematic) appearance.

If the argument set forth above be sound, it is obvious
that the mimetic females of Hypolimnas have, in their
past history, merely exchanged a conspicuous warning
pattern characteristic of the genus for conspicuous patterns
borne by distasteful forms inhabiting the same country.
In other words, the evolution has been of the kind we
should expect upon the Mullerian theory.1

And now in recent years astonishing evidence in
support of the same conclusion has been forthcoming.
The non-mimetic male of Hypolimnas misippus is itself
beautifully mimicked on both upper and under sides by
two Nymphaline butterflies in Western China — Limenitis
albomaculata and Athyma punctata.

The model is abundant in the tropics far away to the
south, but becomes much rarer in Northern India, and has
never been known in Western China, where its mimics
are found. We are driven to suggest two alternative
hypotheses: (1) The model, with its immense powers of
flight, has visited Western China sufficiently often and
for long enough periods to render the mimetic resemblance
advantageous. Against this it may be urged that
H. misippus is a tropical butterfly, and it is most improb-
able that it would reach, or at any rate establish itself,
in such a latitude and elevation as, e.g., Ta-tsien-lu ;
(2) A more probable hypothesis is afforded by the lines
of migratory birds, applying in the temperate zone, where
they nest, the experience learnt in the tropics. If a bird's
experience of H. misippus be an unpleasant one, it follows

1 See Proc. Amer. Ass. Adv. Sc?\, 1897, v°l- x^]> P- 242 > Trans.
Eni. Soc, Lond., 1902, pp. 500-2.

218 HUXLEY AND NATURAL SELECTION

that a modification in the pattern of any other conspicuous
butterfly which suggests the same experience and leads
to a cautious attack, or perhaps averts attack altogether,
will be advantageous. Both the genera to which the
mimics belong are certainly conspicuous, and it is probable
that they, too, are distasteful. It is, of course, necessary
that the same enemy should see both model and mimic ;
but, if this be achieved, it matters not how many hundreds
of miles may intervene between the two. The northern
mimics belong to genera of black, white-marked butter-
flies which have much in common with the black, white-
marked male of H. misippus ; so that it is not difficult to
understand why the latter species, rather than any other
distasteful resident of the tropical areas to the south,
has been imitated. There was, in fact, from the very
first, sufficient likeness for Natural Selection to work upon.1

The hypothesis here suggested demands inquiry into
the habits of the migratory birds of Western China, the
routes followed, and dates of arrival and departure.

The consideration of Hypolimnas misippus as an
example of mimicry, and especially the striking fact that
its male is a model, while its female is a mimic, serves as
an illustration of the changes in interpretation wrought
by the accumulation of new observations. But the out-
come of such modifications — and they are taking place
everywhere in the field of natural history — is that Natural
Selection rests on an ever-broadening foundation. If it
were an erroneous or a merely inadequate theory of
evolution, would not the astonishing increase of know-
ledge again and again bring to light facts which are
absolutely irreconcilable with it ?

The examples brought forward on the present occasion
are but a selection from a vast body of observations which
receive an intelligible interpretation under this theory,
but not under any other.2 When accumulated facts, not

1 See Report of the Delegates of the Oxford University Museum for
1904 in the Oxford University Gazette, 1905.

2 For a detailed statement of the facts of mimicry in relation to
Natural Selection see Li?m. Soc. Journ. Zoo/., vol. xxvi, pp. 558-612,
reprinted as Essay viii, p. 220.

THE CONFIRMATION OF THEORY 219

only of the class here referred to, but of the most diverse
kinds, receive an intelligible explanation upon any theory,
they finally become a solid foundation for the theory itself.
Many theories of transcendent importance are held upon
indirect evidence of precisely this kind. We believe in
evolution, not because we see it taking place, but because
of the immense number of observed facts which it renders
intelligible, and the same is true of our confidence in the
Newtonian Theory.

Whenever a naturalist approaches a problem in the
light of Natural Selection, and is able, by its aid, to pre-
dict a conclusion which subsequent investigation proves
to be correct, he is helping in the production of evidence
in favour of the theory. When a naturalist has found the
formula 1 if Natural Selection be true, so-and-so ought to
happen', the safest of all guides into the Unknown, when
it has brought him success many times and in very diffe-
rent directions, when he knows that many other workers
in other fields of biological inquiry have had a similar
experience, he gradually comes to feel a profound con-
fidence in the permanent truth and the far-reaching-
importance of the great theory which has served him so
well.1

The experiences of the naturalist, the student of living
nature, did not appeal to Huxley, and therefore it is not
remarkable that he was unable to feel much confidence in
Natural Selection. But those who are inspired by it will
never forget how much they owe to Huxley for the leading-
part he took in the great battles which had to be fought
before Evolution, and Natural Selection, too, were accorded
a fair hearing ; and his success went far beyond even
these issues. Whatever stirring and subversive ideas the
future may bring forth, we may be sure that they will
never suffer from the treatment accorded to the Origin
of Species ; and, far more than to any other single man,
the world owes this immense gain to Thomas Henry
Huxley.

1 Poulton, Charles Darwin and the Theory of Natural Selection,
London, 1896, pp. 142. 143.

VIII

NATURAL SELECTION THE CAUSE
OF MIMETIC RESEMBLANCE AND
COMMON WARNING COLOURS

A Paper read before the Linnean Society of London, March 17, 1898.
Reprinted from the Linnean Society's Journal — Zoology, vol. xxvi, p. 558.
Revised : greatly modified : many additions to text and footnotes.

i. Historical Introduction.

Superficial resemblances between animals, especially
numerous in Insecta, were known long before H. W.
Bates's paper, Contributions to an Insect Fauna of the
Amazon Valley, was read before the Linnean Society on
November 21, 1861, and published in the Transactions
the following year.1 Some of the principal records of
these earlier observations are to be found in the Trans-
actions of the same learned Society.

W. S. Macleay, in his Horae Entomologicae,2 alluded
to certain cases which are now included under Mimicry,
viz. the likeness of some Diptera to Hymenoptera, and
interpreted them, together with many other resemblances
of structure and life-history, by the principle of Analogy
as distinct from Affinity in Nature.3 These views were
adopted by Macleay's immediate successors.

The Rev. William Kirby read A Description of some
Insects which appear to exemplify Mr. William S. Mac-
Leays Doctrine of Affinity and Analogy, before the
Linnean Society on December 17, 1822, and the paper
was published in the Transactions \4

1 Vol. xxiii, p. 495. 2 London, 1819 and 182 1.

3 Pt. II, p. 365. 4 Vol. xiv, p. 93.

EARLY WORKS ON MIMICRY 221

Boisduval, in 1836, remarked on the resemblance
between certain West African butterflies belonging to
very different groups.1

Professor Westwood read Illustrations of the Relation-
ships existing amongst Natural Objects, usually termed
Affinity and Analogy, selected from the Class of Insects
before the Linnean Society, on January 17 and May 2,
1837, tne paper appearing in the Transactions? In the
memoir many new examples were published and figured,
while Macleay's views were criticized and expanded in
an interesting manner.

The same recognition of Mimicry is equally well seen
in the names with the termination -formis given to so
many of our moths, indicating their resemblance to wasps,
bees, and other insects. In spite, however, of the know-
ledge of a large number of instances, the subject made no
real progress until the appearance of H. W. Bates's paper.
The view then set forth that the resemblances are in
themselves beneficial to the possessor was, as far as I am
aware, only once suggested before — in the well-known
Introduction by Kirby and Spence. These authors write
as follows : — ' Some singular larvae, with a radiated anus,
live in the nests of humble-bees, and are the offspring of
a particular genus of flies (Volucella, Geoffr., Pterocera,
Meigen), many of the species of which strikingly resemble
those bees in shape, clothing, and colour. Thus has the
Author of nature provided that they may enter those
nests and deposit their eggs undiscovered. Did these
intruders venture themselves amongst the humble-bees
in a less kindred form, their lives would probably pay the
forfeit of their presumption.' 3 This interesting paragraph,
although fully recognizing the utility of Mimetic Resem-
blance in species which were then believed to have been
separately created and to have come into existence fully
formed and complete, sustains a position which is the
very antithesis of that taken up by Bates. The con-
tention that the utility of the resemblance has been the

1 Species General des Lepidopieres, pp. 372, 373.
- Vol. xviii, p. 409.

3 Kirby and Spence, vol. ii, 181 7, p. 223.

222

THEORIES OF MIMICRY

cause of its persistence, and, by the selection of variations
going further in the same direction, of its improvement,
would have been rejected, probably with indignation, by
the distinguished authors of the Introduction.

Bates's great paper dealt with the fauna of tropical
America, and the generalization was manifestly incomplete
until it had been extended to other parts of the world.
This confirmation was not long in coming, being supplied
for the tropical East by A. R. Wallace's paper published
in the Transactions of the Linnean Society,1 and for
Africa by Roland Trimen's paper, also to be found in the
Transactions of the same Society.2

It is remarkable how completely the Linnean Society
has been the medium for the publication of classical
memoirs upon Mimicry. Up to the year 1870 it con-
tained them all ; while in 1858 it served as the channel
through which the parent theory of Natural Selection was
first given to the scientific world. The next great advance
did not take place until 1879, and was published else-
where.

Bates had called attention to certain resemblances
which could not be interpreted under his Theory of
Mimicry, viz. the frequent similarity between the specially
defended forms themselves. Species which are them-
selves the models for Mimicry nevertheless mimic or at
least resemble other models. For such cases Bates could
only suggest the direct action of some unknown local force
or forces, and in this interpretation he was at first followed
by Wallace.

In May, 1879, Fritz Muller published a paper in
Kosmosz which for the first time offered an explanation,
based on the theory of Natural Selection, of these
mysterious resemblances. He suggested that such like-
ness between dominant forms was advantageous, inasmuch
as it facilitated the education of their enemies, reducing
the amount of destruction which must be wrought during
the time in which young birds and other animals are
learning what to eat with impunity and what to reject.

1 1866, vol. xxv, p. 1. 2 1870, vol. xxvi, p. 497.

3 Ituna and Thyridia ; a remarkable case of Mimicry in Butterflies.

ADVANCE OF MULLER'S THEORY 223

The paper was translated by Professor R. Meldola and
published in this country almost immediately after its
appearance.1 The new hypothesis was at once accepted
by Wallace as well as by Meldola, but, to the end of his
life, Bates could never bring himself to believe it. In
1882 Meldola published an important paper 2 containing
new facts and arguments in favour of Muller's hypothesis
and further support was afforded by the present writer in
1887.3

During the past thirteen years the Mullerian theory
has gradually absorbed more and more of the ground
that was formerly believed to be covered by the theory of
Bates — an advance due in chief part to the researches of
Dr. F. A. Dixey.4

The facts which the Mullerian theory sought to explain
concerned the fauna of tropical America ; the naturalist
who explained them was living in the same part of the
world. A few years later, however, F. Moore showed
that there is the same resemblance between the dominant
butterflies of the tropical East5; and in 1897 it was
pointed out by the present writer that the same facts hold
in Africa.6

In 1897 I pointed out that Mullerian Resemblance is
not true Mimicry at all, but rather an example of Common
Warning Colour,7 and with the assistance of Mr. Arthur
Sidgwick the term Synaposematic was proposed as de-
scriptive of it ; the term Aposematic having been pre-
viously suggested for ordinary Warning Colours.8

I have now given a brief account of the leading phases
in the history of Mimicry. Even before the appearance

1 Proc. Ent. Soc, Loud., 1879, p. xx.

2 Ann. and Mag. Nat. Hist., 5th ser., vol. x, Dec. 1882, p. 417.

3 Proc. Zool. Soc, Lond., March 1887, p. 191. 4 ^ee P« 213> n- K

5 Proc. Zool. Soc, Lond., 1883, p. 201.

6 Report 0/ the British Association at Toronto, 1897, pp. 689-91. See
also Roland Trimen's Presidential Address to the Entomological Society.
Jan. 19, 1898 {Proceedings, 1897, p. lxxxv).

7 Proc. Ent. Soc, Lond., 1897, p. xxix ; Report Brit. Assoc, 1897,
p. 691.

b Poulton, Colours of Animals, Internal. Sci. Ser.. London, 1890,
P- 337-

224 THEORIES OF MIMICRY

of Fritz Muller's paper a great effect had been produced.
The immediate stimulus to the investigation of new
examples and fresh aspects of Mimicry which followed
Bates's memoir, must be ascribed to the fact that then for
the first time was offered a good working hypothesis —
a hypothesis which seemed to afford an adequate ex-
planation of one class of known facts, and challenged its
critics to find insuperable difficulties among facts as yet
unknown. In the forty-five years which have elapsed
since the appearance of this great memoir an immense
number of facts bearing upon the subject have been dis-
covered, and many naturalists consider that the Theories
of Mimicry, associated with the names of H. W. Bates
and Fritz Miiller, have stood the test with complete
success, and that an interpretation based on the theory
of Natural Selection is in a far stronger position than in
1861. It is, I believe, true that this opinion is more
generally held among the students of other groups of the
animal kingdom than among those who are specially
devoted to entomology.

2. The various Hypotheses which have been proposed as
Substitutes for Natural Selection as the Explanation of
Mimicry and Common Warning Coloitrs.

All the various suggestions which have been proposed
as substitutes for Natural Selection, may be included
under three heads : —

i. The direct effect of some physical or chemical cause
or causes connected with locality, such as climate, food,
&c. This may be called the Theory of External Causes.

ii. The independent evolution of a similar appearance
in distinct species. Mimetic Resemblance, according to
this hypothesis, is due to internal developmental causes,
compelling different species to pass through similar phases.
My friend Professor Patrick Geddes has told me that he
is in favour of this view, and it is the central idea of
Professor G. H. Eimer's work.1 The hypothesis that
' Laws of Growth ' may cause these resemblances also
falls into this category. The suggestion that such laws

1 Orthoge?iesis der Sc fanetterlinge, Leipzig, 1898.

SUGGESTED CAUSES OF MIMICRY 225

may account for certain phenomena which are usually
explained by the theories of Natural and Sexual Selection
was made by Professor D'Arcy Thompson at the Oxford
meeting of the British Association in 1894.1

The conceptions briefly set forth under this head may
be grouped as the Theory of Internal Causes.

iii. The operation of Sexual Selection. Fritz Mtiller
proposed this idea in a letter to Darwin, who wrote not
unfavourably of it to Professor Meldola, on January 23,
1872. ' You will also see in this letter a strange specula-
tion, 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.' 2

In the present paper the attempt will be made to show
that many of the known facts of Mimetic Resemblance
do not admit of interpretation by any of the three theories
mentioned above, while they do receive a ready explana-
tion on the supposition that the resemblances are useful
and have been produced by Natural Selection. Certain
new observations upon the details of the resemblances in
a large group of insects, undertaken specially to test these
rival theories, will be found to point strongly in the same
direction.3

3. The Relation of the Resemblances tinder Discussion to
other Resemblances in Organic Nature.

To those who accept Natural Selection as the explana-
tion of Mimicry, the facts under discussion fall into their
place as part of the much wider group of Protective

1 Only the title— On some Difficulties of Darwinism — is printed in the
Report of the meeting, p. 689.

2 Charles Darwin and the Theory of Natural Selection. Poulton, London,
1896, p. 202.

3 See Section 12, p. 261.

POULTON Q

226

THEORIES OF MIMICRY

Resemblances in general. Mimicry becomes, as A. R.
Wallace expresses it, merely 'an exceptional form of
protective resemblance \* The following classification
was suggested by the present writer, with the assistance
of Mr. Arthur Sidgwick, in 1890: 2 —

I. Apatetic colours. — Colours re-
sembling some part of the environ-
ment or the appearance of another
species.

II. Sematic co-
lours.— Warning
and Signalling
Colours.

III. Epi-

gamic colours.
— Colours
displayed in
courtship.

A. Cryptic co-
lours. — Protec-
tive and Aggres-
sive Resem-
blances.

B. Pseudo-
sematic colours. —
False Warning
and Signalling
Colours.

1 . Procryptic
colours. — Pro-
tective Resem-
blances.

1. Pseudapose-
matic colours. —
Protective Mimi-
cry.

1. Aposematic
colours. — Warn-
ing Colours.

2. Anticryptic
colours. — Ag-
gressive Resem-
blances.

2. Pseudepise-
matic colours. —
Aggressive Mimi-
cry and Alluring
Coloration.

2. Episematic
colours. — Recog-
nition Markings.

Thus the facts of Mimicry fit into a broad system
which includes many other resemblances in organic
nature. The relation between Protective Resemblance
(I. A. 1) and Protective Mimicry (I. B. 1) is as follows: —
In the former an animal resembles some object which is
of no interest to its enemy, and in doing so is concealed ;
in the latter an animal resembles an object which is well
known and avoided by its enemy, and in doing so becomes
conspicuous. Thus Mimicry as interpreted by H. W.
Bates finds its place in LB. 1, while the resemblance
between protected conspicuous forms (sometimes, but, as
I think, erroneously, called Mimicry), as interpreted by
Fritz Miiller,3 falls into II. 1. Such cases only differ

1 Darwinism, London, 1889, p. 265.

2 The Colours of Animals ; Internat. Sci. Ser., London, 1890, p. 338.

3 Kosmos, May 1879, p. 100, translated by Meldola in Proc. En/. Soc,
Lond., 1879, p. xx.

VARIOUS ANIMAL RESEMBLANCES 227

from ordinary Warning Colours in that the)- are
common to two or more species : hence, as has been
already pointed out, the term Synaposematic Colours, or
Common Warning Colours, may be conveniently applied
to them.

The arguments in favour of Natural Selection as the
explanation of Protective Resemblance run entirely
parallel with those which favour it as the interpretation
of Mimetic Resemblance and Common Warning Colours.
By modifying the examples and, in some cases, the form
of the argument, nearly every section of this paper might
be converted into a defence of the former, and the argu-
ments which are strongest in support of the one are the
strongest in support of the other, viz. those contained in
Sections 4, 5, 6, 7, ri, and 12.

Under the theory of Natural Selection all the resem-
blances among animals, mimetic and other, show the
clearest relationship, and (with the exception of the
debated Epigamic Colours) are to be explained by the
working of a common principle, viz., the selection of
variations which are useful in the struggle for existence.
Under the other theories mentioned above no such
grouping can be readily brought about, and Mimetic
Resemblance becomes due to one set of principles and
the other resemblances to another set. The majority of
those who look on Mimicry as due to External or to
Internal Causes, or to Sexual Selection, would probably
agree in explaining Protective Resemblance by Natural
Selection. And yet these latter cases, while far more
common, are often as detailed and as remarkable as those
of Mimicry. Those who adopt the most extreme form
of the theory of External Causes might perhaps maintain
that the resemblance to twigs, leaves, and bark is to be
explained in the same manner, and would thus bring
Protective and Mimetic Resemblance under the operation
of the same set of forces ; but few will be prepared to
carry the theory so far. Under the theory of Internal
Causes it is impossible to bring the two kinds of
resemblance together ; for while it is held by some that
two or more animals may independently and without

Q 2

228 THEORIES OF MIMICRY

selection arrive at corresponding points in their evolu-
tionary history, which are such as to involve Mimetic
Resemblance, no one could believe that the similarity to
bark or earth has been produced in the same manner.
Those who are inclined to accept Sexual Selection as the
explanation can only bring the two classes of facts together
by supposing that the appearance of some minute portion
of the total vegetable or mineral environment has acted
as a stimulus and has led one sex to select the other
according as it resembled the object in question ; just as
Fritz Miiller suggested in his letter to Darwin1 that
mimicry might be due to Sexual Selection stimulated by
the appearance of another species. Probably no one is
prepared to adopt this view as regards the former class
of facts, although Darwin had, as he states in his letter
to Meldola 2, considered the possibility of the general tints
of the environment influencing the trend of Sexual
Selection in this way.

A fatal objection to any explanation based on the theory
of Sexual Selection is the fact that Protective Resem-
blances are so extremely common and perfect in the
immature stages of insects. The same objection holds,
although with less force, against its use as an explanation
of Mimetic Resemblance.

The conclusion appears inevitable that under no theory
except Natural Selection do the various resemblances of
animals to their organic and inorganic environments fall
together into a natural arrangement and receive a common
explanation. On any theory except Natural Selection
this can only be brought about by the adoption of extreme
views as to the area over which the alternative theory
is to be applied — views which, at any rate, the great
majority of those who are disposed thus to explain Mimetic
Resemblance are not prepared to adopt.

1 See p. 225.

2 See p. 225.

STUDY OF BUTTERFLIES ALONE 229

4. Mimetic Resemblance and Common Warning Colours
between different A rthropod Classes and between various
Insect Orders, and their Relation to Similar Resemblances
within the Limits of a Single Order,

The various criticisms of Natural Selection as the
motive cause of Mimicry have been based almost ex-
clusively upon the phenomena presented by Mimetic
Resemblance and Common Warning Colours among the
species of a single Order of insects (Lepidoptera), and
generally the species of one Family (Nymphalidae), and
one Sub-Family (Pierinae). I cannot but think that this
limitation of the survey to one small part of the field over
which the resemblances commonly occur is, in large part,
the cause of the rejection of Natural Selection and the
substitution of alternative suggestions. There is some-
thing attractive and plausible in the idea that the strong
mutual resemblances within a group of butterflies of
different genera and Sub-Families, inhabiting a single
locality, are due to the direct action of peculiar local
physical or chemical influences; but the suggestion loses
all its attractiveness when it is applied to the resemblance
between a spider and an ant, or a moth and a wasp.
And yet few could bring themselves to believe that the
resemblances which are here contrasted have been built
up by two entirely different sets of forces.

The majority of naturalists will probably agree with
this argument, and, realizing that the theories of External
Causes and of Internal Causes are useless to explain the
mimetic likeness between a wasp and an insect of a
different Order, will reject these theories as unnecessary
to explain the resemblance between one butterfly and
another. But an attempt may be made, in fact has
been made, to discriminate between the relative powers
of the Batesian and Miillerian Theories 'respectively in
these two spheres of Mimetic Resemblance — that which
includes forms of remote affinity and that which includes
those more nearly akin. It has been supposed that the
Miillerian Theory does not explain Mimetic Resemblances
between remote forms, however adequate it may be for

230 THEORIES OF MIMICRY

those between forms closely allied. To the former
examples of Mimicry it has been contended that the
Batesian Theory alone applies. It may be urged on the
contrary that the resemblances between remote forms
have not been as yet sufficiently examined from the
Miillerian standpoint ; and that there are, nevertheless,
and have been for many years, the strongest indications
that here also much of the ground formerly believed to
be covered by the older theory will be found to be
occupied by the newer.

The Miillerian Theory by no means demands that the
methods of defence in the members of a convergent group
should be uniform.

So long ago as 1887 1 the present writer tabulated the
colours and markings of all insects which up to that time
had been experimentally proved to be specially defended,
and was enabled to apply to the whole group of con-
spicuous species which had been tested the explanation
offered by Fritz Muller.2 This general conclusion will be
found to be supported by many facts and considerations
in the paper referred to.

A good example is to be found in the resemblance
which the black-and- yellow-ringed unpalatable larva of
Euchelia jacobaeae (the Cinnabar Moth) bears to a wasp.
It is in this case 'more than probable (as has been
previously suggested by other observers) that the species
rendered conspicuous by alternate rings of black and
yellow gain great advantages from the justly respected
appearance of Hornets and Wasps. It must not be
forgotten, however, that the latter forms also probably
gain to some extent by the greater publicity which follows
from the resemblance.'3

The attention of those who dwell on the excessive
amount of assumption in the theories of Mimicry may be
invited to the numerous tables in the paper quoted above.
In these will be found recorded the whole of the results

1 Proc. Zool. Soc.,Lond., 1887, pp. 191-274, The Experimental Proof
of the Protective Value of Colour and Markings in Insects in reference
to their Vertebrate Enemies.

2 I.e. p. 227. 3 I.e. pp. 235, 238.

MIMICRY BETWEEN DISTINCT ORDERS 231

of actual experiments made, up to 1887, upon the palata-
bility and unpalatability of conspicuous and inconspicuous
insects. It may be safely asserted that the theories in
question are not nearly so devoid of support from the
results of experiment and observation as has been
represented.

Since 1887 further evidence has been forthcoming in
support of the Mlillerian explanation ; for it has been
shown in many cases that insects which resemble specially
defended members of another Order, themselves belong
to a specially defended group within their own Order.
Thus Haase1 points out that the South-American moths
which resemble ' immune ' Coleoptera — the Lycinae,
1 belong to the immune families of the Glaucopidae
(Mintica, Lycomorphd) and Arctiidae {Pionid)l and also
that the South- American Glaucopidae furnish numerous
cases of resemblance to Aculeate Hymenoptera.2

In the year 1897 Dr. L. O. Howard, of Washington,
kindly presented to the Hope Department, Oxford
University Museum, a pair of specimens which prove
that the specially protected moth Lycomorpha lateral la
(Edw.) occurs in the same locality and at the same time
of the year as the protected beetle Lygistopterus rubri-
pennis (Lee), which it closely resembles, the former
having been captured on June 18, the latter on June 5,
1897, m tne Chiricahua Mountains, Arizona, by H. G.
Hubbard.

Furthermore, the resemblance between the species
of the two great sections of the Order Lepidoptera —
the Rhopalocera and Heterocera — is frequently of the
Mlillerian rather than the Batesian kind. Thus Sir
George Hampson has pointed out that the moth Abraxas
etridoides, resembling the butterfly Teracolus etrida, belongs
to a specially protected genus, and that similarly three
genera of the Chalcosid group of Zygaenidae, which are said
to resemble Danaine and Papilionine butterflies, are also

1 Researches on Mimicry, part ii, Stuttgart, 1896, English translation
by C. M. Child, p. 70.

■ I.e. p. 73. In a note to the same page Haase adduces some little
direct evidence for the inedibility of a Glaucopid moth.

232 THEORIES OF MIMICRY

extremely distasteful to insect-eating animals.1 Similarly,
Mr. Roland Trimen, F.R.S., in his Presidential Address to
the Entomological Society,2 points out that the ' abundant
and extremely conspicuous slow-flying diurnal Lithosiid
[Geometrid] moth, Aletis helcita \ together with its ' appa-
rently protected analogues . . . the closely similar Lithosiid
[Hypsid] Phceagarista helcitoides, and Agaristid Euse-
mia falkensteinii\ show great similarity to the group
which is headed by Danais {Limnas) chrysippus — ' so that
from the aspect of warning of distastefulness to enemies
the two sets may be regarded as practically but one.'
Similar facts will probably be found in numerous other
examples of moths which resemble butterflies.

It may be safely asserted that, even with our present
limited knowledge, Mullerian Resemblance, no less than
Batesian Mimicry, can be found in the species of groups
with all degrees of affinity, and that there is no ground
for the contention that the latter theory alone derives
support from the facts presented by the groups which
include species from different Orders.

Under Natural Selection the interpretation of the
whole series of facts is perfectly valid. The dominant
forms which in each locality move towards each other
and towards which less dominant forms also move, are in
some way specially defended. The principles are the
same when the approximation is between the species of
different Orders or Sub-Orders, or between those which
are much more closely related. The Mullerian Theory
explains the resemblance of immense numbers of
stinging insects to each other and of other specially
defended forms to them, whether they be closely or
distantly related : it also explains the resemblance of the
dominant Heliconinae and Ithomiinae in each locality in
South and Central America and of other forms to them.
Batesian Mimicry explains the cases in which the attracted
forms are not specially defended.

The conclusion which emerges most clearly is the
entire independence of zoological affinity exhibited by

1 Nature, 1898, Feb. 7, p. 364.

2 Delivered Jan. 19, 1898 : Proc. Ent. Soc., LoikL, 1897, p. lxxxv.

MIMICRY INDEPENDENT OF AFFINITY 233

these resemblances ; and one of the rare cases in which
Darwin's insight into a biological problem did not lead
him right was when he suggested that a former closer
relationship may help us to a general understanding of
the origin of mimicry.1 The preservation of an original
likeness due to affinity undoubtedly explains certain cases
of Mimicry, but we cannot appeal to this principle in the
most remarkable instances. Further confirmation of this
independence of affinity will be found in the additional
details supplied in the succeeding Section.

When we look at the phenomena of Mimicry and
Common Warning Colours as a whole, it is found that
the theory of Natural Selection is equally applicable
throughout ; while the theories of External Causes and
Internal Causes cannot be applied to some of the most
striking resemblances, those of moths, beetles, and flies
to the stinging Hymenoptera. The theory of Sexual
Selection is less logically assailable on these grounds ;
but with the other two suggested substitutes for Natural
Selection, it entirely fails to account for the attractive
force exercised by specially protected forms. Under any
of these three theories it is a mere coincidence that the
insects which are resembled by species of all kinds happen
to possess stings — that the central types in the groups
of butterflies belong to Sub-Families which are more
abundant and even more unpalatable than the generality
of their Order. It is, furthermore, a mere coincidence
that such groups are formed round the Danainae and
Acraeinae, wherever they occur in all the warmer regions
of the zvorld, and in tropical America also round the
Ithomiinae (Neotropinae), which are closely related to the
former, and the Heliconinae, which are closely related to
the latter.

1 See Darwin's letter to Meldola, dated Jan. 23, 1872 ; Poulton, Charles
Darwin and the Theory of Natural Selection, London, 1896, pp. 201—2 : also
Charles Darwin, The Descent of Man, &c., 10th ed., London, 1874, p. 324.
The passage runs as follows: — 'As some writers have felt much difficulty
in understanding how the first step in the process of mimicry could have
been effected through natural selection, it may be well to remark that the
process probably commenced long ago between forms not widely dissimilar
in colour/ See also Origin of Species, 6th ed., p. 377.

234 THEORIES OF MIMICRY

No theory except Natural Selection explains why the
number of colours and patterns in the dominant groups
of butterflies mentioned above are so few in relation to
the number of species, as was pointed out by Professor
Meldola, F.R.S., in his paper Mimicry between Butter-
flies of Protected Genera} These colours and patterns
have been recently studied very carefully, especially in
the Ithomiinae, by A. G. Mayer,2 who shows that 1 the
200 species of Papilio in South America display 36
distinct colors, while the 450 species of Danaoid Heli-
conidae \I thomiinae~\ exhibit only 1 5. Hence the numbers
of the species and of the colors are almost in inverse ratio
in the two groups. This may be explained by the fact,
that the Danaoid Heliconidae mimic one another, while
the Papilios do not. . . . There is no lack of individual
variability among the species of the Danaoid Heliconidae;
yet the species as a whole vary but little from the two
great types of color-pattern represented by Melinaea and
Ithomia. In order to account for this remarkable fact
I am forced to resort to Fritz Mullers theory of mimicry.'3
Again, on page 225 Mayer remarks : 'It is difficult to
account for the remarkable conservatism in respect to
color- variations among the Heliconidae [here used, as in
Bates's original paper, to include Danainae, Ithomiinae,
and Heliconinae~\, unless we resort to the explanation
afforded by the theory of mimicry ; for, while there is
such remarkable simplicity and uniformity of color-
pattern throughout the whole group of the Heliconidae
individual variations are very common/

It is not from any predisposition or bias in favour of
Natural Selection that these conclusions are reached, but
simply because this theory offers an explanation of so
many remarkable facts which are utterly meaningless
under any other theory yet brought forward.

1 Ann. and Mag. Nat. Hist., 5th ser., vol. x, Dec. 1882, p. 417.

2 Bulletin of the Mus. of Comp. Zool. at Harvard Coll., Feb. 1897,
p. 167.

3 1. c. p. 229.

MIMICRY INDEPENDENT OF AFFINITY 235

5. Resemblances even within the Limits of an Order are
entirely independent of Affinity.

The entire independence of affinity is specially well
seen in the groups of convergent moths and butterflies
which are found in different localities in South America.
Although the resemblance is clear enough throughout all
the members of a large group, it is far closer between
certain species than others. When these are examined
they are found to be not more nearly related than other
members of the group, but frequently the reverse. Thus
it is very common for a species of Heliconius 1 to resem-
ble with the most remarkable precision a species of
Melinaea or some other Ithomiine genus in its locality.
Such resemblance is in these cases far closer than that of
the former to the species of the other genus (Eueides) in
its Sub-Family, and than that of the latter to any species
of the numerous related Ithomiine genera. Thus, to
illustrate this conclusion from some examples in the Hope
Collection, in Honduras by far the strongest resemblance
is to be found between a Heliconius and a Melinaea ; and
this is also the case (both species being different) in
Surinam. In Trinidad the resemblance is closest between
a Heliconius and a Tithorea, another Ithomiine.

Under the theory of Natural Selection this association
is readily explicable. The pairs which thus form the
centres of local groups are probably the dominant forms,
relying more completely than the other members upon
the defence afforded by their warning colours and the
associated unpalatability. As a matter of fact there is
some evidence for their exceptional abundance as com-
pared with the other members of their groups. Again,
they are usually more nearly of the same size than the
other members, so that the perfection of the resemblance
in colour and pattern is aided by resemblance in another
quality.

The theory of External Causes entirely fails to account

1 Although united by Bates in the Family Hcliconidae, the Hcliconinac
and the Ithoiniinae are Sub-Families lying at the very opposite ends of the
great group of Nymphalid butterflies.

236 THEORIES OF MIMICRY

for these facts. Uniform local conditions, if they can
produce any effect at all, must be expected to produce
the closest likeness where there is the closest constitu-
tional similarity — in other words, in the more nearly
related forms, in preference to the less nearly related, in
each locality. With the theory of Internal Causes we
should also expect the facts to be the reverse of those
which exist. At the best it is unable to account for the
observed phenomena.

Any theory of Selection (Natural, Artificial, or Sexual)
affords a logical explanation of the facts, in the sense that
it is quite conceivable that the observed results might be
thus obtained. Hence the objection to Sexual Selection
as a suggested cause is not as strong as the objection
to the other causes which have been brought forward.
Nevertheless, I believe that very few will be found to
support the hypothesis that Sexual Selection supplies the
interpretation we are seeking.

The conclusions here arrived at by a consideration
of the facts presented by the Lepidoptera are entirely
confirmed by those already known in the Coleoptera ;
although as yet but little attention has been paid to the
latter Order in this respect. C. J. Gahan, in an interest-
ing paper,1 clearly shows that the Phytophagous genus
Diabrotica is in the same position as the large protected
groups of butterflies already mentioned (Danainae, Itho-
miinae, Heliconinae, Acraeinae). The individuals of its
species swarm in the localities where they occur; they
are conspicuously coloured, and many of them are known
to feign death when captured and to discharge a yellow
fluid from various parts. The facts at present ascertained
justify the conclusion that these Coleoptera form centres
of Miillerian Resemblance, in that ' some of the species
belonging to one section in this genus are, in colour and
marking, extremely like certain species of the other section
which come from the same localities '.2 Mr. Jacoby has
also 1 recorded that many of the species of his genus Neo-
brolica exhibit most striking resemblances to species of the

1 Trans. Ent. Soc.} Lond.y 1 891, pp. 367-74.

2 I.e. p. 372.

MIMICRY IN BEETLES

closely-related genus Diabrotica 1 (1. c. p. 370). The latter
species are also mimicked by those of the allied genus
Dircema. Mr. Gahan shows, furthermore, that eighteen
species of the genus Lema, belonging to a different Sub-
Family, closely resemble the species of Diabrotica (in
one case the allied genus Cerotoma) found in the same
localities in tropical America. In three cases species
of Neobrotica, and in one a species of Dircema, fall into
the groups thus formed.

Mr. Gahan is disposed to regard the resemblance of
the species of Lema, together with that of the Longicorn,
Oxylymma gibbico/tis, for a species of Diabrotica, as an
example of Batesian Mimicry. Future observation and
experiment must decide upon this as upon so many other
cases concerning which we are uncertain whether to adopt
the Batesian or the Miillerian interpretation. The ten-
dency of recent observation, however, strongly favours
the opinion that the latter theory will explain a much
larger number of resemblances than the former.

But whichever interpretation be ultimately adopted,
the fact remains the same — that the resemblances in the
Coleoptera are of the same character as those in the
Lepidoptera, and are, like the latter, independent of
affinity. They are readily to be explained by the opera-
tion of a theory of selection, but present the same
difficulties as those presented by the Lepidoptera to an
interpretation by any other theory as yet brought forward.

6. The Resemblances in question are not accompanied by
any changes in the direction of the Mimicked Species
except such as assist in the production or strengthening
of a Stiperficial Likeness.

This argument is fatal to any theory as yet advanced
except one based upon the principle of selection directed
to a definite end, viz. the production of resemblance. It
is impossible to explain why external forces or internal
forces should thus act upon a certain set of characters
whose only relationship is that they tend to produce
a superficial likeness to another species — that they should

238 THEORIES OE MIMICRY

act upon these alone to the exclusion of all other sets.
No assistance can be obtained from the conclusion that
the results are recent and therefore superficial, and that
a resemblance in deeper characters will follow in time.
In the first place, the examples of more perfect (and pre-
sumably older) resemblance show no more tendency
towards approximation in characters which do not help
to produce likeness, than the examples in which the
resemblance is comparatively rude (and presumably
recent in origin). In the second place, deep-seated parts
of the organism are affected when the superficial resem-
blance is thereby increased, but not otherwise. To take
a single example, the common British Longicorn, Clytus
arietis, strongly suggests the appearance of a wasp, partly
because of its black and yellow banding, but even more
because of its alert and wasp-like movements. This
implies, of course, appropriate changes in its nervous and
muscular systems. Although Clytus arietis is a rough
and imperfect example of Mimicry, the resemblance, such
as it is, chiefly depends upon deep-seated structures.
We are, in fact, led to infer in Clytus and in an immense
number of other mimics that the deep-seated modifications
were the origin of the resemblance, and that the superficial
modifications of colour, &c., followed later.

The subject is, perhaps, of sufficient interest to warrant
the production of another example, in which the changes
in deep-seated structures are of more importance than
anything else in determining the resemblance. I know
of no more striking instance than the movements and
attitudes of the young (Lepidopterous) larvae of Endro-
mis versicolor, the 1 Kentish Glory ' moth, rendering them
extremely like the larvae of saw-flies (Phytophagous
Hymenoptera). Numerous experiments have convinced
me that the latter are almost invariably distasteful.
During the early stages of their growth the moth larvae
' arrange themselves in small groups upon the leaves and
leaf-stalks of the birch, and when disturbed they raise the
anterior part, bending the head over the dorsal surface
of the posterior part of the body. In this attitude they
strongly remind the observer of those Tenthredo larvae

ATTITUDE AND MOVEMENT 239

which, when irritated, bend the tail forwards over the
anterior part of the body. The fact that the head is
raised in the one, and the tail in the other, does not cause
any conspicuous difference when the larvae are seen from
a little distance. The common Tenthredo larva, Croesus
septentrionalis, is about the same size as these small
Lepidopterous larvae, feeds in similar small groups when
large (when small the groups contain far more individuals),
and also frequents the birch.' 1 Furthermore, the con-
spicuous orange-coloured true legs of the caterpillar
suggest the appearance of the orange ventral glands
of the Croesus, which are everted when the larva is irri-
tated. In my experience, however, the Croesus feeds
much later in the year.

Thus the sources of the resemblances we are discussing
may be deep-seated or may be superficial : the likeness is
however generally due to several kinds of causes in each
category. It is in the latter extremely complex cases,
and these are far the commonest, that the argument for
Natural Selection becomes irresistible. This will be more
thoroughly dealt with in the succeeding Section ; but
even in the case of the simplest element in the resem-
blance, viz. the similarity in colour and pattern taken
alone, the theories of External and Internal Causes are
unable to offer an adequate explanation of certain facts
which are clearly explicable by Natural Selection.

In the males of the South-American Pierine group
Dismorphina, the long-and-narrow-winged appearance of
an Ithomiine butterfly is largely produced by the exces-
sive overlap of the upper upon the under wings. This
results in the concealment of a large part of the upper side
of the under and of the under side of the upper wing ;
and it will be found that the mimetic patterns are with-
held from these hidden surfaces, which often retain some
distinct trace of the old Pierine character, viz. an opaque

1 Poulton, in Proc. Ent. Soc, Loud., 1891, p. xv. W. Holland also
noted the same resemblance in the Entomologist 's Record for Oct. 15,
1 89 1 (see vol. ii, p. 228). His manuscript notes, made at the time and
kindly lent to me, prove that he also observed the saw-fly-larva-like
movements which follow disturbance.

THEORIES OF MIMICRY

white appearance. This fact holds true even for such
a specialized and perfect mimic as Dismorphina orise.

F. D. Godman, F.R.S., and O. Salvin, F.R.S.,1 speak of
these hidden chalky patches, surrounded by a silky area
covered by peculiar scales, as acharacter of the Dismorphina.
The interpretation of the patch as a sexual brand, perhaps
with the nature of a scent-producing organ, does not in
any way disprove the suggestion here adopted — that the
white pigment in the scales is a survival from an ancestral
condition still found over the greater part of the wing-
surface in so many non-mimetic Pierinae, as well as in the
males of many mimetic species (e. g. in the genus Mylo-
thris). It should be noted, however, that the patch is not
white in all species of the Dismorphina. Mr. Belt 2 states
that the white patch is usually concealed by the males,
as indeed may be inferred from the change in character
of the surface, which indicates the normal amount of
overlap of the fore upon the hind wing. The same
author, believing that the white patch is ancestral and
has been retained by the operation of Sexual Selection,
makes the daring suggestion that it may be 1 an attraction
in courtship, to exhibit to the females, and thus gratify
a deep-seated preference for the normal colour of the
order to which the Leptalides [Dismorphina] belong'.

The rigid restriction of mimetic effects to those parts
of the surface which can be seen tells very strongly
against any theory which is not based on the principle
of Selection.

7. Essential Nature of these Resemblances : their A nalysis
into the several kinds of Effect produced.

The resemblances under discussion are made up of
elements of very different kinds combined in single
individuals ; but the essentially composite nature of the
effect easily yields to analysis. Some of these complex
combinations only require to be stated in order to show
the inadequacy of the theory which is most usually

1 In the Biologia Centrali- Americana (Rhopalocera, vol. ii, p. 173).
9 Naturalist in Nicaragua, 2nd ed., London, 1888, pp. 384, 385.

COMPOSITE NATURE OF MIMICRY 241

substituted for Natural Selection, viz. the theory of
External Causes.

A mimetic appearance is commonly made up of (1)
colour, including (a) structural as well as (6) pigment
colours ; (2) pattern ; (3) form ; (4) attitude ; (5) move-
ment.

It may be plausible to hold that direct local influences
determine colour, but the case becomes much more diffi-
cult when structural tints are included, as they frequently
are. Thus it might well be held that the dark pigment
of a female Hypolimnas and of the Euploea which it
resembles are alike the direct effect of the locality they
both inhabit. But the most convinced advocate of direct
local causes would probably hesitate to explain, by the
operation of the same forces, the structurally caused blue
sheen which overspreads the dark pigment in some of
these mimetic pairs. Similarly with pattern, it is much
more difficult to understand the appropriate arrangement
of the colours by direct forces than the production of the
tints themselves ; still more difficult to understand how
such forces could modify shape, and, again, more difficult
to see how they could mould the nervous and muscular
systems so as to produce appropriate attitudes and move-
ments. Most difficult of all to understand, except on a
theory of Selection, how the several elements in the
complex set of changes could be kept in their proper
relationship and guided to a definite end, viz. the pro-
duction of a superficial resemblance to another species.

The objection to the theory of Internal Causes is not
that it is inadequate to produce each of the effects, but
that it is in the highest degree improbable that so com-
plete and harmonious an effect could be frequently
produced accidentally by the combination of such diverse
elements.

It is useless to maintain that these resemblances are
the uniform result of uniform forces peculiar to the
locality; for investigation proves that the results are
very far from uniform. They appear at almost any point
in the structure of the body, superficial or deep-seated,
generally at many points in a single individual both

rOVLTON 1^

242 THEORIES OF MIMICRY

superficial and deep-seated, and the only common bond
which can be established between the various elements
which make up the common effect is that they all co-
operate in producing superficial resemblance to some
other species.

It is here shown that the changes wrought in a single
species are far from uniform. It will be shown later on
(see Sections n and 12, pages 250 and 261) that there is
frequently no uniformity in the methods made use of by
mimic and model, nor any uniformity between the various
mimics of the same model, nor between the different
members of a synaposematic group. These, too, often
have only one thing in common, and that inexplicable
except on a theory of Selection, viz. the subordination of
all these divergent methods to a single end — the attain-
ment of a superficial resemblance.

The arguments in this and the preceding Section are
equally powerful in support of the interpretation of
Protective Resemblances as due to Natural Selection.

Again, Mimetic Resemblances are comparatively rarely
seen in more than one stage of insect life, and are, in the
great majority of cases, restricted to the final stage. In
all such species the total appearance presented by the
final stage, including mimetic resemblance, is prepared
for in the earlier stages, especially the larval. Not only
are the changes in question confined, as has been already
pointed out in this Section, to the parts, tissues, and
organs which influence the superficial appearance, but
they are also generally confined to the final stage of
insect life. During larval life the foods peculiar to the
locality are devoured and the material for the mimetic
stage is stored up. The larval and pupal stages are
together, in the great majority of cases, far longer than
the imaginal stage, and are no less, and, as regards food,
far more, subject to the direct action of the forces peculiar
to the locality. On what theory except Natural Selection
is it possible to explain the rigid limitation of these changes,
in so large a proportion of cases, to the final stage, and
their entire exclusion from the stages during which they
are, in the history of the individual, predetermined ?

MIMICRY AND LIFE-HISTORY 243

8. Conditions of a Species in any locality are chiefly
determined by its Habits and Life-history,

In the last Section it was shown that there is no uni-
formity in the effects produced in any locality. In this
Section it will be made clear that there is no uniformity
in the forces which, by their uniformity, are supposed to
produce the effects. When we are told that common
food, common climate, &c, produce a common effect, we
have the means for proof or disproof in, at any rate, some
striking examples ; for we know the food and conditions
of certain species which exhibit mimetic or common warn-
ing associations. There are many examples of Longicorn
beetles mimicking Lycidae (Malacoderm beetles) in the
same locality ; but during the earlier stages, in which the
appearance of the final stage is determined, the former
lives in a burrow, feeding upon wood or the tissue of
plant-stems, and sheltered from many of the climatic
influences and changes, while the other lives in the open,
freely exposed to them all, and sustained by an exclusively
carnivorous diet. I owe this suggestive comparison and
the Section which arose out of it to a conversation with
Mr. C. J. Gahan, of the British Museum. Similarly in
the case of South-American moths belonging to the
Castniidae, which resemble Ithomiine butterflies (see
Section 12, page 261), the larvae of the former burrow in
plants, while the latter are freely exposed on the leaves
which form their food.

It is hardly necessary to insist on the importance of the
larval stages in this respect. When the imago emerges
from the pupa and its expanded wings have dried, it has
assumed its permanent appearance, and nothing that it
will eat or endure henceforward, produces any further
effect upon its colours or patterns, &c. Hence identity
of food and conditions during the final stage cannot be
of any assistance in the interpretation of Mimicry. It is
necessary to point this out clearly, inasmuch as Beddard
has said, speaking of the resemblance between Eris talis,
the drone-fly, and the hive-bee, * It is an interesting fact,
in connection with the resemblance between this fly and

r 2

244 THEORIES OF MIMICRY

a hive-bee, that it feeds upon pollen and honey. This
fact may have some significance in relation to the effects
of food upon form and coloration.' 1 But the larva of
Eristalis stores up nutriment, out of which the final form
is built, by feeding on putrefying animal matter, a food
as different as possible from that provided for the larval
bee. The peculiar conditions under which the larvae of
stinging Hymenoptera obtain their food invariably con-
trast strongly with the larval condition of their numerous
mimics. We find in this Section, as in the others, that
the suggested interpretation of these resemblances as the
common effect of a common cause or set of causes breaks
down the moment it is analysed. The view is a super-
ficial one, and cannot be sustained when the slightest
attempt is made to understand the nature of the pheno-
mena it professes to explain.

9. Mimetic Resemblance and Common Warning Colours
more characteristic of the Female than the Male Sex.

These resemblances are far commoner in females than
males, and when the two sexes differ in the closeness with
which a likeness to some other form is brought about, it
is the female which always attains the greater perfection.
Examples of mimetic females with non-mimetic males
are extremely abundant, being in fact a high proportion
of all the cases which occur ; examples of the converse
relationship are very nearly unknown. These general
statements hold with Common Warning Colours as well
as with truly mimetic species ; they are equally true in
all the warmer parts of the world where examples of
Mimicry are well known and abundant.

In the numberless cases in which a non-mimetic male
is accompanied by a mimetic female, the male bears
the ancestral appearance, so that when we pass to a land
where both sexes of the representative species are non-
mimetic, both resemble the non-mimetic male of the former
species. In a long series of related species, moreover,
the males are found to be nearly alike, while the females

1 Animal Coloration, London, 1892, p. 232, n.

MIMETIC TENDENCY OE FEMALE 245

diverge in all directions after the species which serve
them for models. Furthermore, the females, by rever-
sion, are in rare instances brought back towards the
ancestral type represented by the males.

It is hardly necessary to point to examples, for these
general principles will probably be at once conceded by
any who have made a study of the subject. I may,
however, allude to the non-mimetic Papilio meriones of
Madagascar and the related forms with similar males but
widely different mimetic females on various parts of the
mainland of Africa ; to the general resemblance between
the males of so many forms of Hypolimnas of the bolina
group to each other and to those of H. misippus, &c. :
to the varying degrees of reversion towards the appear-
ance of the male presented by occasional females of
Hypolimnas bolina.

These relationships are the reverse of those which
usually obtain. Outside the category of Mimetic Resem-
blances it is the rule, when any difference between the
sexes exists, for the female to show us the ancestral type,
the male the more modern development ; and the male
in growth from youth to maturity generally passes through
the condition permanently retained by the female.

Xo probable interpretation of the unusual relationship
lias been offered by any theory except Natural Selection.
The theory of External Causes demands the improbable
hypothesis, for which no evidence can be found, that the
female of certain mimetic species (but not of others) is
constitutionally more ready to respond to the direct action
of external forces than the male, and that the difference
is commonly great enough for the female to have given
a complete and detailed response, when the male, subject
to the same direct forces, does not exhibit the faintest
trace of the operation of an)' such influence.

The facts are equally inexplicable by the theory of
Internal Causes — and not inexplicable only, but the
reverse of what we should expect ; for, as I have already
stated, it is the female which, outside these resemblances,
tends to retain the ancestral form.

The theory of Sexual Selection also fails to account

246 THEORIES OF MIMICRY

for the facts. If it were valid, the selection would be
exerted by the male, for these recent developments are
specially characteristic of the other sex. In other cases
in which male rather than female selection is supposed to
have acted in the production of colour or patterns in
butterflies, there is some direct evidence derived from the
observation of courtship ; but here no such support is
forthcoming.

Under the theory of Natural Selection the facts at
once receive an explanation. Wallace suggested long ago
that the slower flight of the females ' when laden with
eggs, and their exposure to attack while in the act of
depositing their eggs upon leaves, render it especially
advantageous for them to have some additional pro-
tection V In animals which are hidden by Protective
Resemblance, similar causes explain why the female is so
often better concealed than the male. In birds the
dangers of incubation balance the dangers of egg-laying
in insects. But Protective Resemblances are less special
than cases of Mimicry in the sense that the models (bark,
twigs, leaves, &c.) are more generally alike throughout
all countries, and less rapidly change their distribution
than the models of Mimicry and the dominant types of
Common Warning Colours. These and other reasons,
such as the great number and wide geographical range
of species belonging to the same genus and adopting
a single method of concealment, compel the belief that
examples of Protective Resemblance are extremely an-
cient in the past history of the species as compared with
examples of Mimicry, so that we can well understand
how it is that in the former, when the female differs it is
ancestral as compared with its male, while in the latter
the converse relationship obtains, and the appearance
presented by the male is comparatively ancestral.

The main conclusion which emerges is that the advan-
tageous is the thing that is attained. If an ancestral
appearance is advantageous it is retained, especially in
the sex that needs it most ; if a new appearance is

1 Trans. Linn. Soc, Lond., vol. xxv, 1866, p. 22.

SURVIVAL OF THE ADVANTAGEOUS 247

advantageous it is attained, especially by the sex that
needs it most. The female sex becomes conservative or
progressive according to the needs of the species, and
Natural Selection is limited by no bounds of constitutional
difference between the sexes as regards the preservation
of the old or the initiation of the new.

1 o. The Space and Time Relationships of the Resemblance

in Question,

A mimetic group is found in the same locality, or at
least the mimic (Batesian) is not found beyond the range
of its model. The types of Common Warning Colours
are remarkably local, although probably certain members
of the group (being ex hypothesi all specially protected)
may sometimes have a wider range than others. When
such a mimic as Hypolimnas misipptts can invade and
thrive in South America and the Antilles in the absence
of its model (Limnas chrysippus), we probably have to do
with a Mullerian rather than a Batesian association.1

Looking at the examples broadly, the phenomena are
characteristically local. This, although harmonizing with
the other suggested explanations, is quite unintelligible
if the theory of Internal Causes be adopted. Why should
these results if attained independently in the evolution of
various forms be attained in the same locality ? The
number of patterns and the number of forms is so vast
that we must expect a certain amount of accidental
resemblance due to internal causes, as has been suggested
by Beddard,2 but such resemblances will differ from those
under discussion in this among other things — that they
will not be characteristically local. The theory of I nternal
Causes offers us a valid interpretation of such cases, which
are, as a rule, readily distinguishable in other ways from
those which are here considered.

There is another aspect of locality which only receives

1 See also a paper by the present writer on Mimicry in Butterflies of
the Genus Hypolimnas in Proc. Amer. Assoc. for Adv. of Sci, Detroit
Meeting, 1897, vol. xlvi, p. 242, where other arguments in support of this
conclusion are urged.

2 Animal Co/oration, London, 1892, p. 252.

248 THEORIES OF MIMICRY

an explanation on the theory of Natural Selection. Why
should examples of Mimicry and Common Warning
Colours be so much more abundant and perfect in one
country than another ? The physico-chemical influences,
the effects of luxuriant vegetation, as Wallace has pointed
out, are very similar in tropical South America, Malaya,
and West Africa, and yet the first-named country is
pre-eminent in affording examples of the resemblances
under consideration. This is not only true of likenesses
within the Order of Lepidoptera, it appears to be equally
true within the Coleoptera ; it is true of the resemblances
of moths to wasps. It is even more marked in Miillerian
Resemblance between protected forms than in the
examples of Batesian Mimicry. If the direct action of
forces connected with locality cannot explain the immense
predominance of tropical South America in this respect,
we are driven to inquire whether insect life is especially
luxuriant and remarkable in this part of the world, and
whether it is not probable that the struggle for existence
is especially keen. There is no doubt about the answer
to these questions : the variety, peculiarity, and abundance
of insect life is far greater than in any other part of the
world, and it is a fair inference that the conditions are
in an equally marked degree favourable for rapid and
complete modifications under the operation of Natural
Selection.

We have not as yet sufficient evidence that mimetic
groups and groups with a Common Warning coloration
appear at the same time of the year. Such evidence as
we have points in this direction. The rarity of the
mimetic species is usually stated to be due to their being
lost in the swarms of the abundant model. There are,
however, a large number of cases in which the forms have
been caught together by a collector who has passed a
limited time in a given locality.

I am bringing together in the Hope Department of
the Oxford University Museum as many examples as
possible of mimetic species, captured upon the same day
and in the same place as their models. This series, which
is kept separate, even now affords very valuable evidence

TIME RELATIONSHIPS OE MIMICRY 249

on the point. Already it proves that the members of
the groups which converge round Limnas chrysippus,
Amauris ccherm, and the black and white species of
Amanris in Natal are upon the wing together. This
evidence has been very kindly supplied me by Mr. Guy
A. K. Marshall. I have similar, but less complete,
evidence as regards some of the Central and South-
American groups.

It will probably be conceded that the phenomena
generally are likely to exhibit the same relationship in
time which has been already proved to exist for many
of them. This conclusion, however, is a considerable
difficulty in the way of the theory of External Causes as
well as a further difficulty to the theory of Internal
Causes. As regards the latter, the time relationship is
an entirely unexplained coincidence ; as regards the
former, it is a coincidence which leaves much to be
explained. It is difficult enough to believe that local
forces could produce local resemblance ; it is a further
difficulty that the resemblances are contemporaneous.
If, as is probable, the forces are supposed to act during
larval life, they must include in their effects an influence
on the rate of growth and development, an adjustment
of the duration of stages delicate enough to bring; the
various species into the phases in which the resemblance
is shown at similar times of the year. But such effects
are entirely different from those which are manifest in
the resemblance itself, and add a further complexity to
a result already shown to be so complex that the theory
of External Causes fails to supply an interpretation (see
Section 7, p. 240).

But it has been shown in many cases, and is probably
true in all, that the time relationships between the species
which exhibit these resemblances are not confined to their
appearance at the same season of the year. They are
such that they fly together under those conditions of
light which render the resemblance visible to enemies.
When moths resemble butterflies, they are mostly species
which are as truly day-flying as the butterflies themselves ;
in other cases they are species which fly readily by day

250 THEORIES OF MIMICRY

when disturbed. Similarly with the species of various
Orders which resemble Hymenoptera. The case of
Coleoptera recently suggested to me by Mr. Gahan is
peculiarly interesting. It is known in so many cases that
beetles which are about by day possess finely facetted
eyes as compared with the larger fewer facets of the
nocturnal species, that it is possible to infer the habits
from the structure of the eyes. Thus the species of the
Longicorn genus Doliops (Family Lamiidae), which closely
resemble weevils (see p. 261), are, judged by this standard,
diurnal in their habits. The case is all the more inter-
esting, inasmuch as such an eye-structure, such habits,
and such mimicry are quite exceptional in the Longicorn
group, the Niphoninae, to which the genus belongs.

The facts recorded above imply such a relationship
between the nervous systems and sense-organs of the
various species as will make them, like their models,
diurnal (or in some cases semi-diurnal) in their habits.
This constitutes a further grave difficulty in the way of
any explanation based on External or Internal Causes.
If the diurnal habits are supposed to be due to such
causes, the greatly increased complexity of the result is
the difficulty. If the resemblances are supposed to be
thus produced only in the species which are already
diurnal, it is impossible to explain why the external or
internal forces are thus restricted in their operation.

It is hardly necessary to point out that the time and
space relationships, which are such a difficulty in the way
of the other two theories, are entirely necessary to the
explanation based on the theory of Natural Selection.
If they did not exist it would be overthrown.

1 1 . The Resemblances which Insects of various Orders
bear to those of another Order are produced in the most
Diverse Ways.

The most common types for mimetic resemblance
are those of the wasp and ant. These aggressive,
abundant, and successful forms are resembled by insects
of various Orders. Still more interesting is the fact that
the resemblance is produced in the most varied ways.

/

VARIOUS MIMICS OF WASPS 251

A superficial resemblance to stinging Hymenoptera is
probably more general and is brought about by smaller
changes in Diptera than in any other Order of insects.
A fly which gains alternate black and yellow rings on its
body is at once suggestive of an appearance presented by
many common wasps. In more extreme cases, the body
gains a constriction presenting a strong likeness to the
slender petiole of the wasp's abdomen, there are changes
in the manner of folding and sometimes in the colour of
the wings, in the buzz, in the movements of the body
(the latter being such as to suggest the power of stinging),
and (when the humble-bees are mimicked) in the acquisition
of an abundant hairy covering.

A Hemipterous insect or bug requires the most pro-
found modification in the shape of its flattened un-wasp-
like body, and in the display and characteristics of its
wings. Corresponding to these much greater initial
differences, the resemblance is rarer than in Diptera.

A Lepidopterous insect requires above all to gain
transparent wings, and this in the most striking cases
that have been studied is produced by the loose attach-
ment of the scales, so that they easily and rapidly fall oft'
and leave the wing bare except for a marginal line and
along the veins (Hemaris, Trochiliuni). In other cases
again (certain Sesiidae) the scales may remain on the wing,
but themselves become transparent. In the numerous
more perfect instances the body is banded, and may gain
a marked 'waist', while the scales upon it may be lost or
modified, so that the appearance of the hard shining body
of the model is suggested with extraordinary exactness.

The means adopted among Coleoptera, even in closely
related genera, are so curiously different that a longer
description is necessary.

The following examples are all selected from the
Longicorns. The simplest resemblance to a wasp is that
attained by the common beetles of the genus Cfytus, such
as the British C. arietis, the 'Wasp-beetle'. In these
cases there is nothing visible to represent the wings of
a wasp ; but the elytra and thorax are black banded with
yellow, there is a far more pronounced 1 waist ' than is

252 THEORIES OF MIMICRY

usual in Coleoptera, the legs are slender and wasp-like,
and are moved with wasp-like activity and jerkiness. In
spite of the apparent want of wings, the effect produced
is very considerable, and the majority of persons would
hesitate to touch the insect. This, then, is the method
adopted in the group of Clytinae ; but in various other
allied tribes, such as the Necydalinae, the Rhinotraginae,
the Esthesinae, the Callichrominae, and others, the elytra,
which form by far the largest part of the visible dorsal
surface in the Clytinae, become greatly reduced so as to
show the under wings, which, folded over the back or
expanded in flight, in either case strongly suggest the
wings of a wasp, or in some cases an ichneumon.
Furthermore, the elytra are reduced in two different
ways — in some genera to linear rudiments more or less
broadened at their bases; in others to small subquadrate
or oval structures representing the bases alone.

We thus find that wasps and allied forms are resembled
by species of many groups of insects, and the resemblance
is attained in all kinds of different ways.

The numerous mimetic resemblances to the aggressive,
abundant, and well-defended ants supply an even better
illustration. In the majority of mimics the whole body of
the mimetic form is moulded from the ancestral shape-
still exhibited by non-mimetic allies — into that which is
characteristic of an ant. In some groups this means a
large amount of alteration, in others less. In this case,
too, the resemblance extends to forms which are alto-
gether outside the Insecta ; for many small species of
spiders closely mimic ants. In the family of Attidae
alone — and such resemblances occur in other families of
spiders — George W. and Elizabeth G. Peckham state
that about a hundred ant-like species are known from
various parts of the world, and that they are 1 very much
more numerous in South America and in the Malay
Archipelago than in any other countries V viz. in the
very countries in which other examples of Mimicry are
especially abundant. The spider with its two-fold division

1 Occasional Papers of the Natural History Society of Wisconsin, vol. ii,
1892, Milwaukee ; see also a paper by the same authors in vol. i, 1889.

SPIDERS MIMICKING ANTS 253

of body is often made to assume the appearance of an
ant, with its three-fold division, by a constriction which
sometimes crosses the cephalothorax, sometimes the
abdomen. The absence of antennae in the spider is
known to be compensated in some of the species, which
have been studied in the living state, by the habit of
holding up one pair of legs, while the walking legs are
thus reduced to the ant-like number of six. Of two well-
known North-American species, Synageks picata holds up
the second pair, and Synemosyna formica the first. The
habits of seizing and dealing with prey, and the move-

Fig. 1. Fig. 2.

Fig. i.— Two North- American Attid spiders which resemble ants. A is Synageks
picata; B, Synemosyna formica. (From G. W. and F. G. Peckham,
Occasional Papers of the Nat. Hist. Soc. of Wisconsin, vol. i, 1889, pp. no &
112.

Fig. 2 ( x 3). — The young larva of Stauropus fagi seen from above and from the left
side.

merits generally are extremely un-spider-like and most
suggestive of ants ; so that the nervous and muscular
systems, as well as the body-form, have been modified.
The remarkably ant-like appearance of these two species
is shown in the adjoining Fig. 1 (A and B).

Among the Insecta, too, there are many examples of
an ant-like appearance brought about by changes of the
same kind as those mentioned above, although less marked
because the forms to be approximated are less essentially
different. Among the Lepidoptera the young larvae of
a British moth, Stauropus fagi , the ' Lobster', have often
been described as resembling ants. The likeness has

254 THEORIES OF MIMICRY

recently been analysed in much detail by Portschinski.1
This acute observer considers that the head of the larva
represents the globular abdomen of the ant, while the
head and antennae of the latter are suggested by the larval
caudal shield with its two appendages. He believes that
the disturbed larva represents an ant which has seized
and is endeavouring to carry off some object on the
branch which it is exploring. Under these circumstances
the head of the ant, with its mandibles fixed in the object,
would be held low and remain motionless, while the
abdomen would be elevated and the legs in constant
activity, moving the posterior part of the body from side
to side. Such an appearance and such movements, he
maintains, are strongly suggested by the disturbed larva
if we only identify the posterior end of the mimic with
the anterior end of the model. I have to thank Professor
W. R. Morfill for very kindly translating the memoir of
the Russian naturalist. During the summer of 1898
I had the opportunity of studying these larvae. The
young caterpillars were thought to be ants by all the
friends to whom they were shown. One lady considered
that they were ' double ants ' — an interpretation evidently
due to their disproportionate length and to the head-like
appearance of the caudal shield. Drawings of the larvae
at this stage were made by Mr. P. J. Bayzand and are
reproduced in Fig. 2 (p .253), but they fail to convey the
ant-like appearance which depends so largely on move-
ment. I did not, however, observe any attitudes which
support the details of Portschinski's interpretation, nor
did I witness the appearances which he figures.2 His
comparison of the caudal appendage with a head was, on
the other hand, entirely confirmed.

Turning to other Orders which supply examples of the
mimicry of ants, the Hemiptera have perhaps the farthest
distance to travel in the modification of their flattened
bodies. A beautiful example from East Africa, viz. that
of Myrmoplasta mira (Gerstaecker), is shown in Fig. 3.
Gerstaecker states that a single specimen of this insect

1 Coloration marquank et Taches ocelle'es, V. : St. Petersburg, 1897, p. 44.
2 1. c. p. 45, fig. 21.

BUGS, &c. MIMICKING ANTS 255

was sent from Rosako, Usaramo, August, 1888, as 'an
ant', together with two undoubted species of these Hymeno-
ptera (Polyrrhachis gagates and P oner a tar sat a). The
resemblance between the former species of ant and the
Hemipteron, Gerstaecker describes as strong enough to be
deceptive.1 It is principally brought about by the short

Fig. 3. Fig. 4.

Fig. 3 (x 3). — An ant-like East-African Ilemipterous insect, Mynnoplasta mira
(Gerst.), seen from above and from the left side. (From Gerstaecker,
Article 6, Hemiptera, p. 9, in Fr. Stuhlmann's Zool. Ergcb. 1 888-1 890,
Bd. I. Berlin, 1893.)

Fig. 4. — An ant-like N.-American beetle, Euderccs picipes, Fab., seen from above
and from the right side.

globular abdomen, united to the thorax by a constricted
portion, well seen in the side view represented in Fig. 3.

Among Coleoptera the resemblance to ants is very
common. I select as an example a little Longicorn
(Euderces picipes, Fab.), which I found very abundantly
upon the heads of Umbelliferous plants at Pine Lake, Hart-

1 Zool. Ergcb. einer Rase in Osl-Afrika, Fr. Stuhlmann, Bd. I ;
Article 6, Hemiptera, p. 9: Dietrich Reimer, Berlin, 1893.

256 THEORIES OF MIMICRY

land, Wisconsin, in July and August, 1897, when visiting
Dr. C. A. Leuthstrom. Ants were also very common on
the same flower-heads. The appearance and movements
of the beetles were extremely ant-like, the suggestion of
a stalked abdomen being conveyed by an oblique white
line crossing the elytra in a very shallow depression in
which the dark ground-colour of the insect appeared to
be of a more intense black than elsewhere. The increased
darkness was in reality due to the shadow in the depres-
sion combined with the effect of a difference in the texture
of the surface. This combination of characters produced
a strong superficial resemblance between the elytra of the
beetle and the abdomen and thorax of the ant, while the
head of the latter was represented by the beetles head
and thorax together. These resemblances are indicated
in Fig. 4 (p. 255) ; but the living insect is required in order
fully to appreciate them.

In all the cases alluded to above, the resemblance is
attained by a modification in the form of body and limbs,
accompanied by changes in those more deep-seated
structures which affect the habits and movements.

There are, however, other very different means by
which the same end is attained. One of the most inter-
esting of these is the case of a Locustid (Phaneropterides),
Myrmecophana fallax from the Sudan, described by
Brunner von Wattenwyl.1 Brunner's two figures are
reproduced as Fig. 5 on p. 258. Upon the stout body
of this insect the slender- waisted form of an ant is repre-
sented in black pigment, the remainder of the body being
light in colour and presumably invisible against a similar
background. Of the habits of the insect nothing is known,
but the method is of great interest, being so entirely
different from that by which mimetic likeness is usually
effected. In a more recent work 2 Brunner von Watten-
wyl again alludes to this example, and states that the form
of the species ' leads to the conclusion that it lives on the
ground viz. in the position which gives a meaning to the

1 Verhandl. der k.-k. zool.-bolan. Ges. in Wien, 1883, p. 247.

2 Observations on the Coioration 0/ Insects, English translation by E. J.
Blcs, Leipsic, 1897, p. 11.

LOCUSTIDS MIMICKING ANTS 257

resemblance. In spite of this he asks, 1 Is this imitation
an accidental freak of nature ? ' If Myrmecopkana were
the only example of such resemblance the question might
fairly be asked, but in view of the numerous other equally
close resemblances to ants, produced in various ways, it
is quite unnecessary. The suggestion of an 'accidental
freak ' can never explain such close likeness, in appear-
ance, in movements and habits (so far as they are known),
in locality — a likeness, furthermore, to particular insects
in the environment, members of a specially successful and
aggressive group — a likeness not produced in one way but
in many different ways. To suggest an ' accidental freak '
as the explanation shows an amazing credulity, only to be
explained by the bias which is ready to accept any inter-
pretation except that afforded by the theory of Natural
Selection.1

1 Several examples of the kind are now known, although some doubt
has been thrown upon the details of Brunner s interpretation in the case of
Myrmecopkana itself, an insect of which the habits were entirely unknown.
Guy A. K. Marshall has captured a Locustid of the same genus in
company with ants upon a small bushy vetch, near Salisbury, Rhodesia
(Trans. Ent. Soc. Lond., 1902, p. 535, Plate xix, fig. 59). The un-ant-like
parts of the body were green and thus invisible against the leaves ; but in
the dead specimen they have faded to a pale yellowish tint much like that
described by Brunner on the corresponding parts of M.fallax. In fact,
Malcolm Burr is inclined to think that the Rhodesian example is M.fallax
and that Brunner was misled by a faded specimen. But even if this
particular example is to be explained in a slightly different manner —
obliteration by harmony with a green background instead of a glaring one,
several other instances have now come to light, and these are to be
explained precisely in the manner suggested by Brunner. Thus Colonel
J. W. Yerbury has shown me an Asilid fly — Promachus iopterus (Wied.),
from Para, with white patches on the sides of the basal abdominal
segments, leaving the appearance of a slender black stalk like that of so
many Hymenoptera. Again, R. Shelford describes four Bornean
Longxorn beetles of the genera Scytasis and Oberea as ' marked with a
large white patch of pubescence on the sides of the first and second
abdominal segments, which patches, when the beetle is seen in profile,
give an impression of a wasp-like waist, from the posterior end of which
the abdomen appears gradually to swell in size' (Proc. Zool. Soc. Lond.,
1902, vol. ii, p. 238, PI. xix, figs. 13-15). The most interesting case,
however, is that of a common British Reduviid bug, Nobis lativenfris, which
in its immature stages bears an ant-like appearance produced exactly in
the manner described by Brunner. It is remarkable that so interesting a
form of mimicry in such a common insect should have been undescribed

POULTON S

258 THEORIES OF MIMICRY

Another and equally interesting method is adopted by
certain tropical American Rhynchota Homoptera belong-
ing to the family Membracidae. In this remarkable group
the dorsal region of the first thoracic segment (the pro-
notum) is of enormous size, extending upwards and
backwards so as completely to cover the insect with the
exception of the head, limbs, and wings. What Natural

Fig. 6.

Fig. 5.

FlG. 5. — A Locustid from the Sudan, Myrmecophana fallax (Brunner), seen from
above and from the left side. On this insect the appearance of an ant is
represented in black pigment, all other parts being light in colour and
presumably concealed. (From Brunner von Wattenwyl, Verhandl. d. k.-k.
zool.-botan, Ges. in Wien, Bd. xxxiii, 1883, pl« xv> figs- 1 a 8c 1 b.)

Fig. 6. — A Central American Membracid (Rhynchota Homoptera) in which the
prothoracic shield resembles an ant. Thus the body of the insect which is
not like an ant is concealed by an ant-like shield. The species is Heteronotus
trinodosus as seen from above and the left side. The upper of the two
figures seen from the side represents a female, the two other figures, males.
(From W. W. Fowler, Biol. Centr.-Am., Rynch. Homopt., vol. ii, pi. 6, figs.
16, 16 a, & 17.)

Selection effects in the general body-form of other insects
must here be effected, if it is to be of any value, in the
shield, which is seen, and not in the body, which is
concealed. This change has been brought about, and
certain species of the group have their un-ant-like bodies
concealed under an ant-like shield. In other species the

until so late as 1899 (David Sharp, F.R.S., Insec/a, vol. ii, Lond., 1899,
PP. 556> 557> Fig- 269). — E. B. P., Oct. 1906.

MEMBRACIDS MIMICKING ANTS 259

prothoracic shield is modified into a resemblance to various
objects, such as seeds, thorns, &c. — an excellent example
of the parallelism between Mimetic and Protective Resem-
blance pointed out in Section 3, p. 225. The effects pro-
duced in the shield are at least as exact and detailed as
those which in other cases are wrought in the form of the
whole body. Thus, as Mr. W. F. H. Blandford has pointed
out to me, a peculiar characteristic of certain tropical
American ants (viz. the bead-like dilatation in the stalk
of the abdomen) is reproduced in the shield of the Mem-
bracid. This is well seen in Heteronotus Irinodosus, shown
in Fig. 6, copied from Canon W. W. Fowlers Monograph
of the group in the Biologia Centrali- Americana.

Finally, in the same group of Membracidae we meet

Fig. 7. — About three times the natural size. On the right is represented an immature
Membracid {Rhynchota Homopterd) from British Guiana, which resembles
an ant together with the leaf it is carrying. The latter is seen on the left, and
represents the species Atta (Oecodomd) cephalotes from the same locality. The
English leaf shown in the drawing is unlike the semi-circular fragments gnawed
by the ant. (From Poulton, Proc. Zool. Soc. Load., 189 1 , pi. xxxvi, fig. 2.)

with another example which is also incapable of inter-
pretation by any theory as yet brought forward except
Natural Selection. An immature form of Membracid,
with the prothoracic shield not yet formed, found by
W. L. Sclater in British Guiana, strongly resembles one
of the leaf-carrying ants which are so common in that
part of the world ; but the resemblance includes the leaf
as well as the ant ! The dorsal region of the Membracid
is flat and compressed, so that it is as thin as a leaf ; its
border (the dorsal surface, which forms a sharp edge) is
irregularly jagged as if gnawed, and during life it is green
in colour. Beneath this leaf-like expanse the brown head

s 2

26o THEORIES OF MIMICRY

and legs of the insect are visible just as, in the case of
the ant, they appear beneath the piece of leaf which is
carried vertically between the mandibles and thrown over
the back.1 The appearance of the Membracid and leaf-
carrying ant is shown in Fig. 7 (p. 259). It is probable
that certain species of the Orthopterous genus Tettix
(Acridtidae) also resemble ants carrying leaves.

It would of course be ridiculous to ascribe this last resem-
blance to any direct external forces connected with locality,
or to any internal forces, independently producing a like
result, and, as the resemblance appears at an immature
stage, it is equally impossible to invoke the aid of Sexual
Selection.

Natural Selection remains as the only feasible inter-
pretation.

Even more striking than this remarkable example is
the contemplation of all these various methods and their
relation to each other. The means by which the resem-
blance to ants is brought about are diverse, the end —
the resemblance itself — is uniform. Furthermore, the
likeness is almost always detailed and remarkable, how-
ever it is attained, while the methods made use of differ
absolutely. Such a result, it would seem, is the most
complete proof of the operation of Natural Selection that
can be attained, short of the actual demonstration of its
action by observation and statistics. If this argument be
confirmed by a study and comparison of the foregoing
Figs. 1 to 7, I venture to think that it will meet with
general acceptance.

When one insect resembles an ant by the superficial
alteration of its whole body-form, another by the modifi-
cation of a shield-like structure which conceals its unaltered
body, another by having the shape of an ant painted, as
it were, in black pigment upon its body while all other
parts are rendered invisible ; another by a further modifi-
cation of the body, so that it represents not an ant only,
but the object which the ant is almost always carrying, —
when the effect of all these results is heightened by appro-
priate habits and movements, we are compelled to believe
1 Proc. Zool. Soc. Lond., 1891, p. 462.

DIVERSE CAUSES OF RESEMBLANCE 261

that there is something advantageous in the resemblance
to an ant, and that Natural Selection has been at work.
The phenomena do not merelydisprove all other suggested
causes of change ; they constitute the most powerful
indirect proof of the operation of Natural Selection.

1 2. The Resemblances within the Limits of the Order are
also produced in the most Diverse Ways.

Illogical as I believe the position to be, it is quite
possible that many observers may concede the force of
the argument concluded above, and yet continue to hold
that the resemblances within the Order are produced by
External or perhaps by Internal Causes. It can, how-
ever, be shown that the very same conditions which were
true in the wider group are also found in the narrower.
Even within the Order itself resemblances are produced
in very diverse ways, although minute examination is
sometimes necessary before the essential difference which
separates them can be revealed.

Certain Longicorn beetles resemble weevils, the Curcu-
lionidae being, so it is believed, specially defended by
their extremely hard chitinous covering. The weevils
closely resembled by such Longicorns as Doliops cur ac-
tio noides and D.geomelrica have short antennae ending in
a knob. The antennae of the Doliops are nearly three
times as long ; the resemblance to the weevil being
produced by a dilatation of the third joint, which repre-
sents the knob, while all the joints beyond are of such
excessive fineness that they are almost invisible. The
strong resemblance of the Longicorn Estigmenida varia-
bilis to Estigmena chinensis, belonging to the Hispidae
(Phytophaga), is brought about in a similar manner, as
was pointed out by C. J. Gahan. In this case about one-
third of the length of the Longicorns antenna is concealed
by its extreme fineness, while the apparent terminal
thickening is produced by hairs at the end of the stouter
basal section.

In these examples, kindly shown me by Mr. Gahan,
neither the theory of External nor that of Internal Causes
is of any avail. It is impossible to believe that the

262 THEORIES OF MIMICRY

resemblance is a direct effect of climatic or other forces
connected with locality, when the results are in reality so
utterly different and yet superficially so entirely alike.
It is obvious that the methods by which the appearance
of a terminal thickening is produced in the two mimics
are as essentially different as are those by which the
appearance of short antennae is produced in the model
on the one hand, and its two mimics on the other. The
fact which requires explanation is the extraordinary like-
ness in spite of the essential difference, and this, when it
is repeated again and again, cannot be interpreted by any
theory unless based upon the principle of selection.

Many other examples of the same kind could easily be
brought forward : in fact, it maybe admitted as a general
principle that in Protective Mimicry and Common Warn-
ing Colours the resemblance is never attained by precisely
similar methods, and generally by methods which are
extremely unlike. I propose, in concluding this Section,
to discuss a few examples from the Lepidoptera, inasmuch
as the resemblances in question have been chiefly studied
in this group, and because an explanation based on the
theory of External or on that of Internal Causes has been
sought more often and pressed more strongly in the
Mimetic Lepidoptera than in any other Order.

The Pierinae are specially liable to take on these
Resemblances. In tropical America they chiefly resemble
the Ithomiinae, Heliconiuae, and Papilioninae, affording
some of the best and earliest recorded examples of
Mimicry (although Dr. F. A. Dixey has now shown that
they are more probably to be interpreted as Common
Warning Colours). The chemical nature of the wing-
pigments of the Pierinae has recently formed the subject
of an interesting paper by F. Gowland Hopkins.1 The
author shows that the white pigment so common in the
group is an impure uric acid probably uncombined, that
the yellow and orange pigment is a derivative of uric acid
to which he gives the name 'lepidotic acid', while a much
rarer red pigment, less fully investigated, is probably of

1 Proc. Roy. Sor., Ivii, 1894, p. 5, and Phil. Trans., 1895, B. p. 661.

PIGMENTS OF MODELS AND MIMICS 263

a closely similar constitution. These three pigments,
with black, which is apparently intimately associated with
the cuticle of the scales, with a pigment placed between
the two laminae of the wing and with superadded optical
effects due to structure, account for the whole of the
colouring of Pierine butterflies. No pigment of similar
constitution to the Pierine white, yellow, and red, was
found by Mr. Hopkins in any other butterfly — not even
in the allied Papilioninae. The Pierine butterflies which
resemble the Ithomiinae or other butterflies were found
by Mr. Hopkins to achieve this end, not by gaining the
true pigments of their models, but by means of the cha-
racteristic Pierine pigments. The bands of warm red-
brown, the spots of white and yellow, which so closely
resemble the same tints in the Ithomiinae, are in reality
caused by pigments of an entirely different nature, — the
resemblance, even between the pigments themselves, is
wholly superficial.

The argument that the resemblances we are discussing
are a common result of common forces is simply an
improbable assumption. It has been proved again and
again that the results are not common, the resemblance
merely deceptive. And now this has even been shown
for the colours themselves, in some of the best known
and most striking examples of Mimicry.

The last example of similarity in appearance produced
through diversity of method is one which occurred to me
a few years ago when lecturing on Mimicry in the Hope
Department at Oxford. It was worked out in detail
during the summer of 1897, and the general results were
communicated to Section D of the British Association at
Toronto.1

Although the Lepidoptera are characterized as an Order
by the clothing of scales upon the wings, examples are
very frequent in which this covering has been in part,
or almost wholly, lost. By comparison with kindred
unmodified forms, as well as by microscopic examination
of the transparent areas themselves, it is possible to show

1 August 23, 1897. A brief abstract is printed in the Report of the
Meeting, pp. 692-4.

264 THEORIES OF MIMICRY

that this loss is recent, and to trace the steps by which it
has been reached from a condition in which normal scales
were present.

In the very large convergent group of tropical American
Lepidoptera which has sprung up round the best known
species of the Ithomiine genera Methona and Thyridia,
transparency of a large part of the wings is a charac-
teristic feature. Throughout the group the ground-colour
of the wings is transparent, with a black border which
generally passes inwards as two transverse bands in the
fore-wing, separating the transparent part into three
areas, and as one band in the hind-wing, separating it
into two areas. The group consists of Ithomiinae (Neo-
tropinae) of many genera, of Danainae, of Pierinae, and
of moths of the genera Anthomyza and Hyelosia, belong-
ing to the Pericopidae (Hypsidae), and the widely separated
genus Castnia (Castnzidae).

Under the theory of External Causes we should expect
that the transparency would be attained in a similar
manner throughout, by the reduction of scales to hairs,
by the complete loss of scales, or by some other uniform
method. Under the theory of Natural Selection we
should expect the methods would be different in the
different groups. There are many ways in which trans-
parency can be attained, and we should expect that one
group would submit one set of variations making towards
the resemblance, another a different set, to the operation
of Natural Selection. It will be shown that this prediction
is abundantly justified.

Microscopic examination of the Ithomiinae (Ncolro-
pinae) showed that the scales on the wings are of two
kinds, broad and narrow, which alternate more or less
regularly. In the transparent parts both kinds of scale
can still be detected, the narrow being frequently
reduced to fine simple hairs, and, in the most extreme
cases, the broad scales being reduced to Y"snaPec^
hairs.

The two commonest species of the whole group,
probably forming the centre towards which the others
have converged, are the Ithomiine butterflies Methona

DIVERSE CAUSES OF TRANSPARENCY 265

confusa and Thyridia psidii. These species, belonging
to very different genera, afford a good example of the
closeness of resemblance which may be attained by
Common Warning Colours. The two forms are
constantly found intermixed in collections, and super-
ficially are almost exactly alike. Nevertheless, a study
of the transparent part of the wing under the microscope
reveals the fact that the degeneration of the scales has
reached a very different level in the two species. The
broad scales, reduced to small bifid structures, exhibit a
distinctly different form in the two species ; while the
narrow scales are reduced to long extremely fine hairs
in the Methona, and to much broader ones in the
Thyridia. The comparison between the almost identi-
cal appearance of the two insects to the naked eye,
and their real differences when seen by means of
the microscope, affords another good example of the
principle which has been already so abundantly illus-
trated— that when a close superficial resemblance has
been attained no further similarity in the details of
structure is produced. This is apparent enough even in
these two genera belonging to the same sub-family. It
is of course illustrated in a far more striking manner
when the affinity is more remote.

We now pass to the Danainae which fall into the
group. This Sub-Family supplies it with two species,
both belonging to the genus I tuna. The Ithomiinae
were formerly classed with the Danainae, and in any
case form the sub-family which stands next to them.
But, nevertheless, transparency is attained in an entirely
different manner, the scales being neither greatly
lessened in size nor much altered in appearance. It
is the great reduction in numbers which is here the
cause of the transparency. The scales retain their
dark pigment and produce the effect of a grey dusting
over the transparent areas.

Finally, there is a single species belonging to the
distant Family Papilionidae and Sub-Family Picrinae—
Dismorphia orise. In certain parts of Ecuador the
black borders and bands of the Methona model, distin-

266

THEORIES OF MIMICRY

guished as M. psainathe, Godm. and Salv., are much
narrower than in the type form, and we find that
the Dismorphia from the same locality has followed in
the same direction. Microscopic examination reveals
that in Dismorphia the transparency is attained, unlike
Ituna, by a reduction in size of the scales ; while, unlike
the Ithomiinae, the normal shape and outline are pre-
served almost unchanged.

It is a little remarkable that in this large, dominant,
and widely distributed group, no member of the
Heliconinae has yet been shown to find a place.

We now pass to the Heterocerous members of the
group. Microscopic examination proves that the moths
become transparent in two ways, which differ entirely
from each other, and from any of the methods already
described in the butterflies. The scales of Castnia are
not reduced in size, but they have lost their pigment
and are transparent ; they are furthermore set up on
edge so that the light freely passes between them. The
scales towards the centre of the transparent patches are
much more upright than those of the margin, where they
are transitional into the opaque border. The arrange-
ment in Hyelosia is closely similar to that of Castnia,
save that the scales are much reduced in number. The
scales of Anthomyza, on the other hand, are normal in
arrangement as well as in size. They lie flat on the
wing-membrane with the usual overlap, but are so
devoid of pigment that the light passes through them.
Although transparent, they retain a more or less faint
yellow or greenish-yellow tinge, but this is also to be
noticed in the transparent part of the wings of Methona,
Dismorphia, &c.

The comparison of these details is almost a demon-
stration of the operation of the Darwinian theory. We
cannot conceive of Natural Selection acting other than
along some such lines as those which have here been
shown to exist ; for it is impossible to believe that very
different species with very different natures would
present anything but very different variations for its
action. On the other hand, we cannot conceive of any

MIMICRY AND NATURAL SELECTION 267

theory, not dependent upon the principle of Selection,
which could explain such extraordinary superficial re-
semblances among numbers of species by methods which
are entirely unlike in their details.

13. The supposed Dii'ect Effect of Local Forces implies
the Hereditary Transmission of Acquired Characters.

Finally, the hypothesis which is more commonly than
any other substituted for Natural Selection, has the
further disadvantage that it implies the unproved im-
probable hypothesis of the hereditary transmission of
acquired characters.

A discussion of this latter hypothesis cannot be at-
tempted here.1 It will be sufficient to observe that after
years of search no particle of evidence in its favour,
which can stand the test of investigation, has been forth-
coming.

14. General Conclusions : Natttral Selection as the

Cause of Mimetic Resemblance and Common
Warning Colours.

I think it is not too much to claim that, even if the
theories which have been proposed as substitutes for
Natural Selection have not been destroyed in single
Sections of this essay, — and I confidently believe that
they have been thus destroyed over and over again, —
their most convinced supporter will admit that they
must yield to the accumulated pressure of all the argu-
ments here brought forward.

The resemblances of Mimicry and Common Warning
Colours have certain salient features in common, certain
peculiarities which are apt to manifest themselves re-
peatedly ; they also bear certain general relationships to
other resemblances in organic nature. In this paper
I have attempted to set down all the general state-
ments which can be made as to the phenomena under
discussion. These general statements represent an

v 1 The hypothesis in question has been discussed in Essays iii and v,-
pages 95 and 139.

268

THEORIES OF MIMICRY

enormous number of facts observed in many very
different parts of the world. I believe that the generali-
zations will be admitted to be sound and to be well
warranted by the facts. Under any theory which is not
based upon selection, the whole of the facts on which
the generalizations rest become mere coincidences and
receive no explanation of any kind. Under Natural
Selection this vast body of facts becomes at once in-
telligible. Here the accumulated facts of the most
diverse kind, which receive an intelligible explanation
by the theory in question, yield a firm support to the
theory. There are many theories which are held upon
indirect evidence of precisely the same nature. We
believe in evolution, not because we see it taking place,
but because of the immense number of observed facts
which it renders intelligible.

In the case of Natural Selection in relation to Mimicry
and Common Warning Colours it is to be confidently
hoped that direct evidence may yet be added ; indeed,
a considerable amount is even now forthcoming. Pro-
fessor Lloyd Morgan's work 1 upon the activities and
instincts of young birds of many species, proves that
their education is actually of the kind which is pre-
supposed in the theories of H. W. Bates and Fritz
Mtiller. He shows that they have no instinctive know-
ledge of things which are good for food, but that they exam-
ine and test everything. On the other hand, they have
excellent memories, and retain a firm impression of the
appearance of objects which have given them an un-
pleasant experience. Furthermore, there was evidence
that they are influenced in their behaviour towards
other objects resembling the one which has proved ob-
jectionable to them. As to the aggressive Hymeno-
ptera, the evidence of their special methods of defence
is obvious to every one. With regard to specially pro-
tected groups of butterflies there is a large amount of
evidence from observation and experiment, but more is
to be desired. For positive results I may refer to Guy

1 Habit and Instinct, London, 1896.

FINN'S EXPERIMENTS ON BIRDS 269

A. K. Marshall's memoir already often quoted,1 and to
Frank Finn's interesting and important set of papers
especially devoted to this question.2 After a long series
of experiments begun and conducted with a perfectly
open mind, upon Indian insect-eating vertebrates, Mr.
Finn supports the theories based upon Natural Selection
in the following words : 3 —

' I conclude from these experiments —

' 1. That there is a general appetite for butterflies
among insectivorous birds, even though they are rarely
seen when wild to attack them.

' 2. That many, probably most species, dislike, if not
intensely, at any rate in comparison with other butter-
flies, the " warningly-coloured " Danaincey Acraa violce,
Delias eucharis, and Papilio aristolochice ; of these the last
being the most distasteful, and the Danaincz the least so.

* 3. That the mimics of these are at any rate rela-
tively palateable, and that the mimicry is commonly
effectual under natural conditions.

* 4. That each bird has to separately acquire its ex-
perience, and well remembers what it has learned.

4 That therefore on the whole, the theory of Wallace
and Bates is supported by the facts detailed in this and
my former papers, so far as they deal with Birds (and
with the one Mammal used). Professor Poulton's sug-
gestion that animals may be forced by hunger to eat
unpalateable forms is also more than confirmed, as the
unpalateable forms were commonly eaten without the
stimulus of actual hunger — generally, also, I may add,
without signs of dislike.'

Mr. Finn concludes with some valuable suggestions as
to the conduct of future experiments.

The chief objection that has been raised against the
theories of Bates and Fritz Muiler, is the want of evi-
dence that birds are in any important degree the enemies
of butterflies. Many excellent observers have rarely

1 Trans. Ent. Soc. Lond., 1902, p. 287.

2 Journal, Asiatic Society 0/ Bengal, lxiv, pt. ii, 1895, p. 344 ; lxv, pt ii,
1896, p. 42 ; lxvi, pt. ii, 1897, p. 528, and p. 613.

3 Ibtd.} lxvi, pt. ii, 1897, pp. 667-8.

27o THEORIES OF MIMICRY

seen butterflies attacked by birds. On the other hand,
the Mullerian theory presupposes that only young birds
test the palatability of a few members of each convergent
group in their locality, and henceforward, except when
driven by hunger, avoid all the members, so that the
recent tendency to explain so many of these resemblances
on Mullerian rather than on Batesian lines is in harmony
with the conclusion that the members of such groups are
not greatly attacked by adult birds.

As regards butterflies which do not exhibit these
resemblances, I may point out that it is impossible to
exhaust the details of the struggle for existence, even as
regards a single species, in the intervals of the time
devoted to collecting. Such an investigation would
demand the whole time of a first-rate observer, and, so
far as I am aware, the inquiry has never been ap-
proached in so thorough a manner. Even if collectors
would pay attention to the worst specimens instead of
the best, some evidence of the nature and amount of
attack would be forthcoming. During the visit of the
British Association to Canada in 1897 I made a point
of capturing butterflies which had evidently been pecked
by birds. In this way, although I did not witness a
single attack, I obtained indirect proof that butterflies
are not nearly so immune as has been asserted. Similar
observations were made at a much earlier date by Fritz
Muller.1

The review of the whole subject during the past
forty-five years increases our confidence in the theories
of Bates and Fritz Muller, while it disposes of all
alternative hypotheses. Even more than this, — it will,
I believe, be claimed by all who take a broad view over
the whole field of evidence, that the explanation of these
deeply interesting facts, which form so fascinating and
important a department of natural history in the tropics,
is one of the most notable triumphs ever won by the
great theory of Natural Selection.

1 See Trans. Ent. Soc. Lond.y 1902, pp. 353-75, where a large body
of evidence, direct as well as indirect, is published. The direct evidence
is reprinted, p. 282, as an Appendix to the following Essay.

IX

MIMICRY AND NATURAL SELECTION

The English Address to the Fifth International Zoological Congress
held at Berlin. Read at the 1 Allgemeine Sitzung August 15, 1901.
Reprinted from Verhandl. d. V. Internal. Zool. Congr. z. Berlin, Jena,
1902, p. 171.

Revised: an Appendix added.

I feel it to be a great honour and pleasure to be called
on to deliver the address on behalf of the English-speaking
nations to the Fifth International Zoological Congress,
at Berlin. At the same time I am sensible of the great
difficulty of the task, in the attempt to say anything ade-
quate on so wide a subject in the narrow compass of
five and forty minutes.

In attempting to arrive at a decision upon the origin
and cause of Mimetic Resemblance we have no direct
evidence to assist us. We are driven to base our opinion
upon the same ground as that upon which the belief in
the theory of Gravitation is founded. This theory finds
acceptance, not because of direct evidence in its favour,
but because the facts of the Cosmos, so far as we know
them, are consistent with the theory and none of them
inconsistent with it.

It is necessary therefore first to give a brief account of
the theories which have been advanced to explain the
origin of Mimicry, secondly to inquire how far each one
of them is consistent with the main facts of Mimicry.

1. The Theory of Natural Selection as an explanation,
assumes that these resemblances have been produced
because they are or have been useful in the struggle for
existence. There has been, according to this interpreta-
tion, a greater average survival in successive generations
of the forms in which these useful likenesses were more

272 MIMICRY AND NATURAL SELECTION

strongly developed as compared with those in which they
were less strongly developed, and thus in process of time
a very high degree of resemblance has been attained.

2. The Theory of External Causes assumes that
Mimicry has been produced by the direct action upon the
organism of some one or more of the various influences
which exist in the locality, such as food, moisture, dryness,
heat, cold, &c.

3. The Theory of Internal Causes assumes that Mimetic
Resemblances are due to the independent arrival of
different species at the same evolutionary stage, as regards
the characters in which such resemblances are manifest.

4. The Theory of Sexual Selection has occasionally
been invoked to account for Mimicry, the assumption
being that the selection of mates has been influenced by
the colours and patterns of other species living in the
same country.

The last-mentioned theory is held by comparatively
few naturalists, although it was deemed to be worthy of
consideration by Charles Darwin and Fritz Muller.1 The
theory of External Causes is probably more commonly
received as an explanation than any of the others except
Natural Selection itself.

I now propose to bring before you several examples,2
setting forth the main aspects of Mimetic Resemblance,
and to inquire how far each of them is consistent with
these four theories.

The too-exclusive study of Mimicry in Lepidoptera
(butterflies and moths) alone is probably responsible for
a common belief in the theory of External Causes. Thus
when we contemplate a group of many species of
Ithomiine, Danaine, Nymphaline, Heliconine, Erycinid,
and Pierine butterflies from British Guiana and Surinam,
and find that all tend to develop dark hind-wings, it is
plausible to suggest as an interpretation that we are

1 See a letter from Charles Darwin describing Fritz Miiller's thoughts
on this subject. Charles Darwin and the Theory of Natural Selection.
Poulton, London, 1896, p. 202.

2 These examples were illustrated by projections of three-colour illus-
trations prepared by Mr. Sanger- Shepherd from the actual specimens in
the Hope Department of the Oxford University Museum.

MIMETIC S. AMERICAN BUTTERFLIES 273

witnessing the common effect of local influences. But
this and every other explanation, except Natural Selection,
leave as a mere coincidence the fact that the first-named
three groups contribute the vast majority of the species,
and undoubtedly provide the models for the others.
Under Natural Selection the interpretation is easy ; the
groups in question are specially defended by unpalatable
qualities, and it is to their advantage to warn their enemies
by a common advertisement. The Nymphaline, Erycinid,
and Pierine species may also be unpalatable and fall into
the same Miillerian (Synaposematic) 1 combination, or
they may be edible and gain advantage by living on the
reputation of the three nauseous sub-families (Batesian
Mimicry or Pseudaposematic Resemblance). Taking all
available facts into consideration the former is the more
probable view. Not in Guiana alone, but wherever we
may travel in tropical America, groups of species of the
three Sub-Families tend to resemble each other and to
act as models for butterflies of other Families and Sub-
Families. In Venezuela, for example, they are reddish-
brown black-barred insects as in Guiana, but without the
tendency towards preponderant black in the hind-wings ;
in South Eastern Brazil they all possess an especially
light stripe, frequently bright yellow, along the hind-
wings, and a light spot, frequently white, at the apex of
the fore-wings ; at Ega, on the Upper Amazon, they all
gain a rich chestnut-brown ground colour ; still further
west, the brown ground colour is much less dark than at
Ega, and of a very characteristic shade. Why should
these three Sub-Families be so conspicuously subject to
the common influence of locality? Why should they more
than all other butterflies arrive independently at the same
evolutionary stage as regards visible characters ? Why
should Sexual Selection operate so exclusively upon them
in the direction of producing a common likeness ? None
of these questions can be answered. The facts remain
mere coincidences under all theories except Natural
Selection. In other words, Natural Selection is the only
satisfactory interpretation.

1 Proc. Ent. Soc. Land., 1897, p. xxix, n.

POULTON T

274 MIMICRY AND NATURAL SELECTION

Mimicry among Rhopalocera (butterflies) is much less
common as we pass into northern regions, but there is
one excellent example in temperate North America which
serves to show how superficial an interpretation is that
offered by the theory of External Causes, and how com-
pletely it breaks down when examined with a little care.
With comparatively few exceptions the insect fauna of
North America is that of the great northern circumpolar
land-belt. These exceptions are intruders from the
tropical South, and among them is the large Danaine
butterfly Anosia plexippus which now ranges over the
United States and a large part of Canada. In tropical
America closelysimilar representative species, sub-species,
or forms still persist. This abundant Danaine butterfly
affords the model which is closely resembled by an
indigenous Nymphaline butterfly which we should place
in the genus Limenitis, although some American natura-
lists prefer to put the Nearctic species in a separate genus,
Basilar chia. There are also other mimics among the
species of the North American Limenitis (Basilar chia\
but two of them are non-mimetic and enable us to
reconstruct the appearance of their close ally before the
intrusion of the great Danaine model. In the New
World the genus Limeniiis is confined to the Nearctic
Region with the exception of a single species, a form of
the mimetic L. astyanax (Fabr.), which just enters the
borders of Mexico. If butterfly colours and patterns are
the expression of the direct influences of the environment,
then it is clear that the indigenous non-mimetic species of
Limenitis (Basilar chia) are an expression of Nearctic
(temperate North American) conditions, and according to
the theory of External Causes, the invader from the
South should have come to resemble them, instead of
drawing an ancient Nearctic species far away from its
ancestral colours and patterns into a close superficial
likeness to itself. The fact that certain species of a
single genus should thus be entirely mimetic, while others
are entirely non-mimetic and preserve the ancestral
appearance, has been sometimes urged, for example by the
late Professor J. O. Westwood, against the interpretation

MIMETIC AND NON-MIMETIC SPECIES 275

afforded by the theory of Natural Selection. It is a real
difficulty to the theories of External and Internal Causes ;
for, as regards the first, we should expect the closely
related species of a genus to react similarly to the local
conditions, rather than that certain of them should react
quite differently from the others but quite similarly to
the species of distantly related Sub- Families ; and, as
regards the second, we should expect such species to
reach nearly the same evolutionary stage together, rather
than that some should reach one stage and others another
entirely different one, but the same as that reached by
certain species of remote affinity. With Natural Selection
for our explanation such differences are at once intelligible.
The variation which formed the foundation for selection
to build upon may well have been present in certain
species of a genus but not in others ; or slight differences
in life-history or the methods of adaptation, or the attacks
of enemies, may have rendered Mimicry advantageous for
this species but not for that.

When we pass from Mimicry among butterflies to
Mimicry between butterflies and moths, the difficulties
encountered by all theories except Natural Selection
become greater because of the wider structural difference
between model and mimic. To take an example, certain
species of day-flying Chalcosid moths of Borneo mimic
Danaine butterflies while others mimic Pierinae : another
mimics an Agaristid moth.1 Why should part of the
Heteroceran group be acted on by external conditions so
as to cause a superficial resemblance to Danainae, the
others so as to cause a resemblance to Pierinae} Why
out of the same closely related set of species should some
reach the evolutional stage of Danainae, the others of
Pierinae ? Why should the models happen to differ from
butterflies in general in their slow flight and conspicuous
appearance, in the similarity of the patterns on the under
side of the wings to those on the upper side, in the fact
that they are distasteful to the generality of insect-eating

1 See the beautiful plate (xxi) illustrating these resemblances in
R. Shelford's paper in Proc. Zool. Soc. Lortd., 1902 : also pp. 256, 257.
and 259, 260 of the text.

T 2

276 MIMICRY AND NATURAL SELECTION

animals ? Why should the mimics happen to belong to
a day-flying group, although moths are as a rule nocturnal?
All these questions receive an obvious answer when the
theory of Natural Selection is adopted as the explanation
of Mimicry : they cannot be answered by any other
existing theory. Under any other theory the facts are
gratuitous, devoid of meaning.

When the model belongs to one insect Order and the
mimic to another, difficulties of interpretation, except on
the theory of Natural Selection, become even greater.
Why should the models in the vast majority of cases
happen to belong to the Hymenoptera and to possess
stings or other special modes of defence ? Why under
the totally different conditions of Borneo and South Africa
should a local Xylocopid bee be mimicked by a local
Asilid fly (Hyperechid) ? 1 Many moths come to resemble
transparent-winged Hymenoptera by losing, probably
during their first flight, scales which were present on their
wings when they emerged from the pupa. Is any one bold
enough to maintain that a resemblance thus caused is due
to External or Internal Causes or to Sexual Selection ?

The assumption that local influences act uniformly on
different species is by no means justified except in the
case of species with similar habits and life-histories : Mr.
Guy A. K. Marshall has sent me a wonderful group of
reddish brown or ochreous insects with the posterior part
of the visible dorsal surface black. It contains many
species of the Lycid models, and also Coleoptera belonging
to the Telephoridae, Melyridae, Phytophaga, Cantharidae,
and Longicorns, several species of aculeate Hymenoptera,
a few Hemipterous insects, two species of moths and one
of Diptera.2 We have here all kinds of habits and all
kinds of life-histories, larvae living in the open, larvae
burrowing in plant-stems, carnivorous larvae, leaf-eating
larvae, larvae with special food stored in cells. It is

1 R. Shelford in Proc. Zool. Soc. Lond., 1902, pp. 261, 262 ; plate xxii,
figs. 1, 2. G. A. K. Marshall in Trans. En/. Soc. Zona1., 1902, pp. 533,
534; plate xxii, figs. 19, 20.

2 G. A. K. Marshall in Trans. Ent. Soc. Zona1., 1902, pp. 515-18;
plate xviii.

UNIFORMITY IN NAUSEOUS GROUPS 277

simply childish to appeal vaguely to the direct action of
like forces as the explanation of the remarkable resem-
blance which runs through the group. The environing
forces are not like but extremely unlike, because of the
very diverse conditions under which various members of
the group live and grow.

All the butterfly Sub-Families which furnish the chief
models for Mimicry are remarkable for the uniformity of
colour and pattern throughout groups of species in each
of the countries they inhabit. These Sub-Families are
the Danainae, found all over the tropics, and the allied
Ithomiinae (Neoh opinae) of tropical America, the Acrac-
inae, almost confined to Africa and tropical America, and
the allied Heliconinae, practically restricted to the latter.
A very strong family likeness runs through long series of
species, as any one may see by a glance at the successive
drawers of a collection of African Acraeinae or Oriental
Eup/oeini and comparing them with an equal number of
species in any Sub-Family which does not provide nume-
rous models for Mimicry. Compare, for instance, our
European Vanessidae with sets of local species belonging
to any of the four above-named Sub- Families. The species
of Vanessa do indeed possess homologous markings,1 and
many of the gaps between them can be filled up, but we
have to hunt the world in order to do it, and even then
we only obtain a partial continuity between extreme
differences, whereas in the specially protected Sub-
Families there is not only continuity but uniformity in
large groups of species. Mr. A. G. Mayer 2 has found
that among 450 species of Neotropical Ithomiinae and
Heliconinae there are only fifteen shades of colour, whereas
among 200 species of Neotropical Papilioninae there are
thirty-six shades. And this is not by any means due to
the scarcity of variation in the former, for individual
differences in each locality, and geographical differences,
as we pass from one district to another, are very prevalent.
Combined with the uniformity within these Sub-Families
is a marked tendency to resemble other protected Sub-

1 See F. A. Dixey in Trans. Ent. Sac. Loud., 1890. p. 89.

2 Bull. Mus. Comp. Zool. at Harvard Coll., Feb. 1897, \\ 167.

278 MIMICRY AND NATURAL SELECTION

Families inhabiting the same region, a tendency which is
so pronounced in the case of the Ithomiinae and Helico-
ninae that they were long regarded as a single group,
although the structural differences between them, as larva,
pupa, and imago, are strongly marked and indicate that
the first Sub-Family belongs to one side of the great
Nymphalid family and the second to the opposite side.
This remarkable uniformity in the species of certain
butterfly Sub-Families was first explained by Professor
Meldola 1 on the lines suggested by Dr. Fritz Muller 2 in
1879, viz. as an adaptation in order to reduce the amount
of life sacrificed during the period when young and inex-
perienced insect-eating animals are learning to distinguish
between palatable and unpalatable (and perhaps unwhole-
some) food. If two species living intermingled and
equally numerous are superficially exactly alike, and both
nauseous, each will lose only half the number of indivi-
duals which would have been required in order to educate
their enemies if they had been dissimilar. The sacrifice
of life is also reduced by the strong general resemblance
running through the species of each specially protected
Sub-Family in one country. Such resemblance is by no
means confined to the Rhopalocera (butterflies) or the
Lepidoptera. It is found abundantly in all specially
defended insect Orders, principally the Hymenoptera.
If we look at the Australian Aculeata we notice a large
group of species in which the orange ground colour is
deeper and browner than in banded Aculeata generally,
while the black zones are broader and fewer, being in fact
usually reduced to two, one crossing the thorax, another
the abdomen. This very characteristic appearance is to
be found in Abispay Etimenes, Alastor, Odynerus, Bembex
and probably many other genera : it also occurs in mimetic
Diptera (Asilidae), and Longicorn Coleoptera. Here is
a broad fact which receives an intelligible explanation by
Natural Selection, but by no other theory which has been
suggested. We can well understand, on the theory of
Natural Selection, why the members of specially defended

1 Ann. Mag. Nat. Hist., Dec. 1882, p. 417.

2 Kosmos, May 1879, p. 100; also Kosmos, v, 1881.

CHARACTERS OF NAUSEOUS GROUPS 279

groups should be far more alike than those of others, why
they should resemble members of other such groups in
the same region, why they should have conspicuous
patterns and contrasted colours which in Lepidoptera
tend to be the same upon the under as on the upper side
of the wings, why their flight should be slow and flaunt-
ing, why they should be remarkably tenacious of life.
Here are a number of important characters associated
together, and true of all such groups wherever they may
occur in any part of the world. One theory alone explains
all the numerous observations which are here condensed
into a brief statement. It is by no means an assumption
to maintain that the groups in question are specially
defended. This is admitted to be the case with the
Hymenoptera, and there is now a very large mass of
experimental evidence in the Lepidoptera.1

Another admitted fact of wide application is the ten-
dency of Mimetic Resemblance to appear in the female
rather than the male. Thus mimetic female butterflies of
many species are associated with non-mimetic males, while
the converse relationship is almost unknown. Such non-
mimetic males maintain the ancestral appearance which
has been lost in the mimetic females. It is interesting- to
observe, however, that more or less distinct traces of the
original pattern can generally be recovered by the careful
study of individual variation in the females. This is
a remarkable reversal of the ordinary rule that when male
and female differ the latter is the more ancestral. This
striking exception is quite unintelligible except under the
theory of Natural Selection, which offers the convincing
explanation, long ago suggested by Alfred Russel Wallace,
that the slower flight of the heavier females and their
exposure to attack during oviposition render it especially
advantageous for them to resemble conspicuous distaste-
ful species in the same locality.2

Another aspect of Mimicry affords, in my opinion,

1 See especially Frank Finn in Journ. Asia/. Soc. Bengal, lxiv, pt. ii,
l895. p. 344 5 Ixv, pt. ii, 1896, p. 42; lxvi, pt. ii, 1897, p. 528, and
p. 613.

2 Trans. Linn. Soc. Lond., vol. xxv, 1866, p. 22.

28o MIMICRY AND NATURAL SELECTION

perhaps the most powerful argument of all in favour of
an interpretation based on the theory of Natural Selec-
tion. If these resemblances are attained by selection
because they are advantageous in the struggle for life, we
should expect to find that they are produced in a great
variety of ways ; for one species would reach the bene-
ficial end by one path pointed out to it by the structure
it possessed at the beginning and by the trend of its
variation, while another species with a very different initial
structure would reach the same end by a widely different
path. Thus many Diptera, for example species of Ceria,
gain a superficial resemblance to wasps by a narrowing
in the anterior abdominal region which suggests the
characteristic peduncle of a Hymenopterous insect. On
the other hand, Longicorn beetles of the genus Oberea
gain the same effect by a patch of white which obliterates
the anterior abdominal region with the exception of
a small linear remnant representing the peduncle.1 In
brilliant illumination the white marking is not seen as
part of the insect. The resemblance of the Locustid
Myrmecophana fallax to an ant is produced in the same
manner.2 The Homopterous family Membracidae are
characterized by an enormous growth of the dorsal region
of the pro-thorax, which spreads backwards and in many
species covers the insect like a shield. In the American
species which mimic ants, this shield, and not the insect
beneath it, becomes ant-like. Some of the larval Mem-
bracidae are laterally compressed, becoming in the dorsal
region as thin as a leaf, and the body is green like a leaf,
while the head and legs are brown. The whole appear-
ance is singularly like that of the tropical American ant
Atta (Oecodoma) cephalotes, carrying its leaf vertically in
its mandibles, and thrown over its back, so that the brown
head, legs, and part of the body are seen beneath the
green burden.3 It is manifestly absurd to attempt to

1 See R. Shelford in Proc. Zool. Soc. Loud., 1902, pp. 238-40, plate
xix, figs. 13, 14, 15.

2 See pp. 256-7 of the present volume, together with Fig. 5, p. 258.

3 See description and figure of a specimen found by Mr. W. L. Sclater
in British Guiana. Poulton, in Proc. Zool. Soc. Lond., 1891, p. 462,
pi. xxxvi. See also pp. 258-60 of the present volume and Fig. 7, p. 259.

MIMICRY OF ANTS AND WASPS 281

account for this series of Mimetic Resemblances by an
appeal to the operation of External or Internal Causes or
of Sexual Selection. There remains Natural Selection,
which at once offers a convincing interpretation. Ants
and wasps are known to be aggressive dominant insects
avoided by the majority of insect-eating animals, although
certain species are adapted to feed almost exclusively
upon them. It is in every way probable that a superficial
resemblance to ants and wasps would be beneficial in the
struggle for existence. There is, indeed, some experi-
mental evidence to prove that real advantage is conferred.1
We find that species of many groups mimic ants and
wasps in a variety of entirely different ways. The results
are exactly what might have been predicted to occur if
Natural Selection be the efficient cause of Mimetic Resem-
blance.

The attempt has been made, in recent years, to cut
away the foundation of an interpretation based on the
theory of Natural Selection, by calling in question the
conclusion that butterflies are, as a matter of fact, attacked
by insect-eating animals such as birds. I have recently
collected together a great mass of evidence bearing on
this point, most of it obtained in Mashonaland, South
Africa, by the admirable naturalist, Mr. Guy A. K. Mar-
shall. This material conclusively proves that the wings
of fresh unworn specimens of butterflies are constantly
notched, as if by the attacks of birds and lizards, and that
in a considerable proportion of the examples the notches
on opposite sides fit together, proving that the insect was
seized when its wings were in contact. The attacks are
most frequently directed to the posterior angle of the
hind-wing, less frequently to the tip of the fore-wing, still
less frequently to the intermediate borders and angles.
The points of attack are those where special marks and
structures, probably having a directive function, are com-
monly developed. Thus the tip of the fore-wing is often
rendered specially conspicuous and the posterior angle of
the hind-wing is continually produced into so-called 'tails '

1 Poulton, Colours of Animals, London, 1890, p. 247 : Lloyd Morgan.
Animal Behaviour, London, 1900, pp. 164-5.

282 MIMICRY AND NATURAL SELECTION

(Papitio, Charaxes, &c), which in many Lycaenidae are
antenna-like and associated with eye-spots, suggesting the
appearance of a head. The resemblance is further inten-
sified in the resting position by movements of the hind-
wings, which cause the apparent antennae to pass and
repass each other. Such structures and marks are con-
stantly injured or entirely bitten away in fresh specimens.
Direct observation of actual attack by birds and lizards
has also been made by Mr. Marshall and others,1 so that
it may be safely assumed that the doubts thrown upon the
reality of the struggle for life in butterflies have their
origin in the want of observation specially directed to this
end. The majority of naturalist-travellers are chiefly
concerned with collecting, and it is not surprising that
many of them have not seen what they never looked for.

If time had permitted, many other aspects of Mimetic
Resemblance might have been dwelt upon, and it would
have been found, as it has been found with those which
I have had the honour to bring to your notice, that all
are readily explicable by the theory of Natural Selection,
but remain mere coincidences under any other alternative
theory as yet suggested.2

APPENDIX

The evidence collected by Mr. Guy A. K. Marshall,
alluded to on pp. 281-2, is now published in his great me-
moir on The Bionomics of South African Insects? The

1 Two members of the Fifth International Congress who were present
at my lecture informed me afterwards that they had witnessed such
attacks. Professor E. Penard of Geneva saw a bird, probably a sparrow,
persistently pursue and at the third attempt capture a white butterfly
(probably a species of Pieris). The incident happened in the early
summer of 1900, in a park near Geneva. Mr. F. Muir, of Ipswich,
England, expressed surprise that any doubts should have been raised.
He had frequently observed such attacks at Delagoa Bay and other
places on the East coast of Africa, and had seen birds waiting in trees or
bushes and darting out at butterflies as they approached.

2 Further evidence is discussed in the writer's paper in the Journ. Linn.
Soc. Zool.t vol. xxvi, p. 558, reprinted as Essay viii in the present volume
(p. 220).

3 Trans. Ent. Soc. Lond.y 1902, pp. 287-584.

AFRICAN BIRDS EATING BUTTERFLIES 283

indirect evidence supplied by injured specimens of freshly
emerged butterflies is illustrated in Plates ix, x, and xi,
and described on pages 366-75 of the paper. The direct
evidence (pp. 357-66) is so important that, with the kind
consent of Mr. Marshall, Colonel Yerbury, Colonel Bing-
ham, and the Council of the Entomological Society of
London, it is reprinted below : —

12. Records of Attacks on Lepidoptera, especially
Butterflies, by wild South African Birds, by
G. A. K. Marshall.

1897. March 28. While out collecting at Malvern,
Durban, Natal, I saw a Paradise flycatcher (Terpsiphone
perspicillata) catch a specimen of Eronia cleodora. The
butterfly was hovering over a flower when the bird
swooped down, seized it with its feet, and carried it off.

1898. Salisbury, February 27. Saw a Marico wood-
shrike {Brady or nis mariqtcensis) dart down from a tree
and catch a Sarangesa eliminata (Holl.), which was sitting
with outspread wings on a small plant.

March 6. Saw a flycatcher (Pachyprora mo lit or) make
several futile attempts to catch a Tarucus plinius which
was circling round the bush on which it sat.

November 23. Saw a bush kingfisher [Halcyon chclicu-
tensis) catch and eat two butterflies, viz. Junonia cebrene
and Catopsilia florella, both of which were captured
when feeding.

December 1. C. F. M. Swynnerton saw a drongo
(Buchanga assimilis) fly past him with a white butterfly
in its beak, probably C. florella.

December 15. Remains of Papilio dcmodocus found in
the stomach of a cuckoo (Coccystes c after).

1899. Salisbury, January 1. While watching an A tella
phalantha hovering over a bush of its food-plant, a Para-
dise flycatcher (Terpsiphone perspicillata) darted past, and
with a loud snap of its beak tried to catch the butterfly in
its swoop. The latter escaped, however, and on following
it up I found that the tip of one hind-wing had been cut

284 MIMICRY AND NATURAL SELECTION

clean off ; unfortunately I had no net and failed to capture
the insect.

Swynnerton shot a hobby (Palco subbuteo), which had
in its stomach an almost complete Terias. The thorax
and abdomen were quite uninjured, but the tips of the
fore-wings were gone.

April 26. I was watching a drongo hawking insects
from the top of a dead tree ; there were many Pierinae
about, chiefly Teracolus and Beknois, but the bird paid
not the least attention to them. At last a Belenois came
by which had its wings very much shattered, so that its
flight was weak and erratic ; the drongo observed it at
once, and swooped down on it, but I saw the butterfly
drop into the long grass. Whether it was injured by the
bird I could not say, as I was unable to find it, and I did
not see it rise again. This episode would point to the
conclusion that the fact that birds refrain from pursuing
butterflies may be due rather to the difficulty in catching
them, than to any widespread distastefulness on the part
of these insects.

1900. C. F. M. Swynnerton wrote from Gazaland :
* In March [1900] I saw a Praiincola torquata [South
African stonechat] in chase of Tartiais pliniits. Had it
not been frightened off by coming face to face with me,
it would undoubtedly have caught it. I think I told you
long ago of having found the wings of a lot of butterflies,
chiefly P. corinnetis, below the branch of a tree on which
some swallows were constantly settling.'

May 13. Salisbury. Saw a drongo {Buchanga assi-
milis) swoop from a tree and catch what I took to be
an injured Belenois, which it dropped almost at once.
I marked the insect down, and found it to be a common
white moth of the distasteful genus Diacrisia (D. macu-
losa).

1901. December 17. Melsetter, 5,500 feet, Gazaland.
A specimen of the large, conspicuous Hypsid moth Callio-
ralis bellatrix was seized and rejected by a drongo,
undoubtedly a young bird, judging by its plumage. [The
moth, which is now in the Hope Department, has lost
most of the head, but is otherwise uninjured. — E. B. P.]

INDIAN BIRDS EATING BUTTERFLIES 285

13. Records of Attacks on Butterflies by wild Birds
in India and Ceylon, by Colonel J. W. Yerbury, R.A.

[Colonel Yerbury has kindly extracted from his notes
all the observations he has made bearing on this inter-
esting question. — E. B. P.]

About the year 1884 a discussion arose in the Bombay
papers as to whether birds preyed on butterflies, and the
general opinion expressed was that it was comparatively
rare for them to do so. In common with some other
members of the Bombay Natural History Society, I deter-
mined to watch and note the results. My records taken
from old diaries are as follows : —

1884. Neighbourhood of Poona and Aden. None.

1885. September 23. Aden, Campbellpore, and Murree
Hills. Road up Thundiani, near the Kala Pani Bunga-
low. Saw a young king-crow, Dicrums ater, stoop at
a big blue Papilio, either P. polyctor or P. arcturus, and
miss it. The bird did not repeat the attempt.

1886. September 2. Campbellpore, Thundiani, &c.
Road up Thundiani, near top of the hill. Saw a young
king-crow stoop at a specimen of Vanessa kasckmireusis,
and after missing it once take it at the second attempt.
Did not notice whether the insect was eaten.

1887. Rawul Pindi and home, via Japan and America.
None.

1888-9. At home.

1890. June. Ceylon, Trinkomali. No record.

1891. November 14. On the Kandy Road between
Trinkomali and Kanthalai ; butterflies in great numbers
sitting on the wet mud by the roadside ; chiefly Pierinac
(Catophagd), but a few P. nomius with them. These
butterflies rose in clouds as one drove past. A bee-eater,
Merops philippinus, kept flying in front of my carriage
and taking specimens of these butterflies as they rose. .
The bird seemed to select the yellow females, which are
rare, the white females being to them probably in the
proportion of 100 to 1. These flocks of butterflies often
unite and form what are known as snowstorms in Ceylon ;
they then migrate right across the island.

286 MIMICRY AND NATURAL SELECTION

These bee-eaters were often seen catching Pierinae\
in fact, it seems to have occurred so often that I ceased
to record the fact, for I can only find this one reference.
Probably the attacks were always witnessed at the begin-
ning of the N.E. monsoons during the time of the heavy
rains, i.e. September to December.

I am not certain as to the date on which I saw
the Ashy swallow-shrike (Artamus fuscus) catching
specimens of the Euploea, Crastia core. The fact is
associated in my mind with a particular place, and with
the capture of C har axes p sap hon ? there. This is recorded
for April 12, 1891, so this may be the correct date on
which I watched the bird. At least six specimens of the
Crastia were captured by the shrike, all of which it carried
away to a branch high up in a big tree, but I could not
see whether they were eaten.

As regards my experience of birds catching butterflies,
it appears to have occurred more frequently in damp
than in dry districts; e.g. it was frequent in Ceylon, rare
in places with moderate or small rainfall, such as Camp-
bellpore, Poona, and Aden.

In my opinion an all-sufficient reason for the rarity of
the occurrence exists in the fact that in butterflies the
edible matter is a minimum, while the inedible wings,
&c, are a maximum.

[See Proc. Zool. Soc. 1887, p. 210, where Lepidoptera
and especially butterflies are spoken of in almost exactly
these terms, as a suggested explanation of the fact that
lizards, although they eat them, greatly prefer flies or
cryptic larvae. — E. B. P.]

14. Records of Attacks on Butterflies, &c, by wild
Burmese Birds, by Colonel C. T. Bingham.

[Colonel Bingham has kindly sent me the following
extracts from his 1878 diaries, for incorporation in the
present memoir. — E. B. P.]

'April 23. Marched from Kawkaraik to Thinganyina-
ung, fourteen miles. Started about 7.45, rather late as
there was some difficulty in collecting the elephants this
morning. . . . The road, a mere jungle path, followed

ORIENTAL BIRDS EATING BUTTERFLIES 287

the course of the Akya Chaung, a feeder of the Haun-
draw River, and crossed the little stream some twenty or
more times in the first six or seven miles before turning
up the hill to the Taungyah Pass in the Dawnat Range.
From the outskirts of Kawkaraik right up to Thinganyina-
ung on the other side of the Pass, the road goes through
dense evergreen forest, and consequently the collecting is
very good on this road, both for insects and birds. To-day,
the day being hot, butterflies, bees, and dragon-flies
swarmed, and at every opening of the Chaung I found
crowds seated on the damp sand apparently sucking up
the moisture. Collecting as I went, it was past eleven
o'clock before I got to the foot of the Pass. I was hot
and a bit tired, so I sat down on a fallen tree to rest, just
before crossing the Akya Chaung for the last time. I had
not been seated many minutes, looking at the swarms of
butterflies, bees, and dragon-flies, which were flitting about
or sitting on the sands, when my attention was attracted
by a bird, a bee-eater {Merops swinhoei), which, swooping
down from a tree overhead, caught a butterfly, a Cyrestis,
within a few paces of me. The bee-eater seemed to catch
the butterfly with ease, and I distinctly heard the snap of
its bill. Then, holding the butterfly crossways, the bird
flew back to the tree, and sat still for a minute or so, then
came a little jerk of the head, and the wings of the butter-
fly came fluttering to the ground, while the body was
gulped. On the same branch some four or five more
bee-eaters of the same species were seated, and as I sat
very still, one after another these birds swooped close to
me, sometimes after a butterfly, sometimes at a bee or
a dragon-fly. More than once I saw a bird miss a butter-
fly, when the latter would dodge and try to get away
among the bushes of the dense undergrowth around, but
only very seldom was this successful, for the bird would
hover and twist and turn in hot pursuit, and generally
managed to catch the insect. I was greatly interested,
for though I had seen both bee-eaters and king-crows
(Dicrurus) go for butterflies and moths, this was the
first time I had witnessed a continuous ha\vTking of butter-
flies on the part of birds. I sat for nearly half-an-hour

288 MIMICRY AND NATURAL SELECTION

watching. The birds seemed to swoop only for the insects
flying about, never at those on the ground. A drove of
pack bullocks, with their shouting Shan drivers, coming
down the road frightened the bee-eaters, and they flew
off. I got up and prepared to start uphill, when it struck
me that it would be interesting to see what species of
butterfly had been taken by the bee-eaters, so I set to
work and collected all the loose wings I could find. I did
not get many, for the undergrowth was very dense, and
the wings dropped in it were difficult to find. Also the
place swarmed with ants ; I could see them on all sides
carrying off whole wings, or portions bitten out of them.
Again, I was pressed for time, so that I managed to get
together only nineteen wings, most of them odd ones,
luckily. ... I have just sorted out and put away my
collections of the day. The butterflies hawked and eaten
by the bee-eaters belong to the following species — Papilio
erithonius, P. sarpedon, Char axes at hennas, Cyrestis thyo-
damns, and Terias hecabe. A meagre list, for I am certain
I saw the bee-eaters swoop for and catch Prioneris, Hebo-
moia, Junonia, and Precis. I also particularly noticed
that the birds never went for a Danais or Euploea, or
for Papilio macareus, and P. xenocles, which are mimics
of Danais, though two or three species of Danais,
four or five of Euploea, and the two above-mentioned
mimicking Papilios simply swarmed along the whole
road.' 1

Looking through my diaries I find more scattered notes
of my having witnessed birds swoop for and catch butter-
flies and moths, but these were solitary incidents, and
only slight mention is made of them in the diaries, with
one exception, which is given below : —

' Camp Wabosakhan, December 3, 1891. . . . Going
through some fairly open jungle close to the main road I put
up a Melanitis zitenius, which fluttered across the road and
was swooped at by a king-crow (Dicrtcrus), but missed ;
the butterfly dodged, got to the other side of the road

1 I did not then realize the importance of my find, or I should have
spared more time for the collection of the fallen wings of the butter-
flies, and taken more care of them. — C. T. B.

BURMESE BIRDS EATING BUTTERFLIES 289

and dropped to the ground among the herbage and fallen
leaves, as is the habit of Melanitis. The king-crow
hovered for a minute not three feet from the ground
over the exact spot where I had noticed the butterfly
drop, failed to see it, flew off, but returned and again
hovered over the spot, but was again unsuccessful, and
flew up to a tree. I went forward very cautiously, and
having carefully noted the spot where the butterfly had
dropped, was enabled to make it out, but not till after
fully ten minutes of patient and very cautious looking.
The Melanitis was there among dead leaves, its wings
folded, and looking for all the world a dead dry leaf itself.
With regard to Melanitis, I have not seen it recorded
anywhere that the species of this genus when disturbed
fly a little way, drop suddenly into the undergrowth with
closed wings, and invariably lie a little askew and slanting,
which still more increases their likeness to a dead leaf
casually fallen to the ground.

' Only once again did I see the systematic hawking of
butterflies by birds. The second occurrence was also by
bee-eaters ; this time it was the large Merops philippinus.
I had been up in the Salween forests beyond the great
rapids, and had managed to get a bad bout of fever, which
necessitated my returning to Moulmein, my headquarters.
It was a hot steamy day in October, and I was lying with
the hot fever fit on me in the boat on the Salween below
Shwegon, when I noticed clouds of butterflies, chiefly
Catopsilia, migrating, crossing the Salween from east to
west in a continuous stream. These were being persis-
tently hawked by the Merops, mixed with which were
some king-crows.'

With regard to Microhicrax coerulescens catching butter-
flies, I find the following note : —

'March 20, 188 1. . . . Passing through a taungyah on
my way back to camp, I noticed a number of butterflies,
some seated, some hovering round a spot where some
Karens had been eating their food, and had left some rice
and gnapi scattered on the ground. I was approaching
the butterflies cautiously to see what species were there,
when a small black-and-white bird came down from a tree

29o MIMICRY AND NATURAL SELECTION

close by and perched on the ground close to one little
mob of butterflies busy feeding away on the gnapi.
I recognized the bird at once as the pigmy hawk {Micro-
hierax coerulescens). His coming flop down close to the
butterflies disturbed some, but not all. A few were too
intent on their meal. The hawk sat for fully two minutes
looking at the butterflies, then he crouched as birds do
when they are about to rise, and next moment, with a quick
snatch, he had taken a butterfly in his claws, and was
flying to the nearest tree. Though I was watching intently
I am quite unable to say whether he took one of the sitting
butterflies or one that was flying about. I watched him
eat the insect, which he held with his claw against the
branch on which he was seated, and he tore at it just as
the larger hawks do with their prey. I wanted a specimen
of the bird, so shot it, and afterwards picked up the wings
of the butterfly he had eaten ; it was a Papilio sarpedon!

N.B. — That same specimen of Micro hierax is now,
I believe, in a small case by itself in the bird gallery of
the British Museum.

[Colonel C. T. Bingham has also made some interesting
observations on the use of insects' wings as a pad at the
bottom of a hole in a tree, forming the nest of this same
species of bird, the falconet Microliter ax coerulescens, Linn.
(M. eutolmus, Hodgs.). The following account is quoted
from Stray Feathers (vol. v, no. 2, June, 1877, pp. 79-
81). The observations were made in the ' Government
Teak Reserve on the Sinzaway Chaung, a feeder of the
Yoonzaleen River, which it enters about two days' march
below our frontier station of Pahpoon in Tenasserim.'
The nest was found on April 14, ' in a hole on the under
side of a decayed bough of a mighty Pymma tree (Lager-
slroemia Flos Reginae)! The four eggs were found to be
1 stained by resting on the broken leaves, wings of dragon-
flies, and bits of wood which composed the nest'. The
editor appends to this account a note of Davidson's which
had been in his possession for years. On March 25 the
nest of Microhierax fringillarius, Drap., was examined.
It had been made in a hole in a dry tree in an old taungyah
(clearing) ' near Bankasoon at the extreme south of Tenas-

INSECT WINCxS IN BIRDS' NESTS 291

serim 'At the bottom of the hole, which was about
eighteen inches deep, was a soft pad composed of flies
and butterflies' wings, mixed with small pieces of rotten
wood.'

In March, 1878, Colonel Bingham found a second nest
of the same species (M. coerulescens) which he sent to the
late Mr. de Niceville in order to ascertain the species of
insects which had been made use of. Mr. de Niceville
wrote as follows : —

' The fragments of butterfly wings you send are as
follows : —

No. 1 . Portion of fore-wing of Papilio caunus.
„ 2. Fore- and hind-wing of Mycalesis perseus.
,, 3. Hind-wing of Papilio erithonius.
,, 5. Portion of fore- wing of Junonia orithyia.

4, 6, 7, 8, 9, too fragmentary to make out, but
seem to belong to some species of the Lycae-
nidae.

,, 10. Half of fore-wing of Char axes sp. (?)

„ 11, Portion of hind-wing of Symphaedra dirtca ?.

,, 12 to 17 are the wings of dragon-flies.' 1
A passage from another letter of Mr. de Niceville to
Colonel Bingham indicates in a different manner the
severity of the nearly unseen struggle for existence which
butterflies of certain genera pass through. The wings

1 In the Zoologist (4th Series, vol. v, 1901, pp. 224, 225) Colonel
Bingham states that he found, on April 23, 1899, a nest of the same
species of pigmy falcon in a hole on the under side of a branch of a dead
tree 'in a deserted taungya alongside the high road leading from
Thabeitkyin, on the banks of the Irrawaddy above Mandalay, to Mogok,
the site of the famous ruby mines of Upper Burma*. The hole had
evidently been made by a Barbet. It was 15 inches long, and at the end
was slightly enlarged into an oval chamber containing ■ a fairly firm pad
of chips of wood, a few leaves, with an upper stratum quite two inches
thick composed almost entirely of the wings of Cicadas, with a few
butterfly and moth wings interspersed therein/ There were no eggs or
nestlings. 1 Further south, in Tenasserim,' Colonel Bingham continues
(I.e. p. 225), 'I found the eggs of this Falcon in a precisely similar
situation early in April, as well as I can remember. That nest was
composed almost entirely of butterfly wings.' Colonel Bingham informs
me that the last-named nest was the one, described above in the text,
which was found in March 1878, and furnished the wings named by

292 MIMICRY AND NATURAL SELECTION

sent by Colonel Bingham were found by him in 1888.
Mr. de Niceville wrote concerning them : —

'See p. 275 of vol. ii. of my Butterflies. Ferguson
found a single wing of Charaxes schreiberi in Travancore
on the ground. It is curious that the only record so far
of the same species from Burma should be the three wings
you send me, which you say you found on the ground.' —
E. B. P.]

X

THE PLACE OF MIMICRY IN A SCHEME
OF DEFENSIVE COLORATION

The title of this essay formed the subject of a lecture on Mimicry,
delivered September 5, 1890, before the British Association at Leeds,
and published in abstract in Nature, October 2, 1890, p. 557. The
attempt has now been made to bring this lecture up to date by including
a brief account of the most important results which have been published
since its delivery, such as those contained in the writer's article on
Colours of Animals I, Bionomics in the Encyclopaedia Britannica, vol. xxvii,
1902, pp. 146-50, and in numerous memoirs and short communications
by Dr. F. A. Dixey, Mr. G. A. K. Marshall, Mr. R. Shelford, Mr. F.
Merrifield, Mr. A. H. Thayer, Mr. W. J. Kaye, Mr. S. A. Neave, Mr. F.
Finn, Dr. G. B. Longstaff, Mr. W. Holland, Mr. A. H. Hamm, the author,
and others. The examples brought forward as illustrations at Leeds
are, except when otherwise indicated, marked by asterisks.

In this essay the word 'group' is employed to express an arrange-
ment based on affinity, the word 'combination' or 'association' to
express an arrangement founded on bionomic relationship. Thus a genus
or family is spoken of as a group, a set of Mullerian models and mimics
as an association or combination.

CONTENTS

PAGE

I. CRYPTIC COLOURING OR PROTECTIVE AND
AGGRESSIVE RESEMBLANCES ; — PROCRYPTIC
AND ANTICRYPTIC COLOURS

A. Procryptic, or Protective Resemblance

a. General Protective Resemblance .

b. Special Protective Resemblance

1. The Neutralization of Shadow

2. Adjustable Neutralization of Shadow

3. The Reduction of Shadow by Attitude .

4. The Choice of Appropriate Surfaces upon which to Rest

294 THE PLACE OF MIMICRY

PAGE

5. The All- Importance of Instinct in bringing about Protec-

tive Resemblance 301

6. The Hyper tely of B runner von Wattenwyl . . -302

7. Hours during which the Struggle for Life is most Severe 303

8. The Value of Brightly-coloured Surfaces Concealed during

Rest 303

c. The Gregarious Habit may assist Concealment . . 304

10. Adjustable Protective Resemblance . ... 304

a. Rapid ........ 304

b. Slow . 304

1 1. Coincidence between the Colours of Organisms and those

of their Peculiar Environments may be probably
Caused by the Local Operation of Natural Selection . 307

12. The Recent Progressive Darkening of many Species of

Moths in the Lancashire and Yorkshire District . 308

13. Dimorphism and Polymorphism in Procrypiic Defence . 310

14. Seasonal Changes in the Individual . . . .310

15. Seasonal Dimorphism in Procryptic Defence . . .310

16. Syncryptic or Common Protective Resemblance . .312

B. Anticryptic or Aggressive Resemblance. . . .312

C. Allocryptic or Adventitious Protective (and Aggres-

sive) Resemblance 313

II SEMATIC COLOURS, OR WARNING AND SIGNAL-
LING (RECOGNITION) COLOURS ;— APOSEMATIC
AND EPISEMATIC CHARACTERS . . . .315

A, Aposematic or Warning Characters . . . -315

1. Experimental Evidence of Special Protection in Forms

with Warning Colours . . . . . . 316

2. Species with Warning Colours depend for their Existence

upon the Co-Existence of Palatable Species . 317

3. Erroneous Assumption that Warning Colours imply Com-

plete Immunity from Attack . . . . 317

4. Transition fro?n Cryptic to Aposematic Defence . .318

5. Seasonal Transition from Cryptic to Aposematic Defence. 320

6. Geographical Transition from Aposematic to Cryptic

Defence .320

IN DEFENSIVE COLORATION

PAGE

7. A. H. Thayer's Criticism of the Statement that Animals

are Conspicuous 321

8. The All- Importance of Instinctive Attitudes and Move-

ments in the Display of Warning Colours . . 323

9. Warning or Intimidating Sounds . . . . .324

10. Intimidating Attitudes . . . . . . .324

11. Directive Marks and Structures . . . . . 325

12. The Seasonal Development of Directive Marks . .326

\ Synaposematic or Common Warning Colours (Millerian

Mimicry) 327

1. The Mathematical Statement of the Advantage Conferred

by Perfected Mullerian Resemblance . . .328

2. The Advantage Conferred during the Growth of Mullerian

Resemblance. 329

3. Striking Examples of Mullerian Resemblance . . 331

a. The New World 331

b. The Old World 333

4. The Limit to Mullerian Unification of Warning Colours

in any Country ....... 336

5. Seasonal Transition from Cryptic to Synaposematic Defence 339

6. Seasonal Transition in degrees of Synaposematic D fence, or

from Aposematic to Synaposematic Defence . . 341

7. The Gradual Predominance of the Mullerian Hypothesis . 342

8. Diaposematic Resemblance ; Reciprocal Warning Colours . 344

9. Primary and Secondary Mullerian Resemblance ; Prolo-

and Deuterosynaposematic Resemblance . . -345

10. Further Indirect Evidence Supporting a Mullerian or

Synaposematic Interpretation . . . . .346

11. Mullerian Resemblance Associated with Warning Colours;

« Batesian Mimicry Associated with Cryptic Colours . 348

12. Mimetic Patterns in Stations or Localities different from

. those of the Model • 349

13. Classes of Facts which have Recently been Urged in

Support of the Batesian Hypothesis . . .350

a. Butterflies Exhibiting Mimetic Resemblance on the
Upper Surface of the Wings and Procryptic Defence

on the Under Surface . . . . . 350

b. Dimorphic or Polymorphic Mimetic Butterflies with
Forms Resembling Different Models , . .354

296 THE PLACE OF MIMICRY

PAGE

14. A Possible Instance of Observable Change in a Member

of a Miiller ian Group since 1825 . . . . 356

B. Allaposematic Colours, or Adventitious Warning

Colours 356

C. Episematic or Recognition Characters . . . .357

III. PSEUDOSEMATIC RESEMBLANCE, OR PROTEC-
TIVE (BATESIAN) AND AGGRESSIVE MIMICRY;
— PSEUDAPOSEMATIC AND PSEUDEPISEMATIC
RESEMBLANCES • . - . . . . . .358

1. Various Uses of the Term Mimicry: The Essential

Element in Mimicry 359

A. Pseudaposematic Resemblance, or Protective (Batesian)

Mimicry 361

1. Wallace's Statement of the Conditions tinder which Pro-

tective Mimicry Occurs 361

2. The Chief Characteristics of Mimetic Resemblance and

the Attempt to Explain their Evolution , . .362

3. The All-Impor lance of Instinctive Attitudes and Movements

in the Attainment of Mimetic Resemblance . . 363

4. History and Migration may be inferred from Mimicry . 363

5. A History Inferred from Mimicry may be Confirmed by

other Evidence . . . . . . .365

6. Mimetic Rese?nblance between Species of very Different

Size 366

7. Remarkable Examples of Mimicry . . . '3^7

8. Mimetic Resemblance to Cryptic Models . . . .369

9. Butterflies and Moths, chiefly Oriental, selected in 1890,

to Illustrate Various Aspects of Mimicry . . 370

a. Roth Sexes Mimetic: Both Sexes of Model and
Mimic Superficially Alike 371

b. Sexes readily Distinguishable: Male mimics Male,
Female mimics Female. . . . . 37 1

c. Male and Female mimicking Different Species . 372

d. Female Mimetic: Male No?i-Mimetic . . .372

e. Female Mimicking two or more Differ 'ent Species:
Male perhaps Non-Mimetic, or Mimicking still
another Species 373

IN DEFENSIVE COLORATION 297

PAGE

f Non-Mimetic Ancestor preserved on Islands, Sfc. ; on
Adjacent Continent Mimicry developed in one or both
Sexes 1 Remarkable case of Papilio dardanus
(merope) 373

g. Imperfect Resemblance, not to any Particular Species,

but to the General A ppearance of an Unpalatable Group 376

B. PSEUDALLAPOSEMATIC RESEMBLANCE ! MlMETIC REPRESENTA-

TION of some Adventitious Object Associated with

the Model . 377

C. Pseudepisematic Resemblance or Aggressive Mimicry,

including Alluring Colours 377

IV. EPIGAMIC COLOURS 379

NOTE 381

I. CRYPTIC COLOURING, OR PROTECTIVE
AND AGGRESSIVE RESEMBLANCES;
— PROCRYPTIC AND ANTICRYPTIC
COLOURS.

The commonest use of colour is for concealment
(Cryptic), enabling an animal to escape its enemies, or
to approach its prey. In these Protective (Procryptic)
or Aggressive (Anticryptic) resemblances, animals are
concealed by a likeness to some object which is of
no interest to enemies or prey respectively. Similar
effects may be produced by the use of foreign objects
with which the animal covers itself to a greater or
lesser extent (Allocryptic).

A. Procryptic, or Protective Resemblance.

a. General Protective Resemblance. — In this form of
concealment the animal, in consequence of its colour-
ing, produces the same effect as its environment, but
the conditions do not require any great or special
modification of shape and outline. This method of
concealment is chiefly found among the animals
inhabiting some uniformly coloured expanse of the
terrestrial surface, such as an ocean or a desert.

298 THE PLACE OF MIMICRY

On the surface of the ocean it is common for
animals of all shapes to be protected by their transpa-
rency and often by a blue colour : on the desert equally
diverse forms are defended by their likeness to the sand.
Modification of shape in the direction of flattening
occurs in some species. The elimination of shadow,
to be described below, is of the utmost importance on
such a strongly lighted surface as the desert.

The effect of a uniform appearance may be pro-
duced by a combination of tints in startling contrast.
Thus the dark and light stripes of the zebra blend
together at a little distance, and ' their proportion is
such as exactly to match the pale tint which arid
ground possesses when seen by moonlight V

b. Special Protective Resemblance is far commoner
than general, and is the form usually met with on the
diversified surface of the earth, on the shores, and in
shallow water, as well as in the masses of Algae floating
on the ocean, such as those of the Sargasso Sea.

In these environments the Cryptic Colouring of
animals is usually aided by special modifications of
shape, and by the instinct which leads them to assume
particular attitudes. Complete stillness, and the
assumption of a certain attitude also play an essential
part in General Resemblance on land ; but in Special
Resemblance the attitude is often highly elaborated,
and perhaps more important than any other element
in the complex method by which concealment is
effected. In Special Resemblance the combination of
colouring, shape, and attitude is such as to produce
a more or less exact resemblance to some of the objects
in the environment, such as a lump of earth, a stone,
a leaf or twig, a patch of lichen, or flake of bark. The
animal is not merely hidden from view by becoming
indistinguishable from its background, as in the case of
General Resemblance, but it is mistaken for some well-
known object of no interest to its enemy.

A good example in the shallow seas round our coasts

1 F. Galton, South Africa, London, 1889, p. 187.

IN DEFENSIVE COLORATION

is seen in the green pipe-fish (Sip hono stoma typhle*)1 con-
spicuous in the weedless water, but well concealed among
the leaves of Zostera. The brown Lappet moth
(Gastropacha quercifolia*) conspicuous on a smooth deal
board, but well concealed among dead leaves, serves to
show that colour and shape cannot be correctly inter-
preted except by reference to the natural environment.
Many examples of the Protective Resemblance to dead
leaves are given on pp. 203-6. Mr. Abbott H. Thayer
has pointed out 2 that many species bear upon the under
surface of the wings the representation of shadows as
they are cast by such thin objects as dead leaves lying
one over the other on the ground.

1. The Neutralization of Shadow. — The colours of
large numbers of animals are darkest on the back,
becoming gradually lighter on the sides, and passing into
white on the belly. Abbott H. Thayer3 has suggested
that this gradation obliterates the appearance of solidity,
which is due to shadow. A colour-harmony, which is
also essential to concealment, is produced because the
back is of the same tint as the environment (viz. earth),
bathed in the cold blue-white of the sky, while the belly,
being cold blue-white bathed in shadow and yellow
earth reflections, produces the same effect. Thayer has
made and presented models to the Natural History
Museums of Oxford, Cambridge, and London, which
support his interpretation in a very convincing manner.

Special resemblances to twigs, upright stems, &c, are,
Mr. Thayer considers, represented upon a background in
which the shadow is neutralized as described above.
Hence the background, viz. the animal's body, disappears,
while the markings upon it are alone distinctly seen.

For ages the artist has known how to produce the
appearance of solid objects standing out on his canvas,
by painting in the likeness of the shadows. It has
remained for this great artist-naturalist to realize the

1 The asterisk added to this and the following examples indicates that
they were employed as lecture illustrations at Leeds in 1890.

2 Trans. Ent. Soc, Lond., 1903, p. 557.

3 The Auk, vol. xiii, 1896, pp. 124 and 318.

3oo THE PLACE OF MIMICRY

logical antithesis, and show how solid objects may be
made to fade away and become ghost-like, or even
invisible, by painting out the shadows.

Twenty years ago the present writer recognized the
importance of the neutralization of shadow by a com-
pensating lightness of tint, for the purpose of conceal-
ment. But this was only in particular examples, —
a certain Geometrid larva,1 and a chrysalis2 — and the
far-reaching significance of the principle was unseen until
A. H. Thayer's great discovery in 1896.

2. Adjustable Neutralization of Shadow. — An adjust-
able form of Thayer's principle was discovered in the
chameleon in 1905, when Dr. G. B. Longstaff, Pro-
fessor C. V. Boys, and the present writer observed that
the illuminated side of the South African Chamaeleo
pumilus is darkened, the side in shadow brightened in tint.

These pigmentary changes neutralize the effects of
differing illumination on the two sides, and thus remove
the appearance of solidity.3

3. The Reduction of Shadow by Attitude. — It has
been shown, especially by Dr. G. B. Longstaff,4 that
many butterflies, when they come to rest, turn the axis of
the body so that the head is away from the sun. In
this position, when the wings are raised, the shadow cast
is a mere line and inconspicuous. In other positions the
broad wings of a butterfly cast a shadow which, when
the axis of the body approaches a right angle to the sun,
may be far more conspicuous than the insect itself.
Many Satyrine butterflies, when they come to rest, have
a pronounced tilt to one side or 'list'.5 It is probable
that this attitude also is valuable in reducing the

1 Trans. Ent. Soc, Lond., 1887, pp. 292-4.

2 Trans. Ent. Soc, Lond., 1888, pp. 595-7.

3 An account of the observations was read before The Linnean Society
of London, March, 1907. See Zool. Journ. Linn. Soc., vol. xxx, p. 45.

4 Trans. Ent. Soc, Lond., 1905, p. 135; 1906, p. 97.

5 See Dr. LongstafFs papers referred to in the above note : also
Colonel Bingham's observations on Melanitis quoted on p. 289 of the
present volume. Confirmatory observations on the same genus have
been made by Mr. E. E. Green (Spotia Zeylanica, vol. ii, Pt. vi, August
1904, p. 76), and Mr. T. R. Bell {Ent. Mo. Mag., 1906, p. 126).

IN DEFENSIVE COLORATION 301

shadow. Many years ago I observed a Green Hair-
streak Butterfly (Thecla rubi), which, when it settled on
a leaf, let itself down on one side so completely that it
seemed to lie flat on the surface. The obliteration of
shadow was very marked, and forced itself upon me at
the time as the significance of the attitude.1

4. The Choice of Appropriate Surfaces upon which
to Rest.— "Dr. F. A. Dixey 2 and Mr. A. H. Hamm 3 have
produced evidence which suggests that the Small
Garden White, Pieris rapae, tends to select white sur-
faces upon which to rest for the night. An observa-
tion made by Dr. T. A. Chapman 4 upon Colzas edusa
supports this conclusion. Dr. Dixey and Dr. Longstaff
have observed an analogous instinct in Eronia cleodora 5
in South Africa, and have published many records of
similar observations on other species.6 Mr. Hamm's
records7 and photographs of British moths in their
natural attitudes of rest on bark or stone also show
the same co-operation of appropriate instinct with a
Procryptic colouring and form. The manner in which
one of the moths observed by this keen naturalist brings
the main lines of its pattern into parallelism with the
main lines of shadow in its immediate environment has
already been described on p. 156.

5. The A 11- Importance of Instinct in Bringing About
Protective Resemblance. — The appropriate instincts form
probably the most important and essential element in
Procryptic Defence. Several examples have been given
in the two preceding paragraphs, and many others will
be found on pp. 154-66 of the present work, where it
is shown that the appropriate actions are performed

1 Proc. Ent. Soc, Lond., 1906, p. xxviii.
3 Trans. Ent. Soc, Lond., 1906, pp. 1 16-17.

3 Proc. Ent. Soc, Lond., 1904, p. Ixxv ; Proc. Ent. Soc, Lond., 1905,
p. lxxiii ; Proc. Ent. Soc, Lond., 1906, pp. c, ci.

4 1. c. 1905, p. Ixxv.

6 Trans. Ent. Soc, Lond., 1906, pp. 1 13-14; 1907, pi. xxv.

6 See Longstaff in Trans. Ent. Soc, Lond., 1906, pp. 11 3-1 7. A large
number of Dr. Dixey's observations are recorded in this paper. See
Dixey in Proc Ent. Soc, Lond., 1906, p. xxix.

7 Trans. Ent. Soc, Lond., 1906, p. 483, pi. xxix.

302 THE PLACE OF MIMICRY

without intelligence, under the compulsion of hereditary
mechanisms forming part of the nervous system.

6. The Hypertely of B runner von Wattenwyl. — The
very perfection and minute detail of certain Cryptic
Resemblances have been used as an argument that they
cannot have been produced by the operation of Natural
Selection. Thus in the likeness of butterflies to dead
leaves, described on pp. 203-6, or in that of the South
American moth, Draconia rusina? to a leaf attacked by
a fungus which has ' skeletonized ' certain parts, and is
still at work upon others — in cases such as these it is
sometimes objected that the detail goes beyond what
can be conceived of as advantageous in the struggle for
life. The particular examples which led Brunner von
Wattenwyl 2 to suggest the term 'Hypertely', were the
South American Locustids of the genus Pterochroza,
He considered that the exposed anterior wings of certain
species resembled leaves bearing the tracks and marks
of leaf-mining larvae. The same argument is sometimes
employed in relation to the remarkably detailed resem-
blances of mimicry. All such criticism is founded on
our imperfect knowledge of the struggle for existence.
The impressions and judgements of man are immensely
influenced by the ' corroborative detail giving ' artistic
verisimilitude to a bald and unconvincing narrative \
Indeed, the laughter which is invariably raised by this
passage from The Mikado is, I have always thought,
not only or chiefly due to the humour of the application,
but to the way in which a great and familiar truth breaks
in upon the listener with all the pleasing surprise which
belongs to epigram. Birds, the chief enemies of insects,
are known to have powers of sight far superior to those
of man, and, from our experience of them in captivity, it
may be safely asserted that their attention is attracted
by excessively minute detail. Until our knowledge of
the struggle for life is far more extensive than at present,
the argument founded on Hypertely may be left to

1 Proc. Ent. Soc, Lond., 1 906, p. Ixxviii. Trans. Ent. Soc, Lond.t 1 906,

P- 533> pl- xxxii-

a Verh. zool.-bot. Ges. Wten., xxxiii, 1883, p. 248.

IN DEFENSIVE COLORATION

contend with another argument often employed against
the explanation of Cryptic and Mimetic Resemblance by
Natural Selection. Hypertely assumes that there are
unnecessary details in the resemblance, that the resem-
blance is perfect beyond the requirements of the insect :
the second argument maintains that birds are so
supremely sharp-sighted that no resemblance, however
perfect, is of any avail against them. In the meantime
the majority of naturalists will probably reject both
extremes and believe that the enemies are certainly
sharp-sighted and successful in pursuit, but that perfection
in detail makes their task a harder one, and gives to the
individuals possessing it in a higher degree than others,
increased chances of escape, and of becoming the parents
of future generations.

7. Honrs during which the Struggle for Life is most
Severe. — In any attempt to understand the details of the
struggle, it is essential to ascertain its relative severity
during the various periods of the day and night. Mr. N.
Annandale 1 has observed that certain Siamese insects
were active during the hottest hours of the day, a time
when the birds did not hunt for food, and that conversely
the same insects were rarely either seen in motion or found
at rest during the cooler hours of daylight, when enemies
were busily at work. Dr. G. B. Longstaff2 has also
suggested as a result of his experience in South Africa,
that the Cryptic colouring, attitudes, and instincts of
butterflies must be considered in relation to the large
number of hours of daylight during which they are in the
condition of complete rest.

8. The Value of Brightly -co loured Surfaces Concealed
during Rest. — The brightly coloured hind wings of main-
moths (Catocala, Tryphaena, &c.) and grasshoppers
(Oedipoda, &c.) which flash out conspicuously when the
insect becomes active, and disappear equally suddenly
when it alights, probably serve, as Lord Walsingham 3
has suggested, to confuse a pursuing enemy. The same

1 Proc. Roy. Phys. Soc, Edinb., 1900, No. xxix, pp. 439-44.
3 Trans. Ent. Soc, Lond., 1906, p. 118.
8 Proc. Ent. Soc, Lond., 1890, pp. 1-lii.

3o4 THE PLACE OF MIMICRY

interpretation was offered by the late Mr. J. Jenner Weir,1
who brought forward evidence that the bright colours
are also of value in diverting the attention of an enemy.
Hence the insect is likely to be seized by the fragile
hind wing, and to gain an additional chance of escape.
The hind wings of recently emerged moths are often
found chipped and torn as though they had been seized
in this manner. Protection afforded in this latter way
perhaps belongs more properly to a section of the
succeeding division of the subject — Warning or Apose-
matic Colours (see p. 325).

9. The Gregarious Habit may assist Concealment. —
Although the gregarious habit is more commonly asso-
ciated with, and tends to intensify the effects of Warn-
ing Colours, examples are known where cryptic larvae
packed closely side by side produce the appearance
of a brown patch on a leaf. While some of the details
of the resemblance of a group of African Flatidae
(Homoptera), as described and figured by Professor
J. W. Gregory,2 have not been supported by later
observations, yet the main conclusion that they represent
together a cluster of flowers and unopened buds has
been entirely confirmed.3

10. Adjustable Protective Resemblance. — In this, the
highest and most perfect form of concealment as an aid
in the struggle for life, an individual can change its colour
into any tint which would be appropriate in any environ-
ment normal to the species. Such changes are of two
kinds : — ■

a. Rapid, a response to Dynamic Conditions, in which
owing to the rapid movements of the organism one
environment is exchanged for another with speed, and
any number of times. In such forms the adjustment is
effected rapidly, and can be effected any number of times.

b. Slow, a response to the Static Conditions of

1 Trans. Ent. Soc, Lond., 1869, pp. 22-3.

2 The Great Rift Valley, London, 1896, pp. 273-5, and Frontispiece.

3 S. L. Hinde in Trans. Ent. Soc, Lond., 1902, p. 695 : see also the
reproduction in PI. xxvi of Mrs. Hinde's drawings of a cluster of living
insects.

IN DEFENSIVE COLORATION 305

sedentary organisms, a response nevertheless necessary
when the individual may find itself placed in any one
out of several differently coloured environments. In
such cases the adjustment is comparatively slow and the
result long-continued, so that the individual can only
adapt its colours once, or at most a few times in the
course of its life.

Rapid Adjustable Protective Resemblance is suited to
wandering forms which must in the course of their lives
continually pass and repass over environments of different
colours. It is widely found in fish, and also in Amphibia
and Reptilia, the chameleon affording the classical
example. It is also well known to exist in Crustacea
and Cephalopoda (Cuttlefish). All these rapid changes
of colour are due to modifications in shape or position
of superficial pigment cells controlled by the nervous
system. That this control is itself regulated by the
stimulus of reflected light, through the medium of the
eye and optic nerve, has been proved in many cases.

Slow Adjustable Protective Resemblance is found in
sedentary animals passing their life in a single environ-
ment which, however, may be very different in the case
of different individuals. Thus, in many a species of moth
the eggs are deposited now on trees with twigs of one
colour now of another, on young trees or on those with
old lichen-encrusted branches. One caterpillar will wander
on to a surface of one colour, another on to a surface of
a very different colour, in order to become a chrysalis.
In all such cases the power of colour-adjustment is only
needed once, or at most, in certain wandering larvae, two
or three times.

Such changes, so far as they have been studied, appear
to be produced through the nervous system, although
the stimulus of light probably acts on the skin, and not
through the eyes. Parti-coloured surfaces do not pro-
duce parti-coloured chrysalises, probably because the
antagonistic stimuli neutralize each other in the central
nervous system, which then disposes the superficial
pigments so that a neutral or intermediate effect is
produced over the whole surface.

fOLLTON X

3o6 THE PLACE OF MIMICRY

It has been contended by Mr. W. Bateson 1 that there
is no struggle for existence during the pupal stage of
Vanessa urticae (the Small Tortoiseshell Butterfly), and
that, therefore, its power of colour-adjustment is not
related to any danger, and cannot have been evolved by
Natural Selection. An attempt has been made by Miss
C. B. Sanders, Miss M. E. Notley, Miss F. A. Wright,
and the author to test this conclusion by exposing the
pupae of tirticae and allied species upon environments of
various kinds, and keeping a careful watch upon them.
The results, of which only a preliminary statement has
been published,2 prove that there is immense destruction
during the pupal period, short as it is, and that these
angular chrysalises fixed to flat surfaces were in far
greater danger than when suspended against a rough
background. On the other hand, the evidence of pro-
tection afforded by colour-harmony with the environment
was far less clear in these experiments.

The power of individual colour adaptation known to
exist in many larvae and exposed pupae of Lepidoptera
received a striking and novel illustration in some experi-
ments conducted at Oxford in 1893-4.3 The larvae of
the Geometrid moth Odontopera bidentata were found
to be extremely sensitive to the various shades of brown
and grey, colouring the bark of their natural food-plants.
The green of the leaves, on the other hand, did not
produce green but extremely pale brown caterpillars.
It is to be noted, furthermore, that the larvae do not
rest on the leaves by day, but only on the twigs and
branches. So far, the experiment was conducted along
the same lines as the earlier investigations, and yielded
similar results. The exposure of the larvae to lichen-
covered branches produced effects unseen in previous
experiments, viz., brown, bark-like larvae, bearing green,
lichen-like markings. The contrast between the effect of
the continuous green surfaces of the leaves and the scat-
tered green of the lichen was remarkable and striking.

1 Trans. Ent. Soc, Lond., 1892, pp. 2:2-13.

2 Report 0/ the British Association, Bristol Meeting, 1898, pp. 906-9.

3 Fully described in Trans. Ent. Soc, Lond., 1903, p. 311, plates
xvi-xviii.

IN DEFENSIVE COLORATION 307

The experiment was then tried, with equally successful
results, upon the young larvae of Gastropacha quercifolia
(the Lappet Moth). In this case the change was pro-
duced before hybernation, and no subsequent change in
the conditions availed to effect any modification. The
appearance of bark densely covered by masses of grey
lichen was beautifully reproduced on some of the larvae,
and considerable effects were wrought in all exposed to
the above-named conditions.

In these experiments, as in all others of the kind, the
effects produced are those with which the field naturalist
is perfectly familiar. The advance in our knowledge
consists in the proof that such familiar effects are con-
trollable, and in ascertaining the conditions under which
they are evoked.

Adjustable Protective Resemblance, probably of an
analogous kind, is known in Coleoptera. Thus Mr. W.
Holland 1 has observed that the specimens of a well-
known British weevil, Cleonus sulciroslris, are reddish-
brown upon the sands of Boar's Hill, near Oxford, dark
grey on Shotover Hill, also near Oxford, and a pale
grey on the Deal sand-hills. I also observed in 1901
that the very abundant individuals of a species of grass-
hopper in Heligoland were invariably dark reddish brown
like the earth, while on the flat sandy Dime, three-
quarters of a mile away by sea, they were sand-
coloured, or, more rarely, green like the grass. It is
probable that experiment would prove that many such
Coleoptera and Orthoptera, as well as the flower-haunting
spiders, possess a power of individual colour-adjustment
similar to that proved to exist in many Lepidopterous
larvae and pupae. The alternative interpretation sug-
gested in the next Section is probably inapplicable
here.

1 1 . Coincidence betiveen the Colours of Organisms and
those of their Peculiar Environments may be probably
Caused by the Local Operation of Natural Selection, —
It is well known that individuals of the Geometrid moth
Gnophos obscurata are light-coloured when found upon
1 Trans. Ent. Soc, Lond., 1899, p. 430.
X 2

3o8 THE PLACE OF MIMICRY

chalk, dark when found upon peat. Naturalists who
have had much experience of the species in its native
haunts assert that its habits are such as to render these
tints highly protective. Careful experiments 1 have
proved that when nearly full-fed larvae are transferred
from chalk to a very dark background, and kept there
during the whole of the pupal period, the tints of the
resulting moths are in no way affected. Unless the
imaginal colours are determined by stimuli applied still
earlier in the larval life — upon the whole an improbable
conclusion — we can only suppose that the local colour-
harmony has been produced by the gradual destruction
through many generations of the darker forms on chalk
and the paler ones upon peat, &c.

1 2. The Recent Progressive Darkening of many Species
of Moths in the Lancashire and Yorkshire District, — A
great deal of evidence has been brought forward to show
that many moths in the neighbourhood of great centres
of population, and also in distant areas affected by their
smoke, have become very different in appearance from
what they were during the lives of the last generation of
naturalists and even within the memory of many still
living. The latest records on the subject are those of
Mr. G. T. Porritt,2 who does not himself accept the con-
clusion that the change has been caused by Natural
Selection. The smoke from the manufacturing districts
of Yorkshire, driven by the prevalent S.W. wind, has
killed the lichen and rendered the tree trunks and
branches uniformly dark over a wide strip of country.
Their appearance has become utterly different, and the
pale variegated tints formerly borne by the moths in
question would now stand out with startling distinctness
upon them. It is of the utmost importance to gain the
fullest knowledge of the character of the struggle for
existence in these species, and to test the interpretation
founded on Natural Selection in every possible way ;
but the facts as they stand seem to raise an over-
whelming probability in favour of this explanation, which

1 Trans. Ent. Soc, Lond., 1892, pp. 453-8.

8 British Association, York, 1906, Report, p. 316.

IN DEFENSIVE COLORATION 309

was suggested many years ago by Mr. J. W. Tutt.1
Under any circumstances the colour-harmony is not to
be explained, like that of many larvae and pupae, by
susceptibility of the individual at any time in its life to
the darkened tints of its environment. Eggs sent from
the smoky districts and reared in other parts of the
country produce the same dark moths. Furthermore,
the smoky districts act as centres, from which, by inter-
breeding, hereditary influence radiates into the surround-
ing areas ; and even so far off as Oxford, black forms of
some of the species are believed to be more prevalent
than formerly. It is of interest to note that the
changes which have occurred offer little support to the
hypothesis of evolution by mutation. Owing entirely
to artificial conditions, a sudden and rapid change has
occurred in the tints of the environment. In nature we
should rarely meet with such rapid and sudden changes.
In one species, A mphidasys betularia.z. black 'mutation',
the form doubledayaria, existed as a rarity before the
darkening of the environment. Donbledayaria has now
replaced the typical form in the districts we are con-
sidering. But Mr. Porritt tells me that such a sudden
change is quite the exception among the numerous
species which have darkened. In the great majority,
a long series of intermediate varieties can still be found,

1 Entomologists Record, vol. i, 1 890-1. The following passage is
quoted from p. 56 : — ' The vast quantity of smoke, gases, fumes, &c., in
manufacturing towns, brought down by rain, is scarcely credible, and it
is from these impurities I consider the permanent darkening comes.
When the water evaporates, the solid matter is left behind, and as a
result the impurities are left to darken the surfaces to which they have
been carried by the rain-water. The theories of " natural selection " and
"protection" now apply in their fullest sense, the insects become
darkened, " hereditary tendency " perpetuating and intensifying the
melanism. I believe from this (and it appears to be a fair deduction),
that Lancashire and Yorkshire melanism is the result of the combined
action of the " smoke," &c, plus humidity, and that the intensity of York-
shire and Lancashire melanism produced by humidity and smoke, is
intensified by " natural selection " and " hereditary tendency ".' The only
words I should criticize in this passage are those which suggest that the
humidity and smoke have had any effect apart from that due to Natural
Selection.

3io THE PLACE OF MIMICRY

and the transformation appears to be going on very
gradually.1

13. Dimorphism and Polymorphism in Procryptic
Defence. — It is common for different individuals of a
species to adopt two or more different appearances, each
of which resembles some special object that is of no
interest to an enemy. Thus the Oriental 'leaf-butter-
flies' {Kallima) represent many of the well-known
appearances borne by dead leaves. Caterpillars and
chrysalises are also frequently dimorphic — green and
brown, — the two dominant colours of the normal
environment. Such differences extend the area over
which an enemy must search in order to obtain its food.
It has been shown that green forms predominate in the
offspring of green parents, and similarly with the brown.
We are, therefore, led to the conclusion that the two
forms intermixed are more advantageous than either
alone, and that otherwise one would quickly replace the
other altogether.

14. Seasonal Changes in the Individual. — Seasonal
changes may occur in the course of the individual life, as
in the Alpine Hare, Ptarmigan, &c. In many cases it is
known that the change is brought about by moulting, but
if an observation by Captain James Ross can be depended
on, the whitening may begin in an existing coat in the
course of a single night. The animal experimented upon
was the Hudson's Bay Lemming, which was suddenly
exposed to intense cold. The results were so surprising
that it would be most desirable to repeat the experiment.

1 5. Seasonal Dimorphism in Procryptic Defence. — This
mode of protection is seen in many forms with more than
one brood in the course of the year. Concealment is
effected by different colours and even shapes, correspond-
ing to the different environments provided by the two
seasons. Thus it has already been pointed out on
pp. 206-7 tnat tne hooked apex of the fore wing and

1 See also Handbuch der palaarhiischcn Gross-Schmetterlinge, M. Stand-
fuss, Jena, 1896. This author's observations on Melanism are stated in
a condensed form by Dr. F. A. Dixey in Science Progress, vol. Vti (vol. ii
of New Series) ; No. 7, April 1898, pp. 196-202.

IN DEFENSIVE COLORATION 311

produced angle of the hind wing in certain Satyrine and
Nymphaline butterflies are characteristic of the brood of
the dry season, when dead leaves are bent and twisted
and warped, and that the absence of these characters in
the wet season corresponds to a time when such leaves
are sodden and lie flat on the ground. Dr. Dixey has
shown that analogous seasonal changes occur in certain
South American and African Pierinae} In cases where
the character and intensity of the struggle for existence
vary greatly with the seasons, procryptic defence may be
developed in the time of greater stress, the dry season,
and very different methods employed by the broods of the
other season (see pp. 208-11, 320, 339-41). Seasonal
changes of procryptic significance also take place in certain
northern species, such as Selenia illanaria, &c. These
have been the subject of exhaustive investigation pro-
longed over many years by F. Merrifield, who finds that
heat applied to the pupal stage is the stimulus under
which the changes are set on foot. Much excellent
work has also been done on the same subject by
Standfuss of Zurich, earlier by Weismann, and first of
all by Dorfmeister.

The laborious experiments of G. A. K. Marshall in
South Africa have led to a knowledge of interesting
differences in the reactions of different species. Thus, in
the Pierine butterflies Teracolus omphale and T. achine,
a warm, moist atmosphere applied to the larvae produced
wet season butterflies : on the other hand, very little
additional effect was produced when the pupae also were
similarly treated, and hardly any effect at all when damp
heat was applied to the pupae alone. On the other hand,
in another Pierine, Belenois severina, damp heat applied
during the larval stage produced no result, but when the
pupae as well as the larvae were thus treated great
effects were manifest. In this species, too, there were
interesting differences in the character of the effect,
according as heat alone or heat with moisture was applied.
It seems quite clear from these experiments that the
larva is the sensitive stage in Teracolus and the pupa

1 Trans, Ent. Soc, Lotid., 1903, p. 157, plate vii.

312 THE PLACE OF MIMICRY

in Beletiois} Further investigations into the stimuli
under which the seasonal forms develop are briefly men-
tioned on pp. 340, 341.

16. Syncryptic or Common Protective Resemblances. —
Colouring for concealment in similar environments may
incidentally produce superficial resemblances between
species. Thus, desert forms of the most varied kinds
are coloured in the same way, while a Special Protective
Resemblance to lichen, bark, grasses, pine-needles, &c,
may often lead to a tolerably close similarity between
the species which are thus concealed. Such Syncryptic
Resemblance is to be distinguished from Mimicry and
Common Warning Colours, in which the superficial like-
ness is not incidental but an end in itself.

Syncryptic Resemblance has much in common with the
superficial likeness incidentally produced by similar
functional adaptations. Thus mole-like forms adapted
for a burrowing life have been independently evolved in
Insectivora (true moles), Rodentia, and Marsupialia.
Such resemblances, which have been called Analogical
or Adaptive, may be termed Syntechnic, because they
follow from similar modes of life. Syntechnic Resem-
blance is an incidental result of similarity in the dynamic
conditions of life, just as Syncryptic Resemblance is
incidentally produced by similarity in its static conditions.2

B. Anticryptic or Aggressive Resemblance.

It is unnecessary to speak in detail about concealment
for the purpose of attack, inasmuch as all the principles en-
countered are the same as those upon which Procryptic or
Protective Resemblance depends. The colouring of the
lion harmonizing with the desert is a good example of
General Resemblance, a huge constricting serpent lying
in wait for prey and hanging like a broken branch from
a forest tree serves equally to illustrate Special Resem-

1 See Dr. F. A. Dixey's interesting account of these most valuable
experiments in Proc. Ent. Soc, Lo?id., 1906, p. civ ; 1907, p. xii.

2 See the article Mimicry \ in Diet, philos. and psychoid J. M. Bald-
win, New York and London, 1902, vol. ii, pp. 79-80. In this
article the present writer, with the kind help of Mr. Arthur Sidgwick,
introduced the terms Syncryptic and Syntechnic.

IN DEFENSIVE COLORATION 313

blance. The neutralization of shadow is well seen in the
predaceous Carnivora, and, in many of them, characteristic
details are depicted on the shadowless and ghost-like
surface of their general ground-colour ; vistas of upright
stems on the tiger, effects of light and shade, even,
it is said, pin-hole images of the sun as cast by minute
interstices between leaves, on arboreal species. Adjust-
able Resemblance in aggressive species, such as the
Chameleon, Cuttlefish, and many Crustacea, is probably
chiefly protective in function, but there can be little doubt
that it is aggressive as well. Chamaeleo pumilus, slowly
moving to within striking distance of its alert and active
prey, is probably aided by colour adjustment and the
neutralization of shadow. The Seasonal Changes of
northern forms are just as characteristic of the predaceous
Arctic Fox and Ermine as of the Alpine Hare, Lemming,
and Ptarmigan.

C. Allocryptic or Adventitious Protective and
Aggressive Resemblance.

Concealment is often effected by means of a covering
of foreign objects. Such forms are of course hidden in
any environment. When sedentary they are covered
with local materials, when wandering they have the
instinct to reclothe. The great majority of examples are
Alloprocryptic, such as the little English crab Stenor-
rhynchits phalangiuni* , which decks itself with pieces of
seaweed; but examples of Allanticryptic Resemblance
are well known. It will be sufficient to mention two
species : —

1. The large Brazilian frog Ceratophrys comuta*
which squats in a hole in the ground and covers its back
with earth, the exposed parts harmonizing with the
surroundings. The frog remains thus motionless and
concealed, waiting until some small animal approaches or
even walks over it.

2. The ant-lion (Myrnieleon) larva, buried in fine sand
or dust, at the bottom of its crater-like pit.

Allocryptic Resemblance may be both protective and
aggressive at one and the same time.

3H THE PLACE OF MIMICRY

A good example is to be found in the little British
crab Hyas coarctata* \ which covers itself very com-
pletely with Algae, exposing only the pearly pink large
claws. It then climbs into a mass of Alga, to which it
imparts a gentle swaying motion. The attention of small
fish is probably first attracted by the movement, and their
interest excited by the brightly coloured claws which alone
can be seen. They approach to within striking distance,
are seized and devoured by the crab. All this has been
observed in the aquarium by Prof. A. F. Dixon, of Dublin,
to whom I am indebted for the information.1 The Hyas
itself is greedily devoured by larger fish, and it cannot
be doubted that the adventitious covering acts as a
defence against these enemies. This crab affords a good
example of the complexity of the uses of colour. The
covering of Algae is an alloprocryptic defence against
enemies, an allanticryptic assistance in the capture of
prey, a capture also aided by the alluring or psendepi-
sematic colouring of the claws.

A subtle form of allocryptic defence is found in the
use of the colour of the food in the digestive organs
showing through a transparent body, or the still more
remarkable cases in which it is dissolved in the blood
and secreted in the superficial cells of the body. In one
case it has even been shown that the different shades of
green produced by modified chlorophyll from the leaves
of different plants, is preserved in the pupa, collected into
the eggs of the perfect insect, and can still be detected in
the larvae of the next generation when first hatched from
those eggs.-

True or Batesian Mimicry is closely related to the
Cryptic Colours described and illustrated above, but
differs in that the mimetic animal resembles an object

1 On the Marine Invertebrate Fauna near Dublin, by G. Y. and A. F.
Dixon. Proc. Roy. Irish Acad., 3rd ser., vol. ii, no. 1, 1891, p. 30.

2 Smerinthus ocellalus. See Proc. Physiol. Soc. in Journ. Physiol.,
vol. viii, 1887, pp. xxv, xxvi. The fact that modified chlorophyll derived
from food forms an important element in the colouring of certain larvae
has been clearly proved in the case of Tryphaena pronuba. See Proc.
Roy. Soc, vol. liv, 1893, P- 4*7, pi- 3> 4-

IN DEFENSIVE COLORATION

3i5

which positively repels its enemies or positively attracts
its prey, rather than one which is of no interest to either.
It is more convenient, therefore, to defer its considera-
tion until after the description of the Warning Colours
which form the models for Mimicry.

II. SEMATIC COLOURS, OR WARNING AND
SIGNALLING (RECOGNITION) COLOURS;
APOSEMATIC AND EPISEMATIC CHA-
RACTERS.

The second great use of colour is to act as a warning
or signal (Sematic Colours), repelling enemies by the
indication of some unpleasant or dangerous quality
{Aposematic or Warning Colours), or signalling to other
individuals of the same species, and thus assisting them
to escape from danger (Episematic or Recognition Colours),
In a very interesting group of cases (A llaposematic), the
animal warns off its enemies by associating with itself
some other animal with unpleasant qualities and Warning
Colours.

A. Aposematic or Warning Characters.

The use of colour for the purpose of warning is the
exact opposite of the one which has been described on
p. 297, its object being to render the animal so conspicuous
to its enemies that it can be easily seen, well remembered,
and avoided in future. Warning Colours are associated
with some quality or weapon which renders the pos-
sessor unpleasant or dangerous, such as unpalatability,
an evil odour, a sting, the poison-fang, &c. The object
being to warn off an enemy, these colours are called
Aposematic.

Good examples are to be found in the American
skunks [Mephitis mephitica*, Mephitis suffocans* :, Conepatus
ntapuritd*, &c), which possess the power of emitting an
intolerable stench, and are, under ordinary conditions,
slow-moving, conspicuous black and white mammals.

An element of Mimicry exists in the appearance of the
remarkable chrysalis of Limc7iitis populi * as interpreted

3i6 THE PLACE OF MIMICRY

by Portschinski.1 The Russian naturalist considers that
this pupa, which he found to be rejected by birds, bears
the most detailed resemblance to a chrysalis which has
been pecked and seriously injured, but finally abandoned.

It has been objected that in the case of small unpalat-
able animals the individual with Warning Colours is often
injured or destroyed by an enemy before it becomes
aware of the unpleasant quality or other special defence.
But the species benefits by the experience thus gained by
an enemy, even though the individual suffers. It is the
species which is preserved and advanced by Natural
Selection, and when this involves danger to the indivi-
dual— as it continually does, the individual must incur
the risk. An insect-eating animal does not come into
the world with knowledge ; it has to be educated by
experience, and Warning Colours ensure that this
education is conferred by a small instead of a large waste
of life. Nevertheless, the necessary risk to the individual
is reduced to the lowest possible level. Great tenacity
of life is usually possessed by animals with Warning
Colours. The tissues of insects with an Aposematic
appearance often possess great elasticity, toughness, and
power of resistance, so that large numbers of individuals
can recover after very severe treatment.

i. Experimental Evidence of Special Protection in
Forms with Warning Colours. — Apart from the species
armed with the sting or poison fang, a large number of
conspicuous species have been proved to possess an un-
pleasant smell. Dr. Dixey and Dr. Longstaff have made
a special point of investigating the scents of living
African butterflies, and they find that while the scents
confined to the male and presumably employed in court-
ship are pleasant to the human sense, those found in both
sexes (and when there is a difference more thoroughly
developed in the female) are unpleasant to man. Such
disagreeable scents were detected in conspicuous butter-
flies belonging to the Danainae, Nymphalinae, Acraeinae,
and Papilioninae. Dr. Dixey has published several inter-

1 Lepidopterorum Rossiae Biologia, St. Petersburg, 1890.

IN DEFENSIVE COLORATION 317

esting notes on the subject.1 Fritz Miiller has also shown
in S. America that the scents of male butterflies are
agreeable.2 Far stronger evidence is of course afforded
by offering forms with Warning Colours to their natural
enemies, and stronger still by watching the behaviour of
enemies in the wild state and by keeping a precise record
of the food found in their stomachs. Although an im-
mense amount of such evidence is still required, a great
deal has been done. The summary of Mr. Frank Finn's
striking experiments in India has been quoted on p. 26g.z

2. Species with Warning Colours depend for their Exis-
tence upo?i the Co-Existence of Palatable Species. — Apose-
matic Colours, together with the qualities they indicate,
depend for their very existence upon the relative abun-
dance of palatable food supplied by animals with Cryptic
Colouring. Unpalatability or even the possession of a
sting is not sufficient defence unless there is enough food
of another kind to be obtained at the same place and time.4
Hence insects with Warning Colours are not seen in
temperate countries except during the months when insect
life as a whole is most abundant ; and in warmer countries,
with well-marked wet and dry seasons, it is found that
Warning Colours are less developed in the latter season,
which is the time of greater stress. Examples will be
given in later Sections.

3. Erroneous Assumption that Warning Colours imply
Complete Immunity from Attack. — Although animals
with Warning Colours are probably but little attacked
by educated enemies of their class, they have special
foes which keep the numbers down. Thus the
cuckoo appears to be an insectivorous bird which will
freely devour conspicuously coloured larvae unpalatable

1 Proc. Ent. Soc, Lond., 1904, p. lvi ; 1905, pp. xxxvii, liv ; 1906, p. ii.
See also G. B. Longstaff in Proc. Ent. Soc, Lond., 1905, p. xxxv, and
Trans. Ent. Soc, Lond., 1905, p. 136.

2 Jen. Zeit., vol. xi, p. 99 ; Trans. Ent. Soc, Lond., 1878, p. 211.

8 See also Proc. Zool. Soc, Lond., 1887, p. 191, for an account of all
the work done up to that date, and Trans. Ent. Soc, Lond., 1902, p. 287,
for the most important of recent researches on the subject.

4 Proc Zool. Soc, Lond., 1887, p. 191 ; confirmed also by F. Finn :
see p. 269 of the present volume.

3i8 THE PLACE OF MIMICRY

to other birds. Nothing can be further from the truth
than Haase's contention that the species with Warning
or Aposematic Colours are absolutely ' immune ' from
the attacks of all enemies, including parasites.1 There
is indeed much evidence to show that such species are
especially liable to destruction by these latter foes.2
Many groups of predaceous insects also appear especially
to attack the conspicuous, easily-captured prey provided
by the groups with Warning Colours. This has been
observed in the case of the predaceous Asilid flies, Dragon-
flies, Hemiptera, Mantidae and Locustidae?

4. Transition from Cryptic to Aposematic Defence. —
Although these two methods of protection are as a rule
sharply contrasted, intermediate examples are common,
and even more numerous are the cases in which an
individual in the course of its life-history or by an
instantaneous change of attitude passes from the one
category into the other.

The larvae of Cncullia verbasci (the Mullein Shark
Moth) are good intermediate examples. Their colour-
ing harmonizes well with the flowering spike of the
Mullein, and when disturbed their instant fall and active
wriggling movements, tending to concealment among
lumps of earth, roots of grasses, &c, belong to the cate-
gory of Cryptic defence. On the other hand, they are
rendered conspicuous by gregarious habits, while the large
larvae are very visible upon the broad leaves of the food-
plant. Furthermore, experiment shows the existence of
distasteful qualities.4 There is also a considerable element
of concealment in the resemblance of the orange bands
of the larva of Euchelia jacobaeae (the Cinnabar Moth) to
the flowers of its food-plant. I was formerly disposed
to regard these two species as examples of recent transi-
tion from a Cryptic to an Aposematic mode of defence.5
I should now be more inclined to explain the Cryptic

1 Researches on Mimicry, part ii, Stuttgart, 1896, English translation.
8 Trans. Ent Soc, Zona1., 1902, p. 337.

3 Trans. Ent. Soc, Lond., 1906, p. 323.

4 Proc. Zool. Soc, Lond., 1887, pp. 202, 203, 238.

5 Proc. Zool. Soc, Lond., 1887, p. 238.

IN DEFENSIVE COLORATION 319

element as a protection against the special enemies
which attack the species in spite of their unpalatability.
The more completely the larva is concealed from
special enemies, and the more visible it is to enemies
which respect the defence of unpalatability, the greater its
chance of survival. The compromise is effected in these
species by concealment at a distance, passing into con-
spicuousness on a near approach, combined with further
defensive methods when an actual attack is made.

Abrupt changes in the method of protection in the
course of the life-history are very common. Thus the
caterpillar of Cucullia verbasci produces a moth possess-
ing a beautiful Cryptic colouring, the resemblance being
to a splinter of wood. Etichelia jacobaeae, on the other
hand, becomes even more Aposematic in the perfect than
in the larval state. One of the most beautiful instances
of change is afforded by the larva of the rare British
species A crony eta alni. In its young stage the cater-
pillar bears the closest likeness to the excrement of
a bird : at a change of skin it suddenly emerges with
a startling black and yellow pattern which has all the
appearance of a Warning character.

Even more interesting are the species which by some
significant movement pass at once from the Cryptic to
the Aposematic category. The change thus undergone
by certain larvae was described in 1887 1 by the
present writer : — ' Such larvae are apt to pass unnoticed
because of the harmony between their colours and mark-
ings and the artistic effect of their surroundings ; but, if
discovered, or even if an enemy approach so that there is
danger of their being discovered, the protective [cryptic]
attitude is instantly changed for one which renders the
larva conspicuous, and warns the enemy of the presence
of unpleasant attributes (taste or smell), or alarms it by
the resemblance of the new appearance to some object of
terror [the reference is here to C. elpenor as described on
pp. 367, 368]. These facts may even be true of gregarious
larvae. Thus a group of phytophagous Hymenopterous

1 Proc. Zool. Soc, Lond., 1887, pp. 197, 204. See also pp. 206, 207
of the same memoir, where experiments on four species are recorded.

320 THE PLACE OF MIMICRY

larvae may remain inconspicuous while undisturbed, but
nevertheless the approach of an enemy determines
united movements in the colony which render the whole
strikingly conspicuous, and . . . may be attended later by
the emission of an offensive smell from the numerous
ventral glands of all the individuals simultaneously (e. g.
Croesus septentrionalis)!

5. Seasonal Transition from Cryptic to Aposematic
Defence. — It has been pointed out on p. 317 that in
latitudes like our own the insects with Aposematic
colouring are compelled to hide during the periods when
the food of insect-eating animals is scarce. An ana-
logous alternation may be produced by the wet and dry
season broods of certain species. In some African
butterflies of the Nymphaline Genus Precis, the wet
season broods are distinguished by the more or less
conspicuous under sides of the wings, while those of the
dry season are highly Cryptic. The South and East
African species Precis archesia was the one which most
impressed the present writer, and led him to seek for an
interpretation in the conditions of life peculiar to the two
seasons.

It appeared, on comparing a series of specimens,1
that, as described on p. 208, the feature which chiefly v
renders the wet season form conspicuous is derived from
the very marking which is the principal element in the
concealment of the other ! This led directly to the
conclusion that there must be some great difference in
the conditions of the two seasons which made a certain
measure of conspicuousness an advantage in the wet, and
concealment a necessity in the dry. Some account of
these differing conditions and the manner in which such
an astonishing alternation in this and many other species
may have arisen is given on pp. 206-1 1.

6. Geographical Transition fro7n Aposematic to
Cryptic Defence. — The much -mimicked, conspicuous
Limnas chrysippus — perhaps the commonest butterfly
in the world — tends to be replaced on desert areas, and

1 For such a transitional series see Trans. Ent. Soc, Lo?id., 1902,
plate xiii, figs. 5-8. Consult also pp. 428-9 of the same memoir.

IN DEFENSIVE COLORATION

321

in the Somali Desert appears to be completely replaced,
by a form (dorippus = klugii) without the black and white
tip to the wing (see pp. 70-1). Furthermore, in some
of the specimens the tawny colour is replaced by a tint
far more adapted for concealment against a sandy back-
ground. It is probable that under the stress of desert
conditions — constituting, as it were, a permanent dry
season — this highly distasteful form has been compelled
to adopt a measure of Cryptic Defence. Conversely,
in the luxuriant life and abundant food of the tropical
west coast of Africa, a form (the white-hind-winged
alcippus) even more conspicuous than the type, has
become dominant, and, from the mouths of the Niger to
the southern edge of the Sahara, is now apparently the
only form l.

J. A. H. Thayer s Criticism of the Statement that
Animals are Conspicuous,— Mr. Abbott H. Thayer has
criticized, from the artist's point of view, the use of the
term 'conspicuous' by the naturalist.2 In the first place
he states that ' Only unshiny, bright 3 monochrome is intrin-
sically a revealing coloration. As soon as patterns begin,
obliteration of the wearer begins, . . . Nature does not
blunder, and Natural Selection would evolve the mono-
chrome, instead of a patterned surface, were simple con-
spicuousness her aim'. But naturalists, in using the
word ' conspicuous', have not meant to imply a con-
spicuousness as great as the artist could make it ; and
reasons have been given in the preceding Sections why

1 I should have carried the southern limit of the exclusive occurrence
of alcippus considerably further had I not recently seen in the Stockholm
Natural History Museum a male and a female specimen of the type form
captured respectively December 26 and 21, 1890, in the Cameroons, by
my friend Professor Yngve Sjostedt. They were, he told me, excessively
rare as compared with alcippus. In a large amount of material at Tring
and Oxford from far inland and considerably further south — Luebo, on a
southern branch of the Congo — the type form alone is represented. For
the suggested interpretation of the dorippus and alcippus forms, and for
the evidence that chrysippus is the ancestral form, consult Trans. Ent.
Soc, Lond., 1902, p. 473.

2 Trans. Ent. Soc, Lond., 1903, p. 556.

3 Mr. Thayer tells me that he would now omit the words 1 unshinv,
bright \

POULTON Y

322 THE PLACE OF MIMICRY

the aim of nature could not be ' simple conspicuousness '
alone. There is the danger of special enemies, and the
danger of specially hungry enemies ; and it must be
freely admitted that conspicuousness beyond what is
necessary for warning an attacking enemy would be
a danger. Mr. Thayer states that iridescence tends to
render colours less conspicuous, and we certainly observe
that a uniform black appearance unrelieved by pattern is
continually accompanied by iridescence or structural
surface colours of some kind. In view of Mr. Thayer's
suggestion, it becomes probable that dead black would
be too conspicuous for many a well-armed Aculeate or
nauseous Euploea, and that it is therefore modified so
that it obtrudes less upon the distant view of enemies
that * mean business \1

Naturalists have used the term 'conspicuous' relatively,
and furthermore, in using it, have taken into account the
habits, movements, modes of display, &c, which may
be of even more importance than the colouring itself.
The Ithomiine and convergent Heliconine butterflies of
tropical America are no doubt far from possessing an
' intrinsically revealing coloration ' such as Mr. Thayer
describes ; but it is equally true that they fall into an
entirely different category from that which includes the
Cryptic species, with undersides resembling leaves, bark,
&c. Mr. Thayer suggests that they resemble flowers,
and the surroundings of flowers, and that their extra-
ordinary likeness to each other may be incidentally due
to their resembling the same kind of flower — in other
words may be Syncryptic. The British Guiana associa-
tion of Ithomiinae, Heliconinae, &c. (see pp. 331-3) has
been studied in its native haunts far more completely
than any other. Mr. W. J. Kaye, who has devoted
special and prolonged attention to them, states that these
black, ' cow-red, and chrome-yellow ' butterflies, as they
are precisely described by Mr. Thayer, frequent ' the
white flowers of the plant Eupatorium macrophyllum '.2
There is no evidence of Cryptic Resemblance to flowers

1 Trans. En/. Soc, Lond., 1903, p. 575.

2 Trans, Ent. Soc.} Lond., 1906, p. 412.

IN DEFENSIVE COLORATION 323

in any of the representative combinations in other parts of
the tropical New World, while a careful study of the exact
changes which they undergo as we pass from one district
to another enables us to dismiss any such hypothesis.

Mr. Thayer's criticism is considered in this place
because the preceding five Sections show how subtle is
the relationship between two sharply contrasted methods
of defence, and how easily and frequently the barrier
between them is traversed. The determining factors in
each case are to be found in the complex conditions of the
struggle for existence. It is these that have decided the
degree of conspicuousness attained by Warning Colours,
and have kept them far short of an ' intrinsically reveal-
ing coloration ' as defined by the artist.

8. The A 1 1- Importance of Instinctive Attitudes and
Movements in the Display of Warning Colours. —
Warning Colours are, like Cryptic, assisted by special
adaptations of the body-form, and especially by move-
ments which aid in rendering the appearance as conspicu-
ous as possible. On this account forms with Warning
Colours generally move or fly slowly, and it is the rule in
the wings of butterflies that the warning patterns are
similar on both upper and under surfaces, and so far as
there is a difference, that the colours of the under surface
exposed during prolonged rest should be even more
conspicuous than those of the upper surface. The
flight of certain American Danaine butterflies appears
to be especially adapted to display the conspicuous
under surface of the wings.1

Other instincts also assist in Aposematic display.
Thus the effect of the Warning Colours of caterpillars
is often intensified by gregarious habits. Furthermore,
many animals (spiders, beetles, caterpillars, &c.) when
attacked or disturbed, 1 sham death ' (as it is commonly
but wrongly described), falling motionless to the ground.
Well-concealed animals, when once detected, are thus
given a second chance of escape among little fragments
of earth, dead leaves, or the roots of grasses. Animals
with Warning Colours are, on the other hand, enabled
1 Ann. Mag. Nat. Hist., ser. 7, vol. xiii, April, 1904, pp. 358-9.

Y 2

324 THE PLACE OF MIMICRY

to assume a position in which their characters are dis-
played to the full. Thus Portschinski has shown that
the two unpalatable English moths Spilosoma tirticae*
and kS. mendica*, female, when disturbed, assume attitudes
which serve to display their conspicuous yellow and black
colours.1 In both types of so-called 1 sham death ' —
Cryptic and Aposematic — a definite attitude is assumed,
which is not that of death.

9. Warning or Intimidating Sounds. — Sound may be
employed as an Aposematic Character, as in the hiss of
snakes and some lizards. Certain poisonous snakes when
disturbed produce by an entirely different method a far-
reaching sound not unlike the hiss. Thus the Rattle
Snake \Crotalus) of America rapidly vibrates the series
of dry, horny, cuticular cells, movably articulated to each
other and to the end of the tail. The stage through
which the character probably arose is witnessed in
another genus which vibrates its tail among dry leaves
and thus produces a warning sound. The deadly little
Indian snake, Echis carinata (the 'Kuppa') makes a
penetrating swishing sound by writhing the coils of its
body one over the other. Special rows of the lateral
scales are provided with serrated keels which cause the
sound when they are rubbed against each other. Large
birds, when attacked, often adopt a threatening attitude
accompanied by an intimidating sound which usually
suggests more or less closely the hiss of a serpent, and
thus includes an element of Mimicry.

10. Intimidating Attitudes. — The Cobra warns an
intruder chiefly by attitude and by the broadening of its
flattened neck, the effect being heightened in some
species by the 'spectacles'. In such cases we often
witness a combination of Cryptic and Aposematic
methods, the animal being concealed until disturbed,
when it instantly assumes a Warning attitude.

The benefit of such intimidating characters is clear :
a venomous snake gains far more advantage by terrifying
than by killing an animal it cannot eat. By striking,
the serpent temporarily loses its poison and with this
1 Lepidopterorum Rossiae Biologia, St. Petersburg, 1890.

IN DEFENSIVE COLORATION 325

a reserve of defence. Furthermore, the poison does not
cause immediate death, and the enemy would have time
to injure or destroy the snake.

11. Directive Marks and Structures. — Another Apo-
sematic use is of a different kind, viz. to divert attention
from the vital parts and thus give the animal attacked an
extra chance of escape. The large, conspicuous, easily-
torn wings of butterflies and moths act in this way, as is
shown by the numbers of individuals which may be
captured with notches bitten symmetrically out of both
wings when they were in contact. The eye-spots and
1 tails ' so common on the hinder part of the hind wing,
and the conspicuous apex so frequently seen on the fore
wing, probably have this meaning. Their position cor-
responds to the parts which are most often found to be
notched in fresh specimens. In some cases (e. g. many
Lycaenidae) the 1 tail ' and eye-spot combine to suggest
the appearance of a head with antennae at the posterior
end of the butterfly, the deception being aided by move-
ments of the hind wings.1 It has already been pointed
out on p. 303, that the brightly coloured hind wings of
certain moths and grasshoppers are of benefit in the
manner here described.

The flat-topped ' tussocks ' of hair on many caterpillars
look like conspicuous fleshy projections of the body, and
they are held prominently when the larva is attacked.
If seized, the ' tussock ' comes out, and the enemy is
greatly inconvenienced by the fine branched hairs. The
tails of lizards, which easily break off, are to be similarly
explained, the attention of the pursuer being probably
still further diverted by the extremely active movements
of the amputated member. Certain crabs similarly throw
off their claws when attacked, and the claws continue to
snap most actively. The tail of the dormouse, which
easily comes off, and the extremely bushy tail of the
squirrel, are probably of use in the same manner.

The classification of Directive Characters is a matter of

1 This deeply-interesting adaptation has been independently recognized
by many naturalists in many countries. For a list of records see Proc,
Ent. Soc.; Lond., 1906, p. Hi; also Ent. Mo. Mag., 1906, p. ia8.

326 THE PLACE OF MIMICRY

great difficulty. I have here provisionally retained them
in the position originally assigned in The Colours of
A nimals. The ' tussocks ' of hair, themselves providing
distasteful qualities, will probably always be looked upon
as a form of Aposeme. On the other hand, as my friend
Mr. Marshall has pointed out to me, deception and not
unpalatability is the essential element in the protection
generally afforded by eye-spots, and, when this is the
case, they should be regarded as a form of Pseudoseme,
and probably of Pseudepiseme. Huge, terrifying, eye-like
marks, such as those of the Brassolinae, fall into their
place beside the more perfect and specialized Pseud-
aposemes of certain snake-like larvae (see p. 367). Mr.
Marshall observes that there is a marked absence of eye-
spots in the great distasteful groups of butterflies, the
Ithomiinae, Danainae, Heliconinae, and Acraeinae. On
the other hand they form a most characteristic Apose-
matic feature in the much-mimicked Morphine (Amathu-
siine) genus Tenaris, and are often found in Papilios
with a conspicuous pattern on the under surface.

1 2. The Seasonal Development of Directive Marks. —
It has been explained on pp. 2 10- 11 that the eye-spots
developed, especially on the under surface of the wings,
in the wet season broods of many Satyrinae and certain
Nymphalinae are probably adapted to meet the kind of
attack which is chiefly made at this time of plenty, and
that such markings would be too great a danger in the
stress of the dry season ; furthermore, that the eye-spots
are a defence during times of activity, but would be the
reverse in the longer periods of repose of the dry season.
It was the recognition of the same phenomena in such
distantly related butterflies as Satyrinae and Nymphal-
inae that impelled the present writer to seek an inter-
pretation in conditions of life which are common to the
two groups.1

1 Ann. Soc. Ent., France, vol. lxxii, 1903, p. 407.

IN DEFENSIVE COLORATION 327

A*. Synaposematic or Common Warning Colours
(Mullerian Mimicry).

This subject, though logically but a section of Apo-
sematic Colours, is of such vast importance that it is
here converted into a separate heading equivalent to
A. Aposematic, and marked with an A*.

Animals with Warning Colours often tend to resemble
each other superficially, as was pointed out by H. W.
Bates in his paper on the Theory of Mimicry.1 He
showed that the conspicuous, presumably unpalatable,
tropical American butterflies, belonging to very different
groups, which are mimicked by other species, also tend
to resemble each other, the likeness being often remark-
ably exact. The resemblances were not explained by
Bates's Theory of Mimicry, and he could only suppose
that they had been produced by the influence of a
common environment, a suggestion at first adopted by
Wallace but abandoned by him as soon as Fritz Muller's
hypothesis appeared in 1879.2

It seems probable that Bates was misled by a failure to
realize the remoteness of the affinity borne by the Heli-
coninae to the Ithomiinae, and that consequently the mimi-
cry between them did not appeal strongly to him. He
indeed saw and described the important structural differ-
ences, but still left them united as Heliconidae, calling
the Heliconinae, Acraeoid, and the Ithomiinae (including
the Danaine genera Lycoj'ea and I tuna) Danaoid. The
superficial resemblances were so close in shape as well as
pattern of wing that he was driven to accept an arrange-
ment which gave too little weight to characters of greater
importance.

As a solution of the difficulty Fritz Miiller suggested
that life is saved by a resemblance between the Warning
Colours in any area, inasmuch as the education of young

1 Trans. Litm. Soc, Lo?id., vol. xxiii, 1862, p. 495. The fact that
these examples were not figured in the accompanying plates probably
explains the long delay in the appearance of the Mullerian hypothesis.
See pp. 211-12 of the present work.

- Kosmos, May, 1879.

328 THE PLACE OF MIMICRY

inexperienced enemies is facilitated, and insect life saved
in the process. Each species which falls into a group with
Common Warning or Synaposematic Colours1 contributes
to diminish the destruction of the other members. It is
obvious that the amount of learning and remembering,
and consequently of injury and loss of life involved in
these processes, are reduced when many species in one
place possess the same Aposematic colouring, instead of
each exhibiting a different 1 danger-signal \

It has been pointed out that this struggle is in reality
far more severe than has been supposed. At each
breeding season a fresh wave of young enemies is sent
forth, takes its toll of insect life, and, except for an
insignificant fraction, perishes in the struggle with its
own foes.2

Before proceeding to discuss Synaposematic Resem-
blance in some detail, adducing many examples, I desire
to state as prominently as possible that a Mullerian, as
opposed to a Batesian, interpretation is suggested in no
positive or dogmatic spirit. Detailed researches into
the subject are very recent, while new material and the
record of fresh observations are continually appearing.
Hence the explanation of special examples must in many
cases be regarded as provisional. My friend, Mr. G. A. K.
Marshall, would consider that a Batesian or Pseud-
aposematic interpretation is more probable for many of
the examples. On the other hand, so far as I can judge
from existing evidence, I believe — and at any rate for
the most part Dr. Dixey agrees with me — that all of
them fall under the Mullerian Hypothesis of Common
Warning Colours.

i. The Mathematical Statement of the Advantage
Conferred by Perfected Mullerian Resemblance. — The
precise statement of advantage was made by Mr. Blak-
iston and Mr. Alexander, of Tokio. 1 Let there be two

1 These terms were introduced in a note, dated June 14, 1897, to the
report of the discussion on Dr. Dixey's paper on Mimetic Attraction in
Trans. Ent. Soc, Lond., 1897, p. 317. See Proc. Ent. Soc, Lond., 1897,
p. xxix, n.

2 Proc. Ent. Soc, Lond., 1903, p. lxv ; see also pp. 167-8 of the present
work.

IN DEFENSIVE COLORATION

329

species of insects equally distasteful to young birds, and
let it be supposed that the birds would destroy the same
number of individuals of each before they were educated
to avoid them. Then if these insects are thoroughly
mixed and become undistinguishable to the birds, a pro-
portionate advantage accrues to each over its former state
of existence. These proportionate advantages are in-
versely in the duplicate ratio of their respective original
numbers compounded with the ratio of the respective
percentages that would have survived without the
mimicry/ The difference between this hypothesis and
the Mimicry of Bates is well shown in the following
passage, in which it is supposed that B exists in smaller
numbers than A : — ' It must be remembered, however,
that B does no harm to A by mimicking it ; on the
contrary, the act of mimicry is of advantage to A over
its former state of existence as well as to B ; but A being
the more numerous the advantage is less. Still, after the
assimilation neither has an advantage over the other.
Proportionally they suffer from the ravages of birds
equally ; the percentage of losses is the same ; they are
on equal terms. No matter how long they continue the
association, neither gains nor loses on the other ; though
through one being more numerous it loses more indi-
viduals, yet equally in proportion with the other. So
that, if one is twice as numerous as the other at the time
of assimilation, it must always — other conditions being
equal — remain twice as numerous.' 1

2. The Advantage Conferred during the Growth of
Miillerian Resemblance. — The above statement is con-
cerned with a Mullerian Resemblance which has reached
the climax of evolution, when the constituent species
cannot be distinguished by their enemies. It is very
doubtful whether this climax is ever attained except when
affinity comes to the aid of mimicry. At the same time
it is useful to assume indistinguishability in a hypothetical
example, if by this means the advantages of resemblance

1 The full statement here quoted was published by the authors in
Nature, vol. xxix, 1884, PP- 4°5-6 : a preliminary statement had been
published in Nature, vol. xxvii, 1883, pp. 481-2.

330 THE PLACE OF MIMICRY

can be made clear — if we are thus led to realize how
it is that a higher degree of resemblance is more
advantageous than a lower degree. For this reason
I have set forth below, by means of a hypothetical case,
the principles which, in my opinion, have led to the
gradual growth of Synaposematic likeness.

If we suppose (i) that two species of butterfly, A and
B, living in the same locality are equally distasteful to
birds, and that young birds have to learn their qualities
by the test of experience before avoiding them for the
future ; (2) that during this education each young
insectivorous bird destroys or prevents the reproduction
of one example of each pattern ; (3) that the numbers of
A and B are equal, but that half the individuals of B
possess a pattern A , indistinguishable from A, and the
other half, a pattern 0 sufficiently distinct to require
learning by a separate set of tasting experiments, — it
follows that, if the inexperienced insectivorous birds of
a given area be estimated at 20,000 and the two butter-
flies at 1,000,000 each, then 20,000 losses will be suffered
by the 1,500,000 individuals of pattern A + A' and an
equal number by the 500,000 of pattern B\ In other
words, pattern A' will lose if °/o and Bf 40/.

In the vast majority of cases, however, the two species
are not equal in numbers, but those of the mimicking
species very much smaller. If, for the sake of illustration,
we suppose the numbers of A to be 1,750,000 and those
of B 250,000 divided as before into A' and B \ it follows
that A + A' would lose 20,000 out of 1,875,000 or a little
over 1 °/o (about 1-07), and B' 20,000 out of 125,000 or
j6°/. It is thus possible at once to see why, when the
numbers become very disproportionate, the only appre-
ciable approach is from the side with the smaller number
of individuals.

The advantages of Diaposematic or Reciprocal Resem-
blance may be illustrated in the same manner. Taking
the numbers of the first illustration, let us suppose that
half the individuals of A, viz. A*, advance to meet an
equal advance of half the individuals of B} viz. B*, so
that the two form a single pattern A* -f B* separate

IN DEFENSIVE COLORATION 331

from A and also from B. It follows that A* + £* will
incur 20,000 losses out of 1,000,000, or 2 °/o ; while the
two different patterns A and i? will each lose 20,000 out
of 500,000, or 4 °/o.

The examples are of course unnatural in a high degree,
especially in the sharp separation of the patterns into
distinguishable and indistinguishable. But they enable
us to understand the advantage of a close over a rough
resemblance and thus to realize the causes which have
encouraged the growth of a Mullerian likeness through
a long series of generations.

3. Striking Examples of Mullerian Resemblance. —
a. The Neiv World. — The statements in Section 1 on pp.
328-9 apply to the finished product, — the cases of perfect
resemblance which are supposed to be indistinguishable
to the inexperienced enemies. Although the mode of
flight certainly facilitates discrimination,1 we must admit
that the patterns of Melinaea mneme and Heliconius
numafa figured by Mr. W. J. Kaye2 are almost exactly
alike. Their likeness reaches the climax of perfection as
nearly as it is ever reached by these superficial resem-
blances between members of distantly related groups.
The plate shows seven examples of the Ithomiine and
seven of the Heliconine. Each set is arranged to exhibit
the gradual transition from a barred to a black hind wing.
Each of the seven varieties of the Ithomiine is matched
by a corresponding variety of the Heliconine. When
the two patterns are compared it is at once clear that the
Melinaea [Ithomiinae) has acted as the model. It still
presents an entirely characteristic Melinaea pattern which
the Heliconucs has adopted. There is no reason for
believing that the latter is more palatable than its model.
In addition to their mimicry of the Ithomiinae the Helico-

1 H. W. Bates pointed out in the original memoir on Mimicry that the
Heliconines 1 move along in a sailing manner, often circling round for a
considerable time, with their wings horizontally extended'. The Itho-
miines, on the other hand, 1 for the most part, keep near the ground, and
have a very slow irregular flight, settling frequently.' Trans. Linn. Soc,
Lond, vol. xxiii (1862), p. 499. A small but distinct means of discrimi-
nation between the patterns is mentioned on p. 350 of the present work.

2 Trans. Ent. Soc, Lond., 1906, pi. xxvi.

332 THE PLACE OF MIMICRY

ninae extensively mimic each other, and are extensively
mimicked by other Lepidoptera. The Heliconinae which
resemble the Ithomiinae belong to the same group as
those which resemble other Heliconinae. The likeness
is even closer in some pairs made up of Heliconines
than in any made up of an Ithomiine and a Heliconine.
There is no good example of Procryptic colouring in the
whole Sub-Family, and the Heliconine types of Apose-
matic colouring are far more glaring than those of the
Ithomiinae. When, however, we inquire into the relative
numbers, it is seen at once that the Melinaea as an adver-
tisement is hundreds of times as efficient as the Heliconius,
because it is hundreds of times as numerous in the perfect
state. With Mr. Kaye's kind help I obtained two days'
captures of butterflies from the locality near the Potaro
River, British Guiana, where this wonderful Mullerian
combination has been chiefly studied. It was arranged
that butterflies were to be taken as they came, without
any selection. On the first day, August 28, 1903, just
323 butterflies were captured, of which 253 were Melinaea
mneme, while 2 were Heliconinae — 1 Heliconius vetustus,
and 1 Eueides nigrofulva. Of these, the first-named very
perfectly resembles the dark-hind-winged forms of the
Melinaea, while the Etieides is a far more outlying member
of the combination. On the second day, February 23,
1904, out of a total of 325 butterflies, 220 Melinaea mneme
were taken, but not a single Heliconine.1 Mr. Kaye's
experience, extending over many years, quite confirms
the extraordinary difference in numbers which was shown
by the results of these two days' captures. It may be
argued that the very numbers of the Melinaea imply a
higher degree of unpalatability, but this is by no means
necessarily the case. Relative numbers are determined
by many other causes, such as fecundity, attacks (chiefly
parasitic) in the earlier stages, &c.

We are led to conclude that during the period of gradual
approach the varieties of H. numata which were most
conspicuously different from the pattern of Melinaea
mneme suffered most, upon the whole, from experimental
1 Proc. Ent. Soc, Lond.y 1906, p. lxi.

IN DEFENSIVE COLORATION

attacks, and that thus gradually the existing resemblance
was reached and is by the same process maintained.
The immense difference in numbers explains why it is
that this approach appears to have been entirely from
the side of the Heliconius, and why the Melinaea was not
appreciably affected.

It is interesting to note that the same relationship
obtains between the Heliconinae of the special group which
provides the Mullerian mimics, and their models, whether
Ithomiine or Heliconine. In both cases the models exist
in immensely greater numbers. It has been argued on
p. 332 that the Ithomiine models are not more unpalatable
than their Heliconine mimics. There is obviously even
less reason for supposing increased unpalatability when
the models are themselves Heliconinae.

b. The Old World. — We find precisely the same
phenomena in the Old World. The distasteful much-
mimicked Sub-Family, the Danainae, contains in addition
to smaller aggregates two main groups, the Danaini and
the Euploeini. Although the two are closely related,
the last-named make up a homogeneous set of species
with a very characteristic appearance, and it is convenient
to separate them from the far less uniform Danaini. The
Danaini range all over the tropics of the Old World,
are everywhere mimicked, and everywhere enter into
synaposematic combinations within the group itself, and
with distasteful groups outside. A very few of them
enter the New World, where they are mimicked in North
(see p. 274) but apparently not in South America.
The Etcploeini, on the other hand, are almost absolutely
restricted to the Oriental and Australian Regions (includ-
ing Southern China, Malaya, and Polynesia). Within
that area they are predominant, and abound in species.
They are much mimicked, and enter largely into synapo-
sematic combinations ; but the colours and patterns
are almost invariably those of the Euploeini themselves.
The wide difference between the superficial appearance
of the Euploeini and that of other Lepidoptera in their
area of distribution, together with the uniform colouring
and pattern of their abundant species and genera (if,

THE PLACE OF MIMICRY

indeed, these have been rightly made), have doubtless
led to the development of combinations within the limits
of the group, and the necessity imposed upon species of
other groups to adopt the same Warning Colours. Once
begun, such a process would of course tend still further
to increase the uniformity within each combination.1

Now, are there any grounds in the above-mentioned
facts for considering the Danaini more distasteful than
the Etiploeini, or vice versa ? As regards the power of
ranging the world and drawing towards them a variety of
mimics of all kinds, the Danaini must be considered the
superior ; as regards predominance on the one area where
they both meet, the Euploeini take the higher place.
But in respect to unpalatability there is no reason for
considering one more highly protected than the other.
Yet in the few cases where representatives of the two
groups enter the same synaposematic combination, it is,
so far as we know at present, nearly always a Danaine
that is attracted, and assumes the characteristic, superficial
appearance of the Euploeine type. This is readily ex-
plicable, for the reasons given in discussing the case
of Melinaea and Heliconius. The Euploeine type is
far better known and far more valuable as a warning
character than that of the comparatively isolated Danaine
which enters the combination. The same association
contains not one but several species of Euploea, all super-
ficially alike, and between them producing enormous
multitudes of individuals.2 Euploeini of the Trepsichrois

1 See also p. 358, where the possible role of the male scent brands
of the Euploeini is suggested.

2 The same explanation probably holds in a curious example from
South America. A species of the Nymphaline genus Colaenis, — C. telesiphe,
is a beautiful mimic of a Heliconius with the same specific name, both
being black insects with a broad red bar across the fore wing and
a pale narrow stripe along the hind wing. There is no doubt about the
identification of model and mimic, for the pattern of the Colaenis is
isolated, while the Heliconius is in this respect related to many other
species of its Sub-Family. I was therefore much surprised to see the
mimic put down in a dealer's list at a shilling apiece, while the model
was eighteen pence. I wrote for an explanation, and was informed, as
I expected, that the prices represented the relative numbers of the
specimens sent by collectors. It is probable that here, too, the effect

IN DEFENSIVE COLORATION

335

mulciber group form an exception which supports the same
conclusion ; for their females, although acting as models
for the Elymniinae (see p. 372), are undoubtedly them-
selves mimetic of the principal Danaine combination in
their localities.

The same argument holds, and is even more convincing,
in the synaposematic approach between species of the
same genus, where there is even less ground for considering
that the relation of model and mimic is determined by
degrees of unpalatability. Mr. S. A. Neave has shown,
in an interesting paper,1 that two of the dominant Danaini
on the east and south of Africa, Amatcris echeria and
A . albirnaculata, — themselves so alike that they have been
only recently separated on solid grounds, — come on the
borders of their range under the influence of western
species of the same genus with a different pattern. He
shows conclusively, by measuring the diameters of a
certain spot of the fore wing, that the eastern forms exhibit
a more and more considerable synaposematic approach as
they invade the districts where the western forms are
more and more dominant (see also p. 337). Here, too,
there is no reason whatever for regarding the effect as
due to degrees of unpalatability.

We may summarize the above facts, and many more
which are excluded by the exigencies of space, in the con-
clusion that in any given area the more evidence we possess
that certain widely different groups of butterflies are all
specially protected in a high degree, the more certainly will
it be found that (1) within each group there will be Mimicry
between the species of the same genus, and also between
the species of genera both allied and widely separated,
and that (2) there will be Mimicry between the species
of the different groups. Furthermore, the most perfect

of the model is increased by the co-existence of other Heliconinae with
somewhat similar patterns. Whether this interpretation be correct or
not, the facts are opposed to the application of the Batesian Hypothesis.
Mr. Marshall has also pointed out to me that Fritz Muller in 1878
demonstrated the existence of stink-glands in the genus Colaem's (Zei/.
Wiss. Zool.y xxx, p. 168).
1 Trans. Ent. Soc, Lond., 1906, p. 208.

336 THE PLACE OF MIMICRY

resemblances to models will generally be found among
mimics with the highest degree of special protection.

It must be again pointed out, as it has been before
(see pp. 235-7), that these mimetic resemblances are in-
dependent of affinity. In large numbers, even of closely
related species, it can be shown that mimetic likeness is
not ancestral, but has been superposed upon an earlier
pattern which was entirely different.

4. The Limit to Miillerian Unification of Warning
Colours in any Country. — The Miillerian principle of
unification of Warning Colours, as an aid in the education
of enemies, would seem to carry with it the implication
that the process will continue almost indefinitely until
the utmost possible simplification is attained. The facts
brought forward in the last Section might also be con-
sidered to support this conclusion. Nevertheless, there
can be little doubt that a limit is quickly reached, and that
henceforward the main change consists in detaching the
mimics or even the central models, when by migration, or
spreading through increase of numbers, they extend beyond
the influence of the original combination to which they
belonged and come within that of another. The trans-
ference would be, of course, more easily effected if the
pattern of the new combination resembled that of the old.
The Miillerian principle is reciprocal in its action, and
the crowd of mimics in a given combination — the less
perfect as well as the more perfect — all tend to keep the
central member or members stable.

The tendencies of Miillerian Mimicry are best studied
in Africa, where the problem is far simpler than in South
America. The chief Ethiopian models, the Danaini, are
represented by comparatively few species, and of these
a high proportion form the centres of strong Miillerian
combinations. Thus on the East Coast, the common
conspicuous Danaines are Limnas chrysippus, Amauris
niavius (form dominie anus), A. ochlea, A. echeria and
A. albimaeulata. The two last, entering into the closest
synaposematic relationship, form the centre of one strong
combination, the first forms the centre of another, the
second of another, the third of a smaller and less well-

IN DEFENSIVE COLORATION 337

defined association. Some species like Papilio dardanus
(merope) have forms entering two or more of the com-
binations (see below and pp. 373-5). The condition
reached is probably stable: all the central patterns are
clear, well defined, and very distinct from one another, and
there is no reason for anticipating any tendency towards
further unification. When, however, we pass westwards
along the equatorial belt, it has already been pointed out
(see p. 335) that A. echeria and its ally, the central models
of perhaps the most important eastern combination, come
within the sphere of western species of Amauris and show
evident traces of influence. Why should the echeria-albi-
niaculata type be influenced here and not along the East
Coast ? The answer is clear ; because the pattern of the
western Amauris is much nearer to that of the intruders
than any of the eastern species of the same Danaine genus.
This consideration suggests the probably sound conclusion
that it would be impossible for these particular models
from the East and West to form and keep distinct im-
portant combinations on the same area.

When we turn to the West Coast the same phenomena
are met with. The Danaine models, when possessed of
the same general pattern, tend to approach one another,
or if the patterns be bold and isolated, to stand singly — in
either case forming the centres of Mullerian combinations.
In an extremely interesting example from the Cameroons,
an abundant and dominant type of A mater is has drawn
to it a species of a very different Danaine genus, Tirumala
(or Melindd), — T. morgeni. The resemblance is extra-
ordinarily close and deceptive.

Having given examples of the changes that occur in
the central members of Mullerian groups, it is now
necessary briefly to describe the changes that occur in
a few of the outlying members. This can be well
illustrated from the eastern combinations which have
been mentioned above. One of the female forms of
Papilio dardanus (merope), the cenea form, is a beautiful
mimic of the ec/ieria~a/6imacu /a fa-centred combination.
As we pass westward, another bold and conspicuous
model, belonging to the Acraeinae, makes its appearance,

POULTON 2

33^ THE PLACE OF MIMICRY

Planema poggei. This black butterfly with a broad orange
bar across the fore wing, and a white bar across the hind
wing, appears to the east of the Victoria Nyanza, but has
become far more dominant on the west shore, and thence
extends to the west coast of the continent. The models
overlap for some distance on both sides of the lake, and
as far as Toro in Western Uganda. A new female form
of P. dardanus, planemoides, beautifully mimetic of the
Planema, appears on the east side, becomes common on
the west, and extends to the coast. I have specimens of
the cenea female up to the north-eastern shore of the
lake, but not beyond. If they occur at all, they probably
quickly cease westward, and the form has never been
seen anywhere near the West Coast. In the case just
described, one very different model replaces the other,
leading to an equally wide divergence between a mimetic
form and its substitute. It is more usual for the changes
to be less abrupt, both models and mimics being replaced
by closely allied representative species or sub-species.
Thus we find the eastern Amauris niavius (form domini-
canus), with an immense white patch, replaced on the west
by A. niavius, with a considerably smaller white patch.
The two sub-species meet, as described on pp. 68-9, on
the eastern shores of the Victoria Nyanza, and there
interbreed, if we may so conclude from the number of
intermediate examples. Another of the mimetic females
of Papilio dardanus (nierope), the black and white
hippocoon form, undergoes corresponding changes in
pattern, and here, too, intermediate varieties are found in
the neighbourhood of the lake. The equally beautiful
Nymphaline mimic Hypolimnas (Etiralia) ivahlbergi oi the
east is similarly replaced at about the same point by the
closely allied H. anthedon with a smaller white patch. Such
examples might be multiplied almost indefinitely. Those
here brought forward are, however, especially striking,
being large insects with a bold and simple pattern. A
succession of such replacements in an outlying member
of a Miillerian combination, in correspondence with the
successive changes in its other members, is described in
the tropical American genus Protogonius, on pp. 350-2.

IN DEFENSIVE COLORATION 339

It will be admitted that the above account may be taken
as typical of the way in which Mullerian associations
are scattered over a country, and of the changes which
are witnessed as we follow them from one area into
another. There is nothing to lead us to believe that
progressive unification will occur on any given area.
Each tract has developed its own set of important com-
binations. The recognition of these, and a memory of
the implied qualities, is the climax of one important side
of the education of an insect-eating animal.

5. Seasonal Transition from Cryptic to Synaposematic
Defence. — The astonishing discovery by the irrefutable
evidence of breeding, that Precis natalensis is the wet
season form of P. sesamus, is briefly described on p. 208.
The latter forms, with a highly procryptic under surface,
were bred by Mr. Marshall from wet season individuals,
in which the conspicuous colours and pattern of the upper
surface are reproduced, considerably heightened in effect,
upon the under surface. It is particularly interesting
that upon both surfaces this wet season form should bear
a general likeness to some of the larger red and black
Acraeas found in various parts of its wide range.1
Although the shape of these broad-winged butterflies is
very different from that of an Acraea, I do not doubt
that Mr. Marshall is correct in considering the resemblance
roughly mimetic. If we take different habits and modes
of flight into account, it is difficult to believe that the
resemblance would deceive a bird at any distance. It
might well, however, put the bird on its guard and lead to
a cautious attack during which a special defence would be
recognized by the enemy. Hence it appears to be more
reasonable to regard natalensis as a Mullerian than as

1 The present writer was in error in drawing a distinction between the
basal white-marked black patch of the under side in natalensis, and the
black-marked light-coloured patch which occupies the same position in
Acraeinae. Although the foregoing is true of the great majority of
African Acraeas possessing the marking, the particular large species (e.g.,
A. acara and A. anemosa), to which we must suppose that natalensis
bears a general resemblance, exhibit a white-marked black basal patch.
Compare Trans. Ent. Soc, Lond., 1902, pp. 424-8, where the upper and
under surfaces of natalensis are contrasted in detail.

Z 2

340

THE PLACE OF MIMICRY

a Batesian mimic. The same argument holds with greater
force for the allied Precis antilope in which the resemblance
to an A craea is still more imperfect.

It will be of interest at this point to exhibit in a tabular
form some of the remarkable series of appearances which
the wet forms may display in relation to the dry in the
great genus Precis (including Junonia).

S. African habitat
of Species.

Species of the
Genus Precis.

Character of Under Surface of Wings :
Dry season. Wet season.

Forest

[Oriental]
Woodland

Woodland and Open
Open, Swampy (in
Mashonaland)

Woodland
Woodland and Open

^Precis tugela

elgiva

natalica
ahnana
artaxia

archesia

1 ceryne

2 actia

5 antilope
4 sesamus

j Directive marks (eye-
f spots) developed.

\ Far less well concealed
I than the dry forms,
f Archesia I believe to
J be Aposematic.

| Very conspicuous ;
r roughly mimetic of an
J Acraea type.

The types of country alluded to in the table are as
follows : — Forest, with heavy timber affording deep
shade ; Woodland, without timber, trees small, affording
light shade ; Open, nothing higher than small scrub.5

The discovery of the nature of the physiological
stimulus determining the two forms of Precis is a most
interesting problem, to which Mr. Marshall has devoted
an immense amount of labour. The outcome of his
splendid investigations under most difficult conditions is
not yet published, and therefore I will only say that the
results exhibit much that is puzzling and contradictory.
As bearing upon the problem, it may be stated that the wet

5 Dry form bred from wet by Marshall in 1 905 : Proc. Enl. Soc, Lond.,
1906, p. lvii.

2 Dry form bred from wet by Marshall in 1903 : Proc. Enl. Soc, Lond.,
1903, p. xxxii.

9 Dry form bred from wet by Marshall in 1902: Trans. Ent. Soc,
Lond., 1902, pp. 418-20.

4 Dry form bred from wet by Marshall in 1898: Ann. Mag. Nat.
Hist., ser. 7, vol. ii, July 1898, p. 30.

8 Trans. Ent. Soc, Lond., 1902, pp. 422-3.

IN DEFENSIVE COLORATION 341

season ocellated phase of Precis almana, the aster ie form,
is the only one found in the permanently damp forests of
Siam. The wide experience of Mr. T. R. Bell in North
Kanara has led him to the belief that a larval food
consisting of young succulent leaves containing abundant
moisture, is the condition determining the wet season
forms of the dimorphic butterflies that have come under
his observation.1 (See also pp. 311, 312.)

Mr. Marshall also considers that the under surface of
the wet season Nymphaline butterfly, Byblia gotzius is
mimetic of the Acraea serena type of pattern, while the
under surface of the dry forms of it and B. ilithyia is
Procryptic.2 An intermediate ilithyia and a dry gotzius
bred by him from the eggs laid by wet season females
are figured, together with the respective parents, by
Dr. Dixey.5 In order to realize the general resemblance
of these latter to an Acraea it is necessary to imagine
the fore wings almost entirely covered by the hind, as in
the attitude of repose. The application in the early wet
season of dry warmth to the pupae of ilithyia caused
a butterfly to approach the dry season type.4

Dr. Dixey has stated that, while the under surface in
both sexes of Teracolus regina is clearly Procryptic in the
dry season, it is in mimetic association with certain un-
described forms of Belenois in the wet.5

6. Seasonal Transition in degrees of Synaposematic
Defence y or from Aposematic to Synaposematic Defence. —
Dr. F. A. Dixey has recently described the following inter-
esting seasonal changes of Ethiopian Pierinae? The dry
season male of Belenois thysa is a much better mimic of the
male of Mylothris agathina than is the wet season male ;
while the female thysa is an excellent mimic of the female
agathina in the dry season, but does not mimic it at all
in the wet. The Mylothris model shows no seasonal

1 Ent. Mo. Mag., 1906, p. 122.

2 Ent. Mo. Mag., 1902, p. 49.

3 Trans. Ent. Soc, Lond., 1902, p. 189, pi. iv.

4 Trans. Ent. Soc, Lond., 1902, pp. 202, 203.

5 Proc. Ent. Soc, Loiid., 1906, pp. xcvi, xcvii.

c Proc. Ent. Soc, Lond., 1906, pp. xxxvi, xxxvii ; 1907, pp. xxiii,
xxiv.

THE PLACE OF MIMICRY

change. Furthermore, the males of four species of
Teracolus (achine, omphale, evenina, antigone) are often
nearly indistinguishable in the dry season but can be
separated at a glance in the wet. The same comparison
holds, but to a less extent, with the females of the dry
and wet broods. A similar relationship obtains in two
Indian species of the Oriental and Austro- Malayan
Pierine genus Huphina, H. nadina and H. phryne.

It is impossible to leave this part of the subject without
alluding to the European Nymphaline butterfly, Araschnia
levana and its later form prorsa, investigated by Weis-
mann, and proved by him to be susceptible to the
stimulus of temperature in the pupal stage. It has been
suggested that the black white-marked form prorsa is
mimetic of the species of Limenitis (White Admirals),
which, although larger, possess a pattern of the same
general type on both upper and under surfaces. The
earlier brood levana has been similarly compared to a
small Fritillary. If these suggestions be confirmed we
should witness a seasonal transition in the kinds rather
than the degrees of Mimetic and probably Synaposematic
Defence.

7. The Gradual Predominance of the Miillerian
Hypothesis. — A brief history of the discovery of Miil-
lerian Resemblances among the butterflies of South
America, the East, and finally of Africa, has been given
on pp. 222-3 ; their extension to explain the uniformity
in the species of distasteful groups, and the resemblances
between the Warning Colours of all kinds of forms in the
same country, is referred to on pp. 230-4. A fuller
statement of the essential differences between the rival
hypotheses will be found on pp. 21 1-15.

Reasoning, based on the investigations of the last
1 3 years, has tended more and more to remove exam-
ples from the category of Batesian (Pseudaposematic)
Mimicry and transfer them to that of Miillerian (Synapo-
sematic) Resemblance. Thus almost the whole of the
butterflies and moths shown in the lecture before the
British Association (1890) as examples of Batesian
Mimicry would now be looked upon as instances of

IN DEFENSIVE COLORATION

343

Common Warning Colours (Mullerian Resemblance).
Some of the reasons for this change of view are briefly
indicated on pp. 370-6, where a nearly complete list1 of
the examples intended to illustrate Protective Mimicry
is quoted.

The recent sudden growth in the importance of the
Mlillerian Hypothesis in Lepidoptera dates from two
papers2 published by Dr. F. A. Dixey in 1894. In
these it was shown that both Pierines and Papilios enter
Mullerian associations. Two years later Dr. Dixey wrote,3
after again discussing the Mullerian relations between
Heliconines and Pierines : — ' The same argument will
apply to features similar to the above which may be seen
in certain Papilioninae, Nymphalinae, Erycinidae, and
even in some moths. And I may say in passing that
Fritz Muller's principle here referred to appears to me
to be of much wider application than has been hitherto
supposed. There exist several large groups more or less
uniform in their scheme of coloration, though hetero-
geneous in their affinities, which it seems almost certain
will in the main turn out to be cases of " inedible associa-
tions", each one possibly including a few instances of true
mimicry within its borders.'

The wonderful sets of South American butterflies
selected by Mr. W. F. H. Blandford from the Godman-
Salvin Collection, and exhibited at the Entomological
Society of London4 in 1896 and 1897, also nad a marked
effect in stimulating interest in the Mullerian Hypothesis.
It was at once obvious that the most remarkable resem-
blances were those between species belonging to the most
highly protected groups, and especially between the
Ithomiinae and Heliconinae.

The change of opinion is not only due to a re-study
of the old examples, but to entirely new material which

1 The list is complete except for the examples illustrating the history
of the transparent-winged mimics of Hymenoptera. These are quoted
on pp. 365-6.

2 Brit. Assoc. Report, 1894, p. 692. Abstract. Trans. Ent. Soc, Lond.,
1894, p. 298.

8 Trails. Ent. Soc, Lond., 1896, p. 75.

4 Proc. Ent. Soc, Lond., 1896, p. xxxviii ; 1897, p. xxii.

344 THE PLACE OF MIMICRY

seemed at once to call for the Mullerian rather than the
Batesian interpretation. A fine instance is to be found
in the wonderful African group shown by Mr. G. A. K.
Marshall to converge towards the distasteful Lycid beetles.
It is briefly described on p. 276.

The chief lines of indirect evidence in favour of the
Mullerian interpretation are due to the investigations of
Dr. F. A. Dixey. They are briefly set forth in the two
following Sections. These will be succeeded by three
further Sections in which additional lines of indirect
evidence will be considered. The sixth Section from the
present point, Section 13, will be devoted to the discussion
of counterbalancing evidence which is believed to support
the Batesian interpretation.

8. Diaposematic Resemblance ; Reciprocal Warning
Colours. — Dr. F. A. Dixey first recognized the fact that
in certain cases of superficial resemblance the butterfly,
hitherto regarded solely as the model, has itself advanced
to meet the very different species regarded as its mimic.
For this attainment of a resemblance by mutual approach
he suggested the name ' Reciprocal Mimicry V Dr. Dixey
also argued with great clearness and force 1 that
reciprocal mimicry can only take place in Mullerian
associations, not in Batesian ; and that it is therefore . . .
"good evidence of the distastefulness of all the forms
between which it can be shown to occur " '.2 The present
writer has urged 3 that the name • Reciprocal Warning
Colours ' is more appropriate than * Reciprocal Mimicry ',
inasmuch as Mimicry, as first explained by H. W. Bates,
is invariably a deceptive or Pseudaposematic Resem-
blance. In order to include Dr. Dixey's principle in the
terminology proposed in 1890,4 the name ' Diaposematic
Resemblance ' was, with Mr. Arthur Sidgwick's assistance,
suggested for it.5

1 Trans. Ent. Soc, Lond., 1894, p. 298.

2 Trans. Ent. Soc, Lond., 1897, p. 328. In the above passage
Dr. Dixey is quoting from his earlier paper in Trans. Ent. Soc, Lond.,
1896, p. 75.

3 Proc. Ent. Soc, Lond., 1897, pp. xxviii, xxix.

4 Colours of Animals, 1890, pp. 336 et sqq.
r° Proc Ent. Soc, Lond., 1897, p. xxix, n.

IN DEFENSIVE COLORATION

Further examples of Diaposematic Resemblance have
been suggested and considered in recent years by
Mr. S. A. Neave 1 and the present writer.2

9. Primary and Secondary Miillerian Resemblance ;
Proto- and D enter osynaposematic Resemblance. — The prin-
ciples discovered by Dr. Dixey and briefly described
in the preceding Section are further set forth in the
following passage : — ' Every conspicuous and distasteful
form is a centre of attraction for other forms, whether
edible or inedible ; but in the former case (Batesian
Mimicry) the mimetic attraction is limited in operation,
and acts only in one direction, influencing nothing but
the mimic ; while in the latter case (Miillerian Mimicry)
the mimetic attraction is unlimited and mutual, acting
reciprocally in both directions, and influencing each
member of the group.' 3 This and other passages in
Dr. Dixey's important series of papers on the Miillerian
principle,4 have prepared beforehand for the discovery of
many cases, especially in Ethiopian butterflies, where the
species of a single combination, in addition to their primary
resemblance to some central model (almost invariably
a Danaine) have undoubtedly been modified into a
Secondary Resemblance to each other.5 Such Deutero-
synaposematic approach is quite independent of affinity ;
for the blood-relationship of a species to the primary model
may be far closer than it is to a co-mimic towards which
it is drawn by Secondary Resemblance. It is obvious
that the existence of these complex resemblances supports
the interpretation of the group within which they are
manifested as Synaposematic (Miillerian) rather than
Pseudaposematic (Batesian).0 It is interesting to note
that in certain cases the Secondary Resemblance is

1 Trans. E?it. Soc, Lond., 1906, pp. 216-18.

2 Trans. Ent. Soc, Lond., 1902, pp. 488-90.

3 Trans. Ent. Soc, Lond., 1897, pp. 324-5.

4 See p. 213, n. 1.

5 Trans. Ent. Soc, Lond., 1902, pp. 470-2, 485-7. The same
phenomenon has been observed in African Coleoptera, /. c pp. 511-15.

6 Hence it was probably erroneous to suggest the existence of
Secondary Batesian Mimicry (Deuteropseudaposematic Resemblance) :
I.e. p. 515.

346 THE PLACE OF MIMICRY

closer between the species exhibiting a strong Primary
Mimicry than between those exhibiting a weaker resem-
blance to the central model. This suggests that the
Secondary Resemblance is of permanent value, and not a
mere phase which will ultimately be lost in the Primary
Resemblance.1

The very best example of Secondary Mimicry I have
ever seen was shown to me, when a young man, by the
late Professor Westwood. He asked what I thought of
two small transparent - winged, black-marked South
American Lepidoptera with hind wings margined in red
and black. Did I think they were the same species ?
To my inexperienced eyes, attracted by the pattern,
they looked absolutely alike. Did I think they were
the same genus or family, and finally was it possible that
one was a butterfly and the other a moth ? And so it
proved to be ! The model was a small Erycinid
butterfly, itself a mimic of an Ithomiine ; the mimic a
day-flying moth of the same size. In this remarkable
case, the Secondary Mimicry was far closer than the
Primary. Not only is the Erycinid shown to be
specially protected by acting as a model, but the moth
itself was a member of a conspicuous distasteful group.

10. Further Indirect Evidence Stipporting a Miillerian
or Synaposematic Interpretation. — The following generali-
zations, first published in 1902, 2 support the Miillerian
interpretation of a large number of examples previously
explained upon the Batesian Hypothesis.

(a) The fact that mimetic likeness tends to run in
genera or larger groups and is rarely seen in single
isolated species. It is more reasonable to explain this
fact by the hypothesis of some special defence common
to the group in question, than by supposing that all
or almost all of its members are compelled to shelter
themselves under a deceptive likeness to other dominant
and specially defended forms.

(6) In many cases it is known that the mimetic groups
are large and dominant, and the individuals of many of

1 Trans. Ent. Soc, Lond., 1902, p. 485.

2 Trans. E?it. Soc, Lond., 1902, pp. 500-2.

IN DEFENSIVE COLORATION

the species excessively abundant. Some mimetic species
have an immense range, in the case of Hypolimnas
misipptis far exceeding that of the model.1

(c) The marked tendency towards Mimicry in the
species of a single group cannot be explained by here-
ditary transmission of the mimetic form attained by a
single ancestral species, or from the tendency of closely
related species to vary along nearly the same lines. As
a matter of fact, the species of such groups, mimicking
various different models, have been led to diverge in all
kinds of directions.

(d) The non-mimetic species of mimetic groups and
the non-mimetic males of mimetic females are, as
a rule, distinguished by a conspicuous and apparently
Aposematic colouring. Such Aposematic patterns are
especially developed on the under surface of the wings,
where Procryptic colouring is found in other butterflies.

(e) The converse of this last argument is also true, viz.,
some of the species in a group, which is as a whole
markedly conspicuous and itself mimicked, are often
mimetic of quite other groups. Forms closely related
to Mimetic species tend to be Aposematic ; Forms closely
related to Aposematic species tend to be Mimetic.

(/) The non-mimetic species of mimetic groups and the
non-mimetic males2 of mimetic females are sometimes
themselves mimicked.

{g) Species which mimic the best known and pre-
sumably the most unpalatable models are often in certain
points even more conspicuous than their models. They
appear to have retained some traces of Warning
Characters which they possessed before the mimetic
likeness was assumed.3

(/i) The fact that the resemblance between species
belonging to the admittedly distasteful groups is far
closer and more perfect than that between these and the
species of groups believed to be palatable.

1 See p. 216.

2 A good example is described on pp. 217-18.

3 For examples see pp. 371, 375. Another very good instance is seen
in the great Ethiopian Aletis-Euphaedra combination mentioned on p. 232.

348 THE PLACE OF MIMICRY

n. Mullerian Resemblance Associated with Warning
Colours; Batesian Mimicry Associated with Cryptic
Colours. — Protective Mimicry is, as Wallace has stated,
merely ' an exceptional form of protective resemblance '
(see p. 226). On the other hand, Mullerian Resemblance
only differs from ordinary Warning Colours in that it is
common to two or more species. When, therefore, we
desire to obtain a general indication of the probable
interpretation of a certain resemblance it is reasonable
to consider as a whole the group to which the species
exhibiting it belongs. Tested in this way, the vast
majority of the superficial resemblances of the Lepi-
doptera and Coleoptera — for the two Orders supply
wonderfully concordant evidence 1— -are Mullerian and not
Batesian. They are chiefly manifested in groups with
distinct Warning Colours, and, furthermore, the principal
Aposematic sections always seem to include examples of
these resemblances. In the Cryptic groups, on the other
hand, they either do not occur or else they form well-
defined subordinate groups, of which all the members
are Mimetic, or Mimetic and Aposematic. The further
the study of Mimetic Resemblance is carried the more
clear it becomes that the affinity is with Warning and not
with Cryptic Colours. We meet with striking exceptions,
however, in the species with a Mimetic pattern on the
upper and a Procryptic pattern on the under surface (see
pp. 350-4), as well as in the seasonal transitions of certain
species (see pp. 320, 339~4i)-

Equally significant is the ever-increasing evidence that
groups which contain imitators also include other species
which are imitated. The same species may even act in
both capacities, as has been described on pp. 215-18.
A very striking example was discovered by Mr. R.
Shelford in Borneo. Longicorn beetles belonging to
the Clytinae tend, nearly all over the world, to resemble
wasps or other specially defended Hymenoptera. This
is the case with our own Wasp-beetle (Clytus arietis)
as described on pp. 251-2. Well, Mr. Shelford has

1 Trans, EnU Soc, Lond., 1902, pp. 392-7.

IN DEFENSIVE COLORATION

shown1 that in Borneo many non-mimetic Clytinae are
themselves resembled by entirely different Longicorn
beetles, and as soon as attention was directed to the case
Mr. C. J. Gahan found the same thing happening in
Ceylon.2

1 2. Mimetic Patterns in Stations or Localities Different
from those of the Model. — Many examples are already
known in which the mimic inhabits a station where the
model is rare, or even unknown. Thus the Geometrid
moth Abraxas etridoides is found on the hills and its model
Teracolus etrida in the plains of Southern India. Only
recently I have heard from Mr. S. A. Neave that several
of the African mimics of chrysippas, belonging to the
Nymphalinae, Acraeinae, and Lycaenidae prefer the wood-
land while their model is chiefly found in open grassy
places. Still more strikingbutmuch rarer are the instances
in which the mimic is found in a very different locality
from its model (see pp. 217, 218). The spreading of a
mimic beyond the range of the model is probably by no
means rare : a remarkable example is quoted on p. 216.

All these curious relationships are difficult to under-
stand on the Batesian Hypothesis, easy on the Mullerian.
It is impossible to believe that sharp-sighted enemies
would remain deceived by the likeness of a palatable
mimic in one station or locality to a distasteful model in
another. But if we suppose that the mimic also is dis-
tasteful and possessed a warning pattern of its own before
the mimicry began, the interpretation is clear. Its mimetic
pattern still remains a warning of distastefulness, more
easily learnt, that is learnt with less waste of life, because
it is similar to that of a still more abundant distasteful
form well known to the enemy. In this way, too, it is
possible to understand why the growth of a very perfect
resemblance often leaves untouched some small but dis-
tinct discriminating feature. Thus differences in habits
and modes of flight often persist and would be recognized
by an observant enemy as they are by the naturalist.

1 Proc. Zoo/. Soc, Lond., 1902, vol. ii, pp. 250-1. See also the corre-
sponding illustrations on pi. xx.
8 I.e., p. 252.

350 THE PLACE OF MIMICRY

Thus, too, traces of the scalloped border are almost
invariably retained by the mimetic species of Hypolimnas,
and a Heliconine can nearly always be distinguished at
a glance by the short radiate white lines on the black
border of the hind wing under side. These take the
place of roundish white spots which occupy the same
position in the Ithomiine model.

It is possible that simple and easy means of discrimina-
tion such as those described in the last paragraph may
facilitate recognition between the sexes (see p. 358). But
whatever be the value to the species, their persistence is
a far greater difficulty on the Batesian than on the
Mullerian Hypothesis.

13. Classes of Facts which have Recently been Urged in
Support of the Batesian Hypothesis. — Many arguments
have been given in favour of the Mullerian as opposed
to the Batesian interpretation of Mimicry, and now two
counterbalancing considerations remain to be discussed.

a. Butterflies Exhibiting Mimetic Resemblance on the
Upper Surface of the Wings and Procryptic Defence
on the Under Surface.

Instances of this interesting combination of methods
are rather rare, the chief examples being found in a single
Sub-Family in the Old World and a single genus in the
New. Other instances belonging to the Nymphalinae are
however, not uncommon. Dr. Dixey considers that the
same combination is to be found in several Pieriuae, e. g.
in the genera Teracolus and Eronia}

In the tropical American Nymphaline genus Protogonius
the whole of the species or sub-species are imperfect but
undoubted members (as regards the upper surface) of the
principal Ithomiine-centred Synaposematic combinations
of their respective localities. They reproduce roughly
but clearly the characteristic elements of the pattern
whatever they may be : the barred black and tawny
pattern of Central America and Venezuela, the over-
spreading yellow of Trinidad, the darkened hind wing
of the Guianas, the yellow hind wing stripe and white fore

1 For Mimicry in the latter genus see Proc. Ent. Soc> Lond., 1906,
pp. xxx, xxxi.

IN DEFENSIVE COLORATION 351

wing apical spot of Eastern Brazil, the chestnut ground-
colour of the Upper Amazon at Ega, the bold black and
tawny of Ecuador, Bolivia, and Peru. The Procryptic
colouring of the under surface differs from the mimetic
pattern of the upper in its perfection. The resemblance,
invariably to a dead leaf, is remarkably detailed and
beautiful. The general colouring of the upper surface
does indeed influence the under, but never in such a
manner as to interfere in any way with the cryptic effect.
Thus, the under surface of the dark forms from Ega and
Peru is mottled with rich dark shades of brown, while in
the pale and yellowish Protogonius from Trinidad the
shades are light in tint and include prominent greys and
yellows. Similarly in every locality a correspondence
between upper and under surface is at once evident, but
nevertheless the first always remains roughly mimetic,
the second beautifully cryptic. The hind wing in this
genus possesses a well-developed 1 tail ', somewhat ex-
panded at the end, and this is probably Directive during
the active condition, serving to divert attacks from the
body, while during profound rest it may resemble a leaf-
stalk and thus aid in the cryptic effect. This suggestion
requires for its confirmation the careful observation of
the living insect.

The interpretation of the facts presented by this deeply
interesting genus is by no means easy. It has been
brought forward by Mr. R. Shelford 1 as an instance of
Pseudaposematic or Batesian Mimicry, and I have always
thought that it afforded some of the strongest, probably
the very strongest, evidence in support of the existence
of such resemblances among butterflies. The colouring
of the upper surface is undoubtedly displayed during flight,
and has been developed in relation to attacks made when
the butterfly is upon the wing.2 The mimicked Aposematic
pattern would of course make the butterfly extremely
conspicuous, while at the same time the roughness of
the resemblance and different mode of flight would render
it easily distinguishable among the crowd of Ithomiines,

1 At the Entomological Society, June 5, 1907. Unpublished.

2 See W. J. Kaye in Trans. Enl. Soc, Lond.> 1906, p. 431.

352 THE PLACE OF MIMICRY

Heliconines, &c. Again, the fact that every form in the
genus is mimetic leads us back to a mimetic common
ancestor. Now there is no difficulty in understanding
such an evolutionary history in a group of closely related
Miillerian mimics. The common ancestor possessed
some special protection in the way of unpalatability, &c,
and adopted the Warning Colours of other more power-
ful combinations, also specially defended. The species or
forms to which the common ancestor gave rise inherited
the defensive quality, spread into various districts, and
joined the local Synaposematic combinations. It is very
different when we attempt to reconstruct this history on
the hypothesis of H. W. Bates, and try to imagine qualities
in an ancestor which would determine universal Pseud-
aposematic Resemblance among the descendant species.
Upon the whole, therefore, it is probable that Protogonius
is specially protected like so many other Nymphaline
genera, and that the defence holds against the majority
of enemies that attack butterflies upon the wing. Against
these all the advantages of Miillerian Resemblance would
be gained. Such enemies, put on their guard by the
well-known Warning Colours, would learn to avoid this
member of the group with a lessened waste of life from
experimental tasting. Against special enemies that
would devour them in spite of their special defence, the
cryptic colouring would be a valuable safeguard, making
the insects extremely difficult to mark down when they
came to rest. The concealed under surface is also of
importance — probably of supreme importance — as a pro-
tection against the class of enemies that hunt for insects
in a state of complete repose.

Before passing to the consideration of the next group,
I desire to state that the interpretation of these two
difficult cases is put forward in no confident or dogmatic
spirit. The balance of evidence appears to me to
suggest the conclusion here stated. It is impossible
to predict whether the further knowledge, so greatly
needed, will bring with it confirmation or revision.

The chief Old World examples which manifest the
same interesting combination are to be found in the little

IN DEFENSIVE COLORATION

Nymphalid Sub-Family the Elymniinae, closely related
and, by many systematists, united to the Satyrinae. With
a very few possible exceptions the whole of the
Elymniinae are mimetic. Both sexes of the few Ethio-
pian forms resemble Acraeinae — closely upon the upper
surface, more roughly but still distinctly on the under.
The Oriental and Austro-Malayan forms mimic Euploeiniy
Danaini, Pierinae, and Morphinae (or Amathusiinae, as
the Old World representatives of the group are some-
times called). Of all these the Euploeini, forming the
dominant distasteful group of the Regions, are by far
the most important as the models of this Sub-Family.
The females are in many of the species far more
striking mimics than the males, and often mimic
different models. The Mimetic Resemblance on the
under surface is in some species very perfect, in others
imperfect, while in a considerable proportion it is replaced
by a Procryptic Resemblance to dead leaves which,
although wanting the perfection and detail of Protogonius,
is doubtless very efficient in promoting concealment. A
small number of species which do not fall into the above
categories apparently possess Warning Colours peculiar
to themselves, or patterns which, without further evidence,
we cannot as yet interpret.

Mr. Shelford, who has had an intimate experience of
the male of the Bornean species, Elymnias ( Melynias) lais,
describes it as closely resembling, upon the wing, the
abundant Danaines of the genera Caduga, Paralitica, &c,
but disappearing the moment it comes to rest on the
ground among dead leaves, when the procryptic under
surface is alone visible.1 From this he infers, as in
Protogonius, that the butterfly is palatable to birds
which would reject the Danaine model as unpalatable,
but that these enemies do not distinguish the one
from the other when upon the wing : in other words,
he considers the resemblance to be Pseudaposematic, or
an example of Batesian Mimicry. This conclusion may
be sound, both for Protogonius, Elymniinae, and other
forms with the same methods of colouring. It must in any
1 Proc. Zool. Soc.j Lond., 1902, vol. ii, p. 259.

POULTON A a

THE PLACE OF MIMICRY

case be admitted that the Batesian interpretation is more
probable here than in other butterflies. But, for the
reasons given in the discussion upon Protogonius, it ap-
pears to me that the balance of probability is the other
way. The Elymniinae being, almost without exception, a
mimetic Sub-Family, we must certainly assume a mimetic
ancestor with qualities determining mimetic descendants.
It has been already shown that such a history is con-
sistent with the Mullerian interpretation, but with our
present knowledge difficult or perhaps impossible to
reconcile with the Batesian Hypothesis (see p. 352).

b. Dimorphic or Polymorphic Mimetic Butterflies with
Forms Pesembling Different Models. — The phenomenon
described in the title of this Sub-Section is quite common
among mimetic species. Examples will be given in
a later part of this Essay (see pp. 372-5) showing
that the male and female of a mimetic species may
resemble different models ; that the male may resemble
one model, and two kinds of female two others ; that
a non-mimetic male may be accompanied by two, three,
or even four forms of female mimicking different models.
The great example of this latter complex form of mimicry
is of course the Ethiopian Papilio dardanus (merope),
described on pp. 373-5.

At first sight such cases appear strongly to support
the Batesian interpretation. His hypothesis assumes
that the resemblances are a fraud which, if detected,
would lead to the destruction of the mimic. It may be
admitted that great increase in numbers would multiply
the chances of detection, and hence, upon the Batesian
Hypothesis, the advantage to a mimic of dividing its indi-
viduals among two, three, or four models instead of
concentrating all of them upon a single one. Accepting
this conclusion, I was much startled in 1902,1 when
considering the African Acraeine butterfly, Acraea
esebria, to observe that this protected and distasteful
species possessed two forms of mimetic female, both re-
sembling Danainae — one Limnas chrysippus and the
other the black and white species of Amauris.

1 Trans. Ent. Soc, Lond., 1902, p. 469.

IN DEFENSIVE COLORATION 355

4 When an abundant well-protected Acraca thus
approximates to two very different Danaine patterns,
it is obvious that we are not necessarily driven to
a Batesian interpretation of the forms of the female
Papilio cenea [the southern and south-eastern sub-species
of P. dardanus (inerope)\ which approximate to the
appearance of A mauris echeria as well as to . . . two other
Danaine types. . . . The enemies of chrysippus and the
species of A mauris are certainly not precisely the same,
and it may well be an advantage to a Miillerian mimic to
secure that increased protection from [the experimental
attacks of] insect-eating enemies, which is conferred by
belonging to two or more groups. ... It is probably of
advantage to the whole group that the Danaine which
set the pattern should still be the dominant member of
the assemblage of which it is the centre. This dominance
is favoured by the individuals of an abundant species
joining two or more groups, instead of throwing the
whole of their number into a single one.' 1 We may add
to these considerations the advantages that would be
gained from differences in the distribution or local pre-
dominance of the various models, and from any overlap
they may exhibit in time. A Miillerian mimic belonging
to two or three combinations is far more likely to be
surrounded by models and co-mimics in any given place,
or at any given time, than a mimic which belongs to
a single one. Indeed, when we consider it, there is no
essential difference between a mimetic species such as
Hypolimnas misippus, or Acraea encedon, presenting three
forms resembling respectively the three forms of the
single species, Limnas chrysippus, which serves as a model,
and the cases under discussion where models of two
or three very distinct species are mimicked. The
advantages conferred are probably nearly the same, and
a specific identity, or remote affinity, between a set of
models in any area would not in itself affect the selective
process by which they became mimicked by the forms
of a single species.

It is thus seen that the polymorphism of a mimetic

1 Trans. Ent. Soc, Lond,, 1902, p. 469.

A a 2

356 THE PLACE OF MIMICRY

species, leading it to resemble two or more models,
although at first sight suggesting only a Batesian inter-
pretation, does not by any means exclude the Mlillerian.
The facts presented by a dominant well-protected
Acraeine mimic prove that a resemblance to more than
one model cannot serve as a criterion between the two
rival theories.

14. A Possible Instance of Observable Change in
a Member of a Mlillerian Group since 1825-7. — A power-
ful combination 1 of distasteful butterflies in Eastern
Brazil has developed a characteristic pattern of which the
most marked feature is a bright yellow horizontal band
running along the hind wing. The central members are
Ithomiinae and Heliconinae. An outlying member is the
Danaine butterfly Lycorea halia, with a pale band instead
of a bright yellow one. In the Hope Collection at Oxford
there are eight examples, captured by W. J. Burchell,
in Brazil, between Nov. 10, 1825, and Dec. 24, 1827.
There can be no doubt that these specimens, which are
in very good condition, are on the whole further removed
from the combination than captures of recent date, ' inas-
much as the band is but slightly paler than the tawny
ground colour of the wing/ Unless, therefore, there has
been a darkening of tint with age, we have here an example
of approach towards the combination since 1825-7. The
case is precisely of the kind in which some observable
change might be looked for. That a butterfly which is
outlying to-day should have been even more outlying
seventy-five years ago, is not surprising. But many
further observations must be made before the evidence
can be accepted as in any way satisfactory.2

B. Allaposematic Colours, or Adventitious
Warning Colours.

Certain palatable animals make use of the Special
Defence and Warning Colours of other forms. Thus,
the common English hermit-crab, Pagurus bernhardus* ,

1 Blandford's Series iv, Group 3, Division {a) : see Proc. Ent. Soc,
Lond., 1897, p. xxiv.

2 See Ann. Mag. Nat. Hist., ser. 7, vol. xiii, May 1904, pp. 359-60.

IN DEFENSIVE COLORATION 357

commonly carries on its borrowed shell the conspicuous
stinging sea-anemone Sagartia parasitica ; while an-
other English species, Pagurus prideauxii*, inhabits
a shell which is invariably clothed by the flattened
Adamsia palliata. Two crabs (Polydectus cupulifer*
and Me Ha tessellata*), from Mauritius, described by
Mobius, invariably held a sea-anemone in each claw.

Two other groups of animals, sponges and Ascidians,
in addition to sea-anemones, are avoided by enemies of
the Crustacea, and these are also employed by the latter.
Thus the British hermit-crab Pagurus cuanensis* is
found in shells which are covered with a (generally)
brightly-coloured sponge (Suberites domunctcld). Mobius
also describes a Mauritian hermit-crab (Ascidiopkilus
capkyraeformis*) which lives in a case formed by an
Ascidian.

C. Episematic or Recognition Characters.

Episematic Colours are the logical antithesis of Apo-
sematic, their object being to assist in keeping friends toge-
ther instead of keeping enemies at a distance. Episematic
markings help the individuals of the same species to keep
together when their safety depends upon numbers, or to
follow each other to a place of safety, thus enabling the
young and inexperienced to profit by the example of the
older. Episematic characters are far less common than
Aposematic, and these than Cryptic ; although, as regards
the latter comparison, the opposite impression is generally
produced from the very fact that concealment is so
successfully effected.

The white patch near the tail which is frequently seen
in the gregarious Ungulates, such as the Red Deer*,
and is often rendered conspicuous by adjacent black
markings, probably assists the individuals in keeping
together ; and appearances with perhaps the same inter-
pretation are found in many birds. The white, upturned
tail of the Rabbit * is probably of use in enabling the
individuals to follow each other readily. Many of the
sounds made by animals probably have the same meaning,
as also the characteristic flicking movements with which

358 THE PLACE OF MIMICRY

the individuals of certain burrowing species disappear
into their tunnels.

Episematic markings afford a very good illustration of
the subordination of the individual to the community or
species which is so evident in nature whenever we look
beneath the surface. It is only the superficial observer
who sees the triumph of individualism in the sway of
Natural Selection. Nevertheless, the danger of Recog-
nition Characters is reduced to the lowest possible level.

The difference between a typical Aposematic Character
appealing to enemies, and an Episematic Character
intended to assist other individuals of the same species,
is well seen when we compare such examples as (i) the
large, banner-like white tail, conspicuously contrasted
with the black or black and white body, by which the
slow-moving skunk warns enemies of its power of emit-
ting an intolerable odour ; (2) the small, upturned white
tail of the rabbit, only conspicuous when it is likely to be
of use, and when its owner is moving, and, if pursued,
very rapidly moving towards safety in the burrow.

It is by no means improbable that the wonderfully
exact likeness between closely allied butterflies with
Common Warning Colours would tend to confuse the
sexes, and that the remarkable differences in the scent-
patches of males in certain groups (Euploeini, certain
Danaini, Heliconinae x) have been developed in order to
facilitate recognition by females of the same species.2

III. PSEUDOSEMATIC RESEMBLANCE, OR
PROTECTIVE (BATESIAN) AND AGGRES-
SIVE MIMICRY: PSEUDAPOSEMATIC AND
PSEUDEPISEMATIC RESEMBLANCES.

Protective and Aggressive Mimicry may be defined as
False Warning and Signalling Colours {Psendosernatic),
repelling enemies by the deceptive suggestion of some
unpleasant or dangerous quality (Pseitdaposematic), or

1 W. J. Kaye in Proc. Ent. Soc, Lond., 1907, p. xiv. The margin of
glistening scales which by its breadth in the males divides the Heliconinae
into two sub-groups, is in all probability a scent-producing area.

! Poulton in Proc. Ent. Soc, Lond,, June 5, 1907, p. xl.

IN DEFENSIVE COLORATION

alluring prey by the deceptive appearance of something
attractive to them (Pseudepise malic). Even foreign objects
commonly associated with some well-defended and aggres-
sive species may be mimicked by a comparatively defence-
less form (Pseudallaposemalic).

i . Various Uses of the Term ' Mimicry * : The Essen-
tial Element in Batesian Mimicry. — Mimicry is often
extended to include all the superficial resemblances
between animals and any part of their environment.
It was thus employed by Bates, although the character-
istic and original part of his memoir deals exclusively
with Protective Mimicry. Wallace separated the Cryptic
Resemblances already described, and the majority of
naturalists have followed this convenient arrangement.
In Cryptic Resemblance an animal gains a likeness to
some object of no interest to its enemy or prey, and in
so doing is concealed. In Protective Mimicry an animal
resembles some other animal (almost invariably with
Warning Colours) which is especially disliked by its
enemy ; in Aggressive Mimicry an animal or some part
of it resembles an object which is especially attractive to
its prey. In either case conspicuousness to enemy or
prey respectively is the usual incidental result.

Excluding Cryptic Resemblances, the term ' Mimicry' is
generally used to express a resemblance, independent of
affinity, between certain species inhabiting the same
country — a resemblance which appeals to the senses of
enemies, especially to the sense of sight, not uncommonly
to hearing, occasionally to smell and touch. Even this
definition is, however, far too wide, and includes at least
five distinct kinds of resemblance, to only one of
which the term ' Mimicry ' as explained by Bates's well-
known hypothesis is strictly applicable.

a. The resemblance of a mollusc to the coral on which
it lives, or an external parasite to the hair or skin of
its host, would be Procryptic.

b. That between moths which resemble lichen, Syn-
cryptic (see p. 312).

c. That between the Insectivor mole and the Rodent
mole, Syntechnic (see p. 3 1 2).

36o THE PLACE OF MIMICRY

d. That between distasteful insects, Synaposematic
(see p. 327).

e. That between a palatable mimic and its unpalatable
model, Pseudaposematic or Mimetic in the Batesian
sense.1

The essential element in Protective Mimicry is that it
is a False Warning (Pseud-Aposematic) ; in Aggressive
Mimicry that it is a False Attraction (Pseud-Episematic).

Some have considered that Mimicry implies resem-
blance to a moving object, but apart from the various
other likenesses between animals shown in the above
classification, there are common Cryptic Resemblances
to drifting leaves, swaying bits of twig, &c, while true
Mimetic Resemblances are often specially adapted for
the attitude of prolonged rest.

The term ( Mimicry' is generally used to include Synapo-
sematic as well as Pseudaposematic Resemblances, the
former being spoken of as 'Miillerian', the latter as 1 Bate-
sian' Mimicry. It must be borne in mind, however, that
in Synaposematic colouring the warning is genuine, while
in Pseudaposematic it is a sham. These Greek terms, or
their respective English equivalents, 4 Common Warning
Colours' and ' Protective Mimicry', make the essential
distinction sufficiently clear. Nevertheless, it is impossible
to avoid using the term ' Mimicry ' in connexion with a
Miillerian association, because the relationship between
Model and Mimic requires even more consideration in
Synaposematic than in Pseudaposematic Resemblance.
Furthermore, the ultimate position of vast numbers of
examples is still under discussion. It is certain that they
are mimics in the sense of resembling a model, but
opinions differ upon the question whether they are Bate-
sian or Miillerian. In speaking of the origin and growth
of these resemblances the unqualified term ' Mimicry ' may
be conveniently employed, whether the likeness be Pseud-
aposematic or Synaposematic. In speaking of their
bionomic value the unqualified term should never be used.

1 For a further account of each of the heads a.-e., and more numerous
illustrations, consult the writer's article, Mimicry, in Diet. Philos. and
Psychol., J. M. Baldwin, New York and London, 1902, vol. ii, pp. 79, 80.

IN DEFENSIVE COLORATION 361

The term 1 Mimicry ' has led to much misunderstanding
from the fact that in ordinary speech it implies deliberate
imitation. The production of Mimicry in an individual
animal has no more to do with consciousness, or taking
thought, than any of the other processes of growth in the
individual or evolution in the species.

The example described on pp. 217-18, should it be
hereafter confirmed, would provide a striking demonstra-
tion of the production of Mimicry by the selective action
of enemies alone : model and mimic being, as it is
believed, permanently and widely separated by areas and
barriers over which the enemies are supposed to pass.

Protective Mimicry is here defined as an advanta-
geous superficial resemblance of a palatable defenceless
form to another that is specially defended so as to be
disliked or feared by the majority of enemies of the
groups to which both mimic and model belong— a resem-
blance which appeals to the senses of enemies in the
manner described on p. 359, but does not extend to deep-
seated characters, except when the superficial likeness is
affected thereby. Mutatis mutandis, this definition
applies to Aggressive (Pseudepisematic) Mimicry.

a. pseudaposematic resemblance, or protective
(Batesian) Mimicry.

A brief historical account of Protective Mimicry has
been given on pp. 220-3.

H. W. Bates's historic theory is of especial interest
because it was one of the first attempts made by
naturalists to employ the great weapon put into their
hands by the Origin of Species. Natural Selection was
here invoked to offer an intelligible explanation of a
large class of phenomena, up to that time well known
but unexplained.

I. Wallaces Statement of the Conditions under which
Protective Mimicry Occurs. — The five conditions are as
follows : — 1 1. That the imitative species occur in the
same area and occupy the same station as the imitated.

2. That the imitators are always the more defenceless.

3. That the imitators are always less numerous in indi-

362 THE PLACE OF MIMICRY

viduals. 4. That the imitators differ from the bulk of
their allies. 5. That the imitation, however minute, is
external and visible only, never extending to internal
characters or to such as do not affect the external
appearance.' 1

The wide difference between the Mimicry of Bates and
the resemblances explained by Fritz Muller is well seen
when we attempt to apply these conditions to the latter.
A striking exception to the first condition is given on
pp. 217-18, and many instances of divergence in station
could be quoted (see p. 349). It is still more obvious that
the second condition does not apply to such examples.
There is no reason for supposing that a Chalcosid moth
is any more palatable to an insectivorous bird than the
Danaine it mimics (see p. 275). But the Danaine is far
commoner, and its pattern is consequently a far more
effective advertisement of unpalatability than that of the
moth. The third condition also does not appear to be
an invariable rule in cases of Mullerian Resemblance (see
pp. 216 and 334, n.). A good example to the contrary is
brought forward by Dr. F. A. Dixey in Trans. Ent. Soc,
Lond., 1894, P- 2 9&, n.

2. The Chief Characteristics of Mimetic Resemblance
and the Attempt to Explain their Evolution. — In the
two preceding Essays the principal general statements
that can be made about Mimetic Resemblance, both
Batesian and Mullerian,2 have been brought together
and discussed in relation to the various hypotheses which
have been proposed as to their evolutionary origin. It
was argued that statements based on a very broad
foundation of fact receive an adequate explanation on

1 Darwinism, London, 1889, pp. 264-5.

2 The rival interpretations are rarely discriminated, as the discussion of
Bates v. Muller was not the object of Essays VIII and IX. It may be
safely affirmed that not one of the general statements necessarily supports
the hypothesis of Bates. Dr. F. A. Dixey showed in 1894 that the special
tendency towards mimicry exhibited by the female sex (see pp. 244-7)
is witnessed in Mullerian Resemblance, and is in no way to be accepted as
evidence supporting the alternative hypothesis. The Papilio- Euterpe
association defies interpretation on Batesian lines {Trans, Ent. Soc,
Lond., 1902, p. 467, and the references there given).

IN DEFENSIVE COLORATION 363

the hypothesis of Natural Selection, but on no alternative
hypothesis that has been proposed. It is not necessary
to refer further to the origin of Mimicry by means of
Natural Selection, but before proceeding to the discussion
of examples certain additional aspects of the subject may
be considered.

It is of the utmost importance to realize that in the
aspects of the subject discussed in the following five
Sections, and probably even in the sixth, there is nothing
necessarily characteristic of Batesian as opposed to
Mullerian Mimicry. The dominant importance of
instinct — inferences as to past history and migration — the
confirmation of a history inferred from Mimicry by the
study of structure — Mimetic Resemblance independent
of size ; all these are just as applicable to examples
of one kind of Mimicry as of the other. The remark-
able examples mentioned in Sections 7 and 8 require
consideration on their own merits, and oftentimes the
accumulation of further evidence, before they can be
allotted their final place in either category.

3. The A 11- Importance of Instinctive Attitudes and
Movements in the Attai?iment of Mimetic Resemblance. —
The necessity of studying Mimetic Resemblance during
life and under entirely natural conditions, is convincingly
shown by the well-known Indian Longicorn beetle Glenea
pulchella. In the cabinet this insect appears as an obvious
Longicorn, but Mr. Leslie Andrewes found that in the
field it bears a striking resemblance to an Ichneumonid.1
A similar observation was made upon the South African
Longicorn Nitocris nigricornis by Mr. C. N. Barker.2
It is also true of our British Wasp-beetle, Clytus arietis,
and of a very large proportion of the examples of
Mimicry generally.3 It is as true of Mullerian Resem-
blance as it is of Batesian Mimicry.

4. History and Migration may be Inferred from
Mimicry. — Batesian Mimicry and Mullerian Resemblance
may supply evidence of the former migrations and history

1 Proc. Ent. Soc, Lond., 1904, p. vi. 2 Ibid., p. xxxiv.

3 See also pp. 238, 239, 252, 253, 256 of the present volume.

364 THE PLACE OF MIMICRY

of species. The large Danaine butterfly, Anosia plexippus
( archippus ) alluded to on p. 2 74, has now travelled from its
home in the New World to many parts of the Old, but the
effect it has produced upon the butterfly fauna of North
America would always show, even if we had no further
evidence, the position of its ancestral home.1 So, too,
the commonest Danaine in the Old World, Limnas
chrysippus, although ranging through and beyond the
Oriental Region, is clearly shown by the same kind of
evidence to have been an inhabitant of Africa for a far
longer period. Not only is this inference justified, but
it can also be stated that the exclusive predominance of
the white-hind-winged alcippus form of chrysippus on the
west coast of Africa, from the Niger Mouths to the
Sahara (see p. 321), is a result of modern changes in
distribution. It has not affected any of the West Coast
mimics, except perhaps Acraea encedon, in which case
there is some evidence, from one locality in Sierra Leone,
to show that the presence of alcippus has encouraged the
white-hind-winged alcippina form.2 Furthermore, a study
of mimetic forms may enable us to reconstruct the past
stages through which the older model has passed.
When a geologist finds a recognizable fragment of
one rock included in a stratum of another, he infers
with confidence that the latter is the younger. With
equal certainty the zoologist may conclude that the
mimicking species is younger than the model it has come
to resemble. In certain cases the species acting as a
model is di- or trimorphic. Thus the individuals of
Limnas chrysippus fall into three groups, of which two,
as described on pp. 70, 71, are sharply marked off and
unconnected by gradual transition. The individuals of
the two commonest mimics of chrysippus also fall into
three corresponding groups. In both species of mimic,
however, all the groups are connected by abundant
transitional forms. We are led to believe that the
mimics, being younger, present us with a picture of the
former condition of the older model, when transitional

1 Proc. Amer. Ass. Adv. Sci., vol. xlvi, 1897, P- 244-

2 Trans. Ent. Soc, Lond., 1902, p. 480.

IN DEFENSIVE COLORATION 365

forms between the groups now sharply separated had
not been obliterated.1

5. A History Inferred from Mimicry may be Confirmed
by other Evidence.

[The following facts and arguments were first brought
forward in the Leeds lecture, and published in Nature
for October 2, 1890. They have been revised for the
present work.]

Evidence for the evolution of Mimetic Resemblance has
been forthcoming as the result of recent [in 1890] work,
of which the general results are set forth below, but the
details still remain unpublished.

Many moths have lost the scales which are charac-
teristic of the Order of insects to which they belong, so that
their wings become transparent, and they mimic stinging
insects such as humble-bees, wasps, and hornets. This is
the case with two British Hawk Moths (Haemorrkagia
fuciformis* and H. tityus* = bombyliformis). It is known
that when these moths emerge from the chrysalis, the
transparent parts of their wings are thinly covered with
scales which are shaken off during their first flight. The
loss of the scales is due to the rudimentary nature of the
stalk at the base of the scale and of the socket in which
the stalk is inserted. A closely allied Eastern and Ethiopian
moth [Cephonodes hylas *) is still more completely denuded
of scales, but in it also the rudimentary sockets are found
to be thinly scattered over the transparent wings. These
facts suggested that other moths with transparent wings
would be found to repeat, in the course of their own
individual lives, the history of the change by which
transparency has been attained by the species. Investi-
gation has supported this suggestion. The examination
of two British Sesiid moths which resemble hornets
or wasps was especially instructive. In one of these,
Trochilium (Sesia) apiforme*, the mimicry is not so
perfect as in the other, and is therefore presumably of
more recent date ; in this moth the rudimentary scales
which fall off are comparatively perfect, while in the

1 Trans. Ent. Soc, Lond., 1902, pp. 482-4. The mimics alluded to
are Hypolimnas misippus, female, and Acraea cncedon.

366 THE PLACE OF MIMICRY

better mimic, Trochilium (Sesia) crabroniforme* (bembeci-
forme), they are far more degenerate, in accordance with
the presumption that they have been useless to the species
for a longer period of time. It is interesting to note that
these degenerate scales have not been reduced in size in
either species, but are, on the contrary, much larger than
the scales which are retained for the whole life of the
moth. It is probable that the increase of size renders it
even more difficult for the degenerate stalks to retain the
scales during flight. In certain allied ' Clearwings ' of the
genus Sesia (Trochilium) the transparency of the fore
wing has been attained by the transparency of scales
which are retained, as well as by the loss of scales.1

6. Mimetic Resemblance between Species of very
Different Size. — It has been observed for many years
that close mimetic likeness may be found between species
of very different size. One of the most striking examples
is to be seen in Papilio (Drurya) antimachus, an immense
West African swallow-tail butterfly with an obvious
Acraeoid appearance. The Papilio appears to form one
of a complex mimetic group of which the centre is
composed of many comparatively small but dominant
species of Acraea.2 When the members of this mimetic
combination were exhibited, Mr. F. A. Heron suggested 3
an interpretation of such remarkable cases of the want of
accord between size and the other elements which go to
make up a likeness. Size, as correlated with the idea of
distance, was, he pointed out, extremely difficult of
estimation. In fact the huge antimachus, seen far off,
may well appear to be smaller than the comparatively
insignificant Acraeas at a much less distance. Especially
is this likely to be true of young and inexperienced
enemies, and it is precisely these which Mtillerian Resem-
blances are in large part adapted to meet. This interest-

1 See also pp. 264-6 for other examples of transparency attained in
a variety of ways. Consult also W, J. Kaye in Ent. Record, vol. xvii,
nos. 4 & 5, and Mark L. Sykes in Trans. Manch. Microsc. Soc. 1901,
p. 82.

2 Proc. Ent. Soc, Lond., 1903, Nov. 18, pp. lxiii-lxv.

3 Ibid., p. lxv.

IN DEFENSIVE COLORATION 367

ing and convincing suggestion would, however, apply
to Batesian Mimicry as well as to Synaposematic
Resemblance.

7. Remarkable Examples of Mimicry. — Many instances
of Mimetic Resemblance between forms of all degrees of
affinity have been given in Essays VIII and IX. They
have been drawn from the Arthropoda and almost
exclusively from the Insecta, the group in which these
superficial likenesses are developed far more extensively
than in all the others put together.

Mimicry is known, although instances are relatively
rare, among the Vertebrata. Thus the venomous South
American snakes of the genus Elaps are mimicked by
harmless species inhabiting the same areas ; defenceless
birds such as the cuckoos and orioles mimic powerful
aggressive species living in the same countries, and, in
Malaya, tree-shrews mimic the more powerful squirrels.1

The terrifying appearance assumed by certain large
caterpillars, e. g. the British Choerocampa elpenor (the
Elephant Hawk Moth), is founded upon the mimicry, or
rather the caricature of a cobra-like serpent. Many
observations prove that terror is undoubtedly inspired
by the appearance, in man no less than in insect-eating
animals. It is probable that these are examples of true
Batesian Mimicry — Pseudaposematic Resemblance. In
an experiment made by the present writer in 1887, a large
lizard, Lacerta viridis, was for some time immensely
terrified by the larva of elpenor. When, however, the
lizard eventually succeeded in overcoming its fright, it
devoured the caterpillar with apparent relish.2 It is

1 For details consult A. R. Wallace, On Natural Selection, London,
1875, PP- ioi~7« Mr. Shelford informs me that the tree-shrews certainly
possess distasteful qualities and yet that they are undoubtedly the mimics.
It is not improbable that the resemblance is Mullerian. The interpreta-
tion of the likeness as aggressive — the shrews being enabled under the
disguise of squirrels to approach their insect prey — has broken down in
somewhat analogous cases (see p. 378), and would require a great deal
of confirmatory evidence before it can be accepted as probable.

2 Colours of Animals, London, 1890, p. 261. For other earlier
observations on the same species consult the same work, pp. 258-60,
also Proc, Zool. Soc, Lond., 1887, pp. 204, 206-7, together with the

368 THE PLACE OF MIMICRY

interesting to note that this terrifying appearance has
been shown in certain cases to be combined with a highly
cryptic appearance. The larva of elpenor is well concealed
until disturbed, when it instantly assumes an entirely
different method of defence. The suddenness of the
transformation undoubtedly adds to the effect.

Another remarkable group of examples includes the
cases in which the tail of the mimic is so modified and
so held as to resemble the head of its model. An
instance has already been described on p. 254, and
Mr. R. Shelford has described two beautiful instances
discovered at Singapore by Mr. H.N. Ridley, F.R.S. In
one of these the effect is mainly produced by two black
eye-like spots on the abdomen of an ant-like spider.1
The form of the abdomen assists in the resemblance.
In the second example, the appearance of an ant of the
genus Oecophylla is strongly suggested by the form,
markings, and movements of the posterior end of a
caterpillar. Mr. Shelford speaks of 1 the resemblance as
positively startling'.2 In the same manner, the posterior
end of a large Oriental chafer {Lepidiota bimaculatd)
appears to resemble the head of a shrew-like mammal.3
Dr. Longstaff also describes and figures the third pair of
legs of an African beetle (Heterockelus) projecting like
formidable jaws from a flower, in which the beetle itself
is buried head downwards.4

Even more remarkable are the cases in which the
mimicry is of a composite kind, suggesting the appearance
of two entirely different objects. A good example has
been described and figured on pp. 259-60, and an even

references there given. For the snake-like appearance of a Bornean
Choerocampa, seeR. Shelford in Proc Zool. Soc, Lond., 1902, vol. ii, p. 253;
of an African species of the same genus and the terrifying effect produced
on monkeys, see Marshall, Trans. Ent. Soc, Lond., 1902, p. 397. For
the effect of an African Choerocampa larva on man, see S. A. Neave,
Proc. Ent. Soc, Lond., 1905, pp. xxii, xxiii; for the superstitious dread
with which elpenor is regarded in Ireland, see Trans. Ent. Soc, Lond., 1902,
p. 399, and the references there given.

1 Proc. Zool. Soc, Lond., 1902, vol ii, p. 266. 2 Ibid., pp. 254-5.

3 Proc Ent. Soc, Lond., 1906, p. xxi.

* Trans. Ent. Soc, Lond., 1906, p. 94.

IN DEFENSIVE COLORATION 369

more remarkable one has been provided by the acute
observation of Portschinski.1 The great Russian natural-
ist has suggested that the mature and semi-mature larva
of Statiropus fagi (the Lobster Moth) resembles a cater-
pillar attacked by a Pentatomid bug. The bug itself is
represented by the flattened caudal shield, of which
the terminal processes resemble antennae. In its usual
position, this shield is bent forward over the back of the
larva, so that the flattened ventral surface becomes dor-
sal, the convex dorsal surface ventral, the antenna-like
processes anterior. It thus resembles very closely the
appearance of a bug seated on the back of the cater-
pillar and engaged in sucking its juices.

The extraordinary mimetic resemblance of the Mem-
bracidae, in which the appearance is wrought in the
visible shield, and not in the insect which it conceals,
has been described and figured on pp. 258-9. Other
remarkable instances to be found in the same Essay need
not be further mentioned.

8. Mimetic Resemblance to Cryptic Models. — A set of
examples, very rare in Mimicry, is to be found in the
numerous Longicorn beetles which resemble Rhyncho-
phora. Mr. Shelford 2 has shown that in Borneo all three
groups of Rhynchophorous beetles, the Curadionidae
(weevils), the Anthribidae and the Brenthidae are thus
mimicked ; in South Africa, Mr. Marshall 3 has shown
that the first-named group provides models for Longi-
corns. Wallace 4 suggested long ago that the weevils and
Anthribidae are protected by their excessive hardness,
and are on this account mimicked by less well-protected
Longicorns. Although in some cases the Rhyncho-
phorous models possess a conspicuous warning pattern,
the great majority appear to bear a Procryptic colouring.
This appearance is, however, often deceptive, inasmuch
as the habits of the insect may render it conspicuous.

1 Coloration Marquanle et Taches ocellees, V., St. Pe'tersbourg, 1897,
p. 51, fig. 25.

8 Proc. Zool. Soc.} Lotid., 1902, vol. ii, pp. 245-7.

3 Trans. Ent. Soc, Zond., 1902, p. 523. Consult also the whole section
on pp. 522-5.

4 On Natural Selection, London, 1875, p. 94.

POl'LTOK £ b

THE PLACE OF MIMICRY

Thus the dark, stick-like Brenthidae seem to possess a
marked Procryptic appearance when examined in the
cabinet, but Mr. Shelford tells me that they are very
commonly found on flowers where they are most con-
spicuous. Mr. Marshall also states that the large black
African weevils move slowly, and are freely exposed, so
that they, too, must be visible from a great distance.
The examples in which the models appear to be un-
doubtedly Procryptic are probably to be explained by the
peculiar character of the defence. Hardness would not
avail ' against an enemy large enough to swallow the
beetle whole, so that it could be ground down in the
gizzard, or the interior slowly extracted by digestive
fluids gaining access by the joints and other apertures.
Defence by a sting, a nauseous taste or smell, or
unwholesome qualities, is effective against enemies of all
sizes and all degrees of strength, although failing against
occasional specially adapted foes. It is possible that
these considerations may enable us to understand why
it is that certain Rhynchophora are remarkable among
Coleoptera for combining a cryptic colouring with sufficient
immunity to render them feasible models for mimicry'.1

9. Butterflies and Moths, chiefly Oriental, Selected in
1890 to Illustrate Various Aspects of Mimicry. — Almost
all of the following species, shown as examples of Mimicry
at the Lecture to the British Association in 1890, would now
be looked upon as instances of Miillerian (Synaposematic)
Resemblance. The entire list is, however, reprinted in
this place in order to direct attention to the recent change
in interpretation. The examples were selected — except
in one important series of related forms, viz. Papilio dar-
danus (merope), its sub-species and allies — from Oriental
Lepidoptera. The examples of Mimicry hitherto brought
forward in this work are principally South American and
Ethiopian, so that it may be useful to direct attention to
a brief list of mimetic species from the East, especially
when they have been chosen in order to illustrate the
various degrees of complexity with which these superficial
resemblances are attained.

1 Trans. Ent, Soc, Lond.> 1902, p. 523.

IN DEFENSIVE COLORATION 371

With the exception of some of the forms of Papilio
dardanus, the whole of the species arranged under the
following heads, a-g.y were shown in 1890, and it has not
been thought necessary to indicate these particular illus-
trations by asterisks. The first paragraphs under each of
the heads a-g. were published in 1890,1 but the synonyms,
&c, have been as far as possible brought up to date.
The paragraphs in square brackets give a brief account of
the reasons why nearly all the examples employed in 1890
to illustrate Bates's Hypothesis, would at the present day
be looked upon as illustrations of the Hypothesis of Fritz
Mtiller. Repeated evidence will thus make it clear that
fifteen years have brought a fundamental change in the
point of view.

a. Both Sexes Mimetic : Both Sexes of Model and
Mimic Superficially Alike. — Both sexes of the North
Indian Papilio ages tor closely resemble the Danaine
butterfly Caduga tytia.

[The large white spots on the body of the Papilio render
it in this respect more conspicuous than the Danaine.
Furthermore, it is an abundant species, and other members
of the same group tend to approach it in certain points
more closely than the primary Danaine model, so that
there can be hardly any doubt that we are dealing with
an example of Mullerian Resemblance.]

b. Sexes readily Distinguishable : Male Mimics Male,
Female Mimics Female. — An Indian moth (Epicopeia
philenord) similarly mimics an unpalatable butterfly {Papi-
lio protenor), but in this case the male moth mimics the
appearance of the male butterfly, and the female moth
that of the female.

[The moths belong to the Family Uraniidae, and
are probably specially protected. In another still more
wonderful example of likeness between species from the
same groups in New Guinea, although the resemblance is
probably to a certain extent reciprocal (Diaposematic),
the approach is chiefly from the side of the Papilio (P.
laglaizei), rather than from that of the Uraniid moth
(Alcidis aurora).']

1 Nature, 1890, October 2, p. 557.
B b 2

372 THE PLACE OF MIMICRY

c. Male and Female Mimicking Different Species. —
If the mimicking species became common relatively to
the mimicked, the deception would be liable to be detected.
We therefore find that two or more models are often
mimicked by the same species. Thus the male of the
Indian Melynias malelas (Elymnias leucocymd) mimics
Stictoploea harrisi, while the female mimics the female
Trepsichrois mulciber. Both these Euploeas are also
imperfectly mimicked by day-flying moths (Callamesia
midamd). So also the male of the Indian Papilio castor
mimics Papilio chaon, while the female mimics Crastia
core : in Southern India, Papilio chaon is absent, and both
sexes of the species {Papilio dravidarum) which repre-
sents P. castor mimic C. core.

[There is more reason for believing that the Elymniinae
are Batesian mimics than almost any other butterflies.1
The case has been discussed on pp. 353-4, and the
inferences to be drawn from a resemblance to two or more
models on pp. 354-6. The resemblance of Callamesia,
belonging to the highly distasteful Family Zygaenidae, Sub-
Family Chalcosiinae, is certainly Miillerian, and the same
is doubtless true of the Papilios, which are themselves
often mimicked by other species. P. aristolochiae has been
shown (see p. 269) to be extremely distasteful to birds.]

d. Female Mimetic : Male Non-Mimetic. — Female
butterflies are exposed to more dangers than the swiftly-
flying males, and we find many instances in which the
former are mimetic, although the latter are not. Thus
the female of the Indian Hypolimnas bolina mimics
Crastia core, while the male is non-mimetic The same
is true of Hypolimnas misippus, the female of which
mimics Limnas chrysippus. The last-named Danaine
model is trimorphic, and all three forms are mimicked
by the female Hypolimnas.

[Recent evidence renders it probable that the whole
Nymphaline genus Hypolimnas is distasteful, and that
the resemblance is Miillerian : see pp. 215-18.]

1 As argued by Mr. R. Shelford, at the meeting of the Entomological
Society of London, on June 5, 1907. The discussion is not reported in
the Proceedings.

IN DEFENSIVE COLORATION 373

e. Female Mimicking two or more Different Species :
Male perhaps Non-Mimetic, or Mimicking still another
Species. — The mimetic females also often resemble two
or more different species of nauseous butterflies. Thus the
female of Papilio polytes (pammon) appears in two forms,
mimicking respectively Papilio hector and P. aristolochiae ;
while the females of Euripus halitherses (the male of
which is probably also mimetic) mimic Danisepa diocle-
tianus (r had am ant hits) and Penoa deione.

[The conspicuous under side of the non-mimetic male
of Papilio polytes (pammon) suggests special protection,
and renders it probable that the resemblance of the
female is Mtillerian. The genus Euripus is also probably
distasteful, like many other mimetic Nymphaline genera.1
For dimorphism in mimicry, see pp. 354-6.]

f. Non- Mimetic A ncestor preserved on Islands, &c. : on
Adjacent Continent Mimicry developed in one or both
Sexes : Remarkable case of Papilio dardanus (merope). —
There are also striking examples in which the non-
mimetic ancestor of a mimetic species has been preserved,
e. g. in an adjacent island. Thus the female of Elymnias
undularis mimics Salatura plexippus (genutia) in Sikkim
and North-East India ; in Burma there is a common
form of the latter with white hind wings (S. hegesippus),
and the Burmese female of E. undularis is apparently
beginning to mimic this variety ; in South India E.
undularis is represented by E. caudala, in which the
male is also beginning to mimic Salatura plexippus, and
the female is a more perfect mimic than in the other
localities ; in the Andaman Islands Elymnias cottonis
represents E. undularis, and both sexes appear to be
non-mimetic.2

A still more wonderful example is found in Africa
and adjacent islands. Papilio merioncs of Madagascar
is non-mimetic and the sexes are nearly alike ; the
same is true of a closely-allied species, P. humbloti,
in Grand Comoro, and of an Abyssinian sub-species

1 Trans. En/. Soc, Lond., 1902, pp. 500-2.

2 It is not unlikely that E. cottonis bears a general resemblance to
a Euploeine.

374 THE PLACE OF MIMICRY

(antinorii J) of the African P. dardanus (merope).
Wherever it occurs in other parts of the continent
dardanus is represented by sub-species with mimetic
females 2 and non-mimetic males. The sub-species
merope, from the West Coast to the Victoria Nyanza,
possesses three forms of female, hippocoon and trophanius
resembling the Danaines — Amauris niavius and Limnas
chrysippus ; planemoides 3 resembling the Acraeine
Planema poggei. The sub-species polytrophus from the
Kikuyu Escarpment, tibullus from the East Coast, and
cenea from the south and south-east have the additional
female form cenea, mimicking Amauris echeria and
albiniaculata. The planemoides form is wanting from
the sub-species cenea, but exists in polytrophus and may
probably be found in tibullus. The hippocoon form of the
eastern and south-eastern sub-species resembles the form
of Amauris niavius, viz. dominicanus, which is found in
the same district. Ancestral females, the trimeni form,
intermediate between the non-mimetic Abyssinian females
and hippocoon, the most primitive of the mimetic forms,
have been found in polytrophus and tibullus. All the

1 A single mimetic female corresponding to the hippocoon form of
merope, &c, and a single mimetic female corresponding to trophonius, but
both tailed, have now been found.

2 Even the primitive trimeni ioxm is a rough mimic of Amauris niavius,
sub-species dominicanus.

3 The planemoides form is a recent addition of the highest interest to
our knowledge of this classical example of Mimicry. While the other
mimetic female forms all resemble Danaine butterflies, this newly
discovered female bears a beautiful likeness to Planema poggei, one of
the Acraeinae (see also pp. 337-8). The Mimetic Resemblance was first
recognized by Mr. S. A. Neave, M.A., B.Sc, of Magdalen College,
Oxford {Proc Ent. Soc, Lond., 1903, p. xli), while Mr. Roland Trimen,
F.R.S., has described the female form, conferring upon it the appropriate
name planemoides {Proc. Ent. Soc, Lond., 1903, pp. xxxix, xl). This new
form has not yet been proved by breeding to be one of the females of the
merope-group ; but a curious accident has supplied the missing evidence.
Among some examples captured in 1902-3 by Captain T. T. Behrens,
R.E., on the west shore of the Victoria Nyanza, near Entebbe, is a
partial hermaphrodite, in which, upon the left wings, traces of the non-
mimetic male colours and markings are intermingled with the utterly
different mimetic pattern of the female. This interesting individual may
be studied in the Hope Department. (See also Trans. Ent. Soc, Lond.,
1906, p. 281, plate xviii, fig. 4.)

IN DEFENSIVE COLORATION 375

above were shown as illustrations in 1890, except the
sub-species antinorii, polytrophus, and tibulltcs, and the
female forms planemoides and trimeni.1

[The grey, black-spotted body of these Papilios
renders it probable, as in Papilio agestor, that the
resemblance is Mullerian. The examples in which
Papilios are models for mimicry, and the proved un-
palatability of P. aristolochiae should also be taken into
account (see b. and e. on pp. 371, 373 ; also p. 269). Con-
cerning the remarkable division of females into forms
mimicking different models see pp. 354-6.]

[In Professor Weismann's recent important work 2 the
forms of Papilio dardanus (merope) and their models are
for the most part unfortunately represented incorrectly.
Plate I, Fig. 1, described as 'Papilio merope, male,
Africa ', is an Abyssinian female : Fig. 5, 1 Amauris
niavius, South Africa, immune model of Fig. 4/ is the
western sub-species ; the eastern and southern sub-species,
dominicanus, has a much larger white patch like its
mimic from the same area, correctly shown in Fig. 4 :
Fig. 6, 1 Papilio merope, third form of mimetic female,
South Africa,' is the female of Papilio echerioides, a co-
mimic with this third form of the same models, Amauris
echeria and A . albimaculata : Fig. 7, A mauris echeria, South
Africa, immune model of Fig. 6,' is not the model but the
mimic named in the description of Fig. 6, viz. the third
or cenea form of mimetic female of P. dardanus (jnerope),
from the east and south of Africa. The figures are
copied, unfortunately incorrectly, from Haase,3 the
unqualified term ' immune ', to which exception has been
taken on p. 318, being also quoted from the same author.
Professor Weismanns prolific labours and great dis-
coveries give an authority and influence to these unlucky
copyist's errors, and therefore it is of the utmost import-
ance to set them right in detail. Already, indeed, they

1 The above account of P. dardanus has been re-written and much
amplified in accordance with existing knowledge.

3 The Evolution Theory, English transl., London, 1904, vol. i, pi. i.

3 Untersuchungen iiber die Mimicry, plates i and ii, in Biblioiheca Zoo-
logica, Stuttgart, Bd. iii, Heft 8, 189 1-3.

376 THE PLACE OF MIMICRY

have been copied in two books published in the United
States, and one in Germany. On the second plate, exhibit-
ing in Figs. 12-15 a Synaposematic combination from
Eastern Brazil (called a 'Mimicry-Ring' by Professor
Weismann), the descriptions of Figs. 12 and 13 as well
as of 14 and 15 have been transposed.]

g. Imperfect Resemblance, not to any Particular Species,
but to the General Appearance of an Unpalatable Group. —
There are also examples which show us the origin of
mimicry — examples in which the resemblance is very im-
perfect, but, nevertheless, sufficient to afford some protec-
tion. The blue Euploeas of India, &c. (such as Stictoploea
harrisi, Trepsichrois mulciber, and Isamia splendens, in-
cluding irawadd) form a very characteristic group, while
their general type of appearance is imperfectly mimicked
by several day-flying moths belonging to the Chalcosiinae
(Callamesia midama, Amesia aliris, A. sanguiflud). It is
extremely probable that the wonderfully close likeness
of many mimetic species arose by gradual stages from
a general resemblance to a type of colour or pattern
possessed by a large group of unpalatable insects.

[In this case the moths belong to a group admitted to
be distasteful, and the resemblance is clearly Miillerian :
see also c. on p. 372.]

[Considering the great change in the point of view that
has occurred since 1890, when the above-mentioned
examples were shown at Leeds, the question naturally
arises as to whether anything will remain of the hypo-
thesis originated by Bates. The clearest examples
known to me are the cases of close likeness to a poisonous
serpent borne by harmless species, and also by large
caterpillars (see pp. 367-8). It is also likely that many of
the resemblances to stinging insects and ants are Batesian.
Examples to the contrary are mentioned on pp. 230-1.
It must also be mentioned that Miillerian Resemblance
is very extensively developed among the stinging Hyme-
noptera themselves, see p. 278. Numbers of other cases
might be quoted.]

IN DEFENSIVE COLORATION 377

[From this point onwards, asterisks are again employed
to indicate the lecture illustrations.1]

B. PSEUDALLAPOSEMATIC RESEMBLANCE : MlMETIC REPRE-
SENTATION of some Adventitious Object Associated
with the Model.

[The examples hitherto observed fall under the head of
Protective Mimicry (Pseudaposematic Resemblance) and
are therefore given this position. It is not unlikely that
hereafter Pseudallepisematic likeness may be found in
certain cases of Aggressive Mimicry.]

2 A very striking instance was discovered by Mr. W. L.
Sclater in tropical South America. The well-defended
and abundant leaf-carrying ants of the genus Atta*
(Oecodoma) are mimicked by an immature Homopterous
insect* (a Membracid) possessing a shape and colour
which closely resemble the ant together with the piece
of leaf it is carrying. [For other probable instances and
figure see pp. 259-60.]

C. Pseudepisematic Resemblance or Aggressive
Mimicry, including Alluring Colours.

This division not only includes the examples of Aggres-
sive Mimicry, in which an animal resembles another, and
so is enabled to approach and injure it in some way, but
also the cases of Alluring Colouring, in which an animal
possesses a lure which is attractive to its prey. These
latter are often regarded as examples of Aggressive
(Anticryptic) Resemblance, but their logical position is
here.

It has been believed that examples of Aggressive

1 The paragraph on the attainment of transparency by certain
Sphingid and Sesiid moths which appeared in this place has now been
transferred to pp. 365-6.

2 With the exception of the paragraphs in square brackets, the
following statements, as far as the end of the fourth sentence under
1 IV. Epigamic Colours are reproduced from the lecture-notes published
in Nature, 1890, p. 557. They have been revised for the present work.
The Section on Pseudallaposematic Resemblance was originally placed
after that upon Pseudepisematic Resemblance.

378 THE PLACE OF MIMICRY

Mimicry are seen in the flies of the genus Volucella*,
which are enabled to lay their eggs in the nests of
Humble-bees, &c, because of their close resemblance
to the latter. The larvae of the fly have been supposed
to feed upon those of the bee.

[The larvae of Volucella are probably scavengers, and
it is now known that the presence of the flies is not
resented. The resemblance is an example of ordinary
mimetic likeness to a formidable model, and is rendered
all the more effective from the fact that fly and bee are
specially associated.1 Even in cases where Asilid flies
are beautiful mimics of their Hymenopterous victims 2 it
is improbable that the resemblance is aggressive. The
explanation is probably similar to that offered in the case
of Volucella. There is little doubt, however, that the
following examples are truly Pseudepisematic]

Examples of Alluring Colouring. An Asiatic lizard
(Phrynocephalus myslacetis*) possesses pink flower-like
structures at the corners of its mouth, and it is probable
that flies, &c. are thus allured. A Terrapin {Macro-
clemmys temtninckii*) from the Southern States of
America, when hungry, opens its mouth and actively
moves the filaments below the anterior end of its tongue.
These look like worms moving in a crevice in the rocks,
and attract prey. The animal is otherwise perfectly
motionless, and resembles a conferva-covered rock. The
fish Lophius piscatorius * (the Angler or Fishing- Frog)
attracts its prey by a brightly coloured lure placed
over its large mouth, the rest of the body being
concealed. Certain deep-sea fishes allied to Lophius,
(Ceratias bispinosus* \ C. uranoscopus* \ &c.) have a
phosphorescent lure attractive to the other fish on
which they feed.

[Examples are found among insects, in the flower-like
species of Mantidae which attract the other insects forming
their prey. The flower-like appearance is undoubtedly
Procryptic as well as Pseudepisematic.3]

1 See Trans. Eni. Soc, Lond., 1904, pp. 663-5.

2 See ibid., pp. 661-5 ; 1906, p. 378.

3 See N. Annandale, in Proc. Zool. Soc, Lond.} 1900, p. 837, for an

IN DEFENSIVE COLORATION

IV. EPIGAMIC COLOURS.

Epigamic Colours are the bright tints and patterns dis-
played during courtship. As in other classes of colours
the same effects may be produced by the use of foreign
objects (A llepigamic). Examples of this latter are found
in the various beautiful or curious objects collected by
bower-birds for the decoration of their bowers. Especially
interesting in this respect is the A mblyornis inornata* of
New Guinea. Although, strictly speaking, the subject
does not fall into the sphere defined by the title of this
Essay, the Epigamic is so closely related to the other
bionomic uses of animal colours that some brief account
appears to be necessary.

The interpretation of these Secondary Sexual Characters
was first suggested by Darwin in the joint memoir con-
tributed by him and Wallace to the Linnean Society of
London, July 1, 1858. It was further expounded in the
Origin of Species} and published in a complete form in
1 87 1.2 The rivalry between males for the possession of
the female was, Darwin believed, decided by the prefer-
ence of the latter for those individuals with especially
bright colours, highly developed plumes, beautiful
song, &c. Wallace does not accept this theory, but
believes that the direct or indirect action of Natural
Selection accounts for all the facts. Probably the
majority of naturalists follow Darwin in this respect.

The subject is most difficult, and the interpretation of
a great proportion of the examples in a high degree
uncertain, so that a very brief account is here expedient.
That selection of some kind has been operative is indi-
cated by the diversity of the elements into which the
effects can be analysed.

The most complete set of observations on Epigamic

excellent account of the flower-like Mantis, Hymenopus, and an allied
species, in the living state. R. Shelford has shown that the newly-
hatched larvae of Hymenopus bicornis mimic a Reduviid bug ; see Proc.
Z00L Soc, Lond., 1902, vol. ii, pp. 231-2, pi. xix, figs. 16-19.

1 London, 1859, pp. 87-90.

2 Part II of The Descent of Man, and Selection in Relation to Sex.

380 THE PLACE OF MIMICRY

display was made by George W. and Elizabeth G. Peck-
ham upon spiders of the family Attidae} These obser-
vations afforded the authors ' conclusive evidence that the
females pay close attention to the love dances of the
males, and also that they have not only the power, but
the will, to exercise a choice among the suitors for their
favor \ Observations on the courtship of grasshoppers
have also yielded some support to the Darwinian hypo-
thesis of Sexual Selection.2

Epigamic characters are often concealed except during
courtship : they are found almost exclusively in species
which are diurnal or semi-diurnal in their habits, and are
excluded from those parts of the body which move too
rapidly to be seen. They are very commonly closely
associated with the nervous system ; and in certain
fish, and probably in other animals, an analogous
heightening of effect accompanies nervous excitement
other than sexual, such as that due to fighting or
feeding.

Although there is Epigamic display in species with
sexes alike, it is usually most marked in those with
Secondary Sexual Characters specially developed in the
male. These characters are an exception to the rule in
heredity, in that their appearance is normally restricted
to a single sex, although in many of the higher animals
they have been proved to be latent in the other sex, and
may appear after the essential organs of sex have been
removed or rendered functionless. The ' higher animals '
must in this respect be held to include the insects, inas-
much as a development of these latent characters occurs
in bees when the essential reproductive glands have been
destroyed by the parasitic Sty lops. Wallace suggests that
Epigamic Characters are in part to be explained as
Recognition Marks, in part as an indication of surplus
vital activity in the male.3

1 Occasional Papers of the Natural History Society of Wisconsin, vol. i,
1889, Milwaukee: Observations on Sexual Selection in Spiders of the
Family Attidae.

2 Trans. Ent. Soc, Lond., 1896, p. 233.

3 See especially Darwinism, London, 1889, pp. 268-300.

IN DEFENSIVE COLORATION 381

The mutual relationship of the above-mentioned classes
of colours is shown in tabular form on p. 226.

My kind friend, Mr. Arthur Sidgwick, suggested the
whole of the convenient Greek terminology which has
been employed in this brief statement of the bionomic
value of colour and marking in animals, especially
insects.

Note on the Resemblance of a Western Chinese species
of A thy ma and of Limenitis to the male of Hypolimnas
misippus. — This remarkable resemblance has been
described on pp. 217-18. Athyma punctata is the better
and probably the older mimic, and it is likely that
Limenitis albomaczdata has been brought into the com-
bination by a secondary mimetic approach. This conclu-
sion, however, requires a careful study of the related
species for its establishment.

Not until comparatively recently has it been known
that the interesting and puzzling relationship of Athyma
and Limenitis to Hypolimnas misippus only holds in the
male sex of all three species. The Leech Collection
contains no female of either Limenitis or Athyma, and
Monsieur C. Oberthiir, of Rennes, only obtained the
latter in 1 902, the former about ten years earlier.1 Among
hundreds of the male Limenitis he received only eight
females; of the Athyma no more than two. In pattern
the females are quite unlike their males, but resemble
each other as closely as do these latter. We have there-
fore an undoubted association between the Limenitis and
the Athyma extending to both sexes, while the two males
also possess the pattern of the male of H. misippus.

Although it seems certain that the primary model has
never been an inhabitant of the localities from which the
mimics have been received, it is possible, as Mr. R. Shel-
ford has pointed out to me, that these latter may extend,
or may formerly have extended, southward, so as to
overlap the northern boundary of the range of H. misippus.
Although more investigations into the distribution of the

1 Bull.Soc. Ent. Fr. 1902, pp. 16 1-2. See also Etudes d'En/., x\ iiie.
livraison, p. 15, pi. 6, fig. 82, Nov. 1893, Rennes.

382 THE PLACE OF MIMICRY, ETC.

species concerned would be very welcome for the solution
of this difficult problem, it must be remembered that two
great collections have come from this very district. The
Leech Collection of Palaearctic Butterflies in the British
Museum of Natural History gives the following localities :
— H. misippus : Syria, Sultanpore, Kulu, Kashmir, Loo-
choo ; Athyma punctata-. Chang-yang, Central China;
Limenitis albomaculata : Moupin, Western China.1 Mon-
sieur Charles Oberthur, with a much longer and larger
experience than any other naturalist, adds Western China
to the range of the Athyma, summing up the distribution
of both it and the Limenitis in the statement that they
inhabit the frontiers of Western China and Eastern
Thibet, especially Moupin, Siao-Lou, Tien-Tsuen, and
Tse-Kow.2 Monsieur Oberthur also kindly informs me
that he has never received H. misippus from the district
in which the two mimetic males occur.

It is to be hoped that specially directed observations
on the migratory birds of Western China may yield
further evidence bearing upon the provisional hypothesis
proposed on pp. 217-18. It has also been suggested on
p. 218 that the mimicry was favoured by an initial re-
semblance. This probably holds good for the iridescent
blue margins of the principal white markings as well as for
the other elements of the pattern. Thus it is not difficult
to understand how the Athyma may have arisen from
a species like Athyma (Pantoporia) cama from the Hima-
layas, Assam, and Upper Burma. The white markings
of this species are surrounded by a bluish margin, while
the pattern is not very widely different.

The interest and peculiar difficulty of this example of
mimicry have led me to add the above note. The fact
that the females of the Athyma and Limenitis differ from
the males had escaped me, and I owe the opportunity of
now rectifying the omission to my friend Mr. G. A. K.
Marshall.

1 Catalogue of the Leech Collection, by R. South, London, 1902,
pp. 56, 63.

2 Bull Soc. Ent.Fr. 1902, pp. 16 1-2.

APPENDIX

A Classification and Index of the Examples of
Mimicry quoted in the Text

The various sub-families,1 &c, of Butterflies are, allowing for omissions,
arranged in the order followed in most museums and private collections.
In other cases no attempt has been made to adopt sub-groups of equiva-
lent systematic value, and the succession is alphabetical.

Groups from which very few examples were selected (e. g. Hemiptera)
are not classified separately, but appear as models or mimics in the
classification of those which have been more freely quoted in the text.
The mimetic species alone, without models, are given under the mimetic
sections of the classification. Under the sections which are made up of
models the mimetic species are given with their models, except in the few
cases (e. g. ants) where the species or genera of these latter have not been
quoted. Models (with their mimics) are placed before mimics in groups
which primarily act as models, mimics before models in those which are
primarily mimetic.

I. LEPIDOPTERA
A. RHOPALOCERA (BUTTERFLIES)

i. Ithomiinae as models

For Danainae

Models Mimic

Methona con f us a ) Tj , ,

Thyridiap/idii ] ' 4 ' I/una' 2^~6

For Nymphalinae, 272, 273

Model Mimic

Melinaea, &c Protogom'us, 338, 350-2

For Heliconinae, 232, 235, 322, 327, 331, 331 n. 1, 343, 350
Models Mimics

Melinaea Heliconius, 235

Eueides nigrofulva, 332
Melinaea mneme . . . . • Heliconius numala, 331-3

Heliconius vetustus, 332

Tithorea Heliconius, 235

For Erycinidae, 272, 273

1 Three sub-sections of the Danaine sub-family are numbered 2, 3, and 4 in the
series of butterflies. All other numbers in this series imply sub-family rank.

384 CLASSIFICATION AND INDEX OF

For PlERINAE, 272, 273

Models Mimics

Methona psamathe . . . Dismorphia orise (Ecuador f.), 265,

266

Methona confusa ) n . . , . c cc

Thyridia psidii ) ' ' ^'""^"""^240,265,266

For Moths

Models Mimics

Methona con/usa)
Thyridia psidii J

Castniidae, 243, 264, 266
Hypsidae (A n thorny za, Hyelosia), 264,
266

2. Lycoraeini as mimics

Of Ithomiinae
/tuna, 264-6

3. Danaini as models

For other Danaini

Models Mimics

Amauris, Western sp. of . . Amauris albimaculata and echeria,

335, 337

„ „ „ . . Tirumala morgeni, 337

For Euploeini

Models Mimics

Da?iaini Trepsichrois mulciber (female),

334, 335

For Elymniinae, 353

Models Mimics

CparaSntica\ Elymnias lais (male), 353

Salatura hegesippus . . . . Elymnias undularis (female), 373

Salatura pkxippus (genuiia) . Elymnias undularis (female), 373

„ ,, „ E/ymnias caudata, 373

For Nymphalinae, 349

Models Mimics

Amauris niavius .... Hypolimnas anthedon, 338
Amauris niavius f. domini- Hypolimnas wahlbergi, 338
canus

Anosia plexippus (archippus) . Limenitis, 274, 364

Limnas chrysippus .... Euphaedra, 347 n. 3

Limnas chrysippus .... Hypolimnas misippus (female), 215,

216, 247, 347, 355, 361, 365

n. i, 372

For Acraeinae, 349

Models Mimics

Amauris Acraea esebria (female f. A), 354,

355

EXAMPLES OF MIMICRY 385

Limnas chrysippus .... Acraea esebria (female f. B), 354,

355

.... Acraea encedon, 355, 364, 365 n. 1
„ „ f. alcippus „ „ (f. alcippina), 364
For Lycaenidae, 349
For Papilioninae

Models Mimics

A . jr. j, , (P. dardanus (female f. cenea). 337,
Amauris albimaculata and 0 w-vw noon

trheria 1 338' 355, 374

ecnena [ P. echerioides ( female), 3 75

Amauris niavius . . . . P. dardanus (female f. hippocoori),

338, 374, 374 n. 1

Amauris niavius, sub-sp. P. darda?ius (female forms hippo-

dominicanus coon and trimeni), 338, 374,

374 n. 2

Caduga iytia P. ages for, 371

Danaini P. macareus, 288

„ P. xenocles, 288

Limnas chrysippus . . . P. dardanus (female f. frophonius),

374, 374 n. 1

For Moths

Models Mimics

Danaini Chalcosiinae, 275, 362

Limnas chrysippus .... Aletis helcita, 232, 347 n. 3
j, „ .... Eusemia falkensteinii, 232

„ .... Phaeagarista helcitoides, 232

Danaini as mimics

Of Euploeini, 334

4. Euploeini as models

For Danaini, 334

For Elymniinae, 335, 353

Models Mimics

Euploea Elymnias coltonis} 373, 373 n. 2

Sticioploea harrisi .... Elymnias malelas (leucocyma)

(male), 372

Trepsichrois mulciber (female) Elymnias malelas (leucocyma)

(female), 372

For Nymphalinae, 241

Models Mimics

Craslia core Hypolimnas bolina (female), 372

Danisepa diocletianus . . . Euripus halitherses (female f. A),

373

Penoa deione Euripus halitherses (female f. B),

373

For Papilioninae

Models Mimics

Crastia core Papilio castor (female), 372

„ „ P. dravidarum, 372

POULTON Q Q

386 CLASSIFICATION AND INDEX OF

For Moths (Chalcosiinae)

Models Mimics

[Amesia aliris, 376
Blue species of Euploea . . \ Amesia sanguiflua, 376

[Callamesia midama, 372, 376

Euploeini as mimics

Of Danaini

Trepsichrois mulciber (female), 334, 335

5. Elymniinae as mimics

Of Morphinae (Amathusiinae), 353

Of Danaini, 353

Elymnias caudala, 373

E. lais (male), 353

E. undularis (female), 373

Of Euploeini, 335, 353

E. cottonis? 373, 373 n. 2
E. maklas (leucocyma), 372

Of Acraeinae, 353

Of Pierinae, 353

6. Nymphalinae as mimics

Of Ithomiinae

Protogonius, 338, 350-2

Of Danaini, 349

Euphaedra, 347 n. 3
Hypolimnas anihedon, 338

Hypolimnas misippus (female), 215, 216, 247, 347
Hypolimnas wahlbergi, 338
Limenitis, 274, 364

Of Euploeini, 241

Euripus halitherses, 373
Hypolimnas bolina (female), 373

Of Acraeinae

Byblia golzius (wet season f.), 341
Precis antilope ( ,, ,, ), 340

Precis sesamus ( „ „ = nalaknsis), 339, 339 n. 1, 340

Of Heliconinae

Colaenis ielesiphc, 334 n. 2

Nymphalinae as models

For other Nymphalinae

Models Mimics

A thyma punctata (female). . Limenitis albomaculata (female),

381

Fritillary Araschnia levana f. levana, 342

EXAMPLES OF MIMICRY 387

iAthyma punctata (male), 217, 218,
Limemtis albomaculata (male).
217, 218, 361, 381, 382
Limenitis Araschnia levatia f.prorsa, 342

7. Heliconinae as models

For Nymphalinae

Model Mimic

Heliconius telesiphe .... Colaenis telesiphe, 334 n.

Heliconinae as mimics
Of Ithomiinae, 232, 235, 322, 327, 331, 331 n. 1, 343, 350
Eueides nigrofulva, 332
Heliconius, 235
Heliconius numata, 331-3
Heliconius veluslus, 332

8. Acraeinae as models

For Elymniinae, 353

For Nymphalinae

Models Mimics

/Precis ant Hope (wet season f. very

Acraea acara | rough mimic), 340

Acraea anemosa 1 Precis sesamus (wet season f. rough

I mimic), 339, 339 n. 1, 340
Acraea serena, type of. . . Byblia gotzius (wet season f.), 341

For Papilioninae

Models Mimics

Acraeas, large ..... Papilio anlimachus, 366
Planema poggei . .... P. dardanus (female i.planemoides),

338, 374, 374 n. 3, 375

Acraeinae as mimics

Of Danaini, 349

Acraea encedon (type f., alcippina f., &c), 355, 364, 365 n. 1

Acraea esebria, 354, 355
See also

Acraea satis (female). If the resemblance be mimetic, the Papilio
acts as the model, 52 n. 1

9. Pierinae as mimics
Of Ithomiinae, 272, 273

Dismorphia orise, 240, 265, 266

Pierinae as models

For other Pierinae

Models Mimics

Belenois Teracolus regina (wet season f.),

34i

C C 2

88 CLASSIFICATION AND INDEX OF

Mylothris agathina .... Belenois thysa (female in dry sea-
son only, male especially in dry
season), 341

Huphina, mimicry between 2 species of in dry season chiefly, 342
Teracolus, „ „ 4 „ „ „ „ 342

For Elymniinae, 353

For Moths, 275

Model Mimic

Teracolus etrida Abraxas etridoides, 231, 349

10. Papilioninae as mimics

Of Danaini

Papilio ages tor, 371

P. dardanus (except planemoides, all mimetic females of), 336-8,
355» 374, 374 n. 1, 374 n. 2

P. echerioides, 375
P. macareus, 288
P. xenocles, 288

Of EUPLOEINI

P. castor (female), 372
P. dravidarum, 372

Of Acraeinae

P. antimachus, 366

P. dardanus (female f. planemoides), 338, 374, 374 n. 3, 375

Of Moths

P. laglaizei, 371

Papilioninae as models
For other Papilioninae

Models Mimics

P. aristolochiae Papilio polyles (pammon), female

£>373

P. chaon P. castor (male), 372

P. hector P. polyles (pammon), female f., 373

For Acraeinae

P. morania and its allies (if mimicry exists between any of these
species and Acraea satis female, the latter is the mimic), 52 n. 1

For Moths, 231, 232

Model Mimic

P. protenor Epicopeia philenora, 371

. HETEROCERA (MOTHS)

Moths as mimics

Of Ithomiinae

Castniidae, 243, 264, 266

Hypsidae (Anlhomyza, Hyelosia), 264, 266

EXAMPLES OF MIMICRY

389

Of Danaini

Aleiis hekita, 232, 347 n. 3
Chalcosiinae, 275, 362
Eusemiafalkensteinii, 232
Phaeagarista helcitoides, 232

Of EuPLOEIKI

Amesia aliris, 376
Amesia sanguiflua, 376
Callamesia midama, 372, 376

Of PlERINAE

Abraxas etridoides, 231, 349
Chalcosiinae, 275

Of Papilioninae, 231, 232

Epicopeia philenora, 371

Of Lycid Beetles, 276
Lycomorpha, 231
Lycomorpha later cula, 231
Mimic a, 231
Pionia, 231

Of Humble-Bees (Bombus), Xylocopidae, and other Hairy Bees, 251
Cephonodes (Neman's) hylas, 365
Haemorrhagia fuciformis, 365
Haemorrhagia tityus (bombyli/ormis), 365

Of Wasps, Hornets, Fossors, &c, 251
Glaucopidae, 231
Sesia (Trochilium), 251, 366
Trochilium apiforme, 365
Trochilium crabroni/orme (bembeciforme), 366

Larvae of Moths as mimics

Of Ants, 368

Stauropusfagi, 253, 253 (Fig. 2), 254

Of Hemiptera

Stauropusfagi, 369

Of Cobra-like and other Snakes

Choerocampa elpenor, &c, 319, 326, 367, 367 n. 2, 368, 376

Moths as models

For Papilionine Butterfly
Model

Aurora alcidis . . .

Mimic

Papilio laglaizeiy 371

For other Moths
Model

Mimic

Chalcosiinae, 275

Agaristidae

39Q CLASSIFICATION AND INDEX OF

II. COLEOPTERA (BEETLES)
i. Longicornia as mimics of Hymenoptera

Of Ants

Euderces picipes, 255, 255 (Fig. 4), 256

Of Ichneumonids (in the wide sense)
Gle?iea pulchella, 363
Nitocris nigricornis, 363
Oberea, 257 n. 1, 280
Scytasis, 257 n. 1

Of Wasps, Hornets, Fossors, &c.
Callichrominae, 252
Clytus arietis, 238, 251, 252, 348, 363
Esthesinae, 252
Necydalinae, 252
Rhinotraginae, 252

Longicornia as mimics of other Beetles

Of Anthribidae, 369

Of Brenthidae, 369

Of Curculionidae (weevils), 369
Doliops curculionoides, 261
Doliops geometrica, 261
Doliops (Niphoninae), 250

Of Lycidae, 276

Of Phytophaga

Estigmenida variabilis, 261
Oxylymma gibbicollis, 237

Longicornia (Cly/inae) as models

For other Longicornia, 348, 349

2. Lycidae (Lycinae) as models
For Diptera, Hemiptera, and Hymenoptera, 276
For Moths, 276

Lygistopterus rubripennis . . Lycomorpha later rula, 231

For other Beetles
Mimics

Cantharidae, 276
Longicornia, 276
Melyridae, 276
Phytophaga, 276
Telephoridae, 276

Models

Mimics

Lycinae

EXAMPLES OF MIMICRY

3. Phytophaga as models

For Longicorn Beetles
Models

Diabrotica . . .

Mimics

Oxylymma gibbicollis, 237

Estigmena chinensis . . . Estigmenida variabilis, 261
For other Phytophagous Beetles

Neobrotica, 236, 237
Phytophaga as mimics
Of Lycid Beetles, 276

4. Rhynchophora

a. Anthribidae as models
For Longicorn Beetles, 369

b. Brenthidae as models
For Longicorn Beetles, 369

c. Curculionidae (weevils) as models
For Longicorn Beetles, 369

Mimics

Doliops curciilionoides, 261
Doliops geometrica, 261
Doliops (Niphoninae), 250

III. DIPTERA (FLIES, &c)
Diptera as mimics

Of Lycid Beetles, 276

Of Bee {Apis mellifica)
Er is talis, 243, 244

Of Humble-Bees (Bombus), Xylocopidae, and other Hairy Bees,
Hyper echia, 276
Volucella, 221, 378

Of Wasps, Fossors, &c.

Asilidae, 257 n. 1, 278, 378
Ceria, 280

Promachus top tents, 257 n. 1

IV. HYMENOPTERA

1. Ants as models

For Caterpillars, 253, 253 (Fig. 2), 254, 368

For Longicorn Beetle

Euderces picipes, 255, 255 (Fig. 4), 256

Diabrotica

Models

Cerotoma .

Mimics

Lema, 237
Dircema, 237
Lema, 237

392 CLASSIFICATION AND INDEX OF

For Hemiptera

Myrmoplasta mi'ra, 254, 255 (Fig. 3)
Nabis lativentris (larva), 257 n. 1

For Homoptera

Heteronotus Irinodosus, 258, 258 (Fig. 6), 259, 280, 369
Membracid (larva), 259, 259 (Fig. 7), 260, 280, 377

For Orthoptera

Myrmecophanafallax, 256, 257, 257 n. 1, 258 (Fig. 5), 280
Tellix, 260

For Spiders, 252, 368

Synageks picala, 253, 253 (Fig. 1 a)
Synemosyna formica, 253, 253 (Fig. 1 b)

2. Bee {Apis mellificd) as model
For Eristalis (Diptera), 243, 244

3. Humble-Bees (Bombus), Xylocopidae, and other Hairy Bees
as models

For Moths, 251

Mimics

Cephonodes (Hemaris) hylas, 251, 365
Haemorrhagia fuciformis, 365
Haemorrhagia tityas (bombyliformis), 365

For Diptera, 251

Models Mimics

Humble-bees Volucella, 221, 378

Xylocopidae Hyperechia, 276

4. Ichneumonids (in the broad sense) as models
For Longicorn Beetles

Mimics

Glenea pulc/iella, 363
Nitocris nigricornis, 363
Oberea, 257 n. 1, 280
Scy last's, 257 n. 1

5. Wasps, Hornets, Fossors, &c, as models
For Moths, 251

Mimics

Glaucopidae, 231

Sesia (Trochilium), 251, 366

Trochilium apiforme, 365

Trochilium crabroni/orme (be?nbeciforme\ 366

EXAMPLES OF MIMICRY 393

For Longicorn Beetles

Mimics

C attic hrominae, 252

Clytus arietisy 238, 251, 252, 348, 363

Esthesinae, 252

Necydalinae, 352

Rhino Iraginae, 352

For Diptera

Mimics

Asiiidae, 257 n. 1, 278, 378
Ceria, 280

Promachus iop/erus, 257 n. 1

For other Wasps, Fossors, &c.

Abispa . « x

^4 lets toT* I

„ , I Internal mimicry between genera

^mbex f of Australian Wasps, &c., 278

Jbumenes r *

Odynerus, &c '

For Hemiptera, 251

Wasps, &c, as mimics
Of Lycid Beetles, 276

VERTEBRATA

Vertebrates as models and mimics

Birds, 324, 367

Mam?nals, 367, 367 n. 1, 368

Snakes, 319, 324, 326, 367, 367 n. 2, 368, 376

AGGRESSIVE MIMICRY AND ALLURING COLOURS

Examples : —

Ceratias bispinosns, 378
Cer alias uranoscopus, 378
Hyas coarctata, 314
Hymenopus bicornis, 378 n. 3
Lophius piscatorius, 378
Macroclemmys temmiyickii, 378
Man/idae, 378

Phrynocephalus mystaceus, 378

ANALYTICAL INDEX

Names of quoted books, memoirs, journals, and publications of learned
societies are printed in thick (Clarendon) type, and the latter are indexed
under the name of the society.

The substance of the titles of the text is printed in small capitals, and is
followed by the word 'introduction', or 'essay', with its number. The sub-
stance of the sectional headings of the text is followed by the contraction
' introd.', or the number, omitting the word ' essay '.

Quoted titles, beginning with the same word as titles or headings of the text,
precede these latter, and are themselves arranged in the alphabetical order
of the second word. Titles, &c, of the text, beginning with the same word,
are not thus arranged, but are placed in the order of pagination before the
list of references under the same word.

References under one word are generally given in the order of pagination.
In certain cases, however, they are grouped more or less completely accord-
ing to subject.

Footnotes, containing references only, are rarely indexed.

Species are indexed under generic as well as specific names, but the
analysis of text is given under the specific name alone. The generic name is
distinguished by a capital initial letter.

Popular terms with a definite connotation such as 1 beetles ' butterflies ',
' caterpillars ', and ' weevils ', are fully indexed, in preference to their more
technical equivalents ' Coleoptera', ' Rhopalocera ', ' Lepidopterous larvae',
and ' Curculionidae ', respectively. When the connotation is less definite,
e. g. in 1 flies ' and ' bugs ', full references are given under the scientific
equivalents, ' Diptera' and ' Hemiptera' respectively.

'f.' indicates 'form'; 'sub-sp.' indicates 'sub-species'; 'sp.' indicates
'species.'

Abispa, species of, resemble other
Hymenoptera in Australia, 278.

Abnormal conditions unnecessary
for production of Acquired Charac-
ters, 143.

Abraxas etridoides, 231, 349.

Abundance of butterflies, various
causes of, 332.

Abyssinia, antinorii, an ancestral
sub-sp. of the Pap. dardanus group,
373-5 ; female of Abyssinian anti-
norii figured by Weismann in place
of male of another sub-sp. with
different distribution, 375.

acara, Acraea, a model of wet f. of
Precis sesamus, 339 n. 1 .

Accidental likeness, an inadequate
explanation of mimicry, xxiii, 257.

' Accidental ', Prichard's use of term
similar to Darwin's, 185.

Acerata, place in classification of,
33 ; relation of Trilobites to, 39.

acheloia (gbtzius), Hypanis
(Byblia), mating of similar seasonal
forms of, 87 ; dry f. of bred from wet,
341 ; wet f. of a mimic of A. serena
type, dry f. procryptic, 341.

Achievement, contrasted with
faculty in man, 170, 171.

achine, Teracolus, experiments on
seasonal forms of, 311 ; Miillerian
mimicry chiefly in dry f. of, 342.

Acquired Characters, the
Study of Insects and Question
of Transmission of, Essay V,
139-72.

'Acquired Characters' de-
fined^. 140-4 ; see also 73 n. 1.

Acquired Characters (Ex-
perience), bearing of Insect

396 ANALYTICAL INDEX

Mimicry, &c. upon supposed
Transmission of, V. 166-8.

Acquired Characters, Trans-
mission OF, IMPLIED BY THE

Theory of External Causes,
VIII. 267.

Acquired Characters, transmission
of, disputed, 96 ; a factor of La-
marck's theory, 98 ; meaning of
term, no; transmission of, dis-
cussed, 1 10-15 I Lamarckism and,
1 10-15 ; theoretical difficulty of trans-
mission of, in, 112; definition of
somatogenic, centripetal or, 122, 123 ;
pangenesis and inheritance of, 123-7 ;
continuity of the germ-plasm and,
131-2; relation to germ-plasm of,
shown in Diagram II, 132; 'identical'
twins and relation of inherent char-
acters to, 132-5 ; discussion of
transmission of, 136-8 ; direct and
indirect evidence of transmission
of, 136-8 ; mutilation, education,
disease, &c, 136 ; position of medical
faculty [in 1889] with regard to trans-
mission of, 136, 137; origin of indi-
vidual variation and, 1 37 ; instinct and,
1 1 6— 1 9, 138, 154-66; use-inheritance
and, 137, 138 ; confusion caused by
term, 140 ; erroneous assumption
that use of term is only recent, 141
n. 2 ; use of term by Erasmus
Darwin (1794), 140-1; by Lamarck
(1809), 141 ; by J. C. Prichard
(1826), 177, 179; Sir Ray Lankester
on use of, 141 n. 2 ; Prof. Weismann
on, 142 ; Prof. J. Mark Baldwin on,
73, 73 n. 1, 142, 142 n. 2 ; Prof. C.
Lloyd Morgan on, 142, 143 ; Francis
Galton on, 143 ; Sir Edward Fry on,
143, 144; E. B. Poulton on, 143,
144 ; interpenetrated by inherent
elements, 144 ; parental acquired
characters if hereditary would not be
acquired but inherent in offspring,
144 ; inconsistency of Lamarck's
Laws with regard to, 144-6; due to
gravity not inherited in pupae, 1 5 1-2 ;
insect colours and supposed trans-
mission of, 166-8 ; inherent (con-
genital or connate) characters clearly
distinguished from by J. C. Prichard,
I75> 179 J non-transmission of, clearly
apprehended and ably discussed by
Prichard (1826), 174-85; 'acquired
varieties are not transmitted,'
Prichard (1826), 177; 'acquired

characters are transient ; they termi-
nate with the individual, and have no
influence on the progeny,' Prichard
(1826), 179; non-transmission of
considered beneficial by Prichard,
182.

Acraea acara, 339 n. 1 ; — anemosa,

339 n. I ', — encedon, 355, 364, 365 n. 1 ;
— esebria, 354; — satis, 52 n. I ; —
serena, 341 ; — violae, 269.

Acraeinae (see also classification of
examples of mimicry, 384-8), slow-fly-
ing and gregarious, 52 n. 1 ; need for
breeding epigonic series of, 90 ; as
models paralleled by Diabrotica,
236 ; always tend to be mimicked,
233 ; an Indian species of proved to
be unpalateable, 269 ; uniformity
throughout many species of, 277 ;
unpleasant scent in African, 316;
absence of ' eye-spots ' in, 326 ; pre-
ferring station different from that of
model, L. chrysippus, 349.

Acraeoid Heliconidae of Bates =
Heliconinae, 327.

Acridiidae of Commentry Carboni-
ferous (Palaeacridiidae), 36, 37; mi-
micry of leaf-carrying ant by, 260 ;
value of bright hind wings of, 303, 304,
325 ; colour adjustment of, 307 ; ob-
servations on the courtship of, 380.

A crony eta aim, 319; — cuspis, 87
n. 1; — fisi, 87 n. 1; — strigosa, 87
n. 1 ; — tridens, 87 n. 1.

actia, Precis, seasonal forms of,
208; dry f. bred from wet (1903),

340 n. 2 ; under side more conspicuous
in wet than dry seasonal form of, 340 ;
S. African habitat of, 340.

Aculeata Hymenoptera, see
Hymenoptera, and all the groups
there referred to except Ichneu-
monids, and saw-flies.

A da?nsia palliata, 357.

Adaptive or Syntechnic Resem-
blance, 312, 312 n. 2, 359, 360 n. 1.

Adaptation of certain Breeds
to particular local circumstances,
J. C. Prichard, 188-90.

Adaptation, Study of, Stimu-
lates and does not Bar Inquiry,
Introd. xliv-xlvii.

Adaptation for Cross-Fer-
tilization A CAUSE OF ASYNGAMY,
II. 90, 91 ; see also 65.

Adaptation for Cross-Fer-
tilization the cause and not

ANALYTICAL INDEX

397

THE CONSEQUENCE OF INJURIOUS
EFFECTS OF SELF-FERTILIZATION,
II. 91-94.

Adaptation, Darwin's case against
mutation that it cannot explain, xix ;
rigid self-criticism required in the
study of, xlvii; effect of conditions
and, 75 ; for Cross-Fertilization,
Darwin's explanation of, 92 ;
specialized mechanisms for, 153;
essential meaning of, 153, 154; in
Lepidoptera as evidence for Natural
Selection, 203-18 ; in caterpillars,
154; to one environment, but con-
tinual contact of organism with an-
other, 153, 154 ; J. C. Prichard on
locality and, 188; on the 'double
relation' of affinity and, 188, 189;
on the laws of variation resulting in,
190; species and varieties compared
by Prichard as regards, 189, 190; on
locality and climate of human races
and, 190, 191.

Aden, Limnas chrysippus at, 70
n. 1.

Adjustable Aggressive Resem-
blance, 313.

Adjustable Neutralization
of Shadow, X. 300.

Adjustable Protective Re-
semblance, X. 304-7 ; Rapid,
304, 305 ; Slow, 304-7.

Adjustable Protective Resem-
blance, G. J. Romanes on, 152; R.
Meldola on, 153; Natural Selection
and, 152, 153 ; Lamarckism and, 152-
4 ; non-transmission of acquired
characters and, 153 ; rapid in fish,
Reptilia, &c, 305 ; slow in cater-
pillars, 305-7 ; chrysalises, 149,
150, 150 n. 2, 305, 306; cocoons,
149 ; weevils, 307 ; grasshoppers,
307 ; spiders, 307.

Advantages of admission
that Diagnosis is provisional,
II. 76, 77.

Advantage Conferred by
Perfected Mullerian Resem-
blance, X. 328, 329.

Advantage Conferred during
Growth of Mullerian Resem-
blance, X. 329-31.

Advantage conferred by mimicry,
evidence of, 288 ; conferred by
concealment, direct evidence of, 288,
289.

Adventitious or Allocryptic

Protective (and Aggressive)
Resemblance, X. 313, 314.

Adventitious Warning or
Allaposematic Colours, X. 356,
357 ; see also 315.

Adventitious Object Associ-
ated with Model, Mimicked :
Pseudallaposematic Resem-
blance, X. 377 ; see also 359.

Affinity, Mimicry, &c, inde-
pendent of, VIII. Two sections,
229-34 and 235-7 ; see also 345.

Affinity and adaptation, J. C.
Prichard on the 1 double relation ' of,
188, 189.

Affinity and analogy, W. S.
Macleay on, 220 ; Rev. W. Kirby on,
220 ; Professor J. O. Westwood on,
221.

Africa and Adjacent Islands,
the Papilio dardanus (merope)
Group of, X. 373-6 ; see also
dardanus.

Africa, xxvi, 70, 71, 100, 187, 190,

215, 222, 223, 276, 277, 304, 311,
316, 320, 336, 339 n. 1, 340, 341,
342, 344, 345, 345 n. 5, 353, 364, 365,
367 n.2, 368, 370, 373, 374, 375 ; see also
Ethiopian, xxv, xxvi, 336, 365 ; Grand
Comoro, 373 ; Madagascar, 57 n. 1,

216, 245, 373; Sahara, 321, 364;
Sudan, 256, 258; Victoria Nyanza,
xxxv, 69, 338, 374, 374 n. 3.

Africa, East, 254, 255, 282 n. 1,
320, 335-8, 374, 375; see also
Abyssinia, 373-5 ; Delagoa Bay,
282 n. 1 ; Kikuyu, 374 ; Rosako,
Usaramo, 255 ; Somali, 321.

Africa, South, 53, 87, 276, 281, 284,
300, 301, 303, 311, 313, 320, 326, 335,
34o, 363, 369, 374, 375 ; see also
Cape, 87, 88; Durban, 52 n. 1, 71
n. 1,72,283; Gazaland, 284; Malvern,
52 n. 1, 283 ; Melsetter, 284 ; Natal,
52 n. 1, 71 n. 1, 87, 249, 283;
Pretoria, 71 n. 1 ; Rhodesia, 71 n. 1,
257 n. 1 ; Salisbury, 71 n. 1, 257
n. 1, 283, 284.

Africa, West, 248, 321, 335, 337,
338, 364, 366, 374 ; see also Congo,
321 n. 1 ; Entebbe, 374 n. 3 ; Guinea,
187; Luebo, 321 n. 1 ; Niger, 321,
364 ; Toro, 338 ; Uganda, 338.

After-lives of twins, 134, 135.

Agaristed moth mimicked by
Chalcosid moth in Borneo, 275.

agathina, Mylothris as model of

398 ANALYTICAL INDEX

Belenois, 341 ; no seasonal change in,
341, 342.

Age of stratified rocks, 16, 17.

Age of the Earth, A Natura-
list on The, Essay I. 1-45.

Age of the Earth, argument from
tidal retardation and length of day,
7-9; from cooling of earth, 9-13;
from life of sun, 13-15 ; radium and,
15 n. 2 ; geological argument on, 16,

agestor, Papiho, in some respects
more conspicuous than model,
Caduga tytta, 371.

Aggressive Mimicry including
Alluring Colours : Pseudepise-
matic Resemblance, X. 377, 378 :
see also Mimicry Aggressive, &c.

Aggressive or Anticryptic
Resemblance, X. 312, 313.

Aggressive Resemblance Ad-
ventitious or Allocryptic, X.
313, 314.

Aggressive or Anticryptic Resem-
blance, place of in bionomic uses of
colour, 226 ; defined, 297 ; general
and special, 312; elimination of
shadow in, 313 ; seasonal change in,
313 ; adjustable resemblance in, 313 ;
to upright stems and their shadows,
313 ; to supposed images of sun, 313.

ag/aia, Argynnis, probable effect
of gravity on pupal shape of, 152.

Akya Chaung (branch of Haun-
draw R.), Burma, bee-eaters capturing
butterflies at, 287, 288.

Alastor, species of, resemble other
Hymenoptera in Australia, 278.

albimaculata and echeria,Amauris,
western Amauris mimicked by, 335,
337 ; dominant models in E. Africa,
336 ; mimicked by the cenca female
f. of three sub-sp. of Pap. dardanusi
337, 338, 355, 374 I by female of Pap.
cchcrioides, 375.

Albinos, sudden origin of in man,
185.

albomaculata, Limemtis of W.
China mimetic of male H. misippus,
217 ; male only mimics misippus,
381 ; male probably a secondary
mimic of male A. punctata, 381 ;
female resembles female of this
species, 381; distribution of, 382.

alcippbia f. of Acraea encedon,
relation to akippus f. of L. chrys-
ippus of, 364.

alcippus f. of Limnas chrysippus,
increased conspicuousness suggested
as interpretation of, 321 ; distribution
of, 321, 321 n. 1 ; predominance of on
W. coast of Africa recent, 364.

Alcyonaria, resemblance between
Palaeozoic and living forms of, 28.

Aletis-Euphaedra, Mullerian com-
bination, 232; in certain characters
more conspicuous than primary
model, L. chrysippus, 347 n. 3.

Aletis helcita, 232.

Algae, special resemblance to
floating, 298 ; as covering of Stenor-
rhynchus, 313; allopro- and allanti-
cryptic use of by Pfyas, 314.

A Liberal Education, T. H.
Huxley, 198.

a/iris, Ames/a, with allied Chal-
cosiine moths, rough Mullerian
mimics of blue Oriental Euploeas,
376.

Allanticryptic colours of Cerato-
phrys, 313 ; of Myrmeleon larva,
313 ; of Hyas, 314.

Allaposematic or Adventi-
tious Warning Colours, X. 356,
357; see also 315.

Allelomorphs or germinal precur-
sors of Mendelian characters, infer-
ences as to the, xxxi-xxxiii.

Allepigamic collections of bower-
birds, 379.

Allier, fossil insects of Department
of, 35-8.

All-Importance of Instinct
for Protective Resemblance, X.
301, 302.

All - Importance of Instinc-
tive Attitudes and Movements
in the Display of Warning
Colours, X. 323, 324.

all- 1 mportance of instinctive
Attitudes and Movements in
the Attainment of Mimetic
Resemblance, X. 363.

Allocryptic or Adventitious
Protective (and Aggressive)
Resemblance, X. 313, 314.

Allocryptic resemblance defined,
297 ; examples of, 313, 314.

Alloprocryptic colouring of Stenor-
rhynchus, 313 ; of Hyas, 314.

Alluring Colours and Ag-
gressive Mimicry : Pseudepi-
sematic Resemblance, X. 377,
378 ; see Mimicry Aggressive, &c.

ANALYTICAL INDEX

399

ahnana, Precis, under side ocellated
in wet, procryptic in dry season,
340 ; wet ocellated f. of (asterie) per-
manent in damp Siamese forests,
341.

aim, Acronycta, transition from
cryptic to aposematic defence in larva
of, 319.

Alpine Hare, seasonal changes of,
3i°, 313.

Alternation from cryptic to apo-
sematic defence in dry and wet
seasons respectively, 208, 209, 320,
339, 34o.

A?naihusii?iae, see Morphinae.

Amauris, probable importance of
Mendelian principle in the splitting
of species of, xxxv ; see also 68, 69 ;
black and white species of and Natal
mimics in Hope Department, 249 ;
Eastern sp. of influenced by Western
at overlap, 335, 337 ; Eastern sp. of
and mimics replaced at V. Nyanza by
Western sp. and mimics, 336-8 ;
Western sp. of mimicked by T.
morgetii, 337 ; mimicked by one f. of
female, A. esebria, 354, 355 ; advan-
tage of resemblance to chrysippus as
well as to, 355.

Amauris albimaculata, 335-7,
374, 375 I — echeria, 249, 335-7, 355,
.374, 375 5 —niavius, 68, 69, 336,
338, 374, 375 5 —niavius, sub-sp.
dominicamis, 68, 69, 336, 338, 374,
374 n. 2, 375 ; — ochlea, 336.

Amazon, segregation and preferen-
tial mating in butterflies of the, 85,
86.

Amazon, Upper, character of chief
mimetic butterflies at Ega on the,

273,351.

Amblyornis inornata, 379.

America, 187, 315, 323, 324.

America, Central, 232, 249, 258,
350 ; see also Antilles, 247 ; Hon-
duras, 235 ; Mexico, 274 ; Neo-tropi-
cal, xxvi ; West Indies, 178, 187, 216.

America, North, 253, 255, 274,
333 ; see also Arizona, 231 ; Canada,
270, 274; Florida, 216; Hartland,
255, 256; Pine Lake, 255, 256;
Toronto, 263 ; United States, 97,
100, 178, 274, 378; Wisconsin, 118
n. I, 252, 253, 256, 380.

America, South, or Tropical, 87, 178,
187, 222, 223, 231, 233, 235, 237, 239,
243, 247, 249, 252, 258, 259, 264, 273,

277, 280, 302,311, 317, 322, 323, 327,
333, 334 n. 2, 336, 346, 350, 367, 370,
377 ; see also Amazon, 85, 273, 351 ;
Andes, 90; Bolivia, 351; Brazil,
53 n. 1, 216, 273, 313, 351, 356, 376 ;
British Guiana, 259, 259 (Fig. 7), 272,
273, 322, 332, 350 ; Demerara, 216 ;
Ecuador, 265, 351 ; Ega, 273, 351 ;
Guianas, 350 ; Neo-tropical, xxvi ;
Par£, 257 n. 1 ; Patagonia, 187, 225 ;
Peru, 351; Potaro, 332; Surinam,
235, 272; Trinidad, 235, 350, 351;
Venezuela, 273, 350.

American Addresses, T. H.
Huxley, 56.

American Association for the
Advancement of Science, Pro-
ceedings of, 215, 217, 247 n. 1, 364.

American Journal of Science,
35-

American Naturalist, 142 n. 2.

Amesia aliris, 376 ; — sanguiflua,
376.

Amixia of Weismann, 60.

Ammophila, stinging ganglia of
prey, 161.

Ammofthila urnaria, 163.

Amphibia, 26 ; rapid colour adjust-
ment in, 305.

Ainphidasys betiriaria, 143, 309.

Amphimixis of Weismann, 60 n. 3.

Amphioxus, 26, 30.

Anaea, resemblance to dead leaf of,
205.

Analogical or Syntechnic Resem-
blance, 312, 359.

Analogy, W.S. Macleay on affinity
and, 220 ; Rev. W. Kirby and Prof.
J. O. Westwood on affinity and, 220,
221.

Analysis of Mimetic Resem-
blance, VIII. 240-2.

Anatomy and Physiology,
Journal of, 128 n. 1, 136 n. 1.

Ancestor, non-Mimetic of
Mimetic Species preserved on
Islands, &c, X. 373-6.

Ancestor, Miillerian mimicry best
explains origin of divergent mimicry
in descendants of a common mimetic,
352, 354-

Ancestral forms of higher branches
of animals, 26, 27.

Ancestral pattern, effect on origin
of mimicry of, 218, 382 ; persistence
in non-mimetic males of mimetic
females of, 244-7, 279 ; occasional

4oo ANALYTICAL INDEX

varieties of a mimetic female may
show traces of, 279.

Ancon or otter sheep, sudden
origin of, 185.

Andalusian fowl, the blue a hetero-
zygote, xxxvi ; Bateson on natural
selection and the, xxxvi ; suggests
variations useless for evolution, xxxix,
xl.

Andaman Islands, Elymnias
cottonis in, 373, 373 n. 2.

Andes, Peruvian, Harvard branch
observatory in, 90.

Andrewes, Leslie, on mimicry of
Glenea ptclchella, 363.

anemosa, Acraea, a model of Precis
natalensis, 339 n. I.

An Essay on Fertilization, Prof.
M. Hartog, 60 n. 3.

Angiosperms, appearance in late
Mesozoic of, 45 ; relation to Cycado-
phyta of, 45.

Angler or Fishing-Frog, bright
lure of, 378.

Angora breeds, J. C. Prichard on,
187.

Animal Behaviour, Prof. C.
Lloyd Morgan, 154, 281 n. 1.

Animal classification, 25.

Animal Coloration, F. E.
Beddard, 244, 247.

Animals limited by tse-tse fly, 100.

Annales de la Soci6te Entomo-
logique de France, 211, 326.

Annals and Magazine of
Natural History, 49, 53 n. 1, 71
n. 1, 208, 223, 234, 278, 323, 340,
356.

Annandale, N., on hour swhen
insect enemies are inactive, 303 ;
on flower-like species of Mantids, —
Hymenoptts, &c, 378 n. 3.

Anosia plexippus {archippus), 274,

364-

Ant, see Ants.

Antagonism Promoted be-
tween Studies all needed for
attacking problem of evolu-
TION, Introd. xli-xliv.

Antennae, presence or absence of,
important in classification, 33 ; ab-
sence in Crustacea of true, 33 n. 1 ;
possessed by trilobites, 17,39; simu-
lated by legs of mimetic spiders, 253 ;
modification in weevils and mimetic
Longicorn, 261 ; simulated by 'tails'
of Lycaenids, 282, 325, 325 n. 1 ;

mimicked by posterior processes of
S.fagi larva, 369.

anthedon, Hypolimnas (Euralia)
replaced by eastern H. ivahlbergi
near V. Nyanza in accordance with
corresponding geographical replace-
ment of Danaine models, 338.

Anthomyza, sp. of, as mimics of
Ithomiinae, 264; method of obtain-
ing transparency in moths of the
genus, 266.

Anthribidae, see classification of
examples of mimicry, 390-1.

Anthropological Institute,
Journal of, 134.

Anthropology, discoveries of J. C.
Prichard in, 173.

Anticipation of Modern Views
on Evolution, Essay VI, 173-92.

Anticryptic or Aggressive
Resemblance, X. 312, 313.

Anticryptic Resemblance, see
Aggressive, &c.

antigone, Teracolus, Miillerian
mimicry chiefly in dry f. of, 342.

Antilles, H. misippus extends into,
247.

antilope, Precis, seasonal forms of,
208 ; dry f. bred from wet (1902),
340 n. 3 ; reason for considering wet
f. a Miillerian mimic, 340; under
side conspicuous and roughly mimetic
in wet, procryptic in dry season, 340 ;
S. African habitat of, 340.

antimachus, Papilio (Drurya), a
mimic of far smaller Acraeas, 366.

antinorii, Papilio, an Abyssinian
non-mimetic (withexceptions,374n. 1)
member of the dardanus group, 374-
5 ; see also dardanus.

Ant-lion larva, allanticryptic re-
semblance of, 313.

Ants,see also classification of exam-
ples of mimicry, 389-92 ; Lamarckism
and instincts of worker, 165 ; mimicked
in various ways, 252-61 ; peculiarities
of, reproduced by mimics, 259; ad-
vantage of resemblance to, 281 ; many
examples of mimicry of, Batesian,
376 ; resemblance of covering shield
of Membracidae to, 258 (Fig. 6), 258-
60, 280, 369 ; mimicry by immature
Membracid (Homoptera) of leaf as
well as of, 259 (Fig. 7), 260, 280,
377 ; carrying off wings of butterflies,
288.

Apatetic colours, position of, in

ANALYTICAL INDEX 401

a scheme of the bionomic uses of
colour, 226.

apiforme, Trochilium (Scsia),
nature of lost scales of, 365.

Apes, brain in man and, 108.

Aposematic and Episematic
Characters, X. 315-58. For
divisions, sections, and sub-sections,
see 294-6.

Aposematic or Warning Char-
acters, X. 315-26. For sections
see 294-5.

Aposematic colours, see Warning
Colours.

Aposeme,' tussocks ' a form of, 326.

Appendiculata, 25, 27, 28 ; of early
Palaeozoic, 30 ; classification of, 33 ;
evolution of, 33-41 ; imperfect record
in the stratified rocks of evolution of,
41, 42.

Appropriate Surfaces for
resting on, choice of, x. 301.

Aptera, great age of, 52.

Aquinas, St. Thomas, on St. Augus-
tine's views on creation, 55.

Arachnida: see also spiders and
scorpions; place in classification
of, 33 ; highly specialized in early
Palaeozoic, 39-41.

Araschnia lev ana, and its later f.
prorsa, 342.

Arch. f. Entwick.-Mech. d.
Organism., 130 n. t.

Archaediscus, occurrence in Car-
boniferous of, 27.

Archaeopteryx, ancestral features
of, 32.

Archdall Reid, xl n. 2.

archesta, Precis, transition from
cryptic dry to conspicuous wet phase
of, 208, 320, 320 n. 1 ; under side
probably aposematic in wet, pro-
cryptic in dry season, 340 ; S. African
habitat of, 340.

Archipolypoda of Palaeozoic, 34.

archippus, Anosia, see plexippris,
274, 364.

Arctic Fox, aggressive seasonal
change of, 313.

Arctiidae) mimicking Lycinae, 231.

arcturus or polyctor, Papilio,
attacked by King-crow, 285.

Are Acquired Characters Here-
ditary? discussion at Brit. Assoc.
(1887), 155 n. 1.

argentus, Papilio, W. C. Hewitson
on, 57 n. 1.

POULTON £)

Argyll, Duke of, on Natural Selec-
tion, 101-2.

Argynnidae, pupae of, affected by
gravity, 152.

Argynnis aglaia, 152.

arietis, Clytus, mimicry of wasp
by, 238, 251, 252, 348, 363.

aristolochiae, Papilio, shown to be
distasteful, 269, 372, 375 ; mimicked
by female f. of P. polytes, 373.

Aristotle and organic evolution, 56.

Arizona, examples of mimicry from,
231.

Arnold, Matthew, on discovery and
youth, 199.

'Art papers', so-called, 170.

Artamus fuscns, 286.

artaxia, Precis, \m&<zx side ocellated
in wet, procryptic in dry season, 340 ;
S. African habitat of, 340.

Artemia transformed into Bra?ich-

*f**t 73, 74-

Artemia salina, 73.

Arthropoda, classification of, 33;
of the Palaeozoic, 34-41.

Artificial Selection, Diag-
nosis TRAVERSED BY RESULTS OF,
II. 76.

Artificial selection, probable im-
mense importance of Mendelism in,
xxxv ; compared with natural selec-
tion by Darwin : erroneous state-
ment of Darwin's opinion on, xl,
xl n. 2, n. 3, xli ; results of, 76 ; does
not produce sterility, 77-80 ; physio-
logical species and, 79, 80; domestic
breeds and, 83 n. 2 ; J. C. Prichard
on, 186 ; T. H. Huxley on, 201.

Asa Gray, letters from C. Darwin
to, xxvi, 66, 67, 68 ; copy of letter
from Darwin to, included in Darwin's
section of the joint essay (1858), 194
n. 1.

Ascaris, early appearance of germ-
antecedent in, 131.

Ascaris megalocephala, 131.

Ascidians, 30 ; sea-anemones,
sponges and, carried by hermit-
crabs, sea-anemones by crabs, 356,
357.

Ascidiophilus caphyraeformts, 357.

Ashy swallow-shrike capturing
Euploea, 286.

Asiatic lizard with flower-like lures,
378.

Asiatic Society of Bengal,
Journal of, 269, 279 n. 1.

d

ANALYTICAL INDEX

Asilidae, mimicry of Hymenoptera
by, 257 n. I, 276, 278, 378 ; mimicry
of Hymenoptera by, probably not
aggressive, 378 ; attacking specially
defended insects, 318.

Aspects, Various, of Mimicry,
Illustrated by Oriental and
other lepidoptera, x. 370-6.

Ass and horse, sterile progeny of,
78.

assimi/is, Buchanga, capturing
probably Catopsilia florella, 283 ;
chasing a Belenois ; capturing and
rejecting distasteful moths, 284.

1 Association ' or ' Combination ',
use of, contrasted with 'group', 293.

aster ie, Precis, the wet f. of P. al-
mana, 340, 341.

Asteroidea, 30.

astyanax, Lime?iitis (Basilarchia),
extends into Mexico, 274.

ASYMPATRY AS CAUSE OF ASYN-
GAMY, II. 84, 85.

Asympatry, definition of, 62.

Asyngamy, definition of, 60 ; the
true interspecific barrier, 65, 84 ;
sections dealing with various causes
of, 84-91 ; caused without selection,
89.

Atavism, relation to pangenesis of,
125.

Atella phalantha, 283.

ater, Dicrurus, attacking Papilio
and capturing Vanessa, 285.

athamas, Charaxes, eaten by bee-
eater, 288.

Athyma and Limenitis, Resem-
blance of Males to Male Hypo-
limnas misippus, X. 381, 382: see
also 217, 218.

Athyma, conspicuous and probably
distasteful, 218.

Athyma {Pantoporia) cama, 382 ;
punctata, 217, 381, 382.

Atlantic, swarm of H. misippus in
mid-, 216 n. 2.

Atmosphere, energy of sun may
have been conserved by, 14.

Atta (Oecodoma) cephalotes, 259,
259 (Fig. 7), 260, 280, 377.

Attidae, mimicking ants, 252, 253 ;
courtship of spiders belonging to,
380.

Attitude, Reduction of
Shadow by, X. 300, 301.

Attitudes and Movements,
Importance of Instinctive, for

Protective Resemblance, X. 301,
302: see also 289, 298, 300, 301,
318.

Attitudes and Movements,
Importance of Instinctive, in
Display of Warning Colours,
X. 323, 324 : see also 319, 320.

Attitudes, Intimidating, X.
324, 325.

Attitudes and Movements,
Importance of Instinctive, for
Mimicry, X. 363 : see also 241, 319,
34i.

August Thorn Moth, 149, 150.
Augustine, St., on the method of
creation, 55.
Auk, 299.

Auri villus, Prof. Chr., on Amauris
niavius and its form do??iinicanus, 68.

aurora, Alcidis, mimicked by Pap.
laglaizei, 371.

Australia, form of P. cardui Kof,
85 n. 1 ; uniformity among wasps
and Fossores of, 278.

Australian and Oriental Regions,
Euploeini nearly restricted to, 333,
353 ; mimicry in the Elymniinae of,
353-

Australian Region, see Australia,
Austro-Malayan, New Guinea, 371,
379; Polynesia, 333; Ternate, 194.

Austria, hereditary transmission
of inherent peculiarity of lip in Royal
House of, 180.

Austro - Malayan sub - Region,
mimicry in the Ely?nniinae of, 353.

Autobiography, Charles Darwin,
xxix. 92.

Avebury, Lord, on instincts of
Fossorial Hymenoptera, 160, 161.

B

Bacon, Francis, on transmutation
of species, 54, 55; on 'vivification
from putrefaction 54, 55 ; on re-
straining power of seed, 55.

Bairdia, persistence through geo-
logical time of, 39.

Balanoglossus, 26, 30 ; conclusions
of Bateson from study of, xliii.

Baldwin, Professor J. Mark, 312
n. 2 ; on modification and variation,
73, 73 n. I, 142.

Balfour, F. M., on Peripatus, 33.

Ballad of the Ichthyosaurus,
May Kendall, 104.

ANALYTICAL INDEX

403

Bankasoon, S. Tenasserim, nest of
Microhierax at, 290, 291.

Barbet, Microhierax nesting in
hole made by, 291 n. 1.

Bark, cocoons formed of, 158, 159 ;
protective resemblance of moths to,
298, 301 : see also 322 ; colour adjust-
ment of larvae to, 306, 307 ; syn-
cryptic resemblance to, 312.

Barker, C. N., on mimicry of
Nitocris nigricornis, 363.

Barnacles (Cirrhipedes), C. Darwin
on systematic work on, xv, 59, 60, 67.

Basilarchia, see Limenitis.

Bates, H. W., on the wings of
butterflies as registers of evolution, 5 1 ,
51 n. 1; on preferential mating of
butterflies, 85-7 ; letters from Darwin
to, 86 ; theory of mimicry of and
transmission of acquired characters,
167 ; theory of mimicry of, 2 1 1-1 5 : see
also 85, 86 ; publication of theory of
mimicry by (1862), 220-2 ; inter-
pretation of mimicry between models
by, 222, 327, 327 n. 1 ; rejection of
Miillerian mimicry by, 223 ; stimulus
to investigation due to theory of, 224 ;
place in scheme of bionomic uses of
colour of theory of (Pseudaposematic
colours), 226 ; use of term Helico-
nidaeby, 213, 234, 235 n. 1 ; theory of,
consistent with facts, 268 ; objections
to theory of, 269, 270 ; probably mis-
led by mimicry of Ithomiinae by
Heliconinae, 327 ; on different flight
of Ithomiines and Heliconines, 331
n. 1 ; theory of, one of the first
great results of Natural Selection,
361.

Batesian (or Protective)
Mimicry, 361-76. For sections and
sub-sections included under, see 296,
297 : see also 348-56.

Batesian Mimicry, see Mimicry,
Protective, &c.

Bateson, W., exaggerated estimate
of importance for evolution of On
Variation by, xiii, xiv, xl ; on Con-
tinuity and Discontinuity, xiv ; on the
dominance of Discontinuity, xv, xv
n. 1 ; on the sole chance of progress
in evolution, xvi n. 1 ; on the imminent
completion of systematic work, xvi
n. 1 ; on variation as evolution, xvi ; on
Natural Selection necessary, but its
investigation unnecessary, xviii, xviii
n. 1, xix ; on phenomena of hybridiza-

tion perhaps exhibited by Oenothera
la?narckiana, xx ; on Natural Selection
not creative, xxii, xxii n. 3 ; Darwin's
work on the primrose compared with
that of Gregory and, xxvii-xxxiv ; on
the thrum-eyed primrose, xxix n. 4 ;
statement of the problem of evolution
by, xxxiii, xxxiv ; on Panmixia, xxxvii
n. 2 ; exaggerated estimate of effect
of Mendelism by, xxxvii n. 2 ; erro-
neous statement of Darwin's teaching
by, xl ; unreasonable disparagement
of Embryology by, xlii, xliii ; on pet
saltum evolution, 4 ; on absence
of struggle during pupal stage ot
V. urticae, 306.

Bauhin, Kaspar, and fixity of
species, 56.

Bayzand, P. J., drawings of larvae
by, 254.

Beagle, Darwin's experiences on
the voyage of, 193.

Beddard, F. E., on Eristalis and
hive-bee, 243, 244 ; on accidental
resemblances between insects, 247.

Bees (see also classification of
examples of mimicry, 389, 391-2 : see
also humble-bees, 221, 251, 365, 378),
attacked by bee-eaters, 287 ; larvae
of mimic contrasted as regards food,
&c, with larvae of, 244 ; effects of
castration by Stylops of, 380.

Bee-eaters capturing Pierinae in
Ceylon, 285, 286 ; systematically
capturing butterflies, 287, 288.

Bee Orchis, self-fertilization of
the, 64, 92.

Beetles (see also Anthribidae,
Brenthidae, Longicorn, Lycidae,
Phytophagous, weevils : see also
classification of examples of mimicry,
389-93), often wingless in Madeira,
18; late evolution of, 38; protective
instincts of, 155 ; 'sham death' of,
323 ; colour adjustment probable in,
307 ; mimicked by distasteful moths,
&c, 231, 276; predominant mimicry
in S. American, 248 ; diurnal groups
of, mimicked by diurnal members of
nocturnal groups, 250 ; mimetic like-
ness attained in various ways by, 251,
252, 255, 256, 257 n. 1, 261, 262;
mimicry in, independent of affinity,
237; mimicry in Lepidoptera parallel
with that in, 236, 237 ; hardness as
a special protection in, 369 ; head
of shrew-like animal resembled by,

d 2

4o4 ANALYTICAL INDEX

368 ; jaw-like legs of S. African, 368 ;
majority of resemblances Mullerian
and not Batesian, 348.

Behrens, T. T., capture of herm-
aphrodite planemoides, female f. of
Pap. dardanns, by, 374 n. 3.

Belenois, attack of drongo on in-
jured specimen of, 284 ; the model of
wet f. of Teracolus regina, 341.

Belenois severina, 311 ; — thysa,
341.

Bell, T. R., on tilt of Melanitis,
300 n. 5 ; on succulent larval food
as the cause of wet season forms of
butterflies, 341.

bellatrix, Callioratis, a distasteful
moth seized and dropped by young
drongo, 284.

Belt, T., on epigamic display of
white patch by male Dismorphina,
240.

bembeciformis, see crabroniformis,
366.

Betnbex, species of, resemble other
Hymenoptera in Australia, 278.

Berlin, Fifth Internat. Zool. Congr.
at (1901), 271.

bernhardus, Pagurus, carrying
Sagartia parasitica, 356, 357.

betularia, Amphidasis, colour of
larva as example of acquired char-
acter, 143; darkening of in Lanca-
shire and Yorkshire district, 309.

Bibliotheca Zoologica, Stuttgart,
375.

bicornis, Hymenopus, a flower-
like Mantis : mimicry of bug by larva
of, 378 n. 3.

bidentata, Odontopera, colour ad-
justment to lichen, &c, by larva of,
306.

bifida, Dicranyra, cocoon of at-
tacked by birds, 158, 159.

Biglow Papers, J. R. Lowell, 104.

bimaculata, Lepidiota, posterior
end of, with eye-like spots resem-
bling head of shrew-like mammal,
368.

Bingham, T. C, direct evidence of
birds capturing butterflies obtained
by, 283, 286-92 ; on wings of butter-
flies, &c, as pad in nests of Micro-
hierax, 290, 291, 291 n. 1 ; on tilt of
Melanitis, 289, 300 n. 5.

Biologia Centrali - Americana,
F. D. Godman and O. Salvin ;
Rhopalocera, F. D. Godman and

O. Salvin, 240; Rhynchota-Homo-
ptera, Canon W. VV. Fowler, 258
(Fig. 6), 259.

Biological stations needed in tropics,
89, 90.

Biometrika, 130 n. 3.

Bionomics of South African
Insects, G. A. K. Marshall, 282.

Bionomics I, in Colours of
Animals, Encycl. Brit., E. B.
Poulton, 293.

Birds (see also evidence and
enemies), evolution of from reptiles,
32 : see also 26 ; attempt to select
sterility between, 79, 80 ; little modi-
fied in Madeira, 84, 84 n. 2 ; greatly
modified in Galapagos Islands, 84
n. 2 ; intelligence of, 1 16 ; the enemies
of pupae in cocoons, 157-9; edu-
cation of young, 166-8 ; bearing
on mimicry of struggle for existence
in young of, 167, 167 n. 2, 168 ; no in-
stinctive knowledge of qualities of food
possessed by young, 212; northern
mimics of the male H. misippus may
have been caused by migratory, 217,
2 1 8, 382 ; experiments on instincts and
education of, 268, 269 ; indirect evi-
dence of attacks on butterflies by,
270, 270 n. 1, 281-3, 290-2, 325, 325
n. 1 ; insufficient, but considerable,
direct evidence of attacks on butter-
flies by, 269, 270 n. 1 , 282 n. 1 , 283-90 ;
distasteful moths seized and rejected
by, 284 ; evidence of difficulty in cap-
turing butterflies, 284 ; attacks of on
butterflies influenced by climate, 286 ;
powers of sight of, 302, 303 ; pupa
of L.fiopuli rejected by, 31 5-16; cryp-
tic resemblance to excrement of, 319 ;
intimidating attitude of large, 324;
Mullerian mimicry in relation to,
329-31 ; probably not deceived by
mimicry of Precis natalensis, 339 ;
Pap. aristolochiae proved to be dis-
tasteful to, 269, 372 ; powerful species
mimicked by weak (cuckoos, orioles),
367 ; mimetic sounds made by, 324.

Birmingham Philosophical
Society, Proceedings of, 136 n. I.

Birmingham University, Author's
Huxley Lecture before, the original
form of Essay VII, 193.

bispinosus, Ceratias, phosphor-
escent lure of, 378.

Blackness, J. C. Prichard on strong
local development of, 187 ; J. C.

ANALYTICAL INDEX 405

Prichard on protection against heat
by, 190.

Blakiston and Alexander on ad-
vantage of Miiilerian mimicry, 328,
329, 329 n. 1.

Blandford, W. F. H., on mimicry
of ants by Membracidae, 259 ; ex-
amples of Miiilerian mimicry exhibited
by (1896, 1897), 343, 356 n. I.

Blastogenic, see inherent char-
acters.

Blastoids in the early Palaeozoic,
30.

Blastomeres of frog's egg, effect of
destruction of certain, 128, 129.

Blattidae (Palaeoblattidae) of
Commentry Carboniferous, 36, 37.

Blood, transfusion of, 125 ;
coloured by chlorophyll of food, 314.

Blue Andalusian fowl, a hetero-
zygote, xxxvi ; Bateson on Natural
Selection and the, xxxvi ; suggests
variations useless for evolution, xxxix,
xl.

Blue Homer, fertile pairing be-
tween hybrid pigeon and, 83, 84.

' Blues ', see Lycaenidae.

Blumenbach on bile as the cause
of dark skin pigments in man, 176;
on multiple origin of dog, 188.

Body or somatic cells distinguished
from germ-cells, 121, 122.

Boisduval on resemblances be-
ween W. African butterflies, 221.

bolina, Hypolimnas, reversion of
mimetic female towards non-mimetic
male, 245 ; female of, mimics C. core,
male non-mimetic, 372.

Bolivia, Ecuador, and Peru, colours
of the chief Ithomiine-centred com-
bination in, 351.

Bombay, dorippus f. of L. chrysip-
pus at, 70 n. 2.

Bombay Natural History
Society, observations by members
of, on butterflies attacked by birds,
285 ; Journal of, 70 n. 1, n. 2.

Bombus, see humble-bees.

bombyliformis, see tityus, 365.

Borneo, 257 n. 1, 275, 276, 348,
349, 353, 367 n. 2, 369.

Boston Society of Natural
History, Author's Address to,
original form of Essay III, 95 ; Pro-
ceedings of, 95, 155 n. 1, 159 n. 2,
162, 164 n. 1.

Botany, Journal of, xix n. 5, xxi. I

Boulenger, G. A., on Oenothera
lamarckiana not a natural species,
and De Vries's conclusions founded
thereupon, unsound, xxi, xxii.

Boveri, on egg of Ascaris, 131,

Bower-birds, allepigamic collec-
tions of the, 379.

Bowers of bower-birds allepi-
gamic, 379.

Bowker, Colonel, on recent butter-
fly immigrants into Natal, 52 n. 1.

Boys, Prof. C. V., on concealment
of C. pumilus, 300.

Brachiopoda, of early Palaeozoic,
30; rapid decline of, 41, 42; evo-
lution in, 42, 43 ; specialization of
earliest fossils, 42, 43 ; imperfect
record in stratified rocks of, 42, 43.

Brachyura, late evolution of, 40.

Brady ornis mariquensis, 283.

Brain (see also instinct and
intelligence), rapid evolution of,
in higher animals, 29 ; evolution
in Mammalian, 108 ; evolution in
man's, 108 ; instinctive mechanisms
of the, versus the individually ac-
quired, 166.

Brambles, number of British species
of, 47.

Branch, aggressive resemblance of
serpent to, 312.

Branch! pus, Artemia transformed
into, 73, 74.

brassicae, Pieris, pupal groove of,
147, 148.

Brassohnae, the ' eye-spots ' of
pseudaposematic, 326.

Brazil, 53 n. 1, 216, 273, 313, 351,
356, 376.

Breeding between near of kin, 93.

Brenthidae (see also classification
of examples of mimicry, 390, 391),
though stick-like, commonly found
in flowers, 370.

Brightly-coloured Surfaces
concealed during rest, value
OF, 303, 304 : see also 325.

Bristol, J. C. Prichard a physician
at, 173.

British Association for the
Advancement of Science, Reports
of, xvi n. 1, xviii n. 1, xix n. 2, xxii,
xxii n. 3, xxix n. 4, xxxiii, xxxvi,
xxxvii n. 2, xl, xliv, xliv n. 1, xlv, xlvi,
1, 15, 44, 144 n. 1, 148, 155 n. 1,
164 n. 1, 213 n. 1, 223, 225, 263,
306, 308, 343 ; Prof. Huxley's Presi-

406

ANALYTICAL INDEX

dential Address (1870), 1 ; Prof.
Rolleston's Presidential Address
to Zoological Section (1870), 1 ; Dis-
cussion on Acquired Characters
at Zoological Section (1887), 148
n. 1, 155 n. 1 ; Discussion on Ac-
quired Characters at Zoological
Section (1889), 164 n. 1 ; Author's
Evening Lecture on Mimicry
(1890), the foundation of Essay X, 293,
365, 370, 376 ; Sir Archibald Geikie's
Presidential Address (1892), 16,
19 ; Lord Salisbury's Presidential
Address (1894), 2-4, 9, 10 ; Author's
Presidential Address to Zoologi-
cal Section (1896), the original form
of Essay 1, 1 ; Prof. Adam Sedgwick's
Presidential Address to Zoo-
logical Section (1899), 144 n. 1 ;
Discussion of Fertilization at
Zoological Section (1903), 60 n. 3;
Prof. A. C. Seward's Presidential
Address to Botanical Section
( 1903), 44 ; Prof. J. B. Farmer's
Presidential Address to Botanical
Section (1907), xliv-xlvi.

British Guiana, 259, 272, 273, 322,
332, 350-

British : beetle (Ctytus), moths
( Trochilium, Haemorrhagia), and
caterpillar (Euchelia) mimicking
wasp, 230, 238, 251, 252, 348, 363,
365, 366 ; bug larva (Nabis) mimick-
ing ant, 257 n. 1 ; caterpillar (Choero-
campa) mimicking cobra-like snake,
319, 367, 367 n. 2, 368, 376; cater-
pillar (Endromz's) mimicking saw- fly
(Croesus) larva, 238, 239, 239 n. 1 ;
caterpillar (Stauropus) mimicking
ant and bug, 253, 253 (Fig. 2), 254,
369 ; fly ( Volucelld) mimicking hum-
ble-bees, 221, 378, and (Eristalis)
bee, 243, 244 ; moths and butterflies,
choice of resting sites and procryptic
attitudes of, 156, 301 ; insects, slow
adjustable Protective Resemblance
in, 306, 307 ; northern moths, dark-
ening of, 308-10; moths, seasonal
dimorphism of, 311 ; crabs, allocryp-
tic defence of, 313, 314; hermit crabs
carrying sea-anemones and sponges,
356, 357 ; hawk moths, &c, attain-
ment of transparency by, 365, 366.

British species referred to : — aglaia,
A., 152 ; alni, A., 319 ; apiforme, T.,
365 ; archippus (plexippus), A., 274,
364; arietis, C, 238, 251, 252, 348,

363 ; bee, 243, 244 ; bee orchis, 64,
92 ; bembeciforme (crabroniforme),T.,
366 ; bernhardus, P., 356 ; betularia,
A., 143, 309 ; bidentata, O., 306 ;
bifida, D., 158, 159; bombyliformis,
H., 365 ; brambles, 47 ; brassicae, P.,
147, 148 ; C-album, G., 203-5 ;
cardui, P., 85 ; Catocala, 303, 325 ;
coarctata, H., 314; cowslip, xxviii,
47> 63 ; crabroniforme (bembeci-
forme), T., 366; cristatus, T., 130;
cuanensis, P., 357 ; cuckoo, 317, 318 ;
cuspis, A., 87 n. 1 ; edusa, C, 301 ;
elpenor, C, 319, 367, 367 n. 2, 368 ;
Eristalis, 243, 244 ; fagi, S., 253, 253
(Fig. 2), 254, 369; fuciformis, H., 365 ;
hare, Alpine, 310, 313; heath butter-
flies, 210 ; humble-bees, 221, 251, 365,
378 ; illunaria, S., 311 ; jacobaeae, E.,
230 ; 318, 319 ; lamarckiana, O., xix-
xxii,xxxv n. 1 ; lativentris, N., 257 n. 1 ;
leucophaearia, H., 156; meadow
brown butterfly, 210; megaloceph-
ala, A., 131; mendica, S., 324;
misseltoe, xix; neustria, M., 157;
nigra, P., 1 58 ; obscurata, G., 307,
308; ocellatus, S., 314, 314 n. 2;
oxlip,Bardfield, xxviii ; oxlip, common,
xxviii; palliata, A., 357; palumbus,

C, 83, 84; pamphilus, C, 210;
parasitica, S., 357 ; phalangium, S.,
313 ; phlaeas, P., 87 n. 1 ; piscatorius,

378 ; plexippus (archippus), A.,
274, 364; populeti, T., 157 n. 1;
prasinana, H., 149 ; prideauxii, P.,
357 ; primrose, xxvii-xxxiv, 47, 63 ;
pronuba, T., 314 n. 2 ; psi, A., 87 n. 1 ;
quercifolia, G., 299, 307 ; quercinaria,
E., 149, 150; rabbit, 93, 357, 35^1
rapae, P., 93, 147, 301 ; red deer, 357 ;
ringlet butterflies, 210 ; Rock pigeon,
84; rubi, T., 301 ; sambucaria, U.,
150, 150 n. 2; septentrionalis, C, 239,
320; sphex, 161 ; starling, 157 n. 1 ;
strigosa, A., 87 n. 1 ; sulcirostris, C,
307; tremula, P., 157 n. 1 ; tridens,
A., 87 n. 1 ; typhle, S., 299 ; urticae,
S., 324 ; urticae, V., 306 ; verbasci, C,
318, 319; Verbascum, 78, 79; versi-
color, E., 238, 239, 239 n. 1 ; vinula,

D. , 159; Volucella, 221, 378; white
admiral, 342 ; woodpecker, xix ;
Zonosoma (Ephyra), 150; Zostera,
299.

British (Natural History) Museum,
Microhierax in, 290 ; A. H. Thayer's
model in, 299 ; Palaearctic localities

ANALYTICAL INDEX 407

of H. misippus, and A thy ma and
Limenitis mimics of male in, 382.

Brittany, G. A. Boulenger's study
of 0. lamarckiana in, xxi.

Brongniart, Charles, on fossil in-
sects of Commentry, 35-8 ; on the
evolution of insects' wings, 37 ; on the
life-history of carboniferous insects,
37-

Browning, Robert, 155.

Brunner von Wattenwyl,
Hypertely of, X. 302, 303.

Brunner von Wattenwyl on ant-
like Locustid, 256, 257, 257 n. 1, 258

(Fig. 5).

Bitchanga assimi/is, 283, 284.

Buckler, W., figure of A. aglaia
pupa by, 152.

Buds and flowers resembled by
Flatidae, 304, 304 n. 3.

BufTon on direct effect of condi-
tions, 75 ; on origin of colours of
human races, and effect of latitude,
176, 177.

Bugs, see Hemiptera.

Bull sterile with one particular
heifer, 79.

Bull-dog, origin of, 83 n. 2.

Bull. Mus. Comp. Zool. Harvard,
234, 277.

Bull. Soc. Ent. Fr., 381, 382.

Bullidae originate in Trias, 42.

Bumble-bees, see humble-bees.

Burchell, Francis A., discovery of
letters of W. J. Burchell by, 49 n. 3.

Burchell, W. J., letters of, 49, 49
n. 3 ; isolation of, 49, 50 ; Brazilian
and South African butterflies of, 53,
53 n. 1 ; possible change since 1825-
7 indicated by specimens of L. halia
captured by, 356.

Burma, 286-92, 373.

Burn, G. Yi.^dorippus, f.of L. chrys-
ippus, captured in Natal by, 71 n. 1.

Burr, Malcolm, on Rhodesian ant-
like Locustid, 257 n. 1.

Bush kingfisher capturing butter-
flies, 283.

Butler, A. G., on dorippus, f. of
L. chrysippus, in India* 70 n. 2.

Butler, Samuel, on Natural Selec-
tion, 105.

Butterflies, L. de NiceVille, 292.

Butterflies, points in the
Resemblance to Dead Leaves
of, VII. 203-6 : see also 206-8, 289,
299-302, 310, 311, 322, 351,353-

Butterflies, some Seasonal
Changes of, VII. 206-11 : see also
Seasonal.

Butterflies, new Interpreta-
tion of an old example of
Mimicry in, VII. 211-18.

Butterflies and Moths,
chiefly Oriental, Illustrating
Mimicry, X. 370-376.

Butterflies (see also Lepidoptera,
Acraeinae, Danainae^ Elymniznae,
Erycinidae, Heliconinae, Ithomiinae,
Lycaenidae, Morphinae^ Nympk-
alinae, Papilioninae, Pierinae,
Satyrinae : see also classification of
examplesof mimicry, 383-9) : seasonal
changes in, see seasonal ; attacks
by birds on, see birds ; pigments of,
more stable than those of moths, xlv :
see also 53 ; recent immigration into
Natal of species of, 52 n. 1 ; changes of
form or distribution, in about eighty
years of, 53 n. 1, 356; preferential
mating of, 85-8 ; importance of re-
cording captures in coitu of, 87 ;
resemblance to leaves of, 203-8, 289,
299, 300, 300 n. 1, 301, 310, 311,
322, 351, 353; Boisduval on resem-
blance between W. African, 221 ; too
exclusive study of mimicry in, 229,
272, 273 ; mimicry of, by moths fre-
quently Mullerian, 231, 232 ; fewness
of patterns in protected groups of, 234,
277 ; mimicry in, independent of
affinity, 229-37, 345 ; moths which
mimic are day-flying, 249, 250, 275,
276, 372, 376 ; evidence of special
defence of, required, 268; the chief
mimetic combinations of, in Guiana,
272, 273, 322, 331-3, 350; Vene-
zuela, 273, 350 ; S.E. Brazil, 273, 350,
351, 356; Ega, Upper Amazon, 273,
351 ; Ecuador, Bolivia, and Peru,
351 ; females chiefly mimetic, 215-
17; 244-7, 279, 347, 353, 372,
373-4 ; characteristics of distasteful
groups of, 279 ; evidence of distaste-
fulness in models, 269, 279, 279 n. 1,
316,317 ; migration of, in Ceylon, 285 ;
in Burma, 289 ; crowds of, on damp
sand, 287 ; evidence of advantage con-
ferred by cryptic defence of, 288, 289 ;
wings of, in nest of Microhierax, 290,
291, 291 n. 1 ; reduction of shadow by
attitude, 300, 300 n. 5, 301 : see also
289 ; daylight hours in relation to
cryptic colours and instincts of, 303 ;

4o8 ANALYTICAL INDEX

mutual approach between model and
mimic in, 344, 345.

Byatt, H. A., on H. misipfius and
its model, 216 n. I.

Byblia (Hypanis) acheloia (got-
zius), 87'; — gbtzius, 341 ; —
ilithyia, 341.

C

Caduga, the model of E. lais upper
side, 353-

Caduga tytia, 371.

coffer, Coccystes, Papilio demodo-
cus found in stomach of, 283.

C-album,Polygonia(Grapta),mea.n-
ing of 1 comma 1 of, 203-5.

Calcispongiae in the Palaeozoic, 28.

Callamesia of the Chalcosiinae
(Zygaenidae), Miillerian mimics of
Euploeinae, 372, 376.

Callamesia midama, 372, 376.

Callichrominae, mimicry of Hy-
menoptera by, 252.

Callioratis bellatrix, 284.

cama, Athyma (Pantoporia), pro-
bable ancestor of A. punctata, 382;
Oriental localities of, 382.

Cambrian, origin of Vertebrates in
pre-Cambrian or, xliii, 26, 30, 31 ; life
long antecedent to, 6 ; thickness of
deposits from, 16: Coelomate phyla
in, 30; specialized forms in, 30, 31 ;
Crustacea of the, 39, 40 ; dominance
of Trilobites in, 39 ; Ostracodes in,
39; Mollusca in, 41, 42; Gastropoda
in, 42 ; Cephalopoda in, 42 ; Echino-
derma in, 43.

Cameroons, type f. of Z. chrysippus
occurs very rarely in, 321 n. 1.

Campbellpore, dorippus f. of L.
chrysippus at, 70 n. 2.

Cambridge, Trinity College, J. C.
Prichard a member of, 173.

Cambridge Zoological Museum,
A. H. Thayer's model in, 299.

Canada, 270, 274.

Canara, dorippus f. of L. chrysip-
pus rare in, 70 n. 2.

Cantharidae mimicking Lycidae,
276.

Cape, L. chrysippus at, 88.

Cape Town Museum, 87.

caphyraeformis, Ascidiophilus,
living in an Ascidian case, 357.

Carboniferous, size of dragon-fly of
the, 18 ; Foraminifera of, 27 ; sponges
of, 28 ; Myriapoda of, 34 ; insects of

upper, 35-8; Arachnida of, 40;
Pedipalpi of, 40; scorpions of, 40;
spiders of, 40 ; land-plants of lower,
44.

cardui, Pyrameis, wide range and
great uniformity of, 85.

carinata, Echis, swishing sound
made by, 324.

Carnegie Institution of Wash-
ington, xix n. 5, xxii.

Carnivora,aggressive resemblances
of, 312, 313.

Carpenter, P. phlaeas bred by, 87
n. 1.

Carrier and tumbler pigeons, fertile
progeny of, 78.

Carus, Victor, letter from C. Darwin
to, xl n. 3.

Castniidae mimicking Ithomiinae,
243,' 264 ; method of attaining trans-
parency in, 266.

castor, Papilio, male of mimics
Pap. chaon, female mimics Crastia
core, 372.

Castration, effect of,upon secondary
sexual characters, 122, 380.

Catalogue of the Leech Collec-
tion, R. South, 382.

Caterpillars (for other than Lepi-
dopterous larvae see larvae : see also
larval stage) : reasons for passive
defence of, 1 56.

— Procryptic adaptations of : —
variable protective resemblance in,
1 52-4 ; value of slow^colour adjust-
ment to, 305 ; colour adjustment to
various backgrounds, including lichen-
covered bark, 306, 307 ; gregarious
habits in concealment of, 304 ; value
of dimorphism in, 310; movements
essential to cryptic defence of certain,

318, 323 ; value of ' sham death ' in
concealment of, 323.

— Transition between procryptic
and aposematic defence in:— double
protection of C. verbasci, 318 ; tran-
sition from cryptic to aposematic
defence caused by movements of,

319, 320.

— Aposematic adaptations of : —
value of ' sham death ' in aposematic
defence 0^323, 324; gregarious habits
of certain aposematic, 323 ; move-
ments essential to aposematic defence
of certain, 319, 323, 324 ; value of
1 tussocks ' of, 325, 326.

— Mimetic adaptations of (see also

ANALYTICAL INDEX 409

classification of examples of mimic-
ry) 389, 391) :— head of ant mimicked
by tail of. 254, 368 ; clear examples of
Batesian mimicry afforded by, 376 ;
movements essential to mimetic
resemblance of certain, 238, 239,
239 n. 1, 253 (Fig. 2), 254, 319, 368.

— Struggle for existence in : — dan-
ger of experience to, 117,118, 15 5-60 ;
stored up in cells of Fossores, 118,
119; ganglia of, stung by Ammo-
phila, 160-4 ; starlings attacking
T. populeti, 157 n. 1 ; cryptic larvae
preferred to butterflies and moths by
lizards, 286 ; cuckoo devouring apo-
sematic, 317, 318.

Catocala, value of bright hind wings

of, 303-4, 325-

Catophaga, captured by bee-eaters,
285.

Catopsilia) migration of, in Burma,
289 ; persistently captured by Merops
philippinus and king-crows, 289.

Catopsilia florella, 283.

Cats, Angora, J. C. Prichard on,
187.

Cattle, J. C. Prichard on the pro-
duction of breeds of, by selection,
186.

Cattle and horses of plains and
mountains compared by J . C. Prichard,
189.

Caudal shield of S.fagi larva re-
sembles bug, 369.

caudata, Elymnias, female of,
mimics 5. plexippus {genutia), and
male incipient mimic of same model,
373-

caudius, Papilio, VV. C. Hewitson
on, 57 n. 1.

caunus, Papilio, wing of, in nest of
Microhierax, 291.

cebrene, Junonia, captured by Hal-
cyon chelicutensis, 283.

Cell-divisions equivalent or differen-
tiating, 133, 135.

Cell-republics of the higher animals,
120, 121.

Cells, division of labour among,

121.

Celtic, shown by J. C. Prichard to
be an Aryan language, 173.

cenea,*. female f. of three E. and S. E.
sub-sp. (polytrophus, tibullus, ce?iea)
of Papilio dardanus (q.v.), 72, 72 n. 1,

337, 338, 355, 374, 375-
cenea, the S. and S.E. sub-sp. of

Papilio dardanus (merope), 355, 374,
375 : see also dardanus.
Centipedes, 27.

Centrifugal or inherent characters,
in, 123, 142: see also inherent
characters.

Centripetal or acquired characters,
1 10, hi, 123, 142: see also acquired
characters.

Cephalopoda appear in Cambrian,
42 ; evolution in, 42 ; rapid colour
adjustment in, 305 ; colour adjust-
ment of, both aggressive and protec-
tive, 313.

cephalotes, Atta (Oecodoma),
mimicked with its leaf by Membracid
larva, 259, 259 (Fig. 7), 260, 280, 377.

Cephonodes hylas, 365.

Ceratias bispinosus, 378 ; — urano-
scopus, 378.

Ceratophora, place in classification
of, 33-

Ceratophrys cornuta, 313.
Cercospara, attacking leaves, 205
n. I.

Ceria, method of attainment of
mimicry by, 280.

Cerotoma, mimicked by Lema, 237.

ceryne, Precis, dry f. bred from wet
(1905), 340 n. 1 ; under side far more
conspicuous in wet than dry season,
340 ; S. African habitat of, 340.

Ceylon, 70, 70 n. 2, 71, 285, 286,
349-

Chaetopoda, relation to ancestry of
Appendiculata and Arthropoda of,

27, 33, 41.

Chafer, posterior end of, mimicking
shrew-like mammal, 368.

Chalcosiinae (Zygaenidae), highly-
protected diurnal moths, mimicking
Danainae and Papilioninae, 231 ;
Danainae and Pierinae, 275 ;
Danainae, 362 ; Eupioeini, 372, 376 ;
Agaristid moths, 275 ; mimicry of
Mullerian, 231, 232, 362, 372, 376.

Chalk, procryptic colouring of
G. obscurata on, 307, 308.

Challenger, investigations on
ocean basins of, 20-2.

Chainaeleo pumilus, adjustable
neutralization of shadow in, 300, 313.

Chameleon, rapid colour adjust-
ment in, 305 ; aggressive resem-
blance of, 313.

Change Possible in Mullerian
Mimic since 1825, X. 356.

ANALYTICAL INDEX

Changes Seasonal in the
Individual, X. 310.

Changes in mode of defence at
different stages of life-history, 319.

chaon, Papilio, mimicked by male
of Pap. castor, 372.

Chapman, T. A., on evidence of
preferential mating, 87 n. 1 ; on
choice of resting-sites by butterflies,
301.

Charaxes, value of 'tails' of hind
wings of, 281, 282 ; wing of, in nest
of Microhierax, 291.

Char axes athamas, 288; — psaphon,
286 ; — scheiberi, 292.

Charles Darwin and the Theory
of Natural Selection, E. B. Poulton,
83 n. 1, 162 n. 2, 219, 225, 233 n. 1,
272 n. I.

chelicutensis, Halcyon, capturing
Juno?tia cebrene and Catopsilia
fiorella, 283.

Chief Characteristics of
Mimetic Resemblance and
Attempt to Explain their
Evolution, X. 362, 363: see also
Essay VIII, 220-70.

China, 88, 217, 333, 382.

chinensis, Estigmena, mimicked
by Estigmenida variabilis, 261.

Chinese goose fertile with
Common, 83.

Chiricahua Mountains, Arizona,
examples of mimicry from, 231.

Chiton, in early Palaeozoic, 30,42 ;
an ancestral form, 42.

Chlorophyll derived from food, use
of by insects, 314; by larva of 71
pronicba, 314 n. 2; passing through
egg into larva of next generation,
314 n. 2.

Choerocampa, snake-like Bornean
species of, 367 n. 2 ; terror inspired
by snake-like African species of, and
the British C. elpenor, 367 n. 2.

Choerocampa elpenor, 319, 326,
367, 367 n. 2, 368, 376.

Choice of Appropriate Sur-
faces FOR RESTING ON, X. 30I.

Chrysalis, see pupa.

chrysippus, Limnas, forms of, with
theirgeographical distribution : — dis-
tribution of dorippus and type forms
of, 70, 71 ; peculiarity of far eastern
forms of, 88 ; 1 Syngamic chain '
probably formed by, 88, 89 ; type f.
of ancestral, 321 n. 1 ; type f. of, very

rare in Camaroons as compared with
alcippus f., 321 n. 1 ; geographical
transition from aposematic to cryptic
defence of, 320, 321 ; desert form of,
321 ; two of three forms of sharply
marked off, 364 ; corresponding
forms of mimics transitional into
one another, 364, 365 n. 1.

— Mimics of :— as model for mimi-
cry, 215; Miillerian mimicry of by
Aletis helcita and its mimics, 232 ;
Natal mimics of with model, in Hope
Department, 249 ; a dominant model
in E. Africa, 336 ; preferring station
different from that of certain of its
African mimics, 349; mimicked by
one f. of female A. esebria, 354, 355 ;
advantage of resemblance to, as well
as to Amauris, 355 ; three forms of,
mimicked respectively by three
forms of A. encedon, 355, 364, 365,
365 n. 1 ; also by three forms of
female H. misippus, 355, 364, 365,
365 n. I, 372; alcippus f. of, shown
by mimics to be only recently domi-
nant in W. Africa, 364; shown by
mimicry to be ancient inhabitant of
Africa, but a recent intruder into
Oriental Region, 364 ; mimicked by
trophonius, female f. of four sub-
species of Papilio dardanus, 374.

Church Quarterly Review,
56 n. 3.

Cicada, wings of, in nest of Micro-
hierax, 291 n. 1.

Cinnabar moth, 230 ; larva of,
318.

Circumcision, results of, not here-
ditary in spite of antiquity, 182.

Cirrhipedes, continuity the diffi-
culty in Darwin's systematic work
on, xv, 59, 60, 67 ; in Silurian, 39.

Classification of animals, 25 ; of
bionomic uses of animal colours,
226 ; of examples of mimicry, 383-93.

Claws of Crustacea, Lamarckism
and, 113, 114 ; value of the power of
throwing off, 113, 114, 325 ; pseudepi-
sematic or alluring use by Hyas of,
314-

' Clearwings ', transparency of
scales in, 366.

Cleavage, position of future embryo
and planes of, 130.

cleodora, Eronia, captured by fly-
catcher, 283 ; choice of resting-site
by, 301.

ANALYTICAL INDEX

411

Cleonus sulcirostris, 307.

Climate (see also external
causes) : J. C. Prichard on adaptation
of human races to, 191 ; an ex-
planation why human races may not
be changed by, 192 ; on the influence
of, 187-92 ; hypothesis that mimicry
is caused by food, &c, and, 224 ;
influence of, on attacks of birds on
butterflies, 286.

Close, Rev. M. H., on the age of
the earth, 12 n. 1.

Clytinae, as mimics of Hymeno-
ptera, 238, 251, 252, 348, 363; as
models for other Longicorns in
Borneo and Ceylon, 348, 349.

Clytus arietis, 238, 251, 252, 348,
363.

Coal, insects of, 35-8.

coarctata, Hyas, combined allo-
procryptic, allanticryptic, and
pseudepisematic colouring of, 314.

Cobra, cryptic and aposematic
defence 0^324; intimidating attitude
of, 324, 325 ; advantage of intimida-
tion of, 324, 325.

Cobra-like and other snakes
mimicked by caterpillars, 319, 326,
367, 367 n. 2, 368, 376.

Coccystes coffer, 283.

Cockroaches, in early Palaeozoic,
30 ; of Commentry Carboniferous,
36, 37.

Cocoon, Instinct of form-
ing, V. 157-60.

Cocoon, formed prior to experience,
and Lamarckian interpretation there-
fore excluded, 117, 118, 157-60, 164,
164 n. 2 ; probably reasons for decline
of, 148 ; advantage of decline of, 148,
149 ; cryptic colouring of, in times of
stress, 148; colour adjustment of, in
Halias prasinana, 149 ; concealed
on bark, 158, 159.

Coelentera, in relation to classifica-
tion and evolution, 25, 26, 28, 30, 31.

Coelomata, in relation to classifica-
tion and evolution, 25-8, 30, 31, 41,
43-

Coetionympha pamphilus, 210.

coerulescens, Mic?-ohierax, captur-
ing Papilio sarpedon, 290 ; butter-
flies' wings, &c, in nests of, 290, 291.

Co-Existence of Palatable
Food implied by Aposematic
Defence, X. 317.

Coincidence between colours

and Environment probably
caused by Local Natural Selec-
tion, X. 307, 308 : see also 308, 309,

309 n. 1, 310 n. 1.

Colaenis, 'stink glands' of, 334 n. 2.

Colaenis telesiphe, 334 n. 2.

Cold, see external causes ; effect of,
on Hudson's Bay Lemming, 310.

Coleoptera, see beetles.

Co lias edusa, 301.

Coloration marquante et
Taches ocellees, 1897, C. Portschin-
ski, 254, 369.

Colour adjustment, see Adjustable
Protective Resemblance.

Colour, danger of inferring discon-
tinuity from changes in, xvii.

Colours of animals classified, 226 ;
sexual selection of bright, 379.

Colours of Animals, E. B. Poul-
ton, 4, 150 n. 2, 210, 223, 226, 281,
326, 344, 367 n. 2.

Colours of Animals : I, Bionom-
ics, Encycl. Brit., E. B. Poulton,
293-

Colours probably Adjusted
to Environment by Local
Natural Selection, X. 307, 308 :
see also 308, 309, 309 n. 1, 310,

310 n. 1.

Colours, Value of Bright,
Concealed during Rest, X. 303,
304 : see also 325.

Cohcmba palumbus, 83, 84.

Comb-making instinct, 164.

Combination of procryptic and
mimetic colouring, chief examples of,
in butterflies (Protogonhis and Elym-
niinae), 350-4 : see also 324, 368.

1 Combination ' or 1 association
use of, contrasted with 'group', 293.

Comma butterfly, 203-5.

Commentry, fossil insects of,
35-8-

Common goose fertile with
Chinese, 83.

Common or Syncryptic Pro-
tective Resemblance, X. 312:
see also 359.

Common Warning Colours,
Natural Selection the Cause
of Mimicry and (Theories of
Mimicry), Essay VIII, 220-70. See
also Essay IX, Mimicry and
Natural Selection, 271-92.

Common Warning or Synapo-
sematic Colours (Mullerian

412

ANALYTICAL INDEX

Mimicry), X. 327-56. See Mimicry
Mullerian. For sections and sub-
sections of this heading see pp. 295,
296.

Comoro, see Grand Comoro, 373.
Complete Immunity not im-
plied by Warning Colours,

X. 317, 318.

Composite mimicry of two models,
368, 369.

Composite nature of Mimicry,
240-2.

Concealment, aposematic forms
protected in time of stress by, 317,
320.

Concealment Assisted by
Gregarious Habit, X. 304.

Conception, J. C. Prichard on
effect of imagination at the moment
of, 186.

Conclusions on Natural
Selection as the Cause of
Mimicry, &c, VIII. 267-70.

Conclusions supporting Mullerian
Mimicry, 346, 347.

Conditions chiefly deter-
mined by Habits and Life-
history, VIII. 243, 244.

Conditions, see environment,
external causes, and uniformity.

Conductivity in interior of earth,
10-13 » and radium, 15 n. 2.

Conepatus mapurito, 315.

Confirmation of History In-
ferred from Mimicry, X.365, 366.

confusa, Methona, mimics of, 264-
6 ; method of attaining transparency
in, 265 ; Ecuador form of, 265, 266.

Congenital, see inherent charac-
ters, 141.

Congo, type f. of L. chrysippus at
Luebo on S. branch of, 321 n. 1.

Coniferae related to Cordaiteae,
45-

' Connate varieties of structure . . .
are apt to re-appear in . . . offspring ',
J. C. Prichard (1826), 179.

Connate, see inherent characters.

conspicuousness imputed to
Animals Criticized by Thayer,
X. 321-3.

Conspicuousness only not the aim
of nature, 321, 322; danger of un-
necessary, 322 ; relative use of term,
322.

Constitutional, see inherent
characters, 141.

Constricting serpent, aggressive
resemblance of, 312.

Contemporary Review, 161.

Contents, Essay X. 293-7.

Continental Areas, Mimetic
Species on, with Non-Mimetic
Ancestor in Island, X. 373-6.

Continental areas, stability of, 21.

Continuity and Discontinuity
defined, xiv.

Continuity of the germ-plasm, dia-
gram of, described, 127-8, 130-1 ;
heredity and, 127-36 ; blastogenic or
inherent characters and, 127; soma-
togenic or acquired characters and,
127, 131, 132 ; relation between
transmission of acquired characters
and, illustrated in Diagram II, 131,
I32-

Continuity the systematist's diffi-
culty, xv.

Continuous or Discontinuous
Evolution, Introd., xiv-xvi.

Continuous evolution cannot be
claimed as Mutation, xxxviii, xxxviii
n. 1 , xxxix.

Contributions to an Insect
Fauna of the Amazon Valley,
H. W. Bates, 220.

Conularia in Palaeozoic, 42.

Conviction, the basis of scientific,
201, 202.

Cooling of the earth, 9-13.

Cope, E. D., on Natural Selection
not creative, xxii ; on origin of fittest,
109.

Coral, protective resemblance to,
359-

Corals, place in classification of,
25 ; slow evolution in, 28.

Cordaiteae, a group of Palaeozoic
Gymnosperms, 45 ; comparable to
Coniferae, 45.

core, Crastia, captured by Artamus
fuscus, 286 ; mimicked by female of
H. bolina, 372 ; mimicked by female
of Pap. castor and by both sexes of its
S. representative, Pap. dravidarum,
372.

corinneus, Papilio, evidence of
capture by swallow of, 284.

Cork, Prof. J. B. Farmer on utility
as no explanation of, xlv, xlvi.

cornuta, Ceratophrys, allanticryptic
resemblance of, 313.

Correns, rediscovery of Mendel's
principle by, xxix ; on limitation of

ANALYTICAL INDEX 413

Mendel's principle to crosses between
varieties, xxxv n. 2.

Corticata, no fossil records of, 25.

Cosmos, facts of the, consistent
with gravitation, xxvi, 271.

cottonis, Elymnias, non-mimetic or
with general likeness to a Euploea,

373, 373 n- 2.

Courthope, W. J., parody of
Darwinism by, 103-4.

Courtship, Colours Displayed
in, X. 379, 380 ; see also 226.

Courtship, for colours, &o, dis-
played in, see Epigamic Characters
and Sexual Selection.

Cowslip, C. Darwin on specific
distinctness of, xxviii, 47, 63.

crabroti iforme (bembeciforme),
Trochilium (Sesia), nature of scales
lost by, 366.

Crabs throwing off claws, 1 13, 1 14 ;
value of amputated claws of certain
species, 325 ; alloprocryptic, &c,
defence 01,313,314; sea-anemones,
sponges, and Ascidians carried by
hermit-crabs, 356, 357 ; sea-
anemones by crabs, 357.

Crastia core, 286, 372.

Creation, Linnaeus's views on, 54-
9; St. Augustine's views on, 55.

Creation special, a theological
dogma, 56, 57 ; influence of Milton
on belief in, 55, 56.

Creative power of Natural Selec-
tion, xxiii.

Crenis rosa, 52 n. 1.

Crinoids in early Palaeozoic, 30.

cristatus, Triton (Molge), Herlitz-
ka's experiments on egg of, 130.

Criticism by Thayer of Con-
spicuousness imputed to ani-
'mals, X. 321-3.

Croesus septentrionalis, 239, 320.

Cross and Self- Fertilisation in
the Vegetable Kingdom, Charles
Darwin, 92.

Cross-Fertilization, Asyn-
gamy caused by adaptations
for, II. 90, 91 : see also 65.

Cross-Fertilization, possible bene-
fits of, 93-4.

Cross-Fertilization, the In-
jurious Effects of Self-Fertil-
ization the Consequence and
not the Cause of Adaptations
for, II. 91-4.

Crotatus, rattle of, 324.

cruciata, Oenothera, hybrid be-
tween O. lamarckiana and, does not
follow Mendelian principle, xxxv n. 1.

Crustacea in classification, 27, 33 ;
in Cambrian, 39 : see also 30 ; experi-
ments on Artemia, 73, 74 ; rapid
colour adjustment in, 305 ; aggressive
resemblance of, 313 ; alloprocryptic
resemblance of, 313 ; allanticryptic,
&o, resemblance of, 314 ; allapo-
sematic defence of, 356, 357.

Cryptic Colouring, Protec-
tive and Aggressive Resem-
blances: Procryptic and Anti-
cryptic Colours, X. 297-315. For
sections, sub-sections, &c, of, see
Contents, pp. 293, 294.

Cryptic colours (see also Protec-
tive Resemblance and Aggressive
Resemblance) : place of in a scheme
of the bionomic uses of colour, 226 ;
defined, 297.

cuanensis, Pagurus, carrying
brightly-coloured sponge, 357.

Cuban swine, J. C. Prichard on,
187.

Cuckoo, indifference to unpalata-
bility of, 317, 318; mimicking ag-
gressive birds, 367.

Cuckoo (C. caffer), butterfly found
in stomach of, 283.

Cucullia verbasci, 318, 319.

cupulifer, Polydectus, carrying sea-
anemones, 357.

Curculionidae (see also classifica-
tion of examples of mimicry, 390-1) :
colour adjustment probable in
Cleonus, 307 ; conspicuousness of
certain large African, 370 ; hardness
as the defence of, 261, 369, 370.

curculionoides, Doliops, mimicking
weevil, 261.

Curiosity the only true incentive
to inquiry, xliv, xlvii, xlviii.

cuspis, A crony eta, Dr. T. A.
Chapman on, 87 n. 1.

Cuttlefish, rapid colour adjustment
in, 305 ; colour adjustment of, both
aggressive and protective, 313.

Cuvier, W. Whewell on, xlvi n. 1 ;
on species, 56.

Cycadophyta, relation to Angio-
sperms of, 45.

Cyclops, early appearance of germ-
antecedent in, 131.

Cyrestis, captured by Merops
swinhoeiy 287.

ANALYTICAL INDEX

414

Cyrestis thyodamas, 288.
Cystoids, in early Palaeozoic, 30.
Cythere, persistence through geo-
logical time of, 39.

D

Damp, effect on Teracolus and
Belenois of, 311, 312.

Danainae (see also Danaini,
Danais, and Euploeini ; see also
classification of examples of mimicry,
383-9) : Lycorea and Ituna, in-
cluded in Ithomiinaeby Bates, belong
to, 327 ; absence of 'eye-spots' in,
326; unpleasant scent in African,
316 ; Indian proved to be unpalatable,
269; uniformity throughout many
species of, 277 ; as models paralleled
by Diabrotica, 236 ; always tend to
be mimicked, 233 ; the chief distaste-
ful group of the Old World, 333-5 ;
as primary models in Africa, 345 ;
as models and mimics (viz. genera
Lycorea and Itund) everywhere in
tropical America, 273, 356 ; probably
not more unpalatable than a far
rarer Chalcosid mimic, 362 ; as
mimics of Ithomiinae, 264, 265 ;
method of attaining transparency in,
265 ; darkening of mimetic in the
Guianas, 272, 273 ; Lycorea an out-
lying member of a chief Ithomiine
centred combination in E. Brazil,
356 ; possible change in colour of
since 1825-7, 356: see also 53 n. 1.

Danaini (see also classification of
examples of mimicry, 384-9) : com-
parison as models of two chief sub-
groups o(Danainae,ihe Euploeini and,
333—5 ; range of Euploeini compared
with, 333, 334 ; mutual mimetic in-
fluence of Etiploeini and Danaini
compared, 334, 335 ; flight of certain
American species of, adapted to dis-
play under surface, 323 ; few in Africa,
but much mimicked, 336 ; the chief
models in E. Africa belonging to,
336; probable meaning of male scent-
brands of certain, 358.

Danais, species of, not attacked by
bee-eaters, 288.

Danaoid Heliconidae (see Itho-
miinae) of H. W. Bates include the
Ithomiinae, together with the
Danaine genera Ltuna and Lycorea,
327.

Dances of male Attid spiders, 380.

Dangers of the dry season, 208-1 1 ;
of * eye-spots ' in dry season, 210, 21 1,
326.

' Danger-signals ', advantage of
resemblance between, 328.

Danisepa diocletianus (rhadaman-
thus), 373.

dardanus (merope), papilio,
Remarkable Example of
Mimicry, X. 373-6.

dardanus (?nerope), Papilio, 57,
57 n. I, 71, 72, 72 n. I, 337, 338,
354, 355, 37o, 371, 373-5.

— sub-sp. 1, antinom, Abyssinia,

373, 374, 374 n. 1, 375-

— sub-sp. 2, polytrophus, Kikuyu,

374, 375 J female f. trimeni, 374, 374
n- 2, 375 ; female f. hippocoon, 374, 374
n. 1 ; female f. trophonius, 374, 374
n. 1 ; female f. cenea, 374 ; female f.
pianemoides, 374.

— sub-sp. 3, tnerope, Western, 374 ;
female i. hippocoon, 57 n. 1, 338, 374,
374 n. 1 ; female f. trophonius, 374,
374 n. 1 ; female f. pianemoides, 338,

374, 374 n. 3, 375-

— sub-sp. 4, tibullus, E. Coast, 337,
338, 374, 375 I female f. trimeni, 374,
374 n. 2, 375 ; female f. hippocoon, 338,
374, 374 n- 1 ; female f. trophonius,
374, 374 n. I ; female f. cenea, 337, 338,
374-

— sub-sp. 5, cenea, S. and S.E., 72,
72 n. I, 355, 374 ; female f. hippocoon,
72, 72 n. 1, 374, 374 n. 1 ; female f.
trophonius, 72, 72 n. 1, 374, 374 n. 1 ;
female f. cenea, 72, 72 n. 1, 374.

— See also meriones, Papilio,
Madagascar ; humbloti, Papilio,
Comoro I.

— Discovery by Trimenof mimetic
females of, 57 ; all three female forms
bred by G. F. Leigh from one of
them, 72 n. 1 : see also 72 ; three
chief Danaine models of E. Africa
mimicked by female forms of, 337 ;
geographical replacement of models
of at the V. Nyanza, and correspond-
ing changes in mimetic female forms
of dardanus, 337, 338 ; the great
example of polymorphism in mimicry,
354, 355 > brief account of range and
mimetic relationships of all sub-
sp. of, 373-5 ; probable Miillerian
mimicry of, 37 5 ; female forms of, and
their models erroneously figured by
Professor Weismann, 375, 376.

ANALYTICAL INDEX

4i5

Darkening of hind wing in Guiana
mimetic butterflies, 272, 273, 331,
332-

Darkening, Recent, of N.
English Moths, X. 308, 309, 309
n. 1, 310, 310 n. 1.

Darwin, Charles (see also Descent
of Man, &c, Different Forms of
Flowers, Further Letters of, Life
and Letters of, Origin of Species,
Variation under Domestication) :
continuity the difficulty in the sys-
tematic work of, xv ; on Mutation as
expressed in the Vestiges ', xviii,xix; on
the creative power of Natural Selec-
tion, xxiii ; Bateson's and Gregory's
work on the primrose compared with
that of, xxvii-xxxiv ; researches upon
heterostyled plants by, xxvii-xxix ;
on the value of the heterostyled con-
dition, xxvii-xxix ; the importance
of minute variations assumed by,
xxxix ; individual differences con-
sidered of far greater importance
than large single variations by, xl,
xl n. 3, xli ; letter to Wallace aban-
doning evolution by large single
variations, 3 ; on pre-Cambrian time,
5, 6; troubled by Lord Kelvin's views,
6, 11 ; on persistence of oceanic and
continental areas, 21, 22 ; influence
of, upon biological reasoning, 32,
33 ; definition of species by, 46, 47 ;
on species and varieties, 47 ; on prim-
rose and cowslip as true species, xxviii,
47, 63 ; on constancy as a criterion of
species, 47, 63 ; natural selection as
conceived by Wallace and, 48 ;
special value of letters of, 48 ; life of
Burchell compared with that of, 49,
50 ; on theological aspect of species,
56 ; the joint essay (1858) of Wallace
and, 58, 95-7, 194-6 : see also Darwin-
Wallace theory ; on various defini-
tions of species, 59 ; on evolution
and systematic work, 59 ; on subjec-
tive side of systematic work, 59, 60;
definition of 1 close species ' by, 67 ;
on describing species, 67 ; on sus-
ceptibility to different conditions,
73-4 ; on effect of conditions on
plants, 74, 75 ; on interspecific
sterility, 77-80, 201 ; on sterility
between selected races, 78-80 ;
suggestion to W. B. Tegetmeier by,
79 ; on domestic animals derived
from two or three species, 79 ; con-

troversy on interspecific sterility
between Wallace and, 80, 89 ; on
fertile pairing of two species of goose,
83 ; on fertility promoted by domesti-
cation, 83, 84 ; on sterility caused
by asyngamy, 84 ; on preferential
mating, 86, 87 ; on sterility not due to
selection, 89 ; on heterostyled plants
and interspecific sterility, 90, 91 ; on
injurious effects of self-fertilization,
92 ; metaphor of tree by, 94 ; on
origin of life, 95 ; on failure to under-
stand Selection, 102 : see also 96 ;
term 'Natural Selection' proposed by,
105 ; on Selection a true cause, 109 ;
theory of pangenesis of, 123-7 ;
chief reason for adoption of pan-
genesis by, 126 ; unaware of the im-
portant second edition of Prichard's
work, 175, 175 n. 1 ; views of, on
formation of domestic breeds essen-
tially similar to those of Prichard,
186, 187 ; J. C. Prichard as a remark-
able predecessor of Wallace and, 192;
on instincts of Fossorial Hymeno-
ptera, 160, 161 ; and of worker ants,
165 ; discovery of Natural Selection
by> 193> 194 ; consults Lyell and
Hooker about publication of Natural
Selection (1858), 194; disappointed
at reception of early geological
writings (1844 or 1845), 196, 197 ;
on mimicry and affinity, 233,
233 n. 1 ; on sexual selection as
cause of mimicry, 225, 228, 272,
272 n. 1 ; theory of sexual selection
of, 379 ; sexual selection set forth in
the joint essay (1858) by, 379.

— Letters of, referred to in present
work: to H. W. Bates, 86; Victor
Carus, xl n. 3 ; Asa Gray, xxvi, 66,
67, 68, 194 n. 1 ; J. D. Hooker, 59,
60, 63, 67, 76, 84, 86 ; T. H. Huxley,
78, 79, 80, 82, 91, 126, 196; C. Lyell,
56, 75, 83, 83 n. 2 ; R. Meldola, 225,
228, 233, 272 n. 1 (although Meldola's
name is not mentioned in this foot-
note) ; Carl Semper, 74 ; W. B.
Tegetmeier, 79 ; A. R. Wallace, xl n.
3, 3, 6 ; from Hooker to, 74, 74 n. 3 ;
from Huxley to, 4 n. 2, 196.

Darwin, Erasmus, theory of evolu
tion of, 98 ; use of term 1 acquired ' by
(1794), 140, 141 ; on effect of parental
imagination on offspring, 186.

Darwin, Francis, on influence of
Fleming Jenkin upon Charles Darwin ,

4i6 ANALYTICAL INDEX

xl n. 3 ; on Charles Darwin's work on
heterostyled plants, 90, 91 ; on the
Knight-Darwin Law, 92 ; J. C.
Prichard as an evolutionist, con-
sidered by A. C. Seward and, 174
n. 2, 175 n. 1.

Darwin, Sir George, on the life of
the sun, 15 ; on trunks of fossil trees,
18, 19.

Darwin-Wallace theory and the
joint essay (1858), 95-7, 194-6: see
also xxxvii n. 2, 48, 58, 200, 222, 379.

Darwinian Theory, see Natural
Selection.

Darwinians and Mutationists,
essential difference between, xxxviii.

Darwinism, A. R. Wallace, 92,
93, 226, 362, 380.

Darwinism, parodies of, 102-4.

Davidson, note of, on nest of
Microhierax containing insects'
wings, 290, 291.

Davis, Dr. Maurice, J. P., first
perception of significance of Prichard's
writings on heredity by, 174.

Dawnat Range, Burma, 287.

Dawson, Sir William, on Eozoon,
28.

Day, change in length of, 7, 8.

Day-flyingmoths mimicking butter-
flies, 249, 250, 275, 276, 372, 376.

Daylight and cryptic colours,
instincts, &c, 303.

Dead leaves of wet and dry
seasons respectively resembled by
seasonal phases of butterflies, 206,
207,310,311.

Dead Leaves, points in the
Resemblance of Butterflies to,
VII. 203-6 : see also 206-8, 289,
299, 300, 300 n. 5, 310, 311, 322,

351, 353-

Dead leaves, protective (procryptic)
resemblance of moths to, 299, 302 ;
of Locustid to, 302.

Deal, colour of Cleonus on sand-
hills near, 307.

Deccan, doi-ippus f. of L. chry sip-
pus unknown in, 70 n. 2.

Deductive Biology, Sir W.
Thiselton-Dyer, xlvii, xlvii n. 1.

Deep-sea fishes, phosphorescent
lures of, 378.

Deer, Red, recognition marking of,
357.

Definition of Species by
Diagnosis, II. 65-8.

Definition of ' Acquired
Characters', V. 140-4

Definition of instinct, 154.

Definition of Mimicry, 358-61.

Definition of Mutation, xvii,
xvii n. 2.

Degenerate scales of moths, great
size of an element in the loss of, 366.

Degeneration, an older use of,
equivalent to variation, 188.

Degeneration following cessation
of selection, 138; of lost scales
greatest in best moth mimics of
wasps, &c, 365, 366.

deione, Penoa, mimicked by female
f. of E. halitherses, 373.

De l'Afflnite des Langues
Celtiques avec le Sanscrit,
Adolphe Pictet, 173.

Delagoa Bay, attacks of birds on
butterflies witnessed at, 282 n. 1.

Delias eucharis, 269.

Demerara, H. misippus ranges to,
216.

demodocus, Papilio, in stomach of
C oocytes coffer, 283.

de Nice'ville, L., on insects found in
nest of Microhierax, &c, 291, 291 n. 1,
292.

Dentalina in Carboniferous, 27.

Dentalium in early Palaeozoic, 30.

Denudation, rate of, 16.

Deposition of rock, rate of, 16.

Der Gegensatz zwischen
geographischer und niohtgeo-
graphischer Variation,KarlJordan,
84 n. 2.

Descent of Man, &c, Charles
Darwin, 233 n. 1, 379.

Description of some Insects
whioh appear to exemplify, &c,
Rev. W. Kirby, 220.

Desert, general protective resem-
blance to, 297, 298 ; syncryptic resem-
blance to, 312; aggressive resem-
blance to, 312 ; stress of life on, 321 ;
a measure of cryptic resemblance to,
in L. chrysippus, 321.

Development Hypothesis The,
Herbert Spencer, 58.

Devonian Foraminifera, 27 ;
sponges, 28 ; Myriapoda, 34 ; land-
plants appear in, 44 ; appearance of
seed-plants in, 45.

De Vries, Hugo, Evidence in
Favour of Mutation by, Introd.
xvii-xxii ; on the necessity of Natural

ANALYTICAL INDEX

Selection, xviii ; on Oenothera
lamarckiana and Mutation, xix, xx, 4 ;
on intermittent periods of Mutation,
xx ; rediscovery of Mendel's principle
by, xxix; on minute variations in-
capable of permanently raising the
mean of the species, xxxix ; on
Mutation, no.

dexithea, Hypolimnas, probably
ancestral, 216.

Diabrotica, mimicked by Neobro-
tica, Lema, and Dircema, 236, 237.

Diacrisia maculosa, 284.

Diagnosis, Definition of
Species by, II. 65-8; see also sections
and sub-sections, 68-77.

Diagnosis, Linnaean method of,
58, 60; conclusions of provisional,
65, 76, 77 ; transition and, 64, 66, 67,
inadequacy of, 90.

Diagram I, illustrating Pangenesis,
126.

Diagram II, illustrating Continuity
of Germ-plasm, 127, 128, 130-2.

Diagram III, showing develop-
ment of 'identical' twins, 133, 134.

Diaposematic Resemblance,
Reciprocal Warning Colours,

X. 344, 345-

Diaposematic Resemblance, intro-
duction of term, 344 ; illustration
showing advantage of, 330, 331 ;
characteristic of Miillerian mimicry,
344 ; probable between Papilio
and Uraniid moth, 371.

Dicranura bifida, 158, 159; —
vinula, 159.

Dicrurus attacking Lepidoptera,
285, 287 ; unable to find Melanitis,
288, 289.

Dicrurus ater, 285.

Dictionary of Philosophy
and Psychology, J. Mark Baldwin,
73 n. 1, 142 n. 3, 143 n. 2, 312 n. 2,
360 n. 1.

Different Forms of Flowers,

Charles Darwin, xxvii.

Different Models Mimicked
by Male and Female, X. 372.

Different methods of attaining
mimetic resemblance, 250-67, 280.

Differentiating cell-divisions, 133,
135.

Digits, supernumerary, hereditary,
135, 136, 180.

Dimorphism, Diagnosis tra-
versed by Seasonal, II. 72-4.

417

Dimorphism, unique form of, in
larvae and pupae of Zonosoma
(Ephyra) ,150; value of, 310; heredity
in, 310.

Dimorphism and Polymorph-
ism traverse Diagnosis, II.
70-2.

Dimorphism and Polymorph-
ism in Procryptic Defence, X.
310.

Dimorphism and Polymorph-
ism in Mimicry, X. 354-6.

Dimorphism and Polymorphism,
common in mimetic species, 354;
apparent strong support to Batesian
mimicry of, 354 ; facts of, also con-
sistent with Miillerian interpretation,
354, 355, 356; advantages of, in
mimicry, 372 ; examples of, 372-5.

Dimorphism and trimorphism in
both model and mimic, 355, 364, 365
n. 1.

Dimorphism, Seasonal in
Procryptic Defence, X. 310-12.

Dimorphism seasonal in butterflies,
206-11, 339-42.

diocletianus ( r/iadamant/ius ),
Danisepa, mimicked by female f. of
E. halitherses, 373.

Dipnoi, 26.

Diptera (see also classification of
examples of mimicry, 390-3) : minute
changes more evident in Lepidoptera
than, 52 ; W. S. Macleay on resem-
blance to Hymenoptera of, 220;
Kirby and Spence on mimicry of
bees by Volucella, 221 ; preferred to
butterflies by lizards, 286 ; wings of,
in nest of Microhierax, 291 ; pro-
bably not aggressive mimics of
Hymenoptera, 378 ; probably at-
tracted by flower-like lures of lizard,
378.

Dircema mimicking Diabrotica,
237.

Directive Marks and
Structures, X. 325,326; Seasonal
Development of, X. 326.

Directive marks and structures
evidence of value of, 210, 281, 282;
value of movements to, 2S2 ; frequently
injured as if by enemy, 281, 282 ;
difficulty in the classification of :
may be aposemes or pseudosemes
(pseudaposemes or pseudepisemes),
325, 325 n. 1, 326 ; in hind wing of
Protogo7iius, 351.

POULTON

418 ANALYTICAL INDEX

dirtea, Sy?nphaedra, wing of, in nest
of Microhierax, 291.

Discina, persistence of, in time, 43.

Discontinuity, definition of con-
tinuity and, xiv ; the origin of specific,
xv, xvi ; importance of geographical
distribution for the study of, xvi ;
judgement of subjective, xvii ; colour
and, xvii ; as a test of species, 66, 67.

Discontinuous or Continuous
Evolution, Introd. xiv-xvi.

Discriminating features even in
closest mimicry, 349, 350 ; possible
meaning of, 350. 358.

Discussion on Acquired Char-
acters (1889), 164 n. 1.

Discussion on Species, In-
sects ESPECIALLY FITTED FOR, II.
50-4.

Discussion on Species, Intro-
duction to, II. 63-5.

Disease, germs of, 120, 121 ; when
germ-caused, not hereditary, 1 36, 1 84 ;
acquired, not hereditary, 136 ; blasto-
genic origin of certain, 136 ; non-
transmission of constitutional effects
of, 182-4.

Dismorphia orise, 240, 265, 266.

Dismorphina (Pierinae), mimicry
of Ithomiinae by, 239, 240, 265, 266 ;
retention of old Pierine character by
males of, 239, 240 ; sexual brands of
males of, 240 ; T. Belt on epigamic
use of white patches in males of, 240.

Distance, importance of, in mode
of defence, 319 ; effect of, on apparent
size, 366.

Distant, W. L., on dorippus f. of
L. chrysippus in S. Africa, 71 n. 1.

Distasteful, see unpalatable.

Disuse, apparent inherited effects
of, due to cessation of Natural Selec-
tion, 137, 138.

Diverse Ways of production
of Mimicry, &c, between Insects
of various Orders, VIII. 250-61 ;
between Insects of the same
Order, VIII. 261-7 • see also 280.

Diurnal models mimicked by
diurnal members, even of nocturnal
groups, 249, 250 ; moths mimicking
butterflies, 249, 250, 275, 276, 372,
376 ; hours of procryptic defence, 303.

Dixey, Dr. F. A., on mutation and
continuous evolution, xxxviii, xxxix;
on species, 56 ; on word ' species
62 n. 1 ; support to Mtillerian theory

by, 213, 223, 328, 343-5 ; on Reci-
procal Mimicry (Diaposematism),
213, 344, 345 ; memoirs in support of
Mullerian theory by, 213 n. 1 ; on
Mullerian mimicry in Pierinae, 262 ;
on homologous markings of the
Vanessidae, 277 ; results obtained by,
quoted in Essay X, 293 : see also
viii ; on choice of resting-sites by
butterflies, 301, 301 n. 6 ; on Melan-
ism, 310 n. 1 ; on seasonal changes
in the Pierinae, 311, 312, 312 n. I ;
on epigamic and aposematic smell in
African butterflies, 316, 317, 317 n. 1 ;
on Mi?netic Attraction, 328 n. I ; on
wet and dry forms of Byblia gotzius
and B. ilithyia, 341 ; on seasonal
forms of Teracolus regina, 341 ; on
Mullerian mimicry in its relationship
to the seasonal changes of Pierinae,
341, 342 ; on secondary Mullerian
mimicry, 345 ; on combination of
procryptic and mimetic colouring in
Pierinae, 350 ; general applicability
of Wallace's third condition to
Mullerian mimicry controverted by,
362 ; on female mimicry Mullerian
no less than Batesian, 362 n. 2 ; on
the Papilio- Euterpe Mullerian asso-
ciation, 362 n. 2.

Dixon, Professor A. F., and G. Y.,
on habits of Hyas coarctata, 314,
314 n. 1.

Dog, origin of, 83, 83 n. 2; Prichard
on the production of breeds of by
selection, 186 ; Blumenbach on mul-
tiple origin of, 188.

Doleschallia, resemblance to dead
leaf of, 205.

Doliops curculionoides, 261 ; — geo-
7netrica, 261.

Doliops (Lamiidae) mimicking
weevils, 250, 261.

Domestic races, probable immense
importance of Mendelism in, xxxv ;
widely different, 76 ; Darwin's view
of two or three species combined in,
79 ; artificial selection and, 83 n. 2 ;
suggested origin from two or more
wild species, 83-4 ; recognition by
J. C. Prichard that artificial selection
has produced, 174, 186; fertility
between, 201 : see also 77-80.

Domestication,reduction of sterility
by, 79> 83, 83 n. 2.

Dominant and recessive characters,
xxx-xxxiii.

ANALYTICAL INDEX

419

dominicanus, f. of A manris niavius,
3. dominant model in E. Africa, 336 ;
replaced by type f. of niavius at
V. Nyanza, 68, 69, 338 ; correspond-
ing changes in Papilionine and
Nymphaline mimics, 338 ; mimicked
by hippocoon female f. of E. and S.
Pap. dardanus, 374, 375 ; and
roughly by the trimeni female f. of
two sub-sp. of Pap. dardanus, 374
n. 2.

domuncula, Suberites, carried by
Pagurus cuanensis, 357.

Dorfmeister on seasonal changes
of Lepidoptera, 311.

dorippns (=klugii),i. of Limnas
chrysippus, distribution of, 70, 71 ;
suggested interpretation of, as pro-
cryptic adaptation to desert, 321,
321 n. 1.

Dormouse, value of tail of, 325.

doubledayaria, a black mutation
of A. betularia, 309.

Draconia rusina, 302.

Dragon-flies, great size of Car-
boniferous, 18, 37 ; attacked by bee-
eaters, 287 ; wings of, in nest of
Microhierax, 290, 291 ; attacking
specially defended insects, 318.

dravidarum, Papilio, mimicking
Crastia core, 372.

Driesch, experiments of, on egg of
Sea-urchin, 130.

Drone-fly, see Eristalis, 243-4.

Drongo capturing butterflies, 283,
284 ; capturing and rejecting dis-
tasteful moths, 284.

Drurya, see Papilio, 366.

Dry season a time of special stress,
148, 208-11, 31 1, 317, 320, 326 ; form
of butterflies' wings in, 206, 207, 310,
311 ; butterflies of, especially well
concealed, 207-11 ; cryptic forms of
Precis in, 208, 320, 339-41 ; butter-
flies of, prone to hybernate, 209 ;
more alert and active, 209; life of
the, 209 ; eye-spots withheld in, 210,
2ii) 326; warning colours less
developed in, 317; concealment
necessary in the, 320 ; the desert
a permanent, 321.

Dryness, see External Causes.

Dime, near Heligoland, colour of
grasshopper in, 307.

Durban, Natal, 52 n. 1, 71 n. 1,
72, 72 n. 1, 283.

Dynamic Conditions, rapid colour

adjustment a response to, 304, 305 ;
syntechnic resemblance caused by
similarity in, 312.

Ears and tails, mutilations of, not
hereditary, 180, 181.

Earth, Age of the, Essay I,
1-45.

Earth, changing shape of, 8 ; rota-
tion and shape of, 8, 9 ; cooling of,

9- 13 ; conductivity in interior of,

10- 13 ; higher density of interior of,
11 ; protective (procryptic) resem-
blance to colour of, 155,298,307,318,
323 ; allanticryptic use of, by Cerato-
p/irys, 313.

Earthworms, 27.

East Africa, see Africa East.

East Brazil, see Brazil East.

Eastern Origin of the Celtic
Nations, J. C. Prichard, 173.

echeria and albimaculata, Amau-
ris, Natal mimics of, in Hope
Department, 249 ; Western Amauris
mimicked by, 335, 337; dominant
models in E. Africa, 336 ; mimicked
by cetiea female f. of three sub-sp. of
P. dardanus (merope), 337, 338, 355,
374 ; by female of Pap. echerioides,
375-

echerioides, Papilio, female of,
mimicking Amauris albimaculata
and echeria, 375.

Echinoderm (Echinus), Driesch's
experiments on egg of, 130.

Echinoderma, 25 ; small advance
in geological time of, 28 ; of early
Palaeozoic, 30 ; early records of all
except Holothurians, 43 ; earliest
forms of, not primitive, 43 ; classes
of, in Cambrian, 43.

Echinoids in early Palaeozoic, 30.

Echis carinata, 324.

Ecuador, Bolivia, and Peru, colours
of the chief Ithomiine-centred com-
bination in, 351.

Ecuador, form of Methona confusa
and Pierine mimic in, 265, 266.

Edinburgh, J. C. Prichard an M#D.
of, 173.

Edinburgh Review, 56, 66.

'Educability ' a hereditary congeni-
tal character, 165 ; as opposed to
instinct, 165, 166.

Education, results of, not here-
ditary, 136, 165, 166-7; value of

e e 2

ANALYTICAL INDEX

research in, 198, 199; of enemies
facilitated by warning colours and
Miillerian mimicry, 166-8, 212-15,
222, 278, 327-31, 339-

edusa, Cohas, choice of resting-
site by, 301.

Ega, Upper Amazon, colour of the
chief Ithomiine-centred mimetic com-
bination at, 273, 351.

Egg, individual characteristics pre-
determined in the, xxxvi, xxxvii,
xxxvii n. I, 132-5, 183.

— Experiments, &c., on, by Roux,
128-30 ; T. H. Morgan, 129 ;
Hertwig, 129 ; Schulze and Wetzel,
129; Herlitzka, 130; Driesch, 130;
J. W. Jenkinson, 130 ; Boveri, 131.

— Diagrams of development of,
described, 123-8, 130-4.

Eggs of 5. ocellatus, derived
chlorophyll in, 314, 314 n. 2.

Eimer, Prof. G. H., on Natural
Selection not creative, xxii ; on in-
stincts of Fossorial Hymenoptera,
162 ; on internal causes of mimicry,
224.

Elaps mimicked by harmless
snakes, 367.

Elephant Hawk moth, see elpenor,
Choerocampa, 319, 326, 367-8, 376.

e/giva, Precis, under side pro-
cryptic in both wet and dry seasons,
340 ; S. African habitat of, 340.

eliminata, Sarangesa, captured by
Bradyornis mariquensis, 283.

Elimination of shadow, Thayer's
discovery of the, 299, 300 ; adjust-
able form of, 300 ; in aggressive
resemblance, 313.

elpenor, Choerocampa, transition
from cryptic to pseudaposematic
defence in larva of, 319, 368; proof
of terror inspired by snake-like larva
of: superstitious fear of, 367, 367
n. 2 : see also 326 ; lizard terrified by,
but ultimately devoured larva of, 367 ;
mimetic resemblance of Batesian,
367, 376.

Elymnias caudata, 373 ; — cot-
tonis, 373, 373 n. 2 ; — {Melynias)
/ais, 353 ; — leucocyma {Melynias
malelas), 372 ; — undularis, 373.

Ely?nniinae (see also Elytnnias :
see also classification of examples of
mimicry, 284-8) : often united with
Satyrinae, 353; almost every species
of, mimetic, 353 ; females, except in

Africa, often better mimics than males,
353; under surface sometimes mimetic,
sometimes procryptic, 353 ; a few
species of, aposematic or doubtful, 353;
R. Shelford on habits of Bornean
E. lais, 353 ; compared with Proto-
gonius, 353, 354; mimetic common
ancestor of genus suggests Miillerian
interpretation, 354 ; latter interpreta-
tion merely tentative, 352.

Elytra, reduction of, in mimetic
Longicorns, 252.

Embryo, inoculated by disease
germs, 136.

Embryology, unreasonable dis-
paragement of, by Bateson, xlii, xliii ;
experimental, 128-30.

Empire and science, 169.

encedon, Acraea, three forms of,
mimicking three forms of L. chrysip-
Pusi 355 1 three forms of mimic
transitional, while two out of three
corresponding forms of model are
sharply marked off, 364, 365 n. 1 ;
alcippina f. of, perhaps developed in
W. Africa as mimic of alcippus f. of
L. chrysippus, 364.

Encyclopaedia Britannica, 173,
293.

Endromts versicolor, 238.

Enemies of Lepidopteroua Pu-
pae enclosed in bark-formed
Cocoons, E. B. Poulton, 159, 159 n. 1.

Enemies (see also birds and evi-
dence): of pupae in cocoons, 158, 159;
education of, helped by insect warn-
ing colours and Miillerian mimicry,
166-8, 212-15, 222, 278, 327-31, 339,
366 ; effect upon insects of struggle for
life in young, 167, 167 n. 2, 168, 328 ;
of insects in the dry season, 209 ;
confused and attention diverted by
bright hind wings, 303, 304 ; animals
with warning colours attacked by
special, 317, 318 ; not deceived when
model and mimic occupy different
stations, 349 ; judgement of relative
size by young, 366 ; hardness com-
pared with other defences against,
37o.

English colonists unchanged after
many generations in the tropics, 178.

Entebbe, V. Nyanza, hermaphro-
dite planemoides, female f. of Pap.
dardanus, taken at, 374 n. 3.

Enterozoa (Metazoa), place of, in
classification, 25.

ANALYTICAL INDEX

421

Entomological Society of Lon-
don, Proceedings of, 46, 89, 89 n. 1,

139, 153 n. 1, 156, 157 n. 1, 167, 205,
206, 207, 212, 213 n. 1, 216 n. 1, 223,
232, 239, 273, 301, 302, 303, 312 n. 1,
317, 325 n. 1, 328, 328 n. 1, 332, 340,
341, 343, 344, 35o n. 1, 356, 358,
358 n. 1 and n. 2, 363, 366, 367 n. 2,
368, 372 n. 1, 374 n. 3.

Entomological Society of Lon-
don, Transactions of, 57 n. 1, 72,
93. 149, 150, 156, 210, 213 n. I, 217,
236, 269, 270, 270 n. 1, 276, 277,
282, 299, 300, 301, 302, 303, 304, 304
n. 3, 306, 307, 308,311,317,318, 320,
321,321 n. 1, 322, 328 n. 1, 331, 335,
339 n. 1, 340, 341, 343, 344, 345,
346, 348, 35i n. 2, 354, 355, 362, 362
n. 2, 364, 365 n- 1, 367 n. 2, 368-70,
373, 374 n. 3, 378, 380.

Entomological Society of Lon-
don : Author's Presidential Ad-
dresses, 1903, 1904 (read 1904,
1905), the original forms of Essays
II and V respectively, 46, 139;
Roland Trimen's Presidential Ad-
dresses, 1897, 1898 (read 1898, 1899),
89, 89 n. I, 90, 232 ; the Empire and,
169 ; consent of Council for repub-
lishing direct evidence of attacks of
birds on butterflies, 283 ; examples
of Miillerian Mimicry exhibited by
W. H. Blandford at, 343, 356 n. 1 ;
argument that Protogonius and
Elymniinae are Batesian mimics at,
351, 372 n. 1.

Entomologist's Monthly Maga-
zine, 57 n. 1, 157 n. 1, 207 n. 1 and
n. 2, 300, 325 n. 1, 341.

Entomologist's Record, 216 n. 2,
239 n- 1| 3°9 n« 1, 366 n. 1.

Entomostraca in Silurian and
Cambrian, 39.

Entwickelung von Ascaris
megalocephala, Boveri, 131.

Environment, Organism pro-
bably Adjusted to, by Local
Natural Selection, X. 307, 308 :
see also 308-10.

— Environment (see also External
Causes and uniformity) : effect of,
on organisms, 73-5 ; susceptibility
to, 106, 145 ; effect of, on germ-cells,
137 ; influence of, 145 ; organic and
inorganic, 153, 154; lines of pattern
parallel to shadow lines of, 156, 301 ;
evolution transferred from man to,

170, 171 ; incidence of conditions of,
determined by life-history, 243, 244,
276, 277 ; effects of colour of, on
insects, &c, 305-10 ; mimicry be-
tween models interpreted by H. W.
Bates as the effect of a common, 327.
Eozoon, 27.

Ephemeridae (Protoephemeridae)
of Commentry Carboniferous, 37.

Efihyra, see Zonosoma, 1 50.

Epicopeia philenora. 371.

Epigamic Colours, X. 379, 380.

Epigamic characters (see also
Sexual Selection) : place of, in a
scheme of the bionomic uses of
colour, 226, 227 ; pleasant smell of
male butterflies as, 316, 317 ; of Attid
spiders, 380 ; of grasshoppers, 380 ;
often concealed except in courtship :
only exist under conditions of visi-
bility : commonly closely associated
with nervous system : display most
marked when sexes unlike, 380 ;
Wallace's interpretation of, 380 ; ex-
ceptional in heredity, 380 ; of one sex
latent in the other, 380 ; effect of
castration on latent, 122, 380.

Epigonic evidence, need of, 90.

Epigony, definition of, 61,61 n. I ;
the appeal to, 62, 64 ; as test of
species when diagnosis fails, 69 ; in
Limnas chrysippus, 70, 71 ; in P.
dardanns, 72, 72 n. 1 ; in seasonal
dimorphism, 72-3 ; the test of specific
identity when differences are great,
76 ; importance of, to the systematist,
77-

Episematic and Aposematic
Characters, X. 315-58. For divi-
sions, sections, and sub-sections, see
294-6 : see Sematic characters.

Episematic or Recognition
Characters, X. 357, 358 : see
Recognition characters.

Equivalent cell divisions, 133, 135.

Eristalis, a mimic of hive-bee,
243-4 ; food of larva of, contrasted
with that of bee, 244.

erithonius, Papilio, eaten by bee-
eater, 288 ; wing of, in nest of
Microhierax, 291.

Ermine, aggressive seasonal change
°f, 3I3-

Eronia, combination of procryptic
and mimetic colouring in, 350, 350
n. 1.

Eronia cleodora, 283, 301.

422

ANALYTICAL INDEX

Erroneous Assumption that
Warning Colours imply Com-
plete Immunity from Attack,
X. 317, 318.

Erycinidae, darkening of mimetic
in the Guianas, 272 ; mimics be-
longing to, are probably Mullerian,
273 : see also 346 ; Dixey's dis-
cussion of entrance into Mullerian
combinations of, 343; mimicking
Ithomiinae and mimicked by diurnal
moths, 346.

esebria, Acraea, two forms of female
mimicking Danainae, 354, 355 ; ad-
vantages of this dimorphism in, 355.

Essay on Fertilization, Prof.
Marcus Hartog, 60 n. 3.

Essays on Natural Selection,
A. R.Wallace, 51 n. I, 203, 367 n. 1,
369.

Essays, Scientific, Political, and
Speculative, Herbert Spencer, 7 n. 1,
58 n. 1.

Essays upon Heredity, August
Weismann, xxxvi, xxxvii, xxxvii n. I,
60 n. 3.

Essential Nature of Mimicry,
&c, as shown by analysis, viii.
240-2.

Essential Element in Mimic-
ry, X. 359-61.

Esthesinae, mimicry of Hymeno-
ptera by, 252.

Estigmena chinensis, 261.

Estigmenida variabilis, 261.

Ethiopian Region (see Africa) : the
study of mimicry should commence
in, xxv, xxvi, 336.

Ethiopian and Eastern hawk-moth,
attainment of transparency by, 365.

etrida, Teracolus, mimicked by
Abraxas etridoides, 231 ; inhabits
station different from that of its
mimic, 349.

etridoides, Abraxas, mimicking
Teracolus etrida, 231 ; inhabits
station different from that of its
model Teracolus, 349.

Etudes d'Entomologie, Monsieur
Charles Oberthur, 69, 381.

eucharis, Delias, proved to be
unpalatable, 269.

Euchelia jacobaeae, 230, 318.

Euderces picipes, 255 (Fig. 4), 256.

Eueides, 235.

Eueides nigrofitlva, 332.

Eugonia quercinaria, 149, 150.

Eumenes, species of, resemble
other Hymenoptera in Australia,
278.

Eupatorium macrophyllum, 322.

Euploea captured by Ashy swallow-
shrike, 286 ; not attacked by bee-
eaters, 288 ; mimicked by female
Hypolimnas, 241, 372 ; limit to con-
spicuousness of, 322.

Euploeini (see also Euploea'. see
also classification of examples of
mimicry, 384-6, 388-9) : Danaini
compared as models with, 333-5 ;
range of Danaini compared with, 333,
334 ; mutual mimetic influence of
Danaini and Euploeini compared,
334) 335 I dominance over Danaini in
areas where both meet, 333-5 ; homo-
geneity of, compared with Danaini,
333 ; abundance of, 334 ; probably
not more unpalatable than Danaini,
334 ; uniformity throughout many
species of, 277, 333-4 ; the chief
models of the Eastern Elymniinae,
353 ; possible role of male scent-
brands of the, 334 n. 1, 358.

Euralia, see Hypolimnas.

Euripus probably a distasteful
genus, 373 ; mimicry in, 373.

Euripus halitherses, 373.

Europe, mimicry in Araschnia of,
342.

Eusemza falkensteinii, 232.

eutolmus (coerulescens), Micro-
hierax, 289-91.

Evans, Dr. Arthur J., assistance
in terminology rendered by, 61 n. 1.

evenina, Teracolus, Mullerian
mimicry in dry f. chiefly, 342.

Evening Primroses, as the evidence
for mutation in nature, xix-xxii.

Evidence of Special Protec-
tion in Aposematic Forms, X.
316, 317.

Evidence, Indirect, Support-
ing Mullerian Mimicry, X. 346,
347.

Evidence, Recent, in Support
of Batesian Mimicry, X. 350-6.

Evidence, Confirming History
Inferred from Mimicry, X. 365,
366.

Evidence adduced by De Vries in
favour of mutation, xvii-xxii ; indirect
for mimicry, 271 ; of distastefulness
in mimicked butterflies, 269, 279, 279
n. 1 ; of advantage conferred by

ANALYTICAL INDEX 423

mimicry, 269, 281, 288: see also Finn,
F. ; of distastefulness in larva of C.
verbasci, 318.

Evidence of attacks on butterflies by
birds, insufficient, 268-70 ; reasons
for insufficiency, 270, 282.

— Of actual attack by G. A. K.
Marshall, 282-4 ; by E. Penard,
282 n. 1 ; by F. Muir, 282 n. 1 ;
by Col. J. W. Yerbury, 283, 285,
286 ; by Col. Bingham, 283, 286-
90; by C. F. M. Swynnerton, 283,
284. Indirect evidence obtained by
Davidson, 290, 291 ; by Ferguson,
292.

— From following localities :
S. Africa, 281-4 5 Geneva, 282 n. 1 ;
E. Africa, 282 n. 1 ; Malvern, Dur-
ban, Natal, 283; Salisbury, Rhodesia,
283, 284 ; Gazaland, 284 ; Melsetter,
Gazaland, SE. Rhodesia, 284 ; India :
Thundiani, Kala Pani, 285 ; Cey-
lon, Kandy Road (Trinkomali to
Kanthalai), 285, 286 ; Burma, 286-92 ;
Akya Chaung (branch of Haundraw
R.), Kawkaraik to Thinganyinaung,
286-8 ; Wabosakhan Camp, 288,
289; Salween R., below Shwegon,
289 ; Sinzaway Chaung (branch en-
tering Yoonzaleen R., below Pah-
poon, Tenasserim), 290; Banka-
soon, S. Tenasserim, 290 ; Thabeit-
kyin to Mogok, Upper Burma, 291
n. 1 ; Travancore, 292 ; direct evi-
dence only obtained at the first-
named Burmese localities : excellent
indirect evidence at the others : for
indirect evidence see also 270, 270
n. 1, 281-3, 304, 325, 325 n. 1.

Evolution Theory, A. Weismann,
164 n. 2, 375.

Evolution Continuous or
Discontinuous, Introd. xiv-xvi.

Evolution, Antagonism Pro-
moted between Studies all
Needed for Attacking Problem
OF, Introd. xli-xliv.

Evolution, Theories of, Essay
III, 95-119.

Evolution, Remarkable an-
ticipation of Modern Views on,
Essay VI, 173-92.

Evolution of Chief Charac-
teristics of Mimicry, X. 362, 363 :
see also Essays VIII and IX.

Evolution (see also Natural Selec-
tion).

— Bateson's statement of the
problem of, xxxiii, xxxiv ; little help
afforded by Mendelism in solving the
problem of, xxxiii-xxxv; by minute
variation is not Mutation, xxxviii,
xxxix ; uselessness of teratological
phenomena for, xxxix, xl ; slowest
in lower branches of animals, 27-31 ;
most rapid in highest, 29 ; of nervous
system rapid in higher animals, 29 ;
evidence of trend of in pre-Cambrian
time, 31-3 ; within higher animal
phyla, 33-42 ; of insects' wings, 36,
37 ; of Appendiculata, 33-41 ; Arthro-
poda, 33-41; Myriapoda, 34; Insects,
34-8 ; Crustacea, 39, 40 ; Arachnida,
39-41 ; Mollusca, 41, 42 ; Gastro-
poda, 42; Cephalopoda, 42 ; Lamelli-
branchiata, 42 ; Gephyrea, 42, 43 ;
in land-plants, 44, 4$ ; evidence of
will be furnished by museum collec-
tions, 53 ; ancient writers on, 54-6 ;
influence of Milton on, 55, 56; Aubrey
L. Moore on, 54-6 ; Huxley on belief
in special creation, 56 ; Aristotle and,
56 ; contrasted with special creation,
58 ; effect on systematic work of
belief in, 59 ; Asyngamy and, 65,
81-91 ; Asympatry and, 84, 85 ;
Mechanical Selection and, 85 ; Pre-
ferential Mating and, 85-8 : see also
65 ; breaking of Syngamic chain and,
88-90 ; Darwin's metaphor of tree
for, 94 ; Darwin-Wallace theory of,
95-7 ; necessarily follows from factors
of selection, 96 ; Lamarck, Erasmus
Darwin, H. Spencer, theory of, 97-9 ;
belief in innate tendency towards,
100; belief in unknown cause of,
101 ; Lamarck's theory of, appre-
hended easily, Darwin's with great
difficulty, 101-4 ; parodies of, 103,
104 ; utility and, 105-9 ; in brain,
107, 108 ; Palaeontology and, 107,
108 ; selection a true cause of, 109,
no; Mutation and, no: see also
Introduction, especially xiv-xvi,
xvii-xxvi ; of actively used structures,
112; of passive structures, 112; of
joints, 112, 113, 115; of combined
active and passive structures, 113; of
cocoon-making instincts, 1 17-19, 160 ;
of social Hymenoptera, 165 ; Lloyd
Morgan on the trend of human, 170,
171 ; J. C. Prichard on, 174; Huxley's
views on before the Origin, 199,
200 ; Huxley's defence of, 219 ;

424

ANALYTICAL INDEX

belief in, because of consistency with
facts, 268 ; of Miillerian resemblance,
329-31.

Examinations, injurious results of,
197-8.

Examples, Striking, of Mul-
lerian Mimicry in New and Old
World, X. 331-6.

Examples, Remarkable, of
Mimicry, X. 367-9.

Example, Remarkable, of
Mimicry in Papilio dardanus
(merope), X. 373-6-

Excrement of bird, protective
resemblance to, 319.

Exercise, results of, not hereditary,
136.

Existence, struggle for, and selec-
tion, 96.

Experience, bearing of Insect
Mimicry, &c, upon supposed
Hereditary Transmission of,
V. 166-8.

Experience, the Lamarckian inter-
pretation of instinct as inherited, 116,
154-66; dangers to insects of, 117,
118, 154-7; not hereditary, 166-8,
316 ; must be acquired by insecti-
vorous birds, 268, 269.

Experimental Proof of the Pro-
tective Value of Colour and
Markings in Insects in reference
to the Vertebrate Enemies (1887),
E. B. Poulton, 230.

Experimental Evidence of
Special Protection in Apose-
matic Forms, X. 316, 317.

Experimental embryology, 128-30.

Experiments, on birds with dis-
tasteful insects, see Finn, F., 269;
on Artemia, 73, 74 ; on power of
colour adjustment in larvae and pupae,
305-7 ; on seasonal forms of Selenia
illunarict) 3 1 1 ; of Teracohcs omfihale,
311, 312; of — achine, 311, 312;
of Belenois severina, 311, 312; of
Precis, 340 ; of Byblia, 341 ; on
winter change of Hudson's Bay
Lemming, 310.

External Causes (food, climate,
soil, &c.) as suggested interpretation
of mimicry, 224, 272 ; the theory
most commonly substituted for
natural selection as cause of mimicry,
267, 272 ; theory of, requires trans-
mission of acquired characters, 267 ;
belief in theory of, due to too exclu-

sive study of butterflies, 229, 272, 273 ;
obviously inapplicable to mimicry
between remote species, 229 ; mimicry
a special case of protective (pro-
cryptic) resemblance, and yet the
latter clearly cannot be due to, 226-
8 ; various objections to, 227, 229,
233, 235-42, 244, 245, 248-50, 260-3,
266-8, 270, 273-82.

Extinction, belief in innate ten-
dency towards, 100.

Eye, importance of, in rapid colour
adjustment, 305.

Eye-like spots on abdomen of
mimetic spider, 368 ; of Choerocampa
caterpillars, 326 ; of Brassolinae,
326.

Eyes of diurnal beetles different
from nocturnal, 250.

1 Eye-spots 1 or ' ocellated spots '
in wet season broods of Satyrinae
and Nymphalinae, 210, 211, 326;
examined by lizard, 210; pecked by
kestrel, 210; concealed during pro-
longed rest, 210; divert attention
from vital parts, 210, 325, 325 n. 1,
326 ; of butterflies' wings, value of,
281, 282; of Brassolinae, 326; of
Morphinae [Tenaris), yid ; of Papi-
lioninae, 326 ; Pseudaposematic in
snake-like larvae, 326 ; absent from
the chief distasteful butterfly groups,
326 ; difficulty in the bionomic classi-
fication of, 325, 326.

Eyton, on fertile pairing of two
species of goose, 83.

F.A., criticism of mimicry in
Punch by, 213-15.

Fabre, on the instincts of Fossores,
118; on instincts of Fossorial Hymen-
optera, 160, 162 ; Lamarck appar-
ently confused with Darwin by, 162.

Facets of eyes of diurnal beetles
smaller than nocturnal, 250.

Factors of Lamarck's theory, 98,
99-

Factors of Natural Selection, 95-6;
suggested by name itself, 105.

fagi, Stauropus, mimicry of ant by,
253> 253 (Fig. 2), 254; composite
mimicry by larva of, 369.
Falconet, 289-91.
Falco subbuteo, 284.
fallax, Myrmecophana, mimicry of,
256, 257, 258 (Fig. 5), 280.

ANALYTICAL INDEX 425

falkensteinii, Eusemta, Mullerian
mimicry of L. chrysippus by, 232.

False warning and signalling
colours, 226 : see also PSEUDO-
sematic Resemblance and its sub-
divisions, 296, 297.

Families, in classification, subjec-
tive, 65.

Farmer, Professor J. B., on ex-
planation offered by Natural Selec-
tion as a bar to inquiry, xliv-xlvii, xliv
n. 1 ; on stimulus and mechanism,
74 n. 2.

Fawcett, Henry, and Natural Selec-
tion, 96.

Female parent, Prichard on the
supposed influence of, on offspring,
185-6.

Female often better concealed
than male, 246.

Female Catophaga (Pierinae), yel-
low f. of, specially attacked by bee-
eater, 285.

Female preferences, 379.

Female, Mimicry, &c, less
characteristic of male than,
VIII. 244-7: see also 215-17, 279,

347, 353> 372-5.

Female Mimetic: Male Non-
Mimetic, examples under this
heading, X. 372.

Female Mimicking Two or
More Different Species, Male
Non- Mimetic or Mimicking
still Another Species, examples
under this heading, X. 373 : see also
dardanns.

Female, except in mimicry, more
ancestral than male, 245-6; advantage
of mimicry in, 246, 279; tendencies
of non-mimetic males of mimetic,
347-

' Ferns ' of Palaeozoic, mostly seed-
plants, 45.

Fertility, kept up by selection, 81,
82 ; of certain hybrids, 83, 84 ; pro-
moted by domestication, 83, 84 ;
between domestic breeds, 77-84, 201.

Fertilization or zygosis, xxxi ;
inferences as to precursors (Allelo-
morphs) of Mendelian characters in,
xxxi-xxxiii ; syngamy proposed by
Hartog to replace, 60 n. 3 ; zygosis
proposed for, 60 n. 3 ; essential nature
of, 80-2 ; self-, cause of injurious
effects of, 91-4 ; the union of germ-
plasm from two individuals, 127, 128.

Fertilized germ or zygote, Men-
delian inferences as to, xxxi-xxxiii.

Final Causes, W. Whewell on the
study of, as a stimulus to inquiry,
xlvi n. 1.

Finn, F., on education of birds,
167 ; conclusions of, on distastefulness
of butterflies, 269, 317; on evidence
of distastefulness in mimicked butter-
flies, 269, 279 n. 1 ; results obtained
by, quoted in Essay X, 293 ; on
unpalatability no defence against
hungry enemies, 269, 317, 317 n. 4.

Fish, in early Palaeozoic, 30 : see
also 26 ; rapid colour adjustment in,
305 ; defence of Hyas against large,
314; small, attracted and devoured
by Hyas, 314 ; alluring structures in,
378 ; attracted by lures of Ceratias,
378 ; heightened colouring accom-
panies other excitement as well as
sexual in, 3S0.

Fishing-Frog or Angler, bright
lure of, 378.

F/atidae, colony of, resembling
flowers and buds, 304, 304 n. 3.

Fleece, changes of, in tropics, 190.

Fleeming Jenkin, on the swamp-
ing effect of intercrossing on single
variations, xl, xli ; influence upon
Darwin of arguments of, xl, xl n. 3, 3.

Flies, see Diptera.

Flight slow in distasteful butter-
flies, 279, 323 ; of certain Danainae
displays under surface, 323 ; Heli-
conine mimics of Ithomiinae distin-
guished by, 331, 331 n. 1 ; difference
between model and mimic in, 349.

Floras of the Past : their Com-
position and Distribution, Prof.
A. C. Seward, 44.

florella, Catopsilia, captured by
Halcyo7i chelicutensis, and probably
by Buchanga assimilis^ 283.

Florida, H. misippus ranges to,
216.

Flos Retinae, Lagerstroemia, nest
of Microhierax in, 290.

Floor of the ocean, 20-2.

Flower-like alluring Mantidac,
378, 378 n. 3 ; appearance of also
procryptic, 378.

Flowers and buds, resembled by
Flatidae, 304, 304 n. 3 ; cryptic
resemblance to, 318; and surround-
ings considered by Thayer to be
resembled by Ithomiines, &c, 322 ;

426

ANALYTICAL INDEX

pseudepisematic (alluring) resem-
blance to, 378, 378 n. 3.

Fly-catcher seen capturing butter-
fly, 283 ; seen chasing Lycaenid, 283.

Foes, see enemies.

Food, climate, &c, as cause of
mimicry, 224, 272 (see also External
Causes) ; concealment effected by
colour of, 314.

Foraminifera in classification, 25 ;
persistence in geological time of, 27,
28.

Forest country in S. Africa, defini-
tion of, 340.

Form,seasonal change of,in butter-
flies' wings, 206-8, 310, 311.

formica, Synemosyna, mimicry of
ant by, 253 (Fig. I B).

Fossils, limited information con-
veyed by, 100, 107.

Fossores (see also classification of
examples of mimicry, 389-93) : in-
stincts of, 118, 118 n. 1, 119, 160-4;
prophetic instinct of, 119, 163, 164 ;
resemblances between other stinging
insects and, 278, 376 ; see also 232.

Foster, Sir Michael, on curiosity
as the true incentive to inquiry,
xlvii ; on indirect methods of nature,
101.

Fowler, Rev. Canon W. W., on
ant-like Membracidae, 258 (Fig. 6),
259.

Fox, Arctic, aggressive seasonal
change of, 313.

France and Lamarck's theory, 98.

France, Sooiete Entomologique
de, Annates, 211, 326; Bulletin,
381,382.

fringillarius, Microhierax, nest of,
290, 291.

Fritillaries, pupae of, 1 52.

Fritillary, resemblance of A. levana
to, 342.

Frog, Roux's experiments on egg
of, 128-30 ; allanticryptic resem-
blance of, 313.

Frohawk on P.phlaeas, 87 n. 1.

From the Greeks to Darwin,
H. F, Osborn, 56 n. 2, 141 n. 1, 175.

Fry, Sir Edward, on definitions of
acquired characters, 143-4.

fuciformis, Haemorrhagia, loss of
scales by, 365.

Fulgoridae of Commentry Car-
boniferous, 36.

Fungi, leaf-attacking, effects of

resembled by butterflies, 205, 206;
by moths and Locustids, 302.

Further Indirect Evidence
supporting a mullerian or
Synaposematic Interpretation,
X. 346, 347.

fuscus, Artamus, capturing Crastia
core, 286.

Fusilina in the Carboniferous, 27.

G

gagates,Polyrrhachis, with ant-like
bug, 254, 255.

Gahan, C. J., on mimicry in Coleo-
ptera, 236, 237 ; on Miillerian and
Batesian mimicry in beetles, 237 ; on
life-history and mimicry, 243 ; on
mimicry of weevils by diurnal Longi-
corns, 250 ; on Longicorns mimick-
ing weevils and Hispidae, 261 ; on
Cingalese Clytinae as models for
other Longicorns, 349.

Galapagos Islands, birds greatly
modified in, 84 n. 2 ; dull colours of
animals in, 225.

Galton, Francis, on ' recession to-
wards mediocrity', 109, 1 10; on trans-
fusion of blood and pangenesis, 125 ;
on 'identical' turns, 132, 134, 135,
138 n. ; on effect of cessation of selec-
tion, 138; definition of acquired
characters by, 143 ; on invisibility of
zebra, 298.

Gametes, see germ-cells.

Ganoid fish in early Palaeozoic, 30.

Garden White butterflies (P.
brassicae and P. rapae), 93, 147, 148,
213, 301.

Gartner on sterility between
selected races, 78.

Gastropacha quercifolia, 299, 307.

Gastropoda in early Palaeozoic,
30; Pteropoda arose from, 41, 42;
evolution in, 42; appear in Cambrian,
42.

Gauchos, skill in killing cattle, 161.

Gazaland, S.E. Rhodesia, attacks
of birds on butterflies, &c, witnessed
in, 284.

Geddes, P., on anabolic and kata-
bolic tendencies, 100-1 ; on internal
causes of mimicry, 224.

Geikie, Sir Archibald, on age of
the stratified rocks, 16, 17 ; on geo-
logical record of time, 19.

Gemmules of pangenesis, 124-6.

Genera subjective, 65.

ANALYTICAL INDEX

427

General Aggressive Resemblance,
312.

General Protective Resem-
blance, X. 297, 298.

General Survey of the Causes
which have Produced Varieties
in the Human Species, &c, J. C.
Prichard, 176-92.

Genetic, see inherent characters,
141.

Geneva, attack of bird on butterfly
witnessed at, 282 n. 1.

genutia, Salatura, see plexipfius,
373'

Geographical Races or Sub-
species Traverse Diagnosis, II.
75> 76.

Geographical Transition
from aposematic to cryptic
Defence, X. 320, 321.

Geographical data, necessity of,
75-

Geographical varieties, Rothschild
and Jordan on importance for evolu-
tion of, xvi ; species and, 62.

Geological Society of Glasgow,
Transactions of, 4 n. 3.

Geological Society of London,
Presidential Addresses of T. H.
Huxley to (in 1869), 4, 5, 6, 8, and (in
1862), 6 ; of H.Woodward to (in 1895
and 1896), 40.

Geology, Darwin's disappointment
at neglect of his early writings on,
196, 197.

geometrica, Doltops, mimicking
weevil, 261.

Geometridae, decline of cocoon in
certain species of, 149, 150; colour
adjustment in pupae of Uropteryx,
150, 150 n. 2; dimorphism in larva
and pupa of Ephyra, 150 ; importance
of attitude in Hybernia, 156 ; elimina-
tion of shadow in larva of, 300 ;
colour adjustment of larvae of, 306 ;
colours in different environments of
moths of, 307-9 ; Teracolus mimicked
by S. Indian species of, 231 : see also
349-

Gepbyrea, in classification, 25 :
see also 27 ; slight changes in geo-
logical time of, 28 ; of early Palaeo-
zoic, 30 ; evolution in, 42, 43.

Germ-antecedents, early appear-
ance of, in Ascaris egg, 131.

Germ-cells or gametes, Mendelian
inferences as to, xxxi-xxxiii ; on the

halving of the nucleus in preparation
for fertilization of the, xxxi ; natural
selection decides between, xxxvi,
xxxvii, xxxvii n. 1, 73 n. 1, 135, 137,
183 ; union in fertilization of, 60 n. 3 ;
compatability of, secured by Natural
Selection, 80-2 ; interspecific sterility
and, 80-2 ; acquired characters and
the, in, 112; distinguished from
body-cells, 121, 122; early appear-
ance of precursors of, in development,
131 ; inoculated by disease germs,
136, 184; influence of environment
on, 137 ; variation predetermined in
fertilized, 137, 183.

Germ-duct, early appearance of
antecedents of, in Ascaris, 131.

Germinal origin of variation,
xxxvi, xxxvii, xxxvii n. 1, 73 n. 1,
135, 137, 183.

Germ-plasm, continuity of, 127-
36 ; illustrated in Diagram II, 127-8,
130, 131 ; resides in nucleus, 128 ; in
development of ' identical ' twins, 1 34.

Germs, Natural Selection decides
between, rather than between indi-
viduals, xxxvi, xxxvii, xxxvii n. 1, 73

n- h 13S, 137, 183-

Gerstaecker on ant-like bug, 254,
255, 255 (Fig. 3).

gibbicolhs, Oxylymma, mimicking
Diabrotica, 237.

Glands ventral of Croesus larvae,
320.

Glaucopidae mimicking Lycinae,
231 ; mimicking Aculeata, 231 ; evi-
dence of distastefulness adduced by
I Haase, 231 n. 2.

Glenea fiulchella, 363.

Gnophos obscurata, 307, 308.

Goats, Angora, J. C. Prichard on,
187.

Godartia wakejieldii, 52 n. 1.

Godman, F. D., on the sexual
brands of the Dismorphina, 240 ; on
! Ecuador form of M. confusa, 266.

Godman-Salvin Collection, exam-
; pies of Miillerian mimicry from, ex-
hibited in 1896 and 1897, 343.

Goodacre on fertile pairing of two
species of goose, 83.

Goodrich, E. S., definition of
inherent characters, 142.

Goose, fertile offspring of Common
and Chinese, 83.

gbtzius (acheloia), Byb/i<i, tendency
of same seasonal forms of, to inter-

428 ANALYTICAL INDEX

breed, 87 ; dry f. of, bred from wet,
341 ; wet f. of, a mimic of A. serena
type, dry f. procryptic, 341.

Gouty diathesis, transmission of,
discussed by J. C. Prichard, 183, 184.

Gradual Predominance of
Mullerian Mimicry, X. 342-4.

Grafted tissues and pangenesis,
125-6.

Grainger, Benjamin, of Derby,
distinction between inherent and
acquired characters suggested to
J. C. Prichard by, 179.

Grammostomum in Carboniferous,
27.

Grand Comoro, non-mimetic Pap.
humbloti in, 373.

Grapta C-albumy 203-5.

Graptolites in Palaeozoic, 28.

Grasses, protective resemblance
to, 307 ; syncryptic resemblance to,
312 ; concealment among roots of,
3i8, 323.

Grasshoppers (Acridiidae)oi Com-
mentry Carboniferous, 36, 37 ;
mimicry of leaf-carrying ants by,
260 ; value of bright hind wings of,
303, 304, 325 ; colour adjustment of,
307 ; observations on the courtship
of, 380.

Gravitation, evidence for, com-
pared with that for Mimicry, xxvi ;
accepted, though nature not ex-
plained, 97 ; accepted because con-
sistent with the facts of the Cosmos,
219, 271.

Gravity, Effect on Shape of
Pupae of, V. 15 1-2; effect of on
pupae not hereditary, 152.

Gray, Asa, see Asa Gray, xxvi,
66, 67, 68, 194 n. 1.

Great Rift Valley, J. W. Gregory,
3°4-

Green, E. E., on tilt of Melanitis,
300 n. 5.

Green Hairstreak Butterfly, 301.

Gregarious Habit, Conceal-
ment ASSISTED BY, X. 304.

Gregarious habit in aposematic
defence, 318, 323; larvae, transition
from cryptic to aposematic defence
of, 319, 320.

Gregory, Darwin's work on the
primrose compared with that of
Bateson and, xxvii-xxxiv.

Gregory, Professor J. W., on
flower-like Flatidae, 304.

Greyhound, origin of, 83 n. 2.

Groove of Pierine Pupae,
Origin of, V. 147-9.

1 Group ', use of, contrasted with
'combination' or 'association', 293.

Grove, W. B., on leaf-perforating
fungi, 205 n. 1.

Growth of Mullerian Resem-
blance, Advantage conferred
during, X. 329-31 : see also 349.

Guianas, character of the chief
Ithomiine-centred combination in,
350 : see also British Guiana.

Guinea, J. C. Prichard on black-
ness in man and animals in, 187.

Gymnomyxa, the most primitive
animal forms, 25.

Gymnosperms in the Palaeozoic,
45.

H

Haase, Erich, on distasteful moths
mimicking Coleoptera and Hymeno-
ptera, 231 ; on evidence of distasteful-
ness of Glaucopid moths, 231 n. 2 ;
erroneous ideas on * immune ' species
of, 318, 375 ; figures of, erroneously
reproduced in Weismann's Evolu-
tion Theory, 375, 376.

Habit and Instinct, C. Lloyd
Morgan, 170, 171, 212, 268.

Habits and Life-history, im-
portance of in determining
Conditions, VIII. 243, 244.

Habits, see Instinct.

Haemorrhagia fuciformis, 365 ;
— tityus (= bombyliformis), 365.

Hair, of Angora breeds, J. C.
Prichard on, 187 ; protective resem-
blance to skin or, 359.

halia, Lycorea, possible increase
in mimetic likeness since 1825-7,
356.

Halisarcidae unsuited for fossiliza-
tion, 28.

halitherses, Euripus, one female
f. of mimics D. diodetianns (rhada-
manthns), another P. deione, 373.

Hambantotte, Ceylon, dorippus
f. of L. chrysiftpus at, 70 n. 2.

Hamm, A. H., on cryptic attitude
of H. leucophaearia, 156; on birds at-
tacking cocoons of M. neustria, 157 ;
results obtained by, quoted in Essay
X, 293 ; on cryptic attitudes of British
moths, 301 ; on choice of resting-
sites by butterflies and moths, 301.

ANALYTICAL INDEX 429

Hampson, Sir George, on butter-
flies mimicked by specially defended
moths, 231, 232.

Handbuch der palaarktischen
Gross- Schmetterlinge, 1896, M.
Standfuss, 310 n. 1.

Hardness as the special protection
of a model, 261, 369; defence by,
compared with sting, smell, &c,
370-

Hare, Alpine, protective seasonal
changes of, 310, 313.

harrisi, Stictoploea, mimicked by
male of Mel. malelas, 372 ; also im-
perfectly mimicked by diurnal moth,
Callamesia midama, and it allies, 372,
376.

Harrison, A. H., butterflies from
the V. Nyanza collected by, 69.

Hart, Horace, assistance in the
study of paper rendered by, 172.

Hartland (Pine Lake), Wisconsin,
ant-like beetle at, 255, 255 (Fig. 4),
256.

Hartog, Professor Marcus, use of
Syngamy by, 60 n. 3.

Harvard University, Observatory
of, 90 ; Bull. Mus. Comp. Zool. of,
234, 277.

Hawk-moth, attainment of trans-
parency in certain species of, 365.

Head of model resembled by tail
of mimic, 254, 368.

Head-like appearance on hind wing
of Lycaenids, 281, 282, 325, 325
n. I.

Heat, see external causes ; effect
of on pupae of Lepidoptera, 311 ;
effect of on Teracolus and Belenois,
311, 312 ; on Byblia ilithyia pupa,
341.

'Heath Butterflies', meaning of
eye-spots of, 210.

Heaviside, O., verification of Prof.
Perry's calculations by, 10.

Hebomoia captured by bee-eater,
288.

hecabe, Terias, eaten by bee-
eater, 288.

hector, Papilio, mimicked by fe-
male f. of P. polytes, 373.

hegesippus, Salatura, mimicked
by female E. undularis, 373.

Heifer sterile with one bull, but
not with another, 79.

helcita, Aletis, Mullerian mimicry
of L. chrysippus by, 232.

helcitoides, Phaeagarista, Miil-
lerian mimicry of L. chrysippus by,
232.

4 Heliconidae ', as employed by
Bates, a composite group, 213, 234,

235 n. 1, 327 ; Bates's chief models
belong to, 213.

Heliconinae (see also Heliconius ;
see also classification of examples
of mimicry, 383, 386-7): examples
of Mullerian mimicry provided by
resemblance between Ithomiinae
and, 232 ; as models everywhere in
tropical America, 233, 273 ; as
models paralleled by Diabrotica,

236 ; as models for Pieri?iae, 262 ;
pigments of, different from those
of their Pierine mimics, 262, 263 ;
wanting from transparent - winged
Methona- Thyridia- centred combina-
tion, 266 ; darkening in the Guianas
of mimetic, 272, 273, 331-3; uni-
formity throughout many species of,

277 ; long confused with Ithomiinae,

278 ; Ithomiinae mimicked by, are
not extremely conspicuous, 322 ; ab-
sence of eye-spots in, 326 ; Bates
probably misled by mimicry of Itho-
miinae by, 327 ; distinguished by
flight from their Ithomiine models,
331, 331 n. 1 ; mimicry between the
two sub-groups of, 331-3, 358, 358
n. 1 ; remarkable resemblance of
mimetic pairs within the group, 332 ;
models within the group far more
abundant than their mimics, 333 ;
good procryptic resemblance wanting
in, 332; warning patterns more glaring
than those of Ithomiinae, 332 ; first dis-
cussion of Mullerian relation of Pier-
inae to, 343 : see also 213 ; generally
at once distinguishable from Ithomiine
models, 350; central members of
Eastern Brazilian combination pro-
vided by Ithomiinae and, 356 ; resem-
blance to Ithomiinae remarkable in
mimicry, 343 ; probable recognition
of mimetic males by scent, 358.

Heliconius, geographical variation
of, 52 n. 1 ; resemblance to Tithoreaof,
235; resemblance between Heliconius
and Melinaea far closer than between
Heliconius and the nearly allied
Eueides, 235.

Heliconius ?iumata, 331-3; — tele-
siphe, 334 n. 2 ; — thelxiope, 69 ; —
vesta, 69 ; — vctustus, 332.

43© ANALYTICAL INDEX

Heligoland, colour of grasshopper
in, 307.

Helmholz, on loss of heat by the
sun, 13; on energy of sun, 15 n. 2.

Nemaris, mimicry of humble-bees
by, 251: see also 365.

Hemi-embryo transformed into
whole embryo, 129.

Hemiptera, mimicry of wasps, &c,
by, 251; mimicry of ants by, 254,
255, 255 (Fig. 3), 257 n. 1 ; mimick-
ing Lycid beetles, 276 ; attacking
specially defended insects, 318 ;
mimicked by caudal shield of S. fagi
larva, 369 ; mimicked by larval
Mantis, 378 n. 3.

Herbert Spencer, 7, 58, 98, 102 :
see Spencer.

Hereditary transmission of
acquired characters, question
of, and the study of insects,
Essay V, 139-72.

Hereditary Transmission, Laws
of Nature in, J. C. Prichard, 178.

Hereditary transmission of acquir-
ed characters : see acquired charac-
ters ; of inherent peculiarities and
predispositions, 180: see also in-
herent characters.

Heredity, Theories of, Essay
IV, 120-38 : see also 142 n. 1.

Heredity, a factor of Natural Selec-
tion, 96 ; a factor of Lamarck's
theory, 99 ; problem of, 122 ; the two
great theories of, 122, 123 ; pan-
genesis and, 123-7 ; continuity of
germ-plasm and, 127-36; 'identi-
cal' twins and, 134, 138 n. ; mon-
strosities and, 135-6; darkening of
N. moths spread by, 309 ; di- and poly-
morphism and, 310; transmission
of secondary sexual characters to
a single sex by, 380.

Herlitzka, experiments of, on egg
of newt, 130.

Hermit-crabs and crabs, allapose-
matic defence of British and other,
356, 357 ; sea-anemonies, sponges,
and Ascidians carried by, 356, 357.

Heron, F. A., on need of epigonic
evidence, 90 ; on mimicry indepen-
dent of size, 366.

Hertwig, O., experiments on frogs'
eggs by, 129.

Heterocera, see moths.

Heterochelus, jaw-like third legs
of, 368.

Heteronottts trinodosits, 258 (Fig.
6), 259.

Heterostyled condition, meaning
of in life of plant, xxvii-xxix ; Bate-
son's and Gregory's work upon, xxvii,
xxix-xxxiv ; Darwin's work upon,
xxvii-xxix, 90, 91 ; interspecific
sterility and, 90, 91.

Heterozygote (as regards any
character), a fertilized germ in which
the two allelomorphs of the charac-
ter in question represent respectively
its alternative forms, xxxi, xxxii ; com-
pare homozygote, xxxi, xxxii.

Hewitson, W. C, disbelief in
mimetic females of Pap. darda?ius,
57, 57 n. 1 ; on pairing of vierope and
hippocoon, 57 n. 1, 72.

Hexapoda in classification, 33 ; of
the Palaeozoic, 34-8.

Hieracium, Mendel's discovery
that hybrids of do not follow his prin-
ciple, xxxv n. 1.

Hind wings, bright, of moths, &c,
303-4, 325.

Hinde, S. L., on flower-like Flatidae,
304 n. 3.

hippocoon, female f. of Papilio dar-
danus (see also dardanus) : captured
in copula with merope, 57 n. 1 ; bred
from cenea, 72 ; hippocoon, trophonius,
and cenea bred from, 72 n. 1 ; changes
in, near V. Nyanza corresponding to
those of models, 338 ; mimicking
Amauris niavius or its E. form
dominicanus, 338, 374, 374 n. I.

Hispidae mimicked by Longicorns,
261.

Hiss, aposematic significance of,
324 ; mimicked by birds, 324.

Historical Introduction to
Theories of Mimicry, VIII. 220-4.

History and Migration may be
Inferred from Mimicry, X.
363-5-

History Inferred from Mimi-
cry may be Confirmed by other
Evidence, X. 365-6.

History and migration inferred
from Mullerian mimicry no less than
from Batesian, 363.

History of the Inductive
Sciences, W. Whewell, xlvi n. 1.

History of the Rise and Pro-
gress of a Single Biological Doc-
trine, T. H. Huxley, 1.

Hive-bee and Eristalis, 243-4.

ANALYTICAL INDEX

43i

Hobby, butterfly found in stomach
of, 284.

Holland, W., on larvae of T.popu-
leti attacked by starlings, 157 n. 1 ;
on enemies of D. bifida pupae, 158 ;
on mimicry of saw-fly larvae by cater-
pillars, 239 n. 1 ; results obtained by,
quoted in Essay X, 293 ; on colour
adjustment of Cleonus, 307.

Holothurians unsuited for fossiliza-
tion, 43.

Homoptera of Commentry Carboni-
ferous, 35, 37 ; mimicry of ants by,
258, 258 (Fig. 6), 259, 280, 369 ; re-
sembling leaf-carrying ant, 259, 259
(Fig. 7), 260, 280, 377 ; cryptic resem-
blance of to flowers and buds, 304,
304 n. 3.

Homozygote (as regards any char-
acter), a fertilized germ in which both
allelomorphs of the character in
question represent the same one of its
alternative forms, xxxi, xxxii ; com-
pare heterozygote, xxxi, xxxii.

Honduras, examples of mimicry in,
235.

Hong-Kong, L. chrysippus at, 88.

Hooker, Sir Joseph D., Asa Gray
on, 67 ; on effect of external condi-
tions on plants, 74 ; consulted by
Darwin on Wallace's essay (1858),
194; with Huxley in the Rhone
valley, 202 ; references to letters
from C. Darwin to, 59, 60, 63, 67, 76,
84, 86; from T. H. Huxley to, 195 ;
to C. Darwin from, 48, 74, 74 n. 3.

Hope Department, Oxford Univer-
sity Museum, examples of mimicry in,
xxiv, 231, 235, 248, 249, 272 n. 2 ; W.
J. BurchelPs collection in, 53, 53 n. I,
356 ; butterflies from the V. Nyanza
in, 69 ; specimens of L. chrysippus
in, 321 n. 1 ; work on diversity in the
modes by which mimicry is attained
in, 263 ; distasteful moth injured by
drongo in, 284 ; work on the colour-
adjustment of larvae carried on in,
306, 307 ; hermaphrodhep/anemoides
female f. of Pap, dardanus, in, 374 n. 3.

Hope Reports, Oxford, 51 n. 2.

Hopkins, F. Gowland, on pigments
of Pierinae and their models, 262,
263.

Horae Entomologicae, W. S.
Macleay, 220.

Hornets, wasps, and humble-bees
mimicked by moths, 365, 366: see

also classification of examples of
mimicry, 389-93.

Horse, sterile progeny of ass and,
78 ; J. C. Prichard on the production
of breeds of, by selection, 186; and
cattle of mountains compared with
those of plains by J. C. Prichard,
189.

Hound, origin of, 83 n. 2.

Hours when Struggle for
Life most Severe, X. 303.

' How' and 'Why' : both answers
essential, xlvi, xlvii.

Howard, Dr. L. O., on moth
mimicking beetle, 231.

Hubbard, H. G., examples of
mimicry captured by, 231.

Hudson's Bay Lemming, experi-
ment on seasonal changes of, 310.

Humble-bees (see also classification
of examples of mimicry, 389, 391-2) :
mimetic resemblance of Volucella to,
not aggressive, 378.

humbloti, Papiliof of Grand
Comoro, a non-mimetic member of
the mimetic African dardanus group,
373 : see also dardanus.

Hume, T. H. Huxley on, ill.

Humphries, Colonel, on the ancon
or otter sheep, 185.

Huphi?ia nadina, 342 ; — phry?ie,
342.

Huxley, T. H., and the Theory
of Natural Selection : The
Huxley Lecture, Birmingham Uni-
versity (1905), Essay VII, 193-219.

Huxley, T. H., On the Reception
of the Origin of Species, 196 ;
Life and Letters of, 48, 78, 195, 198,
199, 200, 202; President of British
Association (1870), 1 ; at the Oxford
meeting of the British Association,
2, 3 ; acceptance of per saltiuii
evolution by, 4 ; on Biology and
Geological Time, 4, 5 ; great demands
for pre-Cambrian time made by, 6 ;
on tidal retardation, 8 ; special value
of letters of, 48 ; on influence of
Milton, 56 ; discussion of interspecific
sterility by Darwin and, 77-80,82,201 :
see also 49 ; Natural Selection not
fully accepted by, 77-80, 193 ; answer
to criticism of Natural Selection by,
80-4 ; on evidence, 1 1 1 ; a great
champion of Natural Selection, 193 ;
ignorant of contents of joint essay on
Natural Selection (1S58), 195, 196;

432

ANALYTICAL INDEX

suggested causes of ignorance of
joint essay (1858), 196; mutational
views of, 195 ; belief (1859) in trans-
mutation rather than transition, 195,
200; influence of Origin on, 196,
200, 201 ; programme of training in
science (1856), 198 ; voyage of
Rattlesnake, 199 ; views of, on
evolution before Origin, 199, 200 ;
not essentially a naturalist, 200, 202 ;
approves system of W. S. Macleay,
200 ; on the basis of scientific con-
viction, 201, 202 ; opinions on Natural
Selection, 201, 202 ; with J. D.
Hooker in the Rhone valley, 202 ;
the champion of scientific freedom,
219; references to letters from C.
Darwin to, 78, 79, 80, 82, 91, 126, 196 ;
to C. Darwin from, 4, 196 ; to J. D.
Hooker from, 195 ; to C. Kingsley
from, 77, 78 ; to C. Lyell from, 195,
200 ; to W. S. Macleay from, 200.

Huxley's layer of hair, 198, 199.

Hyas coarctata, 314.

Hybernation, of African insects,
209 ; colour adjustment of L. querci-
folia larvae determined before, 307.

Hybernia leucophaearia, 156.

Hybrids which do not follow Men-
deli an principle abundant, xxxv,
xxxv n. 1 ; of Hieracium proved by
Mendel not to follow his principle,
xxxv n. 1 ; sterility of, 63, 64, 77, 78 ;
sterility of, due to Asyngamy,8o~4; of
Common and Chinese goose fertile,
83 ; of Ring Dove and domestic
pigeon fertile, 83, 84 ; ' illegitimate '
seedlings of heterostyled plant com-
pared with, 91.

Hydrocorallina, affinity between
living and Palaeozoic, 28.

Hydrozoa in classification, 25.

Hyelosia as mimics of Ithomiinae,
264 ; method of attaining trans-
parency in, 266.

hylas, Cephonodes, loss of scales
by, 365.

Hylophila (B r alias) prasinana, 149.

Hymenoptera, the Instincts
of, V. 160-6: see also 118, 119,
146, 147.

Hymenoptera (see also Ants, Bees,
Fossores, Humble-bees, Ichneumon-
ids, Saw-flies, Wasps, Xylocopidae ;
see also classification of examples
of mimicry, 389-93) : late evolution
of, 38 ; unique interest of the, 52 ;

di- and polymorphism in, 72 ; tran-
sition in mode of defence of Phyto-
phagous larvae of, 319, 320; best
examples of instinct supplied by
Fossorial, 118, 119, 146, 147, 160-4;
W. S. Macleay and Kirby and Spence
on resemblance of Diptera to, 220,
221 ; mimicry of, by diurnal forms,
250 ; mimicry of, in various ways,
250-60; defence of, evident, 268;
uniformity in groups of, 278, 279 ;
many examples of mimicry of Bate-
sian, 376; also Mullerian, 231, 376 ;
Dipterous mimics of, probably not
aggressive, 378.

Hymenopus bicornis, 378 n. 3.

Hyolithes in Palaeozoic, 42.

Hypa?iis (Byblia) acheloia
{gdtztiis), 87, 341.

Hyperechia, mimetic of Xylocopid
bee in Borneo and S. Africa, 276.

Hypertely of Brunner von
Wattenwyl, X. 302, 303.

Hypoli?nnas a genus mimetic of
Danainae, 216 ; ancestral pattern in
non-mimetic males of, 216; resem-
blance between non-mimetic males
of, 245 ; probably a distasteful genus,
and mimicry of Mullerian, 216, 217,
372 ; complex nature of mimicry of
Eupioea by, 241 ; mimetic species of
at once distinguished from models,
35o.

Hypolimnas {Eur alia) a?ithedon,
338 ; — bolina, 245, 372 ; — dexilhea,
216; — misippus, 215-18, 245, 247,
347, 355> 365 n. I, 372, 381, 382 ;
— (Euraha) wahlbergi, 338.

Hypotheses proposed as sub-
stitutes for Natural Selection
as the Explanation of Mimicry,
&c, VIII. 224, 225 : see also 271-2.

Hypsidae (Pericopidae) as mimics
of Ithomiinae, 264 ; method of at-
taining transparency in, 266 ; African
Hypsid moth seized and rejected by
wild drongo, 284.

I

Ibis, vol. i, 195.

Ichneiwionids (in the broad sense):
see classification of the examples of
mimicry, 390, 392.

'Identical' twins, F.Galton on, 132,
J34) l35> n« I °f tne same sex,
132; enclosed in same embryonic
membranes, 133 ; product of a single

ANALYTICAL INDEX 433

ovum, 133 ; distinguished from multi-
ple births, 133 ; development of,
shown in Diagram III, 133, 134;
after-lives of, 134, 135 ; heredity and,
134, 138 n.; predetermined in the
fertilized ovum, 137.

Idiosyncrasies hereditary, 180.

ilithyta, Bydh'a, intermediate f.
bred from wet, 341 ; wet f. conspicu-
ous, dry f. procryptic, 341 ; dry
warmth apparently the stimulus for
pupae to produce the dry f., 341.

1 Illegitimate ' unions of hetero-
styled plants, importance of, xxviii,
xxviii n. 1, 90-2.

Illogical Geology, Herbert
Spencer, 6.

illunaria^Selenia, seasonal changes
of, 311.

Illustrations of Mimicry,
chiefly from oriental lepido-

PTERA, X. 370-6.

Illustrations of the Kelation-
ships existing amongst Natural
Objects, &c, Prof. J. O. West wood,
221.

Imagination, Prichard on the effect
of parental, at the moment of con-
ception, 186 ; versus memory, 196-8 ;
necessity for the training of, in
youth, 199.

'Immune', an incorrect term ap-
plied by Haase to models for
mimicry, 318 ; also adopted by Weis-
mann, 375.

Immunity, Warning Colours
do not imply Complete, X. 317,
318.

Imperforata in the Palaeozoic, 27.

Importance of Instinctive
Attitudes and Movements for
Mimicry, X. 363.

Inborn : see 1 inherent characters ',
141.

Independence of mimicry and
affinity, 229-37, 336, 345 ; of size as
clear in Miillerian as in Batesian
mimicry, 363, 366.

India, 70, 269, 317, 324, 342, 349,
363, 371, 372, 373, 376.

Indirect evidence of birds attack-
ing butterflies, 270, 270 n. 1, 281-3,
290-2, 325, 325 n. 1.

IndirectEvidenceSupporting
Mullerian Mimicry, X. 346, 347.

Individual Modification tra-
verses Diagnosis, II. 73-5.

POULTON f

Individual Seasonal Changes*
X. 310.

Individual subordinated to the
species, 316, 358.

Individual variation a factor of
selection, 95-6 ; difference, Weis-
mann on causes of, 127, 128 ; colour
adjustment slow in pupae, 149, 150,
152-4, 3C5, 306 ; in a cocoon, 149 ; in
larvae, 152-4, 305-7; probable in
pupae of U. tamSucarta, 150 n. 2 ;
colour adjustment rapid in certain
Vertebrata, Crustacea, and Cephalo-
poda, 300, 305, 313.

Influences of locality, inconsistent
views of J. C. Prichard on, 191, 192.

Inherent characters, definition of,
no, hi, 122, 123, 141, 142 ; heredity
and, 96, 127, 178-85; somatogenic
characters less important than, 132-5 ;
somatogenic characters compared
with, 136 ; other terms used to ex-
press, 110, in, 123, 141, 142;
Weismann's definition of, 142;
Goodrich's definition of, 142 ; clearly
distinguished as congenital or con-
nate from acquired characters by
J. C Prichard (1826), 175, 179.

Injuries to butterfly wings as if
caused by enemies, 270, 270 n. 1,
281-3, 325 : see also 3°4-

Innate, see inherent characters,
141.

Innate tendencies, Lamarck's be-
lief in, 98.

inornatci) Amblyornis, bower of,
379-

Insecta, D. Sharp, 257 n. 1.

Insectivora, moles of the, resem-
bled in other Mammalian Orders,
312, 359-

Insects, especially Lepido-
ptera, pre-eminently fitted for
Discussion on Species, II. 50-4.

Insects, and the question
' Are Acquired Characters
Hereditary?' Essay V, 139-72.

Insects, Variable Protective
Resemblance in, V. 152-4.

Insects, the Instincts of, V.
154-7; see also H7-i9> 146, M7-
157-66.

Insects, bearing on supposed
Hereditary Transmission of
Experience, of Mimicry, &cn in,
V. 166-8.

Insects in the Palaeozoic take

f

434 ANALYTICAL INDEX

place of Pterodactyles and birds, 18 ;
often wingless in oceanic islands, 18 ;
great size of Palaeozoic, 18, 37;
derived from Chaetopod-like an-
cestor, 27 ; in classification, 33 ; of
the Palaeozoic, 34-8 ; of Commentry
Carboniferous, 35-8 ; evolution of
wings of, 36, 37 ; small advance of,
since Carboniferous, 36-8 ; life-history
of Carboniferous, 37 ; pre-eminently
fitted for discussion on species, 50-4 ;
disturbed by effect of wind, 75 ; cross-
fertilization and, 91 ; migration of, 93 ;
the struggle for existence and, 117;
prophetic instincts of, 1 17-19, 1 57-65 ;
importance of, for the question of trans-
mission of acquired characters, 139-
68 ; supposed transmission of experi-
ence, and the warning and mimetic
colours of, 166-8 ; struggle for life in
young birds, and the warning and
mimetic colours of, 167, 167 n. 2, 168 ;
importance of, as food, 167, 167 n. 2,
168 ; less on wing in dry season,
208-11 ; groups of, bury in dry
season, 208 ; Prof. J. O. Westwood
on resemblances between, 221 ;
luxuriance of, in S. America, 248 ;
great development of mimicry in,
367 ; effects of castration of, 380.

Instances of variety in the
Breed, arising from the operation
of external, chiefly of local causes,
J. C. Prichard, 187, 188.

Instances showing the Per-
manency of Complexion in differ-
ent Races, J. C. Prichard, 177, 178.

Instinctive, see instincts.

Instincts and Habits of the
Solitary Wasps, G. W. and E. G.
Peckham, 118 n. 1, 162, 163.

Instincts of Insects, V. 154-7 :
see also 117, 118, 119, 146, 147,
157-66.

Instincts of Cocoon-making,
V. 157-60: see also 117, 118, 164,
164 n. 2.

Instincts of the Hymeno-
ptera, V. 160-6: see also 118, 119,
146, 147.

Instincts All- Important for
Protective Resemblance, X. 301,
302: see also 155-6, 289, 298, 300,
301,318.

Instincts All-Important in
Display of Warning Colours,
X. 323, 324 : see also 319, 320.

Instincts All-Important in
the Attainment of Mimetic
Resemblance, X. 363 : see also 241,
319, 341, 368.

Instincts or Instinct : (see also
intelligence), Lloyd Morgan on,
154; Fabre on, 160; Lord Ave-
bury on, 160, 161 ; G. J. Romanes
on, 160, 161, 166; C. Darwin on,
161, 165; Eimer on, 162; G. W.
and E. G. Peckham on, 162, 163 ;
E. B. Poulton on, 163-5 5 E. Ray
Lankester on, 165, 166 ; G. H. Lewes
on, 166 ; Lamarckian interpretation
of, 116, 154; intelligence and, 116,
117; Natural Selection and, 11 6-9,
138 ; originated through action of
Natural Selection on nervous system,
117; more developed in lower
animals, 117; of sucking, 117; defi-
nition of, 154, 301, 302; difficulties
of Lamarckian interpretation of, 154-
60, 163-6 ; protect from enemies
that are never seen, 1 55-60 ; of larva
to protect against enemies of pupa,
157-60; of Fossorial Hymenoptera,
118, 119, 160-4; of Vespa, 164-5;
of worker ants, 1 65 ; least developed
in highest animals, 165, 166 ; per-
formed but once in a life, 164, 164
n. 2; educability versus, 165, 166;
relation of daylight to mimetic, 249,
250 ; to procrytic, 303 ; Lewes's and
Romanes' view that ' lapsed ' in-
telligence has produced, 166 : see
also 161 ; importance of, in Protective
Resemblance, 298, 301-2, 353 ; in
Aposematic display, 323-4 ; in
Miillerian mimicry no less than in
Batesian, 363.

Intelligence (see also instinct), a
criterion in evolution, 107, 108 ; of
seal and birds, 116; instinct and,
116, 117 : see also 165, 166.

Intemperance, supposed hereditary
effects of, discussed by J. C. Prichard,
183, 184.

Interbreeding, advantages of, 93, 94.

Interbreeding, Asyngamy a
consequence of preferential,
II. 85-8 : see also 65.

Interbreeding between similar
varieties, 85-8.

Intercrossing, supposed swamping
effect of, xl, xln. 3, xli ; importance
of Mendelian principle in averting
swamping effect of, xxxiv, xxxv, xli.

ANALYTICAL INDEX 435

Interest as a stimulus to inquiry,
xliv-xlvi.

Internal Causes, theory of, as sug-
gested explanation of mimicry, 224,
225, 272; obviously inapplicable to
mimicry between remote species, 229;
also inapplicable to protective resem-
blances, 227, 228 ; objections to, as
explanation of mimicry, 227-9, 233,
236-9, 241, 245, 247, 249, 250, 257,
260-2, 266-8, 273, 275, 276, 278-82.

Internal Sci. Ser., 161 n. 1.

Interspecific Sterility as
test of Species, II. 77-80: see
also 59.

Interspecific Sterility caused
by Asyngamy, II. 80-4 : see also
65, 91 ; see also sterility.

Intimidating Attitudes, X.

324, 325-

Intimidating or Warning
Sounds, X. 324.

Introduction, Kirby and Spence,
utility of mimicry suggested in (181 7),
221, 222.

Introduction : Mutation,
Mendelism, and Natural
Selection, xiii-xlviii.

Introduction to Discussion
'What is a Species?' II. 63-5.

Investigation, the Motive
Force of, Introd., xlvii, xlviii.

iopterus, Promachtis, mimicry of
Hymenoptera by, 257 n. 1.

irawada, see splendens, Isamia,
376.

Ireland, dread of snake-like cater-
pillar in, 367 n. 2.

Iridescence, cryptic effect of, 322.
Irravvaddy R., 291 n. 1.

Isamia splendens and irawada,
376.

Islands, Ancestral Non-
Mimetic Forms Preserved on,
X. 373-6.

Islands, oceanic, wingless insects
in, 18.

Isolation and species production,
76 ; leading to * mechanical selec-
tion', 85.

Ithomia, a central type of Ithomiine
pattern, 234.

Ithomiinae (see also classification
of examples of mimicry, 383-4, 386-8):
collected by Burchell in Brazil, 53
n. 1 ; Heliconinae and, as examples of
Mullerian mimicry, 232 ; always tend

F

to be mimicked, 233, 273 ; number of
colours in Neotropical Papilioninae
compared with those of, 234, 277 ; as
models paralleled by Diabrotica, 236 ;
pigments of, different from those of
Pierine mimics, 262, 263 ; trans-
parent-winged species of and mimics,
264-6 ; colours of principal combina-
tions grouped round in various
localities, 272, 273, 322, 331-3, 350,
351) 356; darkening of, in the
Guianas, 272, 273, 331-3 ; dominance
of, in British Guiana, 332 ; uniformity
throughout many species of, 234, 277 ;
long confused with Heliconinae ', 278 ;
not extremely conspicuous, 322 ;
absence of ' eye-spots ' in, 326 ;
equivalent to the Danaoid Helico-
nidae of Bates, save for inclusion in
latter of Danaine Ituna and Lycorea,
327 ; distinguished by flight from
mimicking Heliconinae, 331, 331 n. 1 ;
resemblance of Heliconinae to, re-
markable in mimicry, 343 ; mimicked
by an Erycinid which is itself the
model of diurnal moth, 346 ; Helico-
nine close mimics of, generally at
once distinguishable, 350.

Ituna and Thyridia, a re-
markable case of Mimicry in
Butterflies, Fritz Muller, 222 : see
also 212, 226, 278, 327.

Ituna (Danainae), mimicry of
Ithomiinae by, 265 ; method of
attaining transparency in, 265, 266 ;
included in Ithomiinae by Bates,
327-

J

Jacob, experiments of, on flocks of
Laban, 186.

jacobaeae, Euchelia, larva of a
Mullerian mimic of a wasp, 230 ;
cryptic and aposematic defence of
larva of, aposematic of imago, 318,
3i9-

Jacoby, M., on mimicry in Coleo-
ptera, 236, 237.

Jagellon, intermarriage with, the
cause of a hereditary peculiarity of
lip in Royal House of Austria, 180.

Japan, L. chrysippus reported
from, 88.

Jardin des Plantes, Paris, O.
lamarckiana originally described
from, xxi.

Jen. Zeit., 317.

f 2

436 ANALYTICAL INDEX

Jenkin, Fleeming, xl, xl n. 3, xli,
3 : see Fleeming Jenkin.

Jenkinson, Dr. J. W., on relation
between planes of first egg division
and position of future embryo, 130.

' Jerusalem Jews ' unchanged since
490 a.d. on Malabar Coast, 178 : see,
however, 192.

Jews, see circumcision and Jeru-
salem Jews.

Joints, evolution of forms of, 112,
113; Lamarckian interpretation of
forms of, 114, 115.

Jordan and Rothschild on per
saltum evolution and geographical
distribution, xvi.

Jordan, Dr. Karl, on museum col-
lections as evidence of change, 53
n. 1 ; on correlated and independent
variation, 66 n. 2 ; on provisional
nature of diagnosis, 76, 77 ; on
peculiarities in Madeiran birds, 84
n. 2 ; on 'mechanical selection', 85.

Judgement of Discontinuity
Subjective, Introd., xvii.

Jung and fixity of species, 56.

Junonia, captured by bee-eater,
288 : see Precis.

Junonia cebrene, 283 ; — orithyia,
291.

K

Kala Pani Bungalow, Thundiani,
King-crow attacking Papilio near,
285.

Kallima, protective resemblance
of under surface of, 203-8, 302 ;
seasonal changes in, 206, 207 ; re-
sembling different appearances of
dead leaves, 310.

Kallima paralekta, 207.

Kandy Road, Ceylon, bee-eaters
capturing Pierinae on the, 285, 286.

Karachi, L. chrysippus at, 70 ;
dorippus f. of L. chrysippus at, 70
n. 2.

kasch?nirensis) Vanessa, captured
by King-crow, 285.

Kaye, W. J., results obtained by,
quoted in Essay X, 293 ; on the chief
mimetic association of British
Guiana, 322, 332 ; on exact resem-
blance of H. numata to M. mneme,
331 ; assistance in ascertaining
dominance of Melinaea mneme in
British Guiana, rendered by, 332 ; on
upper surface colouring of Protogo-

nius, 351 ; on the two sub-groups of
the Heliconinae, 358 n. 1; on means
by which transparency may be
attained in mimetic Lepidoptera,
366 n. 1.

Kelvin, Lord, on the age of the
earth, 2, 19 ; works on geological
time of, 411,3; effect on Darwin of
views of, 6; jubilee of (1896), 9; on
the cooling of the earth, 10-13; on
the life of the sun, 13-15 ; meteoric
hypothesis of, 22-4.

Kendall, May, parody of Darwin-
ism by, 104.

Kentish Glory moth, 238.

Kerguelen Land, wingless insects
in, 18.

kershawi, the Australian form of
P. cardui, 85 n. 1.

Kestrel pecking out eye-spot of
butterfly, 210.

Khandalla, dorippus f. of L.
chrysippus at, 70 n. 2.

Kikuyu Escarpment, the locality
of polytrophusy sub-sp. of Pap. dar-
danus, 374.

King-crow attacking butterflies,
285 ; attacking Lepidoptera, 287 ;
searching for but unable to detect
Melanitis, 288, 289 ; capturing
Catopsilia, 289.

Kingsley, Charles, letters on inter-
specific sterility from Huxley to, 77,
78 ; on examinations, 197-8.

Kirby, Rev. William, on resem-
blances between insects, 220 ; utility
of mimicry suggested by Spence and,
221, 222.

klugii, see dorippus.

Knight-Darwin Law, F. Darwin
on, 92.

Kolreuter on sterility between
varieties, 78.
Kosmos, 212, 222, 226, 278, 327.
Kupffer's Festschrift, 131.

' Kuppa' (Echis), 324.

L

Lacerta viridis, 367.

Lackey moth, 157.

Lactic acid bacillus, beneficial
effect of, 121 n. L

La Garde St. Cast, Brittany,
Boulenger's study of O. lamarckiana
at, xxi.

Lagerstroemia Flos Reginae, 290.

ANALYTICAL INDEX

437

laglaizei, Papilio, mimicking At-
cidis aurora, 371.

lais, Elymnias {Mely mas), mimicry
and procryptic defence in, 353.

Lamarck, Second Law of, in-
consistent with his First, V.
144-7 • see also Lamarckism.

Lamarck, use of term ' change-
ments acquis'' by (1809), 141 ; laws
of, 141.

lamarckiana, Oenothera, De Vries's
evidence for Mutation in Nature
derived from, xix, xx ; never found
wild in its supposed native country,
xix, xxi ; fixed hybrids obtained by
Macdougal, Vail, and Shull between
O. cruciata and, xxi, xxii ; Mendelian
principle not followed by hybrid
between 0. cruciata and, xxxv n. 1.

Lamarckism (see also Acquired
Characters and External Causes) :
the theory of evolution originated by
Lamarck, 97-9 ; innate tendency to
perfection and, 100 ; more easily
apprehended than Darwinism, 101 ;
illustrated by parodies of Darwinism,
103, 104 ; acquired characters and,
1 10-15; difficulties of, 1 10-15;
Mammalian skeleton and, 112; form
of joints and, 112,115; passive struc-
tures (e.g. hair, colour) and, 112;
lobsters and crab's claws, lizard's
tail and, 113, 114; protective appear-
ance and, 113; forms of teeth and,
114, 115 ; instinct and, 116 ; the
cocoon-making instinct and, 117, 118,
157-60, 164; instincts of Hymeno-
ptera and, 118, 119, 160-6; variable
protective resemblance and, 152-4;
interpretation of instinct and, 154;
instincts of insects and, 154-66 ;
defended by G. J. Romanes, 160-1,
164 n. 1, 166 ; Darwin's argument
that instincts of worker ants cannot
have arisen by, 165.

Lamellibranchiata in early Palaeo-
zoic, 30 ; evolution in, 42.

Lamiidae, mimicry of weevils by
genus Doliops of, 250, 261.

Lampreys, 26 ; far lower than
earliest fossil fish, 30.

Lancashire and Yorkshire,
Recent Darkening of Moths
in, X. 308-10.

Land-plants, see plants.

Language a result of environment,
106.

Lankester, Sir Ray, on animal
classification, 25 ; on classification
of Appendiculata, 33 ; on Palaeo-
phonus, 40 ; assistance rendered in
Essays I, II, and VI by, 43, 62,
144-6 : see also viii ; on Zygosis, 60
n. 3 ; on discarding word ' species ',
62 ; on a historical criterion of
species, 63, 76 ; on Lamarck's use
of term ' acquired', 141 n. 2 ; on Sir
Edward Fry's criticisms, 143 n. 3 ;
on inconsistency of Lamarck's laws,
144-6 ; on 1 educability ' versus
instinct, 165-6.

Lappet moth, 299, 307.

Larvae of British Butterflies
and Moths, W. Buckler, 152.

Larvae (for Lepidopterous see
caterpillars : see also larval stage) :
reasons for passive defence of, 156;
mimicry by caterpillars of saw-fly
(Tenthredinid), 238, 239, 239 n. 1 ;
sudden assumption of aposematic
movements and attitude by saw-fly,
238, 239, 319, 320; ant mimicked by
Nabis, 257 n. 1 ; leaf-carrying ant
(Atta) with its leaf mimicked by
Membracid, 259 (Fig. 7), 260, 280,
377; DUgs (Hemiptera) mimicked by
Mantid, 378 n. 3.

Larval stage, a mimetic appearance
prepared beforehand in, 242, 243,
244 ; diverse conditions in same
locality determined by, 243, 244,
276, 277 ; seasonal phases determined
by influences upon, 311, 312.

Latent Epigamic characters, 380.

latercula, Lycomorpha, mimicking
Lygistopterus rubripennis, 23 1 .

lativentris, Nabis, larva of, mimick-
ing ant, 257 n. 1.

Latter, O. H., on secretion for
opening D. vinula cocoon, 159.

Laurentian omitted from discus-
sion of age of earth, 27, 28.

' Laws of Growth ' and mimicry,
224, 225.

Laws of Lamarck Incon-
sistent, V. 144-7.

Laws of Lamarck, 141.

Laws of Nature in Hereditary
Transmission, J. C. Prichard, 178-
85.

Laws of the Animal Economy
in regard to the Hereditary
Transmission of Peculiarities of
Structure, J. C. Prichard, 178-85.

438 ANALYTICAL INDEX

Lay Sermons, &c, T. H. Huxley,
198.

Leader, 58 n. 1.

' Leaf-butterflies ' (Kallima), 203-
8, 302, 310.

Leaf-carrying ant (Atta) with its
leaf mimicked by larval Membracid,
259> 259 (Fig. 7), 260, 280, 377;
mimicked by Acridian {Tettix), 260.

Leaf-stalk, protective (procryptic),
resemblance to, 351.

Leaves (see also dead leaves) :
protective (procryptic) resemblance
to, 203-8, 289, 298-9, 300 n. 5, 301,
302, 304, 322, 360 ; procryptic
resemblance of butterflies to, 203-8,
289, 299, 300, 300 n. 1, 301, 310, 311,
322, 351, 353 ; to shadows cast by
dead, 299 ; of moth and Locustid to
injuries caused by fungi and larvae
in, 302 ; of gregarious larvae to brown
patches on, 304 ; colour adjustment
of larvae to, 306 ; procryptic resem-
blance to drifting, 360 ; aggressive
(anticryptic) resemblance to effects
of, 313; warning (aposematic) con-
spicuousness against, 318.

Lecture on Mimicry at Leeds
meeting of British Association (1890),
E. B. Poulton, 293, 299 n. 1, 365, 370,
376, 377, 377 n. 2.

Lectures to Working Men,
T. H. Huxley, 78.

Leech Collection, specimens of
Limenitis albomaculata, Athyma
punctata^ and their model in, 381,
382.

Leeches, Chaetopod-like ancestor
of, 27.

Leeds, lecture on Mimicry at, see
lecture.

Leigh, G. F., on doripfius f. of
L. chrysippus in Natal, 71 n. I ;
males and mimetic females of Pap.
dardanns bred from single mimetic
f. of, by, 72, 72 n. 1.

Lema mimicking Diabrotica and
Cerotoma, 237.

Lemming, experiment on seasonal
changes of Hudson's Bay, 310 ; pro-
tective (procryptic) seasonal change
of, 313.

Lepidiota bimaculata, 368.

Lepidoptera especially fitted
for Discussion on Species, II.
50-4.

Lepidoptera chiefly Orient-

al, Illustrating Mimicry, X.
370-6.

Lepidoptera (see also butterflies
and moths : see also classification
of examples of mimicry, 383-92) :
seasonal changes of, see seasonal ; late
evolution of, 38 ; as sensitive registers
of change, 50-4 ; ' mechanical selec-
tion ' in, 85 ; as evidence in discussion
of acquired characters, 146 ; adapta-
tion in as evidence for Natural Selec-
tion, 203-18; too exclusive study of
mimicry in, 229, 272, 273 ; mimicry
in paralleled by that in beetles
(Coleoptera), 236, 237 ; predominant
mimicry in S. American, 248 ;
mimetic likeness attained in various
ways by, 262-6 ; transparency
attained in various ways by, 263-
6; evidence of distastefulness in
mimicked groups of, 279, 279 n. I :
see also 268-9, 316-17 ; majority of
mimetic resemblances Mullerian and
not Batesian, 348.

Lepidopterorum Rossiae Bio-
logia, 1890, C. Portschinski, 3i6,324.

Lepidotic acid, see uric acid, 262-3.

Leptalides, see Dismorphina, 239-
40, 265-6.

leucocyma, Elymnias (Melynias
malelas), male and female of, mimick-
ing different Euploeas, 372.

leucophaearia, Hyberma, cryptic
attitude of, 156.

Leuthstrom, Dr. C. A., ant-like
beetle in grounds of, 256.

levana, Araschnia, mimetic inter-
pretation of seasonal forms of, 342.

Lewes, G. H., on instinct as lapsed
intelligence, 166.

Lichen, protective (procryptic)
resemblance to, 298, 306, 307 ; syn-
cryptic resemblance to, 312, 359 ;
colour adjustment of larvae to, 306,
307 ; disappearance of, in Lancashire
and Yorkshire district, 308, 309.

Life and Letters of Charles
Darwin, F. Darwin, xxvi, xxix, xl
n. 3> 3, 4> 6, 59, 60, 66 n. 3, 67, 75,
83, 86, 91, 92, 95, 126, 196, 197, 200.

Life and Letters of Thomas
Henry Huxley, L. Huxley, 48, 78,
195, 198, 199, 200, 202.

Life-History and Habits, Im-
portance of, in determining
Conditions, VIII. 243, 244.

Life of sun, see Sun.

ANALYTICAL INDEX

439

Life, origin of, unknown, 95.

Life, struggle for, and Natural
Selection, 96 ; waste of, prevented by
warning colours, 316 ; tenacity of, in
species with warning colours, 316;
saved by Mullerian mimicry, 327-8.

Light, stimulus of, in adjustable
protective resemblance, 305.

Limacina appears in Tertiary, 42.

Limbs, origin of Vertebrate, 108-9.

Limenitis, conspicuous and pro-
bably distasteful, 218; (Basilarchia)
N. American species of, mimicking
A. plexippus, 274; resemblance of
prorsa f. of A. levana to, 342.

Limenitis albomaailata, 217, 381,
382 ; — (Basilarchia) as/yanax, 274 ;
—poptdi, 315, 316.

Limit to Mullerian Unifica-
tion of Warning Colours in any
Country, X. 336-9.

Livinas chrysippus, 70, 71, 88, 89,
215, 232, 249, 320, 321, 336, 354,

355.364, 372, 374-

Limulus, allied forms of, in early
Palaeozoic, 30 ; appears in Trias, 40.

Lingula, among the earliest fossils,
5 ; persistence of in time, 43.

Linnaean Conception of Spe-
cies as Fixed, II. 54-9.

Linnaean definition of species, 54 ;
diagnosis of species, 58.

Linnaean Society of London,
Transactions of, 85, 211, 220, 221,
222, 246, 279, 327, 327 n. 1, 331 ;
Zoological Journal of, 218 n. 2,
220, 282 n. 2, 300 n. 3 ; Darwin-
Wallace, Joint Essay read before
(1858), 194, 379 ; Author's paper read
before, the original form of Essay
VIII, 220; publication of memoirs
on Mimicry by, 222.

Linnaeus (see also Linnaean) : on
abandonment of conception of, 62 ;
interval between Darwin and, 66.

Lion, aggressive resemblance of,
312.

' List ' or tilt of butterflies, 289,
300, 300 n. 5, 301.

Lizard examining eye-spot of
butterfly, 210; terrified by snake-like
caterpillar, 367.

Lizards, value of power of throwing
off* tail possessed by, 114, 325; in-
direct evidence of attacks of, on
butterflies, 281-3 ; preferences of,
286 ; aposematic sounds of, 324.

Lobster moth, larva of, 253 (Fig.
2), 254, 369.

Lobster throwing off claw, 113.

Local conditions, J. C. Prichard
on adaptation to, 188-92.

Local influences, inconsistent views
of J. C. Prichard on, 187, 191, 192.

Locality, influences of, see External
Causes.

Lock, R. H., on the dominance of
discontinuity, xv n. 2 ; on discon-
tinuity and colour changes, xvii, xvii
n. 1 ; on Mutation, xvii, xvii n. 2 ;
on Bateson's and Gregory's work on
the primrose, xxvii ; exaggerated esti-
mate of the importance of Mendelism
by, xxxiii, xxxvi, xxxvii n. 2 ; on the
importance of Mendelism in artificial
selection, xxxv ; erroneous statement
of Darwin's opinion by, xl n. 2.

Locustidae (Protolocustidae) of
Commentry Carboniferous, 36, 37 ;
mimicry of ants by, 256, 257, 257
n. 1, 258 (Fig. 5), 280; procryptic
resemblance to leaves of, 302 ;
specially defended insects attacked
by, 318.

Longicorn beetles (see also classifi-
cation of examples of mimicry, 390-3):
mimicry in relation to life-history of,
243 ; reduction of elytra in mimetic,
252.

LongstafT, Dr. G. B., results ob-
tained by, quoted in Essay X, 293 ;
on concealment of C. pumilus, 300 ;
on reduction of shadow by attitude
of butterflies, 300, 301 ; on choice of
resting-sites by butterflies, 301, 301
n. 6 ; on daylight hours when butter-
flies are at rest, 303 ; on epigamic
and aposematic scents in African
butterflies, 316, 317 n. I ; on jaw-like
third legs of Heterochelus, 368.

Lophins piscatoritts, 378.

Lord Kelvin, see Kelvin.

Lowell, James Russell, parody of
evolution by, 104-5.

Luebo, on S. branch of Congo,
type f. of L. chrysippus from, 321
n. 1.

Lycaenidae, value of head-like
appearance at posterior end of, 281-
3, 325, 325 n. 1 ; meaning of 1 tails '
and 'eye-spots ' on hind wings of, 325,
325 n. 1 ; wing-fragments probably
of, in nest of Microhierax, 291 ;
station different from that of model,

ANALYTICAL INDEX

L, chrysippus, preferred by certain,
349-

Lycidae (see also classification of
examples of mimicry, 389-91, 393) :
moths which mimic are themselves
distasteful, 231; mimicry in relation
to life-history of, 243, 276.

Lycomorpha latercula^ Glaucopid
moth mimicking Lycinae, 231.

Lycorea (Danainae) included in
Ithomiinae by Bates, 327.

Lycorea katia, 356.

Lyell, Sir Charles, on ocean basins,
21 ; letters from Darwin to, 56, 75,
83 ; letters from Huxley to, 195,200;
consulted by Darwin on the joint
essay (1858), 194.

Lygistopterus rubripennis, 231.

M

Macan, Dr. R. W., assistance in
terminology rendered by, 61 n. 1.

Macao, L. chrysippus at, 88.

macareus, Papilio, a mimetic
species not attacked by bee-eaters,
288.

Macdougal, Vail, and Shull, fixed
hybrids between O. lamarckiana and
O. cruciata obtained by, xxi, xxii :
see also xix n. 5, xxxv n. 1.

Macleay, W. S., Huxley's letter to,
approving system, 200 ; on the prin-
ciple of Analogy, 220.

Macroclemmys temminckii, 378.

macrophyllum , Eufiatorium, fre-
quented by chief mimetic butterflies
of British Guiana, 322.

Macrura evolved earlier than
Brachyura, 40.

maculosa, Diacrisia, a distasteful
moth seized and dropped by a
drongo, 284.

Madagascar, 57 n. 1, 216, 245,
373-

Madeira, many beetles wingless in,
18 ; birds slightly modified in, 84, 84
n. 2.

Maize, Gartner on, 78.
Malabar Coast, 178, 187 : see also
192.

Ma/acosoma neustria, 157.

Malacostraca in Palaeozoic, 39, 40.

Malaya, 248, 252, 333, 367.

Male, Mimicry, &c, more
characteristic of female than,
VIII. 244-7: see also 215-17, 279,
372-5.

Male Mimicking Male of
Model, Female its Female, X.
37i.

Male and Female Mimicking
Different Species, X. 372.

Male non-Mimetic : Female
Mimetic, X. 372.

Male, ancestral appearance pre-
served in non-mimetic, 244-7 > except
in mimicry less ancestral than female,
245.

Male parent, Prichard on the sup-
posed influence of on offspring, 185.

Males, non-mimetic, of mimetic
females tend to warning colours and
to become models, 347 ; rivalry
between for possession of females,
379-

malelas, Melynias {Elymnias
leucocyma), male and female of,
mimicking different Euploeas, 372.

Malvern, Durban, Natal, recent
incursion of N. butterflies into
neighbourhood of, 52 n. 1 ; attack on
butterfly witnessed at, 283.

Mammalia, disputed remote an-
cestry of, 26 ; rapid evolution of brain
in higher, 29 ; brain of higher, com-
pared with that of man, 29; brain
evolution in, 107-8 ; skeleton of and
Lamarckism, 1 12; experiments on
Indian insect-eating, 269; warning
colours of, 315 ; mimicry by tree-
shrews of squirrels, 367, 367 n. 1 ;
mimicked by chafer, 368.

Man, brain of, compared with
mammals, 29 ; evolution in brain
of, 108 ; division of labour among
tissues of, 121 ; J. C. Prichard on
adaptation to locality and climate of
races of, 190, 191 ; snake-like cater-
pillars terrifying monkeys and, 367
n. 2.

Manchester Microscopical So-
ciety, Transactions of, 366 n. 1.

Mandalay, 291 n. 1.

Manders, Lieut.-Col. N., on dorip-
pus f. of L. chrysippus in Ceylon,
70 n. 2.

Mantidae attacking specially
defended insects, 318; alluring
flower-like colours of, 378, 378 n. 3 ;
colouring of, also procryptic, 378 ;
Reduviid bug mimicked by larvae of,
378 n. 3.

tnapurito, Conepatus, warning
colours of, 315.

ANALYTICAL INDEX

441

Mare and quagga, supposed en-
during effect of cross (telegony), 185.

Marico wood-shrike, 283.

Marine Invertebrate Fauna
near Dublin, G. Y. and A. F. Dixon,
31411. 1.

mariquensis , Bradyornis, capturing
Sarangesa eliminata, 283.

Mars, the question of water on, 14.

Marshall, Guy A. K., on dorippus
f. of L. chrysippits in Rhodesia,
71 n. 1 ; experiments on seasonal
dimorphism of, 72-3 ; on seasonal
changes in S. African butterflies,
208 ; on Kestrel examining eye-spot
of butterfly, 210 ; members of mimetic
combinations captured on one day
by, 249 ; on a Rhodesian ant-like
Locustid, 257 n. 1 ; evidence of
special defence in conspicuous insects
obtained by, 268, 269 ; on Asilid fly
mimicking Xylocopid bee in S. Africa,
276 ; on complex S. African combina-
tion with Lycid beetle models, 276 ;
indirect evidence of attacks on butter-
flies obtained by, 281-3 5 direct
evidence of attacks by birds on
Lepidoptera obtained by, 282-4 i
results obtained by, quoted in Essay
X, 293 : see also viii, 382 ; experi-
ments on seasonal forms of Pierinae
made by, 311, 312; on absence of
* eye-spots ' from the chief distasteful
butterfly groups, 326 ; on the bio-
nomic classification of ' eye-spots ',
326 ; Batesian mimicry favoured by,
328 ; on ' stink-glands ' of Co/aenis,
334 n. 2 ; on Precis na/a/ensis, a
mimic of Acraeas, 339 ; experiments
on the physiological stimulus in
seasonal dimorphism of Precis made
by, 34°> 341 ; uncertain results of
above-named, 340 ; proof by breeding
of the specific identity of the wet
and dry season forms of following
species obtained by — Precis sesamus
(1898), 339, 34o: P. antilope (1902),
340: P. actia (1903), 340: P. ceryne
(I9°5)» 34° ; dry f. of Byblia goizius
bred from wet by, 341 ; intermediate
f. of B. ilithyia bred from wet by,
341 ; dry warmth proved to be
probable stimulus to the pupa of
Byblia by, 341 ; on wet f. of B. gotzius,
a mimic of Acraea serena type, 341 ;
on a wonderful Lycid-beetle-centred
Mullerian combination, 276, 344 ;

on monkeys terrified by snake-like
larva, 367 n. 2 ; on S. African Longi-
corns mimicking weevils, 369; on
conspicuousness of large African
weevils, 370.

Marsupialia, mole-like forms of,
312.

Materials for the Study of
Variation, W. Bateson, generally
quoted as On Variation, xiii-xvi,
xix, xxviii, xxviii n. 2, xxxiv, xxxvii
n. 2, xl-xliii, 4 : see also Bateson, W. ;
exaggerated estimate of importance
for evolution of, xiv ; disparagement
of other lines of inquiry in, xli-xliii ;
unreasonable disparagement of Em-
bryology in, xlii, xliii.

Maternal impressions, supposed in-
heritance of, rejected by J. C. Prichard,
186.

Mathematical Statement of
Advantage Conferred by Per-
fected Mullerian Resemblance,
X. 328, 329.

Mauritius, sea-anemones and
Ascidians carried by crabs and
hermit-crabs in, 357.

Max Muller, Professor, on neces-
sity for defining words, 46.

Mayer, A. G., on fewness of
colours in Ithomiinae as compared
with Papilioni7tae, 234, 277.

1 Meadow-brown ' butterfly, 210.

Mechanical Incompatibility,
asyngamy as a consequence of,

II. 85.

'Mechanical selection', 85.

Medical faculty [in 1889] and
heredity, 136, 137.

megalocephala, Ascaris, germ-
antecedents in one of first two cells
of egg, 131.

Melanism, recent increase of, in
N. of England, 308, 309, 309 n. I.

Me/ani/is, cryptic effect of slanting
position of, 289; T. R. Bell, C. T.
Bingham, and E. E. Green on tilt of,
300 n. 5.

Me/ani/is zitenius, 288, 2S9.

Meldola, Professor Raphael, on
the power of Natural Selection, 153 ;
on Mullerian mimicry and trans-
mission of acquired characters, 167 ;
on Prichard's anticipation of modern
views on evolution, 174; lizard
attacking eye-spot of butterfly ob-
served by, 210; Fritz Muller's theory

442 ANALYTIC

of mimicry brought forward and
supported by (1879), 2I2> 21 3> 223 ;
letters from Darwin to, 225, 228,
233, 272 n. I (although Meldola's
name is not mentioned in this foot-
note) ; on uniformity throughout
nauseous groups of butterflies, 234,
278.

Melinaea, a central type of Itho-
miine pattern, 234 ; Heliconius re-
sembles the nearly related Eueides far
less closely than it does the remote,
235 ; Danaini and Euploeini com-
pared with Heliconius and, 334.

Melinaea nineme, 331-3.

Melinda, see Tirumala.

Melsetter, Gazaland, S.E.
Rhodesia, attack of drongo on dis-
tasteful moth witnessed at, 284.

Melynias, see Elymnias.

Melynias malelas {Elymnias leuco-
cyma), 372.

Melyridae mimicking Lycidae,
276.

M remb7-acidae , protective (pro-
cryptic) resemblance developed in
shield rather than in insect itself,
258, 259; mimicry of ant developed
in shield rather than in insect itself,
258, 258 (Fig. 6), 259, 280, 369;
resemblance to leaf-carrying ant with
its leaf, of larval, 259, 259 (Fig. 7),
260, 280, 377.

Memory versus imagination, 196-8.

Mendel, Abbd Gregoire, the great
discovery of: see Mendelian prin-
ciple ; Weismann's discoveries appro-
priated under the name of, xiii, xxxvi,
xxxvii, xxxvii n. 1.

Mendelian principle in heredity,
discovery of, xxix ; rediscovery of, by
De Vries, Correns, and Tschermak,
xxix ; nature of, xxix-xxxiii ; infer-
ences from concerning the germ-
cells, xxxi-xxxiii ; a fascinating addi-
tion to knowledge, xxxiii ; value of,
xxxiv, xxxv ; probable immense im-
portance of in Artificial Selection,
xxxv ; the importance of, greatly
exaggerated, xiii, xiv, xxxvii n. 2 ;
affords but little help in solving the
problem of evolution, xxxiii-xxxv;
abundant hybrids which do not follow
the, xxxv, xxxv n. 1 ; proof by Mendel
himself that hybrids of Hieracium
do not follow the, xxxv n. 1 ; Correns
on limitation of, to crosses between

Vh INDEX

varieties, xxxv n. 2 : increasing com-
plexity in the hypothetical germinal
mechanism suggested by, xxxvii n. 2 ;
Natural Selection and, xxvi-xxxv.

Mendelian work on heterostyled
condition of primrose, xxix-xxxi ;
impossibility of long continuance of,
xxx n. 1 ; limited conclusions to be
inferred from, xxx, xxxi.

Mendelism, Mutation, and
Natural Selection, Introduction
xiii-xlviii.

Mendelism and Natural
Selection, Introd. xxvi-xxxv.

Mendelism and Natural
Selection, no Essential Diver-
gence between, Introd. xxxvi-xli.

mendica, Spilosoma, aposematic
attitude of, 324.

mephitica, Mephitis, warning
colours of, 315.

Mephitis mephitica, 315 ; — suffo-
cans, 315.

Mercury, susceptibility to, heredi-
tary, 180.

meriones, Papilio, non-mimetic
ancestor in Madagascar of African
species of Pap. dardanus with
mimetic females, 245, 373 : see also
dardanus.

merope, the W. sub-sp. of Papilio
dardanus, 374 : see also da?'da?ius.

Merops philippi?ius, 285, 286, 289 ;
— swinhoei, 287.

Merostomata, great development
of, in Silurian, 40.

Merrifield, F., results obtained by,
quoted in Essay X, 293 ; on seasonal
changes in British Lepidoptera, 311.

Mesozoic time, waste and sedi-
mentation in, 16 ; Scudder's views
on evolution of higher insects in, 35 ;
Angiosperms appear late in, 45.

Metaphyta compared with Proto-
phyta, 120.

Metazoa, originate from Protozoa,
23 ; the meteoric hypothesis and,
24 ; place in classification of, 25 ;
evolutionary history of phyla of, 26,
27 ; pre- Cambrian evolution in, 31 ;
compared with Protozoa, 120.

Metazoon, development of illus-
trated description of Diagram II,
127, 128, 130, 131.

Meteoric dust on ocean floor, 20 ;
hypothesis of origin of territorial life,
22-4.

ANALYTICAL INDEX

Meteors, sun's energy perhaps
increased by, 14.

Methona confusa, 264-6.

Metschnikoff, Dr. Elias, on the
lactic acid bacillus, 121 n. 1.

Mexico, L. astyanax enters from
N., 274.

Microhierax coertilescens, 289-91 ;
— eutolmics, 290 ; — fringi Harms,
290.

?nidamaf Callamesia, belonging
to the distasteful Zygaenidae {Chal-
cosiinae), a Mullerian mimic of
Euploeas, 372, 376 ; moths allied to,
are similarly Mullerian mimics of
same Oriental models, 376.

Midland Naturalist, 120, 142
n. 1.

Midland Union of Natural
History Societies. Author's Presi-
dential Address (1889) the
foundation of Essay IV, 120.

Migration and History may
be Inferred from Mimicry, X.
363-5.

Migration of insects, 93 ; of butter-
flies in Ceylon, 285 ; in Burma, 289 ;
history and, to be inferred from
Mullerian mimicry no less than from
Batesian, 363-5.

Migratory birds of W. China,
interest in the study of, 217, 218,
382.

Mikado, 302.

Milton, John, influence of, on belief
in special creation, 55, 56.

Mimetic, see mimicry.

Mimetic Attraction, F. A. Dixey,
328 n. 1.

Mimicry, E. B. Poulton, in Diet,
philos. and psychol., J. M. Baldwin,
312 n. 2, 360 n. 1.

Mimicry between Butterflies
of Protected Genera, R. Meldola,
234.

Mimicry in Butterflies of the
Genus Hypolimnas, E. B. Poulton,
247 n. 1.

Mimicry, &c., bearing of, upon
supposed Hereditary Trans-
mission of Experience, V. 166-8.

Mimicry, new Interpretation
of an old example of, vii. 21 1-l8.

Mimicry, Natural Selection
the cause of common warning
Colours and (Theories of
Mimicry), Essay VIII, 220-70.

Mimicry and Natural Se-
lection, Essay IX, 271-82 ; Appen-
dix to Essay IX, containing evidence
of birds attacking butterflies, 282-92.

Mimicry, Place of, in a
Scheme of Defensive Colora-
tion, Essay X, 293-382 ; for divi-
sions, sub-divisions, sections, &c, of
Essay X see Contents, pp. 293-7.

Mimicry Mullerian, Common
Warning or Synaposematic
Colours, X. 327-56 ; for sections
and sub-sections see 295-6.

Mimicry Mullerian (Synaposem-
atic or Common Warning Colours)
see under Mimicry Protective, &c,
Historical Accotmt, where the refer-
ences to both theories are combined :
see also under Mimicry Protective,
&c, Relation to Miillerian Mimicry,
and Bearing upon Theories of Evo-
lution ; order in which to undertake
study of examples of, xxv, xxvi, 336 ;
long delay in appearance of (1862-
1879), 327 n. 1 ; reasons for slow ac-
ceptance of, 213 ; place of in a
scheme of the bionomic uses of
colour, 226 ; logically a section of
warning colours, 327 ; mimetic
patterns derived from warning and
remaining warning, 349; protective
(pseudaposematic) mimicry is decep-
tive while Mullerian (synaposematic)
is a genuine warning, 360; evolu-
tion of a hypothetical example of,
329-31; associations of, with special
(aposematic) protection, 335, 336 ;
between models themselves, 211-15,
222 ; effect of mimics on stability of
model in, 336 ; uniformity in
nauseous groups of butterflies, 234,
277-9 > uniformity in species of
wasps and Fossores, 278, 376 ; high
degree of special protection accom-
panied by, 335 ; perfect in highest
degree when special protection
highest, 335, 336; young enemies
and the evolution of, 167, 167 n. 2,
212, 268,329-31,366; terms 'com-
bination' or 'association' used in
connexion with, 293 ; a combina-
tion exhibiting, called 'Mimicry-
Ring' by Professor Weismann, 376 ;
methods of defence in the same com-
bination may be various, 230 ; more
evidence wanted of simultaneous
occurrence of members of combina-

444

ANALYTICAL INDEX

tions exhibiting, 248 ; especially
found in female, 244-7 ; mimics ex-
hibiting may extend beyond range
of models, '215-18, 247, 349, 381,
382 ; migration and, 363-4 ; inde-
pendent of size, 366, 367 ; erro-
neously supposed not to exist
between remote forms, 229-32 ;
between groups of various degrees of
affinity, 229-34 ; examples of, pro-
bably not truly indistinguishable to
enemies except when species are
closely allied, 329 ; discriminating
features persist even in closest re-
semblance, 349, 350; recognition of
sexes perhaps specially provided for
in, 350, 358 ; Dr. F. A. Dixey on
Diaposematic or Reciprocal Resem-
blance characteristic of, 213, 344,
345 ; Dr. F. A. Dixey on secondary,
345 ; a mimetic common ancestor of
divergent mimetic group best ex-
plained by, 352, 354; consistent
with di- and polymorphism in mimi-
cry, 355, 356.

— Evidence in favour of: — sup-
plied by the tendency of the like-
nesses to run in groups (a), 346 ;
by dominance of mimetic species
and groups {b), 346, 347 ; diver-
gent mimicry in species of same
group (c), 347 ; warning patterns of
non-mimetic males and non-mimetic
species of mimetic groups (d), 347 ;
occurrence of mimetic species in
warningly coloured groups (e), 347 ;
mimicry of the non-mimetic males
and non-mimetic species of mimetic
groups (/), 347 : see also 217-18,348,
349, 371, 375 ; niimics more con-
spicuous in certain points than
models {g), 2,47 closeness of mimi-
cry between the admittedly dis-
tasteful groups (h), 347.

— Examples of: — see classification
of examples of Mullerian and
Batesian (Protective) mimicry, 383-
93. The examples are not discrimi-
nated, inasmuch as the interpretation
is still under discussion: see 328.

Mimicry, Protective and
Aggressive : Pseudaposematic
and pseudepisematic resem-
BLANCES, X. 358-78. For divisions,
sections, and sub-sections see 296,
297 ; place of in a scheme of the
bionomic uses of colour, 226.

Mimicry, Various uses of
Term : the Essential Element
in, X. 359-61.

Mimicry, Protective (Bate-
sian) or Pseudaposematic Resem-
blance, X. 361-76. For sections
and sub-sections see 296, 297.

— Historical Account of Mullerian
Mimicry and : — history of, 220-4 *> re-
cognition of, shown in termination
-formis, 221 ; Kirby and Spence
(1817) on, 221 ; utility of, suggested
by Kirby and Spence, 221 ; W. S.
Macleay (1819 and 1821) on, 220;
Rev. W. Kirby (1822) on, 220 ;
Boisduval (1836) on, 221 ; J. O.
Westwood (1837) on, 221 ; H. W.
Bates (1862) on, 85,86,211,212, 220,
221, 222,223,224, 226,327; theory of,
included in cryptic resemblances by,
359; A. R. Wallace (1866) on, 222,
223, 226, 327 ; Roland Trimen
(1872 and 1897) on, 222, 223 n. 6;
Fritz Muller (1879) on, 166-8,
211-15, 222-4, 226, 278, 327, 328,

342- 4; F. Muller and C. Darwin on
sexual selection as cause of, 225, 272 ;
R. Meldola (1879 and 1882) on, 223 ;
defence of Muller's theory by, 212,
213, 234, 278 ; F. Moore (1883) on,
223; Blakiston and Alexander (1883,
1884), 328, 329, 329 n. 1 ; E. B.
Poulton (1887, 1890, and 1897) on,
223; F. A. Dixey (1894, 1896, and
1897) on, 213 n. 1, 223 ; support to
Muller's theory afforded by, 213, 223,

343- 5 ; W. F. H. Blandford (1896,
1897) on, 343; A. G. Mayer (1897)
on, 234, 277.

— Study of: — definition of, 358-61 ;
place of in a scheme of the bionomic
uses of colour, 226 ; false warning
the essential element in, 344, 360 ;
accidental resemblances distin-
guished from, 247, 257 ; other super-
ficial resemblances distinguished
from, 312, 359, 360; confusion
caused by term, 140, 361 ; various
uses of term, 3 59, 360 ; order in which
to undertake the study of, xxv, xxvi,
336 ; limited examplesof studied, 229,
272 ; necessity for study in the field
of, 363 ; importance of movements in,
238, 239, 241, 252-4, 256, 257, 368 ;
adapted for repose as well as for move-
ment, 360 ; importance of attitude in,
241, 341 ; mimetic sounds, 251, 324 ;

ANALYTIC

AL INDEX 445

space and time relationships of, 247-
50; model and mimic may be
widely separated provided the enemies
can cross the intervening barrier,
217-18, 361, 382 ; both Batesian and
Miillerian largely independent of
size, 366, 367 ; independent of
zoological affinity, 229-34, 232-3,
235—7, 336 ; often closest when
affinity is remote, 235 ; essentially
superficial, 237-40; mimetic like-
ness unaccompanied by any other ap-
proach, 237-40 ; affects deep-seated
parts when superficial likeness is
thereby increased, 238, 239 ; espe-
cially characteristic of female, 215-
17, 244-7, 279, 372-5; special ad-
vantages to female of, 246, 279 ;
ancestral appearance preserved in
non-mimetic male, 244-7 5 Wallace's
conditions of, 361, 362.

— Complexity of: — 239; analysed
into its components, 240-2 ; made up
of colour, pattern, form, attitude, and
movement, 241 ; diverse modes of
attainment of, 250-67, 280, in
members of different Orders, 250-
61, of the same Order, 261-7; at~
tained in diverse ways in Beetles,
251-2, 255-6, 257 n. 1, 261-2, in
Lepidoptera, 251, 262-6; pigments
of mimetic Pierinae different from
those of models, 262, 263 ; attained
in different ways by Ceria (Diptera),
Oberea (Longicorn), &c, and Mem-
bracidae (Homoptera), 280 ; mimetic
transparency produced in variety of
ways in Lepidoptera, 251, 263-6,
276, 365, 366 ; resemblance not in
body but in covering shield of Mem-
bracidae, 258, 258 (Fig. 6), 259, 260,
280, 369 ; composite resemblance to
two objects, 368, 369 ; head of model
(ant) represented at tail of mimic, 254,
368 ; di- or polymorphism in mimetic
species, especially females of, 354,
364, 365 n. 1, 372-6 ; advantage of di-
and polymorphism in, 354-6, 372 ;
seasonal changes of butterflies and,
339-42 ; chiefly seen in imago, but
prepared for in the larval and pupal
stages, 242-4 ; ' eye-spots ' as exam-
ples of, 326.

— Inferences as to Origin and
Growth of:— pattern of non-mimetic
ancestor may determine trend of,
218 ; favoured by initial resem-

blance, 382 ; examples bearing on
origin of, 376 ; mimic being younger
may present a picture of former
condition of model, 364, 365 n. 1 ;
migration and permanence of resi-
dence may be inferred from, 363-4 ;
degeneracy of lost scales greatest in
best moth mimics of wasps, &c,
365, 366.

— Evidence in favour of \ — evidence
for, compared with that for Universal
Gravitation, xxvi, 271 ; Lloyd
Morgan's observations bearing on,
212: evidence of distastefulness in
butterfly models, 269, 279, 279 n. 1 ;
distasteful moths seized and rejected
by wild birds, 284 ; evidence of
advantage conferred by, 281 ; evi-
dence that mimicry averts attack,
288 ; insufficient direct evidence of
attacks, 268-70 ; indirect evidence of
attacks by birds, 281-3 : see also
evidence and birds.

— Relation to Protective {Pro-
cryptic) Resemblance : — relation of,
to other resemblances in nature,
225-8 ; procryptic resemblance
closely related to, 225, 226, 312, 314,
315, 348, 359, 360 ; combined with
procryptic colouring in certain butter-
flies, 350-4; instantaneous tran-
sition from procryptic resemblance
to, 367, 368 ; suggested interpre-
tation of, as a Syncryptic resem-
blance, 322 ; distinguished from
Syncryptic resemblance, 312, 359-
61.

— Relation to Miillerian Mimi-
cry:— see also Mimicry Miillerian;
Batesian and Miillerian mimicry
compared, 211-18, 222-4, 226,
227, 329, 359-62, 370-6; differ-
ences as regard Wallace's conditions
of Miillerian theory and, 362 ; gradual
predominance of Miillerian theory
over Batesian, 212, 213, 223, 342-4,
370-6 ; new interpretation of an
old example (H. misippus)^ 211-18,
'F. A.' in Punch on, 213-15;
Miillerian does not differ from
Batesian mimicry in importance of
instinct, inferences as to history and
migration, independence of size, and
confirmation of history by structure,
363 ; Miillerian mimicry often in-
cluded in Batesian, 360 ; interpreta-
tion as Batesian or Miillerian often

446 ANALYTICAL INDEX

provisional, 328 ; Lepidoptera, 348,
370-6, and Coleoptera, 348, dis-
cussed in relation to Miillerian
mimicryand ; Protogoniusa.ndElym-
niinae in relation to, 350-4, 372 ;
Colaenis in relation to, 334 n. 2 ;
secondary mimicry probably charac-
teristic of Miillerian mimicry, 345,
345 n. 6 ; mimicry of Hymenoptera
in relation to, 376 ; mimicry of
snakes in relation to, 376.

— Bearing upon Theories of Evo-
lution of'.— supposed transmission of
experience and, 166-8; mutation
and, xxii-xxvi ; internal causes sug-
gested to account for, 224, 225, 272,
but break down when investigated,
227-9, 233, 236-9, 241, 245, 247,
249, 250, 257, 260-2, 266-8, 270, 273,
275, 276, 278-82; external or phy-
sico-chemical causes suggested to
account for, 224, 272, but break down
when investigated, 227-9, 233, 235-
42, 244, 245, 248-50, 260-3, 266-8,
270, 273-82 ; contrasted conditions
of model and mimic in same locality,
243, 244, 276 ; sexual selection
suggested as cause of, 225, 228, 272,
but breaks down when investigated,
227, 228, 233, 236, 245, 246, 260, 261,
267, 270, 273, 275, 276, 278-82;
Common Warning Colours ( Miillerian
mimicry) and, explained by Natu-
ral Selection, Essay VIII, 220-70:
see also Essay IX, 271-82; growth
of confidence in interpretation of,
by Natural Selection, 218, 218
n. 2, 219, 224 ; facts of, con-
sistent with interpretation by, Natural
Selection, inconsistent with any
other suggested explanation, 227-9,
233, 235-42, 245, 246-8, 250, 258-
62, 266-70, 273, 275, 276, 278-82;
reason for special development in
S. America of Miillerian mimicry
and, 248.

— Examples of:—see classification
of examples of Protective and
Miillerian Mimicry, 383-93. (The
examples are not discriminated
inasmuch as the interpretation is
still under discussion : see p. 328.)
Batesian or Miillerian interpreta-
tion of examples provisional in
many cases, 328 ; the clearest
examples of Batesian, 367, 376 ;
development of, in Insecta, 367 ;

captured on one day, in Hope
Department, 248, 249 ; examples in
text (except the Leeds series), chiefly
selected from Ethiopian and Neo-
tropical Regions, 370.

Mimicry of Adventitious Ob-
ject (PSEUDALLAPOSEMATIC RE-
SEMBLANCE), 377 : see also 359.

Mimicry Aggressive, and Al-
luring Colours (Pseudepise-
matic Resemblance), 377, 378 : see
also classification of examples of mimi-
cry, 393; place ofinbionomic uses of
colour,226 ; directive characters (' eye-
spots ') may be examples of, 325, 326 ;
definition of, 358-61 ; false attraction
is the essential element in, 360 ; re-
semblance of Volucella to humble-
bees, and Asilidae to their victims
probably not examples of, 378.

jnira, My miopias ta, mimicking ant,

254, 255 (Fig. 3).

misippus, Hypohmnas, female of,
mimicking L. chrysippus, three
forms of female mimicking respec-
tively three forms of model, 355, 372;
three forms of mimetic female tran-
sitional, while two out of three corre-
sponding forms of model are sharply
marked off, 364, 365 n. I ; probably
a Miillerian mimic, and specially de-
fended, 215-17, 247; dominance of,
216; extends beyonds its model into
New World, 216, 247, 347; powers
of flight, 216 ; swarm of, observed in
mid-Atlantic, 216 n. 2; conspicuous-
ness of male, 216, 217 ; ancestral ap-
pearance of male, 216, 245 ; male pat-
tern mimicked by males of two butter-
flies in W. China far beyond its
range, 217, 218, 381, 382; mimicry
of male perhaps due to attacks of
migratory birds, 217, 218, 382; such
a cause, if confirmed, would prove
growth of mimicry by selection alone,
361.

Misseltoe, Darwin on the inade-
quacy of Mutation to account for the,
xix.

Misunderstandings arising from
term ' Mimicry ', 140, 361.

Mivart, St. George, Darwin's reply
to criticisms by, 6.

mneme, Melinaea, exact resem-
blance of Heliconius numatato, 331 ;
parallel transition from barred to
black hind wing in both model and

ANALYTICAL INDEX

447

mimic, 331 ; why considered the
model of H. numata, 331-3 ; far more
abundant than H. numata, 332 ;
abundance of, over Heliconius not
necessarily due to greater unpalata-
bility, 332.

Mobius on Mauritian crabs carry-
ing sea-anemones, 357; and Mauri-
tian hermit-crab living in an Ascidian
case, 357.

Model Outranged by Mimic,

X. 349, 350-

Model and Mimic, both Sexes
of both Alike, X. 371.

Model, Sexes of Different,
and Respectively Resembled by
Mimicking Species, X. 371.

Model, Mimicry of General
Appearance of Group rather
than of Single, X. 376.

Models, Mimicry of Cryptic,
X. 369, 370.

Models, Male and Female
Mimicking Different, X. 372.

Models, two or more Mimick-
ed by Female, X. 373 : see also
374-5-

Models or model (see also Mimi-
cry): resemblance between, 211-
15 ; examples of, far more abundant
than their mimics, 332, 333 ; sta-
bility of, influenced by mimics, 336 ;
advance of, in direction of mimic,
344 ; range of, exceeded by mimic,
349 ; in one locality mimic, in another,
217, 381-2; one species mimicking
two or more, 354-6 ; tail of mimic
resembling head of, 254, 368 ; Miil-
lerian resemblance no less than Bates -
ian implies mimic and, 360 ; mimics
may retain a picture of former con-
dition of, 364, 365 n. 1 ; advantages
of mimicking two or more, 354-6, 372.

Modern Views on Evolution
anticipated by J. C. Prichard,
Essay VI, 173-92.

Modification, Diagnosis tra-
versed by Individual, II. 73-5.

Modification, individual (see also
Acquired Characters), definition of,
73 n. 1, 142.

Mogok, Upper Burma, 291 n. 1.

Moisture, see External Causes;
Pierinae influenced in pupal or
larval state by heat and, 311, 312;
in food as suggested cause of wet
season broods, 341.

Mole-like forms in three Mammal-
ian Orders, 312, 359.

molitor, Pachypror a, chasing Taru-
cus piinius, 283.

Mollusca, in classification, 25 ;
common ancestry with other Phyla,
27 ; evolution in geological time more
marked than in lower Phyla, 28 ; in
early Palaeozoic, 30 ; insufficient
record of, in the stratified rocks, 42 ;
evolution of, 41, 42 ; Silurian and
Cambrian, 41,42 ; environment and,
106 ; procryptic resemblance to coral
of, 359-

Monkeys, brain of compared with
man's, 108 ; terrified by snake-like
caterpillar, 367 n. 2.

Monochrome, conspicuousness of,
321.

Monsters formed by experiments
on frog's eggs, 129 ; valueless for the
study of evolution, xxxix, xl.

Monstrosities, development of, 135,
136; hereditary, 135, 136; predeter-
mined in ovum, 135, 137.

Moore, Frederick, on Oriental
Miillerian mimicry, 223.

Moore, Rev. Aubrey L., on ancient
writers on evolution, 54-6.

Moral Reflections at the
Natural History Museum, I,
F.A., 213.

morania, Papilio, resemblance to
Acraea satis, 52 n. I.

More Letters of Charles Dar-
win, F. Darwin and A. C. Seward,
48, 56 n. 4, 63, 67, 68, 74, 76, 78, 79,
80, 82, 83 n. 2, 84, 86, 89, 174 n. 2.

Morfill, Professor W. R., transla-
tion of Portschinski by, 254.

Morgan, Professor C. Lloyd, on
'Natural Elimination', 105 ; definition
of acquired characters by, 142, 143;
on instinct, 1 54; on education of birds,
167 ; observations on young birds by,
212,268; on trend of human evolu-
tion, 170, 171.

Morgan, Professor T. H.,on Roux's
experiments, 128-30.

morgeni, Tirumala (Melinda), a
mimic of W. African Amauris, 337.

Morphinae (Amathusiinac), 1 eye-
spot' in the mimicked genus, Te nan's,
326 ; as models of the Eastern Elym-
niinae, 353.

Moseley, Professor H. N., on Peri-
patus, 33.

448 ANALYTICAL INDEX

Moths, Recent Darkening of
N. English, X. 308-10.

Moths and Butterflies, chief-
ly Oriental, Illustrating Mi-
micry, 370-6.

Moths (see also Arctiidae, Chalco-
siinae, Glancopidae, Sesiidae, Zygaen-
idae ; see also classification of ex-
amples of mimicry, 384-6, 388-92) :
pigments of, less stable than those
of butterflies, xlv; resemblance to
leaves of, 299, 302; to splinter,
319; to lichen, 359; colour of G.
obscurata in different environments,
307, 308 ; seasonal changes of, 311 ;
value of bright hind wings of,
303, 304, 325 ; hind wings of, torn as
if seized, 304 ; distasteful species of,
seized and rejected by wild birds, 284 ;
wings of, in nest of Microhierax, 291
n. 1 ; mimicry of butterflies by diurnal ,
249, 250, 275, 276, 372, 376; Mul-
lerian mimics of butterflies, 231-2;
Dr. Dixey's discussion of entrance
into Miillerian combinations of, 343 ;
Miillerian mimics of Erycinid mimics
of Ithomiinae, 346 ; attainment of
transparency by, in mimicry of trans-
parent-winged butterflies and Hy-
menoptera, 251, 266, 365, 366; early
recognition of resemblance to Hy-
menoptera by, 221.

Motive Force of Investiga-
tion, Introd. xlvii, xlviii.

Moulting and seasonal change of
colour, 310.

Mountainous country, J. C. Prich-
ard on the horses and cattle of, 1 89.

Movements and Attitudes,
Importance of Instinctive, in
Display of Warning Colours,
X. 323, 324.

Movements and Attitudes, Im-
portance of, for Mimicry, X.
363.

Movements (see also flight) :
importance of, in procryptic defence,
360 ; power of rapid colour adjust-
ment suited to rapid, 304, 305 ;
sudden transition from cryptic to
aposematic or pseudaposematic de-
fence caused by, 318-20; impor-
tance of, in aposematic defence, 322 ;
conspicuousness of slow, 370 ; im-
portance of, as recognition characters,
357> 358 ; importance of, in directive
marks, 282 ; importance of, in the

head-like appearance of Lycaenidae,
325, 325 n. 1 ; importance of, in
mimicry, 238-9, 241, 251-4, 256,
257, 368 ; in aggressive mimicry, 378 ;
aggressive use of, by flyas, 314.

Moving objects, protective (pro-
cryptic) resemblance to, as well as
mimicry of, 360.

Muir, F., direct evidence of attacks
by birds on butterflies obtained by,
282 n. 1.

mulctber, Trefisichrois, females of,
mimic Danaini though themselves
models, 334, 335 ; females of, mimick-
ed by females of Mel. malelas, 372 ;
and with other blue Oriental Euploeas
imperfectly mimicked by diurnal
moth, Callamesia midama^ and allied
species, 372, 376.

Mullein Shark Moth, 318, 319.

Miiller, Dr. Fritz, interpretation of
resemblance between models (Miiller-
ian Mimicry) suggested by (1879),
166-8, 211-15, 222, 223, 226, 278,
327, 328 ; on sexual selection as
possible cause of mimicry, 225, 228,
272 ; on epigamic scent in male
butterflies, 317 ; on * stink-glands' of
Colaenis, 334 n. 2 ; indirect evidence
of birds attacking butterflies obtained
by, 270, 270 n. 1.

Miiller, Johannes, T. H. Huxley
on, in.

Miillerian Mimicry, see Mimicry
Miillerian, &c.

Multiple births of cats, dogs, &c,
distinguished from ' identical ' twins,
133-

Murray, Sir John, on ocean floor,

21.

Museums, necessity for long series
in, 75, 76; as centres of biological
research, 77 ; branch tropical biologi-
cal stations and, 89, 90 ; storing of
epigonic evidence and, 90.

Mutation, Mendelism, and
Natural Selection : Introduction,
xiii-xlviii.

Mutation, De Vries's Evi-
dence in Favour of, Introd. xvii-
xxii.

Mutation and the Facts of
Mimicry, &c, Introd. xxii-xxvi.

Mutation, an old idea, xiv ; De
Vries on intermittent periods of, xx ;
definition of, xvii, xvii n. 2 ; known to
Darwin, xviii, xix ; in the Vestiges of

ANALYTICAL INDEX 449

Creation, xviii, xix ; does not explain
adaptation, xix, xix n. 2 ; Sir W. T.
Thiselton-Dyer on cultural condi-
tions and, xxii ; evolution by small
variations is not, xxxviii, xxxix ; Se-
lection and, no; Palaeontology and,
no; Huxley's views on, 195; dark-
ening of N. moths and, 309 ; double-
dayaria as an example of, 309.

Mutations, Variations, and Re-
lationships of the Oenotheras,
D. T. Macdougal, A. M. Vail and G.
H. Shull, xix n. 5, xxi, xxii.

Mutationists and Darwinians,
essential difference between, xxxviii.

Mutilations and Pangenesis, 125 ;
not hereditary, 136 ; origin of
apparent, 147-9 5 supposed trans-
mission of, discussed and rejected by
J. C. Prichard (1826), 180, 181, 182.

Mycalesis perseus, 291.

Mylothris, ancestral Pierine white
retained in males of S. American
species of, 240.

Mylothris agathina, 341.

Myriapoda in classification, 33 ;
in the Palaeozoic, 34 ; fossil in the
Oligocene, 34 ; no approximation of
insects towards, in fossiliferous rocks,
38.

Myrmecophana fallax, 256, 257,
257 n. 1, 258 (Fig. 5), 280.

Myrmeleon larva, allanticryptic
resemblance of, 313.

Myrmoplasta mira, 254, 255 (Fig.

mystaceus, Phrynocephalus, a lizard
with flower-like lures, 378.

N

Nabis lativentris, 257 n. I.

nadina, Huphina, Miillerian
mimicry especially in dry f. of, 342.

Nansen, Dr. F., on the intelligence
of the seal, 116.

Natal (see also Africa, South) :
recent immigration of N. butterfly
species into, 52 n. 1 ; dorippus f. of
L.chrysippus'm,ji n. 1 ; preferential
mating of butterflies in, 87 ; examples
of mimicry from, in Hope Depart-
ment, 249 ; attack of fly-catcher on
butterfly witnessed in, 283.

natalensis, Precis, wet season form
of P. sesamus, 208 ; the dry season
form (sesamus) bred from (1898),
2°8, 339) 340, 34o n. 4 ; attempt to

determine the physiological cause of
change, 340 ; under surface similar
to but more conspicuous than upper,
339, 340; a rough mimic of an Acraea,
339> 339 n« r> 34° 5 reasons for sup-
posing a Miillerian mimic of an
Acraea, 339 ; S. African habitat of, 340.

natalica, Precis, under side ocellated
in wet, procryptic in dry season, 340 ;
S. African habitat of, 340.

Nat. Hist. (Historia Naturalis
et Experimentalis, &c), Francis
Bacon, 55.

Natural Philosophy, Thomson
and Tait, 4 n. 3.

Natural Selection, On, A. R.
Wallace, 51 n. 1, 203, 367 n. I, 369.

Natural Selection, Mutation,
and Mendelism : Introduction,
xiii-xlviii.

Natural Selection and Men-
delism, Introd. xxvi-xxxv.

Natural Selection and Men-
delism, no Essential Diver-
gence between, Introd. xxxvi-xli.

Natural Selection, Huxley
and the Theory of, Essay VII,
193-219.

Natural Selection, the Cause
of Mimetic Resemblance and
Common Warning Colours,
Essay VIII, 220-70.

Natural Selection and
Mimicry, Essay IX, 271-82;
Appendix to Essay IX containing
evidence of birds attacking butter-
flies, 282-92.

Natural Selection, Colours
probably Adjusted to Environ-
ment by Local Action of, X.
307, 308 : see also 308-10.

Natural Selection, popular dis-
belief in, and its cause, xvii, xviii ;
creative, xxiii ; Mendelism and, xxvi-
xxxv ; decides between germs rather
than individuals, xxxvi, xxxvii, xxxvii
n. 1, 135, 183 ; compared with arti-
ficial, xl, xl n. 2, n. 3, xli ; J. B. Farmer
on the explanation based on, as a
bar to inquiry, xliv-xlvii, xliv n. 1, 74
n. 2 ; the stability of pigments in
Lepidoptera and, xlv ; rigid self-
criticism required in the study of,
xlvii ; a fruitful stimulus to inquiry,
xlvii, xlviii ; protest against facile
speculation based upon, xlvii, xlvii
n. 1 ; Lord Salisbury's criticisms of,

POl'LTON

ANALYTICAL INDEX

2-4 ; sexual instinct and, 65 ; renders
organisms susceptible to stimulus,
73 ; response to stimulus and, 74
n. 2 ; Huxley's doubts upon, 77-80 ;
not the cause of interspecific sterility,
80, 89, 91 ; cessation of, a cause of
interspecific sterility, 80-2 ; fertility
and, 80-2 ; aided by syngamy, 93-4 ;
the Darwin-Wallace joint essay upon
(1858), 95-7, 194-6: see also xxxvii
n. 2, 48, 58, 200, 222, 379 ; does not
explain variation, 96-7 ; Lamarck's
theory compared with, 101 ;
Lamarck's theory confused with,
10 1 -3, 104 ; Duke of Argyll's ex-
planation of belief in, 101-2 ; diffi-
culty with which apprehended, 101-
4 ; parodies on, 102-4 ; utility and,
105-9 ; Natural elimination or, 10$ ;
advantages of name, 105 ; objections
to, 105-10; brain evolution and, 107-
8 ; Palaeontology and, 107-8 ; origin
of organs and, 108-9 ; a true cause of
evolution, 109, no; mutation and,
no; form of joints and, 112, 113;
Crustacean claws and lizards' tails,
113, 114; forms of joints and teeth
and, 115 ; instincts and, 1 16-19, 138,
154-66 ; cryptic adaptation and,
1 54-7 ; the cocoon-making instinct
and, 117, 118, 157-60, 164 ; instincts
of Fossores and, 118, 119, 160-4;
use-inheritance and, 137, 138 ; varia-
tion and, 137 ; effect of cessation of,
137, 138 ; nervous system and, 138;
variable protective resemblance and,
152-4; struggle in young birds
and, 167, 167 n. 2, 168 ; limited but
undoubted use of by J. C. Prichard
(1826), 174, 191 ; Huxley and, 193-
219 ; history of discovery of, 193,
194; Huxley's ignorance of, July,
1858-Nov. 1859, 195, 196; Huxley's
opinion of, 201 , 202 ; basis of belief
in, 202 ; confirmed by observation of
Nature, 202 ; dead-leaf-like butterflies
and, 203-6; adaptation in Lepidoptera
and, 203-18 ; seasonal changes in
butterflies and, 206-11 ; confirmation
of, 218-19 ; prediction and confirma-
tion as test of, 2 1 9 ; H uxley's defence of,
219; evidence of advantage conferred
by concealment, 288, 289 ; Hypertely
used as an argument against, 302,
303 ; proof of severe struggle in pupal
stage of V. urticae, 306 ; darkening
of N. moths and, 308-10; seasonal

changes and, 206-11, 310, 311, 320,
339-42 ; species rather than indivi-
dual benefited by, 316; individual
subordinated to species by, 358.

— Mimicry and'. — Essays VIII
and IX, 220-82 : see also 21 1-1 8 ; the
origin of a mimetic likeness and,
218; increasing confidence in, as an
explanation of mimicry, 224; con-
sistent with facts of mimicry, 225 ;
relation of, to Protective Resemblance
and mimicry the same, 227, 237-42,
259 ; criticism of, founded on study of
limited examples of mimicry, 229 ;
the interpretation of mimicry when
other theories fail, 227-9, 232-3, 235-
42, 245, 246, 248, 250, 258-62, 266-8,
270, 273, 275, 276, 278-82 ; the in-
terpretation of the fewness of colours
in specially protected groups, 234, 277-
8 ; the female sex and, 215-17, 244-7,
279, 353, 372-5 ; favourable conditions
for operation of, in S. America, 248 ;
production of mimicry in covering
shield rather than insect beneath
by, 258, 258 (Fig. 6), 259, 280, 369;
mimicry by Membracid of ant and
leaf carried by it, 259, 259 (Fig. 7), 260,
2^o, 377 ; the cause of mimicry, 267-
70 ; belief in because of consistency
with facts, 268, 271 ; evidence of ad-
vantage conferred by mimicry, 288 ;
Bates's theory of mimicry one first
great result of, 361.

Naturalist in Nicaragua, T.
Belt, 240.

Naturalist on the Amazons,
H. W. Bates, 51, 51 n. 1.

Naturalist upon the Age of
the Earth, Essay I, 1-45.

Naturalist, Natural Selection and
the experience of the, 202.

Nature, xxii, xxxix, xl n. 2, xlvii,
8, 11, 13, 15, 19, 56 n. 2, 62 n. 1,
92, 140, 141 n. 2, 142 n. 5, 143 n. 1,
n. 3, 144 n. 2, 146, 152, 153, 154,
161, 163 n. 3, 164 n. 1, n. 3, 165, 166,
167, 232, 293, 329, 329 n. I, 365, 37i,
377 n. 2.

Nature stronger than nurture, 134,
!35.

Nautilidae among the earliest
fossils, 5, 30 ; rapid decline of, 41.

Nearctic, see America, North.

Neave, S. A., on transition between
African butterflies, 69 ; results ob-
tained by, quoted in Essay X, 293 ;

ANALYTICAL INDEX

on mimicry between species of
Danaine genus Amanris, 335 ; on
examples of Diaposematic Resem-
blance, 345 ; on African mimics of
L. chrysippns preferring station
different from that of their model,
349 ; on terror inspired in natives by
African snake-like caterpillar, 367
n. 2 ; discovery of mimicry in
filanemoides, female f. of Pap.
dardanus, by, 374 n. 3.

Neaves, Lord, parody of Darwin-
ism by, 103.

Nebalia, forms allied to in Cam-
brian, &c, 39.

Necydalinae, mimicry of Hymeno-
ptera by, 252.

Negroes, unchanged by many
generations in United States, 178 ;
J. C. Prichard on adaptation to
tropics of, 190.

Nematophora in classification, 25 ;
relation to ancestry of Vertebrata,
26 ; earliest forms of not primitive,
28.

Neobrotica mimicking Diabrotica,
236, 237.

Neotropical Region, see America,
South, and America, Central ; the
study of mimicry should reach its
climax in, xxvi.

Neotrofiinae, see Ithomiinae.

Nervous system, see also instinct
and intelligence ; evolution of, rapid
in higher animals, 29; evolution in
Mammalian, 107, 108 ; in man, 108 ;
1 instinctive ' mechanisms of the,
versus the 1 individually acquired
166 ; in adjustable Protective Resem-
blance, 305 ; epigamic characters
closely associated with, 380.

Nest of Microhierax with wings of
butterflies, &c, 290, 291, 291 n. 1.

Neuroptera of Commentry Carboni-
ferous, 35-7 ; unique interest of the
social, 52 ; wide difference between
the forms of the social, 72.

neustria, Malacosoma, cocoons of,
opened by birds, 157.

Neutralization of Shadow,
X. 299-300.

Neutralization, Adjustable,
of Shadow, X. 300.

Neutralization of shadow in Ag-
gressive Resemblance, 313.

New Factor in Evolution, Prof.
J. Mark Baldwin, 142 n. 2.

New Guinea, Papilio mimicking
Uraniid moth in, 371 ; bower of
Amblyornis of, 379.

New Interpretation of old
example of mimicry, vi i. 21 1-l8.

New Phytologist, 74 n. 2.

New World, see America.

Newcomb, Prof. Simon, on loss of
heat by the sun, 13 n. 2, 14.

Newt, Herlitzka's experiments on
egg of, 130.

Newton and Gravitation, 97.

Newtonian theory, confirmation of,
compared with that of Natural
Selection, xxvi, 97, 219, 271.

niavius, A mauris, see also domini-
canus ; transitional into dominicanns
f. at the V. Nyanza, xxxv, 68, 69,
338 ; corresponding changes in Papil-
ionine and Nymphaline mimics, 338 ;
mimicked by hippocoon female f. of
Pap. dardanus, sub-sp. merope, 338,
374) 375 j niavius figured by Weis-
mann in place of its eastern f. domi-
nicanns, 375.

Niger mouths to Sahara, exclusive
occurrence of alcippus f. of L.
chrysippus from, 321, 364.

nigricornis, Nitocris, mimics Hy-
menopteron during life, 363.

nigrofulva, Eueides, an outlying
member of the great distasteful com-
bination of B. Guiana, 332.

Nineteenth Century, 101.

Niphoninae, mimicry of weevils in
isolated section of, 250.

Nitocris nigricornis, 363.

Nodosaria, an existing genus in
the Carboniferous, 27.

nomius, Papilio, frequenting wet
mud, 285.

Non-Mimetic Male: Mimetic
Female, X. 372: see also 215-17,
244-7, 279, 347, 353, 373-5-

Non-Mimetic Ancestor Pre-
served on Islands, &c. : Remark-
able Case of Papilio dardanus
(merope), X. 373-6.

North America, see America,
North.

North British Review, xl, xl
n.3,3.

North India, see under India.

North, J.W., A.R.A., assistance in
the study of paper rendered by, 172.

North Kanara, experience in,
bearing on seasonal forms, 341.

G g 2

452 ANALYTICAL INDEX

Notley, Miss M. E., on pupal stage
of V. tirticae, 306.

Novitates Zoologicae, Tring, xvi,
53 n. 1,66 n. 2, 77, 85.

Nuclei of germ-cells in fertilization,
xxxi, 80-2 ; delicacy of mutual adjust-
ment in fertilization, 80-2 ; the seat
of the germ-plasm, 128.

tiumata, Heliconms, exact resem-
blance of to M. nmeme, 331 : see
also mneme ; probable gradual ap-
proach of to M. mneme, 332, 333.

Numbers, effect on mimics of
relative, 328-33.

Nummulina in the Carboniferous,
27.

Nyanza, Victoria, see Victoria
Nyanza, xxxv, 69, 338, 374, 374 n. 3.

Nymphalinae, Pupae of af-
fected by Gravity, V. 151, 152.

Nymphalinae (see also classifica-
tion of examples of mimicry, 383-7) :
methods of pupation in, 151 ;
seasonal changes in, 87, 207-8, 21 1,
310, 311, 320, 320 n. 1, 326, 339-42 ;
eye-spots in wet season forms of,
211, 326, 340-1 ; too exclusive study
of mimicry in Pierinae and, 229 ;
darkening of mimetic species of, in
the Guianas, 272, 273, 350; mimetic
species of, may be Miillerian, 272,
273; unpleasant scent in African
species of, 316; Dr. F. A. Dixey on
entrance into Miillerian combinations
of species of, 343 ; preferring station
different from that of model, Z.
chrysippus, 349 ; combinations of
procryptic and mimetic colouring
not uncommon in, 350.

O

Oberea, mimicry of Hymenoptera
by, 257 n. 1 ; method of attainment
of mimicry by, 280.

Oberthiir, Monsieur Charles, on
variation in Heliconia, 69 ; on the
distribution of Athyma punctata and
Limenitis albomaculata and their
model, and on the females of these
species, 381, 382.

obscurata, Gnophos, colour on
chalk and on peat of, 307, 308.

Observations on Indian Butter-
flies, T. R. Bell, 207 n. 1 : see also
341.

Observations on Sexual
Selection in Spiders of the

Family Attidae, George W. and
Elizabeth G. Peckham, 380.

Observations on the Coloration
of Insects, Brunner von Wattenwyl,
Engl, transl. by E. J. Bles, 256.

Occasional Papers of the Nat.
Hist. Soc. of "Wisconsin, 252, 253,
380.

Ocean, floor of, 20-2 ; basins,
stability of, 21 ; general Protective
(Procryptic) Resemblance to, 297,
298.

Oceanic islands, wingless insects
in, 18.

ocellatus, Smerinthtis ', derived
chlorophyll passing into eggs and
offspring of, 314, 314 n. 2.

ochlea, Amauris, a dominant
model in E. Africa, 336.

Odonata (Protodonata) of Com-
mentry Carboniferous, 18, 37.

Odontopera bidentata, 306.

Odour, see smell.

Odynerus, species of, resemble
other Hymenoptera in Australia,
278.

Oecodoma, see Atta.

Oecophylla, mimicry of, by cater-
pillar, 368.

Oedz'poda, value of bright hind
wings of, 303, 304.

Oenotheras as the evidence for
Mutation, xix-xxii, 4.

Oenothera crttciata, xxi, xxii, xxxv
n. 1 ; — lamarckiana, xix-xxii, xxxv
n. 1, 4.

Of the Causes which have given
rise to Varieties in the Human
Species, J. C. Pri chard, 176, 177.

Of the Relation of particular
Varieties of the Human Species
to Climates, J. C. Prichard, 191,
192.

Old World, Eufiloeini nearly ex-
clusively Austro-Malayan, Danaini in
all tropics of the, 333.

Oligocene, Myriapoda in the, 34.

omphale, Teracohts, experiments on
seasonal forms of, 311 ; Miillerian
mimicry chiefly in dry f. of, 342.

On Geological Time, Lord
Kelvin, 4.

On some Difficulties of Dar-
winism, Prof. D'Arcy Thompson,
225 n. 1.

On the Age of the Sun's Heat,

Lord Kelvin, 4 n. 3.

ANALYTICAL INDEX

453

On the Law which has regu-
lated the Introduction of New
Series, A. R. Wallace, 194.

On the Reception of the Origin
of Species, T. H. Huxley, 196.

On the Secular Cooling of the
Earth, Lord Kelvin, 4 n. 3.

On the Tendency of Varieties
to depart indefinitely from the
Original Type, A. R. Wallace, 194.

On the Variations of the
Evening Primrose, G. A.
Boulenger, F.R.S., xix n. 5 : see also
xxi.

On Variation, see Materials for
the Study of Variation, W.
Bateson.

Open country in S. Africa, defini-
tion of, 340.

Ophiuroids in early Palaeozoic, 30.

Orchidaceae, self-fertilization of
many, 92.

Orchis Bee, self-fertilization of, 64,

Orders of insects, mimicry between
different, 229-31, 250-61.

Organs, origin of, ic8, 109.

Oriental and other Lepido-
ptera Illustrating Mimicry,
X. 370-6.

Oriental Region : see also Anda-
man* 373, 373 n. 2 ; Borneo, 257 n. 1,
275, 276, 348, 349, 353, 367 n. 2,
369 ; Burma, 286-92, 373 ; Bombay,
70 n. 2; Canara, 70 n. 2; Ceylon,
70-1,285,286,349; China,S.,88,333;
Deccan, 70 n. 2; Hambantotte,
70 n. 2 ; Hong-Kong, 88; India, 70,
70 n. 2, 269, 317, 324, 341, 342;
349, 363, 371-3, 376; Irrawaddy,
291 n. 1 ; Kala Pani, 285 ; Kandy,
285 ; Karachi 70, 70 n. 2 ; Khan-
dalla, 70 n. 2 ; Macao, 88; Mala-
bar, 178, 187 ; Malaya, 248, 252,
333, 367 ; Mandalay, 291 n. 1 ;
Mogok, 291 n. 1 ; Moulmein, 289;
North Kanara, 341 ; Pahpoon, 290;
Poona, 70 n. 2 ; Puttalam, 70 n. 2 ;
Salween, 289; Siam, 303, 341;
Sikkim, 373 ; Singapore, 368 ; Sinza-
way, 290 ; Taungyah, 287 ; Tenas-
serim, 290, 291, 291 n. I ; Tha-
beitkyin, 291 n. 1 ; Thundiani, 285 ;
Trincomalie, 70 n. 2 ; Wabosakhan,
288 ; Yoonzaleen, 290.

—The study of mimicry in relation
to, xxvi ; fading in the pigments of

certain museum specimens of Lepi-
doptera from, xlv ; A. R. Wallace on
mimicry in the, 222 ; F. Moore on
mimicry in the, 223 ; uniformity in
Euploeini of, 277, 333, 334 ; ' leaf-
butterflies ' (Kallima) of, 203-8, 302,
310; Euploeini nearly restricted to
Australian and, 333 ; Precis, seasonal
forms of almana of, 340, 341 ;
mimicry in the Elymniinae of, 353 ;
L. chrysippus in, 70, 364 ; mimetic
chafer of, 368 ; blue Euploeas of the,
roughly mimicked by diurnal Chal-
cosiine moths, 372, 376 ; examples of
mimicry chiefly selected from Lepi-
doptera of, 370-6; localities of
A. cama in 382.

Origin of Species, Charles
Darwin, xv, xviii, xix, xxii, xxvi, 5,

21, 25, 46, 47, 48, 57, 58, 63, 67, 84,

91, 94, 139, 162, 165, 175, 175 n. 1,
196, 199, 200, 201, 219, 23311. 1,
361, 379; arguments for pre-
Cambrian time in, 5 ; definition of
species in, 46, 47 ; penetration of
ideas of, 48 ; influence on Huxley of,
200-1 ; twofold aim of, 200, 201.

Origin of the Fittest, Professor
E. D. Cope, 109.

Origin of Pupal Groove in
Pierinae, &c, V. 147-50.

Origin of specific discontinuity, xv,
xvi ; importance of geographical
distribution for the study of, xvi ;
of organs and limbs, 108, 109; of
Mullerian mimicry from warning
colours, 329-31, 349 ; of mimicry,
examples bearing on, 376.

Orioles, mimicry of powerful birds
by, 367.

orise, Dismorphia, perfect mimicry
of Ithomiinae by, 240, 265, 266 ; me-
thod of attaining transparency by,
266 ; Ecuador form of model and
mimic, 265, 266.

orithyia,Junojiia (Precis), wing of,
in nest of Micro hier ax, 291.

Ornithorhynchus, Song of the,
W. J. Courthope, 103, 104.

Orthogenesis der Schmetter-
linge, G. H. Eimer, 224.

Orthoptera (see also Acridiidac,
Blattidae, Locust idae, Mantid,n\
Pliastnidae) : of Commentry Car-
boniferous, 35-7 ; great age of, 52;
mimicking ants, 256, 257, 257 n. 1,
258 (Fig. 5), 280; mimicry of leaf-

ANALYTIC

AL INDEX

carrying ants by, 260 ; procryptic
resemblance to leaf of Pterochroza,
a genus of, 302 ; value of bright hind
wings of Oedipoda, a genus of, 303,
304 ; colour adjustment of, 307 ;
specially defended insects attacked
by predaceous, 318 ; colours of pro-
cryptic and pseudepisematic, 378,
378 n. 3 ; bug mimicked by larva
of, 378 n. 3.

Osborn, Professor H. F., on early
evolutionary ideas, 56 n. 2, 175;
on Lamarck and Erasmus Darwin,
141.

Ostracodes in Cambrian and
Silurian, 39.

Otter or ancon ■ sheep, sudden
origin of, 185.

Ovipositors possessed by Car-
boniferous cockroaches, 36.

Ovum (see also 1 germ- cells ') :
Natural Selection decides between,
xxx vi, xxxvii, xxxvii n. 1, 73 n. 1,
135, 183 ; variation predetermined
in, 137, 183.

Owl and owl's egg, riddle of the,
xxxvi.

Oxford, experiments on colour
adjustment of caterpillars at, 306,
307 ; colour of Cleonus at Boar's
Hill and at Shotover Hill near, 307 ;
darkening of moths at, 309.

Oxford, St. John's College, J. C.
Prichard a member of, 173; and
gentleman commoner of Trinity
College, 173.

Oxford University Gazette
(1905), 218.

Oxford University Museum, A. H.
Thayer's model in, 299: see also
Hope Department.

Oxlip, Bardfield, shown by Darwin
to be a true species, xxviii.

Oxlip common, shown by Darwin
to be a hybrid, xxviii.

Oxylymma gibbicollis, 237.

P

Pachyprora molitor, 283.

Pagurus bemhardus, 356 ; —
cuanensis, 357 ; — prideauxii, 357.

Pahpoon, Tenasserim, nest of
Microhierax found near, 290.

' Painted Lady ' butterfly, 85.

Palaeacridiidae (Acridiidae) of
Commentry Carboniferous, 36, 37.

Palaearctic localities of A thy ma

and Limenitis mimics of male H. mi-
sippus, and their model in British
Museum (Leech Coll.), and as given
by Monsieur Ch. Oberthiir, 382.

Palaeoblattidae(Blattidae) of Com-
mentry Carboniferous, 36, 37.

Palaeodictyoptera, the Palaeozoic
insects, 34, 35.

Palaeontology, limited records of,
100, 107, 108 ; Mutation and, no.

Palaeophonus, possibly an aquatic
scorpion, 40.

Palaeozoic, waste and sedimenta-
tion in, 16; tranquil deposition in,
17; tides, 17; insects, 18, 34-8;
corals, 28 ; Graptolites, 28 ; Verte-
brata, 30; Mollusca, 30, 41-2;
Gephyrea, 30, 42-3 ; Echinoderma,
30, 43 ; Appendiculata, 30 ; Arthro-
poda, 34-41 ; Myriapoda, 34 ; Phyl-
lopoda, 39 ; Malacostraca, 39, 40 ;
Phyllocarida, 39, 40 ; Arachnida, 40,
41; Pteropoda, 41, 42; Pterido-
spermeae, 45 ; Gymnosperms, 45 ;
Cordaiteae, 45.

Pallas on origin of domestic
animals from more than one wild
species, 83, 84.

palliata, Adamsia, carried by
Pagurus prideauxii, 357.

palumbus, Colu?nba, fertile pairing
with domestic pigeon, 83, 84.

pammofty Papilio, 373 : seepoiytes.

pamphilus, Coenonympha, i eye-
spot ' of, examined by lizard, 210.

Pangenesis, Darwin's theory of,
123, 124 ; gemmules of, 124-6 ; dia-
gram of, described, 123, 124, 126;
inheritance of acquired characters
and, 123-7; difficulties of, 124-7;
mutilations and, 125 ; transfusion
of blood and, 125 ; grafted tissues
and, 125-6; atavism and, 125 ; use-
inheritance and, 126; diagram of
use-inheritance in relation to, de-
scribed, 126.

Panmixia, W. Bateson on, xxxvii
n. 2.

Pantopoda in classification, 33.
Pantoporia, see Athyma, 382.
Paper, importance of quality of,
170-2.

Papilio dardanus (merope),
X. 373-6: see also 57, 57 m 1, 71,
72, 72 n. I, 337, 338, 354, 355, 370,

371,373-5-
Papilio ages/or, 371 ; — (Drurya)

ANALYTICAL INDEX

455

antimachus, 366 ; — antinorii, 373,
374, 374 n. I, 375 5 — ardurus, 285 ;

— argentus, 57 n. I ; — aristolochiae,
269, 372, 373, 375 ; — castor, 372 ; —
caudius, 57 n. 1 ; — caunus, 291 ; —
chaon, 372 ; — corinneus, 284 ; —
demodocus,2S$ ; — dravidarum, 372 ;

— echerioides, 375 ; — erithonitts,
288, 291 ; — hector, 373 ; — humbloti,
373 ; — lafrlaizei, 371 ; — macareus,
288 ; — meriones, 245, 373 ; — w^r-

52 n. 1 ; — nomius, 285 ; —
polyctor, 285; — polytes (pammon),
373 ; — protenor, 371 ; — sarpedon,
288, 290 ; — torqitatimts, 57 n. I ; —
torquatus, 57 n. I ; — xenocles, 288.

Papilioninae (see also Papilio: see
also classification of examples of mimi-
cry* 385, 387-9) : compared with 77^#-
miinae as regards number of colours,
234, 277 ; as models for Pierinae,

262 ; pigments of, different from
those of their Pierine mimics, 262,

263 ; an Indian species of, proved un-
palatable, 269 ; value of ' tails ' of
hind wings of, 281, 282 ; mimetic
not attacked by bee-eaters, 288 ;
unpleasant scent in African, 316 ;
eye-spots of, 326 ; Dixey's evidence
of entrance into Miillerian com-
binations of, 343 ; P. agestor as
probable Miillerian mimic, 371 ;
mimicry in species of, probably
Miillerian, 372-3, 375-

Par£, fly from, mimicking Hymeno-
ptera, 257 n. 1.

Paradise fly-catcher capturing
butterflies, 283.

Paradise Lo3t, John Milton, 56.

Paradise of Birds, W. J.
Courthope, 103, 104.

paralekta, Kallima, difference
between sexes of, 207.

Parantica, the Danaine model of
E. lais, upper side, 353.

Parasites, attacks of, on specially
defended insects, 318 ; concealed on
hair or skin of host, 359.

parasitica, Sagartia, carried by
Pagurus bernhardus, 356, 357.

Parents, Prichard on comparison
between hereditary influences of, 185.

Paris, Jardin des Plantes, O. la-
marckiana originally described from,
xxi.

Parodies on theories of evolution,
102-4.

Part-nuclei of germ-cells con-
cerned in fertilization, xxxi, 80-1.

Passive, Lamarckism and structures
whose use is, 112; development
together of active structures and,
113; defence of insects essentially,
156.

Patagonia, J. C. Prichard on
height of man in, 187 ; dull colours
of animals in, 225.

Pattern of under surface tends to
be the more conspicuous in apose-
matic species, 323 ; cryptic effect of,
321 ; often similar on the two sur-
faces of aposematic species, 323.

Peas, Mendel's researches upon,
xxxi-xxxiii.

Peat, procryptic colour of G. obscu-
rata on, 307, 308.

Peckham, George W. and Eliza-
beth G., on instincts of Fossorial
Hymenoptera, 118, 162, 163; on
ant-like spiders, 252, 253, 253 (Fig. 1) ;
on the courtship of Attid spiders,
380.

Pedipalpi in Carboniferous, 40.

Penard, Prof. E., direct evidence
of attack by bird on white butterfly
by, 282 n. 1.

Penoa deione, 373.

Pentatomid bug mimicked by
caterpillar, 369.

Perforata, six existing genera of,
in Carboniferous, 27.

Pericopidae, 264, 266 : see Hypsid-
ae.

Peripatoidea in classification, 33.

Peripatus derived from Chaetopod-
like ancestor, 27 ; ancestral nature
°f> 33> 34 5 no approximation of
earliest fossil insects or Myriapods
towards, 38.

Perlidae (Protoperlidae) of Com-
mentry Carboniferous, 36, 37.

Permian, Foraminifera, 27.

Perry, Professor John, on the
changing shape of the earth, 8 ; on
the cooling of the earth, 9-13; on
the life of the sun, 14; on Radium
and the age of the sun, 15 n. 2;
letter from Lord Kelvin to, 19.

per saltum evolution, Rothschild
and Jordan on, xvi ; Huxley on, 4,
195.

Perseus, Mycalesis, wings of, in
nest of Microhierax, 291.
perspicillata, Tetpsiphone, cap-

456 ANALYTICAL INDEX

turing Eronia cleodora and attacking
Atella phalantha, 283, 284.

Peru, Bolivia, and Ecuador,
colours of the chief Ithomiine-
centred combination in, 351; char-
acter of under surface of mimetic
Protogonius in, 351.

Phaeaga?ista he kit 'aides, 232.

phalangium, Stenorrhynchus, allo-
procryptic resemblance of, 313.

phalantha, Atella, chased and
injured by fly-catcher, 283, 284.

Phatieropterides, mimicry of ants
by, 256,257, 257m 1, 258 (Fig. 5), 280.

Phasmidae of Commentry Car-
boniferous, 36, 37.

philenora, Epicopeia, a mimic
(probably Miillerian) of Papilio
protenor, male and female respec-
tively mimicking sexes of model, 371.

pliilippinus, Merops, attacking
Pierinae in Ceylon, 285, 286; per-
sistently capturing Catopsilia, 289.

Phillips, Professor John, conver-
sation of, with Darwin on species,
68.

Philosophical Transactions of
the Royal Society, 150, 185, 262.

Philosophie Zoologique, La-
marck, 141.

Philosophy of the Inductive
Sciences, W. Whewell, xlvi n. 1.

phlaeas, Polyommatus, evidence of
preferential mating in, 87 n. 1.

phry?te, Huphina, Miillerian
mimicry chiefly in dry f. of, 342.

Phrynocephalus mystaceus, 378.

Phyllidae, wings of Palaeozoic
Protophasmidae resemble those of
female, 36.

Phyllocarida in Palaeozoic, 39, 40.

Phyllopoda in Palaeozoic, 39.

Phy/losticta, attacking leaves,
205 n. 1.

Physico-chemical causes suggested
for mimicry : see External Causes.

Physiological Society, Pro-
ceedings of, 314 n. 2.

Physiological Selection, Asyngamy
the consequence of sterility according
to, 84.

Physiology, Journal of, 314 n. 2.

Phytophagous beetles (see also
classification of examples of mimicry,
390-1): as models comparable with
the great distasteful butterfly groups,
236, 237.

picata, Synageles, mimicry of ant
by, 253, 253 (Fig. 1 A).

picipes, Eude?res, mimicking ants,
255. 255 (Fig. 4), 256.

Pictet, Adolphe, anticipated by
J. C. Prichard, 173.

Pierinae, Origin of Groove
in Pupae of, V. 147-50.

Pierinae (see also classification
of examples of mimicry, 384,
386-9 : see also Pieris): pupae
of, paralleled by those of Zonosoma
(Ephyra), 150; attacked by bee-
eaters in Ceylon, 285, 286 ; sea-
sonal changes in, 311, 312, 341 ;
Belenois, 311, 312, 341 ; Teracolus,
311, 312, 341, 342; Huphina, 342;
Miillerian mimicry in relation to the
seasonal changes of, 341, 342 ; chief
examples of mimicry adduced by
Bates, 213; too exclusive study of
mimicry in Nymphalinae and, 229 ;
ancestral white retained in males
of mimetic species, 240; especially
liable to mimicry, 262 ; pigments
of, different from those of models,
262-3 > probably Miillerian mimics,
262, 272, 273 ; method of attaining
transparency in, 266 ; darkening of
mimetic in the Guianas, 272, 273 ;
Dr. Dixey's evidence of entrance
into Miillerian combinations, 343 ;
combination of procryptic and
mimetic colouring in, 350 ; an
Indian species of, proved unpalat-
able, 269.

Pieris, attack of bird on species
probably of, 282 n. 1.

Pieris brassicae, 1 47 ; — rapae,
93, 147, 301 5 — spilleri, 52 n. 1.

Pigeon, fertile pairing of Ring Dove
with domestic, 83, 84 ; origin of
domestic, 83 n. 2.

Pigments, Natural Selection and
the stability of, in Lepidoptera, xlv ;
of the Pierinae, chemistry of, 262,
263 ; control of, in adjustable pro-
tective resemblance, 305.

Pigmy hawk capturing butterfly,
289, 290 ; wings of butterflies, &c,
in nests of, 290, 291, 291 n. 1.

Pin-eyed and thrum-eyed primrose,
xxvii-xxxiv; Darwin's work on, xxvii-
xxix, xxxiv ; Mendelian work on,
xxix-xxxi.

Pine Lake, Hartland, Wisconsin,
ant-like beetle at, 255, 256.

ANALYTICAL INDEX

457

Pine-needles, syncryptic resem-
blance to, 312.

Pionia, an Arctiid moth mimicking
Lyci?iae, 231.

Pipe-fish, 299.

piscatorius, Lofthius, bright lure
of, 378.

P. L. and A. (Popular Lectures
and Addresses), Lord Kelvin, 19,
19 n. 2.

Place of Mimicry in Scheme
of Defensive Coloration, Essay
X. 293-382. For divisions, sub-
divisions, sections, &c, of Essay X,
see Contents, pp. 293-7.

Plains, J. C. Prichard on the
horses and cattle of, 189.

Planema poggei, 338, 374, 374
n. 3.

planemoides, the only female f. of
P. dardanus mimicking (from Victoria
Nyanza to W. Coast) a non-Danaine
model, viz. Planema Poggei, an
Acraeine, 338, 374, 374 n. 3, 375 :
see also dardanus.

Plants, land, first appear in
Devonian, 44 ; specialization of
earliest, 44, 45 ; wide distribution of,
44; evolution in, 44, 45 ; seed-bearing
appear in Devonian, 45 ; fossil record
reveals only small fraction of evolu-
tion of, 44, 45 ; response to stimulus
of, 74, 75; dwarfed by wind, 75;
Asyngamy from cross-fertilization in,
90, 91 ; cause of injurious effects of
self-fertilization in, 91-4 ; variation
in, caused by environment, 137 ;
adjustable protective (procryptic)
resemblance to different kinds of,
305-7.

Plastidozoa (Protozoa), 23-6, 28,
30, 31, 121 : for analysis of text see
Protozoa.

plexippus {archippus), Anosia,
mimicry proves N. America the an-
cestral home of, 274, 364 ; mimicked
by ind']genousLi;ncnilis(Basilarchia) ,
274.

plexippus (genutia), S a la turn,
mimicked by female, and imperfectly
by male, of E. caudata, and by female
E. undularis, 373.

plinius, Tarucus, chased by
Pachyprora 7>wlitor and Pratincola
torquata, 283, 284.

Plumes in sexual selection, 379.

Podmore, Rev. P. St. M., on fertile

pairing of Ring dove and domestic
pigeon, 83, 84.

poggeiy Planema, mimicked by
planemoides female f. of Pap. dar-
danus, sub-sp. merope and polytro-
p/ius, 338, 374, 374 n. 3.

Points in the Resemblance
of Butterflies to Dead Leaves,
VII. 203-6 : see also 206-8, 289,
298-302, 310, 311, 351, 353.

Poison-fang associated with warn-
ing characters, 315, 316, 324-5.

Polar animals, J. C. Prichard on
whiteness of, 187 ; seasonal changes
in colour of, 310, 313.

Polar bear the enemy of the seal,
116.

Pole, capture of dorippus f. of
L. chrysippus in Ceylon by, 70
n. 2.

polyctor or arcturus, Papilio,
attacked by king-crow, 285.

Polydectus cupulifer, 357.

Polygoni a (Grapta) C- album,
203-5.

Polymorphism and Dimorphism
traverse diagnosis, ii. 70-2.

Polymorphism and Dimorphism
in Procryptic Defence, X. 310.

Polymorphism and Dimorphism
in Mimicry, X. 354-6: see also
372-5.

Polymorphism, value of, 310.

Polynesia, Euploeini in, 333.

Polyommatus phlaeas, 87 n. 1.

Polyrrhachis gagates, 255.

polytes (pammon), Papilio, male
of, non-mimetic and conspicuous ;
one female a mimic (probably Mul-
lerian) of P. aristolochiae, another of
P. hector, 373.

polytrophus, the Kikuyu Escarp-
ment sub-sp. of Papilio dardanus,
374' 375 : see also dardanus.

Polyzoa in early Palaeozoic, 30.

Ponera tarsata, 255.

Poona, dorippus f. of L. chrys-
ippus at, 70 n. 2.

Poplar kitten moth, 1 58-9.

Popular Astronomy, Simon
Newcomb, 13.

Popular Lectures and Ad-
dresses (P. L. and A.), Lord Kelvin,
19.

Population, On, Malthus, relation
of, to Darwin's and to Wallace's dis-
covery of Natural Selection, 194.

458

ANALYTICAL INDEX

populeti, Taeniocampa, larvae of,
attacked by starlings, 157 n. 1.

populi, Limenitis, remarkable de-
fence of pupae of, 315, 316.

Popiclus nigra, cocoons on bark
of, 158, 159 ; — tremula, 157 n. I.

'Porcupine family', peculiarity of,
transmitted, 180, 185.

Porifera in classification, 25 ; in
early Palaeozoic, 28.

Porritt, G. T., on darkening of
N. moths, 308, 309.

Portschinski on ant-like larva of
S. fagi, 254 ; on composite mimicry
of 5. fagi larva, 369 ; on pupa of L.
populi, 316 ; on aposematic attitudes
of disturbed Spilosoma, 324.

Possible Instance of Observ-
able Change in Member of
Mullerian Group since 1825-7,
X. 356.

Post-generation of missing embry-
onic parts, 129.

Potaro River, British Guiana, domi-
nance of Melinaea mneme on the,
332. , .

Poulton, E. B., definition of acquired
characters by, 142,143 ; on Lamarck-
ism and instincts of Hymenoptera,
1 18-9, 163-5 5 on Mullerian mimicry
or Common Warning Colours, 223,
328 ; on mimicry of saw-fly larvae by
caterpillars, 238, 239 ; on ant-like
Membracid larva, 259, 259 (Fig. 7),
260, 280, 377 ; on unpalatable forms
eaten under stress of hunger, 269 ; on
concealment of C. pumilus by adjust-
able neutralization of shadow, 300 ;
on attitude of Thecla rubi, 301 ; on
enemies of pupae, 306 ; on colour
adjustment of larvae, 306, 307 ; on
colour adjustment of grasshopper,
307 ; experiments on colours of G.
obscurata, 308 ; on examples of
Diaposematic Resemblance, 345 ;
Mullerian as against a Batesian
interpretation of mimicry supported
by generalizations of, 346, 347 ; sug-
gestion of, that special development
of male scent-brands enables the
females to recognize males which
closely mimic other species, 350, 358,
358 n. 1 and n. 2.

Power of Loose Analogy, Duke
of Argyll, 101-2.

prasinana, Hylophila (H alias),
colour adjustment of cocoon of, 149.

Pratincola torquata, 284.

Pre-Cambrian evolution, evidence
of, 31-3, 38.

Precis, comparison of under sides
of wings in dry and wet season forms
of, 208, 209, 320, 320 n. 1, 339-41 ;
procryptic resemblance, e. g. to dead
leaf in dry forms of, 205, 208, 320,
339-41 ; mimetic resemblances in wet
forms of, 339, 339 n. 1, 340; con-
spicuousness in wet forms of, 208,
209, 320, 320 n. 1, 339-41 ; eye-spots
in wet forms of, 340, 341 ; advantage
in seasonal changes of, 206-11, 310,
311,320, 339-41; attempt to deter-
mine physiological cause of seasonal
changes of, 340, 341 ; captured by
bee-eater, 288.

Precis actia, 208, 340 ; — almana,
340, 341 ; — antilope, 208, 340; —
archesia, 208, 320, 320 n. 1, 340 ; —
artaxia, 340 ; — asterie (wet f. of
almana), 340-1 ; — ceryne, 340 ; —
elgiva, 340 ; — natalensis (wet f. of
sesamus), 208, 339, 340 ; — natalica,
340 ; — sesamus, 208, 339, 340 ; —
tugela, 340.

Predaceous insects, attacks of, on
specially defended insects, 318.

Prediction and verification as test
of theory, 202, 219.

Predisposition to morbid affections
(e.g. to disorders of the nervous
system, to deafness, to scrofulous
complaints) inherited, 180; what is
inherited is not disease but, 183, 184.

Predominance gradual of
Mullerian Mimicry, X. 342-4:
see also 212-13, 223, 370-6.

Preferential Mating a cause
OF ASYNGAMY, II. 85-8 : see also
65.

Preferential mating of butterflies,
H. W. Bates on, 85-8 ; C. Darwin
on, 85-8 ; R. Trimen on, 86-8 ; of
Lepidoptera, T. A. Chapman on, 87
n. 1.

Pre-formation in frog's egg, 128-30.

Pre-localization in frog's egg, con-
clusions as to, 128-30.

Present Position of Palaeozoic
Botany, Dr. D. H. Scott, 44.

Pretoria, dorippus f. of L. chrys-
ippus at, 71 n. 1.

Prichard, James Cowles, life of,
173 ; anthropological discoveries of,
173 ; anticipation of Adolphe Pictet

ANALYTICAL INDEX

459

by, 173; reasons forneglect of illumin-
ating thoughts of, 175 ; inconsistencies
in arguments of, 174 n. 2, 175, 191—
2 ; on the obscure origin of varia-
tion, 176 ; contention of, that acquired
darkness of complexion cannot be
inherited, and is not cause of dark
races, 177, 178; the use of term
' acquired characters ' by (1826), 177,
179; on varieties predetermined in
the germ, 183 : see also xxxvii n. 1 ;
on comparison between influences of
two parents in heredity, 185 ; on
origin of domestic breeds, 186, 187 ;
limited but undoubted use of Natural
Selection by, 191.

prideaicxii, Pagnrics, carrying
Adamsia palliata, 357.

Primary and Secondary Mul-
lerian Mimicry ; Proto- and
Deuterosynaposematic Resem-
blance, X. 345, 346.

Primrose, Darwin's work compared
with that of Bateson and Gregory on
the, xxvii-xxxiv ; primrose, cowslip,
and Bardfield oxlip shown to be true
species by Darwin, xxviii, 47, 63.

Principles of Biology, Herbert
Spencer, 58 n. 2.

Prioneris, captured by bee-eater,
288.

Procryptic and Anticryptic
Colours, X. 297-315. For the
various divisions, sections, and sub-
sections see pp. 293, 294.

Procryptic Resemblance, X.
297-312. See pp. 293, 294 for the
various sections and sub-sections.

Procryptic Defence, Poly-
morphism and Dimorphism in,
X. 310.

Procryptic Defence, Seasonal
Dimorphism in, X. 310-12.

Procryptic colours, see Protective
(Procryptic) Resemblance.

Progressus Rei Botanicae, 44.

Promachus ioptems, 257 n. I.

pro?tuba, Tryphaena, derived
chlorophyll employed by larvae of,
314 n. 2.

Prophetic instincts of insects, 118,
119, 155-65.

prorsa, Araschma, resemblance to
Lime?iitis of, and earlier levana f. to
fritillary, 342.

Protective and Aggressive
Mimicry, X. 358-78. For the

various divisions, sections, sub-sec-
tions, &c, see pp. 296, 297.

Protective or Batesian Mimi-
cry : Pseudaposematic Resem-
blance, X. 361-76. For the various
sections, &c, see pp. 296, 297.

Protective Mimicry, see Mimicry
Protective, &c.

Protective Resemblance, X.
297-312. For the various sections,
&c, see pp. 293, 294.

Protective Resemblances, and
Aggressive, X. 297-315. For the
various divisions, sections, sub-
sections, &c, see pp. 293, 294.

Protective (Procryptic) Resem-
blance (see also Syncryptic) : de-
fined, 297 ; place of, in a scheme
of the bionomic uses of colour,
226 ; external and internal causes ob-
viously inapplicable as causes of, 227,
228; Lamarckism and, 113; female
often better concealed than male, 246 ;
protective mimicry a form of, 225, 226,
348 ; parallelism with mimicry, 259 ;
mimicry only appears in special sub-
ordinate groups of chief groups with,
348 ; included in mimicry by H. W.
Bates, but separated by A. R.Wallace,
359 ; distinction between Protective
Mimicry and, 225, 226, 358-61 ;
mimetic appearance combined with,
319, 339-41, 348, 350-4, 367, 368;
instantaneous transition from one to
the other, 319, 367, 368; warning or
aposematic defence combined with,
318, 319; e.g. in cobra, 324; transi-
tion to aposematic from, 318-20 ;
transitionfrom aposematic to, in desert
(dorzppus) f. of L, chrysippus, 320,
321 ; may be more advantageous on
pupa than on cocoon, 148, 149 ; re-
lation to daylight of, 303 ; in C. ver-
basci larva and imago, 318, 319 ; in
E. jacobaeae larva, 318 ; iridescence
and, 322 ; importance of 'sham death 1
in, 323 ; evidence of advantage con-
ferred by, 288, 289 ; habits essential
for, 353 ; examples of, more ancient
than those of mimicry, 246.

proteno?-, Papilio, male and female
of, respectively mimicked by sexes
of E. philenora, 37 1 .

Proto- and Deuterosynapose-
matic Resemblance, X. 345, 346.

Protoephemeridae (Ephemeridae)
of Commentry Carboniferous, 37.

46o ANALYTICAL INDEX

Protodonata (Odonata) of Commen-
try Carboniferous, 37 ; great size of,
18, 37-

Protogonws, changes in species of,
in accordance with changes of Miil-
lerian combinations, 338; rough
mimics on upper side, beautifully
dead-leaf-like on under, 350, 351 ;
imperfect mimicry in all species of,
35°> 35 1 ? directive 'tails' of hind
wing of, 351 ; mimetic upper surface
of, effective in flight, 351 ; procryptic
under surface of, effective at rest, 35 1 ;
Miillerian interpretation suggested by
probable mimetic ancestor of, 352;
Elymniinae compared with, 353, 354.

Protolocustidae (Locustidae) of
Commentry Carboniferous, 36, 37.

Protoperlidae (Perlidae) of Com-
mentry Carboniferous, 36, 37.

Protophasmidae of Commentry
Carboniferous, 36.

Protophyta compared with Meta-
phyta, 120.

Protoplasm, unknown origin of
living, 95.

Protozoa, meteoric hypothesis and,
23, 24 ; evolution of Metazoa from,
23, 26 ; in classification, 25 ; rate
of Metazoan evolution compared with
that of, 27-30, 31 ; compared with
Metazoa, 120.

Provisional, Advantages of
Admission that Diagnosis is, II.
76, 77-

Provisional Miillerian interpreta-
tions, 328.

ftsamathe, the Ecuador f. of
Methona confusa, 265, 266.

psaphon, Charaxes, 286.

PSEUDALLAPOSEMATIC RESEM-
BLANCE : Mimetic Representa-
tion of Adventitious Object As-
sociated with Model, X. 377 :
see also 259-60, 280.

Pseudallepisematic Resemblance,
examples of, may hereafter be found,
377.

Pseudaposematic Resem-
blance, or Protective (Bates-
ian) Mimicry, X. 361-76. For
sections, &c, see pp. 296, 297 : see
Mimicry Protective.

Pseudepisematic Resemblance,
or Aggressive Mimicry, includ-
ing Alluring Colours, X. 377,
378: see Mimicry Aggressive, &c.

Pseudosematic Resemblance,
or Protective (Batesian) and
Aggressive Mimicry ; Pseud-
aposematic and Pseudepisem-
atic Resemblances, X. 358-78.
For divisions, sections, sub-sections,
&c, see pp. 296, 297 : see Mimicry
Protective and Aggressive, &c.

Pseudoseme, directive characters
a form of, 325, 326.

psi, Acronycta, uniformity in broods
of, 87 n. I.

psidii, Tkyridia, as model, 264-6;
method of attaining transparency in,
265.

Ptarmigan, protective seasonal
change of, 310, 313.

Pterocera, see Volucella, 221, 378.

Pterochroza, resemblance to dead
leaves of, 302.

Pterodactyles take place of birds,
18.

Pteropoda, Silurian and Cambrian,
30, 41, 42 ; evolved from Gastropoda,
41,42.

Pteridospermeae, Palaeozoic, 45 ;
relation to ferns, 45.

Pterotheca in Palaeozoic, 42.

pulchella, Glenea, mimics Ichneu-
monid during life, 363.

ftiimiluS) Chamaeleo, adjustable neu-
tralization of shadow in, 300 ; resem-
blance of, aggressive as well as pro-
tective, 313.

Punch, parody of Darwinism in,
103 ; criticism of Batesian mimicry
by F. A. in, 213-15.

punctata, Athyma, of W. China,mi-
metic of male H. misippus, 217, 218 ;
male only mimics misippics, 381 ; fe-
male differs and resembled by female
of L. albomaculata, 381 ; distribution
of, 382 ; probable ancestor of, 382.

Pupa, position of Pierine, 147 ;
fatal effect of abnormal position of
Pierine, 148 ; adapted for effective
cryptic colouring, 149 ; individual
colour adjustment in, 149, 152-4,
305, 306 ; effect of gravity upon, not
hereditary, 152 ; value of individual
colour adjustment to, 305 ; value of
dimorphism in, 310 ; sensitiveness of,
in seasonal changes, 311, 312; de-
rived chlorophyll in, 314; of 1. po-
puli rejected by birds, 315-16.

Pupae, effect of Gravity
upon Suspended, V. 151, 152. .

ANALYTICAL INDEX 461

Pupal Groove, Origin of, in
Pierinae, V. 147-50.

Pupation, method of, in Va?iessidae,
151.

Puritan movement opposed to
evolution, 56.
Puss moth, 159.

Puttalam, Ceylon, dorippus f. of L.
chrysippus at, 70 n. 2.

Pymma tree, nest of Microhierax
in, 290.

Pyrameis cardui, 85.

Q

Quagga and mare, supposed endur-
ing effects of cross (telegony), 185.

Quarterly Journal of Micro-
scopical Science, 60 n. 3.

Quarterly Review, 49, 82.

quercifolia^Gast?'Opacha, concealed
among dead leaves, 299 ; colour ad-
justment to lichen, &c., by larva of,
307.

quercinaria^Engonia, slight cocoon
of, 149, 150; cryptic colouring of
larva and pupa of, 149, 150.

R

Rabbits, differences in skeletons of
domestic, 76 ; in-and-in breeding and,
93; J. C. Prichard on Angora, 187 ;
value of recognition marking of, 357;
episematic characters of, compared
with aposematic of skunk, 358.

Races, Diagnosis traversed
by Sub-Species or Geographical,
II. 75, 76.

Races, importance in the origin of
species, of sub-species or geogra-
phical, xvi, 75, 76.

Radiolaria in classification, 25 ;
consideration of, omitted, 28.

Radium, life of the sun and, 15
n. 2 ; heat conductivity argument
and, 15 n. 2.

Raindrops, prints of, as evidence of
uniformity, 19.

rapae, Pieris, in-and-in breeding
and> 93 ; pupal groove of, 147 ; choice
ofresting-site by, 301.

Rapid Adjustable Protective
Resemblance, X. 304, 305.

Rattle of Crota/tis, meaning and
origin of, 324.

Rattlesnake (Crota/us), warning
sound of, 324.

'Rattlesnake', Huxley's voyage
in the, 199.

Ray, John, fixity of species and, 56.

Recent Darkening of N. Eng-
lish Moths, X. 308-10.

Recent Evidence in Support
of Batesian Mimicry, X. 350-6.

Receptaculites in early Palaeozoic,

27. S,- 1

' Recession towards mediocrity,'
no.

Recessive and dominant characters,
xxx-xxxiii.

Recherches pour servir a
l'histoire des inseetes fossiles des
temps primaires, &c, Charles
Brongniart, 35.

Reciprocal mimicry, see Recipro-
cal Warning Colours, &c.

Reciprocal Warning Colours ;
Diaposematic Resemblance, X.
344, 345 = see also 213-15, 330, 331.

Recognition and Warning
Characters, X. 315-58: see
Warning Colours and Signalling
Colours. For divisions, sections, sub-
sections, &c, see pp. 294-6.

Recognition or Episematic
Characters, X. 357, 358.

Recognition characters, place in a
scheme of the bionomic uses of colour,
226; defined, 315, 357; warning
(aposematic) characters compared
with, 357, 358; sounds and move-
ments as, 357, 358; scents as, 350,
358, 358 n. 1 ; of Ungulates, e.g. of red
deer, 357, of rabbit, 357-8 ; Wallace's
interpretation of epigamic characters
as, 380.

Recognition of sexes perhaps aided
by discriminating features persisting
in closest mimicry, 350; probably-
aided by special scent-brands of
males, 358, 358 n. 1.

Red deer, recognition marking
of, 357-

Reduction of Shadow by
Attitude, X. 300, 301.

Peduviidae, ant-like larva of
species of, 257 n. 1 ; mimicked by
larva of Hymenopus bico? ?iis, 378 n. 3.

Regeneration, Professor T. H.
Morgan, 128.

regifia, Teracolus, mimetic of
Belenois in wet season, procryptic in
dry, 341.

Reid, Archdall, on the different

462

ANALYTICAL INDEX

origin of domestic and natural
varieties, xl n. 2.

Relation between Symmetry
of Egg and Symmetry of Embryo
in Frog, J. W. Jenkinson, 130.

Relation of Mimicry, &c, to
other Resemblances in Nature,
VIII. 225-8 : see also 258-9, 312,
358-61.

Remarkable anticipation of
Modern Views on Evolution,
Essay VI, 173-92.

Remarkable Examples of
Mimicry, X. 367-9.

Renewal of lost parts, explanation
of, 136.

Reorganization of injured parts of
egg, 129.

Repair, explanation of, 136.

Repose, Choice of Appropriate
Surfaces for, X. 301.

Reproduction the foundation of
Syngamy and Epigony, 64.

Reptiles, 26 ; rapid evolution of
brain in higher, 29 ; the ancestors of
birds, 32 ; brain in mammals and,
108 ; rapid colour adjustment in,
3°5-

Research, the ultimate justification
of, xlvii, xlviii ; importance of earliest,
197, 198 ; educational value of, 198,
199.

Researches into the Physical
History of Mankind, Ed. 2, 1826,
J. C. Prichard, 174, 176, and through-
out Essay VI, 173-92.

Researches on Mimicry, Erich
Haase, 231, 318, 375.

Resemblance of Butterflies
to Dead Leaves, VII. 203-6: see
also 206-8, 299, 302, 310, 311, 351,
353.

Resemblance, Mimetic, be-
tween Species of very Differ-
ent Size, X. 366-7.

Resemblance, Mimetic, to
Cryptic Models, X. 369, 370.

Resemblance, Mimetic, to
General Appearance of Un-
palatable Group, X. 376.

Resemblance of W. Chinese
Athyma and Limenitis to Male
of Hypolimnas misippus, X. 381,
382 : see also 217-18.

Resemblances, relation between
mimetic and other, 225-8, 258-9,
312, 358-61.

'Responsive' characters, 144, 145.

Reticularia (Foraminifera) in
classification, 25 ; remarkable per-
sistence in geological time of, 27, 28.

rhadamant litis, Danisepa, see
diocletianus, 373.

Rhinotraginae, mimicry of Hy-
menoptera by, 252.

Rhodesia, dorippus f. of L. chrys-
ippus from S., 71 n. 1 ; ant-like
Locustid and models from, in S., 257
n. 1 ; attacks of birds on Lepidoptera
witnessed in S., 283, 284: and in
S.E. (Gazaland), 284.

Rhopalocera, see butterflies.

Rhynchophora, see classification
of examples of mimicry, 390-1 : see
Anthribidae, 369, Brenthidae, 369,
370, Weevils, 250, 261, 307, 369, 370.

Rhynchota, see Hemiptera and
Homoptera.

Ridley, H. N., discovery of ant-
mimic with head represented at
posterior end, by, 368.

Ring Dove, fertile pairing with
domestic pigeon of, 83, 84.

' Ringlet' butterflies, 210.

Robertson, Captain (Major), on
larvae of T. populeti, 157 n. 1.

Rock, Conferva-covered, resem-
bled by Macroclemmys, 378.

Rock Pigeon, 84.

Rodentia, mole-like forms of, 312,
359-

Rolleston, George, President of
Zoological Section British Associa-
tion, 1870, 1.

Romanes, G. J., hypothesis of
' physiological selection ' of, 84 ; on
instinct as inherited experience, 118 ;
on transfusion of blood and pangene-
sis, 125 ; on Lamarckism and vari-
able protective resemblance, 152;
on instincts of Fossorial Hymeno-
ptera, 160, 161, 164 n. 1 ; on instinct
as lapsed intelligence, 166.

Roots of grass, protective (pro-
cryptic) resemblance to, 323.

rosa, Crem's, recent entrance into
Natal of, 52 n I.

Rosako, Usaramo, E. Africa, ant-
like bug from, 255.

Ross, Herefordshire, birthplace of
J. C. Prichard, 173.

Ross, Captain James, experiment
on seasonal changes of Hudson's
Bay Lemming, by, 310.

ANALYTICAL INDEX

463

Rotation in relation to shape of
earth, 8, 9.

Rothschild and Jordan on per
saltum evolution, xvi.

Rotifera derived from Chaetopod-
like ancestor, 27 ; in classification,
33-

Roux, experiments of, on frog's
egg, 128-30.

Royal Dublin Society, 12.

Royal Irish Academy, Pro-
ceedings of, 314 n. 1.

Royal Physical Society of Edin-
burgh, Proceedings of, 303.

Royal Society, Philosophical
Transactions of, 150, 185, 262;
Proceedings of, 262, 314 n. 2.

Royal Society of Edinburgh,
Proceedings of, 4 n. 3.

nibi, Thecla, reduction of shadow
in, 301.

rubripennis, Lygistopterus, mim-
icked by Lycomorpha latercula,
231.

Rudimentary stalks and sockets of
scales in certain mimetic moths, 251,
365-6.

Rugose corals in Palaeozoic, 28.
rusina, Draconia, resemblance to
1 skeletonized ' leaf of, 302.

S

Saccamina, an existing genus in
the Carboniferous, 27.

Sagartia parasitica, 357.

Sahara to Niger mouths, exclusive
occurrence of alcippus f. of Z. chrys-
ippus from, 321, 364.

Salamander, 130 n. 1.

Salatura hegisippus, 373.

Salatura plexippus (gemitia), 373.

salina, Artemia, experiments on,
73, 74-

Salisbury, Rhodesia, dorippus f. of
Z. chrysippus at, 71 n. 1 ; ant -like
Locustid and models from, 257 n. 1 ;
attacks of birds on butterflies wit-
nessed at, 283, 284.

Salisbury, the late Lord, objec-
tions to Natural Selection by, 2-4, 9,
10.

Salix, Wichura's proof that Men-
del's principle is not followed by
hybrids of, xxxv n. 1.

Salvin, O., on the sexual brands of
the Dismorphi?ia, 240; on Ecuador
form of M. confusa, 266.

Sal ween R., below Shwegon,
Burma, butterflies attacked by birds
on, 289.

sambiccaria, Uropteryx, slight
cocoon of, 1 50 ; cryptic pupa of, 1 50 ;
variable protective resemblance
probable in pupa of, 1 50 n. 2.

Sand (see also desert): protective
resemblance to, 298, 307, 321 ; allanti-
cryptic use of, 313.

Sand-wasps, see Fossores.

Sanders, Cora B., on Burchell's
Brazilian butterflies, 53 n. 1 ; on pupal
stage of V. urticae, 306.

Sanger-Shepherd, illustrations of
mimicry prepared by, 272 n. 2.

sangniflua, Amesia, with allied
Chalcosiine moths, rough Miillerian
mimics of blue Oriental Euploeas,
376 : see also 372.

Sarangesa elitninata, 283.

Sargasso Sea, 298.

sarpedon, Papilio, eaten by bee-
eater, 288 ; captured by Microhierax
coerulescens, 289, 290.

satis, Acraea, recent entrance into
Natal of, 52 n. 1 ; resemblance to
Papilio morania of, 52 n. 1.

Satyrinae, Burchell's Brazilian, 53
n. 1 ; seasonal changes in, resemble
those of other sub-families, 207, 210,
211, 310, 311, 326; concealment of
eye-spots of, during prolonged rest,
210 ; eye-spots in wet season forms
of, 210, 211, 326; tilt or 'list' of, 289,
300, 300 n. 5 ; Elymniinae often united
with, 353.

Saw-flies {Tenthredinidae), larvae
of, mimicked by larvae of E. versi-
color, 238, 239, 239 n. 1 ; sudden
assumption of aposematic defence
by, 320.

Scales, diverse modifications of, to
promote mimetic resemblance to
same transparent Ithomiine models,
263-6 ; mimicry attained by loss of,
251, 276, 365, 366 ; by transparency
of, 251, 266, 366 ; degeneracy in
lost scales greatest in best mimics of
wasps, &c, 365, 366; great size an
element in the loss of, 366 ; of Ec/iis
and the production of sound by, 324.

Scent brands of the male Euploeini,
334 n. 1 ; probable episematic use of,
in butterflies, 358, 358 n. 1.

Schmankewitsch, on Arttmta
salina, 73, 74.

464 ANALYTICAL INDEX

Schulze, experiments on frog's egg
by, 129.

Schuster, Professor, on internal
electric conductivity of earth, 11,
12.

schreiberi, Charaxes, isolated
wings the only evidence of, in two
countries, 292.

Science, 159.

Science and the Empire, 169.

Science and the Faith, Aubrey L.
Moore, 54.

Science Progress, 173, 310 n. 1 ;
Author's Paper in, original form of
Essay VI, 173-

Sclater, W. L., example of pseud-
allaposematic resemblance of Mem-
bracid larva to ant with its leaf, dis-
covered by, 259 (Fig. 7), 260, 280,
377.

Scorpions, Chaetopod-like ancestor
of, 27 ; Carboniferous and Silurian,
30, 40 ; perhaps aquatic in Silurian,
40.

Scott, D. H., on evolution in
land-plants, 44, 45.

Scudder, S. H., on fossil insects,
35-

Scytasis, mimicry of Hymenoptera
by, 257 n. 1.

Sea-anemones in classification,
25 ; hermit-crabs carrying sponges,
Ascidians,and, 356, 357 ; crabs carry-
ing, 357-

Sea-urchin, see Echinoderm, 130.

Seaweed as covering of Stenor-
I'hynchns, 313-14.

Seal, intelligence of, 116.

Seasonal Dimorphism tra-
verses Diagnosis, II. 72, 73.

Seasonal Changes of Butter-
flies, VII. 206-11 : see also 310-12,
320, 326, 339-42.

Seasonal broods with epigonic not
syngamic relations, 72.

Seasonal dimorphism probably
a reaction to stimulus, 73 ; changes
of butterflies and Natural Selection,
206-11, 310, 311, 320, 339-42;
change of form in butterflies' wings,
206-8,310,311 ; change of butterflies
in relation to Mullerian mimicry,
339-42.

— Changes in : Satyrinae, 207,
210, 211, 310, 311, 326. Nympha-
linae, 211, 310, 311, 326; Arasch-
m'a, 342 ; Byb/ia (Hyftams), 87, 341 ;

Kallimci) 206-8 ; Precis, 208, 209, 320,
320 n. 1, 339-41- Pierinae, 311,
312, 341 ; Belenois, 311, 312, 341;
Teracolus, 311, 341, 342; Huphi?ia,
342. Moths, 311.

— Changes, experimental investiga-
tion of physiological causes of, 311,
312, 340, 341 ; changes of Alpine
Hare, Ptarmigan, Hudson's Bay
Lemming, 310, 313 ; changes aggres-
sive in Arctic Fox and Ermine, 313.

Seasons, difference between the
struggle in wet and in dry, 208-11,
311,317,320.

Secondary mimetic resemblance
supports Mullerian interpretation,
345, 345 n- 5 5 sometimes closer than
primary, 345, 346.

Secondary reptiles, brain of, con-
pared with Tertiary, 29.

Secondary sexual characters, see
Epigamic Characters and Sexual
Selection.

Sedgwick, Adam, on Peripatus,
33 ; on relation between acquired
and genetic characters, 144 n. 1.

Seed, Bacon's views on restraining
power of, 55.

Segregation of species, H. W.
Bates on, 85-7 : see also 65.

Selection, Diagnosis tra-
versed by results of Artificial,
II. 76.

Selection, J. C. Prichard on the
importance of in domestic races, 174,
186.

Selection, Mechanical, 85.

Selection, Natural, see Natural
Selection.

Selection, Sexual, see Sexual
Selection and Epigamic.

Selenia illunaria, 311.

'Self-adaptation,' failure of, 153;
indistinguishable from 1 internal
developmental force', 153; J. C.
Prichard on, 190-2.

Self-bred plants, cause of injurious
effects seen in, 91-4.

Self-Fertilization, Adapta-
tions for Cross-Fertilization
the cause and not the con-
sequence OF INJURIOUS effects

OF, II. 9I-4.

Self-fertilization of many Orchid-
aceae, 92.

Sematic Colours or Warning
and Signalling (Recognition)

ANALYTICAL INDEX 465

Colours ; Aposematic and Epi-
sematic Characters, X. 315-58.
For divisions, sections, sub-sections,
&c, see pp. 294-6.

Sematic Colours (see Warning
Colours and Signalling Colours) :
place in scheme of the bionomic uses
of colour, 226 ; defined, 315.

Semper, Karl, on Natural Selec-
tion not creative, xxii ; letter from
Darwin to, 74.

Senses, Instincts, and Intelli-
gence of Animals, &c, Sir John
Lubbock, 161.

septentrio?ialis, Croesus, habits of
larvae of, 238, 239 ; transition from
cryptic to aposematic defence in
gregarious larvae of, 319, 320.

serena, Acraea, model of wet f. of
B. gotzius, 341.

Serpents, 312, 319, 324, 326, 367,
367 n. 2, 368, 376. For analysis see
snakes.

sesamus, Precis, seasonal forms of,
208; dry form (sesamus) bred (1898)
from wet (natalensis), 208, 339, 340,
340 n. 4 ; attempt to determine the
physiological cause of change, 340 ;
procryptic under surface of, while
natalensis is a rough mimic of
Acraea, 339, 339 n. 1, 340 ; S. African
habitat of, 340.

Sesia (Trochilium), transparency
of scales in, 251, 366 : see also Troch-
ilium, 251, 365, 366.

Sesiidae, mimicry of Aculeata by,
25i> 365, 366.

severina, Belenois, experiments on
seasonal forms of, 311-12.

Severity of Struggle Great-
est at Certain Hours, X. 303.

Seward, A. C, on the earliest land-
plants, 44 ; F. Darwin and, on
Prichard as an evolutionist, 174 n. 2,
175 n. 1.

Sex, predetermined in ovum, 133.

Sexes Alike of both Model
and Mimic, X. 371.

Sexes Different, Male
Mimicking Male, Female
Female, X. 371.

Sexes of insects, and Natural
Selection, 246, 247 ; mimicry and
the, 215-18, 244-7, 279, 347, 353,
372-5 ; recognition between per-
haps aided by smell in close
mimicry, 358.

POLLTON J J

Sexual reproduction, YVeismann's
interpretation of, 127, 128, 137.

Sexual Selection, Epigamic
Colours, X. 379, 380.

Sexual Selection : see also Epi-
gamic ; a cause of asyngamy,65,85-8 ;
suggested as cause of mimicry, 225,
228, 272 ; objection to as explanation
of protective resemblance, 227, 228 ;
objections to as explanation of
mimicry, 227, 228, 233, 236, 245,
246, 260, 261, 267, 270, 273,
275, 276, 278-82 ; objections to less
strong than to other alternatives to
Natural Selection, 236 ; T. Belt on
white patch of male Dismorphina,
240 ; first suggested by Darwin
(1858), 379; difficulty of theory of,
379 ; selection proved by diversity of
elements co-operating to produce
effect, 379 ; supported by observa-
tions on courtship of spiders, 380;
and of grasshoppers, 380.

Shadow, Neutralization of,
X. 299-300: see also 298, 313.

Shadow, Adjustable Neutral-
ization of, X. 300.

Shadow, Reduction of, by
Attitude, X. 300, 301 : see also
289.

Shadow, importance in desert of,
298 ; parallelism of main pattern lines
of moth with main lines of, 156, 301 ;
cast by dead leaves, resemblance to,
299 ; elimination of, in aggressive
resemblance, 313.

' Sham death ', meanings of, 323,
324 ; appearance of real death
different from that of, 324 ; procryptic
in spiders, beetles, caterpillars, 323 :
see also 155 ; aposematic in un-
palatable moths, 323, 324.

Shape, relation to general and
special protective resemblance of,
297, 298 : see also xxiv n. 2.

Sharks, teeth of, on ocean floor, 20 ;
in early Palaeozoic, 30.

Sharp, David, on ant-like bug
larva, 257 n. 1.

Sheep, Jacob's experiments on,
186; J. C. Prichard on changes of
fleece of, in tropics, 190.

Shelford, R., results obtained by
quoted in Essay X, 293 ; on mimicry
of Hymenoptera by Bornean Longi-
corns, 257 n. 1, 280; on Bornean
Clytinae as models for other Longi-

h

466

ANALYTICAL INDEX

corns, 348, 349; on mimicry by
Longicorns of Bornean Rhyncho-
phora, 369; on habits of Bornean
Brenthidae, 370; on Asilid fly
mimicking Xylocopid bee, 276 ; on
larvae of Bornean Hymenopus
bicornis mimicking bugs, 378 n. 3 ;
on mimetic Bornean Chalcosid moths,
275> 275 d. I ; on Protogonius as
example of Batesian mimicry, 351 ;
on Elymnias lais as a Batesian
mimic, with combination of mimetic
and procryptic defence, 353 ; on the
Elymniinae as examples of Batesian
mimicry, 372 n. 1 ; on head of model
represented at tail of mimic, 368 ;
on snake-like Bornean caterpillar,
367 n. 2 ; on possible former south-
ward extension of Athyma and
Limenitis mimics of male H. miszppus,
381, 382 ; on mimicry of squirrels by
tree-shrews, 367 n. 1.

Shield, caudal, of S. fagi larva
resembles bug, 369; of the Mem-
bracidae, mimicry of ant developed
in rather than insect itself, 258,
258 (Fig. 6), 259, 280, 369; in
other cases protective (procryptic)
resemblance developed in, 258, 259.

Shrew-like mammal mimicked by
posterior end of chafer, 368 : see
also tree-shrews, 367, 367 n. 1.

Shrike, Ashy swallow-, capturing
butterflies, 286.

Shull, see Macdougal, xix n. 5, xxi,
xxii.

Siam, insects' enemies in, 303 ;
wet season f. of Precis almana
permanent in, 341.

Sidgwick, Arthur, assistance ren-
dered in the terminology by, 60 n. 3,
61 n. 1, 223, 226, 312 n. 2, 344, 381.

Signalling and Warning
Colours, &c, X. 315-58: see also
226. For divisions, sections, sub-
sections, &c, see pp. 294-6.

Signalling or Recognition
Marks, &c, X. 357, 358: see also
226.

Significance of certain
Seasonal Changes of Butter-
flies, VII. 206-11.

Sikkim and N.E. India, comparison
of mimicry by E. undidaris in, with
that in other parts of range, 373.

Silicospongiae in early Palaeo-
zoic, 28.

Silken Loop, Origin of Groove
for reception of, in plerine
Pupae, 147-50-

Silken Loop, may be a trace of
former cocoon, 148.

Silkworm, disease of, 136.

Silurian, life long antecedent to,
5, 6 ; tides, 17 ; Foraminifera,
27 ; sponges, 28 ; Coelomate phyla,
30; specialized forms in, 30, 31 ;
Cirrhipedes, 39 ; Ostracodes, 39 ;
Entomostraca, 39 ; Arachnida, 39, 40 ;
Merostomata, 40 ; scorpions, 40 ;
Mollusca, 41, 42 ; Chiton, 42.

Singapore, ant-like spider and
caterpillar from, 368.

Sinzaway Chaung, Tenasserim,
290.

Siphonostoma typhle, 299.

Size, Mimicry Independent
of, X. 366.

Size, independence of, as clear in
Miillerian as in Batesian mimicry,
363 ; a question of distance, 366.

Sjostedt, Professor Yngve, on
alcippus f. of L. chrysippus in the
Cameroons, 321 n. 1.

Skeleton, Lamarckism and the
Mammalian, 112.

Skin, J. C. Prichard on advantage
of black, 1 90 ; protective (procryptic)
resemblance to hair or, 359.

Skunks, warning colours of, 315;
episematic characters of rabbit com-
pared with, 358.

Slow Adjustable Protective
Resemblance, X. 304-7.

Small Garden White, see also
rapae, 93, 147, 301.

'Small Heath' Butterfly, 210.

Small Tortoiseshell Butterfly, 306.

Smell, unpleasant, associated with
warning characters, 315 ; unpleasant
in aposematic butterflies, 316 ;
pleasant epigamic in male butterflies,
316, 317 ; emission by gregarious
larvae of Croesus of, 320 ; aposematic
in Colaenis, 334 n. 2 ; recognition by
females probably aided by special
scent-brands of males, 358, 358 n. 1.

S7>ierinthus ocellatus^ 314, 314 n. 2.

Smith, S. S., on origin of skin
pigments of dark human races, 176,
177.

Smoke, effect of, in Lanes, and
Yorks. district, 308-10.

Snakes, aggressive (anticryptic)

ANALYTICAL INDEX

467

resemblance of constricting, 312;
aposematic sounds of, made in various
ways, 324 ; birds mimicking hiss of,
324 ; caterpillars which mimic cobra-
like and other, 319, 326, 367, 36711.2,
368, 376; latter mimicry Batesian,
376 ; mimicry of venomous (e. g.
Elaps) by harmless, 367, 376.

Soc. de Biol. Paris, 166.

Sockets, loss of scales by rudi-
mentary stalks and, 365.

Solidity, appearance of, removed
by eliminating shadow, 299, 300, 313.

' Solution ' of heterostyled condi-
tion arrived at by Bateson and
Gregory, xxvii, xxix-xxxiv.

Somali Desert, dorippics f. of
L. chrysippus adapted to, 321.

Somatogenic characters, see
Acquired, no, 127, 142; defined,
122, 123, 140-4 ; less important than
blastogenic, 132-5.

Some Problems of Reproduc-
tion, Prof. M. Hartog, 60 n. 3.

Song in sexual selection, 379.

Sounds, Warning or Intimi-
dating, X. 324.

Sounds of warning significance : —
snakes' hiss, rattle, vibration of tail,
swish of serrated scales (Echis) 324 ;
mimetic, of insects, 251 ; of birds,
324; importance of, in recognition,
357-

South, R., on Palaearctic localities
of HyftolimnaS) A thy ma, and Limen-
itis, 382.

South Africa, F. Galton, 298.

South, S.E., &c, Africa, see Africa,
South, S.E., &c.

South African Museum, Cape
Town, 87.

South America, see America,
South.

South China, see China, South.

South India, see India, South.

South United States, see United
States, South.

South-East Rhodesia,see Rhodesia,
South-East.

Space and Time Relationship
of Mimicry, VIII. 247-50.

Spanish colonists unchanged after
many generations in the tropics, 178.

Special Aggressive (Anti-
cryptic) Resemblance, 312, 313.

Special Creation a theological
dogma, 56, 57; contrasted with

H

evolution by H. Spencer, 58 ;
Lamarck's theory and, 98.

Special Protective (Pro-
cryptic) Resemblance, X. 298,
299.

Special Protection, Evidence
of, in Aposematic Forms, X. 316,
317.

Special protection accompanied by
mimicry, within and without the
group, 335 ; often associated with
highest perfection of mimicry, 335,
336.

Specially protected insects, the
enemies of, 317, 318.

Species and Varieties, Hugo
De Vries, xx n. 1 .

Species General des Lepido-
pteres, Boisduval, 221.

Species, What is a? Essay II,
46-94.

Species with Warning
Colours Depend for their
Existence upon the Co-Exist-
ence of Palatable Species, X.
317.

Species of very Different
Size Mimetic, X. 366.

Species (see also sterility) :
Aquinas, St. Thomas, on, 55 ; Augus-
tine, St., on, 55 ; Bacon, Francis, on,

54, 55 ; Bates, H. W., on segregation
of, 86 ; Bauhin, Kaspar, on, 56 ;
Cuvier on, 56 ; Darwin, Charles, defi-
nition of, by, 46, 47 ; on various defini-
tions of, 59; on 4 close species', 67 ;
attempts to produce physiological
species by 79, 80 ; Dixey, F. A., on, 56,
62 n. 1 ; Huxley, T. H., 011,56 ; on phy-
siological and morphological species,
78 ; Jung on, 56 ; Lankester, E. Ray,
on discarding the word, 62 ; on histori-
cal criterion of, 63 ; Linnaeus, Carolus,
on the fixity of, 54-8 ; diagnosis of, by,
58 ; Milton, John, on creation of,

55, 56 ; Moore, Aubrey L., on, 54-6 ;
Poulton, E. B., on, 46-94 ; Prichard,
J. C, on the comparison of adapta-
tion in varieties and, 189, 190; Ray,
John, on, 56; Thiselton-Dyer, W.
T., on, 56, 66 ; species and varie-
ties, 47, 66-8 ; sterility between,
49> 59> 77-8o, 80-4, 201 ; discus-
sion of, best illustrated by insects,
50-4 ; theological aspects of, 56,
57; various conceptions of, 59-63;
systematic work not affected by

h 2

468 ANALYTICAL INDEX

disbelief in permanence of, 59 ; sub-
jective element in describing, 59, 60 ;
diagnosis of, 60, 65-8 ; interbreeding
and, 60 ; structural relationships of,
60 ; syngamic, 60 ; importance of
asyngamy in relation to, 60, 65 ;
descent from common ancestors and,
61 ; synepigonic, 61 ; geographical
distribution (Sympatry) and, 62 ;
introduction to discussion of, 63-5 ;
constancy a criterion of, 63 ; sterility
of hybrids between, 63, 64 ; import-
ance of transition in relation to, 64 ;
diagnosis of, provisional, 65, 76, 77 ;
origin by preferential interbreeding
of, 65 ; asyngamy the barrier
between, 65 ; sterility between,
caused by asyngamy, 65 ; objective
reality of, 65 ; definition by dia-
gnosis of, 65-8 ; transition underlying
diagnosis, 66 ; the subjective ele-
ment in diagnosis, 66, 67 ; only
strongly defined varieties, 66; dis-
continuity as a test of, 66, 67 ; failure
of diagnosis of, 69-76 ; dimorphism,
&c, and, 70-2 ; seasonal dimorphism
and, 72-3 ; individual modification
and, 73-5 ; geographical races or
sub-species and, 75-6 ; results of arti-
ficial selection and, 76 ; provisional
conclusions of diagnosis of, 76, 77 ;
sterility as test of distinction between,
77-80 ; sterility between certain
artificially selected races, 78-80 ;
sterility reduced by domestication,
79 ; attempts to produce phy-
siological, 79, 80 ; sterility between,
caused by asyngamy, 80-4 ; by
asympatry, 84, 85 ; by mechani-
cal incompatibility, 85 ; by sexual
selection, 85-8 ; importance of
recording captures in coitu, 87 ;
asyngamy from breaking of syngamic
chain, 88 ; subordination of the
individual to the, 316, 358.

Specific Stability and Mutation,
Sir W. T. Thiselton-Dyer, xxii.

' Spectacles ' of Cobra, meaning of,
324.

Spencer, Herbert, great demands
for pre-Cambrian time made by, 7 ;
evolution and special creation con-
trasted by, 58 ; Lamarck's theory
and, 98 ; on survival of the fittest,
102.

Sp/iex, stinging ganglia of insect
prey, 161 : see also 118, 1 19, 160-4.

Spiders, remote ancestor of,
Chaetopod-like, 27 ; Carboniferous,
40 ; ' sham death ' of, 323 ; mimicry
of ants by, 252, 253, 253 (Fig. 1),
368 ; methods by which mimicry of
ant is attained by, 252, 253, 253
(Fig. 1) ; colour adjustment of flower-
haunting, 307 ; courtship of, 380.

spilleri, Pieris, recent entrance
into Natal of, 52 n. 1.

Spilosoma mendica, 324 ; — urti-
cae, 324.

Spinalis appears in Tertiary, 42.

splendens and irawada, fsamza,
and other blue Oriental Euploeas
roughly mimicked by diurnal
Chalcosiine moths, 376: see also 372.

Splinter of wood, protective resem-
blance to, 319.

Spolia Zelanica, 300.

Sponges in classification, 25 ;
long persistence with little change
of, 28; sea-anemones, Ascidians, and,
carried by hermit-crabs, 356, 357.

Spontaneous tendencies are alone
hereditary, J. C. Prichard (1826),
183.

Squirrels, value of tails of, 325 ;
mimicked by tree-shrews, 367,
367 n. 1.

Stability of Lepidopterous pig-
ments and Natural Selection, xlv.

Stalks, loss of scales by rudi-
mentary sockets and, 365-6.

Standfuss, M., on Melanism,
310 n. 1 ; on seasonal changes of
Lepidoptera, 311.

St. Anne's-on-the-Sea, N. Lanca-
shire, C. Bailey's study of O. la-
marckiana at, xxi.

Starlings attacking T. populeti
larvae, 157 n. 1.

Static conditions, slow colour
adjustment a response to, 305-7 ;
syncryptic resemblance caused by
similarity in, 312.

Stauropus fagi, 253 (Fig. 2), 254,
369-

Stems, protective resemblance to,
299 ; aggressive resemblance to,
313.

Stenorrhynchus phalangium, 313.

Sterility as a test of
Species, II. 77-80 : see also 59.

Sterility between Species an
incidental consequence of
Asyngamy, II. 80-4 : see also 65 ,91.

ANALYTICAL INDEX

469

Sterility, of hybrids, bearing of
Darwin's work on heterostyled plants
upon, xxviii, 90, 91 ; between species,
49 ; difference between Darwin's
and Wallace's views on, 49, 80, 89 ;
between Darwin's and Huxley's
views on, 49, 77-80, 82, 201 ;
of hybrids, 63, 64, 77, 78 ; be-
tween species characteristic, but be-
tween domestic races very rare, 77-
80; between certain artificially selec-
ted races, 78-80; reduced by domes-
tication, 79 ; attempt to induce by
selection, 79, 80 ; not due to Natural
Selection, 80, 89 ; causes of, 80-2 ;
germinal causes of, 80-2 ; various
causes of, 81 n. 1 ; possible between
ends of ' syngamic chain ', 89 ; inci-
dental rather than selected, 91 ; cross-
fertilization and, 90, 91 : see also
xxviii ; not a test of specific dis-
tinctness, 91.

Sticks, protective (procryptic)
resemblance to, 370.

Stictopioea harrisi, 372, 376.

Stillness essential in protective
resemblance, 298.

Stimulus and Mechanism as
Factors in Organization, J. B.
Farmer, 74 n. 2.

Stimulus to inquiry, interest as
a, xliv-xlvi.

Stimulus of light in adjustable
protective resemblance, 305 ; experi-
mental investigation into seasonal
changes and physiological, 311, 312,
340-2.

Sting, associated with warning
colours, 315, 316; no defence if food
scanty, 317 ; hardness as a defence,
compared with smell, &c, and, 370.

Stinging insects, Batesian mimics
of, 376 ; Mullerian mimics of, 376 :
see also 230-1 ; see also bees, Fos-
sores and wasps.

Stockholm Natural History
Museum, type f. of L. chrysippus
from Cameroons in, 321 n. 1.

Stone, protective (procryptic)
resemblance to, 298, 301.

Stonechat, South African,
Lycaenid chased by, 284.

Stratified rocks, thickness of, 16 ;
lapse of time during deposition of,
16, 17 ; uniformity of conditions
during deposition of, 17-19.

Stray Feathers, 290.

strigosa, Acronycta, fertile with
wild but not with bred males,
87 n. 1.

Striking Examples of Mul-
lerian Mimicry, X. 331-6; (a)
the New World, 331-3 ; (b) the
Old World, 333-6.

Stripes of zebra, invisibility pro-
duced by, 298.

Struggle for Life, hours
when most Severe, X. 303.

Struggle for life : see also Natural
Selection ; a factor of selection, 96 ;
utility in the, 105-9 I Palae-
ontology and, 107-8 ; conditions of,
in insects, 117, 155-7; especially
severe in winter, 148 ; in the dry
season, 148, 208-11; during pupal
period, 157-60; in young birds,
167, 167 n. 2, 168; insufficiently
appreciated by J. C. Prichard, 191 ;
in S. America, 248 ; curious evidence
of, 291, 292 ; imperfect knowledge
of details of, 302, 303 ; complexity
°f> 323 1 effect upon insect life ot
enemies', 328.

Strutt, Hon. R. J., on radium in
rock, 15 n. 2.

Study of Adaptation Stimu-
lates AND DOES NOT BAR
Inquiry, Introd. xliv-xlvii : see also
74 n. 2.

Study of Insects and Ques-
tion 'Are Acquired Char-
acters Hereditary?' Essay V,
139-72.

Stylops, effect of, upon bees, 380.

subbuteo, Falco, Terias found in
stomach of, 284.

Sitbei-ites domunarfa, 357.

Subjective Judgement of
Discontinuity, Introd. xvii.

Sub-species or Geographical
Races traverse Diagnosis, 11.
75-76.

Sub-species, importance for the
study of evolution, of geographical,
xv i ; united by syngamy, 75, 76.

Sucking, an instinctive action, 117.

Sudan, ant-like Locustid from,
256, 257, 258 (Fig. 5), 280.

saffocans, Mephitis, warning
colours of, 315.

sulcirostris, Cleonus, colour ad-
justment probable in, 307.

Summa Theol., St. T. Aquinas,
55-

47© ANALYTICAL INDEX

Sun, life of the, 13-15; radium
and life of, 1 5 n. 2 ; hypothesis that
the colours of human races have been
caused by, 176; pinhole images of,
said to be resembled, 313.

Superfluous causes, elimination
of, 113.

Supernumerary digits markedly
hereditary, 180, 185.

Surfaces, Choice of Appro-
priate for Resting on, X. 301.

Surfaces, Value of Brightly-
Coloured, Concealed during
Rest, X. 303, 304 : see also 325.

Surinam, examples of mimicry in,
235 ; darkening of mimetic butter-
flies in, 272.

Survival of the fittest, see Natural
Selection, 102.

Swainson, W., letters from W. J.
Burchell to, 49 n. 3.

Swallows attacking butterflies in
S. Africa, 284.

Swallow-tail butterfly, eye-spot of,
pecked by kestrel, 210.

Swallow-tail butterfly, value of
' tails' of hind wings of, 281, 282.

Swallow-tail Moth, 150.

' Swamping effect of inter-crossing',
importance of Mendelian principle
in preventing, xxxiv, xxxv ; Darwin
impressed by Fleeming Jenkin's
argument upon, xl, xl n. 3, 3.

Swine, J. C. Prichard on Cuban,
187 ; relation to localities of, 189, 190.

Swinhoe, Col. C, on dorippus f.
of L. chrysippus in India, 70 n. 2.

swinhoei, Merops, capturing
butterflies, 287, 288.

Swynnerton, C. F. M., attacks on
butterflies and birds witnessed by,
283, 284.

Sykes, Mark L., on means by
which transparency may be attained
and on different forms of scales in
mimetic Lepidoptera, 366 n. 1.

Symmetrical injuries to wings of
Lepidoptera, 281-3, 325 : see also
270, 270 n. 1.

Sympatric groups, 62.

Sympatrid, 61 n. 1.

Sympatriote, 61 n. 1.

Sympatry, definition of, 62.

Symphaedra dirtea, 291.

Synageles picata, 253 (Fig. 1. A).

Synaposematic or Common
Warning Colours (Mullerian

Mimicry), X. 327-56. For sections
and sub-sections see pp. 295, 296.

Synaposematic Defence, Sea-
sonal Transition from Cryptic
to, X. 339-41.

Synaposematic Defence, Sea-
sonal Transitions in, or from
Aposematic to, X. 341, 342.

Synaposematic Resemblance : see
Mimicry Mullerian : introduction of
term (1897), 223, 328 n. 1.

Syncryptic or Common Pro-
tective Resemblance, X. 312.

Syncryptic Resemblance, 312, 312
n' 2> 359> 360 n. 1 ; definition of, 312 ;
distinguished from mimicry and com-
mon warning colours, 312, 359, 360;
analogy with syntechnic resem-
blance, 312; suggested as interpre-
tation of mimicry, 322.

Syndiagnostic groups, 60.

Synemosyna formica, 253 (Fig. I. B).

Synepigonic groups, 61, 61 n. 1 :
see also epigony ; of Pap. dardanus
{merope), 72, 72 n. 1.

Syngamic Chain, Asyngamy as
a consequence of the Breaking
OF, II. 88-90 : see also 94.

Syngamic groups, 60.

Syngamy underlies Diagnosis,
II. 68, 69.

Syngamy, definition of, 60 ; history
of word, 60, 60 n. 3, 61 n. 1 ; pro-
posed by M. Hartog to replace
fertilization, 60 n. 3 ; E. B. Poulton's
use of, 60, 60 n. 3 ; summary of
significance of, in study of species,
64, 65 ; as test of species when
diagnosis fails, 69 ; in Limnas chrys-
ippus, 70, 71 ; in Pap. dardanus
(merope), 72 ; rare between individ-
uals of the wet season brood and
the dry, 72-3 : sub-species united by,
75, 76 ; the test when structural
differences are great, 76 ; importance
of, to the systematist, 77 ; implied in
transition, 84 ; mechanical pre-
vention of, 85 ; widespread in P.
cardui because of powers of dis-
persal, 85 ; preferential, 85-8 : see
also 65 ; cross-fertilization and, 91 ;
advantages of, 93, 94.

Syntechnic Resemblance, 312, 312
n« 2> 359) 360 n. 1 ; definition of,
312; analogy with syncryptic, 312;
distinguished from mimicry, &c, 312,
359, 360.

ANALYTICAL INDEX

471

Syphilis, apparent hereditary
transmission of, explained by ' a
peculiar mode of infection' (1826),
184.

Systematic work, provisional nature
of conclusions of, 76, 77.

Systematise continuity the diffi-
culty of the, xv, 59, 60, 67 ; how
affected by views of the Origin, 46,
47, 59.

T

Taeniocampa populeti, 157 n. I.

Tail of lizard and Lamarckism,
114; directive value of lizard's, dor-
mouse's, and squirrel's, 325 ; warning
sound made by vibration of snake's,
324 ; head of model resembled by
mimic's, 254, 368.

Tails and ears, mutilation of, not
hereditary, 180, 181.

' Tails ' of butterflies' wings, value
of, 281, 282, 325, 325 n. 1, 351.

Tait, Professor, on the age of the
earth, 2, 8, 15, 24 ; on the cooling of
the earth, 11, 12.

Tardigrada in classification, 33.

tarsata, Ponera, with ant-like bug,
254, 255.

Tartccus phnius, 283, 284.

Ta-tsien-lu, W. China, home of
mimics of male //. misippns, 217:
see also 382-3.

Taungyah Pass, Dawnat Range,
Burma, 287.

Teeth, Lamarckian interpretation
of forms of, 114, 115.

Tegetmeier, W. B., breeding ex-
periment suggested by Darwin to,
79-

Telegony, supposed example of,
185.

Telephoridae mimicking Lycidae,
276.

telesiphe, Colaenis, a mimic of a
rarer Heliconius, 334 n. 2.

telesiphe, Heliconius, though rarer,
the model of C. telesiphe, 334 n. 2.

temminckii, Macroclemmys, with
worm-like lures, 378.

Temperature (see also External
Causes) : increment of, with depth
into earth's crust, 10 ; a stimulus to
change in the pupae of moths, 311 ;
of Byblia, 341 ; of Araschm'a, 342 ;
seasonal changes of Pierinae effected
by moisture and, 311, 312.

Tenacity of life and warning
colours, 316.

Tenaris, * eye-spots ' of, 326 ; much
mimicked (by Elymniinae, Hypo-
llmnaSf and Papilio), 326.

Tenasserim, nests of Microhierax
with insects' wings found in, 290, 291,
291 n. 1.

Tenthredinidae, see Saw-flies, 238-
9, 320.

Teracolus, seasonal changes in,
311, 312, 341, 342; experiments on
physiological cause of seasonal
changes in, 311, 312; combination
of procryptic and mimetic colouring
in, 341, 350.

Teracolns achine, 311, 342; —
antigone, 342; — etrida, 231, 349;
— evefiina, 342 ; — omphale, 311,
342; — regina, 341.

Teratology, the material of, valu-
able for study of individual develop-
ment, valueless for evolution, xxxix,
xl ; Prof. Windle on, 136 n. 1.

Terms, found in stomach of Falco
subbnteo, 284.

Terias he cab e, 288.

Ternate, Moluccas, Wallace dis-
covers Natural Selection at, 194-5.

Terpsiphone perspicillata, 283.

Terrapin, with worm-like lures,
378.

Terror, in man and animals, in-
spired by snake-like caterpillars, 367
367 n. 2, 368.

Tertiary, brain of Secondary rep-
tiles compared with, 29 ; brain of
later mammals compared with early,
29 ; oldest Pteropoda not known
before, 42.

tessellata, Melia, carrying sea-
anemones, 357.

Tettix, mimicry of leaf-carrying
ant by, 260.

Textularia, an existing genus in
the Carboniferous, 27.

Thabeitkyin, Upper Burma, 291
n. 1.

Thayer, Criticism of the
Statement that Animals are
Conspicuous by, X. 321-3.

Thayer, A. H., results obtained
by, quoted in Essay X, 293 ; on
resemblances to dead leaves, 299 ;
on neutralization of shadow, 299,
300 ; adjustable form of principle of,
300; on conspicuousness of the

ANALYTICAL INDEX

monochrome and cryptic effect of
pattern, 321-3, 321 n. 3 ; on cryptic
effect of iridescence, 322 ; mimicry
interpreted as syncryptic resemblance
by, 323.

Thee la rubi, 301.

thelxiope, Heliconius, varieties of,
69.

Theories of Evolution, Essay

III, 95-119.

Theories of Heredity, Essay

IV, 120-38 : see also 142 n. 1.
Theories of Mimicry, Essay

VIII, 220-70.

Theory of Natural Selection
and T. H. Huxley, Essay VII, 193-
219.

Theory of the Origin of
Varieties, J. C. Prichard, 185-7.

Theory, the Evolution, A. Weis-
mann, Eng. transl., 164 n. 2, 375.

Thiselton-Dyer, Sir W. T., on
mutations due to cultural conditions,
xxii ; on Deductive Biology, xlvii,
xlvii n. 1 ; on older writers on species,
56 ; on diagnosis of species, 66.

Thompson, D'Arcy, on Laws of
Growth, 224, 225.

Thomson, Sir W., see Kelvin,
Lord.

1 Throwing back ', see atavism, 125.

Thrum-eyed and pin-eyed prim-
rose, Darwin's, Bateson's, and
Gregory's work on, xxvii-xxxi.

Thundiani, king-crow attacking
butterflies at, 285.

thyodamas, Cyres/is, eaten by bee-
eater, 288.

Thyridia psidii, 264, 265.

thysa, Belenois, Mullerian mimicry
of Mylothris far more developed in
dry than in wet f. of, 341.

Thysanoptera of Commentry Car-
boniferous, 35.

tibullus, the E. sub-sp. of Papi/io
dardanus (merope), 337, 338, 374,
374 n. 1, 375 : see also dardanus.

Tidal retardation, 7, 8.

Tides, did not prevent tranquil
deposition in Silurian, 17.

Tiger, aggressive resemblance of,
313.

Time and Space Relation-
ships of Mimicry, &c, VIII.
247-50.

Times, 78.

Tirumala {Melindd) ??to?-geni, 337.

Tissues, animal, derived from cells,
121.

Tithorea, resemblance of Heli-
eonius to, 235.

tityus,Haemorrhagia, loss of scales

by, 365.

Tobacco, Kolreuter on varieties of,
78.

Tongue, worm-like lures of Macro-
clemmys beneath, 378.

Toro, W. Uganda, overlapping of
eastern Danaine {Amauris) and
western Acraeine (Planema) models
in, 338.

Toronto meeting of the British
Association (1897), 263.

torquata, Pratineo/a, chasing
Tarucus plinius, 284.

torquatinus, Papilio, W. C. Hewit-
son on, 57 n. 1.

torquatiiS) Papilio, W. C. He wit-
son on, 57 n. 1.

Tradition as an incentive to re-
search, xlii ; paper the material
basis of, 170-2.

Training, results of, not hereditary,
136.

Transfusion of blood and pan-
genesis, 125.

Transition from Cryptic to
Aposematic Defence, X. 318-20.

Transition Geographical
from Aposematic to Cryptic
Defence, X. 320-1.

Transition, importance to the
systematist of, 64 : see also Con-
tinuity, xiv, xv ; the foundation of
diagnosis, 64 ; diagnosis and, 66 ;
as a test of varieties, 66, 67 ; sub-
jective element in, 66, 67 ; Huxley's
belief (1859) that species are uncon-
nected by, 195.

Transitions seasonal, in modes of
protection, 320, 339-42.

Transmission of Acquired
Characters, Bearing of Study
of Insects upon, Essay V, 139-72.

Transmission of Acquired
Characters (Experience), bear-
ing of Insect Mimicry and
Warning Colours upon, V. 166-8.

Transmission of Acquired
Characters implied by the
Theory of External Causes,
VIII. 267.

Transmission of Acquired Char-
acters by heredity : see also Acquired

ANALYTICAL INDEX 473

Characters ; essential to Lamarck's
theory, 99; forms of teeth and, 114,
115 ; forms of joints and, 112, 114,
115; the germ-plasm and, 13 1-2 ;
discussed and rejected by J. C.
Prichard (1826), 177-84 ; required by
the interpretation of mimicry by the
theory of external causes, 267.

Transmutation of species, Huxley's
belief in (1859), 195 ; older beliefs in,
54-6.

Transparency, attained in diverse
ways in Lepidoptera, 263-6 ; by loss
of scales in mimetic moths, 251, 276,
365 ; by transparency of scales, 251,
266, 366 ; in oceanic forms, 298.

Tree-shrews mimicking squirrels,
367, 367 n. 1 ; distasteful qualities of,
367 n. 1.

Trees, fossil, as evidence of uni-
formity of conditions, 18, 19.

Trepsichrois mulciber, 372, 376.

Trias, appearance of Limulus in, 40.

tridensy A crony eta, uniformity in
broods of, 87 n. 1.

Trilobites among the earliest
fossils, 5, 30 ; preserved with anten-
nae, 17, 39; ancestral position of,
38, 39 ; dominance of, in oldest
rocks, 39 ; rapid decline of, 41.

Trimen, Roland, on recent changes
in the distribution of African butter-
flies, 52 n. I ; discovery of mimetic
females of Pap. dardanus by, 57,
57 n. 1 ; on dorippus f. of L. chrys-
ippus in S. Africa, 71 n. 1 ; on
preferential mating of African butter-
flies, 86-7 ; on seasonal forms of
Hypanis (Byblia) acheloia, 87 ; on
tropical biological stations, 89, 89 n. 1,
90 ; on African mimicry, 222 ; on
African Mullerian mimicry, 223 n. 6 ;
on Mullerian mimicry of Aletis, &c,
for L. chrysippus, 232 ; description of
pla?iemoides female f. of Pap. dar-
danus by, 374 n. 3.

trimeni, a primitive female f. of
the Papilio dardamts group, 374,
375 ; roughly mimicking Amauris
ni alius f. douii/u'canus, 374 n. 2 :
see also dardanus.

Trincomalie, Ceylon, dorippus f.
of L. chrysippus at, 70 n. 2.

Tring Zoological Museum, re-
searches on geographical distribution
at, xvi ; specimens of L. chrysippus
in, 321 n. 1.

Trinidad, examples of mimicry in,
235 ; colour of the chief Ithomiine-
centred combination in, 350; char-
acter of under surface of mimetic
Protogonius in, 351.

trinodosus, Heteronotus, mimicry
of ant by, 258 (Fig. 6), 259.

Tristram, Canon H. B., on colours
of desert animals (1859), 195, 196.

Triton, see newt, 130.

Trochammina, an existing genus
in the Permian, 27.

Trochiliuni (see also Sesia) :
method of attaining transparency in
mimicry of wasps by, 251, 365, 366.

Trochilium {Sesia) apiforme, 365 ;
— crabroniforme {bembeciforme), 366.

tropho?iius, a female f. of the
Papilio dardamts group, mimicking
Litnnas chrysippus, 374, 374 n. 1 ;
bred from female forms trophonius
and hippocoon, 72 n. 1 : see also
dardamts.

Tropical America : see America,
Central and South.

Tropics, change of fleece in, 190.

Tryphaena, value of bright hind
wings of, 303, 304.

Tryphaena pronuba, 314 n. 2.

Tschermak, rediscovery of Mendel's
principle by, xxix.

Tse-tse fly, limit imposed on higher
animals by, 100.

tugela, Precis, under side procryp-
tic in both wet and dry seasons, 340 ;
S. African habitat of, 340.

Tunicates. uncertain ancestry of,
26.

' Tussocks ', fine branched hairs of,
325 ; defence afforded by, 325, 326.

Tutt, J. W., on darkening of N.
moths, 309, 309 n. 1.

Twins, see 1 identical ' twins.

Twins with differences greater than
between ordinary brothers and sisters,

I3S*

Twigs, protective (procryptic) re-
semblance to, 298, 299 ; procryptic
resemblance to swaying, 360.

Tylor, Professor E. B., on origin
of implements, 109 ; life of J. C.
Prichard by, 173.

typhi e, Siphonostoma, concealed
among leaves of Zostera in shallow
water, 298, 299.

tytia, Caduga, mimicked by Pap.
age st or, 371.

474 ANALYTICAL INDEX

u

Uganda, overlapping of eastern
Danaine {Amauris) and western
Acraeine (Plane??ia) models in, 338.

Umbelliferae, E. picipes on, 255.

undularis, Elymnias, female of
mimics Salatura plexippus {geniitia)
in N. E. India and Sikkim, and S.
hegesippus in Burma, 373.

Ungulates, episematic markings in,
357-

Uniformity of conditions during de-
positions of stratified rocks, 17-19 ;
shown by flying organisms, 18 ;
shown by fossil trees, 18, 19 ; shown
by prints of raindrops, 19 ; of pat-
tern throughout nauseous groups,
reasons for, 234, 277-9 I of Australian
Hymenoptera Aculeata, 278.

United States and Lamarck's
theory, 97, 98 ; opinions on evolution
in, 100 ; negroes unchanged by
many generations in, 178 ; mimicry in
butterflies of, 274 ; Terrapin (Macro-
ciemmys) with worm-like lures in
southern, 378.

Universal Review, 7.

Unpalatability associated with
warning colours, 315; no defence if
food scanty, 269, 317, 317 n. 4.

Unpalatable insects, special ene-
mies of, 317, 318.

Unpleasant smell as a protection,
see smell.

Untersuchungen iiber die Mimi-
cry, Erich Haase, 231, 318, 375.

Upper Amazon, see Amazon,
Upper, 273.

Uraniidae, Papilio mimicked by
moth (Epicopeia) belonging to, 371 ;
Papilio mimicking moth (Alcidis)
belonging to, 371.

Uranium and radium, bearing
upon life of the sun of, 15 n. 2.

unmoscopus, Ceratias, phosphor-
escent lure of, 378.

Uric acid and derivatives in Pierine
pigments, 262, 263.

7i?'?iaria, Ammophila, instincts of,
163.

Uropteryx sambucarta, 150, 150
n. 2.

urticae, Spilosoma, aposematic
attitude of, 324.

tirticae, Vanessa, struggle severe in
pupal stage of, 306 ; power of colour
adjustment of pupae of, 306.

Usaramo (Rosako), E. Africa, ant-
like bug from, 254, 255, 255 (Fig. 3).

Use and disuse of parts, hereditary
transmission of (use -inheritance) :
see also Acquired Characters ; La-
marck's theory and, 98 ; an attractive
conception, 101 ; transmission of
'acquired characters' involved by,
no; arguments against, 114, 115;
pangenesis and, 126 ; continuity of
germ-plasm and, 131, 132 ; heredity
and, 137; Natural Selection explains
effects apparently caused by, 137,
138.

Utility, see also Natural Selection ;
Natural Selection and, 105-7 ; Palae-
ontology and, 107, 108 ; Kirby and
Spence on mimicry and, 221.

V

Vail, see Macdougal, xix n. 5,
xxi, xxii.

Value of Brightly-Coloured
Surfaces Concealed during
Rest, X. 303, 304 : see also 325.

Valvulina, an existing genus in the
Carboniferous, 27.

Van Beneden, on the preparation
for fertilization of the germ-cells,
xxxi.

Vanessa kaschmirensis , 285;
— urticae, 306.

Vanessidae, method of pupation
in, 151 ; pupae of, affected by gravity,
151, 152; compared with nauseous
groups as regards uniformity, 277 ;
species of, captured by king-crow, 285;
colour adjustment of pupae of, 306 ;
struggle for life in pupae of, 306.

variabilis, Estigme?iida, mimicking
Hispidae, 261.

Variable Protective Resem-
blance in Insects, V. 152-4: see
also 149, 150, and Adjustable
Protective Resemblance, X.
3°4~7-

Variation des Heliconia Thel-
xiope et Vesta, M. Charles
Oberthiir, 69.

Variation, Heredity and Evo-
lution, R. H. Lock, xv n. 2, xvii n. 1
and n. 2, xix n. 5, xx, xx n. 2, xxiv,
xxiv n. 2, xxvii, xxix, xxxvi, xxxvii
n. 2.

Variation in Animals and
Plants, H. M. Vernon, xxxv n. 2.

ANALYTICAL INDEX

475

Variation under Domestica-
tion, C. Darwin, xxiii, 79.

Variation, independent and corre-
lated, 66 n. 2 ; modification distin-
guished from, 73 n. 1 ; interbreeding
checks excessive, 94 ; a factor of
selection, 95-6 ; not explained by
selection, 96, 97 ; sudden large, no;
Weismann's hypothesis on causes of,
127, 128, 137 ; believed to be due to
hereditary influence of environment,
137; predetermined in fertilized
ovum, 137, 142, 183: see also xxxvi,
xxxvii, xxxvii n. I ; the raison d'etre
of sexual reproduction, 137 ; variable
protective resemblance and the causes
of, 153, 154; Prichard on the obscure
origin of, 176 ; Prichard on adapta-
tion as caused by laws of, 190.

Varieties, species and, 47, 66-8 ;
transition as test of, 66, 67 ; tendency
towards interbreeding between simi-
lar, 85-8 ; ' produced in the race,
have their beginning in the original
structure of some particular ovum or
germ' (1826), Prichard, 183; sudden
origin of human, 185 ; Prichard on
adaptation in species and, 189, 190.

Various conceptions of
Species, II. 59-63.

Various uses of Term Mimi-
cry : Essential Element in
Mimicry, X. 359-61.

Venation, importance of, as com-
pared with colour, xvii.

Venezuela, character of chief mi-
metic butterflies in, 273.

Venezuela and Central America,
colours of a chief Ithomiine-centred
combination in, 350.

Ventral glands of Croesus larvae,
239, 320.

Venus, the question of water on, 14.

verbasci, Cucullia, cryptic resem-
blance of moth of, 319; transition
from aposematic to cryptic defence
of larvae of, 318; evidence of dis-
tastefulness of, 318.

Verdascum, Gartner on, 78 ; Dar-
win on sterility between varieties of,
79-

Verhandl. der k.-k. zool.-botan.
Ges. in Wien (1883), 256, 258, 302.

Verhandl. d. V. Internat. Zool.
Congr. z. Berlin, 271.

Vernon, H. M., introduction to the
study of Mendelism by, xxxv n. 2.

versicolor, Endromis , mimicry of
saw-fly larvae by larvae of, 238, 239,
239 n. 1.

Vertebrata, bearing of In-
sect Mimicry, &c, upon supposed
Hereditary Transmission of
Experience in, V. 166-8.

Vertebrata, 43 : see also classifica-
tion of examples of mimicry, 393; evo-
lution of, xliii, 26, 27, 30, 31 ; in classi-
fication, 25 ; progressive changes of
lower Phyla even slower than those
of, 28 ; of early Palaeozoic, 30, 31 ;
specialized character of earliest
known, 30, 31 ; past history inferred
from comparative anatomy of, 32 ;
origin of limbs of, 108, 109 ; intelli-
gence of the higher, 116, 117; in-
stincts of, 116, 117.

Vespa, comb-making instinct of,
prior to experience, 164, 165.

vesta, Heliconius, varieties of, 69.

Vestiges of the Natural History
of Creation, R. Chambers, xviii, xix,
104, 105, 175.

Vetch, ant-like Locustid and models
on Rhodesian, 257 n. 1.

vetustus, Heliconius, mimics
Melinaea in B. Guiana, 332.

Victoria Nyanza, eastern and west-
ern sub-sp. of Amauris meeting at,
xxxv, 69 : see also 335 ; the meeting
place of certain E. and W. African
models and their mimics, 338 ; range
of merope, sub-sp. of Pap. dardanus,
from W. coast to, 374, 374 n. 3.

Vines, Prof. S. H., on the study of
adaptation as a stimulus to inquiry,
xlvi n. I.

vinula, Dicranura, caustic potash
for softening cocoon secreted by, 159.

violae, Acraea, proved to be un-
palatable, 269.

viridis,Lac~erla,terr\fied by, but ulti-
mately relished snake-like caterpillar,
367.

Volcanic dust on ocean floor, 20.

Volucella, resemblance to humble-
bees of, 221: see also 251 ; resemblance
not aggressive, 378 ; larvae of, proba-
bly beneficial to humble-bees, 378.

W

Wabosakhan Camp, Burma, king-
crow unable to detect Melanitis at,
288, 289.

waMbergii Hypolimnas (Euralia),

476 ANALYTICAL INDEX

replaced by western H. anthedon
near V. Nyanza, in accordance with
corresponding geographical replace-
ment of Danaine models, 338.

wakefieldii) Godartia, recent en-
trance into Natal of, 52 n. 1.

Walker, Commander J. J., on
enemies of D. bifida pupae, 158.

Wallace, Statement of Con-
ditions UNDER WHICH PROTECTIVE

Mimicry Occurs, by, X. 361, 362.

Wallace, Alfred Russel, letters
from Darwin to, on individual differ-
ences and single variations, xl n. 3, 3 ;
and on geological time, 6 ; minute
differences the basis of evolution
according to Darwin and, 3 ; concep-
tion of Natural Selection by Darwin
and, 48 ; controversy with Darwin on
interspecific sterility, 49, 80,89; Bates
quoted by, 51 n. 1 ; joint essay of
Darwin and (1858), 95-7, 194-6: see
also xxxvii n. 2, 48, 58, 200, 222, 379 ;
on selection and self-fertilization, 92
n. 4 ; on in-and-in breeding, 93 ; on
struggle for life in youngbirds, 167 n. 2 ;
J. C. Prichard as a remarkable pre-
decessor of Darwin and, 192 ; writings
on evolution by, before discovery of
Natural Selection, 194; discovery of
Natural Selection by, 194, 195 ; on
protective resemblance of Kallima,
203, 206, 207 ; on mimicry in the
Oriental Region, 222 ; early views of,
on mimicry between models, 222 ;
early acceptance of Miillerian mimi-
cry by, 223, 327 ; on mimicry a form
of protective resemblance, 226,
348 ; on advantages of female mimi-
cry, 246, 279 ; on similarity of con-
ditions in W.Africa, S. America, and
Malaya, 248 ; on mimicry in verte-
brates, 367, 367 n. 1 ; on the mimicry
of Rhynchophora by Longicorns, 369;
on hardness the special defence of
weevils and Anthribidae^ 369 ; re-
jection of sexual selection by, 379;
interpretation of epigamic characters
as recognition marks and as due to
surplus activity, 380.

Walsingham, Lord, on the value of
bright hind wings of moths, &c,
3°3-

Warning Colours and Mimi-
cry, bearing on supposed Here-
ditary Transmission of Expe-
rience of, V. 166-8.

Warning and Signalling
(Recognition), or Sematic
Colours ; Aposematic and Epi-
sematic Characters, X. 315-58.
For divisions, sections, sub-sections,
&c., see pp. 294-6.

Warning or Aposematic
Characters, X. 315-26. For sec-
tions see pp. 294, 295.

Warning in Common or Syn-
aposematic Characters, X. 327-
56. For sections and sub-sections
see pp. 295, 296.

Warning colours (aposematic
characters), see also Mimicry
Miillerian ; place of, in a scheme of
the bionomic uses of colour, 226,
227 ; definition of, 315 ; introduction
of term 'aposematic' (1890), 223;
recognition characters compared
with, 357, 358 ; protective (pro-
cryptic) resemblance contrasted with,
315 ; education of enemies and insect,
166-8 ; supposed hereditary trans-
mission of experience and, 166-8,
268, 269, 316; especial development
in wet season of, 208-9, 317, 339-42 ;
male H. misippus and, 217 ; flight
slow in insects with, 323 ; patterns of
upper and under surface often simi-
lar in butterflies with, 323 ; special
conspicuousness of the under surface
of butterflies with, 323 ; Finn's ex-
periments on insects with, 269, 279
n. 1, 317, 317 n. 4 ; evidence of
rejection by wild birds of moths with,
284 ; species rather than individual
benefited by, 316 ; tenacity of life in
species with, 316 ; waste of life pre-
vented by, 316; various means of
special defence associated with, 315;
evidence by F. A. Dixey and G. B.
Longstaff of unpleasant smell in
butterflies with, 316, 317, 317 n. 1 ;
more evidence required of special
defence in insects with, 317 ; chiefly
developed when insect life abundant.
3 1 7 ; a danger in time of hunger, 317;
special enemies (e.g. cuckoo), of
forms with, 3 1 7, 3 18 ; noreal immunity
of forms with, 318 ; forms with, com-
pelled to hide in time of stress, 320:
see also Dry Season and Winter ;
importance of instincts for display of,
323, 324; importance of ' sham death '
in forms with, 323, 324 ; gregarious
habit in forms with, 318, 320; transi-

ANALYTICAL INDEX

tion to a measure of protective (pro-
cryptic) resemblance from, in L.chrys-
ifipus, 320, 321 ; transitions between
protective resemblance and warning
colours, 318-21, 323, 324; limits
to effect of, in Aculeates, Euploeas,
Ithomiines, &c, 322, 323 ; conditions
of struggle determine degree of con-
spicuousness of, 323 ; advantage of
resemblance between forms with,
327-8 ; mimicry often combined with,
347 ; mimicry especially found in
groups with, 347, 348 ; habits of cer-
tain Brenthtdae and weevils bring
about, 369-70.

Wasp-beetle, 238, 251, 252, 348,
3°3-

Wasps, Social and Solitary,
G. W. and E. G. Peckham, 118 n. I.

Wasps (see also classification of
examples of mimicry, 389-93) :
mimicked by diverse methods, 250-2,
280 ; uniformity throughout many
species of (Miillerian mimicry), 232,
278; advantage of resemblance to,
281 ; limit to conspicuousness of,
322 ; many examples of mimicry of,
Batesian, 376 : others Miillerian,
230-2, 376.

Waste of life prevented by warn-
ing colours, 316.

Waterhouse, G. R., on wide differ-
ence between domestic races, 76.

W ATTEN W YL, BRUNNER VON,

Hypertely of, X. 302, 303.

Weevils (see also classification of
examples of mimicry, 390-1) : colour
adjustment probable in Cleomts, 307 ;
hardness as the defence of, 261, 369,
370 ; conspicuousness of certain large
African, 370.

Weir, J. Jenner, on the value of
bright hind wings of moths, &c,

303, 304.

Weismann, August, appropriation
under the name of Mendel of dis-
coveries made by, xiii, xxxvi, xxxvii,
xxxvii n. 1 ; on characters predeter-
mined in the germ, xxxvi, xxxvii,
xxxvii n. 1, 135; Amixia of, 60;
Amphimixis of, 60 n. 3 : on Acquired
characters or Somatogenic char-
acters, no, 123; on causes of germ
variation and significance of sexual
reproduction, 127, 128, 137; con-
tinuity of the germ-plasm of, 127-36 ;
on germ-plasm in the nucleus, 128 ;

on heredity and transmission of
acquired characters, 132 ; on effect
of cessation of Natural Selection
(panmixia), 138 : see also xxxvii n. 2 ;
stimulating effect of writings of, 139 ;
definition of acquired and inherent
characters by, 142 ; on Lamarckism
and the cocoon-making instinct, 164
n. 2 ; views of, on heredity and
acquired and inherent characters
anticipated by J. C. Prichard, 174,
175, 178, 179, 183 ; first led to doubt
transmission of acquired characters
on theoretical grounds, 181 ; on
seasonal changes of Lepidoptera,
311 ; on seasonal forms of Araschnia,
342 ; use of incorrect term ' immune '
adopted from Haase by, 375 ;
mimicry in Pap. dardanus (merope)
and in butterflies of Eastern Brazil
erroneously figured by, 375, 376 ;
' Mimicry-ring' of, 376.

West Africa, see Africa, West.

West China, see China, West.

West Indies, J. C. Prichard on
English colonists unchanged after
many generations in, 178 : see how-
ever 187 ; H. misippus ranges to,
216.

Westminster Review, 78.

West wood, Prof. J. O., on non-
mimetic species of mimetic genera,
274, 275 ; on a wonderful example of
secondary Miillerian mimicry, 346.

Wet season, the time of plenty,
208, 209, 317, 326; form of butter-
flies' wings in, 206, 207, 310, 311 ;
warning colours and ' eye-spots 5
specially characteristic of, 208-11,
317, 326, 339-341 ; aposematic forms
of African Precis in, 208, 209, 320,
320 n. 1, 339-41 ; butterflies much
upon the wing in, 209 ; advantage of
warning colours and 'eye-spots' in,
209-n, 317, 320, 326 ; mimicry
developed in broods {Precis, Byblia.
Teracohcs) of, 339, 339 n. I, 340-1 ;
mimicry less developed in broods
(Be/enois, Teracohts, Huphind) of,
341, 342.

Wetzel, experiments on frog's egg
of, 129.

Whale, ear-bones of, on ocean floor,
20.

' What is a Species ? ' Essay II,
46-94.

'What is a Species?' Intro-

478 ANALYTICAL INDEX

duction to Discussion on, II.
63-5.

Whewell, W., on the study of
Final Causes as a stimulus to inquiry,
xlvi n. 1.

White Admiral, 342 : see also
Li 'menitis , 218, 274, 342.

White under surface of animals
interpreted by A. H. Thayer, 299.

Whiteness, J. C. Prichard on local
development of, 187.

1 Why ' and ' How', both answers
essential, xlvi, xlvii.

Wichura, proof that hybrids of Salix
do not follow Mendel's principle
by, xxxv n. 1.

Wiggins, C. A., butterflies from the
V. Nyanza collected by, 69 ; on H.
misippus and its model, 216 n. 1.

Wight, Isle of, effect on plants of
wind in, 75.

Windle, Prof. B. C. A., on Roux's
researches, 128 n. 1 ; on Teratology,
136 n. 1.

Wings, stability of pigments in
butterflies', xlv, xlv n. 1, 53 ; as evi-
dence of uniformity of conditions in
geological times, 18 ; insects in
oceanic islands often without, 18 ;
immense size of, in Carboniferous
dragon-flies, 18, 37 ; fully developed
in Carboniferous Phasmids, 36 ; evo-
lution of insects', 36, 37 ; ancient
insects probably with six, 37; seasonal
change of form in butterflies', 206,
207, 310, 311; eye-spots especially
developed on under surface of, 210,
211, 326, 340, 341 ; of butterflies
injured as if by enemies, 270, 270 n. 1,
281-3, 325 ; darkening of hind, in
Guiana mimetic butterflies, 272,
273, 331, 332, 35°; of dragon-flies,
butterflies, moths, flies, and cicadas
in nests of Microhierax, 290, 291,
291 n. 1.

Winter moth, 156.

Winter, the time of stress, 148,
209, 317, 320: see also dry season.

Wisconsin, 118 n. 1, 252, 253, 256,
380.

Wisconsin Geological and
Natural History Survey, 118 n. 1.

Wood splinter, protective resem-
blance to, 319.

Woodland in S. Africa, definition
of, 340.

Woodpecker, Darwin on the in-

adequacy of Mutation to account for
the, xix.

Woodward, Henry, on evolution
of Crustacea, 40 n. 1.

Worms, prey allured by pseud-
episematic resemblance to, 378.

Wortman, Dr., on formation of
joints by pressure, 115.

Wright, Miss F. A., on pupal
stage of V. urticae, 306.

X

xenocles, Papilio, a Danaine mimic
not attacked by bee-eaters, 288.

Xylocopidae, see classification of
examples of mimicry, 389, 391-2.

Y

Yerbury, Col. J. W., on forms of
Limnas chrysippus, 70 n. I, n. 2 ; on
Para fly mimicking Hymenoptera, 257
n. 1 ; direct evidence of the attacks
of birds on butterflies obtained by,
283, 285, 286.

Yoonzaleen River, Burma, 290.

Yorkshire and Lancashire, recent
darkening of moths in, 308-10.

Young enemies, Miillerian mimicry
and, 166-8, 212-15, 222, 278, 327-
31, 366; advantage of episematic
markings to, 357.

Z

Zea, Darwin on sterility between
selected varieties of, 79.

Zebra, invisibility of, 298.

Zeitschr. f. Wissenschaft. Zool.,
84 n. 2, 334 n. 2.

zitenius, Melanitis, king-crow
unable to find, 288, 289.

Zittel, Karl A., Palaeontologie
by, consulted for Essay I, 43.

Zonosoma (Ephyra), cocoon re-
placed by loop, &c, in, 1 50 ; parallel-
ism with Pierinae, 150 ; cryptic
colours of larva and pupa of, 150;
unique dimorphism in larva and
pupa of, 1 50.

Zool. Ergeb. einer Reise in Ost-
Afrika, F. Stuhlmann, Hemiptera,
Gerstaecker, 255.

Zoological Congress at Berlin
(1901), Author's English Address to,
the original form of Essay IX, 271 ;
Report of the, 271.

Zoological Society of London,

ANALYTICAL INDEX

479

Proceedings of, 70 n. 2, 153 n. I,

223, 230, 257 n. 1, 259, 260, 275,
276, 280, 286, 317, 318, 319, 319
n- h 349, 353, 3^7 n. 2, 368, 369, 378,
378 n. 3.

Zoologist, 84, 155 n. 1, 159 n. 2,
291 n. 1.

Zoonomia, Erasmus Darwin, 140,
141.

Zostera, S\ typhle concealed among
leaves of, 298, 299.

Zygaenidae, a distasteful family of
diurnal moths, Mullerian mimicry

in, 372 ; Chalcosiinac, a sub-family
of, mimicking Danainae and Papilio-
ninae, 231 ; rough Mullerian mimics
of blue Oriental Euploeas, 372, 376.

Zygosis or fertilization, xxxi ; in-
ferences as to precursors (allelo-
morphs) of Mendelian characters in,
xxxi-xxxiii; proposed by Lankesterto
replace fertilization, 60 n. 3.

Zygote or fertilized germ, Mendel-
ian inferences as to, xxxi-xxxiii ; the
immediate product of fertilization,
60 n. 3.

OXFORD

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Essays on evolution 1889-1907,

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